Dual-component degradable pressure-sensitive adhesive and degradable pressure-sensitive adhesive tape

Abstract

The present disclosure relates to a dual-component degradable pressure-sensitive adhesive and a degradable pressure-sensitive adhesive tape. The two-component degradable pressure-sensitive adhesive comprises a component A and a component B. The component A comprises, in parts by mass, 80-98 parts of a hydroxyl-terminated polyester copolymer, 2-15 parts of a small-molecule chain extender, 0.1-0.5 parts of a catalyst, and 1-5 parts of an auxiliary agent. The component B comprises an isocyanate-containing polyurethane prepolymer. The hydroxyl-terminated polyester copolymer is a copolymer of carboxyl-terminated polybutylene succinate and amorphous polypropylene carbonate diol, and has a number average molecular weight of 10000-20000. The isocyanate-containing polyurethane prepolymer is a product of an alcoholysis product of polyhydroxy fatty acid ester reacting with diisocyanate, and has a number average molecular weight of 3000-10000. The small-molecule chain extender is one or more of C2-C6 diols.

Description

Two-component biodegradable pressure-sensitive adhesive and biodegradable pressure-sensitive adhesive tape

[0001] This disclosure claims priority to Chinese Patent Application No. 2024115209403, filed on October 29, 2024, entitled "Two-component biodegradable pressure-sensitive adhesive and biodegradable pressure-sensitive tape", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure belongs to the field of pressure-sensitive adhesive tape technology, specifically, this disclosure relates to two-component biodegradable pressure-sensitive adhesive and biodegradable pressure-sensitive tape. Background Technology

[0003] With the development of pressure-sensitive adhesive (PSAs) technology, PAs have been widely used in tapes, labels, packaging, wallpaper, and other fields. However, along with the widespread use of PAs, PAs waste is also increasing, and the pollution problems it causes to the environment are becoming increasingly prominent. To address this issue, society has begun to strengthen research and development of renewable resources, hoping to find renewable and efficient biomass raw materials to replace non-renewable petroleum products, and strive to make the adhesive industry move towards green and sustainable development.

[0004] Currently, for pressure-sensitive adhesive tape technology, the pressure-sensitive adhesive substrate can be prepared using biodegradable materials, but most pressure-sensitive adhesives still use traditional non-biodegradable materials. In recent years, a technology has proposed a scheme to prepare biodegradable pressure-sensitive adhesives using polymers of carbon dioxide polyols and polybutylene succinate, but its adhesive performance is still difficult to meet the requirements of market applications. Summary of the Invention

[0005] Based on this, the present disclosure aims to overcome at least one defect of the conventional technology and provide a two-component biodegradable pressure-sensitive adhesive. The two-component pressure-sensitive adhesive has a high degradation rate, a fast degradation speed, excellent bonding performance, and is solvent-free, thus having good environmental performance. At the same time, it achieves good holding power, peel strength, and no adhesive residue. In addition, it also has a good aging performance retention rate.

[0006] Another aspect of this disclosure is to provide a biodegradable pressure-sensitive tape.

[0007] The technical solution disclosed herein is as follows:

[0008] A two-component biodegradable pressure-sensitive adhesive, comprising the following components:

[0009] Component A: by weight, it includes 80-98 parts of hydroxyl-terminated polyester copolymer, 2-15 parts of small molecule chain extender, 0.1-0.5 parts of catalyst, and 1-5 parts of additives;

[0010] Component B: includes isocyanate-containing polyurethane prepolymers, such as isocyanate-containing polyurethane prepolymers or mixtures thereof with isocyanates.

[0011] The hydroxyl-terminated polyester copolymer is a copolymer of carboxyl-terminated polybutylene succinate and non-crystalline polypropylene carbonate diol, with a number average molecular weight of 10,000 to 20,000; further, the number average molecular weight is preferably 12,000 to 16,000.

[0012] The small molecule chain extender is one or more C2-C6 diols;

[0013] The isocyanate-containing polyurethane prepolymer is a reaction product of alcoholysis of polyhydroxy fatty acid ester and diisocyanate, with a number average molecular weight of 3000-10000.

[0014] The molar ratio of the hydroxyl group of component A to the isocyanate group of component B is 1:(1.5~2.5).

[0015] The multi-component biodegradable pressure-sensitive adhesive disclosed herein comprises two components, A and B. Component A contains a hydroxyl-terminated polyester copolymer, which is a copolymer of carboxyl-terminated polybutylene succinate (PBS) and amorphous polypropylene carbonate diol (PPC). Amorphous polypropylene carbonate diol is a carbon dioxide-based diol, exhibiting rapid and high degradation rates. The carboxyl-terminated PBS itself is also biodegradable, thus making the hydroxyl-terminated polyester copolymer completely biodegradable. Furthermore, the polymers of PBS and PPC possess good cohesive strength, enabling its application in the pressure-sensitive adhesive field to meet the adhesive performance requirements. Component B is an isocyanate-containing polyurethane prepolymer, which is a polyhydroxyalkanoate. The alcoholysis products of polyhydroxy fatty acid esters react with diisocyanates. The alcoholysis products of polyhydroxy fatty acid esters have excellent degradability, which can further improve the degradation performance of pressure-sensitive adhesives. The isocyanate in component B can react with the hydroxyl-terminated polyester copolymer, small molecule chain extender or chemical substances with active hydrogen in component A to form polyurethane / polyurea. The generated isocyanate bonds or urea bonds can improve the cohesive force or adhesive force of pressure-sensitive adhesives. The role of the chain extender is to participate in the isocyanate reaction. By controlling the ratio of isocyanate, hydroxyl-terminated polyester copolymer and small molecule chain extender, a specific content of soft / hard segment structure can be formed and a cross-linked structure can be formed, resulting in excellent mechanical properties and making it suitable for preparing biodegradable polyurethane pressure-sensitive adhesives.

[0016] For component A: preferably, the acid value of the carboxyl-terminated polybutylene succinate is 56-112 mgKOH / g; and / or, the hydroxyl value of the amorphous polypropylene carbonate diol is 20 mgKOH / g-115 mgKOH / g, preferably 22 mgKOH / g-50 mgKOH / g, and more preferably 25-39 mgKOH / g.

