Preparation method of nano calcium carbonate filler for new energy vehicle aluminum battery box anti-stone impact paint

Abstract

The application belongs to the technical field of paint preparation, and discloses a preparation method of nano calcium carbonate filler for anti-stone-impact paint of an aluminum battery box of a new energy vehicle, which comprises the following steps: adding a two-component crystal form control agent into cooled calcium hydroxide slurry, introducing kiln gas to perform carbonization, preparing nano calcium carbonate slurry with a particle size of 20-40 nanometers and a cubic crystal form; adding a dispersing agent, adjusting the PH value to 6.5-7.5, adding a composite coating agent saponified emulsion to perform coating treatment; performing pressure filtration to obtain slurry filter cake, and then performing drying and depolymerization. The nano calcium carbonate filler prepared by the method has a particle size of about 20-40 nanometers, a whiteness greater than 90, and an oil absorption value controlled within 30-35. The nano calcium carbonate filler has high adhesion, high strength, high thixotropy and other performances in the anti-stone-impact paint, and has good compatibility with resin.

Description

Technical Field

[0001] This application relates to the field of coating preparation technology, and more specifically, to a method for preparing nano-calcium carbonate filler for stone-impact resistant coatings for aluminum battery boxes of new energy vehicles. Background Technology

[0002] With the widespread adoption of new energy vehicles, aluminum alloys are increasingly used for components such as engine parts, battery housings, and chassis parts to reduce vehicle weight. The batteries in the power systems of new energy vehicles are mostly located under the vehicle's floor, exposed to harsh operating environments. The battery housing, as the carrier of the power battery, plays a crucial role in ensuring its safe and reliable operation. During vehicle operation, the battery housing is frequently subjected to impacts and erosion from mud, gravel, and sewage, making the undercarriage components highly susceptible to corrosion and loss of protection. Therefore, anti-stone-impact coatings are required in this area. However, traditional automotive anti-stone-impact coatings have poor adhesion to aluminum battery housings, easily peeling off and failing to meet usage requirements.

[0003] CN107384052A discloses an aluminum plate-type anti-stone chip coating, which increases the adhesion of the aluminum substrate by adding modified epoxy resin. However, the epoxy resin has a high viscosity, and adding too much will affect the sprayability of the anti-stone chip coating, while adding too little will result in limited increase in adhesion.

[0004] In recent years, with the continuous research and development of new anti-stone impact coatings, nano-calcium carbonate has been applied as a modifier and filler in various anti-stone impact coating systems. Nano-calcium carbonate possesses characteristics such as quantum size effect, surface effect, highly activated surface atoms, and strong interfacial interactions with polymers. When applied to anti-stone impact coatings for automotive chassis, it imparts modified properties such as reinforcement, transparency, thixotropy, and leveling, effectively improving the impact resistance, adhesion, and other indicators of anti-stone impact coatings. Moreover, nano-calcium carbonate, as an inexpensive filler, significantly reduces production costs. Currently, anti-stone impact coatings are mainly classified into asphalt systems, PVC plastisol systems, polyurethane elastic systems, and acrylic systems.

[0005] Nano-calcium carbonate is widely used in various industries and sectors such as rubber, papermaking, coatings, pharmaceuticals, and cosmetics. Different industries have different requirements for the morphology, particle size, and surface properties of calcium carbonate. Therefore, the synthesis of nano-calcium carbonate materials with controllable morphology and structure is one of the research hotspots in the calcium carbonate industry. Currently, with the help of various crystal form control agents, nano-calcium carbonate with controllable morphology, size, and structure has been prepared by solution synthesis. Among them, various morphologies, sizes, and crystal forms of spherical aragonite calcium carbonate, disc-shaped aragonite calcium carbonate, cubic, spindle-shaped, spherical, and needle-shaped calcite calcium carbonate have been prepared by changing the template and additives. In order to enhance the application performance of calcium carbonate in plastics, rubber, and coatings, research on the modification of calcium carbonate using various modifiers such as surfactants, silanes, esters, copolymers, and inorganic substances has also been reported. In general, calcium carbonate with different morphologies, particle sizes and crystal forms is first prepared by adding morphology control agents, and then modified without modifiers. In other words, morphology control and modification are carried out in steps, and the morphology control agents and modifiers are two different substances.

