JP2019116590A - Sbr latex foam and manufacturing method therefor - Google Patents

Abstract

To provide a SBR latex foam capable of being manufactured without setting complex processes, and excellent in abrasion resistance and flexibility, and a manufacturing method therefor.SOLUTION: There is provided a manufacturing method of a latex foam having a process for foaming a composition containing a rubber latex, the composition contains at least a SBR latex, and a carboxy modified latex having glass transition temperature of -30 to 40°C as emulsions, and solid component mass percentage of the SBR latex based on total of all emulsions contained in the composition is 50 to 97 mass% and solid component mass percentage of the carboxy modified latex is 3 to 50 mass%.SELECTED DRAWING: None

Description

  The present invention relates to an SBR latex foam excellent in abrasion resistance and flexibility and a method for producing the same.

  SBR latex foams made of SBR latex and foamed by mechanical floss method have high friction and poor tearability, and are inferior in abrasion resistance compared with NR latex and NBR latex, so they have the problem of being unsuitable for practical use. .

  Generally, the following methods are known as methods for improving the abrasion resistance of latex foams.

  Method (1) is a method of blending a vulcanizing agent. Specifically, the degree of vulcanization is adjusted according to the amount of sulfur and the type of vulcanization accelerator, and the distance between vulcanization is reduced to improve the strength of the latex foam.

  Method (2) is a method of adding a filler and a plasticizer to latex foam. Specifically, as disclosed in Patent Document 1 and Non-patent Document 1, a method of adding a filler such as carbon, silica, or clay effective for reinforcing a latex foam to a raw material, or improving slipperiness It is a method of adding a plasticizer to the raw material.

  Method (3) is a method of densifying latex foam.

Publication No. 2003-192824

Rubber Industry Handbook <Fourth Edition>, The Japan Rubber Association, 1994, p. 139 Friction and wear of rubber

  However, the above methods (1) to (3) have problems in the following points.

  According to the method (1), in consideration of scorch and safety, the types of usable vulcanization accelerators are very limited, and it is difficult to significantly improve the abrasion resistance with a vulcanization system alone.

  According to the method (2), the addition of a small amount of filler has a small influence on the abrasion resistance, and when an excess amount of filler is added, molding defects such as thickening of the emulsion composition and shrinkage of the foam may occur. In addition, when a plasticizer is added, not only it becomes easy to break due to the decrease of mechanical strength, but the process of emulsifying the plasticizer in advance and the process of preparing the emulsion composition are separate, which complicates the manufacturing process. The storage stability of the emulsion is also reduced.

  According to method (3), the excellent elasticity and soft touch inherent to latex foam are impaired.

  Then, this invention makes it a subject to be able to manufacture without providing a complicated process, and to provide SBR latex foam excellent in abrasion resistance and flexibility, and its manufacturing method.

  The present inventors have conducted intensive studies and found that the above problems can be solved by adding a specific component to a conventional SBR latex in a specific amount to produce an SBR latex foam. Completed. That is, the present invention is as follows.

The present invention (1) is
A method of producing SBR latex foam, comprising the step of foaming a composition comprising rubber latex,
The composition comprises, as an emulsion, at least an SBR latex and a carboxy-modified latex having a glass transition temperature of -30 to 40 ° C.,
The solid content ratio by mass of the SBR latex is 50 to 97% by mass, and the solid content ratio by mass of the carboxy-modified latex is 3 to 50% by mass with respect to the total of all the emulsions contained in the composition. , SBR latex foam manufacturing method.
The present invention (2) is
The SBR latex foam has a weight reduction rate of 10% or less after 500 times of reciprocal abrasion with an abrasion tester according to JIS L 8049, and the measured value with an Asker hardness meter F type is 50 to 90. It is a manufacturing method of SBR latex foam of invention (1).
The present invention (3) is
It is a manufacturing method of SBR latex foam of the said invention (1) or (2) whose said SBR latex foam is for cosmetic puffs.
The present invention (4) is
An SBR latex foam obtained by foaming a composition comprising a rubber latex,
The composition comprises, as an emulsion, at least an SBR latex and a carboxy-modified latex having a glass transition temperature of -30 to 40 ° C.,
The solid content ratio by mass of the SBR latex is 50 to 97% by mass, and the solid content ratio by mass of the carboxy-modified latex is 3 to 50% by mass with respect to the total of all the emulsions contained in the composition. , SBR latex foam.
The present invention (5) is
The SBR of the invention (4) according to the invention (4), wherein the weight reduction rate after 500 cycles of reciprocal abrasion with an abrasion tester according to JIS L 8049 is 10% or less and the measured value with an Asker hardness meter F type is 50 to 90. It is a latex foam.
The present invention (6) is
It is SBR latex foam of the said invention (4) or (5) which is for cosmetic puffs.

