High anti-blocking and yellowing-resistant PU matte clear topcoat and preparation method thereof

Abstract

The present application relates to the technical field of paint, in particular to a high anti-sticking and yellowing-resistant PU matte clear finish and a preparation method thereof, the present application adopts two components formed by a hydroxyl acrylic resin with an OH value of 80 and a Tg point of 20 and a hydroxyl acrylic resin with an OH value of 36 and a Tg of -10 to balance the crosslinking density and flexibility, so that the present application has both yellowing resistance and anti-sticking property. The present application can not only solve the sticking problem of large panel furniture in Middle East countries, but also overcome the yellowing problem caused by the strong sunlight climate conditions in Middle East countries, and the present application can also help furniture factories solve the stacking problem of large area furniture.

Description

Technical Field

[0001] This invention relates to the field of topcoat technology, specifically to a high-anti-blocking and yellowing-resistant PU matte clear topcoat and its preparation method. Background Technology

[0002] Due to the unique geographical environment and customs of Middle Eastern countries, their furniture generally requires high resistance to yellowing, and the large surface area and weight of the furniture necessitate high anti-blocking properties. Existing anti-yellowing matte PU topcoats often suffer from stacking and sticking issues during actual furniture factory production, affecting production efficiency. In open or semi-open processes with high gloss, the coating not only needs to be very thin and smooth, but also must not yellow under prolonged exposure to sunlight or ultraviolet radiation. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing technologies by providing a high-anti-blocking and yellowing-resistant matte clear PU topcoat and its preparation method.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] A highly anti-blocking and yellowing-resistant matte clear PU topcoat, composed of component A and component B in a weight ratio of 4:1.

[0006] Component A consists of the following raw materials by weight percentage:

[0007] Hydroxy acrylic resin 60-70%,

[0008] Cellulose acetate butyrate 1-3%,

[0009] 1-3% polyether siloxane copolymer

[0010] UV absorber 1-3%,

[0011] Light stabilizer 1-3%,

[0012] 2-6% polytetrafluoroethylene modified polyethylene wax powder

[0013] Fumed silica 2-6%,

[0014] Defoamer 0.1-0.5%,

[0015] Anti-settling agent 1-3%,

[0016] Dispersant 1-3%,

[0017] Solvent 10-20%,

[0018] Component B consists of the following raw materials by weight percentage:

[0019] HDI 40-60%,

[0020] Solvent 40-60%,

[0021] Dehydrating agent 0.5-1%.

[0022] The hydroxyl acrylic resin is composed of a hydroxyl acrylic resin with an OH value of 80 and a Tg point of 20, and a hydroxyl acrylic resin with an OH value of 36 and a Tg point of -10, in a mass ratio of (5-6):(1-2). The OH value of the hydroxyl acrylic resin is expressed in mgKOH / g, and the Tg is expressed in °C. The hydroxyl acrylic resin with an OH value of 80 and a Tg point of 20 is the product KENXON KN5452P from Guangdong Kelisen Resin Co., Ltd., and the hydroxyl acrylic resin with an OH value of 36 and a Tg point of -10 is the product KENXON KN5018P from Guangdong Kelisen Resin Co., Ltd.

[0023] The first ultraviolet absorber is a benzotriazole ultraviolet absorber. Specifically, the first ultraviolet absorber is EVERSORB 81.

[0024] The light stabilizer is a non-basic hindered amine radical scavenger. Specifically, BASF Tinuvin 249-DW(N) light stabilizer is used.

[0025] The particle size of the fumed silica is 4.5 micrometers.

[0026] The anti-settling agent used is Disparlon 6900-HV, the dispersant is DISPERBYK-103, and the defoamer is BYK-141. The dehydrating agent used is F-5 PU product sold by Shanghai Deyude Trading Co., Ltd.

