JPH03247334A - Cold insulant - Google Patents

Abstract

PURPOSE:To achieve a process inexpensive with a simplification thereof along with excellence in cold insulating property and in softening at a low temperature by dispersing a hydrogel containing water with a surface thereof covered in a matrix mainly composed of a liquid rubber to crosslink. CONSTITUTION:A hydrogel containing water with a surface thereof covered previously is dispersed in a liquid rubber containing a crosslinking agent and then, a crosslinking is performed. With such an arrangement, a cold insulant can be produced very easily using a widely used agitator at a relatively low temperature. The covering of the surface of the hydrogel containing water prevents coagulation between the hydrogels with a high dispersiveness thereof in the liquid rubber so that softness can be maintained even at a temperature near -20 deg.C and hence, a cold insulating can be obtained with an excellent shape maintaining property and with a longer cold insulating period. The liquid rubber herein used as main component of a matrix means a vulcanized type rubber with a fluid vulcanizing property indicating a liquid or half-liquid condition at a normal temperature. The hydrogel containing water means a widely known hydrogel such as starch-based hydrogel to which a proper amount of water is added to be contained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a cold insulating material that has excellent flexibility, elasticity, and shape retention at low temperatures, and has a large amount of heat retention.

(Prior art and its problems) Many commercially available cold insulation materials use gels made by adsorbing water to water-soluble polymers such as gelatin, polyvinyl alcohol, or polyethylene oxide (Japanese Patent Publication No. 56-
45977), this gel solidifies very hard at low temperatures and has no low temperature flexibility. Therefore, it is unsuitable for use as a substitute for water pillows.

Japanese Patent Publication No. 47-18409 discloses an oily gel consisting of an unvulcanized elastic block copolymer and paraffin oil, but although these are flexible, they are poor in cold retention.

JP-A No. 60-79061 discloses a continuous phase consisting of a teleblock copolymerized elastomer and an oil component in which water-containing water-absorbing cross-linked polymer particles are dispersed, and JP-A No. 60-11738 discloses discloses a water-in-oil emulsion in which an aqueous dispersoid is dispersed in a homogeneous dispersion medium containing a high-boiling oily substance, natural rubber, or synthetic rubber, which is crosslinked in the presence of a crosslinking agent to form a gel. ing. Although all of these have excellent cold retention and flexibility at low temperatures,
The process becomes complicated and expensive. Additionally, when the amount of water increases, mechanical and thermal stability may be impaired and water separation may be observed.

(Means for Solving the Problems) The present inventors studied various materials, and as a result, they arrived at the present invention.

That is, the present invention provides a cold insulating material obtained by dispersing and crosslinking a water-containing hydrogel whose surface is coated in a matrix mainly composed of liquid rubber.

By dispersing the surface-coated water-containing hydrogel in a liquid rubber containing a cross-linking agent and then cross-linking, it can be produced very easily using a commonly used stirrer.
It can be produced at relatively low temperatures. By coating the surface of water-containing hydrogel, it has good dispersibility in liquid rubber and prevents agglomeration of hydrogels, maintains flexibility even at temperatures around -20°C, has excellent shape retention, and has a long cold storage time. wood is obtained.

The liquid rubber used as the main component of the matrix component in the present invention means a fluid vulcanized rubber that is liquid or semi-liquid at room temperature. Such liquid rubbers include liquid polymers of conjugated diene compounds such as butadiene, isoprene, dimethylbutadiene, piperylene, or chlorobrene, or liquid polymers thereof, and combinations of the above conjugated diene compounds and styrene, methylstyrene, acrylonitrile, and methacrylonitrile. , a liquid copolymer of a vinyl compound copolymerizable with the conjugated diene compound such as ethylene, propylene, butylene or imbutylene, and liquid thiocol.

