Preparation method of high-adhesion composite coating for metal product

Abstract

The invention discloses a preparation method of a high-adhesion composite coating for a metal product, and relates to the technical field of metal surface treatment. According to the coating, polyurethane resin is adopted as a matrix, and a curing agent, an elastomer modifier, a lubricant and an adhesion promoter are added, so that the adhesion, toughness and impact resistance of the coating are improved. The coating is formed through spraying and curing processes, has excellent wear resistance and adhesive force, and is suitable for surface treatment of various metal products. The preparation method is simple and easy to implement, low in cost and suitable for industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of metal surface treatment, in particular to a method for preparing a high-adhesion composite coating for metal products. Background Art

[0002] Metal hooks are a type of metal product, widely used in a variety of fields such as hanging clothes, fixing pipes, connecting mechanical parts, etc. During use, hooks are often exposed to various harsh environments, such as moisture, acid and alkali corrosion, friction and impact, which puts high demands on the durability of their surface coatings. However, traditional metal product coatings still have many shortcomings in practical applications, mainly in the following aspects: Poor adhesion: The metal surface is smooth and chemically inert, and traditional coatings often have difficulty forming a strong bond with the metal surface after application. Especially when subjected to mechanical stress or environmental changes, the coating is prone to fall off or peel off, which not only affects the appearance of the hook, but may also reduce its functionality and service life.

[0003] Insufficient wear resistance: During use, metal hooks often come into contact with other objects or rub against each other, causing the coating to wear out. Traditional coatings are not hard enough or have insufficient wear resistance. After long-term use, scratches, dents and other wear marks are likely to appear on the surface, thus affecting the overall performance of the hook.

[0004] Poor chemical corrosion resistance: In some special applications, such as chemical plants and outdoor facilities, metal hooks are often exposed to corrosive environments such as acids and alkalis. Traditional coating materials have weak tolerance to chemical corrosion and are prone to decomposition, aging or dissolution, resulting in the failure of the coating protection. The metal surface is directly exposed to the corrosive medium, which accelerates the corrosion of the metal.

[0005] The construction process is complex and costly: Traditional coatings often require complex surface pretreatment processes during construction, such as grinding, degreasing, sandblasting, etc., to ensure that the coating can adhere to the metal surface. This not only increases the difficulty of construction, but also increases the overall cost of the coating. In addition, some high-performance coating materials are expensive, further limiting their promotion in large-scale industrial applications.

[0006] In order to overcome the above problems, some modified coating technologies have been gradually introduced in the prior art, such as the use of polymer composite coatings, the addition of reinforcing agents and lubricants, etc. However, these methods still have certain limitations and cannot fully meet the use requirements of metal products in practical applications. Therefore, it is particularly important to develop a new composite coating that has high adhesion, chemical corrosion resistance, simple construction process and moderate cost. Summary of the invention

[0007] This method aims to provide a high-adhesion composite coating specifically for metal product applications through innovative formulation and process design, overcome the shortcomings of existing technologies, and provide a more efficient and durable solution for the surface treatment of metal products in industrial and civilian products.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows: A method for preparing a high-adhesion composite coating for a metal product, the composite coating comprising the following components in parts by weight: Two-component polyurethane resin: 50-70 parts; Polyisocyanate curing agent: 10-20 parts; Elastomer modifier: 5-15 parts; Lubricant: 2-10 parts; Adhesion promoter: 1-5 parts.

[0009] The two-component polyurethane resin includes polyether polyurethane and polyester polyurethane, the proportion of polyether polyurethane is 70-90wt%, the proportion of polyester polyurethane is 10-30wt%, and the molecular weight of the polyurethane resin is in the range of 2000-4000.

[0010] The curing agent is one or more of toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI) or isophorone diisocyanate (IPDI).

[0011] The elastomer modifier is one or more of polybutadiene rubber (PBD), polyetheramine or ethylene-propylene-diene monomer (EPDM).

[0012] The lubricant is a silicone or fluoride lubricant, specifically including one or more of polydimethylsiloxane (PDMS), polytetrafluoroethylene (PTFE) micropowder or fluorinated paraffin.