  According to the present invention, it is possible to provide an SBR latex foam having excellent abrasion resistance and flexibility and a method for producing the same, which can be produced without providing complicated processes, and also has excellent abrasion resistance and flexibility.

  Hereinafter, the SBR latex foam according to the present invention and the method for producing the same will be described in detail, but the present invention is not limited to these.

The method for producing the SBR latex foam according to the present invention will be described in the following order.
1 Production method of SBR latex foam 1-1 Raw material 1-2 Production process 2 SBR latex foam

<<< Production method of SBR latex foam >>>
The method for producing SBR latex foam according to the present embodiment is a method for producing SBR latex foam which is a foam having a cell structure from a composition (emulsion composition) containing SBR latex as the main component of the emulsion, and the following method Is adopted. That is, the emulsion composition in which other emulsions and various additives are added is foamed with SBR latex which is an aqueous dispersion of styrene butadiene rubber (SBR) polymer particles, and a gelling agent is added as necessary. And deactivating the dispersant (surfactant) stabilizing the dispersion of polymer particles and the like. As a result, the polymer particles fuse and aggregate, and solidify while containing bubbles to form an SBR latex foam.

  Hereinafter, the manufacturing method of SBR latex foam which concerns on this form is demonstrated in detail in the order of the raw material and manufacturing process. Here, in the present embodiment, in particular, a rubber-based emulsion is used as a rubber latex.

<< raw material >>
The raw material used in the method for producing SBR latex foam according to the present embodiment contains at least SBR latex and carboxy-modified latex as an emulsion, and may further contain other emulsions and other additives as necessary. It may be Each will be described in detail below. Hereinafter, each will be described, but the raw material of the method for producing SBR latex foam according to the present embodiment is not limited thereto.

<Emulsion>
First, an emulsion usable in the method for producing SBR latex foam according to the present embodiment will be described.

  As described above, the emulsion used in the production method according to the present embodiment essentially comprises (1) SBR latex (non-modified SBR latex) and (2) carboxy-modified latex (preferably carboxy-modified SBR latex). I assume. By blending such an emulsion in an amount to be described later, an SBR latex foam excellent in abrasion resistance and flexibility can be obtained.

  In addition, the emulsion composition is not limited to (1) SBR latex and (2) carboxy modified latex as an emulsion, but also other emulsions (for example, 1 of the emulsions to be described later) within the range not to inhibit the effects of the present invention. It may contain species or two or more species.

  Hereinafter, the emulsion and the latex, including the SBR latex and the carboxy-modified latex which are essential components, will be described in detail.

  An emulsion is a dispersion in which polymer particles are stably dispersed in a dispersion medium by a dispersing agent. The polymer particles may be particles of rubber (referred to as rubber polymer) or particles of polymers other than rubber polymer (referred to as resin polymer). Here, the dispersion medium in the emulsion is, for example, water or a mixture of water and a water-soluble solvent. Examples of the water-soluble solvent include alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, ethyl carbitol, ethyl cellosolve and butyl cellosolve, polar solvents such as N-methyl pyrrolidone and the like, and one or more of them are used. A mixture of or the like may be used.

  As a rubber polymer, for example, natural rubber (NR), butadiene rubber (BR), acrylonitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), isoprene rubber (IR), acrylate- Synthetic rubbers such as butadiene rubber, methyl methacrylate-butadiene rubber (MBR), ethylene propylene diene rubber (EPDM) and the like can be mentioned. Further, as the rubber latex, rubber polymers in styrene-butadiene-vinylpyridine latex, DPL (depolymerized latex) or chlorosulfonated polyethylene latex, and the like can also be mentioned.

  Rubber polymers also exist in the form of modified rubber polymers. The modified rubber polymer may be, for example, one having at least a part thereof having a carboxyl group as a functional group (carboxyl modified rubber polymer). As such a modified rubber polymer, for example, carboxy-modified styrene-butadiene rubber, carboxy-modified acrylonitrile-butadiene rubber and the like can be mentioned. Thus, the emulsion when the rubber polymer particles are carboxyl modified rubber polymer is taken as carboxy modified latex. In addition, as a modified rubber polymer, what has another functional group, for example, the hydroxyl-modified rubber polymer etc. which have a hydroxyl group as a functional group are also mentioned.

  Examples of the resin polymer include ethylene vinyl acetate copolymer, acrylonitrile butadiene copolymer, acrylonitrile butadiene isoprene copolymer, epihalohydrin copolymer, acrylic resin such as acrylate polymer, polyurethane, silicone, polyolefin ( For example, polymers containing one or more of polyethylene, polystyrene and the like can be mentioned.

  In addition, the emulsion containing these polymer particles can be manufactured by a well-known method. For example, when the polymer particles are natural rubber, an emulsion may be a rubber sap, one obtained by concentrating the same, or one in which a preservative or the like is further blended with the rubber sap or the like. When the polymer particles are a synthetic rubber or resin, the emulsion is generally prepared by emulsion polymerization. Alternatively, the polymer obtained by a method such as solution polymerization can be prepared by emulsifying with a surfactant and water and removing the solvent as required.

