Waterborne polyurethane dispersion liquid and preparation method thereof

Abstract

The invention relates to a waterborne polyurethane dispersion liquid, which is characterized by being prepared from the following raw materials in percentage by weight: 5 to 25 percent of diisocyanate, 5 to 20 percent of polymer dihydric alcohol, 1 to 5 percent of hydrophilic chain extender, 1 to 10 percent of micromolecular polyol, 0.2 to 2 percent of neutralizer, 0.01 to 0.1 percent of catalyst, 0.3 to 3 percent of amine chain extender, 5 to 15 percent of alkylene monomer, 1 to 5 percent of methacrylic acid higher aliphatic ester, 0.3 to 3 percent of ethylene-acrylic acid copolymer resin and 0.02 to 0.4 percent of initiator. 0.2-2% of organic bentonite and 40-70% of water. The invention also provides a preparation method of the waterborne polyurethane dispersion liquid. The waterborne polyurethane dispersion liquid disclosed by the invention is used for manufacturing waterborne coating paper (coated on raw paper), and an obtained paper product has good water resistance (low water absorption), anti-leakage performance, grease resistance, heat sealing strength, blocking resistance and recoverability.

Description

Technical Field

[0001] The invention relates to a coating composition, in particular to an aqueous polyurethane dispersion and a preparation method thereof. Background Art

[0002] Paper, plastic, metal and glass are the four major traditional packaging materials, among which paper packaging and plastic packaging occupy a dominant position. Since plastic packaging materials take decades or even hundreds of years to degrade, plastic pollution has become one of the most serious environmental problems in the world. Paper products are easy to re-pulp, recycle, degrade and compost, and are an environmentally friendly packaging material. The implementation of global plastic ban policies in recent years will bring new demands for plastic substitutes in many fields such as catering takeaway, food, medicine and daily chemicals, electronic appliances, industrial product packaging, e-commerce express delivery, supermarket cold chain, etc., among which paper products and biodegradable products are the main ones. In the future, the demand for paper packaging products will increase significantly, and "replacing plastic with paper" will become the backbone of plastic substitution.

[0003] In order to obtain barrier properties against water, oil, etc., as well as heat-seal properties, it is traditionally necessary to coat the base paper with a layer of plastic film (coating). Currently, the vast majority of the paper on the market is polyethylene (PE) coating. Paper coated with polyethylene coating is extremely strong, and it cannot be soaked in water, and the pulp cannot be beaten out. It is difficult to separate the polyethylene coating from the paper. Due to the presence of this layer of polyethylene plastic film, the pulp cannot be successfully extracted during the recycling process, and the recycling fails. Therefore, polyethylene coating products have the disadvantages of being non-degradable, non-repulpable, and difficult to recycle.

[0004] In response to the industry's green and environmental protection needs, foreign companies have developed biodegradable plastic coatings and water-based coating products.

[0005] Degradable plastic coating products are degradable plastics (PLA or Bio-PBS) coated on base paper. They are degradable and environmentally friendly products. However, the production technology threshold and cost of degradable plastics are high, which hinders their promotion and application. Moreover, the so-called degradable plastics need to be completely degraded under relatively harsh conditions (temperature, degradable bacteria, etc.). If the degradation of degradable plastics is not carried out under certain conditions, their degradation rate is no different from that of ordinary plastics. Many degradable plastics are not only unable to achieve complete biodegradation, but may also have negative effects on the environment and human health. Therefore, in March 2019, the European Union formally passed a number of proposals on disposable plastic products, including the ban on oxo-degradable plastics products; in the same year, the European Parliament passed the European Union Directive (EU) 2019 / 904, which included a ban on the circulation of disposable plastic products made of oxo-degradable plastics in the markets of EU member states.

[0006] Water-based coating products are new products developed in recent years to replace traditional coated paper. However, the water-based coating products on the market currently generally have deficiencies in heat sealing strength, barrier properties, anti-adhesion, and recyclability. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide an aqueous polyurethane dispersion and a preparation method thereof, wherein the aqueous polyurethane dispersion is used to manufacture aqueous coated paper (coated on base paper), and the obtained paper product has good water resistance (low water absorption), anti-leakage performance, grease resistance, heat sealing strength, anti-adhesion and recyclability. The technical scheme adopted is as follows: A waterborne polyurethane dispersion, characterized in that it is made of the following raw materials in weight ratio: 5-25% of diisocyanate, 5-20% of polymer diol, 1-5% of hydrophilic chain extender, 1-10% of small molecule polyol, 0.2-2% of neutralizer, 0.01-0.1% of catalyst, 0.3-3% of amine chain extender, 5-15% of olefin monomer, 1-5% of methacrylate higher fatty ester, 0.3-3% of ethylene-acrylic acid copolymer resin, 0.02-0.4% of initiator, 0.2-2% of organic bentonite and 40-70% of water.

