A kind of PUR hot melt adhesive and preparation method thereof

Abstract

The present invention relates to the technical field of polymer materials, and in particular to a PUR hot melt adhesive and a preparation method thereof. The preparation method of the PUR hot melt adhesive comprises the following steps: (1) mixing polyester polyol, polyether polyol and diphenylmethane diisocyanate, reacting at a temperature of 110-120°C for 40-60min to obtain a polyurethane prepolymer; (2) cooling the polyurethane prepolymer to 96-105°C, adding a chain extender, reacting for 30-50min, then adding acrylic resin, silane coupling agent, acrylamide, hydroxymethyl cellulose and a stabilizer, stirring, reacting at a temperature of 85-95°C for 40-60min to obtain the PUR hot melt adhesive. The PUR hot melt adhesive prepared by the present invention has good bonding strength, mechanical properties and water resistance, and improves the comprehensive use performance of the PUR hot melt adhesive. The preparation method of the PUR hot melt adhesive is easy to operate and control, and is conducive to industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a PUR hot melt adhesive and a preparation method thereof. Background Art

[0002] PUR hot melt adhesive is a reactive polyurethane hot melt adhesive that can be applied under molten conditions, has a certain initial viscosity, and solidifies to produce strong adhesion after reacting with moisture on the surface of the substrate. At present, PUR hot melt adhesive has become one of the important varieties in the adhesive industry and is widely used in electronics, automobiles, aerospace, packaging, wood processing, textiles and other economic fields. However, with the development of science and technology and the progress of society, the performance requirements for PUR hot melt adhesives are getting higher and higher. Existing PUR hot melt adhesives often have problems with low water resistance and mechanical properties, and their adhesion needs to be further improved. Summary of the invention

[0003] In order to overcome the shortcomings and deficiencies in the prior art, the object of the present invention is to provide a PUR hot melt adhesive and a preparation method thereof. The preparation method of the PUR hot melt adhesive is easy to operate and control, is conducive to industrial production, and the prepared hot melt adhesive product has stable quality, good mechanical properties and water resistance, good adhesion, and is easy to construct and use.

[0004] The object of the present invention is achieved by the following technical solution: A method for preparing a PUR hot melt adhesive comprises the following steps:

[0005] (1) mixing polyester polyol, polyether polyol and diphenylmethane diisocyanate, wherein the molar ratio of isocyanate groups in diphenylmethane diisocyanate to hydroxyl groups in polyester polyol and polyether polyol is 1.8-2.1, that is, the isocyanate index (R value) is 1.8-2.1; reacting at a temperature of 110-120° C. for 40-60 minutes to obtain a polyurethane prepolymer;

[0006] (2) Cooling the polyurethane prepolymer obtained in step (1) to 96-105° C., adding a chain extender, wherein the molar ratio of the chain extender to the polyurethane prepolymer is 0.15-0.3:1; reacting for 30-50 minutes, then adding acrylic resin, silane coupling agent, acrylamide, hydroxymethyl cellulose and stabilizer, stirring, and reacting at a temperature of 85-95° C. for 40-60 minutes to obtain a PUR hot melt adhesive.

[0007] The PUR hot melt adhesive of the present invention uses polyester polyol, polyether polyol and diphenylmethane diisocyanate as main raw materials to prepare a prepolymer with -NCO group end-capping, and adopts a chain extender to improve the molecular weight and various properties of the PUR hot melt adhesive; the present invention creatively extends the chain of the polyurethane prepolymer and then combines it with raw materials such as acrylic resin, silane coupling agent, acrylamide, hydroxymethyl cellulose and stabilizer, so that the prepared PUR hot melt adhesive has good bonding strength, mechanical properties and water resistance, and improves the comprehensive use performance of the PUR hot melt adhesive.

[0008] Furthermore, in the step (1), the molar ratio of polyester polyol to polyether polyol is 1.7-2.8:1. The molecular chain of polyester diol contains a large number of ester bonds (-COO-), which has good polarity, cohesive strength and crystallization performance. The obtained PUR hot melt adhesive has excellent bonding strength and water resistance, but the ester group is easily hydrolyzed at high temperature, resulting in a decrease in bonding strength and a defect of poor water resistance; while the molecular chain of polyether polyol contains ether bonds (-COC-), which are not easy to hydrolyze, have low cohesive energy, and are easy to rotate. The obtained PUR hot melt adhesive has a relatively low glass transition temperature, good flexibility, hydrolysis resistance and weather resistance, etc., but low mechanical properties. Polyether polyol has good compatibility with other raw materials such as isocyanate and good processing performance; the present invention adopts the compounding of polyester polyol and polyether polyol, so that the PUR hot melt adhesive has good bonding strength, good water resistance and excellent comprehensive performance.

