CN109135544B

CN109135544B - Two-component polyurethane coating capable of wetting and spraying

Info

Publication number: CN109135544B
Application number: CN201811009028.6A
Authority: CN
Inventors: 殷骏; 郭小平
Original assignee: Wuhu Chunfeng New Material Co ltd
Current assignee: Wuhu Chunfeng New Material Co ltd
Priority date: 2018-08-30
Filing date: 2018-08-30
Publication date: 2020-11-06
Anticipated expiration: 2038-08-30
Also published as: CN109135544A

Abstract

The invention discloses a wet-spraying water-based two-component polyurethane coating, belonging to the field of coating preparation. The coating comprises a primer and a finish, wherein hydrophilic fumed silica is added into both the primer and the finish, and the adding weight of the hydrophilic fumed silica in the primer is more than that of the hydrophilic fumed silica in the finish. The invention overcomes the defects of difficult wet spraying and low production efficiency of the coating in the prior art, can effectively realize the wet spraying process, thereby improving the production efficiency, reducing the production energy consumption, being widely applied in the coating field, and particularly having good effect in the low-temperature coating field which relates to the vehicle body and the related requirements of two-layer coating and one-time baking.

Description

Two-component polyurethane coating capable of wetting and spraying

Technical Field

The invention relates to the technical field of coating preparation, in particular to a wet-spraying water-based two-component polyurethane coating.

Background

With the strict requirements of the current national environmental protection policy, the waterborne low-temperature coating product with low VOC and low energy consumption is produced at the same time. The solvent-based paint gradually replaces the traditional solvent-based paint, is equivalent to the solvent-based paint in aspects of common workability, gloss leveling and the like, can easily realize wet spraying and wetting through process and formula design, realizes a coating and baking process of two-coating and one-baking, and greatly reduces the production energy consumption. However, in the construction of water-based paint, two-coating one-baking is required, because the physical properties of water and organic solvent in various aspects such as evaporation heat, surface tension and the like are greatly different, the water-based paint product can be coated and baked only one time, the production efficiency is greatly influenced, and the energy consumption is high. Therefore, the development of the coating which is equivalent to a solvent-based coating and can easily realize a wet spraying process has important significance for improving the production efficiency and reducing the production energy consumption!

Through retrieval, the prior patent of the wet spraying technology is disclosed, such as Chinese patent application number: 2016102233096, filing date: in 2016, 4, 12 days, the invention and creation name is: the application discloses a wet spraying process for coating engineering machinery, which comprises the following steps: pre-treating; spraying a primer; drying; coating and scraping putty; polishing; middle coating and spraying; spraying finish paint; and (5) drying. The primer coating composition adopted by the application spray coating comprises a primer, fluorozirconic acid and sodium fluorozirconate, and further comprises formic acid, acrylic acid, potassium chloride and polyvinyl ether. The wet spraying process for coating the engineering machinery reduces energy consumption, is beneficial to improving the adhesive force of paint and finish paint, and improves the product quality. However, the application is only limited to the optimization of the primer, and the practical service performance of the primer is still greatly improved.

Disclosure of Invention

1. Technical problem to be solved by the invention

The invention aims to overcome the defects that the water-based paint is difficult to wet spray and has low production efficiency in the prior art, and provides a wet-spraying water-based two-component polyurethane paint which can effectively realize a wet spraying process, thereby improving the production efficiency, reducing the production energy consumption, being widely applied in the coating field, and particularly having good effects in the low-temperature coating field which relates to vehicle bodies and related requirements of two-layer coating and one-time baking.

2. Technical scheme

In order to achieve the purpose, the technical scheme provided by the invention is as follows:

the wet-spraying water-based two-component polyurethane coating comprises a primer and a finish, wherein hydrophilic fumed silica is added into both the primer and the finish, and the adding weight of the hydrophilic fumed silica in the primer is more than that of the hydrophilic fumed silica in the finish.

Further, the primer comprises the following raw materials in parts by weight:

furthermore, the finish paint comprises the following raw materials in parts by weight:

furthermore, the ratio of the adding weight portion of the hydrophilic fumed silica in the finishing coat to the adding weight portion of the hydrophilic fumed silica in the primer is 1 to (1.2-5).

Furthermore, the ratio of the adding weight portion of the hydrophilic fumed silica in the finishing coat to the adding weight portion of the hydrophilic fumed silica in the primer is 1 to (2-2.5).

Further, the deionized water has a conductivity in the range of 0.1 to 20 us/cm.

