Two-component polyurethane hot melt adhesive and use method thereof

Abstract

The present invention relates to a two-component polyurethane hot melt adhesive and a method for using the same, and belongs to the technical field of polyurethane. The present invention creatively performs prepolymerization with excess diphenylmethane diisocyanate and polytetrahydrofuran to prepare a first prepolymer, first performs prepolymerization with excess diphenylmethane diisocyanate and castor oil, and then adds epoxy resin, and the isocyanate group and the hydroxyl group on the epoxy resin react to consume part of the isocyanate group, graft the active epoxy group, and prepare the second prepolymer, so that the two are compounded in a certain weight ratio as a curing agent; the product containing terminal alcohol hydroxyl groups obtained by ring-opening substitution of propylene carbonate and phenolic hydroxyl groups of tannic acid is coordinated with polyester polyol and polyether amine in a certain weight ratio and mixed as a main agent; finally, the two-component polyurethane hot melt adhesive provided by the present invention is obtained, which can have excellent initial adhesion on the one hand, and good boiling resistance on the other hand when actually used.

Description

Technical Field

[0001] The invention belongs to the technical field of polyurethane, and in particular relates to a two-component polyurethane hot melt adhesive and a use method thereof. Background Art

[0002] Two-component solvent-free polyurethane adhesive refers to a system without any solvent added. It is composed of two components, including a prepolymer curing agent containing terminal isocyanate group -NCO and a polyol main agent containing terminal hydroxyl group -OH (the curing agent and / or the main agent may also contain a certain amount of auxiliary agent). When used, by adjusting the content ratio of the curing agent and the main agent, it can be cross-linked and cured to achieve bonding between materials. In particular, in the flexible packaging industry, two-component solvent-free polyurethane adhesives have been widely used to bond packaging materials such as composite bags and composite films. However, compared with solvent-based adhesives, although solvent-free adhesives can be more environmentally friendly, It has the advantages of safety and security, but it has lower initial adhesion, or even almost no initial adhesion. This leads to the need to increase the amount of glue applied in actual use to achieve a better bonding effect, which is not in line with economic benefits. At the same time, due to the low initial adhesion, "spots" and "orange peel" are prone to appear at the bonding point, which affect the appearance. In addition, since food packaging is very common in the flexible packaging industry, and high-temperature sterilization is an inevitable procedure for food processing, this requires that the two-component solvent-free polyurethane adhesive needs to have excellent cooking resistance, and it must still show good bonding strength after high-temperature treatment and is not prone to debonding. Summary of the invention

[0003] In view of the problems existing in the prior art, the purpose of the present invention is to provide a two-component polyurethane hot melt adhesive and a method for using the same. The present invention creatively performs prepolymerization with excess diphenylmethane diisocyanate and polytetrahydrofuran to prepare a first prepolymer, first performs prepolymerization with excess diphenylmethane diisocyanate and castor oil, and then adds epoxy resin, and the isocyanate group and the hydroxyl group on the epoxy resin react to consume part of the isocyanate group, and grafts the active epoxy group to prepare a second prepolymer, so that the two are compounded in a certain weight ratio as a curing agent; the product containing terminal alcohol hydroxyl groups obtained by ring-opening substitution of propylene carbonate and phenolic hydroxyl groups of tannic acid is mixed with polyester polyol and polyether amine in a certain weight ratio as a main agent; and finally the two-component polyurethane hot melt adhesive provided by the present invention is obtained, which can have excellent initial adhesion on the one hand and good boiling resistance on the other hand when actually used.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] A two-component polyurethane hot melt adhesive comprises a component A and a component B; the component A is formed by mixing a first prepolymer and a second prepolymer; the mass ratio of the first prepolymer to the second prepolymer is 1:0.2-0.3; the component B is formed by mixing 3-4 parts by weight of modified tannic acid, 15-20 parts by weight of polyester polyol and 5-7 parts by weight of polyether amine; the molar ratio of the isocyanate group of the component A to the hydroxyl group of the component B is 1.1-1.5:1.