Also, natural rubber (NR), synthetic polyisoprene rubber (I
R), polybutadiene rubber (BR), styrene-butadiene (random) copolymer rubber (SBR), styrene-isoprene (random) copolymer:'mu (SIR), acrylonitrile-butadiene copolymer rubber (NBR) Also included are liquid rubbers obtained by depolymerizing solid combs such as , acrylonitrile-isoprene copolymer rubber (NIR), or butyl rubber (IIR). Note that modified liquid rubbers in which functional groups such as carboxylic groups, hydroxyl groups, epoxy groups, isocyanate groups, or acid anhydride groups are introduced into the liquid rubber, or low molecular weight rubbers in which these functional groups are reacted, are also used.

As mentioned above, the present invention is based on liquid rubber, and by appropriately selecting the liquid rubber, the hydrogel coated on the surface in a greenhouse can be easily dispersed to obtain a uniform and stable hydrogel. However, if it is difficult to disperse at room temperature, the water-containing hydrogel coated on the surface may be dispersed by heating to a temperature below which water evaporates to lower the viscosity. Further, a plasticizer may be added within a range that does not cause problems of bleat or localization. The plasticizers used here are process oil, paraffin, machine oil, cylinder oil,
It is an oily substance that is liquid at room temperature, such as transformer oil or rosin oil.

In the present invention, the crosslinking treatment is carried out, and the crosslinking agents for the liquid rubber used here include sulfur, peroxide,
Examples include those used in conventional vulcanization methods such as quinoids or amines. These are added with vulcanizing chemicals such as vulcanization accelerators and subjected to crosslinking by conventional methods.

Furthermore, the term "hydrated hydrogel" refers to a generally known hydrogel such as a starch-based hydrogel, an acrylic acid-based hydrogel, an acrylic acid-vinyl alcohol-based hydrogel, etc., to which an appropriate amount of water is added to make it hydrated. It is preferable to use this product in an amount of 1 to 8% by weight, particularly 5 to 6% by weight, based on water, while still retaining some of the water absorption ability of the hydrogel.

If it is less than 1% by weight, there is a drawback that water once absorbed into the hydrogel will be released by external pressure, etc., and if it is less than 8% by weight.
If it exceeds this, the absorption rate of each water-containing hydrogel becomes non-uniform, which has the disadvantage that the cooling time becomes short.

In the present invention, the water-containing hydrogel described above is further surface-coated. In this case, the surface-coated hydrogel surface may be cured before use. If such surface treatment is not performed, the water retaining material composition will easily separate, making it difficult to form a uniform composition.

As surface coating agents, protective colloids such as sodium alginate, gelatin, gum arabic, tragacanthcomb and polymeric polyhydric alcohols such as polyvinyl alcohol are used. As auxiliary agents for hardening, soaps such as calcium salts and aluminum salts of higher fatty acids, inorganic acids such as hydrochloric acid, sulfuric acid, and boric acid, and organic acids such as oleic acid and acetic acid are used. These surface coating and curing methods include 10 of these surface coating agents.
~15% aqueous solution to 1/2 of the water-containing hydrogel~
Add the same amount as it is, or add 10 to 2
Add 0% by weight and perform a curing treatment. The water used in the present invention may or may not contain anti-icing agents such as ethylene glycol and diethylene glycol.

Further, in the present invention, fillers may be used depending on the purpose. Fillers used include white carbon, talc, titanium oxide, inorganic oxides such as oil-absorbing calcium carbonate, long-chain fatty acid salts, especially calcium stearate, magnesium stearate, aluminum stearate, and calcium oleate. These may be used alone or in combination of two or more. The finer the particles of these fillers, the better.

(Effect of the invention) The thus obtained cold insulating material composition not only retains its flexibility at -20°C even when immersed in boiling water but also has excellent shape retention and can be repeatedly heated and cooled. No matter what I do, I don't see any change. Therefore, it is very easy to use (and also has excellent thermal efficiency).

The cold insulating material according to the present invention is used for cold insulating pillows, various parts of the body, blood, frozen desserts, foodstuffs, and the like.

(Example) The present invention will be explained in more detail below using Examples, but is not limited thereto.

