Preparation method of modified calcium carbonate for PVC (polyvinyl chloride) automobile chassis stone chip resistant coating

Abstract

The invention provides a preparation method of modified calcium carbonate for a PVC (polyvinyl chloride) automobile chassis stone chip resistant coating, in the preparation process of the modified calcium carbonate, carbon dioxide generated by a thermal decomposition reaction of calcium carbonate in the step S1 is collected and recycled, and a gas collection pipeline is arranged on the side wall of a lime kiln close to the bottom; carbon dioxide is collected through the gas collecting pipeline, and carbon dioxide gas is larger than air in mass, so that more carbon dioxide gas is left close to the bottom of the lime kiln, and the carbon dioxide is convenient to collect; in the step S3, the hydration process needs to be carried out in a closed reactor, and a retarder (such as molasses) needs to be added to adjust the solidification speed of the slaked lime.

Description

Technical Field

[0001] The invention belongs to the technical field of PVC anti-stone coatings, and in particular relates to a preparation method of modified calcium carbonate for PVC automobile chassis anti-stone coatings. Background Art

[0002] Nano-calcium carbonate is widely used in various industries and sectors, including rubber, papermaking, coatings, medicine, 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 a hot topic in the calcium carbonate industry. Currently, nano-calcium carbonate with controllable morphology, size, and structure has been prepared using solution synthesis methods with the help of various crystal form control agents. By varying the template and additives, various morphologies, sizes, and crystal forms have been prepared, including spherical vaterite calcium carbonate, disc-shaped vaterite-type calcium carbonate, spindle-shaped, spherical, and needle-shaped calcite-type calcium carbonate. In order to enhance the application performance of calcium carbonate in plastics, rubber, and coatings, studies have also been reported on its modification using various modifiers such as surfactants, silanes, esters, copolymers, and inorganic substances. Generally speaking, calcium carbonate with different morphologies, particle sizes and crystal forms is first prepared by adding a morphology control agent, and then modified by a modifier. That is to say, morphology control and modification are carried out in steps, and the morphology control agent and modifier are two different substances.

[0003] Currently, the calcium carbonate used in the anti-stone chip coating for PVC automobile chassis requires the injection of carbon dioxide gas during its preparation. However, a large amount of gas is generated when limestone is calcined to produce calcium oxide. If the generated gas is collected and reused at this time, it can not only reduce costs but also further protect the environment by preventing the emission of carbon dioxide gas and pollution. In the prior art, when calcium oxide and water are mixed to produce calcium hydroxide, the coagulation rate of calcium hydroxide is difficult to control, which affects the quality of calcium hydroxide. Therefore, the present invention proposes a preparation method for modified calcium carbonate for PVC automobile chassis anti-stone chip coating to solve the above problems. Summary of the Invention

[0004] The present invention provides a preparation method of modified calcium carbonate for PVC automobile chassis anti-stone chip coating, aiming to solve the problems raised by the background technology.

[0005] The present invention is achieved by a method for preparing modified calcium carbonate for PVC automobile chassis anti-stone chip coating, comprising the following steps:

[0006] S1: Preparation of calcium oxide and carbon dioxide: High-purity limestone is placed in a lime kiln for calcination, that is, heated to 1000-1200℃ and maintained for 6-8 hours. In the high temperature environment, calcium carbonate undergoes thermal decomposition reaction to produce calcium oxide and carbon dioxide. The carbon dioxide gas inside the lime kiln is first collected, and then the lime kiln is naturally cooled to room temperature to obtain porous block calcium oxide;

[0007] S2: Grinding the porous block calcium oxide, placing the porous block calcium oxide obtained in step S1 in a grinder under moisture-proof conditions and grinding it to obtain calcium oxide powder;

[0008] S3: preparing lime paste, placing the calcium oxide powder obtained in step S2 in a stirring tank, and then adding water, wherein the ratio of calcium oxide to water is 1:3, stirring the mixture of calcium oxide and water in a closed environment in the stirring tank at a constant speed to cause an exothermic reaction to obtain calcium hydroxide, wherein a retarder may be added during the stirring process to adjust the setting speed of the calcium hydroxide, and the lime paste is obtained after cooling, and then the cooled lime paste is added;

[0009] S4: preparing a calcium hydroxide solution, taking out the lime paste obtained in step S3 and placing it in a container, adding water to the container and stirring thoroughly to dissolve the calcium hydroxide in the water to obtain a calcium hydroxide solution;

[0010] S5: preparing a calcium hydroxide suspension, filtering the calcium hydroxide solution obtained in step S4 through gauze to remove undissolved residues to obtain a calcium hydroxide suspension;

[0011] S6: injecting the carbon dioxide gas collected in step S1 into the calcium hydroxide suspension obtained in step S5 at a rate of 10-30 L / H and stirring uniformly, so that the carbon dioxide and the calcium hydroxide suspension react to form a calcium carbonate solution, which is then dried and crushed to produce calcium carbonate powder;

[0012] S7: The calcium carbonate powder obtained in step S6 is placed in a stirring tank, and a modifier is added to the stirring tank, wherein the modifier is 1.5% titanate and 3% stearic acid, and then stirred for 2-4 hours to fully disperse the modifier on the outer surface of the calcium carbonate powder to obtain modified calcium carbonate.

