Modified polyvinyl chloride reinforced chlorinated polyvinyl chloride composite material and preparation method thereof

Abstract

The invention provides a modified polyvinyl chloride reinforced chlorinated polyvinyl chloride composite material and a preparation method thereof, and belongs to the technical field of high polymer material modification. The preparation method comprises the following steps: grafting a flexible chain segment of an ethylene-vinyl acetate copolymer (EVA) onto a polyvinyl chloride molecular chain to obtain modified polyvinyl chloride, and then blending the modified polyvinyl chloride with chlorinated polyvinyl chloride to obtain the modified polyvinyl chloride reinforced chlorinated polyvinyl chloride composite material. According to the chlorinated polyvinyl chloride composite material, the compatibility of polyvinyl chloride and chlorinated polyvinyl chloride is improved by introducing a polar group; according to the invention, by adjusting the proportion of the modified polyvinyl chloride in the chlorinated polyvinyl chloride composite material, the mechanical properties and processability of the composite material are balanced, the melt viscosity is reduced, and the chlorinated polyvinyl chloride composite material has good practicability.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer material modification, and particularly relates to a modified polyvinyl chloride reinforced chlorinated polyvinyl chloride composite material and a preparation method thereof. Background Art

[0002] Polyvinyl chloride (PVC) is one of the five most common plastics. Its advantages include low cost, corrosion resistance, and excellent mechanical properties, making it widely used in construction, pipelines, cables, and other fields. However, PVC suffers from defects such as poor thermal stability, high brittleness, and insufficient high-temperature resistance (typically operating temperatures below 60°C), which limit its application. To expand its application, chlorinated polyvinyl chloride (CPVC) is obtained by further chlorination of PVC, increasing its chlorine content to 63%-69%. This significantly improves its heat resistance (up to 90-100°C), flame retardancy, and chemical stability, making it an ideal material for high-temperature pipelines and chemical containers.

[0003] Currently, CPVC still has several key limitations, primarily in terms of processing performance, mechanical properties, and compatibility. Regarding processing performance, CPVC's high chlorine content significantly increases its melt viscosity, narrowing the processing window and making it susceptible to thermal degradation during high-temperature processing. This places higher demands on production process control. Regarding mechanical properties, CPVC's prominent low-temperature brittleness limits its application in extremely cold or high-impact environments, impacting the material's long-term durability. Furthermore, CPVC has poor compatibility with other polymers or fillers, making phase separation a common phenomenon during blending and modification. This can disrupt the material's homogeneity and reduce the performance stability of the final product. Existing technologies primarily utilize physical blending and chemical modification to address these issues. Physical blending techniques (such as blending with materials like ABS and CPE) can improve toughness to a certain extent, but often at the expense of heat resistance. Furthermore, additive migration during blending can lead to performance degradation over time. Although chemical modification methods (such as polyurethane grafting, nanocomposite filling, etc.) can more effectively optimize material properties, they have problems such as complex processes and high costs, which limit their large-scale industrial applications. Therefore, while the aforementioned studies have partially addressed the single performance drawbacks of CPVC, they struggle to simultaneously balance its heat resistance, processability, and mechanical properties. Simply adding lubricants or stabilizers cannot simultaneously improve both processability and mechanical properties. Therefore, there is an urgent need to develop a multi-scale synergistic modification technology. Through molecular design or composite processes, this technology could overcome performance bottlenecks while retaining CPVC's inherent advantages, resulting in a more efficient and stable modification strategy to expand CPVC's application range. Summary of the Invention

[0004] In response to some deficiencies in the prior art, the present invention provides a modified polyvinyl chloride reinforced chlorinated polyvinyl chloride composite material, and a preparation method and application thereof. In the present invention, a flexible chain segment of an ethylene-vinyl acetate copolymer (EVA) is grafted onto a polyvinyl chloride molecular chain to obtain a modified polyvinyl chloride, and then the modified polyvinyl chloride is blended with chlorinated polyvinyl chloride to obtain a modified polyvinyl chloride reinforced chlorinated polyvinyl chloride composite material. The chlorinated polyvinyl chloride composite material improves the compatibility of polyvinyl chloride and chlorinated polyvinyl chloride by introducing polar groups. The present invention balances the mechanical properties and processing properties of the composite material and reduces the melt viscosity by adjusting the proportion of the modified polyvinyl chloride in the chlorinated polyvinyl chloride composite material, thereby having good practicality.

