High-pressure-resistant heat-resistant PVC (polyvinyl chloride) insulating electrical conduit and preparation method thereof

Abstract

The invention discloses a high-pressure-resistant heat-resistant PVC (polyvinyl chloride) insulating electrical conduit and a preparation method thereof, and belongs to the technical field of PVC pipes for buildings. The PVC electrical conduit with high compression resistance and heat resistance is prepared from the following raw materials in parts by weight: 75 to 85 parts of PVC resin, 15 to 25 parts of maleic anhydride grafted CPVC, 2.5 to 3.5 parts of calcium-zinc stabilizer, 0.2 to 0.5 part of internal lubricant, 0.4 to 1.2 parts of external lubricant, 25 to 40 parts of EVA and furyl semi-aromatic polyamide cross-linked modified calcium carbonate-mica powder mixture, 0 to 3 parts of talcum powder, 0.5 to 1.5 parts of impact-resistant ACR resin, 0.5 to 1.5 parts of organic silicon toughening agent, 2 to 4 parts of CPE and 0.1 to 0.3 part of antioxidant. And 1-2 parts of rutile type titanium dioxide. According to the PVC insulating electrical conduit disclosed by the invention, the toughness, the thermal deformation resistance and the impact resistance of the conduit are improved by optimizing the formula design.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of PVC pipes for buildings, and particularly relates to a high-pressure-resistant heat-resistant PVC insulating electrical sleeve and a preparation method thereof. BACKGROUND

[0002] PVC electrical sleeves are important internal wire conduits for buildings, with advantages such as corrosion resistance, light weight, and easy bending, and are widely used in the concrete of buildings, between floors, or in walls. However, the existing PVC electrical sleeves still have some problems. First, due to the low toughness and poor impact resistance of PVC materials, brittle fracture easily occurs during storage, transportation, installation, and use, especially in low temperature environments. Second, in the traditional PVC electrical sleeve formula, the commonly used filling system is mainly calcium carbonate, but this filling method has poor compatibility with organic matter and insufficient rigidity, resulting in weak compression resistance. In addition, in order to improve production capacity, some producers try to add PE wax as a lubricant, but this will limit the compatibility of PE wax in PVC systems containing calcium-zinc stabilizers, and PE wax is easily precipitated, affecting the mechanical properties of the product.

[0003] In order to solve these problems, researchers have been exploring new material formulas and preparation methods. Currently, the common improvement direction is to add elastomer-based modifiers such as CPE, ACR, and MBS to improve toughness and flexibility. However, these improvements often have some side effects, such as increasing production costs, affecting the heat resistance or flame retardance of the material, etc., which need to be further optimized.

[0004] Therefore, developing a new formula that can improve the compression resistance and toughness of PVC electrical sleeves while maintaining good heat resistance and flame retardance has become the focus of current research. At the same time, it is also necessary to consider how to reduce production costs and improve production efficiency while ensuring product quality. This requires innovation in formula design, reasonable selection and optimization of the ratio and types of components to achieve a balance of performance and maximize application value. SUMMARY

[0005] The application provides a high-pressure-resistant heat-resistant PVC insulating electrical sleeve and a preparation method thereof, which can solve the problems of poor compression resistance and insufficient heat resistance in the modification of PVC electrical sleeves in the prior art.

[0006] The purpose of the application can be achieved by the following technical solutions: The application discloses a high-pressure-resistant and heat-resistant PVC electrician sleeve, which comprises the following raw materials in parts by weight: 75-85 parts of PVC resin, 15-25 parts of maleic anhydride grafted CPVC, 2.5-3.5 parts of calcium-zinc stabilizer, 0.2-0.5 parts of internal lubricant, 0.4-1.2 parts of external lubricant, 25-40 parts of EVA and furan-based semi-aromatic polyamide cross-linked modified calcium carbonate-mica powder mixture, 0-3 parts of talc, 0.5-1.5 parts of impact-resistant ACR resin, 0.5-1.5 parts of silicone toughening agent, 2-4 parts of CPE, 0.1-0.3 parts of antioxidant and 1-2 parts of rutile titanium white powder.

[0007] Further, the PVC resin is a general SG-5 type resin with a viscosity number of 108-120.

[0008] Further, the preparation steps of the maleic anhydride grafted CPVC are as follows: Maleic anhydride is dissolved in acetone to obtain a maleic anhydride solution with a concentration of 0.5-1.5 g / mL, PVC powder is added into the maleic anhydride solution, the mass ratio of PVC and maleic anhydride is 12-16:1, after stirring and mixing, the mixture is transferred into a reaction kettle and is left to stand for 12-24 h, the temperature is raised to 50-60 DEG C, and stirring reaction is carried out for 1-3 h, then the temperature is cooled to room temperature, chlorine gas is introduced to discharge the air in the reaction kettle, the chlorine gas is continuously introduced at a rate of 100-150 g / min per cubic reaction system, and chlorination reaction is carried out at a constant temperature of 120-140 DEG C, the chlorine content is controlled to be 66%-69%, the chlorine gas is stopped, the temperature is cooled to below 100 DEG C, and after the chlorine gas is extracted, air is introduced to discharge residual chlorine, the obtained crude product is dissolved in tetrahydrofuran, methanol is added for precipitation, impurities are removed, filtration and drying are carried out to obtain the maleic anhydride grafted CPVC.

[0009] Further, the calcium-zinc stabilizer is an environment-friendly calcium-zinc stabilizer, and the components include zinc stearate and calcium stearate.

[0010] Further, the internal lubricant is at least one of monoglyceride, OPE and stearic acid.

