JPS63284201A - Preparation of organosol of fluorine-containing polymer - Google Patents

Abstract

PURPOSE:To make possible the production of an organosol which is stable regardless of the kind of a fluorine-contg. polymer, by polyerizing a polyfluoroalkyl group-contg. monomer in an aqueous dispersion of a fluorine- contg. polymer and subsequently replacing the water medium with an anhydrous organic solvent. CONSTITUTION:An organosol of a fluorine-contg. polymer is prepared by polymerizing a polyfluoroalkyl group-contg. monomer [pref. a polyfluoroalkyl group- contg. (meth)acrylate, e.g. a compound of the formula as shown] in an aqueous dispersion of a fluorine-contg. polymer (e.g. polytetrafluoroethylene) and subsequently replacing the water medium with a substantially anhydrous organic solvent (e.g. toluene, acetone, etc.). This method makes it possible to produce an organosol which is stable not only for a single high-MW polytetrafluoroethylene system but also for every fluorine-contg. polymer, whose production has heretofore been difficult.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a stable organosol of a fluoropolymer.

[Prior Art] Fluoropolymer organosols are widely used for coating articles, and are also used as film-forming materials and for mixing with other resins. However, organosols themselves are very unstable and have a tendency to solidify irreversibly. Therefore, various attempts have been made and proposals have been made to develop stable organosols of fluoropolymer or methods for producing the organosol6. For example, the use of low molecular weight polytetrafluoroethylene (PTFE) as a fluoropolymer has been proposed. Unexamined Japanese Patent Publication 1973
-31096, PTFE and tetrafluoroethylene-hexafluoropropylene copolymer (FE
Using a mixture of P) is disclosed in JP-A-411-17F+4.
It is disclosed in Publication No. 8. On the other hand, gJ of organosol
As a manufacturing method, a layer inversion method in which the aqueous dispersion of a fluoropolymer is transferred from the aqueous layer to an organic solvent as a layer inversion agent is disclosed in JP-A-49-17016. An azeotropic method in which water is removed azeotropically by heating an organic liquid that is insoluble and forms an azeotrope with water was disclosed in Japanese Patent Application Laid-Open No. 49-1877.
5, further adds an aqueous dispersion to an organic solvent,
A mill processing method in which the azeotrope is extracted with steam, the separated organic solvent is returned, and the resulting material is milled was disclosed in Japanese Patent Application Laid-Open No. 5.
It is disclosed in Japanese Patent No. 1-45619.

Therefore, the polymer ff, which is the most difficult to convert into an organosol,
Regarding 1PTFE alone, the above method is not sufficient, and it has not been possible to produce a stable organosol regardless of the type of fluoropolymer.

[Problems to be Solved by the Invention] The present invention has been made to solve the problems that cannot be solved by the conventional techniques, as described above, and is based on the results of studies on the method for producing organosols of fluoropolymer. , by polymerizing a monomer containing a polyfluoroalkyl group in an aqueous dispersion of zero fluorine polymers, and then replacing the aqueous medium with a substantially anhydrous organic solvent, fluorine polymers with excellent stability can be obtained. The present invention was completed based on the discovery that an organosol of the system polymer can be obtained.

Therefore, the purpose of the present invention is to provide a new production method that can produce organosols that are stable not only for high molecular weight PTFE alone, for which production of organosols has been extremely difficult, but also for all types of fluoropolymers. It is something.

[Means for Solving the Problems] That is, the present invention involves polymerizing a tttm compound containing a polyfluoroalkyl group in an aqueous dispersion of a fluoropolymer, and then converting the aqueous medium into a substantially anhydrous organic solvent. The present invention provides a method for producing a fluoropolymer organosol, which is characterized by substituting fluoropolymer organosol.

Examples of the fluoropolymer in the present invention include polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), and tetrafluoroethylene-hexafluoropropylene copolymer (FEP).
, tetrafluoroethylene-hexafluoropropylene-perfluorovinylether copolymer (EPE), polyvinylidene fluoride (PVdF), polyvinyl fluoride (PVF), tetrafluoroethylene-ethylene copolymer (ETFE), chlorotrifluoroethylene -Ethylene copolymer (ECTFE), tetrafluoro.

Ethylene-perfluorovinyl ether copolymer (PF
A) etc.

