Calcium sulfate whisker reinforced and toughened polyvinyl chloride pipe and preparation method thereof

Abstract

The invention provides a calcium sulfate whisker reinforced and toughened polyvinyl chloride pipe and a preparation method thereof, and belongs to the technical field of polyvinyl chloride pipes. The plastic comprises the following components in parts by mass: 100 parts of polyvinyl chloride resin, 5-15 parts of calcium sulfate whiskers, 0.5-3 parts of a coupling agent, 2-4 parts of a heat stabilizer, 0.5-1.5 parts of a lubricant and 1-3 parts of a processing aid, wherein the adding amount of the calcium sulfate whiskers is 5-15% of the mass of the polyvinyl chloride resin. The coupling agent is used for treating the calcium sulfate crystal whiskers, so that the treated calcium sulfate crystal whiskers can be infiltrated by the polyvinyl chloride matrix, and a good interface layer is formed between the calcium sulfate crystal whiskers and the polyvinyl chloride matrix; the calcium sulfate whisker treated by the silane coupling agent can play a role of a filling agent and impact resistance, replaces calcium carbonate, achieves a filling effect, can improve the strength, hardness, dimensional stability and heat resistance of the pipe, and can reduce the production cost due to the fact that the calcium sulfate whisker is a low-price environment-friendly material.

Description

Technical Field

[0001] This invention relates to the field of polyvinyl chloride (PVC) pipe technology, and in particular to a calcium sulfate whisker-reinforced and toughened PVC pipe and its preparation method. Background Technology

[0002] Currently, the commonly used fillers for PVC materials are still calcium carbonate and fly ash, which play a skeletal role in PVC products, improving the dimensional stability, hardness, rigidity, and heat resistance of plastic products, and reducing product costs. However, they are insufficient in improving the tensile strength and impact strength of PVC products, and expensive impact modifiers must be added to improve performance, leading to increased raw material costs.

[0003] Calcium sulfate whiskers are fibrous single crystals that combine the advantages of reinforcing fibers and ultrafine inorganic fillers. They possess high strength, high modulus, high toughness, high insulation, wear resistance, high temperature resistance, corrosion resistance, easy surface treatment, easy polymer compounding, non-toxicity, and low cost. As a toughening and reinforcing material, they can be widely used in industries and fields such as rubber, plastics, and adhesives. However, in existing technologies, the interfacial bonding between calcium sulfate whiskers and PVC is poor, and direct addition can lead to material embrittlement. To address this, the inventors applied calcium sulfate whiskers to PVC rigid composite pipes, replacing more expensive impact modifiers, thereby reducing production costs while improving the mechanical properties of the pipes. Summary of the Invention

[0004] The purpose of this invention is to provide a calcium sulfate whisker-reinforced and toughened polyvinyl chloride pipe and its preparation method, thereby solving the existing technical problems.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A calcium sulfate whisker-reinforced and toughened polyvinyl chloride pipe is composed of the following components in parts by weight: 100 parts polyvinyl chloride resin, 5-15 parts calcium sulfate whiskers, 0.5-3 parts coupling agent, 2-4 parts heat stabilizer, 0.5-1.5 parts lubricant, and 1-3 parts processing aid; The amount of calcium sulfate whiskers added is 5-15% of the mass of polyvinyl chloride resin.

[0006] Furthermore, the calcium sulfate whiskers have a length of 10-200 μm, an aspect ratio of 10:1-50:1, and a purity of ≥95%.

[0007] Furthermore, the coupling agent is a silane coupling agent, a titanate coupling agent, or an aluminate coupling agent, and the amount of the coupling agent is 3-10% of the mass of the calcium sulfate whiskers. The coupling agent can improve the interfacial compatibility and bonding force between the calcium sulfate whiskers and the polyvinyl chloride resin.

[0008] Furthermore, the heat stabilizer is one or a mixture of several of the following: zinc stearate, calcium stearate, polyol, β-diketone, hydrotalcite, and antioxidant.

