Novel PTFE composite material for corrugated pipe and preparation method thereof

Abstract

The invention relates to a PTFE composite material for a novel corrugated pipe and a preparation method of the PTFE composite material, and belongs to the technical field of composite materials. The PTFE composite material for the novel corrugated pipe is prepared from the following raw materials in parts by weight: 70-90 parts of novel modified PTFE resin, 20-35 parts of a reactive ionomer, 8-12 parts of a toughening filler, 1-3 parts of a lubricant and 1-3 parts of an antistatic agent. The preparation method of the PTFE composite material comprises the following steps: weighing the raw materials according to the formula, adding the novel modified PTFE resin, the reactive ionomer, the toughening filler, the lubricant and the antistatic agent into a mixer, and stirring and mixing to obtain a mixture; and transferring the mixed material into a double-screw extruder for melt extrusion, cooling and pelletizing to obtain the PTFE composite material for the novel corrugated pipe. The novel modified PTFE resin is combined with the reactive ionomer in an ionic bond manner, so that the compatibility of the novel modified PTFE resin and the reactive ionomer is remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite materials, in particular to a novel PTFE composite material for corrugated pipes and a preparation method thereof. BACKGROUND

[0002] As a common elastic member, corrugated pipes utilize the elasticity of materials to realize conversion, compensation, connection and energy storage and other functions, have good stretchability, corrosion resistance, high pressure resistance, light weight and other characteristics, and thus have a wide range of applications in the fields of petroleum chemical industry, construction, water supply and drainage, electric power communication and the like, and play an important role in connection, compensation, sealing and shock absorption. Due to its compact structure and the use of corrugated structure design, the pipe has great flexibility in bending and stretching, and is convenient to install and disassemble.

[0003] Efforts to improve the performance of corrugated pipes have always been pursued by those skilled in the art. Chinese patent CN119060477A discloses a PTFE composite material for corrugated pipe fittings and a preparation method thereof. The preparation method comprises the following steps: weighing each raw material according to the formula, mixing and stirring the modified PTFE resin, polyamide resin, polyethylene resin, toughening filler, lubricant and antistatic agent in a mixer to obtain a mixture; transferring the mixture into a twin-screw extruder for melt extrusion, cooling and granulation to obtain the PTFE composite material for corrugated pipe fittings. In the invention, the modified PTFE resin is prepared by using tetrafluoroethylene, perfluorobutyl ethylene and perfluoro-2-butene as monomers and then treating with a modification liquid after polymerization. It is claimed in the invention that the modified PTFE resin is prepared by using tetrafluoroethylene, perfluorobutyl ethylene and perfluoro-2-butene as monomers and then treating with a modification liquid after polymerization. The polymerization modification greatly improves the processing performance of the PTFE resin while maintaining its original physical and chemical properties. By adding a certain proportion of perfluorobutyl ethylene and perfluoro-2-butene for copolymerization, the monomers are introduced into the molecular structure of the PTFE resin, breaking the original linear, unbranched and symmetrical structure, thereby reducing the melt viscosity of the PTFE resin and improving the processing performance.

[0004] However, in practice, this scheme has the following problems: even if the melt viscosity of the PTFE resin is reduced by using perfluoro-2-butene and other monomers for copolymerization, the melt viscosity of the modified PTFE resin obtained is still as high as 10 6 -10 7 Pa·s (380℃). At the same time, the viscosities of polyamide (PA) and polyethylene (PE) are: the viscosity of PA at 240℃ is 10 2 -10 3 Pa·s, and the viscosity of PE at 200℃ is 10 3 -10 4Pa·s, so when the three are blended at 260℃, the viscosity difference between PTFE and PA / PE reaches 3-5 orders of magnitude, thus it is impossible to realize molecular dispersion, phase separation is inevitable, resulting in poor compatibility, which is a potential fatal defect for corrugated pipes that need long-term pressure. SUMMARY

[0005] The present application aims to provide a new type of PTFE composite material for corrugated pipes and a preparation method thereof, to solve the problem of poor compatibility of traditional modified PTFE resin combined with polyamide (PA) and polyethylene (PE) components to prepare PTFE composite material for corrugated pipes.

