Wet-on-wet epoxy primer and preparation method thereof

Abstract

The invention relates to the technical field of primers, in particular to a wet-on-wet epoxy primer and a preparation method thereof.The single-component epoxy primer is prepared from epoxy resin, a polymeric dispersant, superfine barium sulfate, superfine talcum powder, carbon black, corrosion-resistant auxiliary xylene, cyclohexanone, n-butyl alcohol and propylene glycol monomethyl ether as main raw materials, a curing agent is not added, and the epoxy primer can be applied to wet-on-wet coating. The paint can be directly coated on a metal base material, pretreatment of the metal base material is avoided, meanwhile, the epoxy primer does not need to be dried, all kinds of acrylic amino finish paint can be coated and dried at high temperature after standing for 5-10 minutes after coating, operation time and energy consumption are saved, operation efficiency is improved, gloss and appearance of the finish paint are not affected, overall flexibility is better highlighted, and the paint has good application prospects. And the paint has excellent water resistance, acid and salt mist resistance and chemical resistance, and is suitable for being applied to coating of hardware articles such as bathrooms, doors and locks.

Description

Technical Field

[0001] The present invention relates to the technical field of primer paints, and particularly to a wet-on-wet epoxy primer and a preparation method thereof. Background Art

[0002] Currently, the substrates of sanitary wares, door industries, and locks are mostly metals. Due to long-term exposure to oxygen, water, heat or cold, salt, and other chemicals, environmental damage occurs, resulting in corrosion of the substrates in the environment. At present, the pretreatment protection for such metal substrates is usually carried out by electroplating, electrophoresis, passivating metals, copper / alkali blackening to enhance the anti-corrosion performance of the substrates and then painting; however, such pretreatment protection often leads to the generation of waste water, causing environmental pollution problems and disposal problems.

[0003] Subsequently, epoxy primers emerged, but most epoxy primers are two-component operations. Such epoxy paints need to add curing agents, and the drying time after painting is long, which affects the construction efficiency. Moreover, after adding more curing agents, the pot life is short and they cannot be used for a long time. In addition, the previous epoxy primers either need to be baked dry and then top-coated with finish paints, resulting in a long production baking line, consuming man-hours and energy. When the epoxy primer and the finish paint are wet-on-wet, the intermediate drying time is long, affecting the efficiency; if the drying time is short, it will cause blooming and cracking of the finish paint. Summary of the Invention

[0004] The purpose of the present invention is to provide a wet-on-wet epoxy primer and a preparation method thereof for the deficiencies in the prior art.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A wet-on-wet epoxy primer is composed of the following raw materials in parts by weight:

[0007]

[0008]

[0009] Preferably, the epoxy equivalent (EEW) of the epoxy resin is 360 - 440 g / eq, and the viscosity (25°C) is 15000 - 17500 mPa·s. Within this range, a dense but not overly rigid network structure can be formed, forming coordination bonds with Zn2+ of zinc phosphate in the anti-corrosion auxiliary agent and grafting reactions with the urethane groups of PUD, improving the interlayer bonding force. The epoxy resin used in the present invention is the EPICLON H-304-40 of King Industries and the DIC high molecular weight modified epoxy resin. It has good flexibility, adhesion, recoatability, and impact resistance, can be naturally dried, has a fast surface drying speed, and is suitable for wet-on-wet painting methods.

[0010] Preferably, the polymer dispersant is a polyester dispersant. The polymer dispersant used in the present invention is the D-346 polymer dispersant of Guangzhou Suibo Trading Co., Ltd. It has excellent wetting and dispersing properties, is effective for carbon black, organic / inorganic pigments, has good storage stability for paints, and the block structure provides long-term stability, preventing material flocculation, and is suitable for the rapid curing requirements of the wet-on-wet process.

[0011] Preferably, the anti-corrosion auxiliary agent is composed of the following raw materials in parts by weight:

[0012]

[0013]

[0014] The preparation method of the above anti-corrosion auxiliary agent is as follows:

[0015] First: Pre-disperse the formulated amount of tetra-arm polyethylene glycol diethylenetriamine pentaacetic acid in 50% by weight of deionized water, and stir for 10 - 20 minutes until it becomes a transparent colloidal state to obtain the pretreated 4-Arm-PEG-DTPA colloid;

[0016] Second: Add the formulated amount of propylene glycol methyl ether and the remaining deionized water into the reaction kettle, stir and heat up to 40°C, and sequentially add the pretreated 4-Arm-PEG-DTPA colloid and the formulated amount of benzotriazole, maintain the temperature at 40 ± 2°C, and stir for 30 - 60 minutes;

[0017] Third: Slowly add the formulated amount of zinc phosphate and sodium molybdate into the reaction kettle, stir and disperse for 60 - 90 min, then cool down to 30°C, add the formulated amount of waterborne polyurethane dispersion, triethanolamine, and polyether-modified polysiloxane, and stir for 30 - 60 minutes to obtain the anti-corrosion auxiliary agent.

[0018] Preferably, the MW of tetra-arm polyethylene glycol diethylenetriamine pentaacetic acid is 10,000.

[0019] Preferably, the ultrafine barium sulfate is 5000-mesh barium sulfate powder.

[0020] Preferably, the ultrafine talc powder is 5000-mesh barium sulfate powder.

[0021] A preparation method of an epoxy primer that can be used for wet-on-wet, which includes the following technological steps:

[0022] Step (1): Mix epoxy resin with xylene and cyclohexanone, and stir for 10 - 15 min;

[0023] Step (2): Add the polymer dispersant while stirring, and stir for 10 - 15 min;

[0024] In step (3), carbon black is added while stirring, stirred and dispersed for 50 - 70 min, and ground to a fineness of less than 10 μm;

[0025] In step (4), ultrafine barium sulfate and ultrafine talc powder are added in sequence while stirring, and stirred and dispersed for 50 - 70 min;

[0026] In step (5), n-butanol, propylene glycol methyl ether and an anti-corrosion additive are added in sequence while stirring, and mixed for 15 - 20 min to obtain a wet-on-wet epoxy primer.

[0027] Preferably, the stirring speed in steps (1), (2) and (5) is 500 - 700 revolutions per minute, and the stirring speed in steps (3) and (4) is 900 - 1100 revolutions per minute.

[0028] The anti-corrosion additive of the present invention contains a chelating polymer. When coated on the metal surface in a metal coating, it can form a dense passivator, effectively prevent flash rust and delay the occurrence of rust, and at the same time has good corrosion inhibition performance. Specifically, tetra-armed polyethylene glycol diethylenetriamine pentaacetic acid in the anti-corrosion additive has good water solubility, extremely strong affinity for metal ions such as copper and iron, forms a stable complex with metal ions, prevents oxidation reactions, and also enhances the flexibility of the coating film through the polyethylene glycol chain segment, adapting to the wet-on-wet process. The passivator benzotriazole can form a dense passivation film, effectively inhibiting the oxidation reaction on the copper surface; the corrosion inhibitor uses a combination of zinc phosphate and sodium molybdate to achieve the synergy of anodic passivation and cathodic inhibition, further slowing down the corrosion process; the aqueous polyurethane dispersion PUD improves the continuity and adhesion of the coating film, has good compatibility with epoxy resin, and avoids interface peeling during wet-on-wet coating; the solvent system uses propylene glycol methyl ether and deionized water to ensure rapid volatilization in the solvent-based system to form an initial film, without affecting the rapid surface drying after coating; the stabilizer triethanolamine adjusts the pH and system stability, and the surfactant polyether-modified polysiloxane is used for wetting, dispersing and anti-cratering.

[0029] When the anti-corrosion additive of the present invention is used in combination with the epoxy resin of the present invention, the high molecular weight structure of the epoxy resin (EPICLON H-304-40) forms a rigid three-dimensional network, which forms an interpenetrating network with the flexible segments of the waterborne polyurethane dispersion (PUD) and tetra-armed polyethylene glycol diethylenetriamine pentaacetic acid in the anti-corrosion additive. This structure with both rigidity and flexibility maintains sufficient mechanical support during wet recoating, avoiding interlayer deformation caused by the penetration of the topcoat. Tetra-armed polyethylene glycol diethylenetriamine pentaacetic acid forms hydrogen bonding with the hydroxyl groups of the epoxy resin through the terminal carboxylic acid groups, improving the interfacial wettability and forming chemical "anchoring points" between the uncured primer and the topcoat. In the solvent system of the present invention, xylene / cyclohexanone / propylene glycol methyl ether in the anti-corrosion additive forms a gradient volatilization mechanism: low-boiling xylene (139 °C) volatilizes preferentially to form an initial film structure; medium-boiling cyclohexanone (155 °C) maintains the coating open time; high-boiling propylene glycol methyl ether (120 °C) extends the interfacial activation period in the additive. This system ensures a wet-on-wet operation window of 45 - 60 minutes and a more than 30% increase in interlayer adhesion. Benzotriazole in the anti-corrosion additive of the present invention preferentially adsorbs on the metal active sites through N→Fe coordination bonds, forming a spatial-chemical double protection with the barrier effect of the epoxy resin and improving the acidic salt spray performance.

[0030] The ultrafine barium sulfate is 5000-mesh barium sulfate powder, which has better compatibility with the resin, small particle size, is easy to disperse evenly, and has excellent rust and corrosion prevention performance.

[0031] The ultrafine talc powder is 5000-mesh barium sulfate powder, which has better compatibility with the resin, small particle size, is easy to disperse evenly, improves hydrolysis resistance, filling property, and enhances the adhesion in the multi-powder state.

[0032] The carbon black is general common black carbon black powder, which is easy to disperse and grind.

[0033] The beneficial effects of the present invention: The present invention uses epoxy resin, high molecular dispersant, ultrafine barium sulfate, ultrafine talc powder, carbon black, anti-corrosion additives xylene, cyclohexanone, n-butanol, and propylene glycol methyl ether as the main raw materials to prepare a one-component epoxy primer. It does not require a curing agent and can be directly coated on the metal substrate, eliminating the pretreatment of the metal substrate. At the same time, the epoxy primer does not need to be dried. After coating, it only needs to be left standing for 5 - 10 minutes, and then various types of acrylic amino topcoats can be applied and baked together at high temperature, saving operation time and energy consumption, improving operation efficiency, and not affecting the gloss and appearance of the topcoat. Moreover, it better highlights the overall flexibility, impact resistance, and has excellent water resistance, acid salt spray resistance, and chemical resistance, making it suitable for the coating of hardware products such as bathrooms, door industries, and locks. Detailed Embodiments

[0034] The present invention will be further described in conjunction with the following embodiments.

[0035] Example 1

[0036] An epoxy primer that can be used for wet-on-wet consists of the following raw materials in parts by weight:

[0037]

[0038]

[0039] Among them, the epoxy equivalent (EEW) of the epoxy resin is 360 - 440 g / eq, and the viscosity (25 °C) is 15000 - 17500 mPa·s. The epoxy resin used in the present invention is the EPICLON H-304-40 model of King Industries and the DIC high molecular weight modified epoxy resin.

[0040] Among them, the high molecular dispersant is a polyester dispersant. The high molecular dispersant used in the present invention is the D-346 high molecular dispersant of Guangzhou Suibo Trading Co., Ltd.

[0041] Among them, the anti-corrosion aid consists of the following raw materials in parts by weight:

[0042]

[0043] The preparation method of the above anti-corrosion aid is as follows:

[0044] First: Pre-disperse the formulated amount of tetra-arm polyethylene glycol diethylenetriamine pentaacetic acid in 50% by weight of deionized water and stir for 10 minutes until it becomes a transparent colloidal state to obtain the pretreated 4-Arm-PEG-DTPA colloid;

[0045] Second: Add the formulated amount of propylene glycol methyl ether and the remaining deionized water to the reaction kettle, stir and heat up to 40 °C, and sequentially add the pretreated 4-Arm-PEG-DTPA colloid and the formulated amount of benzotriazole, maintain the temperature at 40 ± 2 °C, and stir for 30 minutes;

[0046] Third: Slowly add the formulated amounts of zinc phosphate and sodium molybdate to the reaction kettle, stir and disperse for 60 min, then cool down to 30 °C, add the formulated amounts of aqueous polyurethane dispersion, triethanolamine, and polyether-modified polysiloxane, and stir for 30 minutes to obtain the anti-corrosion aid.

[0047] Among them, the MW of tetra-arm polyethylene glycol diethylenetriamine pentaacetic acid is 10000.

[0048] Among them, the ultrafine barium sulfate is 5000-mesh barium sulfate powder.

[0049] Among them, the ultrafine talc powder is 5000-mesh barium sulfate powder.

[0050] A preparation method of an epoxy primer that can be used for wet-on-wet coating, which comprises the following technological steps:

[0051] Step (1): Mix epoxy resin with xylene and cyclohexanone, and stir for 10 minutes;

[0052] Step (2): Add a high molecular dispersant while stirring, and stir for 10 minutes;

[0053] Step (3): Add carbon black while stirring, stir and disperse for 50 minutes, and grind to a fineness of less than 10 μm;

[0054] Step (4): Add ultrafine barium sulfate and ultrafine talc powder in sequence while stirring, and stir and disperse for 50 minutes;

[0055] Step (5): Add n-butanol, propylene glycol methyl ether and an anti-corrosion additive in sequence while stirring, and mix for 15 minutes to obtain an epoxy primer that can be used for wet-on-wet coating.

[0056] Among them, the stirring speed in steps (1), (2) and (5) is 500 revolutions per minute, and the stirring speed in steps (3) and (4) is 900 revolutions per minute.

[0057] Example 2

[0058] An epoxy primer that can be used for wet-on-wet coating, which is composed of the following raw materials in parts by weight:

[0059]

[0060]

[0061] Among them, the epoxy equivalent (EEW) of the epoxy resin is 360 - 440 g / eq, and the viscosity (25 °C) is 15000 - 17500 mPa·s. The epoxy resin used in the present invention is the EPICLON H-304-40 type epoxy resin with the brand of DIC high molecular weight modified epoxy resin produced by King Industries.

[0062] Among them, the high molecular dispersant is a polyester dispersant. The high molecular dispersant used in the present invention is the D-346 high molecular dispersant produced by Guangzhou Suibo Trading Co., Ltd.

[0063] Among them, the anti-corrosion additive is composed of the following raw materials in parts by weight:

[0064]

[0065] The preparation method of the above anti-corrosion additive is as follows:

[0066] First: Pre-disperse the formulated amount of tetra-arm polyethylene glycol diethylenetriamine pentaacetic acid in 50% by weight of deionized water, and stir for 15 minutes until it becomes a transparent colloidal state to obtain the pretreated 4-Arm-PEG-DTPA colloid;

[0067] Second: Add the formulated amount of propylene glycol methyl ether and the remaining deionized water into the reaction kettle, stir and heat up to 40 °C, and sequentially add the pretreated 4-Arm-PEG-DTPA colloid and the formulated amount of benzotriazole, maintain the temperature at 40 ± 2 °C, and stir for 45 minutes;

[0068] Third: Slowly add the formulated amount of zinc phosphate and sodium molybdate into the reaction kettle, stir and disperse for 77 min, then cool down to 30 °C, add the formulated amount of aqueous polyurethane dispersion, triethanolamine, and polyether-modified polysiloxane, and stir for 45 minutes to obtain the anti-corrosion additive.

[0069] Among them, the MW of tetra-arm polyethylene glycol diethylenetriamine pentaacetic acid is 10,000.

[0070] Among them, the ultrafine barium sulfate is 5000-mesh barium sulfate powder.

[0071] Among them, the ultrafine talc powder is 5000-mesh barium sulfate powder.

[0072] A preparation method of an epoxy primer that can be used for wet-on-wet application, which includes the following process steps:

[0073] Step (1): Mix epoxy resin with xylene and cyclohexanone, and stir for 12 min;

[0074] Step (2): Add the polymer dispersant while stirring, and stir for 12 min;

[0075] Step (3): Add carbon black while stirring, stir and disperse for 60 min, and grind to a fineness of less than 10 μm;

[0076] Step (4): Sequentially add ultrafine barium sulfate and ultrafine talc powder while stirring, and stir and disperse for 60 min;

[0077] Step (5): Sequentially add n-butanol, propylene glycol methyl ether and the anti-corrosion additive while stirring, and mix for 18 min to obtain an epoxy primer that can be used for wet-on-wet application.

[0078] Among them, the stirring speed in steps (1), (2) and (5) is 600 revolutions per minute, and the stirring speed in steps (3) and (4) is 1000 revolutions per minute.

[0079] Example 3

[0080] An epoxy primer that can be used for wet-on-wet application, which is composed of the following raw materials in parts by weight:

[0081]

[0082]

[0083] Among them, the epoxy equivalent weight (EEW) of the epoxy resin is 360 - 440 g / eq, and the viscosity (25°C) is 15000 - 17500 mPa·s. The epoxy resin used in the present invention is the EPICLON H-304-40 epoxy resin of King Industries, with the brand of DIC high molecular weight modified epoxy resin.

[0084] Among them, the high molecular dispersant is a polyester dispersant. The high molecular dispersant used in the present invention is the D-346 high molecular dispersant of Guangzhou Suibo Trading Co., Ltd.

[0085] Among them, the anti-corrosion auxiliary agent is composed of the following raw materials in parts by weight:

[0086]

[0087] The preparation method of the above anti-corrosion auxiliary agent is as follows:

[0088] First: Pre-disperse the formulated amount of tetra-arm polyethylene glycol diethylenetriamine pentaacetic acid in 50% by weight of deionized water, and stir for 20 minutes until it becomes a transparent colloid state to obtain the pretreated 4-Arm-PEG-DTPA colloid;

[0089] Second: Add the formulated amount of propylene glycol methyl ether and the remaining deionized water into the reaction kettle, stir and heat up to 40°C, and sequentially add the pretreated 4-Arm-PEG-DTPA colloid and the formulated amount of benzotriazole, maintain the temperature at 40 ± 2°C, and stir for 60 minutes;

[0090] Third: Slowly add the formulated amount of zinc phosphate and sodium molybdate into the reaction kettle, stir and disperse for 90 min, then cool down to 30°C, add the formulated amount of waterborne polyurethane dispersion, triethanolamine, and polyether-modified polysiloxane, and stir for 60 minutes to obtain the anti-corrosion auxiliary agent.

[0091] Among them, the MW of tetra-arm polyethylene glycol diethylenetriamine pentaacetic acid is 10000.

[0092] Among them, the ultrafine barium sulfate is 5000-mesh barium sulfate powder.

[0093] Among them, the ultrafine talc powder is 5000-mesh barium sulfate powder.

[0094] A preparation method of a wet-on-wet epoxy primer, which includes the following process steps:

[0095] Step (1): Mix the epoxy resin with xylene and cyclohexanone, and stir for 15 min;

[0096] In step (2), a polymer dispersant is added while stirring, and the mixture is stirred and mixed for 15 min.

[0097] In step (3), carbon black is added while stirring, stirred and dispersed for 70 min, and ground to a fineness of less than 10 μm.

[0098] In step (4), ultrafine barium sulfate and ultrafine talc powder are added in sequence while stirring, and stirred and dispersed for 70 min.

[0099] In step (5), n-butanol, propylene glycol methyl ether and an anti-corrosion additive are added in sequence while stirring, and mixed for 20 min to obtain a wet-on-wet epoxy primer.

[0100] Among them, the stirring speed in steps (1), (2) and (5) is 700 revolutions per minute, and the stirring speed in steps (3) and (4) is 1100 revolutions per minute.

[0101] Comparative Example 1

[0102] The difference between Comparative Example 1 and Example 2 is that: the epoxy resin used in this example is the commercially available Phoenix brand E44 epoxy resin.

[0103] Comparative Example 2

[0104] The difference between Comparative Example 2 and Example 2 is that: the anti-corrosion additive used in this example is DX506 of commercially available Dexu New Materials (Guangzhou) Co., Ltd.

[0105] The experimental data are shown in Table 1.

[0106] Table 1

[0107]

[0108]

[0109] It can be seen from the above table that in Examples 1-3 of the present invention, through the synergistic effect of epoxy resin and anti-corrosion additive, the comprehensive performance is the best. In Comparative Example 1, the epoxy resin was replaced, and in Comparative Example 2, the anti-corrosion additive was replaced. The main reason is that the epoxy resin and the anti-corrosion additive cannot cooperate with each other, especially cannot form an interpenetrating network, and cannot maintain sufficient mechanical support during wet recoating, resulting in poor performance due to the penetration of the topcoat.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. An epoxy primer that can be used for wet-on-wet applications, characterized in that: It is composed of the following raw materials in parts by weight:

2. The wet-on-wet epoxy primer according to claim 1, characterized in that: The epoxy equivalent of the epoxy resin is 360-440 g / eq, and the viscosity (25° C.) is 15000-17500 mPa·s.

3. The wet-on-wet epoxy primer according to claim 1, characterized in that: The polymer dispersant is a polyester dispersant.

4. The method for preparing a wet-on-wet epoxy primer according to claim 1, characterized in that: The antiseptic additive is composed of the following raw materials in parts by weight: The preparation method of the above-mentioned antiseptic additive is: First, pre-disperse the formulated amount of four-arm polyethylene glycol diethyltriamine pentaacetic acid in 50% by weight of deionized water, and stir for 10-20 minutes until a transparent colloidal state is obtained to obtain a pre-treated 4-Arm-PEG-DTPA colloid; Second: add the formula amount of propylene glycol methyl ether and the remaining deionized water to the reactor, stir and heat to 40°C, add the pretreated 4-Arm-PEG-DTPA colloid and the formula amount of benzotriazole in sequence, maintain the temperature at 40±2°C, and stir for 30-60 minutes; Third: slowly add the formulated amount of zinc phosphate and sodium molybdate into the reactor, stir and disperse for 60-90 minutes, cool to 30°C, add the formulated amount of aqueous polyurethane dispersion, triethanolamine, and polyether modified polysiloxane, stir for 30-60 minutes, and obtain the anticorrosion additive.

5. The wet-on-wet epoxy primer according to claim 4, characterized in that: The MW of the four-arm polyethylene glycol diethyltriamine pentaacetic acid is 10,000.

6. The wet-on-wet epoxy primer according to claim 1, characterized in that: The ultrafine barium sulfate is 5000 mesh barium sulfate powder.

7. The wet-on-wet epoxy primer according to claim 1, characterized in that: The ultrafine talcum powder is 5000 mesh barium sulfate powder.

8. The method for preparing a wet-on-wet epoxy primer as claimed in claim 1, characterized in that: It includes the following process steps: Step (1) mixing epoxy resin with xylene and cyclohexanone, and stirring for 10-15 minutes; Step (2) adding a polymer dispersant while stirring, and stirring and mixing for 10-15 minutes; Step (3) adding carbon black while stirring, stirring and dispersing for 50-70 minutes, and grinding to a fineness of less than 10 μm; step (4) adding ultrafine barium sulfate and ultrafine talcum powder in sequence while stirring, stirring and dispersing for 50-70 minutes; step (5) adding n-butanol, propylene glycol methyl ether and an antiseptic additive in sequence while stirring, mixing for 15-20 minutes, to obtain an epoxy primer that can be used for wet-on-wet coating.

9. The method for preparing a wet-on-wet epoxy primer according to claim 8, characterized in that: The stirring speed in steps (1), (2) and (5) is 500-700 rpm, and the stirring speed in steps (3) and (4) is 900-1100 rpm.

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