JPH03162479A - Water-retaining agent for heat-generation composition - Google Patents

Abstract

PURPOSE:To provide the subject water-retaining agent composed of a crosslinked polymer produced by polymerizing a mixture of a specific (meth)acrylic acid ester monomer and a carboxyl-containing unsaturated monomer at a specific ratio and giving a composition having excellent water-absorbing and retaining property and high fluidity. CONSTITUTION:The objective composition is composed of a crosslinked polymer produced by polymerizing a monomer mixture consisting of (A) 20-80wt.% of a (meth)acrylic acid ester monomer of formula (R is H or methyl; X is 2-4C oxyalkylene containing >=50mol% of oxyethylene group based on total oxyalkylene group; Y is 0H, 1-5C alkoxy, phenoxy or oxyalkylphenyl having 1-3 substituents consisting of 1-9C alkyl; n is 3-100) [e.g. hydroxypolyethylene glycol mono(meth)acrylate] and (B) 20-80wt.% of a water-soluble unsaturated monomer containing carboxyl group [e.g. (meth)acrylic acid] optionally in the presence of a crosslinking agent.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a water retention agent for exothermic compositions.

More specifically, in exothermic compositions such as disposable body warmers that utilize heat generated by the oxidation reaction of metal powder, the oxidation reaction is suitably suppressed by absorbing and retaining salt water added to promote the oxidation reaction of the metal powder. The present invention relates to a water-retaining agent for exothermic compositions that can be used in exothermic compositions.

(Prior Art) Exothermic compositions that utilize heat generated by the oxidation reaction of metal powder are well known and are widely used as disposable body warmers. It is also known that salt water is added to such exothermic compositions as a catalyst for oxidizing the metal powder, and that a water retention agent is used to absorb and retain this salt water to suppress the oxidation reaction.

Examples of the water-retaining agent include carboxymethyl cellulose, neutralized starch-acrylic acid graft polymers,
Carboxyl group-containing polymers such as partially neutralized crosslinked polyacrylic acid are known.

(Problems to be Solved by the Invention) However, conventionally used water retaining agents have the disadvantage that their water absorption capacity for salt water is low and that their water absorption capacity changes over time.

Therefore, a large amount of water retaining agent must be added to the exothermic composition, which increases the weight and size of the entire product, making it inconvenient to carry. Furthermore, when the amount of water-retaining agent is reduced, when producing the composition, the water-retaining agent that absorbs salt water and thickens causes the metal powder to form lumps, making it impossible to achieve uniform mixing. Furthermore, the salt water absorbed by the water retention agent during composition production is released from the water retention agent during storage of the composition, resulting in problems such as unstable product quality during use.

The present invention solves the above problems.

Therefore, an object of the present invention is to provide a water retention agent for exothermic compositions that has excellent water absorption ability for salt water and can achieve uniform mixing with metal powder and other additives even if the amount incorporated into the exothermic composition is reduced. The goal is to provide the following. Another object of the present invention is to provide a compact pyrogenic composition that does not deteriorate in quality during storage.

(Means and effects for solving the problem) As a result of extensive research to achieve the above object, the present inventors have developed a (meth)acrylic acid ester monomer having a specific structure and a carboxyl group-containing monomer. We have discovered that all of the above problems can be solved by using a crosslinked polymer obtained by polymerizing unsaturated monomers in a specific ratio as a water retention agent for exothermic compositions, and have completed the present invention. .

That is, the present invention is based on the general formula RO (where R is hydrogen or a methyl group, and
An oxyalkylene group having 2 to 4 carbon atoms, which is the above,
Y is an oxyalkylphenyl group having 1 to 3 substituents of a hydroxyl group, an alkoxy group having 1 to 5 carbon atoms, a phenoxy group, or an alkyl group having 1 to 9 carbon atoms;
n is a number from 3 to 100 on average. ) A (meth)acrylic acid ester monomer (A
) (hereinafter referred to as monomer (A)) 20 to 80% by weight and carboxyl group-containing water-soluble unsaturated monomer (B) (hereinafter referred to as
A water-retaining composition for exothermic compositions comprising a crosslinked polymer obtained by polymerizing a monomer mixture (I) comprising 20 to 80% by weight of monomer (8) in the presence or absence of a crosslinking agent. This is related to drugs.

