Water-based woodware seal primer suitable for thin coating working condition and preparation method of water-based woodware seal primer

Abstract

The invention discloses a water-based woodware seal primer suitable for a thin coating working condition and a preparation method of the water-based woodware seal primer. The primer is composed of a cationic polyurethane aqueous dispersion, a cationic polyacrylate emulsion, acidic silica sol, a titanate chelate, polyethyleneimine, zirconium acetate, a cosolvent, an auxiliary agent and water. Due to the adoption of an inorganic sol modified cationic resin system and a special color fixing scheme, the obtained coating is high in permeability, quick to dry and easy to polish, pigments and grease can be effectively sealed, wood thorns and expansion ribs can be quickly hardened, and meanwhile the natural texture and texture of wood products are reserved.

Description

Technical Field

[0001] The present invention relates to the technical field of wood coatings, and in particular to a water-based sealing primer suitable for thin coating conditions, having high permeability, quick drying, and easy polishing, while being able to effectively seal pigments and grease and quickly harden wood splinters and bulging tendons, and a preparation method thereof. Background Art

[0002] Volatile organic compounds (VOCs), one of the main causes of haze, are currently the focus of national air pollution control. Statistics show that my country's annual VOC emissions reach 20 to 30 million tons. Among them, organic solvents such as aromatic hydrocarbons, alkanes, ketones, and esters used in traditional solvent-based coatings generate VOC emissions of more than 3 million tons annually. Water-based coatings, because they use water instead of traditional organic solvents as the dispersion medium for coatings, can significantly reduce the addition and emission of volatile organic compounds. They are an important direction for the current environmental transformation of the coatings and coatings industry.

[0003] Wood coatings, a key component of residential coatings, have seen a significant shift toward water-based coatings since 2000, with the introduction of water-based coatings such as polyacrylates and polyurethanes to replace traditional PU and NC coatings. However, this transition to water-based wood coatings also presents numerous challenges, such as deformation, bulging, oil bleeding, and color bleeding during the coating process.

[0004] Wood is a loose, hydrophilic material composed of cellulose and lignin. Its numerous internal pores and capillaries can absorb water and expand upon contact with water-based paint, causing deformation in the product and resulting in surface defects such as splinters and bulging tendons. Wood is also rich in water-soluble polyphenolic pigments (such as tannins) and flavonoids. Polyphenolic pigments are easily oxidized to quinone groups, which also readily form conjugated fused rings through coupling to produce color. Flavonoid pigments are inherently light yellow or yellow. During the coating process, these pigments dissolve in the aqueous phase and slowly diffuse as the paint film dries, eventually migrating to the surface, forming yellow or brown spots and potentially darkening the entire paint surface. Furthermore, many woods, such as pine, contain various plant oils and fats. Because water-based paints form slowly through the accumulation, fusion, and diffusion of polymer particles, the low density of the coating during initial application creates microchannels for the infiltration of pigments and oils, exacerbating the occurrence of defects.

[0005] In order to deal with the problems of deformation and color bleeding of wood products when exposed to water, the industry has developed water-based sealing and bonding primers based on various technical routes, such as: (1) Water-based single-component cationic resin primer. Cationic polymers and tannic acid react quickly to fix them inside the wood to prevent migration to the paint film. For example, castor oil-modified cationic self-crosslinking polyurethane polyurea aqueous dispersion and polyacrylate cationic emulsion are used to prepare primers. (2) Water-based primers using low-particle acrylic emulsions. Taking advantage of its small particle size penetration, it penetrates deep into the wood vessels to achieve the effect of sealing and relieving swelling. (3) Water-based primers with added sealants. Common sealants are mainly ammonium-stabilized zirconium compounds, which alleviate the migration of pigments by complexing metal ions with pigments; (4) Two-component thermosetting primers composed of water-based hydroxy acrylic emulsions and various curing agents. Optional curing agents include water-dispersible isocyanates, aziridines, etc. This type of coating has a higher crosslinking density and better bonding and barrier effects than single-component primers, but is also more expensive.