[0011] Further, the external lubricant is at least one of polyethylene wax, Fischer-Tropsch wax and paraffin wax.

[0012] Further, the preparation steps of the EVA and furan-based semi-aromatic polyamide cross-linked modified calcium carbonate-mica powder mixture are as follows: EVA, calcium carbonate and mica powder are mixed according to a mass ratio of 1: (4-6) : (2.5-4), furan-based semi-aromatic polyamide is added according to 40-60% of the mass of EVA, and dicumyl peroxide is synchronously added as an initiator, after stirring and mixing, melt extrusion granulation is carried out in a twin-screw extruder at 190-220 DEG C to obtain the EVA and furan-based semi-aromatic polyamide cross-linked modified calcium carbonate-mica powder mixture.

[0013] EVA and furan-based semi-aromatic polyamide form a crosslinked network under the action of initiator, and form a coating on inorganic materials (calcium carbonate and mica powder) to prepare a modified material, the furan-based semi-aromatic polyamide has high thermal stability, the rigid furan group introduced can improve the compressive strength of the PVC sleeve, and the presence of the fatty chain can enhance the toughness of the material, the presence of polar groups and non-polar groups in the EVA and furan-based semi-aromatic polyamide has better compatibility with PVC resin, and the difference in polarity is smaller, so that the modified material can be better dispersed. The introduced furan group can react with the grafted CPVC by maleic anhydride at high temperature to form crosslinking, which can enhance the interfacial bonding force between different materials on the one hand, and reduce brittleness, improve stress concentration and improve impact resistance on the other hand. The modified material has better compatibility with other raw materials in the PVC electrical sleeve, and improves the compressive strength and heat resistance.

[0014] Further, the VA content of the EVA is 20-25%, and the melt index is 4-8 g / min.

[0015] Further, the particle size of the mica powder is 5-20 μm, and the diameter-thickness ratio is > 50. The particle size distribution D50 of the calcium carbonate is 1-5 μm, the purity is ≥ 99.5%, the specific surface area is ≥ 30 m 2 / g, and the pore volume is 0.5-1.5 cm 3 / g.

[0016] Further, the furan-based polyamide is prepared by polymerization reaction of 2,5-furandicarboxylic acid chloride and 1,6-hexanediamine.

[0017] Further, the dicumyl peroxide is 1-10% of the mass of the EVA.

[0018] Further, the molecular weight of the impact-resistant ACR resin is 300000-1000000.

[0019] Further, the antioxidant is a hindered phenolic antioxidant.

[0020] Further, the particle size of the rutile titanium dioxide is 0.5-1 μm.

[0021] The application also provides a preparation method of the high-compressive-strength heat-resistant PVC electrical sleeve. Step one, weigh the raw materials according to the above formula, and prepare for use. Step two, the PVC resin, maleic anhydride grafted CPVC, impact ACR resin, CPE, silicone toughening agent is added into the high-speed mixer, the rotation speed is set to 1000-1500rpm, start mixing and stirring, after the material is uniformly mixed, EVA and furan-based semi-aromatic polyamide crosslinked modified calcium carbonate-mica powder mixture is added, continue to stir and mix, after mixing uniformly, calcium-zinc stabilizer, internal lubricant, external lubricant, talc, antioxidant, rutile titanium dioxide is added, after stirring and mixing uniformly, it is sent into the cooling mixer, the rotation speed is set to 50-100rpm, start low-speed stirring, cool to 45℃~55℃ discharge, obtain the cold mixture; Step three, the cold mixture is removed by vibrating screen, and is transported to the storage tank for standing for more than 3h, to obtain the PVC dry mixture; Step four, the PVC dry mixture is transported to the double screw extruder for extrusion molding, to obtain the high compression resistance and heat resistance type PVC insulating electrical sleeve.

[0022] Further, the double screw extruder barrel processing temperature is 170℃~190℃, the die head port mold temperature is 195~205℃, the mold temperature is 180℃~190℃, the main machine screw rotation speed is 50~70r / min, and the melt pressure is 21MPa~23.5MPa.

[0023] The beneficial effects of the present application are: (1) The PVC insulating electrical sleeve of the present application optimizes the formula design, uses PVC and maleic anhydride grafted CPVC in combination, significantly improves the heat deformation resistance of the material, and the scientific combination of impact ACR resin, CPE, silicone toughening agent and other materials improves the toughness and impact resistance of the pipe material, effectively solves the problem of brittle fracture of traditional PVC electrical sleeve during storage, transportation, installation and use, prolongs the service life and safety of the product.

[0024] (2) The present application uses EVA and furan-based semi-aromatic polyamide crosslinked modified calcium carbonate-mica powder mixture as a filling material, which replaces the traditional precipitated calcium carbonate filling system, improves the compatibility of the filling material and the organic matter, enhances the rigidity and compression resistance of the material, and significantly improves the compression resistance of the PVC electrical sleeve, which meets the high compression resistance requirement.

[0025] (3) In the present application, EVA and furan-based semi-aromatic polyamide crosslinked modified calcium carbonate-mica powder mixture and maleic anhydride grafted CPVC form a crosslinked structure in the melting process by using the reaction of furan group and maleic anhydride group, the introduction of furan ring rigid group enhances the compression strength and improves the heat resistance, the crosslinked structure enhances the interfacial bonding force, improves the stress concentration and improves the impact resistance.

[0026] (4) The PVC electrical sleeve has good use performance and service life, can meet the use requirements of building internal wire conduits, has the advantages of corrosion resistance, light weight, easy bending and the like, and is suitable for various complex building environments. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to 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 work fall within the protection scope of the present application.

