Hydroxyl acrylic resin, preparation method thereof, hydroxy acrylic resin modified TPU (Thermoplastic Polyurethane) film for swelling adhesive tape base material and preparation method of TPU film

Abstract

The invention discloses hydroxy acrylic resin and a preparation method thereof, a hydroxy acrylic resin modified TPU (thermoplastic polyurethane) film for a swelling adhesive tape base material and a preparation method of the TPU film. The high-TG hydroxy acrylic resin is prepared by compounding specific raw materials, the hydroxy acrylic resin is used for modifying a TPU film for a swelling adhesive tape base material, and the hydroxy acrylic resin has a high glass transition temperature and contains rigid chain segments such as polymethyl methacrylate, polystyrene and polyacrylonitrile, so that the hydroxy acrylic resin has relatively high hardness and good bearing performance, and can be used for preparing the TPU film for the swelling adhesive tape base material. After the hydroxy acrylic resin modified TPU film is added into the TPU film, the hydroxy acrylic resin modified TPU film has a good supporting effect on the TPU film, the stiffness and surface hardness of the TPU film are improved, the temperature resistance of the TPU film is enhanced, and the prepared hydroxy acrylic resin modified TPU film has the advantages of being high in expansion rate, good in temperature resistance and good in stability, and the strength of the hydroxy acrylic resin modified TPU film cannot be reduced after the hydroxy acrylic resin modified TPU film is soaked in electrolyte for a long time.

Description

A hydroxyl acrylic resin, its preparation method, a hydroxyl acrylic resin-modified TPU film for use as a substrate in swelling tape, and the method for preparing the TPU film. Technical Field

[0001] This invention relates to the field of swelling tapes, and more particularly to a hydroxyl acrylic resin, its preparation method, a hydroxyl acrylic resin-modified TPU film for swelling tape substrates, and the preparation method of the TPU film. Background Technology

[0002] Cylindrical batteries are a crucial type of lithium-ion battery, characterized by mature technology, high cell uniformity, high automation in production, and low cost. They are widely used in consumer electronics, electric vehicles, power tools, and energy storage systems. The cylindrical battery structure primarily consists of a casing, an organic electrolyte, and a cylindrical core formed by the rolling of positive and negative electrodes and a separator. A gap exists between the casing and the cylindrical core, which, when the battery is shaken, can easily lead to damage or displacement of internal components, short circuits, and increased resistance, posing safety risks. To address these issues, swelling tape is used. After absorbing the electrolyte, the swelling tape expands in length, width, and thickness, significantly increasing its volume. This effectively fills the gap between the casing and the internal cells, making the internal components more stable, reducing safety risks, and increasing the overall stability of the cylindrical battery. Swellable tape is made by coating an expandable base film with polyacrylate pressure-sensitive adhesive. After absorbing the electrolyte of a lithium-ion battery, the expandable base film can expand in the length, width and thickness directions, thereby increasing its volume significantly. Commonly used expandable base films mainly include oriented polystyrene (OPS) film or thermoplastic polyurethane (TPU) film.