Such a fluoropolymer can be easily obtained as a stable aqueous dispersion by means such as emulsion polymerization, and usually has a particle size of 0.1 to 3 μm. The polyfluoroalkyl used in the production method of the present invention in which a monomer containing a polyfluoroalkyl group is polymerized in such an aqueous dispersion, and then the aqueous medium is replaced with an organic solvent. The group-containing monomer is preferably an acrylic ester and/or a methacrylic ester having a polyfluoroalkyl group. Such esters are not particularly limited, but the following may be exemplified as suitable ones.

CF * (CF nl s (Cl1m) 5OcO
c (CHm) -CLCF* [CFx) aclli
OcOc (C1ls) Mei CI.

CFa (CFi). (C11m) iocOc (CH
s) Snow CI+.

CFs (CFn) act amount 5OcOc 1IcLC
Fs (CFs)? (C1lli JCOCI
I-C1liCF! CFa (CFs)ysOJ (Call?) (CIl
l) tOcOclI-C1l*CFs (CFa) t
(C11m) 40cOcll-CIlxCF s
(CF l)? 5OIN (CIls) (Clli
) 10cOcll (CIls) = Cll5CFs
(CFi) tsOJ (Cillg) (CL)
*OCO(Cllsl;C1InCF-(CF,)t
sOJ(Calls)(CHi)*0COCll=CI
InCFs (CFri?C0NH(CIls) JC
OCll-ICllaF3 CFa CF2 CF3(CF,)a(CL)aOcOcll=clIx
CFa (CF,) a (C1lal JCOC(C
1ls) -CllaFacI 1)TcF,). CII, OCOCII-CI
+□CFzC1 (CFi) r oclIJcOc (
Clls) ・ClLa In the acrylic ester or methacrylic ester having a polyfluoroalkyl group as exemplified above, it is preferable that the polyfluoroalkyl group has 3 to 21 carbon atoms, and if the number of carbon atoms is too small, the Since the fluorine content decreases, the contribution to stabilization of the organosol becomes low. Also,
The polyfluoroalkyl group is preferably a perfluoroalkyl group, but may be one substituted with an element other than fluorine. In polymerization, even if an acrylic ester or a methacrylic ester having a polyfluoroalkyl group is used alone,
It is also possible to use them in combination. Furthermore, the polymer in the present invention is not limited to monomers containing a fluoroalkyl group, especially only acrylic ester and/or methacrylic ester monomers containing a fluoroalkyl group, but can be used in various copolymerizable forms. A copolymer can be produced using about 5 to 95 wt % of monomers. Examples of such copolymerizable monomers include:
Diene monomers such as butadiene and isoprene, styrene, styrene derivatives such as methylstyrene, acrylic acid alkyl esters such as methyl acrylate, methacrylic acid alkyl esters such as methyl methacrylate, vinyl esters such as vinyl acetate, and vinyl ethers such as vinyl methyl ether. , vinyl ketones such as vinyl methyl ketone, vinyl halides such as vinyl chloride, other acrylamides, N-vinylpyrrolidone, vinylimidazole, vinylpyridine, maleic acid dialkyl esters,
Examples include allyl alcohol. It is also possible to use two or more of the above monomers to obtain a copolymer.

Additionally, monomers containing reactive functional groups, such as glycidyl methacrylate, isocyanatoethyl methacrylate, acrylic acid, methacrylic acid, maleic anhydride, itaconic acid, hydroxyethyl methacrylate, etc., can be added to monomers containing polyfluoroalkyl groups. If copolymerized with acrylic acid or methacrylic acid having a polyfluoroalkyl group, the reactivity can be improved when producing a mixed polymer composition of a fluoropolymer and a thermoplastic or thermosetting resin. The functional groups act as grafting points to improve uniformity, mechanical properties, electrical properties, etc.

In the present invention, the method of polymerizing the monomer containing a polyfluoroalkyl group in an aqueous dispersion of a fluoropolymer can be either ionic polymerization or radical polymerization. From the viewpoint of polymerization, it is more preferable to employ radical polymerization.

The amount of the polyfluoroalkyl group-containing monomer used in polymerization is basically sufficient to modify the surface of the fluoropolymer particles dispersed in water; Generally, the amount is 0.1 to 100 parts by weight, preferably 0.5 to 50 parts by weight, per 100 parts by weight of the fluoropolymer. If this amount is too small, the contribution to the stabilization of the organosol will be low, and if it is too large, the properties of the fluoropolymer dispersed in water will be deteriorated.