[0028] Embodiment 1

[0029] A high-pressure-resistant heat-resistant PVC electrical sleeve, according to parts by weight, the PVC electrical sleeve comprises the following raw materials: PVC resin (SG-5 type) 80 parts, maleic anhydride grafted CPVC 20 parts, environmentally friendly calcium-zinc stabilizer 3 parts, OPE 0.35 parts, polyethylene wax 0.9 parts, EVA and furan-based semi-aromatic polyamide cross-linked modified calcium carbonate-mica powder mixture 30 parts, talc 1 part, impact-resistant ACR resin (molecular weight is 300000-1000000) 1 part, silicone toughening agent 1 part, CPE 3 parts, antioxidant 1010 0.2 parts, rutile titanium dioxide (particle size is 0.5-1 μm) 1.3 parts.

[0030] Preparation of maleic anhydride grafted CPVC: Maleic anhydride is dissolved in acetone to obtain a maleic anhydride solution with a concentration of 1.0 g / mL, PVC powder is added to the maleic anhydride solution, the mass ratio of PVC to maleic anhydride is 15:1, after stirring and mixing, it is transferred to a reaction kettle and left for 24 h, the temperature is raised to 60℃ and stirred for 2 h, then cooled to room temperature, chlorine gas is introduced to displace the air in the reaction kettle, the chlorine gas is continuously introduced at a rate of 120 g / min per cubic reaction system, and the chlorination reaction is carried out at a constant temperature of 130℃, the chlorine gas introduced after the start of the chlorination reaction accounts for 66%-69% of the mass of PVC, so as to control the chlorine content to be 66%-69%, and the chlorine gas is stopped when the content is reached, and the temperature is cooled to below 100℃, and after the chlorine gas is extracted, air is supplemented to displace the residual chlorine, the obtained crude product is dissolved in tetrahydrofuran, precipitated by adding methanol, impurities are removed, filtered, and dried to obtain maleic anhydride grafted CPVC.

[0031] Preparation of furan-based semi-aromatic polyamide: 5 mol of 2,5-furandicarboxylic acid chloride is dissolved in 150 mL of dichloromethane to obtain an oil phase reaction solution, 0.5 mol of tetrabutylammonium bromide and 5 mol of 1,6-hexanediamine are dissolved in 150 mL of 1 mol / L KOH aqueous solution to obtain an aqueous phase reaction solution, the aqueous phase reaction solution is added dropwise into the oil phase reaction solution, stirring is carried out for 40 min, after filtration, deionized water, anhydrous methanol and dichloromethane are sequentially used for washing, and the product is placed in a 80℃ vacuum drying box for 24 h, and is dried to obtain furan-based semi-aromatic polyamide.

[0032] Preparation of EVA and furan-based semi-aromatic polyamide cross-linked modified calcium carbonate-mica powder mixture: EVA (VA content of 20-25%, melt index of 4-8 g / min) is mixed with calcium carbonate and mica powder according to a mass ratio of 1:5:3, furan-based semi-aromatic polyamide is added according to 50% of the mass of EVA, and dicumyl peroxide is simultaneously added as an initiator, the mass of dicumyl peroxide is 5% of the mass of EVA, after uniform stirring and mixing, melt extrusion granulation is carried out in a double screw extruder at 200℃ to obtain an EVA and furan-based semi-aromatic polyamide cross-linked modified calcium carbonate-mica powder mixture. The particle size distribution D50 of calcium carbonate is 1-5 μm, the purity is ≥99.5%, the specific surface area is ≥30 m 2 / g, the pore volume is 0.5-1.5 cm 3 / g, the particle size of mica powder is 5-20 μm, and the diameter-thickness ratio is >50.

[0033] Preparation of PVC electrical conduit: Step one, the raw materials are weighed according to the above formula, and are ready for use.

[0034] Step two, the PVC resin, maleic anhydride grafted CPVC, impact ACR resin, CPE, and silicone toughening agent are added into a high-speed mixer, the rotation speed is set to 1200 rpm, the mixing and stirring are started, after the materials are uniformly mixed, the EVA and furan-based semi-aromatic polyamide cross-linked modified calcium carbonate-mica powder mixture is added, the stirring and mixing are continued, after uniform mixing, the calcium-zinc stabilizer, internal lubricant, external lubricant, talc, antioxidant, and rutile titanium dioxide are added, after uniform stirring and mixing, the product is sent into a cooling mixer, the rotation speed is set to 80 rpm, the low-speed stirring is started, and the product is discharged after cooling to 45℃ to obtain a cold mixture.

[0035] Step three, the cold mixture is passed through a vibrating screen to remove lumps, and is conveyed to a storage tank for standing for more than 3 h to obtain a PVC dry mixture.

[0036] Step four, the PVC dry mixture is transported to the twin-screw extruder to be extruded into a shape, the die head of the material blank is cooled, shaped after passing through the sizing sleeve, vacuum tank, water tank, etc., and then the high pressure-resistant and heat-resistant PVC insulating electrical conduit is obtained by printing and length cutting. The processing temperature of the twin-screw extruder barrel is set as follows: 170℃ for the first zone, 190℃ for the second zone, 185℃ for the third zone, and 180℃ for the fourth zone; the mold temperature is set as follows: 185℃ for the first zone to the second zone, and 190℃ for the third zone to the sixth zone; the temperature of the die head die is set as 200℃; the main machine screw speed is 60 r / min; the main machine current is 85-90 A; and the melt pressure is 22.5 MPa-23.0 MPa.

