MXPA01008518A - Processes for the rapid preparation of foam materials from high internal phase emulsions at high temperatures and pressures - Google Patents

Abstract

This application relates to flexible, microporous, open-celled polymeric foam materials with physical characteristics that make them suitable for a variety of uses. This application particularly relates to high temperature processes having short curing times for preparing such foam materials from high internal phase emulsions.

Description

PROCESSES FOR THE RAPID PREPARATION OF FOAM MATERIALS FROM HIGH-PHASE INTERNAL EMULSIONS AT TEMPERATURES AND HIGH PRESSURES FIELD OF THE INVENTION This application relates to the rapid curing of high internal phase emulsions to produce open cell, microporous polymer foam materials with physical characteristics that make them suitable for a variety of uses.

BACKGROUND OF THE INVENTION The development of microporous foams is the subject of substantial commercial interest. Said foams have found utility in various applications such as thermal, acoustic, electrical and mechanical insulators (for example, for cushioning or packaging), absorbent materials, filters, membranes, floor mats, toys, carriers for inks, dyes, lubricants, and lotions, and the like. References describing said uses and the properties of the foam include Oertel, G., Polvurethane Handbook. Hanser Publishers, Muchich, 1985, and Gibson, L.J .; Ashby, M.F., Cellular Solids.

Structure and Properties, Pergamon Press, Oxford, 1988. The term "insulator" refers to any material that reduces the transfer of energy from one site to another. The term "absorbent" refers to materials that imbibe and retain or distribute fluids, usually liquids, an example being a sponge. The term "filter" refers to materials that pass a fluid, either liquid or gaseous, while retaining impurities within the material by size exclusion. Other uses for the foams are generally obvious to one skilled in the art. Open cell foams prepared from high internal phase emulsions (hereinafter referred to as "HIPE") are particularly useful in a variety of applications including disposable absorbent articles (patents of the United States Nos. 5,331, 015 (DesMarais et al.) Issued on July 19, 1994, 5,260,345 (DesMarais et al.) Issued on November 9, 1993, 5,268,224 (DesMarais et al.) Issued on December 7, 1993, 5,632,737 ( Stone et al.) Issued on May 27, 1997, 5,387,207 (Dyer et al.) Issued on February 7, 1995, 5,786,395 (Stone et al.) Of July 28, 1998, 5,795,921 (Dyer et al.) Issued August 18. 1998), insulation (thermal, acoustic, mechanical) (U.S. Patent Nos. 5,770,634 (Dyer et al.) issued June 23, 1998, 5,753,359 (Dyer et al.) issued May 19, 1998, and 5,633,291 (Dyer et al.) Issued May 27, 1997), filtration (Bhumgara, Z. Filtration &Separation 1995, March, 245-251; Walsh et al. J. Aerosol Sci. 1996, 27, 5629-5630; PCT application published WO / 97/37745, published on October 16, 1997, in the name of Shell Oil Co.), and other miscellaneous uses. The patents and references cited above are incorporated herein by reference. The HIPE process provides easy control over density, cell and pore size and distribution, ratio of cell struts to windows, and porosity in these foams. An important situation when making commercially attractive HIPE foams is economic. The economy of HIPE foams depends on the amount and cost of the monomers used per unit volume of the foam, as well as the cost of converting the monomers to a usable polymer foam (process costs). The development of economically attractive HIPE foams may require the use of: (1) less total monomer per unit volume of foam, (2) less expensive monomers, (3) a less expensive process to convert these monomers to a HIPE foam. usable, or (4) combinations of these factors. The monomer formulation and operating conditions must be such that the properties of the HIPE foam meet the requirements for the particular application. The physical properties of the foam are governed by: (1) the properties of the polymer from which the foam is comprised, (2) the density of the foam, (3) the structure of the foam (ie, the thickness, shape and aspect ratio of the polymer struts, cell size, pore size, pore size distribution, etc.), and (4) the surface properties of the foam (for example, if the surface of the foam is hydrophilic or hydrophobic). Once these parameters have been defined and obtained for a particular application, an economically attractive process for preparing the material is desired. A key aspect of this process is the rate of polymerization and crosslinking, jointly referred to as curing, of the oil phase of a HIPE to form a cross-linked network of the polymer. Previously, this curing step requires that the emulsion be maintained at an elevated temperature (40 ° C-82 ° C) for a relatively long period of time (typically from 2 hours to 18 hours or more). Such long curing times require relatively low rates of expenditure, as well as high capital and production costs. Previous efforts to devise commercially successful schemes for producing HIPE foams have involved, for example, emptying the HIPE into a large holding container which is placed in a heated area for curing (see for example U.S. Pat. 5,250,576 (DesMarais) issued October 5, 1993). U.S. Patent Nos. 5,189,070 (Brownscombe et al.), Issued February 23, 1993; 5,290,820 (Brownscombe et al.) Issued on 1 st. March 1994; and 5,252,619 (Brownscombe et al.) issued October 12, 1993 reports the curing of the HIPE in multiple stages. The first stage is conducted at a temperature of less than about 65 ° C until the foam reaches a state of partial cure. Then the temperature is increased between 70 ° C and 175 ° C to effect the final curing quickly. The total process takes approximately 3 hours. Another scheme for producing HIPE foams involves placing the emulsion on a layer of impermeable film which would then be cooled and placed in a curing chamber (U.S. Patent No. 5,670,101 (Nathoo, et al.) Issued September 23. of 1997). The cooled film / emulsion sandwich can then be cured using the sequential temperature sequence disclosed in the Brownscombe patents and others discussed above. U.S. Patent No. 5,849,805 issued to Dyer on December 15, 1998 discloses the formation of the HIPE at a temperature of 82 ° C (pouring temperature in example 2) and curing the HIPE at 82 °. C for 2 hours. However, none of these approaches offers the combination of very rapid conversion (eg, in minutes or seconds) of the HIPE to the polymeric foam that would provide a relatively simple, low capital process to produce HIPE foams both economically and economically. with the series of desired properties. The technique also discloses using pressure to control the volatility of the monomers, which would otherwise be removed by boiling at a suitable polymerization / curing temperature. For example, commonly assigned U.S. Patent No. 5,767,168, issued to Dyer et al. On June 16, 1998, discloses the suitability of pressurization to control the volatility of relatively volatile conjugated diene monomers. However, the cure time for the foams disclosed there is still greater than two hours such that there is still a substantial opportunity for a substantial improvement in curing speed that would improve the economic attractiveness of the HIPE foams.

Accordingly, it would be desirable to develop a rapid and efficient process for preparing open cell polymeric HIPE foam materials with the desired properties.

