Single-component solvent-free polyurethane adhesive as well as preparation method and application thereof

Abstract

The invention discloses a single-component solvent-free polyurethane adhesive and a preparation method and application thereof, the single-component solvent-free polyurethane adhesive is composed of a main material and an auxiliary agent, based on 100 wt% of the single-component solvent-free polyurethane adhesive, the main material comprises 40 wt%-65 wt% of polyether polyol, 4 wt%-15 wt% of polyester polyol, 15 wt%-45 wt% of isocyanate and 1 wt%-9 wt% of a chain extender; the auxiliary agent is prepared from 0.1 wt% to 1 wt% of a tackifier, 0.05 wt% to 0.5 wt% of a coupling agent, 0.03 wt% to 0.06 wt% of a catalyst and 0.002 wt% to 0.02 wt% of a stabilizer. When the single-component solvent-free polyurethane adhesive provided by the invention is used for paper-plastic compounding, after the single-component solvent-free polyurethane adhesive is cured for 12 hours in an environment with the temperature of 35 DEG C and the humidity of 70%, paper fibers are completely transferred, and the requirements of good initial adhesion, high bonding strength and high curing speed in the field of paper-plastic compound packaging are met.

Description

Technical Field

[0001] The invention belongs to the technical field of adhesive preparation, and specifically relates to a one-component solvent-free polyurethane adhesive and a preparation method and application thereof. Background Art

[0002] Compared with solvent-based adhesives, one-component solvent-free polyurethane adhesives do not cause pollution caused by solvent emissions, have compact equipment and low cost, and meet the increasingly stringent national environmental protection requirements. At the same time, compared with two-component solvent-free polyurethane adhesives, they have the advantages of not requiring a curing agent, eliminating the glue preparation process, and saving equipment investment. Therefore, one-component solvent-free adhesives have broad market prospects.

[0003] Paper-plastic composite uses paper as the basic structural material in soft packaging materials. Its packaging materials have the characteristics of good foldability, excellent printing performance, and good high temperature resistance. It is generally compounded with PET film, BOPP film, aluminum film and other film materials to solve the problems of poor oxygen barrier and moisture resistance. It is widely used in food packaging, medical packaging, clothing packaging and other industries. In the prior art, there is a single-component reactive hot melt adhesive used in the paper-plastic composite process, and the free NCO group in the adhesive participates in the moisture curing reaction to form adhesion, but there are disadvantages such as slow curing speed, low initial adhesion, and less paper fiber transfer.

[0004] A Chinese patent document with publication number CN109651998A and publication date April 19, 2019 discloses a polyurethane hot melt adhesive used in the paper-plastic composite process. The polyurethane hot melt adhesive is prepared using isocyanate-terminated polyurethane prepolymers, polyisocyanates and other additives. It has good coatability and good later adhesion, but has problems such as slow curing speed, low initial adhesion, and high process requirements. The paper-plastic composite film after roller composite needs to be placed at room temperature for 24 hours or placed in a 50°C drying room for curing for 15 hours before the paper fibers can be transferred to the BOPP film, which cannot meet the existing market demand. Summary of the invention

[0005] The present invention provides a one-component solvent-free polyurethane adhesive and a preparation method and application thereof, aiming to improve the curing speed, initial adhesion and paper fiber transfer amount in a paper-plastic composite scenario.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: The first aspect of the present invention provides a one-component solvent-free polyurethane adhesive for paper-plastic composite, which is composed of a main ingredient and an auxiliary agent, and the total amount of the one-component solvent-free polyurethane adhesive is 100wt%: The main material includes 40wt% to 65wt% of polyether polyol, 4wt% to 15wt% of polyester polyol, 15wt% to 45wt% of isocyanate, and 1wt% to 9wt% of chain extender; The auxiliary agent comprises 0.1wt% to 1wt% of a tackifier, 0.05wt% to 0.5wt% of a coupling agent, 0.03wt% to 0.06wt% of a catalyst, and 0.002wt% to 0.02wt% of a stabilizer.

[0007] In conjunction with the first aspect of the present invention, in some embodiments, the weight average molecular weight of the polyether polyol is 500 to 3000 g / mol; and / or, The weight average molecular weight of the polyester polyol is 500 to 3000 g / mol; and / or, The polyether polyol is at least one of polyethylene oxide diol, polypropylene oxide diol, polytetramethylene oxide diol and polypropylene oxide triol; and / or The polyester polyol is composed of adipic acid-diethylene glycol type polyester and polyether-modified polyester polyol, wherein the proportion of self-made polyether-modified polyester polyol in the polyester polyol is not less than 30%.

[0008] In combination with the first aspect of the present invention, in some embodiments, the polyether-modified polyester polyol is formed by polycondensation of monomer A, monomer B, monomer C, monomer D, and monomer E, wherein: The polyether-modified polyester polyol is prepared by polycondensation of monomer A, monomer B, monomer C, monomer D, and monomer E, wherein: Monomer A is at least one of 1,6-hexanediol, 1,8-octanedioic acid, 1,9-nonanediol, 1,10-decanedioic acid, and 1,11-undecanedioic acid; Monomer B is at least one of succinic anhydride, adipic anhydride, azelaic anhydride, isophthalic anhydride and phthalic anhydride; Monomer C is at least one of polyethylene glycol, polypropylene glycol and polytetrahydrofuran diol; Monomer D is at least one of 2-methyl-1,3-propanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, and 2-butyl-2-ethylpropanediol; The monomer E is at least one of ethylene glycol, 1,4-butanediol and diethylene glycol.

