JPH1135694A - Granulation of fluorine-containing polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the efficient granulation of the subject polymer excellent in heat, solvent and chemical resistances without using a medium producing the environmental disruption by previously producing a fluorine-containing polymer containing a specific granulation medium and then bringing the resultant polymer into contact with water at a specified temperature under stirring. SOLUTION: A (polyfluoroalkyl)alkyl ether represented by the formula R-O-R' (R is a 2-6C fluoroalkyl; R' is a 1-2C alkyl) [e.g. (CF3 )2 CFOCH3 ] is initially used as a granulation medium to previously produce a fluorine-containing polymer containing the granulation medium when producing the fluorine-containing polymer containing a fluoroolefin unit as a main constituent unit (preferably tetrafluoroethylene/ethylene copolymer). The resultant fluorine-containing polymer is then brought into contact with water at 20-150 deg.C under stirring to thereby carry out the removal of the granulation medium and granulation of the fluorine-containing polymer. The amount of the granulation medium present when bringing the fluorine-containing polymer into contact with the water is preferably 1,000 2,500 pts.wt. based on 100 pts.wt. fluorine-containing polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method for granulating a fluorine-containing polymer, and more particularly, to a method for heat resistance, solvent resistance, chemical resistance, etc., using a granulation medium which hardly causes environmental destruction. The present invention relates to a method for efficiently granulating a good fluoropolymer.

[0002]

2. Description of the Related Art Fluoropolymers are high-molecular materials having excellent heat resistance, solvent resistance, chemical resistance, etc., and are utilized in various applications by utilizing their characteristics.

As a method for producing a fluoropolymer, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method are known. As a polymerization medium for the solution polymerization method and the suspension polymerization method, an inert solvent such as chlorofluorocarbon is used. Solvents are generally used from the viewpoint of obtaining a high molecular weight copolymer and the polymerization rate. Specific examples of chlorofluorocarbon include trichlorofluoromethane, dichlorodifluoromethane,
Examples thereof include trichlorotrifluoroethane and dichlorotetrafluoroethane, but trichlorotrifluoroethane has been mainly used from the viewpoint of handling. Also,
By bringing the fluoropolymer containing these media into contact with water with stirring, the above granulation medium is expelled from the fluoropolymer and the fluoropolymer is granulated, and the powder fluidity and moldability A method for improving the above has been known (Japanese Patent Publication No. 50-17230).

[0004] In recent years, the destruction of the ozone layer has been taken up internationally as a global environmental destruction problem, and the use of specific chlorofluorocarbons as a causative substance has been banned. Therefore, there is a great demand for the development of a substitute for chlorofluorocarbon used when granulating a fluoropolymer.

As a substitute for the chlorofluorocarbon, a perfluorocarbon or a hydrofluorocarbon containing a hydrogen atom has been proposed because of its small ozone depletion potential.

[0006]

SUMMARY OF THE INVENTION Under such circumstances, the present invention is to eliminate the use of chlorofluorocarbon having a large ozone depletion potential and to use perfluorocarbon which contributes to global warming. Another object of the present invention is to provide a method for efficiently granulating a fluoropolymer having excellent heat resistance, solvent resistance and chemical resistance.

[0007]

According to the present invention, in granulating a fluoropolymer containing a fluoroolefin unit as a main constituent unit, a (polyfluoroalkyl) alkyl ether of the formula 1 is used as a granulating medium, The above-mentioned fluoropolymer containing a granulating medium is prepared in advance, and this fluoropolymer is brought into contact with water at a temperature of 20 to 150 ° C. with stirring to expel the medium from the fluoropolymer and to contain the medium. Provided is a method for granulating a fluoropolymer, which comprises granulating a fluoropolymer.

R—O—R ′ Formula 1 wherein R is a fluoroalkyl group having 2 to 6 carbon atoms,
R ′ is an alkyl group having 1 or 2 carbon atoms.

In the present invention, the fluoropolymer containing a fluoroolefin unit as a main constituent unit may be prepared by polymerizing a fluoroolefin monomer alone or in combination of two or more kinds, or by copolymerizing with a fluoroolefin monomer. It is produced by copolymerizing monomers other than olefin monomers.

