A phase change waterproof and breathable packaging film and a preparation method and application thereof

Abstract

The application relates to the field of films, and discloses a phase-change waterproof and breathable packaging film and a preparation method and application thereof. The phase-change waterproof and breathable packaging film comprises the following raw materials in parts by weight: hydrophilic TPU particles, 100 parts; phase-change microcapsules with a particle size of 100-350 microns and a phase-change temperature of 50-60 DEG C, 5-25 parts; polyurethane hydrogel, 10-45 parts; and a pore former with a particle size of 0.1-1 micron, 3-20 parts. The phase-change waterproof and breathable packaging film is specially designed for the long-acting moisture control material of the applicant. The phase-change waterproof and breathable packaging film has a moisture absorption and heat storage function, and can prevent the long-acting moisture control material from releasing a large amount of moisture when the ambient temperature rises after the long-acting moisture control material is packaged, thereby preventing the vehicle lamp from fogging, and meeting the application requirements of the vehicle lamp.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of films, in particular to a phase change waterproof and breathable packaging film and a preparation method and application thereof. BACKGROUND

[0002] When the vehicle lamp is in a high-humidity environment (for example, rainy days), due to the large temperature difference between the inside and outside of the lampshade, the water vapor in the vehicle lamp is easy to condense to form fine water droplets, thereby causing the vehicle lamp to be covered with fog. The light emitted by the vehicle lamp is scattered, which reduces the illumination intensity of the vehicle lamp and brings great safety hazards to vehicle driving.

[0003] In view of the above technical problems, the current common solution is to coat a anti-fog coating agent in the lampshade of the vehicle lamp for dehumidification. However, the anti-fog coating agent will be affected by ultraviolet rays, temperature and humidity outdoors, and other factors, and will have degradation phenomena such as whitening or sagging.

[0004] The applicant's prior patent CN115157810B discloses a long-acting humidity control material for battery pack and a preparation method thereof, which has the function of automatically absorbing and releasing humidity according to the environmental humidity to maintain the humidity control in a relatively closed environment. The applicant tried to apply it to the vehicle lamp to replace the traditional anti-fog coating agent, and found that it can effectively prevent the vehicle lamp from fogging to ensure that the optical devices in the vehicle lamp work normally, and the effect is better. However, in further subsequent tests, we found that the material still has some shortcomings: when the material has absorbed a certain amount of water vapor, if the environmental temperature in the vehicle lamp increases (for example, when the vehicle lamp switches from low beam to high beam, the working temperature increases), the material will "not absorb but release", which will increase the risk of fogging of the vehicle lamp.

[0005] Therefore, how to eliminate the humidity release behavior of the material caused by the increase of the environmental temperature in the vehicle lamp has become the key to the application of the material in the vehicle lamp. SUMMARY

[0006] In order to solve the above technical problems, the present application provides a phase change waterproof and breathable packaging film for long-acting humidity control material and a preparation method and application thereof. The phase change waterproof and breathable packaging film for long-acting humidity control material is specially designed according to the performance characteristics of the long-acting humidity control material of the applicant. The phase change waterproof and breathable packaging film has the functions of moisture absorption and heat storage, and can prevent the long-acting humidity control material from releasing a large amount of moisture when the environmental temperature increases after being packaged, thereby preventing the vehicle lamp from fogging and meeting the application requirements of the vehicle lamp.

[0007] The specific technical scheme of the present application is as follows:

[0008] In the first aspect, the present application provides a phase change waterproof and breathable packaging film for long-acting humidity control material, which comprises the following raw materials by weight:

[0009] 100 parts of hydrophilic TPU particles;

[0010] Phase change microcapsules with particle size of 100-350 microns and phase change temperature of 50-60 DEG C, 5-25 parts;

[0011] Polyurethane hydrogel, 10-45 parts;

[0012] Pore-forming agent with particle size of 0.1-1 micron, 3-20 parts.

[0013] The phase change microcapsules have paraffin with melting point of 50-60 DEG C as core material, chitosan as inner wall material, and silicon dioxide modified with aluminum hydroxide as outer wall material.

[0014] The phase change waterproof and breathable packaging film of the application is specially designed for the application of the long-acting moisture control material of the applicant to vehicle lamps. In view of the shortcoming that the long-acting moisture control material is prone to releasing a large amount of moisture at high temperature, the phase change waterproof and breathable packaging film has the functions of moisture absorption and heat storage, and can prevent the long-acting moisture control material from releasing a large amount of moisture when the ambient temperature rises after the long-acting moisture control material is packaged, thereby preventing the vehicle lamp from fogging. The specific principle is that:

[0015] The hydrophilic TPU particles are used as the main base material of the packaging film, and the film has the advantages of simple film-making process and excellent tensile strength, tear strength and elongation.

[0016] The polyurethane hydrogel, as an important component of the packaging film, has a three-dimensional network structure, can lock the moisture in the packaging film and maintain the moisture content in the packaging film. Since water has a high specific heat capacity, a part of heat can be absorbed, and the long-acting moisture control material can be kept at a relatively low temperature.