Further, the primer is prepared according to the following method:

A. preparing raw materials, adding 0.8-1.5 parts by weight of aqueous dispersing agent, 0.4-0.8 part by weight of aqueous defoaming agent, 8-15 parts by weight of deionized water, 0.0-0.3 part by weight of antiseptic bactericide, 20-25 parts by weight of rutile titanium dioxide and 0.1-0.5 part by weight of hydrophilic fumed silica into 55-60 parts by weight of aqueous hydroxyl acrylic acid secondary dispersion under the condition of stirring, and uniformly stirring and grinding the mixture until the fineness is less than 10 micrometers;

B. adding 0.2-0.4 part by weight of water-based leveling agent, 0.8-1.6 part by weight of aqueous liquid rheological aid and 3-5 parts by weight of propylene glycol diacetate into the obtained mixture under the stirring condition, uniformly stirring to obtain the raw paint, and filtering the raw paint by adopting a 150-mesh and 250-mesh filter screen to obtain the primer.

Further, in the step A, the aqueous hydroxy acrylic acid secondary dispersion is stirred under the condition of 300-; in the step B, the mixture is stirred and other raw materials are added under the conditions of 300-700 r/min.

Further, the finishing coat is prepared according to the following method:

a. preparing raw materials, adding 0.7-1.5 parts by weight of aqueous dispersing agent, 0.4-0.8 part by weight of aqueous defoaming agent, 6-10 parts by weight of deionized water, 0.0-0.3 part by weight of antiseptic bactericide, 3-5 parts by weight of organic pigment and 0.05-0.25 part by weight of hydrophilic fumed silica into 77-83 parts by weight of aqueous hydroxyl acrylic acid secondary dispersion under the condition of stirring, and uniformly stirring and grinding the mixture until the fineness is less than 10 microns;

b. and adding 0.4-0.8 part by weight of water-based leveling agent, 0.8-1.6 parts by weight of aqueous liquid rheological aid and 3-5 parts by weight of propylene glycol diacetate into the obtained mixture under the stirring condition, uniformly stirring to obtain the raw paint, and filtering the raw paint by adopting a 150-mesh and 250-mesh filter screen to obtain the finish paint.

Further, in the step a, the aqueous hydroxy acrylic acid secondary dispersion is stirred under the condition of 300-700 r/min and other raw materials are added, after the addition is finished, the mixture is stirred for 10-15min under the condition of 700-1200 r/min and then is ground; in the step b, the mixture is stirred at the conditions of 300-700 r/min and other raw materials are added.

3. Advantageous effects

Compared with the prior art, the technical scheme provided by the invention has the following remarkable effects:

(1) according to the wettable spray-wet water-based two-component polyurethane coating, the hydrophilic fumed silica is added into the primer and the finish, the adding weight of the hydrophilic fumed silica in the primer is more than that of the hydrophilic fumed silica in the finish, so that the requirements of no sagging and good leveling property in normal vertical face construction of the primer are met, the requirement for high appearance effect of the finish is met, a necessary guarantee is provided for a wet spray-wet construction process, the primer does not need to be dried or pre-baked when the coating is used, a paint film coating system can be formed by one-time baking after the two coatings are sprayed, the production efficiency is improved, the production energy consumption is reduced, and the coating is very convenient to apply in wet spray-wet construction.

(2) According to the wet-spraying water-based two-component polyurethane coating, the primer and the finish are matched for use, each coating is not required to be baked and cured, the production efficiency is improved, the production cost is reduced, meanwhile, the whole exposure of a wet film of the coating in a production environment can be reduced for too long time, and the surface cleanliness of a dry film is improved.

(3) According to the wettable water-spray two-component polyurethane coating, the water-based defoaming agent meets the requirements of inhibiting and eliminating bubble microbubbles in the color paste grinding and construction processes, and a small amount of propylene glycol diacetate is introduced to further reduce the foamability of a paint film, further improve the surface effect of the paint film and improve the workability.

(4) According to the wet-spraying water-based two-component polyurethane coating, the addition of the pH value regulator and the anticorrosive bactericide is beneficial to ensuring the storage stability of a coating product, so that the raw materials are mutually matched to obtain the primer and the finish with excellent comprehensive properties, and the good appearance effect of the product is ensured.

(5) According to the wettable spray-wet water-based two-component polyurethane coating, the primer provides an excellent effect of starting and stopping up between the base material and the finish, the outstanding adhesive force and covering power of the primer provide a good foundation for improving the flatness of the base material and providing high surface appearance quality of a composite coating, and the coating effect of the primer and the finish after double coating and single baking is that the finish is uniformly covered, no primer is exposed, no shrinkage cavity is formed, and the quality is obviously improved.

