JPH0144745B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to improved exothermic compositions. Many heat-generating compositions have been known in the past, some of which are commercially available as so-called disposable hand warmers. These exothermic compositions usually generate heat through a chemical reaction caused by mixing metal powder, carbon material, water and oxygen. As a commercially available disposable pocket warmer, before use, the three components, metal powder, water, and carbon material, are separated by a partition that prevents either the metal powder or the water from coming into contact with the other two components, and an oxygen-permeable material is used. A mixture of metal powder, carbon material, and water is placed in an inner bag with good oxygen permeability. There is a method in which the mixture is packaged in an air-impermeable outer bag and the outer bag is removed when the mixture is used, thereby bringing the mixture into contact with air and generating heat. In the former case, a partition must be placed between the metal powder or water and the remaining two components and the two components must be packed in separate bags, making packing the bag cumbersome, and the bag itself may tear when the partition is torn during use. However, many of the latter types are commercially available because they are easy to operate during bagging and use. However, in the latter case, hydrogen gas is generated during storage, causing the outer bag to swell and reduce the product value. It is impossible to avoid long-term storage due to the intrusion of foreign substances. In view of the above-mentioned drawbacks, the present inventors have conducted various studies on compositions that generate heat when in contact with oxygen, which are easy to operate during bagging and use, and have found that if a carbon material with low surface oxide is used, hydrogen will be generated. It was found that a heat-generating composition that can be stored for a long time without any heat generation can be obtained. That is, the present invention provides a composition containing metal powder, a carbon material, and water that generates heat upon contact with oxygen,
A heat-generating composition characterized by using a carbon material whose surface oxide per 100 g (according to the surface oxide measuring method using barium hydroxide from B.R. Puri) is 30 milliequivalent or less. It is a thing. The metal powder may be any metal powder used as a heat-generating metal powder in known heat-generating compositions, but iron powder is most preferred. The carbon materials used in the present invention include raw ash obtained by carbonizing sawdust, coke made from caking coal, char made from lignite, carbonized coconut shells, carbonized wood bark, and activated carbon obtained by further activating these. The surface oxide measured by B.R. Puri's surface oxide measurement method is 30 milliequivalent or less per 100 g of carbon material. B.R. Puri's surface oxide measurement method using barium hydroxide is
“Carbon Vol.1, No.1 (October 1963),
"Page 458, left column, lines 26 to 45"
Vacuum dry it below and crush it in a mortar. This 05g
Transfer to a 250 ml Erlenmeyer flask, add 100 ml of 0.2N barium hydroxide aqueous solution, seal tightly, and react at 60°C for 72 hours. After the reaction is complete, take 25 ml of the supernatant liquid, perform back titration with 0.2N hydrochloric acid using methyl red as an indicator, and calculate the surface oxide from the difference from the blank test. Surface oxide per 100g of carbon material (milliequivalent) = 160 x [Blank test titration number (ml) - Titration number (ml)] x 0.2N hydrochloric acid factor If the above surface oxide is more than the specified amount, use this When used as a heat-generating composition, hydrogen gas is generated and it cannot be stored in an airtight state for a long period of time. The carbon material with a low surface oxide used in the present invention is, for example, a normal carbon material with a high surface oxide (usually carbon material has an amount of 100 to 500 milliequivalents per 100 g of carbon material (oxygen content of 2 to 15% by weight according to elemental analysis). )
[having a certain degree of surface oxide] in the absence of oxygen at 600-1200°C for about 1 hour, and then cooling in the absence of oxygen. Conditions in which oxygen does not exist may be achieved by replacing the air by blowing in an inert gas such as nitrogen, helium, or argon, or a reducing gas such as hydrogen. The heat generating composition of the present invention can be obtained by mixing the carbon material with low surface oxide, metal powder, and water. These may be mixed in any order and the proportions of each component may be the same as conventional ones, but usually 100 parts by weight of metal powder, 20 to 300 parts by weight of water, preferably 50 to 150 parts by weight, and charcoal. Materials range from 1 to 300
Parts by weight, preferably 5 to 100 parts by weight. In the composition of the present invention, it is sufficient that the carbon material is mixed in an amount sufficient to retain water, but if the amount of carbon material is not sufficient to retain water, it is necessary to mix the carbon material in an amount sufficient to retain water. It is best to mix it with a water retention agent. If necessary, reaction aids such as sodium chloride, potassium chloride, magnesium chloride, iron chloride, copper chloride, iron oxide, sodium sulfate, potassium sulfate, magnesium sulfate, iron sulfate, and copper sulfate may also be included. Since the composition of the present invention generates heat when it comes into contact with oxygen, it is usually stored in an oxygen-permeable inner bag and then in an air-impermeable outer bag. When the outer bag is removed during use and exposed to air, it begins to generate heat. The heat-generating composition of the present invention does not generate hydrogen gas by using a carbon material with less surface oxide.
It can be stored in a bag with extremely low oxygen permeability and can be stored for a long period of time. EXAMPLES The present invention will be described in more detail with reference to Examples below. Example 1 A quartz tube with an inner diameter of 3 cm is filled with 100 ml of carbon material, and the front and back of the tube are covered with quartz wool. The air is cut off and the tube is placed in an electric furnace, but a gas that does not contain oxygen atoms is passed through one end of the quartz tube at a rate of 150 ml/min, and the other end is heated to 950℃ while being exhausted into a draft.
After heating for a period of time, the quartz tube is taken out from the electric ring furnace, cooled to room temperature, and then the carbon material is taken out. Type of carbon material, circulating gas, amount of surface oxide (beam)
(according to R. Puri's measurement method) are as shown in Table 1.

