JP2015227431A - Production method of latex foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of latex foam which uses a material having a small environmental load as a foam stabilizer when a hexafluorosilicate is sued as a gelatinizer and provides a latex foam having a cell structure finer than that in the case of using the 'Torimen(TM)' base.SOLUTION: A production method of latex foam comprises adding at least a vulcanizer, a foaming agent and a foam stabilizer to a rubber latex containing a dispersion medium and a dispersant to prepare a latex composition and mixing the latex composition with a gelatinizer and air to foam and gelatinize and heating and vulcanizing to produce a latex foam of a specified shape. The foaming agent is an anionic surfactant; the gelatinizer is a hexafluorosilicate; and the foam stabilizer is an amphoteric surfactant.

Description

  The present invention relates to a method for producing a latex foam obtained by foaming a latex composition containing rubber latex as a main raw material and adding various additives to rubber latex and gelling with a gelling agent.

  Latex foam used in cosmetic puffs, etc. is a compounded liquid (latex composition) in which rubber latex is added with various chemicals such as rubber vulcanizing chemicals (sulfur, vulcanization accelerator), antibacterial agents, plasticizers and pigments. It is manufactured by the so-called Dunlop method in which a whipped cream-like product is mixed with gas using a hexafluorosilicate such as sodium fluorosilicate as a gelling agent. In this Dunlop method, hydrogen fluoride is generated by the addition of hexafluorosilicate such as sodium silicofluoride, and the pH is rapidly lowered by this hydrogen fluoride, thereby causing rapid gelation. When such a rapid gelation occurs, there is a problem that bubbles generated by the mixed gas are broken or coalesced.

  In order to solve such problems, in the Dunlop method, it has been widely performed to add Trimenbase (registered trademark) as a foam stabilizer to rubber latex (see, for example, Patent Documents 1 and 2). This trimene base has a function to moderate rapid gelation by sodium silicofluoride. Therefore, by adding the trimene base to the latex composition, bubble breakage and coalescence generated by the mixed gas can be suppressed. Thus, trimene base is an essential agent for obtaining a latex foam having a relatively fine and uniform cell structure, and has been widely used in the production of latex foam.

JP-A-6-14811 Japanese Patent No. 4872016

  However, the trimene base used in the techniques described in Patent Documents 1 and 2 above is a reaction product of chloroethane, ammonia, and formaldehyde, and the working environment and biosafety during latex foam manufacturing work, or latex foam There is a growing social awareness that the environmental impact of wastewater discharged during production is significant.

  In addition, depending on the application of latex foam, a high level of flexibility, softness, good touch per skin, etc. are required. To use in such applications, a very fine cell structure (bubbles) Need to form. However, when the above trimene base is used, it is difficult to form such a very fine cell structure.

  Under such circumstances, development of materials and / or raw material blends that replace trimene bases has been demanded as foam stabilizers used in the production of latex foam.

  Therefore, the present invention has been made in view of the above circumstances, and when hexafluorosilicate is used as a gelling agent, a material having a low environmental impact is used as a foam stabilizer, and when using a trimene base. Another object of the present invention is to provide a method for producing a latex foam, which can obtain a latex foam having a fine cell structure.

  As a result of intensive studies to solve the above problems, the present inventors have been able to reduce the environmental burden by using an amphoteric surfactant as an alternative material (bubble stabilizer) for the trimene base, while reducing the environmental load. It has been found that a latex foam having a finer cell structure than that at the time of use can be obtained, and the present invention has been completed based on this finding.

That is, the present invention provides foaming and gel by mixing a gelling agent and air into a latex composition in which at least a vulcanizing agent, a foaming agent and a bubble stabilizer are added to a rubber latex containing a dispersion medium and a dispersing agent. And a method for producing a latex foam of a predetermined shape by heat vulcanization, using an anionic surfactant as the foaming agent, using hexafluorosilicate as the gelling agent, An amphoteric surfactant is used as a foam stabilizer, which is a method for producing a latex foam.
In the method for producing a latex foam, the amphoteric surfactant is preferably a betaine-type amphoteric surfactant.
In the method for producing a latex foam, the betaine-type amphoteric surfactant is more preferably at least one selected from the group consisting of alkylbetaines, imidazolinium betaines, and carbobetaines.
In the method for producing a latex foam, the anionic surfactant is preferably a C12-24 anionic surfactant having an HLB in the range of 15-50.
In the method for producing a latex foam, an amphoteric surfactant may be further added to the rubber latex.