[0037] Example 2-3

[0038] The difference from Example 1 is only that the raw material ratio of the PVC electrical conduit is different, and the preparation steps are the same as those of Example 1. The specific ratio is shown in Table 1: Table 1

[0039] Example 4

[0040] The difference from Example 1 is only that the weight fraction of the EVA and furan-based semi-aromatic polyamide cross-linked modified calcium carbonate-mica powder mixture is adjusted to 25 parts, and other preparation steps are the same as those of Example 1.

[0041] Example 5

[0042] The difference from Example 1 is only that the weight fraction of the EVA and furan-based semi-aromatic polyamide cross-linked modified calcium carbonate-mica powder mixture is adjusted to 40 parts, and other preparation steps are the same as those of Example 1.

[0043] Example 6

[0044] The difference from Example 1 is only that when preparing the EVA and furan-based semi-aromatic polyamide cross-linked modified calcium carbonate-mica powder mixture, the mass ratio of EVA to calcium carbonate and mica powder is adjusted to 1:4:2.5, and other preparation steps are the same as those of Example 1.

[0045] Example 7

[0046] The difference from Example 1 is only that when preparing the EVA and furan-based semi-aromatic polyamide cross-linked modified calcium carbonate-mica powder mixture, the mass ratio of EVA to calcium carbonate and mica powder is adjusted to 1:6:4, and other preparation steps are the same as those of Example 1.

[0047] Example 8

[0048] The difference from Example 1 is that the amount of dicumyl peroxide added in the preparation of the EVA and furan-based semi-aromatic polyamide crosslinking modified calcium carbonate-mica powder mixture is 1% of the mass of EVA, and other preparation steps are the same as those of Example 1.

[0049] Example 9

[0050] The difference from Example 1 is that the amount of dicumyl peroxide added in the preparation of the EVA and furan-based semi-aromatic polyamide crosslinking modified calcium carbonate-mica powder mixture is 10% of the mass of EVA, and other preparation steps are the same as those of Example 1.

[0051] Comparative Example 1

[0052] The difference from Example 1 is that CPVC is used instead of maleic anhydride grafted CPVC.

[0053] A PVC electrical conduit, the PVC electrical conduit comprises the following raw materials in parts by weight: PVC resin (type SG-5) 80 parts, CPVC (chlorine content of 66% to 69%) 20 parts, environmentally friendly calcium-zinc stabilizer 3 parts, OPE 0.35 parts, polyethylene wax 0.9 parts, EVA and furan-based semi-aromatic polyamide crosslinking modified calcium carbonate-mica powder mixture 30 parts, talc 1 part, impact-resistant ACR resin (molecular weight of 300000 to 1000000) 1 part, silicone toughening agent 1 part, CPE 3 parts, antioxidant 1010 0.2 parts, rutile titanium dioxide (particle size of 0.5 to 1 μm) 1.3 parts.

[0054] The steps for preparing the furan-based semi-aromatic polyamide are the same as those of Example 1.

[0055] The steps for preparing the EVA and furan-based semi-aromatic polyamide crosslinking modified calcium carbonate-mica powder mixture are the same as those of Example 1.

[0056] Preparation of the PVC electrical conduit: Step one, weigh the raw materials according to the above formula and prepare.

[0057] Step two, add the PVC resin, CPVC, impact-resistant ACR resin, CPE, and silicone toughening agent into a high-speed mixer, set the rotation speed to 1200 rpm, start mixing and stirring, and then add the EVA and furan-based semi-aromatic polyamide crosslinking modified calcium carbonate-mica powder mixture, continue stirring and mixing, and then add the calcium-zinc stabilizer, internal lubricant, external lubricant, talc, antioxidant, and rutile titanium dioxide, mix uniformly, and then send to a cooling mixer, set the rotation speed to 80 rpm, start low-speed stirring, cool to 45°C, and discharge to obtain the cold mixture.

[0058] Step three, the cold mixture is sent to the storage tank through the vibration screen to remove the agglomerates and is left for more than 3 hours to obtain the PVC dry mixture.

[0059] Step four, the PVC dry mixture is sent to the double screw extruder for extrusion molding, and the pellet outlet die is cooled and shaped through the sizing sleeve, vacuum box, water tank, etc. to obtain the PVC insulating electrical conduit. The processing temperature of the double screw extruder barrel is set as follows: the first zone is 170℃, the second zone is 190℃, the third zone is 185℃, and the fourth zone is 180℃; the mold temperature is set as follows: the first zone to the second zone is 185℃, the third zone to the sixth zone is 190℃, the die head die temperature is set to 200℃, the main machine screw speed is 60 r / min, the main machine current is 85-90 A, and the melt pressure is 22.5 MPa-23.0 MPa.

[0060] Comparative Example 2

[0061] The difference from Example 1 is that the calcium carbonate-mica powder mixture is used to replace the EVA and furan-based semi-aromatic polyamide cross-linked modified calcium carbonate-mica powder mixture.

[0062] A PVC electrical conduit, the PVC electrical conduit comprises the following raw materials in parts by weight: PVC resin (type SG-5) 80 parts, maleic anhydride grafted CPVC 20 parts, environmentally friendly calcium-zinc stabilizer 3 parts, OPE 0.35 parts, polyethylene wax 0.9 parts, calcium carbonate-mica powder mixture 30 parts, talc 1 part, impact-resistant ACR resin (molecular weight 300000-1000000) 1 part, organic silicon toughening agent 1 part, CPE 3 parts, antioxidant 1010 0.2 parts, rutile titanium dioxide (particle size 0.5-1 μm) 1.3 parts.

