PVC wire tube additive and application thereof

Abstract

This invention discloses a PVC conduit additive and its application, relating to the field of additive technology. The PVC conduit additive provided by this invention uses acetyl-1,8-octanediol dioleate acetylacetone ester, prepared from castor oil through a series of reactions, as a vegetable oil-based plasticizer. When applied to the formulation of PVC conduits, the low-temperature mechanical properties of PVC conduits in rigid PVC systems are improved through the synergistic effect of specific proportions of active nano-calcium carbonate, impact enhancers, and plasticizers.

Description

Technical Field

[0001] This invention relates to the field of additive technology, and more specifically, to a PVC conduit additive and its application. Background Technology

[0002] Currently, there are over 500 types of industrially produced plasticizers, but petroleum-based phthalate plasticizers still dominate the PVC plasticizer market. Statistics show that in 2020, my country's total plasticizer production was approximately 6000 kt, making it the world's largest producer and consumer of plasticizers. Phthalate plasticizers accounted for 75% of the total consumption. Representative phthalate plasticizers include dioctyl phthalate (DOP), dibutyl phthalate (DBP), diisobutyl phthalate (DIBP), and diisononyl phthalate (DINP). Dioctyl phthalate (DOP) is not cold-resistant and can generally only be used above 0°C. Commonly used cold-resistant plasticizers such as DOA and DOS, due to their poor compatibility with PVC and tendency to migrate, can only be used as auxiliary plasticizers and need to be mixed with primary plasticizers such as DOP, which greatly limits their application. However, in cold regions around the world, including large areas of my country, the average winter temperature is usually below 0°C, and the demand for plastic products in these regions continues to increase. But in low-temperature environments, the choice of plasticizers is extremely limited, so the development of cold-resistant plasticizers has great practical value.

[0003] To address the shortcomings of existing cold-resistant plasticizers, such as poor compatibility with PVC, easy migration, and poor low-temperature performance of PVC conduits, it is urgent to develop a high-performance cold-resistant plasticizer for use in PVC conduits. This plasticizer would lower the glass transition temperature of PVC materials, thereby endowing PVC conduits with excellent low-temperature mechanical properties.

[0004] Existing technology discloses the synthesis and application of a highly stable bio-based plasticizer extracted from castor oil acid. Acetyl 1,8-octanediol dioleate acetylacetonate was synthesized and used as a plasticizer in PVC systems to improve the low-temperature mechanical properties of PVC systems. However, this PVC system is a flexible PVC system, requiring the addition of a large amount of plasticizer. When using acetyl 1,8-octanediol dioleate acetylacetonate as a plasticizer in this system, the amount of plasticizer needs to reach more than 50 wt% of the PVC. Summary of the Invention

[0005] To address the problem that existing technologies struggle to improve the low-temperature mechanical properties of PVC conduits in rigid PVC systems, this invention provides a PVC conduit additive. It uses acetyl 1,8-octanediol dioleate acetylacetone ester as a vegetable oil-based plasticizer and applies it to the formulation of PVC conduits. Through its synergistic effect with active nano-calcium carbonate and impact-resistant agents, the low-temperature mechanical properties of PVC conduits in rigid PVC systems are improved.

[0006] Another object of the present invention is to provide an application of an electrical conduit additive.

[0007] Another object of the present invention is to provide a PVC conduit material.

[0008] Another object of the present invention is to provide a PVC electrical conduit.

[0009] The above-mentioned objective of this invention is achieved through the following technical solution:

[0010] An additive for PVC electrical conduits includes active nano-calcium carbonate, an impact-resistant agent, and a vegetable oil-based plasticizer, wherein the mass ratio of the active nano-calcium carbonate, the impact-resistant agent, and the vegetable oil-based plasticizer is (5-40):(2.4-16):1;

[0011] The vegetable oil-based plasticizer has the structure shown in the following formula:

[0012]

