Single-component moisture-curing polyurethane hot melt adhesive and preparation method thereof

Abstract

The invention discloses a single-component moisture-curing polyurethane hot melt adhesive and a preparation method thereof, and mainly through the design of raw materials and proportions, especially the design of specific liquid polyester polyol, the polyurethane hot melt adhesive prepared by the invention has the advantages that on the premise of ensuring the final bonding effect, the moisture-curing effect is good, and the moisture-curing effect is good. Meanwhile, the adhesive has the characteristics of low viscosity, high initial viscosity and soft hand feeling after curing, can be applied to sizing at low temperature, and is very suitable for bonding and compounding application of light and thin / sensitization type high-grade base materials.

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, high initial adhesion, and soft hand feeling after curing, and a preparation method thereof, which is particularly suitable for bonding and laminating thin / dense high-grade fabrics, 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 a polyurethane prepolymer with an isocyanate end group. This kind of adhesive is generally prepared by reacting a polyol with an excessive amount of isocyanate. It is usually solid at room temperature, can be softened into a liquid when heated, and can quickly cool to form a relatively high initial bonding strength after applying the adhesive. Subsequently, the isocyanate reacts with water vapor in the environment to form the final bonding strength. With the continuous development of the one-component moisture-curing polyurethane hot melt adhesive technology, its application fields have gradually expanded and have been gradually refined according to the specific requirements of the application fields.

[0003] The bonding of composite fabrics is a major application field of PUR. According to different sizing processes and composite fabric substrates, adhesives with different systems and performance requirements are required. Among them, for the bonding and laminating of thin substrates such as films and fabrics, the adhesive is required to have a relatively high initial bonding strength to meet the winding step of the substrate on the premise of ensuring the final bonding strength; at the same time, the adhesive is also required to have a relatively low system viscosity, otherwise it will cause film shrinkage and lead to defects in the appearance of the substrate; in addition, the adhesive is also required to have a relatively soft hand feeling after curing to meet the requirements of thin substrates. At present, there is no PUR product on the market that fully meets the above requirements. Patent CN102336883B discloses a preparation method of a reactive polyurethane hot melt adhesive for fabric lamination, which mainly constructs a PUR system with high final bonding strength and resistance to dry / water washing by using a chain extender and an adhesion promoter, but the system viscosity index is not mentioned in the literature, and the system viscosity of currently high-final-bonding PUR is generally relatively large (generally greater than 10000 mPa·s); the industry is also currently researching and developing high-grade PUR products with low viscosity and high initial adhesion. The existing products are mainly suitable for bonding heavy substrates that are not resistant to high temperatures. When they are used for bonding thin high-grade substrates, the hand feeling is too hard; especially when bonding and laminating TPU films and polyester fabrics, the initial bonding strength is significantly reduced.

[0004] Therefore, how to provide a PUR product suitable for bonding and laminating thin high-grade substrates such as TPU films and polyester fabrics, and fully meeting the requirements of low-temperature bonding, low viscosity, high initial adhesion, and soft hand feeling has become a problem to be solved. Summary of the Invention

[0005] The purpose of the present invention is to solve the above technical problems and provide a one-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 the characteristics of low viscosity, high initial adhesion, and soft feel after curing while ensuring the final bonding effect. It can be applied at low temperature and is very suitable for the bonding and composite application of thin and high-end substrates.

[0006] The technical solution adopted by the present invention is: a one-component moisture-curing polyurethane hot melt adhesive, the raw material composition of which, by weight, is specifically: 15-25 parts of polyether polyol; 15-20 parts of amorphous solid polyester polyol; Customized liquid polyester polyol 15-25 parts; 20-30 parts of polyisocyanate; 0-20 parts of tackifying resin; Thermoplastic resin 0-15 parts; Stabilizer 0.05-0.1 part; Antioxidant 0.5-1 part; Catalyst 0.2-0.5 parts; Adhesion promoter 0.5-1 part.

[0007] 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. Preferably, the amorphous solid polyester polyol is selected from one of polyethylene terephthalate diol, polyethylene phthalate diol and polybutylene isophthalate diol.

