Impact-resistant modifier and application thereof in PVC (polyvinyl chloride) pipe

Abstract

The invention discloses an anti-impact modifier and application thereof in PVC (polyvinyl chloride) pipes, and mainly relates to the technical field of polymeric high-molecular compounds. Compared with the prior art, the impact-resistant modifier is applied to preparation of the PVC pipe and can synergistically improve the impact resistance and deformation resistance of the PVC pipe, methyl acrylate is polymerized on the surface of polytetrafluoroethylene to form a grafted copolymer with a core-shell structure, and polymethyl acrylate on the outer layer has good film-forming property, so that the PVC pipe has good impact resistance and deformation resistance. Inorganic fibers and other components can be adhered to the surface of the polytetrafluoroethylene-methyl acrylate core-shell structure grafted copolymer, and when the polytetrafluoroethylene-methyl acrylate core-shell structure grafted copolymer is added to preparation of a PVC matrix, impact stress can be fully dispersed, and pipe deformation and even breakage caused by local excessive accumulation of stress are avoided. The inorganic glass fiber is further added, the bearing load is improved by enhancing the strength, the water flow impact force and the external pressure are better resisted, and finally the purpose of improving the impact resistance and the deformation resistance of the pipe is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of polymerized macromolecular compounds, in particular to an impact modifier and application thereof to PVC pipes. Background Art

[0002] Impact modifiers are a type of additive that can significantly improve the impact resistance of materials. They mainly change the internal structure and intermolecular forces of the material, so that the material can effectively absorb and disperse energy when it is impacted by external forces, thereby reducing the possibility of rupture or damage. During installation, transportation and long-term use, pipes in the water treatment field may be subjected to various external impacts, such as construction collisions, soil settlement extrusion, water flow impact, etc. Pipes with impact modifiers added can reduce the risk of pipe rupture and leakage, ensure the stable operation of the water treatment system, and extend the service life of the pipe. At the same time, it also helps to reduce the maintenance cost and resource waste caused by pipe damage, and plays an indispensable role in the construction of modern water treatment engineering infrastructure.

[0003] In the preparation of impact modifiers, functional additives can be added to play a supporting role similar to that of a skeleton. When there is an external force impact, it can share part of the energy and prevent the material from excessive deformation. At the same time, in terms of pipe design, a multi-layer composite structure can also be used to combine materials with different properties, and the advantages of each layer of material can be used to complement each other to achieve the purpose of improving the impact resistance and deformation resistance, and ultimately the impact resistance and deformation resistance can be comprehensively improved.

[0004] CN108822436A discloses a PVC double-wall corrugated pipe and a preparation method thereof. The impact modifier is any one of chlorinated polyethylene or methacrylic acid polymer, so that the invention can effectively improve the stiffness and impact resistance, toughness strength and bending strength of the PVC double-wall corrugated pipe.

[0005] CN114854144A discloses a large-diameter PVC-U pipe and a preparation method thereof. The invention improves the impact resistance, thermal stability and mechanical properties of the PVC-U pipe through the synergistic effect of γ-alumina nanofibers and reactive monomers in the PVC system, and makes the plasticization degree of the PVC-U pipe more uniform.

[0006] The above invention solution does not solve the problems of impact resistance and tensile properties of PVC pipe products at the same time. Summary of the invention

[0007] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is to provide an impact modifier applied to PVC pipes, which can simultaneously improve the impact resistance and deformation resistance of PVC pipe products.

[0008] To achieve the above object, the present invention provides an impact modifier and its application in PVC pipes.

