High-solid low-viscosity polyurethane functional adhesive and preparation method thereof

Abstract

The invention discloses a high-solid low-viscosity polyurethane functional adhesive and a preparation method thereof, and relates to the technical field of chemical adhesives. On one hand, the invention provides the high-solid low-viscosity polyurethane functional adhesive which comprises a main agent and a curing agent in a mass ratio of 10: (2-20), the main agent comprises a straight chain type isocyanate-terminated polyurethane prepolymer and a branched chain type isocyanate-terminated polyurethane prepolymer, the NCO content is 4%-6%, the rotary viscosity at 25 DEG C is 2000-4000 mPa.s, and the solid content is 70%-80%; the rotary viscosity of the curing agent at 25 DEG C is 1000-3000 mPa.s, and the solid content is 70%-80%. On the other hand, the invention provides a preparation method of the high-solid low-viscosity polyurethane functional adhesive. The invention aims to solve the problem that the existing functional glue cannot consider low viscosity, heat resistance and medium resistance at the same time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical adhesives, in particular to a high-solid low-viscosity polyurethane functional adhesive and a preparation method thereof. BACKGROUND

[0002] With the upgrading of consumption and the improvement of food safety awareness, the demand for functional packaging in the soft packaging industry continues to grow. Functional packaging requires materials to have water boiling (85-100℃), cooking (121-135℃), medium resistance (oil resistance, acid resistance, small molecule resistance), and high heat resistance (>135℃) and other properties to meet the needs of different application scenarios. Currently, functional packaging accounts for more than 30% of the soft packaging market, with an average annual growth rate of more than 8%, becoming an important direction of industry development.

[0003] In the existing functional packaging production process, solvent-based polyurethane adhesives are widely used due to their excellent performance. However, traditional functional adhesives have obvious technical limitations: first, due to their high molecular weight, the working viscosity is high, so the working concentration can usually only reach 30-35%, and the use of a large amount of solvent not only increases production costs but also causes environmental pollution problems; second, under high viscosity conditions, the adhesive coating uniformity is poor, and the compound machine speed needs to be reduced to 80-150 meters / minute to ensure quality, which seriously affects production efficiency; third, the VOCs emission problem of traditional high-solvent adhesives has become a bottleneck restricting enterprise development.

[0004] In recent years, soft packaging composite equipment manufacturing technology has made significant progress. Domestic and foreign well-known equipment manufacturers such as Bosch, North, and Automa have launched a new generation of flexographic printing and composite equipment. The design speed of these devices can reach 200-300 meters / minute, supporting a working concentration of up to 45% for coating. The technological innovation of the equipment puts forward new requirements for the performance of the adhesive: the adhesive needs to have lower viscosity and better leveling to adapt to high-speed compounding and high-concentration coating production requirements.

[0005] However, traditional functional adhesives cannot meet the technical requirements of the new generation of flexographic equipment due to their high molecular weight and high viscosity. Although there are some low-viscosity adhesive products on the market, these products often sacrifice heat resistance and medium resistance performance when reducing viscosity, making it difficult to meet the strict requirements of functional packaging. Therefore, developing a high-solid low-viscosity functional laminating adhesive that can adapt to high-speed, high-concentration production processes and maintain excellent heat resistance and medium resistance performance has become a technical problem that needs to be solved in the industry. SUMMARY

[0006] The present application provides a high-solid low-viscosity polyurethane functional adhesive and a preparation method thereof, aiming to solve the problem that existing functional adhesives cannot balance low viscosity and heat resistance and medium resistance performance.

[0007] In one aspect, the application provides a high-solid and low-viscosity polyurethane functional adhesive, comprising a main agent and a curing agent, with a mass ratio of 10: (2-20); The main agent comprises linear and branched isocyanate-terminated polyurethane prepolymers, with an NCO content of 4%-6%, a rotational viscosity of 2000-4000 mPa.s at 25°C, and a solid content of 70%-80%. The linear isocyanate-terminated polyurethane prepolymer contains aromatic diisocyanate monomers, special polyol P1, ethyl acetate, and small molecular polyol. The curing agent has a rotational viscosity of 1000-3000 mPa.s at 25°C and a solid content of 70%-80%. The curing agent comprises ethyl acetate, special polyol P2, and special additives.

[0008] The application adopts a two-component design, and the main agent comprises linear and branched isocyanate-terminated polyurethane prepolymers. The linear isocyanate-terminated polyurethane prepolymer is prepared by using specific raw materials and has high reactivity, while the reactivity of the branched isocyanate-terminated polyurethane prepolymer is relatively low. With the aid of a specific curing agent design, the curing reaction can be carried out in sequence. The high-activity prepolymer is preferentially reacted with the curing agent to realize rapid linear extension of the molecular chain and build the basic framework of the mechanical properties of the material. The prepolymer with low activity gradually participates in the reaction to establish a stable three-dimensional network structure between the linear long chains formed, effectively ensuring that the functional adhesive has low viscosity and high working concentration in the uncured state, and at the same time, after curing, it can form a compact configuration comparable to traditional high-molecular-weight adhesive resins, thereby simultaneously meeting the requirements of modern flexo high-speed composite processes and functional packaging for heat resistance and medium resistance.

