JPH0725850B2 - Method for producing fluorine-containing copolymer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a fluorine-containing copolymer. More specifically, it relates to a method for producing a fluorine-containing copolymer which has not only excellent weather resistance and chemical resistance but also has antifouling property and can form a transparent coating film.

[Conventional technology]

Fluorine-containing copolymers are generally known to have excellent weather resistance and chemical resistance, but on the other hand, it is also well known that copolymers having a high fluorine content have poor solvent solubility. ing.

As a method for improving this solvent solubility, a method of copolymerizing a fluorine-containing olefin and an alkyl vinyl ether is known. For example, U.S. Pat.No. 2,834,767 describes tetrafluoroethylene and ethyl vinyl ether or 2-chloroethyl vinyl ether. Is described, and it is stated that an elastic copolymer was obtained thereby. One of the main purposes of solvent solubilization is film formation, but there is no description of transparency regarding the above elastic copolymer, and in fact, such a composition gives only a white and opaque film. Absent.

[Problems to be solved by the invention]

The present inventors previously found a fluorine-containing copolymer capable of forming a transparent coating film with further improved weather resistance and chemical resistance as compared with conventionally known fluorine-containing copolymers. As a result of various investigations conducted, it was possible to effectively achieve the above object by copolymerizing a fluorine-containing olefin, 2-chloroethyl vinyl ether and alkyl vinyl ether with a monomer having a functional group. Kaisho 63-83108
Issue).

The fluorine-containing copolymer obtained by copolymerizing each of these monomers achieved the intended purpose, but had some problems in terms of antifouling property.

Therefore, as a result of further studies in order to obtain a fluorine-containing copolymer having not only a problem in terms of transparency but also an antifouling property, (fluoro) alkyl perfluorovinyl ether was used instead of 2-chloroethyl vinyl ether. It was found that such problems can be solved at the same time by copolymerization.

[Means for solving problems]

Therefore, the present invention relates to a method for producing a fluorocopolymer,
The fluorine-containing copolymer is produced by (a) about 20 to 70 mol% of a fluorinated olefin, (b) about 5 to 40 mol% of an alkyl perfluorovinyl ether or fluoroalkyl perfluorovinyl ether, and (c) about an alkyl vinyl ether.
10 to 40 mol% and (d) functional group-containing monomer about 1 to 15
It is carried out by copolymerizing mol% in the presence of a polymerization initiator.

As the fluorine-containing olefin as the component (a), tetrafluoroethylene, chlorotolufluoroethylene or vinylidene fluoride is preferably used, but hexafluoropropene, hexafluoroisobutene and the like can also be used.

The alkyl perfluorovinyl ether or fluoroalkyl perfluorovinyl ether as the component (b) is represented by the general formula CF ₂ ═CFOR, and R is a chain or cyclic alkyl group having 1 to 8 carbon atoms or hydrogen of such chain alkyl group. A fluoroalkyl group in which some or all of the atoms are replaced by fluorine atoms,
For example CF ₃ CH ₂ , CF ₃ CF ₂ CH ₂ CH ₂ , H (CF ₂ CF ₂ ) _{1 to 3} CH ₂ , CF ₃ C
It is a group such as F ₂ CH ₂ .

As the alkyl vinyl ether as the component (c), ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, n-hexyl vinyl ether, 2-chloroethyl vinyl ether and the like are generally used, but also tert-butyl vinyl ether, cyclohexyl vinyl ether, 4-tert-Butylcyclohexyl vinyl ether or the like can be used, and further, a fluoroalkyl vinyl ether in which an alkyl group is fluorine-substituted can be used.

As the functional group-containing monomer of the component (d), 2-hydroxyethyl vinyl ether having a hydroxyl group, an epoxy group or a trialkoxysilyl group as a functional group,
3-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, allyl alcohol, 2-hydroxyethyl acrylate, glycidyl vinyl ether, allyl glycidyl ether, vinyltrimethoxysilane, allyltrimethoxysilane, 3- (trimethoxysilyl)-
Propyl (meth) acrylate or the like is used.

About 20 to 70 mol% of (a) component, (b)
About 5-40 mol%, preferably about 5-30 mol%,
About 10 to 40 mol% of the component (c) and about 1 to about the component (d).
It is subjected to a copolymerization reaction at a rate of 15 mol%.

