Self-heating material and preparation method and application thereof

Abstract

The invention discloses a self-heating material and a preparation method and application thereof, and relates to the field of self-heating products. The self-heating material comprises the following raw materials in parts by weight: 38-41 parts of iron powder, 9-11 parts of activated carbon, 12-15 parts of silane modified diatomite, 3-4 parts of super absorbent resin, 1.0-1.5 parts of sodium chloride and 30-35 parts of water. The super absorbent resin is prepared from the following raw materials: acrylic acid, acrylamide, a cross-linking agent, diatomite, white carbon black and an initiator. The self-heating material has the heating effects of quick start and long-term endurance, the material is prevented from being thick and heavy, and the wearing comfort of the product is improved.

Description

Technical Field

[0001] This application relates to the field of self-heating products, and in particular to a self-heating material, its preparation method, and its application. Background Technology

[0002] Self-heating products that utilize the energy released by the oxidation reaction of iron powder to generate heat are widely used in daily life, including hand warmers, foot warmers, IV drip warmers, and moxibustion patches. Their reaction principle is based on the corrosion of iron in humid air through oxygen absorption. The "rapid start-up" and "long-lasting power" of self-heating products are key to their effectiveness.

[0003] Existing self-heating materials are made from raw materials including iron powder, activated carbon, water, superabsorbent resin, and sodium chloride. These materials either prioritize "rapid start-up" but suffer from shortened battery life, or while offering slightly longer battery life, they suffer from slow start-up, making it difficult to simultaneously meet the dual requirements of "rapid start-up" and "long-lasting battery life." Furthermore, traditional self-heating materials often use vermiculite as a filler; however, vermiculite has a high density and strong compaction properties, resulting in heavy products and poor wearing comfort. Summary of the Invention

[0004] The main purpose of this application is to propose a self-heating material, its preparation method and application, which aims to solve the problems that existing self-heating materials cannot simultaneously achieve "quick start-up" and "long-lasting operation", as well as the poor comfort caused by their weight.

[0005] In the first aspect, the self-heating material provided in this application comprises the following raw materials in weight fractions: 38-41 parts iron powder, 9-11 parts activated carbon, 12-15 parts silane-modified diatomaceous earth, 3-4 parts superabsorbent resin, 1.0-1.5 parts sodium chloride, and 30-35 parts water. The raw materials for preparing the superabsorbent resin include acrylic acid, acrylamide, crosslinking agent, diatomaceous earth, silica, and initiator, and the weight ratio of acrylic acid, acrylamide, crosslinking agent, diatomaceous earth, silica, and initiator is (35-45):(30-35):(0.005-0.015):(15-25):(5-15):(0.10-0.15). The iron powder includes iron powder with a particle size of 60-100 mesh and iron powder with a particle size of 500-1000 mesh.

[0006] By adopting the above technical solution, an organic-inorganic composite network structure is formed using acrylic acid, acrylamide, diatomaceous earth, and precipitated silica. Diatomaceous earth and precipitated silica form the network nodes, resulting in a superabsorbent resin with a moderate degree of crosslinking. The prepared superabsorbent resin can effectively balance water absorption performance and oxygen permeability rate. While ensuring excellent water absorption performance, it also avoids the problems of uncontrollable heating or unstable heat generation caused by excessively fast or slow oxygen permeability rates during use. Furthermore, this superabsorbent resin also helps to disperse other raw materials more uniformly and stably, ensuring that each component plays a more complete role.

[0007] The superabsorbent resin ensures a suitable oxygen permeation rate during use. Fine iron powder with smaller particle size has a higher specific surface area, which helps accelerate the initial reaction. With a suitable oxygen permeation rate, a rapid start-up effect is achieved, effectively shortening the time required for the material to reach its heating temperature of 40℃ from room temperature. Conversely, coarser iron powder with larger particle size has a slower reaction rate, helping to maintain sustained operation in the later stages, effectively extending the time the heating temperature remains above 40℃. Furthermore, silane-modified diatomaceous earth, as a functional component for heat preservation, water absorption, and water release, also plays a crucial role in both "rapid start-up" and "long-lasting operation." Silane-modified diatomaceous earth adjusts the hydrophilicity of diatomaceous earth, effectively preventing excessive water adsorption during the initial heating stage, which would lead to a slow reaction, affecting the rapid start-up effect and causing uneven local heating. Moreover, silane-modified diatomaceous earth retains a relatively large number of pores in diatomaceous earth, maintaining a suitable amount of water for stable later reactions, achieving a dynamic balance between water adsorption and reactivity.