[0013] The aforementioned vegetable oil-based plasticizer is acetyl 1,8-octanediol dioleate acetylacetonate, which contains a large number of polar groups, such as ester and carbonyl groups. These groups can form hydrogen bonds with hydrogen atoms in PVC chains. Therefore, the vegetable oil-based plasticizer used in this invention has excellent compatibility with PVC and can insert into the spaces between PVC molecular chains, increasing the distance between different PVC molecular chains and increasing the free volume of the PVC molecular chains, making the molecular chains easier to displace under external stress. Simultaneously, the ester groups in the plasticizer structure have lubricating properties between PVC chains, reducing intermolecular friction between PVC molecular chains when the PVC conduit is strained, further reducing the resistance encountered when the PVC molecular chains move. Furthermore, this vegetable oil-based plasticizer has excellent low-temperature resistance; therefore, the PVC conduit additive provided by this invention can improve the low-temperature bending performance of PVC conduits.

[0014] It should be noted that to improve the low-temperature mechanical properties of PVC conduits, the PVC conduit additive provided in this invention also requires the addition of activated nano-calcium carbonate and an impact-resistant agent. The activated nano-calcium carbonate acts as a stiffening filler. In the actual production of PVC conduits, to improve their mechanical properties while reducing costs, stiffening fillers are often added to the system. This reduces the PVC content in the conduit (to lower costs) while simultaneously improving its mechanical properties. Industrially, calcium carbonate is commonly used as a stiffening filler in PVC systems. Depending on the industrial preparation method, calcium carbonate that can be used as a filler is classified into three types: heavy calcium carbonate, light calcium carbonate, and activated calcium carbonate. The inventors were surprised to discover in their experiments that only by using nano-sized activated calcium carbonate as a stiffening filler, and by controlling the mass ratio of activated nano-calcium carbonate, impact agent, and vegetable oil-based plasticizer to be activated nano-calcium carbonate: impact agent: vegetable oil-based plasticizer = (5-40):(2.4-16):1, could the vegetable oil-based plasticizer acetyl 1,8-octanediol dioleate acetylacetone ester exert its effect and improve the low-temperature mechanical properties of PVC conduit. If light or heavy calcium carbonate is used as a filler, or if too much or too little impact agent is added, the vegetable oil-based plasticizer will fail to improve the low-temperature mechanical properties of PVC conduit. This demonstrates that there is a synergistic effect between the vegetable oil-based plasticizer and a specific mass of impact agent and activated nano-calcium carbonate.

[0015] In a specific embodiment of the present invention, the preparation method of the above-mentioned vegetable oil-based plasticizer acetyl 1,8-octanediol dioleate acetylacetone ester includes the following steps:

[0016] S1. Ricinoleic acid and 1,8-octanediol are esterified in the presence of tetrabutyl titanate to obtain 1,8-octanediol dicarboxylate.

[0017] S2. In the presence of p-toluenesulfonic acid, the 1,8-octanediol dicarboxylate obtained in step S1 is reacted with levulinic acid. After the reaction is complete, 1,8-octanediol dioleate acetylacetone ester is obtained.

[0018] S3. The 1,8-octanediol dioleate acetylacetonate obtained in step S2 is reacted with hydrogen peroxide and formic acid under acidic conditions. After the reaction is complete, epoxy 1,8-octanediol dioleate acetylacetonate is obtained.

[0019] S4. React the epoxy 1,8-octanediol dioleate acetylacetonate obtained in step S3 with acetic anhydride under acidic conditions. After the reaction is complete, acetyl 1,8-octanediol dioleate acetylacetonate can be obtained.

[0020] The active nano-calcium carbonate in this invention refers to nano-calcium carbonate with higher reactivity after being treated with a surface modifier. Conventional calcium carbonate modifiers in the art include any one or more of stearic acid, silane coupling agents, lead ester coupling agents, titanate coupling agents, and phosphate ester coupling agents.

[0021] Preferably, the average particle size of the active nano-calcium carbonate is 90-100 nm.

[0022] Using activated nano-calcium carbonate with the above-mentioned particle size as a filler for PVC electrical conduits can more fully leverage the synergistic effect between activated nano-calcium carbonate and vegetable oil-based plasticizers, resulting in PVC electrical conduits with superior low-temperature mechanical properties.

