JPH0124195B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to improvements in exothermic agents that generate heat in the presence of air. More specifically, the present invention relates to a heat generating agent in which hydrogen generation is substantially suppressed by adding at least two kinds of hydrogen suppressants to the iron-based heat generating agent. Recently, research on iron-based exothermic agents that generate heat upon contact with air has been actively conducted, and there are two types of exothermic agents used as exothermic agents. one of them
One is to fill an inner bag with a mixture of iron powder, a reaction aid, a water retention agent, and water, and when it is used, the outer bag is torn open and brought into contact with air to generate heat. The other method is to mix and store iron powder, a reaction aid, and a water retaining agent, and then, when used, mix this with water and bring it into contact with air to generate heat. However, in the former case, hydrogen is generated during storage, and the hydrogen concentration gradually increases, so that the outer bag expands during long-term storage, creating a risk of the outer bag bursting, catching fire, or exploding. On the other hand, the latter method does not pose the risk of hydrogen generation during storage, but has disadvantages such as a complicated filling structure, which makes it impossible to increase the production rate and increases costs. For this reason, phosphates, thiosulfates, and sulfites (Japanese Patent Application Laid-Open Nos. 55-52377 and 55-56180) have been used alone as hydrogen inhibitors for the former, but none of them suppress hydrogen. The effect was insufficient, and from the viewpoint of long-term storage of the heating element, it did not completely eliminate the dangers such as bursting of the outer bag, ignition, and explosion. Moreover, even if such a situation does not occur, the outer bag expands, which impairs the commercial value of the heating element. Furthermore, in order to increase the hydrogen suppression effect, it is necessary to increase the basicity of the exothermic agent by using a strong basic substance such as sodium hydroxide or potassium hydroxide instead of the above-mentioned salt, and this exothermic agent can be used as a body warmer. When used, there is a danger to the human body due to strong basic substances seeping out from the inner bag of the heating element. In order to overcome the above-mentioned drawbacks and create a heating element that is safe and has commercial value, the inventors of the present invention have conducted intensive studies and found that a group consisting of an oxidizing agent, an alkaline substance, sulfur, antimony, selenium, phosphorus, and tellurium has been developed. The present invention has been completed by discovering that by adding at least two selected hydrogen inhibitors to an iron-based exothermic agent, the synergistic effect results in hydrogen generation being suppressed to a degree that could not be achieved by adding them alone. I came to the conclusion. As is well known, iron-based exothermic agents utilize the oxidation reaction of iron. The oxidation reaction is explained as follows. That is, at the anode part of the iron surface undergoing oxidation, Fe→Fe ²⁺ +2e (1) at the cathode part, 2H ⁺ +2e→H ₂ (2) 2H ₂ O+2e→H ₂ +2OH ^- (3) or The reaction H ₂ O + 1/2O ₂ + 2e→2OH ^- (4) is occurring. The ferrous ion Fe ²⁺ generated at the anode further forms an oxide through the following reaction. Fe ²⁺ +2OH ^- →Fe(OH) ₂ (5) 2Fe(OH) ₂ +1/2O ₂ →Fe ₂ O ₃ +2H ₂ O (6) In this way, since hydrogen is generated at the cathode, the heating element As such, the amount of hydrogen generated cannot be ignored, and there is an urgent need to suppress it. Therefore, as a method to suppress this hydrogen generation, () aluminum, magnesium,
Suppress the reaction (1) by contacting an amphoteric metal such as zinc. () Increasing PH and inhibiting reactions (2), (3), and (4). () Passivates iron to suppress reactions (5) and (6). There are three possible methods. Furthermore, () the generated hydrogen is removed. There are other possible methods. In the method (), hydrogen is likely to be generated depending on the PH range of the exothermic agent. Therefore, as a countermeasure against hydrogen accumulating in the outer bag of the heating element, (), (), ()
Possible methods are: For this reason, in the present invention, hydrogen is suppressed by adding at least two hydrogen suppressants selected from the group consisting of alkaline substances, oxidizing agents, sulfur, antimony, selenium, phosphorus, and tellurium to the iron-based exothermic agent. It is something. The present invention will be explained below. The present invention can be applied to any developing agent containing iron powder, a reaction aid, a water retention agent, and water, and will be specifically explained as follows. That is, the iron powder is powdered or granular electrolytic iron, reduced iron, cast iron, etc., and among these, iron powder with a high graphite content is preferable. Iron powder with a high graphite content should have a graphite content of 0.5% or more, preferably 1.7%.
Examples of the cast irons mentioned above include gray cast iron and malleable cast iron. Examples of reaction aids include sodium chloride, sodium sulfate, potassium sulfate, ferrous sulfate, and ferric sulfate. Water retention agents include activated carbon, sawdust charcoal, charcoal, silica gel, and alumina powder. In addition, the oxidizing agent of the present invention includes nitrates, nitrites, oxides, peroxides, oxyhalides,
