The invention relates to an invention combustion engine comprising a cylinder head (1) with at least one inlet port (4) and at least one injection device (6) per cylinder (2), which extends into the combustion chamber. In order to reduce wear of the injection device while preventing depositions in the region of the injector pocket, the top wall (22) of the combustion chamber is provided with an injector pocket (7) in the area of the mouth (6a) of the injection device (6). Preferably, at least one scavenging duct arrangement (10) extends into the injector pocket (7).

1. Field of the Invention
The invention relates to an internal combustion engine comprising a cylinder head with at least one intake port and at least one fuel injection device per cylinder, which extends into the combustion chamber. The invention also relates to a method for operating an internal combustion engine with at least two exhaust valves per cylinder, where in at least one operating region of the engine exhaust gas is recirculated into the combustion chamber from the exhaust ports via the exhaust valves, and where a swirl flow is generated in the combustion chamber due to differing closing times of the exhaust valves. Furthermore the invention relates to an internal combustion engine comprising a cylinder head with at least two intake and two exhaust valves per cylinder, and with a valve actuating device which permits closing of the exhaust valves at different times. The invention further relates to a cylinder head for an internal combustion engine with at least two intake ports per cylinder opening into the combustion chamber, each intake port being provided with a valve seat in the area where it opens into the combustion chamber, and the openings being partly surrounded by masks formed by material projections of the top face of the combustion chamber.
2. The Prior Art
From DE 103 26 054 A1 there is known an internal combustion engine with a cylinder head, an injection device injecting fuel directly into the combustion chamber, and two intake ports per cylinder, where the intake openings are provided with rib-shaped masks surrounding the disks of the intake valves semi-circularly and facing the injection nozzle. These masks deflect the combustion air flow approximately in parallel to the lateral fuel jet in order to initiate a tumble flow in the combustion chamber. In the area of the fuel jet at least one of the masks is divided by a gap, exposing the fuel jet immediately to part of the inflowing combustion air. This should increase the efficiency of the internal combustion engine and improve ignition reliability. The gap extending over the whole height of the mask will however impair the effect of the mask.
In conventional direct-injection internal combustion engines the injection device extends into the combustion chamber. The exposed situation of the injector tip causes increased wear.
From U.S. Pat. No. 6,502,541B2 there is known an internal combustion engine in which exhaust gas can be recirculated into the combustion chamber via the exhaust valves. Internal exhaust gas recirculation is used to improve fuel consumption especially in part-load operation. To generate a swirl of the recirculated exhaust gas in the combustion chamber the exhaust valves are closed at different times. Different closing times are achieved by a phase shift in the timing of the two exhaust valves. The exhaust valves are thus also opened at different times. In order to adjust the valve timing for both valves independently of each other complex technology is required.
In U.S. Pat. No. 5,870,993 another internal combustion engine is disclosed with two intake and two exhaust valves per cylinder, in which internal exhaust gas recirculation from the exhaust ports into the combustion chamber can be achieved by shifting the lifting curves of the exhaust valves. By masks in the area of the two exhaust ports a swirl may be imparted to the recirculated exhaust gas in the combustion chamber. The masking of the two exhaust ports is disadvantageous at full load.
From EP 0 764 770 B1 there is known a cylinder head which is partially provided with masks in the area where the intake ports open into the combustion chamber, wherein the walls of the intake ports on one side of the opening are configured in such a way that the flow cross-section at low lift of the intake valve is narrowed over an angle region of approximately 180°. At low-load or part-load operation this creates a tumble flow which arises from the intake ports.
U.S. Pat. No. 4,974,566A discloses an internal combustion engine with two intake ports opening into the cylinder, whose walls are configured such that at small valve lifts the intake cross-section for the flow through the intake ports is narrowed in a region defined by a certain angle around the movement axis of the intake valve in such a way that at small valve lifts a tumble flow is generated. For large valve lifts the intake cross-section extends along the whole periphery of the valves, which permits satisfactory filling of the cylinder. In the part-load region the engine is operated with small valve lifts, thus giving good thermodynamic conditions for combustion due to the prevailing tumble flow. At full load the engine is operated with full valve lifts, thus achieving sufficient filling of the cylinder and sufficient torque.
It is the object of the present invention to minimize the above mentioned wear of the injection device in an internal combustion engine. Furthermore, the forming of deposits in the area around the entry of the injection device into the combustion chamber is to be avoided. A further aim of the invention is to achieve good fuel economy at part load without impairing full load performance. Furthermore it is an object of the invention to design a cylinder head with which combustion conditions especially at part load may be improved and emissions may be further reduced.
The invention achieves these aims by providing that the top of the combustion chamber has an injector pocket in the area where the injection device enters the combustion chamber, preferably with at least one arrangement of scavenging passages opening into the injector pocket. Scavenging air enters the injector pocket via the scavenging passage arrangement, thus preventing the formation of deposits. The method of scavenging the injector will not, or only slightly, impair the effectiveness of the masking.
In a first variant of the invention, which has no negative influence on the effectiveness of the masking, it is provided that the scavenging passage arrangement is located in the region of at least one squish surface of the combustion chamber top preferably formed by the cylinder head. Preferentially it is provided that the scavenging passage arrangement has at least one scavenging passage which starts from a flat entry area and opens into the injector pocket via a nozzle region. Advantageously the depth of the scavenging passage increases in the direction towards the injector pocket. Preferably the scavenging passage narrows in the form of a nozzle, thus causing the scavenging air to enter the injector pocket with high flow velocity. As the piston approaches upper dead center scavenging air is pressed via the squish surface into the scavenging passage arrangement and further into the injector pocket, thus cleaning out deposits from the injector pocket.
In a second variant of the invention it is provided that the scavenging passage arrangement departs from an intake port, preferably from the valve seat area of the intake port. If at least one intake port is furnished with a mask, it is of particular advantage if the scavenging passage arrangement is formed into the mask. Advantageously in this case at least one scavenging passage is positioned essentially radially relative to the intake port between the intake port and the entry point of the injection device.
In a particularly simple variant of the invention it is provided that the scavenging passage has a cross-section which is open towards the combustion chamber and is configured preferably as a slot or a groove. The slot or groove may be machined into the cylinder head in a simple manner. It is also possible, however, that the scavenging passage at least partly has a closed cross-section and is preferably formed by a bore. Preferentially it is provided that the scavenging passage arrangement has a certain distance from the bottom of the mask. The effective mechanism of the mask will be much less impaired by this measure than by a gap in the mask extending over its whole height, as shown in DE 103 26 054 A1.
It is provided by the invention that the longitudinal axis of at least one scavenging passage forms an angle greater than 0°, preferably between 30° and 60°, with a plane defined by the cylinder axis and the axis of the injection device.
To achieve a sufficient swirl effect it is advantageous if the mask extends around the intake port over an angle of 150° to 180°. In this instance the height of the mask should be between 1.5 mm and 4 mm. Preferably it is provided that the distance from the mask to the rim of the valve disk is about 0.3 mm to 0.7 mm.
To improve on fuel consumption at part load without impairing full-load performance it is proposed that the two exhaust valves be opened for differing lengths of time, both exhaust valves preferably opening at the same time. Via a phase adjuster the opening point of the exhaust valves may be shifted synchronously. In the case of cam-controlled operation in particular, it may be provided that the exhaust valves have exhaust valve lift curves of differing length.
The invention is also suitable for cam-less operation, however.
By simultaneously opening both exhaust valves a relatively large volume of exhaust gas may be fed into the exhaust ports at the beginning of the exhaust stroke. In this way a favourable emptying behaviour of the combustion chamber may be achieved with minimal throttling losses. This will result in a high power yield, especially at full load.
In the context of the invention it is provided that the difference between the closing points of the exhaust valves is 10° to 80° of crank angle, and preferably 20° to 60° of crank angle, a first exhaust valve preferably being closed immediately after upper dead center of the charge exchange process and a second exhaust valve being closed at 20° to 60° crank angle after upper dead center of the charge exchange process. The closing point is here defined as that point in time at which the exhaust valve has a residual lift of 1 mm. Differing closing points will cause swirl to be generated when exhaust gas is sucked back into the cylinder from the exhaust duct. To achieve strong swirl components it is advantageous if the recirculated exhaust gas is guided over a flow guiding surface formed by a mask in the area of at least one exhaust valve. The mask may be provided in the area of one exhaust valve only. In this way flow losses during outflow from the cylinder at full load may be kept small. In order to achieve a sufficient swirl effect it is advantageous if the mask extends around the center of the exhaust port through an angle of approximately 150° to 180°. The height of the mask should be 1.5 mm to 4 mm. Preferably it is provided that the distance of the mask from the rim of the valve disk is 0.3 mm to 0.7 mm approximately.
The different closing times of the exhaust valves may be realised by an asymmetrical shape of the cam of at least one exhaust valve. Preferentially it is provided that each exhaust valve is actuated by its own cam, with the cams having different closing flanks. Furthermore it may be provided that the cams have identical opening flanks and/or identical maximal cam lobes.
In addition, the swirl in the combustion chamber due to the intake flow from the intake ports can be increased by asymmetrical intake ports, one intake port being preferably configured such that it can be closed down.
Combustion conditions and emissions can be improved if the contour of the mask of at least one intake port has a flat main part of maximum height between an ascending and a descending flank and in a developed view is of asymmetrical shape, ascending and descending flanks preferably having different slope angles.
It is particularly advantageous if the flank of the profile closer to the combustion chamber wall has a smaller slope than the flank nearer to the center of the combustion chamber. The intake flow may thus be specifically guided to a central cylinder region generating a tumble flow in the direction of the piston axis.
It has been found by experiments that a particularly high stability of combustion can be attained if the mask of each port extends over an angle of 120° to 210°, measured around the center of the port opening, and preferably over an angle between 160° and 180°. Preferentially it is provided that at each port a main axis running approximately through the middle of the main part of the mask forms an angle of 70° to 120°, preferably between 80° and 110°, with a straight reference line running through the centers of the port openings.
The height of the mask is chosen such that at partial valve lift the opening of each intake port is laterally covered on the intake side. At full valve lift the intake valve is beyond the mask and the full intake cross-section is available. The height of the mask is 1.2 mm to 3.5 mm approximately, and preferably 1.6 mm to 2.5 mm, and even more preferably 1.6 mm to 2.2 mm. In order to avoid heavy throttling of the intake flow especially under full load it is of advantage if a clearance is provided between the mask and the valve disk, which should not exceed a quarter of the height of the mask, preferably.
In a particularly preferable variant of the invention it is provided that the depth of the injector recess is at most about equal to the height of the mask. By positioning the injector orifice in the area of the injector recess of the mask, the injector nozzle may extend relatively deeply into the combustion chamber. The depth of the injector recess will thus correspond to the height of the mask at most. It is furthermore of advantage if the injector recess is at a distance from the wall of the mask, this distance being at least 1 mm. This minimum distance between injector recess and wall of the mask will avoid negative influence on the intake flow.
The invention will now be described in more detail with reference to the enclosed drawings.


