Special material composition for high-elongation PVC-M pipe

Abstract

The invention relates to the technical field of PVC-M pipes, and discloses a high-elongation PVC-M pipe special material composition, which is prepared from the following components by weight: 100 parts of PVC resin, 3.5 parts of a stabilizer, 12 parts of an impact modifier, 3.6 parts of a lubricant, 12 parts of a filler, and 4 parts of a processing aid ACR. According to the technical scheme, modified MBS-2501 is adopted as an impact modifier, a small amount of butadiene is copolymerized and organic silicon is introduced into a core layer, polyethylene glycol (PEG) is introduced into a modified PMMA shell layer, the rubber phase toughness and impact resistance of the material are enhanced, it is ensured that sufficient flexibility is kept at low temperature through a built-in polyethylene glycol segment, and the service life of the material is prolonged. Therefore, the ductility of the whole pipe in a low-temperature environment is improved; calcium carbonate is modified by using a titanate coupling agent, so that the compatibility of calcium carbonate and PVC resin is improved, a hydrophobic organic molecular film is formed, the interface bonding strength is enhanced, and the overall mechanical property and weather resistance of the material are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of PVC-M pipes, and in particular to a special material composition for high elongation PVC-M pipes. Background Art

[0002] PVC-M pipes are a new type of pipes prepared based on polyvinyl chloride (PVC) resin through physical or chemical modification technologies. Compared with traditional PVC-U pipes, PVC-M pipes significantly improve the toughness and impact resistance of materials by adding impact modifiers (such as MBS, CPE, etc.), while maintaining the excellent chemical corrosion resistance and processing performance of PVC materials. They are widely used in fields such as urban water supply, drainage, gas transmission, and trenchless engineering, and are particularly suitable for working conditions with complex geological conditions and vulnerable to external force impacts.

[0003] In the process of realizing the present invention, the inventor found that there are at least the following problems in the prior art: Existing special material compositions for high elongation PVC-M pipes use MBS-561 to improve elongation. However, MBS-561 is a terpolymer of methyl methacrylate (M)-butadiene (B)-styrene (S) (core-shell structure), and butadiene, as the rubber phase, provides high elongation. It is necessary to form a sea-island structure to disperse impact energy. However, the butadiene rubber phase is prone to hardening at low temperatures, resulting in a decrease in toughness, leading to problems that affect the elongation performance and potential performance risks of the special material composition for PVC-M pipes in low-temperature environments.

[0004] Therefore, the above technical problems need to be solved. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, the present invention proposes an agricultural machinery suspension shock absorption stroke detection device to solve the problem that existing special material compositions for high elongation PVC-M pipes use butadiene as the rubber phase to provide high elongation. However, the butadiene rubber phase is prone to hardening at low temperatures, resulting in a decrease in toughness, leading to problems that affect the elongation performance and potential performance risks of the special material composition for PVC-M pipes in low-temperature environments.

[0006] To solve the above technical problems, the basic technical solution proposed by the present invention is: A special material composition for high elongation PVC-M pipes, which is made of the following components in parts by weight: PVC resin: 100 parts, stabilizer: 4 - 9 parts, impact modifier: 10 - 15 parts, lubricant: 2.5 - 4.5 parts, filler: 10 - 15 parts, processing aid ACR: 3 - 5 parts.

[0007] Preferably, it is made of the following components in parts by weight: PVC resin: 100 parts, stabilizer: 3.5 parts, impact modifier: 12 parts, lubricant: 3.6 parts, filler: 12 parts, processing aid ACR: 4 parts.

[0008] Preferably, the stabilizer is a compound of organotin stabilizer and composite anti-aging agent. Among them, the organotin stabilizer is 1.8 parts, and the composite anti-aging agent is composed of antioxidant 2246, ultraviolet absorber UV-9, and antioxidant 1010. The composite anti-aging agent and the organotin stabilizer synergistically improve the weather resistance of PVC-M pipes; The dosage of antioxidant 2246 is 0.6 parts, the dosage of ultraviolet absorber UV-9 is 0.4 parts, and the dosage of antioxidant 1010 is 0.7 parts; Antioxidant 2246 and ultraviolet absorber UV-9 synergistically improve the anti-photoaging property; antioxidant 2246 and antioxidant 1010 synergistically improve the long-term thermal stability; antioxidant 1010 and ultraviolet absorber UV-9 act synergistically to improve the anti-aging performance.

[0009] Preferably, the impact modifier uses modified MBS S-2501, which has a core-shell structure composed of methyl methacrylate MMA, acrylate AC, and silicone Si. The cross-linked acrylate and silicone copolymer is the core, and the grafted polymethyl methacrylate PMMA is the shell; The modification of MBS S-2501 is realized through core layer modification and shell layer modification. Specifically: By copolymerizing a small amount of butadiene in the core layer to construct a ternary structure of methyl methacrylate (M)-butadiene (B)-silicone (Si), and using lauryl acrylate (LA) to replace part of methyl methacrylate (MMA) to extend the flexibility of the core layer chain segment; Introduce polyethylene glycol PEG block into the PMMA shell; Core layer modification: Modified MBS S-2501 constructs a ternary structure of methyl methacrylate (M)-butadiene (B)-silicone (Si) by copolymerizing a small amount of butadiene in the core layer to improve the elongation rate of the S-2501 rubber phase; And use lauryl acrylate (LA) to replace part of methyl methacrylate MMA to extend the flexibility of the core layer chain segment.

