A silane-modified epoxy resin and its application in emission-free coating

Abstract

The present invention belongs to the field of emission-free coating technology, and particularly relates to a silane-modified epoxy resin and its application in emission-free coating, in parts by weight: the silane-modified epoxy resin includes 50-75 parts by weight of acrylic acid-modified epoxy resin, 5-8 parts by weight of silane coupling agent, 5-7 parts by weight of neutralizer and 20-30 parts by weight of solvent; the molecular weight of the silane-modified epoxy resin is 15000-20000, and the pH value is 7.5-8.5. The silane-modified epoxy resin of the present invention can effectively improve the performance of the metal pretreatment agent, so that it has higher storage stability resistant to complex environments (such as resistance to moisture and heat, resistance to bacteria, resistance to oil, resistance to hydrolysis, etc.); the silane-modified epoxy resin is applied in emission-free coating, has better use stability, can ensure that the coating pretreatment process meets the long-term stable water-free washing, significantly improves the adhesion and salt spray resistance of the coating product, and has a wide range of application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of emission-free coating, and in particular relates to a silane-modified epoxy resin and application thereof in emission-free coating. Background Art

[0002] Silane pretreatment is a widely used process for metal surface treatment. It improves the wettability and adhesion of the metal surface through the reaction of silane compounds, providing a good foundation for subsequent coating. Silane pretreatment is both acidic and alkaline. Acidic silane pretreatment is mainly used to remove oil and oxide layers on the metal surface. Chemical reactions in acidic environments, such as the reduction of hydrogen ions, can effectively improve the cleanliness of the metal surface and provide good adhesion conditions for subsequent coatings. Alkaline silane pretreatment focuses more on improving the adhesion between the coating and the metal surface. In an alkaline environment, silane compounds react with the oxides on the metal surface to form a dense silane film. This film can enhance the bonding between the coating and the metal, thereby improving the durability and corrosion resistance of the coating.

[0003] Silane modified resin is a kind of silane pretreatment agent, which is a material modified by organic silane on organic polymer. In the pretreatment and coating industry, silane modified resin and its derivatives mainly play the role of rust prevention and increasing the combination with powder coating. However, the existing silane modified resins generally have problems such as unstable storage performance, short service life of the coating after pretreatment and coating, and poor rust prevention performance of the pretreatment layer.

[0004] Therefore, the prior art needs to be improved. Summary of the invention

[0005] In order to solve the above problems in the prior art, the present invention provides a silane-modified epoxy resin and its application in emission-free coating, which can effectively improve the performance of the metal pretreatment agent and make it have higher storage and use stability.

[0006] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0007] According to the first aspect of the present invention: a silane-modified epoxy resin, comprising, by weight: 50-75 parts by weight of an acrylic-modified epoxy resin, 5-8 parts by weight of a silane coupling agent, 5-7 parts by weight of a neutralizing agent, and 20-30 parts by weight of a solvent;

[0008] The molecular weight of the silane-modified epoxy resin is 15,000-20,000 and the pH value is 7.5-8.5.

[0009] Further, the preparation method of silane-modified epoxy resin is as follows:

[0010] S1: Add acrylic modified epoxy resin into a clean reactor and stir, heat to 60-80°C, add silane coupling agent, react for 2-3h to obtain reactant 1;

[0011] S2: Cooling the reactant 1 to 50-60°C, adding a neutralizing agent and reacting for 1-1.5h to obtain reactant 2;

[0012] S3: Add the solvent to the reactant 2 and stir for 30-60 minutes to obtain a silane-modified epoxy resin.

[0013] Further, the silane coupling agent is one or more of propyl silane, epoxy silane, dipropyl silane and amino silane;

[0014] The neutralizing agent is dimethylethanolamine;

[0015] The solvent is one or more of dimethylol butyl ether, propylene glycol methyl ether acetate and ethylene glycol resin butyl ether;

[0016] The acid value of reactant 1 is less than or equal to 10.

[0017] Further, the acrylic acid modified epoxy resin includes 35-55 parts by weight of oleic acid modified epoxy resin, 0.01-0.05 parts by weight of initiator and 15-20 parts by weight of acrylic acid monomer.