[0013] The preparation method of the adhesion promoter is: According to weight parts, 0.3-0.9 parts of diamminetitanium tetrachloride, 0.002-0.05 parts of propenyltriphenyltin, 2-5 parts of diethylamine, and 200-300 parts of DMF are added into a closed stirring reactor, nitrogen is introduced, and the reaction is stirred at 60-70° C. for 100-150 minutes; Then add 24-48 parts of γ-glycidyloxypropyltrimethoxysilane, stir and react at 60-70° C. for 120-160 minutes, and distill to remove DMF to obtain silane containing titanium chloride complex and triphenyltin complex, i.e., adhesion promoter.

[0014] The spraying process of the composite coating is as follows: (1) Coating preparation: two-component polyurethane resin, polyisocyanate curing agent, elastomer modifier, lubricant, and adhesion promoter are mixed in the above proportions and stirred thoroughly until a uniform coating is formed; (2) Surface pretreatment of metal products: degreasing, rust removal and sandblasting of the surface of metal products to enhance the adhesion of the coating; (3) Paint spraying: spray the prepared paint evenly on the pre-treated metal product surface to control the coating thickness; (4) Coating curing: The sprayed metal product is cured at high temperature to form a composite coating with strong adhesion and chemical corrosion resistance.

[0015] The coating thickness is 10-50 microns.

[0016] The coating has a curing temperature of 60-80° C. and a curing time of 1-2 hours.

[0017] Adhesion promoter reaction mechanism: One amino group of the diammine titanium tetrachloride undergoes an amino-acryl addition reaction with allyl triphenyl tin, and another amino group undergoes an amino-epoxy ring-opening addition reaction with γ-glycidyloxypropyl trimethoxy silane to obtain a silane containing a titanium chloride complex and a triphenyl tin complex, namely an adhesion promoter.

[0018] Adhesion promoter reaction mechanism: 1) The epoxy group in γ-glycidyloxypropyltrimethoxysilane can react chemically with the hydroxyl group or other active groups on the metal surface to form a strong chemical bond, thereby enhancing the bonding force between the coating and the metal surface. At the same time, this silane coupling agent can also form a cross-linked structure inside the coating, improving the density and durability of the coating.

[0019] 2) When the amino group reacts with the propenyl group, the lone pair of electrons on the nitrogen atom will fill the π antibonding orbital of the propenyl group to form a new σ bond. This orbital overlap and hybridization process helps to form a stable chemical bond, thereby improving the adhesion of the coating. The silane containing the titanium chloride complex and the triphenyltin complex has a specific spatial configuration, which is conducive to its adsorption and arrangement on the metal surface. By optimizing the spatial arrangement of the molecules, the stress concentration inside the coating can be reduced, and the stability and durability of the coating can be improved.

[0020] Technical effect: The high-adhesion composite coating of the present invention significantly improves the adhesion and wear resistance of the coating by rationally selecting and proportioning the components. Compared with traditional coatings, the composite coating of the present invention is not easy to fall off during use, can effectively protect the surface of metal products, extend the service life of products, and reduce maintenance costs. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0022] Example 1 A method for preparing a high-adhesion composite coating for a metal product, the composite coating comprising the following components in parts by weight: Two-component polyurethane resin: 50g; Polyisocyanate curing agent: 10g; Elastomer modifier: 5g; Lubricant: 2g; Adhesion promoter: 1g.

[0023] The two-component polyurethane resin includes polyether polyurethane and polyester polyurethane, the proportion of polyether polyurethane is 70wt%, the proportion of polyester polyurethane is 30wt%, and the molecular weight of the polyurethane resin is in the range of 2000 to 4000.

[0024] The curing agent is toluene diisocyanate (TDI).

[0025] The elastomer modifier is polybutadiene rubber (PBD).

[0026] The lubricant is polydimethylsiloxane (PDMS).

[0027] The preparation method of the adhesion promoter is: 0.3 g of diamminetitanium tetrachloride, 0.002 g of propenyltriphenyltin, 2 g of diethylamine, and 200 g of DMF were added to a closed stirred reactor, nitrogen was introduced, and the reaction was stirred at 60° C. for 100 minutes; Then, 24 g of γ-glycidyloxypropyltrimethoxysilane was added, and the mixture was stirred at 60° C. for 120 minutes. DMF was removed by distillation to obtain the silane containing the titanium chloride complex and the triphenyltin complex, i.e., the adhesion promoter.