[0006] Although there are many types of water-based primer solutions for wood, and many solutions have been successfully put into production, the coating effect of the current solutions is still not ideal under the conditions of open coating (i.e., the coating style that does not completely fill the wood ducts and exposes the natural texture of the wood) that require thin coating. Summary of the Invention

[0007] The purpose of the present invention is to provide a water-based sealing primer suitable for thin coating conditions, with high permeability, quick drying, easy polishing, and the ability to effectively seal pigments and grease, and quickly harden wood splinters and expanded tendons, as well as a preparation method thereof.

[0008] The purpose of the present invention can be achieved through the following technical solutions:

[0009] A water-based wood sealing primer, the coating is composed of the following ingredients:

[0010]

[0011] In some preferred technical solutions, the coating is composed of the following components:

[0012]

[0013]

[0014] In the technical solution of the present invention: the cationic polyurethane aqueous dispersion is an epoxy-modified polycarbonate polyurethane aqueous dispersion, preferably: Siwo Chemical PUD-2517; the cationic polyacrylate emulsion is one of Covestro NeocrylXK350 or Intech Chemical SYNTRAN 6306.

[0015] In the technical solution of the present invention: the average particle size of the acidic silica sol is 10 to 25 nm, preferably: Better New Material P2510A or Better New Material HP4010A; the titanate chelate is a hydrolysis-stable titanium chelate, preferably: DuPont Tyzor371.

[0016] In the technical solution of the present invention: the number average molecular weight of the polyethyleneimine is 1000-3000.

[0017] In the technical solution of the present invention, the cosolvent is a mixture of dipropylene glycol butyl ether, propylene glycol butyl ether and ethanol, and the mass ratio of the three is (1-2): (1-2): (2-5).

[0018] In the technical solution of the present invention: the substrate wetting agent is a mixture of an organosilicon twin structure surfactant and an acetylene glycol surfactant; preferably: the substrate wetting agent is a mixture of TEGO Twin 4100 and Evonik SURFYNOL 104E in a mass ratio of 0.1-1:0.5-2.

[0019] In the technical solution of the present invention: the defoaming agent is Foamex 810 from Digo; and the polyurethane thickener is TAFIGELPUR 40 from Mingling.

[0020] A method for preparing the above-mentioned water-based wood sealing primer comprises the following steps:

[0021] Add water, cationic polyurethane aqueous dispersion and cationic polyacrylate emulsion into the paint mixing kettle and stir evenly; add acidic silica sol and titanate chelate in sequence and stir for 0.5-1h; after uniform dispersion, let stand at room temperature for 6-24h, restart stirring, add cosolvent, substrate wetting agent and defoamer in sequence, and disperse at high speed until the system is uniform and free of shrinkage cavities; then add polyethyleneimine, zirconium acetate aqueous solution and isothiazolinone fungicide, and finally add polyurethane thickener to adjust the system viscosity to 60-120s (apply 4 cups), filter, and you can get the water-based wood sealing primer.

[0022] Beneficial effects of the present invention:

[0023] The water-based wood sealing primer disclosed in the present invention has the following technical advantages: (1) A combined wetting agent scheme (organic silicone twin structure surfactant and acetylene glycol surfactant) is adopted. This scheme can effectively balance the dynamic and static surface tensions of the coating system, so that the spray atomization particle size of the coating is lower, the leveling property is better, and the penetration efficiency is higher. While taking into account the penetration property and transparency, the product can also assist in improving the sealing and curing efficiency of the coating, and obtain a product appearance with a natural texture and clear texture. (2) An inorganic sol-modified cationic resin system is adopted. This system has a fast drying speed, high hardness, and good coating properties. It can quickly fill the wood ducts and obtain a product surface that is easy to polish and not prone to secondary water absorption and expansion. (3) A "modified cationic resin + polyethyleneimine + zirconium acetate" pigment curing scheme is adopted. This scheme can form stable macromolecular products with various pigments such as tannic acid, effectively reducing pigment migration.

