JPS6365224B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydrogel comprising water-containing water-absorbing crosslinked polymer particles dispersed in a continuous phase consisting of a certain kind of elastomer and an oil component. By dispersing water-absorbing crosslinked polymer particles, the present invention aims to provide a hydrogel that possesses unique physical, mechanical, and chemical properties not found in conventional aqueous gels or oil-based gels.

As relatively flexible aqueous gels, those using various water-soluble organic polymer compounds such as starch, cellulose derivatives, polyvinyl alcohol, polyacrylic acid, polyethylene oxide, etc. are known. It is used for purposes such as fireproofing, heat insulation, and cold insulation.

However, most of these aqueous gels are in the form of the above-mentioned water-soluble polymer compound absorbing water and swelling, and therefore, water forms a continuous phase in the aqueous gel. Most of them. For this reason, the strength of aqueous gels is not very strong when the water content is relatively high, and the storage stability of the gel is generally affected, especially when the water contained in it evaporates easily when left in the air. There are disadvantages that can be lost. Furthermore, when used as a cold insulating material, if stored at temperatures below 0°C, the gel as a whole freezes and becomes very hard and brittle, resulting in a loss of flexibility.

On the other hand, as a gel having particularly flexibility and high elasticity among oil-based gels, a highly elastic gel consisting of an elastic block copolymer and a certain type of oil or higher fatty acid is described in Japanese Patent Publication No. 18409/1983. The oil-based gel described therein is a gel that easily deforms when stress is applied, but instantly recovers when stress is removed; it has so-called rubber-like rebound resilience, and therefore has very poor stress dispersion properties. . In addition, such oily gels are flammable, making them unsuitable as fire retardants, and since they do not have a water-dispersed phase, they have practically no cold-retaining effect as cold-retaining materials.

In order to solve the above-mentioned problems of water-based gels and oil-based gels, we developed a continuous phase and emulsification system consisting of an A-B-A type teleblock copolymer elastomer and an oil component, as described in JP-A-51-125442. succeeded in solving the problems of the above-mentioned aqueous gel or oil-based gel by inventing a hydrogel consisting of a water particle dispersed phase,
Although considerable effects could be achieved, this hydrogel also had the drawback that under conditions of severe mechanical stress, the emulsified water particle dispersed phase became unstable and water separated.

The present invention is a further improvement of our invention described in JP-A No. 51-125442 mentioned above. Another object of the present invention is to provide a hydrogel that can be molded by heating and has a novel structural form characterized by dispersing water-containing water-absorbing crosslinked polymer particles.

Another object of the present invention is to provide a gel with remarkable stress dispersion properties, i.e., to be easily deformed when stress is applied, by the presence of a dispersed phase of water held by water-absorbing cross-linked polymer particles in the gel structure. However, when the stress is removed, the deformation gradually recovers to about 1~
A gel product that completely recovers to its original shape after 2 minutes.
For example, an object of the present invention is to provide a gel mat that is effective in preventing lumbar depression in severely injured patients.

Furthermore, another object of the present invention is that the gel has the above-described novel structural form, so that it is substantially stable even when the water content in the gel structure is not only small but up to about 85% by weight. Moreover, it is an object of the present invention to provide a water-containing gel that has excellent properties such as cold retention, self-extinguishing properties, sound absorption properties, and lubrication properties without losing its flexibility even at -20°C, and has high utility value.

The hydrogel of the present invention has a water content of 99.5 to 10.0% by weight in a system in which an A-B-A type teleblock copolymer elastomer is dissolved in an excess amount of an oil component under heating.
The water-containing water-absorbing crosslinked polymer particles are dispersed to form a continuous phase consisting of the elastomer and an oil component.
Easily produced by forming a W/O emulsion containing 95% by weight and 85 to 5% by weight of a dispersed phase of water retained in water-absorbing crosslinked polymer particles, followed by gelation by cooling to room temperature. be done.

