JPH05186733A - Aqueous resin dispersion for coating - Google Patents

Abstract

PURPOSE:To provide the title dispersion made from a fluorocopolymer. CONSTITUTION:The title dispersion is prepared from a resin which is a reaction product of an aliphatic epoxy compound with a fluorocopolymer consisting of 15-60mol% fluoroolefin monomer unit, 20-78mol% vinyl monocarboxylate monomer unit, 7-30mol% crotonic acid monomer unit and 0-30mol% other copolymerizable monomer unit and having a number-average molecular weight of 5,000 or higher and in which a part or the whole of the carboxyl groups in the reaction product are neutralized with a basic compound. The copolymerizable monomer used with the fluoroolefin as the constituent unit of the fluorocopolymer can be selected in both type and amount in a wide range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorine-based water-based coating material which is non-polluting and resource-saving in that it does not use an organic solvent. It has excellent coating performance and can be widely used as a paint.

[0002]

PRIOR ART AND PROBLEMS THEREOF
Due to its excellent chemical resistance, it is widely used in the fields of construction and automobiles. However, in spite of its excellent coating film performance, since commonly used fluorine-based paints are organic solvent type, they contain a large amount of organic solvents and have problems in terms of environmental pollution and safety and hygiene. In order to solve the above problems, some proposals have been made for making a fluorine-based coating water-based. For example, a monomer such as fluoroolefin, olefin and hydroxyvinyl ether is co-polymerized with an unsaturated carboxylic acid such as crotonic acid. Used as a polymer to produce an aqueous fluorine-containing copolymer coating composition by emulsion polymerization (JP-A-2-240154), or a solution polymerization method to synthesize a fluorine-containing copolymer having a hydroxyl group, A method in which a dicarboxylic acid anhydride is partially reacted with to introduce a carboxyl group and then neutralized with a basic compound to obtain an aqueous resin dispersion of a fluorine-containing copolymer having a hydroxyl group (JP-A-62- No. 59676). However, since the water-based coating material obtained by emulsion polymerization contains an emulsifier, the adhesion to the substrate or the stain resistance of the coating film surface is just one step, while the hydroxyl group-containing copolymer reacts with the divalent carboxylic anhydride. According to this method, the physical properties of the coating material are not deteriorated by the emulsifier, but there is a problem in that the process of making the composition aqueous is complicated and the practicality thereof is poor. Further, the present situation is that the physical properties of the coating film are remarkably inferior with an aqueous solution type fluorine-based paint, rather than a resin dispersion type water-based paint such as the above-mentioned proposed paint.

Under such circumstances, the present inventors have proposed a copolymer of fluoroolefin, crotonic acid, a vinyl monomer having a hydroxyl group and a vinyl ester of carboxylic acid, the crotonic acid monomer being a constituent unit of the copolymer. A water-based resin for coatings, which comprises a fluorine-containing copolymer obtained by neutralizing a carboxyl group in the copolymer with a basic compound, using a copolymer containing units in a proportion of 7 to 30 mol% A patent application has been filed for the dispersion (Japanese Patent Application No. 3-1
31996), and when the ratio of crotonic acid in the fluorine-containing copolymer is relatively high, about 20 to 30 mol%, depending on the types and ratios of other copolymerizable monomers to be used in combination. It was found that it became water-soluble and an aqueous dispersion could not be obtained with good reproducibility.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a hydroxyl group-containing vinyl which is excellent in dispersion stability in an aqueous medium and is used as a comonomer with a fluoroolefin in order to obtain desired coating properties. The present invention provides an aqueous resin dispersion in which the amounts and types of monomers and vinyl carboxylates used are not limited to a narrow range.