[0024] The water-based wood primer disclosed by the present invention has high permeability, good transparency, and excellent gluing and sealing efficiency, and is an environmentally friendly wood coating product suitable for thin coating conditions. DETAILED DESCRIPTION

[0025] The present invention will be further described below with reference to the embodiments, but the scope of protection of the present invention is not limited thereto:

[0026] The sources of some raw materials in the examples of the present invention are as follows:

[0027] Siwo Chemical PUD-2517 polyurethane aqueous dispersion:

[0028] https: / / www.siwochem.com / 06

[0029] Covestro Neocryl XK350 emulsion:

[0030] https: / / www.puchem.com / detail-1604.html

[0031] Intai Chemical SYNTRAN 6306 emulsion:

[0032] http: / / mchf.cn.makepolo.com / product / 100268156718.html

[0033] Better New Materials HP2510A, HP4010A acidic silica sol:

[0034] http: / / www.99better.cn / cpxq / 93.html

[0035] DuPont Tyzor371 Titanate Chelate:

[0036] https: / / www.4006787252.com / article_read_21597.html

[0037] TEGO Twin 4100:

[0038] https: / / b2b.baidu.com / land?id=5b5b6a01ce59ad5844c89ace10d133a910

[0039] Evonik SURFYNOL 104E:

[0040] https: / / baijiahao.baidu.com / s?id=1828998471672695762&wfr=spider&for=pc

[0041] Digo Foamex 810:

[0042] https: / / b2b.baidu.com / land?id=1d39ae52ec3087958732fbd760d4a74c10

[0043] Mingling TAFIGEL PUR 40:

[0044] https: / / www.4006787252.com / article_read_14458.html

[0045] The preparation steps of the water-based wood sealing primer of Examples 1 and 2 are as follows (see Table 1 for the material ratio):

[0046] Add water, cationic polyurethane aqueous dispersion and cationic polyacrylate emulsion into the paint mixing kettle and stir evenly; add acidic silica sol and titanate chelate in sequence and stir for 40 minutes; after uniform dispersion, let it stand at room temperature for 10 hours, restart stirring, add cosolvent, substrate wetting agent and defoamer in sequence, and disperse at high speed until the system is uniform and free of shrinkage holes; then add polyethyleneimine, zirconium acetate aqueous solution and isothiazolinone fungicide, and finally add polyurethane thickener to adjust the system viscosity to 60-120s (apply 4 cups), filter, and you can get a water-based wood sealing primer.

[0047] The material proportions of the water-based wood sealing primers of Comparative Examples 1 to 4 are as follows:

[0048] Comparative Example 1: In Example 2, “45 g PUD-2517 cationic polyurethane aqueous dispersion and 20 g SYNTRAN 6306 cationic polyacrylate emulsion” were replaced with “65 g SYNTRAN 6306 cationic polyacrylate emulsion”, and the remaining material proportions were the same as in Example 2.

[0049] Comparative Example 2: The “0.8 g of titanate chelate Tyzor 371” in Example 2 was removed, and the remaining material proportions were the same as those in Example 1.

[0050] Comparative Example 3: The “3 g polyethyleneimine (molecular weight 1000) and 1 g zirconium acetate” in Example 2 were replaced with “3 g Neocryl XK350 cationic polyacrylate emulsion and 1 g XTAIN L-44 tannic acid inhibitor from HALOX Company, USA”, and the remaining material proportions were the same as in Example 2.

[0051] The coating was prepared and maintained according to the requirements of national and industry standards, and physical and chemical performance tests were completed (test results are shown in Tables 2 and 3). Some indicators were evaluated using the following methods:

[0052] (1) Anti-bleeding test: Take a white ash solid wood board as the base material and polish it until it is burr-free. Apply a 5wt% tannic acid aqueous solution once and let it dry naturally for 1 day. Spray a water-based sealing primer with a coating amount of 80-100g / m 2 After drying for 6 hours, use 400-grit sandpaper to lightly sand to remove wood burrs (do not sand through); spray with a single-component water-based acrylic white topcoat with a coating amount of 100-120g / m 2 The test was repeated using a substrate that was not coated with tannic acid solution as a blank control group and the color difference was compared with the test group.

