JPH075678B2 - Method for producing fluorine-containing copolymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a method for producing a fluorinated copolymer containing a carboxyl group, which is useful as a raw material for a fluororesin coating material, and particularly to a method for producing a small amount of halogen ions. Regarding

[Conventional technology and its problems]

By copolymerizing a vinyl ether having a carboxyl group and a fluoroolefin, a fluororesin having a carboxyl group can be produced, but a vinyl ether having a carboxyl group is difficult to synthesize. For example, even if a hydroxyalkyl vinyl ether is reacted with a dibasic acid anhydride (half-esterification) to synthesize a vinyl ether having a carboxyl group, the carboxyl group and the vinyl group react with each other to cyclize in the molecule, I can't get things.

Therefore, the fluorine-containing copolymer containing a carboxyl group is, for example, a copolymer of vinyl ether containing a hydroxyl group and a fluoroolefin is produced, and then a hydroxyl group and a dibasic acid anhydride are contained in the copolymer. Method of reacting (half-esterification) (Japanese Patent Publication No. 61-4
9323 gazette). However, in this method, since half-esterification is carried out after the copolymerization, there is a problem that it is difficult to use an inexpensive alcohol or the like which reacts with a dibasic acid anhydride as a solvent for the copolymerization.

The present inventors have conducted extensive studies on a method for producing a vinyl ether containing a carboxyl group, and as a result, when reacting a hydroxylalkyl vinyl ether with a dibasic acid anhydride, if a basic compound is allowed to exist in the system, an intramolecular ring That the carboxyl group of the obtained vinyl ether takes the form of the salt of the basic compound, the stability is improved, and the yield is significantly improved when it is copolymerized with the fluoroolefin. I found it.

By the way, a composition for electrodeposition coating containing a fluoropolymer is known to give a coating film having remarkably excellent chemical resistance, weather resistance, etc. as compared with a composition containing a conventional acrylic resin. (For example, JP-A-62-59676, JP-A-62-59676)
62-127362).

However, when electrodeposition is carried out using a composition having a fluoropolymer, various problems are caused by the presence of halogen ions.

For example, according to the research conducted by the present inventors, the following are the effects of halogen ions in the composition for electrodeposition coating in electrodeposition.

(1) Elution of anode metal In this respect, when an anion-based electrodeposition coating composition in which the object to be coated serves as an anode is greatly affected, particularly when the object to be coated is aluminum, fluorine ions are not used. Al ₂ O
_{3 + 6HF → 2AlF 3 + 3H} 2 O + 112kcal / mol that reaction occurs, fatal defect occurs alumite layer is destroyed.

(2) Decrease in stability of composition for electrodeposition coating Due to salting action due to halogen ions, water solubility and water dispersibility of the fluoropolymer are impaired and storage stability is reduced.

(3) Increase in specific electric conductivity Coulomb yield decreases due to increase in specific electric conductivity, and coating defects occur due to high electrodeposition voltage.

Although such an effect occurs with other halogen ions, fluorine ion has the greatest effect.

On the other hand, halogen ions are inevitably generated in the copolymerization reaction of the carboxyl group-containing vinyl ether monomer composition and the fluoroolefin. Therefore, as a result of diligent study of the copolymerization reaction, as described below, the halogen ether generation was suppressed as much as possible by setting the vinyl ether (Ia) or (Ib) in the vinyl ether monomer composition to a specific amount of (II). Found that it is possible to obtain a fluorine-containing copolymer in high yield,
The present invention has been completed.

[Means for Solving the Problems]

 The present invention has been made to solve the above problems.
Yes, formula (Ia): CH₂= CHOR¹OC (= O) R²C (= O) OM (Ia) (In the formula, R¹Is a divalent aliphatic group having 2 to 10 carbon atoms, R²Is
A divalent organic group, M is an alkali metal)
Vinyl ether (hereinafter referred to as vinyl ether (Ia))
Or formula (Ib): CH₂= CHOR¹OC (= O) R²C (= O) O ・ HY  (Ib) (In the formula, R¹And R²Is the same as above, Y is a nitrogen atom or
Is a compound containing a phosphorus atom, and its pKa is 6 to 1
2 is a monofunctional basic compound which is 2)
Vinyl ether (hereinafter referred to as vinyl ether (Ib).
However, in the following, (Ia) and (Ib) are combined and referred to as (I)
There is also a case) and formula (II): CH₂= CHOR¹OC (= O) R²C (= O) OH (II) (In the formula, R¹And R²Is the same as above)
Vinyl ether having a carboxyl group (hereinafter referred to as vinyl
Ether (II)), vinyl ether
(I) is 1 to 50 mol% of vinyl ether (II), preferably
Vinyl ether monomer containing 5 to 50 mol%
-Special feature of copolymerizing the composition with fluoroolefin
As a result, the amount of halogen ion generated from the fluorine-containing copolymer is low.
There is no manufacturing method.