  According to the present invention, when hexafluorosilicate is used as a gelling agent, the environmental load can be reduced by using an amphoteric surfactant as a foam stabilizer, and finer than when using a trimene base. A method for producing a latex foam capable of obtaining a latex foam having a cell structure can be provided.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

The method for producing a latex foam according to the present invention will be described in the following order.
1 Method for producing latex foam 1-1 Raw materials 1-2 Production process 2 Structure and physical properties of latex foam 3 Use of latex foam

<Latex foam production method>
The method for producing a latex foam according to the present invention comprises mixing a gelling agent and air into a latex composition in which at least a vulcanizing agent, a foaming agent and a cell stabilizer are added to a rubber latex containing a dispersion medium and a dispersing agent. This is a method of producing a latex foam having a predetermined shape by foaming and gelation, and heat vulcanization. More specifically, in the present invention, the following method is employed as a method for producing a latex foam which is a foam having a cell structure from rubber latex. That is, a latex composition in which various additives are added to a rubber latex that is an aqueous dispersion of rubber polymer particles is foamed, and a gelling agent such as sodium fluorosilicate is added to stabilize the dispersion of the rubber polymer particles. The dispersant (surfactant) that is present is deactivated. As a result, the rubber polymer particles are fused and agglomerated and solidified while containing bubbles. At this time, conventionally, by adding trimene base as a bubble stabilizer, the pH decrease due to hydrogen fluoride generated from sodium silicofluoride is moderated, thereby suppressing bubble breakage due to rapid gelation and uniform. It has been widely practiced to produce a foam (latex foam) having a cell structure.

  However, as described above, when the trimene base is used, there are problems of environmental load and a problem that a sufficiently fine cell cannot be formed depending on the application.

  Therefore, in the present invention, an amphoteric surfactant is used as the bubble stabilizer. This not only demonstrates the same or higher rapid gelation suppression effect (gelation stability effect) with the same amount of use as Trimen Base, but also makes cells finer, for example, for use in cosmetic puffs, etc. In the case of using for the skin, it is possible to improve a high level of flexibility, soft feeling, good per touch and the like. Furthermore, since the amphoteric surfactant does not contain ammonia or formaldehyde unlike the trimene base, the environmental load can be significantly reduced. Hereinafter, the method for producing a latex foam according to the present invention will be described in detail in the order of the raw materials and the production process.

[material]
Examples of the raw material used in the method for producing a latex foam according to the present invention include rubber latex as a main raw material for latex foam, and additives including at least a vulcanizing agent, a foaming agent, a gelling agent, and a cell stabilizer.

(Rubber latex)
The rubber latex is one in which rubber polymer particles are stably dispersed in a dispersion medium (such as an aqueous medium) by a dispersant.

[Rubber latex]
The rubber latex usable in the present invention is not particularly limited. For example, acrylonitrile-butadiene rubber (NBR), isoprene rubber (IR), styrene-butadiene rubber (SBR), ethylene-propylene-diene rubber ( EPDM), chloroprene rubber (CR), butadiene rubber (BR), butyl rubber (IIR), natural rubber (NR) and other rubber polymer latexes. Among these, as the rubber latex of the present invention, it is preferable to use, as a main component, NBR latex that is excellent in weather resistance, oil resistance, hygiene (mainly, the effect of suppressing generation of microorganisms) and the like.

[Dispersant]
The dispersant has a role of improving the dispersibility of rubber polymer particles and various additives in a latex composition obtained by adding various additives to rubber latex. Since the latex composition can be made uniform by adding the dispersant, the gas to be mixed can be dispersed in a good state (fine and uniform). The dispersant is not particularly limited as long as it improves the dispersibility of the latex composition and the surface activity is deactivated by the addition of a bubble stabilizer described later. For example, the fatty acid alkali metal salt, alkylsulfonic acid Anionic surfactants such as alkali metal salts and alkali metal salts of alkylbenzene sulfonates; such as sorbitan fatty acid ester, polyoxyethylene glycerin fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene hydrogenated castor oil, polyoxyethylene alkyl ether Nonionic surfactants and the like can be used.

  Although the addition amount of a dispersing agent changes also with the kind etc. of rubber latex, it is 0.01-5.0 mass parts normally with respect to 100 mass parts of solid content in rubber latex, Preferably it is 0.02. It is -3.0 mass part.