[0006] A new type of PTFE composite material for corrugated pipes in the present application is prepared from the following raw materials by weight: 70-90 parts of a new modified PTFE resin, 20-35 parts of a reactive ionomer, 8-12 parts of a toughening filler, 1-3 parts of a lubricant, and 1-3 parts of an antistatic agent; The preparation method of the new modified PTFE resin is as follows: tetrafluoroethylene and 3.0-4.0 mol% of perfluoro-2-butene monomers are mixed with ammonium persulfate initiator at 80±0.5℃ and 2.0Mpa to undergo emulsion polymerization reaction; after a period of reaction, 0.8-1.2 mol% of perfluoro octyl acrylate is added, and the reaction continues until the concentration of the terminal -COOH of the reaction product is 0.05-0.10 mmol / g, and then the new modified PTFE resin is obtained after drying; The reactive ionomer is a block copolymer having the structure shown in formula (I) as follows: PFPE(Mn=3500-4500)-b-P(E-co-AA-Na) Formula (I); Wherein, PFPE represents a perfluoropolyether chain segment with a number average molecular weight of 3500-4500; P(E-co-AA-Na) represents a copolymer chain segment of ethylene and sodium acrylate; Wherein, the amount of acrylic acid units accounts for 15-20 mol% of the total monomer charge of the ethylene-acrylic acid copolymer chain segment; the mass of the sodium acrylate chain segment accounts for 35 ± 2 wt% of the total mass of the entire reactive ionomer.

[0007] Further, the preparation method of the reactive ionomer is as follows, including the following steps: S1. Synthesis of macromolecular initiator (PFPE-Br): PFPE-diol (Mn=4000±500), 2-bromoisobutyryl bromide (BIBB) and triethylamine (TEA) in a molar ratio of 1 : 2.1 : 2.2 in anhydrous tetrahydrofuran under an inert atmosphere and ice bath conditions, and after the reaction is completed, the macromolecular initiator PFPE-Br with bromoisobutyrate groups at both ends is obtained by precipitation and drying; the end of the reaction is judged by the disappearance of the O-H characteristic peak (3400 cm -1 ) in Fourier transform infrared spectroscopy (FTIR); S2. Synthesis of block copolymer (PFPE-b-P(E-co-AA)): PFPE-Br obtained in step S1, acrylic acid (AA), catalyst CuBr, and ligand PMDETA are dissolved in anisole solvent, and after oxygen removal by freeze-vacuum-thaw cycle, ethylene gas is filled into the reaction system to a pressure of 0.5 MPa, and atom transfer radical polymerization (ATRP) reaction is carried out at 90±2 ° for 8 hours; wherein the molar ratio of the acrylic acid to ethylene is 15-20 : 80-85; the end of the reaction is judged by determining the acid value of the reactant to be 120 ± 5 mg KOH / g; after the reaction is completed, copper is removed, precipitated, and dried to obtain the block copolymer PFPE-b-P(E-co-AA); S3. Preparation of ionomer by salt formation reaction: The block copolymer PFPE-b-P(E-co-AA) obtained in step S2 is dissolved in a mixed solvent of ethanol and water, and at 75 ± 2 °C, an aqueous sodium hydroxide solution with an equimolar amount of carboxyl and an excess of 5% is added for neutralization reaction for 4 hours; the end of the reaction is judged by monitoring the pH value of the reaction solution to 7.0 ± 0.2 by potentiometric titration method, and by FTIR confirming that the C=O stretching vibration peak at 1700 cm -1 is basically disappeared, and COO - characteristic peak appears at 1560 cm -1 ; after the reaction is completed, it is concentrated and dried to obtain the final reactive ionomer PFPE-b-P(E-co-AA-Na).

[0008] Further, the melt flow rate of the new modified PTFE resin under test conditions of 190 °C and 2.16 kg is 11.8-12.4 g / 10 min.

