A pressure-resistant PVC-U pipe and its preparation method

Abstract

The present invention discloses a pressure-resistant PVC-U pipe and a preparation method thereof, and relates to the technical field of PVC pipes. A pressure-resistant PVC-U pipe is provided with an inner pipe, a fiber-reinforced layer and an outer pipe in sequence from the inside to the outside, wherein the inner pipe and the outer pipe are both made by extrusion of PVC resin, and the fiber-reinforced layer includes silane-coupled modified glass fibers woven and wrapped around the outer surface of the inner pipe. By compounding a fiber-reinforced layer formed by weaving silane-coupled modified glass fibers in the PVC-U pipe, the ring stiffness and impact strength of the PVC-U pipe can be effectively improved, thereby improving the compressive performance of the PVC-U pipe.

Description

Technical Field

[0001] The invention relates to the technical field of PVC pipes, and in particular to a pressure-resistant PVC-U pipe and a preparation method thereof. Background Art

[0002] PVC (polyvinyl chloride) is the world's largest general-purpose plastic with a wide range of applications. Among them, PVC-U pipes, also known as rigid polyvinyl chloride pipes, have excellent physical and chemical properties, chemical corrosion resistance, high impact strength, low fluid resistance, 30% higher flow rate than cast iron pipes of the same caliber, aging resistance, long service life (≥50 years), light and durable, easy to transport and install, and lower price than cast iron pipes of the same specifications. It can save construction costs and effectively speed up the construction progress. Therefore, PVC-U pipes are also widely used in various fields.

[0003] However, due to its material formula and structure, conventional PVC-U pipes have low ring stiffness and poor compressive resistance. Under high external pressure, the pipes are prone to deformation or even rupture, which directly affects the normal use of the pipes and their service life. Summary of the invention

[0004] In order to improve the compression resistance of PVC-U pipes and increase the compressive strength of PVC-U pipes, the present application provides a pressure-resistant PVC-U pipe and a preparation method thereof.

[0005] In the first aspect, the present application provides a pressure-resistant PVC-U pipe adopting the following technical solution:

[0006] A pressure-resistant PVC-U pipe, which is provided with an inner pipe, a fiber-reinforced layer and an outer pipe in sequence from the inside to the outside;

[0007] The inner tube comprises the following raw materials in parts by weight: 80-100 parts of PVC resin, 3-6 parts of calcium zinc stabilizer, 3-6 parts of composite reinforcing toughening agent, 1-1.2 parts of ACR processing aid, 0.6-0.8 parts of PE wax, 0.8-1.2 parts of stearic acid, 1.4-2 parts of titanium dioxide, and 25-30 parts of inner tube reinforcing filler;

[0008] The fiber-reinforced layer comprises silane-coupled modified glass fibers which are braided, wound and coated on the outer surface of the inner tube;

[0009] The outer tube comprises the following raw materials in parts by weight: 40-50 parts of PVC resin, 1-1.5 parts of tribasic lead sulfate, 0.2-0.4 parts of dibasic lead phosphite, 0.6-0.8 parts of ACR processing aid, 1.2-1.6 parts of CPE, 0.3-0.5 parts of PE wax, 0.2-0.4 parts of stearic acid, 1-1.2 parts of titanium dioxide, 0.01-0.015 parts of fluorescent whitening agent, and 5-8 parts of outer tube toughening filler.

[0010] By adopting the above technical solution, a fiber reinforcement layer formed by woven glass fibers is compounded in the PVC-U pipe, and a multi-layer composite structure of inner pipe-fiber reinforcement layer-outer pipe is formed, which can effectively improve the ring stiffness and impact strength of the PVC-U pipe, and is beneficial to improving the compression resistance of the PVC-U pipe, and improving the compressive strength of the PVC-U pipe.

[0011] Optionally, the preparation of the silane-modified glass fiber comprises the following steps:

[0012] A1. First, fully soak and clean the glass fiber with anhydrous ethanol, and then fully immerse the glass fiber in a mixed acid solution after drying. After heating and continuous stirring, take it out after reaction, and then soak and clean it with distilled water for multiple times until the cleaning solution is neutral. After drying, the acid-etched glass fiber is obtained;

[0013] A2. Soak the acid-etched glass fiber obtained in step A1 in a KH550 silane coupling agent solution, heat and continuously stir to react, then take it out and dry it to obtain the silane-coupled modified glass fiber.

[0014] By adopting the above technical scheme and using KH550 silane coupling agent to modify the glass fiber, the compatibility between the glass fiber and PVC can be improved, so that the inner tube and the outer tube can be fully compounded with the fiber reinforcement layer, and the bonding strength between the pipe layers is improved. This is not only beneficial to improving the reinforcing effect of the fiber reinforcement layer formed by the glass fiber on the PVC-U pipe, but also can make the inner tube and the outer tube not easy to be delaminated and separated from the glass fiber after aging, which is beneficial to maintain the excellent compressive performance of the PVC-U pipe for a long time.

[0015] Optionally, the inner tube reinforcing filler is a mixture of ultrafine calcium carbonate and nano-magnesium hydroxide, and the ultrafine calcium carbonate and the nano-magnesium hydroxide are mixed in a weight ratio of 1:(0.1-0.3).

