JPH08283338A - Production of fluoropolymer - Google Patents

Abstract

PURPOSE: To fluorinate polymer particles by a gas-solid reaction in such a manner that the buildup of static electricity can be prevented and therefore troubles caused by static electricity can be eliminated in the production. CONSTITUTION: A process for producing a fluoropolymer by reacting polymer particles with a fluorine gas by a gas-solid reaction, which comprises performing the reaction in the state in which a liquid perfluorocompound is present on at least part of the surfaces of the polymer particles desirably in the state in which 0.5-30 pts.wt. liquid perfluorocompound is present per 100 pts.wt. polymer particles.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a fluorinated polymer.

[0002]

2. Description of the Related Art A polymer having a fluorine atom in its molecule (hereinafter referred to as a fluorinated polymer) has a unique physical property derived from a fluorine atom and is used in a wide industrial field.

As a method for producing a fluorinated polymer, there is generally a method by a homopolymerization reaction or a copolymerization reaction using a fluorinated monomer corresponding to the desired structure of the fluorinated polymer. However, in the copolymerization reaction by this production method, the composition of the obtained copolymer is governed by the value unique to each monomer, such as the composition ratio of the monomers used, and thus the copolymerization of the copolymer produced in some cases. The problem arises that the composition of the coalescence is limited.

As a method for avoiding the above problems, the production of a desired fluorinated polymer by fluorinating a polymer having a group capable of substituting with fluorine by using a fluorinating agent such as fluorine gas. The method is known. For example, as a method for producing a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether (hereinafter referred to as PFA) in JP-A-2-28206, a fluorine-containing vinyl ether having hydrogen in the molecule and tetrafluoro It has been proposed to fluorinate with fluorine gas after performing copolymerization with ethylene.

PFA is often used in the semiconductor manufacturing process because of its chemical resistance and melt moldability. However, it usually has an unstable group (--CO) at the polymer terminal.
F, -COOH, -COOCH _3, because it has -CONH _2, etc.), has become a semiconductor of pollution problems by fluorine ions generated therefrom. Therefore, as a measure against such a problem, for example, in Japanese Patent Laid-Open No. 4-83,
A method has been proposed in which PFA is reacted with fluorine gas to stabilize unstable groups.

Further, for the purpose of improving chemical resistance, heat resistance, surface properties, etc., it has been proposed to fluorinate polyethylene, polypropylene or the like with fluorine. Furthermore,
It has also been proposed to react polytetrafluoroethylene with fluorine to fluorinate the unstable group at the terminal to improve water repellency, or to cut the main chain to produce low-molecular weight polytetrafluoroethylene for lubrication. ing.

[0007]

As described above, treatment of a polymer with fluorine makes it possible to discover a useful function, and many applications have been made. However, it is generally known that fluorine gas and an organic compound cause a considerably violent reaction depending on conditions. For this reason, when such a reaction is carried out by a so-called gas-solid reaction in which solid polymer particles are reacted with fluorine gas for the purpose of simplifying the process, stirring is sufficiently performed to prevent heat accumulation of reaction heat. It becomes necessary to plan.

However, when the fluorination reaction proceeds in a state where the polymer particles move by stirring or the like as described above, static electricity is generated because the polymer particles come into contact with each other or with the inner wall of the reactor or the stirring device. To do. Then, the problem that the charged fluorinated polymer adheres to the inner wall of the reactor or the stirrer due to the attractive force of static electricity arises, and the heat removal becomes insufficient, and in addition, there is a strong oxidizing atmosphere such as the presence of fluorine gas. There are also concerns about the danger of flammable discharges below. Further, since the fluorinated polymer is charged with static electricity after completion of the reaction, there arises a problem in handling the polymer such as adhesion to a metal device or repulsion between the fluorinated polymers. When particles having a small particle size are used as the polymer particles, the above-mentioned obstacle due to electrostatic charging becomes very remarkable.

Generally, a polymer has a high electric insulating property, and it is difficult to remove static electricity once charged. There are several known methods for removing static electricity from general resins, such as humidification and addition of an antistatic agent, but these methods cannot be used under extremely active conditions such as the presence of fluorine gas. Can not.

