JP2005068233A - Hygroscopic sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prepare a hygroscopic sheet that has excellent hygroscopicity, is readily produced and is suitable as a shoe insole. <P>SOLUTION: This hygroscopic sheet is obtained by molding hydrophilic polyolefin-based resin foam being foam of a mixture comprising at least a polyolefin-based resin, a thermoplastic water-absorbing resin, a crosslinking agent and a blowing agent. The hygroscopic sheet is useful as the shoe insole. The hydrophilic polyolefin-based resin foam is composed of a destroyed resin film constituting closed cells by film removal treatment or physical compression and has air permeability by communication by a film removal treatment or resin film destruction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a hygroscopic sheet, and more particularly to a hygroscopic sheet suitable as an insole for shoes.

  Polyethylene cross-linked foams and cross-linked foams of ethylene vinyl acetate copolymers are often used as insoles for shoes because of their buffering properties. Further, as the insole, if it is too soft, the foam is completely compressed by a load and sufficient buffering properties are not exhibited, so that an insole is used (see Patent Document 1).

  The insole using the closed-cell foam is not breathable, and not only does the moisture increase due to sweating, but it also causes unpleasantness, and causes ringworm fungus growth and odor. Therefore, in order to solve these problems, a fibrous clay mineral having a large specific surface area is provided as a first base material, and a second base material made of cellulose fiber or glass fiber is further provided to impart shape retention and reinforcing effects. It has been proposed (see Patent Document 2). However, since this has a multi-layer structure, the number of steps is increased and the cost is increased.

Moreover, although the insole which uses charcoal for the hygroscopic improvement is proposed, it becomes a black insole and becomes a thing with poor fashionability (refer patent document 3).
Special table 2003-504444 gazette JP 10-323203 A JP 2000-70658 A

  In view of the above, the present invention provides a hygroscopic sheet that has good hygroscopicity, is easy to manufacture, and is suitable as an insole for shoes.

  The hygroscopic sheet according to the present invention is formed by molding a hydrophilic polyolefin-based resin foam that is a foam of a kneaded material including at least a polyolefin-based resin, a thermoplastic water-absorbing resin, a crosslinking agent, and a foaming agent. The hygroscopic sheet is preferably used as an insole for shoes.

  Since the hygroscopic sheet of the present invention contains a thermoplastic water-absorbing resin, it absorbs moisture in the air under high humidity conditions, and absorbs moisture in shoes when used as an insole. The effect of lowering can be exerted, and discomfort caused by stuffiness can be made difficult to occur.

  The hygroscopic sheet of the present invention has a desired shape, such as an insole, by cutting a hydrophilic polyolefin resin foam, which is a foam of a kneaded product containing at least a polyolefin resin, a thermoplastic water absorbent resin, a crosslinking agent and a foaming agent. When used as, it is formed into an insole shape.

  A polyolefin resin is a preferred resin as a foam for a shoe insole in terms of water resistance and non-contamination. Examples of polyolefin resins used in the present invention include ethylene vinyl acetate copolymer (EVA), low density polyethylene (LDPE), high density polyethylene (HDPE), ethylene-propylene copolymer, ethylene-butene copolymer, Mention may be made of a copolymer of ethylene and methyl, ethyl, propyl or butyl acrylate, or a chlorinated product thereof, or a mixture thereof, and a mixture of them with isotactic polypropylene or atactic polypropylene. it can.

  Further, among the polyolefin resins, an ethylene vinyl acetate copolymer is preferable. Since the foam of ethylene vinyl acetate copolymer has a higher impact resilience (based on JIS K 6400) than the foam made of low density polyethylene (LDPE) or the like, the hygroscopic sheet used as an insole for shoes is Is preferred.

  Furthermore, it is desirable that the polyolefin resin has a vinyl acetate content of 10 to 50%, more preferably 10 to 25% in a total amount of 100% by weight of the polyolefin resin. When the vinyl acetate content is less than 10% by weight, the resulting hygroscopic sheet has an excessively low impact resilience, making it difficult to say that it is preferable as an insole. On the other hand, when it exceeds 50% by weight, a vinyl component as a rubber component is contained in a large amount, and it becomes difficult to obtain a foam having a desired expansion ratio.

  The thermoplastic water-absorbing resin is a thermoplastic resin having water-absorbing property, and a known one such as a registered trademark Aqua Coke (manufactured by Sumitomo Seika Co., Ltd.) can be used. The amount of the thermoplastic water-absorbing resin is 10 to 60, preferably 10 to 50, based on 100 parts by weight of the polyolefin resin. When the amount is less than 10 parts by weight, the hygroscopic effect of the hygroscopic sheet of the present invention is not sufficient. On the other hand, when the amount is more than 60 parts by weight, foaming tends to be hindered, making it difficult to obtain a hygroscopic sheet satisfactorily. .

  Examples of the crosslinking agent include organic peroxides such as dicumyl peroxide, 2,5-dimethyl-2,5-bis-tertiary butyl peroxyhexane, 1,3-bis-tertiary peroxy-isopropylbenzene, and the like. be able to. The amount of the crosslinking agent is usually 0.50 to 1.3 parts by weight with respect to 100 parts by weight of the polyolefin resin.