(Vulcanizing agent)
The vulcanizing agent has a role of vulcanizing (crosslinking) the rubber polymer in order to ensure the elasticity and the like of the latex rubber. As the vulcanizing agent, for example, sulfur (for example, colloidal sulfur, fine powder sulfur), sulfur compounds (for example, sulfur dichloride, dipentamethylene thiuram tetrasulfide, etc.), organic peroxides, phenol compounds, etc. A known vulcanizing agent can be used.

  The addition amount of the vulcanizing agent varies depending on the type of rubber latex, the vulcanization mechanism and the vulcanizing agent, but is usually 0.02 to 20 parts per 100 parts by mass of the solid content (rubber polymer) in the rubber latex. It is a mass part, Preferably it is 0.1-10 mass part.

(Foaming agent)
The foaming agent has a role of foaming the latex composition when gas is mixed into the latex composition. As the foaming agent in the present invention, a C12-24 anionic surfactant having an HLB in the range of 15-50 is preferably used. By using such an anionic surfactant and using an amphoteric surfactant as a bubble stabilizer, as described later, a finer and more uniform cell structure than when using a conventional trimene base is used. A latex foam having the same can be obtained. From the viewpoint of making the cell finer and uniform, the HLB is more preferably 16 to 48, and still more preferably 18 to 45. Similarly, from the viewpoint of making the cell finer and more uniform, the carbon number of the anionic surfactant is more preferably C12-22, and further preferably C12-18. As the HLB value, a value calculated based on the number of atomic groups defined by the Davis method was used.

  Examples of such anionic surfactants include fatty acids such as sodium laurate, sodium myristate, sodium stearate, ammonium stearate, sodium oleate, potassium oleate, castor oil potassium soap, and palm oil potassium soap. Salts: Lauroyl sarcosine sodium, myristoyl sarcosine sodium, oleyl sarcosine sodium, cocoyl sarcosine sodium, sarcosine salts; palm oil alcohol sodium sulfate, polyoxyethylene lauryl ether sulfate sodium sulfate; dioctyl sulfosuccinate sodium, lauryl sulfo Examples thereof include sulfonates such as sodium acetate, sodium dodecylbenzene sulfonate, and sodium α-olefin sulfonate.

  The addition amount of the foaming agent is usually 0.01 to 10 parts by mass, preferably 0.02 to 5 parts by mass as the solid content with respect to 100 parts by mass of the solid content in the rubber latex.

(Gelling agent)
The gelling agent has a role of aggregating and polymerizing rubber polymer particles dispersed in the latex composition. At this time, since the latex composition gels while maintaining the dispersed state of the bubbles generated by the gas mixed in the latex composition, the gelled latex composition is heated and vulcanized to obtain a uniform cell. A latex foam having a structure can be obtained.

  Here, the mechanism by which the latex composition gels will be described. The latex composition has become alkaline due to the addition of the above-described dispersant and foaming agent, and the dispersant maintaining the dispersibility of the rubber polymer particles has a surface active function on the alkaline side. When a gelling agent is added to such a latex composition, an acid is generated due to the decomposition of the gelling agent, and the pH is rapidly lowered. When the latex composition moves to the acidic side due to the decrease in pH, the surface active function of the dispersant is deactivated, and the dispersed rubber polymer particles are aggregated and gelled.

  In the present invention, as the gelling agent, for example, a liquid material in which hexafluorosilicate such as sodium silicofluoride (SSF), potassium silicofluoride or calcium silicofluoride is in an aqueous solution state is used. As the gelling agent in the present invention, sodium silicofluoride is particularly preferably used because reaction control such as gelation start time is easy.

  The addition amount of the gelling agent is preferably about 0.1 to 10 parts by mass as the solid content with respect to 100 parts by mass of the solid content in the rubber latex.

(Bubble stabilizer)
As described above, the foam stabilizer has a role to moderate a rapid pH drop of the latex composition due to an acid (for example, hydrogen fluoride generated from sodium silicofluoride) generated by the addition of the gelling agent. Thereby, the foam breakage by rapid gelation of a latex composition can be suppressed, and the latex foam which has a uniform cell structure can be obtained.

