JP5210332B2 - Foam rubber containing softener and method for producing the same - Google Patents

Description

  The present invention relates to a foam rubber containing a softener, and a production method and use thereof.

  As a material for members that come into direct contact with human skin, such as insoles of shoes, gloves or cosmetic puffs, it can provide a soft touch with excellent elasticity, and has high resistance to oil that oozes with sweat on the skin surface Foam rubber is preferably used. In particular, when used for a member that directly contacts the skin, a foam rubber that is highly flexible is preferable.

  In order to soften the foam rubber and give elasticity, there are two methods: (1) a method of reducing the density by increasing the cell ratio and (2) a method of blending a softener.

  However, the above method (1) is not suitable for practical use because it softens the foam rubber while decreasing the mechanical strength to facilitate breakage. In the method (2), the softening agent is added to the monomer during the production of the synthetic latex, directly added to the latex, or added after emulsification (Non-Patent Document 1). In such a softener addition method, the softener and the latex are easily separated, and it is difficult to obtain a foam rubber containing the softener. Further, since a pre-process such as pre-emulsification of the softening agent is required, the production cost increases, and the storage stability of the obtained foam rubber is low.

Emulsion / Latex Handbook Editorial Committee, “Emulsion / Latex Handbook”, first edition, Taiseisha Co., Ltd., March 25, 1975, 430-435 pages

  An object of this invention is to provide the foam rubber containing a softening agent, and the method of manufacturing it easily.

Conventionally, foam rubber is usually obtained by mixing latex and required auxiliary materials, adding a gelling agent and air to the resulting mixture to form a gel-like product in the form of bubbles, and then molding and crosslinking it. At this time, in order to avoid mixing air, the latex and the required auxiliary materials are mixed by a person using a stick slowly by hand, or at a maximum shear rate set to 9 min ⁻¹ or less. However, under such mixing conditions, even if the softening agent is added, it is not sufficiently mixed and separation occurs immediately, so it is difficult to obtain a foam rubber in which the softening agent is uniformly dispersed. there were.

  However, as a result of extensive research, the present inventor has added a cell stabilizer known to adopt specific mixing conditions and to increase the stability of the bubbles in the foam rubber to facilitate the formation of bubbles. As a result, it was found that a foam rubber in which the softener was uniformly dispersed could be easily obtained, and the present invention was completed.

That is, this invention relates to the foam rubber containing a rubber-type polymer and a softening agent, and its use.
The present invention also relates to a method for producing foam rubber from latex, in which latex, softener and bubble stabilizer are mixed for 30 minutes or more at a maximum shear rate set in the range of 10 to 10,000 min ^−1. The present invention also relates to a method including a step of causing
Furthermore, the present invention also relates to a foam rubber obtained by this production method.
In the present invention, the foam rubber refers to a foam produced from latex.

According to the present invention, when producing a foam rubber from a latex as a raw material, it is added to a monomer during the production of a synthetic latex, a softener is added in advance to the raw material latex, or emulsified with another solvent, etc. This pre-process is not necessary, and the softening agent can be mixed with the latex and required auxiliary materials, so that the manufacturing cost can be reduced. Further, according to the present invention, the foam rubber can be easily taken out from the mold after being molded.
Furthermore, according to the present invention, the foam rubber can be softened and given elasticity without increasing the bubble rate, and therefore, a flexible and excellent foam rubber can be obtained. .
In addition, according to the present invention, it is possible to obtain a foam rubber having a moisturizing effect and having high safety for a living body.

