Low-viscosity high-initial-viscosity single-component moisture-curing polyurethane hot melt adhesive and preparation method thereof

Abstract

The invention discloses a low-viscosity high-initial-viscosity single-component moisture-curing polyurethane hot melt adhesive and a preparation method thereof, a low-viscosity system is constructed mainly through the design of raw materials and proportions, especially the design of specific liquid polyester polyol, so that the PUR prepared by the invention can be used for curing at lower temperature and higher initial viscosity. And the adhesive has higher initial bonding strength and better final bonding effect, and is particularly suitable for low-temperature compounding in the field of heat-labile / heavy substrates.

Description

Technical Field

[0001] The present invention relates to a one-component moisture-curing polyurethane hot melt adhesive and a preparation method thereof, in particular to a one-component moisture-curing polyurethane hot melt adhesive with low viscosity and high initial viscosity and a preparation method thereof, which is particularly suitable for bonding relatively heavy substrate fabrics such as leather / fabric, and belongs to the field of polyurethane adhesives. Background Art

[0002] One-component moisture-curing polyurethane hot melt adhesive (hereinafter referred to as PUR) is usually composed of polyurethane prepolymers with isocyanate as the terminal group. This adhesive is generally made by reacting polyols and excess isocyanate. It is usually solid at room temperature, softens and becomes liquid when heated, and can be quickly cooled after application to form a high initial bonding strength. Subsequently, the isocyanate reacts with the water vapor in the environment to form the final bonding strength. With the continuous development of one-component moisture-curing polyurethane hot melt adhesive technology, its application areas are gradually expanding and are gradually refined according to the specific needs of the application areas.

[0003] The bonding of composite fabrics is a major application area of ​​PUR. Depending on the sizing process and the composite fabric substrate, adhesives with different systems and performance requirements need to be used. Among them, for heavy fabrics such as leather, denim, canvas and chenille, when the substrates are online composited without debonding, a large-area roller coating sizing process is generally used. This requires the adhesive itself to have a lower system viscosity and a better initial adhesion effect, as well as a lower sizing temperature. However, conventional high initial viscosity PUR currently has a higher system viscosity, which is not conducive to specific field applications. For example, patent document CN110564354A discloses a polyurethane adhesive with high initial adhesion for roller coating and a preparation method thereof, which uses 2-3 functional polyester polyols as the main raw materials to prepare PUR, and has a higher initial bonding strength for a variety of materials. However, due to the use of high-functionality polyols, the system viscosity is relatively large, and the wettability to some substrates will be poor. When it is used for bonding relatively heavy substrate fabrics such as leather / fabric, it cannot meet the relevant requirements. Summary of the invention

[0004] The purpose of the present invention is to solve the above-mentioned technical problems and provide a single-component moisture-curing polyurethane hot melt adhesive and a preparation method thereof, so that the polyurethane hot melt adhesive prepared by the present invention has both low viscosity and high initial adhesion properties, can be applied at low temperatures, and is very suitable for applications in the field of bonding and laminating of heat-sensitive thick substrates or substrates that are prone to deformation at high temperatures.

[0005] The technical solution adopted by the present invention is: a low-viscosity, high initial viscosity, single-component, moisture-curing polyurethane hot melt adhesive, the raw material composition of which, by weight, is specifically: 10-20 parts of polyether polyol; 10-20 parts of amorphous solid polyester polyol; 15-20 parts of liquid polyester polyol; 0-25 parts of tackifying resin; Thermoplastic resin 0-25 parts; Polyisocyanate 20-35 parts; Stabilizer 0.01-0.1 parts; Antioxidant 0.1-0.5 parts; Catalyst 0.1-0.3 parts; Adhesion promoter 0.5-1 part.