[0008] In this application's technical solution, under the guarantee of a suitable oxygen permeability rate of the superabsorbent resin and the dynamic balance of effective moisture adsorption and reactivity of silane-modified diatomaceous earth, the appropriately proportioned coarse and fine iron powder can achieve a heating effect of "rapid start-up" and "long-lasting operation." The superabsorbent resin, silane-modified diatomaceous earth, and coarse and fine iron powder work together to achieve this heating effect. Furthermore, this application uses lightweight diatomaceous earth as a filler, effectively achieving a lightweight heating material, avoiding material bulkiness, and improving the product's wearing comfort.

[0009] Optionally, the weight ratio of the silane-modified diatomaceous earth to the superabsorbent resin is (13-14):(3.3-3.6).

[0010] By adopting the above technical solution and controlling the ratio of silane-modified diatomaceous earth to superabsorbent resin, the two can be stably and synergistically promoted. With the superabsorbent resin having a suitable oxygen permeability rate and the silane-modified diatomaceous earth having a dynamic balance between effective water adsorption and reactivity, the iron powder with the appropriate ratio of coarse to fine particles can achieve the heating effect of "rapid start-up" and "long-lasting operation".

[0011] Optionally, in the superabsorbent resin, the weight ratio of diatomaceous earth to silica is (20-25):(5-10).

[0012] By adopting the above technical solution and controlling the ratio of diatomaceous earth to silica, the oxygen permeability rate of the obtained superabsorbent resin can be effectively guaranteed.

[0013] Optionally, the method for preparing the superabsorbent resin includes the following steps: (1) Provide acrylic acid, place the acrylic acid in a constant temperature water bath at 0°C, and add sodium hydroxide solution dropwise to the acrylic acid under stirring until the pH value is 5-6 to obtain the first mixture; (2) Add acrylamide, crosslinking agent, diatomaceous earth and fumed silica to the first mixture obtained in step (1), stir and ultrasonically disperse to obtain the second mixture; (3) Add the initiator to the second mixture obtained in step (2), stir, and place it in a vacuum drying oven at 70-95°C to react. Dry and pulverize the product obtained from the reaction to obtain the superabsorbent resin.

[0014] By adopting the above technical solution, an organic-inorganic composite network structure is formed using acrylic acid, acrylamide, diatomaceous earth, and precipitated silica, with diatomaceous earth and precipitated silica forming network nodes, resulting in a superabsorbent resin with a suitable degree of crosslinking. The prepared superabsorbent resin can effectively balance water absorption performance and oxygen permeability.

[0015] Optionally, the preparation method of the silane-modified diatomaceous earth includes the following steps: Step 1: Dry the diatomaceous earth to obtain pretreated diatomaceous earth; Step 2: Dissolve the silane coupling agent in ethanol to obtain a silane coupling agent solution; Step 3: Place the diatomaceous earth pretreated in Step 1 into a constant temperature water bath at 70-95°C. Under stirring, add the silane coupling agent solution obtained in Step 2 to the pretreated diatomaceous earth, stir and react, and then separate the solid and liquid products and dry them to obtain the silane-modified diatomaceous earth.

[0016] By employing the above technical solution, diatomaceous earth, rich in silanol groups, exhibits strong hydrophilicity and is prone to excessive water adsorption, leading to initial reaction inhibition and slow start-up. Modifying diatomaceous earth with a silane coupling agent adjusts its hydrophilicity, effectively preventing excessive water adsorption during the initial heating phase, which would otherwise hinder rapid start-up and cause uneven localized heating. Furthermore, the silane-modified diatomaceous earth retains a relatively large porous structure, maintaining a suitable level of water for later stable reactions, thus achieving a dynamic balance between water adsorption and reactivity.

[0017] Optionally, the weight ratio of diatomaceous earth in step one to silane coupling agent in step two is (45-50):(1-6).

[0018] By adopting the above technical solution and controlling the ratio of silane coupling agent to diatomaceous earth, the hydrophilic groups on the surface of diatomaceous earth can be effectively controlled, thus effectively preventing the material from excessively absorbing moisture in the early stage of heating, which would lead to a slow reaction and affect the material's rapid start-up effect.