Polymerization requires an initiator, which can be used such as benzoyl peroxide, lauroyl peroxide,
L-butyl perbenzoate, acetyl peroxide,
Peroxides such as t-butyl octadroperoxide, cumene hydroperoxide, di-butyl peroxide, a, α'-azopisisobutyronitrile, azobiscyclohexylcarbonitrile, dimethyl-a, a' - Azo compounds such as azobisisobutylade are exemplified.

Therefore, in view of polymerization in an aqueous system, hydrogen peroxide, sodium barborate, sodium versalphate, potassium versalphate, ammonium versalphate, or these peroxides and Fe2+ salt or Na
It is preferable to use a redox initiator in combination with a water-soluble inorganic reducing agent such as 1lSOi and an organic reducing agent such as alcohol or polyamine.

An aqueous dispersion of a fluoropolymer usually contains an emulsifier to stabilize its particles. Therefore, in the polymerization of the present invention, the desired effect can be achieved without adding a new emulsifier. However, in order to further improve the stability of the polymerization reaction and the stability of the obtained organosol, A nonionic emulsifier or the like may also be added. Such emulsifiers include anionic emulsifiers such as sodium stearate, sodium lauryl sulfate, sodium dodecylbenzene sulfonate, cationic emulsifiers such as dodecylammonium chloride, cetyltrimethylammonium bromide, etc.
Examples include nonionic emulsifiers such as polyethylene oxide, polyvinyl alcohol, hydroxyethyl cellulose, and the like.

In addition, a chain transfer agent, a solvent, etc. may be added during the polymerization, if necessary.

As a conventional technique, there is a method of polymerizing a monomer having an ethylenically unsaturated group in an aqueous dispersion of a fluoropolymer in order to improve the processability, durability, and physical properties of the fluoropolymer. It is disclosed in Japanese Patent Application Laid-Open No. 62-32102. However, the monomer used here must not contain fluorine, and the fluorine-based polymer 1
It requires 110 parts by weight or more of the monomer to be polymerized per 00 parts by weight, and it is said that the effect is expressed only under such conditions, so the purpose, method, conditions, and effects are completely different from the present invention. It is something.

In the present invention, after polymerizing a monomer containing a polyfluoroalkyl group in an aqueous dispersion of a fluoropolymer,
The aqueous medium is replaced with a substantially anhydrous organic solvent, and the method for replacing the medium is conventionally known method 1.
For example, an azeotropic method in which an organic solvent that can be azeotropic with water is added dropwise to an aqueous dispersion of a fluoropolymer that has completed polymerization while heating, and water is removed as an azeotropic mixture of the organic solvent; A layer transfer agent made of an organic solvent that is insoluble or refractory to water and does not physically or chemically damage the fluoropolymer is added to the aqueous dispersion and stirred, thereby transferring the fluoropolymer from the aqueous layer to the layer transfer agent. It is possible to adopt a layer inversion method that causes the layer to migrate. In addition to this method, in the present invention, the aqueous dispersion of the fluoropolymer after polymerization is filtered as it is, or after adding an organic solvent, the filter cake of the fluoropolymer obtained by filtration is reused in the organic solvent. It is possible to employ a filtration method that involves dispersion, and it has the characteristic that a stable organosol can be obtained similarly to the azeotropic method and fish waste method described above.

When the fluoropolymer organosol obtained by the production method of the present invention is mixed with other resins, the emulsifier, stabilizer, etc. contained in the aqueous dispersion may have an undesirable effect. As a solution to this problem, emulsifiers, stabilizers, etc. can be removed during organosolization. Specifically, such means are carried out by extraction with water in the case of the layer inversion method in the above-mentioned solvent replacement, or by washing, etc. in the case of the filtration method.

A further feature of the production method of the present invention is that various methods can be applied when replacing the solvent.
The range of solvent selection is extremely wide. Solvents that can be used as the organosol medium include aliphatic and aromatic hydrocarbons such as pentane, hexane, and benzene, alcohols such as methanol, butanol, benzyl alcohol, and phenol, butyl ether, tetrahydrofuran, benzyl ether, and acetal. Ethers, carbonyl compounds such as acetaldehyde and acetone, acids such as acetic acid, oleic acid and acetic anhydride, acid anhydrides, esters such as ethyl acetate, propyl benzoate, butyrolactone and dimethyl maleate, fluorobenzene, 1.1 .2-trichlorotrifluoroethane,
Halogen compounds such as chloroform, bromobenzene, iodoethane, nitro compounds such as nitroben7ine, nitrile compounds such as acetonitrile, benzyl cyanide, benzonitrile, butylamine, aminobenzene,
Amines such as triethylamine, virol, and pyridine, amides such as N,N-dimethylacetamide and ε-caprolactam, sulfur compounds such as carbon disulfide, thiophenol, diethyl sulfide, and dimethyl sulfoxide, or these functional groups in one molecule. Examples include solvents containing two or more of these, and mixtures thereof.

