Superfine ground calcium carbonate for PVC (Polyvinyl Chloride) cable as well as preparation method and application of superfine ground calcium carbonate

Abstract

The invention provides superfine ground calcium carbonate for a PVC (polyvinyl chloride) cable as well as a preparation method and application thereof, and belongs to the technical field of mineral fillers. The preparation method comprises the following steps: sequentially carrying out primary crushing and secondary crushing on calcite raw ore, carrying out ring roller grinding and primary grading on the obtained crushed material, carrying out ball milling on the obtained ground calcium carbonate powder, a grinding aid, a silane coupling agent and stearic acid, and carrying out secondary grading to obtain the superfine ground calcium carbonate for the PVC cable. The obtained superfine heavy calcium carbonate is small in fineness, high in oil absorption value, high in activation degree and good in processing fluidity and dispersity in the PVC cable preparation process, and the mechanical property and the surface brightness of the prepared PVC cable are improved.

Description

Technical Field

[0001] The invention relates to the technical field of mineral fillers, and in particular to ultrafine heavy calcium carbonate for PVC cables and a preparation method and application thereof. Background Art

[0002] Calcium carbonate is one of the earliest developed inorganic ultrafine materials, and calcium carbonate filling and modifying PVC is a common modification method for PVC. In the PVC cable filling formula system, calcium carbonate is the most common and largest inorganic non-metallic powder filler. Heavy calcium carbonate is rich in resources, widely distributed, and has a simple processing technology. It has many excellent properties such as low price, non-toxic and odorless, high whiteness, good color, and good thermal stability. Therefore, heavy calcium carbonate is widely used in plastic industries such as wires and cables.

[0003] With the development of PVC cable material application technology, the requirements for calcium carbonate are getting higher and higher. In recent years, with the continuous in-depth research on fillers towards ultrafine and functionalization, the research and development of ultrafine heavy calcium carbonate has become a research hotspot in the calcium carbonate industry, and ultrafine heavy calcium carbonate has gradually become an important functional filler. Ultrafine heavy calcium carbonate has a special surface effect that makes it have excellent reinforcement compared with conventional fillers, and can improve the mechanical properties and surface brightness of PVC cables. In order to meet the high requirements for high brightness and mechanical properties of the surface of PVC cables, a preparation method of ultrafine heavy calcium carbonate for PVC cables has been specially developed. Summary of the invention

[0004] The object of the present invention is to provide an ultrafine heavy calcium carbonate for PVC cables and a preparation method and application thereof. The obtained ultrafine calcium carbonate has good processing fluidity and dispersibility and can improve the mechanical properties and surface brightness of the cable.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing ultrafine heavy calcium carbonate for PVC cables, comprising the following steps:

[0007] The small calcite ore is subjected to primary crushing and secondary crushing in sequence to obtain crushed material;

[0008] The crushed materials are subjected to roller grinding and primary classification in sequence to obtain heavy calcium carbonate powder;

[0009] The heavy calcium carbonate powder is ball-milled with a grinding aid, a silane coupling agent and stearic acid, and then subjected to secondary classification to obtain ultrafine heavy calcium carbonate for PVC cables.

[0010] Preferably, the frequency of the classifier used in the primary classification is 22-25 Hz, and the rotation speed is 650-750 r / min.

[0011] Preferably, the particle size of the heavy calcium carbonate powder is 400-600 mesh.

[0012] Preferably, the grinding aid includes one or more of sodium hexametaphosphate, triethanolamine and monoethanoldiisopropanolamine, and the mass of the grinding aid is 3-7‰ of the mass of heavy calcium carbonate powder.

[0013] Preferably, the mass of the silane coupling agent is 8-12‰ of the mass of the heavy calcium carbonate powder, and the silane coupling agent includes one or more of γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, γ-diethylenetriaminepropyltrimethoxysilane or γ-aminopropylmethyldiethoxysilane; the mass of the stearic acid is 3-5‰ of the mass of the heavy calcium carbonate powder.

[0014] Preferably, the ball mill used for ball milling is divided into a front chamber and a rear chamber at a distance of 2.2 m from the feed port of the ball mill. Taking the total mass content of the grinding medium in the front chamber as 100%, the grinding medium in the front chamber includes 10-30% ceramic balls with a diameter of 40-45 mm, 20-55% ceramic balls with a diameter of 30-35 mm, and 10-40% ceramic balls with a diameter of 15-20 mm; taking the total mass content of the grinding medium in the rear chamber as 100%, the grinding medium in the rear chamber includes 10-35% ceramic balls with a diameter of 20-40 mm, 15-55% ceramic balls with a diameter of 10-15 mm, and 10-35% ceramic balls with a diameter of 5-10 mm.