  As such an emulsion, an emulsion having a content of polymer particles of 40 to 70% by mass is generally used, but preferably 50 to 70% by mass because a stable foam can be formed. An emulsion containing polymer particles is used. However, in the present embodiment, it goes without saying that an emulsion out of the above content range may be used. For example, a powder obtained by removing the dispersion medium from the dispersion may be handled as an emulsion.

  The solid content ratio of the total of all the emulsions (SBR latex, carboxy modified latex and other emulsions) to the entire emulsion composition is not particularly limited, but is preferably 70 to 99% by mass, preferably 75 to 90%. More preferably, it is%.

  The solid content ratio of the SBR latex to the total of all the emulsions (SBR latex, carboxy modified latex and other emulsions) in the emulsion composition is 50 to 97 mass%, and 60 to 95 mass%. preferable.

  The solid content ratio of the carboxy modified latex to the total of all the emulsions (SBR latex, carboxy modified latex and other emulsions) in the emulsion composition is 3 to 50% by mass, and 5 to 40% by mass Is preferred.

  The Tg (glass transition temperature) of the carboxy-modified latex is -30 to 40 ° C, and preferably -30 to 0 ° C. The Tg of the carboxy-modified latex is preferably higher than the Tg of the SBR latex. More specifically, the Tg of the SBR latex is preferably less than -30 ° C, more preferably -40 ° C or less, and particularly preferably -50 ° C or less. The lower limit of the Tg of the SBR latex is not particularly limited, and is, for example, -75 ° C. In addition, such Tg is measured according to JIS K 6240.

  Although the particle size of the polymer particle in these emulsions is not specifically limited, For example, the diameter of 0.05-1.0 micrometer is preferable.

<Other additives>
Other additives include dispersing agents, gelling agents, crosslinking agents, crosslinking accelerators, antiaging agents, foaming agents, antifoaming agents, softeners and other additives.

(Dispersant)
The dispersant has a role of improving the dispersibility of polymer particles and various additives in the emulsion composition in which various additives are added to the emulsion. By adding the dispersant, the emulsion composition can be made uniform, so that the gas to be mixed can be dispersed in a good state (fine and uniform). Examples of the dispersant include those which improve the dispersibility of the emulsion composition and in which the surface activity is inactivated by the addition of a gelling agent described later, and are not particularly limited. Examples thereof include fatty acid alkali metal salts and alkyls. Anionic surfactants such as alkali metal sulfonates and alkali metal sulfonates, sorbitan fatty acid ester, polyoxyethylene glycerin fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene hydrogenated castor oil, polyoxyethylene alkyl Nonionic surfactants such as ether may be used. In addition, the above-mentioned anionic surfactant may be used at the time of emulsification of a polymer particle.

  The addition amount of the dispersant is usually 0.25 to 1.00 parts by mass, preferably 0.50 to 0.75 parts by mass, with respect to 100 parts by mass of the solid content in the emulsion composition.

(Gelling agent)
The gelling agent reduces the chemical stability of the polymer particles present in the emulsion state, ie, the state of the emulsion in the emulsion composition, and aggregates the particles into a so-called gelled state. It is a substance of As this gelling agent, it is possible to use, for example, hexafluorosilicates such as sodium silicofluoride, potassium silicofluoride, calcium silicofluoride; or acetates of cyclohexylamine, cyclohexylamines such as sulfamate, etc. In general, liquid substances in which these compounds are in the form of an aqueous solution are used. Among these, sodium silicofluoride is particularly preferably used because reaction control such as control of gelation initiation time is easy.

  In the method for producing SBR latex foam according to the present embodiment, a lactone compound may be used as a gelling agent.

  The lactone compound is not particularly limited, but gluconolactone (glucono-δ-lactone), D-(+)-ribono-1,4-lactone, L-(+)-gulonic acid γ-lactone, 2,3- O-isopropylidene-D (-)-ribono-1,4-lactone, α-amino-γ-butyrolactone hydrobromide and the like can be exemplified.

  In order to gel the entire SBR latex foam uniformly, it is preferable to disperse the lactone compound in the liquid medium, and the solubility of the lactone compound (the solubility of the lactone compound in the liquid medium) is 40 (g / 100 g) or less It is more preferred to use a liquid medium.

  The liquid medium is not particularly limited, but alkylene glycol (eg, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol etc.), alkylene ether glycol Polyhydric or higher polyols such as diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, etc .; stearic acid, palmitic acid, linoleic acid, oleic acid, linolenic acid, Fatty acids such as ricinoleic acid, lauric acid; phthalic acid esters (bis (2-ethylhexyl) phthalate, dibutyl phthalate, diisononyl phthalate, etc.), sebacic acid esters (bis (2- Chilhexyl) sebacate, dibutyl sebacate, diethyl sebacate, dimethyl sebacate, etc., trimellitic acid ester (tris (2-ethylhexyl) trimellitate, trinloctyl octyl trimellitate, triisodecyl trimellitate, etc.) benzoate Examples thereof include carboxylic acid esters (esters of monocarboxylic acid or polycarboxylic acid) such as (ethylene glycol dibenzoate, dipropylene glycol dibenzoate etc.).

