阅读说明：本技术 发泡体 (Foaming body ) 是由 谷山友哉 伊贺隆志 于 2018-12-10 设计创作，主要内容包括：本发明提供了一种发泡体,其含有含腈基共轭二烯系共聚物和聚氨酯系聚合物,在将上述含腈基共轭二烯系共聚物与所述聚氨酯系聚合物的合计作为100重量％的情况下,上述含腈基共轭二烯系共聚物小于90重量％,上述聚氨酯系聚合物超过10重量％,在上述含腈基共轭二烯系共聚物中,烯属不饱和腈单体单元的含有比例超过31重量％,该发泡体的密度为0.08～0.30g/cm<Sup>3</Sup>,在观察上述发泡体的任意的截面的情况下,在其截面出现的气泡截面的平均直径为350μm以下,在其截面出现的直径为0.6mm以上的气泡截面的存在个数为0.062个/mm<Sup>2</Sup>以下。(The present invention provides a foam comprising a nitrile group-containing conjugated diene copolymer and a polyurethane polymer, wherein the nitrile group-containing conjugated diene copolymer is less than 90% by weight and the polyurethane polymer is more than 10% by weight, the nitrile group-containing conjugated diene copolymer contains more than 31% by weight of ethylenically unsaturated nitrile monomer units, and the foam has a density of 0.08 to 0.30g/cm, where the total amount of the nitrile group-containing conjugated diene copolymer and the polyurethane polymer is 100% by weight 3 When any cross section of the foam is observed, the average diameter of the cross section of the cells appearing on the cross section is 350 μm or less, and the number of the cross sections of the cells having a diameter of 0.6mm or more appearing on the cross section is 0.062 cells/mm 2 The following.)

1. A foam comprising a nitrile group-containing conjugated diene copolymer and a polyurethane polymer,

wherein the nitrile group-containing conjugated diene copolymer is less than 90% by weight and the urethane polymer is more than 10% by weight, based on 100% by weight of the total amount of the nitrile group-containing conjugated diene copolymer and the urethane polymer,

the content ratio of the ethylenically unsaturated nitrile monomer unit in the nitrile group-containing conjugated diene copolymer is more than 31% by weight,

the density of the foam is 0.08 to 0.30g/cm³，

When any section of the foam is observed, the average diameter of the section of the cells appearing on the section is 350 [ mu ] m or less, and the number of the sections of the cells having a diameter of 0.6mm or more appearing on the section is 0.062 cells/mm²The following.

2. The foam according to claim 1, wherein the nitrile group-containing conjugated diene copolymer is 85% by weight or less and the polyurethane polymer is 15% by weight or more, based on 100% by weight of the total amount of the nitrile group-containing conjugated diene copolymer and the polyurethane polymer.

3. The foam according to claim 1 or 2, wherein the nitrile group-containing conjugated diene copolymer contains an ethylenically unsaturated nitrile monomer unit in a proportion of 32 to 80 wt% and a conjugated diene monomer unit in a proportion of 20 to 68 wt%.

4. The foam according to any one of claims 1 to 3, which further comprises an ultraviolet absorber.

Technical Field

The present invention relates to a foam, and more particularly, to a foam which is excellent in flexibility and impregnation properties of a cosmetic, can uniformly apply a cosmetic to the skin, is less likely to be deformed and is less worn even when the cosmetic is applied thereto.

Background

Rubber foams (foamed rubbers) produced using polymer latexes are used in various applications such as mattresses, puffs (cosmetic sponges), rollers, vibration dampers, and the like. Among the uses of these rubber foams, the rubber foam for a puff is particularly required to have a good foaming state, a uniform foamed structure, and an excellent balance between elasticity and texture.

For example, patent document 1 discloses a method for producing a high-physical-property cosmetic puff base material, which is characterized in that: mixing air into a composition containing a water-soluble NBR (nitrile butadiene rubber) emulsion, a water-soluble polyurethane emulsion, a crosslinking agent, a surfactant and a gelling agent, stirring the mixture to foam the mixture, and then heating and vulcanizing the foamed mixture to manufacture a puff base material in a predetermined shape; the water-soluble NBR emulsion has a solid content concentration of 60 wt% or more, and the water-soluble polyurethane emulsion is blended in a proportion of 5 to 15 wt% in terms of solid content based on the total solid content of the two emulsions. However, the technique of patent document 1 has the following problems: the obtained high-physical-property cosmetic puff base material is easily deformed when being stained with a cosmetic, and if the puff base material is continuously used in a state of being stained with the cosmetic, abrasion of the puff base material becomes large.

