JP2005139281A - Rubber foam, composition for forming the same and manufacturing method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber foam having a large and homogeneous cell size, a composition suitable for manufacturing the same and a manufacturing method of the rubber foam. <P>SOLUTION: The composition for forming the rubber foam comprises (A) a latex comprising a polymer comprising an uncrosslinked or partially crosslinked natural or synthetic rubber, a crosslinking agent and a foaming agent dispersed in water, (B) a foam stabilizer, and (C) a polyorganosiloxane. The manufacturing method of the rubber foam comprises foaming and curing the composition. The rubber foam has an excellently homogeneous cell size of at least 400 μm on average. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rubber foam obtained from latex, and also relates to a composition suitable for its formation and a production method. More specifically, the present invention relates to the rubber foam having a large cell diameter and a uniform cell diameter, a composition suitable for formation thereof, and a production method.

  A rubber polymer foam is prepared by emulsion polymerization, or is collected as a rubber sap, or obtained by a method such as concentrating them. Then, it is manufactured by foaming and curing (Non-patent Document 1). By such a method, a foam having a small cell diameter can be obtained as a homogeneous and good foam, but if the cell diameter is 400 μm or more, the cell diameter becomes non-uniform and rubber having uniform bubbles is obtained. It was difficult to obtain a porous foam.

As a solution to this problem, the following method is used.
(I) a method of mixing a large amount of gas, for example, air, nitrogen, etc. during foaming;
(Ii) a method of adding a foam breaker such as polyalkylene glycol; and (iii) a method of increasing the curing time by lowering the blending amount of a coagulant such as sodium fluorosilicate or lowering the curing temperature. .

However, in the method (i), the density of the obtained foam is lowered, and the required strength cannot be obtained. With the method (ii), a foam having a sufficiently uniform cell diameter cannot be obtained. In the method (iii), the production cycle becomes longer, the efficiency is lowered, and a foam having a sufficiently uniform cell diameter cannot be obtained. Therefore, a method for producing a foam having a cell diameter of 400 μm or more and a sufficiently uniform cell diameter has not been found.
Emulsion Latex Handbook (Hideo Sasaki, Taiseisha, published in 1975)

  In view of the above problems, an object of the present invention is to provide a rubber foam having a large cell diameter and a homogeneity, a composition suitable for the production thereof, and a method for producing the rubber foam.

  As a result of repeated research to achieve the above-mentioned problems, the present inventor has formulated a specific amount of a bubble stabilizer into the raw material latex and blended polyorganosiloxane to foam and cure the problem. The inventors have found that this can be achieved and have completed the present invention.

That is, the present invention
(A) Latex in which a polymer which is an uncrosslinked or partially crosslinked natural or synthetic rubber, a crosslinking agent and a foaming agent are dispersed in water An amount of 100 parts by weight of the polymer in the latex;
(B) a foam stabilizer 0.1 to 10 parts by weight; and (C) a composition for forming a rubbery foam, comprising 0.5 to 10 times the amount of polyorganosiloxane (B); (A) A method for producing a rubber foam in which a polymer, a crosslinker and a foaming agent, which are uncrosslinked or partially cross-linked natural or synthetic rubber, foam and cure a latex in which water is dispersed, ) 0.1 to 10 parts by weight of (B) cell stabilizer and 100 parts by weight of polymer in the latex, and (C) polyorganosiloxane is 0.5 to 10 parts by weight of (B). The present invention relates to a method for producing a rubber foam, comprising foaming and curing a composition for forming a rubber foam obtained by blending a double amount.

  Further, the present invention provides a rubbery material obtained from the above latex, having an average cell diameter of 400 μm or more; and a distribution in which the cell diameter is contained in the range of 50 to 150% of the average cell diameter. Relates to foam.

  According to the present invention, a large-diameter cell, in particular, a rubber foam having a cell diameter of 400 μm or more and having open cells having homogeneity satisfying the cell diameter can be stably obtained. The method of the present invention is particularly suitable for the production of a large pore diameter foam having a cell diameter of 400 μm or more, which cannot obtain a uniform cell diameter by other methods.

  The latex (A) used in the present invention is a latex in which an uncrosslinked or partially crosslinked polymer of natural or synthetic rubber is dispersed in water together with a crosslinking agent and a foaming agent. When the polymer is natural rubber, a rubber sap, a concentrated product thereof, and a compound containing a preservative are used. When the polymer is a synthetic rubber, it is generally prepared by emulsion polymerization. Alternatively, a polymer obtained by a method such as solution polymerization can be prepared by emulsifying with a surfactant and water and removing the solvent if necessary. As the raw material of the foam, a latex having a polymer content of 55 to 70% by weight and a stable foam can be usually formed, and therefore preferably 60 to 68% by weight of latex is used. The latex may contain a surfactant such as a fatty acid alkali metal salt, an alkyl sulfonic acid alkali metal salt, or an alkyl benzene sulfonic acid alkali metal salt, which is used for emulsion polymerization or used for emulsification of the polymer.

