Water-resistant polyurethane finish paint and preparation method therefor

Abstract

The present invention provides a water-resistant polyurethane finish paint and a preparation method therefor. For the water-resistant polyurethane finish paint, a two-component aqueous polyurethane finish paint is used, wherein component A comprises 40-50 parts of an aqueous hydroxyl acrylic resin, 1-2 parts of hydrophobically modified sodium alginate, 0.1-0.5 parts of a dispersing agent, 0.1-0.5 parts of a defoaming agent, 5-15 parts of a pigment, 10-20 parts of a filler, 0.1-0.5 parts of a preservative, and 10-20 parts of water; component B is a water-soluble isocyanate; and the mass ratio of component A to component B is 3:2, and component A is prepared by mixing all the raw materials and then carrying out high-pressure homogenization. Because the hydrophobically modified sodium alginate is used in the water-resistant polyurethane finish paint of the present invention, not only can this ingredient provide good film-forming properties, but also a uniform hydrophobic layer can be formed on the surface of the resulting paint film, so that the water resistance and the anti-blushing performance are improved; in addition, sodium alginate has good weather resistance and stain resistance. The present invention has a good application prospect.

Description

Water-resistant polyurethane topcoat and preparation method thereof Technical Field

[0001] The present invention relates to the technical field of coatings, in particular to a water-resistant polyurethane topcoat and a preparation method thereof. Background Art

[0002] Polyurethane topcoat is an important polymer coating among coatings. It has excellent wear resistance and chemical corrosion resistance. At the same time, its high hardness can effectively protect the substrate, and the hydrogen bonding structure between molecules gives it good weather resistance.

[0003] In order to improve environmental protection, the polyurethane topcoats widely used on the market currently all adopt water-based polyurethane technology. Water-based polyurethane uses water-soluble isocyanate. Therefore, after the topcoat is cured into a film, hydrophilic groups will also remain on the surface of the paint film. These hydrophilic groups will cause the waterproofness of the paint film surface to decrease, and the water resistance will also be reduced. Therefore, how to improve the water resistance of polyurethane topcoat has become one of the technical problems that need to be solved urgently.

[0004] Summary of the Invention

[0005] In view of this, the present invention proposes a water-resistant polyurethane topcoat, aiming to obtain a water-based polyurethane with better water resistance through an improved formula.

[0006] The technical solution of the present invention is achieved as follows: The present invention provides a water-resistant polyurethane topcoat, the raw materials of the water-resistant polyurethane topcoat are composed of component A and component B, and the mass ratio of component A to component B is 3:2;

[0007] Wherein, component A, calculated by weight, includes 40-50 parts of water-based hydroxy acrylic resin, 1-2 parts of hydrophobically modified sodium alginate, 0.1-0.5 parts of dispersant, 0.1-0.5 parts of defoaming agent, 5-15 parts of pigment, 10-20 parts of filler, 0.1-0.5 parts of preservative and 10-20 parts of water;

[0008] The component is water-soluble isocyanate.

[0009] In the above embodiment, the water-based hydroxylated acrylic resin is Fuqisen AQUAPAC-8239 water-based hydroxylated acrylic resin; and the water-soluble isocyanate is Bayer 3100 water-soluble isocyanate.

[0010] In the above embodiment, sodium alginate has good hydrophilicity. After hydrophobic modification, the hydrophobically modified sodium alginate becomes an amphiphilic molecule, and sodium alginate is easily gathered in the paint film of the polyurethane topcoat. In particular, in water-based polyurethane topcoat, the hydrophobic modified group preferentially gathers in the outermost layer of the paint film, eventually forming a hydrophobic protective film. The hydrophilic group is the main body of the molecular chain of alginic acid. On the one hand, this part can be riveted with the molecules deep in the paint film, thereby improving the distribution stability of the hydrophobic group. On the other hand, the hydrophilic group part can be intertwined with each other, making the paint film formed by alginic acid more compact and not easy to be destroyed. Moreover, the alginic acid body can react with polyurethane to form stable chemical bonds, providing good stress resistance. In addition, alginic acid itself is a good film-forming agent that can improve the quality of the polyurethane topcoat paint film. Alginic acid also has good chemical resistance, weather resistance and mildew resistance, and can therefore improve the performance of the polyurethane paint film as a whole.

