foam

Abstract

The present invention provides a foamed body containing a nitrile group-containing conjugated diene-based copolymer and a polyurethane-based polymer, wherein the total of the nitrile group-containing conjugated diene-based copolymer and the polyurethane-based polymer is 100% by weight, the nitrile group-containing conjugated diene-based copolymer is less than 90% by weight, the polyurethane-based polymer is more than 10% by weight, the content of ethylenically unsaturated nitrile monomer units in the nitrile group-containing conjugated diene-based copolymer is more than 31% by weight, and the foamed body has a density of 0.08 to 0.30 g / cm 3 In any cross section of the foamed body, the average diameter of the cross sections of the bubbles appearing in the cross section is 350 μm or less, and the number of bubbles having a diameter of 0.6 mm or more appearing in the cross section is 0.062 or less per mm 2 The following.

Description

Technical Field

[0001] This invention relates to a foam, and more specifically, to a foam that exhibits excellent softness and cosmetic impregnation properties, is capable of uniformly applying cosmetics to the skin, and is not easily deformed or worn even when covered with cosmetics. Background Technology

[0002] Rubber foams (foamed rubber) made from polymer latex are used in various applications such as mattresses, powder puffs (cosmetic sponges), rollers, and shock absorbers. Among these applications, rubber foams used in powder puffs especially require good foaming properties, a uniform foam structure, and an excellent balance between elasticity and feel.

[0003] For example, Patent Document 1 discloses a method for manufacturing a high-performance cosmetic puff substrate, characterized in that: air is mixed into a composition comprising a water-soluble NBR (nitrile butadiene rubber) emulsion, a water-soluble polyurethane emulsion, a crosslinking agent, a surfactant, and a gelling agent, and stirred to cause foaming; then, the mixture is vulcanized by heating to manufacture a puff substrate of a predetermined shape; the solid content concentration of the water-soluble NBR emulsion is 60% by weight or more, and the proportion of the water-soluble polyurethane emulsion, calculated in terms of solid content, is 5 to 15% by weight relative to the total solid content of the two emulsions. However, the technology in Patent Document 1 has the following problem: the obtained high-performance cosmetic puff substrate is prone to deformation when contaminated with cosmetics, and if it continues to be used while contaminated with cosmetics, its wear will increase.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Publication No. 8-5988. Summary of the Invention

[0007] The problem the invention aims to solve

[0008] The present invention was made in view of the current situation, and its purpose is to provide a foam that has excellent softness and cosmetic impregnation properties, can be evenly applied to the skin with cosmetics, and is not easily deformed and has low wear even when covered with cosmetics.

[0009] Solution for solving the problem

[0010] In order to achieve the above objectives, the inventors conducted in-depth research and found that by using a nitrile-containing conjugated diene copolymer with a specific monomer composition, adjusting the ratio of the nitrile-containing conjugated diene copolymer to the polyurethane polymer, and adjusting the density of the foam and the size of the bubbles in the foam, the above objectives can be achieved, thus completing the present invention.

[0011] That is, according to the present invention, a foam containing a nitrile-containing conjugated diene copolymer and a polyurethane polymer can be provided.

[0012] When the total weight of the above-mentioned nitrile-containing conjugated diene copolymer and the above-mentioned polyurethane polymer is 100% by weight, the above-mentioned nitrile-containing conjugated diene copolymer is less than 90% by weight, and the above-mentioned polyurethane polymer is more than 10% by weight.

[0013] In the above-mentioned nitrile-containing conjugated diene copolymers, the content of olefinically unsaturated nitrile monomer units exceeds 31% by weight.

[0014] The density of the above-mentioned foam is 0.08–0.30 g / cm³. 3 ,

[0015] When observing any cross-section of the foam, the average diameter of the bubbles in that cross-section is less than 350 μm, and the number of bubbles with a diameter greater than 0.6 mm is 0.062 per mm. 2 the following.

[0016] In the foam of the present invention, when the total of the above-mentioned acrylonitrile-containing conjugated diene copolymer and the above-mentioned polyurethane polymer is 100% by weight, it is preferable that the above-mentioned acrylonitrile-containing conjugated diene copolymer is 85% by weight or less and the above-mentioned polyurethane polymer is 15% by weight or more.

[0017] In the foam of the present invention, preferably, the content of olefinically unsaturated nitrile monomer units in the above-mentioned nitrile-containing conjugated diene copolymer is 32-80% by weight, and the content of conjugated diene monomer units is 20-68% by weight.

[0018] The foam of the present invention preferably further contains an ultraviolet absorber.

[0019] Invention Effects

[0020] According to the present invention, a foam with excellent softness and cosmetic impregnation properties, capable of uniformly applying cosmetics to the skin, and not easily deformed and with low wear even when covered with cosmetics, can be provided. Attached Figure Description

[0021] Figure 1Here is an example of a microscope photograph (30x magnification) of an arbitrary cross-section of a foam.

[0022] Figure 2 (A) is observed at a magnification of 100x. Figure 1 After obtaining region 13 (1mm × 1mm) of the microscope image, a schematic diagram was created based on the obtained microscope image. Figure 2 In (A), the cross-section of each bubble with a diameter of 50 μm or more is approximated as a circle. Figure 2 (B) is for the purpose of illustrating in Figure 2 (A) shows a schematic diagram of the cross-sections of an independent bubble and a continuous bubble in the bubble cross-section. Detailed Implementation

[0023] The foam of the present invention is characterized in that it contains a nitrile-containing conjugated diene copolymer and a polyurethane polymer, wherein, when the total amount of the nitrile-containing conjugated diene copolymer and the polyurethane polymer is 100% by weight, the nitrile-containing conjugated diene copolymer is less than 90% by weight, the polyurethane polymer is more than 10% by weight, and in the nitrile-containing conjugated diene copolymer, the content of olefinically unsaturated nitrile monomer units is more than 31% by weight, and the density of the foam is 0.08 to 0.30 g / cm³. 3 When observing any cross-section of the foam, the average diameter of the bubbles in the cross-section is less than 350 μm, and the number of bubbles with a diameter greater than 0.6 mm is 0.062 per mm. 2 the following.

[0024] First, the nitrile-containing conjugated diene copolymer and polyurethane polymer contained in the foam of the present invention will be described.