[0017] Preferably, the mass ratio of the carboxyl-terminated polybutylene succinate to the amorphous polypropylene carbonate diol is (25-33):(67-75).

[0018] For example, the preparation process of hydroxyl-terminated polyester copolymers is as follows:

[0019] Preparation of carboxyl-terminated polybutylene succinate: 30-40 parts (e.g., 35 parts) of 1,4-butanediol and 50-60 parts (e.g., 56 parts) of succinic acid are added to a reaction vessel, and then the temperature is raised to 160-170℃. 0.1-0.5 wt% of tetrabutyl titanate catalyst (the total mass of 1,4-butanediol and succinic acid) is added, and the reaction is carried out for about 2-4 hours. Then the temperature is raised to 170-190℃ and the reaction is carried out for about 0.5-1.5 hours. Then the temperature is raised to 190-210℃ and vacuum polycondensation is carried out for 0.5-1.5 hours. The ester content is tested. When the acid value reaches 56-112 mg KOH / g, the mixture is cooled to room temperature to obtain carboxyl-terminated polybutylene succinate.

[0020] The non-crystalline polypropylene carbonate diol is commercially available, for example, it can be purchased from Huizhou Daya Bay Dazhi Fine Chemical Co., Ltd.

[0021] 25-33 parts of carboxyl-terminated polybutylene succinate and 67-75 parts of amorphous polypropylene carbonate diol were added to a reaction vessel. The temperature was then raised to 170-190℃, and 0.1-0.3 wt% of tetrabutyl titanate catalyst (the total mass of carboxyl-terminated polybutylene succinate and polypropylene carbonate diol) was added. The reaction was carried out for 1-3 hours, and then the temperature was raised to 210-230℃ for 3 hours. Vacuum polycondensation was then carried out for about 2-4 hours. After cooling to room temperature, a polyester copolymer containing terminal hydroxyl groups was obtained.

[0022] Preferably, the small molecule chain extender is one or a combination of at least two of ethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,2-propanediol, methylpropanediol, 1,3-butanediol, diethylene glycol, 1,6-hexanediol, or neopentyl glycol; more preferably, the small molecule chain extender is one or more of ethylene glycol, diethylene glycol, butanediol, and hexanediol; more preferably, the combination of ethylene glycol and butanediol, with a molar ratio of 2-8:2-8 (e.g., a molar ratio of 1:1).

[0023] Preferably, the catalyst is one or more of triethylamine, carbamate, triethylenediamine, triethylenediamine, organobismuth, organozinc, and organotin. For example, the organobismuth is one or more of bismuth neodecanoate, bismuth isooctanoate, and bismuth laurate; the organozinc is one or more of stannous octoate, dibutyltin dilaurate, dibutyltin dichloride, tributyltin oxide, and dioctyltin oxide; and the organozinc is one or more of zinc isooctanoate, zinc neodecanoate, diethylzinc, dimethylzinc, and 2-thienylzinc bromide.

[0024] Preferably, the additives include at least one of water absorbent, defoamer, and dispersant.

[0025] Preferably, component A comprises, by weight, 85-95 parts of hydroxyl-terminated polyester copolymer, 4-12 parts of small molecule chain extender, 0.2-0.5 parts of catalyst, and 2-5 parts of additives.

[0026] Preferably, the alcoholysis product of polyhydroxy fatty acid ester is the alcoholysis diol of polyhydroxybutyrate.

[0027] Preferably, the molecular weight of the polyhydroxybutyrate is 45,000 to 55,000.

[0028] For example, the method for preparing the alcoholysis diol of the polyhydroxybutyrate includes the following steps:

[0029] (1) Purification of polyhydroxybutyrate: Polyhydroxybutyrate was dissolved in chloroform at a mass ratio of 1:(5-20), stirred until completely dissolved, filtered under reduced pressure, and then the filtrate was transferred to a rotary evaporator. The filtrate was concentrated by rotary evaporation, and the concentrated liquid was poured into ice-cold methanol and stirred until precipitation. After vacuum filtration, a yellow flocculent substance was obtained. After drying under reduced pressure to constant weight, purified polyhydroxybutyrate was obtained.

[0030] (2) The purified polyhydroxybutyrate and chloroform are added to a flask at a mass ratio of 1:(5-20), a condenser is installed and the flask is heated to 40-50°C in a magnetic stirrer and stirred until fully dissolved. Then, 3-8 times the molar amount of polyhydroxybutyrate diol ester exchanger (such as 1,4-butanediol) and 1-3 wt‰ of catalyst (such as tetrabutyl titanate) are added to carry out the esterification reaction. The reaction is carried out for 3-6 hours. After the reaction is completed, the system naturally separates. Cool to room temperature; then pour the solution into a separatory funnel, wash with water at least 2 to 5 times, filter under reduced pressure to obtain a yellow liquid, evaporate by rotary evaporation to obtain a concentrated liquid, add the concentrated liquid to ice-cold methanol and stir until precipitation, filter under reduced pressure to obtain a yellow powder, dry under vacuum to constant weight to obtain the alcoholysis diol of polyhydroxybutyrate, wherein the number average molecular weight of the alcoholysis diol of polyhydroxybutyrate is 1000 to 5000, the functionality is greater than or equal to 1, and the hydroxyl value is 22.4 to 112.2 mg KOH / g.

[0031] Preferably, the number-average molecular weight of the alcoholysis diol of the polyhydroxybutyrate is 2000-3000.

[0032] The diisocyanate may be one or a mixture of toluene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, diphenylmethane diisocyanate, and carbodiimide-modified liquefied diphenylmethane diisocyanate.

