JP6590678B2 - Method for producing latex foam and gelling agent - Google Patents

Description

  The present invention relates to a method for producing a latex foam having high environmental and biological safety and excellent properties, and a gelling agent used therefor.

  A method for producing an open cell foam (foam) from an emulsion is to foam the emulsion, which is a resin dispersion, and then add a solidifying agent to the emulsion to lose the surfactant that disperses and stabilizes the resin particles. There are chemical methods for fusing and solidifying the reaction system, and thermal gelation using cloud points. Since the latter achieves gelation by heat, the mixed foam is easily broken or united, and is not suitable for producing a thick molded body. As the former, a technique using sodium silicofluoride is widely used. Specifically, gelation occurs due to a pH drop due to hydrogen fluoride generated from sodium silicofluoride. Further, at this time, it is possible to suppress foam breakage due to rapid gelation by using a foam stabilizer as an auxiliary agent. This technique of combining sodium silicofluoride and cell stabilizer is essential for the production of foams having a uniform open cell structure.

  However, sodium silicofluoride has been designated as a toxic poison and generates hydrogen fluoride by a reaction that solidifies the emulsion. This is designated as a hydrogen fluoride poison and a poisonous medicine for poisonous substances under the Law on the Control of Deleterious Substances, and the working environment and waste water discharged during foam production are regarded as problems. Accordingly, there is a need for a method capable of producing a foam having a uniform open cell structure without using sodium silicofluoride.

  Here, as a foam manufacturing method not using sodium silicofluoride, for example, Patent Document 1 describes a method of forming a foam by bringing a solidified gas into contact with a foamed emulsion.

JP2007-9110A

  However, in the method according to Patent Document 1, it is difficult to produce a large molded article, and the series of pore cells is long distance, and the cell structure is different from the texture preferred for a cosmetic puff, for example. Compared with the foam obtained by the conventional chemical method combining sodium silicofluoride and a bubble stabilizer, there was a further improvement point.

  Therefore, the present invention can obtain a foam having excellent properties as well as a chemical method combining sodium silicofluoride and a bubble stabilizer without using sodium silicofluoride, It is an object of the present invention to provide a method for producing a latex foam that is highly safe to living bodies.

  As a result of diligent research, the present inventors have been able to form a desired foam without using sodium silicofluoride by using a mixture containing a lactone compound having a specific property and a solvent as a gelling agent. The present invention was completed. That is, the present invention is as follows.

The present invention is a method for producing a latex foam, comprising a step of foaming a latex composition containing a rubber latex in which rubber polymer particles are dispersed in a dispersion medium,
Including a gelling step of adding a gelling agent to the latex composition;
The gelling agent comprises a solid lactone compound and a liquid medium,
The lactone compound is soluble in water,
In this method, the solubility of the lactone compound in the liquid medium is 50 (g / 100 g) or less.
In addition, it is preferable that the said liquid medium contains 1 type, or 2 or more types selected from the group which consists of a bivalent or more polyol, fatty acid, and carboxylic acid ester as a main component.
Here, the present invention is a gelling agent for producing latex foam,
The gelling agent comprises a solid lactone compound and a liquid medium,
The lactone compound is soluble in water,
The liquid medium may be a gelling agent in which the solubility of the lactone compound is 50 (g / 100 g) or less.
In addition, it is preferable that the said liquid medium contains 1 type, or 2 or more types selected from the group which consists of a bivalent or more polyol, fatty acid, and carboxylic acid ester as a main component.

  According to the present invention, it is an object to provide a method for producing a latex foam that is highly safe to the working environment and a living body and that can obtain a foam having excellent properties, and a gelling agent used therefor. And

FIG. 1 is a photograph of a foam according to an example. FIG. 2 is a photograph relating to the evaluation of whether or not the entire gelation is possible.

  Hereinafter, preferred embodiments of the present invention will be described in detail, but the present invention is not limited thereto.

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>
In the method for producing a latex foam according to this embodiment, a gelling agent and a gas are added to a latex composition in which a vulcanizing agent, a foaming agent, a foam stabilizer and a softening agent are added to a rubber latex containing a dispersion medium and a dispersing agent. This is a method for producing a latex foam by foaming and gelling by mixing and heat vulcanization.