[0016] By adopting the above technical scheme, a small amount of magnesium hydroxide is mixed into the inner tube reinforcing filler, which can improve the flame retardant performance and thermal stability of PVC, and improve some performances of the pipe to a certain extent. When ultrafine calcium carbonate and nano magnesium hydroxide are mixed in a weight ratio of 1: (0.1-0.3), the comprehensive performance of PVC-U pipe is better, with good flame retardant performance and high ring stiffness and impact strength.

[0017] Optionally, the inner tube reinforcing filler is subjected to coupling pretreatment before mixing, and the coupling pretreatment comprises the following steps: A1, adding isopropyl titanate triisostearate to an ethanol solution of a certain concentration, then heating it to a certain temperature, and then slowly adding the inner tube reinforcing filler, maintaining the temperature after the addition and continuously stirring the reaction for a period of time, filtering, and then washing and filtering the filter residue with clean water for multiple times, and obtaining the inner tube reinforcing filler subjected to coupling pretreatment after drying.

[0018] By adopting the above technical scheme and using titanate coupling agent to modify the inner tube reinforcing filler, the compatibility of the inner tube reinforcing filler and PVC resin can be fully improved, so that the inner tube reinforcing filler can be evenly dispersed in the inner tube, which is not only conducive to the inner tube reinforcing filler to fully exert its reinforcing effect and further improve the ring stiffness and impact strength of the PVC-U pipe, but also can reduce the powdering and precipitation of the filler on the surface of the inner tube after aging, which is conducive to maintaining the reinforcing effect of the inner tube reinforcing filler for a long time.

[0019] Optionally, the inner tube is a double-layer hollow structure, wherein the inner tube includes an inner tube outer wall and an inner tube inner wall, a plurality of connecting ribs are arranged between the inner tube outer wall and the inner tube inner wall, the connecting ribs are evenly arranged and distributed along the circumference of the inner tube, and cavities are formed between adjacent connecting ribs and the inner tube outer wall and the inner tube inner wall.

[0020] By adopting the above technical solution, the inner tube is set as a double-layer hollow structure, and a number of connecting ribs cooperate with each other to improve the radial bending strength of the inner tube, which is beneficial to structurally improve the pipe's ability to resist external pressure loads, thereby improving the compression resistance of the PVC-U pipe.

[0021] Optionally, the outer tube toughening filler is ASA-coated modified ultrafine calcium carbonate.

[0022] By adopting the above technical scheme, the ultrafine calcium carbonate is modified by coating with ASA, which can not only effectively improve the compatibility of ultrafine calcium carbonate with PVC, promote the uniform dispersion of the toughening filler of the outer tube and fully combine with PVC, but also rely on the excellent weather resistance and good toughening effect of ASA to produce a synergistic effect with the ultrafine calcium carbonate, which is beneficial to further improve the weather resistance and mechanical properties of the outer tube.

[0023] Optionally, the preparation of the ASA-coated modified ultrafine calcium carbonate comprises the following steps:

[0024] C1. ASA high-rubber powder and ultrafine calcium carbonate are fully stirred and dispersed in a weight ratio of (1.2-1.5):1, the temperature is increased to 60-75°C and hot air drying is performed for 30-60 minutes to remove moisture, then the temperature is increased to 90-105°C and stirring is continued, calcium stearate is added while stirring, and the reaction is continued for 15-30 minutes. After cooling, the mixture is taken out and fully crushed to obtain ASA-coated ultrafine calcium carbonate; wherein the amount of calcium stearate added is 0.8%-1% of the weight of the ultrafine calcium carbonate.

[0025] By adopting the above technical scheme, the mixture of ASA high-gel powder and ultrafine calcium carbonate is first dried with hot air to reduce the influence of moisture on the melt coating of ASA high-gel powder. Secondly, calcium stearate can be used to improve the surface tension of ultrafine calcium carbonate, so that it can blend with molten ASA and improve the coating effect of molten ASA.

[0026] Optionally, the composite reinforcing and toughening agent is N9-2C.

[0027] By adopting the above technical scheme, the N9-2C type composite reinforcing and toughening agent is made by modifying and grafting PVC itself, and has the same polar splitting anisotropic structure as PVC, and has excellent compatibility and processing coordination with PVC, which is beneficial to improving the hot Vicat softening temperature of PVC-U pipes. At the same time, it can play a good coordination effect in improving the soft-hard contradiction of ring stiffness and impact strength, which is beneficial to improving the compressive performance of the pipe.

[0028] Optionally, the titanium dioxide is rutile titanium dioxide, and the fluorescent brightener is FP-127.

[0029] By adopting the above technical scheme, rutile titanium dioxide scatters light more greatly and also has excellent shielding effect on ultraviolet rays, while fluorescent brightener FP-127 has excellent whitening effect on PVC. By using rutile titanium dioxide and fluorescent brightener FP-127 to cooperate with each other, it is not only beneficial to improve the surface appearance of the outer tube, but also beneficial to improve the weather resistance of the outer tube, so that PVC-U can maintain good compressive resistance for a long time.

