CN114933883A

CN114933883A - Waterborne polyurethane adhesive and preparation method thereof

Info

Publication number: CN114933883A
Application number: CN202210498476.7A
Authority: CN
Inventors: 王丹; 张博; 周玉波; 蒲源; 张远豪; 王洁欣; 曾晓飞; 陈建峰
Original assignee: Beijing University of Chemical Technology; Ningbo Solartron Technology Co Ltd
Current assignee: Beijing University of Chemical Technology; Ningbo Solartron Technology Co Ltd
Priority date: 2022-05-09
Filing date: 2022-05-09
Publication date: 2022-08-23
Anticipated expiration: 2042-05-09
Also published as: CN114933883B

Abstract

The invention discloses a waterborne polyurethane adhesive and a preparation method thereof. The invention firstly discloses a preparation method of a waterborne polyurethane adhesive, which comprises the following steps: stirring and reacting a polyisocyanate monomer and a polyol monomer under the conditions of inert gas protection and condensation to obtain a reactant A; adding a hydrophilic chain extender and a micromolecular chain extender to perform chain extension reaction, cooling, and adding a solvent to adjust the viscosity of the system to obtain a reactant B; adding a neutralizing agent for neutralization reaction, and then cooling to obtain a prepolymer; and (3) conveying the prepolymer and the nanoparticle dispersion to a rotary packed bed for emulsification, removing the solvent by rotary evaporation, and adding an auxiliary agent to obtain the waterborne polyurethane adhesive. Further discloses the aqueous polyurethane adhesive prepared by the method. The preparation method of the waterborne polyurethane adhesive has the advantages of low cost, low energy consumption and simple process, and the obtained adhesive is green and environment-friendly, has good storage stability, good mechanical property and strong bonding effect, is easy to clean and is suitable for bonding of various different substrates.

Description

Waterborne polyurethane adhesive and preparation method thereof

Technical Field

The invention relates to the technical field of adhesive preparation. More particularly, it relates to a waterborne polyurethane adhesive and a preparation method thereof.

Background

In recent years, the rapid development of various fields in China, and the adhesive becomes an indispensable important material for modern industry and life. Along with the development of the technological level and the improvement of the living standard of people, more strict requirements are also put forward on the adhesive. The adhesives can be classified into resin type (epoxy resin, polyurethane, silicone, polyimide, acrylate, etc.), rubber type (fluororubber, fluorosilicone rubber, polythioether, etc.), and composite type (resin-rubber) according to their chemical structures. The main resin molecules of the polyurethane adhesive contain a large amount of polar groups and reactive groups, so the polyurethane adhesive has good adhesion to various base materials (such as metal, plastic, glass, wood and the like), and meanwhile, the polyurethane adhesive has a plurality of raw materials, a large adjustable range of formula structures and various corresponding performance characteristics, and can meet the requirements of adhesion and use conditions of different base materials.

Nowadays, polyurethane adhesives mainly have the following problems: (1) the solvent is volatilized and remains. Various organic auxiliary agents can be used in the synthesis process of the adhesive so as to improve the storage stability of the adhesive, and the adhesive inevitably discharges organic solvents to the environment in the use process, thereby polluting the environment and harming the health of production workers. Meanwhile, in the process of processing and using the adhesive, a small amount of solvent is not completely volatilized and remains in the adhesive layer of the base material, so that potential safety hazards exist. (2) And (5) residual glue. When the adhesive is peeled off the substrate, there is often a residual tack and it is difficult to remove it with conventional green solvents. The main components of the common viscose removers comprise toluene, xylene, acetone and lipid compounds, which have strong odor and can damage the surface layer of some substrates (such as plastics) and influence the appearance and normal use.

Therefore, the development of a solvent-free and easily-cleaned green environment-friendly adhesive is of great significance.

Disclosure of Invention

The invention aims to provide a preparation method of a water-based polyurethane adhesive, which has simple process and low energy consumption.

The invention also aims to provide the aqueous polyurethane adhesive prepared by the preparation method, which has the characteristics of no solvent (green and environment-friendly) and easy removal of residual adhesive (easy cleaning) and is suitable for bonding multiple substrates.

