Self-initiated high-adhesion uv adhesive for new energy batteries and preparation method thereof

Abstract

This invention discloses a self-initiating high-adhesion UV adhesive for new energy batteries and its preparation method, applied in the field of UV adhesive technology. The adhesive comprises a self-initiating polyurethane acrylate oligomer and a flame retardant. The oligomer is obtained by stepwise polymerization of diisocyanate, macromolecular diol, highly active chain extender, self-initiating chain extender, highly polar chain extender, and hydroxyl-terminated acrylate. The self-initiating chain extender eliminates the need for external small-molecule photosensitizers, avoiding residue problems; the highly polar chain extender enhances adhesion to aluminum substrates; and the stepwise feeding process prevents gelation. The product is obtained by mixing and grinding the oligomer and flame retardant. This invention's adhesive is solvent-free, has high bonding strength (up to 44.89 N / 25mm at 180° peel strength), excellent resistance to damp heat aging (nearly 100% strength retention after aging), and a flame retardant rating of UL94 V-0, effectively solving problems such as easy peeling of protective films, low adhesion, and photosensitizer residue in new energy batteries.

Description

Technical Field

[0001] This invention relates to the field of UV adhesive technology, and in particular to a self-initiating high-adhesion UV adhesive for new energy batteries and its preparation method. Background Technology

[0002] With the booming development of the new energy vehicle industry, the demand for new, efficient, and safe new energy batteries is also rising, thus creating a booming opportunity for the development of adhesive films for new energy batteries. However, there are still many problems with current adhesive films for new energy batteries: 1. Poor weather resistance. Due to the long-term corrosion of adhesive films by moisture, acidic gases, salt spray, etc. in the air, the adhesion performance of conventional adhesive films to the substrate will gradually decrease until they completely lose adhesion. Especially in areas with long-term humid climates, the requirements for the weather resistance of adhesive films are even more stringent; 2. Low adhesion strength. Because vehicles experience bumps during normal driving, the battery pack may also undergo slight displacement, which will generate a large peeling force and shear force on the battery protective film. For a long time, many battery manufacturers have used pressure-sensitive adhesive films to directly bond to the battery metal shell, but with the development of the industry, more and more downstream customers have reported that the adhesion strength of pressure-sensitive tape to aluminum alloys is difficult to withstand large external forces, and have proposed using structural adhesives to replace self-adhesive films.

[0003] UV adhesives are favored by customers in the electronics, 3C, and automotive industries due to their solvent-free, low-VOCs, high efficiency, and environmental friendliness. Traditional UV adhesive formulations consist of a main resin, a certain amount of reactive monomers, a small amount of photosensitizers, and other additives. Because of the rapid UV reaction rate, unsaturated components and photosensitizers in the formulation often fail to react completely. These residues can manifest as adhesive layer defects over time, leading to problems such as hardening, loss of tack, and delamination. Therefore, developing a self-initiating, residue-free, and highly adhesive UV adhesive is a crucial way to solve this industry challenge.

[0004] Chinese patent CN2021102098358 discloses a fast-bonding UV / moisture dual-curing adhesive, characterized by initial UV curing of the adhesive layer, followed by slow reaction of the moisture-curing component in the adhesive with moisture on the substrate surface after bonding, thereby improving both cohesive strength and overall peel strength. Chinese patent CN202210133939X discloses a UV cationic curing adhesive containing epoxy resin, an iodonium salt-based cationic photoinitiator, and a photosensitizer. The epoxy resin used has all or part of its epoxy functional groups as ethylene oxide three-membered rings, and each carbon atom of the ethylene oxide three-membered ring has at most one hydrogen atom. The cationic UV-curable adhesive provided by this invention can be deeply cured and does not generate negative ions upon hydrolysis; Chinese patent CN2022112095990 discloses a UV adhesive comprising polyurethane acrylate oligomers, reactive diluents, and photosensitizers, which has the characteristics of being removable, flexible, having high bonding strength, and being resistant to high temperature and humidity; Chinese patent CN2022110469585 discloses a flame-retardant UV-curable adhesive, which obtains flame-retardant properties by copolymerizing diisocyanate with flame-retardant polyols through chain extension, without affecting the compatibility between the components in the adhesive, thus ensuring that the adhesive has excellent adhesive performance. The UV adhesives disclosed in the above patents are all multi-component mixed formulation adhesives; self-initiating high-adhesion UV adhesives for new energy batteries have not yet been mentioned. Summary of the Invention