[0030] In the second aspect, the present application provides a method for preparing a pressure-resistant PVC-U pipe using the following technical solution:

[0031] A method for preparing a pressure-resistant PVC-U pipe comprises the following steps:

[0032] S1. Weigh PVC resin, calcium zinc stabilizer, composite reinforcing and toughening agent, ACR processing aid, PE wax, stearic acid, titanium dioxide and inner tube reinforcing filler according to weight components, then add them into a blender, stir and disperse them, and dry them to obtain inner tube material; weigh PVC resin, tribasic lead sulfate, dibasic lead phosphite, ACR processing aid, CPE, PE wax, stearic acid, titanium dioxide, fluorescent brightener, outer tube toughening filler according to weight components, then add them into a blender, stir and disperse them, and dry them to obtain outer tube material;

[0033] S2. The inner tube material is melt-extruded by the first extruder to obtain an inner tube, and then the silane-modified glass fiber is woven and wrapped around the outer surface of the inner tube by a braiding machine to form a fiber reinforcement layer. Finally, the outer tube material is melt-extruded by the second extruder and covered on the outer surface of the fiber reinforcement layer to form an outer tube. After the entire tube is completely cooled, a pressure-resistant PVU-U tube is obtained.

[0034] By adopting the above technical scheme, an inner tube is first extruded and then the surface of the inner tube is directly woven and wound with surface silane-coupled modified glass fiber to form a fiber reinforcement layer. Finally, an outer tube is extruded and composited on the outer surface of the fiber reinforcement layer. The production process is simple, the required equipment investment is small, the cost is low, and it is conducive to subsequent mass production.

[0035] In summary, the technical solution of this application has at least one of the following beneficial effects:

[0036] 1. By compounding a fiber reinforcement layer formed by woven glass fiber in the PVC-U pipe, the ring stiffness and impact strength of the PVC-U pipe can be effectively improved, thereby improving the compressive performance of the PVC-U pipe.

[0037] 2. By mixing a small amount of magnesium hydroxide into the inner tube reinforcing filler, the flame retardant properties and thermal stability of PVC can be improved, and some mechanical properties of the pipe can be improved to a certain extent.

[0038] 3. By using ASA coated modified ultrafine calcium carbonate as the outer tube toughening filler, it can not only effectively improve the compatibility of ultrafine calcium carbonate with PVC, promote the uniform dispersion of the outer tube toughening filler and fully combine with PVC, but also rely on the excellent weather resistance and good toughening effect of ASA, and produce a synergistic effect with ultrafine calcium carbonate, which can further improve the weather resistance and mechanical properties of the outer tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a cross-sectional view of a pressure-resistant PVC-U pipe in Example 1 of the present application.

[0040] Figure 2It is a cross-sectional view of a pressure-resistant PVC-U pipe in Example 7 of the present application.

[0041] Description of reference numerals:

[0042] 1. Inner tube; 11. Outer wall of inner tube; 12. Inner wall of inner tube; 13. Connecting ribs; 14. Cavity; 2. Fiber reinforced layer; 3. Outer tube. DETAILED DESCRIPTION

[0043] The present application is further described in detail below with reference to embodiments and comparative examples.

[0044] The PVC resin selected is SG-5 PVC resin powder.

[0045] The glass fiber was purchased from Jiujiang Lianfeng Glass Fiber Co., Ltd., and the model number was 2116, 100g alkali-free glass fiber.

[0046] The titanium dioxide was purchased from Pangang Group Co., Ltd. and the brand was R-248 rutile titanium dioxide.

[0047] The fluorescent brightener was purchased from Shanghai Lianben Fine Chemical Co., Ltd. and the brand name was FP-127.

[0048] The ultrafine calcium carbonate was purchased from Wuxinxin Materials Co., Ltd., and the brand name was VS-525 ultrafine calcium carbonate.

[0049] The composite reinforcing and toughening agent was purchased from Foshan Ruijian Composite Materials Co., Ltd. and the brand name is N9-2C PVC reinforcing and toughening agent.

[0050] Example

[0051] [Example 1]

[0052] A pressure-resistant PVC-U pipe, refer to Figure 1 , an inner tube 1, a fiber reinforced layer 2 and an outer tube 3 are arranged in sequence from the inside to the outside, wherein the inner tube 1 and the outer tube 3 are both single-layer structures.

[0053] In this embodiment, the inner tube 1 is prepared from the following raw materials by weight: 100kg PVC resin, 4.8kg calcium zinc stabilizer, 6kg composite reinforcing toughening agent, 1kg ACR processing aid, 0.6kg PE wax, 1kg stearic acid, 2kg titanium dioxide, and 30kg inner tube toughening filler.

[0054] The fiber-reinforced layer 2 is formed by weaving, winding and coating silane-coupled modified glass fibers on the outer surface of the inner tube.

[0055] The outer tube 3 is prepared from the following raw materials by weight: 50kg PVC resin, 1.2kg tribasic lead sulfate, 0.3kg dibasic lead phosphite, 0.8kg ACR processing aid, 1.2kg CPE, 0.4kg PE wax, 0.3kg stearic acid, 1kg titanium dioxide, 0.015kg fluorescent whitening agent, and 5kg outer tube toughening filler.

[0056] Among them, ultrafine calcium carbonate is used as the inner tube toughening filler and the outer surface toughening filler.

