Hot compress bag capable of preventing self-activation and preparation method thereof
By introducing a phase change layer and low-temperature phase change microcapsules into the heat pack, the problem of easy activation of the heat pack at low temperatures is solved, achieving stable storage and use in low-temperature environments, and improving product stability and user experience.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIANGSU INTCO MEDICAL PROD CO LTD
- Filing Date
- 2025-12-15
- Publication Date
- 2026-05-12
AI Technical Summary
Disposable hot compress bags are prone to premature activation in low-temperature environments, leading to inconvenient storage and affecting product quality and brand reputation.
The heat pack design incorporates a phase change layer containing a phase change fluid and initiating material. Mechanical stimulation triggers the exothermic crystallization of the phase change fluid. Low-temperature phase change microcapsules and thickeners are used to improve the stability of the phase change fluid. An additional insulation layer and protective layer are added to prevent self-activation.
It effectively prevents the heating pack from activating prematurely in low-temperature environments, ensuring product stability during storage and transportation, and improving user experience and product quality.
Smart Images
Figure SMS_1
Abstract
Description
Technical Field
[0001] This invention relates to the field of heat pack technology, specifically to a heat pack that prevents self-activation and its preparation method. Background Technology
[0002] Hot compresses are a common physical therapy that introduces heat into the body, causing the capillaries in the treated area to dilate and promoting local blood circulation. This can relieve muscle spasms and promote the absorption of inflammation. In addition, hot compresses can be used in combination with some medications to achieve the effect of direct drug delivery to the affected area through the skin.
[0003] Compared to reusable hot compress bags, disposable hot compress bags have advantages such as not needing preheating, ease of use, low price, and cleanliness. However, a common problem with disposable hot compress bags is that they may be prematurely activated during transportation and storage due to impacts, low temperatures, or improper storage. Specifically, hot compress bags prematurely activated by impacts or punctures may have damaged packaging or internal seals, allowing transport and sales personnel to easily separate them from normal hot compress bags without affecting their storage and sale. However, hot compress bags prematurely activated by low temperatures, without damaged packaging, may be sold to consumers along with usable hot compress bags, undoubtedly leading to a poor consumer experience and impacting product quality and brand reputation. Summary of the Invention
[0004] The purpose of this invention is to provide a heat pack that prevents self-activation and its preparation method, thereby solving the problems of heat packs being easily activated prematurely at low temperatures and being difficult to store.
[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A heat pack to prevent self-activation, the heat pack comprising a phase change layer, the phase change layer containing a sealed bag containing a phase change fluid and an initiating material; The preparation method of the phase change fluid is as follows: Sodium thiosulfate pentahydrate, sodium acetate trihydrate, and deionized water are mixed evenly and heated in a sealed water bath at 70-80°C for 20-30 minutes, with continuous agitation during heating to ensure complete melting. The temperature is then raised to 80-90°C, a thickener is added, and the mixture is stirred evenly and then ultrasonically dispersed for 5-15 minutes. After dispersion, the mixture is sealed and quickly transferred to an environment at -20 to -30°C, and allowed to cool completely to room temperature to obtain a phase change fluid.
[0006] As a further limitation of the present invention, the thickener is a mixture of polyvinyl alcohol, maleic acid, polyacrylamide, carrageenan and glycerol, and the mass fraction of the thickener in the phase change fluid is 20-30%; the mass fraction of glycerol in the thickener is 80-90%.
[0007] As a further limitation of the present invention, the mass ratio of sodium sulfate pentahydrate, sodium acetate trihydrate, and deionized water is (50~60):(30~40):(5~10).
[0008] As a further limitation of the present invention, the sealed bag is provided with a low-temperature phase change microcapsule layer, wherein the preparation method of the low-temperature phase change microcapsules is as follows: Mix n-tetane, styrene, and methyl methacrylate, stir evenly at room temperature and 400-500 rpm, add benzoyl peroxide, and continue stirring for 5-10 minutes to obtain a n-tetane mixture; Mix polyvinyl alcohol, tricalcium phosphate and deionized water, and stir at 80~90℃ and 400~500rpm for 5~10min to fully dissolve them and obtain a polyvinyl alcohol solution. Add n-tetane mixture to polyvinyl alcohol solution at 50-60℃ and keep at 50-60℃ for 10-20 min. Then raise the temperature to 80-90℃ and react at 80-90℃ for 4-6 h. After the reaction is complete, cool to room temperature, wash with deionized water, and dry to obtain low-temperature phase change microcapsules.
