Transparent screen cloth coating

Abstract

The invention provides a screen cloth transparent coating, and relates to the technical field of polymer coatings. The screen cloth transparent coating contains not less than 90% by weight of polyurethane and not more than 9% by weight of inorganic filler with D50 particle size of 1-10 [mu] m; the light transmittance of the coating in the visible light range is not lower than 75%. Preferably, the coating provided by the invention contains a certain amount of organic silicon.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer coatings and relates to a transparent coating for mesh fabric. Background Art

[0002] Coating a transparent coating on a mesh fabric can replace transparent plastic products and can also be designed with various patterns to meet the needs of consumers. The transparent coating generally uses polyurethane material. From the perspective of environmental protection, waterborne polyurethane materials are generally used to prepare waterborne coatings and then made into transparent coatings. Due to the existence of hollow mesh holes in the mesh fabric, after the waterborne polyurethane coating is coated on the mesh fabric, the uncured coating at the mesh holes will settle, especially when the size of the mesh holes is large (for example, the average size of the mesh holes reaches 1 mm or higher), which is more obvious, resulting in an uneven coating surface, or even uneven and bumpy, seriously affecting the appearance of the coating.

[0003] In view of the above problems, a solution is to add inorganic fillers with high thixotropy to the waterborne polyurethane coating, but there are still deficiencies in that the thixotropy is not good enough, and it will also cause a decrease in the transparency and anti-bending performance of the coating. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a transparent coating for mesh fabric.

[0005] The technical solution of the present invention is as follows:

[0006] A transparent coating for mesh fabric, the coating contains polyurethane with a weight content of not less than 90% and inorganic fillers with a particle size of 1-10 μm and a weight content of not more than 9%. 50

[0007] The light transmittance of the coating in the visible light range is not less than 75%.

[0008] Preferably, the coating contains silicone with a weight content of not more than 5%.

[0009] Preferably, the raw material components of the coating include the following components A-1), A-2) and A-3);

[0010] A-1) Aqueous polyurethane dispersion;

[0011] A-2) Inorganic fillers;

[0012] A-3) Organosilicon-modified aqueous polyurethane.

[0013] More preferably, the concentrations of the aqueous polyurethane dispersion and the organosilicon-modified aqueous polyurethane are each 20-60 wt%.

[0014] ​More preferably, the weight ratio of the inorganic filler to the aqueous polyurethane dispersion is 1-7%.

[0015] Preferably, the D of the inorganic filler 50 particle size is 3-8 μm.

[0016] Preferably, the inorganic filler is selected from one or a combination of two or more of silica, alumina, wollastonite, and aluminized silica.

[0017] More preferably, the weight ratio of the organosilicon-modified aqueous polyurethane to the aqueous polyurethane dispersion is 1-15%.

[0018] Further preferably, the weight ratio of the organosilicon-modified aqueous polyurethane to the aqueous polyurethane dispersion is 3-10%.

[0019] More preferably, the organosilicon weight content in the organosilicon-modified aqueous polyurethane is 5-30%.

[0020] The beneficial effects of the present invention are:

[0021] (1) The coating of the present invention is formed on a mesh-type mesh cloth, having good flatness, abrasion resistance, flexibility, and light transmittance.

[0022] (2) In the aqueous polyurethane coating of the present invention, micron-sized inorganic fillers are added, making the aqueous polyurethane coating have good thixotropy and abrasion resistance. When the coating is applied on a mesh-type mesh cloth, even if the mesh holes are large, a uniform coating can be formed, and even after multiple coatings, a uniform coating can still be obtained. The cured coating has good flatness and abrasion resistance. However, adding micron-sized inorganic fillers is not conducive to the transparency and anti-bending performance of the coating. In the aqueous polyurethane coating of the present invention, organosilicon-modified polyurethane is further added, improving the transparency and anti-bending performance of the coating, so that the transparent coating still maintains high transparency and anti-bending performance on the basis of good uniformity and wear resistance. Description of the Drawings

[0023] Figure 1 is the cross-sectional structure of the mesh cloth transparent coating of the present invention,

[0024] wherein, 1 - transparent coating, 2 - mesh-type mesh cloth.

[0025] Figure 2 is the appearance photo of the mesh cloth transparent coating of Example 1. Detailed Embodiments

[0026] The technical solutions of the present invention will be further described and described through the following detailed embodiments.