The organosol of the fluoropolymer obtained in this way can be used as a coating agent, impregnated into woven fabrics and nonwoven fabrics made of glass fibers, carbon fibers, etc., as well as used as a coating agent, in the same way as is normally done with aqueous dispersions. By drying after casting, filling, etc., it can be used as a molding material for various molded products such as films and tubes. In particular, since it is easy to uniformly mix with other resins or their solutions, which is difficult with aqueous dispersions, fluoropolymers can be mixed with various thermosetting resins and thermoplastic resins to make molded products, and are used in woven fabrics. By applying it as an impregnating agent or coating agent for nonwoven fabrics, etc., a laminate thereof can have excellent properties.

[Function] In the production method of the present invention, after polymerizing a monomer containing a polyfluoroalkyl group, especially an acrylic ester and/or a methacrylic ester containing a polyfluoroalkyl group, in an aqueous dispersion, Although the mechanism of action by which a stable organosol can be obtained by substituting other organic solvents is not necessarily clear, the effect is observed even when the monomer containing a polyfluoroalkyl group to be polymerized is extremely small. Therefore, it is presumed that the surface of the fluoropolymer in the aqueous dispersion is modified and aggregation becomes less likely to occur during organosol formation.

[Example] Next, the present invention will be explained in more detail with reference to Examples.
It goes without saying that the present invention is not limited to these examples in any way.

Example 1 300m equipped with stirrer, reflux condenser and dropping funnel
A PTFE aqueous dispersion (particle size 0.1-0.
3μm 1 polymer content 60% by weight) 200g, ammonium persulfate 1. CFs (CFa) 5 (C11□l, i
0 COCII-C11 was added dropwise over a period of about 5 minutes, and after the addition, the mixture was further stirred at room temperature for 5 minutes. Subsequently, the temperature in the system was raised to 60° C. and the reaction was carried out for 8 hours. Even after the zero reaction, there was no change in the emulsification state in the system, and no aggregation occurred. Methyl isobutyl ketone is added to the resulting aqueous dispersion that has completed the reaction in this way, and after stirring, the cake is suction-filtered, and washing with methyl isobutyl ketone is repeated while keeping the cake constantly wet with methyl isobutyl ketone. Methyl isobutyl ketone was added to the fluoropolymer cake obtained in the 0th step and stirred vigorously to prepare an organosol having a solid content of 30%.

When the obtained organosol was passed through a 150-mesh stainless steel wire gauze, more than 99% passed through, and almost no aggregates were observed.

In addition, the moisture content was measured using a Karl Fischer device and the result was 0.
．． It was 1%.

Example 2 A FEP aqueous dispersion (particle size Q
, 1-0.3μm, polymer content 50% by weight) 200g
, 0.3 g of sodium persulfate was added, and CF, (CF,) was added through the dropping funnel while stirring at room temperature.

+C11,), 0COC(CI+,)・Cll55.
0g was added dropwise over about 5 minutes. After dropping, continue at room temperature for 5 minutes.
Stir for a minute.

Subsequently, the temperature in the system was raised to 50°C, and the reaction was carried out for 24 hours. Even after the reaction, there was no change in the emulsification state in the system, and no aggregation occurred.

Next, 200 g of toluene was placed in the same reactor as above, heated and boiled while stirring, and 100 g of the aqueous dispersion obtained above was gradually added dropwise from the dropping funnel. Since water in the aqueous dispersion evaporates as an azeotrope with toluene, only toluene is refluxed and returned to the reactor, and water is removed by a water separator. The aqueous dispersion was added dropwise over a period of approximately 5 hours, and after the completion of the addition, heating was continued for an additional 2 hours to completely remove water and obtain a stable organosol containing 21% solids.

When the obtained organosol was passed through a 150-mesh stainless wire gauze, more than 99% passed through, and almost no aggregates were observed. Further, the moisture content was measured using a Karl Fischer apparatus and was found to be 0.05%.