  Examples of polymers include natural rubber; synthetic rubbers such as IR, BR, SBR, carboxyl-modified SBR, NBR, carboxyl-modified NBR, EPM, EPDM, CR, and copolymers thereof, and mixtures thereof. NBR is preferred for applications that require safety.

  As the crosslinking agent, sulfur, an organic peroxide, a phenol compound, or the like is used depending on the type of polymer and the crosslinking reaction mechanism. In the case of crosslinking with sulfur, colloidal sulfur, 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. In the case of 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, Alkyl peroxides such as 5-dimethyl-2,5-bis (t-butoxyperoxy) hexane; peroxyesters such as t-butoxyperoxy-3,3,5-trimethylcyclohexanoate, t-butoxyperoxybenzoate; Peroxyketals such as 1,1-bis (t-butoxyperoxy) cyclohexane, 1,1-bis (t-butoxyperoxy) -3,3,5-trimethylcyclohexa; t-butoxyperoxyisopropyl carbonate Organic peroxides such as t- butoxy peroxycarbonate such as peroxy-2-ethylhexyl carbonate can be used. Organic peroxides may be blended as they are, adsorbed onto inorganic powders such as molecular sieves, dissolved in hydrocarbons and plasticizers, and mixed with inert liquids such as polydimethylsiloxane. The stabilized product may be used for blending. In the case of crosslinking with a phenol compound, an alkylphenol formaldehyde resin can be used. The amount of the crosslinking agent is usually 0.02 to 20 parts by weight, preferably 0.1 to 10 parts by weight per 100 parts by weight of the polymer, although it varies depending on the type of polymer, the crosslinking mechanism and the crosslinking agent.

  As foaming agents, fatty acid salts such as sodium laurate, sodium myristate, sodium stearate, ammonium stearate, sodium oleate, potassium oleate, castor oil potassium soap, palm oil potassium soap; lauroyl sarcosine sodium, myristoyl Sarcosine salts such as sodium sarcosine, sodium oleyl sarcosine, sodium cocoyl sarcosine; sulfates such as sodium palm oil alcohol sulfate, sodium polyoxyethylene lauryl ether sulfate; sodium dioctyl sulfosuccinate, sodium lauryl sulfoacetate, dodecylbenzene sulfonic acid Sodium, sulfonates such as sodium α-olefin sulfonate; stearyldimethylammonium chloride, benzalkoni chloride Such as cationic surfactants, such as beam are exemplified. The blending amount of the foaming agent is usually 1.0 to 10 parts by weight, preferably 1.5 to 6.0 parts by weight per 100 parts by weight of the polymer.

  Examples of the (B) foam stabilizer used in the present invention include reaction products obtained by reacting alkyl chloride such as ethyl chloride with formaldehyde and ammonia; alkyl quaternary ammonium chlorides; and alkylaryl sulfonates. Is used, and the reaction product of alkyl chloride, formaldehyde, and 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 0.2 to 6.0 parts by weight per 100 parts by weight of the polymer in the component (A).

  The (C) polyorganosiloxane used in the present invention is a characteristic component blended in the production method of the present invention. The polyorganosiloxane is preferably an oily substance, i.e., silicone oil, in addition to the usual types of silicone oils such as polydimethylsiloxane and polymethylphenylsiloxane; polysiloxane with polyoxyethylene chain, polyoxypropylene chain, or oxyethylene・ Polysiloxane grafted with oxypropylene copolymer chain ・ Polyether graft copolymer; Long chain alkyl with 6 or more carbon atoms, such as hexyl, octyl, decyl, dodecyl, in which part of methyl group bonded to silicon atom And a polyorganosiloxane having an aralkyl group such as 2-phenylethyl and 2-phenylpropyl, and having a long-chain alkyl group having 6 or more carbon atoms and / or an aralkyl group bonded to a silicon atom. Hexane is by a suitable foam breaking effect, particularly preferable because homogeneous foam is obtained. The polyorganosiloxane may be blended as it is, or may be blended in the form of an oil-in-water emulsion with a surfactant. In order to obtain a foam having a uniform pore size, the blending amount of such an oil that is not compatible with water is 0.5 to 10 times the weight of the above (B) cell stabilizer, The amount is preferably 1.0 to 7.5 times. When this ratio is less than 0.5 times, a foam having a cell diameter of 300 μm or more cannot be obtained. Moreover, when it exceeds 10 times, it will bubble-break and a foam cannot be obtained. Furthermore, the amount of the component (C) is preferably 0.1 to 5.0 parts by weight per 100 parts by weight of the polymer in the component (A).