[0025] Nitrile-containing conjugated diene copolymers

[0026] Nitrile-containing conjugated diene copolymers are copolymerized from conjugated diene monomers and olefinically unsaturated nitrile monomers. In addition, other olefinically unsaturated monomers that can be copolymerized with them can also be copolymerized as needed.

[0027] As an olefinically unsaturated nitrile monomer, there is no particular limitation as long as it contains a nitrile group; examples include acrylonitrile, methacrylonitrile, fumaric acid, α-chloroacrylonitrile, and α-cyanoethylacrylonitrile. Among these, acrylonitrile and methacrylonitrile are preferred, and acrylonitrile is more preferred. These olefinically unsaturated nitrile monomers can be used alone or in combination of two or more.

[0028] In nitrile-containing conjugated diene copolymers, the content of olefinically unsaturated nitrile monomer units formed from olefinically unsaturated nitrile monomers exceeds 31% by weight, preferably 32-80% by weight, more preferably 33-70% by weight, and even more preferably 34-60% by weight. By keeping the content of olefinically unsaturated nitrile monomer units within the above range, the resulting foam can possess the following characteristics: excellent softness and cosmetic impregnation properties, the ability to uniformly apply cosmetics to the skin, and resistance to deformation and low abrasion even when coated with cosmetics. When the content of olefinically unsaturated nitrile monomer units is too low, a foam with excellent softness and cosmetic impregnation properties, the ability to uniformly apply cosmetics to the skin, and resistance to deformation and low abrasion even when coated with cosmetics cannot be obtained. When the content of olefinically unsaturated nitrile monomer units is too high, there is a tendency for decreased cold resistance and increased embrittlement temperature.

[0029] Examples of conjugated diene monomers include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene, and chlorobutadiene. Among these, 1,3-butadiene and isoprene are preferred. These conjugated diene monomers can be used alone or in combination of two or more.

[0030] In the nitrile-containing conjugated diene copolymer, the proportion of conjugated diene monomer units formed from conjugated diene monomers is preferably less than 69% by weight, more preferably 20-68% by weight, even more preferably 30-67% by weight, and particularly preferably 40-66% by weight. By keeping the proportion of conjugated diene monomer units within the above range, the resulting foam can have the following characteristics: better softness and cosmetic impregnation properties, more uniform application of cosmetics to the skin, and less deformation and wear even when covered with cosmetics.

[0031] Furthermore, from the viewpoint that the resulting foam can have better softness and cosmetic impregnation properties, can be more evenly applied to the skin, and is less prone to deformation and wear even when covered with cosmetics, it is preferable to use 1,3-butadiene and isoprene. In the nitrile-containing conjugated diene copolymer, the ratio of 1,3-butadiene units to isoprene units is preferably in the range of 5 / 5 to 9 / 1.

[0032] Other olefinically unsaturated monomers that can copolymerize with conjugated diene monomers and olefinically unsaturated nitrile monomers include, for example, olefinically unsaturated carboxylic acids such as (meth)acrylic acid, maleic acid (anhydride), fumaric acid, and itaconic acid; monoalkyl or dialkyl esters of olefinically unsaturated carboxylic acids such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, monomethyl maleate, dimethyl maleate, monoethyl fumarate, diethyl fumarate, mono-n-butyl fumarate, di-n-butyl fumarate, mono-n-butyl itaconic acid, and di-n-butyl itaconic acid; and methoxy acrylates, ethoxy acrylates, and methoxyethoxyethyl acrylates. Alkoxyalkyl esters of olefinically unsaturated carboxylic acids; hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate; glycidyl (meth)acrylate; (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, and their derivatives; amino acrylates such as dimethylaminomethyl acrylate and diethylaminomethyl acrylate; aromatic vinyl monomers such as styrene, α-methylstyrene, vinyltoluene, and chlorostyrene; α-olefins such as ethylene and propylene; and non-conjugated diene monomers such as dicyclopentadiene and vinylnorbornene. These monomers can be used alone or in combination of two or more. In nitrile-containing conjugated diene copolymers, the content of other monomer units formed from other olefinically unsaturated monomers is preferably 40% by weight or less, more preferably 30% by weight or less, and even more preferably 20% by weight or less. By ensuring that the proportions of other monomer units are within the aforementioned range, the resulting foam can possess the following characteristics: superior softness and cosmetic impregnation properties, enabling more even application of cosmetics to the skin, and less deformation and wear even when covered with cosmetics.

[0033] Polyurethane polymers

[0034] Polyurethane polymers are polymers containing urethane bonds, and the polymers contained in polyurethane polymer latexes can be used. There are no particular limitations on the latex used as a polyurethane polymer; for example, a latex obtained by reacting an active hydrogen compound, a compound with hydrophilic groups, and a polyisocyanate to obtain an organic solvent solution or organic solvent dispersion of a polyurethane resin with hydrophilic groups, mixing an aqueous solution containing a neutralizing agent into the organic solvent solution or dispersion, and removing the organic solvent as needed, thereby obtaining a latex. Alternatively, a polyurethane polymer latex may also be obtained by reacting an active hydrogen compound, a compound with hydrophilic groups, and a polyisocyanate to obtain a polyurethane prepolymer with hydrophilic groups and isocyanate groups at the ends, mixing an aqueous solution containing a neutralizing agent and a polyamine into the prepolymer, and reacting the polyamine, thereby obtaining a latex.

[0035] As compounds containing active hydrogen, there are no particular limitations, but examples include, for instance, polyester polyols, polyether polyols, polycarbonate polyols, polyacetal polyols, polyacrylate polyols, polyesteramide polyols, polysulfide polyols, polybutadiene-based polyolefin polyols, and other polyols; ethylene glycol compounds, glycerol, trimethylolethane, trimethylolpropane, sorbitol, pentaerythritol, and other polyhydroxy compounds used as raw materials for polyester polyols; ethylenediamine, 1,6-hexanediamine, piperazine, 2,5-dimethylpiperazine, isophorone diamine, 4,4'-dicyclohexylmethanediamine, 3,3'-dimethyl-4,4'-dicyclohexylmethanediamine, 1,4-cyclohexanediamine, 1,2-propanediamine, hydrazine, diethylenetriamine, triethylenetetramine, and other amine compounds.