[0005]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found that a reaction product of a fluorocopolymer having a specific constitution and an aliphatic epoxy compound is dissolved in an aqueous medium. It was found that the aqueous dispersion dispersed in the composition had excellent dispersion stability, and the present invention was completed. That is, in the present invention, based on the total amount of all monomer units, (a) fluoroolefin monomer units 15 to 6 are used.
0 mol%, (b) monocarboxylic acid vinyl ester monomer unit 20 to 78 mol%, (c) crotonic acid monomer unit 7
Of 30 to 30 mol% and (d) 0 to 30 mol% of other copolymerizable monomer units, and a fluorine-containing copolymer having a number average molecular weight of 5000 or more and an aliphatic epoxy compound. An aqueous resin dispersion for paints, which is a reaction product and comprises a resin in which some or all of the carboxy groups in the reaction product are neutralized with a basic compound.

The present invention will be described in more detail below. First, the fluorine-containing copolymer used in the present invention will be described. Examples of the fluoroolefin used for the synthesis of the fluorine-containing copolymer include vinyl fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene,
Examples thereof include chlorotrifluoroethylene and hexafluoropropylene, which can be used alone or in combination of two or more kinds. From the viewpoint of polymerization reactivity, tetrafluoroethylene and chlorotrifluoroethylene are preferable, and chlorotrifluoroethylene is particularly preferable. The content of the fluoroolefin unit in the copolymer is 15 to 60 mol% based on the total amount of all the monomer units constituting the copolymer. If it is less than 15 mol%, the weather resistance which is a characteristic of the fluorinated copolymer is not sufficiently expressed, while if it exceeds 60 mol%, the solubility in an organic solvent is poor and the polymer is difficult to be synthesized by a solution polymerization method. .. More preferably, it is 30 to 55.
Mol%.

The second monomer, a monocarboxylic acid vinyl ester, has the following hydrolysis resistance and weather resistance.
A vinyl ester composed of a monocarboxylic acid having an alkyl group having 3 or more carbon atoms, a cycloalkyl group or an aryl group is preferable. Specific examples include vinyl butyrate, vinyl pivalate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl versatate, vinyl stearate, vinyl benzoate, tertiary butyl vinyl benzoate and hydrogenated benzoic acid. Examples include vinyl.
A monocarboxylic acid vinyl ester having an alkyl group having 1 or 2 carbon atoms can also be used, but if it is used, water resistance and weather resistance are likely to be lowered. The amount of the monocarboxylic acid vinyl ester monomer unit in the fluorocopolymer is 20 to 20.
78 mol%, more preferably 35-55 mol%
Is. When the amount of the monocarboxylic acid vinyl ester monomer unit is less than 20 mol%, the solubility and the coating film strength are poor,
On the other hand, if it exceeds 78 mol%, the weather resistance and curability will be insufficient.

The other essential component, crotonic acid monomer unit, must be contained in the fluorocopolymer in a proportion of 7 to 30 mol%. If the amount of the crotonic acid monomer unit is less than 7 mol%, the water dispersibility decreases, and the storage stability of the aqueous dispersion is poor, while if it exceeds 30 mol%, the water resistance of the coating film decreases. In addition, a large amount of unreacted crotonic acid remains and the polymerization yield decreases, which is industrially disadvantageous. A more preferable amount is 7 to 20 mol%.

