Briefly stated, the present invention is an orthography board game having an apiarian theme. The game consists of a game board having a plurality of hexagonal playing spaces arranged in an overall hexagonal pattern. Selected playing spaces on the board are assigned predetermined characteristics which alter the play of the game, creating bonus locations and penalty locations. A plurality of hexagonally shaped game tiles are provided, each game tile sized to fit within a playing space on the game board and assigned a letter or symbol having a predetermined distribution with the complete set of game tiles. A plurality of six-sided game cubes or dice are provided, together with a rolling cup, and are utilized to determine a players score during each round of game play.

The present invention relates generally to a word-based board game and method of play, and in particular, to a word-based board game apparatus and method of play for multiple players wherein an object of play is accumulation of points via the placement of letter tiles on a hexagonal playing board and the rolling of a scoring dice.
In traditional word-based board games, such as the well known game Scrabble™ the object of play is to accumulate points by placing letter tiles on a game board to form words. Each letter tile placed on the board is assigned a value based in part on the letter on the tile, and in part upon the location on the game board. The total of all letter tiles utilized during a players turn is added, to achieve a total score for that turn of play. Additional bonus points are awarded for placing letter tiles on specific locations distributed about the game board. This style of game rewards players having an extensive vocabulary, and who are capable of placing a limited set of letters onto the game board in a manner which maximizes available points. As such, games such as Scrabble™ are difficult to play with multiple players having either different skill levels or different vocabularies, i.e. with a combination of adults and children.
Accordingly, it would be advantageous to provide a method and an apparatus for play of a word-based board game in which game play among adults and children is independent of a player's skill and vocabulary, and which is equally entertaining for players of all ages, while simultaneously serving as a learning or teaching aid for younger players.

Method and apparatus for orthography board game


A hydrogen generator of the invention includes: a reformer for generating a hydrogen-rich gas from a feed gas and water by a reaction using a reforming catalyst body and sending it out from an outlet port; a material feed system for feeding the feed gas to the reformer; a burner for supplying, to the reforming catalyst body, heat generated by mixing a fuel gas with air and burning it; and an air supply system for supplying air to the burner; wherein, when purging an interior of the reformer using the feed gas in shutting down the hydrogen generator, an amount of the air supplied is increased to put out a flame of the burner, and a purge gas sent out from the outlet port by the purging is mixed and diluted with the air in the burner and is discharged outside.

1. Field of the Invention
The present invention relates to a hydrogen generator and a method of shutting down its operation as well as a fuel cell system, and more particularly to a hydrogen generator in which an interior of a reformer can be purged so that a combustible gas emitted to its outside can be appropriately processed and a method of shutting down its operation as well as a fuel cell system.
2. Description of the Related Art
There are known reformers (reformer systems) that generate a reformed gas containing hydrogen as its main component by a steam reforming reaction with steam and an organic material such as natural gas or naphtha.
Among reforming catalyst bodies that contribute to this steam reforming reaction is one in which a carrier such as alumina carries a Ni-based or a Ru-based catalyst. The performance of the reforming catalyst body, however, greatly depends on the atmosphere of the surrounding environment; for example, the Ni-based catalyst can exhibit its expected performance in a reduced state but its catalytic activity deteriorates in an oxidized state. Likewise, the Ru-based catalyst tends to volatilize easily and therefore shows degraded catalytic activity in an oxidized state at high temperature.
Particularly during a shutdown period of the reformer, there is a possibility of air (oxygen) intruding therein from the outside of the equipment due to the depressurizing effect originating from the temperature decrease of a high-temperature remaining gas in the reformer, and there is an increasing concern over the deterioration of the reforming catalyst body by oxidation. Therefore, it is necessary to take a measure to inhibit oxidation of catalysts during a shutdown period of the reformer. For this purpose, the following method has been adopted; after ceasing maintaining the temperature of the reforming catalyst body at a high reforming temperature (at 700° C., for example), purging is performed in such a manner that an inert gas such as nitrogen is introduced into the interior of the reformer and the interior of the reformer is filled with nitrogen in order to replace the high-temperature remaining gas in the interior of the reformer; thereafter, the upstream and downstream of the reformer are closed by sealing valves to inhibit deterioration of the reforming catalyst body.
Another method in which a hydrogen generator is purged with a feed gas for the hydrogen generator itself in place of nitrogen has been proposed as remedies for the increased cost and complexity associated with obtaining nitrogen. (See, for example, Japanese Unexamined Patent Publication 2000-95504.) With this method, the interior of the reformer can be appropriately purged without using nitrogen after shutting down the reformer, and cost reduction and simplification of the gas supply system are made possible.
Although the foregoing publication does not mention post-processing of a combustible purge gas that is forced out by purging the reformer, a post-processing method normally assumed for effectively utilizing existing equipment is such that a purge gas is returned to a burner for heating the reforming catalyst body of the reformer and then combustion-treated with the burner.
When the interior of the reformer is purged with a feed gas, it is important to reduce the temperature of the reforming catalyst body as quickly as possible so as not to thermally decompose the feed gas and to complete the purging operation for the reformer within a minimum time, from the viewpoint of saving the energy required for the purging. Nevertheless, the above-described combustion of the purge gas in the burner functions to reduce the rate of the temperature decrease of the reforming catalyst body and thereby delays the purging of the reformer, leading to an increase in energy loss in the hydrogen generator. Moreover, if a purge gas that is useful as a power generation gas is burnt in the burner when purging the reformer, the amount of heat that is to be produced by this combustion cannot be utilized effectively, and effective utilization of energy cannot be attained.

Hydrogen generator, method of shutting down operation of hydrogen generator, and fuel cell system


A valve has a valve housing and a stem projecting from the housing and rotatable relative thereto about an axis. A handle assembly for the valve has an abutment directed angularly in one direction of the axis and fixed relative to the housing, a knob, and formations on the knob and stem for rotationally fixing the knob on the stem and for axial displacement of the knob on the stem between a normal use position and an override position. A knob abutment projecting axially from the knob is directed angularly opposite the housing abutment. The knob abutment is angularly engageable with the housing abutment in the normal use position but is able to pass angularly past the housing abutment in the override position. Thus the knob is in the normal use position most of the time. In order, however, to gain increased flow, a higher temperature, or divert water from the tub to the shower, it is displaced into the override position. The same knob used for flow control or temperature adjustment is simply pulled or pushed as it is turned, normally pulled, in order to go beyond the normal end position defined by engagement of the abutments with each other.

In commonly owned U.S. Pat. No. 5,421,364 a flow-control valve is disclosed having a valve housing and a valve element in the housing rotatable about an axis through at most 360.degree. between a fully open position for substantially unimpeded fluid flow through the housing and a fully closed position for substantially no fluid flow through the housing and through intermediate positions for intermediate levels of flow through the housing. A spindle coupled to the element extends along and is jointly pivotal with the element about the axis. A handle or knob fixed on the spindle is provided offset from the axis with a handle stop so that the handle stop orbits about the axis as the handle and spindle are rotated to adjust the valve. An abutment body or sleeve fixed on the housing adjacent the knob carries a housing stop that is radially deflectable on the abutment body between a normal position angularly engageable with the handle stop for limiting angular movement of the handle and spindle and a deflected position out of angular engagement with the handle stop and permitting unimpeded angular movement of the handle.
Thus with this system the stop normally limits the angular stroke or travel of the valve spindle. This housing stop can, however, be depressed radially to let the handle stop pass, allowing the full range of adjustment to the handle.
While such a system is relatively effective, the radially depressible button is an extra part that increases construction costs. In addition manipulating such a valve requires a simultaneous radial pressure and rotation, just the type of unpopular biaxial actuation used for uncapping medicine containers to prevent casual opening and making even intentional use difficult.

Handle with adjustable stop for flow-control valve


Disclosed are compositions and methods for controlling or slowing down the coloration of keratin fibers such as hair involving providing compositions comprising coconut water which contains catalase-peroxidase and at least one antioxidant, wherein the pH of the composition is from about 2 to about 6.

It is known that consumers desire to use cosmetic and personal care compositions that enhance the appearance of keratin fibers such as hair by changing the color of the hair and/or by imparting various properties to hair such as shine and conditioning. The process of changing the color of hair can involve either depositing an artificial color onto the hair which provides a different shade or color to the hair or lifting the color of the hair, such as for example, from a dark brown shade to a medium brown or a light brown shade.
However, there are difficulties presented with obtaining consistent and uniform color on hair when consumers dye or alter the color of their hair. For example, the hair will grow out, creating a visible demarcation line between the regrowth of the roots and the last dye session. Artificial color on hair also has the tendency to fade over time, especially during the shampooing process, resulting in a dull or matte look to the hair fiber. Furthermore, the processing times for hair color compositions vary greatly for undyed virgin hair (not chemically processed hair) and heavily colored or chemically processed hair. The level of skill required to preserve the condition of overly colored and processed hair when applying a fresh coat of hair color while also maintaining a uniform shade of color from root to tip is very high.
It has now been discovered that by providing an acidic hair pretreatment composition comprising coconut water and at least one antioxidant, it is possible to form a film or coating on a substrate that has certain desirable properties, such as a protective barrier that will control or slow down the coloration process. Said compositions may be used prior to dyeing to either enhance or reduce the dye penetration into the fiber. Said compositions may also be applied on overly chemically processed hair before coloring or altering the color of the hair in order to preserve the condition of the hair and to also provide a uniform color of the hair from the root to the tip. In particular, the compositions can be used in re-coloring or re-dyeing the hair. Typically, a visible demarcation line at a point along the shaft of artificially colored hair can be observed as new hair grows out from the roots. As the hair grows out, the color of the hair from the demarcation line down the length of the hair is generally different from the color of the new hair. Accordingly, the hair pretreatment compositions of the invention, that aid in the uniform distribution of coloring agents onto the hair fiber or in obtaining uniformly colored hair along the length of the hair fiber or in satisfactory gray hair coverage can be useful in increasing the efficiency of hair coloring agents and/or of hair coloring processes.
In addition, applying the acidic pretreatment composition of the present invention onto hair in order to create a barrier or coating on hair may also be useful in highlighting, lowlighting, and bleaching of hair. Such a barrier or coating allows the selective coloration or alteration of the color of portions of hair while leaving other portions of hair unchanged and/or uncolored, resulting in color alterations only in selected portions of the hair. Accordingly, the acidic hair pretreatment compositions of the invention can also aid in achieving a multi-toned or multi-colored or highlighted or lowlighted hair in a more convenient and easy manner.
Surprisingly and unexpectedly, the inventors have discovered that using an acidic pretreatment composition on hair before coloring or altering the color of the hair wherein the composition comprises coconut water and at least one antioxidant resulted in a method for controlling or slowing down the coloration of the hair in order to allow for more uniform hair coloring. The current invention allows for easy and improved coloration of the hair fibers to get a uniform hair color from root to ends of the hair. When applied starting from the visible demarcation line which is generally in the middle of the hair shaft (mid-shaft) down the length of artificially colored hair, the pretreatment composition of the invention will create a barrier or coating on the hair to impede a subsequent hair color altering or hair coloring composition from penetrating into the shaft as fast as it would without the pretreatment composition on the hair.