[0005] The core of this invention lies in addressing the problems of poor weather resistance and low peel strength in current protective films for new energy batteries. It proposes a method for preparing a self-initiating, high-adhesion UV adhesive for new energy batteries, resulting in an improved film with high adhesive strength, excellent weather resistance, and highly effective flame retardancy. To solve the above problems, the present invention adopts the following technical solution.

[0006] A self-initiating high-adhesion UV adhesive for new energy batteries is characterized by comprising a self-initiating polyurethane acrylate oligomer and a flame retardant. The self-initiating polyurethane acrylate oligomer is obtained by polymerization of raw materials comprising the following mass percentages: 8-13% diisocyanate, 79-89% macromolecular diol, 0.12-0.16% highly active chain extender, 0.12-0.25% self-initiating chain extender, 0.12-0.14% highly polar chain extender, 1.2-1.7% hydroxyl-terminated acrylate, 0.01-0.04% polymerization inhibitor, and 0.01-0.04% organometallic catalyst.

[0007] Furthermore, the diisocyanate is one or a combination of at least two of the following: isoflurone diisocyanate, hexamethylene diisocyanate, toluene-2,6-diisocyanate, m-phenylenediamine diisocyanate, L-lysine diisocyanate, 1,3-phenylenediamine diisocyanate, terephthalic diisocyanate, poly(hexamethylene diisocyanate), 4-chloro-6-methylm-phenylene diisocyanate, and dicyclohexamethane 4,4'-diisocyanate; preferably, the diisocyanate is toluene-2,6-diisocyanate.

[0008] Furthermore, the macromolecular diol is one or a combination of at least two of the following: polypropylene glycol 2000, polypropylene glycol 1000, polytetrahydrofuran 2000, polytetrahydrofuran 1000, polyethylene glycol 2000, polyethylene glycol 1000, polyester diol 2000, polyester diol 1000, and polycarbonate diol 2000; preferably, the macromolecular diol is polycarbonate diol 2000.

[0009] Furthermore, the highly active chain extender is one or a combination of at least two of the following: 1,3-butanediol, 1,4-butanediol, ethylene glycol, 1,3-propanediol, polyethylene glycol 200, polyethylene glycol 400, butene glycol, 1,4-yntynediol, 1,4-pentanediol, 1,2-pentanediol, 1,2-hexanediol, 2,4-pentanediol, 2,5-hexanediol, 1,5-pentanediol, p-phenylenediamine, 1,8-octanediamine, 1,2-propanediamine, and o-phenylenediamine; preferably, the highly active chain extender is 1,4-butanediol.

[0010] Furthermore, the self-initiating chain extender is one of 2,4-dihydroxybenzophenone and 2,4-diaminobenzophenone; preferably, the self-initiating chain extender is 2,4-dihydroxybenzophenone.

[0011] Furthermore, the highly polar chain extender is one of 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid, 2,5-dimethyloltetrahydrofuran, and 2,2-dimethylolaniline; preferably, the highly polar chain extender is 2,2-dimethylolpropionic acid.

[0012] Furthermore, the hydroxyl-terminated acrylate is one or a combination of at least two of hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxymethyl methacrylate, hydroxypropyl acrylate, hydroxybutyl methacrylate, and hydroxypropyl methacrylate; preferably, the hydroxyethyl acrylate is hydroxyethyl acrylate.

[0013] Furthermore, the feature is that: the polymerization inhibitor is one of 2,6-di-tert-butyl-p-cresol, hydroquinone methyl ether, p-benzoquinone, and nitrobenzene; and the organometallic catalyst is one of dibutyltin dilaurate and bismuth neodecanoate.