[0027] In order to obtain a flat coating with high transparency on a mesh fabric, the present invention provides a transparent coating for the fabric, the coating containing polyurethane with a weight content of not less than 90% and D with a weight content of not more than 9% 50 inorganic fillers with a particle size of 1-10 μm;

[0028] The light transmittance of the coating in the visible light range is not less than 75%.

[0029] The transparent coating of the fabric of the present invention is formed on the fabric and covers the fabric, and the cross-sectional structure (at the mesh cross-section) is as shown in the appendix Figure 1 As shown, the main material of the coating is polyurethane, which has the characteristics of high transparency, good flexibility, wear resistance, etc., and can be processed in the form of water-based paint, which is green and environmentally friendly. In addition, the transparent coating contains a certain amount of inorganic fillers. Combining with the main material of polyurethane, the coating can achieve the characteristics of wear resistance, transparency, flatness, etc.

[0030] Specifically, the coating contains polyurethane with a weight content of not less than 90%. Here, the polyurethane includes unmodified polyurethane and modified polyurethane, including the polyurethane in the following raw material component A-1) and the organosilicon-modified polyurethane in the raw material component A-3). The weight content of polyurethane can be calculated according to the following formula (1):

[0031] Η = W1·n / W2 (1)

[0032] Wherein, H is the weight content of polyurethane, W1 is the weight of the polyurethane dispersion, n is the concentration of the polyurethane dispersion, and W2 is the weight of the coating.

[0033] For the weight content of the inorganic fillers in the coating, it can be any value among 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, etc. or any value between them; for the D 50 particle size of the inorganic fillers, it can be any value among 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, etc. or any value between them. The weight content of the inorganic fillers can also be calculated with reference to the above formula (1).

[0034] For the light transmittance of the coating in the visible light range, it can be any value among 75%, 76%, 77%, 78%, 79%, 80%, etc. or any value between them. The light transmittance can be detected by a light transmittance tester in the visible light wavelength range.

[0035] In some embodiments, the coating contains silicone with a weight content of no more than 5%. The inclusion of silicone in the transparent coating of the present invention can at least improve the flexibility of the coating (equivalent to improving the anti-bending performance), the smooth feel, and the abrasion resistance. For the weight content of silicone in the coating, by way of example, it can be any value among 5%, 4%, 3%, 2%, 1%, etc. or any value between them. Since the coating of the present invention has a relatively thick thickness, if the content of silicone is too high, it may affect the recoating performance.

[0036] In some embodiments, the raw material components of the coating comprise the following components A-1), A-2) and A-3);

[0037] A-1) Aqueous polyurethane dispersion;

[0038] A-2) Inorganic filler;

[0039] A-3) Silicone-modified aqueous polyurethane.

[0040] The raw material components of the coating of the present invention comprise the above three components. Among them, component A-1) functions as the main film-forming substance, component A-2) functions to thicken, provide high thixotropy and abrasion resistance, and component A-3) compensates for the problems of decreased transparency and hardening of the coating caused by component A-2). After the aqueous polyurethane coating composed of the raw material components containing the above components is coated (such as screen printing, roll coating, etc.) on the mesh-type mesh fabric, the aqueous polyurethane coating can penetrate and cover the entire mesh fabric (including the mesh holes), forming a wet film with good flatness. After drying, a coating with good flatness, abrasion resistance, high transparency and good anti-bending property is obtained. Due to the relatively low specific surface energy of the silicone in component A-3), it also has certain dispersion, leveling and smoothness effects. Therefore, no additional dispersion aids, leveling aids and / or wetting aids need to be added to the above aqueous polyurethane coating.

[0041] There is no particular limitation on the preparation of the above aqueous polyurethane coating. By way of example, at room temperature, the aqueous polyurethane dispersion and the silicone-modified aqueous polyurethane can be mixed evenly, the inorganic filler is added, and methods such as ultrasonic dispersion, high-speed stirring dispersion or homogenization dispersion are used for dispersion, and then stirred for a certain period of time. Then the prepared aqueous polyurethane coating is coated on the surface of the mesh-type mesh fabric by means of screen printing, roll coating or brush coating, in one or multiple processes. If it is a multiple-process, the next construction needs to be carried out after the coating of the previous process is surface-dried. After obtaining a wet film through coating, it can be baked at a certain temperature for a period of time, such as being placed at room temperature for 24 h, baked at 60 - 70 °C for 10 - 30 min, etc.