[0010] The lubricant is modified metal soaps and modified waxes; The modified metal soaps are composed of a compound of barium stearate BaSt, calcium stearate CaSt, and zinc stearate ZnSt. Among them, the dosage of BaSt is 1.0 part, the dosage of CaSt is 1.5 parts, and the dosage of ZnSt is 0.5 part; The modified waxes are composed of a compound of paraffin wax and oxidized polyethylene wax. The dosage of oxidized polyethylene wax is 0.3 part and the dosage of paraffin wax is 0.7 part; Metal soaps promote resin plasticization, and paraffin wax and oxidized polyethylene wax reduce the risk of melt fracture. The two work together to improve melt fluidity and processing efficiency; When BaSt, CaSt, and ZnSt are used in combination, a more comprehensive synergistic effect can be produced. By utilizing the long-term stability of BaSt, the plasticization promotion of CaSt, and the initial lubricity of ZnSt, complementary lubrication aging can be formed. BaSt provides initial stabilization, CaSt provides long-term thermal stability, and ZnSt further enhances the stabilization effect by forming a synergistic complex. Oxidized polyethylene wax provides internal lubrication and improves filler dispersion, while paraffin wax acts as an external lubricant to reduce melt-equipment friction, synergistically enhancing the plasticization efficiency.

[0011] Preferably, the filler is modified calcium carbonate, and the calcium carbonate filler is surface-treated with a titanate coupling agent to improve its interfacial bonding with the PVC resin matrix. The titanate coupling agent forms a molecular bridge through its amphiphilic structure, with one end reacting with the hydroxyl groups on the surface of calcium carbonate and the other end binding to the polymer molecular chain. The surface of the modified calcium carbonate is covered with an organic molecular film, and the contact angle increases from <30° (hydrophilic) before modification to >90° (hydrophobic), significantly improving its compatibility with PVC.

[0012] A special material composition for high elongation PVC-M pipes is prepared by the following steps: Step 1: Add PVC resin, modified calcium carbonate, and ACR to a high-speed mixer at a speed of 300 - 500 revolutions per minute, and premix at low speed for 45 seconds to initially disperse the powder. Through low-frequency vibration, the powder is initially depolymerized to reduce the energy consumption of subsequent high-speed mixing. Step 2: Add MBS S-2501, BaSt, CaSt, ZnSt, oxidized polyethylene wax, and paraffin wax to the high-speed mixer, increase the speed to 1400 - 1600 revolutions per minute, ensure the uniform dispersion of the additives for 8 - 10 minutes, control the temperature at 100 - 105°C, and use the stepwise heating method, maintaining at 95°C for the first 5 minutes and then rising to 105°C in the last 3 minutes to improve the uniform dispersion of the lubricant. Step 3: Transfer the material after high-speed mixing to a cooling mixer, displace the air in the cooling mixer with nitrogen to avoid the oxidation of additives caused by high-temperature residues, and then add antioxidant 2246, ultraviolet absorber UV-9, and antioxidant 1010 to prevent the premature decomposition of additives at high temperatures. The speed is 80 - 120 revolutions per minute to reduce shear and protect the molecular structure of the additives. The temperature is 35 - 40°C for 5 - 8 minutes to ensure the uniform loading of the additives. Step 4: Adopt the three-stage cooling method from 40°C to 35°C to 30°C, with each stage cooled for 2 minutes to prevent the phase separation of MBS caused by a sudden temperature drop. After the material is cooled and shaped, the special material composition for high elongation PVC-M pipes is obtained.

