Calcium carbonate filled masterbatch and method for its production

Abstract

The application discloses a calcium carbonate filling master batch and a preparation method thereof, and relates to the technical field of filling master batches. Marble raw materials are prepared into second calcium carbonate powder with a particle size of less than or equal to 13 microns through primary crushing, secondary crushing, primary modification grinding and secondary modification grinding, a certain weight part of linear low-density polyethylene, polyethylene wax and stearic acid is added to be mixed into a mixture, and the calcium carbonate filling master batch with a length of 3-5 mm is prepared through mixing and extruding, cooling and pelletizing. The calcium carbonate filling master batch prepared through two-stage crushing, two-stage modification grinding, premixing, mixing and extruding and cooling and pelletizing has good uniformity, no agglomerated calcium carbonate particles in the inside, and good applicability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of filling master batch, in particular to a calcium carbonate filling master batch and a preparation method thereof. BACKGROUND

[0002] Calcium carbonate has the characteristics of high chemical stability, low cost and easy availability, and is an excellent inorganic filler, which has wide application value in the plastic, paint, papermaking, rubber and other industries. In order to improve the convenience of application of calcium carbonate, calcium carbonate is usually mixed, mixed and granulated with carrier resin, additives and the like to prepare calcium carbonate filling master batch, which is convenient for transportation, and is helpful to simplify the production process of enterprises, improve the production efficiency of enterprises and reduce the dust in the production process of enterprises.

[0003] However, the existing calcium carbonate filling master batch has poor uniformity, and there are agglomerated calcium carbonate particles in the master batch, which causes the agglomerated calcium carbonate particles in the calcium carbonate filling master batch to be unable to open when the calcium carbonate filling master batch is applied in the production of plastic film, and a large number of white spots or even hard particles are formed on the plastic film, which affects the quality and appearance of the plastic film. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the prior art, and the present application provides a calcium carbonate filling master batch and a preparation method thereof. The calcium carbonate filling master batch with good uniformity is prepared by two-stage crushing, two-stage modified grinding, premixing, mixing and extruding and cooling and granulating, and there are no agglomerated calcium carbonate particles in the master batch, and the application is good.

[0005] The present application provides a preparation method of a calcium carbonate filling master batch, comprising the following steps:

[0006] First crushing, the marble raw material after cleaning is sent into a jaw crusher for first crushing to obtain marble coarse material with a particle size of ≤100mm;

[0007] Second crushing, the marble coarse material is sent into an impact crusher for second crushing to obtain marble fine material with a particle size of ≤40mm;

[0008] First modified grinding, the marble fine material and 2.5-3.5% of a surface modifier are uniformly stirred and then put into a first grinding machine to form first calcium carbonate powder with a particle size of ≤100μm;

[0009] Second modified grinding, the first calcium carbonate powder and 7.5-8.5% of the surface modifier are uniformly stirred and then put into a second grinding machine to form second calcium carbonate powder with a particle size of ≤13μm;

[0010] Pre-mixing, 80-120 parts by weight of the second calcium carbonate powder, 7-11 parts of linear low density polyethylene, 3.5-7.5 parts of polyethylene wax and 0.6-1.0 parts of stearic acid are put into a mixer and mixed at 110-125℃ for 15-45min to form a mixture;

[0011] Mixing extrusion, the mixture is put into a screw extruder for mixing extrusion to obtain a strand, the screw rotation speed of the screw extruder is set to 450-650rpm, and the mixing temperature of the screw extruder is set to 110-125℃;

[0012] Cooling and pelletizing, the strand is cooled using cold air at 2-8℃, and then the cooled strand is cut into calcium carbonate filling masterbatch with a length of 3-5mm using a pelletizer.

[0013] Specifically, before the primary crushing, it further comprises:

[0014] Washing, the marble raw material is washed using a water gun with a pressure of 0.5-1.5MPa, or is blown using an air gun with a pressure of 1.0-1.6MPa.