  Here, the function of the bubble stabilizer will be described in more detail. As described above, when a gelling agent is added to the latex composition, an acid is generated due to the decomposition of the gelling agent, and the pH is rapidly lowered. When the latex composition shifts to the acidic side due to this pH decrease, the surface active function of the dispersant is deactivated, and the foaming agent that retains bubbles generated by the gas mixture in the latex composition is also deactivated. Resulting in. As a result, bubble breakage occurs in the latex composition, and a latex foam having a uniform cell structure cannot be obtained. However, in the present invention, since the amphoteric surfactant is used as the foam stabilizer, the rapid decrease in pH due to the gelling agent is suppressed, and the deactivation of the surfactant function of the foaming agent is suppressed, while the dispersion The surface active function of the agent can be deactivated. That is, according to the method for producing a latex foam according to the present invention, only the dispersant in which the rubber polymer particles are dispersed is lost by the gelling agent while stably holding the air bubbles that become the cells of the latex foam (foam). The rubber polymer particles can be aggregated and gelled. Thus, although the reason why rapid gelation can be suppressed by using an amphoteric surfactant is not clear, the present inventors have entered betaine surfactant between foaming agent molecules, It is presumed that the bubbles are further stabilized by relaxing the electrical repulsion between the foaming agents. In addition, the betaine surfactant is also less likely to be affected by changes in pH.

  The amphoteric surfactant that can be used in the present invention is not particularly limited, and amphoteric surfactants such as amino acid type, betaine type, and amine oxide type can be used.

  Examples of amino acid type amphoteric surfactants include N-alkyl or alkenyl amino acids or salts thereof. In the N-alkyl or alkenyl amino acid, an alkyl group or an alkenyl group is bonded to a nitrogen atom, and one or two “—R—COOH” (wherein R represents a divalent hydrocarbon group, preferably An alkylene group, particularly preferably having 1 to 2 carbon atoms.). In a compound in which one “—R—COOH” is bonded, a hydrogen atom is further bonded to the nitrogen atom. One “—R—COOH” is called a mono form, and two are called a di form. As the amphoteric surfactant according to the present invention, any of these mono- and di-forms can be used. In the N-alkyl or alkenyl amino acid, the alkyl group and alkenyl group may be linear or branched. Specifically, examples of the amino acid type amphoteric surfactant include sodium lauryl diaminoethylglycine, sodium trimethylglycine, sodium cocoyl taurine, sodium cocoyl methyl taurine, sodium lauroyl glutamate, potassium lauroyl glutamate, lauroyl methyl-β-alanine and the like. It is done.

  Examples of betaine-type amphoteric surfactants include alkyl betaines, imidazolinium betaines, carbobetaines, amide carbobetaines, amide betaines, alkylamide betaines, sulfobetaines, amide sulfobetaines, phosphobetaines, and the like. Specifically, as a betaine type amphoteric surfactant, lauryl betaine, stearyl betaine, lauryl dimethylaminoacetic acid betaine, stearyl dimethylaminoacetic acid betaine, lauric acid amidopropyl dimethylaminoacetic acid betaine, isostearic acid amidoethyl dimethylaminoacetic acid betaine, Isostearic acid amidopropyl dimethylaminoacetic acid betaine, isostearic acid amidoethyl diethylaminoacetic acid betaine, isostearic acid amidopropyl diethylaminoacetic acid betaine, isostearic acid amidoethyl dimethylaminohydroxysulfobetaine, isostearic acid amidopropyl dimethylaminohydroxysulfobetaine, isostearic acid amidoethyl diethylamino Hydroxysulfobetaine, isostearamide Lopyldiethylaminohydroxysulfobetaine, N-lauryl-N, N-dimethylammonium-N-propylsulfobetaine, N-lauryl-N, N-dimethylammonium-N- (2-hydroxypropyl) sulfobetaine, N-lauryl- N, N-dimethyl-N- (2-hydroxy-1-sulfopropyl) ammonium sulfobetaine, lauryl hydroxysulfobetaine, dodecylaminomethyldimethylsulfopropylbetaine, octadecylaminomethyldimethylsulfopropylbetaine, 2-alkyl-N-carboxy Methyl-N-hydroxyethylimidazolinium betaine (2-lauryl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine 2-stearyl-N-carboxymethyl-N-hydroxy Betaine and the like), coconut oil fatty acid amidopropyl betaine, coconut oil fatty acid amide propyl hydroxy sultaine and the like.

