JPH0240714B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to improvements in exothermic compositions that generate heat in the presence of oxygen or air. For details, see metal powder, water,
The present invention relates to a heat-generating composition that suppresses hydrogen generation in a heat-generating composition containing a water retention agent and a reaction aid as main components. In recent years, research has been actively conducted on heat-generating compositions that utilize the heat of oxidation of metals in the presence of oxygen or air, and include metal powder, water, water retention agents, and reaction aids as main components. It does not require an ignition source when used, it controls the temperature when it generates heat, and the mounting structure has been improved and devised. Consumers have praised the comfort of the product as it fits well on various parts of the body, and it has come to be widely used as a body warmer for sports, leisure, and various medical purposes. However, metal powder, water, water retention agent, and reaction aid are uniformly mixed in advance and filled into a breathable inner bag.
Conventionally, heating elements housed in non-breathable outer bags have had disadvantages such as expansion of the outer bag due to generation of hydrogen during storage and risk of ignition and explosion due to leakage of hydrogen. In other words, since the metal powder is in contact with water over a wide area from the time it is manufactured until it is used, a corrosion reaction of the metal occurs, albeit slowly, and hydrogen is generated even if there is no contact with oxygen. However, as a result, the outer bag expands with hydrogen gas, which is extremely dangerous. Furthermore, when an alkali metal halide or the like is present as a reaction aid, the reaction may be further accelerated. One way to avoid the dangers caused by hydrogen generation is to store the metal powder and water separately to prevent them from coming into contact with each other before use (two-component type).
However, it requires mixing before use, which is troublesome. Therefore, it has become necessary to suppress hydrogen generation using a one-component mixture of metal powder, water, reaction aid, etc. Conventionally, a mixed powder of fibrous, carbonaceous, etc. is impregnated with an aqueous solution of a 005 to 1 normal alkali or a weak acid salt of an alkali and an appropriate amount of neutral salts, and an appropriate amount of iron powder is mixed with this. Occurrence suppressed 1
There is a method of manufacturing component type
52377). However, this method also generates a considerable amount of hydrogen even at room temperature, and an even larger amount of hydrogen is generated at 50° C., so it is difficult to say that this is a sufficient method. As a result of intensive research into the above-mentioned one-component exothermic composition with low hydrogen generation, the present inventors found that
The exothermic composition has a metal sulfide or an unsaturated bond in a composition that combines one or more alkalis and one or more weak alkali salts, or one or more alkalis and one or more weak alkali salts. By containing a combination of alcohols, we succeeded in suppressing the amount of hydrogen generation to virtually nothing. The present invention can be easily applied to any exothermic composition whose main components are metal powder, water, a water retention agent, and a reaction aid, but the exothermic composition will be specifically explained below. do. Examples of the metal powder include powdered or granulated iron, zinc, aluminum, tin, etc., and iron powder is particularly preferred. As the iron powder, any of crushed iron powder, reduced iron powder, electrolytic iron powder, and atomized iron powder can be used. Examples of reaction aids include sodium chloride, potassium chloride, calcium chloride, ferrous chloride, ferric chloride, magnesium chloride, aluminum chloride,
Metal halides such as cuprous chloride, cupric chloride, ferrous bromide, and ferric bromide; metal sulfates such as sodium sulfate, potassium sulfate, ferrous sulfate, ferric sulfate, and magnesium sulfate. However, for practical purposes, sodium chloride is preferably used. As the water-retaining agent, activated carbon, wood flour, raw ash, perlite, vermiculite, pumice powder, water-absorbing polymer, silica gel, etc. can be used alone or in combination. Examples of alkalis include hydroxides of alkali metals and alkaline earth metals, specifically sodium hydroxide, potassium hydroxide, barium hydroxide, etc., and weak alkali salts include carbonates, hydrogen carbonates, and sulfites. , phosphates, monohydrogen phosphates, dihydrogen phosphates, polyphosphates, thiosulfates, borates, metaborates, tetraborates and organic acid salts,
Specifically, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, sodium metaborate, sodium tetraborate decahydrate (borax), sodium sulfite, disodium phosphate, sodium phosphate, monopotassium phosphate, phosphorus. acid dipotassium, N,
These include sodium N-dimethylglycine, sodium diethylbarbiturate, sodium pivalate, and sodium sorbate. A preferred combination of an alkali and a weak alkali salt is a combination of an alkali metal hydroxide, phosphoric acid, and monohydrogen phosphate. The total amount of these alkalis and weak alkali salts is based on 100 parts of iron powder used in exothermic compositions.
0.03 to 5 parts, preferably 0.05 to 3 parts. Metal sulfides include sodium sulfide, potassium sulfide, sodium polysulfide, sodium hydrosulfide,
Inorganic metal sulfides such as potassium hydrosulfide and calcium sulfide, used in an amount of 0.2 to 5 parts per 100 parts of iron powder.
parts, preferably 0.4 to 3 parts. Examples of alcohols having unsaturated bonds include propargyl alcohol, butynediol, butenediol, and sorbyl alcohol having 3 to 6 carbon atoms. The amount used is 0.2 to 5 parts, preferably 0.4 to 3 parts, per 100 parts of iron powder. The hydrogen inhibitor described above can be easily added to the exothermic composition by adding it together with the reaction aid in the form of an aqueous solution or suspension in water, but it may be added separately as long as it is in the above proportion. Now, the effects of adding the hydrogen suppressant of the present invention are compared with a conventional single-component hydrogen suppressant based on a few examples from the examples.

[Method of measuring hydrogen generation amount]

The heat-generating composition is filled into an inner bag having ventilation holes, and is housed in an aluminum foil outer bag laminated with polyethylene film. After the air in this aluminum foil outer bag was almost completely sucked out using an aspirator, 100 ml of nitrogen gas was sealed and the bag was left at room temperature (20° C.) and in a 50° C. incubator for 300 to 500 hours. Thereafter, the gas in the bag was sampled, and the amount of hydrogen generated from the exothermic composition was measured by gas chromatography analysis. [Method for measuring heat generation performance] A breathable inner bag is filled with the specified heat generation composition, and after being left in a non-breathable outer bag overnight, the heat generation performance is measured using a temperature recorder with a platinum resistance thermometer. did.

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Claims (1)

[Claims] 1. In an exothermic composition that contains metal powder, water, a water retention agent, a reaction aid, an alkali and a weak alkali acid salt and generates heat in the presence of air, the total content of the alkali and the weak alkali acid salt is For 100 parts by weight of metal powder
A heat-generating composition characterized in that the amount is 1.5 parts or less and a weak alkali salt is contained in a larger amount than the alkali. 2. The exothermic composition according to claim 1, wherein the metal powder is iron powder. 3 Alkali and alkali weak acid salts are hydroxides and carbonates, bicarbonates, sulfites, monohydrogen phosphates, dihydrogen phosphates, phosphates, and polyphosphates of alkali metals or alkaline earth metals, respectively. , thiosulfate, borate, metaborate, tetraborate or organic acid salt.
Or the exothermic composition according to item 2. 4 Claim 3 in which the alkali is an alkali metal hydroxide and the alkali weak acid salt is an alkali metal monohydrogen phosphate and an alkali metal phosphate.
The exothermic composition described in Section 1. 5 Claims 1, 2, and 3 in which the alkali content is 0.1 part or less based on 100 parts by weight of metal powder.
Or the exothermic composition according to item 4.