[0015] Specifically, the air temperature for the blowing ranges from 70 to 80℃.

[0016] Specifically, the surface modifier is one or more of surfactants, coupling agents, organic oligomers, organic acids, and water-soluble polymers.

[0017] Specifically, when the pre-mixing is performed, 1-5 parts of dry ice is added to the mixer, and the particle size of the dry ice is 1-3cm.

[0018] Specifically, when the pre-mixing is performed, the second calcium carbonate powder, the linear low density polyethylene, the polyethylene wax and the stearic acid are first mixed at 10-30℃ for 3-5min, and then the temperature is raised to 110-125℃ for 15-45min to form the mixture.

[0019] Specifically, the melt flow rate of the mixture is controlled to be 3-6g / 10min.

[0020] Specifically, the pre-mixing comprises:

[0021] First stage, the mixer is mixed at a speed of 50-80rpm for 3-5min;

[0022] Second stage, the mixer is mixed at a speed of 100-130rpm for 5min;

[0023] Third stage, the mixer is mixed at a speed of 200-230rpm for 5min;

[0024] In the fourth stage, the mixer is operated at a speed of 300-330 rpm for 5 minutes;

[0025] The second stage to the fourth stage is repeated 0-2 times.

[0026] Specifically, the screw extruder is a double-screw extruder or a triple-screw extruder.

[0027] The application also provides a calcium carbonate filled master batch prepared by the preparation method.

[0028] Compared with the prior art, the application has the following beneficial effects:

[0029] The application first sequentially subjects the cleaned marble to primary crushing, secondary crushing, primary modified grinding and secondary modified grinding to produce second calcium carbonate powder with a particle size of ≤13 μm, the second calcium carbonate powder is uniform in form, regular in shape, small in particle difference, and has good dispersibility and flowability; then pre-mixes the second calcium carbonate powder with a certain weight fraction of linear low-density polyethylene, polyethylene wax and stearic acid to form a mixture, the components in the mixture are uniformly dispersed, and the second calcium carbonate powder has good cross-linking with the linear low-density polyethylene; then further subjects the mixture to mixing and extrusion to obtain a strand, the components in the mixture are further dispersed and blended in the screw extruder, so that the second calcium carbonate powder and the linear low-density polyethylene are more uniformly mixed, and the agglomerated calcium carbonate particles are avoided; finally, cools and granulates the strand to produce calcium carbonate filled master batch with good uniformity, no agglomerated calcium carbonate particles in the interior, and good applicability, so that the calcium carbonate filled master batch applied in the production of plastic film does not cause white spots, hard particles and other defects in the plastic film, effectively improves the quality of the plastic film, and improves the appearance of the plastic film. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only constitute some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0031] Figure 1 is a flow chart of the preparation method of the calcium carbonate filled master batch in the embodiments of the application. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0033] Figure 1 A flow chart of a preparation method of the calcium carbonate filled master batch in the embodiments of the present application is shown, comprising the following steps:

[0034] S1, primary crushing;

[0035] The cleaned marble raw material is sent into a jaw crusher for the first crushing to obtain marble coarse material with a particle size of ≤100 mm.

[0036] The marble raw material carries dirt, sand and other impurities on the surface, which will affect the whiteness and purity of the calcium carbonate powder prepared subsequently, so the marble raw material needs to be cleaned. Optionally, a water gun with a pressure of 0.5-1.5 MPa is used to flush the marble raw material, and the water flow with pressure can easily flush away the dirt, sand and other impurities on the surface of the marble raw material, and also can reduce dust raising. Optionally, an air gun with a pressure of 1.0-1.6 MPa is used to blow the marble raw material, and the airflow with pressure can also easily blow away the dirt, sand and other impurities on the surface of the marble raw material, and can save water, and further, the gas temperature range for the blowing is 70-80℃, the hot airflow can fully dry the surface of the marble raw material, reduce the water carried by the marble raw material, reduce the probability of powder adhesion in the machine during crushing of the marble raw material, and is conducive to stable operation of the crusher.