Compositions comprising catalase-peroxidase and methods for altering the color of hair


A closing plug for receipt by a threaded flange that is assembled into a drum end includes an externally-threaded body for receipt by the threaded flange. A radial flange is arranged adjacent a first end of the threaded body and the radial flange has a modified hex shape, thereby providing six flange portions. An outer section of each flange portion is formed into an axially-protruding projection such that as the closing plug is advanced into the radial flange, the axially-protruding projections abut up against a portion of the drum end in order to limit the threaded advancement of the plug. The abutment of the axially-protruding projections occurs after the desired tightening torque on the plug as received by the threaded flange has been achieved.

The present invention relates to the design and construction of a closure assembly that includes a receiving flange, a seal, and a closing plug that is constructed and arranged to be received by the flange. The receiving flange is secured to a container, such as in the drum end of a large industrial container. More specifically, the present invention relates to a unique design and construction for the closing plug of the closure assembly that includes in one embodiment a torque-limiting feature. In a related embodiment of the present invention, the closing plug is constructed and arranged to capture the seal.
Large, industrial, metal containers are typically configured with a filling/dispensing opening and a smaller vent opening. These openings must be securely and tightly closed and sealed whenever product is shipped. These are normally over-the-road shipments and several Department of Transportation (D.O.T.) standards or regulations apply. While there may be any number of additional industry standards depending on the container specifics and the product being shipped, it is important for the container openings to be securely closed and the realities of the container construction and the applicable D.O.T. standards dictate a fairly limited range of design options for fabricating and closing the two openings. One of these container construction realities is the limited thickness of the metal comprising the drum end where the two openings are typically and preferably located.
One fabrication technique that has proven to be successful is to pierce an opening in the metal drum end or "head" and form the surrounding metal into a raised receiving boss. An internally-threaded metal flange with a serrated peripheral edge is then assembled into the receiving boss. A metal forming operation follows and this operation shapes the drum end metal around the serrations as well as under and over the flange in order to securely and tightly anchor the flange into the receiving boss. The forming operation is performed in a manner that results in the drum end metal overlaying the upper surface of the flange immediately adjacent the threaded opening of the flange. The flange thickness in the area of the threads is greater than the material thickness of the drum end, thereby enabling a sufficient number of threads to be formed in the flange for receipt of the closing plug. The drum end alone is too thin to yield a sufficient number of threads for adequate threaded capture of the closing plug based upon the applicable D.O.T. standards that have to be met.
Since the transported, stored, and dispensed contents of containers (i.e., drums) of the type described are liquid, it is important to include an annular gasket or seal that is compressed between the drum end metal that overlays the flange and the plug surface to help seal the interface between the flange and the closing plug. One of the concerns expressed for this type of closure is the possibility that the closing plug is not properly tightened into the receiving flange. This could be either not tightened enough to adequately compress the seal or tightened too much such that the seal looses its resiliency.
Typically, the determination of proper plug tightening relies on a torque wrench and proper tightening by the filler of the drum. Visually, there is no way to tell if the closing plugs have been properly installed and thus a drum shipment could be loaded where one or more of the plugs do not meet the D.O.T. requirements. If the truck is stopped and the load inspected by a D.O.T. officer, it could fail the D.O.T. inspection. The inspection procedure includes applying a torque wrench to one or more of the closing plugs of the shipment in order to test whether those plugs are properly tightened and meet the torque level set by the D.O.T. If any one closing plug is not properly tightened, the container fails and the entire shipment can be rejected and must then be returned in order to have all of the closing plugs checked and tightened. Since each drum is not checked by the D.O.T. officer and since many or most of the drums could in fact meet the D.O.T. requirements, the penalty of finding any one closing plug that is not properly tightened is relatively harsh.
In order to address this concern, a first embodiment of the present invention was conceived and includes a new design for the closing plug such that visual confirmation can be made as to whether or not the closing plug is properly tightened into the receiving flange such that it will pass the D.O.T. inspection. An additional benefit derived from the present invention is the ability to set the torque on the closing plug within the desired range such that the cooperating annular seal is properly compressed. Importantly, all of this occurs without the need to utilize a torque wrench at the time of filling or at the time of shipment.
These invention benefits are achieved by redesigning the closing plug to include axially-protruding portions that abut up against that portion of the drum end that overlays the upper surface of the receiving flange. By properly sizing the axial length of these protruding portions based on the thread pitch of the plug and flange, any taper of the plug threads, and the size and composition of the annular gasket, the desired tightening torque occurs as the advancing surface of each protruding portion first contacts the drum end portion overlaying the receiving flange, according to the first embodiment of the present invention. Preferably, the desired tightening torque is reached and the protruding portions then abut up against the drum end portion within one further revolution of the closing plug. Ideally, abutment occurs within one-half of a revolution of the closing plug.
The plug construction, according to the first embodiment of the present invention, provides a unique torque limiting structure that also provides a visual indication of whether or not the proper torque has been set on the closing plug. If the protruding portions are in contact with the drum end portion, then it is known, based on the calculations that can be performed, that the correct tightening torque for the closing plug is "automatically" set. Once it is understood that protruding portion contact equates to the proper torque setting, any D.O.T. inspection can be done visually. Importantly, the filler and/or shipper can also perform a visual inspection at any time after the plug is threaded into the receiving flange. This enables the filler and/or shipper to ensure that whatever containers are loaded for shipment will pass any D.O.T. inspection.
Another benefit of the present invention relates to the axial compression of the annular gasket. A square-cut annular gasket may be used or an O-ring gasket can be used. With a square-cut circular gasket that has an inside diameter size slightly smaller than the outside diameter of the plug at the assembly location, the gasket can actually be preassembled to the plug. As the plug is tightened, the gasket is compressed. Since there is nothing surrounding or enclosing the gasket in the prior art arrangement, it is possible for the gasket to move radially outwardly as plug compression occurs. With a fixed volume of material, this radial movement reduces the axial thickness of the gasket, potentially requiring additional threaded advancement of the plug into the flange in order to achieve the requisite sealing.
A first embodiment of the present invention focuses on the abutment of the protruding portions against the drum end portion overlaying the flange. A second embodiment of the present invention focuses on the use of the protruding portions as a structure that encloses the gasket, thereby controlling any radial shift and/or radial expansion. With the present invention, the protruding portions are positioned radially outwardly of the gasket and, as a result, they actually enclose the gasket. Depending on the size of the gasket, its material and compressibility, and depending upon its positioning or alignment relative to the plug, if there would be the risk of substantial outward radial movement of the gasket during compression, the protruding portions are effective to capture the gasket and limit any such outward radial movement and thereby help to maintain an axial thickness for proper sealing. Accordingly, the structural improvement made to the closing plug in the form of the protruding portions constitutes a novel and unobvious advance in the art.


An adaptive beamformer includes at least first and second microphones that generate respective audio signals that include speech and noise, a controller that detects occurrences of speech and noise within the audio signals, an adaptive speech cancelling filter that cancels speech from the audio signal of the second microphone to provide a speech-cancelled signal, an adaptive mixing block that combines the speech-cancelled signal and the second microphone audio signal to provide a noise reference signal in a weighted manner such that a weight of the second microphone signal is increased proportionally with an amount of the detected noise and a weight of the speech-cancelled signal is increased proportionally with an amount of the detected speech, and an adaptive noise cancelling filter that uses the noise reference signal to remove the noise from the first microphone audio signal.

Traditionally, audio devices were used to facilitate speech communications, e.g., telephone voice calls. The primary consideration, or paradigm, in the design of audio devices for speech communications has long been to reproduce the speech from the talker to the listener with high fidelity, e.g., with minimal speech distortion. Often voice calls are made in noisy environments, sometimes in diverse and harsh acoustic conditions such as automobiles, airports, restaurants, etc. Examples of noise include road noise, babble, engine noise, competing talkers, mechanical devices (e.g., washing machines, dishwashers), and speeding vehicle noise. Noise cancellation was developed to reduce the noise in speech communications. In particular, noise cancellation has been largely facilitated by the presence of multiple microphones (a microphone array) in audio devices. Microphone array processing (e.g., beamforming) can reduce noise while preserving speech to make voice calling clearer. Minimization of speech distortion has remained the paradigm in the development of noise cancellation systems. Thus, conventional microphone array processing has been optimized to minimize speech distortion at the expense of noise reduction. That is, conventional beamformers cancel as much noise as possible without distorting speech, which is the goal in the voice calling scenario.
Today, a significant amount of audio processing is performed for the purpose of Automatic Speech Recognition (ASR) in which an artificial listener, rather than a human, is parsing the received audio signal. Noisy environments may also cause difficulty for ASR, and the paradigm of reducing as much noise as possible without minimizing speech distortion has also improved ASR accuracy relative to the absence of noise reduction. However, the present inventors have discovered that a different paradigm of prioritizing noise reduction at the expense of some speech distortion may improve the accuracy of ASR in some cases.

