阅读说明：本技术 一种亲水异氰酸酯交联剂及其制备方法 (Hydrophilic isocyanate crosslinking agent and preparation method thereof ) 是由 谭星 欧阳洁 于 2021-07-22 设计创作，主要内容包括：本发明公开了一种亲水异氰酸酯交联剂及其制备方法,属于水性交联剂技术领域。本发明亲水异氰酸酯交联剂的制备方法为：将端位含有两个羟基的聚醚聚硅氧烷A与过量的二异氰酸酯混合,反应完全,得含有氨基甲酸酯键的异氰酸酯封端的聚醚聚硅氧烷C；接着向前述反应完全的体系中加入催化剂催化剩余的二异氰酸酯和含有氨基甲酸酯键的异氰酸酯封端的聚醚聚硅氧烷C反应完全,最后除去仍剩余的二异氰酸酯,得亲水异氰酸酯交联剂。采用该制备方法得到的亲水异氰酸酯交联剂作为水性双组份聚氨酯涂料的异氰酸酯组分所得到的涂料具有优异的耐划伤性和耐磨性。(The invention discloses a hydrophilic isocyanate crosslinking agent and a preparation method thereof, belonging to the technical field of water-based crosslinking agents. The preparation method of the hydrophilic isocyanate crosslinking agent comprises the following steps: mixing polyether polysiloxane A with two hydroxyl groups at the end positions with excessive diisocyanate, and completely reacting to obtain isocyanate-terminated polyether polysiloxane C with a urethane bond; and then adding a catalyst into the completely reacted system to catalyze the residual diisocyanate to completely react with the isocyanate-terminated polyether polysiloxane C containing the urethane bond, and finally removing the residual diisocyanate to obtain the hydrophilic isocyanate crosslinking agent. The hydrophilic isocyanate crosslinking agent obtained by the preparation method is used as an isocyanate component of the aqueous two-component polyurethane coating, and the obtained coating has excellent scratch resistance and wear resistance.)

1. A preparation method of a hydrophilic isocyanate crosslinking agent is characterized by comprising the following steps:

(1) mixing polyether polysiloxane A with excessive diisocyanate, and completely reacting to obtain isocyanate-terminated polyether polysiloxane C containing a urethane bond;

(2) adding a catalyst into the system completely reacted in the step (1) to catalyze the residual diisocyanate to completely react with the isocyanate-terminated polyether polysiloxane C containing a urethane bond, and then removing the residual diisocyanate to obtain a hydrophilic isocyanate crosslinking agent;

wherein, the structural formula of the polyether polysiloxane A is as follows:

wherein n is 5 to 30, and x is 5 to 30.

2. The method for preparing a hydrophilic isocyanate crosslinking agent according to claim 1, wherein in the step (1), the diisocyanate is hexamethylene diisocyanate, pentamethylene diisocyanate, isophorone diisocyanate or dicyclohexylmethane-4, 4' -diisocyanate.

3. The preparation method of the hydrophilic isocyanate crosslinking agent according to claim 1, wherein in the step (1), the molar ratio of diisocyanate to polyether polysiloxane A is 10-20: 1.

4. the preparation method of the hydrophilic isocyanate crosslinking agent according to claim 1, wherein in the step (1), the reaction temperature is 90-130 ℃ and the reaction time is 2-4 h.

5. The method of claim 1, wherein in the step (2), the catalyst is zinc isooctanoate, bismuth isooctanoate, zirconium isooctanoate, dibutyl tin dilaurate or stannous octoate.

6. The method for preparing the hydrophilic isocyanate crosslinking agent according to claim 1, wherein in the step (2), the amount of the catalyst is 0.01-0.1% of the total weight of the reaction materials.

7. The preparation method of the hydrophilic isocyanate crosslinking agent according to claim 1, wherein in the step (2), the reaction temperature is 90-130 ℃ and the reaction time is 8-30 h.

8. The method for preparing a hydrophilic isocyanate crosslinking agent according to claim 1, wherein in the step (2), the diisocyanate remaining is removed by evaporation.

9. A hydrophilic isocyanate crosslinking agent, which is characterized by being prepared by the preparation method of the hydrophilic isocyanate crosslinking agent as claimed in any one of claims 1 to 8.

10. A coating material containing a hydrophilic isocyanate crosslinking agent, comprising the hydrophilic isocyanate crosslinking agent according to claim 9.

Technical Field

The invention belongs to the technical field of water-based crosslinking agents, and particularly relates to a hydrophilic isocyanate crosslinking agent and a preparation method thereof.