[0009] Furthermore, the lubricant is one or a mixture of several of stearic acid, polyethylene wax, paraffin, and calcium stearate.

[0010] Furthermore, the processing aid is an acrylate polymer.

[0011] A method for preparing calcium sulfate whisker-reinforced and toughened polyvinyl chloride pipe includes the following steps: (1) Place calcium sulfate whiskers and coupling agent in a high-speed mixer and treat for 10-30 minutes; (2) Add the treated calcium sulfate whiskers and polyvinyl chloride resin to a high-speed mixer in proportion and mix for 10-20 minutes; (3) Add the heat stabilizer, lubricant and processing aid to a high-speed mixer in proportion and mix for 15-25 minutes to obtain a mixture; (4) Transfer the mixture to a cold mixer, cool it to 40-50℃, and then convey it to a twin-screw extruder; (5) The tube blank is melt-extruded by a twin-screw extruder at a temperature of 160-180℃; the length-to-diameter ratio of the screw of the twin-screw extruder is 35-45:1 and the rotation speed is 300-500 rpm; (6) Finished pipes are produced after sizing, traction, and length cutting.

[0012] Furthermore, in step (1), the processing temperature is 80-120℃.

[0013] Furthermore, in step (2), the mixing temperature is 80-90℃.

[0014] Furthermore, in step (3), the mixing temperature is 100-115℃.

[0015] The present invention, by adopting the above-described technical solution, has the following beneficial effects: 1. This invention uses a coupling agent to treat calcium sulfate whiskers, so that the treated calcium sulfate whiskers can be wetted by polyvinyl chloride, thereby creating a good interface layer between the calcium sulfate crystals and the polyvinyl chloride, which is beneficial to improving the overall mechanical properties of the pipe.

[0016] 2. The present invention uses calcium sulfate whiskers treated with silane coupling agent, which can act as a filler and impact reducer, replacing calcium carbonate to achieve the filling effect and improve the strength, hardness, dimensional stability and heat resistance of the pipe.

[0017] 3. In the preparation method of the present invention, when calcium sulfate whiskers are used to replace calcium carbonate as filler for the processing of PVC products, there are no special requirements for the production process and processing equipment. The price of calcium sulfate whiskers is only about 25% of the price of impact modifiers, making it an inexpensive, green and environmentally friendly material that can reduce production costs. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, preferred embodiments are described below to further illustrate the invention in detail. However, it should be noted that many details listed in the specification are merely to provide the reader with a thorough understanding of one or more aspects of the invention, and these aspects can be achieved even without these specific details.

[0019] A calcium sulfate whisker-reinforced and toughened polyvinyl chloride pipe is composed of the following components in parts by weight: 100 parts polyvinyl chloride resin, 5-15 parts calcium sulfate whiskers, 0.5-3 parts coupling agent, 2-4 parts heat stabilizer, 0.5-1.5 parts lubricant, and 1-3 parts processing aid; The amount of calcium sulfate whiskers added is 5-15% of the mass of polyvinyl chloride resin.

[0020] The whiskers form a three-dimensional network skeleton in the polyvinyl chloride matrix, which enables stress to be efficiently transferred through the whisker axis (whisker breakage rather than debonding).

[0021] The polyvinyl chloride resin is a polyvinyl chloride resin powder, model number SG5.

[0022] The calcium sulfate whiskers have a length of 10-200 μm, an aspect ratio of 10:1-50:1, and a purity of ≥95%.

[0023] The coupling agent is a silane coupling agent, a titanate coupling agent, or an aluminate coupling agent, and the amount of the coupling agent is 3-10% of the mass of the calcium sulfate whiskers. The coupling agent can improve the interfacial compatibility and bonding force between calcium sulfate whiskers and polyvinyl chloride resin.

[0024] The heat stabilizer is one or a mixture of several of the following: zinc stearate, calcium stearate, polyol, β-diketone, hydrotalcite, and antioxidant. The heat stabilizer prevents polyvinyl chloride resin from being degraded (decomposed, discolored) by heat and light during processing and use; hydrotalcite neutralizes trace amounts of H2SO4 on the whisker surface, preventing catalytic degradation; calcium stearate provides both stabilization and internal lubrication, reducing melt viscosity; and β-diketone chelates the Ca2+ on the whisker surface. 2+ This eliminates the catalytic effect of metal ions on the deHCl removal of PVC.

