CN111285954B - Preparation method of high molecular weight modified polytetrafluoroethylene dispersion resin and dispersion concentrated solution - Google Patents

Preparation method of high molecular weight modified polytetrafluoroethylene dispersion resin and dispersion concentrated solution Download PDF

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CN111285954B
CN111285954B CN202010179936.0A CN202010179936A CN111285954B CN 111285954 B CN111285954 B CN 111285954B CN 202010179936 A CN202010179936 A CN 202010179936A CN 111285954 B CN111285954 B CN 111285954B
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modified polytetrafluoroethylene
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CN111285954A (en
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陈越
李宝杰
马鹏飞
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Shandong Dongyue Polymer Material Co Ltd
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    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F214/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen
    • C08F214/18—Monomers containing fluorine
    • C08F214/26—Tetrafluoroethene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2/00—Processes of polymerisation
    • C08F2/38—Polymerisation using regulators, e.g. chain terminating agents, e.g. telomerisation
    • C08F2/40—Polymerisation using regulators, e.g. chain terminating agents, e.g. telomerisation using retarding agents

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Abstract

The invention provides a preparation method of high molecular weight modified polytetrafluoroethylene dispersion resin and a dispersion concentrated solution. Adding a stabilizer, a dispersant, a pH regulator and a modifier into an aqueous medium, introducing a tetrafluoroethylene monomer, adding persulfate to initiate a polymerization reaction, and adding a free radical polymerization inhibitor when the reaction reaches a specified amount of the tetrafluoroethylene monomer; after the reaction is finished, collecting the modified polytetrafluoroethylene dispersion liquid, and obtaining high molecular weight modified polytetrafluoroethylene dispersion resin through coagulation, washing and drying; or concentrating the collected modified polytetrafluoroethylene dispersion liquid to obtain a high molecular weight modified polytetrafluoroethylene dispersion concentrated liquid. The polytetrafluoroethylene dispersion resin prepared by the invention has high molecular weight and narrow molecular weight distribution, is applied to paste extrusion to prepare porous materials, and the obtained porous materials have low environmental load, high breaking strength and good homogeneity; the obtained modified polytetrafluoroethylene concentrated solution has high thermal stability, aging resistance and radiation resistance.

Description

Preparation method of high molecular weight modified polytetrafluoroethylene dispersion resin and dispersion concentrated solution
Technical Field
The invention relates to a preparation method of high molecular weight modified polytetrafluoroethylene dispersion resin and a dispersion concentrated solution, belonging to the technical field of high molecules.
Background
The polytetrafluoroethylene has high chemical stability, excellent lubricity, extremely strong corrosion resistance and high and low temperature resistance, and has wide application in the fields of chemical industry, machinery, electricity, construction, medical treatment and the like. Polytetrafluoroethylene is widely used as a sole polymer of tetrafluoroethylene or a copolymer of tetrafluoroethylene with other trace monomers. In the production of polytetrafluoroethylene, a method of suspension polymerization of tetrafluoroethylene in an aqueous medium or a method of emulsion polymerization of tetrafluoroethylene in the presence of a fluorine-containing surfactant may be employed. The polytetrafluoroethylene particles are emulsified and dispersed in an aqueous dispersion obtained by emulsion polymerization, and a polytetrafluoroethylene dispersion resin powder is obtained by applying a mechanical shearing force to the aqueous dispersion and then conducting condensation drying, and a polytetrafluoroethylene dispersion concentrate is obtained by concentrating the aqueous dispersion.
Polytetrafluoroethylene has a high melt viscosity and cannot be melt-molded by a common thermoplastic resin method. Therefore, as a molding method of the polytetrafluoroethylene resin, a paste extrusion molding method, in which a lubricant is added to the polytetrafluoroethylene resin and then extrusion molding is performed, can be used. A molded product obtained by paste extrusion molding of a polytetrafluoroethylene-dispersed resin is stretched to obtain a porous body which can be used in clothing, tents, industrial precision filters, separation membranes, sealing materials, and the like. With the progress of the forming and processing technology of the dispersion resin and the widening of the application range of the polytetrafluoroethylene resin, the quality of the extrusion type polytetrafluoroethylene dispersion resin is promoted to be improved and developed to a high end. The modified polytetrafluoroethylene dispersion resin with high molecular weight has high molecular weight, and can be used for processing and preparing more homogeneous and higher breaking strength extension porous material. The high molecular weight modified polytetrafluoroethylene concentrated solution has high thermal stability, aging resistance and radiation resistance, and is widely applied to various industries.
Chinese patent document CN107868162A provides a high molecular weight polytetrafluoroethylene dispersion resin and a preparation method thereof. A stabilizing agent, a dispersing agent, an anti-sticking agent and the like are added into an aqueous medium, and a tetrafluoroethylene monomer is added to carry out dispersion polymerization at a certain temperature and under a certain pressure through an oxidation-reduction initiation system under the action of a modifier, so that the polytetrafluoroethylene dispersion resin with SSG of 2.14-2.15 is obtained, but the molecular weight of the polytetrafluoroethylene dispersion resin obtained by the method is low.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a preparation method of a high molecular weight modified polytetrafluoroethylene dispersion resin and a dispersion concentrated solution. The modified polytetrafluoroethylene dispersion resin obtained by the invention has high molecular weight and narrow molecular weight distribution, is applied to paste extrusion to prepare porous plastid materials, has small extrusion pressure, and the obtained porous plastid materials have low environmental load, high breaking strength and good homogeneity; the obtained modified polytetrafluoroethylene dispersion concentrated solution has higher thermal stability, aging resistance and radiation resistance.