[0017] The phase change microcapsule of the present application takes paraffin with a melting point of 50-60℃ as the core material. The reason for setting this material is that the present application found in the previous test that the long-acting moisture control material in the vehicle lamp will accelerate moisture release when the ambient temperature is higher than 60℃, so it is necessary to control the temperature inside the vehicle lamp below 60℃ as much as possible. That is, when the temperature inside the vehicle lamp exceeds the allowable temperature of the long-acting moisture control material, the paraffin in the phase change microcapsule in the phase change waterproof and breathable packaging film will absorb a large amount of heat and then melt, thereby preventing the long-acting moisture control material in the packaging film from heating and releasing moisture. At the same time, the phase change microcapsule takes chitosan as the inner wall material and silicon dioxide modified with aluminum hydroxide as the outer wall material, having a double-wall material structure. The reason for setting this structure is that the present application found in the previous test that when the silicon dioxide layer is used as a single wall material, it has the following shortcomings: on the one hand, the silicon dioxide as a single wall material layer is not ideal for the encapsulation rate of the paraffin core material, and cannot completely wrap the paraffin, so the paraffin is prone to leakage after melting; on the other hand, since the volume of paraffin increases after absorbing heat and melting, and the silicon dioxide layer has poor flexibility, the wall material layer is easily broken, thereby causing paraffin leakage. Therefore, the present application adopts a double-layer wall material structure, which on the one hand can greatly improve the coating rate of paraffin to prevent paraffin leakage, and on the other hand, the chitosan with excellent toughness as the inner wall material can buffer the volume expansion of paraffin after melting, and the silicon dioxide with excellent heat resistance and light aging resistance as the outer wall material can make up for the shortcomings of chitosan, thereby prolonging the service life of the phase change microcapsule and the phase change waterproof and breathable packaging film in high temperature and light environment. In addition, the silicon dioxide layer is modified with aluminum hydroxide, which can further improve the light and heat aging resistance and mechanical properties of the phase change microcapsule and the phase change waterproof and breathable packaging film.

[0018] It should be noted that the present application found that the particle size of the above phase change microcapsule also significantly affects its phase change performance. If the particle size is too large, it is not conducive to the dispersion of the phase change microcapsule in the system, and if the particle size is too small, it will result in an unsatisfactory phase change heat storage effect. After repeated research, it is found that the particle size of the phase change microcapsule is best controlled in the range of 100-350 microns.

[0019] The role of the pore-forming agent is to form breathable micropores during the preparation of the phase change waterproof and breathable packaging film. The particle size of the pore-forming agent determines the size of the breathable micropores, so its particle size has a significant impact on the waterproof and breathable properties of the film. If the particle size is too small, it will result in a low air permeability of the film, hindering the moisture absorption and release of the encapsulated long-acting moisture control material; if the particle size is too large, it will result in poor waterproofness (water can directly pass through) and cause the internal long-acting moisture control material to absorb and release moisture too quickly, and it is not conducive to locking in moisture.

[0020] Further, the phase change waterproof and breathable packaging film further comprises the following raw materials by weight:

[0021] Solvent A, 40-60% by weight of the hydrophilic TPU particles and the polyurethane hydrogel;

[0022] Solvent B, 40-60% by weight of the hydrophilic TPU particles and the polyurethane hydrogel;

[0023] Dispersant A, 2-5% by weight of the phase change microcapsules;

[0024] Thickening agent, 1-5% by weight of the polyurethane hydrogel;

[0025] Dispersant B, 3-8% by weight of the pore-forming agent;

[0026] Defoaming agent, 0.1-2.5% by weight of the solvent B.

[0027] As a preferred, the solvent A is tetrahydrofuran; the solvent B is acetone; the dispersant A is aqueous aminosilane; the dispersant B is BYK-9810; the thickening agent is sodium hydroxymethyl cellulose; the pore-forming agent is calcium carbonate particles; the defoaming agent is Wacker SC-129.

[0028] As a preferred, the preparation method of the phase change microcapsules is:

[0029] A: melt paraffin and emulsifier are added to water at 65-80℃, and paraffin emulsion is obtained after stirring and emulsification; the paraffin emulsion is added to chitosan acetic acid solution heated in a water bath at 65-80℃ and dispersed uniformly, and alkali is added to adjust pH≥7, and then it is left to stand, chitosan gradually precipitates with paraffin emulsion particles as the core, and after chitosan no longer precipitates, it is filtered, washed and dried to obtain chitosan-coated paraffin microcapsules.

[0030] In step A, the paraffin emulsion is added to the chitosan acetic acid solution, and then the pH is adjusted to be greater than or equal to 7. Since chitosan is only soluble in acidic aqueous solution and not soluble in neutral or alkaline aqueous solution, chitosan will gradually precipitate with the dispersed paraffin emulsion particles as the core and form a coating layer, thereby obtaining chitosan-coated paraffin microcapsules.

[0031] B: chitosan-coated paraffin microcapsules are dispersed in water, p-azidobenzoic acid is added, left to stand, filtered, and dried to obtain chitosan-coated paraffin microcapsules with p-azidobenzoic acid adsorbed on the surface.

[0032] In step B, since chitosan is positively charged in the solution, and p-azidobenzoic acid is negatively charged, p-azidobenzoic acid can quickly gather on the surface of chitosan-coated paraffin microcapsules and form an electrostatic adsorption layer of p-azidobenzoic acid.

[0033] C: dispersing the paraffin microcapsules coated with chitosan adsorbed with p-azidobenzoic acid on the surface in an alkaline ethanol aqueous solution, dropping tetraethyl orthosilicate under stirring, standing, filtering, cleaning and drying, and treating the obtained product with ultraviolet light to obtain the paraffin microcapsules coated with chitosan and silica with voids inside.

[0034] In step C, the present application forms the double-wall structure by in-situ hydrolysis of the paraffin microcapsules coated with chitosan adsorbed with p-azidobenzoic acid on the surface to generate a silica layer. On this basis, p-azidobenzoic acid is decomposed and nitrogen is generated under ultraviolet light irradiation, thereby forming local voids between the chitosan layer and the silica layer. The voids are arranged to provide a certain space allowance for the volume expansion of the chitosan layer, which can further ensure that the silica layer is not broken (if the chitosan layer and the silica layer are closely attached without space allowance, the silica layer is still prone to breakage when the volume of the chitosan layer is expanded).