Drawings

FIG. 1 is a schematic flow diagram of a method of preparing a primer according to the present invention;

FIG. 2 is a schematic flow diagram of a method of preparing a topcoat of the present invention;

fig. 3 is a schematic flow chart of a method for using a wet-sprayable aqueous two-component polyurethane coating of the present invention.

Detailed Description

For a further understanding of the invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

The present invention will be further described with reference to the following examples.

Example 1

As shown in fig. 1-3, the wet-sprayable aqueous two-component polyurethane coating of the present embodiment includes a primer and a topcoat, wherein hydrophilic fumed silica is added to both the primer and the topcoat, and the weight of the hydrophilic fumed silica in the primer is greater than that of the hydrophilic fumed silica in the topcoat. Specifically, the primer in this embodiment includes the following raw materials in parts by weight:

the preparation method of the primer in the embodiment is as follows:

A. preparing raw materials according to the formula amount, stirring the aqueous hydroxy acrylic acid secondary dispersion under the condition of 300 revolutions per minute, adding 0.2-0.4 part by weight of pH value regulator (the addition amount is determined according to the pH value of the selected aqueous hydroxy acrylic acid secondary dispersion), aqueous dispersant, aqueous defoaming agent, deionized water, antiseptic bactericide, rutile type titanium dioxide and hydrophilic fumed silica under the stirring condition, stirring the mixture for 10 minutes under the condition of 700 revolutions per minute after the addition is finished, and grinding the mixture until the fineness is less than 10 micrometers;

B. and D, stirring the mixture obtained in the step A at 300 revolutions per minute, adding the aqueous flatting agent, the aqueous liquid rheological aid and the propylene glycol diacetate according to the formula amount under the stirring condition, uniformly stirring to obtain the raw paint, and filtering the raw paint by using a 200-mesh filter screen to obtain the primer.

Specifically, in the preparation of the primer in this embodiment, half of the aqueous hydroxy acrylic acid secondary dispersion, the aqueous dispersant, and the aqueous defoamer may be uniformly dispersed into deionized water under stirring to form a first mixture; then adding the antiseptic bactericide, rutile titanium dioxide and hydrophilic fumed silica into the first mixture, uniformly mixing to form a second mixture, and dispersing and grinding the second mixture until the fineness is less than 10 micrometers; and then adding the rest half of the aqueous hydroxy acrylic acid secondary dispersion, the pH value regulator, the aqueous leveling agent, the aqueous liquid rheological aid and the propylene glycol diacetate into a second mixed species under the condition of low-speed dispersion, uniformly stirring at a medium speed to obtain the raw paint, and then filtering to obtain the primer.

The waterborne defoamer in the base paint formula in the embodiment consists of a winning paint additive TEGOFoamex830 and a Surfynol MD-20 (original air chemical industry, now the winning paint additive), wherein the TEGOFoamex830 is used for grinding the early-stage color paste, and the Surfynol MD-20 is used for adding in the later-stage finished paint formula; the hydrophilic fumed silica is N20ST fumed silica from wacke chemical (Chinese) limited company (WACKER), and the aqueous liquid rheological additive is prepared from BYK-420 and BYK-425 from BYK company; the antiseptic bactericide is a KATHON LXE high-performance antiseptic bactericide provided by Dow chemical (DOW) company.

The finish paint in the embodiment comprises the following raw materials in parts by weight:

the finish paint in the embodiment is prepared by the following method:

step a, preparing raw materials according to the formula amount, stirring the aqueous hydroxyl acrylic acid secondary dispersion under the condition of 300 revolutions per minute, adding 0.2-0.4 part by weight of pH value regulator (the addition amount is determined according to the pH value of the selected aqueous hydroxyl acrylic acid secondary dispersion), aqueous dispersant, aqueous defoaming agent, deionized water, antiseptic bactericide, organic pigment and hydrophilic fumed silica under the stirring condition, stirring the mixture for 10 minutes under the condition of 700 revolutions per minute after the addition is finished, and grinding the mixture until the fineness is less than 10 micrometers after the uniform stirring;

b. and adding the water-based leveling agent, the water-based liquid rheological aid and propylene glycol diacetate into the obtained mixture under the stirring condition of 300 r/min, uniformly stirring to obtain the raw paint, and filtering the raw paint by using a 200-mesh filter screen to obtain the finish paint.

In the embodiment, the conductivity of deionized water used for the primer and the finish paint is 0.1uS/cm, and the lower conductivity is adopted, so that the performance of the water-based paint is more stable, and the storage stability period is relatively prolonged.