The technical scheme of the invention is as follows:
a method for preparing high molecular weight modified polytetrafluoroethylene dispersion resin and dispersion concentrate comprises the following steps:
(1) adding deionized water, a stabilizer, a dispersant and a pH regulator into a reaction kettle, heating the reaction kettle to 60-65 ℃ in a closed manner, vacuumizing and replacing with nitrogen to ensure that the oxygen content is less than or equal to 20 ppm;
(2) adding a modifier, heating to 65-85 ℃ under the stirring condition, introducing a tetrafluoroethylene monomer to maintain the pressure in the kettle to be 2.3-3.5MPa, and then adding persulfate to initiate polymerization; then heating to 75-115 ℃, and keeping constant temperature for reaction; adding a free radical polymerization inhibitor when the tetrafluoroethylene monomer with a specified amount is reacted;
(3) after the reaction is finished, collecting the modified polytetrafluoroethylene dispersion liquid, and obtaining high molecular weight modified polytetrafluoroethylene dispersion resin through coagulation, washing and drying; or concentrating the collected modified polytetrafluoroethylene dispersion liquid until the solid content is 45-70% to obtain the high molecular weight modified polytetrafluoroethylene dispersion concentrated liquid.
According to the invention, preferably, the stabilizer in the step (1) is paraffin wax, and the adding amount of the stabilizer is 2-7% of the mass of the deionized water.
According to the present invention, it is preferable that the dispersant described in the step (1) is a fluorine-containing carboxylic acid having 6 to 8 carbon atoms and having 1 to 5 ether bonds in its main chain and a fluorine-containing carboxylate thereof; more preferably C3F7OCF2CF2COOH、C4F9OCF2COOH、CF3OCF2CF2OCF2CF2COOH、C2F5OCF2CF2OCF2COOH、CF3O(CF 2O)3CF2COOH、C3F7OCF(CF3)COOH、C3F7OCF2CF2OCF2COOH、C4F9OCF2CF2COOH、CF3CF2OCF2CF2OCF2CF2COOH、CF3OCF2CF2OCF2CF2OCF2COOH、CF3OCF(CF3)OCF(CF3)COOH、CF3O(CF2O)4CF2COOH、C2F5OCF(CF3)OCF(CF3)COOH、C4F9OCF2CF2OCF2COOH、C2F5OCF2CF2OCF2CF2OCF2COOH and ammonium and alkali metal salts thereofOne kind of (1).
According to the invention, the addition amount of the dispersing agent in the step (1) is preferably 0.08-0.2% of the mass of the deionized water.
According to the invention, preferably, the pH regulator in the step (1) is succinic acid, and the addition amount of the pH regulator is 0.005-0.1% of the mass of the deionized water.
According to the present invention, preferably, the modifier in the step (2) is perfluoroalkyl ethylene, and further preferably, the modifier is perfluorohexyl ethylene, perfluorobutyl ethylene, perfluoroethyl ethylene and perfluoropropyl ethylene;
preferably, the modifier is added in an amount of 0.0005 to 0.1% by mass based on the tetrafluoroethylene monomer.
According to the present invention, it is preferable that the persulfate in the step (2) is ammonium persulfate or potassium persulfate; the addition amount of the persulfate is 0.0002-0.004 percent of the mass of the deionized water.
According to the present invention, the radical polymerization inhibitor in the step (2) is preferably one or a combination of two or more of an aromatic hydroxy compound, an aromatic amine compound and a quinone compound;
more preferably, the aromatic hydroxy compound is one of 4-nitrophenol, 3-nitrophenol, 2-nitrophenol, 4-nitrosophenol, 4-aminophenol, 3-aminophenol, 2-aminophenol, 1-naphthol, 2-naphthol, catechol, resorcinol, hydroquinone, 2, 4-dihydroxytoluene, 1,2, 3-trihydroxybenzene, 1,3, 5-trihydroxybenzene, 1, 3-dihydroxynaphthalene, 1, 4-dihydroxynaphthalene, 3,4, 5-trihydroxybenzoic acid, 2-hydroxybenzoic acid, 2, 5-dihydroxybenzoic acid, 2,4, 6-trihydroxybenzoic acid;
more preferably, the aromatic amine compound is one of 1, 2-diaminobenzene, 1, 3-diaminobenzene and 1, 4-diaminobenzene;
more preferably, the quinone compound is one of 1, 2-benzoquinone and 1, 4-benzoquinone.
According to the present invention, it is preferable that the mass ratio of the radical polymerization inhibitor to the persulfate in the step (2) is 0.2 to 0.8: 1.