[0013] Preferably, in step S1, a gas collecting pipe is provided on the side wall of the lime kiln near the bottom, and the carbon dioxide is collected through the gas collecting pipe.

[0014] Preferably, in step S1, a collecting pipe is provided at the bottom of the lime kiln, and the porous block calcium oxide is collected through the collecting pipe.

[0015] Preferably, the retarder in step S3 is honey.

[0016] Preferably, the container in step S4 is a stirring tank.

[0017] Preferably, the mesh size of the gauze in step S5 is 40-80 meshes.

[0018] Preferably, the drying temperature in step S6 is 70-100°C.

[0019] Preferably, the stirring speed of the stirring tank in step S7 is 1000-3000 r / min.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] During the preparation process of the modified calcium carbonate of the present invention, in step S1, carbon dioxide generated by the thermal decomposition reaction of calcium carbonate is collected and reused. A gas collection pipe is provided near the bottom of the side wall of the lime kiln, and carbon dioxide is collected through the gas collection pipe. Since carbon dioxide gas has a greater mass than air, more carbon dioxide gas remains near the bottom of the lime kiln, making it easier to collect carbon dioxide. In step S3, the hydration process needs to be carried out in a closed reactor, wherein a retarder (such as molasses) needs to be added to adjust the setting rate of slaked lime. DETAILED DESCRIPTION

[0022] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0023] The components of the embodiments of the present invention generally described and shown herein may be arranged and designed in a variety of different configurations. Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention.

[0024] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0025] 1. Preparation of modified calcium carbonate

[0026] Example 1:

[0027] The present invention provides a technical solution: a method for preparing modified calcium carbonate for PVC automobile chassis anti-stone chip coating, comprising the following steps:

[0028] S1: Preparation of calcium oxide and carbon dioxide: High-purity limestone is placed in a lime kiln for calcination, that is, heated to 1000°C and maintained for 6 hours. In the high temperature environment, calcium carbonate undergoes thermal decomposition reaction to produce calcium oxide and carbon dioxide. The carbon dioxide gas inside the lime kiln is first collected, and then the lime kiln is naturally cooled to room temperature to obtain porous block calcium oxide;

[0029] S2: Grinding the porous block calcium oxide, placing the porous block calcium oxide obtained in step S1 in a grinder under moisture-proof conditions and grinding it to obtain calcium oxide powder;

[0030] S3: preparing lime paste, placing the calcium oxide powder obtained in step S2 in a stirring tank, and then adding water, wherein the ratio of calcium oxide to water is 1:3, stirring the mixture of calcium oxide and water in a closed environment in the stirring tank at a constant speed to cause an exothermic reaction to obtain calcium hydroxide, wherein a retarder may be added during the stirring process to adjust the setting speed of the calcium hydroxide, and the lime paste is obtained after cooling, and then the cooled lime paste is added;

[0031] S4: preparing a calcium hydroxide solution, taking out the lime paste obtained in step S3 and placing it in a container, adding water to the container and stirring thoroughly to dissolve the calcium hydroxide in the water to obtain a calcium hydroxide solution;

[0032] S5: preparing a calcium hydroxide suspension, filtering the calcium hydroxide solution obtained in step S4 through gauze to remove undissolved residues to obtain a calcium hydroxide suspension;

[0033] S6: injecting the carbon dioxide gas collected in step S1 into the calcium hydroxide suspension obtained in step S5 at a rate of 10 L / H and stirring the mixture evenly. The carbon dioxide and the calcium hydroxide suspension react to form a calcium carbonate solution, which is then dried and crushed to produce calcium carbonate powder.

[0034] S7: The calcium carbonate powder obtained in step S6 is placed in a stirring tank, and a modifier is added to the stirring tank, wherein the modifier is 1.5% titanate and 3% stearic acid, and then stirred for 2 hours to fully disperse the modifier on the outer surface of the calcium carbonate powder to obtain modified calcium carbonate.