[0023] Preferably, the active nano-calcium carbonate is obtained by surface treatment of nano-calcium carbonate with stearic acid.

[0024] The active nano-calcium carbonate obtained by surface modification of nano-calcium carbonate with stearic acid has better compatibility with PVC matrix and can more fully exert the synergistic effect with vegetable oil-based plasticizers and impact-resistant agents, giving PVC conduit better low-temperature mechanical properties.

[0025] Preferably, the impact-resistant agent is CPE.

[0026] Compared to impact modifiers such as ACR (methyl methacrylate-acrylate copolymer) and MBS (methyl methacrylate-butadiene-styrene terpolymer), CPE (chlorinated polyethylene) exhibits better low-temperature toughness, especially CPE-135A. Using CPE as an impact modifier can further improve the low-temperature mechanical properties of PVC conduit.

[0027] Preferably, the mass ratio of active nano-calcium carbonate, impact-resistant agent and vegetable oil-based plasticizer in the PVC conduit additive is (6-20):(3-7):1.

[0028] Active nano-calcium carbonate, impact-resistant agents, and vegetable oil-based plasticizers within the above-mentioned mass ratio have a stronger synergistic effect on improving the low-temperature mechanical properties of PVC electrical conduits.

[0029] The present invention also protects the application of the above-mentioned PVC conduit additive in the preparation of PVC conduit materials.

[0030] This invention also protects a PVC electrical conduit material comprising the following components in parts by weight:

[0031] 100 PVC units

[0032] Other adjuvants: 6-10.5 parts

[0033] The above-mentioned PVC conduit additives are 35 to 65 parts.

[0034] The mass fraction of the PVC conduit additive is the total mass fraction of the active nano-calcium carbonate, impact agent, and vegetable oil-based plasticizer. PVC conduit is a rigid PVC product. To ensure its rigidity, the amount of plasticizer needs to be controlled below 8 wt% of the PVC matrix (generally not exceeding 5 wt%). Therefore, the mass fraction of the PVC conduit additive in the PVC conduit material of this invention cannot exceed 65 parts. However, if the amount of additive is too low, it will be difficult to improve the low-temperature mechanical properties of the PVC conduit. Therefore, the mass fraction of the PVC conduit additive in the PVC conduit material needs to be higher than 35 parts.

[0035] In the actual production process of PVC conduit, heat stabilizers and other additives are often required. Conventional additives in this field are all applicable to this invention, but their mass fraction should be within the range of 6 to 10.5.

[0036] Preferably, the other additives include any one or more of heat stabilizers, lubricants, or pigments.

[0037] PVC is a polymer with poor thermal stability, decomposing at around 110°C. However, conventional pipe manufacturing processes in this field require processing at around 180°C, necessitating the addition of heat stabilizers to the PVC system. However, heat stabilizers themselves can also affect the mechanical properties of the pipe, therefore their mass fraction should not exceed 6 parts.

[0038] In the actual production process of PVC pipes, lubricant needs to be added to ensure that the pipes do not crack due to friction during extrusion, thus preventing them from failing to meet actual production requirements. Excessive lubricant reduces the frictional heat generated during processing, affecting the plasticization of the pipes (part of the plasticization of the pipes relies on machine heating, and another part is further promoted by the frictional heat generated during the plasticization of the PVC system in the screw). Simultaneously, excessive lubricant can thin the system, making plasticization impossible.

[0039] Existing pipes exhibit uneven coloring without pigment, making them unsuitable for commercialization. The pigment content is limited to 1-3 parts by weight because within this range, PVC plastic can be successfully and uniformly colored without causing a decline in physical and mechanical properties such as shrinkage due to excessive pigment filling.

[0040] Preferably, the PVC conduit additive is present in a mass fraction of 50 to 60 parts.

[0041] When the mass fraction of the PVC conduit additive is 50 to 60 parts, the proportion of the additive in the PVC conduit system is appropriate, which is conducive to giving full play to its role and improving the low-temperature mechanical properties of the PVC conduit.