[0063] The preparation of maleic anhydride grafted CPVC is the same as that of Example 1.

[0064] Preparation of calcium carbonate and mica powder mixture: The calcium carbonate and mica powder are mixed according to a mass ratio of 5:3 to obtain the calcium carbonate-mica powder mixture. The calcium carbonate has a particle size distribution D50 of 1-5 μm, a purity ≥99.5%, a specific surface area ≥30 m 2 / g, and a pore volume of 0.5-1.5 cm 3 / g, and the mica powder has a particle size of 5-20 μm and a diameter-thickness ratio > 50.

[0065] Preparation of PVC electrical conduit: Step one, the raw materials are weighed according to the above formula and are ready for use.

[0066] Step two, PVC resin, maleic anhydride grafted CPVC, impact ACR resin, CPE, silicone toughening agent into the high-speed mixer, set the speed of 1200 rpm, start mixing, the material is mixed evenly, add calcium carbonate-mica powder mixture, continue to stir and mix, mix evenly, add calcium zinc stabilizer, internal lubricant, external lubricant, talc, antioxidant, rutile titanium dioxide, mix evenly, send into the cooling mixer, set the speed of 80 rpm, start low speed stirring, cool to 45℃, discharge, get cold mix.

[0067] Step three, the cold mixture is removed by vibrating screen, transported to the storage tank for more than 3h, get PVC dry mixture.

[0068] Step four, the PVC dry mixture is transported to the twin-screw extruder for extrusion molding, the die head is cooled, shaped by sizing sleeve, vacuum tank, water tank, etc., and then printed, length cut to get PVC insulating electrical conduit. Set the processing temperature of the twin-screw extruder barrel, zone one is 170℃, zone two is 190℃, zone three is 185℃, zone four is 180℃; set the mold temperature, zone one to zone two is 185℃, zone three to zone six is 190℃, set the die head temperature to 200℃, the main machine screw speed is 60 r / min, the main machine current is 85-90A, the melt pressure is 22.5MPa-23.0MPa.

[0069] Comparative example 3

[0070] The difference from example 1 is only that EVA is used to modify calcium carbonate and mica powder.

[0071] A PVC electrical conduit, by weight, the PVC electrical conduit includes the following raw materials: PVC resin (SG-5 type) 80 parts, maleic anhydride grafted CPVC 20 parts, environmentally friendly calcium zinc stabilizer 3 parts, OPE 0.35 parts, polyethylene wax 0.9 parts, EVA modified calcium carbonate-mica powder mixture 30 parts, talc 1 part, impact ACR resin (molecular weight 300000-1000000) 1 part, silicone toughening agent 1 part, CPE 3 parts, antioxidant 1010 0.2 parts, rutile titanium dioxide (particle size 0.5-1 μm) 1.3 parts.

[0072] Prepare maleic anhydride grafted CPVC step same as example 1.

[0073] Prepare EVA modified calcium carbonate-mica powder mixture: EVA (VA content 20-25%, melt index 4-8 g / min) was mixed with calcium carbonate, mica powder in a mass ratio of 1:5:3, and dicumyl peroxide was added as an initiator, the amount of dicumyl peroxide was 5% of the mass of EVA. After stirring and mixing uniformly, the mixture was melt-extruded and granulated in a twin-screw extruder at 200°C to obtain an EVA modified calcium carbonate-mica powder mixture. The particle size distribution D50 of the calcium carbonate was 1-5 μm, the purity was ≥99.5%, the specific surface area was ≥30 m 2 / g, the pore volume was 0.5-1.5 cm 3 / g, and the mica powder had a particle size of 5-20 μm and a diameter-thickness ratio > 50.

[0074] Preparation of PVC electrical conduit: Step one, weigh the raw materials according to the above formula, and prepare them for use.

[0075] Step two, add PVC resin, maleic anhydride grafted CPVC, impact ACR resin, CPE, and silicone toughening agent into a high-speed mixer, set the rotation speed to 1200 rpm, and start mixing and stirring. After the materials are uniformly mixed, add the EVA modified calcium carbonate-mica powder mixture, continue to mix and stir, and then add calcium-zinc stabilizer, internal lubricant, external lubricant, talc, antioxidant, and rutile titanium dioxide. After uniform mixing, send the mixture into a cooling mixer, set the rotation speed to 80 rpm, start low-speed stirring, cool to 45°C, and discharge to obtain the cold mixture.

[0076] Step three, pass the cold mixture through a vibrating screen to remove lumps, and then convey it to a storage tank for at least 3 hours to obtain PVC dry mixture.

[0077] Step four, convey the PVC dry mixture to a twin-screw extruder for extrusion molding. After the extrudate exits the die, it is cooled, shaped, and then printed, measured, and cut to obtain the PVC insulating electrical conduit. The processing temperature of the twin-screw extruder barrel is set as follows: zone one is 170°C, zone two is 190°C, zone three is 185°C, and zone four is 180°C. The die temperature is set as follows: zone one to zone two is 185°C, and zone three to zone six is 190°C. The temperature of the die head is set to 200°C. The rotation speed of the main screw is 60 r / min, the current of the main machine is 85-90 A, and the melt pressure is 22.5 MPa-23.0 MPa.

[0078] Comparative Example 4

[0079] The difference from Example 1 is that EVA and furan-based polyamide are directly blended to modify calcium carbonate and mica powder.