When the component (a) is used in a proportion less than this, not only is it unfavorable in terms of weather resistance and chemical resistance, but also the production rate is not increased, which is a disadvantage in manufacturing. On the other hand, if it is used in a proportion higher than this, not only inconvenience in terms of production but also in the obtained copolymer, the solvent solubilization purpose cannot be achieved. Regarding the component (b), if it is used in a ratio less than this, the hardness and antifouling property of the coating film will decrease, while if it is used more than this, the transparency of the coating film,
Flexibility is reduced. In the case of component (c),
Contrary to the component (b), if it is used in a proportion higher than this, the transparency of the coating film is lowered, and if it is used in a lower proportion, the elongation of the coating film is lowered. Further, with respect to the component (d), such a ratio is used in order to introduce a cured site necessary for forming a cured coating film of the copolymer.

Other than the above components, other monomers within a range that does not impair the properties required for this copolymer, for example, perfluoroalkyl perfluorovinyl ether, ethylene, propylene, isobutylene, vinyl chloride, vinylidene chloride, Acrylic acid ester, methacrylic acid ester, maleic acid diester, maleic acid monoester, acrylic acid, methacrylic acid, vinyl acetate, allyl acetate, vinyl butyrate and the like can be copolymerized.

The copolymerization reaction can be carried out in the presence of a commonly used polymerization initiator by any polymerization method such as solution polymerization, suspension polymerization and emulsion polymerization.

At that time, when vinylidene fluoride is used as the fluorinated olefin, the copolymerization reaction becomes a reaction in which polymerization and decomposition compete with each other, and the vinyl ethers are deteriorated because the polymerization system becomes acidic as the reaction progresses, and Since it causes inhibition, it is preferable to carry out the reaction while allowing the acid acceptor to exist therein. Examples of the acid acceptor include oxides, hydroxides, carbonates, hydrogen carbonates, and carboxylates of sodium, potassium, cesium, rubidium, magnesium, calcium, barium, copper, iron, etc. It is used in an amount of about 0.1 to 1% with respect to the monomer.

The obtained copolymer utilizes a functional group such as a hydroxyl group, an epoxy group or a trialkoxysilyl group introduced as a curing site in the copolymer, and a curing agent is used to obtain about 0 to 0.
It can be cured at 200 ° C. to form a coating film having a crosslinked structure. As the curing agent, when the functional group is a hydrosil group, hexamethylene diisocyanate, polyisocyanates such as isophorone diisocyanate, butylated or methylated melamine resin, butylated or methylated urea resin, etc. are used, and the functional group is epoxy. In the case of the group, various amines, polyfunctional epoxy compounds and the like are used.

In forming a coating film, the copolymer according to the present invention utilizes the property of being soluble in a solvent, xylene, aromatic hydrocarbons such as toluene, alcohols such as n-butanol, and esters such as butyl acetate. , A solution type paint such as ketones such as methyl isobutyl ketone, glycol ethers such as ethyl cellosolve, and commercially available thinners can be used.

〔The invention's effect〕

The copolymer obtained by the method of the present invention preferably uses tetrafluoroethylene, chlorotrifluoroethylene or vinylidene fluoride as the fluorinated olefin to increase the fluorine content in the copolymer, thereby improving the weather resistance and Transparency will be impaired only by further improving the chemical resistance and copolymerizing it with an alkyl vinyl ether, but by further copolymerizing a (fluoro) alkyl perfluoro vinyl ether therewith, weather resistance and chemical resistance will be improved. The hardness of the coating film can be increased without substantially losing the excellent properties such as the above, thereby making it possible to obtain a solvent-soluble copolymer having antifouling property and high transparency. Improves the adhesion and solvent resistance of the coating film by cross-linking and curing using the curing site introduced in the coalescence.

As described above, the copolymer according to the present invention is soluble in a solvent and thus can be applied as a solution type coating material to various shapes of base materials, and the coating film formed thereon has high transparency. It forms a coating film which has antifouling property due to its high surface hardness.

〔Example〕

 Next, the present invention will be described with reference to examples.

