JP2005139300A - Foam rubber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a foam rubber exhibiting liquid-absorbing properties persisting for a long term and having solvent resistance and oil resistance. <P>SOLUTION: The foam comprises a hydrophilic rubber polymer. Preferably, the foam rubber comprises the hydrophilic rubber polymer bearing at least one group selected from the group consisting of hydroxy, carbonyl, amino, sulfonic acid and carboxy groups. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to foam rubber and a method for producing the same 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 a high resistance to oil that oozes with sweat on the skin surface Rubber is preferably used.

  Patent Document 1 discloses a latex foam capable of reducing a friction coefficient and improving oil resistance by mixing a synthetic latex rubber and a natural latex rubber and using them as a main raw material, and a method for producing the latex foam Is described.

  In Patent Document 2, a tactile sensation-improving substance such as a coefficient of friction is reduced or adhered only to the surface of the latex foam while maintaining excellent physical properties without using a means such as heating. Thus, a cosmetic puff having excellent physical properties respectively possessed by the latex foam and the tactile sensation improving material, and a method for producing the cosmetic puff are described.

  In Patent Document 3, interaction between the rubber component of the obtained latex foam and the silica powder is achieved by adding silica powder that satisfies the required conditions to latex rubber, which is the main raw material of latex foam. Thus, a latex foam capable of improving the structural mechanical strength without impairing the characteristics of the rubber such as flexibility and elongation rate, and a method for producing the latex foam are described.

  Patent Document 4 describes excellent physical properties of the latex foam by forcibly peeling and removing the skin layer while the latex foam has a predetermined viscosity, and exposing the foam layer to the surface of the obtained base material. In addition, a latex foam capable of exhibiting high air permeability and slipperiness, and a method for producing the latex foam are described.

  In Patent Document 5, a desired concavo-convex pattern is formed on the surface of a substrate made of latex foam, and the contact area is reduced, thereby adding design properties and the like while taking advantage of the excellent physical properties of the latex foam. A latex foam capable of exhibiting a typical action and a method for producing the latex foam are described.

  Since the rubber-based polymer in the above latex is hydrophobic, it is difficult for the foam rubber produced therefrom to absorb an aqueous liquid such as water. In order to impart liquid absorbency to such a foam rubber, (1) a surfactant is impregnated in a subsequent step after the foam is formed, and (2) a hydrophilic group on the surface of the pores of the foam with fluorine and ozone gas. The method of forming (4) making a hole in the foam surface, or (5) substituting with urethane foam has been adopted.

  However, in the above method (1), the cost is excessive and the surfactant flows out, so that the liquid absorbing property is not maintained and the surroundings are contaminated. In the method (2), since the formed hydrophilic group is chemically unstable, it is difficult to maintain the liquid absorbency for a long time, and it is preferable to avoid the use of gas from the viewpoint of health and safety. In the method (3), the cost is excessive. In the method (4), since the urethane resin is likely to be hydrolyzed, it is difficult to obtain a foam having sufficient oil resistance and solvent resistance.

Patent Document 6 discloses a method for producing a water-swellable polymer composition containing a carboxyl group or a group capable of forming a carboxyl group. A foam containing a rubber-based polymer containing such a carboxyl group is disclosed in Patent Document 6. It was not known.
JP 2003-192826 A JP 2003-192826 A JP 2003-192824 A JP 2003-176377 A JP 2003-175519 A JP-A-2-150460

  An object of the present invention is to provide a foam rubber having a liquid absorption property that lasts for a long period of time and has solvent resistance and oil resistance.

As a result of extensive research, the present inventor has added an appropriate amount of a bubble stabilizer to a hydrophilic rubber-based polymer such as a carboxyl-modified rubber, and when two or more types of rubber-based polymers are used, It has been found that a foam rubber containing a hydrophilic rubber polymer can be obtained by mixing two or more latexes containing a rubber polymer at an appropriate maximum shear rate, and the present invention has been completed.
That is, the present invention relates to a foam rubber containing a hydrophilic rubber-based polymer.