[0033] For example, the preparation method of the isocyanate-containing polyurethane prepolymer includes the following steps: mixing and reacting the alcoholysis diol of polyhydroxybutyrate with a diisocyanate compound at a molar ratio of 1:(3-6), stirring at a speed of 100 rpm to 400 rpm, reacting at a temperature of 60-90°C, and reacting until the NCO content of the reaction product reaches the expected value (X), then cooling and discharging to obtain the isocyanate-containing polyurethane prepolymer;

[0034] Where X = [(A1-A2) / (a1+a2)]×100%, A1 is the total mass of NCO groups in diisocyanate, A2 is the mass of NCO groups required for the complete reaction of the hydroxyl groups in the alcoholysis diol of polyhydroxybutyrate, a1 is the mass of diisocyanate, and a2 is the mass of the alcoholysis diol of polyhydroxybutyrate.

[0035] A1 = [(a1×b) / M2]×42, where M2 is the molar mass of the diisocyanate, 42 is the molar mass of the NCO group, and b is the functionality of the isocyanate group (-NCO) in the diisocyanate.

[0036] A2 = [(a2×c) / 56100]×42, where 42 is the molar mass of the NCO group, 56100 is the product of the molar mass of KOH and 1000, and c is the hydroxyl value of the alcoholysis diol of polyhydroxybutyrate.

[0037] Preferably, the stirring speed is 200 rpm to 300 rpm and the reaction temperature is 70 to 80°C.

[0038] A biodegradable pressure-sensitive adhesive tape includes a base film and a pressure-sensitive adhesive layer attached to the base film. The pressure-sensitive adhesive layer is composed of the multi-component biodegradable pressure-sensitive adhesive and is obtained by mixing and curing components A and B.

[0039] Details of one or more embodiments of this disclosure are set forth in the following description. Other features, objects, and advantages of this disclosure will become apparent from the specification and claims.

[0040] The two-component biodegradable pressure-sensitive adhesive disclosed herein includes component A and component B. Component A contains a hydroxyl-terminated polyester copolymer with a molecular weight preferably of 10,000-20,000, which is prepared from carboxyl-terminated polybutylene succinate with a certain acid value and non-crystalline polypropylene carbonate diol with a certain hydroxyl value. When the chain extender of the hydroxyl-terminated polyester copolymer is a small molecule chain extender, and the number average molecular weight of the polyurethane prepolymer containing isocyanate in component B is 3,000-10,000, and the molar ratio of hydroxyl groups in component A to isocyanates in component B is 1:(1.5-2.5), the resulting pressure-sensitive adhesive can achieve good degradation effect and good comprehensive performance.

[0041] Regarding degradation performance, the main component of component A in this disclosure, a hydroxyl-terminated polyester copolymer, is a copolymer of carboxyl-terminated polybutylene succinate and non-crystalline polypropylene carbonate diol, exhibiting excellent degradation performance and good cohesive strength. The main component of component B, an isocyanate-containing polyurethane prepolymer, is a reaction product of the alcoholysis product of polyhydroxyalkanoates and diisocyanate. The alcoholysis product of polyhydroxyalkanoates has excellent degradation properties, which can further improve the degradation performance of the pressure-sensitive adhesive. Both the isocyanate-containing polyurethane prepolymer and the isocyanate in component B... It contains isocyanate groups, which can react with hydroxyl-terminated polyester copolymers, small molecule chain extenders, or chemicals with active hydrogen in component A to form polyurethane / polyurea. The generated isocyanate bonds or urea bonds can improve the cohesive force or adhesive force of the pressure-sensitive adhesive. By controlling the ratio of isocyanate groups, hydroxyl-terminated polyester copolymers, and small molecule chain extenders, a specific content of soft / hard segment structures can be formed, as well as a cross-linked structure, resulting in excellent mechanical properties. This makes it suitable for preparing biodegradable polyurethane pressure-sensitive adhesives. Through components A and B, the overall excellent biodegradability of the polyurethane pressure-sensitive adhesive is achieved.

[0042] This disclosure achieves a high biodegradability rate, better holding power, and excellent peel strength through the corresponding defined combinations of components A and B, while leaving no residue; the solution described in this disclosure has a good aging performance retention rate and excellent overall performance. Embodiments of the present invention

[0043] The embodiments disclosed herein are for illustrative purposes only and should not be construed as limiting the scope of this disclosure.

[0044] For simplicity, this paper only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an undefined range; and any lower limit can be combined with other lower limits to form an undefined range, just as any upper limit can be combined with any other upper limit to form an undefined range. Furthermore, although not explicitly stated, every point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can serve as its own lower or upper limit and be combined with any other point or individual value, or with other lower or upper limits, to form an undefined range.

[0045] The foregoing description of this application is not intended to describe every disclosed implementation or method. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments that can be used in various combinations. The examples listed are representative only and should not be construed as exhaustive.

[0046] The preparation process of carboxyl-terminated polybutylene succinate 1 (PBS1) is as follows: 35 parts of 1,4-butanediol and 56 parts of succinic acid were added to a reaction vessel, and then the temperature was raised to 165°C. Tetrabutyl titanate catalyst with a total mass of 0.3 wt% of 1,4-butanediol and succinic acid was added and reacted for about 3 hours. Then the temperature was raised to 180°C and reacted for about 1 hour. Then the temperature was raised to 200°C and vacuum polycondensed for 1 hour. The acid ester was tested. When the acid value was close to 75 mg KOH / g (number average molecular weight of 1500), the carboxyl-terminated polybutylene succinate 1 was obtained after cooling to room temperature.

[0047] The preparation process of carboxyl-terminated polybutylene succinate 2 (PBS2) is as follows: 35 parts of 1,4-butanediol and 56 parts of succinic acid were added to a reaction vessel, and then the temperature was raised to 165°C. Tetrabutyl titanate catalyst with a total mass of 0.3 wt% of 1,4-butanediol and succinic acid was added and reacted for about 3 hours. Then the temperature was raised to 180°C and reacted for about 1 hour. Then the temperature was raised to 200°C and vacuum polycondensed for 1 hour. The acid ester was tested. When the acid value was close to 112 mg KOH / g (number average molecular weight of 1000), the carboxyl-terminated polybutylene succinate 2 was obtained after cooling to room temperature.