[0008] The liquid polyester polyol is a homemade or customized mixed acid polyester polyol, and its number average molecular weight is 3000-5000, and the glass transition temperature of the liquid polyester polyol is less than 15°C; and the structural ratio of the aromatic acid in the liquid polyester polyol is 20%-40%; 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 the conventional esterification and polycondensation reactions of aromatic dicarboxylic acids, aliphatic dicarboxylic acids and diols. The aromatic dicarboxylic acid is selected from at least one of terephthalic acid, phthalic acid and isophthalic acid; the aliphatic dicarboxylic acid is selected from one of adipic acid, sebacic acid and succinic acid, and the diol is selected from one of ethylene glycol, propylene glycol, 1,4-butanediol and 1,6-hexanediol; The above-mentioned tackifying resin is selected from one or a combination of acrylic resins, petroleum resins, rosin resins, terpene resins; The above-mentioned thermoplastic resin is selected from one or more of ethylene-vinyl acetate and polyolefin resins; The above-mentioned isocyanate is diphenylmethane diisocyanate; the above-mentioned stabilizer is phosphoric acid; the above-mentioned antioxidant grade is 1010 or 168; the above-mentioned adhesion promoter is one of γ-aminopropyltriethoxysilane, γ-glycidyletheroxypropyltrimethoxysilane, phenylaminomethyltriethoxysilane, phenylaminopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane; The above-mentioned catalyst is one of dibutyltin dilaurate, stannous octoate and tetrabutyl titanate.

[0009] When preparing the above-mentioned one-component moisture-curing polyurethane hot melt adhesive, first, according to a preset ratio, the stabilizer, antioxidant, tackifying resin and thermoplastic resin are put into a vacuum reaction kettle, heated to 130 °C, and mixed and stirred until molten; then polyether polyol, amorphous solid polyester polyol and liquid polyester polyol are added, stirred until molten, and dehydrated under the condition of vacuum ≤ -0.098 MPa for 1 h - 2 h until the water content < 500 ppm; then cooled to 85 °C, isocyanate is added, mixed and stirred evenly, heated to 120 °C, and vacuum reacted for 1 h; then the catalyst and adhesion promoter are added, and vacuum degassing reaction is carried out for 0.5 h - 1 h; finally, it is discharged, sealed and packaged to obtain.

[0010] The innovation and beneficial effects of the present invention are as follows: Through the design and selection of raw materials, especially the structural design of the liquid polyester polyol therein, the PUR prepared by the present invention can be applied for bonding to thin substrates such as TPU films and polyester fabrics at a relatively low temperature, and has the characteristics of low viscosity and high initial adhesion, and the cured product has a soft hand feeling, meeting the bonding requirements of high-grade substrates. Detailed implementation mode

[0011] Next, in combination with the embodiments of the present invention, the technical solutions of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0012] Meanwhile, in each embodiment of the present invention, commercially available products that meet the relevant characteristic requirements known to those skilled in the art, as well as self-made / customized raw materials that meet the relevant characteristic requirements, can be used. Example 1

[0013] Preparation method of a one-component moisture-curing polyurethane hot melt adhesive: First, 14 parts of acrylic resin, 5 parts of polyolefin resin, 0.5 part of antioxidant, and 0.05 part of phosphoric acid are put into a vacuum reaction kettle, heated to 130 °C, and mixed and stirred until melted; then 18 parts of polyoxypropylene glycol, 18 parts of polyhexylene adipate glycol, and a customized liquid polyester polyol (aromatic structure accounts for 30%, Tg is 10 °C) are added, stirred until melted, and dehydrated under the condition of vacuum ≤ -0.098 MPa for 1 h - 2 h until the water content < 500 ppm; then cooled to 85 °C, 25 parts of MDI are added, after mixing and stirring evenly, heated to 120 °C, and reacted under vacuum for 1 h; then 0.5 part of stannous octoate and 0.5 part of γ-aminopropyltriethoxysilane are added, and vacuum degassing reaction is carried out for 0.5 h - 1 h; finally, it is discharged, sealed, and packaged to obtain the product.

[0014] Comparative Example 1

[0015] Compared with Example 1, except for the selection of the liquid polyester polyol being different (using the commercially available brand DYNACOLL 7250, which is a pure aliphatic polyester polyol), the others are the same. Example 2

[0016] Preparation method of a one-component moisture-curing polyurethane hot melt adhesive: First, 15 parts of ethylene-vinyl acetate, 1 part of antioxidant, and 0.1 part of phosphoric acid are put into a vacuum reaction kettle, heated to 130 °C, and mixed and stirred until melted; then 25 parts of polyoxypropylene-ethylene glycol, 15 parts of polyethylene glycol phthalate glycol, and a customized liquid polyester polyol (aromatic structure accounts for 40%, Tg is -5 °C) are added, stirred until melted, and dehydrated under the condition of vacuum ≤ -0.098 MPa for 1 h - 2 h until the water content < 500 ppm; then cooled to 85 °C, 20 parts of MDI are added, after mixing and stirring evenly, heated to 120 °C, and reacted under vacuum for 1 h; then 0.4 part of dibutyltin dilaurate and 1 part of γ-glycidoxypropyltrimethoxysilane are added, and vacuum degassing reaction is carried out for 0.5 h - 1 h; finally, it is discharged, sealed, and packaged to obtain the product. Comparative Example 2