[Preferred Embodiment] The vinyl ether monomer composition used in the present invention is
Like vinyl ether (II) alone
And the storage stability is improved in each stage. The reason is cheap
A specific vinyl ether (I) is used in an amount of 1 mol% or more of (II),
Coexistence of 5 mol% or more in vinyl ether
H that promotes cyclization of (II) Because the concentration in the system decreases
Is estimated to be

Among the vinyl ether monomer compositions, the vinyl ether (I) is a hydroxyalkyl vinyl ether represented by the formula: CH ₂ ═CHOR ¹ OH (wherein R ¹ is the same as above), and the formula: (In the formula, R ² is the same as above) and an alkali metal compound or a compound containing a nitrogen atom or a phosphorus atom, and its pKa (acid dissociation index at 25 ° C in water) Can be obtained by reacting a monofunctional basic compound of 6 to 12 (hereinafter, simply referred to as a base when the two are not distinguished).

Specific examples of the hydroxyalkyl vinyl ether which is a raw material of this production method include 4-hydroxybutyl vinyl ether, 2-hydroxyethyl vinyl ether, 3-hydroxy-n-propyl vinyl ether, 2-hydroxy-iso-propyl vinyl ether and 2-hydroxy-2.
-Methylethyl vinyl ether, 2-hydroxy-1,1
-Cymethyl ethyl vinyl ether, 4-hydroxy cyclohexyl vinyl ether, 3-hydroxy cyclohexyl vinyl ether, 2-hydroxy cyclohexyl vinyl ether, 4-hydroxy benzooxy vinyl etc. can be mentioned.

R ² contained in the dibasic acid anhydride and vinyl ether (I) or (II) has the formula (i): CHX ¹ _p CX ² _{2 q} (i) [wherein, X ¹ is a hydrogen atom or a carbon atom]. An alkyl group having 1 to 3 atoms, X ² represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and p and q represent 0 or an integer of 1 to 11 (however, they cannot be 0 at the same time). A group represented by formula (ii): CH _{2 r} CX ³ = CH _s (ii) [In the formula, r is 0 or an integer of 1 to 3, s is an integer of 1 to 3, X ³ is a hydrogen atom or carbon. A group represented by an alkyl group having 1 to 3 atoms], formula (iii): [In the formula, R ⁷ is a CHX ⁴ _t group (provided that X ⁴ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and t is an integer of 1 to 4), —CH ₂ CH═CHCH ₂ — group. , A group represented by the formula (iv): [In the formula, R ⁸ is a CHX ⁵ _u group (provided that X is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, u is an integer of 3 to 4) or a CX ⁶ = CX ⁷ _v group (provided that X ⁶ and X ⁷ are the same or different and each represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, v is an integer of 2 to 3], a group represented by the formula (v): —C (= CH ₂ ) —CH ₂ — (v) group or formula (vi): And the like.

Specific examples of the dibasic acid anhydride, maleic anhydride,
Succinic anhydride, methylsuccinic anhydride, phthalic anhydride, adipic anhydride, glutaric anhydride, glutaconic anhydride, itaconic anhydride, 1,8-naphthalic acid, citraconic anhydride, 1,2-cyclohexanedicarboxylic anhydride, anhydrous 4-
Methyl-1,2-hexanedicarboxylic acid, cis-4-cyclohexene-1,2-dicarboxylic acid anhydride, 1-cyclohexene-1,2-dicarboxylic acid anhydride, cyclopentadiene and maleic anhydride by Diels-Under reaction And so on.

Generally, the reaction of a hydroxyl compound and a dibasic acid anhydride proceeds according to the following formula in the presence of a basic catalyst.