[0009] The application also provides a preparation method of a new PTFE composite material for corrugated pipes, comprising the following steps: According to the formula, each raw material is weighed, and the new modified PTFE resin, the reactive ionomer, the toughening filler, the lubricant, and the antistatic agent are added to a mixer for stirring and mixing to obtain a mixture; The above mixture is transferred into a twin-screw extruder for melt extrusion, cooling, and granulation to obtain the novel PTFE composite material for corrugated pipes.

[0010] The mechanism of the present application: In the novel modified PTFE in the present application, during the preparation process: tetrafluoroethylene + perfluoro-2-butene (3 mol%) → emulsion polymerization (80°C, ammonium persulfate initiation) → branched PTFE (melt viscosity reduced to 10 5 Pa·s), and then perfluoro octyl acrylate is added at the end of polymerization, thereby introducing carboxyl groups into the PTFE branches.

[0011] At the same time, the reactive ionomer in the present application: perfluoropolyether (PFPE, Mn=3500-4500)-b-poly(ethylene-co-sodium acrylate), wherein the perfluoropolyether segment is similar in structure to the novel modified PTFE and the two are combined through physical entanglement and van der Waals forces, and the sodium acrylate segment is combined with the carboxyl groups at the end of the PTFE branches through ionic bonds.

[0012] The beneficial effects of the present application are: The novel PTFE composite material for corrugated pipes in the present application is based on the novel modified PTFE resin and the reactive ionomer as the main body for preparing the PTFE composite material for corrugated pipes, and the traditional polyamide (PA) and polyethylene (PE) raw materials are discarded, and the new modified PTFE resin is combined with the reactive ionomer through ionic bonds during the combination process, so the compatibility is significantly improved; at the same time, the PTFE composite material in the present application has a notch impact strength level comparable to the PTFE composite material disclosed in the prior art CN119060477A, but its tensile strength is even more excellent. DETAILED DESCRIPTION

[0013] The embodiments of the present application will be described in more detail below with reference to the examples. Although the embodiments show the embodiments of the present application, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present application more thorough and complete, and to convey the scope of the present application to those skilled in the art. Example 1

[0014] The novel PTFE composite material for corrugated pipes in this example 1 is composed of the following raw materials by weight: novel modified PTFE resin 70 parts, reactive ionomer 35 parts, toughening filler 12 parts, lubricant 2 parts, and antistatic agent 1 part.

[0015] The preparation of the novel modified PTFE resin is as follows: The monomers of tetrafluoroethylene and 4.0 mol% perfluoro-2-butene are mixed with ammonium persulfate initiator at 80±0.5°C and 2.0 MPa to undergo emulsion polymerization; after a period of reaction, 1.0 mol% perfluoro octyl acrylate is added, and the reaction continues until the concentration of the end-COOH of the reaction product is 0.08 mmol / g, and the new modified PTFE resin is obtained after drying.

[0016] The melt flow rate of the new modified PTFE resin under the test conditions of 190° and 2.16 kg is 12.2 g / 10 min. Specifically, the preparation of the reactive ionomer includes the following steps: S1. Preparation of the macroinitiator (PFPE-Br): A 1L three-necked round-bottom flask equipped with a stirrer, a dropping funnel and a nitrogen inlet tube was charged with 100 g of perfluoropolyether diol (PFPE-diol, Mn=4000, 0.025 mol) and 500 mL of anhydrous THF. Under nitrogen protection and ice water bath cooling, 16.2 g of triethylamine (TEA, 0.16 mol) was slowly added dropwise, and after the dropwise addition was completed, the mixture was stirred for 15 minutes. Then, 15.3 g of 2-bromoisobutyryl bromide (BIBB, 0.066 mol) was slowly added dropwise at <5°C, and the dropwise addition was completed in about 1 hour. The ice bath was removed, and the reaction was continued at room temperature (25°C) for 12 hours. The disappearance of the O-H characteristic absorption peak at 3400 cm -1 The reaction solution was filtered to remove triethylamine hydrochloride, and the filtrate was concentrated by rotary evaporation, then poured into cold methanol at -20°C for precipitation. The white solid was collected by filtration, washed with cold methanol, and dried at 60°C under vacuum for 24 hours to obtain the product PFPE-Br 102 g with a yield of 95%.

