JPS61228008A - Copolymerization of tetrafluoroethylene - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field This invention relates to methods for producing melt processable copolymers.
Tetrafluoroethylene and B, such as hexafluoropropylene (RFP), non-fluoropropyl vinyl ether (ppVE), and also combinations thereof.
It relates to improvements in the copolymerization of at least one ethylenically unsaturated comonomer.

Background Copolymerization of tetrafluoroethylene (TFE) and ethylenically unsaturated comonomers to produce melt-processable copolymers can be carried out in an aqueous reaction medium in the presence of a dispersant and an initiator. The dispersant commonly used for this polymerization is ammonium perfluorooctanoate C1
F1sCOONH. The use of other dispersants with better performance has long been a goal.

SUMMARY OF THE INVENTION The present invention employs a novel dispersant for use in the copolymerizations described above, which surprisingly provides higher comonomer dispersion at a given polymerization rate than the octanoates described above. content, or vice versa, provides higher polymerization rates at a given comonomer content. The new dispersants are 2n-C, F1. C00N perfluorononanoic acid or its salt, where M is hydrogen,
Ammonium or alkali metal. Mixtures of such nonanoate salts can also be used if desired.

DESCRIPTION OF THE INVENTION The copolymerization of tetrafluoroethylene and the above comonomers to provide melt-processable copolymers is known in the art. Tetrafluoroethylene is reacted with an ethylenically unsaturated 5fO comonomer, generally in an aqueous medium containing a polymerization initiator and a dispersant. Usually, the gaseous sulfur is introduced into the aqueous medium under pressure. Typical conditions are 20~120℃, preferably 7o~
Polymerization temperature of 110°C; and 0.7-5.5 M Pα,
Preferably 2.1 to 4.5. Includes pressure of MPα.

Polymerization is usually carried out in a stirred autoclave.

Representative fluorinated ethylenically unsaturated comonomers that can be copolymerized with tetrafluoroethylene are represented by the following formula: where Rx a Rf -R1X -OR1 or -
〇-R7-X, in which (DRY is a mother fluoroalkyl group of 1 to 12 carbon atoms), -R1-a1~
12Jl [Children's] arm-fluoroalkylene dilasocal in which the bonding atom is 1 tut.

at each end of the chain, and X is H or C1; and R1 is -R1 or -R1-X.

Particular copolymerizable fluorinated ethylenically unsaturated comonomers include hexafluoropropylene, no-9-fluoro(methyl vinyl ether), perfluoro(exo-propyl vinyl ether), no-fluoro(n-hebutyl vinyl ether), 3, 3.3-trifluoropropylene-1,
5,3,4,4゜5.5,6,6.6-nonafluorohexene-1,3-hydroperfluoro(propyl vinyl ether), and mixtures of hahexafluoropropylene and perfluoro(propyl vinyl ether) It's a mixture of them. Preferably, the comonomer is selected from compounds of the formula % (Nyl ether), or hahexafluoropropylene, or compounds of the formula Rf-CH=CH, in which -R1 is .I- of 1 to 12 carbon atoms. It is a fluoroalkyl group.

The comonomer content can range from 0.5 mole percent to about 20 mole percent, and 1
A variety of comonomers can also be present.

The polymerization initiator must have a sufficient half-life to maintain the reaction under the reaction conditions and achieve the desired molecular weight, such as peroxides, persulfates, azo compounds, etc. It can be a compound. It is also possible to use promoters for the decomposition of the initiator, such as iron salts.

The amount of initiator used depends on the polymerization temperature, the type of initiator, the presence of chain transfer agents or molecular weight regulators, the desired polymer molecular weight and the desired reaction rate.

The amount of initiator used is thus determined by the desired molecular weight and polymerization rate. Chain transfer agents or molecular weight regulators can be saturated hydrocarbons or alcohols of 1 to 15 carbon atoms, which may be partially fluorinated or chlorinated.