[0009] In some embodiments, the mass ratio of the linear end isocyanate-based polyurethane prepolymer and the branched end isocyanate-based polyurethane prepolymer is (80-90):(10-20); the branched end isocyanate-based polyurethane prepolymer is Bayer L-75 curing agent; preferably, the weight ratio of each raw material component of the linear end isocyanate-based polyurethane prepolymer includes: 10-35 parts of aromatic diisocyanate monomer, 20-35 parts of special polyol P1, 1-5 parts of small molecule polyol, 16-20 parts of ethyl acetate, and 1-3 parts of special additive B1; more preferably, the aromatic diisocyanate monomer is selected from 4,4'-diphenyl methane diisocyanate; more preferably, the weight ratio of each raw material component of the special polyol P1 includes: 3-7 parts of neopentyl glycol, 1-3 parts of ethylene glycol, 0-3 parts of diethylene glycol, 0-10 parts of 2-butyl-2-ethyl-1,3-propanediol, 4-8 parts of adipic acid, 0-2 parts of sunflower acid, 2-4 parts of isophthalic acid, 2-4 parts of terephthalic acid, and 2-4 parts of phthalic anhydride; the weight ratio of each component of the small molecule polyol includes: 0-5 parts of 1,4-butanediol and 0-5 parts of 1,6-hexanediol; more preferably, the weight ratio of each component of the special additive B1 includes: 1-3 parts of 3-aminopropyl triethoxysilane and 0.5-1 part of phosphoric acid.

[0010] The more accurate design of the main agent raw material ratio can further ensure the compactness, heat resistance and medium resistance of the cured functional glue, and can also effectively improve the bonding performance of the cured functional glue.

[0011] In some embodiments, the weight ratio of each raw material component of the curing agent includes: 20-30 parts of ethyl acetate, 50-70 parts of special polyol P2, and 1-10 parts of special additive B2; preferably, the weight ratio of each raw material component of the special polyol P2 includes: 15-20 parts of neopentyl glycol, 5-10 parts of diethylene glycol, 15-25 parts of adipic acid, and 10-15 parts of isophthalic acid; preferably, the weight ratio of each component of the special additive B2 includes: 1-2 parts of KH-560, 1-2 parts of phthalic anhydride, and 0-8 parts of TMEG-200.

[0012] The more accurate design of the curing agent raw material ratio can effectively achieve the purpose of more orderly sequence of the curing reaction, thereby enabling the functional glue of the present application to form a more stable three-dimensional network structure, further reducing the viscosity, and improving the performance of the functional glue.

[0013] In another aspect, the present application provides a preparation method of the above-mentioned high-solid low-viscosity polyurethane functional glue, which includes: The raw material components of the special polyol P1 are subjected to esterification reaction and vacuum polycondensation reaction to prepare the special polyol P1; the raw material components of the special polyol P2 are subjected to esterification reaction and vacuum polycondensation reaction to prepare the special polyol P2; The special polyol P1 and the small molecule polyol are subjected to vacuum dehydration, then mixed with ethyl acetate, and then the aromatic diisocyanate monomer is added, and the reaction is carried out until the NCO content reaches the requirement, to prepare the isocyanate-terminated polyurethane prepolymer, which is mixed with other components of the main agent to prepare the main agent. The special polyol P2 is subjected to vacuum dehydration, then mixed with ethyl acetate, and then mixed with the curing agent and other components to prepare the curing agent.

[0014] Compared with the prior art, the application has the following advantages: 1. The application adopts a two-component design, the main agent includes linear isocyanate-terminated polyurethane prepolymer and branched isocyanate-terminated polyurethane prepolymer, the linear isocyanate-terminated polyurethane prepolymer is prepared by using specific raw materials, and has high reactivity, while the reactivity of the branched isocyanate-terminated polyurethane prepolymer is relatively low, supplemented by a specific curing agent design, the curing reaction can be carried out in sequence, the high-activity prepolymer is preferentially reacted with the curing agent to realize rapid linear extension of the molecular chain, and the basic framework of the mechanical properties of the material is constructed, and the prepolymer with lower activity gradually participates in the reaction to establish a stable three-dimensional network structure between the linear long chains formed, which effectively ensures that the functional glue has low viscosity and high working concentration in the uncured state, and can form a compact configuration comparable to traditional high molecular weight glue resins after curing, thereby simultaneously meeting the requirements of modern flexographic high-speed composite process and functional packaging for heat resistance and medium resistance.

[0015] 2. The preparation method of the functional glue is relatively simple, and the preparation cost is relatively low. DETAILED DESCRIPTION

[0016] To make the purpose, technical scheme and advantages of the application clearer, the technical scheme of the application will be described clearly and completely below in combination with the embodiments of the application. Obviously, the described embodiments are part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0017] The technical difficulties of the high-solid low-viscosity functional laminating adhesive mainly lie in: how to reduce the molecular weight to reduce the viscosity while maintaining or even improving the heat resistance and medium resistance of the adhesive. The essence of this technical problem is the contradiction between low molecular weight and high performance in molecular structure design. Traditional high molecular weight resins provide mechanical properties and heat resistance through molecular chain entanglement and interaction, while low molecular weight systems need to achieve performance balance through innovative molecular structure design, curing mechanism and medium barrier / capturing technology.

[0018] Therefore, it is necessary to develop a new type of high-solid low-viscosity functional laminating adhesive that can meet the process requirements of modern high-speed flexographic equipment, provide excellent functional performance, and comply with environmental policy guidelines, promoting the technological progress and sustainable development of the soft packaging industry.