[0036] There are no particular limitations on the type of compound having a hydrophilic group. Examples of such compounds include: ionic compounds having one or more active hydrogen atoms in the molecule and containing at least one functional group selected from carboxylate, sulfonate, phosphate, quaternary ammonium, carboxylate, sulfonic acid, phosphate, tertiary amine, and betaine groups; and nonionic compounds having one or more active hydrogen atoms in the molecule and containing a group formed from repeating units of ethylene oxide or a group formed from repeating units of ethylene oxide and other repeating units of alkyl oxidases.

[0037] As an isocyanate, there is no particular limitation, and examples include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-biphenyl diisocyanate, 3,3'-dimethoxy-4,4'-biphenyl diisocyanate, 3,3'-dichloro-4,4'-biphenyl diisocyanate, 1,5-naphthalene diisocyanate, 1 ,5-Tetrahydronaphthalene diisocyanate, tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, dodecamethyl diisocyanate, trimethylhexamethylene diisocyanate, 1,3-cyclohexene diisocyanate, 1,4-cyclohexene diisocyanate, phenylenediamine diisocyanate, tetramethylphenylenediamine diisocyanate, hydrogenated phenylenediamine diisocyanate, lysine diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 3,3'-dimethyl-4,4'-dicyclohexylmethane diisocyanate, etc.

[0038] From the viewpoint of achieving a foam with superior softness and cosmetic impregnation properties, enabling more even application of cosmetics to the skin, and reducing deformation and abrasion even when coated with cosmetics, the tetrahydrofuran-insoluble component in the polyurethane polymer is preferably 3% by weight or more, more preferably 5% by weight or more. A high tetrahydrofuran-insoluble component refers to the polyurethane polymer containing a high concentration of high molecular weight substances.

[0039] From the viewpoint of excellent operability during manufacturing, the ability to produce foams with softness and superior cosmetic impregnation properties, the ability to apply cosmetics evenly to the skin, and the characteristics of being less prone to deformation and less wear even when covered with cosmetics, polyurethane polymers, when producing latex with a solid content concentration of 50% by weight, preferably have a latex with a viscosity of 6000 Pa·s or less when measured at 23°C, and more preferably have a polyurethane polymer with a viscosity of 5000 Pa·s or less when measured at 23°C.

[0040] foam

[0041] In the foam of the present invention, when the total amount of the nitrile-containing conjugated diene copolymer and the polyurethane polymer is 100% by weight, the nitrile-containing conjugated diene copolymer is less than 90% by weight and the polyurethane polymer is more than 10% by weight. Preferably, the nitrile-containing conjugated diene copolymer is 85% by weight or less and the polyurethane polymer is 15% by weight or more. More preferably, the nitrile-containing conjugated diene copolymer is 50 to 85% by weight and the polyurethane polymer is 15 to 50% by weight. By keeping the content ratio of the nitrile-containing conjugated diene copolymer to the polyurethane polymer within the above range, the resulting foam can have the following characteristics: excellent softness and cosmetic impregnation performance, able to uniformly apply cosmetics to the skin, and not easily deformed even when covered with cosmetics, with little wear. When the content ratio of the nitrile-containing conjugated diene copolymer is too high, deformation and wear caused when covered with cosmetics cannot be suppressed. When the content ratio of the polyurethane polymer is too high, there is a risk that the softness and cosmetic impregnation performance will deteriorate, and it will be difficult to uniformly apply cosmetics to the skin.

[0042] The density of the foam body of the present invention is 0.08–0.30 g / cm³. 3 The preferred value is 0.10–0.28 g / cm³. 3 More preferably, it is 0.12–0.25 g / cm³. 3 By maintaining the density of the foam within the aforementioned range, the foam can possess the following characteristics: excellent softness and cosmetic impregnation properties, enabling even application of cosmetics to the skin, and minimal deformation and abrasion even when coated with cosmetics. If the density of the foam is too low, it will be unable to suppress abrasion when coated with cosmetics; if the density is too high, both softness and cosmetic impregnation properties will deteriorate.

[0043] The average diameter of the bubble cross-section appearing on the cross-section of the foam body of the present invention is 350 μm or less, preferably 100 to 300 μm, and more preferably 130 to 270 μm. By keeping the average diameter of the bubble cross-section within the above range, the foam body can have the following characteristics: excellent softness and cosmetic impregnation performance, the ability to uniformly apply cosmetics to the skin, and minimal deformation and abrasion even when cosmetics are present. When the average diameter of the bubble cross-section is too large, it is impossible to uniformly apply cosmetics to the skin, and it is impossible to suppress abrasion when cosmetics are present. When the average diameter of the bubble cross-section is too small, there is a risk that the softness of the foam body and the cosmetic impregnation performance will deteriorate.

[0044] The average diameter of the bubble cross-section is the average of the cross-sectional diameters of bubbles observed at any cross-section of the foam. The average diameter of the bubble cross-section is determined by the following method: Using an optical microscope (digital microscope VHX-900F, manufactured by KEYENCE CORPORATION), an arbitrary cross-section of the foam is observed at 100x magnification. Among the bubble cross-sections observed in any 1mm × 1mm region, bubble cross-sections with a diameter of 50μm or more are selected, and each cross-section is approximated as a circle. The diameter of these circles is measured. This measurement is repeated for nine other arbitrary regions. Then, based on the measured values ​​of each bubble cross-section within a total of 10 regions, the average diameter of the bubble cross-section is calculated. Furthermore, when selecting any 1mm × 1mm region, regions containing bubble cross-sections with a diameter of 0.6mm or more are not selected.

[0045] The number of air bubbles with a diameter of 0.6 mm or more present on the cross-section of the foam of the present invention is 0.062 per mm. 2 The preferred value is 0.049 pieces / mm. 2 The preferred value is 0.037 pieces / mm. 2 The following describes how, by ensuring the number of large-diameter bubble cross-sections is within the aforementioned range, the foam can possess the following characteristics: excellent softness and cosmetic impregnation properties, enabling uniform application of cosmetics to the skin, and minimal deformation and wear even when cosmetics are present. When the number of large-diameter bubble cross-sections is excessive, it becomes impossible to apply cosmetics evenly to the skin. The lower limit is not particularly limited, but fewer is better, preferably 0 bubbles / mm. 2 The above, but even at 0.001 per mm 2 The above or 0.012 pieces / mm 2 In practical applications, the above has no impact.

