High impact PVC cable protection pipe and method for its production

Abstract

The application belongs to the technical field of power cable protection pipes, and particularly discloses a high-impact PVC cable protection pipe and a preparation method thereof. The protection pipe comprises the following raw material components in mass fractions: 100 parts of PVC resin, 3-6 parts of maleic anhydride grafted ethylene-octene copolymer, 1-5 parts of methyl methacrylate-butadiene-styrene copolymer, 2-8 parts of acrylate core-shell copolymer, 4-6 parts of calcium-zinc-rare earth composite stabilizer, 0.8-1.5 parts of lubricant and 2-3 parts of nano reinforcing filler. The high-impact PVC cable protection pipe and the preparation method thereof have the mechanical stability for long-term service in a coastal saline-alkali and humid oxygen-rich buried environment while maintaining excellent low-temperature impact resistance.

Description

Technical Field

[0001] This invention relates to the field of power cable protection pipe technology, and in particular to a high-impact PVC cable protection pipe and its preparation method. Background Technology

[0002] With the continuous advancement of municipal power distribution network upgrades and new energy infrastructure construction, high-impact polyvinyl chloride (HPVC) cable protection pipes are widely used in underground power cable protection projects due to their excellent insulation, flame retardancy, corrosion resistance, and low-temperature impact resistance. In coastal areas such as the Lingang Industrial Park, the soil is characterized by slight salinity, humidity, high oxygen content, and low-temperature freeze-thaw cycles in winter, which places higher demands on the long-term service stability of HPVC pipes.

[0003] HPVC cable protection pipes commonly use single or binary blends of acrylic core-shell impact modifiers (ACR), chlorinated polyethylene (CPE), and methyl methacrylate-butadiene-styrene copolymer (MBS) for toughening modification. However, these systems exhibit significant aging and degradation defects under long-term buried conditions in coastal saline-alkali environments. MBS molecules contain a large number of unsaturated butadiene double bonds, which are prone to oxidative hydrolysis under long-term exposure to humid, hot, oxygen-containing, and saline-alkali media. This leads to the gradual failure of the rubber core-shell toughening structure, a significant decrease in pipe toughness, and a marked increase in the risk of brittle cracking in the later stages. Although the CPE modification system has excellent overall weather resistance, alkaline soil environments catalyze the slow dehydrochlorination of its molecular chains. The released hydrogen chloride further induces a chain degradation of the PVC matrix, forming a self-accelerating aging cycle. While ACR acrylic core-shell modifiers have the best resistance to acid and alkali aging, their low-temperature impact resistance is limited when used alone, failing to meet the low-temperature drop hammer impact requirements for high-impact power conduits in the DL / T 802.3 standard.

[0004] In existing technologies, the performance is often compromised by binary or ternary compounding of ACR / CPE / MBS, which cannot simultaneously meet the dual requirements of ultra-low temperature impact resistance and long-term aging stability in coastal saline-alkali areas. After long-term service, the mechanical properties of the pipes deteriorate rapidly and the service life is short, making it difficult to meet the engineering requirements of long-term design life in port industrial parks. Summary of the Invention

[0005] The purpose of this invention is to provide a high-impact PVC cable protection pipe and its preparation method, which maintains excellent low-temperature impact resistance while possessing mechanical stability for long-term service in coastal saline-alkali, humid, and oxygen-rich buried environments.

[0006] To achieve the above objectives, the present invention provides a high-impact PVC cable protection pipe, comprising the following raw material components in parts by weight: 100 parts of PVC resin; 3-6 parts of maleic anhydride-grafted ethylene-octene copolymer (POE-g-MAH); 1-5 parts of methyl methacrylate-butadiene-styrene copolymer (MBS); Acrylic core-shell copolymer (ACR) 2-8 parts; 4-6 parts of calcium-zinc-rare earth composite stabilizer; Lubricant 0.8~1.5 parts; 2-3 parts of nano-reinforcing filler; No chlorinated polyethylene (CPE) is added to the raw material system.

[0007] Preferably, the degree of polymerization of the PVC resin is 800~1300, and it is more preferably SG-5 type polyvinyl chloride resin.

[0008] Preferably, the grafting rate of the maleic anhydride-grafted ethylene-octene copolymer is 0.8%~2.0%, and the octene mass fraction is 25%~30%. The grafted POE molecular backbone has a saturated polyolefin structure and does not contain unsaturated double bonds that can be oxidized or alkali-degraded. At the same time, the maleic anhydride groups can improve its compatibility with the PVC matrix, allowing it to be uniformly dispersed in PVC and exert a toughening effect.

