A rigid polyvinyl chloride pipe and a method for producing the same

Abstract

The application discloses a hard polyvinyl chloride pipe and a preparation method thereof, and relates to the technical field of materials. The hard polyvinyl chloride pipe comprises the following raw material components in parts by weight: 80-90 parts of super-high-polymerization-degree polyvinyl chloride; 10-20 parts of super-low-polymerization-degree polyvinyl chloride; 2-4 parts of nanometer boehmite; 4-5 parts of stabilizer; 8-12 parts of plasticizer; 0.6-1.2 parts of lubricant; 15-25 parts of filling agent; and 3-5 parts of core titanium white. The super-high-polymerization-degree polyvinyl chloride has a polymerization degree of 1500-1800; and the super-low-polymerization-degree polyvinyl chloride has a polymerization degree of 600-800. The hard polyvinyl chloride pipe has excellent processing performance, thermal stability, impact resistance, flame resistance, insulation performance and surface gloss.

Description

Technical Field

[0001] This invention relates to the technical field of materials, and in particular to a rigid polyvinyl chloride pipe and its preparation method. Background Technology

[0002] Rigid polyvinyl chloride (PVC-U) conduit offers significant cost-effectiveness advantages in conventional civil electrical engineering due to its excellent insulation properties, strong corrosion resistance, convenient construction, low cost, and wide applicability. A typical PVC conduit production process includes: mixing PVC resin and additives → high-temperature extrusion molding → cooling and shaping → cutting → quality inspection.

[0003] However, the following problems currently exist in the production process of PVC:

[0004] 1. Environmental pollution risk

[0005] Vinyl chloride monomer (VCM) release: When the processing temperature is between 160-200℃, PVC may release VCM. VCM is a known carcinogen, and long-term exposure to high concentrations of vinyl chloride monomer may increase the risk of cancer.

[0006] 2. Difficulty in controlling thermal degradation

[0007] Narrow decomposition temperature window: PVC resin decomposes rapidly at 240-260℃, requiring precise control of the extrusion temperature.

[0008] Yellowing index: Conjugated double bonds may be generated during the processing, causing the pipe to turn yellow.

[0009] 3. High equipment wear and tear

[0010] Screw wear: Calcium carbonate filler and pigment additives shorten the life of twin screws.

[0011] Material buildup at the die opening: This requires periodic shutdowns for cleaning, reducing equipment utilization.

[0012] Equipment corrosion: PVC decomposes during processing to produce hydrogen chloride (HCl) gas, which is corrosive and may corrode the screw and metal mold. Summary of the Invention

[0013] The purpose of this invention is to overcome the shortcomings of the prior art and provide a rigid polyvinyl chloride (PVC) pipe and its preparation method. The rigid PVC pipe of this invention has excellent processing performance, thermal stability, impact resistance, flame retardancy, insulation performance, and surface gloss.

[0014] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0015] In a first aspect, the present invention provides a rigid polyvinyl chloride pipe, comprising the following raw material components in parts by weight:

[0016] 80-90 parts of ultra-high degree of polymerization polyvinyl chloride (HPVC); 10-20 parts of ultra-low degree of polymerization polyvinyl chloride (LPVC); 2-4 parts of nano-boehmite; 4-5 parts of stabilizer; 8-12 parts of plasticizer; 0.6-1.2 parts of lubricant; 15-25 parts of filler; 3-5 parts of nuclear titanium dioxide;

[0017] The degree of polymerization of the ultra-high degree of polymerization polyvinyl chloride is 1500-1800; the degree of polymerization of the ultra-low degree of polymerization polyvinyl chloride is 600-800.

[0018] This invention, by incorporating two polyvinyl chloride (PVC) compounds with different degrees of polymerization, not only improves the strength of rigid PVC pipes but also enhances processing fluidity, resulting in superior impact resistance. The addition of nano-boehmite for physical flame retardancy not only improves the flame retardancy and impact strength of the rigid PVC pipes but also imparts a good surface gloss. The hardness of the nuclear titanium dioxide is lower than that of titanium dioxide powder, effectively reducing wear on the screw from the raw materials; simultaneously, the nuclear titanium dioxide has high lubricity, increasing the fluidity of the raw materials and reducing heat generation during production, thereby reducing PVC resin decomposition, decreasing harmful substance emissions, and inhibiting yellowing during processing. Therefore, this invention, through the synergistic effect of its components, gives rigid PVC pipes excellent processing performance, thermal stability, impact resistance, flame retardancy, insulation properties, and surface gloss.

