JPH07216020A - Production of fluorine-containing copolymer containing carboxyl group - Google Patents

Abstract

PURPOSE:To obtain the subject copolymer excellent in liquid stability in water dispersing and useful as a base resin, etc., of aqueous electrocoating by reacting a fluorine-containing copolymer containing a hydroxyl group binding to secondary or tertiary carbon with an acid anhydride of a dibasic acid. CONSTITUTION:Chlorotrifluoroethylene, ethylvinyl ether, cyclohexylvinyl ether, 2,5-dimethyl-2,5-hexanediol monovinyl ether, 2,5-dimethyl-2,5-hexanediol monovinyl ether, xylene and azobisisobutylonitrile are charged into an autoclave and reaction of these monomers is carried out at 65 deg.C for 16hr and the resultant hydroxyl group-containing and fluorine-containing copolymer having a hydroxyl group binding to the secondary or tertiary carbon is reacted with an acid anhydride of a dibasic acid (e.g. hexahydrophthalic anhydride) to provide the objective carboxyl group-containing fluorine-containing copolymer, excellent in liquid stability in the case of dispersing in water and having good stability with passage of time when used as a base resin of aqueous coating such as electrocoating.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a process for producing a carboxylic acid group-containing fluorocopolymer.

[0002]

2. Description of the Related Art Conventionally, there are many cases in which an acid anhydride / acid imide compound is introduced into a polymer substance to improve / introduce adhesiveness, polymer reactivity, dyeability, pigment affinity, ion exchangeability, etc. There are many examples of industrialization of general polymer substances.

On the other hand, as a method for producing a carboxylic acid group-containing fluorine-containing copolymer, a hydroxyl group-containing fluorine-containing copolymer is reacted with a dibasic acid anhydride in an organic medium so that at least a part of the hydroxyl groups is a carboxylic acid-containing ester group. The method of converting into is proposed.

[0004]

This method has a problem in that the hydroxyl group of the hydroxyl group-containing fluorocopolymer is bonded to the primary carbon, so that the ester structure produced may be hydrolyzed.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and a hydroxyl group-containing fluorocopolymer having a hydroxyl group bonded to a secondary or tertiary carbon is added to a dibasic acid. A method for producing a carboxyl group-containing fluorocopolymer, which comprises reacting an anhydride.

In the present invention, a fluorine-containing copolymer containing a hydroxyl group having a hydroxyl group bonded to a secondary or tertiary carbon is produced by a monomer having a hydroxyl group bonded to a secondary or tertiary carbon and an ethylenically unsaturated bond. (1) Copolymerizing a monomer having a hydroxyl group bonded to a primary carbon and a monomer having an ethylenically unsaturated bond, and then subjecting this to 2 Method (2) of converting to a hydroxyl group bonded to a primary or tertiary carbon, or converting a primary carbon of a monomer having a hydroxyl group bonded to a primary carbon into a hydroxyl group bonded to a secondary or tertiary carbon A method (3) of copolymerizing the monomer to be used with a monomer having an ethylenically unsaturated bond can be mentioned.

The hydroxyl group bonded to the primary carbon has a secondary or tertiary hydroxyl group.
Examples of the method of converting to a hydroxyl group bonded to a primary carbon include a method of reacting a hydroxyl group bonded to a primary carbon with an epoxide such as propylene oxide, isobutylene oxide, or cyclohexene oxide.

The monomer having a hydroxyl group bonded to a secondary or tertiary carbon is obtained by reacting a diol such as cyclohexanedimethanol, 1,2-butanediol, neopentyl glycol or 1,2-pentanediol with the above epoxides. And vinyl ethers obtained by reacting acetylene with acetylene, or vinyl ethers obtained by reacting diol such as 2,5-dimethylhexane-2,5-diol with acetylene.

As the acid anhydride of dibasic acid, various compounds represented by Chemical formula 1, specifically, succinic anhydride, glutaric anhydride, itaconic anhydride, adipic anhydride, 1,2-anhydride.
Examples thereof include cyclohexanedicarboxylic acid, cis-4-cyclohexene anhydride, 1,2-dicarboxylic acid, phthalic anhydride, 1,8-naphthalic anhydride, and maleic anhydride.
In consideration of reactivity, a non-aromatic dibasic acid anhydride is preferable, and one in which R in Chemical formula 1 is an alkylene group having 2 to 8 carbon atoms is preferable.

[0010]

[Chemical 1] However, R represents a divalent organic group.