[0080] A PVC electrical conduit, the PVC electrical conduit comprises the following raw materials in parts by weight: PVC resin (type SG-5) 80 parts, maleic anhydride grafted CPVC 20 parts, environmentally friendly calcium-zinc stabilizer 3 parts, OPE 0.35 parts, polyethylene wax 0.9 parts, EVA and furan-based semi-aromatic polyamide blended modified calcium carbonate-mica powder mixture 30 parts, talc 1 part, impact-resistant ACR resin (molecular weight 300000-1000000) 1 part, silicone toughening agent 1 part, CPE 3 parts, antioxidant 1010 0.2 parts, rutile titanium dioxide (particle size 0.5-1 μm) 1.3 parts.

[0081] The step of preparing maleic anhydride grafted CPVC is the same as in Example 1.

[0082] The step of preparing furan-based semi-aromatic polyamide is the same as in Example 1.

[0083] Preparation of EVA and furan-based semi-aromatic polyamide blended modified calcium carbonate-mica powder mixture: EVA (VA content 20-25%, melt index 4-8 g / min) is mixed with calcium carbonate and mica powder at a mass ratio of 1:5:3, furan-based semi-aromatic polyamide is added at 50% of the mass of EVA, and after stirring and mixing uniformly, it is melt-extruded and granulated in a twin-screw extruder at 200°C to obtain an EVA and furan-based semi-aromatic polyamide blended modified calcium carbonate-mica powder mixture. The calcium carbonate has a particle size distribution D50 of 1-5 μm, a purity ≥ 99.5%, a specific surface area ≥ 30 m 2 / g, and a pore volume of 0.5-1.5 cm 3 / g, and the mica powder has a particle size of 5-20 μm and an aspect ratio > 50.

[0084] Preparation of a PVC electrical conduit: Step one, weigh the raw materials according to the above formula and prepare.

[0085] Step two, add PVC resin, maleic anhydride grafted CPVC, impact-resistant ACR resin, CPE, and silicone toughening agent to a high-speed mixer, set the speed to 1200 rpm, start mixing, and when the materials are uniformly mixed, add EVA and furan-based semi-aromatic polyamide blended modified calcium carbonate-mica powder mixture, continue stirring and mixing, and after mixing uniformly, add calcium-zinc stabilizer, internal lubricant, external lubricant, talc, antioxidant, and rutile titanium dioxide, stir and mix uniformly, and then send to a cooling mixer, set the speed to 80 rpm, start low-speed stirring, cool to 45°C, and discharge to obtain a cold mixture.

[0086] Step three, pass the cold mixture through a vibrating screen to remove lumps, and then convey to a storage tank for 3 hours or more to obtain a PVC dry mixture.

[0087] Step four, the PVC dry mixture is transported to a twin-screw extruder for extrusion molding. After the exit die of the parison is cooled, shaped by a sizing sleeve, a vacuum tank, a water tank, etc., printing, length counting and cutting are performed to obtain the PVC insulating electrician sleeve. The processing temperature of the barrel of the twin-screw extruder is set as follows: 170℃ for the first zone, 190℃ for the second zone, 185℃ for the third zone, and 180℃ for the fourth zone. The mold temperature is set as follows: 185℃ for the first zone to the second zone, and 190℃ for the third zone to the sixth zone. The temperature of the die head die is set as 200℃. The rotation speed of the main screw is 60 r / min. The main machine current is 85-90 A. The melt pressure is 22.5 MPa-23.0 MPa.

[0088] Comparative Example 5

[0089] The difference from Example 1 is that EVA, furan-based polyamide, calcium carbonate and mica powder are directly added to the raw materials.

[0090] A PVC electrician sleeve, by weight fraction, comprises the following raw materials: PVC resin (type SG-5) 80 parts, maleic anhydride grafted CPVC 20 parts, environmentally friendly calcium-zinc stabilizer 3 parts, OPE 0.35 parts, polyethylene wax 0.9 parts, EVA 3.2 parts, furan-based semi-aromatic polyamide 1.6 parts, calcium carbonate 15.8 parts, mica powder 9.4 parts, talc 1 part, impact-resistant ACR resin (molecular weight 300000-1000000) 1 part, organic silicon toughening agent 1 part, CPE 3 parts, antioxidant 1010 0.2 parts, rutile titanium dioxide (particle size 0.5-1 μm) 1.3 parts. Among them, the VA content of EVA is 20-25%, the melt index is 4-8 g / min, the particle size distribution D50 of calcium carbonate is 1-5 μm, the purity is ≥99.5%, the specific surface area is ≥30 m 2 / g, the pore volume is 0.5-1.5 cm 3 / g, the particle size of mica powder is 5-20 μm, and the diameter-thickness ratio is >50.

[0091] The preparation of maleic anhydride grafted CPVC is the same as that in Example 1.

[0092] The preparation of furan-based semi-aromatic polyamide is the same as that in Example 1.

[0093] Preparation of PVC electrician sleeve: Step one, the raw materials are weighed according to the above formula and prepared.

[0094] Step two, PVC resin, maleic anhydride grafted CPVC, impact ACR resin, CPE, silicone toughening agent into the high-speed mixer, set the speed of 1200 rpm, start mixing, stirring, until the material is mixed evenly add EVA, furan-based semi-aromatic polyamide, calcium carbonate and mica powder, continue to stir and mix, mix evenly, add calcium zinc stabilizer, internal lubricant, external lubricant, talc, antioxidant, rutile titanium dioxide, stir and mix evenly, send into the cooling mixer, set the speed of 80 rpm, start low speed stirring, cool to 45℃ discharge, get cold mix.