[0014] Furthermore, the flame retardant is one of aluminum hydroxide, magnesium hydroxide, ammonium polyphosphate, antimony trioxide, triphenyl phosphate, tetrabromobisphenol A, or melamine derivatives; the mass ratio of self-initiating polyurethane acrylate oligomer to flame retardant is 75-80:20-25.

[0015] A method for preparing a self-initiating high-adhesion UV adhesive for new energy batteries includes the following steps: S1. Preparation of self-initiated polyurethane acrylate oligomers: S11. Weigh out 8-13% of diisocyanate and 79-89% of macromolecular diol by mass percentage and add them to the reaction vessel. Gradually raise the temperature from 60℃ to 100℃ at a rate of 5℃ / 30min and keep the temperature for 6-7h. S12. Reduce the temperature to 80℃, add 0.12-0.16% of a highly active chain extender, 0.12-0.25% of a self-initiating chain extender, and 0.12-0.14% of a highly polar chain extender, and continue the reaction for 4-5 hours. S13, add 1.2-1.7% of hydroxyl-terminated acrylate and 0.01-0.04% of polymerization inhibitor, and react at 80°C for 4-5 hours; S14. Add 0.01-0.04% organometallic catalyst dropwise, react at 80℃ for 4-5 hours, detect the NCO value, and terminate the reaction when the NCO value is ≤0.1mgKOH / g to obtain self-initiated polyurethane acrylate oligomer. S2. Mix the obtained self-initiating polyurethane acrylate oligomer with the flame retardant at a mass ratio of 75-80%:20-25%, disperse by high-speed stirring at 1200-1500r / min, and then grind it with a three-roll mill until the particle size is 10-15μm to obtain a flame-retardant self-initiating high-adhesion UV adhesive.

[0016] Compared with the prior art, the advantages of this invention are: Self-initiated curing with no small molecule photosensitizer residue: By introducing a self-initiating chain extender (such as 2,4-dihydroxybenzophenone) to participate in the synthesis of the polyurethane backbone, the adhesive itself has photoinitiation ability, eliminating the need for external small molecule photosensitizers and avoiding problems such as adhesive layer aging and loss of adhesion caused by photosensitizer residue in traditional UV adhesives.

[0017] High bonding strength and excellent resistance to damp heat aging: Example tests show that the adhesive has a maximum 180° peel strength of 44.89 N / 25mm on aluminum alloy substrates, and the peel strength retention rate is close to 100% after high temperature and high humidity aging, which is far superior to conventional products and can meet the long-term use requirements of new energy batteries in harsh environments such as humidity and bumps.

[0018] Flame retardant performance reaches V-0 level: By adding flame retardants such as ammonium polyphosphate, the flame retardant level of the adhesive can reach UL94V-0 level, effectively improving the safety performance of new energy batteries.

[0019] Solvent-free, low VOCs, and environmentally friendly: The entire preparation and use process requires no addition of organic solvents, meets environmental protection requirements, and satisfies the application trend of low-volatile materials in the new energy battery industry. Attached Figure Description

[0020] Figure 1 This is a flowchart of the preparation method of the present invention; Figure 2 Here is a list of the components that differ from those in Examples 1-6 of this invention; Figure 3 This is a summary table of the flame-retardant self-initiating high-adhesion UV adhesives obtained in Examples 1-6 of the present invention. Figure 4 This is a summary table of the product test results obtained from Comparative Examples 1-5 of the present invention. Detailed Implementation

[0021] The technical solutions will now be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention.

[0022] The general formulation and preparation method of a self-initiating high-adhesion UV adhesive for new energy batteries are as follows: A self-initiating high-adhesion UV adhesive for new energy batteries comprises a self-initiating polyurethane acrylate oligomer and a flame retardant; the self-initiating polyurethane acrylate oligomer is obtained by polymerization reaction of raw materials comprising the following mass percentages: 8-13% diisocyanate, 79-89% macromolecular diol, 0.12-0.16% highly active chain extender, 0.12-0.25% self-initiating chain extender, 0.12-0.14% highly polar chain extender, 1.2-1.7% hydroxyl-terminated acrylate, 0.01-0.04% polymerization inhibitor, and 0.01-0.04% organometallic catalyst.

