JP2010159354A - Water-in-oil type emulsion for foam sheet and method for preparing the same, and foam sheet and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-in-oil type emulsion which is excellent in safety and can be polymerized into a foam sheet, and to provide a foam sheet using the same. <P>SOLUTION: This water-in-oil type emulsion comprises the following components (a), (b) and (c). (a) A continuous oil phase component comprising (i) a prepolymer syrup obtained by partially polymerizing a polymerizable composition comprising at least one ethylenic unsaturated monomer, (ii) at least one polymerization initiator, and (iii) at least one cross-linking agent; (b) at least one co-continuous or discontinuous phase component immiscible with the continuous phase component, and (c) at least one surfactant. The emulsion is polymerized and dehydrated to produce the foam sheet. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a novel water-in-oil emulsion and a method for preparing the same. The present invention further relates to a method for producing a foam sheet using such a water-in-oil emulsion and the foam sheet obtained thereby. The resulting foam may be closed or open, depending on the microstructure of the water-in-oil emulsion.

  Water-in-oil emulsions with a relatively high ratio of water relative oil phase are known in the art as highly discontinuous phase emulsions ("HIPEs" or "HIPE" emulsions).

  The properties and properties of the porous polymer foam material formed by polymerizing the HIPE emulsion also vary greatly depending on the type of components that make up the polymerizable HIPE emulsion and the conditions of each process used to form the emulsion. It is known. For example, a method for preparing an absorbent porous polymer (ie, foam) from a highly discontinuous phase emulsion comprising at least 90 parts by weight of water and 10 parts by weight of an oil phase containing a polymerizable monomer, a surfactant and a polymerization catalyst. (Patent Document 1), or about 100 mg which can be molded as desired by repeating washing and dehydration from a highly discontinuous phase emulsion comprising at least an aqueous phase, a polymerizable monomer, an oil phase containing a surfactant and a polymerization catalyst A method for preparing a dry hydrophobic foam having a dry density of less than / cc and a toughness index of at least about 75 (Patent Document 2) has been proposed. A method for producing a porous cross-linked polymer capable of continuously performing from the supply of HIPE to the polymerization is also disclosed (Patent Document 3). Furthermore, a method for producing a foam by photopolymerizing HIPE is disclosed (Patent Document 4).

  Although the existence and synthesis of polymerizable HIPE emulsions are known in the art, as described in the above patent document, there is no problem in preparing HIPE emulsions suitable for polymerizing them into useful foam materials. Is not something that is done. Such a HIPE emulsion, specifically, a HIPE emulsion having a very high water relative oil phase ratio, tends to be unstable. Even if the monomer / crosslinker content that is the continuous phase component of water-in-oil emulsions, the choice of emulsifier type, the concentration and temperature of the emulsion components, and / or the stirring conditions change only slightly, these emulsions are “broken”. They may clearly separate at least some into the water and oil phases. In particular, in order to obtain an emulsifier-stable emulsion, the incorporation of an emulsifier is essential, and sorbitan monooleate, inorganic fine particles subjected to surface hydrophobization treatment and layered clay mineral are used as a lipophilic emulsifier. Alternatively, a method for preparing a water-in-oil emulsion containing fine solid spherical particles of polyalkylsilesquioxane without containing a surfactant is disclosed (Patent Document 5).

  Therefore, an emulsifier or an emulsifier substitute material is essential for the formation of stable HIPE. Typically, 30 parts of the emulsifier is added to 100 parts by weight of the reactive phase in the continuous oil phase composed of the reactive phase and the emulsifier. Up to parts by weight are required. For this reason, even if a stable emulsion is obtained, if the emulsion composition and processing conditions change, the properties and characteristics of the final polymeric foam material may be significantly affected. May be significantly different from the desired physical properties.

  For example, typically the emulsion begins to break down after a long time in each step, i.e., the bubbles often coalesce or the bubble walls often collapse. Polymeric foams made from aged emulsions are made from the same emulsion, but are larger than polymerized polymerized immediately after emulsification and result in increased bubble size variation or reduced cell count.

Japanese Examined Patent Publication No. 3-66323 Special table 2003-514052 gazette Special table 2001-163904 gazette Japanese translation of PCT publication No. 2003-510390 Japanese Patent No. 2656226

  An object of this invention is to provide the water-in-oil emulsion containing the HIPE emulsion excellent in the stability which can superpose | polymerize to a foam sheet, and its preparation method.

  Another object of the present invention is to provide a method for producing a foam sheet from such a water-in-oil emulsion and a foam sheet obtained thereby.

  As a result of intensive studies to solve the above problems, the present inventors have found the following water-in-oil emulsion and have completed the present invention.

  That is, the present invention provides a water-in-oil emulsion comprising the following components (a), (b), and (c): (a) i) a polymerizable composition comprising at least one ethylenically unsaturated monomer A prepolymer syrup obtained by partial polymerization of the product, ii) at least one polymerization initiator, and iii) a continuous oil phase component comprising at least one crosslinking agent; (b) immiscible with the continuous oil phase component At least one co-continuous or discontinuous phase component; and (c) at least one surfactant.