  The lactone compound and the liquid medium may be used alone or in combination of two or more.

  The amount of the gelling agent added is usually 5 to 25 parts by mass, preferably 5 to 15 parts by mass, with respect to 100 parts by mass of the solid content in the emulsion composition.

(Cross-linking agent, cross-linking accelerator, anti-aging agent)
A crosslinking agent (for example, a vulcanizing agent) is an additive for crosslinking rubber polymers with each other, and a crosslinking accelerator (for example, a vulcanization accelerator) is an additive for promoting a crosslinking reaction by a crosslinking agent. The anti-aging agent is an additive formulated to prevent the aging of the rubber and extend the life of the rubber product.

  As a crosslinking agent, sulfur, an organic peroxide, a phenol compound, etc. are used according to the kind of rubber polymer, and a crosslinking reaction mechanism. In the case of crosslinking by sulfur, in addition to colloidal sulfur and finely powdered sulfur, sulfur compounds such as sulfur dichloride and dipentamethylenethiuram tetrasulfide can be used. In the case of crosslinking with organic peroxides, hydroperoxides such as t-butyl hydroperoxide and cumene hydroperoxide; acyl peroxides such as benzoyl peroxide and m-toluyl peroxide; t-butyl cumyl peroxide, dicumyl peroxide, 2, 5- Alkyl peroxides such as dimethyl-2,5-bis (t-butoxyperoxy) hexane; peroxy esters such as t-butoxyperoxy-3,3,5-trimethylcyclohexanoate, t-butoxyperoxybenzoate; 1,1- Peroxyketals such as bis (t-butoxyperoxy) cyclohexane, 1,1-bis (t-butoxyperoxy) -3,3,5-trimethylcyclohexa etc; t-butoxyperoxyisopropyl carbonate, t-butoxy pero Shi-2-ethylhexyl-carbonitrile organic peroxides such as peroxy carbonate such diisocyanates can be used. The organic peroxide may be blended as it is, or may be adsorbed by adsorption onto an inorganic powder such as molecular sieve, dissolved in a hydrocarbon or a plasticizer, or mixed with an inert liquid such as polydimethylsiloxane. May be used in the formulation. In the case of crosslinking with a phenol compound, an alkyphenol-formaldehyde resin, a sulfurized-p-tert-butylphenol resin, an alkylphenol-sulfide resin and the like can be used.

  The blending amount of the crosslinking agent is preferably 1 to 4 parts by mass, and more preferably 1 to 2 parts by mass with respect to 100 parts by mass of the solid content in the emulsion composition.

  Although various substances can be used as the crosslinking accelerator, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc di-n-butyldithiocarbamate, zinc dibenzyldithiocarbamate, ethylphenyl are preferred because they lower the swelling property to polar oils. Zinc dithiocarbamates, zinc dithiocarbamates such as zinc N-pentamethylene dithiocarbamate; tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, N, N'-dimethyl-N, N ' Thiphenyls such as diphenylthiuram disulfide, dipentamethylenethiuram tetrasulfide; N, N-diisopropyl-2-benzothialylsulfenamide N-t-butyl- -Benzothiallylsulfenamide, N-cyclohexyl-2-benzothiazylsulfenamide, N, N-dicyclohexyl-2-benzothiazylsulfenamide, N-oxydiethylene-2-benzothiazylsulfenamide, etc. Sulfenamides; 2-mercaptobenzothiazole and salts thereof (sodium salt, zinc salt, cyclohexylamine salt, dicyclohexylamine salt, etc.), 2- (4'-morpholinodithio) benzothiazole, 4-morpholinyl-2-benzo Thiazolyl disulfide, benzothiazoles such as 2- (N, N-diethylthiocarbamoylthio) benzothiazole; and mixtures thereof are preferred. Among these, zinc dithiocarbamates are more preferable, and zinc dibutyldithiocarbamate is particularly preferable.

  0.5-2.5 mass parts is preferable with respect to 100 mass parts of solid content in emulsion composition, and, as for the compounding quantity of a crosslinking accelerator, 0.5-1.5 mass parts is more preferable.

  Examples of anti-aging agents include diphenylamine compounds such as N-phenyl-N '-(p-toluenesulfonyl) -p-phenylenediamine; condensates of aromatic amines and aliphatic ketones; 2-mercaptobenzimidazole and the like Imidazole compounds such as zinc salts; mono-phenolic compounds such as 2,6-di-t-butyl-4-methylphenol; bis-, tris, polyphenol compounds and the like.