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made in view of such a situation, and an object thereof is to provide a foam which is excellent in flexibility and impregnation performance of a cosmetic, can uniformly apply the cosmetic to the skin, is less likely to be deformed and is less worn even when the cosmetic is applied thereto.

Means for solving the problems

The present inventors have conducted extensive studies to achieve the above object and as a result, have found that the above object can be achieved by using a nitrile group-containing conjugated diene copolymer having a specific monomer composition, adjusting the content ratio of the nitrile group-containing conjugated diene copolymer to the polyurethane polymer, and adjusting the density of the foam and the size of cells in the foam, and have completed the present invention.

That is, according to the present invention, there is provided a foam comprising a nitrile group-containing conjugated diene copolymer and a polyurethane polymer,

when the total amount of the nitrile group-containing conjugated diene copolymer and the polyurethane polymer is defined as 100% by weight, the nitrile group-containing conjugated diene copolymer is less than 90% by weight and the polyurethane polymer is more than 10% by weight,

in the above-mentioned nitrile group-containing conjugated diene copolymer, the content of the ethylenically unsaturated nitrile monomer unit is more than 31% by weight,

the foam has a density of 0.08 to 0.30g/cm³，

When any section of the foam is observed, the average diameter of the cross section of the cells appearing on the section is 350 [ mu ] m or less, and the number of the cross sections of the cells having a diameter of 0.6mm or more appearing on the section is 0.062 cells/mm²The following.

In the foam of the present invention, when the total amount of the nitrile group-containing conjugated diene copolymer and the polyurethane polymer is defined as 100% by weight, it is preferable that the nitrile group-containing conjugated diene copolymer is 85% by weight or less and the polyurethane polymer is 15% by weight or more.

In the foam of the present invention, it is preferable that: in the nitrile group-containing conjugated diene copolymer, the content of the ethylenically unsaturated nitrile monomer unit is 32 to 80 wt%, and the content of the conjugated diene monomer unit is 20 to 68 wt%.

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

Effects of the invention

The present invention provides a foam which is excellent in flexibility and impregnation properties of a cosmetic, can uniformly apply the cosmetic to the skin, is hardly deformed even when the cosmetic is applied thereto, and is less worn.

Drawings

FIG. 1 is an example of a photomicrograph (magnification: 30 times) of an arbitrary section of a foam.

Fig. 2(a) is a schematic view produced from the obtained photomicrograph after observing the area 13(1mm × 1mm) of the photomicrograph of fig. 1 at a magnification of 100 times, in fig. 2(a), the shape of the cross section of each bubble having a diameter of 50 μm or more is approximated to a circle, and fig. 2(B) is a schematic view for explaining the cross section of an isolated bubble and the cross section of an interconnected bubble in the cross section of a bubble shown in fig. 2 (a).

Detailed Description

The foam of the present invention is characterized by containing a nitrile group-containing conjugated diene copolymer and a polyurethane polymer, wherein when the total amount of the nitrile group-containing conjugated diene copolymer and the polyurethane polymer is taken as 100% by weight, the nitrile group-containing conjugated diene copolymer is less than 90% by weight and the polyurethane polymer is more than 10% by weight, the nitrile group-containing conjugated diene copolymer contains an ethylenically unsaturated nitrile monomer unit in a proportion of more than 31% by weight, and the foam has a density of 0.08 to 0.30g/cm³When any cross section of the foam is observed, the average diameter of the cross section of the cells appearing on the cross section is 350 μm or less, and the number of the cross sections of the cells having a diameter of 0.6mm or more appearing on the cross section is 0.062 cells/mm²The following.

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

Nitrile group-containing conjugated diene copolymer

The nitrile group-containing conjugated diene copolymer is obtained by copolymerizing a conjugated diene monomer and an ethylenically unsaturated nitrile monomer, and in addition, other ethylenically unsaturated monomers that can be used as needed and copolymerized therewith may be copolymerized together.

The ethylenically unsaturated nitrile monomer is not particularly limited as long as it is an ethylenically unsaturated monomer containing a nitrile group, and examples thereof include acrylonitrile, methacrylonitrile, fumaronitrile, α -chloroacrylonitrile, α -cyanoethylacrylonitrile and the like.