  In the water-in-oil emulsion, the prepolymer syrup constituting the component (a) contains at least one ethylenically unsaturated monomer and at least one polar monomer copolymerizable with the ethylenically unsaturated monomer. It may be at least one prepolymer syrup obtained by partial polymerization of a polymerizable composition comprising:

  In the water-in-oil emulsion, the ethylenically unsaturated monomer may include at least one alkyl (meth) acrylate having 1 to 20 carbon atoms in the alkyl group.

  In the water-in-oil emulsion, the co-continuous or discontinuous phase component can be water.

  In the water-in-oil emulsion, the co-continuous or discontinuous phase component may comprise at least 74 volume percent of the total emulsion.

  In the water-in-oil emulsion, the amount of the crosslinking agent in the continuous oil phase component may be 5 parts by weight or more with respect to 100 parts by weight of the prepolymer syrup.

The present invention is also a method for preparing any of the above water-in-oil emulsions,
(a) i) partial polymerization of a polymerizable composition comprising at least one ethylenically unsaturated monomer to obtain a prepolymer syrup; ii) at least one polymerization initiator in the prepolymer syrup; Obtaining a continuous oil phase component by mixing at least one crosslinking agent; and (b) at least one co-continuous or discontinuous phase component immiscible with the continuous oil phase component; and (c) at least And a step of mixing one surfactant.

  In the method for preparing the water-in-oil emulsion, the polymerizable composition may further include at least one polar monomer copolymerizable with the ethylenically unsaturated monomer.

The present invention is also a method for producing a foam sheet,
(a) forming a water-in-oil emulsion obtained by the above preparation method;
(b) a step of exposing the water-in-oil emulsion to thermal energy capable of activating the polymerization initiator in the water-in-oil emulsion, far infrared rays, ultraviolet rays, or visible light to form a highly water-containing crosslinked polymer. And (c) a step of dehydrating the high water content crosslinked polymer, and a method for producing a foam sheet.

  In the method for producing a foam sheet, (a) preparation and molding step of the water-in-oil emulsion, (b) formation step of the high water content cross-linked polymer, and (c) dehydration step of the high water content cross-linked polymer. May be performed continuously.

  The present invention also relates to a foam sheet obtained by any one of the above-described production methods having a closed cell structure.

  The present invention also relates to a foam sheet obtained by any one of the above-described production methods having an open cell structure.

  The water-in-oil emulsion of the present invention is excellent in stability and can be polymerized into a foam sheet. A continuous foam sheet can be stably produced using such a water-in-oil emulsion.

  The foam sheet produced from the water-in-oil emulsion of the present invention has a three-dimensional network structure by crosslinking and has excellent heat resistance.

  Furthermore, in the conventional foam molding method, it is necessary to prepare the foam thickness by processing such as slicing. However, in the foam sheet of the present invention, the monomer composition is formed into a sheet shape with an arbitrary thickness. It is possible to produce a foam sheet having a desired thickness continuously with high accuracy.

It is a figure which shows the cross-sectional SEM photograph (1200 time) of the acrylic resin foam obtained in Example 1. FIG. It is a figure which shows the cross-sectional SEM photograph (1200 time) of the acrylic resin foam obtained in Example 2. FIG. It is a figure which shows the cross-sectional SEM photograph (1200 time) of the bridge | crosslinking type foam sheet obtained by the comparative example 1. FIG. It is a figure which shows the cross-sectional SEM photograph (1200 time) of the bridge | crosslinking type foam sheet obtained by the comparative example 2. FIG.

The water-in-oil emulsion of the present invention comprises the following components (a), (b), and (c):
(A) i) a prepolymer syrup obtained by partial polymerization of a polymerizable composition comprising at least one ethylenically unsaturated monomer, ii) at least one polymerization initiator, and iii) at least one kind A continuous oil phase component comprising a crosslinking agent;
(B) at least one co-continuous or discontinuous phase component immiscible with the continuous oil phase component; and (c) at least one surfactant.

  Here, in the water-in-oil emulsion of the present invention, optionally, the prepolymer syrup constituting the component (a) is copolymerized with at least one ethylenically unsaturated monomer and the ethylenically unsaturated monomer. It can be at least one prepolymer syrup obtained by partial polymerization of a polymerizable composition comprising at least one polar monomer possible.

  Here, the ethylenically unsaturated monomer is preferably at least one alkyl (meth) acrylate having at least one alkyl group having 1 to 20 carbon atoms.

  In the present specification, the term “alkyl (meth) acrylate having 1 to 20 carbon atoms in an alkyl group” refers to a linear or branched alkyl group having 1 to 20 carbon atoms (meta ) Refers to acrylates and excludes those containing an aromatic ring in the structure. The average carbon number of the alkyl group is preferably 2-18. (Meth) acrylate refers to acrylate and / or methacrylate, and (meth) of the present invention has the same meaning.

  Specific examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, s-butyl (meth) acrylate, and t-butyl (meth) ) Acrylate, isobutyl (meth) acrylate, n-pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, isoamyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-dodecy (Meth) acrylate, isomyristyl (meth) acrylate, n-tridecyl (meth) acrylate, n-tetradecyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) Examples include acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate, eicosyl (meth) acrylate, and isostearyl (meth) acrylate. Especially, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, etc. can be illustrated and these can be used individually or in combination of 2 or more types.