There are permanganates, chromates, e.g.
NaNo ₃ , KNO ₃ , NaNO ₂ , KNO ₃ , CuO,
_MnO2 , _H2O2 , NaClO, _NaClO3 , _{NaClO4 ,}
Examples include NaMnO ₄ , KMnO ₄ , Na ₂ CrO ₄ , K ₂ CrO ₄ and the like. Alkaline substances include silicates,
There are borates, diphosphates, tertiary phosphates, sulfites, thiosulfates, carbonates, and bicarbonates, such as Na ₂ SiO ₃ , Na ₄ SiO ₄ , NaBO ₂ , Na ₂ B ₄ O ₇ ,
KBO ₂ , Na ₂ HPO ₄ , Na ₂ SO ₃ , K ₂ SO ₃ ,
Examples include weak alkali salts such as Na ₂ S ₂ O ₃ , Na ₂ CO ₃ and NaHCO ₃ . In the present invention, two or more hydrogen inhibitors are used in combination, and preferred combinations include the following. That is, weak alkali salt - weak alkali salt; Na ₂ SO ₃ −Na ₂ SiO ₃ , Na ₂ SO ₃ −
Na ₂ S ₂ O ₃ , Na ₂ SO ₃ −Na ₂ B ₄ O ₇ , Na ₂ B ₄ O ₇ −
Na ₃ PO ₄ , Na ₂ CO ₃ −NaHCO ₃ −Na ₂ SO ₃ , oxidizing agent – weak alkali salt; NaNO ₂ −Na ₂ SiO ₃ , NaNO ₂
−Na ₂ HPO ₄ , NaNO ₂ −Na ₂ SO ₃ , NaNO ₂ −
Na ₂ S ₂ O ₃ , NaNO ₃ −Na ₂ SiO ₃ , NaNO ₃ −
Na ₂ HPO ₄ , NaNO ₃ −Na ₂ SO ₃ , NaNO ₃ −
Na ₂ S ₂ O ₃ , MnO ₂ −Na ₂ SiO ₃ , MnO ₂ −
Na ₂ HPO ₄ , MnO ₂ −Na ₂ S ₂ O ₃ , NaClO−
Na ₂ SiO ₃ , NaClO−Na ₂ HPO ₄ , NaClO−
Na ₂ SO ₃ , KMnO ₄ −Na ₂ SiO ₃ , KMnO ₄ −
Na ₂ HPO ₄ , KMnO ₄ -Na ₂ SO ₃ , sulfur-alkali weak acid salt; S-Na ₂ SiO ₃ , S-Na ₂ HPO ₄ , S-
It is a combination of Na ₂ SO ₃ and S-Na ₂ S ₂ O ₃ . The amount of hydrogen inhibitor used is 0.05 to 12.0% by weight, preferably 0.5 to 12.0% by weight of the iron powder, in total amount of each hydrogen inhibitor.
It is 2.0% by weight. If it is less than 0.05% by weight, the effect of suppressing hydrogen generation is poor, while if it exceeds 12.0% by weight, although there is an effect of suppressing hydrogen generation, the exothermic temperature decreases, which is not appropriate. The method of adding it is as follows:
From the viewpoint of workability and uniformity of mixing, it is preferable to add it as an aqueous solution, but even if it is added as a solid separately from water, the hydrogen suppression effect is almost the same as in the case of an aqueous solution. However, since oxidizing agents such as peroxides and oxyhalides cause catalytic decomposition when added to exothermic agents, it is better to suppress hydrogen by immersing iron powder in an aqueous solution of the oxidizing agent in advance. effective. Regarding nitrites and nitrates,
When added to exothermic agents, ammonia gas may be generated. Therefore, it is easier to remove the ammonia odor by soaking the iron powder in an aqueous solution of nitrites and nitrates and then neutralizing it.
It is more preferable to add it. As described above, the present invention has an extremely excellent hydrogen generation suppressing effect due to the synergistic effect of using two or more hydrogen suppressants. This will be explained based on Examples and Comparative Examples described later. That is, when a single hydrogen inhibitor is added (for example, Comparative Examples 1, 2, 3, and 4), the hydrogen concentration in a forced test at 50°C for 7 days is set to 100 when no hydrogen inhibitor is added. Concentrations range from 40 to 80. On the other hand, in the case of addition of two or more hydrogen inhibitors (Examples 1 and 2 corresponding to the above comparative example), the hydrogen concentration in the forced test at 50°C for 10 days is 100 compared to that without the addition of hydrogen inhibitors. So it's only about 10. As described above, the present invention has an effect of suppressing hydrogen generation four times or more compared to the case where a single hydrogen inhibitor is added. Therefore, a mixture of iron powder, a reaction aid, a water retention agent, a water-based exothermic agent, and a hydrogen suppressant was filled into a breathable inner bag, and the inner bag was then placed in a non-breathable bag. When enclosed in an outer bag and used as a heating element, the present invention produces the following effects. (1) Since hydrogen can be suppressed, there is almost no risk of rupture of the outer bag of the heating element, ignition, explosion, etc. due to expansion of the outer bag of the heating element, and long-term storage of the heating element is possible. (2) Since the mechanism for filling the inner bag is simple, high-speed filling is possible using a general-purpose automatic bag making and filling machine. Furthermore, the exothermic performance of the exothermic agent of the present invention is hardly impaired compared to the case where no hydrogen inhibitor is added. The present invention will be specifically explained below with reference to Examples.
The present invention is not limited to these. Examples 1 to 6 and Comparative Examples 1 to 9 135 g of iron powder, 20 g of activated carbon, 40 g of water retention agent, 12 g of reaction aid, 50 g of water, and various hydrogen inhibitors shown in Table 1 were mixed to make an inner bag nonwoven fabric. Fill and seal the effective part of (paper) with dimensions of 8 x 12 cm. Then fill and seal the inner bag into the non-breathable outer bag.
Seal to obtain a heating element. This heating element is subjected to a forced test in a 50℃ thermostat, and the hydrogen concentration (vol%) in the outer bag is analyzed using a gas chromatograph. Table 1 shows the ratio of hydrogen concentration in each Example and Comparative Example, with the case without hydrogen inhibitor added as 100 (the same applies to the following Examples and Comparative Examples).