[0019] The purpose of the present application is to solve the above technical problems, and to provide a high-solid low-viscosity functional laminating adhesive with excellent comprehensive performance and a preparation method thereof.

[0020] The present application provides a high-solid low-viscosity polyurethane functional adhesive, which comprises a main agent and a curing agent, and the mass ratio is 10: (2-20); The main agent comprises linear isocyanate-terminated polyurethane prepolymer and branched isocyanate-terminated polyurethane prepolymer, the NCO content is 4%-6%, the rotational viscosity at 25°C is 2000-4000 mPa.s, and the solid content is 70%-80%. The linear isocyanate-terminated polyurethane prepolymer contains aromatic diisocyanate monomer, special polyol P1, ethyl acetate and small molecule polyol. The rotational viscosity of the curing agent at 25°C is 1000-3000 mPa.s, and the solid content is 70%-80%. The curing agent comprises ethyl acetate, special polyol P2 and special additives.

[0021] The present application adopts a two-component design, the main agent comprises linear isocyanate-terminated polyurethane prepolymer and branched isocyanate-terminated polyurethane prepolymer, the linear isocyanate-terminated polyurethane prepolymer is prepared by using specific raw materials and has high reactivity, while the reactivity of the branched isocyanate-terminated polyurethane prepolymer is relatively low. With the design of a specific curing agent, the curing reaction can proceed in sequence. The high-activity prepolymer reacts with the curing agent first, realizes the rapid linear extension of the molecular chain, and builds the basic framework of the mechanical properties of the material. The prepolymer with lower activity gradually participates in the reaction and establishes a stable three-dimensional network structure between the linear long chains that have been formed, effectively ensuring that the functional adhesive has low viscosity and high working concentration in the uncured state, and at the same time, after curing, it can form a compact configuration comparable to traditional high molecular weight adhesive resins, thereby simultaneously meeting the requirements of modern flexographic high-speed compounding process and functional packaging for heat resistance and medium resistance.

[0022] In some embodiments, the mass ratio of the linear isocyanate-terminated polyurethane prepolymer to the branched isocyanate-terminated polyurethane prepolymer is (80-90):(10-20); the branched isocyanate-terminated polyurethane prepolymer is Bayer L-75 curing agent; preferably, the weight proportions of each raw material component of the linear isocyanate-terminated polyurethane prepolymer include: 10-35 parts of aromatic diisocyanate monomer, 20-35 parts of special polyol P1, 1-5 parts of small molecule polyol, 16-20 parts of ethyl acetate, and special additive B1. 1-3 parts; more preferably, the aromatic diisocyanate monomer is selected from 4,4'-diphenylmethane diisocyanate; more preferably, the weight ratio of each raw material component of the special polyol P1 includes: neopentyl glycol 3-7 parts, ethylene glycol 1-3 parts, diethylene glycol 0-3 parts, 2-butyl-2-ethyl-1,3-propanediol 0-10 parts, adipic acid 4-8 parts, sebacic acid 0-2 parts, isophthalic acid 2-4 parts, terephthalic acid 2-4 parts, phthalic anhydride 2-4 parts; the weight ratio of each component of the small molecule polyol includes: 1,4-butanediol 0-5 parts, 1,6-hexanediol 0-5 parts; more preferably, the weight ratio of each component of the special auxiliary agent B1 includes: 3-aminopropyltriethoxysilane 1-3 parts, phosphoric acid 0.5-1 part.

[0023] By adopting a more precise formulation of the main raw materials, the density, heat resistance, and media resistance of the functional adhesive after curing can be further ensured; at the same time, the bonding performance of the functional adhesive after curing can also be effectively improved.

[0024] In some embodiments, the weight ratio of each raw material component of the curing agent includes: 20-30 parts of ethyl acetate, 50-70 parts of special polyol P2, and 1-10 parts of special additive B2; preferably, the weight ratio of each raw material component of the special polyol P2 includes: 15-20 parts of neopentyl glycol, 5-10 parts of diethylene glycol, 15-25 parts of adipic acid, and 10-15 parts of isophthalic acid; preferably, the weight ratio of each component of the special additive B2 includes: 1-2 parts of KH-560, 1-2 parts of phthalic anhydride, and 0-8 parts of TMEG-200.

[0025] By adopting a more precise curing agent raw material ratio design, the curing reaction can be effectively carried out in a more orderly sequence, thereby enabling the functional adhesive of this application to form a more stable three-dimensional network structure, further reducing viscosity and improving various properties of the functional adhesive.

[0026] On the other hand, this application provides a method for preparing the above-mentioned high-solids, low-tack polyurethane functional adhesive, including: Special polyol P1 is prepared by esterification and vacuum polycondensation of the raw material components of special polyol P1; special polyol P2 is prepared by esterification and vacuum polycondensation of the raw material components of special polyol P2. Special polyol P1 and small molecule polyol are dehydrated under vacuum, then ethyl acetate is added and mixed. Aromatic diisocyanate monomers are then added and reacted until the NCO content reaches the required level to obtain isocyanate-terminated polyurethane prepolymer. After mixing with other components of the main agent, the main agent is obtained. Special polyol P2 is dehydrated under vacuum, then ethyl acetate is added and mixed. Finally, curing agent and other components are added and mixed to obtain the curing agent.

[0027] The technical solutions provided in this application will be described in detail below with reference to the embodiments.