The fluoroolefin monomer used in the present invention is an olefin having at least one fluorine atom in the molecule, and preferably has 2 or 3 carbon atoms in view of polymerizability and properties of the obtained polymer. Is a fluoroolefin monomer.

Specific examples of such fluoroolefin monomers include CF ₂ CF ₂ , CF ₂ ＣＦCFCl,
Fluoroethylenes such as F ₂な ど CH ₂ , CF ₂ ＣＦCF
It is a fluoropropylene type such as CF ₃ and CF ₂ ＣＨCHCF ₃ . These fluoroolefin monomers may be used alone or in combination of two or more.

Further, as a monomer copolymerized with these fluoroolefin monomers, CF ₃ CF ₂ CF ₂ CF ₂ C
(Perfluoroalkyl) ethylenes having 4 to 12 carbon atoms in perfluoroalkyl groups such as H = CH ₂ and CF ₃ CF ₂ CF ₂ CF ₂ CF = CH ₂ , R ^f (OCFXCF
₂ ) perfluoro such as _m OCF = CF ₂ (wherein, R ^f represents a perfluoroalkyl group having 1 to 6 carbon atoms, X represents a fluorine atom or a trifluoromethyl group, and m represents an integer of 1 to 6). Vinyl ethers, CH ₃ OC (＝ O) CF ₂
CF ₂ CF ₂ OCF = CF ₂ or FSO ₂ CF ₂ CF ₂ O
It can be used in combination with a vinyl ether having a group which can be easily converted to a carboxylic acid group or a sulfonic acid group such as CF (CF ₃ ) CF ₂ OCF ＯCF ₂ . Moreover, you may combine with olefin-type monomers, such as ethylene, propylene, and isobutylene.

A particularly preferred fluoropolymer is a tetrafluoroethylene / ethylene copolymer. As monomers further copolymerizable with tetrafluoroethylene and ethylene, for example, fluoroolefins other than tetrafluoroethylene, such as vinyl fluoride, vinylidene fluoride, chlorotrifluoroethylene, hexafluoropropylene, and (perfluoroalkyl) ethylene , Fluorovinyl ethers, acrylic acid, methacrylic acid, vinyl chloride and the like.

The granulating medium used in the present invention is PF
It is necessary to use AE. If the number of carbon atoms in the PFAE is too small, the boiling point is too low and gas is generated at room temperature, which is inconvenient to handle. If it is too large, the PFAE has a high boiling point and it is difficult to separate it from the fluoropolymer. Therefore, R in Formula 1 is preferably a fluoroalkyl group having 2 to 6 carbon atoms, and more preferably a perfluoroalkyl group having 3 or 4 carbon atoms. R may have a straight-chain structure or a branched structure. R ′ is preferably a methyl group or an ethyl group. A specific example of PFAE is CF
₃ CF ₂ CF ₂ CF ₂ OCH ₃ , CF ₃ CF ₂ CF ₂ C
F ₂ OCH ₂ CH ₃ , CF ₃ CF ₂ CF ₂ OCH ₃ ,
(CF ₃ ) ₂ CFOCH ₃ . The same organic compound may be used for the granulating medium and the polymerization medium, or different organic compounds may be used.

Further, since PFAE contains hydrogen, it is characterized in that its global warming potential is lower than that of perfluoro compounds. For example, the estimated lifetime value that is an indicator of the global warming potential is approximately 100 for C ₆ F _14.
Year, C ₆ F ₁₃ H is 20 to 30 years, but CF ₃ CF ₂
CF ₂ OCH ₃ was 1.9 years old, CF ₃ CF ₂ CF ₂ CF ₂
OCH ₃ is as small as 1.2 years.

In the present invention, the term "fluorine-containing polymer containing a granulating medium in advance" refers to the case where a fluorinated polymer is produced by polymerizing a fluoroolefin monomer using PFAE as a polymerization medium. And it is said that the fluorinated polymer contains PFAE of the resulting polymerization suspension.
Further, when the PFAE is produced using a polymerization medium different from PFAE, PFAE is added as a granulation medium, and the PFAE in the polymer and the PFAE in the resulting polymerization suspension also contain the fluoropolymer.