[0023] The diisocyanate is one or a combination of at least two of the following: isoflurone diisocyanate, hexamethylene diisocyanate, toluene-2,6-diisocyanate, m-phenylenediamine diisocyanate, L-lysine diisocyanate, 1,3-phenylenediamine diisocyanate, terephthalic diisocyanate, poly(hexamethylene diisocyanate), 4-chloro-6-methyl-m-phenylene diisocyanate, and dicyclohexamethane 4,4'-diisocyanate. Preferably, the diisocyanate is toluene-2,6-diisocyanate.

[0024] The macromolecular diol is one or a combination of at least two of the following: polypropylene glycol 2000, polypropylene glycol 1000, polytetrahydrofuran 2000, polytetrahydrofuran 1000, polyethylene glycol 2000, polyethylene glycol 1000, polyester diol 2000, polyester diol 1000, and polycarbonate diol 2000. Preferably, the macromolecular diol is polycarbonate diol 2000. The highly active chain extender is 1,3-butanediol or 1,4-butanediol. The chain extender is one or a combination of at least two of the following: glycol, ethylene glycol, 1,3-propanediol, polyethylene glycol 200, polyethylene glycol 400, butene glycol, 1,4-acetylenide, 1,4-pentanediol, 1,2-pentanediol, 1,2-hexanediol, 2,4-pentanediol, 2,5-hexanediol, 1,5-pentanediol, p-phenylenediamine, 1,8-octanediamine, 1,2-propanediamine, and o-phenylenediamine. Preferably, the highly active chain extender is 1,4-butanediol.

[0025] The self-initiating chain extender is one of 2,4-dihydroxybenzophenone and 2,4-diaminobenzophenone, preferably 2,4-dihydroxybenzophenone; the highly polar chain extender is one of 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid, 2,5-dimethyloltetrahydrofuran, and 2,2-dimethylolaniline, preferably 2,2-dimethylolpropionic acid; the hydroxyl-terminated acrylate is one or a combination of at least two of hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxymethyl methacrylate, hydroxypropyl acrylate, hydroxybutyl methacrylate, and hydroxypropyl methacrylate, preferably hydroxyethyl acrylate.

[0026] The polymerization inhibitor is one of 2,6-di-tert-butyl-p-cresol, hydroquinone methyl ether, p-benzoquinone, and nitrobenzene; the organometallic catalyst is one of dibutyltin dilaurate and bismuth neodecanoate; the flame retardant is one of aluminum hydroxide, magnesium hydroxide, ammonium polyphosphate, antimony trioxide, triphenyl phosphate, tetrabromobisphenol A, and melamine derivatives; the mass ratio of self-initiating polyurethane acrylate oligomer to flame retardant is 75-80:20-25.

[0027] like Figure 1 A method for preparing a self-initiating high-adhesion UV adhesive for new energy batteries includes the following steps: S1. Preparation of self-initiated polyurethane acrylate oligomers: S11. Weigh out 8-13% of diisocyanate and 79-89% of macromolecular diol by mass percentage and add them to the reaction vessel. Gradually raise the temperature from 60℃ to 100℃ at a rate of 5℃ / 30min and keep the temperature for 6-7h. S12. Reduce the temperature to 80℃, add 0.12-0.16% of a highly active chain extender, 0.12-0.25% of a self-initiating chain extender, and 0.12-0.14% of a highly polar chain extender, and continue the reaction for 4-5 hours. S13, add 1.2-1.7% of hydroxyl-terminated acrylate and 0.01-0.04% of polymerization inhibitor, and react at 80°C for 4-5 hours; S14. Add 0.01-0.04% organometallic catalyst dropwise, react at 80℃ for 4-5 hours, detect the NCO value, and terminate the reaction when the NCO value is ≤0.1mgKOH / g to obtain self-initiated polyurethane acrylate oligomer. S2. Mix the obtained self-initiating polyurethane acrylate oligomer with the flame retardant at a mass ratio of 75-80%:20-25%, disperse by high-speed stirring at 1200-1500r / min, and then grind it with a three-roll mill until the particle size is 10-15μm to obtain a flame-retardant self-initiating high-adhesion UV adhesive.