[0010]

Means for Solving the Problems Accordingly, the present inventors have:
In the method of reacting polymer particles and fluorine gas by a gas-solid reaction, intensive studies have been conducted for the purpose of extremely reducing the amount of static electricity generated. As a result, they found that the presence of a perfluoro compound having specific physical properties on the surface of polymer particles can suppress the generation of static electricity, and completed this study.

That is, in the present invention, when a fluorinated polymer is produced by reacting polymer particles with a fluorine gas by a gas-solid reaction, a liquid perfluoro compound is present on at least a part of the surface of the polymer particles. The method for producing a fluorinated polymer is characterized in that the reaction is carried out in an open state.

In the present invention, the polymer used as a raw material is not particularly limited as long as it can react with fluorine gas to produce a fluorinated polymer. Usually, those having a group capable of substituting for fluorine in the molecule and capable of being fluorinated into a perfluoro body or a partially fluorinated body by a reaction with fluorine gas are mentioned. Here, as the group capable of substituting for fluorine,
Hydrogen atom or -COF, -COOH, -COOCH _3, -
CONH ₂ etc. can be applied without limitation. Also, the present invention
It is also applicable to the reaction of reacting a perfluoropolymer such as polytetrafluoroethylene with fluorine gas to randomly cut the main chain of the polymer to produce a low molecular weight fluorinated polymer. A perfluoropolymer can also be used as a raw material polymer.

In the present invention, specific examples of the target raw material polymer include polyethylene, polypropylene,
Polyvinyl chloride, polyvinyl fluoride, polyvinylidene fluoride, polyvinyl trifluoride, polytetrafluoroethylene, tetrafluoroethylene and the following general formula (I) CF ₂ = CFOC _a F _b X _c H _{(2a + 1-bc)} (I) (wherein 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, c is 0 or 1, and 0 ≦ b + c ≦ 2a + 1 And a fluoroalkyl vinyl ether copolymer represented by the following general formula (I
I) CF ₂ ═CFC _a F _b H _{(2a + 1-b)} (II) (wherein X is a chlorine atom or a bromine atom, a is an integer of 1 or more, and b is an integer of 0 to 2a + 1. And has a relationship of 0 ≦ b ≦ 2a + 1), a copolymer with a fluoroolefin, a copolymer of tetrafluoroethylene and ethylene, and the like.

Specific examples of the fluoroalkyl vinyl ether represented by the above general formula (I) include:

[0015]

Embedded image

And the like.

Further, the composition of the copolymer of tetrafluoroethylene and the fluoroalkyl vinyl ether represented by the general formula (I) is substantially such that the copolymer does not melt at the reaction temperature with the fluorine gas of the present invention. The shape of the monomer unit based on fluoroalkyl vinyl ether is 0.5 to 40 mol%, preferably 1 to 2
0 mol%, tetrafluoroethylene-based monomer units 99.5-60 mol%, preferably 99-80
Mol%.

Specific examples of the fluoroolefin represented by the general formula (II) are as follows:

[0019]

Embedded image

And the like.

Further, the composition of the copolymer of 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, and As long as the shape is maintained, the fluoroolefin-based monomer unit is 0.5 to
40 mol%, preferably 1 to 20 mol%, the monomer unit based on tetrafluoroethylene is 99.5 to 60
It is mol%, preferably 99-80 mol%.

Further, -COF, -COOH, -COOC
H _3, also perfluoropolymer and copolymers of PFA or tetrafluoroethylene and hexafluoropropylene having at least a portion of the labile group -CONH ₂ or the like (CF ₂ = CFCF _3), applicable to the present invention It is a raw material polymer that can be obtained.

Further, there is no problem even if the above-mentioned polymer contains other monomer components as long as the practice of the present invention is not impaired.

The particle size of particles made of such a polymer is
Although not particularly limited, it is generally preferable that the particles having a size of 3 mm or less account for 90% by weight or more of the whole particles. In the case of such a particle size distribution, the antistatic effect is most remarkably exhibited, and the fluorination reaction itself can be carried out uniformly.

