A bio-based reactive one-component polyurethane hot melt adhesive with low free isocyanate content and preparation method and application thereof

Abstract

The invention belongs to the field of polyurethane adhesives, and relates to a bio-based reactive one-component polyurethane hot melt adhesive with low free isocyanate content. The bio-based reactive one-component polyurethane hot melt adhesive comprises the following components: bio-based polyol, low-free polyether polyol-based polyurethane prepolymer, low-free polyester polyol-based polyurethane prepolymer, tackifying resin, and catalyst. The free isocyanate content of the low-free polyether polyol-based polyurethane prepolymer is less than 0.1%, and the free isocyanate content of the low-free polyester polyol-based polyurethane prepolymer is less than 0.1%. The bio-based reactive one-component polyurethane hot melt adhesive with low free isocyanate content of the invention has the characteristics of low melt viscosity, long open time, high bonding strength, and low free isocyanate content (<0.1wt%).

Description

Technical Field

[0001] The invention belongs to the field of bio-based polyurethane adhesives, and particularly relates to a bio-based reactive one-component polyurethane hot melt adhesive with low free isocyanate content, and a preparation method and application thereof. Background Art

[0002] Traditional reactive polyurethane hot melt adhesive (PUR) is a polyurethane prepolymer prepared by the reaction of excess isocyanate and polyol. Due to the excess isocyanate, insufficient reaction of polyol and excess isocyanate, and the reaction is blocked under high viscosity, unreacted free isocyanate is often present in the final product. Free isocyanate monomers will vaporize at 85-200°C to form irritating, allergic or toxic substances, which will endanger the health of practitioners. The draft of the restriction of free isocyanates drafted by the European Chemicals Agency (ECHA) shows that when the free isocyanate content in the reactive polyurethane hot melt adhesive is >1wt%, there is a risk of carcinogenesis; if the free isocyanate content is between 0.1-1wt%, there is a risk of inhalation or skin contact; products with a free isocyanate content of more than 0.1wt% will be restricted in use in industry and certain professional fields unless the safety of users can be protected. Products with a free isocyanate content of <0.1wt% are exempt from this regulatory restriction.

[0003] Traditional reactive polyurethane hot melt adhesives are made from petroleum-based chemical raw materials, which are non-renewable raw materials, not sustainable, and not conducive to achieving sustainable development. Producing chemical raw materials with bio-based raw materials is an important way to achieve sustainable development. The research on existing bio-based products has become one of the important research directions in the world's science and technology field, and the development of bio-based products has received more and more attention. Existing bio-based reactive polyurethane hot melt adhesives are mainly obtained by reacting bio-based polyols with excess isocyanate monomers. Although the use of bio-based polyols increases the amount of renewable raw materials and enhances the sustainability of development, the product contains a high content of free isocyanate monomers, which will irritate the human respiratory tract and have a carcinogenic risk, which will endanger the health of related practitioners.

[0004] Among the existing solutions for low-free reactive polyurethane hot melt adhesives, there is a technology that uses low-free isocyanate oligomers with a free isocyanate content of less than 0.1% to replace isocyanate monomers and react with polyols to prepare reactive polyurethane hot melt adhesives with low free isocyanates. For example, in patent US20170002239A, Bayer's low-free MDI oligomer VPLS2397 is used to replace MDI monomers with polyols in an equal molar amount to prepare reactive polyurethane hot melt adhesives. The free MDI monomer of the final product is <0.1wt%, but it does not use bio-based polyols, and is not a bio-based reactive polyurethane hot melt adhesive. Moreover, the bulk strength of the reactive polyurethane hot melt adhesive prepared by using VPLS2397 in an equal molar amount to replace MDI monomers is significantly reduced.

[0005] In summary, the existing technology mainly has the following problems:

[0006] (1) Reactive polyurethane hot melt adhesives are produced from petrol-based raw materials, which are non-renewable and unsustainable.

[0007] (2) Existing bio-based reactive polyurethane hot melt adhesives (PUR) are polyurethane prepolymers prepared by reacting excess isocyanate monomers with bio-based polyols. Due to the excess isocyanate monomers, the final product often contains about 1-4wt% free isocyanate monomers. Although the use of bio-based polyols increases the amount of renewable raw materials and enhances the sustainability of development, the presence of free isocyanate monomers in the product will irritate the human respiratory tract and has a carcinogenic risk, which will endanger the health of related practitioners;

[0008] (3) The low free reactive polyurethane hot melt adhesive prepared by the prior art is a non-biobased product prepared from petroleum-based polyols and isocyanate prepolymers and is not sustainable.