[0009] As a further limitation of the present invention, the mass ratio of n-tetane, styrene, methyl methacrylate and deionized water is (35~40):(5~10):(10~15):(70~90).
[0010] As a further limitation of the present invention, the initiating material is a metal sheet or metal powder.
[0011] As a further limitation of the present invention, the metal powder is one or more of the following: iron powder, copper powder, copper oxide powder, iron oxide powder, ferrous oxide powder, and aluminum oxide powder.
[0012] As a further limitation of the present invention, a heat insulation layer is provided outside the phase change layer, which is polyethylene foam or EPDM rubber foam with a thickness of 1~3mm.
[0013] As a further limitation of the present invention, the outermost layer of the hot compress bag is a protective layer, and the material of the protective layer is one or more combinations of polyethylene nonwoven fabric, polypropylene nonwoven fabric, polyvinyl alcohol nonwoven fabric, polylactic acid nonwoven fabric, and polyimide nonwoven fabric.
[0014] A method for preparing a heat pack to prevent self-activation includes: taking a sealed bag, filling it with a phase change fluid and an initiating material and sealing it; then, placing the sealed bag into a large sealed bag pre-filled with low-temperature phase change microcapsules; adjusting the position of the sealed bag in the large sealed bag and sealing the large sealed bag to form a phase change layer; then, attaching insulation material to both sides of the phase change layer to form a structure with insulation layers on both sides of the phase change layer; finally, placing the bag into a bag composed of two protective layer materials and heat-sealing it to form a protective layer structure on the outside of the insulation layer, thus obtaining a heat pack to prevent self-activation.
[0015] When using the anti-self-activation heat pack provided by this invention, first, pry open the metal sheet inside the heat pack to trigger the crystallization and heat release of the phase change fluid (when the initiating material is a metal sheet), or press the product firmly to break the separator membrane of the sealed bag inside the phase change layer of the product. Then, shake the product to ensure that the phase change fluid in the sealed bag inside the phase change layer comes into full contact with the initiating material (when the initiating material is metal powder). Subsequently, place the product on the area requiring heat application and secure it with a strap to achieve the heat application process.
[0016] It should be noted that whether it is initiated by metal sheet or metal powder, the initiation mechanism is essentially the same, which is to induce nucleation through mechanical stimulation.
[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention prepares a ternary phase change material with a low eutectic point by mixing three single-component phase change materials: sodium thiosulfate pentahydrate, sodium acetate trihydrate, and deionized water through melt blending. After blending, the melting point of the ternary phase change material is reduced, and it can only crystallize and undergo phase change at a temperature lower than the melting point of its own system. Therefore, when the external conditions meet the supercooling requirements, the ternary phase change material can remain at a lower temperature without undergoing phase change.
[0018] Adding organic compounds such as polyvinyl alcohol and glycerol to a phase change system as a thickener allows the glycerol and organic molecules to disperse within the system. The intermolecular hydrogen bonds between these molecules hinder crystallization during cooling, thereby increasing the supercooling of the phase change system and enabling it to remain at a lower temperature without undergoing a phase change. This also inhibits phase separation, increasing the stability of the phase change system.
[0019] Low-temperature phase change microcapsules with tridecane as the core material are used to protect the outer layer of the phase change fluid. As the temperature decreases, at -5℃, the tridecane in the microcapsules changes from liquid to solid, releasing latent heat, which replenishes the phase change fluid with heat. At -17℃, the tridecane in the microcapsules undergoes a solid-solid phase transition, a crystal form change, and releases latent heat, which replenishes the phase change fluid with heat again, thus slowing down the occurrence of crystallization. Detailed Implementation
[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0021] Polyvinyl alcohol (PVA-1788, degree of hydrolysis: 88%), metal flakes (stainless steel flakes), iron powder (particle size: 200 mesh), resealable bags (PE material, single layer thickness: 0.1mm), polyethylene foam (thickness: 1mm), polypropylene nonwoven fabric (weight: 80g / m³) 2 ).