[0008] The water used as the dispersant is preferably deionized water.

[0009] The above-mentioned diisocyanate is used as the hard segment of the aqueous polyurethane dispersion to impart strength, temperature resistance and other properties to the coating. Preferably, the above-mentioned diisocyanate is one of isophorone diisocyanate (IPDI), 4,4′-dicyclohexylmethane diisocyanate (HMDI), hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), meta-xylylene diisocyanate (m-XDI), hydrogenated xylylene diisocyanate (H-XDI) and diphenylmethane diisocyanate (MDI) or a combination of more than one thereof.

[0010] More preferably, the diisocyanate is one or a combination of 4,4′-dicyclohexylmethane diisocyanate (HMDI), hexamethylene diisocyanate (HDI) and hydrogenated xylylene diisocyanate (H-XDI). H-XDI, HMDI and HDI can reduce the reaction rate of polyurethane while ensuring the consistency of prepolymer molecular weight and regularity of molecular structure.

[0011] The polymer diol is used as a soft segment component of the aqueous polyurethane dispersion to impart flexibility, adhesion, solvent resistance, and heat sealability to the coating. Preferably, the polymer diol is a bifunctional polyester diol or polyether diol, such as polycarbonate diol, polycaprolactone diol, 1,4-butylene succinate, hexamethylene glycol polyoxalate, polyadipate-1,4-butylene glycol, polytetrahydrofuran ether diol, polyoxyethylene ether diol, or polyethylene glycol. Preferably, the molecular weight of the polymer diol is 500-3000. More preferably, the polymer diol is crystalline polytetrahydrofuran ether diol or polycarbonate diol, and its molecular weight Mn (number average molecular weight) is 3000.

[0012] Preferably, the hydrophilic chain extender is 2,2-dimethylol propionic acid or 2,2-dimethylol butyric acid. The hydrophilic chain extender introduces hydrophilic groups into the molecular chains of the polyurethane prepolymer molecules, turning the polyurethane molecules into internal emulsifiers with hydrophilic and lipophilic properties.

[0013] The above-mentioned small molecule polyol is a hard segment component of the aqueous polyurethane dispersion, which is used to increase the polymer molecular weight and hard segment content, and improve the barrier properties of the coating. Preferably, the above-mentioned small molecule polyol is one of ethylene glycol, neopentyl glycol, diethylene glycol, 1,4-butanediol, bisphenol A, hydrogenated bisphenol A, hydroquinone dihydroxyethyl ether and 1,6-hexanediol, or a combination of multiple thereof. More preferably, the above-mentioned small molecule polyol is a symmetrical diol, such as ethylene glycol and 1,4-butanediol.

[0014] Preferably, the neutralizing agent is triethylamine, aqueous ammonia, sodium hydroxide, potassium hydroxide, dimethylethanolamine or triethanolamine.

[0015] The catalyst is used to catalyze the reaction of isocyanate and polyester diol, small molecule chain extender, etc., so as to make the reaction more complete. The catalyst can be an organic bismuth catalyst, dibutyltin dilaurate, stannous octoate or potassium isooctanoate catalyst; for safety and environmental protection, an organic bismuth catalyst is preferred.

[0016] The above-mentioned amine chain extender is added to the reaction material after emulsification to increase the polymer molecular weight and hard segment content, improve the coating cohesion, and improve the barrier performance of the coating. Preferably, the above-mentioned amine chain extender is ethylenediamine, isophoronediamine, N-(2-aminoethyl)ethanolamine, dicyclohexylmethanediamine or hexamethylenediamine; more preferably, ethylenediamine.

[0017] The above-mentioned olefin monomers are modified monomers and reactive solvents, which can reduce the viscosity of the prepolymer, dissolve organic bentonite, and improve the heat sealing, anti-adhesion and barrier properties of the coating. Olefin monomers mainly include vinyl monomers and propylene monomers, such as methyl methacrylate, methyl acrylate, butyl acrylate, butyl methacrylate, dibutyl maleate, 2-ethylhexyl acrylate, styrene, vinyl trimethoxysilane, versatate, 4-tert-butylcyclohexane acrylate, vinyl acetate, dimethyl maleate, diethyl maleate, etc. Preferred are olefin monomers with good film-forming properties, weak polarity or non-polarity, such as styrene, dimethyl maleate, diethyl maleate, dibutyl maleate, etc.

