CN113105815A

CN113105815A - Wear-resistant waterborne polyurethane matting coating and preparation method and application thereof

Info

Publication number: CN113105815A
Application number: CN202110333779.9A
Authority: CN
Inventors: 彭晓宏; 王玮
Original assignee: South China University of Technology SCUT
Current assignee: South China University of Technology SCUT
Priority date: 2021-03-29
Filing date: 2021-03-29
Publication date: 2021-07-13
Anticipated expiration: 2041-03-29
Also published as: CN113105815B

Abstract

The invention discloses a wear-resistant waterborne polyurethane extinction coating and a preparation method thereof. The preparation method comprises the steps of dehydrating fatty polyol, hydroxyl-terminated polydimethylsiloxane and dimethylolpropionic acid, and adding isophorone diisocyanate and an organic tin catalyst for reaction; then adding trimethylolpropane for crosslinking; neutralizing with a neutralizing agent to form salt, and adding water under high-speed stirring to form stable aqueous polyurethane emulsion; and finally, adding an amine or hydrazine chain extender with higher reaction activity and an amine silane coupling agent to completely react the residual isocyanate. The self-extinction type waterborne polyurethane prepared by the invention has the characteristic of high wear resistance, solves the problem of poor wear resistance of self-extinction resin, and is suitable for the surfaces of products such as high-grade sofa leather, automobile interior trim leather and the like.

Description

Wear-resistant waterborne polyurethane matting coating and preparation method and application thereof

Technical Field

The invention relates to a polyurethane coating, in particular to a wear-resistant waterborne polyurethane extinction coating and a preparation method and application thereof.

Background

In the present society, urban light pollution is serious, and the light pollution causes great health damage to human beings. The white pollution mainly means that light is reflected on an object, so that the object is bright and dazzling, and is one of the main forms of light pollution. Matting coatings reduce light pollution by diffuse reflection of light at the coating surface. In addition, the extinction coating has excellent hand feeling, low appearance, luxury and large market demand at home and abroad. There are many methods for realizing extinction of the waterborne polyurethane coating, and two methods are common: firstly, the delustering agent is added into the resin to achieve delustering, and secondly, the delustering is achieved through the resin, namely, the delustering is self-delustered. Although the matting effect of the matting agent is remarkable, the addition thereof results in increased brittleness of the coating, poor hand feeling, and decreased rubbing resistance, folding resistance, and rubbing fastness. In addition, precipitation of the matting agent leads to poor storage stability and gives coatings having a difference in gloss. The waterborne polyurethane self-extinction resin is formed by synthesizing proper extinction similar particles without using any extinction agent, so that an extinction effect is achieved. The self-extinction resin gets rid of the negative influence caused by the extinction agent, and provides a brand new scheme for the waterborne polyurethane extinction resin.

The application scene of the coating generally has friction. For some high-grade leather products, people not only need to have good delustering property, but also need to have excellent wear resistance. Such products are used in scenes where friction is often generated, such as matte high-end sofa leather and automotive interior leather. The abrasion resistance of a coating is actually an ability of a coating film to resist friction, scratching, which is related to many properties of the coating film, including surface hardness, cohesion, tensile strength, elastic modulus, toughness, and the like. Most of the water polyurethane extinction coatings on the market at present are polyether type polyurethane and polyester type polyurethane, and the extinction coatings have the advantages of good hand feeling, good elasticity, low temperature resistance and low cost, but relatively low hardness, poor mechanical property, and non-wear and non-scratch resistance. The paint surface is easy to generate abrasion and scratch during long-term use, and even breaks through the coating when the paint is serious. In addition, the self-extinction type waterborne polyurethane coating constructs a rough surface to achieve extinction, the rough surface can improve the friction coefficient, so that the friction resistance is increased, the larger the resistance is, the easier the polyurethane coating is worn, and finally, the self-extinction type waterborne polyurethane is not wear-resistant and scratch-resistant. Therefore, the problem that the self-extinction waterborne polyurethane is not wear-resistant is solved, and certain challenges are provided.

Chinese patent 2013106160226 discloses a water-based acrylic polyurethane matting resin with a phase separation structure, which comprises the following components in parts by weight: 30-68 parts of acrylic ester; 10-34 parts of ionic blocking polyurethane; 5-17 parts of nonionic polyurethane; 0.18-0.41 part of initiator; 0.03-0.068 part of chain transfer agent; 4.2-11.7 parts of a basic compound; and 90-204 parts of water. The acrylic polyurethane extinction resin prepared by the method has the advantages of low-temperature curing property, excellent mold trace shielding property, high extinction efficiency, water resistance, acid resistance, alkali resistance, good wear resistance and the like. However, the preparation process of the acrylic polyurethane matting resin is complex, anionic blocked polyurethane and nonionic polyurethane need to be prepared simultaneously, and then the two polyurethanes are copolymerized with the acrylate mixture, so that the whole reaction needs more than 20 hours. In addition, the matt resin prepared by the patent does not form a rough surface, and the emulsion particles collapse in the film forming process to form a flat surface, so the matt effect is poor, and the 60-DEG gloss is 17.5GU at the lowest.

