JPS6058250B2 - Super absorbent resin molded body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel molded article containing an acrylic superabsorbent resin as a main component and having the characteristics described below.

Super absorbent resins such as super absorbent acrylic resins are generally commercially available in the form of white powder, flakes, sheets, or transparent gel-like substances containing several tens of percent water, and are used as thickeners, water retaining agents for agriculture and horticulture, etc. It is already used in sanitary products, sludge dehydration coagulants, oil-water separators (remove water from oil), etc.

However, none of the commercially available super absorbent resins mentioned above expands into a fixed shape after absorbing water, but expands into irregular shapes.

The present inventor has developed a novel super-absorbent material that has the property of absorbing water and expanding while maintaining a certain shape in a similar manner, and contracting while retaining its shape in a similar manner even when water is lost. We succeeded in producing a plastic molded product.

This can be manufactured by adding an appropriate amount of polymerization catalyst, crosslinking agent, etc. to a prepolymer or monomer of an acrylic superabsorbent resin, and then performing a molding operation. It is also possible to use means such as irradiation with light such as IL pcal + 6 = ιA. Examples of the polymer of the acrylic superabsorbent resin used in the present invention include acrylic acid, methacrylic acid,
Monomers having polymerizable unsaturated bonds such as maleic acid, polymerizable unsaturated monomers that can form the above monomers by hydrolysis, such as acrylonitrile, methacrylonitrile, acrylic esters, methacrylic esters, acrylamide, methacrylamide, etc. Single or copolymer,
or a partial hydrolyzate thereof.

Preferred polymers are those containing acrylic acid or methacrylic acid as a main component, particularly preferably those having 30 to 10% (unit) of these components, and furthermore 50 to 10% (unit) of the polymer components. 100% (unit) is Na
or neutralized with.

The above polymers may be prepared by copolymerizing the sodium salts of carboxylic acid monomers with other water-insoluble monomers, if necessary, or by copolymerizing monomers that form carboxylic acid groups by hydrolysis. After polymerization, this may be hydrolyzed with an alkali.

A crosslinking agent is added to these prepolymers to carry out a crosslinking reaction in a mold to obtain the molded article of the present invention. The monomers used in the present invention are the same as those used in the prepolymer described above.

These monomers are mixed with a crosslinking agent, a polymerization catalyst, etc., and the reaction proceeds in a mold to obtain a molded article. As a crosslinking agent, a compound having at least two polymerizable double bonds (non-conjugated) (polyvinyl compound, di- or polyester of unsaturated mono- or polycarboxylic acid and polyol, bisacrylamide compound), and at least two Among them, dimethacrylate of alkylene glycol or polyalkylene glycol, N,N-methylenebisacrylamide, diglycidyl ether of alkylene glycol or polyalkylene glycol, etc. are particularly preferred.

The amount of crosslinking agent used is preferably 0.01 to 10%, particularly preferably 0.05 to 10%. As the polymerization catalyst, a redox polymerization catalyst is suitable. Preferred polymerization catalysts are ammonium persulfate-sodium bisulfite, ammonium persulfate-hydrosulfite, and ammonium persulfate-hydrosulfite.
These are sodium thiosulfate, H2O2 ferrous monosulfate, etc., and are usually used in an amount of 0.05 to 1% based on the monomer. The polymerization is preferably carried out at room temperature or in an aqueous medium under heating, and particularly when polymerization and crosslinking are carried out simultaneously in a mold, it is preferably carried out at room temperature. The superabsorbent resin that is the main component of the obtained molded product has a carboxyl group content of 0.2 to 1.2 mol, preferably 0.6 to 1.2 mol, per 100 grams of the crosslinked polymer. mol, particularly preferably 0.8 to 1
．． It is 2 moles. As the amount of carboxyl groups becomes smaller or the degree of crosslinking becomes larger, the water absorption rate, ie, the expansion rate, decreases significantly. Therefore, in order to adjust the water absorption rate, that is, the expansion rate, the degree of crosslinking and the proportion of carboxyl groups may be adjusted by blending the raw materials during production of the molded article. Moreover, once the molded body is obtained, the expansion rate can be adjusted by changing the PHL ionic strength of the water for water absorption (for example, addition of common salt, etc.) and the water absorption time.