[0009] Therefore, there is an urgent need to develop a bio-based one-component reactive polyurethane hot melt adhesive with low free isocyanate content to meet the application needs of low free bio-based one-component reactive polyurethane hot melt adhesives in the fields of automobiles, new energy, consumer electronics, etc. Summary of the invention

[0010] The first purpose of the present invention is to overcome the problems that the existing traditional reactive polyurethane hot melt adhesive is not environmentally friendly and contains excessive free isocyanate monomers, which endangers the health of practitioners, and the existing low free isocyanate PUR has insufficient bonding performance, and to provide a bio-based reactive one-component polyurethane hot melt adhesive with low free isocyanate content.

[0011] The second object of the present invention is to provide a method for preparing the above-mentioned bio-based reactive one-component polyurethane hot melt adhesive.

[0012] The third object of the present invention is to provide the application of the above-mentioned bio-based reactive one-component polyurethane hot melt adhesive in the bonding and sealing of electronic consumer products, new energy batteries, and automobiles.

[0013] Specifically, the present invention provides a bio-based reactive one-component polyurethane hot melt adhesive with low free isocyanate content, and the bio-based reactive one-component polyurethane hot melt adhesive comprises the following components:

[0014] Bio-based polyols;

[0015] Low free polyether polyol based polyurethane prepolymer;

[0016] Low free polyester polyol based polyurethane prepolymer;

[0017] Tackifying resin;

[0018] catalyst;

[0019] The free isocyanate content of the low-free polyether polyol-based polyurethane prepolymer is less than 0.1 wt%;

[0020] The free isocyanate content of the low free polyester polyol-based polyurethane prepolymer is less than 0.1 wt %.

[0021] The above-mentioned bio-based reactive one-component polyurethane hot melt adhesive with low free isocyanate content, wherein the molar equivalent ratio of hydroxyl groups in the bio-based polyol to isocyanate groups in the low-free polyether polyol-based polyurethane prepolymer is 1:(2.5-4.5).

[0022] The above-mentioned bio-based reactive one-component polyurethane hot melt adhesive with low free isocyanate content, wherein, based on the total weight of the bio-based reactive one-component polyurethane hot melt adhesive, the weight of the low-free polyester polyol-based polyurethane prepolymer accounts for 10-25%, the content of the tackifying resin is 10-20%, and the content of the catalyst is 0.1-1%.

[0023] In the above-mentioned bio-based reactive one-component polyurethane hot melt adhesive with low free isocyanate content, the bio-based polyol is a polyol that can be completely or partially prepared by reacting one or more bio-based monomer raw materials.

[0024] The above-mentioned bio-based reactive one-component polyurethane hot melt adhesive with low free isocyanate content, wherein the low-free polyether polyol-based polyurethane prepolymer is obtained by reacting polyether polyol with polyisocyanate monomers.

[0025] The above-mentioned bio-based reactive one-component polyurethane hot melt adhesive with low free isocyanate content, wherein the low-free polyester polyol-based polyurethane prepolymer is obtained by reacting polyester polyol with polyisocyanate monomers.

[0026] 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.

[0027] The above-mentioned bio-based reactive one-component polyurethane hot melt adhesive with low free isocyanate content, wherein the catalyst is selected from one or more of dibutyltin dilaurate, stannous octoate, triethylamine, diethylenetriamine, triethylenediamine, N-ethylmorpholine and 2,2-dimorpholinodiethyl ether.

[0028] The above-mentioned bio-based reactive one-component polyurethane hot melt adhesive with low free isocyanate content, wherein 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.

[0029] The present invention also provides a method for preparing a bio-based reactive one-component polyurethane hot melt adhesive with low free isocyanate content, the preparation method comprising the following steps:

[0030] S1: Dehydrating the bio-based polyol and the tackifying resin by vacuum stirring at 100-120° C. and 100-200 r / min for 1-5 h, and then cooling to 70-90° C. to obtain a pretreated product;

[0031] S2: adding a low-free polyether polyol-based polyurethane prepolymer and a catalyst to the pretreated product, stirring the mixture in a vacuum at 70-90° C. and at a speed of 100-200 r / min for 1-5 hours to obtain a reaction intermediate product;

[0032] S3: Add low-free polyester polyol-based polyurethane prepolymer to the reaction intermediate product, stir and mix under vacuum at 70-90°C and 100-200 r / min for 30 min-2 h, and discharge the material to obtain a bio-based reactive one-component polyurethane hot melt adhesive with low free isocyanate content, which is then vacuum sealed for storage.

