Adhesive for use in dip coating and use thereof

Abstract

The application relates to the technical field of adhesives, and discloses an adhesive used by a dip coating method and application of the adhesive, wherein the adhesive raw materials are as follows: 5-15% of high-elasticity polymer, 1-13% of cross-linking resin, 5-10% of an additive, 1-10% of alkaline inorganic substance, 2-12% of filler, and the rest of solvent, with the total amount being 100%. The number average molecular weight Mn of the high-elasticity polymer is 10000-120000, the softening point of the cross-linking resin is 80-130 DEG C, and the average diameter of particles in the adhesive is 5-80 mu m. The prepared adhesive has excellent bonding strength, appropriate fluidity and stability, can be coated on a metal surface by the dip coating method, and is used for bonding between metals and rubber.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of adhesives, C09J115 / 00, and particularly relates to an adhesive used by dip coating method and application thereof. BACKGROUND

[0002] Bonding rubber and metal can obtain composite systems with different configurations and characteristics, and such systems have been widely used in industry, such as flexible joints of engines, auxiliary frame bushings of automobiles, hydraulic bushings, crankshaft torsional dampers, power absorbers, support cushion pads of bridges, and the like. Rubber and metal are two different materials with great differences in chemical structure and mechanical properties, so it is difficult to bond them with high strength, and therefore it is always a hot research topic to develop adhesives with high performance and wide application range.

[0003] Dip coating is a coating method with high efficiency, labor saving, and good film forming state, and has been adopted by more and more enterprises, and the adaptability of adhesives to the dip coating process is a key to coating quality. Most adhesives on the market need to be diluted with organic solvents before use, but the use of such organic solvents will bring more VOC emissions, which is not friendly to the environment, and will also make the sagging of the adhesive on the metal surface more serious, resulting in a large difference in film thickness gradient between the upper and lower parts of the adhesive layer, which is extremely unfavorable to the subsequent bonding of metal and rubber. Therefore, in order to solve the existing problems, it is necessary to improve the dip coating performance of traditional adhesives to optimize their use experience.

[0004] In USP4537815, in order to enhance the bonding effect between metal and rubber, a silane coupling agent is used as a surface treatment agent to treat the metal surface, but such a substance is unstable and can be easily hydrolyzed, and must be treated in a water-free or low-moisture environment. The treated metal must be bonded immediately, otherwise the bonding effect will be adversely affected.

[0005] CN101531881B discloses a fluorosilicone rubber and metal bonding adhesive and a preparation method thereof, but such an adhesive has a relatively narrow application range and is only suitable for bonding between fluorosilicone rubber and metal, and the bonding strength still needs to be improved. SUMMARY

[0006] In order to solve the above technical problems, the present application provides an adhesive used by dip coating method and application thereof.

[0007] Firstly, the present application provides an adhesive used by dip coating method, and the raw materials of the adhesive are as follows: high-elasticity polymer 5%-15%, cross-linking resin 1%-13%, auxiliary agent 5%-10%, alkaline inorganic substance 1%-10%, filler 2%-12%, and solvent to make up the rest to 100% of the total amount, based on the total weight of the adhesive.

[0008] The adhesive strength and viscosity are improved by the intermolecular forces and molecular chain entanglement between the highly elastic polymer and the cross-linked resin. Alkaline inorganic substances are used to absorb acidic substances in the raw materials and improve the stability of the adhesive. However, if the amount of alkaline inorganic substances is too large, they are easy to precipitate in the adhesive and cause discoloration, which affects the adhesive performance. If the filler is too small, the adhesive viscosity is not large enough. The coating amount after the first dip coating of the metal is too small and the coating thickness does not meet the requirements. Second or multiple dip coatings are required. However, if the amount of filler is too large, the film-forming performance of the adhesive layer deteriorates and it is easy to crack and powder off.

[0009] Further, based on the total weight of the adhesive, the adhesive raw materials are: 5%-15% high elastic polymer, 1%-9% crosslinking resin, 5%-10% additives, 2%-10% alkaline inorganic substances, 5%-12% filler, and solvent supplemented to make up the total amount to 100%.

[0010] Furthermore, the highly elastic polymer is one or a combination of several of the following: ethylene propylene rubber, fluororubber, chlorinated polyethylene rubber, chlorinated polyether rubber, chlorosulfonated polyethylene rubber, hydrogenated carboxylated nitrile butadiene rubber, chlorinated polyether nitrile butadiene rubber, hydrogenated nitrile butadiene rubber, styrene-butadiene rubber, polyurethane rubber, acrylate rubber, natural rubber, isoprene rubber, and silicone rubber.

[0011] Furthermore, the highly elastic polymer is one or a combination of several of the following: silicone rubber, chlorinated polyethylene rubber, chlorinated polyether rubber, chlorosulfonated polyethylene rubber, hydrogenated carboxylated nitrile rubber, and chlorinated polyether nitrile rubber.

[0012] Furthermore, the highly elastic polymer is one or a combination of several of chlorosulfonated polyethylene rubber, chlorinated polyether nitrile rubber, and chlorinated polyethylene rubber.

[0013] Furthermore, the number-average molecular weight Mn of the highly elastic polymer is 10,000-120,000.

[0014] Furthermore, the number average molecular weight Mn of the high elastic polymer is 20,000-80,000. By limiting the molecular weight of the high elastic polymer, the degree of cross-linking between the polymer and the resin can be reasonably controlled, thereby further controlling the viscosity of the adhesive. The adhesive prepared by the high elastic polymer at this number average molecular weight does not need to be diluted during use, and the adhesive layer can be uniformly coated by immersing the metal for a certain period of time.

[0015] Furthermore, the number-average molecular weight Mn of the highly elastic polymer is 20,000-60,000.

[0016] In a preferred embodiment, the adhesive prepared has the best adhesion and flowability when the number average molecular weight Mn of the high-elasticity polymer is 50,000. It is presumed that when the number average molecular weight of the high-elasticity polymer is too high, the degree of cross-linking with the resin becomes small, the concentration of the adhesive decreases, and after metal dip-coating, sagging occurs easily, resulting in uneven thickness of the adhesive layer coated on the metal surface. When the number average molecular weight of the high-elasticity polymer is too low, the molecular interaction between the high-elasticity polymer and the resin becomes strong, the degree of mobility of the molecular chain decreases, the viscosity of the adhesive becomes too high, and after metal dip-coating, the adhesive does not transfer easily, and it is necessary to add some solvent to dilute the adhesive by stirring, but this increases the manufacturing process and generates more VOC emissions.

[0017] Further, the cross-linking resin is one or more of an epoxy resin, a phenol resin, a silicone resin, a polyurethane resin, and a fluorine resin.

[0018] Further, the cross-linking resin is one or more of a polyphenol glycidyl ether epoxy resin, an aliphatic glycidyl ether epoxy resin, a diphenol propane glycidyl ether, a rosin-modified phenol resin, a butanol etherified phenol resin, an oil-soluble phenol resin, an alcohol-soluble phenol resin, a silicone resin, a polyurethane resin, and a fluorine resin.

[0019] Further, the cross-linking resin is one or more of a polyphenol glycidyl ether epoxy resin, a butanol etherified phenol resin, an oil-soluble phenol resin, an alcohol-soluble phenol resin, and a silicone resin.

[0020] Further, the softening point of the cross-linking resin is 80-130°C. The softening point is defined to better control the adhesion and flowability of the adhesive; when the softening point of the cross-linking resin is too high, the adhesive prepared has a high use temperature, low flowability, and low elasticity, and the adhesion to the adherend is not high, but when the softening point is too low, the viscosity of the adhesive is too low, and after metal dip-coating, the adhesive easily sags, resulting in uneven thickness of the coating layer and reduced adhesion.

[0021] Further, the softening point of the cross-linking resin is 80-120°C.

[0022] Further, the softening point of the cross-linking resin is 80-100°C.

[0023] Further, the adjuvant is an organic peroxide or a nitro compound.

[0024] Further, the organic peroxide is one of dibenzoyl peroxide, dicumyl peroxide, and n-butyl-4,4-di(tert-butylperoxy)valerate.

[0025] Further, the nitro compound is an aliphatic nitro compound or a nitro aromatic compound.

[0026] Further, the nitro compound is one or a combination of several of p-dibenzoyl benzoquinone dioxime, N-nitrosomethylethylamine, p-dinitrosobenzene, N-nitrosodi-n-butylamine.

[0027] Further, the basic inorganic substance is one or a combination of several of zinc oxide, aluminum oxide, magnesium oxide, calcium oxide, magnesium-aluminum hydrotalcite.

[0028] Further, the filler is inert pigment and inert bulk filler, including but not limited to calcium carbonate, carbon black, silicon dioxide, aluminum oxide, ceramic powder, kaolin, bentonite.

[0029] Further, the mass ratio of inert bulk filler to inert pigment is (10-1):1.

[0030] Further, the solvent is one or a combination of several of ester solvent (such as ethyl acetate, butyl acetate), benzene solvent (such as toluene, xylene, ethyl benzene, phenol), ketone solvent (such as acetone, butanone, cyclohexanone), chlorinated organic solvent (such as dichloromethane, tetrachloroethane), solvent oil (such as #120 solvent oil).

[0031] The preparation method of the adhesive is to mix the adhesive raw material, dispersion medium and ball milling medium, and then grind.

[0032] Further, the dispersion medium is one or a combination of several of methyl isobutyl ketone, butanone, acetone, toluene or xylene.

[0033] Further, the ball milling medium is one of hard alloy microspheres, hard ceramic, zirconium oxide, agate.

[0034] Further, the weight ratio of dispersion medium to adhesive raw material is (1-3):1.

[0035] Further, the ratio of the total weight of dispersion medium and adhesive raw material to the weight of ball milling medium is 1:(3-7).

[0036] Further, the average particle diameter of the adhesive after grinding is 5-80 μm.

[0037] Further, the average particle diameter of the adhesive after grinding is 5-50 μm.

[0038] In a preferred embodiment, the average particle diameter of the adhesive is 15 μm; it is speculated that the average particle diameter of the adhesive is too large, the viscosity of the adhesive is reduced and the contact area between the adhesive and the metal is reduced, the bonding performance is reduced, and after long storage, sedimentation may occur; for the prepared adhesive layer, the increase of the distance between the particles will lead to the entry of part of the air, and the bonding stability of the adhesive layer and the adherend is also significantly reduced.

[0039] Secondly, the application further provides the application of the adhesive, the adhesive can be attached to the metal surface to be bonded by dip coating method, and is used for bonding between metal and rubber.

[0040] Further, the adhesive can be used for single coating, or can be used for double coating, when used as a top coating of double coating, the adhesive can be coated after brushing the primer adhesive on the surface of the metal base material.

[0041] Beneficial effects:

[0042] 1. By controlling the content of each component of the raw material and the preparation process, the adhesive of the application has excellent bonding performance and suitable flow performance, can be applied to the metal surface by dip coating method, and can better realize the bonding between metal and rubber.

[0043] 2. The adhesive of the application controls the number average molecular weight of the high-elasticity polymer to better control the intermolecular interaction and molecular chain entanglement of the crosslinking resin, so that the adhesive of the application has a suitable viscosity range (300-500 cps, rotary viscometer, 25 DEG C), is convenient for metal dip coating, and has a uniform thickness of the adhesive layer; the softening point of the crosslinking resin is specified, the energy consumption of the production process is reduced, and the bonding performance of the prepared adhesive is more stable.

[0044] 3. The adhesive of the application has high solid content and suitable flowability, and the specified adhesive layer thickness can be achieved by one-time dip coating, which optimizes the dip coating operation process.

[0045] 4. The adhesive of the application can obtain excellent flowability without adding additional organic solvents during use, has high solid content, has low VOC emission, meets the new standard GB 33372-2020 Limit of Volatile Organic Compounds in Adhesives, and is environmentally friendly. DETAILED DESCRIPTION

[0046] Embodiment

[0047] Embodiment 1

[0048] An adhesive used by dip coating method, according to the total weight of the adhesive, the raw material of the adhesive is: high-elasticity polymer 8%, crosslinking resin 4%, additive 6%, alkaline inorganic matter 5%, filler 8%, solvent supplementing the balance to the total amount of 100%.

[0049] The high-elasticity polymer is chlorosulfonated polyethylene rubber (Shanduo Chemical Co., Ltd., model: M4035), and the number average molecular weight Mn thereof is 50000.

[0050] The cross-linking resin is phenol-formaldehyde resin (Jinan Shengquan Group Co., Ltd., model: RT4010), the auxiliary agent is p-dinitrosobenzene, the alkaline inorganic substance is magnesium oxide, the filler is calcium carbonate, and the solvent is dimethylbenzene.

[0051] The preparation method of the adhesive is as follows: the adhesive raw material, the dispersion medium, and the ball milling medium are mixed, and then a horizontal sand mill is used for grinding; the weight ratio of the dispersion medium to the adhesive raw material is 2:1; the ratio of the total weight of the dispersion medium and the adhesive raw material to the weight of the ball milling medium is 1:5, the grinding temperature is controlled to be not higher than 50 ℃, and the average diameter of particles in the adhesive after grinding is 15 μm.

[0052] Example 2

[0053] An adhesive used by the dip coating method, according to the total weight of the adhesive, the adhesive raw material is: high-elasticity polymer 5%, cross-linking resin 13%, auxiliary agent 5%, alkaline inorganic substance 2%, filler 12%, and solvent supplementing the rest to the total amount of 100%.

[0054] The high-elasticity polymer is chlorosulfonated polyethylene rubber (Shandao Chemical Co., Ltd., model: M5035), and the number average molecular weight Mn thereof is 80000.

[0055] The cross-linking resin is phenol-formaldehyde resin (Jinan Shengquan Group Co., Ltd., model: RT4010), the auxiliary agent is p-dinitrosobenzene, the alkaline inorganic substance is magnesium oxide, the filler is calcium carbonate, and the solvent is dimethylbenzene.

[0056] The preparation method of the adhesive is as follows: the adhesive raw material, the dispersion medium, and the ball milling medium are mixed, and then a horizontal sand mill is used for grinding; the weight ratio of the dispersion medium to the adhesive raw material is 2:1; the ratio of the total weight of the dispersion medium and the adhesive raw material to the weight of the ball milling medium is 1:5, the grinding temperature is controlled to be not higher than 50 ℃, and the average diameter of particles in the adhesive after grinding is 15 μm.

[0057] Example 3

[0058] An adhesive used by the dip coating method, according to the total weight of the adhesive, the adhesive raw material is: high-elasticity polymer 15%, cross-linking resin 2%, auxiliary agent 10%, alkaline inorganic substance 8%, filler 2%, and solvent supplementing the rest to the total amount of 100%.

[0059] The high-elasticity polymer is chlorosulfonated polyethylene rubber (Shandao Chemical Co., Ltd., model: M3525), and the number average molecular weight Mn thereof is 30000.

[0060] The cross-linking resin is phenol-formaldehyde resin (Jinan Shengquan Group Co., Ltd., model: RT4010), the auxiliary agent is p-dinitrosobenzene, the alkaline inorganic substance is magnesium oxide, the filler is calcium carbonate and carbon black, the mass ratio of the two is 4:1, and the solvent is dimethylbenzene.

[0061] The preparation method of the adhesive is that the adhesive raw material, the dispersion medium and the ball milling medium are mixed and then ground by using a horizontal sand mill; the weight ratio of the dispersion medium to the adhesive raw material is 3:1; the ratio of the total weight of the dispersion medium and the adhesive raw material to the weight of the ball milling medium is 1:7, the grinding temperature is controlled to be not higher than 50 ℃, and the average particle diameter of the adhesive after grinding is 5 μm.

[0062] Comparative Example 1

[0063] The difference from Example 1 is that the high-elasticity polymer is chlorosulfonated polyethylene rubber (Shandao Chemical Co., Ltd., model: M8035), and the number average molecular weight Mn thereof is 120000.

[0064] Comparative Example 2

[0065] The difference from Example 1 is that the adhesive raw material is: high-elasticity polymer 5%, cross-linking resin 13%, auxiliary agent 5%, alkaline inorganic substance 2%, filler 15%, and solvent supplementing the rest to the total amount of 100%.

[0066] Comparative Example 3

[0067] The difference from Example 1 is that the average particle diameter of the adhesive after grinding is 150 μm.

[0068] Performance test method:

[0069] 1. Glue flow hanging property: the standard metal test piece is sandblasted and cleaned, the metal test piece is directly immersed in the adhesive sample, taken out after about 5 s, completely dried at room temperature, and then the adhesive layer thickness of the upper, middle and bottom of the metal test piece is measured respectively by using a film thickness meter, and the surface state of the dry adhesive film is observed. The adhesive layer thickness difference of the upper and middle of the metal test piece and the dry adhesive film state are shown in Table 1.

[0070] 2. Peel strength: when used as single coating, the adhesive of the example is brushed on the surface of the metal substrate, the dry film thickness of the adhesive is controlled to be 25 μm, then the rubber (natural rubber with A hardness of 60°) is cured with the metal substrate coated with the adhesive at 165 ℃, 8-10 MPa for 8 min, and after the mold is taken out, it is placed at room temperature for 24 hours, and the 90° peel strength is measured according to the standard GB / T 7760-2003, and the test results are shown in Table 1.

[0071] Performance test results:

[0072] Table 1

[0073] Sample No. Dry film state Difference in adhesive layer thickness μm Peeling strength kN / m Example 1 Smooth and flat 2 16.8 Example 2 Smooth and flat 3 16.4 Example 3 Smooth and flat 2 15.9 Comparative Example 1 Smooth, but clearly cracked 6 5.5 Comparative Example 2 Smooth, slightly cracked 3 12.1 Comparative Example 3 Smooth, slightly cracked 5 7.3

Claims

1. An adhesive used by dip coating, characterized in that, The adhesive raw materials, based on the total weight of the adhesive, are: 5%-15% high elastic polymer, 1%-13% crosslinking resin, 5%-10% additives, 1%-10% alkaline inorganic substances, 2%-12% filler, and solvent supplemented to make up the balance to 100% of the total. The high-elasticity polymer is chlorosulfonated polyethylene rubber; the number-average molecular weight Mn of the high-elasticity polymer is 20,000-60,000. The auxiliary agent is a nitro compound; The average particle diameter in the adhesive after grinding is 5-50 μm; The crosslinking resin is one or more of epoxy resin, phenolic resin, silicone resin, polyurethane resin, and fluororesin; The softening point of the crosslinked resin is 80-130℃.

2. The adhesive used by dip coating according to claim 1, characterized in that, The alkaline inorganic substance is one or more of zinc oxide, aluminum oxide, magnesium oxide, calcium oxide, and magnesium aluminum hydrotalcite.

3. The application of an adhesive by dip coating according to any one of claims 1-2, characterized in that, The adhesive is used for bonding between metal and rubber.