System and method for optimized noise reduction in the presence of speech distortion using adaptive microphone array


A system, method and apparatus for treating wastewater containing biodegradable material wherein a submerged stand alone perforated cylinder reactor pod containing aerobic bacterial growth media and a draft tube with air pressure induced pumping action creates a spray or splash pattern so as to recirculated aerated liquor through the media and also to the area surrounding the cylinder pod. Free interchange of mixed and unmixed liquor is provided via the perforations in the cylindrical pod wall. Provision is also made for back flushing the media and returning mixed liquor to an area remote from the reactor pod.

1. Field of the Invention
The present invention relates to on-site wastewater (sewage) treatment systems and processes, and more particularly to a stand-alone aerobic treatment unit or pod system for promoting oxygen transfer and aerobic bacterial activity in conjunction with conventional septic tank systems for family residences and commercial establishments.
2. Description of the Prior Art
At present, many single and multiple family dwelling units as well as small commercial installations rely upon the well known process of wastewater (sewage) disposal involving a septic tank and drain field installation. In these installations the biodegradable wastewater contains a wide variety of solid and liquid materials which are introduced directly from the source into a septic tank for primary treatment. The septic tank itself functions as a settling chamber in which the solids are allowed to settle out in a quiescent zone with both liquids and solids being subjected to digestion exclusively by anaerobic micro organisms. The anaerobic liquor or effluent, free of most solids, is then discharged directly into a drain field for final disposal. One common form of septic tank system includes at least two chambers with the primary chamber receiving the raw wastewater where the solids are allowed to settle to the bottom. The liquor then transfers to a second chamber where further settling and anaerobic digestion is allowed to proceed. The effluent then drains off to a drain field. The anaerobic treatment system is extremely slow compared to aerobic processes whereby oxygen is introduced and absorbed into the wastewater so that aerobic micro organisms are relied upon to provide aerobic metabolism of sewage organics. The aerobic system of sewage treatment is not only more rapid than anaerobic treatment but also eliminates offensive odors and oft times pollution of the environment caused by odiferous insufficiently treated wastewater from aging or overloaded septic tank systems. A multitude of systems have been proposed in the prior art for increasing the efficiency and effectiveness of septic tank systems in the nature of chemical treatment plants, filter systems and secondary sewage treatment systems for aeration of the liquids discharged, either from the septic tank or directly from the source. Filter systems and/or chemical treatment processes have been used for both large and smaller installations, however, such systems tend to be complex, expensive to install, unreliable and difficult to maintain. Examples of prior art secondary sewage treatment systems using aeration and aerobic bacterial growth media are disclosed in U.S. Pat. Nos. 5,030,353; 5,200,081; 5,202,027; and 5,609,754.
In some instances, reactors containing microbial growth media and/or filtering devices incorporating aeration features to treat the liquid effluent have been proposed for use in conjunction with septic tanks. One example of this type of device may be found in U.S. Pat. No. 5,554,996. In this type of device, air is diffused into a reactor chamber so as to cause liquor to recirculate within the reactor chamber in the presence of microbial growth media with the reactor chamber being connected directly to the outflow of the treatment tank. Thus, only the liquor-effluent within the reactor chamber is being aerated and mixed, leaving the balance of the volume within the settlement tank untreated. The major part of the septic tank thus remains anaerobic with the usual inefficient and slow odor producing decomposition attendant standard septic tank systems. In addition, all wastewater entering the septic tank must pass through the reactor chamber on its way to the outlet of the tank. The volume of liquor treated is thus limited and frequent clogging of the media and/or filter system may occur with ultimate failure of the tank system during overload periods or after long use. Systems of this type may also employ pumping devices which must be regulated in such a manner as to accommodate variations in flow volume and timed dosing, resulting in frequent failures and a fluctuating liquid depth within the septic tank. Since all sewage is not created equal and may vary widely over any given time period in terms of strength, volume and composition, these shortcomings are of great concern.
In view of the foregoing, there remains a continuing need for a system with greater efficiency and reliability for the treatment of wastewater and sewage in primary treatment systems such as standard septic tanks of all configurations as well as other traditional anaerobic digestion systems. To be successful, the system must be of a nature that is adaptable for retrofitting existing septic tank systems of all sizes and have the ability to increase the dissolved oxygen content of the otherwise anaerobic liquor so as to promote aerobic microbial digestion processes in the entire tank volume. Expensive pumping systems and dosing mechanisms which require constant maintenance must be avoided. There is also a need for the ability to back-flush and clear the microbial growth medium of organic build up to prevent clogging and to increase effectiveness without extensive reworking or modification of the system. Back flushing may also be used in situations where the unit is organically overloaded and additional air entrainment points are required to increase the available oxygen necessary for treatment. In order to provide for increased usage or loading of the septic system, provision must also be made for increasing or decreasing the treatment units within an existing septic system without major overhaul or reworking of the existing septic system.


The present invention provides an array substrate and a method for manufacturing the same, and a display device. In the method for manufacturing the array substrate, a one-time patterning process is employed to form a channel region, a source electrode and a drain electrode of the array substrate. Specifically, a channel region, a source region and a drain region that are consisted of a metal oxide layer are formed via a one-time patterning process, and a heat treatment is carried out on the metal oxide layer of the source region and the drain region in hydrogen gas, thereby forming a conducting source electrode and a conducting drain electrode, respectively. By the technical solution of the invention, the manufacturing process of the array substrate can be simplified, and the manufacturing cost of the array substrate can be lowered.

In the prior art, it has been difficult for a hydrogenized amorphous silicon Thin Film Transistor (TFT) to meet the demands of liquid crystal TVs with an ever-increasing size and drive circuits with higher performance. Transparent amorphous oxide semiconductor TFT gains researchers' favor due to its advantages, and it develops rapidly in recent years. It has a high mobility, a good uniformity, a good transparency and a simple manufacturing process, so it may better meet the demands of large-size liquid crystal displays and Organic Light-Emitting Diode (OLED) displays. Moreover, the production line for manufacturing a transparent amorphous oxide semiconductor TFT has a good adaptability with that of the existing Liquid Crystal Display (LCD), and it is easy for product transformation, thus high-performance transparent amorphous oxide semiconductor TFT gains many attentions, and it becomes a research hotspot in the current.
However, the manufacturing process of the existing transparent amorphous oxide semiconductor TFT is complex, and the manufacturing of a bottom gate-type array substrate can only be accomplished with at least five patterning processes. Moreover, the performance stability of TFT can only be guaranteed with a multi-layer protection of an Etch stopping layer (ESL) and a passivation layer (PVX), thereby the manufacturing cost is very high.

Array substrate and method for manufacturing the same, and display device


An apparatus and method for the measurement of a resistance of a switching contact of an electrical circuit breaker. A first resistance value across the circuit breaker is determined while the circuit breaker is grounded at both sides and the switching contact is closed. Further, a second resistance value across the circuit breaker is determined while the circuit breaker is grounded at both sides and the switching contact is open. The resistance of the closed switching contact is then determined based on the first resistance value and the second resistance value.

The present invention relates to a method and an apparatus for the measurement of a resistance of a switching contact of an electrical power switch (a so-called circuit breaker) as well as a method and an apparatus for the measurement of resistances of switching contacts arranged in a series connection of an electrical circuit breaker. In particular, the present invention relates to a measurement of transition resistances or contact resistances of a closed switching contact or of closed switching contacts of such an electrical circuit breaker.
Power switches, which are also called high voltage switches, load switches or circuit breakers, are used in the field of power engineering or energy technology to establish an electrical connection under load or to disconnect such a connection. The nominal voltages of circuit breakers may be in the range from a few volts to some hundred kilovolts. in the event of a short circuit, the switched load currents may be in the range of some ten kiloamperes. Therefore, for a reliable operation of the circuit breaker, for example the transition resistance of a switching contact or of a plurality of switching contacts connected in series of the electrical circuit breaker are tested in the course of revisions.
Circuit breakers for medium voltage equipment usually have only one switching contact which can be opened or closed. Circuit breakers in high voltage or ultra-high voltage systems can comprise a plurality of switching contacts, so-called interrupter units, in a series connection. In such a series connection of a plurality of interrupter units, generally capacitors dimensioned in the range of some pikofarads are arranged in parallel to the individual interrupter units so as to uniformly distribute the voltage over the individual interrupter units. In general, several interrupter units in a phase of a circuit breaker are opened and closed at the same time.
The resistance measurement at a closed switching contact, which is also referred to as micro-ohm measurement, is for circuit breakers a standard process for the assessment of the quality or the wear condition of the circuit breaker.
The micro-ohm measurement is usually conducted by impressing a high direct current of 100 ampere, for example, over the closed switching contact. For this purpose, the current is supplied via current clamps that are clamped at both sides of the circuit breaker to the conductors that lead away from the circuit breaker. With the aid of further clamps the voltage is tapped at both sides of the circuit breaker as well. The voltage clamps are usually mounted closer to the switching contact of the circuit breaker, a 4-wire measurement being conducted with this arrangement. This prevents that the voltage drop at the current clamps is measured with the measurement, which would falsify the measurement result. The resistance of the closed switching contact, including the resistance of the conductors from the voltage clamps to the switching contact, can be determined from the impressed current and the measured voltage. Alternatively, so-called Kelvin clamps may be used instead of separate current and voltage clamps. In Kelvin clamps, two jaws of a respective clamp are electrically isolated from one another, and the current is supplied via one of the two jaws, while the voltage is tapped via the other of the two jaws. The advantage of such Kelvin claws resides in that only one clamp is to be clamped at each side of the circuit breaker.
As described above, for the micro-ohm measurement a current source and a voltage meter can be used so that voltage measurements can be successively conducted at the different switching contacts. A plurality of voltage meters may be used as well, the current being impressed with the aid of a common current source via several contacts and a plurality of voltage values being determined with the plurality of voltage meters.
As dangerous high voltage can occur at many places in a power engineering installation, for example in a transformer station, it is necessary that the circuit breaker is grounded during the micro-ohm measurement. For example, the circuit breaker can be disconnected at both sides from the remaining energy network and can be grounded at one side. The micro-ohm measurement can then precisely be conducted when the switching contact is closed or when the switching contacts are closed. Often further measurements have to be conducted at the circuit breaker, which require that the switching contact is at least temporarily opened, for example a measurement of the time that takes the switch to open. For such measurements a grounding at both sides of the switch is recommendable to avoid that persons conducting the measurement are exposed to danger. Therefore, for the micro-ohm measurement, one of the two groundings will be removed for the duration of the measurement, which however is very cumbersome, or in the case of a grounding at both sides the micro-ohm measurement becomes inaccurate due to the parallel grounding loop.
In order to be able to efficiently conduct a micro-ohm measurement at a circuit breaker, the circuit breaker may be grounded at both sides, and with a DC-current clamp or a shunt the portion of the current which flows from the current source through the grounding equipment can be determined and can be used to correct the measured resistance. While this method is very precise, it is disadvantageous in that additional measurements are necessary by means of the current clamp or the shunt.
Therefore, it is the object of the present invention to enable an efficient resistance measurement or micro-ohm measurement for one or a plurality of switching contacts of an electrical circuit breaker with exposure of personnel conducting the resistance measurement to danger being avoided.

