A flame-retardant coating for mobile phone PC substrates and its usage method

Abstract

The present invention provides a flame retardant coating applied to the PC substrate of a mobile phone, which comprises the following components: adhesion promoter A component, adhesion promoter B component, acrylic primer, curing agent, diluent, prefabricated flame retardant paste, flame retardant intermediate coat paint, flame retardant top coat paint and ultraviolet curable coating. The flame retardant coating for the PC substrate of the mobile phone shell prepared by the present invention passes the needle flame test of GB-T 5169.5, that is, after applying a flame to the mobile phone PC shell coated with the flame retardant coating for 120 seconds, no holes are generated on the mobile phone PC shell, greatly improving the safety and service life of the mobile phone.

Description

Technical Field

[0001] The present invention relates to the field of coatings, and particularly to a flame retardant coating for mobile phone PC substrates and a preparation method thereof. Background Art

[0002] Most of the mobile phone shell materials are mainly plastics and metals. Among them, polycarbonate plastic (abbreviated as PC) is mainly used for the shells of mid - to - low - end smart phones in the market due to its advantages such as light weight, easy processing, high toughness, impact resistance, and low cost. Smart phones have become a necessity in people's lives. Mobile phone batteries are mainly lithium polymer batteries or lithium - ion batteries. Fast charging and discharging, over - charging, large game software, and long - time operation of multiple APPs at the same time are likely to cause the phenomenon of mobile phone overheating. If the heat dissipation of the mobile phone is not good, it may lead to the spontaneous combustion or even explosion of lithium batteries, affecting the personal safety of consumers. The functional flame retardant coating developed in this project is applied to the PC substrate of mobile phones. After the entire large area of the PC material is coated with the flame retardant coating series, it is then machined into different mobile phone shells according to the model and specifications of the mobile phone. The coating film dries quickly, has high flexibility, rich colors, and high coating efficiency. When the mobile phone PC material shell coated with the flame retardant coating series is subjected to the needle - flame open - flame combustion test, the phosphorus - nitrogen halogen - free flame retardant in the coating film decomposes to produce inert gases, dilutes the combustible gases, reduces the decomposition temperature of the combustibles, and decomposes by heat to form a dense carbon layer, slowing down the heat transfer and the outward diffusion of small molecules and particles inside the material, achieving the flame retardant effect. Summary of the Invention

[0003] Technical problems to be solved: The purpose of the present invention is to provide a flame retardant coating for the PC substrate of mobile phone shells, which can pass the GB - T5169.5 needle - flame test, that is, after applying a flame to the mobile phone PC shell coated with the flame retardant coating for 120 seconds, no holes are generated in the mobile phone PC shell, greatly improving the safety and service life of mobile phones.

[0004] Technical solution: A flame retardant coating for mobile phone PC substrates includes the following components: adhesion promoter A component, adhesion promoter B component, acrylic primer, curing agent, thinner, pre - prepared flame retardant paste, flame retardant intermediate coat paint, flame retardant topcoat paint, and ultraviolet - curable coating.

[0005] Preferably, the adhesion promoter A component is composed of the following components by weight percentage: hydroxy - polyester - acrylate copolymer resin: 20 - 30 parts, ethyl acetate: 30 - 40 parts, butyl acetate: 15 - 30 parts, silane coupling agent: 1 - 2 parts, cellulose acetate butyrate: 0.5 - 1 part, organic bismuth drier: 0.1 - 0.5 part;

[0006] The adhesion promoter B component is composed of the following components by weight percentage: benzylidene diisocyanate adduct: 60 - 70 parts, butyl acetate: 30 - 40 parts;

[0007] The acrylic base paint is composed of the following components by weight percentage: high-TG hydroxyl-containing acrylic resin: 50-60 parts, cellulose acetate butyrate: 1-2 parts, color paste: 10-20 parts, pearlescent pigment or aluminum silver paste: 5-10 parts, ethyl acetate: 10-15 parts, butyl acetate: 10-15 parts, anti-settling additive: 3-5 parts, wetting agent: 0.1-0.5 part;

[0008] The curing agent is composed of the following components by weight percentage: HDI trimer adduct: 60-70 parts, butyl acetate: 30-40 parts;

[0009] The thinner is composed of the following components by weight percentage: ethyl acetate: 60-70 parts, dimethyl isobutyl ketone: 30-40 parts;

[0010] The prefabricated flame retardant paste is composed of the following components by weight percentage: high-TG hydroxyl-containing acrylic resin: 10-20 parts, butyl acetate: 10-20 parts, dispersant: 1-2 parts, anti-settling agent: 0.5-1 part, phosphorus-nitrogen-based halogen-free flame retardant powder: 60-70 parts;

