Reactive single-component polyurethane hot melt adhesive, preparation method and application thereof

Abstract

The application belongs to the field of polyurethane adhesives, and relates to a reactive one-component polyurethane hot melt adhesive with low melt viscosity, long open time, high bonding strength and low free isocyanate content, which comprises the following components in parts by weight: low-free polyether polyol-based polyurethane prepolymer 20-60 parts; low-free polyester polyol-based polyurethane prepolymer 15-60 parts; tackifying resin 10-25 parts; catalyst 0.1-2 parts; water absorbent 0.2-3 parts. The reactive polyurethane hot melt adhesive has the characteristics of low melt viscosity, long open time, high bonding strength, excellent high-temperature and high-humidity aging resistance, and low free isocyanate content (<0.1 wt%), and the comprehensive performance is better than that of the low-free reactive polyurethane hot melt adhesive prepared by the prior art.

Description

Technical Field

[0001] The invention belongs to the field of polyurethane adhesives, and in particular relates to a reactive one-component polyurethane hot melt adhesive with low melt viscosity, long open time, high bonding strength and low free isocyanate content. Background Art

[0002] Traditional reactive polyurethane hot-melt adhesives are polyurethane prepolymers produced by reacting excess isocyanate with polyols. Due to the excess isocyanate, incomplete reaction between the polyol and the excess isocyanate, and the hindrance of the reaction at high viscosity, unreacted free isocyanate often remains in the final product. Free isocyanate monomers vaporize at temperatures between 85°C and 200°C, forming irritants, allergens, or toxic substances that pose a health risk to workers. The draft regulation on free isocyanate restrictions drafted by the European Chemicals Agency (ECHA) states that when the free isocyanate content in reactive polyurethane hot-melt adhesives exceeds 1wt%, there is a carcinogenic risk; when the free isocyanate content is between 0.1wt% and 1wt%, there is a risk of inhalation or skin contact. Products with a free isocyanate content exceeding 0.1wt% will be restricted for use in industrial and certain professional settings unless user safety can be protected. Products with a free isocyanate content less than 0.1wt% are exempt from this regulation. Therefore, there is an urgent need to develop a reactive polyurethane hot melt adhesive with excellent bonding properties and low free isocyanate content to meet the application needs of low-free reactive polyurethane hot melt adhesives in the fields of automobiles, new energy, consumer electronics, woodworking, textiles, etc.

[0003] Existing solutions for producing low-free reactive polyurethane hot melt adhesives include physical methods such as vacuum distillation to remove free isocyanate monomers. However, these methods are only suitable for a small number of low-boiling-point isocyanate monomers and require expensive equipment and complex processes. Other technologies utilize low-free isocyanate oligomers with a free isocyanate content of less than 0.1% to replace isocyanate monomers and react with polyols to produce low-free isocyanate reactive polyurethane hot melt adhesives. However, the disadvantage of using oligomers with polyols to produce polyurethane hot melt adhesives is that they exhibit high melt viscosity and low bonding strength. For example, in patent US20170002239A, Bayer's low-free MDI oligomer VPLS2397 is used to replace MDI monomer, and a reactive polyurethane hot melt adhesive is prepared by reacting the low-free MDI oligomer with polyols. The free MDI monomer of the final product is <0.1wt%, but the bulk strength decreases by about 50%; when part of the MDI monomer and the low-free MDI oligomer VPLS2397 are used to react with polyols, the bulk strength of the resulting reactive polyurethane hot melt adhesive is improved, but the content of the free MDI monomer increases to 0.4-1%.

[0004] In summary, the existing technology has the following defects:

[0005] (1) Since reactive polyurethane hot melt adhesive (PUR) is a polyurethane prepolymer prepared by the reaction of excess isocyanate and polyol, due to the excess isocyanate, the reaction between polyol and excess isocyanate is not sufficient, and the reaction is hindered under high viscosity, etc., there is often unreacted free isocyanate remaining in the final product.

[0006] (2) The existing low-free reactive polyurethane hot melt adhesive is obtained by reacting part of the isocyanate monomer and part of the low-free polyurethane oligomer (free isocyanate content is less than 0.1wt%) with polyol. Although the polyurethane oligomer with a free isocyanate content of less than 0.1wt% is used, a small amount of the added isocyanate monomer still remains, so that the final free isocyanate content is still higher than 0.1%.

[0007] (3) The existing low-free reactive polyurethane hot melt adhesive prepared by the reaction of low-free polyurethane oligomers (free isocyanate content less than 0.1wt%) to completely replace isocyanate monomers and polyols can achieve a free isocyanate content of less than 0.1wt% in the final product. However, since the polyurethane prepolymer has more flexible chain components than the isocyanate monomer, the molecular weight of the polyurethane prepolymer is larger. For the same mass fraction of polyurethane prepolymer and isocyanate monomer, the molar number of isocyanate groups in the polyurethane prepolymer is lower. When the polyurethane prepolymer is used to completely replace the isocyanate monomer and the polyol to form the polyurethane hot melt adhesive, the hard segment component will be relatively small and the soft segment component will be relatively high. The isocyanate content of the final product will be relatively low and the molecular weight will be relatively large. Therefore, the low-free polyurethane hot melt adhesive prepared by this method has the defects of high melt viscosity, short open time and low bonding strength.