[0009] In some embodiments of the present invention, the polyether-modified polyester polyol is prepared by the following method: After monomer A, monomer B, monomer C, monomer D and monomer E are uniformly mixed, under the protection of inert gas, the temperature is raised to 130-150°C with stirring, and the temperature is kept for 2±0.5h, and then the reaction system is dehydrated; the temperature is further raised to 190-210°C, and the temperature is kept for 2±0.5h; the temperature is further raised to 220-230°C, a polyester catalyst is added, and the temperature is kept to react until the acid value is less than 2mgKOH / g and the hydroxyl value is 40-100mgKOH / g, and then the reaction is terminated to obtain a polyether-modified polyester polyol; The concentration of the polyester catalyst in the reaction solution is 10 to 500 ppm; the polyester catalyst is selected from at least one of stannous octoate, dibutyltin dilaurate, dibutyltin, tetrabutyl titanate, and tetraisopropyl titanate.

[0010] In conjunction with the first aspect of the present invention, in some embodiments, the isocyanate is at least one of diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, polymethylene polyphenyl polyisocyanate; and / or, The chain extender is at least one of ethylene glycol, diethylene glycol, 1,4-butanediol, 1,6-hexanediol, and trimethylolpropane; and / or, The catalyst is at least one of dibutyltin dilaurate, stannous octoate, organic bismuth, triethylenediamine, dimorpholine triethyl ether, and bismorpholinyl diethyl ether; and / or, The tackifier is at least one of terpene resin, modified rosin resin, C5 petroleum resin, and acrylic resin; and / or, The coupling agent is at least one of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane and γ-glycidyloxypropyltrimethoxysilane; wherein γ-glycidyloxypropyltrimethoxysilane accounts for 50-80% of the total mass of the coupling agent; and / or, The stabilizer is at least one of benzoyl chloride, phosphoric acid, tributyl borate and methyl p-toluenesulfonate.

[0011] In combination with the first aspect of the present invention, in some embodiments, the auxiliary agent further includes at least one of an antioxidant and an ultraviolet absorber.

[0012] In conjunction with the first aspect of the present invention, in some embodiments, the antioxidant is at least one of antioxidant 1010, antioxidant 168, and antioxidant 1076; and / or, The ultraviolet absorber is at least one of ultraviolet absorber UV-1 and ultraviolet absorber UV-326.

[0013] In combination with the first aspect of the present invention, in some embodiments, the one-component solvent-free polyurethane adhesive is prepared by the following method: The polyether polyol, polyester polyol and tackifier are uniformly mixed at 80-120° C., and vacuum dehydrated to a water content of less than 0.03 wt %, to obtain a polyol mixture; The polyol mixture is cooled to below 50° C., isocyanate and stabilizer are added, and the mixture is reacted at 85-95° C. until the viscosity of the reaction system is stable, thereby obtaining a first prepolymer system; A chain extender is added to the first prepolymer system, and the reaction is carried out at 90-110° C. until the NCO value of the reaction system is 2wt%-9wt% and the viscosity at 50° C. is 30000 mPa·s-60000 mPa·s, a coupling agent and a catalyst are added, and vacuum degassing is carried out at 100-120° C. to obtain a one-component solvent-free polyurethane adhesive.

[0014] In conjunction with the first aspect of the present invention, in some embodiments, a stabilizer is added while adding the isocyanate; and / or, The coupling agent is added together with an antioxidant and / or a UV absorber.

[0015] A second aspect of the present invention provides a method for preparing a one-component solvent-free polyurethane adhesive, comprising: Prepare raw materials for a one-component solvent-free polyurethane adhesive, the raw materials consisting of a main material and an auxiliary agent, based on the total amount of the one-component solvent-free polyurethane adhesive being 100wt%: the main material includes 40wt% to 65wt% of a polyether polyol, 4wt% to 15wt% of a polyester polyol, 15wt% to 45wt% of an isocyanate, and 1wt% to 9wt% of a chain extender; the auxiliary agent includes 0.1wt% to 1wt% of a tackifier, 0.05wt% to 0.5wt% of a coupling agent, 0.03wt% to 0.06wt% of a catalyst, and 0.002wt% to 0.02wt% of a stabilizer; The polyether polyol, polyester polyol and tackifier are uniformly mixed at 80-120° C., and vacuum dehydrated to a water content of less than 0.03 wt %, to obtain a polyol mixture; The polyol mixture is cooled to below 50° C., isocyanate and stabilizer are added, and the mixture is reacted at 85-95° C. until the viscosity of the reaction system is stable, thereby obtaining a first prepolymer system; A chain extender is added to the first prepolymer system, and the reaction is carried out at 90-110° C. until the NCO value of the reaction system is 2wt%-9wt% and the viscosity at 50° C. is 30000 mPa·s-60000 mPa·s, a coupling agent and a catalyst are added, and vacuum degassing is carried out at 100-120° C. to obtain a one-component solvent-free polyurethane adhesive.

[0016] In conjunction with the second aspect of the present invention, in some embodiments, a stabilizer is added while adding the isocyanate; and / or, The coupling agent is added together with an antioxidant and / or a UV absorber.