[0028] The spraying process of the composite coating is as follows: (1) Coating preparation: two-component polyurethane resin, polyisocyanate curing agent, elastomer modifier, lubricant, and adhesion promoter are mixed in the above proportions and stirred thoroughly until a uniform coating is formed; (2) Surface pretreatment of metal products: degreasing, rust removal and sandblasting of the surface of metal products to enhance the adhesion of the coating; (3) Paint spraying: spray the prepared paint evenly on the pre-treated metal product surface to control the coating thickness; (4) Coating curing: The sprayed metal product is cured at high temperature to form a composite coating with strong adhesion and chemical corrosion resistance.

[0029] The coating thickness was 40 microns.

[0030] The coating curing temperature is 60° C. and the curing time is 2 hours.

[0031] Example 2 A method for preparing a high-adhesion composite coating for a metal product, the composite coating comprising the following components in parts by weight: Two-component polyurethane resin: 60g; Polyisocyanate curing agent: 15g; Elastomer modifier: 10g; Lubricant: 5g; Adhesion promoter: 2.5g.

[0032] The two-component polyurethane resin includes polyether polyurethane and polyester polyurethane, the proportion of polyether polyurethane is 80wt%, the proportion of polyester polyurethane is 20wt%, and the molecular weight of the polyurethane resin is in the range of 2000 to 4000.

[0033] The curing agent is hexamethylene diisocyanate (HDI).

[0034] The elastomer modifier is polyetheramine.

[0035] The lubricant is polytetrafluoroethylene (PTFE) powder.

[0036] The preparation method of the adhesion promoter is: 0.6 g of diamminetitanium tetrachloride, 0.02 g of propenyltriphenyltin, 3 g of diethylamine, and 250 g of DMF were added to a closed stirred reactor, nitrogen was introduced, and the reaction was stirred at 65° C. for 125 minutes; Then, 32 g of γ-glycidyloxypropyltrimethoxysilane was added, and the mixture was stirred at 65° C. for 140 minutes. DMF was removed by distillation to obtain the silane containing the titanium chloride complex and the triphenyltin complex, i.e., the adhesion promoter.

[0037] The spraying process of the composite coating is as follows: (1) Coating preparation: two-component polyurethane resin, polyisocyanate curing agent, elastomer modifier, lubricant, and adhesion promoter are mixed in the above proportions and stirred thoroughly until a uniform coating is formed; (2) Surface pretreatment of metal products: degreasing, rust removal and sandblasting of the surface of metal products to enhance the adhesion of the coating; (3) Paint spraying: spray the prepared paint evenly on the pre-treated metal product surface to control the coating thickness; (4) Coating curing: The sprayed metal product is cured at high temperature to form a composite coating with strong adhesion and chemical corrosion resistance.

[0038] The coating thickness was 40 microns.

[0039] The coating curing temperature is 70° C. and the curing time is 1 hour.

[0040] Example 3 A method for preparing a high-adhesion composite coating for a metal product, the composite coating comprising the following components in parts by weight: Two-component polyurethane resin: 60g; Polyisocyanate curing agent: 15g; Elastomer modifier: 10g; Lubricant: 7.5g; Adhesion promoter: 3.5g.

[0041] The two-component polyurethane resin includes polyether polyurethane and polyester polyurethane, the proportion of polyether polyurethane is 80wt%, the proportion of polyester polyurethane is 20wt%, and the molecular weight of the polyurethane resin is in the range of 2000 to 4000.

[0042] The curing agent is hexamethylene diisocyanate (HDI).

[0043] The elastomer modifier is polyetheramine.

[0044] The lubricant is polytetrafluoroethylene (PTFE) powder.

[0045] The preparation method of the adhesion promoter is: 0.9 g of diamminetitanium tetrachloride, 0.05 g of propenyltriphenyltin, 5 g of diethylamine, and 300 g of DMF were added to a closed stirred reactor, nitrogen was introduced, and the reaction was stirred at 70° C. for 150 minutes; Then, 40 g of γ-glycidyloxypropyltrimethoxysilane was added, and the mixture was stirred at 65° C. for 140 minutes. DMF was removed by distillation to obtain the silane containing the titanium chloride complex and the triphenyltin complex, i.e., the adhesion promoter.