[0006] As a preferred technical solution of the present invention, the first prepolymer is prepared by the following steps:

[0007] Step X: Add dibutyltin dilaurate to diphenylmethane diisocyanate, then add polytetrahydrofuran dropwise at 70-80° C. under nitrogen atmosphere with stirring. After the addition is complete, continue stirring at constant temperature for 1.5-2 h, cool naturally to room temperature, and store in a sealed container filled with nitrogen.

[0008] Furthermore, in step X, the molar ratio of the diphenylmethane diisocyanate to the polytetrahydrofuran is 3.5:1; the temperature of the polytetrahydrofuran is 45-50° C.; the molecular weight of the polytetrahydrofuran is 2000; and the amount of the dibutyltin dilaurate is 0.1-0.3% of the sum of the mass of the diphenylmethane diisocyanate and the polytetrahydrofuran.

[0009] Furthermore, the dripping rate in step X is controlled at 1-3 drops / s.

[0010] As a preferred technical solution of the present invention, the second prepolymer is prepared by the following steps:

[0011] Step Y: Add dibutyltin dilaurate to diphenylmethane diisocyanate, then add castor oil dropwise at 70-80°C under nitrogen atmosphere with stirring, continue stirring at constant temperature for 2-3h after the addition is completed, raise the temperature to 85-90°C, add epoxy resin, keep stirring at this temperature for 1-2h, cool naturally to room temperature, and store in a sealed container filled with nitrogen.

[0012] Furthermore, in step Y, the molar ratio of the isocyanate group of the diphenylmethane diisocyanate, the hydroxyl group of the castor oil and the hydroxyl group of the epoxy resin is 3-3.5:1:0.5-0.8; and the amount of the dibutyltin dilaurate is 0.1-0.3% of the sum of the mass of the diphenylmethane diisocyanate and the castor oil.

[0013] Furthermore, the epoxy resin in step Y is at least one of epoxy resin E-51 and epoxy resin E-44.

[0014] Furthermore, the dripping rate in step Y is controlled at 1-3 drops / s.

[0015] Furthermore, the heating rate in step Y is controlled at 1-2°C / min.

[0016] As a preferred technical solution of the present invention, the modified tannic acid is prepared by the following steps:

[0017] Step Z: Add 2-3 parts by weight of tannic acid and 0.05-0.1 parts by weight of 1,8-diazabicycloundec-7-ene to 20-25 parts by weight of propylene carbonate, and then stir at 180-190° C. for 4-5 hours, and distill under reduced pressure to obtain a mixture, wash with ether, and finally vacuum dry at 50-60° C. until constant weight.

[0018] Furthermore, the reduced pressure distillation in step Z refers to distillation at 80° C. for 2-3 hours under a vacuum degree of -0.09 MPa to remove volatiles.

[0019] As a preferred technical solution of the present invention, the polyester polyol is poly(1,4-butylene adipate diol); the hydroxyl value of the poly(1,4-butylene adipate diol) is 70-80 mgKOH / g.

[0020] As a preferred technical solution of the present invention, the polyetheramine is polyetheramine D-230.

[0021] An application of a two-component polyurethane hot melt adhesive, wherein the two-component polyurethane hot melt adhesive is applied to flexible packaging materials.

[0022] A method for using a two-component polyurethane hot melt adhesive, the method comprising the following steps:

[0023] (1) Preheating component A at 90-100° C. for 5-10 min to obtain material A;

[0024] (2) preheating component B at 100-120° C. for 5-10 min to obtain material B;

[0025] (3) stirring the material A and the material B for 5-10 minutes to obtain material C;

[0026] (4) Roll-coat the material C on the surface of the flexible packaging material, bond it, heat cure it at 40-45° C. for 20-36 hours, and naturally cool it to room temperature.

[0027] Furthermore, the speed of the roller coating in step (4) is 10-100 m / min; the coating amount of the roller coating is 1-30 g / m 2 .