In the nitrile group-containing conjugated diene copolymer, the content of the ethylenically unsaturated nitrile monomer unit derived from the ethylenically unsaturated nitrile monomer is more than 31% by weight, preferably 32 to 80% by weight, more preferably 33 to 70% by weight, and still more preferably 34 to 60% by weight. By setting the content ratio of the ethylenically unsaturated nitrile monomer units within the above range, the resulting foam can be made to have the following properties: the cosmetic has excellent flexibility and impregnation property, can be uniformly applied to the skin, is hardly deformed even when the skin is stained with the cosmetic, and has less abrasion. When the content ratio of the ethylenically unsaturated nitrile monomer unit is too small, a foam which is excellent in flexibility and impregnation property of a cosmetic, can uniformly apply the cosmetic to the skin, is less likely to be deformed even when the cosmetic is applied thereto, and is less worn, cannot be obtained. When the content ratio of the ethylenically unsaturated nitrile monomer unit is too large, the cold resistance tends to be poor, and the embrittlement temperature tends to be high.

Examples of the conjugated diene monomer include 1, 3-butadiene, isoprene, 2, 3-dimethyl-1, 3-butadiene, 2-ethyl-1, 3-butadiene, 1, 3-pentadiene, chloroprene, and the like. Among them, 1, 3-butadiene and isoprene are preferable. These conjugated diene monomers can be used alone or in combination of 2 or more.

In the nitrile group-containing conjugated diene copolymer, the content of the conjugated diene monomer unit derived from the conjugated diene monomer is preferably less than 69% by weight, more preferably 20 to 68% by weight, still more preferably 30 to 67% by weight, and particularly preferably 40 to 66% by weight. When the content ratio of the conjugated diene monomer unit is within the above range, the obtained foam can have the following properties: the cosmetic composition is more excellent in flexibility and impregnation property of the cosmetic composition, can be applied to the skin more uniformly, and is less likely to be deformed and worn even when the cosmetic composition is applied thereto.

In addition, from the viewpoint of enabling the obtained foam to have more excellent flexibility and impregnation performance of a cosmetic, enabling the cosmetic to be applied to the skin more uniformly, and enabling the cosmetic to be less likely to deform and wear even when the skin is stained with the cosmetic, it is preferable to use two types of 1, 3-butadiene and isoprene, and the ratio of the 1, 3-butadiene unit and the isoprene unit in the nitrile group-containing conjugated diene copolymer is preferably in the range of 5/5 to 9/1 in terms of the ratio of 1, 3-butadiene unit to isoprene unit.

Examples of the other ethylenically unsaturated monomer copolymerizable with the conjugated diene monomer and the ethylenically unsaturated nitrile monomer include ethylenically unsaturated carboxylic acids such as (meth) acrylic acid, maleic acid (anhydride), fumaric acid, itaconic acid, 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 itaconate, di-N-butyl itaconate and other ethylenically unsaturated carboxylic acids, alkoxyalkyl esters of ethylenically unsaturated carboxylic acids such as methoxy acrylate, ethoxy acrylate, methoxyethoxyethyl acrylate and the like, 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate and other hydroxyalkyl (meth) acrylates, (meth) acrylic acid glycidyl (meth) acrylate, meth) acrylamide, N-hydroxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide and the like, and other ethylenically unsaturated monomers such as copolymers containing ethylene, vinyl chloride, styrene.

Polyurethane polymer

The polyurethane polymer is a polymer having a urethane bond, and a polymer contained in a latex of the polyurethane polymer can be used. The latex of the polyurethane polymer is not particularly limited, and examples thereof include the following: the latex is obtained by reacting an active hydrogen-containing compound, a compound having a hydrophilic group, and a polyisocyanate to obtain an organic solvent solution or an organic solvent dispersion of a polyurethane resin having a hydrophilic group, mixing an aqueous solution containing a neutralizing agent with the organic solvent solution or the organic solvent dispersion, and removing the organic solvent as necessary. Alternatively, the latex of the polyurethane polymer may be the following latex: the latex is obtained by reacting an active hydrogen-containing compound, a compound having a hydrophilic group, and a polyisocyanate to obtain a polyurethane prepolymer having a hydrophilic group and having an isocyanate group at the terminal, and mixing an aqueous solution containing a neutralizer and a polyamine with the prepolymer to react the polyamine.

The active hydrogen-containing compound is not particularly limited, and examples thereof include polyols such as polyolefin polyols including polyester polyol, polyether polyol, polycarbonate polyol, polyacetal polyol, polyacrylate polyol, polyesteramide polyol, polythioether polyol, and polybutadiene; polyhydric compounds such as ethylene glycol compounds, glycerin, trimethylolethane, trimethylolpropane, sorbitol, pentaerythritol, and the like, which are used as raw materials for polyester polyols; amine compounds such as ethylenediamine, 1, 6-hexamethylenediamine, piperazine, 2, 5-dimethylpiperazine, isophoronediamine, 4' -dicyclohexylmethanediamine, 3 ' -dimethyl-4, 4' -dicyclohexylmethanediamine, 1, 4-cyclohexanediamine, 1, 2-propanediamine, hydrazine, diethylenetriamine, and triethylenetetramine.