According to the present invention, it is preferable that the radical polymerization inhibitor is added in the step (2) for a period of time of 10 to 60%, more preferably 30 to 40% of the total amount of the tetrafluoroethylene monomer reacted.
According to the invention, preferably, in the step (2), sulfite or bisulfate is also added, wherein the sulfite is ammonium sulfite or sodium sulfite, the bisulfate is sodium bisulfite, and the mass ratio of the sulfite or bisulfate to the persulfate is 0.2-1.5: 1;
further preferably, the addition time of the sulfite or the bisulfate is as follows: the amount of tetrafluoroethylene monomer reacted is 5 to 65%, more preferably 45 to 60% of the total amount.
According to the present invention, it is preferable that the finishing temperature of the polymerization reaction in the step (2) is higher than the starting temperature by 5 ℃ or more.
According to the present invention, it is preferred that the persulfate is added in the step (2), and the temperature is raised to 75-115 ℃ within 100-120 min.
According to the present invention, it is preferred that the reaction is terminated when the dispersion in step (3) has a solids content of 31 to 33%.
According to the present invention, the preparation of the modified polytetrafluoroethylene dispersion resin and the modified polytetrafluoroethylene dispersion concentrate of high molecular weight in step (3) is prior art.
According to the present invention, the modified polytetrafluoroethylene dispersion resin obtained has an SSG of 2.130-2.140, a crystalline melting point of 346. + -. 2 ℃, a half-width of the crystalline melting point of 3.0-4.0 ℃ and an endothermic ratio of the crystalline melting point peak of 0.10 or less. The modified polytetrafluoroethylene prepared by the invention has high average molecular weight, concentrated molecular weight distribution and high proportion of large molecular weight particles.
The invention has the following technical characteristics and beneficial effects:
1. the free radical polymerization inhibitor is added in the preparation process, and the free radical decomposed from the initiator is consumed by adding the free radical polymerization inhibitor, so that the concentration of the initiator in the later polymerization stage is reduced, the reaction monomer is promoted to be converted towards the chain growth direction, and the modified polytetrafluoroethylene dispersion liquid with high molecular weight and narrow molecular weight distribution is obtained, and the modified polytetrafluoroethylene dispersion resin and the dispersion concentrated liquid with high molecular weight are obtained; meanwhile, the growth of molecular chains with large molecular weight can be controlled by controlling the adding time of the polymerization inhibitor.
2. The preparation method of the invention controls the reaction temperature, so that the temperature is rapidly increased in the early stage of polymerization, the rapid decomposition of the initiator is promoted, the half-life period of the decomposition of the initiator is shortened, and the concentration of the initiator in the later stage is reduced, thereby reducing the formation of low molecular weight particles in the later stage of reaction.
3. The modified polytetrafluoroethylene dispersion resin prepared by the invention has high molecular weight and narrow molecular weight distribution, is applied to paste extrusion to prepare porous plastid materials, has small extrusion pressure, and the obtained porous plastid materials have low environmental load, high breaking strength and good homogeneity; the obtained modified polytetrafluoroethylene concentrated solution has higher thermal stability, aging resistance and radiation resistance.
Detailed Description
The present invention is further illustrated by, but is not limited to, the following specific examples.
Meanwhile, the experimental methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials are commercially available, unless otherwise specified.
Example 1
A method for preparing high molecular weight modified polytetrafluoroethylene dispersion resin and dispersion concentrate comprises the following steps:
(1) 9kg of deionized water, 0.5kg of paraffin wax and a dispersant CF were charged into a horizontal polymerization vessel having 4 paddles and a capacity of 15L stainless steel (SUS316L)3OCF2CF2OCF2CF2OCF2COONH49.0g of succinic acid solution, 105g of succinic acid solution, wherein 5g of succinic acid is dissolved in 100g of deionized water; heating the polymerization kettle to make the temperature in the polymerization kettle reach 65 ℃, vacuumizing the polymerization kettle and replacing the polymerization kettle with nitrogen to make the oxygen content in the polymerization kettle below 20 ppm.
(2) Adding 0.47g of modifier perfluorohexyl ethylene (PFHE) into a vacuum polymerization kettle, opening the polymerization kettle and stirring to 180 pm; heating a polymerization kettle to enable the temperature in the kettle to reach 70 ℃, adding tetrafluoroethylene monomer to boost the pressure to 2.8MPa, adding 0.45g of ammonium persulfate aqueous solution with the mass fraction of 5% into the kettle, starting reaction, continuously adding the tetrafluoroethylene monomer to enable the pressure in the kettle to keep 2.8MPa, starting reaction to release heat after adding an initiator, controlling the temperature to rise to 90 ℃ within 120 minutes, and then keeping the constant temperature of 90 ℃ for reaction; when the reaction amount of the tetrafluoroethylene monomer reached 1.45kg, 0.01g of 2-nitrophenol as a radical polymerization inhibitor was added.
(3) When the reaction amount of the tetrafluoroethylene monomer reaches 4.24kg and the solid content of the dispersion liquid is 33%, the introduction of the tetrafluoroethylene monomer is stopped, the stirring of the polymerization kettle is stopped, and the replacement is carried out. The reaction time was 162 minutes, the maximum reaction rate was 1.81 mol/l/hr, and the final reaction rate was 1.05 mol/l/hr. The polymer dispersion was collected and the polymer particle diameter was 221 nm.