The monomer (A) used in the present invention is a (meth)acrylic acid ester monomer represented by the above general formula, for example, hydroxypolyethylene glycol mono (
meth)acrylate, hydroxypolyethylene glycol/polypropylene glycol mono(meth)acrylate, hydroxypolyethylene glycol/polybutylene glycol mono(meth)acrylate, methoxypolyethylene glycol mono(meth)acrylate, methoxypolyethylene glycol/polypropylene glycol mono(meth)acrylate, Methoxypolyethylene glycol/polybutylene glycol mono(meth)acrylate, ethoxypolyethylene glycol mono(meth)
Acrylate, ethoxypolyethylene glycol/polypropylene glycol mono(meth)acrylate, ethoxypolyethylene glycol ●Polybutylene glycol mono(meth)acrylate, phenoxypolyethylene glycol mono(meth)acrylate, penzyloxypolyethylene glycol mono(meth)acrylate, etc. These types (1) or two or more types can be used.

The mole fraction of oxyethylene groups to all oxyalkylene groups in monomer (A) must be 50% or more, and those with this mole fraction of less than 50%, such as alkoxypolypropylene glycol mono(meth)acrylate and fluorine If enoxypolybutylene glycol mono(meth)acrylate or the like is used instead of the monomer (^), a crosslinked polymer that is effective as a water retention agent with a high water absorption capacity cannot be obtained.

In addition, if the end of the side chain of monomer (A) is a hydroxyl group, if high temperatures are applied during polymer production or preparation of exothermic composition, a crosslinking reaction will occur and the water absorption capacity of the water retention agent will decrease. Therefore, when selecting such polymer production conditions or exothermic composition adjustment conditions, it is necessary to
It is preferable to use one having a hydrophobic functional group at the end of the side chain.

The monomer (B) used in the present invention is not particularly limited as long as it has a carboxyl group and is water-soluble.
Examples include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, citraconic acid, maleic acid, fumaric acid, and salts thereof, and one or more of these can be used.

In the present invention, in the monomer mixture (I), the monomer (^
) is used in a proportion of 20 to 80% by weight, and monomer (B) is used in a proportion of 20 to 80% by weight. If the amount of monomer (^) is small, such as less than 20% by weight, the ability of the resulting water retention agent to absorb and retain salt water will be reduced, and the effect of using monomer (A) will not be apparent.

Moreover, if a large amount of monomer (A) is used in excess of 80% by weight, the water absorption capacity of the resulting water retention agent decreases. It should be noted that monomers other than monomer (A) and monomer (B) may be partially mixed with the monomer mixture (1) as long as the performance of the water retention agent of the present invention is not impaired. good.

The crosslinked polymer effective as a water retention agent of the present invention can be obtained by polymerizing the monomer mixture (I) in the presence or absence of a crosslinking agent, and the water retention capacity of the resulting crosslinked polymer is It is preferable to carry out the polymerization in the presence of a crosslinking agent, since the water retention agent can be freely controlled and a water retention agent suitable for use in exothermic compositions can be easily obtained.

Examples of the crosslinking agent in the present invention include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, and triethylene glycol di(meth)acrylate. Methylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol di(meth)acrylate, N
, N-methylenebis(meth)acrylamide, triallyl isocyanurate, trimethylolpropane diallyl ether, etc. Compounds having two or more ethylenically unsaturated groups in one molecule; a functional group that reacts with the carboxyl group in the monomer (Bl) For example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, polyglycerin, propylene glycol, diethanolamine, triethanolamine, polypropylene glycol,
Polyhydric alcohols such as pentaerythritol, sorbitol, sorbitan, glucose, mannitol, mannitan, sucrose, glucose, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene Examples include polyepoxy compounds such as glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, trimethylolpropane triglycidyl ether, and glycerin triglycidyl ether. One or more of these can be used. When using a polyhydric alcohol as a crosslinking agent, heat treatment is preferably performed at 150 to 250°C, and when using a polyepoxy compound, heat treatment is preferably performed at 50 to 250°C during or after polymerization.

When the monomer mixture (I) is polymerized in the presence of a crosslinking agent, the amount of the crosslinking agent used is preferably in the range of 0.001 to 5.0 mo1% based on the monomer mixture (I).

5. If the amount exceeds 0 mol %, the crosslinking density of the resulting crosslinked polymer tends to become too high and the water retention capacity tends to decrease. On the contrary, O'. If the amount is less than 0.001 mol %, the crosslinking density will be too low and the crosslinked polymer will become sticky after absorbing salt water, making it difficult to mix uniformly with metal powder and other additives.

The polymerization method for obtaining the crosslinked polymer effective as a water retention agent for exothermic compositions of the present invention can be any conventionally known method, such as a method using a radical polymerization catalyst, a method using radiation/electron beams, etc.・Methods such as irradiation with ultraviolet rays etc. can be mentioned. Examples of radical polymerization catalysts include hydrogen peroxide,
Peroxides such as penzoyl peroxide and cumene hydroperoxide; azobisisobutyronitrile, 2
Examples include azo compounds such as 2'-azobis-2-amidinopropane hydrochloride; persulfates such as ammonium persulfate, potassium persulfate, and sodium persulfate. These polymerization initiators can also be used in combination of two or more,
Furthermore, it may be used as a redox initiator in combination with a reducing agent such as sulfite, L-ascorbic acid, or ferric salt.