The present invention also provides:
(Production Method 1) A method for producing the foam rubber of the present invention from latex, wherein 2 to 10 parts by weight of a bubble stabilizer is added to 100 parts by weight of a rubber-based polymer in the latex;
(Manufacturing method 2) In the case of producing foam rubber from two or more kinds of latexes, the method comprises mixing these latexes at a maximum shear rate set in the range of 10 to 10,000 min ⁻¹ for 30 minutes or more. Production method 1; and (Production method 3) The production method 2 above, wherein the two or more types of latex comprise one or more types of hydrophilic rubber latex and one or more types of hydrophobic rubber latex.
Also related.

  Furthermore, this invention relates also to the foam rubber of this invention obtained by the method in any one of said manufacturing method 1-3.

The foam rubber obtained by the present invention has good water resistance, organic solvent resistance, acid resistance, alkali resistance and oil resistance.
In addition, the foam rubber of the present invention has good liquid absorbency with respect to water, alcohol, organic solvent, acidic aqueous solution, alkaline aqueous solution, oil and the like, and can maintain liquid absorbency for a long period of time.
Further, since the surfactant is not used for imparting liquid absorbency, the surfactant does not flow out and the surrounding environment is not contaminated.
Furthermore, since the foam rubber of the present invention does not require a post-process or a step of opening a hole at the time of manufacture, it can be easily manufactured and the manufacturing cost can be reduced.
In addition, unlike urethane resin, it is difficult to be hydrolyzed, so it can withstand long-term use.

Examples of the hydrophobic rubber-based polymer of the present invention include polymers containing at least one monomer unit such as ethylene, styrene, butadiene, acrylic acid ester, methacrylic acid ester, vinyl acetate, acrylamide, acrylamide derivatives, vinyl ether and vinyl pyrrolidone.
Examples of such a hydrophobic rubber-based polymer include natural rubber (NR); butadiene rubber (BR), acrylonitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), and isoprene rubber (IR). ), Synthetic rubbers such as acrylate-butadiene rubber, methyl methacrylate-butadiene rubber (MBR) and ethylene propylene diene rubber (EPDM) (these rubbers may be supplied in latex form); and styrene-butadiene-vinylpyridine And latex polymers, DPL (depolymerized latex), and polymers in chlorosulfonated polyethylene latex.
The hydrophobic rubber-based polymer is preferably natural rubber, isoprene rubber, acrylonitrile-butadiene rubber, styrene-butadiene rubber, chloroprene rubber and ethylene propylene diene rubber, and more preferably acrylonitrile-butadiene rubber and styrene-butadiene. It is rubber.
In the present invention, the hydrophobic rubber-based polymer may be used alone or in combination of two or more.

  Examples of the hydrophilic rubber polymer of the present invention include rubber polymers containing a hydrophilic group.

  Examples of the hydrophilic group include a hydroxyl group, a carbonyl group, an amino group, a sulfonic acid group, and a carboxyl group. Preferred are a carboxyl group and a hydroxyl group. The hydrophilic rubber-based polymer of the present invention can contain one or more of these hydrophilic groups.

Examples of the hydrophilic rubber-based polymer of the present invention include carboxy-modified styrene-butadiene rubber and carboxy-modified acrylonitrile-butadiene rubber. Carboxy-modified acrylonitrile-butadiene rubber is preferable.
In the present invention, the hydrophilic rubber-based polymer may be used alone or in combination of two or more.

The hydrophilic rubber-based polymer of the present invention can be obtained by polymerizing a monomer having a hydrophilic group or by introducing a hydrophilic group into the hydrophobic rubber-based polymer.
Examples of the monomer having a hydrophilic group include ethylenically unsaturated carboxylic acid.
These hydrophilic rubber-based polymers may be supplied in the form of latex.

  In the present invention, the rubber-based polymer includes both a hydrophobic rubber-based polymer and a hydrophilic rubber-based polymer unless otherwise specified.