[0019] Optionally, the iron powder includes iron powder with a particle size of 80 mesh and iron powder with a particle size of 600 mesh, and the weight ratio of the 80 mesh iron powder to the 600 mesh iron powder is 1:1.

[0020] By adopting the above technical solution, 600-mesh iron powder has a higher specific surface area, which helps to accelerate the initial reaction and achieve a rapid start-up effect under the condition of a suitable oxygen permeability rate, that is, effectively shorten the time required for the material to rise from room temperature to 40°C. Meanwhile, 80-mesh iron powder has a more gradual reaction rate, which helps to maintain the subsequent operation, that is, effectively prolongs the period during which the heating temperature is above 40°C.

[0021] Preferably, the weight ratio of the acrylic acid, the acrylamide, the crosslinking agent, the diatomaceous earth, the silica, and the initiator is 40:32:0.01:(15-25):(5-15):0.12.

[0022] Secondly, this application proposes a method for preparing a self-heating material as described in any of the above claims, comprising the following steps: S1. Mix the superabsorbent resin with water and stir to obtain a superabsorbent resin premix. S2. Iron powder, activated carbon, silane-modified diatomaceous earth, sodium chloride, and the superabsorbent resin premixed liquid phase obtained in step S1 are mixed and stirred at a stirring rate of 500-3000 rpm to obtain the self-heating material.

[0023] By adopting the above technical solutions, the superabsorbent resin ensures a suitable oxygen permeability rate, the silane-modified diatomaceous earth effectively maintains a dynamic balance between moisture adsorption and reactivity, and the iron powder with a suitable ratio of coarse to fine particles achieves both "rapid start-up" and "long-lasting" heating effects. Furthermore, this application uses lightweight diatomaceous earth, effectively achieving a lighter heating material and improving the product's wearing comfort.

[0024] Thirdly, this application also provides a hand warmer, including a non-woven bag and a self-heating material filled in the non-woven bag, wherein the self-heating material is any of the self-heating materials described above.

[0025] By adopting the above technical solution and using the self-heating material provided in this application, it has the performance of rapid start-up, long battery life, and lightweight, effectively solving the technical defects of existing hand warmers such as "the contradiction between rapid start-up and long battery life" and "the contradiction between bulkiness and comfort".

[0026] In summary, this application includes at least one of the following beneficial technical effects: 1. In the technical solution of this application, under the guarantee of a suitable oxygen permeability rate of the superabsorbent resin and the guarantee of a dynamic balance between effective water adsorption and reactivity of silane-modified diatomaceous earth, the iron powder with a mixture of coarse and fine particles can achieve the heating effect of "rapid start-up" and "long-lasting operation". The superabsorbent resin, silane-modified diatomaceous earth, and coarse and fine iron powder work together to achieve the heating effect of "rapid start-up" and "long-lasting operation". Moreover, this application abandons the use of heavy vermiculite as a filler and uses lightweight diatomaceous earth as a filler, which effectively realizes the lightweight of the heating material, avoids the weight of the material, and improves the wearing comfort of the product.

[0027] 2. An organic-inorganic composite network structure is formed using acrylic acid, acrylamide, diatomaceous earth, and precipitated silica, with diatomaceous earth and precipitated silica forming network nodes, resulting in a superabsorbent resin with a moderate degree of crosslinking. The prepared superabsorbent resin effectively balances water absorption and oxygen permeability, ensuring excellent water absorption while avoiding uncontrollable heating or unstable heat generation caused by excessively fast or slow oxygen permeability. Furthermore, this superabsorbent resin also facilitates the uniform and stable dispersion of other raw materials, ensuring that each component functions effectively.

[0028] 3. Silane-modified diatomaceous earth adjusts the hydrophilicity of diatomaceous earth, effectively preventing excessive water adsorption during the initial heating stage, which would lead to slow reaction, affect the rapid start-up effect of the material, and cause uneven local heating. Furthermore, silane-modified diatomaceous earth still retains a large number of pore structures, which can maintain a suitable amount of water for later stable reactions, achieving a dynamic balance between water adsorption and reaction activity. Detailed Implementation

[0029] The present application will be further described in detail below with reference to the embodiments.