[0028] After obtaining the flame-retardant, self-initiating, high-adhesion UV adhesive, the prepared adhesive was subjected to a coating test. The specific steps were as follows: (1) The aluminum alloy substrate, UV adhesive and PET film are tightly bonded together by the film coating method to ensure that there is no air residue between the adhesive layer and the film; (2) Curing is performed by irradiation with a UV-LED lamp at a wavelength of 365nm, a curing energy of 2500-3000mJ / cm2, and a curing time of 20-30s; (3) After curing, let it stand for 20 minutes to eliminate internal stress and restore room temperature before conducting performance tests.

[0029] The bonding strength was tested according to the GB / T2790-1995 test method for 180° peel strength of adhesives; the aging resistance test was conducted according to the GB / T32368-2015 test method for high temperature and high humidity aging resistance of adhesive tapes; and the flame retardancy test was conducted according to the UL94 Underwriters Laboratories standard.

[0030] Based on the aforementioned general formulation and preparation method of high-adhesion UV adhesives, six embodiments are proposed, with the specific differences lying in the different mass percentages of each component. In particular, the amounts of diisocyanate (toluene-2,6-diisocyanate), macromolecular diol (polycarbonate diol), and hydroxyl-terminated acrylate (hydroxyethyl acrylate) exhibit gradient changes. See details below. Figure 2 .

[0031] The amounts of other components (chain extenders, polymerization inhibitors, catalysts, flame retardants, etc.) remained constant. Therefore, these six examples investigated the effect of different main raw material ratios on bonding performance. Example 5 achieved the highest peel strength (44.89 N / 25 mm), while in Example 6, the strength actually decreased due to a drop in crosslinking density caused by excessively low diisocyanate content. The above six implementation methods allow for gradient optimization of the formulation.

[0032] like Figure 3 As described in the six embodiments above, the flame-retardant self-initiating high-adhesion UV adhesive obtained has the following resistance test results: The adhesive strength of the flame-retardant self-initiating high-adhesion UV adhesive in Example 1 was tested according to the GB / T2790-1995 test method for 180° peel strength of adhesives, and the test result was 1.55 N / 25 mm; the aging resistance test was conducted according to the GB / T32368-2015 test method for high temperature and high humidity aging resistance of adhesive tapes, and the test result was 1.49 N / 25 mm; the flame retardancy test was conducted according to the UL94 Underwriters Laboratories standard, and the test result was V-0.

[0033] In Example 2, the adhesive strength of the flame-retardant self-initiating high-adhesion UV adhesive was tested according to GB / T2790-1995 Adhesives 180° Peel Strength Test Method, and the test result was 2.45 N / 25 mm; the aging resistance test was conducted according to GB / T32368-2015 Adhesive Tape High Temperature and High Humidity Aging Resistance Test Method, and the test result was 2.46 N / 25 mm; the flame retardancy test was conducted according to UL94 Underwriters Laboratories standard, and the test result was V-0 level.

[0034] In Example 3, the adhesive strength of the flame-retardant self-initiating high-adhesion UV adhesive was tested according to the GB / T2790-1995 test method for 180° peel strength of adhesives, and the test result was 11.38 N / 25 mm; the aging resistance test was conducted according to the GB / T32368-2015 test method for high temperature and high humidity aging resistance of adhesive tapes, and the test result was 12.55 N / 25 mm; the flame retardancy test was conducted according to the UL94 Underwriters Laboratories standard, and the test result was V-0.

[0035] In Example 4, the adhesive strength of the flame-retardant self-initiating high-adhesion UV adhesive was tested according to the GB / T2790-1995 test method for 180° peel strength of adhesives, and the test result was 24.71 N / 25 mm; the aging resistance test was conducted according to the GB / T32368-2015 test method for high temperature and high humidity aging resistance of adhesive tapes, and the test result was 24.30 N / 25 mm; the flame retardancy test was conducted according to the UL94 Underwriters Laboratories standard, and the test result was V-0.

