WO2020045103A1 - Latex composition, molded body and foam rubber - Google Patents

Abstract

Provided is a latex composition which contains: a latex that contains a butyl rubber, an anionic emulsifying agent and water; and a sulfur-based crosslinking agent. The present invention is able to provide a latex composition which enables the achievement of a molded body that has excellent oil resistance, while exhibiting excellent gelling properties.

Description

Latex composition, molded article and foam rubber

{Circle over (1)} The present invention relates to a latex composition capable of providing a molded article having excellent gelling properties and excellent oil resistance, and a molded article and foam rubber using the same.

フ ォ ー ム Foam rubber (rubber foam) manufactured using polymer rubber latex is used for various applications as a mattress, a cosmetic sponge (puff), a roll, a shock absorber and the like. Among foam rubber applications, in particular, puffs are sponges that have good oil resistance to cosmetics, are easy to incorporate cosmetics, and have good adhesion (adhesion) to the skin of cosmetics. It has been demanded.

As a polymer latex for obtaining such a rubber foam, acrylonitrile-butadiene copolymer rubber (NBR) latex has been conventionally used from the viewpoint of good oil resistance (for example, Patent Document 1). reference). On the other hand, while various components are contained in cosmetics, rubber foams obtained using acrylonitrile-butadiene copolymer rubber latex have oil resistance depending on the types of components used as cosmetics. It may not be sufficient, more specifically, oil resistance is not sufficient for ultraviolet absorbers such as octyl paramethoxycinnamate, and therefore, a polymer latex showing oil resistance to such components is not sufficient. Was desired.

JP-A-6-32942

The present invention has been made in view of such circumstances, and has excellent gelling properties, and a latex composition capable of providing a molded article having excellent oil resistance, and a molded article using the same. And to provide foam rubber.

The present inventors have found that a latex composition containing butyl rubber, an anionic emulsifier, and water, and a latex composition containing a sulfur-based crosslinking agent can provide a foam rubber excellent in gelling properties and oil resistance. This has led to the completion of the present invention.

That is, according to the present invention, there is provided a latex composition containing a latex containing butyl rubber, an anionic emulsifier, and water, and a sulfur-based crosslinking agent.
In the latex composition of the present invention, the anionic emulsifier is preferably a fatty acid salt having 6 to 30 carbon atoms.
In the latex composition of the present invention, the content ratio of the butyl rubber is preferably 50% by weight or more.
In the latex composition of the present invention, the butyl rubber preferably has a Mooney viscosity (ML1 + 8, 125 ° C.) of 20 to 70.
In the latex composition of the present invention, the content of the sulfur-based crosslinking agent is preferably 0.1 to 15 parts by weight based on 100 parts by weight of the butyl rubber.

It is preferable that the latex composition for foam rubber of the present invention further contains a crosslinking accelerator.
The foam rubber latex composition of the present invention preferably further contains a foam stabilizer.

Further, according to the present invention, there is provided a molded article obtained using the latex composition of the present invention.
Alternatively, according to the present invention, there is provided a foam rubber obtained using the latex composition of the present invention.
Furthermore, according to the present invention, there is provided the method for producing a latex composition of the present invention, wherein the butyl rubber solution obtained by dissolving butyl rubber in a solvent is mixed with water in the presence of an anionic emulsifier to obtain an emulsion. Obtaining a latex containing butyl rubber, an anionic emulsifier, and water by removing the solvent from the emulsion, and adding the sulfur-based cross-linking agent to the latex. A method of making a latex composition is provided.
In the method for producing a latex composition of the present invention, the solvent is hexane, isohexane, pentane, cyclohexane, heptane, isooctane, xylene, toluene, benzene, and at least selected from the group consisting of carbon dioxide in a supercritical state. Preferably, it is one.

According to the present invention, it is possible to provide a latex composition which is excellent in gelling property and can provide a molded article having excellent oil resistance, and a molded article and a foam rubber using the same.

<Latex composition>
The latex composition of the present invention contains a latex containing butyl rubber, an anionic emulsifier, and water, and a sulfur-based crosslinking agent.
First, the latex constituting the latex composition of the present invention will be described.

The butyl rubber used in the present invention is a rubber comprising a polymer having a repeating unit derived from isobutylene (isobutene). More specifically, a rubber comprising a copolymer of isobutylene and a small amount of isoprene (isobutylene-isoprene rubber) ). The butyl rubber may be a halogenated butyl rubber obtained by halogenating a part of a copolymer of isobutylene and a small amount of isoprene.

The content ratio of the isobutylene unit in the butyl rubber is not particularly limited, but is preferably 95 mol% or more and less than 100 mol%, and more preferably 97 to 99.9 mol%. Further, the content ratio (unsaturation degree) of the isoprene unit in the butyl rubber is not particularly limited, but is preferably more than 0 mol%, 5 mol% or less, and more preferably 0.1 to 3 mol%. By setting the content ratio of the isobutylene unit and the isoprene unit in the above range, the oil resistance of the obtained molded article can be more appropriately increased.