[0009] A method for preparing an impact modifier is as follows, in parts by weight:

[0010] 4-8 parts of polytetrafluoroethylene aqueous dispersion are added to 150-250 parts of water and stirred for 0.5-1 hour, the temperature is raised to 70-80°C, 4-8 parts of methyl acrylate are added dropwise and stirring is continued for 0.5-1 hour, 2-4 parts of ammonium persulfate aqueous solution are added and stirring is continued for 4-6 hours to obtain a graft copolymer aqueous dispersion; 2-6 parts of inorganic fiber, 0.1-1 parts of coconut acid monoethanolamide, and 0.1-1 parts of 3-isocyanatepropyltrimethoxysilane are added and stirring is continued for 1-2 hours at room temperature, 0.1-1 parts of demulsifier are added and stirring is continued for 0.5-1 hour, centrifugation is carried out, the filter cake is washed with water, and the impact modifier is obtained after drying.

[0011] The ammonium persulfate aqueous solution is a 4-6 wt % ammonium persulfate aqueous solution.

[0012] The demulsifier is ethylene glycol.

[0013] The inorganic fiber is one of glass fiber and modified glass fiber.

[0014] The preparation method of the modified glass fiber is as follows, in parts by weight:

[0015] Add 1-4 parts of silane coupling agent, 2-4 parts of nonylphenol polyoxyethylene ether, and 1-2 parts of emulsifier to 100-150 parts of water and stir for 0.5-1 hour to obtain a modified latex; add 4-6 parts of glass fiber to 40-60 parts of H2O2 aqueous solution, soak at 30-40°C for 0.5-1 hour to increase the activity of surface hydroxyl groups, filter, wash the filter cake with water and dry it, and then add it to the above-mentioned modified latex; soak at 40-50°C for 1-2 hours, filter, wash the filter cake with water and dry it to obtain the modified glass fiber.

[0016] The silane coupling agent is one of KH-171, KH-550 and KH-570.

[0017] The emulsifier is one of sodium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium stearoyl lactylate and dodecyltrimethylammonium chloride.

[0018] The H2O2 aqueous solution is a 2-6 wt% H2O2 aqueous solution.

[0019] The impact modifier can be used in the preparation of PVC pipes; the PVC pipes are made of PVC resin as the main raw material, with an appropriate amount of additives added, and are processed and formed through mixing, extrusion, sizing, cooling, cutting and expansion processes; preferably, the impact modifier can be used in any one of rigid polyvinyl chloride (PVC-U) pipe fittings for water supply, rigid polyvinyl chloride (PVC-U) pipe fittings for building drainage, rigid polyvinyl chloride (PVC-U) electrical sheath pipe fittings, polyvinyl chloride pipe fittings for agricultural water supply and drainage, and chlorinated polyvinyl chloride sheaths for power cables.

[0020] The impact modifier of the present invention is applied to the preparation of PVC pipes to synergistically improve the impact resistance and deformation resistance of the PVC pipes, wherein methyl acrylate is polymerized on the surface of polytetrafluoroethylene to form a graft copolymer with a core-shell structure, the polymethyl acrylate in the outer layer has good film-forming properties, and components such as inorganic fibers can be adhered to the surface of the polytetrafluoroethylene-methyl acrylate core-shell structure graft copolymer; the polytetrafluoroethylene inner core provides rigid support and preliminarily buffers impact, the polymethyl acrylate outer shell disperses energy through deformation, and the core-shell structure enables the graft copolymer to fully disperse the impact stress in the PVC matrix, thereby avoiding local excessive accumulation of stress to cause deformation or even rupture of the pipe. Coconut acid monoethanolamide, as a surfactant, promotes the dispersion of polytetrafluoroethylene-methyl acrylate copolymer and inorganic fiber in water by reducing the interfacial energy of the system, making the contact between the components more sufficient; 3-isocyanatepropyltrimethoxysilane improves the bonding strength and adhesion stability between inorganic fiber and polytetrafluoroethylene-methyl acrylate copolymer, and prevents the sedimentation, agglomeration and phase separation of glass fiber; finally, the demulsifier is added to adjust the emulsification state of the system, promote the aggregation and solidification of the components, and form a stable impact modifier structure.