[0003] It is worth further understanding that the base film for currently used lithium battery swelling tapes mainly uses oriented polystyrene (OPS) film or thermoplastic polyurethane (TPU) film. Both of these films can expand to a certain extent when immersed in electrolyte. However, OPS film has poor temperature resistance and shrinks significantly under high-temperature conditions, posing certain safety risks and limiting its use to lower-end products. Thermoplastic polyurethane (TPU) film has better temperature resistance, a high expansion rate, and can expand in all three dimensions (length, width, and height). Therefore, the lithium battery industry mainly uses TPU film as the base film for lithium-ion battery swelling tapes. In existing technologies, such as Chinese patent application number CN111518481A, a lithium battery-specific swelling tape and its manufacturing process are disclosed. Its swelling base film is made of TPU particles, E... The swollen tape prepared by this method is made by dissolving components such as VA particles, styrene resin, (titanium dioxide) pigment, crosslinking agent, and catalyst in solvents such as DMF and toluene, and then coating it onto the surface of a release film to form a film of a certain thickness. After contacting the electrolyte, the swollen tape can swell and deform in the length and width directions, increasing its area to more than 200% of the original. However, the styrene, EVA and other components selected in this method are non-reactive substances and do not contain active functional groups. After film formation, they are not connected to components such as TPU through chemical bonds. Therefore, the swollen tape prepared by this method is easy to partially dissolve after long-term immersion in electrolyte, resulting in the swollen tape becoming soft, losing strength and even losing its shape, and cannot continuously fill the cell and casing of the cylindrical battery. Chinese patent application CN114213983A discloses a base film and a swelling tape for lithium batteries. This method involves melting a mixture of ethylene-ester copolymers, organic peroxides, slip agents, and antioxidants at high temperatures, mixing them uniformly, and then extruding the mixture into a film using a screw extruder. A hot-melt pressure-sensitive adhesive is then coated onto the film to form a swelling tape. This invention allows the swelling tape to expand at a high rate in electrolyte, maintain a certain strength and shape in three dimensions, and not shrink at high temperatures. However, this method requires proprietary screw extrusion equipment, resulting in high equipment investment, low production efficiency, and high hot-melt adhesive costs, making large-scale application difficult. Therefore, a more comprehensive solution is urgently needed to address the shortcomings of the existing technology. Summary of the Invention

[0004] To address the technical problem of poor TPU film performance and difficulty in production in existing expandable adhesive tapes, this invention provides a solution.

[0005] To achieve the above objectives, the present invention provides a hydroxyl acrylic resin, which, by weight, has the following specific composition:

[0006] Hard monomer 20-40 parts, soft monomer 15-25 parts, functional monomer 10-20 parts, initiator 0.1-2 parts, organic solvent 30-100 parts;

[0007] The hard monomer is one or more of methyl methacrylate, butyl methacrylate, styrene, and acrylonitrile.

[0008] As an improvement of this application, the soft monomer is mainly one or more of isooctyl acrylate, butyl acrylate, and ethyl acrylate.

[0009] As an improvement to this application, the functional monomer is one or more of acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxypropyl acrylate, and hydroxyethyl methacrylate.

[0010] As an improvement to this application, the initiator is one or both of azobisisobutyronitrile (AIBN) and benzoyl peroxide (BPO).

[0011] As an improvement to this application, the solvent is one or more of toluene, xylene, ethyl acetate, butyl acetate, and butanone.

[0012] This application also provides a method for preparing a hydroxyl acrylic resin, comprising the following steps:

[0013] According to the formula, the hard monomer, soft monomer, functional monomer and 80% initiator are mixed and stirred evenly, and then added to the constant pressure dropping funnel. 50% of the organic solvent is added to the reaction vessel. Nitrogen gas is introduced into the reaction vessel and the temperature is raised to 140±2℃. Then the mixture in the constant pressure dropping funnel is added dropwise to the reaction vessel, and the addition is completed in 3-5 hours. After the addition is completed, the temperature is maintained for 1-2 hours. Then the remaining 15% organic solvent and 20% initiator are added dropwise to the reaction vessel in 10-20 minutes. The temperature is maintained for 2 hours, and then 35% organic solvent is added for dilution. The temperature is lowered to 60℃ and the material is discharged to obtain hydroxyl acrylic resin with a solid content of 60%.

[0014] This application also provides a hydroxyl acrylic resin modified TPU film for swelling tape substrate, which, by weight, has the following specific composition: 50-70 parts of polyester TPU particles, 10-25 parts of polycarbonate TPU particles, 0-10 parts of polyether TPU particles, 10-20 parts of hydroxyl acrylic resin with a solid content of 60% as described above, 5-10 parts of polyether polyol, 5-15 parts of curing agent, 1-10 parts of antioxidant, and 100-200 parts of organic solvent.

[0015] As an improvement to this application, the polyester-type TPU particles are mainly one or more of BASF Elastollan® C85A10 and Elastollan® C95A10.

[0016] As an improvement to this application, the polycarbonate-type TPU particles are mainly one or more of MIRATHANE C85 and MIRATHANE C90 from MIRATHANE New Materials.

[0017] As an improvement to this application, the polyether-type TPU is mainly one or more of BASF's Elastollan® 1185A, Elastollan® 1190 A, and MIRATHANE M90.