  In the present invention, the “polar monomer” includes (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, ω-carboxy-polycaprolactone monoacrylate, monohydroxyethyl acrylate phthalate, itaconic acid, malee Carboxyl group-containing monomers such as acid, fumaric acid and crotonic acid; acid anhydride monomers such as maleic anhydride and itaconic anhydride; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, (meta ) 4-hydroxybutyl acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, (4 -Hydroxyme Hydroxyl group-containing monomers such as tilcyclohexyl) methyl (meth) acrylate; amide group-containing monomers such as N, N-dimethyl (meth) acrylamide and N, N-diethyl (meth) acrylamide, and the like. It can be used in combination of more than one species.

  As described above, a prepolymer syrup obtained by partially polymerizing a polymerizable composition comprises a polymerizable composition comprising the above ethylenically unsaturated monomer and / or a polar monomer copolymerizable with the ethylenically unsaturated monomer. This is a prepolymer syrup obtained by partial polymerization. Here, although depending on the type and combination of the ethylenically unsaturated monomer and the polar monomer, it is preferably in the range of 0 to 30 parts by weight of the polar monomer with respect to 70 to 100 parts by weight of the ethylenically unsaturated monomer Preferably it is the range of 5-20 weight part of polar monomers with respect to 80-95 weight part of ethylenically unsaturated monomers. When the usage-amount of the said polar monomer exceeds 30 weight part, the water-in-oil emulsion formed at an emulsification process may become a gel form, and it may become difficult to shape | mold the said water-in-oil emulsion.

  The method for producing a prepolymer syrup by partially polymerizing the polymerizable composition is not particularly limited, and a known polymer syrup production method can be applied. Such a method is not limited. For example, the polymerizable composition contains a small amount of a polymerization initiator, and is exposed to thermal energy, ultraviolet rays, far infrared rays, visible light, or the like depending on the kind of the polymerization initiator. And adjusting to the desired viscosity and base. The viscosity of the prepolymer syrup is 1 to 50 Pa · s, preferably 5 to 30 Pa · s, and more preferably 5 to 20 Pa · s. Here, the viscosity is measured at 25 ° C. using a B-type viscosity type.

  The base in the prepolymer syrup is 1 to 50% by weight, preferably 5 to 40% by weight, more preferably 5 to 30% by weight. The base of the prepolymer syrup is precisely weighed about 0.5 g of the prepolymer syrup and weighed after drying for 2 hours at 130 ° C. to determine the weight loss (volatile matter (unreacted monomer weight)). And can be calculated by the following equation.

  Prepolymer syrup base (%) = [1− (weight loss) / (weight of prepolymer syrup before drying)] × 100

  Mw (weight average molecular weight) of the prepolymer syrup is 100,000 to 10 million, preferably 200,000 to 9 million, and 200,000 to 8 million.

The weight average molecular weight (Mw) can be measured by gel permeation chromatograph (GPC). More specifically, as a GPC measuring device, the product name “HLC-8120GPC” (manufactured by Tosoh Corporation) can be used to measure and obtain a polystyrene-converted value under the following GPC measurement conditions.
GPC measurement conditions and sample concentration: 0.1% by weight (tetrahydrofuran solution)
Sample injection volume: 100 μl
・ Eluent: Tetrahydrofuran (THF)
・ Flow rate (flow rate): 0.5 mL / min
Column temperature (measurement temperature): 40 ° C
-Column: Two "TSK GEL GMHHR-H (20)" (manufactured by Tosoh Corporation) are connected.-Detector: Differential refractometer

  In the present invention, the polymerization initiator used in achieving the partial polymerization in the above prepolymer syrup, or mixed with the prepolymer syrup, and used to prepare the continuous oil phase component of the present invention ii) The polymerization initiator as a component includes a polymerization initiator such as a radical polymerization initiator, an anionic polymerization initiator, and a cationic polymerization initiator. Furthermore, examples of the radical polymerization initiator include a thermal polymerization initiator, a photopolymerization initiator, and a redox polymerization initiator. Examples of the thermal polymerization initiator include azo compounds, peroxides, peroxycarbonic acid, peroxycarboxylic acid, potassium persulfate, t-butylperoxyisobutyrate, and 2,2′-azobisisobutyronitrile. . Examples of the photopolymerization initiator include 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone (for example, Ciba Japans, trade name: Darocur 2959), α-hydroxy-α, α'-dimethylacetophenone (for example, Ciba Japans, trade name: Darocur 1173), methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone (for example, Ciba Japans, trade name: Irgacure) 651) 2-hydroxy-2-cyclohexylacetophenone (for example, Ciba Japan's product name; Irgacure 184) and other acetophenone-based photopolymerization initiators, benzyldimethyl ketal and other ketal-based photopolymerization initiators, and others Halogenated ketones, acylphosphine oxides (for example, Ciba Japans , Trade name, mention may be made of Irgacure 819), and the like. These polymerization initiators may be used alone or in combination of two or more.