[0042] More preferably, the heat stabilizer, lubricant, and pigment in the other additives are in the following proportions: 4-6 parts by mass, 1-1.5 parts by mass, and 1-3 parts by mass, respectively.

[0043] The present invention also protects a PVC conduit made from the above-mentioned conduit material.

[0044] The above-mentioned method for preparing PVC electrical conduit includes the following steps:

[0045] All components of the PVC conduit material are fed into a high-speed mixer (capacity 500L). After feeding, the mixture is first stirred at low speed (80rpm) for 30s, and then stirred at high speed (500rpm). After heating to 115℃, the material is discharged into a low-speed cold mixing cylinder (capacity 1500L). When the temperature of the cold mixing cylinder drops to 45℃, the material is discharged and conveyed to a conical twin-screw extruder. The material is plasticized by the extruder (150-200℃), formed by a support mold, sized by an immersion cooling water tank, and cut to a fixed length by a traction cutter to obtain the PVC conduit.

[0046] Preferably, the glass transition temperature (Tg) of the PVC conduit is ≤75℃.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] The PVC conduit additive provided by this invention uses acetyl 1,8-octanediol dioleate acetylacetone ester prepared from castor oil acid as a vegetable oil-based plasticizer. By utilizing the synergistic effect between this plasticizer, active nano-calcium carbonate, and impact-resistant agent, the low-temperature mechanical properties of PVC conduit are improved, reducing the glass transition temperature of PVC conduit to 70-72°C, and exhibiting excellent impact resistance and bending performance at both room temperature and low temperature. Detailed Implementation

[0049] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0050] Example 1

[0051] An additive for PVC electrical conduits includes active nano-calcium carbonate, an impact-resistant agent, and a vegetable oil-based plasticizer, wherein the mass parts of active nano-calcium carbonate, impact-resistant agent, and vegetable oil-based plasticizer are 35, 14, and 3 parts respectively, that is, the mass ratio of active nano-calcium carbonate, impact-resistant agent, and vegetable oil-based plasticizer is 11.67:4.67:1;

[0052] The active nano-calcium carbonate was purchased from Guangxi Huana New Materials Co., Ltd., product model CCR-1, with an average particle size of 95nm. It was obtained by surface treatment of nano-calcium carbonate with stearic acid.

[0053] The impact-resistant agent was purchased from Shandong Rike Chemical Co., Ltd., product model CPE-135A;

[0054] The above-mentioned vegetable oil-based plasticizer has the structure shown in the following formula:

[0055]

[0056] Example 2

[0057] A PVC conduit additive, which differs from Example 1 in that the mass parts of active nano-calcium carbonate, impact-resistant agent and vegetable oil-based plasticizer are 25, 14 and 2 parts respectively, that is, the mass ratio of active nano-calcium carbonate, impact-resistant agent and vegetable oil-based plasticizer is 12.5:7:1.

[0058] Example 3

[0059] A PVC conduit additive, which differs from Example 1 in that the mass parts of active nano-calcium carbonate, impact-resistant agent and vegetable oil-based plasticizer are 40, 14 and 4 parts respectively, that is, the mass ratio of active nano-calcium carbonate, impact-resistant agent and vegetable oil-based plasticizer is 10:3.5:1.

[0060] Example 4

[0061] A PVC conduit additive, which differs from Example 1 in that:

[0062] The mass fraction of the vegetable oil-based plasticizer is 1 part, that is, the mass ratio of active nano calcium carbonate, impact resistant agent and vegetable oil-based plasticizer is 35:14:1.

[0063] Example 5

[0064] A PVC conduit additive, which differs from Example 1 in that:

[0065] The plant oil-based plasticizer has a mass ratio of 5 parts, which means that the mass ratio of active nano calcium carbonate, impact-resistant agent and plant oil-based plasticizer is 7:2.8:1.

[0066] Example 6

[0067] A PVC conduit additive, which differs from Example 1 in that:

[0068] The impact-resistant agent has a mass ratio of 12 parts, which means that the mass ratio of active nano-calcium carbonate, impact-resistant agent and vegetable oil-based plasticizer is 11.67:4:1.

