Method for preparing plastic master batch from nano calcium carbonate

Abstract

The invention discloses a method for preparing a plastic master batch from nano calcium carbonate, and relates to the technical field of plastic master batch production, and the method comprises the following steps: feeding dried white carbon black, modified nano calcium carbonate, nano titanium dioxide and low density polyethylene into a stirring kettle for mixing to prepare a mixed auxiliary material; feeding a dispersing agent, linear low-density polyethylene, a light stabilizer, an antioxidant and a lubricating agent into an ultrasonic dispersion machine together to prepare a mixed additive; feeding the mixed auxiliary material and the mixed auxiliary agent into a high-speed kneading machine, kneading, crushing, feeding the crushed material into a double-screw extruder, and extruding and granulating to obtain a primary finished product; and cooling the primary finished product, and conveying the cooled primary finished product to a granulator to prepare the finished plastic master batch with the particle size of 3-5mm. Therefore, by coating the ultraviolet light absorber, the modified nano calcium carbonate can effectively improve the ultraviolet resistance.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of plastic master batch production, in particular to a method for preparing plastic master batch by using nano calcium carbonate. BACKGROUND

[0002] The plastic master batch is an indispensable key material in the modern plastic industry, which can efficiently concentrate various additives in the resin carrier, so that the plastic products have more characteristics and functions.

[0003] In order to ensure the anti-ultraviolet ability of the plastic master batch, a light stabilizer is often added in the production process of the plastic master batch, however, the light stabilizer cannot fully coat the calcium carbonate as the "skeleton" of the plastic master batch, which causes the ultraviolet light to often break through the "skeleton", so that the plastic products still appear yellow after long-time use. Therefore, how to further improve the resistance of the plastic master batch to ultraviolet light is a problem faced at present. SUMMARY

[0004] In view of the above defects, the purpose of the application is to provide a method for preparing plastic master batch by using nano calcium carbonate, which aims to solve the problem of low resistance of the plastic master batch to ultraviolet light in the prior art.

[0005] To solve the above technical problems, the technical scheme of the application is: A method for preparing plastic master batch by using nano calcium carbonate, comprising the following steps: Step one, the dried white carbon black, modified nano calcium carbonate, nano titanium dioxide and low-density polyethylene are sent into a stirring kettle for mixing to prepare mixed accessories; Step two, the dispersing agent, linear low-density polyethylene, light stabilizer, antioxidant and lubricant are sent into an ultrasonic dispersing machine to prepare mixed additives; Step three, the mixed accessories and the mixed additives are sent into a high-speed kneader for kneading and crushing, and the crushed materials are sent into a double-screw extruder for extrusion and granulation to prepare a primary product; the primary product is cooled and then sent to a pelletizer to prepare a finished plastic master batch with a particle size of 3-5 mm; The preparation method of the modified nano calcium carbonate is: S1, a refined lime milk solution and deionized water are prepared into a lime milk diluent according to a mass ratio of 1:5.5-6, the lime milk diluent is pumped into a carbonization reaction kettle, then a crystal form control agent and a composite dispersing agent are added into the carbonization reaction kettle, and at the same time, kiln gas is sent into the carbonization reaction kettle; when the pH value of the material liquid in the carbonization reaction kettle is 6.8-7.5, the kiln gas is stopped, and an intermediate slurry is prepared; S2, the composite coating agent and the compound modifier are put into the intermediate slurry, and the modified nano calcium carbonate slurry is prepared after ultrasonic mixing; S3, the modified nano calcium carbonate slurry is obtained by pressure filtration, drying and crushing; The composite coating agent is composed of 80-90 parts of coupling agent and 10-20 parts of ultraviolet absorber, and the amount of the composite coating agent is 0.45%-1.5% of the mass fraction of the dry calcium hydroxide substrate.

[0006] The white carbon black is 4-8 parts, the nano titanium dioxide is 4-6 parts, the modified nano calcium carbonate is 10-12 parts, the low-density polyethylene is 50-60 parts, the dispersing agent is 2-3 parts, the linear low-density polyethylene is 30-40 parts, the light stabilizer is 1.2-2.2 parts, the antioxidant is 0.5-1.5 parts, and the lubricant is 1-3 parts.