[0027] The fumed silica is a UV absorber-grafted fumed silica. The specific process is as follows: fumed silica is dispersed in anhydrous ethanol (mass ratio of fumed silica:anhydrous ethanol = 1:20), and ultrasonically treated for 30-40 minutes; then, silane coupling agent KH-550 (mass ratio of SiO2:KH-550 = 10:1) is added, and the reaction is carried out at 75-85℃ for 3-4 hours; finally, UV absorber Tinuvin 1600 (Tinuvin 1600 to SiO2 mass ratio 1:5) is added, and the reaction continues for 2-3 hours, followed by washing and drying to obtain the final product. After grafting UV absorber II onto fumed silica, 1. the micron-level rough surface of silica reduces the contact area and prevents adhesion; 2. UV absorber II is directly anchored on the SiO2 surface, and the grafted UVA directly absorbs ultraviolet light, reducing photodegradation of the resin matrix and improving yellowing resistance; 3. Synergistic effect: the UV absorber Tinuvin 1600 in the modified fumed SiO2 belongs to the triazine UV absorber formulation, and the free benzotriazole UV absorbers work together to not only broaden the absorption band, but also form gradient protection and extend the weather resistance life.

[0028] The solvent for component A is butyl acetate and propylene glycol methyl ether acetate in a mass ratio of (1-2):(2-1), and the solvent for component B is butyl acetate and propylene glycol methyl ether acetate in a mass ratio of (3-4):(1-2).

[0029] The HDI used is an aliphatic HDI trimer, using Bayer's Desmodur N75, avoiding the use of aromatic isocyanates (which are prone to yellowing).

[0030] A method for preparing a high-anti-blocking and yellowing-resistant PU matte clear topcoat, wherein the preparation method of component A includes the following steps:

[0031] Step A1: Add hydroxyl acrylic resin, part of the solvent, dispersant and anti-settling agent to the container and stir for 15-20 minutes;

[0032] Step A2: Slowly add cellulose acetate butyrate to the resin mixture from step A1 and stir at a higher speed for 10-20 minutes.

[0033] Step A3: Slowly add fumed silica and polytetrafluoroethylene modified polyethylene wax powder to the resin mixture in step A2, and continue stirring at a higher speed for 10-20 minutes.

[0034] Step A4: Add the mixture from Step A3 to the remaining solvent, polyether silicone copolymer, UV absorber I, light stabilizer, and defoamer, and stir for 20-30 minutes to obtain component A.

[0035] The preparation method of component B includes the following steps:

[0036] Step B1: Add the solvent and dehydrating agent in sequence and stir for 5-10 minutes;

[0037] Step B2: Add HDI to the mixture from Step B1 and stir for 5-10 minutes to obtain Component B.

[0038] The stirring speed in step (A1) is 550-650 rpm; the stirring speed in step (A2) is 750-850 rpm; the stirring speed in step (A3) is 1100-1300 rpm; the stirring speed in step (A4) is 550-650 rpm; and the stirring speed in steps (B1) and (B2) is 600-800 rpm.

[0039] This invention uses hydroxyl acrylic resin as the main film-forming substance, providing film hardness, weather resistance, and adhesion. Furthermore, this invention employs a two-component approach to balance crosslinking density and flexibility, taking into account both yellowing resistance and resistance to deformation and adhesion. While a high crosslinking density (through a high hydroxyl value resin) improves yellowing resistance (dense network blocks oxidation), it can lead to an overly hard film, causing adhesion even with slight deformation. Conversely, a low crosslinking density (low hydroxyl value resin), while offering good flexibility and preventing adhesion, reduces yellowing resistance (due to easier UV penetration).

[0040] Cellulose acetate butyrate's rapid solvent release properties can shorten surface drying time (to 20-30 minutes), reducing the risk of adhesion of undried paint films. At the same time, the rigid molecular chains of cellulose acetate butyrate reduce plastic deformation of the paint film surface and work synergistically with PTFE wax powder to reduce the coefficient of friction.