[0035] D: dispersing the paraffin microcapsules coated with chitosan and silica in water, adding aluminum chloride, adjusting the pH to alkaline, heating and reacting, filtering, cleaning and drying to obtain the phase change microcapsules with paraffin with a melting point of 50-60°C as the core material, chitosan as the inner wall material, and silica modified with aluminum hydroxide as the outer wall material.

[0036] In step D, the present application generates aluminum hydroxide in-situ on the surface of the paraffin microcapsules coated with chitosan and silica. Specifically, since the silica is negatively charged in an alkaline environment, the positively charged aluminum ions are attracted to the surface of the paraffin microcapsules coated with chitosan and silica under the electrostatic action, and are converted to aluminum hydroxide under alkaline conditions, thereby obtaining the phase change microcapsules modified with aluminum hydroxide on the surface.

[0037] Preferably, in step A, the concentrations of paraffin and emulsifier in the paraffin emulsion are 1-2 wt% and 0.3-0.7 wt%, respectively; the stirring speed for emulsification is 300-700 rpm; the concentrations of chitosan and acetic acid in the chitosan acetic acid solution are 2-3 wt% and 1.5-2.5 wt%, respectively; and the mass ratio of the paraffin emulsion to the chitosan acetic acid solution is 1:(1.5-2.5).

[0038] Preferably, in step B, the mass ratio of the paraffin microcapsules coated with chitosan, p-azidobenzoic acid and water is 1:(0.1-0.3):(80-120).

[0039] As preferred, in step C, the mass ratio of the chitosan-coated paraffin microcapsule, tetraethyl orthosilicate and the basic ethanol aqueous solution adsorbed on the surface is 1:(0.6-0.8):(80-120), the concentration of ethanol in the basic ethanol aqueous solution is 80-90wt%, the pH of the basic ethanol aqueous solution is 8-10, and the ultraviolet light irradiation time is 5-10min.

[0040] As preferred, in step D, the mass ratio of the silica / chitosan-coated paraffin microcapsule, aluminum chloride and water is 1:(0.6-0.8):(80-120), the pH is adjusted to 8-9 by adding alkali, and the heating reaction temperature is 40-45℃.

[0041] In a second aspect, the present application provides a preparation method of the above-mentioned phase change waterproof and breathable packaging film, comprising the following steps:

[0042] S1: Dissolve the hydrophilic TPU particles and the polyurethane hydrogel into the solvent A to obtain a mixed solution.

[0043] S2: After adding the defoaming agent, the dispersant A and the dispersant B in the solvent B, stirring uniformly, adding the phase change microcapsule and the pore-forming agent and dispersing uniformly, then adding the mixed solution and stirring, finally adding the thickening agent and stirring, a film solution is obtained.

[0044] S3: Coating the film solution on the release film, removing the solvent by heating, and obtaining a semi-finished film.

[0045] S4: Immersing the semi-finished film in an acidic solution until the pore-forming agent is completely reacted to form breathable micropores, then taking out, washing and drying to obtain the phase change waterproof and breathable packaging film.

[0046] As preferred, in S3, the heating temperature is 75-85℃, and the thickness of the semi-finished film is 0.1-0.5mm.

[0047] As preferred, the acidic solution is a 5-15wt% hydrochloric acid solution, and the reaction temperature is 40-45℃.

[0048] In a third aspect, the present application provides the application of the above-mentioned phase change waterproof and breathable packaging film in packaging long-acting moisture control materials.

[0049] As preferred, the long-acting moisture control material is used for vehicle lamp anti-fogging, and is composed of 1-5 layers of moisture control sheets stacked together; each of the moisture control sheets comprises a substrate and a modified moisture control polymer coating layer covering the surface of the substrate; the raw materials of the modified moisture control polymer coating layer include the following raw materials by weight: 1-10 parts of modified superabsorbent polymer, 15-25 parts of potassium salt, 5-10 parts of chloride salt and 30-50 parts of solvent.

[0050] In a fourth aspect, the present application provides a vehicle lamp anti-fogging material, comprising:

[0051] The long-acting moisture control material is formed by stacking 1-5 layers of moisture control sheets, each of which comprises a substrate and a modified moisture control polymer coating layer on the surface of the substrate, and the raw materials of the modified moisture control polymer coating layer include the following components by weight: 1-10 parts of modified superabsorbent polymer, 15-25 parts of potassium salt, 5-10 parts of chloride salt, and 30-50 parts of solvent.

[0052] The phase change waterproof and breathable packaging film for packaging the long-acting moisture control material.

[0053] As a preferred, the fogging time of the vehicle lamp anti-fog material is ≥25 min.

[0054] Compared with the prior art, the present application has the following technical effects:

[0055] (1) The phase change waterproof and breathable packaging film of the present application is specially designed for the performance characteristics required when the long-acting moisture control material of the applicant is applied to vehicle lamps, and has a moisture absorption and heat storage function, so that the long-acting moisture control material will not release a large amount of moisture when the ambient temperature rises, thereby preventing the vehicle lamp from fogging.