Adding deionized water and nitric acid into a part of dispersion liquid, coagulating, cleaning, and drying at 160 ℃ to obtain high molecular weight modified polytetrafluoroethylene dispersion resin, wherein the physical property data of the obtained dispersion resin is shown in Table 1; and adding a part of dispersion liquid into a non-ionic surfactant perfluoroalkyl polyoxyethylene ether, and concentrating until the solid content is 60% to obtain the high molecular weight modified polytetrafluoroethylene dispersion concentrated solution.
Example 2
A method for preparing high molecular weight modified polytetrafluoroethylene dispersion resin and dispersion concentrate comprises the following steps:
(1) to a horizontal polymerization vessel having 4 paddles and a capacity of 15L stainless steel (SUS316L), 9kg of deionized water, 0.5kg of paraffin wax and a dispersant CF were charged3OCF2CF2OCF2CF2OCF2COONH49.0g of succinic acid solution (105 g) obtained by dissolving 5g of succinic acid in 100g of deionized water, heating a polymerization reactor to a temperature of 65 ℃ in the polymerization reactor, and then evacuating the polymerization reactor and replacing the polymerization reactor with nitrogen gas to reduce the oxygen content in the polymerization reactor to 20ppm or less.
(2) Adding 0.47g of modifier perfluorohexyl ethylene (PFHE) into a vacuum polymerization kettle, opening the polymerization kettle and stirring to 180 pm; heating a polymerization kettle to enable the temperature in the kettle to reach 70 ℃, adding tetrafluoroethylene monomer to boost the pressure to 2.8MPa, adding 0.36g of ammonium persulfate aqueous solution with the mass fraction of 5% into the kettle, starting reaction, continuously adding the tetrafluoroethylene monomer to enable the pressure in the kettle to keep 2.8MPa, releasing heat in the reaction, controlling the temperature to rise to 90 ℃ within 120 minutes, and then keeping the temperature of 90 ℃ for constant-temperature reaction; when the reaction amount of the tetrafluoroethylene monomer reaches 1.45kg, 0.01g of free radical polymerization inhibitor 2-nitrophenol is added; when the reaction amount of the tetrafluoroethylene monomer reached 2.54kg, 0.30g of an aqueous solution of ammonium sulfite having a mass fraction of 3% was added.
(3) When the reaction amount of the tetrafluoroethylene monomer reaches 4.24kg and the solid content of the dispersion liquid is 33%, the introduction of the tetrafluoroethylene monomer is stopped, the stirring of the polymerization kettle is stopped, and the replacement is carried out. The reaction time was 143 minutes, the maximum reaction rate was 3.45 mol/l/hr, and the final reaction rate was 3.00 mol/l/hr. The polymerized dispersion was collected and the polymer particles had a diameter of 200 nm.
Adding deionized water and nitric acid into a part of dispersion liquid, coagulating, cleaning, and drying at 160 ℃ to obtain high molecular weight modified polytetrafluoroethylene dispersion resin, wherein the physical property data of the obtained dispersion resin is shown in Table 1; and adding a part of dispersion liquid into a non-ionic surfactant perfluoroalkyl polyoxyethylene ether, and concentrating until the solid content is 60% to obtain the high molecular weight modified polytetrafluoroethylene dispersion concentrated solution.
Example 3
A method for preparing high molecular weight modified polytetrafluoroethylene dispersion resin and dispersion concentrate comprises the following steps:
(1) to a horizontal polymerization vessel having 4 paddles and a capacity of 15L stainless steel (SUS316L), 9kg of deionized water, 0.5kg of paraffin wax and a dispersant CF were charged3OCF2CF2OCF2CF2OCF2COONH49.0g, 105g of succinic acid solution, which is obtained by dissolving 5g of succinic acid in 100g of deionized water. Heating the polymerization kettle to make the temperature in the polymerization kettle reach 65 ℃, vacuumizing the polymerization kettle and replacing the polymerization kettle with nitrogen to make the oxygen content in the polymerization kettle below 20 ppm.
(2) Adding 0.47g of modifier perfluorobutyl ethylene (PFBE) into a vacuum polymerization kettle, opening the polymerization kettle, stirring to 180pm, heating the polymerization kettle to enable the temperature in the polymerization kettle to reach 70 ℃, adding tetrafluoroethylene monomer, boosting the pressure to 2.8MPa, adding 0.36g of ammonium persulfate aqueous solution with the mass fraction of 5%, starting reaction, continuously adding the tetrafluoroethylene monomer to enable the pressure in the polymerization kettle to be kept at 2.8MPa, releasing heat in the reaction, controlling the temperature to rise to 90 ℃ within 120 minutes, and then keeping the temperature of 90 ℃ for constant-temperature reaction; when the reaction amount of the tetrafluoroethylene monomer reaches 1.45kg, 0.01g of free radical polymerization inhibitor 2-nitrophenol is added; when the reaction amount of the tetrafluoroethylene monomer reached 2.54kg, 0.30g of an ammonium sulfite aqueous solution having a mass fraction of 3% was added.