[0007] The concentration of calcium hydroxide in the lime milk diluent is 7-12%, the volume concentration of carbon dioxide in the kiln gas is 25-35%, the conveying speed of the kiln gas is 0.4-1 m / s, and the initial temperature in the carbonization reactor is 20-36℃. 3

[0008] The crystal form control agent is composed of 30-40 parts of carboxymethyl cellulose, 10-20 parts of sodium laurate and 40-50 parts of soluble starch, and the amount of the crystal form control agent is 1.8%-4.2% of the mass fraction of the dry calcium hydroxide substrate.

[0009] The composite dispersing agent is composed of 30-40 parts of sodium hexametaphosphate, 25-35 parts of sodium octadecenoate and 8-15 parts of cetyltrimethylammonium bromide, and the amount of the composite dispersing agent is 0.5%-1.2% of the mass fraction of the dry calcium hydroxide substrate.

[0010] The coupling agent is composed of 20-40 parts of sodium stearate, 25-30 parts of bisalkyl phosphate, 30-40 parts of triisostearyl isopropyl titanate and 30-40 parts of bis-[3-(triethoxysil)propyl]-disulfide.

[0011] The ultraviolet absorber is composed of 60-70 parts of UV-9, 10-20 parts of UV-531 and 10-20 parts of UV-327.

[0012] ​The complex modifier is composed of 20-30 parts of cetyl trimethyl ammonium bromide, 40-50 parts of distearyl oxy isopropyl borate, and 20-30 parts of lauric acid amide, and the amount of the complex modifier is 0.2%-1.5% of the mass fraction of the dry calcium hydroxide substrate.

[0013] After the above technical scheme is adopted, the application has the following beneficial effects: First, in the modification process of the nano calcium carbonate, the nano calcium carbonate after modification can effectively improve the ultraviolet resistance by coating the ultraviolet absorber; and the plastic master batch produced by using the nano calcium carbonate as raw material has a practical improvement in ultraviolet resistance. Second, the use of the crystal form control agent can make the nano calcium carbonate particles more conducive to scattering and reflecting ultraviolet rays, thereby reducing the ultraviolet rays received by the plastic master batch, and further improving the ultraviolet resistance of the plastic master batch. DETAILED DESCRIPTION

[0014] It should be understood that the specific embodiments described herein are merely intended to explain the application and are not intended to limit the application.

[0015] A method for preparing a plastic master batch by using nano calcium carbonate, comprising the following steps: Step one, sending the dried white carbon black, modified nano calcium carbonate, nano titanium dioxide, and low-density polyethylene into a stirred tank for mixing to obtain a mixed auxiliary material; Step two, sending the dispersing agent, linear low-density polyethylene, light stabilizer, antioxidant, and lubricant into an ultrasonic dispersing machine to obtain a mixed auxiliary agent; Step three, sending the mixed auxiliary material and the mixed auxiliary agent into a high-speed kneader for kneading and crushing, and then sending the crushed material into a double-screw extruder for extruding and granulating to obtain a primary product; and then sending the primary product into a pelletizer for cooling to obtain a finished plastic master batch with a particle size of 3-5 mm.

[0016] According to the mass fraction, the white carbon black is 4-8 parts, the nano titanium dioxide is 4-6 parts, the modified nano calcium carbonate is 10-12 parts, the low-density polyethylene is 50-60 parts, the dispersing agent is 2-3 parts, the linear low-density polyethylene is 30-40 parts, the light stabilizer is 1.2-2.2 parts, the antioxidant is 0.5-1.5 parts, and the lubricant is 1-3 parts; the dispersing agent is one of stearic acid amide, stearic acid, and calcium stearate; the light stabilizer is decanedioic acid dibutyl ester bis(2,2,6,6-tetramethylpiperidinol) ester or bis(2,2,6,6-tetramethyl-4-piperidyl) adipate; the antioxidant is one of tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid] pentaerythritol ester, β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid n-octadecanol ester, and tris[2.4-di-tert-butylphenyl] phosphite; and the lubricant is glyceryl stearate.