[0033] The present invention also provides a bio-based reactive one-component polyurethane hot melt adhesive with low free isocyanate content for use in bonding and sealing electronic consumer products, automobiles and new energy batteries.

[0034] Since there is a large difference between low-free polyurethane prepolymer (free isocyanate content less than 0.1wt%) and isocyanate monomer, the low-free reactive polyurethane hot melt adhesive prepared by simply reacting the same molar amount of low-free polyurethane prepolymer with polyol has large performance defects, such as high melt viscosity, short open time, low bonding strength, etc. The present invention uses bio-based polyol to first react with a large excess of low-free polyurethane prepolymer (free isocyanate content less than 0.1wt%), and then further adds low-free prepolymer to adjust the melt viscosity, open time, and bonding strength of the system. The present invention uses commercially available bio-based polyols, low-free polyether polyol-based polyurethane prepolymers, low-free polyester polyol-based polyurethane prepolymers, tackifying resins, catalysts, and a process combining chemical reaction and physical blending to prepare a bio-based reactive polyurethane hot melt adhesive with low free isocyanate content. The bio-based reactive polyurethane hot melt adhesive prepared by this method has the characteristics of low melt viscosity, long open time, high bonding strength and low free isocyanate content (<0.1wt%). DETAILED DESCRIPTION

[0035] Examples of the above-mentioned bio-based monomer raw materials include succinic acid, adipic acid, sebacic acid, dimer fatty acids, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, C2-C4 diols, C8-C16 dicarboxylic acids, C6-C12 lactides, castor oil and its derivative polyols, etc.; the sources of the above-mentioned bio-based monomer raw materials may be renewable raw materials such as wheat, straw, corn, soybeans, castor oil, etc.; examples of commercially available bio-based polyols include Evonik's Dynacoll Terra EP481.01, Dynacoll Terra EP480.01, Dynacoll Terra EP480.02, Dynacoll Terra EP424.01, Dynacoll Terra EP424.02, Dynacoll Terra EP413.01, Dynacoll Terra EP413.02, Dynacoll Terra EP413.03, Dynacoll Terra EP413.04, Croda's Priplast 3238, Priplast1838, Velvetol H2000 from Allessa GmbH.

[0036] As the above-mentioned low-free polyether polyol-based polyurethane prepolymer, the free isocyanate content contained in it is less than 0.1wt%. The low-free polyether polyol-based polyurethane prepolymer can be obtained by reacting polyether polyol with polyisocyanate monomers. Wherein, the polyether polyol can be a ring-opening polymer of ethylene glycol, propylene glycol, tetrahydrofuran, 3-methyltetrahydrofuran, or a random copolymer or block copolymer of ethylene glycol, propylene glycol, tetrahydrofuran, 3-methyltetrahydrofuran or its derivatives, or one or more mixtures thereof. The polyisocyanate monomer can be one or more 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. Examples of commercially available low-free polyether polyol-based polyurethane prepolymers include Adiprene LF TE 915, Adiprene LF TE 1050, Adiprene LF TE 980, Adiprene LF TE 330, Adiprene LF TE 365, Adiprene LF TE 440, Adiprene LFM G730, Adiprene LFM G750, Adiprene LFM G600, Adiprene LFM I G600, and Adiprene LFMI G1000 from LANXESS.

[0037] As the above-mentioned low-free polyester polyol-based polyurethane prepolymer, the free isocyanate content contained in it is less than 0.1wt%. The low-free polyester polyol-based polyurethane prepolymer can be obtained by reacting polyester polyol with polyisocyanate monomers. Among them, the polyester polyol can be one or more of polyethylene adipate diol, polypropylene adipate diol, polybutylene adipate diol, polybutylene adipate diol, polybutylene adipate diol, polyneopentyl adipate diol, and polyhexane adipate diol. The polyisocyanate monomer may be one or more 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. Commercial raw materials for low-free polyester polyol-based polyurethane prepolymers include Adiprene LFM S200, Adiprene LFM S300, and Adiprene LFM S500 from LANXESS.