[0013] The beneficial effects of the present invention are: The technical solution of the present invention can significantly improve the elongation of PVC-M pipes by scientifically proportioning PVC resin, stabilizer, impact modifier, lubricant, filler and processing aid, and still maintain good flexibility in low-temperature environments, effectively coping with working conditions of complex geological conditions and external force impacts; its working principle is as follows: First, modified MBS S-2501 is used as an impact modifier. By copolymerizing a small amount of butadiene in the core layer and introducing silicone, and introducing polyethylene glycol (PEG) into the modified PMMA shell layer, the rubber phase toughness and impact resistance of the material are enhanced. The built-in polyethylene glycol segment ensures sufficient softness at low temperatures, thereby improving the elongation of the overall pipe at low temperatures and solving the problems of affecting its elongation performance and potential performance risks in low-temperature environments. Secondly, modified metal soaps and compound titanate coupling agents are used to modify calcium carbonate, improve its compatibility with PVC resin, form a hydrophobic organic molecular film, enhance the interfacial bonding strength, and improve the overall mechanical properties and weather resistance of the material. The lubricant is compounded by modified metal soaps and modified waxes, achieving complementary internal and external lubrication, not only reducing friction and sticking problems during processing, but also improving the processing performance and product quality of the material. Thirdly, ACR, antioxidant 2246, ultraviolet absorber UV-9 and antioxidant 1010 in the formula act synergistically to improve the aging resistance and thermal stability of PVC-M pipes, effectively capturing free radicals, reducing intermolecular forces and reducing thermal degradation, thereby extending the service life. Finally, by precisely controlling the rotation speed and using a segmented cooling method, it ensures the uniform dispersion and stable combination of each component. The material shows low viscosity and good processing fluidity during processing and curing, improving the quality and performance of the finished product, and finally preparing a special material for PVC-M pipes with high elongation, impact resistance and excellent anti-aging performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a flowchart for preparing a special material composition for high-elongation PVC-M pipes in the present invention; Figure 2 It is a flowchart for constructing an MBS-Si ternary structure in the present invention; Figure 3 It is a flowchart for preparing a PMMA-b-PEG-b-PMMA triblock copolymer in the present invention; Figure 4 It is a flowchart for preparing modified calcium carbonate in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] The following will be combined with the attached Figure 1 to the attached Figure 4The technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0016] A special material composition for high elongation PVC-M pipes is made of the following components in parts by weight: PVC resin: 100 parts, stabilizer: 3.5 parts, impact modifier: 12 parts, lubricant: 3.6 parts, filler: 12 parts, processing aid ACR: 4 parts.

[0017] The stabilizer is a combination of an organotin stabilizer and a composite anti-aging agent. Among them, the organotin stabilizer is 1.8 parts, and the composite anti-aging agent is composed of antioxidant 2246, ultraviolet absorber UV-9, and antioxidant 1010. The composite anti-aging agent and the organotin stabilizer synergistically improve the weather resistance of PVC-M pipes; The dosage of antioxidant 2246 is 0.6 parts, the dosage of ultraviolet absorber UV-9 is 0.4 parts, and the dosage of antioxidant 1010 is 0.7 parts.

[0018] Antioxidant 2246 and ultraviolet absorber UV-9 synergistically improve the anti-photoaging property; antioxidant 2246 and antioxidant 1010 synergistically improve the long-term thermal stability; antioxidant 1010 and ultraviolet absorber UV-9 act synergistically to improve the anti-aging performance; Antioxidant 2246: A hindered phenol antioxidant that interrupts the oxidation chain reaction by capturing free radicals (R· or ROO·), and has excellent protection against thermal oxygen, weather aging, flexing aging, and oxidation catalyzed by variable valence metals; Ultraviolet absorber UV-9: Absorbs ultraviolet light of 270-340 nm, reduces photo-initiated free radicals, and prevents photodegradation; Antioxidant 1010: A polyphenol antioxidant containing 4 functional groups, focusing on thermal oxygen aging and providing long-term thermal stability; Antioxidant 2246 and ultraviolet absorber UV-9 act synergistically. The photo-antioxidant 2246 provides the ability to capture free radicals, and the ultraviolet absorber UV-9 provides a light shielding effect, forming a "light shielding + free radical capture" double protection, significantly improving the anti-photoaging performance; Antioxidant 2246 and antioxidant 1010 act synergistically. Antioxidant 2246 makes up for the deficiencies of antioxidant 1010 in weather and flexing aging, and antioxidant 1010 enhances the long-term thermal stability, forming a "multi-target antioxidant network"; The antioxidant 1010 and the UV absorber UV-9 act synergistically. The antioxidant 1010 makes up for the deficiency of the UV absorber UV-9 in thermal stability, and UV-9 enhances the light shielding effect, forming a double protection of "light shielding + thermal stability" and improving the overall anti-aging performance; The antioxidant 2246 (hindered phenol type) and the antioxidant 1010 (phosphite type) are compounded to synergistically capture free radicals; UV-9 absorbs the energy of ultraviolet rays, and the triple protection delays photo-oxidative aging; The impact modifier uses modified MBS S-2501, which has a core-shell structure composed of methyl methacrylate MMA, acrylate AC, and silicone Si. The cross-linked acrylate and silicone copolymer is the core, and the grafted polymethyl methacrylate PMMA is the shell; the modification of MBS S-2501 is achieved through core layer modification and shell layer modification. Specifically: by copolymerizing a small amount of butadiene in the core layer to construct a ternary structure of methyl methacrylate (M)-butadiene (B)-silicone (Si), and using lauryl acrylate (LA) to replace part of methyl methacrylate (MMA) to extend the flexibility of the core layer chain segment; introducing a polyethylene glycol PEG block into the PMMA shell; Core layer modification: Modified MBS S-2501 constructs a ternary structure of methyl methacrylate (M)-butadiene (B)-silicone (Si) by copolymerizing a small amount of butadiene in the core layer, improving the elongation rate of the S-2501 rubber phase; and using lauryl acrylate (LA) to replace part of methyl methacrylate MMA to extend the flexibility of the core layer chain segment; Among them, the weight fraction of MMA is 42%, the weight fraction of acrylate AC is 35%, the weight fraction of silicone is 10%, the weight fraction of lauryl acrylate LA is 8.5 mol%, the weight fraction of cross-linking agent DVB is 0.6%, the weight fraction of initiator AIBN is 0.2%, and the weight fraction of butadiene is 9.7%; The starvation feeding method is adopted. First, 42% of MMA, 35% of acrylate AC, 10% of silicone, and 8.5 mol% of lauryl acrylate LA are put into the reaction kettle in proportion and mixed evenly, and then 0.6% of cross-linking agent DVB and 0.2% of initiator AIBN are added to the reaction kettle and stirred and mixed. The stirring rate is 200 - 300 rpm, and the polymerization reaction is carried out under a set temperature of 50 - 80 °C and a negative pressure environment. The reaction time is controlled within 4 - 8 hours; After the reaction is stable, 9.7% of butadiene is slowly added dropwise at a dropping rate of 0.5 - 1.0 g / min; the content of C=C double bonds in the reaction system is monitored by on-line infrared (FTIR) to ensure that butadiene is completely copolymerized; after monitoring that butadiene is completely copolymerized, a termination solution is added to stop the polymerization reaction; Neutralize the unreacted monomers with 5% NaOH solution and wash with deionized water until the pH is 7 - 8; then dry in a vacuum drying oven at 60 °C for 4 - 6 h to remove residual solvents and moisture; extrude the dried polymer through an extruder, control the front - section temperature at 170 - 220 °C, the middle - section temperature at 190 - 250 °C, the end - section temperature at 220 - 260 °C, and the extrusion time at 1 - 2 hours. After pelletizing and cooling, obtain the MBS - Si ternary - structure material.