[0041] The beneficial effects of this invention are as follows: This invention uses a two-component system consisting of a hydroxyl acrylic resin with an OH value of 80 and a Tg point of 20, and a hydroxyl acrylic resin with an OH value of 36 and a Tg point of -10, to balance crosslinking density and flexibility, thereby enabling the invention to simultaneously possess resistance to yellowing and anti-blocking properties. Adhesion is enhanced through a synergistic system of wax powder, fumed silica, and organosilicon. This is achieved by adding cellulose acetate butyrate to utilize its rapid solvent release characteristics for short surface drying time, adding polyether siloxane copolymer to reduce the surface tension of the coating, and adding polytetrafluoroethylene-modified polyethylene wax powder and fumed silica to reduce the coefficient of friction of the coating film. Furthermore, resistance to yellowing is further enhanced by adding benzotriazole UV absorbers, non-alkaline hindered amine free radical scavengers, and UV absorber-grafted fumed silica, synergistically with aliphatic HDI trimers. This invention can not only effectively solve the problem of large panel furniture adhesion in Middle Eastern countries, but also overcome the problem of yellowing caused by the strong sunlight climate in Middle Eastern countries. At the same time, this invention can also help furniture factories solve the problem of stacking large-area furniture. Detailed Implementation

[0042] The present invention will be further described in conjunction with the following embodiments.

[0043] Example 1

[0044] A highly anti-blocking and yellowing-resistant matte clear PU topcoat, composed of component A and component B in a weight ratio of 4:1.

[0045] Component A consists of the following raw materials by weight percentage:

[0046] Hydroxy acrylic resin 60%,

[0047] 3% cellulose acetate butyrate

[0048] 3% polyether siloxane copolymer

[0049] UV absorber 13%,

[0050] Light stabilizer 3%,

[0051] 5.5% polytetrafluoroethylene modified polyethylene wax powder

[0052] 6% fumed silica

[0053] Defoamer 0.5%,

[0054] Anti-settling agent 3%,

[0055] Dispersant 3%,

[0056] Solvent 10%,

[0057] Component B consists of the following raw materials by weight percentage:

[0058] HDI 40%,

[0059] Solvent 59%,

[0060] Dehydrating agent 1%.

[0061] The hydroxyl acrylic resin is composed of a hydroxyl acrylic resin with an OH value of 80 and a Tg point of 20, and a hydroxyl acrylic resin with an OH value of 36 and a Tg point of -10, in a mass ratio of 5:1. The OH value of the hydroxyl acrylic resin is expressed in mgKOH / g, and the Tg is expressed in °C. The hydroxyl acrylic resin with an OH value of 80 and a Tg point of 20 is the product KENXON KN5452P from Guangdong Kelisen Resin Co., Ltd., and the hydroxyl acrylic resin with an OH value of 36 and a Tg point of -10 is the product KENXON KN5018P from Guangdong Kelisen Resin Co., Ltd.

[0062] The HDI used is an aliphatic HDI trimer, manufactured using Bayer's Desmodur N75.

[0063] The first ultraviolet absorber is a benzotriazole ultraviolet absorber. Specifically, the first ultraviolet absorber is EVERSORB 81.

[0064] The light stabilizer is a non-basic hindered amine radical scavenger. Specifically, BASF Tinuvin 249-DW(N) light stabilizer is used.

[0065] The particle size of the fumed silica is 4.5 micrometers.

[0066] The anti-settling agent used is Disparlon 6900-HV, the dispersant is DISPERBYK-103, and the defoamer is BYK-141. The dehydrating agent used is F-5 PU product sold by Shanghai Deyude Trading Co., Ltd.

[0067] The fumed silica is a UV absorber-grafted fumed silica. The specific process is as follows: fumed silica is dispersed in anhydrous ethanol (mass ratio of fumed silica:anhydrous ethanol = 1:20), and ultrasonically treated for 30 minutes; then, silane coupling agent KH-550 (mass ratio of SiO2:KH-550 = 10:1) is added, and the reaction is carried out at 75°C for 3 hours; finally, UV absorber Tinuvin 1600 (Tinuvin 1600 to SiO2 mass ratio 1:5) is added, and the reaction continues for 2 hours, followed by washing and drying to obtain the final product.