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to a process for obtaining open cell foams by polymerizing a high internal phase emulsion, or, HIPE, which has a relatively small amount of a continuous phase of oil and a relatively greater amount of an aqueous discontinuous phase. The present invention relates particularly to relatively high temperature processes for curing the oil phase. This allows the foam to be prepared in a much shorter interval than has previously been possible. This allows the practical processes of continuous production of HIPE foams which have up to this point been done through batch processes. The process of the present invention generally comprises the steps of: 1) forming a water-in-oil emulsion (HIPE) wherein the oil phase comprises polymerizable monomers; 2) polymerizing and crosslinking (i.e., curing) the monomers at temperatures greater than about 90 ° C to form a HIPE foam. Specifically, the oil phase comprises: 1) from about 85 to 99% by weight of a monomer component capable of forming a copolymer having a Tg of about 90 ° C or less, wherein the monomer component comprises a mixture of monofunctional monomers, crosslinking agents, and comonomers capable of modifying the properties of the foam; and 2) from about 1 to about 20% of an emulsifier component capable of forming a stable HIPE. The aqueous phase comprises from about 0.2 to about 40% by weight of a water soluble electrolyte and an effective amount of a polymerization initiator. The volume to weight ratio of the aqueous phase to the oil phase is between about 8: 1 and about 140: 1. After polymerization, the aqueous fraction of the HIPE foam can be removed by a variety of techniques to produce the low density, microporous, open cell product. The curing of the HIPE in a relatively short period of time at high temperatures allows for increased production and improved economy in relation to the previously described methods. Any of the processes can be used by batch or continuous. In any case, due to the vapor pressure of both phases in the emulsion increases as the temperature increases, some containment and / or pressurized system may be required to avoid the volatilization of the HIPE components during the curing steps. high temperature and / or emulsification. The volatilization that forms gas or vapor bubbles can damage the fine structure, particularly the cell size distribution, of the HIPE and the resulting HIPE foam, and this will generally be avoided. This can be carried out by applying pressure from an external source such as a pump or cylinder with pressurized gas, heating the emulsion in a closed container with relatively small head volume, heating a portion of the composition below the surface of the emulsion in an open container so that the "hydrostatic" pressure prevents the volatilization of liquid comprising the emulsion, or by any other method or device generally known to those skilled in the art. The elements of these approaches can be combined to develop an appropriate process for the rapid curing of HIPE foams.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an electronic photomicrograph at a 500-fold amplification of a control HIPE foam in its expanded state where the emulsion was formed at 47 ° C and cured at 65 ° C under ambient pressure according to the prior art. Figure 2 is an electronic photomicrograph at a 500-fold amplification of a representative polymer foam in its expanded state according to the present invention described as described in example 1. Figure 3 is an electron photomicrograph at a magnification of 1000 times of a control foam in its expanded state wherein the emulsion was formed at 47 ° C and cured at 65 ° C under ambient pressure according to the prior art. Figure 4 is an electronic photomicrograph at a 1000-fold amplification of a representative polymer foam in its expanded state according to the present invention prepared as described in the example. Figure 5 is an electronic photomicrograph at a 2500-fold amplification of a HIPE control foam in its expanded state where the emulsion was formed at 47 ° C and cured at 65 ° C under ambient pressure according to the prior art . Figure 6 is an electronic photomicrograph at a 2500 fold amplification of a representative polymer foam in its expanded state according to the present invention prepared as described in the example. Figure 7 is a schematic diagram of the curing chamber used to prepare the foams illustrated in Figures 1 and 2.

Figure 8 is a schematic diagram of a continuous process for preparing HIPE foams.

DETAILED DESCRIPTION OF THE INVENTION I. Definitions The following definitions are offered in relation to the present invention. "Curing" is the process of converting a HIPE into a HIPE foam. The curing involves the polymerization of the monomers in polymers. One more step included in the curing process is the reticulate. A cured HIPE foam is one that has the physical properties, e.g., mechanical integrity, that are maintained in the later stages of processing (which may include post curing treatment to confer desired final properties). Generally, curing is carried out by the application of heat. An indication of the cure limit is the mechanical strength of the foam, as measured by the yield point stress described in the Test Methods section below. "Polymerization" is the part of the curing process by which the monomers of the oil phase are converted to a relatively high molecular weight polymer. "Crosslinking" is the part of the curing process by which monomers having more than one functional group with respect to free radical polymerization are copolymerized in more than one chain of the growing polymer. "Hydrostatic" is related to the pressure conferred by a column of liquid in a gravitational field, sometimes referred to as "hydrostatic height". The liquid is not necessarily water, but it can be a solution, emulsion, aqueous suspension or other liquid.

I. Polymeric foam derived from an emulsion of high internal phase A. General characteristics of the foam 1. Components of the oil phase The continuous oil phase of the HIPE comprises monomers that are polymerized to form a solid foam structure and the emulsifier necessary to stabilize the emulsion. In general, the monomers will include from about 20 to about 95% by weight of at least one monofunctional substantially water-insoluble monomer capable of forming an atactic amorphous polymer having a glass transition temperature (Tg) of about 35 ° C or less . This comonomer is added to the lowest total Tg of the resulting HIPE foam. Exemplary monomers of this type include C 4 -C 4 alkyl acrylates and C 6 -C 16 methacrylates such as 2-ethylhexyl acrylate, n-butyl acrylate, hexyl acrylate, n-octyl acrylate, nonyl acrylate, acrylate. decyl, isodecyl acrylate, tetradecyl acrylate, benzyl acrylate, nonyl phenyl acrylate, hexyl methacrylate, octyl methacrylate, nonyl methacrylate, decyl methacrylate, isodecyl methacrylate, dodecyl methacrylate, and tetradecyl methacrylate; substituted acrylamides, such as N-octadecyl acrylamide; dienes such as isoprene, butadiene, chloroprene, piperylene, 1, 3,7-octatriene, ß-myrcene and amyl butadiene; C4-C 2 -substituted styrenics such as p-n-octyl styrene; and combinations of said monomers. Monofunctional monomers that reduce Tg will generally comprise from 20% to about 95%, more preferably from 45% to about 65%, by weight of the monomer component.