A method to make libraries of hybrid polynucleotide molecules of two parental polynucleotide molecules utilizing single-stranded DNA was invented. Example of the method comprises several steps: (i) preparation of two single-stranded polynucleotide molecules comprising sequences containing one or more parts of homology and one or more parts of heterology, (ii) random or non-random fragmentation of said polynucleotides, (iii) hybridization of the fragmented molecules followed by de novo polynucleotide synthesis (i.e. polynucleotide chain elongation) on the hybridized molecules, (iv) separation of the chain elongation products (i.e. double-stranded polynucleotide molecules) into single-stranded polynucleotide molecules (denaturation) (v) hybridization of the resultant single-stranded polynucleotide molecules followed by de novo polynucleotide synthesis on the hybridized molecules, and (vi) repeating at least two further cycles of steps (iv) and (v).

1. Field of the Invention
The present invention relates to a method for the production of hybrid polynucleotide molecules from two parental polynucleotide molecules using single-stranded polynucleotides, which can achieve superior effects to the existing methods, such as a higher frequencies.
2. Description of the Related Art
DNA shuffling is a developed technique that allows accelerated and directed protein evolution in vitro. In this method, the acquisition of genes encoding improved proteins is done in two steps. In the first step, a single gene is mutagenized, and desired mutant genes are selected. In the second step, the mutant genes are fragmented by DNase I, and subsequently recombined in vitro by using PCR. Among the recombinants, (i.e., the products of DNA shuffling), those producing most favored proteins are isolated (FIG. 1; 1, 2). The modified versions of the DNA shuffling exist: (i) random priming was used to generate DNA fragment instead of the DNase I digestion (3); (ii) PCR conditions with very short annealing/extension steps were employed to increase the frequency of recombination (4). Using these techniques, a number of improved enzymes have been obtained (1-9). When the DNA shuffling is done using a set of homologous genes instead of a set of mutant genes derived from a single gene, this technique is called family shuffling. Family shuffling utilizes naturally occurring nucleotide substitutions among family genes as the driving force for the in vitro evolution. The application of the family shuffling strategy has also provided many successful examples (10-15).
A potential problem of the family shuffling is a low yield of recombinants (i.e., hybrid molecules constituted from several family gene sequences). When two parental genes of 80% nucleotide sequence identity were shuffled, the frequency of hybrid formation was less than 1% (16-17). The low recombination yield may be due to a lower frequency of the heteroduplex formation compared to the frequency of the homoduplex formation (FIG. 2; 16).
Thus, it is desirable to develop methods which allow for the high frequency production of recombinant molecules of two or more family genes. We have reported a technique which is the shuffling of restriction endonuclease-digested DNA fragments instead of the shuffling of randomly fragmented DNA (16). The annealing of endonuclease-digested DNA fragments would produce homoduplex at a high frequency, but significant DNA elongation only occurs on the heteroduplex molecules.

Synthesis of hybrid polynucleotide molecules using single-stranded polynucleotide molecules


An input device for inputting a command and information to a device, includes a body shape input section acquiring body shape information of a user and a display information generation section generating a display image necessary for the user to input the command and the information. Further, the input device includes an operation section having an operation surface corresponding to the display image, a body shape extraction section extracting a portion corresponding to the operation surface from the body shape information acquired by the body shape input section and generating a body image, an image composition section making a composite image of the display image generated by the display information generation section and the body image generated by the body shape extraction section, and a display section displaying the composite image made by the image composition section.

Conventionally, as an input device for allowing a user to input a command and information using his/her finger and the like based on information displayed on a display screen such as a display, devices are disclosed in, for example, Patent Document 1 and Patent Document 2. These devices each capture a touch panel operation surface by grid matrix type scanning means or a camera, extract a hand shape portion from the acquired data, and display a composite image of the hand shape portion and a GUI (Graphical User Interface) and the like displayed on a display. Based on the above-described structure, the user can, without once moving the line of sight to a touch panel installed remotely from the display screen and seeing the touch panel with his/her own eyes while driving, input the command and the information while viewing the image of an operating finger virtually displayed on the display screen.
Additionally, by using the devices disclosed in Patent Document 1 and Patent Document 2, the hand shape of the user may be acquired by pattern matching from an image captured by the camera, and thus it is possible to allow the user to operate the device after the hand shape of the user is recognized as a hand shape, and also it is possible to interpret the user input by sensing a gesture which is time-varying patterns of the hand shape and the hand position of the user.    Patent Document 1: Japanese Laid-Open Patent Publication No. 9-77622    Patent Document 2: Japanese Laid-Open Patent Publication No. 2000-6687


A control system for a hydraulic percussion rock drill and feed mechanism including a single constant power hydraulic pump for supplying pressure fluid to operate the feed mechanism, drill stem rotation motor, and the percussion hammer. The drill feed, rotation and percussion functions are controlled by individual manually actuated pressure compensated valves. Fluid pressure to the feed mechanism is controllable at one of two selectable pressures and is automatically reduced if fluid pressure to the drill stem rotation motor exceeds a predetermined limit. The drill percussion blow intensity and frequency is controlled by a mechanism responsive to a fluid pressure signal which is automatically operated to provide for a high blow frequency and low blow intensity operating mode when the drill is retracted away from the workface. The constant power hydraulic pump is provided with a control which will adjust the pump output to a partial displacement setting when the drill is being retracted away from the workface. Alternatively, the pump control may be set to full displacement with a power limit and the drill percussion mechanism fluid supply may be automatically throttled when the drill is being retracted away from the workface.

Hydraulic percussion rock drills have been developed which provide for substantially all drill functions, except drill hole flushing, to be performed by hydraulic pressure fluid. Drill percussion mechanisms as well as drill stem rotation motors and feed motors are desirably hydraulically powered for greater efficiency for deriving more power from a smaller machine than has been possible with pneumatic powered drills. The development of hydraulic percussion drills has, however, resulted in more complex control circuits due to the fact that hydraulic fluid return lines must be provided and, heretofore, it has been deemed desirable to use multiple pumps for supplying pressure fluid to the various motors on the drill and the associated feed mechanism. Moreover, the more powerful hydraulic drills have made it more desirable that the relationship of feed force, drill stem rotation effort, and percussive energy should be controlled to provide optimum drilling rates. However, the automatic control of each of these functions becomes difficult and requires expensive components when multiple hydraulic circuits are used.
The development of hydraulic percussion drills has further resulted in the desire to provide even greater drilling rates by the use of controls to vary the percussion blow intensity and blow frequency to suit the particular drilling conditions. Improvements in such controls as well as the provision of a hydraulic percussion drill powered by a constant power hydraulic source is the subject of the invention disclosed and claimed in U.S. Pat. No. 3,995,700 assigned to the assignee of the present invention.
In the further development of percussion drills having variable percussion blow frequency controls it has been determined that it is desirable to vary blow frequency and blow intensity in relation to resistance to forward feeding of the drill and also in relation to resistance to rotation of the drill stem and bit. Moreover, it is considered desirable that on retraction of the drill from the work that blow intensity be decreased to prevent possible damage to the percussion mechanism.
The problems associated with prior control systems for hydraulic drills as well as certain improvements foreseen as being desirable in the art of hydraulic percussion drills have been dealt with in developing the invention disclosed and claimed herein.


The retrofit patient call system retrofits onto the preexisting patient call system. The retrofit system includes a wireless patient call unit mounted on a patient using a wristband or strap and a wall unit retrofit mounted near the preexisting patient call system room port. The patient call unit allows the patient to activate a user actuated control coupled to a transmitter which generates a radio frequency (RF) patient call signal. The wall unit receives the RF patient call signal and produces a patient alarm signal which is sent via the preexisting room port and patient call system to a central monitoring station. The wall unit is programmed either to send the patient alarm signal in the same form as the preexisting hard-wired patient call switch or to activate the preexisting room port to generate the alarm. The wall unit may include a reset and a display for other valuable information.