[0017] The preparation method of the modified nano-calcium carbonate is as follows: S1. A diluted lime slurry is prepared by mixing refined lime slurry solution with deionized water at a mass ratio of 1:5.5-6. The diluted lime slurry solution is pumped into a carbonization reactor. Then, a crystal form control agent and a composite dispersant are added to the carbonization reactor. At the same time, kiln gas is introduced into the carbonization reactor. When the pH value of the liquid in the carbonization reactor is 6.8-7.5, the supply of kiln gas is stopped, and an intermediate slurry is obtained. S2, a modified nano-calcium carbonate slurry is prepared by adding a composite coating agent and a compound modifier to an intermediate slurry and mixing them with ultrasonic waves. S3, modified nano-calcium carbonate slurry is obtained by pressure filtration, drying and crushing.

[0018] The calcium hydroxide concentration in the lime slurry diluent is 7-12%; the carbon dioxide volume concentration in the kiln gas is 25-35%, and the kiln gas conveying velocity is 0.4-1 m / s. 3 / s, the initial temperature inside the carbonization reactor is 20-36℃, and the empty volume of the reactor is 20M. 3 The actual fill volume was 14M. 3 .

[0019] The crystal form control agent is composed of 30-40 parts carboxymethyl cellulose, 10-20 parts sodium laurylate and 40-50 parts soluble starch; the amount of crystal form control agent is 1.8% to 4.2% of the dry matrix mass fraction of calcium hydroxide.

[0020] The composite dispersant is composed of 30-40 parts sodium hexametaphosphate, 25-35 parts sodium octadecenoate, and 8-15 parts hexadecyltrimethylammonium bromide. The amount of the composite dispersant is 0.5% to 1.2% of the dry matrix mass of calcium hydroxide.

[0021] The composite coating agent consists of 80-90 parts of coupling agent and 10-20 parts of ultraviolet absorber, and the amount of the composite coating agent is 0.45% to 1.5% of the mass fraction of the dry calcium hydroxide matrix.

[0022] The coupling agent is composed of 20-40 parts sodium stearate, 25-30 parts dialkyl phosphate, 30-40 parts isopropyl triisostearoyl titanate and 30-40 parts bis-[3-(triethoxysilyl)propyl]-disulfide.

[0023] The ultraviolet absorber is composed of 60-70 parts of UV-9, 10-20 parts of UV-531, and 10-20 parts of UV-327.

[0024] The compound modifier is composed of 20-30 parts of hexadecyltrimethylammonium bromide, 40-50 parts of distearate isopropyl borate, and 20-30 parts of laurylamide. The amount of the compound modifier is 0.2% to 1.5% of the dry matrix mass of calcium hydroxide.

[0025] Example 1: Plastic masterbatch is prepared according to the above method, wherein: By weight, the composition includes 4 parts silica, 4 parts nano-titanium dioxide, 10 parts modified nano-calcium carbonate, 50 parts low-density polyethylene, 2 parts dispersant, 30 parts linear low-density polyethylene, 1.2 parts light stabilizer, 0.5 parts antioxidant, and 1 part lubricant; the dispersant is stearamide; the light stabilizer is dibutyl sebacate bis(2,2,6,6-tetramethylpiperidinol) ester; the antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; and the lubricant is glyceryl stearate.

[0026] In S1, a diluted lime slurry is prepared by mixing refined lime slurry solution with deionized water at a mass ratio of 1:5.5; when the pH value of the liquid in the carbonization reactor reaches 6.8, the supply of kiln gas is stopped.

[0027] The calcium hydroxide concentration in the lime slurry diluent is 7%; the volume concentration of carbon dioxide in the kiln gas is 25%, and the kiln gas conveying velocity is 0.4 m / s. 3 / s, the temperature inside the carbonization reactor is 20℃.

[0028] The crystal form control agent is composed of 30 parts carboxymethyl cellulose, 10 parts sodium laurate and 40 parts soluble starch; the amount of crystal form control agent is 1.8% of the dry matrix mass fraction of calcium hydroxide.

[0029] The composite dispersant is composed of 30 parts sodium hexametaphosphate, 25 parts sodium octadecenoate and 8 parts hexadecyltrimethylammonium bromide, and the amount of the composite dispersant is 0.5% of the mass fraction of the dry calcium hydroxide matrix.