[0017] The third aspect of the present invention provides application of the above-mentioned one-component solvent-free polyurethane adhesive in the field of paper-plastic composite.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects: (1) The present invention significantly accelerates the wet curing reaction rate of the isocyanate prepolymer. After aging for 12 hours in an environment of 35°C and 70% humidity, the paper fibers are completely transferred, which significantly shortens the aging time after the paper and plastic substrate are composited.

[0019] (2) The one-component solvent-free polyurethane adhesive of the present invention has good initial adhesion, a rotational viscosity of 30,000 mPa·s to 60,000 mPa·s at 50°C, and a viscosity of 800 to 2,000 mPa·s at 100°C, thereby improving the bonding strength between paper and plastic substrates.

[0020] (3) In the present invention, polyether small molecules and side group small molecule alcohols are introduced to synthesize polyester polyols. While the polar groups provide strong cohesive force, they also ensure good flexibility, which is beneficial to the contact between the adhesive and the bonding substrate and enhances the bonding strength. When applied to the composite scene of paper and plastic substrates, paper fibers are obviously transferred or completely transferred. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 : Flow chart of the preparation method of the one-component solvent-free polyurethane adhesive provided by the present invention. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are 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.

[0023] For simplicity, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form an unambiguous range; and any lower limit can be combined with other lower limits to form an unambiguous range. Similarly, any upper limit can be combined with any other upper limit to form an unambiguous range. In addition, although not explicitly stated, each point or single value between the range endpoints is included in the range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit or with other lower limits or upper limits to form an unambiguous range.

[0024] It should be noted that, in the description of this article, unless otherwise specified, "above", "below" include the number, and the meaning of "multiple" in "one or more" is two or more. Relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of more restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the process, method, article or equipment including the elements.

[0025] In the description of this specification, the description with reference to the terms "any embodiment / method", "one embodiment / method", "some embodiments / methods", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment / method or example are included in at least one embodiment / method or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment / method or example. Moreover, the specific features, structures, materials or characteristics described may be combined in a suitable manner in any one or more embodiments / methods or examples. In addition, those skilled in the art may combine and combine the different embodiments / methods or examples described in this specification and the features of the different embodiments / methods or examples, unless they are contradictory.

[0026] The above summary of the invention of the present invention is not intended to describe each disclosed embodiment or each implementation in the present invention. The following description more specifically illustrates exemplary embodiments. These embodiments can be used in various combinations. In each example, the enumeration is only used as a representative group and should not be interpreted as exhaustive.

[0027] The one-component solvent-free polyurethane adhesive for paper-plastic composite provided by the present invention is composed of a main material and an auxiliary agent, and the total amount of the one-component solvent-free polyurethane adhesive is 100wt%: The main material includes 40wt% to 65wt% of polyether polyol, 4wt% to 15wt% of polyester polyol, 15wt% to 45wt% of isocyanate, and 1wt% to 9wt% of chain extender; The auxiliary agent comprises 0.1wt% to 1wt% of a tackifier, 0.05wt% to 0.5wt% of a coupling agent, 0.03wt% to 0.06wt% of a catalyst, and 0.002wt% to 0.02wt% of a stabilizer.

[0028] The invention controls the adding ratio of polyether polyol, polyester polyol, isocyanate and chain extender to synthesize the isocyanate prepolymer which is suitable for the adhesive in the paper-plastic composite application.

[0029] The invention improves the bonding ability of the adhesive between paper and the surface of a difficult-to-bond substrate by adding modified rosin resin and silane coupling agent, wherein the silane coupling agent can interact with both the hydroxyl group in the inorganic substance and the long molecular chain in the organic polymer to couple the two materials with different properties, and the addition of the tackifier modified rosin resin increases the bonding force of the polymer and improves the initial adhesion.

[0030] The invention accelerates the wet curing reaction speed of the isocyanate prepolymer by adding a catalyst, and can significantly reduce the aging time after the composite between paper and the substrate. The film is manually torn off for detection after 10 minutes of lamination at room temperature, and the results show that the paper fibers have been obviously transferred. After aging for 12 hours in an environment of 35°C and a humidity of 70%, the paper fibers are completely transferred, meeting the needs of the field of paper-plastic composite packaging that require good initial adhesion, high bonding strength and fast curing speed.

[0031] In some embodiments of the present invention, the weight average molecular weight of the polyether polyol is 500-3000 g / mol; and / or the polyether polyol is at least one of polyoxyethylene diol, polyoxypropylene diol, polytetrahydrofuran diol, and polyoxypropylene triol; preferably, the weight average molecular weight of the polyether polyol is 1000-2500 g / mol, and the polyether polyol is at least one of polyoxypropylene diol and polyoxypropylene triol.

[0032] In some embodiments of the present invention, the weight average molecular weight of the polyester polyol is 500-3000 g / mol; the weight average molecular weight of the polyester polyol is preferably 1000-2500 g / mol. The polyester polyol is composed of adipic acid-diethylene glycol type polyester and polyether-modified polyester polyol, wherein the proportion of polyether-modified polyester polyol is not less than 30wt%, preferably, the proportion of polyether-modified polyester polyol in the polyester polyol is 45wt%-85wt%. The polyester polyol of the present invention is composed of adipic acid-diethylene glycol type polyester and polyether-modified polyester polyol, which not only increases the polar groups and the cohesive energy of the adhesive, but also improves the flexibility of the glue through polyether polyol and side diol, thereby enhancing the bonding performance of the adhesive.