The present invention relates to a wireless patient call system for retrofitting onto preexisting patient call systems.
Most hospitals, nursing homes and other healthcare facilities utilize a hard-wired patient call system. Each patient room is wired with a patient-activated call switch. The call switch is usually an independent push-button or a patient-actuated control switch mounted on a small box together with other control switches (e.g. volume for a television, etc). The call switch is connected to a nearby room port via flexible electrical conductors. Each room is electronically connected to a central monitoring station, usually located at a nurse""s station or other healthcare provider locale. Such patient call systems have serious limitations because a patient can only call for assistance if the patient is able to reach the patient call switch. If the patient""s mobility is limited, a nurse or healthcare provider must position the call switch or push-button near the patient""s hand. If the patient is mobile, or accidentally falls away from the general area of the patient call switch, the patient will not be able to activate the call switch unless he or she is able to reach for the switch. Many times the call switch will fall from the patient""s hospital bed or just be out of the patient""s reach. There is a need for a patient call system which does not require the patient to be physically linked to a room port. There is a need for a patient call system in which a patient can call for assistance by simply activating a wireless call switch located on the patient""s person (preferably near the patient""s hand). There is also a need for such a patient call system which can be retrofitted onto an existing patient call system thereby making it economically feasible for healthcare facilities to upgrade existing systems.
Although wireless patient call systems exist, the cost of replacing an existing hard-wired system for a new wireless system is either cost prohibitive or cannot be justified. Most patient call systems found in healthcare facilities were installed during construction or during a major renovation of the facility and include hardware embedded into the building""s walls and difficult-to-reach locations. Accordingly, there is a need for a wireless patient call system which can be retrofitted onto a preexisting patient call system thereby eliminating the need to replace the entire system.
U.S. Pat. No. 5,600,305 to Stafford and Bock, discloses a portable patient monitoring system used to detect when a patient attempts to exit the hospital bed or the patient room. The system consists of a master unit with an infrared emitter and detector, and a portable external reflector which reflects an infrared beam from the emitter back to the detector. The system is set up so that if a patient crosses the infrared beam, a light on the master unit is activated as well as a switch to the nurses station.
U.S. Pat. No. 5,838,223 to Gallant, et al., discloses a patient/nurse call system with patient stations capable of generating hospital calls and a remote master station which prioritizes and stores calls. Hall units outside patient rooms identify the rooms from which the calls originate and the type of call. Nurse-worn badges transmit pulse-coded infrared signals which are received by receivers at the patient stations and in response, the systems generates identity and location signals which are stored at the master station. Receipt of a nurse""s infrared signal at a room station automatically cancels a patient call originating from the room and actuates a display indicating a nurse""s presence. By using the nurse call button, a patient can establish telephonic communication between the patient station and a wireless telephone being carried by the remotely located nurse.
U.S. Pat. No. 5,877,675 to Rebstock and Rast, discloses a portable, three-way wireless communication and locator system. The system provides a direct voice-communication link between a patient and the patient""s care-giver, as well as to a central station. Each patient is equipped with a portable communication device which can be worn on the wrist. Each care-giver is also equipped with a portable communication device. The central station acts as a backup, in the event a care-giver cannot timely respond to a patient. The system works through a series of repeaters located throughout the facility. Each communication device contains identifying information. A particular patient is located by polling the communication device throughout the system and obtaining which repeater received the strongest signal.
U.S. Pat. No. 5,963,137 to Waters, discloses an audible, visual and remote alarm system designed to monitor the status of a person in another room to know when assistance may be needed. It is used primarily to monitor patients who may become mobile and may not be able to rationalize the need to summon help, such as Alzheimer patients, sleep walkers, etc. However, the system can also be used by individuals who can consciously summon assistance by activating a magnetic switch. The system utilizes a magnetic switch fastened to the patient. The opening of the magnetic switch completes the hard-wired circuitous path, thereby activating a visual alarm and an audio alarm.
U.S. Pat. No. 5,995,007 to Borja and Valdez, discloses a child proximity monitoring device. The device includes a wrist mounted portable module including a radio device. Also included is a monitoring unit also including a radio device and an indicator for indicating when the two radio devices have separated by a predetermined distance. During operation, the monitoring unit sends a continuous monitoring signal to the portable module. Upon receipt of the out-of-range signal, the monitoring unit sounds an alarm.
It is an object of the present invention to provide a wireless patient call system which can be retrofit onto an existing hard-wired patient call system.
It a further object of the present invention to provide a patient with a patient call unit which the patient can wear on his or her wrist to enable that patient to summon the assistance of a healthcare provider.
It is another object of the present invention to provide a patient with a patient call unit which when activated by the patient sends a radio frequency signal to a wall unit retrofit mounted near the preexisting patient room port. The wall unit is retrofit onto the preexisting room port such that upon receipt of the radio frequency signal from the patient call unit, the wall unit sends a patient alarm signal substantially similar to the alarm signal sent by the preexisting hard-wired patient call unit to the preexisting central monitoring station.
The patient call system, in accordance with the principles of the present invention, is adapted to retrofit onto a preexisting patient call system. The patient call system, retrofit onto the preexisting system, consists of a patient call unit which is securely mounted on a patient using a wristband or strap and a wall unit retrofit mounted near the preexisting patient call system room port. The patient call unit allows the patient to activate a user actuated control electrically coupled to a transmitter which generates a radio frequency (RF) patient call signal. The wall unit, which is in communication with the RF transmitter in the patient call unit, receives the patient call signal and produces a patient alarm signal. The wall unit is electrically coupled to the preexisting room port and sends the patient alarm signal to the room port upon receipt of the patient call signal. The wall unit is programmed either to send the patient alarm signal in the same form as the preexisting hard-wired patient call switch or to activate the preexisting room port to generate the alarm. The patient alarm signal is then received by the preexisting central monitoring station in the same manner as if the alarm signal had been sent by the preexisting patient call switch. The retrofit patient call system includes a coupling interface with the preexisting patient call switch (such as a T coupler) to permit a healthcare facility to utilize both the present invention and the preexisting patient call switch (the switch at the end of the flexible cable or conductors). The patient call unit may include a fall detector electrically coupled to the transmitter. If the patient falls or the fall detector otherwise detects an abrupt jarring (a measurement of acceleration), the transmitter sends an RF patient call signal to the wall unit. The wall unit may include a display which displays information such as time elapsed since receipt of a patient call signal, the time of receipt of a patient call signal, programming information and power source information. The wall unit may also include a reset switch to reset the system after receipt of a patient call signal. The wall unit can be programmed to send multiple patient alarm signals at predetermined time intervals to the preexisting patient call system after receipt of a patient alarm signal from the patient call unit typically strapped to the patient""s wrist.

Retrofit for patient call system and method therefor


A blend which comprises;