[0028] Beneficial effects of the present invention:

[0029] (1) The present invention creatively performs prepolymerization with excess diphenylmethane diisocyanate and polytetrahydrofuran to prepare a first prepolymer, first performs prepolymerization with excess diphenylmethane diisocyanate and castor oil, and then adds epoxy resin, and consumes part of the isocyanate groups through the reaction between the isocyanate groups and the hydroxyl groups on the epoxy resin, and grafts active epoxy groups to prepare a second prepolymer, so that the two are compounded in a certain weight ratio as a curing agent; the product containing terminal alcohol hydroxyl groups obtained by ring-opening substitution of propylene carbonate and the phenolic hydroxyl groups of tannic acid is mixed with polyester polyol and polyether amine in a certain weight ratio as a main agent; and finally the two-component polyurethane hot melt adhesive provided by the present invention is obtained, which can have excellent initial adhesion on the one hand and good boiling resistance on the other hand when actually used.

[0030] (2) The present invention creatively adds epoxy resin to the prepolymer obtained by prepolymerizing excess diphenylmethane diisocyanate and castor oil to modify it, so that active epoxy groups are grafted on it to prepare a second prepolymer. When it is compounded with the first prepolymer at a certain weight ratio as a curing agent, on the one hand, the introduction of active epoxy groups can cooperate with isocyanate groups to greatly promote the energy of the entire system, the reaction activity is improved, and it can quickly interact with the hydroxyl / amino groups of the main agent to cross-link and solidify and adhere to the surface of the substrate to obtain excellent initial adhesion. On the other hand, the epoxy resin also contains benzene ring groups, has high rigidity, is heat-resistant and resistant to aging. The cooking resistance is also promoted to a certain extent; at the same time, the present invention also uses propylene carbonate to perform ring-opening substitution on tannic acid to obtain a product containing terminal alcohol hydroxyl groups, which is mixed with polyester polyols and polyether amines in a certain weight ratio as a main agent. The tannic acid after the modification has a "diffusion" structure similar to "hyperbranching" from the molecular structure. A large number of terminal alcohol hydroxyl groups can quickly locate cross-linking groups in the system to form a "precursor polymer" with strong adhesion, good bonding strength with the substrate and excellent initial adhesion. In addition, since tannic acid also contains rigid groups such as benzene rings, it can also synergistically enhance the cooking resistance.

[0031] (3) The present invention creatively combines and optimizes the components of the curing agent and the main agent to produce a synergistic effect. When used in practice, the two-component polyurethane hot melt adhesive composed of the two can have excellent initial adhesion and boiling resistance, and is particularly suitable for the bonding and adhesion of flexible packaging materials. DETAILED DESCRIPTION

[0032] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with the embodiments.

[0033] The epoxy resin E-51 in all the embodiments and comparative examples of the present invention was purchased directly from Shandong Guohua Chemical Co., Ltd.; the castor oil was purchased directly from Shandong Zhouhe Chemical Co., Ltd.; the polyetheramine D-230 was purchased directly from Huntsman; the material of the flexible packaging material was PET, and the material of the material bonded thereto was also PET.

[0034] Example 1

[0035] A two-component polyurethane hot melt adhesive comprises a component A and a component B; the component A is formed by mixing a first prepolymer and a second prepolymer; the mass ratio of the first prepolymer to the second prepolymer is 1:0.2; the component B is formed by mixing 3 parts by weight of modified tannic acid, 15 parts by weight of polyester polyol and 5 parts by weight of polyether amine; the molar ratio of the isocyanate group of the component A to the hydroxyl group of the component B is 1.1:1.

[0036] The first prepolymer is prepared by the following steps:

[0037] Step X: Add dibutyltin dilaurate to diphenylmethane diisocyanate, then add polytetrahydrofuran dropwise at 70°C with stirring under a nitrogen atmosphere. After the addition is complete, continue stirring at a constant temperature for 1.5 hours, cool naturally to room temperature, and store in a sealed container filled with nitrogen.

[0038] In step X, the molar ratio of the diphenylmethane diisocyanate to the polytetrahydrofuran is 3.5:1; the temperature of the polytetrahydrofuran is 45° C.; the molecular weight of the polytetrahydrofuran is 2000; and the amount of the dibutyltin dilaurate is 0.1% of the sum of the mass of the diphenylmethane diisocyanate and the polytetrahydrofuran.

[0039] The rate of dripping in step X is controlled at 1 drop / s.

