A transparent coating composition for stainless steel coil and preparation method thereof

Abstract

The present invention discloses a clear coating composition, comprising the following components by weight: 0-100 parts of a hydroxyl resin; 0-40 parts of an amino resin; 0-50 parts of a blocked isocyanate; 15-100 parts of an organic-inorganic hybrid silicone resin; 0-30 parts of a color paste; 5-30 parts of a solvent; and 0-10 parts of an additive; wherein the hydroxyl resin, amino resin, and blocked isocyanate are not all present in 0 parts. The clear coating composition is used to coat the surface of stainless steel to form a high-hardness coating film that prevents scratches on the metal surface while retaining the metal surface's inherent gloss. The present invention also provides a method for preparing the clear coating composition.

Description

Technical Field

[0001] The present invention relates to the field of coatings, in particular to the field of coatings for coils, and in particular to a clear coating composition for stainless steel coils. Background Art

[0002] Due to its unique corrosion resistance, stainless steel has been widely used in many fields since its advent, such as building materials, chemicals, automobiles, electronics and other fields.

[0003] On the other hand, with the development of science and technology and the improvement of living standards, people's pursuit of aesthetics in decorative materials is becoming increasingly higher. As a decorative material, stainless steel, due to its unique luster, appears noble and comfortable when used in decorative spaces. This has led to the increasing application of stainless steel in home decoration.

[0004] Stainless steel surfaces can be processed into a variety of finishes, such as brushed, mirrored, frosted, and sandblasted, giving them a high level of aesthetic appeal. However, these treated surfaces are easily scratched or oxidized by hard objects, which in turn undermines their aesthetic appeal. Therefore, there is an urgent need to develop a coating composition or surface treatment technology for stainless steel that can prevent scratches while retaining the vibrant colors that characterize stainless steel.

[0005] In response to the above requirements, the prior art provides a variety of coating compositions or stainless steel coatings for stainless steel materials.

[0006] For example, Chinese invention patent application CN107652391A relates to a water-based acrylic resin for stainless steel and a preparation method thereof, which discloses a water-based acrylic resin. By applying a coating prepared with the water-based acrylic resin to the surface of stainless steel, a transparent coating with a hardness of H can be obtained.

[0007] For example, Chinese invention patent application CN110759720A relates to stainless steel coatings, methods for preparing stainless steel coatings, and methods for preparing solid-phase components. It discloses a stainless steel coating composed of the following specific ratios of metal oxides: silicon dioxide, calcium oxide, boron oxide, aluminum oxide, cobalt oxide, etc., which is applied to the surface of stainless steel and then sintered to obtain high-temperature resistant, oxidation-resistant stainless steel products.

[0008] The above stainless steel coatings are all applied to the surface of stainless steel products to meet the requirements of their application. However, the above stainless steel coating methods are currently difficult to meet the increasing demand for personalized design, especially the requirement for high hardness of stainless steel product surfaces.

[0009] In view of this, it is necessary to develop a coating composition that is compatible with the existing high-efficiency and environmentally friendly roller coating method for pre-coated plates for coating stainless steel coils, thereby meeting the increasingly wide application needs of the back-end market. Summary of the Invention

[0010] An object of the present invention is to provide a clear coating composition for coating the surface of, for example, a stainless steel coil to form a protective high-hardness coating film on the surface.

[0011] Another object of the present invention is to provide an organic-inorganic hybrid silicone resin for use in the above-mentioned clear coating composition.

[0012] Another object of the present invention is to provide a method for preparing the transparent coating composition and the organic-inorganic hybrid silicone resin.

[0013] In order to achieve the above object, the present invention adopts the following technical solutions:

[0014] According to a first aspect of the present invention, there is provided a clear coating composition, wherein the clear coating composition comprises the following components in parts by weight:

[0015] 0-100 parts of hydroxy resin;

[0016] 0-40 parts of amino resin;

[0017] Blocked isocyanate 0-50 parts;

[0018] 15-100 parts of organic-inorganic hybrid silicone resin;

[0019] Color paste 0-30 parts;

[0020] 5-30 parts of solvent;

[0021] 0-10 parts of additives;

[0022] The hydroxy resin, amino resin and blocked isocyanate are not all 0 parts at the same time.

