Copolyester hot melt adhesive for laser edge sealing and preparation method thereof

Abstract

The invention discloses a copolyester hot melt adhesive for laser edge sealing and a preparation method thereof. The copolyester hot melt adhesive is prepared from the following raw materials in percentage by mass: 51 to 56 percent of binary acid, 40 to 45 percent of dihydric alcohol, 0.1 to 1.5 percent of laser absorbent, 0.025 to 0.06 percent of catalyst, 0.01 to 0.03 percent of heat stabilizer, 0.1 to 1 percent of antioxidant, 0.2 to 0.5 percent of trimethylolpropane and 0 to 0.3 percent of inorganic hardening agent. The laser absorbent is one or more of cesium tungsten bronze or lanthanide hexaboride, the particle size is 30-80 nm, and the specific surface area is 20-50 m < 2 > / g. According to the invention, the laser absorbent uniformly enters the hot melt adhesive through in-situ polymerization, so that the effect of absorbing laser melting is achieved; meanwhile, a polar monomer, a hardening agent and a reasonable material ratio are introduced, so that the copolyester hot melt adhesive which can be used for laser edge sealing and is heat-resistant and high in peel strength is prepared.

Description

Technical Field

[0001] This invention belongs to the field of polyester hot melt adhesive technology, specifically relating to a copolyester hot melt adhesive for laser edge sealing and its preparation method. Background Technology

[0002] Laser edge banding is a relatively new technology that uses a laser to instantly irradiate an edge banding tape pre-coated with hot melt adhesive, causing the adhesive layer to melt and bond with the substrate. This technology offers advantages such as high processing efficiency, aesthetically pleasing adhesive lines, suitability for complex-shaped boards, and environmental friendliness.

[0003] To achieve laser edge sealing, the key lies in developing a specialized hot melt adhesive. This hot melt adhesive must have efficient absorption and conversion capabilities for near-infrared lasers (common wavelengths of approximately 940–1060 nm), be able to melt instantly, rapidly wet the substrate, and ultimately possess excellent bonding strength and heat resistance.

[0004] Currently, the conventional method for preparing laser-sealed hot melt adhesive involves blending a laser absorber with pre-synthesized resins such as PA, TPU, and EVA. However, this method suffers from several drawbacks, including uneven dispersion (the laser absorber tends to agglomerate during melt blending, affecting product performance uniformity and potentially leading to poor localized melting or overheating during edge sealing), performance degradation (the copolyester resin is prone to polymer degradation after high-temperature melt processing, affecting molecular weight and final mechanical properties), cumbersome processes (synthesis and modification are carried out separately, increasing production energy costs), and high costs.

[0005] Patent document CN119931585A discloses a laser sealing adhesive raw material resin, comprising the following reactants: antioxidant (0.5%-3% by mass), light absorber (0.5%-2% by mass), thermally conductive agent (0-1% by mass), colorant (0-1% by mass), adhesion promoter (0-1% by mass), nucleating agent (0.5%-2% by mass), and hardener (0-2%); the remainder is hot melt adhesive resin, wherein the light absorber is antimony tin oxide, lanthanum hexaboride, copper pyrophosphate, etc. However, this document also has problems such as the laser absorber easily agglomerating and unevenly dispersing in the resin, resulting in unstable laser absorption efficiency and poor product quality uniformity; secondary heating and shearing processes can lead to thermo-oxidative degradation of polymer molecular chains, yellowing, and decreased mechanical properties.