Although the polymerization temperature varies depending on the type of catalyst used, it is preferably in the range of 20 to 100°C in order to ensure that the molecular weight of the resulting crosslinked polymer is sufficiently large and to complete the polymerization.

It is also possible to subject the monomer mixture (I) to polymerization after dissolving and diluting it in a solvent. Examples of such polymerization solvents include water, methanol, ethanol, acetone, dimethylformamide, etc., and mixtures thereof. can be used.

When using a solvent solution of monomer mixture (I), there is no particular restriction on the concentration of the solution, but considering ease of control of the polymerization reaction, yield, and economy, it is 20% by weight to saturated concentration or less. It is preferable.

Examples of the polymerization form include sorbitan fatty acid ester,
Sucrose fatty acid esters, glycerin fatty acid esters, polyglycerin fatty acid esters, cellulose esters such as ethyl cellulose and cellulose acetate, cellulose ethers, carboxyl group-containing polymers such as α-olefin-maleic anhydride copolymers, etc. are used as dispersants to make them hydrophobic. A reverse phase suspension polymerization method in which an aqueous monomer solution is dispersed in a neutral organic solvent, a casting polymerization method, a method in which a hydrogel polymer is polymerized while being fragmented by the shear force of a double-armed seconder,
Various methods such as thin film polymerization, spray polymerization, etc. can be employed.

Furthermore, in the water retention agent for exothermic compositions of the present invention, the vicinity of the surface of the crosslinked polymer obtained by polymerizing the monomer mixture (D) in the presence or absence of a crosslinking agent is further crosslinked with a hydrophilic crosslinking agent. However, a crosslinked polymer with a crosslinked density gradient introduced between the vicinity of the surface and the inside can also be used as a water retention agent.

A water retention agent obtained by further crosslinking near the surface of a crosslinked polymer has a faster initial water absorption rate than a water retention agent that is not crosslinked near the surface, so the time required for the process of absorbing salt water can be shortened.

The hydrophilic crosslinking agent used for crosslinking near the surface of the crosslinked polymer may be a hydrophilic compound containing two or more functional groups in the molecule that can react with carboxyl groups and/or carboxylate groups. , such as glycerin,
Polyhydric alcohols such as ethylene glycol and pentaerythritol; polyepoxy compounds such as ethylene glycol diglycidyl ether; polyhydric amines such as ethylenediamine, diethylenetriamine, triethylenetetraamine, tetraethylenepentamine, pentaethylenehexamine, and polyethyleneimine. ; Polyvalent aldehydes such as glutaraldehyde and glyoxal; Polyvalent metal salts such as aluminum chloride, magnesium chloride, calcium chloride, aluminum sulfate, magnesium sulfate, and calcium sulfate.

The amount of these hydrophilic crosslinking agents used is preferably in the range of 0.005 to 5% by weight based on the crosslinked polymer to be crosslinked near the surface.

Furthermore, there are no particular restrictions on the method for crosslinking near the surface of the crosslinked polymer, such as a method in which a hydrophilic crosslinking agent is mixed with the powder of the crosslinked polymer as it is or in the form of a solution, and then heated if necessary. A method may be adopted in which a hydrophilic crosslinking agent is added to a dispersion obtained by dispersing the powder in a hydrophobic organic solvent, and then heating is performed if necessary.

The composition of the exothermic composition using the water retention agent of the present invention may be conventionally known, including metal powder, various salts as reaction aids,
The main ingredients are water and a water retention agent, and it is also possible to use additives for adjusting the heat generation rate, other additives, and fillers as necessary.

The method for producing the exothermic composition using the water retention agent of the present invention may be any conventionally known method. For example, after dissolving a reaction aid or a water-soluble additive in water, this aqueous solution is mixed with the water retention agent of the present invention. An exothermic composition can be obtained by allowing the agent to absorb water, then mixing metal powder, water-insoluble additives, etc. with a water retention agent, and placing the mixture in a container as required.

(Effects of the Invention) Since the water retention agent of the present invention has sufficient water absorption and retention ability for water containing reaction aids such as salts, exothermic compositions can be prepared using the water retention agent of the present invention. For example, there is no adhesion of metal powder or the like to the surface of the water-retaining agent, and a composition with excellent fluidity can be obtained, making subsequent transportation and bagging easy.