[0025] The lubricant is one or a mixture of several of stearic acid, polyethylene wax, paraffin wax, and calcium stearate. The lubricant reduces internal friction within the material and friction between the material and the equipment surface, improving processing flowability and mold release properties. Oxidized polyethylene wax forms a nano-coating on the whisker surface, reducing friction with the screw.

[0026] The processing aid is an acrylate polymer. The processing aid promotes plasticization, accelerates the melting and homogenization of PVC resin particles, improves melt strength, enhances the resistance of molten PVC to tensile and tearing, which is crucial for extrusion molding (such as pipe shaping) to prevent melt fracture, and improves surface finish.

[0027] A method for preparing calcium sulfate whisker-reinforced and toughened polyvinyl chloride pipe includes the following steps: (1) Place calcium sulfate whiskers and coupling agent in a high-speed mixer for 10-30 min at a temperature of 80-120℃; (2) Add the treated calcium sulfate whiskers and polyvinyl chloride resin to a high-speed mixer in proportion and mix for 10-20 minutes at a mixing temperature of 80-90℃. (3) Add the heat stabilizer, lubricant and processing aid to a high-speed mixer in proportion and mix for 15-25 minutes at a mixing temperature of 100-115℃ to obtain a mixture; (4) Transfer the mixture to a cold mixer, cool it to 40-50℃, and then convey it to a twin-screw extruder; (5) The tube blank is melt-extruded by a twin-screw extruder at a temperature of 160-180℃; the length-to-diameter ratio of the screw of the twin-screw extruder is 35-45:1 and the rotation speed is 300-500 rpm; (6) Finished pipes are produced after sizing, traction, and length cutting.

[0028] Example 1 A calcium sulfate whisker-reinforced and toughened polyvinyl chloride pipe is composed of the following components in parts by weight: 100 parts polyvinyl chloride resin, 5 parts calcium sulfate whiskers, 0.5 parts coupling agent, 2 parts heat stabilizer, 0.5 parts lubricant and 1 part processing aid; Its preparation method includes the following steps: (1) Place calcium sulfate whiskers and coupling agent in a high-speed mixer for 10-30 min at a temperature of 80-120℃; (2) Add the treated calcium sulfate whiskers and polyvinyl chloride resin to a high-speed mixer in proportion and mix for 10-20 minutes at a mixing temperature of 80-90℃. (3) Add the heat stabilizer, lubricant and processing aid to a high-speed mixer in proportion and mix for 15-25 minutes at a mixing temperature of 100-115℃ to obtain a mixture; (4) Transfer the mixture to a cold mixer, cool it to 40-50℃, and then convey it to a twin-screw extruder; (5) The tube blank is melt-extruded by a twin-screw extruder at a temperature of 160-180℃; the length-to-diameter ratio of the screw of the twin-screw extruder is 35-45:1 and the rotation speed is 300-500 rpm; (6) Finished pipes are produced after sizing, traction, and length cutting.

[0029] Example 2 A calcium sulfate whisker-reinforced and toughened polyvinyl chloride pipe is composed of the following components in parts by weight: 100 parts polyvinyl chloride resin, 10 parts calcium sulfate whiskers, 2 parts coupling agent, 3 parts heat stabilizer, 1.0 part lubricant, and 2 parts processing aid; Its preparation method includes the following steps: (1) Place calcium sulfate whiskers and coupling agent in a high-speed mixer for 10-30 min at a temperature of 80-120℃; (2) Add the treated calcium sulfate whiskers and polyvinyl chloride resin to a high-speed mixer in proportion and mix for 10-20 minutes at a mixing temperature of 80-90℃. (3) Add the heat stabilizer, lubricant and processing aid to a high-speed mixer in proportion and mix for 15-25 minutes at a mixing temperature of 100-115℃ to obtain a mixture; (4) Transfer the mixture to a cold mixer, cool it to 40-50℃, and then convey it to a twin-screw extruder; (5) The tube blank is melt-extruded by a twin-screw extruder at a temperature of 160-180℃; the length-to-diameter ratio of the screw of the twin-screw extruder is 35-45:1 and the rotation speed is 300-500 rpm; (6) Finished pipes are produced after sizing, traction, and length cutting.