As the monomer having an ethylenically unsaturated bond, fluoroolefins are particularly preferable, and CClF = C
F ₂ , CHCl = CF ₂ , CCl ₂ = CF ₂ , CClF = CClF, CHF = CCl ₂ , CH ₂ = C
Fluoroethylenes such as ClF, CCl ₂ = CClF, CF ₂ = CF ₂ , CF ₂ = CH ₂ , CF ₂ ClCF = CF ₂ , CF ₃ CCl = CF ₂ , CF ₃ CF = CFCl, CF ₂ ClCCl
= CF ₂ , CF ₂ Cl CF = CFCl, CFCl ₂ CF = CF ₂ , CF ₃ CCl = CClF, CF ₃ CC
l = CCl ₂ , CClF ₂ CF = CCl ₂ , CCl ₃ CF = CF ₂ , CF ₂ ClCCl = CCl ₂ , CF
Cl ₂ CCl = CCl ₂ , CF ₃ CF = CHCl, CClF ₂ CF = CHCl, CH ₃ CCl = CHC
l, CHF ₂ CCl = CCl ₂ , CF ₂ ClCH = CCl ₂ , CF ₂ ClCCl = CHCl, CCl ₃ CF
_{= CHCl, CCl 3 CF = CHCl} , CHBrCF = CCl 2 CF 2 = CFOCF 3, CF 2 = CFO
Fluoroprohens such as C ₃ F ₇ , CF ₃ CCl = CFCF ₃ , CF ₂ = CFCF
_{2 CClF 2, CF 3 CF 2} CF = CCl 4 or more of the fluoroolefins Tansoko such _2. These fluoroolefins may be used alone or in combination of two or more.

The copolymerization ratio of fluoroolefins in the carboxyl group-containing fluorocopolymer is 20 to 80 mol%, preferably 30 to 70 mol%. The copolymerization ratio of the monomer having a hydroxyl group is 5 to 70 mol%, preferably 1
It is 0 to 60 mol%.

Further, another monomer copolymerizable with the carboxyl group-containing fluorine-containing copolymer can be copolymerized in a proportion of 1 to 40 mol% within a range not losing its characteristics. The following monomers can be exemplified.

Olefins such as ethylene, propylene and isobutylene, haloolefins such as vinyl chloride and vinylidene chloride, vinyl acetate, vinyl butyrate, vinyl pivalate, vinyl benzoate, vinyl carboxylates such as vinyl versatate and ethyl vinyl ether. Alkyl vinyl ethers such as n-butyl vinyl ether, octyl vinyl ether, neopentyl vinyl ether and cyclohexyl vinyl ether, aromatic vinyl ethers such as phenyl vinyl ether, benzyl vinyl ether and naphthyl vinyl ether, methyl isopropenyl ether,
Isopropenyl ethers such as propyl isopropenyl ether, allyl formate, allyl butyrate, allyl benzoate,
Examples thereof include allyl carboxylates such as allyl cyclohexanecarboxylate, allyl ethers such as allyl ethyl ether and allyl phenyl ether, and (meth) acrylic acid esters such as ethyl acrylate and methyl methacrylate.

The carboxyl group-containing fluorocopolymer of the present invention has a number average molecular weight of 2,000 to 100,000,
It is preferably 6,000 to 30,000 and has a molecular weight distribution of 4.0 or less, preferably 3.0 or less. If the molecular weight is less than 2,000, the weather resistance and chemical resistance are inferior, and if it exceeds 1,000 to 100,000, the viscosity of the coating material is high, and there is a problem in workability. When the molecular weight distribution is more than 4, the workability also suffers.

The carboxyl group-containing fluorocopolymer of the present invention is prepared by coexisting a monomer mixture in a predetermined ratio with a polymerization catalyst,
Alternatively, it can be produced by allowing a polymerization initiator or a polymerization initiation source such as ionizing radiation to act in the absence of coexistence to cause a copolymerization reaction.

As the polymerization initiator, a water-soluble one or an oil-soluble one can be appropriately used depending on the type of polymerization or the polymerization medium.