[0056] (2) The phase change waterproof and breathable packaging film of the present application uses hydrophilic TPU particles as the main substrate of the packaging film, which has the advantages of simple film-making process and excellent tensile strength, tear strength and elongation rate. The polyurethane hydrogel has a three-dimensional network structure and can maintain the moisture content in the packaging film. Since water has a high specific heat capacity, it can absorb a part of the heat and keep the long-acting moisture control material in a relatively low temperature state. The phase change microcapsule of the present application uses paraffin as the core material, which can absorb a large amount of heat when the temperature in the lampshade rises, thereby preventing the long-acting moisture control material in the packaging film from releasing moisture due to temperature rise. At the same time, the phase change microcapsule has a double-wall material layer structure, which not only has a high coating rate of paraffin, but also the inner layer of chitosan has excellent toughness, which can buffer the volume expansion of paraffin after melting, and the outer layer of silicon dioxide has excellent heat resistance and light aging resistance, which can prolong the service life of the phase change microcapsule and the phase change waterproof and breathable packaging film in high temperature and light environment. In addition, the aluminum hydroxide modified on the surface of the silicon dioxide layer can further improve the excellent light and heat aging resistance and mechanical properties of the phase change microcapsule and the phase change waterproof and breathable packaging film. DETAILED DESCRIPTION

[0057] The present application will be further described below in conjunction with examples.

[0058] General examples

[0059] A long-acting moisture control material phase change waterproof and breathable packaging film, comprising the following raw materials by weight: hydrophilic TPU particles, 100 parts; phase change microcapsules with a particle size of 100-350 microns and a phase change temperature of 50-60 DEG C, 5-25 parts; polyurethane hydrogel, 10-45 parts; pore-forming agent calcium carbonate particles with a particle size of 0.1-1 micron, 3-20 parts; solvent A, 40-60% of the weight of the hydrophilic TPU particles and the polyurethane hydrogel; solvent B, 40-60% of the weight of the hydrophilic TPU particles and the polyurethane hydrogel; dispersant A, 2-5% of the weight of the phase change microcapsules; thickening agent, 1-5% of the weight of the polyurethane hydrogel; dispersant B, 3-8% of the weight of the pore-forming agent; defoaming agent, 0.1-2.5% of the weight of the solvent B.

[0060] Wherein, the solvent A is tetrahydrofuran; the solvent B is acetone; the dispersant A is water-based amino silane; the dispersant B is BYK-9810; the thickening agent is sodium hydroxymethyl cellulose BKY420; and the defoaming agent is Wacker SC-129.

[0061] The phase change microcapsule takes paraffin with a melting point of 50-60 DEG C as a core material, takes chitosan as an inner wall material, and takes modified aluminum hydroxide silicon dioxide as an outer wall material, and its preparation method is as follows:

[0062] A: melt paraffin and emulsifier are added to water at 65-80 DEG C, and the emulsion is obtained after stirring at a speed of 300-700 rpm; the emulsion is added to a chitosan acetic acid solution heated in a water bath at 65-80 DEG C at a mass ratio of 1:(1.5-2.5) to disperse uniformly, alkali is added to adjust the pH to be greater than or equal to 7, and then the chitosan is gradually precipitated with the paraffin emulsion particles as the core, until the chitosan no longer precipitates, then filtered, washed and dried to obtain chitosan-coated paraffin microcapsules.

[0063] B: the chitosan-coated paraffin microcapsules are dispersed in water, and p-azidobenzoic acid is added, then left to stand, filtered and dried to obtain chitosan-coated paraffin microcapsules with p-azidobenzoic acid adsorbed on the surface. The mass ratio of chitosan-coated paraffin microcapsules, p-azidobenzoic acid and water is 1:(0.1-0.3):(80-120).

[0064] C: The chitosan-coated paraffin microcapsules with p-azidobenzoic acid adsorbed on the surface are dispersed in an alkaline ethanol aqueous solution (ethanol concentration 80-90 wt%) with a pH of 8-10, and tetraethyl orthosilicate is added dropwise under stirring. After standing, filtering, and cleaning and drying, the obtained product is subjected to ultraviolet light irradiation treatment for 5-10 min to obtain silica / chitosan-coated paraffin microcapsules with voids inside. The mass ratio of the chitosan-coated paraffin microcapsules with p-azidobenzoic acid adsorbed on the surface, the tetraethyl orthosilicate, and the alkaline ethanol aqueous solution is 1:(0.6-0.8):(80-120).

[0065] D: The silica / chitosan-coated paraffin microcapsules are dispersed in water, and aluminum chloride is added. The pH is adjusted to alkaline (preferably 8-9) by adding a base. The reaction is carried out at 40-45°C. After filtering, cleaning, and drying, phase change microcapsules with a paraffin with a melting point of 50-60°C as the core material, chitosan as the inner wall material, and silica modified with aluminum hydroxide as the outer wall material are obtained. The mass ratio of the silica / chitosan-coated paraffin microcapsules, the aluminum chloride, and the water is 1:(0.6-0.8):(80-120).

[0066] The preparation method of the above-mentioned phase change waterproof and breathable packaging film comprises the following steps:

[0067] S1: Dissolve the hydrophilic TPU particles and the polyurethane hydrogel into the solvent A to obtain a mixed solution.

[0068] S2: After adding the defoaming agent, the dispersant A, and the dispersant B in the solvent B and stirring uniformly, the phase change microcapsules and the pore-forming agent are added and dispersed uniformly. Then, the mixed solution is added and stirred. Finally, the thickening agent is added and stirred to obtain a film solution.

[0069] S3: The film solution is coated on a release film, and the solvent is removed by heating at 75-85°C to obtain a semi-finished film with a thickness of 0.1-0.5 mm.

[0070] S4: The semi-finished film is immersed in an acidic solution (preferably a 5-15 wt% hydrochloric acid solution) and heated at 40-45°C until the pore-forming agent is completely consumed to form breathable micropores. After taking out, cleaning, and drying, the phase change waterproof and breathable packaging film is obtained.