Chinese patent application 2020107932286 discloses hydroxyl-containing self-extinction waterborne polyurethane and high-performance self-extinction coating composed of the hydroxyl-containing self-extinction waterborne polyurethane. The hydroxyl-containing self-extinction waterborne polyurethane comprises the following components in parts by weight: 15-25 parts of polymer polyol, 5-15 parts of isocyanate monomer, 0.2-0.8 part of dimethylolpropionic acid or dimethylolbutyric acid, 0.1-0.7 part of pH value regulator, 0.5-3.0 parts of hydroxyalkyl ethylenediamine chain extender, 0.1-4.0 parts of dialkyl hydramine end-capping agent, 0.2-1.5 parts of diamine sulfonate chain extender, 0.01-0.05 parts of catalyst, 2-10 parts of organic solvent, 50-80 parts of deionized water and 0.1-3 parts of thickener. The method is characterized in that hydroxyl is introduced into a polymer molecular chain through hydroxyalkyl ethylenediamine chain extension and dialkyl alcohol amine end capping in the post chain extension stage of the waterborne polyurethane so as to provide more crosslinking points. When water dispersible polyisocyanate or amino resin cross-linking agent is added, high-performance two-component or one-component self-extinction water-based paint can be prepared. However, the self-extinction waterborne polyurethane prepared by the technology uses more organic solvents, and the organic solvents are not easy to remove at the later stage, so that the environmental pollution is great.

The Chinese invention patent CN110041493B discloses a delustering waterborne polyurethane emulsion and a preparation method thereof, and the delustering waterborne polyurethane emulsion comprises the following components in parts by weight: 10-20 parts of high-molecular dihydric alcohol, 8-10 parts of castor oil, 20-45 parts of isocyanate, 5-8 parts of hydrophilic chain extender, 1-3 parts of glycol chain extender, 3-5 parts of diamine chain extender, 6-7 parts of salt forming agent, 200 parts of solvent A100, 8-16 parts of solvent B, 7-10 parts of trimethylolpropane, 10-15 parts of acrylate and 9-12 parts of dehydroabietic acid. According to the technology, the castor oil is added to promote the polyurethane material to generate emulsion particles with larger particle size, so that the surface of the film has larger roughness to achieve the extinction effect. In the preparation process, the acrylate is added into the castor oil modified polyurethane emulsion, the blended emulsion makes up for the deficiencies in performance, and the obtained resin has good wear resistance and low glossiness. But the blending emulsion of the acrylic ester and the waterborne polyurethane has the problem of poor compatibility, the stability of the emulsion is influenced, the emulsion is easy to delaminate after being placed for a long time, and the storage period of the product is shortened. In addition, since the excessively crosslinked prepolymer is difficult to disperse to form an emulsion, it is difficult to prepare an aqueous matt polyurethane having a high degree of crosslinking by using trimethylolpropane alone as a crosslinking agent in the patent.

Disclosure of Invention

The invention aims to solve the problems of poor wear resistance, poor glossiness and poor blending compatibility of the existing waterborne polyurethane matting resin and the environmental protection problem, and provides an environment-friendly wear-resistant waterborne polyurethane matting coating without additional matting auxiliary agent and wear-resistant filler and a preparation method thereof, wherein the 60-degree glossiness of the obtained coating is within 8GU, the abrasion loss is within 20mg, and the coating can be applied to the surface of leather.

In order to achieve the purpose, the invention adopts the technical scheme that:

a preparation method of a wear-resistant water-based polyurethane extinction coating comprises the following steps:

1) dehydrating polymer polyol, dimethylolpropionic acid and hydroxyl-terminated polydimethylsiloxane, controlling the temperature to be 50-55 ℃, adding diisocyanate and an organic tin catalyst under the protection of nitrogen, stirring uniformly, slowly heating to 60-65 ℃, and reacting for 1.0-1.5 h; then heating to 80-85 ℃ again, and reacting for 2.0-2.5 h; the polymer polyol is polyester diol or polycarbonate diol;

2) adding trimethylolpropane into the product obtained in the step 1), reacting at 80-85 ℃ for 1.5-2.0 h, and cooling the product to 40-45 ℃;

3) adding an alkaline neutralizing agent into the product obtained in the step 2) for reaction to obtain a waterborne polyurethane prepolymer;

4) keeping the temperature at 40-45 ℃, adding deionized water into the waterborne polyurethane prepolymer in the step 3) under stirring for dispersion, and continuing stirring after forming an emulsion;

5) dropwise adding a hydrazine chain extender or an amine chain extender into the emulsion obtained in the step 4), keeping the temperature at 40-45 ℃ for reaction, cooling to 10-20 ℃, and dropwise adding an amine silane coupling agent for reaction to obtain a water-based polyurethane emulsion;

6) and (3) cooling and discharging, filtering the product obtained in the step 5) by using a screen, adding a flatting agent, a thickening agent and a defoaming agent, and uniformly dispersing to obtain the wear-resistant waterborne polyurethane extinction coating.

In order to further achieve the purpose of the invention, preferably, the raw materials used in the preparation of the aqueous polyurethane emulsion are, by mass: 35 to 55 percent of polymer polyol, 1.8 to 3.6 percent of dimethylolalkanoic acid, 5 to 20 percent of hydroxyl-terminated polydimethylsiloxane, 0.02 to 0.10 percent of organic tin catalyst, 24 to 40 percent of diisocyanate, 0.3 to 2 percent of trimethylolpropane, 0.6 to 3.5 percent of neutralizer, 0.5 to 2 percent of hydrazine chain extender or amine chain extender and 3 to 6 percent of amine silane coupling agent; the molar ratio of the alkaline neutralizing agent to the dimethylolpropionic acid is 0.8-1.1: 1.

Preferably, the molecular weight of the polymer polyol in the step 1) is 1000-2000; the polymer polyol is one or more of polycarbonate diol, polycaprolactone diol, polyethylene adipate diol and polypropylene adipate diol.