[0057] Wherein, the preparation of silane-modified glass fiber comprises the following steps:

[0058] A1. First, the glass fiber is fully soaked and cleaned with anhydrous ethanol, and then fully immersed in a mixed acid solution after drying, wherein the mixed acid solution includes a mixture of a 10% nitric acid solution and a 5% sulfuric acid solution in a ratio of 1:2, heated to 85°C and stirred for 30 minutes, then taken out, and then soaked and cleaned with distilled water for multiple times until the cleaning solution is neutral, and then dried to obtain an acid-etched glass fiber;

[0059] A2. Soak the acid-etched glass fiber obtained in step A1 in a KH550 silane coupling agent solution, heat to 60° C. and continue stirring for 15 minutes, then take it out and dry it to obtain the silane-modified glass fiber.

[0060] A pressure-resistant PVC-U pipe comprises the following preparation steps:

[0061] S1. Weigh PVC resin, calcium zinc stabilizer, composite reinforcing and toughening agent, ACR processing aid, PE wax, stearic acid, titanium dioxide and inner tube reinforcing filler according to weight components, then add them into a blender, stir and disperse them, and dry them to obtain inner tube material; weigh PVC resin, tribasic lead sulfate, dibasic lead phosphite, ACR processing aid, CPE, PE wax, stearic acid, titanium dioxide, fluorescent brightener, outer tube toughening filler according to weight components, then add them into a blender, stir and disperse them, and dry them to obtain outer tube material;

[0062] S2. The inner tube material is melt-extruded by the first extruder to obtain an inner tube 1 with a wall thickness of about 2 mm, and then the silane-modified glass fiber is woven and wrapped around the outer surface of the inner tube by a braiding machine to form a fiber reinforced layer 2. Finally, the outer tube material is melt-extruded by the second extruder and covered on the outer surface of the fiber reinforced layer 2 to form an outer tube 3 with a wall thickness of about 1 mm. The average outer diameter of the entire tube is about 160 mm. After the entire tube is completely cooled, a pressure-resistant PVU-U tube is obtained.

[0063] [Example 2]

[0064] A pressure-resistant PVC-U pipe, refer to Figure 1 , an inner tube 1, a fiber reinforced layer 2 and an outer tube 3 are arranged in sequence from the inside to the outside, wherein the inner tube 1 and the outer tube 3 are both single-layer structures.

[0065] In this embodiment, the inner tube 1 is prepared by the following weight raw materials: 80kg PVC resin, 3kg calcium zinc stabilizer, 3kg composite reinforcing toughening agent, 1kg ACR processing aid, 0.8kg PE wax, 1.2kg stearic acid, 1.4kg titanium dioxide, and 25kg inner tube reinforcing filler.

[0066] The fiber-reinforced layer 2 is formed by weaving, winding and coating silane-coupled modified glass fibers on the outer surface of the inner tube.

[0067] The outer tube 3 is prepared from the following raw materials in parts by weight:

[0068] 45kg PVC resin, 1.5kg tribasic lead sulfate, 0.4kg dibasic lead phosphite, 0.6kg ACR processing aid, 1.4kg CPE, 0.3kg PE wax, 0.2kg stearic acid, 1.2kg titanium dioxide, 0.012kg fluorescent brightener, 6kg outer tube toughening filler.

[0069] Among them, ultrafine calcium carbonate is used as the reinforcing filler of the inner tube, and ultrafine calcium carbonate is used as the toughening filler of the outer tube.

[0070] Wherein, the preparation of silane-modified glass fiber comprises the following steps:

[0071] A1. First, the glass fiber is fully soaked and cleaned with anhydrous ethanol, and then fully immersed in a mixed acid solution after drying, wherein the mixed acid solution includes a mixture of a 10% nitric acid solution and a 5% sulfuric acid solution in a ratio of 1:2, heated to 70°C and stirred for 30 minutes, then taken out, and then soaked and cleaned with distilled water for multiple times until the cleaning solution is neutral, and then dried to obtain an acid-etched glass fiber;

[0072] A2. Soak the acid-etched glass fiber obtained in step A1 in a KH550 silane coupling agent solution, heat to 50° C., continue stirring and reacting for 30 minutes, then take it out and dry it to obtain a silane-coupled modified glass fiber.

[0073] A pressure-resistant PVC-U pipe comprises the following preparation steps:

[0074] S1. Weigh PVC resin, calcium zinc stabilizer, composite reinforcing and toughening agent, ACR processing aid, PE wax, stearic acid, titanium dioxide and inner tube reinforcing filler according to weight components, then add them into a blender, stir and disperse them, and dry them to obtain inner tube material; weigh PVC resin, tribasic lead sulfate, dibasic lead phosphite, ACR processing aid, CPE, PE wax, stearic acid, titanium dioxide, fluorescent brightener, outer tube toughening filler according to weight components, then add them into a blender, stir and disperse them, and dry them to obtain outer tube material;

[0075] S2. The inner tube material is melt-extruded by the first extruder to obtain an inner tube 1 with a wall thickness of about 2 mm, and then the silane-modified glass fiber is woven and wrapped around the outer surface of the inner tube by a braiding machine to form a fiber reinforced layer 2. Finally, the outer tube material is melt-extruded by the second extruder and covered on the outer surface of the fiber reinforced layer 2 to form an outer tube 3 with a wall thickness of about 1 mm. The average outer diameter of the entire tube is about 160 mm. After the entire tube is completely cooled, a pressure-resistant PVU-U tube is obtained.

