Waterborne polyurethane, preparation method thereof and heat-sealing adhesive
阅读说明：本技术 水性聚氨酯及其制备方法、热封胶粘剂 (Waterborne polyurethane, preparation method thereof and heat-sealing adhesive ) 是由 陈宇 周妙兰 韩航 孙同兵 李金禹 吕铭华 崔正 张春辉 于 2020-06-17 设计创作，主要内容包括：本发明涉及热封胶技术领域,具体涉及水性聚氨酯及其制备方法、热封胶粘剂,所述水性聚氨酯包含来自羟基丙烯酸酯的结构单元A,来自二异氰酸酯的结构单元B,来自多元醇的结构单元C和来自扩链剂的结构单元D。本发明提供的水性聚氨酯粘度低、固含量高,适合在室温下高速涂布,且在制备和使用过程中均无VOC排放,无污染,对环境友好。(The invention relates to the technical field of heat seal adhesives, and particularly relates to waterborne polyurethane, a preparation method thereof and a heat seal adhesive. The waterborne polyurethane provided by the invention has low viscosity and high solid content, is suitable for high-speed coating at room temperature, has no VOC (volatile organic compound) emission in the preparation and use processes, is pollution-free and is environment-friendly.)
1. An aqueous polyurethane, characterized in that the aqueous polyurethane comprises a structural unit A derived from a hydroxyacrylate, a structural unit B derived from a diisocyanate, a structural unit C derived from a polyol and a structural unit D derived from a chain extender;
wherein the content of the first and second substances,the structural formula of the structural unit A isR1Selected from H or methyl, R2Is selected from C2-C4At least one of alkylene groups of (a);
the structural formula of the structural unit B is
the structural formula of the structural unit C is
the chain extender is at least one selected from N- (2-aminoethyl) -2-aminoethane sulfonic acid sodium salt, dimethylolpropionic acid and dimethylolbutyric acid.
2. The aqueous polyurethane of claim 1, wherein the weight ratio of the structural unit a, the structural unit B, the structural unit C, and the structural unit D is 1:30-80:65-250: 3-10;
preferably, the viscosity of the aqueous polyurethane at 25 ℃ is 150-1000 mPas.
3. A preparation method of waterborne polyurethane is characterized by comprising the following steps:
(1) carrying out polymerization reaction on diisocyanate and hydroxyl acrylate monomer according to the weight ratio of 10-90:1 to obtain acrylate modified diisocyanate;
(2) and carrying out contact reaction on the acrylate modified diisocyanate, the polyol, the chain extender and the catalyst in acetone to obtain the waterborne polyurethane.
4. The production method according to claim 3, wherein in the step (1), the conditions of the polymerization reaction include: the weight ratio of the diisocyanate to the hydroxyl acrylate monomer is 60-80:1, the polymerization temperature is 70-90 ℃, and the polymerization time is 2-3 h.
5. The production method according to claim 3 or 4, wherein the hydroxy acrylate monomer is selected from a linear hydroxy acrylate monomer and/or a methyl group-containing hydroxy acrylate monomer;
preferably, the linear hydroxy acrylate monomer is selected from hydroxyethyl acrylate and/or hydroxypropyl acrylate;
preferably, the methyl-containing hydroxy acrylate monomer is selected from hydroxyethyl methacrylate and/or hydroxypropyl methacrylate.
6. The production method according to any one of claims 3 to 5, wherein the diisocyanate is selected from a cycloaliphatic diisocyanate and/or an aliphatic diisocyanate;
preferably, the cycloaliphatic diisocyanate is isophorone diisocyanate;
preferably, the aliphatic diisocyanate is hexamethylene diisocyanate.
7. The production method according to claim 3, wherein the polyol is selected from at least one of polyester diol, small molecule diol, and polyether diol;
preferably, the polyol comprises a polyester diol, a small molecule diol, and optionally a polyether diol;
preferably, the weight ratio of the polyester diol, the polyether diol and the small molecular diol is 55-100:0-4: 1.
8. The production method according to claim 7, wherein the polyester diol is at least one selected from the group consisting of polyethylene glycol adipate, polypropylene glycol adipate, polyethylene-diethylene glycol adipate, polyethylene-1, 2-butanediol adipate, polyethylene-1, 3-butanediol adipate, polyethylene-1, 4-butanediol adipate, polyethylene-1, 6-hexanediol adipate, polyethylene-1, 8-octanediol adipate, and polyethylene-1, 9-nonanediol adipate;
preferably, the relative molecular weight of the polyester diol is 1000-3000;
preferably, the polyether glycol is at least one selected from polypropylene glycol polyether, polyethylene glycol polyether and polytetramethylene glycol polyether;
preferably, the polyether diol has a relative molecular weight of 1000-3000;
preferably, the small molecule diol is selected from at least one of ethylene glycol, propylene glycol, 1, 4-butanediol, and diethylene glycol.