The perfluoro compound used in the present invention may be any compound which is partially or wholly present as a liquid under the conditions of the fluorination reaction with the fluorine gas of the present invention. As such a perfluoro compound, known compounds can be used without particular limitation, but preferably have 8 carbon atoms.
-20, preferably a perfluoro compound having 10 to 18 carbon atoms is preferable. In this case, there is no problem even if the molecule contains a nitrogen atom or an oxygen atom in addition to the carbon atom and the fluorine atom.

Examples of the perfluoro compound which can be preferably used in the present invention include the perfluoroalkane represented by the general formula C _n F _{2n + 2} and the general formula N having the above carbon number.
(C _n F _{2n +} 1) perfluoro amine represented by _3, the general formula _{C n F 2n + 2 O,} (C n F 2n + 2 O) m or C _n F _2n O linear represented , Or cyclic perfluoroether. In the present invention, the above perfluoro compounds may be used alone or two or more of them may be used without any problem. Such a perfluoro compound is generally present on the surface of the polymer particles in the state of such a perfluoro body and is subjected to a fluorination reaction, and is fluorinated during the fluorination reaction to form the perfluoro compound. It may be provided by being present on the surface of polymer particles in the form of the precursor.

In the present invention, the gas-solid reaction is carried out by allowing the liquid perfluoro compound to adhere or be adsorbed on at least a part of the surface of the polymer particles. At that time, the amount of the perfluoro compound used is not limited as long as the gas-solid reaction is maintained. In order to maintain good fluidity of particles without antistatic effect or granulation, 0.5 to 30 parts by weight, preferably 1.5 to 20 parts by weight, relative to 100 parts by weight of polymer particles. It is preferable to use.

When the perfluoro compound is used in the above range, the appearance of the polymer particles is slightly moist. When stirring was performed in the reactor, although almost no difference was observed in the fluidity as powder, almost no electrostatic charge was expected from the appearance, which is surprising.

The perfluoro compound may be allowed to exist on the surface of the polymer particles by mixing the polymer particles and the perfluoro compound prior to the fluorination reaction. Also, depending on the reaction conditions, the reaction temperature may be raised during the reaction, and it is possible that a part of the perfluoro compound that was already present may vaporize.In such a case, the perfluoro compound is added during the reaction. Mixing with polymer particles is also an effective method. At this time, the perfluoro compound may be introduced as a liquid, and there is no problem even if it is gasified by heating and introduced and cooled in the reactor to be liquefied. Further, in the flow method in which fluorine gas is continuously supplied and the batch method in which fluorine gas is replaced, part of the perfluoro compound may be discharged from the reactor along with the flow of waste gas. In such a case, it is also effective to introduce the perfluoro compound intermittently or continuously.

The fluorination method using fluorine gas employs a gas-solid reaction in which the polymer particles are directly fluorinated with fluorine diluted with an inert gas, if necessary. In this case, it is preferable to use a reactor made of a material having corrosion resistance to fluorine gas. In addition, the reaction is preferably carried out in a state where the polymer particles move under stirring or under vibration in order to improve the contact between the polymer particles and the fluorine gas and prevent the heat of reaction generated from being accumulated. . In that case, the antistatic effect of the present invention is most significantly exhibited. Examples of the reaction method include a flow method in which fluorine gas is circulated in a reactor containing polymer particles while fluorinating, and a batch method in which fluorine gas having a predetermined concentration is contained and fluorinated.

It is known that depending on the reaction conditions, the fluorine gas and the polymer particles cause a fairly vigorous reaction. Therefore, when fluorine gas is initially introduced into the reactor, it is preferable to once cool the reactor, fill it with fluorine gas, and then raise the temperature to the reaction temperature. In case of batch method,
If the amount of fluorine gas introduced at one time is not sufficient to convert the polymer particles to the desired degree of fluorination, after a certain reaction time has elapsed, the gas in the reactor is exhausted and a new fluorine gas is added. Gas may be introduced. Also in this case, it is preferable to once cool the reactor and introduce the fluorine gas. The introduction temperature of the fluorine gas is slightly different depending on the type of polymer particles, the reaction mode, etc., but is generally room temperature or lower. Further, when the fluorine gas is replaced during the reaction, the fluorine gas may be introduced at a higher temperature than the initial introduction of the fluorine gas, depending on the degree of progress of the reaction. Further, in the case of the flow method, in addition to cooling the reactor at the time of starting the introduction of fluorine gas, starting the concentration of the introduced fluorine gas from a low concentration and gradually increasing the concentration also in order to carry out the reaction gently. Is valid.