[0033] The adipic acid-diethylene glycol type polyester used in the present invention is a conventional commercially available product, preferably the HDPOL-5510 series product of Huide Technology.

[0034] In some embodiments of the present invention, the polyether-modified polyester polyol is formed by polycondensation of monomer A, monomer B, monomer C, monomer D, and monomer E, wherein: Monomer A is at least one of 1,6-hexanedioic acid, 1,8-octanedioic acid, 1,9-zelaic acid, 1,10-sebanic acid, and 1,11-undecanedioic acid; Monomer B is at least one of succinic anhydride, adipic anhydride, azelaic anhydride, isophthalic anhydride and phthalic anhydride; Monomer C is at least one of polyethylene glycol, polypropylene glycol, polyoxypropylene glycol, and polytetramethylene glycol; Monomer D is a pendant diol, selected from at least one of 2-methyl-1,3-propanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, and 2-butyl-2-ethylpropanediol; The monomer E is at least one of ethylene glycol, 1,4-butanediol and diethylene glycol.

[0035] In some embodiments of the present invention, the weight average molecular weight of monomer C is 500-800, preferably 600±50. In an embodiment of the present invention, monomer C is PPG-600.

[0036] In some embodiments of the present invention, the polyether-modified polyester polyol is prepared by the following method: After monomer A, monomer B, monomer C, monomer D and monomer E are uniformly mixed, under the protection of inert gas, the temperature is raised to 130-150°C with stirring, and the temperature is kept for 2±0.5h, and then the reaction system is dehydrated; the temperature is continued to be raised to 190-210°C, and the temperature is kept for 2±0.5h; the temperature is continued to be raised to 220-230°C, a polyester catalyst is added, and the temperature is kept to react until the acid value is less than 2mgKOH / g and the hydroxyl value is 40-100mgKOH / g, and the reaction is terminated to obtain a polyether-modified polyester polyol.

[0037] The concentration of the polyester catalyst in the reaction solution is 10-500 ppm; the polyester catalyst is selected from one or more of stannous octoate, dibutyltin dilaurate, dibutyltin, tetrabutyl titanate, and tetraisopropyl titanate.

[0038] The polyether-modified polyester polyol increases the density and regularity of polar groups in the polyester structure by introducing symmetrical small-molecule short-chain even-numbered diols and monomer B, thereby increasing the cohesion of the adhesive. At the same time, monomer C is introduced and the proportion of monomer D and monomer E is adjusted to control the degree of crystallization of the polyether-modified polyester polyol, improve its compatibility and hydrolysis resistance, and prepare polyester polyols with low viscosity, high reactivity, good compatibility and hydrolysis resistance, thereby broadening the selectivity of raw materials in the development of solvent-free one-component polyurethane adhesives.

[0039] In the embodiment of the present invention, the polyether-modified polyester polyol is prepared by the following method: Based on the total weight of 100 parts by weight of the polyether-modified polyester polyol raw materials, 38.34 parts by weight of adipic acid, 9.20 parts by weight of phthalic anhydride, 3.83 parts by weight of terephthalic acid, 11.50 parts by weight of small molecule polypropylene glycol, 3.83 parts by weight of neopentyl glycol, 19.79 parts by weight of diethylene glycol, 5.98 parts by weight of 2-methyl-1,3-propanediol and 7.52 parts by weight of 1,4-butanediol were added into the reaction kettle with an alcohol-acid ratio of 1.30, and stirring was started while the temperature was raised. Under nitrogen protection, stir and heat to 130-150°C, keep warm for 2±0.5h, remove water from the system; continue to heat to 190-210°C, keep warm for 2±0.5h; continue to heat to 220-230°C, add tetrabutyl titanate, keep warm until the acid value is less than 2mgKOH / g and the hydroxyl value is 40-100mgKOH / g, terminate the reaction, and obtain polyether-modified polyester polyol. Preferably, 2-methyl-1,3-propanediol and 1,4-butanediol account for 25-45% of the total mass of the alcohol, and the small molecule polyether polyol is PPG-600.

[0040] In some embodiments of the present invention, the isocyanate is at least one of diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, and polymethylene polyphenyl polyisocyanate; preferably, the isocyanate is at least one of diphenylmethane diisocyanate and polymethylene polyphenyl polyisocyanate.

[0041] In some embodiments of the present invention, the chain extender is at least one of ethylene glycol, diethylene glycol, 1,4-butanediol, 1,6-hexanediol, and trimethylolpropane; preferably, the chain extender is at least one of diethylene glycol, 1,4-butanediol, and trimethylolpropane.

[0042] In some embodiments of the present invention, the catalyst is at least one of dibutyltin dilaurate, stannous octoate, organic bismuth, triethylenediamine, dimorpholine triethyl ether, and bismorpholinyl diethyl ether; in view of the fact that tertiary amine catalysts have stronger catalytic activity than metal catalysts for the wet curing process of isocyanate, and no heavy metal element tin remains during the composite process, therefore, the preferred catalyst of the present invention is dimorpholine triethyl ether, and its addition amount is 0.04wt% to 0.06wt% of the total mass of the single-component solvent-free polyurethane adhesive.

[0043] In some embodiments of the present invention, the tackifier is at least one of terpene resin, modified rosin resin, C5 petroleum resin, and acrylic resin; preferably, it is modified rosin resin, wherein the addition amount is 0.5wt% to 1wt% of the total mass of the one-component solvent-free polyurethane adhesive, and the modified rosin resin is a highly hydrogenated rosin resin, preferably HMEHR of Guangxi Dinghong Resin Co., Ltd.