[0030] The composite coating agent consists of 80 parts coupling agent and 10 parts ultraviolet absorber, and the amount of the composite coating agent is 0.45% of the dry matrix mass of calcium hydroxide.

[0031] The coupling agent is composed of 20 parts sodium stearate, 25 parts dialkyl phosphate, 30 parts isopropyl triisostearoyl titanate and 30 parts bis-[3-(triethoxysilyl)propyl]-disulfide.

[0032] The ultraviolet absorber is composed of 60 parts UV-9, 10 parts UV-531, and 10 parts UV-327.

[0033] The compound modifier is composed of 20 parts hexadecyltrimethylammonium bromide, 40 parts distearate isopropyl borate, and 20 parts laurylamide. The amount of the compound modifier is 0.2% of the dry matrix mass of calcium hydroxide.

[0034] Example 2: The difference between this embodiment and Embodiment 1 is that: By weight, the composition includes 5 parts silica, 4.5 parts nano-titanium dioxide, 10.5 parts modified nano-calcium carbonate, 54 parts low-density polyethylene, 2.4 parts dispersant, 34 parts linear low-density polyethylene, 1.5 parts light stabilizer, 0.8 parts antioxidant, and 1.5 parts lubricant. The dispersant is stearic acid; the light stabilizer is bis(2,2,6,6-tetramethyl-4-piperidinyl)adipic acid ester; the antioxidant is β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol ester; and the lubricant is glyceryl stearate.

[0035] In S1, a diluted lime slurry is prepared by mixing refined lime slurry solution with deionized water at a mass ratio of 1:5.6; when the pH value of the liquid in the carbonization reactor reaches 7.3, the supply of kiln gas is stopped.

[0036] The calcium hydroxide concentration in the lime slurry diluent is 10.5%; the carbon dioxide volume concentration in the kiln gas is 27%, and the kiln gas conveying velocity is 0.6 m / s. 3 / s, the temperature inside the carbonization reactor is 25℃.

[0037] The crystal form control agent consists of 34 parts carboxymethyl cellulose, 14 parts sodium laurate, and 44 parts soluble starch; the amount of the crystal form control agent is 2.8% of the dry matrix mass fraction of calcium hydroxide.

[0038] The composite dispersant is composed of 34 parts sodium hexametaphosphate, 27 parts sodium octadecenoate, and 10 parts hexadecyltrimethylammonium bromide. The amount of the composite dispersant is 0.7% of the dry matrix mass fraction of calcium hydroxide.

[0039] The composite coating agent consists of 84 parts coupling agent and 14 parts ultraviolet absorber, and the amount of the composite coating agent is 0.5% of the mass fraction of the dry calcium hydroxide matrix.

[0040] The coupling agent is composed of 24 parts sodium stearate, 26 parts dialkyl phosphate, 34 parts isopropyl triisostearoyl titanate and 34 parts bis-[3-(triethoxysilyl)propyl]-disulfide.

[0041] The ultraviolet absorber is composed of a mixture of 64 parts UV-9, 14 parts UV-531, and 14 parts UV-327.

[0042] The compound modifier is composed of 24 parts hexadecyltrimethylammonium bromide, 44 parts distearate isopropyl borate, and 24 parts laurylamide. The amount of the compound modifier is 0.5% of the dry matrix mass of calcium hydroxide.

[0043] Example 3: The difference between this embodiment and Embodiment 1 is that: By weight, the composition includes 6 parts of silica, 5 parts of nano-titanium dioxide, 11 parts of modified nano-calcium carbonate, 58 parts of low-density polyethylene, 2.8 parts of dispersant, 38 parts of linear low-density polyethylene, 1.8 parts of light stabilizer, 1 part of antioxidant, and 2 parts of lubricant. The dispersant is calcium stearate; the light stabilizer is dibutyl sebacate bis(2,2,6,6-tetramethylpiperidinol) ester; the antioxidant is tris[2,4-di-tert-butylphenyl] phosphite; and the lubricant is glyceryl stearate.

[0044] In S1, a diluted lime slurry is prepared by mixing refined lime slurry solution with deionized water at a mass ratio of 1:5.8; when the pH value of the liquid in the carbonization reactor reaches 7.3, the supply of kiln gas is stopped.