[0015] Preferably, the classifier used for the secondary classification is two groups of tandem classifiers, each of the two groups of tandem classifiers is composed of three grading wheels with a diameter of 315 mm; the frequency of the classifier used for the secondary classification is 60-76 Hz, and the rotation speed is 3200-3800 r / min.

[0016] The invention provides ultrafine heavy calcium carbonate for PVC cables prepared by the preparation method.

[0017] The present invention also provides application of the ultrafine heavy calcium carbonate for PVC cables in PVC cables.

[0018] Beneficial effects of the present invention: The present invention uses ball milling to ultrafinely grind high-quality small calcite, and then performs surface modification on the powder. After the ultrafine grinding and surface modification, the powder has the characteristics of good processing fluidity and good dispersibility in the process of preparing PVC cables, which can improve the mechanical properties and surface brightness of the cables. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1This is a flow chart of the method for preparing ultrafine heavy calcium carbonate for PVC cables of the present invention;

[0020] Figure 2 This is an electron microscope photograph of the ultrafine heavy calcium carbonate powder obtained in Example 1, magnified 5000 times. DETAILED DESCRIPTION

[0021] The present invention provides a method for preparing ultrafine heavy calcium carbonate for PVC cables, comprising the following steps:

[0022] The small calcite ore is subjected to primary crushing and secondary crushing in sequence to obtain crushed material;

[0023] The crushed materials are subjected to roller grinding and primary classification in sequence to obtain heavy calcium carbonate powder;

[0024] The heavy calcium carbonate powder is ball-milled with a grinding aid, a silane coupling agent and stearic acid, and then subjected to secondary classification to obtain ultrafine heavy calcium carbonate for PVC cables.

[0025] In the present invention, unless otherwise specified, the required raw materials for preparation are all commercially available products well known to those skilled in the art.

[0026] The present invention preferably subjects the small calcite ore to coarse crushing, washing and primary crushing to obtain ore with a diameter of 5 to 10 cm, which is then placed in a silo for secondary crushing to obtain crushed material with a diameter of 5 to 10 mm.

[0027] The small calcite ore of the present invention is preferably sourced from the Yongfengcengshan Mine in Ji'an, Jiangxi Province, and the purity of the small calcite ore is preferably 96-98%.

[0028] In the present invention, the crushed material is preferably subjected to ring roller grinding by a 198 type ring roller mill, and is subjected to a primary classification after grinding to obtain heavy calcium carbonate powder; in the present invention, the frequency of the classifier used for the primary classification is preferably 22 to 25 Hz, more preferably 22 to 24 Hz, and more preferably 24 Hz; the rotation speed of the classifier is preferably 650 to 750 r / min, more preferably 680 to 750 r / min, and more preferably 700 to 750 r / min; the particle size of the heavy calcium carbonate powder is preferably 400 to 600 mesh, more preferably 450 to 600 mesh, and more preferably 500 to 600 mesh.

[0029] The present invention preferably transports heavy calcium carbonate powder to a full ceramic ball mill through a pipeline for grinding, adds a grinding aid, a silane coupling agent and stearic acid at the inlet of the ball mill, and obtains ultrafine heavy calcium carbonate for PVC cables after ball milling and secondary classification.

[0030] In the present invention, the grinding aid preferably includes one or more of sodium hexametaphosphate, triethanolamine and monoethanol diisopropanolamine, further preferably includes one or more of sodium hexametaphosphate, triethanolamine and monoethanol diisopropanolamine, more preferably one or more of sodium hexametaphosphate and monoethanol diisopropanolamine. When the grinding aid includes two or more types, the present invention does not specifically limit the mass ratio between the grinding aids. In an embodiment of the present invention, the grinding aid is preferably sodium hexametaphosphate and monoethanol diisopropanolamine in a mass ratio of 1:1; the mass of the grinding aid is preferably 3-7‰ of the mass of the heavy calcium carbonate powder, further preferably 4-7‰, and more preferably 5-7‰.