[0011] The flame retardant intermediate coat paint is composed of the following components by weight percentage: high-TG hydroxyl-containing acrylic resin: 10-20 parts, white paste: 30-40 parts, prefabricated flame retardant paste: 30-40 parts, ethyl acetate: 10-15 parts, butyl acetate: 5-10 parts, wetting agent: 0.1-0.5 part;

[0012] The flame retardant topcoat paint is composed of the following components by weight percentage: high-TG hydroxyl-containing acrylic resin: 10-20 parts, white paste: 10-20 parts, black paste: 10-20 parts, prefabricated flame retardant paste: 40-50 parts, ethyl acetate: 10-15 parts, butyl acetate: 5-10 parts, wetting agent: 0.1-0.5 part;

[0013] The UV-curable coating is composed of the following components by weight percentage: photoinitiator: 2-5 parts, ethyl acetate: 20-30 parts, butyl acetate: 10-20 parts, n-butanol: 5-10 parts, ethylene glycol monobutyl ether: 5-10 parts, diacetone alcohol: 5-10 parts, 1,6-hexanediol diacrylate: 5-10 parts, trimethylolpropane tripropionate: 10-20 parts, 3-functional polyurethane acrylate: 10-20 parts, 9-functional polyurethane acrylate: 20-30 parts, wetting agent: 0.1-0.5 part, leveling agent: 0.1-0.5 part.

[0014] Preferably, the TG of the high-TG hydroxyl-containing acrylic resin in the acrylic base paint, the flame retardant intermediate coat paint, and the flame retardant topcoat paint is ≥90, and the hydroxyl content is less than 0.5%.

[0015] Preferably, the general curing agent HDI trimer adduct is a hexamethylene diisocyanate adduct.

[0016] Preferably, the phosphorus-nitrogen based halogen-free flame retardant powder in the prefabricated flame retardant paste contains nitrogen and phosphorus elements, does not contain halogens, and is a new type of flame retardant with phosphorus-nitrogen based flame retardant mechanisms and phosphorus-nitrogen synergistic flame retardant effects.

[0017] Preferably, the color paste, white paste, and black paste in the acrylic base paint, flame retardant intermediate paint, and flame retardant topcoat are solvent-based resin-free general color pastes with good dispersion and compatibility and good weather resistance.

[0018] Preferably, the photoinitiator in the ultraviolet curable coating is composed of α-hydroxy ketone, benzoyl formate, and acylphosphine oxide.

[0019] Preferably, the weight ratio of the trifunctional polyurethane acrylate to the nonafunctional polyurethane acrylate in the ultraviolet curable coating is 1:2.

[0020] Preferably, the wetting agent and leveling agent in the formulation are polyether-modified polydimethylsiloxane copolymer solutions, and the dispersant is a polymer copolymer solution containing a pigment affinity group.

[0021] The usage method of the above-mentioned flame retardant coating applied to the mobile phone PC substrate includes the following steps:

[0022] Step 1: Mix the adhesion agent component A and adhesion agent component B in a mass ratio of 100:3, and spray and construct on the A side of the PC material;

[0023] Step 2: After spraying, dry at 70°C for 10 - 15 minutes;

[0024] Step 3: Mix the acrylic acid base paint, general curing agent, and diluent in a mass ratio of 8:1:3 - 4, and continue spraying and constructing;

[0025] Step 4: After spraying, dry at 0°C for 10 - 15 minutes;

[0026] Step 5: Mix the flame retardant intermediate paint, general curing agent, and diluent in a mass ratio of 8:1:3 - 4, and continue spraying and constructing;

[0027] Step 6: After spraying, dry at 70°C for 10 - 15 minutes;

[0028] Step 7: Mix the flame retardant topcoat: general curing agent and diluent in a mass ratio of 8:1:3 - 4, and continue spraying and constructing;

[0029] Step 8: After spraying, dry at 70°C for 120 - 150 minutes, and then mechanically process the PC material into a mobile phone shell;

[0030] Step 9: Directly spray and apply the UV-curable coating on the B side of the PC material;

[0031] Step 10: After spraying, dry at 60 °C for 5 - 8 minutes;

[0032] Step 11: Finally, perform UV curing.