[0036] In Example 5, the adhesive strength of the flame-retardant self-initiating high-adhesion UV adhesive was tested according to the GB / T2790-1995 test method for 180° peel strength of adhesives, and the test result was 44.89 N / 25 mm; the aging resistance test was conducted according to the GB / T32368-2015 test method for high temperature and high humidity aging resistance of adhesive tapes, and the test result was 45.12 N / 25 mm; the flame retardancy test was conducted according to the UL94 Underwriters Laboratories standard, and the test result was V-0.

[0037] In Example 6, the adhesive strength of the flame-retardant self-initiating high-adhesion UV adhesive was tested according to GB / T2790-1995 Adhesives 180° Peel Strength Test Method, and the test result was 20.64 N / 25 mm; the aging resistance test was conducted according to GB / T32368-2015 Adhesive Tape High Temperature and High Humidity Aging Resistance Test Method, and the test result was 20.77 N / 25 mm; the flame retardancy test was conducted according to UL94 Underwriters Laboratories standard, and the test result was V-0.

[0038] The above embodiments are merely descriptions of the preferred additive formulation content of the present invention and are not intended to limit the overall concept and scope of protection of the present invention. The results show that when other components remain unchanged, when the mass fraction of toluene-2,6 diisocyanate is 9%, polycarbonate diol is 87%, and hydroxyethyl acrylate is 1.3%, the peel strength can reach 44.89 N / 25 mm. After aging test, the peel strength is 45.12 N / 25 mm, and the flame retardancy can reach V-0 level.

[0039] like Figure 4 For Example 5, which has the highest peel strength, comparative implementations were conducted by changing one key variable (missing a self-initiating chain extender, missing a highly polar chain extender, missing a flame retardant, changing the feeding method, and changing the amount of diisocyanate) based on the formulation and process of Example 5: Comparative Example 1 (lacking a self-initiating chain extender, a traditional small molecule photoinitiator was used instead): Formulation differences: 2,4-Dihydroxybenzophenone (a self-initiating chain extender) is omitted; instead, 2.5% of 1-hydroxycyclohexylphenyl ketone (photoinitiator 184) is added to the final system. The remaining components are the same as in Example 5: 9% toluene-2,6-diisocyanate, 87% polycarbonate diol, 0.12% 1,4-butanediol, 0.12% 2,2-dimethylolpropionic acid, 1.3% hydroxyethyl acrylate, 0.04% hydroquinone methyl ether, 0.015% dibutyltin dilaurate, and 20% ammonium polyphosphate.

[0040] Preparation differences: No self-initiating unit was introduced during the synthesis of polyurethane acrylate; a photoinitiator was added when it was finally mixed with the flame retardant.

[0041] Performance testing: 180° peel strength: 28.63 N / 25mm; Peel strength after high temperature and humidity aging: 15.47 N / 25mm (significantly decreased after aging); Flame retardant rating: V-0.

[0042] It can be seen that although the addition of small molecule photoinitiator can cure, the residue causes a significant decrease in adhesion after aging, and the initial peel force is also lower than that of Example 5 (44.89 N / 25 mm).

[0043] Comparative Example 2 (lacking highly polar chain extenders): Formulation differences: 2,2-dimethylolpropionic acid (a highly polar chain extender) is not added; otherwise, it is the same as in Example 5.

[0044] Performance testing: 180° peel strength: 18.22 N / 25mm; peel strength after aging: 17.05 N / 25mm; flame retardant rating: V-0.

[0045] This indicates that the lack of highly polar chain extenders reduces the adhesive's wetting and chemical bonding ability to the polar aluminum substrate, resulting in a significant decrease in peel strength.

[0046] Comparative Example 3 (without flame retardant): Formulation differences: Ammonium polyphosphate is not added, i.e., the self-initiated polyurethane acrylate oligomer is 100%, and the rest is the same as in Example 5.

[0047] Performance testing: 180° peel strength: 46.31 N / 25mm (slightly higher than Example 5 due to the lack of flame retardant filler); peel strength after aging: 46.02 N / 25mm; flame retardant rating: HB (no flame retardant rating, continues to burn when exposed to fire).