Not Applicable
This invention describes resin formulations having a flexural modulus of greater than or equal to 100,000 psi or less than or equal to 30,000 psi, which also yield previously inaccessible high melt strengths at a given melt index. This invention also provides fabricated articles including foams made from these resin formulations.
Blends of low density polyethylene (LDPE) and linear low density polyethylene (LLDPE) are known in the prior art. For example, Ghijsels et al., in xe2x80x9cMelt Strength Behavior of Polyethylene Blendsxe2x80x9d, Intern. Polymer Processing VII (1992), p. 44-50, exemplifies blends of LDPE and LLDPE, where the LLDPE has a melt index (I2) of 0.1 g/10 min and the final blend densities are approximately 0.92 g/cm3, and which show a synergistic improvement in melt strength. A polyethylene resin density of 0.92 g/cc corresponds approximately to a flexural modulus of 40,000 psi. However, Ghijsels neither exemplifies nor gives any indication of the range of the ethylenic blend components in which synergy would be observed for blends having a flexural modulus greater than or equal to 100,000 psi, nor less than or equal to 30,000 psi.
U.S. Pat. Nos. 5,863,665 and 5,582,923 describe an ethylene polymer extrusion composition comprising from about 75 to 95 percent of at least one ethylene/xcex1-olefin interpolymer composition selected from the group consisting of a substantially linear ethylene polymer composition, a homogeneously branched linear 5 ethylene polymer composition and a heterogeneously branched linear ethylene polymer composition, (wherein the ethylene/xcex1-olefin polymer is characterized as having a density in the range of 0.85 g/cc to 0.940 g/cc) and from about 5 to 25 percent of at least one high pressure ethylene polymer characterized as having a melt index, I2, of less than 6.0 g/10 minutes, a density of at least 0.916 g/cc, a melt strength of at least 9 cN as determined using a Gottfert Rheotens unit at 190xc2x0 C., a Mw/Mn ratio of at least 7.0 and a bimodal molecular weight distribution as determined by gel permeation chromatography, wherein the ethylene polymer extrusion composition has a melt index, I2, of at least 1.0 g/10 minutes. The blends of this composition would have flexural modulus less than about 115,000 psi. In contrast, the blends of the present invention would have flexural modulus xe2x89xa7120,000 psi at comparable melt strength. Furthermore, this patent does not teach, exemplify or claim foams.
U.S. Pat. No. 4,649,001 describes a process for producing a polyethylene extruded foam, which comprises melting and kneading a composition of a polyethylene-based resin containing a foaming agent followed by extrusion-foaming. A linear low-density polyethylene having a broad molecular weight distribution is used as the polyethylene-based resin. The linear low-density polyethylene used has a density of 0.920 to 0.940 g/cm3; a melt flow rate of 0.3 to 10 g/10 min and a relationship between a weight average molecular weight and a number average molecular weight (Mw/Mn) greater than or equal to 4. Low density polyethylene of 0.918 to 0.923 g/cm3 density may also be blended to make foams. The foams were all extruded. Cross-linked foams were not claimed. The highest flexural modulus of the resins used to make the extruded foams would correspond to about 120,000 psi (at a resin density of 0.940 g/cm3), but this would not be a blend. Furthermore, the density of the linear low-density polyethylene was 0.940 g/cm3or less.
U.S. Pat. No. 4,226,946 discloses polyethylene blend foams having density from about 3.0 to about 15.0 pounds per cubic foot, substantially closed-cell structure and average compressive strength at 10 percent deformation of from about 7 to about 170 psi, preferably about 7 to about 60 psi, and an improved method and a means for making the same from polyethylene blends and at least one blowing agent using gel-forming extrusion technology. The polyethylene blend comprises from about 35 to about 60 weight percent of low density branched polyethylene (0.910 to 0.930 g/cc density) in admixture with from about 40 to about 65 weight percent of intermediate density linear polyethylene (0.931 to 0.940 g/cc density). The densities of the resulting blends would be less than 0.9365 g/cc (corresponding to a flexural modulus less than about 100,000 psi) and greater than 0.9180 g/cc (corresponding to a flexural modulus greater than about 40,000 psi).
However, there is still a need for resin compositions which, while achieving a required flexural modulus xe2x89xa7100,000 psi or xe2x89xa630,000 psi, can also exhibit high melt strength and/or melt extensibility, at a given melt index. We have surprisingly found that certain compositions exhibit synergistic improvements in melt strength and, in some cases, even more surprisingly, in melt extensibility at this melt strength. Branched resins can""t achieve the modulus possible with linear polyethylene resins, and linear resins would have to have much lower melt index than branched resins of comparable melt strength. Furthermore, the melt strength achieved with the blends used in the present invention may exceed, at a given melt index, the melt strength achievable with any branched resin or linear resin at the same melt index and/or density. Consequently, the blends used in the present invention exhibit greatly improved melt strength compared with a linear polyethylene resin of the same density.
The extrusion foam manufacturing process requires a resin of sufficiently high melt strength to allow the bubble structure to maintain its integrity during the expansion process immediately after extrusion from the die. Prior to this invention, the only resins capable of meeting this requirement at the melt index suitable for processing (I2 greater than 0.5, preferably  greater than 1 g/10min) were branched resins such as LDPE, EVA and the like. Hence, the flexural modulus was limited to that obtainable with these branched resins (i.e. about 80,000 psi or less, equivalent to an LDPE of density less than or equal to approximately 0.930 g/cm3). It would be highly desirable to produce a foam using resin of higher modulus ( greater than 100,000 psi), as this allows the overall density of the foam to be reduced, while maintaining the compressive strength of higher density foam made from a branched resin (although this resin has the limitation of lower modulus).
The present invention describes blends comprising branched resins (eg LDPE) and linear resins (eg LLDPE prepared by for example Ziegler and/or metallocene catalysts). These blends provide a unique combination of increased melt strength and modulus at a given melt index, I2. Optionally, specific blend formulations may also be selected to provide modulus both higher or lower than that achievable with LDPE alone. Thus this invention can provide blends of flexural modulus greater than or equal to 100,000 psi or less than 30,000 psi, at melt strengths similar to or greater than those associated with LDPE or linear polyethylene having similar melt index, I2.
The blends of the present invention are useful for fabricating high modulus foams, the preparation of which requires high melt strength. The resulting high modulus compositions (i.e., greater than 100,000 psi flexural modulus) are particularly suitable for manufacture of crosslinked and noncrosslinked foams. Thus the foams of the present invention have compressive strength and load bearing capacity similar to that of foams made from branched polyethylenes, but the inventive foams have significantly lower foam density (allowing a significant reduction in the amount of resin, by weight, necessary to produce such foams). In addition, the upper service temperature of the foams of this invention may also be improved, resulting in subsequent improvement in foam dimensional stability. No resin with this combination of properties is currently available.
The high modulus foams of the present invention comprise blends of high melt strength branched resin of relatively low modulus, with linear resin of higher density and therefore higher modulus, to yield a final blended resin of modulus greater than 100,000 psi. Commercially available branched ethylenic resins cannot achieve this modulus.
Also included in the present invention are so called xe2x80x9csoftxe2x80x9d foams. These foams comprise blends of high melt strength branched resin of relatively low modulus, with linear resin of lower density and therefore lower modulus, to yield a final blended resin of flexural modulus less than or equal to 30,000 psi. Commercially available low density polyethylene cannot achieve this modulus either. Ethylenic copolymers such as ethylene vinyl acetate (EVA) and ethylene acrylic acid (EAA) can have flexural modulus less than 30,000 psi, but these resins are not thermally stable at high temperatures (i.e., degrade readily) and often result in significant discolouration and/or smell. Thus, these resins only have limited utility for extruded, non-crosslinked foams.
A blend which comprises;
A) a heterogeneous or homogenous linear ethylene homopolymer or interpolymer;
B) a branched homopolymer or interpolymer;
xe2x80x83wherein said blend has;
1) a melt index, I2, of about 0.05 to about 20 g/10 min;
2) a flexural modulus of xe2x89xa7100,000 psi or xe2x89xa630,000 psi;
3) a melt strength of xe2x89xa72 cN;
4) a melt extensibility of xe2x89xa725 mm/sec; and
5) wherein said melt strength of said blend meets the following relationship;
Melt strengthxe2x89xa7FMS*[(f*A)+((1xe2x88x92f)*B)]; where:
A=3.3814*(I2)xe2x88x920.6476 and B=16.882*(I2)xe2x88x920.6564; where
I2 is the measured melt index of the blend; f is the weight fraction of the linear polyethylene in the blend and FMS is xe2x89xa71.1.
Definitions
All references herein to elements or metals belonging to a certain Group refer to the Periodic Table of the Elements published and copyrighted by CRC Press, Inc., 1989. Also any reference to the Group or Groups shall be to the Group or Groups as reflected in this Periodic Table of the Elements using the IUPAC system for numbering groups.
Any numerical values recited herein include all values from the lower value to the upper value in increments of one unit provided that there is a separation of at least 2 units between any lower value and any higher value. As an example, if it is stated that the amount of a component or a value of a process variable such as, for example, temperature, pressure, time and the like is, for example, from I to 90, preferably from 20 to 80, more preferably from 30 to 70, it is intended that values such as 15 to 85, 22 to 68, 43 to 51, 30 to 32 etc. are expressly enumerated in this specification. For values which are less than one, one unit is considered to be 0.0001, 0.001, 0.01 or 0.1 as appropriate. These are only examples of what is specifically intended and all possible combinations of numerical values between the lowest value and the highest value enumerated are to be considered to be expressly stated in this application in a similar manner.
The term xe2x80x9chydrocarbylxe2x80x9d as employed herein means any aliphatic, cycloaliphatic, aromatic, aryl substituted aliphatic, aryl substituted cycloaliphatic, aliphatic substituted aromatic, or aliphatic substituted cycloaliphatic groups.
The term xe2x80x9chydrocarbyloxyxe2x80x9d means a hydrocarbyl group having an oxygen linkage between it and the carbon atom to which it is attached.
The term xe2x80x9cinterpolymerxe2x80x9d is used herein to indicate a polymer wherein at least two different monomers are polymerized to make the interpolymer. This includes copolymers, terpolymers, etc.
The term xe2x80x9csoft foamxe2x80x9d is used herein to indicate a foam which has an Asker C hardness less than about 30, preferably less than about 25 and most preferably less than about 20. The hardness of the present foams was measured using an Asker C durometer for cellular rubber and yarn in accordance with ASTM D2240-97 (but with a spherical indentor of about 5 mm diameter).
Melt Index (I2, g/10 min) was determined by ASTM D-1238 (190xc2x0 C./2.16 kg).
Density (g/cm3) was determined by ASTM D-792.
Flexural Modulus was measured in accordance with ASTM D-790-91, Method 1, Procedure B. A bar of rectangular cross-section was tested using a three-point loading system and a 10 pound load cell.
Melt Tensionxe2x80x94The melt tension (in grams) was measured at 190xc2x0 C. using a 2.16 kg load and pulling strands of molten polymers at 50 rpm around a pulley system for a haul-off rate over a thirty second period. The melt tension was the average force over this period.
Melt Strength (MS, measured in cN) and Melt Extensibility (ME, measured in mm/s)xe2x80x94The measurements were conducted by pulling strands of the molten polymers or blends at constant acceleration until breakage occurred. The experimental set-up consisted of a capillary rheometer and a Rheotens apparatus as take-up device. The force required to uniaxially extend the strands was recorded as a function of the take-up velocity. The maximum force attained before either draw resonance or breakage occurred was defined as the melt strength. The velocity at which draw resonance or breakage occurred was defined as the melt extensibility. Draw resonance, which terminated in breakage, was indicated by the onset of a periodic oscillation of increasing amplitude in the measured force profile. In the absence of any observable draw resonance, the melt strength was defined as the force at break. These tests were run under the following conditions:
Mass flow rate: 1.35 gram/min
Temperature: 190xc2x0 C.
Capillary length: 41.9 mm
Capillary diameter: 2.1 mm
Piston diameter: 9.54 mm
Piston velocity: 0.423 mm/s
Shear rate: 33.0 sxe2x88x921
Draw-down distance (die exit to take-up wheels): 100 mm
Cooling conditions: ambient air
Acceleration: 2.4 mm/s2
Upper Service Temperature (UST)xe2x80x94A thermomechanical analyzer (TMA) commercially available from Perkin Elmer Corporation under the trade designation model TMA 7 was used to measure the upper service temperature (UST) of the polymers and blends. Probe force of 102 g and heating rate of 5xc2x0 C./min were used. Each test specimen was a disk with thickness of 3.3 mm and 7.8 mm diameter, prepared by compression molding at 205xc2x0 C. and air-cooling to room temperature. The temperature at the probe penetration of 1 mm was taken as the upper service temperature (UST).
The Blend Compositions.
The blend compositions of the present invention comprise one or more linear homopolymers or interpolymers (Component A) and one or more branched homopolymers or interpolymers (Component B).
Component A The linear homopolymers and interpolymers comprising Component A, are those prepared using so called coordination catalysis including Ziegler and metallocene type catalyst systems. The linear interpolymers can be further divided into homogeneous or heterogeneous polymers, depending upon how the comonomer is distributed within the interpolymer molecules.
The linear homogeneous polymers and interpolymers used as Component A in the blends of the present invention are herein defined as defined in U.S. Pat. No. 39645,992 (Elston), the disclosure of which is incorporated herein by reference. Accordingly, homogeneous polymers and interpolymers are those in which the comonomer is randomly distributed within a given interpolymer molecule and wherein substantially all of the interpolymer molecules have the same ethylene/comonomer ratio within that interpolymer. The homogeneous polymers have a narrow composition distribution.
The term xe2x80x9cnarrow composition distributionxe2x80x9d used herein describes the comonomer distribution for homogeneous interpolymers and means that the homogeneous interpolymers have only a single melting peak and essentially lack a measurable xe2x80x9clinearxe2x80x9d polymer fraction. The narrow composition distribution homogeneous interpolymers can also be characterized by their SCBDI (short chain branch distribution index) or CDBI (composition distribution branch index). The SCBDI or CBDI is defined as the weight percent of the polymer molecules having a comonomer content within 50 percent of the median total molar comonomer content.
The CDBI of a polymer is readily calculated from data obtained from techniques known in the art, such as, for example, temperature rising elution fractionation (abbreviated herein as xe2x80x9cTREFxe2x80x9d) as described, for example, in Wild et al, Journal Of Polymer Science, Poly. Phys. Ed., Vol. 20, p. 441 (1982), or in U.S. Pat. No. 4,798,081, and U.S. Pat. No. 5,008,204 and WO 93/04486, the disclosures of all of which are incorporated herein by reference. The SCBDI or CDBI for the narrow composition distribution homogeneous interpolymers and copolymers of the present invention is preferably greater than about 30 percent, especially greater than about 50 percent. The narrow composition distribution homogeneous interpolymers and copolymers used in this invention essentially lack a measurable xe2x80x9chigh densityxe2x80x9d (i.e., homopolymer) fraction as measured by the TREF technique. The linear homogeneous interpolymers and polymers also have a degree of branching less than or equal to 2 methyls/1000 carbons in about 15 percent (by weight) or less, preferably less than about 10 percent (by weight), and especially less than about 5 percent (by weight).
Useful linear homogeneous homopolymers or interpolymers also include the so-called substantially linear polymers defined as in U.S. Patent No. 5,272,236 (Lai et al.), and in U.S. Pat. No. 5,278,272, the entire contents of which are incorporated by reference.
Linear heterogeneous homopolymers and interpolymers can also be used as Component A in the blends of the present invention. Heterogeneous interpolymers are those in which substantially all of the interpolymer molecules do not have the same ethylene/comonomer ratio and have a broad composition distribution.
The term xe2x80x9cbroad composition distributionxe2x80x9d used herein describes the comonomer distribution for heterogeneous interpolymers and means that the heterogeneous interpolymers have a xe2x80x9clinearxe2x80x9d fraction and that the heterogeneous interpolymers have multiple melting peaks (i.e., exhibit at least two distinct melting peaks). The linear heterogeneous interpolymers and polymers also have a degree of branching less than or equal to 2 methyls/1000 carbons in about 10 percent (by weight) or more, preferably more than about 15 percent (by weight), and especially more than about 20 percent (by weight). The heterogeneous interpolymers also have a degree of branching equal to or greater than 25 methyls/1000 carbons in about 25 percent or less (by weight), preferably less than about 15 percent (by weight), and especially less than about 10 percent (by weight) of the total polymer.
The linear homogeneous and heterogeneous polymers and interpolymers used to make the novel polymer compositions used in the present invention can be ethylene homopolymers or interpolymers of ethylene with at least one C3-C20 xcex1-olefin. Preferred monomers include ethylene, 1-propene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene. Other preferred monomers include styrene, halo- or alkyl substituted styrenes, vinylbenzocyclobutane, 1,4-hexadiene, cyclopentene, cyclohexene and cyclooctene.
Component B
The branched polymers and interpolymers used as Component B in the blends of the present invention are defined herein as those that are partly or entirely homopolymerized or interpolymerized in autoclave or tubular reactors at pressures above 14,500 psi (100 MPa) with the use of free-radical initiators.
Such branched polymers and interpolymers, include, but are not limited to, low density ethylene polymers such as high pressure low density ethylene homopolymer (LPDE), ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer (EAA), ethylene-carboxylic acid copolymers and ethylene acrylate copolymers as well as olefin polymers produced at low to medium pressures such as polybutylene (PB).
Suitable high pressure ethylene interpolymers include ethylene interpolymerized with at least one, xcex1,xcex2-ethylenically unsaturated comonomers (for example, acrylic acid, methacrylic acid and vinyl acetate) as described by McKinney et al. in U.S. Pat. No. 4,599,392. Preferred high pressure ethylene interpolymers comprise from 0.1 to 55 total weight percent comonomer, and more preferably from 1 to 35 total weight percent comonomer, and most preferably from 2 to 28 total weight percent comonomer, and can be chemically and/or physically modified by any known technique such as, for example, by ionomerization and extrusion grafting.
Properties of the Blend Compositions of the Present Invention.
The blends of the present invention may be prepared by any suitable means known in the art such as, for example, dry blending in a pelletized form in desired proportions followed by melt blending in an apparatus such as a screw extruder or a Banbury mixer. Dry blended pellets may be directly melt processed into a final solid state article by, for example, extrusion or injection molding. The blends may also be made by direct polymerization without isolating blend components. Direct polymerization may use, for example, one or more catalysts in a single reactor or two or more reactors in series or parallel and vary at least one of operating conditions, monomer mixtures and catalyst choice. Blending the branched and linear resins at melt temperatures greater than 230xc2x0 C. may lead to a further increase in melt strength.
We have found, unexpectedly, that by blending certain branched polyethylene resins with higher density linear polyethylene resins, we obtain a resin blend of a certain melt index range with the necessary melt strength to permit foam production. This melt strength is synergistically much higher than that expected from a linear combination of the two components.
The melt strength of the blend meets the following relationship;
Melt strengthxe2x89xa7FMS*[(f*A)+((1xe2x88x92f)*B)] where:
A=3.3814*(I2)xe2x88x920.6476 and
B=16.882*(I2)xe2x88x920.6564
Where I2 is the measured melt index of the blend; f is the weight fraction of the linear polyethylene (Component A) in the blend.
FMS is a measure of synergy in melt strength in a blend. When FMS=1.0, the blend exhibits no synergistic improvement in melt strength with respect to the melt index of the blend. It is often observed that the blend melt index is unexpectedly low, which in itself leads to unexpectedly high melt strength. Thus the definition of synergy herein is very conservative and Fms greater than 1 always indicates a substantial level of synergy and unexpectedly high melt strength. When FMSxe2x89xa71, the blend is synergistic in that it shows greater melt strength than expected (or predicted) from a combination of linear and branched ethylenic polymers at the melt index of the blend.
For the blends of the present invention, FMS is xe2x89xa71.1, preferably xe2x89xa71.25, more preferably xe2x89xa71.5, even more preferably xe2x89xa72.0, most preferably xe2x89xa72.5.
The final melt index, I2, of the blend composition is from about 0.05 to about 20, preferably from about 0.1 to about 10, more preferably from about 0.2 to about 7, even more preferably 0.5 to 5 g/10 min.
The final melt strength of the blend composition is greater than or equal to 2 cN, more preferably greater than or equal to 7 cN, most preferably greater than or equal to 10 cN.
The final melt extensibility of the blend composition is greater than or equal to 25, preferably greater than or equal to 50, most preferably greater than or equal to 75 mm/sec.
The final flexural modulus of the blend composition is greater than or equal to 100,000 psi, more preferably greater than or equal to 120,000 psi and, most preferably greater than or equal to 130,000 psi.
In another embodiment, the final flexural modulus of the blend composition is less than or equal to 30,000 psi, preferably less than or equal to 25,000 psi and most preferably less than or equal to 20,000 psi.
For the blends with flexural modulus greater than or equal to 100,000 psi, the upper service temperature (UST) of the blends will be greater than about 115xc2x0 C., preferably greater than about 118xc2x0 C., more preferably greater than about 121xc2x0 C. and even more preferably greater than about 125xc2x0 C.
The melt index, I2, of Component A, is less than about 60 g/10 min, preferably less than about 30 g/10 min, more preferably less than about 15 g/10 min and most preferably less than about 10 g/10 min.
Suitable branched ethylenic polymers, Component B, include EVA, LDPE and EAA of melt index of 0.05-10 g/10 min. It is most preferable to use LDPE. For the blends with flexural modulus greater than or equal to 100,000 psi, Component A, should have a modulus greater than about 138,000 psi, preferably greater than about 164,000 psi, and more preferably greater than about 210,000 psi. It is most preferred that Component A be an ethylene homopolymer.
For the blends with flexural modulus less than or equal to 30,000 psi, Component A should have a modulus less than about 28,000 psi, preferably less than about 25,000 psi, more preferably less than about 22,000 psi.
The blends of the present invention may optionally comprise xe2x80x9cadditional polymersxe2x80x9d including one or more other thermoplastics to provide additional improvements in properties including but not limited to processability, upper service temperature, modulus, compressive strength, hardness, toughness, increased foam cell size, and aesthetics of the final foams or articles fabricated therefrom. Examples of the xe2x80x9cadditional polymersxe2x80x9d include, but are not limited to, low density polyethylene (LDPE), high density polyethylene (HDPE), linear low density polyethylene (LLDPE), ethylene styrene interpolymers (ESI), polypropylene (PP), polystyrene (PS), ethylene-propylene rubber and styrene-butadiene rubber. In one embodiment, the blends of the present invention may be further blended with alkenyl aromatic polymers (such as polystyrene) to make, for example, alkenyl aromatic polymer foams with increased cell size.
Applications of these blends include those in which melt strength, modulus and/or upper service temperature are key performance requirements, for example, non-crosslinked foams for cushion packaging, sports and leisure, building and construction, etc; non-crosslinked blowmolded articles; crosslinked foams for applications such as automotive; non-crosslinked foam bottle labels; films; fibers; wire and cable; and extrusion coatings.
The Foams of the Present Invention.
The present invention provides blends with flexural modulus above about 100,000 psi simultaneously with high melt strength and high melt extensibility at comparatively higher melt indices, therefore broadening the applicability of high modulus resins into foam structures and processes not previously attainable or viable with traditional linear or substantially linear polyethylene. It is not possible to achieve these MS, ME and MI combinations using linear polymers of flexural modulus of 100,000 psi or more. With a branched ethylenic polymer, it is possible to achieve the MS and ME but the flexural modulus will be 80,000 psi or less.
The present invention also provides blends with flexural modulus less than about 30,000 psi simultaneously with high melt strength and high melt extensibility at comparatively higher melt indices, therefore broadening the applicability of low modulus resins into foam structures and processes not previously attainable or viable with traditional linear polyethylene. It is not possible to achieve these melt strength, high melt extensibility and melt index combinations using linear polymers of flexural modulus of 30,000 psi or less. With a branched ethylenic polymer other than EVA, it is not possible to achieve the MS and ME and the flexural modulus will be greater than 30,000 psi. In the case of EVA such benefits only come with unacceptable additional properties such thermal instability, and odor.
The flexural modulus of these blends is higher than previously described in the prior art, giving greater stiffness and therefore greater compressive strength than existing compositions, yet with the required melt strength and melt extensibility to allow satisfactory fabrication into foams. The reduced amount of resin required in these foams results in economic and environmental advantages over current technology. At any given melt index, no previously described polyethylene provides the combination of melt strength, extensibility and modulus above about 100,000 psi as described in this invention.
To prepare commercially acceptable foams of any modulus, one needs to have a minimum melt strength of about 2 cN, preferably greater than about 7 cN and most preferably greater than 10 cN, and a minimum extensibility of about 25 mm/sec, preferably greater than about 50 mm/s and most preferably greater than about 75 mm/s. LDPE resins exhibit these properties but cannot yield the required modulus (greater than about 100,000 psi or alternatively less than 30,000 psi) or stiffness. HDPE or LLDPE resins can only achieve the required melt strength at a melt index (I2) less than 3 g/10 min, often  less than 1 g/10 min. This causes difficulties in foam processability, for instance, due to excessive shear heating.
This very high melt strength is a necessary requirement for successful foam production and is greater than that required of branched resins such as LDPE, and is not attainable at the same melt index and density with previously known branched polyethylenes. This is particularly true for the high modulus foams of the present invention, a result of the higher foaming temperature necessary due to the increased melting point of the higher density resin, and the increased amount of blowing agent required to create the lower density foam product, both of which tend to reduce the viscosity of the extrudate. Without the high melt strength, the foam would collapse due to collapse of the foam cell structure prior to solidification.
The foams will comprise 0.05 to 100, preferably 0.1 to 100 and most preferably 0.2 to 100 weight percent of the blend of Components A and B (based on total amount of polymers present in the foam).
The polymer compositions described above may be converted to foam products using physical and/or chemical blowing agents and any conventional process. Foam products include, for example, extruded thermoplastic polymer foam, extruded polymer strand foam, expandable thermoplastic foam beads, expanded thermoplastic foam beads or expanded and fused thermoplastic foam beads, and various types of crosslinked foams. The foam products may take any known physical configuration, such as sheet, round, strand geometry, rod, film, solid plank, laminated plank, coalesced strand plank, profiles and bun stock. The foam products may be converted into fabricated articles using any conventional process or method. For example, any one or more of expansion, coalescing and welding may be used in making such articles, especially from expandable foam beads. One may also mold expandable beads into any known configuration that employs foam products, including, but not limited to the foregoing configurations.
Foam forming steps of the process are known in the art. For instance as exemplified by the teachings to processes for making ethylenic polymer foam structures and processing them in C. P. Park. xe2x80x9cPolyolefin Foamxe2x80x9d, Chapter 9, Handbook of Polymer Foams and Technology, edited by D. Klempner and K. C. Frisch, Hanser Publishers, Munich, Vienna, New York, Barcelona (1991), which is incorporated here in by reference.
Foams of the present invention may be substantially noncrosslinked. That is, the foam structure contains 50 or less, preferably 40 or less, more preferably 30 or less, even more preferably 20 or less, most preferably 10 or less weight percent gel based upon the total weight of foam or polymer, as measured according to ASTM D-2765-84, Method A.
Alternatively, the polymer compositions could be used to make foams which are substantially cross-linked (that is, contain greater than 50 weight percent gel based upon the total weight of foam or polymer, as measured according to ASTM D-2765-84 Method A) by further addition of any known cross-linking agent. The various crosslinking agents and technologies are described in the art. Cross-linking may be induced by addition of a cross-linking agent. Induction of cross-linking and exposure to an elevated temperature to effect foaming or expansion may occur simultaneously or sequentially. If a chemical cross-linking agent is used, it is incorporated into the polymer material in the same manner as the chemical blowing agent. Further, if a chemical cross-linking agent is used, the foamable melt polymer material is heated or exposed to a temperature of preferably less than 150xc2x0 C. to prevent decomposition of the cross-linking agent or the blowing agent and to prevent premature cross-linking. If radiation cross-linking is used, the foamable melt polymer material is heated or exposed to a temperature of preferably less than 160xc2x0 C. to prevent decomposition of the blowing agent. The foamable melt polymer material is extruded or conveyed through a die of desired shape to form a foamable structure. The foamable structure is then cross-linked and expanded at an elevated or high temperature (typically, 150xc2x0 C.-250xc2x0 C.) such as in an oven to form a foam structure. If radiation cross-linking is used, the foamable structure is irradiated to cross-link the polymer material, which is then expanded at the elevated temperature as described above. The present structure can advantageously be made in sheet or thin plank form according to the above process using either cross-linking agents or radiation.
The term xe2x80x9ccross-linking agentxe2x80x9d as used herein means a compound or mixture of compounds used for the purposes of substantially crosslinking a polymer or polymer blend. The cross-linking agent used to prepare the foams and articles of the present invention include, but are not limited to peroxides, silanes, radiation, azides, phenols, aldehyde-amine reaction products, substituted ureas, substituted guanidines, substituted xanthates, substituted dithiocarbamates, sulfur-containing compounds, thiazoles, imidazoles, sulfenamides, thiuramidisulfides, paraquinonedioxime, dibenzoparaquinonedioxime, sulfur; and combinations thereof.
The various crosslinking technologies are described in U.S. Pat. No""s. 5,869,591 and 5,977,271, the entire contents of both of which are herein incorporated by reference. Dual cure systems, which use a combination of heat, moisture cure, and radiation steps, may be effectively employed. Dual cure systems are disclosed and claimed in U.S. Pat. No. 6,124,370, incorporated herein by reference. For instance, it may be desirable to employ peroxide coupling agents in conjunction with silane coupling agents, peroxide coupling agents in conjunction with radiation, sulfur-containing coupling agents in conjunction with silane coupling agents, etc.
The foam structures of the present invention are optionally made by a conventional extrusion foaming process. The structure is advantageously prepared by heating the polymer or blend to form a plasticized or melt polymer material, incorporating therein a blowing agent to form a foamable gel, and extruding the gel through a die to form the foam product. Depending upon the die (with an appropriate number of apertures) and operating conditions, the product may vary from an extruded foam plank or rod through a coalesced foam strand product, to foam beads and eventually to chopped strands of foamable beads. Prior to mixing with the blowing agent, the polymer material is heated to a temperature at or above its glass transition temperature or melting point. The blowing agent is optionally incorporated or mixed into the melt polymer material by any means known in the art such as with an extruder, mixer, blender, or the like. The blowing agent is mixed with the melt polymer material at an elevated pressure sufficient to prevent substantial expansion of the melt polymer material and to advantageously disperse the blowing agent homogeneously therein. Optionally, a nucleator is optionally blended in the polymer melt or dry blended with the polymer material prior to plasticizing or melting. Prior to extruding foamable gel through the die, one typically cools the gel to an optimum temperature. The foamable gel is typically cooled to a lower temperature to optimize physical characteristics of the foam structure. This temperature, often referred to as the foaming temperature, is typically above each component""s polymer glass transition temperature (Tg), or for those having sufficient crystallinity, near the peak crystalline melting temperature (Tm). xe2x80x9cNearxe2x80x9d means at, above, or below and largely depends upon where stable foam exists. The temperature desirably falls within 30xc2x0 centigrade (xc2x0 C.) above or below the Tm. For foams of the present invention, an optimum foaming temperature is in a range in which the foam does not collapse. The gel may be cooled in the extruder or other mixing device or in separate coolers. The gel is then extruded or conveyed through a die of desired shape to a zone of reduced or lower pressure to form the foam structure. The zone of lower pressure is at a pressure lower than that in which the foamable gel is maintained prior to extrusion through the die. The lower pressure is optionally superatmospheric or subatmospheric (vacuum), but is preferably at an atmospheric level.