In this case, it is at most 0 to obtain the target product with a yield of 90% or more.
It is sufficient to use 5 mol% (based on dibasic acid anhydride) of base. However, according to the research conducted by the present inventors, when a cation-reactive hydroxyl vinyl ether is used as the hydroxyl compound, the reaction cannot be obtained without the presence of a base, as described later, and 0.5 mol% If the degree is low, the yield of the desired product is low, and the stability is poor, so it is not suitable as a monomer for polymerization.

However, the presence of the above-mentioned base in an amount of 1 mol% or more makes the yield more than 90%, and the obtained product becomes stable, so that the decrease in the yield can be prevented. It is considered that the reason is that the base prevents the reaction between the carboxyl group and the vinyl group and also prevents the cyclization of the vinyl ether (II) produced as described above. Although the base reacts stoichiometrically with the carboxyl group, it may be present in the reaction system in an amount of 1 mol% or more with respect to the acid anhydride as described above, in which case the vinyl ether (I) and (II) A mixture is obtained.

Further, the monomer composition is vinyl ether (I) and (II)
It can also be obtained by adding a base to a mixture with and reacting with vinyl ether (II). The base added afterwards may be the same as or different from the base present during the reaction. Also in this case, the carboxyl group of vinyl ether (II) and the base react stoichiometrically.

As the base, an alkali metal compound and a specific monofunctional basic compound are used as described above.

As the alkali metal compound, a compound of Li, K or Na is preferable, and for example, lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate,
Examples thereof include potassium carbonate, sodium methylate, sodium ethylate and potassium methylate.

The specific monofunctional basic compound is a compound containing a nitrogen atom or a phosphorus atom as described above, and its pK
a is a 6-12 basic compound, preferably 8-11 basic compound. p
Those having Ka in this range have high salt-forming ability and have a large stabilizing effect on vinyl ether (II). That is, a dibasic acid anhydride having a higher pKa than that of the carboxylic acid has a high salt-forming ability, and particularly 3% higher than that of the corresponding carboxylic acid.
Those with a pKa of ~ 8 are preferred. Suitable monofunctional basic compounds include ammonia, amines, phosphines and the like. Specific examples of amines include, for example, methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, sec-butylamine, 1,2-dimethylpropylamine, 2-ethylhexylamine, tridecylamine, Dimethylamine, diethylamine, di-n-propylamine, di-isopropylamine, dibutylamine, di-isobutylamine, di-sec-butylamine,
Di-2-ethylhexylamine, trimethylamine, triethylamine, tri-n-propylamine, tri-n
-Butylamine, N-methylbutylamine, N-ethylbutylamine, N, N-dimethylethylamine, N, N-dimethylisopropylamine, N, N-dimethyltetradecylamine, N, N-dimethyloctadecylamine, 2-methoxyethylamine, 3-ethoxyethylamine, cyclohexylamine, N, N-dimethylcyclohexylamine, dicyclohexylamine, benzylamine, N, N-
Examples thereof include dimethylbenzylamine, 4-methoxyphenylethylamine, ethanolamine, diethanolamine, triethanolamine, isopropanolamine, dimethylethanolamine, pyrrolidine, piperidine, 1-methylpiperidine, 4-methylpiperidine, and morpholine.

Specific examples of phosphines include, for example, trimethylphosphine, triethylphosphine, tripropylphosphine, tributylphosphine, trioctylphosphine, trilaurylphosphine, tristearylphosphine, dimethylphosphine, diethylphosphine, dibutyl. Di- or trialkylphosphines such as phosphine, dioctylphosphine and dilaurylphosphine; tris (3-hydroxypropyl) phosphine, tris (2-cyanoethyl)
Phosphine, tris (2-methoxyethyl) phosphine, tris (2-chloroethyl) phosphine, tris (2-methoxycarbonyl) phosphine, tris (2- (2-dimethylaminoethoxy) carbonyl) phosphine, tris (2-ethoxycarbonyl) Di- or tri-substituted alkylphosphines such as phosphine, bis (3-hydroxypropyl) phosphine, bis (2-cyanoethyl) phosphine; dicyclopentylphosphine, dicyclohexylphosphine, tricyclopentylphosphine, tricyclohexylphosphine Alicyclic phosphines; triphenylphosphine, tris (4-methylphenyl)
Di- or triarylphosphines such as phosphine, diphenylphosphine, bis (4-methylphenyl) phosphine; tribenzylphosphine,
Di- or tri-aralkylphosphines such as triphenethylphosphine, dibenzylphosphine and diphenethylphosphine; phosphines having a phosphorus atom in the ring such as tetramethylenephosphine and tetramethylene-methylphosphine; diphenyl Examples thereof include phosphines such as methylphosphine, diphenylethylphosphine, and phenyldiethylphosphine in which two or three different organic groups are bonded to a phosphorus atom. A tertiary amine is particularly preferable.