The contact angle with respect to water at 25 ° C. of the hydrophilic rubber-based polymer of the present invention is preferably 70 ° or less, more preferably 50 ° or less, particularly preferably 30 ° or less, from the viewpoint of exhibiting good liquid absorbency. Preferably it is 20 degrees or less.
In the present invention, the contact angle can be determined by dropping water onto the surface of the hydrophilic rubber-based polymer test piece at 25 ° C. and using a conventional contact angle meter.
For example, a rubber polymer containing 0.5 to 10% by weight, particularly 0.5 to 5% by weight of ethylenically unsaturated carboxylic acid monomer with respect to the total amount of the rubber polymer can be mentioned.

  The foam rubber of the present invention can contain one or more hydrophobic rubber-based polymers in addition to the hydrophilic rubber-based polymer. Examples of such a hydrophobic rubber-based polymer include NR and synthetic rubber exemplified above. The foam rubber of the present invention can contain any amount of the hydrophobic rubber-based polymer, for example, 1 part by weight or more with respect to 100 parts by weight of the hydrophilic rubber-based polymer, as long as the effects of the present invention are not impaired. In order to exhibit a good liquid absorbency, it is preferable that the hydrophobic rubber-based polymer is contained in an amount of 10 parts by weight or less, particularly 5 parts by weight or less, particularly 3 parts by weight or less based on 100 parts by weight of the hydrophilic rubber-based polymer.

The foam rubber of the present invention may be manufactured according to a method including the following steps 1 to 3 using latex as a raw material, but the method of manufacturing the foam rubber of the present invention is not limited to this method.
In the present invention, latex containing a hydrophilic rubber polymer is referred to as hydrophilic rubber latex, and latex containing a hydrophobic rubber polymer is referred to as hydrophobic rubber latex.

(Process 1)
The mixed latex foam raw material is prepared by sufficiently mixing the required auxiliary raw material with the hydrophilic rubber latex.
Foam rubber containing two or more kinds of rubber-based polymers, for example, foam rubber containing two or more kinds of hydrophilic rubber-based polymers or foam rubber containing hydrophilic rubber-based polymers and hydrophobic rubber-based polymers, etc. In order to prevent unevenness in properties, it is preferable that the respective rubber-based polymers exist uniformly in the foam rubber. Therefore, prior to mixing the secondary raw material, two or more latexes containing these rubber-based polymer, respectively, 10～10000Min ^-1, preferably in the range of 100～10000Min ^-1, more preferably 3000～7000Min ^-1 It is desirable that the maximum shear rate is set to 30 minutes or more, preferably 40 minutes or more, more preferably 60 minutes or more. The means used for the mixing is not particularly limited as long as the maximum shear rate can be obtained, and examples thereof include a mixing tank equipped with a stirring blade, a homogenizer, or a homomixer. In order to easily adjust the foam density, a mixing tank equipped with stirring blades is suitable.
By this latex mixing step, a foam rubber containing two or more kinds of rubber polymers and having uniform properties in each part can be produced.
After the latex mixing process or during the mixing process, the necessary auxiliary materials are added and mixed thoroughly to prepare a mixed latex foam material for producing foam rubber containing two or more rubber polymers. To do.

Said shear rate (min < ^-1 >) is calculated | required from the following formula, when mixing 2 or more types of latex, for example in the mixing tank provided with the stirring blade.
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)

  Examples of the auxiliary material include a bubble stabilizer. In the present invention, the blending amount of the foam stabilizer with respect to 100 parts by weight of the rubber-based polymer in the mixed latex foam raw material is 2 parts by weight or more, preferably in order to increase the stability of the foam in the foam and facilitate foam formation. 3 parts by weight or more, more preferably 4 parts by weight or more, and 10 parts by weight or less, preferably 8 parts by weight or less, more preferably in order to reduce the cost of the bubble stabilizer or shorten the gel time. Is 7 parts by weight or less. By this step, a foam rubber containing a hydrophilic rubber-based polymer that could not be produced conventionally can be produced.

  As the above bubble stabilizer, for example, a reaction product obtained by reacting alkyl chloride such as ethyl chloride with formaldehyde and ammonia, for example, ethyl chloride formaldehyde ammonia reaction product; alkyl quaternary ammonium chloride; alkylaryl sulfonic acid Salt; and higher fatty acid ammonium, etc. are used, and the reaction product of alkyl chloride / formaldehyde / ammonia is preferred because of its excellent bubble stabilizing effect. The blending amount of the foam stabilizer is usually 0.1 to 10 parts by weight, preferably 2 to 6 parts by weight, per 100 parts by weight of the rubber-based polymer in the mixed latex foam raw material.