The compound having a hydrophilic group is not particularly limited, and examples thereof include the following compounds: a compound having 1 or more active hydrogen atoms in a molecule and containing at least one functional group selected from a carboxylate group, a sulfonate group, a phosphate group, a quaternary ammonium salt group, a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, a tertiary amine group, and a betaine group, and having ionic properties; nonionic compounds having 1 or more active hydrogen atoms in the molecule and containing a group formed from a repeating unit of ethylene oxide, a group formed from a repeating unit of ethylene oxide and a repeating unit of another alkylene oxide, and the like.

The isocyanate is not particularly limited, and examples thereof include 2, 4-tolylene diisocyanate, 2, 6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4 '-diphenylmethane diisocyanate, 2' -diphenylmethane diisocyanate, 3 '-dimethyl-4, 4' -biphenyl diisocyanate, 3 '-dimethoxy-4, 4' -biphenyl diisocyanate, 3 '-dichloro-4, 4' -biphenyl diisocyanate, 1, 5-naphthalene diisocyanate, 1, 5-tetrahydronaphthalene diisocyanate, tetramethylene diisocyanate, 1, 6-hexamethylene diisocyanate, 2, 6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4 '-diphenylmethane diisocyanate, 2' -diphenylmethane diisocyanate, 3 '-dichloro-4, 4' -biphenyl diisocyanate, 1, 5-naphthalene diisocyanate, 1,5-, Dodecamethylene diisocyanate, trimethylhexamethylene diisocyanate, 1, 3-cyclohexylene diisocyanate, 1, 4-cyclohexylene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, hydrogenated xylylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, 4' -dicyclohexylmethane diisocyanate, 3 ' -dimethyl-4, 4' -dicyclohexylmethane diisocyanate, and the like.

The tetrahydrofuran-insoluble content in the polyurethane polymer is preferably 3 wt% or more, more preferably 5 wt% or more, from the viewpoints of providing a foam having more excellent flexibility and impregnation properties of a cosmetic, enabling a more uniform application of the cosmetic to the skin, and further being less likely to deform and wear even when the cosmetic is applied. The high tetrahydrofuran insoluble content means that the polyurethane polymer contains a large amount of high molecular weight substances.

From the viewpoint of excellent workability in production, the ability to give a foam having flexibility and excellent impregnation properties for cosmetics, the ability to apply cosmetics to the skin more uniformly, the ability to be less likely to deform even when the cosmetic is applied thereto, and the ability to wear less, the polyurethane-based polymer is preferably one which gives a latex having a viscosity of 6000Pa · s or less as measured at a temperature of 23 ℃ and more preferably one which gives a latex having a viscosity of 5000Pa · s or less as measured at a temperature of 23 ℃ when the latex has a solid content concentration of 50 wt%.

Foaming body

In the foam of the present invention, when the total amount of the nitrile group-containing conjugated diene copolymer and the polyurethane polymer is defined as 100% by weight, the nitrile group-containing conjugated diene copolymer is less than 90% by weight and the polyurethane polymer exceeds 10% by weight. Preferably, the nitrile group-containing conjugated diene copolymer is 85% by weight or less and the polyurethane polymer is 15% by weight or more. More preferably, the nitrile group-containing conjugated diene copolymer is 50 to 85% by weight, and the polyurethane polymer is 15 to 50% by weight. When the content ratio of the nitrile group-containing conjugated diene copolymer to the polyurethane polymer is within the above range, the obtained foam can have the following properties: the cosmetic has excellent flexibility and impregnation property, can be uniformly applied to the skin, is hardly deformed even when the skin is stained with the cosmetic, and has less abrasion. When the content ratio of the nitrile group-containing conjugated diene copolymer is too large, deformation and abrasion which occur when the cosmetic is applied cannot be suppressed. When the content ratio of the polyurethane-based polymer is too large, there is a risk that: softness and impregnation property of the cosmetic become poor, and it is difficult to uniformly apply the cosmetic to the skin.

The density of the foam of the present invention is 0.08 to 0.30g/cm³Preferably 0.10 to 0.28g/cm³More preferably 0.12 to 0.25g/cm³. By setting the density of the foam within the above range, the foam can be made to have the following characteristics: the cosmetic has excellent flexibility and impregnation property, can be uniformly applied to the skin, is hardly deformed even when the skin is stained with the cosmetic, and has less abrasion. When the density of the foam is too low, abrasion caused when the foam is stained with a cosmetic cannot be suppressed, and when the density of the foam is too high, flexibility and impregnation performance of the cosmetic are deteriorated.