[0068] The solvent for component A is butyl acetate and propylene glycol methyl ether acetate in a mass ratio of 1:2, and the solvent for component B is butyl acetate and propylene glycol methyl ether acetate in a mass ratio of 3:1.

[0069] A method for preparing a high-anti-blocking and yellowing-resistant PU matte clear topcoat, wherein the preparation method of component A includes the following steps:

[0070] Step A1: Add hydroxy acrylic resin, half the total weight of solvent, dispersant and anti-settling agent to the container, and stir for 15 minutes.

[0071] Step A2: Slowly add cellulose acetate butyrate to the resin mixture from step A1 and stir at a higher stirring speed for 10 minutes.

[0072] Step A3: Slowly add fumed silica and polytetrafluoroethylene modified polyethylene wax powder to the resin mixture from step A2, and continue stirring at a higher speed for 10 minutes.

[0073] Step A4: Add the mixture from Step A3 to the remaining solvent, polyether silicone copolymer, UV absorber I, light stabilizer, and defoamer, and stir for 20 minutes to obtain component A.

[0074] The preparation method of component B includes the following steps:

[0075] Step B1: Add the solvent and dehydrating agent in sequence and stir for 5 minutes;

[0076] Step B2: Add HDI to the mixture from step B1 and stir for 5 minutes to obtain component B.

[0077] The stirring speed in step (A1) is 550 rpm; the stirring speed in step (A2) is 750 rpm; the stirring speed in step (A3) is 1100 rpm; the stirring speed in step (A4) is 550 rpm; and the stirring speed in steps (B1) and (B2) is 600 rpm.

[0078] Example 2

[0079] A highly anti-blocking and yellowing-resistant matte clear PU topcoat, composed of component A and component B in a weight ratio of 4:1.

[0080] Component A consists of the following raw materials by weight percentage:

[0081] 65% hydroxyl acrylic resin

[0082] 2% cellulose acetate butyrate

[0083] 2% polyether siloxane copolymer

[0084] UV absorber 12%,

[0085] 2% light stabilizer

[0086] 2% polytetrafluoroethylene modified polyethylene wax powder

[0087] Fumed silica 5.5%,

[0088] Defoaming 0.5%,

[0089] Anti-settling agent 2%,

[0090] Dispersant 2%,

[0091] Solvent 15%,

[0092] Component B consists of the following raw materials by weight percentage:

[0093] HDI 51.2%,

[0094] Solvent 48%,

[0095] Dehydrating agent 0.8%.

[0096] The hydroxyl acrylic resin is composed of a hydroxyl acrylic resin with an OH value of 80 and a Tg point of 20, and a hydroxyl acrylic resin with an OH value of 36 and a Tg point of -10, in a mass ratio of 3:1. The OH value of the hydroxyl acrylic resin is expressed in mgKOH / g, and the Tg is expressed in °C. The hydroxyl acrylic resin with an OH value of 80 and a Tg point of 20 is a product of Guangdong Kelisen Resin Co., Ltd., model KENXON KN5452P, and the hydroxyl acrylic resin with an OH value of 36 and a Tg point of -10 is a product of Guangdong Kelisen Resin Co., Ltd., model KENXON KN5018P.

[0097] The HDI used is an aliphatic HDI trimer, manufactured using Bayer's Desmodur N75.

[0098] The first ultraviolet absorber is a benzotriazole ultraviolet absorber. Specifically, the first ultraviolet absorber is EVERSORB 81.

[0099] The light stabilizer is a non-basic hindered amine radical scavenger. Specifically, BASF Tinuvin 249-DW(N) light stabilizer is used.

[0100] The particle size of the fumed silica is 4.5 micrometers.

[0101] The anti-settling agent used is Disparlon 6900-HV, the dispersant is DISPERBYK-103, and the defoamer is BYK-141. The dehydrating agent used is F-5 PU product sold by Shanghai Deyude Trading Co., Ltd.