[0008] (4) Since currently available commercially available polyurethane oligomers with low free isocyanate content (<0.1 wt%) are usually obtained by reacting general polyester polyols or polyether polyols with isocyanates, traditional polyester polyols or polyether polyols often have poor heat resistance and are prone to hydrolysis in high temperature and high humidity environments, reactive polyurethane hot melt adhesives prepared using only traditional commercially available low free prepolymers have poor resistance to high temperature and high humidity, posing a high safety risk during the long-term service of the adhesive. Summary of the Invention

[0009] The first purpose of the present invention is to overcome the problems of excessive free isocyanate monomers in existing traditional reactive polyurethane hot melt adhesives, which endanger the health of practitioners. The existing low-free isocyanate PUR has poor bonding performance and poor high-temperature and high-humidity aging resistance, and there is a risk of bonding failure. Instead, a reactive one-component polyurethane hot melt adhesive with low melt viscosity, long open time, high bonding strength and low free isocyanate content is provided.

[0010] The second object of the present invention is to provide a method for preparing the above-mentioned reactive one-component polyurethane hot melt adhesive.

[0011] The third object of the present invention is to provide the application of the above-mentioned reactive one-component polyurethane hot melt adhesive in the bonding and sealing of electronic consumer products and new energy batteries.

[0012] Specifically, the present invention provides a reactive one-component polyurethane hot melt adhesive having low melt viscosity, long open time, high bonding strength, and low free isocyanate content. The reactive one-component polyurethane hot melt adhesive comprises the following components in parts by weight:

[0013]

[0014] In a preferred embodiment, the reactive one-component polyurethane hot melt adhesive further comprises 20-60 parts by weight of a low-free polycarbonate-based polyurethane prepolymer.

[0015] In a preferred embodiment, the low-free polycarbonate-based polyurethane prepolymer is prepared from a polycarbonate polyol, a polyisocyanate, and a silane coupling agent containing an active hydrogen functional group; the molar equivalent ratio of the hydroxyl group in the polycarbonate polyol, the isocyanate group in the polyisocyanate, and the active hydrogen functional group in the silane coupling agent is 1:(1.8-2):(0.8-1).

[0016] In a preferred embodiment, the polycarbonate polyol is selected from at least one of polycarbonate 1,6-hexanediol ester polyol, polycarbonate-1,4-butanediol-1,6-hexanediol ester diol, polycarbonate-1,5-pentanediol-1,6-hexanediol ester diol, polycarbonate-caprolactone hexane diol, polycarbonate-1,4-cyclohexanedimethanol-1,6-hexanediol ester diol, polyethylene carbonate diol, polypropylene carbonate diol, polybutylene carbonate diol, and polyhexane carbonate diol; the polyisocyanate is selected from isophorone diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, hexamethylene diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, hydrogenated MDI, polymeric MDI, 1,5-naphthalene diisocyanate, 1,4 -At least one of phenylene diisocyanate, xylylene diisocyanate, tetramethylxylene diisocyanate and norbornane diisocyanate; the silane coupling agent containing an active hydrogen functional group is selected from at least one of (3-mercaptopropyl)trimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, bis(3-trimethoxysilylpropyl)amine, bis(3-triethoxysilylpropyl)amine, N-(n-butyl)-3-aminopropyltrimethoxysilane, N-(n-butyl)-3-aminopropyltriethoxysilane, 3-(N-cyclohexylamino)propyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-cyclohexyl-3-aminopropylmethyldimethoxysilane and N-(2-dimethylaminoethyl)-3-aminopropylmethyldimethoxysilane.

[0017] In a preferred embodiment, the low-free polyether polyol-based polyurethane prepolymer has a free isocyanate content of less than 0.1 wt%.

[0018] In a preferred embodiment, the low-free polyester polyol-based polyurethane prepolymer has a free isocyanate content of less than 0.1 wt%.

[0019] In a preferred embodiment, the low-free polyether polyol-based polyurethane prepolymer is obtained by reacting polyether polyol with polyisocyanate monomers.

[0020] In a preferred embodiment, the low-free polyester polyol-based polyurethane prepolymer is obtained by reacting polyester polyol with polyisocyanate monomers.

[0021] In the present invention, both ends of the low-free polyether polyol-based polyurethane prepolymer and the low-free polyester polyol-based polyurethane prepolymer are capped with isocyanate groups.

[0022] In a preferred embodiment, the catalyst is selected from one or more of dibutyltin dilaurate, stannous octoate, triethylamine, diethylenetriamine, triethylenediamine, N-ethylmorpholine, and 2,2-dimorpholinodiethyl ether.