In order to achieve the purpose, the invention firstly provides a preparation method of the water-based polyurethane adhesive, which comprises the following steps:

1) carrying out stirring reaction on a polyisocyanate monomer and a polyol monomer under the conditions of inert gas protection and condensation to obtain a reactant A;

2) adding a hydrophilic chain extender and a micromolecular chain extender into the reactant A, performing chain extension reaction, cooling, and adding a solvent to adjust the viscosity of the system to obtain a reactant B;

3) adding a neutralizer into the reactant B for neutralization reaction, and then cooling to obtain a prepolymer;

4) and (3) conveying the prepolymer and the nanoparticle dispersion to a rotary packed bed for emulsification, removing the solvent by rotary evaporation, and adding an auxiliary agent to obtain the waterborne polyurethane adhesive.

In the process of preparing the aqueous polyurethane adhesive, the aqueous polyurethane adhesive is obtained through prepolymerization, chain extension, neutralization and emulsification, and has the characteristics of easy cleaning, environmental protection, good toughness, no solvent volatilization and wide application range.

In a specific embodiment of the present invention, in step 1), the polyisocyanate monomer is one or more of isophorone diisocyanate, toluene diisocyanate, and diphenylmethane diisocyanate, and the polyol monomer is one or two of polytetrahydrofuran ether glycol and polypropylene glycol; preferably, the polyisocyanate monomer is isophorone diisocyanate and the polyol monomer is polypropylene glycol 2000. The polyisocyanate monomer and the polyol monomer are main bodies for preparing the waterborne polyurethane adhesive, and the adhesive prepared by selecting other reaction monomers has weaker comprehensive performance.

In a specific embodiment of the present invention, in step 1), the mass ratio of the polyisocyanate monomer to the polyol monomer is 1:1.21 to 1: 2.71. The mass ratio of the polyisocyanate to the polyol monomer is outside the range, the content of the isocyanic acid radical is low if the mass ratio is less, the curing time of the adhesive is long, the bonding strength is low, the side reactions are increased if the mass ratio is more, and the stability of the adhesive is poor.

In a specific embodiment of the invention, in the step 1), the temperature of the stirring reaction is 85-95 ℃ and the time is 1.5-2.5 h; preferably, the inert protective gas is high-purity nitrogen with the purity of more than or equal to 99.999% (V/V). In the invention, the reaction temperature is outside the range, the reaction activity is low at low temperature, the side reaction is increased at high temperature, and the energy consumption is high; when the reaction time is outside the range, the reaction is incomplete at a low temperature, side reactions are increased at a high temperature, and the product yield is low.

In a specific embodiment of the present invention, in step 2), the hydrophilic chain extender is 2, 2-dimethylolpropionic acid, and the small-molecule chain extender is 1, 4-butanediol. In the invention, hydrophilic groups are introduced into the hydrophilic chain extender to endow the waterborne polyurethane with self-emulsifying property; the small molecular chain extender improves the molecular weight of the waterborne polyurethane adhesive and improves the adhesive property of the waterborne polyurethane adhesive.

In a specific embodiment of the present invention, in step 2), the amount of the hydrophilic chain extender is 3 to 5 wt% of the total amount of the polyisocyanate monomer and the polyol monomer; the using amount of the micromolecular chain extender is 0-7 wt% of the total amount of the polyisocyanate monomer and the polyol monomer; the hydrophilic chain extender is outside the range, the emulsification is difficult at low temperature, the stability of the adhesive is poor, the water resistance of the product is poor at high temperature, and the actual use effect is poor; the small molecular chain extender is outside the range, the low molecular weight is small, the performance is poor, and the high molecular chain extender is high in reaction viscosity and difficult to control.

In a specific embodiment of the invention, in the step 2), the temperature of the chain extension reaction is 85-95 ℃ and the time is 25-35 min. In the invention, the chain extension temperature is out of the range, the reaction activity is low when the chain extension temperature is low, side reactions are increased when the chain extension temperature is high, and the energy consumption is high; and the chain extension time is out of the range, the chain extension reaction is incomplete at low level, and the economic benefit is low at high level.

In a specific embodiment of the present invention, in step 2), the solvent is acetone. In the invention, the acetone is used for reducing the viscosity of the reaction system and maintaining the reaction.