[0009] Preferably, the butadiene rubber phase of the methyl methacrylate-butadiene-styrene copolymer has a mass fraction of 60%~70% and an average particle size of 80~120nm; MBS provides excellent low-temperature drop hammer impact performance.

[0010] Preferably, the acrylate core-shell copolymer has a weight-average molecular weight of 800,000 to 1,200,000; the ACR molecular chain does not contain carbon-carbon double bonds, and has excellent weather resistance and acid and alkali aging resistance, serving as the main component for constructing an aging-resistant basic framework.

[0011] Preferably, the lubricant is a mixture of calcium stearate and polyethylene wax in a mass ratio of 1:1.

[0012] Preferably, the nano-reinforcing filler is a mixture of surface-modified nano-talc powder and nano-hydrotalc in a mass ratio of 2:1.

[0013] This invention also provides a method for preparing a high-impact PVC cable protection pipe, comprising the following steps: S1. High-speed mixing: Weigh each raw material, put the PVC resin into a high-speed mixer with a stirring speed of 800~1500r / min, heat to 80~90℃, then add calcium zinc rare earth composite stabilizer, lubricant, and nano reinforcing filler in sequence, continue to heat to 105~115℃, add methyl methacrylate-butadiene-styrene copolymer MBS, acrylate core-shell copolymer ACR, and maleic anhydride grafted ethylene-octene copolymer POE-g-MAH, mix at high speed until the material temperature reaches 120~125℃, then discharge to obtain the mixture. S2. Cooling and maturation: Transfer the mixed materials into a cold mixer for stirring and cooling. When the material temperature drops to below 40°C, discharge the material and let it stand to mature, thus obtaining a dry mixture. S3. Extrusion molding: Add the dry mixture to the screw extruder, control the barrel temperature to 150~180℃ and the die head temperature to 170~185℃, and after melting and plasticizing, extrude it through the die head to form the final product; S4. Sizing, Cooling, Traction Cutting and Flaring: The extruded tube blank is shaped by a vacuum sizing sleeve, and then enters a graded cooling water tank for gradual cooling. The cooling water temperature is gradually reduced from 60℃ to room temperature. After being pulled at a constant speed by a traction machine, it is cut to a fixed length and then the socket is flared to obtain the finished product.

[0014] Preferably, in S2, the settling and ripening time is 20~24h.

[0015] When the temperature reaches the range of 105~115℃, three modifiers are added at once. At this point, the PVC resin has reached a preliminary gelation state, with a sticky surface and optimal rheological properties, and the additives have formed a uniform coating layer. After the three modifiers are added, they can uniformly adhere to and embed on the surface of the resin particles, avoiding agglomeration. Among them, ACR plays the leading role in plasticizing and promoting, optimizing melt viscosity, and further helping MBS and grafted POE to achieve micron-level uniform dispersion, forming a gradient phase structure of "low-temperature main toughening + ultra-low-temperature bottom toughening".

[0016] Furthermore, MBS contains butadiene unsaturated double bonds and is a heat-sensitive toughening agent. When the temperature exceeds this range, the rubber core is prone to thermo-oxidative degradation, the core-shell structure is destroyed, and the low-temperature toughening effect is directly lost. The maleic anhydride groups grafted with POE will also undergo side reactions at high temperatures, weakening the interfacial compatibility. Therefore, the endpoint temperature must be strictly controlled.

[0017] Therefore, the present invention employs the above-mentioned high-impact PVC cable protection pipe and its preparation method, and the beneficial effects are as follows: (1) Improved aging resistance: CPE makes the system face the risk of dehydrochlorination degradation in alkaline environment, and the unsaturated double bonds of MBS are easily oxidized under humid and hot oxygen conditions, resulting in toughness decay; This invention abandons CPE as toughening modification component, eliminating the hidden danger of alkaline catalytic dehydrochlorination degradation in coastal saline-alkali soil from the root; At the same time, the amount of MBS is reduced, the total amount of unsaturated double bonds in the system is reduced, and the polyolefin segments grafted with POE have strong hydrophobicity. After uniform dispersion, they form a large number of hydrophobic micro-regions in the matrix, which delays the penetration rate of water, chloride ions and hydroxide ions into the pipe, and improves the long-term aging resistance stability of the pipe in saline-alkali, humid and oxygen-rich buried environment.