  0.5-2.5 mass parts is preferable with respect to 100 mass parts of solid content in emulsion composition, and, as for the compounding quantity of antiaging agent, 1.0-2.0 mass parts is more preferable.

  As for the crosslinking agent, the crosslinking accelerator and the antiaging agent, in order to improve the dispersibility in the emulsion composition, these auxiliary materials are dispersed in water using a dispersing agent etc. in advance to make a paste (Vulcanizing paste) may be prepared and added to the emulsion composition as this vulcanizing paste.

(Foaming agent, foam breaking inhibitor)
As a foaming agent, sodium laurate, sodium myristate, sodium stearate, ammonium stearate, sodium oleate, sodium oleate, potassium oleate, potassium ester of castor oil, fatty acid salt such as potassium soap of coconut oil, sodium lauroyl sarcosine, myristoyl ester Sarcosine sodium, oleyl sarcosine sodium, sarcosine salt such as cocoyl sarcosine sodium; coconut oil alcohol sodium sulfate, polyoxyethylene lauryl ether sodium sulfate such as sodium dioctyl sulfosuccinate, sodium lauryl sulfoacetate, dodecyl benzene sulfonic acid Sodium, sulfonates such as sodium α-olefin sulfonate; stearyldimethyl ammonium chloride, benzalkoni chloride Cationic surfactants such as arm, and the like.

  0.1-0.5 mass part is preferable with respect to 100 mass parts of solid content in an emulsion composition, and, as for the compounding quantity of a foaming agent, 0.1-0.3 mass part is more preferable.

  As a foam-break inhibitor, for example, a reaction product obtained by reacting an alkyl chloride such as ethyl chloride with formaldehyde and ammonia, such as an ethyl chloride-formaldehyde-ammonia reaction product; an alkyl quaternary ammonium chloride; an alkyl aryl Sulfonates; and higher fatty acid ammonium and the like are exemplified. Among these, the reaction product of alkyl chloride / formaldehyde / ammonia is more preferable because the cell stability effect is excellent.

  In addition, in the manufacturing method of SBR latex foam which concerns on this form, you may use a polyethyleneimine and / or a polyethyleneimine derivative as a foam-break inhibitor.

  Polyethyleneimine, commonly referred to as polyethylene "imine", is a copolymer of ethyleneamine, diethylenetriamine or monoethanolamine with ethyleneimine. Polyethyleneimine can be obtained by a known synthesis method (for example, a method according to the method described in JP-B-49-33120, JP-B-43-8828, etc.). Specifically, polyethyleneimine can be obtained, for example, by reacting ethyleneimine with a base amine such as ethylenediamine, diethylenetriamine, monoethanolamine or the like under an acid catalyst such as hydrochloric acid, sulfuric acid or p-toluenesulfonic acid. Moreover, you may use a commercial item as polyethylene imine in this form. As a commercial item, EPOMIN (trademark) SP series (made by Nippon Shokubai), Lupasol series (made by BASF Corporation), LUGALVAN-G15000 (made by BASF Corporation) etc. are mentioned.

  Moreover, a polyethyleneimine derivative can also be used as a foam-break inhibitor which concerns on this form. As such a polyethyleneimine derivative, for example, an epoxy-modified polyethyleneimine obtained by reacting polyethyleneimine with an epoxy compound such as epichlorohydrin, an acrylic-modified polyethyleneimine obtained by reacting polyethyleneimine with an acrylic compound such as acrylonitrile, an alkylated polyethyleneimine Halogen modified polyethyleneimine reacted with a halogen compound such as halide, isocyanate modified polyethyleneimine obtained by reacting polyethyleneimine with an isocyanate compound such as alkyl isocyanate, fatty acid modified polyethyleneimine obtained by reacting polyethyleneimine with fatty acid, and the like.

  The said polyethyleneimine and its derivative (s) can be used individually by 1 type, or in mixture of 2 or more types.

  0.1-0.9 mass part is preferable with respect to 100 mass parts of solid content in an emulsion composition, and, as for the compounding quantity of a foam-break inhibitor, 0.3-0.6 mass part is more preferable.

(Softener)
The softener is a component that imparts appropriate flexibility to the SBR latex foam of this embodiment. Examples of softeners include hydrocarbon process oils such as paraffinic process oils, naphthene process oils, aromatic process oils and the like, spindle oils, hydrocarbon oils such as petrolatum and liquid paraffin, etc .; castor oil, safflower oil, cottonseed oil Vegetable oil such as linseed oil, rapeseed oil, soybean oil, falling green oil, palm oil, coconut oil, olive oil, corn oil etc. and animal oil, and fatty acid ester such as fatty acid ester oil obtained by dehydrating or hydrogenating them Oils such as dehydrated castor oil etc .; dibutyl phthalate, dioctyl phthalate, di- (2-ethylhexyl) phthalate, di (2-ethylhexyl) tetrahydrophthalic acid, di-n-octyl adipate, di (2-ethylhexyl adipate ), Diisodecyl adipate, tricresyl phosphate, alkyl allyl phosphate Plasticizers such as butyl phthalyl butyl glycolate, di-n-butyl sebacate, di (2-ethylhexyl) sebacate, triethylene glycol di (2-ethyl hexoate), acetyl tri-n-butyl citrate And mixtures thereof; aromatic esters of trimellitic acid, pyromellitic acid, benzoic acid and the like.