In a specific embodiment of the invention, in step 2), 1.5-2.5mL of the solvent is added to the reactor every 10-15min after the chain extension reaction for 1 h. The viscosity change of the precursor system is small after the chain extension reaction is carried out for 1 hour, and the influence of the added solvent on the reaction is small, so that the waste is caused; the time interval for adding the solvent is out of the range, if the time interval is low, the addition amount of the solvent is too much, the economic benefit is low, and if the time interval is high, the viscosity control effect is poor, and the reaction process is difficult; when the amount of the solvent added is outside this range, the effect of reducing the viscosity of the system cannot be achieved at a low amount, and waste is caused at a high amount.

In a specific embodiment of the present invention, in step 3), the neutralizing agent is triethylamine. The neutralizer neutralizes the introduced carboxyl to form salt, which is more favorable for the storage stability of the adhesive.

In a specific embodiment of the present invention, in step 3), the molar ratio of the neutralizing agent to the hydrophilic chain extender is from 1:1 to 1.2: 1. In the invention, the neutralizing agent is outside the range, the neutralization is incomplete when the neutralizing agent is low, the storage stability of the adhesive is poor, and triethylamine is excessive when the neutralizing agent is high, so that the catalytic reaction is difficult to control.

In a specific embodiment of the invention, in the step 3), the temperature of the neutralization reaction is 45-55 ℃ and the time is 25-35 min. In the invention, the neutralization temperature is out of the range, the reaction activity is small at low temperature, and the energy consumption is large at high temperature; the neutralization time is out of the range, the neutralization is incomplete at low level, and the energy consumption is high at high level.

In a specific embodiment of the invention, in the step 4), the nanoparticle dispersion is a short organic acid modified nano zirconia dispersion, and the nano zirconia can overcome the defects of low crosslinking degree and poor mechanical property of the water-based polyurethane; preferably, the short organic acid is any one of tartaric acid and citric acid, the short organic acid can improve the dispersibility of the nano-zirconia in a water phase, and other short organic acids are selected to not obviously improve the dispersibility of the nano-zirconia; more preferably, the pH value of the short organic acid modified nano zirconium oxide dispersion is 8-10, the pH value is out of the range, and both too low and too high dispersion effects are poor; most preferably, the short organic acid-modified nano zirconia dispersion has a solid content of 0 to 10 wt%.

In a specific embodiment of the invention, in the step 4), the mass ratio of the nanoparticle dispersion to the prepolymer is 1.1:1-2.3: 1. The amount of the nanoparticle dispersion used in the present invention is outside this range, and low amounts are difficult to emulsify or poor emulsion stability; high solids content results in too low a solids content, which increases transportation costs.

In a specific embodiment of the invention, in the step 4), the feeding speed ratio of the nanoparticle dispersion to the prepolymer during emulsification is 2:1-1:1, and after the feeding is completed, the nanoparticle dispersion and the prepolymer are circulated at a speed of 500mL/min for each strand for 5-15min at a temperature of 25-35 ℃ and a rotating speed of the rotating packed bed of 1500-.

In a specific embodiment of the invention, in the step 4), the auxiliary agent is one or more of DF-8102, DF-8205, DF-831 and EFKA-3033; preferably, the amount of the auxiliary agent is 0 to 0.6 wt% of the total amount of the synthetic raw materials (i.e., polyisocyanate monomer, polyol monomer, hydrophilic chain extender, small-molecule chain extender and neutralizing agent). The auxiliary agent can reduce the generation of bubbles of the adhesive and enhance the wettability of the adhesive.

The waterborne polyurethane adhesive prepared by the preparation method is also within the protection scope of the invention.

The aqueous polyurethane adhesive obtained by the invention has good mechanical property, the tensile strength is between 12 and 15MPa, and the elongation at break is between 450 and 720 percent; the bonding effect is strong, and the bonding strength is between 1.5 and 2.3 MPa; the cleaning is easy, and the residual glue can be wiped and removed by ethanol after being stripped; no organic solvent, environmental protection, good storage stability, and suitability for various fields of metal, glass and plastic.

The scope of the present invention includes the endpoints and any number between the endpoints and any subrange between the endpoints or any number between the endpoints.

The invention has the following beneficial effects:

the preparation method of the waterborne polyurethane adhesive has the advantages of low cost, low energy consumption, simple process and good development prospect. The waterborne polyurethane adhesive prepared by the preparation method has the advantages of no solvent volatilization, environmental protection, good storage stability, good mechanical property, strong bonding effect, easy cleaning, suitability for bonding of various substrates such as metal, glass, plastic and the like, and further widens the application range of the waterborne polyurethane adhesive.