[0102] The fumed silica is a UV absorber-grafted fumed silica. The specific process is as follows: fumed silica is dispersed in anhydrous ethanol (mass ratio of fumed silica:anhydrous ethanol = 1:20), and ultrasonically treated for 35 minutes; then, silane coupling agent KH-550 (mass ratio of SiO2:KH-550 = 10:1) is added, and the reaction is carried out at 80°C for 3 hours; finally, UV absorber Tinuvin 1600 (Tinuvin 1600 to SiO2 mass ratio 1:5) is added, and the reaction continues for 3 hours, followed by washing and drying to obtain the final product.

[0103] The solvent for component A is butyl acetate and propylene glycol methyl ether acetate in a mass ratio of 1:1, and the solvent for component B is butyl acetate and propylene glycol methyl ether acetate in a mass ratio of 2:1.

[0104] A method for preparing a high-anti-blocking and yellowing-resistant PU matte clear topcoat, wherein the preparation method of component A includes the following steps:

[0105] Step A1: Add hydroxyl acrylic resin, part of the solvent, dispersant and anti-settling agent to the container, and stir for 15 minutes;

[0106] Step A2: Slowly add cellulose acetate butyrate to the resin mixture from step A1 and stir at a higher speed for 15 minutes.

[0107] Step A3: Slowly add fumed silica and polytetrafluoroethylene modified polyethylene wax powder to the resin mixture from step A2, and continue stirring at a higher speed for 15 minutes.

[0108] Step A4: Add the mixture from Step A3 to the remaining solvent, polyether silicone copolymer, UV absorber I, light stabilizer, and defoamer, and stir for 25 minutes to obtain component A.

[0109] The preparation method of component B includes the following steps:

[0110] Step B1: Add the solvent and dehydrating agent in sequence and stir for 8 minutes;

[0111] Step B2: Add HDI to the mixture from Step B1 and stir for 8 minutes to obtain Component B.

[0112] The stirring speed in step (A1) is 600 rpm; the stirring speed in step (A2) is 800 rpm; the stirring speed in step (A3) is 1200 rpm; the stirring speed in step (A4) is 600 rpm; and the stirring speed in steps (B1) and (B2) is 700 rpm.

[0113] Example 3

[0114] A highly anti-blocking and yellowing-resistant matte clear PU topcoat, composed of component A and component B in a weight ratio of 4:1.

[0115] Component A consists of the following raw materials by weight percentage:

[0116] Hydroxy acrylic resin 68%,

[0117] 1% cellulose acetate butyrate

[0118] 1% polyether siloxane copolymer

[0119] UV absorber 1%,

[0120] 1% light stabilizer

[0121] Polytetrafluoroethylene modified polyethylene wax powder 3.5%,

[0122] 4% fumed silica

[0123] Defoamer 0.5%,

[0124] Anti-settling agent 3%,

[0125] Dispersant 3%,

[0126] Solvent 14%,

[0127] Component B consists of the following raw materials by weight percentage:

[0128] HDI 54%,

[0129] Solvent 45%,

[0130] Dehydrating agent 1%.

[0131] The hydroxyl acrylic resin is composed of a hydroxyl acrylic resin with an OH value of 80 and a Tg point of 20, and a hydroxyl acrylic resin with an OH value of 36 and a Tg point of -10, in a mass ratio of 5:2. The OH value of the hydroxyl acrylic resin is expressed in mgKOH / g, and the Tg is expressed in °C. The hydroxyl acrylic resin with an OH value of 80 and a Tg point of 20 is the product KENXON KN5452P from Guangdong Kelisen Resin Co., Ltd., and the hydroxyl acrylic resin with an OH value of 36 and a Tg point of -10 is the product KENXON KN5018P from Guangdong Kelisen Resin Co., Ltd.

[0132] The HDI used is an aliphatic HDI trimer, manufactured using Bayer's Desmodur N75.

[0133] The first ultraviolet absorber is a benzotriazole ultraviolet absorber. Specifically, the first ultraviolet absorber is EVERSORB 81.

[0134] The light stabilizer is a non-basic hindered amine radical scavenger. Specifically, BASF Tinuvin 249-DW(N) light stabilizer is used.