Background

With the increasing strictness of environmental regulations, the limitation of volatile organic compounds of coatings is increasing, and water-based coatings using water as a dispersion medium have been used in many fields to replace conventional solvent-based resins. The hydrophilic modified isocyanate cross-linking agent can be dispersed and emulsified in a water phase, and can be matched with water-based hydroxyl resin to obtain a high-performance water-based two-component polyurethane coating which is comparable to a solvent-based coating.

Patents US4433095 and US4663377 report that mono-alkyl terminated polyether is used as hydrophilic modifier to synthesize non-ionic hydrophilic isocyanate cross-linking agent, which can be used in aqueous two-component polyurethane coating, but this modification method can reduce the functionality of isocyanate, resulting in insufficient chemical resistance. Patent US6426414 reports that allophanatized nonionic hydrophilic isocyanate crosslinking agents are synthesized by using monoalkyl terminated polyether as a hydrophilic modifier and adding a metal catalyst, and the crosslinking agents synthesized by the method have high functionality and excellent chemical resistance. Patent US 67958 reports the synthesis of anionic hydrophilic isocyanate crosslinkers of the sulfonate type with 3- (cyclohexylamine) -1-propanesulfonic acid or 3- (cyclohexylamine) -1-ethanesulfonic acid as hydrophilic modifier, with excellent hardness and chemical resistance. However, the hydrophilic isocyanate crosslinking agents described in the patent US6426414 and the patent US6767958 do not introduce polysiloxane segments, and the scratch resistance and abrasion resistance of the prepared coating are general. Patent CN101855274A reports that polysiloxane modified polyisocyanate can significantly improve the scratch resistance of coating by graft reaction of polysiloxane containing hydroxyl group to polyisocyanate, but this method can synthesize modified polyisocyanate with very low content of silicone segment and no hydrophilic segment, and can only be used in solvent-based system.

Disclosure of Invention

The present invention has been made to overcome the above-mentioned disadvantages of the prior art and to provide a hydrophilic isocyanate crosslinking agent having high functionality and excellent chemical properties and a method for preparing the same.

In order to achieve the purpose, the invention adopts the technical scheme that: a method for preparing a hydrophilic isocyanate crosslinking agent, comprising the steps of:

(1) mixing polyether polysiloxane A with excessive diisocyanate, and completely reacting to obtain isocyanate-terminated polyether polysiloxane C containing a urethane bond;

(2) adding a catalyst into the system completely reacted in the step (1) to catalyze the residual diisocyanate and the isocyanate-terminated polyether polysiloxane C containing the urethane bond to completely react, and then removing the residual diisocyanate to obtain the hydrophilic isocyanate crosslinking agent.

Wherein, the structural formula of the polyether polysiloxane A is as follows:

wherein n is 5 to 30, and x is 5 to 30.

According to the technical scheme, polyether polysiloxane A with two hydroxyl groups at the terminal positions is selected to be completely reacted with excessive diisocyanate, then no post-treatment is needed, a catalyst is directly added into a first-step reaction complete system to enable the remaining diisocyanate to further react with a first-step product, and finally the remaining diisocyanate after the two-step reaction is removed, so that the hydrophilic isocyanate crosslinking agent is obtained. The hydrophilic isocyanate crosslinking agent obtained by the technical scheme of the invention has high crosslinking density, high functionality and high polysiloxane chain segment content, the theoretical functionality is 4, the crosslinking agent contains polyether hydrophilic chain segments, the hydrophilic isocyanate crosslinking agent can be well dispersed and emulsified in water, and a paint film with excellent scratch resistance and wear resistance can be obtained by matching with aqueous hydroxyl resin.

As a preferred embodiment of the method for preparing the hydrophilic isocyanate crosslinking agent of the present invention, in the step (1), the diisocyanate is Hexamethylene Diisocyanate (HDI), Pentamethylene Diisocyanate (PDI), isophorone diisocyanate (IPDI), or dicyclohexylmethane-4, 4' -diisocyanate (hydrogenated MDI).

As a preferred embodiment of the preparation method of the hydrophilic isocyanate crosslinking agent of the present invention, in the step (1), the molar ratio of diisocyanate to polyether polysiloxane a is 10 to 20: 1. too low a molar ratio of diisocyanate to polyether polysiloxane a results in longer reaction times and incomplete reaction; too high a molar ratio of diisocyanate to polyether polysiloxane A would increase the amount of diisocyanate recovered by evaporation in step (2), increasing the cost of the process.

As a preferred embodiment of the preparation method of the hydrophilic isocyanate crosslinking agent, in the step (1), the reaction temperature is 90-130 ℃, the reaction time is 2-4 h, and the reaction end point is determined when hydroxyl is completely consumed by infrared detection.