[0019] Shell modification: Introduce polyethylene glycol (PEG) block into the PMMA shell to enhance interfacial lubricity; Select PEG with a molecular weight of not less than 750, dissolve it in dichloromethane solvent; add succinic anhydride as a carboxylating reagent and react under the action of a catalyst DMAP to activate the hydroxyl groups of PEG. React the activated PEG with glycidyl methacrylate (GMA). The epoxy group of GMA undergoes a ring - opening reaction with the hydroxyl group of PEG and react at room temperature for 24 hours; after the reaction, purify the product through precipitation, washing, drying and other steps to obtain methacrylic acid mono - capped polyethylene glycol (MA - PEG). Mix MA - PEG and methyl methacrylate (MMA) in a certain ratio of 1:100 molar ratio, add initiator bipyridine, catalyst ascorbic acid and toluene solvent, place the reaction mixture in a reactor, and pass nitrogen to remove oxygen; control the reaction temperature at 70 °C and carry out the polymerization reaction for 24 hours. During the reaction, MA - PEG acts as a macromonomer and copolymerizes with MMA to form a PMMA - b - PEG - b - PMMA triblock copolymer; after the reaction, wash with deionized water until the pH is 7 - 8. Then dry in a vacuum drying oven at 60 °C for 4 - 6 h to remove unreacted monomers, catalysts and solvents; obtain a pure PMMA - b - PEG - b - PMMA triblock copolymer.