[0040] The second prepolymer is prepared by the following steps:

[0041] Step Y: Add dibutyltin dilaurate to diphenylmethane diisocyanate, then add castor oil dropwise at 70°C under nitrogen atmosphere with stirring. After the addition is completed, continue to stir at a constant temperature for 2 hours, raise the temperature to 85°C, add epoxy resin, keep stirring for 1 hour, cool naturally to room temperature, and store in a sealed container filled with nitrogen.

[0042] In step Y, the molar ratio of the isocyanate group of the diphenylmethane diisocyanate, the hydroxyl group of the castor oil and the hydroxyl group of the epoxy resin is 3:1:0.5; the amount of the dibutyltin dilaurate is 0.1% of the sum of the mass of the diphenylmethane diisocyanate and the castor oil.

[0043] The epoxy resin in step Y is epoxy resin E-51.

[0044] The rate of dripping in step Y is controlled at 1 drop / s.

[0045] The heating rate in step Y is controlled at 1°C / min.

[0046] The modified tannic acid is prepared by the following steps:

[0047] Step Z: Add 2 parts by weight of tannic acid and 0.05 parts by weight of 1,8-diazabicycloundec-7-ene to 20 parts by weight of propylene carbonate, and then stir at 180° C. for 4 hours, distill under reduced pressure to obtain a mixture, wash with ether, and finally vacuum dry at 50° C. until constant weight.

[0048] The reduced pressure distillation in step Z refers to distilling at 80° C. for 2 h under a vacuum degree of -0.09 MPa to remove volatiles.

[0049] The polyester polyol is poly(1,4-butylene adipate diol); the hydroxyl value of the poly(1,4-butylene adipate diol) is 70 mgKOH / g.

[0050] The polyetheramine is polyetheramine D-230.

[0051] An application of a two-component polyurethane hot melt adhesive, wherein the two-component polyurethane hot melt adhesive is applied to flexible packaging materials.

[0052] A method for using a two-component polyurethane hot melt adhesive, the method comprising the following steps:

[0053] (1) Preheating component A at 90°C for 5 min to obtain material A;

[0054] (2) preheating component B at 100°C for 5 min to obtain material B;

[0055] (3) stirring the material A and the material B for 5 minutes to obtain material C;

[0056] (4) The material C is coated on the surface of the flexible packaging material by a roller, bonded, heat cured at 40° C. for 20 h, and naturally cooled to room temperature.

[0057] The speed of the roller coating in step (4) is 10 m / min; the coating amount of the roller coating is 1 g / m 2 .

[0058] Example 2

[0059] A two-component polyurethane hot melt adhesive comprises a component A and a component B; the component A is formed by mixing a first prepolymer and a second prepolymer; the mass ratio of the first prepolymer to the second prepolymer is 1:0.3; the component B is formed by mixing 4 parts by weight of modified tannic acid, 20 parts by weight of polyester polyol and 7 parts by weight of polyether amine; the molar ratio of the isocyanate group of the component A to the hydroxyl group of the component B is 1.5:1.

[0060] The first prepolymer is prepared by the following steps:

[0061] Step X: Add dibutyltin dilaurate to diphenylmethane diisocyanate, then add polytetrahydrofuran dropwise at 80° C. under nitrogen atmosphere with stirring. After the addition is complete, continue stirring at constant temperature for 2 h, cool naturally to room temperature, and store in a sealed container filled with nitrogen.

[0062] In step X, the molar ratio of the diphenylmethane diisocyanate to the polytetrahydrofuran is 3.5:1; the temperature of the polytetrahydrofuran is 50° C.; the molecular weight of the polytetrahydrofuran is 2000; and the amount of the dibutyltin dilaurate is 0.3% of the sum of the mass of the diphenylmethane diisocyanate and the polytetrahydrofuran.

[0063] The rate of dripping in step X is controlled at 3 drops / s.

[0064] The second prepolymer is prepared by the following steps:

[0065] Step Y: Add dibutyltin dilaurate to diphenylmethane diisocyanate, then add castor oil dropwise at 80°C under nitrogen atmosphere with stirring. After the addition is completed, continue stirring at a constant temperature for 3 hours, raise the temperature to 90°C, add epoxy resin, keep stirring for 2 hours, cool naturally to room temperature, and store in a sealed container filled with nitrogen.