As the rubber polymer of the present invention, ethylene, propylene, styrene, butadiene, isoprene, chloroprene, acrylic acid ester, methacrylic acid ester, acrylonitrile, vinyl acetate, acrylamide, acrylamide derivatives, vinyl ether, vinyl pyrrolidone and the like are used as monomer units. The polymer containing above is mentioned.
Examples of the rubber polymer include natural rubber (NR); butadiene rubber (BR), acrylonitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), isoprene rubber (IR), and acrylate. -Synthetic rubbers such as butadiene rubber, methyl methacrylate-butadiene rubber (MBR) or ethylene propylene diene rubber (EPDM); or modified rubber-based polymers such as carboxy-modified styrene-butadiene rubber or carboxy-modified acrylonitrile-butadiene rubber. Also included are polymers in styrene-butadiene-vinylpyridine latex, DPL (depolymerization latex) or chlorosulfonated polyethylene latex.
Preferred examples of the rubber-based polymer include natural rubber, isoprene rubber, acrylonitrile-butadiene rubber, styrene-butadiene rubber, chloroprene rubber, ethylene propylene diene rubber, or carboxy-modified acrylonitrile-butadiene rubber, and more preferably acrylonitrile- Butadiene rubber, styrene-butadiene rubber or carboxy-modified acrylonitrile-butadiene rubber.
The foam rubber of the present invention can contain one or more of these rubber polymers.

The softener of the present invention is a component that imparts moderate flexibility to the foam rubber of the present invention. Examples of the softener include hydrocarbon process oils such as paraffin 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, coconut oil, olive oil, corn oil and other vegetable and animal oils, and biogenic fatty acid esters 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 allyl, butyl phthalyl butyl glycolate, di-n-butyl sebacate, di (2-ethylhexyl) sebacate, triethylene glycol di (2-ethyl hexoate), acetyl tri-n-butyl citrate And plasticizers thereof, as well as mixtures thereof.
In the present invention, the paraffinic process oil is a process oil containing 50% by weight or more of paraffinic hydrocarbons based on the total carbon content, and the naphthenic process oil is the total carbon content of the naphthenic hydrocarbon. The process oil containing 30 to 45% by weight, and the aromatic process oil refers to a process oil containing 35% by weight or more of the aromatic hydrocarbon carbon based on the total amount of carbon.
In hydrocarbon oils, paraffinic process oils and liquid paraffin are preferred in order to suppress yellowing of foam rubber and increase safety to the human body, and the content of paraffinic hydrocarbons relative to the total carbon content is high. For example, paraffinic process oil containing 70% by weight or more of paraffinic hydrocarbons with respect to the total amount of carbon and 30% by weight or less of naphthenic hydrocarbons as the balance is more preferable, and liquid paraffin is particularly preferable.
As a preferable softener in the present invention, castor oil, safflower oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, fallen raw oil, palm oil, palm oil, olive oil, corn oil, etc. Vegetable oils and animal oils are particularly preferred, and vegetable oils such as falling raw oil, corn oil, olive oil, soybean oil, safflower oil and cottonseed oil are particularly preferred.
Moreover, the foam rubber of this invention can contain 1 or more types of these softening agents.

  The content of the softening agent with respect to 100 parts by weight of the rubber-based polymer in the foam rubber is not particularly limited as long as the effects of the present invention are not impaired, but preferably gives an appropriate flexibility and excellent elongation to the foam rubber. 5 parts by weight or more, more preferably 0.7 parts by weight or more, particularly preferably 1.0 parts by weight or more, preferably 30 parts by weight in order to prevent the softener from bleeding from the foam rubber and contaminating the surroundings. Below, more preferably 20 parts by weight or less, particularly preferably 10 parts by weight or less.

  In the present invention, an embodiment for producing a foam rubber containing the softener of the present invention using latex as a raw material is shown below, but the method for producing the foam rubber of the present invention is not limited to this embodiment.

(Process 1)
First, a latex, a softening agent, and a bubble stabilizer are mixed to prepare a mixed latex foam raw material.

  In the present invention, latex refers to a material in which the rubber polymer is stably dispersed in an aqueous medium.

Examples of the bubble stabilizer of the present invention include an alkyl chloride / formaldehyde / ammonia reaction product obtained by reacting an alkyl chloride such as ethyl chloride with formaldehyde and ammonia. The number of carbon atoms in the alkyl of this reaction product is preferably 4 or less. Examples of such reaction products include ethyl chloride / formaldehyde / ammonia reaction products. In addition, alkyl quaternary ammonium chloride, preferably alkyl quaternary ammonium chloride having 4 or less carbon atoms; alkyl aryl sulfonate, preferably alkyl aryl sulfonate having 4 or less carbon atoms; Also, higher fatty acid ammonium, preferably higher fatty acid ammonium having alkyl having 4 or less carbon atoms, can be used as the bubble stabilizer of the present invention.
In order to uniformly disperse the softener as the bubble stabilizer of the present invention, an alkyl chloride / formaldehyde / ammonia reaction product, particularly an alkyl chloride / formaldehyde / ammonia reaction product having an alkyl carbon number of 4 or less, Ethyl chloride / formaldehyde / ammonia reaction products are preferred.