  More specifically, in this embodiment, the following method is adopted as a method for producing a latex foam which is a foam having a cell structure from rubber latex. In other words, a latex composition in which various additives are added to rubber latex, which is an aqueous dispersion of rubber polymer particles, is foamed and a gelling agent is added to disperse and stabilize the rubber polymer particles (interface) Deactivate the activator). As a result, the rubber polymer particles are fused and agglomerated and solidified while containing bubbles. Hereinafter, the method for producing a latex foam according to this embodiment will be described in detail in the order of the raw materials and the production process.

[material]
The raw material used in the method for producing the latex foam according to the present embodiment includes at least a rubber latex as a main raw material of the latex foam and a gelling agent, and further, as necessary, a vulcanizing agent and a vulcanizing aid. Further, vulcanization accelerators, anti-aging agents, foaming agents, foam stabilizers, softeners and other additives may be used. Each will be described in detail below.

[Rubber latex]
The rubber latex is one in which rubber polymer particles are stably dispersed in a dispersion medium (an aqueous medium or other water-containing dispersion medium) by a dispersant. Hereinafter, although each is demonstrated, the rubber latex which concerns on this form is not limited to this.

(Rubber polymer)
The rubber latex used in this embodiment is one in which an uncrosslinked or partially crosslinked polymer of natural rubber or synthetic rubber (hereinafter referred to as “rubber polymer”) is dispersed in water as particles. When the rubber polymer is natural rubber, a rubber sap, a concentrated one thereof, or a rubber sap or the like further blended with a preservative or the like is used. When the rubber polymer is a synthetic rubber, the rubber latex 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 necessary. As a raw material for latex foam, a latex having a rubber polymer content of 55 to 70% by mass is usually used. However, since a stable foam (foam) can be formed, preferably 60 to 68% by mass of rubber is used. Latex containing polymer is used. However, in this embodiment, it is of course possible to use a rubber latex outside the above content range. For example, when a carboxyl-modified rubber latex is used as described later, the content of the rubber polymer is out of the above range. Latex may be used.

  The rubber polymer of this embodiment is not particularly limited as long as it is a rubber-based polymer, but as a monomer unit, ethylene, propylene, styrene, butadiene, isoprene, chloroprene, acrylic acid ester, methacrylic acid ester, acrylonitrile, vinyl acetate, acrylamide, A polymer containing at least one kind of acrylamide derivative, vinyl ether, vinyl pyrrolidone and the like can be used. Examples of such polymers include natural rubber (NR), butadiene rubber (BR), acrylonitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), isoprene rubber (IR), Synthetic rubbers such as acrylate-butadiene rubber, methyl methacrylate-butadiene rubber (MBR), ethylene propylene diene rubber (EPDM) and the like can be mentioned. Examples of the rubber polymer that can be used in this embodiment include rubber polymers in styrene-butadiene-vinylpyridine latex, DPL (depolymerization latex), or chlorosulfonated polyethylene latex.

  In this embodiment, at least a part of the rubber polymer contained in the mixture has a carboxyl group or a hydroxyl group as a functional group (hereinafter referred to as “carboxyl-modified rubber polymer” or “hydroxyl-modified rubber polymer”). May be described). Examples of such a modified rubber polymer include carboxy-modified styrene-butadiene rubber and carboxy-modified acrylonitrile-butadiene rubber. When such a modified rubber polymer is used, the mass ratio between the unmodified rubber polymer and the modified rubber polymer (unmodified rubber polymer: modified rubber polymer) is the latex in which each rubber polymer is dispersed. For example, it may be set to 90:10 to 0: 100, although it varies depending on the content of the rubber polymer.

  In this embodiment, the rubber polymer as described above may be used alone, or two or more kinds may be used in combination.

(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 alkylbenzene sulfonic acid alkali metal salts may be used, and sorbitan fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene curing as necessary. A nonionic surfactant such as castor oil or polyoxyethylene alkyl ether may be used in combination.

  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.

(Gelling agent)
Next, after describing the gelation mechanism by the gelling agent according to this embodiment, the lactone compound and the liquid medium contained in the gelling agent according to this embodiment will be described in detail. In addition, the gelling agent which concerns on this form may contain the other component (for example, additive) etc. in the range which does not inhibit the effect of this invention.