In this embodiment, a white primer and a red topcoat are specifically used in combination, a red organic pigment may be selected from the topcoat raw material, other raw materials used in the topcoat are substantially the same as those in the primer, and the addition weight part of the hydrophilic fumed silica in the topcoat is less than that of the hydrophilic fumed silica in the primer, the ratio of the addition weight part of the aqueous leveling agent in the topcoat to that of the aqueous leveling agent in the primer is (1.5-3) to 1, specifically, in this embodiment, the ratio of the addition weight part of the aqueous leveling agent in the topcoat to that of the aqueous leveling agent in the primer is 2: 1, and the ratio of the addition weight part of the hydrophilic fumed silica in the topcoat to that of the hydrophilic fumed silica in the primer is 1: 2.

When the primer is prepared in the embodiment, the hydrophilic fumed silica, the aqueous liquid rheological additive and the appropriate aqueous leveling agent are adopted to be matched, so that the requirements of no sagging and good leveling property of normal vertical face construction of the primer are met, and meanwhile, a necessary guarantee is provided for a wet spraying construction process; specifically, the hydrophilic fumed silica in this embodiment can provide a rheology control capability in a liquid system due to its surface chemistry and chain structure, and at the same time, has a rheology control capability of preventing the occurrence of "photo frame" and "thick edge" phenomena, and can limit the microscopic movement of the internal components of the coating during the curing and drying reaction of the wet coating, and improve the "holding power" of the coating, thereby achieving the effect of being beneficial to preventing the paint film from being "bitten" by the finish when wet-sprayed; the proper water-based leveling agent can provide lower surface tension of a wet paint film surface layer, makes up possible tiny flaws possibly existing in the holding force function of hydrophilic fumed silica in the curing process of a wet film coating, and further ensures the performance of a paint film wet spraying process; the aqueous liquid rheological additive is beneficial to ensuring good stability of the coating in the storage process, avoiding obvious phenomena of water diversion and pigment and filler precipitation and improving the sagging resistance of the coating in the vertical spraying process; the aqueous defoaming agent provides requirements for inhibiting and eliminating bubble microbubbles in the color paste grinding and construction processes, and a small amount of propylene glycol diacetate is introduced to further reduce the foamability of a paint film, further improve the surface effect of the paint film and improve the workability; the addition of the pH value regulator and the anticorrosive bactericide is beneficial to ensuring the storage stability of the paint product, so that the raw materials are mutually matched to obtain the primer with excellent comprehensive performance. In the same way, in the preparation process of the finish paint, the hydrophilic fumed silica and the aqueous liquid rheological additive are matched with a proper aqueous leveling agent, and the adding weight of the hydrophilic fumed silica is lower than that of the primer, so that the requirement of the finish paint on high appearance effect is met, and necessary guarantee is provided for a wet spraying construction process; the aqueous defoaming agent provides requirements for inhibiting and eliminating bubble microbubbles in the color paste grinding and construction processes, and a small amount of propylene glycol diacetate is introduced to further reduce the foamability of a paint film, further improve the surface effect of the paint film and improve the workability; the addition of the pH value regulator and the anticorrosive bactericide is beneficial to ensuring the storage stability of the paint product, so that the raw materials are mutually matched to obtain finish paint with excellent comprehensive performance, and the good appearance effect of the product is ensured. The primer of the embodiment is matched with the water-based hydroxy acrylic acid secondary dispersion and the rutile type titanium dioxide, has high adhesion and high covering power matched with corresponding substrates, provides adhesion, high covering power and ground color required by a wet spraying process, provides the required color and corresponding physical indexes for the finish paint, is matched with the primer for use, has good water resistance, and has high matching with the substrates and the finish paint.

The primer provides excellent effect of starting and stopping between the base material and the finish paint, the outstanding adhesive force and covering power of the primer provide good foundation for improving the flatness of the base material and providing high surface appearance quality of the composite coating, and the finish paint layer realizes rich color decoration and meets the requirement of bright color of the paint. The coating effect of the primer and the finish prepared by the formula of the embodiment after the primary coating and baking is uniform in finish covering, free of primer exposure and shrinkage cavity, and the quality is obviously improved. In addition, when the primer and the finish paint are used in a matched manner, each coating does not need to be baked and cured, the production efficiency is improved, the production cost is reduced, meanwhile, the whole exposure of a wet film of the coating in a production environment for a long time can be reduced, and the surface cleanliness of a dry film is improved.

