JPH11158218A - Method for producing fluorinated polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a fluorinated polymer by circulating unreacted fluorine gas in a fluorination reaction while maintaining a high reaction rate and increasing the utilization efficiency of fluorine gas. SOLUTION: After removing at least a part of by-produced hydrogen fluoride from a gas mixture containing unreacted fluorine gas and by-produced hydrogen fluoride obtained from a fluorination reaction system for producing a fluorinated polymer, the fluorine is removed. Used for circulation in the chemical reaction system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a fluorinated polymer. More specifically, the present invention relates to a method for producing a fluorinated polymer by effectively utilizing fluorine while circulating unreacted fluorine gas to a reaction system and maintaining a high reaction rate.

[0002]

2. Description of the Related Art JP-A-2-28206 discloses that tetrafluoroethylene and a certain kind of fluorinated alkyl vinyl ether are copolymerized in an organic solvent, and the obtained copolymer is reacted with molecular fluorine. A method for making a perfluoroalkylated copolymer is disclosed. The publication discloses that the subsequent reaction with fluorine may be carried out by either a liquid phase method or a gas phase method, or may be carried out by either a continuous method or a batch method. No mention is made of the cyclic use of this.

Conventionally, in such a reaction, it is difficult to separate a mixture of unreacted fluorine gas and hydrogen fluoride, and there is no economical method. Therefore, unreacted fluorine gas has been discarded without being circulated or collected. Therefore, not only is the utilization efficiency of fluorine gas insufficient, but it cannot be released into the environment as it is, so it must be neutralized, then converted to calcium fluoride, and then discarded. There was a problem that required the cost. Further, when the reaction is carried out in a batch system, there is a problem to be improved that the reaction rate gradually decreases with the progress of the reaction in which fluorine is consumed.

[0004]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for producing a fluorinated polymer at a high reaction rate and with a high fluorine utilization efficiency. Another object of the present invention is to provide an industrially excellent method for producing a fluorinated polymer which includes a step of circulating and using unreacted fluorine in a reaction system. Still other objects and advantages of the present invention will become apparent from the following description.

[0005]

According to the present invention, the above objects and advantages of the present invention are attained by reacting a polymer containing a hydrogen atom in a molecule with fluorine gas to form a fluorinated polymer product and an unreacted polymer. A first step of producing a gas mixture containing reactive fluorine gas and by-product hydrogen fluoride; a second step of removing at least a part of the by-product hydrogen fluoride from the gas mixture;
The third step of circulating the gas mixture containing the unreacted fluorine gas obtained in the second step as a part of the fluorine gas of the first step, and the fourth step of recovering a fluorinated polymer which is a product of the first step This is achieved by a method for producing a fluorinated polymer, which comprises: In the first step of the present invention,
A fluorination reaction between a polymer containing a hydrogen atom in the molecule (hereinafter referred to as a hydrogen-containing polymer) and fluorine gas is performed.

In the first step of the present invention, the hydrogen-containing polymer used as a raw material for the fluorination reaction is not particularly limited as long as it is fluorinated by reaction with fluorine gas. As the hydrogen-containing polymer, for example, polyethylene,
Polypropylene, polyvinyl fluoride, polyvinylidene fluoride, polyvinyl trifluoride, a copolymer of tetrafluoroethylene and a fluoroalkyl vinyl ether represented by the following general formula (I), represented by tetrafluoroethylene and the following general formula (II) And a copolymer of tetrafluoroethylene and ethylene.

[0007] _{CF 2 = CFOC a F b X} c H (2a + 1-bc) (I) ( where, X is a chlorine atom or a bromine atom, a is an integer of 1 or more, b is 0～2A + 1 And c is 0 or 1, and has a relationship of 0 ≦ b + c ≦ 2a + 1.) CF ₂ ＣＦCFC _{a Fb} H _{(2a + 1-b)} (II) (where X is a chlorine atom Or a bromine atom, a is an integer of 1 or more, b is an integer of 0 to 2a + 1, and has a relationship of 0 ≦ b ≦ 2a + 1.)

Specific examples of the fluoroalkyl vinyl ether represented by the above general formula (I) include CF ₂ ＣC
FOCH ₃ , CF ₂ ＣＦCFOCH ₂ CH ₃ , CF ₂ ＣＦCFO
_{CF 3, CF 2 = CFOCF 2} CF 3, CF 2 = CFOCF 2
CF ₂ CF ₃ , CF ₂ ＣＦCFOCH ₂ CF ₃ , CF ₂ ＣＦCFO
CH ₂ CF ₂ CF ₃ , CF ₂ ＣＦCFOCH ₂ CF ₂ CF ₂ H,
CF ₂ ＣＦCFOCH ₂ (CF ₂ ) ₂ CF ₃ , CF ₂ ＣＦCFOC
H ₂ (CF ₂ ) ₃ CF ₃ , CF ₂ ＣＦCFOCH ₂ (CF ₂ ) ₄ C
_{F 3, CF 2 = CFOCH 2} (CF 2) 5 CF 3, CF 2 = C
FOCH ₂ (CF ₂ ) ₆ CF ₃ , CF ₂ ＣＦCFOCH ₂ (CF
₂ ) ₇ CF ₃ , CF ₂ ＣＦCFOCH ₂ CF ₂ Cl, CF ₂ ＣC
FOCH ₂ CF ₂ Br, CF ₂ = CFOCH ₂ CF ₂ CF ₂ C
1, CF ₂ ＣＦCFOCH ₂ CF ₂ CF ₂ Br, CF ₂ ＣＦCF
OCH ₂ (CF ₂ ) ₂ CF ₂ Cl, CF ₂ ＣＦCFOCH ₂ (C
F ₂ ) ₂ CF ₂ Br, CF ₂ ＣＦCFOCH ₂ (CF ₂ ) ₃ CF ₂
Cl, CF ₂ ＣＦCFOCH ₂ (CF ₂ ) ₃ CF ₂ Br and the like. These can be used alone or in combination of two or more.

The composition of the copolymer of the above tetrafluoroethylene and the fluoroalkyl vinyl ether represented by the general formula (I) is such that the copolymer does not melt at the reaction temperature with the fluorine gas of the present invention, and What is necessary is just to be in the range which maintains a shape. The monomer unit based on fluoroalkyl vinyl ether is preferably 0.5 to 40 mol%, more preferably 1 to 20 mol%, and the monomer unit based on tetrafluoroethylene is preferably 99.5 to 60 mol%. , More preferably 99 to 80 mol%.

Specific examples of the fluoroolefin represented by the general formula (II) include CF ₂ ＣＦCFCF ₃ , CF
₂ = CFCF ₂ CF ₃ , CF ₂ = CFCF ₂ CF ₂ CF ₃ , C
F ₂ = CFCH ₂ CF ₃ , CF ₂ = CFCH ₂ CF ₂ CF ₃ ,
_{CF 2 = CFCH 3, CF 2} = CFCH 2 CH 3, CF 2 = C
F (CH ₂ ) ₂ CH ₃ and the like. These can be used alone or in combination of two or more.

The composition of the copolymer of the above tetrafluoroethylene and the fluoroolefin represented by the general formula (II) is such that the copolymer does not melt at the reaction temperature with the fluorine gas of the present invention, What is necessary is just to be in the range which maintains a shape. The monomer unit based on the fluoroolefin is preferably 0.5 to 40 mol%, more preferably 1 to 20 mol%.
And the monomer unit based on tetrafluoroethylene is preferably 99.5 to 60 mol%, more preferably 99 to 60 mol%.
~ 80 mol%. Further, there is no problem even if the above-mentioned copolymer contains other monomer components as long as the practice of the present invention is not hindered.

The shape of the hydrogen-containing polymer used in the first step is not particularly limited, and may be powdery, particulate, flake, or the like.
In addition to the rod shape and the pellet shape, a plate shape, a film shape, or a general molded body can be used. In the first step of the present invention, a known reactor can be used without any particular limitation. The reactor preferably used is an internal stirring type reactor having stirring blades inside the reactor, or an external stirring type reactor capable of stirring and mixing the polymer inside by rotating and vibrating the reactor itself. A reactor may be mentioned. When the fluoropolymer used is in the form of a plate, a film, or another molded product, it is preferable to use a reactor having a built-in holder for holding the molded product. The inner wall of the reactor is preferably made of a material having corrosion resistance to fluorine gas.

[0013] In the method of the present invention, the fluorination reaction is carried out in a flow method in which fluorination is carried out while flowing a fluorine gas through a reactor in which a hydrogen-containing polymer is present, and in a reactor in which a hydrogen-containing polymer is present. Contain a predetermined concentration of fluorine gas,
When the desired reaction rate cannot be obtained due to a decrease in the concentration of fluorine gas due to the reaction, the gas in the reactor is discharged,
A batch method or the like in which a fluorine gas is newly enclosed and the reaction is continued to fluorinate can be employed without any particular limitation.
Of these, the distribution method is preferred.