[0076] [Example 3]

[0077] A pressure-resistant PVC-U pipe, refer to Figure 1 , an inner tube 1, a fiber reinforced layer 2 and an outer tube 3 are arranged in sequence from the inside to the outside, wherein the inner tube 1 and the outer tube 3 are both single-layer structures.

[0078] In this embodiment, the inner tube 1 is prepared by the following weight raw materials: 90kg PVC resin, 6kg calcium zinc stabilizer, 4kg composite reinforcing toughening agent, 1.2kg ACR processing aid, 0.8kg PE wax, 0.8kg stearic acid, 2kg titanium dioxide, and 27.5kg inner tube reinforcing filler.

[0079] The fiber-reinforced layer 2 is formed by weaving, winding and coating silane-coupled modified glass fibers on the outer surface of the inner tube.

[0080] The outer tube 3 is prepared from the following raw materials in parts by weight:

[0081] 45kg PVC resin, 1.5kg tribasic lead sulfate, 0.4kg dibasic lead phosphite, 0.6kg ACR processing aid, 1.4kg CPE, 0.3kg PE wax, 0.2kg stearic acid, 1.2kg titanium dioxide, 0.012kg fluorescent brightener, 6kg outer tube toughening filler.

[0082] Among them, the inner tube reinforcing filler includes a mixture of ultrafine calcium carbonate and nano magnesium hydroxide. Specifically, the ultrafine calcium carbonate and nano magnesium hydroxide are mixed in a weight ratio of 1:0.1, that is, in this embodiment, the addition amount of ultrafine calcium carbonate is 25kg, and the addition amount of nano magnesium hydroxide is 2.5kg; the outer tube toughening filler is ultrafine calcium carbonate.

[0083] Wherein, the preparation of silane-modified glass fiber comprises the following steps:

[0084] A1. First, the glass fiber is fully soaked and cleaned with anhydrous ethanol, and then fully immersed in a mixed acid solution after drying, wherein the mixed acid solution includes a mixture of a 10% nitric acid solution and a 5% sulfuric acid solution in a ratio of 1:2, heated to 70°C and stirred for 30 minutes, then taken out, and then soaked and cleaned with distilled water for multiple times until the cleaning solution is neutral, and then dried to obtain an acid-etched glass fiber;

[0085] A2. Soak the acid-etched glass fiber obtained in step A1 in a KH550 silane coupling agent solution, heat to 50° C., continue stirring and reacting for 30 minutes, then take it out and dry it to obtain a silane-coupled modified glass fiber.

[0086] A pressure-resistant PVC-U pipe comprises the following preparation steps:

[0087] S1. Weigh PVC resin, calcium zinc stabilizer, composite reinforcing and toughening agent, ACR processing aid, PE wax, stearic acid, titanium dioxide and inner tube reinforcing filler according to weight components, then add them into a blender, stir and disperse them, and dry them to obtain inner tube material; weigh PVC resin, tribasic lead sulfate, dibasic lead phosphite, ACR processing aid, CPE, PE wax, stearic acid, titanium dioxide, fluorescent brightener, outer tube toughening filler according to weight components, then add them into a blender, stir and disperse them, and dry them to obtain outer tube material;

[0088] S2. The inner tube material is melt-extruded by the first extruder to obtain an inner tube 1 with a wall thickness of about 2 mm, and then the silane-modified glass fiber is woven and wrapped around the outer surface of the inner tube by a braiding machine to form a fiber reinforced layer 2. Finally, the outer tube material is melt-extruded by the second extruder and covered on the outer surface of the fiber reinforced layer 2 to form an outer tube 3 with a wall thickness of about 1 mm. The average outer diameter of the entire tube is about 160 mm. After the entire tube is completely cooled, a pressure-resistant PVU-U tube is obtained.

[0089] [Example 4]

[0090] A pressure-resistant PVC-U pipe, which differs from [Example 1] in that the inner pipe reinforcing filler used is different.

[0091] In this embodiment, the inner tube reinforcing filler is replaced by an equal amount of a mixture of ultrafine calcium carbonate and nano-magnesium hydroxide. Specifically, the ultrafine calcium carbonate and nano-magnesium hydroxide are mixed in a weight ratio of 1:0.2, that is, in this embodiment, the addition amount of ultrafine calcium carbonate is 25 kg, and the addition amount of nano-magnesium hydroxide is 5 kg.

[0092] [Example 5]

[0093] A pressure-resistant PVC-U pipe, which differs from [Example 1] in that the inner pipe reinforcing filler used is different.

[0094] In this embodiment, the inner tube reinforcing filler is replaced by an equal amount of a mixture of ultrafine calcium carbonate and nano magnesium hydroxide. Specifically, the ultrafine calcium carbonate and nano magnesium hydroxide are mixed in a weight ratio of 1:0.3, that is, in this embodiment, the addition amount of ultrafine calcium carbonate is 23.08 kg, and the addition amount of nano magnesium hydroxide is 6.92 kg.