[0020] The lubricants are modified metal soaps and modified waxes; the modified metal soaps are compounded from barium stearate (BaSt), calcium stearate (CaSt) and zinc stearate (ZnSt), where the dosage of BaSt is 0.9 parts, the dosage of CaSt is 1.2 parts, and the dosage of ZnSt is 0.5 parts. The modified waxes are compounded from paraffin wax and oxidized polyethylene wax, with the dosage of oxidized polyethylene wax being 0.4 parts and the dosage of paraffin wax being 0.6 parts. As a polar wax, oxidized polyethylene wax can improve the external lubrication effect when compounded with paraffin wax, while maintaining the melt fluidity; as a non - polar wax, paraffin wax forms a complement with oxidized polyethylene wax to further reduce the melt viscosity and improve the fluidity. The polar groups of paraffin wax and oxidized polyethylene wax are compatible with PVC resin, and the long-chain alkyl groups form a microscopic lubricating film inside the resin to reduce the resistance of chain segment displacement and balance the lubrication effect; BaSt: BaSt mainly provides external lubrication, reduces the friction between the PVC melt and processing equipment, prevents adhesion, and the strong interaction between barium ions and the PVC chain repairs the chain defects generated by ultraviolet radiation to form a dynamic protection barrier; the barium ions of barium stearate have a strong dipole interaction with the PVC chain to form a stable coordination bond, inhibit the dehydrochlorination reaction of chlorine atoms, and improve the weather resistance of PVC; its hydrophobic group (long carbon chain) forms a hydrophobic layer on the surface of PVC to block the penetration of moisture and further slow down the rate of photo-oxidative aging; ZnSt: ZnSt inhibits initial coloring. The benzene ring structure of ZnSt absorbs ultraviolet light, reduces the breakage of PVC chains. ZnSt can undergo a substitution reaction with the active allyl chloride atoms in the PVC molecular chain to form a stable organozinc compound, thereby stabilizing the PVC molecular structure, reducing the formation of conjugated double bonds, and delaying initial coloring. CaSt: The polar groups of CaSt (Ca²⁺ and -COO⁻ of stearate) interact with the polar groups of PVC (such as the dipole of vinyl chloride link) to reduce the intermolecular force and lower the melt viscosity; at the same time, its long-chain alkyl groups also provide external lubrication effect to form an internal and external lubrication balance. CaSt has both internal and external lubrication, promotes resin plasticization, and reduces the melt viscosity. CaSt wets the PVC and metal surfaces, and non-polar paraffin wax molecules insert between the non-polar "tails" of adjacent calcium stearates to form a low-resistance slip layer, generating an effective external lubrication effect, and CaSt promotes the dispersion of paraffin wax and avoids the voids between primary particles; CaSt reacts with HCl to generate CaCl 2 , which can neutralize the HCl released in the later stage of PVC processing, prevent the formation of dark-colored products caused by self-catalytic degradation, and improve the long-term thermal stability of the products; ZnSt and CaSt show significant synergistic effects of internal lubrication and thermal stability in the PVC-M pipe special material composition: ZnSt and CaSt can insert between the PVC molecular chains, reduce the intermolecular force of PVC, lower the melt viscosity, and improve the melt fluidity; when ZnSt and CaSt are used in compound with oxidized polyethylene wax, they can balance the internal and external lubrication of PVC and further improve the processing performance and product quality of PVC; CaSt (melting point 150 - 160 °C) as the core of initial lubrication, ZnSt (melting point 120 - 130 °C) continuously releases lubrication effect at high temperature stages; the formation of a dynamic synergistic effect ensures that PVC has good lubrication performance at different processing stages; ZnSt provides a rapid initial stabilization effect, replaces active chlorine atoms, and delays initial coloring; while CaSt adsorbs ZnCl generated by the decomposition of ZnSt 2, inhibit its failure and provide long-term thermal stability; Specifically, ZnSt may react with HCl generated by thermal decomposition during the PVC processing to form ZnCl 2 ; Ca²⁺ from CaSt combines with Cl⁻ in ZnCl 2 through electrostatic interaction to form CaCl 2 precipitate. After Ca²⁺ combines with ZnCl 2 , the active sites of Zn²⁺ are covered, preventing it from contacting the PVC chain, thereby inhibiting catalytic degradation; after Ca²⁺ combines with ZnCl 2 , a complex can be formed to reduce the catalytic activity of ZnCl 2 , further inhibiting the degradation of PVC; ZnSt replaces active chlorine atoms, reduces the formation of conjugated double bonds, and delays initial coloring; CaSt neutralizes the HCl released later, preventing the formation of dark products caused by autocatalytic degradation; ZnSt and BaSt have synergistic weather resistance to resist photo-oxidative aging: after ZnSt absorbs ultraviolet light, part of the energy is transferred to the hydrophobic layer of BaSt through intermolecular vibration, reducing the overall energy density of the system. Specifically, the conjugated π-electron system in the ZnSt molecule can absorb ultraviolet light, causing electrons to transition from the ground state to the excited state; after absorbing ultraviolet light, hydrogen bond cleavage and molecular isomerization occur within the ZnSt molecule, accompanied by thermal vibration of the intramolecular structure; this thermal vibration energy can be transferred to the hydrophobic layer of BaSt through intermolecular vibration. After the energy is transferred to the hydrophobic layer, it is dissipated through heat or converted into other forms of energy, reducing the overall energy density of the system. The energy transfer and dissipation mechanism helps protect the material from photo-oxidative aging caused by ultraviolet light; The conjugated π-electron system (derived from the stearic acid chain) in the ZnSt molecule absorbs ultraviolet light in the 280 - 380 nm band, and electrons transition from the ground state to the excited state; After absorbing ultraviolet light, the chelate ring formed by the ortho-hydroxy phenyl (-C 6 H 4 (OH)-) and zinc ion (Zn²⁺) in the ZnSt molecule breaks, and molecular isomerization (such as cis-trans isomerization) occurs; molecular isomerization is accompanied by changes in bond length / angle, generating thermal vibration of about 10¹² - 10¹ 4 Hz (corresponding to the infrared band), and the vibration energy level difference is about 0.1 - 1 eV; the thermal vibration energy of ZnSt is transferred to the hydrophobic layer (long carbon chain structure) of barium stearate through van der Waals force (London dispersion force); Synergistic effect of BaSt and CaSt: BaSt acts as a long-term heat stabilizer to neutralize HCl generated by the decomposition of PVC; CaSt has both internal lubrication and external lubrication functions. When BaSt and CaSt are used in combination, the external lubrication characteristics of CaSt form a relay with BaSt to further improve fluidity; BaSt can effectively neutralize HCl released during PVC processing and provide long-term heat stability; CaSt reduces the plasticization torque, shortens the plasticization time, and reduces the risk of thermal degradation; the synergy of the two can broaden the processing window and improve the weather resistance of products; the external lubrication effect of BaSt reduces the melt-equipment friction, and the internal lubrication effect of CaSt reduces the internal cohesion between molecular chains. The combined action reduces the plasticization torque and increases the extrusion volume; BaSt dominated by external lubrication reduces surface defects, and CaSt dominated by internal lubrication improves the melt uniformity. Under the synergistic effect, the surface finish of the pipe is significantly improved; BaSt provides rapid initial stabilization, while CaSt provides long-term heat stability; The synergistic effect of lubricants promotes the orientation arrangement of molecular chains and improves the elongation of PVC-M pipes; Metal soaps promote resin plasticization, and paraffin and oxidized polyethylene wax reduce the risk of melt fracture. The combined action of the two improves melt fluidity and processing efficiency; When BaSt, CaSt, and ZnSt are used in combination, a more comprehensive synergistic effect can be produced. Utilize the long-term stability of BaSt, the plasticization promotion of CaSt, and the initial lubricity of ZnSt to form complementary lubrication aging; and BaSt provides initial stabilization, CaSt provides long-term heat stability, while ZnSt further enhances the stabilization effect by forming a synergistic complex; oxidized polyethylene wax provides internal lubrication and improves filler dispersion, and paraffin acts as an external lubricant to reduce melt-equipment friction, synergistically improving the plasticization efficiency.