[0033] Beneficial effects: The PC substrate flame-retardant coating for the mobile phone shell of the present invention has the following advantages:

[0034] In the present invention, the A component of the adhesion promoter uses a hydroxyl-containing polyester-acrylic copolymer resin. Acrylic acid provides fast drying and heat resistance, and polyester provides adhesion and flexibility. The coating film has a certain elasticity, which is beneficial to the secondary processing of the PC material. The hydroxyl group of the resin is less than 0.5%. It is paired with the B component curing agent benzylidene diisocyanate adduct. The overall coating film dries quickly and has excellent adhesion, good interlayer adhesion, and good resistance to boiling water;

[0035] In the present invention, the base paint and the flame-retardant paint use a high-TG hydroxyl-containing acrylic resin, TG≥90. The resin has good compatibility with color pastes, pigments, and flame-retardant powders, can meet the different color requirements of customers, the coating film dries quickly, there is no biting phenomenon after multiple coatings, high TG and hydroxyl group less than 0.5%, paired with the curing agent HDI trimer adduct, the coating film has good surface chemical resistance, good water resistance, and good toughness;

[0036] In the present invention, the flame-retardant intermediate paint and the flame-retardant topcoat use a phosphorus-nitrogen halogen-free flame-retardant powder, which does not contain halogens, is pollution-free, and meets the environmental protection requirements. When the material containing this kind of flame retardant is exposed to high temperature, a uniform carbonaceous layer can be formed on the surface, which plays a role in heat insulation, oxygen isolation, smoke suppression, and prevents the occurrence of dripping phenomenon, and has good flame-retardant performance. If the addition amount of the flame-retardant powder is too high, the adhesion and strength of the coating film will decrease. If the addition amount of the flame-retardant powder is too low, the flame-retardant effect will be poor. When the addition amount of the flame-retardant powder is 30 - 40%, the flame-retardant effect is better and the adhesion of the coating film is better. The flame-retardant intermediate paint is overlaid with the flame-retardant topcoat for two coatings, and the content of the flame-retardant powder gradually increases to ensure a higher coating film thickness and a better flame-retardant effect. The coating film passes the GB-T5169.5 needle flame test, that is, after applying a flame to the mobile phone PC shell coated with the flame-retardant coating for 120 seconds, no holes are generated on the mobile phone PC shell. Detailed implementation manners

[0037] The present invention will be further described below in conjunction with embodiments. The following embodiments are explanations of the present invention and the present invention is not limited to the following embodiments:

[0038] In the following examples and comparative examples, the product grades of various resins and polymer compounds are as follows: Product grade of hydroxyl-containing polyester-acrylic copolymer resin: Resin SE-100 of Asahi Chemical Industry Co., Ltd., Japan; Product grade of xylylene diisocyanate adduct: D-188N of Mitsui Chemicals, Inc., Japan; Product grade of high-TG hydroxyl-containing acrylic resin: WXU-880 of Zhongshan DIC Chemical Co., Ltd.; Product grade of HDI trimer adduct: HT-100 of Wanhua Chemical Group Co., Ltd. Example 1

[0039] The flame-retardant coating applied to the mobile phone PC substrate contains the following components:

[0040] The adherent A component consists of the following components by weight percentage: Hydroxyl-containing polyester-acrylic copolymer resin: 20 parts, ethyl acetate: 30 parts, butyl acetate: 30 parts, silane coupling agent: 1 part, cellulose acetate butyrate: 0.5 part, organic bismuth drier: 0.5 part;

[0041] The adherent B component consists of the following components by weight percentage: Xylylene diisocyanate adduct: 60 parts, butyl acetate: 40 parts;

[0042] The acrylic base coat consists of the following components by weight percentage: High-TG hydroxyl-containing acrylic resin: 50 parts, cellulose acetate butyrate: 1 part, color paste: 20 parts, pearlescent pigment or aluminum silver paste: 5 parts, ethyl acetate: 10 parts, butyl acetate: 10 parts, anti-settling agent: 3 parts, wetting agent: 0.5 part;

[0043] The curing agent consists of the following components by weight percentage: HDI trimer adduct: 70 parts, butyl acetate: 30 parts;

[0044] The thinner consists of the following components by weight percentage: Ethyl acetate: 70 parts, dimethyl isobutyl ketone: 30 parts;

[0045] The prefabricated flame-retardant paste consists of the following components by weight percentage: High-TG hydroxyl-containing acrylic resin: 10 parts, butyl acetate: 20 parts, dispersant: 1 part, anti-settling agent: 1 part, phosphorus-nitrogen-based halogen-free flame-retardant powder: 60 parts;

[0046] The flame-retardant intermediate coat consists of the following components by weight percentage: High-TG hydroxyl-containing acrylic resin: 10 parts, white paste: 30 parts, prefabricated flame-retardant paste: 30 parts, ethyl acetate: 15 parts, butyl acetate: 5 parts, wetting agent: 0.5 part;