[0053] (2) Anti-expansion test: Take a rubber wood blank solid board as the base material, grind it flat until there is no burr. Spray water-based sealing primer with a coating amount of 80-100g / m 2 After drying for 6 hours, use 400-grit sandpaper to lightly sand to remove wood burrs (do not sand through); spray with a single-component water-based acrylic white topcoat with a coating amount of 100-120g / m 2 . Observe the surface condition of the board after natural drying for 2 days.

[0054] (3) Grease sealing test: Take undegreased pine wood blank solid wood board as the base material, grind it flat until there is no burr. Spray water-based sealing primer with a coating amount of 100-120g / m 2 After natural drying for 6 hours, use 400 grit sandpaper to lightly sand to remove wood burrs (do not sand through). Spray one-component water-based acrylic white topcoat with a coating amount of 100-120g / m 2, and dry naturally for 2 days. Then heat-treat in a 35℃ oven for 7 days, and observe the discoloration of the white coating.

[0055] (4) Hot and cold cycle test of red oak specimens: Take red oak white blank solid wood board as the base material, grind it flat until there is no burr. Spray water-based sealing primer, the coating amount is 60-80g / m 2 and 100-120g / m 2 After natural drying for 6 hours, use 400 grit sandpaper to lightly sand to remove wood burrs (do not sand through). Spray one-component water-based acrylic white topcoat with a coating amount of 100-120g / m 2 After two days of natural drying, the panels were subjected to a thermal cycling test. One cycle consisted of "10 hours in a 50°C oven, 2 hours in a 25°C cooler, 10 hours in a 4°C refrigerator, and 2 hours in a 25°C refrigerator." After seven cycles, the panels were inspected for appearance and discoloration of the white coating.

[0056] Table 1 Material addition amount (g) of Example 1 and Example 2

[0057] Material Name Example 1 Example 2 water 11.5 7.7 PUD-2517 cationic polyurethane aqueous dispersion 35 45 SYNTRAN6306 cationic polyacrylate emulsion 30 20 Acidic silica sol P2510A 10 12 Titanate chelate Tyzor371 0.5 0.8 Dipropylene glycol butyl ether 1.5 1.8 Propylene glycol butyl ether 1.5 2 ethanol 3 4 TEGOTwin4100 wetting agent 0.3 0.4 SURFYNOL104E wetting agent 1 1.2 Foamex810 defoaming agent 0.3 0.3 Polyethyleneimine (molecular weight 1000) 4 3 Zirconium acetate 0.8 1 Isothiazolinone fungicide 0.1 0.1 TAFIGELPUR40 polyurethane thickener 0.5 0.7

[0058] Table 2 Main technical indicators of water-based wood sealing primers in Example 1 and Example 2

[0059]

[0060]

[0061] Table 3 Main technical indicators of water-based wood sealing primers in comparative examples 1 to 3

[0062]

[0063] The test results show (Table 2) that both Example 1 and Example 2 provide a single-component water-based wood coating that dries quickly, is easy to polish, can be applied thinly to seal pigments and grease, and can harden wood burrs and prevent secondary water absorption and swelling of wood.

[0064] Among the many materials, the choice of cationic resin system is crucial to coating performance. The cationic PUD-2517 epoxy-modified polycarbonate polyurethane aqueous dispersion serves as the rigid sealing component, while SYNTRAN 6306 or Neocryl XK350 cationic polyacrylate emulsions serve as the flexible sealing component. The combination of the two produces a primer coating with excellent shielding properties, a balanced toughness / hardness, and high transparency. If a single SYNTRAN 6306 or Neocryl XK350 emulsion is used for wood sealing (as in Comparative Example 1), coating strength will decrease, along with sandability and anti-bulking properties. Furthermore, a single emulsion solution cannot effectively resist color bleeding and oil bleed from the substrate under heat treatment conditions of 35-60°C. Conversely, if PUD-2517 polyurethane aqueous dispersion is used alone for wood sealing, the coating's toughness will decrease (impact resistance will not pass), and there is also a risk of cracking under alternating hot and cold temperatures.