The amount of 9-fluorononanoic acid or salt thereof added to the polymerization reactor depends on the weight of water and the expected polymer. Generally, relatively high dispersant concentrations are required if relatively high polymer concentrations are expected in the final dispersion. Additionally, the amount of dispersant will also depend on the desired degree of dispersion stability. Generally, the amount of polymer in the final product dispersion is from 15 to 45% by weight and the dispersant concentration is from 0.02 to α5% by weight of the final product dispersion, preferably from 0.05 to 0.
．． It is in the range of 2% by weight. Dispersants are usually added before the start of polymerization.

The solubility and therefore the usefulness of surfactants and their salts is related to the pH of the reaction medium and the optional presence of other salts.

Solvents for the monomers and optionally for the initiator may be added to the reaction mixture. This solvent is 1=1t2
-1'lichloro-1,2,2-trifluoroethane, 1
, 2-cyclo1,1,2°2-tetrafluoroethane, trichlorofluoromethane, sochlorosofluoromethane or perfluorocyclobutane.

The term "melt processable" means that the polymer has an apparent melt viscosity of 1 x 10' poise at 372°C. The melt viscosity of the tetrafluoroethylene copolymer is Using a cylinder made of a corrosive alloy, Highness Stellite 19, a No. 1 J frame and a piston plus, (2) a 5.Of sample was charged into a cylinder with an inner diameter of 9.53 tm maintained at 372 ± 1 ° C., (3) 5 minutes after charging, diameter 2.10fi, length a
o 500o through Oriais with a square edge of Ow.
Push out under a load of f (piston plus weight) (this is C
ASTM D-
1258-527. Melt viscosity in poise is calculated by dividing 53170 by the extrusion rate, measured in grams per minute.

The amount of comonomer units present in the copolymer is usually
The amount is sufficient to provide satisfactory mechanical properties of the resin. For HFpl it is 6-9 mol%'),
For PPVE it is α4-10 mol%.

Relatively high comonomer incorporation into these copolymers is advantageous for enhancing the physical properties of certain resins. High polymerization rates are desirable to maximize production rates. Additionally, it has been found that the polymerization reactor can be cleaned very easily after polymerization using ammonium fluorononanoate dispersants.

In the examples, comonomer content was determined as follows: HF in the TFElHFP copolymers described herein.
The p content is determined by measuring the ratio of the infrared absorbance at 1α18 micrometers to the absorbance at 4.25 micrometers. This ratio is called the HFP index or HFPI.
It is written as A similar infrared analysis is performed on a comparison film of known HFp content as determined by F19NMH to calibrate the HFpl. The molar percentage of HFp present is equal to 2.1 times that of HFPI. Approximately 0.10-0.11
A compression molded film with a thickness of ta is scanned under a nitrogen atmosphere.

The ppVE content in the TFElPPVE copolymers described in the examples is also determined by infrared spectroscopy. 10.07
The ratio of the absorbance at the micromedle to the absorbance at 4.25 micrometers is measured under a nitrogen atmosphere using a film approximately 0.05 fi thick. After the film is compression molded at 350°C, it is immediately quenched in ice water. This absorbance was then used to determine 1) PP according to a calibration curve established by a reference film of known ppVE content.
Determine the content of VE. F19NMRt is used as the primary standard for calibration of the reference film.

For TFE/HFP/PPVE terpolymers - is
Since some absorption bands overlap, U.S. Pat.
As noted in No. 868, corrections must be made in the analysis.

The invention will be explained in further detail in the following examples.

Example 1 and Comparative Example A In a cylindrical, horizontally arranged, stirred stainless steel reactor with an aqueous tube having a length to diameter ratio of about 1.5 and a water capacity of 80 parts, 55 Add 1 part water and α077 parts dispersant. The mixture is heated to 65° C. and the reactor is then vacuumed and purged with tetrafluoroethylene (TFE). The reaction temperature was then raised to 95°C, and 34
Start stirring at revolutions/minute. The reactor was filled with comonomer (HF
P) to the desired level (570 paig or 2
．． 6MPα) then 600pstg by TFH
Pressurize to (4,1 MPα). Freshly prepared α015
A solution of ammonium persulfate (1.32 parts) of M
0.037 M potassium persulfate initiator solution is added at a rate of 0.022 parts/min for the remainder of the batch. α07M
After polymerization has started, as indicated by a pressure drop of Pα (<10 ps), additional TFE is added at 0.115 ps.
Add 150 parts of additional TFE to the reactor at a rate of 150 parts per minute until completion. The stirring speed was varied to control the transfer of the 7-mer into the liquid phase, thus 6002ay(
A constant pressure level of 4.1 MPa) is maintained. The reaction temperature is maintained at 95°C.