Example 2

The coating of the two-component wet-wettable spray water-based polyurethane coating comprises a primer and a finish, and is basically the same as that in example 1, except that the primer in the present embodiment comprises the following raw materials in parts by weight:

the preparation method of the primer in the embodiment is as follows:

A. preparing raw materials according to the formula amount, stirring the aqueous hydroxy acrylic acid secondary dispersion under the condition of 500 revolutions per minute, adding 0.2-0.4 part by weight of pH value regulator (the addition amount is determined according to the pH value of the selected aqueous hydroxy acrylic acid secondary dispersion), aqueous dispersant, aqueous defoaming agent, deionized water, antiseptic bactericide, rutile type titanium dioxide and hydrophilic fumed silica under the stirring condition, stirring the mixture for 12min under the condition of 1000 revolutions per minute after the addition is finished, and grinding the mixture until the fineness is less than 10 micrometers;

B. and B, stirring the mixture obtained in the step A at 500 revolutions per minute, adding the aqueous flatting agent, the aqueous liquid rheological aid and the propylene glycol diacetate according to the formula amount under the stirring condition, uniformly stirring to obtain the raw paint, and filtering the raw paint by using a 150-mesh filter screen to obtain the primer.

in the embodiment, the ratio of the adding parts by weight of the hydrophilic fumed silica in the top coat to the adding parts by weight of the hydrophilic fumed silica in the primer is 1: 2.1, the ratio of the adding parts by weight of the water-based leveling agent in the top coat to the adding parts by weight of the water-based leveling agent in the primer is 3: 1, and the electric conductivity of deionized water used for the primer and the top coat is 20 us/cm.

The finish paint in the embodiment is prepared by the following method:

step a, preparing raw materials according to the formula amount, stirring the aqueous hydroxyl acrylic acid secondary dispersion under the condition of 500 revolutions per minute, adding 0.2-0.4 part by weight of pH value regulator (the addition amount is determined according to the pH value of the selected aqueous hydroxyl acrylic acid secondary dispersion), aqueous dispersant, aqueous defoaming agent, deionized water, antiseptic bactericide, organic pigment and hydrophilic fumed silica under the stirring condition, stirring the mixture for 12 minutes under the condition of 1000 revolutions per minute after the addition is finished, and grinding the mixture until the fineness is less than 10 micrometers after the uniform stirring;

b. and adding the water-based leveling agent, the water-based liquid rheological aid and propylene glycol diacetate into the obtained mixture under the stirring condition of 500 revolutions per minute, uniformly stirring to obtain the raw paint, and filtering the raw paint by adopting a 150-mesh filter screen to obtain the finish paint.

Example 3

the preparation method of the primer in the embodiment is as follows:

A. preparing raw materials according to the formula amount, stirring the aqueous hydroxy acrylic acid secondary dispersion under the condition of 700 revolutions per minute, adding 0.2-0.4 part by weight of pH value regulator (the addition amount is determined according to the pH value of the selected aqueous hydroxy acrylic acid secondary dispersion), aqueous dispersant, aqueous defoaming agent, deionized water, antiseptic bactericide, rutile type titanium dioxide and hydrophilic fumed silica under the stirring condition, stirring the mixture for 15min under the condition of 1200 revolutions per minute after the addition is finished, and grinding the mixture until the fineness is less than 10 microns;

B. and B, stirring the mixture obtained in the step A at 700 revolutions per minute, adding the aqueous flatting agent, the aqueous liquid rheological aid and the propylene glycol diacetate according to the formula amount under the stirring condition, uniformly stirring to obtain the raw paint, and filtering the raw paint by using a 250-mesh filter screen to obtain the primer.

in this example, the ratio of the added weight parts of the hydrophilic fumed silica in the top coat to the added weight parts of the hydrophilic fumed silica in the primer is 1: 2, the ratio of the added weight parts of the water-based leveling agent in the top coat to the added weight parts of the water-based leveling agent in the primer is 2: 1, and the conductivity of the deionized water used in the primer and the top coat is 10 us/cm.

The finish paint in the embodiment is prepared by the following method:

step a, preparing raw materials according to the formula amount, stirring the aqueous hydroxyl acrylic acid secondary dispersion under the condition of 700 revolutions per minute, adding 0.2-0.4 part by weight of pH value regulator (the addition amount is determined according to the pH value of the selected aqueous hydroxyl acrylic acid secondary dispersion), aqueous dispersant, aqueous defoaming agent, deionized water, antiseptic bactericide, organic pigment and hydrophilic fumed silica under the stirring condition, stirring the mixture for 15min under the condition of 1200 revolutions per minute after the addition is finished, and grinding the mixture until the fineness is less than 10 microns after uniform stirring;

b. and adding the water-based leveling agent, the water-based liquid rheological aid and propylene glycol diacetate into the obtained mixture under the stirring condition of 700 revolutions per minute, uniformly stirring to obtain the raw paint, and filtering the raw paint by using a 250-mesh filter screen to obtain the finish paint.