  In the present invention, the amount of the foam stabilizer added to 100 parts by weight of the rubber-based polymer in the latex is 2 parts by weight or more, preferably 3 parts by weight or more, more preferably in order to disperse the softener uniformly in the foam rubber. 3.5 parts by weight or more, and 8 parts by weight or less, preferably 7 parts by weight or less, more preferably 5 parts by weight or less in order to reduce the cost of the bubble stabilizer or shorten the gelation time. is there.

Latex, softeners and foam stabilizers set, in order to uniformly disperse the softening agent in a foam rubber, 10～10000Min ^-1, preferably in the range of 100～10000Min ^-1, more preferably 3000～7000Min ^-1 It is desirable to mix at a maximum shear rate of 30 minutes or more, preferably 40 minutes or more, more preferably 60 minutes or more.
The means used for this mixing is not particularly limited as long as the above maximum shear rate can be obtained, and examples include a mixing tank equipped with a stirring blade, a homogenizer, or a homomixer. In order to facilitate the adjustment of the bubble ratio at, a mixing tank equipped with stirring blades is suitable.

In the present invention, the shear rate (min ⁻¹ ) is obtained from the following equation, for example, when mixing in a mixing tank equipped with stirring blades.
Shear rate = (P × circumference × S) / V
P: Stirring blade diameter (mm), S: Number of rotations of stirring blade per minute, V: Distance of the narrowest part in the clearance (clearance) between the stirring blade and the wall of the mixing tank (mm)

In addition, when manufacturing the foam rubber containing 2 or more types of latex, it is preferable that each rubber-type polymer exists uniformly in this foam rubber. For this reason, before mixing the latex, the softening agent, and the cell stabilizer, it is desirable to mix two or more types of latex under the same conditions as the mixture of the latex, the softening agent, and the cell stabilizer described above. .
By this latex mixing step, a foam rubber containing two or more kinds of rubber-based polymers and having uniform properties in each part can be produced.
When two or more types of latex are used, after the mixing step of the two or more types of latex, or during the mixing step, a softener and a bubble stabilizer are added and mixed under the same mixing conditions as described above. A mixed latex foam raw material for producing foam rubber containing a softener may be prepared.

  In the present invention, the latex, the softening agent, and the bubble stabilizer may be mixed together with required auxiliary materials. As such an auxiliary material, for example, a crosslinking agent, a foaming agent, an antiaging agent and the like can be used.

  As the cross-linking agent, sulfur, an organic peroxide, a phenol compound, or the like is used depending on the type of rubber polymer and the cross-linking reaction mechanism. In the case of crosslinking with sulfur, in addition to colloidal sulfur and fine powder sulfur; sulfur compounds such as sulfur dichloride and dipentamethylene thiuram tetrasulfide can be used. Further, a vulcanization accelerator such as 2-mercaptobenzothiazole may be used in combination. For crosslinking with organic peroxides, 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-buto Organic peroxides such as peroxy carbonate such as Shiperuokishi 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. You may use for the compounding. In the case of crosslinking with a phenol compound, an alkylphenol-formaldehyde resin, a sulfurized p-tert-butylphenol resin, and an alkylphenol-sulfide resin can be used. The addition amount of the crosslinking agent and vulcanization accelerator varies depending on the type of rubber polymer, the crosslinking mechanism and the crosslinking agent, but is usually 0.02 to 20 parts by weight, preferably 0, per 100 parts by weight of the rubber polymer in the latex. .1 to 10 parts by weight.

