JPH1160629A - Preparation of fluororesin solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for preparing a fluororesin soln. which can improve the storage stability by bringing an org. solvent soln. of a fluorine- contg. copolymer, prepd. by copolymerizing an olefin monomer having a hydro lyzable silyl group, a (meth)acrylic ester, and a fluoroolefin, into contact with an acid-eliminating agent. SOLUTION: An olefin monomer having a hydrolyzable silyl group represented by the formula: R-SiXn Y3-n (wherein R represents a group having an olefinically unsatd. bond; X represents a 1-20C alkyl; Y represents a hydrolyzable group; and (n) is 0 to 2) in an amt. of 0.5 to 20 mol%, 20 to 80 mol% (meth)acrylic ester, and 10 to 70 mol% fluoroolefin are copolymerized in an org. solvent in the presence of a radical generation type polymn. initiator under a pressure of 1 to 200 kg/cm<2> at a temp. of 20 to 100 deg.C to obtain an org. solvent soln. contg. a fluorinecontg. copolymer having a mol.wt. of 3000 to 500000. This org. solvent soln. is passed through a column packed with an acideliminating agent having a particle diameter of 106 μm to 2.36 mm to remove an acid or a halogen ion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a fluorine-containing resin solution, and more particularly to a method for forming a coating film having excellent weather resistance and having excellent storage stability of the solution. It relates to a manufacturing method.

[0002]

2. Description of the Related Art Conventionally, fluorine-containing resin coatings have been widely used in the fields of construction, civil engineering and heavy-duty corrosion as high-performance coatings that provide coatings that do not deteriorate over a long period of time and do not require repainting. In general, a fluorine-containing resin containing a hydroxyl group is used for a fluorine-containing resin paint, but a curing agent is required to form a tough coating film at room temperature, and a so-called two-pack type paint is used. In recent years, the toxicity of isocyanate used as a curing agent has been regarded as a problem, and development of a one-pack type fluorine-containing resin paint that does not use isocyanate has been desired.
Fluorine-containing resin coatings containing a hydrolyzable silyl group have been intensively studied as the above-mentioned one-pack type fluorine-containing resin coatings (Japanese Patent Publication No. 1-14055). The pH decreases due to the influence of acids such as hydrogen chloride and hydrogen fluoride generated therein. Therefore, when this polymerization solution is used directly as a paint,
There is a problem in terms of storage stability of the solution, which results in thickening or gelling during storage. As a solution to this, there has been proposed a method of performing polymerization in the presence of a deoxidizing agent or a method of adding a deoxidizing agent to a fluorine-containing resin solution after polymerization (Japanese Patent Laid-Open No. 2-15).
No. 1610, JP-A-5-271349). However, these methods have a problem in that a part of the deoxidizing agent used becomes fine powder and is dispersed in the solution, so that it takes a long time in a filtration step to remove the acid removing agent. Therefore, a simple method for producing a fluororesin solution having excellent storage stability has been desired.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a fluororesin solution having excellent storage stability by a simple operation.

[0004]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, by passing a fluororesin solution through a column filled with a deoxidizer, an extremely short time has passed. It has been found that a fluorine-containing resin solution having excellent storage stability can be obtained in a short processing time by the processing time, and the present invention has been completed. That is, the present invention provides an organic solvent solution of a fluorinated copolymer obtained by copolymerizing a monomer mixture comprising an olefinic monomer having a hydrolyzable silyl group, a (meth) acrylate and a fluoroolefin. Is contacted with a deoxidizing agent.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail. The olefinic monomer having a hydrolyzable silyl group constituting the fluorinated copolymer in the present invention is a compound represented by the following formula (1). _{R-SiX n Y 3-n} (1) ( wherein, R is a group having an olefinic unsaturated bond, X represents an alkyl group having 1 to 20 carbon atoms, Y is a hydrolyzable radical, n Is 0, 1 or 2. When there are a plurality of X and Y, they may be the same or different.) In the above formula (1), R is a vinyl group or an allyl. Group,
Butenyl group, vinyloxy group, allyloxy group, acryloyl group, methacryloyl group, CH ₂ ＣＨCHO (CH ₂ )
_{3 -, CH 2 = CHCOO (} CH 2) 3 -, CH 2 = C
_{HOCO (CH 2) 3 -,} CH 2 = C (CH 3) COO
(CH ₂ ) ₃ — and CH ₂ ＣC (CH ₃ ) COO (C
H ₂ ) ₂ —O— (CH ₂ ) ₃ — and the like. X in the formula (1) includes a methyl group, an ethyl group, a propyl group, an octyl group and an octadecyl group. Examples of Y in the formula (1) include hydrolyzable groups such as an alkoxy group, an amino group, an acyloxy group, a phenoxy group, a mercapto group and an iminooxy group, and among them, an alkoxy group is particularly preferable. Specific examples thereof include a methoxy group, an ethoxy group, a propoxy group, a butoxy group and a methoxyethoxy group. Among them, those in which R is a vinyl group are preferable, and those in which Y is a methoxy group or an ethoxy group are preferable.