[0045] The calcium hydroxide concentration in the lime slurry diluent is 11%; the carbon dioxide volume concentration in the kiln gas is 30%, and the kiln gas conveying velocity is 0.8 m / s. 3 / s, the temperature inside the carbonization reactor is 30℃.

[0046] The crystal form control agent is composed of 38 parts carboxymethyl cellulose, 18 parts sodium lauryl ester and 48 parts soluble starch; the amount of crystal form control agent is 3.8% of the dry matrix mass fraction of calcium hydroxide.

[0047] The composite dispersant is composed of 38 parts sodium hexametaphosphate, 30 parts sodium octadecenoate, and 12 parts hexadecyltrimethylammonium bromide. The amount of the composite dispersant is 1% of the mass fraction of the dry calcium hydroxide matrix.

[0048] The composite coating agent consists of 88 parts coupling agent and 18 parts ultraviolet absorber, and the amount of the composite coating agent is 0.8% of the dry matrix mass of calcium hydroxide.

[0049] The coupling agent is composed of 34 parts sodium stearate, 28 parts dialkyl phosphate, 38 parts isopropyl triisostearoyl titanate and 38 parts bis-[3-(triethoxysilyl)propyl]-disulfide.

[0050] The ultraviolet absorber is composed of 68 parts UV-9, 18 parts UV-531, and 18 parts UV-327.

[0051] The compound modifier is composed of 28 parts hexadecyltrimethylammonium bromide, 48 parts distearate isopropyl borate, and 28 parts laurylamide. The amount of the compound modifier is 1.4% of the mass fraction of the dry calcium hydroxide matrix.

[0052] Example 4: The difference between this embodiment and Embodiment 1 is that: By weight, the composition includes 8 parts of silica, 6 parts of nano-titanium dioxide, 12 parts of modified nano-calcium carbonate, 60 parts of low-density polyethylene, 3 parts of dispersant, 40 parts of linear low-density polyethylene, 2.2 parts of light stabilizer, 1.5 parts of antioxidant, and 3 parts of lubricant. The dispersant is stearamide; the light stabilizer is bis(2,2,6,6-tetramethyl-4-piperidinyl)adipic acid ester; the antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; and the lubricant is glyceryl stearate.

[0053] In S1, a diluted lime slurry is prepared by mixing refined lime slurry solution with deionized water at a mass ratio of 1:6; when the pH value of the liquid in the carbonization reactor reaches 7.5, the supply of kiln gas is stopped.

[0054] The calcium hydroxide concentration in the lime slurry diluent is 12%; the carbon dioxide volume concentration in the kiln gas is 35%, and the kiln gas conveying velocity is 1 m / s². 3 / s, the temperature inside the carbonization reactor is 36℃.

[0055] The crystal form control agent consists of 40 parts carboxymethyl cellulose, 20 parts sodium laurate, and 50 parts soluble starch; the amount of the crystal form control agent is 4.2% of the dry matrix mass fraction of calcium hydroxide.

[0056] The composite dispersant is composed of 40 parts sodium hexametaphosphate, 35 parts sodium octadecenoate, and 15 parts hexadecyltrimethylammonium bromide. The amount of the composite dispersant is 1.2% of the mass fraction of the dry calcium hydroxide matrix.

[0057] The composite coating agent consists of 90 parts coupling agent and 20 parts ultraviolet absorber, and the amount of the composite coating agent is 1.5% of the mass fraction of the dry calcium hydroxide matrix.

[0058] The coupling agent is composed of 40 parts sodium stearate, 30 parts dialkyl phosphate, 40 parts isopropyl triisostearoyl titanate and 40 parts bis-[3-(triethoxysilyl)propyl]-disulfide.

[0059] The ultraviolet absorber is composed of 70 parts UV-9, 20 parts UV-531, and 20 parts UV-327.

[0060] The compound modifier is composed of 30 parts hexadecyltrimethylammonium bromide, 50 parts distearate isopropyl borate, and 30 parts laurylamide. The amount of the compound modifier is 1.5% of the mass fraction of the dry calcium hydroxide matrix.