Drawings

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.

FIG. 1 is a stress-strain curve of the test piece of example 1.

FIG. 2 is a bonding curve of the stainless steel material in example 1.

Fig. 3 is a picture of the erasing effect of the residual glue in the embodiment 1.

FIG. 4 is a stress-strain curve of the test piece of example 2.

FIG. 5 is a bonding curve of the glass substrate in example 2.

Fig. 6 is a picture showing the erasing effect of the residual glue in the embodiment 2.

FIG. 7 is a stress-strain curve of the test piece of example 3.

FIG. 8 shows the adhesion curve of the PET plastic of example 3.

Fig. 9 is a picture showing the erasing effect of the residual glue in the embodiment 3.

FIG. 10 is a stress-strain curve of the test piece of example 4.

Fig. 11 is a bonding curve of wood in example 4.

Fig. 12 is a picture showing the erasing effect of the residual glue in the embodiment 4.

Fig. 13 is a bonding curve of the glass substrate in comparative example 5.

Detailed Description

In order to more clearly illustrate the present invention, the present invention is further described below with reference to preferred embodiments and the accompanying drawings. Similar components in the figures are denoted by the same reference numerals. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and is not to be taken as limiting the scope of the invention.

All starting materials in the present invention are commercially available, unless otherwise specified, and the equipment used in the present invention may be performed by conventional equipment in the art or by reference to the prior art in the art.

Example 1 preparation of a waterborne polyurethane adhesive

A preparation method of a water-based polyurethane adhesive comprises the following steps:

weighing 15g of isophorone diisocyanate and 27.6g of polypropylene glycol 2000, putting the isophorone diisocyanate and 27.6g of polypropylene glycol 2000 into a four-neck flask with a stirring, condensing and nitrogen protection device, heating to 90 ℃, and stirring for reacting for 2 hours to obtain a reactant A;

adding 1.7g of 2, 2-dimethylolpropionic acid and 1.69g of 1, 4-butanediol into the reactant A, performing chain extension reaction for 3 hours at 90 ℃, adding 2mL of acetone into the reactor every 15min after the chain extension reaction for 1 hour so as to reduce the system viscosity, and cooling to 50 ℃ to obtain a reactant B;

adding 1.41g of triethylamine into the reactant B, carrying out neutralization reaction for 0.5h at 50 ℃, and cooling to 30 ℃ to obtain a prepolymer;

starting a rotary packed bed, adjusting the rotating speed to 2000rpm, conveying 71.1g of tartaric acid modified nano zirconium oxide dispersion (the solid content is 1 wt%, and the pH value is 10) and 47.4g of prepolymer to the rotary packed bed together at a feeding speed ratio of 1.5:1 for emulsification, building a magnetic stirring device at an outlet, circulating at a speed of 420mL/min for 10min each strand after feeding is finished, removing residual acetone by rotary evaporation at the temperature of 30 ℃, under the vacuum degree of 0.09MPa and at the temperature of 40 ℃, and adding 0.2g of EFKA-3033 when no bubbles bulge out to obtain the waterborne polyurethane adhesive.

And (3) introducing the waterborne polyurethane adhesive into a centrifuge tube, and centrifuging for 15min at the temperature of 25 ℃ and the rotating speed of 3000rpm, wherein the result shows that no obvious precipitate is generated at the bottom of the centrifuge tube, and the prepared waterborne polyurethane adhesive has better storage stability.

Pouring the waterborne polyurethane adhesive into a polytetrafluoroethylene mold, preparing a dumbbell test piece according to GB/T16777-. The stress-strain curve of the waterborne polyurethane adhesive is obtained by a universal tensile machine, and the result is shown in figure 1, so that the tensile strength of the prepared waterborne polyurethane adhesive reaches 14.9MPa, the elongation at break reaches 712%, and the waterborne polyurethane adhesive has better mechanical property.

The water-based polyurethane adhesive is taken to test the adhesion effect on stainless steel, and the adhesion area is as follows: 1cm × 1 cm. The adhesive property curve of the aqueous polyurethane adhesive to the stainless steel is obtained by a universal tensile machine, and the result is shown in figure 2, and the figure shows that the adhesive strength of the aqueous polyurethane adhesive to the stainless steel is 2.05MPa, and the adhesive has a better adhesive effect.