[0006] The polyether polyol is selected from one of polyoxypropylene glycol, polyoxyethylene glycol, polyoxypropylene-ethylene glycol, polyoxypropylene triol or polytetramethylene ether glycol, and has a number average molecular weight of 1000-5000, preferably 2000-4000; The amorphous solid polyester polyol is an aromatic polyester polyol with a number average molecular weight of 2000-5000 and a glass transition temperature of >20°C. Specifically, the dibasic acid of the amorphous polyester polyol is selected from at least one of terephthalic acid, phthalic acid or isophthalic acid, and the diol is selected from one or more of ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 2-methyl-1,3-propanediol, 1,4-cyclohexanediol, neopentyl glycol, and 3-methyl-1,5-pentanediol; The liquid polyester polyol is a homemade or customized mixed acid polyester polyol, and its number average molecular weight is 2000-5000, and the glass transition temperature of the liquid polyester polyol is less than -10°C; and the structural ratio of the aromatic acid in the liquid polyester polyol is greater than 60%; specifically, the structural ratio of the aromatic acid in the liquid polyester polyol refers to the molar ratio of the aromatic acid in the mixed acid; Furthermore, the liquid polyester polyol is obtained by esterification and polycondensation of aromatic dibasic acid, aliphatic dibasic acid and diol. The aromatic dibasic acid is selected from at least one of terephthalic acid, phthalic acid and isophthalic acid; the aliphatic dibasic acid is selected from at least one of adipic acid, sebacic acid and succinic acid; the diol is selected from one or more of ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 2-methyl-1,3-propanediol, 1,4-cyclohexanediol, neopentyl glycol and 3-methyl-1,5-pentanediol; to prepare the liquid polyester polyol, firstly add the selected aromatic dibasic acid, aliphatic dibasic acid and diol into a reaction kettle; then slowly heat up to 80°C, replace with nitrogen, heat up to 145°C, react at 145°C-185°C for 3h-4h; then react at 185°C-225°C for 6h-7h, wherein when the reaction temperature reaches 215°C, start the vacuum pump until the reaction is completed; then stop the vacuum and stir, then discharge the material; The tackifying resin is selected from acrylic resin, petroleum resin, rosin resin, terpene resin, poly-α-methylstyrene resin, indene - coumarone resin in one or more combinations; The thermoplastic resin is selected from one or more of ethylene vinyl acetate, polyurethane elastomer, high molecular weight polyester resin, and polyolefin resin; The above isocyanate is one of diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, isophorone diisocyanate toluene diisocyanate, hexamethylene diisocyanate, and dicyclohexylmethane diisocyanate; The stabilizer is one of phosphoric acid, polyphosphoric acid, p-toluenesulfonyl isocyanate, sebacic acid, benzoyl chloride, and azelaic acid; The antioxidant is one of antioxidant 1010, antioxidant 168, antioxidant 1035, antioxidant 1076, antioxidant 1135, antioxidant 5057 and triphenyl phosphite; The adhesion promoter is one of γ-aminopropyl triethoxysilane, γ-glycidyloxypropyl trimethoxysilane, benzylaminomethyl triethoxysilane, benzylaminopropyl trimethoxysilane, γ-methacryloxypropyl trimethoxysilane, γ-mercaptopropyl triethoxysilane, and γ-mercaptopropyl trimethoxysilane; The catalyst is one of dibutyltin dilaurate, stannous octoate, tetrabutyl titanate, triethylenediamine, 1,4-dimethylpiperazine, bismorpholinyl diethyl ether, bismorpholinyl triethyl ether and dimorpholine polyoxyethylene ether.

[0007] The present invention also provides a method for preparing a low-viscosity, high initial viscosity, single-component moisture-curing polyurethane hot melt adhesive, which is based on the raw material composition of the low-viscosity, high initial viscosity, single-component moisture-curing polyurethane hot melt adhesive, and comprises the following steps: (1) According to the preset proportion, the stabilizer, antioxidant, tackifying resin and thermoplastic resin are put into a vacuum reactor, the temperature is raised to 130°C, and the mixture is mixed, stirred and melted; (2) Add polyether polyol, amorphous solid polyester polyol and liquid polyester polyol, stir and melt, and dehydrate for 1h-2h under vacuum ≤-0.098MPa; (3) Cool down to 85°C, add isocyanate, mix and stir evenly, then heat to 120°C and react in vacuum for 1 hour; (4) Adding a catalyst and an adhesion promoter, and performing a vacuum degassing reaction for 0.5 h to 1 h; (5) After unloading, sealing and packaging, it is ready.

[0008] The innovation and beneficial effects of the present invention lie in that a low-viscosity system is constructed through the design and selection of raw materials, so that the PUR prepared by the present invention can be glued at a relatively low temperature (<100°C) and has a relatively high initial bonding strength, thereby solving the problem of low-temperature compounding of existing PUR products with heat-sensitive / thick substrates; at the same time, compared with the technical solution of the traditional high initial viscosity system which generally has a relatively high viscosity, the present invention is more convenient for industrial gluing, especially roller gluing, due to the relatively low viscosity of the system, and ensures that the substrate does not come off after pressure is applied; in addition, the raw materials of the system of the present invention are highly compatible, the product is highly transparent and smooth, and has little effect on the appearance of the bonded substrate. DETAILED DESCRIPTION

[0009] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0010] Meanwhile, in each embodiment of the present invention, commercially available products that meet the relevant property requirements and homemade / customized raw materials that meet the relevant property requirements known to those skilled in the art may be used.