[0046] The diameter of the bubble cross-section is the diameter of the bubble cross-section observed at any cross-section of the foam. The number of bubble cross-sections with a diameter of 0.6 mm or more is determined by the following method: Using an optical microscope (digital microscope VHX-900F, manufactured by KEYENCE CORPORATION), observe any cross-section of the foam at 30x magnification. For bubble cross-sections observed within any 9mm × 9mm area, approximate the shape of each cross-section as a circle, measure the diameter of these circles, and count the number of bubble cross-sections with a diameter of 0.6 mm or more. If bubble cross-sections with a diameter of 0.6 mm or more are located on the boundary line of the observation area, the ratio of the area of ​​bubble cross-sections within the observation area to the total area of ​​bubble cross-sections can be estimated, and 1 multiplied by this ratio is taken as the count. For example, if a bubble cross-section with a diameter of 0.6 mm or more is located on the boundary line and 30% of it is within the observation area, it can be counted as 0.3.

[0047] UV absorber

[0048] The foam of the present invention preferably further contains an ultraviolet absorber. By containing an ultraviolet absorber, even when the foam is coated with cosmetics, especially cosmetics containing an ultraviolet absorber, it is less prone to deformation and wear.

[0049] In the foam of the present invention, the proportion of ultraviolet absorber relative to a total of 100 parts by weight of the nitrile-containing conjugated diene copolymer and the polyurethane polymer is preferably 1 to 10 parts by weight, more preferably 3 to 7 parts by weight. By keeping the proportion of ultraviolet absorber within the above range, even when the foam is contaminated with cosmetics, it is less prone to deformation and wear.

[0050] As a UV absorber, there are no particular limitations, but examples include cinnamic acid-based UV absorbers such as octyl p-methoxycinnamate (ethylhexyl p-methoxycinnamate), isopropyl p-methoxycinnamate, and glyceryl mono-2-ethylhexanoate; benzoic acid-based UV absorbers such as p-aminobenzoic acid and methyl anthranilate; salicylic acid-based UV absorbers such as octyl salicylate and phenyl salicylate; UV absorbers such as urocanic acid and ethyl urocanic acid; benzophenone-based UV absorbers such as 2-hydroxy-4-methoxybenzophenone and dihydroxybenzophenone; benzotriazole-based UV absorbers; and 2-phenylbenzimidazole-5-sulfonic acid.

[0051] Method for manufacturing foam

[0052] The foam of the present invention can be manufactured by foaming and coagulating a polymer latex comprising a nitrile conjugated diene copolymer and a polyurethane polymer at a desired foaming ratio.

[0053] Polymer latex can be manufactured, for example, by mixing latex containing nitrile-based conjugated diene copolymers and latex containing polyurethane polymers.

[0054] There are no particular limitations on the methods for adjusting the density and bubble size of the foam body of the present invention, and examples include: adjusting the content ratio of defoamer in polymer latex, adjusting the content ratio of bubble stabilizer in polymer latex, adjusting the foaming ratio, adjusting the content ratio of bubble stabilizer during foam body production, and adjusting the type and amount of coagulant.

[0055] There are no particular limitations on defoamers, and examples include oil-based defoamers, mineral oil-based defoamers such as modified hydrocarbon oils with mineral oil as a base, silicone-based defoamers such as silicone oil, and polymer-based defoamers. Among these, mineral oil-based defoamers and silicone-based defoamers are preferred. These defoamers can be used alone or in combination of two or more.

[0056] The content of the defoamer in the polymer latex is preferably 0.001 to 1.0 parts by weight, more preferably 0.005 to 0.8 parts by weight, and even more preferably 0.005 to 0.6 parts by weight, relative to 100 parts by weight of the polymer in the polymer latex. The defoamer can be one of those defoamers found in latexes containing nitrile-containing conjugated diene copolymers used to adjust the polymer latex content. By keeping the content of the defoamer in the polymer latex within the above range, the density and bubble size of the foam can be adjusted to an appropriate range.

[0057] There are no particular limitations on the use of bubble stabilizers. Examples include reaction products obtained by reacting chloroalkanes such as chloroethane with formaldehyde and ammonia, such as chloroethane, formaldehyde, and ammonia reaction products; alkyl quaternary ammonium chlorides; alkyl aryl sulfonates; and higher fatty acid ammonium compounds. Among these, the reaction products of chloroethane, formaldehyde, and ammonia are preferred. These bubble stabilizers can be used alone or in combination of two or more.

[0058] The content of the bubble stabilizer in the polymer latex is preferably 0.5 to 5 parts by weight, more preferably 1 to 5 parts by weight, relative to 100 parts by weight of the polymer in the polymer latex. By keeping the content of the bubble stabilizer in the polymer latex within the above range, the density and bubble size of the foam can be adjusted to an appropriate range.

[0059] The foaming ratio of the polymer latex is preferably 3 to 7 times, more preferably 4 to 6 times. By controlling the foaming ratio within the above range, the density and bubble size of the foam can be adjusted to an appropriate range.

[0060] Latex containing nitrile conjugated diene copolymers can be obtained by emulsion polymerization, which involves copolymerizing the monomers that make up the polymer contained in the latex, and then subjecting the resulting emulsion to particle size enlargement treatment and concentration.

[0061] The particle size enlargement treatment is performed as follows: after terminating the polymerization reaction, the resulting emulsion is enlarged by causing the polymer particles in the emulsion to bind together. By implementing the particle size enlargement treatment, the particle size distribution of the resulting acrylonitrile-containing conjugated diene copolymer latex can be controlled to achieve the desired distribution, and the adjustment of the foam density and bubble size also becomes easier.

[0062] There are no particular limitations on the methods for particle size enlargement treatment. Examples include (1) adding conjugated diene compounds such as 1,3-butadiene and toluene as solvents to the emulsion after polymerization termination and then stirring vigorously, and (2) adding particle size enlargers such as carboxyl polymer latex to the emulsion and then stirring vigorously.

[0063] When performing particle size increase treatment using the method described in (1) above, the amount of solvent added is preferably 30 to 300 parts by weight relative to 100 parts by weight of polymer in the emulsion. Furthermore, when performing particle size increase treatment using the method described in (1) above, there are no particular limitations on the stirring conditions. For example, methods using a stirring device such as a paddle-type stirrer, a rotational speed preferably of 50 to 2500 rpm, and a stirring time preferably of 0.5 to 12.0 hours can be cited.