[0022] Example 1 A method for preparing a heat pack to prevent self-activation, specifically comprising: Step 1: Preparation of phase change materials Mix 50g sodium thiosulfate pentahydrate, 40g sodium acetate trihydrate, and 5g deionized water thoroughly. Heat the mixture in a sealed water bath at 70℃ for 30 minutes, continuously agitating it during heating to ensure complete melting. Then, raise the temperature to 80℃, add 5g polyvinyl alcohol and 20g glycerol, stir thoroughly, and ultrasonically disperse for 15 minutes. After dispersion, seal the mixture and quickly transfer it to an environment at -30℃. Allow it to cool completely to room temperature to obtain a phase change fluid.
[0023] Step 2: Preparation of low-temperature phase change microcapsules 37g of n-tetane, 8g of styrene, and 12g of methyl methacrylate were mixed and stirred at 450 rpm at room temperature until homogeneous. 1g of benzoyl peroxide was added, and stirring was continued for 10 min to obtain a n-tetane mixture. 1g of polyvinyl alcohol, 1g of tricalcium phosphate, and 80g of deionized water were mixed and stirred at 450 rpm at 80°C for 10 min until fully dissolved to obtain a polyvinyl alcohol solution. The n-tetane mixture was added to the polyvinyl alcohol solution at 60°C and kept at 60°C for 10 min. The temperature was then raised to 80°C and reacted at 80°C for 6 h. After the reaction was completed, the mixture was cooled to room temperature, washed with deionized water, and dried to obtain low-temperature phase change microcapsules.
[0024] Step 3: Prepare a heat pack to prevent self-activation The phase change fluid prepared above was filled into one side of the separator membrane inside the sealed bag and sealed. 5g of iron powder was added to the other side and then sealed. 50g of low-temperature phase change microcapsules were pre-filled into the large sealed bag, and then the sealed bag containing phase change fluid and iron powder was placed inside. The distribution of the phase change microcapsules was adjusted so that they were evenly distributed around the sealed bag containing phase change fluid and iron powder. Polyethylene foam was pasted on both sides of the large sealed bag and then placed inside a bag composed of two pieces of polypropylene non-woven fabric. The bag was then heat-sealed at 110°C to obtain a heat pack that prevents self-activation.
[0025] Example 2 A method for preparing a heat pack to prevent self-activation, specifically comprising: Step 1: Preparation of phase change materials Mix 53g sodium thiosulfate pentahydrate, 37g sodium acetate trihydrate, and 5g deionized water thoroughly. Heat the mixture in a sealed water bath at 70°C for 30 minutes, continuously agitating it during heating to ensure complete melting. Then, raise the temperature to 80°C, add 5g polyvinyl alcohol and 25g glycerol, stir thoroughly, and ultrasonically disperse for 15 minutes. After dispersion, seal the mixture and quickly transfer it to an environment at -30°C. Allow it to cool completely to room temperature to obtain a phase change fluid.
[0026] Step 2: Preparation of low-temperature phase change microcapsules 37g of n-tetane, 8g of styrene, and 12g of methyl methacrylate were mixed and stirred at 450 rpm at room temperature until homogeneous. 1g of benzoyl peroxide was added, and stirring was continued for 10 min to obtain a n-tetane mixture. 1g of polyvinyl alcohol, 1g of tricalcium phosphate, and 80g of deionized water were mixed and stirred at 450 rpm at 80°C for 10 min until fully dissolved to obtain a polyvinyl alcohol solution. The n-tetane mixture was added to the polyvinyl alcohol solution at 60°C and kept at 60°C for 10 min. The temperature was then raised to 80°C and reacted at 80°C for 6 h. After the reaction was completed, the mixture was cooled to room temperature, washed with deionized water, and dried to obtain low-temperature phase change microcapsules.
[0027] Step 3: Prepare a heat pack to prevent self-activation The phase change fluid prepared above was filled into one side of the separator membrane inside the sealed bag and sealed. 5g of iron powder was added to the other side and then sealed. 50g of low-temperature phase change microcapsules were pre-filled into the large sealed bag, and then the sealed bag containing phase change fluid and iron powder was placed inside. The distribution of the phase change microcapsules was adjusted so that they were evenly distributed around the sealed bag containing phase change fluid and iron powder. Polyethylene foam was pasted on both sides of the large sealed bag and then placed inside a bag composed of two pieces of polypropylene non-woven fabric. The bag was then heat-sealed at 110°C to obtain a heat pack that prevents self-activation.