The reaction temperature is preferably −100 ° C. to 200 ° C., preferably −50 ° C. to 180 ° C. In order to carry out the reaction efficiently, stepwise or continuously within the above temperature range. It is also effective to raise the temperature. The fluorine gas to be introduced is preferably diluted with an inert gas such as nitrogen, carbon dioxide, or helium to 5 to 100%, preferably 10 to 50%. The pressure of the fluorine gas is not particularly limited, but is 0.1 to 2 from the viewpoint of reaction safety.
0 kg / cm ^2, preferably it is better to carry out the reaction under a pressure of 0.5 to 10 / cm ^2. Further, the reaction time cannot be unconditionally specified depending on the reaction conditions, but generally, the fluorination may be performed for 1 to 100 hours, preferably 5 to 50 hours.

After the reaction, the perfluoro compound contained in the fluorinated polymer can be easily separated from the fluorinated polymer by heating and washing, if necessary.

[0034]

As can be understood from the above description, according to the present invention, a liquid perfluoro compound is present on the surface of polymer particles, and the polymer particles are reacted with fluorine gas for fluorination. By doing so, the amount of electrostatic charge of the polymer inside the reactor is significantly reduced, so sufficient stirring for the purpose of heat removal is possible, and the fluorination reaction can be effectively performed.

Further, the amount of charge of the fluorinated polymer obtained by the reaction is small, so that not only obstacles such as existence and repulsion due to static electricity can be avoided, but dust is hardly generated even when fine powder is used. Also brings the effect.

In the present invention, the degree of fluorination can be widely changed from the partially fluorinated form to the perfluoro form depending on the reaction conditions, and further, it can be applied to the reaction of cleaving the main chain of the perfluoro form. Further, the fluorinated polymer produced by the present invention can be used in the industrial field where the characteristics as a fluororesin such as surface characteristics, chemical resistance and electric characteristics are required.

[0037]

EXAMPLES The following examples are given for illustrating the present invention further in detail, but the present invention is not limited to these examples.

The electrostatic charge amount was obtained as a charge amount per unit weight from the indicated voltage and the resin weight by placing the sample in a Faraday cage.

Example 1 6 mol% of 2,2,3,3,3-pentafluoro obtained by copolymerizing tetrafluoroethylene and 2,2,3,3,3-pentafluoropropyltrifluorovinyl ether Copolymer powder containing monomer units derived from propyltrifluorovinyl ether (particle size 0.5 to 1
(mm powder) 12 g, and an internal volume of a perfluoropentylamine liquid that can be rotated by a motor 12
The reactor was placed in a 0 mL nickel reactor, the inside of the reactor was thoroughly degassed, and then fluorine gas diluted with nitrogen to 80% by volume under ice cooling was introduced up to 3 kg / cm ² -G. Next, the reactor was put in an oil bath of 10 ° C., and the temperature of the oil bath was raised to 150 ° C. at a rate of 1 ° C./minute while rotating. 150
After reacting at 8 ° C. for 8 hours, the inside was thoroughly replaced with nitrogen,
Open the reactor, put the contents into the Faraday cage,
The charge amount was measured. This experiment was repeated to examine the relationship between the amount of perfluoropentylamine added and the amount of charge. The results obtained are shown in Table 1.

[0040]

[Table 1]

Comparative Example 1 The same reaction as in Example 1 was carried out except that no perfluorotripentylamine was added. The charge amount of the obtained fluorinated polymer was 11.0 to 12.3 nC / kg.