  In the case of the polymerization initiator used for achieving the partial polymerization in the prepolymer syrup, the amount of the polymerization initiator used is 0.1% with respect to 100 parts by weight of the mixed monomer of the alkyl (meth) acrylate and the polar monomer. It is 03-1 weight part, Preferably, it is 0.05-0.5 weight part.

  The amount of the polymerization initiator mixed with the prepolymer syrup is, depending on the combination of the monomer component and the polymerization initiator, a prepolymer syrup or a continuous oil phase component composed of the prepolymer syrup and a crosslinking agent. It is preferable that it is the range of 0.05-5.0 weight part with respect to 100 weight part of the whole, More preferably, it is 0.1-1.0 weight part. When the amount of the polymerization initiator used is less than 0.05 parts by weight, the amount of unreacted monomer components may increase, and the amount of residual monomers in the resulting porous material tends to increase. become. On the other hand, when the usage-amount of the said polymerization initiator exceeds 5.0 weight part, the mechanical property of the foam material obtained may deteriorate.

  The amount of radicals generated by the photopolymerization initiator also varies depending on the type and intensity of light to be irradiated, time, the amount of dissolved oxygen in the monomer and solvent mixture, and the like. When the amount of dissolved oxygen is large, the amount of radicals generated is suppressed, the polymerization does not proceed sufficiently, and unreacted substances may increase. Therefore, before the light irradiation, it is preferable that an inert gas such as nitrogen is blown into the composition to replace oxygen with nitrogen.

  When a photopolymerization initiator is used as the polymerization initiator, it can be produced without containing an environmentally hazardous substance such as an organic solvent, if desired. Furthermore, it is not necessary to heat the monomer composition for a long time during polymerization. Therefore, it is not necessary to consider the boiling temperature of the co-continuous or discontinuous phase component immiscible with the continuous oil phase component constituting the water-in-oil emulsion, and a foam having a desired molecular structure in the course of photopolymerization Sheets can be obtained continuously in a short time.

  The cross-linking agent used in the present invention is typically present to connect polymer chains together to produce a more three-dimensional molecular structure. The selection of the particular type and amount of crosslinker depends on the structural, mechanical, and fluid treatment characteristics desired for the resulting foam. The selection of the specific type and amount of crosslinker is important in the final realization of the preferred foam with the desired combination of structure and mechanical properties. Such cross-linking agents include methacrylates, acrylamides, methacrylamides and mixtures thereof. These include di, tri and tetra-acrylates, di, tri and tetra-methacrylates, di, tri and tetra-acrylamides, di, tri and tetra-methacrylamides, and mixtures of these crosslinkers. Suitable acrylate and methacrylate crosslinkers can be derived from diols, triols and tetraols including 1,10 decanediol, 1,8 octanediol, 1,6 hexanediol, 1,4 butanediol, 1, 3 butanediol, 1,4 butane 2ene diol, ethylene glycol, diethylene glycol, trimethylolpropane, pentaerythritol, hydroquinone, catechol, resorcinol, triethylene glycol, polyethylene glycol, sorbitol, etc. (acrylamide and methacrylamide crosslinkers are Can be derived from the corresponding diamines, triamines and tetraamines). Preferred diols have at least 2, more preferably at least 4, and most preferably 6 carbon atoms. The amount of the crosslinking agent used depends on the combination of the ethylenically unsaturated monomer and the polar monomer constituting the continuous oil phase component, but is at least one prepolymer syrup obtained by partially polymerizing the polymerizable composition. It is preferable that it is the range of 5-30 weight part with respect to a part, More preferably, it is 10-30 weight part. When the amount of the crosslinking agent used is less than 5 parts by weight, the cell structure may be lost due to shrinkage in the step of dehydrating the highly hydrous crosslinked polymer due to a decrease in heat resistance. On the other hand, when the usage-amount of the said crosslinking agent exceeds 30 weight part, since the mechanical property of the foam material obtained is deteriorated, it is unpreferable.

  The continuous oil phase component of the present invention comprises such a polymerizable composition comprising (i) an ethylenically unsaturated monomer and optionally at least one polar monomer copolymerizable with the ethylenically unsaturated monomer. A prepolymer syrup obtained by partial polymerization, (ii) at least one polymerization initiator, and (iii) at least one crosslinking agent can be uniformly mixed.

  The co-continuous or discontinuous phase component b) used in the present invention can use any fluid that is substantially immiscible with the continuous oil phase component. The best known immiscible fluid is water. The immiscible fluid may contain a photoinitiator.

  The water-in-oil emulsion of the present invention does not require a salt to stabilize the emulsion, but a salt may be added. Examples of the salt include, but are not limited to, sodium carbonate, calcium carbonate, potassium carbonate, sodium phosphate, calcium phosphate, potassium phosphate, sodium chloride, potassium chloride and the like.

  The relative amount of the co-continuous or discontinuous phase component that is immiscible with the continuous oil phase component used to form the water-in-oil emulsion of the present invention depends on the structural, mechanical, and performance of the resulting polymer foam. Is important in determining physical characteristics. Because the volume ratio of the continuous oil phase component to the immiscible co-continuous or discontinuous phase component affects the characteristics of the foam, such as density, cell size, cell structure, and the dimensions of the walls that form the foam structure. When it is desired to obtain a rigid foam foam, the discontinuous phase component is decreased. When a flexible foam foam is desired, the discontinuous phase component is increased.

  Specifically, in the present invention, the entire emulsion is kept stable even in a state where the proportion of immiscible co-continuous or discontinuous phase components is high. Therefore, the immiscible co-continuous or discontinuous phase component may be 74% by weight or more, and preferably 74% by weight or more and 99% by weight or less based on the whole emulsion.

  The density and microstructure of the foam will also depend on the mode of production of the emulsion, that is, the rate of addition of the immiscible co-continuous or discontinuous phase component to the continuous oil phase component, the stirring method. Therefore, when obtaining a fine structure, it is preferable to slow down the addition rate and add under high shear conditions. When increasing the diameter, it is preferred to speed up the addition and add under low shear conditions.

  The water-in-oil emulsion of the present invention further contains a surfactant. The surfactant used in the present invention is not particularly limited as long as it has an action of generating a water-in-oil emulsion, but is not particularly limited as long as it has an action of generating a water-in-oil emulsion. However, surfactants with a hydrophilic / lipophilic balance (hereinafter abbreviated as HLB) of about 3.5 to 6.0 are suitable. For example, sorbitan high grades such as sorbitan sesquioleate, sorbitan monooleate, and sorbitan monostearate. Examples thereof include glycerol such as fatty acid ester, glycerol stearate and polyglycerol oleate, and higher fatty acid ester of polyglycerol. These surfactants may be used in combination of two or more in order to obtain a desired effect.

  Furthermore, these surfactants and surfactants having high HLB, for example, polyoxyethylene alkylphenyl ethers such as polyoxyethylene nonylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene Nonionic surfactants including polyoxyethylene alkyl ethers such as oleyl ether, polyoxyethylene lauryl ether, and fatty acid esters of polyoxyethylene such as polyoxyethylene oleate, polyoxyethylene lauryl ether, polyoxyethylene tri Polyoxyethylene alkyl ether phosphates such as decyl ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene dinonyl phenyl ether Ether the H.L.B. by mixing with such anionic surfactants including phosphate esters of polyoxyethylene alkyl phenyl ethers such as it may be used after adjusted to about 3.5 to 6.0. In particular, at least one surfactant selected from sorbitan sesquioleate, sorbitan monooleate, and sorbitan monostearate, and a phosphate ester of polyoxyethylene alkyl ether or polyoxyethylene alkyl aryl ether having an HLB of 6.5 to 11.5 What mixed the at least 1 sort (s) of selected surfactant and adjusted HLB to about 3.5-6.0 can change the magnitude | size of a pore in a wide range easily.

    The ratio of the surfactant c) to the continuous oil phase component a) is desirably 1 to 30 parts by weight, more preferably 5 to 20 parts by weight with respect to 100 parts by weight of the continuous oil phase component a). When the amount of the surfactant used is less than 1 part by weight, the original function and effect of the surfactant may not be sufficiently exhibited. On the other hand, when the usage-amount of the said surfactant exceeds 30 weight part, the foam sheet obtained may become weak, the further effect corresponding to a usage-amount cannot be expected, and it is uneconomical.

  Emulsions are typically prepared by methods such as shaking using an emulsifier such as a blade mixer or pin mixer, and use of a magnetic stir bar under low shear conditions, i.e., providing gentle mixing of the continuous and dispersed phases. Is done.

  High shear conditions may be achieved by a rotor-stator mixer, a homogenizer, or a microfluidizer. The emulsion of the present invention may be produced by continuous or batch operation.

  Suitable equipment for continuously producing the emulsion includes a static mixer, a rotor-stator mixer, and a pin mixer. More intense agitation may be achieved by increasing the agitation speed or by using an apparatus designed to finely disperse the emulsifier in the emulsion by a mixing method. Batch process emulsions may be made by mixing or shaking the combined ingredients by hand or machine. For example, a driven blade mixer or a three-blade propeller mixing blade may be used to achieve more intense agitation in the batch process.

  In addition, the water-in-oil emulsion contains, as optional components, tackifying resin, talc, calcium carbonate, magnesium carbonate, silicic acid and its salts, clay, mica powder, aluminum hydroxide, magnesium hydroxide, zinc white, vent Nine, carbon black, silica, alumina, aluminum silicate, acetylene black, aluminum powder and other conventionally known additives such as pigments and dyes are used as long as they do not impair emulsion stability and polymerization reactivity. Can be blended.

  In the present invention, in order to shape and polymerize a water-in-oil emulsion, in the formation of a water-in-oil emulsion, a continuous oil phase component and a co-continuous or discontinuous phase component are continuously supplied to an emulsifier. Forming a water-in-water emulsion, polymerizing the resulting water-in-oil emulsion to obtain a highly hydrous crosslinked polymer, followed by a "continuous method" in which the process of dehydrating the highly hydrous crosslinked polymer is continuously performed, Appropriate amounts of water phase and oil phase are supplied to an emulsifier, and a water-in-oil emulsion in the emulsifier is used to obtain a highly water-containing crosslinked polymer, which is then used in any of the “batch methods” for dehydration. it can. The continuous polymerization method in which the water-in-oil emulsion is continuously polymerized is a preferable method because the production efficiency is high and the effect of shortening the polymerization time and the shortening of the polymerization apparatus can be most effectively utilized.