[0135] The particle size of the fumed silica is 4.5 micrometers.

[0136] The anti-settling agent used is Disparlon 6900-HV, the dispersant is DISPERBYK-103, and the defoamer is BYK-141. The dehydrating agent used is F-5 PU product sold by Shanghai Deyude Trading Co., Ltd.

[0137] The fumed silica is a UV absorber-grafted fumed silica. The specific process is as follows: fumed silica is dispersed in anhydrous ethanol (mass ratio of fumed silica:anhydrous ethanol = 1:20), and ultrasonically treated for 40 minutes; then, silane coupling agent KH-550 (mass ratio of SiO2:KH-550 = 10:1) is added, and the reaction is carried out at 85°C for 4 hours; finally, UV absorber Tinuvin 1600 (Tinuvin 1600 to SiO2 mass ratio 1:5) is added, and the reaction continues for 3 hours, followed by washing and drying to obtain the final product.

[0138] The solvent for component A is butyl acetate and propylene glycol methyl ether acetate in a mass ratio of 2:1, and the solvent for component B is butyl acetate and propylene glycol methyl ether acetate in a mass ratio of 4:1.

[0139] A method for preparing a high-anti-blocking and yellowing-resistant PU matte clear topcoat, wherein the preparation method of component A includes the following steps:

[0140] Step A1: Add hydroxyl acrylic resin, part of the solvent, dispersant and anti-settling agent to the container and stir for 20 minutes;

[0141] Step A2: Slowly add cellulose acetate butyrate to the resin mixture from step A1 and stir at a higher speed for 20 minutes.

[0142] Step A3: Slowly add fumed silica and polytetrafluoroethylene modified polyethylene wax powder to the resin mixture from step A2, and continue stirring at a higher speed for 20 minutes.

[0143] Step A4: Add the mixture from Step A3 to the remaining solvent, polyether silicone copolymer, UV absorber I, light stabilizer, and defoamer, and stir for 30 minutes to obtain component A.

[0144] The preparation method of component B includes the following steps:

[0145] Step B1: Add the solvent and dehydrating agent in sequence and stir for 10 minutes;

[0146] Step B2: Add HDI to the mixture from Step B1 and stir for 10 minutes to obtain Component B.

[0147] The stirring speed in step (A1) is 650 rpm; the stirring speed in step (A2) is 850 rpm; the stirring speed in step (A3) is 1300 rpm; the stirring speed in step (A4) is 650 rpm; and the stirring speed in steps (B1) and (B2) is 800 rpm.

[0148] Comparative Example 1

[0149] The difference between Comparative Example 1 and Example 2 is that in this example, only the hydroxy acrylic resin used is a hydroxy acrylic resin with an OH value of 80 and a Tg point of 20 at a mass ratio of 3:1.

[0150] Comparative Example 2

[0151] The difference between Comparative Example 2 and Example 2 is that this example only uses hydroxyl acrylic resin with an OH value of 36 and a Tg of -10.

[0152] Comparative Example 3

[0153] The difference between Comparative Example 3 and Example 2 is that: this example does not modify the fumed silica, that is, it does not use ultraviolet absorber grafted fumed silica, but only ordinary fumed silica.

[0154] The experimental data are shown in Table 1.

[0155] Table 1

[0156]

[0157] As can be seen from the comparison in Table 1, Examples 1-3 are significantly superior to the Comparative Example in terms of core performance in anti-blocking and yellowing resistance, while also taking into account other comprehensive performance aspects. In Comparative Example 1, excessive high-OH resin (3:1) leads to an overly brittle paint film, causing stress concentration and easy adhesion during stacking; the residual benzene ring structure in the high-OH resin increases the risk of photo-oxidation; excessive high-Tg resin accelerates surface drying but easily generates microcracks; excessive cross-linking of OH resin leads to increased internal stress and decreased adhesion; the single resin system has insufficient thermal stability, and chain segment movement exacerbates discoloration at high temperatures.