Other copolymerizable monomers include methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether and t-.
Butyl vinyl ether, n-pentyl vinyl ether,
Alkyl vinyl ethers such as n-hexyl vinyl ether, n-octyl vinyl ether and 2-ethylhexyl vinyl ether; cycloalkyl vinyl ethers such as cyclopentyl vinyl ether, cyclohexyl vinyl ether and 4-methylcyclohexyl vinyl ether; 2-hydroxyethyl vinyl ether, 3-hydroxy Hydroxy such as propyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 3-hydroxybutyl vinyl ether, 5-hydroxypentyl vinyl ether, 6-hydroxyhexyl vinyl ether, 4-hydroxycyclohexyl vinyl ether. Alkyl vinyl ethers; 4
-Hydroxycyclohexyl vinyl ethers such as hydroxycyclohexyl vinyl ether and 4-hydroxymethyl cyclohexyl vinyl ether; hydroxyalkyl allyl ethers such as ethylene glycol monoallyl ether, diethylene glycol monoallyl ether and 3-hydroxypropyl allyl ether, 2-hydroxyethyl crotonic acid, 2-hydroxypropyl crotonic acid, 3-hydroxypropyl crotonic acid, 3-hydroxybutyl crotonic acid, 4-hydroxybutyl crotonic acid, 5-hydroxypentyl crotonic acid, crotonic acid 6
-Hydroxyalkyl crotonates such as hydroxyhexyl. The resin component in the aqueous resin dispersion for coating material of the present invention can be a curable resin by means such as heat baking curing, in which case, a hydroxyl group-containing unit amount that easily reacts with a curing agent such as an amino resin. A fluorine-containing copolymer containing 3 to 15 mol% of a body unit is preferable, and as the hydroxyl group-containing monomer used in that case, a hydroxyalkyl crotonic acid ester is preferable from the viewpoint of stability during polymerization and curability.

The copolymerization of the above-mentioned monomers is carried out at a polymerization temperature of 30 to 30 in the presence of a radical-generating type polymerization initiator as shown below.
It is preferable to carry out the solution polymerization method under the conditions of about 80 ° C. and a pressure of 3 to 10 kg / cm ² . As the radical-generating polymerization initiator, peroxides such as diisopropyl peroxydicarbonate, tertiary butyl peroxypivalate, trimethylhexanoyl peroxide, benzoyl peroxide, lauroyl peroxide; azobisisobutyronitrile, azo Examples thereof include azo compounds such as bisisovaleronitrile. Polymerization solvents used for solution polymerization include aromatic hydrocarbon compounds such as toluene and xylene; esters such as ethyl acetate and butyl acetate;
Ketones such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; nitrogen-containing compounds such as dimethylformamide, dimethylacetamide and pyridine;
Examples thereof include halogen-containing compounds such as 1,1-trichloroethane and trichloroethylene; alcohols such as butanol and hexanol. The copolymer solution obtained by the above polymerization is preferably heated under reduced pressure and evaporated to dryness to evaporate the unpolymerized monomer and isolate the copolymer.

For the coating composition of the present invention, the fluorine-containing copolymer obtained by the above method is used and reacted with an aliphatic epoxy compound and a basic compound described below, for example, by the following method. The resin component of the aqueous resin dispersion can be obtained. (A) A method of reacting an aliphatic epoxy compound with a copolymer obtained by partially or completely neutralizing the above-mentioned fluorine-containing copolymer (hereinafter referred to as unneutralized copolymer) with a basic compound. (B) A method of reacting an unneutralized copolymer with an aliphatic epoxy compound in the presence of a basic compound. Furthermore, although the reactivity is poor, by reacting the unneutralized copolymer with the aliphatic epoxy compound in the absence of a basic compound,
A method of partially or completely neutralizing the obtained product with a basic compound can also be adopted.

The aliphatic epoxy compound used in the present invention is a compound having no aromatic skeleton in the molecule, having a main skeleton of an aliphatic or alicyclic structure, and having at least one oxirane group. A preferred aliphatic epoxy compound is an aliphatic epoxy compound having two or more oxirane groups in one molecule in terms of excellent curability and weather resistance of a coating film. Typical examples thereof include glycidyl. Ether-type aliphatic epoxy compounds such as ST-3000, YH-300, and PG manufactured by Tohto Kasei Co., Ltd.
-202, PG-207 and the like, and glycidyl ester type aliphatic epoxy compounds such as CY-184 manufactured by Ciba-Geigy Co., Ltd. and YD-1 manufactured by Tohto Kasei Co., Ltd.
There is 71 mag.

The basic compounds include inorganic hydroxides such as potassium hydroxide and sodium hydroxide, ammonia, alkylamines such as triethylamine and diisopropylamine, amino alcohols such as triethanolamine and dimethylethanolamine. And amino alcohols are preferable. In any method, the basic compound is preferably used in an amount of 0.3 to 1.0 equivalent with respect to the amount of the carboxyl group in the fluorocopolymer.