  Examples of the amine oxide type amphoteric surfactant include lauryl dimethylamine-N-oxide, oleyldimethylamine-N-oxide, and the like.

  Among the amphoteric surfactants described above, it is preferable to use a betaine-type amphoteric surfactant in the method for producing a latex foam according to the present invention. Among the betaine-type surfactants, alkylbetaines (particularly, alkyl groups having C12 to C12) are used. 24), imidazolinium betaine and carbobetaine are particularly preferred. Examples of alkylbetaines that can be used in the present invention include stearyl betaine and lauryl betaine. Examples of imidazolinium betaines include 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine. .

  Moreover, it is preferable that the absolute value of the difference between the carbon number of the betaine-type amphoteric surfactant in the present invention and the carbon number of the foaming agent described above is 2 or less. In such a case, not only the electrical repulsion of the anionic surfactant is inhibited, but also the foam is more firmly held by the van der Waals force with the alkyl chain of the surfactant as the foaming agent. Therefore, a latex foam having a finer and more uniform cell structure can be obtained.

  The addition amount of the amphoteric surfactant is preferably 0.01 to 5.0 parts by mass, more preferably 0.05 to 3 parts by mass with respect to 100 parts by mass of the solid content in the rubber latex. .

[Polyethyleneimine and its derivatives]
Here, in the method for producing a latex foam according to the present invention, polyethyleneimine and / or a polyethyleneimine derivative may be further added to the rubber latex as a bubble stabilizer as long as the effects of the present invention are not impaired. . This polyethyleneimine and / or polyethyleneimine derivative has a function to moderate the rapid pH decrease by the gelling agent and improve the stability of the mixed bubbles based on the synergistic action with the amphoteric surfactant described above. It is.

  Polyethyleneimine, commonly referred to as polyethylene “imine”, is a copolymer of ethylenediamine, diethylenetriamine or monoethanolamine and 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, for example, polyethyleneimine can be obtained by reacting a base amine such as ethylenediamine, diethylenetriamine, or monoethanolamine with ethyleneimine under an acid catalyst such as hydrochloric acid, sulfuric acid, or paratoluenesulfonic acid. Moreover, you may use a commercial item as polyethyleneimine in this invention. Examples of commercially available products include Epomin (registered trademark) SP series (manufactured by Nippon Shokubai), Lupasol series (manufactured by BASF), LUGALVAN-G15000 (manufactured by BASF), and the like.

  Moreover, a polyethyleneimine derivative can also be used as the bubble stabilizer according to the present invention. Examples of such a polyethyleneimine derivative include 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, and a polyethyleneimine alkyl Examples thereof include halogen-modified polyethyleneimine obtained by reacting with a halogen compound such as halide, isocyanate-modified polyethyleneimine obtained by reacting polyethyleneimine with an isocyanate compound such as alkyl isocyanate, and fatty acid-modified polyethyleneimine obtained by reacting polyethyleneimine with a fatty acid.

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

  Moreover, it is preferable that the number average molecular weights of the said polyethyleneimine and / or a polyethyleneimine derivative are 100-500,000. When the number average molecular weight is 100 to 500,000, a latex foam having a finer and more uniform cell structure can be obtained than when a conventional trimene base is used. From the viewpoint of making the cell finer and uniform, the number average molecular weight is more preferably 100 to 400,000, still more preferably 100 to 10,000, and more preferably 100 to 3,000. It is particularly preferred. In addition, the number average molecular weight of polyethyleneimine and / or a polyethyleneimine derivative is a number average molecular weight calculated | required by the boiling point rise method in polyalkyleneimine aqueous solution.

In addition, as the polyethyleneimine and / or polyethyleneimine derivative that can be used in the present invention, for example, as shown in the following structural formula (1), not a complete linear polymer but a primary amino group in a molecular skeleton. A branched structure containing a group, a secondary amino group and a tertiary amino group, and the ratio of the primary amino group is a primary amino group, a secondary amino group and a tertiary amino group It is preferable that it is 50 mol% or less with respect to the whole. From the viewpoint of making the cell finer and more uniform, the ratio of the primary amino group is more preferably 45 mol% or less. The lower limit of the ratio of primary amino groups is preferably 20 mol% or more, more preferably 25 mol% or more, and further preferably 30 mol% or more. If the ratio of primary amino groups is too high, the number of reactive sites with hexafluorosilicate decreases, and a large amount of polyethylenimine and / or polyethylenimine derivatives is required to stabilize bubbles due to the pH buffering effect. It becomes. On the other hand, if the ratio of primary amino groups is too low, agglomerates are generated due to reaction with carbon dioxide in the air, and mechanical stability is reduced, making it difficult to form uniform cells. Become. In addition, the ratio of the primary amino group, secondary amino group, and tertiary amino group in polyethyleneimine and / or a polyethyleneimine derivative can be calculated | required by measuring < ¹³ > C-NMR, for example.