[0017] 2. Preparation of the block copolymer (PFPE-b-P(E-co-AA)): To a 500 mL autoclave were added 50 g PFPE-Br (0.012 mol), 21.6 g acrylic acid (AA, 0.3 mol), 0.86 g CuBr (0.006 mol), 2.1 g PMDETA (0.012 mol), and 300 mL anisole. After sealing, the autoclave was subjected to three freeze-vacuum-thaw cycles to remove oxygen. Ethylene gas was introduced into the autoclave to a pressure of 0.5 MPa, then the temperature was raised to 90°C to initiate the reaction, with continuous stirring and maintaining a constant ethylene pressure. After 8 hours of reaction, a sample was taken and the acid value was determined to be 118 mgKOH / g, indicating endpoint. The reaction mixture was cooled to room temperature and the pressure was released. The reaction mixture was passed through a neutral alumina column to remove the copper catalyst, followed by precipitation with n-hexane. After filtration, the solid product was vacuum-dried at 50°C to yield 65 g of a block copolymer with a yield of 91%. The copolymer was calculated to contain approximately 16 mol% acrylic acid units.

[0018] S3. Preparation of Reactive Ionomer (PFPE-bP(E-co-AA-Na)) by Salt Formation: 70 g of the block copolymer obtained in step S2 (acid value 118 mg KOH / g, containing approximately 0.84 mol of -COOH) was added to a 1 L flask containing 500 mL of a mixed solvent of ethanol / water (v / v = 8:2) and heated to 80°C with stirring to dissolve. A 20% aqueous solution of 4.8 g of NaOH (0.12 mol, 1.05 eq) was then slowly added dropwise. After completion of the addition, the mixture was reacted at 75°C for 4 hours. The pH value of the reaction solution was stabilized at 7.1 as monitored by potentiometric titration. FTIR showed a peak at 1700 cm -1 The peak at 1560 cm -1 A strong absorption peak appeared at . The solution was concentrated by rotary evaporation and then dried in a vacuum oven at 80°C for 12 hours to obtain 72 g of a reactive ionomer as a white powder. Elemental analysis revealed that the sodium acrylate segment accounted for approximately 35.5 wt%.

[0019] The toughening filler is a toughening filler in the PTFE composite material for corrugated pipe fittings and its preparation method according to Chinese patent CN119060477A. ​​The preparation method of the toughening filler is as follows: talc powder, L-lysine diisocyanate and N2N-dimethylformamide are mixed, ultrasonically treated, and then epoxy resin is added, stirred for reaction, centrifuged, and dried to obtain epoxy-modified talc powder; epoxy-modified talc powder, N-(2-hydroxyethyl) dodecylamide and N2N-dimethylformamide are mixed, stirred for reaction, then heated and continued to stir for reaction, centrifuged, and dried to obtain the toughening filler. Calcium stearate is used as lubricant. The antistatic agent is ethoxylated alkylamine.

[0020] The preparation method of the PTFE composite material for corrugated pipe comprises the following steps: According to the formula, each raw material is weighed, the new modified PTFE resin, the reactive ionomer, the toughening filler, the lubricant, and the antistatic agent are added into a mixer and stirred and mixed for 5 minutes to obtain a mixture; The above mixture is transferred into a twin-screw extruder for melt extrusion, cooling, and granulation to obtain the PTFE composite material for corrugated pipe. The extrusion temperature is: 240°C for the first zone, 250°C for the second zone, 255°C for the third zone, 255°C for the fourth zone, 260°C for the die head, and 120 rpm for the screw rotation speed. Example 2

[0021] A new PTFE composite material for corrugated pipe is composed of the following raw materials by weight: new modified PTFE resin 80 parts, reactive ionomer 25 parts, toughening filler 8 parts, lubricant 1 part, and antistatic agent 3 parts.