[0019] Preferably, the degree of polymerization of the ultra-high degree of polymerization polyvinyl chloride is 1700, and the degree of polymerization of the ultra-low degree of polymerization polyvinyl chloride is 700.

[0020] Preferably, the average particle size of the nanoboehmite is 30-60 nm, and more preferably 50 nm.

[0021] Preferably, the average particle size of the nuclear titanium dioxide is 500-550 nm, and more preferably 520 nm.

[0022] Preferably, the stabilizer is a calcium-zinc stabilizer, and the mass ratio of Ca to Zn is 2:1. Furthermore, the addition of 0.3 parts of β-diketone is beneficial to improving the initial whiteness of rigid polyvinyl chloride pipes.

[0023] Preferably, the plasticizer is epoxidized soybean oil (ESO) with an epoxy value of 6-8%. By adding the plasticizer, the plasticizing temperature can be reduced.

[0024] Preferably, the lubricant comprises at least one of oxidized polyethylene wax, polyethylene wax, calcium stearate, zinc stearate, glyceryl monostearate, and pentaerythritol ester.

[0025] Preferably, the filler includes at least one of heavy calcium carbonate, nano-calcium, talc, kaolin, and barium sulfate.

[0026] Preferably, the filler has a particle size of 800-1500 mesh, and more preferably 1250 mesh.

[0027] Secondly, the present invention also provides a method for preparing rigid polyvinyl chloride pipe, comprising the following steps:

[0028] The components are mixed evenly, and then melt-extruded in an extruder to obtain the rigid polyvinyl chloride pipe.

[0029] Preferably, the parameters of the extruder are as follows: feeding section temperature is 145-150℃, compression section temperature is 160-165℃, metering section temperature is 170-175℃, die head temperature is 180-185℃, screw speed is 25-30 rpm, and traction speed is 1.5-2.0 m / min.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] This invention, by incorporating two polyvinyl chloride (PVC) compounds with different degrees of polymerization, not only improves the strength of rigid PVC pipes but also enhances processing fluidity, resulting in superior impact resistance. The addition of nano-boehmite for physical flame retardancy not only improves the flame retardancy and impact strength of the rigid PVC pipes but also imparts a good surface gloss. Nuclear titanium dioxide has a lower hardness than titanium dioxide powder and exhibits higher lubricity, increasing the fluidity of the raw materials, effectively reducing wear on the screw, and decreasing heat generation during production. This reduces PVC resin decomposition, minimizes harmful substance emissions, and inhibits yellowing during processing. Therefore, this invention, through the synergistic effect of its components, enables rigid PVC pipes to possess excellent processing performance, thermal stability, impact resistance, flame retardancy, insulation properties, and surface gloss. Detailed Implementation

[0032] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments, but the scope of protection and implementation of the present invention are not limited thereto.

[0033] Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0034] Example 1

[0035] This embodiment discloses a rigid polyvinyl chloride pipe, comprising the following raw material components in parts by weight:

[0036] 85 parts of ultra-high degree of polymerization polyvinyl chloride; 15 parts of ultra-low degree of polymerization polyvinyl chloride; 3 parts of nano-boehmite; 4.5 parts of stabilizer; 10 parts of plasticizer; 0.8 parts of lubricant; 20 parts of filler; 4 parts of nuclear titanium dioxide.

[0037] The ultra-high degree of polymerization polyvinyl chloride has a degree of polymerization of 1700, is manufactured by Formosa Plastics in Taiwan, and is model PR-G.

[0038] The ultra-low degree polyvinyl chloride has a degree of polymerization of 700, is manufactured by Xinjiang Tianye, and is model SG-8.

[0039] The nano-boehmite has an average particle size of 50 nm, is manufactured by Huaxiang Kejie, and has a model number of 1318-23-6.

[0040] The stabilizer is a calcium-zinc stabilizer, and the mass ratio of Ca to Zn is 2:1. The manufacturer is Yinuosen, and the model is PCZ238.

[0041] The plasticizer is epoxidized soybean oil with an epoxy value of 6%, manufactured by Adico, and model number B-22.

[0042] The lubricant is oxidized polyethylene wax, manufactured by Honeywell, and model AC629A.

[0043] The filler is heavy calcium carbonate with a particle size of 1250 mesh, manufactured by Jinlinda, and model number T1250.

[0044] The titanium dioxide mentioned is manufactured by Jianfa Ruitong and its model number is RTR-201.