As a preferred embodiment of the method for preparing the hydrophilic isocyanate crosslinking agent according to the present invention, in the step (2), the catalyst is zinc isooctanoate, bismuth isooctanoate, zirconium isooctanoate, dibutyl tin dilaurate or stannous octoate.

As a preferred embodiment of the preparation method of the hydrophilic isocyanate crosslinking agent, in the step (2), the amount of the catalyst is 0.01-0.1% of the total weight of the materials.

As a preferred embodiment of the preparation method of the hydrophilic isocyanate crosslinking agent, in the step (2), the reaction temperature is 90-130 ℃, the reaction time is 8-30 h, and the reaction end point is determined when the allophanate group is completely consumed by infrared detection.

As a preferred embodiment of the preparation method of the hydrophilic isocyanate crosslinking agent, in the step (2), after the reaction is completed, phosphoric acid is added to terminate the allophanatization reaction, wherein the amount of the phosphoric acid is 0.01-0.1% of the total weight of the materials.

As a preferred embodiment of the preparation method of the hydrophilic isocyanate crosslinking agent, in the step (2), the method for removing the residual diisocyanate by evaporation is film evaporation, and the excess diisocyanate is recycled by evaporation with a film evaporator, so that the recycling of the excess diisocyanate can be realized, and the energy conservation and the environmental protection are realized.

As a preferred embodiment of the method for preparing the hydrophilic isocyanate crosslinking agent according to the present invention, in the step (2), the obtained hydrophilic isocyanate crosslinking agent may be diluted without using a solvent, or may be diluted with a suitable solvent to reduce the viscosity. Among the suitable solvents are inert solvents of the esters and ethers which do not react with isocyanates, such as propylene glycol methyl ether acetate, propylene glycol diacetate, dipropylene glycol dimethyl ether, diethylene glycol dimethyl ether.

In addition, the invention also provides the hydrophilic isocyanate crosslinking agent prepared by the method.

In addition, the invention also provides a coating containing the hydrophilic isocyanate crosslinking agent prepared by the method.

Compared with the prior art, the invention has the beneficial effects that: the preparation method is simple and feasible, and the used excessive diisocyanate can be recovered, so that the method is economic and environment-friendly. The hydrophilic isocyanate crosslinking agent obtained by the technical scheme of the invention has high crosslinking density, high functionality and high polysiloxane chain segment content, the theoretical functionality is 4, the crosslinking agent contains polyether hydrophilic chain segments, the hydrophilic isocyanate crosslinking agent can be well dispersed and emulsified in water, and a paint film with excellent scratch resistance and wear resistance can be obtained by matching with aqueous hydroxyl resin.

Detailed Description

To better illustrate the objects, aspects and advantages of the present invention, the present invention will be further described with reference to specific examples.

The synthesis method and steps are shown in specific examples, except that the raw material polyether polysiloxane A is synthesized by the applicant, and the rest of the reagents or instruments used are not indicated by manufacturers, and are all conventional products which can be obtained by commercial purchase. The preparation method of the hydrophilic isocyanate crosslinking agent comprises the following steps.

Example 1

The hydrophilic isocyanate crosslinking agent E1 of the embodiment of the invention takes polyether polysiloxane A1(n is 11.4, x is 10.0) as a starting material, the molar ratio of the polyether polysiloxane A1(n is 11.4, x is 10.0) to hexamethylene diisocyanate is 1:15, and the catalyst is zinc isooctanoate, and the preparation method is as follows:

(1) synthesis of polyether polysiloxane a1(n ═ 11.4, x ═ 10.0): 306.0kg of polyethylene glycol monoallyl ether having a molecular weight of 500 and 3.0kg of a Kaster catalyst (platinum content 1000ppm) were added to a reaction vessel filled with nitrogen, stirred, heated to 100 ℃, 292.7kg of terminal hydrogen-containing silicone oil having a hydrogen content of 0.205% was added dropwise, reaction was continued at 100 ℃ for 4 hours after about 1 hour of dropwise addition, and the Si-H conversion rate was monitored to 98% by dehydrogenation with n-butanol under alkaline conditions. Finally, vacuumizing to remove low-boiling-point impurities, and filtering to obtain 580.0kg of near-colorless liquid, namely polyether polysiloxane A1(n is 11.4, and x is 10.0);