The reaction temperature is generally −80 to 100 ° C., preferably 20 to 50 ° C. A solvent is usually used, but it can be carried out without using it. The solvent can be used except for alcohols that react with dibasic acid anhydrides, but ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone may cause a decrease in the reactivity of raw materials and coloring of the reaction mixture. It is preferable because it does not exist. The amount of the base used is usually 0.01 to 1.2 with respect to the above dibasic acid anhydride, preferably
It is 0.05 to 1.0 (however, molar ratio).

In the production method of the present invention, when the vinyl ether monomer composition and a fluoroolefin are copolymerized, the vinyl ether (I) in the vinyl ether monomer composition is 1 to 50 mol% of the vinyl ether (II), preferably 5 to 50 mol. It is characterized by%.

When the vinyl ether (I) exceeds 50 mol% of (II),
The stability of the monomer composition itself is not a problem, but the amount of halogen ions generated is large, and the salt composition has poor stability when used in an aqueous liquid such as an aqueous paint. When it is used as an electrodeposition paint, the above-mentioned adverse effects are further exerted.

On the other hand, when the amount is less than 1 mol%, the amount of halogen ions generated is suppressed, but the vinyl ether composition is poor in stability and not only the yield is lowered, but also the decomposition product thereof causes the coating film performance (armpit and Repelling, etc.) will decrease. Furthermore, in the case of electrodeposition paint, it leads to an increase in miscellaneous ions (such as acetate ions).

According to the production method of the present invention, the fluorine ion in the produced copolymer is 500 ppm or less, and the total amount of fluorine ion and chlorine ion is
It can be suppressed to 1500 ppm or less, and the yield can be maintained at 90% or more.

The copolymerization system basically comprises a vinyl monomer composition, a fluoroolefin, a solvent and a polymerization initiator. As the polymerization method, emulsion polymerization, suspension polymerization, solution polymerization and the like can be adopted.

The polymerization temperature can be appropriately changed depending on the type of the initiator and the solvent, but is usually −20 to 150 ° C., preferably 5 to 95.
℃. The reaction pressure can be appropriately selected, but is usually 0 to
It is 50 kg / cm ² G.

Examples of fluoroolefins include tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, trifluoroethylene, vinylidene fluoride, vinyl fluoride and the like.

In the present invention, the reaction molar ratio of vinyl ether (I), (II) and fluoroolefin is usually vinyl ether / fluoroolefin = 0.1-80 / 20-99.9.

When using a fluorocopolymer as a water-soluble paint,
In order to improve the water solubility of this copolymer, it is preferable that the vinyl ethers (I) and (II) are contained in an amount of 5 to 60 mol%, and the carboxyl groups thereof are neutralized by 30% or more. Is more preferable (for electrodeposition coating). Examples of the compound used for neutralization include those exemplified as the above base.

When the fluorine-containing copolymer is dissolved in an organic solvent and used as a so-called solvent type coating material, vinyl ether (I),
The content of (II) is 1 to 15 mol% in terms of adhesion to the base material.
Is preferable, and 2-10 mol% is preferable from the viewpoint of pigment dispersibility.