[0018] (2) Excellent low-temperature impact resistance: This invention uses grafted POE to replace CPE to undertake the toughening function, uses ACR to construct an aging-resistant basic skeleton, and a small amount of MBS to provide low-temperature drop hammer impact resistance. The grafted POE with saturated polyolefin structure utilizes the elastomer dispersed phase for toughening and its own lower glass transition temperature to undertake the toughening function in ultra-low temperature environments below -10℃, and reduces the total amount of unsaturated double bonds. It works synergistically with MBS to toughen, making up for the deficiency of low-temperature impact resistance when ACR is used alone, so that the pipe still has good impact resistance at low temperatures and meets the requirements of power conduit specifications.

[0019] (3) Good processing performance and excellent comprehensive performance: The maleic anhydride polar groups of grafted POE form polar interactions with the PVC molecular chain and the acrylate segments of ACR. With the help of the interfacial transition effect of ACR, the POE particles are uniformly dispersed in the matrix with a small particle size, without agglomeration, delamination and precipitation, which improves the melt flowability and processability of PVC, which is conducive to extrusion molding. The surface quality of the pipe is good. At the same time, the pipe has the advantages of high impact resistance, high ring stiffness, salt and alkali aging resistance and low temperature resistance, and has the mechanical stability for long-term service of cable protection pipes in coastal saline-alkali areas.

[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0021] Figure 1 The mechanical properties of the products in Example 2 and Comparative Example 1 of the present invention are as follows: (a) is tensile strength, (b) is elongation at break, (c) is ring stiffness, and (d) is Vicat softening temperature. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0024] Example 1 A high-impact PVC cable protection pipe, with specifications of Φ110×5.0mm, has the following raw material composition by weight: 100 parts of SG-5 type PVC resin, 3 parts of POE-g-MAH (grafting rate 1.0%, octene content 28%), 5 parts of MBS, 2 parts of ACR, 5 parts of calcium zinc rare earth composite stabilizer, 0.5 parts of calcium stearate, 0.5 parts of polyethylene wax, 2 parts of nano talc powder, and 1 part of nano hydrotalcite.

[0025] Its preparation method is as follows: S1. High-speed mixing: SG-5 type PVC resin is put into a high-speed mixer with a stirring speed of 1200r / min. After heating to 85℃, calcium zinc rare earth composite stabilizer, calcium stearate, polyethylene wax, nano talc powder, and nano hydrotalc are added in sequence. The temperature is further raised to 110℃, and MBS, ACR, and POE-g-MAH are added. The mixture is then discharged after high-speed mixing until the material temperature reaches 120℃ to obtain the mixed material. S2. Cooling and maturation: Transfer the mixed materials into a cold mixer for stirring and cooling. When the material temperature drops below 40℃, discharge the material and let it stand for 24 hours to obtain a dry mixture. S3. Extrusion molding: The dry mixture is added to the screw extruder, the barrel temperature is controlled at 170℃ and the die head temperature is controlled at 175℃, and after melting and plasticizing, it is extruded through the die head to form the final product. S4. Sizing, Cooling, Traction Cutting and Flaring: The extruded tube blank is shaped by a vacuum sizing sleeve, and then enters a graded cooling water tank for gradual cooling. The cooling water temperature is gradually reduced from 60℃ to room temperature. After being pulled at a constant speed by a traction machine, it is cut to a fixed length and then the socket is flared to obtain the finished product.

[0026] Example 2 A high-impact PVC cable protection pipe, with specifications of Φ110×5.0mm, has the following raw material composition by weight: 100 parts of SG-5 type PVC resin, 4.5 parts of POE-g-MAH (grafting rate 1.0%, octene content 28%), 3 parts of MBS, 2.5 parts of ACR, 5 parts of calcium zinc rare earth composite stabilizer, 0.5 parts of calcium stearate, 0.5 parts of polyethylene wax, 2 parts of nano talc powder, and 1 part of nano hydrotalcite.

[0027] The preparation method is the same as in Example 1.

[0028] Example 3 A high-impact PVC cable protection pipe, with specifications of Φ110×5.0mm, has the following raw material composition by weight: 100 parts of SG-5 type PVC resin, 6 parts of POE-g-MAH (grafting rate 1.0%, octene content 28%), 1 part of MBS, 3 parts of ACR, 5 parts of calcium zinc rare earth composite stabilizer, 0.5 parts of calcium stearate, 0.5 parts of polyethylene wax, 2 parts of nano talc powder, and 1 part of nano hydrotalcite.

[0029] The preparation method is the same as in Example 1.

[0030] Comparative Example 1 A traditional ACR+CPE+MBS ternary system cable protection pipe, without the addition of POE-g-MAH, has a specification of Φ110×5.0mm. The raw material composition, by weight, is: 100 parts of SG-5 type PVC resin, 8 parts of CPE 135A, 5 parts of MBS, 2 parts of ACR, 5 parts of ordinary calcium-zinc stabilizer, 0.5 parts of calcium stearate, 0.5 parts of polyethylene wax, and 15 parts of heavy calcium carbonate.