[0045] This embodiment also discloses a method for preparing rigid polyvinyl chloride pipe, including the following steps:

[0046] (1) Mix nano-boehmite, nuclear titanium dioxide and epoxidized soybean oil, and treat with an ultrasonic disperser for 30 min at a frequency of 40 kHz and a power of 500 W to obtain a stable suspension; place heavy calcium carbonate in an oven at 110 ℃ and dry for 2 hours to make its moisture content ≤0.3% to obtain pretreated heavy calcium carbonate.

[0047] (2) The ultra-high degree of polymerization polyvinyl chloride, ultra-low degree of polymerization polyvinyl chloride, calcium zinc stabilizer, suspension, pretreated heavy calcium carbonate and oxidized polyethylene wax are added to the high-speed mixer in sequence. The mixing temperature is 105℃, the mixing time is 10min, the speed of the high-speed mixing stage is 1200rpm, the speed of the cooling mixing stage is 100rpm, the material is discharged when cooled to 45℃, and then cooled to room temperature. Finally, it is aged and left to stand for 12h to obtain the mixture.

[0048] (3) The mixture is melt-extruded in an extruder to obtain the rigid polyvinyl chloride pipe. The parameters of the extruder are: feeding section temperature of 145-150℃, compression section temperature of 160-165℃, metering section temperature of 170-175℃, die temperature of 180-185℃, screw speed of 25-30rpm, and traction speed of 1.5-2.0m / min.

[0049] Example 2

[0050] The difference from Example 1 is that the rigid polyvinyl chloride pipe comprises the following raw material components in parts by weight:

[0051] 80 parts of ultra-high degree of polymerization polyvinyl chloride; 20 parts of ultra-low degree of polymerization polyvinyl chloride; 2 parts of nano-boehmite; 4 parts of stabilizer; 12 parts of plasticizer; 0.6 parts of lubricant; 25 parts of filler; 3 parts of nuclear titanium dioxide.

[0052] Example 3

[0053] The difference from Example 1 is that the rigid polyvinyl chloride pipe comprises the following raw material components in parts by weight:

[0054] 90 parts of ultra-high degree of polymerization polyvinyl chloride; 10 parts of ultra-low degree of polymerization polyvinyl chloride; 4 parts of nano-boehmite; 5 parts of stabilizer; 8 parts of plasticizer; 1.2 parts of lubricant; 15 parts of filler; 5 parts of nuclear titanium dioxide.

[0055] Example 4

[0056] The difference from Example 1 is that the degree of polymerization of the ultra-high degree polyvinyl chloride is 1500, the manufacturer is Ningbo Formosa Plastics, and the model is PR-1500.

[0057] The ultra-low degree polyvinyl chloride has a degree of polymerization of 800, is manufactured by Xinjiang Tianye, and is model SG-7.

[0058] Example 5

[0059] The difference from Example 1 is that the degree of polymerization of the ultra-high degree polyvinyl chloride is 1800, the manufacturer is Formosa Plastics Ningbo, and the model is S-80.

[0060] The ultra-low degree polyvinyl chloride has a degree of polymerization of 600, is manufactured by Beiyuan Group, and is model BY650.

[0061] Comparative Example 1

[0062] The difference from Example 1 is that the raw material of the rigid PVC pipe does not contain ultra-high degree of polymerization PVC, that is, the rigid PVC pipe comprises the following raw material components in parts by weight:

[0063] 100 parts of ultra-low degree polyvinyl chloride; 3 parts of nano-boehmite; 4.5 parts of stabilizer; 10 parts of plasticizer; 0.8 parts of lubricant; 20 parts of filler; 4 parts of nuclear titanium dioxide.

[0064] Comparative Example 2

[0065] The difference from Example 1 is that the raw material of the rigid PVC pipe does not contain ultra-low degree polymerized PVC, that is, the rigid PVC pipe comprises the following raw material components in parts by weight:

[0066] 100 parts of ultra-high degree of polymerization polyvinyl chloride; 3 parts of nano-boehmite; 4.5 parts of stabilizer; 10 parts of plasticizer; 0.8 parts of lubricant; 20 parts of filler; 4 parts of nuclear titanium dioxide.

[0067] Comparative Example 3

[0068] The difference from Example 1 is that an equal mass of SG-5 type PVC (degree of polymerization 1150) is used instead of ultra-high degree of polymerization polyvinyl chloride.

[0069] Comparative Example 4

[0070] The difference from Example 1 is that an equal mass of SG-5 type PVC (degree of polymerization 1150) is used instead of ultra-low degree polyvinyl chloride.

[0071] Comparative Example 5

[0072] The difference from Example 1 is that an equal mass of magnesium hydroxide is used instead of nanoboehmite.