When an appropriate amount of coloring agent (preferably a water-insoluble coloring agent) is added during the above manufacturing process and molded into the shape of an animal, flower, fruit, or artistic sculpture, the superabsorbent resin molding has a beautiful color. You get a body.

When this molded body is left in water, its volume expands significantly while retaining its shape, e.g., it expands several to hundreds of times or more. On the other hand, when it is taken out of water and dried, water evaporates and it shrinks significantly. do. A molded article having such characteristics has not been known at all in the past, that is, it is new and can be advantageously used, for example, as a toy, a humidity regulator, etc., as described later. For example, in the case of a molded object for a toy, one with a size of 1 to 1 cm (water content of about 30 to 50%) has a high temperature that expands by water absorption of 3 to 5 times both vertically and horizontally. A water-absorbing resin molded body can be made.

This is interesting for young children. As a humidity control material, for example, make a molded object in the shape of a 1-millimeter vinyl or a thinking person, place it on a plate filled with water,
By placing it on a tabletop in a closed room during winter heating or summer cooling, it maintains the appropriate humidity in the room, helps prevent throat irritation and colds, and improves the aesthetics of the room. . Examples will be described below.

Example 1 Na0H32y is dissolved in 104q of water, and 72V of acrylic acid is added to neutralize it.

0.9y of polyethylene glycol dimethacrylate is dissolved in this sodium acrylate solution, and the solution is sufficiently replaced with nitrogen. Add 7.5y of 10% ammonium persulfate solution to this.
Add 10y of 10% sodium bisulfite solution and colorant and stir quickly. This is placed in a fruit mold of approximately 1 cT1 size and left at room temperature for 8 hours. The solution undergoes polymerization crosslinking and hardening in the mold, yielding a water-insoluble semi-elastic molded body. The fruits obtained were red apples, orange mandarin oranges, and green marimo. If each of these is placed in a 500ml beaker containing pure water and left to stand,
After several hours, it expanded in a similar manner to about 150 cT1. When 0.5% by weight saline solution was used in place of pure water, slightly hard expanded bodies of about 50 c11 were obtained.

Moreover, when these expanded bodies were dried, they shrunk, and finally shrunk to their original shape and size. Example 2 Na0H3
Dissolve 4y in 106y of pure water and add 36y of acrylic acid to this.
1 Methacrylic acid 22y1 Itaconic acid 16f is added to neutralize.

Diethylene glycol dimethacrylate 1y is dissolved in this soda solution of carboxylic acid, and the system is purged with nitrogen gas. To this are added 10% ammonium persulfate solution 8y110% sodium bisulfite solution 11V and colorant and stir quickly. The content of the obtained solution is approximately 1 c! The mixture is placed in a mold for goldfish and cattails having a size of 1 liter, and reacted at room temperature for 3 hours to obtain water-insoluble molded bodies, namely red goldfish and brown cattails.

When this was put into pure water, it expanded to about 200 d after about one cry. This material can repeatedly contract and expand due to dehydration and water absorption. Example 3 10 y of ethyl acrylate and 65 y of acrylic acid were added to 2 y of water.
In addition to 20y, ammonium persulfate 1y is used as an initiator to polymerize at about 60°C for 2 hours.

After polymerization, 29y of NaOH is dissolved in 63y of water to neutralize the polymer, and when it becomes a viscous liquid with a viscosity of about 200 ■Ps,
Cool to about 40°C, add and dissolve ethylene glycol diglycidyl ether 1y, place in a doll mold, and let stand at 40°C for 2 hours. The resulting water-expandable doll was insoluble in water and expanded to approximately 40 f8 when placed in pure water. Although several embodiments of the invention have been described in detail, those skilled in the art will recognize that the invention can be practiced in a wide variety of ways.

Claims (1)

[Claims] 1. A molded article made of a cross-linked acrylic superabsorbent resin, which can expand or contract while maintaining a uniform shape during water absorption or dehydration.