[0018] As an improvement to this application, the polyether polyol is mainly one or more of difunctional or trifunctional polyether polyols.

[0019] As an improvement of this application, the curing agent is mainly an isocyanate or amino resin such as toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), diphenylmethane diisocyanate (MDI), and isophorone diisocyanate (IPDI).

[0020] As an improvement of this application, the antioxidant is mainly one or two of antioxidant 1010 and antioxidant 405.

[0021] As an improvement of this application, the organic solvent is mainly one or more of acetone, ethyl acetate, and DMF.

[0022] A method for preparing a hydroxyl acrylic resin modified TPU film for use as a swellable tape substrate is also provided, comprising the following steps:

[0023] According to the formula, TPU particles are dissolved in an organic solvent by heating until a TPU solution with a solid content of 35% is obtained. During the dissolution process, the mixture is stirred and heated at a temperature of 60±5℃. Then, hydroxyl acrylic resin, polyether polyol, antioxidant, and curing agent with a pre-set solid content of 60% are added to the TPU solution. After stirring evenly, the mixture is filtered through a 400-mesh filter and allowed to stand for 20-30 minutes to defoam. The resulting solution is then coated onto a 50µm double-sided silicone release film and dried to form a 40-50µm thick hydroxyl acrylic modified TPU film for use as a substrate for swelling tape.

[0024] The beneficial effects of this invention are as follows: Compared with the prior art, the hydroxyl acrylic resin, its preparation method, the hydroxyl acrylic resin-modified TPU film for swelling tape substrate, and the preparation method of the TPU film provided by this invention have the following beneficial effects:

[0025] 1) This invention prepares a hydroxyl acrylic resin with a high glass transition temperature by compounding specific raw materials, and uses it to modify TPU film for swelling tape substrate. The hydroxyl acrylic resin has a high glass transition temperature and contains rigid segments such as polymethyl methacrylate, polystyrene, and polyacrylonitrile, so it has high hardness and good load-bearing capacity. After being added to TPU film, it provides good support for TPU film, improves the stiffness and surface hardness of TPU film, and enhances the temperature resistance of TPU film.

[0026] 2) The hydroxyl acrylic resin modified TPU film used as the substrate for swelling tape can expand in three dimensions (length, width, and thickness) when immersed in electrolyte. The expansion rate is fast and the expansion rate is high. After immersion in electrolyte at room temperature for 1 hour, the thickness expansion rate is >20% and the volume expansion rate is >200%.

[0027] 3) Hydroxy acrylic resin modified TPU film used as substrate for swelling tape. During use, because hydroxy acrylic resin contains reactive functional group - hydroxyl, it can form chemical bonds with thermoplastic polyurethane (TPU), polyether polyol and crosslinking agent. The prepared TPU film has high crosslinking density, good temperature resistance, will not dissolve after long-term immersion in electrolyte, will not decrease in strength, is not easy to deform, and has good stability.

[0028] 4) Hydroxy acrylic resin modified TPU film used as substrate for swelling tape: During use, because hydroxy acrylic resin contains acrylate polymer segments, it has a high affinity with polyacrylate pressure-sensitive adhesive. After the swelling tape is made, the polyacrylate pressure-sensitive adhesive has good adhesion to its surface and is not easy to delaminate. Attached Figure Description

[0029] Figure 1 is a flowchart of the present invention. Detailed Implementation

[0030] To more clearly illustrate the present invention, the invention will be further described below with reference to the accompanying drawings.

[0031] In the following description, specific examples are given to provide a more in-depth understanding of the invention. It is obvious that the described embodiments are merely some, not all, of the embodiments of the invention. It should be understood that the specific embodiments described are for illustrative purposes only and are not intended to limit the scope of the invention.

[0032] It should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of the said feature, integral, step, operation, element, or component, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, or combinations thereof.

[0033] To address the aforementioned technical problems, this application provides a hydroxyl acrylic resin, as shown in Figure 1. The specific composition, by mass parts, is as follows:

[0034] Hard monomer 20-40 parts, soft monomer 15-25 parts, functional monomer 10-20 parts, initiator 0.1-2 parts, organic solvent 30-100 parts;

[0035] The hard monomer is one or more of methyl methacrylate, butyl methacrylate, styrene, and acrylonitrile; the selection of styrene and acrylonitrile as hard monomers is mainly to improve the polymer's chemical resistance, thermal stability, and strength.