[0066] In step Y, the molar ratio of the isocyanate group of the diphenylmethane diisocyanate, the hydroxyl group of the castor oil and the hydroxyl group of the epoxy resin is 3.5:1:0.8; the amount of the dibutyltin dilaurate is 0.3% of the sum of the mass of the diphenylmethane diisocyanate and the castor oil.

[0067] The epoxy resin in step Y is epoxy resin E-51.

[0068] The rate of dripping in step Y is controlled at 3 drops / s.

[0069] The heating rate in step Y is controlled at 2°C / min.

[0070] The modified tannic acid is prepared by the following steps:

[0071] Step Z: Add 3 parts by weight of tannic acid and 0.1 parts by weight of 1,8-diazabicycloundec-7-ene to 25 parts by weight of propylene carbonate, and then stir at 190° C. for 5 hours, distill under reduced pressure to obtain a mixture, wash with ether, and finally vacuum dry at 60° C. until constant weight.

[0072] The reduced pressure distillation in step Z refers to distilling at 80° C. for 3 h under a vacuum degree of -0.09 MPa to remove volatiles.

[0073] The polyester polyol is poly(1,4-butylene adipate diol); the hydroxyl value of the poly(1,4-butylene adipate diol) is 80 mgKOH / g.

[0074] The polyetheramine is polyetheramine D-230.

[0075] An application of a two-component polyurethane hot melt adhesive, wherein the two-component polyurethane hot melt adhesive is applied to flexible packaging materials.

[0076] A method for using a two-component polyurethane hot melt adhesive, the method comprising the following steps:

[0077] (1) Preheating component A at 100°C for 10 min to obtain material A;

[0078] (2) preheating component B at 120°C for 10 min to obtain material B;

[0079] (3) stirring the material A and the material B for 10 minutes to obtain material C;

[0080] (4) The material C is coated on the surface of the flexible packaging material by a roller, bonded, heat cured at 45° C. for 36 hours, and naturally cooled to room temperature.

[0081] The speed of the roller coating in step (4) is 100 m / min; the coating amount of the roller coating is 30 g / m 2 .

[0082] Example 3

[0083] A two-component polyurethane hot melt adhesive comprises a component A and a component B; the component A is formed by mixing a first prepolymer and a second prepolymer; the mass ratio of the first prepolymer to the second prepolymer is 1:0.25; the component B is formed by mixing 3.5 parts by weight of modified tannic acid, 18 parts by weight of polyester polyol and 6 parts by weight of polyether amine; the molar ratio of the isocyanate group of the component A to the hydroxyl group of the component B is 1.3:1.

[0084] The first prepolymer is prepared by the following steps:

[0085] Step X: Add dibutyltin dilaurate to diphenylmethane diisocyanate, then add polytetrahydrofuran dropwise at 75°C with stirring under a nitrogen atmosphere. After the addition is complete, continue stirring at a constant temperature for 1.8 hours, cool naturally to room temperature, and store in a sealed container filled with nitrogen.

[0086] In step X, the molar ratio of the diphenylmethane diisocyanate to the polytetrahydrofuran is 3.5:1; the temperature of the polytetrahydrofuran is 48° C.; the molecular weight of the polytetrahydrofuran is 2000; and the amount of the dibutyltin dilaurate is 0.2% of the sum of the mass of the diphenylmethane diisocyanate and the polytetrahydrofuran.

[0087] The rate of dripping in step X is controlled at 2 drops / s.

[0088] The second prepolymer is prepared by the following steps:

[0089] Step Y: Add dibutyltin dilaurate to diphenylmethane diisocyanate, then add castor oil dropwise at 75°C under nitrogen atmosphere with stirring. After the addition is completed, continue stirring at a constant temperature for 2.5 hours, raise the temperature to 88°C, add epoxy resin, keep stirring at this temperature for 1.5 hours, cool naturally to room temperature, and store in a sealed container filled with nitrogen.

[0090] In step Y, the molar ratio of the isocyanate group of the diphenylmethane diisocyanate, the hydroxyl group of the castor oil and the hydroxyl group of the epoxy resin is 3.3:1:0.7; the amount of the dibutyltin dilaurate is 0.2% of the sum of the mass of the diphenylmethane diisocyanate and the castor oil.