[0028] Unless otherwise specified, the raw materials used in the examples and comparative examples are all commercially available.

[0029] Preparation Example 1: Example 1 of this application provides a linear isocyanate-terminated polyurethane prepolymer, the raw materials of which are in the following weight ratios: 10 parts tetramethylxylene diisocyanate, 20 parts special polyol P1, 1 part 1,4-butanediol, 10.6 parts ethyl acetate, and 1 part phosphoric acid. The weight ratio of each raw material component of the special polyol P1 is as follows: 4 parts ethylene glycol, 8 parts diethylene glycol, 8 parts adipic acid, 6 parts isophthalic acid, 6 parts terephthalic acid, and 2 parts phthalic anhydride.

[0030] The weighed raw material of special polyol P1 is put into the reactor. Under nitrogen protection, the temperature is raised to 145-155℃. Water is discharged from the reaction system. The temperature is maintained at 155℃ for 1.5 hours. The temperature is then raised to 200±2℃ and maintained for 2 hours. The temperature is then raised to 230±2℃ and maintained until the acid value is ≤20mgKOH / g, thus completing the esterification reaction. The polyester synthesis reactor was evacuated, and the vacuum level was reduced from atmospheric pressure to 5±0.5 kPa at a rate of 0.5 kPa / min. The temperature was maintained at 230±2℃, and the reaction was continued until the acid value was ≤5 mgKOH / g. The vacuum was then further reduced to ≤1 kPa, and the reaction continued until the acid value was ≤1.5 mgKOH / g and the hydroxyl value was within the acceptable range, thus completing the vacuum polycondensation reaction and obtaining the special polyol P1.

[0031] Final preparation: Accurate amounts of special polyol P1, 1,4-butanediol, and phosphoric acid were added to a reaction vessel. The temperature was raised to 100℃-110℃, and the vacuum degree was -0.1 mPa. The raw material moisture content was dehydrated until it was below 300 ppm. Ethyl acetate was added to the vessel and stirred until homogeneous. The material temperature was maintained at 45℃-55℃, and tetramethylxylene diisocyanate was added. The temperature was gradually raised to 80℃, and the reaction continued until NCO was in the range of 4%-6%. The temperature was lowered to 65℃, and the reaction continued until NCO was 4%. The rotational viscosity at 25℃ was 2050 mPa·s. The solid content was 75%, yielding a linear isocyanate-terminated polyurethane prepolymer.

[0032] Preparation Example 2 The difference between this preparation example and Preparation Example 1 is that the linear isocyanate-terminated polyurethane prepolymer of this preparation example has the following raw material weight ratios: 35 parts tetramethylxylene diisocyanate, 35 parts special polyol P1, 5 parts 1,4-butanediol, 20 parts ethyl acetate, and 3 parts phosphoric acid.

[0033] Preparation Example 3 The difference between this preparation example and Preparation Example 1 is that the linear isocyanate-terminated polyurethane prepolymer of this preparation example has the following raw material weight ratios: 28 parts tetramethylxylene diisocyanate, 24 parts special polyol P1, 4 parts 1,4-butanediol, 18 parts ethyl acetate, and 1.5 parts phosphoric acid.

[0034] Preparation Example 4 The difference between this preparation example and Preparation Example 1 is that the linear isocyanate-terminated polyurethane prepolymer of this preparation example has the following raw material weight ratios: 28.3 parts tetramethylxylene diisocyanate, 20.8 parts special polyol P1, 2 parts 1,4-butanediol, 2 parts 1,6-hexanediol, 18.5 parts ethyl acetate, 0.5 parts phosphoric acid, and 2 parts 3-aminopropyltriethoxysilane; The weight proportions of each raw material component of the special polyol P1 include: 5 parts neopentyl glycol, 2 parts ethylene glycol, 2 parts diethylene glycol, 5 parts 2-butyl-2-ethyl-1,3-propanediol, 8 parts adipic acid, 2 parts sebacic acid, 2 parts isophthalic acid, 2 parts terephthalic acid, and 2 parts phthalic anhydride.

[0035] The preparation process of this example differs from that of Preparation Example 1 in that the final preparation involves: adding precise amounts of special polyol P1, 1,4-butanediol, 1,6-hexanediol, and phosphoric acid to a reaction vessel, heating to 100℃-110℃, maintaining a vacuum of -0.1 mPa, and dehydrating the raw material until the moisture content is below 300 ppm; adding ethyl acetate to the vessel and stirring until homogeneous; maintaining the material temperature at 45℃-55℃, adding tetramethylxylene diisocyanate, and gradually heating to 80℃ until the NCO content is in the range of 4%-6%; cooling to 65℃, adding 3-aminopropyltriethoxysilane, and reacting until the NCO content is 4%; the rotational viscosity at 25℃ is 2150 mPa·s; and the solid content is 75%, thus obtaining a linear isocyanate-terminated polyurethane prepolymer.

[0036] Preparation Example 5 The difference between this preparation example and preparation example 4 is that the linear isocyanate-terminated polyurethane prepolymer of this preparation example has the following raw material weight ratios: 26.2 parts tetramethylxylene diisocyanate, 20.2 parts special polyol P1, 2 parts 1,4-butanediol, 2 parts 1,6-hexanediol, 17.4 parts ethyl acetate, 0.5 parts phosphoric acid, and 2 parts 3-aminopropyltriethoxysilane; The weight proportions of each raw material component of the special polyol P1 include: 6.5 parts neopentyl glycol, 2 parts ethylene glycol, 2 parts diethylene glycol, 5 parts 2-butyl-2-ethyl-1,3-propanediol, 8 parts adipic acid, 2 parts sebacic acid, 2 parts isophthalic acid, 2 parts terephthalic acid, and 2 parts phthalic anhydride.