[0006] Furthermore, in-depth research revealed that not all copolyester hot melt adhesives are suitable for this specific process. If the melting point of the copolyester is too high, the laser energy is insufficient to melt it quickly, resulting in poor adhesion; if the melting point is too low, the heat resistance after edge sealing cannot be guaranteed. If the crystallization rate is too slow, strength cannot be quickly established after pressing, making peeling easy. If the hardness is too low, issues such as sticking to the knife, excess adhesive, and poor high-temperature resistance are likely to occur. Therefore, developing a new laser edge sealing copolyester hot melt adhesive with excellent overall performance and reasonable cost, and its preparation method, to fundamentally solve the dispersion problem of laser absorber and simplify the process, is of great significance for improving the performance of laser edge sealing hot melt adhesives and promoting industrial progress. Summary of the Invention

[0007] The purpose of this invention is to provide a copolyester hot melt adhesive for laser sealing and its preparation method. The laser absorber is introduced in one step through in-situ polymerization to achieve molecular-level dispersion, avoiding secondary processing. The process is simple and efficient, and the resulting copolyester hot melt adhesive has high laser absorption efficiency, uniform performance, suitable melt viscosity, and high bonding strength.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A copolyester hot melt adhesive for laser edge sealing comprises the following raw materials in the indicated mass fractions: 51%–56% diacid, 40%–45% diol, 0.1%–1.5% laser absorber, 0.025%–0.06% catalyst, 0.01%–0.03% heat stabilizer, 0.1%–1% antioxidant, 0.2%–0.5% trimethylolpropane, and 0%–0.3% inorganic hardening agent; The laser absorber is one or more of cesium tungsten bronze or lanthanide hexaborides, with a particle size of 30–80 nm and a specific surface area of ​​20–50 m². 2 / g; the lanthanide hexaboride is at least one of lanthanum hexaboride, neodymium hexaboride, and persimmon hexaboride; The molar ratio of the dicarboxylic acid to the diol is 1:(1.4 to 1.5). The diacid is a mixture of aromatic diacid and aliphatic diacid in a molar ratio of (0.90-0.98):(0.02-0.1); the aromatic diacid is one or more of terephthalic acid, sodium isophthalate-5-sulfonate, isophthalic acid, and phthalic acid; the aliphatic diacid is one or more of 1,4-succinic acid, 1,6-adipic acid, sebacic acid sebacic acid (CAS No.: 111-20-6), and dodecanoic acid (CAS No.: 693-23-2). The diol is one or more selected from ethylene glycol, 1,3-malonic acid, 1,4-butanediol, diethylene glycol, 1,4-cyclohexanediol, and 1,6-hexanediol. The catalyst is one or more of tetrabutyl titanate, antimony trioxide, and dibutyltin dilaurate; The heat stabilizer is triphenyl phosphate and / or trimethyl phosphate; the antioxidant is a compound of hindered phenolic antioxidant 1010 and phosphite antioxidant 168 in a mass ratio of 1:(1-1.2). The inorganic hardening agent is 800-1500 mesh wollastonite and / or 1000-1500 mesh talc.

[0009] The present invention discloses a method for preparing a copolyester hot melt adhesive for laser edge sealing, comprising the following steps: S1, trimethylolpropane, laser absorber and diol accounting for 20% to 35% of the formula are mixed and dispersed at high speed to obtain dispersion A; S2, under the action of a catalyst, the dispersion A, the remaining diol and the dicarboxylic acid are reacted at 170-195℃ for 40-60 min, and then reacted at 195-220℃ for 120-180 min; when the amount of water distilled is 95% or more of the theoretical amount of water, the esterification reaction ends and esterified liquid B is obtained. S3, esterification liquid B is injected into the polycondensation reactor under nitrogen pressure, while heat stabilizer, antioxidant and inorganic hardening agent are added. The reaction is carried out at 200-230℃ and 1000-500Pa vacuum for 50-70 minutes. The temperature is then raised to 235-238℃ and the vacuum is 50-100Pa to continue the reaction. After the melt index is qualified, nitrogen is introduced to release the vacuum, and the material is fed while hot, granulated and dried.

[0010] Furthermore, the melt index of the copolyester hot melt adhesive at 160°C and 2.16 kg is 35-40 g / 10 min.