  In addition to the bubble stabilizer, for example, a crosslinking agent, a foaming agent, and an antiaging agent can be used as the auxiliary material.

  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. 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, and an alkylphenol-sulfide resin can be used. The blending amount of the crosslinking agent and the vulcanization accelerator varies depending on the type of rubber polymer, the crosslinking mechanism and the crosslinking agent. Preferably it is 0.1-10 weight part.

  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 mixed latex foam raw material.

  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-phenolic compounds such as 2,6-di-tert-butyl-4-methylphenol; bis-, tris and polyphenols. 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 mixed latex foam raw material.

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

Examples of the gelling agent include hexafluorosilicate such as sodium silicofluoride (SSF), potassium silicofluoride or calcium silicofluoride; or cyclohexylamine salt such as cyclohexylamine acetate or sulfamate. An aqueous solution 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 hexaflurosilicate, particularly sodium silicofluoride, is 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 be a closed cell or an open cell, and is not particularly limited, but is preferably an open cell from the viewpoint of enhancing liquid absorbency.

  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, parts by weight of the hydrophilic rubber latex and the hydrophobic rubber latex represent parts by weight of the rubber-based polymer contained in each latex.

Preparation of Examples 1 to 7 and Comparative Example 1 According to the formulation shown in Table 1, hydrophilic rubber latex (carboxy-modified acrylonitrile-butadiene rubber latex, trade name Nipol 550L, manufactured by Nippon Zeon Co., Ltd.) or it and hydrophobic rubber latex A mixture of (acrylonitrile-butadiene rubber latex, trade name Nipol 531, manufactured by Nippon Zeon Co., Ltd.) and a cross-linking agent-containing emulsion (40% sulfur and 10% dispersant (casein)) emulsified in 50% water. 1 part by weight, manufactured by Karuizawa Seisakusho Co., Ltd., 1.5 parts by weight of a vulcanization accelerator (zinc di-n-butyldithiocarbamate, trade name Noxeller BZ, manufactured by Ouchi Shinsei Chemical Co., Ltd.), a foaming agent ( Oleic acid potassium soap, FR14, manufactured by Kao Corporation) 2.5 parts by weight, foam stabilizer (ethyl chloride formaldehyde ammonia Product, trimene base, manufactured by Uniroyal Chemical Company) 2.5 parts by weight and anti-aging agent (2,6-di-tert-butyl-4-methylphenol, trade name Sumitizer BHT, manufactured by Sumitomo Corporation) 2 parts by weight were mixed to obtain a mixed latex foam raw material. To this, 3 parts by weight of a gelling agent (sodium silicofluoride, manufactured by Mitsui Chemicals, Inc.) and air were added for gelation. After molding by casting, heat treatment was performed at 140 ° C. for 40 hours, A test piece (100 × 100 × 1 mm) was prepared.

Preparation of Comparative Example 2 Glycerin oxypropylene adduct (polyoxypropylene triol having an average molecular weight of 3,000; washing with water to remove low molecular weight aldehydes and the like present as impurities, 100% by weight, water removed by heating for a period of time, 0.4 part by weight of N, N-dimethylaminohexanol, 0.1 part by weight of tin (II) octoate, 4 parts by weight of water and polydimethylsiloxane-polyoxy 1 part by weight of a propylene block copolymer was melted by heating, dehydrated and degassed while mixing to prepare a uniform polyol premix. This polyol premix and 52.5 parts by weight of a separately prepared toluene diisocyanate mixture (2,6-: 2,4- = 8: 2) are mixed, molded by casting, and then heated. And cured to produce a urethane foam test piece (100 × 100 × 1 mm).