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

  Here, the mechanism by which the latex composition gels will be described. In the latex composition, the dispersant that maintains the dispersibility of the rubber polymer particles has a surface active function on the alkaline side (in order to maintain the dispersibility of the rubber polymer particles, the latex composition is on the alkaline side). Adjusted). When a gelling agent is added to such a latex composition, an acid derived from the gelling agent is generated and the pH is 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 conventional latex foam production methods, sodium silicofluoride is used as the gelling agent, and the dispersant is deactivated by the pH decrease due to hydrogen fluoride generated from sodium silicofluoride to fuse and agglomerate rubber polymer particles. Has been used. However, as described above, when sodium silicofluoride is used, there is a problem of environmental impact, and when sodium silicofluoride is not used, there is a case where a cell having a property sufficient to be required by the application cannot be formed. there were.

  In this embodiment, the gelling agent contains a lactone compound that is soluble in water and in a solid state, and a liquid medium, and the solubility of the lactone compound in the liquid medium (lactone solubility) is 50 (g / g). 100 g) or less.

  Here, the lactone compound is ring-opened in an aqueous alkaline solution to produce a carboxylic acid, which contributes to the gelation of the latex. However, when the lactone compound is used as a gelling agent, if all of the lactone compound that contributes to the gelation reaction is in the form of a solution or liquid, the reactivity of the lactone compound is extremely increased, and the contact portion between the latex and the gelling agent Only reacts rapidly and agglomeration occurs, and the entire latex cannot be uniformly gelled.

  When the gelling agent according to the present embodiment has the above-described configuration, when blended in the latex composition, at least a part of the lactone compound that contributes to the gelation reaction remains solid, and the entire latex composition It is considered that the reaction mechanism is that the lactone compound is hydrolyzed by moisture in the latex composition and the carboxylic acid is gradually released into the latex composition over time. Therefore, rapid aggregation in the latex composition is prevented, and the entire latex can be uniformly gelled.

-Lactone compound As described above, the lactone compound is required to be present in a solid state in the gelling agent in order to achieve sustained release in the latex composition.

  Furthermore, as described above, when the gelling agent contains a liquid lactone compound, it is difficult to achieve uniform aggregation. Therefore, in the gelling agent, the liquid lactone compound is preferably 30% by mass or less (including 0% by mass) with respect to the entire lactone compound.

  The temperature condition when the lactone compound is “solid” (or “liquid”) may be any condition that is equal to the temperature condition of the gelling agent used in the specific production stage. When no special condition is used as the condition, the temperature condition may be normal temperature (for example, 23 to 27 ° C.).

  Further, as described above, the lactone compound according to this embodiment is required to cause a hydrolysis reaction in an alkaline aqueous solution. Therefore, the lactone compound according to this embodiment needs to be soluble in water. Here, in the present invention, that the lactone compound is “soluble in water” means that it can be hydrolyzed (more specifically, the solubility of the lactone compound in water is 0.1 g / 100 g). That means that) Note that the temperature condition in the case of “soluble in water” may be a condition equal to the temperature condition of the latex composition used in a specific production stage, but a special condition is used as the production condition. If not, the temperature condition may be room temperature (for example, 23 to 27 ° C.).

  Such lactone compounds are not particularly limited, but include 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. Among these, gluconolactone is preferable from the viewpoint of reactivity and safety.

  The shape of the solid lactone compound is not particularly limited, but as described above, it is preferably granular (particularly powder) in order to uniformly diffuse in the latex composition.

  These lactone compounds may be used alone or in combination of two or more.

-Liquid medium The liquid medium requires that the solubility of the lactone compound described above (solubility of the lactone compound in the liquid medium) be 50 (g / 100 g) or less, and be 40 (g / 100 g) or less. Is preferred. If the solubility with respect to the lactone compound exceeds 50 (g / 100 g), as described above, rapid aggregation occurs at the contact portion between the lactone dissolved in the liquid medium and the latex composition, and the latex The entire foam cannot be uniformly gelled. Note that the temperature condition in the “solubility” may be a condition equal to the temperature condition of the gelling agent used in the specific production stage, but when no special condition is used as the production condition, The temperature condition may be normal temperature (for example, 23 to 27 ° C.). Here, the solubility of the lactone compound in the liquid medium is measured according to the following method.