[0011] Compared with the prior art, the beneficial effects of the present invention are: This invention utilizes in-situ polymerization to uniformly introduce laser absorbers into the hot melt adhesive, achieving the effect of absorbing laser melting; at the same time, it introduces polar monomers, hardeners, and reasonable material ratios to prepare a copolyester hot melt adhesive that can be used for laser edge sealing with heat resistance and high peel strength.

[0012] The copolyester hot melt adhesive of the present invention has the following characteristics: (1) excellent dispersibility and uniform performance: the laser absorber is introduced during the polymer polymerization stage and achieves uniform dispersion at the nanoscale under long-term mechanical stirring and high temperature, which completely solves the agglomeration problem of the post-mixing process, making the hot melt adhesive extremely sensitive and consistent to the laser, and the edge sealing quality is stable; (2) excellent comprehensive performance: through specific comonomers and proportions, a class of copolyester hot melt adhesives suitable for laser edge sealing process are synthesized. At the same time, the secondary melting degradation of copolyester hot melt adhesive is avoided, maintaining its high molecular weight and inherent excellent mechanical properties; (3) simplified process and reduced cost: the synthesis and modification are combined into one, reducing production steps, reducing energy consumption and production costs, and better meeting the requirements of green manufacturing. Detailed Implementation

[0013] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] Example 1 A method for preparing a copolyester hot melt adhesive for laser edge sealing includes the following steps: S1, 100g of 1,4-butanediol, 2g of trimethylolpropane and 1g of cesium tungsten bronze are uniformly dispersed under the action of a high-speed disperser to obtain dispersion A; S2, under the action of 0.3g tetrabutyl titanate catalyst, dispersion A, 181.2g 1,4-butanediol, 77.7g diethylene glycol and diacids (240.5g terephthalic acid, 14.8g sodium isophthalate-5-sulfonate, 160g isophthalic acid, 23.9g dodecanoic acid) were reacted at 170℃ for 60min, and then the temperature was increased to 200℃ for 153min. The amount of water distilled off was 95% of the theoretical amount of water, and the esterification reaction was completed, yielding esterified liquid B; S3, esterification liquid B is injected into the polycondensation reactor under nitrogen pressure, and 0.15g triphenyl phosphate, 0.5g antioxidant 1010, 0.5g antioxidant 168 and 2.5g wollastonite (1000 mesh) are added at the same time. The reaction is carried out at 205℃ and low vacuum 800Pa for 55min. Then the temperature is raised to 235℃ and the vacuum is maintained at 50Pa to carry out the polycondensation reaction. After the melt index is qualified (38.4g / 10min), nitrogen is introduced to release the vacuum. The material is fed while hot, granulated and dried.

[0015] Example 2 A method for preparing a copolyester hot melt adhesive for laser edge sealing includes the following steps: S1, 100g of 1,4-butanediol, 2.5g of trimethylolpropane and 2g of cesium tungsten bronze are uniformly dispersed under the action of a high-speed disperser to obtain dispersion A; S2, under the action of 0.28g tetrabutyl titanate catalyst, dispersion A, 197.6g 1,4-butanediol, 60g diethylene glycol and diacids (245.6g terephthalic acid, 15g sodium isophthalate-5-sulfonate, 171.8g isophthalic acid and 25g dodecanoic acid) were reacted at 175℃ for 60min, and then the temperature was raised to 210℃ for 147min. The amount of water distilled off was 95% of the theoretical amount of water, and the esterification reaction was completed, yielding esterified solution B; S3, esterification liquid B is injected into the polycondensation reactor under nitrogen pressure, and 0.12g of triphenyl phosphate, 0.5g of antioxidant 1010, 0.6g of antioxidant 168 and 2.5g of talc (1500 mesh) are added at the same time. The reaction is carried out at 210℃ and low vacuum of 800Pa for 60min. Then the temperature is raised to 235℃ and the vacuum is maintained at 50Pa to carry out the polycondensation reaction. After the melt index is qualified (36.5g / 10min), nitrogen is introduced to release the vacuum. The material is fed while hot, granulated and dried.