Example 3 PTFE aqueous dispersion 200 was placed in the same reactor as in Example 1.
g, potassium persulfate 0.3 g, sodium bisulfite 0.
1g, sodium dodecylbensene sulfonate 1.0
CFs (CFI) while stirring at room temperature.
C0NII (C1la) JCOCII・CH* 6
．． A mixture of 3.0 g of 0g% acrylic acid was added dropwise from the dropping funnel over about 5 minutes. After the dropwise addition, the mixture was stirred at room temperature for 5 minutes, and then the reaction system was heated to 40° C. and reacted for 24 hours. Even after polymerization, there was no change in the emulsification state within the system, and no aggregation occurred.

1,1 as a layer inversion liquid to the aqueous dispersion thus obtained.
．． Add 200g of 2-trichlorotrifluoroethane,
By adding 100 g of acetone as a layer inversion agent while stirring vigorously, the fluoropolymer migrates into the layer inversion liquid in the system separated into two layers. Next, while adding 1.1.2-trichlorotrifluoroethane as appropriate, the upper aqueous layer was repeatedly removed by decantation to reduce the solid content to 2.
A 5% stable organosol was prepared.

When the obtained organosol was passed through a 150-mesh stainless wire gauze, more than 99% of the rollers passed through it. The moisture content was measured using a Karl Fischer apparatus and was found to be 0.3%.

Example 4 PTFE aqueous dispersion 200 was placed in the same reactor as in Example 1.
g, ammonium persulfate 0. Charge Ig and add CF3 (CFI) tS from the dropping funnel while stirring at room temperature.
OJ (C1ls) (Ctl*) 5OcOc (c
12 g of ll, l-cll was added dropwise over about 5 minutes. After the dropwise addition, the system was stirred for another 5 minutes at room temperature, and the system was heated to 60 g.
Even after one polymerization in which the temperature was raised to .degree. C. and the reaction was carried out for 8 hours, there was no change in the emulsified state in the system, and no aggregation occurred.

Tetrahydrofuran was added to the resulting aqueous dispersion and mixed with stirring, followed by suction filtration. At this time, the cake was washed repeatedly with tetrahydrofuran while keeping it constantly wet with tetrahydrofuran. Tetrahydrofuran was added to the obtained fluoropolymer cake to prepare an organosol having a solid content of 30%.

When this organosol was passed through a 150-mesh stainless wire mesh, more than 99% passed through. The moisture content was measured using a Karl Fischer apparatus and was found to be 0.08%.

Comparative Example 1 PTFE aqueous dispersion 200 was placed in the same reactor as in Example 1.
Add 30 g of methyl isobutyl ketone while stirring.
After 6 drops, stirring was continued for about 10 minutes, and suction filtration was performed to obtain a cake. Methyl isobutyl ketone was added to this fluoropolymer cake so that the solid content was 30%, and vigorous stirring was performed to redisperse it, but the cake coagulated and could not be redispersed.

Comparative Example 2 200 g of toluene was placed in the same reactor as in Example 1, and heated and boiled while stirring. Then P T F
E 100 g of aqueous dispersion was gradually added dropwise from the dropping funnel. Thereafter, water was removed by the same azeotropic method as in Example 2 to obtain an organosol with a solid content of ZO%.

When the organosol thus obtained was passed through a 150-mesh stainless wire mesh, it was found that 10% of the PTFE
It only passed. In addition, the obtained organosol was subjected to a 2-hour linear granulation operation using a ball mill, and then passed through a 150-mesh stainless steel wire mesh.
Only 30% of E passed through.

[Effects of the Invention] The fluoropolymer of the present invention can be obtained by a method of polymerizing a monomer containing a polyfluoroalkyl group in an aqueous dispersion and then replacing the aqueous medium with a substantially anhydrous organic solvent. The fluoropolymer organosol produced is characterized by extremely high stability, and has excellent effects that cannot be achieved by conventional techniques. Furthermore, the type of fluoropolymer is not particularly limited, and the selection range is extremely wide.

Claims (2)

[Claims] (1) After polymerizing a monomer containing a polyfluoroalkyl group in an aqueous dispersion of a fluoropolymer, the aqueous medium is replaced with a substantially anhydrous organic solvent. Method for producing a combined organosol. (2) Acrylic ester and/or monomer containing a polyfluoroalkyl group
or methacrylic ester, the manufacturing method according to claim 1.