[0035] Furthermore, in step S1, a gas collecting pipe is provided on the side wall of the lime kiln near the bottom, and carbon dioxide is collected through the gas collecting pipe.

[0036] Furthermore, in step S1, a collecting pipe is provided at the bottom of the lime kiln, and the porous block calcium oxide is collected through the collecting pipe.

[0037] Furthermore, in step S3, the retarder is honey.

[0038] Furthermore, the container in step S4 is a stirring tank.

[0039] Furthermore, the mesh number of the gauze in step S5 is 40 meshes.

[0040] Furthermore, the drying temperature in step S6 is 70°C.

[0041] Furthermore, the stirring speed of the stirring tank in step S7 is 1000 r / min.

[0042] In this embodiment, in step S1, when high-purity limestone (calcium carbonate) is calcined, calcium carbonate undergoes a thermal decomposition reaction: CaCO3→CaO+CO2↑. The calcium oxide decomposed in this step is a porous block calcium oxide. For the convenience of subsequent processing, the porous block calcium oxide needs to be ground into calcium oxide powder. After the calcium oxide is prepared, it needs to be isolated from moisture to avoid premature reaction with water vapor to cause agglomeration and failure. In step S3, the calcium oxide is mixed with water in proportion, and a violent exothermic reaction occurs: CaO+H2O→Ca(OH)2 hydration reaction. The process needs to be carried out in a closed reactor, wherein a retarder (such as molasses) needs to be added to adjust the setting speed of the slaked lime, and the reaction speed is controlled by stirring to prevent local overheating and splashing. The generated calcium hydroxide needs to be sealed and packaged after drying and screening and avoid contact with air to prevent it from reacting with CO2 to form calcium carbonate and hardening. In step S5, the calcium hydroxide residue that is not dissolved in water needs to be filtered out to avoid affecting the subsequent modification reaction. In step S7, the modifiers added are 1.5% titanate and 3% stearic acid, which can increase the activity of calcium carbonate.

[0043] In step S1, carbon dioxide generated by the thermal decomposition reaction of calcium carbonate is collected and reused. A gas collection pipe is provided near the bottom of the lime kiln sidewall, and carbon dioxide is collected through the gas collection pipe. Since carbon dioxide gas has a greater mass than air, more carbon dioxide gas remains near the bottom of the lime kiln, making it easier to collect carbon dioxide. In step S3, the hydration process needs to be carried out in a closed reactor, and a retarder (such as molasses) needs to be added to adjust the setting rate of the slaked lime.

[0044] Example 2:

[0045] A method for preparing modified calcium carbonate for PVC automobile chassis anti-stone chip coating comprises the following steps:

[0046] S1: Preparation of calcium oxide and carbon dioxide: High-purity limestone is placed in a lime kiln for calcination, that is, heated to 1100°C and maintained for 7 hours. In the high temperature environment, calcium carbonate undergoes thermal decomposition reaction to produce calcium oxide and carbon dioxide. The carbon dioxide gas inside the lime kiln is first collected, and then the lime kiln is naturally cooled to room temperature to obtain porous block calcium oxide;

[0047] S2: Grinding the porous block calcium oxide, placing the porous block calcium oxide obtained in step S1 in a grinder under moisture-proof conditions and grinding it to obtain calcium oxide powder;

[0048] S3: preparing lime paste, placing the calcium oxide powder obtained in step S2 in a stirring tank, and then adding water, wherein the ratio of calcium oxide to water is 1:3, stirring the mixture of calcium oxide and water in a closed environment in the stirring tank at a constant speed to cause an exothermic reaction to obtain calcium hydroxide, wherein a retarder may be added during the stirring process to adjust the setting speed of the calcium hydroxide, and the lime paste is obtained after cooling, and then the cooled lime paste is added;

[0049] S4: preparing a calcium hydroxide solution, taking out the lime paste obtained in step S3 and placing it in a container, adding water to the container and stirring thoroughly to dissolve the calcium hydroxide in the water to obtain a calcium hydroxide solution;

[0050] S5: preparing a calcium hydroxide suspension, filtering the calcium hydroxide solution obtained in step S4 through gauze to remove undissolved residues to obtain a calcium hydroxide suspension;

[0051] S6: injecting the carbon dioxide gas collected in step S1 into the calcium hydroxide suspension obtained in step S5 at a rate of 20 L / H and stirring the mixture evenly. The carbon dioxide and the calcium hydroxide suspension react to form a calcium carbonate solution, which is then dried and crushed to produce calcium carbonate powder.

[0052] S7: The calcium carbonate powder obtained in step S6 is placed in a stirring tank, and a modifier is added to the stirring tank, wherein the modifier is 1.5% titanate and 3% stearic acid, and then stirred for 3 hours to fully disperse the modifier on the outer surface of the calcium carbonate powder to obtain modified calcium carbonate.