[0095] [Example 6]

[0096] A pressure-resistant PVC-U pipe, which differs from [Example 4] in that the inner pipe reinforcing filler used is different.

[0097] In this embodiment, the inner tube reinforcing filler is subjected to coupling pretreatment before being mixed and added. Specifically, the coupling pretreatment of the inner tube reinforcing filler includes the following processing steps:

[0098] B1. Add isopropyl titanate triisostearate to an 80% ethanol solution, then heat to 50°C, slowly add the inner tube reinforcing filler within 30 minutes, maintain the temperature and continue stirring the reaction for 60 minutes after the addition is completed, filter, and then use clean water to wash and filter the filter residue several times, and obtain the inner tube reinforcing filler pretreated by coupling after drying.

[0099] [Example 7]

[0100] A pressure-resistant PVC-U pipe, which differs from [Example 6] in that the structure of the inner pipe is different.

[0101] In this embodiment, refer to Figure 2 The inner tube 1 is a double-layer hollow structure. Specifically, the inner tube 1 includes an inner tube outer wall 11 and an inner tube inner wall 12. A plurality of connecting ribs 13 are arranged between the inner tube outer wall 11 and the inner tube inner wall 12. The plurality of connecting ribs 13 are evenly arranged along the circumference of the inner tube 1, and a certain cavity 14 is formed between adjacent connecting ribs 13 and the inner tube outer wall 11 and the inner tube inner wall 12.

[0102] Furthermore, in this embodiment, the thickness of the inner tube outer wall 11 and the inner tube inner wall 12 is about 1 mm, and the overall thickness of the inner tube 1 is about 3.5 mm.

[0103] [Example 8]

[0104] A pressure-resistant PVC-U pipe, which differs from [Example 7] in that the toughening filler of the outer pipe is different.

[0105] In this embodiment, the outer tube toughening filler is replaced by ASA coated modified ultrafine calcium carbonate in equal amounts. Specifically, the preparation of ASA coated modified ultrafine calcium carbonate includes the following steps:

[0106] C1. Fully mix and disperse 6kg of ASA high-gel powder and 5kg of ultrafine calcium carbonate. At this time, the ASA high-gel powder and the ultrafine calcium carbonate are mixed in a weight ratio of 1.2:1. The temperature is raised to 75°C and hot air drying is performed for 30 minutes to remove moisture. Then the temperature is raised to 90°C and stirred continuously. Calcium stearate is added while stirring, wherein the amount of calcium stearate added is 0.04kg. The reaction is continued for 30 minutes. After cooling, it is taken out and fully crushed to obtain ASA-coated ultrafine calcium carbonate.

[0107] [Example 9]

[0108] A pressure-resistant PVC-U pipe, which differs from [Example 7] in that the toughening filler of the outer pipe is different.

[0109] In this embodiment, the outer tube toughening filler is replaced by ASA coated modified ultrafine calcium carbonate in equal amounts. Specifically, the preparation of ASA coated modified ultrafine calcium carbonate includes the following steps:

[0110] C1. Fully mix and disperse 7.5kg ASA high-gel powder and 5kg ultrafine calcium carbonate. At this time, ASA high-gel powder and ultrafine calcium carbonate are mixed in a weight ratio of 1.5:1. The temperature is raised to 60°C and hot air drying is performed for 60 minutes to remove moisture. Then the temperature is raised to 105°C and stirred continuously. Calcium stearate is added while stirring, wherein the amount of calcium stearate added is 0.05kg. The reaction is continued for 30 minutes. After cooling, it is taken out and fully crushed to obtain ASA-coated ultrafine calcium carbonate.

[0111] Comparative Example

[0112] [Comparative Example 1]

[0113] A PVC-U pipe, which differs from [Example 1] in that no fiber reinforcement layer 2 is provided between the inner pipe 1 and the outer pipe 3.

[0114] [Comparative Example 2]

[0115] A PVC-U pipe, which differs from [Example 1] in that the fiber reinforcement layer is different.

[0116] In this comparative example, the fiber-reinforced layer 2 is formed by directly weaving and winding glass fibers and coating the outer surface of the inner tube.

[0117] Performance test data

[0118] 1. Compression test: According to GB / T 9647-2015 Determination of ring stiffness of thermoplastic plastic pipes, ring stiffness test was carried out, and the ring stiffness (kN / m 2 ).

[0119] 2. Impact resistance test: According to the provisions of GB / T 18743.1-2022 Determination of simply supported beam impact strength of thermoplastic plastic pipes Part 1: General test method" and GB / T 18743.2-2022 Determination of simply supported beam impact strength of thermoplastic plastic pipes Part 2: Test conditions for pipes of different materials, single notch impact test is carried out according to the provisions of sample type 6 in method B, and the average impact strength (kJ / mm 2 ).

[0120] 3. Weathering test: First, an automatic cycle exposure test was performed according to the provisions of Table 3 Method A Cycle No. 1 in "GB / T 16422.2-2014 Plastic Laboratory Light Source Exposure Test Method", with an exposure time of 1000 h. The outer surface of the outer tube of the tube was facing the side of the xenon light source, and the inner wall of the inner tube was facing away from the side of the xenon light source. After aging, the surface state of the tube was observed and the impact resistance test was performed, and the appearance changes and average impact strength of each embodiment and comparative example after xenon lamp aging were recorded.