[0064] Furthermore, when performing particle size enlargement treatment, from the viewpoint of suppressing foaming that occurs with stirring, it is preferable to add an antifoaming agent to the emulsion and perform particle size enlargement treatment in the presence of the antifoaming agent.

[0065] Furthermore, it is preferable that after the latex containing nitrile-based conjugated diene copolymer is obtained through particle size enlargement treatment, the latex containing nitrile-based conjugated diene copolymer is concentrated to adjust the solid content concentration of the latex containing nitrile-based conjugated diene copolymer. The method of concentration treatment is not particularly limited, and examples include vacuum distillation, atmospheric distillation, centrifugation, membrane concentration, etc., among which vacuum distillation is preferred.

[0066] When the latex containing acrylonitrile conjugated diene copolymer is concentrated by vacuum distillation, the conditions for concentration treatment are preferably a pressure of 100 to 0 kPa, more preferably 95 to 1.0 kPa, and a temperature of 30 to 100 °C, more preferably 40 to 95 °C.

[0067] When performing concentration processing, based on the viewpoint of suppressing foaming during concentration, it is also preferable to add an antifoaming agent to the latex and perform concentration processing in the presence of the antifoaming agent.

[0068] In addition, the defoamer may be added only during either the particle size increase treatment or the concentration treatment, or the same or different defoamers may be added during the two treatments respectively. However, it is preferable to add the defoamer at least during the particle size increase treatment. This is because if this is done, foaming can be suppressed by the defoamer not only during the particle size increase treatment, but also during the concentration treatment after the particle size increase treatment.

[0069] The total amount of defoamer added during the particle size enlargement treatment and the concentration treatment is preferably 0.001 to 1.0 parts by weight, more preferably 0.005 to 0.8 parts by weight, and even more preferably 0.005 to 0.6 parts by weight, relative to 100 parts by weight of the polymer in the resulting acrylonitrile-containing conjugated diene copolymer latex. When the amount of defoamer added is less than 0.001 parts by weight, there is a risk that foaming will become more intense during the particle size enlargement treatment, particle size enlargement will not be carried out properly, and the desired particle size distribution will not be obtained. Alternatively, during the concentration treatment, there is a risk that foaming will become more intense and the latex productivity will decrease. On the other hand, when the amount of defoamer added exceeds 1.0 parts by weight, the content of defoamer in the final polymer latex will become excessive, the Young's modulus of the resulting foam will become too low, and the elasticity will also deteriorate.

[0070] In addition, the defoamer may be added only during either the particle size increase treatment or the concentration treatment, or the same or different defoamers may be added during the two treatments respectively. However, it is preferable to add the defoamer at least during the particle size increase treatment. This is because if this is done, foaming can be suppressed by the defoamer not only during the particle size increase treatment, but also during the concentration treatment after the particle size increase treatment.

[0071] As a polymer latex, it is preferable to use a polymer latex that has incorporated a crosslinking agent or other compounding agent. That is, it is preferable to use it in the form of a polymer latex composition.

[0072] Examples of crosslinking agents include powdered sulfur, sublimed sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur; sulfur chloride, sulfur dichloride, morpholine disulfide, alkylphenol disulfide, and N,N'-dithio-bis(hexahydro-2H-aza) Sulfur-containing compounds such as ketone-2), phosphorus-containing polysulfides, high-molecular-weight polysulfides, and 2-(4'-morpholinodithio)benzothiazole are preferred among these. A single crosslinking agent can be used, or a combination of two or more.

[0073] The content of the crosslinking agent is not particularly limited, but is preferably 0.1 to 10 parts by weight, more preferably 0.2 to 3 parts by weight, relative to 100 parts by weight of the polymer in the polymer latex. By keeping the content of the crosslinking agent within the above range, the strength of the obtained foam can be further improved.

[0074] Furthermore, the polymer latex used in this invention preferably contains a crosslinking accelerator.

[0075] As a crosslinking accelerator, crosslinking accelerators commonly used in the manufacture of foams can be used, such as dithiocarbamates and their zinc salts, including diethyldithiocarbamate, dibutyldithiocarbamate, di-2-ethylhexyldithiocarbamate, dicyclohexyldithiocarbamate, diphenyldithiocarbamate, dibenzyldithiocarbamate, etc.; 2-mercaptobenzothiazole, 2-mercaptobenzothiazole zinc, 2-mercaptothiazoline, and dibenzothiazole disulfide. Examples of crosslinking accelerators include 2-(2,4-dinitrophenylthio)benzothiazole, 2-(N,N-diethylthio / methylthio)benzothiazole, 2-(2,6-dimethyl-4-morpholinothio)benzothiazole, 2-(4'-morpholinodithio)benzothiazole, dithio-4-morpholino-2-benzothiazole, and 1,3-bis(2-benzothiazole / mercaptomethyl)urea, with zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, and zinc 2-mercaptobenzothiazole being preferred. One crosslinking accelerator can be used alone, or in combination of two or more.

[0076] The content of the crosslinking accelerator relative to 100 parts by weight of the polymer in the polymer latex is preferably 0.1 to 5 parts by weight, more preferably 0.2 to 4 parts by weight. By keeping the content of the crosslinking accelerator within the above range, the strength of the obtained foam can be further improved.

[0077] Furthermore, the polymer latex used in this invention preferably contains zinc oxide.

[0078] The zinc oxide content is not particularly limited, but is preferably 0.5 to 10 parts by weight, more preferably 0.5 to 8 parts by weight, relative to 100 parts by weight of the polymer in the polymer latex. By keeping the zinc oxide content within the above range, good emulsion stability can be achieved, and the strength of the resulting foam can be further improved.

[0079] The polymer latex used in this invention can be further formulated with anti-aging agents, colorants, and dispersants (such as NAF (sodium salt of naphthalenesulfonic acid formalin condensate)) to stabilize the various compounding agents in the latex, thickeners (such as polyacrylic acid and its sodium salt, sodium alginate, polyvinyl alcohol, etc.), and surfactants as foaming agents (such as aliphatic alkaline soaps such as potassium oleate, sulfates of higher alcohols such as sodium dodecyl sulfate, etc.).