[0018] Further, the preparation method of acrylic acid modified epoxy resin is as follows:

[0019] Put oleic acid modified epoxy resin and initiator into a clean reaction kettle and stir, heat to 140-160°C, add acrylic acid monomer, react at 140-160°C for 2-4h to obtain acrylic acid modified epoxy resin.

[0020] Further, the acid value of the acrylic modified epoxy resin is less than or equal to 20;

[0021] The acrylic monomer is one or more of acrylic acid, methyl acrylate, isobutyl acrylate, methyl methacrylate, isobornyl acrylate and hydroxyethyl acrylate;

[0022] The initiator is one or more of peroxide, oxide and phosphorus pentoxide.

[0023] Further, the oleic acid-modified epoxy resin includes 20-30 parts by weight of bisphenol A epoxy resin, 0.01-0.05 parts by weight of a catalyst and 15-25 parts by weight of oleic acid.

[0024] Further, the preparation method of oleic acid modified epoxy resin is as follows:

[0025] Add bisphenol A epoxy resin and catalyst into a clean reactor and stir, heat to 185-230°C, add oleic acid, and carry out esterification reaction at 185-230°C for 6-8h to obtain oleic acid-modified epoxy resin.

[0026] Further, the acid value of the oleic acid-modified epoxy resin is less than or equal to 20;

[0027] The bisphenol A type epoxy resin is one or both of E-03 and E-51;

[0028] The catalyst is one or more of peroxide, oxide and phosphorus pentoxide;

[0029] The oleic acid is one or more of dehydrated ricinoleic acid, linoleic acid, periodoleic acid and eleostearic acid.

[0030] According to a second aspect of the present invention, a silane-modified epoxy resin is used in emission-free coating. The silane-modified epoxy resin is prepared into an emission-free pretreatment agent and applied in emission-free coating.

[0031] The beneficial effects of the present invention are:

[0032] (1) Silane-modified epoxy resin can effectively enhance the adhesion of metal workpieces (such as iron, aluminum, galvanized, etc.) after emission-free pre-treatment. The adhesion test can reach level 0 after 2 hours of boiling in water;

[0033] (2) Silane-modified epoxy resin can effectively enhance the salt spray performance test of metal workpieces after emission-free pre-treatment, and the neutral salt spray can reach more than 400 hours, with the maximum single edge distance ≤2mm;

[0034] (3) Compared with traditional silane or silicone resin, the silane-modified epoxy resin of the present invention can effectively improve the performance of metal pretreatment agents, making them more resistant to complex environments (such as moisture and heat resistance, bacteria resistance, oil resistance, hydrolysis resistance, etc.) and have higher storage stability; the silane-modified epoxy resin is applied in emission-free coating, which has better use stability, can ensure that the coating pretreatment process meets the long-term stable water-free washing, significantly improves the adhesion and salt spray resistance of the coating products, and has broad application prospects. . DETAILED DESCRIPTION

[0035] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation methods.

[0036] In order to illustrate the scheme and technical advancement of the present invention, the technical scheme and technical application designed are as follows:

[0037] According to a first aspect of the present invention, a silane-modified epoxy resin comprises, in parts by weight: 50-75 parts by weight of an acrylic modified epoxy resin, 5-8 parts by weight of a silane coupling agent, 5-7 parts by weight of a neutralizing agent, and 20-30 parts by weight of a solvent; the silane coupling agent is one or more of propyl silane, epoxy silane, dipropyl silane, and amino silane; the neutralizing agent is dimethylethanolamine; the solvent is one or more of dimethyl alcohol butyl ether, propylene glycol methyl ether acetate, and ethylene glycol resin butyl ether;

[0038] The molecular weight of the silane-modified epoxy resin is 15,000-20,000 and the pH value is 7.5-8.5.

[0039] Preferably, the preparation method of silane-modified epoxy resin is as follows:

[0040] S1: Add acrylic modified epoxy resin into a clean reactor and stir, heat to 60-80°C, add silane coupling agent, react for 2-3h to obtain reactant 1; the acid value of reactant 1 is less than or equal to 10;

[0041] S2: Cooling the reactant 1 to 50-60°C, adding a neutralizing agent and reacting for 1-1.5h to obtain reactant 2;

[0042] S3: Add the solvent to the reactant 2 and stir for 30-60 minutes to obtain a silane-modified epoxy resin.