The oil phase will also comprise from about 5 to about 80% by weight of a first polyfunctional crosslinking agent, substantially insoluble in water. This comonomer is added to confer resistance to the resulting HIPE foam. Exemplary crosslinking monomers of this type encompass a wide variety of monomers containing two or more activated vinyl groups, such as the divinyl benzenes and analogs thereof. These analogs include mixtures of / 77, p-divinyl benzene with ethyl styrene, divinyl naphthalene, trivinyl benzene, divinyl alkyl benzenes, divinyl biphenyls, divinyl phenyl ethers, divinyl ferrocenes, divinyl furans, and the like. Other useful crosslinking agents may be selected from a group derived from the reaction of acrylic acid or methacrylic acid with polyfunctional alcohols and amines. Non-limiting examples of this group include 1, 6-hexanedioldiacrylate, 1,4-butanediolmethacrylate, trimethylolpropane triacrylate, hexamethylene bisacrylamide, and the like. Other examples of crosslinking monomers include divinyl sulfide, divinyl sulfone, and trivinyl phosphine. Other crosslinkers useful in this regard are well known to those skilled in the art. It should be distinguished that the weight fraction of the crosslinking component is calculated on the basis of the pure crosslinker in cases where the crosslinking monomer is commonly used as a mixture (for example, divinyl benzene is often a pure mixture at 55% with the balance that is ethyl styrene). Any third comonomer substantially insoluble to the water can be added to the oil phase in percentages by weight from about 0% to about 70%, preferably from about 15% to about 40%, to modify the properties in another way. In certain cases, the "hardening" monomers may be desired which impart toughness to the resulting HIPE foam equivalent to that provided by the styrene. These include styrenics such as styrene and ethyl styrene and methyl methacrylate. Also included are styrenics and other compounds that may also help reduce Tg or improve the strength of the resulting HIPE foam such as p-n-octyl styrene. The monomers may be added to confer flame retardance as disclosed in the commonly assigned, co-pending, United States of America patent application Serial No. 09 / 118,613 (Dyer) filed July 17, 1998. The monomers can be added to confer color, fluorescent properties, radiation resistance, radiation opacity (eg, lead tetraacrylate), to disperse the charge, to reflect incident infrared light, to absorb radio waves, to form a surface moistened on the struts of the HIPE foam, or for any other purpose. 2. Components of the aqueous phase The discontinuous internal water phase of the HIPE is generally an aqueous solution containing one or more dissolved components. An essential dissolved component of the water phase is a water soluble electrolyte. The dissolved electrolyte minimizes the tendency of the monomers, comonomers and crosslinkers that are mainly soluble in oil to also dissolve in the water phase. Another component of the aqueous phase is a water-soluble free radical initiator as may be known in the art. The initiator may be present in up to about 20 mol percent based on the total moles of the polymerizable monomers present in the oil phase. More preferably, the initiator is present in an amount of about 0.001 to about 10 mol percent based on the total moles of the polymerizable monomers in the oil phase. Suitable initiators include ammonium persulfate and potassium persulfate. 3. Emulsifier The emulsifier is necessary to form and stabilize the HIPE. The emulsifier is generally included in the oil phase and tends to be relatively hydrophobic in character. (See, for example, Williams, J.M., Lanqmuir 1991, 7, 1370-1377, incorporated herein by reference). An example of an emulsifier that works very well is diglycerol monooleate. Other emulsifiers of this general type also include diglycerol monomiristate, diglycerol monoisostearate, diglycerol monoesters of coconut fatty acids, sorbitan monooleate, sorbitan monomiristate, sorbitan monoesters of coconut fatty acids, sorbitan isostearate, and similar compounds and mixtures thereof. same. U.S. Patent No. 5,786,395 (Stone et al.) Issued July 28, 1998 offers more examples of these emulsifiers and is incorporated herein by reference. Said emulsifiers are advantageously added to the oil phase in such a way that it comprises from about 1% to about 15% thereof. Obviously, emulsifiers that are particularly capable of stabilizing HIPE at elevated temperature are preferred. The diglycerol monooleate is illustrative in this respect. Coemulsifiers can also be used to provide additional control of cell size, cell size distribution, and emulsion stability. The co-emulsifiers include phosphatidyl cholines and compositions containing phosphatidyl choline, aliphatic betaines, dialiphatic long-chain C12-C22, quaternary dialiphatic ammonium salts of short chain C? -C, dialkoyl (alkenoyl) -2-hydroxyethyl long chain C12-C22, short-chain dialiphatic quaternary ammonium salts of CrC, C12-C22 long-chain dialiphatic imidazolinium quaternary ammonium salts, short-chain dialiphatic C-C-benzyl quaternary ammonium salts of long chain, monoaliphatic of C? 2-C22, C12-C22 long chain dialcoyl (alkenoyl) -2-aminoethyl, short chain monoaliphatic C4 C, short chain monohydroxyaliphatic dC. Particularly preferred is dimodimethyl ammonium methyl sulfate. Said coemulsifiers and additional examples are described in greater detail in U.S. Patent No. 5,650,222 (DesMarais et al.) Issued July 22, 1997, the disclosure of which is incorporated herein by reference. 4. Optional Ingredients Various optional ingredients can also be included in any of the water or oil phase for various reasons. Examples include antioxidants (e.g., hindered phenolic light stabilizers, hindered amine stabilizers, ultraviolet ray absorbers), plasticizers (e.g., dioctyl phthalate, dinonyl sebacate), flame retardants (e.g., halogenated hydrocarbons, phosphates, borates, inorganic salts such as antimony trioxide or ammonium phosphate or magnesium hydroxide), dyes and pigments, fluorescing agents, filler particles (eg, starch, carbon dioxide, carbon black, or calcium carbonate), fibers, chain transfer agents, odor absorbers, such as activated carbon particles , polymers and dissolved oligomers, and said other agents as are commonly added to polymers for a variety of reasons. Such additives can be added to confer color, fluorescent properties, radiation resistance, radiation opacity (eg, lead compounds), to disperse the charge, to reflect incident infrared light, to absorb radio waves, to form a wet surface on the foam struts of HIPE, or for any other purpose.

B. Processing conditions to obtain the HIPE foams The foam preparation typically involves the steps of: 1) forming a stable high internal phase emulsion (HIPE); 2) curing this stable emulsion under suitable conditions to form a cellular polymer structure; 3) optionally squeezing and washing the cellular polymeric structure to remove or remove the original residual water phase from the polymeric foam structure and, if necessary, treat the polymeric foam structure, with a hydrophilizing surfactant and / or a hydratable salt for depositing any hydrophilizing surfactant / hydratable salt needed, and 4) subsequently dehydrating this polymeric foam structure. 1. Formation of the HIPE The HIPE is formed by combining the components of the water and oil phase in a ratio between approximately 8: 1 and 140: 1. Preferably, the ratio is between about 10: 1 and about 75: 1, more typically between about 13: 1 and about 65: 1. As discussed above, the oil phase will typically contain the required monomers, comonomers, crosslinkers, and emulsifiers, as well as the optional components. The water phase will typically contain the electrolyte or electrolytes and initiators or initiators of the polymerization. The HIPE can be formed from the combined water and oil phases by subjecting these combined phases to shear agitation. The shear agitation is generally applied to the point and for a period of time necessary to form a stable emulsion. Said process may be conducted in a manner, either batch or continuous and is generally carried out under suitable conditions to form an emulsion where the drops of the water phase are dispersed to such a limit that the resulting polymeric foam will have the structural characteristics required. Emulsification of the combination of the oil and water phases will often involve the use of a mixing or stirring device such as a stirrer.

A preferred method for forming the HIPE involves a continuous process that combines and emulsifies the required phases of water and oil. In said process, a liquid stream comprising the oil phase is formed. Concurrently, a separate liquid stream comprising the water phase is also formed. The two separate streams are provided to a suitable mixing chamber at a suitable emulsification pressure and combined there so that the specified pre-specified water-to-oil weight ratios are obtained. In the mixing chamber or zone, the combined streams are generally subjected to shear agitation provided, for example, by an agitator of suitable configuration and dimensions, or by any other means for imparting the shear or turbulent mixing generally known by those skilled in the art. The shear stress will typically be applied to the combined oil / water phase stream at an appropriate rate and grade. Once formed, the stable liquid HIPE can then be removed or pumped from the chamber or mixing zone. This preferred method for forming HIPE by means of a continuous process is described in greater detail in U.S. Patent No. 5,149,720 (DesMarais et al.), Issued September 22, 1992, which is incorporated by reference. Also see the commonly assigned United States Patent No. 5,827,909 (DesMarais) issued October 27, 1998 (incorporated herein by reference), which describes an improved continuous process having a recirculation cycle for the HIPE. The process also allows the formation of two or more different types of HIPE in the same container as disclosed in U.S. Patent No. 5,817,704 (Shiveley et al.) Issued October 6, 1998, incorporated herein by reference. In this example, two or more pairs of oil and water streams can be mixed separately and then mixed as required. 2. Polymerization / curing of the oil phase of the HIPE The present invention relates to the polymerization / curing of the oil phase of the emulsion at elevated curing temperatures for short periods. The HIPE formed as described above can be polymerized / cured in a batch process, or in a continuous process. A measure of the cure degree of the polymer is the resistance of the foam, as measured by the stress to yield point described in the section of Test Methods below. Another measure of the degree of cure of the polymer is the degree to which it swells in a good solvent such as toluene (being crosslinked, the HIPE foam does not dissolve without being chemically altered). Without being bound by theory, it is believed that curing comprises two overlapping but distinct processes. The first involves the polymerization of the monomers. The second is the formation of the lattices between the active sites in the main chains of adjacent polymers. Crosslinking is essential for the formation of HIPE foams with strength and integrity essential for handling and further use. The step of controlling the speed of this crosslinking reaction is believed to be related to the diffusion rate of the active sites attached to the polymer chains. It has been surprisingly discovered that an increase in the production rate of free radicals in HIPE does not accelerate curing in a useful manner. However, increasing the diffusion rate of the active sites by increasing the temperature of the system in a conventional curing process is limited by the volatility of the components of the emulsion. The present invention provides for the curing of the emulsion under high pressure in order to allow the high temperatures and fast cure times that are obtained without excessive volatilization of the emulsion components. It should be noted that the oil phase and the aqueous phase of the emulsion may contain dissolved gases. At elevated temperatures, the solubility of these gases in the liquid phase is reduced, and the gas can be released to form bubbles in the emulsion. These bubbles can disrupt the structure of the HIPE and cause undesirable gaps in the finished structure of the foam. The formation of said voids can be reduced or eliminated by: 1) degassing the aqueous and / or oil phases of the emulsion before heating, 2) using sufficient pressure to reduce or eliminate the formation of bubbles at the curing temperature, or combinations of these approaches. Because the amount of the aqueous phase is typically much greater than the amount of the oil phase in the HIPE, most of the gas dissolved in the system can be removed by degassing only the aqueous phase. Degassing can be obtained by heating the liquid, or by applying a vacuum, with or without a nucleating agent (for example, boiling media, available from Aldrich Chemical Co., Milwaukee, Wl), or by another technique known to those skilled in the art. The liquid can be degassed in a batch process, or preferably in a continuous process immediately prior to the formation of the HIPE. It has been found that the structural disorganization of the HIPE is minimized if one or both of the phases used to form the HIPE is degassed so that the level of a tracer gas (e.g., oxygen) is reduced to at least half of its value start after the step of degassing and before the formation of the HIPE. Preferably, the tracer gas level is reduced to 25% of its initial value by the degassing step. More preferably, the tracer gas level is reduced to less than about 15% of its initial value (the amount of tracer gas in a phase that is measured when the phase is at room temperature (~ 25 ° C) and at a pressure of 1 atmosphere). The exposure of the liquid to be degassed to a vacuum of at least about 24 inches of mercury with a residence time of about 20 seconds has been found to reduce the dissolved gas to an adequate level within a reasonable time. A person skilled in the art will recognize that variables such as the amount of liquid to be degassed, the vacuum level, the temperature of the liquid, the surface area of the exposed liquid, and other similar variables all interact to determine the amount of time under vacuum that is required to reduce the initial level of the dissolved gas to an acceptable level. Such a determination is easily made by those who are knowledgeable in chemical engineering techniques. It should be distinguished that as the temperature of the system increases, both the polymerization and depolymerization rates typically increase. At some elevated temperature, the polymerization rates of the monomers and the polymer depolymerization may become the same under specific curing conditions. This is analogous to the maximum temperature observed for many polymerization systems under a pressure of 1 atmosphere (see "Textbook of Polymer Science 2nd Ed." 1971, pp. 306, F.W. Billmeyer, John Wiley & amp;; Sons, New York). This limits the practical upper limit of the curing temperature for a particular system. The following describes the non-limiting illustrative embodiments of this invention. In the first embodiment, the HIPE is formed in a batch process, as described in Example 1 below. The formed HIPE is transferred to a suitable reaction vessel 200, such as that shown in Figure 7, capable of withstanding pressures (typically from about 2 to about 40 atmospheres) necessary to allow curing at the desired temperature (typically about 90). ° up to approximately 250 ° C). As will be recognized, such pressure is necessary to avoid the volatilization or evaporation of one or more of the components of the HIPE. The temperature at which the HIPE is provided to the container can be significantly lower than the polymerization / curing temperature. Figure 7 is an illustrative reaction vessel 200 which is suitable for the batch curing of the HIPE according to the present invention. The container 200 comprises a container body 210 having sufficient volume to cure the desired amount of HIPE. The container body can have any desired shape including cylindrical, cubic, rectangular solid, or other irregular shape as may be desired. The container must be constructed so that the polymerized / cured solid foam material can be easily removed for further processing after the polymerization / curing has been carried out to the desired degree.

For certain purposes where the cured HIPE is further processed in a web of material by cutting it as described in U.S. Patent Application Serial No. 08 / 939,172, filed in the name of Sabatelli, and others, on September 29, 1997, a cylindrical shape has been found to be useful. The closure of the container 220 has a shape that is complementary to the shape of the container body 210 to provide a closure thereto. The seal 230 is interposed between the closure 220 and the body 210 to provide resistance to leakage of the materials enclosed within the reaction vessel 200 during the curing process. The container 200 should be constructed of materials that are capable of withstanding the pressures necessary to cure the HIPE at the desired temperature as discussed above. The closure means (not shown) capable of resisting said pressure are also necessary in order to keep the container 200 in a sealed condition during the curing process. The container 200 may further be lined with a material compatible with the HIPE such that it does not cause the HIPE to degrade on the interior surfaces of the container that are in contact with the HIPE. Illustrative surfaces in this regard include: stainless steel, titanium, glass, polyethylene, polypropylene, and polytetrafluoroethylene. One skilled in the art will recognize that the choice of materials will depend on the environmental factors that the material will experience. For example, curing temperatures greater than the softening point of a polymer surface will render the polymeric liner inadequate. For curing conditions that will require the surface to be exposed to the high concentration of the chlorine ion (of the aqueous phase of the HIPE) and the combination of high pressure and temperature that provide the accelerated cure described herein, a titanium surface is suitable. The container 200 is filled with the HIPE to minimize the top space volume before it is sealed. By minimizing the volume of the upper space, the degree to which the volatilization of the emulsion components can occur is limited. The container 200 can be pressurized simply by heating the container and its contents, for example in an oven. In such a case, the pressure inside the container is determined by the partial vapor pressures of the components of the emulsion. Alternatively, pressure can be introduced through an appropriate valve from an external source of pressure such as a pump which can provide an incompatible fluid to raise the pressure or use a cylinder with pressurized gas. Suitable curing conditions will vary depending on the composition of the oil and aqueous phases of the emulsion (especially the emulsifying systems used), the type and the amounts of the polymerization initiators used. Frequently, however, suitable conditions of cure will involve maintaining the HIPE at elevated temperatures above about 90 ° C, more preferably above about 100 ° C, most preferably between about 125 ° C and 165 ° C (from 2.5 to 7 atmospheres), for a period of time ranging from about 20 seconds to about 1 hour, more preferably from about 40 seconds to about 20 minutes, most preferably from about 1 minute to about 10 minutes. Figures 1 to 6 are photomicrographs comparing illustrative foams produced according to the prior art and according to the present invention as described in Example 1 in various amplifications.