[0121] 4. Test according to GB 8624-2006 Classification of Combustion Performance of Building Materials and Products, and record the combustion performance classification of each embodiment and comparative example according to Section 5.1.3.

[0122] Table 1 Pipe physical properties test data

[0123]

[0124]

[0125] Combining Example 1 with Comparative Examples 1-2 and the data in Table 1, it can be seen that when a fiber-reinforced layer 2 formed by weaving glass fibers is compounded in PVC-U, and a multi-layer composite structure of an inner tube 1, a fiber-reinforced layer 2, and an outer tube 3 is sequentially formed, the ring stiffness and impact strength of the PVC-U pipe can be effectively improved, which is beneficial to improving the compression resistance of the PVC-U pipe and improving the compressive strength of the PVC-U pipe. Secondly, after the glass fiber is modified by a silane coupling agent, the reinforcing effect of the fiber-reinforced layer 2 formed by the glass fiber on the PVC-U pipe can be further improved, and after long-term aging, the glass fiber and the inner tube 1 and the outer tube 3 will not be delaminated and separated. This may be because the compatibility between unmodified glass fiber and PVC resin is not good, resulting in low bonding strength between pipe layers during multi-layer composite. PVC resin is easily separated from glass fiber after aging. After the glass fiber is surface treated with silane coupling agent, the compatibility between glass fiber and PVC can be improved, so that the inner tube 1 and the outer tube 3 can be fully composited with the fiber reinforcement layer 2, the bonding strength between the pipe layers is improved, and the inner tube 1 and the outer tube 3 are not easy to separate from the glass fiber after aging, which is conducive to maintaining the excellent compressive performance of PVC-U pipes for a long time.

[0126] Combining Example 1 with Example 4-5 and the data in Table 1, it can be known that by mixing a small amount of magnesium hydroxide into the inner tube reinforcing filler, the flame retardant properties of the pipe can be improved, and the impact resistance of the pipe can be improved in a small amount at the same time. As the content of magnesium hydroxide increases and the content of ultrafine calcium carbonate decreases, the ring stiffness and impact strength of the inner tube 1 decrease to a certain extent, resulting in the deterioration of the mechanical properties of the pipe. This may be due to the fact that magnesium hydroxide has certain flame retardant properties and thermal stability, and can improve the flame retardant properties and thermal stability of PVC when mixed in a small amount. At the same time, magnesium hydroxide has a certain toughening effect on PVC, thereby improving some of the properties of the pipe. However, in the inner tube reinforcing filler system mixed with magnesium hydroxide and nano-calcium carbonate, nano-calcium carbonate plays a major reinforcing role. As the content of magnesium hydroxide increases and the content of nano-calcium carbonate decreases, the main reinforcing effect of the inner tube reinforcing filler decreases, thereby resulting in a decrease in the mechanical properties of the pipe.

[0127] Combining Example 1 with Example 6 and the data in Table 1, it can be seen that by modifying the inner tube reinforcing filler with a titanate coupling agent, the ring stiffness and impact strength of the pipe can be further improved. This may be because the titanate coupling agent can fully improve the compatibility of the inner tube reinforcing filler with the PVC resin, not only making the inner tube reinforcing filler uniformly dispersed in the inner tube 1, further exerting a reinforcing effect, but also reducing the powdering and precipitation of the filler on the surface of the inner tube 1 after long-term aging, and maintaining the reinforcing effect of the inner tube reinforcing filler for a long time.

[0128] Combining Example 1 with Example 7 and the data in Table 1, it can be seen that setting the inner tube 1 as a double-layer hollow structure can effectively improve the ring stiffness of the tube, which is conducive to improving the tube's ability to resist external pressure loads. This may be because in the inner tube of the double-layer hollow structure, a number of connecting ribs are arranged along the circumference, and the several connecting ribs cooperate with each other to further improve the radial bending strength of the inner tube, thereby improving the ring stiffness and impact strength of the tube by improving the overall structure of the tube.

[0129] Combining Example 1 with Examples 8-9 and the data in Table 1, it can be seen that the use of ASA-coated modified ultrafine calcium carbonate as an outer tube toughening filler can slightly improve the impact strength of the pipe, and can also effectively improve the aging resistance of the surface of the pipe appearance, and reduce the occurrence of yellowing. This may be because ASA has excellent weather resistance, a certain toughening effect, and good compatibility with PVC. After using ASA to coat ultrafine calcium carbonate, not only the compatibility of ultrafine calcium carbonate with PVC is improved, and then the outer tube toughening filler is evenly dispersed and fully combined with PVC is promoted, and ASA and ultrafine calcium carbonate cooperate with each other, which is conducive to further improving the weather resistance and mechanical properties of the outer tube 3.