(1) Set the environmental temperature (for example, 23 ° C.).
(2) Put 100 g of liquid medium in a glass bottle, and add 0.1 g of lactone compound.
(3) Seal the glass bottle and stir (100 rpm) with a mix rotor.
(4) If the lactone compound does not dissolve, stirring is continued for 24 hours.
(3) When the lactone compound is dissolved (when the solid lactone compound becomes invisible), 0.1 g of the lactone compound is further added.
(6) The above steps (3) to (5) are repeated, and the measurement is completed when the lactone compound is not dissolved even after stirring for 24 hours.
(7) The maximum addition amount at which the lactone compound is dissolved one stage before the end of measurement is defined as the solubility (g / 100 g) of the lactone compound in the liquid medium.

  The liquid medium according to the present embodiment is not particularly limited as long as it has the above-described properties. However, the organic medium is a main component (for example, the total amount of components of the organic medium is 50% by mass with respect to the entire liquid medium). (It is preferable that it is 80% by mass or more.) (The organic medium may be a mixture of a plurality of types). Furthermore, the liquid medium according to this embodiment is mainly composed of one or more organic media selected from the group consisting of divalent or higher polyols, fatty acids, and carboxylic acid esters (monocarboxylic acid or polycarboxylic acid esters). It is more preferable to use a component, and it is particularly preferable to use a divalent or higher polyol as a main component. By using these as an organic medium, it becomes possible to perform more uniform gelation.

  Although it does not specifically limit as polyol more than bivalence, For example, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol etc. , Alkylene ether glycols (eg, diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, etc.), aliphatic polyhydric alcohols having two or more hydroxyl groups (eg, glycerin, etc.) Etc. can be illustrated.

  The fatty acid may be a saturated fatty acid or an unsaturated fatty acid, and is not particularly limited. Examples thereof include stearic acid, palmitic acid, linoleic acid, oleic acid, linolenic acid, ricinoleic acid, and lauric acid.

  The carboxylic acid ester is not particularly limited and may be a full ester or a partial ester. However, a phthalic acid ester (bis (2-ethylhexyl) phthalate, dibutyl phthalate, diisononyl phthalate, etc.), sebacic acid ester ( Bis (2-ethylhexyl) sebacate, dibutyl sebacate, diethyl sebacate, dimethyl sebacate, etc.), trimellitic acid ester (trimellitic acid tris (2-ethylhexyl), trimellitic acid tri-normal octyl, trimellitic acid triisodecyl, etc.) And plasticizers such as benzoic acid esters (ethylene glycol dibenzoate, dipropylene glycol dibenzoate, etc.).

  Here, in the aqueous medium which concerns on this form, vegetable oil can also be conveniently used as an organic medium containing a fatty acid and fatty acid ester. Although it does not specifically limit as vegetable oil, Cotton seed oil, peanut oil, sesame oil, rice oil, olive oil, castor oil etc. can be illustrated.

  The liquid medium is not particularly limited as long as it has the above-mentioned properties, but is preferably water-soluble or water-emulsifiable (including oil, plasticizer, etc.) and water-soluble. It is more preferable that it is sex. When the liquid medium has such properties, the gelling agent in which the lactone compound is dispersed is further easily dispersed in the latex foam. Therefore, the dispersibility of the gelling agent (and the lactone compound) in the latex composition is improved. And the uniformity of the cells in the latex foam is improved. In the present invention, that the liquid medium is “water-soluble” means that the water solubility is 0.1 g / 100 g. The temperature condition in this case may be a condition equal to the temperature condition of the latex composition in a specific production stage, but if no special condition is used as the production condition, the temperature condition is normal temperature ( For example, it is good as 23-27 degreeC.

  The production method of the gelling agent according to the present embodiment is not particularly limited as long as the lactone compound and the liquid medium described above are mixed by an appropriate method, but the lactone compound is contained in the liquid medium using a mill or the like ( It is preferably in the form of a paste that is uniformly dispersed.

  Here, in the gelling agent, the blending ratio of the lactone compound and the liquid medium is not particularly limited, and the lactone compound: liquid medium (mass ratio) may be 1:99 to 99: 1, It is suitable to set it as 10: 90-90: 10.

  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.

  In the method for producing a latex foam according to the present embodiment, the gelling agent according to the present embodiment and other known gelling agents may be used in combination as long as the effects of the present invention are not impaired.