[0030] Example 3 A calcium sulfate whisker-reinforced and toughened polyvinyl chloride pipe is composed of the following components in parts by weight: 100 parts polyvinyl chloride resin, 15 parts calcium sulfate whiskers, 3 parts coupling agent, 4 parts heat stabilizer, 1.5 parts lubricant, and 3 parts processing aid; Its preparation method includes the following steps: (1) Place calcium sulfate whiskers and coupling agent in a high-speed mixer for 10-30 min at a temperature of 80-120℃; (2) Add the treated calcium sulfate whiskers and polyvinyl chloride resin to a high-speed mixer in proportion and mix for 10-20 minutes at a mixing temperature of 80-90℃. (3) Add the heat stabilizer, lubricant and processing aid to a high-speed mixer in proportion and mix for 15-25 minutes at a mixing temperature of 100-115℃ to obtain a mixture; (4) Transfer the mixture to a cold mixer, cool it to 40-50℃, and then convey it to a twin-screw extruder; (5) The tube blank is melt-extruded by a twin-screw extruder at a temperature of 160-180℃; the length-to-diameter ratio of the screw of the twin-screw extruder is 35-45:1 and the rotation speed is 300-500 rpm; (6) Finished pipes are produced after sizing, traction, and length cutting.

[0031] Comparative Example 1 A type of polyvinyl chloride pipe, comprising the following components in parts by weight: 100 parts polyvinyl chloride resin, 10 parts calcium carbonate, 3 parts heat stabilizer, 1.0 part lubricant, and 2 parts processing aid; Its preparation method includes the following steps: (1) Add calcium carbonate and polyvinyl chloride resin to a high-speed mixer in proportion and mix for 10-20 minutes at a mixing temperature of 80-90℃; (2) Add the heat stabilizer, lubricant and processing aid to a high-speed mixer in proportion and mix for 15-25 minutes at a mixing temperature of 100-115℃ to obtain a mixture; (3) Transfer the mixture to a cold mixer, cool it to 40-50℃, and then convey it to a twin-screw extruder; (4) The tube blank is melt-extruded by a twin-screw extruder at a temperature of 160-180℃; the length-to-diameter ratio of the screw of the twin-screw extruder is 35-45:1 and the rotation speed is 300-500 rpm; (5) The finished pipe is produced after sizing, traction and length cutting.

[0032] Comparative Example 2 A type of polyvinyl chloride pipe, comprising the following components in parts by weight: 100 parts polyvinyl chloride resin, 10 parts calcium sulfate whiskers, 3 parts heat stabilizer, 1.0 part lubricant, and 2 parts processing aid; Its preparation method includes the following steps: (1) Add calcium sulfate whiskers and polyvinyl chloride resin to a high-speed mixer in proportion and mix for 10-20 minutes at a mixing temperature of 80-90℃; (2) Add the heat stabilizer, lubricant and processing aid to a high-speed mixer in proportion and mix for 15-25 minutes at a mixing temperature of 100-115℃ to obtain a mixture; (3) Transfer the mixture to a cold mixer, cool it to 40-50℃, and then convey it to a twin-screw extruder; (4) The tube blank is melt-extruded by a twin-screw extruder at a temperature of 160-180℃; the length-to-diameter ratio of the screw of the twin-screw extruder is 35-45:1 and the rotation speed is 300-500 rpm; (5) The finished pipe is produced after sizing, traction and length cutting.