  In addition to the components described above, fillers, colorants such as pigments and dyes, flavors, thickeners, stabilizers, fungicides and the like may be further added, as necessary.

<< process >>
Next, a representative example of the method for producing SBR latex foam according to the present embodiment will be described. In addition, as long as the manufacturing method of SBR latex foam includes the process of foaming and forming the emulsion composition containing SBR latex and carboxy modified latex, a well-known manufacturing method is applicable. For example, SBR latex foam is prepared based on the method described in JP-A-2017-110082, JP-A-2016-033172, JP-A-2016-033171, JP-A-2015-227431, JP-A-2015-227430, JP-A-2014-210899, etc. It may be manufactured.

  The method for producing SBR latex foam according to the present embodiment includes a raw material preparation step, a foaming / gelling step, and a heating step.

Raw material preparation process
At a raw material preparation process, the emulsion composition containing the above-mentioned emulsion which is an essential component is prepared. If necessary, the above-mentioned other emulsions and other additives may be added to the emulsion composition. In addition, after mixing several emulsions beforehand, another additive may be added, and all the components may be added and mixed simultaneously.

  Although the preparation method of the specific emulsion composition in the said preparation process is not specifically limited, For example, what is necessary is to mix while stirring in containers, such as a mixing tank which mixes each component.

<Foaming / gelation process>
In the foaming / gelling step, a foaming gas and a gelling agent are added to the emulsion composition obtained in the above-mentioned raw material preparation step, and these are sufficiently mixed to make a large number of bubbles in the emulsion composition. , To obtain a gelled emulsion composition.

  This foaming / gelling step is usually carried out by sufficiently mixing the emulsion composition obtained in the raw material preparation step, the foaming gas and the gelling agent with a mixing device such as a mixing head. In addition, the gelled emulsion composition referred to here does not refer to only the emulsion composition completely gelled, but is obtained in the raw material preparation step by the gelling agent added in the foaming / gelling step. Emulsion compositions that are gradually becoming gelled and those that are completely gelled.

(Foaming gas)
The foaming gas mixed into the emulsion composition in the foaming / gelling step is to form cells (cells) in the SBR latex foam, and the foaming ratio of the obtained SBR latex foam depends on the amount of the foaming gas mixed. And the density is determined. In order to adjust the density of SBR latex foam, the required emulsion composition is required from the density of the desired SBR latex foam and the volume of the emulsion composition (for example, the internal volume of the mold into which the emulsion composition is injected). The weight of the bubbling gas may be calculated, and the amount of the bubbling gas may be determined so as to obtain the desired volume in this weight. In addition, although air is mainly used as a kind of the bubbling gas, other inert gases such as nitrogen, carbon dioxide, helium, argon and the like can also be used.

(Foaming method, foaming conditions)
The foaming method used in the method of producing the SBR latex foam is not particularly limited as long as it is a method generally used in the production of latex foam, but for example, the mechanical floss (mechanical foaming) method can be used . The mechanical froth method is a method in which air in the atmosphere is mixed with the emulsion composition to foam by stirring the emulsion composition with a stirring blade or the like. As a stirring apparatus, although the stirring apparatus generally used for a mechanical floss method can be used without a restriction | limiting especially, For example, a homogenizer, a dissolver, a mechanical floss foaming machine etc. can be used. According to this mechanical floss method, it is possible to obtain a latex foam having a density suitable for various uses by adjusting the mixing ratio of the emulsion composition and air.

  The mixing time of the emulsion composition and the air is not particularly limited, but can be appropriately changed depending on the stirring apparatus used, etc., but is usually 1 to 10 minutes, preferably 2 to 6 minutes. The mixing temperature is also not particularly limited, but is usually at normal temperature. Moreover, the stirring speed in the above-mentioned mixing is suitably adjusted according to the stirring apparatus etc. to be used.

(Molding, gelation)
The emulsion composition foamed and gelled as described above is formed into a sheet or the like according to the desired SBR latex foam thickness by a known means such as a doctor knife or a doctor roll.

  Also, upon completion of the above-mentioned gelation, the bubbling gas present in the gelled emulsion composition is held as bubbles. The size of the air bubbles determines the cell diameter, since the air bubbles directly become the cells of the finally obtained SBR latex foam. The bubble size basically depends on the gelation time. That is, if the gelation time is long, the air bubbles mixed in the gelled emulsion composition come into contact with each other, coalesce and enlarge, or are discharged out of the gelled emulsion composition. The smaller the gelation time, the smaller the cell diameter.