[0071] A vehicle lamp anti-fog material comprises a long-acting moisture control material and a phase change waterproof and breathable packaging film therefor. The long-acting moisture control material adopts the moisture control layer in the prior patent CN115157810B of the applicant, which is composed of 1-5 layers of moisture control sheets stacked together. Each of the moisture control sheets comprises a substrate and a modified moisture control high polymer coating layer covering the surface of the substrate. The raw materials of the modified moisture control high polymer coating layer include the following raw materials by weight: 1-10 parts of modified superabsorbent polymer, 15-25 parts of potassium salt, 5-10 parts of chloride salt, and 30-50 parts of solvent. Specific embodiments

[0073] Example 1 and Comparative Example 1-4 of phase change microcapsule preparation

[0074] Example 1 (chitosan inner wall material + aluminum hydroxide / silica outer wall material)

[0075] A: 100 g of melted paraffin wax 56 (melting point 56 °C) and emulsifier Tween-80 were added to deionized water at 70 °C, and after stirring and emulsification at a speed of 500 rpm, a paraffin wax emulsion was obtained (paraffin wax concentration 1.5 wt%, emulsifier concentration 0.5 wt%); 1000 g of the paraffin wax emulsion was added to 2000 g of a chitosan acetic acid solution (chitosan concentration 2.5 wt%, acetic acid concentration 2.0 wt%) heated in a water bath at 70 °C and dispersed uniformly, and alkali was added to adjust the pH to 7.5, and then it was left to stand, and chitosan gradually precipitated with the paraffin wax emulsion as the core, until no more chitosan precipitated, then it was filtered, washed and dried to obtain chitosan-coated paraffin wax microcapsules.

[0076] B: 10 g of chitosan-coated paraffin wax microcapsules were dispersed in 1000 mL of deionized water, and 2 g of p-azidobenzoic acid was added, and then it was left to stand, filtered and dried to obtain chitosan-coated paraffin wax microcapsules with p-azidobenzoic acid adsorbed on the surface.

[0077] C: 5 g of chitosan-coated paraffin wax microcapsules with p-azidobenzoic acid adsorbed on the surface were dispersed in 500 mL of an alkaline ethanol aqueous solution (ethanol concentration 85 wt%) with a pH of 9, and 3.5 g of tetraethyl orthosilicate was added dropwise under stirring, and then it was left to stand, filtered, washed and dried, and the obtained product was subjected to ultraviolet light irradiation treatment for 8 min to obtain silica / chitosan-coated paraffin wax microcapsules with voids inside.

[0078] D: 5 g of silica / chitosan-coated paraffin wax microcapsules were dispersed in 500 mL of deionized water, and 3.5 g of aluminum chloride was added, and then the pH was adjusted to 8.5, and it was heated at 42 °C for reaction, and then it was filtered, washed and dried to obtain phase change microcapsules.

[0079] Comparative Example 1 (silica single-layer wall material)

[0080] 100 g of melted paraffin wax 56 (melting point 56 °C), 70 g of tetraethyl orthosilicate and emulsifier Tween-80 were added to deionized water at 70 °C, and after stirring and emulsification at a speed of 500 rpm, a paraffin wax emulsion was obtained (paraffin wax concentration 1.5 wt%, emulsifier concentration 0.5 wt%); sodium hydroxide solution was added dropwise under stirring to adjust the pH of the emulsion to 9, and then it was left to stand, filtered, washed and dried to obtain silica-coated paraffin wax microcapsules.

[0081] Comparative Example 2 (chitosan single-layer wall material)

[0082] A: 100 g of melted paraffin wax 56 (melting point 56 °C) and emulsifier Tween-80 were added to deionized water at 70 °C, and after emulsification with stirring at a speed of 500 rpm, a paraffin wax emulsion was obtained (paraffin wax concentration 1.5 wt%, emulsifier concentration 0.5 wt%); 1000 g of the paraffin wax emulsion was added to 2000 g of a chitosan acetic acid solution (chitosan concentration 2.5 wt%, acetic acid concentration 2.0 wt%) heated in a water bath at 70 °C, and the pH was adjusted to 7.5 with alkali. After standing, the chitosan gradually precipitated with the paraffin wax emulsion particles as the core, and after the chitosan no longer precipitated, filtration, washing and drying were performed to obtain chitosan-coated paraffin wax microcapsules.

[0083] Comparative Example 3 (chitosan inner wall material + aluminum hydroxide / silicon dioxide outer wall material, no gap)

[0084] A: 100 g of melted paraffin wax 56 (melting point 56 °C) and emulsifier Tween-80 were added to deionized water at 70 °C, and after emulsification with stirring at a speed of 500 rpm, a paraffin wax emulsion was obtained (paraffin wax concentration 1.5 wt%, emulsifier concentration 0.5 wt%); 1000 g of the paraffin wax emulsion was added to 2000 g of a chitosan acetic acid solution (chitosan concentration 2.5 wt%, acetic acid concentration 2.0 wt%) heated in a water bath at 70 °C, and the pH was adjusted to 7.5 with alkali. After standing, the chitosan gradually precipitated with the paraffin wax emulsion particles as the core, and after the chitosan no longer precipitated, filtration, washing and drying were performed to obtain chitosan-coated paraffin wax microcapsules.

[0085] B: 5 g of chitosan-coated paraffin wax microcapsules were dispersed in 500 mL of an alkaline ethanol aqueous solution (ethanol concentration 85 wt%) with a pH of 9, and 3.5 g of tetraethyl orthosilicate was added dropwise under stirring. After standing, filtration, washing and drying were performed to obtain silicon dioxide / chitosan-coated paraffin wax microcapsules.