PFAE contained in a fluoropolymer
The amount is not particularly limited, but if it is too small, the effect of the present invention will not be sufficiently achieved, and if it is too large, there will be no effect on the effect, but it will be economical, processing equipment and work viewpoint. Is not preferred. Usually, the amount of PFAE present at the time of contact treatment with water depends on the amount of the fluoropolymer 10
50 parts by weight or more based on 0 parts by weight, preferably 100 to 100 parts by weight
About 3000 parts by weight, especially about 1000 to 2500 parts by weight is employed.

The amount of water used in the contact treatment is not particularly limited, but is preferably about 50 to 500% by volume based on the total amount of PFAE and the fluoropolymer.
In the present invention, the temperature during the contact treatment with water is important, and good results are usually obtained at a temperature in the range of 20 to 150 ° C. It is desirable that the optimum temperature be appropriately selected according to the type and amount of PFAE, the contact treatment time, and the like. Particularly preferably, it is about 30 to 100 ° C. If the temperature is too low, it generally requires a long processing time and it is difficult to obtain good results in terms of the effects. If the temperature is too high, the pressure in the system will increase and the operability will decrease, and the properties of the copolymer may deteriorate. Further, the processing time is usually about 15 minutes to 30 hours in the above temperature range, and at least a sufficient time for separating and removing PFAE is required.

The contact treatment with water in the present invention is usually carried out by stirring the mixture of the PFAE-containing fluoropolymer and water under the above-mentioned conditions in a treatment apparatus equipped with a stirring blade. The device may be an ordinary stirring tank or a device provided with a baffle plate. The stirring blade is a turbine blade,
Good results are obtained with commonly used stirring blades such as chi-type blades. The mixture of the fluorinated polymer and PFAE is not compatible with water and has settled at the bottom of the tank because of its high density, and the fluorinated polymer separated from PFAE is floating on the water surface. Therefore, the conditions for efficiently bringing the fluoropolymer into contact with water are appropriately set to optimal ranges depending on the ratio of the fluoropolymer and PFAE, the ratio of the mixture of the fluoropolymer and PFAE and water, and the like. I can do it.

The particle size of the fluoropolymer granulated particles obtained in the present invention can be appropriately changed depending on the initial stirring conditions in which PFAE is present. For example, the particle diameter of the fluoropolymer can be reduced by increasing the initial stirring speed. In addition, the initial stirring temperature for determining the particle size is usually preferably not too high, and is desirably lower than the boiling point of the PFAE used. Therefore, in the present invention, the fluorinated polymer containing PFAE is stirred in water, and the stirring speed is adjusted at a temperature lower than the boiling point of the granulation solvent in the initial stage to adjust the particle diameter to the optimum size, and then the temperature is increased. By performing the stirring treatment while driving out the granulating solvent, preferable particles having a uniform particle diameter can be efficiently obtained.

[0021]

【Example】

[Example 1] Tetrafluoroethylene, ethylene and (perfluorobutyl) ethylene were charged at a ratio of 4/1 / 0.05 (molar ratio), and CF ₃ CF ₂ CF ₂ CF ₂ OCH ₂ CH
_The copolymer was copolymerized in the solvent of No. ₃ . The charge weight ratio of solvent / monomer is 15.2 / 1. 0.09 based on monomer
% By weight of a polymerization initiator perbutyl IB (manufactured by NOF Corporation) was added, and a copolymerization reaction was performed at a reaction temperature of 65 ° C. As a result, 8% by weight of tetrafluoroethylene /
A suspension of an ethylene copolymer (polymerized units based on tetrafluoroethylene / polymerized units based on ethylene / polymerized units based on (perfluorobutyl) ethylene = 53/46/1 mol%) was obtained. 500 ml of the mixture was charged together with 1000 ml of water into a stirrer equipped with six turbine blades and two baffles, and heated at 90 ° C. at a rate of 2 ° C./min.
And processed at a rotation speed of 400 rpm for 1 hour. The obtained copolymer had a particle size of about 1.0 mm and a bulk density of 0.60 g / cc. The plate having a thickness of 5 mm formed by compression molding at 300 ° C. was a clean plate without bubbles.