[0011] In some embodiments, the preparation method of hydrophobically modified sodium alginate includes: mixing sodium alginate, octadecyltrimethoxysilane and deionized water in a mass ratio of 1: (0.2-0.5): 10, heating to 60-65 ° C, stirring for 30-60 minutes, cooling to room temperature, and drying to obtain hydrophobically modified sodium alginate.

[0012] The preparation method of the above embodiment can prepare hydrophobically modified sodium alginate with good film-forming properties and stability.

[0013] In some embodiments, the weight average molecular weight of sodium alginate is 10,000 Da to 30,000 Da.

[0014] In the above embodiment, when the weight average molecular weight of sodium alginate is between 10,000 Da and 30,000 Da, various properties of the paint film formed are optimized, and the use effect of the prepared polyurethane topcoat is better.

[0015] In some embodiments, the dispersant is polyacrylamide.

[0016] In some embodiments, the defoaming agent is polyvinyl ether.

[0017] In some embodiments, the filler is at least one of talc, diatomaceous earth, barite powder, and glass powder, and the pigment is at least one of titanium dioxide, iron oxide, chromium oxide green, cobalt blue, and mica powder.

[0018] In some embodiments, the preservative is p-hydroxyphenol.

[0019] In a second aspect, the present invention further provides a method for preparing a water-resistant polyurethane topcoat, comprising the following steps:

[0020] Step 1: Mix and stir the water-based hydroxy acrylic resin, hydrophobically modified sodium alginate, dispersant, defoamer, preservative and water evenly;

[0021] Step 2: Continue adding pigment and filler, mix and stir evenly, add to high-pressure homogenizer and perform high-pressure homogenization for 10-30 minutes to obtain component A;

[0022] Step 3: Evenly mix the water-soluble isocyanate of component A and component B in proportion to obtain a water-resistant polyurethane topcoat.

[0023] The water-resistant polyurethane topcoat of the present invention has the following beneficial effects compared to the prior art:

[0024] The present invention adopts a raw material modification process and adds hydrophobically modified sodium alginate to the raw material of component A of a two-component water-resistant polyurethane topcoat. On the one hand, sodium alginate can be used as a film-forming agent to improve the film-forming effect of the topcoat. Secondly, after hydrophobic modification, the hydrophobic groups in the water-based topcoat are preferentially gathered on the outer surface of the paint film, thereby forming a hydrophobic layer, which improves the water resistance of the paint film. In addition, sodium alginate itself has good mechanical properties, weather resistance, anti-pollution and antibacterial properties, which can improve the quality of the paint film. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of the present invention belong. If the definitions set forth in this section are contrary to or otherwise inconsistent with definitions set forth in the patents, patent applications, published patent applications, and other publications incorporated herein by reference, the definitions listed in this section take precedence over the definitions incorporated herein by reference.

[0027] Example 1

[0028] This embodiment provides a water-resistant polyurethane topcoat and a preparation method thereof. The water-resistant polyurethane topcoat includes component A and component B, wherein component A is composed of the following raw materials: 4 kg of water-based hydroxy acrylic resin, 100 g of hydrophobically modified sodium alginate, 10 g of polyacrylamide, 10 g of polyethylene ether, 500 g of titanium dioxide, 1 kg of talc, 10 g of p-hydroxyphenol, and 1 L of water; component B is composed of the following raw materials: 4.42 kg of water-soluble isocyanate.

[0029] The preparation method of the hydrophobically modified sodium alginate includes: uniformly mixing 1 kg of sodium alginate with a weight-average molecular weight of 10,000 Da, 200 g of octadecyltrimethoxysilane and 10 L of water, then heating to 60° C., stirring at this temperature for 30 minutes, cooling to room temperature, and vacuum drying at room temperature to obtain the hydrophobically modified sodium alginate.