The average diameter of the cross section of the cells appearing on the cross section of the foam of the present invention is 350 μm or less, preferably 100 to 300 μm, and more preferably 130 to 270 μm. By setting the average diameter of the cell cross section within the above range, the following properties can be imparted to the foam: the cosmetic has excellent flexibility and impregnation property, can be uniformly applied to the skin, is hardly deformed even when the skin is stained with the cosmetic, and has less abrasion. When the average diameter of the cross section of the air bubbles is too large, the cosmetic cannot be uniformly applied to the skin, and abrasion generated when the cosmetic is stained cannot be suppressed. When the average diameter of the cross section of the cells is too small, there is a risk that the softness of the foam and the impregnation property of the cosmetic are deteriorated.

The average diameter of the cross section of the cells is an average value of the cross section diameter of the cells observed in an arbitrary cross section of the foam, and the average diameter of the cross section of the cells is determined by a method in which the arbitrary cross section of the foam is observed at a magnification of 100 times using an optical microscope (digital microscope VHX-900F, manufactured by KEYENCE CORPORATION), and the cross section of the cells observed in an arbitrary region of 1mm × mm is measured by selecting the cross section of the cells having a diameter of 50 μm or more, approximating the cross section to a circle, and measuring the diameter of the circle, and repeating the same for arbitrary regions at the other 9 points.

The foam of the present invention has a cross section of 0.6mm or more diameter cells, and the number of cells present per mm is 0.062 cells/mm²Hereinafter, the number of the particles is preferably 0.049/mm²Hereinafter, more preferably 0.037 pieces/mm²The following. When the number of the cross sections of the large-diameter cells is within the above range, the foam can have the following properties: the cosmetic has excellent flexibility and impregnation property, can be uniformly applied to the skin, is hardly deformed even when the skin is stained with the cosmetic, and has less abrasion. When the number of cross sections of the large-diameter bubbles is too large, the cosmetic cannot be uniformly applied to the skin. The lower limit is not particularly limited, but the smaller the number is, the better, and the number is preferably 0/mm²Above, but even 0.001 pieces/mm²Above or 0.012 pieces/mm²As described above, the present invention has no effect in practical use.

The diameter of the cross section of the cells is the diameter of the cross section of the cells observed on any cross section of the foam, and the number of the cross sections of the cells having a diameter of 0.6mm or more is determined by observing any cross section of the foam at a magnification of 30 times using an optical microscope (digital microscope VHX-900F, manufactured by KEYENCE CORPORATION), approximating the cross sections to circles for the cross sections of the cells observed in any region of 9mm × 9mm, measuring the diameters of the circles, and counting the number of the cross sections of the cells having a diameter of 0.6mm or more, and when the cross section of the cells having a diameter of 0.6mm or more is located on the boundary line of the observation region, it is estimated that the ratio of the area of the cross section of the cells located in the observation region to the total area of the cross sections of the cells is 1 times the ratio as a number.

Ultraviolet absorber

The foam of the present invention preferably further contains an ultraviolet absorber. By containing the ultraviolet absorber, even when the foam is stained with a cosmetic, particularly a cosmetic containing the ultraviolet absorber, the foam is less likely to be deformed and less likely to be worn.

In the foam of the present invention, the content ratio of the ultraviolet absorber is preferably 1 to 10 parts by weight, more preferably 3 to 7 parts by weight, based on 100 parts by weight of the nitrile group-containing conjugated diene copolymer and the urethane polymer in total. By setting the content of the ultraviolet absorber within the above range, even when the foam is stained with a cosmetic, the foam is less likely to be deformed and less worn.

The ultraviolet absorber is not particularly limited, and examples thereof include cinnamic acid-based ultraviolet absorbers such as octyl p-methoxycinnamate (ethylhexyl methoxycinnamate), isopropyl p-methoxycinnamate, and glyceryl mono-2-ethylhexanoate di-p-methoxycinnamate; benzoic acid-based ultraviolet absorbers such as p-aminobenzoic acid, anthranilic acid-based ultraviolet absorbers such as methyl anthranilate; salicylic acid-based ultraviolet absorbers such as octyl salicylate and phenyl salicylate; ultraviolet absorbers such as urocanic acid and ethyl urocanic acid; benzophenone-based ultraviolet absorbers such as 2-hydroxy-4-methoxybenzophenone and dihydroxybenzophenone; benzotriazole-based ultraviolet absorbers; 2-phenylbenzimidazole-5-sulfonic acid, and the like.