The butyl rubber preferably has a Mooney viscosity (ML1 + 8, 125 ° C.) in the range of 20 to 70, more preferably 20 to 65, and still more preferably 25 to 60. By using a butyl rubber having a Mooney viscosity within the above range, the gelling property of the latex composition can be more appropriately increased.

The method for producing butyl rubber is not particularly limited, and examples thereof include a method in which aluminum chloride is used as a catalyst and slurry polymerization of isobutylene and isoprene is carried out in methylene chloride at −100 to −90 ° C. When the butyl rubber is a halogenated butyl rubber, it is obtained by slurry polymerization in hexane at 4 to 60 ° C. using bromine (Br ₂ ) or chlorine (Cl ₂ ) as a halogenating agent. Can be produced by a method of halogenating butyl rubber.

The latex used in the present invention is, for example, a step of obtaining an emulsion by mixing a solution of butyl rubber in which butyl rubber is dissolved in a solvent with water in the presence of an anionic emulsifier, and removing the solvent from the obtained emulsion. And a removing step.

As the butyl rubber solution, a polymerization solution obtained by slurry polymerization may be used as it is, or a solid butyl rubber is taken out from the polymerization solution obtained by slurry polymerization, and is then obtained by dissolving in a solvent again. May be used. The solvent used at this time is not particularly limited, but preferably includes hexane, isohexane, pentane, cyclohexane, heptane, isooctane, xylene, toluene, benzene, carbon dioxide in a supercritical state, and among these, the present invention From the viewpoint that a latex containing butyl rubber, an anionic emulsifier and water used in the above can be more appropriately obtained, cyclohexane is preferred.

The method of emulsifying the butyl rubber solution by mixing it with water in the presence of an anionic emulsifier to obtain an emulsion is not particularly limited, and a method of mixing a butyl rubber solution with an aqueous solution containing an anionic emulsifier, And a method in which an anionic emulsifier is added to a butyl rubber solution and mixed with water, and a method in which a solution in which an anionic emulsifier is added to a butyl rubber solution and an aqueous solution containing an anionic emulsifier are mixed. When these are mixed and emulsified, an emulsifying apparatus can be used, and as the emulsifying apparatus, those generally marketed as emulsifiers or dispersers can be used without limitation.

Examples of the emulsifying apparatus include batch-type emulsifiers such as “Homogenizer” (trade name, manufactured by IKA), “Polytron” (trade name, manufactured by Kinematica), and “TK Auto Homo Mixer” (trade name, manufactured by Tokushu Kika Kogyo). Machine: Trade name "TK Pipeline Homomixer" (manufactured by Tokushu Kika Kogyo), trade name "Colloid Mill" (manufactured by Shinko Pantech), trade name "Thrasher" (manufactured by Nippon Coke Industry), trade name " Trigonal wet pulverizer (Mitsui Miike Kakoki Co., Ltd.), trade name "Cavitron" (Eurotech), trade name "Milder" (Taikai Kiko Co., Ltd.), trade name "Fine Flow Mill" (Taikai Kiko Co., Ltd.) Continuous emulsifier such as “Microfluidizer” (manufactured by Mizuho Industries), “Nanomizer” (manufactured by Nanomizer), and “APV Gaurin” (trade name) High-pressure emulsifier such as Rin Co., Ltd .; membrane emulsifier such as "Membrane Emulsifier" (manufactured by Reika Kogyo Co., Ltd.); Ultrasonic emulsifiers such as “Ultrasonic homogenizer” (manufactured by Branson); and the like. The conditions of the emulsification operation are not particularly limited, and a processing temperature, a processing time, and the like may be appropriately selected so that a desired dispersion state is obtained.

Examples of the anionic emulsifier include, but are not particularly limited to, fatty acid salts such as sodium laurate, potassium myristate, sodium palmitate, potassium oleate, and sodium linolenate; sodium dodecylbenzenesulfonate, potassium dodecylbenzenesulfonate, and decylbenzenesulfone. Alkylbenzene sulfonates such as sodium silicate, potassium decylbenzenesulfonate, sodium cetylbenzenesulfonate, potassium cetylbenzenesulfonate; sodium di (2-ethylhexyl) sulfosuccinate, potassium di (2-ethylhexyl) sulfosuccinate, dioctylsulfosuccinate Alkyl sulfosuccinates such as sodium; alkyl sulfate esters such as sodium lauryl sulfate and potassium lauryl sulfate; polyoxyethylene Polyoxyethylene alkyl ether sulfates such as sodium lauryl ether sulfate and polyoxyethylene lauryl ether potassium sulfate; monoalkyl phosphates such as sodium lauryl phosphate and potassium lauryl phosphate; rosin such as sodium rosinate and potassium rosinate Acid salts; and the like. Among these, a fatty acid salt having 6 to 30 carbon atoms (ie, a carboxylate of a chain hydrocarbon having no ring structure) is preferable from the viewpoint that the storage stability of the obtained latex can be further improved, A fatty acid salt having 10 to 24 carbon atoms is preferable, a fatty acid salt having 13 to 21 carbon atoms is more preferable, and potassium oleate is particularly preferable. The anionic emulsifier acts as a foaming agent when producing a molded article such as foam rubber in addition to the action of emulsifying and dispersing butyl rubber in the latex composition of the present invention. In the present invention, by using an anionic emulsifier as the emulsifier, the latex composition can be made to have excellent gelling properties. In addition, by using an anionic emulsifier as an emulsifier, the latex composition can be made to have high foaming power in addition to excellent gelling properties, thereby making it suitable for foam rubber applications. It can be.