[0044] In some embodiments of the present invention, the coupling agent is at least one of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, and γ-glycidyloxypropyltrimethoxysilane; wherein γ-glycidyloxypropyltrimethoxysilane accounts for 50 to 80% of the total mass of the coupling agent.

[0045] In some embodiments of the present invention, the auxiliary agent further includes at least one of an antioxidant and an ultraviolet absorber. The antioxidant can delay the aging of the adhesive, and the ultraviolet absorber can reduce the destructive effect of ultraviolet rays on the adhesive. Both of them can improve the durability of the adhesive and extend the service life of the product.

[0046] In some embodiments of the present invention, the stabilizer is at least one of benzoyl chloride, phosphoric acid, tributyl borate, and methyl p-toluenesulfonate; preferably, the stabilizer is phosphoric acid and / or benzoyl chloride, wherein the amount of the stabilizer added accounts for 0.004wt% to 0.008wt% of the total mass of the one-component solvent-free polyurethane adhesive. The stabilizer can slow down the reaction rate of polyol and isocyanate, and avoid the violent reaction between the two to cause heat accumulation and gelation.

[0047] In some embodiments of the present invention, the antioxidant is at least one of antioxidant 1010, antioxidant 168, and antioxidant 1076; preferably antioxidant 1076, which can improve the long-term thermal stability of the adhesive, wherein the added amount accounts for 0.1wt% to 0.15wt% of the total mass of the single-component solvent-free polyurethane adhesive.

[0048] In some embodiments of the present invention, the ultraviolet absorber is at least one of ultraviolet absorber UV-1 and ultraviolet absorber UV-326; preferably ultraviolet absorber UV-326, wherein the added amount accounts for 1.5wt% to 2wt% of the total mass of the single-component solvent-free polyurethane adhesive.

[0049] In some embodiments of the present invention, the one-component solvent-free polyurethane adhesive is prepared by the following method: The polyether polyol, polyester polyol and tackifier are uniformly mixed at 80-120° C., and vacuum dehydrated to a water content of less than 0.03 wt %, to obtain a polyol mixture; The polyol mixture is cooled to below 50° C., isocyanate and stabilizer are added, and the mixture is reacted at 85-95° C. until the viscosity of the reaction system is stable, thereby obtaining a first prepolymer system; A chain extender is added to the first prepolymer system, and the reaction is carried out at 90-110° C. until the NCO value of the reaction system is 2wt%-9wt% and the viscosity at 50° C. is 30000 mPa·s-60000 mPa·s, a coupling agent and a catalyst are added, and vacuum degassing is carried out at 100-120° C. to obtain a one-component solvent-free polyurethane adhesive.

[0050] The present invention provides a method for preparing a one-component solvent-free polyurethane adhesive, comprising: Prepare raw materials for a one-component solvent-free polyurethane adhesive, the raw materials consisting of a main material and an auxiliary agent, based on the total amount of the one-component solvent-free polyurethane adhesive being 100wt%: the main material comprises 40wt% to 65wt% of a polyether polyol, 4wt% to 15wt% of a polyester polyol, 15wt% to 45wt% of an isocyanate, and 1wt% to 7wt% of a chain extender; the auxiliary agent comprises 0.1wt% to 1wt% of a tackifier, 0.05wt% to 0.5wt% of a coupling agent, 0.03wt% to 0.06wt% of a catalyst, and 0.002wt% to 0.02wt% of a stabilizer; The polyether polyol, polyester polyol and tackifier are uniformly mixed at 80-120° C., and vacuum dehydrated to a water content of less than 0.03 wt %, to obtain a polyol mixture; The polyol mixture is cooled to below 50° C., isocyanate and stabilizer are added, and the mixture is reacted at 85-95° C. until the viscosity of the reaction system is stable, thereby obtaining a first prepolymer system; A chain extender is added to the first prepolymer system, and the reaction is carried out at 90-110° C. until the NCO value of the reaction system is 2wt%-9wt% and the viscosity at 50° C. is 30000 mPa·s-60000 mPa·s, a coupling agent and a catalyst are added, and vacuum degassing is carried out at 100-120° C. to obtain a one-component solvent-free polyurethane adhesive.

[0051] The invention removes water after physically mixing polyether polyol, polyester polyol and tackifier, thereby reducing the reaction between water and isocyanate; cools the polyol mixture to below 50°C and then adds isocyanate and stabilizer, thereby reducing the reaction rate and avoiding gelation caused by excessively high reaction temperature; prepares the first prepolymer first and then performs chain extension reaction, thereby controlling the weight average molecular weight of the final prepolymer; and adjusts the addition amount of the chain extender by detecting the 50°C viscosity of the reaction system, thereby finally controlling the 50°C viscosity to be between 30000mPa·s and 60000mPa·s.

[0052] The present invention can prevent negative paper by controlling the addition amount of the chain extender to adjust the 50°C viscosity of the reaction system to between 30000mPa·s and 60000mPa·s.

[0053] In some embodiments of the present invention, a stabilizer is added simultaneously with the addition of an isocyanate; and / or an antioxidant and / or an ultraviolet absorber is added simultaneously with the addition of a coupling agent.

[0054] The invention provides application of a single-component solvent-free polyurethane adhesive in the field of paper-plastic composites.