[0065] Secondly, a resin modification scheme using "acidic silica sol + titanate chelate" was employed. This scheme not only introduces high-strength inorganic units into the film-forming system, improving duct filling and polishability, but also seals free hydrophilic units within the system, enhancing the film's water and chemical resistance. In comparison, without this doping modification (as in Comparative Example 2), the system's adhesive bonding and wood pore sealing efficiency are reduced, and the risk of substrate expansion and discoloration increases.

[0066] Furthermore, the present invention uses "ethyleneimine + zirconium acetate" as an auxiliary sealant. Experimental results show that this combination is highly compatible with the inorganic sol-modified cationic film-forming system. It can significantly inhibit pigment migration through complexation and amination, achieving a more comprehensive sealing effect than the traditional XTAIN L-44 tannic acid inhibitor system (Comparative Example 3).

[0067] Finally, the other materials disclosed in this invention were selected after extensive experimentation. Random substitutions can affect the overall performance of the coating. For example, the preferred materials include Better New Materials P2510A Silica Sol, Better New Materials HP4010A Silica Sol, Digo TEGOTwin 4100 Wetting Agent, Evonik SURFYNOL 104E Wetting Agent, dipropylene glycol butyl ether, and propylene glycol butyl ether. Random substitutions can reduce the coating's permeability, drying properties, and sealing properties.

Claims

1. A water-based wood sealing primer, characterized in that The paint consists of the following ingredients:

2. A water-based wood sealing primer, characterized in that The paint consists of the following ingredients:

3. The water-based wood sealing primer according to claim 1, characterized in that: The cationic polyurethane aqueous dispersion is an epoxy-modified polycarbonate polyurethane aqueous dispersion, preferably PUD-2517 from Siwo Chemical; the cationic polyacrylate emulsion is one of Covestro Neocryl XK350 and Intech Chemical SYNTRAN 6306.

4. The water-based wood sealing primer according to claim 1, characterized in that The average particle size of the acidic silica sol is 10-25 nm, preferably: Better New Material P2510A or Better New Material HP4010A; the titanate chelate is a hydrolysis-stable titanium chelate, preferably: DuPont Tyzor 371.

5. The water-based wood sealing primer according to claim 1, characterized in that The number average molecular weight of the polyethyleneimine is 1000-3000.

6. The water-based wood sealing primer according to claim 1, characterized in that The cosolvent is a mixture of dipropylene glycol butyl ether, propylene glycol butyl ether and ethanol, and the mass ratio of the three is (1-2): (1-2): (2-5).

7. The water-based wood sealing primer according to claim 1, characterized in that The substrate wetting agent is a mixture of an organosilicon twin structure surfactant and an acetylene glycol surfactant; preferably, the substrate wetting agent is a mixture of TEGO Twin 4100 and Evonik SURFYNOL 104E in a mass ratio of 0.1-1:0.5-2.

8. The water-based wood sealing primer according to claim 1, characterized in that: The defoaming agent is Foamex 810 from Digo; the polyurethane thickener is TAFIGELPUR 40 from Mingling.

9. A method for preparing the water-based wood sealing primer according to claim 1, characterized in that The method comprises the following steps: Add water, cationic polyurethane aqueous dispersion and cationic polyacrylate emulsion into the paint mixing kettle and stir evenly; add acidic silica sol and titanate chelate in sequence and stir for 0.5-1h; after uniform dispersion, let stand at room temperature for 6-24h, restart stirring, add cosolvent, substrate wetting agent and defoamer in sequence, and disperse at high speed until the system is uniform and free of shrinkage cavities; then add polyethyleneimine, zirconium acetate aqueous solution and isothiazolinone fungicide, and finally add polyurethane thickener to adjust the system viscosity to 60-120s (apply 4 cups), filter, and you can get the water-based wood sealing primer.

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