[0037] The jaw crusher is commonly known as a jaw crusher, which is composed of two jaw plates, a moving jaw and a stationary jaw, and is a crusher that simulates the movement of the two jaws of an animal to complete the crushing of materials. It is widely used for crushing various ores and large materials, is solid and durable, is suitable for use as a "main" crusher, has strong feeding capacity, high output, low noise, less dust, large crushing ratio, uniform discharge particle size, and can efficiently produce marble coarse material with a particle size of ≤100 mm.

[0038] S2, secondary crushing;

[0039] The marble coarse material is sent into a counterattack crusher for second crushing to obtain marble fine material with a particle size of less than or equal to 40 mm; the counterattack crusher is a crushing machine using impact energy to crush the material, and can process the material with a side length of 100-500 mm, and the compressive strength can be up to 350 MPa, has the advantages of large crushing ratio, the crushed material is cubic particle, and is suitable for crushing the marble coarse material, has the advantages of large production capacity and small discharge particle size, and can efficiently produce the marble fine material with a particle size of less than or equal to 40 mm, which is convenient for subsequent modification and grinding, and reduces the grinding difficulty.

[0040] The marble raw material can be crushed into the required marble fine material more quickly through two-stage crushing, the crushing process time is shortened, and the production efficiency is improved; the second crushing can be performed immediately after the first crushing, and continuous production is realized.

[0041] In some specific embodiments, the marble fine material is also dried by sunning, air drying or baking, so that the water content of the marble fine material is reduced to less than or equal to 1%, the modified grinding is facilitated, the powder aggregation and adhesion in the grinding process are avoided, and the modified grinding efficiency is improved.

[0042] S3, primary modified grinding;

[0043] The marble fine material and 2.5-3.5% of the surface modifier are uniformly stirred and then fed into the first grinding machine to form first calcium carbonate powder with a particle size of less than or equal to 100 microns; the marble fine material and the surface modifier are uniformly stirred and then fed into the first grinding machine, so that the marble fine material and the surface modifier can be fully contacted, the modification effect is improved, and the amount of the surface modifier is reduced.

[0044] The surface modifier is one or more of a surfactant, a coupling agent, an organic oligomer, an organic acid and a water-soluble polymer, and has good dispersion, lubrication and compatibility; the surface modifier is adsorbed on the surface of the first calcium carbonate powder, can reduce the surface energy between the first calcium carbonate powder, weaken the intermolecular force, eliminate static electricity, prevent the first calcium carbonate powder from aggregating, and achieve uniform dispersion; the surface modifier can also reduce the risk of the first calcium carbonate powder adhering to the first grinding machine, reduce the intermolecular force of the first calcium carbonate powder, increase the processing fluidity and uniformity of the first calcium carbonate powder, and improve the compatibility of the first calcium carbonate powder with other substances, which is beneficial to the subsequent preparation of the calcium carbonate filling master batch.

[0045] The surface modifier can enhance the toughness, strength, hardness, dispersibility and fluidity of the first calcium carbonate powder, and facilitate further deep processing. Specifically, the surface active agent includes anionic surface active agent [stearic acid (salt), sulfonate and ester thereof, high-grade phosphate ester salt, etc.], cationic surface active agent [high-grade amine salt (primary amine, secondary amine, tertiary amine and quaternary ammonium salt)], and non-ionic surface active agent (such as polyethylene glycol, polyhydric alcohol), etc.; the coupling agent mainly includes silane, titanate, aluminate, zirconium aluminate, etc.; the organic oligomer mainly includes random polypropylene, polyethylene wax, epoxy resin, etc.; the organic acid mainly includes acrylic acid, methacrylic acid, butenoic acid, maleic acid, chloroacrylic acid, etc.; and the water-soluble polymer mainly includes polyacrylic acid (salt) and copolymer thereof, polyvinyl alcohol, polymaleic acid, etc.