  Specifically, as a continuous polymerization method for a sheet-like porous polymer, a water-in-oil emulsion of the present invention is continuously applied on a traveling belt having a structure in which the belt surface of a belt conveyor is heated by a heating device. A method of polymerizing by heating while forming a smooth sheet on the belt; or using a device that irradiates actinic radiation in place of the heating device, and on the running belt of the present invention. There is a method in which a water-in-oil emulsion is continuously fed and polymerized by actinic light while forming a smooth sheet on a belt.

  Therefore, as one aspect, a porous polymer can be obtained by supplying a water-in-oil emulsion to the polymerization apparatus and heating it. In the water-in-oil emulsion of the present invention, it is preferable to heat the water-in-oil emulsion in the range of room temperature to 150 ° C., and preferably from 70 to 150 ° C. from the viewpoint of the stability of the water-in-oil emulsion and the polymerization rate. More preferably, it is 80-130 degreeC, Most preferably, it is the range of 90-110 degreeC. When the polymerization temperature is less than room temperature, the polymerization takes a long time, which is not preferable for industrial production. On the other hand, when the polymerization temperature exceeds 150 ° C., the pore diameter of the obtained porous material becomes non-uniform, and the strength of the porous material is lowered, which may be undesirable. Further, the polymerization temperature may be changed in two stages or even multiple stages during the polymerization, and this polymerization method is not excluded.

  On the other hand, in consideration of productivity, a method of polymerizing and crosslinking by forming water-in-oil emulsions and then exposing them to actinic rays such as ultraviolet rays and visible rays is also preferably used.

  At this time, after the water-in-oil emulsions are formed, they may be exposed to actinic radiation such as ultraviolet rays and visible rays to be polymerized and crosslinked. Preferably, light in the visible and / or ultraviolet range (200 nm to 800 nm) is used to polymerize the water-in-oil emulsion of the present invention. Since water-in-oil emulsions have a strong tendency to scatter light, it is preferable to use long wavelengths in this range that can better penetrate water-in-oil emulsions. Preferred wavelengths are 200-800 nm, more preferably 300-800 nm, most preferably 300-450 nm due to the availability of photoinitiators that can be activated at these wavelengths and the availability of light sources. . The photopolymerization initiator used must be able to absorb the wavelength (s) of the light source used. In the present invention, as a typical lamp used for light irradiation, an ultraviolet lamp capable of performing ultraviolet irradiation includes a lamp having a spectral distribution in a wavelength region of 300 to 400 nm. Examples thereof include a chemical lamp and a black light. (Trade name manufactured by Toshiba Lighting & Technology Co., Ltd.), metal halide lamps.

  The ultraviolet illuminance in the present invention is set to the desired illuminance by adjusting the distance from the ultraviolet lamp to the ultraviolet irradiated object (water-in-oil emulsion) and the voltage, but this is disclosed in JP-A-2003-13015. In the method, ultraviolet irradiation in each step is performed in a plurality of stages, whereby the adhesion performance can be adjusted more precisely. This ultraviolet irradiation is carried out in a nitrogen gas atmosphere, an inert gas atmosphere or flowing to the substrate in order to prevent as much as possible the influence on the polymer polymerization rate, molecular weight and molecular weight distribution from which oxygen having a polymerization inhibiting action is obtained. It is preferable to carry out by laminating a film which blocks ultraviolet rays such as polyethylene terephthalate coated with a release agent such as silicone, but blocks oxygen, on the spread ultraviolet ray polymerizable monomer composition.

  In the method for producing a foam sheet according to the present invention, for example, the water-in-oil emulsion is coated on one surface of a thermoplastic resin film, and is coated with a release agent such as silicone under an inert gas atmosphere. A step of irradiating light in a state where oxygen is blocked by coating with a film can also be included.

  Examples of such a thermoplastic resin film include, but are not limited to, plastic films and sheets such as polyester, olefin resin, and polyvinyl chloride.

  In the present invention, the method for coating the water-in-oil emulsion on one surface of the substrate is not particularly limited, and it is performed using a commonly used roll coater, die coater, knife coater, or the like. Can do.

  In the present invention, the inert gas atmosphere during photopolymerization refers to an atmosphere in which oxygen in the light irradiation zone is replaced with an inert gas such as nitrogen. Therefore, it is desirable that oxygen is not present as much as possible in the inert gas atmosphere, and the oxygen concentration is preferably 5000 ppm or less.

  After polymerizing the water-in-oil emulsion, the co-continuous or discontinuous phase components are typically still present in the porous polymer. This residual co-continuous or discontinuous phase component may be removed by drying the porous polymer. Suitable drying methods include, for example, vacuum drying, freeze drying, press drying, microwave drying, drying in a heat oven, infrared drying, or a combination of these techniques.