[0028] Example 3 A method for preparing a heat pack to prevent self-activation, specifically comprising: Step 1: Preparation of phase change materials Mix 55g sodium thiosulfate pentahydrate, 35g sodium acetate trihydrate, and 5g deionized water thoroughly. Heat the mixture in a sealed water bath at 70°C for 30 minutes, continuously agitating it during heating to ensure complete melting. Then, raise the temperature to 80°C, add 5g polyvinyl alcohol and 30g glycerol, stir thoroughly, and ultrasonically disperse for 15 minutes. After dispersion, seal the mixture and quickly transfer it to an environment at -30°C. Allow it to cool completely to room temperature to obtain a phase change fluid.
[0029] Step 2: Preparation of low-temperature phase change microcapsules 37g of n-tetane, 8g of styrene, and 12g of methyl methacrylate were mixed and stirred at 450 rpm at room temperature until homogeneous. 1g of benzoyl peroxide was added, and stirring was continued for 10 min to obtain a n-tetane mixture. 1g of polyvinyl alcohol, 1g of tricalcium phosphate, and 80g of deionized water were mixed and stirred at 450 rpm at 80°C for 10 min until fully dissolved to obtain a polyvinyl alcohol solution. The n-tetane mixture was added to the polyvinyl alcohol solution at 60°C and kept at 60°C for 10 min. The temperature was then raised to 80°C and reacted at 80°C for 6 h. After the reaction was completed, the mixture was cooled to room temperature, washed with deionized water, and dried to obtain low-temperature phase change microcapsules.
[0030] Step 3: Prepare a heat pack to prevent self-activation The prepared phase change fluid was filled into a sealed bag and sealed together with a metal sheet. 50g of low-temperature phase change microcapsules were pre-filled into a large sealed bag, and then placed into a sealed bag containing the phase change fluid and metal sheet. The distribution of the phase change microcapsules was adjusted so that they were evenly distributed around the sealed bag containing the phase change fluid and metal sheet. After attaching polyethylene foam to both sides of the large sealed bag, it was placed into a bag composed of two pieces of polypropylene nonwoven fabric and heat-sealed at 110°C to obtain a heat pack that prevents self-activation.
[0031] Example 4 A method for preparing a heat pack to prevent self-activation, specifically comprising: Step 1: Preparation of phase change materials Mix 57g sodium thiosulfate pentahydrate, 33g sodium acetate trihydrate, and 5g deionized water thoroughly. Heat the mixture in a sealed water bath at 70°C for 30 minutes, continuously agitating it during heating to ensure complete melting. Then, raise the temperature to 80°C, add 5g polyvinyl alcohol and 35g glycerol, stir thoroughly, and ultrasonically disperse for 15 minutes. After dispersion, seal the mixture and quickly transfer it to an environment at -30°C. Allow it to cool completely to room temperature to obtain a phase change fluid.
[0032] Step 2: Preparation of low-temperature phase change microcapsules 37g of n-tetane, 8g of styrene, and 12g of methyl methacrylate were mixed and stirred at 450 rpm at room temperature until homogeneous. 1g of benzoyl peroxide was added, and stirring was continued for 10 min to obtain a n-tetane mixture. 1g of polyvinyl alcohol, 1g of tricalcium phosphate, and 80g of deionized water were mixed and stirred at 450 rpm at 80°C for 10 min until fully dissolved to obtain a polyvinyl alcohol solution. The n-tetane mixture was added to the polyvinyl alcohol solution at 60°C and kept at 60°C for 10 min. The temperature was then raised to 80°C and reacted at 80°C for 6 h. After the reaction was completed, the mixture was cooled to room temperature, washed with deionized water, and dried to obtain low-temperature phase change microcapsules.
[0033] Step 3: Prepare a heat pack to prevent self-activation The phase change fluid prepared above was filled into one side of the separator membrane inside the sealed bag and sealed. 5g of iron powder was added to the other side and then sealed. 50g of low-temperature phase change microcapsules were pre-filled into the large sealed bag, and then the sealed bag containing phase change fluid and iron powder was placed inside. The distribution of the phase change microcapsules was adjusted so that they were evenly distributed around the sealed bag containing phase change fluid and iron powder. Polyethylene foam was pasted on both sides of the large sealed bag and then placed inside a bag composed of two pieces of polypropylene non-woven fabric. The bag was then heat-sealed at 110°C to obtain a heat pack that prevents self-activation.