[0030] The raw materials used in the embodiments of this application are all commercially available products, wherein, Diatomaceous earth: Shanghai Yuanye Biotechnology Co., Ltd.; Activated carbon: Shanghai Xinyuda Energy Chemical Co., Ltd.; Silica: Fumed silica from Jiangxi Hongbai New Materials Co., Ltd.; Vermiculite: Guangdong Yuanfeng Chemical Reagent Co., Ltd.

[0031] Preparation Example 1 A method for preparing silane-modified diatomaceous earth includes the following steps: Step 1: Provide 50g of diatomaceous earth and dry it under vacuum at 60℃ for 4 hours to obtain pretreated diatomaceous earth; Step 2: Add 1g of coupling agent KH-570 to 40mL of anhydrous ethanol and stir at 300rpm for 10min to obtain a silane coupling agent solution. Step 3: Place the pretreated diatomaceous earth from Step 1 in a constant temperature water bath at 90℃ and stir at a stirring rate of 100 rpm. Add the silane coupling agent solution obtained in Step 2 to the pretreated diatomaceous earth at a feeding rate of 0.5 g / min and stir at a stirring rate of 1000 rpm for 2 hours. Take out the reaction product and centrifuge at 8000 rpm for 5 minutes to obtain a solid. Wash the solid three times with anhydrous ethanol and dry it under vacuum at 60℃ for 4 hours to obtain silane-modified diatomaceous earth.

[0032] Preparation Examples 2-3 Preparation Examples 2 and 3 are based on Preparation Example 1, with the difference being that the total mass of diatomaceous earth in step one and coupling agent KH-570 in step two remains constant at 51g, while the ratio of their amounts is adjusted. Other steps remain the same as in Preparation Example 1. Specifically, in Preparation Example 2, the amount of diatomaceous earth used is 48g, and the amount of coupling agent KH-570 used is 3g, i.e., the weight ratio of diatomaceous earth to coupling agent KH-570 is 48:3.

[0033] In Preparation Example 3, the amount of diatomaceous earth used was 45g, and the amount of coupling agent KH-570 used was 6g, that is, the weight ratio of diatomaceous earth to coupling agent KH-570 was 45:6.

[0034] Preparation Example 4 A method for preparing a superabsorbent resin includes the following steps: (1) Provide 40g of acrylic acid, place the acrylic acid in a constant temperature water bath at 0℃, stir at a stirring rate of 200rpm, add a 1mol / L sodium hydroxide aqueous solution dropwise into the acrylic acid until the pH value is 5.5, and obtain the first mixture. (2) Add 32g acrylamide, 0.01g N,N'-methylenebisacrylamide, 20g diatomaceous earth, 10g silica and 2.4g sodium lignosulfonate to the first mixture obtained in step (1), stir at 300rpm for 20min, and ultrasonically disperse at 300W for 15min to obtain the second mixture. (3) Add 0.12g of sodium persulfate to 40mL of distilled water and stir at 100rpm for 5min to obtain sodium persulfate solution. Add the sodium persulfate solution to the second mixture obtained in step (2) and stir at 200rpm for 20min. Place it in a vacuum drying oven at 90℃ for 4h and dry it in a drying oven at 90℃ for 24h. Take it out, crush it, and sieve it to obtain superabsorbent resin with a particle size of 100 mesh.

[0035] Preparation Examples 5-6 Preparation Examples 5 and 6 are based on Preparation Example 4, the difference being that in step (2), the total mass of diatomaceous earth and silica remains constant at 30g, but the ratio of their amounts is adjusted; the other steps are the same as in Preparation Example 4. Specifically, In Preparation Example 5, the amount of diatomaceous earth used was 15g and the amount of silica used was 15g, that is, the weight ratio of diatomaceous earth to silica was 1:1. In Preparation Example 6, the amount of diatomaceous earth used was 25g and the amount of silica used was 5g, that is, the weight ratio of diatomaceous earth to silica was 5:1.

[0036] Preparation of Comparative Examples 1-2 Preparation Examples 1 and 2 are based on Preparation Example 4, the difference being that step (2) does not contain diatomaceous earth or silica, while the other steps are the same as in Preparation Example 4. Specifically, The preparation of Comparative Example 1, step (2) is as follows: 32g acrylamide, 0.01g N,N'-methylenebisacrylamide, 30g diatomaceous earth and 2.4g sodium lignosulfonate are added to the first mixture obtained in step (1), stirred at a stirring rate of 300rpm for 20min, and ultrasonically dispersed at an ultrasonic power of 300W for 15min to obtain the second mixture.