The water-soluble initiator may be a persulfate such as potassium persulfate, hydrogen peroxide or a redox initiator composed of hydrogen peroxide or a reducing agent such as sodium bisulfite or sodium thiosulfate, and a small amount of them. Inorganic initiators such as those containing iron, ferrous salt, silver nitrate, etc., or dibasic acid oxides such as disuccinic acid peroxide, diglutaric acid peroxide, monosuccinic acid peroxide, azobisisobutylamidine dibasic acid salt Organic initiators such as

As the oil-soluble initiator, peroxyester type peroxides such as t-butylperoxyacetate, dialkylperoxydicarbonates such as diisopropylperoxydicarbonate, benzoyl peroxide, azobisisocarbonate. Butyronitrile and the like are exemplified.

The amount of the polymerization initiator used can be appropriately changed according to the type and the conditions of the copolymerization reaction, but usually 0.05 to 0.5% by weight based on the total amount of the monomers to be copolymerized. % Is used.

In the above copolymerization reaction, the reaction mode is not particularly limited, and bulk polymerization, suspension polymerization, emulsion polymerization, solution polymerization and the like can be adopted, but the stability of the polymerization operation, the copolymer produced. From the standpoint of ease of separation, etc., emulsion polymerization in an aqueous medium or alcohols such as t-butanol,
Solution polymerization using an ester, a saturated halogenated hydrocarbon containing one or more fluorine atoms, an aromatic hydrocarbon such as xylene, etc. as a solvent is preferable. Reaction temperature is 10 ° C to 90 ° C
The degree is adopted, and the reaction pressure can be appropriately selected,
Usually 0 to 100 kg / cm ² G, especially 0 to 50 k
It is desirable to adopt g / cm ² G or so.

The carboxyl group-containing fluorocopolymer obtained by the present invention is preferably used as a base resin for paints. In this case, the intrinsic viscosity, acid value and hydroxyl value of the copolymer are preferably within the ranges described below.

The carboxyl group-containing fluorine-containing copolymer has an intrinsic viscosity of about 0.05 to 2.0 dl / g. In order to suppress this range, a reaction medium having a relatively large chain transfer constant is used, It is preferable to carry out the copolymerization reaction in the coexistence of a chain transfer agent as appropriate.

The reaction for converting the hydroxyl groups of the fluoropolymer to the carboxyl groups may be carried out either partially or entirely. However, the acid value of the carboxyl group-containing fluorocopolymer is at least 10 mgK
OH / g is preferable.

When the amount of carboxyl groups is too small, that is, when the acid value is less than 10 mgKOH / g, it is difficult to make the aqueous solution, and when the acid value is too large, the coating film has poor alkali resistance and boiling water resistance. May decrease,
Not preferable. A fluorine-containing polymer having an acid value of about 10 to 150 mgKOH / g, particularly about 10 to 100 mgKOH / g is preferably adopted.

Further, it is preferable that at least a part of the above-mentioned hydroxyl group remains because it is possible to react with the curing agent and obtain a coating film excellent in solvent resistance and the like. In particular, those containing a hydroxyl group at a hydroxyl value of about 10 to 150 mgKOH / g are preferably adopted.

Further, the fluoropolymer having a carboxyl group may be composed of only the above-mentioned polymerized unit based on fluoroolefin, the polymerized unit having a carboxyl group and the polymerized unit having a hydroxyl group. Also, other copolymerizable monomers may be copolymerized. An alkyl vinyl ether, an alkyl allyl ether, an alkyl vinyl ester, an alkyl allyl ester, a fluoroalkyl vinyl ether, etc. may be appropriately copolymerized depending on desired physical properties of the coating film (hardness, gloss, pigment dispersibility, etc.). Even when these monomers are copolymerized, it is preferable that the content ratio of the polymerized unit based on the fluoroolefin, the acid value, and the hydroxyl value are within the above ranges.

[0028]

EXAMPLES Examples will be shown below to more specifically describe the present invention. In addition, the number of parts in the examples means part by weight unless otherwise specified.

Example 1 [Synthesis of Fluorine-Containing Polymer as Raw Material] Stainless Steel with Internal Volume of 200 cc
Less autoclave with stirrer (pressure resistance 50kg / cm ² 
G) 35 parts chlorotrifluoroethylene, ethyl vinyl
6.6 parts of luether, cyclohexyl vinyl ether
7.8 parts, 2,5-dimethyl-2,5-hexanedio
26 parts of rumono vinyl ether, 98 parts of xylene, ethano
28 parts, azobisisobutyronitrile 0.5 parts, nothing
Charge 1.5 parts of potassium hydrogen carbonate and cool with liquid nitrogen.
After removing dissolved air by solidification degassing,
Reaction was carried out for 6 hours to obtain a hydroxyl group-containing fluoropolymer.