[0055] Example The technical scheme of the present invention is described in detail below through examples. If the manufacturer's brand or preparation method is not specified, the raw materials, equipment or solvents used are all common raw materials, equipment or solvents on the market. The adipic acid-diethylene glycol type polyester is the conventional adipic acid-diethylene glycol type polyester of the HDPOL-5510 series produced by Huide Technology, and the modified rosin resin is the HMEHR produced by Guangxi Dinghong Resin Co., Ltd.

[0056] The polyether-modified polyester polyols used in the following examples were prepared by the following method: Based on the total weight of 100 parts by weight of the polyether-modified polyester polyol raw materials, 38.34 parts by weight of adipic acid, 9.20 parts by weight of phthalic anhydride, 3.83 parts by weight of terephthalic acid, 11.50 parts by weight of small molecule polypropylene glycol, 3.83 parts by weight of neopentyl glycol, 19.79 parts by weight of diethylene glycol, 5.98 parts by weight of 2-methyl-1,3-propanediol, and 7.52 parts by weight of 1,4-butanediol were added into the reactor with an alcohol-acid ratio of 1.30, and stirring was started while the temperature was raised. Under nitrogen protection, stir and heat to 130-150°C, keep warm for 2±0.5h, and remove water from the system; continue to heat to 190-210°C, keep warm for 2±0.5h; continue to heat to 220-230°C, add tetrabutyl titanate, and keep warm to react until the acid value is less than 2mgKOH / g and the hydroxyl value is 40-100mgKOH / g, then terminate the reaction to obtain polyether modified polyester polyol.

[0057] Example 1 1) First, 567 g of polyethylene glycol (Mn=1000), 10 g of modified rosin resin (Mn=300), 34 g of adipic acid-diethylene glycol type polyester (Mn=1500), and 28 g of polyether modified polyester polyol (Mn=2000) were weighed and put into a reaction device, the temperature was raised to 100°C, stirring was started, and vacuum was drawn to reduce the water content of the mixture in the reaction device to below 0.03%; 2) Then the temperature was lowered to 50°C, 332g of 4,4′-diphenylmethane diisocyanate and 0.05g of stabilizer phosphoric acid were added, and the reaction temperature was controlled at 90°C for 5h to stabilize the NCO content; 3) Add 30 g of 1,4-butanediol, and control the reaction temperature to react at 100° C. for 3 h, and adjust the viscosity of the polyurethane adhesive at 50° C. to between 30000 mPa·s and 60000 mPa·s; 4) After the reaction is completed, add 2g KH560, 0.5g dimorpholine triethyl ether, 1g antioxidant 1076, and 20g ultraviolet absorber UV-326, continue stirring for 0.5h, and then vacuum degas at 100-120°C for 20min, then discharge and fill to obtain a one-component solvent-free polyurethane adhesive.

[0058] Example 2 1) First, 601g of polyethylene glycol (Mn=1000), 10g of modified rosin resin (Mn=300), 20g of adipic acid-diethylene glycol type polyester (Mn=1500), and 90g of polyether modified polyester polyol (Mn=2000) were weighed and put into a reaction device, and the temperature was raised to 100°C, stirring was started, and vacuum was drawn to reduce the water content of the mixture in the reaction device to below 0.03%; 2) Then the temperature was lowered to 50°C, 200g of 4,4′-diphenylmethane diisocyanate and 122g of 2,4′-diphenylmethane diisocyanate, 0.05g of stabilizer phosphoric acid were added, and the reaction temperature was controlled at 90°C for 5h to stabilize the NCO content; 3) Add 25 g of 1,4-butanediol, and control the reaction temperature to react at 100°C for 3 hours, and adjust the viscosity of the polyurethane adhesive at 50°C to between 30000 mPa·s and 60000 mPa·s; 4) Finally, after the reaction is completed, 1.5 g of KH560 and KH550 (weight ratio is 2:1), 0.5 g of dimorpholine triethyl ether, 1.5 g of antioxidant 168, and 20 g of ultraviolet absorber UV-326 are mixed and added, and stirring is continued for 0.5 h. After vacuum degassing at 100-120 ° C for 20 min, the single-component solvent-free polyurethane adhesive can be discharged and filled.

[0059] Comparative Example 1 1) First, 578g of polyethylene glycol (Mn=1000), 100g of polyethylene triol (Mn=1000), 10g of modified rosin resin (Mn=300), 41g of adipic acid-diethylene glycol type polyester (Mn=1500), and 19g of polyether modified polyester polyol (Mn=2000) were weighed and put into a reaction device, and the temperature was raised to 100°C, stirring was started, and vacuum was drawn to reduce the water content of the mixture in the reaction device to below 0.03%; 2) Then the temperature was lowered to 50°C, 205g of polymethylene polyphenyl polyisocyanate and 0.05g of stabilizer benzoyl chloride were added, and the reaction temperature was controlled at 90°C for 5h to stabilize the NCO content; 3) Add 46 g of trimethylolpropane, and control the reaction temperature to 100° C. for 3 h, and adjust the viscosity of the polyurethane adhesive at 50° C. to between 30,000 mPa·s and 60,000 mPa·s; 4) Finally, after the reaction is completed, add 1.5g KH560, 0.5g dimorpholine triethyl ether, 1.5g antioxidant 168, and 15g ultraviolet absorber UV-326, continue stirring for 0.5h, and then vacuum degas at 100-120°C for 20min, then discharge and fill to obtain a one-component solvent-free polyurethane adhesive.