Example 2 CF ₃ CF ₂ CF ₂ CF ₂ O
CF ₃ CF ₂ CF ₂ CF ₂ OC instead of CH ₂ CH ₃
Polymerization and granulation were carried out in the same manner as in Example 1 except that H ₃ was used. The obtained copolymer has a particle size of 1.3 mm.
And the bulk density was 0.55 g / cc. 30
The plate having a thickness of 5 mm formed by compression molding at 0 ° C. was a clean plate without bubbles.

Example 3 CF ₃ CF ₂ CF ₂ CF ₂ O
Polymerization and granulation were carried out in the same manner as in Example 1 except that (CF ₃ ) ₂ CFOCH ₃ was used instead of CH ₂ CH ₃ . The obtained copolymer had a particle size of about 1.5 mm and a bulk density of 0.40 g / cc. The plate having a thickness of 5 mm formed by compression molding at 300 ° C. was a clean plate without bubbles.

Comparative Example 1 CF ₃ CF ₂ CF ₂ CF ₂ O
CF ₃ CF ₂ CF ₂ CF ₂ CF instead of CH ₂ CH ₃
Polymerization and granulation were carried out in the same manner as in Example 1 except that ₂ CF ₃ was used, and di (perfluorobutyryl) peroxide was used as a polymerization initiator, and polymerization was performed at a polymerization temperature of 50 ° C. The obtained copolymer is a brittle particle having a particle size of about 0.8 mm and a low bulk density of 0.25 g / cc,
The powder had poor fluidity and was difficult to handle.
Also, due to the low bulk density, air bubbles were present in a 5 mm thick plate formed by compression molding at 300 ° C.

[Comparative Example 2] Polymerization was carried out in the same manner and under the same conditions as in Example 1 to obtain a copolymer suspension solution 500.
Hexane (1000 ml) was added to the resulting mixture, and the mixture was stirred and mixed uniformly. This mixture was composed of a medium-only part and a medium-containing copolymer part. About 300 ml of the medium-containing copolymer part was separated and recovered. 1000 ml of hexane was further added to the separated and recovered copolymer portion, and the mixture was uniformly stirred and mixed.
0 ml was separated and collected. This operation was repeated 5 times such that about 95% by weight of the medium in the copolymerized portion containing the medium was hexane. Hexane was added to the copolymer containing this medium to make 500 ml, and the mixture was stirred and mixed with 10 parts of water.
After adding 00 ml, granulation was performed in the same manner as in Example 1. However, granulation could not be performed, and only powdery materials could be formed.
Further, the bulk density was as low as 0.15 g / cc, and bubbles were present in the compression-molded product.

[0026]

EFFECT OF THE INVENTION According to the method of the present invention, a fluorinated polymer having good heat resistance, solvent resistance, chemical resistance and the like can be efficiently produced by using PFAE having a much lower ozone destruction effect. .

Claims (3)

[Claims] (1) In granulating a fluoropolymer containing a fluoroolefin unit as a main constituent unit, a (polyfluoroalkyl) alkyl ether of the formula 1 is used as a granulating medium, and the granulating medium is previously contained. A fluorinated polymer is produced, and the fluorinated polymer is prepared at 20 to 150
A method for granulating a fluorinated polymer, comprising expulsing the medium from the fluorinated polymer and granulating the fluorinated polymer by bringing the medium into contact with water at a temperature of ° C under stirring. R—O—R ′ Formula 1 In the formula, R is a fluoroalkyl group having 2 to 6 carbon atoms, and R ′ is an alkyl group having 1 or 2 carbon atoms. 2. The granulation method according to claim 1, wherein the fluoropolymer is a tetrafluoroethylene / ethylene copolymer. 3. The granulation medium is CF ₃ CF ₂ CF ₂ CF ₂ O.
CH ₃ , CF ₃ CF ₂ CF ₂ CF ₂ OCH ₂ CH ₃ , C
F ₃ CF ₂ CF ₂ OCH ₃ or (CF ₃ ) ₂ CFOC
Granulating method according to claim 1 or 2 wherein the H _3.