[0048] The preparation process of carboxyl-terminated polybutylene succinate 3 (PBS3) is as follows: 35 parts of 1,4-butanediol and 56 parts of succinic acid were added to a reaction vessel, and then the temperature was raised to 165°C. Tetrabutyl titanate catalyst with a total mass of 0.3 wt% of 1,4-butanediol and succinic acid was added and reacted for about 4 hours. Then the temperature was raised to 180°C and reacted for about 1 hour. Then the temperature was raised to 220°C and vacuum polycondensed for 2.5 hours. The acid ester was tested. When the acid value was close to 56 mg KOH / g (number average molecular weight of 2000), the carboxyl-terminated polybutylene succinate 3 was obtained after cooling to room temperature.

[0049] The following are examples of non-crystalline polypropylene carbonate diols: PPCD-242 (hydroxyl value 27±2 mgKOH / g); PPCD-237 (hydroxyl value 37±2 mgKOH / g); PPCD-222 (hydroxyl value 56±2 mgKOH / g); Huizhou Daya Bay Dazhi Fine Chemical Co., Ltd.

[0050] The preparation process of the hydroxyl-terminated polyester copolymer 1 described in the following examples is as follows:

[0051] 33 parts of carboxyl-terminated PBS1 and 67 parts of amorphous polypropylene carbonate diol (PPCD-237) were added to a reactor. The mixture was then heated to 180°C, and 0.2 wt% tetrabutyl titanate catalyst (the total mass of PBS1 and polypropylene carbonate diol) was added. The reaction was carried out for 2 hours, followed by a further heating to 220°C and a reaction for 3 hours. Vacuum polycondensation was then performed for approximately 3 hours, and the mixture was cooled to room temperature to obtain hydroxyl-containing polyester copolymer 1. The molecular weight of the hydroxyl-containing polyester copolymer 1 was measured, and the number average molecular weight was approximately 20,000.

[0052] The preparation process of the hydroxyl-terminated polyester copolymer 2 described in the following examples is as follows:

[0053] 33 parts of carboxyl-terminated PBS1 and 67 parts of amorphous polypropylene carbonate diol (PPCD-242) were added to a reactor. The mixture was then heated to 180°C, and 0.2 wt% tetrabutyl titanate catalyst (the total mass of PBS1 and polypropylene carbonate diol) was added. The reaction proceeded for 2 hours, followed by a further heating to 220°C and a reaction for 3 hours. Vacuum polycondensation was then performed for approximately 3 hours, and the mixture was cooled to room temperature to obtain hydroxyl-containing polyester copolymer 2. The molecular weight of the hydroxyl-terminated polyester copolymer 2 was measured, and the number average molecular weight was found to be approximately 10,000.

[0054] The preparation process of the three-component hydroxyl-terminated polyester copolymer described in the following examples is as follows:

[0055] 33 parts of carboxyl-terminated PBS1 and 67 parts of amorphous polypropylene carbonate diol (PPCD-222) were added to a reactor. The mixture was then heated to 180°C, and 0.2 wt% tetrabutyl titanate catalyst (the total mass of PBS1 and polypropylene carbonate diol) was added. The reaction was carried out for 2 hours, followed by a further heating to 220°C and a reaction for 3 hours. Vacuum polycondensation was then performed for approximately 2 hours, and the mixture was cooled to room temperature to obtain hydroxyl-containing polyester copolymer 3. The molecular weight of the hydroxyl-terminated polyester copolymer 3 was measured to be approximately 17,000.

[0056] The preparation process of the four-component hydroxyl-terminated polyester copolymer described in the following examples is as follows:

[0057] 33 parts of carboxyl-terminated PBS3 and 67 parts of amorphous polypropylene carbonate diol (PPCD-237) were added to a reactor. The mixture was then heated to 175°C, and 0.3 wt% tetrabutyl titanate catalyst (the total mass of PBS1 and polypropylene carbonate diol) was added. The reaction was carried out for 2 hours, followed by a further heating to 220°C and a reaction for 3 hours. Vacuum polycondensation was then performed for approximately 3 hours, and the mixture was cooled to room temperature to obtain hydroxyl-containing polyester copolymer 3. The molecular weight of the hydroxyl-containing polyester copolymer 3 was measured, and the number average molecular weight was approximately 16,800.

[0058] The alcoholysis product of the polyhydroxy fatty acid ester disclosed herein is the alcoholysis diol of polyhydroxybutyrate, and its preparation process is as follows:

[0059] Alcoholization diols of polyhydroxybutyrate 1:

[0060] Purification of polyhydroxybutyrate: Polyhydroxybutyrate with a number average molecular weight of approximately 50,000 was dissolved in chloroform at a mass ratio of 1:10. The solution was stirred until completely dissolved, filtered under reduced pressure, and then the filtrate was transferred to a rotary evaporator. The filtrate was concentrated by rotary evaporation, and the concentrated liquid was poured into ice-cold methanol and stirred until precipitation occurred. After vacuum filtration, a yellow flocculent substance was obtained. The substance was dried under reduced pressure at 40°C to constant weight to obtain purified polyhydroxybutyrate.

[0061] (2) The purified polyhydroxybutyrate and chloroform were added to a flask at a mass ratio of 1:10. A condenser was installed and the flask was heated to 40-50°C in a magnetic stirrer and stirred until fully dissolved. Eight times the molar amount of polyhydroxybutyrate diol ester exchanger 1,4-butanediol and 3 wt‰ of catalyst tetrabutyl titanate were added to carry out the esterification reaction. The reaction was carried out for 24 hours and vacuum polycondensation for 1.5 hours. After the reaction was completed, the system was naturally cooled to room temperature. The solution was then poured into a separatory funnel, washed with water at least 3 times, and filtered under reduced pressure to obtain a yellow liquid. After rotary evaporation, a concentrated liquid was obtained. The concentrated liquid was added to ice-cold methanol and stirred until precipitation. After vacuum filtration, a yellow powder was obtained. After vacuum drying at 40°C to constant weight, the alcoholysis diol of polyhydroxybutyrate was obtained. The number average molecular weight of the alcoholysis diol 1 of polyhydroxybutyrate was about 2000, the functionality was di, and the hydroxyl value was 56.1 mg KOH / g.