(3) When the reaction amount of the tetrafluoroethylene monomer reaches 4.24kg and the solid content of the dispersion liquid is 33%, the introduction of the tetrafluoroethylene monomer is stopped, the stirring of the polymerization kettle is stopped, and the replacement is carried out. The reaction time was 223 minutes, the maximum reaction rate was 2.83 mol/l/hr, and the final reaction rate was 1.70 mol/l/hr. The polymerized dispersion was collected and the polymer particles had a diameter of 187 nm.
Adding deionized water and nitric acid into a part of dispersion liquid, coagulating, cleaning, and drying at 160 ℃ to obtain high molecular weight modified polytetrafluoroethylene dispersion resin, wherein the physical property data of the obtained dispersion resin is shown in Table 1; and adding a part of dispersion liquid into a non-ionic surfactant perfluoroalkyl polyoxyethylene ether, and concentrating until the solid content is 60% to obtain the high molecular weight modified polytetrafluoroethylene dispersion concentrated solution.
Example 4
A method for preparing high molecular weight modified polytetrafluoroethylene dispersion resin and dispersion concentrate comprises the following steps:
(1) to a horizontal polymerization vessel having 4 paddles and a capacity of 15L stainless steel (SUS316L), 9kg of deionized water, 0.5kg of paraffin wax and a dispersant CF were charged3OCF2CF2OCF2CF2OCF2COONH49.0g of succinic acid solution, 105g of succinic acid solution, wherein 5g of succinic acid is dissolved in 100g of deionized water; heating the polymerization kettle to make the temperature in the polymerization kettle reach 65 ℃, vacuumizing the polymerization kettle and replacing the polymerization kettle with nitrogen to make the oxygen content in the polymerization kettle below 20 ppm.
(2) Adding 1.272g of modifier perfluorohexyl ethylene (PFHE) into a vacuum polymerization kettle, opening the polymerization kettle, stirring to 180pm, heating the polymerization kettle to enable the temperature in the polymerization kettle to reach 70 ℃, adding tetrafluoroethylene monomer, boosting the pressure to 2.8MPa, adding 0.36g of ammonium persulfate aqueous solution with the mass fraction of 5%, starting reaction, continuously adding the tetrafluoroethylene monomer to enable the pressure in the polymerization kettle to be kept at 2.8MPa, releasing heat in the reaction, controlling the temperature to rise to 90 ℃ within 120 minutes, and then keeping the temperature of 90 ℃ for constant-temperature reaction; when the reaction amount of the tetrafluoroethylene monomer reaches 1.45kg, 0.01g of free radical polymerization inhibitor 2-nitrophenol is added; when the reaction amount of the tetrafluoroethylene monomer reached 2.54kg, 0.30g of a 3% ammonium sulfite aqueous solution was added.
(3) When the reaction amount of the tetrafluoroethylene monomer reaches 4.24kg and the solid content of the dispersion liquid is 33%, the introduction of the tetrafluoroethylene monomer is stopped, the stirring of the polymerization kettle is stopped, and the replacement is carried out. The reaction time was 206 minutes, the maximum reaction rate was 2.70 mol/l/hr, and the final reaction rate was 2.18 mol/l/hr. The polymer particle diameter of the resulting dispersion was 177 nm.
Adding deionized water and nitric acid into a part of dispersion liquid, coagulating, cleaning, and drying at 160 ℃ to obtain high molecular weight modified polytetrafluoroethylene dispersion resin, wherein the physical property data of the obtained dispersion resin is shown in Table 1; and adding a part of dispersion liquid into a non-ionic surfactant perfluoroalkyl polyoxyethylene ether, and concentrating until the solid content is 60% to obtain the high molecular weight modified polytetrafluoroethylene dispersion concentrated solution.
Example 5
A method for preparing high molecular weight modified polytetrafluoroethylene dispersion resin and dispersion concentrate comprises the following steps:
(1) to a horizontal polymerization vessel having 4 paddles and a capacity of 15L stainless steel (SUS316L), 9kg of deionized water, 0.5kg of paraffin wax and a dispersant CF were charged3OCF2CF2OCF2CF2OCF2COONH49.0g of succinic acid solution, 105g of succinic acid solution, wherein 5g of succinic acid is dissolved in 100g of deionized water; heating the polymerization kettle to make the temperature in the polymerization kettle reach 65 ℃, vacuumizing the polymerization kettle and replacing the polymerization kettle with nitrogen to make the oxygen content in the polymerization kettle below 20 ppm.