[0158] Comparative Example 2: Low-OH resin makes the paint film too soft, increases the contact area, and significantly worsens adhesion; low-OH resin has insufficient crosslinking density, and free radical diffusion exacerbates yellowing; low-Tg resin cures slowly and prolongs the drying time; low-OH resin has insufficient crosslinking, resulting in low paint film strength; single resin system has insufficient thermal stability, and chain segment movement exacerbates discoloration at high temperatures.

[0159] Comparative Example 3: Without the use of UV absorber grafted fumed silica, the anti-blocking properties and other properties were reduced, especially the yellowing resistance was severely reduced. This is mainly because the absorption band of the UV absorber is narrowed, and it is impossible to form gradient protection.

[0160] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A high-anti-blocking and yellowing-resistant matte clear PU topcoat, characterized in that: It consists of component A and component B in a weight ratio of 4:

1. Component A consists of the following raw materials by weight percentage: Hydroxy acrylic resin 60-70%, Cellulose acetate butyrate 1-3%, 1-3% polyether siloxane copolymer UV absorber 1-3%, Light stabilizer 1-3%, 2-6% polytetrafluoroethylene modified polyethylene wax powder Fumed silica 2-6%, Defoamer 0.1-0.5%, Anti-settling agent 1-3%, Dispersant 1-3%, Solvent 10-20%, The sum of the weight percentages of all raw materials in component A is 100%. Component B consists of the following raw materials by weight percentage: HDI 40-60%, Solvent 40-60%, Dehydrating agent 0.5-1%, The sum of the weight percentages of all raw materials in component B is 100%. The hydroxy acrylic resin is composed of a hydroxy acrylic resin with an OH value of 80 and a Tg point of 20 in a mass ratio of (5-6):(1-2) and a hydroxy acrylic resin with an OH value of 36 and a Tg of -10. The fumed silica is ultraviolet absorber-grafted fumed silica.

2. The high anti-blocking and yellowing-resistant PU matte clear topcoat according to claim 1, characterized in that: The ultraviolet absorber is a benzotriazole ultraviolet absorber, and the light stabilizer is a non-basic hindered amine free radical scavenger.

3. The high anti-blocking and yellowing-resistant PU matte clear topcoat according to claim 1, characterized in that: The particle size of the fumed silica is 4.5 micrometers.

4. The high anti-blocking and yellowing resistant PU matte clear topcoat according to claim 1, characterized in that: The solvent for component A is butyl acetate and propylene glycol methyl ether acetate in a mass ratio of (1-2):(2-1), and the solvent for component B is butyl acetate and propylene glycol methyl ether acetate in a mass ratio of (3-4):(1-2).

5. The preparation method of a high anti-blocking and yellowing resistant PU matte clear topcoat as described in claim 1, characterized in that: The preparation method of component A includes the following steps: Step A1: Add hydroxyl acrylic resin, part of the solvent, dispersant and anti-settling agent to the container and stir for 15-20 minutes; Step A2: Slowly add cellulose acetate butyrate to the resin mixture from step A1 and stir at a higher speed for 10-20 minutes. Step A3: Slowly add fumed silica and polytetrafluoroethylene modified polyethylene wax powder to the resin mixture in step A2, and continue stirring at a higher speed for 10-20 minutes. Step A4: Add the mixture from Step A3 to the remaining solvent, polyether silicone copolymer, UV absorber I, light stabilizer, and defoamer, and stir for 20-30 minutes to obtain component A. The preparation method of component B includes the following steps: Step B1: Add the solvent and dehydrating agent in sequence and stir for 5-10 minutes; Step B2: Add HDI to the mixture from Step B1 and stir for 5-10 minutes to obtain Component B.

6. The preparation method of a high anti-blocking and yellowing resistant PU matte clear topcoat according to claim 5, characterized in that: The stirring speed in step (A1) is 550-650 rpm; the stirring speed in step (A2) is 750-850 rpm; the stirring speed in step (A3) is 1100-1300 rpm; the stirring speed in step (A4) is 550-650 rpm; and the stirring speed in steps (B1) and (B2) is 600-800 rpm.

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