[0018] The above-mentioned higher fatty methacrylate is a reactive methacrylate monomer, which can improve the water barrier performance of the product application and improve the anti-adhesion property. The higher fatty methacrylate is a methacrylate with 12 or more alkyl carbon atoms, such as octadecyl methacrylate, dodecyl methacrylate, hexadecyl methacrylate, etc., preferably octadecyl methacrylate.

[0019] The ethylene-acrylic acid copolymer resin can improve the barrier properties, solvent resistance and heat sealability of the coating. The ethylene-acrylic acid copolymer resin can be an ethylene-acrylic acid copolymer resin with an acrylic acid content of 5-22%, preferably an ethylene-acrylic acid copolymer resin with an acrylic acid content of 18-22%, such as Dow 5990, DuPont 2022, DuPont 5980, etc.

[0020] The initiator is a polymerization catalyst of olefin monomers and methacrylate esters. The metal peroxide initiator is used to initiate polymerization of the olefin monomers under the same activation energy, and the olefin monomers in the molecular chain are arranged neatly, thereby improving the comprehensive application performance of the coating. The initiator can be sodium persulfate, ammonium persulfate or potassium persulfate, preferably potassium persulfate.

[0021] The above-mentioned organic bentonite is a quaternary ammonium salt modified bentonite, which can further improve the barrier property and anti-adhesion property of the coating and increase the strength and stiffness of paper products, such as the existing brands of Walter organic bentonite BP-186 and BP-183.

[0022] The present invention also provides a method for preparing the aqueous polyurethane dispersion, which is characterized by comprising the following steps: (1) The following raw materials are prepared by weight: 5-25% diisocyanate, 5-20% polymer diol, 1-5% hydrophilic chain extender, 1-10% small molecule polyol, 0.2-2% neutralizer, 0.01-0.1% catalyst, 0.3-3% amine chain extender, 5-15% olefin monomer, 1-5% methacrylate higher fatty ester, 0.3-3% ethylene-acrylic acid copolymer resin, 0.02-0.4% initiator, 0.2-2% organic bentonite, and 40-70% water; The water is divided into three parts: the first part of water accounts for 8-15% of the total water volume, and is used to dissolve the amine chain extender to obtain an amine chain extender aqueous solution for standby use; the second part of water accounts for 3-8% of the total water volume, and is used to dissolve the initiator to obtain an initiator aqueous solution for standby use; the remaining water is used as the third part of water, and the third part of water is used to dissolve the ethylene-acrylic acid copolymer resin, and a neutralizer accounting for 15-25% of the total amount of the neutralizer is added during the dissolution, and the neutralizer and the ethylene-acrylic acid copolymer resin are added to the water and then heated to 70-90° C., stirred until the ethylene-acrylic acid copolymer resin is completely dissolved, and then cooled to 20-30° C. to obtain an ethylene-acrylic acid copolymer resin solution for standby use; Adding organic bentonite to the olefin-based monomer and stirring until the organic bentonite is completely dissolved to obtain an organic bentonite olefin-based monomer mixture for standby use; The diisocyanate is divided into two parts, the first part of the diisocyanate accounts for 20-40% of the total diisocyanate, and the second part of the diisocyanate accounts for 60-80% of the total diisocyanate; (2) Adding the polymer diol into a dehydration reactor equipped with a stirrer and a vacuum dehydration system to remove the water contained therein; (3) Add the dehydrated polymer diol and the hydrophilic chain extender into a polymerization reactor equipped with a stirrer, then dropwise add the first portion of diisocyanate while stirring, and heat to 70-90° C. for reaction for 2-4 hours; (4) Adjust the temperature in the polymerization reactor to 50-65°C, and then add the second part of isocyanate; then add the small molecule polyol dropwise while stirring, and control the temperature during the addition process to be between 70-80°C; keep the temperature at 70-80°C for 1-2 hours after the addition of the small molecule polyol; then add the catalyst and react at 70-80°C for 1-2 hours; then add the organic bentonite olefin monomer mixture and stir evenly; (5) Adjust the temperature in the polymerization reactor to 55-65°C, add methacrylate, then cool to 40-50°C, add the remaining neutralizer, and stir for 15-25 minutes; (6) adjusting the temperature in the polymerization reactor to 40-50° C. and setting the stirring speed of the polymerization reactor to 1000-3000 rpm, adding the ethylene-acrylic acid copolymer resin solution into the polymerization reactor within 20-30 minutes, emulsifying for 10-20 minutes, and then dripping the amine chain extender aqueous solution, stirring for 20-40 minutes, to obtain a polyurethane pre-emulsion; (7) Adjust the temperature in the polymerization reactor to 70-75°C, then add the initiator aqueous solution to the polyurethane pre-emulsion, heat to 80-85°C after the addition is complete, keep warm for 2-3 hours while stirring, then cool to 20-30°C, filter the material, and obtain the desired aqueous polyurethane dispersion.