Method and apparatus for the measurement of a resistance of a switching contact of an electrical circuit breaker


A polyvinyl alcohol having at least 1.9 mol % of 1,2-glycol bonds is used as a dispersant for emulsion polymerization or a dispersant for suspension polymerization, and this ensures good polymerization stability even when its amount used is reduced. The aqueous emulsion comprising the polyvinyl alcohol is resistant to water and the viscosity of the aqueous emulsion depends little on ambient temperatures. The vinylic polymers obtained through suspension polymerization in the presence of the polyvinyl alcohol are yellowed little, and the waste water in the suspension polymerization pollutes little the environment.

The present invention relates to an aqueous emulsion that comprises a polyvinyl alcohol having at least 1.9 mol % of 1,2-glycol bonds (this will be hereinafter referred to as the first aspect of the invention), and to a dispersant for suspension polymerization that comprises the polyvinyl alcohol (this will be hereinafter referred to as the second aspect of the invention).
According to the invention, the polyvinyl alcohol having at least 1.9 mol % of 1,2-glycol bonds is used as a dispersant for emulsion polymerization or a dispersant for suspension polymerization, and this ensures good polymerization stability even when its amount used is reduced; the aqueous emulsion comprising the polyvinyl alcohol is resistant to water and the viscosity of the aqueous emulsion depends little on ambient temperatures; the vinylic polymers obtained through suspension polymerization in the presence of the polyvinyl alcohol are yellowed little; and the waste water in the suspension polymerization pollutes little the environment.
 less than 1 greater than  Background Art of the First Aspect of the Invention, Aqueous Emulsion
Heretofore, polyvinyl alcohol (hereinafter referred to as PVA) is widely used as protective colloid in emulsion polymerization of an ethylenic unsaturated monomer, especially a vinyl ester monomer such as typically vinyl acetate. Aqueous emulsions of vinyl ester polymers obtained through emulsion polymerization with PVA serving as protective colloid have many applications in various fields of adhesives for paper products, wood products, plastics, etc., binders for dip-coated paper, non-woven fabrics, etc., as well as admixtures, jointing agents, coating compositions, paper processing agents, fiber processing agents, etc.
Controlling the degree of hydrolysis of PVA therein makes it possible to change the physical properties of such aqueous emulsions, some of which will have low viscosity just like Newtonian fluid, and will be relatively highly resistant to water, while some others will have high viscosity relatively independently of ambient temperatures. Depending on such their properties, aqueous emulsions containing PVA have many applications in various fields.
However, some aqueous emulsions containing PVA have drawbacks in that they are not resistant to water and that their viscosity greatly varies depending on ambient temperatures.
PVA serving as a dispersant for emulsion polymerization is generally grouped into xe2x80x9ccompletely hydrolyzed PVAxe2x80x9d having a degree of hydrolysis of 98% or so and xe2x80x9cpartially hydrolyzed PVAxe2x80x9d having a degree of hydrolysis of 88 mol % or sol Aqueous emulsions containing the former PVA could have relatively good water resistance but are problematic in that their viscosity greatly varies depending on ambient temperatures. On the other hand, the viscosity of aqueous emulsions containing the later PVA does not so much depend on ambient temperatures but its temperature dependency is not still negligible, and, in addition, the aqueous emulsion is are poor in their water resistance. To solve the problems with these aqueous emulsions containing PVA, using the two types of PVA as combined in aqueous emulsions, or using PVA having an intermediate degree of hydrolysis therein is tried. However, no one has heretofore succeeded in realizing aqueous, PVA-containing emulsions that satisfy the two requirements of good water resistance and temperature independence for their viscosity. In that situation, PVA with ethylene units therein has been proposed for use in aqueous emulsions (Japanese Patent Laid-Open No. 81666/1996). Containing it, aqueous emulsions having improved water resistance and low-temperature storage stability. However, their water resistance is not satisfactory as yet and their temperature independence is not also satisfactory (see Comparative Example 7 given hereinafter). Also known is using a mercapto-terminated PVA as a dispersant for emulsion polymerization, as in Comparative Example 6 given hereinafter (Japanese Patent Laid-Open No. 24481/1991). As in Comparative Example 6, however, this is not satisfactory in point of its water resistance, and its temperature dependence of the viscosity is not satisfactorily lowered.
Given that situation, the first aspect of the invention is to provide an aqueous emulsion having the advantages of improved water resistance and lowered temperature dependence of the viscosity, and to provide a method for producing such an aqueous emulsion having the advantage of good polymerization stability, especially that still having the advantage of good polymerization stability even when the amount of the dispersant added is reduced.
 less than 2 greater than  Background Art of the First Aspect of the Invention, Dispersant for Suspension Polymerization
For producing vinylic polymers such as polyvinyl chloride resins and the like on an industrial scale, for example, widely employed is a method of suspension polymerization that comprises dispersing a vinylic compound such as vinyl chloride or the like in an aqueous medium in the presence of a dispersant followed by polymerizing it in the presence of an oil-soluble initiator. In general, the factors that govern the quality of vinylic polymers produced through such suspension polymerization include the polymerization conversion, the ratio of monomer to water, the polymerization temperature, the type and the amount of the initiator, the type of the polymerization reactor, the stirring speed, and the type of the dispersant. Above all, the type of the dispersant has the most significant influence on the polymer quality.
The necessary properties of the dispersant for suspension polymerization of vinylic compounds are that  less than 1 greater than  it is effective for narrowing as much as possible the particle size distribution of the vinylic polymer particles obtained,  less than 2 greater than  it is effective for making the polymer particles porous in order that the polymer particles can rapidly absorb a plasticizer so as to be readily processed, that the monomer such as vinyl chloride or the like remaining in the polymer particles can be readily removed, and that the shaped articles of the polymer particles are prevented from having fish eyes and other defects therein,  less than 3 greater than  it is effective for making the polymer particles have a large bulk density,  less than 4 greater than  it ensures stable polymerization even when its amount added is small, and the waste water in the process of polymerization pollutes little the environment, and  less than 5 greater than  it does not have any negative influence on the heat resistance of the vinylic polymers obtained.
Vinylic compounds such as vinyl chloride are generally polymerized in a mode of batch-system suspension polymerization. One typical process of batch-system suspension polymerization of vinylic compounds comprises feeding an aqueous medium, a dispersant, a polymerization initiator and a vinylic compound into a polymerization reactor, then optionally adding necessary additives thereto, and heating the reactor to polymerize the monomer therein. For improving the productivity in the process, the recent tendency in the art is toward shortening the time to be taken in one batch polymerization. For this, for example, a reflux condenser or the like is installed in the system of suspension polymerization of vinylic compounds to thereby increase the efficiency of removing polymerization heat from the system; or an aqueous medium having been previously heated is charged into the system to shorten the heating time in the system (hot-charge process). However, conventional dispersants for suspension polymerization of vinylic compounds foam greatly in polymerization reactors to reduce the effective reactor capacity and to lower the polymer productivity. In particular, when such a conventional dispersant is used in a polymerization reactor equipped with a reflux condenser, it interferes with temperature control in the reactor; or when it is used in the hot-charge process, the vinylic polymer particles produced could not be porous. These are fatal defects of conventional dispersants. On the other hand, if a defoaming agent is added to the polymerization system to prevent it from foaming, it presents another problem in that the heat stability of the vinylic polymer particles produced is lowered.
For dispersants for suspension polymerization of vinylic compounds, heretofore used are cellulose derivatives such as methyl cellulose and carboxymethyl cellulose, and partially hydrolyzed PVA, either singly or as combined. In Poval (published by the Polymer Publishing in 1984xe2x80x94reference (a)), described is PVA having a degree of polymerization of 2000 and a degree of hydrolysis of 80 mol %, and this serves as a dispersant for suspension polymerization of vinyl chloride. In WO 91/15518 (reference (b)), described is a dispersant for suspension polymerization of vinylic compounds, which comprises PVA having an amino group, an ammonium group, a carboxyl group or a sulfonic acid group at the terminal and having a degree of polymerization of at least 100 and a degree of hydrolysis of from 50 to 90 mol %. In Japanese Patent Laid-Open No. 25307/1997 (reference (c)), described is a dispersant for suspension polymerization of vinylic compounds, which comprises PVA having a hydroxyalkyl group. In Japanese Patent Laid-Open No. 283313/1996 (reference (d)), described is a dispersant for suspension polymerization of vinylic compounds, which is specifically defined in point of the UV absorbance of its aqueous solution and the block character of the acetic acid group remaining therein. In Japanese Patent Laid-Open No. 115587/1976 (reference (e)), described is a method of producing polyvinyl chloride resins in the presence of a partially hydrolyzed PVA. The partially hydrolyzed PVA used therein has a degree of hydrolysis of from 60 to 90 mol %, and the degree of methanol release from it at temperature of 55xc2x0 C. falls between 10 and 60%. In Japanese Patent Laid-Open No. 110797/1977 (reference (f)), described is a secondary dispersant for suspension polymerization of vinyl chloride, which comprises a polyvinyl acetate having a degree of hydrolysis of from 30 to 60 mol %. However, the dispersants described in reference (a) and reference (b) do not satisfy the requirements  less than 1 greater than  to  less than 4 greater than  mentioned above, and, in addition, they are further defective in that they foam greatly in polymerization systems. The dispersants described in reference (c) and reference (d) are good is some degree, as they do not foam so much in polymerization systems and their plasticizer absorbability is good. However, they do not satisfy the requirements  less than 1 greater than  and  less than 3 greater than  to  less than 5 greater than  mentioned above. The dispersant used in the method described in reference (e) has relatively well balanced properties in point of the requirements  less than 1 greater than  to  less than 3 greater than , but does not satisfy the requirements  less than 4 greater than  and  less than 5 greater than . In addition, it is defective in that it greatly foams in polymerization systems. The secondary dispersant described in reference (f) cannot stabilize the system of suspension polymerization of vinylic compounds, when used alone. In addition when it is combined with a conventional partially hydrolyzed PVA, it presents a serious problem in that the polymerization system in the reactor greatly foams.