[0031] Its preparation method is as follows: Weigh each raw material according to the formula and add it to a high-speed mixer. Heat mix at a stirring speed of 1200 r / min until the material temperature reaches 120℃. Then transfer it to a cold mixer to cool it to below 40℃ and let it stand for 24 hours to mature. The resulting dry mixture is added to a screw extruder, where it is melted, plasticized, and extruded. The die head temperature is 175℃, the barrel temperature is 170℃, and the screw speed is 25 r / min. The extruded preform is then vacuum-formed, cooled, drawn, and cut to obtain the finished product.

[0032] Comparative Example 2 A type of ACR+MBS binary system cable protection pipe, without the addition of CPE 135A and POE-g-MAH, with specifications of Φ110×5.0mm, and the raw material composition by weight is: 100 parts of SG-5 type PVC resin, 12 parts of MBS, 3 parts of ACR, 5 parts of ordinary calcium-zinc stabilizer, 0.5 parts of calcium stearate, 0.5 parts of polyethylene wax, 2 parts of nano talc powder, and 1 part of nano hydrotalcite.

[0033] Its preparation method is the same as that of Comparative Example 1.

[0034] Comparative Example 3 A type of ACR+CPE binary system cable protection pipe, without the addition of MBS and POE-g-MAH, with specifications of Φ110×5.0mm, and the raw material composition by weight is: 100 parts of SG-5 type PVC resin, 12 parts of CPE 135A, 3 parts of ACR, 5 parts of ordinary calcium and zinc stabilizer, 0.5 parts of calcium stearate, 0.5 parts of polyethylene wax, 2 parts of nano talc powder, and 1 part of nano hydrotalcite.

[0035] Its preparation method is the same as that of Comparative Example 1.

[0036] Test The basic mechanical properties (tensile strength, elongation at break, ring stiffness, and Vicat softening temperature) of the products from Example 2 and Comparative Example 1 were tested. Tensile strength and elongation at break were tested according to GB / T 1040.1-2018, ring stiffness according to GB / T 9647-2015, and Vicat softening temperature (A50 method) according to GB / T 1633-2000. The results are as follows: Figure 1 As shown.

[0037] Depend on Figure 1It can be seen that the Vicat softening temperatures of the two are basically the same, the tensile yield strength of both meets the general requirement of ≥35MPa for HPVC power pipes, and the ring stiffness of both reaches SN10 level or above, meeting the pressure-bearing requirements for buried under municipal roadways.

[0038] The accelerated aging test was conducted using a salt-alkali humid heat method. The test medium was an artificial salt-alkali solution with pH=8.5 (containing 3.5% NaCl, 0.5% Na2SO4, and NaOH to adjust the pH). The test temperature was 60℃, and the cycle consisted of 12 hours of immersion followed by 12 hours of humid heat air. The various properties were tested before aging and after 1000 hours of accelerated aging.

[0039] 1. Comparison of impact strength retention rate after long-term buried aging: The impact strength of a simply supported beam with notched section was tested according to GB / T 1043.1. The sample thickness was 4 mm, with a V-notch, and the test temperature was 23℃. The impact strength retention rate after aging was calculated, and the results are shown in Table 1.

[0040] Table 1 Impact strength retention rate after aging

[0041] As shown in Table 1, the impact strength retention rate of the embodiments of the present invention after aging is close to 90%, which is about 29 percentage points higher than that of the traditional Comparative Example 1. Comparative Example 1 has a dual aging pathway of MBS double bond oxidation hydrolysis and CPE alkaline dechlorination degradation, resulting in significant failure of the toughening system; although Comparative Example 2 does not have the problem of CPE dechlorination, the high amount of MBS and the large total amount of double bonds lead to significant oxidative hydrolysis attenuation.

[0042] 2. Comparison of the degree of dehydrochlorination of the system: The Congo red method was used to test the thermal stability time at 180℃. At the same time, the amount of chloride ions precipitated in the medium after soaking in salt and alkali for 500h was measured to characterize the degree of dehydrochlorination degradation. The results are shown in Table 2.

[0043] Table 2 Degree of dehydrochlorination

[0044] As shown in Table 2, the chloride ion release of the comparative example containing CPE was significantly higher, and the thermal stability time was shorter, proving that the dehydrochlorination reaction of CPE was obvious under alkaline conditions and would accelerate the degradation of the PVC matrix. The system of this invention completely eliminates CPE, and the chloride ion release is only about 1 / 9 of that of the comparative example, and the thermal stability time is increased by about 40%. It eliminates the chain reaction of alkaline-catalyzed dechlorination aging from the root, and is suitable for long-term service in coastal alkaline soils.