[0005] In order to achieve the above technical objectives, the present invention adopts the following technical means: The present invention first provides a method for preparing a modified polyvinyl chloride reinforced chlorinated polyvinyl chloride composite material, the preparation method comprising: (1) Ethylene vinyl acetate, polyvinyl chloride, a stabilizer, a lubricant, and an initiator are uniformly mixed, and then extruded and granulated by a single-screw extruder to obtain graft-modified modified polyvinyl chloride; (2) The modified polyvinyl chloride, chlorinated polyvinyl chloride, stabilizer, lubricant, plasticizer, processing aid and whitening agent are uniformly mixed to obtain a mixed material; the mixed material is kneaded into sheets by a double-roll mixer to obtain the modified polyvinyl chloride reinforced chlorinated polyvinyl chloride composite material.

[0006] Preferably, in step (1), the mass ratio of ethylene vinyl acetate, polyvinyl chloride, stabilizer, lubricant, and initiator is 760~560:40~240:32:4:3.2.

[0007] Preferably, the mass ratio of ethylene vinyl acetate, polyvinyl chloride, stabilizer, lubricant and initiator is 560:240:32:4:3.2.

[0008] Preferably, in step (1), the stabilizer comprises: any one or more of a calcium zinc stabilizer and an organic tin stabilizer; The lubricant includes PE wax; The initiator includes: any one or more of dicumyl peroxide and benzoyl peroxide; The ethylene-vinyl acetate includes any ethylene-vinyl acetate having a VAc content of 18% and a melt index of 8-110 g / min; The polyvinyl chloride model is PVC-SG5.

[0009] Preferably, in step (1), the temperature of each zone of the single screw extruder is set to: 140-150℃ for the first zone, 145-155℃ for the second zone, 155-165℃ for the third zone, and 160-170℃ for the die.

[0010] Preferably, the temperature of each zone of the single screw extruder is set to: 145℃ for the first zone, 150℃ for the second zone, 160℃ for the third zone, and 165℃ for the die.

[0011] Preferably, in step (2), the mass ratio of modified polyvinyl chloride, chlorinated polyvinyl chloride, stabilizer, lubricant, plasticizer, processing aid, and whitening agent is 5-20:95-80:2.5:1.6:2:8:3.

[0012] Preferably, the mass ratio of modified polyvinyl chloride, chlorinated polyvinyl chloride, stabilizer, lubricant, plasticizer, processing aid, and whitening agent is 10:90:2.5:1.6:2:8:3.

[0013] Preferably, in step (2), the stabilizer includes any one or more of calcium-zinc stabilizer, organic tin stabilizer; The lubricant includes PE wax. The plasticizer includes PA-20. The processing aid includes methyl methacrylate-butadiene-styrene copolymer (MBS). The whitening agent includes titanium white.

[0014] Preferably, in step (2), the temperature of the double-roll mixing machine is 190℃.

[0015] The application also provides a chlorinated polyvinyl chloride composite material prepared by the above preparation method, which includes modified polyvinyl chloride and chlorinated polyvinyl chloride; the modified polyvinyl chloride is prepared by grafting ethylene-vinyl acetate onto polyvinyl chloride.

[0016] Compared with the prior art, the application has the following advantages: The present invention provides a method for preparing a modified polyvinyl chloride-reinforced chlorinated polyvinyl chloride composite material. In this method, an initiator attacks allyl chloride or tertiary chloride sites in the polyvinyl chloride (PVC) to form macromolecular free radicals, as well as tertiary carbons near vinyl acetate units or tertiary hydrogens in ethylene segments. These polyvinyl chloride free radicals can initiate chain scission or crosslink with other free radicals. The ethylene-vinyl acetate free radicals tend to undergo crosslinking reactions (due to the high flexibility of EVA chains, which facilitates free radical coupling). Free radical coupling between the ethylene-vinyl acetate (EVA) molecular chains forms a lightly crosslinked network. Short chains generated by polyvinyl chloride (PVC) chain scission may partially intersperse within the EVA crosslinked network, and the two free radicals can generate partial co-crosslinks. Physically blending the modified polyvinyl chloride and chlorinated polyvinyl chloride forms a homogeneous or microphase-separated structure, which can reduce interfacial defects or achieve complementary composite material properties. Adding a certain proportion of a second blending component can effectively improve the mechanical properties and processing rheological properties of the chlorinated polyvinyl chloride.