[0034] Example 5 A method for preparing a heat pack to prevent self-activation, specifically comprising: Step 1: Preparation of phase change materials Mix 60g sodium thiosulfate pentahydrate, 30g sodium acetate trihydrate, and 5g deionized water thoroughly. Heat the mixture in a sealed water bath at 70℃ for 30 minutes, continuously agitating it during heating to ensure complete melting. Then, raise the temperature to 80℃, add 6g polyvinyl alcohol and 24g glycerol, stir thoroughly, and ultrasonically disperse for 15 minutes. After dispersion, seal the mixture and quickly transfer it to an environment at -30℃. Allow it to cool completely to room temperature to obtain a phase change fluid.
[0035] Step 2: Preparation of low-temperature phase change microcapsules 37g of n-tetane, 8g of styrene, and 12g of methyl methacrylate were mixed and stirred at 450 rpm at room temperature until homogeneous. 1g of benzoyl peroxide was added, and stirring was continued for 10 min to obtain a n-tetane mixture. 1g of polyvinyl alcohol, 1g of tricalcium phosphate, and 80g of deionized water were mixed and stirred at 450 rpm at 80°C for 10 min until fully dissolved to obtain a polyvinyl alcohol solution. The n-tetane mixture was added to the polyvinyl alcohol solution at 60°C and kept at 60°C for 10 min. The temperature was then raised to 80°C and reacted at 80°C for 6 h. After the reaction was completed, the mixture was cooled to room temperature, washed with deionized water, and dried to obtain low-temperature phase change microcapsules.
[0036] Step 3: Prepare a heat pack to prevent self-activation The phase change fluid prepared above was filled into one side of the separator membrane inside the sealed bag and sealed. 5g of iron powder was added to the other side and then sealed. 50g of low-temperature phase change microcapsules were pre-filled into the large sealed bag, and then the sealed bag containing phase change fluid and iron powder was placed inside. The distribution of the phase change microcapsules was adjusted so that they were evenly distributed around the sealed bag containing phase change fluid and iron powder. Polyethylene foam was pasted on both sides of the large sealed bag and then placed inside a bag composed of two pieces of polypropylene non-woven fabric. The bag was then heat-sealed at 110°C to obtain a heat pack that prevents self-activation.
[0037] Example 6 A method for preparing a heat pack to prevent self-activation, specifically comprising: Step 1: Preparation of phase change materials Mix 60g sodium thiosulfate pentahydrate, 30g sodium acetate trihydrate, and 7g deionized water thoroughly. Heat the mixture in a sealed water bath at 70℃ for 30 minutes, continuously agitating it during heating to ensure complete melting. Then, raise the temperature to 80℃, add 8g polyvinyl alcohol and 32g glycerol, stir thoroughly, and ultrasonically disperse for 15 minutes. After dispersion, seal the mixture and quickly transfer it to an environment at -30℃. Allow it to cool completely to room temperature to obtain a phase change fluid.
[0038] Step 2: Preparation of low-temperature phase change microcapsules 37g of n-tetane, 8g of styrene, and 12g of methyl methacrylate were mixed and stirred at 450 rpm at room temperature until homogeneous. 1g of benzoyl peroxide was added, and stirring was continued for 10 min to obtain a n-tetane mixture. 1g of polyvinyl alcohol, 1g of tricalcium phosphate, and 80g of deionized water were mixed and stirred at 450 rpm at 80°C for 10 min until fully dissolved to obtain a polyvinyl alcohol solution. The n-tetane mixture was added to the polyvinyl alcohol solution at 60°C and kept at 60°C for 10 min. The temperature was then raised to 80°C and reacted at 80°C for 6 h. After the reaction was completed, the mixture was cooled to room temperature, washed with deionized water, and dried to obtain low-temperature phase change microcapsules.