[0069] Example 7

[0070] A PVC conduit additive, which differs from Example 1 in that:

[0071] The impact-resistant agent has a mass ratio of 16 parts, which means that the mass ratio of active nano-calcium carbonate, impact-resistant agent and vegetable oil-based plasticizer is 11.67:5.3:1.

[0072] Example 8

[0073] A PVC conduit additive, which differs from Example 1 in that:

[0074] The active nano-calcium carbonate was purchased from Guangxi Huana New Materials Co., Ltd., product model CCR-3, with an average particle size of 105nm. It was obtained by surface treatment of nano-calcium carbonate with stearic acid.

[0075] Example 9

[0076] A PVC conduit additive, which differs from Example 1 in that:

[0077] The active nano-calcium carbonate was purchased from Guangxi Huana New Materials Co., Ltd., product model CCR-5, with an average particle size of 75nm. It was obtained by surface treatment of nano-calcium carbonate with stearic acid.

[0078] Example 10

[0079] A PVC electrical conduit material, comprising the following components in parts by weight:

[0080]

[0081]

[0082] The specific formula for the PVC conduit material in this embodiment is as follows:

[0083]

[0084] Example 11

[0085] A PVC conduit material, which differs from Example 10 in that it comprises the following components in parts by weight:

[0086]

[0087] The specific formula for the PVC conduit material in this embodiment is as follows:

[0088]

[0089] Example 12

[0090] A PVC conduit material, which differs from Example 10 in that it comprises the following components in parts by weight:

[0091]

[0092] The specific formula for the PVC conduit material in this embodiment is as follows:

[0093]

[0094] Example 13

[0095] A PVC conduit material, which differs from Example 10 in that it comprises the following components in parts by weight:

[0096]

[0097] The specific formula for the PVC conduit material in this embodiment is as follows:

[0098]

[0099]

[0100] Example 14

[0101] A PVC conduit material, which differs from Example 10 in that it comprises the following components in parts by weight:

[0102]

[0103] The specific formula for the PVC conduit material in this embodiment is as follows:

[0104]

[0105] Example 15

[0106] A PVC conduit material, which differs from Example 10 in that it comprises the following components in parts by weight:

[0107]

[0108] The specific formula for the PVC conduit material in this embodiment is as follows:

[0109]

[0110]

[0111] Example 16

[0112] A PVC conduit material, which differs from Example 10 in that it comprises the following components in parts by weight:

[0113]

[0114] The specific formula for the PVC conduit material in this embodiment is as follows:

[0115]

[0116] Example 17

[0117] A PVC conduit material, which differs from Example 10 in that:

[0118] The PVC conduit additive provided in Example 1 was replaced with the PVC conduit additive provided in Example 8, namely, active nano calcium carbonate, which was purchased from Guangxi Huana New Material Co., Ltd., product model CCR-3, with an average particle size of 105nm, and was obtained by surface treatment of nano calcium carbonate with stearic acid.

[0119] Example 18

[0120] A PVC conduit material, which differs from Example 10 in that:

[0121] The PVC conduit additive provided in Example 1 was replaced with the PVC conduit additive provided in Example 9, namely, active nano calcium carbonate, which was purchased from Guangxi Huana New Material Co., Ltd., product model CCR-5, with an average particle size of 75nm, and was obtained by surface treatment of nano calcium carbonate with stearic acid.

[0122] Comparative Example 1

[0123] A PVC conduit material, which differs from Example 10 in that:

[0124] No vegetable oil-based plasticizers are added.

[0125] Comparative Example 2

[0126] A PVC conduit material, which differs from Example 10 in that:

[0127] The plasticizer DOA was used to replace the vegetable oil-based plasticizer.

[0128] Comparative Example 3

[0129] A PVC conduit material, which differs from Example 10 in that:

[0130] The plant oil-based plasticizer DOS was replaced with plasticizer.