[0062] The alcoholysis diol of polyhydroxybutyrate 2:

[0063] Purification of polyhydroxybutyrate: Polyhydroxybutyrate with a number average molecular weight of approximately 50,000 was dissolved in chloroform at a mass ratio of 1:10. The solution was stirred until completely dissolved, filtered under reduced pressure, and then the filtrate was transferred to a rotary evaporator. The filtrate was concentrated by rotary evaporation, and the concentrated liquid was poured into ice-cold methanol and stirred until precipitation occurred. After vacuum filtration, a yellow flocculent substance was obtained. The substance was dried under reduced pressure at 40°C to constant weight to obtain purified polyhydroxybutyrate.

[0064] (2) The purified polyhydroxybutyrate and chloroform were added to a flask at a mass ratio of 1:10. A condenser was installed and the flask was heated to 40-50°C in a magnetic stirrer and stirred until fully dissolved. Five times the molar amount of polyhydroxybutyrate diol ester exchanger 1,4-butanediol and 2 wt‰ of catalyst tetrabutyl titanate were added to carry out the esterification reaction. The reaction was carried out for 24 hours and vacuum polycondensation for 3 hours. After the reaction was completed, the system was naturally cooled to room temperature. The solution was then poured into a separatory funnel, washed with water at least 3 times, and filtered under reduced pressure to obtain a yellow liquid. After rotary evaporation, a concentrated liquid was obtained. The concentrated liquid was added to ice-cold methanol and stirred until precipitation. After vacuum filtration, a yellow powder was obtained. After vacuum drying at 40°C to constant weight, the alcoholysis diol of polyhydroxybutyrate was obtained. The number average molecular weight of the alcoholysis diol 2 of polyhydroxybutyrate was about 3000, the functionality was di, and the hydroxyl value was 37.4 mg KOH / g.

[0065] The calculation of the NCO content X mentioned in the preparation process of the following isocyanate-containing polyurethane prepolymers (or mixtures thereof with isocyanates) for components B1, B2, B3, B4, and B5 is as follows:

[0066] X=[(A1-A2) / (a1+a2)]×100%,

[0067] A1 is the total mass of NCO groups in diisocyanate, A2 is the mass of NCO groups required for the complete reaction of the hydroxyl groups in the alcoholysis diol of polyhydroxybutyrate, a1 is the mass of diisocyanate, and a2 is the mass of the alcoholysis diol of polyhydroxybutyrate.

[0068] A1 = [(a1×b) / M2]×42, where M2 is the molar mass of the diisocyanate, 42 is the molar mass of the NCO group, and b is the functionality of the isocyanate group (NCO) in the diisocyanate.

[0069] A2 = [(a2×c) / 56100]×42, where 42 is the molar mass of the NCO group, 56100 is the product of the molar mass of KOH and 1000, and c is the hydroxyl value of the alcoholysis diol of polyhydroxybutyrate.

[0070] The preparation process of component B1 described in the following examples is as follows:

[0071] The alcoholysis product 1 of polyhydroxy fatty acid ester was mixed with isoflurane diisocyanate at a molar ratio of 1:3 and stirred at a stirring speed of 200 rpm. The reaction temperature was about 85°C. When the NCO content X of the reaction product was 4.58, the product was cooled and discharged to obtain polyurethane prepolymer 1 containing isocyanate, with a number average molecular weight of about 8500.

[0072] The preparation process of component B2 described in the following examples is as follows:

[0073] The alcoholysis product 1 of polyhydroxy fatty acid ester was mixed with isoflurane diisocyanate at a molar ratio of 1:6 and stirred at a stirring speed of 200 rpm. The reaction temperature was about 85°C. When the NCO content X of the reaction product was 9.69, the product was cooled and discharged to obtain polyurethane prepolymer 2 containing isocyanate, with a number average molecular weight of about 3800.

[0074] The preparation process of component B3 described in the following examples is as follows:

[0075] The alcoholysis product 1 of polyhydroxy fatty acid ester was mixed with isoflurane diisocyanate at a molar ratio of 1:4 and stirred at a stirring speed of 200 rpm. The reaction temperature was about 85°C. When the NCO content X of the reaction product was 6.48%, the product was cooled and discharged to obtain polyurethane prepolymer 3 containing isocyanate, with a number average molecular weight of about 6800.

[0076] The preparation process of component B4 described in the following examples is as follows:

[0077] The alcoholysis product 1 of polyhydroxy fatty acid ester was mixed with diphenylmethane diisocyanate at a molar ratio of 1:4 and stirred at a stirring speed of 200 rpm. The reaction temperature was about 75°C. When the NCO content X of the reaction product was 6.30, the product was cooled and discharged to obtain polyurethane prepolymer 4 containing isocyanate, with a number average molecular weight of about 7000.

[0078] The preparation process of component B5 described in the following examples is as follows:

[0079] The alcoholysis product 2 of polyhydroxy fatty acid ester was mixed with isoflurane diisocyanate at a molar ratio of 1:4 and stirred at a stirring speed of 200 rpm. The reaction temperature was about 85°C. When the NCO content X of the reaction product was 10.31%, the product was cooled and discharged to obtain polyurethane prepolymer 5 containing isocyanate, with a number average molecular weight of about 4200.

[0080] Example 1

[0081] A two-component biodegradable pressure-sensitive adhesive, comprising:

[0082] Component A1: By weight, it includes 90 parts of hydroxyl-terminated polyester copolymer, 4 parts of small molecule chain extender butanediol, 4 parts of small molecule chain extender ethylene glycol, 0.3 parts of catalyst dibutyltin dilaurate, 1 part of dispersant (BYK-034, the same below), and 0.7 parts of defoamer (BYK-024, the same below).

[0083] Component B1;

[0084] The molar ratio of the hydroxyl group in component A1 to the isocyanate group in component B1 is 1:2.

[0085] The preparation process of the two-component biodegradable pressure-sensitive adhesive is as follows:

[0086] Mix the hydroxyl-terminated polyester copolymer 1, small molecule chain extender, catalyst, dispersant, and defoamer in the specified proportions until homogeneous;

[0087] Calculate the dosage of components A1 and B1 according to the molar ratio of hydroxyl group of component A1 to isocyanate group of component B1 as 1:2. Then mix the calculated dosage of components A1 and B1, stir evenly, and degas under vacuum for 30 seconds.