[0021] The filler is modified calcium carbonate, and the surface of the calcium carbonate filler is treated with a titanate coupling agent to improve its interfacial bonding with the PVC resin matrix; The titanate coupling agent forms a molecular bridge through its amphiphilic structure, with one end reacting with the hydroxyl groups on the surface of calcium carbonate and the other end binding to the polymer molecular chain: The alkoxy groups (such as -O-C 3 H 7 ) of the titanate coupling agent are easily hydrolyzed to generate hydroxyl groups (-OH), which undergo a condensation reaction with the hydroxyl groups (-OH) on the surface of calcium carbonate to form a strong Ti-O chemical bond, reducing the surface energy of calcium carbonate and changing it from hydrophilic to hydrophobic; The long aliphatic chain (such as -C 18 H 37 ) at the other end of the coupling agent physically entangles with the PVC molecular chain to act as a "molecular bridge" and improve the interfacial bonding strength; The surface of the modified calcium carbonate is covered with an organic molecular film, and the contact angle increases from <30° (hydrophilic) before modification to >90° (hydrophobic), significantly improving the compatibility with PVC; Disperse calcium carbonate in an ethanol / water (7:3) mixed solvent, add a titanate coupling agent, and use a PVP / polyethylene glycol (PEG) composite dispersant with a mass ratio of 3:1. The total dosage of the dispersant is 0.3 wt%. Through Zeta potential analysis, the surface charge density of the particles reaches -45 mV at this concentration, and the dispersion stability is the best; Add 0.1 mol / L acetic acid buffer solution (pH = 5.5), add 3 wt% tetrahydrofuran (THF) as a co-solvent, and utilize its plasticizing effect on PVP to reduce the glass transition temperature (Tg) of the dispersant from 120 °C to 95 °C, improving the low-temperature dispersion efficiency; Introduce nitrogen gas (flow rate 50 mL / min), maintain the oxygen content in the reaction system <0.5%, prevent the oxidative degradation of PVP, and then use a combined stirring paddle (anchor type + turbine type). The rotation speed in the first stage is 80 rpm to promote macro mixing, and it is increased to 200 rpm in the second stage to enhance micro mass transfer. Stir and react at 80 °C for 1 - 2 hours, and use a three-stage temperature rise: Stage 1: Ultrasonic pretreatment at 40 °C for 10 minutes (power 200 W), and utilize the cavitation effect to break the soft agglomerates of calcium carbonate; Stage 2: Keep warm at 60 °C for 45 minutes to achieve the physical adsorption of the titanate coupling agent; Stage 3: React at 80 °C for 75 minutes to activate the chemical coupling reaction, enabling the coupling agent to fully react with calcium carbonate; Then adopt two-stage centrifugation. In the first stage, remove large particles at 3000 rpm, and collect the modified product at 8000 rpm in the second stage; wash 3 times with an ethanol / acetone (1:1) mixed solvent; adopt three-stage temperature control (from 50 °C to 60 °C to 70 °C), shorten the drying time by 40%, and prevent the formation of hard agglomerates; the size of the modified calcium carbonate agglomerates decreases from >100 μm to <50 μm; Adding 0.1 mol / L acetic acid buffer solution (pH = 5.5) can inhibit the over-hydrolysis of the titanate, increasing the concentration of the effective coupling agent.