[0048] Therefore, although the bonding performance is slightly higher, it is not flame retardant at all and cannot meet the safety requirements of new energy batteries.

[0049] Comparative Example 4 (Synthesized using a one-pot method, without stepwise addition of chain extenders) Formula differences: The raw material ratio is exactly the same as in Example 5, but all raw materials (diisocyanate, macromolecular diol, three small molecule chain extenders, hydroxyl-terminated acrylate, catalyst) are added at once during synthesis and the temperature is raised to 100°C for reaction.

[0050] Preparation phenomenon: After the reaction started, the viscosity of the system increased sharply, the temperature soared out of control to above 130℃, the product showed obvious gelation and could not be discharged normally.

[0051] Performance testing: Unable to produce a usable adhesive (gelled).

[0052] Therefore, it is evident that the stepwise addition of the feed in this invention (first adding diisocyanate and macromolecular diol for chain extension, then adding small molecule chain extender after cooling) is necessary to avoid gelation caused by excessively rapid reaction.

[0053] Comparative Example 5 (the amount of diisocyanate used exceeds the scope of this invention): Formulation differences: The amount of toluene-2,6 diisocyanate was changed to 18%, and the amount of polycarbonate diol was reduced to 78% accordingly. Other aspects were the same as in Example 5.

[0054] Performance testing: 180° peel strength: 8.75 N / 25mm; peel strength after aging: 6.33 N / 25mm; flame retardant rating: V-0.

[0055] Therefore, it can be concluded that excessive diisocyanate leads to excessive cross-linking, increased brittleness of the adhesive layer, and a significant decrease in peel strength.

[0056] In summary, this invention effectively solves the problems of poor weather resistance and low peel strength in current protective films for new energy batteries through the synergistic effect of self-initiating chain extenders, high-polarity chain extenders, flame retardants, and stepwise feeding processes. If any key component is missing or the process conditions deviate from those defined in this invention, it is difficult to simultaneously meet the requirements of high adhesion, self-initiation, flame retardancy, and good processability: although adding a small-molecule photoinitiator can cure the film, the residue leads to a significant decrease in adhesion after aging; the lack of a high-polarity chain extender weakens the interfacial bonding with the aluminum substrate; without flame retardants, the safety level of new energy batteries cannot be achieved; one-pot synthesis results in gelation due to the vigorous reaction; and excessive diisocyanate content increases the brittleness of the adhesive layer and drastically reduces peel strength. Therefore, under the protection of the types of components, dosage range, and step-by-step synthesis process of this solution, a high peel strength of 44.89 N / 25mm, a strength retention rate of nearly 100% after aging, a UL94 V-0 flame retardant rating, and gel-free processability can be achieved, thus truly meeting the stringent requirements of new energy battery protective films for comprehensive performance.

[0057] The above description is merely a preferred embodiment of the present invention; it encompasses all the protection scope of the present invention. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in the present invention, based on the technical solutions and improved concepts of the present invention, should be covered within the protection scope of the present invention.

Claims

1. A self-initiating high-adhesion UV adhesive for new energy batteries, characterized in that: The product includes self-initiating polyurethane acrylate oligomers and flame retardants; the self-initiating polyurethane acrylate oligomers are obtained by polymerization of raw materials comprising the following mass percentages: 8-13% diisocyanate, 79-89% macromolecular diol, 0.12-0.16% highly active chain extender, 0.12-0.25% self-initiating chain extender, 0.12-0.14% highly polar chain extender, 1.2-1.7% hydroxyl-terminated acrylate, 0.01-0.04% polymerization inhibitor, and 0.01-0.04% organometallic catalyst.

2. The self-initiating high-adhesion UV adhesive for new energy batteries according to claim 1, characterized in that: The diisocyanate is one or a combination of at least two of the following: isoflurone diisocyanate, hexamethylene diisocyanate, toluene-2,6-diisocyanate, m-phenylenediamine diisocyanate, L-lysine diisocyanate, 1,3-phenylenediamine diisocyanate, terephthalic diisocyanate, poly(hexamethylene diisocyanate), 4-chloro-6-methylm-phenylene diisocyanate, and dicyclohexamethane 4,4'-diisocyanate.