[0037] Preparation Example 6 The difference between this preparation example and preparation example 4 is that the linear isocyanate-terminated polyurethane prepolymer of this preparation example has the following raw material weight ratios: 28.8 parts tetramethylxylene diisocyanate, 20 parts special polyol P1, 2 parts 1,4-butanediol, 2 parts 1,6-hexanediol, 18.2 parts ethyl acetate, 0.5 parts phosphoric acid, and 2 parts 3-aminopropyltriethoxysilane; The weight proportions of each raw material component of the special polyol P1 include: 7 parts neopentyl glycol, 2 parts ethylene glycol, 2 parts diethylene glycol, 6.5 parts 2-butyl-2-ethyl-1,3-propanediol, 8 parts adipic acid, 2 parts sebacic acid, 2 parts isophthalic acid, 2 parts terephthalic acid, and 2 parts phthalic anhydride.

[0038] Preparation Example 7 The curing agent in this preparation example has the following weight ratios: 17 parts ethyl acetate, 250 parts special polyol P, and 1 part phthalic anhydride.

[0039] The weight ratio of each raw material component of the special polyol P2 is as follows: 28 parts neopentyl glycol and 38 parts isophthalic acid.

[0040] The weighed raw material components of the special polyol P2 were added to the reactor. Under nitrogen protection, the temperature was raised to 145-155℃, and water was discharged from the reaction system. The temperature was maintained at 155℃ for 1.5 hours. The temperature was then raised to 200±2℃ and maintained for 2 hours. The temperature was then raised to 230±2℃ and maintained until the acid value was ≤20mgKOH / g. The polyester synthesis reactor was then evacuated, and the vacuum degree was reduced from atmospheric pressure to 5±0.5kPa at a rate of 0.5kPa / min. The temperature was maintained at 230±2℃, and the reaction was continued until the acid value was ≤5mgKOH / g. The vacuum was further reduced to ≤1kPa, and the reaction was continued until the acid value was ≤1.5mgKOH / g and the hydroxyl value was 10~15mgKOH / g. The reaction was then terminated to obtain the special polyol P2.

[0041] Special polyol P2 was added to a reactor, heated to 100℃-110℃, and subjected to a vacuum of -0.1 mPa for 1 hour to dehydrate until the moisture content of the raw material was below 300 ppm. Ethyl acetate was then added to the reactor and stirred until homogeneous. The remaining raw material was added while maintaining the material temperature at 45℃-55℃, and stirring was continued until the mixture was homogeneous. The curing agent had a rotational viscosity of 2580 mPa·s at 25℃ and a solid content of 75%.

[0042] Preparation Example 8 The difference between this preparation example and preparation example 7 is that the weight ratio of each raw material component of the curing agent in this preparation example is: 30 parts of ethyl acetate, 70 parts of special polyol P2, and 10 parts of phthalic anhydride.

[0043] Preparation Example 9 The difference between this preparation example and preparation example 7 is that the weight ratio of each raw material component of the curing agent in this preparation example is: 25 parts of ethyl acetate, 65 parts of special polyol P2, and 4 parts of phthalic anhydride.

[0044] Preparation Example 10 The difference between this preparation example and preparation example 7 is that the weight ratio of each raw material component of the curing agent in this preparation example is as follows: 25 parts ethyl acetate, 65 parts special polyol P2, 1 part KH-560, 2 parts phthalic anhydride, and 7 parts TMEG-200.

[0045] The weight ratio of each raw material component of the special polyol P2 is as follows: neopentyl glycol 18.5 parts, diethylene glycol 10 parts, adipic acid 25 parts, and isophthalic acid 15 parts.

[0046] Preparation Example 11 The difference between this preparation example and preparation example 7 is that the weight ratio of each raw material component of the curing agent in this preparation example is as follows: 25 parts ethyl acetate, 65 parts special polyol P2, 1 part KH-560, 2 parts phthalic anhydride, and 7 parts TMEG-200.

[0047] The weight ratio of each raw material component of the special polyol P2 is as follows: neopentyl glycol 19.5 parts, diethylene glycol 10 parts, adipic acid 25 parts, and isophthalic acid 15 parts.

[0048] Preparation Example 12 The difference between this preparation example and preparation example 7 is that the weight ratio of each raw material component of the curing agent in this preparation example is as follows: 25 parts ethyl acetate, 65 parts special polyol P2, 1 part KH-560, 2 parts phthalic anhydride, and 7 parts TMEG-200.

[0049] The weight ratio of each raw material component in the special polyol P2 is as follows: 20 parts neopentyl glycol, 10 parts diethylene glycol, 23.5 parts adipic acid, and 15 parts isophthalic acid.

[0050] Example 1 The high-solids, low-tack polyurethane functional adhesive of this embodiment is prepared by mixing the main agent and the curing agent at a mass ratio of 10:18. The main agent is prepared by mixing the linear isocyanate-terminated polyurethane prepolymer of Preparation Example 1 and the branched isocyanate-terminated polyurethane prepolymer of Bayer L-75 curing agent at a mass ratio of 88:12 and stirring at 50°C; the curing agent is the curing agent of Preparation Example 7.