[0091] The epoxy resin in step Y is epoxy resin E-51.

[0092] The rate of dripping in step Y is controlled at 2 drops / s.

[0093] The heating rate in step Y is controlled at 1.5°C / min.

[0094] The modified tannic acid is prepared by the following steps:

[0095] Step Z: Add 2.5 parts by weight of tannic acid and 0.08 parts by weight of 1,8-diazabicycloundec-7-ene to 23 parts by weight of propylene carbonate, and then stir at 185° C. for 4.5 hours, distill under reduced pressure to obtain a mixture, wash with ether, and finally vacuum dry at 55° C. until constant weight.

[0096] The reduced pressure distillation in step Z refers to distilling at 80° C. for 2.5 h under a vacuum degree of -0.09 MPa to remove volatiles.

[0097] The polyester polyol is poly(1,4-butylene adipate diol); the hydroxyl value of the poly(1,4-butylene adipate diol) is 75 mgKOH / g.

[0098] The polyetheramine is polyetheramine D-230.

[0099] An application of a two-component polyurethane hot melt adhesive, wherein the two-component polyurethane hot melt adhesive is applied to flexible packaging materials.

[0100] A method for using a two-component polyurethane hot melt adhesive, the method comprising the following steps:

[0101] (1) Preheating component A at 95°C for 8 min to obtain material A;

[0102] (2) preheating component B at 110°C for 8 min to obtain material B;

[0103] (3) stirring the material A and the material B for 8 minutes to obtain material C;

[0104] (4) The material C is coated on the surface of the flexible packaging material by a roller, bonded, heat cured at 43° C. for 30 h, and naturally cooled to room temperature.

[0105] The speed of the roller coating in step (4) is 50 m / min; the coating amount of the roller coating is 15 g / m 2 .

[0106] Comparative Example 1

[0107] On the basis of Example 1, the first prepolymer was replaced by the second prepolymer of the same weight, and the rest remained unchanged.

[0108] Comparative Example 2

[0109] On the basis of Example 1, the second prepolymer was changed to the first prepolymer of equal weight, and the rest remained unchanged.

[0110] Comparative Example 3

[0111] On the basis of Example 1, the modified tannic acid was replaced by an equal weight of polyester polyol, and the rest remained unchanged.

[0112] Comparative Example 4

[0113] Based on Example 1, the modified tannic acid was replaced by an equal weight of polyetheramine, and the rest remained unchanged.

[0114] Comparative Example 5

[0115] On the basis of Example 1, the polyetheramine was replaced by an equal weight of modified tannic acid, and the rest remained unchanged.

[0116] Comparative Example 6

[0117] Based on Example 1, the polyetheramine was replaced by an equal weight of polyester polyol, and the rest remained unchanged.

[0118] Comparative Example 7

[0119] On the basis of Example 1, the modified tannic acid was replaced with tannic acid of equal weight, and the rest remained unchanged.

[0120] Test Example 1

[0121] Initial adhesion test:

[0122] The shear strength is used to represent the initial adhesion. The greater the shear strength, the greater the initial adhesion. The shear strength of Examples 1-3 and Comparative Examples 1-7 was tested according to the relevant method of standard GB / T 7124-2008 after 15 minutes of thermal curing.

[0123] Table 1. Initial adhesion test results

[0124]

[0125]

[0126] Test Example 2

[0127] Retort resistance test:

[0128] The flexible packaging adhesive materials obtained after completely heat curing in Examples 1-3 and Comparative Examples 1-7 and naturally cooling to room temperature were completely immersed in boiling water at a temperature of 100 degrees and heated, and the time required for debonding to occur was counted.

[0129] Table 2. Boiling resistance test results

[0130]

[0131]

[0132] Comparison between Example 1 and Comparative Examples 1-7 shows that:

[0133] The difference between Comparative Example 1 and Example 1 is that the first prepolymer is replaced by the second prepolymer of the same weight.

[0134] The difference between Comparative Example 2 and Example 1 is that the second prepolymer is replaced by an equal weight of the first prepolymer.

[0135] The difference between Comparative Example 3 and Example 1 is that the modified tannic acid is replaced by an equal weight of polyester polyol.