[0023] In a preferred embodiment, the tackifying resin is selected from one or more of thermoplastic acrylic resin, polyurethane resin, amorphous poly-α-olefin resin, rosin resin, rosin pentaerythritol ester, petroleum resin, terpene resin and EVA resin.

[0024] In a preferred embodiment, the water absorbent is selected from one or more of a molecular sieve desiccant, an oxazolidine desiccant, p-toluenesulfonyl isocyanate, and triethyl orthoformate.

[0025] In a preferred embodiment, the low-free polycarbonate-based polyurethane prepolymer is prepared according to the following method:

[0026] S1. Dehydrating the polycarbonate polyol at 100-120° C. and 100-200 r / min under vacuum stirring for 1-5 h, and then cooling to 70-90° C. to obtain a pretreated product;

[0027] S2. reacting the pretreated product with polyisocyanate at 70-90° C. and 100-200 r / min under vacuum stirring for 1-5 h to obtain an isocyanate di-terminated prepolymer;

[0028] S3. React the isocyanate di-terminated prepolymer and the silane coupling agent containing an active hydrogen functional group at a temperature of 70-90° C. and a rotation speed of 100-200 r / min under vacuum stirring for 1-5 hours to obtain a low-free polycarbonate-based polyurethane prepolymer, which is then vacuum-sealed for storage.

[0029] The present invention also provides a method for preparing a reactive one-component polyurethane hot melt adhesive having low melt viscosity, long open time, high bonding strength and low free isocyanate content. The preparation method comprises the following steps:

[0030] Step 1: vacuum stirring a low-free polyether polyol-based polyurethane prepolymer, a tackifying resin, and a water absorbent at a temperature of 100-120° C. and a speed of 100-200 r / min for 1-3 hours, and obtaining a premix after the tackifying resin is completely melted;

[0031] Step 2: Add low-free polyester polyol-based polyurethane prepolymer, low-free polycarbonate-based polyurethane prepolymer and catalyst to the premix, stir the premix at a speed of 100-200 r / min for 30 minutes to 1 hour under vacuum conditions, and discharge the material.

[0032] The application also provides application of the reactive one-component polyurethane hot melt adhesive with low melt viscosity, long open time, high bonding strength and low free isocyanate content in bonding and sealing of electronic consumer products and new energy batteries.

[0033] Due to the large difference between the low free polyurethane prepolymer (free isocyanate content less than 0.1 wt%) and the isocyanate monomer, the low free reactive polyurethane hot melt adhesive prepared by simply replacing the isocyanate monomer with the low free polyurethane prepolymer and reacting with polyols has large performance defects and large difference from the performance of the traditional reactive polyurethane hot melt adhesive prepared by directly using the isocyanate monomer and reacting with polyols. The application discards the method of using the low free polyurethane oligomer to replace the isocyanate monomer and reacting with polyols to prepare the low free reactive polyurethane hot melt adhesive, and directly uses the commercial low free polyurethane prepolymer as one of the components of the reactive polyurethane hot melt adhesive. In addition, the application uses the polycarbonate diol with good aging resistance, the isocyanate monomer and the silane coupling agent with active hydrogen functional groups to self-prepare a low free isocyanate content polyurethane prepolymer based on polycarbonate polyol through chemical reaction. The free isocyanate monomer in the self-prepared prepolymer can be completely consumed by the silane coupling agent with active hydrogen functional groups, and the free isocyanate content in the final prepolymer can be less than 0.1 wt%. The application uses the commercial low free polyether polyol based polyurethane prepolymer, the low free polyester polyol based polyurethane prepolymer, tackifying resin, auxiliary agent, and the self-prepared low free polycarbonate polyol based polyurethane prepolymer to prepare a low free isocyanate content reactive polyurethane hot melt adhesive through a physical blending process. The reactive polyurethane hot melt adhesive has the characteristics of low melt viscosity, long open time, high bonding strength, excellent high temperature and high humidity aging resistance, and low free isocyanate content (<0.1 wt%), and the comprehensive performance is better than that of the low free reactive polyurethane hot melt adhesive prepared by the prior art. DETAILED DESCRIPTION

[0034] The application will be described in detail below through synthesis examples and examples.

[0035] Synthesis Example 1

[0036] By weight, 69.2 g (0.035 mol) of polycarbonate 1,6 hexanediol with a number average molecular weight of 2000 was added to a reaction bottle, heated to 110° C., and vacuum dehydrated for 2 hours under stirring conditions at 150 r / min; then the temperature was lowered to 80° C., 17.3 g (0.069 mol) of 4,4′-diphenylmethane diisocyanate (MDI) was added, and the reaction was carried out for 2 hours under stirring conditions at 150 r / min; then 13.6 g (0.069 mol) (3-mercaptopropyl) trimethoxysilane was added, and the reaction was carried out for 2 hours under stirring conditions at 150 r / min, and then the material was discharged to obtain a low-free polycarbonate-based polyurethane prepolymer, recorded as LFP-1, which was vacuum-sealed and stored.