Specific examples of the olefinic monomer having a hydrolyzable silyl group include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinylmethyldimethoxysilane, vinyldimethylmethoxysilane, vinyltris (β- Methoxyethoxy) silane, trimethoxysilylethyl vinyl ether, trimethoxysilylbutyl vinyl ether, methyldimethoxysilylethyl vinyl ether, trimethoxysilylpropyl vinyl ether, vinyltriisopropenyloxysilane, vinylmethyldiisopropenyloxysilane, triisopropenyloxysilylethyl Vinyl ether, triisopropenyloxysilylpropyl vinyl ether, triisopropenyloxysilylbutyl vinyl ether, Rutorisu (dimethyl imino oxy) silane, vinyltris (methyl ethyl imino-oxy) silane, vinyl methyl bis (dimethyl imino oxy) silane, vinyl dimethyl (dimethyl imino oxy)
Silane, tris (dimethyliminooxy) silylethyl vinyl ether, methylbis (dimethyliminooxy)
Silylethyl vinyl ether, tris (dimethyliminooxy) silylbutyl vinyl ether, γ- (meth) acryloyloxypropyltrimethoxysilane, γ-
(Meth) acryloyloxypropyltriethoxysilane, γ- (meth) acryloyloxypropylmethyldiethoxysilane and γ- (meth) acryloyloxypropyltriisopropenyloxysilane.

The alkyl (meth) acrylate constituting the fluorine-containing copolymer in the present invention is preferably one having an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group and a halogen-containing alkyl group as an ester chain. In addition, atoms such as oxygen, nitrogen and sulfur may be contained in the ester chain as long as physical properties are not impaired. Specific examples of the compound include methyl (meth) acrylate,
Ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, (meth)
S-butyl acrylate, t-butyl (meth) acrylate, neopentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, (meth) acryl Tridecyl acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, tricyclodecynyl (meth) acrylate,
Tetrahydrofurfuryl (meth) acrylate, (meth)
Methoxyethyl acrylate, dimethylaminoethyl (meth) acrylate, chloroethyl (meth) acrylate,
Trifluoroethyl (meth) acrylate and (meth)
And pentafluoropropyl acrylate. Among these, the use of acrylates is preferred in view of the polymerizability with the fluoroolefin and the flexibility of the copolymer. Further, these monomers can be used alone or in combination of several kinds.

The fluoroolefin constituting the fluorine-containing copolymer in the present invention is exemplified by tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, dichlorodifluoroethylene, trifluoroethylene, vinylidene fluoride, vinyl fluoride and the like. Is done. Among these, tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene and trifluoroethylene are preferred from the viewpoint of polymerizability, and chlorotrifluoroethylene and trifluoroethylene are more preferred. Further, a plurality of the above monomers may be used in combination.

In the fluorine-containing copolymer of the present invention, other copolymerizable monomers can be used, if necessary, in addition to the above essential components. Such monomers include:
Olefins such as ethylene, propylene, isobutylene, norbornene and norbornadiene, chloroethylenes such as vinyl chloride and vinylidene chloride, vinyl acetate, vinyl propionate, vinyl caproate, vinyl pivalate, and Vova-9 [manufactured by Shell Chemical Co., Ltd.] ], Vinyl carboxylate such as vinyl cyclohexanecarboxylate, vinyl benzoate and vinyl laurate,
Examples are vinyl ethers such as ethyl vinyl ether and butyl vinyl ether, and allyl ethers such as ethyl allyl ether and cyclohexyl allyl ether.