[0080] There are no particular limitations on the method of mixing various compounding agents into polymer latex. For example, one can obtain polymer latex as described above, and then use a disperser such as a ball mill, kneader, or homogenizer to mix various compounding agents into the polymer latex as needed; or use the aforementioned disperser to prepare an aqueous dispersion of the compounding components other than polymer latex, and then mix the aqueous dispersion into the polymer latex.

[0081] Foaming of polymer latex typically uses air, but it can also utilize gas-generating substances such as carbonates like ammonium carbonate and sodium bicarbonate; azo compounds like azodicarboxylate and azobisisobutyronitrile; and benzenesulfonyl hydrazine. When using air, foaming is achieved by agitating the polymer latex to incorporate air. In this case, foaming machines such as Oakes foaming machines and ultrasonic foaming machines can be used.

[0082] After foaming the polymer latex, the foamed polymer latex is solidified to fix the foamed state. The solidification method can be any method that gels and solidifies the latex; existing known methods can be used. For example, the Dunlop method (room temperature solidification method) can be used, which adds room temperature coagulants such as sodium hexafluorosilicate (sodium fluorosilicate), potassium hexafluorosilicate (potassium fluorosilicate), or sodium titanium fluorosilicate and other fluorinated silicon compounds to the foamed polymer latex; the thermosensitive solidification method can be used, which adds thermosensitive coagulants such as organopolysiloxanes, polyvinyl methyl ether, or zinc ammonium sulfate complex salts to the foamed polymer latex; and the freeze-solidification method. The content of coagulants such as room temperature coagulants and thermosensitive coagulants is not particularly limited, but is preferably 0.5 to 10 parts by weight, more preferably 0.5 to 8 parts by weight, relative to 100 parts by weight of the polymer in the polymer latex.

[0083] Furthermore, for already foamed polymer latex, a foamed body can be obtained by adding a coagulant and then transferring it to a mold of the desired shape for coagulation. When a crosslinking agent is incorporated into the polymer latex, it is preferable to heat it after coagulation to induce crosslinking. The crosslinking conditions can be set at a temperature preferably 100–160°C and a heat treatment preferably lasting 15–60 minutes.

[0084] The obtained foam is preferably washed after being removed from the mold. There are no particular limitations on the washing method; for example, it can be washed in a washing machine with water at approximately 20–70°C for 5–15 minutes. Preferably, after washing, the water is removed, and the foam is dried at a temperature of approximately 30–90°C in a manner that does not damage its feel. The resulting foam can be cut to a specified thickness, and after being cut into a specified shape, the sides can be polished by rotating a whetstone, thus enabling its use as a powder puff (cosmetic sponge), etc.

[0085] The foam of the present invention has excellent softness, and is therefore preferably used in various applications such as mattresses, powder puffs (cosmetic sponges), rollers, and shock absorbers. In particular, the foam of the present invention has excellent softness and cosmetic impregnation properties, can evenly apply cosmetics to the skin, and is not easily deformed or worn even when covered with cosmetics. Therefore, it is preferably used as a powder puff (cosmetic sponge) for applying liquid cosmetics.

[0086] Example

[0087] The present invention will be specifically described below with examples and comparative examples. Unless otherwise specified, "parts" refers to weight. Furthermore, the tests and evaluations were conducted as follows.

[0088] Content ratio of acrylonitrile unit

[0089] According to JIS K6384, the nitrogen content in nitrile-containing conjugated diene copolymers is determined by the Kjeldahl method, and then calculated.

[0090] Tetrahydrofuran (THF) insoluble components

[0091] 1 g of polyurethane polymer latex was added to 50 g of THF solvent and shaken at 25°C for 24 hours to dissolve it. The supernatant was separated from the resulting solution using a centrifuge, the solvent was evaporated, and the remaining residue was dried and weighed. The THF-insoluble component was calculated based on the weight of the residue and the weight of the polyurethane polymer contained in the latex.

[0092] Viscosity at a solid component concentration of 50% by weight

[0093] The solids concentration of the polyurethane polymer latex was adjusted to 50% by weight. The viscosity of the latex was measured at 25°C using a viscometer (BII type viscometer, model name: BLII, manufactured by TOKI SANGYO CO.,LTD).

[0094] density

[0095] The weight of the foam is measured, and its weight is divided by its volume to calculate the volume.

[0096] The number of air bubbles with a diameter of 0.6 mm or larger present.

[0097] Using an optical microscope (digital microscope VHX-900F, manufactured by KEYENCE CORPORATION), any cross-section of the foam was observed at 30x magnification. For any bubble cross-section observed in an arbitrary area of ​​9mm × 9mm, the cross-sectional shape was approximated as a circle, the diameter of these circles was measured, and the number of bubble cross-sections with a diameter of 0.6mm or more was counted.

[0098] Figure 1 An example is shown in a microscope photograph (30x magnification) of an arbitrary cross-section of a foam. Figure 1 In the microscope photograph shown, five bubble cross sections with a diameter of 0.6 mm or more can be identified in any region 11 of 9 mm × 9 mm.

[0099] Average diameter of bubble cross section

[0100] Using an optical microscope (VHX-900F digital microscope, manufactured by KEYENCE CORPORATION), any cross-section of the foam was observed at 100x magnification. Among the bubble cross-sections observed in any 1mm × 1mm region, those with a diameter greater than 50μm were selected. The cross-sectional shape of each selected bubble cross-section was approximated as a circle, and the diameter of this circle was measured. This measurement was repeated in nine other arbitrary regions. Then, based on the measured values ​​of all bubble cross-sections within the total of 10 regions, the average diameter of the bubble cross-section was calculated.

[0101] Figure 2 (A) is observed at a magnification of 100x. Figure 1 A schematic diagram was created based on a microscope image of region 13 (1mm × 1mm), in which the cross-sectional shape of each bubble with a diameter of 50μm or more is approximated as a circle. Figure 2 In the schematic diagram shown in (A), multiple bubble cross sections 14 with diameters less than 0.6 mm and greater than 50 μm can be observed.

[0102] Thus, when determining the average diameter of the bubble cross-section, the area observed by the optical microscope is selected so that it does not include bubble cross-sections with a diameter greater than 0.6 mm. Then, as... Figure 2 As shown in (A), among the bubble cross-sections contained in the selected region, bubble cross-sections with a diameter of 50 μm or more are selected, and the shape of each cross-section is approximated as a circle. Then, the diameter of the approximate circle is calculated for each. This operation is performed on a total of 10 individual regions, and the average diameter of all selected bubble cross-sections is calculated.