[0037] Synthesis example 2

[0038] By weight, 72.4 g (0.036 mol) of polycarbonate-1,4-butanediol-1,6-hexanediol ester diol with a number average molecular weight of 2000 was added to a reaction bottle, heated to 110° C., and vacuum dehydrated for 2 hours under stirring conditions at 150 r / min; then cooled to 80° C., 16.3 g (0.065 mol) of 4,4'-diphenylmethane diisocyanate (MDI) was added, and the reaction was carried out for 2 hours under stirring conditions at 150 r / min; then 11.3 g (0.058 mol) (3-mercaptopropyl) trimethoxysilane was added, and the reaction was carried out for 2 hours under stirring conditions at 150 r / min, and then the material was discharged to obtain a low-free polycarbonate-based polyurethane prepolymer, recorded as LFP-2, which was vacuum-sealed and stored.

[0039] Synthesis example 3

[0040] By weight, 57.4 g (0.057 mol) of polycarbonate-1,4-butanediol-1,6-hexanediol ester diol with a number average molecular weight of 1000 was added to a reaction bottle, heated to 110° C., and vacuum dehydrated for 2 hours under stirring conditions at 150 r / min; then cooled to 80° C., 18.3 g (0.109 mol) of hexamethylene diisocyanate (HDI) was added, and the reaction was carried out for 2 hours under stirring conditions at 150 r / min; then 24.3 g (0.103 mol) of N-n-butyl-3-aminopropyltrimethoxysilane was added, and the reaction was carried out for 2 hours under stirring conditions at 150 r / min, and then the material was discharged to obtain a low-free polycarbonate-based polyurethane prepolymer, recorded as LFP-3, which was vacuum-sealed and stored.

[0041] Synthesis example 4

[0042] By weight, 54.2 g (0.054 mol) of polycarbonate-1,4-cyclohexanedimethanol-1,6-hexanediol ester diol with a number average molecular weight of 1000 was added to a reaction bottle, heated to 110° C., and vacuum dehydrated for 2 hours under stirring conditions at 150 r / min; then cooled to 80° C., 18.2 g (0.108 mol) of hexamethylene diisocyanate (HDI) was added, and the reaction was carried out for 2 hours under stirring conditions at 150 r / min; then 27.6 g (0.108 mol) of N-phenyl-3-aminopropyltrimethoxysilane was added, and the reaction was carried out for 2 hours under stirring conditions at 150 r / min, and then the material was discharged to obtain a low-free polycarbonate-based polyurethane prepolymer, recorded as LFP-4, which was vacuum-sealed and stored.

[0043] Synthesis example 5

[0044] By weight, 50.2 g (0.050 mol) of polycarbonate-1,4-cyclohexanedimethanol-1,6-hexanediol ester diol with a number average molecular weight of 1000 was added to a reaction bottle, heated to 110° C., and vacuum dehydrated for 2 hours under stirring conditions at 150 r / min; then cooled to 80° C., 26.3 g (0.100 mol) of 4,4-diisocyanate dicyclohexylmethane was added, and the reaction was carried out for 2 hours under stirring conditions at 150 r / min; then 23.6 g (0.100 mol) of N-n-butyl-3-aminopropyltrimethoxysilane was added, and the reaction was carried out for 2 hours under stirring conditions at 150 r / min, and then the material was discharged to obtain a low-free polycarbonate-based polyurethane prepolymer, recorded as LFP-5, which was vacuum-sealed and stored.

[0045] Synthesis example 6

[0046] By weight, 49.2 g (0.049 mol) of polycarbonate-1,4-butanediol-1,6-hexanediol ester diol with a number average molecular weight of 1000 was added to a reaction bottle, heated to 110° C., and vacuum dehydrated for 2 hours under stirring conditions of 150 r / min; then cooled to 80° C., 25.8 g (0.098 mol) of 4,4-diisocyanate dicyclohexylmethane was added, and the mixture was reacted for 2 hours under stirring conditions of 150 r / min; then 25.1 g (0.098 mol) of N-phenyl-3-aminopropyltrimethoxysilane was added, and the mixture was reacted for 2 hours under stirring conditions of 150 r / min and then discharged to obtain a low-free polycarbonate-based polyurethane prepolymer, recorded as LFP-6, which was vacuum-sealed and stored.

[0047] Example 1

[0048] 36.1 parts of low-free polyether polyol-based polyurethane prepolymer Adiprene LF TE330, 12.0 parts of acrylic resin BM751, and 0.5 parts of water absorbent Additive OF were added to a reaction bottle, heated to 110° C., and stirred at a stirring speed of 150 r / min under vacuum conditions for 2 hours; then 39.7 parts of low-free polyester polyol-based polyurethane prepolymer Adiprene LFM S300, 15.0 parts of low-free polycarbonate polyol-based polyurethane prepolymer LFP-1, and 0.1 part of dibutyltin dilaurate were added, and the mixture was stirred at a speed of 150 r / min under vacuum conditions for 40 minutes. The material was discharged to obtain a reactive polyurethane hot melt adhesive with a low free isocyanate content, which was vacuum-sealed for storage.