[0023] In the preferred step (2), the polymer diol is added to a dehydration reaction kettle equipped with a stirrer and a vacuum dehydration system, heated to 110-120°C while stirring, and water is pumped out for 1-3 hours at a vacuum degree of -0.01 MPa to -0.02 MPa to remove the water contained therein.

[0024] Preferably, in step (7), the stirring speed is 100-500 rpm.

[0025] The waterborne polyurethane dispersion synthesized by the above process is a waterborne coating with a core-shell structure.

[0026] The aqueous polyurethane dispersion of the present invention is used to manufacture aqueous coated paper with heat-sealing and barrier properties to replace coated paper. The aqueous coated paper has the advantages of good water resistance (low water absorption), grease resistance, barrier property (anti-leakage property), heat-sealing property, anti-adhesion property and recyclability.

[0027] The dry coating amount of the aqueous polyurethane dispersion on paper is reduced to less than 40% of the thickness of the PE coating, so that the performance requirements of traditional coated paper products such as water resistance, leakage prevention, heat sealability, anti-adhesion, high heat seal strength, etc. are achieved, and the barrier property problem of paper packaging is solved. In addition, the water-based coated paper manufactured by using the aqueous polyurethane dispersion of the present invention has the advantages of safety, hygiene, repulpability and recyclability. DETAILED DESCRIPTION

[0028] Example 1

[0029] In this embodiment, the preparation method of the aqueous polyurethane dispersion comprises the following steps: (1) The following raw materials are prepared by weight: diisocyanate 12.22% (all 4,4'-dicyclohexylmethane diisocyanate), polymer diol 11.46% (all polytetramethylene ether diol with a molecular weight of 3000, brand name Hyosung PTMG-3000), hydrophilic chain extender 1.03% (all 2,2-dihydroxymethylpropionic acid), small molecule polyol 1.47% (all ethylene glycol), neutralizer 0.68% (all triethylamine), catalyst 0.03% (all stannous octoate), amine chain extender 0.53% (all ethylenediamine), olefin monomer 9.41% (including 3.53% diethyl maleate and 5.88% styrene), 2.35% methacrylate higher fatty ester (all octadecyl methacrylate), 1.47% ethylene-acrylic acid copolymer resin (all ethylene-acrylic acid copolymer resin with the brand name Dow 5990), 0.05% initiator (all potassium persulfate), 0.59% organic bentonite (all organic bentonite with the brand name BP-186), 58.71% water (all deionized water); The water is divided into three parts: the first part of water accounts for 10% of the total water volume, and is used to dissolve the amine chain extender to obtain an amine chain extender aqueous solution for standby use; the second part of water accounts for 5% of the total water volume, and is used to dissolve the initiator to obtain an initiator aqueous solution for standby use; the remaining water is used as the third part of water, and the third part of water is used to dissolve ethylene-acrylic acid copolymer resin, and a neutralizer accounting for 20% of the total amount of the neutralizer is added during the dissolution, and the neutralizer and ethylene-acrylic acid copolymer resin are added to the water and then heated to 70° C., stirred until the ethylene-acrylic acid copolymer resin is completely dissolved, and then cooled to 25° C. to obtain an ethylene-acrylic acid copolymer resin solution for standby use; Adding organic bentonite to the olefin-based monomer and stirring until the organic bentonite is completely dissolved to obtain an organic bentonite olefin-based monomer mixture for standby use; The diisocyanate is divided into two parts, the first part of diisocyanate accounts for 37.8% of the total diisocyanate, and the second part of diisocyanate accounts for 62.2% of the total diisocyanate; (2) Adding the polymer diol into a dehydration reactor equipped with a stirrer and a vacuum dehydration system to remove the water contained therein; In this step (2), the polymer diol is added to a dehydration reaction kettle equipped with a stirrer and a vacuum dehydration system, heated to 120° C. while stirring, and water is pumped out for 2 hours at a vacuum degree of -0.01 MPa to remove the water contained therein; (3) Add the dehydrated polymer diol (polymer diol cooled to 65°C) and the hydrophilic chain extender into a polymerization reactor equipped with a stirrer, then dropwise add the first portion of diisocyanate while stirring, and heat to 85°C for reaction for 2 hours; (4) Adjust the temperature in the polymerization reactor to 65°C, and then add the second part of isocyanate; then add the small molecule polyol dropwise while stirring, and control the temperature during the addition process to be between 70-80°C; keep the temperature at 75°C for 1 hour after the addition of the small molecule polyol; then add the catalyst and react at 75°C for 1 hour; then add the organic bentonite olefin monomer mixture and stir evenly; (5) Adjust the temperature in the polymerization reactor to 60°C, add methacrylate, then cool to 45°C, add the remaining neutralizer, and stir for 20 minutes; (6) The temperature in the polymerization reactor was adjusted to 45°C, and the stirring speed of the polymerization reactor was set to 2000 rpm. The ethylene-acrylic acid copolymer resin solution was added to the polymerization reactor within 30 minutes. After emulsification for 10 minutes, an amine chain extender aqueous solution was added dropwise, and stirred for 30 minutes to obtain a polyurethane pre-emulsion. (7) Adjust the temperature in the polymerization reactor to 75°C, then add the initiator aqueous solution to the polyurethane pre-emulsion. After the addition is completed, heat to 80°C and keep warm for 3 hours while stirring (stirring speed is 200 rpm). Then cool to 25°C and filter the material to obtain the desired aqueous polyurethane dispersion.