[0053] Furthermore, in step S1, a gas collecting pipe is provided on the side wall of the lime kiln near the bottom, and the carbon dioxide is collected through the gas collecting pipe.

[0054] Furthermore, in step S1, a collecting pipe is provided at the bottom of the lime kiln, and the porous block calcium oxide is collected through the collecting pipe.

[0055] Furthermore, in step S3, the retarder is honey.

[0056] Furthermore, the container in step S4 is a stirring tank.

[0057] Furthermore, the mesh number of the gauze in step S5 is 60 meshes.

[0058] Furthermore, the drying temperature in step S6 is 85°C.

[0059] Furthermore, the stirring speed of the stirring tank in step S7 is 2000 r / min.

[0060] Example 3:

[0061] A method for preparing modified calcium carbonate for PVC automobile chassis anti-stone chip coating comprises the following steps:

[0062] S1: Preparation of calcium oxide and carbon dioxide: High-purity limestone is placed in a lime kiln for calcination, that is, heated to 1200°C and maintained for 8 hours. In the high temperature environment, calcium carbonate undergoes thermal decomposition reaction to produce calcium oxide and carbon dioxide. The carbon dioxide gas inside the lime kiln is first collected, and then the lime kiln is naturally cooled to room temperature to obtain porous block calcium oxide;

[0063] S2: Grinding the porous block calcium oxide, placing the porous block calcium oxide obtained in step S1 in a grinder under moisture-proof conditions and grinding it to obtain calcium oxide powder;

[0064] S3: preparing lime paste, placing the calcium oxide powder obtained in step S2 in a stirring tank, and then adding water, wherein the ratio of calcium oxide to water is 1:3, stirring the mixture of calcium oxide and water in a closed environment in the stirring tank at a constant speed to cause an exothermic reaction to obtain calcium hydroxide, wherein a retarder may be added during the stirring process to adjust the setting speed of the calcium hydroxide, and the lime paste is obtained after cooling, and then the cooled lime paste is added;

[0065] S4: preparing a calcium hydroxide solution, taking out the lime paste obtained in step S3 and placing it in a container, adding water to the container and stirring thoroughly to dissolve the calcium hydroxide in the water to obtain a calcium hydroxide solution;

[0066] S5: preparing a calcium hydroxide suspension, filtering the calcium hydroxide solution obtained in step S4 through gauze to remove undissolved residues to obtain a calcium hydroxide suspension;

[0067] S6: injecting the carbon dioxide gas collected in step S1 into the calcium hydroxide suspension obtained in step S5 at a rate of 30 L / H and stirring the mixture evenly. The carbon dioxide and the calcium hydroxide suspension react to form a calcium carbonate solution, which is then dried and crushed to produce calcium carbonate powder.

[0068] S7: The calcium carbonate powder obtained in step S6 is placed in a stirring tank, and a modifier is added to the stirring tank, wherein the modifier is 1.5% titanate and 3% stearic acid, and then stirred for 4 hours to fully disperse the modifier on the outer surface of the calcium carbonate powder to obtain modified calcium carbonate.

[0069] Furthermore, in step S1, a gas collecting pipe is provided on the side wall of the lime kiln near the bottom, and the carbon dioxide is collected through the gas collecting pipe.

[0070] Furthermore, in step S1, a collecting pipe is provided at the bottom of the lime kiln, and the porous block calcium oxide is collected through the collecting pipe.

[0071] Furthermore, in step S3, the retarder is honey.

[0072] Furthermore, the container in step S4 is a stirring tank.

[0073] Furthermore, the mesh number of the gauze in step S5 is 80 meshes.

[0074] Furthermore, the drying temperature in step S6 is 100°C.

[0075] Furthermore, the stirring speed of the stirring tank in step S7 is 3000 r / min.

[0076] 2. Application of modified calcium carbonate

[0077] In order to verify the performance of the modified calcium carbonate powder prepared by the present invention, an application comparison experiment was conducted using unmodified nano calcium carbonate and the products prepared in Examples 1-3 to prepare PVC automotive anti-stone chip coatings. The performance was measured and the results are shown in Table 1.