[0049] Example 2

[0050] 33.9 parts by weight of a low-free polyether polyol-based polyurethane prepolymer Adiprene LF TE440, 15.0 parts of an acrylic resin BR106, and 1.0 part of a water absorbent Additive OF were added to a reaction flask, heated to 110° C., and stirred at a stirring speed of 150 r / min under vacuum conditions for 2 hours; then 29.8 parts of a low-free polyester polyol-based polyurethane prepolymer Adiprene LFM S500, 20.0 parts of a low-free polycarbonate polyol-based polyurethane prepolymer LFP-2, and 0.3 parts of dibutyltin dilaurate were added, and the mixture was stirred at a speed of 150 r / min under vacuum conditions for 40 minutes. The material was discharged to obtain a reactive polyurethane hot melt adhesive with a low free isocyanate content, which was vacuum-sealed for storage.

[0051] Example 3

[0052] 28.7 parts of low-free polyether polyol-based polyurethane prepolymer Adiprene LF 900A, 17.0 parts of acrylic resin BR113, and 1.2 parts of water absorbent Additive TI were added to a reaction bottle, heated to 110° C., and stirred at a stirring speed of 150 r / min under vacuum conditions for 2 hours; then 27.6 parts of low-free polyester polyol-based polyurethane prepolymer Adiprene LFM S200, 25.0 parts of low-free polycarbonate polyol-based polyurethane prepolymer LFP-3, and 0.5 parts of 2,2-dimorpholinodiethyl ether were added, and the mixture was stirred at a speed of 150 r / min under vacuum conditions for 40 minutes. The material was discharged to obtain a reactive polyurethane hot melt adhesive with a low free isocyanate content, which was vacuum-sealed and stored.

[0053] Example 4

[0054] 27.0 parts by weight of a low-free polyether polyol-based polyurethane prepolymer Adiprene LF G730, 20.0 parts of an amorphous poly-α-olefin resin VESTOPLAST 520, and 1.2 parts of a water absorbent Additive TI were added to a reaction bottle, heated to 110° C., and stirred at a stirring speed of 150 r / min under vacuum conditions for 2 hours; then 26.3 parts of a low-free polyester polyol-based polyurethane prepolymer Adiprene LFM S500, 25.0 parts of a low-free polycarbonate polyol-based polyurethane prepolymer LFP-4, and 0.2 parts of dibutyltin dilaurate were added, and the mixture was stirred at a speed of 150 r / min under vacuum conditions for 40 minutes. The material was discharged to obtain a reactive polyurethane hot melt adhesive with a low free isocyanate content, which was vacuum-sealed for storage.

[0055] Example 5

[0056] 36.4 parts by weight of a low-free polyether polyol-based polyurethane prepolymer Adiprene LF TE365, 25.0 parts of a polyurethane resin Pearlbond 539, and 1.2 parts of a molecular sieve desiccant Siliporite SA1702 were added to a reaction flask, heated to 110° C., and stirred at a stirring speed of 150 r / min under vacuum conditions for 2 hours; then 22.1 parts of a low-free polyester polyol-based polyurethane prepolymer Adiprene LFM S300, 15.0 parts of a low-free polycarbonate polyol-based polyurethane prepolymer LFP-5, and 0.3 parts of stannous octoate were added, stirred at a speed of 150 r / min under vacuum conditions for 40 minutes, and discharged to obtain a reactive polyurethane hot melt adhesive with a low free isocyanate content, which was vacuum-sealed for storage.

[0057] Example 6

[0058] 20.0 parts of low-free polyether polyol-based polyurethane prepolymer Adiprene LF TE915, 10.0 parts of polyurethane resin Pearlbond 523, and 0.7 parts of water absorbent Additive OF were added to a reaction bottle, heated to 110° C., and stirred at a stirring speed of 150 r / min under vacuum conditions for 2 hours; then 38.3 parts of low-free polyester polyol-based polyurethane prepolymer Adiprene LFM S200, 30.0 parts of low-free polycarbonate polyol-based polyurethane prepolymer LFP-6, and 1.0 part of 2,2-dimorpholino diethyl ether were added, and the mixture was stirred at a speed of 150 r / min under vacuum conditions for 40 minutes. The material was discharged to obtain a reactive polyurethane hot melt adhesive with a low free isocyanate content, which was vacuum-sealed for storage.

[0059] Example 7

[0060] 36.1 parts by weight of a low-free polyether polyol-based polyurethane prepolymer Adiprene LF TE330, 12.0 parts of an acrylic resin BM751, and 0.5 parts of a water absorbent Additive OF were added to a reaction flask, heated to 110° C., and stirred at a stirring speed of 150 r / min under vacuum conditions for 2 hours. Then, 54.7 parts of a low-free polyester polyol-based polyurethane prepolymer Adiprene LFM S300 and 0.1 parts of dibutyltin dilaurate were added, and the mixture was stirred at a speed of 150 r / min under vacuum conditions for 40 minutes. The material was discharged to obtain a reactive polyurethane hot melt adhesive with a low free isocyanate content, which was vacuum-sealed for storage.