In the fluorination reaction of the first step, it is preferable to use, as the fluorine gas, a fluorine gas diluted with an inert gas. Nitrogen, carbon dioxide, helium, or the like can be used as the inert gas.

In the reaction of the first step, the concentration and the pressure of the fluorine gas are related to each other, and cannot be determined unconditionally by the reaction conditions such as the kind of the raw material resin, the degree of the reaction and the temperature. The pressure is preferably 5 to 40%, more preferably 10 to 30%, and the fluorine gas pressure is preferably 1 to 6.0 kg / cm ² , more preferably 1.3 to 5 kg / cm ² . Is advantageous. When the concentration and pressure of the fluorine gas are lower than these values, not only does it take a long time for the fluorination reaction to proceed, but it may be difficult to complete the fluorination reaction, and as a result, the resulting fluorinated polymer is obtained. Problems in physical properties such as the heat resistance of the coalescence tend to be inferior easily occur. If the concentration and pressure of the fluorine gas are higher than these values, the reaction may become vigorous and the reaction temperature may increase depending on other reaction conditions such as the reaction temperature, and control may be difficult. In extreme cases, significant decomposition of the polymer may occur.

In the present invention, the pressure of the fluorine gas in the reactor may be read by a pressure gauge installed in the reactor. It should also be understood that the concentration of fluorine gas in the reactor is equal to the concentration of fluorine gas contained in the gas discharged from the reactor. That is, the amount of fluorine gas contained in the gas discharged from the reactor is determined by gas analysis at the reactor outlet or removal of a part of by-product hydrogen fluoride gas provided for the reaction gas circulation as described later. After the gas is analyzed, it can be determined.

Here, the range of the concentration and the pressure of the fluorine gas should be maintained substantially within the range where the reaction is carried out. The concentration and pressure of the fluorine gas may temporarily deviate from the above ranges, such as during sampling. However, also in this case, 9 of the hydrogen atoms to be fluorinated
In a range where 5% or more, preferably 98% or more reacts with the fluorine gas, the fluorine gas concentration and the pressure may be set in the above ranges.

The reaction temperature of the fluorination reaction in the first step is preferably from -50 ° C to 200 ° C, more preferably from 0 ° C to 1 ° C.
70 ° C. (temperature below the melting temperature of the polymer to be treated). In order to carry out the reaction efficiently, it is also effective to raise the temperature stepwise or continuously within the above temperature range.
In addition, although it cannot be unconditionally specified depending on the reaction time and reaction conditions, it is generally 1 to 100 hours, preferably 5 to 50 hours.

In the first step, a fluorinated polymer is produced as a target product, and a gas mixture containing unreacted fluorine gas and by-product hydrogen fluoride is obtained. In the gas mixture taken out continuously or intermittently from the fluorination reactor, at least a part of the by-product hydrogen fluoride gas contained is removed in the second step. Removal of by-product hydrogen fluoride gas from the gas mixture is usually carried out by introducing the gas mixture into a condenser to condense and separate easily condensed hydrogen fluoride. Usually, the temperature of the condenser is set in the range of 20 to -50C, preferably 0 to -40C. If condensable fluorine-containing decomposition gas derived from raw materials or products is present during the condensation, part or all of the condensable fluorine-containing decomposition gas is also condensed and removed.

In the second step, preferably at least 40% and more preferably at least 60% of the by-product hydrogen fluoride is removed. The gas mixture containing fluorine gas obtained after removing at least a part of the by-product hydrogen fluoride is then circulated in the third step as a part of the raw material fluorine gas of the first step for use in the fluorination reaction. You. Circulation can be continuous or intermittent. The gas mixture circulated in the third step is returned to room temperature by introducing the gas mixture from the condenser in the second step to a preheater as needed, and is further pressurized by a pressure booster. Thereby, the circulated gas mixture can be smoothly introduced into the fluorination reactor for performing the first step. Also the first
When the reaction temperature in the process is lower than room temperature, the temperature of the circulated gas mixture is adjusted to be the reaction temperature after mixing with the newly added fluorine gas.

It is to be noted that a buffer tank or a drum for suppressing the pressure fluctuation of the pressurized gas mixture or, if necessary, a tank or a drum for temporarily storing the gas mixture between the pressurizer and the reactor. desirable. The concentration of fluorine gas in the circulated gas mixture is low at the beginning of the reaction, for example 1 to 30%, generally 5%.
Approximately 25%, and when approaching the end of the reaction, the concentration of fluorine in the feed gas almost becomes, for example, approximately 5 to 40%.