(Vulcanizing agent)
As the vulcanizing agent, sulfur, an organic peroxide, a phenol compound, or the like is used depending on the type of rubber polymer and the crosslinking reaction mechanism. In the case of crosslinking with sulfur, colloidal sulfur and fine powder sulfur; sulfur dichloride and sulfur compounds such as dipentamethylene thiuram tetrasulfide can be used. In the case of crosslinking with an organic peroxide, hydroperoxides such as t-butyl hydroperoxide and cumene hydroperoxide; acyl peroxides such as benzoyl peroxide and m-toluyl peroxide; t-butylcumyl peroxide, dicumyl peroxide, 2,5- Alkyl peroxides such as dimethyl-2,5-bis (t-butoxyperoxy) hexane; peroxyesters such as t-butoxyperoxy-3,3,5-trimethylcyclohexanoate, t-butoxyperoxybenzoate; 1,1- Peroxyketals such as bis (t-butoxyperoxy) cyclohexane and 1,1-bis (t-butoxyperoxy) -3,3,5-trimethylcyclohexa; t-butoxyperoxyisopropyl carbonate, t-butoxyper Organic peroxides peroxycarbonate such as carboxymethyl-2-ethylhexyl carbonate can be used. Organic peroxides can be blended as they are, and are stable when adsorbed on inorganic powders such as molecular sieves, dissolved in hydrocarbons and plasticizers, and mixed with inert liquids such as polydimethylsiloxane. What was converted may be used for a mixing | blending. In the case of crosslinking with a phenol compound, an alkylphenol / formaldehyde resin, a sulfurized p-tert-butylphenol resin, an alkylphenol / sulfide resin, or the like can be used.

  The amount of the vulcanizing agent varies depending on the type of rubber polymer, the cross-linking mechanism, and the type of vulcanizing agent, but in the rubber latex mixture, 0.02 to 20 parts by mass with respect to 100 parts by mass of the rubber polymer. Preferably, 0.1-10 mass parts is more preferable.

(Vulcanization aid)
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.

(Vulcanization accelerator)
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 benzothiazylsulfenamide, N, N-dicyclohexyl-2-benzothiazylsulfenamide, N-oxydiethylene-2-benzothiazylsulfenamide; 2-mercaptobenzothiazole and Its salts (sodium salt, zinc salt, cyclohexylamine salt, dicyclohexylamine salt, etc.), 2- (4′-morpholinodithio) benzothiazole, 4-morpholinyl-2-benzothiazyl disulfide, 2- (N, N-diethyl) Benzothiazoles such as thiocarbamoylthio) benzothiazole; and mixtures thereof can be used.

(Anti-aging agent)
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.

  For vulcanizing agents, vulcanizing aids, vulcanization accelerators, and anti-aging agents, these auxiliary materials are previously dispersed in water using a dispersant or the like in order to improve dispersibility in rubber latex. It is also possible to prepare a paste (vulcanized paste) and add this vulcanized paste into the rubber latex. Further, the blending amounts of the vulcanization aid, the vulcanization accelerator and the anti-aging agent may be set appropriately according to the blending amount of the vulcanizing agent.

(Foaming agent)
As foaming agents, fatty acid salts such as sodium laurate, sodium myristate, sodium stearate, ammonium stearate, sodium oleate, potassium oleate, castor oil potassium soap, palm oil potassium soap; lauroyl sarcosine sodium, myristoyl Sarcosine salts such as sodium sarcosine, sodium oleyl sarcosine, sodium cocoyl sarcosine; sulfates such as sodium palm oil alcohol sulfate, sodium polyoxyethylene lauryl ether sulfate; sodium dioctyl sulfosuccinate, sodium lauryl sulfoacetate, dodecylbenzene sulfonic acid Sodium, sulfonates such as sodium α-olefin sulfonate; stearyldimethylammonium chloride, benzalkoni chloride Cationic surfactants such as arm, and the like.

  0.1-10 mass parts is preferable with respect to 100 mass parts of rubber polymers in the mixture of rubber latex, and, as for the compounding quantity of a foaming agent, 0.2-6.0 mass parts is more preferable.

(Bubble stabilizer)
Examples of the bubble stabilizer include a reaction product obtained by reacting alkyl chloride such as ethyl chloride with formaldehyde and ammonia, such as ethyl chloride / formaldehyde / ammonia reaction product; alkyl quaternary ammonium chloride; alkylaryl sulfone. Acid salts; and higher fatty acid ammonium. Of these, the reaction product of alkyl chloride, formaldehyde, and ammonia is more preferable because of its excellent bubble stabilizing effect.