In the hydrogel of the present invention, the A-B-A type teleblock copolymer elastomer (hereinafter simply abbreviated as teleblock elastomer) used to form the continuous phase consists of a hard polymer A and a soft polymer B. The A block is a hard polymer of a vinyl compound such as styrene or methylstyrene, and has a glass transition temperature of 70°C or higher, and has a glass transition temperature of about 1000°C or higher.
Polymers with average molecular weights in the range 100,000 are useful. In addition, the B block is a soft polymer of a conjugated diene compound such as butadiene, isoprene, etc.
Its glass transition temperature is -50 to 30℃, approximately
Polymers with average molecular weights in the range 4,500 to 1,000,000 are useful.

The terminal A block of the teleblock elastomer comprises approximately 15-65% by weight of the teleblock elastomer.

Furthermore, the oil component, which is another component used to form the continuous phase, may include an oily substance that is liquid at room temperature and is compatible with the B block of the teleblock elastomer and incompatible with the A block. Preferably, oil, cylinder oil, transformer oil, rosin oil, or various liquid paraffins are used, but these oily substances may be heated with paraffin wax with a melting point of 120°C or less, wax-like low molecular weight polyethylene with a melting point of 150°C or less, etc. Also useful as the oil component of the present invention are mixtures to which substances exhibiting an oily form are added.

The amount of the oil component to be used is 100 parts by weight based on 5 to 30 parts by weight of the teleblock elastomer, which is effective for forming a continuous phase of the hydrogel.
The amount of teleblock elastomer used is determined primarily by the relationship between the water content of the final hydrogel product and its desired flexibility.

In addition, in the present invention, in order to increase the toughness of the final hydrogel product, if necessary, an effective crosslinking agent may be used in conjunction with the teleblock elastomer. In this case, vulcanizing agents and vulcanization accelerators commonly used for vulcanizing rubbers are effective. The appropriate amount of the vulcanizing agent and vulcanization accelerator to be used is 0.01 to 2 parts by weight per 100 parts by weight of the teleblock elastomer, and the optimum amount to be used is determined from the relationship between the toughness and flexibility of the final hydrogel product. .

In addition, in the present invention, antiaging agents, antioxidants, reinforcing fillers, coloring pigments or dyes are added to the teleblock elastomer or oil component to prevent thermal deterioration, oxidative deterioration, photodegradation, etc. etc. can be added.

Examples of the water-absorbing crosslinked polymer used in the present invention include a graft polymer of acrylic acid and starch, a copolymer of acrylic acid and polyvinyl alcohol, and polyethylene oxide. Commercially available products include Sunwet IM-300 manufactured by Sanyo Chemical Industries, Sumikagel S-100 manufactured by Sumitomo Chemical Co., Ltd., and PEO-18 manufactured by Steel Chemical Co., Ltd., respectively. These water-absorbing cross-linked polymers come in powder, flake,
Particulate forms are available, but particulate forms are particularly desirable.

Such water-absorbing crosslinked polymers are neutral and have a high water absorption rate, and their water absorption rate reaches 400 to 500 times their own weight. The water-containing water-absorbing crosslinked polymer particles used in the present invention can be easily produced by allowing the water-absorbing crosslinked polymer described above to absorb 10 to 200 times its own weight of water. The diameter of the obtained water-containing particles is preferably 0.1 to 5 mm. Absorbing too much water is undesirable because it reduces the strength of the water-containing particles.

It is desirable to use an emulsifier to facilitate the dispersion of the water-containing particles into the continuous phase consisting of the teleblock elastomer and the oil component. Nonionic surfactants are particularly effective as emulsifiers, such as polyethylene glycol oleyl ether, polyethylene glycol nonyl phenyl ether,
Examples include polyethylene glycol decyl phenyl ether and sorbitan monolaurate.
The amount used is preferably in the range of 0.1 to 5% by weight based on the total weight.