Preferably, the molecular weight of the hydroxyl-terminated polydimethylsiloxane in the step 1) is 500-2000;

the hydroxyl terminated polydimethylsiloxane has the structural formula:

preferably, the diisocyanate in step 1) is one or more of isophorone diisocyanate, 1, 6-hexamethylene diisocyanate, xylylene diisocyanate and dicyclohexylmethane diisocyanate; the organic tin catalyst is stannous octoate or dibutyltin dilaurate; the alkaline neutralizing agent is one or more of triethylamine, tripropylamine, triethanolamine, methylamine, diethylenetriamine, ammonia water and sodium hydroxide and potassium hydroxide.

Preferably, the hydrazine chain extender is one or more of hydrazine hydrate, carbohydrazide, dimethylhydrazine, oxalic dihydrazide and adipic dihydrazide; the amine chain extender is one or more of ethylenediamine, di-o-chlorodiphenylamine methane and N, N-dihydroxy (diisopropyl) aniline; the amine silane coupling agent is one or more of KH-550 and KH-792.

Preferably, the dehydration of the polymer polyol, the dimethylolpropionic acid and the hydroxyl-terminated polydimethylsiloxane is carried out at 100-120 ℃; the time for adding the alkaline neutralizing agent for reaction is 25-30 min; the deionized water is added under the stirring condition for dispersion, and the stirring rotating speed is 600-1000 rpm; the time for continuously stirring after the emulsion is formed is 20-30 min, and the rotating speed is 600-1000 rpm; dropwise adding a hydrazine chain extender or an amine chain extender under stirring, wherein the stirring speed is 300-500 rpm; the reaction time is 20-30 min when the temperature is kept at 40-45 ℃; the time for dropping the amine silane coupling agent for reaction is 20-30 min.

Preferably, in the step 6), the filtering screen is a 100-200 mesh grid; the leveling agent is one or more of BYK-346, Tego482 and Tego 450; the thickening agent is Gel LW 44; the defoaming agent is one or more of BYK-019, Foamex843 and GSK 716.

A wear-resistant waterborne polyurethane extinction coating, which is prepared by the preparation method; the raw materials comprise, by mass, 70-95% of aqueous polyurethane emulsion, 0.1-2% of defoaming agent, 0.1-2% of thickening agent, 0.1-2% of flatting agent, and the balance of deionized water; the solid content of the aqueous polyurethane emulsion is 25-35 wt%; the average particle diameter of latex particles of the aqueous polyurethane emulsion is 500 nm-5000 nm.

The wear-resistant waterborne polyurethane extinction coating is applied as a PVC and PU leather surface finishing agent.

Compared with the prior art, the invention has the following advantages:

1) in the preparation process of the aqueous polyurethane emulsion, hydroxyl-terminated polydimethylsiloxane modified polyurethane is used, trimethylolpropane is used as a front chain extender, an amine silane coupling agent is used as a rear chain extender, under the condition of not using an organic solvent and a wear-resistant filler, the two chain extenders, namely the front chain extender and the rear chain extender, are matched for use, the viscosity of a prepolymer in the synthesis process is controlled, a cross-linked network structure can be formed among polyurethane molecular chains in the early period, and methoxy groups on the amine silane coupling agent can be subjected to dehydration condensation to carry out self-crosslinking, the wear resistance is further improved through the control of cross-linking density, the surface energy of a coating is reduced, the smoothness of the coating is improved, the surface energy of the coating is also reduced by the hydroxyl-terminated polydimethylsiloxane modified polyurethane in the raw material, the smoothness of the coating is improved, and the wear resistance and water resistance of the coating are improved, the four factors are cooperated, the abrasion loss of the obtained coating is less than 20mg under the condition that the gloss at 60 degrees is within 8GU, and the obtained coating can be used in places where friction is frequently generated, such as matte high-grade sofa leather and automobile interior leather.

2) Under the condition of not using any extinction auxiliary agent at all, the latex particles are generated in the resin synthesis process, and the original shape of the particles is kept in the drying process, so that the surface roughness of the coated object is increased, and the aim of extinction of the body is fulfilled; the 60-degree gloss of the obtained coating is within 8GU, and the requirement of low gloss of the leather surface can be met.

3) The invention provides a method for simply and effectively improving the wear resistance of self-extinction resin, organic solvent is not used, the prepared coating is safe and environment-friendly, and the wear resistance is excellent while low glossiness is realized.

4) The amine silane coupling agent added in the later period of the invention has better hydrophilicity and can also improve the stability of the emulsion.

Drawings

FIG. 1 is an SEM photograph of the apparent morphology of the waterborne polyurethane coating film prepared in example 1 of the present invention, magnified 1 thousand times.

Fig. 2 is a comparison graph of the extinction effect of the waterborne polyurethane coating film prepared in example 1 of the present invention and a blank glass under strong light.

Detailed Description

The present invention is further described with reference to the following examples, which should be construed as being without limitation to the scope of the invention as claimed.

The test methods referred to in the examples are illustrated below:

1) NCO group content: the NCO group content of the prepolymer was determined by di-n-butylamine (calibrated) titration.

2) Solid content: determined according to GB/T1725-1979 coating solids assay.

3) Emulsion particle size: particle diameter the particle diameter of the latex particles was measured at (25. + -. 05 ℃ C.) using a model N5 nanometer particle size analyzer from Beckman Coulter, USA.

4) The preparation method of the coating film comprises the following steps: according to the general preparation method of paint films of GB/T1727-1992, the prepared low-gloss aqueous polyurethane resin is coated on a clean glass plate by a roll coating method, the thickness of the film is (35 +/-5) mu m, then the film is baked for 1min in an oven at 110 ℃, and after complete drying, the film is cooled to room temperature for standby.

5) Coating film glossiness: the 60 ℃ gloss of the coating was determined according to ISO/2813 using a 500MC gloss meter from Erichsen, Germany, on a glass substrate.