In addition to vinyl ether and fluoroolefin, the fluorine-containing copolymer may contain another kind of ethylenically unsaturated compound in an amount ratio of 80 mol% or less with respect to the fluorine-containing copolymer. Other types of ethylenically unsaturated compounds, for example the _{formula: CH 2 = CH-OC =} O) k R 3 ( wherein, R ³ is an aliphatic group having a carbon number of 1 to 17, carbon atoms 3 to 17 Alicyclic group, fluoroalkyl group having 1 to 20 carbon atoms, hydroxyl group-containing aliphatic group having 1 to 17 carbon atoms, hydroxyl group containing alicyclic group having 3 to 17 carbon atoms, or 6 carbon atoms
Alkyl vinyl ether or vinyl ester represented by 20 hydroxyl group-containing aromatic groups, k is 0 or 1, and specific examples include methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n- Butyl vinyl ether, isobutyl vinyl ether, t-butyl vinyl ether, n-pentene vinyl ether, n-hexyl vinyl ether, n-octyl vinyl ether, 2
-Ethylhexyl vinyl ether, cyclohexyl vinyl ether, lauryl vinyl ether, stearyl vinyl ether, 2,2,2-trifluoroethyl vinyl ether, 2,2,3,3-tetrafluoropropyl vinyl ether, 2,2,3,3,3-pentafluoropropyl Vinyl ether, 2,2,3,3,4,4,5,5-octafluoropentene vinyl ether, 2,2,3,3,4,4,4-heptafluorobutyl vinyl ether, vinyl acetate, vinyl propionate , Vinyl acetate, pivalic acid vinyl ester, caproic acid vinyl ester, lauric acid vinyl ester, versatic acid vinyl ester, cyclohexanecarboxylic acid vinyl ester, 4-hydroxybutyl vinyl ether, 2-hydroxyethyl vinyl ether,
3-hydroxy-n-propyl vinyl ether, 2-hydroxy-iso-propyl vinyl ether, 2-hydroxy-2-methylethyl vinyl ether, 2-hydroxy-1,1-dimethylethyl vinyl ether, 4-hydroxycyclohexyl vinyl ether, 3-hydroxycyclohexyl Examples thereof include vinyl ether, 2-hydroxycyclohexyl vinyl ether and 4-hydroxybenzooxy vinyl.

Furthermore, the formula: CH ₂ ═CX ⁸ C (═O) O) _m R ⁹ (wherein, X ⁸ is a hydrogen atom, a chlorine atom, a fluorine atom, a methyl group or a trifluoromethyl group, and R ⁹ is a hydrogen atom or a chlorine atom. An aliphatic group having 1 to 17 carbon atoms, an aliphatic group having 1 to 17 carbon atoms having a hydroxyl group, an alicyclic group having 3 to 17 carbon atoms or a fluoroalkyl group having 1 to 20 carbon atoms, m represents 0 or 1), and specific examples include ethylene, propylene, 1-butene, isobutene, styrene, vinyl chloride, vinylidene chloride, isobutyl acrylate, methyl acrylate,
Ethyl methacrylate, 2,2,3,3,3-pentafluoropropyl α-fluoroacrylate, 2,2,3,3,4,4,5,5,6,
6,7,7-dodecafluoropentyl α-trifluoromethyl acrylate, 2-hydroxyethyl methacrylate, cyclohexyl acrylate, 2,2,3,3,4,4,5,5,6,
6,7,7,8,8,9,9,10,10,11,11,12,12,13,13,14,14,15,15,
15-Nonacosafluoropentadecyl acrylate, 2-
Examples thereof include hydroxypropyl α-chloroacrylate, octyl α-chloroacrylate and octadecyl acrylate.

Further, the formula: CH ₂ ═CHCH ₂ X ⁹ (wherein, X ⁹ is a carbon atom, a hydroxyl group or a carbon number of 1 to 8).
Which represents an aliphatic oxy group of), and specific examples thereof include allyl alcohol, allyl chloride, allyl methyl ether, allyl isopropyl ether, and allyl octyl ether.

If necessary, a small amount of polyvalent metal (for example, M
g, Ca, Zn, Al) or polyfunctional compounds containing nitrogen or phosphorus atoms (eg alkyldiamine,
Polyamines such as alkyltriamine, polydiphosphines such as alkyldiphosphine and alkyltriphosphine) and divinyl ether or trivinyl ether, which is a salt of vinyl ether (II), can be present as a copolymerization component. When it is partially gelled, it can be used for matting.

As the polymerization solvent, halogenated hydrocarbons such as trichlorotrifluoroethane and dichlorotetrafluoroethane, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, esters such as ethyl acetate and butyl acetate, and aromatics such as toluene and xylene. Examples thereof include group hydrocarbons, alcohols such as methanol, ethanol, propanol, butanol, glycol ethers such as ethyl cellosolve, butyl cellosolve, monoglyme and diglyme, and water.

