Ink jet printer dispersion inks are provided which contain a dispersant having basic or acid groups and a non-destabilizing amount of a neutralizer for said groups. The inks exhibit improved non-wetting characteristics leading to lengthening of the duration of periods of continuous printing that can be achieved before cleaning or replacement of the nozzle plate of the ink jet print head is required.

This invention relates to ink jet printer dispersion inks.
In ink jet printing, a fluid ink is forced under pressure, and sometimes at elevated temperature, through a very small nozzle in a printing head. In one kind of printer, known as a xe2x80x9ccontinuousxe2x80x9d printer, ink droplets which are produced continuously are passed through a charging area where individual droplets receive an electrical charge in response to a signal and are directed towards a substrate to be printed. The droplets then pass through an electrical field causing them to be deflected by an amount which is dependent on the intensity of the charge and the field. Droplets not required to form print on the substrate are directed to a by-pass gutter. Inks for use in such printers need to be conductive.
In another kind of printer, known as a xe2x80x9cdrop-on-demandxe2x80x9d (DOD) printer, the ink droplets are expelled from the nozzle of a print head only when required during the printing process. Drop-on-demand printers can use an electrostatically accelerated ink jet or droplet sequences ejected by pressure impulse actuation. In the latter kind of DOD printer, each drop of ink is individually ejected from a nozzle by means of pressure pulses induced e.g. by use of a piezo-electric actuator acting on the ink in the channel supplying the nozzle or by generation of a vapour bubble in response to a thermal pulse.
In general, there are two classes of ink for use in such ink-jet printers, namely solvent inks in which the colourant, usually a dye, is dissolved in a solvent, and dispersion inks wherein the colourant, i.e. pigment, is dispersed in a diluent. The present invention is concerned with the latter class.
One particular problem that is encountered with continuous printing with an ink jet printer is that a small amount of the tail of the droplet being ejected tends to separate from the droplet and collect on the surface of that part of the area of the nozzle plate immediately surrounding the nozzle. In general, provided the surface energy of the plate is sufficiently low this ink deposit will simply recede into the nozzle and be ejected as part of a later droplet; however as the frequency of droplet ejection is increased, there is less opportunity for the ink to recede before ejection of the next droplet and a pool of ink commences to form on the surface of the nozzle plate the size of which can increase until it reaches a level at which it, or airborne dust or other contaminant which is attracted to the thus- wetted nozzle plate, interferes with droplet ejection and prevents reliable operation of the printer. The problem is further exacerbated by the trend towards increasing the number of nozzles per unit area of the nozzle plate and thus reducing internozzle spacing. Moreover any residue of ink on the nozzle plate surface can be disadvantageous where different coloured inks are being used because of the risk of contaminating one colour with another. It thus becomes necessary from time to time to clean the face of the nozzle plate, e.g. by wiping. This is undesirable because it means interrupting the printing run and because repeated wiping of the nozzle plate face can damage its surface.
Improved treatment of the relevant part of the surface of the nozzle plate of the printhead to reduce its surface energy, e.g. by provision of a so-called non-wetting coating e.g. of fluorocarbon or fluorosilane, can substantially reduce the problem and increase the duration of acceptable operation before cleaning or replacement of the nozzle plate is required; however, with commercial demands for ever increasing reliability and reduced down time for servicing, still further improvement would be welcomed and therefore the applicants have addressed not only the nature of the surface of the printhead nozzle plate but also the nature of the ink.
One class of inks which has proved particularly attractive for their print quality and performance is dispersion inks. Of particular interest are those which employ an ionic dispersant, more preferably a macromolecular polyionic dispersant, to improve the stability of the disperse phase. Ionic dispersants, as the term is used herein, describes dispersants comprising molecules having acid or basic groups, and macromolecular polyionic dispersants, as the term is used herein, comprise large molecules, e.g. oligomers or polymers, sometimes of imprecisely known size or structure, carrying a large number of either acidic or basic groups, eg. in the form of repeating units having acid or basic groups in the polymeric or oligomeric structure.
Ink jet printers employing dispersion inks based on ionic dispersants can produce excellent print reliability for substantial periods; however, a still further improvement in their performance, and in particular the duration of the periods of continuous printing that can be achieved before cleaning, eg. wiping, or replacement of the nozzle plate of the ink jet print head, would be desirable.
We have now found in accordance with the present invention that such an improvement may be obtained by including in the ink a non-destabilising amount of a compound (hereinafter referred to as a neutraliser) containing at least one group capable of neutralising the acidic or basic groups, respectively, of the dispersant. Moreover, when using the ink in an ink jet printer head of a drop-on-demand printer, greater negative ink supply pressure can be withstood without ingesting air and greater short term positive pressure surges, eg. due to acceleration or deceleration of the print head on ashuttle, can be tolerated without flooding.
As the amount of dispersant included in a dispersion ink is increased from zero, we have found from earlier work that the viscosity of the ink decreases until it reaches a minimum and then commences to increase again and that the optimum amount of dispersant from the point of view of overall properties of ink is approximately that which results in the minimum viscosity or slightly in excess thereof; e.g. from 100% to 200% of that amount, and more generally from 100% to 150% of that amount. This generally equates to about 0.1 to 1, more usually about 0.1 to 0.7 part, per part of pigment, by weight. While not wishing to be bound by this theory, it is believed that at this concentration of dispersant, the acidic or basic groups provided by the dispersant are in excess of those required to stabilise the dispersion of pigment in the diluent and that the excess increases the ability of the ink to wet a surface. In any event, it has been found that adding a small proportion of a compound containing a moiety or moieties capable of neutralising the acidic or basic groups of the dispersant increases the speed with which the ink deposit left by the droplet on the surface of the nozzle plate recedes into the nozzle and thus reduces the risk of forming a pool on the surface of the nozzle plate. A direct indication of this property can be obtained by measuring the dewetting or receding meniscus velocity (RMV) of the ink on a surface.
For a discussion of dewetting velocity and its measurement, reference is made to the article by Redon et al in Physical Review Letters, Vol 66, No. 6, Feb. 11, 1991, pages 715-718.
While the invention will be illustrated by reference to non-aqueous inks it is believed that it is generally applicable to both aqueous and non-aqueous inks. Particular attention, however, has been given to inks wherein the diluent is non-aqueous or substantially non-aqueous (that is to say, it contains less than 2% water by weight), and has a low polar solubility parameter, e.g. of not greater than 7.0 MPaxc2xd. References herein to polar solubility parameter are to the values obtained according to the method of Hansen, C. M. and Skaarup, K., Journal of Paint Technology, 39 No. 51, pp. 511-514 (1967) as detailed by Patton, T.C. xe2x80x9cPaint Flow and Pigment Dispersionxe2x80x9d 2nd Ed., Wiley Interscience, 1979. Particular examples of non-aqueous diluents with a low polar solubility parameter eg. a polar solubility parameter of 7.0 MPaxc2xd or less, are non-polar organic solvents and mixtures thereof with polar solvents, e.g. containing a minor amount by weight, preferably 5 to 40% by weight, of polar solvent or solvents. Examples of polar solvents are alcohols, esters including mixtures such as marketed under the trade name Coasol, ketones and, especially, ethers, particularly mono- and di-alkyl ethers of glycols and polyglycols, e.g. monomethyl ethers of mono-, di- and tri-propylene glycols and the mono-n-butyl ethers of ethylene, diethylene and triethylene glycols. Examples of suitable non-polar solvents are aliphatic and aromatic hydrocarbons having at least six carbon atoms and mixtures thereof including refinery distillation products and by-products.
While diluents with a low polar solubility parameter are preferred, other diluents, e.g. consisting essentially of polar constituents, may be used. The diluent, which should be single phase, preferably has the following properties:
Boiling point: at least 100xc2x0 C., preferably at least 200xc2x0 C.;
Viscosity: not greater than 30 mPas, preferably not greater than 15 mPas, more preferably not greater than 12 mPas measured at 30xc2x0 C. using a Bohlin CS Rheometer with CP4/40 measuring system;
Freezing point: not more than 10xc2x0 C., preferably not more than 7xc2x0 C.;
Polar solubility parameter: up to 7 MPaxc2xd, more preferably 0.1 or 0.2 to 2 MPaxc2xd.
Particular examples of diluents are aliphatic hydrocarbon solvents such as those sold under the trade names Exxsol, Solvesso, Exxon naphtha, Isopar, Pegasol and Shellsol, mixtures of such solvents with alcohols, especially long chain alcohols, e.g. containing 535 wt.% alcohol, and mixtures of such solvents with alcohols, especially long chain alcohols, and ethers, e.g. containing 90 to 45% by weight of the hydrocarbon. By a long chain alcohol we mean an alcohol containing at least 10, eg. 10 to 30, carbon atoms. In general, the diluent will form from 60 to 98.5%, and preferably from 75 to 90%, by weight of the ink.
While the invention is applicable to any inks containing dispersants having acid or basic groups and capable of stabilising the dispersion of the chosen pigment in the chosen diluent, it is particularly applicable to inks containing macromolecular polyionic dispersants. It is preferred that the dispersant is soluble in the diluent or is so highly solvated that the mixture of diluent and dispersant is substantially indistinguishable from a true solution. Examples of dispersants for use in non-aqueous diluents such as organic solvents e.g. having a polar solubility parameter less than 7 MPaxc2xd are polyester amine dispersants such as those sold by Zeneca Colours under the trade name SOLSPERSE and dispersants sold under the trade name EFKA. Mixtures of dispersants may also be used.
Any suitable pigment may be used provided it will form a stable dispersion in the chosen diluent. Examples are phthalocyanines, quinacridones, Lithol Rubine 4B toners, isoindolinones, and Rhodamine G lakes (triphenyl methane derivatives). Preferred pigments are found amongst those characterised as pigment dyes in The Colour Index. Preferably the pigment will be of a primary subtractive hue. The pigment should be lightfast, and thermally stable even with repeated warming. Carbon blacks may also be used. The appropriate concentration of pigment will depend upon its nature but in general will be in the range of from 2 to 20%, preferably from 4 to 15%, by weight of the ink.
The nature of the active group of the neutraliser will depend upon whether the dispersant has acidic groups or basic groups. For example, where the dispersant is a polyamine, the neutraliser is suitably an acid. Any suitable acid may be employed as a neutraliser provided it is compatible with the ink and preferably soluble in the diluent; examples are Lewis acids, inorganic acids, organic acids and phenols. The neutraliser may also be a small molecule or a polymer. Examples are organic carboxylic acids such as acetic, citric, tartaric, toluic and xcex2-naphthoic; organic sulphonic acids such as 2-naphthalene sulphonic and p-toluene sulphonic; simple phenols, e.g. resorcinol and 2-naphthol; alkyl phenols e.g. nonyl phenol; alkyl partial esters of acids of phosphorus, e.g. phosphoric acid and phosphinic acid; and polymeric compounds containing phenolic groups, for example novolaks, e.g. having the repeating units containing the following structure:
where R is an alkyl group e.g. as in butyl or octyl, e.g. Uravar FN5.
Where the dispersant contains acidic groups, the neutraliser may suitably be an amine.
The most suitable neutraliser for a given ink and the amount required, which will depend on its nature and its equivalent weight, can best be determined by simple experiment, e.g. by plotting concentration against the value obtained for the RMV of the resultant ink. In general, even a small amount of neutraliser will provide an improvement and increasing the amount increases the RMV up to a maximum after which further increases in the amount of neutraliser employed may result in a reduction in the RMV. However, an amount, which will vary with the nature of the compound employed, will eventually be reached at which the ink will be destabilized; that is to say, sedimentation and/or an increase in viscosity is detected in the ink within 28 days of standing at 25xc2x0 C. This amount is generally about equal to that which yields the maximum value for RMV and thus the preferred amount of neutraliser is generally in the range of about 25 to 100%, more preferably 50 to 95%, of that which yields the maximum RMV value.
The dispersion inks according to the invention may be made by a method including the steps of (a) forming a stable dispersion comprising colourant, a dispersant having basic or acidic groups, and a diluent; and thereafter (b) adding a non-destabilising amount of neutraliser.
The invention is now illustrated by the following Examples in which all parts are expressed as parts by weight except where otherwise indicated.