[Table] Using carbon materials (1) to (5) prepared by the above method and using untreated carbon material as a control,
A sample is prepared by mixing parts by weight, 25 parts by weight of carbon material, and 25 parts by weight of 5% sodium chloride solution while excluding air. Regarding these samples, gas generation and calorific value were investigated using the following test methods. The results are shown in Table 2. (Measurement method for gas generation) Measure 50g of sample using a 4-layer laminate film with extremely low gas permeability.Dimensions of effective part width 9cm x length
Fill a 12cm square flat bag and heat seal it. The 4-layer laminate film used was
PVDC2.5μ/PE10μ/PVDC2.5μ/PE60μ Oxygen permeability <0.5cc/m ²・24hrs.atm.Water vapor permeability 3
g/ ^m2 . 24hrs. was used. The sealed bag containing the sample was stored at 37°C for 20 days to accelerate gas generation, and the presence or absence of swelling in the bag was examined. (Method for measuring exothermic properties) Approximately 0.15 g of the sample is filled into a 2 ml powder ampoule with the air removed, and then sealed. This ampoule is set in a microcalorimeter (Model CM204S ₁ ) manufactured by Applied Electric Research Institute Co., Ltd. in a constant temperature room at 37°C, the ampoule is crushed, the sample is brought into contact with air, and the amount of heat generated is measured. The amount of heat generated within 24 hours is expressed per 50g of sample.

【table】

[Table] Example 2 Sample ~ prepared in Example 1 was placed in a non-woven polyethylene laminate perforated bag (effective inner dimensions width 8cm
After filling 50g of each in 10cm) and heat sealing,
Place in a laminated outer bag and seal. After 90 days had elapsed, the outer bag was removed and the products were used as body warmers, and each product provided a comfortable feeling of use for more than 12 hours.

Claims (1)

[Scope of Claims] 1. In a composition containing metal powder, carbon material, and water that generates heat upon contact with oxygen, the surface oxide per 100 g [barium hydroxide from B.R. Puri] Based on the surface oxide measurement method using
1. A heat-generating composition characterized by using a carbon material having a carbon content of 30 milliequivalents or less.