[0088] Example 2 (The only difference from Example 1 is the chain extender)

[0089] A two-component biodegradable pressure-sensitive adhesive, comprising:

[0090] Component A2: by weight, it includes 90 parts of hydroxyl-terminated polyester copolymer, 1.8 parts of small molecule chain extender butanediol, 0.3 parts of catalyst dibutyltin dilaurate, 1 part of dispersant, and 0.7 parts of defoamer;

[0091] Component B1;

[0092] The molar ratio of the hydroxyl group in component A2 to the isocyanate group in component B1 is 1:2.

[0093] The preparation process of the two-component biodegradable pressure-sensitive adhesive is as follows:

[0094] Mix the hydroxyl-terminated polyester copolymer 2, small molecule chain extender, catalyst, dispersant, and defoamer in the specified proportions until homogeneous;

[0095] Calculate the dosage of components A2 and B1 according to the molar ratio of hydroxyl group of component A2 to isocyanate group of component B1 of 1:2. Then mix the calculated dosage of components A2 and B1, stir evenly, and degas under vacuum for 30 seconds.

[0096] Example 3 (The only difference from Example 1 is that the hydroxyl-terminated polyester copolymer 2 replaces the hydroxyl-terminated polyester copolymer 1)

[0097] A two-component biodegradable pressure-sensitive adhesive, comprising:

[0098] Component A3: By weight, it includes 90 parts of hydroxyl-terminated polyester copolymer, 2 and 4 parts of small molecule chain extender butanediol, 4 parts of small molecule chain extender ethylene glycol, 0.3 parts of catalyst dibutyltin dilaurate, 1 part of dispersant, and 0.7 parts of defoamer;

[0099] Component B1;

[0100] The molar ratio of the hydroxyl group in component A3 to the isocyanate group in component B1 is 1:2.

[0101] The preparation process of the two-component biodegradable pressure-sensitive adhesive is as follows:

[0102] Mix the hydroxyl-terminated polyester copolymer 2, small molecule chain extender, catalyst, dispersant, and defoamer in the specified proportions until homogeneous;

[0103] Calculate the dosage of components A3 and B1 according to the molar ratio of hydroxyl group of component A3 to isocyanate group of component B1 of 1:2. Then mix the calculated dosage of components A3 and B1, stir evenly, and degas under vacuum for 30 seconds.

[0104] Example 4 (The only difference from Example 1 is that the hydroxyl-terminated polyester copolymer 3 replaces the hydroxyl-terminated polyester copolymer 1)

[0105] A two-component biodegradable pressure-sensitive adhesive, comprising:

[0106] Component A4: By weight, it includes 90 parts of hydroxyl-terminated polyester copolymer, 3-4 parts of small molecule chain extender butanediol, 4 parts of small molecule chain extender ethylene glycol, 0.3 parts of catalyst dibutyltin dilaurate, 1 part of dispersant, and 0.7 parts of defoamer.

[0107] Component B1;

[0108] The molar ratio of the hydroxyl group in component A4 to the isocyanate group in component B1 is 1:2.

[0109] The preparation process of the two-component biodegradable pressure-sensitive adhesive is as follows:

[0110] Mix the hydroxyl-terminated polyester copolymer 3, small molecule chain extender, catalyst, dispersant, and defoamer in the specified proportions until homogeneous;

[0111] Calculate the amounts of components A3 and B1 according to the molar ratio of hydroxyl groups in component A4 to isocyanates in component B1 of 1:2. Then mix the calculated amounts of components A4 and B1, stir evenly, and degas under vacuum for 30 seconds.

[0112] Example 5

[0113] A two-component biodegradable pressure-sensitive adhesive, comprising:

[0114] Component A5: By weight, it includes 90 parts of hydroxyl-terminated polyester copolymer, 4 parts of small molecule chain extender butanediol, 4 parts of small molecule chain extender ethylene glycol, 0.3 parts of catalyst dibutyltin dilaurate, 1 part of dispersant, and 0.7 parts of defoamer.

[0115] Component B2;

[0116] The molar ratio of the hydroxyl group in component A4 to the isocyanate group in component B2 is 1:2.5.

[0117] The preparation process of the two-component biodegradable pressure-sensitive adhesive is as follows:

[0118] Mix the hydroxyl-terminated polyester copolymer 4, small molecule chain extender, catalyst, dispersant, and defoamer in the specified proportions until homogeneous;

[0119] Calculate the amounts of components A3 and B1 according to the molar ratio of hydroxyl groups in component A4 to isocyanates in component B2 of 1:2.5. Then mix the calculated amounts of components A3 and B1, stir evenly, and degas under vacuum for 30 seconds.

[0120] Comparative Example 1

[0121] A multi-component biodegradable pressure-sensitive adhesive has the same components as the multi-component biodegradable pressure-sensitive adhesive described in Example 1, except that component A1 is different. The preparation process of component A in Comparative Example 1 is as follows:

[0122] 33 parts of carboxyl-terminated PBS1 and 67 parts of amorphous polypropylene carbonate diol (PPCD-237) were added to a reactor. The temperature was then raised to 180°C, and 0.2 wt% tetrabutyl titanate catalyst (the total mass of PBS1 and polypropylene carbonate diol) was added. The reaction was carried out for 2 hours, followed by a further increase in temperature to 220°C and a reaction for 3 hours. Vacuum polycondensation was then performed for approximately 6 hours, and the mixture was cooled to room temperature to obtain hydroxyl-containing polyester copolymer 1. The molecular weight of the hydroxyl-containing polyester copolymer 1 was measured, and the number average molecular weight was approximately 37,500.

[0123] Comparative Example 2

[0124] A multi-component biodegradable pressure-sensitive adhesive has the same components as the multi-component biodegradable pressure-sensitive adhesive described in Example 1, and the molar ratio of the hydroxyl group of component A1 to the isocyanate group of component B1 is 1:2. The only difference is that component B1 is different; in this Comparative Example 2, component B1 is replaced with isoflurane diisocyanate.