9. The production method according to any one of claims 3 to 8, wherein the chain extender is selected from at least one of N- (2-aminoethyl) -2-aminoethanesulfonic acid sodium salt, dimethylolpropionic acid, and dimethylolbutyric acid; and/or
The catalyst is selected from at least one of stannous octoate, dibutyltin dilaurate, dibutyltin diacetate and 2, 2-dimorpholinyl diethyl ether.
10. The method of any one of claims 3-8, wherein the ratio of the number of total NCO equivalents in the diisocyanate to the number of total OH equivalents in the polyol is 1.8-2.5: 1.
11. The production method according to any one of claims 3 to 10, wherein the step (2) comprises: mixing the acrylate modified diisocyanate, polyester diol, micromolecular diol and optional polyether diol in acetone, and reacting at 75-90 ℃ for 2-3 h; then continuously reacting the product with a chain extender for 1-2h at the temperature of 80-90 ℃; adding a catalyst into the obtained mixture, reacting for 2-3h at the temperature of 80-95 ℃, measuring the percentage content of NCO in the reaction product every 1h, cooling to 55-65 ℃ when the percentage content of NCO is reduced to be stable, adding a neutralizer to adjust the system to be neutral, adding organic amine to react for 0.5-1h, and removing acetone.
12. The production method according to claim 11, wherein a raw material for producing the aqueous polyurethane comprises: 0.2-20 parts of hydroxyl acrylate, 8-30 parts of diisocyanate, 50-75 parts of polyester diol, 0-10 parts of polyether diol, 0-4 parts of micromolecular diol, 1-5 parts of neutralizer, 0.1-0.5 part of organic amine, 0-4 parts of chain extender and 0.1-0.5 part of catalyst.
13. A heat-sealing adhesive comprising the aqueous polyurethane according to claim 1 or the aqueous polyurethane obtained by the production method according to any one of claims 3 to 12;
preferably, the solid content of the heat-seal adhesive is more than or equal to 48 wt%.
Technical Field
The invention relates to the technical field of heat-seal adhesives, in particular to waterborne polyurethane, a preparation method thereof and a heat-seal adhesive.
Background
The heat sealing glue is a kind of glue for packing, has good adhesive force, is especially suitable for the adhesion of paper, etc., and the adhesion is completed immediately after hot pressing. The hot-seal adhesive is low in viscosity ratio of a coating surface after being dried, and pressure-sensitive property does not exist; the paper can not be firmly adhered to the backing material such as paper when being rolled and stored, so the paper is easy to unwind. The heat-sealing glue needs to be sealed by hot pressing, and the packaging paper and the like can be damaged once being torn, so that the heat-sealing glue can be used for packaging important objects and plays a good role in preventing theft and keeping secret.
At present, most of heat-sealing glue on the market is polyurethane solid glue or liquid glue containing an organic solvent, the polyurethane solid heat-sealing glue has the defects of high softening point, high melt viscosity, complex construction process and the like, and the liquid glue containing the organic solvent uses the organic solvent, so that the liquid glue has large smell and serious pollution. The waterborne polyurethane can realize the coating process at normal temperature, the required equipment is simple and convenient, and water is used as a dispersion medium, so that the waterborne polyurethane is environment-friendly, nontoxic, tasteless and pollution-free, is favored by the industry and has a good market. The existing waterborne polyurethane is mostly in a linear structure, a certain amount of hydrophilic groups are contained in a skeleton of the existing waterborne polyurethane, the viscosity of the waterborne polyurethane is high, the amount of water to be added during dispersion is large, and the solid content of the waterborne polyurethane is low and is generally lower than 40%.
CN109651998A discloses a low viscosity single component solvent-free polyurethane adhesive, a preparation method and an application thereof, the low viscosity single component solvent-free polyurethane adhesive takes isocyanate-terminated polyurethane prepolymer and polyisocyanate as main components, wherein, the isocyanate-terminated polyurethane prepolymer adopts diisocyanate to simultaneously carry out end-capping reaction on polyol and hydroxyl acrylate under the condition of no solvent, the viscosity of the polyurethane prepolymer obtained by the method is still relatively high (1500 mPa.s), and the polyurethane prepolymer is not suitable for high-speed coating at room temperature.