[0047] The flame-retardant top coat consists of the following components by weight percentage: High-TG hydroxyl-containing acrylic resin: 10 parts, white paste: 20 parts, black paste: 10 parts, prefabricated flame-retardant paste: 50 parts, ethyl acetate: 10 parts, butyl acetate: 10 parts, wetting agent: 0.1 part;

[0048] The UV-curable coating is composed of the following components by weight percentage: photoinitiator: 5 parts, ethyl acetate: 20 parts, butyl acetate: 10 parts, n-butanol: 10 parts, ethylene glycol monobutyl ether: 5 parts, diacetone alcohol: 10 parts, 1,6-hexanediol diacrylate: 5 parts, trimethylolpropane tripropionate: 20 parts, 3-functional polyurethane acrylate: 10 parts, 9-functional polyurethane acrylate: 20 parts, wetting agent: 0.1 part, leveling agent: 0.5 part. Example 2

[0049] The flame-retardant coating applied to the mobile phone PC substrate contains the following components:

[0050] The adherent A component is composed of the following components by weight percentage: hydroxyl-containing polyester-acrylic copolymer resin: 30 parts, ethyl acetate: 40 parts, butyl acetate: 15 parts, silane coupling agent: 2 parts, cellulose acetate butyrate: 1 part, organic bismuth drier: 0.1 part;

[0051] The adherent B component is composed of the following components by weight percentage: benzene dimethylene diisocyanate adduct 70 parts, butyl acetate: 30 parts;

[0052] The acrylic base paint is composed of the following components by weight percentage: high-TG hydroxyl-containing acrylic resin: 60 parts, cellulose acetate butyrate: 2 parts, color paste: 10 parts, pearlescent pigment or aluminum silver paste: 10 parts, ethyl acetate: 15 parts, butyl acetate: 15 parts, anti-settling agent: 5 parts, wetting agent: 0.1 part;

[0053] The curing agent is composed of the following components by weight percentage: HDI trimer adduct: 60 parts, butyl acetate: 40 parts;

[0054] The thinner is composed of the following components by weight percentage: ethyl acetate: 60 parts, dimethyl isobutyl ketone: 40 parts;

[0055] The said prefabricated flame-retardant paste is composed of the following components by weight percentage: high-TG hydroxyl-containing acrylic resin: 20 parts, butyl acetate: 10 parts, dispersant: 2 parts, anti-settling agent: 0.5 part, phosphorus-nitrogen-based halogen-free flame-retardant powder: 70 parts;

[0056] The flame-retardant intermediate coat paint is composed of the following components by weight percentage: high-TG hydroxyl-containing acrylic resin: 20 parts, white paste: 40 parts, prefabricated flame-retardant paste: 40 parts, ethyl acetate: 10 parts, butyl acetate: 10 parts, wetting agent: 0.1 part;

[0057] The flame-retardant topcoat is composed of the following components by weight percentage: high-TG hydroxyl-containing acrylic resin: 20 parts, white paste: 10 parts, black paste: 20 parts, prefabricated flame-retardant paste: 40 parts, ethyl acetate: 15 parts, butyl acetate: 5 parts, wetting agent: 0.5 part;

[0058] The UV-curable coating is composed of the following components by weight percentage: photoinitiator: 2 parts, ethyl acetate: 30 parts, butyl acetate: 20 parts, n-butanol: 5 parts, ethylene glycol monobutyl ether: 10 parts, diacetone alcohol: 5 parts, 1,6-hexanediol diacrylate: 10 parts, trimethylolpropane tripropionate: 10 parts, 3-functional polyurethane acrylate: 15 parts, 9-functional polyurethane acrylate: 30 parts, wetting agent: 0.5 part, leveling agent: 0.1 part. Example 3

[0059] The flame-retardant coating applied to the mobile phone PC substrate contains the following components:

[0060] The adherent A component is composed of the following components by weight percentage: hydroxyl-containing polyester-acrylic copolymer resin: 22 parts, ethyl acetate: 36 parts, butyl acetate: 18 parts, silane coupling agent: 2 parts, cellulose acetate butyrate: 0.6 part, organic bismuth drier: 0.4 part;

[0061] The adherent B component is composed of the following components by weight percentage: phthalylenediisocyanate adduct: 65 parts, butyl acetate: 35 parts;

[0062] The acrylic primer is composed of the following components by weight percentage: high-TG hydroxyl-containing acrylic resin: 52 parts, cellulose acetate butyrate: 2 parts, color paste: 12 parts, pearlescent pigment or aluminum silver paste: 9 parts, ethyl acetate: 11 parts, butyl acetate: 14 parts, anti-settling agent: 5 parts, wetting agent: 0.2 part;

[0063] The curing agent is composed of the following components by weight percentage: HDI trimer adduct: 65 parts, butyl acetate: 35 parts;