[0016] Example 3 A method for preparing a copolyester hot melt adhesive for laser edge sealing includes the following steps: S1, 120g of 1,4-butanediol, 1.8g of trimethylolpropane, 1g of cesium tungsten bronze and 1.5g of lanthanum hexaboride are uniformly dispersed in a high-speed disperser to obtain dispersion A; S2, under the action of 0.3g tetrabutyl titanate catalyst, dispersion A, 225.3g 1,4-butanediol, 8.1g ethylene glycol and dicarboxylic acid (250.6g terephthalic acid, 15.6g sodium isophthalate-5-sulfonate, 178.7g isophthalic acid, 10g 1,6-adipic acid) were reacted at 180℃ for 50min, and then the temperature was raised to 215℃ for 145min. The amount of water distilled off was 96% of the theoretical amount of water, and the esterification reaction was completed, yielding esterified solution B; S3, esterification liquid B is injected into the polycondensation reactor under nitrogen pressure, and 0.15g of triphenyl phosphate, 0.85g of antioxidant 1010 and 0.95g of antioxidant 168 are added at the same time. The reaction is carried out at 210℃ and low vacuum of 700Pa for 55min. Then the temperature is raised to 236℃ and the vacuum is maintained at 50Pa to carry out the polycondensation reaction. After the melt index is qualified (38.2g / 10min), nitrogen is introduced to release the vacuum at the same time. The material is fed while hot, granulated and dried.

[0017] Comparative Example 1 Comparative Example 1 is a comparative example of Example 1, comprising the following steps (the difference being that 14.8 g of sodium isophthalic acid-5-sulfonate is not added in step S2): S1, 100g of 1,4-butanediol, 2g of trimethylolpropane and 1g of cesium tungsten bronze are uniformly dispersed under the action of a high-speed disperser to obtain dispersion A; S2, under the action of 0.3g tetrabutyl titanate catalyst, dispersion A, 181.2g 1,4-butanediol, 77.7g diethylene glycol and diacids (240.5g terephthalic acid, 160g isophthalic acid, 23.9g dodecyl diacid) were reacted at 170℃ for 60min, and then the temperature was increased to 200℃ for 135min. The amount of water distilled was 95% of the theoretical amount of water, and the esterification reaction was completed, yielding esterified solution B; S3, esterification liquid B is pressurized into the polycondensation reactor by purging with nitrogen, and 0.15g triphenyl phosphate, 0.5g antioxidant 1010, 0.5g antioxidant 168 and 2.5g 800 mesh wollastonite are added at the same time. The reaction is carried out at 205℃ and low vacuum of 800Pa for 55min. Then the temperature is raised to 235℃ and the vacuum is maintained at 50Pa to carry out the polycondensation reaction. After the melt index is qualified (35.5g / 10min), nitrogen is purged to release the vacuum, and the material is fed while hot, granulated and dried.

[0018] Comparative Example 2 Comparative Example 2 is a comparative example of Example 2, and includes the following steps: S1, 50g of 1,4-butanediol, 2.5g of trimethylolpropane and 2g of cesium tungsten bronze are uniformly dispersed in a high-speed disperser to obtain dispersion A; S2, under the action of 0.28g of tetrabutyl titanate catalyst, 297.6g of 1,4-butanediol, 60g of diethylene glycol and diacids (245.6g of terephthalic acid, 15g of sodium isophthalate-5-sulfonate, 171.8g of isophthalic acid and 25g of dodecanoic acid) were reacted at 175℃ for 60min, and then the temperature was raised to 210℃ for 150min. The amount of water distilled was 96% of the theoretical amount of water, and the esterification reaction was completed, yielding esterified liquid B; S3, esterification liquid B is pressurized into the polycondensation reactor under nitrogen gas, and the above dispersion A, 0.12g triphenyl phosphate, 0.5g antioxidant 1010, 0.6g antioxidant 168 and 2.5g talc (1500 mesh) are added at the same time. The reaction is carried out at 210℃ and low vacuum 800Pa for 60min. Then the temperature is raised to 235℃ and the vacuum is maintained at 50Pa to carry out the polycondensation reaction. After the melt index is qualified (37.3g / 10min), nitrogen gas is introduced to release the vacuum at the same time. The material is fed while hot, granulated and dried.