[0042] In some embodiments, the concentration of the aqueous polyurethane dispersion and the silicone-modified aqueous polyurethane is independently 20-60 wt%. For the aqueous polyurethane dispersion and the silicone-modified aqueous polyurethane, there is no particular limitation on the concentration. By way of example, it can be any value among 20 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, etc. or any value between them. Further, the concentration of the aqueous polyurethane dispersion and the silicone-modified aqueous polyurethane can independently be 40-60 wt%. There is no particular limitation on the source of the aqueous polyurethane dispersion and the silicone-modified aqueous polyurethane. They can be prepared by the methods of the prior art or directly purchased from the market, such as Anhui Dawei Huatai New Material Technology Co., Ltd., Evonik Degussa, Guangzhou Judong New Material Technology Co., Ltd., Xiamen Aikema Chemical Co., Ltd., Guangzhou Slok New Material Co., Ltd., Hefei Hengtian New Material Technology Co., Ltd., etc.

[0043] In some embodiments, the weight ratio of the inorganic filler to the aqueous polyurethane dispersion is 1-7%. By way of example, the weight ratio can be any value among 1%, 2%, 3%, 4%, 5%, 6%, 7%, etc. or any value between them. Further, the weight ratio of the inorganic filler to the aqueous polyurethane dispersion does not exceed 5%. In the field of coatings, nano-scale inorganic fillers are commonly used as thickeners and thixotropic agents, such as fumed silica. However, in the present invention, if fumed silica is used, the invention object of the present invention cannot be achieved. The possible reasons are as follows: (1) Fumed silica is difficult to disperse in aqueous coatings and a dispersion aid needs to be added, but the addition of the dispersion aid will reduce the transparency of the coating; (2) If too much fumed silica is added, the thickening property is too high and the thixotropic property is too good, which is not conducive to the construction of aqueous coatings; (3) If too little fumed silica is added, the thickening property and thixotropic property are insufficient, the coating is prone to collapse, is likely to be uneven and the transparency decreases.

[0044] In some embodiments, the D 50 particle size of the inorganic filler is 3-8 μm. By way of example, the D 50 particle size of the inorganic filler is any value among 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, etc. or any value between them.

[0045] In some embodiments, the inorganic filler is selected from one or a combination of two or more of silica, alumina, wollastonite, and aluminized silica. These inorganic fillers can all be directly obtained from the market. For example, the aluminized silica can be Evonik SIPERANT 820A, and the silica can be Zhuzhou Xinglong Superfine Nano Material Co., Ltd., etc.

[0046] In some embodiments, the weight ratio of the silicone-modified waterborne polyurethane to the waterborne polyurethane dispersion is 1-15%. For example, the weight ratio can be any value among 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc. or any value between them. Further, the weight ratio of the silicone-modified waterborne polyurethane to the waterborne polyurethane dispersion is 3-10%.

[0047] In some embodiments, the silicone weight content in the silicone-modified waterborne polyurethane is 5-30%. For example, the silicone content can be any value among 5%, 7%, 8%, 10%, 12%, 13%, 15%, 16%, 18%, 20%, 22%, 24%, 25%, 27%, 28%, 30%, etc. or any value between them. Further, the silicone weight content in the silicone-modified waterborne polyurethane can be 5-20%. In the present invention, the silicone in the silicone-modified waterborne polyurethane can be polysiloxane and / or silane. The silicone-modified waterborne polyurethane is generally formed by reacting silicone compounds such as hydroxy-terminated polysiloxane, amino-terminated polysiloxane, hydroxyalkylsilane, and aminosilane with isocyanate groups. Therefore, the silicone weight content can be the weight content of the added silicone compound in the formed polyurethane. For example, if the added silicone compound is 5 g and the weight of the formed polyurethane is 100 g, then the silicone weight content is 5%.

[0048] The above waterborne polyurethane coating of the present invention can also be added with other components. For example, when the curing film-forming temperature is relatively low, a film-forming aid can be added.