[0043] In step S1, the acrylic modified epoxy resin comprises 35-55 parts by weight of oleic acid modified epoxy resin, 0.01-0.05 parts by weight of initiator and 15-20 parts by weight of acrylic monomer, and the acid value of the acrylic modified epoxy resin is less than or equal to 20. The acrylic monomer is one or more of acrylic acid, methyl acrylate, isobutyl acrylate, methyl methacrylate, isobornyl acrylate and hydroxyethyl acrylate; the initiator is one or more of peroxide, oxide and phosphorus pentoxide.

[0044] The preparation method of acrylic acid modified epoxy resin is as follows:

[0045] Put oleic acid modified epoxy resin and initiator into a clean reaction kettle and stir, heat to 140-160°C, add acrylic acid monomer, react at 140-160°C for 2-4h to obtain acrylic acid modified epoxy resin.

[0046] Preferably, the oleic acid modified epoxy resin comprises 20-30 parts by weight of bisphenol A epoxy resin, 0.01-0.05 parts by weight of catalyst and 15-25 parts by weight of oleic acid, and the acid value of the oleic acid modified epoxy resin is less than or equal to 20. The bisphenol A epoxy resin is one or both of E-03 and E-51; the catalyst is one or more of peroxide, oxide and phosphorus pentoxide; and the oleic acid is one or more of dehydrated ricinoleic acid, linoleic acid, periodic oleic acid and eleostearic acid.

[0047] The preparation method of oleic acid modified epoxy resin is as follows:

[0048] Add bisphenol A epoxy resin and catalyst into a clean reactor and stir, heat to 185-230°C, add oleic acid, and carry out esterification reaction at 185-230°C for 6-8h to obtain oleic acid-modified epoxy resin.

[0049] Through the technical solution of the present invention:

[0050] (1) Increase water-resistant functional groups: The esterification reaction between low molecular weight epoxy resin and oleic acid substances can achieve the ring opening of epoxy resin and increase the molecular chain length of epoxy resin. At the same time, water-resistant functional groups such as chain-extended polycarbonate and carboxyl groups in oleic acid are introduced into the reaction, thereby improving the water resistance of epoxy resin.

[0051] (2) Adding functional groups that improve adhesion: The epoxy resin modified with oleic acid is then copolymerized with acrylic monomers to block or graft acrylic groups onto the epoxy resin. This can introduce some hydrophilic groups in acrylic acid into the epoxy resin molecular chain, adding functional groups such as phosphate, silane, and titanate that improve adhesion, thereby enhancing the adhesion between the coating and the metal substrate.

[0052] (3) Self-emulsification property: The epoxy resin modified by acrylic acid is reacted with silane to obtain the self-emulsification property of the epoxy resin, thereby changing the epoxy resin from oily to water-based, which can improve the physical properties of the subsequent organic coating, such as adhesion, impact strength, salt spray and other properties. That is, these modified properties of silane-modified epoxy resin are conducive to subsequent pretreatment, so that the surface of the substrate after pretreatment can adhere well to the coating, thereby improving the physical properties of the coating.

[0053] (4) Water dispersibility: The epoxy resin modified by silane grafting is neutralized with amines. After acid-base neutralization, the epoxy resin becomes water dispersible, which helps to improve the uniformity and stability of the coating.

[0054] (5) Formation of strong polar functional groups: Elements such as Si, S, and N introduced during epoxy resin modification form strong polar functional groups. These functional groups are intertwined and embedded with the main resin of the coating, thereby achieving the effect of improving the adhesion, corrosion resistance, and salt spray resistance of the coating.

[0055] (6) In each step of the reaction, the acid value is used as the standard for the completion of the reaction step to ensure that the raw materials in each step meet the requirements of the experimental design after the reaction, and finally the silane-modified epoxy resin of the present invention can be obtained; and the solid content and pH value of the finished product are adjusted to adjust the viscosity of the epoxy resin to facilitate the packaging and use of the product.