It is also possible to copolymerize monomers having functional groups such as a hydroxyl group, an epoxy group and a carboxyl group. Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 4-hydroxy (meth) acrylate.
Hydroxyl-containing monomers such as hydroxybutyl, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, allyl alcohol, cinnamon alcohol, N-methylol (meth) acrylamide, 2-hydroxyethyl crotonic acid and 4-hydroxybutyl crotonic acid; Other compounds obtained by ring-opening addition of ε-caprolactam and ethylene oxide to these hydroxyl-containing monomers, and unsaturated carboxylic acids such as (meth) acrylic acid, maleic acid, fumaric acid, crotonic acid and itaconic acid. Monomers which are reaction products with polyhydric alcohols such as ethylene glycol, ethylene oxide, propylene glycol, propylene oxide, butylene glycol, cyclohexanedimethanol, glycerin and trimethylolpropane are exemplified. . Examples of the monomer having an epoxy group include glycidyl (meth) acrylate, allyl glycidyl ether, and glycidyl vinyl ether. Examples of the monomer having a carboxyl group include (meth) acrylic acid, maleic acid, fumaric acid, itaconic acid and crotonic acid. In addition, since the solubility of the fluorine-containing copolymer containing a hydroxyl group-containing monomer or a carboxyl group-containing monomer in an aliphatic hydrocarbon decreases, the amount of these monomers used is 5% of the total amount of the monomers. It is preferably at most mol%.

The composition ratio of each monomer in the fluorinated copolymer is from 0.5 to 20 olefinic monomer having a hydrolyzable silyl group in view of weather resistance and coating film properties.
Mol%, (meth) acrylic acid ester: 20 to 80 mol%, and fluoroolefin: 10 to 70 mol%, and more preferably, an olefinic monomer having a hydrolyzable silyl group: 2 to 10 Mole%,
(Meth) acrylic acid ester: 30 to 75 mol% and fluoroolefin: 20 to 60 mol%. Also,
The other monomers are preferably used in the range of 0 to 30 mol%.

The molecular weight of the fluorocopolymer in the present invention is preferably from 3,000 to 500,000 in terms of polystyrene by gel permeation chromatography (GPC) from the viewpoint of the properties of the coating film.
More preferably, it is 0 to 30,000. Further, the glass transition temperature (Tg) is preferably from -20C to 60C, and particularly preferably from 0C to 50C.

The above-mentioned fluorine-containing copolymer can be produced by a method of copolymerizing the above-mentioned monomer mixture in the presence of a radical-generating polymerization initiator. As a polymerization method, a usual method such as solution polymerization in an organic solvent is used. Is used. Examples of the radical-generating polymerization initiator include peroxides such as diisopropylperoxydicarbonate, tert-butylperoxypivalate, benzoyl peroxide and lauroyl peroxide, azobisisobutyronitrile and azobisisovaleronitrile. Azo compounds, and inorganic peroxides such as ammonium persulfate and potassium persulfate.
It is preferable to use 1 to 10 parts by weight. Examples of the organic solvent in the solution polymerization include cyclic ethers such as tetrahydrofuran and dioxane; aliphatic carbons such as n-hexane, cyclohexane, mineral spirit, industrial gasoline No. 4 volatile oil, No. 3 volatile oil, kerosene and turpentine oil; Hydrogens; aromatic hydrocarbon compounds such as toluene and xylene; esters such as ethyl acetate and butyl acetate; ketones such as acetone, methyl ethyl ketone and cyclohexanone; ethanol, isopropanol;
Examples thereof include alcohols such as n-butanol and n-butyl cellosolve, and ortho acid esters such as trimethyl orthoformate, triethyl orthoformate, trimethyl orthoacetate and triethyl orthoacetate, and one or more of these can be used. The amount of the organic solvent used is preferably 20 to 200 parts by weight based on 100 parts by weight of all monomers.

The polymerization conditions are not particularly limited.
The preferred polymerization temperature in the preferred reaction is 20-100 ° C
And the preferred pressure is between 1 and 200 kg / cm ² . The monomers used in the polymerization may be initially charged in batches at the beginning, or some of the monomers may be added sequentially as the polymerization proceeds.

The production method of the present invention is characterized in that a fluorine-containing resin solution obtained by dissolving the above-mentioned fluorine-containing copolymer in an organic solvent is brought into contact with an acid remover described later. As the organic solvent, those exemplified as the solvent for the solution polymerization can be used, and the solution obtained by the solution polymerization can be used as it is as a fluorinated resin solution, or after polymerization, after isolating the copolymer, again The fluororesin solution may be prepared by dissolving it in an organic solvent. It is preferable to use the organic solvent in an amount of 20 to 200 parts by weight based on 100 parts by weight of the fluorinated copolymer.