[0009] Furthermore, in the step (2), the weight proportions of the polyurethane prepolymer, acrylic resin, silane coupling agent, acrylamide, hydroxymethyl cellulose and stabilizer are 100 parts, 6-10 parts, 2-4 parts, 2-4 parts, 3-6 parts and 0.05-0.2 parts respectively. After the polyurethane prepolymer is chain extended, it is combined with raw materials such as acrylic resin, silane coupling agent, acrylamide, hydroxymethyl cellulose and stabilizer, which is beneficial to improve the bonding strength of the PUR hot melt adhesive and improve the comprehensive performance of the PUR hot melt adhesive.

[0010] Furthermore, in the step (2), the stabilizer is at least one of silicon dioxide, suberic acid and polyphosphoric acid. Preferably, the stabilizer is composed of silicon dioxide, suberic acid and polyphosphoric acid in a weight ratio of 1:0.1-0.3:0.1-0.3. The present invention helps to keep the viscosity of the PUR hot melt adhesive stable when it is used and stored at high temperatures by using the above stabilizer, and does not cause bonding failure, and helps to improve the bonding strength, hydrolysis resistance and ease of use of the PUR hot melt adhesive.

[0011] Furthermore, in step (2), the silane coupling agent is at least one of r-aminopropyltriethoxysilane, γ-(methacryloyloxy)propyltrimethoxysilane, vinyltrimethoxysilane and vinyltri(β-methoxyethoxy)silane.

[0012] Furthermore, in step (2), the method for preparing the chain extender comprises the following steps:

[0013] S1, taking dimerized rosin and adding it to a solvent to completely dissolve it, then slowly adding phosphorus trichloride and N,N-dimethylformamide dropwise and stirring for 4-8 hours, wherein the molar ratio of dimerized rosin, phosphorus trichloride and N,N-dimethylformamide is 1:1.5-3:0.1-0.2, to obtain a mixture A;

[0014] S2, evaporating the mixture A under reduced pressure to remove excess solvent and phosphorus trichloride, adding ethylene glycol and pyridine, wherein the molar ratio of dimerized rosin, ethylene glycol and pyridine is 1:1.1-1.5:1.1-1.5; reacting at 50-60° C. for 4-5 hours, then cooling to room temperature, filtering to remove residual ethylene glycol, pyridine, pyridine hydrochloride and other by-products, and obtaining an organic phase;

[0015] S3. Washing and drying the obtained organic phase to obtain a chain extender.

[0016] The present invention adopts the above method to modify dimerized rosin to obtain a terminal hydroxyl polyurethane chain extender, which can introduce the characteristic structure of rosin into the PUR molecular chain, effectively solve the problem of poor compatibility existing in direct physical blending of rosin and PUR, and effectively improve the mechanical properties and thermal stability of PUR hot melt adhesive.

[0017] Furthermore, the solvent is tetrahydrofuran.

[0018] The present invention provides a PUR hot melt adhesive made by the above-mentioned preparation method of the PUR hot melt adhesive.

[0019] The beneficial effects of the present invention are as follows: the PUR hot melt adhesive of the present invention uses polyester polyol, polyether polyol and diphenylmethane diisocyanate as main raw materials to prepare a prepolymer with -NCO group end-capping, and uses a chain extender to improve the molecular weight and performance of the PUR hot melt adhesive; the present invention creatively extends the chain of the polyurethane prepolymer, and then adds acrylic resin, silane coupling agent, acrylamide, hydroxymethyl cellulose and stabilizer to compound the polyurethane prepolymer, so that the prepared PUR hot melt adhesive has good bonding strength, mechanical properties and water resistance, and improves the comprehensive use performance of the PUR hot melt adhesive. The preparation method of the PUR hot melt adhesive is easy to operate and control, and is conducive to industrial production. DETAILED DESCRIPTION

[0020] In order to facilitate the understanding of those skilled in the art, the present invention is further described below in conjunction with embodiments, and the contents mentioned in the implementation modes are not intended to limit the present invention.