The cleaning effect of wiping the residual aqueous polyurethane adhesive with ethanol is obtained by camera shooting, and as shown in fig. 3, the prepared aqueous polyurethane adhesive has the characteristic of easy cleaning.

Example 2 preparation method of aqueous polyurethane adhesive

weighing 15g of isophorone diisocyanate and 26.7g of polypropylene glycol 2000, putting the isophorone diisocyanate and the polypropylene glycol 2000 into a four-neck flask with a stirring, condensing and nitrogen protection device, heating to 95 ℃, and stirring for reacting for 1.5 hours to obtain a reactant A;

adding 1.25g of 2, 2-dimethylolpropionic acid and 1.54g of 1, 4-butanediol into the reactant A, performing chain extension reaction for 3 hours at 95 ℃, adding 1.8mL of acetone into the reactor every 13min after the chain extension reaction is performed for 1 hour so as to reduce the system viscosity, and cooling to 55 ℃ to obtain a reactant B;

adding 1.04g of triethylamine into the reactant B, carrying out neutralization reaction at 55 ℃ for 0.5h, and cooling to 30 ℃ to obtain a prepolymer;

starting a rotary packed bed, adjusting the rotating speed to 2500rpm, conveying 84.6g of deionized water and 45.53g of prepolymer into the rotary packed bed together at a feeding speed ratio of 1.3:1 for emulsification, building a magnetic stirring device at an outlet, and circulating at a speed of 450mL/min per strand for 8min at a temperature of 30 ℃ after feeding is finished; under the vacuum degree of 0.09MPa, residual acetone is evaporated in a rotary manner at 40 ℃, when no bubbles are blown out, 0.1g of EFKA-3033 and 0.1g of DF-831 are added to obtain the aqueous polyurethane adhesive.

Pouring the waterborne polyurethane adhesive into a polytetrafluoroethylene mold, preparing a dumbbell test piece according to GB/T16777-. The stress-strain curve of the waterborne polyurethane adhesive is obtained by a universal tensile machine, the result is shown in figure 4, and the figure shows that the tensile strength of the prepared waterborne polyurethane adhesive reaches 12.08MPa, the elongation at break reaches 580%, and the waterborne polyurethane adhesive has better mechanical property.

The water-based polyurethane adhesive is taken to test the bonding effect on the glass substrate, and the bonding area is as follows: 1cm × 1 cm. The bonding performance curve of the aqueous polyurethane adhesive to the glass substrate is obtained by a universal tensile machine, and the result is shown in fig. 5, and the figure shows that the bonding strength of the aqueous polyurethane adhesive to the glass substrate is 1.7MPa, and the aqueous polyurethane adhesive has a better bonding effect.

The cleaning effect of wiping the residual waterborne polyurethane adhesive with ethanol is obtained by shooting with a camera, and as shown in fig. 6, the prepared waterborne polyurethane adhesive has the characteristic of easy cleaning.

Example 3 preparation method of aqueous polyurethane adhesive

weighing 15g of diphenylmethane diisocyanate and 32.9g of polypropylene glycol 2000, putting the diphenylmethane diisocyanate and the polypropylene glycol 2000 into a four-neck flask with a stirring, condensing and nitrogen protection device, heating to 90 ℃, and stirring for reaction for 2 hours to obtain a reactant A;

adding 1.92g of 2, 2-dimethylolpropionic acid and 0.8g of 1, 4-butanediol into the reactant A, performing chain extension reaction for 3 hours at 90 ℃, adding 1.5mL of acetone into the reactor every 10min after the chain extension reaction for 1 hour so as to reduce the system viscosity, and cooling to 50 ℃ to obtain a reactant B;

adding 1.6g of triethylamine into the reactant B, carrying out neutralization reaction for 0.5h at 50 ℃, and cooling to 30 ℃ to obtain a prepolymer;

starting a rotary packed bed, adjusting the rotation speed to 1500rpm, conveying 57.42g of citric acid modified nano zirconium oxide dispersoid (the solid content is 5 wt%, and the pH value is 9) and 52.2g of prepolymer into the rotary packed bed together at a feeding speed ratio of 1:1 for emulsification, building a magnetic stirring device at an outlet, and circulating at the speed of 400mL/min per strand for 10min at the temperature of 30 ℃ after the feeding is finished; under the vacuum degree of 0.09MPa, residual acetone is evaporated in a rotary manner at 40 ℃, when no bubbles are blown out, 0.2g of EFKA-3033 is added to obtain the water-based polyurethane adhesive.