[0030] Example 2

[0031] In this embodiment, the preparation method of the aqueous polyurethane dispersion comprises the following steps: (1) The following raw materials were prepared by weight: 14.05% diisocyanate (all diphenylmethane diisocyanate), 7.32% polymer diol (all poly (1,4-butylene adipate with a molecular weight of 2000, brand name Huafeng PE-3020), 1.29% hydrophilic chain extender (all 2,2-dihydroxymethylpropionic acid), 4.39% small molecule polyol (all hydrogenated bisphenol A), 0.35% neutralizer (all sodium hydroxide), 0.06% catalyst (all stannous octoate), 2.20% amine chain extender ( All of them are N-(2-aminoethyl)ethanolamine), olefin monomer 5.85% (including dibutyl maleate 2.34%, styrene 3.51%), methacrylate higher fatty ester 2.93% (all of them are dodecyl methacrylate), ethylene-acrylic acid copolymer resin 1.02% (all of them are ethylene-acrylic acid copolymers with the brand DuPont 2022), initiator 0.06% (all of them are potassium persulfate), organic bentonite 1.46% (all of them are organic bentonite with the brand BP-186), water 59.02% (all of them are deionized water); The water is divided into three parts: the first part of water accounts for 12% of the total water volume, and is used to dissolve the amine chain extender to obtain an amine chain extender aqueous solution for standby use; the second part of water accounts for 6% of the total water volume, and is used to dissolve the initiator to obtain an initiator aqueous solution for standby use; the remaining water is used as the third part of water, and the third part of water is used to dissolve ethylene-acrylic acid copolymer resin, and a neutralizer accounting for 16% of the total amount of the neutralizer is added during the dissolution, and the neutralizer and ethylene-acrylic acid copolymer resin are added to the water and then heated to 85° C., stirred until the ethylene-acrylic acid copolymer resin is completely dissolved, and then cooled to 30° C. to obtain an ethylene-acrylic acid copolymer resin solution for standby use; Adding organic bentonite to the olefin-based monomer and stirring until the organic bentonite is completely dissolved to obtain an organic bentonite olefin-based monomer mixture for standby use; The diisocyanate is divided into two parts, the first part of diisocyanate accounts for 24.8% of the total diisocyanate, and the second part of diisocyanate accounts for 75.2% of the total diisocyanate; (2) Adding the polymer diol into a dehydration reactor equipped with a stirrer and a vacuum dehydration system to remove the water contained therein; In this step (2), the polymer diol is added to a dehydration reaction kettle equipped with a stirrer and a vacuum dehydration system, heated to 120° C. while stirring, and water is pumped out for 2 hours at a vacuum degree of -0.01 MPa to remove the water contained therein; (3) Add the dehydrated polymer diol (polymer diol cooled to 65°C) and the hydrophilic chain extender into a polymerization reactor equipped with a stirrer, then dropwise add the first portion of diisocyanate while stirring, and heat to 70°C for reaction for 4 hours; (4) Adjust the temperature in the polymerization reactor to 60°C, and then add the second part of isocyanate; then add the small molecule polyol dropwise while stirring, and control the temperature during the addition process to be between 70-80°C; keep the temperature at 70°C for 2 hours after the addition of the small molecule polyol; then add the catalyst and react at 70°C for 1.5 hours; then add the organic bentonite olefin monomer mixture and stir evenly; (5) Adjust the temperature in the polymerization reactor to 60°C, add methacrylate, then cool to 40°C, add the remaining neutralizer, and stir for 25 minutes; (6) The temperature in the polymerization reactor was adjusted to 45°C, and the stirring speed of the polymerization reactor was set to 3000 rpm. The ethylene-acrylic acid copolymer resin solution was added to the polymerization reactor within 20 minutes. After emulsification for 15 minutes, an amine chain extender aqueous solution was added dropwise, and stirred for 25 minutes to obtain a polyurethane pre-emulsion. (7) Adjust the temperature in the polymerization reactor to 75°C, then add the initiator aqueous solution to the polyurethane pre-emulsion. After the addition is complete, heat to 85°C and keep warm for 2 hours while stirring (stirring speed is 500 rpm). Then cool to 30°C and filter the material to obtain the desired aqueous polyurethane dispersion.