[0030] Among the above raw materials, the water-based hydroxy acrylate is derived from the water-based hydroxy acrylate with the brand AQUAPAC-8239 produced by Fuqisen; and the water-soluble isocyanate is derived from the water-soluble isocyanate with the brand 3100 produced by Bayer.

[0031] Preparation method of water-resistant polyurethane topcoat:

[0032] 4 kg of water-based hydroxy acrylic resin, 100 g of hydrophobically modified sodium alginate, 10 g of polyacrylamide, 10 g of polyvinyl ether, 10 g of p-hydroxyphenol, and 1 L of water were mixed and stirred for 10 minutes, and then 500 g of titanium dioxide and 1 kg of talc were added and mixed and stirred for 10 minutes. The mixture was then transferred to a high-pressure homogenizer, heated to 50° C., and subjected to high-pressure homogenization at a pressure of 1000 bar for 10 minutes to obtain component A;

[0033] The component A prepared above was evenly mixed with 4.42 kg of component B to obtain a water-resistant polyurethane topcoat.

[0034] Example 2

[0035] This embodiment provides a water-resistant polyurethane topcoat and a preparation method thereof. The specific implementation method is basically the same as that of Example 1, except that in component A, the amount of each raw material is: 4.5 kg of water-based hydroxy acrylic resin, 150 g of hydrophobically modified sodium alginate, 25 g of polyacrylamide, 25 g of polyethylene ether, 1 kg of titanium dioxide, 1.5 kg of talc, 25 g of p-hydroxyphenol, and 1.5 L of water; component B is composed of the following raw materials: 5.81 kg of water-soluble isocyanate.

[0036] Example 3

[0037] This embodiment provides a water-resistant polyurethane topcoat and a preparation method thereof. The specific implementation method is basically the same as that of Example 1, except that in component A, the amount of each raw material is: 5 kg of water-based hydroxy acrylic resin, 200 g of hydrophobically modified sodium alginate, 50 g of polyacrylamide, 50 g of polyethylene ether, 1.5 kg of titanium dioxide, 2 kg of talc, 50 g of p-hydroxyphenol, and 2 L of water; component B is composed of the following raw materials: 7.23 kg of water-soluble isocyanate.

[0038] Example 4

[0039] This embodiment provides a water-resistant polyurethane topcoat and a preparation method thereof. The specific implementation method is basically the same as that of Example 1, except that when preparing the hydrophobically modified sodium alginate, the weight-average molecular weight of the raw material sodium alginate is 20,000 Da.

[0040] Example 5

[0041] This embodiment provides a water-resistant polyurethane topcoat and a preparation method thereof. The specific implementation method is basically the same as that of Example 1, except that when preparing the hydrophobically modified sodium alginate, the weight-average molecular weight of the raw material sodium alginate is 30,000 Da.

[0042] Example 6

[0043] This embodiment provides a water-resistant polyurethane topcoat and a preparation method thereof. The specific implementation method is basically the same as that of Example 1, except that when preparing the hydrophobically modified sodium alginate, the weight-average molecular weight of the raw material sodium alginate is 5000 Da.

[0044] Example 7

[0045] This embodiment provides a water-resistant polyurethane topcoat and a preparation method thereof. The specific implementation method is basically the same as that of Example 1, except that when preparing the hydrophobically modified sodium alginate, the weight-average molecular weight of the raw material sodium alginate is 50,000 Da.

[0046] Example 8

[0047] This embodiment provides a water-resistant polyurethane topcoat and a preparation method thereof. The specific implementation method is basically the same as that of Example 1, except that, when preparing hydrophobically modified sodium alginate, the mass ratio of sodium alginate, octadecyltrimethoxysilane and deionized water is 1:0.5:10, the heating temperature is 65°C, and the stirring time is 60 minutes.

[0048] Comparative Example 1

[0049] This embodiment provides a water-resistant polyurethane topcoat and a preparation method thereof. The specific implementation method is basically the same as that of Example 1, except that the hydrophobically modified sodium alginate in component A is replaced with sodium alginate of the same mass.