The object of the second aspect of the invention is to provide a dispersant for suspension polymerization of vinylic compounds, of which the advantages are that it enables stable polymerization of vinylic compounds, that its amount to be used can be reduced and therefore the vinylic polymers obtained through suspension polymerization in the presence of it are yellowed little and the waste water in the polymerization system does not so much pollute the environment, that it does not foam the polymerization system in a reactor, and that it satisfies all the requirements mentioned above.
 less than 1 greater than  First described is the first aspect of the invention, aqueous emulsion.
The object of the first aspect of the invention can be attained by providing an aqueous emulsion which comprises, as the dispersoid, a polymer that contains vinyl ester monomer units, and, as the dispersant, a polyvinyl alcohol that contains at least 1.9 mol % of 1,2-glycol bonds, and of which the viscosity profile is such that the ratio of T0xc2x0 C./T30xc2x0 C. is at most 5 and the ratio of T60xc2x0 C./T30xc2x0 C. is at most 1.5 with T60xc2x0 C. indicating the viscosity of the aqueous emulsion at 60xc2x0 C., T30xc2x0 C. indicating the viscosity thereof at 30xc2x0 C. and T0xc2x0 C. indicating the viscosity thereof at 0xc2x0 C.
The polyvinyl alcohol having at least 1.9 mol % of 1,2-glycol bonds and serving as the dispersant in the aqueous emulsion of the invention is not specifically defined for its production, and may be produced in any known method. For example, it may be produced by copolymerizing a vinylene carbonate with a vinyl ester to have the 1,2-glycol bond content as above; or by polymerizing a vinyl ester at a temperature higher than that for ordinary vinyl ester polymerization, for example, at a temperature falling between 75 and 200xc2x0 C., under pressure. In the latter method, the polymerization temperature preferably falls between 95 and 190xc2x0 C., more preferably between 100 and 180xc2x0 C. Regarding the pressure for polymerization, it is important that the pressure is so controlled that the temperature of the polymerization system does not exceed the boiling point thereof. For this, preferably, the polymerization pressure is at least 0.2 MPa, more preferably at least 0.3 MPa. Its uppermost limit is preferably at most 5 MPa, more preferably at most 3 MPa. Under the condition, the monomer may be polymerized in the presence of a radical polymerization initiator in any mode of bulk polymerization, solution polymerization, suspension polymerization or emulsion polymerization, for which, however, preferred is solution polymerization, and especially preferred is solution polymerization with a solvent of methanol. The vinyl ester polymer thus produced is hydrolyzed in an ordinary manner to obtain a polyvinyl alcohol for use herein. The 1,2-glycol bond content of the polyvinyl alcohol must be at least 1.9 mol %. More preferably, it is at least 1.95 mol %, even more preferably at least 2.0 mol %, most preferably at least 2.1 mol %. If the 1,2-glycol bond content of the polyvinyl alcohol is smaller than 1.9 mol %, the aqueous emulsion containing it will be poorly resistant to water. If so, in addition, the emulsion viscosity will much depends on ambient temperatures and the polymerization stability in producing the emulsion will be poor. Preferably, the 1,2-glycol bond content of the polyvinyl alcohol is at most 4 mol %, more preferably at most 3.5 mol %, most preferably at most 3.2 mol %. The 1,2-glycol bond content of the polyvinyl alcohol can be obtained through NMR spectrometry of the polymer.
The vinyl ester monomer includes, for example, vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, vinyl caproate, vinyl caprylate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate, vinyl benzoate, etc. Especially preferred is vinyl acetate.
For the dispersant, favorable are those produced by hydrolyzing the polymers of vinyl esters mentioned above, such as vinyl acetate. Not interfering with the object and the effect of the invention, the polymers may contain any other monomer units. Additional monomers employable herein include, for example, xcex1-olefins such as propylene, n-butene, isobutylene, etc.; acrylic acid and its salts; acrylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, etc.; methacrylic acid and its salts; methacrylates such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, iso-propyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, etc.; acrylamide and its derivatives such as N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetonacrylamide, acrylamidopropanesulfonic acid and its salts, acrylamidopropyldimethylamine and its salts and quaternary salts, N-methylolacrylamide and its derivatives, etc.; methacrylamide and its derivatives such as N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidopropanesulfonic acid and its salts, methacrylamidopropyldimethylamine and its salts and quaternary salts, N-methylolmethacrylamide and its derivatives, etc.; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, iso-propyl vinyl ether, n-butyl vinyl ether, iso-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether, etc.; nitriles such as acrylonitrile, methacrylonitrile, etc.; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, vinyl bromide, etc.; allyl compounds such as allyl acetate, allyl chloride, sodium allylsulfonate, etc.; unsaturated carboxylic acids such as fumaric acid, maleic acid (anhydride), itaconic acid, and their salts and esters, etc.; vinylsilyl compounds such as vinyltrimethoxysilane, etc.; isopropenyl acetate; tetrafluoroethylene; sodium vinylsulfonate; and N-vinyl compounds such as N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide, etc. Mercapto-terminated or carboxyl-terminated, modified polyvinyl alcohols that are produced by polymerizing a vinyl ester monomer such as vinyl acetate in the presence of a thiol compound such as thiolacetic acid or mercaptopropionic acid followed by hydrolyzing the resulting polymer may also be used in the invention.
The degree of hydrolysis of the polyvinyl alcohol that contains at least 1.9 mol % of 1,2-glycol bonds and serves as the dispersant in the aqueous emulsion of the invention is not specifically defined, but is generally at least 60 mol %, more preferably at least 70 mol %, even more preferably at least 75 mol %. If its degree of hydrolysis is smaller than 60 mol %, the polyvinyl alcohol will lose solubility in water intrinsic to ordinary polyvinyl alcohols. For attaining the object of the invention to obtain good aqueous emulsions, it is desirable that the degree of polymerization (in terms of the viscosity-average degree of polymerization) of the polyvinyl alcohol to be therein falls between 100 and 8000, more preferably between 300 and 3000.
The vinyl ester monomer to constitute the dispersoid in the aqueous emulsion of the invention includes, for example, vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, vinyl caproate, vinyl caprylate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate, vinyl benzoate, etc. Especially preferred is vinyl acetate.
The polymer (dispersoid) that contains vinyl ester monomer units is a vinyl ester (co)polymer, including polyvinyl esters, and copolymers of vinyl esters with comonomers capable of copolymerizing with vinyl esters. The comonomers capable of copolymerizing with vinyl esters include, for example, olefins such as ethylene, propylene, isobutylene, etc.; vinyl halides such as vinyl chloride, vinyl fluoride, vinylidene chloride, vinylidene fluoride, etc.; acrylic acid, methacrylic acid; acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, 2-hydroxyethyl acrylate, etc.; methacrylates such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, 2-hydroxyethyl methacrylate, etc.; dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, and their quaternated derivatives; acrylamide monomers such as acrylamide, methacrylamide, N-methylolacrylamide, N,N-dimethylacrylamide, acrylamido-2-methylpropanesulfonic acid and its sodium and potassium salts, etc.; styrene monomers such as styrene, xcex1-methylstyrene, p-styrenesulfonic acid and its sodium and potassium salts, etc.; other vinyl compounds such as N-vinylpyrrolidone, etc.; and dienic monomers such as butadiene, isoprene, chloroprene, etc. One or more of these comonomers are copolymerized with the vinyl ester monomer, either singly or as combined. Preferably, the amount of the comonomer such as ethylene that is copolymerized with the vinyl ester monomer is at most 50% by weight, more preferably at most 40% by weight of all the monomers to be copolymerized. Of the polymers that contain vinyl ester monomer units, most preferred are polyvinyl esters and vinyl ester-ethylene copolymers.
Regarding the viscosity profile of the aqueous emulsion of the invention, it is important that the ratio of the emulsion viscosity at 0xc2x0 C., T0xc2x0 C., to the emulsion viscosity at 30xc2x0 C., T30xc2x0 C., or that is the ratio of T0xc2x0 C./T30xc2x0 C. is at most 5. The ratio T0xc2x0 C./T30xc2x0 C. is measured according to the method mentioned hereinunder. The ratio T0xc2x0 C./T30xc2x0 C. of at most 5 means that the emulsion viscosity increase at around 0xc2x0 C. is retarded, or that is, the temperature dependence of the emulsion at around 0xc2x0 C. is small. More preferably, T0xc2x0 C./T30xc2x0 C. is at most 4, even more preferably at most 3.