  In the method for producing a latex foam according to this embodiment, polyethyleneimine and / or polyethyleneimine derivatives may be used as the bubble stabilizer.

  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 form. 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 embodiment. 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.

  The blending amount of the bubble stabilizer is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 6.0 parts by mass with respect to 100 parts by mass of the rubber polymer in the rubber latex mixture.

(Softener)
A softening agent is a component which provides moderate softness | flexibility to the latex foam of this form. 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 And mixtures thereof; trimellitic acid-based, pyromellitic acid-based, benzoic acid-based aromatic esters, and the like.

  Although the addition amount of a softening agent changes also with kinds of softening agent, it is preferable that the addition amount of a softening agent is 1-100 mass parts with respect to 100 mass parts of solid content in rubber latex, and 3-50 masses. Part is more preferable, and 6 to 30 parts by mass is more preferable.

(Other additives)
In addition, in the method for producing a latex foam according to the present embodiment, as an additive to be added to the rubber latex, a colorant such as an antibacterial agent, a filler, a pigment and a dye, a fragrance, and the like, as long as the effect of the present invention is not impaired. Thickeners, dispersants, stabilizers, antifungal agents and the like may be used.

[Manufacturing process]
Next, the manufacturing process of the latex foam of this embodiment will be described in detail. The method for producing the latex foam according to the present embodiment is not particularly limited as long as the above-mentioned gelling agent is used. For example, (Step 1: Mixing Step) Rubber latex is vulcanized paste (vulcanizing agent, vulcanizing aid, Vulcanization accelerator, anti-aging agent), foaming agent, foam stabilizer, softener and other additives are mixed to form a latex composition (step 2: foaming and gelling step) latex composition A step of forming a foamed gel-like product by mixing and foaming with a gelling agent and a gas, (Process 3: Molding / heating step) A step of producing a latex foam by heating and vulcanizing the foamed gel-like product ,including. Hereinafter, each process is explained in full detail. In addition, since the raw material used at each process is as above-mentioned, description may be abbreviate | omitted.

(Step 1: Mixing step)
First, vulcanizing paste (vulcanizing agent, vulcanization aid, vulcanization accelerator, anti-aging agent), foaming agent, foam stabilizer, softener and other additives are added to rubber latex as necessary. A liquid latex composition containing various additives is prepared.

  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 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: Foaming and gelation process)
Next, 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 foam and gel, thereby obtaining a foamed gel-like material. , The latex composition in which gelation is in progress (the gelation is incomplete) is also a latex composition}.

  Here, the foaming method used in the method for producing a latex foam according to the present embodiment is not particularly limited as long as it is a method generally used in the production of latex foam, but more specifically, mechanical floss ( Mechanical foaming) method can be used. The mechanical flossing method is a method in which air in the atmosphere is mixed with the latex composition and foamed by stirring the latex composition with a stirring blade or the like. As the stirring device, a stirring device generally used in the mechanical floss method can be used without particular limitation, and for example, a homogenizer, a dissolver, a mechanical floss foaming machine, or the like can be used. According to this mechanical flossing method, latex foam having a density suitable for various applications can be obtained by adjusting the mixing ratio of the latex composition and air.

  In consideration of production efficiency, the gelling agent is preferably added before gas mixing or simultaneously with gas mixing. However, if the gelling agent can be sufficiently mixed with the latex composition. Even if it is added after the gas is mixed, it is technically possible. In consideration of the gelling speed of the gelling agent and the convenience of equipment, it is preferable to mix the gas within a short time (for example, within 1 to several minutes) after the gelling agent is added.

  The foaming gas mixed into the latex composition forms bubbles (cells) in the latex foam, and the foaming ratio and density of the resulting latex foam are determined by the amount of the foaming gas mixed therein. In order to adjust the density of the latex foam, the required weight of the latex composition is determined from the density of the desired latex foam and the volume of the latex composition (for example, the inner volume of the mold into which the latex composition is injected). And the amount of the foaming gas may be determined so that the desired volume is obtained at this weight. Here, as the gas used in this manufacturing process, air is most preferable because it is inexpensive and easily available. Moreover, other gas can also be used as needed. Examples of other gases include inert gases such as nitrogen, carbon dioxide, helium, and argon, and fluorocarbons that are usually gases at ambient temperature.