[0019] Comparative Example 3 Comparative Example 3 is a comparative example of Example 3, and includes the following steps: S1, under the action of 0.3g of tetrabutyl titanate catalyst, 345.3g of 1,4-butanediol, 8.1g of ethylene glycol, 1.8g of trimethylolpropane and dicarboxylic acid (250.6g of terephthalic acid, 15.6g of sodium isophthalate-5-sulfonate, 178.7g of isophthalic acid and 10g of 1,6-adipic acid) were reacted at 180℃ for 50min, and then the temperature was raised to 215℃ for 163min. The amount of water distilled was 96% of the theoretical amount of water, and the esterification reaction was completed, yielding esterified liquid B; S2, esterification liquid B was pressurized into the polycondensation reactor under nitrogen gas, and 0.15g of triphenyl phosphate, 0.85g of antioxidant 1010 and 0.95g of antioxidant 168 were added at the same time. The reaction was carried out at 210℃ and low vacuum of 700Pa for 55min. Then the temperature was raised to 236℃ and the vacuum was maintained at 50Pa to carry out the polycondensation reaction. After the melt index was qualified (38.4g / 10min), nitrogen gas was introduced to release the vacuum. The sample was fed while hot, granulated and dried to obtain sample R3. S3: Sample R3, 1g of cesium tungsten bronze, and 1.5g of lanthanum hexaboride were added to a twin-screw extruder and extruded, granulated, and dried at 180–200°C.

[0020] Test Experiment Example The physical properties of the copolyester hot melt adhesives for laser edge sealing prepared in Examples 1-3 and Comparative Examples 1-3 are listed in Table 1; then the tests were performed, and the results are listed in Table 1.

[0021] Heat resistance test: The copolyester hot melt adhesive was made into standard bonding samples, placed in an 80°C forced-air drying oven, and removed after 24 hours. After cooling to room temperature, the samples were observed to see if any edge curling or delamination occurred.

[0022] Peel strength test: Copolyester hot melt adhesive was applied to the ABS edge banding strip, and then laser edge banding was used to bond it to the workpiece to be edge banded. The laser power was 3KW. Then, the peel strength of the edge banding strip was tested according to GB / T 2792-2014 standard.

[0023] Table 1 Performance test results of Examples 1-3 and Comparative Examples 1-3 As can be seen from Table 1, compared with Comparative Examples 1-3, Examples 1-3 have extremely sensitive and consistent response to laser, stable edge sealing quality, good heat resistance, and significantly improved peel strength.

[0024] Compared with Comparative Example 1, Example 1 added sodium isophthalate-5-sulfonate, a monomer that increases polarity. This gave the copolyester hot melt adhesive higher polarity, increased the bonding strength with edge banding strips such as ABS and PVC, and improved the peel strength between the overall edge banding strip and the workpiece to be edge-banded.

[0025] Compared with Example 2, Comparative Example 2 shows that the peel strength of the laser absorber added during the polycondensation stage is slightly lower than that added during the esterification stage. Compared with Example 3, Comparative Example 3 shows that the peel strength of the sample blended with the laser absorber through screw extrusion is significantly reduced, and cracking also occurred during the heat resistance test.