In the invention, it is also important that the ratio of the emulsion viscosity at 60xc2x0 C., T60xc2x0 C., to the emulsion viscosity at 30xc2x0 C., T30xc2x0 C., or that is the ratio of T60xc2x0 C./T30xc2x0 C. is at most 1.5. The ratio T60xc2x0 C./T30xc2x0 C. is measured according to the method mentioned hereinunder. The viscosity of vinyl ester polymer-containing aqueous emulsions often increase at around 60xc2x0 C. In the invention, however, the ratio T60xc2x0 C./T30xc2x0 C. is defined to be at most 1.5. This means that the emulsion viscosity increase at around 60xc2x0 C. is retarded, or that is, the temperature dependence of the emulsion at around 60xc2x0 C. is small. More preferably, T60xc2x0 C./T30xc2x0 C. is at most 1.3, even more preferably at most 1.2. To that effect, the temperature dependence of the aqueous emulsion of the invention is small both at low temperatures and at high temperatures, and the workability and the handlability of the aqueous emulsion are extremely good.
The aqueous emulsion of the invention can be obtained by polymerizing a vinyl ester monomer through emulsion polymerization in the presence of (1) a polyvinyl alcohol that contains at least 1.9 mol % of 1,2-glycol bonds and serves as a dispersant, and (2) at least one polymerization initiator selected from hydrogen peroxide, ammonium persulfate and potassium persulfate in a molar ratio to the vinyl ester monomer of from 0.001 to 0.03, in such a polymerization mode that (3) from 5 to 20% by weight of the vinyl ester monomer, based on the total amount of the monomer (that is, based on the total amount of the vinyl ester monomer to be polymerized), is fed into the reactor in the initial stage of polymerization and the polymerization initiator is fed thereinto all at a time in a molar ratio to the initial feed of the vinyl ester monomer of from 0.001 to 0.05.
To attain the object of the invention, the amount of the polyvinyl alcohol having at least 1.9 mol % of 1,2-glycol bonds to be used in the polymerization process preferably falls between 1 and 20 parts by weight relative to 100 parts by weight of the vinyl ester monomer (in case where the monomer is combined with a comonomer capable of copolymerizing with it, the total of the monomer and the comonomer), more preferably between 3 and 20 parts by weight, even more preferably between 5 and 15 parts by weight. One characteristic feature of the invention is that, even when the amount of the polyvinyl alcohol having at least 1.9 mol % of 1,2-glycol bonds used in the polymerization process is small, for example, even when the amount of the polyvinyl alcohol used therein falls between 1 and 5 parts by weight, it surely attains the object of the invention.
According to the polymerization process, obtained is the aqueous emulsion that satisfies the requirements of T0xc2x0 C./T30xc2x0 C. of at most 5 and T60xc2x0 C./T30xc2x0 C. of at most 1.5.
As is obvious from the Examples given hereinunder, another characteristic feature of the polymerization process employed in the invention is that the filtration residue after emulsion polymerization therein is small, and this means good polymerization stability in the process.
In producing the aqueous emulsion of the invention, it is important to use at least one polymerization initiator selected from hydrogen peroxide, ammonium persulfate and potassium persulfate. Of these, especially preferred is hydrogen peroxide. In the step of emulsion polymerization in the invention, it is also extremely important to define the molar ratio of the polymerization initiator to the vinyl ester monomer to fall between 0.001 and 0.03, preferably between 0.0015 and 0.025, more preferably between 0.0018 and 0.023.
As the case may be, the polymerization initiator will be combined with a reducing agent to give a redox system reagent for use in the invention. In that case, in general, hydrogen peroxide will be combined with tartaric acid, L-ascorbic acid, Rongalit or the like; and ammonium or potassium persulfate will be combined with sodium hydrogensulfite, sodium hydrogencarbonate or the like. The amount of the reducing agent is not specifically defined, but may generally fall between 0.05 and 3 equivalents, preferably between 0.1 and 2 equivalents, more preferably between 0.3 and 1.5 equivalents to the polymerization initiator to be combined therewith.
Regarding the mode of adding the polymerization initiator to the reaction system, favorably employed herein is a method of adding it thereto all at a time in the initial stage of polymerization, or that is, adding it in one shot thereto. Concretely, from 5 to 20% by weight of all the vinyl ester monomer to be polymerized is first fed into a reactor in the initial stage of polymerization, and the polymerization initiator is fed thereinto all at a time in a molar ratio to the initial feed of the vinyl ester monomer of from 0.001 to 0.05, preferably from 0.0012 to 0.045, more preferably from 0.0013 to 0.04.
One shot addition of the predetermined amount of the polymerization initiator to the reaction system in the initial stage of polymerization improves the water resistance of the aqueous emulsion produced and lowers the temperature dependence thereof, enabling stable polymerization of the monomer, and the filtration residue from the polymerized emulsion is thereby reduced.
For initial polymerization, the monomer and the polymerization initiator are added to an aqueous solution of the dispersant, and polymerized at a temperature falling between 50 and 70xc2x0 C., preferably between 55 and 65xc2x0 C., for a period of time falling between 5 and 60 minutes, preferably between 10 and 50 minutes. In the initial stage of polymerization, the monomer is preferably fed into the reactor all at a time.
The initial polymerization shall be terminated when the concentration of the remaining vinyl ester monomer (in terms of % by weight of the polymer produced) has reached at most 10%, preferably at most 5%, more preferably at most 1%. The initial polymerization is followed by final polymerization. Also in the stage of final polymerization, the polymerization initiator may be added to the reaction system all at a time (in a mode of one shot addition), but, as the case may be, it may be added thereto in a continuous or intermittent addition mode. The polymerization temperature in the final polymerization stage is preferably higher by from 5 to 30xc2x0 C. than that in the initial polymerization stage. Concretely, it may fall between 55 and 100xc2x0 C., preferably between 60 and 95xc2x0 C., more preferably between 70 and 90xc2x0 C.
The polymerization pressure may be atmospheric pressure both for initial polymerization and final polymerization, but, as the case may be, increased pressure will be needed. In particular, in case where copolymer emulsions of a vinyl ester with any other comonomer, for example, with ethylene are produced, the monomers must be polymerized under increased pressure.
The aqueous emulsion of the invention obtained in the manner as above has improved water resistance and is therefore favorably used for various applications that require water resistance. In addition, the viscosity of the aqueous emulsion of the invention depends little on ambient temperatures and its viscosity does not increase even when it is stored, transported or used at low or high temperatures. Therefore, the aqueous emulsion has the advantage of good processability and handlability.
The aqueous emulsion of the invention produced according to the method as above may be directly used as it is, but, if desired, it may be combined with any other known emulsions not interfering with the object and the effect of the invention.
The dispersant to be in the aqueous emulsion of the invention is the above-mentioned PVA polymer having at least 1.9 mol % of 1,2-glycol bonds. If desired, however, it may be combined with any known anionic, nonionic or cationic surfactants, and hydroxyethyl cellulose. Also not interfering with the object and the effect of the invention, it may be combined with a polyvinyl alcohol of which the 1,2-glycol bond content is smaller than 1.9 mol %.
As the aqueous emulsion is highly resistant to water and its viscosity depends little on ambient temperatures, the aqueous emulsion of the invention is favorably used in various fields of paper-processing adhesives for paper or pulp products such as paper tubes, paper bags, paper laminates, corrugated cardboard, etc.; wood-processing adhesives for flush panels, wood laminates, butt-welded wood plates, plywood products, secondary worked plywood products (for jointing them), other ordinary wood products, etc.; adhesives for plastics; binders for dip-coated paper, non-woven fabrics, etc.; as well as admixtures, jointing agents, coating compositions, paper processing agents, fiber processing agents, etc.
 less than 2 greater than  Next described is the second aspect of the invention, dispersant for suspension polymerization.
The object of the second aspect of the invention can be attained by providing a dispersant for suspension polymerization, which comprises a PVA polymer (A) having at least 1.9 mol % of 1,2-glycol bonds.
One preferred embodiment of the second aspect of the invention is a dispersant for suspension polymerization of vinylic compounds, which comprises a PVA polymer (A) having at least 1.9 mol % of 1,2-glycol bonds and having a degree of polymerization of from 100 to 4000.
Another preferred embodiment thereof is a dispersant for suspension polymerization of vinylic compounds, which comprises a PVA polymer (A) having at least 1.9 mol % of 1,2-glycol bonds and having a degree of polymerization of from 100 to 4000 and a block character of the residual acetic acid group of from 0.35 to 0.8.
Still another preferred embodiment thereof is a dispersant for suspension polymerization of vinylic compounds, which comprises a PVA polymer (A) having at least 1.9 mol % of 1,2-glycol bonds and having a degree of polymerization of from 100 to 4000, a block character of the residual acetic acid group of from 0.35 to 0.8, and a methanol soluble content of from 0.05 to 40% by weight.
Still another preferred embodiment thereof is a dispersant for suspension polymerization of vinylic compounds, which comprises the PVA polymer (A) as above and a polyvinyl ester polymer (B) having a degree of hydrolysis of smaller than 60 mol %, in a ratio by weight of the component (A) to the component (B), (A)/(B) falling between 40/60 and 95/5.
The PVA polymer (A) having at least 1.9 mol % of 1,2-glycol bonds for use in the invention is not specifically defined for its production, and may be produced in any known method. For example, it may be produced by copolymerizing a vinylene carbonate with a vinyl ester monomer to have the 1,2-glycol bond content as above, followed by hydrolyzing the resulting copolymer; or by polymerizing a vinyl ester monomer at a temperature higher than that for ordinary vinyl ester polymerization, for example, at a temperature falling between 75 and 200xc2x0 C., under pressure, followed by hydrolyzing the resulting polymer. In the latter method, the polymerization temperature preferably falls between 95 and 190xc2x0 C., more preferably between 100 and 180xc2x0 C.