[0036] It is not difficult to understand that the traditional preparation method for the base film of the cylindrical battery swelling tape mainly involves dissolving TPU particles, EVA resin, and non-reactive components such as color paste, along with crosslinking agents and catalysts, into an organic solvent and mixing them evenly. Then, a coating process is used to coat the mixture onto a release film and dry it to form a film. However, this invention synthesizes a high-TG hydroxyl acrylic resin and uses it to modify TPU films in the swelling tape substrate without adding any non-reactive components. The hydroxyl acrylic resin synthesized in this invention contains rigid segments such as polystyrene, acrylonitrile, and polymethyl methacrylate. At the same time, the hydroxyl groups it contains can chemically react with the crosslinking agent, connecting TPU, hydroxyl acrylic resin, polyether polyol, and other components together through chemical bonds, thereby forming a modified TPU film with a high crosslinking density and thus obtaining better overall performance.

[0037] As a preferred option, the soft monomer is mainly one or more of isooctyl acrylate, butyl acrylate, and ethyl acrylate;

[0038] As a preferred option, the functional monomer is one or more of acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxypropyl acrylate, and hydroxyethyl methacrylate.

[0039] As a preferred option, the initiator is one or both of azobisisobutyronitrile (AIBN) and benzoyl peroxide (BPO).

[0040] As a preferred option, the solvent is one or more of toluene, xylene, ethyl acetate, butyl acetate, and butanone.

[0041] As a general inventive concept, this application also provides a method for preparing a hydroxyl acrylic resin, comprising the following steps:

[0042] According to the formula, the hard monomer, soft monomer, functional monomer and 80% initiator are mixed and stirred evenly, and then added to the constant pressure dropping funnel. 50% of the organic solvent is added to the reaction vessel. Nitrogen gas is introduced into the reaction vessel and the temperature is raised to 140±2℃. Then the mixture in the constant pressure dropping funnel is added dropwise to the reaction vessel, and the addition is completed in 3-5 hours. After the addition is completed, the temperature is maintained for 1-2 hours. Then the remaining 15% organic solvent and 20% initiator are added dropwise to the reaction vessel in 10-20 minutes. The temperature is maintained for 2 hours, and then 35% organic solvent is added for dilution. The temperature is lowered to 60℃ and the material is discharged to obtain hydroxyl acrylic resin with a solid content of 60%.

[0043] As a general inventive concept, this application also provides a hydroxyl acrylic resin modified TPU film for swelling tape substrate, which, by weight parts, has the following specific composition: 50-70 parts of polyester TPU particles, 10-25 parts of polycarbonate TPU particles, 0-10 parts of polyether TPU particles, 10-20 parts of hydroxyl acrylic resin with a solid content of 60% of any of the above, 5-10 parts of polyether polyol, 5-15 parts of curing agent, 1-10 parts of antioxidant, and 100-200 parts of organic solvent;

[0044] Compared to traditional techniques that involve melting and mixing film-forming polymer particles, crosslinking agents, and other components at high temperatures before extruding them into a film using a screw extruder, this invention uses a coating process to produce hydroxyl acrylic resin modified TPU films for swelling tape base films. This involves dissolving TPU particles, synthetic hydroxyl acrylic resin, polyether polyol, crosslinking agents, and other components in an organic solvent and stirring them evenly before coating them onto a double-sided silicone oil release film and drying them to form a film. The entire production process is simpler.

[0045] As a preferred option, the polyester-type TPU granules are mainly one or more of BASF's Elastollan® C85A10 and Elastollan® C95A10.

[0046] As a preferred option, the polycarbonate-type TPU particles are mainly one or more of MIRATHANE C85 and MIRATHANE C90 from MIRATHANE New Materials.

[0047] As a preferred option, the polyether-type TPU is mainly one or more of BASF's Elastollan® 1185A, Elastollan® 1190 A, and MIRATHANE M90.