3. The self-initiating high-adhesion UV adhesive for new energy batteries according to claim 1, characterized in that: The macromolecular diol is one or a combination of at least two of the following: polypropylene glycol 2000, polypropylene glycol 1000, polytetrahydrofuran 2000, polytetrahydrofuran 1000, polyethylene glycol 2000, polyethylene glycol 1000, polyester diol 2000, polyester diol 1000, and polycarbonate diol 2000.

4. The self-initiating high-adhesion UV adhesive for new energy batteries according to claim 1, characterized in that: The highly active chain extender is one or a combination of at least two of the following: 1,3-butanediol, 1,4-butanediol, ethylene glycol, 1,3-propanediol, polyethylene glycol 200, polyethylene glycol 400, butene glycol, 1,4-yntynediol, 1,4-pentanediol, 1,2-pentanediol, 1,2-hexanediol, 2,4-pentanediol, 2,5-hexanediol, 1,5-pentanediol, p-phenylenediamine, 1,8-octanediamine, 1,2-propanediamine, and o-phenylenediamine.

5. The self-initiating high-adhesion UV adhesive for new energy batteries according to claim 1, characterized in that: The self-initiating chain extender is one of 2,4-dihydroxybenzophenone and 2,4-diaminobenzophenone.

6. The self-initiating high-adhesion UV adhesive for new energy batteries according to claim 1, characterized in that: The highly polar chain extender is one of 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid, 2,5-dimethyloltetrahydrofuran, and 2,2-dimethylolaniline.

7. The self-initiating high-adhesion UV adhesive for new energy batteries according to claim 1, characterized in that: The hydroxyl-terminated acrylate is one or a combination of at least two of the following: hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxymethyl methacrylate, hydroxypropyl acrylate, hydroxybutyl methacrylate, and hydroxypropyl methacrylate.

8. The self-initiating high-adhesion UV adhesive for new energy batteries according to claim 1, characterized in that: The polymerization inhibitor is one of 2,6-di-tert-butyl-p-cresol, hydroquinone methyl ether, p-benzoquinone, and nitrobenzene; the organometallic catalyst is one of dibutyltin dilaurate and bismuth neodecanoate.

9. The self-initiating high-adhesion UV adhesive for new energy batteries according to claim 1, characterized in that: The flame retardant is one of aluminum hydroxide, magnesium hydroxide, ammonium polyphosphate, antimony trioxide, triphenyl phosphate, tetrabromobisphenol A, and melamine derivatives; the mass ratio of the self-initiating polyurethane acrylate oligomer to the flame retardant is 75-80:20-25.

10. A method for preparing a self-initiating high-adhesion UV adhesive for new energy batteries according to any one of claims 1-9, characterized in that: Includes the following steps: S1. Preparation of self-initiated polyurethane acrylate oligomers: S11. Weigh out 8-13% of diisocyanate and 79-89% of macromolecular diol by mass percentage and add them to the reaction vessel. Gradually raise the temperature from 60℃ to 100℃ at a rate of 5℃ / 30min and keep the temperature for 6-7h. S12. Reduce the temperature to 80℃, add 0.12-0.16% of a highly active chain extender, 0.12-0.25% of a self-initiating chain extender, and 0.12-0.14% of a highly polar chain extender, and continue the reaction for 4-5 hours. S13, add 1.2-1.7% of hydroxyl-terminated acrylate and 0.01-0.04% of polymerization inhibitor, and react at 80°C for 4-5 hours; S14. Add 0.01-0.04% organometallic catalyst dropwise, react at 80℃ for 4-5 hours, detect the NCO value, and terminate the reaction when the NCO value is ≤0.1mgKOH / g to obtain self-initiated polyurethane acrylate oligomer. S2. Mix the obtained self-initiating polyurethane acrylate oligomer with the flame retardant at a mass ratio of 75-80%:20-25%, disperse by high-speed stirring at 1200-1500r / min, and then grind it with a three-roll mill until the particle size is 10-15μm to obtain a flame-retardant self-initiating high-adhesion UV adhesive.

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