(Other additives)
In addition, in the method for producing a latex foam according to the present invention, as an additive to be added to the rubber latex, in addition to the above-described vulcanizing agent, dispersing agent, foaming agent, gelling agent and cell stabilizer, As long as the effect is not impaired, a vulcanization aid, a vulcanization accelerator, a softening agent, and an anti-aging agent may be used as necessary, and further, an antibacterial agent, a filler, a colorant, a fragrance, and a thickener. Etc. may be used.

  The vulcanization aid promotes the function of the vulcanizing agent. As the vulcanization aid, for example, inorganic compounds such as zinc oxide and magnesium oxide, and organic substances such as stearic acid and amines can be used.

  The vulcanization accelerator is used for the purpose of shortening the vulcanization time. Examples of the vulcanization accelerator include zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc di-n-butyldithiocarbamate, zinc dibenzyldithiocarbamate, zinc ethylphenyldithiocarbamate, and zinc N-pentamethylenedithiocarbamate. Zinc dithiocarbamates; such as tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, N, N'-dimethyl-N, N'-diphenylthiuram disulfide, dipentamethylenethiuram tetrasulfide Thiurams; N, N-diisopropyl-2-benzothialylsulfenamide, Nt-butyl-2-benzothialylsulfenamide, N-cyclohexyl Sulfenamides such as 2-benzothiazylsulfenamide, N, N-dicyclohexyl-2-benzothiazylsulfenamide, N-oxydiethylene-2-benzothiazylsulfenamide; 2-mercaptobenzothiazole And salts thereof (sodium salt, zinc salt, cyclohexylamine salt, dicyclohexylamine salt, etc.), 2- (4′-morpholinodithio) benzothiazole, 4-morpholinyl-2-benzothiazyl disulfide, 2- (N, N— Benzothiazoles such as diethylthiocarbamoylthio) benzothiazole; and mixtures thereof can be used.

  A softening agent is a component which provides moderate softness | flexibility to the latex foam of this invention. Examples of the softener include hydrocarbon process oils such as paraffinic process oil, naphthenic process oil, aromatic process oil, hydrocarbon oils such as spindle oil, petrolatum, and liquid paraffin; castor oil, safflower oil, cottonseed oil , Linseed oil, rapeseed oil, soybean oil, falling raw oil, palm oil, palm oil, olive oil, corn oil and other vegetable oils and animal oils, and fatty acid ester oils such as fatty acid ester oils obtained by dehydrating or hydrogenating them Oils such as dehydrated castor oil; dibutyl phthalate, dioctyl phthalate, di- (2-ethylhexyl) phthalate, di (2-ethylhexyl) tetrahydrophthalate, di-n-octyl adipate, di (2-ethylhexyl) adipate ), Diisodecyl adipate, tricresyl phosphate, alkyl aliphosphate Plastics 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 Agents; and mixtures thereof.

  Antiaging agents include, for example, diphenylamine compounds such as N-phenyl-N ′-(p-toluenesulfonyl) -p-phenylenediamine; condensates of aromatic amines and aliphatic ketones; 2-mercaptobenzimidazole, Examples thereof include imidazole compounds such as zinc salts; monophenol compounds such as 2,6-di-t-butyl-4-methylphenol; bisphenol compounds, trisphenol compounds and polyphenol compounds.

[Manufacturing process]
Next, the manufacturing process of the latex foam of this invention is demonstrated in detail. The method for producing a latex foam according to the present invention comprises foaming and gelation by mixing a rubber composition with a latex containing at least a vulcanizing agent, a foaming agent and a foam stabilizer, and a gelling agent and air. And a method of producing a latex foam having a predetermined shape by heat vulcanization, and more specifically, a method including the following (Step 1) to (Step 3).