(2) adding the polyether polysiloxane A1(n is 11.4, x is 10.0) (55.3kg, 27.98mol) obtained in the step (1) and hexamethylene diisocyanate (70.6kg, 419.76mol) into a reaction vessel filled with nitrogen, stirring, heating to 110 ℃, reacting for 3 hours, adding zinc isooctanoate (0.065kg) into the reaction system after no hydroxyl group remains in the reaction system in infrared (FT-IR) detection, keeping the temperature constant, continuing stirring for 12 hours, adding phosphoric acid (0.065kg) to terminate the allophanatization reaction after no urethane bond remains in the reaction system in infrared (FT-IR) detection, and sampling to obtain the NCO content of 24.0%. And finally, removing the residual hexamethylene diisocyanate in the reaction system by a thin film evaporator at the temperature of 140 ℃/0.05kPa to obtain 72.3kg of the hydrophilic isocyanate crosslinking agent E1. The hydrophilic isocyanate crosslinking agent E1 had an isocyanate content of 6.2% as determined by the di-n-butylamine method and a viscosity of 4200cps (25 ℃ C.), the theoretical polysiloxane segment content being 37% (w/w). The product can be rapidly dispersed in 10 times the mass of water by hand stirring to form a white emulsion with blue light.

Example 2

The hydrophilic isocyanate crosslinking agent E2 of the embodiment of the invention takes polyether polysiloxane A2(n is 14.5, x is 6.6) as a starting material, the molar ratio of the polyether polysiloxane A2(n is 14.5, x is 6.6) to hexamethylene diisocyanate is 1:15, and the catalyst is zinc isooctanoate, and the preparation method is as follows:

(1) synthesis of polyether polysiloxane a2(n ═ 14.5, x ═ 6.6): 214.2kg of polyethylene glycol monoallyl ether having a molecular weight of 350 and 3.0kg of a Kaster catalyst (platinum content 1000ppm) were added to a reaction vessel filled with nitrogen, stirred, heated to 100 ℃, 361.5kg of terminal hydrogen-containing silicone oil having a hydrogen content of 0.166% were added dropwise, the reaction was continued at 100 ℃ for 4 hours after the dropwise addition was completed for about 1 hour, and the Si-H conversion rate was monitored to be 98% by dehydrogenation with n-butanol under alkaline conditions. Finally, low-boiling point impurities are removed by vacuum pumping, and 559.2g of nearly colorless liquid is obtained by suction filtration, namely polyether polysiloxane A2(n is 14.5, and x is 6.6).

(2) The polyether polysiloxane a2(n is 14.5, x is 6.6) (53.3kg, 27.98mol) obtained in step (1) and hexamethylene diisocyanate (70.6kg, 419.76mol) were added to a reaction vessel filled with nitrogen, stirred, heated to 110 ℃ for 3 hours, after no hydroxyl group remained in the reaction system as measured by infrared (FT-IR), zinc isooctanoate (0.065kg) was added to the reaction system, the reaction was stirred for 12 hours while keeping the temperature constant, and after no urethane bond remained in the reaction system as measured by infrared (FT-IR), phosphoric acid (0.065kg) was added to terminate the allophanatization reaction, and the NCO content was measured by sampling to be 24.4%. And finally, removing the residual hexamethylene diisocyanate in the reaction system by a thin film evaporator at the temperature of 140 ℃/0.05kPa to obtain 70.7kg of the hydrophilic isocyanate crosslinking agent E2. The hydrophilic isocyanate crosslinking agent E2 had an isocyanate content of 6.4% as determined by the di-n-butylamine method and a viscosity of 3800cps (25 ℃ C.), the theoretical polysiloxane segment content being 47% (w/w). The product can be rapidly dispersed in 10 times the mass of water by hand stirring to form a white emulsion with blue light.

Example 3

The hydrophilic isocyanate crosslinking agent E3 of the embodiment of the invention takes polyether polysiloxane A3(n is 25.2, x is 21.4) as a starting material, the molar ratio of the polyether polysiloxane A3(n is 25.2, x is 21.4) to hexamethylene diisocyanate is 1:15, and the catalyst is zinc isooctanoate, and the preparation method is as follows:

(1) synthesis of polyether polysiloxane a3(n ═ 25.2, x ═ 21.4): 612.0kg of polyethylene glycol monoallyl ether having a molecular weight of 1000 and 6kg of a Kaster catalyst (platinum content 1000ppm) were added to a reaction vessel filled with nitrogen, stirred, heated to 100 ℃, 600.0kg of terminal hydrogen-containing silicone oil having a hydrogen content of 0.100% was added dropwise, reaction was continued at 100 ℃ for 4 hours after about 1 hour of dropwise addition, and the Si-H conversion rate was monitored to 98% by dehydrogenation with n-butanol under alkaline conditions. Finally, low-boiling point impurities are removed by vacuum pumping, and 1172.0g of nearly colorless liquid is obtained by vacuum filtration, namely polyether polysiloxane A3(n is 25.2, and x is 21.4).