  As a foaming agent, what decomposes | disassembles by heating and generate | occur | produces gas is used, and it does not restrict | limit in particular. For example, azodicarbonamide, 2,2'-azobisisobutyronitrile, diazoaminobenzene, benzenesulfonyl hydrazide, benzene-1,3-sulfonyl hydrazide, diphenyl oxide-4,4'-disulfonyl hydrazide, 4,4 ' -Oxybisbenzenesulfonyl hydrazide, paratoluenesulfonyl hydrazide, N, N'-dinitrosopentamethylenetetramine, N, N'-dinitroso-N, N'-dimethylphthalamide, terephthalazide, pt-butylbenzazide, One or more of sodium bicarbonate, ammonium bicarbonate and the like are used. In particular, azodicarbonamide and 4,4′-oxybisbenzenesulfonyl hydrazide are preferable. As addition amount, it is 2-30 weight part normally with respect to 100 weight part of polyolefin resin.

  Further, a surfactant may be added to the kneaded product. The surfactant is not particularly limited, and the HLB is not limited, either ionic (anionic, cationic, zwitterionic) or nonionic. Examples of anionic (anionic) surfactants include fatty acid-based, alkylbenzene-based, alcohol-based, and alpha-olefin-based surfactants. Cationic (cationic) surfactants include amino salts and ammonium salts. Zwitterionic surfactants include carboxylic acid-based, sulfate-based, sulfonic acid-based and phosphate-based surfactants, and nonionic (nonionic) surfactants include fatty acids. Type, higher alcohol type, nitrogen-containing type and the like. The addition amount of the activator is 1 to 7 parts by weight, preferably 3 to 5 parts by weight with respect to 100 parts by weight of the polyol resin.

  Other auxiliary agents added as appropriate include foaming auxiliary agents and nucleating agents. Examples of the foaming aid include metal oxides such as zinc oxide and lead oxide, lower or higher fatty acids or metal salts thereof, urea and derivatives thereof. Moreover, calcium carbonate etc. can be mentioned as a nucleating agent.

  The hygroscopic sheet is produced according to a known polyolefin resin foaming method using the kneaded product obtained by kneading the components with a kneader or a roll. The foaming method is performed by filling the kneaded material in a closed mold and releasing the pressure after heating under pressure.

  Further, in the hydrophilic polyolefin resin foam constituting the hygroscopic sheet of the present invention, the resin film constituting the closed cell (also referred to as cell film) is formed by a known film removal treatment such as explosion or melting. Alternatively, it may be destroyed by physical compression and thereby communicated to provide air permeability.

  The composition shown in Table 1 was adjusted and kneaded with a 1 L kneader so that the total kneading amount was about 900 g, and then kneaded for 5 minutes with a 10-inch mixing roll to obtain a kneaded product. Polyolefin resin 1 in Table 1 is an ethylene vinyl acetate copolymer having a vinyl acetate content of 25% by weight, product number: Ultrasen 634, manufactured by Tosoh Corporation, and polyolefin resin 2 is an ethylene vinyl acetate having a vinyl acetate content of 10% by weight. Copolymer, product number: Ultrasen 540, manufactured by Tosoh Corporation, foaming agent is product number: AC MK-1, manufactured by Eiwa Chemical Industry Co., Ltd. Zinc oxide second type was used as a foaming aid, zinc stearate was used as a lubricant, and dicumyl peroxide was used as a crosslinking agent. As the thermoplastic water-absorbing resin, registered trademark Aqua Coke TWB, manufactured by Sumitomo Seika Co., Ltd. was used. Surfactants are product numbers: acetylenol E40, manufactured by Kawaken Fine Chemical Co., Ltd.

  The kneaded product was filled in a 15 mm × 200 mm × 200 mm mold and sealed, heated at 150 ° C. for 40 minutes in a pressurized state, and then depressurized to thereby reduce the pressure of Examples 1-4 and Comparative Examples 1-2. Hydrophilic polyolefin resin foams were obtained. Furthermore, the hydrophilic polyolefin resin foams of Examples 1 to 4 and Comparative Examples 1 and 2 thus obtained were cut into 5 × 100 × 100 mm sheets, and Examples 1 to 4 and Comparative Examples 1 to 2 were cut. A water absorbent sheet was obtained. In Comparative Example 3, foaming failure occurred and no foam was obtained.

  Each of the hygroscopic sheets of Examples and Comparative Examples thus obtained was housed in a wet heat dryer at 60 ° C. × 95%, and the weight increase after a predetermined time was measured. The weight increase amount per unit surface area of the hygroscopic sheet was calculated from the obtained weight increase amount, and the hygroscopicity was evaluated using the weight increase amount per unit surface area as the moisture absorption amount. The surface area of the hygroscopic sheet was the sum of the upper surface, the lower surface and the side surface of the hygroscopic sheet. The results are shown in Table 2. FIG. 1 is a graph of the results in Table 2.

  As apparent from Table 2 and FIG. 1, the hygroscopic sheets of Examples 1 to 4 have a higher hygroscopic amount than the hygroscopic sheets of Comparative Examples 1 to 2 and exhibit good hygroscopicity over a long period of time. doing.

  Moreover, the hydrophilic polyolefin-type resin foam of Examples 1-4 was pressed, the resin film which comprises the closed cell was destroyed, and the hydrophilic polyolefin-type resin foam of Examples 1A-4A was obtained. Further, the hydrophilic polyolefin resin foams of Examples 1A to 4A were cut into 5 × 100 × 100 mm sheets to obtain the hygroscopic sheets of Examples 1A to 4A.

It is a graph which shows the result of the hygroscopicity test to the hygroscopic sheet of an example and a comparative example.

Claims (2)

  A hygroscopic sheet obtained by molding a hydrophilic polyolefin-based resin foam, which is a foam of a kneaded product containing at least a polyolefin-based resin, a thermoplastic water-absorbing resin, a crosslinking agent, and a foaming agent. The hygroscopic sheet according to claim 1, wherein the hygroscopic sheet is used as an insole for shoes.

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