[0073] Comparative Example 6

[0074] The difference from Example 1 is that an equal mass of titanium dioxide (Longmang, R-996) is used instead of nuclear titanium dioxide.

[0075] Comparative Example 7

[0076] The difference from Example 1 is that the degree of polymerization of the ultra-high degree polyvinyl chloride is 1900.

[0077] Comparative Example 8

[0078] The difference from Example 1 is that the degree of polymerization of the ultra-low degree polyvinyl chloride is 550.

[0079] Performance testing

[0080] I. The following performance tests were performed on the titanium dioxide in Example 1 and the titanium dioxide in Comparative Example 6, respectively.

[0081] 1. The hardness of nuclear titanium dioxide and titanium dioxide powder was tested, and the testing method was in accordance with the invention patent "A characterization method for the hardness of rutile titanium dioxide powder" (patent application number: CN201710873464.7).

[0082] Test results: The hardness of nuclear titanium dioxide is 0.9kN, while the hardness of titanium dioxide powder is 1.4kN. It can be seen that the hardness of nuclear titanium dioxide is less than that of titanium dioxide powder.

[0083] 2. The lubricity of nuclear titanium dioxide and titanium dioxide powder was tested.

[0084] The test method is as follows: (1) Mix 85 parts of ultra-high degree of polymerization polyvinyl chloride, 15 parts of ultra-low degree of polymerization polyvinyl chloride, 3 parts of nano-boehmite, 4.5 parts of calcium zinc stabilizer, 10 parts of epoxidized soybean oil, 0.8 parts of oxidized polyethylene wax, 20 parts of heavy calcium carbonate, and 4 parts of nuclear titanium dioxide evenly to obtain mixture A. Then, add mixture A to a torque rheometer (model Thermo Scientific). TM HAAKE TM PolyLab TM In QC, the temperature was set to 160℃, the speed to 40rpm, and the mixing time to 10min, and the final balance torque was measured.

[0085] (2) Replace the nuclear titanium dioxide with an equal mass of titanium dioxide powder and mix it evenly with other components to obtain mixture B. Then add mixture B into a torque rheometer, set the temperature to 160℃, the speed to 40rpm, and the mixing time to 10min, and measure the final equilibrium torque.

[0086] Test results: The equilibrium torque of mixture A after mixing is 8.9 Nm, and the equilibrium torque of mixture B after mixing is 12.7 Nm. It can be seen that the lubricity of nuclear titanium dioxide is higher than that of titanium dioxide powder.

[0087] 3. The performance parameters of nuclear titanium dioxide and titanium dioxide powder during the production process were tested, and the test results are shown in Table 1.

[0088] Table 1

[0089] Parameters during the production process Example 1 Comparative Example 6 Extruder metering section material temperature (°C) 182 181 Pressure bar before the filter screen in the extruder 2.8 3.3 Material temperature at the die of the extruder (°C) 188 195 Cleaning time from startup to shutdown (h) 12.4 8.5

[0090] In summary, nuclear titanium dioxide has a lower hardness than titanium dioxide powder and has higher lubrication properties, which can increase the fluidity of raw materials, effectively reduce the wear of raw materials on the screw, and reduce the heat generated during the production process, thereby reducing the decomposition of PVC resin, reducing the emission of harmful substances, and inhibiting yellowing during processing.

[0091] II. The rigid polyvinyl chloride pipes prepared in Examples 1-5 and Comparative Examples 1-8 were subjected to the following performance tests.

[0092] 1. Thermal stability: Refer to the Congo Red method in GB / T 2917.1-2002 "Determination of hydrogen chloride and any other acidic products at high temperature in blends and products mainly composed of vinyl chloride homopolymers and copolymers", with a test temperature of 200℃. The longer the Congo Red test paper changes color, the better the thermal stability of the rigid PVC tube.

[0093] 2. Volume resistivity: Refer to GB / T 1410-2006 "Test methods for volume resistivity and surface resistivity of solid insulating materials".

[0094] 3. Notched impact strength: Refer to GB / T 1843-2008 "Determination of impact strength of plastic cantilever beam".

[0095] 4. Oxygen Index: Refer to GB / T 2406-2008 "Determination of Combustion Behavior by Oxygen Index Method for Plastics".

[0096] 5. Surface gloss: Refer to GB / T 8807-1988 "Test method for mirror gloss of plastics".

[0097] 6. Whiteness of pipes: Refer to GB / T 2913-1982 "Test Method for Whiteness of Plastics". The larger the L value and the smaller the b value, the whiter the pipe.

[0098] The test results are shown in Table 2.