[0046] Adding the surface modifier with a proper proportion to the marble fines can increase the dispersibility of the powder and enhance the cross-linking of the powder with other substances, effectively reduce the probability of agglomeration of the first calcium carbonate powder, and improve the performance of the first calcium carbonate powder as a filler.

[0047] The first grinding machine is one of a ring roller mill, a Raymond mill or a vertical mill, which has high grinding efficiency, strong grinding capacity, large output and low energy consumption, can quickly refine the marble fines into the first calcium carbonate powder, promote the compatibility of the surface modifier with the powder, achieve the effect of coating modification, realize efficient output of the modified first calcium carbonate powder with a particle size of ≤100 μm, and shorten the time of the primary modification grinding.

[0048] In some embodiments, when the primary modification grinding is performed, the method further includes:

[0049] The ion wind with a temperature of 60-70°C is introduced into the first grinding machine, the ion wind is prepared by ionizing hot air through corona discharge by using an ion wind machine to generate a large number of positive and negative charges, the positive and negative charges in the ion wind can neutralize the heterogeneous charges on the powder to eliminate static electricity, avoid agglomeration of the powder, and improve the grinding efficiency; at the same time, the ion wind with a temperature of 60-70°C can also dry the powder, reduce the water content of the powder, and avoid adhesion of the powder to the inside of the equipment to affect the grinding efficiency; in addition, the ion wind with a temperature of 60-70°C can also adjust the working temperature of the primary modification grinding, improve the uniform coating modification effect of the surface modifier, and promote the fusion of the first calcium carbonate powder with the surface modifier to improve the modification efficiency.

[0050] Further, the ion wind has a wind speed of 3.4 m / s to 5.4 m / s, and the powder with a particle size of ≤100 μm is taken away into the next process as qualified first calcium carbonate powder, and the powder with a particle size of >100 μm is continuously left in the first grinding machine for grinding, so as to facilitate the secondary modification grinding; the relative humidity of the ion wind is less than 10%, which is beneficial to ensure the dry grinding environment of the primary modification grinding, prevent the powder from agglomerating in the grinding process, and prevent the powder from adhering to the grinding cavity of the first grinding machine, and can improve the efficiency of the primary modification grinding.

[0051] In order to realize the continuous primary modification grinding, the surface modifier is continuously added in a linkage manner with the feeding speed of the marble fines before the marble fines and the surface modifier are fed into the first grinding machine, so as to facilitate the rapid and sufficient stirring and mixing of the marble fines and the surface modifier, and the uniformly stirred and mixed material can be continuously conveyed into the first grinding machine.

[0052] S4, secondary modification grinding;

[0053] After the first calcium carbonate powder and 7.5% to 8.5% of the surface modifier are uniformly stirred, the first calcium carbonate powder and the surface modifier are fed into the second grinding machine to form second calcium carbonate powder with a particle size of ≤13 μm, and the first calcium carbonate powder and the surface modifier are fed into the second grinding machine after being uniformly stirred, so that the first calcium carbonate powder and the surface modifier can be fully contacted, the modification effect can be improved, and the amount of the surface modifier can be reduced.

[0054] The surface modifier is one or more of a surfactant, a coupling agent, an organic oligomer, an organic acid, and a water-soluble polymer, and has good dispersion, lubrication, and compatibility; the surface modifier is adsorbed on the surface of the second calcium carbonate powder, can reduce the surface energy between the second calcium carbonate powder, weaken the intermolecular force, and eliminate static electricity, so as to prevent the second calcium carbonate powder from agglomerating and achieve uniform dispersion; the surface modifier can also reduce the risk of the second calcium carbonate powder adhering to the second grinding machine, reduce the intermolecular force between the second calcium carbonate powder, and increase the processing fluidity and uniformity of the second calcium carbonate powder; the surface modifier can also improve the compatibility of the second calcium carbonate powder with other substances, which is beneficial to the subsequent preparation of the calcium carbonate filling master batch.