A pallet assembly includes an upper deck and a lower deck spaced by a plurality of columns. The weight of the pallet is reduced without significant reduction in strength by providing only a single cross beam in each of the upper and lower reinforcement members and orienting them perpendicular to one another. The reinforcement members are minimized for weight reduction and for improved performance in heat tests. The peripheral rail of the upper reinforcement member is reduced such that it rests on only an inwardly open recess on an inner corner of each of the corner columns. This reduces the size and weight of the upper reinforcement member, while still providing support to the upper deck. Additionally, the peripheral rails of both the upper and lower decks are reduced in length such that either ledge does not directly support them while the pallet is stored on a rack. As a result, in the case of sufficient heat source on the pallets, the pallets will eventually collapse without interference from the reinforcement members and at least partially smother the heat source.

The present invention relates to a pallet assembly and more particularly to a plastic pallet with reinforcement members.
Pallets are often used to store and transport goods. Pallets maintain the goods at a distance above the floor such that they can readily be lifted and moved by a forklift. Plastic pallets are lighter and more durable than wooden pallets. Elongated metal or composite reinforcement members have been used in some plastic pallets in order to increase the stiffness and load-bearing capacity of the pallet.
Some pallets comprise upper and lower decks separated by a plurality of columns that maintain the space between the upper and lower decks. The pallets may have reinforcement bars sandwiched between two layers in the upper deck or the lower deck. Traditionally, the reinforcement bars were straight bars inserted into the upper deck. One pallet previously developed by the assignee of the present invention includes reinforcement members with a frame or peripheral rail extending continuously and completely about the outer periphery of the deck and a pair of perpendicular cross beams connected to the peripheral rail. The cross beams are centered on the columns for support and the peripheral rail is also either centered on the columns or positioned outwardly of center of the columns.
It is desirable to minimize the number of components of the pallet and minimize the weight of the pallet while retaining the rigidity of the pallet. Additionally, some plastic pallets are evaluated for their performance under Underwriters Laboratories, Inc. (UL) Standard 2335, which, in part, evaluates the heat release performance of plastic pallets while stored on racks having inwardly extending ledges upon which the pallets are supported. Ways have been sought to manufacture the pallets of fire-retardant materials.


A refrigeration unit for a shipping container exposed to end loads and rack loads. The refrigeration unit has a frame, a back panel, a plurality of structural support brackets secured to the back panel, a condenser cover secured to the plurality of structural support brackets so that the condenser cover, the plurality of structural support brackets, the frame, and the back panel form a structural member sufficient to support end loads and rack loads. The refrigeration unit also has a condenser coil having a first end and a second end, a first coil support member secured to one of the structural support brackets and secured around the first end, and a second coil support member secured to one of the structural support brackets and secured around the second end. The first and second coil support members maintain the condenser coil unstressed from the end loads and rack loads.

1. Field of the Invention
The present disclosure is related to refrigeration units. More particularly, the present disclosure is related to refrigeration units for use with shipping containers.
2. Description of Related Art
Shipping containers are used for many purposes including storage and transportation of various types of goods. The shipping containers can be transported from one location to another, e.g. from a manufacture site to a desired location, via a variety of modes of transportation. For example, containers can be loaded on a truck or train. Or, in situations where goods need to be transported across bodies of water, for example international trade, the containers can be loaded onto ships. On the ships, the containers are usually stacked upon each other. Therefore, it is essential that containers be sturdy enough to withstand both rack loads and end loads to prevent the containers from crushing and damaging the goods. Rack loads are forces that are exerted on a container when containers are stacked upon one another. End loads are the forces exerted on a container due to the shifting of cargo.
Many of the goods that are stored and transported in containers require refrigeration systems. As such, it is common for refrigeration units to be attached to containers in order to preserve the goods. In most cases, containers and the associated refrigeration units are designed so that the refrigeration unit plays an essential role in the structure of the container. Typically, the condenser coils are made of very durable materials, such as copper and copper tube sheets, and are very strong. It is the condenser coil specifically that when attached to the frame plays an integral role giving structure and support to the container.
Accordingly, it has been determined by the present disclosure that there exists a need for a refrigeration unit that is designed so that the condenser coil is not a factor in the strength of the container so that smaller, lightweight coils can be used.

Refrigeration unit with integrated structural condenser coil support


The invention relates to a process for dewatering sewage sludges using plate filters, wherein the flocculated sewage sludge treated by means of organic polymer flocculation aids and optionally other auxiliary agents is separated from the major amount of water of the flocculated sewage sludge on a plate filter by means of hydrostatic filtration, whereafter the partially dewatered sewage sludge is subjected to pressure filtration. The plate filters employed have filtrate outlet systems permitting filtrate discharge at a flow rate of 1.0 m/s at maximum. By conducting the process in this way, the dewatering capacity is substantially increased.