[0021] The main component of glass fiber is silicon oxide, and the main functional group is Si-OH, which can react with the hydroxyl group hydrolyzed by the silane coupling agent. The high strength characteristics of glass fiber can improve the bearing load by enhancing the strength in the impact modifier, and better resist the impact force of water flow and external pressure. The role of the emulsifier in the preparation of modified glass fiber is to maintain the stable dispersion state of the modified emulsion and ensure that the components such as silane coupling agent and nonylphenol polyoxyethylene ether are evenly distributed and fully contacted; the hydroxyl groups on the fiber surface treated with H2O2 aqueous solution increase, and the reaction activity with silane coupling agent and nonylphenol polyoxyethylene ether is enhanced; the long chain structure and oxygen atoms of nonylphenol polyoxyethylene ether wetting agent can form hydrogen bonds and other interactions with the hydroxyl groups on the surface of glass fiber and the hydrolysis product of silane coupling agent, thereby improving the wettability and chemical activity of the fiber surface, making the bonding between the fiber and polytetrafluoroethylene-methyl acrylate copolymer more firm, enhancing the interfacial compatibility, and enabling stress to be more effectively transferred from the PVC substrate to the fiber reinforcement phase. The synergistic effect between the components can be fully exerted, and finally the purpose of improving the compatibility, improving the interfacial performance, and enhancing the impact resistance and deformation resistance of the pipe in the preparation of the impact modifier is achieved.

[0022] Beneficial effects of the present invention:

[0023] Compared with the prior art, the impact modifier of the present invention can be used in the preparation of PVC pipes to synergistically improve the impact resistance and deformation resistance of PVC pipes, wherein methyl acrylate is polymerized on the surface of non-water-soluble polytetrafluoroethylene to form a graft copolymer with a core-shell structure, and the polymethyl acrylate of the outer layer has good film-forming properties, which can make inorganic fibers and other components adhere to the surface of the core-shell structure graft copolymer of polytetrafluoroethylene-methyl acrylate, and can be added to the PVC matrix to fully disperse the impact stress during preparation, avoiding the excessive accumulation of stress in the local area to cause deformation or even rupture of the pipe. The added inorganic glass fiber increases the load-bearing capacity by enhancing the strength, and better resists the impact force of water flow and external pressure; after being modified with silane coupling agent and nonylphenol polyoxyethylene ether, the bonding between the polytetrafluoroethylene-methyl acrylate copolymer is more firm, and the interface compatibility is enhanced, and finally the purpose of improving the compatibility, improving the interface performance, and improving the impact resistance and deformation resistance of the pipe in the preparation of PVC pipes is achieved. DETAILED DESCRIPTION

[0024] The parameters of the specific chemical substances used in the examples are from the following sources:

[0025] Polytetrafluoroethylene aqueous dispersion: solid content is 35%, dispersion particle size is 0.245μm, brand is DuPont, USA, grade is DISP 35.

[0026] Polymethyl acrylate: The manufacturer is Tengyi Material Supply Station in Xigong District, Luoyang City, and the item number is HH4170WQTDEO.

[0027] Glass fiber: diameter 13 μm, short cut length 3.0 mm.

[0028] Example 1

[0029] A method for preparing an impact modifier is as follows:

[0030] 6 g of polytetrafluoroethylene aqueous dispersion is added to 200 g of water and stirred for 0.5 hour, the temperature is raised to 75° C., 6 g of methyl acrylate is added dropwise, stirring is continued for 0.5 hour, 3 g of 5 wt% ammonium persulfate aqueous solution is added, stirring is continued for 6 hours to obtain a graft copolymer aqueous dispersion; 0.5 g of coconut acid monoethanolamide and 0.5 g of 3-isocyanatepropyltrimethoxysilane are added, stirring is continued for 1.5 hours at room temperature, 0.15 g of ethylene glycol is added, stirring is continued for 0.5 hour, centrifugation is performed, the filter cake is washed with water, and the impact modifier is obtained after drying.