Pouring the waterborne polyurethane adhesive into a polytetrafluoroethylene mold, preparing a dumbbell test piece according to GB/T16777-. The stress-strain curve of the waterborne polyurethane adhesive is obtained by a universal tensile machine, the result is shown in figure 7, and the figure shows that the tensile strength of the prepared waterborne polyurethane adhesive reaches 12.8MPa, the elongation at break reaches 612%, and the waterborne polyurethane adhesive has better mechanical properties.

The water-based polyurethane adhesive is taken to test the bonding effect on PET plastics, and the bonding area is as follows: 1cm × 1 cm. The bonding performance curve of the waterborne polyurethane adhesive to the PET plastic is obtained by a universal tensile machine, and the result is shown in figure 8, and the figure shows that the bonding strength of the waterborne polyurethane adhesive to the PET plastic is 1.57MPa, so that the waterborne polyurethane adhesive has a better bonding effect.

The cleaning effect of wiping the residual waterborne polyurethane adhesive with ethanol is obtained by shooting with a camera, and as shown in fig. 9, the prepared waterborne polyurethane adhesive has the characteristic of easy cleaning.

Example 4 preparation method of easily-cleaned waterborne polyurethane adhesive

weighing 15g of isophorone diisocyanate and 26.9g of polypropylene glycol 2000, putting the isophorone diisocyanate and the polypropylene glycol 2000 into a four-neck flask with a stirring, condensing and nitrogen protection device, heating to 90 ℃, and stirring for reacting for 2 hours to obtain a reactant A;

adding 1.67g of 2, 2-dimethylolpropionic acid and 1.24g of 1, 4-butanediol into the reactant A, performing chain extension reaction for 3 hours at 90 ℃, adding 2mL of acetone into the reactor every 15min after the chain extension reaction is performed for 1 hour so as to reduce the system viscosity, and cooling to 50 ℃ to obtain a reactant B;

adding 1.39g of triethylamine into the reactant B, carrying out neutralization reaction for 0.5h at 50 ℃, and cooling to 30 ℃ to obtain a prepolymer;

starting a rotary packed bed, adjusting the rotating speed to 2000rpm, conveying 69.3g of citric acid modified nano zirconium oxide dispersoid (the solid content is 3 wt%, and the pH value is 9.5) and 46.2g of prepolymer together into the rotary packed bed at a feeding speed ratio of 1:1 for emulsification, building a magnetic stirring device at an outlet, and circulating at a speed of 420mL/min per strand for 10min at the temperature of 30 ℃ after the feeding is finished; under the vacuum degree of 0.09MPa, residual acetone is evaporated in a rotary way at 40 ℃, and when no bubbles bubble out, the aqueous polyurethane adhesive is obtained.

Pouring the waterborne polyurethane adhesive into a polytetrafluoroethylene mold, preparing a dumbbell test piece according to GB/T16777-. The stress-strain curve of the waterborne polyurethane adhesive is obtained by a universal tensile machine, the result is shown in figure 10, and the figure shows that the tensile strength of the prepared waterborne polyurethane adhesive reaches 13.7MPa, the elongation at break reaches 475%, and the adhesive has better mechanical property.

The bonding effect of the waterborne polyurethane adhesive on the wood board is tested, and the bonding area is as follows: 1cm × 1 cm. The bonding performance curve of the waterborne polyurethane adhesive to the wood board is obtained by a universal tensile machine, and the result is shown in fig. 11, and the bonding strength of the waterborne polyurethane adhesive to the wood board is 2.2MPa, so that the waterborne polyurethane adhesive has a good bonding effect.

The cleaning effect of wiping the residual waterborne polyurethane adhesive with ethanol is obtained by shooting with a camera, and as shown in fig. 12, the prepared waterborne polyurethane adhesive has the characteristic of easy cleaning.

Comparative example 1

Example 1 was repeated with the difference that: the amount of tartaric acid-modified nano-zirconia dispersion added was 40g, and the other steps were the same. The comparative example had too high a viscosity during emulsification and failed emulsification.