The acid remover in the present invention is a substance which adsorbs or ion-exchanges an acid or a halogen ion, and specific compounds include metal oxides such as magnesium oxide, aluminum oxide, silicon oxide, calcium oxide and barium oxide; Calcium hydroxide, magnesium hydroxide,
Metal hydroxides such as aluminum hydroxide, potassium hydroxide and hydrotalcite. Further, as a specific example of hydrotalcite, Mg _4.5 Al ₂ (OH) ₁₃ CO
₃ 3.5H ₂ O, Mg ₆ Al ₂ (OH) ₁₆ CO ₃ 4H ₂ O and the like. Among these, preferred acid removers are aluminum hydroxide and hydrotalcite. Further, as commercial products, Kyoward 200SN and Kyoward 500SN manufactured by Kyowa Chemical Industry Co., Ltd. can be used.

In the present invention, it is presumed that the acid or the halogen ion is removed from the solution by bringing the fluorine-containing resin solution into contact with the acid removing agent, and as a result, the storage stability of the solution is improved. I do. The method of bringing the acid remover into contact with the solution is not particularly limited. For example, a method of passing the fluororesin solution through a column filled with the acid remover is simple and preferable.

The particle size of the acid scavenger is determined according to JIS Z8801.
In a sieve test using the described sieve, 106 μm
It is preferably in the range of 2.36 mm, more preferably 150 μm to 1.7 mm. If the particle size is too small, it takes time to pass the fluorine-containing resin solution.On the other hand, if the particle size is too coarse, the amount of the acid scavenger used becomes large, or the fluorine-containing resin solution is passed through the column. It is not preferable in terms of economy and operation, for example, the number of times of operation is increased. The amount of the acid remover used is 0.0 per 100 parts by weight of the fluorocopolymer.
It is preferably at least 5 parts by weight. If the amount is less than 0.05 part by weight, the effect may not be sufficiently exhibited, and an operation of passing the liquid through the column many times is required, which is not efficient. Although there is no particular upper limit to the amount of the acid remover used, an excessively large amount is not economical, and furthermore, the pressure loss increases and the liquid passing speed in the column becomes slow, so that the treatment time becomes long.

The column to be filled with the above-mentioned acid-removing agent is not limited as long as it has a structure in which the inside of the column can be filled with the acid-removing agent and the fluorine-containing resin solution can sufficiently contact the acid-removing agent. The material of the column is preferably one that does not dissolve or corrode by the solution. The solution is passed through the column in a batch or continuous manner by means of a pump or press-fitting, and if a single pass does not provide a sufficient effect, the solution may be passed a plurality of times. Further, the solution can be circulated by connecting the inlet and the outlet of the column. Further, when the viscosity of the solution is high, the flow rate becomes slow. Therefore, it is preferable to further dilute the solution with an organic solvent to reduce the solid content, or to pass the solution through a column in a heated state.

The fluororesin solution obtained by the production method of the present invention is suitable for use in paint applications, and depending on the purpose of use, a pigment, an ultraviolet absorber, a dispersion stabilizer, an antioxidant, and a silane cup. Various additives such as a ring agent, a curing catalyst, and other resins can be blended. Further, the fluorine-containing resin solution can be used by using various methods used as a usual paint, but is particularly preferably used as a one-component type fluorine-containing resin solution for paint because of its excellent storage stability. be able to.

[0021]

The present invention will be described in detail with reference to the following Examples, but it should not be construed that the invention is limited thereto. Example 1 In a 2 liter autoclave equipped with a stirrer, 250 g of toluene, 50 g of methanol, 19.4 g of cyclohexyl acrylate (hereinafter, referred to as "CHA"), and vinyltrimethoxysilane (hereinafter, referred to as "VMS") 1.3.
g, t-butyl peroxypivalate [Nippon Oil & Fats Co., Ltd.
(1.5 g) was cooled to 5 ° C. or lower. After repeating vacuum degassing and nitrogen replacement, chlorotrifluoroethylene (hereinafter referred to as “CTFE”) 480
g was introduced into the autoclave and the temperature was raised. After the temperature was raised to 55 ° C., 174.9 g of CHA, 11.8 g of VMS,
A mixture of 50 g of toluene was pumped into the autoclave at a constant speed using a pump over a period of 6 hours. Ten hours after the completion of the heating, the autoclave was cooled, unreacted CTFE was purged, and then the autoclave was opened. The weight of the obtained fluororesin solution was 650 g, and its solid content was 40% by weight.
And the pH was 4.0. Advantech Toyo Co., Ltd. stainless steel pressure filter KST-90 was supplied with Kyoward 200SN (alumina granule manufactured by Kyowa Chemical Co., Ltd., average particle size of about 250 μm) and a nominal size of 150 μm.
m (hereinafter referred to as “150 μm sifted product”) and filled with 20 g of fine powder removed by sieving through a sieve.
As a result of passing the fluorinated resin solution through the filter under a nitrogen pressure, the pH of the filtrate was 4.5. Further, as a result of passing the filtrate through the same operation, the pH rose to 5.0. The filtrate is concentrated to a solid content of 60% by weight using an evaporator, 100 parts by weight of this solution are mixed with 5 parts by weight of methanol and 1 part by weight of trimethyl orthoformate, and the mixture is placed in a sealed bottle and stored at 50 ° C. for 1 month. The test was performed, but no gelation was observed.