6) Wear resistance: the wear resistance of the paint and varnish is measured according to the method of measuring the wear resistance of GB/T1768-2006 by a rotating rubber grinding wheel. The coating was loaded at 750g and rotated 500 revolutions and the amount of abrasion was recorded.

7) Pencil hardness: the hardness of the paint film is determined according to GB/T6739-2006 paint and varnish pencil method.

8) Emulsion stability: and (3) carrying out a centrifugal sedimentation experiment on the waterborne polyurethane emulsion at room temperature, centrifuging for 15min at the rotating speed of 3000r/min of a centrifuge, and observing whether the emulsion has a sedimentation phenomenon.

9) Coating film blocking resistance: the determination is carried out according to GB/T8949-2008 'polyurethane cool dry artificial leather'. Level 1: can not be peeled off; and 2, stage: peeling under gravity; and 3, level: the peeling can be realized with a certain force; 4, level: peeling with slight force; and 5, stage: can be peeled off with light force.

10) Folding fastness of the coating film: the test specimens were clamped in a refractometer for testing in accordance with QB/T2714-2005, "determination of the folding fastness of leather in physical and mechanical tests".

Example 1

(1) 81g of polycarbonate diol (PCDL-1000, 1000g/mol), 9g of hydroxyl-terminated polydimethylsiloxane (PDMS-1000, 1000g/mol) and 2.97g of dimethylolpropionic acid were put in a reaction flask and dehydrated at 100 ℃. The temperature was reduced to 50 ℃ and 0.08g of dibutyltin dilaurate catalyst was added dropwise in a nitrogen atmosphere. After being uniformly mixed, 40.54g of isophorone diisocyanate is continuously added, the temperature is slowly increased to 65 ℃, then the reaction is carried out for 1 hour, and then the temperature is continuously increased to 85 ℃, and the reaction is carried out for 2 hours.

(2) Adding 1.25g of trimethylolpropane into the product obtained in the step (1), reacting at 85 ℃ for 2 hours, measuring the content of the residual NCO group to a theoretical value by adopting a di-n-butylamine method in the reaction process, and cooling the prepolymer to 45 ℃.

(3) And (3) adding 2.24g of triethylamine into the product obtained in the step (2), reacting for 20min, and neutralizing to form salt.

(4) And (4) increasing the rotating speed of a stirring paddle to 800rpm, slowly adding 315g of deionized water into the product obtained in the step (3) for emulsification and dispersion, and continuing stirring for 20min after an emulsion is formed.

(5) Keeping the temperature at 45 ℃, reducing the stirring speed to 400rpm, dropwise adding 1.52g of hydrazine hydrate into the emulsion obtained in the step (4), and reacting for 20 min; then cooling to 30 ℃, dripping 6.76g of silane coupling agent KH-792, and reacting for 30min to complete the reaction of the residual isocyanate, thereby obtaining the aqueous polyurethane emulsion.

(6) And (3) discharging after cooling, filtering the product obtained in the step (5) by using a 100-mesh screen, adding 0.4g of a flatting agent (BYK-346), 0.4g of a thickening agent (Gel LW44, Borchers Borchi) and 0.4g of a defoaming agent (BYK-019), and stirring at the rotating speed of 1000rpm for 10min to obtain the waterborne polyurethane coating with the solid content of 29.15% and the average particle size of 3471 nm.

FIG. 1 is an SEM photograph of the apparent morphology of the waterborne polyurethane coating film prepared in example 1 of the present invention, magnified 1 thousand times. According to the invention, hydrazine hydrate and amine silane coupling agent react with residual isocyanate in emulsion particles, so that the rigidity and particle size of the emulsion particles are increased, and after drying and film forming, the emulsion particles on the surface of a coating film can be kept in an original state, and the particles are mutually stacked without collapse to form a rough surface with holes. FIG. 1 shows that the coating film indeed forms a rough surface with holes, and the rough surface causes light to be reflected for multiple times between the particle surface and the holes to form diffuse reflection, so that the surface gloss of the coating is reduced, and the purpose of self-extinction of the resin is achieved.

Fig. 2 is a comparison graph of the extinction effect of the waterborne polyurethane coating film prepared in example 1 of the present invention and a blank glass under strong light. It was found that the blank glass sheet reflected light heavily under strong light irradiation, while no reflection was seen on the abrasion-resistant self-matting resin coating coated with example 1, indicating that the resin prepared in example 1 had low gloss and good matting effect.

Example 2

(1) 81g of polycarbonate diol (PCDL-1000, 1000g/mol), 9g of hydroxyl-terminated polydimethylsiloxane (PDMS-1000, 1000g/mol) and 2.97g of dimethylolpropionic acid were put in a reaction flask and dehydrated at a temperature of 120 ℃. The temperature was reduced to 55 ℃ and 0.08g of dibutyltin dilaurate catalyst was added dropwise in a nitrogen atmosphere. After being mixed evenly, 40.54g of isophorone diisocyanate is continuously added, the temperature is slowly increased to 60 ℃, then the reaction is carried out for 1.5h, and then the temperature is continuously increased to 80 ℃ for 2.5 h.

(2) Adding 1.25g of trimethylolpropane into the product obtained in the step (1), reacting at the temperature of 80 ℃ for 2 hours, measuring the content of the residual NCO group to a theoretical value by adopting a di-n-butylamine method in the reaction process, and cooling the prepolymer to 40 ℃.

(3) And (3) adding 1.79g of triethylamine into the product obtained in the step (2) to react for 30min, and neutralizing to form salt.

(4) And (4) increasing the rotating speed of a stirring paddle to 600rpm, slowly adding 315g of deionized water into the product obtained in the step (3) for emulsification and dispersion, and continuing stirring for 30min after an emulsion is formed.