[0078] Preparation of PVC automobile chassis anti-stone chip coating: modified polyvinyl chloride paste resin, modified calcium carbonate, phthalate, tackifier, diluent, thixotropic agent, foaming agent, heat stabilizer, pigment and adhesion promoter, which, by weight percentage, contains 15-20% modified polyvinyl chloride paste resin, 30-35% modified calcium carbonate, 30-35% phthalate, 1.5-2% tackifier, 1.5-3% diluent, 1-2% thixotropic agent, 1-2% foaming agent, 0.5-1% heat stabilizer, 0.05-0.2% pigment, and 0.5-1% adhesion promoter. The above components are mixed and stirred according to weight percentage to obtain the PVC anti-stone chip coating, and the obtained PVC anti-stone chip coating is a viscous paste with a solid content greater than 95%.

[0079] Table 1: Comparative results of application examples

[0080] index Thixotropic ring area (Pa / s) Yield value (Pa) Viscosity (mPa·s) Unmodified nano calcium carbonate 2472 158 237 Example 1 19874 169 388 Example 2 22137 175 429 Example 3 20157 167 400

[0081] From the above results, it can be seen that the various indicators of the PVC coating prepared with the modified calcium carbonate powder obtained in Examples 1-3 of this scheme exceed those of the unmodified nano calcium carbonate and basically reach the technical indicators of nano calcium carbonate.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing modified calcium carbonate for PVC automobile chassis anti-stone chip coating, characterized by: The following steps are involved: S1: Preparation of calcium oxide and carbon dioxide: High-purity limestone is placed in a lime kiln for calcination, that is, heated to 1000-1200℃ and maintained for 6-8 hours. In the high temperature environment, calcium carbonate undergoes thermal decomposition reaction to produce calcium oxide and carbon dioxide. The carbon dioxide gas inside the lime kiln is first collected, and then the lime kiln is naturally cooled to room temperature to obtain porous block calcium oxide; S2: Grinding the porous block calcium oxide, placing the porous block calcium oxide obtained in step S1 in a grinder under moisture-proof conditions and grinding it to obtain calcium oxide powder; S3: preparing lime paste, placing the calcium oxide powder obtained in step S2 in a stirring tank, and then adding water, wherein the ratio of calcium oxide to water is 1:3, stirring the mixture of calcium oxide and water in a closed environment in the stirring tank at a constant speed to cause an exothermic reaction to obtain calcium hydroxide, wherein a retarder may be added during the stirring process to adjust the setting speed of the calcium hydroxide, and the lime paste is obtained after cooling, and then the cooled lime paste is added; S4: preparing a calcium hydroxide solution, taking out the lime paste obtained in step S3 and placing it in a container, adding water to the container and stirring thoroughly to dissolve the calcium hydroxide in the water to obtain a calcium hydroxide solution; S5: preparing a calcium hydroxide suspension, filtering the calcium hydroxide solution obtained in step S4 through gauze to remove undissolved residues to obtain a calcium hydroxide suspension; S6: injecting the carbon dioxide gas collected in step S1 into the calcium hydroxide suspension obtained in step S5 at a rate of 10-30 L / H and stirring uniformly, so that the carbon dioxide and the calcium hydroxide suspension react to form a calcium carbonate solution, which is then dried and crushed to produce calcium carbonate powder; S7: The calcium carbonate powder obtained in step S6 is placed in a stirring tank, and a modifier is added to the stirring tank, wherein the modifier is 1.5% titanate and 3% stearic acid, and then stirred for 2-4 hours to fully disperse the modifier on the outer surface of the calcium carbonate powder to obtain modified calcium carbonate.

2. The method for preparing modified calcium carbonate for PVC automobile chassis anti-stone chip coating according to claim 1, characterized in that: In step S1, a gas collecting pipe is provided on the side wall of the lime kiln near the bottom, and the carbon dioxide is collected through the gas collecting pipe.

3. The method for preparing modified calcium carbonate for PVC automobile chassis anti-stone chip coating according to claim 1, characterized in that: In step S1, a collecting pipe is provided at the bottom of the lime kiln, and the porous block calcium oxide is collected through the collecting pipe.

4. The method for preparing modified calcium carbonate for PVC automobile chassis anti-stone chip coating according to claim 1, characterized in that: In step S3, the retarder is honey.

5. The method for preparing modified calcium carbonate for PVC automobile chassis anti-stone chip coating according to claim 1, characterized in that: The container in step S4 is a stirring tank.

6. The method for preparing modified calcium carbonate for PVC automobile chassis anti-stone chip coating according to claim 1, characterized in that: The mesh number of the gauze in step S5 is 40-80 meshes.

7. The method for preparing modified calcium carbonate for PVC automobile chassis anti-stone chip coating according to claim 1, characterized in that: The drying temperature in step S6 is 70-100°C.

8. The method for preparing modified calcium carbonate for PVC automobile chassis anti-stone chip coating according to claim 1, characterized in that: The stirring speed of the stirring tank in step S7 is 1000-3000 r / min.