[0037] The preparation of Comparative Example 2, step (2) is as follows: 32g acrylamide, 0.01g N,N'-methylenebisacrylamide, 30g silica and 2.4g sodium lignosulfonate are added to the first mixture obtained in step (1), stirred at 300rpm for 20min, and ultrasonically dispersed at 300W for 15min to obtain the second mixture.

[0038] Examples 1-6 Examples 1-6 provide a method for preparing a hand warmer. The specific raw materials and their amounts are shown in Table 1 below. The specific preparation method includes the following steps: S1. Mix the superabsorbent resin with deionized water and stir at a stirring rate of 200 rpm for 30 min to obtain a superabsorbent resin premix. S2. Add iron powder, activated carbon, silane-modified diatomaceous earth, sodium chloride, and the superabsorbent resin premix obtained in step S1 to a high-speed mixer and stir at 1000 rpm for 30 minutes. Transfer to a sealed bag and allow to cool naturally to 25°C to obtain a self-heating material. Weigh 40g of the self-heating material and fill it into a non-woven bag (13cm in length and 10cm in width; with a pressure difference of 1.21KPa, the air permeability is 45000±50s / 100mL). Place the non-woven bag into an oxygen-barrier sealed plastic bag to obtain a hand warmer.

[0039] Among them, the superabsorbent resin is the superabsorbent resin prepared in Preparation 4; the silane-modified diatomaceous earth is the silane-modified diatomaceous earth prepared in Preparation Example 1; and the iron powder is obtained by mixing iron powder with a particle size of 80 mesh and iron powder with a particle size of 600 mesh in a weight ratio of 1:1.

[0040] Table 1. Raw materials and dosage of self-heating materials for hand warmers (unit: g) Examples 7-8 Examples 7 and 8 are based on Example 3, the difference being that the source of the superabsorbent resin is different, while the other steps remain the same as in Example 3. Specifically, In Example 7, the superabsorbent resin is the superabsorbent resin prepared in Preparation Example 5.

[0041] In Example 8, the superabsorbent resin was the superabsorbent resin prepared in Preparation Example 6.

[0042] Examples 9-10 Examples 9 and 10 are based on Example 3, the difference being that the source of the silane-modified diatomaceous earth is different, while the other steps remain the same as in Example 3. Specifically, In Example 9, the silane-modified diatomaceous earth was the silane-modified diatomaceous earth prepared in Preparation Example 2.

[0043] In Example 10, the silane-modified diatomaceous earth was the silane-modified diatomaceous earth prepared in Preparation Example 3.

[0044] Comparative Example 1 This comparative example is based on Example 3, except that an equal weight of diatomaceous earth is used to replace the silane-modified diatomaceous earth, while the other steps remain the same as in Example 3.

[0045] Comparative Example 2 This comparative example is based on Example 3, except that vermiculite of equal weight is used to replace silane-modified diatomaceous earth, while the other steps remain the same as in Example 3.

[0046] Comparative Example 3 This comparative example is based on Example 3, except that an equal weight of the superabsorbent resin prepared in Comparative Example 1 is used to replace the superabsorbent resin prepared in Example 4, while the other steps remain the same as in Example 3.

[0047] Comparative Example 4 This comparative example is based on Example 3, except that: the superabsorbent resin prepared in Comparative Example 2 is used in place of the superabsorbent resin prepared in Example 4, while the other steps are the same as in Example 3.

[0048] Comparative Example 5 This comparative example is based on Example 1, the difference being that the iron powder contains only 80-mesh iron powder, while the other steps are the same as in Example 3.

[0049] Performance testing The oxygen-barrier plastic strips of the hand warmers prepared in Examples 1-10 and Comparative Examples 1-5 were removed, and the non-woven bags containing self-heating material were taken out as samples. The heating temperature of the samples was then measured. The experimental results are shown in Table 2 below.

[0050] Heating temperature detection: The sample was placed in an environment of 25±2℃ and relative humidity of 50±5%, and the temperature of the sample was detected every 1 minute using a temperature recorder. The specific test indicators are: (1) Record the time required for the sample to rise from room temperature to 40℃, i.e., the onset time; (2) Record the highest temperature of the sample during the entire heating process; (3) Record the total time from when the sample rises from room temperature to 40℃ until it drops below 40℃, i.e., the effective heating time.