Disclosure of Invention
The invention aims to overcome the problems of high viscosity and low solid content of the waterborne polyurethane in the prior art, and provides the waterborne polyurethane with low viscosity and high solid content, a preparation method thereof and a heat-sealing adhesive.
In order to achieve the above object, a first aspect of the present invention provides an aqueous polyurethane comprising a structural unit a derived from a hydroxyacrylate, a structural unit B derived from a diisocyanate, a structural unit C derived from a polyol and a structural unit D derived from a chain extender;
wherein the structural formula of the structural unit A isR1Selected from H or methyl, R2Is selected from C2-C4At least one of alkylene groups of (a);
the structural formula of the structural unit B isR3Selected from hexamethylene,
the structural formula of the structural unit C isWherein R is4Is selected from C2-C6Alkylene and
the chain extender is at least one selected from N- (2-aminoethyl) -2-aminoethane sulfonic acid sodium salt, dimethylolpropionic acid and dimethylolbutyric acid.
The second aspect of the present invention provides a method for preparing an aqueous polyurethane, comprising:
(1) carrying out polymerization reaction on diisocyanate and hydroxyl acrylate monomer according to the weight ratio of 10-90:1 to obtain acrylate modified diisocyanate;
(2) and carrying out contact reaction on the acrylate modified diisocyanate, the polyol, the chain extender and the catalyst in acetone to obtain the waterborne polyurethane.
The third aspect of the invention provides a heat-sealing adhesive which comprises the waterborne polyurethane.
Through the technical scheme, the hydroxyl acrylate monomer is firstly reacted with the diisocyanate, the acrylate monomer is introduced into the molecular chain of the diisocyanate, the reactivity of-NCO groups in the diisocyanate is reduced, and the reaction degree of isocyanate and polyol can be effectively controlled when the hydroxyl acrylate monomer is reacted with the polyol, so that the waterborne polyurethane with low viscosity (150-1000mPa & s) and high solid content (more than 48 wt%) is obtained; the waterborne polyurethane is suitable for high-speed coating at room temperature, has good adhesive force (more than or equal to 8.3N/15mm) for paper, and can be widely used for heat sealing of paper products; the waterborne polyurethane provided by the invention has no VOC emission, no pollution and environmental friendliness in the preparation and use processes.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
An aqueous polyurethane comprising a structural unit a from a hydroxy acrylate, a structural unit B from a diisocyanate, a structural unit C from a polyol and a structural unit D from a chain extender;
wherein the structural formula of the structural unit A is
the structural formula of the structural unit B is
the structural formula of the structural unit C isWherein R is4Is selected from C2-C6Alkylene and
the chain extender is at least one selected from N- (2-aminoethyl) -2-aminoethane sulfonic acid sodium salt, dimethylolpropionic acid and dimethylolbutyric acid.
In the present invention, preferably, R is4Is selected from C2-C4Alkylene (may be, for example, -CH)2CH2-、-CH2CH2CH2-、-CH2CH2CH2CH2At least one of) and
In the present invention, the weight ratio of the structural unit A, the structural unit B, the structural unit C and the structural unit D is preferably 1:30-80:65-250:3-10, more preferably 1:35-70:70-200: 6-8.
In the present invention, it is preferable that the viscosity of the aqueous polyurethane at 25 ℃ is 150-1000 mPas.
The invention also provides a preparation method of the waterborne polyurethane, which comprises the following steps:
(1) carrying out polymerization reaction on diisocyanate and hydroxyl acrylate monomer according to the weight ratio of 10-90:1 to obtain acrylate modified diisocyanate;
(2) and carrying out contact reaction on the acrylate modified diisocyanate, the polyol, the chain extender and the catalyst in acetone to obtain the waterborne polyurethane.
In the invention, firstly, hydroxyl acrylate monomer is reacted with diisocyanate, and acrylate monomer is introduced into the molecular chain of diisocyanate, so that the reactivity of-NCO group in diisocyanate is reduced, and the reaction degree of isocyanate and polyol can be effectively controlled when the hydroxyl acrylate monomer is reacted with polyol, thereby obtaining the waterborne polyurethane with low viscosity (150-1000mPa & s) and high solid content (more than 48 wt%).