In a preferred embodiment of the present invention, the concentration of fluorine gas in the gas mixture containing unreacted fluorine gas obtained in the second step, for example, the gas mixture in the above-mentioned tank or drum, is subjected to quantitative analysis to determine the concentration. Thus, the supply amount of the new fluorine gas in the amount of the fluorine gas required for the first step can be determined. Quantitative analysis can be performed by various means, but it is advantageous to use gas chromatography because of the accuracy and speed of the analysis.

In consideration of the results of the quantitative analysis, new fluorine gas is supplied to the reactor so that the concentration of fluorine gas in the reactor in the first step becomes 5 to 40% by volume, preferably 10 to 30% by volume. It is desirable to supply to. After performing the reaction for a predetermined time, in a fourth step, the fluorinated polymer which is a product of the first step is recovered from the reaction apparatus.

The fluorinated polymer produced by the present invention, for example, a perfluoropolymer or a higher-order fluorinated polymer is excellent in surface properties, chemical resistance, electric properties and the like, and is required to have properties as a fluororesin. It can be suitably used in the industrial field. In particular, perfluoropolymers having the following monomer units are extremely useful industrially.

[0025]

Embedded image Here, a is an integer of 1 to 7, m and n are positive integers and n /
(M + n) is 0.5 to 40%.

[0026]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention.

Example 1 6.5 mol% of 2,2,3,3,3- obtained by copolymerizing tetrafluoroethylene and 2,2,3,3,3-pentafluoropropyl trifluorovinyl ether. 25 kg of a copolymer powder containing a monomer unit derived from pentafluoropropyl trifluorovinyl ether (particle size <200 μm, bulk density (ρ) = 0.8 g / cc) was filled with 120 kg of internal volume.
1 internal stirring type horizontal reactor (inner diameter (D) = 400 mm,
Length (L) = 950 mm, gap (d) between the stirring blade and the inner wall of the vessel = 3 mm, helical ribbon blade), and the system was purged with nitrogen.

After stirring at a peripheral speed of the stirring blade of 0.4 m / sec, 30 vol% fluorine diluted with nitrogen was supplied at 5 l / min while maintaining the resin temperature at 20 ° C. After raising the pressure to 1.9 kg / cm ² -G, while maintaining this pressure, the pressure booster was started up, circulation was started at 1 m ³ / hour, and the supply of 30% by volume fluorine was stopped.

After the pressurizer was started, by-products (hydrogen fluoride, decomposition gas, etc.) generated as the reaction proceeded were condensed by a condenser, and the liquefied by-product was stored in a storage tank. The non-condensable nitrogen and fluorine are returned to room temperature with a preheater, and while circulating to the reactor, the gas in the tank provided on the discharge side of
Perform analysis by gas chromatography every 0 minutes,
100% by volume of fluorine was fed from the reactor inlet by feedback control so that the inside of the reactor system had a fluorine gas concentration of 15 to 20% by volume.

The supply of 30% by volume fluorine was started for 0 hour,
One hour later, the temperature of the resin was raised from 20 ° C. to 130 ° C. in 10 hours, and kept at 130 ° C. for 2 hours to terminate the reaction.

After the completion of the reaction, the inside of the reactor was replaced with nitrogen while cooling the reactor, and the resin inside the reactor was taken out.
As a result of measuring the amounts of the hydrogen-containing ether bond and the perfluoroether bond using FT-IR, the fluorinated monomer unit was 4.3 mol%. Also, 2,
All hydrogen atoms derived from 2,3,3,3-pentafluoropropyl trifluorovinyl ether have disappeared,
It was confirmed that the raw material polymer was perfluorinated. The amount of fluorine used in this reaction was 1.1 equivalent per hydrogen atom of the raw material resin.

[0032]

According to the present invention, by circulating and using unreacted fluorine gas in the reaction system, the fluorinated polymer can be industrially advantageously used by effectively utilizing fluorine while maintaining a high reaction rate. It is possible to manufacture.

Claims (2)

[Claims] 1. A method comprising reacting a polymer containing a hydrogen atom in a molecule with fluorine gas to produce a fluorinated polymer product and a gas mixture containing unreacted fluorine gas and by-product hydrogen fluoride. 1 step: removing at least a part of by-product hydrogen fluoride from the gas mixture; 2nd step; circulating the gas mixture containing the unreacted fluorine gas obtained in the 2 step as a part of the fluorine gas in the first step Third step and first step
A fourth step of recovering the fluorinated polymer that is the product of the step. 2. The method according to claim 1, wherein the concentration of the fluorine gas in the mixture containing the unreacted fluorine gas obtained in the second step is determined by quantitative analysis to determine the amount of new fluorine gas to be supplied to the first step. the method of.