[0033] The pipes obtained in Examples 1-3 and Comparative Examples 1-2 were subjected to performance tests, and the resulting structures are shown in Table 1. Table 1 Performance Test Results As can be seen from Table 1, the notched impact strength, tensile strength, elongation at break, and Vicat softening point of the pipes obtained in Examples 1-3 are higher than those in Comparative Examples 1-2, and the cost of Examples 1-3 is lower than that of Comparative Examples 1-2. The comprehensive mechanical properties of the pipe obtained by replacing calcium sulfate whiskers with calcium carbonate in Comparative Example 1 and without adding a coupling agent are lower than those of the pipe obtained by the present invention. The notched impact strength of the pipe obtained by Comparative Example 2 without treating the calcium sulfate whiskers with a coupling agent only reaches 19.5 kJ / m², indicating that it is necessary to use a coupling agent to treat the calcium sulfate whiskers to achieve interface modification.

[0034] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A calcium sulfate whisker-reinforced and toughened polyvinyl chloride pipe, characterized in that: It consists of the following components in parts by mass: 100 parts polyvinyl chloride resin, 5-15 parts calcium sulfate whiskers, 0.5-3 parts coupling agent, 2-4 parts heat stabilizer, 0.5-1.5 parts lubricant, and 1-3 parts processing aid; The amount of calcium sulfate whiskers added is 5-15% of the mass of polyvinyl chloride resin.

2. The calcium sulfate whisker-reinforced and toughened polyvinyl chloride pipe according to claim 1, characterized in that: The calcium sulfate whiskers have a length of 10-200 μm, an aspect ratio of 10:1-50:1, and a purity of ≥95%.

3. The calcium sulfate whisker-reinforced and toughened polyvinyl chloride pipe according to claim 1, characterized in that: The coupling agent is a silane coupling agent, a titanate coupling agent, or an aluminate coupling agent, and the amount of the coupling agent is 3-10% of the mass of calcium sulfate whiskers.

4. The calcium sulfate whisker-reinforced and toughened polyvinyl chloride pipe according to claim 1, characterized in that: The heat stabilizer is one or a mixture of several of the following: zinc stearate, calcium stearate, polyol, β-diketone, hydrotalcite, and antioxidant.

5. The calcium sulfate whisker-reinforced and toughened polyvinyl chloride pipe according to claim 1, characterized in that: The lubricant is one or a mixture of several of the following: stearic acid, polyethylene wax, paraffin wax, and calcium stearate.

6. The calcium sulfate whisker-reinforced and toughened polyvinyl chloride pipe according to claim 1, characterized in that: The processing aid is an acrylate polymer.

7. A method for preparing calcium sulfate whisker-reinforced and toughened polyvinyl chloride pipe as described in any one of claims 1-6, characterized in that: Includes the following steps: (1) Place calcium sulfate whiskers and coupling agent in a high-speed mixer and treat for 10-30 minutes; (2) Add the treated calcium sulfate whiskers and polyvinyl chloride resin to a high-speed mixer in proportion and mix for 10-20 minutes; (3) Add the heat stabilizer, lubricant and processing aid to a high-speed mixer in proportion and mix for 15-25 minutes to obtain a mixture; (4) Transfer the mixture to a cold mixer, cool it to 40-50℃, and then convey it to a twin-screw extruder; (5) The tube blank is melt-extruded by a twin-screw extruder at a temperature of 160-180℃; the length-to-diameter ratio of the screw of the twin-screw extruder is 35-45:1 and the rotation speed is 300-500 rpm; (6) Finished pipes are produced after sizing, traction, and length cutting.

8. The method for preparing a calcium sulfate whisker-reinforced and toughened polyvinyl chloride pipe according to claim 7, characterized in that: In step (1), the processing temperature is 80-120℃.

9. The method for preparing a calcium sulfate whisker-reinforced and toughened polyvinyl chloride pipe according to claim 7, characterized in that: In step (2), the mixing temperature is 80-90℃.

10. The method for preparing a calcium sulfate whisker-reinforced and toughened polyvinyl chloride pipe according to claim 7, characterized in that: In step (3), the mixing temperature is 100-115℃.

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