In another embodiment, the resulting foam structure is optionally formed in a coalesced strand form by extrusion of the polymer material through a multi-orifice die. The orifices are arranged so that contact between adjacent streams of the molten extrudate occurs during the foaming process and the contacting surfaces adhere to one another with sufficient adhesion to result in a unitary foam structure. The streams of molten extrudate exiting the die take the form of strands or profiles, which desirably foam, coalesce, and adhere to one another to form a unitary structure. Desirably, the coalesced individual strands or profiles should remain adhered in a unitary structure to prevent strand delamination under stresses encountered in preparing, shaping, and using the foam. Apparatuses and method for producing foam structures in coalesced strand form are seen in U.S. Pat. Nos. 3,573,152 and 4,824,720.
Alternatively, the resulting foam structure is conveniently formed by an accumulating extrusion process and apparatus as seen in U.S. Pat. No. 4,323,528 and U.S. Pat. No. 5,817,705. This apparatus, commonly known as an xe2x80x9cextruder-accumulator systemxe2x80x9d allows one to operate a process on an intermittent, rather than a continuous, basis. The apparatus includes a holding zone or accumulator where foamable gel remains under conditions that preclude foaming. The holding zone is equipped with an outlet die that opens into a zone of lower pressure, such as the atmosphere. The die has an orifice that may be open or closed, preferably by way of a gate that is external to the holding zone. Operation of the gate does not affect the foamable composition other than to allow it to flow through the die. Opening the gate and substantially concurrently applying mechanical pressure on the gel by a mechanism (for example, a mechanical ram) forces the gel through the die into a zone of lower pressure. The mechanical pressure is sufficient to force foamable gel through the die at a rate fast enough to preclude significant foaming within the die yet slow enough to minimize and preferably eliminate generation of irregularities in foam cross-sectional area or shape. As such, other than operating intermittently, the process and its resulting products closely resemble those made in a continuous extrusion process.
In the accumulating extrusion process, low density foam structures having large lateral cross-sectional areas are prepared by: 1) forming under pressure a gel of the polymer or blend material and a blowing agent at a temperature at which the viscosity of the gel is sufficient to retain the blowing agent when the gel is allowed to expand; 2) extruding the gel into a holding zone maintained at a temperature and pressure which does not allow the gel to foam, the holding zone having an outlet die defining an orifice opening into a zone of lower pressure at which the gel foams, and an openable gate closing the die orifice; 3) periodically opening the gate; 4) substantially concurrently applying mechanical pressure by a movable ram on the gel to eject it from the holding zone through the die orifice into the zone of lower pressure, at a rate greater than that at which substantial foaming in the die orifice occurs and less than that at which substantial irregularities in cross-sectional area or shape occurs; and 5) permitting the ejected gel to expand unrestrained in at least one dimension to produce the foam structure.
The present foam structures may also be formed into foam beads suitable for molding into articles by expansion of pre-expanded beads containing a blowing agent. The beads may be molded at the time of expansion to form articles of various shapes. Processes for making expanded beads and molded expanded beam foam articles are described in Plastic Foams, Part II, Frisch and Saunders, pp. 544-585, Marcel Dekker, Inc. (1973) and Plastic Materials, Brydson, 5th ed., pp. 426-429, Butterworths (1989). Expandable and expanded beads can be made by a batch or by an extrusion process, and may be substantially non-crosslinked or substantially crosslinked.
The batch process of making expandable beads is similar to manufacturing expandable polystyrene (EPS). The resulting foam structure is formed into non-crosslinked foam beads suitable for molding into articles. Discrete resin particles, such as granules made from the blends of the present invention, made either by melt blending or in-reactor blending, are impregnated with a blowing agent (and optionally a cross-linking agent) in an aqueous suspension or in an anhydrous state in a pressure vessel at an elevated temperature and pressure. In the case of the aqueous supsension, the blowing agent (and, optionally, cross-linking agent) is/are introduced into the liquid medium in which the granules are substantially insoluble (such as water) at an elevated pressure and temperature in an autoclave or other pressure vessel. The granules are either discharged rapidly into an atmosphere or a region of reduced pressure to expand the granules into foam beads or cooled and discharged as unexpanded beads. In a separate step, the unexpanded beads are heated to expand them, for example, with steam or with hot air. This process for making bead foams is well taught in U.S. Pat. Nos. 4,379,859 and 4,464,484.
In a modification of the bead process, styrene monomer is optionally impregnated into the suspended pellets of the blend compositions of the present invention prior to their impregnation with blowing agent to form a graft interpolymer with the polymer material. The resulting interpolymer beads are cooled and discharged from the vessel substantially unexpanded. The beads are then expanded and molded by an expanded polystyrene bead molding process within the skill in the art. Such a process of making such polyethylene/polystyrene interpolymer beads is described for instance in U.S. Pat. No. 4,168,353.
A variation of the foregoing extrusion process readily yields expandable thermoplastic polymer beads. The method tracks with the conventional foam extrusion process described above up to the die orifice, which now contains one or multiple holes. The variation requires (a) cooling the foamable gel to a temperature below that at which foaming occurs, (b) extruding cooled gel through a die containing one or more orifices to form a corresponding number of essentially continuous expandable thermoplastic strands, (c) optionally quenching the strands exiting the die orifice in a cold water bath; and (d) and pelletizing the expandable thermoplastic strands to form expandable thermoplastic beads. Alternatively, the strands are converted to foam beads by cutting the strands into pellets or granules at the die face and allowing the granules to expand.
The foam beads can also be prepared by preparing a mixture of the polymer blend compositions of the present invention, cross-linking agent, and chemical blowing agent in a suitable mixing device or extruder and form the mixture into pellets, and heat the pellets to cross-link and expand.
In another process for making cross-linked foam beads suitable for molding into articles, the blends of this invention are melted and mixed with a physical blowing agent in a conventional foam extrusion apparatus to form an essentially continuous foam strand. The foam strand is granulated or pelletized to form foam beads. The foam beads are then cross-linked by radiation. The cross-linked foam beads may then be coalesced and molded to form various articles as described above for the other foam bead process. Additional teachings to this process are seen in U.S. Pat. No. 3,616,365 and C. P. Park, xe2x80x9cPolyolefin Foamxe2x80x9d, Handbook of Polymer Foams and Technology, edited by D. Klempner and K. C. Frisch, Hanser Publishers, Munich, Vienna, New York, Barcelona (1991), pp. 224-228.
The foam beads may then be molded by any means known in the art, such as charging the foam beads to the mold, compressing the mold to compress the beads, and heating the beads such as with steam to effect coalescing and welding of the beads to form the article. Optionally, the beads may be impregnated with air or other blowing agent at an elevated pressure and temperature prior to charging to the mold. Further, the beads may optionally be heated prior to charging. The foam beads are conveniently then molded to blocks or shaped articles by a suitable molding method known in the art. Some of the methods are taught in U.S. Pat. Nos. 3,504,068 and 3,953,558. Excellent teachings of the above processes and molding methods are seen in C. P. Park, supra, p. 191, pp. 197-198, and pp. 227-233, U.S. Pat. No. 3,886,100, U.S. Pat. No. 3,959,189, U.S. Pat. No. 4,168,353 and U.S. Pat. No. 4,429,059.
The present crosslinked foam structure may also be made into a continuous plank structure by an extrusion process utilizing a long-land die as described in GB 2,145,961A. In that process, the polymer, chemical blowing agent and cross-linking agent are mixed in an extruder, heating the mixture to let the polymer cross-link and the blowing agent to decompose in a long-land die; and shaping and conducting away from the foam structure through the die with the foam structure and the die contact lubricated by a proper lubrication material.
The present crosslinked foam structure may be made in bun stock form by two different processes. One process involves the use of a cross-linking agent and the other uses radiation.
The present crosslinked foam structure may be made in bun stock form by mixing the polymer compositions of this invention, a cross-linking agent, and a chemical blowing agent to form a slab, heating the mixture in a mold so the cross-linking agent can cross-link the polymer material and the blowing agent can decompose, and expanding by release of pressure in the mold. Optionally, the bun stock formed upon release of pressure may be re-heated to effect further expansion.
Foam may be made from cross-linked polymer sheet by either irradiating polymer sheet with high energy beam or by heating a polymer sheet containing chemical cross-linking agent. The cross-linked polymer sheet is cut into the desired shapes and impregnated with nitrogen in a higher pressure at a temperature above the softening point of the polymer; releasing the pressure effects nucleation of bubbles and some expansion in the sheet. The sheet is re-heated at a lower pressure above the softening point, and the pressure is then released to allow foam expansion.
Blowing agents useful in making the foam structures of the present invention include inorganic agents, organic blowing agents and chemical blowing agents. Suitable inorganic blowing agents include carbon dioxide, nitrogen, argon, water, air, sulfur hexafluoride (SF6) and helium. Organic blowing agents include aliphatic hydrocarbons having 1-9 carbon atoms, aliphatic alcohols having 1-3 carbon atoms, and fully and partially halogenated aliphatic hydrocarbons having 1-4 carbon atoms. Aliphatic hydrocarbons include methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane, neopentane. Aliphatic alcohols include methanol, ethanol, n-propanol, and isopropanol. Fully and partially halogenated aliphatic hydrocarbons include fluorocarbons, chlorocarbons, and chlorofluorocarbons. Examples of fluorocarbons include methyl fluoride, perfluoromethane, ethyl fluoride, 1,1-difluoroethane (HFC-152a), fluoroethane (HFC-161), 1,1,1-trifluoroethane (HFC-143a), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,2,2-tetrafluoroethane (HFC-134), 1,1,1,3,3-pentafluoropropane, pentafluoroethane (HFC-125), difluoromethane (HFC-32), perfluoroethane, 2,2-difluoropropane, 1,1,1-trifluoropropane, perfluoropropane, dichloropropane, difluoropropane, perfluorobutane, perfluorocyclobutane. Partially halogenated chlorocarbons and chlorofluorocarbons for use in this invention include methyl chloride, methylene chloride, ethyl chloride, 1,1,1-trichloroethane, 1,1-dichloro-1 fluoroethane (HCFC-141b), 1-chloro-1,1-difluoroethane (HCFC-142b), chlorodifluoromethane (HCFC-22), 1,1-dichloro-2,2,2-trifluoroethane (HCFC-123) and 1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124). Fully halogenated chlorofluorocarbons include trichloromonofluoromethane (CFC-11), dichlorodifluoromethane (CFC-12), trichlorotrifluoroethane (CFC-113), dichlorotetrafluoroethane (CFC-114), chloroheptafluoropropane, and dichlorohexafluoropropane. Chemical blowing agents include azodicarbonamide, azodiisobutyro-nitrile, barium azodicarboxylate, N,Nxe2x80x2-dimethyl-N,Nxe2x80x2-dinitrosoterephthalamide, and benzenesulfonhydrazide, 4,4-oxybenzene sulfonyl semicarbazide, and p-toluene sulfonyl semicarbazide, trihydrazino triazine and mixtures of citric acid and sodium bicarbonate such as the various products sold under the name Hydrocerol(trademark) (a product of Boehringer Ingelheim). Any of the foregoing blowing agents may be used singly or in combination with one or more other blowing agents. Preferred blowing agents include isobutane, carbon dioxide, HFC-152a, and mixtures of the foregoing.