Example 1 2.0 g of hydrogel (S-50 manufactured by Seihi Kagaku Co., Ltd.) and 37 g of water
Mix 0g well to make it hydrated, add a solution of 10g of sodium alginate dissolved in 200g of water, stir, and add 10g of oleic acid1 20g of calcium stearate.
were added and mixed (Step ■).

Separately, liquid polybutadiene (R-45EPI manufactured by Idemitsu Oil Co., Ltd.)
150 g of DOP and 300 g of S DOAI OOg were thoroughly stirred at room temperature (Step ①). The composition obtained in step (1) was added to the composition obtained in step I above, and 50 g of amine (manufactured by H312 Rawhide Rubber) was added as a crosslinking agent, followed by thorough stirring. After being left at room temperature for one day, a cold insulating material with shape retention was obtained. The obtained cold insulating material is flexible enough to fit the affected area even when cooled to -20°C, has shape retention properties, and does not sag when used vertically, and the gel is uniformly present in all parts. Ta. It did not become hard even after repeated use.Next, the material that had been cooled to -20°C was heated in boiling water for 15 minutes, kneaded by hand, frozen again to -20°C, and this operation was repeated.Similarly. A hydrogel without surface coating was prepared and the above operation was repeated.The surface coated sample did not become hard even after repeating the operation 50 times, but the surface coated sample became hard after 5 times.

Further, JP-A-1-12139.1 discloses a cold insulating material in which a surface-coated hydrous gel is dispersed in a vinyl chloride resin gelled with a plasticizer.

This has excellent cold retention and remains flexible even at around -20℃.
Although it has shape retention properties and does not cause water separation, it may not be suitable for some applications due to its shape retention properties. For example, in the case of a large and thin ice pack, there will be areas where the gel will run out.

Furthermore, when the cold pack is used vertically, it has the disadvantage that it sag downward. Therefore, there is a demand for a cold insulating material that maintains flexibility even at around -20°C, has excellent shape retention, and has a long cooling time.

Example 2 Liquid polyisoprene rubber (manufactured by Kuraray Co., Ltd., Kuraprene IR-30) 1 was added to the composition obtained in Step 1 of Example 1.
．． 509, process oil (Sansen 450, manufactured by Sun Oil Co., Ltd.) Zn109 stearate, 5 g of sulfur, and vulcanization accelerator (manufactured by Ohmukai Shinko Chemical Industry) (EZ109, M2.
59, PX79) and stirred thoroughly (Step 2).

The composition of (Step 1) and the composition of (Step 2) were thoroughly stirred, the resulting composition was placed in a bag, and the mixture was placed in an oven at 60°C for 2 hours.
Vulcanization was carried out for 0 hours. The resulting cold insulating material is flexible enough to fit the affected area even when cooled to -20°C, retains its shape, does not lean when used vertically, and has gel uniformly on all parts. was.

It did not become hard even after repeated use. Then -2
The mixture that had been cooled at 0°C was heated with boiling water for 15 minutes, kneaded by hand, frozen again to ~20°C, and this operation was repeated. Similarly, a water-containing hydrogel without surface coating was prepared, and the above operation was repeated. The surface-coated specimen did not become hard even after 50 repetitions of the operation, but the non-surface-coated specimen became hard after 5 repetitions.

[Cold retention time measurement test kit] The cold retention materials prepared in Examples 1 and 2 were each used for 1000
2503 g! Put it in a JFX 200MII polyethylene bag, freeze it at -20℃ for 12 hours or more, take it out, leave it at room temperature of 25℃, and let the temperature of the cold insulation material rise by +1
The time until the temperature reached 0°C was measured.

Water was also measured for comparison.

Both Examples 1 and 2 were kept at around 0°C for a long time.

Claims (2)

[Claims] 1. A cold insulating material obtained by dispersing and crosslinking a surface-coated water-containing hydrogel in a matrix whose main component is liquid rubber. 2. 2. The cold insulating material according to item 1, wherein the surface coating is made of a protective colloid or a polymeric polyhydric alcohol.