[0021] Example 1

[0022] In this embodiment, a method for preparing a PUR hot melt adhesive comprises the following steps:

[0023] (1) mixing polyester polyol, polyether polyol and diphenylmethane diisocyanate, wherein the molar ratio of isocyanate groups in diphenylmethane diisocyanate to hydroxyl groups in polyester polyol and polyether polyol is 1.9, reacting at 115° C. for 50 min to obtain a polyurethane prepolymer; wherein the molar ratio of polyester polyol to polyether polyol is 2.5:1;

[0024] (2) The polyurethane prepolymer obtained in step (1) is cooled to 98° C., a chain extender is added, the molar ratio of the chain extender to the polyurethane prepolymer is 0.2:1, and the reaction is carried out for 40 minutes. Then, acrylic resin, silane coupling agent, acrylamide, hydroxymethyl cellulose and stabilizer are added, stirred, and reacted at 90° C. for 50 minutes to obtain a PUR hot melt adhesive.

[0025] In this embodiment, the polyester polyol is polyester polyol BY-3001B, the polyether polyol is polyether polyol DL-2000D, and the acrylic resin is Mitsubishi acrylic resin BR-116.

[0026] Furthermore, in step (2), the weight portions of the polyurethane prepolymer, acrylic resin, silane coupling agent, acrylamide, hydroxymethyl cellulose and stabilizer are 100 parts, 8 parts, 3 parts, 3 parts, 4 parts and 0.1 parts respectively; and the silane coupling agent is r-aminopropyltriethoxysilane.

[0027] Furthermore, in step (2), the stabilizer is composed of silicon dioxide, suberic acid and polyphosphoric acid in a weight ratio of 1:0.2:0.15.

[0028] Furthermore, in step (2), the method for preparing the chain extender comprises the following steps:

[0029] S1, taking dimerized rosin and adding it into tetrahydrofuran to completely dissolve it, then slowly adding phosphorus trichloride and N,N-dimethylformamide dropwise and stirring for 5 hours, wherein the molar ratio of dimerized rosin, phosphorus trichloride and N,N-dimethylformamide is 1:2.5:0.15, to obtain a mixture A;

[0030] S2, evaporating the mixture A under reduced pressure to remove excess tetrahydrofuran and phosphorus trichloride, adding ethylene glycol and pyridine, wherein the molar ratio of dimerized rosin, ethylene glycol and pyridine is 1:1.2:1.2; reacting at 55° C. for 5 h, then cooling to room temperature, filtering to remove residual ethylene glycol, pyridine, pyridine hydrochloride and other by-products, and obtaining an organic phase;

[0031] S3. Washing the obtained organic phase with water and drying it to obtain a chain extender.

[0032] The PUR hot melt adhesive provided in this embodiment is made by the above-mentioned preparation method of the PUR hot melt adhesive.

[0033] Example 2

[0034] In this embodiment, a method for preparing a PUR hot melt adhesive comprises the following steps:

[0035] (1) mixing polyester polyol, polyether polyol and diphenylmethane diisocyanate, wherein the molar ratio of the isocyanate group in the diphenylmethane diisocyanate to the hydroxyl group in the polyester polyol and the polyether polyol is 1.8, and reacting at 110° C. for 60 minutes to obtain a polyurethane prepolymer; wherein the molar ratio of the polyester polyol to the polyether polyol is 1.7:1;

[0036] (2) The polyurethane prepolymer obtained in step (1) is cooled to 96° C., a chain extender is added, the molar ratio of the chain extender to the polyurethane prepolymer is 0.15:1, and the reaction is carried out for 50 minutes. Then, acrylic resin, silane coupling agent, acrylamide, hydroxymethyl cellulose and stabilizer are added, stirred, and reacted at 85° C. for 60 minutes to obtain a PUR hot melt adhesive.