Specifically, the foam of Figures 1, 3 and 5 was produced according to condition 2 of Example 1 and the foam of Figures 2, 4 and 6 was produced according to condition 7 of Example 1. As can be seen comparing the process conditions given in Table 1, the only substantial difference in curing is the curing temperature, with the resulting reduction in curing time. As is clearly evident from the properties data in Table 1 below and comparing the various pairs of figures, the rapid curing process of the present invention provides foams having essentially the same properties as the foams produced in accordance with the prior art using curing processes that required substantially longer cure times. In the alternative embodiments of batch processes, a plurality of reaction vessels 200 may be attached, for example, to a continuous web that moves the containers from a HIPE filling station through the heating zone to a section that it expels the cured HIPE foam into a processing line and carries the containers back to the filling zone (after any washing process that may be needed to re-establish the containers to the usable condition). In a second embodiment, the HIPE is formed in a continuous process, as shown schematically in Figure 8 and described in Example 2 below.

Figure 8 describes a method and apparatus 300 suitable for continuously forming the HIPE foams according to the present invention. A HIPE is made using the methods generally described in the aforementioned US Patents Nos. 5,149,720 and 5,827,909. That is, the oil phase (the desired monomer mixture and emulsifier) is prepared and stored in a supply container of oil phase 305. Similarly, the desired aqueous phase (mixture of water, electrolyte and initiator) is prepared and stored in a supply container of the aqueous phase 310. The oil phase and the aqueous phase are supplied in the desired proportions towards the mixing head 330 by means of a pump supplying the oil phase 315 and a supply pump of the aqueous phase 325. The mixing head 330 supplies the mechanical energy (shear) necessary to form the HIPE. If desired, a HIPE 335 recirculation pump can be used. The formed HIPE is pumped into an elongate curing chamber 340 with specific cross-sectional shape and dimensions as desired for the foam product. The oil phase supply pump 315 and the water phase supply pump can be used to pump the HIPE from the mixing head 330 to the curing chamber 340. In this case, the emulsification will occur at substantially the pressure of curing. One skilled in the art will recognize that the emulsification pressure must be a little greater than the curing pressure to allow the flow to occur. Alternatively, an optional lift pump 345 may be used to pump the HIPE from the mixing head 330 into the curing chamber 340. In this case, the emulsification may occur at a lower pressure and / or temperature than the curing step. . In an alternative embodiment of the present invention (not shown), multiple systems, similar to those described above, can be used to make multiple HIPEs having different combinations of properties (eg, pore dimensions, mechanical properties, etc.). Multiple can be introduced into the curing chamber 340 to provide a cured foam having regions of variable properties as may be desired for a particular end use. The chamber 340 may also be lined with a material compatible with the HIPE in such a way that it does not cause the degradation of the structure of the HIPE on the interior surfaces that are with the HIPE, and is not degraded by the components of the phase of oil or water at the attempted elevated temperatures. Optionally, a slip layer can be provided between the cured HIPE and the walls of the chamber to minimize non-uniform flow patterns as the HIPE progresses through the chamber 340. As with the liner discussed above, the slip layer it must be compatible with the components of the oil and water phase of the HIPE and have sufficient mechanical stability at the curing temperature to be effective. Said slip layer has particular utility when used with curing chamber designs that incorporate the "hydrostatic head" as discussed below. At least a portion of the chamber 340 is heated in order to drive the HIPE to the curing temperature attempted as it passes through this section or zone. Any manner of heating this zone or section can be employed in order to achieve and maintain the desired temperature in a controlled manner. Examples include heating by electrical resistance elements, steam, hot oil or other fluids, hot air or other gases, or any other heating method known to those skilled in the art. Optionally, a static mixer / heat exchanger and another heat exchanger can be used by forced convection in the heating section to improve heat transfer to the HIPE. Once the HIPE starts to gel, the composition can no longer be mixed because of the risk of damaging or even destroying the structure of the foam. The chamber 340 should be designed so that the pressure required to pump the emulsion and / or the cured foam through the chamber under constant state conditions is sufficient to prevent volatilization of the emulsion components at the curing temperature. The chamber 340 may be in a horizontal, inclined or vertical position. The inclined and vertical orientations can be used to provide the additional "hydrostatic" back pressure to help avoid volatilization of the HIPE components, thus allowing a shorter curing chamber to be employed. The length of the optional heated section, the temperature of the optional heated section and the speed at which the emulsion is pumped through the tube are selected to allow sufficient residence time within the chamber 340 for adequate thermal transfer to the center of the 340 camera in order to achieve the complete cure. If optional heating is done within the chambers 340, then chambers 340 with relatively thin cross-sectional dimensions are preferred in order to facilitate rapid heat transfer. The HIPE is sufficiently cured in a HIPE foam at the time it leaves the curing chamber 340. Optionally, a raised extension 350 may be located above and downstream of the curing chamber 340 to provide the hydrostatic head. The curing chamber 340 may have any desired cross section that is consistent with the flow requirements of the cured HIPE pump. For example, the cross section may be rectangular, circular, triangular, annular, oval, hourglass, dog bone, asymmetrical, etc., as may be desired for a particular use of the cured HIPE. Preferably, the cross-sectional dimensions of the chamber 340 are such that the polymerized HIPE foam is produced in the sheet-like shape with the desired cross-sectional dimensions. Alternatively, the cross-sectional shape may be designed to facilitate the manufacture of the desired product in subsequent processes. For example, a cross-section in the form of an hourglass (or co-joined hourglass sections) of the appropriate size can facilitate the manufacture of disposable absorbent products such as diapers by cutting relatively thin slices or sheets of the formed HIPE foam. Other sizes and shapes can be prepared to make feminine hygiene pads, surgical towels, facial masks, and the like. Regardless of the cross-sectional dimensions of the curing chamber 340, the resulting HIPE foam can be cut or sliced into a sheet-like shape of suitable thickness for the intended application. The cross section of the healing chamber 340 may be varied along the length of the chamber in order to increase or decrease the pressure required to pump the HIPE through the chamber. For example, the cross-sectional area of a vertical healing chamber can be increased above the point at which the HIPE foam is cured, in order to reduce the flow resistance caused by friction between the walls of the chamber and the foam. healed Alternatively, the cross-sectional area of a healing chamber 340 can be decreased past the point at which the HIPE foam is cured, in order to increase the pressure required to pump the HIPE through the chamber thus allowing a chamber of shortest healing to be used. An initiator solution can optionally be injected into the HIPE at a point between the mixing head 330 and the curing chamber 340 (not shown). If the injection of the optional initiator is chosen, the aqueous phase, as provided from the supply container of the aqueous phase, is substantially free of initiator.