[0055] The surface modifier can enhance the toughness, strength, hardness, dispersibility and fluidity of the second calcium carbonate powder, and facilitate further deep processing. Specifically, the surface active agent includes anionic surfactants [stearic acid (salt), sulfonate and ester thereof, high-grade phosphate ester salt, etc.], cationic surfactants [high-grade amine salt (primary amine, secondary amine, tertiary amine and quaternary ammonium salt)], and non-ionic surfactants (such as polyethylene glycol, polyhydric alcohol), etc.; the coupling agent mainly includes silane, titanate, aluminate, zirconium aluminate, etc.; the organic oligomer mainly includes atactic polypropylene, polyethylene wax, epoxy resin, etc.; the organic acid mainly includes acrylic acid, methacrylic acid, butenoic acid, maleic acid, chloroacrylic acid, etc.; and the water-soluble polymer mainly includes polyacrylic acid (salt) and copolymer thereof, polyvinyl alcohol, polymaleic acid, etc.

[0056] Adding the surface modifier to the first calcium carbonate powder in a proper proportion can further increase the dispersibility of the powder and further enhance the cross-linking property of the powder with other substances, significantly reduce the probability of agglomeration of the second calcium carbonate powder, and improve the performance of the second calcium carbonate powder as a filler.

[0057] The second grinding machine is one of a sand mill, a stirring mill or a ball mill, and grinding media can be filled into the second grinding machine to sufficiently grind and modify the first calcium carbonate powder, further refine the particle size of the powder, improve the morphology of the powder, and reduce the particle size difference of the powder, so as to obtain the modified second calcium carbonate powder with a particle size of ≤13 μm.

[0058] Specifically, the grinding media include at least one of zirconium silicate beads, aluminum oxide beads, zirconium dioxide beads, rare earth metal stabilized zirconium dioxide beads or steel beads, and the filling rate of the grinding media is 50-70%. The grinding media and the first calcium carbonate powder continuously replace positions in the grinding cavity, and generate intense movement. In this process, the first calcium carbonate powder is crushed by the extrusion, impact and shearing of the grinding media, so as to refine the first calcium carbonate powder with a particle size of ≤100 μm, and obtain the second calcium carbonate powder with a particle size of ≤13 μm.

[0059] Specifically, when the diameter of the grinding media is 0.5-0.75 mm, the filling rate of the grinding media is 50-60%; when the diameter of the grinding media is 1-10 mm, the filling rate of the grinding media is 60-65%; and when the diameter of the grinding media is 15-25 mm, the filling rate of the grinding media is 65-70%.

[0060] In order to continuously perform the secondary modification and grinding, the surface modifier is continuously added in linkage with the feeding speed of the first calcium carbonate powder before the first calcium carbonate powder and the surface modifier are fed into the second grinding machine, so as to facilitate rapid and sufficient stirring and mixing of the first calcium carbonate powder and the surface modifier. The uniformly stirred and mixed material can be continuously fed into the second grinding machine.

[0061] Further, in the secondary modification grinding, the working temperature is controlled at 130-180 DEG C, which can effectively promote the fusion of the surface modifier and the calcium carbonate powder, improve the modification efficiency and enhance the modification effect.

[0062] The present application can realize excellent modification effect with less surface modifier by the two-stage modification grinding, thereby reducing the use cost of the surface modifier.

[0063] In some embodiments, after the secondary modification grinding, the method further comprises:

[0064] In addition to iron, the second calcium carbonate powder is subjected to iron removal by using an electromagnetic dry powder iron remover. The marble raw material can contain iron, and the wear of crushing equipment and powder grinding equipment during the powder processing can cause fine metal particles to enter the powder, which can affect the whiteness of the powder, even form red and brown spots in the calcium carbonate filled masterbatch, affect the appearance of the product, and also affect the quality and appearance of the plastic film when the calcium carbonate filled masterbatch is applied to the preparation of the plastic film.