(5) Maintaining the temperature at 45 ℃, reducing the stirring speed to 300rpm, dropwise adding 2.74g carbohydrazide into the emulsion obtained in the step (4), and reacting for 30 min; then cooling to 10 ℃, dripping 6.76g of silane coupling agent KH-550, and reacting for 20min to finish the reaction of the residual isocyanate to obtain the aqueous polyurethane emulsion.

(6) And (3) discharging after cooling, filtering the product obtained in the step (5) by using a 200-mesh screen, adding 0.3g of a flatting agent (Tego450), 0.4g of a thickening agent (Gel LW44, Borchers Borchi) and 0.4g of a defoaming agent (BYK-019), and stirring at the rotating speed of 1000rpm for 10min to obtain the waterborne polyurethane coating with the solid content of 29.37% and the average particle size of 2789 nm.

Example 3

(1) 81g of polycaprolactone diol (PCL-1000, 1000g/mol), 9g of hydroxy-terminated polydimethylsiloxane (PDMS-1000, 1000g/mol) and 2.97g of dimethylolpropionic acid were added to a reaction flask and dehydrated at 100 ℃. The temperature was reduced to 50 ℃ and 0.08g of dibutyltin dilaurate catalyst was added dropwise in a nitrogen atmosphere. After being mixed evenly, 40.54g of isophorone diisocyanate is continuously added, the temperature is slowly increased to 60 ℃, then the reaction is carried out for 1 hour, and then the temperature is continuously increased to 80 ℃ and the reaction is carried out for 2 hours.

(3) And (3) adding 2.24g of triethylamine into the product obtained in the step (2) to react for 30min, and neutralizing to form salt.

(5) Keeping the temperature at 45 ℃, reducing the stirring speed to 500rpm, dropwise adding 1.83g of ethylenediamine into the emulsion obtained in the step (4), and reacting for 30 min; then cooling to 20 ℃, dripping 6.76g of silane coupling agent KH-550, and reacting for 30min to finish the reaction of the residual isocyanate to obtain the aqueous polyurethane emulsion.

(6) And (3) discharging after cooling, filtering the product obtained in the step (5) by using a 100-mesh screen, adding 0.5g of a flatting agent (Tego482), 0.4g of a thickening agent (Gel LW44, Borchers Borchi) and 0.2g of a defoaming agent (GSK716), and stirring at the rotating speed of 1000rpm for 10min to obtain the waterborne polyurethane coating with the solid content of 29.03% and the average particle size of 2594 nm.

Example 4

(1) 81g of neopentyl glycol adipate diol (PNA-1000, 1000g/mol), 9g of hydroxyl-terminated polydimethylsiloxane (PDMS-500, 500g/mol), 2.97g of dimethylolpropionic acid were charged in a reaction flask, and dehydration treatment was performed at a temperature of 110 ℃. The temperature was reduced to 50 ℃ and 0.08g of dibutyltin dilaurate catalyst was added dropwise in a nitrogen atmosphere. After being mixed evenly, 40.54g of isophorone diisocyanate is continuously added, the temperature is slowly increased to 60 ℃, then the reaction is carried out for 1 hour, and then the temperature is continuously increased to 80 ℃ and the reaction is carried out for 2 hours.

(3) And (3) adding 0.88g of sodium hydroxide into the product obtained in the step (2) to react for 30min, and neutralizing to form salt.

(4) And (4) increasing the rotating speed of a stirring paddle to 1000rpm, slowly adding 315g of deionized water into the product obtained in the step (3) for emulsification and dispersion, and continuing stirring for 30min after an emulsion is formed.

(5) Keeping the temperature at 40 ℃, reducing the stirring speed to 400rpm, dropwise adding 1.52g of hydrazine hydrate into the emulsion obtained in the step (4), and reacting for 20 min; then cooling to 20 ℃, dripping 6.76g of silane coupling agent KH-792, and reacting for 30min to complete the reaction of the residual isocyanate, thereby obtaining the aqueous polyurethane emulsion.

(6) And (3) discharging after cooling, filtering the product obtained in the step (5) by using a 200-mesh screen, adding 0.4g of a flatting agent (Tego482), 0.4g of a thickening agent (Gel LW44, Borchers Borchi) and 0.4g of a defoaming agent (Foamex843), and stirring at the rotating speed of 1000rpm for 10min to obtain the waterborne polyurethane coating with the solid content of 28.95% and the average particle size of 1864 nm.

Example 5

(1) 81g of polyethylene glycol adipate (1000g/mol), 9g of hydroxyl-terminated polydimethylsiloxane (PDMS-2000, 2000g/mol) and 2.97g of dimethylolpropionic acid were charged in a reaction flask, and dehydration treatment was performed at a temperature of 110 ℃. The temperature was reduced to 50 ℃ and 0.08g of dibutyltin dilaurate catalyst was added dropwise in a nitrogen atmosphere. After uniform mixing, 34.38g of xylylene diisocyanate is continuously added, the temperature is slowly increased to 60 ℃, the reaction is carried out for 1h, and then the temperature is continuously increased to 80 ℃ for 2 h.

(3) And (3) adding 2.28g of diethylenetriamine into the product obtained in the step (2) to react for 30min, and neutralizing to form salt.

(4) And (4) increasing the rotating speed of a stirring paddle to 1000rpm, slowly adding 319g of deionized water into the product obtained in the step (3) for emulsification and dispersion, and continuing stirring for 30min after an emulsion is formed.

(6) And (3) discharging after cooling, filtering the product obtained in the step (5) by using a 100-mesh screen, adding 0.4g of a flatting agent (BYK-346), 0.4g of a thickening agent (Gel LW44, Borchers Borchi) and 0.4g of a defoaming agent (GSK716), and stirring at the rotating speed of 1000rpm for 10min to obtain the waterborne polyurethane coating with the solid content of 30.45% and the average particle size of 3165 nm.