[0011] Example 1 A low-viscosity, high-initial-tack, one-component moisture-curing polyurethane hot melt adhesive, the raw material composition of which, by weight, is specifically shown in the following Table 1: raw material Mass fraction Polyether polyol (polyoxypropylene glycol, Mn=1000) 15 Amorphous polyester polyol (Mn=3000, Tg is 26℃) 20 Homemade / customized liquid polyester polyol (Mn=5000, Tg is -30℃, of which aromatic acid structure accounts for 65%) 20 Isocyanate (MDI) 20 Acrylic resin (BR113, Tg 75°C) 25 Adhesion promoter (KH590) 0.5 Stabilizer (phosphoric acid) 0.05 Antioxidant (1010) 0.5 Catalyst (bismorpholinyl diethyl ether) 0.2 Table 1: Composition of raw materials used in Example 1.

[0012] When preparing the low-viscosity, high-initial-tack, single-component moisture-curing polyurethane hot melt adhesive, first add the stabilizer, antioxidant, and tackifying resin into a vacuum reactor, heat to 130°C, and stir and melt; then add polyether polyol, amorphous solid polyester polyol, and homemade / customized liquid polyester polyol, stir and melt, and dehydrate for 1h-2h under vacuum conditions of ≤-0.098MPa until the water content is ≤500ppm; cool the system to 85°C, then add isocyanate and stir and mix evenly, then heat to 120°C and react for 1h; then add a catalyst and an adhesion promoter, and perform a vacuum degassing reaction for 0.5h-1h until the viscosity and NCO% reach the preset targets; the product is obtained after discharging, sealing, and packaging.

[0013] Comparative Example 1 Compared with Example 1, except for the selection of liquid polyester polyol (the commercially available brand Kuraray P-2010 is selected), other raw material compositions and preparation steps are the same.

[0014] Example 2 A low-viscosity, high-initial-tack, one-component moisture-curing polyurethane hot melt adhesive, the raw material composition of which, by weight, is specifically shown in Table 2 below: raw material Mass fraction Polyether polyol (polytetramethylene ether glycol, Mn=2000) 20 Amorphous solid polyester polyol (Mn=5000, Tg is 21℃) 10 Homemade / customized liquid polyester polyol (Mn=4000, Tg is -20℃, of which aromatic acid structure accounts for 70%) 15 Isocyanate (MDI) 30 TPU resin (Elastollan SP9324) 25 Adhesion promoter (KH560) 1 Stabilizer (p-toluenesulfonyl isocyanate) 0.1 Antioxidants (168) 0.1 Catalyst (Stannoic acid) 0.3 Table 2: Composition of raw materials used in Example 2.

[0015] When preparing the low-viscosity, high-initial-tack, single-component moisture-curing polyurethane hot melt adhesive, first add a stabilizer, an antioxidant, and a thermoplastic resin into a vacuum reactor, heat to 130°C, and stir and melt; then add polyether polyol, amorphous solid polyester polyol, and homemade / customized liquid polyester polyol, stir and melt, and dehydrate for 1h-2h under vacuum conditions of ≤-0.098MPa until the water content is ≤500ppm; cool the system to 85°C, then add isocyanate and stir to mix evenly, then heat to 120°C and react for 1h; then add a catalyst and an adhesion promoter, and perform a vacuum degassing reaction for 0.5h-1h until the viscosity and NCO% reach the preset targets; the product is obtained after discharging, sealing, and packaging.

[0016] Comparative Example 2 Compared with Example 2, except that the Tg of the customized liquid polyester polyol is greater than -10°C (specifically -5°C), other raw material compositions and preparation steps are the same.

[0017] Example 3 Compared with Example 2, the difference lies in the raw material composition and ratio design, and the preparation steps are the same. The specific raw material composition and ratio are shown in Table 3 below: raw material Mass fraction Polyether polyol (polyoxypropylene triol, Mn=4000) 10 Amorphous polyester polyol (Mn=2000, Tg is 36℃) 15 Homemade / customized liquid polyester polyol (Mn=2000, Tg is -18℃, of which aromatic acid structure accounts for 70%) 20 Isocyanate (MDI) 35 Polyester resin (DYNACOLL SP1402) 20 Adhesion promoter (KH590) 0.8 Stabilizer (triphenyl phosphite) 0.01 Antioxidant (1010) 0.3 Catalyst (tetrabutyl titanate) 0.1 Table 3: Composition of raw materials used in Example 3.