[0006] Regarding the modification of nano-calcium carbonate, existing publicly available modifiers include alumina titanate, stearic acid, bis(dioctyloxypyrophosphate) ethylene titanate, palm oil or a mixture of palm oil and sodium dodecyl sulfate or a mixture of palm oil and polyethylene glycol, and a mixed saponification solution of fatty acids and iron-sodium diethylenetriaminepentaacetic acid complex, etc.

[0007] Chinese patent CN104403433B discloses a method for preparing precipitated calcium carbonate for PVC anti-stone chip coating. The process involves adjusting lime slurry to a specific gravity of 1.040–1.080 and introducing kiln gas at a flow rate of 6–10 m³ / h. 3 When the pH of the reaction solution drops below 7.0, the specific surface area of ​​the slurry is controlled at 16–40 m² / g. A compound surface treatment agent is added at 50–90℃ for coating, with the total amount of surface treatment agent being 1.5–5.0% of the dry basis of calcium carbonate. The slurry is then pressure filtered, dehydrated, dried, pulverized, and packaged to obtain the precipitated calcium carbonate product for PVC anti-stone chip coating. The precipitated calcium carbonate prepared by this method has low hygroscopicity, effectively controls the thixotropy, yield value, and viscosity of the filled PVC plasticizer, and improves the rheological stability of the PVC plasticizer. However, the modification and preparation process of calcium carbonate in this invention is relatively cumbersome. The compatibility of the modified calcium carbonate obtained by this method with the resin system is not ideal, and its adhesion and strength improvement in practical applications is limited.

[0008] In summary, existing anti-stone chip coatings for automotive aluminum battery boxes suffer from insufficient adhesion, strength, and thixotropic properties to meet application requirements. Therefore, there is an urgent need to develop a nano-calcium carbonate filler for aluminum battery box anti-stone chip coatings that can effectively improve the adhesion, strength, and thixotropic properties of anti-stone chip coatings while also exhibiting good resin compatibility. Summary of the Invention

[0009] To address the aforementioned issues, this application provides a method for preparing nano-calcium carbonate filler for stone-impact resistant coatings in aluminum battery boxes for new energy vehicles.

[0010] The preparation method of nano-calcium carbonate filler for stone-impact resistant coating of aluminum battery boxes for new energy vehicles provided in this application adopts the following technical solution:

[0011] A method for preparing nano-calcium carbonate filler for stone-impact resistant coating of aluminum battery boxes for new energy vehicles includes the following steps:

[0012] After adding a two-component crystal form control agent to the cooled calcium hydroxide slurry, kiln gas is introduced for carbonation. The carbonation temperature is controlled to be no higher than 20°C, and nano-calcium carbonate slurry with a particle size of 20-40 nanometers and a cubic crystal form is obtained.

[0013] The nano-calcium carbonate slurry is added to a dispersant, the pH value is adjusted to 6.5-7.5, and a composite coating agent saponified emulsion is added for coating treatment.

[0014] The coated slurry is filtered to obtain a slurry filter cake, which is then dried, pulverized, and depolymerized a second time to obtain the nano-calcium carbonate filler product.

[0015] Furthermore, the cooled calcium hydroxide slurry is a calcium hydroxide slurry prepared by refining and cooling to 18°C, and the weight concentration of the calcium hydroxide slurry is 8.0%.

[0016] Furthermore, the two-component crystal form control agent is sucrose and citric acid in a weight ratio of 3:1, and the amount added is 1.5 to 2.0% of the weight of calcium carbonate.

[0017] Furthermore, the initial temperature for carbonization is 18°C.

[0018] Furthermore, the kiln gas is CO2 gas with a volume percentage concentration of 28-31%, and the kiln gas flow rate is 0.8 cubic meters per minute.

[0019] Furthermore, the initial pH value of the nano-calcium carbonate slurry is not higher than 9.0.

[0020] Furthermore, the coating treatment includes two coating processes. In the first coating process, the coating agent added to the saponified emulsion is stearic acid, and the coating dosage is 4% of the weight of calcium carbonate. In the second coating process, the coating agent added to the saponified emulsion is coconut oil, and the coating dosage is 1% of the weight of calcium carbonate.

[0021] Furthermore, the preparation method of the composite coating agent saponified emulsion includes: adding the corresponding coating agent to hot water at 90°C, and then adding 13-15% of a solid alkali to saponify and dissolve the coating agent in hot water to form an emulsion, which is then clarified to obtain the emulsion.