[0039] Step 3: Prepare a heat pack to prevent self-activation The prepared phase change fluid was filled into a sealed bag and sealed together with a metal sheet. 50g of low-temperature phase change microcapsules were pre-filled into a large sealed bag, and then placed into a sealed bag containing the phase change fluid and metal sheet. The distribution of the phase change microcapsules was adjusted so that they were evenly distributed around the sealed bag containing the phase change fluid and metal sheet. After attaching polyethylene foam to both sides of the large sealed bag, it was placed into a bag composed of two pieces of polypropylene nonwoven fabric and heat-sealed at 110°C to obtain a heat pack that prevents self-activation.
[0040] Based on Example 1, the following comparative experiments were conducted, specifically Comparative Example 1 and Comparative Example 2, as described below: Comparative Example 1: This comparative example relates to a method for preparing a heat pack to prevent self-activation. The difference from Example 1 is that sodium thiosulfate pentahydrate was not added to the phase change fluid. Specifically: Step 1: Preparation of phase change materials Mix 40g sodium acetate trihydrate and 5g deionized water evenly, heat in a sealed water bath at 70℃ for 30min, and continuously agitate during heating to ensure complete melting. Then raise the temperature to 80℃, add 5g polyvinyl alcohol and 20g glycerol, stir evenly, and ultrasonically disperse for 15min. After dispersion, seal the mixture and quickly transfer it to an environment at -30℃. Cool it fully to room temperature to obtain a phase change fluid.
[0041] Step 2: Preparation of low-temperature phase change microcapsules 37g of n-tetane, 8g of styrene, and 12g of methyl methacrylate were mixed and stirred at 450 rpm at room temperature until homogeneous. 1g of benzoyl peroxide was added, and stirring was continued for 10 min to obtain a n-tetane mixture. 1g of polyvinyl alcohol, 1g of tricalcium phosphate, and 80g of deionized water were mixed and stirred at 450 rpm at 80°C for 10 min until fully dissolved to obtain a polyvinyl alcohol solution. The n-tetane mixture was added to the polyvinyl alcohol solution at 60°C and kept at 60°C for 10 min. The temperature was then raised to 80°C and reacted at 80°C for 6 h. After the reaction was completed, the mixture was cooled to room temperature, washed with deionized water, and dried to obtain low-temperature phase change microcapsules.
[0042] Step 3: Prepare a heat pack to prevent self-activation The phase change fluid prepared above was filled into one side of the separator membrane inside the sealed bag and sealed. 5g of iron powder was added to the other side and then sealed. 50g of low-temperature phase change microcapsules were pre-filled into the large sealed bag, and then the sealed bag containing phase change fluid and iron powder was placed inside. The distribution of the phase change microcapsules was adjusted so that they were evenly distributed around the sealed bag containing phase change fluid and iron powder. Polyethylene foam was pasted on both sides of the large sealed bag and then placed inside a bag composed of two pieces of polypropylene non-woven fabric. The bag was then heat-sealed at 110°C to obtain a heat pack that prevents self-activation.
[0043] Comparative Example 2: This comparative example relates to a method for preparing a heat pack to prevent self-activation. The difference from Example 1 is that no thickener is added to the phase change fluid. Specifically: Step 1: Preparation of phase change materials Mix 50g sodium thiosulfate pentahydrate, 40g sodium acetate trihydrate, and 5g deionized water evenly. Heat the mixture in a sealed water bath at 70℃ for 30 minutes, continuously agitating it during heating to ensure complete melting. Then, raise the temperature to 80℃, stir evenly, and ultrasonically disperse for 15 minutes. After dispersion, seal the mixture and quickly transfer it to an environment at -30℃. Allow it to cool completely to room temperature to obtain a phase change fluid.
[0044] Step 2: Preparation of low-temperature phase change microcapsules 37g of n-tetane, 8g of styrene, and 12g of methyl methacrylate were mixed and stirred at 450 rpm at room temperature until homogeneous. 1g of benzoyl peroxide was added, and stirring was continued for 10 min to obtain a n-tetane mixture. 1g of polyvinyl alcohol, 1g of tricalcium phosphate, and 80g of deionized water were mixed and stirred at 450 rpm at 80°C for 10 min until fully dissolved to obtain a polyvinyl alcohol solution. The n-tetane mixture was added to the polyvinyl alcohol solution at 60°C and kept at 60°C for 10 min. The temperature was then raised to 80°C and reacted at 80°C for 6 h. After the reaction was completed, the mixture was cooled to room temperature, washed with deionized water, and dried to obtain low-temperature phase change microcapsules.