[0038] Examples of the tackifier resin include one or more of thermoplastic acrylic resins, polyurethane resins, amorphous poly-α-olefin resins, rosin resins, rosin pentaerythritol esters, petroleum resins, terpene resins, and EVA resins.

[0039] The catalyst compound may be one or more of dibutyltin dilaurate, stannous octoate, triethylamine, diethylenetriamine, triethylenediamine, N-ethylmorpholine, and 2,2-dimorpholinyl diethyl ether.

[0040] In the following examples and comparative examples, bio-based polyester diols with the brands of Dynacoll Terra EP Terra 481.01 and DynacollTerra EP Terra424.01 were purchased from Evonik; bio-based polyester diols with the brand of Stepanpol PDP70 were purchased from Stepan; bio-based polyether diols with the brand of Velvetol H2000 were purchased from Allessa; bio-based dimer acid polyester diols with the brand of Priplast3238 were purchased from Croda; bio-based dimer acid polyester diols with the brand of 7287 were purchased from Shanghai Xiaoyan Technology Co., Ltd.; bio-based castor oil derivative diols with the brand of Polycin D2000 were purchased from Vertellus; and bio-based castor oil derivative diols with the brand of Adiprene LF TE915, Adiprene LF TE1050, Adiprene LF TE980, Adiprene LF900A, Adiprene LF TE440, Adiprene LF Low free polyurethane prepolymers of G730, Adiprene LF S200, Adiprene LF S300, and Adiprene LF S500 were purchased from LANXESS.

[0041] Example 1

[0042] By weight, 25.4 g (7.258 mmol) of bio-based polyester diol Dynacoll Terra EP481.01 with a number average molecular weight of 3500, 14.5 g (7.258 mmol) of bio-based polyether diol Velvetol H2000 with a number average molecular weight of 2000, and 10 g of polyurethane resin Pearlbond539 were 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, 40.0 g (43.55 mmol) of low-free polyether polyol-based polyurethane prepolymer Adiprene LF TE915 with isocyanate functional groups at both ends and 0.1 g of dibutyltin dilaurate were added, and the reaction was carried out under stirring conditions of 150 r / min for 2 hours; then 10.0 g of low-free polyester polyol-based polyurethane prepolymer Adiprene LFM S300, mixed for 1 hour under stirring conditions of 150 r / min, and then discharged to obtain a bio-based reactive one-component polyurethane hot melt adhesive with low free isocyanate content, which was vacuum sealed and stored.

[0043] Example 2

[0044] By weight, 26.4 g (7.549 mmol) of DynacollTerra EP424.01, a bio-based polyester diol with a number average molecular weight of 3500, 12.1 g (7.549 mmol) of Stepanpol PDP70, a bio-based polyester diol with a number average molecular weight of 1600, and 15.0 g of Pearlbond 523, a polyurethane resin, were added to a reaction bottle, heated to 110°C, and vacuum dehydrated for 2 hours at 150 r / min stirring; then cooled to 80°C, 31.4 g (39.25 mmol) of Adiprene LF TE1050, a low-free polyether polyol-based polyurethane prepolymer with isocyanate functional groups at both ends, and 0.1 g of stannous octoate were added, and the mixture was reacted for 2 hours at 150 r / min stirring; then 15.0 g of Adiprene LFM, a low-free polyester polyol-based polyurethane prepolymer, was added. S200, mixed for 1 hour under stirring conditions of 150 r / min, and then discharged to obtain a bio-based reactive one-component polyurethane hot melt adhesive with low free isocyanate content, which was vacuum sealed and stored.

[0045] Example 3

[0046] By weight, 14.6 g (7.324 mmol) of bio-based dimer acid polyester diol Priplast3238 with a number average molecular weight of 2000, 14.6 g (7.324 mmol) of bio-based castor oil derivative diol Vertelluspolycin D2000 with a number average molecular weight of 2000, and 20.0 g of acrylic resin BR106 were 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, 37.7 g (43.94 mmol) of low-free polyether polyol-based polyurethane prepolymer Adiprene LF TE980 with isocyanate functional groups at both ends and 1.0 g of 2,2-dimorpholinyl diethyl ether were added, and the reaction was reacted for 2 hours under stirring conditions of 150 r / min; then 12.0 g of low-free polyester polyol-based polyurethane prepolymer Adiprene LFMS500, mixed for 1 hour under stirring conditions of 150 r / min, and then discharged to obtain a bio-based reactive one-component polyurethane hot melt adhesive with low free isocyanate content, which was vacuum sealed and stored.