[0061] Comparative Example 1: The difference between this comparative example and Example 1 is that commercially available nano-calcium carbonate is used instead of modified nano-calcium carbonate.

[0062] Comparative Example 2: The difference between this comparative example and Example 1 is that no ultraviolet absorber was added to the composite coating agent.

[0063] Comparative Example 3: The difference between this comparative example and Example 1 is that the crystal form control agent is sucrose.

[0064] The plastic masterbatches prepared in Examples 1-4 and Comparative Examples 1-3 were first hot-pressed for 42 minutes at 190°C in a flat vulcanizing machine, and then cold-pressed for 4 minutes at 30°C to obtain circular test specimens with a diameter of 8 cm and a thickness of 4 mm. The performance of the specimens was tested as follows: (1) The main mechanical properties of the plastic specimens were tested using the following methods and standards: tensile strength GB / T1040-2006, elongation at break GB / T1040-2006, impact strength GB / T1843-2008, and flexural strength GB / T9341-2000. Five plastic specimens were taken for each test group, and the average value was used as the final test result. The test results are shown in Table 1.

[0065] UV aging resistance: Proceed according to GB / T14522-2008.

[0066] Experimental equipment: QUV type test chamber.

[0067] Experimental conditions: The above-mentioned experimental products were placed in a QUV test chamber and irradiated for 7 days with ultraviolet lamps of wavelengths of 200–275 nm, 275–320 nm, and 320–400 nm, respectively, with an ultraviolet light intensity of 20 W / cm². 2 The sample was placed 40cm away from the ultraviolet light. After 7 days of ultraviolet aging, the retention rate of the tensile strength, elongation at break, impact strength, and flexural strength of the sample was tested.

[0068] The test results are as follows:

[0069] A comparison of the two tables shows that after high-intensity ultraviolet (UV) irradiation, the properties of the plastic samples in Examples 1-4 and Comparative Examples 1-2 all decreased significantly. However, a comparison reveals that the performance degradation of Comparative Example 1, which uses conventional nano-calcium carbonate, after aging is far greater than that of Examples 1-4. This demonstrates that the nano-calcium carbonate modified using this method can effectively resist aging. A comparison of Comparative Example 2 with Examples 1-4 shows that although no UV absorber was added to the coating agent, the modified nano-calcium carbonate still exhibits slightly stronger UV resistance than conventional nano-calcium carbonate. Comparative Examples 2 and 3 show that while different crystal forms of nano-calcium carbonate exhibit varying UV resistance, the key difference lies in the addition of a UV absorber during the modification process. This results in Comparative Example 3 having a lower UV resistance than Examples 1-4, but still significantly stronger than Comparative Example 2.

[0070] When nano-calcium carbonate is mixed with UV absorbers, plastic masterbatches can effectively combat UV aging.

[0071] In summary, the advantages of this solution are as follows: First, during the modification process of nano-calcium carbonate, the coating with ultraviolet absorbers effectively improves the UV resistance of the modified nano-calcium carbonate; furthermore, the plastic masterbatch produced using it as a raw material exhibits a substantial improvement in UV resistance. Second, the use of crystal form control agents makes the nano-calcium carbonate particles more conducive to scattering and reflecting ultraviolet rays. This facilitates the scattering and reflection of ultraviolet rays, thereby reducing the amount of ultraviolet rays received by the plastic masterbatch and thus improving its UV resistance.

[0072] This invention is not limited to the specific embodiments described above. Any modifications made by those skilled in the art based on the above concept without creative effort are within the scope of protection of this invention.