[0031] In the present invention, the silane coupling agent preferably includes one or more of γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, γ-diethylenetriaminepropyltrimethoxysilane or γ-aminopropylmethyldiethoxysilane, further preferably includes one or more of γ-aminopropyltrimethoxysilane or γ-aminopropylmethyldimethoxysilane, and more preferably includes γ-aminopropyltrimethoxysilane. The mass of the silane coupling agent is preferably 8 to 12‰ of the mass of the heavy calcium carbonate powder, further preferably 9 to 11‰, and more preferably 10 to 11‰; the mass of the stearic acid is preferably 3 to 5‰ of the mass of the heavy calcium carbonate powder, further preferably 3 to 4‰, and more preferably 3.2 to 4‰.

[0032] In the present invention, the ball mill used for the ball milling is preferably a full ceramic ball mill, and the size is preferably: 2.0m in diameter, 7.5m in length, the lining is a full ceramic structure, and the grinding medium is a ceramic ball; the present invention is preferably divided into a front bin and a rear bin at 2.2m away from the feed inlet of the ball mill, and the total content of the grinding medium in the front bin is 100%, and the grinding medium in the front bin preferably includes 10-30% of ceramic balls with a diameter of 40-45mm, 20-55% of ceramic balls with a diameter of 30-35mm, and 10-40% of ceramic balls with a diameter of 15-20mm. The step preferably includes 20-30% of ceramic balls with a diameter of 40-45mm, 20-40% of ceramic balls with a diameter of 30-35mm, and 15-30% of ceramic balls with a diameter of 15-20mm, and more preferably includes 25-30% of ceramic balls with a diameter of 40-45mm, 25-30% of ceramic balls with a diameter of 30-35mm, and 20-30% of ceramic balls with a diameter of 15-20mm; the diameter of the grinding media in the front chamber preferably includes 40-45mm, 30-35mm, and 15-20mm, and further preferably includes 43-4 5mm, 30-33mm, 15-18mm, more preferably including 45mm, 30mm, 15mm; if the total content of the grinding media in the rear bin is 100%, the grinding media in the rear bin preferably includes 10-35% of ceramic balls with a diameter of 20-40mm, 15-55% of ceramic balls with a diameter of 10-15mm, and 10-35% of ceramic balls with a diameter of 5-10mm, and further preferably includes 20-30% of ceramic balls with a diameter of 20-40mm, 15-30% of ceramic balls with a diameter of 10-15mm, 15-35% of ceramic balls have a diameter of 5-10mm, more preferably 25-30% of ceramic balls have a diameter of 20-40mm, 25-30% of ceramic balls have a diameter of 10-15mm, and 15-30% of ceramic balls have a diameter of 5-10mm; the diameter of the grinding media in the rear bin preferably includes 20-40mm, 10-15mm, and 5-10mm, further preferably includes 30-40mm, 12-15mm, and 6-10mm, and more preferably includes 35-40mm, 13-15mm, and 8-10mm.

[0033] In the present invention, the classifier used for the secondary classification is preferably two groups of tandem classifiers, and each group of tandem classifiers in the two groups of tandem classifiers is preferably composed of 3 grading wheels with a diameter of 315 mm; the frequency of the classifier used for the secondary classification is preferably 60-76 Hz, further preferably 60-72 Hz, and more preferably 64-75 Hz; the rotation speed of the classifier used for the secondary classification is preferably 3200-3800 r / min, further preferably 3200-3700 r / min, and more preferably 3200-3600 r / min.

[0034] The present invention provides ultrafine heavy calcium carbonate for PVC cables prepared by the above preparation method, wherein the particle size of the ultrafine heavy calcium carbonate powder for PVC cables is preferably 6000 meshes.

[0035] The present invention also provides application of the ultrafine heavy calcium carbonate for PVC cables in PVC cables.

[0036] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0037] The dimensions of the all-ceramic ball mill used in Examples 1 to 6 are: 2.0 m in diameter, 7.5 m in length, the inner lining is an all-ceramic structure, the grinding medium is ceramic balls, and it is divided into a front chamber and a rear chamber 2.2 m away from the feed inlet of the ball mill.