[0037] Furthermore, in step (2), the weight parts of the polyurethane prepolymer, acrylic resin, silane coupling agent, acrylamide, hydroxymethyl cellulose and stabilizer are 100 parts, 10 parts, 2 parts, 2 parts, 3 parts and 0.05 parts respectively; the silane coupling agent is γ-(methacryloyloxy)propyltrimethoxysilane

[0038] Furthermore, in step (2), the stabilizer is composed of silicon dioxide, suberic acid and polyphosphoric acid in a weight ratio of 1:0.1:0.3.

[0039] Furthermore, in step (2), the method for preparing the chain extender comprises the following steps:

[0040] S1, taking dimerized rosin and adding it into tetrahydrofuran to completely dissolve it, then slowly adding phosphorus trichloride and N,N-dimethylformamide dropwise and stirring for 5 hours, wherein the molar ratio of dimerized rosin, phosphorus trichloride and N,N-dimethylformamide is 1:2:0.1, to obtain a mixture A;

[0041] S2, evaporating the mixture A under reduced pressure to remove excess tetrahydrofuran and phosphorus trichloride, adding ethylene glycol and pyridine, wherein the molar ratio of dimerized rosin, ethylene glycol and pyridine is 1:1.1:1.5; reacting at 50° C. for 5 h, then cooling to room temperature, filtering to remove residual ethylene glycol, pyridine and pyridine hydrochloride, and obtaining an organic phase;

[0042] S3. Washing and drying the obtained organic phase to obtain a chain extender.

[0043] The rest of the contents of this embodiment are the same as those of Embodiment 1 and will not be described again here.

[0044] Example 3

[0045] In this embodiment, a method for preparing a PUR hot melt adhesive comprises the following steps:

[0046] (1) mixing polyester polyol, polyether polyol and diphenylmethane diisocyanate, wherein the molar ratio of isocyanate groups in diphenylmethane diisocyanate to hydroxyl groups in polyester polyol and polyether polyol is 2.1, reacting at 120° C. for 40 minutes to obtain a polyurethane prepolymer; wherein the molar ratio of the polyester polyol to the polyether polyol is 2.8:1;

[0047] (2) The polyurethane prepolymer obtained in step (1) is cooled to 105° C., a chain extender is added, the molar ratio of the chain extender to the polyurethane prepolymer is 0.3:1, and the reaction is carried out for 30 minutes. Then, acrylic resin, silane coupling agent, acrylamide, hydroxymethyl cellulose and stabilizer are added, stirred, and reacted at 95° C. for 60 minutes to obtain a PUR hot melt adhesive.

[0048] Furthermore, in step (2), the weight portions of the polyurethane prepolymer, acrylic resin, silane coupling agent, acrylamide, hydroxymethyl cellulose and stabilizer are 100 parts, 6 parts, 4 parts, 4 parts, 6 parts and 0.2 parts respectively; and the silane coupling agent is vinyltrimethoxysilane.

[0049] Furthermore, in step (2), the stabilizer is composed of silicon dioxide, suberic acid and polyphosphoric acid in a weight ratio of 1:0.3:0.1.

[0050] Furthermore, in step (2), the method for preparing the chain extender comprises the following steps:

[0051] S1, taking dimerized rosin and adding it into tetrahydrofuran to completely dissolve it, then slowly adding phosphorus trichloride and N,N-dimethylformamide dropwise and stirring for 6 hours, wherein the molar ratio of dimerized rosin, phosphorus trichloride and N,N-dimethylformamide is 1:3:0.2, to obtain a mixture A;

[0052] S2, evaporating the mixture A under reduced pressure to remove excess tetrahydrofuran and phosphorus trichloride, adding ethylene glycol and pyridine, wherein the molar ratio of dimerized rosin, ethylene glycol and pyridine is 1:1.5:1.1; reacting at 50-60°C for 4-5h, then cooling to room temperature, filtering to remove residual ethylene glycol, pyridine and pyridine hydrochloride, and obtaining an organic phase;

[0053] S3. Washing and drying the obtained organic phase to obtain a chain extender.

[0054] The rest of the contents of this embodiment are the same as those of Embodiment 1 and will not be described again here.