[0086] C: 5 g of silicon dioxide / chitosan-coated paraffin wax microcapsules were dispersed in 500 mL of deionized water, and 3.5 g of aluminum chloride was added. The pH was adjusted to 8.5 with alkali, and heating was performed at 42 °C. After filtration, washing and drying were performed to obtain phase change microcapsules.

[0087] Comparative Example 4 (chitosan inner wall material + silicon dioxide outer wall material)

[0088] A: 100 g of melted paraffin wax 56 (melting point 56 °C) and emulsifier Tween-80 were added to 70 °C deionized water, and after emulsification with stirring at a speed of 500 rpm, a paraffin wax emulsion was obtained (paraffin wax concentration 1.5 wt%, emulsifier concentration 0.5 wt%); 1000 g of the paraffin wax emulsion was added to 2000 g of a chitosan acetic acid solution (chitosan concentration 2.5 wt%, acetic acid concentration 2.0 wt%) heated in a water bath at 70 °C, and the pH was adjusted to 7.5 by adding alkali. After standing, the chitosan gradually precipitated with the paraffin wax emulsion particles as the core, and after the chitosan no longer precipitated, it was filtered, washed and dried to obtain chitosan-coated paraffin wax microcapsules.

[0089] B: 10 g of chitosan-coated paraffin wax microcapsules were dispersed in 1000 mL of deionized water, and 2 g of p-azidobenzoic acid was added. After standing, filtering and drying, chitosan-coated paraffin wax microcapsules with p-azidobenzoic acid adsorbed on the surface were obtained.

[0090] C: 5 g of chitosan-coated paraffin wax microcapsules with p-azidobenzoic acid adsorbed on the surface were dispersed in 500 mL of a basic ethanol aqueous solution (ethanol concentration 85 wt%) with a pH of 9, and 3.5 g of tetraethyl orthosilicate was added dropwise under stirring. After standing, filtering, washing and drying, the obtained product was subjected to ultraviolet light irradiation treatment for 8 min to obtain silica / chitosan-coated paraffin wax microcapsules with voids inside.

[0091] Cyclic stability test of phase change microcapsules: 5 g of phase change microcapsules of Example 1 and Comparative Examples 1-4 with intact surface and no adhesion between particles were selected and placed in a photothermal aging oven, with a 100 W LED light source, heated to 80 °C, then taken out and cooled to room temperature, counted as one cycle, and repeated for several cycles. The morphology of the phase change microcapsules was observed under a microscope, and the results are recorded as follows:

[0092]

[0093]

[0094] The phase change microcapsules were tested under the conditions of heat and light aging. As can be seen from the above table, the phase change microcapsules prepared in Example 1 have the strongest light aging and heat aging resistance. After 150 cycles, the surface of the phase change microcapsules is still intact and almost no damage, and there is no adhesion between the particles, indicating that the double-layer wall material has good encapsulation of the internal paraffin wax, and the paraffin wax still does not leak after repeated several times. Only after 200 cycles, the surface of the phase change microcapsules becomes rough and there is slight damage and slight adhesion between the particles, indicating that a small amount of paraffin wax leaks.

[0095] Comparative Example 1 uses only a single layer of silica wall material. After 10 cycles, the surface is slightly damaged and the particles are slightly adhered to each other, indicating that the single layer of silica wall material has poor toughness. After 100 cycles, the surface is severely damaged and the particles are severely adhered to each other, and the particles cannot withstand the repeated changes in volume of the paraffin during the test, easily breaking and causing paraffin to leak.

[0096] Comparative Example 2 uses only a single layer of chitosan wall material. After 10 cycles, the surface is almost undamaged, indicating that the single layer of chitosan wall material has better toughness than the single layer of silica wall material. After 50 cycles, the surface is slightly damaged and the particles are slightly adhered to each other. After 100 cycles, the surface is severely damaged and the particles are severely adhered to each other, indicating that the single layer of chitosan wall material has poorer light and heat aging resistance than the wall material of Example 1, and the encapsulation of paraffin is poor after multiple cycles, with severe leakage of paraffin.

[0097] Comparative Example 3 has a surface that is slightly damaged and the particles are slightly adhered to each other after 150 cycles. After 200 cycles, the surface is severely damaged and the particles are severely adhered to each other. Compared with Example 1, although Comparative Example 3 also uses a double layer of wall material, no local gap is formed between the chitosan layer and the silica layer during preparation, so that when the chitosan layer is expanded by the heat of the paraffin, there is no space for the outer layer of silica with poor toughness to expand, causing the outer layer of silica to easily break after multiple cycles, resulting in a shorter service life than Example 1.

[0098] Comparative Example 4 differs from Example 1 in that it does not have aluminum hydroxide on the surface of the silica wall material, resulting in a surface that is slightly damaged after 100 cycles. After 150 cycles, the surface is slightly damaged and the particles are slightly adhered to each other. After 200 cycles, the surface is severely damaged and the particles are severely adhered to each other. This further indicates that the light and heat aging resistance of the silica wall material is further improved after modification with aluminum hydroxide, thus further extending the service life of the phase change microcapsules of Example 1.

[0099] Phase change waterproof and breathable packaging films of Examples 2-8 and Comparative Examples 5-12

[0100] The raw materials for the phase change waterproof and breathable packaging films of Examples 2-8 and Comparative Examples 5-12 are as follows (all in parts by weight):

[0101]

[0102]

[0103] In the above table, the source of the hydrophilic TPU particles is Lubrizol Tecophilic series, and the source of the polyurethane hydrogel is Dow Aquasorb.