(2) The polyether polysiloxane a3(n is 25.2, x is 21.4) (111.9kg, 27.98mol) obtained in step (1) and hexamethylene diisocyanate (70.6kg, 419.76mol) were added to a reaction vessel filled with nitrogen, stirred, heated to 110 ℃ for 3 hours, after no hydroxyl group remained as detected by infrared (FT-IR), zinc isooctanoate (0.095kg) was added to the reaction system, the reaction was stirred for 15 hours while keeping the temperature constant, after no urethane bond remained as detected by infrared (FT-IR), phosphoric acid (0.095kg) was added to terminate the allophanatization reaction, and the NCO content was measured by sampling to be 16.6%. Finally, the reaction system is passed through a film evaporator at 140 ℃/0.05kPa to remove the hexamethylene diisocyanate still remained in the reaction system, thus obtaining 127.8kg of the hydrophilic isocyanate crosslinking agent E3. The hydrophilic isocyanate crosslinking agent E3 had an isocyanate content of 3.6% and a viscosity of 5800cps (25 ℃ C.) as determined by the di-n-butylamine method, and a theoretical polysiloxane segment content of 43% (w/w). The product can be rapidly dispersed in 10 times the mass of water by hand stirring to form a white emulsion with blue light.

Example 4

The hydrophilic isocyanate crosslinking agent E5 of the embodiment of the invention takes polyether polysiloxane A1(n is 11.4, x is 10.0) as a starting material, the molar ratio of the polyether polysiloxane to the isophorone diisocyanate is 1:10, and the catalyst is dibutyl tin dilaurate, and the preparation method is as follows:

polyether polysiloxane a1 (n: 11.4, x: 10.0) (83.0kg, 42.00mol) obtained in step (1) of example 1 and isophorone diisocyanate (93.4kg, 420.00mol) were charged into a reaction vessel filled with nitrogen, stirred, heated to 110 ℃ for 5 hours, reacted for 5 hours, after no hydroxyl group remained as detected by infrared (FT-IR), dibutyl tin dilaurate (0.088kg) was added to the reaction system, the reaction was stirred for 18 hours, and after no urethane bond remained as detected by infrared (FT-IR), phosphoric acid (0.088kg) was added to terminate the allophanatization reaction, and the NCO content was measured as 15.8% by sampling. Finally, the reaction mixture system is removed by a thin film evaporator at 160 ℃/0.05kPa to obtain 170.1kg of hydrophilic isocyanate crosslinking agent E4 after being diluted by 51.6kg of PMA. The solid content of the hydrophilic isocyanate crosslinking agent E4, measured by the di-n-butylamine method, was 70%, the isocyanate content was 4.0%, the viscosity was 400cps (25 ℃), and the theoretical polysiloxane segment content was 34% (w/w) of the solid content. The product can be rapidly dispersed in 10 times the mass of water by hand stirring to form a white emulsion with blue light.

Example 5

The hydrophilic isocyanate crosslinking agent E5 of the embodiment of the invention takes polyether polysiloxane A1(n is 11.4, x is 10.0) as a starting material, the molar ratio of the polyether polysiloxane to dicyclohexylmethane-4, 4' -diisocyanate is 1:20, and the catalyst is zirconium isooctanoate, and the preparation method is as follows:

polyether polysiloxane a1(n 11.4, x 10.0) (41.4kg, 20.96mol) obtained in step (1) of example 1 and dicyclohexylmethane-4, 4' -diisocyanate (110.0kg, 419.26mol) were charged into a reaction vessel filled with nitrogen, stirred, heated to 110 ℃, reacted for 3 hours, after no hydroxyl group remained as detected by infrared (FT-IR), zirconium isooctanoate (0.066kg) was added to the reaction system, the reaction was kept at a constant temperature, stirred for 12 hours, after no urethane group remained as detected by infrared (FT-IR), phosphoric acid (0.066kg) was added to terminate the allophanatization reaction, and the NCO content was measured by sampling to be 20.7%. Finally, the reaction mixture system is removed by a thin film evaporator at 160 ℃/0.05kPa to obtain the residual dicyclohexylmethane-4, 4' -diisocyanate in the reaction system, and then diluted with 27.2kg of PMA to obtain 89.9kg of hydrophilic isocyanate crosslinking agent E5. The solid content of the hydrophilic isocyanate crosslinking agent E5, determined by the di-n-butylamine method, was 70%, the isocyanate content was 3.8%, the viscosity was 300cps (25 ℃), the theoretical polysiloxane segment content was 32% (w/w). The product can be rapidly dispersed in 10 times the mass of water by hand stirring to form a white emulsion with blue light.