[0064] The thinner is composed of the following components by weight percentage: ethyl acetate: 62 parts, dimethyl isobutyl ketone: 38 parts;

[0065] The prefabricated flame-retardant paste is composed of the following components by weight percentage: high-TG hydroxyl-containing acrylic resin: 12 parts, butyl acetate: 12 parts, dispersant: 1 part, anti-settling agent: 1 part, phosphorus-nitrogen-based halogen-free flame-retardant powder: 63 parts;

[0066] The flame-retardant intermediate coat is composed of the following components by weight percentage: high-TG hydroxyl-containing acrylic resin: 12 parts, white paste: 33 parts, prefabricated flame-retardant paste: 33 parts, ethyl acetate: 15 parts, butyl acetate: 5 parts, wetting agent: 0.4 part;

[0067] The flame-retardant topcoat consists of the following components by weight percentage: high-TG hydroxyl-containing acrylic resin: 12 parts, white paste: 18 parts, black paste: 12 parts, prefabricated flame-retardant paste: 46 parts, ethyl acetate: 12 parts, butyl acetate: 8 parts, wetting agent: 0.2 part;

[0068] The UV-curable coating consists of the following components by weight percentage: photoinitiator: 3 parts, ethyl acetate: 28 parts, butyl acetate: 12 parts, n-butanol: 9 parts, ethylene glycol monobutyl ether: 6 parts, diacetone alcohol: 9 parts, 1,6-hexanediol diacrylate: 6 parts, trimethylolpropane tripropionate: 12 parts, 3-functional polyurethane acrylate: 10 parts, 9-functional polyurethane acrylate: 20 parts, wetting agent: 0.4 part, leveling agent: 0.2 part. Example 4

[0069] The flame-retardant coating applied to the mobile phone PC substrate contains the following components:

[0070] The adherent A component consists of the following components by weight percentage: hydroxyl-containing polyester-acrylic copolymer resin: 28 parts, ethyl acetate: 32 parts, butyl acetate: 25 parts, silane coupling agent: 1 part, cellulose acetate butyrate: 0.8 part, organic bismuth dryer: 0.2 part;

[0071] The adherent B component consists of the following components by weight percentage: xylylene diisocyanate adduct: 70 parts, butyl acetate: 30 parts;

[0072] The acrylic basecoat consists of the following components by weight percentage: high-TG hydroxyl-containing acrylic resin: 58 parts, cellulose acetate butyrate: 1 part, color paste: 18 parts, pearlescent pigment or aluminum silver paste: 6 parts, ethyl acetate: 14 parts, butyl acetate: 11 parts, anti-settling agent: 3 parts, wetting agent: 0.4 part;

[0073] The curing agent consists of the following components by weight percentage: HDI trimer adduct: 70 parts, butyl acetate: 30 parts;

[0074] The thinner consists of the following components by weight percentage: ethyl acetate: 68 parts, dimethyl isobutyl ketone: 33 parts;

[0075] The prefabricated flame-retardant paste consists of the following components by weight percentage: high-TG hydroxyl-containing acrylic resin: 18 parts, butyl acetate: 18 parts, dispersant: 2 parts, anti-settling agent: 0.5 part, phosphazene-based halogen-free flame-retardant powder: 68 parts;

[0076] The flame-retardant intermediate paint consists of the following components by weight percentage: high-TG hydroxyl-containing acrylic resin: 18 parts, white paste: 36 parts, prefabricated flame-retardant paste: 38 parts, ethyl acetate: 12 parts, butyl acetate: 8 parts, wetting agent: 0.2 part;

[0077] The flame-retardant topcoat consists of the following components by weight percentage: high-TG hydroxyl-containing acrylic resin: 12 - 18 parts, white paste: 12 parts, black paste: 18 parts, prefabricated flame-retardant paste: 42 parts, ethyl acetate: 14 parts, butyl acetate: 6 parts, wetting agent: 0.4 part;

[0078] The UV-curable coating consists of the following components by weight percentage: photoinitiator: 4 parts, ethyl acetate: 22 parts, butyl acetate: 18 parts, n-butanol: 6 parts, ethylene glycol monobutyl ether: 9 parts, diacetone alcohol: 6 parts, 1,6-hexanediol diacrylate: 9 parts, trimethylolpropane tripropionate: 18 parts, 3-functional polyurethane acrylate: 15 parts, 9-functional polyurethane acrylate: 30 parts, wetting agent: 0.3 part, leveling aid: 0.4 part.