[0023] Preferably, the transparent coating composition comprises the following components in parts by weight:

[0024] 0-60 parts of hydroxy resin;

[0025] 20-40 parts of amino resin;

[0026] 2-10 parts of blocked isocyanate;

[0027] 15-75 parts of organic-inorganic hybrid silicone resin;

[0028] Color paste 0-10 parts;

[0029] 10-30 parts of solvent;

[0030] 2-8 parts of additives.

[0031] More preferably, the clear coating composition comprises the following components in parts by weight:

[0032] 40-60 parts of hydroxy resin;

[0033] 20-30 parts of amino resin;

[0034] 3-5 parts of blocked isocyanate;

[0035] 50-60 parts of organic-inorganic hybrid silicone resin;

[0036] Color paste 0-5 parts;

[0037] 10-30 parts of solvent;

[0038] 2-8 parts of additives.

[0039] Furthermore, the hydroxy resin includes one or more of hydroxy acrylic resin, modified hydroxy acrylate resin, hydroxy polyester resin, modified hydroxy polyester resin or epoxy resin, wherein the solid content hydroxy value of the hydroxy resin is in the range of 20-120 mg KOH / g.

[0040] Preferably, the acrylic resin is selected from at least one or more of 7327-XS-60 commercially available from Changxing Company, LB-1555 commercially available from Dongsheng Company, and ARKEMA EEP 75 from Arkema Company; the hydroxy polyester resin is selected from OF67 homemade by Nippon Paint Company; and the epoxy resin is selected from commercially available 609 epoxy resin.

[0041] Furthermore, the amino resin is at least one or more selected from the group consisting of melamine amino resin, urea amino resin and phenylamino resin.

[0042] Preferably, the melamine amino resin is selected from fully etherified or partially etherified melamine resins, wherein the fully etherified or partially etherified amino resins include at least one or more of methyl etherified melamine, butyl etherified melamine, and mixed etherified amino resins.

[0043] More preferably, the amino resin is selected from at least one or more of Cymel 303LF, 325, 327, 1158, and ETERMINO 9115-60 amino resins commercially available from Allnex, or at least one or more of Luwipal 018, 066, 072, and 069 amino resins commercially available from BASF.

[0044] Furthermore, the blocked isocyanate is selected from at least one or more of blocked polytetramethylene 1,4-diisocyanate, blocked polyhexamethylene 1,6-diisocyanate, blocked poly 2,2,4-trimethylhexane 1,6-diisocyanate, blocked polyethylene diisocyanate, and blocked poly 1,12-dodecane diisocyanate.

[0045] Preferably, the blocked isocyanate is selected from Covestro BL 1100 / 1, BL 3175A, BL 3272MPA, BL 3370MPA, BL3475BA / SN, BL 4265SN, At least one or more of BL 5375.

[0046] Furthermore, the transparent color paste is a commercially available transparent color paste, such as the transparent black paste provided by Nippon Paint.

[0047] Furthermore, the solvent is selected from at least one or more of acetone, methyl ethyl ketone, methyl isobutyl ketone, butyl acetate, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, ethylene glycol ethyl ether acetate, isophorone, diacetone alcohol, ethyl acetate, S100, S150, isopropyl alcohol, n-butanol, isobutanol, ethylene glycol butyl ether, and propylene glycol methyl ether.

[0048] Furthermore, the auxiliary agent includes at least one or more of a wetting agent, a leveling agent, a defoaming agent or a catalyst.

[0049] Preferably, the weight portion of the wetting agent in the transparent coating composition is 0-0.8 parts, wherein the wetting agent is selected from TEGO@wet28 of Tego Company.

[0050] Preferably, the weight portion of the leveling agent in the transparent coating composition is 0-0.8 parts. The wetting agent is selected from BYK354 from BYK.

[0051] Preferably, the weight portion of the defoaming agent in the transparent coating composition is 0-0.8 parts. The defoaming agent is selected from TEGO@Ariex945 produced by Digo Company.