[0125] Comparative Example 3

[0126] A multi-component biodegradable pressure-sensitive adhesive has the same components as the multi-component biodegradable pressure-sensitive adhesive described in Example 1, except that component A does not use a chain extender.

[0127] Comparative Example 4

[0128] A multi-component biodegradable pressure-sensitive adhesive has the same components as the multi-component biodegradable pressure-sensitive adhesive described in Example 1, except that component A uses dihydroxyethyl terephthalate as a chain extender.

[0129] Comparative Example 5

[0130] A multi-component biodegradable pressure-sensitive adhesive, the components of which are the same as those of the multi-component biodegradable pressure-sensitive adhesive described in Example 1, the only difference being that the same preparation method as the corresponding B1 component in Example 1 is used to control the number average molecular weight of the final polyurethane prepolymer containing isocyanate to be 12000.

[0131] Comparative Example 6

[0132] A multi-component biodegradable pressure-sensitive adhesive, the components of which are the same as those of the multi-component biodegradable pressure-sensitive adhesive described in Example 1, the only difference being that the same preparation method as the corresponding B1 component in Example 1 is used to control the number average molecular weight of the final polyurethane prepolymer containing isocyanate to be 2500.

[0133] The multi-component pressure-sensitive adhesives described in the above embodiments and comparative examples were formulated into pressure-sensitive adhesive solutions and then made into pressure-sensitive adhesive tapes. The specific formulations and preparation methods are as follows:

[0134] (1) Add an appropriate amount of chloroform solution to each of the two-component biodegradable pressure-sensitive adhesives to obtain a pressure-sensitive adhesive solution with a solid content of 20 wt%.

[0135] (2) The pressure-sensitive adhesive solution is coated onto the PET film using a coating machine. After being kept at 80°C for 10 minutes, the chloroform evaporates. The thickness of the pressure-sensitive adhesive layer of the resulting pressure-sensitive tape is approximately 15 μm.

[0136] The prepared pressure-sensitive tape was subjected to performance tests, the test items are as follows:

[0137] (1) Biodegradation rate: Tested according to GB / T 19277.1.

[0138] (2) Initial tack: Tested according to Method A in GB / T 4852-2002, with the inclined plane tilted at 30°.

[0139] (3) Holding power: The test shall be conducted in accordance with Method A of GB / T 4851-2014. The width of the biodegradable tape sample shall be 25 mm, the length of the bonding surface between the sample and the steel plate shall be (12±0.5 mm), and the mass of the weight shall be (1000±5 g).

[0140] (4) 180 peel strength: Tested according to the provisions of GB / T 2792.

[0141] (5) At a temperature of 70℃ and a humidity of 75%, the adhesive was bonded to a glass plate for 144 hours and the residual adhesive was tested. No residual adhesive means 0% of the area is residual adhesive; almost no residual adhesive means less than 5% of the area is residual adhesive; slightly residual adhesive means 5-12% of the area is residual adhesive; more residual adhesive means more than 12% of the area is residual adhesive.

[0142] (6) Aging resistance: The tape was placed in a constant temperature and humidity aging chamber at 70°C and 95% humidity for 72 hours, and then its peel strength was measured.

[0143] The test results are shown in Tables 1 and 2. The test results of Example 1 represent the sequencing results of the pressure-sensitive tape prepared from the multi-component biodegradable pressure-sensitive adhesive described in Example 1, and the test results of Example 2 represent the sequencing results of the pressure-sensitive tape prepared from the multi-component biodegradable pressure-sensitive adhesive described in Example 2, and so on.

[0144] Table 1

[0145] Test Items Initial Tack (Ball Size) Holding Tack (h) 180 Peel Strength (N / 25mm) Aging Peel Strength (N / 25mm) Residual Adhesive Example 16 14 49.3 5 9.07 No Residual Adhesive Example 25 11 47.7 4 7.21 Almost No Residual Adhesive Example 35 14 29.2 1 8.89 No Residual Adhesive Example 44 12 0 7.8 5 7.23 Almost No Residual Adhesive Example 55 13 28.4 5 8.07 No Residual Adhesive Comparative Example 16 9 66 1 4.8 Slight Residual Adhesive Comparative Example 24 7 55 5.2 2 4.1 More Residual Adhesive Comparative Example 35 7 35.8 7 4.32 More Residual Adhesive Comparative Example 45 8 26.3 7 4.52 Slight Residual Adhesive Comparative Example 55 8 76.8 9 5.16 Slight Residual Adhesive Comparative Example 66 9 25.4 6 4.32 Slight Residual Adhesive

[0146] Table 2

[0147] Test Item Biodegradation Rate (% / 80d) Biodegradation Rate (% / 120d) Biodegradation Rate (% / 160d) Biodegradation Rate (% / 200d) Example 1 76.5 89.7 96.7 98.9 Example 2 64.2 73.5 83.7 89.2 Example 3 75.2 86.5 92.3 95.4 Example 4 62.1 71.2 79.8 87.6 Implementation Example 573.887.693.196.5 Comparative Example 151.260.367.573.2 Comparative Example 247.557.662.369.8 Comparative Example 352.361.968.674.6 Comparative Example 453.762.469.772.5 Comparative Example 550.259.867.275.6 Comparative Example 648.656.763.471.8