Comparative example 1

(1) 81g of polycarbonate diol (PCDL-1000, 1000g/mol), 9g of hydroxyl-terminated polydimethylsiloxane (PDMS-1000, 1000g/mol) and 2.97g of dimethylolpropionic acid were put into a reaction flask and dehydrated at a temperature of 110 ℃. The temperature was reduced to 40 ℃ and 0.08g of dibutyltin dilaurate catalyst was added dropwise under a nitrogen atmosphere. After being mixed evenly, 40.54g of isophorone diisocyanate is continuously added, the temperature is slowly increased to 60 ℃, then the reaction is carried out for 1 hour, and then the temperature is continuously increased to 80 ℃ and the reaction is carried out for 2 hours.

(4) And (4) increasing the rotating speed of a stirring paddle to 800rpm, slowly adding 315g of deionized water into the product obtained in the step (3) for emulsification and dispersion, and continuing stirring for 30min after an emulsion is formed.

(5) And (4) keeping the temperature at 40 ℃, reducing the stirring speed to 400rpm, dropwise adding 3.04g of hydrazine hydrate into the emulsion obtained in the step (4), and continuing to react for 30min to finish the reaction of the residual isocyanate to obtain the aqueous polyurethane emulsion.

(6) And (3) discharging after cooling, filtering the product obtained in the step (5) by using a 100-mesh screen, adding 0.4g of a flatting agent (BYK-346), 0.4g of a thickening agent (Gel LW44, Borchers Borchi) and 0.4g of a defoaming agent (BYK-019), and stirring at the rotating speed of 1000rpm for 10min to obtain the waterborne polyurethane coating with the solid content of 29.57% and the average particle size of 2012 nm.

Comparative example 2

(1) 90g of polycarbonate diol (PCDL-1000, 1000g/mol) and 2.82g of dimethylolpropionic acid were charged into a reaction flask, and dehydration treatment was carried out at a temperature of 110 ℃. The temperature was reduced to 40 ℃ and 0.08g of dibutyltin dilaurate catalyst was added dropwise under a nitrogen atmosphere. After being uniformly mixed, 35.53g of isophorone diisocyanate is continuously added, the temperature is slowly increased to 60 ℃, then the reaction is carried out for 1 hour, and then the temperature is continuously increased to 80 ℃ and the reaction is carried out for 2 hours.

(2) And (3) cooling the prepolymer to 40 ℃, adding 2.13g of triethylamine into the product obtained in the step (1), reacting for 30min, and neutralizing to form salt.

(3) And (3) increasing the rotating speed of a stirring paddle to 800rpm, slowly adding 300g of deionized water into the product obtained in the step (2) for emulsification and dispersion, and continuing stirring for 30min after an emulsion is formed.

(4) And (4) keeping the temperature at 40 ℃, reducing the stirring speed to 400rpm, dropwise adding 2.67g of hydrazine hydrate into the emulsion obtained in the step (3), and continuing to react for 30min to finish the reaction of the residual isocyanate to obtain the aqueous polyurethane emulsion.

(5) And (3) discharging after cooling, filtering the product obtained in the step (4) by using a 100-mesh screen, adding 0.4g of a flatting agent (BYK-346), 0.4g of a thickening agent (Gel LW44, Borchers Borchi) and 0.4g of a defoaming agent (BYK-019), and stirring at the rotating speed of 1000rpm for 10min to obtain the waterborne polyurethane coating with the solid content of 29.46% and the average particle size of 1926 nm.

Comparative example 3

(1) 90g of polytetrahydrofuran diol (PTMG-1000, 1000g/mol) and 2.82g of dimethylolpropionic acid were charged into a reaction flask, and dehydration treatment was carried out at a temperature of 110 ℃. The temperature was reduced to 40 ℃ and 0.08g of dibutyltin dilaurate catalyst was added dropwise under a nitrogen atmosphere. After being uniformly mixed, 35.53g of isophorone diisocyanate is continuously added, the temperature is slowly increased to 60 ℃, then the reaction is carried out for 1 hour, and then the temperature is continuously increased to 80 ℃ and the reaction is carried out for 2 hours.

(5) And (3) discharging after cooling, filtering the product obtained in the step (4) by using a 100-mesh screen, adding 0.4g of a flatting agent (BYK-346), 0.4g of a thickening agent (Gel LW44, Borchers Borchi) and 0.4g of a defoaming agent (BYK-019), and stirring at the rotating speed of 1000rpm for 10min to obtain the waterborne polyurethane coating with the solid content of 29.76% and the average particle size of 1857 nm.

Comparative example 4 is a commercial delustering aqueous polyurethane resin (brand Meijiale WR-8394A) applied to a leather finish.

Table 1 shows the results of the performance tests of examples and comparative examples of the present invention

In Table 1, the larger the resin wear, the worse the wear resistance; the lower the gloss, the better the matting effect.

As can be seen from Table 1, the waterborne polyurethane prepared by the invention has good matting property and wear resistance (60 ℃ gloss is less than 8GU, and abrasion loss is less than 20 mg. compared with domestic commercial matting resin Meijiale WR-8394A (comparative example 4), the abrasion loss is 62mg, 60 ℃ gloss is 6.5GU, and the abrasion resistance of the resin in the examples is obviously improved under the condition that the gloss difference is not large.