[0018] Comparative Example 3 Compared with Example 3, except for the selection of liquid polyester polyol (the commercially available brand DYNACOLL7250 is selected), other raw material compositions and preparation steps are the same.

[0019] Example 4 A low-viscosity, high-initial-tack, one-component, moisture-curing polyurethane hot melt adhesive, the raw material composition of which, by weight, is specifically shown in Table 4 below: raw material Mass fraction Polyether polyol (polyoxypropylene-oxyethylene glycol ester, Mn=5000) 18 Amorphous polyester polyol (Mn=3000, Tg is 24℃) 18 Homemade / customized liquid polyester polyol (Mn=4500, Tg is -15℃, of which aromatic acid structure accounts for 80%) 18 Isocyanate (MDI) 26 Acrylic resin (MB-7022) 10 Polyester resin (DYNACOLL SP1402) 10 Adhesion promoter (Silquest A-189) 06 Stabilizer (triphenyl phosphite) 0.08 Antioxidant (1076) 0.2 Catalyst (Dibutyltin dilaurate) 0.2 Table 4: Composition of raw materials used in Example 4.

[0020] When preparing the low-viscosity, high-initial-tack, single-component moisture-curing polyurethane hot melt adhesive, first add a stabilizer, an antioxidant, a tackifying resin, and a thermoplastic resin into a vacuum reactor, heat to 130°C, and stir and melt; then add polyether polyol, amorphous solid polyester polyol, and homemade / customized liquid polyester polyol, stir and melt, and dehydrate for 1h-2h under vacuum conditions of ≤-0.098MPa until the water content is ≤500ppm; cool the system to 85°C, then add isocyanate and stir to mix evenly, then heat to 120°C and react for 1h; then add a catalyst and an adhesion promoter, and perform a vacuum degassing reaction for 0.5h-1h until the viscosity and NCO% reach the preset targets; the product is obtained after discharging, sealing, and packaging.

[0021] Example 5 Compared with Example 4, the difference lies in the raw material composition and ratio design, and the preparation steps are the same. The specific raw material composition and ratio are shown in Table 5 below: raw material Mass fraction Polyether polyol (polyoxypropylene triol, Mn=4000) 15 Amorphous polyester polyol (Mn=4000, Tg is 26℃) 15 Homemade / customized liquid polyester polyol (Mn=5000, Tg is -15℃, of which aromatic acid structure accounts for 88%) 15 Isocyanate (MDI) 30 Acrylic resin (BR113) 15 Polyester resin (DYNACOLL SP1402) 20 Adhesion promoter (KH590) 0.6 Stabilizer (triphenyl phosphite) 0.04 Antioxidant (1010) 0.3 Catalyst (tetrabutyl titanate) 0.1 Table 5: Composition of raw materials used in Example 5.

[0022] Performance Testing The products obtained in the above-mentioned Examples 1-5 and Comparative Examples 1-3 were used for bonding thicker composite fabrics, especially for bonding leather and ordinary polyester fabrics from the same batch, and were tested and compared after being sizing by roller gluing. The test standard for viscosity was referenced to GB / T 2794, and the test standard for peel strength was referenced to GB / T 2791. The specific performance results are shown in Table 6 below.

[0023] Example 1 Comparative Example 1 Example 2 Comparative Example 2 Example 3 Comparative Example 3 Example 4 Example 5 Viscosity (mPa.s, 100℃) 4000 3400 4360 5100 4500 4400 4760 5000 Peel strength (1min, 25℃) N / 25mm 6.9 4.3 7.3 8.2 7.6 4.7 7.3 7.6 Peel strength (24h, 25℃) N / 25mm <![CDATA[ 15.2 ]]> <![CDATA[ 16.9 ]]> <![CDATA[ 16.1 ]]> <![CDATA[ 8.3 ]]> <![CDATA[ 17.8 ]]> <![CDATA[ 16.3 ]]> <![CDATA[ 11.8 ]]> <![CDATA[ 11.2 ]]> Table 6: Performance test results.

[0024] From Table 6 above, it can be clearly seen that although Comparative Examples 1-3 also have relatively low viscosity, Comparative Examples 1 and 3, due to not selecting liquid polyester polyols with specific requirements, although they also have good final adhesion strength, the initial adhesion strength is too low (<5N / 25mm), which cannot meet the actual needs; and Comparative Example 2, due to selecting liquid polyester polyols with slightly higher Tg, although the product has a higher initial adhesion strength, it seriously affects the final adhesion effect, and the final adhesion strength is <10N / 25mm, which cannot meet the requirements.