The amount of blowing agent incorporated into the polymer melt material to make a foam-forming polymer gel is from 0.05 to 5.0, preferably from 0.2 to 3.0, and most preferably from 0.5 to 2.5 gram moles per kilogram of polymer.
Foams are optionally perforated to enhance or accelerate gaseous permeation exchange wherein blowing agent exits from the foam and air enters into the foam. The resulting perforated foams have defined therein a multiplicity of channels that are preferably free of direction with respect to the longitudinal extension of the foam. The channels extend from one foam surface at least partially through the foam, and sometimes completely through the foam from one external surface to another external surface. The channels are advantageously present over substantially an entire exterior foam surface, preferably with uniform or substantially uniform spacing. Suitable spacing intervals may be up to and including 2.5 centimeters (cm), preferably up to and including 1.3 cm. The foams optionally employ a stability control agent of the type described above in combination with perforation to allow accelerated permeation or release of blowing agent while maintaining a dimensionally stable foam. U.S. Pat. No. 5,424,016, U.S. Pat. No. 5,585,058, WO 92/19439 and WO 97/22455, provide excellent information relative to perforation. If desired, the foams of this invention may be post-treated by any known means to increase foam open cell content. Such post-treatment methods include, without limit, mechanically compressing the foam and expanding the foam by exposure to steam and/or hot air.
Foams of the present invention generally have a density less than 900, preferably less than 850, more preferably less than 800 kg/m3, even more preferably from 5 to 700 kilograms per cubic meter, and most preferably from 5 to 200 kilograms per cubic meter (in accordance with ASTM D3575-93, Suffix W, Method B). The foams may be microcellular (i.e, with a cell size from less than about 0.05 mm, preferably from about 0.001 mm, to about 0.05 mm) or macrocellular (i.e., cell size of about 0.05 mm or more). The macrocellular foam has an average cell size of about 0.05 to about 15, preferably from about 0.1 to about 10.0, and more preferably from about 0.1 to about 5 millimeters, preferably from about 0.2 to about 3 millimeters, and more preferably about 0.2 to about 2 millimeters as measured according to the procedures of ASTM D3576-77. The preferred ranges of density and cell size should not be taken as limiting the scope of this invention.
Foams of the present invention preferably exhibit excellent dimensional stability. Preferred foams retain 80 or more percent of their initial volume when measured one month after an initial volume measurement within 30 seconds after foam expansion. Volume is measured by any suitable method such as cubic displacement of water.
The foams of the present invention have an open cell content that ranges from 0 to 100 volume percent based on the total volume of foam, as measured according to ASTM D2856-94, depending upon component selection and process condition variations. Foams with an open cell content of 30 vol percent or less generally fall in a class known as closed cell foams. Those known as open cell foams typically have an open cell content greater than 30, preferably greater than 40, and more preferably greater than 50 vol percent. The open cell content is desirably 100 vol percent or less, preferably 95 vol percent or less, and more preferably 90 vol percent or less.
The foams of density less than 100 kg/m3 generally have an Asker-C hardness of xe2x89xa690, desirably xe2x89xa680, and preferably xe2x89xa670. Hardness measurements of the foams use an Asker C durometer for cellular rubber and yarn in accordance with ASTM D2240-97, using a 5 mm diameter spherical indentor.
If the foam is in the shape of a sheet or plank, it has a thickness that is generally xe2x89xa70.5 mm, preferably xe2x89xa71 mm and a width that is generally 25 mm, preferably xe2x89xa710 mm. As used herein xe2x80x9cthicknessxe2x80x9d of a foam plank or sheet refers to its smallest cross-sectional dimension (for example, as measured from one planar surface to an opposing planar surface). When the foam is present as a round or rod, it has a diameter that is generally xe2x89xa75 mm, preferably xe2x89xa710 mm.
The foam has a drop-test optimum C-factor (ASTM-D1596) of xe2x89xa66, desirably xe2x89xa65, and preferably xe2x89xa64.
Various additives may optionally be incorporated into the compositions or foams of the present invention. The additives include, without limitation, stability control agents, nucleating agents, inorganic fillers, conductive fillers, pigments, colorants, antioxidants, acid scavengers, ultraviolet absorbers or stabilizers, flame retardants, processing aids, extrusion aids, anti-static agents, cling additives (for example, polyiso-butylene), antiblock additives, other thermoplastic polymers. Certain of the additives, such as inorganic and conductive fillers, may also function as nucleating agents and/or open cell promoters for foams. Examples of antioxidants are hindered phenols (such as, for example, Irganox(trademark) 1010) and phosphites (for example, Irgafos(trademark) 168) both trademarks of, and commercially available from, Ciba Geigy Corporation.
The additives are advantageously employed in functionally equivalent amounts known to those skilled in the art. For example, the amount of antioxidant employed is that amount which prevents the polymer or polymer blend from undergoing oxidation at the temperatures and environment employed during storage and ultimate use of the polymers. Such amount of antioxidants is usually in the range of from 0.01 to 10, preferably from 0.02 to 5, more preferably from 0.03 to 2 percent by weight based upon the weight of the polymer or polymer blend. Similarly, the amounts of any of the other enumerated additives are the functionally equivalent amounts.
A nucleating agent is optionally added to control the size of foam cells. Preferred nucleating agents include inorganic substances such as calcium carbonate, talc, clay, titanium dioxide, silica, barium stearate, calcium stearate, diatomaceous earth, mixtures of citric acid and sodium bicarbonate, and the like. When used, the amount of nucleating agent employed advantageously ranges from about 0.01 to about 5 parts by weight per hundred parts by weight of a polymer resin.
In the manufacture of foams, a stability control agent (also known as permeability modifier) is optionally added to the present foam to enhance dimensional stability. Preferred agents include amides and esters of C10-24 fatty acids. Such agents are seen in U.S. Pat. Nos. 3,644,230 and 4,214,054. Esters may also reduce static during and after foam manufacture. Most preferred agents include stearyl stearamide, glyceromonostearate, glycerol monobehenate, and sorbitol monostearate. When used, such stability control agents are typically employed in an amount ranging from xe2x89xa70 to about 10 parts per hundred parts of the polymer.
The foams of the present invention may be used in any application where foams of comparable density and open or closed cell contents are used today. Such applications include, without limit, cushion packaging (for example, corner blocks, braces, saddles, pouches, bags, envelopes, overwraps, interleafing, encapsulation) of finished electronic goods such as computers, televisions, and kitchen appliances; packaging or protection of explosive materials or devices; material handling (trays, tote boxes, box liners, tote box inserts and dividers, shunt, stuffing, boards, parts spacers and parts separators); work station accessories (aprons, table and bench top covers, floor mats, seat cushions); automotive (headliners, impact absorption in bumpers or doors, carpet underlayment, sound insulation); flotation (for example, life jackets, vests and belts); sports and leisure or athletic and recreational products (for example, gym mats and bodyboards); egg cartons, meat trays, fruit trays, thermal insulation (such as that used in building and construction for wall sheathing, roofing, foundation insulation and residing underlayment); acoustical insulation (for example, for appliances and building and construction); pipe insulation, insulation for refrigeration, buoyancy applications (e.g., floatintg docks and rafts), floral and craft products, pallets, luggage liners, desk pads, footwear (including shoe soles), insulation blankets for greenhouses, case inserts, display foams, gaskets, grommets, seals; sound attenuation for printers and typewriters; display case insert; missile container padding; military shell holder; blocking and bracing of various items in transport; preservation and packaging; automotives anti-rattle pads, seals; medical devices, skin contact pads; cushioned pallet; and vibration isolation pad. The foregoing list merely illustrates a number of suitable applications. Skilled artisans can readily envision additional applications without departing from the scope or spirit of the present invention.
In another aspect, the polymer compositions of this invention may be used to make foamed films. The film of the present invention may be a monolayer or a multilayer film. One or more layers of the film may be oriented or foamed. A multi-layer film of the present invention may contain one, two or more layers comprising a blend as defined herein. In one embodiment, the film according to the invention has a thickness of 0.5 to 100 mils. Preferably, the present invention pertains to a tough and stiff film, comprising the blends of this invention. The film of the invention may be printed. The film of the invention is obtainable according to methods known in the art. The film may be made using a blown or a cast film extrusion process, including co-extrusion and extrusion coating. One or more layers of the film may be expanded, for example with a conventional blowing agent, to make foamed film. One or more films may be laminated to form a multi-layer structure. Preferred are two-layer or three-layer films with one or two surface layers and the foamed layer being the core layer. The surface layers may or may not comprise the blends of this invention. In a three layer structure, preferably, the foamed layer is the core or middle layer. The films may be (further) oriented after forming via tenter frame, double-bubble or other blown film techniques.
Foamed film is especially suitable for use as label or in thermoformable articles of manufacture. To make foamed film structures, either physical or chemical blowing agents may be used. A multilayer film of the invention comprising one or more foamed layers comprising the polymer compositions as defined herein is obtainable according to methods known in the art, for example, using a co-extrusion process.
The label film may be constructed from printed, slit to width, rolls of film with the labels glued to a container, for example a bottle, using conventional adhesives and glues known to the industry. In addition, the films of this invention may be printed, coated with pressure sensitive adhesives, laminated to release papers or films and applied to bottles, containers or other surfaces by conventional pressure sensitive techniques. The bottle may be a glass bottle or a PET bottle. Covering or affixed to a glass bottle, the label may also serve a protective purpose. If the bottle is a PET bottle, the preferred label is a wrap-around label.
The foregoing list merely illustrates a number of suitable applications. Skilled artisans can readily envision additional applications without departing from the scope or spirit of the present invention.

Blends of ethylenic polymers with improved modulus and melt strength and articles fabricated from these blends

Abstract: A blend which comprises;

Abstract: xe2x80x83wherein said blend has;

Abstract: 3) a melt strength of xe2x89xa72 cN;

Abstract: xe2x80x83I2 is the measured melt index of the blend; f is the weight fraction of the linear polyethylene in the blend and FMS is xe2x89xa71.1. Also included in the present invention are foams, films, fibers, blow molded articles, wire and cable articles and extrusion coatings comprising said blend.