[0060] Comparative Example 2 1) First, 330 g of polyoxyethylene triol (Mn=1000), 15 g of modified rosin resin (Mn=300), 19 g of adipic acid-diethylene glycol type polyester (Mn=1500), and 29 g of polyether modified polyester polyol (Mn=2000) were weighed and put into a reaction device, the temperature was raised to 100°C, stirring was started, and vacuum was drawn to reduce the water content of the mixture in the reaction device to below 0.03%; 2) Then the temperature was lowered to 50°C, 335 g of 2,4′-diphenylmethane diisocyanate and 0.05 g of stabilizer phosphoric acid were added, and the reaction temperature was controlled at 90°C for 5 hours to stabilize the NCO content; 3) Add 46 g of diethylene glycol and control the reaction temperature to 100° C. for 3 h, and adjust the viscosity of the polyurethane adhesive at 50° C. to between 30,000 mPa·s and 60,000 mPa·s; 4) Finally, after the reaction is completed, add 2g KH560, 0.5g dimorpholine triethyl ether, 1.5g antioxidant 168, and 18g ultraviolet absorber UV-326, continue stirring for 0.5h, and then vacuum degas at 100-120°C for 20min, then discharge and fill to obtain a one-component solvent-free polyurethane adhesive.

[0061] The method for testing the parameters of polyester polyols is as follows: 1) Acid value determination: Tested according to HG / T 2708~1995 standard; 2) Determination of hydroxyl value: Tested according to HG / T 2709-1995 standard; 3) Viscosity measurement: Tested according to GB / T 2794-2013 standard (rotational viscometer method). The method for testing the parameter indicators of paper-plastic composite adhesive is as follows: 1) Determination of moisture content: Tested according to GB / T 6283~2008 standard; 2) Viscosity determination: Tested according to GB / T 2794-2013 standard (rotational viscometer method); 3) NCO determination: Tested according to HG / T 2409-1992 standard.

[0062] Peel strength performance test: Peel strength test (substrate: white kraft paper; film material: BOPP film, thickness 20 μm; aluminum film, thickness 6.5 μm): The one-component solvent-free polyurethane adhesive prepared in Examples 1-2 of the present invention and Comparative Examples 1-2 is roll-coated or blade-coated on the BOPP film or aluminum film by a Nordmec solvent-free laminating machine, and then laminated with the white kraft paper at room temperature. Coating temperature: 90°C, glue amount: 3.5 g / m 2 , the film is manually torn off and tested 10 minutes after the composite is off the machine, and then it enters the aging room for 12 hours to start testing the paper fiber transfer to evaluate the peel strength of the glue.

[0063] The performance index test results of the one-component solvent-free polyurethane adhesive prepared by Examples 1-2 of the present invention and Comparative Examples 1-2 are shown in Table 1 below.

[0064] Table 1

[0065] The one-component solvent-free polyurethane adhesives prepared in the above Examples 1 to 2 can achieve the following performances after being tested on a Nordmec solvent-free laminating machine: initial adhesion: paper fibers have begun to transfer 10 minutes after leaving the machine; bonding strength: the paper fibers can be completely transferred after the composite film is placed at 35°C for 24 hours; 100°C viscosity: 800-2000mPa·s; composite speed: the machine speed can reach 200-400m / min using Nordmec solvent-free laminating equipment; storage stability: >6 months; no bubbling, which can fully meet the requirements of paper-plastic composite packaging customers. Among them, the paper fiber transfer effect of Example 2 is significantly better than that of Example 1, which shows that the increase in the proportion of polyether-modified polyester polyol is conducive to improving the initial adhesion and final bonding strength.

[0066] After the one-component solvent-free polyurethane adhesives prepared in the above comparative examples 1 to 2 were tested on a Nordmec solvent-free laminating machine, the viscosity of comparative example 1 was too high, the machine could not run at high speed, and the laminating speed was only 100 to 150 m / min. The initial adhesion of comparative example 2 was small, and there was a "negative paper" phenomenon. The initial adhesion did not increase significantly after 2 hours off the machine. The film material after the lamination was in an environment of 35°C and 70% humidity, and the amount of paper fiber transfer was small, which could not meet the requirements of customers for paper-plastic composite packaging.

[0067] The above is only a specific embodiment of the present invention, so that those skilled in the art can understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features applied herein.

Claims

1. A one-component solvent-free polyurethane adhesive for paper-plastic composite, consisting of a main ingredient and an auxiliary agent, characterized in that: Based on the total amount of single-component solvent-free polyurethane adhesive as 100wt%: The main material includes 40wt% to 65wt% of polyether polyol, 4wt% to 15wt% of polyester polyol, 15wt% to 45wt% of isocyanate, and 1wt% to 9wt% of chain extender; The auxiliary agent comprises 0.1wt% to 1wt% of a tackifier, 0.05wt% to 0.5wt% of a coupling agent, 0.03wt% to 0.06wt% of a catalyst, and 0.002wt% to 0.02wt% of a stabilizer.

2. The one-component solvent-free polyurethane adhesive according to claim 1, characterized in that: The weight average molecular weight of the polyether polyol is 500 to 3000 g / mol; and / or, The weight average molecular weight of the polyester polyol is 500 to 3000 g / mol; and / or, The polyether polyol is at least one of polyethylene oxide diol, polypropylene oxide diol, polytetramethylene oxide diol and polypropylene oxide triol; and / or The polyester polyol is composed of adipic acid-diethylene glycol type polyester and polyether modified polyester polyol, wherein the proportion of polyether modified polyester polyol in the polyester polyol is not less than 30%.