The invention relates to a process for dewatering sludges, preferably municipal sewage sludges in sewage treatment with rapid pressure filters, particularly chamber filter presses and membrane filter presses, using water-soluble polyelectrolytes as flocculation aids in sludge conditioning.
In addition to agricultural utilization, the obligatory disposal of sewage sludges is effected by thermal treatment of the sewage sludge with combustion or degassing and gasification, and predominantly via landfill.
Sewage sludges represent compositions including exceedingly high levels of water, so that both in landfill and in thermal processes, the solids content of the sludge is increased by at least one mechanical dewatering stage, preferably using screen belt presses, centrifuges or pressure filtration. Particularly in improving such dewatering on filter presses, the sludge preconcentrated by thickening has to be conditioned by means of an additional treatment. To this end, the sewage sludge is flocculated using organic, polymeric flocculation aids, preferably high molecular weight cationic polyelectrolytes, and subsequently subjected to dewatering in a batchwise procedure using chamber filter presses or membrane filter presses.
According to EP-B-19176, dewatering can be performed in two steps. Initially, the flocculated sludge is subjected to dewatering in a screening drum or on separate screening belts and collected in an intermediate container, subsequently fed into the chamber filter press using a piston membrane pump or an eccentric screw pump, and filtrated under a pressure of up to 15 bars. Owing to the previous dewatering, this process is remarkable for its shorter batch times in the chamber filter press. However, this advantage is compensated by the measures and time required for the first step of the process.
In gfw-wasser/abwasser 126 (1985), pp. 124-130, V. Zees, T. Clausdorf and G. Gerardts make the supplementary statement that following sludge conditioning and removal of supernatant water, only limited dewatering of the flocculated sludge in the chamber filter press is possible because no sufficient stability of the flocs is achieved for this purpose.
According to K. J. Thomxc3xa9-Kozmiensky, Klxc3xa4rschlammentwxc3xa4sserung, TK-Verlag K. J. Thomxc3xa9-K., Neuruppin, 1998, p. 266, polymer conditioning of sewage sludge for dewatering on filter presses is advantageous only in those cases where high demands with respect to shear strength are not made.
Therefore, a dewatering process is known according to EP-A-151,747 wherein the flocculent is metered to the conveyed amount of sludge as a function of sludge density and the sludge thus pretreated is fed directly into the chamber filter press. With pressure times of 3 hours, a dewatered sewage sludge having a dry matter content of 30-40 wt.-% is achieved in the press discharge.
However, this procedure involves the disadvantageous process that the water which is difficult to remove from the sludge flocs is not predominantly withdrawn during pressure filtration and also, those amounts of water in the flocculated sludge mixture already made free of turbidities by flocculation undergo filtration through a developing layer having a filtering effect and compacting under pressure exposure. Consequently, this dewatering process on chamber filter presses which is widely used for sewage sludges involves considerable technical and economical drawbacks.
DE-OS-38 20 110 describes a process wherein the conditioning of sewage sludge is performed using at least two organic polymer flocculation aids having low and high molecular weights, respectively. Again, partial dewatering of the flocculated sludge is possible upstream the chamber filter press.
According to WO 88/03048, previous dewatering is effected on screen belts arranged in a story-like fashion, by means of which the sludge is conveyed to a sludge silo without the use of pumps.
Furthermore, a process is known according to U.S. Pat. No. 4,861,492, wherein sewage sludge is flocculated using polymeric flocculation aids, sedimented, and subsequently held in a rest phase without mechanical load for at least 2 minutes. Thereafter, the supernatant waste water is decanted, and the thickened sludge is subjected to dewatering in a rapid pressure filter with additional flocculant aid. This process requires additional equipment-related input for decanting, as well as time and means to stabilize the flocculated state.
In another process, according to Chem. Ing. Techn. 66, No. 9 (1994), pp. 1222, 1223, the sewage sludge previously added with flotation coal and ashes is subjected to a pressure flocculation in a pressure-resistant flocculation reactor; the flocculated sludge is to reach the filter press without further mechanical stress, and minimum filter drag throughout the feeding cycle is to be ensured.
In 44th Purdue Industrial Waste Conference Proceedings, 1990, Lewis Publishers, Inc., Chelsea Mich. 48118, 1989 (1990), pp. 513-518, J. T. Shah reports on the possibilities of optimizing the dewatering process on chamber filter presses by stepwise pressure increase during the dewatering process, thus enabling an increase of the filter cake solids content.
DE 93 07 712 U1 describes a special design of a sludge dewatering press wherein the pressurized air used in secondary pressing subsequently is utilized to blow out the dewatered sludge. By using this sludge dewatering press, the high consumption of pressurized air is intended to be reduced.
DE 93 20 903 U1 describes a filtering means for liquids, particularly swimming pool water, where the liquid to be filtrated is sucked out of a container over filtering elements with precoat filter layer. The design of this filtering means is intended to improve the cleaning operation, i.e., removal and disposal of the consumed filtering aid, and reduce the amount of water required for this purpose.
DE 36 17 519 A1 describes a process and a device for removing residual impurities from a pre-clarified potable liquid, wherein a filter press having precoated layers of filtering aids is used. Here, the structure of the regeneratable layer of filtering aids is regarded as crucial to the invention, precoating with said layer of filtering aids being effected at a specific flow rate. Filtration in the filter press is performed under pressure as usual.
DE 41 19 167 A1 describes a method of determining the characteristics and parameters essential for the sizing and dimensioning of filter presses, as well as a device for performing said method. It is a measuring procedure wherein a hydrostatic pressure corresponding to the previous filtration pressure is applied in the filter chamber, which hydrostatic pressure is continuously monitored in order to detect the pressure drop characteristic of completion of the filtration process.
U.S. Pat. No. 5,275,740 describes a method and a device for controlling the sludge pressure in a filter press and, in particular, for controlling the final pressure of the stepwise and automatic filtration cycles in order to have simultaneous optimization of the press feeding process and to maintain a constant pump pressure. In this case as well, filtration is effected in the press under pressure and in a way previously known from prior art.
JP 07124600 A describes a process and a device for the treatment of organic sludges, wherein the organic sludge initially is flocculated using an organic polymer flocculant and subsequently subjected to dewatering on a filter press using gravity filtration, i.e., solely by the hydrostatic pressure of sludge supplied to the filter press.
Depending on type and amount of organic and mineral components, municipal sludges exhibit diverse, frequently varying properties affecting the dewatering behavior, particularly during flocculation of dispersed solids by means of organic flocculation aids and during filtration. Particularly in the dewatering of municipal sludges on chamber filter presses, the individual operations of the process therefore have to be optimized and balanced. In addition to selecting suitable flocculation aids and apparatus, the dewatering process consequently is controlled by computer-controlled systems where the flocculation aid is metered to the sewage sludge pump at the pressure or suction side, and flocculation is optimized using a floc probe and mixing energy control. Also, with currently common initial feed capacities of 0.15-0.30 m3 of sludge per m2 filter area and hour, conveying of sludge to feed the chamber filter press during the filling phase and the pressure filtrationxe2x80x94the latter taking a prolonged period of timexe2x80x94is controlled electronically in a way so as to avoid an excessively rapid pressure increase by means of control, because such an increase would give rise to massive, irreversible compacting of the developing filter cake, thereby affecting the dewatering process. At present, the sludge dewatering capacity of such a process is 6 m3 of sludge per m3 filter volume and hour or 0.09 m3 of sludge per m2 filter area and hour at maximum.
Accordingly, the well-known dewatering processes are characterized in that a dynamic pressure is generated in the system even by sludge conveying of the pumps during the first phase of filtration, which pressure is increased by an augmenting filtration drag caused by simultaneous compacting of the developing filter cake as a result of this process.
Accordingly, the well-known dewatering processes on chamber filter presses involve process operations of complicated structure, which also are expensive because these processes have to performed separately and in multiple stages.
It was therefore the object of the present invention to find a straightforward process for dewatering sewage sludge or other sludges, which process would meet the requirements of improved technical conditions and reduction in costs. In particular, the object was to find a process for removing the water which is contained in the sewage sludge after polymer conditioning and free of dispersed solids without impairing the shear stability of the flocculated sewage sludge, and without the other drawbacks encountered when performing separate process steps. The object is supplemented by the additional aspect of optionally improving the plate filters as well, namely, in a way so as to be suitable in performing an improved dewatering process, preferably for improving the plate filter feeding process.
According to ATV-Handbuch Klxc3xa4rschlamm, Ernst and Sohn Verlag Berlin, 4th edition, 1996, pp. 357 and 358, the chamber filter presses currently employed are constructed in such a way that the filtrate free of solids is discharged via filtrate discharge channels or collecting channels in the plate assembly at the bottom and, towards the end of filtration, at the top as well. With high specific throughput capacities, the hydraulic conditions in the filtrate discharge channels, characterized as drags, represent a limitation, i.e., a bottleneck according to Abwassertechnik No. 2, 1991, pp. 44-48.