Method for producing foam

The foam of the present invention can be produced by foaming and coagulating a polymer latex containing a nitrile group-containing conjugated diene copolymer and a polyurethane polymer at a desired expansion ratio.

The polymer latex can be produced by, for example, mixing a latex of a nitrile group-containing conjugated diene copolymer with a latex of a polyurethane polymer.

The method for adjusting the density and the cell size of the foam of the present invention is not particularly limited, and examples thereof include: a method of adjusting the content ratio of the defoaming agent in the polymer latex, a method of adjusting the content ratio of the bubble stabilizer in the polymer latex, a method of adjusting the expansion ratio, a method of adjusting the content ratio of the bubble stabilizer at the time of producing the foam, a method of adjusting the kind and amount of the coagulant, and the like.

The defoaming agent is not particularly limited, and examples thereof include an oil-and-fat defoaming agent, a mineral oil defoaming agent such as modified hydrocarbon oil containing mineral oil as a base, a silicone defoaming agent such as silicone oil, and a polymer defoaming agent, and among these, a mineral oil defoaming agent and a silicone defoaming agent are preferable. These antifoaming agents can be used alone in 1 kind or in combination of 2 or more kinds.

The content of the defoaming agent in the polymer latex is preferably 0.001 to 1.0 part by weight, more preferably 0.005 to 0.8 part by weight, and still more preferably 0.005 to 0.6 part by weight, based on 100 parts by weight of the polymer in the polymer latex. The antifoaming agent may be those contained in the latex of the nitrile group-containing conjugated diene copolymer used for the adjustment of the polymer latex. By making the content of the defoaming agent in the polymer latex within the above range, the density of the foam and the size of the bubbles can be adjusted to be within appropriate ranges.

The bubble stabilizer is not particularly limited, and examples thereof include reaction products obtained by reacting chloroalkanes such as ethyl chloride with formaldehyde and ammonia gas, such as reaction products of ethyl chloride, formaldehyde and ammonia gas; alkyl quaternary ammonium chlorides; an alkyl aryl sulfonate; higher fatty acid ammonium, and the like. Among them, a reaction product of ethyl chloride, formaldehyde and ammonia gas is preferable. These bubble stabilizers can be used alone in 1 kind or in combination of 2 or more kinds.

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, based on 100 parts by weight of the polymer in the polymer latex. By making the content of the bubble stabilizer in the polymer latex within the above range, the density of the foam and the size of the bubbles can be adjusted to be within appropriate ranges.

The expansion ratio when the polymer latex is expanded is preferably 3 to 7 times, more preferably 4 to 6 times. By controlling the expansion ratio within the above range, the density of the foam and the size of the cells can be adjusted within appropriate ranges.

The latex of the nitrile group-containing conjugated diene copolymer can be obtained by a method of copolymerizing monomers constituting a polymer contained in the latex by an emulsion polymerization method, and subjecting the obtained emulsion to a particle size enlarging treatment and concentration.

The particle size increasing treatment was as follows: after the termination of the polymerization reaction, the resulting emulsion is subjected to a treatment for increasing the size of the emulsion by binding the polymer particles in the emulsion to each other. By performing the particle diameter enlarging treatment, the particle diameter distribution of the obtained nitrile group-containing conjugated diene copolymer-containing latex can be controlled to a desired distribution, and the density of the foam and the size of the cells can be easily adjusted.

The method of the particle size increasing treatment is not particularly limited, and examples thereof include (1) a method of adding a conjugated diene compound such as 1, 3-butadiene and the like and toluene and the like as a solvent to the emulsion after the completion of the polymerization and strongly stirring the mixture, (2) a method of adding a particle size increasing agent such as a carboxyl group-containing polymer latex to the emulsion and strongly stirring the mixture, and the like.

When the particle size is increased by the method (1), the amount of the solvent to be added is preferably 30 to 300 parts by weight based on 100 parts by weight of the polymer in the emulsion. In the case of the particle size increasing treatment by the method (1), the stirring conditions are not particularly limited, and examples thereof include a method in which a stirring device such as a paddle type stirring blade is used, the rotation speed is preferably 50 to 2500rpm, and the stirring time is preferably 0.5 to 12.0 hours.

In addition, when the particle size increasing treatment is performed, it is preferable to add an antifoaming agent to the emulsion and perform the particle size increasing treatment in the presence of the antifoaming agent, from the viewpoint of suppressing foaming caused by stirring.