Examples of the polymerization initiator include persulfates (ammonium persulfate, potassium persulfate, etc.), persulfates and sulfites (potassium sulfite, sodium sulfite, etc.), or acidic sulfites (potassium acid sulfite, sodium acid sulfite, etc.). Examples include redox initiators, organic peroxides (diisopropyl peroxydicarbonate, tert-butyl peroxybutyrate, benzoyl peroxide, isobutyryl peroxide, etc.), azo compounds (azobisisobutyronitrile, etc.), etc. You can The amount of the initiator used is 0 with respect to all the monomers normally used.
It is 001 to 5% by weight, preferably 0.05 to 2.0% by weight.

The operation system of the production method of the present invention may be a batch system, a continuous system, or a semi-continuous system.

Next, the present invention will be described based on examples, but the present invention is not limited to these examples.

Reference Example 1 In a 1000 ml flask, anhydrous 1,2-cyclohexanedicarboxylic acid (anhydride) 405 g (2.63 mol) and acetone 40 g
Solution containing triethylamine (base: pKa = 1
0.72) 2.63 g (0.28 mol) was added, and the mixture was stirred with a magnetic stirrer for 5 minutes.

While cooling this mixture with ice water to 0 to 10 ° C, 305 g (2.63 mol) of hydroxybutyl vinyl ether was added.
Was added dropwise at a rate of 2 g / min.

Fourier Transform Nuclear Magnetic Resonance Analysis (FT-N) of the reaction mixture
MR, ¹³ C, tetramethylsilane standard) was performed, and the following vinyl ether (I) of the present invention (hereinafter referred to as cHHEM salt) and corresponding free vinyl ether (II) (hereinafter referred to as cHHEM salt) were used.
It was confirmed that HEM) was produced in a yield of about 10/85 (molar ratio). The chemical shift of each carbon atom (denoted by a to m) is shown.

Shows the chemical shift of.

δ (ppm) = 85.6 (a), 151.5 (b), 67.2 (c), 2
5.3-25.6 (d), 62.8 (e), 173.3 (f), 42.9
(G), 27.4 (h), 24.4 (i), 43.5 (j), 176.2
(K), 44.9 (i), 9.1 (m) Reference property 2 A monomer comprising cHHEM salt and cHHEM in the same procedure as in Reference Example 1 except that the amount of triethylamine in Reference Example 1 was changed to the amount shown in Table 1. A composition was produced. The yields analyzed by FT-NMR are shown in Table 1.

Further, the decomposition rate (%) of the obtained reaction product when stored at 20 ° C and -20 ° C was examined by ¹³ C-NMR.
The results are also shown in Table 1.

Reference Example 3 Reaction product obtained under the condition of Experiment No. 2 of Reference Example 2 (cH
The bases shown in Table 2 were added to (HEM salt / cHHEM = 0.1 / 84.9: molar ratio) to convert cHHEM into a cHHEM salt, and the decomposition rate was examined in the same manner as in Reference Example 2. The results are shown in Table 2.

As is clear from Table 2, the basic compound having a pKa of less than 6 has a weak basicity and thus has a small contribution to the stabilization of cHHEM.

Example 1 160 g of monoglyme was charged into a glass autoclave having a volume of 800 ml equipped with a stirrer, solidified with liquid nitrogen, and then deaerated.

Then, 128.2 g of chlorotrifluoroethylene (hereinafter referred to as CTFE) was charged, and the system was heated to 65 ° C. Next,
Vinyl ether monomer composition separately obtained in Reference Example 1 (cH
HEM salt / cHHEM = 10/85, molar ratio) 72.83 g, hydroxybutyl vinyl ether (hereinafter referred to as HBVE) 49.9 g, vinyl ester of a carboxylic acid having an alkyl group having 10 carbon atoms [Coba Chemical's Veova 10 ( Hereinafter referred to as VA)] 6
1.4 g and azobisisobutyronitrile (hereinafter referred to as AIBN) 1.64 g were mixed, and the monomer mixture degassed after solidification with liquid nitrogen was continuously charged for 4 hours. The system temperature was maintained at 65 ° C. After the completion of the charging, the reaction was continued at 65 ° C. for 16 hours to obtain a carboxyl group-containing fluorocopolymer.
The yield was 451 g and the copolymer concentration was 64.3% (yield, 9
8.9%. The theoretical copolymer concentration was 65%).