[0047] Example 4

[0048] By weight, 12.6 g (3.597 mmol) of bio-based polyester diol DynacollTerra EP424.01 with a number average molecular weight of 3500, 3.6 g (1.798 mmol) of bio-based polyether diol Velvetol H2000 with a number average molecular weight of 2000, and 11.0 g of polyalphaolefin resin VESTOPLAST 520 were added to a reaction bottle, heated to 110°C, and vacuum dehydrated for 2 hours at 150 r / min stirring conditions; then cooled to 80°C, 47.2 g (21.58 mmol) of low-free polyether polyol-based polyurethane prepolymer Adiprene LF TE440 with isocyanate functional groups at both ends and 0.6 g of 2,2-dimorpholinyl diethyl ether were added, and the reaction was carried out at 150 r / min stirring conditions for 2 hours; then 25.0 g of low-free polyester polyol-based polyurethane prepolymer Adiprene LFMS500, mixed for 1 hour under stirring conditions of 150 r / min, and then discharged to obtain a bio-based reactive one-component polyurethane hot melt adhesive with low free isocyanate content, which was vacuum sealed and stored.

[0049] Comparative Example 1

[0050] By weight, 3.46 g (9.872 mmol) of polyhexanediol adipate diol with a number average molecular weight of 3500, 19.7 g (9.872 mmol) of polyoxypropylene ether diol with a number average molecular weight of 2000, 15.8 g (9.872 mmol) of polyneopentyl phthalate diol with a number average molecular weight of 1600, and 15.0 parts of polyacrylic resin BM751 were added to a reaction bottle, heated to 110°C, and vacuum dehydrated for 2 hours under stirring conditions of 150 r / min; then 14.8 g (59.23 mmol) of 4,4'-diphenylmethane diisocyanate (MDI) and 0.1 parts of dibutyltin dilaurate 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 petroleum-based reactive polyurethane hot melt adhesive, which was vacuum sealed and stored.

[0051] Comparative Example 2

[0052] By weight, 3.46 g (9.872 mmol) of bio-based polyester diol DynacollTerra EP481.01 with a number average molecular weight of 3500, 19.7 g (9.872 mmol) of bio-based polyether diol Velvetol H2000 with a number average molecular weight of 2000, 15.8 g (9.872 mmol) of bio-based polyester diol Stepanpol PDP70 with a number average molecular weight of 1600, and 15.0 parts of polyacrylic resin BM751 were added to a reaction bottle, heated to 110°C, and vacuum dehydrated for 2 hours under stirring conditions of 150 r / min; then 14.8 g (59.23 mmol) of 4,4'-diphenylmethane diisocyanate (MDI) and 0.1 parts of dibutyltin dilaurate were added, and the reaction was carried out under vacuum conditions at a stirring speed of 150 r / min for 2 hours before discharging to obtain a traditional bio-based reactive polyurethane hot melt adhesive, which was vacuum sealed and stored.

[0053] Comparative Example 3

[0054] By weight, 14.7 g (4.197 mmol) of Dynacoll Terra EP481.01, a bio-based polyester diol with a number average molecular weight of 3500, 8.4 g (4.197 mmol) of Velvetol H2000, a bio-based polyether diol with a number average molecular weight of 2000, 6.7 g (4.197 mmol) of Stepanpol PDP70, a bio-based polyester diol with a number average molecular weight of 1600, and 15.0 parts of polyacrylic resin BM751 were added to a reaction bottle, heated to 110° C., and vacuum dehydrated for 2 h under stirring conditions of 150 r / min; then 55.1 g (25.18 mmol) of Adiprene LF, a low-free polyether polyol-based polyurethane prepolymer with isocyanate functional groups at both ends, was added. 900A, 0.1 parts of dibutyltin dilaurate, react at a stirring speed of 150r / min under vacuum conditions for 2h and then discharge the material to obtain a low-free bio-based reactive polyurethane hot melt adhesive prepared by reacting a low-free polyether polyol-based polyurethane prepolymer to replace isocyanate monomer with bio-based polyol, which is then vacuum-sealed and stored.