[0079] Prepare the coatings according to the formulations of the examples. The coating preparation process is as follows:

[0080] Adhesive A component: Take a clean stainless-steel container, with an ambient temperature of 25°C and a humidity of less than 60%. First, add ethyl acetate and butyl acetate and stir at a speed of 300 revolutions per minute. Slowly add the hydroxyl-containing polyester-acrylic copolymer resin and stir for 4 minutes at a speed of 300 revolutions per minute. While stirring, slowly add the silane coupling agent, cellulose acetate butyrate, and organic bismuth drier in sequence and stir for 20 minutes at a speed of 500 revolutions per minute. Filter the coating through a 300-mesh filter and then package it.

[0081] Adhesive B component: Take a clean stainless-steel container, with an ambient temperature of 25°C and a humidity of less than 60%. First, add the phthalylenediisocyanate adduct and butyl acetate and stir for 15 minutes at a speed of 300 revolutions per minute. Filter the coating through a 300-mesh filter and then package it.

[0082] Acrylic base paint: Take a clean stainless-steel container, with an ambient temperature of 25°C and a humidity of less than 60%. First, add the high-TG acrylic resin, cellulose acetate butyrate, ethyl acetate, and butyl acetate and stir for 4 minutes at a speed of 300 revolutions per minute. While stirring, add the anti-settling agent and wetting agent in sequence, and stir for 25 minutes at a speed of 500 revolutions per minute. While stirring, slowly add the color paste, pearlescent pigment or aluminum silver paste, and stir for 25 minutes at a speed of 500 revolutions per minute. Then, adjust the color according to customer requirements. Filter the coating through a 300-mesh filter and then package it.

[0083] General curing agent: Take a clean stainless steel container, with an ambient temperature of 25°C and a humidity of less than 60%. Sequentially add HDI trimer adduct and butyl acetate, and stir at a speed of 300 revolutions per minute for 15 minutes. After filtering the coating through a 300-mesh filter, it is packaged.

[0084] Preformed flame retardant paste: Take a clean stainless steel container, with an ambient temperature of 25°C and a humidity of less than 60%. Sequentially add high-TG acrylic resin, butyl acetate, dispersant, and anti-settling agent, and stir at a speed of 300 revolutions per minute for 4 minutes. Slowly add the phosphorus-nitrogen halogen-free flame retardant powder under stirring, and stir at a speed of 1000 revolutions per minute for 25 minutes. Grind it with a sand mill until the scraping fineness is less than 5 microns. After filtering the flame retardant paste through a 150-mesh filter, it is packaged.

[0085] Flame retardant intermediate coat paint: Take a clean stainless steel container, with an ambient temperature of 25°C and a humidity of less than 60%. Sequentially add high-TG acrylic resin, ethyl acetate, butyl acetate, and white paste, and stir at a speed of 300 revolutions per minute for 4 minutes. Slowly add the preformed flame retardant paste in sequence under stirring, and stir at a speed of 500 revolutions per minute for 25 minutes. Finally, add the wetting agent and stir at a speed of 300 revolutions per minute for 4 minutes. After cooling, filter it through a 250-mesh filter and then package it.

[0086] Flame retardant topcoat paint: Take a clean stainless steel container, with an ambient temperature of 25°C and a humidity of less than 60%. Sequentially add high-TG acrylic resin, ethyl acetate, butyl acetate, white paste, and black paste, and stir at a speed of 300 revolutions per minute for 4 minutes. Slowly add the preformed flame retardant paste in sequence under stirring, and stir at a speed of 500 revolutions per minute for 20 - 30 minutes. Finally, add the wetting agent and stir at a speed of 300 revolutions per minute for 4 minutes. After cooling, filter it through a 250-mesh filter and then package it.

[0087] Thinner: Take a clean stainless steel container, with an ambient temperature of 25°C and a humidity of less than 60%. Sequentially add ethyl acetate and dimethyl isobutyl ketone, and stir at a speed of 300 revolutions per minute for 8 minutes. After filtering through a 300-mesh filter, it is packaged.

[0088] UV-curable coating: Take a clean stainless steel container, with an ambient temperature of 25°C and a humidity of less than 60%. Sequentially add photoinitiator, ethyl acetate, butyl acetate, n-butanol, ethylene glycol monobutyl ether, and diacetone alcohol, and stir at a speed of 300 revolutions per minute for 10 minutes until the photoinitiator is completely dissolved without particles. Slowly add 1,6-hexanediol diacrylate and trimethylolpropane triacrylate in sequence under stirring, and stir at a speed of 300 revolutions per minute for 4 minutes. Slowly add 3-functional polyurethane acrylate and 9-functional polyurethane acrylate under stirring, and stir at a speed of 800 revolutions per minute for 100 minutes. Finally, add the wetting agent and leveling agent, and stir at a speed of 300 revolutions per minute for 10 minutes. After cooling, filter it through a 500-mesh filter and then package it.