  Examples of the foaming agent include sodium laurate, sodium myristate, sodium stearate, ammonium stearate, sodium oleate, potassium oleate, castor oil potassium soap, and palm oil potassium soap; fatty lauroyl sarcosine sodium; Sarcosine salts such as sodium myristoyl 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, sodium dodecylbenzene sulfonate , Sulfonates such as sodium α-olefin sulfonate; stearyldimethylammonium chloride, benzalkonium chloride And cationic surfactants such as are exemplified. The blending amount of the foaming agent is usually 1 to 10 parts by weight, preferably 2 to 8 parts by weight per 100 parts by weight of the rubber-based polymer in the latex.

  Examples of the anti-aging agent include diphenylamine compounds such as N-phenyl-N ′-(p-toluenesulfonyl) -p-phenylenediamine; condensates of aromatic amines and aliphatic ketones; 2-mercaptobenzimidazole and its Illustrative are imidazole compounds such as zinc salts; mono-phenols such as 2,6-di-t-butyl-4-methylphenol; bis-, tris, polyphenols and the like. The blending amount of the antioxidant is preferably 1 to 10 parts by weight, more preferably 2 to 6 parts by weight, per 100 parts by weight of the rubber-based polymer in the latex.

(Process 2)
For example, according to the Dunlop method or the like, required air and a gelling agent are added to the mixed latex foam raw material prepared in Step 1, and the mixture is sufficiently mixed to form bubbles and gelled to obtain a gel-like product.

Examples of the gelling agent include hexafluorosilicates such as sodium silicofluoride (SSF), potassium silicofluoride or calcium silicofluoride; or cyclohexylamine salts such as cyclohexylamine acetate or sulfamate. The liquid material in a state is used, and the amount thereof is preferably about 1 to 10 parts by weight with respect to 100 parts by weight of the rubber-based polymer in the mixed latex foam raw material. As the gelling agent, the above hexafluorosilicate, particularly sodium silicofluoride is particularly preferably used because the reaction control such as the gelation start time is easy.
Alternatively, a heat-sensitive agent such as zinc ammonium complex salt, 2-mercaptobenzimidazole zinc salt, polypropylene glycol or polymethyl vinyl ether is added in an amount of 1 to 10 parts by weight based on 100 parts by weight of the rubber-based polymer in the mixed latex foam raw material. The latex can be coagulated by heating to 40 to 100 ° C.

(Process 3)
The gel-like material is processed into a desired shape by a method such as casting, casting or extrusion, and then heated to 50 to 200 ° C. according to the type of the crosslinking agent to sufficiently advance the crosslinking reaction. Then, processing can be appropriately performed to obtain a foam rubber having a desired shape. The heating method here is not particularly limited as long as the gelling raw material can be crosslinked.

The foam rubber of the present invention may have closed cells, open cells or both, and is not particularly limited. However, when it is desired to improve the liquid absorbability of the obtained foam rubber, it is preferable to have open cells. .
That is, when the foam rubber of the present invention has only closed cells, the water absorption rate is usually less than 5%, but when it has open cells or both closed cells and open cells, the water absorption rate is usually 5% or more. The water absorption of the foam rubber of the present invention is preferably 5% or more, more preferably 10% or more, particularly preferably 50% or more, particularly preferably 100% or more, and most preferably 300% or more. The water absorption rate is measured according to ASTM D1056.

  Hereinafter, the present invention will be described in more detail by way of examples. The present invention is not limited by the examples. In the following examples, unless otherwise specified, the weight part of the latex represents the weight part of the rubber-based polymer contained in the latex.