Approximately 60 wt% xylene solution of the obtained hydroxyl group-containing fluoropolymer (having a hydroxyl value of approximately 110 mgKOH / g resin) was heated to 90 ° C., and hexahydrophthalic anhydride was added to 100 parts of the polymer. Add 4 parts, and add 0.
2 parts of triethylamine was added and reacted for 10 hours. When the infrared spectrum of the reaction solution was measured, the characteristic absorption of phthalic anhydride observed before the reaction (1850 cm ^-1 , 1
780 cm ⁻¹ ) has disappeared after the reaction, and carboxylic acid (1710 cm ⁻¹ ) and ester (1735c
m ⁻¹ ) absorption was observed. Thus, the acid value of the fluoropolymer having a carboxyl group introduced is 40 mgKOH / g.
It was a resin. In the obtained fluoropolymer, the xylene solvent was replaced with an isopropyl alcohol solvent to give a solution of about 60% by weight.

Next, after adding 2.04 parts of triethylamine to 135 parts of this fluoropolymer solution while continuing stirring,
Butyl cellosolve (26 parts) was added, and deionized water was further added to obtain an aqueous dispersion having a resin solid content concentration of 10% by weight.

The acid value change (ΔAV) and the pH change (Δp) after this aqueous dispersion was kept at a temperature of 40 ° C. for 2 weeks
H) was measured. The results are shown in Table 1.

Examples 2 to 4 The fluorine-containing polymer was synthesized and the stability test was conducted in the same manner as in Example 1 except that the type of hydroxyl group-containing vinyl ether was changed. The results are shown in Table 1.

Example 5 A fluorine-containing polymer was synthesized by using 4-hydroxybutyl vinyl ether instead of 2,5-dimethyl-2,5-hexanediol monovinyl ether in Example 1. Next, the hydroxyl group of the fluoropolymer was reacted with potassium methoxide and then with isobutylene oxide. The test was conducted after the removal of methanol and the purification treatment. Then, the reaction was performed with hexahydrophthalic anhydride in the same manner as in Example 1 to obtain an isopropyl solution. The test results are shown in Table 1.

Comparative Example 1 In Example 5, an isopropyl solution of a fluoropolymer having an acid value of 40 mgKOH / g resin was obtained without addition reaction of isobutylene oxide. The test results are shown in Table 1.

[0036]

[Table 1]

[0037]

INDUSTRIAL APPLICABILITY The resin of the present invention has excellent liquid stability when dispersed in water, and has good temporal stability when used as a base resin for aqueous paints such as electrodeposition paints.

Claims (6)

[Claims] 1. A method for producing a fluorinated copolymer containing a carboxyl group, which comprises reacting an acid anhydride of a dibasic acid with a fluorinated copolymer containing a hydroxyl group having a hydroxyl group bonded to a secondary or tertiary carbon. Method. 2. A hydroxyl group-containing fluorine-containing copolymer having a hydroxyl group bonded to a secondary or tertiary carbon is obtained by copolymerizing a monomer having a hydroxyl group bonded to a secondary or tertiary carbon with a fluoroolefin. The method of claim 1, which is: 3. The method according to claim 2, wherein the monomer having a hydroxyl group bonded to secondary or tertiary carbon is vinyl ether obtained by the reaction of secondary or tertiary alcohol and acetylene. 4. A fluorine-containing copolymer containing a hydroxyl group having a hydroxyl group bonded to a secondary or tertiary carbon is obtained by copolymerizing a monomer having a hydroxyl group bonded to a primary carbon and a fluoroolefin. The hydroxyl group bonded to the primary carbon of the copolymer having a hydroxyl group bonded to the primary carbon is a secondary or tertiary hydroxyl group.
The method according to claim 1, which is obtained by converting to a hydroxyl group bonded to a primary carbon. 5. A hydroxyl group-containing fluorocopolymer having a hydroxyl group bonded to a secondary or tertiary carbon, wherein the hydroxyl group bonded to the primary carbon of the monomer having a hydroxyl group bonded to the primary carbon is secondary or The method according to claim 1, which is obtained by copolymerizing a fluoroolefin with a monomer obtained by converting it into a hydroxyl group bonded to a tertiary carbon. 6. A hydroxyl group bonded to primary carbon is secondary or tertiary.
The method according to claim 4 or 5, wherein the method of converting to a hydroxyl group bonded to a primary carbon is a method of reacting an epoxide with a hydroxyl group bonded to a primary carbon.