Also, in the present invention, any emulsifier may be used as long as it uses an anionic emulsifier, but an emulsifier other than the anionic emulsifier, for example, a cationic emulsifier or a nonionic emulsifier may be used in combination. In this case, the content of the anionic emulsifier in the emulsifier used is preferably 5% by weight or more, and more preferably 7% by weight or more, from the viewpoints of the foaming power and the gelling property of the obtained latex composition. Is more preferably 10% by weight or more, and it is preferable to use an emulsifier consisting essentially of an anionic emulsifier.

Next, a latex containing butyl rubber, an anionic emulsifier, and water can be obtained by performing an operation of removing the solvent from the obtained emulsion. The method for removing the solvent from the emulsion is not particularly limited as long as the content of the solvent in the obtained latex can be adjusted to 500 ppm by weight or less. Methods such as distillation, steam distillation, and centrifugation can be employed.

Distillation under reduced pressure can be performed by heating the emulsion under reduced pressure of preferably 500 to 900 hPa. The temperature in the distillation under reduced pressure may be appropriately selected according to the type of the solvent used, but is preferably from 50 to 90 ° C.

The centrifugation is performed, for example, by using a centrifugal separator such as a continuous centrifuge and setting the centrifugal force to preferably in the range of 100 to 10,000 G, more preferably in the range of 2,000 to 8,000 G. Can be. When a continuous centrifuge is used, the flow rate fed into the centrifuge is preferably 500 to 1700 Kg / hr, and the back pressure (gauge pressure) of the centrifuge is preferably 0.03 to 1.6 MPa. It is preferable to carry out under the conditions. By the centrifugation operation, a latex containing butyl rubber, an anionic emulsifier, and water can be obtained as a light liquid after the centrifugation.

ラ テ ッ ク ス Further, the latex obtained by removing the solvent may be subjected to a concentration treatment, if necessary, to adjust the solid content concentration. Examples of the concentration treatment include a method of partially evaporating water under reduced pressure, a method of centrifugation, and the like.

ブ チ ル The content ratio (solid content) of butyl rubber in the latex used in the present invention is preferably 50% by weight or more, more preferably 55 to 70% by weight, and further preferably 60 to 70% by weight. By setting the content ratio of the butyl rubber in the above range, the foaming power and the gelling property can be more appropriately improved. The content ratio of the butyl rubber can be adjusted by, for example, an operation of removing a solvent and a concentration treatment.

含有 The content of the anionic emulsifier in the latex used in the present invention is preferably 2 to 10 parts by weight based on 100 parts by weight of butyl rubber. By setting the content of the anionic emulsifier in the above range, the obtained latex composition can have excellent foaming power and gelling property.

The rubber particles composed of butyl rubber contained in the latex used in the present invention preferably have a volume cumulative particle size d50 (particle size at which the cumulative volume is 50% in a volume-based particle size distribution) of 100 to 5, 000 nm, more preferably 150 to 4,000 nm, further preferably 250 to 3,000 nm, particularly preferably 500 to 2,000 nm. By setting the volume cumulative particle diameter d50 of the rubber particles composed of butyl rubber in the above range, the storage stability of the latex can be more appropriately increased. The volume cumulative particle size d50 of the rubber particles composed of butyl rubber can be controlled by, for example, the type and amount of the anionic emulsifier to be used, emulsification conditions during emulsification, and the like.

The latex composition of the present invention contains a sulfur-based crosslinking agent in addition to the latex containing butyl rubber, anionic emulsifier, and water described above.

Examples of the sulfur-based crosslinking agent include sulfur such as powdered sulfur, sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur; sulfur chloride, sulfur dichloride, morpholine disulfide, alkylphenol disulfide, and N, N ′. And sulfur-containing compounds such as -dithio-bis (hexahydro-2H-azepinone-2), phosphorus-containing polysulfide, polymer polysulfide, and 2- (4'-morpholino dithio) benzothiazole. Among these, sulfur can be preferably used. The sulfur-based crosslinking agent can be used alone or in combination of two or more.