<Heating process>
In the heating step, sufficient heating is carried out to allow the crosslinking of the emulsion composition injected into the mold to proceed sufficiently, and the crosslinking (curing) reaction of the rubber polymer is allowed to proceed and complete to form an SBR latex foam. Specifically, the rubber polymers are crosslinked by the above-described crosslinking agent to form a cured rubber. The heating means in this case is not particularly limited as long as the emulsion composition can be sufficiently heated to crosslink (cure) the rubber polymer, but for example, a tunnel type heating furnace can be used. . Further, the heating temperature and the heating time may be any temperature and time that can crosslink (cure) the rubber polymer, for example, at 80 to 150 ° C. (particularly, about 120 ° C. is preferable) and about 1 hour Good.

  Further, in this heating step, the water in the emulsion composition is released as water vapor, and the passage when the water vapor is released is communicated from the inside to the outside of the SBR latex foam. Therefore, in the SBR latex foam according to the present invention, since the passage through which the water vapor escapes remains as open cells, usually at least a part of the air bubbles present in the SBR latex foam become open cells. However, when the foaming gas mixed in the foaming / gelling step remains as it is, the resulting SBR latex foam becomes a closed cell, and the mixed foaming gas loses water vapor in this step. When communicated, the resulting SBR latex foam is an open cell. That is, in the SBR latex foam, all or some of the cells may be open cells, but all foams may be closed cells.

<<< SBR Latex Foam >>>
As mentioned above, although the manufacturing method of SBR latex foam which concerns on this form was demonstrated in detail, SBR latex foam which concerns on this invention obtained by such a manufacturing method next is demonstrated.

<< Physical Properties / Structures >>
The density (apparent density) of the SBR latex foam is not particularly limited, but is preferably, for example, 100 to 300 kg / m ³ .

  The SBR latex foam can have a weight reduction rate of 10% or less after 500 cycles of reciprocating abrasion with an abrasion tester according to JIS L8049.

  It is preferable that the Asker hardness measured by Asker hardness meter F type | mold of SBR latex foam is F50-F90.

<< Application of SBR Latex Foam >>
The SBR latex foam obtained by the manufacturing method according to the present embodiment can be used, for example, as a cosmetic puff applied directly to the skin, a sheet to be applied to the face, mascara, etc. Is preferred. In addition to the above, the latex foam of the present invention can be used as a mattress, Japanese and western pillows, mattresses, household goods such as cushions for chairs, seat cushions for vehicles such as trains, airplanes and automobiles, and carpet backings and door packings. It can also be used as a sealing material and shock absorbing material for electronic devices and household appliances.

  The present invention will be described in more detail by the following Examples and Comparative Examples, but the present invention is not limited thereto.

<< Formation of foam >>
<Raw material>
The following were used as a raw material of the emulsion composition of each Example and each comparative example.
・ Synthetic rubber latex 1
Styrene-butadiene rubber latex Solid content = 50%, Tg = -60 ° C
・ Synthetic rubber latex 2
Carboxy-modified styrene-butadiene rubber latex Solid content = 50%, Tg = -10 ° C
・ Rubber latex 3
Carboxy-modified styrene-butadiene rubber latex solid content = 50%, Tg = -30 ° C
・ Synthetic rubber latex 4
Carboxy-modified styrene-butadiene rubber latex Solid content = 50%, Tg = 40 ° C
・ Synthetic rubber latex 5
Carboxy-modified styrene-butadiene rubber latex solid content = 50%, Tg = -50 ° C
・ Synthetic rubber latex 6
Carboxy-Modified Styrene-Butadiene Rubber Latex Solid Content = 50%, Tg = 50 ° C
・ Synthetic rubber latex 7
Carboxy-modified acrylonitrile-butadiene rubber latex Solid content = 50%, Tg = -20 ° C
・ Synthetic rubber latex 8
Styrene-butadiene rubber latex solid fraction = 50%, Tg = 60 ° C
・ Synthetic rubber latex 9
Acrylonitrile-butadiene rubber latex Solid content = 50%, Tg = -20 ° C
・ Natural rubber latex 1
Carboxy-modified natural rubber latex Solid fraction = 50%, Tg = -20 ° C
Vulcanizing paste:
Product name Fine powder sulfur (vulcanizing agent); manufactured by Hosoi Chemical product name: Noxcella MZ (vulcanization accelerator); manufactured by Ouchi Emerging Chemical Industry Co., Ltd. Product name: Zinc oxide two types (vulcanization accelerator); Product name Adekastab AO-60 (Anti-aging agent); Made by ADEKA Co., Ltd. Product name: Demol N (dispersant); Kao Co., Ltd., foaming agent Brand name: potassium oleate soap; Kao Co., Ltd .; Agent Product name Trimene base; made by Uniroyal Co., Ltd. Gelling agent Product name Sodium fluorosilicate; made by Mitsui Chemicals Co., Ltd.