[0026] The above comparison shows that adding the laser absorber during the esterification stage yields the best results. This is because adding the laser absorber during the synthesis stage allows the surface of the laser absorber nanoparticles to contain a small number of active functional groups such as hydroxyl groups. These groups interact with ester bonds or terminal hydroxyl groups, thus partially anchoring the absorber within the polymer's molecular chain network. This helps reduce interfacial separation caused by internal stress during use, thereby increasing laser absorption and peel strength.

Claims

1. A copolyester hot melt adhesive for laser edge sealing, characterized in that, The raw materials include the following components by mass fraction: 51%–56% diacid, 40%–45% diol, 0.1%–1.5% laser absorber, 0.025%–0.06% catalyst, 0.01%–0.03% heat stabilizer, 0.1%–1% antioxidant, 0.2%–0.5% trimethylolpropane, and 0%–0.3% inorganic hardening agent; The laser absorber is one or more of cesium tungsten bronze or lanthanide hexaborides, with a particle size of 30–80 nm and a specific surface area of ​​20–50 m². 2 / g.

2. The copolyester hot melt adhesive according to claim 1, characterized in that, The lanthanide hexaboride is at least one of lanthanum hexaboride, neodymium hexaboride, and persimmon hexaboride.

3. The copolyester hot melt adhesive according to claim 1, characterized in that, The molar ratio of the diacid to the diol is 1:(1.4-1.5); the diacid is a mixture of aromatic diacid and aliphatic diacid in a molar ratio of (0.90-0.98):(0.02-0.1).

4. The copolyester hot melt adhesive according to claim 3, characterized in that, The aromatic dicarboxylic acid is one or more of terephthalic acid, sodium isophthalate-5-sulfonate, isophthalic acid, and phthalic acid; the aliphatic dicarboxylic acid is one or more of 1,4-succinic acid, 1,6-adipic acid, sebacic acid, sebacic acid, and dodecanoic acid.

5. The copolyester hot melt adhesive according to claim 1, characterized in that, The diol is one or more of ethylene glycol, 1,3-malonic acid, 1,4-butanediol, diethylene glycol, 1,4-cyclohexanediol, and 1,6-hexanediol.

6. The copolyester hot melt adhesive according to claim 1, characterized in that, The catalyst is one or more of tetrabutyl titanate, antimony trioxide, and dibutyltin dilaurate.

7. The copolyester hot melt adhesive according to claim 1, characterized in that, The heat stabilizer is triphenyl phosphate or / and trimethyl phosphate; the antioxidant is a compound of hindered phenolic antioxidant 1010 and phosphite antioxidant 168 in a mass ratio of 1:(1-1.2).

8. The copolyester hot melt adhesive according to claim 1, characterized in that, The inorganic hardening agent is 800-1500 mesh wollastonite and / or 1000-1500 mesh talc.

9. The method for preparing the copolyester hot melt adhesive for laser edge sealing according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1, trimethylolpropane, laser absorber and diol accounting for 20% to 35% of the formula are mixed and dispersed at high speed to obtain dispersion A; S2, under the action of a catalyst, the dispersion A, the remaining diol and the dicarboxylic acid are reacted at 170-195℃ for 40-60 min, and then reacted at 195-220℃ for 120-180 min; when the amount of water distilled is 95% or more of the theoretical amount of water, the esterification reaction ends and esterified liquid B is obtained. S3, esterification liquid B is injected into the polycondensation reactor under nitrogen pressure, while heat stabilizer, antioxidant and inorganic hardening agent are added. The reaction is carried out at 200-230℃ and 1000-500Pa vacuum for 50-70 minutes. The temperature is then raised to 235-238℃ and the vacuum is 50-100Pa to continue the reaction. After the melt index is qualified, nitrogen is introduced to release the vacuum, and the material is fed while hot, granulated and dried.

10. The method for preparing the copolyester hot melt adhesive for laser edge sealing according to claim 9, characterized in that, The melt index of the copolyester hot melt adhesive at 160℃ and 2.16kg is 35-40g / 10min.

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