For controlling the block character of the residual acetic acid of the PVA polymer for use in the invention to fall between 0.35 and 0.8, for example, the starting polyvinyl ester may be alcoholyzed or hydrolyzed in the presence of a known alkali or acid catalyst. In the process, the block character of the PVA polymer to be produced can be controlled by specifically selecting the type of the hydrolysis catalyst and the type of the solvent to be used. In general, acid hydrolysis gives a PVA polymer having a higher block character than alkali hydrolysis. The block character of the PVA polymer obtained through alkali hydrolysis may be further increased through heat treatment of the polymer. For the PVA polymer for use herein, most preferred is hydrolysis with a sodium hydroxide (NaOH) catalyst in a solvent of methanol, as it is simple.
For controlling the methanol soluble content of the PVA polymer for use in the invention to fall between 0.1 and 40% by weight, various methods such as those mentioned below may be employed either singly or as combined. For this, concretely mentioned are a method of washing the hydrolyzed PVA polymer with an organic solvent such as acetone, methanol, methyl acetate or the like, in which the type of the solvent to be used, the ratio of the solvent to the PVA polymer, the washing time and the washing temperature are specifically controlled so as to make the thus-washed PVA polymer have a predetermined methanol soluble content; a method of adding a PVA polymer having a low degree of polymerization and/or having a low degree of hydrolysis to the washed and/or non-washed PVA polymer; a method of adding an agent for controlling a degree of polymerization, such as acetaldehyde, butyraldehyde, trichloroethylene, perchloroethylene, mercaptans or the like, to the polymerization system that gives a non-hydrolyzed polyvinyl ester polymer, to thereby make the polymer contain an additional component having a low degree of polymerization; a method of multi-stage polymerization to give a non-hydrolyzed polyvinyl ester polymer, in which the degree of polymerization of the polymer produced in every polymerization stage is specifically controlled; and a method of producing a non-hydrolyzed polyvinyl ester polymer through polymerization, in which the polymerization conversion of the polymer produced is specifically controlled.
The vinyl ester monomers for the PVA polymer (A) for use herein may be the same as those for the dispersant in the aqueous emulsion of the first aspect of the invention mentioned hereinabove, and especially preferred is vinyl acetate.
Not interfering with the object and the effect of the invention, the PVA polymer (A) for use herein may contain any other monomer units such as those mentioned hereinabove for use in the dispersant of the aqueous emulsion of the first aspect of the invention.
For producing the vinyl ester polymers through polymerization, employable is any known mode of solution polymerization, bulk polymerization, suspension polymerization or emulsion polymerization, like for those mentioned hereinabove. Depending on the polymerization mode employed, the polymerization initiator to be used for producing the polymers may be selected from azo initiators, peroxide initiators and redox initiators.
If desired, the PVA polymer (A) for use herein may be modified by introducing thereinto an ionic group such as an ammonium group, a carboxyl group or a sulfone group to thereby increase its solubility in water, or may be modified by introducing thereinto a nonionic group or a (long-chain) alkyl group or the like. Of such modified polymers, the degree of hydrolysis shall be determined from the ratio of the vinyl alcohol group to the vinyl ester group in the polymers, and shall not include the degree of hydrolysis of the ionic group, the nonionic group or the (long-chain) alkyl group introduced into the polymers. Terminal-modified polymers obtained in a known method of polymerizing a vinyl ester monomer such as vinyl acetate in the presence of a thiol compound such as thiolacetic acid or mercaptoproionic acid followed by hydrolyzing the resulting polymer are also employable herein.
The PVA polymer (A) for use in the invention has at least 1.9 mol % of 1,2-glycol bonds in the polymer chain. Preferably, the 1,2-glycol bond content of the PVA polymer (A) is at least 1.95 mol %, more preferably at least 2.0 mol %, most preferably at least 2.1 mol %. If the 1,2-glycol bond content of the PVA polymer (A) in its polymer chain is smaller than 1.9 mol %, the PVA polymer (A) could not ensure good polymerization stability in suspension polymerization of vinylic compounds, when its amount added to the polymerization system is reduced. Therefore, the amount of the PVA polymer (A) to be added thereto must be increased. If so, in addition, the vinyl polymer obtained through suspension polymerization in the presence of the PVA polymer (A) will be readily yellowed, the residual PVA polymer (A) in the polymerization waste water will increase and pollute the environment, and the polymerization system will foam greatly. The 1,2-glycol bond content of the PVA polymer (A) in its polymer chain is preferably at most 4 mol %, more preferably at most 3.5 mol %, most preferably at most 3.2 mol %. If it oversteps 4 mol %, the productivity of the PVA polymer (A) will lower.
The viscosity-average degree of polymerization (hereinafter referred to as xe2x80x9cdegree of polymerizationxe2x80x9d) of the PVA polymer (A) for use in the invention preferably falls between 100 and 4000. More preferably, its lowermost limit is at least 150, even more preferably at least 200. Its uppermost limit is more preferably at most 3500, even more preferably at most 3000. If the degree of polymerization of the PVA polymer (A) is lower than 100, the polymerization stability in suspension polymerization of vinylic compounds in the presence of the polymer will be not good; but if larger than 4000, the PVA polymer (A) will be difficult to handle and its productivity will be low.
The block character of the residual acetic acid group of the PVA polymer (A) for use in the invention preferably falls between 0.35 and 0.8, more preferably between 0.35 and 0.75, even more preferably between 0.4 and 0.7. If its block character is smaller than 0.35, the PVA polymer (A) will be ineffective for stabilizing the suspension polymerization of vinylic compounds; but if larger than 0.8, the plasticizer absorbability of the vinylic polymers produced will lower and the particle size distribution of the vinylic polymers will broaden. If so, in addition, the productivity of the PVA polymer (A) will be low. The block character of the residual acetic acid group of PVA referred to herein is an index that indicates the chain distribution condition of the residual acetic acid group of partially-hydrolyzed PVA, and a method for determining it is described in detail in Poval (published by the Polymer Publishing in 1984) and in Macromolecules, 10, 532 (1977).
The methanol soluble content of the PVA polymer (A) for use in the invention preferably falls between 0.05 and 40% by weight. Its lowermost limit is more preferably at least 0.1% by weight, even more preferably at least 0.15% by weight. Its uppermost limit is more preferably at most 37% by weight, even more preferably at most 35% by weight. If the methanol soluble content thereof is smaller than 0.05% by weight, the productivity of the PVA polymer (A) will be low; but if larger than 40% by weight, the PVA polymer (A) will be readily yellowed and it will therefore yellow the vinylic polymers to be produced in the presence of it.
The degree of hydrolysis of the PVA polymer (A) for use in the invention is not specifically defined. However, in case where the PVA polymer (A) is used herein as the primary dispersant, the degree of hydrolysis thereof is preferably at least 60 mol %. Its lowermost limit is more preferably at least 65 mol %, even more preferably at least 68 mol %. Its uppermost limit is preferably at most 98 mol %, more preferably at most 95 mol %, even more preferably at most 90 mol %. If the degree of hydrolysis of the polymer is smaller than 60 mol %, the solubility thereof in water will be low and the polymer will be difficult to handle. If so, therefore, the capability of the polymer to serve as a protective colloid will be poor. In case where it is used as the primary dispersant, the PVA polymer (A) is preferably soluble in water at 5 to 100xc2x0 C., more preferably at 10 to 90xc2x0 C.
In case where the PVA polymer (A) is used herein as the secondary dispersant for suspension polymeriazation, the degree of hydrolysis thereof is preferably smaller than 60 mol %. Its uppermost limit is more preferably at most 57 mol %, even more preferably at most 55 mol %. Its lowermost limit is preferably at least 20 mol %, more preferably at least 25 mol %. If the degree of hydrolysis thereof is 60 mol % or higher, the polymer will be ineffective for improving the plasticizer absorbability of the vinylic polymers produced in the presence of it. In case where the PVA polymer (A) is used as the secondary dispersant for suspension polymerization, it is desirable that this is combined with the above-mentioned PVA polymer (A) having a degree of hydrolysis of at least 60 mol % and serving as the primary dispersant. Not limited to this, however, the secondary dispersant for suspension polymerization of the PVA polymer (A) may be combined with any other ordinary PVA polymer serving as the primary dispersant.
Also preferably, the dispersant for suspension polymerization of the invention comprises the PVA polymer (A) having at least 1.9 mol % of 1,2-glycol bonds and a polyvinyl ester polymer (B) having a degree of hydrolysis of smaller than 60 mol %, in a ratio by weight of the component (A) to the component (B), (A)/(B) falling between 40/60 and 95/5. The lowermost limit of the ratio of (A)/(B) is more preferably at least 50/50, even more preferably at least 60/40; and the uppermost limit thereof is more preferably at most 90/10, even more preferably at most 80/20. In this, the polyvinyl ester polymer (B) serves as the secondary dispersant for suspension polymerization. Combining the PVA polymer (A) with the polyvinyl ester polymer (B) enables one to obtain vinylic polymers having good plasticizer absorbability.
The polyvinyl ester polymer (B) can be produced in any known method of polymerizing a vinyl ester monomer followed by hydrolyzing the resulting polymer. For this, a vinyl ester monomer may be polymerized under the same condition as that for the PVA polymer (A). For hydrolyzing the resulting polymer into the polyvinyl ester polymer (B), employable is ordinary alcoholysis or hydrolysis with a known alkali or acid catalyst. For this, most preferred is hydrolysis with an NaOH catalyst in a solvent of methanol, as it is simple.
The vinyl ester monomers for the polyvinyl ester polymer (B) may be the same as those for the PVA polymer (A) mentioned above, and especially preferred is vinyl acetate.