[0048] As a preferred option, the polyether polyol is mainly one or more of difunctional or trifunctional polyether polyols.

[0049] As a preferred option, the curing agent is mainly an isocyanate or amino resin such as toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), diphenylmethane diisocyanate (MDI), and isophorone diisocyanate (IPDI).

[0050] As a preferred option, the antioxidant is mainly one or two of antioxidant 1010 and antioxidant 405.

[0051] As a preferred option, the organic solvent is mainly one or more of acetone, ethyl acetate, and DMF.

[0052] As a general inventive concept, this application also provides a method for preparing a hydroxyl acrylic resin modified TPU film for a swelling tape substrate, comprising the following steps:

[0053] According to the formula, TPU particles are dissolved in an organic solvent by heating until a TPU solution with a solid content of 35% is obtained. During the dissolution process, the mixture is stirred and heated at a temperature of 60±5℃. Then, hydroxyl acrylic resin, polyether polyol, antioxidant, and curing agent with a pre-set solid content of 60% are added to the TPU solution. After stirring evenly, the mixture is filtered through a 400-mesh filter and allowed to stand for 20-30 minutes to defoam. The resulting solution is then coated onto a 50µm double-sided silicone release film and dried to form a 40-50µm thick hydroxyl acrylic modified TPU film for use as a substrate for swelling tape.

[0054] The features and performance of the present invention will be further described in detail below with reference to embodiments;

[0055] Example 1

[0056] Preparation of hydroxyl acrylic resin: Add 20 parts xylene to a four-necked flask equipped with a thermometer and a constant-pressure dropping funnel. Weigh out 7.5 parts methyl methacrylate, 20 parts butyl acrylate, 12 parts hydroxyethyl acrylate, 16 parts styrene, 5 parts acrylonitrile, and 0.8 parts initiator benzoyl peroxide, and mix thoroughly. Add the mixture to the constant-pressure dropping funnel, purge the reaction vessel with nitrogen, and heat to 140±2℃. Then, add the mixture from the constant-pressure dropping funnel dropwise to the reaction vessel, controlling the addition to be completed within 3 hours. After the addition is complete, maintain the temperature for 1.5 hours. Then, mix 6g xylene with 0.2 parts benzoyl peroxide thoroughly and add the mixture dropwise to the reaction vessel, completing the addition within 10 minutes. After the addition is complete, maintain the temperature for 2 hours, and then add 13.5g xylene to the reaction vessel while stirring and cooling. After cooling to 60℃, discharge the material to obtain the hydroxyl acrylic resin solution with a solid content of 60%.

[0057] Preparation of TPU film: Weigh 7 parts of polyester TPU granules of type Elastollan® C85A10 and 20 parts of polycarbonate TPU granules of type MIRATHANE C90, add 167 parts of DMF, heat and stir at 60°C for 2 hours until all TPU granules are completely dissolved, add 10 parts of hydroxyl acrylic resin with a solid content of 60% as described in step one, 10 parts of trifunctional polyether polyol, 2 parts of antioxidant, and 10 parts of MDI curing agent, stir for 30 minutes, filter through a 400-mesh filter, let stand for 30 minutes to defoam, and then coat it onto a 50µm double-sided silicone release film. After drying, a 40µm thick hydroxyl acrylic modified TPU film for swelling tape substrate is prepared.

[0058] Example 2

[0059] Referring to Example 1, the difference from Example 1 is that the styrene is adjusted from 16 parts to 18 parts, and the acrylonitrile is adjusted from 5 parts to 3 parts; the other technical features are the same as those in Example 1.

[0060] Example 3

[0061] Referring to Example 1, the difference from Example 1 is that the functional monomer is changed from hydroxyethyl acrylate to hydroxypropyl acrylate, while the amount added remains unchanged. All other technical features are the same as in Example 1.

[0062] Example 4

[0063] Referring to Example 1, the difference from Example 1 is that 5 parts of Elastollan® 1190 A polyether-type TPU particles were added during the preparation of the TPU film for the swelling tape substrate. All other technical features are the same as in Example 1.