The content of the sulfur crosslinking agent is not particularly limited, but is preferably 0.1 to 15 parts by weight, more preferably 0.2 to 8 parts by weight, based on 100 parts by weight of the butyl rubber in the latex. By setting the content of the sulfur-based crosslinking agent in the above range, the strength of the obtained molded article such as foam rubber can be further increased.

Further, the latex composition of the present invention preferably contains a crosslinking accelerator.
As the crosslinking accelerator, those usually used in the production of a molded article obtained by using a latex composition, such as foam rubber, can be used. For example, diethyl dithiocarbamic acid, dibutyl dithiocarbamic acid, di-2-ethylhexyl dithiocarbamic acid, Dithiocarbamic acids such as dicyclohexyldithiocarbamic acid, diphenyldithiocarbamic acid, and dibenzyldithiocarbamic acid, and dithiocarbamic acid-based crosslinking accelerators such as zinc salts thereof; 2-mercaptobenzothiazole, zinc 2-mercaptobenzothiazole, 2-mercaptothiazoline, dibenzothia Zyl disulfide, 2- (2,4-dinitrophenylthio) benzothiazole, 2- (N, N-diethylthiocarbamoylthio) benzothiazole, 2- (2,6 Thiazole crosslinking accelerators such as dimethyl-4-morpholinothio) benzothiazole and 2- (4'-morpholino dithio) benzothiazole; TMTD (tetramethylthiuram disulfide), tetraethylthiuram disulfide, tetramethylthiuram monosulfide, dipenta Tyrium compounds such as methylenethiuram disulfide; N-cyclohexyl-2-benzothiazylsulfenamide, Nt-butyl-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N Sulfenamide-based cross-linking accelerators such as -oxyethylene-2-benzothiazolesulfenamide, N, N'-diisopropyl-2-benzothiazolesulfenamide; and the like. The crosslinking accelerator can be used alone or in combination of two or more.

The content of the crosslinking accelerator is preferably 0.1 to 15 parts by weight, more preferably 0.2 to 10 parts by weight, based on 100 parts by weight of the butyl rubber in the latex. By setting the content of the crosslinking accelerator in the above range, the strength of the obtained molded article such as foam rubber can be further increased.

Further, the latex composition of the present invention preferably contains a crosslinking aid.
As the crosslinking aid, those usually used in the production of a molded article obtained by using a latex composition such as foam rubber can be used, and examples thereof include zinc oxide, stearic acid and a zinc salt thereof.

The content of the crosslinking accelerator is preferably 0.5 to 10 parts by weight, more preferably 0.5 to 8 parts by weight, based on 100 parts by weight of the butyl rubber in the latex. By setting the content of the crosslinking accelerator in the above range, the strength of the obtained molded article such as foam rubber can be further increased while improving the emulsion stability.

ラ テ ッ ク ス Furthermore, the latex composition of the present invention preferably further contains a foam stabilizer. By including the foam stabilizer, when the latex composition of the present invention is used for foam rubber, bubbles contained in the obtained foam rubber can be made fine and uniform, and thereby, the flexibility can be improved. The property and strength can be improved.

Examples of the foam stabilizer include an alkyl chloride-formaldehyde-ammonia reaction product obtained by reacting an alkyl chloride such as ethyl chloride with formaldehyde and ammonia. The alkyl chloride-formaldehyde-ammonia reaction product is preferably an alkyl product having 4 or less carbon atoms, and specific examples thereof include an ethyl chloride-formaldehyde-ammonia reaction product. An alkyl quaternary ammonium chloride, preferably an alkyl quaternary ammonium chloride having 4 or less carbon atoms in the alkyl; an alkylaryl sulfonate, preferably an alkylaryl sulfonate having 4 or less carbon atoms in the alkyl; And higher fatty acid ammonium, preferably higher fatty acid ammonium having alkyl of 4 or less; hexafluorosilicate; and the like can also be used as the foam stabilizer. Among these, alkyl chloride-formaldehyde-ammonia reaction products are preferred from the viewpoint of a high addition effect, and alkyl chloride-formaldehyde-ammonia reaction products having 4 or less carbon atoms in the alkyl are more preferred, and ethyl chloride. Formaldehyde-ammonia reaction products are particularly preferred. As the ethyl chloride / formaldehyde / ammonia reaction product, commercially available products such as “Trimen Base” (manufactured by Crompton Corp.) can be used.

含有 The content of the foam stabilizer is preferably 0.4 to 10 parts by weight, more preferably 0.4 to 6 parts by weight, based on 100 parts by weight of butyl rubber in the latex. By setting the content of the cell stabilizer in the above range, the cells contained in the obtained molded article such as foam rubber can be made fine and uniform, and the flexibility and strength can be further improved.