Not interfering with the object and the effect of the invention, the polyvinyl ester polymer (B) may contain any other monomer units such as those mentioned hereinabove for the PVA polymer (A).
For producing the vinyl ester polymer (B) through polymerization, employable is any known mode of solution polymerization, bulk polymerization, suspension polymerization or emulsion polymerization, as in the above. Depending on the polymerization mode employed, the polymerization initiator to be used for producing the polymer may be selected from azo initiators, peroxide initiators and redox initiators.
The polyvinyl ester polymer (B) for use herein is insoluble in water or dispersible in water. It may be modified by introducing thereinto an ionic group such as an ammonium group, a carboxyl group or a sulfone group to thereby make the polymer self-emulsifiable, or may be modified by introducing thereinto a nonionic group or a (long-chain) alkyl group or the like. Terminal-modified polymers obtained in a known method of polymerizing a vinyl ester monomer such as vinyl acetate in the presence of a thiol compound such as thiolacetic acid or mercaptoproionic acid followed by hydrolyzing the resulting polymer are also employable herein.
The degree of hydrolysis of the polyvinyl ester polymer (B) for use herein is smaller than 60 mol %. Its uppermost limit is more preferably at most 57 mol %, even more preferably at most 55 mol %; and its lowermost limit is preferably at least 20 mol %, more preferably at least 25 mol %. If the degree of hydrolysis of the polyvinyl ester polymer (B) is 60 mol % or more, the vinylic polymers produced could not have improved plasticizer absorbability.
In case where the PVA polymer (A) is used as the primary dispersant in the invention, the 1,2-glycol bond content of the polyvinyl ester polymer (B) to be combined with it is preferably at least 1.9 mol %, more preferably at least 2.0 mol %, most preferably at least 2.1 mol %. Also preferably, the block character of the residual acetic acid group of the polymer (B) falls between 0.35 and 0.8, more preferably between 0.35 and 0.75, even more preferably between 0.4 and 0.7. Controlling the 1,2-glycol bond content and/or the block character of the residual acetic acid group of the polymer (B) for use herein enables more stable polymerization of vinylic compounds, and more effectively prevents the polymerization system from foaming.
The ratio by weight of the PVA polymer (A) to the polyvinyl ester polymer (B) in this embodiment, (A)/(B) falls between 40/60 and 95/5, preferably between 50/50 and 90/10, more preferably between 60/40 and 80/20. If the ratio by weight of the component (A) to the component (B), (A)/(B) is larger than 95/5, the vinylic polymers produced in the presence of the combination of (A) and (B) could not have improved plasticizer absorbability; but if smaller than 40/60, the combination of (A) and (B) will lose the ability to stabilize the polymerization of vinylic compounds.
The viscosity-average degree of polymerization of the polyvinyl ester polymer (B) for use in the invention is preferably at most 1000. Its lowermost limit is preferably at least 200, more preferably at least 230. Its uppermost limit is more preferably at most 700, even more preferably at most 600. If the degree of polymerization of the polymer (B) oversteps 1000, it is often unfavorable since the solubility of the polymer (B) in water is poor and the dispersibility thereof is also poor.
Next described is the method of producing vinylic polymers through suspension polymerization of vinylic compounds in the presence of the dispersant of the invention. The temperature of the aqueous medium in the method of producing vinylic polymers is not specifically defined. Not only cold water at about 20xc2x0 C. but also hot water at 90xc2x0 C. or higher is favorable to the production method. In case where the polymerization is effected according to a hot-charge process, more preferably used is hot water at 40 to 95xc2x0 C., even more preferably at 50 to 90xc2x0 C. The hot aqueous medium may be not only pure water but also an aqueous solution containing various additives. In addition, it may be an aqueous medium containing any other organic solvent. The amount of the hot aqueous medium to be fed into the polymerization system may be such that the medium fed thereinto can sufficiently heat the polymerization system. For increasing the efficiency of heat removal from the polymerization system, favorable is a method of using a reflux condenser-equipped polymerization reactor, or a hot-charge process of using a reflux condenser-equipped polymerization reactor. The temperature for the suspension polymerization preferably falls between 30 and 80xc2x0 C., more preferably between 40 and 75xc2x0 C.
In the suspension polymerization of vinylic compounds, the amount of the dispersant ((A) or the total of (A) and (B)) to be used is not specifically defined. In general, however, the amount of the dispersant is preferably at most 5 parts by weight, relative to 100 parts by weight of the vinylic compound to be polymerized, more preferably at most 1 parts by weight, even more preferably at most 0.5 parts by weight, still more preferably at most 0.1 parts by weight, further more preferably at most 0.09 parts by weight. The lowermost limit of the amount of the dispersant to be used is preferably at least 0.01 parts by weight, more preferably at least 0.02 parts by weight. In the suspension polymerization of vinylic compounds in the presence of the dispersant of the invention, the ratio of the components to be fed into the reactor and the polymerization temperature may be determined in accordance with the condition generally employed in ordinary suspension polymerization of vinylic compounds such as vinyl chloride.
Using hot water in the suspension polymerization of vinylic compounds is preferred. In addition, it is also preferable to previously heat the vinylic compounds before they are fed into the polymerization reactor.
The dispersant of the invention may be combined with any of ordinary PVA, water-soluble cellulose ethers such as methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropylmethyl cellulose, etc.; water-soluble polymers such as gelatin, etc.; oil-soluble emulsifiers such as sorbitan monolaurate, sorbitan trioleate, glycerin tristearate, ethylene oxide-propylene oxide block copolymers, etc.; water-soluble emulsifiers such as polyoxyethylene sorbitan monolaurate, polyoxyethylene glycerin oleate, sodium laurate, etc. Their amount to be added is not specifically defined, but preferably falls between 0.01 and 1.0 part by weight relative to 100 parts by weight of the vinylic compounds to be polymerized such as vinyl chloride.
If desired, any other additives may also be added to the polymerization system. The additives include, for example, agents for controlling a degree of polymerization such as acetaldehyde, butyraldehyde, trichloroethylene, perchloroethylene, mercaptans, etc.; polymerization inhibitors such as phenolic compounds, sulfur compounds, N-oxide compounds, etc.; and pH-controlling agents, scale inhibitors and crosslinking agents. Any of these additives may be optionally added to the polymerization system. If desired, two or more these additives may be combined. On the other hand, the polymerization initiator for the suspension polymerization may be any ordinary one which is soluble in vinylic compounds and is generally used for polymerization of vinylic compounds such as vinyl chloride. It includes, for example, percarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, diethoxyethyl peroxydicarbonate, etc.; perester compounds such as t-butyl peroxyneodecanate, xcex1-cumyl peroxyneodecanate, t-butyl peroxyneodecanate, etc.; peroxides such as acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl 2-peroxyphenoxyacetate, etc.; azo compounds such as 2,2xe2x80x2-azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobis(4-methoxy-2,4-dimethylvaleronitrile), etc. These may be combined with any of potassium persulfate, ammonium persulfate and hydrogen peroxide.
The vinylic compounds capable of being polymerized through suspension polymerization in the presence of the dispersant of the invention concretely include vinyl chloride alone, and also monomer mixtures consisting essentially of vinyl chloride (that is, monomer mixtures containing at least 50% by weight of vinyl chloride). The comonomers capable of being copolymerized with vinyl chloride include vinyl esters such as vinyl acetate, vinyl propionate, etc.; (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, etc.; olefins such as ethylene, propylene, etc.; and other monomers capable of copolymerizing with vinyl chloride, such as maleic anhydride, acrylonitrile, itaconic acid, styrene, vinylidene chloride, vinyl ether, etc. In addition, the dispersant of the invention is also applicable to homopolymerization or copolymerization of vinylic compounds not containing vinyl chloride, such as those mentioned above.
 less than 1 greater than  First described in detail is the aqueous emulsion of the first aspect of the invention, with reference to the following Examples 1 to 7 and Comparative Examples 1 to 7. In the following Examples and Comparative Examples, xe2x80x9cpartsxe2x80x9d and xe2x80x9c%xe2x80x9d are all by weight unless otherwise specifically indicated. The water resistance (water resistant bonding strength) and the temperature dependence of the viscosity of the emulsions obtained were evaluated according to the methods mentioned below.
(Evaluation of Emulsions)
(1) Water Resistant Bonding Strength (to lumber)
The aqueous emulsion obtained herein is applied onto a piece of straight-grained hemlock fir lumber in an amount of 150 g/m2, and this is stuck on another piece of the same lumber. The two with the emulsion therebetween are pressed under a pressure of 7 kg/m2 for 16 hours. After released from the pressure, this is cured at 20xc2x0 C. and 65% RH for 5 days. Next, this is immersed in cold water at 20xc2x0 C. for 4 days. While still wet, the compression shear strength of the test sample is measured.
(2) Temperature Dependence
T0xc2x0 C./T30xc2x0 C. and T60xc2x0 C./T30xc2x0 C. of each aqueous emulsion are measured, and these indicate the temperature dependence of the emulsion. T0xc2x0 C. is the viscosity of the emulsion measured after conditioned at 0xc2x0 C.; T30xc2x0 C. is the viscosity of the emulsion measured after conditioned at 30xc2x0 C.; and T60xc2x0 C. is the viscosity of the emulsion measured after conditioned at 60xc2x0 C. To measure the viscosity, used is a B-type viscometer (20 rpm).
(3) Polymerization Stability
After having been prepared through polymerization, the aqueous emulsion is filtered through a 60-mesh stainless steel gauze filter, and the filtration residue (%, relative to the emulsion) is measured. A smaller value of the filtration residue thus obtained indicates better polymerization stability in producing the emulsion.

Aqueous emulsion and dispersant for suspension polymerization of vinyl compounds