[0022] The preparation of the new modified PTFE resin is as follows: The monomers of tetrafluoroethylene and 3.0 mol% perfluoro-2-butene are mixed with ammonium persulfate initiator at 80±0.5°C and 2.0Mpa to undergo emulsion polymerization reaction; after a period of reaction, 1.2 mol% perfluoro octyl acrylate is added, and the reaction continues until the concentration of the reaction product terminal -COOH is 0.10 mmol / g, and then it is dried to obtain the modified PTFE resin.

[0023] The melt flow rate of the new modified PTFE resin under the test conditions of 190°, 2.16kg is 12.4g / 10min.

[0024] The preparation method of the reactive ionomer is as in Example 1.

[0025] The toughening filler is as in Example 1.

[0026] The lubricant is selected from paraffin wax. The antistatic agent is selected from ethoxylated alkyl amine.

[0027] The preparation method of the new PTFE composite material for corrugated pipe is the same as in Example 1. Example 3

[0028] A new PTFE composite material for corrugated pipe is composed of the following raw materials by weight: new modified PTFE resin 90 parts, reactive ionomer 20 parts, toughening filler 10 parts, lubricant 3 parts, and antistatic agent 1 part.

[0029] The preparation of the new modified PTFE resin is as follows: Tetrafluoroethylene and 4.0 mol% perfluoro-2-butene monomers were mixed with ammonium persulfate as an initiator at 80±0.5°C and 2.0 MPa, and then an emulsion polymerization reaction was carried out. After a period of reaction, 0.8 mol% perfluorooctyl acrylate was added, and the reaction was continued until the terminal -COOH concentration of the reaction product reached 0.06 mmol / g. The new modified PTFE resin was obtained by drying.

[0030] Among them, the melt flow rate of the new modified PTFE resin under the test conditions of 190° and 2.16kg is 11.8g / 10min.

[0031] The preparation method of the reactive ionomer is the same as that in Example 1.

[0032] The toughening filler is the same as that in Example 1.

[0033] Calcium stearate is used as lubricant. The antistatic agent is ethoxylated alkylamine.

[0034] The preparation method of the novel PTFE composite material for corrugated pipes is the same as that in Example 1.

[0035] The tensile properties of the PTFE composite materials obtained in Examples 1-3 were measured using the method described in GB / T 1040.2-2022 at a tensile rate of 50 mm / min using dumbbell-shaped specimens measuring 80 × 10 × 4 mm. The impact resistance of the PTFE composite materials obtained in Examples 1-3 was also measured using the method described in GB / T 1843-2008 using an A-notch specimen measuring 80 × 10 × 4 mm. Five parallel sets of measurements were performed, and the average values ​​were calculated and compared with the average values ​​obtained in Examples 1-3 of CN119060477A. ​​The results are shown in Table 1.

[0036] Table 1

[0037] As can be seen from the results in Table 1, the present application abandons the traditional polyamide (PA) and polyethylene (PE) components as preparation raw materials, and the PTFE composite material prepared based on the new modified PTFE resin and reactive ionomer as the main body of the PTFE composite material for corrugated pipes is basically equivalent to the notched impact strength level of the existing PTFE composite material disclosed in CN119060477A, ​​but the tensile strength of the PTFE composite material in this application is even better.

[0038] At the same time, the melt flow rate of the novel modified PTFE resin in the present application is higher than that of the modified PTFE resin disclosed in CN119060477A under the same test conditions, indicating that the processing performance of the novel modified PTFE resin is even better.

[0039] Having described various embodiments of the application above, the descriptions are not exhaustive and are not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art. The selection of terms to be used in the description is intended to best explain the principles of the embodiments, practical application, or improvement over the technology in the art, or to enable other ordinary skilled persons in the art to understand the embodiments disclosed herein.