(Process 1)
First, a latex composition is prepared by adding at least various additives including a vulcanizing agent, a foaming agent and a cell stabilizer to rubber latex. In order to uniformly disperse these additives in the rubber latex, it is preferable to sufficiently stir and mix with a mixer or the like. In addition, when using 2 or more types of rubber latex as a rubber latex, it is preferable that each rubber latex exists uniformly in the obtained latex foam. Therefore, it is preferable to go through a step of uniformly mixing two or more types of rubber latex before adding various additives to the rubber latex. However, various additives may be added during these mixing steps as long as two or more types of rubber latex can be uniformly mixed.

(Process 2)
Next, in accordance with the Dunlop method, etc., the latex composition prepared in Step 1 is mixed with a gas such as a gelling agent and air, and sufficiently stirred and mixed to be foamed and gelled. obtain. In consideration of production efficiency, the gelling agent is preferably added before air mixing or simultaneously with air mixing, but if the gelling agent can be sufficiently mixed with the latex composition. It is technically possible to add it after mixing with air. In consideration of the gelling speed of the gelling agent and the convenience of equipment, it is preferable to mix air within a short time (for example, within 1 to several minutes) after the gelling agent is added.

(Process 3)
Next, the gel-like product obtained in step 2 is processed into a desired shape by a method such as casting, casting or extrusion molding, and further heated to 50 to 200 ° C. according to the type of vulcanizing agent. Sufficiently vulcanize (advance the crosslinking reaction). The heating method here is not particularly limited as long as the gel can be vulcanized. Finally, a latex foam having a predetermined shape can be obtained by appropriate processing.

<Structure and physical properties of latex foam>
The latex foam obtained by the production method according to the present invention described above may have closed cells, open cells or both, and is not particularly limited. However, when it is desired to increase the liquid absorbency of the obtained latex foam, open cells are used. It is preferable to have.

<Uses of latex foam>
The latex foam obtained by the production method according to the present invention can be used for, for example, a cosmetic puff applied directly to the skin, a sheet to be applied to the face, a mascara, and the like. In addition, the latex foam of the present invention includes mattresses, Japanese and Western pillows, mattresses, chair cushions and other household items, trains, airplanes, seat cushions for vehicles such as automobiles, carpet lining and door packing, It can also be used as a sealing material and cushioning material for electronic devices and household appliances. The latex foam of the present invention can also be used for wiping materials, sponge scrubs, water absorption rolls, water absorption mats, and the like. Among these, the latex foam of the present invention is particularly suitable for use in a cosmetic puff.

  Next, although an example and a comparative example explain the present invention still more concretely, the present invention is not limited at all by these examples.

<Raw material>
In the present examples and comparative examples, the following materials were used as latex foam materials.
Synthetic latex rubber: Trade name Nipol LX531B (acrylonitrile-butadiene rubber latex); manufactured by Nippon Zeon Co., Ltd., vulcanized paste: trade name Sulfur (vulcanizing agent); Agent); manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name: Zinc oxide 2 types (vulcanization accelerator); manufactured by Sakai Chemical Industry Co., Ltd., trade name: ADK STAB AO-60 (anti-aging agent); ADEKA Corporation, trade name Demol N (dispersing agent); Kao Co., Ltd./Foaming agent: Brand name Oleic acid potassium soap; Kao Co., Ltd./amphoteric surfactant 1: Brand name Anhitoal 86B; Kao Corporation / amphoteric surfactant 2: Product name: Amphital 20Y-B; manufactured by Kao Corporation, amphoteric surfactant 3: Product name: Amphital 24B; manufactured by Kao Corporation: amphoteric surfactant 4: product NISSAN ANON LG-R; manufactured by NOF Corporation, amphoteric surfactant 5: trade name Unisafe A-SM; manufactured by NOF Corporation, amphoteric surfactant 6: trade name: Amphital 20BS; manufactured by Kao Corporation, polyethyleneimine: Product name Epomin SP003; Nippon Shokubai Co., Ltd., Trimen Base; Uniroyal Chemical Company, Nonionic Surfactant: Product Name Nonion K-204; NOF Corporation, Gelling Agent: Product Name Sodium Silicofluoride; Mitsui Made by Chemical Co., Ltd.

<Latex foam production process>
Next, regarding the latex foam production process, preparation of vulcanized paste (a vulcanizing agent, a vulcanization accelerator, an anti-aging agent, a paste (for improving the dispersibility of the vulcanizing paste), etc.) The latex foam will be described in the order of production.