[0051] Example 2 The high-solids, low-tack polyurethane functional adhesive of this embodiment is prepared by mixing the main agent and the curing agent at a mass ratio of 10:18. The main agent is prepared by mixing the linear isocyanate-terminated polyurethane prepolymer of Preparation Example 2 and the branched isocyanate-terminated polyurethane prepolymer of Bayer L-75 curing agent at a mass ratio of 88:12 and stirring at 50°C; the curing agent is the curing agent of Preparation Example 8.

[0052] Example 3 The high-solids, low-tack polyurethane functional adhesive of this embodiment is prepared by mixing the main agent and the curing agent at a mass ratio of 10:18. The main agent is prepared by mixing the linear isocyanate-terminated polyurethane prepolymer of Preparation Example 3 and the branched isocyanate-terminated polyurethane prepolymer of Bayer L-75 curing agent at a mass ratio of 88:12 and stirring at 50°C; the curing agent is the curing agent of Preparation Example 9.

[0053] Example 4 The high-solids, low-tack polyurethane functional adhesive of this embodiment is prepared by mixing the main agent and the curing agent at a mass ratio of 10:18. The main agent is prepared by mixing the linear isocyanate-terminated polyurethane prepolymer of Preparation Example 4 and the branched isocyanate-terminated polyurethane prepolymer of Bayer L-75 curing agent at a mass ratio of 88:12 and stirring at 50°C; the curing agent is the curing agent of Preparation Example 10.

[0054] Example 5 The high-solids, low-tack polyurethane functional adhesive of this embodiment is prepared by mixing the main agent and the curing agent at a mass ratio of 10:18. The main agent is prepared by mixing the linear isocyanate-terminated polyurethane prepolymer of Preparation Example 5 and the branched isocyanate-terminated polyurethane prepolymer of Bayer L-75 curing agent at a mass ratio of 88:12 and stirring at 50°C; the curing agent is the curing agent of Preparation Example 11.

[0055] Example 6 The high-solids, low-tack polyurethane functional adhesive of this embodiment is prepared by mixing the main agent and the curing agent at a mass ratio of 10:18. The main agent is prepared by mixing the linear isocyanate-terminated polyurethane prepolymer of Preparation Example 6 and the branched isocyanate-terminated polyurethane prepolymer of Bayer L-75 curing agent at a mass ratio of 88:12 and stirring at 50°C; the curing agent is the curing agent of Preparation Example 12.

[0056] Example 7 The high-solids, low-tack polyurethane functional adhesive of this embodiment is prepared by mixing the main agent and the curing agent at a mass ratio of 10:18. The main agent is prepared by mixing the linear isocyanate-terminated polyurethane prepolymer of Preparation Example 1 and the branched isocyanate-terminated polyurethane prepolymer of Bayer L-75 curing agent at a mass ratio of 88:12 and stirring at 50°C; the curing agent is the curing agent of Preparation Example 8.

[0057] Example 8 The high-solids, low-tack polyurethane functional adhesive of this embodiment is prepared by mixing the main agent and the curing agent at a mass ratio of 10:18. The main agent is prepared by mixing the linear isocyanate-terminated polyurethane prepolymer of Preparation Example 2 and the branched isocyanate-terminated polyurethane prepolymer of Bayer L-75 curing agent at a mass ratio of 88:12 and stirring at 50°C; the curing agent is the curing agent of Preparation Example 9.

[0058] Example 9 The high-solids, low-tack polyurethane functional adhesive of this embodiment is prepared by mixing the main agent and the curing agent at a mass ratio of 10:18. The main agent is prepared by mixing the linear isocyanate-terminated polyurethane prepolymer of Preparation Example 3 and the branched isocyanate-terminated polyurethane prepolymer of Bayer L-75 curing agent at a mass ratio of 88:12 and stirring at 50°C; the curing agent is the curing agent of Preparation Example 7.

[0059] Example 10 The high-solids, low-tack polyurethane functional adhesive of this embodiment is prepared by mixing the main agent and the curing agent at a mass ratio of 10:18. The main agent is prepared by mixing the linear isocyanate-terminated polyurethane prepolymer of Preparation Example 4 and the branched isocyanate-terminated polyurethane prepolymer of Bayer L-75 curing agent at a mass ratio of 88:12 and stirring at 50°C; the curing agent is the curing agent of Preparation Example 11.

[0060] Example 11 The high-solids, low-tack polyurethane functional adhesive of this embodiment is prepared by mixing the main agent and the curing agent at a mass ratio of 10:18. The main agent is prepared by mixing the linear isocyanate-terminated polyurethane prepolymer of Preparation Example 5 and the branched isocyanate-terminated polyurethane prepolymer of Bayer L-75 curing agent at a mass ratio of 88:12 and stirring at 50°C; the curing agent is the curing agent of Preparation Example 12.

[0061] Example 12 The high-solids, low-tack polyurethane functional adhesive of this embodiment is prepared by mixing the main agent and the curing agent at a mass ratio of 10:18. The main agent is prepared by mixing the linear isocyanate-terminated polyurethane prepolymer of Preparation Example 6 and the branched isocyanate-terminated polyurethane prepolymer of Bayer L-75 curing agent at a mass ratio of 88:12 and stirring at 50°C; the curing agent is the curing agent of Preparation Example 10.