[0022] Furthermore, the moisture content of the slurry filter cake is less than 50%, the drying temperature of the slurry filter cake is 80-110℃, and the slurry filter cake needs to be crushed and depolymerized twice after drying.

[0023] In summary, this application includes at least one of the following beneficial technical effects:

[0024] The nano-calcium carbonate filler prepared by this invention has a particle size of about 20 to 40 nanometers, a cubic crystal form, a whiteness greater than 90, and an oil absorption value controlled at 30-35. It has high adhesion, high strength, high thixotropy and other properties in anti-stone chip coatings, and good compatibility with resin. Detailed Implementation

[0025] The technical solutions in the embodiments of this application will be clearly and completely described below; obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] Example 1:

[0027] This application discloses a method for preparing nano-calcium carbonate filler for stone-impact resistant coatings in aluminum battery boxes for new energy vehicles, comprising the following steps:

[0028] A calcium hydroxide slurry with a weight concentration of 8.0% was prepared by cooling the refined calcium hydroxide slurry to 18°C. A two-component crystal form control agent, consisting of sucrose and citric acid in a weight ratio of 3:1, was added to the cooled calcium hydroxide slurry at a rate of 1.5% of the weight of calcium carbonate. Carbonation was then carried out by introducing kiln gas, specifically CO2 gas with a volume percentage concentration of 28% at a flow rate of 0.8 cubic meters per minute. The initial carbonation temperature was 18°C, and the carbonation temperature was controlled to not exceed 20°C. This yielded a nano-calcium carbonate slurry with a particle size of 20–40 nanometers and a cubic crystal form. The initial pH value of the slurry was controlled to not exceed 9.0. By adding a two-component crystal form control agent during the carbonation process, small-particle-size nano-calcium carbonate particles can be synthesized at a lower temperature.

[0029] The nano-calcium carbonate slurry was mixed with a dispersant and the pH was adjusted to 6.5. A coating agent saponified emulsion was added in two separate steps for coating treatment. In the first coating treatment, the coating agent saponified emulsion contained stearic acid, and the coating dosage was 4% of the weight of calcium carbonate. In the second coating treatment, the coating agent saponified emulsion contained coconut oil, and the coating dosage was 1% of the weight of calcium carbonate.

[0030] As a further preferred embodiment, the composite coating agent saponified emulsion is prepared by adding the composite coating agent to hot water at 90°C, followed by adding 13% of the total amount of the composite coating agent in solid alkali, allowing the composite coating agent to saponify and dissolve into an emulsion in the hot water, and then clarifying it. This method improves the wet coating effect of calcium carbonate, specifically resulting in a higher activation rate of the prepared nano-calcium carbonate filler, better dispersibility in the coating, increased filler content, and reduced coating production costs.

[0031] The coated slurry is pressed and filtered to obtain a filter cake. After the moisture content of the slurry filter cake is less than 50%, it is dried and pulverized at a drying temperature of 100℃. Then, it undergoes a second depolymerization to obtain the nano calcium carbonate filler product.

[0032] Example 2:

[0033] This application discloses a method for preparing nano-calcium carbonate filler for stone-impact resistant coatings in aluminum battery boxes for new energy vehicles, comprising the following steps:

[0034] A calcium hydroxide slurry with a weight concentration of 8.0% was prepared by cooling the refined calcium hydroxide slurry to 18°C. A two-component crystal form control agent, consisting of sucrose and citric acid in a weight ratio of 3:1, was added to the cooled calcium hydroxide slurry at a rate of 1.5% of the weight of calcium carbonate. Carbonation was then carried out by introducing kiln gas, specifically CO2 gas with a volume percentage concentration of 30% at a flow rate of 0.8 cubic meters per minute. The initial carbonation temperature was 18°C, and the carbonation temperature was controlled to not exceed 20°C. This yielded a nano-calcium carbonate slurry with a particle size of 20–40 nanometers and a cubic crystal form. The initial pH value of the slurry was controlled to not exceed 9.0. By adding a two-component crystal form control agent during the carbonation process, small-particle-size nano-calcium carbonate particles can be synthesized at a lower temperature.

[0035] The nano-calcium carbonate slurry was mixed with a dispersant and the pH was adjusted to 7.0. A coating agent saponified emulsion was added in two separate steps for coating treatment. In the first coating treatment, the coating agent saponified emulsion contained stearic acid, and the coating dosage was 4% of the weight of calcium carbonate. In the second coating treatment, the coating agent saponified emulsion contained coconut oil, and the coating dosage was 1% of the weight of calcium carbonate.