[0055] Example 4

[0056] In this embodiment, a method for preparing a PUR hot melt adhesive comprises the following steps:

[0057] (1) mixing polyester polyol, polyether polyol and diphenylmethane diisocyanate, wherein the molar ratio of the isocyanate group in the diphenylmethane diisocyanate to the hydroxyl group in the polyester polyol and the polyether polyol is 2, and reacting at 115° C. for 60 minutes to obtain a polyurethane prepolymer; wherein the molar ratio of the polyester polyol to the polyether polyol is 2.5:1;

[0058] (2) The polyurethane prepolymer obtained in step (1) is cooled to 100° C., a chain extender is added, the molar ratio of the chain extender to the polyurethane prepolymer is 0.25:1, and the reaction is carried out for 40 minutes. Then, acrylic resin, silane coupling agent, acrylamide, hydroxymethyl cellulose and stabilizer are added, stirred, and reacted at 90° C. for 50 minutes to obtain a PUR hot melt adhesive.

[0059] Furthermore, in step (2), the weight portions of the polyurethane prepolymer, acrylic resin, silane coupling agent, acrylamide, hydroxymethyl cellulose and stabilizer are 100 parts, 7 parts, 3 parts, 3 parts, 4 parts and 0.15 parts respectively.

[0060] Furthermore, in step (2), the method for preparing the chain extender comprises the following steps:

[0061] S1, taking dimerized rosin and adding it into tetrahydrofuran to completely dissolve it, then slowly adding phosphorus trichloride and N,N-dimethylformamide dropwise and stirring for 7 hours, wherein the molar ratio of dimerized rosin, phosphorus trichloride and N,N-dimethylformamide is 1:1.5-3:0.1-0.2, to obtain a mixture A;

[0062] S2, evaporating the mixture A under reduced pressure to remove excess tetrahydrofuran and phosphorus trichloride, adding ethylene glycol and pyridine, wherein the molar ratio of dimerized rosin, ethylene glycol and pyridine is 1:1.2:1.3; reacting at 60° C. for 4.5 h, then cooling to room temperature, filtering to remove residual ethylene glycol, pyridine and pyridine hydrochloride, and obtaining an organic phase;

[0063] S3. Washing and drying the obtained organic phase to obtain a chain extender.

[0064] The rest of the contents of this embodiment are the same as those of Embodiment 1 and will not be described again here.

[0065] Comparative Example 1

[0066] The difference between this comparative example and Example 1 is that in this comparative example, a method for preparing a PUR hot melt adhesive comprises the following steps:

[0067] (1) mixing polyester polyol, polyether polyol and diphenylmethane diisocyanate, wherein the molar ratio of isocyanate groups in diphenylmethane diisocyanate to hydroxyl groups in polyester polyol and polyether polyol is 1.9, reacting at 115° C. for 50 min to obtain a polyurethane prepolymer; wherein the molar ratio of polyester polyol to polyether polyol is 2.5:1;

[0068] (2) The polyurethane prepolymer obtained in step (1) is cooled to 98° C., and then acrylic resin, silane coupling agent, acrylamide, hydroxymethyl cellulose and stabilizer are added, stirred, and reacted at 90° C. for 50 min to obtain a PUR hot melt adhesive.

[0069] Furthermore, in the step (2), the weight ratio of the polyurethane prepolymer, acrylic resin, silane coupling agent, acrylamide, hydroxymethyl cellulose and stabilizer is the same as the weight ratio of the polyurethane prepolymer, acrylic resin, silane coupling agent, acrylamide, hydroxymethyl cellulose and stabilizer after reacting with the chain extender in Example 1.

[0070] Comparative Example 2

[0071] The difference between this comparative example and Example 1 is that calcium sulfonate is used in step (2) to replace the stabilizer in Example 1. The rest of the contents of this comparative example are the same as those in Example 1 and will not be repeated here.

[0072] The performance tests of the PUR hot melt adhesives of Example 1 and Comparative Examples 1-2 are shown in the following table:

[0073]

[0074]

[0075] The melt viscosity is measured according to HG / T3660-1999. The prepared PUR hot melt adhesive is placed in an oven at 120°C and heated for 30 minutes. After the PUR hot melt adhesive is completely melted, it is quickly poured into the sleeve of the rotary viscometer and kept for 10 minutes before the melt viscosity is measured.

[0076] The method for determining the open time is as follows: heat the PUR hot melt adhesive to 120°C, and immediately apply a 0.1mm thick adhesive layer on the polytetrafluoroethylene plate after it turns into a molten state. Record the time from the start of coating to the time when the surface of the PUR hot melt adhesive becomes non-sticky, which is taken as the open time of the PUR hot melt adhesive.