According to the ATV manual referred to above, chamber filter presses having open filtrate outlets are also well-known, where the filtrate is discharged from the separate plates through lateral outlets, normally on one side. Particularly due to malodors caused by digester gas or ammonia in an optionally required lime conditioning, such chamber filter presses are not used in sewage sludge dewatering.
It has now been found that dewatering of sewage sludge can be improved considerably according to the process specified in claim 1 where the sewage sludge is subjected to conditioning using at least one organic flocculation aid and optionally other auxiliary agents, and the treated and flocculated sewage sludge is introduced into the plate filterxe2x80x94also referred to as filter press hereinbelowxe2x80x94which is a chamber filter press or a membrane filter press or a frame filter press. Therein, hydrostatic filtration is effected, removing the major amount of water from the treated, flocculated sewage sludge, whereafter the partially dewatered sewage sludge is subjected to pressure filtration. At least 50 wt.-%, preferably at least 60 wt.-%, more preferably at least 70 wt.-% of the water is removed in the first step of the hydrostatic filtration.
The invention is based on the finding that, in a hydrostatic filtration of flocculated sewage sludge, the amount of water of the flocculated sewage sludge mixtures which is largely free of non-dispersed solids can easily be removed in a plate filter by introducing the flocculated amount of solids together with the amount of water into the chamber filter press wherein these amounts are subjected to said straightforward filtration without equipment-related pressure load.
According to the invention, it has also been established that, compared to the conventional filter press feeding operation, the amount of flocculated sludge conveyed to the filter press can be substantially increased in the initial phase of the filtration process, i.e., during hydrostatic filtration.
In performing the process of the invention, filter presses are used that are provided with filtrate discharge channels permitting filtrate discharge at a flow rate of 1.0 m/s at maximum. Thus, in particular, plate filters (filter presses) are used where the filtrate can be discharged through filtrate outlets having large cross-sectional areas, or plate filters having open filtrate outlets or open filtrate outlet systems comprised of single outlets and/or discharge manifolds and optionally other outlet elements, so that each filtrate can discharge at a flow rate of 1.0 m/s at maximum. Such plate filters are well-known but have been used for other purposes until now.
Furthermore, plate filters having closed filtrate outlets can be modified in a way so as to have open filtrate outlets exclusively or partially or additionally, so that the specified value of the filtrate flow rate would not be exceeded. For example, another improvement of the process according to the invention is achieved by optionally enlarging the cross-section of the filtrate collecting channels formed by the corner borings of the plates in the plate assembly, and/or by providing additional openings in least part of the filter plates, preferably in the lower lateral section of the filter plates, in the vicinity of the filtrate outlets that are present. Optionally, the discharging filtrate can be passed through open pipes or grooves arranged on the outlet openings. According to the invention, plate filters according to DE 197 07 167 A1 are also used in this process.
On the whole, short filtration times and high flow rates of sewage sludge, as well as filtrates free of solids are to be achieved in the batchwise dewatering of sewage sludge on filter presses. According to the process of the invention, conveying of the flocculated sewage sludge during the feeding phase is performed at an initial feed capacity of at least 0.3 m3 sludge per m2 filter area and hour, preferably in a range of 0.35-0.70, and more preferably in a range of 0.40-0.60 m3 sludge per m2 filter area and hour. The specified capacity range inevitably results from the flocculation behavior and the flocculation properties of the sewage sludge and the process-related and equipment-related situation resulting therefrom.
In addition, the process offers the advantage of conveying the flocs of sewage sludge and the water to the filter press in a gentle fashion. Towards the end of the feeding phase, the amount of flocculated sewage sludge undergoes compacting in the filled chambers as a result of the hydrostatic filtration, thereby generating a pressure increase throughout the filter press system. During the next phase of pressure filtration, the feed capacity is reduced to values in a range of below 0.3 m3 sludge per m2 filter and hour and down to a selected lower value, the so-called turn-off value, with maximum pressure values ranging from 10 to 20 bars, preferably from 10 to 15 bars being adjusted in the plate filter.
The dewatering process according to the invention is suitable for municipal and/or industrial sludges having solids levels ranging from 0.5 to 15 wt.-%. Primary, excess and activated sludges, as well as mineralized and preferably, digested sludges, as well as mixtures thereof are employed as municipal sludges. The sludges, normally preconcentrated in a concentrator, are subjected to conditioning by treatment with organic polymer flocculation aids, optionally with addition of inorganic and/or organic builder substances such as lime, iron salts, ashes, filter dust, coal fines, and finely divided parts of plants, such as sawdust or chopped straw or mixtures thereof. Water-soluble and/or largely water-soluble, partially crosslinked polymers, co- and terpolymers of water-soluble non-ionogenic and/or ionic monomers and comonomers are used as organic flocculation aids in the form of a powder, as an aqueous solution, or as a water-in-water dispersion, or as a water-in-oil dispersion. Such polymers are homo-, co- and terpolymers of monoethylenically unsaturated monomers having acid groups present at least in part as salts, or their esters with di-C1-2-alkylamino-C2-6-alkylalcohols or their amides with di-C1-2-alkylamino-C2-6-alkylamines present in a protonated or quaternized form, such as described in EP-A 113,038 and EP-A 13,416, and optionally other monoethylenically unsaturated monomers.
Preferably, homo- and/or copolymers of monoethylenically unsaturated carboxylic acids and sulfonic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, crotonic acid, and/or their alkali salts, preferably sodium, potassium or ammonium salts, vinylsulfonic acid, acrylamidoand methacrylamidoalkylsulfonic acids, such as 2-acrylamido-2-methylpropanesulfonic acid, 2-sulfoethyl methacrylate and styrenesulfonic acid and/or their alkali salts, preferably sodium, potassium or ammonium salts are suitable as anionic polyelectrolytes, and also, vinylphosphonic acid and styrenephosphonic acid, as well as their alkali salts, preferably sodium, potassium or ammonium salts.
Preferably, cationically active flocculants, e.g. homo- and/or copolymers and/or terpolymers of water-soluble, monoethylenically unsaturated vinyl compounds, such as acrylic acid esters and methacrylic acid esters of dialkylaminoalkylalcohols in protonated or quaternized form, such as dimethylaminoethyl acrylate, acrylic acid amides and methacrylic acid amides of dialkylaminoalkylamines in protonated or quaternized form, such as acrylamidopropyltrimethylammonium chloride and/or acrylamidopropyltrimethylammonium methylmethosulfate are employed, preferably together with acrylamide. Copolymers which can be used according to the invention are also described in EP-B-228,637.
The copolymers can be formed of ionic monomers and non-ionogenic, water-soluble, monoethylenically unsaturated monomers, such as acrylamide, methacrylamide, N-C1-2-alkylated (meth)acrylamides, and also with N-vinylamide, vinylformamide, N-vinylacetamide, N-vinyl-N-methylacetamide, N-vinylpyrrolidone. In addition, suitable water-soluble monomers are N-methylolacrylamide, N-methylolmethacrylamide, as well as N-methylol(meth)acrylamides partially or completely etherified with monohydric C1-4 alcohols, and diallyldimethylammonium chloride.
Likewise, the copolymers may include limited amounts of ethylenically unsaturated monomers sparingly soluble and/or insoluble in water, such as (meth)acrylic acid alkyl esters and vinyl acetate, as long as the solubility or swellability of the copolymers in water is retained.
In addition, the polymers can be produced using at least bi-reactive monomers, preferably diethylenically unsaturated monomers, so as to have swellability in water or limited solubility therein, or, they may be comprised of water-soluble and water-swellable polymers.
According to the invention, water-soluble or water-swellable amphiphilic copolymers formed of cationic and anionic monomers and optionally non-ionogenic monomers may also be employed.
The flocculation aid is selected using flocculation and dewatering tests on sewage sludges on a laboratory and pilot plant scale. The agents are employed in the form of a 0.05-0.5% aqueous practical solution.
In total, the process according to the invention achieves sludge dewatering capacities of 0.1-0.175 m3 sludge per m2 filter and hour, or more than 6 m3, preferably 6-12 m3 sludge per m3 filter volume and hour.
Furthermore, the procedure of the process according to the invention is characterized by the advantage of short batch times. A short time period of a filter press feeding phase is followed by a pressure filtration phase which is massively reduced in time compared to conventional processes, the time period of which being reduced to 50-20%, preferably 35-25%, relative to the previous pressure filtration time, with comparable values of dry solids content in the filter cake in either case, which range from 30 to 42 wt.-% in the process of the invention when exclusively using organic polymer flocculation aids.
The process according to the invention preferably is performed on chamber filter presses or membrane filter presses, the membrane filter presses achieving additional advantages, particularly a further reduced batch time, as well as a further increased dry solids content. Relative to the filter area per plate level, the size of the filter plates used in the process of the invention is at least 1 m2, preferably 1-6 m2, more preferably 1-4 m2, corresponding to filter plate dimensions of from 1.0xc3x971.0 m to 2.0xc3x972.0 m, for example.
Moreover, the dewatering process of the invention is characterized in that the sewage sludge is flocculated by said conditioning and partially dewatered during hydrostatic filtration in such a way that feeding of the plate filter with sludgexe2x80x94largely in a controlled fashion at presentxe2x80x94can be cut down or optionally omitted because the major amount of sludge is introduced into the filter chambers during the hydrostatic filtration.