[0104] The preparation method of the above phase change waterproof and breathable packaging film is as follows:

[0105] S1: Dissolve the hydrophilic TPU particles and the polyurethane hydrogel into the solvent A to obtain a mixed solution.

[0106] S2: After adding the defoaming agent, dispersant A and dispersant B in the solvent B, stir until uniform, then add the phase change microcapsules and pore-forming agent and disperse uniformly, then add the mixed solution and stir, finally add the thickening agent and stir to obtain a coating solution.

[0107] S3: Coat the coating solution on a release film, heat at 80°C to remove the solvent, and obtain a semi-finished film with a thickness of 0.3 mm.

[0108] S4: Dip the semi-finished film in a 10wt% hydrochloric acid solution, heat at 45°C until the pore-forming agent is completely consumed to form breathable micropores, then take it out, wash and dry to obtain a phase change waterproof and breathable packaging film.

[0109] Performance test of phase change waterproof and breathable packaging film

[0110] The performance test data of the phase change waterproof and breathable packaging film of each example and comparative example are as follows:

[0111] (1) Fogging time test: the phase change waterproof and breathable packaging film of each example, comparative example and conventional hydrophobic expanded polytetrafluoroethylene film is packaged with long-acting moisture control material (long- width thickness size of 4cm*4cm*2cm, using the moisture control layer of example 1 in the applicant's prior patent CN115157810B), first absorbs moisture at 85% humidity and temperature 25°C for 24 hours, then put into the car lamp, then light up and heat the back of the car lamp to 80°C, spray water on the lampshade, water temperature 5°C, observe the fogging time inside the car lamp;

[0112] (2) Heat absorption test: 3mm thick material (3mm film is prepared according to the same method), place the packaging film on the hot plate at 80°C, test the highest temperature of the other side (cold side) within 20 minutes;

[0113] (3) Air permeability: refer to JIS P8117;

[0114] (4) Water permeation pressure: refer to JIS L 10926.1 method B;

[0115] (5) Tensile strength: refer to ASTM D638-14;

[0116] (6) Tear strength: refer to ASTM D1004-13(2018);

[0117] (7) Elongation: refer to ASTM D638-141.

[0118]

[0119] From the data comparison of the above table, it can be seen that:

[0120] Compared with conventional hydrophobic expanded polytetrafluoroethylene films, each embodiment has been significantly improved in terms of misting time, heat absorption test, tensile strength, tear strength, and elongation.

[0121] The difference between Comparative Examples 5-6 and Example 2-4 is that the content of phase change microcapsules is different, which directly leads to significant differences in the data of the obtained encapsulation film in terms of misting time and heat absorption test. From the comparison, it can be seen that as the content of phase change microcapsules increases, the misting time gradually increases and the cold side temperature gradually decreases. Comparative Example 5 has the shortest misting time and the highest cold side temperature because it does not contain phase change microcapsules. Comparative Example 6 has lower tensile strength, tear strength, and elongation than Examples 2-4 because of the excessive content of phase change microcapsules.

[0122] The difference between Comparative Examples 7-8 and Examples 3, 5-6 is that the content of polyurethane hydrogel is different. From the comparison, it can be seen that this difference directly leads to significant differences in the data of the encapsulation film in terms of misting time, cold side temperature, and mechanical properties. Comparative Example 7 has a shorter misting time and a higher cold side temperature because it does not contain polyurethane hydrogel. Comparative Example 8 has significantly lower mechanical properties (tensile strength, tear strength, and elongation) because of the excessive content of polyurethane hydrogel.

[0123] The difference between Comparative Examples 9 and 10 and Example 3 is that the particle size of the porogen is different. Comparative Example 9 has a smaller particle size of the porogen, resulting in lower air permeability and higher water permeability of the encapsulation film. Comparative Example 10 has a larger particle size of the porogen, resulting in higher air permeability and lower water permeability of the encapsulation film, and at the same time, its mechanical properties (tensile strength, tear strength, and elongation) are poorer.

[0124] The difference between Comparative Examples 11-12 and Examples 3, 7-8 is that the content of the porogen is different. Comparative Example 11 has a lower content of the porogen, resulting in lower air permeability and higher water permeability. Comparative Example 12 has a higher content of the porogen, resulting in higher air permeability and lower water permeability, and at the same time, its mechanical properties (tensile strength, tear strength, and elongation) are poorer.

[0125] The raw materials and equipment used in the present application are conventional in the art unless otherwise specified; the methods used in the present application are conventional in the art unless otherwise specified.

[0126] The above is only the preferred embodiment of the present application, and does not limit the present application, and any simple modification, change and equivalent transformation of the above embodiment according to the technical essence of the present application still belongs to the protection scope of the technical scheme of the present application.

Claims

1. A phase change waterproof and breathable packaging film for long-acting moisture control material, characterized in that: The raw materials include the following weight parts: hydrophilic TPU particles, 100 parts; phase change microcapsules with a particle size of 100-350 microns and a phase change temperature of 50-60℃, 5-25 parts; polyurethane hydrogel, 10-45 parts; porogen with a particle size of 0.1-1 micron, 3-20 parts; The phase change microcapsules use paraffin with a melting point of 50-60℃ as the core material, chitosan as the inner wall material, and modified aluminum hydroxide silica as the outer wall material.

2. The phase change waterproof and vapor permeable packaging film according to claim 1, characterized in that: The raw materials also include the following weight parts: solvent A, 40-60% of the weight of the hydrophilic TPU particles and the polyurethane hydrogel; solvent B, 40-60% of the weight of the hydrophilic TPU particles and the polyurethane hydrogel; dispersant A, 2-5% of the weight of the phase change microcapsules; thickening agent, 1-5% of the weight of the polyurethane hydrogel; dispersant B, 3-8% of the weight of the porogen; defoaming agent, 0.1-2.5% of the weight of solvent B.