[0056] In summary, the silane-modified epoxy resin prepared by the technical scheme of the present invention has good stability in use, can improve the physical and chemical properties between the metal substrate and the coating after pretreatment, and has higher storage stability; when used in emission-free coating pretreatment, the strongly polar functional groups formed by the elements Si, S, N, etc. contained in the modified epoxy resin can be entangled and embedded with the main resin of the coating, thereby achieving the effect of improving the adhesion, corrosion resistance and salt spray resistance of the coating.

[0057] According to a second aspect of the present invention, a silane-modified epoxy resin is used in emission-free coating. The silane-modified epoxy resin is prepared into an emission-free pretreatment agent and applied in emission-free coating.

[0058] Through the above technical scheme, the silane-modified epoxy resin of the present invention is used to prepare an emission-free pretreatment agent, and the workpiece is treated with the pretreatment agent and then coated, and the formed coating has excellent adhesion, chemical stability and salt spray resistance.

[0059] Embodiment 1:

[0060] The preparation method of silane-modified epoxy resin is as follows:

[0061] S1: Add acrylic modified epoxy resin into a clean reactor and stir, heat to 60-80°C, add silane coupling agent, react for 2-3h to obtain reactant 1; the acid value of reactant 1 is less than or equal to 10;

[0062] The preparation method of acrylic acid modified epoxy resin is as follows: put oleic acid modified epoxy resin and initiator into a clean reaction kettle and stir, heat to 140-160° C., add acrylic acid monomer, react at 140-160° C. for 2-4 hours to obtain acrylic acid modified epoxy resin;

[0063] The preparation method of oleic acid modified epoxy resin is as follows: bisphenol A epoxy resin and catalyst are added into a clean reaction kettle and stirred, the temperature is raised to 185-230° C., oleic acid is added, and esterification reaction is carried out at 185-230° C. for 6-8 hours to obtain oleic acid modified epoxy resin;

[0064] S2: Cooling the reactant 1 to 50-60°C, adding a neutralizing agent and reacting for 1-1.5h to obtain reactant 2;

[0065] S3: Add the solvent to the reactant 2 and stir for 30-60 minutes to obtain a silane-modified epoxy resin.

[0066] Wherein: in parts by weight: the silane-modified epoxy resin includes 75 parts by weight of acrylic modified epoxy resin, 8 parts by weight of silane coupling agent, 7 parts by weight of neutralizing agent and 30 parts by weight of solvent; the silane coupling agent is propylsilane KH-550; the neutralizing agent is dimethylethanolamine; the solvent is dibutyl ether and propylene glycol methyl ether acetate.

[0067] The acrylic modified epoxy resin comprises 55 parts by weight of oleic acid modified epoxy resin, 0.05 parts by weight of initiator and 20 parts by weight of acrylic monomer, and the acid value of the acrylic modified epoxy resin is less than or equal to 20. The acrylic monomer is methyl acrylate; and the initiator is tert-butyl peroxybenzoate.

[0068] The oleic acid modified epoxy resin comprises 30 parts by weight of bisphenol A epoxy resin, 0.05 parts by weight of a catalyst and 25 parts by weight of oleic acid, and the acid value of the oleic acid modified epoxy resin is less than or equal to 20. The bisphenol A epoxy resin is E-03; the catalyst is zinc oxide; and the oleic acid is dehydrated ricinoleic acid.

[0069] The molecular weight of the silane-modified epoxy resin is 15,000-20,000 and the pH value is 8.1.

[0070] Embodiment 2:

[0071] Different from Example 1, this example adopts:

[0072] In parts by weight: the silane-modified epoxy resin includes 50 parts by weight of acrylic modified epoxy resin, 5 parts by weight of silane coupling agent, 5 parts by weight of neutralizer and 20 parts by weight of solvent; the silane coupling agent is propyl silane KH-550 and epoxy silane KH-560; the neutralizer is dimethylethanolamine; and the solvent is ethylene glycol resin.