Comparative example 1

The hydrophilic isocyanate crosslinking agent E6 of the embodiment of the invention takes polyether polysiloxane A6(n is 11.4, x is 1.0) as a starting material, the molar ratio of the polyether polysiloxane A6(n is 11.4, x is 1.0) to hexamethylene diisocyanate is 1:15, and the catalyst is zinc isooctanoate, and the preparation method is as follows:

(1) synthesis of polyether polysiloxane a6(n ═ 11.4, x ═ 1.0): 62.5kg of ethylene glycol monoallyl ether having a molecular weight of 102 and 3.0kg of a Kaster catalyst (platinum content 1000ppm) were added to a reaction vessel filled with nitrogen, stirred, heated to 100 ℃ and 292.7kg of terminal hydrogen-containing silicone oil having a hydrogen content of 0.205% were added dropwise, the reaction was continued at 100 ℃ for 4 hours after about 1 hour of dropwise addition, and the Si-H conversion rate was monitored to 98% by dehydrogenation with n-butanol under alkaline conditions. Finally, vacuumizing to remove low-boiling-point impurities, and performing suction filtration to obtain 345.2kg of near-colorless liquid, namely polyether polysiloxane A6(n is 11.4, and x is 1.0);

(2) adding the polyether polysiloxane A6(n is 11.4, x is 1.0) (33.0kg, 27.98mol) obtained in the step (1) and hexamethylene diisocyanate (70.6kg, 419.76mol) into a reaction vessel filled with nitrogen, stirring, heating to 110 ℃, reacting for 3 hours, adding zinc isooctanoate (0.065kg) into the reaction system after no hydroxyl group remains in the reaction system in infrared (FT-IR) detection, keeping the temperature constant, continuing stirring for 12 hours, adding phosphoric acid (0.065kg) to terminate the allophanatization reaction after no urethane bond remains in the reaction system in infrared (FT-IR) detection, and sampling to obtain the NCO content of 29.3%. And finally, removing the residual hexamethylene diisocyanate in the reaction system by a thin film evaporator at the temperature of 140 ℃/0.05kPa to obtain 72.3kg of the hydrophilic isocyanate crosslinking agent E1. The hydrophilic isocyanate crosslinking agent E6 had an isocyanate content of 9.0% and a viscosity of 2800cps (25 ℃ C.) as determined by the di-n-butylamine method, and a theoretical polysiloxane segment content of 53% (w/w). The product is not stable in dispersion in the aqueous phase and phase separation occurs, and therefore cannot be used in aqueous systems.

Comparative example 2

The hydrophilic isocyanate crosslinking agent E7 of the embodiment of the invention takes polyether polysiloxane A7(n is 11.4, x is 44.1) as a starting material, the molar ratio of the polyether polysiloxane A7(n is 11.4, x is 44.1) to hexamethylene diisocyanate is 1:15, and the catalyst is zinc isooctanoate, and the preparation method is as follows:

(1) synthesis of polyether polysiloxane a7(n ═ 11.4, x ═ 44.1): 62.5kg of ethylene glycol monoallyl ether having a molecular weight of 2000 and 3.0kg of a Kaster catalyst (platinum content 1000ppm) were added to a reaction vessel filled with nitrogen, stirred, heated to 100 ℃, 292.7kg of terminal hydrogen-containing silicone oil having a hydrogen content of 0.205% were added dropwise, the reaction was continued at 100 ℃ for 6 hours after about 1 hour of dropwise addition, and the Si-H conversion rate was monitored to 97% by dehydrogenation with n-butanol under alkaline conditions. Finally, vacuumizing to remove low-boiling-point impurities, and performing suction filtration to obtain 1463.3kg of near-colorless liquid, namely polyether polysiloxane A7(n is 11.4, and x is 44.1);

(2) adding the polyether polysiloxane A7(n is 11.4, x is 44.1) (139.2kg, 27.98mol) obtained in the step (1) and hexamethylene diisocyanate (70.6kg, 419.76mol) into a reaction vessel filled with nitrogen, stirring, heating to 110 ℃, reacting for 3 hours, adding zinc isooctanoate (0.11kg) into the reaction system after no hydroxyl group remains detected by infrared (FT-IR), keeping the temperature unchanged, continuing stirring for reaction for 12 hours, adding phosphoric acid (0.11kg) to terminate the allophanatization reaction after no urethane bond remains detected by infrared (FT-IR), and sampling to obtain the NCO content of 14.3%. Finally, the reaction mixture system is removed by a film evaporator under 140 ℃/0.05kPa to obtain 155.3kg of hydrophilic isocyanate crosslinking agent E1. The hydrophilic isocyanate crosslinker E7 had an isocyanate content of 3.0% and a viscosity of 7800cps (25 ℃ C.) as determined by the di-n-butylamine method, the theoretical polysiloxane segment content being 17% (w/w). When the product is dispersed in an aqueous system, the product cannot be uniformly dispersed after being stirred for a long time, but a large amount of white solid lumps are formed, so that the product cannot be used in the aqueous system.