  Many polymer foams made from the above water-in-oil emulsions of the present invention are typically closed cell, but open cell foams can also be made. This means that most or all of the bubbles are in undisturbed communication with adjacent bubbles.

  Foam bubbles, particularly those formed by polymerization of a monomer-containing continuous oil phase surrounding a relatively monomer-free, immiscible, co-continuous or discontinuous phase droplet, tend to be substantially spherical in shape. For the majority of applications, the bubble size is typically in the range of 1 to 200 μm, preferably less than 100 μm, more preferably less than 50 μm, and most preferably less than 20 μm.

  The foam sheet of the present invention is suitable for countless applications such as cushion materials, insulating materials, heat insulating materials, soundproofing materials, dustproofing materials, and filtering materials.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In addition, the part in each example is based on weight, and% is based on capacity. The room temperature standing conditions not specifically defined below are all 23 ° C. and 65% RH (1 hour). Evaluation items in Examples and the like were measured as follows.

(Preparation of prepolymer syrup)
(Preparation of Syrup 1) 90 parts by weight of 2-ethylhexyl acrylate (manufactured by Toa Gosei Co., Ltd., hereinafter abbreviated as “2EHA”) as an ethylenically unsaturated monomer, acrylic acid (manufactured by Toa Gosei Co., Ltd., hereinafter “AA”) as a polar monomer 2,2-dimethoxy-1,2-diphenylethane-1-one (trade name “IRGACURE 651” manufactured by Ciba Japan Co., Ltd.) for 100 parts by weight of the mixed monomer solution consisting of 10 parts by weight. A solution to which 0.05 part by weight of 0.05 part by weight of 1-hydroxy-cyclohexyl-phenyl-ketone (manufactured by Ciba Japan Co., Ltd., trade name “IRGACURE 184”) was added to a four-necked flask, A partially polymerized base of 7.1% monomer syrup was obtained by partial photopolymerization by exposure to UV light.

(Preparation of syrup 2) In the preparation of 2EHA / AA = 95/5 syrup 1, the base 7 was prepared in the same manner as in the preparation of syrup 1 except that 2EHA was changed to 66.7 parts by weight and AA was changed to 33.3 parts by weight. Obtained 1% monomer syrup.

(Example 1) 100 parts by weight of partially polymerized prepolymer syrup 1, 30 parts by weight of 1,9-nonanediol diacrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd .; trade name: Viscote # 260), diphenyl (2,4 , 6-trimethylbenzoyl) phosphine oxide (example: BASF, trade name; Lucillin TPO) 0.5 parts by weight, 2-hydroxy-2-cyclohexylacetophenone (example: Ciba Japans, trade name; Irgacure 184) 0.1 part by weight was uniformly mixed to obtain a continuous oil phase component (hereinafter referred to as “oil phase”). To 100 parts by weight of the oil phase component, 15 parts by weight of sorbitan monooleate (manufactured by Kao Corporation, trade name: Rheodor SP-O10V) was added as a surfactant, and the mixture was sufficiently stirred and mixed with a stirrer in a nitrogen atmosphere. On the other hand, 700 parts by weight of ion-exchanged water as a co-continuous or discontinuous phase component (hereinafter referred to as “water phase”) is continuously dropped into a stirring mixer which is an emulsifier charged with the oil phase component at room temperature. Feeded to form a stable HIPE.

The obtained HIPE was coated on a substrate subjected to various peeling treatments so that the thickness after light irradiation was 300 μm and continuously molded. Further, a polyethylene terephthalate film having a thickness of 38 μm and subjected to a release treatment was placed thereon. This sheet was irradiated with ultraviolet rays having a light illuminance of 5 mW / cm ² (measured with Topcon UVR-T1 having a peak sensitivity maximum wave of 350 nm) using black light (15 W / cm) to obtain a highly hydrous crosslinked polymer having a thickness of 300 μm. . Next, the top film was peeled off, and the high water content cross-linked polymer was heated at 130 ° C. for 10 minutes to obtain a cross-linked foam sheet having a thickness of about 300 μm.

(Example 2) In Example 1, syrup 2 was used as a continuous oil phase component, and 17 parts by weight of Rhedol SP-O10V as a surfactant and ion-exchanged water as an aqueous phase with respect to 100 parts by weight of the continuous oil phase component. A crosslinked foam sheet having a thickness of about 300 μm was obtained in the same manner as in Example 1 except that 1150 parts by weight were blended.

(Comparative Example 1) In Example 1, IRGACURE 651 was added in an amount of 0.001 to 100 parts by weight of a mixed monomer composed of 90 parts by weight of 2EHA as an ethylenically unsaturated monomer and 10 parts by weight of AA as a polar monomer. A high water content crosslinked polymer having a thickness of about 300 μm was obtained in the same manner as in Example 2 except that a monomer solution containing 05 parts by weight and 0.05 part by weight of IRGACURE 184 was used. Within minutes, free water was confirmed on the surface of the HIPE emulsion. Free water was also confirmed in the molding process and polymerization process of the HIPE emulsion. A heat-drying treatment gave a crosslinked foam sheet of about 300 μm. Here, the mixed monomer does not include a prepolymer.