[0038] Example 1

[0039] The raw calcite with a purity of 96-98% is fed into a hammer crusher, and after primary crushing and secondary crushing, a crushed material with a diameter of 5-10 mm is obtained;

[0040] The crushed materials are subjected to roller grinding and primary classification in sequence. The frequency of the classifier used for the primary classification is 24 Hz and the speed is 700 r / min. After classification, 400 mesh heavy calcium carbonate powder is obtained;

[0041] The heavy calcium carbonate powder is transported to the all-ceramic ball mill through a pipeline. The total content of the grinding media in the front bin is 100%, and the grinding media in the front bin of the ball mill includes 30% ceramic balls with a diameter of 45mm, 25% ceramic balls with a diameter of 30mm, and 15% ceramic balls with a diameter of 15mm. The total content of the grinding media in the rear bin is 100%, and the grinding media in the rear bin includes 30% ceramic balls with a diameter of 40mm, 25% ceramic balls with a diameter of 15mm, and 15% ceramic balls with a diameter of 10mm. A composite grinding aid of sodium hexametaphosphate and monoethanol diisopropanolamine in a mass ratio of 1:1 was added to the mill, with a mass ratio of 4‰ of the heavy calcium carbonate powder, and a composite surface modifier of γ-diethylenetriaminepropyltrimethoxysilane with a mass of 8‰ of the heavy calcium carbonate powder and stearic acid with a mass of 3‰ of the heavy calcium carbonate powder were added, and ball milling and secondary classification were performed in sequence. The frequency of the classifier used for the secondary classification was 67 Hz and the rotation speed was 3800 r / min to obtain the ultrafine heavy calcium carbonate for PVC cable of Example 1.

[0042] Example 2

[0043] The only difference from Example 1 is:

[0044] If the total content of the grinding media in the front bin is 100%, the grinding media in the front bin of the ball mill includes 25% ceramic balls with a diameter of 45 mm, 30% ceramic balls with a diameter of 30 mm, and 20% ceramic balls with a diameter of 15 mm. If the total content of the grinding media in the rear bin is 100%, the grinding media in the rear bin includes 25% ceramic balls with a diameter of 40 mm, 30% ceramic balls with a diameter of 15 mm, and 20% ceramic balls with a diameter of 10 mm.

[0045] The mass of the composite grinding aid is 6‰ of the mass of the heavy calcium carbonate powder;

[0046] The composite surface modifier is 8‰ of the weight of the heavy calcium carbonate powder and 3.2‰ of the weight of the heavy calcium carbonate powder.

[0047] The ultrafine heavy calcium carbonate for PVC cable of Example 2 was obtained.

[0048] Example 3

[0049] The only difference from Example 1 is:

[0050] If the total content of the grinding media in the front bin is 100%, the grinding media in the front bin of the ball mill includes 20% of ceramic balls with a diameter of 45 mm, 25% of ceramic balls with a diameter of 30 mm, and 30% of ceramic balls with a diameter of 15 mm. If the total content of the grinding media in the rear bin is 100%, the grinding media in the rear bin includes 20% of ceramic balls with a diameter of 40 mm, 25% of ceramic balls with a diameter of 10 mm, and 30% of ceramic balls with a diameter of 10 mm.

[0051] The mass of the composite grinding aid is 7‰ of the mass of the heavy calcium carbonate powder;

[0052] The composite surface modifier is γ-aminopropyltrimethoxysilane at a weight of 10‰ based on the weight of the heavy calcium carbonate powder and stearic acid at a weight of 4‰ based on the weight of the heavy calcium carbonate powder;

[0053] The ultrafine heavy calcium carbonate for PVC cable of Example 3 was obtained.

[0054] Example 4

[0055] The only difference from Example 1 is:

[0056] If the total content of the grinding media in the front bin is 100%, the grinding media in the front bin of the ball mill includes 30% of ceramic balls with a diameter of 40 mm, 25% of ceramic balls with a diameter of 20 mm, and 15% of ceramic balls with a diameter of 15 mm. If the total content of the grinding media in the rear bin is 100%, the grinding media in the rear bin includes 30% of ceramic balls with a diameter of 30 mm, 25% of ceramic balls with a diameter of 15 mm, and 15% of ceramic balls with a diameter of 5 mm.

[0057] The mass of the composite grinding aid is 5‰ of the mass of the heavy calcium carbonate powder;

[0058] The composite surface modifier is γ-aminopropyltrimethoxysilane at a weight of 12‰ based on the weight of the heavy calcium carbonate powder and stearic acid at a weight of 4‰ based on the weight of the heavy calcium carbonate powder;

[0059] The ultrafine heavy calcium carbonate for PVC cable of Example 4 was obtained.