[0051] Table 2 Heating results of the samples As shown in Table 2, the experimental results demonstrate that, in the technical solution of this application, under the guarantee of a suitable oxygen permeation rate of the superabsorbent resin and the dynamic balance between effective water adsorption and reactivity of the silane-modified diatomaceous earth, the combination of coarse and fine iron powder can achieve both "rapid start-up" and "long-lasting operation" heating effects. The superabsorbent resin, silane-modified diatomaceous earth, and coarse and fine iron powder work together to achieve these heating effects.

[0052] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Identical components are indicated by the same reference numerals. Therefore, all equivalent changes made to the structure and principles of this application should be covered within the scope of protection of this application.

Claims

1. A self-heating material, characterized in that, The raw materials include the following weight fractions: 38-41 parts iron powder, 9-11 parts activated carbon, 12-15 parts silane-modified diatomaceous earth, 3-4 parts superabsorbent resin, 1.0-1.5 parts sodium chloride, and 30-35 parts water. The raw materials for preparing the superabsorbent resin include acrylic acid, acrylamide, crosslinking agent, diatomaceous earth, silica, and initiator, and the weight ratio of acrylic acid, acrylamide, crosslinking agent, diatomaceous earth, silica, and initiator is (35~45):(30~35):(0.005~0.015):(15~25):(5~15):(0.10~0.15). The iron powder includes iron powder with a particle size of 60-100 mesh and iron powder with a particle size of 500-1000 mesh.

2. The self-heating material according to claim 1, characterized in that, The weight ratio of the silane-modified diatomaceous earth to the superabsorbent resin is (13~14):(3.3~3.6).

3. The self-heating material according to claim 1, characterized in that, In the superabsorbent resin, the weight ratio of diatomaceous earth to silica is (20~25):(5~10).

4. The self-heating material according to claim 1, characterized in that, The preparation method of the superabsorbent resin includes the following steps: (1) Provide acrylic acid, place the acrylic acid in a constant temperature water bath at 0°C, and add sodium hydroxide solution dropwise to the acrylic acid under stirring until the pH value is 5~6 to obtain the first mixture; (2) Add acrylamide, crosslinking agent, diatomaceous earth and fumed silica to the first mixture obtained in step (1), stir and ultrasonically disperse to obtain the second mixture; (3) Add the initiator to the second mixture obtained in step (2), stir, and place it in a vacuum drying oven at 70~95℃ to react. Dry and pulverize the product obtained from the reaction to obtain the superabsorbent resin.

5. The self-heating material according to claim 1, characterized in that, The preparation method of the silane-modified diatomite includes the following steps: Step 1: Dry the diatomaceous earth to obtain pretreated diatomaceous earth; Step 2: Dissolve the silane coupling agent in ethanol to obtain a silane coupling agent solution; Step 3: Place the diatomaceous earth pretreated in Step 1 into a constant temperature water bath at 70~95℃. Under stirring, add the silane coupling agent solution obtained in Step 2 to the pretreated diatomaceous earth, stir and react, and then separate the solid and liquid products and dry them to obtain the silane-modified diatomaceous earth.

6. The self-heating material according to claim 5, characterized in that, The weight ratio of diatomaceous earth in step one to silane coupling agent in step two is (45~50):(1~6).

7. The self-heating material according to claim 1, characterized in that, The iron powder includes iron powder with a particle size of 80 mesh and iron powder with a particle size of 600 mesh, and the weight ratio of the 80 mesh iron powder to the 600 mesh iron powder is 1:

1.

8. The self-heating material according to claim 1, characterized in that, The weight ratio of the acrylic acid, the acrylamide, the crosslinking agent, the diatomaceous earth, the silica, and the initiator is 40:32:0.01:(15~25):(5~15):0.

12.

9. A method for preparing a self-heating material as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Mix the superabsorbent resin with water and stir to obtain a superabsorbent resin premix. S2. Iron powder, activated carbon, silane-modified diatomaceous earth, sodium chloride, and the superabsorbent resin premixed liquid phase obtained in step S1 are mixed and stirred at a stirring rate of 500~3000 rpm to obtain the self-heating material.

10. A hand warmer, characterized in that, It includes a nonwoven bag and a self-heating material filled in the nonwoven bag, wherein the self-heating material is the self-heating material according to any one of claims 1 to 8.

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