[0064] Example 5

[0065] Referring to Example 1, the difference from Example 1 is that in the process of preparing the TPU film for the substrate of the swelling tape, the polyether polyol is changed from a trifunctional polyether polyol to a difunctional polyether polyol, while the amount added remains unchanged. All other technical features are the same as in Example 1.

[0066] Example 6

[0067] Referring to Example 1, the difference from Example 1 is that 10 parts of MDI curing agent are replaced with 6 parts of MDI curing agent and 5 parts of TDI curing agent. The remaining technical features are the same as in Example 1.

[0068] Example 7

[0069] Referring to Example 1, the difference from Example 1 is that 10 parts of MDI curing agent are replaced with 12 parts of amino resin curing agent and 2 parts of p-toluenesulfonic acid catalyst. The remaining technical features are the same as in Example 1.

[0070] Comparative Example 1

[0071] Referring to Example 1, the difference from Example 1 is that, in the process of preparing the TPU film for the substrate of the swelling tape, hydroxyl acrylic resin is not added, but 6 parts of styrene resin with non-reactive functional groups are added. All other technical features are the same as in Example 1.

[0072] Comparative Example 2

[0073] Referring to Example 1, the difference from Example 1 is that hydroxyl acrylic resin is not added during the preparation of the TPU film for the swelling tape substrate. All other technical features are the same as in Example 1.

[0074] Comparative Example 3

[0075] Referring to Example 1, the difference from Example 1 is that no polyether polyol is added during the preparation of the TPU film for the swelling tape substrate. All other technical features are the same as in Example 1.

[0076] Test items and corresponding methods:

[0077] Expansion rate test: The TPU films prepared in Examples 1-7 and Comparative Examples 1-3 were cut into test pieces with a size of 30mm*40mm. Multiple test groups were set up, with 5 pieces tested in each group. The corresponding test pieces were placed in a PE bottle and electrolyte was poured in, ensuring that the electrolyte completely submerged the test pieces. The PE bottle was sealed and stored for 1 hour. After the test pieces were taken out, they were flattened. The length and width of each test piece were measured with a ruler, and the thickness of each test piece was measured with a thickness gauge. The volume expansion factor was calculated by dividing the volume of the test piece after soaking in the electrolyte by the volume of the test piece before soaking in the electrolyte. The thickness expansion factor was calculated by dividing the thickness of the test piece after soaking in the electrolyte by the thickness of the test piece before soaking in the electrolyte.

[0078] Tensile strength test: determined in accordance with GB / T 1040.3 2005 "Standard for Tensile Testing of Plastic Sheets", unit is MPa.

[0079] Post-swelling state test: The TPU films prepared in Examples 1-7 and Comparative Examples 1-3 were cut into test samples with a size of 50mm*50mm and immersed in an electrolyte at 85℃ for 4 hours. The changes in shape and strength of the test samples were observed. The specific test results are shown in Table 1 below.

[0080] Table 1

[0081]

[0082] As shown in Table 1 above, in this embodiment of the invention, the chemical cross-linking network formed by hydroxyl acrylic resin and TPU achieves synergistic breakthroughs in key performance aspects. The volume expansion rate is within the range of 204.7%–238.5%, while the thickness expansion rate is within the range of 20.7%–23.4%. The tensile strength remains at a high level of 31.4–36.7 MPa, and the structure remains intact without significant changes in a high-temperature electrolyte environment of 85℃×4h. In contrast, the comparative examples, due to the absence of hydroxyl acrylic resin, replacement with non-reactive resin, or omission of polyether polyol, all exhibit problems such as insufficient expansion rate, high-temperature softening, or strength degradation. This data clearly demonstrates that this invention, through precise component ratio and cross-linking design, successfully solves the core defects of traditional swelling tapes in lithium battery applications, such as easy dissolution, strength decay, and poor thermal stability. While ensuring high swelling response, it also takes into account mechanical reliability and environmental tolerance, providing a more stable technical solution for high-performance lithium battery encapsulation materials.