  The composition of the present invention is a rubber foam-forming composition containing the above components (A), (B) and (C) as essential components. However, the blending order of the component (B) and the component (C) is arbitrary, and the polymer, which is an uncrosslinked or partially crosslinked natural or synthetic rubber, which is the basic composition of the component (A), is dispersed in water. A composition may be prepared by blending the component (B) and the component (C) after blending other components, for example, a crosslinking agent and a foaming agent, with the basic latex, and the crosslinking agent and / or the foaming agent. (B) component and / or (C) component may be blended before, during or simultaneously with blending.

  An antiaging agent can be further blended with the composition of the present invention. Anti-aging agents include diphenylamine compounds such as N-phenyl-N ′-(p-toluenesulfonyl) -p-phenylenediamine; condensates of aromatic amines and aliphatic ketones; 2-mercaptobenzimidazole and its zinc Examples include imidazole compounds such as salts; monophenol compounds and the like. The blending amount of the antioxidant is preferably 1 to 10 parts by weight, more preferably 2.0 to 6.0 parts by weight per 100 parts by weight of the polymer in the component (A).

  In the composition of the present invention, if necessary, a dispersing agent such as polyvinyl alcohol, sodium polyacrylate, methylcellulose, sodium carboxymethylcellulose, casein, sodium polyphosphate; a stabilizer such as a chelating agent; guar gum, xanthan gum A thickener such as: a coloring agent can be blended.

  Added to the composition of the present invention is a gelling agent such as hexafluorosilicate such as sodium silicofluoride, potassium silicofluoride, calcium silicofluoride; or cyclohexylamine salt such as cyclohexylamine acetate or sulfamate. Or a heat-sensitive agent such as zinc ammonium complex salt, 2-mercaptobenzimidazole zinc salt, polypropylene glycol, polymethyl vinyl ether and heating to 40-100 ° C. to coagulate the latex. be able to.

  For example, foaming and gelation can be achieved by adding the above-mentioned gelling agent and mixing air into the composition of the present invention prepared by blending each necessary component using a mixing means such as a stirring and mixing tank. To form a foamed gel. The amount of the gelling agent is preferably 1 to 10 parts by weight with respect to 100 parts by weight of the polymer in the composition. Next, a rubber foam is produced by processing into a desired shape by a method such as casting, casting, extrusion molding, etc., and heating to 50 to 200 ° C. according to the type of the crosslinking agent to cause crosslinking. Can do.

  The average cell diameter of the foam can be controlled by changing the type and weight ratio of the bubble stabilizer and polyorganosiloxane. The foam thus obtained has open cells with an average cell diameter of 300 to 2,000 μm, preferably 400 to 1,500 μm. The cell diameter is homogeneous so as to show a distribution in which 50% or more, preferably 60% or more of the formed cells are included in the range of 50 to 150% of the average cell diameter.

  Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited by these examples. In the following examples, unless otherwise specified, parts are parts by weight, and% of the composition represents% by weight.

The following raw materials were used in Examples and Comparative Examples.
A-1: NBR latex obtained by emulsion polymerization by a conventional method using sodium dodecylbenzenesulfonate as an emulsifier, 37.5% by weight of acrylonitrile units in the polymer, and a polymer content of 64.1%;
B-1: Ethyl chloride, formaldehyde, ammonia reaction product;
C-1: Methyl, decyl, 2-phenylpropyl group-containing linear polysiloxane, viscosity at 23 ° C., 1,600 mm ² / s;
C-2: methylpolysiloxane-polyoxyethylene graft copolymer, viscosity 180 mm ² / s at 23 ° C .;
C-3: polydimethylsiloxane, viscosity 200 mm ² / s at 23 ° C .;
D-1: Crosslinker-containing emulsion obtained by emulsifying 10% sulfur, 15% 2-mercaptobenzothiazole, 20% 2-mercaptobenzimidazole and 5% casein in 50% water.

The average cell diameter and the homogeneity of the foam were measured as follows.
(1) Apparent density, tensile strength, elongation: Measured using JIS K6400 (No. 1 type).
(2) Average cell diameter of foam: The pore diameter of cells existing in the range of 20 mm in diameter at the center of the surface was observed with an optical micrograph to determine the average value.
(3) Cell diameter homogeneity: The ratio of the pore diameter within 50 to 150% of the average value was determined out of all the cells on the foam surface existing in the above range.