Additional mixing means, such as a continuous mixer (not shown) may also be desirably downstream of the injection point and upstream of the curing chamber 340 to ensure that the initiator solution is distributed throughout the HIPE. Said arrangement has the advantage of substantially reducing the risk of undesirable curing in the mixing head 330 in the event of an unanticipated stoppage of the equipment. An open cell HIPE foam, filled with water, porous, is the product obtained after curing in the reaction chamber. As noted above, the cross-sectional dimensions of the chamber 340 are preferably such that the polymerized HIPE foam is produced in the shape resembling a sheet or sheet with the desired cross-sectional dimensions. Alternative cross-sectional dimensions can be employed, but without considering the shape of the curing chamber 340, the resulting HIPE foam can be cut or sliced into a sheet-like shape with the desired thickness for the intended application. The sheets of the HIPE cured foam are easier to process during the subsequent treatment / washing and dehydration stages, as well as to prepare the HIPE foam for use in the intended applications. Alternatively, the product of the HIPE foam can be cut, milled or otherwise crushed into desired particles, cubes, rods, spheres, plates, filaments, fibers, or other shapes. The remaining aqueous phase with the HIPE is typically removed by compressing the foam. The residual moisture can be removed as desired by conventional evaporative drying techniques. As noted above, in the continuous curing process, the emulsification step can be carried out at a relatively low pressure and the preformed emulsion pumped into the curing chamber under relatively high pressure using the lift pump 345. An alternative process links the pump the oil phase and the aqueous phase into the mixing chamber under relatively high pressure using the oil phase supply pump 315 and the supply pump of the aqueous phase 325. In this case, the emulsification step occurs under pressure relatively high, and the emulsion leaves the mixing chamber directly into the curing chamber under the required pressure. This eliminates the need to actively pump the preformed emulsion into the healing chamber. The HIPE may comprise at least one monomer with a boiling point less than about 60 ° C. Exemplary monomers include chloroprene, isoprene, and butadiene. These volatile monomers are not easily handled with the HIPE curing processes disclosed to date. When these are employed in the present invention, the process pressure must be sufficient to prevent undue volatilization of these monomers even with the heating necessary to effect rapid cure. The foams that use these monomers in an appropriate manner can be biodegradable as disclosed in the aforementioned U.S. Patent No. 5,767,168, in which the HIPE foams made with isoprene are prepared at a pressure of about 2 atmospheres and a temperature of 50 ° C for 48 hours or more. The process according to the present invention allows the curing time to be shortened significantly by applying higher temperatures and pressures. Chloroprene-based foams can be flame retardants, as disclosed in the aforementioned copending United States patent application No. 09/1 18,613. As taught in each of these references, the inclusion of antioxidants may be especially preferred for HIPE foams made with 1,3-dienes. lll. Test Methods Test methodologies to measure Tg, the yield point stress, expansion factors, and stability in the compressed state are disclosed in U.S. Patent No. 5,753,359. Methodologies for measuring resistance to compression deflection (RTCD), and free absorbent capacity (FAC) are disclosed in U.S. Patent No. 5,849,805. Swelling ratio: The swelling ratio can be used as a relative measurement of the degree of crosslinking of the polymer comprising the HIPE foam. The degree of crosslinking is the critical part of curing as defined herein above. The swelling ratio is determined by cutting a cylindrical sample of foam 2 to 6 mm thick, 2.5 cm in diameter. The foam sample is vigorously washed with water and 2-propanol to remove any residual salts and / or emulsifiers. This will be achieved by placing the sample on a piece of filter paper in a Büchner el attached to a filter flask. A vacuum is applied to the filter flask by means of a laboratory aspirator and the sample is vigorously washed with distilled water and then with 2-propanol so that water and 2-propanol are entrained through the porous foam by vacuum . The washed foam sample is then dried in a 65 ° C oven for three hours, the oven removed, and allowed to cool to room temperature before measuring the swelling ratio. The sample is weighed within ± 1 mg, to obtain the dry weight of the sample, Wd. The sample is then placed in a vacuum flask containing enough methanol to completely immerse the foam sample. The remnants of the air bubbles in the foam structure are removed by gently reducing the pressure inside the flask by means of a laboratory aspirator. A gentle vacuum is applied and released several times until no more bubbles are seen coming out of the foam sample when the vacuum is applied, and the foam sample settles when the vacuum is released. The fully saturated foam sample is gently removed from the flask and weighed within ± 1 mg, taking care not to squeeze the methanol from the sample during the weighing process. After the weight of the sample saturated with methanol is recorded, (Wm), the sample is dried again by gently squeezing most of the methanol followed by drying in the oven at 65 ° C for 1 hour. The dry sample is then placed in a vacuum flask containing enough toluene to completely immerse the foam sample. The residual air trapped within the pores of the foam is removed by gentle application and vacuum release, as described above. The weight saturated with toluene in the sample, Wt, is also obtained as described above. The swelling ratio can be calculated from the needs of methanol and toluene, and the weights recorded in the above procedure as follows: Swelling ratio = [(Wt - Wd) / (Wm-Wd)] x 0.912 where 0.912 is the ratio of the densities of methanol and toluene. Effort to the transfer point: The effort to the transfer point is the most practical measurement of the degree of cure and related to the compressive strength of the HIPE foam. The effort to the yield point is the effort at which a marked change in the inclination of the stress-strain curve occurs. This is practically determined by the intersection of the extrapolated regions of the stress-strain curve above and below the elastic point, as described in more detail below.

The general test method for measuring the transfer point effort is disclosed in U.S. Patent No. 5,753,359. Specifically, for the purposes of this application, the following method is used: Apparatus: Rheometrics RSA-2 DMA, as available from Rheometrics Inc., of Piscataw, NJ.

Arrangements: Tension rate of 0.1% per second for 600 seconds (up to 60% tension) using parallel plates of 2.5 cm in diameter in compression mode; Temperature of the oven at 31 ° C maintained for 10 minutes before starting the test, and throughout the test. Sample: HIPE foam samples cut into cylinders from 2 to 6 mm thick and 2.5 cm in diameter. The resulting stress-strain curve can be analyzed by adjusting the line of the initial elastic and linear portions of the graph using a linear regression method. The intersection of the two lines thus obtained gives the effort to the transfer point (and tension to the transfer point). Density: The density of the foam can be measured in dry, expanded foams, using any reasonable method. The method used herein is disclosed in the aforementioned U.S. Patent No. 5,387,2087. Determination of the curing speed: The HIPE are prepared at specific temperatures and placed in suitable containers for specific times at the cure temperatures. The HIPE foams produced in this way are submerged in an ice bath to cool the healing process. The cooled foams are removed and processed for analysis, usually comprising removing the water by using pressure, washing in water and / or organic solvent, and drying followed by slicing and / or cutting to the desired dimensions.

V. Specific Examples These non-limiting examples illustrate the specific preparation of the HIPE foams according to the present invention.