[0089] The usage method of the flame retardant coating applied to the mobile phone PC substrate in the embodiment includes the following steps:

[0090] Step 1: After mixing component A of the adhesion promoter and component B of the adhesion promoter according to a mass ratio of 100:3, spray and construct on the A side of the PC material;

[0091] Step 2: After spraying, dry at 70 °C for 15 minutes;

[0092] Step 3: After mixing the acrylic acid base paint, the general curing agent and the diluent according to a mass ratio of 8:1:4, continue spraying and construction;

[0093] Step 4: After spraying, dry at 0 °C for 15 minutes;

[0094] Step 5: After mixing the flame retardant intermediate paint, the general curing agent and the diluent according to a mass ratio of 8:1:4, continue spraying and construction;

[0095] Step 6: After spraying, dry at 70 °C for 15 minutes;

[0096] Step 7: After mixing the flame retardant topcoat: the general curing agent and the diluent according to a mass ratio of 8:1:4, continue spraying and construction;

[0097] Step 8: After spraying, dry at 70 °C for 140 minutes, and then machine-process the PC material into a mobile phone shell;

[0098] Step 9: Directly spray and construct the ultraviolet light-curing coating on the B side of the PC material;

[0099] Step 10: After spraying, dry at 60 °C for 6 minutes;

[0100] Step 11: Finally, perform ultraviolet light curing.

[0101] Comparative Example 1

[0102] Compared with Example 4, in this comparative example, only component A of the adhesion promoter is used, and component B of the adhesion promoter is not contained.

[0103] Comparative Example 2

[0104] Compared with Example 4, in this comparative example, only ordinary acrylic resin is used, and high-TG hydroxyl-containing acrylic resin is not used.

[0105] Comparative Example 3

[0106] Compared with Example 4, in this comparative example, after the color paint spraying construction, the flame retardant topcoat is directly sprayed, and the flame retardant intermediate paint is not used.

[0107] According to the above-mentioned examples and comparative examples and in combination with the above-mentioned preparation method, after the flame-retardant coating for mobile phone PC substrates is spray-coated and cured, the performance parameters of the obtained coating film are shown in Table 1, Table 2 and Table 3:

[0108]

[0109]

[0110] Table 3

[0111] Needle Flame Test (GB-T5169.5 / Burning for 60 seconds) Needle Flame Test (GB-T5169.5 / Burning for 120 seconds) Example 1 The material has no holes The material has no holes Example 2 The material has no holes The material has no holes Example 3 The material has no holes The material has no holes Example 4 The material has no holes The material has no holes Comparative Example 1 The material has no holes The material has no holes Comparative Example 2 The material has no holes The material has no holes Comparative Example 3 The material has holes The material has holes