[0055] Comparative Example 4

[0056] By weight, 12.4 g (3.552 mmol) of Dynacoll Terra EP481.01, a bio-based polyester diol with a number average molecular weight of 3500, 7.1 g (3.552 mmol) of Velvetol H2000, a bio-based polyether diol with a number average molecular weight of 2000, and 5.7 g (3.552 mmol) of Stepanpol PDP70 and 15.0 parts of polyacrylic resin BM751 were added to the reaction bottle, heated to 110°C, and vacuum dehydrated for 2 hours under stirring conditions of 150 r / min; then 59.7 g (21.31 mmol) of low-free polyester polyol-based polyurethane prepolymer Adiprene S300 with isocyanate functional groups at both ends and 0.1 parts of dibutyltin dilaurate were added, and the reaction was carried out under vacuum conditions at a stirring speed of 150 r / min for 2 hours before discharging the material to obtain a low-free bio-based reactive polyurethane hot melt adhesive prepared by reacting the low-free polyester polyol-based polyurethane prepolymer to replace the isocyanate monomer with the bio-based polyol, which was then vacuum sealed for storage.

[0057] Comparative Example 5

[0058] By weight, 20.6 g (5.890 mmol) of DynacollTerra EP481.01, a bio-based polyester diol with a number average molecular weight of 3500, 11.8 g (5.890 mmol) of Velvetol H2000, a bio-based polyether diol with a number average molecular weight of 2000, 9.4 g (5.890 mmol) of Stepanpol PDP70, a bio-based polyester diol with a number average molecular weight of 1600, and 15.0 parts of polyacrylic resin BM751 were added to a reaction bottle, heated to 110°C, and vacuum dehydrated for 2 hours under stirring conditions of 150 r / min; then 4.4 g (17.67 mmol) of 4,4'-diphenylmethane diisocyanate (MDI) and 38.7 g (17.67 mmol) of Adiprene LF, a low-free polyether polyol-based polyurethane prepolymer with isocyanate functional groups at both ends, were added. 900A, 0.1 parts of dibutyltin dilaurate, react at a stirring speed of 150r / min under vacuum conditions for 2h and then discharge to obtain a low-free bio-based reactive polyurethane hot melt adhesive prepared by partially replacing isocyanate monomer with bio-based polyol by low-free polyester polyol-based polyurethane prepolymer, which is then vacuum-sealed for storage.

[0059] Test Case

[0060] The samples of the embodiment and the comparative example were subjected to comparative tests in the following manner:

[0061] (1) Melt viscosity: Place the well-sealed polyurethane hot melt adhesive in a syringe heater at 110°C for 10 minutes. At this time, the hot melt adhesive has become a molten fluid. Quickly pour it into the sleeve of the Brookfield-DV2T viscometer, set the heater temperature at 110°C and keep it for 10 minutes to make the internal temperature of the hot melt adhesive uniform and degas. At a temperature of 110°C, measure the constant temperature melt viscosity of the hot melt adhesive.

[0062] (2) Open time: Use a glue dispensing machine to apply the hot melt adhesive obtained in the examples and comparative examples onto a polycarbonate substrate with a width of about 2 mm. Start timing when the glue dispensing is completed. Lightly touch the glue line with your finger. When the glue line is not sticky, the timing ends. This time is recorded as the open time of the reactive polyurethane hot melt adhesive.

[0063] (3) Bonding strength after 30 min and 24 h: Use a glue dispenser to dispense the hot melt adhesive obtained in the examples and comparative examples at 110°C, and apply a 25 mm*25 mm rectangular glue frame on the polycarbonate substrate with a width of about 1 mm. Then, another polycarbonate substrate is attached to the polycarbonate substrate. After the glue dispensing and lamination is completed, the sample is cured in an environment of 25°C and 50% RH for 30 min and 24 h. Then, a universal material testing machine is used to run the prepared bonding sample along the pulling direction at a speed of 10 mm / min until the sample fails to bond. The maximum force value 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.

[0064] (4) Free isocyanate content: Use a high performance liquid chromatograph (HPLC) with liquid as the mobile phase and a high pressure infusion system to pump the mobile phase into a chromatographic column containing a stationary phase. After the components are separated in the column, they enter the detector for detection to obtain a chromatogram of the test substance. Use the external standard method to quantitatively calculate the content of free isocyanate monomers in the reactive polyurethane hot melt adhesive. Record the chromatograms of the sample to be tested and the standard separately. Calculate the content of free isocyanate in the sample to be tested based on the integrated area of ​​the specific peak on the chromatogram.