Example 1: Batch preparation of the foam from a HIPE A) Preparation of the HIPE Anhydrous calcium chloride (12.0 g) and potassium persulfate (0.150 g) are dissolved in 300 ml of water. This provides the aqueous phase that is to be used in the formation of the HIPE. To a combination of monomer comprising 2-ethylexylacrylate (EHA) (5.50 g), divilbenzene (42% purity with the balance being ethyl styrene) (DVB42) (3.30 g), and 1,6-hexanediol diacrylate (HDDA) (1.20 g) is added a diglycerol monooleate of high purity (DGMO) (0.6 g), and disebodimethylammonium methyl sulfate (DTDMAMS) (0.1 g). (DVB42) can be obtained from Dow Chemical Midland, Ml; other monomers can be obtained from Aldrich Chemical Co., Milwaukee, Wl; DGMO can be obtained from Danisco Ingredients, Brabrand, Denmark; and DTDMAMS can be obtained from Witco Corp., Greenwich CT). The diglycerol monoleate emulsifier comprises approximately 81% of diglycerol monoleate, 1% of other diglycerol monoesters, 3% of polyglycerols, and 15% of other polyglycerol esters, imparts a minimum interfacial tension value of the oil phase / water phase of about 2.5 dino / cm and has a critical aggregation concentration of about 2.9 weight percent. This provides the oil phase that is to be used in the formation of the HIPE. The percentages by weight of the monomer are 55% EHA, 33% DVB42, and 12% HDDA. A portion of the oil phase (5.00 g) is weighed in a high density polyethylene cup with vertical sides and a flat bottom. The internal diameter of the cup is 70 mm and the height of the cup is 120 mm. The oil phase is agitated using an overhead stirrer equipped with a stainless steel stirrer attached to the bottom of a 9.5 mm diameter stainless steel shaft. The agitator has 6 arms extending radially from a central mass, each arm having a square cross section of 3.5 mm x 3.5 mm, and a length of 27 mm average from the arrow to the tip of the arm. The oil phase is agitated with the agitator rotating at 250 to 300 revolutions per minute while adding 240 ml of the preheated aqueous phase (47 ° C) dropwise over a period of 4 minutes to form a high internal phase emulsion thick. The agitator is raised and lowered into the emulsion during the addition of the aqueous phase to obtain uniform mixing of the components. After all the aqueous phase has been added, the emulsion is stirred for an additional 1 minute with the agitator speed of 400 revolutions per minute to obtain a uniform, thick but pliable HIPE.

B) Polymerization / Healing of the HIPE A part of the emulsion is emptied into a cylindrical stainless steel vessel (see Figure 7) with a wall thickness of 3 mm, a depth of 16 mm and an internal diameter of 3.8 cm to fill completely the container. A 6 mm stainless steel lid equipped with an O-ring is used to seal the container, the lid being secured by means of an O clamp. The entire vessel is immersed in a bath of silicone oil preheated to the desired temperature of healing during the required length of time. When removing from the oil bath, the container is immediately immersed in a bath containing a mixture of ice and water in order to cool the container and its contents quickly. After several minutes, the container is removed from the ice / water bath and the cured foam inside is carefully removed for washing, dehydration, and characterization, as described in the section on Test Methods above.

C) Washing and dehydrating the foam The cured HIPE foam is removed from the container. The foam at this point has the residual water phase (containing dissolved or suspended emulsifiers, electrolyte, initiator residues, and initiator) about 48 times the weight of the polymerized monomers. The foam is dehydrated by placing the sample on a piece of filter paper in a Büchner funnel attached to a filter flask. A vacuum is applied to the filter flask by means of a laboratory aspirator and the sample is vigorously washed with distilled water and then with 2-propanol so that water and 2-propanol are removed through the porous foam by the empty. The washed foam sample is then dried in an oven at 65 ° C for 3 hours, removed from the oven, and allowed to cool to room temperature before characterization as described in the section on Test Methods above. The illustrative data are presented in Table 1 below. Table 1 * Comparative conditions 1 and 2 show the curing at ambient pressure according to the prior art. Prolonged cure times (typically> 8 hours) are required to obtain the total cure at 65 ° C, as evidenced by the data of effort to transfer point. At 65 ° C, it is not able to recover foam in healing times of less than approximately 2. 5 hours, ie a minimum of approximately 2.5 hours is required for the HIPE to cure sufficiently to have sufficient mechanical integrity to be recovered.

Example 2: Continuous preparation of the foam from a HIPE A) Preparation of the HIPE Anhydrous calcium chloride (36.32 kg) and potassium persulfate (189 g) are dissolved in 378 ml of water. This provides the current of the water phase that is used in a continuous process to form the HIPE. To a monomeric combination comprising DVB42 (2100 g), 2-EHA (330 g), and HDDA (600 g) is added a DGMO (very high purity (360 g), and Tinuvin 765 (30 g). After mixing, this emulsifier mixture is allowed to settle overnight. No visible residue is formed and the entire mixture is removed and used in the oil phase as the emulsifier in the formation of the HIPE. Separate streams from the oil phase (25 ° C) and the water phase (65 ° C) are fed to a dynamic mixing apparatus as in Example 1 of U.S. Patent No. 5,827,909. A portion of the material exiting the dynamic mixing apparatus is removed and recirculated by a recirculation cycle as shown and described in the aforementioned US Pat. No. 5,827,909 to the point of entry of the flow currents of the oil and water phase to the dynamic mixing zone.

The combined mixing and recirculating apparatus is filled with the oil phase and the water phase at a ratio of 4 parts of water to 1 part of oil. The dynamic mixing apparatus is vented to allow air to escape while the apparatus is completely filled. The flow rates during filling are 3.78 g / sec of the oil phase and 15.12 cm3 / sec of the water phase with approximately 15 cm3 / sec in the recirculation cycle. During the start phase, the HIPE produced is diverted to a holding tank until the production conditions are obtained. Once the installation of the apparatus is filled, the flow rate of the water phase is cut in half to reduce the pressure buildup while the vent is closed. Agitation is then initiated into dynamic mixing, with the agitator rotating at 1800 revolutions per minute. The flow rate of the water phase is then increased steadily to a rate of 45.4 cm3 / sec over a period of time of about 1 min, and the flow rate of the oil phase is reduced to 0.757 g / sec. for a period of time for 2 min. The rate of recirculation is constantly increased to approximately 44 cm3 / sec during the last period of time. The back pressure created by the dynamic and static mixers at this point is approximately 69 kPa. The speed of the Waukesha pump is then steadily decreased to produce a recirculation velocity of approximately 11 cm3 / sec.

B) Polymerization / cure of the HIPE Once the constant state production of the HIPE is obtained, a portion of the emulsion flowing from the static mixer is pumped to the bottom of a vertical stainless steel chamber with a rectangular cross section which has internal dimensions of 5 mm x 300 mm, and a length (height) of 15 meters. A section near the bottom of the tube is packed and oil at 140 ° C is pumped continuously through the jacket. The emulsion is pumped through the chamber at a speed such that the residence time in the heated section is 10 minutes. During this 10 minute period, the oil phase is polymerized / cured to form an open cell foam.