The latex composition of the present invention may further contain an antioxidant, a coloring agent, or a dispersant for stably dispersing the above-mentioned various compounding agents in the latex (for example, NASF (formalin naphthalenesulfonate)). Condensate sodium salt) and the like, and a thickener (for example, polyacrylic acid and its sodium salt, sodium alginate, polyvinyl alcohol, etc.) can be added as necessary.

The method for preparing the latex composition of the present invention is not particularly limited. For example, as described above, after obtaining a latex containing butyl rubber, an anionic emulsifier, and water, dispersion using a ball mill, a kneader, a disper, or the like is performed. Using a mixer, the obtained latex, a method of mixing a sulfur-based crosslinking agent and various compounding agents to be blended as necessary, or using the above disperser, such as a sulfur-based crosslinking agent, other than latex After preparing the aqueous dispersion of the compounding component, a method of mixing the aqueous dispersion with the latex may, for example, be mentioned.

<Molded body>
The molded article of the present invention is obtained using the latex composition of the present invention described above.
The molded article of the present invention is not particularly limited, but a film-shaped molded article obtained by molding into a film by a method of applying the latex composition on a substrate or the like, by dip molding the latex composition. The obtained dip molded product, or various molded products obtained by coagulating the latex composition and molding the obtained coagulated rubber into a desired shape, and the like.In the present invention, a foam rubber is used. Is preferred. Hereinafter, the case where the molded article of the present invention is foam rubber will be described as an example, but the molded article of the present invention is not particularly limited to foam rubber.

フ ォ ー ム The foam rubber of the present invention can be obtained by using the latex composition described above. Specifically, the foam rubber of the present invention can be obtained by foaming and coagulating the above-mentioned latex composition at a desired expansion ratio.

空 気 Air is usually used for foaming, but carbonates such as ammonium carbonate and sodium bicarbonate; azo compounds such as azodicarboxylic amide and azobisisobutyronitrile; and gas generating substances such as benzenesulfonyl hydrazide can also be used. When air is used, the latex composition can be agitated and bubbled by entraining the air. At this time, for example, an Oaks foaming machine, an ultrasonic foaming machine, or the like can be used.

(4) After the latex composition is foamed, the foamed latex composition is solidified in order to fix the foamed state. The coagulation method may be any method capable of gelling and solidifying the latex, and conventionally known methods can be used. For example, sodium hexafluorosilicate (sodium silicate), potassium hexafluorosilicate (silicate) Dunlop method (room temperature coagulation method) in which a room temperature coagulant such as a silicon fluoride compound such as potassium fluoride and titanium sodium silicate is added to the foamed latex composition; organopolysiloxane, polyvinyl methyl ether, zinc sulfate A heat-sensitive coagulation method in which a heat-sensitive coagulant such as an ammonium complex salt is added to the foamed latex composition; The amount of the coagulant such as a room temperature coagulant and a heat-sensitive coagulant is not particularly limited, but is preferably 0.5 to 10 parts by weight, more preferably 0.5 to 10 parts by weight, based on 100 parts by weight of butyl rubber in the latex constituting the latex composition. Is 0.5 to 8.

Then, after adding a coagulant to the expanded latex composition, the foamed latex composition is transferred to a mold having a desired shape and coagulated, whereby a foam rubber can be obtained. After coagulation, heating may be performed to crosslink the latex composition. The conditions for the crosslinking may be such that a heat treatment is preferably performed at a temperature of 100 to 160 ° C., preferably for 15 to 120 minutes.

フ ォ ー ム It is preferable to wash the obtained foam rubber after removing it from the mold. The method for washing is not particularly limited, and examples thereof include a method of washing with stirring with water at about 20 to 70 ° C. for about 5 to 15 minutes using a washing machine or the like. After washing, it is preferable to drain and dry at a temperature of about 30 to 90 ° C. so as not to impair the feel of the foam rubber. The foam rubber thus obtained can be used as a puff (cosmetic sponge) or the like by, for example, slicing it to a predetermined thickness, cutting it into a predetermined shape, and polishing the side surface with a rotating grindstone or the like. it can.

フ ォ ー ム The foam rubber obtained by using the latex composition of the present invention can be suitably used for various applications such as mattresses, puffs (cosmetic sponges), rolls, and shock absorbers. In particular, the foam rubber obtained by using the latex composition of the present invention is oil-resistant to a plurality of components used as cosmetics, and in particular, paraffin and an external absorbent (eg, paramethoxy) used as components of cosmetics. Since it has excellent oil resistance to octyl cinnamate (ethylhexyl methoxycinnamate), it can be suitably used as a puff (cosmetic sponge) impregnated with a liquid cosmetic or the like.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. The “parts” in each example are based on weight unless otherwise specified.
Various physical properties and characteristics were evaluated according to the following methods.