[0103] In addition, such as Figure 2 As shown in (B), on the cross-section of the foam, there are cross-sections 15 of independent bubbles, where each bubble exists alone, and cross-sections 16 of continuous bubbles formed by the combination of two or more bubbles. Even the cross-sections of continuous bubbles are assumed to be the cross-sections of independent bubbles, and the cross-sectional shape is approximated as a circle to determine the diameter.

[0104] Difficulty of deforming foam when it is contaminated with liquid cosmetics

[0105] The foam was immersed in liquid cosmetic (ANESSA Perfect UV Aquabooster, manufactured by Shiseido Company Limited) at 23°C for 3 days. The ratio of the volume of the foam after immersion to the volume of the foam before immersion was calculated (swelling rate (%) = (volume of foam after immersion) / (volume of foam before immersion) × 100), and evaluated using the following criteria.

[0106] 〇: The swelling rate is below 115%.

[0107] ×: Swelling rate exceeds 115%.

[0108] Abrasiveness of foam when it comes into contact with liquid cosmetics

[0109] The foam was immersed in liquid cosmetic (ANESSA Perfect UV Aqua booster, manufactured by Shiseido Company Limited), and the wear loss was measured using a Martindale abrasion tester (STM633, manufactured by SATRA) at a test temperature of 23°C, a load of 9 kPa, and 1000 rotations of the polishing wheel. The results were evaluated using the following benchmarks.

[0110] 〇: Wear loss is less than 30%.

[0111] ×: Wear loss exceeds 30%.

[0112] The impregnation properties of liquid cosmetics

[0113] The following benchmarks were used to evaluate the impregnation performance of a liquid cosmetic (ANESSA Perfect UV Aqua booster, manufactured by Shiseido Company Limited) on foams.

[0114] 〇: It can easily cause the foam to be impregnated with liquid cosmetics.

[0115] ×: It is difficult to impregnate the foam with liquid cosmetics.

[0116] Softness of foam

[0117] The foam was evaluated by touching it with the fingers, using the following criteria.

[0118] 〇: Soft.

[0119] ×: hard.

[0120] Uneven application of cosmetics

[0121] The foam was coated with a liquid cosmetic (ANESSA Perfect UV Aqua booster, manufactured by Shiseido Company Limited), and the liquid cosmetic was applied to the skin using the foam. The results were evaluated based on the following criteria.

[0122] 〇: It can evenly apply liquid cosmetics.

[0123] ×: This can cause uneven application of liquid cosmetics.

[0124] Example 1

[0125] A latex containing a nitrile-based conjugated diene copolymer (trade name "LX531B", manufactured by Zeon Corporation of Japan, with a solids concentration of 65% by weight and an acrylonitrile unit content of 35% by weight) and a latex containing a polyurethane polymer (SUPERFLEX (registered trademark) E-2000, manufactured by DKS Co. Ltd, with a solids concentration of 50% by weight, a THF insoluble content of 6.5% by weight, and a viscosity of 4100 Pa·s at a solids concentration of 50% by weight) were mixed in a solids weight ratio of 85 / 15 to obtain a latex mixture.

[0126] In the latex mixture obtained above, relative to 100 parts of the polymer in the latex mixture, 4 parts of a vulcanizing aqueous dispersion (colloidal sulfur / dithiocarbamate vulcanizing accelerator NOCCELER EZ (manufactured by OUCHI SHINKOCHEMICAL INDUSTRIAL CO.,LTD) / thiazole vulcanizing accelerator NOCCELER MZ (manufactured by OUCHI SHINKOCHEMICAL INDUSTRIAL CO.,LTD) = 2 / 1 / 1 (weight ratio), with a solid content concentration of 50% by weight), 3 parts of a zinc oxide aqueous dispersion (with a solid content concentration of 50% by weight), and 1 part of a bubble stabilizer (Trimene base: manufactured by Crompton Corp) are added to ensure thorough dispersion, thereby obtaining a polymer latex composition.

[0127] The polymer latex composition was stirred using a vertical mixer (model "ESM945", manufactured by Electrolux) until it foamed approximately 5 times its original volume. Then, 1.5 parts of an aqueous dispersion of sodium fluorosilicate (solid content concentration 20% by weight) were added, and the mixture was stirred for another 1 minute to obtain the foamed product.

[0128] Next, the obtained foam was poured into a molding template (7 cm in diameter and 8 cm in height). After solidification, it was heated at 110°C for 1 hour for vulcanization. Then, it was removed from the template, washed with water at 40°C for 10 minutes, and further dried in an oven at 60°C for 4 hours. It was then cut along the height direction to a thickness of 0.8 cm, thus obtaining a circular plate-shaped foam. Then, following the above method, the density, average diameter of the bubble cross-section, and the number of bubbles with a diameter of 0.6 mm or larger were measured on the obtained foam. Furthermore, the difficulty of deformation when the foam was contaminated with liquid cosmetics, the abrasiveness of the foam when contaminated with liquid cosmetics, the impregnation performance of liquid cosmetics, the softness of the foam, and the unevenness of cosmetic application were evaluated. The results are shown in Table 1.

[0129] Example 2

[0130] The solid content weight ratio of the "nitrile-containing conjugated diene copolymer / polyurethane polymer" was changed to 80 / 20, and the process was otherwise the same as in Example 1 to obtain a foam, which was then evaluated in the same manner. The results are shown in Table 1.

[0131] Example 3

[0132] The solid content weight ratio of the "nitrile-containing conjugated diene copolymer / polyurethane polymer" was changed to 70 / 30, and the process was otherwise the same as in Example 1 to obtain a foam, which was then evaluated in the same manner. The results are shown in Table 1.

[0133] Example 4

[0134] In the latex mixture, 5 parts of octyl p-methoxycinnamate as a UV absorber were added relative to a total of 100 parts of acrylonitrile-containing conjugated diene copolymer and polyurethane polymer. Otherwise, the process was carried out in the same manner as in Example 1 to obtain a foam, which was then evaluated in the same way. The results are shown in Table 1.