(Comparative Example 2) In Example 2, 66.7 parts by weight of 2EHA and 33.3 parts by weight of IBXA were used as the ethylenically unsaturated monomer in the continuous oil phase component, and 100 parts by weight of the mixed monomer containing no polar monomer. A highly water-containing crosslinked polymer having a thickness of about 300 μm was obtained by the same operation as in Example 2 except that a monomer solution containing 0.05 part by weight of IRGACURE 651 and 0.05 part by weight of IRGACURE 184 was used. Free water was confirmed on the surface of the HIPE emulsion within 30 minutes from the end of the emulsification step. Free water was also confirmed in the molding process and polymerization process of the HIPE emulsion. A heat-drying treatment gave a crosslinked foam sheet of about 300 μm. Here, the mixed monomer does not include a prepolymer.

(Test evaluation)
The test pieces obtained in the above examples and comparative examples were tested for foamability. The results are shown in Table 1.

(Emulsion stability) About 30 g of the water-in-oil emulsion prepared in the emulsification step is weighed into a container with a capacity of 50 ml, and the generation of free water is observed 1 hour, 3 hours and 10 hours after the emulsification step. The stationary storage stability at room temperature was evaluated. ○: No free water even after 4 hours, Δ: Free water generated after 4 hours, ×: Free water generated by 0.5 hours

(Measurement of average cell diameter) A foam sample prepared by cutting in the thickness direction with a microtome cutter was used as a measurement sample. The cut surface of the measurement sample was photographed at 120 times with a scanning electron microscope (manufactured by Hitachi, S-4800). And the bubble diameter of the bubble of the arbitrary range was measured using the image | photographed image, and the average bubble diameter was computed from the measured value.

(Sheet Shrinkage after Heating Drying) The foam sheet thus prepared was cut in the thickness direction with a microtome cutter and used as a measurement sample. The cut surface of the measurement sample was photographed at 120 × with a scanning electron microscope (Hitachi, S-4800), and the bubble structure was observed. ○: No bubbles collapsed due to shrinkage, Δ: There are few bubbles collapsed due to shrinkage, ×; Cell structure cannot be maintained due to shrinkage. The evaluation results described above are shown in Tables 1 and 2 below.

Claims (12)

A water-in-oil emulsion comprising the following components (a), (b), and (c):
(A) i) a prepolymer syrup obtained by partial polymerization of a polymerizable composition comprising at least one ethylenically unsaturated monomer, ii) at least one polymerization initiator, and iii) at least one kind A continuous oil phase component comprising a crosslinking agent;
(B) at least one co-continuous or discontinuous phase component immiscible with the continuous oil phase component; and (c) at least one surfactant.   The prepolymer syrup constituting the component (a) comprises a polymerizable composition comprising at least one ethylenically unsaturated monomer and at least one polar monomer copolymerizable with the ethylenically unsaturated monomer. 2. The water-in-oil emulsion according to claim 1, which is at least one prepolymer syrup obtained by polymerization.   The water-in-oil emulsion according to claim 1 or 2, wherein the ethylenically unsaturated monomer contains at least one alkyl (meth) acrylate having 1 to 20 carbon atoms in the alkyl group.   The water-in-oil emulsion according to any one of claims 1 to 3, wherein the co-continuous or discontinuous phase component is water.   5. A water-in-oil emulsion according to any one of claims 1 to 4, wherein the co-continuous or discontinuous phase component comprises at least 74 volume percent of the total emulsion.   The water-in-oil emulsion according to any one of claims 1 to 5, wherein the amount of the crosslinking agent in the continuous oil phase component is 5 parts by weight or more with respect to 100 parts by weight of the prepolymer syrup. A method for preparing a water-in-oil emulsion according to any one of claims 1-6,
(a) i) a step of partially polymerizing a polymerizable composition comprising at least one ethylenically unsaturated monomer to obtain a prepolymer syrup;
ii) obtaining a continuous oil phase component by mixing the prepolymer syrup with at least one polymerization initiator and at least one crosslinking agent;
(b) mixing at least one co-continuous or discontinuous phase component immiscible with the continuous oil phase component and (c) at least one surfactant.
A preparation method comprising:   The method for preparing a water-in-oil emulsion according to claim 7, wherein the polymerizable composition further comprises at least one polar monomer copolymerizable with the ethylenically unsaturated monomer. A method for producing a foam sheet, comprising:
(a) forming a water-in-oil emulsion obtained by the preparation method according to claim 7;
(b) a step of exposing the water-in-oil emulsion to thermal energy capable of activating the polymerization initiator in the water-in-oil emulsion, far infrared rays, ultraviolet rays, or visible light to form a highly water-containing crosslinked polymer. ;and
(c) dehydrating the high water content crosslinked polymer;
The manufacturing method of the foam sheet containing this.   The process of (a) preparing and forming the water-in-oil emulsion, (b) forming the highly hydrous crosslinked polymer, and (c) dehydrating the hydrous crosslinked polymer, are performed continuously. The method for producing a foam sheet according to 9.   The foam sheet obtained by the manufacturing method according to claim 9, having a closed cell structure. The foam sheet obtained by the manufacturing method according to claim 9, which has an open cell structure.