Further, it is preferable that: after the particle diameter is increased to obtain a latex of the nitrile group-containing conjugated diene copolymer, the latex of the nitrile group-containing conjugated diene copolymer is concentrated to adjust the solid content concentration of the latex of the nitrile group-containing conjugated diene copolymer. The method of the concentration treatment is not particularly limited, and examples thereof include methods such as distillation under reduced pressure, distillation under atmospheric pressure, centrifugal separation, and membrane concentration, and among them, distillation under reduced pressure is preferable.

When the latex of the nitrile group-containing conjugated diene copolymer is concentrated by distillation under reduced pressure, the concentration is preferably carried out under a pressure of 100 to 0kPa, more preferably 95 to 1.0kPa, and at a temperature of 30 to 100 ℃, more preferably 40 to 95 ℃.

In the concentration treatment, it is also preferable to add an antifoaming agent to the latex and perform the concentration treatment in the presence of the antifoaming agent, from the viewpoint of suppressing foaming during concentration.

The defoaming agent may be added only when either one of the particle size enlarging treatment and the concentration treatment is performed, or the same or different defoaming agents may be added to each of the two treatments, but it is preferable to add the defoaming agent at least when the particle size enlarging treatment is performed because if so, foaming can be suppressed by the defoaming agent not only in the particle size enlarging treatment but also in the concentration treatment performed after the particle size enlarging treatment.

The total amount of the antifoaming agent added during the particle size increasing treatment and the concentration treatment is preferably 0.001 to 1.0 part by weight, more preferably 0.005 to 0.8 part by weight, and still more preferably 0.005 to 0.6 part by weight, based on 100 parts by weight of the polymer in the obtained latex containing the nitrile-based conjugated diene copolymer. When the amount of the antifoaming agent is less than 0.001 part by weight, there is a risk that foaming becomes severe and particle size enlargement cannot be appropriately performed in the case of particle size enlargement treatment, and a desired particle size distribution cannot be obtained, or there is a risk that foaming becomes severe and the productivity of latex decreases in the case of concentration treatment. On the other hand, when the amount of the defoaming agent added exceeds 1.0 part by weight, the content of the defoaming agent in the finally obtained polymer latex becomes too large, the young's modulus of the obtained foam becomes too low, and the elasticity also becomes poor.

The defoaming agent may be added only when either one of the particle size enlarging treatment and the concentration treatment is performed, or the same or different defoaming agents may be added to each of the two treatments, but it is preferable to add the defoaming agent at least when the particle size enlarging treatment is performed because if so, foaming can be suppressed by the defoaming agent not only in the particle size enlarging treatment but also in the concentration treatment performed after the particle size enlarging treatment.

As the polymer latex, a polymer latex blended with a compounding agent such as a crosslinking agent is preferably used. That is, it is preferably used in the form of a polymer latex composition.

Examples of the crosslinking agent include sulfur such as powdery sulfur, sublimed sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur; sulfur chloride, sulfur dichloride, morpholine disulfide, alkylphenol disulfide, N' -dithio-bis (hexahydro-2H-aza)Ketone-2), phosphorus-containing polysulfide, high-molecular polysulfide, 2- (4' -morpholinodithio) benzothiazole, and other sulfur-containing compounds. Among them, sulfur can be preferably used. The crosslinking agent can be used alone in 1 kind, or in combination of 2 or more kinds.

The content of the crosslinking agent is not particularly limited, and is preferably 0.1 to 10 parts by weight, more preferably 0.2 to 3 parts by weight, based on 100 parts by weight of the polymer in the polymer latex. When the content of the crosslinking agent is within the above range, the strength of the obtained foam can be further improved.

The polymer latex used in the present invention preferably further contains a crosslinking accelerator.

As the crosslinking accelerator, crosslinking accelerators generally used in the production of foams can be used, and examples thereof include dithiocarbamic acids such as diethyldithiocarbamic acid, dibutyldithiocarbamic acid, di-2-ethylhexyldithiocarbamic acid, dicyclohexyldithiocarbamic acid, diphenyldithiocarbamic acid, dibenzyldithiocarbamic acid, and zinc salts thereof; 2-mercaptobenzothiazole, 2-mercaptobenzothiazole zinc, 2-mercaptothiazoline, dibenzothiazyl disulfide, 2- (2, 4-dinitrophenylthio) benzothiazole, 2- (N, N-diethylthio/methylthio) benzothiazole, 2- (2, 6-dimethyl-4-morpholinothio) benzothiazole, 2- (4' -morpholinodithio) benzothiazole, dithio-4-morpholinyl-2-benzothiazole, 1, 3-bis (2-benzothiazolyl/mercaptomethyl) urea and the like, preferably zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate and zinc 2-mercaptobenzothiazole. The crosslinking accelerator can be used alone in 1 kind, or in combination of 2 or more kinds.