3. The phase change waterproof and breathable packaging film according to claim 2, characterized in that: the solvent A is tetrahydrofuran; the solvent B is acetone; the dispersant A is aqueous amino silane; the dispersant B is BYK-9810; the thickening agent is sodium hydroxymethyl cellulose; the porogen is calcium carbonate particles; the defoaming agent is Wacker SC-129.

4. The phase change waterproof and vapor permeable packaging film according to claim 1, characterized in that: The preparation method of the phase change microcapsules is as follows: A: Add melted paraffin and emulsifier to water at 65-80℃, stir and emulsify to obtain a paraffin emulsion; add the paraffin emulsion to a preheated chitosan acetic acid solution at 65-80℃, disperse uniformly, adjust the pH to ≥7 with alkali, stand, filter, wash and dry to obtain chitosan-coated paraffin microcapsules; B: Disperse the chitosan-coated paraffin microcapsules in water, add p-azidobenzoic acid, stand, filter, and dry to obtain chitosan-coated paraffin microcapsules with p-azidobenzoic acid adsorbed on the surface; C: Disperse the chitosan-coated paraffin microcapsules with p-azidobenzoic acid adsorbed on the surface in an alkaline ethanol aqueous solution, add tetraethyl orthosilicate dropwise under stirring, stand, filter, wash and dry, and perform ultraviolet light irradiation treatment on the obtained product to obtain silica / chitosan-coated paraffin microcapsules with voids inside; D: Disperse the silica / chitosan-coated paraffin microcapsules in water, add aluminum chloride, adjust the pH to alkaline with alkali, heat and react, filter, wash and dry to obtain phase change microcapsules.

5. The phase change waterproof and breathable packaging film according to claim 4, characterized in that: In step A, the concentrations of paraffin and emulsifier in the paraffin emulsion are 1-2wt% and 0.3-0.7wt%, respectively; the stirring speed for emulsification is 300-700rpm; the concentrations of chitosan and acetic acid in the chitosan acetic acid solution are 2-3wt% and 1.5-2.5wt%, respectively; and the mass ratio of paraffin emulsion to chitosan acetic acid solution is 1:(1.5-2.5); In step B, the mass ratio of chitosan-coated paraffin microcapsules, p-azidobenzoic acid and water is 1:(0.1-0.3):(80-120). In step C, the mass ratio of chitosan-coated paraffin microcapsules with p-azidobenzoic acid, tetraethyl orthosilicate and alkaline ethanol solution is 1: (0.6-0.8): (80-120), the concentration of ethanol in the alkaline ethanol solution is 80-90wt%, the pH of the alkaline ethanol solution is 8-10, and the ultraviolet irradiation time is 5-10min. In step D, the mass ratio of silica / chitosan-coated paraffin microcapsules, aluminum chloride and water is 1: (0.6-0.8): (80-120), the pH is adjusted to 8-9 by adding alkali, and the reaction temperature is 40-45℃.

6. A method of producing the phase change waterproof and air-permeable packaging film according to any one of claims 1 to 5, characterized by The method comprises the following steps: S1: Dissolve the hydrophilic TPU particles and the polyurethane hydrogel into solvent A to obtain a mixed solution; S2: After adding the defoaming agent, dispersant A and dispersant B in solvent B and stirring uniformly, add the phase change microcapsules and pore-forming agent and disperse uniformly, then add the mixed solution and stir, and finally add the thickening agent and stir to obtain a film solution; S3: Coat the film solution on a release film, remove the solvent by heating, and obtain a semi-finished film; S4: Dip the semi-finished film in an acidic solution until the pore-forming agent is completely reacted to form breathable micropores, then take it out, wash and dry to obtain a phase change waterproof and breathable packaging film.

7. The preparation method of claim 6, wherein: In S3, the heating temperature is 75-85℃, and the thickness of the semi-finished film is 0.1-0.5mm; In S4, the acidic solution is a 5-15wt% hydrochloric acid solution, and the reaction temperature is 40-45℃.

8. Use of the phase change waterproof and air-permeable packaging film according to any one of claims 1-5 or the phase change waterproof and air-permeable packaging film obtained by the preparation method of claims 6 or 7 in packaging long-acting moisture control materials, characterized in that: The long-acting moisture control material is used for vehicle lamp anti-fogging, and is stacked by 1-5 layers of moisture control sheets; each of the moisture control sheets comprises a substrate and a modified moisture control polymer coating layer covering the surface of the substrate; the raw materials of the modified moisture control polymer coating layer include the following raw materials by weight: 1-10 parts of modified superabsorbent polymer, 15-25 parts of potassium salt, 5-10 parts of chloride salt and 30-50 parts of solvent.

9. An anti-fog material for vehicle lights, characterized by: It comprises: a long-acting moisture control material; stacked by 1-5 layers of moisture control sheets; each of the moisture control sheets comprises a substrate and a modified moisture control polymer coating layer covering the surface of the substrate; the raw materials of the modified moisture control polymer coating layer include the following raw materials by weight: 1-10 parts of modified superabsorbent polymer, 15-25 parts of potassium salt, 5-10 parts of chloride salt and 30-50 parts of solvent; a phase change waterproof and breathable packaging film as claimed in any one of claims 1-5 or obtained by the preparation method of claims 6 or 7 for packaging the long-acting moisture control material.

10. The anti-fog material for vehicle lamps according to claim 9, wherein: The fogging time is ≥25min.

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