[0036] As a further preferred embodiment, the composite coating agent saponified emulsion is prepared by adding the composite coating agent to hot water at 90°C, followed by adding 14% of the total amount of the composite coating agent in solid alkali, allowing the composite coating agent to saponify and dissolve into an emulsion in the hot water, and then clarifying it. The advantage of this method is that it improves the wet coating effect of calcium carbonate, specifically resulting in a high activation rate of the prepared nano-calcium carbonate filler, good dispersibility in the coating, increased filler content, and reduced coating production costs.

[0037] The coated slurry is pressure filtered to obtain a slurry filter cake with a water content of less than 50%. The cake is then dried and pulverized at 105°C, followed by a second depolymerization process to obtain the nano-calcium carbonate filler product.

[0038] Example 3:

[0039] This application discloses a method for preparing nano-calcium carbonate filler for stone-impact resistant coatings in aluminum battery boxes for new energy vehicles, comprising the following steps:

[0040] A calcium hydroxide slurry with a weight concentration of 8.0% was prepared by cooling the refined calcium hydroxide slurry to 18°C. A two-component crystal form control agent, consisting of sucrose and citric acid in a weight ratio of 3:1, was added to the cooled calcium hydroxide slurry at a rate of 2.0% of the weight of calcium carbonate. Carbonation was then carried out by introducing kiln gas, specifically CO2 gas with a volume percentage concentration of 31% at a flow rate of 0.8 cubic meters per minute. The initial carbonation temperature was 18°C, and the carbonation temperature was controlled to not exceed 20°C. This yielded a nano-calcium carbonate slurry with a particle size of 20–40 nanometers, and the initial pH value of the slurry was controlled to not exceed 9.0. By adding a two-component crystal form control agent during the carbonation process, small-particle-size nano-calcium carbonate particles can be synthesized at a lower temperature.

[0041] The nano-calcium carbonate slurry was mixed with a dispersant and the pH was adjusted to 7.5. A coating agent saponified emulsion was then added in two stages for coating treatment. In the first coating treatment, the coating agent in the saponified emulsion was stearic acid, and the coating dosage was 4% of the weight of calcium carbonate. In the second coating treatment, the coating agent in the saponified emulsion was coconut oil, and the coating dosage was 1% of the weight of calcium carbonate.

[0042] As a further preferred embodiment, the composite coating agent saponified emulsion is prepared by adding the composite coating agent to hot water at 90°C, followed by adding 15% of the total amount of the composite coating agent in solid alkali, allowing the composite coating agent to saponify and dissolve into an emulsion in the hot water, followed by clarification. This method improves the wet coating effect of calcium carbonate, specifically resulting in a higher activation rate of the prepared nano-calcium carbonate filler, better dispersibility in the coating, increased filler content, and reduced coating production costs.

[0043] The coated slurry is pressure filtered to obtain a slurry filter cake with a water content of less than 50%. The cake is then dried and pulverized at 110°C, followed by a second depolymerization process to obtain the nano-calcium carbonate filler product.

[0044] Performance testing:

[0045] 1. Whiteness test: Take a certain amount of three sets of product samples and put them into a powder press to press them into three sample plates with a smooth surface, no texture, no blemishes and no stains; take three sample plates from each set and place them on the measuring hole of the colorimeter to measure the tristimulus value of each sample plate, and take the average value of the measurement results of the three sample plates in each set.

[0046] The chromaticity coordinates of the sample are calculated as follows:

[0047] x = X / (X + Y + Z)

[0048] y = Y / (X + Y + Z)

[0049] z = 1 - xy = Z / (X + Y + Z)

[0050] In the formula: X, Y, and Z are the tristimulus values ​​of a 10° field of view; x, y, and z are the chromaticity coordinates of the sample; the arithmetic mean of parallel measurements is taken as the measurement result; whiteness is expressed in W, and the value is expressed in degrees, calculated according to the following formula:

[0051] W = Y + 400x - 1000y + 205.5

[0052] The whiteness values ​​of each sample are shown in Table 1 below:

[0053] sample Whiteness Example 1 94.5 Example 2 93.4 Example 3 92.8

[0054] 2. Oil absorption value test:

[0055] Weigh 1.5g of the sample and place it on a glass or glazed porcelain plate. Add DOP dropwise using a dropper bottle containing a known mass of dioctyl phthalate (DOP). While adding the sample, continuously stir and grind it with a spatula. Initially, the sample is dispersed, but it gradually clumps together until it is completely wetted by DOP. The endpoint is reached when DOP is saturated by calcium carbonate and slightly precipitates out. Weigh the dropper bottle.