Examples 1-4
In ion-exchanged water, C-1 and two polyoxyethylene nonylphenyl ethers (mixed HLB: 10.8) having different degrees of polymerization of polyoxyethylene chains as an emulsifier were blended and premixed, and then pressurized. An oil-in-water emulsion C-1e containing 54% C-1, 3% emulsifier and 43% ion-exchanged water was prepared by emulsification with a homogenizer.

  A-1 was taken in a stirring and mixing tank, and predetermined amounts of B-1, C-1e, and sodium oleate were sequentially blended while stirring, and further D-1 was blended. This was blended with sodium silicofluoride at a temperature of 25 ° C. to obtain a gel.

  This was cast and heated to 140 ° C. with pressurized steam to foam and cure into a cube having a side of 100 mm to prepare a foam sample. The apparent density, tensile strength, elongation, average cell diameter and cell diameter homogeneity of this sample were measured.

Example 5
A foaming latex was prepared in the same manner as in Example 1 except that C-2 was blended in place of C-1e. This was foamed and cured in the same manner as in Example 1 to produce a foam sample, and the same evaluation as in Example 1 was performed.

Example 6
The ion-exchanged water was C-3 and two polyoxyethylene nonylphenyl ethers similar to those used in Example 1, but with a mixed HLB of 10.5. To prepare an oil-in-water emulsion C-3e containing 35% C-3, 2% emulsifier and 63% ion-exchanged water. A foaming latex was prepared in the same manner as in Example 1 except that this was used in place of C-1e. This was foamed and cured in the same manner as in Example 1 to produce a foam sample, and the same evaluation as in Example 1 was performed.

Comparative Examples 1-3
Comparative Example 1 is the same as Example 1 except that the component (C) or an oily substance substituted therefor is not blended, and Comparative Example 2 is the same as Example 1 except that liquid paraffin is blended instead of C-1e. In Comparative Example 3, each latex for foaming was prepared in the same manner as in Example 1 except that castor oil was blended in place of C-1e. This was foamed and cured in the same manner as in Example 1 to produce a foam sample, and the same evaluation as in Example 1 was performed.

  Table 1 shows the average cell diameter and the homogeneity of the foams obtained in the above Examples and Comparative Examples together with other physical property values. In addition, in the compounding table | surface of Table 1, about A-1, the polymer part in it is shown for convenience. The compounding amount as A-1 is 156 parts. Further, the surfactant used in preparing A-1 and the surfactant used in preparing the emulsion from C-1 and C-3, respectively, are omitted in Table 1.

  As is clear from Table 1, the rubber foams obtained by the present invention all had an average cell diameter of 400 μm or more, and were excellent in cell diameter homogeneity.

The rubber foam obtained in the present invention is useful for applications such as filter media, cell culture beds, puffs, medical supplies, and household products by making use of the homogeneous cell diameter.

Claims (8)

(A) Latex in which a polymer which is an uncrosslinked or partially crosslinked natural or synthetic rubber, a crosslinking agent and a foaming agent are dispersed in water An amount of 100 parts by weight of the polymer in the latex;
(B) Bubble stabilizer 0.1-10 weight part; And (C) 0.5-10 times amount of polyorganosiloxane (B), The composition for rubber-like foam formation characterized by the above-mentioned.   The composition according to claim 1, wherein (B) is a reaction product of alkyl chloride, formaldehyde and ammonia.   The composition according to claim 1 or 2, wherein (C) is a polyorganosiloxane having a long-chain alkyl group having 6 or more carbon atoms and / or an aralkyl group bonded to a silicon atom.   (A) A method for producing a rubber foam in which a polymer, a crosslinker and a foaming agent, which are uncrosslinked or partially cross-linked natural or synthetic rubber, foam and cure a latex in which water is dispersed, ) 0.1 to 10 parts by weight of (B) cell stabilizer and 100 parts by weight of polymer in latex, and 0.5 to 10 times the weight of (B) polyorganosiloxane by weight ratio. A method for producing a rubber foam, comprising foaming and curing a composition for forming a rubber foam obtained by blending.   The production method according to claim 4, wherein (B) is a reaction product of alkyl chloride, formaldehyde, and ammonia.   The production method according to claim 4 or 5, wherein (C) is a polyorganosiloxane having a long-chain alkyl group having 6 or more carbon atoms and / or an aralkyl group bonded to a silicon atom.   (A) An average cell diameter of 400 μm or more obtained by foaming and curing a latex in which a polymer, a crosslinking agent and a foaming agent, which are uncrosslinked or partially crosslinked natural or synthetic rubber, are dispersed in water Yes; and a rubber foam showing a distribution in which the cell diameter is 50% or more within the range of 50 to 150% of the average cell diameter. The rubber-like foam of Claim 7 manufactured by the manufacturing method of any one of Claims 4-6.