[0031] Comparative Example 1

[0032] A method for preparing an impact modifier is as follows:

[0033] 12 g of polytetrafluoroethylene aqueous dispersion was added to 200 g of water and stirred for 0.5 hour; 0.5 g of coconut oil monoethanolamide and 0.5 g of 3-isocyanatepropyltrimethoxysilane were added and stirred for 1.5 hours at room temperature; 0.15 g of ethylene glycol was added and stirred for 0.5 hour; the mixture was centrifuged, the filter cake was washed with water, and the impact modifier was obtained after drying.

[0034] Comparative Example 2

[0035] A method for preparing an impact modifier is as follows:

[0036] 12 g of polymethyl acrylate was added to 200 g of water and stirred for 0.5 hour; 0.5 g of coconut oil monoethanolamide and 0.5 g of 3-isocyanatepropyltrimethoxysilane were added and stirred for 1.5 hours at room temperature; 0.15 g of ethylene glycol was added and stirred for 0.5 hour; the mixture was centrifuged, the filter cake was washed with water, and the impact modifier was obtained after drying.

[0037] Example 2

[0038] A method for preparing an impact modifier is as follows:

[0039] 6 g of polytetrafluoroethylene aqueous dispersion is added to 200 g of water and stirred for 0.5 hour, the temperature is raised to 75° C., 6 g of methyl acrylate is added dropwise, stirring is continued for 0.5 hour, 3 g of 5 wt% ammonium persulfate aqueous solution is added, stirring is continued for 6 hours to obtain a graft copolymer aqueous dispersion; 5 g of glass fiber, 0.5 g of coconut acid monoethanolamide, and 0.5 g of 3-isocyanatepropyltrimethoxysilane are added, stirring is continued for 1.5 hours at room temperature, 0.15 g of ethylene glycol is added, stirring is continued for 0.5 hour, centrifugation is performed, the filter cake is washed with water, and the impact modifier is obtained after drying.

[0040] Example 3

[0041] A method for preparing an impact modifier is as follows:

[0042] 6 g of polytetrafluoroethylene aqueous dispersion is added to 200 g of water and stirred for 0.5 hour, the temperature is raised to 75° C., 6 g of methyl acrylate is added dropwise, stirring is continued for 0.5 hour, 3 g of 5 wt% ammonium persulfate aqueous solution is added, stirring is continued for 6 hours to obtain a graft copolymer aqueous dispersion; 5 g of modified glass fiber, 0.5 g of coconut oil monoethanolamide, and 0.5 g of 3-isocyanatepropyltrimethoxysilane are added, stirring is continued for 1.5 hours at room temperature, 0.15 g of ethylene glycol is added, stirring is continued for 0.5 hour, centrifugation is performed, the filter cake is washed with water, and the impact modifier is obtained after drying.

[0043] The preparation method of the modified glass fiber is as follows:

[0044] Add 2g of silane coupling agent KH-570, 3g of nonylphenol polyoxyethylene ether, and 1g of sodium stearoyl lactylate to 120g of water and stir for 0.5 hour to obtain a modified emulsion; add 5g of glass fiber to 50g of 5wt% H2O2 aqueous solution, soak at 35°C for 1 hour to increase the surface hydroxyl activity, filter, wash the filter cake with water and dry it, and then add it to the above-mentioned modified emulsion; soak at 45°C for 1 hour, filter, wash the filter cake with water and dry it to obtain the modified glass fiber.