<Solid content concentration>
A sample (2 g) was precisely weighed (weight: X2) in an aluminum dish (weight: X1), and dried in a hot-air dryer at 105 ° C. for 2 hours. Next, after cooling in a desiccator, the weight of the entire aluminum plate was measured (weight: X3), and the solid content concentration was calculated according to the following formula.
Solid content concentration (% by weight) = (X3-X1) × 100 / X2

<Swelling ratio to liquid paraffin>
A latex for foam rubber was applied on a substrate and dried at 23 ° C. for 5 days to obtain a latex film having a thickness of 0.4 mm. Then, the obtained film is punched into a cylindrical shape having a diameter of 33 mm and a thickness of 0.4 mm, immersed in liquid paraffin at 23 ° C. for 24 hours, and a ratio of the diameter of the film after immersion to the film before immersion. (Swelling ratio (%) = (diameter of film after immersion) / (diameter of film before immersion) × 100) was calculated. In addition, it can be judged that the lower the swelling ratio, the more excellent the molded article such as foam rubber obtained by using the latex composition containing the latex for foam rubber is in oil resistance to liquid paraffin.

<Swelling ratio for UV absorber>
A foam rubber latex film having a thickness of 0.4 mm was obtained by applying the foam rubber latex on the base material and drying at 23 ° C. for 5 days. Then, the obtained film was punched out into a columnar shape having a diameter of 33 mm and a thickness of 0.4 mm, and this was put into an ultraviolet absorbent (product name “Escalor 557”, manufactured by ISP Japan, ethylhexyl methoxycinnamate) at 23 ° C. For 24 hours, and the ratio of the diameter of the film after immersion to the film before immersion (swelling ratio (%) = (diameter of film after immersion) / (diameter of film before immersion) × 100) was calculated. . In addition, it can be judged that the lower the swelling ratio, the better the molded article such as foam rubber obtained by using the latex composition containing the latex for foam rubber has oil resistance to the ultraviolet absorbent.

<Foaming power>
The latex composition for foam rubber was foamed by stirring using a stand mixer (manufactured by Electrolux, ESM945). When the expansion ratio becomes 5 times or more (that is, the volume after stirring is 5 times or more with respect to the volume before stirring) within 5 minutes from the start of stirring, it is evaluated as “OK”, and stirring is performed for 5 minutes. Even when the expansion ratio did not reach 5 times, it was evaluated as "impossible". It can be determined that the higher the foaming power, the higher the productivity of a molded article such as foam rubber which is excellent in flexibility.

<Gelling property>
To 100 parts of the rubber component of the foam rubber latex composition, 6 parts (30 parts as an aqueous dispersion) of an aqueous dispersion of sodium silicofluoride (solid content concentration: 20% by weight) was added, followed by stirring for 1 minute. After that, it was left still for 10 minutes, and it was examined whether or not it had solidified. When solidified after 10 minutes (the composition had completely lost fluidity), it was evaluated as “OK”, and when solidification was not completed after 10 minutes, or when solidification was insufficient. Rated “impossible”. The better the gelling property, the shorter the molding time is possible, which makes it possible to determine that a desired molded body can be obtained in a short time, and further, from the viewpoint of obtaining a foam rubber, Since the higher the conversion property, the higher the foaming ratio, the higher the gelability, the more highly flexible the foam rubber can be obtained with high productivity.

<Example 1>
(Preparation of latex for foam rubber (A-1))
100 parts of butyl rubber (product name "JSR BUTYL365", manufactured by JSR Corporation, Mooney viscosity (ML1 + 8, 125 ° C): 33, degree of unsaturation: 2.3 mol%) are mixed with 550 parts of cyclohexane, and the temperature is adjusted to 60 with stirring. By raising the temperature to ° C, the butyl rubber was dissolved to obtain a butyl rubber solution.
Separately, potassium oleate and water were mixed to obtain a 1.0% by weight aqueous solution of potassium oleate.

Then, the butyl rubber solution obtained above and the potassium oleate aqueous solution prepared above were mixed in a multiline mixer (product name “Multiline Mixer MS26-MMR-”) so that the weight ratio was 1: 1. 5.5L ", manufactured by Satake Chemical Machinery Co., Ltd., followed by mixing and emulsification at 15,000 rpm using an emulsifier (product name" Milder MDN310 ", manufactured by Taiheiyo Kiko Co., Ltd.). Thus, an emulsion was obtained.

Next, the obtained emulsion is heated to 75 ° C. under a reduced pressure of 700 to 800 hPa to distill cyclohexane, and then concentrated at 80 ° C. under a reduced pressure of 800 hPa, A latex for foam rubber (A-1) having a solid content of 60% by weight was obtained. Using the obtained latex for foam rubber (A-1), the swelling ratio with respect to liquid paraffin and the swelling ratio with respect to an ultraviolet absorbent were measured in accordance with the above-mentioned methods. Table 1 shows the results.