Comparative example 1 and example 1 are different in that hydrazine hydrate is used as a post-chain extender in comparative example 1, and an amine silane coupling agent is added to a small amount, and the rest is the same as in example 1. As can be seen from Table 1, the above-mentioned differences result in a great difference in properties between the two, the pencil hardness of the coating film is reduced from 4H to 2H, the anti-blocking grade is reduced from 3 to 2, the 60 ℃ gloss is increased from 3.5GU to 7.6GU, and particularly the abrasion loss is increased from 8.8 to 33mg, the emulsion stability is deteriorated, and a large amount of precipitates are generated after high-speed centrifugation. It can be directly seen that the amine silane coupling agent added on the basis of the comparative example 1 not only can reduce the glossiness of the coating film, but also can increase the hydrophilicity of the emulsion, thereby improving the stability of the emulsion. It can also be shown that, in the film forming process, the methoxyl groups in the amine silane coupling can be subjected to dehydration condensation to generate self-crosslinking, so that the crosslinking degree of the coating is increased, and the wear resistance of the coating is improved.

Comparative example 2 is different from comparative example 1 in that polydimethylsiloxane and trimethylolpropane are not added to comparative example 2, and the rest is the same as comparative example 1. The abrasion loss of the resin prepared in the comparative example 2 reaches 49mg, and is obviously increased compared with 33mg of the resin prepared in the comparative example 1, which also shows that on the basis of the comparative example 12, the surface energy can be obviously reduced by adding the hydroxyl-terminated polydimethylsiloxane, and meanwhile, the smoothness of the coating can be increased, and the wear resistance is improved. It is also shown that the addition of the hydroxyl-terminated polydimethylsiloxane is of great significance in the system of the invention, and the wear resistance can be further improved by matching with the technical measures of the invention.

Comparative example 3 differs from comparative example 2 in that comparative example 3 uses a polyether diol instead of a polyester diol or a polycarbonate diol, and the other is the same as in comparative example 2. The test result shows that the abrasion amount of the resin prepared in the comparative example 3 is also greatly increased compared with the abrasion amount of the resin 49mg prepared in the comparative example 2, which shows that the polyester diol and the polycarbonate diol have great contribution to the abrasion resistance of polyurethane, because ether bonds are relatively soft and the prepared polyether polyurethane has low hardness.

As can be seen from the comparison between example 1 and comparative examples 1 to 3, in the preparation process of the aqueous polyurethane emulsion, the selection of the hydroxyl-terminated polydimethylsiloxane modified polyurethane, the selection of the diol, and the matching use of the front chain extender and the rear chain extender all have important influence on the performance of the product. The invention generates latex particles in the resin synthesis process, keeps the original shape of particles in the drying process, and increases the surface roughness of the coated object to realize the aim of the invention, but in the process, the invention uses hydroxyl-terminated polydimethylsiloxane modified polyurethane, simultaneously uses trimethylolpropane as a front chain extender and an amine silane coupling agent as a rear chain extender, and uses the two chain extenders of the front chain extender and the rear chain extender in a matching way to realize the control of the viscosity of a prepolymer in the synthesis process, can form a cross-linked reticular structure among polyurethane molecular chains in the early period, can carry out self-crosslinking by dehydration condensation in cooperation with methoxyl on the amine silane coupling agent, further improves the wear resistance by controlling the cross-linking density, reduces the surface energy of a coating, increases the smoothness of the coating, and reduces the surface energy of the coating by using the hydroxyl-terminated polydimethylsiloxane modified polyurethane in the raw material, the smoothness of the coating is improved, the wear resistance and the water resistance of the coating are improved, the four factors are cooperated, the abrasion loss of the obtained coating is less than 20mg under the condition that the glossiness of 60 degrees is within 8GU, and the obtained coating can be used in places frequently generating friction, such as matte high-grade sofa leather and automobile interior leather.

The best test result of the invention and the waterborne acrylic polyurethane matting resin in the Chinese invention patent 2013106160226 is that the coating C has a 60-degree gloss of 17.5GU, and the waterborne acrylic polyurethane matting resin needs to prepare two polyurethanes first and then polymerize with acrylic acid, so that the process is complex and the reaction time is long. According to the invention, only one polyurethane needs to be prepared, so that the reaction time is short, the efficiency is high, the amine chain extender (hydrazine hydrate and amine silane coupling agent) is added into the emulsion, the reaction activity of amine and isocyanate is high, the rigidity and the particle size of emulsion particles are increased after the reaction, the emulsion particles on the surface of a coating film can be kept in the original state after the film is dried and formed, the particles are mutually stacked, collapse cannot occur, a rough surface with holes is formed, and the surface glossiness is reduced. The example 2 with the worst extinction property of the invention has a 60 ℃ gloss of 7.9GU, but is still much lower than 17.5GU of the Chinese patent 2013106160226.

The waterborne polyurethane flatting paint on the market at present has relatively low hardness, low crosslinking degree and poor wear resistance, and cannot be applied to high-wear-resistance scenes, such as matte automobile indoor leather. This is because the self-matting aqueous polyurethane coating forms a rough surface to achieve matting, which increases the friction coefficient and thus increases the frictional resistance, and the more the resistance, the more easily the polyurethane coating is worn away. Secondly, the aqueous polyurethane extinction resin emulsion on the market is unstable, is easy to generate precipitate and has short shelf life. In order to solve the problem of wear resistance, in the preparation process of a preparation method of a delustering waterborne polyurethane resin disclosed in the invention patent CN110041493A of China, acrylic ester is added into castor oil modified polyurethane emulsion, the performance of the blended emulsion is made up for the deficiencies of each other, the obtained resin has good wear resistance and lower glossiness, and the technical glossiness is the best and the wear resistance is also the best in example 4, 60-degree glossiness 3GU and the wear resistance is 0.03 g. However, the compatibility between the acrylate and the waterborne polyurethane is poor, the emulsion stability is poor, and the problem of delamination exists after long-term storage. In addition, since the excessively crosslinked prepolymer is difficult to disperse to form an emulsion, it is difficult to prepare a water-based matt polyurethane having a high crosslinking degree by using trimethylolpropane alone as a crosslinking agent in the technique. According to the invention, the amine silane coupling agent is introduced into the polyurethane chain segment through a chemical reaction after the emulsification stage, the amine silane coupling agent has good hydrophilicity and can improve the stability of the emulsion, and the emulsion does not have the problem of poor compatibility of the blended emulsion, so that the stability is better, and only a small amount of precipitate is generated under high-speed centrifugation; in addition, the amine silane coupling agent can generate self-crosslinking in emulsion to form the high-crosslinking-degree matt waterborne polyurethane, and the abrasion resistance of a coating film is greatly improved, so that the abrasion loss of example 4 with the worst abrasion resistance is 18.8mg, which is much better than that of the resin in the Chinese invention patent CN110041493A, and the abrasion resistance of the polyurethane is far better than that of the currently-sold matt waterborne polyurethane (comparative example 4, the abrasion loss is 62 mg).