[0095] Step three, the cold mixture is passed through a vibrating screen to remove lumps, and is transported to a storage tank for standing for more than 3h to obtain a PVC dry mixture.

[0096] Step four, the PVC dry mixture is transported to a twin-screw extruder for extrusion molding. After the die head outlet die is cooled, shaped through a sizing sleeve, a vacuum box, a water tank, etc., printing, length counting and cutting to obtain a PVC insulating electrical conduit. The processing temperature of the twin-screw extruder barrel is set as follows: 170℃ for the first zone, 190℃ for the second zone, 185℃ for the third zone, and 180℃ for the fourth zone. The die temperature is set as follows: 185℃ for the first zone to the second zone, and 190℃ for the third zone to the sixth zone. The die head die temperature is set as 200℃. The main machine screw speed is 60 r / min. The main machine current is 85-90A. The melt pressure is 22.5MPa-23.0MPa.

[0097] Comparative example 6

[0098] The difference from example 1 is that the maleic anhydride grafted CPVC resin is replaced by PVC resin.

[0099] A PVC electrical conduit, by weight parts, the PVC electrical conduit comprises the following raw materials: PVC resin (SG-5 type) 100 parts, environmentally friendly calcium zinc stabilizer 3 parts, OPE 0.35 parts, polyethylene wax 0.9 parts, EVA and furan-based semi-aromatic polyamide cross-linked modified calcium carbonate-mica powder mixture 30 parts, talc 1 part, impact ACR resin (molecular weight 300000-1000000) 1 part, silicone toughening agent 1 part, CPE 3 parts, antioxidant 1010 0.2 parts, rutile titanium dioxide (particle size 0.5-1 μm) 1.3 parts.

[0100] The preparation of furan-based semi-aromatic polyamide is the same as that of example 1.

[0101] The preparation of EVA and furan-based semi-aromatic polyamide cross-linked modified calcium carbonate-mica powder mixture is the same as that of example 1.

[0102] Preparation of PVC electrical conduit: Step one, weigh the raw materials according to the above formula, and prepare for use.

[0103] Step two, add PVC resin, impact ACR resin, CPE, silicone toughening agent into a high-speed mixer, set the rotation speed to 1200 rpm, start mixing and stirring, and when the materials are uniformly mixed, add EVA and furan-based semi-aromatic polyamide cross-linked modified calcium carbonate-mica powder mixture, continue stirring and mixing, and after uniform mixing, add calcium-zinc stabilizer, internal lubricant, external lubricant, talc, antioxidant, and rutile titanium dioxide, uniformly stir and mix, then send to a cooling mixer, set the rotation speed to 80 rpm, start low-speed stirring, cool to 45℃, and discharge to obtain cold mixed materials.

[0104] Step three, pass the cold mixed materials through a vibrating screen to remove lumps, and transport to a storage tank for standing for more than 3h to obtain PVC dry mixed materials.

[0105] Step four, transport the PVC dry mixed materials to a twin-screw extruder for extrusion molding, and after the die head is cooled, shaped by a sizing sleeve, vacuum tank, water tank, etc., printing, length counting and cutting to obtain a PVC insulating electrical conduit. Set the processing temperature of the twin-screw extruder barrel to 170℃ in the first zone, 190℃ in the second zone, 185℃ in the third zone, and 180℃ in the fourth zone; set the mold temperature to 185℃ in the first and second zones, and 190℃ in the third to sixth zones; set the die head temperature to 200℃; set the main machine screw rotation speed to 60 r / min; set the main machine current to 85-90A; and set the melt pressure to 22.5MPa-23.0MPa.

[0106] The PVC electrical conduit (specification: 305-20) prepared in Examples 1-9 and Comparative Examples 1-6 above was subjected to performance testing according to the GB / T 43815-2024 "Building Hard Polyvinyl Chloride (PVC-U) Insulated Electrical Conduit and Fittings" standard, and the test results are shown in Table 2.

[0107] Table 2

[0108] It can be seen from Table 1 that in Examples 1-3, by optimizing the raw material ratio, the performance indicators of Example 2 are optimal, but from the perspective of cost-effectiveness, the amount of maleic anhydride grafted CPVC in Example 2 is relatively large, which will increase the cost. Based on the formulation of Example 1, Examples 4 and 5 further optimize the formulation. The modified calcium carbonate-mica powder mixture in Example 5 is added in an excessive amount, which, as a filler, will destroy the continuous phase of the organic material, and the mechanical properties of the PVC sleeve prepared at this time will be reduced. In Examples 1, 6 and 7, the amount of EVA is low during modification, which has limited effect on improving compatibility. The high amount of EVA leads to excessive coating, and at this time, the proportion of inorganic materials in the modified mixture of equal quality is reduced, and the compression resistance and heat resistance of the PVC sleeve will also be reduced. In Examples 8 and 9, the amount of initiator affects the crosslinking degree of EVA and furan-based semi-aromatic polyamide. When the crosslinking degree is low, the crosslinking degree of maleic anhydride grafted CPVC in the raw material will also decrease, at which time the interfacial bonding force is weakened, and the comprehensive performance is reduced. Excessive initiator will induce more self-crosslinking of EVA, at which time the interpenetrating crosslinking structure of EVA and furan-based semi-aromatic polyamide cannot be formed, and the improvement effect on compression resistance and heat resistance will also be reduced. The compression resistance and heat deformation resistance of the PVC insulating electrical sleeve prepared in the examples of the present application are significantly higher than those of the comparative examples, and the purpose of the present application is achieved in high compression resistance and heat resistance performance indicators.