[0052] Preferably, the weight portion of the catalyst in the clear coating composition is 0-0.8 parts. The catalyst is selected from XK-675 of King Company.

[0053] Furthermore, the T4 cup viscosity of the transparent coating composition at 23° C. ranges from 60 to 140 seconds; and the solid content of the transparent coating composition is 60-70%.

[0054] According to a second aspect of the present invention, there is provided a method for preparing the above-mentioned clear coating composition, which comprises the following steps:

[0055] The following components are added in sequence under stirring: hydroxyl resin, amino resin, blocked isocyanate, organic-inorganic hybrid silicone resin, color paste, solvent, and additives, and then dispersed in a high-speed disperser for 15-30 minutes to mix uniformly to obtain a clear coating composition, wherein the stirring rate is controlled at 1500-2000 rpm.

[0056] According to a third aspect of the present invention, an organic-inorganic hybrid silicone resin is provided, which can be used to prepare the above-mentioned transparent coating composition. The organic-inorganic hybrid silicone resin comprises the following components in parts by weight:

[0057] 5-10 parts deionized water;

[0058] 2-10 parts of isopropyl alcohol;

[0059] Formic acid 0.1-1 part;

[0060] 50-60 parts of ethyl orthosilicate;

[0061] 20-30 parts of methyltrimethoxysilane;

[0062] Silane coupling agent 0.2-5 parts.

[0063] According to a fourth aspect of the present invention, there is provided a method for preparing the above-mentioned organic-inorganic hybrid silicone resin, which comprises the following steps:

[0064] Deionized water, isopropyl alcohol, and formic acid are added to a reaction container, and after sufficient stirring, ethyl orthosilicate, methyltrimethoxysilane, and a silane coupling agent are added in sequence. After sufficient stirring for at least 4 hours, the mixture is aged for at least 12 hours to obtain the organic-inorganic hybrid silicone resin.

[0065] According to a fifth aspect of the present invention, there is provided a use of the above-mentioned clear coating composition, wherein the clear coating composition is used for coating the surface of a stainless steel material.

[0066] In addition to being applied to the surface of stainless steel materials, the transparent coating composition can also be applied to the surfaces of other metal coils. It can provide a decorative effect while ensuring that the surface of the metal material has ultra-high hardness.

[0067] The beneficial effects of the present invention are as follows:

[0068] Compared to the prior art, the present invention introduces an organic-inorganic hybrid silicone resin into the clear coating composition. Therefore, the clear coating composition can form a high-hardness coating film on the metal surface to which it is applied, such as stainless steel, while meeting other performance requirements. On the one hand, it can prevent scratches on the metal surface, and on the other hand, it can retain the unique gloss of the metal surface itself, thereby making the metal coil have better decorative properties and a wider range of applications.

[0069] Furthermore, the clear coating composition of the present invention has a fast curing property, making it suitable for high-efficiency coil coating processes. Furthermore, the clear coating composition of the present invention can be applied by spraying, roller coating, and other application methods depending on actual needs. DETAILED DESCRIPTION

[0070] In order to explain the present invention more clearly, the present invention is further described below in conjunction with preferred embodiments. Those skilled in the art should understand that the following specific description is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0071] Example 1 Preparation of organic-inorganic hybrid silicone resin

[0072] 9 g of deionized water, 10 g of isopropyl alcohol, and 0.6 g of formic acid were added to a reaction vessel and stirred thoroughly. Then, 60 g of ethyl orthosilicate, 20 g of methyltrimethoxysilane, and 0.2 g of a silane coupling agent (KH560) were added in sequence. After stirring thoroughly for 4 hours, the mixture was aged for 12 hours to obtain 99.8 g of an organic-inorganic hybrid silicone resin.