[0017] Compared with Example 2, other conditions are the same except that the proportion of the aromatic structure of the customized liquid polyester polyol is >40% (specifically 50%). Example 3

[0018] Preparation method of one-component moisture-curing polyurethane hot-melt adhesive: First, put 6 parts of terpene resin, 14 parts of ethylene-vinyl acetate, 0.8 part of antioxidant, and 0.08 part of phosphoric acid into a vacuum reactor, heat up to 130°C, and mix and stir until molten; then add 15 parts of polytetrahydrofuran ether glycol, 20 parts of polybutylene terephthalate glycol, and a customized liquid polyester polyol (aromatic structure accounts for 40%, Tg is -12°C), stir until molten, and dehydrate for 1 h - 2 h under the condition of vacuum ≤ -0.098 MPa until the water content < 500 ppm; then cool down to 85°C, add 30 parts of MDI, mix and stir evenly, heat up to 120°C, and react under vacuum for 1 h; then add 0.3 part of dibutyltin dilaurate and 0.8 part of γ-glycidoxypropyltrimethoxysilane, and carry out vacuum degassing reaction for 0.5 h - 1 h; finally, discharge, seal, and package to obtain the product. Comparative Example 3

[0019] Compared with Example 3, other conditions are the same except that the proportion of the aromatic structure of the customized liquid polyester polyol is <20% (specifically 15%). Example 4

[0020] Preparation method of one-component moisture-curing polyurethane hot-melt adhesive: First, put 10 parts of rosin resin, 10 parts of ethylene-vinyl acetate, 0.6 part of antioxidant, and 0.1 part of phosphoric acid into a vacuum reactor, heat up to 130°C, and mix and stir until molten; then add 21 parts of polyethylene glycol, 19 parts of polybutylene terephthalate glycol, and a customized liquid polyester polyol (aromatic structure accounts for 20%, Tg is -24°C), stir until molten, and dehydrate for 1 h - 2 h under the condition of vacuum ≤ -0.098 MPa until the water content < 500 ppm; then cool down to 85°C, add 20 parts of MDI, mix and stir evenly, heat up to 120°C, and react under vacuum for 1 h; then add 0.3 part of tetrabutyl titanate and 0.6 part of γ-mercaptopropyltrimethoxysilane, and carry out vacuum degassing reaction for 0.5 h - 1 h; finally, discharge, seal, and package to obtain the product. Example 5

[0021] Preparation method of one-component moisture-curing polyurethane hot melt adhesive: First, put 20 parts of rosin resin, 0.8 part of antioxidant, and 0.08 part of phosphoric acid into a vacuum reactor, heat up to 130 °C, and mix and stir to melt; then add 23 parts of polyoxypropylene triol, 17 parts of polyethylene glycol adipate, and a customized liquid polyester polyol (aromatic structure accounts for 35%, Tg is -15 °C), stir and melt, and dehydrate for 1 h - 2 h under the condition of vacuum ≤ -0.098 MPa until the water content < 500 ppm; then cool down to 85 °C, add 22 parts of MDI, mix and stir evenly, heat up to 120 °C, and react under vacuum for 1 h; then add 0.5 part of stannous octoate and 0.8 part of γ-mercaptopropyltrimethoxysilane, and carry out vacuum degassing reaction for 0.5 h - 1 h; finally, discharge, seal, and package to obtain the product.

[0022] Performance testing For the products obtained in the above Examples 1 - 5 and Comparative Examples 1 - 3, bond to light / thin or dense substrates, especially the composite bonding of the same batch of TPU films and polyester fabrics. After applying glue using the roller gluing process, conduct test comparisons. Among them, the test standard for viscosity refers to GB / T 2794, the test standard for peel strength refers to GB / T 2791, and the feel after curing is qualitatively determined by the average feeling of at least 5 people.

[0023] The specific performance results are shown in Table 1 below: Example 1 Comparative Example 1 Example 2 Comparative Example 2 Example 3 Comparative Example 3 Example 4 Example 5 Viscosity (mPa.s, 100 °C) 5000 4500 6000 7700 6500 6200 5700 4800 Peel strength (1 min, 25 °C) N / 25 mm 5.4 2.9 5.2 6.2 6 3.8 6.1 5.8 Peel strength (24 h, 25 °C) N / 25 mm <![CDATA 10.9 > <![CDATA 12.8 > <![CDATA 11.8 > <![CDATA 8.7 > <![CDATA 11 > <![CDATA 11.9 > <![CDATA 12.9 > <![CDATA 11.5 > Hand feeling (after curing) <![CDATA Soft > <![CDATA Very soft > <![CDATA Soft > <![CDATA Relatively hard > <![CDATA Soft > <![CDATA Relatively soft > <![CDATA Soft > <![CDATA Soft > Table 1: Performance result test table.