[0065] The electromagnetic dry powder iron remover has a high-strength electromagnetic field, can automatically remove iron, has high iron removal efficiency, is easy to use, and is suitable for removing iron from powder.

[0066] S5, premixing;

[0067] According to weight parts, 80-120 parts of the second calcium carbonate powder, 7-11 parts of linear low-density polyethylene, 3.5-7.5 parts of polyethylene wax, and 0.6-1.0 parts of stearic acid are put into a mixer and mixed at 110-125 DEG C for 15-45 min to form a mixture. The melted linear low-density polyethylene, polyethylene wax, and stearic acid are mixed into the second calcium carbonate powder to form a uniform and stable mixture. The greater the weight parts of the second calcium carbonate powder, the greater the proportion, and the lower the raw material cost of the prepared calcium carbonate filled masterbatch. Linear low-density polyethylene is a carrier resin that can crosslink with the second calcium carbonate powder to form a stable system. Polyethylene wax has good lubricity, can prevent adhesion, promote uniform dispersion of the second calcium carbonate powder, and prevent the second calcium carbonate powder from agglomerating during crosslinking with linear low-density polyethylene. Hard acid can improve the flowability of linear low-density polyethylene in the molten state and enhance the crosslinking effect of the second calcium carbonate powder and linear low-density polyethylene, thereby improving the uniformity and stability of the mixture.

[0068] The materials are pre-mixed and then enter the subsequent mixing and extruding process, effectively ensuring the uniformity of the materials, reducing the difficulty of mixing, and avoiding uneven distribution of the second calcium carbonate powder.

[0069] In some embodiments, when the pre-mixing is performed, 1-5 parts of dry ice with a particle size of 1-3 cm is added to the mixer. A small amount of dry ice involved in the pre-mixing can release a large amount of carbon dioxide, which can adjust the state of the mixture and prevent the mixture from becoming paste-like and causing difficulty in discharging. At the same time, carbon dioxide can assist in mixing and remove residual moisture, improving the mixing effect of the materials and reducing the agglomeration of the second calcium carbonate powder.

[0070] In some embodiments, when the pre-mixing is performed, the second calcium carbonate powder, the linear low-density polyethylene, the polyethylene wax, and the stearic acid are mixed at 10-30℃ for 3-5 min, and then heated to 110-125℃ for 15-45 min to form the mixture. The materials are first mixed uniformly at room temperature, and then heated to promote the melting of the linear low-density polyethylene, the polyethylene wax, and the stearic acid, so that the melted materials are fully and uniformly mixed with the second calcium carbonate powder, reducing the risk of agglomeration of the second calcium carbonate powder.

[0071] Further, the melt flow rate of the mixture is controlled to be 3-6 g / 10 min. If the melt flow rate is less than 3 g / 10 min, it is difficult to discharge, affecting production efficiency. If the melt flow rate is greater than 6 g / 10 min, it is not conducive to subsequent mixing and extrusion, and the formed tensile bar has insufficient toughness.

[0072] Specifically, the pre-mixing includes:

[0073] In the first stage, the mixer is mixed at a speed of 50-80 revolutions / min for 3-5 min. The materials are first mixed uniformly at a lower speed. The first stage is performed at 10-30℃.

[0074] In the second stage, the mixer is mixed at a speed of 100-130 revolutions / min for 5 min.

[0075] In the third stage, the mixer is mixed at a speed of 200-230 revolutions / min for 5 min.

[0076] In the fourth stage, the mixer is mixed at a speed of 300-330 revolutions / min for 5 min.

[0077] The second stage to the fourth stage is repeated 0-2 times, and the second stage to the fourth stage is performed at 110-125℃.

[0078] The first stage to the fourth stage, the speed of the mixer is gradually increased to match the mixing state of the material, so as to achieve better mixing effect, improve the uniformity of the material mixing, and avoid material aggregation; then, the second stage to the fourth stage can be repeated 0-2 times, so as to adjust the state of the mixed material, so that the mixed material meets the requirements of the subsequent process.