According to the invention, the diisocyanate is modified by adopting the acrylate, and the acrylate group is introduced into the molecular chain of the diisocyanate, so that the steric hindrance of the diisocyanate is increased, and the reactivity of the diisocyanate and the polyol is reduced, thereby enabling the molecules of the product to be smaller and the viscosity to be reduced, wherein the content of the hydroxyl acrylate monomer is one of the factors influencing the reactivity of the modified diisocyanate. Preferably, the weight ratio of the diisocyanate to the hydroxy acrylate monomer is 10-90:1 (e.g., 10:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1 or any value therebetween), and more preferably 60-80: 1.
In order to further reduce the viscosity of the waterborne polyurethane and increase the solid content of the waterborne polyurethane, the polymerization temperature is 70-90 ℃ under the preferable conditions, and the polymerization time is 2-3 h.
Preferably, the hydroxy acrylate monomer is selected from a linear hydroxy acrylate monomer and/or a methyl group-containing hydroxy acrylate monomer; the hydroxyl acrylate containing methyl is introduced into the molecular chain of the diisocyanate, so that the steric hindrance of the diisocyanate can be further improved, and the reactivity of the diisocyanate with the polyol can be reduced. More preferably, the linear hydroxy acrylate monomer is selected from hydroxyethyl acrylate and/or hydroxypropyl acrylate; more preferably, the methyl group-containing hydroxy acrylate monomer is selected from hydroxyethyl methacrylate and/or hydroxypropyl methacrylate.
In the present invention, the diisocyanate is selected from the group consisting of alicyclic diisocyanate and/or aliphatic diisocyanate; in order to further control the reactivity of the diisocyanate and reduce the viscosity of the product, it is preferred that the diisocyanate comprises an aliphatic diisocyanate and a cycloaliphatic diisocyanate. More preferably, the cycloaliphatic diisocyanate is isophorone diisocyanate; more preferably, the aliphatic diisocyanate is hexamethylene diisocyanate.
In the invention, acrylate modified diisocyanate can react with polyol to generate aqueous polyurethane, and in order to improve the crosslinking density and cohesive strength of the acrylic modified polyurethane, the functionality of the polyol is 2-3 under the preferable condition, and the polyol is more preferably selected from at least one of polyester diol, small molecule diol and polyether diol. The polyester diol contains a soft ester bond structure which can be chemically bonded with hydroxyl on the surface of a base material (paper material), so that the polyester diol has high bonding strength to the base material; the liquid polyether polyol can fully mix the acrylate modified diisocyanate with other materials; preferably, the polyol comprises a polyester diol, a small molecule diol, and optionally a polyether diol; in order to further improve the adhesive strength between the acrylic modified polyurethane and the substrate and reduce the viscosity thereof, the weight ratio of the polyester diol, the polyether diol and the small molecule diol is preferably 55-100:0-4:1 (for example, 55:3:1, 60:0:1, 65:3.5:1, 70:3:1, 80:3.5:1, 90:4:1, 100:4:1 or any value therebetween); more preferably 60-80:3-3.5: 1.
In the present invention, it is preferable that the polyester diol is at least one selected from the group consisting of polyethylene glycol adipate, polypropylene glycol adipate, polyethylene-diethylene glycol adipate, polyethylene-1, 2-butanediol adipate, polyethylene-1, 3-butanediol adipate, polyethylene-1, 4-butanediol adipate, polyethylene-1, 6-hexanediol adipate, polyethylene-1, 8-octanediol adipate, and polyethylene-1, 9-nonanediol adipate; further preferably, the relative molecular weight of the polyester diol is 1000-3000.
Preferably, the polyether glycol is at least one selected from polypropylene glycol polyether, polyethylene glycol polyether and polytetramethylene glycol polyether; further preferably, the polyether glycol has a relative molecular weight of 1000-.
Preferably, the small molecule diol is selected from at least one of ethylene glycol, propylene glycol, 1, 4-butanediol, and diethylene glycol.
In the present invention, in order to react the acrylate-modified isocyanate with the polyol to produce the polyurethane while increasing the solid content and decreasing the viscosity of the polyurethane, it is preferable that the chain extender is at least one selected from the group consisting of N- (2-aminoethyl) -2-aminoethane sulfonic acid sodium salt, dimethylolpropionic acid and dimethylolbutyric acid; preferably, the catalyst is at least one selected from stannous octoate, dibutyltin dilaurate, dibutyltin diacetate and 2, 2-dimorpholinodiethyl ether.