[0032] Example 3

[0033] In this embodiment, the preparation method of the aqueous polyurethane dispersion comprises the following steps: (1) The following raw materials were prepared by weight: 10.34% of diisocyanate (including 7.58% of hexamethylene diisocyanate and 2.76% of hydrogenated xylylene diisocyanate), 5.52% of polymer diol (all of which were polycarbonate diols with a molecular weight of 900, brand name Ube UM90 (3 / 1)), 1.72% of hydrophilic chain extender (all of which were 2,2-dihydroxymethylbutyric acid), 2.07% of small molecule polyol (all of which were 60g of 1,4-butanediol), 1.31% of neutralizer (all of which were triethylamine), 0.05% of catalyst (all of which were organic Bismuth catalyst), amine chain extender 0.86% (all ethylenediamine), olefin monomer 6.21% (including dimethyl maleate 2.76%, styrene 3.45%), methacrylate higher fatty ester 4.14% (all octadecyl methacrylate), ethylene-acrylic acid copolymer resin 0.86% (all ethylene-acrylic acid copolymer with the brand name Dow 5990), initiator 0.10% (all potassium persulfate), organic bentonite 1.38% (all organic bentonite with the brand name BP-183), water 65.44% (all deionized water); The water is divided into three parts: the first part of water accounts for 8% of the total water volume, and is used to dissolve the amine chain extender to obtain an amine chain extender aqueous solution for standby use; the second part of water accounts for 4% of the total water volume, and is used to dissolve the initiator to obtain an initiator aqueous solution for standby use; the remaining water is used as the third part of water, and the third part of water is used to dissolve ethylene-acrylic acid copolymer resin, and a neutralizer accounting for 22% of the total amount of the neutralizer is added during the dissolution, and the neutralizer and ethylene-acrylic acid copolymer resin are added to the water and then heated to 80° C., stirred until the ethylene-acrylic acid copolymer resin is completely dissolved, and then cooled to 30° C. to obtain an ethylene-acrylic acid copolymer resin solution for standby use; Adding organic bentonite to the olefin-based monomer and stirring until the organic bentonite is completely dissolved to obtain an organic bentonite olefin-based monomer mixture for standby use; The diisocyanate is divided into two parts, the first part of diisocyanate accounts for 27% of the total diisocyanate (all hexamethylene diisocyanate), and the second part of diisocyanate accounts for 73% of the total diisocyanate; (2) Adding the polymer diol into a dehydration reactor equipped with a stirrer and a vacuum dehydration system to remove the water contained therein; In this step (2), the polymer diol is added to a dehydration reaction kettle equipped with a stirrer and a vacuum dehydration system, heated to 115° C. while stirring, and water is pumped out for 3 hours at a vacuum degree of -0.015 MPa to remove the water contained therein; (3) Add the dehydrated polymer diol (polymer diol cooled to 65°C) and the hydrophilic chain extender into a polymerization reactor equipped with a stirrer, then dropwise add the first portion of diisocyanate while stirring, and heat to 80°C for reaction for 2.5 hours; (4) Adjust the temperature in the polymerization reactor to 60°C, and then add the second part of isocyanate; then add the small molecule polyol dropwise while stirring, and control the temperature during the addition process to be between 70-80°C; keep the temperature at 75°C for 1 hour after the addition of the small molecule polyol; then add the catalyst and react at 75°C for 1 hour; then add the organic bentonite olefin monomer mixture and stir evenly; (5) Adjust the temperature in the polymerization reactor to 60°C, add methacrylate, then cool to 45°C, add the remaining neutralizer, and stir for 20 minutes; (6) The temperature in the polymerization reactor was adjusted to 45°C, and the stirring speed of the polymerization reactor was set to 2000 rpm. The ethylene-acrylic acid copolymer resin solution was added to the polymerization reactor within 30 minutes. After emulsification for 10 minutes, an amine chain extender aqueous solution was added dropwise, and stirred for 30 minutes to obtain a polyurethane pre-emulsion. (7) Adjust the temperature in the polymerization reactor to 75°C, then add the initiator aqueous solution to the polyurethane pre-emulsion. After the addition is complete, heat to 85°C and keep warm for 3 hours while stirring (stirring speed is 200 rpm). Then cool to 30°C and filter the material to obtain the desired aqueous polyurethane dispersion.

