JPH0446913A - Production of fluorinated copolymer - Google Patents

Abstract

PURPOSE:To produce a fluorinated copolymer improved in surface hardness, gloss, solvent resistance, staining resistance and weathering resistance by copolymerizing a radical-polymerizable fluorinated monomer with a specified cyclic vinylidene monomer. CONSTITUTION:5-95mol% radical-polymerizable fluorinated monomer (e.g. tetrafluoroethylene) is copolymerized with 95-5mol% cyclic vinylidene monomer of the formula (wherein R1 and R2 are each H or methyl; and A is an organic group) and optionally 50mol% or below copolymerizable ethylenically unsaturated monomer at 0-100 deg.C under a pressure of 1-100kg/cm<2> under basic conditions of a pH of 7 or above in the presence of 0.005-5wt.%, based on the total monomer, radical polymerization initiator (e.g. benzoyl peroxide) to obtain a fluorinated copolymer having an intrinsic viscosity (in tetrahydrofuran at 30 deg.C) of 0.05-2.0dl/g.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a novel fluorine-containing copolymer.

[Prior Art] Fluorine-containing copolymers obtained by copolymerizing polyfluoroolefins and alkyl vinyl ethers are known,
It is used as a raw material for paints that is soluble in solvents and can be cured at room temperature, and can provide coatings with excellent weather resistance, chemical resistance, gloss, etc., as well as excellent adhesion to substrates. Are known.

[Problems to be Solved by the Invention] In recent years, with the expansion of the uses of fluorine-based solvent-based paints, there has been an increasing demand for a wide range of paints, from paints with rubber elasticity to paints with high surface hardness. However, with conventional fluorine-based solvent-based paints, there is a limit to the improvement of surface hardness, and there is a strong need for improvement.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and consists of a radically polymerizable fluorine-containing monomer and the general formula [I] (R1 and Rt are hydrogen or methyl A method for producing a fluorine-containing copolymer is provided, which comprises copolymerizing a cyclic monomer having a vinylidene group represented by (A represents an organic group) in the presence of a radical polymerization initiator. It is.

The radically polymerizable fluorine-containing monomer used in the present invention includes fluorine-containing olefins such as tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropene, and perfluorovinylether, polyfluoroalkyl acrylate, and polyfluoroalkyl methacrylate. Examples include ester, polyfluorocarboxylic acid vinyl ester, and the like. In particular, fluorine-containing olefins are preferably used from the viewpoints of copolymerization reactivity, weather resistance and durability of the coating film, repaintability of the coating film, and the like. In addition, fluorine-containing olefin is
It is a compound having a fluorine-substituted vinyl group, and in addition to the above compounds, examples include vinylidene fluoride and trifluoroethylene.

Further, the cyclic monomer having a vinylidene group is a monomer represented by the general formula [I]. It is important that such a monomer has carbon and oxygen bonded to the vinylidene group to form an ether bond. Cyclic monomers with vinylidene groups having other structures are difficult to copolymerize with radically polymerizable fluorine-containing monomers, and the ring-opening reaction occurs violently during copolymerization, making it impossible to obtain the desired physical properties. The cyclic monomer having a vinylidene group in the present invention, which cannot be employed due to the difficulty in synthesizing the monomer, is preferably one in which the number of atoms constituting the ring is about 4 to 15. If the number of atoms constituting the ring is less than 3, or if it is too large, it is practically difficult to produce, and if it is too large, the copolymerizability with the radically polymerizable fluorine-containing monomer will decrease, which is undesirable. Furthermore, the ring structure of the cyclic monomer having a vinylidene group is at least one
It has ether bonds, but it may also have other ether bonds, ester bonds, etc., or it may only have carbon-carbon bonds. At least a portion thereof may be substituted with halogen, alkyl group, etc.