[0049] The technical solutions of the present invention are further described and illustrated below according to each embodiment. Unless otherwise specified, the parts mentioned in the following embodiments are parts by weight.

[0050] Example 1

[0051] The waterborne polyurethane coating is composed of the following three raw material components: waterborne polyurethane dispersion (PU), Evonik SIPERANT 820A, and silicone-modified waterborne polyurethane. Among them, the weight ratio of 820A to the waterborne polyurethane dispersion is 5%, and the weight ratio of the silicone-modified waterborne polyurethane (Si-PU) to the waterborne polyurethane dispersion is 3%.

[0052] The concentration of the waterborne polyurethane dispersion is 50 wt%; the concentration of the silicone-modified waterborne polyurethane is 50 wt%, and the silicone content is 10%.

[0053] At room temperature, the above-mentioned aqueous polyurethane dispersion and organosilicon-modified aqueous polyurethane were mixed and stirred at a stirring speed of 300 rpm for 15 min. Then the stirring speed was increased to 1200 rpm, and Evonik SIPERANT 820A was added. Stirring was continued for 20 min, and then the stirring speed was reduced to 400 rpm and stirring was continued for another 30 min to obtain the aqueous polyurethane coating.

[0054] Example 2

[0055] The difference between this example and Example 1 is that in Example 1, the weight ratio of Evonik SIPERANT 820A to the aqueous polyurethane dispersion was adjusted from 5% to 3%. The remaining steps remained unchanged.

[0056] Example 3

[0057] The difference between this example and Example 1 is that in Example 1, the weight ratio of Evonik SIPERANT 820A to the aqueous polyurethane dispersion was adjusted from 5% to 1%. The remaining steps remained unchanged.

[0058] Example 4

[0059] The difference between this example and Example 1 is that in Example 1, the weight ratio of Evonik SIPERANT 820A to the aqueous polyurethane dispersion was adjusted from 5% to 7%. The remaining steps remained unchanged.

[0060] Comparative Example 1

[0061] The difference between this comparative example and Example 1 is that in Example 1, Evonik SIPERANT 820A was replaced with an equal weight ratio of Evonik fumed silica A200. The remaining steps remained unchanged.

[0062] The viscosity of the aqueous polyurethane coating obtained in this comparative example was too high, and its fluidity at room temperature was poor, making it impossible to effectively coat on the mesh-type mesh fabric.

[0063] Comparative Example 2

[0064] The difference between this comparative example and Comparative Example 1 is that in Comparative Example 1, the weight ratio of fumed silica A200 to the aqueous polyurethane dispersion was adjusted from 5% to 1%. The remaining steps remained unchanged.

[0065] Comparative Example 3

[0066] The difference between this comparative example and Example 1 is that in Example 1, the organosilicon-modified aqueous polyurethane was replaced with an equal weight ratio of the aqueous polyurethane dispersion in Example 1. The remaining steps remained unchanged. That is, the organosilicon-modified aqueous polyurethane was not added in this comparative example.

[0067] Example 5

[0068] The difference between this example and Example 1 is that in Example 1, the silicone content in the silicone-modified waterborne polyurethane is adjusted from 10% to 20%. The remaining steps remain unchanged.

[0069] Example 6

[0070] The difference between this example and Example 1 is that in Example 1, the silicone content in the silicone-modified waterborne polyurethane is adjusted from 10% to 5%. The remaining steps remain unchanged.

[0071] Example 7

[0072] The waterborne polyurethane coating consists of the following three raw material components: waterborne polyurethane dispersion, D 50 Silica with a particle size of 3 μm and silicone-modified waterborne polyurethane. Among them, the weight ratio of silica to the waterborne polyurethane dispersion is 3%, and the weight ratio of the silicone-modified waterborne polyurethane to the waterborne polyurethane dispersion is 10%.

[0073] The concentration of the waterborne polyurethane dispersion is 50 wt%; the concentration of the silicone-modified waterborne polyurethane is 45 wt%, and the silicone content is 5%.

[0074] Example 8

[0075] The difference between this example and Example 7 is that in Example 7, the weight ratio of the silicone-modified waterborne polyurethane to the waterborne polyurethane dispersion is adjusted from 10% to 3%. The remaining steps remain unchanged.