[0034] Experimental example The samples of Examples 1-3 of the present invention and the comparative samples (existing imported similar products BT-62 and A2092 on the market) were coated on one side of the paper cup base paper under the same conditions. The coating rod was a 15μm wire rod and the dry coating amount was 6g / m2. After the coating was completed, it was dried at 90°C for 1 hour and then balanced at room temperature for 2 hours to obtain water-based coated paper. According to the standard of T / CPA 001-2021 "Water-based Coated Paper Cups (including Water-based Coated Paper Cup Paper)", the water resistance (low water absorption), barrier properties (leakage resistance), grease resistance, heat sealing performance, anti-adhesion and recyclability of water-based coated paper were tested. The test results are shown in Table 1 below.

[0035] As can be seen from Table 1, the water-based coated paper manufactured using the water-based polyurethane coating of the present invention has better water resistance (low water absorption), anti-leakage performance, grease resistance, heat sealing strength, anti-adhesion and recyclability than similar products currently available on the market.

[0036] Table 1: Detection indicators

Claims

1. An aqueous polyurethane dispersion, characterized in that The invention is prepared from the following raw materials in weight proportion: 5-25% of diisocyanate, 5-20% of polymer diol, 1-5% of hydrophilic chain extender, 1-10% of small molecule polyol, 0.2-2% of neutralizer, 0.01-0.1% of catalyst, 0.3-3% of amine chain extender, 5-15% of olefin monomer, 1-5% of methacrylate higher fatty ester, 0.3-3% of ethylene-acrylic acid copolymer resin, 0.02-0.4% of initiator, 0.2-2% of organic bentonite and 40-70% of water.

2. The aqueous polyurethane dispersion according to claim 1, characterized in that: The polymer diol is one of polycarbonate diol, polycaprolactone diol, 1,4-butylene succinate, hexamethylene oxalate, poly1,4-butylene adipate, polytetramethylene ether diol, polyoxyethylene ether diol and polyethylene glycol, or a combination of multiple thereof.

3. The aqueous polyurethane dispersion according to claim 2, characterized in that: The molecular weight of the polymer diol is 500-3000.

4. The aqueous polyurethane dispersion according to claim 1, characterized in that: The hydrophilic chain extender is 2,2-dimethylol propionic acid or 2,2-dimethylol butyric acid.

5. The aqueous polyurethane dispersion according to claim 1, characterized in that: The small molecule polyol is one of ethylene glycol, neopentyl glycol, diethylene glycol, 1,4-butanediol, bisphenol A, hydrogenated bisphenol A, hydroquinone dihydroxyethyl ether and 1,6-hexanediol, or a combination of multiple thereof.

6. The aqueous polyurethane dispersion according to claim 1, characterized in that: The amine chain extender is ethylenediamine, isophoronediamine, N-(2-aminoethyl)ethanolamine, dicyclohexylmethanediamine or hexamethylenediamine.

7. The aqueous polyurethane dispersion according to claim 1, characterized in that: The olefin-based monomer is one of methyl methacrylate, methyl acrylate, butyl acrylate, butyl methacrylate, dibutyl maleate, 2-ethylhexyl acrylate, styrene, vinyl trimethoxysilane, vinyl versatate, 4-tert-butyl cyclohexane acrylate, vinyl acetate, dimethyl maleate and diethyl maleate, or a combination of more than one of them.