As a particularly preferred cyclic monomer having a vinylidene group, A in the above general formula [I] is -(CH2). +(1
, (C arrow, (l is O or 1. o+ is O or 1. n is an integer of 1 to 9, and the sum of n, m, and 1 is an integer of 1 to 9) (provided that , methylene group, ether group,
The ester groups do not necessarily have to be arranged in this order). Specific examples include 2-methylenetetrahydrofuran, 2-methylenetetrahydrobilane, α-methyleneoxetane, 4-methylene-1,3 dioxane, and diketene.

In the present invention, the radically polymerizable fluorine-containing monomer and the vinylidene group-containing cyclic monomer may be copolymerized singly or in combination.

Further, other ethylenically unsaturated monomers copolymerizable with these may be copolymerized at the same time.

Such ethylenically unsaturated monomers include vinyl ether compounds, vinyl ester compounds, allyl ether compounds, allyl ester compounds, isopropenyl ether compounds, impropenyl ester compounds, a
-Olefins are exemplified. It is preferable to select the darkening ethylenically unsaturated monomer according to additional purposes such as gloss of the coating film and dispersibility of pigments, as well as solvent solubility, control of coating hardness, weather resistance, etc. Taking this into account, vinyl ether compounds or vinyl ester compounds are preferred. In particular, linear chains with about 2 to 15 carbon atoms,
Vinyl ethers or vinyl esters having a branched or alicyclic alkyl group are preferred.

In addition, when using the fluorine-containing copolymer obtained by the present invention as a coating material, in order to improve the toughness and solvent resistance of the coating film, it is necessary to use hydroxyl groups, epoxy groups, amino groups, active hydrogen-containing groups, alkoxysilyl groups, etc. It is preferable to copolymerize a curable functional group-containing monomer such as a curable functional group such as a hydroxyl group-containing monomer such as a hydroxyl group-containing vinyl ether such as hydroxybutyl vinyl ether, a hydroxyl group-containing allyl compound such as allyl alcohol, a hydroxyl group-containing allyl compound such as glycidyl Ethylenically unsaturated monomers containing curable functional groups are preferably employed, such as vinyl ethers containing epoxy groups such as vinyl ether, vinyl ethers containing amino groups such as aminobutyl vinyl ether, and vinyl compounds containing alkoxysilyl groups such as trimethoxyvinylsilane.

Further, the copolymerization of each monomer is preferably carried out at a ratio of 5/95 to 9515 (molar ratio) of the fluorine-containing monomer and the cyclic monomer having a vinylidene group. If it is outside the above range, it is unfavorable from the viewpoint of weather resistance, solvent solubility, and production efficiency, and when copolymerizing a monomer other than a fluorine-containing monomer or a cyclic monomer having a vinylidene group, the total monomer The content is preferably 50 mol % or less based on the body, and if this range is exceeded, the original purpose of the present invention may be impaired.

Further, the manufacturing method of the present invention can be carried out by the following method. In particular, cyclic monomers having a vinylidene group tend to cause isomerization, decomposition, or homopolymerization in acidic conditions, so it is preferable to conduct the copolymerization under basic conditions in order to stably proceed the copolymerization. In particular, it is preferable to carry out the reaction at a pH of about 8 to 9.

The copolymers according to the invention have an intrinsic viscosity of 0.05 to 2.0, measured in the uncured state in tetrahydrofuran at 30°C.
OdQ/g, preferably 0.15-0.8 dG! /g
, more preferably 0.2 to 0.5 dQ/g. If the viscosity is too low, the mechanical strength will decrease, while if it is too high, when applied as a solution-based paint, the solution concentration will tend to be low due to viscosity, impairing workability. Both are undesirable.

Examples of the radical polymerization initiation source in the production method of the present invention include a radical polymerization initiator and ionizing radiation.