  The mixing time of the latex composition and air is not particularly limited, but is usually 1 to 10 minutes, preferably 2 to 6 minutes. The mixing temperature is not particularly limited, but is usually room temperature. Further, the stirring speed in the above mixing is preferably 200 rpm or more in order to make bubbles fine (more preferably 500 rpm or more), and 2000 rpm or less is preferable in order to smoothly discharge the foam (latex foam) from the foaming machine. (800 rpm or less is more preferable).

  By the completion of the gelation described above, the foaming gas present in the gelled latex composition is retained as bubbles. Since the bubbles become cells of the latex foam finally obtained as they are, the size of the bubbles determines the cell diameter. The bubble diameter basically depends on the gelation time. In other words, if the gelation time is long, bubbles mixed in the latex composition gelled in the meantime may be brought into contact with each other to be united and enlarged, or discharged out of the gelled latex composition. Therefore, the shorter the gelation time, the smaller the cell diameter.

(Process 3: Molding / heating process)
Next, the foamed gel material 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. depending on the type of vulcanizing agent. Fully vulcanize (the crosslinking reaction proceeds). The heating method here is not particularly limited as long as it can vulcanize the foamed gel. Finally, a latex foam having a predetermined shape can be obtained by appropriate processing.

  In this step, the foamed gel material injected into the mold is sufficiently heated to sufficiently crosslink, and the rubber polymer crosslinking (curing) reaction proceeds and completes to form a latex foam. Specifically, the rubber polymers are cross-linked by the above-described cross-linking agent to form a cured rubber. The heating means in this case is not particularly limited as long as it can sufficiently heat the foamed gel material and crosslink (harden) the rubber polymer. For example, a tunnel heating furnace or the like can be used. it can. Further, the heating temperature and the heating time may be any temperature and time that can cause the rubber polymer to be crosslinked (cured), for example, 50 to 200 ° C, preferably 80 to 150 ° C (particularly about 120 ° C is preferable). ) For about one hour.

  In addition, the water contained in the latex composition escapes as water vapor from the foamed gel during heating in this step, and the path when this water vapor escapes communicates from the inside of the latex foam to the outside. . Therefore, in the latex foam according to this embodiment, the passage when the water vapor escapes remains as open cells, so that at least some of the bubbles existing in the latex foam become open cells. Here, if the foaming gas in the foamed gel-like material remains as it is even after passing through this step, it becomes closed cells in the obtained latex foam, and the mixed foaming gas is water vapor in this step. In the case where they are communicated at the time of evacuation, open cells are formed in the obtained latex foam. In this embodiment, some of the bubbles in the latex foam may be open cells, and the remaining bubbles may be closed cells, or all the bubbles may be open cells.

<Structure and physical properties of latex foam>
The latex foam obtained by the manufacturing method according to the present embodiment described above has a fine and uniform cell structure. In addition, the cell structure of the latex foam according to the present embodiment 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 embodiment 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, cushions for chairs, seat cushions for vehicles such as trains, airplanes and 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.

<Raw material>
[Rubber latex]
(Synthetic latex rubber)
Product name Nipol LX531B [acrylonitrile-butadiene rubber latex]; manufactured by Nippon Zeon Co., Ltd. [gelator (gelator paste)]
[Lactone compound]
(1) Glucono-δ-lactone; manufactured by Wako Pure Chemical Industries, Ltd. (2) L-(+)-gulonic acid γ-lactone (3) ε-caprolactone [liquid medium]
(1) Ethylene glycol; Wako Pure Chemical Industries, Ltd. (2) Propylene glycol (3) Propanediol (4) Polyethylene glycol (5) Cottonseed oil (6) Benzoflex (dipropylene glycol dibenzoate)
(7) Water [dispersant]
Product name Demol N; manufactured by Kao Corporation [foaming agent]
Product name FR-14 (potassium oleate soap); manufactured by Kao Corporation [Bubble Stabilizer]
(1) Product name Epomin SP003 (cationic polymer); made by Nippon Shokubai Co., Ltd. (2) Product name Trimen Base; made by Uniroyal Corporation [vulcanized paste]
(Vulcanizing agent)
Product name Sulfur; made by Hosoi Chemical Co., Ltd. (vulcanization accelerator)
Product name Noxeller MZ; Ouchi Shinsei Chemical Co., Ltd. (vulcanization accelerator)
Product name 2 types of zinc oxide; manufactured by Sakai Chemical Industry Co., Ltd. (anti-aging agent)
Product name ADK STAB AO-60; ADEKA Corporation

  Tables 1 and 2 show properties of the lactone compound and the liquid medium according to this example. The solubility of the lactone compound is measured by the method described above.