The content of the crosslinking accelerator is preferably 0.1 to 5 parts by weight, and more preferably 0.2 to 4 parts by weight, based on 100 parts by weight of the polymer in the polymer latex. When the content of the crosslinking accelerator is in the above range, the strength of the obtained foam can be further improved.

Further, the polymer latex used in the present invention preferably contains zinc oxide.

The content of zinc oxide is not particularly limited, but is preferably 0.5 to 10 parts by weight, more preferably 0.5 to 8 parts by weight, based on 100 parts by weight of the polymer in the polymer latex. When the content of zinc oxide is within the above range, the emulsion stability is improved and the strength of the obtained foam can be further improved.

The polymer latex used in the present invention may further contain, if necessary, an anti-aging agent, a coloring agent, a dispersant (for example, NASF (sodium salt of naphthalenesulfonic acid formalin condensate) or the like) for stably dispersing the above-mentioned various compounding agents in the latex, a thickener (for example, polyacrylic acid and its sodium salt, sodium alginate, polyvinyl alcohol or the like), a surfactant (for example, aliphatic alkaline soap such as potassium oleate, sulfate of higher alcohol such as sodium lauryl sulfate or the like) as a foaming agent, and the like.

The method of mixing various compounding agents with the polymer latex is not particularly limited, and examples thereof include a method of obtaining the polymer latex as described above, and then mixing the polymer latex with various compounding agents as necessary using a dispersing machine such as a ball mill, a kneader, or a homogenizer; a method of preparing an aqueous dispersion of compounding ingredients other than the polymer latex by using the above-mentioned dispersing machine and then mixing the aqueous dispersion into the polymer latex.

Foaming of the polymer latex usually uses air, but gas generating substances such as carbonates such as ammonium carbonate and sodium bicarbonate; azo compounds such as azodicarboxylic acid amide and azobisisobutyronitrile; benzenesulfonyl hydrazide and the like. In the case of using air, the polymer latex can be stirred to mix in the air, thereby foaming. In this case, for example, an oxx (Oakes) foaming machine, an ultrasonic foaming machine, or the like can be used.

After the polymer latex is foamed, the foamed polymer latex is coagulated to fix the foamed state. As the coagulation method, any conventionally known method can be used as long as it can gel and solidify the latex, and for example, there can be used: a Dunlop method (ambient temperature coagulation method) in which an ambient temperature coagulant such as silicon fluoride compounds, e.g., sodium hexafluorosilicate (sodium silicofluoride), potassium hexafluorosilicate (potassium silicofluoride), sodium titanium silicofluoride, etc., is added to a foamed polymer latex; a heat-sensitive coagulation method in which a heat-sensitive coagulant such as organopolysiloxane, polyvinyl methyl ether, zinc sulfate ammonium complex salt, or the like is added to a foamed polymer latex; freezing and solidifying method, etc. The content of the coagulant such as a normal temperature coagulant or a heat-sensitive coagulant is not particularly limited, but is preferably 0.5 to 10 parts by weight, more preferably 0.5 to 8 parts by weight, based on 100 parts by weight of the polymer in the polymer latex.

In addition, the foamed polymer latex can be transferred to a mold having a desired shape after adding a coagulant and coagulated to obtain a foam. When a crosslinking agent is blended in the polymer latex, it is preferable to crosslink the latex by heating after coagulation. The crosslinking condition may be a condition in which the heat treatment is preferably performed at a temperature of 100 to 160 ℃ for 15 to 60 minutes.

The obtained foam is preferably removed from the mold and then washed. The washing method is not particularly limited, and examples thereof include a method of washing with water at about 20 to 70 ℃ for about 5 to 15 minutes by stirring using a washing machine or the like. Preferably: and removing water after cleaning, and drying at a temperature of about 30-90 ℃ in a manner that the hand feeling of the foam is not damaged. The foam obtained in this way can be cut into a predetermined thickness, for example, and after being cut into a predetermined shape, the side surface is polished by a rotary grindstone, and thus, the foam can be used as a puff (cosmetic sponge) or the like.

The foam of the present invention is excellent in flexibility, and therefore can be suitably used for various applications such as mattresses, powder puffs (cosmetic sponges), rollers, and vibration dampers. In particular, the foam of the present invention has excellent flexibility and impregnation properties of a cosmetic, can uniformly apply a cosmetic to the skin, is hardly deformed even when the cosmetic is applied thereto, and has little abrasion, and therefore, can be preferably used as a puff (cosmetic sponge) for dipping a liquid cosmetic or the like.