8. The aqueous polyurethane dispersion according to claim 1, characterized in that: The diisocyanate is one or a combination of multiple of isophorone diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, meta-xylylene diisocyanate, hydrogenated xylylene diisocyanate and diphenylmethane diisocyanate; The neutralizing agent is triethylamine, ammonia water, sodium hydroxide, potassium hydroxide, dimethylethanolamine or triethanolamine; The catalyst may be an organic bismuth catalyst, dibutyltin dilaurate, stannous octoate or potassium isooctanoate catalyst; The methacrylate higher fatty ester is one or a combination of more than one of octadecyl methacrylate, dodecyl methacrylate and hexadecyl methacrylate; The ethylene-acrylic acid copolymer resin is an ethylene-acrylic acid copolymer resin having an acrylic acid content of 5-22%; The initiator is sodium persulfate, ammonium persulfate or potassium persulfate; The water is deionized water.

9. A method for preparing the aqueous polyurethane dispersion according to claim 1, characterized in that The steps include: (1) The following raw materials are prepared by weight: 5-25% diisocyanate, 5-20% polymer diol, 1-5% hydrophilic chain extender, 1-10% small molecule polyol, 0.2-2% neutralizer, 0.01-0.1% catalyst, 0.3-3% amine chain extender, 5-15% olefin monomer, 1-5% methacrylate higher fatty ester, 0.3-3% ethylene-acrylic acid copolymer resin, 0.02-0.4% initiator, 0.2-2% organic bentonite, and 40-70% water; The water is divided into three parts: the first part of water accounts for 8-15% of the total water volume, and is used to dissolve the amine chain extender to obtain an amine chain extender aqueous solution for standby use; the second part of water accounts for 3-8% of the total water volume, and is used to dissolve the initiator to obtain an initiator aqueous solution for standby use; the remaining water is used as the third part of water, and the third part of water is used to dissolve the ethylene-acrylic acid copolymer resin, and a neutralizer accounting for 15-25% of the total amount of the neutralizer is added during the dissolution, and the neutralizer and the ethylene-acrylic acid copolymer resin are added to the water and then heated to 70-90° C., stirred until the ethylene-acrylic acid copolymer resin is completely dissolved, and then cooled to 20-30° C. to obtain an ethylene-acrylic acid copolymer resin solution for standby use; Adding organic bentonite to the olefin-based monomer and stirring until the organic bentonite is completely dissolved to obtain an organic bentonite olefin-based monomer mixture for standby use; The diisocyanate is divided into two parts, the first part of the diisocyanate accounts for 20-40% of the total diisocyanate, and the second part of the diisocyanate accounts for 60-80% of the total diisocyanate; (2) Adding the polymer diol into a dehydration reactor equipped with a stirrer and a vacuum dehydration system to remove the water contained therein; (3) Add the dehydrated polymer diol and the hydrophilic chain extender into a polymerization reactor equipped with a stirrer, then dropwise add the first portion of diisocyanate while stirring, and heat to 70-90° C. for reaction for 2-4 hours; (4) Adjust the temperature in the polymerization reactor to 50-65°C, and then add the second part of isocyanate; then add the small molecule polyol dropwise while stirring, and control the temperature during the addition process to be between 70-80°C; keep the temperature at 70-80°C for 1-2 hours after the addition of the small molecule polyol; then add the catalyst and react at 70-80°C for 1-2 hours; then add the organic bentonite olefin monomer mixture and stir evenly; (5) Adjust the temperature in the polymerization reactor to 55-65°C, add methacrylate higher fatty ester, then cool to 40-50°C, add the remaining neutralizer, and stir for 15-25 minutes; (6) adjusting the temperature in the polymerization reactor to 40-50° C. and setting the stirring speed of the polymerization reactor to 1000-3000 rpm, adding the ethylene-acrylic acid copolymer resin solution into the polymerization reactor within 20-30 minutes, emulsifying for 10-20 minutes, and then dripping the amine chain extender aqueous solution, stirring for 20-40 minutes, to obtain a polyurethane pre-emulsion; (7) Adjust the temperature in the polymerization reactor to 70-75°C, then add the initiator aqueous solution to the polyurethane pre-emulsion, heat to 80-85°C after the addition is complete, keep warm for 2-3 hours while stirring, then cool to 20-30°C, filter the material, and obtain the desired aqueous polyurethane dispersion.

10. A method for preparing an aqueous polyurethane dispersion according to claim 9, characterized in that: In step (2), the polymer diol is added to a dehydration reaction kettle equipped with a stirrer and a vacuum dehydration system, heated to 110-120° C. while stirring, and water is pumped out for 1-3 hours at a vacuum degree of -0.01 MPa to -0.02 MPa to remove the water contained therein; In step (7), the stirring speed is 100-500 rpm.

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