[0045] Step 3: Prepare a heat pack to prevent self-activation The phase change fluid prepared above was filled into one side of the separator membrane inside the sealed bag and sealed. 5g of iron powder was added to the other side and then sealed. 50g of low-temperature phase change microcapsules were pre-filled into the large sealed bag, and then the sealed bag containing phase change fluid and iron powder was placed inside. The distribution of the phase change microcapsules was adjusted so that they were evenly distributed around the sealed bag containing phase change fluid and iron powder. Polyethylene foam was pasted on both sides of the large sealed bag and then placed inside a bag composed of two pieces of polypropylene non-woven fabric. The bag was then heat-sealed at 110°C to obtain a heat pack that prevents self-activation.
[0046] Testing experiment: The hot compress bag samples required for the experiment were prepared according to the preparation methods in Example 1, Example 2, Example 3, Comparative Example 1, and Comparative Example 2, respectively.
[0047] Excitation Temperature Test: The excitation temperature of the phase change fluid inside the heat pack was tested using a cDAQ-9188 data acquisition chassis, an NI-9214 data acquisition card (operating ambient temperature: -40~70℃), and a T-type thermocouple (temperature measurement range: -200~300℃). After removing the phase change layer from each heat pack, the phase change fluid inside the phase change layer was placed into a glass bottle and sealed. The glass bottle containing the phase change fluid was then placed in a 70℃ water bath for 30 minutes with continuous oscillation during the heating process. After 30 minutes, the heating was stopped, and the bottle was allowed to cool naturally to room temperature. The T-type thermocouple wrapped with insulation cotton was then attached tightly to the outside of the glass bottle as the temperature measuring contact. The height of the temperature measuring contact on the outer surface of the glass bottle was consistent with the center height of the fluid inside the bottle. After attaching the temperature measuring contact, the glass bottle was placed in a cryogenic chamber with the cryogenic temperature set to -35℃. The temperature changes were monitored in real time using the temperature measuring contact, and the excitation temperature of each phase change fluid was recorded.
[0048] Maximum Temperature Test: The maximum temperature reached after activation of the phase change fluid in the heat pack was tested using a cDAQ-9188 data acquisition chassis, an NI-9214 data acquisition card (operating ambient temperature: -40~70℃), and a T-type thermocouple (temperature measurement range: -200~300℃). After removing the phase change layer from each heat pack, the phase change fluid inside the layer was placed into a glass bottle and sealed. The glass bottle containing the phase change fluid was then placed in a 70℃ water bath for 30 minutes with continuous oscillation during heating. After 30 minutes, heating was stopped, and the bottle was allowed to cool naturally to room temperature. The T-type thermocouple wrapped with insulation cotton was then attached to the outside of the glass bottle as a temperature measuring contact. The height of the temperature measuring contact on the outer surface of the glass bottle was consistent with the center height of the fluid inside the bottle. After attaching the temperature measuring contact, an aluminum wire was used as the trigger material, and a stepper motor was used to send the aluminum wire into the center of the phase change fluid to trigger the phase change heat release. The temperature change was monitored in real time using the temperature measuring contact, and the maximum temperature reached after activation of each phase change fluid was recorded.
[0049] Low-temperature stability test: After removing the phase change layer from each heat pack, the phase change fluid inside the phase change layer was placed into 10mL glass bottles and sealed. 100 glass bottles were filled with each type of phase change fluid. The glass bottles containing the phase change fluid were then placed in a water bath at 70℃ and heated for 30 minutes with continuous shaking during the heating process. After 30 minutes, the heating was stopped, and the bottles were allowed to cool naturally to room temperature before being placed in a cryogenic freezer protected from light for 7 days at a temperature of -10℃. After 7 days, the glass bottles were removed, and it was observed whether the phase change fluid inside the glass bottles was activated and whether crystallization occurred. The inactivation rate of the samples was calculated.
[0050]
[0051] Conclusion: Based on the test data of each embodiment and comparative example, it can be seen that compared with the phase change fluid prepared by the preparation method of the comparative example, the phase change fluid prepared by the preparation method in the embodiments has a lower excitation temperature in a low-temperature environment, and the highest temperature reached by the phase change fluid after excitation is similar. The non-activation rate after 7 days of storage in a low-temperature environment is higher, indicating that the phase change fluid prepared by the preparation method in the embodiments is relatively stable, not easily affected by low temperature and actively activated, and can be stored in a low-temperature environment. After being made into a heat pack, the heat pack is not easily activated prematurely in a low-temperature environment and can be stored stably.