The concentrations of fluorine ion and chlorine ion in the obtained copolymer were measured.

Fluorine ion concentration in polymer: 220ppm Chloride ion concentration in polymer: 351ppm (Measurement method of halogen ion content) Fluorine-containing polymer 1.0g was dissolved in methyl isobutyl ketone 100g, ion-exchanged water 100g was put, and 300cc of The mixture was shaken well with a separating funnel and then separated, and the fluorine ion and chlorine ion concentrations in the aqueous phase were measured by an ion chromatography method. The ionic content is the value for the polymer.

Examples 2 to 5 and Comparative Examples 1 to 2 Copolymerization was carried out in the same manner as in Example 1 using the polymerization systems shown in Table 3 to obtain fluorine-containing copolymers. Their yields and copolymer concentrations are shown in Table 3.

In Table 3, EVE is ethyl vinyl ether and succinic acid HEM is The succinic acid HEM salt represents its triethylamine salt.

[Effects of the Invention] According to the production method of the present invention, it is possible to suppress the amount of halogen ions generated while maintaining a high yield, and therefore a water-based coating using the obtained copolymer, particularly an electrodeposition coating is stable. The coating properties are good and the coating film formed is homogeneous and of high performance.

Claims (8)

[Claims] 1. Formula (Ia): CH₂= CHOR¹OC (= O) R²C (= O) OM (Ia) (In the formula, R¹Is a divalent aliphatic group having 2 to 10 carbon atoms, R²Is
A divalent organic group, M is an alkali metal)
Vinyl ether, or formula (Ib): CH₂= CHOR¹OC (= O) R²C (= O) O ・ HY  (I
b) (In the formula, R¹And R²Is the same as above, Y is a nitrogen atom or
Is a compound containing a phosphorus atom, and its pKa is 6 to 1
2 is a monofunctional basic compound which is 2)
Vinyl ether and formula (II): CH₂= CHOR¹OC (= O) R²C (= O) OH (II) (In the formula, R¹And R²Is the same as above)
Vinyl ether consisting of ether and represented by formula (Ia)
Tellur or vinyl ether represented by formula (Ib)
Containing 1 to 50 mol% of vinyl ether represented by (II)
The vinyl ether monomer composition prepared by
Halogen-iod characterized by being copolymerized with reffin
A method for producing a fluorine-containing copolymer that generates a small amount of hydrogen. 2. The method according to claim 1, wherein the alkali metal is Na, K or Li. 3. The method according to claim 1, wherein the basic compound has a pKa of 8-11. 4. The method according to claim 1, wherein the basic compound is ammonia, amines or phosphines. 5. The method according to claim 4, wherein the basic compound is a tertiary amine. 6. The method according to claim 1, wherein R ² is a divalent hydrocarbon group. 7. R ² is of the formula (i) CHX ¹ _p CX ² _{2 q} (i) [wherein, X ¹ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and X ² is a hydrogen atom or a carbon atom. A group represented by formula (ii): CH _{2 r} CX ³ ═CH, wherein p and q are 0 or an integer of 1 to 11 (however, they are not 0 at the same time) _s (ii) [wherein r is 0 or an integer of 1 to 3, s is an integer of 1 to 3, X ³ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms], a group (Iii): [In the formula, R ⁷ is a CHX ⁴ _t group (provided that X ⁴ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and t is an integer of 1 to 4), —CH ₂ CH═CHCH ₂ — group. , A group represented by the formula (iv): [In the formula, R ⁸ is a CHX ⁵ _u group (provided that X is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, u is an integer of 3 to 4) or a CX ⁶ = CX ⁷ _v group (provided that X ⁶ and X ⁷ are the same or different and each represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, v is an integer of 2 to 3], a group represented by the formula (v): —C (═CH ₂ ) —CH ₂ — (v) group or formula (vi): The method according to claim 6, which is a group represented by: 8. The method according to claim 1, wherein the fluoroolefin is selected from the group consisting of tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, trifluoroethylene, vinylidene fluoride and vinyl fluoride.