The test results in Table 1 show that the folding fastness and the blocking resistance of the invention in the examples 1-5 reach the use standard of leather finishing agents, and the wear-resistant waterborne polyurethane matting coating prepared by the invention can be applied as PVC and PU leather finishing agents.

Claims

1. A preparation method of wear-resistant waterborne polyurethane matt paint is characterized by comprising the following steps:

2. The preparation method of the wear-resistant waterborne polyurethane matt coating as claimed in claim 1, wherein the raw materials used in the preparation of the waterborne polyurethane emulsion comprise, by mass: 35 to 55 percent of polymer polyol, 1.8 to 3.6 percent of dimethylolalkanoic acid, 5 to 20 percent of hydroxyl-terminated polydimethylsiloxane, 0.02 to 0.10 percent of organic tin catalyst, 24 to 40 percent of diisocyanate, 0.3 to 2 percent of trimethylolpropane, 0.6 to 3.5 percent of neutralizer, 0.5 to 2 percent of hydrazine chain extender or amine chain extender and 3 to 6 percent of amine silane coupling agent; the molar ratio of the alkaline neutralizing agent to the dimethylolpropionic acid is 0.8-1.1: 1.

3. The preparation method of the wear-resistant water-based polyurethane extinction coating of claim 1, wherein the molecular weight of the polymer polyol in the step 1) is 1000-2000; the polymer polyol is one or more of polycarbonate diol, polycaprolactone diol, polyethylene adipate diol, poly neopentyl glycol adipate diol and poly propylene adipate diol.

4. The preparation method of the wear-resistant water-based polyurethane extinction coating according to claim 1, wherein the molecular weight of the hydroxyl-terminated polydimethylsiloxane in the step 1) is 500-2000;

the hydroxyl terminated polydimethylsiloxane has the structural formula:

5. the method for preparing the wear-resistant waterborne polyurethane matt coating as claimed in claim 1, wherein the diisocyanate in step 1) is one or more of isophorone diisocyanate, 1, 6-hexamethylene diisocyanate, xylylene diisocyanate and dicyclohexylmethane diisocyanate; the organic tin catalyst is stannous octoate or dibutyltin dilaurate; the alkaline neutralizing agent is one or more of triethylamine, tripropylamine, triethanolamine, methylamine, diethylenetriamine, ammonia water and sodium hydroxide and potassium hydroxide.

6. The method for preparing the wear-resistant waterborne polyurethane matting coating according to claim 1, characterized in that the hydrazine chain extender is one or more of hydrazine hydrate, carbohydrazide, dimethylhydrazine, oxalic dihydrazide and adipic dihydrazide; the amine chain extender is one or more of ethylenediamine, di-o-chlorodiphenylamine methane and N, N-dihydroxy (diisopropyl) aniline; the amine silane coupling agent is one or more of KH-550 and KH-792.

7. The preparation method of the wear-resistant water-based polyurethane extinction coating is characterized in that the dehydration of the polymer polyol, the dimethylolpropionic acid and the hydroxyl-terminated polydimethylsiloxane is carried out at 100-120 ℃; the time for adding the alkaline neutralizing agent for reaction is 25-30 min; the deionized water is added under the stirring condition for dispersion, and the stirring rotating speed is 600-1000 rpm; the time for continuously stirring after the emulsion is formed is 20-30 min, and the rotating speed is 600-1000 rpm; dropwise adding a hydrazine chain extender or an amine chain extender under stirring, wherein the stirring speed is 300-500 rpm; the reaction time is 20-30 min when the temperature is kept at 40-45 ℃; the time for dropping the amine silane coupling agent for reaction is 20-30 min.

8. The preparation method of the wear-resistant waterborne polyurethane extinction coating according to claim 1, wherein in the step 6), the filtering screen is a 100-200 mesh grid; the leveling agent is one or more of BYK-346, Tego482 and Tego 450; the thickening agent is Gel LW 44; the defoaming agent is one or more of BYK-019, Foamex843 and GSK 716.

9. A wear-resistant waterborne polyurethane extinction coating is characterized by being prepared by the preparation method of any one of claims 1 to 8; the raw materials comprise, by mass, 70-95% of aqueous polyurethane emulsion, 0.1-2% of defoaming agent, 0.1-2% of thickening agent, 0.1-2% of flatting agent, and the balance of deionized water; the solid content of the aqueous polyurethane emulsion is 25-35 wt%; the average particle diameter of latex particles of the aqueous polyurethane emulsion is 500 nm-5000 nm.

10. Use of the abrasion-resistant aqueous polyurethane matting coating according to claim 1 as a surface finish for PVC and PU leather.