[0135] Comparative Example 1

[0136] As the latex, a latex containing a nitrile conjugated diene copolymer was used instead of a polyurethane-based polymer. Otherwise, the process was the same as in Example 1 to obtain a foam, which was then evaluated in the same manner. The results are shown in Table 1.

[0137] Comparative Example 2

[0138] Using a latex containing a nitrile-based conjugated diene copolymer (referred to as "latex C2" in Table 1) (with a solids concentration of 65% by weight and an acrylonitrile unit content of 38% by weight), the same procedure as in Comparative Example 1 was performed to obtain a foam, which was then evaluated in the same manner. The results are shown in Table 1.

[0139] Comparative Example 3

[0140] Latex containing nitrile conjugated diene copolymers (trade name "LX531B", manufactured by Zeon Corporation, Japan, with a solid content concentration of 65 wt% and an acrylonitrile unit content of 35 wt%), latex containing nitrile conjugated diene copolymers (trade name "LX531", manufactured by Zeon Corporation, Japan, with a solid content concentration of 65 wt% and an acrylonitrile unit content of 25 wt%), and latex containing polyurethane polymers (SUPERFLEX (registered trademark) E-2000, manufactured by DKS Co. Ltd, with a solid content concentration of 50 wt%, a THF insoluble content of 6.5 wt%, and a viscosity of 4100 Pa·s at a solid content concentration of 50 wt%) were mixed in a solid content weight ratio of 50 / 40 / 10 to obtain a latex mixture.

[0141] Using the latex mixture obtained above, except as described in Example 1, a foam was obtained and evaluated in the same manner. The results are shown in Table 1.

[0142] Comparative Example 4

[0143] The solid content weight ratio of "acrylonitrile-containing conjugated diene copolymer (LX531B) / acrylonitrile-containing conjugated diene copolymer (LX531) / polyurethane polymer" was changed to 50 / 30 / 20. Otherwise, the process was the same as in Comparative Example 3 to obtain foamed products, which were then evaluated in the same manner. The results are shown in Table 1.

[0144] Comparative Example 5

[0145] The polymer latex composition was foamed in a manner that increased its volume by approximately eight times, otherwise the process was the same as in Example 1, resulting in a foamed body, which was then evaluated in the same manner. The results are shown in Table 1.

[0146] Comparative Example 6

[0147] The polymer latex composition was foamed in a manner that increased its volume by approximately two times, otherwise the process was the same as in Example 1, resulting in a foamed body, which was then evaluated in the same manner. The results are shown in Table 1.

[0148] Comparative Example 7

[0149] The amount of bubble stabilizer added was changed to 0.3 parts, and the process was otherwise the same as in Example 1 to obtain a foamed body, which was then evaluated in the same manner. The results are shown in Table 1.

[0150] Comparative Example 8

[0151] 1.0 part of defoamer was added to the latex mixture, and the process was otherwise carried out in the same manner as in Example 1 to obtain a foamed body, which was then evaluated in the same way. The results are shown in Table 1.

[0152] [Table 1]

[0153]

[0154] As shown in Table 1, for foams containing less than 90% by weight of nitrile-based conjugated diene copolymers and more than 10% by weight of polyurethane polymers, where the proportion of olefinically unsaturated nitrile monomer units in the nitrile-based conjugated diene copolymer exceeds 31% by weight, the density of the foam is 0.08–0.30 g / cm³. 3 The average diameter of the bubble cross-section is less than 350 μm, and the number of bubbles with a diameter greater than 0.6 mm is 0.062 per mm. 2 The following foams have excellent softness and cosmetic impregnation properties, can be evenly applied to the skin, and are not easily deformed even when covered with cosmetics, with little wear (Examples 1-4).

[0155] On the other hand, foams that do not contain polyurethane polymers will deform and wear out when they are exposed to cosmetics (Comparative Examples 1-2).

[0156] Furthermore, for foams containing 31% by weight or less of olefinically unsaturated nitrile monomer units in nitrile-containing conjugated diene copolymers, they deform and wear out significantly when exposed to cosmetics (Comparative Examples 3-4).

[0157] Furthermore, when the density is less than 0.08 g / cm³ 3 When the foamed material is contaminated with cosmetics, it will experience abrasion (Comparative Example 5), and its density will exceed 0.30 g / cm³. 3 The foam has poor softness and poor cosmetic impregnation properties (Comparative Example 6).

[0158] Furthermore, foams with an average bubble cross-section diameter exceeding 350 μm cannot be evenly applied to the skin with cosmetics, and abrasion occurs when the foam is covered with cosmetics (Comparative Example 7). The number of bubble cross-sections with a diameter of 0.6 mm or more exceeds 0.062 per mm. 2 The foam cannot be evenly applied to the skin as a cosmetic (Comparative Example 8).

[0159] Explanation of icon numbers

[0160] 11. Any area of ​​9mm × 9mm

[0161] 12, 14 bubble cross sections

[0162] 13 Arbitrary region of 1mm × 1mm

[0163] 15 Cross-sections of independent bubbles

[0164] 16 Cross-section of continuous bubbles

Claims

1. A foam comprising a nitrile-containing conjugated diene copolymer and a polyurethane polymer, When the total weight of the nitrile-containing conjugated diene copolymer and the polyurethane polymer is 100% by weight, the nitrile-containing conjugated diene copolymer is less than 90% by weight, and the polyurethane polymer is more than 10% by weight. The olefinically unsaturated nitrile monomer units of the nitrile-containing conjugated diene copolymer are present in an amount of 34-60% by weight. The density of the foam is 0.11-0.16 g / cm 3 , In the case where any cross section of the foamed body is observed, the average diameter of the cross section of the bubbles appearing on the cross section is 155 to 250 μm, and the number of bubbles appearing on the cross section having a diameter of 0.6 mm or more is 0.012 to 0.037 pieces / mm 2 .

2. The foam according to claim 1, wherein, When the total of the acrylonitrile-containing conjugated diene copolymer and the polyurethane polymer is taken as 100% by weight, the acrylonitrile-containing conjugated diene copolymer is 85% by weight or less, and the polyurethane polymer is 15% by weight or more.

3. The foam according to claim 1 or 2, wherein, In the nitrile-containing conjugated diene copolymer, the proportion of conjugated diene monomer units is 40 to 66 by weight.

4. The foam according to claim 1 or 2, further comprising an ultraviolet absorber.

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