Here, as the polymerization initiator, water-soluble or oil-soluble ones can be used as appropriate depending on the polymerization type or polymerization medium. Specifically, the water-soluble initiator is
A redox initiator consisting of a persulfate such as potassium persulfate, hydrogen peroxide, or a combination of these with a reducing agent such as sodium bisulfite or sodium thiosulfate, as well as small amounts of iron, ferrous salts, silver nitrate, etc. An inorganic initiator such as a system in which a combination of dibasic acid peroxide, diglutaric acid peroxide, monosuccinic acid peroxide, and an organic initiator such as azobisisobutyramidine dibasic acid salt can also be used. As the oil-soluble initiator, peroxy ester type peroxides such as t-butyl peroxyisobutyrate and t-butyl peroxy acetate, dialkyl peroxy dicarbonates such as diisopropyl peroxy dicarbonate, benzoyl peroxide, Examples include azobisisobutyronitrile.

The amount of the polymerization initiator used can be changed as appropriate depending on the type, copolymerization reaction conditions, etc., but it is usually 0.005 to 5% by weight, especially 0.005 to 5% by weight, based on the total amount of monomers to be copolymerized. ．．
About 0.05 to 0.5% by weight is adopted.

In the above copolymerization reaction, the reaction format is not particularly limited, and bulk polymerization, suspension polymerization, emulsion polymerization, solution polymerization, etc. can be adopted, but the stability of the polymerization reaction operation and the separation of the produced copolymer can be improved. For ease of use, emulsion polymerization in an aqueous medium or aromatic compounds such as xylene and toluene, alcohols such as t-butanol, esters, and saturated herogenated hydrocarbons containing one or more fluorine atoms, etc. Solution polymerization using a solvent is preferably employed. In addition, when carrying out a copolymerization reaction in an aqueous medium, it is preferable to add a basic buffer so that the pH value of the liquid during polymerization does not fall below 7, preferably 8. Addition of a basic substance is also effective in solution polymerization. Moreover, it goes without saying that the method of the present invention can be carried out by batchwise, semi-continuous, continuous, etc. operations.

In this copolymerization reaction, the copolymerization reaction temperature is -30°C.
The optimum value can be appropriately selected within the range of ~+150°C depending on the polymerization initiation source, the type of polymerization medium, etc.; however, when the copolymerization reaction is carried out in an aqueous medium, the temperature is 0°C ~ +100°C, preferably lO C. to about 90.degree. C. may be employed. In addition, the reaction pressure can be selected as appropriate, but is usually 1 to 100 kg.
/c+a'', it is desirable to adopt niha2~sokg/c■3.

Furthermore, in order to suppress the intrinsic viscosity of the resulting copolymer within the above range, the copolymerization reaction may be carried out in the presence of an appropriate chain transfer agent.

When a hydroxyl group, an epoxy group, etc. are introduced into the copolymer as a curable functional group, the copolymer can be cured by using a curing agent.
It can be cured at ~250''C to form a coating film having a crosslinked structure.

That is, it can be heated and cured using a melamine curing agent, a urea resin curing agent, a polybasic acid curing agent, etc., such as those used in acrylic paints. Examples of the melamine curing agent include butylated melamine, methylated melamine, epoxy-modified melamine, etc. Depending on the application, various degrees of modification can be used from 0 to 6, and the degree of self-condensation can also be selected appropriately. can. Examples of the urea resin include methylated urea, butylated urea, and the like. In addition, as a polybasic acid curing agent,
Long-chain aliphatic dicarboxylic acids, aromatic polycarboxylic acids or their anhydrides, block polyvalent isocyanates, and the like are useful. When using melamine or urea hardeners, curing can be accelerated by adding an acidic catalyst.

The copolymer according to the present invention can also be further cured at room temperature using polyvalent isocyanates. As polyvalent incyanate, hexamethylene diisocyanate,
Non-yellowing diisocyanates such as isophorone diisocyanate and adducts thereof are particularly useful. When curing is carried out at room temperature using isocyanates, it is also possible to accelerate curing by adding a known catalyst such as dibutyltin dilaurate.

In making the copolymer of the present invention into a solution-type coating, various solvents can be used, including aromatic hydrocarbons such as xylene and toluene, alcohols such as n-butanol, esters such as butyl acetate, In addition to ketones such as methyl isobutyl ketone, glycol ethers such as ethyl cellosolve, and the like, various commercially available thinners can also be used.