[0050] Comparative Example 2

[0051] This embodiment provides a water-resistant polyurethane topcoat and a preparation method thereof. The specific implementation method is basically the same as that of Example 1, except that the hydrophobically modified sodium alginate in component A is replaced by a water-based hydroxy acrylic resin of the same mass.

[0052] Comparative Example 3

[0053] This embodiment provides a water-resistant polyurethane topcoat and a preparation method thereof. The specific implementation method is basically the same as that of Example 1, except that, when preparing hydrophobically modified sodium alginate, the mass ratio of sodium alginate, octadecyltrimethoxysilane and deionized water is 1:0.1:10, the heating temperature is 60°C, and the stirring time is 30 minutes.

[0054] Comparative Example 4

[0055] This embodiment provides a water-resistant polyurethane topcoat and a preparation method thereof. The specific implementation method is basically the same as that of Example 1, except that, when preparing hydrophobically modified sodium alginate, the mass ratio of sodium alginate, octadecyltrimethoxysilane and deionized water is 1:1:10, the heating temperature is 60°C, and the stirring time is 30 minutes.

[0056] Performance testing:

[0057] The waterborne polyurethane topcoat prepared in the above examples and comparative examples was applied to the surface of a sandblasted steel plate to form a 50 μm paint film. The steel plate with the paint film was then placed in 40°C hot water for 1200 hours of immersion insulation treatment. The surface condition of the paint film was observed, and the following results were obtained:

[0058] It can be seen from the above examples that the water-resistant polyurethane topcoat of the present invention can significantly improve the water resistance of the polyurethane topcoat after using hydrophobically modified sodium alginate. The raw material of hydrophobically modified sodium alginate is cheap and easy to prepare, and has good application prospects.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A water-resistant polyurethane topcoat, characterized in that: The raw materials of the water-resistant polyurethane topcoat are composed of component A and component B, and the mass ratio of component A to component B is 3:2; Component A includes, by weight: 40-50 parts of water-based hydroxy acrylic resin, 1-2 parts of hydrophobically modified sodium alginate, 0.1-0.5 parts of dispersant, 0.1-0.5 parts of defoamer, 5-15 parts of pigment, 10-20 parts of filler, 0.1-0.5 parts of preservative and 10-20 parts of water; Component B is a water-soluble isocyanate.

2. The water-resistant polyurethane topcoat according to claim 1, characterized in that: The preparation method of the hydrophobically modified sodium alginate comprises: mixing sodium alginate, octadecyltrimethoxysilane and deionized water in a mass ratio of 1:(0.2-0.5):10, heating to 60-65° C., stirring for 30-60 minutes, cooling to room temperature, and drying to obtain the hydrophobically modified sodium alginate.

3. The water-resistant polyurethane topcoat according to claim 2, characterized in that: The weight average molecular weight of the sodium alginate is 10000Da-30000Da.

4. The water-resistant polyurethane topcoat according to claim 1, characterized in that: The dispersant is polyacrylamide.

5. The water-resistant polyurethane topcoat according to claim 1, characterized in that: The defoaming agent is polyvinyl ether.

6. The water-resistant polyurethane topcoat according to claim 1, characterized in that: The filler is at least one of talcum powder, diatomaceous earth, barite powder, and glass powder; the pigment is at least one of titanium dioxide, iron oxide, chrome oxide green, cobalt blue, and mica powder.

7. The water-resistant polyurethane topcoat according to claim 1, characterized in that: The preservative is p-hydroxyphenol.

8. A method for preparing a water-resistant polyurethane topcoat according to any one of claims 1 to 8, characterized in that: The steps include: Step 1: Mix and stir the water-based hydroxy acrylic resin, hydrophobically modified sodium alginate, dispersant, defoamer, preservative and water evenly; Step 2: Continue to add pigment and filler, mix and stir evenly, add into the high pressure homogenizer and carry out high pressure homogenization for 10-30 minutes to obtain component A; Step 3: Evenly mix the water-soluble isocyanate of component A and component B according to a certain proportion to obtain a water-resistant polyurethane topcoat.

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