Example 1 A stainless steel autoclave with a stirrer having a capacity of 200 ml was charged with the following components, and cyclohexyl perfluorovinyl ether 18.0 g (20
Ethyl vinyl ether 7.2g (20mol%) 4-Hydroxybutyl vinyl ether 5.8g (10mol%) Methyl isobutyl ketone 100ml Azobisisobutyronitrile 0.1g Tetrafluoroethylene after solidification and degassing with liquid nitrogen 25 g (50 mol%) was introduced, and the internal temperature of the autoclave was gradually raised until it reached 65 ° C. After that, the reaction was continued under stirring for 8 hours, and when the pressure dropped to almost 0 on the gauge, the autoclave was water-cooled to stop the reaction.

A colorless transparent slightly viscous solution was obtained, and this solution was put into methanol and stirred to precipitate a white polymer. Upon drying, 51.5 g of a white elastic polymer was obtained, which corresponds to a yield of 92%.

10 g of the obtained copolymer was dissolved in a mixed solution of 10 g of xylene and 10 g of methyl isobutyl ketone, and 2 g of a curing agent (Nippon Polyurethane Product Coronate EH) was added to the solution to give a mixture of 7 × 15 cm.
Was applied to the aluminum plate of No. 1 using an applicator.
When this aluminum plate was heated and cured in an oven at 80 ° C. for 4 hours, a transparent coating film was formed. This coating is
A 33.3% copolymer solution of pencil hardness F (scratched), 4H (peeling), T-bending 1T, goggle test 100/100, toluene dilutability (equal amount mixture of xylene / methyl isobutyl ketone) was prepared. Diluting the solution with 5 times the amount of toluene to see if it becomes cloudy) OK, antifouling property (whether it is completely wiped off when blue magic ink is applied to the cured coating and wiped off with benzine after 2 hours) It was OK.

Examples 2 to 7 and Comparative Example A copolymer reaction was carried out using the following monomers, and various observations and measurements were carried out in the same manner as in Example 1 using the resulting copolymer. The obtained results are shown in Table 1 below together with the charged amount of the monomer.

In Example 5, 0.1 g of cetyldimethylbenzylammonium chloride was used as a curing accelerator instead of the curing agent, and in Example 6, the curing agent was not used.

(Monomer abbreviation) TFE: Tetrafluoroethylene CTFE: Chlortolufluoroethylene HFiB: Hexafluoroisobutene CHFVE: Cyclohexyl perfluorovinyl ether FPFVE: 2,2,3,3-Tetrafluoropropyl perfluorovinyl ether EVE: Ethyl vinyl ether iBVE: Isobutyl vinyl ether CEVE: 2-Chloroethyl vinyl ether HBVE: 4-Hydroxybutyl vinyl ether GVE: Glycidyl vinyl ether VTMS: Vinyltrimethoxysilane (Common measurement results) T-bending test: 1T Goggle test: 100/100 Antifouling property: All except the comparative example OK Toluene dilutability: OK Examples 8 to 12 Vinylidene fluoride alone or as a fluorine-containing olefin. Used in combination, the same copolymerization reaction and heat curing as in Example 1 were performed. During the copolymerization reaction, about 0.1 g of calcium carbonate was added per 10 g of all the comonomers. The obtained results are shown in Table 2 below together with the charged amount of the monomer.

(Monomer abbreviation) VDF: Vinylidene fluoride FPVE: Perfluoro (propyl vinyl ether) (Common measurement results) T-bending test: 1T Goggle test: 100/100 Antifouling property: OK Toluene dilutability: OK

Continuation of front page (56) Reference JP-A-2-28206 (JP, A) JP-A-2-191613 (JP, A) JP-A-63-83108 (JP, A)

Claims (2)

[Claims] 1. A fluorine-containing olefin (a) 20 to 70 mol%,
(B) 5 to 40 mol% of alkyl perfluorovinyl ether or fluoroalkyl perfluorovinyl ether, 10 to 40 mol% of (c) alkyl vinyl ether, and (d) monomers 1 to 15 containing hydroxyl group, epoxy group or trialkoxysilyl group. A method for producing a fluorine-containing copolymer, which comprises copolymerizing mol% in the presence of a polymerization initiator. 2. The method for producing a fluorine-containing copolymer according to claim 1, wherein the component (a) is tetrafluoroethylene, chlorotrifluoroethylene or vinylidene fluoride.