[0131] Comparative Example 4

[0132] A PVC conduit material, which differs from Example 10 in that:

[0133] Light calcium carbonate was used to replace active nano calcium carbonate. The light calcium carbonate was purchased from Guangxi Huana New Materials Co., Ltd., product model MP-1.

[0134] Comparative Example 5

[0135] A PVC conduit material, which differs from Example 10 in that:

[0136] Heavy calcium carbonate was used to replace active nano calcium carbonate. The heavy calcium carbonate was purchased from Jiangmen Huixiong Nonmetallic Materials Co., Ltd., product model BT-2.

[0137] Comparative Example 6

[0138] A PVC conduit additive, which differs from Example 1 in that:

[0139] The impact-resistant agent has a mass ratio of 6 parts, which means that the mass ratio of active nano-calcium carbonate, impact-resistant agent and vegetable oil-based plasticizer is 11.67:2:1.

[0140] Comparative Example 7

[0141] A PVC conduit material, which differs from Example 10 in that it comprises the following components in parts by weight:

[0142]

[0143]

[0144] The specific formula for the PVC conduit material in this comparative example is as follows:

[0145]

[0146] Performance testing

[0147] Preparation of PVC conduit: The conduit materials obtained in the examples and comparative examples are used to prepare PVC conduit. The specific method is as follows: each component of the PVC conduit material is put into a high-speed mixer (capacity 500L). After the input is complete, it is first stirred at low speed (80rpm) for 30 seconds, and then stirred at high speed (500rpm). After heating to 115°C, the material is discharged into a low-speed cold mixing cylinder (capacity 1500L). When the temperature of the cold mixing cylinder drops to 45°C, the material is discharged and conveyed to a conical twin-screw extruder. After plasticizing in the extruder (150-200°C), it is formed by a support mold, sized by an immersion cooling water tank, and cut to a fixed length by a traction cutter to obtain PVC conduit.

[0148] The mechanical properties of the above-mentioned PVC conduit were tested, and the specific test results are shown in Table 1 below.

[0149] The mechanical property testing includes impact performance, room temperature bending performance, and low temperature (-5℃) bending performance. The specific testing methods are as follows:

[0150] Impact performance: The testing standard is JG 3050-1998 "Insulating electrical conduits and fittings for building".

[0151] The bending properties at room temperature and -5℃ were tested using the standard JG 3050-1998 method.

[0152] The test method of standard JG 3050-1998 "Insulating Electrical Conduit and Fittings for Buildings" is to bend the conduit with a spring inside. However, this performance cannot meet the actual needs of the northern market. Therefore, the bending test of this invention (at room temperature and low temperature -5℃) is to bend directly without a spring.

[0153] Table 1. Test Results

[0154]

[0155]

[0156] It should be noted that the method for testing low-temperature bending performance in this invention is different from the national standard because only by meeting the performance requirement of bending without springs and without cracks can PVC conduit meet the actual needs of the northern market (northern temperatures are low, especially in winter, and conduit is prone to breakage).

[0157] As shown in Table 1, the PVC conduit in Comparative Example 1 without plasticizer exhibited poor impact and bending properties, especially with complete breakage during low-temperature (-5℃) bending. Its glass transition temperature (Tg) was also relatively high at 79.8℃. Comparative Examples 2 and 3, after adding conventional cold-resistant plasticizers DOA and DOS, showed a decrease in glass transition temperature and an improvement in bending properties. Specifically, the pass rate for room-temperature bending performance was higher than that of the PVC conduit without vegetable oil-based plasticizers. However, breakage / visible cracks still occurred during low-temperature bending, and the impact performance deteriorated. This is because the cold-resistant plasticizers DOA and DOS have poor compatibility with PVC, leading to a decrease in some of its mechanical properties. Comparative Examples 4 and 5, with the addition of light and heavy calcium carbonate respectively, still failed to meet bending performance standards. Comparative Example 7, obtained by adding the PVC conduit additives provided in Comparative Example 6, also failed to meet bending performance standards even with only 6 parts of impact agent added.