[0061] Example 8

[0062] 36.1 parts by weight of a low-free polyether polyol-based polyurethane prepolymer Adiprene LF TE330, 10 parts of an acrylic resin BM751, and 0.3 parts of a water absorbent Additive OF were added to a reaction bottle, heated to 110° C., and stirred at a stirring speed of 150 r / min under vacuum conditions for 2 hours. Then, 15 parts of a low-free polyester polyol-based polyurethane prepolymer Adiprene LFM S300 and 0.2 parts of dibutyltin dilaurate were added, and the mixture was stirred at a speed of 150 r / min under vacuum conditions for 40 minutes. The material was discharged to obtain a reactive polyurethane hot melt adhesive with a low free isocyanate content, which was vacuum-sealed for storage.

[0063] Example 9

[0064] 60 parts by weight of a low-free polyether polyol-based polyurethane prepolymer Adiprene LF TE330, 25 parts of an acrylic resin BM751, and 3 parts of a water absorbent Additive OF were added to a reaction bottle, heated to 110° C., and stirred at a stirring speed of 150 r / min under vacuum conditions for 2 hours. Then, 60 parts of a low-free polyester polyol-based polyurethane prepolymer Adiprene LFM S300 and 2 parts of dibutyltin dilaurate were added, and the mixture was stirred at a speed of 150 r / min under vacuum conditions for 40 minutes. The material was discharged to obtain a reactive polyurethane hot melt adhesive with a low free isocyanate content, which was then vacuum-sealed for storage.

[0065] Comparative Example 1

[0066] By weight, 20.6 parts of poly(hexamethylene adipate) diol with a number average molecular weight of 3000, 27.5 parts of polyoxypropylene ether diol with a number average molecular weight of 2000, 20.6 parts of poly(neopentyl adipate) diol with a number average molecular weight of 2000, 15.0 parts of polyacrylic resin BM751, and 0.5 parts of water absorbent Additive TI were added to a reaction bottle, heated to 110° C., and vacuum dehydrated for 2 hours under stirring conditions of 150 r / min; then 15.5 parts of 4,4'-diphenylmethane diisocyanate (MDI) and 0.2 parts of 2,2-dimorpholinodiethyl ether were added, and the mixture was reacted for 2 hours under vacuum conditions at a stirring speed of 150 r / min, and then discharged to obtain a traditional reactive polyurethane hot melt adhesive, which was vacuum-sealed for storage.

[0067] Comparative Example 2

[0068] In parts by weight, 12.4 parts of poly(hexamethylene adipate) diol with a number average molecular weight of 3000, 16.6 parts of polyoxypropylene ether diol with a number average molecular weight of 2000, 12.4 parts of poly(neopentyl adipate) diol with a number average molecular weight of 2000, 15.0 parts of polyacrylic resin BM751, and 0.5 parts of water absorbent Additive TI were added to a reaction bottle, heated to 110° C., and vacuum dehydrated for 2 hours under stirring conditions of 150 r / min; then 42.9 parts of low-free polyether polyol-based polyurethane prepolymer Adiprene LFM G730 and 0.2 parts of 2,2-dimorpholinodiethyl ether were added, and the mixture was reacted for 2 hours under vacuum conditions at a stirring speed of 150 r / min, and then discharged to obtain a low-free reactive polyurethane hot melt adhesive prepared by reacting the low-free polyether polyol-based polyurethane prepolymer completely replacing the MDI monomer with the polyol, which was vacuum-sealed for storage.

[0069] Comparative Example 3

[0070] By weight, 15.5 parts of polyhexamethylene adipate diol with a number average molecular weight of 3000, 20.7 parts of polyoxypropylene ether diol with a number average molecular weight of 2000, 15.5 parts of polyneopentyl adipate diol with a number average molecular weight of 2000, 15.0 parts of polyacrylic resin BM751, and 0.5 parts of water absorbent Additive TI were added to a reaction bottle, heated to 110°C, and vacuum dehydrated at 150r / min for 2h; then 26.8 parts of low-free polyether polyol-based polyurethane prepolymer Adiprene LFM were added. G730, 5.8 parts of 4,4'-diphenylmethane diisocyanate (MDI), and 0.2 parts of 2,2-dimorpholinodiethyl ether are reacted at a stirring speed of 150 r / min under vacuum conditions for 2 hours and then discharged to obtain a low-free reactive polyurethane hot melt adhesive prepared by the reaction of low-free polyether polyol-based polyurethane prepolymer partially replacing MDI monomer with polyol, and the mixture is vacuum-sealed for storage.

[0071] Test Case

[0072] The samples of the embodiment and the comparative example were subjected to comparative tests in the following manner:

[0073] (1) Melt viscosity: Place the sealed polyurethane hot melt adhesive in a syringe heater at 110°C for 10 minutes. At this point, the hot melt adhesive has become a molten fluid. Quickly pour it into the sleeve of a Brookfield-DV2T viscometer. Set the heater temperature to 110°C and maintain it for 10 minutes to make the internal temperature of the hot melt adhesive uniform and degas. Measure the constant-temperature melt viscosity of the hot melt adhesive at 110°C.