The following table 1 shows the raw material composition of the primer in the above three examples:

TABLE 1 primer raw Material composition

The following table 2 shows the raw material composition of the top-coat in the above three examples:

TABLE 2 Top-coat raw Material composition

When the wet-spraying water-based two-component polyurethane coating provided by the embodiment is used, the primer and the finish are used in a matched manner, and the specific method comprises the following steps:

step one, uniformly blending the primer, a general waterborne curing agent and deionized water according to the ratio of (3-5) to (1-2) to 1;

step two, uniformly blending the finish paint, a general waterborne curing agent and deionized water according to the ratio of (2-4) to (1-2) to 1;

thirdly, spraying the prepared primer on the surface of the workpiece, and leveling for 1-3min at normal temperature;

spraying the prepared finish paint on the primer layer, and leveling and drying the two coatings at normal temperature for 20-30 min; then curing and baking for 25-35min at the temperature of 80 +/-5 ℃ to form a paint film coating system.

The first step and the second step are not required in sequence, and the universal water-based curing agent is a water-based isocyanate curing agent and specifically comprises the following raw materials in parts by weight: 40-50 parts of IPDI (isophorone diisocyanate) -based hydrophilic modified aliphatic polyisocyanate; 40-50 parts of HDI-based hydrophilic modified aliphatic polyisocyanate; 5-15 parts of propylene glycol diacetate; the preparation method of the general waterborne curing agent comprises the following steps: the raw materials in the formula ratio are uniformly mixed and stirred for at least 10min to prepare the universal water-based curing agent. The conductivity of the deionized water used is likewise from 0.1 to 20 us/cm.

Specifically, the universal aqueous curing agent in this embodiment comprises the following raw materials in parts by weight: based on IPDI (isophorone diisocyanate) hydrophilic modified aliphatic polyisocyanate 45 parts; 45 parts of HDI-based hydrophilic modified aliphatic polyisocyanate; 10 parts of propylene glycol diacetate. When the paint is used, uniformly blending the primer, the universal water-based curing agent and deionized water according to a ratio of 4: 1, uniformly blending the finish paint, the universal water-based curing agent and the deionized water according to a ratio of 3: 1, spraying the blended primer on the surface of a workpiece, and leveling for 1min at normal temperature; spraying the prepared finish paint on the primer layer, and leveling and drying the two coatings for 20min at normal temperature; and then curing and baking for 25min at the temperature of 75 ℃ to form a paint film coating system. When the paint is used, the primer and the finish paint are sequentially sprayed on the surface of a workpiece, the primer is not required to be dried or prebaked, a paint film coating system can be formed by once baking after the two coatings are sprayed, and the paint is very convenient to apply in wet spraying construction.

Comparative example 1

The coating of the comparative example comprises a primer and a finish, wherein the primer comprises the following raw materials in parts by weight:

the preparation method of the primer in the comparative example is basically the same as the above example, the pH value regulator, the aqueous dispersant, the aqueous defoamer a, the deionized water, the antiseptic bactericide and the rutile titanium dioxide are added into the aqueous hydroxyacrylic acid secondary dispersion according to the formula amount under the stirring condition of 300-700 r/min, after the addition is finished, the mixture is stirred for 10-15min under the stirring condition of 700-1200 r/min, and then the mixture is ground until the fineness is less than 10 microns; and then adding the water-based antifoaming agent b, the water-based leveling agent, the water-based liquid rheological aid a, the water-based liquid rheological aid b and the propylene glycol diacetate into the obtained mixture under the stirring condition of 300-700 r/min, uniformly stirring, and filtering by adopting a 150-filter 250-mesh filter screen to prepare the primer.

The finish paint in the comparative example comprises the following raw materials in parts by weight:

the preparation method of the finish paint in the comparative example is basically the same as that in the above example, the pH value regulator, the aqueous dispersant, the aqueous defoamer a, the deionized water, the antiseptic bactericide and the red organic pigment are added into the aqueous hydroxyl acrylic acid dispersoid under the stirring condition of 300-700 r/min, after the addition is finished, the mixture is stirred for 10-15min under the stirring condition of 700-1200 r/min, and then the mixture is ground until the fineness is less than 10 microns; and then adding the water-based antifoaming agent b, the water-based leveling agent, the water-based liquid rheological aid a, the water-based liquid rheological aid b and the propylene glycol diacetate into the obtained mixture under the stirring condition of 300-700 r/min, uniformly stirring, and filtering by using a 150-filter 250-mesh filter screen to obtain the finish paint.