[0046] The spraying process of the composite coating is as follows: (1) Coating preparation: two-component polyurethane resin, polyisocyanate curing agent, elastomer modifier, lubricant, and adhesion promoter are mixed in the above proportions and stirred thoroughly until a uniform coating is formed; (2) Surface pretreatment of metal products: degreasing, rust removal and sandblasting of the surface of metal products to enhance the adhesion of the coating; (3) Paint spraying: spray the prepared paint evenly on the pre-treated metal product surface to control the coating thickness; (4) Coating curing: The sprayed metal product is cured at high temperature to form a composite coating with strong adhesion and chemical corrosion resistance.

[0047] The coating thickness was 40 microns.

[0048] The coating curing temperature is 70° C. and the curing time is 1 hour.

[0049] Example 4 A method for preparing a high-adhesion composite coating for a metal product, the composite coating comprising the following components in parts by weight: Two-component polyurethane resin: 70g; Polyisocyanate curing agent: 20g; Elastomer modifier: 15g; Lubricant: 10g; Adhesion promoter: 5g.

[0050] The two-component polyurethane resin includes polyether polyurethane and polyester polyurethane, the proportion of polyether polyurethane is 90wt%, the proportion of polyester polyurethane is 10wt%, and the molecular weight of the polyurethane resin is in the range of 2000 to 4000.

[0051] The curing agent is isophorone diisocyanate (IPDI).

[0052] The elastomer modifier is ethylene-propylene-diene monomer (EPDM).

[0053] The lubricant is fluorinated paraffin.

[0054] The preparation method of the adhesion promoter is: 0.9 g of diamminetitanium tetrachloride, 0.05 g of propenyltriphenyltin, 5 g of diethylamine, and 300 g of DMF were added to a closed stirred reactor, nitrogen was introduced, and the reaction was stirred at 70° C. for 150 minutes; Then, 48 g of γ-glycidyloxypropyltrimethoxysilane was added, and the mixture was stirred at 70° C. for 160 minutes. DMF was removed by distillation to obtain the silane containing the titanium chloride complex and the triphenyltin complex, i.e., the adhesion promoter.

[0055] The spraying process of the composite coating is as follows: (1) Coating preparation: two-component polyurethane resin, polyisocyanate curing agent, elastomer modifier, lubricant, and adhesion promoter are mixed in the above proportions and stirred thoroughly until a uniform coating is formed; (2) Surface pretreatment of metal products: degreasing, rust removal and sandblasting of the surface of metal products to enhance the adhesion of the coating; (3) Paint spraying: spray the prepared paint evenly on the pre-treated metal product surface to control the coating thickness; (4) Coating curing: The sprayed metal product is cured at high temperature to form a composite coating with strong adhesion and chemical corrosion resistance.

[0056] The coating thickness was 40 microns.

[0057] The coating curing temperature is 80° C. and the curing time is 1 hour.

[0058] Comparative Example 1 A method for preparing a high-adhesion composite coating for a metal product, the composite coating comprising the following components in parts by weight: Two-component polyurethane resin: 50g; Polyisocyanate curing agent: 10g; Elastomer modifier: 5g; Lubricant: 2g; Adhesion promoter: 1g.

[0059] The two-component polyurethane resin includes polyether polyurethane and polyester polyurethane, the proportion of polyether polyurethane is 70wt%, the proportion of polyester polyurethane is 30wt%, and the molecular weight of the polyurethane resin is in the range of 2000 to 4000.

[0060] The curing agent is toluene diisocyanate (TDI).

[0061] The elastomer modifier is polybutadiene rubber (PBD).

[0062] The lubricant is polydimethylsiloxane (PDMS).

[0063] The adhesion promoter is γ-glycidyloxypropyltrimethoxysilane.

[0064] The composite coating spraying process is as follows: (1) Coating preparation: two-component polyurethane resin, polyisocyanate curing agent, elastomer modifier, lubricant, and adhesion promoter are mixed in the above proportions and stirred thoroughly until a uniform coating is formed; (2) Surface pretreatment of metal products: degreasing, rust removal and sandblasting of the surface of metal products to enhance the adhesion of the coating; (3) Paint spraying: spray the prepared paint evenly on the pre-treated metal product surface to control the coating thickness; (4) Coating curing: The sprayed metal product is cured at high temperature to form a composite coating with strong adhesion and chemical corrosion resistance.

[0065] The coating thickness was 40 microns.

[0066] The coating curing temperature is 60° C. and the curing time is 2 hours.