Method of dewatering slurries using leaf filters (filter presses)


The invention relates to a pyrotechnical composition which is intended both for a hybrid gas-generating material and for a purely pyrotechnical gas-generating material for use in gas-actuated car safety devices, and which comprises a first obligatory constituent in the form of 5-95 wt % of guanyl urea dinitramide and a second obligatory constituent in the form of 5-50 wt % of an oxidizing agent (calculated on the total amount of solids), together withxe2x80x94if it is necessary to increase the rate of burningxe2x80x94a combustion moderator in the form of 0-90 wt % of guanidine dinitramide or up to 10 wt % of finely divided metallic boron, as well as up to 10 wt % of a binder. The pyrotechnical composition according to the invention is characterized e.g. by a low pollutant emission, low smoke formation, and the fact that its rate of burning can be adjusted to suit any type of car safety device by varying the ratio between the constituents within the limits specified in the invention.

The function of pyrotechnical gas-generating substances used in air-bag assemblies is to fill the fabric pouch of the air bag with a gas quickly, in order to provide a flexible protecting medium between the passenger and the equipment in the car. Pyrotechnical gas-generating substances and the gas formed by them must meet a number of requirements in order to ensure that the air-bag assembly works properly and reliably, and that the environment is not harmed. The same requirements are also placed on the pyrotechnical gas-generating substances used in other gas-actuated safety devices fitted in cars, such as safety-belt tighteners, inflatable neck supports, etc.
Thus, the gas formed in all such car safety devices should not contain any hot solid particles that could burn through the main part of the system and set fire to the gas-filled fabric pouch and injure the passengers or jeopardize the entire operation of the safety device. Sodium azide, the most common pyrotechnical gas-generating substance used for this purpose nowadays, does not fully meet this requirement and must therefore be employed with specially reinforced fabric pouches to stop the penetration of the solid particles formed in the combustion of sodium azide. The need for this extra reinforcement means that such a safety device is larger and heavier than strictly necessary for its operation.
Furthermore, the environmental requirements placed on the pyrotechnical gas-generating substances used for the purpose in question stipulate that these substances must not form gaseous mixtures that contain poisonous gases in an amount that is harmful to health. The poisonous gases that are mainly relevant in this context because they are formed in the combustion of gas-generating substances are nitrogen oxides (NOx) and carbon monoxide. If the gas-generating substance contains chlorine, then hydrochloric acid is also formed.
Furthermore, the pyrotechnical gas-generating substances used in a gas-actuated car safety device must have a high efficiency, i.e. they should form a large amount of gas per unit weight or volume of the gas-generating substance. However, the efficiency of sodium azide is not particularly high, since it only forms gas in an amount of about 40% of the solid substance. This low efficiency makes it difficult to meet the car manufacturers, requirement of car safety devices with a low weight and a small size when sodium azide is employed as a gas-generating substance. The main reason why sodium azide is still so widely used is that no better gas-generating substance has yet been found.
A further requirement placed on pyrotechnical gas-generating substances is that they should all be thermally stable in the sense that they should not be affected much by the high temperatures that can occur in the dashboard in countries with a warm climate. Nitrocellulose is an example of a substance that does not meet this requirement, but which might otherwise be suitable, and in fact it is used nowadays for this purpose, although it limits the service life of the car safety devices in question.
In addition to the above requirements, the product used in car safety devices as a pyrotechnical gas-generating substance must also meet several requirements concerning its combustion characteristics if a fully satisfactory operation is to be ensured. Thus, the ideal pyrotechnical gas-generating substance in this connection should have a high rate of burning and one that does not vary much with the pressure or the temperature. Sodium azide is an ideal substance from this point of view, but it has several disadvantages, as mentioned above.
There is another group of substances that generate gases when combusted and which have been tried as gas-generating materials for car safety devices. This group comprises nitramine-based gunpowder analogue compositions such as RDX, which are used e.g. in a mixture with cellulose acetyl butyrate. However, the disadvantage of nitramine-based gunpowder analogues is that their rate of burning depends on the pressure to a large extent. If the pressure is too low, the burning is completely extinguished, while if the pressure is too high, the combustion has an explosive course. According to U.S. Pat. No. 5,695,216, these disadvantages can be corrected by constructing a powerful container for the gas-generating substance and equipping the container with decompression means. However, even though this works (and works very well), the construction still requires extra parts and costs more.
The developments in the field of gas-actuated car safety devices therefore show that it is very difficult to find a completely ideal gas-releasing substance for this purpose.
The aim of the present invention is to solve this problem by using a substance that is completely new, at least in the context of gas-actuated safety devices and whichxe2x80x94especially if combined with one or more other well-defined substances in accordance with the specific rules given belowxe2x80x94provides a gas-generating composition (material) for the present purpose, that has almost optimum combustion characteristics and exhibits several other useful properties, described below, irrespective of whether the gas generators used with it are of the hybrid type or not. However, the mixing ratio of the substances according to the invention does depend to some extent on the type of safety device in question and on the protective function envisaged for it.
The first of the pyrotechnical gas-generating substances according to the invention, which is also the main component of the material according to the invention, is guanyl urea dinitramide (GUDN), which has the following chemical formula.
Guanyl urea dinitramide is relatively easily prepared by reacting guanyl urea with ammonium dinitramide. Pure guanyl urea dinitramide burns much less fast than sodium azide. In the pure form, its combustion is fairly independent of the pressure and temperature, and it stable even at a low pressure. Furthermore, guanyl urea dinitramide scores over sodium azide by burning entirely without forming any solid particles, due to its good intrinsic oxygen balance. In addition, it is thermally stable, with a melting point of over 160xc2x0 C., and a decomposition temperature of 180xc2x0 C.
As its structural formula shows, guanyl urea dinitramide has an extra carbon atom, which means that it must be burned with an oxygen excess to ensure that no carbon monoxide persists as a residual product. The necessary oxygen excess can come from a solid substance that forms part of the pyrotechnical gas-generating material releasing a gas on its combustion, or else it can come to various extents from a substance supplied in the gaseous phase. This latter is the case with a xe2x80x9chybridxe2x80x9d gas-generating material, which comprises both a pyrotechnical gas-generating part (releasing a gas during its combustion) and a gaseous component that is supplied in the form of a compressed gas from the beginning. The oxygen excess can then be partly provided by this gaseous component, which can be e.g. pure oxygen or nitrous oxide (N2O), also called xe2x80x9claughing gasxe2x80x9d. The oxygen-rich component is thus the second constituent according to the present invention. When this second component is a solid substance, it can be chosen from one or more of the following three groups of substances:
Group 1: nitrates, perchlorates and permanganates of alkali metals
Group 2: oxides of iron, nickel, cobalt and metals in the manganese group
Group 3: oxides of the transition metals in Groups 7-12 of the Periodic Table.
However, the rate of burning of pure guanyl urea dinitramide is so much lower than that of sodium azide even in the presence of an oxygen excess that in certain cases it can be too low for some of the applications in question. However, it closely resembles chemically another substancexe2x80x94guanidine dinitramide (GDN)xe2x80x94which has been proposed for a similar purpose before and which has a considerably higher rate of burning. This makes both these substances particularly suitable for use as each other""s combustion moderators for regulating the rate of burning of their mixtures with each other. By mixing these two substances it has therefore been possible to prepare gas-generating materials with a rate of burning suitable for each particular purpose. Guanidine dinitramide is thus the third component according to the present invention, even if it is an optional component, which can be omitted when there is no need for a particularly high rate of burning.
Guanidine dinitramide, which has the following chemical formula, can be relatively easily prepared from guanidine and ammonium dinitramide.
Pure guanidine dinitramide burns very fast even at a low pressure, and its combustion is not very pressure-dependent, having a pressure exponent of about 0.8. At atmospheric pressure, guanidine dinitramide burns faster than nitrocellulose and almost as fast as sodium azide. A significant advantage over sodium azide is, furthermore, that guanidine dinitramide does not form any solid combustion products but is instead fully converted into gases on combustion. This means in turn that, when guanidine dinitramide is used as a gas-generating substance in air-bag assemblies, no extra reinforcement is needed for the gas pouches in order to prevent the substance from burning through them. This fact enables the designers of such car safety devices to reduce the weight and size of the latter without jeopardizing their operation. Moreover, guanidine dinitramide only contains one carbon atom, so that advantageously little carbon monoxide is formed in its combustion. In addition, guanidine dinitramide has an ideal thermal stability, with a melting point in excess of 130xc2x0 C. and a decomposition temperature of over 160xc2x0 C.
A way of increasing the rate of burning of guanyl urea dinitramide, if necessary, is therefore to admix guanidine dinitramide to it in amounts ofxe2x80x94if necessaryxe2x80x94up to 90 wt %, calculated on the total composition.
Anotherxe2x80x94previously unknownxe2x80x94way of increasing the rate of burning of guanyl urea dinitramide in an oxygen excess is to add small amounts of finely divided metallic boron, which then replaces guanidine dinitramide and is needed in considerably smaller amounts. Suitable amounts of boron acting as a combustion moderator are up to 10 wt % and preferably in the range 0.5-3 wt %. The addition of boron in this range makes it possible to fully replace guanidine dinitramide, while guanyl urea dinitramide remains the main gas-generating substance. Apart from the advantage of being able to use a relatively small amount of boron, the combustion curve for the mixture becomes even less pressure-dependent, and its temperature dependence is very low.
Both guanyl urea dinitramide (GUDN) and guanidine dinitramide (GDN) are finely crystalline substances with a normal particle size of under 100 mesh. With their normal crystallite size they can be pressed into shapes and have a good mechanical strength in the pressed form. This also applies in general when these compounds are used in mixtures with other finely divided substances. In most cases, it should therefore be appropriate to use either the pure substances or their mixtures with each other, in the form of pressed tablets. If required, a binder used in a small amountxe2x80x94preferably not more than 10 wt %, calculated on the total amount of solidsxe2x80x94may be added to confer an even better mechanical strength on the pressed tablets. Especially certain solid oxidizing agents may call for the addition of a binder.
The main component (guanyl urea dinitramide) and the optionally added substance (guanidine dinitramide) according to the invention have the further advantage that, when they finish their service life as potential gas-generating substances in a car safety device, which hopefully has not seen active use, they can be easily recovered for re-use as gas-generating substances in a similar or a different product.
When preparing new chemicals nowadays, it is essential to bear in mind, for environmental reasons, how they can be recovered and re-used. Yet none of the materials employed nowadays as gas-generating substances in car safety devices can be recovered in a simple manner when they have come to the end of their service life without active use. Besides, as these car safety devices are products that preferably should not see active service, it can be expected that the number of unused units of such gas-generators that have to be collected after the vehicles equipped with them are scrapped will increase at the rate at which these safety devices are installed in new cars.
Sodium azide, which is nowadays used in car safety devices on a large scale, is in fact always employed in a mixture also comprising Fe2O3 and silicates, and no effective way of re-using these substances is known today. Furthermore, sodium azide is very toxic, which is another reason why it must be destroyed as soon as possible when the car safety device incorporating it has reached the end of its service life. Similarly, nitrocellulose cannot be re-used either, because it is unstable and decomposes in the course of time. The only practical method of destroying nitrocellulose collected from scrapped products is therefore exactly the same as in the case of sodium azide, i.e. incineration.
By contrast, guanyl urea dinitramide and guanidine dinitramide are uniform and stable crystalline products that can furthermore be easily recrystallized. If despite everything they undergo decomposition to some extent, they can still be re-used after recrystallization. The fact is that this process removes any decomposition products, and so the recrystallized compound is entirely comparable with the newly produced one. A further advantage is that these two compounds can be recrystallized from water without the use of solvents. This possibility of recovering and recycling the gas-generating substances from scrapped car safety devices of the kind considered here has of course significant environmental benefits in comparison with the currently customary azides and nitrocellulose-based gunpowder analogues, which must always be destroyed by incineration.
Guanyl urea dinitramide is fairly insoluble in cold water, is not hygroscopic but moderately soluble in warm water, whereas guanidine dinitramide is moderately soluble in water at room temperature. Both compounds can therefore be recrystallized from water at a low temperature. This is a particularly simple and cheap process, which should make it possible to recover and re-use the gas-generating substances from non-deployed scrapped air-bag assemblies and other similar pyrotechnically actuated car safety devices.
As mentioned before, the present invention relates to a composite gas-generating material for car safety devices, as mentioned before. According to the invention, this gas-generating material comprises a first obligatory component in the form of guanyl urea dinitramide (GUDN), which can be complemented by the optional gas-generating substance, guanidine dinitramide (GDN), if a higher rate of burning is required. Guanidine dinitramide is used in a relatively large amount (see later), but it can be advantageously replaced according to the present invention by a considerably smaller amount of finely divided boron. In addition, an oxygen source (Component C), chosen from one or more of the above groups 1-3, is incorporated as an obligatory component. However, in the case of hybrid gas-generating materials, part of this oxygen source can be replaced by gaseous oxygen, as mentioned before.
The invention therefore consists of a gas-releasing pyrotechnical substance with the following composition, formulated for use in car safety devices:
5-95 wt % of guanyl urea dinitramide (GUDN)
5-50 wt % of a solid oxygen source (Component C)
if a higher rate of combustion is required
0-90 wt % of guanidine dinitramide (GDN)
or 0.5-10 wt % of finely divided metallic boron, together with not more than 10 wt % of a possibly combustible binder, calculated on the total solid composition.
Furthermore, the oxygen source (Component C) can be replaced by an oxygen-rich gaseous substance to various extents, as described below.
The invention therefore also stipulates that the amount of the solid oxygen-rich substance (Component C) should be 5-15 wt % and preferably of t he order of magnitude of 10 wt %, calculated on the total amount of solid substances when mixtures of guanyl urea dinitramide (GUDN) and guanidine dinitramide (GDN) are used as gas-generating substances in a hybrid gas-generating composition. The remaining oxygen requirement is then provided by the compressed gas component of the hybrid gas-generating composition.
However, the situation is somewhat different when mixtures of guanyl urea dinitramide and boron are used as the main gas-generating substances in hybrid gas-generating compositions. The fact is that it has been found that in such a case an amount of up to 50 wt % and preferably 30-40 wt % of an oxygen-rich so lid component is needed (calculated on the total solids) in order to ensure the maxi mum combustion of the resulting carbon monoxide into carbondioxide, and the remaining oxygen requirement is then again supplied by the compressed gas component of the hybrid gas-generating composition. The reason for this difference between the various mixtures is that guanidine dinitramide has a better oxygen balance than guanyl urea dinitramide.
The present invention also stipulates that the combustion of the gas-generating material always takes place in an oxygen excess, and it has been found that this has a favourable effect on the pressure exponent during the combustion.
The pyrotechnical gas-generating material according to the invention produces very little smoke when combusted, so that when it burns and the air bag assembly is released, one never gets the impression that a fire has started in the car, as happened before with air bag assemblies operating e.g. with sodium azide.
Another advantage of the pyrotechnical composition according to the present invention is that harmful residual products like NOx and CO are formed in small amounts during the combustion. The usual requirement in the automobile sector is that the amount of carbon monoxide should not exceed 400-600 ppm and the amount of nitrogen oxides should not exceed 50-70 ppm in a car interior of 2.5 m3. This can be achieved without difficulty when the pyrotechnical substances according to the present invention are used.
The invention is specified in the Claims and explained in more detail in the following Examples, where:

Composite gas-generating material for gas-actuated car safety devices


Process for making butyraldehyde from an n-butenyl ester of a carboxylic acid, wherein the n-butenyl ester is hydrolyzed to form the corresponding n-butenyl alcohol n-butenyl alcohol so produced is isomerized to form butyraldehyde.