Example 2 The acrylate was changed to CHA (15.5 g initially charged,
139.9 g of post-addition), butyl acrylate (hereinafter, referred to as butyl acrylate)
(Referred to as “BA”) (initial charge 3.2 g, post-addition 2)
9.1 g), polymerization was carried out in the same manner as in Example 1 except that the amount of CTFE charged was changed to 700 g, and the time for adding the post-added monomer was changed to 7 hours.
% Of a fluororesin solution having a pH of 3.5 was obtained.
Kyoword 500S instead of Kyoword 200SN
The same procedure as in Example 1 was repeated except that 20 g of a 150 μm sieve having a mean particle size of 250 μm with synthetic hydrotalcite manufactured by Kyowa Chemical Industry Co., Ltd. was charged. The pH was increased to 5.0 when the solution was passed. This solution was concentrated to a solid content of 60% by weight using an evaporator, and 2 g of trimethyl orthoformate was mixed with 100 parts by weight of this solution, and a storage stability test was carried out in the same manner as in Example 1, but no gelation was observed. .

Example 3 The fluorine-containing resin polymerization solution of Example 1 was diluted to a solid content of 20% by weight with Naphtha No. 6 (hydrocarbon solvent manufactured by Exxon). The resulting solution was applied to Kyoward 200SN 15
Except that 30 g of the 0 μm sieving product was used, the same operation as in Example 1 was performed to remove the acid, and as a result, the pH of the solution was 5.
It has risen to zero. This solution was solidified with an evaporator to a solid content of 5%.
The solution was concentrated to 5% by weight, and 100 g of this solution was mixed with 2 g of trimethyl orthoformate. A storage stability test was carried out in the same manner as in Example 1, but no gelation was observed.

Example 4 A fluorine-containing resin solution was obtained in the same manner as in Example 1 except that 20 g of Kyoward 200SN, which had not been subjected to sieving, was used. Although the solution was clear, the liquid passing time was 10 times or more that of Example 1.

Comparative Example 1 20 g of 150 μm sieve product of Kyoward 200SN
Is carried out in the same manner as in Example 1 in the presence of
650 g of a fluorine-containing resin solution having a weight percentage of pH 5.0 was obtained. However, the solution became cloudy, and this cloudiness could not be removed by ordinary filtration.

Comparative Example 2 The fluorine-containing resin solution of Example 1 was not subjected to an acid removing treatment.
The mixture was concentrated to a solid content of 60% by weight using an evaporator. 5 parts by weight of methanol and 1 part by weight of trimethyl orthoformate were mixed with 100 parts by weight of this solution, and the mixture was placed in a sealed bottle and 50 ° C. × 1
When the storage stability test was performed for a month, it turned into a gel.

[0027]

According to the production method of the present invention, a fluorine-containing resin solution having excellent storage stability can be obtained by a simple method, and the obtained fluorine-containing resin solution is particularly useful for one-pack type coatings. It is useful as a fluorine-containing resin solution.

Claims (3)

[Claims] An organic solvent solution of a fluorinated copolymer obtained by copolymerizing a monomer mixture comprising an olefinic monomer having a hydrolyzable silyl group, a (meth) acrylate and a fluoroolefin. A method for producing a fluorine-containing resin solution, which is brought into contact with an acid scavenger. 2. The method for producing a fluorine-containing resin solution according to claim 1, wherein the organic solvent solution of the fluorine-containing copolymer is passed through a column filled with a deacidifier. 3. The particle size of said deoxidizer is 106 μm to 2.36.
The method for producing a fluororesin solution according to claim 1 or 2, wherein the diameter is in the range of mm.