JP2913100B2 - Method for producing fluorinated aqueous resin composition - Google Patents

Description

The present invention relates to a method for producing a fluorinated aqueous resin composition.

[Conventional technology]

Recently, fluorine-containing resins have attracted attention as paint resins having excellent weather resistance.

Conventionally, a typical example of a fluorine-containing resin paint has been developed in which polyvinylidene fluoride fine powder is dispersed in an acrylic resin solution, but since it is a dispersion type, the appearance of the coating film is inferior or the baking temperature is 200 ° C or higher. And high disadvantages.

In order to improve these disadvantages, 200
Fluororesins that can be cured at a temperature between ℃ and room temperature have been developed. For example, Japanese Patent Application Laid-Open (JP-A) No. 57-34107, however, the coating methods for forming these coating films are spray, roll coater, dipping, brush coating, etc., and contain a large amount of an organic solvent. It was accompanied by dangers such as air pollution and fire.

[Problems to be solved by the invention]

The present invention provides a method for producing a water-soluble, fluorine-containing aqueous resin composition which can be spray-coated, roll-coated, dipped, brushed and the like, as well as electrodeposition-coated.

With respect to such a fluorine-containing aqueous resin, JP-A-58-13660
5, 62-59676, 62-127362.

In these methods, a dibasic acid anhydride is allowed to act on a hydroxyl group in a hydroxyl group-containing fluororesin, and at least a part of the hydroxyl group is represented by a general formula -OCR-COOH (where R is the number of carbon atoms). (2 to 10 organic groups), and converting the ester group into an ester group and introducing a carboxylic acid. However, according to this method, due to the ester group,
Since the carboxylic acid is introduced into the fluorine-containing resin through an ester bond, it is easily neutralized and water-soluble by an alkaline component, usually various amines, and then easily hydrolyzed, thereby stably maintaining the aqueous solution and excellent electrodeposition. It is difficult to obtain a coating.

[Means for solving the problem]

The present invention has good bath stability, as a result of intensive studies on the composition and production method for obtaining a fluorinated aqueous resin, upon introduction of carboxylic acid into the fluorinated resin, hydrolysis occurs in an alkaline region. I found a difficult method.

More specifically, using an alkoxysilane group-containing compound, the alkoxysilane compound is introduced into the fluororesin by a dealcoholation reaction with a part of the hydroxyl groups in the fluororesin, and a carboxyl group is introduced into the alkoxysilane compound. I found a way to do it.

That is, the present invention carries out a dealcoholization reaction between (a) the hydroxyl group-containing fluoropolymer and (b) the α-β unsaturated alkoxysilane group-containing vinyl compound, and further comprises (c) α
A process for producing a fluorinated aqueous resin composition, characterized in that a β-unsaturated carboxylic acid is reacted and then neutralized with an alkaline component to make it water-soluble.

In the method of the present invention, the alkoxysilane compound is introduced into the fluorine-containing resin as described above,
As the alkoxysilane compound, a method in which an alkoxysilane-containing vinyl monomer is introduced into a fluorine-containing resin by a dealcoholization reaction, and then an acid group such as an α-β unsaturated carboxylic acid is additionally introduced into the vinyl group. is there.

The carboxyl group-introduced hydroxyl group-containing fluororesin obtained by the method of the present invention can be easily prepared by neutralizing the carboxyl group with an alkali component, commonly used various amines such as an alkylamine such as triethylamine and an alkanolamine such as diethanolamine. Can be made water-soluble.

In neutralization, the molar ratio is preferably 0.3 to 1.8, and more preferably 0.4 to 1.0. The hydroxyl group-containing fluororesin of the present invention obtained as described above can be used in combination with a curing agent and, if necessary, various auxiliaries such as various sulfonic acids and tin compounds as a curing accelerator.

Similarly, various alcoholic solvents and various emulsifiers can be used as water-solubilizing aids. The water-soluble resin thus obtained can be sprayed, brushed, and the like, and further can be subjected to coating by electrodeposition.

As a matter of course, the composition of the present invention can use coloring pigments such as TiO ₂ , extenders such as kaolin, and various rust-preventive pigments.

In the electrodeposition coating, a water-insoluble solvent such as MIBK or mineral spirit may be included for adjusting the viscosity of the resin.

The hydroxyl group-containing fluoropolymer (a) used in the present invention may be any known one without particular limitation.
-34107 and JP-A-59-102962.

Examples of the (b) α-β unsaturated alkoxysilane group-containing vinyl compound used in the present invention include vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltris-
β-methoxysilane, divinyldimethoxysilane, divinyldi-β-methoxyethoxysilane, γ- (meth) acryloxypropyltrimethoxysilane, γ- (meth)
Acryloxypropyltriethoxysilane, γ- (meth) acryloxypropylmethyldimethoxysilane and the like can be mentioned.

The (c) α-β unsaturated carboxylic acid used in the present invention is a monomer component that imparts water solubility to the vinyl copolymer, and contains a radical polymerizable unsaturated double bond and a carboxyl group in one molecule. And a group-containing monomer. Specifically, for example, (meth) acrylic acid, maleic acid, itaconic acid and the like can be mentioned.

Further, in the present invention, other radically polymerizable unsaturated compounds can be polymerized in addition to the above compounds. Examples of such compounds include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, -Ethylhexyl (meth) acrylate, lauryl (meth) acrylate, (meth) acrylonitrile,
(Meth) acrylamide, N-methylolacrylamide, N-butoxymethylacrylamide, styrene, α
-Fluorine-containing monomers such as methylstyrene, vinyl toluene, vinyl acetate, vinyl hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hexafluorobutyl methacrylate, and tetrafluoropropyl methacrylate.