Examples 1-3 and Comparative Examples 1-2
100 parts by weight of latex (acrylonitrile-butadiene rubber latex, trade name: Nipol 531, manufactured by Nippon Zeon Co., Ltd.), cotton seed oil (manufactured by Kanto Chemical Co., Inc.) in the blending amounts shown in Table 1, and bubble stabilizer (ethyl chloride / formaldehyde / ammonia reaction) Product, trade name: Trimenbase, manufactured by Uniroyal Chemical Company, 2.5 parts by weight, cross-linking agent-containing emulsion (40% sulfur and 10% dispersant (casein) emulsified in 50% water, Inc. 1 part by weight of Karuizawa Smelter), 1.5 parts by weight of vulcanization accelerator (zinc di-n-butyldithiocarbamate, trade name Noxeller BZ, manufactured by Ouchi Shinsei Chemical Co., Ltd.), foaming agent (potassium oleate) Soap, trade name FR14, manufactured by Kao Corporation) 2.5 parts by weight and anti-aging agent (2,6-di-t-butyl-4-methylphenol) Lumpur, trade name Sumilizer BHT, and Sumitomo Chemical Industries, Ltd.) 2 parts by weight, in a mixing tank equipped with a stirring blade, and mixed for 40 minutes at maximum shear speed set in 4500Min ^-1, mixed latex foam The raw material was obtained. To this, 3 parts by weight of a gelling agent (sodium silicofluoride, manufactured by Mitsui Chemicals, Inc.) and the amount of air shown in Table 1 were added for gelation, followed by heat treatment at 140 ° C. for 40 hours after molding by casting. A foam rubber test piece (100 × 100 × 1 mm) was prepared.

Comparative Example 3
The maximum shear rate instead of mixing is set to 4500min ^-1, except that a mixture is set to 9min ^-1, it was tried to prepare a test piece of foam rubber in the same manner as in Example 1 above.

Comparative Example 4
After 100 parts by weight of cottonseed oil and 5 parts by weight of oleic acid were mixed using a colloid mill by high speed stirring (8000 min ⁻¹ , 6 hours), this mixture was mixed in 5% by weight of aqueous ammonia at high speed (10000 min). ^-1 for 30 minutes). Stirring was further continued for 6 hours, and then allowed to stand at room temperature for 24 hours to confirm storage stability, and a softener emulsion was prepared. A foam rubber test piece was tried in the same manner as in Comparative Example 3 except that this softener emulsion was added in an amount corresponding to 4 parts by weight of cottonseed oil instead of cottonseed oil.

About the test piece of Examples 1-3 produced above and Comparative Examples 1-2, it measured according to the method shown below, and the obtained result was shown in Table 1.
(1) Measurement of density: According to JIS K6400, the apparent density was measured at room temperature.
(2) Measurement of tensile strength and elongation: According to JIS K6400, a test piece was punched into a No. 1 type dumbbell shape and measured.
(3) Measurement of hardness: Measured using an Asker hardness meter F type (manufactured by Kobunshi Keiki Co., Ltd.).

In Table 1, when Examples 1 to 3 and Comparative Example 1 are compared, the foam rubber containing the softening agent has the same mechanical strength and flexibility as compared with the foam rubber containing no softening agent even if the density is the same. Was found to be excellent.
Further, from Comparative Example 2, it was found that the foam rubber having a reduced density had a low mechanical strength but was difficult to stretch although it was soft.
In Comparative Examples 3 and 4, the test piece could not be prepared because the softener was separated during the mixing process of the latex, the softener and the bubble stabilizer.

  Since the foam rubber of the present invention is excellent in flexibility and elasticity, it can be used for cosmetic puffs directly applied to the skin, sheets to be applied to the face, mascara and the like. In addition, the foam rubber of the present invention includes mattresses, Japanese / 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 foam rubber of the present invention can also be used for wiping materials, sponge scrubs, water absorption rolls, water absorption mats, and the like.

Claims (2)

A method for producing foam rubber from latex,
(Step 1) a latex containing 100 parts by weight of a rubber-based polymer;
0.5-30 parts by weight of a softener that is vegetable or animal oil;
2 to 8 parts by weight of a bubble stabilizer;
1 to 10 parts by weight of a foaming agent is mixed at a maximum shear rate set in a range of 3000 to 7000 min ⁻¹ to obtain a mixed latex foam raw material,
(Step 2) Air and 1-10 parts by weight of a gelling agent are added to and mixed with the mixed latex foam raw material to obtain a gel-like product,
(Step 3) A method for producing a foam rubber, wherein the gel-like product is molded and then heated to cause a crosslinking reaction to proceed. The manufacturing method of the foam rubber of Claim 1 whose mixing time in the process 1 is 30 minutes or more.