[0073] The acrylic modified epoxy resin comprises 35 parts by weight of oleic acid modified epoxy resin, 0.01 parts by weight of initiator and 15 parts by weight of acrylic monomer, and the acid value of the acrylic modified epoxy resin is less than or equal to 20. The acrylic monomer is one or more of acrylic acid, methyl methacrylate, isobornyl acrylate and hydroxyethyl acrylate; the initiator is manganese oxide and phosphorus pentoxide.

[0074] The oleic acid modified epoxy resin comprises 20 parts by weight of bisphenol A epoxy resin, 0.03 parts by weight of catalyst and 15 parts by weight of oleic acid, and the acid value of the oleic acid modified epoxy resin is less than or equal to 20. The bisphenol A epoxy resin is E-51; the catalyst is phosphorus pentoxide; and the oleic acid is dehydrated ricinoleic acid and eleostearic acid.

[0075] The molecular weight of the silane-modified epoxy resin is 15,000-20,000 and the pH value is 7.8.

[0076] Embodiment 3:

[0077] Different from Example 1, this example adopts:

[0078] In parts by weight: the silane-modified epoxy resin includes 62 parts by weight of acrylic modified epoxy resin, 6.5 parts by weight of silane coupling agent, 6 parts by weight of neutralizer and 25 parts by weight of solvent; the silane coupling agent is dipropyl silane and aminosilane KH-792; the neutralizer is dimethylethanolamine; the solvent is dibutyl ether, propylene glycol methyl ether acetate and ethylene glycol resin butyl ether.

[0079] The acrylic modified epoxy resin comprises 45 parts by weight of oleic acid modified epoxy resin, 0.03 parts by weight of initiator and 17 parts by weight of acrylic monomer, and the acid value of the acrylic modified epoxy resin is less than or equal to 20. The acrylic monomer is isobutyl acrylate and methyl methacrylate; the initiator is phosphorus pentoxide.

[0080] The oleic acid modified epoxy resin comprises 25 parts by weight of bisphenol A epoxy resin, 0.03 parts by weight of catalyst and 20 parts by weight of oleic acid, and the acid value of the oleic acid modified epoxy resin is less than or equal to 20. The bisphenol A epoxy resin is E-03 and E-51; the catalyst is benzoyl peroxide and zinc oxide; and the oleic acid is dehydrated ricinoleic acid, periodic oleic acid and eleostearic acid.

[0081] The molecular weight of the silane-modified epoxy resin is 15,000-20,000 and the pH value is 8.4.

[0082] The application of the silane-modified epoxy resin obtained in Example 1, Example 2 and Example 3 in emission-free coating is to add the above-mentioned silane-modified epoxy resin to a metal pretreatment agent to obtain an emission-free pretreatment agent, and the emission-free pretreatment agent is applied to emission-free coating:

[0083] Surface treatment: Thoroughly remove foreign matter such as oil and rust from the test plate substrate, and use a non-emission pretreatment agent to pre-treat the test plate to obtain a test plate after non-emission pretreatment.

[0084] Coating steps: spray the test panel, and after the surface is naturally dry, place it in an oven or drying tunnel for drying to obtain a coating.

[0085] The coating was tested and the test results are shown in Table 1.

[0086] Table 1

[0087]

[0088]

[0089] Through the coating test of Example 1, Example 2 and Example 3, it can be known that the silane-modified epoxy resin of the present invention is added to the metal pretreatment agent to obtain an emission-free pretreatment agent. The emission-free pretreatment agent is applied to the emission-free coating, which can make the coating formed after coating have excellent adhesion, stability and salt spray resistance. Specifically: (1) The silane-modified epoxy resin can effectively enhance the adhesion of metal workpieces (such as iron, aluminum, galvanized, etc.) after emission-free pretreatment, and the adhesion test can reach level 0 after 2 hours of boiling in water; (2) The silane-modified epoxy resin can effectively enhance the salt spray performance test of metal workpieces after emission-free pretreatment, and the neutral salt spray can reach more than 400 hours, and the maximum single edge distance is ≤2mm; (3) Compared with traditional silane or silicone resin, the silane-modified epoxy resin of the present invention has higher storage and use stability.