About the test piece of each Example created above and a comparative example, it measured according to the method shown below, and the obtained result was shown in Table 1.
(1) Measurement of water absorption time: 0.5 ml of tap water was dropped on a test piece, and the time until completely absorbed was measured.
(2) Measurement of linear expansion coefficient: The test piece was immersed in tap water for 30 minutes. The length of the test piece before and after immersion was measured, and the linear expansion coefficient was determined from the following equation.
Linear expansion coefficient = (L ₁ −L ₀ ) / L ₀ × 100
(L ₁ : Length of test piece after immersion, L ₀ : Length of test piece before immersion)
(3) Evaluation of water resistance, acid resistance and alkali resistance: The test piece was immersed in water, 10% hydrochloric acid or 10% aqueous sodium hydroxide solution at 70 ° C. for 24 hours, and then taken out and dried naturally. The tensile strength of the test piece before and after immersion was measured according to JIS K6400, and the strength retention was determined from the following equation.
Strength retention = (I ₀ −I ₁ ) / I ₀ × 100
(I ₁ : Tensile strength of test specimen after immersion, I ₀ : Length of tensile strength before immersion)
And water resistance, acid resistance, and alkali resistance are "good" when the strength retention is 100 to 80, "good" when the strength retention is 80 to 60, and the strength retention is 60 or less. The case was evaluated as “impossible”.

For the test piece according to Example 1, the following measurements were also performed.
(1) Evaluation of organic solvent resistance, etc .: The strength retention and linear expansion coefficient were determined according to the method described above. The results are shown in Table 2.
(2) Measurement of water absorption amount: The test piece was submerged for 3 minutes, the weight of the test piece before and after submersion was measured, and the water absorption amount was determined from the following equation. The results are shown in Table 3.
Water absorption = (W ₁ −W ₀ ) / W ₀ × 100
(W ₁ : Weight of test piece after submersion, W ₀ : Volume of test piece before submersion)
(3) Measurement of physical property values: Physical property values were measured in accordance with JIS K6400. The results are shown in Table 3.

From Table 1, it was found that the test pieces of the examples exhibited good water absorption characteristics, and the water absorption effect tended to decrease as the content of the hydrophobic rubber polymer with respect to the hydrophilic rubber polymer increased.
Also, from Table 1 and Table 2, the test pieces of the examples have good water resistance, organic solvent resistance, acid resistance, alkali resistance and oil resistance against water, alcohol, organic solvent, acidic aqueous solution, alkaline aqueous solution and oil. It was also found to have sex.

The foam rubber of the present invention includes mattresses, Japanese and Western pillows, mattresses, cushions for chairs, seat cushions for vehicles such as trains, airplanes and automobiles, as well as carpet lining and door packing, as well as electronic equipment and household use. It can be used as a sealing material and cushioning material for electrical appliances. In particular, taking advantage of the liquid absorbency of the foam rubber of the present invention, it is also used for products for absorbing or holding liquids such as water, chemicals and oil, such as wiping materials, sponge scrubbing, water absorption rolls and water absorption mats. it can.

Claims (8)

  Foam rubber containing a hydrophilic rubber polymer.   The foam rubber according to claim 1, wherein the hydrophilic rubber-based polymer is a rubber-based polymer containing at least one group selected from the group consisting of hydroxyl group, carbonyl group, amino group, sulfonic acid group and carboxyl group.   The foam rubber according to claim 1, further comprising a hydrophobic rubber-based polymer.   The foam rubber according to claim 3, comprising 10 parts by weight or less of a hydrophobic rubber-based polymer with respect to 100 parts by weight of the hydrophilic rubber-based polymer.   A method for producing the foam rubber according to any one of claims 1 to 4, wherein 2 to 10 parts by weight of a cell stabilizer is added to 100 parts by weight of a rubber-based polymer in the latex. And how to. In the case of producing a foam rubber of two or more kinds of latex, characterized in that mixing at a maximum shear rate set these latex range 10~10,000min ^-1 30 minutes or more, according to claim 5, wherein the method of.   The method according to claim 6, wherein the two or more types of latex comprise one or more types of hydrophilic rubber latex and one or more types of hydrophobic rubber latex. A wiping material, a water absorption roll, and a water absorption mat including the foam rubber according to any one of claims 1 to 4.