[0024] From Table 1 above, it can be clearly seen that although Comparative Examples 1 - 3 also constructed a low-viscosity system, due to the lack of using self-made / customized liquid polyester polyols that meet specific requirements, there are deficiencies in terms of initial bonding strength, final bonding strength, or feel; while the PUR prepared by Examples 1 - 5 of the present invention, for the bonding of light / thin or dense substrates, especially for the bonding and composite application of TPU films and polyester fabrics, while ensuring the final bonding effect, simultaneously has the characteristics of low viscosity, high initial adhesion, and soft feel after curing, can be applied with glue at low temperature, and is very suitable for the bonding and composite application of light / thin high-grade substrates.

Claims

1. A one-component moisture-curing polyurethane hot melt adhesive, characterized in that, Its raw material composition, by mass parts, includes: 15 - 25 parts of polyether polyol; 15 - 20 parts of amorphous solid polyester polyol; 15 - 25 parts of self - made / customized liquid polyester polyol; 20 - 30 parts of polyisocyanate; 0 - 20 parts of tackifying resin; 0 - 15 parts of thermoplastic resin; 0.05 - 0.1 part of stabilizer; 0.5 - 1 part of antioxidant; 0.2 - 0.5 part of catalyst; 0.5 - 1 part of adhesion promoter; The amorphous solid polyester polyol is an aromatic polyester polyol with a number - average molecular weight of 2000 - 5000 and a glass transition temperature > 20°C; the self - made / customized liquid polyester polyol is a mixed - acid polyester polyol with a number - average molecular weight of 3000 - 5000, a glass transition temperature < 15°C, and the structural proportion of aromatic acid is 20% - 40%.

2. The one-component moisture-curing polyurethane hot melt adhesive according to claim 1, wherein: The solid polyester polyol is selected from one of polyhexamethylene adipate diol, polyethylene terephthalate glycol, and polybutylene terephthalate glycol.

3. The one-component moisture-curing polyurethane hot melt adhesive according to claim 1, wherein: The self - made / customized liquid polyester polyol is obtained by the conventional esterification and polycondensation reactions of aromatic dibasic acids, aliphatic dibasic acids, and diols.

4. The one-component moisture-curing polyurethane hot melt adhesive according to claim 3, wherein: 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 one of adipic acid, sebacic acid, and succinic acid; the diol is selected from one of ethylene glycol, propylene glycol, 1,4 - butanediol, and 1,6 - hexanediol.

5. The one-component moisture-curing polyurethane hot melt adhesive according to claim 1, wherein: The tackifying resin is selected from one of acrylic resin, petroleum resin, rosin resin, and terpene resin; the thermoplastic resin is selected from one of ethylene - vinyl acetate and polyolefin resin; the isocyanate is diphenylmethane diisocyanate; the stabilizer is phosphoric acid; the antioxidant grade is 1010 or 168; the adhesion promoter is selected from one of γ - aminopropyltriethoxysilane, γ - glycidoxypropyltrimethoxysilane, phenylaminomethyltriethoxysilane, phenylaminopropyltrimethoxysilane, γ - methacryloxypropyltrimethoxysilane, γ - mercaptopropyltriethoxysilane, and γ - mercaptopropyltrimethoxysilane; the catalyst is selected from one of dibutyltin dilaurate, stannous octoate, and tetrabutyl titanate.

6. The preparation method of the one-component moisture-curing polyurethane hot melt adhesive according to any one of claims 1-5, characterized in that: First, according to the preset ratio, put the stabilizer, antioxidant, tackifying resin, and thermoplastic resin into a vacuum reactor, heat up to 130°C, and mix and stir until molten; then add polyether polyol, amorphous solid polyester polyol, and liquid polyester polyol, stir until molten, and dehydrate for 1h - 2h under the condition of vacuum ≤ - 0.098MPa until the water content < 500ppm; then cool down to 85°C, add polyisocyanate, mix and stir evenly, heat up to 120°C, and carry out a vacuum reaction for 1h; then add the catalyst and adhesion promoter, and carry out a vacuum defoaming reaction for 0.5h - 1h; finally, discharge, seal, and package to obtain the product.