Claims

1. A new type of PTFE composite material for bellows, characterized in that: It is prepared from the following raw materials in parts by weight: 70-90 parts of new modified PTFE resin, 20-35 parts of reactive ionomer, 8-12 parts of toughening filler, 1-3 parts of lubricant, 1-3 parts of antistatic agent; The novel modified PTFE resin is prepared by mixing tetrafluoroethylene and 3.0-4.0 mol% perfluoro-2-butene monomers with ammonium persulfate as an initiator at 80±0.5°C and 2.0 MPa, and then performing an emulsion polymerization reaction. After a period of reaction, 0.8-1.2 mol% perfluorooctyl acrylate is added, and the reaction is continued until the terminal -COOH concentration of the reaction product reaches 0.05-0.10 mmol / g. The novel modified PTFE resin is then dried to obtain the novel modified PTFE resin. The reactive ionomer is a block copolymer having a structure represented by the following formula (I): PFPE(Mn=3500-4500)-bP(E-co-AA-Na) formula (I); Among them, PFPE represents a perfluoropolyether segment with a number average molecular weight of 3500-4500; P(E-co-AA-Na) represents the copolymer segment of ethylene and sodium acrylate; The acrylic acid unit accounts for 15-20 mol% of the total feed amount of the ethylene-acrylic acid copolymer segment monomer; the mass of the sodium acrylate segment accounts for 35±2 wt% of the total mass of the entire reactive ionomer.

2. A novel PTFE composite material for corrugated pipes according to claim 1, characterized in that: The preparation method of the reactive ionomer is as follows, comprising the following steps: S1. Synthesis of Macroinitiator (PFPE-Br): Under inert atmosphere and ice bath conditions, perfluoropolyether diol (PFPE-diol, Mn=4000±500), 2-bromoisobutyryl bromide (BIBB) and triethylamine (TEA) in a molar ratio of 1:2.1:2.2 were subjected to esterification in anhydrous tetrahydrofuran. After the reaction, the macroinitiator PFPE-Br with bromoisobutyrate groups at both ends was obtained by precipitation and drying. The endpoint of the reaction was determined by the characteristic OH peak (3400 cm-1) in Fourier transform infrared spectroscopy (FTIR). -1 ) disappearance; S2. Synthesis of Block Copolymer (PFPE-bP(E-co-AA)): The PFPE-Br obtained in step S1, acrylic acid (AA), catalyst CuBr, and ligand PMDETA were dissolved in anisole solvent, and after deoxygenation through a freeze-vacuum-thaw cycle, ethylene gas was introduced into the reaction system to a pressure of 0.5 MPa, and atom transfer radical polymerization (ATRP) was carried out at 90±2° for 8 hours; wherein the molar ratio of acrylic acid to ethylene was 15-20:80-85; the reaction endpoint was determined by measuring the acid value of the reactants to reach 120±5 mg KOH / g; after the reaction, copper removal, precipitation, and drying were performed to obtain a block copolymer PFPE-bP(E-co-AA); S3. Preparation of ionomers by salt formation reaction: The block copolymer PFPE-bP(E-co-AA) obtained in step S2 was dissolved in a mixed solvent of ethanol and water, and a 5% excess of sodium hydroxide aqueous solution in an equimolar amount to the carboxyl group was added for neutralization at 75±2°C for 4 hours. The pH value of the reaction solution was monitored by potentiometric titration to 7.0±0.2 at the end of the reaction, and the pH value at 1700 cm was confirmed by FTIR. -1 The C=O stretching vibration peak at 1560 cm -1 COO appears - After the reaction is completed, the final reactive ionomer PFPE-bP (E-co-AA-Na) is obtained by concentration and drying.

3. The novel PTFE composite material for bellows according to claim 1, characterized in that: The melt flow rate of the novel modified PTFE resin under the test conditions of 190°C and 2.16kg is 11.8-12.4g / 10min.

4. A method for preparing a novel PTFE composite material for corrugated pipes as claimed in any one of claims 1 to 3, characterized in that: The following steps are involved: Weigh the raw materials according to the formula, add the new modified PTFE resin, reactive ionomer, toughening filler, lubricant and antistatic agent into a mixer, stir and mix to obtain a mixture; The mixed material is transferred into a twin-screw extruder for melt extrusion, cooled, and pelletized to obtain the novel PTFE composite material for corrugated pipes.

Images