[0074] (2) Open time: Use a dispensing machine to apply the hot melt adhesive obtained in the examples and comparative examples to a polycarbonate substrate with a width of about 2 mm. Start timing when dispensing is completed. Gently touch the adhesive line with your finger. When the adhesive line is no longer sticky, the timing ends. This time is recorded as the open time of the reactive polyurethane hot melt adhesive.

[0075] (3) Bonding strength

[0076] Bond Strength after 30 Minutes and 24 Hours: The hot melt adhesive prepared in the Examples and Comparative Examples was dispensed at 110°C using a dispensing machine, applying a 25mm x 25mm rectangular adhesive frame to a polycarbonate substrate with a width of approximately 1mm. Another polycarbonate substrate was then laminated onto the polycarbonate substrate. After adhesive dispensing and lamination, the samples were cured in an environment of 25°C and 50% RH for 30 minutes and 24 hours, respectively. The resulting bonded samples were then tested using a universal testing machine at a speed of 10mm / min in the pull direction until failure occurred. The maximum force displayed by the instrument was recorded, and the bond strength of the hot melt adhesive to the polycarbonate substrate was calculated based on the bonded area.

[0077] Adhesion strength after aging at 85°C / 85RH% for 7 days: Use a dispensing machine to dispense the hot melt adhesive obtained in the Examples and Comparative Examples at 110°C, applying a 25mm*25mm rectangular adhesive frame to a polycarbonate substrate with a width of approximately 1mm. Next, another polycarbonate substrate is attached to the polycarbonate substrate. After the dispensing and lamination are completed, the sample is cured for 24 hours in an environment of 25°C and 50%RH. The cured sample is placed in an oven at 85°C / 85RH% for 7 days, removed and allowed to warm to room temperature. The prepared adhesive sample is then run in the pulling direction at a speed of 10mm / min using a universal material testing machine until the sample fails. The maximum force displayed by the instrument is recorded, and the bonding strength of the hot melt adhesive to the polycarbonate substrate is calculated based on the bonding area.

[0078] (4) Free isocyanate content: A high-performance liquid chromatograph (HPLC) was used, with a liquid as the mobile phase and a high-pressure infusion system. The mobile phase was pumped into a chromatographic column containing a stationary phase. After the components were separated within the column, they were detected by a detector to obtain a chromatogram of the test substance. The content of free isocyanate monomers in the reactive polyurethane hot melt adhesive was quantitatively calculated using the external standard method. The chromatograms of the test sample and the standard were recorded separately. The free isocyanate content in the test sample was calculated based on the integrated area of ​​the specific peaks on the chromatograms.

[0079] The data obtained from the above test are shown in Table 1 below.

[0080] Table 1

[0081]

[0082] By comparing Examples 1-9 with Comparative Example 1, it can be seen that the free isocyanate content of the reactive polyurethane hot melt adhesive of the present invention is all below 0.1wt%, and the free isocyanate content is significantly reduced, which increases the safety of using the reactive polyurethane hot melt adhesive and avoids endangering the health of practitioners. By comparing Examples 1-9 with Comparative Example 2, it can be found that the reactive polyurethane hot melt adhesive prepared by the present invention by physically blending a low-free polyurethane prepolymer with a non-reactive component such as a tackifying resin has a lower melt viscosity, a longer open time, and a higher bonding strength. By comparing Examples 1-9 with Comparative Example 3, it can be seen that the present invention does not introduce an isocyanate monomer, significantly reducing the content of free isocyanate in the system, achieving a balance between low free isocyanate content and excellent comprehensive performance. Further, by adding the self-made low-free polycarbonate-based polyurethane oligomer of the present invention to the reactive polyurethane hot melt adhesive of the present invention, the bonding strength after high temperature and high humidity aging can be further improved. In summary, the reactive polyurethane hot melt adhesive of the present invention has a low isocyanate content and excellent comprehensive properties.

[0083] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and purpose of the present invention.