[0060] Example 5

[0061] The only difference from Example 1 is:

[0062] If the total content of the grinding media in the front bin is 100%, the grinding media in the front bin of the ball mill includes 25% of ceramic balls with a diameter of 40 mm, 30% of ceramic balls with a diameter of 20 mm, and 20% of ceramic balls with a diameter of 15 mm. If the total content of the grinding media in the rear bin is 100%, the grinding media in the rear bin includes 25% of ceramic balls with a diameter of 35 mm, 30% of ceramic balls with a diameter of 15 mm, and 20% of ceramic balls with a diameter of 5 mm.

[0063] The mass of the composite grinding aid is 6‰ of the mass of the heavy calcium carbonate powder;

[0064] The composite surface modifier is γ-aminopropyltrimethoxysilane at a weight of 10‰ based on the weight of the heavy calcium carbonate powder and stearic acid at a weight of 5‰ based on the weight of the heavy calcium carbonate powder;

[0065] The ultrafine heavy calcium carbonate for PVC cable of Example 5 was obtained.

[0066] Example 6

[0067] The only difference from Example 1 is:

[0068] If the total content of the grinding media in the front bin is 100%, the grinding media in the front bin of the ball mill includes 20% of ceramic balls with a diameter of 40 mm, 25% of ceramic balls with a diameter of 20 mm, and 30% of ceramic balls with a diameter of 15 mm. If the total content of the grinding media in the rear bin is 100%, the grinding media in the rear bin includes 20% of ceramic balls with a diameter of 35 mm, 25% of ceramic balls with a diameter of 15 mm, and 30% of ceramic balls with a diameter of 5 mm.

[0069] The mass of the composite grinding aid is 7‰ of the mass of the heavy calcium carbonate powder;

[0070] The composite surface modifier is γ-aminopropyltrimethoxysilane at a weight of 11‰ based on the weight of the heavy calcium carbonate powder and stearic acid at a weight of 5‰ based on the weight of the heavy calcium carbonate powder;

[0071] The ultrafine heavy calcium carbonate for PVC cable of Example 6 was obtained.

[0072] Comparative Example 1

[0073] The difference from Example 1 is:

[0074] No ball milling ultrafine grinding is performed. Specifically, the small calcite ore is coarsely crushed and then ground and classified by a ring roller mill to obtain the ultrafine heavy calcium carbonate of Comparative Example 1.

[0075] Comparative Example 2

[0076] The difference from Example 1 is:

[0077] No ball milling ultrafine grinding is performed. Specifically, the small calcite ore is coarsely crushed and then ground and classified by a vertical mill to obtain the ultrafine heavy calcium carbonate of Comparative Example 2.

[0078] Comparative Example 3

[0079] No ball milling ultrafine grinding is performed. Specifically, the small calcite ore is coarsely crushed and then ground and classified by air flow mill to obtain the ultrafine heavy calcium carbonate of Comparative Example 3.

[0080] Performance Testing

[0081] 1. The performance indexes of the ultrafine heavy calcium carbonate prepared in Examples 1 to 6 and Comparative Examples 1 to 3 were tested as follows. The test results are shown in Table 1.

[0082] D50: Tested in accordance with GB / T19077-2016;

[0083] D90: Tested in accordance with GB / T19077-2016;

[0084] Oil absorption value: tested in accordance with GBT 19281-2014;

[0085] Activation degree: tested in accordance with GBT 19281-2014;

[0086] Moisture: Tested in accordance with GBT 19281-2014;

[0087] Table 1 Performance indicators of ultrafine heavy calcium carbonate of Examples 1 to 6 and Comparative Examples 1 to 3

[0088] Detection indicators D50(μm) D97(μm) Oil absorption value (mL / 100g) Activation degree / % Moisture / % Example 1 0.33 1.28 31 96 0.18 Example 2 0.31 1.21 31 97 0.19 Example 3 0.18 1.16 32 98 0.20 Example 4 0.34 1.29 30 96 0.19 Example 5 0.32 1.22 31 98 0.18 Example 6 0.30 1.19 31 98 0.18 Comparative Example 1 0.95 2.41 28 94 0.20 Comparative Example 2 0.85 2.27 29 92 0.19 Comparative Example 3 1.35 3.36 27 89 0.18

[0089] 2. The ultrafine heavy calcium carbonate prepared in Examples 1 to 6 and Comparative Examples 1 to 3 were respectively mixed with PVC resin and additives by banburying and then subjected to twin-screw extrusion granulation. The particles were then extruded into low-smoke halogen-free flame-retardant cables by a single-screw extruder. The cable performance indicators were tested according to the following method. The test results are shown in Table 2.