Further, since the water retention agent of the present invention can be used in a reduced amount without affecting performance, it is possible to reduce the weight and size of products made of exothermic compositions. Moreover, since the water retention agent of the present invention does not release the saline water that has been absorbed during composition production during storage, it is possible to obtain an exothermic composition that does not deteriorate in performance even when stored for a long period of time.

(Examples) The present invention will be explained in detail below with reference to Examples, but the scope of the present invention is not limited only to these Examples.

Example 1 Internal volume 21, opening 1 60mm x 150mm
A jacketed stainless steel double-armed kneader with two sigma-type blades, 135 m deep and 70 mm in rotational diameter, was fitted with a lid, and methoxypolyethylene glycol acrylate (on average, 10 particles per molecule) was placed in the kneader. (containing ethylene oxide units), 94.0 g of sodium acrylate, 36.0++ of acrylic acid, and 0.89 g of trimethylolpropane triacrylate were dissolved in 480 g of ion-exchanged water to prepare an aqueous monomer solution with a monomer concentration of 50%. Nitrogen gas was blown into this aqueous monomer solution to drive out oxygen dissolved in the aqueous solution.

Then, two sigma type vanes were placed at 67 and 56 respectively.
0.5 g of ammonium persulfate and 0.025 g of L-ascorbic acid were added as polymerization initiators while rotating at a speed of +pm and heating by passing hot water at 80° C. through the jacket. Polymerization started 20 minutes after adding the polymerization initiator. 60 minutes after adding the polymerization initiator, the temperature inside the reaction system was 9.
The temperature reached 1°C, and the produced hydrogel polymer was finely divided into fine particles with a diameter of about 3 mm. After 90 minutes of continued stirring and initiation of polymerization, the lid was removed and the hydrogel polymer was taken out.

The obtained hydrogel polymer was spread on a 50-mesh wire gauze and dried with hot air at a temperature of 150° C. for 2 hours. The water retention agent (1) of the present invention was obtained by pulverizing this dried product using a vibration mill.

Comparative Example 1 Sodium acrylate 30 was added to the same secondary as in Example 1.
5.3 g, acrylic acid 77.9 g and trimethylolpropane triacrylate l. 28g of ion-exchanged water 5
A monomer aqueous solution having a monomer concentration of 40% was prepared by dissolving 74.1 g of the monomer. Nitrogen gas was blown into this aqueous monomer solution to drive out oxygen dissolved in the aqueous solution.

Then the two sigma type vanes are 67 and 5, respectively.
While rotating at a speed of 6 rpm and heating 40° C. hot water through the jacket, 0.5 g of ammonium peroxide and 0.025 g of L-ascorbic acid were added as polymerization initiators. Polymerization started 3 minutes after the addition of the polymerization initiator. 15 minutes after the addition of the polymerization initiator, the temperature in the reaction system reached 95° C., and the produced hydrogel polymer had been subdivided into small pieces with a diameter of about 3 degrees. After 90 minutes of continued stirring and initiation of polymerization, the lid was removed and the hydrogel polymer was taken out.

The obtained hydrogel polymer was dried and crushed in the same manner as in Example 1 to obtain a comparative water retention agent (1).

Example 2 ↓g of the water retention agent (1) of the present invention obtained in Example 1 was made to absorb 20g of 3% by weight saline solution, and 40g of iron powder and 8g of activated carbon were added.
g to prepare exothermic composition (1). During this preparation, iron powder and activated carbon were not attached to the water retaining agent and could be mixed uniformly, and the obtained exothermic composite (1) had good fluidity.

Comparative Example 2 A comparative exothermic composition (1
) was prepared. However, 3 of comparative water retention agent (1)
Because the water absorption capacity for the wt% saline solution was insufficient, the water retention agent was found to be sticky after absorbing the saline solution, and when mixed with iron powder and activated carbon, these adhered to the water retention agent and formed a lump-like shape.

Claims (1)

[Claims] 1. General formula ▲ Numerical formulas, chemical formulas, tables, etc.
An oxyalkylene group having 2 to 4 carbon atoms, which is the above,
Y is an oxyalkylphenyl group having 1 to 3 substituents of a hydroxyl group, an alkoxy group having 1 to 5 carbon atoms, a phenoxy group, or an alkyl group having 1 to 9 carbon atoms;
n is a number from 3 to 100 on average. ) A (meth)acrylic acid ester monomer (A
) 20 to 80% by weight of a carboxyl group-containing water-soluble unsaturated monomer (B) and 20 to 80% by weight of a monomer mixture (I) in the presence or absence of a crosslinking agent. A water retention agent for exothermic compositions comprising a crosslinked polymer.