Comparative example 3

The hydrophilic isocyanate crosslinking agent E8 of the embodiment of the invention takes polyether polysiloxane A8(n is 0, x is 10.0) as a starting material, the molar ratio of the polyether polysiloxane A8(n is 0, x is 10.0) to hexamethylene diisocyanate is 1:15, and the catalyst is zinc isooctanoate, and the preparation method is as follows:

(1) synthesis of polyether polysiloxane A8(n ═ 0, x ═ 10.0): 306.0kg of polyethylene glycol monoallyl ether having a molecular weight of 500 and 3.0kg of a Kaster catalyst (platinum content: 1000ppm) were added to a reaction vessel filled with nitrogen, stirred, heated to 100 ℃, 40.3kg of a hydrogen-containing double head (tetramethyldihydrodisiloxane) was added dropwise, the reaction was continued at 100 ℃ for 2 hours after about 1 hour of dropwise addition, and the Si-H conversion rate was monitored to be 99% by dehydrogenation with n-butanol under alkaline conditions. Finally, low-boiling point impurities are removed by vacuum pumping, 333.2kg of near-colorless liquid is obtained by suction filtration, namely polyether polysiloxane A8(n is 0, x is 10.0);

(2) adding the polyether polysiloxane A8(n is 0, x is 10.0) (31.7kg, 27.98mol) obtained in the step (1) and hexamethylene diisocyanate (70.6kg, 419.76mol) into a reaction vessel filled with nitrogen, stirring, heating to 110 ℃, reacting for 3 hours, adding zinc isooctanoate (0.065kg) into the reaction system after no hydroxyl group remains in the reaction system in infrared (FT-IR) detection, keeping the temperature unchanged, continuing stirring for reaction for 12 hours, adding phosphoric acid (0.065kg) to terminate the allophanatization reaction after no urethane bond remains in the reaction system in infrared (FT-IR) detection, and sampling to obtain the NCO content of 29.6%. And finally, removing the residual hexamethylene diisocyanate in the reaction system by a thin film evaporator at the temperature of 140 ℃/0.05kPa to obtain 72.3kg of the hydrophilic isocyanate crosslinking agent E8. The hydrophilic isocyanate crosslinking agent E8 had an isocyanate content of 9.2% and a viscosity of 3500cps (25 ℃ C.) as determined by the di-n-butylamine method, and the theoretical polysiloxane segment content was 7% (w/w). The product can be rapidly dispersed in 10 times the mass of water by hand stirring to form a white emulsion with blue light.

Comparative example 4

The hydrophilic isocyanate crosslinking agent E9 of the embodiment of the invention takes polyether polysiloxane A9(n is 88.3, x is 10.0) as a starting material, the molar ratio of the polyether polysiloxane A9(n is 88.3, x is 10.0) to hexamethylene diisocyanate is 1:15, and the catalyst is zinc isooctanoate, and the preparation method is as follows:

(1) synthesis of polyether polysiloxane a9(n ═ 88.3, x ═ 10.0): 306.0kg of polyethylene glycol monoallyl ether having a molecular weight of 500 and 10.0kg of a Kaster catalyst (platinum content 1000ppm) were added to a reaction vessel filled with nitrogen, stirred, heated to 100 ℃, 2000kg of terminal hydrogen-containing silicone oil having a hydrogen content of 0.03% was added dropwise, reaction was continued at 100 ℃ for 2 hours after about 1 hour of dropwise addition, and the Si-H conversion rate was monitored to 97% by dehydrogenation with n-butanol under alkaline conditions. Finally, vacuumizing to remove low-boiling-point impurities, and filtering to obtain 2251.2kg of near-colorless liquid, namely polyether polysiloxane A9(n is 88.3, and x is 10.0);

(2) adding the polyether polysiloxane A9(n is 88.3, x is 10.0) (214.5kg, 27.98mol) obtained in the step (1) and hexamethylene diisocyanate (70.6kg, 419.76mol) into a reaction vessel filled with nitrogen, stirring, heating to 110 ℃, reacting for 3 hours, adding zinc isooctanoate (0.15kg) into the reaction system after no hydroxyl residue is detected by infrared (FT-IR), keeping the temperature unchanged, continuing stirring and reacting for 30 hours, and detecting that still obvious urethane bonds remain by infrared (FT-IR) and the reaction is not complete.