[0065] The data obtained from the above test are shown in Table 1 below

[0066] Table 1

[0067]

[0068] It can be seen from Examples 1-4 and Comparative Example 1 that the bio-based reactive polyurethane hot melt adhesive of the present invention has similar melt viscosity, open time, and bonding strength as the traditional petroleum-based reactive polyurethane hot melt adhesive. The present invention can replace the application of traditional petroleum-based reactive polyurethane hot melt adhesive, and the use of bio-based renewable raw materials enhances the sustainability of development. It can be seen from Examples 1-4 and Comparative Examples 1 and 2 that the traditional petroleum-based or bio-based reactive polyurethane hot melt adhesive prepared using isocyanate monomers has a high free isocyanate monomer, while the free isocyanate content of the bio-based reactive polyurethane hot melt adhesive of the present invention is all below 0.1wt%, and the free isocyanate monomer content is significantly reduced, which increases the safety of using bio-based reactive polyurethane hot melt adhesives and avoids harming the health of practitioners. From Examples 1-4 and Comparative Examples 3 and 4, it can be found that the low-free reactive polyurethane hot melt adhesive prepared by simply using low-free polyurethane prepolymers in an equal molar ratio to replace isocyanate monomers in Comparative Examples 3 and 4 has a high melt viscosity, a short open time and a low bonding strength, which is not conducive to practical applications. The low-free reactive polyurethane hot melt adhesive prepared by optimizing the ratio of the addition amount between the low-free prepolymer and the bio-based polyol of the present invention significantly improves the comprehensive performance of the adhesive. From Examples 1-4 and Comparative Example 5, it can be seen that the present invention does not use isocyanate monomers, which significantly reduces the content of free isocyanates. In summary, the bio-based reactive polyurethane hot melt adhesive of the present invention has a low isocyanate monomer content and excellent comprehensive performance.

[0069] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary 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 intent of the present invention.

Claims

1. A bio-based reactive one-component polyurethane hot melt adhesive with low free isocyanate content, characterized in that: The bio-based reactive one-component polyurethane hot melt adhesive comprises the following components: Bio-based polyols; Low free polyether polyol based polyurethane prepolymer; Low free polyester polyol based polyurethane prepolymer; Tackifying resin; catalyst; 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%; The molar equivalent ratio of the hydroxyl group in the bio-based polyol to the isocyanate group in the low-free polyether polyol-based polyurethane prepolymer is 1:(2.5-4.5); Based on the total weight of the bio-based reactive one-component polyurethane hot melt adhesive, the weight of the low-free polyester polyol-based polyurethane prepolymer accounts for 10-25%, the content of the tackifying resin is 10-20%, and the content of the catalyst is 0.1-1%.

2. The bio-based reactive one-component polyurethane hot melt adhesive with low free isocyanate content according to claim 1, characterized in that: The bio-based polyol is a polyol that can be completely or partially prepared by reacting one or more bio-based monomer raw materials.

3. The bio-based reactive one-component polyurethane hot melt adhesive with 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 bio-based reactive one-component polyurethane hot melt adhesive with 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 bio-based reactive one-component polyurethane hot melt adhesive with 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-dimorpholinyl diethyl ether.

6. The bio-based reactive one-component polyurethane hot melt adhesive with 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-alpha-olefin resin, rosin resin, petroleum resin, terpene resin and EVA resin.

7. A method for preparing a bio-based reactive one-component polyurethane hot melt adhesive with low free isocyanate content as claimed in any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: S1: Dehydrating the bio-based polyol and the tackifying resin by vacuum stirring at 100-120° C. and 100-200 r / min for 1-5 h, and then cooling to 70-90° C. to obtain a pretreated product; S2: adding a low-free polyether polyol-based polyurethane prepolymer and a catalyst to the pretreated product, stirring the mixture in a vacuum at 70-90° C. and at a speed of 100-200 r / min for 1-5 hours to obtain a reaction intermediate product; S3: Add low-free polyester polyol-based polyurethane prepolymer to the reaction intermediate product, stir and mix under vacuum at 70-90°C and 100-200 r / min for 30 min-2 h, and discharge the material to obtain a bio-based reactive one-component polyurethane hot melt adhesive with low free isocyanate content, which is then vacuum sealed for storage.

8. An application of a bio-based reactive one-component polyurethane hot melt adhesive with low free isocyanate content as claimed in any one of claims 1 to 6, characterized in that: The bio-based reactive one-component polyurethane hot melt adhesive is used in the bonding and sealing of electronic consumer products, automobiles and new energy batteries.

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