The amount of water-containing water-absorbing crosslinked polymer particles that can be dispersed in the hydrogel of the present invention is from 5% to 85% by weight.
If the amount is increased beyond this range, the stability of the water-containing gel will deteriorate, or the W/O type will undergo phase inversion, resulting in an O/W type emulsion, which will become impossible to gel. Therefore, the hydrogel of the present invention is substantially stable in the range of 85 to 5% by weight of the water-containing water-absorbing crosslinked polymer dispersed phase, while the continuous phase consisting of the teleblock elastomer and oil component is in the range of 15 to 95% by weight. % by weight.

Next, the present invention will be explained by examples, but the present invention is not limited to these examples. In addition, the parts described in the examples mean parts by weight.

Example: Into a 13-necked flask equipped with an efficient stirrer, reflux condenser, and _N2 gas inlet, 100 parts of liquid paraffin (Kyodo Oil Co., Ltd., Kyodo Oil Co., Ltd. liquid paraffin-350) with a viscosity of 400 poise (20°C) was placed. , 20 parts of styrene-butadiene-styrene teleblock elastomer (Califlex TR-1107, manufactured by Schiel Kagaku Co., Ltd.) were added and heated to about 120° C. with stirring in a N ₂ gas stream to dissolve. Add emulsifier (Solgen) to this solution.
50) After adding 1 part, lower the temperature inside the flask to about 80~
Keep at 90℃. On the other hand, 5 parts of water-absorbing crosslinked polymer and 120 parts of water.
Water gel particles are prepared by adding 50% of water to absorb water, and the water gel particles are gradually added to the above-mentioned stirring flask to form a W/O emulsion. The obtained emulsion was poured into a mold with a depth of 20 mm and then cooled to room temperature to obtain a flexible hydrogel with a volume of 100 x 100 x 20 mm.

The hydrogel obtained in the present invention can be molded into various shapes. That is, a W/O emulsion is poured into a suitable mold while maintaining the temperature range of about 70 to 90°C, or extruded with an extruder,
Various hydrogel products can be obtained by applying the product to the surface of cloth, paper, release paper, etc. using a coating device, and then cooling it to room temperature.

The hydrogel of the present invention is composed of a W/O emulsion structure, and water is retained by a water-absorbing crosslinked polymer, so it does not separate even when subjected to severe mechanical stress, and it does not separate from the teleblock elastomer. It is more stable than a hydrogel obtained by dispersing water particles in a continuous phase consisting of an oil component.

After leaving the hydrogel of the present invention in a -20°C freezer for 15 hours, the gel taken out into the room was flexible enough to be deformed even when pressed with a fingertip, while the entire hydrogel was at room temperature (20°C). It took about 8 hours for the temperature to recover (°C). Therefore, the hydrous gel of the present invention is excellent as a cold insulating material that utilizes the large heat capacity of the water contained in the gel. Furthermore, the hydrogel of the present invention is flexible and tough, has excellent stress dispersion properties, and gradually recovers its original shape when subjected to stress deformation. This stress dispersion property appears as a result of the water-containing particles in the gel deforming easily in response to external forces, and the absorbing region functioning to disperse the external solution. Therefore, gel mats utilizing this property are particularly effective in preventing pressure sores such as congestion caused by pressure on the lumbar region of patients who have been ill for a long period of time.

Claims (1)

[Scope of Claims] 1. Water-absorbent water contained in a continuous phase consisting of a teleblock copolymer elastomer having a bonding form of (hard polymer A)-(soft polymer B)-(hard polymer A) and an oil component. A hydrogel characterized by dispersing crosslinked polymer particles. 2. A continuous phase consisting of a teleblock copolymer elastomer and an oil component having a bonding form of (hard polymer A)-(soft polymer B)-(hard polymer A) is 15 to
At 95% by weight, the water-containing water-absorbing crosslinked polymer particles are 85% by weight.
5% by weight, and the water-containing water-absorbing crosslinked polymer particles have a water content of 99.5-10% by weight.