Effects of the embodiment

From the experimental results of the examples and the comparative examples, it can be seen that the crosslinking agents synthesized in the examples 1 to 5 can be well dispersed in water. However, the polyethylene glycol segment of comparative example 1 was too short (x ═ 1.0), and the resulting crosslinking agent E6 was not sufficiently hydrophilic and could not be dispersed and emulsified in water, and thus could not be used in an aqueous system; the polyethylene glycol segment in comparative example 2 is too long (x is 44.1), the too long polyethylene glycol results in strong crystallinity, and the obtained cross-linking agent E7 cannot be uniformly dispersed in the aqueous phase by stirring for a long time, so that the polyethylene glycol segment is difficult to use in an aqueous system; the polyether polysiloxane A9 used in comparative example 4 had too long a polysiloxane segment (n: 88.3), too large a molecular weight, low reactivity and, after a long reaction time (> 30h) with hexamethylene diisocyanate, had not been completely converted into the desired allophanatized product. Therefore, the values of n and x in the polyether polysiloxane A can have a significant influence on the hydrophilicity of the product, and then in order to explore the application of the cross-linking agent in an aqueous system, the cross-linking agents capable of being used in the aqueous system of the above examples 1-5 and comparative example 3 are selected for effect testing.

The hydrophilic isocyanate crosslinking agent prepared by the above examples and comparative examples was mixed with a commercial aqueous hydroxy acrylic acid secondary dispersion (trade mark PA-3330, Guangzhou New Material, solid content: 43%, hydroxyl content in solid content: 3.3%) to prepare an aqueous two-component polyurethane coating according to the formulation in Table 1 for performance test and performance comparison. Wherein, the adding amount of each component in the hydroxyl component is added according to the mass percentage of each component; wherein the addition amount of the cross-linking agent is calculated by the NCO/OH ratio of the cross-linking agent to the aqueous hydroxyl resin being 1.5.

Table 1: aqueous two-component polyurethane coating formula

The curing construction conditions of the water-based two-component polyurethane coating prepared according to different formulas are as follows: and (3) spraying the PC plastic base material, placing the base material at room temperature for 20 minutes, then placing the base material in a blast oven at 80 ℃ for 2 hours, and then placing the base material at room temperature for 1 day for testing.

The scratch resistance test is carried out on the water-based two-component polyurethane coating prepared according to different formulas, wherein the scratch resistance test process comprises the following steps: the scratch test was performed using a hammer with a weight of 800g fitted with steel wool or polished paper. The hammer must be carefully placed at right angles on the coated surface and passed over the coating in a trajectory without tilting and additional external forces. The coating was then wiped clean with a cloth after 10 double scratches and then measured for gloss. The scratch resistance test results are shown in table 2:

table 2: scratch resistance test result of aqueous two-component polyurethane coating

The RCA paper tape wear resistance test is carried out on the water-based double-component polyurethane coating prepared according to different formulas, wherein the RCA paper tape wear resistance test process comprises the following steps: the sample surface was subjected to a tape abrasion resistance test using an RCA tape abrasion resistance instrument with a load of 175g, and the number of times required for the coating to wear through was observed. The results of the RCA tape abrasion resistance test are shown in table 3:

table 3: RCA paper tape wear resistance test result of water-based double-component polyurethane coating

The hydrophilic isocyanate crosslinking agents E1, E2, E3, E4 and E5 synthesized by the technical scheme are respectively used in the paint formulas 1-5, and compared with a paint formula 8 and a paint formula 9 which respectively use Bayhydur 305 and Bayhydur XP 2655, the paint formula has obviously excellent scratch resistance and wear resistance. The use of Bayhydur 305 and a hydrophilic isocyanate crosslinker E1 as the mixed isocyanate component in paint formulation 7 also clearly demonstrated better scratch and abrasion resistance than Bayhydur 305 alone in paint formulation 8. Therefore, the coating obtained by using the hydrophilic isocyanate crosslinking agent as an isocyanate component of the aqueous two-component polyurethane coating has excellent scratch resistance and wear resistance, and the coating formulas 1-5 show obviously excellent scratch resistance and wear resistance compared with the coating formula 6, and further, the values of n and x in the polyether polysiloxane A not only bring remarkable influence on hydrophilicity, but also have influence on the scratch resistance and wear resistance of the coating.

Finally, it should be noted that the above embodiments are intended to illustrate the technical solutions of the present invention and not to limit the scope of the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications and equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.