[0017] The present invention takes polyvinyl chloride as the main body and introduces a flexible chain while improving the melt viscosity of polyvinyl chloride. After blending with chlorinated polyvinyl chloride, a "low viscosity phase enveloping a high viscosity phase" structure is formed, thereby reducing the overall melt viscosity and improving the processing performance.

[0018] The grafted polyvinyl chloride (PVC) and chlorinated polyvinyl chloride (CPVC) described in the present invention both contain a PVC backbone structure, providing a foundation for intrinsic compatibility. Furthermore, the polar groups in the grafted flexible segments can further form hydrogen bonds or interact with the -Cl groups of the CPVC, inhibiting phase separation.

[0019] In this invention, the flexible chains grafted onto modified PVC are dispersed in the dispersed phase after blending with CPVC, absorbing impact energy. The polar groups (such as esters and anhydrides) of the grafted chains form a strong interfacial interaction with the chlorine atoms of CPVC, preventing the toughening phase from becoming a "weak interface." The CPVC continuous phase continues to act as a rigid framework to bear high-temperature loads. This low-ratio blending not only improves the performance of various additives but also significantly reduces preparation costs, making it more economical and practical in practical applications.

[0020] Compared with existing technologies, this invention overcomes the technical bottlenecks of traditional CPVC modification. Through a molecular design combining a rigid CPVC backbone with flexible grafted chains, it overcomes the "seesaw effect" of material performance. The strong interaction between the polar grafted groups and CPVC achieves molecular compatibility, avoiding the phase separation failure associated with traditional physical blending. With no small molecule migration, the lifecycle performance degradation rate is reduced by over 50%, meeting sustainable development requirements. This reduces reliance on additives, lowers processing energy consumption, and reduces overall costs by 20-30%, promoting CPVC's potential as a replacement for pipes in high-end applications such as nuclear power and the chemical industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the infrared test picture of PVC-EVA.

[0022] Figure 2 This is a graph showing the tensile strength test of composite materials.

[0023] Figure 3 This is a graph showing the impact strength test of composite materials.

[0024] Figure 4 : Scanning electron microscope (SEM) images of the fracture surface of the composite material; from left to right (a~c) in the figure are Examples 1~3 respectively.

[0025] Figure 5 This is a test chart of the rheological properties of composite materials processing.

[0026] Figure 6 This is the Vicat softening temperature test diagram of the composite material. DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0028] Example 1: Preparation of modified polyvinyl chloride reinforced chlorinated polyvinyl chloride composite material (1) Preparation of modified polyvinyl chloride: Add 240g of ethylene-vinyl acetate copolymer powder, 3.2g of dicumyl peroxide, 32g of calcium zinc stabilizer, 4g of stearic acid and 560g of polyvinyl chloride powder into a high-speed mixer, start high-speed stirring for 1 minute to mix them evenly, and take them out after mixing is completed.

[0029] The mixed materials are fed into a single-screw extruder with set temperature zones: 145°C for zone 1, 150°C for zone 2, 160°C for zone 3, and 165°C for the die. Extrusion is performed at a specific speed, with the feed rate adjusted accordingly. After solidification by air or water cooling, the grafted PVC pellets are pelletized.

[0030] from Figure 1 It can be seen that the modified polyvinyl chloride has corresponding characteristic groups, indicating that ethylene-vinyl acetate is successfully grafted onto the polyvinyl chloride.

[0031] (2) Preparation of chlorinated polyvinyl chloride composite materials: Add 342g of chlorinated polyvinyl chloride resin and 9g of organotin stabilizer to a high-speed mixer and start high-speed stirring for 1 minute. Then add 5.76g of lubricant PE wax, 7.2g of plasticizer PA-20, 10.8g of titanium dioxide, and 28.8g of processing aid MBS. Stir for 10 minutes before discharging and setting aside. The mixture is plasticized on a two-roll mill at 190°C. During this time, 18g of modified polyvinyl chloride pellets are added and blended, plasticized into a uniform sheet to obtain a chlorinated polyvinyl chloride composite material.