【table】

[Table] Examples 7 to 9 and Comparative Examples 10 to 13 After immersing 135 g of iron powder in 200 ml of 6% NaOCl solution for 10 minutes, filtering and drying at 25°C for 72 hours.
Obtain NaOCl-treated iron powder. This treated iron powder is used instead of the iron powder in Examples 1 to 6, and sulfur is added in Example 7, selenium is added in Example 8, and sodium sulfite is added as a hydrogen suppressant in Example 9. Thereafter, a heating element was prepared, a forced test, and an analysis was performed in the same manner as in Examples 1 to 6. The results are shown in Table-2.
For comparison, Table 2 also shows the results when sulfur, selenium, sodium sulfite, and NaOCl were used alone.

[Table] Examples 10 to 11 and Comparative Example 14 After immersing 135 g of iron powder in 200 ml of 5% NaNO ₂ solution for 10 minutes, filtering and drying at 25°C for 72 hours, the iron powder was soaked in N-H ₂ SO ₄ solution. Adjust the pH to 7 and wash with water at 50℃.
Use iron powder that has been dried for 24 hours. For mixing, the above-mentioned treated iron powder was used instead of the iron powder of Examples 1 to 6, and sulfur was used in Example 10, and Na ₂ SO ₃ was mixed in Example 11.
is added as a hydrogen inhibitor. Thereafter, a heating element was prepared, a forced test, and an analysis was performed in the same manner as in Examples 1 to 6. The results are shown in Table-3.

【table】

Claims (1)

[Scope of Claims] 1. An exothermic agent containing iron powder, a reaction aid, a water retention agent, and water, and at least two selected from the group consisting of an oxidizing agent, an alkaline substance, sulfur, antimony, selenium, phosphorus, and tellurium. An exothermic agent characterized by containing a hydrogen inhibitor. 2. The exothermic agent according to claim 1, wherein the oxidizing agent is a nitrite, a nitrate, an oxide, a peroxide, a permanganate, a chromate, or an oxyhalide salt. 3. The exothermic agent according to claim 1, wherein the alkaline substance is a silicate, borate, sulfite, dibasic phosphate, tertiary phosphate, or thiosulfate. 4. The exothermic agent according to claim 1, wherein the iron powder is previously treated with an oxidizing agent (excluding oxides), and the other hydrogen inhibitor is at least one hydrogen inhibitor other than the oxidizing agent.