[0062] Example 13 The high-solids, low-tack polyurethane functional adhesive of this embodiment is prepared by mixing the main agent and the curing agent at a mass ratio of 10:18. The main agent is prepared by mixing the linear isocyanate-terminated polyurethane prepolymer of Preparation Example 4 and the branched isocyanate-terminated polyurethane prepolymer of Bayer L-75 curing agent at a mass ratio of 88:12 and stirring at 50°C; the curing agent is the curing agent of Preparation Example 12.

[0063] Example 14 The high-solids, low-tack polyurethane functional adhesive of this embodiment is prepared by mixing the main agent and the curing agent at a mass ratio of 10:18. The main agent is prepared by mixing the linear isocyanate-terminated polyurethane prepolymer of Preparation Example 5 and the branched isocyanate-terminated polyurethane prepolymer of Bayer L-75 curing agent at a mass ratio of 88:12 and stirring at 50°C; the curing agent is the curing agent of Preparation Example 10.

[0064] Example 15 The high-solids, low-tack polyurethane functional adhesive of this embodiment is prepared by mixing the main agent and the curing agent at a mass ratio of 10:18. The main agent is prepared by mixing the linear isocyanate-terminated polyurethane prepolymer of Preparation Example 6 and the branched isocyanate-terminated polyurethane prepolymer of Bayer L-75 curing agent at a mass ratio of 88:12 and stirring at 50°C; the curing agent is the curing agent of Preparation Example 11.

[0065] Example 16 The difference between this embodiment and Example 12 is that 4,4'-diphenylmethane diisocyanate is used instead of tetramethylxylene diisocyanate.

[0066] Example 17 The difference between this embodiment and Embodiment 16 is that the linear isocyanate-terminated polyurethane prepolymer and the Bayer L-75 curing agent branched isocyanate-terminated polyurethane prepolymer are used in a mass ratio of 80:20.

[0067] Example 18 The difference between this embodiment and Embodiment 16 is that the linear isocyanate-terminated polyurethane prepolymer and the Bayer L-75 curing agent branched isocyanate-terminated polyurethane prepolymer are used in a mass ratio of 90:10.

[0068] Example 19 The difference between this embodiment and Embodiment 16 is that the linear isocyanate-terminated polyurethane prepolymer and the Bayer L-75 curing agent branched isocyanate-terminated polyurethane prepolymer are used in a mass ratio of 84:16.

[0069] Example 20 The difference between this embodiment and Embodiment 16 is that the main agent and the curing agent are used in a mass ratio of 10:2.

[0070] Example 21 The difference between this embodiment and Embodiment 16 is that the main agent and the curing agent are used in a mass ratio of 10:20.

[0071] Example 22 The difference between this embodiment and Embodiment 16 is that the main agent and the curing agent are used in a mass ratio of 10:5.

[0072] Example 23 The difference between this embodiment and Embodiment 16 is that the main agent and the curing agent are used in a mass ratio of 10:8.

[0073] Example 24 The difference between this embodiment and Embodiment 16 is that the main agent and the curing agent are used in a mass ratio of 10:15.

[0074] Comparative Example 1 This application uses Henkel's LIOFOL LA 363-22 two-component solvent-based flexible packaging composite adhesive as comparative example 1. When using it, the adhesive and hardener are compounded at a mass ratio of 7:1, with a viscosity greater than 8500 Pa·s and a solid content greater than 70%.

[0075] Composite effect test The specific composite process is as follows: Composite equipment: BOBST DA800; Composite machine speed: 200-300 m / min; Working concentration: 50%; Composite substrate: PET 12um / ALu 6um / RCPP 75um; Media type: 3‰ ethyl maltol aqueous solution: vinegar: chili oil = 1:1:1; Media resistance test method: The composite film was heat-sealed (heat-sealing temperature 220℃) to form a 5cm*10cm three-side seal bag. 20g of media (3‰ ethyl maltol aqueous solution: vinegar: chili oil = 1:1:1) was placed into the bag and sealed. The bag was then subjected to a PCT high-pressure retort test chamber at 121℃ for 40 minutes. The peel strength of the packaging bag before and after retort testing and the appearance of the packaging bag after retort testing were measured. The test results are shown in Table 1.

[0076] Table 1 Test Results

[0077] As can be seen from the data in Table 1, the functional adhesives of Examples 1-24 of this application, when heat-laminated, exhibit superior bonding strength to the existing high-quality flexible packaging adhesives provided in Comparative Example 1. After boiling, the bonding strength of the functional adhesives of Examples 1-24 of this application did not change significantly or even increased, while the bonding strength of the flexible packaging adhesive in Comparative Example 1 decreased significantly. Furthermore, the packaging bags bonded by the functional adhesives of Examples 1-24 of this application and the functional adhesive of Comparative Example 1 did not break after boiling, meeting the most basic requirements for flexible packaging bonding. Therefore, the polyurethane functional adhesive of this application demonstrates significantly superior resistance to media and boiling compared to existing flexible packaging adhesives. In addition, the polyurethane functional adhesive of this application has a lower viscosity, ranging from 2000 to 4000 Pa·s, and a solid content of not less than 75%, making it highly suitable for existing high-speed flexible packaging heat lamination processes; while the adhesive viscosity of Comparative Example 1 exceeds 8500 Pa·s, which does not fully meet the technical requirements of next-generation flexographic printing equipment.