(2) Adding 0.6g of modifier perfluorohexyl ethylene (PFHE) into a vacuum polymerization kettle, opening the polymerization kettle, stirring to 180pm, heating the polymerization kettle to enable the temperature in the polymerization kettle to reach 70 ℃, adding tetrafluoroethylene monomer, boosting the pressure to 2.8MPa, adding 0.36g of ammonium persulfate aqueous solution with the mass fraction of 5%, starting reaction, continuously adding the tetrafluoroethylene monomer to enable the pressure in the polymerization kettle to be kept at 2.8MPa, releasing heat in the reaction, controlling the temperature to rise to 95 ℃ within 120 minutes, and then keeping the temperature of 95 ℃ for constant reaction; when the reaction amount of the tetrafluoroethylene monomer reaches 1.45kg, 0.01g of free radical polymerization inhibitor 2-nitrophenol is added; when the reaction amount of the tetrafluoroethylene monomer reached 2.54kg, 0.30g of an ammonium sulfite aqueous solution having a mass fraction of 3% was added.
(3) When the reaction amount of the tetrafluoroethylene monomer reaches 4.24kg and the solid content of the dispersion liquid reaches 33%, the introduction of the tetrafluoroethylene monomer is stopped, the stirring of the polymerization kettle is stopped, and the replacement is carried out. The reaction time was 200 minutes, the maximum reaction rate was 2.70 mol/l/hr, and the final reaction rate was 2.18 mol/l/hr. The polymer particle diameter of the resulting dispersion was 194 nm.
Adding deionized water and nitric acid into a part of dispersion liquid, coagulating, cleaning, and drying at 160 ℃ to obtain high molecular weight modified polytetrafluoroethylene dispersion resin, wherein the physical property data of the obtained dispersion resin is shown in Table 1; and adding a part of dispersion liquid into a non-ionic surfactant perfluoroalkyl polyoxyethylene ether, and concentrating until the solid content is 60% to obtain the high molecular weight modified polytetrafluoroethylene dispersion concentrated solution.
Example 6
A method for preparing high molecular weight modified polytetrafluoroethylene dispersion resin and dispersion concentrate comprises the following steps:
(1) to a horizontal polymerization vessel having 4 paddles and a capacity of 15L stainless steel (SUS316L), 9kg of deionized water, 0.5kg of paraffin wax and a dispersant CF were charged3OCF2CF2OCF2CF2OCF2COONH49.0g of succinic acid solution, 105g of succinic acid solution, wherein 5g of succinic acid is dissolved in 100g of deionized water; heating the polymerization kettle to make the temperature in the polymerization kettle reach 65 ℃, vacuumizing the polymerization kettle and replacing the polymerization kettle with nitrogen to make the oxygen content in the polymerization kettle below 20 ppm.
(2) Adding 0.47g of modifier perfluorobutyl ethylene (PFBE) into a vacuum polymerization kettle, opening the polymerization kettle, stirring to 180pm, heating the polymerization kettle to enable the temperature in the polymerization kettle to reach 73 ℃, adding tetrafluoroethylene monomer, boosting the pressure to 2.8MPa, adding 0.90g of ammonium persulfate aqueous solution with the mass fraction of 5%, starting reaction, continuously adding the tetrafluoroethylene monomer to enable the pressure in the polymerization kettle to be kept at 2.8MPa, releasing heat in the reaction, controlling the temperature to rise to 95 ℃ within 120 minutes, and then keeping the temperature of 95 ℃ for constant reaction; when the reaction amount of the tetrafluoroethylene monomer reaches 1.45kg, 0.01g of free radical polymerization inhibitor 2-nitrophenol is added; when the reaction amount of the tetrafluoroethylene monomer reached 2.54kg, 0.30g of an ammonium sulfite aqueous solution having a mass fraction of 3% was added.
(3) When the reaction amount of the tetrafluoroethylene monomer reaches 4.24kg and the solid content of the dispersion liquid is 33%, the introduction of the tetrafluoroethylene monomer is stopped, the stirring of the polymerization kettle is stopped, and the replacement is carried out. The reaction time was 201 minutes, the maximum reaction rate was 3.43 mol/l/hr, and the final reaction rate was 1.13 mol/l/hr. The polymer particle diameter of the resulting dispersion was 194 nm.
Adding deionized water and nitric acid into a part of dispersion liquid, coagulating, cleaning, and drying at 160 ℃ to obtain high molecular weight modified polytetrafluoroethylene dispersion resin, wherein the physical property data of the obtained dispersion resin is shown in Table 1; and adding a part of dispersion liquid into a non-ionic surfactant perfluoroalkyl polyoxyethylene ether, and concentrating until the solid content is 60% to obtain the high molecular weight modified polytetrafluoroethylene dispersion concentrated solution.
Example 7
A method for preparing high molecular weight modified polytetrafluoroethylene dispersion resin and dispersion concentrate comprises the following steps:
(1) to a horizontal polymerization vessel having 4 paddles and a capacity of 15L stainless steel (SUS316L), 9Kg of deionized water, 0.5Kg of paraffin wax and a dispersing agent CF were charged3OCF2CF2OCF2CF2OCF2COONH49.0g, 5g of succinic acid dissolved with 100g of deionized water; after the polymerization vessel was heated to a temperature of 65 ℃ in the vessel, the polymerization vessel was evacuated and replaced with nitrogen gas so that the oxygen content in the vessel was 20ppm or less.