Mixing of the copolymer and the solvent can be carried out using various equipment commonly used for forming paints, such as a ball mill, paint shaker, sand mill, jet mill, three-roll mill, kneader, and the like. At this time, pigments, dispersion stabilizers, viscosity modifiers, leveling agents, gelling inhibitors, ultraviolet absorbers, etc. can also be added.

When the copolymer of the present invention is used as a heat-curable so-called baking paint, a curing agent such as melamine, urea resin, polybasic acid or its anhydride, or block polyvalent incyanate is also mixed at the same time. It is used as a one-component paint.

On the other hand, in the case of a room-temperature curable coating material using non-blocking polyvalent isocyanates, the curing agent component is prepared separately and a two-component coating material is prepared. In this case, by adjusting the type and amount of isocyanate and catalyst added, the copolymer concentration, the content of units based on hydroxyalkyl vinyl ether in the copolymer, etc., the pot life can be increased from about 1 to 10 hours. It is possible to produce a coating that cures at room temperature in several hours to several days and provides a coating film with good physical properties.

When used as a paint base, the copolymer of the present invention provides a coating film with excellent surface hardness and gloss, as well as excellent solvent resistance, stain resistance, and weather resistance under mild conditions. It is useful not only as a baking paint for colored steel plates, colored aluminum plates, aluminum sash, etc., but also as an air-drying paint that can be applied on-site, and the base material is not limited to metal. Inorganic materials such as glass, cement, and concrete, plastics such as FRP, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, nylon, acrylic, polyester, ethylene-polyvinyl alcohol copolymer, vinyl chloride, vinylidene chloride, and organic materials such as wood. It is also extremely useful for coating materials. They are also useful in certain applications such as aluminum boules, exterior colored glass, and cement girders.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

[Example] Example 1 Xylene 39 was placed in a stainless steel autoclave with an internal volume of 200 cc (pressure resistance 25 kg/cta'') and equipped with a stirrer.
．． 1 g of ethyl alcohol, 9.9 g of 2-methylenetetrahydrofuran (2M-THF), 0.275 g of potassium carbonate, and 0.11 g of azobisisobutyronitrile (AIBN), solidified with liquid nitrogen, Dissolved air is removed by degassing. Thereafter, 22.0 g of chlorotrifluoroethylene was introduced into the autoclave and the temperature was gradually raised. When the temperature in the autoclave reached 65℃, the pressure was increased to 3.2kg/
cm"G. Then, the reaction was continued with stirring for 3 hours,
When the pressure drops to 1.5 kg/c+o”G, the autoclave is cooled with water to stop the reaction. After reaching room temperature, unreacted monomers are purged and the autoclave is opened. The resulting polymer solution is poured into water. After the polymer is deposited, the polymer is recovered by washing and drying.

The polymer yield was 13.5 g, and the polymer concentration was 18
, 9%, monomer reaction rate 57.1%, average polymerization rate 14
．． It was 0 g/(!-h.

Intrinsic viscosity of the obtained polymer (in tetrahydrofuran.

30°C) ([η]) was o, lo di/g, and the glass transition temperature (Frico viscoelasticity meter) was 90°C. "C.
- As a result of composition analysis with mr, CTFE/2M-TH
The molar ratio of F was 51.0/49.0. 10 g of the obtained polymer was mixed with 1 xylene.

It was applied to a chromate-treated aluminum plate using an applicator and dried at 140°C for 30 minutes. The pencil hardness (scratches) of the resulting coating film (film thickness: 2011) was 2H.

Examples 2 to 6, Comparative Examples 1 to 2 Polymerization was carried out under the same conditions as in Example 1. The conditions and results are shown in Table 1.