Example 2 97 mol% of tetrafluoroethylene and 3 mol% of 2,2,3,3,4, having a particle size of 3 mm or less.
20 g of powder of a copolymer with 4,5,5,6,6,6-undecafluorohexyl trifluorovinyl ether,
After mixing 1.0 g of liquid of perfluorotripentylamine, it was possible to rotate with a motor.
After being placed in a mL reactor made of nickel and thoroughly degassing the inside of the reactor, 75% by volume of fluorine gas diluted with nitrogen under ice cooling was introduced up to 2 kg / cm ² -G. Then place the reactor at 10 ° C.
The temperature of the oil bath was raised to 95 ° C. at a rate of 1 ° C./min while rotating. After reacting at 95 ° C. for 2 hours, the inside was replaced with nitrogen. Next, after cooling the reactor with ice, the same fluorine gas introduction and temperature raising operations were repeated, and the reaction was carried out at 95 ° C. for 2 hours, 95 ° C. for 9 hours, and 135 ° C. for 9 hours. After completion of the reaction, the inside of the reactor was sufficiently replaced with nitrogen, the reactor was opened, and the contents were put into a Faraday cage. At this time, the polymer powder did not adhere to the inner wall of the reactor. The charge amount was 0.20 nC / kg.

Comparative Example 2 The same reaction as in Example 2 was carried out except that no perfluorotripentylamine was added. After the completion of the reaction, when the contents were opened in a Faraday cage, the polymer powder adhered to the inner wall of the reactor and the whole amount could not be transferred to the Faraday cage. The charge amount of the fluorinated polymer transferred into the Faraday cage was 21.5 nC / kg.

Example 3 Perfluoro-2-butyl-as a perfluoro compound
Example 1 except that 6 g of tetrahydrofuran liquid was used
The same reaction was carried out. The charge amount of the fluorinated polymer after the reaction was 0.31 nC / kg.

Example 4 Approximately 30 terminal carboxylic acid fluoride groups and about 120 per 1 million carbon atoms having a particle size of 1 mm or less.
25 g of a copolymer of 98 mol% tetrafluoroethylene and 2 mol% of perfluoropropyl vinyl ether having 1 terminal methyl ester group was mixed with 1 g of perfluorotripentylamine liquid, and then rotated by a motor. In a nickel reactor with an internal volume of 120 mL, the inside of the reactor was thoroughly degassed, and then 25% by volume of fluorine gas diluted with nitrogen under ice cooling was added at 2 kg / cm ^2.
-G was introduced. Next, the reactor was put in an oil bath of 10 ° C., and the temperature of the oil bath was raised to 150 ° C. at a rate of 1 ° C./minute while rotating. The reaction was carried out at 150 ° C for 8 hours. After completion of the reaction, the inside of the reactor was sufficiently replaced with nitrogen, the reactor was opened, and the contents were put into a Faraday cage. At this time, the polymer powder did not adhere to the inner wall of the reactor. The charging voltage was 0.15 nC / kg. When the obtained fluorinated polymer was analyzed, terminal carboxylic acid fluoride groups and methyl ester groups were not detected at all.

Comparative Example 3 The same reaction as in Example 4 was carried out except that perfluorotripentylamine was not used. The charge amount of the polymer after completion of the reaction was 14.2 nC / kg.

Example 5 25.5 g of polyethylene having a particle diameter of 1 mm or less and 0.6 g of a liquid of perfluorononane were mixed, and the mixture was placed in a stainless reactor having an inner volume of 150 mL equipped with a stirrer, and the pressure of the reactor was adjusted. While maintaining the atmospheric pressure (1 kg / cm ² ), the inside of the reactor was cooled to −20 ° C. while introducing nitrogen at 100 mL / min. After the reactor internal temperature reached −20 ° C., fluorine gas was introduced into the reactor at a rate of 10 mL / min. After 10 hours, only the introduction of fluorine gas was stopped, and the reactor was heated to room temperature while introducing nitrogen. The nitrogen gas was stopped, the reactor was opened, and the contents were placed in a Faraday cage. At this time, the polymer powder did not adhere to the inner wall of the reactor. The charge amount is 0.32 nC /
It was kg.

Comparative Example 4 The same reaction as in Example 5 was carried out except that perfluorononane was not used. The charge amount of the polymer after the reaction is 12.5n
It was C / kg.

Claims (1)

[Claims] 1. When producing a fluorinated polymer by reacting polymer particles with a fluorine gas by a gas-solid reaction, the reaction is carried out in the state where a liquid perfluoro compound is present on at least a part of the surface of the polymer particles. A method for producing a fluorinated polymer, which comprises: