Water-based conductive composite coating modified by modified petroleum resin and preparation method of water-based conductive composite coating

Abstract

The invention relates to a water-based conductive coating, which is prepared from the following raw materials: water-based conductive slurry, a water-based resin base material and a water-based auxiliary agent, the water-based conductive paste comprises carbon black, graphite, a wetting dispersant and water. The water-based resin base material comprises water-based resin, plasma modified C9 petroleum resin, a water-based curing agent and water. The plasma modified C9 petroleum resin can be stably dispersed and combined onto the hydroxyl water-based resin to form a good coating film. And uniform conductivity is presented in the plane direction, so that the problems of current aggregation and hot spots caused by non-uniform conductivity are avoided. The water-based conductive coating disclosed by the invention forms a multifunctional coating on metal, and the hydrophobicity and the water resistance are obviously improved compared with those of a common water-based conductive coating.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of water-based paint, and relates to a modified petroleum resin modified water-based conductive composite paint and a preparation method thereof. BACKGROUND

[0002] With the rapid development of electronic devices, electric vehicles and energy storage power stations, the performance and safety of secondary batteries such as alkaline manganese primary batteries and lithium ion batteries are increasingly required. The protective performance of the battery steel shell, which serves as a physical barrier between the internal environment of the battery and the external space, is crucial. To prevent internal micro-short circuits in the battery and resist external environmental corrosion, a layer of conductive paint is often coated on the inner wall of the battery steel shell. Meanwhile, the increasingly stringent environmental protection regulations have promoted the rapid development of water-based paint technology. Currently, most of the water-based conductive paints on the market are prepared by using water-based acrylic resin, water-based polyurethane or their composite system as the film-forming material, and supplemented with conductive fillers (such as graphite, carbon black, conductive graphene, etc.). Although such paints have the advantages of environmental protection and low VOC (volatile organic compounds), they still have a key technical defect when applied to battery steel shells.

[0003] Conventional water-based resins such as water-based acrylic resin and water-based polyurethane contain a large number of hydrophilic groups (such as carboxyl and hydroxyl) in their molecular chains, resulting in a certain degree of hydrophilicity and water absorption of the cured coating film. When such a coating is applied to a battery steel shell, the coating will slowly absorb water from the environment, leading to corrosion of the electrode material, decomposition of the electrolyte, and generation of gas, which causes a series of serious problems such as increased internal pressure of the battery, capacity decay, and shortened cycle life, greatly reducing the storage stability and use safety of the battery. Therefore, it is crucial to develop a water-based paint with excellent conductivity and outstanding hydrophobicity (low water absorption) to prolong the service life of the battery and improve the safety of the battery.

[0004] To improve the hydrophobicity of the coating, the existing technology usually adopts the method of adding organic silicon or organic fluorine hydrophobic agents or hydrophobically modifying the resin. However, the cost of organic silicon and organic fluorine additives is high, and they may not be compatible with the base resin, affecting the uniformity and adhesion of the coating. In addition, these methods often focus on surface hydrophobicity and have limited improvement on the water resistance of the coating body.

[0005] Therefore, there is an urgent need in the art for an innovative technical solution that can prepare a composite coating with both hydrophobicity and stable conductivity to meet the needs of battery steel shells and other applications with extremely high anti-permeation requirements. SUMMARY

[0006] In view of the above, the present application starts from composite conductive paint, uses graphite and carbon black as main functional conductive filler, and uses plasma technology to modify C9 petroleum resin and water-based polyacrylic resin as film-forming material, aiming to develop a water-based conductive paint suitable for industrial production, which has conductivity and hydrophobicity. The specific preparation method of the water-based conductive paint and the application in the preparation of lithium ion battery shell coating are also provided.

[0007] In order to achieve the above purpose, the present application provides the following technical scheme:

[0008] 1. A water-based conductive paint, the raw materials of the water-based conductive paint include water-based conductive slurry, water-based resin base and water-based additive; the mass ratio is 1:0.9-1.1:0.01-0.03; the water-based conductive slurry contains carbon black, graphite, wetting dispersant and water; the water-based resin base contains water-based resin, plasma modified C9 petroleum resin and water.

[0009] C9 petroleum resin is a thermoplastic resin obtained by polymerization of petroleum cracking by-product C9 fraction, and its molecular structure is mainly aromatic ring, which has excellent intrinsic hydrophobicity, acid and alkali resistance and electrical insulation. The present application successfully introduces C9 petroleum resin into the water-based conductive paint system, and brings multiple synergistic benefits: first, its non-polar aromatic hydrocarbon structure can construct a "hydrophobic skeleton" from the molecular level of the film-forming material, which fundamentally enhances the bulk hydrophobicity and moisture resistance of the coating, thereby significantly improving the long-term storage stability of the battery; second, as a thermoplastic resin, its molecular chain can intertwine with the acrylic resin, which helps to optimize the hardness, wear resistance and density of the coating; in addition, C9 petroleum resin is widely available and low in price, which can effectively control the cost while achieving key performance breakthroughs, and has very high industrial application value.

[0010] It is found in many experiments that the compatibility of unmodified C9 petroleum resin with water-based system is very poor, and it is difficult to be directly stably dispersed, which easily leads to uneven coating performance. Finally, it is found that the plasma modified C9 petroleum resin can be stably dispersed and combined with the hydroxyl water-based resin to form a good coating film. In the plane direction, it presents uniform conductive properties, avoiding the problem of current aggregation and hot spots caused by uneven conductivity.

[0011] Further, based on the total weight of the water-based conductive slurry, the carbon black and graphite account for 10-20 wt%, the weight ratio of carbon black to graphite is 2-3:2, the wetting dispersant is 2-10 wt%, and the distilled water is 70-85 wt%.

[0012] Further, the water-based resin emulsion is 20-40 wt%, the plasma-modified C9 petroleum resin is 5-15 wt%, and the water is 70-85 wt%, based on the total mass of the water-based resin base.

[0013] Further, the water-based auxiliary agent comprises a water-based rheological auxiliary agent, a water-based defoaming agent, and / or a water-based film-forming auxiliary agent.

[0014] Further, the water-based defoaming agent is 20-40 wt%, the water-based rheological agent is 40-60 wt%, and the water-based film-forming auxiliary agent is 20-35 wt%, based on the total mass of the water-based auxiliary agent.

[0015] Further, the plasma-modified C9 petroleum resin is a C9 petroleum resin subjected to plasma treatment in an O2 / Ar mixed atmosphere.

[0016] Further, the wet dispersant is one or a combination of polyvinylpyrrolidone, methylnaphthalene sulfonate formaldehyde condensate, and sodium carboxymethyl cellulose; the water-based resin is any one of a water-based polyacrylate or a water-based polyurethane, and the water-based curing agent is a polyisocyanate curing agent.

[0017] Further, the water-based rheological auxiliary agent is any one of a polyether-modified silicone or an associated polyurethane thickener, the water-based defoaming agent is any one of a polysiloxane defoaming agent or a polyolefin solution, and the water-based film-forming auxiliary agent can be an alcohol ester twelve film-forming auxiliary agent.

[0018] Further, the carbon black powder is conductive carbon black with a purity of >99.9%, and the graphite powder is semi-expanded graphite powder with a particle size of 2000 mesh.

[0019] 2. A preparation method of the water-based conductive coating is also provided, and the specific preparation method comprises the following steps:

[0020] a. The carbon black and graphite powder, wet dispersant, and water are weighed and added to a sand mill, and are subjected to high-speed stirring and dispersion at 1200 rpm-1800 rpm for 40-60 min to obtain a water-based conductive slurry;

[0021] b. The C9 petroleum resin is powdered and is placed in a preheated plasma device, and O2 gas and inert gas are first subjected to air extraction to reach a set value of a vacuum degree of 1×10 -2 Pa to 1×10 -4 Pa, and then a mixed atmosphere of O2 / inert gas is introduced, and plasma treatment is performed at a power of 200-600 w to obtain a plasma-modified C9 petroleum resin;

[0022] c.In the above conductive paste, add water-based resin base, plasma modified C9 petroleum resin, then add water-based rheological additives, stir evenly, then add water-based film forming additives, finally add water-based defoaming agent, high speed stirring dispersion 1h-3h, get water-based paint.

[0023] Further, the ratio of the flow rates of O2 and inert gas in the mixed atmosphere is 5:1 to 5:4, and the flow rate of O2 is 20 to 40 cm 3 / s.

[0024] The inert gas is argon or nitrogen.

[0025] 3. The water-based conductive paint according to any one of the preceding items, and the use of the preparation method of the water-based conductive paint in the preparation of a battery shell coating are also within the scope of the present application.

[0026] The water-based conductive paint of the present application is sprayed on the inner wall of the battery steel shell, and dried at a high temperature of 110 to 130 DEG C.

[0027] The battery shell can be made of nickel-plated stainless steel, aluminum alloy, or the like.

[0028] A multifunctional coating is formed on the metal, realizing that a single coating has multiple protections and functions of "conductivity" and "hydrophobicity", and the hydrophobicity and water resistance are obviously improved compared with ordinary water-based conductive coatings. Moreover, the coating has strong adhesion, good mechanical durability, strong bonding force between the coating and the metal substrate, good wear resistance and scratch resistance, and ensures long-term effectiveness under complex working conditions. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to make the purpose, technical scheme and beneficial effects of the present application clearer, the present application provides the following drawings for illustration:

[0030] Figure 1 The figure is for the static contact angle test of the coating 1-5.

[0031] Figure 2 The figure is an optical photograph of the coating 1-5 immersed in water for 10 days. DETAILED DESCRIPTION

[0032] The preferred technical scheme of the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. The experimental methods not specified in the embodiments are usually performed according to the conventional conditions or the conditions suggested by the manufacturers.

[0033] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having" or the like are open-ended terms that are intended to mean including, but not limited to.

[0034] The sand mill used in the present application is a disc type sand mill produced by Shanghai Muxuan Industrial Co., Ltd., with a power of 1.1Kw, a volume of 1L, and a medium of 2-3mm zirconia beads.

[0035] The plasma equipment used is a drum type vacuum plasma equipment produced by Shenzhen Chengfeng Intelligent Manufacturing Co., Ltd., which uses an ENI radio frequency power supply and an Aifukr CRB60 dry vacuum pump.

[0036] The carbon black used is MD-C510 conductive carbon black produced by Zhongshan Runze Nanotechnology Co., Ltd., and the graphite is semi-expanded graphite of 2000 mesh produced by Qingdao Zhongdong Graphite Co., Ltd.

[0037] The present application will be further described below in conjunction with specific examples

[0038] Example 1

[0039] The specific formulation of the raw materials of the water-based conductive coating is shown in Table 1 below:

[0040] Table 1

[0041]

[0042] The preparation steps of the water-based conductive coating are as follows, and the amount of each component is referred to Table 1:

[0043] (1) According to Table 1, carbon black, graphite powder, polyvinylpyrrolidone and methyl naphthalene sulfonate formaldehyde condensate are weighed, 144g of distilled water is added to the sand mill, and high-speed stirring is performed at 1500rpm for 1h to obtain a water-based conductive slurry.

[0044] (2) The C9 petroleum resin is powdered (200-400 mesh), the plasma equipment is preheated for 30min, and the treated C9 petroleum resin powder is then placed in the plasma equipment. The O2 gas cylinder and Ar gas cylinder are connected to the low-temperature plasma treatment system, and first, the system is pumped to a vacuum degree of 1x10 -2 Pa, and then O2 / Ar mixed gas with a flow rate ratio of 5:2 is introduced, wherein the O2 flow rate is 20-40 cm 3 / s, and the plasma treatment is performed at a power of 600w for 3min to obtain modified C9 petroleum resin.

[0045] (3) In the above conductive slurry, 12 g of modified C9 petroleum resin, 60 g of water-based polyacrylate resin emulsion, and 128 g of distilled water were sequentially added, stirred for 20-30 min, and then, after the viscosity of the system was stabilized, 0.6 g of alcohol ester twelve film-forming aid, 0.9 g of polysiloxane defoaming agent, and 1.5 g of polyether-modified siloxane water-based rheological aid were added, and high-speed stirring was performed at 1500 rpm for 1 h to obtain water-based conductive paint 1.

[0046] The above paint was sprayed on a nickel-plated stainless steel shell, and the water-based conductive coating 1 was obtained after drying at a high temperature of 110-130°C for 10 min.

[0047] Through experimental testing, it was found that the sanding dispersion time of carbon black / graphite should be controlled within 40 min-60 min. If the time is too short, sanding will not be sufficient, and if the time exceeds 1 h, the probability of the conductive particles being completely covered by the aid will be higher, and the probability of the conductive particles passing through the coating layer will be lower, thereby increasing the resistivity of the coating.

[0048] In step (2), the plasma-modified C9 petroleum resin should be used within 12 h after the plasma modification is completed. After the water-based defoaming agent is added, the stirring time should not be too long, as this will affect the defoaming effect.

[0049] Example 2

[0050] (1) 24 g of carbon black, 16 g of graphite powder, 8 g of polyvinylpyrrolidone, and 8 g of methyl naphthalene sulfonate formaldehyde condensate were weighed, 144 g of distilled water was added to a sanding machine, and high-speed stirring was performed at 1500 rpm for 1 h to obtain a water-based conductive slurry.

[0051] (2) The C9 petroleum resin was powdered, the plasma equipment was preheated for 30 min, and then the treated C9 petroleum resin powder was placed in the plasma equipment. The O2 gas cylinder, Ar gas cylinder, and low-temperature plasma treatment system were connected, and the system was first pumped to a vacuum degree of 1 x 10 -2 Pa, and then an O2 / Ar mixed gas atmosphere with a flow rate ratio of 5:2 was introduced, wherein the O2 flow rate was 20-40 cm 3 / s, and the plasma treatment was performed at a power of 600 w for 3 min to obtain modified C9 petroleum resin.

[0052] (3) In the above conductive slurry, 20 g of modified C9 petroleum resin, 60 g of water-based polyacrylate resin emulsion, and 120 g of distilled water were sequentially added, stirred for 20-30 min, and then, after the viscosity of the system was stabilized, 0.6 g of alcohol ester twelve film-forming aid, 0.9 g of polysiloxane defoaming agent, and 1.5 g of polyether-modified siloxane water-based rheological aid were added, and high-speed stirring was performed at 1500 rpm for 1 h to obtain water-based conductive paint 2.

[0053] The above coating is sprayed on the nickel-plated stainless steel shell, and is dried at high temperature of 110-130°C for 10 min to obtain water-based conductive coating 2.

[0054] Example 3

[0055] (1) 24 g of carbon black, 16 g of graphite powder, 8 g of polyvinylpyrrolidone and 8 g of methyl naphthalene sulfonate formaldehyde condensate are weighed, 144 g of distilled water is added to a sand mill, and high-speed stirring is performed at 1500 rpm for 1 h to obtain a water-based conductive slurry.

[0056] (2) The C9 petroleum resin is powdered, the plasma equipment is started and preheated for 30 min, the treated C9 petroleum resin powder is then put in, the O2 gas cylinder and the Ar gas cylinder are connected with the low-temperature plasma treatment system, and first, the system is pumped to a vacuum degree of 1 x 10 -2 Pa, and then O2 / Ar mixed gas with a flow rate ratio of 5:2 is introduced, wherein the O2 flow rate is 20-40 cm 3 / s, and the plasma treatment is performed at a power of 600 w for 3 min to obtain modified C9 petroleum resin.

[0057] (3) 12 g of modified C9 petroleum resin, 60 g of water-based polyurethane resin emulsion (Wanhua 6410), and 122 g of distilled water are sequentially added to the above conductive slurry, and after stirring for 20-30 min, 0.6 g of alcohol ester twelve film forming additives, 0.9 g of polysiloxane defoaming agent, and 1.5 g of polyether modified silicone water-based rheological additives are added, and high-speed stirring is performed at 1500 rpm for 1 h to obtain water-based conductive coating 3.

[0058] The above coating is sprayed on the nickel-plated stainless steel shell, and is dried at high temperature of 110-130°C for 10 min to obtain water-based conductive coating 3.

[0059] Example 4

[0060] The specific formulation of the water-based conductive coating of the present example is the same as that of Example 1, and the specific preparation steps are as follows:

[0061] (1) 24 g of carbon black, 16 g of graphite powder, 8 g of polyvinylpyrrolidone and 8 g of methyl naphthalene sulfonate formaldehyde condensate are weighed, 144 g of distilled water is added to a sand mill, and high-speed stirring is performed at 1500 rpm for 1 h to obtain a water-based conductive slurry.

[0062] (2) The C9 petroleum resin is powdered, the plasma equipment is started and preheated for 30 min, the treated C9 petroleum resin powder is then put in, the O2 gas cylinder and the Ar gas cylinder are connected with the low-temperature plasma treatment system, and first, the system is pumped to a vacuum degree of 1 x 10 -2The ratio of the set value of Pa to the flow rate of the O2 / N2 mixed atmosphere is 5:4, wherein the O2 flow rate is 20-40 cm 3 The modified C9 petroleum resin is subjected to plasma treatment at a power of 600 w for 3 min to obtain a modified C9 petroleum resin.

[0063] (3) 12 g of the modified C9 petroleum resin, 60 g of the water-based polyacrylate resin emulsion, and 128 g of distilled water are sequentially added to the conductive slurry, and after stirring for 20-30 min, 0.6 g of alcohol ester twelve film-forming aids, 0.9 g of polysiloxane defoaming agents, and 1.5 g of polyether-modified siloxane water-based rheological aids are added after the viscosity of the system is stable, and high-speed stirring is performed at 1500 rpm for 1 h to obtain the water-based conductive coating 4.

[0064] The coating is sprayed on the nickel-plated stainless steel shell, and the water-based conductive coating 4 is obtained after drying at a high temperature of 110-130 °C for 10 min.

[0065] Comparative Example 1

[0066] (1) 24 g of carbon black, 16 g of graphite powder, 8 g of polyvinylpyrrolidone, and 8 g of methyl naphthalene sulfonate formaldehyde condensate are weighed, and 144 g of distilled water is added to a sand mill, and high-speed stirring is performed at 1500 rpm for 1 h to obtain a water-based conductive slurry.

[0067] (2) 72 g of the water-based polyacrylate resin emulsion and 128 g of distilled water are sequentially added to the conductive slurry, and after stirring for 20-30 min, 0.6 g of alcohol ester twelve film-forming aids, 0.9 g of polysiloxane defoaming agents, and 1.5 g of polyether-modified siloxane water-based rheological aids are added after the viscosity of the system is stable, and high-speed stirring is performed at 1500 rpm for 1 h to obtain the water-based conductive coating 1.

[0068] The coating is sprayed on the nickel-plated stainless steel shell, and the comparative water-based conductive coating 5 is obtained after drying at a high temperature of 110-130 °C for 10 min.

[0069] Example 5

[0070] The main properties of the water-based conductive coatings 1-5 are tested, and the test results are shown in Table 2. It is found that the water-based conductive coating modified by the petroleum resin has a slight increase in volume resistivity, and the hydrophobicity and water resistance are obviously improved compared with the ordinary water-based conductive coating. Figure 1 The static contact angle test diagram of the coatings 1-5. Figure 2 From left to right, the optical photographs of the coatings 1-5 immersed in water for 10 days.

[0071] Table 2:

[0072]

[0073] The performance of the water-based conductive composite paint in the battery was tested:

[0074] (1) The water-based conductive paint 1-5 was sprayed on the inner wall of the battery steel shell, and the water-based conductive coating was formed by baking in the oven at 130°C for 10 min.

[0075] (2) The sprayed steel shell was applied to prepare a No. 5 primary alkaline-manganese battery, and the performance test of 1.5W pulse ((1500mW2s 650mW28s) 10T / h 24h / d to 1.05V) project was carried out, and the results are shown in Table 3. It is shown that the coating modified by petroleum resin improves the storage performance of the battery at high temperature and high humidity.