[0056] Oil absorption is expressed in units of w, and is the mass (g) of DOP absorbed by 100g of active calcium carbonate, calculated using the following formula:

[0057] w=(m1-m2) / m×100

[0058] In the formula: m1 is the mass of the dropping bottle and DOP before adding DOP, m2 is the mass of the dropping bottle and DOP after adding DOP, and m is the mass of the sample. All units are grams (g).

[0059] The arithmetic mean of the parallel test results was taken as the test result. The measured oil absorption values ​​are shown in Table 2 below:

[0060] sample Oil absorption value Example 1 32.4 Example 2 31.6 Example 3 33.3

[0061] 3. Application Test:

[0062] The products from the above embodiments were formulated into anti-stone chip coating plastic pastes according to common formulations, and the test results are shown in Table 3 below:

[0063]

[0064]

[0065] The nano-calcium carbonate filler prepared by this invention has a particle size of about 20-40 nanometers, a cubic crystal form, a whiteness greater than 90, and an oil absorption value controlled at 30-35. It has high adhesion, high strength, and high thixotropy properties in anti-stone chip coatings, good compatibility with resins, and good market prospects.

[0066] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for preparing nano-calcium carbonate filler for stone-impact resistant coating of aluminum battery boxes for new energy vehicles, characterized in that, Includes the following steps: A two-component crystal form control agent is added to the cooled calcium hydroxide slurry. The two-component crystal form control agent is sucrose and citric acid in a weight ratio of 3:1, and the amount added is 1.5 to 2.0% of the weight of calcium carbonate. Then, kiln gas is introduced for carbonation. The carbonation start temperature is controlled at 18°C ​​and the carbonation temperature is not higher than 20°C to obtain nano-calcium carbonate slurry with a particle size of 20 to 40 nanometers and a cubic crystal form. The nano-calcium carbonate slurry is added to a dispersant, and the pH value is adjusted to 6.5-7.5 for coating treatment. The coating treatment includes two coating processes: First, the coating agent added in the first coating treatment is stearic acid in the saponified emulsion, and the coating agent is 4% of the weight of calcium carbonate; second, the coating agent added in the second coating treatment is coconut oil in the saponified emulsion, and the coating agent is 1% of the weight of calcium carbonate. After the coated slurry is filtered by pressure to obtain a slurry filter cake, it is dried and depolymerized to obtain the nano calcium carbonate filler product.

2. The preparation method of nano-calcium carbonate filler for anti-stone impact coating of aluminum battery boxes for new energy vehicles according to claim 1, characterized in that: The cooled calcium hydroxide slurry is a calcium hydroxide slurry prepared by refining and cooling to 18°C, and the weight concentration of the calcium hydroxide slurry is 8.0%.

3. The preparation method of nano-calcium carbonate filler for anti-stone impact coating of aluminum battery boxes for new energy vehicles according to claim 1, characterized in that: The kiln gas is CO2 gas with a volume percentage concentration of 28-31%, and the kiln gas flow rate is 0.8 cubic meters per minute.

4. The preparation method of nano-calcium carbonate filler for anti-stone impact coating of aluminum battery boxes for new energy vehicles according to claim 1, characterized in that: The initial pH value of the nano-calcium carbonate slurry is not higher than 9.

0.

5. The preparation method of nano-calcium carbonate filler for anti-stone impact coating of aluminum battery boxes for new energy vehicles according to claim 1, characterized in that, The preparation method of the coating agent saponified emulsion includes: adding the corresponding coating agent to hot water at 90°C, then adding 13-15% of a solid alkali to saponify and dissolve the coating agent in hot water to form an emulsion, and then clarifying it to obtain the emulsion.

6. The preparation method of nano-calcium carbonate filler for anti-stone impact coating of aluminum battery box for new energy vehicles according to claim 1, characterized in that: The moisture content of the slurry filter cake is less than 50%, and the drying temperature of the slurry filter cake is 80-110℃.

7. The preparation method of nano-calcium carbonate filler for anti-stone impact coating of aluminum battery box for new energy vehicles according to claim 1, characterized in that: The slurry filter cake needs to be crushed and depolymerized twice after drying.

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