The present invention relates to a process for making butyraldehyde by hydrolysing an n-butenyl ester to form the corresponding n-butenyl alcohol and isomerising the latter to form butyraldehyde.
It is known that butyraldehyde can be produced by a number of routes. For instance, U.S. Pat. No. 5,705,707 discloses a method of making n-butyraldehyde and/or n-butanol by reacting butadiene with an alcohol in the presence of an acidic catalyst. The reaction produces a mixture of isomeric adducts, 1-alkoxybutene-2 (a) (also known as crotyl ether) and 3-alkoxybutene-1 (b):
CH3.CHxe2x95x90CH.CH2.ORxe2x80x83xe2x80x83(a)
CH2xe2x95x90CHCH(OR).CH3xe2x80x83xe2x80x83(b)
Compound (b) can be isomerised into compound (a). Compound (a) is isomerised in the presence of a homogeneous or heterogeneous transition metal catalyst to form the enol ether of the formula (c):
CH3CH2CHxe2x95x90CHORxe2x80x83xe2x80x83(c)
Ether (c) reacts with water to liberate butyraldehyde. This hydrolysis reaction is catalysed by acids and bases. The butyraldehyde product can be hydrogenated with suitable homogeneous or heterogeneous catalysts to yield n-butanol. Thus compound (c) in the presence of water and hydrogen and a homogeneous or heterogeneous catalyst produces butanol and the parent alcohol ROH. The parent alcohol can then be recycled to the addition reaction stage.
A similar isomerisation hydrolysis reaction has been repeated with amines in DE-A-4431528. This document describes a process for the production of butyraldehyde which comprises the addition of an amine to a butadiene. The reaction produces a mixture of isomers, CH3CHxe2x95x90CHCH2NR2 and CH3CH(NR2)CHxe2x95x90CH2. The CH3CH(NR2)CHxe2x95x90CH2 isomer is recycled back to the addition reaction, whilst the CH3CHxe2x95x90CHCH2NR2 isomer is converted to the corresponding enamine, CH3CH2CHxe2x95x90CHNR2. This enamine is hydrolysed to produce butyraldehyde for possible further processing and also liberates the initial amine for re-use. The butyraldehyde may be hydrogenated to the corresponding alcohol, if desired. The process of DE-A-4431528 is summarised in the diagram below:
The selectivity of the above processes has been found to be limited by the formation of by-products. Such by-products include C8 and higher species formed, for example, by dimerisation and oligomerisation reactions of C4 species. In the process of DE-A-4431528 , by-products may also be produced by amine catalysed aldol condensation reactions of butyraldehyde.
We have now found that the selectivity of the butyraldehyde production process can be increased by forming butyraldehyde from a butenyl ester.
Accordingly, the present invention provides a process for making butyraldehyde from an n-butenyl ester of a carboxylic acid, said process comprising i) hydrolysing the n-butenyl ester to form the corresponding n-butenyl alcohol and ii) isomerising the n-butenyl alcohol produced in step i) to form butyraldehyde.
By xe2x80x9cisomerisingxe2x80x9d is meant performing any process which results in the direct or indirect conversion of the n-butenyl alcohol to butyraldehyde.
Steps i) and ii) may be carried out simultaneously or sequentially. Whilst carrying out steps i) and ii) simultaneously may allow the process to be operated more economically, the sequential hydrolysis and isomerisation stages may increase the selectivity of the overall process.
Step i) may also be carried out before step ii). Thus, in one embodiment of the present invention, n-butenyl ester is first hydrolysed to form n-butenyl alcohol, which is conveniently separable from the hydrolysis mixture as an azeotrope. The separated n-butenyl alcohol is then isomerised into the butyraldehyde product.
Preferably, the n-butenyl ester is an n-butenyl ester of a saturated, aliphatic carboxylic acid.
In the present process, the n-butenyl ester (also known as xe2x80x9ccrotyl esterxe2x80x9d) may not be readily available commercially. Instead it may be produced by reacting butadiene with a saturated, aliphatic carboxylic acid. As butadiene is a relatively inexpensive by-product of the refining process, it provides a convenient feedstock for making butyl esters. Thus, a preferred embodiment of the present invention provides a process for the production of butyraldehyde which comprises:
a) the addition reaction of butadiene to a carboxylic acid to produce a mi)cture of sec-butenyl ester and n-butenyl ester; and
b) (i) hydrolysing the n-butenyl ester formed in step a) to form the corresponding n-butenyl alcohol, and (ii) isomerising of the n-butenyl alcohol produced in step bi) to form butyraldehyde.
Steps (i) and (ii) may be carried out simultaneously or sequentially.
The diagram below summarises the reactions which may take place in this preferred embodiment of the invention.
In step a), butadiene is reacted with a carboxylic acid Rxe2x80x2CO2H in the presence of an addition catalyst, catalyst 1. Catalyst 1 may be a homogeneous or heterogeneous catalyst. Heterogeneous catalysts may be advantageous in certain situations as they facilitate separation of, for example, reaction products from the reaction mixture. They may also allow the catalyst to be conveniently separated from reaction by-products (which typically comprise high boiling point butadiene oligomeric species). The preferred catalysts are based on strong acid ion-exchange resins, such as Amberlyst 15(copyright) and Amberlite IR120(copyright). Other suitable examples of heterogeneous catalysts include fluorinated ion-exchange resins such as Nafion(copyright), phosphoric acid functionalised polymers, and acidic oxides, for example, HY zeolites.
A proportion of the acidic sites of such ion-exchange catalysts may be exchanged with bulky counterions, such as alkyl pyridinium, quaternary alkyl ammonium, quaternary arsonium and quaternary phosphonium. These counterions exchange with some of the acid sites on the support and can be added to the catalysts as salts, such as halides, sulphates or carboxylates.
The heterogeneous catalyst phase may be a partially or fully insoluble liquid phase. Such catalysts may take the form of acidic ionic liquids, liquid acidic polymers and partially solvated polymers. The catalyst may also be a solid phase, for example, I) an HY zeolite, II) a strong acid macroreticular, macronet or gel ion-exchange resin, or III) a heteropolyacid of tungsten or molybdenum, which has been ion-exchanged and/or supported on a carrier material.
In certain circumstances, the activity of heterogeneous catalysts may decrease considerably after prolonged periods of use. In such cases, it may be advantageous to carry out the process of the present invention in a homogeneous phase. Suitable homogeneous catalysts include sulphonic acids, heteropolyacids, triflic acid (i.e. trifluoromethane sulphonic acid) and triflate salts. Suitable heteropolyacids include Keggin structure heteropolyacids based on tungsten, and strong acid ionic liquids such as those described in prior published EP-A-693088, WO-A-95/21872 and EP-A-558187. Suitable organic sulphonic acids include methane sulphonic acid, p-toluenesulphonic acid and sulphonated calixarenes. Examples of triflate salts include lanthanide triflates, such as lanthanum trifluoromethanesulphonic acid salts.
The presence of water as a reaction adjuvant can also beneficially affect the activity and selectivity of the catalysts. It has been found that moderately low levels of water are required: at levels above 5%w/w the catalyst activity is significantly reduced, whereas at levels below 0.05%w/w, the activity though high is rapidly lost due to deactivation of the catalyst. Consequently the water level in the reaction zone is suitably in the range from 0.05 to 5%w/w on the carboxylic acid, preferably from 0.05 to 1%w/w.
The butadiene feedstock may be employed either as a purified chemical, or in the form of a hydrocarbon stream comprising butadiene. Such hydrocarbon streams include refinery streams such as mixed C4 streams containing butadiene, as well as other C4 species such as butane, 1-butene, 2-butene, isobutane, and isobutene. The addition reaction (step (a)) can be used to remove butadiene from such hydrocarbon streams, thereby avoiding the need to remove butadiene in a separate processing stage.
The butadiene employed may be dissolved in the reaction mixture, or introduced into the reactor as a gaseous reactant. In certain embodiments, the reaction is carried out in multi-phase, with butadiene being present in the liquid reaction mixture, and as a gaseous phase.
The carboxylic acid (RCO2H) feedstock suitably comprises any saturated carboxylic acid feedstock. Dicarboxylic acids such as succinic acid may be employed, although mono-carboxylic acids, and in particular, aliphatic mono-carboxylic acids are generally preferred. Suitable mono-carboxylic acids comprise 1-6 carbon atoms. Preferably, the acid is acetic acid.
The relative mole ratios of butadiene to the carboxylic acid reactant in the addition reaction is suitably in the range from 5:1 to 1:50, preferably in the range from 1:1 to 1:10.