(2) 1.41g of modifier perfluorohexyl ethylene (PFHE) is added into a vacuum polymerization kettle, and the polymerization kettle is opened to stir until the mixture reaches 180 pm; heating the polymerization kettle to enable the temperature in the kettle to reach 73 ℃, adding a tetrafluoroethylene monomer and boosting the pressure to 2.8 MPa. Adding 0.90g of ammonium persulfate aqueous solution with the mass fraction of 5% into the kettle, starting the reaction, continuously adding tetrafluoroethylene monomer to keep the pressure in the kettle at 2.8MPa, releasing heat in the reaction, controlling the temperature to rise to 95 ℃ within 120 minutes, and then keeping the temperature of 95 ℃ for constant-temperature reaction; when the reaction amount of the tetrafluoroethylene monomer reaches 1.45kg, 0.01g of free radical polymerization inhibitor 2-nitrophenol is added; when the reaction amount of the tetrafluoroethylene monomer reached 2.54kg, 0.30g of an ammonium sulfite aqueous solution having a mass fraction of 3% was added.
(3) When the reaction amount of the tetrafluoroethylene monomer reaches 4.24kg and the solid content of the dispersion liquid is 33%, the introduction of the tetrafluoroethylene monomer is stopped, the stirring of the polymerization kettle is stopped, and the replacement is carried out. The reaction time was 228 minutes, the maximum reaction rate was 3.43 mol/l/hr, and the final reaction rate was 0.98 mol/l/hr. The polymer particle diameter of the resulting dispersion was 180 nm.
Adding deionized water and nitric acid into a part of dispersion liquid, coagulating, cleaning, and drying at 160 ℃ to obtain high molecular weight modified polytetrafluoroethylene dispersion resin, wherein the physical property data of the obtained dispersion resin is shown in Table 1; and adding a part of dispersion liquid into a non-ionic surfactant perfluoroalkyl polyoxyethylene ether, and concentrating until the solid content is 60% to obtain the high molecular weight modified polytetrafluoroethylene dispersion concentrated solution.
Comparative example 1
A high molecular weight modified polytetrafluoroethylene dispersion resin and dispersion concentrate were prepared as described in example 1, except that no free radical polymerization inhibitor was added.
Comparative example 2
A high molecular weight modified polytetrafluoroethylene dispersion resin and dispersion concentrate were prepared as described in example 2, except that no free radical polymerization inhibitor was added.
Comparative example 3
A high molecular weight modified polytetrafluoroethylene dispersion resin and dispersion concentrate were prepared as described in example 3, except that no free radical polymerization inhibitor was added.
Test examples
The modified polytetrafluoroethylene dispersion resins prepared in examples 1 to 7 and comparative examples 1 to 3 were subjected to DSC, extrusion pressure and tensile film appearance (15 times) tests, and the results are shown in Table 1.
And (3) carrying out Differential Scanning Calorimetry (DSC) analysis on the prepared modified polytetrafluoroethylene dispersion resin, and analyzing the half-height width, heat absorption ratio and area ratio of an endothermic peak of the modified polytetrafluoroethylene dispersion resin according to the melting crystallization peak of the modified polytetrafluoroethylene dispersion resin.
The extrusion pressure was determined according to the provisions of appendix A of Standard HG/T2899-1997, with a forming ratio of 400: 1.
The tensile film appearance (15 times) was tested by: mixing the prepared modified polytetrafluoroethylene dispersion resin with Isopar oil, wherein the addition amount of the Isopar oil is 25 percent of the mass of the dispersion resin, then drying and deoiling the mixture at 180 ℃, and carrying out tensile test on the deoiled dispersion resin at 220 ℃ by using a tensile machine.
TABLE 1 physical Properties of modified Polytetrafluoroethylene Dispersion resin
Figure BDA0002412147630000111
As can be seen from Table 1, the SSG of the modified polytetrafluoroethylene dispersion resin prepared by the invention is lower than that of the modified polytetrafluoroethylene dispersion resin prepared by comparative examples 1-3 without adding a radical polymerization inhibitor, which indicates that the molecular weight of the modified polytetrafluoroethylene dispersion resin prepared by the invention is high; meanwhile, the half-height width of the endothermic peak is smaller, and the heat absorption is smaller, further showing that the modified polytetrafluoroethylene dispersion resin obtained by the invention has high average molecular weight and centralized molecular weight distribution; the area of the modified polytetrafluoroethylene dispersion resin prepared by the invention is larger, which shows that the proportion of high molecular weight particles of the modified polytetrafluoroethylene dispersion resin prepared by the invention is concentrated; the modified polytetrafluoroethylene dispersion resin prepared by the invention has smaller extrusion pressure and uniform appearance (15 times) of the stretched film, while the modified polytetrafluoroethylene dispersion resin prepared by the comparative example without adding the free radical polymerization inhibitor has larger extrusion pressure and nonuniform appearance (15 times) of the stretched film.