[0073] Example 1 Preparation of Clear Coating Composition 1

[0074] The following components were added to a reaction vessel in order according to the formulated amounts under stirring: 60 g of acrylate resin LB-1555, 20 g of amino resin Cymel303LF, 3 g of blocked isocyanate BL 3175, 50 g of the organic-inorganic hybrid silicone resin prepared as described in Example 1, 5 g of isopropyl alcohol solvent and 10 g of ethylene glycol butyl ether, 0.5 g of leveling agent BYK354, 0.2 g of defoamer TEGO@Ariex 945, and 0.3 g of wetting agent TEGO@wet 280. The mixture was stirred for 15-30 minutes to mix uniformly, with the stirring rate being controlled at 1500-2000 rpm to obtain 149 g of a clear coating composition having a T4 cup viscosity of 120 s at 23° C. and a solid content of 65%.

[0075] Example 2 Preparation of Clear Coating Composition 2

[0076] The following components were added to a reaction vessel in the following order according to the formulated amounts: 20 g of amino resin Cymel 303LF, 3 g of blocked isocyanate BL 3175, 80 g of the organic-inorganic hybrid silicone resin prepared as described in Example 1, 5 g of isopropyl alcohol and 10 g of ethylene glycol butyl ether, 0.5 g of leveling agent BYK 354, 0.2 g of defoamer TEGO@Ariex 945, 0.3 g of wetting agent TEGO@wet 280, and 0.5 g of catalyst XK-675. The mixture was stirred for 15-30 minutes to mix thoroughly, with the stirring rate controlled at 1500-2000 rpm. A clear coating composition (119.5 g) having a T4 cup viscosity of 60 seconds at 23°C and a solids content of 70% was obtained.

[0077] Example 3 Preparation of Clear Coating Composition 3

[0078] The following components were added to a reaction vessel in the following order: 20 g of amino resin Cymel 303LF, 3 g of blocked isocyanate BL 3175, 80 g of the organic-inorganic hybrid silicone resin prepared as described in Example 1, 5 g of isopropyl alcohol solvent, 10 g of ethylene glycol butyl ether, 5 g of transparent black paste, 0.5 g of leveling agent BYK 354, 0.2 g of defoamer TEGO@Ariex 945, 0.3 g of wetting agent TEGO@wet 280, and 0.5 g of catalyst XK-675, while stirring for 15-30 minutes to mix thoroughly. The stirring rate was controlled at 1500-2000 rpm. 124.5 g of a clear coating composition having a T4 cup viscosity of 60 seconds at 23°C and a solids content of 70% was obtained.

[0079] Comparative Example Preparation of a Clear Coating Composition as a Comparative Example

[0080] The following components were added in order according to the formulated amounts while stirring: 60g of acrylate resin LB-1555, 20g of amino resin Cymel 303LF, 3g of blocked isocyanate BL 3175, 5g of isopropyl alcohol solvent, 10g of ethylene glycol butyl ether, 0.5g of leveling agent BYK 354, 0.2g of defoamer TEGO@Ariex 945, and 0.3g of wetting agent TEGO@wet 280. The mixture was stirred for 15-30 minutes to uniformly mix, with the stirring rate controlled at 1500-2000 rpm. This yielded 99g of a comparative clear coating composition having a T4 cup viscosity of 120s at 23°C and a solids content of 65%.

[0081] It should be noted that the transparent coating composition of this comparative example does not contain the organic-inorganic hybrid silicone resin described in the present invention, and is therefore only used as a comparative example.

[0082] Performance Testing

[0083] The clear coating compositions of Examples 1, 2, 3 and the comparative example were tested.

[0084] The test method is as follows:

[0085] The clear coating compositions obtained in Examples 1, 2, 3, and the comparative example were applied to the surface of a stainless steel coil using a wire coating. The coatings were then baked in a dedicated coil coating chain oven. The baking conditions were: 40-60 seconds, with a peak substrate temperature (PMT) of 224°C. After completion, the following properties were tested:

[0086] (1) Visual appearance; (2) Film thickness; (3) Hardness; (4) MEK resistance; (5) T-bend. The test standard is GB / T30791 Metal Material Bending Test Method, where the smaller the TC (T crack) / TT (Tape off) data value, the better the T-bend performance. The test results are shown in Table 1 below:

[0087] Table 1

[0088] Coating composition Clear coating composition 1 Clear coating composition 2 Clear coating composition 3 Coating composition of Comparative Example 1 Coated substrate stainless steel plate stainless steel plate stainless steel plate stainless steel plate Visual appearance Flat and smooth Flat and smooth Flat and smooth Flat and smooth Film thickness / μm 2-3 2-3 2-3 2-3 hardness 4H 4H 4H 3H MEK resistant >150 >150 >150 >150 T-bend TC / TT 2TC / 2TT 0TC / 0TT 0TC / 0TT 2TC / 4TT

[0089] As shown in the table above, the surface hardness of the stainless steel plates coated with the clear coating compositions 1, 2, and 3 of the present invention reached 4H, while the surface hardness of the stainless steel plates coated with the comparative example was only 3H. According to the T-bend test results, the surfaces of the stainless steel plates coated with the clear coating compositions 2 and 3 had T-bend test values ​​of 0°C / 0TT, demonstrating excellent T-bend performance. Furthermore, the surfaces of the stainless steel plates coated with the clear coating compositions 1, 2, and 3 of the present invention also exhibited excellent visual appearance, film thickness, and MEK resistance.

[0090] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. Any obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A use of a clear coating composition for coating the surface of a stainless steel material: the clear coating composition is applied to the surface of a stainless steel coil using a wire board, and then baked in a chain oven dedicated to coil coating, with baking conditions of 40-60 seconds and a peak substrate temperature (PMT) of 224°C. The transparent coating composition is composed of the following components in parts by weight: 20-40 parts of amino resin; 2-10 parts of blocked isocyanate; 15-100 parts of organic-inorganic hybrid silicone resin; Color paste 0-30 parts; 5-30 parts of solvent; 0-10 parts of additives; The T4 cup viscosity of the clear coating composition at 23° C. is in the range of 60 to 140 seconds; the solid content of the clear coating composition is 60-70%; The organic-inorganic hybrid silicone resin is composed of the following components in parts by weight: 5-10 parts deionized water; 2-10 parts of isopropyl alcohol; 0.1-1 part of formic acid; 50-60 parts of ethyl orthosilicate; 20-30 parts of methyltrimethoxysilane; Silane coupling agent 0.2-5 parts; Wherein, the silane coupling agent is KH560; The preparation method of the organic-inorganic hybrid silicone resin comprises the following steps: Deionized water, isopropyl alcohol, and formic acid are added to a reaction container, and after sufficient stirring, ethyl orthosilicate, methyltrimethoxysilane, and a silane coupling agent are added in sequence. After sufficient stirring for at least 4 hours, the mixture is aged for at least 12 hours to obtain the organic-inorganic hybrid silicone resin.

2. The method according to claim 1, wherein the amino resin is at least one or more selected from the group consisting of melamine amino resin, urea amino resin and phenylamino resin.

3. The method according to claim 2, wherein the melamine amino resin is selected from fully etherified or partially etherified melamine resins.

4. The method according to claim 1, wherein the blocked isocyanate is selected from at least one of blocked polytetramethylene 1,4-diisocyanate, blocked polyhexamethylene 1,6-diisocyanate, blocked poly-2,2,4-trimethylhexane 1,6-diisocyanate, blocked polyethylene diisocyanate, and blocked poly-1,12-dodecane diisocyanate.

5. The method according to claim 1, wherein the solvent is selected from at least one of acetone, methyl ethyl ketone, methyl isobutyl ketone, butyl acetate, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, ethylene glycol ethyl ether acetate, isophorone, diacetone alcohol, ethyl acetate, S100, S150, isopropyl alcohol, n-butanol, isobutyl alcohol, ethylene glycol butyl ether, and propylene glycol methyl ether.

6. The method according to claim 1, wherein the auxiliary agent comprises at least one or more of a wetting agent, a leveling agent, a defoaming agent or a catalyst.

7. The use according to any one of claims 1 to 6, wherein the preparation method of the transparent coating composition comprises the following steps: The following components are added in sequence while stirring: amino resin, blocked isocyanate, organic-inorganic hybrid silicone resin, color paste, solvent, and additives, and then dispersed in a high-speed disperser for 15-30 minutes to mix uniformly to obtain a clear coating composition, wherein the stirring rate is controlled at 1500-2000 rpm.