[0045] Test Example 1

[0046] The impact modifier obtained by the preparation method of Examples 1-3 is applied to the preparation of rigid polyvinyl chloride (PVC-U) pipe fittings for water supply, and the PVC-U pipe samples with a pipe length of 200mm, a wall thickness of 5mm, and an outer diameter of 50mm are obtained by segmentation. The test is based on the M-level test of the drop hammer impact test in the national standard GB / T 10002.1-2023 "Rigid polyvinyl chloride (PVC-U) pipes for water supply"; the hammer head mass is 0.5kg, and the drop hammer height is 1000mm; each group of embodiments is set with 20 samples for external impact resistance test at 0°C, and each sample should be drawn with 3 lines, that is, the total number of impacts is 30 times. The test first makes the drop hammer impact on the No. 1 marking line. If the sample is not damaged, the No. 2 marking line is impacted again until the sample is damaged or all markings are impacted once, and the judgment result is obtained; the average value of the TIR value of the drop hammer impact test test data is summarized as shown in Table 1.

[0047] Table 1 Test results of external impact resistance

[0048] Example 0℃ external impact resistance / TIR value Example 1 4.7％ Example 2 4.0％ Example 3 2.9％

[0049] In the external impact resistance test of Test Example 1, the impact modifiers of Examples 1-3 were added to the preparation of PVC-U pipe samples, wherein Example 1 used polytetrafluoroethylene aqueous dispersion and methyl acrylate as the main raw materials to synthesize the core-shell structure graft copolymer, and then added coconut oil monoethanolamide, 3-isocyanate propyl trimethoxysilane and other additives as the basic formula of the impact modifier; Examples 2-3 added glass fiber and modified glass fiber on the basis of Example 1, and it can be seen from the above table that Example 3 with modified glass fiber added has the lowest TIR value and the best external impact resistance. The impact modifier of Example 2 with glass fiber added can further disperse stress inside the pipe, prevent crack propagation, and improve the impact resistance of the pipe; the glass fiber itself has high strength and rigidity, and when the pipe is subjected to external impact, its own high strength characteristics can be used to prevent excessive deformation of the pipe. Compared with Example 2, Example 3 modifies the glass fiber, and the combination with other components in the impact modifier is more firmly, the interface compatibility with the PVC substrate is enhanced, and the impact resistance of the pipe is better improved; the glass fiber is modified by using a silane coupling agent KH-570, nonylphenol polyoxyethylene ether and sodium stearoyl lactylate, KH-570 undergoes a hydrolysis reaction on the surface of the glass fiber, and the generated silanol group undergoes a condensation reaction with the hydroxyl group on the surface of the glass fiber to form a chemical bond, and is cross-linked with 3-isocyanatepropyltrimethoxysilane to form a more firmly modified glass fiber structure, so that the compatibility and interface bonding force between the surface of the modified fiber and the graft copolymer are enhanced, showing a better stress transfer effect, improving the compatibility of the impact modifier with the PVC pipe, and significantly improving the impact resistance of the pipe.

[0050] Test Example 2

[0051] The impact modifiers obtained by the preparation methods of Examples 1-3 and Comparative Examples 1-2 were used in the preparation of rigid polyvinyl chloride (PVC-U) pipes for water supply to conduct tensile yield stress tests. The test was conducted in accordance with the national standard GB / T 5836.1-2018 "Rigid polyvinyl chloride (PVC-U) pipes for building drainage", with 6 specimens set for each group of examples, and the test data are summarized in Table 2.

[0052] Table 2 Tensile yield stress test results

[0053] Example Tensile yield stress / MPa Example 1 40.0 Comparative Example 1 38.6 Comparative Example 2 36.5 Example 2 45.6 Example 3 48.5