This addition reaction is suitably carried out at a temperature in the range from 20 to 150xc2x0 C., preferably from 40 to 90xc2x0 C. The reaction is suitably carried out at the autogeneous reaction pressure which is determined by factors such as the reaction temperature, presence of absence of solvent, excess of reactants and impurities present in the butadiene stream. An additional pressure may be applied to the system if the reaction is carried out in a single phase, for example, if substantially all the butadiene present is present in the liquid phase in the reaction mixture.
It may also be advantageous to use polymerisation inhibitors such as eg alkylated phenols such as 2,6-di-tert-butyl-p-cresol (also known as xe2x80x9cBHTxe2x80x9d or butylated hydroxytoluene). Other related compounds include the Irganox(copyright) series of materials (ex Ciba Gigy), the Lowinox(copyright) series of materials (ex Great Lakes Chemical Corporation); the Tropanol(copyright) series (ex ICI), t-butylcatechol, nitroxides such as di-tert-butylnitroxide, N,N-dimethyl-4-nitrosoaniline, nitric oxide, and stable radicals, such as 2,2,6,6-tetramethyl-piperidine-1-oxyl, 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl and 2,2,6,6-tetramethylpyrrolidine-1-oxyl.
The reaction between butadiene and the carboxylic acid produces a mixture of butenyl esters: n-butenyl ester and sec-butenyl ester. The n-butenyl ester is converted into the butyraldehyde end-product by hydrolysis isomerisation (step (b)). The sec-butenyl ester, on the other hand, may be removed, for example, for use, sale or further reaction. An example of such a further reaction is the conversion of sec-butenyl ester into methyl ethyl ketone and carboxylic acid. Such a conversion step may be carried out by subjecting the ester to simultaneous or sequential stages of hydrolysis and isomerisation. As with the n-butenyl isomer, simultaneous hydrolysis and isomerisation may allow the process to be operated more economically. However, sequential hydrolysis and isomerisation stages may increase the selectivity of the overall process.
Where the hydrolysis and isomerisation steps are carried out sequentially, it is preferable for the sec-butenyl ester to be hydrolysed before it is isomerised. This is because the conversion of the allylic ester to its vinyl isomer has been found to be thermodynamically unfavourable. Thus, in one embodiment of the present invention, sec-butenyl ester is first hydrolysed to form but-l-en-3-ol, which is conveniently separable from the hydrolysis mixture as an azeotrope. The separated alcohol is then isomerised into the ketone product.
Instead of (or in addition to) converting the sec-butenyl ester into methyl ethyl ketone, the sec-butenyl ester may also be recycled back to the addition reaction (step (a)). Under the reaction conditions, sec-butenyl interconverts with butadiene, free carboxylic acid and the n-butenyl ester. Rather than recycling the sec-butenyl ester to the addition reaction directly, however, it is also possible to convert the sec-butenyl ester back into butadiene and carboxylic acid separately. The conversion of the sec-butenyl ester to free carboxylic acid and butadiene can be achieved by treatment in the vapour phase with an acidic support. Suitable supports include silica-aluminas. The butadiene and carboxylic acid produced may then be returned to the addition reactor. This may have a beneficial effect on productivity and selectivity. Alternatively, at least one of the butadiene and carboxylic acid may be sold, or used for further reaction.
The addition reaction may be carried out in a plug flow reactor, with the unused butadiene being flashed off and recycled to the reactor via a vapour liquid separator. Some of the butadiene may be present as a separate gas phase, whilst the remainder of the butadiene is dissolved in the reaction mixture. This results in either a trickle bed or bubble bed operation. A typical LHSV (liquid hourly space velocity=volume of liquid feed /catalyst bed volume) for the carboxylic acid is 0.5 to 20 more preferably 1 to 5.
The addition reactor may alternatively be carried out in a slurry reactor. In such a reactor, the deactivated catalyst may be continuously removed from the reactor as a bleed stream. It is economically advantageous to run with catalyst in various stages of deactivation to improve the utilisation of catalyst. In this case, the total loading of catalyst (activated+deactivated) can reach high levels such as 50%w/w of the reaction charge.
The butadiene may be added gradually to the carboxylic acid, for example, by multiple injection at constant pressure. This may be carried out in a batch reactor. By adding the butadiene gradually in this manner, side reactions leading to, for example, the polymerisation of the butadiene may be minimized.
The products produced by the addition reaction may be separated from the reactants by distillation. A small amount of water azeotroping of reaction products may occur due to the low levels of water employed. However, this is minor and does not significantly effect the separation of the isomeric butenyl esters, i.e. the n-butenyl ester and secondary butenyl ester.
The n-butenyl ester produced in the addition step is converted to butyraldehyde in step b). This is achieved by i) hydrolysis and ii) isomerisation. Where steps i) and ii) are carried out simultaneously, a transition metal catalyst may be used in the presence of an acid or base to perform the purpose of catalysts 2 and 3 (see diagram). Preferred transition metal complexes are those containing elements from Group Ib, Vb, VIb, VIIb and VIIIb of the Periodic Table of Elements on pages 448 and 449 of the Handbook of Physics and Chemistry (44th Edition) published by the Chemical Rubber Publishing Company, Ohio USA (Reprint, April 1962), particularly copper, vanadium, chromium, molybdenum, tungsten, manganese, rhenium, iron, cobalt, nickel, ruthenium, rhodium, palladium, platinum, osmium and/or iridium. Preferably, a transition metal catalyst supported on an acidic residue is employed. Examples of suitable acidic residues include strongly acidic ion-exchange resins and sulphonic acids such as para-toluene sulphonic acid. Mineral acids such as sulphuric acid and halogen acids; acidic oxides such as HY zeolite; Lewis acids such as lanthanide triflates; and organic acids such as triflic acid may also be suitable. One advantage of carrying out the hydrolysis and isomerisation steps simultaneously is that it minimises the total number of process stages required for the production of the final product. The butyraldehyde produced may be recovered from the reaction mixture by distillation, preferably, whilst the hydrolysis/isomerisation reaction is in process.
The simultaneous hydrolysis and isomerisation step may be carried out in the liquid phase, optionally, in the presence of a solvent such as an aromatic hydrocarbon solvent. Suitable solvents include toluene and ethers, such as methyl tertiary butyl ether and tetrahydrofuran. The reaction may be carried out at a temperature of from 25 to 250xc2x0 C., preferably, from 50 to 150xc2x0 C. and more preferably, from 80 to 120xc2x0 C.
When the hydrolysis and isomerisation steps are carried out sequentially, the hydrolysis step may be carried out in the presence of an acid or a base, such as a Bronsted acid or base (catalyst 2). Suitable isomerisation catalysts (catalyst 3) include transition metal complexes. Preferred transition metal complexes are those containing elements from Group Ib, Vb, VIb, VIIb and VIIIb of the Periodic Table of Elements on pages 448 and 449 of the Handbook of Physics and Chemistry (44th Edition) published by the Chemical Rubber Publishing Company, Ohio USA (Reprint, April 1962), particularly copper, vanadium, chromium, molybdenum, tungsten, manganese, rhenium, iron, cobalt, nickel, ruthenium, rhodium, palladium, platinum, osmium and/or iridium.
The n-butenyl ester, upon hydrolysis, will produce an equilibrium mixture of n-butenyl (i.e. crotyl) alcohol and the carboxylic acid. In order to force the equilibrium in the desired direction it may be necessary to remove the carboxylic acid, or alcohol from the equilibrium mixture. This may be achieved by removing the alcohol as an azeotrope.
The hydrolysis step may be carried out in the liquid phase, optionally, in the presence of a solvent such as an aromatic hydrocarbon solvent. Suitable solvents include toluene and ethers, such as methyl tertiary butyl ether and tetrahydrofuran. The reaction may be carried out at a temperature of from 25 to 250xc2x0 C., preferably, from 50 to 150xc2x0 C. and more preferably, from 80 to 120xc2x0 C. The crotyl alcohol formed as a result of this hydrolysis step may be recovered by distillation or by phase separation into a suitable solvent. This crotyl alcohol is then isomerised in a separate stage to give butyraldehyde.