For the foam rubber latex (A-1) obtained in Example 1, the volume-based particle size distribution was measured using a laser diffraction particle size distribution analyzer (“SALD-7100” manufactured by Shimadzu Corporation). As a result of the measurement, the volume cumulative particle diameter d50 was 1,650 nm. Further, when the latex for foam rubber (A-1) obtained in Example 1 was stored at 20 ° C. for 10 days, floating separation did not occur and the storage stability was excellent. .

(Preparation of latex composition for foam rubber (B-1))
To 100 parts of the butyl rubber in the foam rubber latex (A-1) obtained above, a cross-linking aqueous dispersion (colloidal sulfur / dithiocarbamic acid-based cross-linking accelerator (zinc diethyldithiocarbamate (product name “NOCSELA EZ”)) was used. ), Ouchi Shinko Chemical Co., Ltd.) / Thiazole crosslinking accelerator (zinc salt of 2-mercaptobenzothiazole (product name "Noxeller MZ", Ouchi Shinko Chemical Co., Ltd.)) = 2/1/1 (weight) Ratio), 4 parts of solid content concentration: 4 parts, aqueous dispersion of zinc oxide (solid content concentration: 50% by weight), 3 parts, foam stabilizer (product name "Trimene base", manufactured by Crompton Corp., ethyl chloride / formaldehyde / ammonia) 1 part of a reaction product) and sufficiently dispersed to obtain a foam rubber latex composition (B-1). Using foam rubber latex composition (B-1), according to the method described above, it was measured foaming power and gelling. The results are shown in Table 1.

<Example 2>
(Preparation of latex for foam rubber (A-2))
A butyl rubber solution and a 1.0% by weight aqueous solution of potassium oleate were obtained in the same manner as in Example 1, and these were similarly mixed and emulsified to obtain an emulsion. Then, the obtained emulsion is heated to 75 ° C. under reduced pressure of 700 to 800 hPa to distill cyclohexane, and then centrifuged at 4,000 to 6,000 G using a centrifuge. As a result, a latex for foam rubber (A-2) having a solid content of 65% by weight was obtained as a light liquid by performing a concentration operation. Using the obtained foam rubber latex (A-2), the swelling ratio with respect to liquid paraffin and the swelling ratio with respect to an ultraviolet absorbent were measured in accordance with the above-mentioned methods. Table 1 shows the results.

For the foam rubber latex (A-2) obtained in Example 2, the volume-based particle size distribution was measured using a laser diffraction particle size distribution analyzer (“SALD-7100” manufactured by Shimadzu Corporation). Upon measurement, the volume cumulative particle diameter d50 was 1,580 nm. Further, when the latex for foam rubber (A-2) obtained in Example 2 was stored at 20 ° C. for 10 days, no flotation occurred and the storage stability was excellent. .

(Preparation of latex composition (B-2) for foam rubber)
A foam rubber latex composition (B-2) was prepared and measured in the same manner as in Example 1 except that the foam rubber latex (A-2) obtained above was used. . Table 1 shows the results.

<Comparative Example 1>
(Preparation of latex (A-3) for foam rubber)
100 parts of synthetic polyisoprene (product name "NIPOL IR2200L", manufactured by Zeon Corporation) are mixed with 1200 parts of cyclohexane, and the temperature is raised to 60 ° C with stirring to dissolve the synthetic polyisoprene and synthesize. A solution of polyisoprene was obtained.
Separately, 10 parts of sodium rosinate and 5 parts of sodium dodecylbenzenesulfonate are mixed with water, and a mixture of sodium rosinate / sodium dodecylbenzenesulfonate = 2/1 by weight is contained. A surfactant aqueous solution having a concentration of 1.5% by weight was prepared at a temperature of 60 ° C.

Then, the solution of the synthetic polyisoprene obtained above and the aqueous solution of the surfactant prepared above are mixed in a multi-line mixer (product name “Multi-line mixer”) so that the weight ratio is 1: 1.5. MS26-MMR-5.5L "(manufactured by Satake Chemical Machinery Co., Ltd.), followed by emulsification (product name" Milder MDN310 ", manufactured by Taiheiyo Kiko Co., Ltd.) at 15,000 rpm. An emulsion was obtained by mixing and emulsifying.

Then, the obtained emulsion is heated to 75 ° C. under reduced pressure of 700 to 800 hPa to distill cyclohexane, and then centrifuged at 4,000 to 6,000 G using a centrifuge. As a result, a latex for foam rubber (A-3) having a solid content of 62% by weight was obtained as a light liquid by performing a concentration operation. Using the obtained latex for foam rubber (A-3), the swelling ratio with respect to liquid paraffin and the swelling ratio with respect to an ultraviolet absorber were measured in accordance with the above-mentioned methods. Table 1 shows the results.

(Preparation of latex composition for foam rubber (B-3))
A latex composition for foam rubber (B-3) was prepared in the same manner as in Example 1, except that the latex for foam rubber (A-3) obtained above was used, and the measurement was carried out in the same manner. . Table 1 shows the results.