[Example 7] Xylene 77.3 was placed in a stainless steel autoclave with an internal volume of ZOOcc (pressure resistance 25 kg/cm'') and equipped with a stirrer.
g, ethanol 27.6 g, 2-methylenetetrahydrofuran (2-MT HF) 7.9 g, ethyl vinyl ether (EVE) 6.8 g% W-hydroxybutyl vinyl, T-thyl (HBVE) 10.9 g, potassium carbonate 0 .58g, azobisisobutyronitrile (A
I B N ) 0.22 g was charged, solidified with liquid nitrogen, and dissolved air was removed by degassing.

Afterwards, 27.3 g of chlorotrifluoroethylene
into the autoclave and gradually raise the temperature. When the temperature inside the autoclave reaches 65℃, the pressure increases to 3.5K.
g/clI"G. Then, the reaction is continued under stirring for 6 hours, and when the pressure drops to 0.0 kg/cm"G, the autoclave is cooled with water to stop the reaction. After reaching room temperature, purge the unreacted tops and open the autoclave. The resulting polymer solution is poured into water to precipitate the polymer, which is then washed and dried to recover the polymer. The polymer yield was 16.8 g, the polymer concentration was 29.0%, the monomer reaction rate was 82.5%, and the average polymerization rate was 43.8 g/Q-h. Intrinsic viscosity of the obtained polymer (in tetrahydrofuran, 30°C) ([η])
was 0.11 d(!/g) and the glass transition temperature (Frico viscoelasticity meter) was 56°C."As a result of composition analysis with C-nor, CTFE/2-MTHF/EVE/HBV
The T4 ratio of E is 50, 9/ 14.3/ 14.1/
It was 20.7.

This copolymer log was dissolved in a mixed solvent of 4 g of xylene and 12 g of methyl isobutyl ketone, and 4.2 g of titanium oxide (CR-90 manufactured by 6 Hara Sangyo) was added and mixed for 1 hour in a paint shaker. The resulting paint has good dispersion (particle gauge 5μ or less). To this, 8 g of hexamethylene diisocyanate O and 1.5×l'l-'g of dibutyltin dilaurate were added and applied to a chromate-treated aluminum plate using an applicator. After about 7 hours, the coating film became tack-free, and after 3 days, a robust coating film with a thickness of 20 μm that would not be eroded even when wiped with xylene was obtained. Surface gloss was 60°-60° and specular reflection was 80%. As a result of subjecting the coating film to JIS and various commonly performed tests, the results shown in Table 2 were obtained.

Table 2 [Examples 8 to 11, Comparative Examples 3 to 4] Polymerization and coating film evaluation tests were carried out under the same conditions as in Example 7. The conditions and results are shown in Table 3.

Table A, No trace left B: Almost no trace left C1 Some trace left D: Completely left a trace [Effects of the invention] The copolymer obtained by the present invention is a combination of conventional fluorine-containing olefin and alkyl vinyl ether, It has weather resistance, chemical resistance, and antifouling properties comparable to vinyl ester copolymers, and the strength of the coating film can be controlled over a wide range (especially at high hardness).

Claims (3)

[Claims] (1) Radically polymerizable fluorine-containing monomer and general formula [I] ▲Mathematical formulas, chemical formulas, tables, etc. are available▼・・・・・・・・・
[I] (R_1, R_2 are hydrogen or methyl groups, A is an organic group) A cyclic monomer having a vinylidene group represented by the following is copolymerized in the presence of a radical polymerization initiator. Method for producing fluorine copolymer. (2) Radically polymerizable fluorine-containing monomer, general formula [I] ▲Mathematical formulas, chemical formulas, tables, etc. are available▼・・・・・・・・・
[I] A cyclic monomer having a vinylidene group represented by (R_1, R_2 is a hydrogen group or a methyl group, and A is an organic group) and other ethylenically unsaturated monomers copolymerizable with these are radicalized. A method for producing a fluorine-containing copolymer, which comprises copolymerizing in the presence of a polymerization initiation source. (3) The method for producing a fluorine-containing copolymer according to claim 1 or 2, wherein the copolymerization is carried out under basic conditions.