[0136] The difference between Comparative Example 4 and Example 1 is that the modified tannic acid is replaced by an equal weight of polyetheramine.

[0137] The difference between Comparative Example 5 and Example 1 is that the polyetheramine is replaced by an equal weight of modified tannic acid.

[0138] The difference between Comparative Example 6 and Example 1 is that the polyetheramine is replaced by an equal weight of polyester polyol.

[0139] The difference between Comparative Example 7 and Example 1 is that tannic acid is not modified by using propylene carbonate.

[0140] From the comparison between Example 1 and Comparative Examples 1-7 in Test Example 1, it can be seen that the two-component polyurethane hot melt adhesive provided by the present invention has excellent initial adhesion.

[0141] From the comparison between Example 1 and Comparative Examples 1-7 in Test Example 2, it can be seen that the two-component polyurethane hot melt adhesive provided by the present invention has excellent boiling resistance.

[0142] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A two-component polyurethane hot melt adhesive, characterized in that: The two-component polyurethane hot melt adhesive comprises component A and component B; the component A is formed by mixing a first prepolymer and a second prepolymer; the mass ratio of the first prepolymer to the second prepolymer is 1:0.2-0.3; the component B is formed by mixing 3-4 parts by weight of modified tannic acid, 15-20 parts by weight of polyester polyol and 5-7 parts by weight of polyether amine; the molar ratio of the isocyanate group of the component A to the hydroxyl group of the component B is 1.1-1.5:1; The first prepolymer is prepared by the following steps: Step X: Add dibutyltin dilaurate to diphenylmethane diisocyanate, then dropwise add polytetrahydrofuran at 70-80° C. under nitrogen atmosphere while stirring, continue to stir at constant temperature for 1.5-2 h after the dropwise addition is completed, cool naturally to room temperature, and store in a sealed container filled with nitrogen; The second prepolymer is prepared by the following steps: Step Y: Add dibutyltin dilaurate to diphenylmethane diisocyanate, then add castor oil dropwise at 70-80°C under nitrogen atmosphere while stirring, continue to stir at constant temperature for 2-3h after the addition is completed, raise the temperature to 85-90°C, add epoxy resin, keep stirring at this temperature for 1-2h, cool naturally to room temperature, and store in a sealed container filled with nitrogen; The modified tannic acid is prepared by the following steps: Step Z: Add 2-3 parts by weight of tannic acid and 0.05-0.1 parts by weight of 1,8-diazabicycloundec-7-ene to 20-25 parts by weight of propylene carbonate, and then stir at 180-190° C. for 4-5 hours, and distill under reduced pressure to obtain a mixture, wash with ether, and finally vacuum dry at 50-60° C. until constant weight.

2. A two-component polyurethane hot melt adhesive according to claim 1, characterized in that: In step Y, the molar ratio of the isocyanate group of the diphenylmethane diisocyanate, the hydroxyl group of the castor oil and the hydroxyl group of the epoxy resin is 3-3.5:1:0.5-0.8; the amount of the dibutyltin dilaurate is 0.1-0.3% of the sum of the mass of the diphenylmethane diisocyanate and the castor oil.

3. A two-component polyurethane hot melt adhesive according to claim 1, characterized in that: The epoxy resin in step Y is at least one of epoxy resin E-51 and epoxy resin E-44.

4. A two-component polyurethane hot melt adhesive according to claim 1, characterized in that: The polyester polyol is poly(1,4-butylene adipate diol); the hydroxyl value of the poly(1,4-butylene adipate diol) is 70-80 mgKOH / g.

5. The two-component polyurethane hot melt adhesive according to claim 1, characterized in that: The polyetheramine is polyetheramine D-230.

6. A method for using the two-component polyurethane hot melt adhesive according to any one of claims 1 to 5, characterized in that: The method of use comprises the following steps: (1) Preheat component A at 90-100°C for 5-10 minutes to obtain material A; (2) Preheating component B at 100-120°C for 5-10 min to obtain material B; (3) Stirring the material A and the material B for 5-10 minutes to obtain material C; (4) Roller-coat the material C on the surface of the flexible packaging material, bond it, heat-cure it at 40-45° C. for 20-36 hours, and naturally cool it to room temperature.

Images