[0077] The shear strength is measured as follows: PC boards are bonded together using PUR hot melt adhesive at a temperature of 120°C and a bonding time of 20 seconds, and the test is conducted in accordance with GB / T7124-2008. The elongation at break is measured by cutting the sample after the PUR hot melt adhesive is cured and measuring it in accordance with GB / T528-2009.

[0078] The method for determining the hydrolysis resistance is as follows: After bonding the PC board and the PC board with PUR hot melt adhesive, soak them in 80°C hot water for 48 hours, dry them in an environment of 25°C and 60% RH for 24 hours, and then measure the shear strength and compare the shear strength before and after soaking.

[0079] From the above content, it can be seen that the PUR hot melt adhesive of the present invention has excellent bonding strength, mechanical properties and water resistance, and has a suitable melt viscosity, which can prevent the melt viscosity from being too high and causing the application temperature to be too high, is easy to construct and use, and has excellent comprehensive performance.

[0080] The above embodiments are preferred implementation schemes of the present invention. In addition, the present invention may also be implemented in other ways. Any obvious replacement without departing from the concept of the present invention is within the protection scope of the present invention.

Claims

1. A method for preparing a PUR hot melt adhesive, characterized in that: The steps include: (1) Mixing polyester polyol, polyether polyol and diphenylmethane diisocyanate, wherein the molar ratio of isocyanate groups in diphenylmethane diisocyanate to hydroxyl groups in polyester polyol and polyether polyol is 1.8-2.1, and reacting at a temperature of 110-120° C. for 40-60 minutes to obtain a polyurethane prepolymer; (2) Cooling the polyurethane prepolymer obtained in step (1) to 96-105° C., adding a chain extender, reacting for 30-50 min, then adding acrylic resin, silane coupling agent, acrylamide, hydroxymethyl cellulose and a stabilizer, stirring, and reacting at 85-95° C. for 40-60 min to obtain a PUR hot melt adhesive; the stabilizer is composed of silicon dioxide, suberic acid and polyphosphoric acid in a weight ratio of 1:0.1-0.3:0.1-0.3; the weight parts of the polyurethane prepolymer, acrylic resin, silane coupling agent, acrylamide, hydroxymethyl cellulose and stabilizer are 100 parts, 6-10 parts, 2-4 parts, 2-4 parts, 3-6 parts and 0.05-0.2 parts respectively; The preparation method of the chain extender comprises the following steps: S1. Take dimerized rosin and add it into a solvent to completely dissolve it, then add phosphorus trichloride and N,N-dimethylformamide and stir to obtain a mixture A; S2, evaporating the mixture A to remove excess solvent and phosphorus trichloride, adding ethylene glycol and pyridine, reacting at 50-60° C. for 4-5 hours, then cooling to room temperature, filtering, and obtaining a filtered organic phase; S3. Washing and drying the obtained organic phase to obtain a chain extender.

2. The method for preparing the PUR hot melt adhesive according to claim 1, characterized in that: In the step (1), the molar ratio of polyester polyol to polyether polyol is 1.7-2.8:

1.

3. The method for preparing the PUR hot melt adhesive according to claim 1, characterized in that: In the step (2), the molar ratio of the chain extender to the polyurethane prepolymer is 0.15-0.3:

1.

4. The method for preparing the PUR hot melt adhesive according to claim 1, characterized in that: In the step (2), the silane coupling agent is at least one of r-aminopropyltriethoxysilane, γ-(methacryloyloxy)propyltrimethoxysilane, vinyltrimethoxysilane and vinyltri(β-methoxyethoxy)silane.

5. The method for preparing PUR hot melt adhesive according to claim 1, characterized in that: In the step S1, the molar ratio of the dimerized rosin, phosphorus trichloride and N,N-dimethylformamide is 1:1.5-3:0.1-0.

2.

6. The method for preparing PUR hot melt adhesive according to claim 1, characterized in that: In the step S2, the molar ratio of the dimerized rosin, ethylene glycol and pyridine is 1:1.1-1.5:1.1-1.

5.

7. A PUR hot melt adhesive, characterized in that: The hot melt adhesive is prepared by the preparation method of the PUR hot melt adhesive according to any one of claims 1 to 6.

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