[0083] The advantages of this invention are:

[0084] This invention relates to a high-TG hydroxyl acrylic resin prepared by compounding specific raw materials, which is then used to modify TPU films used as substrates for swollen adhesive tapes. The hydroxyl acrylic resin has a high glass transition temperature and contains rigid segments such as polymethyl methacrylate, polystyrene, and polyacrylonitrile, thus exhibiting high hardness and good load-bearing capacity. When added to TPU films, it provides better support for the TPU films, improves the stiffness and surface hardness of the TPU films, and enhances the temperature resistance of the TPU films.

[0085] The above-disclosed embodiments are merely a few specific examples of the present invention, but the present invention is not limited thereto. Any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A hydroxyl acrylic resin, characterized in that, The specific composition, measured by mass parts, is as follows: 20-40 parts hard monomer, 15-25 parts soft monomer, 10-20 parts functional monomer, 0.1-2 parts initiator, and 30-100 parts organic solvent; wherein the hard monomer is one or more of methyl methacrylate, butyl methacrylate, styrene, and acrylonitrile.

2. The hydroxyl acrylic resin according to claim 1, characterized in that, The soft monomer is mainly one or more of isooctyl acrylate, butyl acrylate, and ethyl acrylate.

3. The hydroxyl acrylic resin according to claim 1, characterized in that, The functional monomer is one or more of acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxypropyl acrylate, and hydroxyethyl methacrylate.

4. The hydroxyl acrylic resin according to claim 1, characterized in that, The initiator is one or both of azobisisobutyronitrile (AIBN) and benzoyl peroxide (BPO).

5. A method for preparing a hydroxyl acrylic resin, characterized in that, The process includes the following steps: According to the formula, the hard monomer, soft monomer, functional monomer and 80% initiator are mixed and stirred evenly, and then added to a constant pressure dropping funnel. 50% of the organic solvent is added to the reaction vessel. Nitrogen gas is introduced into the reaction vessel and the temperature is raised to 140±2℃. Then the mixture in the constant pressure dropping funnel is added dropwise to the reaction vessel, and the addition is completed in 3-5 hours. After the addition is completed, the temperature is maintained for 1-2 hours. Then the remaining 15% organic solvent and 20% initiator are added dropwise to the reaction vessel in 10-20 minutes. The temperature is maintained for 2 hours, and then 35% organic solvent is added for dilution. The temperature is lowered to 60℃ and the product is discharged to obtain hydroxyl acrylic resin with a solid content of 60%.

6. A hydroxyl acrylic resin modified TPU film for use in swelling tape substrates, characterized in that, The specific composition, by weight parts, is as follows: 50-70 parts of polyester TPU particles, 10-25 parts of polycarbonate TPU particles, 0-10 parts of polyether TPU particles, 10-20 parts of hydroxyl acrylic resin as described in any one of claims 1-5, 5-10 parts of polyether polyol, 5-15 parts of curing agent, 1-10 parts of antioxidant, and 100-200 parts of organic solvent.

7. The hydroxyl acrylic resin modified TPU film for swelling tape substrate according to claim 6, characterized in that, The polyester-type TPU granules are mainly one or more of BASF's Elastollan® C85A10 and Elastollan® C95A10.

8. The hydroxyl acrylic resin modified TPU film for swelling tape substrate according to claim 6, characterized in that, The polyether polyols mentioned are mainly one or more of difunctional or trifunctional polyether polyols.

9. The hydroxyl acrylic resin modified TPU film for swelling tape substrate according to claim 6, characterized in that, The organic solvents mentioned are mainly one or more of acetone, ethyl acetate, and DMF.

10. A method for preparing a hydroxyl acrylic resin modified TPU film for use as a substrate for swelling adhesive tape, characterized in that, The process includes the following steps: According to the specified ratio, TPU particles are dissolved in an organic solvent by heating until a TPU solution with a solid content of 35% is obtained. During the dissolution process, the mixture is stirred and heated at a temperature of 60±5℃. Then, a predetermined ratio of 60% hydroxyl acrylic resin, polyether polyol, antioxidant, and curing agent with a solid content is added to the TPU solution. After stirring evenly, the mixture is filtered through a 400-mesh filter and allowed to stand for 20-30 minutes to defoam. The resulting solution is then coated onto a 50µm double-sided silicone release film and dried to form a 40-50µm thick hydroxyl acrylic modified TPU film for use as a substrate for swollen adhesive tapes.

Images