[0090] Tensile strength: tested in accordance with GB / T1040.1-2018;

[0091] Elongation at break: Tested in accordance with GB / T1040.1-2018;

[0092] Surface brightness: tested in accordance with GB 8807-1988;

[0093] Table 2 Performance indicators of cables obtained from ultrafine heavy calcium carbonate powders of Examples 1 to 6 and Comparative Examples 1 to 3

[0094] Detection indicators Tensile strength / MPa Elongation at break / % Surface brightness / degree Example 1 22.6 192.6 89.2 Example 2 22.9 195.3 89.7 Example 3 23.4 196.4 90.2 Example 4 22.2 194.3 89.3 Example 5 22.5 192.2 89.1 Example 6 23.1 197.3 90.5 Comparative Example 1 20.3 174.7 86.4 Comparative Example 2 20.6 179.8 87.1 Comparative Example 3 19.8 171.7 85.4

[0095] It can be seen from Examples 1 to 6 and Comparative Examples 1 to 3 in combination with Table 1 that the ultrafine heavy calcium carbonate obtained by the present invention has smaller fineness, higher oil absorption value and higher activation degree than the ultrafine heavy calcium carbonate obtained by the existing grinding method, which shows that the present invention realizes ultrafine grinding by designing the number of ball mill bins and the proportion of ceramic ball diameters in the bins. Through ultrafine grinding and surface modification treatment, the ultrafine heavy calcium carbonate obtained has small fineness, high oil absorption value and high activation degree.

[0096] It can be seen from Examples 1 to 6 and Comparative Examples 1 to 3 in combination with Table 2 that the ultrafine heavy calcium carbonate obtained in the present invention has the characteristics of good processing fluidity and good dispersibility in the process of preparing PVC cables, and the prepared cables have good mechanical properties and high surface brightness.

[0097] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing ultrafine heavy calcium carbonate for PVC cables, characterized in that: The following steps are involved: The small calcite ore is subjected to primary crushing and secondary crushing in sequence to obtain crushed material; The crushed materials are subjected to roller grinding and primary classification in sequence to obtain heavy calcium carbonate powder; The heavy calcium carbonate powder is ball-milled with a grinding aid, a silane coupling agent and stearic acid, and then subjected to secondary classification to obtain ultrafine heavy calcium carbonate for PVC cables.

2. The preparation method according to claim 1, characterized in that: The frequency of the classifier used in the primary classification is 22-25 Hz, and the rotation speed is 650-750 r / min.

3. The preparation method according to claim 1, characterized in that: The particle size of the heavy calcium carbonate powder is 400-600 meshes.

4. The preparation method according to claim 1, characterized in that: The grinding aid comprises one or more of sodium hexametaphosphate, triethanolamine and monoethanoldiisopropanolamine, and the mass of the grinding aid is 3-7‰ of the mass of heavy calcium carbonate powder.

5. The preparation method according to claim 1, characterized in that: The mass of the silane coupling agent is 8-12‰ of the mass of the heavy calcium carbonate powder, and the silane coupling agent includes one or more of γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, γ-diethylenetriaminopropyltrimethoxysilane or γ-aminopropylmethyldiethoxysilane; the mass of the stearic acid is 3-5‰ of the mass of the heavy calcium carbonate powder.

6. The preparation method according to claim 1, characterized in that: The ball mill used for ball milling is divided into a front bin and a rear bin at a distance of 2.2 m from the feed port of the ball mill. If the total mass content of the grinding media in the front bin is 100%, the grinding media in the front bin includes 10-30% of ceramic balls with a diameter of 40-45 mm, 20-55% of ceramic balls with a diameter of 30-35 mm, and 10-40% of ceramic balls with a diameter of 15-20 mm; if the total mass content of the grinding media in the rear bin is 100%, the grinding media in the rear bin includes 10-35% of ceramic balls with a diameter of 20-40 mm, 15-55% of ceramic balls with a diameter of 10-15 mm, and 10-35% of ceramic balls with a diameter of 5-10 mm.

7. The preparation method according to claim 1, characterized in that: The classifiers used for the secondary classification are two groups of tandem classifiers, each of which is composed of three 315mm diameter classifying wheels; the frequency of the classifiers used for the secondary classification is 60-76Hz, and the rotation speed is 3200-3800r / min.

8. The ultrafine heavy calcium carbonate for PVC cable prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the ultrafine heavy calcium carbonate for PVC cables according to claim 8 in PVC cables.

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