[0022] The acrylate segment of the processing aid ACR forms a dipole-dipole interaction with the chlorine atoms of PVC, reducing the interfacial tension and promoting the rapid fusion of resin particles during the plasticization stage; its low molecular weight component can penetrate to the interface of PVC primary particles, shortening the plasticization time at a processing temperature of 160 - 180 °C; the rubber core of MBS initiates crazes when stressed, and ACR, as a rigid particle, can terminate the propagation of crazes; The comb-like branched chain structure of ACR forms a physical adsorption layer on the surface of the modified calcium carbonate, and the carboxylic acid groups of ACR react with the hydroxyl groups on the calcium carbonate surface to form chemical anchoring points.

[0023] The comparison of the special material compositions for high elongation PVC-M pipes in Examples 1 - 7 is as shown in the following table: Component / Serial Number Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 PVC Resin 100 100 100 100 100 100 100 Organotin Stabilizer 1.8 2.3 1.8 2.3 2.0 1.7 1.5 Antioxidant 2246 0.6 0.5 0.7 0.5 0.5 0.6 0.8 Ultraviolet Absorbent UV-9 0.4 0.2 0.5 0.3 0.4 0.5 0.4 Antioxidant 1010 0.7 0.5 0.5 0.4 0.6 0.7 0.8 MBS S-2501 14 11 12 13 14 14 10 BaSt 0.9 0.8 0.7 0.8 0.9 0.7 0.7 CaSt 1.2 1.3 1.2 1.2 1.2 1.1 1.0 ZnSt 0.5 0.5 0.5 0.5 0.3 0.5 0.6 Oxidized Polyethylene Wax 0.4 0.5 0.4 0.4 0.5 0.5 0.4 Paraffin Wax 0.6 0.5 0.8 0.7 0.7 0.7 0.9 Modified Calcium Carbonate 12 12 15 15 13 10 10 Processing Aid ACR 4 4 3 4 3 5 5 Among them, the components in Example 1 are the optimal ratio, with the best comprehensive performance, good stability, durability and processing performance, and are suitable for scenarios with high requirements for the comprehensive performance of materials; In Example 2, the organotin stabilizer is excessive (2.2 parts), resulting in an increase in melt viscosity and a decrease in plasticization efficiency; when the dosage of antioxidant 2246 is 0.5 part, the antioxidant performance slightly decreases, and the dosage of paraffin wax is low, resulting in insufficient lubricity; In Example 3, the dosage of ultraviolet absorber UV-9 is too high (0.48 part), which may cause yellowing; the reduction of ACR leads to a decrease in plasticization quality, and the processing temperature needs to be increased; In Example 4, the organotin stabilizer is excessive (2.2 parts); the dosage of modified calcium carbonate is too high (14.2 parts), which may reduce the toughness of the material; the reduction of the anti-aging agent leads to a decrease in long-term weather resistance; In Example 5, the dosage of ZnSt is low (0.31 part), which affects long-term stability, the toughness decreases, and the reduction of ACR affects the plasticization quality; In Example 6, the dosage of modified calcium carbonate is low (10.6 parts), which affects the rigidity of the pipe; the processing aid ACR is excessive (4.7 parts), which may cause a decrease in melt strength and an increase in the risk of surface precipitation, and the die temperature needs to be strictly controlled; In Example 7, the dosage of organotin stabilizer is low (1.55 parts), which affects long-term thermal stability; the dosage of paraffin wax is too high (0.83 part), resulting in precipitation and high cost; A special material composition for high elongation PVC-M pipes is prepared by the following steps: Step 1: Add PVC resin, modified calcium carbonate and ACR to a high-speed mixer at a rotation speed of 300 - 500 revolutions per minute, and premix at a low speed for 45 seconds to preliminarily disperse the powder; make the powder preliminarily depolymerize through low-frequency vibration to reduce the energy consumption of subsequent high-speed mixing Step 2: Add MBS S-2501, BaSt, CaSt, ZnSt, oxidized polyethylene wax, and paraffin wax to the high-speed mixer, increase the rotation speed to 1400 - 1600 revolutions per minute, ensure the uniform dispersion of the additives, the time is 8 - 10 minutes, and the temperature is controlled at 100 - 105 °C. The segmented heating method is adopted, maintaining at 95 °C for the first 5 minutes and rising to 105 °C in the last 3 minutes to improve the uniform dispersion of the lubricant; the BaSt / CaSt / ZnSt compound lubricant forms a gradient melting layer at 100 - 105 °C, and the entanglement efficiency with the PVC molecular chain is improved; MBS S-2501 utilizes the "lubricating wrapping" effect of ACR in high-speed mixing to prevent excessive shearing of MBS particles Step 3: Transfer the materials after high-speed mixing to a cooling mixer, displace the air in the cooling mixer with nitrogen to avoid oxidation of the additives caused by high-temperature residues, and then add antioxidant 2246, ultraviolet absorber UV-9, and antioxidant 1010 to avoid premature decomposition of the additives at high temperatures. The rotation speed is 80 - 120 revolutions per minute to reduce shear and protect the molecular structure of the additives. The temperature is 35 - 40 °C and the time is 5 - 8 minutes to ensure uniform loading of the additives; antioxidant 2246, ultraviolet absorber UV-9, and antioxidant 1010 migrate to the material surface during the cooling process to form a gradient protective layer. Step 4: Adopt a three-stage cooling method from 40 °C to 35 °C to 30 °C, with each stage cooled for 2 minutes to prevent phase separation of MBS caused by a sudden temperature drop. After the materials are cooled and shaped, the special material composition for high elongation PVC-M pipes is obtained.