[0076] Table 3:

[0077]

[0078] Finally, it should be pointed out that the above preferred embodiments are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present application.

Claims

1. An aqueous conductive coating, characterized by, The raw materials of the water-based conductive coating include a water-based conductive slurry, a water-based resin base and a water-based auxiliary agent, and the mass ratio is 1:0.9-1.1:0.01-0.03; the water-based conductive slurry comprises carbon black, graphite, a wet dispersant and water; and the water-based resin base comprises a water-based resin, plasma-modified C9 petroleum resin and water.

2. The aqueous conductive coating according to claim 1, characterized in that, The carbon black and graphite account for 10-20 wt% of the total weight of the water-based conductive slurry, the weight ratio of carbon black to graphite is 2-3:2, the wet dispersant accounts for 2-10 wt%, and the distilled water accounts for 70-85 wt%.

3. The aqueous conductive coating of claim 1, wherein, The water-based resin accounts for 20-40 wt% of the total mass of the water-based resin base, the plasma-modified C9 petroleum resin accounts for 5-15 wt%, and the water accounts for 45-70 wt%.

4. The aqueous conductive coating of claim 1, wherein, The water-based auxiliary agent comprises a water-based rheological auxiliary agent, a water-based defoaming agent and / or a water-based film-forming auxiliary agent.

5. The aqueous conductive coating of claim 4, wherein, The water-based defoaming agent accounts for 20-40 wt% of the total mass of the water-based auxiliary agent, the water-based rheological agent accounts for 40-60 wt%, and the water-based film-forming auxiliary agent accounts for 20-35 wt%.

6. The aqueous conductive coating according to any one of claims 1 to 5, characterized in that, The plasma-modified C9 petroleum resin is C9 petroleum resin subjected to plasma treatment in an O2 / Ar mixed atmosphere.

7. The aqueous conductive coating according to claim 6, characterized in that, The wet dispersant is one or a combination of two of polyvinylpyrrolidone, methylnaphthalene sulfonate formaldehyde condensate and sodium carboxymethyl cellulose; the hydroxyl water-based resin is any one of a water-based polyacrylate or a water-based polyurethane, and the water-based curing agent is a polyisocyanate curing agent.

8. The process for the preparation of an aqueous conductive paint according to any one of claims 1 to 7, characterized in that, The preparation method comprises the following steps: a. carbon black and graphite powder are weighed, the wet dispersant and water are added to a sand mill, high-speed stirring and dispersion are carried out at 1200 rpm-1800 rpm for 40-60 min to obtain a water-based conductive slurry; b. The C9 petroleum resin is powdered and placed in a preheated plasma device. O2 gas and inert gas are first pumped to a vacuum degree of 1 x 10 -2 Pa, and then a mixed gas atmosphere of O2 / inert gas is introduced. Plasma treatment is performed at a power of 200-600 w to obtain a plasma-modified C9 petroleum resin. -4 Pa, and then a mixed gas atmosphere of O2 / inert gas is introduced. Plasma treatment is performed at a power of 200-600 w to obtain a plasma-modified C9 petroleum resin. c. the water-based resin base, the plasma-modified C9 petroleum resin, the water-based rheological auxiliary agent and the water-based film-forming auxiliary agent are added to the conductive slurry, stirring is carried out until they are uniformly mixed, the water-based defoaming agent is finally added, and high-speed stirring and dispersion are carried out at 1200 rpm-1800 rpm for 40-60 min to obtain a water-based coating.

9. The method of claim 8, wherein the aqueous conductive paint is prepared by adding the conductive filler to the aqueous base paint, and then adding the dispersant to the mixture. O2 / inert gas mixture in a ratio of 5:1 to 5:4, wherein the O2 flow is 20-40 cm 3 / s.

10. Application of the water-based conductive coating of any one of claims 1-7 or the preparation method of the water-based conductive coating of any one of claims 8-9 to the preparation of a battery shell coating.

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