[0076] Example 9

[0077] The difference between this example and Example 7 is that in Example 7, the weight ratio of the silicone-modified waterborne polyurethane to the waterborne polyurethane dispersion is adjusted from 10% to 15%. The remaining steps remain unchanged.

[0078] The data of the waterborne polyurethane coatings and the cured coatings in Examples 1-9 and Comparative Examples 2-3 are shown in Table 1 below.

[0079] Table 1

[0080]

[0081] The waterborne polyurethane coatings of Examples 1-9 and Comparative Examples 2-3 were screen-printed on a mesh-type fabric (the average size of the mesh holes was 1 mm). Each waterborne polyurethane coating was applied 10 times, and then dried at 60 °C for 30 min to obtain a coating with an average thickness of 0.5 mm.

[0082] The properties of the coatings are shown in Table 2 below, where the control sample is a coating obtained by forming a film from the waterborne polyurethane dispersion in Example 1 alone.

[0083] Light transmittance: It is measured within the visible light range using a light transmittance tester.

[0084] Surface flatness: Observe whether the surface of the coating is flat with the naked eye under a fluorescent lamp.

[0085] Wear resistance: Refer to the standard QB / T 4545-2013 and test it using a Taber-5135 abrasion tester under the test conditions of an H-22 grinding wheel and a 1 kg weight, accurate to the nearest hundred.

[0086] Flex resistance: Test it according to the method of GB / T 3903.1-2008 "Footwear - Test methods for whole shoes - Flexing performance", accurate to the nearest thousand.

[0087] Recoatability: Conduct the next printing process after the surface of the previous process has dried to touch, and observe whether there is poor wetting in the wet film. There are no recoat problems in Examples 1-9 and Comparative Example 2 above, and there is a problem of poor wetting during recoating in Comparative Example 3.

[0088] Table 2

[0089]

[0090] Therefore, based on the data results in Table 2 above, it can be known that for the transparent coating of the mesh fabric of the present invention, even when applied to a mesh fabric with a relatively large pore size, a transparent coating with good flatness, good wear resistance, and good flex resistance can be obtained.

[0091] As described above, the basic principles, main features, and advantages of the present invention have been shown and described. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and the above embodiments are only preferred embodiments of the present invention. The scope of implementation of the present invention cannot be limited thereby. That is, equivalent changes and modifications made according to the scope of the present invention patent and the content of the specification should still fall within the scope covered by the present invention. The scope of protection required by the present invention is defined by the appended claims and their equivalents.

Claims

1. A mesh fabric transparent coating, characterized in that, The coating contains polyurethane with a weight content of not less than 90% and D with a weight content of not more than 9%. 50 inorganic fillers with a particle size of 1-10 μm; The light transmittance of the coating in the visible light range is not less than 75%.

2. The mesh fabric transparent coating according to claim 1, wherein, The coating contains silicone with a weight content of not more than 5%.

3. The mesh fabric transparent coating according to claim 1, wherein The raw material components of the coating include the following components A-1), A-2) and A-3); A-1) Aqueous polyurethane dispersion; A-2) Inorganic filler; A-3) Silicone-modified aqueous polyurethane.

4. The mesh fabric transparent coating according to claim 3, characterized in that, The concentrations of the aqueous polyurethane dispersion and the silicone-modified aqueous polyurethane are each 20-60 wt%.

5. The mesh fabric transparent coating according to claim 3, characterized in that, The weight ratio of the inorganic filler to the aqueous polyurethane dispersion is 1-7%.

6. The mesh fabric transparent coating according to claim 1, characterized in that, The D of the inorganic filler 50 has a particle size of 3 - 8 μm.

7. The mesh fabric transparent coating according to claim 1, wherein The inorganic filler is selected from one or a combination of two or more of silica, alumina, wollastonite and aluminized silica.

8. The mesh transparent coating according to claim 3, characterized in that, The weight ratio of the silicone-modified aqueous polyurethane to the aqueous polyurethane dispersion is 1-15%.

9. The mesh fabric transparent coating according to claim 8, characterized in that, The weight ratio of the silicone-modified aqueous polyurethane to the aqueous polyurethane dispersion is 3-10%.

10. The mesh transparent coating according to claim 3, wherein The weight content of silicone in the silicone-modified aqueous polyurethane is 5-30%.

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