[0052] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.
Claims
1. A heat pack to prevent self-activation, characterized in that, The hot compress bag includes a phase change layer, and the phase change layer contains a sealed bag containing a phase change fluid and an initiating material. The preparation method of the phase change fluid is as follows: Sodium thiosulfate pentahydrate, sodium acetate trihydrate, and deionized water are mixed evenly and heated in a sealed water bath at 70-80°C for 20-30 minutes, with continuous agitation during heating to ensure complete melting. The temperature is then raised to 80-90°C, a thickener is added, and the mixture is stirred evenly and then ultrasonically dispersed for 5-15 minutes. After dispersion, the mixture is sealed and quickly transferred to an environment at -20 to -30°C, and allowed to cool completely to room temperature to obtain a phase change fluid.
2. The heat pack for preventing self-activation according to claim 1, characterized in that, The thickener is a mixture of polyvinyl alcohol, maleic acid, polyacrylamide, carrageenan and glycerol, with a mass fraction of 20-30% in the phase change fluid; the mass fraction of glycerol in the thickener is 80-90%.
3. The heat pack for preventing self-activation according to claim 1, characterized in that, The mass ratio of sodium sulfate pentahydrate, sodium acetate trihydrate, and deionized water is (50~60):(30~40):(5~10).
4. The heat pack for preventing self-activation according to claim 1, characterized in that, The sealed bag is provided with a low-temperature phase change microcapsule layer, wherein the preparation method of the low-temperature phase change microcapsules is as follows: Mix n-tetane, styrene, and methyl methacrylate, stir evenly at room temperature and 400-500 rpm, add benzoyl peroxide, and continue stirring for 5-10 minutes to obtain a n-tetane mixture; Mix polyvinyl alcohol, tricalcium phosphate and deionized water, and stir at 80~90℃ and 400~500rpm for 5~10min to fully dissolve them and obtain a polyvinyl alcohol solution. Add n-tetane mixture to polyvinyl alcohol solution at 50-60℃ and keep at 50-60℃ for 10-20 min. Then raise the temperature to 80-90℃ and react at 80-90℃ for 4-6 h. After the reaction is complete, cool to room temperature, wash with deionized water, and dry to obtain low-temperature phase change microcapsules.
5. The heat pack for preventing self-activation according to claim 4, characterized in that, The mass ratio of n-tetane, styrene, methyl methacrylate and deionized water is (35~40):(5~10):(10~15):(70~90).
6. The heat pack for preventing self-activation according to claim 1, characterized in that, The initiating material is a metal sheet or metal powder.
7. The heat pack for preventing self-activation according to claim 6, characterized in that, The metal powder is one or more of the following: iron powder, copper powder, copper oxide powder, iron oxide powder, ferrous oxide powder, and aluminum oxide powder.
8. The heat pack for preventing self-activation according to claim 1, characterized in that, An insulation layer is provided outside the phase change layer. The insulation layer is made of polyethylene foam or EPDM rubber foam with a thickness of 1-3 mm.
9. The heat pack for preventing self-activation according to claim 1, characterized in that, The outermost layer of the hot compress bag is a protective layer, and the material of the protective layer is one or more combinations of polyethylene nonwoven fabric, polypropylene nonwoven fabric, polyvinyl alcohol nonwoven fabric, polylactic acid nonwoven fabric, and polyimide nonwoven fabric.
10. A method for preparing a heat pack to prevent self-activation, characterized in that, Specifically, the process involves taking a sealed bag, filling it with phase change fluid and initiating material, and sealing it. Then, the sealed bag is placed into a large sealed bag pre-filled with low-temperature phase change microcapsules. The position of the sealed bag within the large sealed bag is adjusted, and the large sealed bag is sealed to form a phase change layer. Subsequently, insulation material is pasted onto both sides of the phase change layer to form a structure where the phase change layer has insulation layers on both sides. Finally, the bag is placed into a bag consisting of two protective layer materials, and the opening is sealed by heat pressing. A protective layer structure is formed on the outside of the insulation layer, resulting in a heat pack that prevents self-activation.