Claims

1. A reactive one-component polyurethane hot melt adhesive having low melt viscosity, long open time, high bonding strength and low free isocyanate content, characterized in that: The reactive one-component polyurethane hot melt adhesive comprises the following components in parts by weight: The low-free polycarbonate-based polyurethane prepolymer is prepared from polycarbonate polyol, polyisocyanate and a silane coupling agent containing an active hydrogen functional group, wherein the molar equivalent ratio of the hydroxyl group in the polycarbonate polyol, the isocyanate group in the polyisocyanate and the active hydrogen functional group in the silane coupling agent is 1:(1.8-2):(0.8-1); the free isocyanate content of the low-free polyether polyol-based polyurethane prepolymer is less than 0.1wt%; the free isocyanate content of the low-free polyester polyol-based polyurethane prepolymer is less than 0.1wt%; and the free isocyanate content of the low-free polycarbonate-based polyurethane prepolymer is less than 0.1wt%. The low-free polycarbonate-based polyurethane prepolymer is prepared according to the following method: S1. Dehydrating the polycarbonate polyol at 100-120° C. and 100-200 r / min under vacuum stirring for 1-5 h, and then cooling to 70-90° C. to obtain a pretreated product; S2. reacting the pretreated product with polyisocyanate at 70-90° C. and 100-200 r / min under vacuum stirring for 1-5 h to obtain an isocyanate di-terminated prepolymer; S3, reacting the isocyanate di-terminated prepolymer and the silane coupling agent containing an active hydrogen functional group at a temperature of 70-90° C. and a rotation speed of 100-200 r / min under vacuum stirring for 1-5 hours to obtain a low-free polycarbonate-based polyurethane prepolymer, which is then vacuum-sealed and stored; The silane coupling agent containing an active hydrogen functional group is selected from at least one of bis(3-trimethoxysilylpropyl)amine, bis(3-triethoxysilylpropyl)amine, N-(n-butyl)-3-aminopropyltrimethoxysilane, N-(n-butyl)-3-aminopropyltriethoxysilane, 3-(N-cyclohexylamino)propyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-cyclohexyl-3-aminopropylmethyldimethoxysilane and N-(2-dimethylaminoethyl)-3-aminopropylmethyldimethoxysilane.

2. The reactive one-component polyurethane hot melt adhesive having low melt viscosity, long open time, high bonding strength and low free isocyanate content according to claim 1, characterized in that: The polycarbonate polyol is selected from at least one of polycarbonate 1,6-hexanediol polyol, polycarbonate-1,4-butanediol-1,6-hexanediol diol, polycarbonate-1,5-pentanediol-1,6-hexanediol diol, polycarbonate-caprolactone hexane diol, polycarbonate-1,4-cyclohexanedimethanol-1,6-hexanediol diol, polyethylene carbonate diol, polypropylene carbonate diol, polybutylene carbonate diol, and polyhexane carbonate diol; the polyisocyanate The ester is selected from at least one of isophorone diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, hexamethylene diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, hydrogenated MDI, polymeric MDI, 1,5-naphthalene diisocyanate, 1,4-phenylene diisocyanate, xylylene diisocyanate, tetramethylxylene diisocyanate and norbornane diisocyanate.

3. The reactive one-component polyurethane hot melt adhesive having low melt viscosity, long open time, high bonding strength and low free isocyanate content according to claim 1, characterized in that: The low-free polyether polyol-based polyurethane prepolymer is obtained by reacting polyether polyol with polyisocyanate monomers.

4. The reactive one-component polyurethane hot melt adhesive having low melt viscosity, long open time, high bonding strength and low free isocyanate content according to claim 1, characterized in that: The low-free polyester polyol-based polyurethane prepolymer is obtained by reacting polyester polyol with polyisocyanate monomers.

5. The reactive one-component polyurethane hot melt adhesive having low melt viscosity, long open time, high bonding strength and low free isocyanate content according to claim 1, characterized in that: The catalyst is selected from one or more of dibutyltin dilaurate, stannous octoate, triethylamine, diethylenetriamine, triethylenediamine, N-ethylmorpholine and 2,2-dimorpholinodiethyl ether.

6. The reactive one-component polyurethane hot melt adhesive having low melt viscosity, long open time, high bonding strength and low free isocyanate content according to claim 1, characterized in that: The tackifying resin is selected from one or more of thermoplastic acrylic resin, polyurethane resin, amorphous poly-α-olefin resin, rosin resin, rosin pentaerythritol ester, petroleum resin, terpene resin and EVA resin.

7. The reactive one-component polyurethane hot melt adhesive having low melt viscosity, long open time, high bonding strength and low free isocyanate content according to claim 1, characterized in that: The water absorbent is selected from one or more of a molecular sieve desiccant, an oxazolidine desiccant, p-methylbenzenesulfonyl isocyanate and triethyl orthoformate.

8. A method for preparing a reactive one-component polyurethane hot melt adhesive having low melt viscosity, long open time, high bonding strength and low free isocyanate content as claimed in any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: Step 1: vacuum stirring a low-free polyether polyol-based polyurethane prepolymer, a tackifying resin, and a water absorbent at a temperature of 100-120° C. and a speed of 100-200 r / min for 1-3 hours, and obtaining a premix after the tackifying resin is completely melted; Step 2: Add low-free polyester polyol-based polyurethane prepolymer, low-free polycarbonate-based polyurethane prepolymer and catalyst to the premix, stir at a speed of 100-200 r / min for 30 minutes to 1 hour under vacuum conditions, and discharge the material.

9. A use of a reactive one-component polyurethane hot melt adhesive having low melt viscosity, long open time, high bonding strength and low free isocyanate content as claimed in any one of claims 1 to 7, characterized in that: The reactive one-component polyurethane hot melt adhesive is used in the bonding and sealing of electronic consumer products and new energy batteries.

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