[0032] like Figure 2 、 3 As shown in Figure 5, the blended composite material obtained with this ratio (PVC-EVA addition amount is 5phr) has a tensile strength of >45MPa and an impact strength of >16KJ / m -2 , and the processing rheological properties are significantly improved. Figure 4 It can be seen that there is no obvious phase separation on the fracture surface. Figure 6 It can be seen from the figure that the Vicat softening temperature of the composite material is 115.7℃.

[0033] Example 2: Preparation of modified polyvinyl chloride reinforced chlorinated polyvinyl chloride composite material (1) Preparation of modified polyvinyl chloride: Add 240g of ethylene-vinyl acetate copolymer powder, 3.2g of dicumyl peroxide, 32g of calcium zinc stabilizer, 4g of stearic acid and 560g of polyvinyl chloride powder into a high-speed mixer, start high-speed stirring for 1 minute to mix them evenly, and take them out after mixing is completed.

[0034] The mixed materials are fed into a single-screw extruder with set temperature zones: 145°C for zone 1, 150°C for zone 2, 160°C for zone 3, and 165°C for the die. Extrusion is performed at a specific speed, with the feed rate adjusted accordingly. After solidification by air or water cooling, the grafted PVC pellets are pelletized.

[0035] (2) Preparation of chlorinated polyvinyl chloride composite materials: Add 324g of chlorinated polyvinyl chloride resin and 9g of organotin stabilizer to a high-speed mixer and start high-speed stirring for 1 minute. Then add 5.76g of lubricant PE wax, 7.2g of plasticizer PA-20, 10.8g of titanium dioxide, and 28.8g of processing aid MBS. Stir for 10 minutes before discharging and setting aside. The mixture is plasticized on a two-roll mill at 190°C. During this time, 36g of modified polyvinyl chloride pellets are added and blended, plasticized into a uniform sheet to obtain a chlorinated polyvinyl chloride composite material.

[0036] like Figure 2 、 3As shown in Figure 5, the blended composite material obtained with this ratio (PVC-EVA addition amount is 10phr) has a tensile strength of >45MPa and an impact strength of >16KJ / m -2 , and the processing rheological properties are significantly improved. Figure 4 It can be seen that there is no obvious phase separation on the fracture surface. Figure 6 It can be seen from the graph that the Vicat softening temperature of the composite material is 113.4℃.

[0037] Example 3: Preparation of modified polyvinyl chloride reinforced chlorinated polyvinyl chloride composite material (1) Preparation of modified polyvinyl chloride: Add 240g of ethylene-vinyl acetate copolymer powder, 3.2g of dicumyl peroxide, 32g of calcium zinc stabilizer, 4g of stearic acid and 560g of polyvinyl chloride powder into a high-speed mixer, start high-speed stirring for 1 minute to mix them evenly, and take them out after mixing is completed.

[0038] The mixed materials are fed into a single-screw extruder with set temperature zones: 145°C for zone 1, 150°C for zone 2, 160°C for zone 3, and 165°C for the die. Extrusion is performed at a specific speed, with the feed rate adjusted accordingly. After solidification by air or water cooling, the grafted PVC pellets are pelletized.

[0039] (2) Preparation of chlorinated polyvinyl chloride composite materials: Add 288g of chlorinated polyvinyl chloride resin and 9g of organotin stabilizer to a high-speed mixer and start high-speed stirring for 1 minute. Then add 5.76g of lubricant PE wax, 7.2g of plasticizer PA-20, 10.8g of titanium dioxide, and 28.8g of processing aid MBS. Stir for 10 minutes before discharging and setting aside. The mixture is then plasticized on a two-roll mill at 190°C. During this time, 72g of modified polyvinyl chloride pellets are added and blended, plasticized into a uniform sheet to obtain a chlorinated polyvinyl chloride composite material.

[0040] like Figure 2 、 3 As shown in Figure 5, the blended composite material obtained with this ratio (PVC-EVA addition amount is 20phr) has a tensile strength of >45MPa and an impact strength of >15KJ / m -2 , and the processing rheological properties are significantly improved. Figure 4 It can be seen that there is no obvious phase separation on the fracture surface. Figure 6 It can be seen from the figure that the Vicat softening temperature of the composite material is 104.2℃.