[0025] The PUR prepared by Examples 1-5 of the present invention not only constructs a low-viscosity system for easy gluing, but also allows the product to be glued at a relatively low temperature (<100°C), thereby solving the bonding and lamination problem of heat-sensitive substrates. When used in leather / fabric composite bonding, it also has a relatively high initial bonding strength (≥6.9N / 25mm) and a relatively good final bonding effect (≥11.2N / 25mm), thereby improving the bonding effect on thick and heavy substrates.

Claims

1. A low-viscosity, high initial-adhesion, one-component moisture-curing polyurethane hot melt adhesive, characterized in that: The raw material composition of the single-component moisture-curing polyurethane hot melt adhesive is specifically as follows, by weight: 10-20 parts of polyether polyol; 10-20 parts of amorphous solid polyester polyol; 15-20 parts of liquid polyester polyol; 0-25 parts of tackifying resin; Thermoplastic resin 0-25 parts; Polyisocyanate 20-35 parts; Stabilizer 0.01-0.1 parts; Antioxidant 0.1-0.5 parts; Catalyst 0.1-0.3 parts; Adhesion promoter 0.5-1 part; Wherein, the amorphous solid polyester polyol is an aromatic polyester polyol, and its number average molecular weight is 2000-5000, and its glass transition temperature is greater than 20°C; The liquid polyester polyol is a mixed acid polyester polyol obtained by esterification and polycondensation of aromatic dibasic acid, aliphatic dibasic acid and diol; its number average molecular weight is 2000-5000, and its glass transition temperature is less than -10°C; and the structural proportion of aromatic acid in the liquid polyester polyol is greater than 60%.

2. The low-viscosity, high initial viscosity, one-component moisture-curing polyurethane hot melt adhesive according to claim 1, characterized in that: In the liquid polyester polyol, the structural ratio of the aromatic acid is the molar ratio of the aromatic acid in the mixed acid.

3. The low-viscosity, high initial viscosity, one-component moisture-curing polyurethane hot melt adhesive according to claim 1, characterized in that: The polyether polyol is selected from one of polyoxypropylene glycol, polyoxyethylene glycol, polyoxypropylene-ethylene glycol, polyoxypropylene triol or polytetramethylene glycol, and has a number average molecular weight of 1000-5000.

4. The low-viscosity, high initial viscosity, one-component moisture-curing polyurethane hot melt adhesive according to claim 3, characterized in that: The number average molecular weight of the polyether polyol is 2000-4000.

5. The low-viscosity, high initial-adhesion, one-component moisture-curing polyurethane hot melt adhesive according to claim 1, characterized in that: The dibasic acid of the amorphous solid polyester polyol is selected from at least one of terephthalic acid, phthalic acid or isophthalic acid, and the diol is selected from one or more of ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 2-methyl-1,3-propanediol, 1,4-cyclohexanediol, neopentyl glycol, and 3-methyl-1,5-pentanediol.

6. The low-viscosity, high initial viscosity, one-component moisture-curing polyurethane hot melt adhesive according to claim 1, characterized in that: The aromatic dibasic acid of the liquid polyester is selected from at least one of terephthalic acid, phthalic anhydride and isophthalic acid; the aliphatic dibasic acid is selected from at least one of adipic acid, sebacic acid and succinic acid; the diol is selected from one or more of ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 2-methyl-1,3-propanediol, 1,4-cyclohexanediol, neopentyl glycol and 3-methyl-1,5-pentanediol.

7. The method for preparing a low-viscosity, high initial viscosity, one-component moisture-curable polyurethane hot melt adhesive according to any one of claims 1 to 6, characterized in that: The steps include: (1) According to the preset proportion, the stabilizer, antioxidant, tackifying resin and thermoplastic resin are put into a vacuum reactor, the temperature is raised to 130°C, and the mixture is mixed, stirred and melted; (2) Add polyether polyol, amorphous solid polyester polyol and liquid polyester polyol, stir and melt, and dehydrate for 1h-2h under vacuum ≤-0.098MPa; (3) Cool down to 85°C, add isocyanate, mix and stir evenly, then heat to 120°C and react in vacuum for 1 hour; (4) Adding a catalyst and an adhesion promoter, and performing a vacuum degassing reaction for 0.5 h to 1 h; (5) After unloading, sealing and packaging, it is ready.