3. The one-component solvent-free polyurethane adhesive according to claim 2, characterized in that: The polyether-modified polyester polyol is prepared by polycondensation of monomer A, monomer B, monomer C, monomer D, and monomer E, wherein: Monomer A is at least one of 1,6-hexanediol, 1,8-octanedioic acid, 1,9-nonanediol, 1,10-decanedioic acid, and 1,11-undecanedioic acid; Monomer B is at least one of succinic anhydride, adipic anhydride, azelaic anhydride, isophthalic anhydride and phthalic anhydride; Monomer C is at least one of polyethylene glycol, polypropylene glycol, and polytetrahydrofuran diol; Monomer D is at least one of 2-methyl-1,3-propanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, and 2-butyl-2-ethylpropanediol; The monomer E is at least one of ethylene glycol, 1,4-butanediol and diethylene glycol.

4. The one-component solvent-free polyurethane adhesive according to claim 3, characterized in that: The polyether-modified polyester polyol is prepared by the following method: After monomer A, monomer B, monomer C, monomer D and monomer E are uniformly mixed, under the protection of inert gas, the temperature is raised to 130-150°C with stirring, and the temperature is kept for 2±0.5h, and then the reaction system is dehydrated; the temperature is further raised to 190-210°C, and the temperature is kept for 2±0.5h; the temperature is further raised to 220-230°C, a polyester catalyst is added, and the temperature is kept to react until the acid value is less than 2mgKOH / g and the hydroxyl value is 40-100mgKOH / g, and then the reaction is terminated to obtain a polyether-modified polyester polyol; The concentration of the polyester catalyst in the reaction solution is 10 to 500 ppm; the polyester catalyst is selected from at least one of stannous octoate, dibutyltin dilaurate, dibutyltin, tetrabutyl titanate, and tetraisopropyl titanate.

5. The one-component solvent-free polyurethane adhesive according to claim 1, characterized in that: The isocyanate is at least one of diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, and polymethylene polyphenyl polyisocyanate; and / or The chain extender is at least one of ethylene glycol, diethylene glycol, 1,4-butanediol, 1,6-hexanediol, and trimethylolpropane; and / or, The catalyst is at least one of dibutyltin dilaurate, stannous octoate, organic bismuth, triethylenediamine, dimorpholine triethyl ether, and bismorpholinyl diethyl ether; and / or, The tackifier is at least one of terpene resin, modified rosin resin, C5 petroleum resin, and acrylic resin; and / or, The coupling agent is at least one of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane and γ-glycidyloxypropyltrimethoxysilane; wherein γ-glycidyloxypropyltrimethoxysilane accounts for 50% to 80% of the total mass of the coupling agent; and / or, The stabilizer is at least one of benzoyl chloride, phosphoric acid, tributyl borate and methyl p-toluenesulfonate.

6. The one-component solvent-free polyurethane adhesive according to claim 1, characterized in that: The auxiliary agent also includes at least one of an antioxidant and an ultraviolet absorber.

7. The one-component solvent-free polyurethane adhesive according to claim 6, characterized in that: The antioxidant is at least one of antioxidant 1010, antioxidant 168, and antioxidant 1076; and / or, The ultraviolet absorber is at least one of ultraviolet absorber UV-1 and ultraviolet absorber UV-326.

8. A method for preparing a one-component solvent-free polyurethane adhesive, characterized in that: include: Prepare raw materials for a one-component solvent-free polyurethane adhesive, the raw materials consisting of a main material and an auxiliary agent, based on the total amount of the one-component solvent-free polyurethane adhesive being 100wt%: the main material includes 40wt% to 65wt% of a polyether polyol, 4wt% to 15wt% of a polyester polyol, 15wt% to 45wt% of an isocyanate, and 1wt% to 9wt% of a chain extender; the auxiliary agent includes 0.1wt% to 1wt% of a tackifier, 0.05wt% to 0.5wt% of a coupling agent, 0.03wt% to 0.06wt% of a catalyst, and 0.002wt% to 0.02wt% of a stabilizer; The polyether polyol, polyester polyol and tackifier are uniformly mixed at 80-120° C., and vacuum dehydrated to a water content of less than 0.03 wt %, to obtain a polyol mixture; The polyol mixture is cooled to below 50° C., isocyanate and stabilizer are added, and the mixture is reacted at 85-95° C. until the viscosity of the reaction system is stable, thereby obtaining a first prepolymer system; A chain extender is added to the first prepolymer system, and the reaction is carried out at 90-110° C. until the NCO value of the reaction system is 2wt%-9wt% and the viscosity at 50° C. is 30000 mPa·s-60000 mPa·s, a coupling agent and a catalyst are added, and vacuum degassing is carried out at 100-120° C. to obtain a one-component solvent-free polyurethane adhesive.

9. The method for preparing the one-component solvent-free polyurethane adhesive according to claim 8, characterized in that: Adding the stabilizer at the same time as the isocyanate; and / or, The coupling agent is added together with an antioxidant and / or a UV absorber.

10. Use of the one-component solvent-free polyurethane adhesive according to any one of claims 1 to 7 in the field of paper-plastic composites.

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