Comparative example 2

Example 1 was repeated with the difference that: the emulsification is not carried out by adopting a rotary packed bed, the emulsification is carried out by adopting the traditional mechanical stirring, and other steps are the same. The aqueous polyurethane adhesive of this comparative example had poor storage stability.

Comparative example 3

Example 1 was repeated with the difference that: the acetic acid modified nano zirconium oxide dispersoid is added, and other steps are the same. The acetic acid modified nano-zirconia dispersoid of the comparative example directly causes the instability and the caking of the aqueous polyurethane adhesive.

Comparative example 4

Example 1 was repeated with the difference that: 1g of 2, 2-dimethylolpropionic acid was added, and the other steps were the same. The aqueous polyurethane adhesive of this comparative example had poor storage stability.

Comparative example 5

The adhesion effect of a commercially available adhesive on a glass substrate was measured, and the adhesion performance curve of the commercially available adhesive on the glass substrate was obtained by a universal tensile machine, and the result is shown in fig. 13. The comparative example had an adhesive strength of 1.05MPa, but the residual adhesive was not easily removed.

It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention, and it will be obvious to those skilled in the art that other variations or modifications may be made on the basis of the above description, and all embodiments may not be exhaustive, and all obvious variations or modifications may be included within the scope of the present invention.

Claims

1. The preparation method of the water-based polyurethane adhesive is characterized by comprising the following steps:

2. The preparation method according to claim 1, wherein the polyisocyanate monomer is one or more of isophorone diisocyanate, toluene diisocyanate and diphenylmethane diisocyanate, and the polyol monomer is one or two of polytetrahydrofuran ether glycol and polypropylene glycol; preferably, the polyisocyanate monomer is isophorone diisocyanate, and the polyol monomer is polypropylene glycol 2000; more preferably, the mass ratio of the polyisocyanate monomer to the polyol monomer is from 1:1.21 to 1: 2.71.

3. The preparation method according to claim 1, wherein the temperature of the stirring reaction is 85-95 ℃ and the time is 1.5-2.5 h; preferably, the inert shielding gas is high purity nitrogen.

4. The preparation method according to claim 1, wherein the hydrophilic chain extender is 2, 2-dimethylolpropionic acid, and the small-molecule chain extender is 1, 4-butanediol; preferably, the hydrophilic chain extender is used in an amount of 3 to 5 wt% of the total amount of the polyisocyanate monomer and the polyol monomer; the using amount of the micromolecular chain extender is 0-7 wt% of the total amount of the polyisocyanate monomer and the polyol monomer; more preferably, the temperature of the chain extension reaction is 85-95 ℃ and the time is 25-35 min.

5. The method of claim 1, wherein the solvent is acetone; preferably, 1.5-2.5mL of the solvent is added every 10-15min after the chain extension reaction is performed for 1 h.

6. The method of claim 1, wherein the neutralizing agent is triethylamine; preferably, the molar ratio of the neutralizing agent to the hydrophilic chain extender is 1:1 to 1.2: 1; more preferably, the temperature of the neutralization reaction is 45-55 ℃ and the time is 25-35 min.

7. The method for preparing according to claim 1, wherein the nanoparticle dispersion is a short organic acid-modified nano zirconia dispersion; preferably, the short organic acid is any one of tartaric acid and citric acid; more preferably, the pH of the short organic acid-modified nano zirconia dispersion is 8 to 10; most preferably, the short organic acid-modified nano zirconia dispersion has a solid content of 0 to 10 wt%.

8. The preparation method according to claim 1, wherein the mass ratio of the nanoparticle dispersion to the prepolymer is 1.1:1-2.3: 1; preferably, the feeding speed ratio of the nanoparticle dispersion to the prepolymer during emulsification is 2:1-1:1, and after the feeding is finished, the mixture is circulated at the speed of 500mL/min for each strand of 400-.

9. The preparation method of claim 1, wherein the auxiliary agent is one or more of DF-8102, DF-8205, DF-831 and EFKA-3033; preferably, the amount of the auxiliary agent is 0 to 0.6 wt% of the total amount of the polyisocyanate monomer, the polyol monomer, the hydrophilic chain extender, the small molecule chain extender and the neutralizing agent.

10. An aqueous polyurethane adhesive prepared by the process according to any one of claims 1 to 9.