JP3078888B2 - Water absorbent molded product - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded article having the ability to absorb water, and relates to water-swellable packing, agricultural and horticultural materials,
An object of the present invention is to provide a molded product that can be used as a humidity adjusting material, a material for maintaining freshness, a toy, and the like.

[0002]

2. Description of the Related Art In recent years, the use of water-absorbing polymer products represented by disposable disposable diapers has been increasing. As the water-absorbing polymer, a polyvinyl alcohol type, a polyacrylate type and the like are known. However,
Since the form of these water-absorbing polymers is powdery or fibrous, they are used by being dispersed and held on a fibrous base material such as paper or nonwoven fabric for shaping, or kneaded with other polymers. . For this reason, the water absorption capacity is not fully utilized at present. Therefore, in order to give shapeability, using a polyalkylene oxide capable of thermoplastic molding, we examined a molded product that was cross-linked by irradiation with ionizing radiation. It was found that the water absorption capacity was insufficient for the intended use.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to obtain a molded article which can be thermoplastically molded and has a high water absorbing ability. A water-absorbent molded article is obtained by irradiating ionizing radiation to a molded article obtained by mixing and holding a highly water-absorbent resin in an alkylene oxide to crosslink a polyalkylene oxide.

Hereinafter, the present invention will be described in detail. The polymer that is the main component of the molded article of the present invention is a polyalkylene oxide, and polyethylene oxide or an ethylene oxide copolymer can be used alone or in a blend. Components copolymerized with ethylene oxide include alkylene oxides such as propylene oxide and butylene oxide, and / or vinyl ethers such as vinyl methyl ether and vinyl ethyl ether. Polymers having a molecular weight of 10,000 to 500,000 can be used. If it is less than 10,000, the secondary workability is inferior, and 50
If it exceeds 000, thermoplastic molding becomes difficult. The polymer may be used alone or may contain additives such as a filler, a crosslinking agent, a plasticizer, and a coloring agent.

[0005] The molding is performed by thermoplastic molding. As the molding means, the same method as that of commonly known polymers such as polyethylene and polyvinyl chloride can be employed. By extrusion molding, calendar molding, injection molding, press molding, etc., a film / sheet, plate, or solid Various shaped products.

Since polyalkylene oxide is water-soluble,
The molded article is crosslinked and insolubilized by irradiation with ionizing radiation. As ionizing radiation, electron beam, γ-ray, Χ
A line or the like is used. The irradiation amount of the ionizing radiation varies depending on the thickness of the molded product and the like.
A range of 0 Mrad is appropriate. When it is less than 0.5 Mrad, the polyalkylene oxide remains water-soluble, and when it is more than 50 Mrad, it is disadvantageous for practical use and the water absorption tends to decrease.

The super water-absorbing resin held in the polyalkylene oxide molded article includes polyacrylates,
Acrylic acid-vinyl alcohol copolymer, vinyl acetate-
Saponified acrylate copolymer, polyvinyl alcohol-maleic anhydride reactant, isobutylene-maleic acid copolymer saponified product, polyacrylonitrile-based saponified product, starch-acrylonitrile grafted polymer saponified product, starch-acrylic acid grafted polymer And cross-linked carboxymethyl cellulose. These superabsorbent resins are powdery or fibrous, do not melt by heat, and cannot be thermoplastically molded. Therefore, in order to retain these superabsorbent resins in the polyalkylene oxide molded article, the polyalkylene oxide powder or pellets are dispersed and mixed with the superabsorbent resin particles, and thermoplastically molded, and the molded article is exposed to ionizing radiation. A method of irradiating, a method of thermoplastically molding a polyalkylene oxide into a film or a sheet, or the like, and press-mixing the molded product with a highly water-absorbent resin by hot press molding or the like are employed. The amount of the superabsorbent resin varies depending on the intended use, but when mixed, the amount is preferably equal to or less than the polyalkylene oxide.

[0008] Since the superabsorbent resin generally has a water absorption ratio of several hundred times or more (weight ratio obtained by dividing the weight of a molded product after absorbing water sufficiently by the weight of the molded product before absorbing water), the water absorption ratio is high. Is maintained about 10 to 20 times in a crosslinked polyalkylene oxide molded article, whereby the water absorbing ability can be greatly increased. In addition, compared to the conventional super-absorbent resin that is dispersed and held in another resin that does not have water absorption,
Since the crosslinked polyalkylene oxide itself, which is the binder, also has water absorbency, the water absorbency is increased.

[0009]

[Example] Polyethylene oxide was converted to T by a single screw extruder.
Extrusion was performed at a die temperature of 90 ° C., and a cast sheet having a thickness of 100 μm was collected. The sheet was irradiated with an electron beam irradiation apparatus at an acceleration voltage of 200 KV and an absorbed dose of 10 Mrad, and the water absorption ratio was measured to be about 14 times.
Next, between the two cast sheets, particles of an acrylic acid / vinyl alcohol copolymer, which is a highly water-absorbent resin,
When the sheet is sandwiched so that the weight ratio of the cast sheet: the superabsorbent resin is 80:20, and hot pressed at a temperature of 90 ° C.,
The particles of the superabsorbent resin were pushed into the cast sheet and the cast sheets were fused together, so that the superabsorbent resin was held at the center of the sheet. The sheet was irradiated with an electron beam irradiation device at an acceleration voltage of 200 KV and an absorbed dose of 10 Mrad, and the water absorption ratio was measured to be about 130 times.

[0010]

According to the molded article of the present invention, a superabsorbent resin is mixed and dispersed in a crosslinked polyalkylene oxide molded article, and the conventional superabsorbent resin is dispersed and retained in another resin having no water absorption. Since the crosslinked polyalkylene oxide itself, which is a retention / binding body, also has water absorption,
Increases water absorption capacity. Further, since the molded article is obtained by thermoplastic molding, it is easy to manufacture and the handling of the molded article becomes easy. Further, the superabsorbent resin is dispersed and held when the polyalkylene oxide is in a thermoplastic state, that is, in a state of being melted or softened, so that it becomes a state of being uniformly mixed and dispersed in the polyalkylene oxide, and has a sufficient water absorbing ability. Can be demonstrated.

Claims (1)

(57) [Claims] 1. Polyalkyleneoxy in a thermoplastic state
Molded products obtained by mixing and holding superabsorbent resin
Irradiating the polyalkylene oxide with ionizing radiation
A water-absorbent molded article obtained by cross-linking.