Comparative example 2

The coating of the comparative example comprises a primer and a finish, and is basically the same as the comparative example 1, except that the primer comprises the following raw materials in parts by weight:

the following table 3 shows the raw material composition of the primer in the above two pairs of proportions:

TABLE 3 raw material composition of primer

The following table 4 shows the raw material composition of the two pairs of intermediate coats:

TABLE 4 raw Material composition of topcoat

The primer and the finish prepared in the above examples 1 to 3 and comparative examples 1 and 2 are respectively blended with a matched universal water-based curing agent and deionized water, and then sprayed on a related substrate, the specific method refers to the method for using the primer and the finish in example 3, and the performance of the paint film is detected after the paint film coating is formed, and the detection results are shown in the following table 5.

TABLE 5 paint film Performance test results

The detection standards of the above properties are as follows:

the performance suitable for spraying: the primer and the finish paint have good dispersibility, moderate leveling property, good thixotropy, uniform coating, no obvious orange peel, no pinhole bubbles and no impurities when being sprayed; no appearance defects such as sagging, bottom exposure, light loss and the like;

the hardness of a paint film is more than or equal to HB mitsubishi pencil;

and (3) testing the adhesive force: the hundred-grid test method has no broken edge falling off, no falling off in the coating grid, and no paint spot on the 3M adhesive tape;

gloss: the gloss test value is more than or equal to 85(60 degrees);

water-soaking resistance: the periphery of the sample plate is sealed, the sample plate is placed in a neutral water tank at 23 +/-2 ℃, the sample plate is taken out after being soaked in water for 7 days, and the sample plate is tested after being recovered for 2 hours, wherein the paint coating surface is free from expansion, water bubbles, falling off and light loss, and the adhesion force test is less than or equal to 0 grade;

the paint film has acid resistance (25 ℃ multiplied by 24H), does not bubble, fall off and has no obvious light loss and color change under the condition of 0.1NH2SO 4;

alkali resistance (25 ℃ multiplied by 7d), 0.1NNaoH and 23 +/-2 ℃ multiplied by 7d, and a paint film has no obvious light loss, color change, foaming, expansion and falling off;

artificial accelerated aging resistance: ultraviolet light aging is carried out for 500 hours, the pulverization of a paint film is less than or equal to level 1, the delustering of the paint film is less than or equal to level 1, the color change of the paint film is less than or equal to level 2, and the cracking of the paint film is less than or equal to level 1.

The primer and the finish of the coating prepared by the processing of the embodiment meet the following requirements: the primer and the finish paint are water-based environment-friendly two-component polyurethane low-temperature curing coating, so that the environment is protected, the restriction instruction of harmful substances of European Union ROHS is met, and the system and environment protection requirements are met; the coating has no dust, particles and impurities in appearance, has good fluidity and does not form a stretched skin shape or solidified glue joint; the shelf life of the paint is not less than 12 months under normal temperature and not less than 6 months after the paint is opened.

Example 4

in the embodiment, the ratio of the adding weight parts of the hydrophilic fumed silica in the top coat to the adding weight parts of the hydrophilic fumed silica in the primer is 1: 2; the ratio of the added weight parts of the water-based leveling agent in the finish paint to the added weight parts of the water-based leveling agent in the primer paint is 1.5: 1.

When the wettable spray-wet water-based two-component polyurethane coating is used, the primer is matched with the finish, and specifically, the primer, a general water-based curing agent and deionized water are uniformly mixed according to the ratio of 3: 2: 1; uniformly blending finish paint, a universal water-based curing agent and deionized water according to the ratio of 2: 1, spraying the blended primer paint on the surface of a workpiece, leveling at normal temperature for 3min, spraying the blended finish paint on the primer paint, and leveling and drying at normal temperature for 30min for two coatings; then curing and baking for 35min at the temperature of 85 ℃ to form a paint film coating system.

The universal water-based curing agent is a water-based isocyanate curing agent and specifically comprises the following raw materials in parts by weight: 40 parts of IPDI (isophorone diisocyanate) -based hydrophilic modified aliphatic polyisocyanate; 40 parts of HDI-based hydrophilic modified aliphatic polyisocyanate; 5 parts of propylene glycol diacetate. Example 5

in the embodiment, the ratio of the adding parts by weight of the hydrophilic fumed silica in the top coat to the adding parts by weight of the hydrophilic fumed silica in the primer is 1: 2.5, and the ratio of the adding parts by weight of the water-based leveling agent in the top coat to the adding parts by weight of the water-based leveling agent in the primer is 3: 1.