[0090] In summary, through the technical scheme of the present invention, the silane-modified epoxy resin can effectively improve the performance of the metal pretreatment agent, so that it has higher storage stability resistant to complex environments (such as moisture and heat resistance, bacteria resistance, oil resistance, hydrolysis resistance, etc.); the silane-modified epoxy resin is used in emission-free coating, which has better use stability, can ensure that the pre-treatment process of coating meets the long-term stable water-free washing requirements, significantly improves the adhesion and salt spray resistance of the coating product, and has broad application prospects.

[0091] Finally, it should be noted that the above-described embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A silane-modified epoxy resin, characterized in that: In parts by weight: comprising 50-75 parts by weight of acrylic modified epoxy resin, 5-8 parts by weight of silane coupling agent, 5-7 parts by weight of neutralizing agent and 20-30 parts by weight of solvent; The molecular weight of the silane-modified epoxy resin is 15,000-20,000 and the pH value is 7.5-8.

5.

2. A silane-modified epoxy resin according to claim 1, characterized in that: The preparation method of silane-modified epoxy resin is as follows: S1: Add acrylic modified epoxy resin into a clean reactor and stir, heat to 60-80°C, add silane coupling agent, react for 2-3h to obtain reactant 1; S2: Cooling the reactant 1 to 50-60°C, adding a neutralizing agent and reacting for 1-1.5h to obtain reactant 2; S3: Add the solvent to the reactant 2 and stir for 30-60 minutes to obtain a silane-modified epoxy resin.

3. A silane-modified epoxy resin according to claim 2, characterized in that: The silane coupling agent is one or more of propyl silane, epoxy silane, dipropyl silane and amino silane; The neutralizing agent is dimethylethanolamine; The solvent is one or more of dimethylol butyl ether, propylene glycol methyl ether acetate and ethylene glycol resin butyl ether; The acid value of reactant 1 is less than or equal to 10.

4. A silane-modified epoxy resin according to claim 1, characterized in that: The acrylic acid modified epoxy resin comprises 35-55 parts by weight of oleic acid modified epoxy resin, 0.01-0.05 parts by weight of an initiator and 15-20 parts by weight of an acrylic acid monomer.

5. A silane-modified epoxy resin according to claim 4, characterized in that: The preparation method of acrylic acid modified epoxy resin is as follows: Put oleic acid modified epoxy resin and initiator into a clean reaction kettle and stir, heat to 140-160°C, add acrylic acid monomer, react at 140-160°C for 2-4h to obtain acrylic acid modified epoxy resin.

6. A silane-modified epoxy resin according to claim 4, characterized in that: The acid value of the acrylic modified epoxy resin is less than or equal to 20; The acrylic monomer is one or more of acrylic acid, methyl acrylate, isobutyl acrylate, methyl methacrylate, isobornyl acrylate and hydroxyethyl acrylate; The initiator is one or more of peroxide, oxide and phosphorus pentoxide.

7. A silane-modified epoxy resin according to claim 4, characterized in that: The oleic acid-modified epoxy resin comprises 20-30 parts by weight of bisphenol A epoxy resin, 0.01-0.05 parts by weight of a catalyst and 15-25 parts by weight of oleic acid.

8. A silane-modified epoxy resin according to claim 7, characterized in that: The preparation method of oleic acid modified epoxy resin is as follows: Add bisphenol A epoxy resin and catalyst into a clean reactor and stir, heat to 185-230°C, add oleic acid, and carry out esterification reaction at 185-230°C for 6-8h to obtain oleic acid-modified epoxy resin.

9. A silane-modified epoxy resin according to claim 7, characterized in that: The acid value of the oleic acid modified epoxy resin is less than or equal to 20; The bisphenol A type epoxy resin is one or both of E-03 and E-51; The catalyst is one or more of peroxide, oxide and phosphorus pentoxide; The oleic acid is one or more of dehydrated ricinoleic acid, linoleic acid, periodoleic acid and eleostearic acid.

10. Application of a silane-modified epoxy resin in emission-free coating, characterized in that: The silane-modified epoxy resin described in any one of claims 1 to 9 is used to prepare an emission-free pretreatment agent for use in emission-free coating.

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