[Preparation of vulcanized paste]
50 parts by mass of 10 parts by mass of vulcanizing agent, 6.0 parts by mass of Noxeller MZ, 18 parts by mass of zinc oxide, 13 parts by mass of anti-aging agent, and 3.0 parts by mass of dispersant. In addition to water, it was dispersed in a ball mill for 48 hours to prepare a vulcanized paste.

[Production of latex foam]
Next, a method for producing a latex foam in each example and comparative example will be described.

Example 1
In accordance with the composition shown in Table 1, 7.6 parts by mass of vulcanized paste, 0.2 parts by mass of foaming agent, 0.4 parts by mass of amphoteric surfactant 1 with respect to 100 parts by mass of NBR latex (emulsion). Was added to obtain a latex composition. To this composition, 10 parts by mass of a gelling agent and air were added and foamed and gelled with an Oaks mixer, and then heated at 100 ° C. for 30 minutes to prepare a latex foam.

(Examples 2-7, Comparative Examples 2-3)
A latex foam was prepared in the same manner as in Example 1 except that the raw materials shown in Table 1 and Table 2 were blended.

(Comparative Example 1)
A latex foam was produced in the same manner as in Example 1 except that the amphoteric surfactant was not added.

<Evaluation of latex foam>
[Latex foam evaluation method and evaluation criteria]
The cell states (cell fineness and uniformity) were evaluated for the latex foams of Examples and Comparative Examples produced as described above. The evaluation regarding “cell state” is “◎◎” when “the cell is very fine and uniform”, “◎” when “the cell is fine and uniform”, and “a little fineness and uniformity of the cell”. The case of “poor” was performed on the basis of “◯”, the case of “rough cell” was “Δ”, and the case of “cell very rough and no cell was formed” was based on “x”. The results of the above evaluation are shown in Tables 1 and 2.

[Evaluation results]
As shown in Table 1 and Table 2, Examples 1 to 7 in which an amphoteric surfactant was blended as a foam stabilizer all had good cell states. Here, as the amphoteric surfactants, Examples 1-3, 6, and 7 using betaine type are particularly excellent in the cell state, and Examples 1, 2, and 7 using alkylbetaine are in the cell state. In Example 7, which contained both an amphoteric surfactant and polyethyleneimine, the cell state was the best. As in Examples 1, 2, and 7, in Example 6 using alkylbetaine, the difference between the carbon number of the bubble stabilizer and the carbon number of the foaming agent exceeded 2, so the cell state was Compared with Examples 1, 2, and 7, the results were slightly inferior.

  On the other hand, Comparative Example 1 in which no cell stabilizer was used and Comparative Example 3 in which a surfactant other than an amphoteric surfactant (nonionic surfactant) was used as the cell stabilizer were extremely poor in cell state. . In addition, Comparative Example 2 using a conventional trimene base as a bubble stabilizer seems to be difficult to use particularly in applications requiring a fine and uniform cell structure, although the cell state is relatively excellent. It is. In addition, as in the present invention, by using an amphoteric surfactant as a foam stabilizer, it has a cell state equivalent to or better than that of a conventional trimene base, and can be molded without considering the environmental load. became.

The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above-described embodiment. That is, it is understood that other forms or various modifications that can be conceived by those skilled in the art within the scope of the invention described in the claims belong to the technical scope of the present invention.

Claims (4)

A latex composition containing at least a vulcanizing agent, a foaming agent and a cell stabilizer added to a rubber latex containing a dispersion medium and a dispersing agent is foamed and gelled by mixing a gelling agent and air, followed by heat vulcanization. A method for producing a latex foam having a predetermined shape,
As the foaming agent, an anionic surfactant is used,
As the gelling agent, hexafluorosilicate is used,
A method for producing a latex foam, wherein an amphoteric surfactant is used as the foam stabilizer.   The method for producing a latex foam according to claim 1, wherein the amphoteric surfactant is a betaine-type amphoteric surfactant.   The method for producing a latex foam according to claim 2, wherein the betaine-type amphoteric surfactant is at least one selected from the group consisting of alkylbetaines, imidazolinium betaines, and carbobetaines. The method for producing a latex foam according to any one of claims 1 to 3, wherein a polyethyleneimine and / or a polyethyleneimine derivative is further added to the rubber latex.