[0045] 3. Comparison of embrittlement temperature changes before and after accelerated aging in saline-alkali soil: The low-temperature embrittlement temperature of the pipe was tested according to B / T 5470. The changes in embrittlement temperature before and after aging were compared to characterize the low-temperature performance stability. The results are shown in Table 3.

[0046] Table 3 Degree of dehydrochlorination

[0047] As shown in Table 3, the initial embrittlement temperature of the embodiments of the present invention can reach below -18℃, meeting the requirements for construction and service in winter in the frigid northern regions; the embrittlement temperature rises by only about 2℃ after aging, with minimal degradation in low-temperature performance. The comparative examples not only have insufficient initial low-temperature performance, but also experience a significant rise in embrittlement temperature of over 6℃ after aging, making them highly susceptible to brittle fracture failure under frozen soil conditions in winter. The ternary system of the present invention, through the synergy of saturated elastomer and core-shell toughening agent, balances initial ultra-low temperature toughness with low-temperature stability after long-term aging, making it suitable for saline-alkali + low-temperature composite working conditions.

[0048] Therefore, the present invention adopts the above-mentioned high-impact PVC cable protection pipe and its preparation method, which maintains excellent low-temperature impact resistance while having mechanical stability for long-term service in coastal saline-alkali and humid oxygen-rich buried environments.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A high-impact PVC cable protection pipe, characterized in that, The raw material components include the following parts by weight: 100 parts of PVC resin; 3-6 parts of maleic anhydride-grafted ethylene-octene copolymer; 1-5 parts of methyl methacrylate-butadiene-styrene copolymer; 2-8 parts of acrylate core-shell copolymer; 4-6 parts of calcium-zinc-rare earth composite stabilizer; Lubricant 0.8~1.5 parts; 2-3 parts of nano-reinforcing filler.

2. The high-impact PVC cable protection pipe according to claim 1, characterized in that: The degree of polymerization of the PVC resin is 800~1300.

3. The high-impact PVC cable protection pipe according to claim 1, characterized in that: The grafting rate of the maleic anhydride-grafted ethylene-octene copolymer is 0.8% to 2.0%, and the octene mass fraction is 25% to 30%.

4. The high-impact PVC cable protection pipe according to claim 1, characterized in that: The butadiene rubber phase of the methyl methacrylate-butadiene-styrene copolymer has a mass fraction of 60%~70% and an average particle size of 80~120nm.

5. The high-impact PVC cable protection pipe according to claim 1, characterized in that: The weight-average molecular weight of the acrylate core-shell copolymer is 800,000 to 1,200,000.

6. The high-impact PVC cable protection pipe according to claim 1, characterized in that: The lubricant is a mixture of calcium stearate and polyethylene wax in a mass ratio of 1:

1.

7. The high-impact PVC cable protection pipe according to claim 1, characterized in that: The nano-reinforcing filler is a mixture of surface-modified nano-talc powder and nano-hydrotalc in a mass ratio of 2:

1.

8. A method for preparing a high-impact PVC cable protection pipe as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1. High-speed mixing: Weigh each raw material, put the PVC resin into a high-speed mixer with a stirring speed of 800~1500r / min, heat to 80~90℃, then add calcium zinc rare earth composite stabilizer, lubricant, and nano reinforcing filler in sequence, continue to heat to 105~115℃, add methyl methacrylate-butadiene-styrene copolymer MBS, acrylate core-shell copolymer ACR, and maleic anhydride grafted ethylene-octene copolymer POE-g-MAH, mix at high speed until the material temperature reaches 120~125℃, then discharge to obtain the mixture. S2. Cooling and maturation: Transfer the mixed materials into a cold mixer for stirring and cooling. When the material temperature drops to below 40°C, discharge the material and let it stand to mature, thus obtaining a dry mixture. S3. Extrusion molding: The dry mixture is added to the screw extruder, melted and plasticized, and then extruded through the die to form the final product. S4. Sizing, Cooling, Traction Cutting and Flaring: The extruded tube blank is shaped by a vacuum sizing sleeve, then enters a graded cooling water tank for gradual cooling. The traction machine pulls it at a constant speed, and after cutting it to a fixed length, the socket is flared to obtain the finished product.

9. The method for preparing a high-impact PVC cable protection pipe according to claim 8, characterized in that, In S2, the settling and maturation time is 20~24h.

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