[0099] Table 2

[0100]

[0101] As shown in Table 2, the rigid polyvinyl chloride pipe of the present invention has excellent impact resistance, thermal stability, flame retardancy, insulation performance, and surface gloss.

[0102] Comparing Comparative Examples 1-2 with Example 1, it can be seen that adding only ultra-high degree of polymerization PVC or ultra-low degree of polymerization PVC will decrease the performance of rigid PVC pipes. Furthermore, comparing Comparative Examples 3-4 with Example 1, it can be seen that replacing ultra-high degree of polymerization PVC or ultra-low degree of polymerization PVC with conventional PVC will also affect the performance of rigid PVC pipes. This indicates that only by using a combination of ultra-high degree of polymerization PVC and ultra-low degree of polymerization PVC can the rigid PVC pipes of this invention achieve excellent overall performance.

[0103] Comparing Comparative Examples 5-6 with Example 1, it can be seen that if conventional flame retardants are used instead of nano-boehmite, the flame retardant and impact resistance properties of rigid PVC pipes are affected. This indicates that not any flame retardant can give rigid PVC pipes excellent flame retardant and impact resistance properties. If titanium dioxide is used instead of nuclear titanium dioxide, the insulation properties and thermal stability are affected. This shows that by adding nuclear titanium dioxide, the present invention helps to improve the insulation properties and thermal stability of rigid PVC.

[0104] Comparing Comparative Examples 7-8 with Example 1, it can be seen that if the degree of polymerization of ultra-high degree polyvinyl chloride is too high or the degree of polymerization of ultra-low degree polyvinyl chloride is too low, the performance of rigid polyvinyl chloride pipe will be affected. This indicates that controlling the degree of polymerization of ultra-high degree polyvinyl chloride and ultra-low degree polyvinyl chloride within the range defined by the present invention is beneficial to improving the overall performance of rigid polyvinyl chloride pipe.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. 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 be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A rigid polyvinyl chloride pipe, characterized in that, The raw material components include the following parts by weight: 80-90 parts of ultra-high degree of polymerization polyvinyl chloride; 10-20 parts of ultra-low degree of polymerization polyvinyl chloride; 2-4 parts of nano-boehmite; 4-5 parts of stabilizer; 8-12 parts of plasticizer; Lubricant 0.6-1.2 parts; 15-25 parts filler; 3-5 parts nuclear titanium dioxide; The degree of polymerization of the ultra-high degree of polymerization polyvinyl chloride is 1500-1800; the degree of polymerization of the ultra-low degree of polymerization polyvinyl chloride is 600-800. The titanium dioxide mentioned is manufactured by Jianfa Ruitong and its model number is RTR-201.

2. The rigid polyvinyl chloride pipe as described in claim 1, characterized in that, The degree of polymerization of the ultra-high degree polyvinyl chloride is 1700, and the degree of polymerization of the ultra-low degree polyvinyl chloride is 700.

3. The rigid polyvinyl chloride pipe as described in claim 1, characterized in that, The average particle size of the nanoboehmite is 30-60 nm; and / or, the average particle size of the nuclear titanium dioxide is 500-550 nm.

4. The rigid polyvinyl chloride pipe as described in claim 1, characterized in that, The stabilizer is a calcium-zinc stabilizer, and the mass ratio of Ca to Zn in the calcium-zinc stabilizer is 2:

1.

5. The rigid polyvinyl chloride pipe as described in claim 1, characterized in that, The plasticizer is epoxidized soybean oil with an epoxy value of 6-8%.

6. The rigid polyvinyl chloride pipe as described in claim 1, characterized in that, The lubricant includes at least one of oxidized polyethylene wax, polyethylene wax, calcium stearate, zinc stearate, glyceryl monostearate, and pentaerythritol ester.

7. The rigid polyvinyl chloride pipe as described in claim 1, characterized in that, The filler includes at least one of heavy calcium carbonate, nano-calcium, talc, kaolin, and barium sulfate.

8. The rigid polyvinyl chloride pipe as described in claim 1, characterized in that, The filler has a particle size of 800-1500 mesh.

9. A method for preparing a rigid polyvinyl chloride pipe as described in any one of claims 1-8, characterized in that, The components are mixed evenly, and then melt-extruded in an extruder to obtain the rigid polyvinyl chloride pipe.

10. The method for preparing rigid polyvinyl chloride pipe as described in claim 9, characterized in that, The parameters of the extruder are as follows: feeding section temperature is 145-150℃, compression section temperature is 160-165℃, metering section temperature is 170-175℃, die head temperature is 180-185℃, screw speed is 25-30 rpm, and traction speed is 1.5-2.0 m / min.

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