[0130] This specific implementation manner is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the specific implementation manner as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A pressure-resistant PVC-U pipe, characterized in that: An inner tube (1), a fiber reinforcement layer (2) and an outer tube (3) are sequentially arranged from the inside to the outside; The inner tube (1) comprises the following raw materials in parts by weight: 80-100 parts of PVC resin, 3-6 parts of calcium zinc stabilizer, 3-6 parts of composite reinforcing toughening agent, 1-1.2 parts of ACR processing aid, 0.6-0.8 parts of PE wax, 0.8-1.2 parts of stearic acid, 1.4-2 parts of titanium dioxide, and 25-30 parts of inner tube reinforcing filler pretreated by coupling, wherein the inner tube reinforcing filler is a mixture of ultrafine calcium carbonate and nano magnesium hydroxide in a weight ratio of 1:(0.1-0.3), and is pretreated by coupling with isopropyl triisostearate titanate; The fiber reinforcement layer (2) is formed by weaving and winding silane-coupled modified glass fibers and coating the outer surface of the inner tube (1); The outer tube (3) comprises the following raw materials in parts by weight: 40-50 parts of PVC resin, 1-1.5 parts of tribasic lead sulfate, 0.2-0.4 parts of dibasic lead phosphite, 0.6-0.8 parts of ACR processing aid, 1.2-1.6 parts of CPE, 0.3-0.5 parts of PE wax, 0.2-0.4 parts of stearic acid, 1-1.2 parts of titanium dioxide, 0.01-0.015 parts of fluorescent whitening agent, and 5-8 parts of ASA coated modified ultrafine calcium carbonate, wherein the ASA coated modified ultrafine calcium carbonate is obtained by modifying ultrafine calcium carbonate with ASA high rubber powder and calcium stearate; The inner tube (1) is a double-layer hollow structure, the inner tube (1) comprising an inner tube outer wall (11) and an inner tube inner wall (12), a plurality of connecting ribs (13) are arranged between the inner tube outer wall (11) and the inner tube inner wall (12), the connecting ribs (13) are evenly arranged and distributed along the circumference of the inner tube (1), and cavities (14) are formed between adjacent connecting ribs (13) and the inner tube outer wall (11) and the inner tube inner wall (12).

2. A pressure-resistant PVC-U pipe according to claim 1, characterized in that: The preparation of the silane-coupled modified glass fiber comprises the following steps: A1. First, fully soak and clean the glass fiber with anhydrous ethanol, and then fully immerse the glass fiber in a mixed acid solution after drying. After heating and continuous stirring, take it out after reaction, and then soak and clean it with distilled water for multiple times until the cleaning solution is neutral. After drying, the acid-etched glass fiber is obtained; A2. Soak the acid-etched glass fiber obtained in step A1 in a KH550 silane coupling agent solution, heat and continuously stir to react, then take it out and dry it to obtain the silane-coupled modified glass fiber.

3. The pressure-resistant PVC-U pipe according to claim 1, characterized in that: The coupling pretreatment of the inner tube reinforcing filler comprises the following steps: Add isopropyl titanate triisostearate to the ethanol solution, heat it, and then slowly add the inner tube reinforcing filler. After the addition is completed, maintain the temperature and continue to stir the reaction, filter, and then use clean water to wash and filter the filter residue several times. After drying, obtain the coupling pretreated inner tube reinforcing filler.

4. The pressure-resistant PVC-U pipe according to claim 1, characterized in that: The preparation of the ASA coated modified ultrafine calcium carbonate comprises the following steps: ASA high-rubber powder and ultrafine calcium carbonate are fully stirred and dispersed in a weight ratio of (1.2-1.5):1, the temperature is raised to 60-75°C and hot air drying is performed for 30-60 minutes to remove moisture, and then the temperature is raised to 90-105°C and stirred continuously, calcium stearate is added while stirring, and the reaction is continued for 15-30 minutes. After cooling, the mixture is taken out and fully crushed to obtain ASA-coated ultrafine calcium carbonate; Wherein, the added amount of calcium stearate is 0.8%-1% by weight of the ultrafine calcium carbonate.

5. The pressure-resistant PVC-U pipe according to claim 1, characterized in that: The composite reinforcing and toughening agent is N9-2C.

6. The pressure-resistant PVC-U pipe according to claim 1, characterized in that: The titanium dioxide is rutile titanium dioxide, and the fluorescent brightener is FP-127.

7. The method for preparing any one of the pressure-resistant PVC-U pipes according to claims 1 to 6, characterized in that: The following steps are involved: S1. Weigh PVC resin, calcium zinc stabilizer, composite reinforcing and toughening agent, ACR processing aid, PE wax, stearic acid, titanium dioxide and inner tube reinforcing filler according to weight components, then add them into a blender, stir and disperse them, and dry them to obtain inner tube material; weigh PVC resin, tribasic lead sulfate, dibasic lead phosphite, ACR processing aid, CPE, PE wax, stearic acid, titanium dioxide, fluorescent brightener, outer tube toughening filler according to weight components, then add them into a blender, stir and disperse them, and dry them to obtain outer tube material; S2. The inner tube material is melt-extruded by a first extruder to obtain an inner tube (1). The silane-modified glass fiber is then braided and wrapped around the outer surface of the inner tube (1) by a braiding machine to form a fiber-reinforced layer (2). Finally, the outer tube material is melt-extruded by a second extruder and covered on the outer surface of the fiber-reinforced layer (2) to form an outer tube (3). After the entire tube is completely cooled, a pressure-resistant PVC-U tube is obtained.

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