[0078] By comparing the test data of the functional adhesives prepared in Examples 1 to 24 of this application with the data in Table 1, it can be seen that after optimizing the specific raw material composition ratio of the main agent and the curing agent of the functional adhesive, the linear isocyanate-terminated polyurethane prepolymer of the main agent can react with the curing agent to form a denser and more stable three-dimensional network structure, and the bonding performance is further significantly improved. In addition, after adopting the optimized composition ratio, some specific functional groups are introduced, which can further improve the media resistance of the functional adhesive.

[0079] By comparing the test data of the functional adhesives prepared in Examples 1 to 24 of this application with the data in Table 1, it can be seen that the functional adhesive system of this application, using 4,4'-diphenylmethane diisocyanate, can give the functional adhesive the best performance. In addition, the ratio of the main agent to the curing agent in the functional adhesive of this application also has a significant impact on the performance of the functional adhesive, and the optimal mass ratio is 10:(15~20).

[0080] In the description of this specification, the references to terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0081] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this application, "a plurality of" means at least two, such as two, three, etc., unless otherwise expressly specified.

[0082] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A high-solids, low-tack polyurethane functional adhesive, characterized in that, It includes a main agent and a curing agent, with a mass ratio of 10:(2-20); The main agent includes linear isocyanate-terminated polyurethane prepolymer and branched isocyanate-terminated polyurethane prepolymer, with an NCO content of 4%-6%, a rotational viscosity of 2000-4000 mPa·s at 25°C, and a solid content of 70%-80%. The linear isocyanate-terminated polyurethane prepolymer contains aromatic diisocyanate monomers, special polyol P1, ethyl acetate, and small molecule polyols. The curing agent has a rotational viscosity of 1000-3000 mPa·s at 25°C and a solid content of 70%-80%. The curing agent includes ethyl acetate, special polyol P2, and special additives.

2. The high-solids, low-tack polyurethane functional adhesive as described in claim 1, characterized in that, The mass ratio of the linear isocyanate-terminated polyurethane prepolymer to the branched isocyanate-terminated polyurethane prepolymer is (80~90):(10~20); the branched isocyanate-terminated polyurethane prepolymer is Bayer L-75 curing agent.

3. The high-solids, low-tack polyurethane functional adhesive as described in claim 2, characterized in that, The weight proportions of each raw material component in the linear isocyanate-terminated polyurethane prepolymer include: 10-35 parts of aromatic diisocyanate monomer, 20-35 parts of special polyol P1, 1-5 parts of small molecule polyol, 16-20 parts of ethyl acetate, and 1-3 parts of special additive B1.

4. The high-solids, low-tack polyurethane functional adhesive as described in claim 3, characterized in that, The aromatic diisocyanate monomer is selected from 4,4'-diphenylmethane diisocyanate.

5. The high-solids, low-tack polyurethane functional adhesive as described in claim 3, characterized in that, The weight proportions of each raw material component of the special polyol P1 include: 3-7 parts neopentyl glycol, 1-3 parts ethylene glycol, 0-3 parts diethylene glycol, 0-10 parts 2-butyl-2-ethyl-1,3-propanediol, 4-8 parts adipic acid, 0-2 parts sebacic acid, 2-4 parts isophthalic acid, 2-4 parts terephthalic acid, and 2-4 parts phthalic anhydride; the weight proportions of each component of the small molecule polyol include: 0-5 parts 1,4-butanediol and 0-5 parts 1,6-hexanediol.

6. The high-solids, low-tack polyurethane functional adhesive as described in claim 3, characterized in that, The special additive B1 comprises the following components in the following weight proportions: 1-3 parts of 3-aminopropyltriethoxysilane and 0.5-1 part of phosphoric acid.

7. The high-solids, low-tack polyurethane functional adhesive as described in claim 1, characterized in that, The curing agent comprises the following components in the following weight proportions: ethyl acetate 20-30 parts, special polyol P2 50-70 parts, and special additive B2 1-10 parts.

8. The high-solids, low-tack polyurethane functional adhesive as described in claim 7, characterized in that, The weight proportions of each raw material component of the special polyol P2 include: 15-20 parts neopentyl glycol, 5-10 parts diethylene glycol, 15-25 parts adipic acid, and 10-15 parts isophthalic acid.

9. The high-solids, low-tack polyurethane functional adhesive as described in claim 7, characterized in that, The weight ratio of each component of the special additive B2 includes: 1-2 parts of KH-560, 1-2 parts of phthalic anhydride, and 0-8 parts of TMEG-200.

10. A method for preparing a high-solids, low-viscosity polyurethane functional adhesive as described in claim 1, characterized in that, include: Special polyol P1 is prepared by esterification and vacuum polycondensation of the raw material components of special polyol P1; special polyol P2 is prepared by esterification and vacuum polycondensation of the raw material components of special polyol P2. Special polyol P1 and small molecule polyol are dehydrated under vacuum, then ethyl acetate is added and mixed. Aromatic diisocyanate monomers are then added and reacted until the NCO content reaches the required level to obtain isocyanate-terminated polyurethane prepolymer. After mixing with other components of the main agent, the main agent is obtained. Special polyol P2 is dehydrated under vacuum, then ethyl acetate is added and mixed. Finally, curing agent and other components are added and mixed to obtain the curing agent.

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