[0079] S6, mixing and extruding;

[0080] The mixed material is put into a screw extruder for mixing and extruding to obtain a strand, the screw speed of the screw extruder is set to 450-650 rpm, and the mixing temperature of the screw extruder is set to 110-125℃. At a certain temperature, the screw extruder relies on the pressure and shear force generated by the rotation of the screw to further plasticize and mix the mixed material, and then extrudes the mixed material through a die to form a strand, which is convenient for subsequent granulation.

[0081] Specifically, the screw extruder is a double-screw extruder or a triple-screw extruder. The double-screw extruder has good feeding performance, mixing and plasticizing performance, exhaust performance, and extrusion stability, and is commonly used for granulation. The triple-screw extruder has better mixing and plasticizing performance than the double-screw extruder, and the residence time of the material at high temperature is short, which effectively saves energy and reduces emissions.

[0082] S7, cooling and granulating;

[0083] The strand is cooled by cold air at 2-8℃, and then the cooled strand is cut into calcium carbonate filling master batches with a length of 3-5mm by using a granulator. The cold air cooling of the strand can keep the strand dry, so that the calcium carbonate filling master batches obtained by cutting are kept in a dry state without the need for additional drying. The calcium carbonate filling master batches with a length of 3-5mm are convenient to use and can be quickly melted and uniformly mixed with the base resin and other materials in a short time.

[0084] Further, after the cooling and granulating, it further includes packaging, which is sealed into a calcium carbonate filling master batch package according to a predetermined specification, and 0.1-0.3% by weight of a desiccant package is added to each calcium carbonate filling master batch package. The sealed package and the addition of the desiccant package can prevent the calcium carbonate filling master batch from being damp and ensure the stability of the properties of the calcium carbonate filling master batch.

[0085] The invention first carries out first-stage crushing, second-stage crushing, first-stage modified grinding and second-stage modified grinding on the cleaned marble in sequence to make second calcium carbonate powder with a particle size of ≤13 μm, the second calcium carbonate powder is uniform in form, regular in shape, small in particle difference, and has good dispersibility and flowability; then the second calcium carbonate powder is premixed with a certain weight of linear low-density polyethylene, polyethylene wax and stearic acid to form a mixture, the components in the mixture are uniformly dispersed, and the second calcium carbonate powder has good cross-linking with the linear low-density polyethylene; then the mixture is mixed and extruded to obtain a draw bar, the components in the mixture are further dispersed and blended in the screw extruder, so that the mixing uniformity of the second calcium carbonate powder and the linear low-density polyethylene is better, and the agglomerated calcium carbonate particles are avoided; finally, the draw bar is cooled and granulated to obtain calcium carbonate filling master batch with good uniformity, no agglomerated calcium carbonate particles in the inside, and good applicability, so that the calcium carbonate filling master batch applied in the production of plastic film will not cause white spots, hard particles and other defects in the plastic film, effectively improving the quality of the plastic film and improving the appearance of the plastic film.

[0086] In the invention, the first-stage crushing and the second-stage crushing can be carried out on the mining site of the marble raw material, and the marble raw material is crushed into marble fines, which is more convenient for transportation and handling; the first-stage modified grinding, the second-stage modified grinding, the premixing, the mixing and extruding and the cooling and granulating can be carried out in the same factory building, which is convenient for monitoring the quality of the intermediate products in each process flow, convenient for quality control, and guarantees the stability of the calcium carbonate filling master batch product; moreover, the modification, the powder grinding, the mixing, the mixing and extruding and the granulating are completed in the same factory building, which saves the packaging and transportation costs of the calcium carbonate powder, avoids the problems of denaturation and pollution of the calcium carbonate powder, and makes the production process of the calcium carbonate filling master batch more efficient and energy-saving.