Claims

1. A method for preparing plastic masterbatch using nano-calcium carbonate, characterized in that, Includes the following steps: Step 1: Dry precipitated silica, modified nano-calcium carbonate, nano-titanium dioxide, and low-density polyethylene are fed into a mixing tank and mixed to obtain a mixed auxiliary material. Step 2: The dispersant, linear low-density polyethylene, light stabilizer, antioxidant, and lubricant are fed into an ultrasonic disperser to obtain a mixed additive. Step 3: The mixed excipients and mixed additives are fed into a high-speed kneader and kneaded and then crushed. The crushed material is then fed into a twin-screw extruder for extrusion and granulation to obtain a primary finished product. After cooling, the primary finished product is sent to a pelletizer to obtain finished plastic masterbatch with a particle size of 3-5mm. The preparation method of the modified nano-calcium carbonate is as follows: S1. A diluted lime slurry is prepared by mixing refined lime slurry solution with deionized water at a mass ratio of 1:5.5-6. The diluted lime slurry solution is pumped into a carbonization reactor. Then, a crystal form control agent and a composite dispersant are added to the carbonization reactor. At the same time, kiln gas is introduced into the carbonization reactor. When the pH value of the liquid in the carbonization reactor is 6.8-7.5, the supply of kiln gas is stopped, and an intermediate slurry is obtained. S2, a modified nano-calcium carbonate slurry is prepared by adding a composite coating agent and a compound modifier to an intermediate slurry and mixing them with ultrasonic waves. S3, modified nano-calcium carbonate slurry is obtained by pressure filtration, drying and crushing. The composite coating agent consists of 80-90 parts of coupling agent and 10-20 parts of ultraviolet absorber, and the amount of the composite coating agent is 0.45% to 1.5% of the mass fraction of the dry calcium hydroxide matrix.

2. The method for preparing plastic masterbatch using nano-calcium carbonate according to claim 1, characterized in that, By weight, the composition includes 4-8 parts of silica, 4-6 parts of nano-titanium dioxide, 10-12 parts of modified nano-calcium carbonate, 50-60 parts of low-density polyethylene, 2-3 parts of dispersant, 30-40 parts of linear low-density polyethylene, 1.2-2.2 parts of light stabilizer, 0.5-1.5 parts of antioxidant, and 1-3 parts of lubricant; the dispersant is one of stearamide, stearic acid, and calcium stearate; the light stabilizer is sebacic acid. Dibutyl bis(2,2,6,6-tetramethylpiperidinol) ester or bis(2,2,6,6-tetramethyl-4-piperidinyl) adipate; the antioxidant is one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, or tris[2,4-di-tert-butylphenyl]phosphite; the lubricant is glyceryl stearate.

3. The method for preparing plastic masterbatch using nano-calcium carbonate according to claim 1, characterized in that, The calcium hydroxide concentration in the lime slurry diluent is 7-12%; the carbon dioxide volume concentration in the kiln gas is 25-35%, and the kiln gas conveying velocity is 0.4-1 m / s. 3 / s, the initial temperature inside the carbonization reactor is 20-36℃.

4. The method for preparing plastic masterbatch using nano-calcium carbonate according to claim 1, characterized in that, The crystal form control agent is composed of 30-40 parts carboxymethyl cellulose, 10-20 parts sodium laurylate and 40-50 parts soluble starch; the amount of crystal form control agent is 1.8% to 4.2% of the dry matrix mass fraction of calcium hydroxide.

5. The method for preparing plastic masterbatch using nano-calcium carbonate according to claim 1, characterized in that, The composite dispersant is composed of 30-40 parts sodium hexametaphosphate, 25-35 parts sodium octadecenoate, and 8-15 parts hexadecyltrimethylammonium bromide. The amount of the composite dispersant is 0.5% to 1.2% of the dry matrix mass of calcium hydroxide.

6. The method for preparing plastic masterbatch using nano-calcium carbonate according to claim 1, characterized in that, The coupling agent is composed of 20-40 parts sodium stearate, 25-30 parts dialkyl phosphate, 30-40 parts isopropyl triisostearoyl titanate and 30-40 parts bis-[3-(triethoxysilyl)propyl]-disulfide.

7. The method for preparing plastic masterbatch using nano-calcium carbonate according to claim 1, characterized in that, The ultraviolet absorber is composed of 60-70 parts of UV-9, 10-20 parts of UV-531, and 10-20 parts of UV-327.

8. The method for preparing plastic masterbatch using nano-calcium carbonate according to claim 1, characterized in that, The compound modifier is composed of 20-30 parts of hexadecyltrimethylammonium bromide, 40-50 parts of distearate isopropyl borate, and 20-30 parts of laurylamide. The amount of the compound modifier is 0.2% to 1.5% of the dry matrix mass of calcium hydroxide.

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