(Preparation of vulcanized paste)
10 parts by mass of sulfur, 6.0 parts by mass of Noxceler MZ, 18 parts by mass of zinc oxide 2 types, 13 parts by mass of Adekastab AO-60, and 3.0 parts by mass of demol N in 50 parts by mass of ion exchange water And dispersed in a ball mill for 48 hours to prepare a vulcanized paste.

Preparation of Example 1
According to the composition shown in Table 1, 80 parts by mass of the synthetic latex rubber 1 and 20 parts by mass of the synthetic latex rubber 2 were compounded to obtain a synthetic latex rubber mixed liquid. Next, an emulsion composition is prepared by blending 7.6 parts by mass of the vulcanized paste, 0.2 parts by mass of a foaming agent, and 0.4 parts by mass of an antifoaming agent with 100 parts by mass of the synthetic latex rubber mixed liquid I got a thing. To this composition, 10 parts by mass of a gelling agent and air were added and the mixture was foamed and gelled with an oaks mixer, and then heated at 100 ° C. for 30 minutes to produce an SBR latex foam.

Preparation of Example 2-8 and Comparative Example 1-6
An SBR latex foam was produced in the same manner as in Example 1 except that the raw materials shown in Tables 1 and 2 were blended.

<< Evaluation >>
The SBR latex foams of the examples and comparative examples prepared as described above were evaluated according to the methods shown below. Each evaluation result is shown in Table 1 and Table 2.

(1) Evaluation of Cell State The cell state was evaluated visually.
(Evaluation criteria)
"◎" means "cell is finely divided and uniform", "○" is "cell size and uniformity are slightly inferior", "は" is "cell rough" and "x" is "cell extremely Show rough and no cells are formed.

(2) Evaluation of Moldability (Shrinkage Ratio) The shrinkage ratio of each of the longitudinal, lateral, and height was calculated by measuring the dimensions of the latex foam before and after vulcanization, and evaluated according to the following criteria.
(Evaluation criteria)
“◎” means “average shrinkage rate is 0.5% or less”, “○” means “average shrinkage rate is more than 0.5% and 1% or less”, “Δ” means “average shrinkage rate is more than 1% 5 “% Or less” and “x” indicate “average contraction is more than 5%”, respectively.

(3) Measurement of density According to JIS K6400, it measured at room temperature as an apparent density.

(4) Measurement of hardness It measured using Asker hardness meter F type (made by Kobunshi Keiki Co., Ltd.), and evaluated according to the following standard.
(Evaluation criteria)
“○” indicates “hardness 50 or more and 70 or less”, “Δ” indicates “hardness 70 more than 90 or less”, and “x” indicate “hardness 90 more than”.

(5) Evaluation of Abrasivity According to JIS L 8049, a test piece was subjected to reciprocating friction 500 times with a wear tester to measure a weight loss, and evaluation was made according to the following criteria.
(Evaluation criteria)
“◎” means “decreased amount is 2% or less”, “o” means “decreased amount is more than 2% and 5% or less”, “Δ” means “decreased amount is more than 5% and 10% or less”, “x "Indicates that" reduction amount is more than 10% or penetration ", respectively.

Claims (6)

A method of producing SBR latex foam, comprising the step of foaming a composition comprising rubber latex,
The composition comprises, as an emulsion, at least an SBR latex and a carboxy-modified latex having a glass transition temperature of -30 to 40 ° C.,
The solid content ratio by mass of the SBR latex is 50 to 97% by mass, and the solid content ratio by mass of the carboxy-modified latex is 3 to 50% by mass with respect to the total of all the emulsions contained in the composition. A method of producing SBR latex foam, characterized in that   The SBR latex foam has a weight reduction rate of 10% or less after 500 times of reciprocal abrasion with an abrasion tester according to JIS L 8049, and a measured value with an Asker hardness meter F type is 50 to 90. The manufacturing method of SBR latex foam as described in item 1.   The method for producing SBR latex foam according to claim 1 or 2, wherein the SBR latex foam is for cosmetic puffs. An SBR latex foam obtained by foaming a composition comprising a rubber latex,
The composition comprises, as an emulsion, at least an SBR latex and a carboxy-modified latex having a glass transition temperature of -30 to 40 ° C.,
The solid content ratio by mass of the SBR latex is 50 to 97% by mass, and the solid content ratio by mass of the carboxy-modified latex is 3 to 50% by mass with respect to the total of all the emulsions contained in the composition. SBR latex foam that is characterized.   The SBR latex according to claim 4, having a weight reduction rate of 10% or less after 500 times of reciprocal abrasion with an abrasion tester according to JIS L 8049, and a measured value with an Asker hardness meter F type of 50 to 90. Form. The SBR latex foam according to claim 4 or 5, which is for cosmetic puffs.