[0148] As can be seen from Table 1, the solution described in this disclosure achieves good tack, peel strength, no residue, good biodegradability, and good aging performance retention by considering various components in Component A (hydroxyl-terminated polyester copolymer, chain extender) and Component B (polyurethane prepolymer containing isocyanate (or a mixture thereof)). Examples 1-5 show that only when the hydroxyl-terminated polyester copolymer in component A is composed of carboxyl-terminated polybutylene succinate (acid value 56-112 mgKOH / g) and non-crystalline polypropylene carbonate diol (hydroxyl value 22 mgKOH / g-50 mgKOH / g, more preferably 25-39 mgKOH / g), and the molecular weight of the hydroxyl-terminated polyester copolymer is 10000-20000, the chain extender is a small molecule chain extender (which can be a combination of butanediol and ethylene glycol), and the number average molecular weight of the polyurethane prepolymer containing isocyanate in component B is 3000-10000, and the molar ratio of hydroxyl groups in component A to isocyanates in component B is 1:(1.5-2.5), can it exhibit good holding power, peel strength, no residue, and a relatively high aging performance retention rate while maintaining good biodegradability. In Comparative Example 1, the number-average molecular weight of the hydroxyl-containing polyester copolymer was 37,500; in Comparative Example 2, isoflurane diisocyanate was used as component B; in Comparative Example 3, no chain extender was used; in Comparative Example 4, dihydroxyethyl terephthalate was used as a macromolecular chain extender; the number-average molecular weight of the isocyanate-containing polyurethane prepolymers corresponding to Comparative Examples 5 and 6 did not fall within the range of this disclosure, and their corresponding biodegradability was lower than that of this disclosure, as were their holding power, peel strength, residual adhesive test results, and aging performance retention. It is evident that the two-component biodegradable pressure-sensitive adhesive and the prepared biodegradable pressure-sensitive tape described in this disclosure have excellent overall performance.

[0149] Obviously, the above embodiments of this disclosure are merely examples for clearly illustrating the technical solutions of this disclosure, and are not intended to limit the specific implementation of this disclosure. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the claims of this disclosure should be included within the protection scope of the claims of this disclosure.

Claims

1. A two-component biodegradable pressure-sensitive adhesive, characterized in that, include: Component A: by weight, it includes 80-98 parts of hydroxyl-terminated polyester copolymer, 2-15 parts of small molecule chain extender, 0.1-0.5 parts of catalyst, and 1-5 parts of additives; Component B: includes isocyanate-containing polyurethane prepolymer; The hydroxyl-terminated polyester copolymer is a copolymer of carboxyl-terminated polybutylene succinate and non-crystalline polypropylene carbonate diol, with a number average molecular weight of 10,000 to 20,000. The small molecule chain extender is one or more C2-C6 diols; The isocyanate-containing polyurethane prepolymer is a reaction product of alcoholysis of polyhydroxy fatty acid ester and diisocyanate, with a number average molecular weight of 3000-10000. The molar ratio of the hydroxyl group of component A to the isocyanate group of component B is 1:(1.5~2.5).

2. The two-component biodegradable pressure-sensitive adhesive according to claim 1, characterized in that, The alcoholysis products of polyhydroxy fatty acid esters are the alcoholysis diols of polyhydroxybutyrate.

3. The two-component biodegradable pressure-sensitive adhesive according to claim 2, characterized in that, The method for preparing the alcoholysis diol of the polyhydroxybutyrate includes the following steps: (1) Purification of polyhydroxybutyrate: Polyhydroxybutyrate was dissolved in chloroform at a mass ratio of 1:(5-20), stirred until completely dissolved, filtered under reduced pressure, and then the filtrate was transferred to a rotary evaporator. The filtrate was concentrated by rotary evaporation, and the concentrated liquid was poured into ice-cold methanol and stirred until precipitation. After vacuum filtration, a yellow flocculent substance was obtained. After drying under reduced pressure to constant weight, purified polyhydroxybutyrate was obtained. (2) Add the purified polyhydroxybutyrate and chloroform to a flask at a mass ratio of 1:(5-20), install a condenser liquid seal device, place it in a magnetic stirrer and heat to 40-50°C, stir until fully dissolved, add 3-8 times the molar amount of diol ester exchanger and 1-3 wt‰ of catalyst to carry out esterification reaction, react for 3-6 hours, and after the reaction is completed, let the system cool naturally to room temperature; The solution was then poured into a separatory funnel, washed with water at least 2 to 5 times, filtered under reduced pressure to obtain a yellow liquid, and concentrated by rotary evaporation. The concentrated liquid was added to ice-cold methanol and stirred until a precipitate formed. After filtration under reduced pressure, a yellow powder was obtained. After vacuum drying to constant weight, the alcoholysis diol of polyhydroxybutyrate was obtained.

4. The two-component biodegradable pressure-sensitive adhesive according to claim 1, characterized in that, The diisocyanate is one or a mixture of diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, and hexamethylene isocyanate.

5. The two-component biodegradable pressure-sensitive adhesive according to claim 1, characterized in that, The method for preparing the polyurethane prepolymer containing isocyanate includes the following steps: mixing the alcoholysis diol of polyhydroxybutyrate with a diisocyanate compound in a molar ratio of 1:(3-6) and stirring to react at a reaction temperature of 60-90°C until the NCO content of the reaction product reaches the expected level, then cooling down and discharging the product.

6. The multi-component biodegradable pressure-sensitive adhesive according to claim 1, characterized in that, The acid value of the carboxyl-terminated polybutylene succinate is 56–112 mg KOH / g; and / or the hydroxyl value of the amorphous polypropylene carbonate diol is 20 mg KOH / g–115 mg KOH / g, preferably 22 mg KOH / g–50 mg KOH / g.

7. The multi-component biodegradable pressure-sensitive adhesive according to claim 1 or 6, characterized in that, The mass ratio of the carboxyl-terminated polybutylene succinate to the amorphous polypropylene carbonate diol is (25-33):(67-75).

8. The two-component biodegradable pressure-sensitive adhesive according to any one of claims 1 to 7, characterized in that, The chain extender is one or more of ethylene glycol, ethylene glycol monohydrate, butanediol, and hexanediol; more preferably, the small molecule chain extender is a combination of ethylene glycol and butanediol.

9. The two-component biodegradable pressure-sensitive adhesive according to any one of claims 1 to 7, characterized in that, The catalyst is one or more of triethylamine, carbamate, triethylenediamine, triethylenediamine, organobismuth, organozinc, and organotin; and / or the additives include at least one of desiccant, defoamer, and dispersant.

10. A biodegradable pressure-sensitive adhesive tape, characterized in that, It includes a base film and a pressure-sensitive adhesive layer attached to the base film. The pressure-sensitive adhesive layer is composed of the multi-component biodegradable pressure-sensitive adhesive as described in any one of claims 1 to 9. The pressure-sensitive adhesive layer is obtained by mixing and curing component A and component B.