[0158] As can be seen from the data in Table 1, after adding vegetable oil-based plasticizers in Examples 10-12, 15, and 16, the glass transition temperature decreased to 70-72 °C, and the impact performance and the test results of normal temperature / low temperature bending were all qualified. This shows that when the mass ratio of active nano calcium carbonate, impact resistance agent, and vegetable oil-based plasticizer in the PVC wire pipe modifier is within the preferred range of (6-20):(3-7):1 in the present invention, the PVC wire pipe added with additives has more excellent low temperature mechanical properties; for the additives in Example 4 used in Example 13, only 1 part of vegetable oil-based plasticizer was added, and the mass ratio of active nano calcium carbonate, impact resistance agent, and vegetable oil-based plasticizer was 35:14:1. The glass transition temperature of the PVC wire pipe decreased to 74.5 °C, the impact performance and normal temperature bending were all qualified, and the low temperature bending was partially qualified; for the additives in Example 5 used in Example 14, after adding 5 parts of vegetable oil-based plasticizer, the mass ratio of active nano calcium carbonate, impact resistance agent, and vegetable oil-based plasticizer was 7:2.8:1. The glass transition temperature of the PVC wire pipe decreased to 68.9 °C, the normal temperature bending and low temperature bending were all qualified, but the pipe broke during the impact experiment. The above results show that adding vegetable oil-based plasticizer in the PVC formula can reduce the glass transition temperature Tg of the wire pipe and endow it with excellent bending properties. When the added amount is less (Example 13), the improved bending properties are limited. When the added amount is more (Example 14), although the low temperature bending performance is improved, the too low glass transition temperature will instead reduce its impact performance. Therefore, considering all mechanical properties, the best mass ratio of active nano calcium carbonate, impact resistance agent, and vegetable oil-based plasticizer is (6-20):(3-7):1. Within this range, all mechanical properties of the PVC wire pipe are qualified. In Examples 17 and 18, active nano calcium carbonate with different sizes was used, and their bending properties were also all qualified. However, in actual production, if the particle size of active nano calcium carbonate is too small, it is easy to adhere to the feeding port, and if it is too large, the feeding is prone to bridging phenomenon. Therefore, the present invention prefers to use active nano calcium carbonate with a particle size of 90-100 nm.

[0159] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all implementation manners here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A PVC conduit additive, characterized in that, It includes active nano-calcium carbonate, impact-resistant agent and vegetable oil-based plasticizer, wherein the mass ratio of active nano-calcium carbonate, impact-resistant agent and vegetable oil-based plasticizer is (5~40):(2.4~16):1; The vegetable oil-based plasticizer has the structure shown in the following formula: ； The active nano-calcium carbonate is nano-calcium carbonate with a surface modified by an agent, which includes any one or more of stearic acid, silane coupling agent, lead ester coupling agent, titanate coupling agent, and phosphate coupling agent. The impact-resistant agent is CPE.

2. The PVC conduit additive as described in claim 1, characterized in that, The average particle size of the active nano-calcium carbonate is 90~100 nm.

3. The PVC conduit additive as described in claim 1, characterized in that, The active nano-calcium carbonate is obtained by surface treatment of nano-calcium carbonate with stearic acid.

4. The PVC conduit additive as described in claim 1, characterized in that, The mass ratio of active nano-calcium carbonate, impact-resistant agent, and vegetable oil-based plasticizer in the PVC conduit additive is (6~20):(3~7):

1.

5. The use of the PVC conduit additive according to any one of claims 1 to 4 in the preparation of PVC conduit materials.

6. A PVC electrical conduit material, characterized in that, Includes the following components, calculated by parts by mass: 100 PVC units Other adjuvants: 6-10.5 parts. 35 to 65 parts of the PVC conduit additive as described in any one of claims 1 to 4.

7. The PVC conduit material as described in claim 6, characterized in that, The other additives include any one or more of heat stabilizers, lubricants, or pigments.

8. A PVC conduit made from the PVC conduit material of claim 6 or 7.

9. The PVC conduit as described in claim 8, characterized in that, The glass transition temperature (Tg) of the PVC conduit is ≤75℃.

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