[0067] Comparative Example 2 A method for preparing a high-adhesion composite coating for a metal product, the composite coating comprising the following components in parts by weight: Two-component polyurethane resin: 50g; Polyisocyanate curing agent: 10g; Elastomer modifier: 5g; Lubricant: 2g; Adhesion promoter: 1g.

[0068] The two-component polyurethane resin includes polyether polyurethane and polyester polyurethane, the proportion of polyether polyurethane is 70wt%, the proportion of polyester polyurethane is 30wt%, and the molecular weight of the polyurethane resin is in the range of 2000 to 4000.

[0069] The curing agent is toluene diisocyanate (TDI).

[0070] The elastomer modifier is polybutadiene rubber (PBD).

[0071] The lubricant is polydimethylsiloxane (PDMS).

[0072] The preparation method of the adhesion promoter is: 0.3 g of diamminetitanium tetrachloride, 2 g of diethylamine, and 200 g of DMF were added into a sealed stirred reactor, nitrogen was introduced, and the mixture was stirred at 60° C. for 100 minutes; Then, 24 g of γ-glycidyloxypropyltrimethoxysilane was added, and the mixture was stirred at 60° C. for 120 minutes. DMF was removed by distillation to obtain the silane containing the titanium chloride complex and the triphenyltin complex, i.e., the adhesion promoter.

[0073] The spraying process of the composite coating is as follows: (1) Coating preparation: two-component polyurethane resin, polyisocyanate curing agent, elastomer modifier, lubricant, and adhesion promoter are mixed in the above proportions and stirred thoroughly until a uniform coating is formed; (2) Surface pretreatment of metal products: degreasing, rust removal and sandblasting of the surface of metal products to enhance the adhesion of the coating; (3) Paint spraying: spray the prepared paint evenly on the pre-treated metal product surface to control the coating thickness; (4) Coating curing: The sprayed metal product is cured at high temperature to form a composite coating with strong adhesion and chemical corrosion resistance.

[0074] The coating thickness was 40 microns.

[0075] The coating curing temperature is 60° C. and the curing time is 2 hours.

[0076] Comparative Example 3 A method for preparing a high-adhesion composite coating for a metal product, the composite coating comprising the following components in parts by weight: Two-component polyurethane resin: 50g; Polyisocyanate curing agent: 10g; Elastomer modifier: 5g; Lubricant: 2g; Adhesion promoter: 1g.

[0077] The two-component polyurethane resin includes polyether polyurethane and polyester polyurethane, the proportion of polyether polyurethane is 70wt%, the proportion of polyester polyurethane is 30wt%, and the molecular weight of the polyurethane resin is in the range of 2000 to 4000.

[0078] The curing agent is toluene diisocyanate (TDI).

[0079] The elastomer modifier is polybutadiene rubber (PBD).

[0080] The lubricant is polydimethylsiloxane (PDMS).

[0081] The preparation method of the adhesion promoter is: 0.002 g of allyltriphenyltin, 2 g of diethylamine, and 200 g of DMF were added into a sealed stirred reactor, nitrogen was introduced, and the mixture was stirred at 60° C. for 100 minutes; Then, 24 g of γ-glycidyloxypropyltrimethoxysilane was added, and the mixture was stirred at 60° C. for 120 minutes. DMF was removed by distillation to obtain the silane containing the titanium chloride complex and the triphenyltin complex, i.e., the adhesion promoter.

[0082] The spraying process of the composite coating is as follows: (1) Coating preparation: two-component polyurethane resin, polyisocyanate curing agent, elastomer modifier, lubricant, and adhesion promoter are mixed in the above proportions and stirred thoroughly until a uniform coating is formed; (2) Surface pretreatment of metal products: degreasing, rust removal and sandblasting of the surface of metal products to enhance the adhesion of the coating; (3) Paint spraying: spray the prepared paint evenly on the pre-treated metal product surface to control the coating thickness; (4) Coating curing: The sprayed metal product is cured at high temperature to form a composite coating with strong adhesion and chemical corrosion resistance.

[0083] The coating thickness was 40 microns.

[0084] The coating curing temperature is 60° C. and the curing time is 2 hours.

[0085] In order to verify the technical effect of the high adhesion composite coating of the present invention, the following tests were conducted, and the test results are shown in Table 1.

[0086] 1) Adhesion test: Test standard: Cross-cut test according to ISO 2409.