Process for making butyraldehyde from butadiene


A heater for footwear includes a seat having a space centrally defined therein. A spring is compressively received in the space in the seat. A friction mechanism is received in the seat. A cap is sleeved on the seat. The cap has a driving unit longitudinally extending therefrom. The driving unit extends through the friction mechanism for movably abutting against the spring in the space in the seat. When the cap is pressed/released, the driving is unit moved relative to the seat for engaging the friction mechanism to warm up the footwear.

1. Field of the Invention
The present invention relates to a heater, and more particularly to a heater for footwear.
2. Description of Related Art
A conventional heater for footwear includes shoes and boots in which an insole is provided with a heater element having leads extending therefrom to either the tongue area or a side area opposed to the arch of the shoe. A power source in the form of a battery pack is adapted to be mounted either in the tongue area or the side area by means of an enclasping means affixed externally of the battery pack.
However, the battery of the conventional heater is necessary for providing power source. It is inconvenient that the battery usually is needed to be recharged. Even worst, the battery is well known that causes pollution for the environment. It can not usefully use a green energy, especially the energy produced from human naturally walking. Furthermore, the conventional heater uses an electric system for providing a heating effect. It is hard to be assembled and costs more money.
The present invention has arisen to mitigate and/or obviate the disadvantages of the conventional heater.