[0041] In summary, the present invention grafts the flexible chain segments of ethylene-vinyl acetate copolymer (EVA) onto polyvinyl chloride molecular chains to obtain modified polyvinyl chloride, and then blends the modified polyvinyl chloride with chlorinated polyvinyl chloride to obtain a modified polyvinyl chloride-reinforced chlorinated polyvinyl chloride composite material; the chlorinated polyvinyl chloride composite material improves the compatibility of polyvinyl chloride and chlorinated polyvinyl chloride by introducing polar groups; the present invention balances the mechanical properties and processing properties of the composite material and reduces the melt viscosity by adjusting the proportion of the modified polyvinyl chloride in the chlorinated polyvinyl chloride composite material, thereby having good practicality.

[0042] The embodiments described are preferred implementations of the present invention, but the present invention is not limited to the above implementations. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention are within the scope of protection of the present invention.

Claims

1. A method for preparing a modified polyvinyl chloride reinforced chlorinated polyvinyl chloride composite material, characterized in that: The preparation method comprises: (1) Ethylene vinyl acetate, polyvinyl chloride, a stabilizer, a lubricant, and an initiator are uniformly mixed, and then extruded and granulated by a single-screw extruder to obtain graft-modified modified polyvinyl chloride; (2) The modified polyvinyl chloride, chlorinated polyvinyl chloride, stabilizer, lubricant, plasticizer, processing aid and whitening agent are uniformly mixed to obtain a mixed material; the mixed material is kneaded into sheets by a double-roll mixer to obtain the modified polyvinyl chloride reinforced chlorinated polyvinyl chloride composite material.

2. The method for preparing the modified polyvinyl chloride reinforced chlorinated polyvinyl chloride composite material according to claim 1, characterized in that: In step (1), the mass ratio of ethylene vinyl acetate, polyvinyl chloride, stabilizer, lubricant and initiator is 760~560:40~240:32:4:3.

2.

3. The method for preparing the modified polyvinyl chloride reinforced chlorinated polyvinyl chloride composite material according to claim 2, characterized in that: The mass ratio of the ethylene vinyl acetate, polyvinyl chloride, stabilizer, lubricant and initiator is 560:240:32:4:3.

2.

4. The method for preparing the modified polyvinyl chloride reinforced chlorinated polyvinyl chloride composite material according to claim 1, characterized in that: In step (1), the temperature of each zone of the single-screw extruder is set to: 140-150°C for zone 1, 145-155°C for zone 2, 155-165°C for zone 3 and 160-170°C for the die head.

5. The method for preparing the modified polyvinyl chloride reinforced chlorinated polyvinyl chloride composite material according to claim 4, characterized in that: The temperatures of the zones of the single-screw extruder were set as follows: 145° C. for zone 1, 150° C. for zone 2, 160° C. for zone 3, and 165° C. for the die head.

6. The method for preparing the modified polyvinyl chloride reinforced chlorinated polyvinyl chloride composite material according to claim 1, characterized in that: In step (2), the mass ratio of modified polyvinyl chloride, chlorinated polyvinyl chloride, stabilizer, lubricant, plasticizer, processing aid and whitening agent is 5~20:95~80:2.5:1.6:2:8:

3.

7. The method for preparing the modified polyvinyl chloride reinforced chlorinated polyvinyl chloride composite material according to claim 1, characterized in that: The ratio of modified polyvinyl chloride, chlorinated polyvinyl chloride, stabilizer, lubricant, plasticizer, processing aid and brightener is 10:90:2.5:1.6:2:8:

3.

8. The method for preparing the modified polyvinyl chloride reinforced chlorinated polyvinyl chloride composite material according to claim 1, characterized in that: In step (2), the stabilizer includes any one or more of a calcium zinc stabilizer and an organic tin stabilizer; The lubricant includes PE wax; Plasticizers include PA-20; Processing aids include methyl methacrylate-butadiene-styrene copolymer (MBS); Whitening agents include titanium dioxide.

9. The method for preparing the modified polyvinyl chloride reinforced chlorinated polyvinyl chloride composite material according to claim 1, characterized in that: In step (2), the temperature of the twin-roll mixer is 190°C.

10. The chlorinated polyvinyl chloride composite material prepared by the preparation method according to any one of claims 1 to 9, characterized in that: The chlorinated polyvinyl chloride composite material comprises modified polyvinyl chloride and chlorinated polyvinyl chloride; the modified polyvinyl chloride is obtained by grafting ethylene-vinyl acetate.

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