<Comparative Example 2>
(Preparation of latex for foam rubber (A-4))
In the same manner as in Example 2 except that potassium oleate as an anionic emulsifier was replaced with the same amount of polyoxyethylene lauryl ether (product name "Emulgen 120", manufactured by Kao Corporation) as a nonionic emulsifier A latex for foam rubber (A-4) having a solid content of 63% by weight was obtained. Using the obtained latex for foam rubber (A-4), the swelling ratio with respect to liquid paraffin and the swelling ratio with respect to an ultraviolet absorbent were measured in accordance with the above-mentioned methods. Table 1 shows the results.

(Preparation of latex composition for foam rubber (B-4))
A foam rubber latex composition (B-4) was prepared and measured in the same manner as in Example 1 except that the foam rubber latex (A-4) obtained above was used. . Table 1 shows the results.

<Comparative Example 3>
(Latex for foam rubber (A-5))
A styrene-butadiene copolymer latex (product name "Nipol LX4850A", manufactured by Zeon Corporation) was adjusted to a solid content concentration of 66% by weight, and this was used as a foam rubber latex (A-5). Then, using the latex for foam rubber (A-5), the swelling ratio with respect to liquid paraffin and the swelling ratio with respect to the ultraviolet absorbent were measured in accordance with the above-mentioned method. Table 1 shows the results.

(Preparation of latex composition for foam rubber (B-5))
A foam rubber latex composition (B-5) was prepared in the same manner as in Example 1 except that the foam rubber latex (A-5) was used, and the measurement was performed in the same manner. Table 1 shows the results.

<Comparative Example 4>
(Latex for foam rubber (A-6))
Latex of a nitrile group-containing conjugated diene copolymer (product name “Nipol LX531B”, manufactured by Zeon Corporation, solid content concentration: 66% by weight) was used as it was and used as foam rubber latex (A-6). Then, using the latex for foam rubber (A-6), the swelling ratio with respect to liquid paraffin and the swelling ratio with respect to the ultraviolet absorbent were measured in accordance with the above-mentioned method. Table 1 shows the results.

(Preparation of latex composition for foam rubber (B-6))
A foam rubber latex composition (B-6) was prepared in the same manner as in Example 1 except that the foam rubber latex (A-6) was used, and the measurement was performed in the same manner. Table 1 shows the results.

As shown in Table 1, according to the foam rubber latex containing butyl rubber, an anionic emulsifier, and water, both the swelling ratio with respect to liquid paraffin and the swelling ratio with respect to the ultraviolet absorber are low, and the oil resistance is excellent. Further, the foaming power was high and the gelling property was excellent (Examples 1 and 2).
On the other hand, when a rubber other than butyl rubber was used, the swelling ratio with respect to the ultraviolet absorber was high and the oil resistance was poor (Comparative Examples 1, 3, and 4).
In addition, even a foam rubber latex containing butyl rubber was inferior in foaming power and gelling property when a nonionic emulsifier was used instead of an anionic emulsifier (Comparative Example 2).

Claims (11)

1. A latex composition comprising a latex containing butyl rubber, an anionic emulsifier, water, and a sulfur-based crosslinking agent.
2. ラ テ ッ ク ス The latex composition according to claim 1, wherein the anionic emulsifier is a fatty acid salt having 6 to 30 carbon atoms.
3. 3. The latex composition according to claim 1, wherein the content of the butyl rubber is 50% by weight or more.
4. The latex composition according to any one of claims 1 to 3, wherein the butyl rubber has a Mooney viscosity (ML1 + 8, 125 ° C) of 20 to 70.
5. (5) The latex composition according to any one of (1) to (4), wherein the content of the sulfur-based crosslinking agent is 0.1 to 15 parts by weight based on 100 parts by weight of the butyl rubber.
6. The latex composition according to claim 5, further comprising a crosslinking accelerator.
7. 7. The latex composition according to claim 5, further comprising a foam stabilizer.
8. (8) A molded article obtained by using the latex composition according to any one of (1) to (7).
9. フ ォ ー ム Foam rubber obtained by using the latex composition according to any one of claims 1 to 7.
10. A method for producing a latex composition according to any one of claims 1 to 7,
    A step of obtaining an emulsion by mixing a butyl rubber solution in which butyl rubber is dissolved in a solvent with water in the presence of an anionic emulsifier,
    Removing the solvent from the emulsion to obtain a latex containing butyl rubber, an anionic emulsifier, and water;
    Adding a sulfur-based cross-linking agent to the latex.
11. The latex according to claim 10, wherein the solvent is at least one selected from the group consisting of hexane, isohexane, pentane, cyclohexane, heptane, isooctane, xylene, toluene, benzene, and carbon dioxide in a supercritical state. A method for producing the composition.