[0087] The calcium carbonate filling master batch and the preparation method thereof provided by the embodiment of the invention are described in detail above, and the principles and implementation manners of the invention are described by using specific examples in this paper; the above embodiment description is only used to help understand the method and the core idea of the invention; meanwhile, according to the idea of the invention, the specific implementation manner and the application range will be changed by the general technical personnel in the field; in summary, the content of the specification should not be understood as a limitation of the invention.

Claims

1. A method for preparing calcium carbonate filler masterbatch for use in the production of plastic films, characterized in that, Includes the following steps; Primary crushing involves feeding the cleaned marble raw material into a jaw crusher for the first crushing to obtain marble coarse material with a particle size ≤100mm. Secondary crushing involves feeding the coarse marble material into an impact crusher for a second crushing process to obtain fine marble material with a particle size ≤40mm. First-stage modified grinding involves mixing the marble fines and 2.5-3.5% surface modifier evenly, then grinding them in a first grinding mill to form first calcium carbonate powder with a particle size ≤100μm. Secondary modified grinding: the first calcium carbonate powder and 7.5-8.5% of the surface modifier are stirred evenly and then fed into a second grinding mill to form a second calcium carbonate powder with a particle size ≤13μm; Premixing: By weight, 80-120 parts of the second calcium carbonate powder, 7-11 parts of linear low-density polyethylene, 3.5-7.5 parts of polyethylene wax, and 0.6-1.0 parts of stearic acid are added to a mixer and mixed at 110-125°C for 15-45 minutes to form a mixture. During the premixing, 1-5 parts of dry ice with a particle size of 1-3 cm are added to the mixer. The dry ice releases carbon dioxide during the premixing process, which is used to adjust the state of the mixture and prevent it from becoming a paste, as well as to remove residual moisture from the second calcium carbonate powder and reduce its agglomeration. The mixture is fed into a screw extruder for compounding and extrusion to obtain strands. The screw speed of the screw extruder is set to 450-650 rpm, and the compounding temperature of the screw extruder is set to 110-125℃. Cooling and pelletizing: The strips are cooled with cold air at 2-8°C, and then the cooled strips are cut into calcium carbonate filler masterbatches with a length of 3-5 mm using a pelletizer.

2. The preparation method according to claim 1, characterized in that, Prior to the primary crushing, the process also includes: For cleaning, use a water gun with a pressure of 0.5 to 1.5 MPa to rinse the marble raw material, or use an air gun with a pressure of 1.0 to 1.6 MPa to blow and wash the marble raw material.

3. The preparation method according to claim 2, characterized in that, The temperature range of the air used for blowing and rinsing is 70–80°C.

4. The preparation method according to claim 1, characterized in that, The surface modifier is one or more of surfactants, coupling agents, organic oligomers, organic acids, and water-soluble polymers.

5. The preparation method according to claim 1, characterized in that, During the premixing process, the second calcium carbonate powder, the linear low-density polyethylene, the polyethylene wax, and the stearic acid are first mixed at 10-30°C for 3-5 minutes, and then heated to 110-125°C and mixed for 15-45 minutes to form the mixture.

6. The preparation method according to claim 1, characterized in that, The melt flow rate of the mixture is controlled to be 3-6 g / 10 min.

7. The preparation method according to claim 1, characterized in that, The premix includes: In the first stage, the mixer mixes at a speed of 50-80 rpm for 3-5 minutes. In the second stage, the mixer mixes at a speed of 100-130 rpm for 5 minutes. In the third stage, the mixer mixes at a speed of 200-230 rpm for 5 minutes. In the fourth stage, the mixer mixes at a speed of 300-330 rpm for 5 minutes; Repeat the second stage to the fourth stage 0 to 2 times.

8. The preparation method according to claim 1, characterized in that, The screw extruder is a twin-screw extruder or a three-screw extruder.

9. A calcium carbonate filler masterbatch for use in the production of plastic films, characterized in that, The calcium carbonate filler masterbatch is prepared by the preparation method according to any one of claims 1 to 8.

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