At the end of the reaction, the TFE charge and stirring are stopped. Cooling water is circulated through the reactor shell and the reactor is evacuated. The addition of the initiator solution is stopped, any remaining monomer in the reactor is purged with nitrogen, and the aqueous copolymer dispersion is flushed off. The dispersion is solidified by vigorous stirring to obtain a melt-processable TFElHFP copolymer as a fluff, which is dried and then analyzed.

Example 1 and Comparative Example A are summarized in Table 1.

Ammonium-fluorononanoate dispersant of the present invention (
It is shown in the table that a higher HFP content can be obtained when using ammonium .9-fluoro-rooctanoate (denoted as C-8).

Example 2 and Comparative Example In the same reactor as described in Example 1 and Comparative Example A, 4
8 parts deionized water, 80 parts a0 7% sodium carbonate and r
Charge jQ, 066 parts of ammonium perfluorononanoate. Close the reactor, maintain the reactor temperature at about 20°C, apply suction and add tetrafluoroethylene (TFE).
After purging three times, aspirate again. Ethane is introduced until a pressure increase of j15 kPα occurs. 056 parts f) A-fluoropropyl vinyl ether (PPVE) and 1.19 parts Freon 113 (CCI) were then added to the reactor.
, FCCIF, ). Start stirring and add contents to 8
Heat to 0°C. The reactor was heated to 2.2 MPα by TFH.
(3000pasg) and at the same time α011M
A solution of ammonium persulfate initiator (1.19 parts) is introduced. After initiation of polymerization has occurred (pressure drop of 007 MPa or 1 Qpsi), additional PPVE and 0.
005 The MAPS solution is injected for the subsequent polymerization at a rate of α20 and 1.32 parts per hour, respectively. By changing the stirring speed, 2.2MPα
0 per minute to maintain a constant pressure of (300 psig)
．． Control the reaction rate to require 1 part additional TFE. After 15.4 parts of TFE have been added (starting amount), the TFE and ppVE feeds are stopped and stirring is stopped. The initiator solution continues to be pumped until the reactor is free of unreacted monomer.

After purging the reactor of residual monomer with nitrogen, the aqueous copolymer dispersion is poured off. The dispersant used is 0.093% by weight based on the final product dispersion.

The dispersion is coagulated and dried as in Example 1 before being analyzed. Analysis shows that the produced polymer is 6X at 372°C.
It has a melt viscosity of 10'-az and contains 1.45 mol% ppVE.

The same procedure as above is followed except that the same amount of ammonium fluorooctanoate is used in place of ammonium fluorononanoate. In this case, the melt viscosity is 10.2X10' poise, and the PPV of the polymer is
It is observed that the E content is only 1.07 mol%.

Outside 1ro

Claims (1)

[Claims] Tetrafluoroethylene in an aqueous medium in the presence of an initiator and a dispersant to obtain a melt-processable copolymer having up to 1.20 mole percent of comonomer units. In the polymerization with two ethylenically unsaturated comonomers, a perfluorononanoate salt of the formula n-C_8H_1_7-COOM in which M is hydrogen, ammonium or an alkali metal or a corresponding acid is used as a dispersant, and the dispersion A method characterized in that the agent is used in an amount of about 0.02% to 0.5% by weight based on the final product dispersion. 2. The method of claim 1, wherein M is ammonium. 3. The method of claim 1, wherein the perfluorononanoate or corresponding acid is present in an amount of 0.05% to 0.2% based on the final product dispersion. 4. The method according to claim 1, wherein a water-insoluble solvent is also present during the polymerization. 5. The method according to claim 1, wherein a molecular weight regulator is also present during the polymerization.