C) Washing and dehydration of the foam The cured HIPE foam leaves the upper part of the chamber in the form of a continuous sheet or sheet with the same cross section as that of the curing chamber (300 mm wide, 5 mm thick). The foam at this point has a residual aqueous phase (containing dissolved or suspended emulsifiers, electrolyte, initiator residues, and initiator) of about 50 to 60 times (50-60X) the weight of the polymerized monomers. The foam sheet is then subjected to compression in a series of 2 porous vacuum-equipped gripping rollers which gradually reduces the residual content of the water phase of the foam to approximately 6 times (6X) the weight of the polymerized material. At this point, the sheet is then re-saturated with a 1.5% CaCl2 solution at 60 ° C, and a series of 3 porous vacuum-laden gripping rollers is pressed to a water phase content of about 4X. The CaCl2 content of the foam is between 8 and 10%. The foam remains compressed after the final grip at a thickness of approximately 0.053 cm. The foam is then dried in air for approximately 16 hours. Said drying reduces the moisture content to about 9 to 17% by weight of the polymerized material. At this point, the foam sheets are very capable of wrapping. The foam also contains about 5% by weight of the residual diglycerol monooleate emulsifier. In the collapsed state, the density of the foam is about 0.14 g / cm3. When it expands in water, its absorbent free capacity is approximately 60 ml / g and has a glass transition temperature of approximately 23 ° C: Example 3. Alternate formulations The process of Example 2 is replicated with different types of monomers and proportions and other conditions as shown in Table 2 below.

Table 2 * EHA = 2-ethylhexyl acrylate; DVB42 = divinyl benzene 42% purity; STY = styrene; HDDA = 1,6-hexanediol diacrylate; ISO = sopreno; CPR = chloroprene, used in article No. 6 only, where the emulsification is carried out under a pressure of 7 atmospheres. The foams produced in these examples are open cell and sufficiently cured at the time noted to have useful properties. Each can be treated later to be either hydrophilic or hydrophobic, depending on the intended use. The foam number 1, for example, can be used as a packing or insulation foam, among other uses. The foam 2 is biodegradable. The foam 3 can be used as a material to rapidly acquire urine, for example. Foams 4 and 5 can be used in floor mats applications where a high degree of toughness and abrasion resistance is required. The foam 6 is an example of a foam that does not burn when exposed to open flames. (An optional adjuvant in foam 6 is, for example, antimony trioxide microparticles added to the oil phase prior to emulsification.) Each of these uses is illustrative, but not limiting. The formulations can be altered in each parameter to modify the properties such as Tg (add more Tg reducing monomer), cell size (decrease by increasing shear or RPM), density (decrease by increasing the W: O ratio), tenacity (increase by adding styrene), and the like. Disclosures of all patents, patent applications (and any patents issued thereon, as well as any corresponding published foreign patent applications), and publications mentioned throughout this description are hereby incorporated by reference here. However, it is not expressly admitted that any of the documents incorporated by reference herein teach or disclose the present invention. Although the particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, it is intended to protect all of these changes and modifications within the scope of this invention in the attached claims.

Claims (9)

1 . A method for the preparation of a polymeric foam material comprising the steps of: A) forming a water-in-oil emulsion from: 1) an oil phase comprising: a) from about 85 to about 99% by weight of a monomeric component capable of forming a copolymer having a Tg value of about 90 ° C or less, the monomeric component comprising: i) from about 5 to about 80% by weight of a monofunctional monomer substantially insoluble in water capable of forming a polymer having a Tg of about 35 ° C or less; ii) from about 0 to about 70% by weight of a monofunctional comonomer substantially insoluble in water, capable of imparting other desired properties to the foam; iii) from about 5 to 80% by weight of at least one polyfunctional crosslinking agent, substantially insoluble in water; and b) from about 1 to about 20% by weight of an emulsifying component that is soluble in the oil phase and which is suitable for forming a stable water-in-oil emulsion, the emulsifier preferably comprising emulsification components selected from the group consisting of of diglycerol mooleate, diglycerol monomiristate, diglycerol monoisostearate, diglycerol monoesters of coconut fatty acids, sorbitan monooleate, sorbitan monomiristate, sorbitan monoesters of coconut fatty acids, sorbitan isostearate, dikebo, dimethyl ammonium methyl sulfate , and mixtures thereof and at least about 70% by weight of the emulsifying components; and 2) a water phase comprising an aqueous solution containing: (a) from about 0.2 to about 40% by weight of a water-soluble electrolyte; and (b) an effective amount of a polymerization initiator, preferably the polymerization initiator is selected from the group consisting of ammonium persulfate and potassium persulfate; wherein the emulsion has a volume to weight ratio of the water phase to the oil phase in the range of from about 8: 1 to about 140: 1, preferably from about 10: 1 to about 75: 1, more preferably from about 13: 1 to about 65: 1; B) characterized by providing means for minimizing the volatilization of the components of the emulsion; and C) curing the monomer component in the oil phase of the water-in-oil emulsion using a polymerization reaction which is conducted at a cure temperature that is between about 90 ° C and about 250 ° C to form a polymer foam.

2. The process according to claim 1, wherein: 1) the oil phase comprises: a) from about 90 to about 97% by weight of a monomer component capable of forming a copolymer having a Tg value of about 15 ° to about 50 ° C, the monomeric component comprising: i) from about 40 to about 70% by weight of the monomer selected from the group consisting of alkyl acrylates of C -C? 4, aryl acrylates, C6-C16 alkyl methacrylates, dienes, C4-C12 alkyl styrenes and mixtures thereof, the monomer preferably being selected from the group consisting of butyl acrylate, hexyl, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, isodecyl acrylate, tetradecyl acrylate, benzyl acrylate, nonyl phenyl acrylate, hexyl methacrylate, octyl methacrylate, nonyl methacrylate, methacrylate of decyl, isodecyl methacrylate, dodecyl methacrylate, tetradecyl methacrylate, N-octadecyl acrylamide; p-n-octylstyrene, isoprene, butadiene, chloroprene, ß-myrcene and mixtures thereof; ii) from about 15 to about 23% by weight of the comonomer selected from the group consisting of styrene, ethyl styrene and mixtures thereof; iii) from about 5 to about 18% by weight of divinyl benzene; and b) from about 3 to about 10% by weight of the emulsifying component; and 2) The water phase comprises from about 1 to about 40% of the calcium chloride.

3. The process according to any of the preceding claims, wherein the monomer component in the oil phase is cured at a temperature between about 125 ° C and about 165 ° C.

4. The process according to any of the preceding claims, wherein the volume to weight ratio of the water phase to the oil phase is within the range of from about 10: 1 to about 75: 1.

5. The process according to any of the preceding claims, wherein the means for minimizing the volatilization of the components comprises conducting the polymerization and crosslinking at a curing pressure greater than atmospheric pressure, preferably the curing pressure is provided. by a hydrostatic height. The process according to claim 5, wherein the emulsion is formed at an emulsification pressure and the emulsification pressure is substantially equal to the curing pressure. The process according to claim 5, wherein the emulsion is formed at an emulsification pressure and the emulsification pressure is less than the curing pressure 8. The process according to any of the preceding claims, wherein the process comprises the additional step of dehydrating the polymeric foam material. 9. A polymeric foam prepared according to the process of any of the preceding claims.