[0109] It should be noted that, in this document, the terms such as first and second are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between such entities or operations. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus including a series of elements includes not only those elements, but also other elements not explicitly listed or inherent to such process, method, article or apparatus.

[0110] Although embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A high pressure and heat resistant PVC insulated electrical conduit, characterized in that, The following raw materials are included by weight parts: PVC resin 75-85 parts, maleic anhydride grafted CPVC 15-25 parts, calcium-zinc stabilizer 2.5-3.5 parts, internal lubricant 0.2-0.5 parts, external lubricant 0.4-1.2 parts, EVA and furan-based semi-aromatic polyamide cross-linked modified calcium carbonate-mica powder mixture 25-40 parts, talc 0-3 parts, impact ACR resin 0.5-1.5 parts, silicone toughening agent 0.5-1.5 parts, CPE 2-4 parts, antioxidant 0.1-0.3 parts, rutile titanium dioxide 1-2 parts.

2. A high pressure and heat resistant PVC insulated electrical conduit as claimed in claim 1, wherein, The PVC resin is a general type SG-5 resin with a viscosity number of 108-120.

3. A high pressure and heat resistant PVC electrical conduit as claimed in claim 1, wherein, The preparation steps of the maleic anhydride grafted CPVC are as follows: Dissolve maleic anhydride in acetone to obtain a maleic anhydride solution with a concentration of 0.5-1.5 g / mL, add PVC powder to the maleic anhydride solution with a mass ratio of PVC to maleic anhydride of 12-16:1, stir and mix, then transfer to a reaction kettle and stand for 12-24 h, heat to 50-60℃ and stir for 1-3 h, cool to room temperature, introduce chlorine to displace the air in the reaction kettle, continue to introduce chlorine at a rate of 100-150 g / min per cubic reaction system, and perform chlorination reaction at a constant temperature of 120-140℃, control the chlorine content to be 66%-69%, stop introducing chlorine, cool to below 100℃, and after the chlorine is extracted, supplement air to displace the residual chlorine, dissolve the obtained crude product in tetrahydrofuran, add methanol to precipitate and separate, remove impurities, filter, dry, and obtain maleic anhydride grafted CPVC.

4. A high pressure and heat resistant PVC electrical conduit as claimed in claim 1, wherein, The calcium-zinc stabilizer is an environmentally friendly calcium-zinc stabilizer, and the components include zinc stearate and calcium stearate.

5. A high pressure and heat resistant PVC electrical conduit as claimed in claim 1, wherein, The internal lubricant is at least one of glycerol monostearate, OPE, and stearic acid. The external lubricant is at least one of polyethylene wax, Fischer-Tropsch wax, and paraffin wax.

6. A high pressure and heat resistant PVC electrical conduit as claimed in claim 1, wherein, The preparation steps of the EVA and furan-based semi-aromatic polyamide cross-linked modified calcium carbonate-mica powder mixture are as follows: Mix EVA with calcium carbonate and mica powder according to a mass ratio of 1:(4-6):(2.5-4), add furan-based semi-aromatic polyamide according to 40-60% of the mass of EVA, and simultaneously add dicumyl peroxide as an initiator, stir and mix uniformly, then melt and extrude in a twin-screw extruder at 190-220℃ to obtain an EVA and furan-based semi-aromatic polyamide cross-linked modified calcium carbonate-mica powder mixture.

7. A high pressure and heat resistant PVC insulated electrical conduit as claimed in claim 6, wherein, The VA content of the EVA is 20-25%, and the melt index is 4-8 g / min. The particle size of the mica powder is 5-20 μm, and the diameter-thickness ratio is >50. The particle size distribution D50 of the calcium carbonate is 1-5 μm, the purity is ≥99.5%, the specific surface area is ≥30 m2 / g, and the pore volume is 0.5-1.5 cm3 / g. The furan-based polyamide is prepared by polymerization reaction of 2,5-furandicarboxylic acid chloride and 1,6-hexanediamine.

8. A high pressure and heat resistant PVC insulated electrical conduit as claimed in claim 6, wherein, The dicumyl peroxide is 1-10% of the mass of EVA.

9. A high pressure and heat resistant PVC electrical conduit as claimed in claim 1, wherein, The molecular weight of the impact ACR resin is 300000-1000000. The antioxidant is a hindered phenolic antioxidant. The rutile titanium dioxide has a particle size of 0.5-1 μm.

10. A process for the preparation of a high pressure and heat resistant PVC electrical conduit as claimed in any one of claims 1 to 9, characterized in that, The method comprises the following steps: Step one, weigh the raw materials according to the formula, and prepare; Step two, add PVC resin, maleic anhydride grafted CPVC, impact ACR resin, CPE and silicone toughening agent into a high-speed mixer, set the rotating speed to 1000-1500 rpm, start mixing and stirring, and then add EVA and furan-based semi-aromatic polyamide cross-linked modified calcium carbonate-mica powder mixture, continue stirring and mixing, add calcium-zinc stabilizer, internal lubricant, external lubricant, talc, antioxidant and rutile titanium dioxide after mixing uniformly, and then send the mixture into a cooling mixer, set the rotating speed to 50-100 rpm, start low-speed stirring, and discharge the mixture after cooling to 45-55 ℃ to obtain cold mixture; Step three, remove the agglomerates of the cold mixture through a vibrating screen, and then convey the mixture into a storage tank to stand for more than 3 hours to obtain PVC dry mixture; Step four, convey the PVC dry mixture into a double-screw extruder to extrude and form, and then obtain high-pressure and heat-resistant PVC insulating electrical sleeve.

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