[0054] In test example 2, tensile yield stress tests were performed on examples 1-3 and comparative examples 1-2, wherein example 1 was the basic formula, examples 2-3 were added with glass fiber and modified glass fiber respectively, and comparative examples 1-2 were different from example 1 in that polytetrafluoroethylene aqueous dispersion and polymethyl acrylate were used to replace the polytetrafluoroethylene-methyl acrylate core-shell structure graft copolymer of example 1, respectively, and the raw material components of comparative examples 1-2 were more single, and the polytetrafluoroethylene in the core-shell structure graft copolymer in examples 1-3 provided the main rigid support, and the polymethyl acrylate shell with elasticity and film-forming properties could improve the deformation resistance, and when the pipe was subjected to tensile stress, the rigid structure of polytetrafluoroethylene could bear part of the stress, and at the same time, the polymethyl acrylate shell dispersed the stress through elastic deformation, and the synergistic effect of the core-shell structure made the pipe have a certain tensile yield stress. It can be seen from the above table that the tensile yield stress value of example 3 with modified glass fiber added was larger, and the deformation resistance was better. In Example 2, glass fiber is added on the basis of Example 1, and in Example 3, modified glass fiber is added. After modification, it has better bonding and compatibility with other components in the impact modifier; during the stretching process, the modified glass fiber can more effectively transfer stress between the PVC substrate and the polytetrafluoroethylene-methyl acrylate graft copolymer; the modified stable structure enables the stress to be more evenly distributed inside the pipe when subjected to tensile stress, avoiding stress concentration in local areas leading to material yield, and ultimately making the pipe have higher tensile yield stress and better deformation resistance.

[0055] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for preparing an impact modifier, characterized in that: The method comprises the following steps, in parts by weight: 4-8 parts of polytetrafluoroethylene aqueous dispersion are added to 150-250 parts of water and stirred for 0.5-1 hour, the temperature is raised to 70-80°C, 4-8 parts of methyl acrylate are added dropwise and stirring is continued for 0.5-1 hour, 2-4 parts of ammonium persulfate aqueous solution are added and stirring is continued for 4-6 hours to obtain a graft copolymer aqueous dispersion; 2-6 parts of inorganic fiber, 0.1-1 parts of coconut acid monoethanolamide, and 0.1-1 parts of 3-isocyanatepropyltrimethoxysilane are added and stirring is continued for 1-2 hours at room temperature, 0.1-1 parts of demulsifier are added and stirring is continued for 0.5-1 hour, centrifugation is carried out, the filter cake is washed with water, and the impact modifier is obtained after drying.

2. The method for preparing the impact modifier according to claim 1, characterized in that: The ammonium persulfate aqueous solution is a 4-6 wt % ammonium persulfate aqueous solution.

3. The method for preparing the impact modifier according to claim 1, characterized in that: The demulsifier is ethylene glycol.

4. The method for preparing the impact modifier according to claim 1, characterized in that: The inorganic fiber is one of glass fiber and modified glass fiber.

5. The method for preparing the impact modifier according to claim 4, characterized in that: The preparation method of the modified glass fiber is as follows, in parts by weight: Add 1-4 parts of silane coupling agent, 2-4 parts of nonylphenol polyoxyethylene ether, and 1-2 parts of emulsifier to 100-150 parts of water and stir for 0.5-1 hour to obtain a modified latex; add 4-6 parts of glass fiber to 40-60 parts of H2O2 aqueous solution, soak at 30-40℃ for 0.5-1 hour to increase the activity of surface hydroxyl groups, filter, wash the filter cake with water and dry it, and then add it to the above modified latex; Soaking at 40-50° C. for 1-2 hours, filtering, washing the filter cake with water and drying to obtain the modified glass fiber.

6. The method for preparing the impact modifier according to claim 5, characterized in that: The silane coupling agent is one of KH-171, KH-550 and KH-570.

7. The method for preparing the impact modifier according to claim 5, characterized in that: The emulsifier is one of sodium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium stearoyl lactylate and dodecyltrimethylammonium chloride.

8. The method for preparing the impact modifier according to claim 5, characterized in that: The H2O2 aqueous solution is a 2-6 wt% H2O2 aqueous solution.

9. An impact modifier, characterized in that: Prepared according to any one of claims 1 to 8.

10. An application of an impact modifier, characterized in that: The impact modifier as claimed in claim 9 can be applied to the preparation of PVC pipes.