Claims (7)

1. A method for preparing high molecular weight modified polytetrafluoroethylene dispersion resin and dispersion concentrate comprises the following steps:
(1) adding deionized water, a stabilizer, a dispersant and a pH regulator into a reaction kettle, heating the reaction kettle to 60-65 ℃ in a closed manner, vacuumizing and replacing with nitrogen to ensure that the oxygen content is less than or equal to 20 ppm; the dispersant is C3F7OCF2CF2COOH、C4F9OCF2COOH、CF3OCF2CF2OCF2CF2COOH、C2F5OCF2CF2OCF2COOH、CF3O（CF２O）３CF2COOH、C3F7OCF(CF3)COOH、C3F7OCF2CF2OCF2COOH、C4F9OCF2CF2COOH、CF3CF2OCF2CF2OCF2CF2COOH、CF3OCF2CF2OCF2CF2OCF2COOH、CF3OCF(CF3)OCF(CF3)COOH、CF3O(CF2O)4CF2COOH、C2F5OCF(CF3)OCF(CF3)COOH、C4F9OCF2CF2OCF2COOH、C2F5OCF2CF2OCF2CF2OCF2COOH and one of ammonium salt and alkali metal salt thereof; the addition amount of the dispersing agent is 0.08-0.2% of the mass of the deionized water; the pH regulator is succinic acid; the addition amount of the pH regulator is 0.005-0.1% of the mass of the deionized water; the stabilizer is paraffin, and the addition amount of the stabilizer is 2-7% of the mass of the deionized water;
(2) adding a modifier, heating to 65-85 ℃ under the stirring condition, introducing a tetrafluoroethylene monomer to maintain the pressure in the kettle to be 2.3-3.5MPa, and then adding persulfate to initiate polymerization; then heating to 75-115 ℃, and keeping constant temperature for reaction; adding a free radical polymerization inhibitor when the tetrafluoroethylene monomer with a specified amount is reacted; the modifier is perfluoroalkyl ethylene; the addition amount of the modifier is 0.0005-0.1% of the mass of the tetrafluoroethylene monomer; the free radical polymerization inhibitor is one or the combination of more than two of aromatic hydroxyl compounds, aromatic amine compounds and quinone compounds; the mass ratio of the free radical polymerization inhibitor to the persulfate is 0.2-0.8: 1; adding free radical polymerization inhibitor for 30-40% of tetrafluoroethylene monomer; the finishing temperature of the polymerization reaction is higher than the starting temperature by more than 5 ℃; the addition amount of the persulfate is 0.0002-0.004% of the mass of the deionized water;
(3) after the reaction is finished, collecting the modified polytetrafluoroethylene dispersion liquid, and obtaining high molecular weight modified polytetrafluoroethylene dispersion resin through coagulation, washing and drying; or concentrating the collected modified polytetrafluoroethylene dispersion liquid until the solid content is 45-70% to obtain the high molecular weight modified polytetrafluoroethylene dispersion concentrated liquid.
2. The process for preparing a dispersion resin and a dispersion concentrate of a high molecular weight modified polytetrafluoroethylene according to claim 1, wherein said modifier in step (2) is perfluorohexylethylene, perfluorobutylethylene, perfluoroethylethylene and perfluoropropylethylene.
3. The process for producing a high molecular weight modified polytetrafluoroethylene dispersion resin and dispersion concentrate according to claim 1, wherein said persulfate in step (2) is ammonium persulfate or potassium persulfate.
4. The method for preparing a dispersion resin and a dispersion concentrate of high molecular weight modified polytetrafluoroethylene according to claim 1, wherein said aromatic hydroxy compound in step (2) is 4-nitrophenol, 3-nitrophenol, 2-nitrophenol, 4-nitrosophenol, 4-aminophenol, 3-aminophenol, 2-aminophenol, 1-naphthol, 2-naphthol, catechol, resorcinol, hydroquinone, 2, 4-dihydroxytoluene, 1,2, 3-trihydroxybenzene, 1,3, 5-trihydroxybenzene, 1, 3-dihydroxynaphthalene, 1, 4-dihydroxynaphthalene, 3,4, 5-trihydroxybenzoic acid, 2-hydroxybenzoic acid, 2, 5-dihydroxybenzoic acid, 2,4, one of 6-trihydroxybenzoic acid; the aromatic amine compound is one of 1, 2-diaminobenzene, 1, 3-diaminobenzene and 1, 4-diaminobenzene; the quinone compound is one of 1, 2-benzoquinone and 1, 4-benzoquinone.
5. The method for preparing a high molecular weight modified polytetrafluoroethylene dispersion resin and dispersion concentrate according to claim 1, wherein in step (2) a sulfite or a bisulfate is further added, said sulfite being ammonium sulfite or sodium sulfite, said bisulfate being sodium bisulfite, the mass ratio of said sulfite or bisulfate to persulfate being 0.2-1.5: 1; the addition time of the sulfite or the bisulfate is as follows: the reaction amount of the tetrafluoroethylene monomer is 5-65% of the total amount.
6. The process for preparing a dispersion resin and a dispersion concentrate of a high molecular weight modified polytetrafluoroethylene according to claim 1, wherein said temperature is raised to 75-115 ℃ at 100-120min after adding said persulfate in said step (2).
7. The process for producing a high molecular weight modified polytetrafluoroethylene dispersion resin and dispersion concentrate according to claim 1, wherein said reaction is terminated when the solid content of the dispersion in step (3) is 31 to 33%.
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