[0024] Based on the explanations and teachings in the above specification, those skilled in the art to which the present invention pertains can also make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims

1. A high elongation PVC-M pipe special material composition, characterized in that: It is made of the following components in parts by weight: PVC resin: 100 parts, stabilizer: 4-9 parts, impact modifier: 10-15 parts, lubricant: 2.5-4.5 parts, filler: 10-15 parts, processing aid ACR: 3-5 parts.

2. The high elongation PVC-M pipe material composition according to claim 1, characterized in that: It is made of the following components in parts by weight: PVC resin: 100 parts, stabilizer: 3.5 parts, impact modifier: 14 parts, lubricant: 3.6 parts, filler: 12 parts, processing aid ACR: 4 parts.

3. A high elongation PVC-M pipe special material composition according to claim 1 or 2, characterized in that: The stabilizer is a compound of an organic tin stabilizer and a composite anti-aging agent, wherein the organic tin stabilizer is 1.2-2.4 parts, and the composite anti-aging agent is a compound of an antioxidant 2246, an ultraviolet absorber UV-9, and an antioxidant 1010. The composite anti-aging agent and the organic tin stabilizer synergistically improve the weather resistance of the PVC-M pipe. The dosage of antioxidant 2246 is 0.5-0.8 parts, the dosage of ultraviolet absorber UV-9 is 0.2-0.5 parts, and the dosage of antioxidant 1010 is 0.5-1 parts.

4. A high elongation PVC-M pipe special material composition according to claim 1 or 2, characterized in that: The impact modifier adopts modified MBS S-2501, which has a core-shell structure composed of methyl methacrylate MMA, acrylate AC and silicone Si, wherein cross-linked acrylate and silicone copolymer is the core and grafted polymethyl methacrylate PMMA is the shell; MBS S-2501 is modified by core layer modification and shell layer modification, specifically: a small amount of butadiene is copolymerized in the core layer to construct a ternary structure of methyl methacrylate M-butadiene B-silicone Si, lauryl acrylate LA is used to replace part of methyl methacrylate MMA, and the flexibility of the core layer chain segment is extended; and polyethylene glycol PEG blocks are introduced into the PMMA shell.

5. A high elongation PVC-M pipe special material composition according to claim 1 or 2, characterized in that: The lubricant is a modified metal soap or a modified wax; the modified metal soap is compounded by barium stearate BaSt, calcium stearate CaSt and zinc stearate ZnSt, wherein the amount of BaSt is 0.5-1.0 parts, the amount of CaSt is 1.0-1.5 parts, and the amount of ZnSt is 0.3-0.8 parts; The modified wax is compounded by paraffin wax and oxidized polyethylene wax, wherein the weight portion of the oxidized polyethylene wax is 0.3-0.5 part and the weight portion of the paraffin wax is 0.5-1.0 part.

6. A high elongation PVC-M pipe special material composition according to claim 1 or 2, characterized in that: The filler is modified calcium carbonate, and the calcium carbonate filler is surface treated with a titanate coupling agent to improve the interface bonding between the calcium carbonate filler and the PVC resin matrix.

7. A high elongation PVC-M pipe special material composition according to claim 1 or 2, characterized in that: Prepared by the following steps: Step 1: Add PVC resin, modified calcium carbonate and ACR into a high-speed mixer at a speed of 300-500 rpm, and premix at low speed for 45 seconds to initially disperse the powder; Step 2: Add MBS S-2501, BaSt, CaSt, ZnSt, oxidized polyethylene wax and paraffin wax to a high-speed mixer, increase the speed to 1400-1600 rpm for 8-10 minutes, control the temperature at 100-105°C, and use a staged heating method, maintaining the temperature at 95°C for the first 5 minutes and then raising the temperature to 105°C for the next 3 minutes; Step 3: Transfer the high-speed mixed materials to a cooling mixer, replace the air in the cooling mixer with nitrogen, and then add antioxidant 2246, ultraviolet absorber UV-9 and antioxidant 1010, with a rotation speed of 80-120 rpm, a temperature of 35-40°C, and a time of 5-8 minutes; Step 4: adopt a three-stage cooling method from 40°C to 35°C to 30°C, with each stage cooling for 2 minutes. After the material is cooled and shaped, a high elongation PVC-M pipe special material composition is obtained.

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