In the present invention, the higher the NCO/OH ratio in the reaction system, the smaller the molecules of the resulting polyurethane and the lower the viscosity, and in order to lower the viscosity of the resultant acrylated polyurethane, it is preferred that the ratio of the total NCO equivalents of the diisocyanates to the total OH equivalents of the polyols is 1.8 to 2.5:1 (e.g., 1.8:1, 2:1, 2.3:1, 2.5:1 or any value therebetween), more preferably 2: 1.
In the present invention, in order to further reduce the viscosity of the aqueous polyurethane and increase the solid content thereof, preferably, the step (2) further comprises: mixing the acrylate modified diisocyanate, polyester diol, micromolecular diol and optional polyether diol in acetone, and reacting at 75-90 ℃ for 2-3 h; then continuously reacting the product with a chain extender for 1-2h at the temperature of 80-90 ℃; adding a catalyst into the obtained mixture, reacting for 2-3h at the temperature of 80-95 ℃, measuring the percentage content of NCO in the reaction product every 1h, cooling to 55-65 ℃ when the percentage content of NCO is reduced to be stable, adding a neutralizer to adjust the system to be neutral, adding organic amine to react for 0.5-1h, and removing acetone.
Preferably, the organic amine is at least one selected from dimethylamine, ethylenediamine, diethylamine, trimethylamine, triethylamine, propylenediamine and butylenediamine, and most preferably ethylenediamine.
Preferably, the kind of the neutralizing agent may be known to those skilled in the art, and may be, for example, at least one of organic amine, alkali metal hydroxide, and alkaline earth metal hydroxide, preferably organic amine, and more preferably triethylamine.
In order to further reduce the viscosity and increase the solid content of the aqueous polyurethane, in a preferred embodiment of the present invention, the raw materials for preparing the aqueous polyurethane comprise: 0.2-20 parts of hydroxyl acrylate, 8-30 parts of diisocyanate, 50-75 parts of polyester diol, 0-10 parts of polyether diol, 0-4 parts of micromolecular diol, 1-5 parts of neutralizer, 0.1-0.5 part of organic amine, 0-4 parts of chain extender and 0.1-0.5 part of catalyst; more preferably, the raw material composition comprises 0.3-5 parts by weight of hydroxyl acrylate, 9-30 parts by weight of diisocyanate, 55-70 parts by weight of polyester diol, 2.5-3.5 parts by weight of polyether diol, 0.7-1 part by weight of small molecular diol, 2.5-4 parts by weight of neutralizing agent, 0.15-0.25 part by weight of organic amine, 2-3 parts by weight of chain extender and 0.15-0.35 part by weight of catalyst.
In the present invention, the structural unit and the content thereof in the obtained product can be measured by infrared, nuclear magnetic, or the like, or can be estimated from the type and content of the raw material to be charged.
The invention also provides a heat-sealing adhesive which comprises the waterborne polyurethane, wherein the solid content of the heat-sealing adhesive is more than or equal to 48 wt%, the heat-sealing adhesive can be used for paper/paper bonding, plastic/plastic bonding and paper/plastic bonding, and the plastic can be PVC.
In the present invention, the heat-seal adhesive may further contain an auxiliary agent such as a defoaming agent and a leveling agent, and the defoaming agent and the leveling agent may be known to those skilled in the art, for example, the defoaming agent may be at least one of a fatty acid ester defoaming agent, a phosphate ester defoaming agent, an amide defoaming agent, and the like; the leveling agent may be polydimethylsiloxane and/or polymethylphenylsiloxane.
The present invention will be described in detail below by way of examples. In the following examples, the determination of the solids content is described in GB/T2793-1995; the viscosity was measured according to GB/T2794-1995, at a temperature of (25. + -. 1). degree.C.
In the following examples, PBA is a commercially available product of Jining HuaKai resin Co., Ltd., and has a number average molecular weight of 2000; the polyethylene glycol polyether is a commercial product of Wanhua chemistry, and the number average molecular weight of the polyethylene glycol polyether is 2000; the dehydrated polyethylene glycol adipate was a commercially available product of Jining HuaKai resin Co., Ltd, and had a number average molecular weight of 2000.
In the following examples, before the reaction, both PBA and polyethylene glycol adipate were dehydrated by the following processes: PBA and polyethylene glycol adipate are put into a four-neck flask and heated to 120 ℃ at the temperature of 100 ℃ and stirred for 2 to 3 hours under the vacuum degree of-0.09 +/-0.005 MPa.
In the following examples, the weight ratio of the structural unit a, the structural unit B, the structural unit C and the structural unit D in the aqueous polyurethane is estimated from the content of the charged raw materials.