[0112] Obviously, the above examples are merely illustrations for clear explanation and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A flame retardant coating applied to the PC substrate of a mobile phone, characterized in that, It includes the following components: Adhesive A component, Adhesive B component, Acrylic base paint, Curing agent, Thinner, Prefabricated flame retardant paste, Flame retardant intermediate paint, Flame retardant topcoat and UV-curable coating; Among them, the Adhesive A component is composed of the following components by weight percentage: Hydroxyl-containing polyester-acrylic copolymer resin: 20 - 30 parts, Ethyl acetate: 30 - 40 parts, Butyl acetate: 15 - 30 parts, Silane coupling agent: 1 - 2 parts, Cellulose acetate butyrate: 0.5 - 1 part, Organic bismuth drier: 0.1 - 0.5 part; The Adhesive B component is composed of the following components by weight percentage: Benzene diisocyanate methylene adduct: 60 - 70 parts, Butyl acetate: 30 - 40 parts; The Acrylic base paint is composed of the following components by weight percentage: High Tg hydroxyl-containing acrylic resin: 50 - 60 parts, Cellulose acetate butyrate: 1 - 2 parts, Color paste: 10 - 20 parts, Pearlescent pigment or aluminum silver paste: 5 - 10 parts, Ethyl acetate: 10 - 15 parts, Butyl acetate: 10 - 15 parts, Anti-settling additive: 3 - 5 parts, Wetting agent: 0.1 - 0.5 part; The Curing agent is composed of the following components by weight percentage: HDI trimer adduct: 60 - 70 parts, Butyl acetate: 30 - 40 parts; The Thinner is composed of the following components by weight percentage: Ethyl acetate: 60 - 70 parts, Dimethyl isobutyl ketone: 30 - 40 parts; The Prefabricated flame retardant paste is composed of the following components by weight percentage: High Tg hydroxyl-containing acrylic resin: 10 - 20 parts, Butyl acetate: 10 - 20 parts, Dispersant: 1 - 2 parts, Anti-settling agent: 0.5 - 1 part, Phosphorus-nitrogen-based halogen-free flame retardant powder: 60 - 70 parts; The Flame retardant intermediate paint is composed of the following components by weight percentage: High Tg hydroxyl-containing acrylic resin: 10 - 20 parts, White paste: 30 - 40 parts, Prefabricated flame retardant paste: 30 - 40 parts, Ethyl acetate: 10 - 15 parts, Butyl acetate: 5 - 10 parts, Wetting agent: 0.1 - 0.5 part; The Flame retardant topcoat is composed of the following components by weight percentage: High Tg hydroxyl-containing acrylic resin: 10 - 20 parts, White paste: 10 - 20 parts, Black paste: 10 - 20 parts, Prefabricated flame retardant paste: 40 - 50 parts, Ethyl acetate: 10 - 15 parts, Butyl acetate: 5 - 10 parts, Wetting agent: 0.1 - 0.5 part; The UV-curable coating is composed of the following components by weight percentage: Photoinitiator: 2 - 5 parts, Ethyl acetate: 20 - 30 parts, Butyl acetate: 10 - 20 parts, n-Butanol: 5 - 10 parts, Ethylene glycol monobutyl ether: 5 - 10 parts, Diacetone alcohol: 5 - 10 parts, 1,6-Hexanediol diacrylate: 5 - 10 parts, Trimethylolpropane tripropionate: 10 - 20 parts, 3-functional polyurethane acrylate: 10 - 20 parts, 9-functional polyurethane acrylate: 20 - 30 parts, Wetting agent: 0.1 - 0.5 part, Flow leveling agent: 0.1 - 0.5 part.

2. The flame retardant coating applied to the mobile phone PC substrate according to claim 1, wherein: In the Acrylic base paint, Flame retardant intermediate paint, and Flame retardant topcoat, the Tg of the high Tg hydroxyl-containing acrylic resin ≥ 90°C, and the hydroxyl content is less than 0.5%.

3. The flame retardant coating applied to the mobile phone PC substrate according to claim 1, wherein: The HDI trimer adduct in the curing agent is a hexamethylene diisocyanate adduct.

4. The flame retardant coating applied to the mobile phone PC substrate according to claim 1, wherein: The color pastes, white pastes, and black pastes in the acrylic base paint, flame-retardant intermediate paint, and flame-retardant topcoat are solvent-based resin-free general color pastes, with good dispersion and compatibility and good weather resistance.

5. The flame retardant coating applied to the mobile phone PC substrate according to claim 1, wherein: The photoinitiator in the ultraviolet (UV) curable coating consists of α-hydroxy ketones, benzoyl formates, and acylphosphine oxides.

6. The flame retardant coating applied to the mobile phone PC substrate according to claim 1, characterized in that: In the UV curable coating, the weight ratio of the trifunctional polyurethane acrylate to the nonafunctional polyurethane acrylate is 1:

2.

7. The flame retardant coating applied to the mobile phone PC substrate according to claim 1, wherein: The wetting agent and leveling agent in the formulation are polyether-modified polydimethylsiloxane copolymer solutions, and the dispersant is a polymer copolymer solution containing a pigment affinity group.

8. The method of using the flame retardant coating applied to the mobile phone PC substrate according to any one of claims 1 to 7, characterized in that, It includes the following steps: Step 1: Mix component A and component B of the adherent in a mass ratio of 100:3, and then spray and apply it to the A side of the PC material for construction. Step 2: After spraying, dry it at 70 °C for 10 - 15 minutes. Step 3: Mix the acrylic base paint, curing agent, and diluent in a mass ratio of 8:1:3 - 4, and then continue spraying for construction. Step 4: After spraying, dry it at 0 °C for 10 - 15 minutes. Step 5: Mix the flame-retardant intermediate paint, curing agent, and diluent in a mass ratio of 8:1:3 - 4, and then continue spraying for construction. Step 6: After spraying, dry it at 70 °C for 10 - 15 minutes. Step 7: Mix the flame-retardant topcoat, curing agent, and diluent in a mass ratio of 8:1:3 - 4, and then continue spraying for construction. Step 8: After spraying, dry it at 70 °C for 120 - 150 minutes, and then machine-process the PC material into a mobile phone shell. Step 9: Directly spray and apply the UV curable coating to the B side of the PC material. Step 10: After spraying, dry it at 60 °C for 5 - 8 minutes. Step 11: Finally, perform UV curing.

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