When the wettable spray-wet water-based two-component polyurethane coating is used, the primer is matched with the finish, and specifically, the primer, a general water-based curing agent and deionized water are uniformly mixed according to the ratio of 5: 2: 1; uniformly blending finish paint, a universal water-based curing agent and deionized water according to the ratio of 4: 2: 1, spraying the blended primer paint on the surface of a workpiece, leveling at normal temperature for 2min, spraying the blended finish paint on the primer paint, and leveling and drying at normal temperature for 25 min; then curing and baking for 30min at the temperature of 80 ℃ to form a paint film coating system.

The universal water-based curing agent is a water-based isocyanate curing agent and specifically comprises the following raw materials in parts by weight: 50 parts of IPDI (isophorone diisocyanate) -based hydrophilic modified aliphatic polyisocyanate; 50 parts of HDI-based hydrophilic modified aliphatic polyisocyanate; 15 parts of propylene glycol diacetate.

Example 6

in the embodiment, the ratio of the adding parts by weight of the hydrophilic fumed silica in the top coat to the adding parts by weight of the hydrophilic fumed silica in the primer is 1: 5, and the ratio of the adding parts by weight of the water-based leveling agent in the top coat to the adding parts by weight of the water-based leveling agent in the primer is 1.5: 1.

The difference between the primer and the universal water-based curing agent and the deionized water is that the primer, the universal water-based curing agent and the deionized water are uniformly mixed according to the ratio of 5: 1; the finish paint, the general waterborne curing agent and the deionized water are uniformly mixed according to the ratio of 4: 1.

Example 7

in the embodiment, the ratio of the adding parts by weight of the hydrophilic fumed silica in the top coat to the adding parts by weight of the hydrophilic fumed silica in the primer is 1: 1.2, and the ratio of the adding parts by weight of the water-based leveling agent in the top coat to the adding parts by weight of the water-based leveling agent in the primer is 2.5: 1.

The difference between the primer and the finish paint is that in the embodiment, the primer, the general water-based curing agent and the deionized water are uniformly mixed according to the ratio of 5: 1.5: 1; the finish paint, the general waterborne curing agent and the deionized water are uniformly mixed according to the ratio of 4: 1.5: 1.

The present invention and its embodiments have been described above schematically, without limitation, and what is shown in the drawings is only one of the embodiments of the present invention, and the actual structure is not limited thereto. Therefore, if the person skilled in the art receives the teaching, without departing from the spirit of the invention, the person skilled in the art shall not inventively design the similar structural modes and embodiments to the technical solution, but shall fall within the scope of the invention.

Claims

1. A two-component polyurethane coating capable of wetting and spraying is characterized in that: the coating comprises a primer and a finish, wherein hydrophilic fumed silica is added into both the primer and the finish, and the adding weight of the hydrophilic fumed silica in the primer is more than that of the hydrophilic fumed silica in the finish; the ratio of the adding weight parts of the hydrophilic fumed silica in the finishing coat to the adding weight parts of the hydrophilic fumed silica in the primer is 1: (1.2-5); the ratio of the added weight parts of the water-based leveling agent in the finish paint to the added weight parts of the water-based leveling agent in the primer paint is (1.5-3): 1;

the primer comprises the following raw materials in parts by weight:

the finish paint comprises the following raw materials in parts by weight:

2. the wet-sprayable aqueous two-component polyurethane coating of claim 1, wherein: the ratio of the adding weight parts of the hydrophilic fumed silica in the finishing coat to the adding weight parts of the hydrophilic fumed silica in the primer is 1: (2-2.5).

3. The wet-sprayable aqueous two-component polyurethane coating of claim 1, wherein: the conductivity of the deionized water is in the range of 0.1-20 us/cm.

4. The wet-sprayable aqueous two-component polyurethane coating of claim 1, wherein: the primer is prepared by the following method:

5. The wet-sprayable aqueous two-component polyurethane coating of claim 4, wherein: in the step A, stirring the aqueous hydroxy acrylic acid secondary dispersion under the condition of 300-700 r/min, adding other raw materials, stirring the mixture for 10-15min under the condition of 700-1200 r/min, and then grinding; in the step B, the mixture is stirred and other raw materials are added under the conditions of 300-700 r/min.

6. The wet-sprayable aqueous two-component polyurethane coating of claim 1, wherein: the finish paint is prepared by the following method:

7. The wet-sprayable aqueous two-component polyurethane coating of claim 6, wherein: step a, stirring the aqueous hydroxy acrylic acid secondary dispersion under the condition of 300-700 r/min, adding other raw materials, stirring the mixture for 10-15min under the condition of 700-1200 r/min, and then grinding; in the step b, the mixture is stirred at the conditions of 300-700 r/min and other raw materials are added.