The hydroxyl group-containing fluororesin used in the method of the present invention is OH
Preferred are those having a value of 20-150 mg KOH / g solids, preferably 50-120 mg KOH / g.

The characteristic value of the final resin in which an acidic group (carboxyl group) or a basic group (amino group) is introduced into the above hydroxyl group-containing fluororesin is an OH value of 15 to 145 mg KOH / g solid, an acid value (or base value) of 5 to 5. 135mgKOH / g solid (0.09 ~ 2.41meq / g solid)
It is preferable to have an OH value of 30 to 120 mgK.
OH / g solid content, acid value 20-100 (or base value) 0.36-0.78meq
/ g solid content).

Therefore, in the present invention, the blending amounts of the essential components (a), (b), and (c) and the polymerizable optional component should be selected so as to obtain such characteristics. The thus obtained fluorinated aqueous resin is mixed with a curing agent such as an amino resin and various blocked isocyanates, and then coated and coated at 120 ° C to 2 ° C.
By baking at 00 ° C., a coating film having good chemical resistance and good weather resistance can be formed.

The mixing ratio (solid content ratio) between the fluorinated aqueous resin and the curing agent such as amino resin or blocked isocyanate is 80:20 to 50:
Although 50 may be used, an appropriate ratio is determined by the OH group value, the acid value (base number), and the number of functional groups of the curing agent.

Examples of the amino resin used include a melamine resin and a urea resin benzognamine resin. In order to exhibit the original weather resistance of the fluororesin, methylol melamine and alkoxymethylol melamine are suitable.

Various blocked isocyanates include aromatic isocyanates such as tolylene diisocyanate and alicyclic isocyanates such as hexamethylene diisocyanate as the isocyanate. Useful to take advantage of its properties. In addition, since these isocyanates are dispersed in water, it is necessary to previously block the -NCO group. However, alcohols known as blocking agents. Lactams and the like are used.

In addition, in selecting these curing agents, it is necessary to consider the weather resistance of the curing agent itself as described above. More specifically, when an acidic group (carboxylic acid) is introduced for aqueous conversion, the resin is acidic, and curing with an amino resin is easy.

〔Example〕

Hereinafter, the present invention will be described specifically with reference to examples. All parts in the examples are by weight.

Example 1 100 parts of a hydroxyl group-containing fluororesin (Lumiflon LF manufactured by Asahi Glass Co., Ltd.)
−200AV = OOHV = 53.3 g solid content NV = 60%) 7.5 parts of γ-methacryloxypropyltrimethoxysilane are charged into a four-necked flask by a conventional method, and the temperature is gradually raised from room temperature with stirring. 0.97 parts of methanol was distilled off at ℃. Thereafter, a mixture of 15 parts of butyl cellosolve, 2.6 parts of methacrylic acid, and 0.1 part of azobisisobutylnitrile was dropped by a dropping funnel with stirring. During this time,
The temperature in the flask was maintained at 80 ° C to 90 ° C, and the dropwise addition was completed in one hour. Thereafter, the temperature was maintained at the same temperature for about 2 hours, and then cooled to room temperature. At this time, the resin had a solid content of 55.2% and an acid value of 24.
mgKOH / g solids.

Further, 15 parts of Cymel # 300 (hexamethoxymethylol melamine manufactured by Mitsui Cyanamid Co., Ltd.) were added and mixed, and then 3 parts of triethylamine was added. Then, deionized water was added to make a total of 840 parts, thereby containing the present invention. A fluorinated aqueous resin solution was obtained. The solid content of the obtained resin solution was 10%, and the PH was 8.0, and the specific resistance of the solution was 1020 Ωcm. This resin solution was used as a bath solution and supplied to an electrodeposition paint under the following conditions by a conventional method. Distance between poles = 12cm, bath temperature = 22
The coating was performed at 100 V for 2 minutes at ℃, using the coated material as an anode (SUS304 was used as a cathode and the pole ratio = positive 2/1).

The object to be coated was prepared by subjecting a 6063S aluminum alloy plate to a 7 μm alumite sulfate treatment. By the usual method,
After washing with water, it was baked and dried at 180 ° C. for 20 minutes.

 Various properties of the obtained coating film were as follows.

Film thickness = 7 μm, appearance = good, hardness = 3H, gloss (60 °) = 65%, adhesion = 100/100 (gohan) Gloss retention after 3000 hours accelerated weathering test = 93% (S,
This bath solution was warmed and stored at 40 ° C. for 1 week.

As a result, the solid content was 10%, PH was 8.0, and SR was 1010 Ωcm, and there was almost no change in PH and SR as compared to before heating.
By applying a current of 100 ° C. × 2 minutes × 100 V, a coating film of 7 μm was obtained and had the same properties as before heating.

〔The invention's effect〕

The fluorinated aqueous resin composition obtained by the production method of the present invention is not only excellent in weather resistance, but also excellent in storage stability, and is water-soluble, and does not require high temperature for curing, and is sprayable. Since electrodeposition coating is possible as well as brush coating, it can be expected to be used in a wide range of industrial fields.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C08L 27/12 C09D 127/12

Claims (1)

(57) [Claims] (1) A dealcoholization reaction is carried out between (a) a hydroxyl group-containing fluoropolymer and (b) an α-β unsaturated alkoxysilane group-containing vinyl compound, and (c) an α-β unsaturated carboxylic acid is further produced. After reacting,
A method for producing a fluorinated aqueous resin composition, wherein the composition is made water-soluble by neutralization with an alkali component.