[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.

[Preparation of gelling agent]
[Gelling agent 1]
50 parts by mass of glucono-δ-lactone was added to 50 parts by mass of ethylene glycol and dispersed in a ball mill for 12 hours to prepare gelling agent 1.
[Gelling agent 2-9]
Gelling agents 2 to 9 were prepared in the same manner as the gelling agent 1 except that the lactone compound and the liquid medium were those shown in Tables 3 and 4.
[Gelling agent 10]
As a reference gelling agent, sodium silicofluoride (gelling agent 10) was prepared.

<Latex foam>
[Preparation of Example 1]
A mixed latex foam raw material is obtained by blending 16 parts by mass of vulcanized paste, 1.0 part by mass of a foaming agent, and 1.0 part by mass of a cell stabilizer (Epomin SP003) with 150 parts by mass of NBR latex. Then, 3.0 parts by mass of the gelling agent 1 and air were added to this raw material and foamed with an Oaks mixer, and then vulcanized to produce a foam according to Example 1. An appearance photograph of the foam according to Example 1 is shown in FIG.

[Preparation of Examples 2 to 8 and Comparative Examples 1 to 3]
Foams according to Examples 2 to 8 and Comparative Examples 1 to 3 were produced in the same manner as in Example 1 except that the raw materials and the blending amounts thereof were shown in Tables 3 and 4.

<Evaluation>
In the preparation of Examples 1 to 8 and Comparative Examples 1 to 3 described above, the following items were evaluated.

(Geltime)
The time from the addition of the gelling agent to the start of gelation (min's) was evaluated as the gel time. When aggregation starts immediately after the addition of the gelling agent, the gel time is set to “0'00”.

(Whether whole gel is possible)
In the foaming step, the case where the entire foamed material was gelled was evaluated as ◯, only a part thereof was aggregated, and the case where the whole was not gelled was evaluated as x.

  In addition, FIG. 2 is a photograph relating to whether or not the entire gelation is possible according to Comparative Example 2 (example in which the entire gelation is possible or not). As shown in FIG. 2, when the whole is not gelled and only a part thereof is aggregated, it is difficult to form a foam.

Claims (4)

A method for producing a latex foam, comprising the step of foaming a latex composition comprising a rubber latex in which rubber polymer particles are dispersed in a dispersion medium,
Including a gelling step of adding a gelling agent to the latex composition;
The gelling agent comprises a solid lactone compound and a liquid medium,
The lactone compound is soluble in water,
Ri der solubility 50 (g / 100g) following the lactone compound to said liquid medium,
The lactone compounds include gluconolactone (glucono-δ-lactone), D-(+)-ribono-1,4-lactone, L-(+)-gulonic acid γ-lactone, 2,3-O-isopropylidene One or more selected from the group consisting of -D (-)-ribono-1,4-lactone and α-amino-γ-butyrolactone hydrobromide , A method for producing latex foam.   The said liquid medium is a manufacturing method of Claim 1 containing 1 type, or 2 or more types selected from the group which consists of a polyol, a fatty acid, and carboxylic acid ester as a main component. A gelling agent for producing latex foam,
The gelling agent comprises a solid lactone compound and a liquid medium,
The lactone compound is soluble in water,
Ri der solubility 50 (g / 100g) following the lactone compound to said liquid medium,
The lactone compounds include gluconolactone (glucono-δ-lactone), D-(+)-ribono-1,4-lactone, L-(+)-gulonic acid γ-lactone, 2,3-O-isopropylidene One or more selected from the group consisting of -D (-)-ribono-1,4-lactone and α-amino-γ-butyrolactone hydrobromide , Gelling agent.   The gelling agent according to claim 3, wherein the liquid medium contains, as a main component, one or more selected from the group consisting of polyol, fatty acid, and carboxylic acid ester.