[0087] Test steps: After the coating is cured, use a grid cutter to scratch six parallel lines on the coating surface, and then scratch six perpendicular parallel lines to form a grid. Use tape to stick on the grid and quickly tear it off to observe the peeling of the coating.

[0088] Evaluation criteria: According to the peeling situation, the coating is rated from 0B to 5B, where 5B means no peeling of the coating and 0B means complete peeling of the coating.

[0089] 2) Wear resistance test: Test standard: According to ASTM D4060, using Taber abrasion tester for testing.

[0090] Test steps: Fix the coated sample on the Taber abrasion tester, load a 1000g grinding wheel to wear the coating, and record the change in coating thickness after wear.

[0091] Evaluation criteria: The weight loss (mg) after abrasion is used as the evaluation index of wear resistance. The smaller the weight loss, the better the wear resistance.

[0092] Table 1 The above test results show that the high-adhesion composite coating of the present invention has significant advantages in adhesion and wear resistance. The above performance can significantly extend the service life of the product and reduce maintenance costs. These excellent performances verify the effectiveness and practicality of the method of the present invention.

[0093] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the present invention specification under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for preparing a high-adhesion composite coating for a metal product, the composite coating comprising the following components in parts by weight: Two-component polyurethane resin: 50-70 parts; Polyisocyanate curing agent: 10-20 parts; Elastomer modifier: 5-15 parts; Lubricant: 2-10 parts; Adhesion promoter: 1-5 parts; The adhesion promoter is prepared by reacting diammine titanium tetrachloride, allyl triphenyltin and gamma-glycidyl ether oxypropyl trimethoxy silane.

2. The method for preparing a high-adhesion composite coating for metal products according to claim 1, characterized in that: The two-component polyurethane resin includes polyether polyurethane and polyester polyurethane, the proportion of polyether polyurethane is 70-90wt%, the proportion of polyester polyurethane is 10-30wt%, and the molecular weight of the polyurethane resin is in the range of 2000-4000.

3. The method for preparing a high-adhesion composite coating for metal products according to claim 1, characterized in that: The curing agent is one or more of toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI) or isophorone diisocyanate (IPDI).

4. The method for preparing a high-adhesion composite coating for metal products according to claim 1, characterized in that: The elastomer modifier is one or more of polybutadiene rubber (PBD), polyetheramine or ethylene-propylene-diene monomer (EPDM).

5. The method for preparing a high-adhesion composite coating for metal products according to claim 1, characterized in that: The lubricant is a silicone or fluoride lubricant, specifically including one or more of polydimethylsiloxane (PDMS), polytetrafluoroethylene (PTFE) micropowder or fluorinated paraffin.

6. The method for preparing a high-adhesion composite coating for metal products according to claim 1, characterized in that: The preparation method of the adhesion promoter is: According to weight parts, 0.3-0.9 parts of diamminetitanium tetrachloride, 0.002-0.05 parts of propenyltriphenyltin, 2-5 parts of diethylamine, and 200-300 parts of DMF are added into a closed stirring reactor, nitrogen is introduced, and the reaction is stirred at 60-70° C. for 100-150 minutes; Then add 24-48 parts of γ-glycidyloxypropyltrimethoxysilane, stir and react at 60-70° C. for 120-160 minutes, and distill to remove DMF to obtain silane containing titanium chloride complex and triphenyltin complex, i.e., adhesion promoter.

7. The method for preparing a high-adhesion composite coating for metal products according to claim 1, characterized in that: The spraying process of the composite coating is as follows: (1) Coating preparation: two-component polyurethane resin, polyisocyanate curing agent, elastomer modifier, lubricant, and adhesion promoter are mixed in the above proportions and stirred thoroughly until a uniform coating is formed; (2) Surface pretreatment of metal products: degreasing, rust removal and sandblasting of the surface of metal products to enhance the adhesion of the coating; (3) Paint spraying: spray the prepared paint evenly on the pre-treated metal product surface to control the coating thickness; (4) Coating curing: The sprayed metal product is cured at high temperature to form a composite coating with strong adhesion and chemical corrosion resistance.

8. The method for preparing a high-adhesion composite coating for metal products according to claim 7, characterized in that: The coating thickness is 10-50 microns.

9. The method for preparing a high-adhesion composite coating for metal products according to claim 7, characterized in that: The coating curing temperature is 60-80° C. and the curing time is 1-2 hours.

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