The amount of the aliphatic epoxy compound used is based on the total amount of carboxyl groups in the fluorocopolymer used in each method, that is, the total amount of unneutralized and / or neutralized carboxyl groups. , The oxirane group is 0.0
It is preferably used in an amount of 2 to 0.7 equivalent. More preferably, the amount of the oxirane group is 0.02 to 0.5 equivalent with respect to the total amount of carboxyl groups in the fluorocopolymer. If the amount of the aliphatic epoxy compound is less than 0.02 equivalent, sufficient coating film physical properties cannot be obtained. On the other hand, if the amount exceeds 0.7 equivalent, unreacted aliphatic epoxy resin tends to remain, and after the reaction, The amount of free carboxyl groups is insufficient and water dispersibility tends to be insufficient. The aliphatic epoxy compound easily reacts with the neutralized carboxyl group in the fluorocopolymer.

A specific operation for obtaining a resin component for forming an aqueous resin dispersion in the present invention will be described by taking the case of using the method (b) as an example. The reaction between the fluorinated copolymer and the aliphatic epoxy compound is carried out in the presence of a basic compound in a solvent such as aromatic hydrocarbons, ketones, esters, alcohols, glycol ethers or glycol ether acetates. Below the reaction temperature 50-1
It can be carried out under the conditions of 40 ° C. and a reaction time of 1 to 6 hours. As the reaction solvent, either a single solvent or a mixed solvent can be used, but a solvent containing a hydrophilic alcohol or glycol ether in a proportion of 40% or more of the total solvent is used to obtain a stable aqueous dispersion. It is preferable in terms. Also, when the method (a) is adopted, the fluorine-containing copolymer can be neutralized in a solvent similar to the above solvent, so that the objective can be achieved by almost the same operation as described above. ..

An organic solvent solution of the reaction product of the fluorine-containing copolymer and the aliphatic epoxy compound (hereinafter simply referred to as a reaction solution) obtained by the above method is vigorously stirred, and an appropriate amount of water is dropped therein. Thereby, the aqueous resin dispersion for coating material of the present invention can be obtained. Further, as the fluorine-containing copolymer, a low-temperature baking type using a fluorine-containing copolymer having a hydroxyl group-containing monomer unit such as crotonic acid hydroxyalkyl ester and further using a curing agent such as an amino resin shown below In the case of obtaining the coating composition (1), it is preferable to add an appropriate amount of a curing agent to the above reaction liquid and then drop water in the obtained solution. Preferred curing agents include Cymel 303 and Cymel 30 manufactured by Mitsui Cyanamid Co., Ltd.
7 and the like, butylated melamine resins such as Uban 20SE60 and Uban 20HS manufactured by Mitsui Toatsu Chemicals, and blocked isocyanates such as Coronate 2507 and Coronate 2515 manufactured by Nippon Polyurethane Chemical Co., Ltd., and the like. The amount thereof used may be the amount generally used in the heat-bake type paint.
In addition to the resin component used for forming a coating, components such as an organic solvent, a pigment, a flow regulator, an ultraviolet absorber, a dispersion stabilizer and an antioxidant may be the reaction solution or the aqueous solution, depending on their properties. It may be added to the resin dispersion. Further, as a coating method of the coating material comprising the aqueous resin dispersion of the present invention, known methods such as electrodeposition coating, roll coating, spray coating can be adopted, and as the coating object, aluminum, iron,
In addition to stainless steel, there are mortar and concrete.

[0017]

EXAMPLES The present invention will be described in more detail below with reference to examples. Example 1 a. Synthesis of Fluorine-Containing Copolymer (A-1) In a 2 liter autoclave equipped with a stirrer, 278 g of xylene and 3,5,5-trimethylhexanoyl peroxide [Perloyl 355 manufactured by NOF CORPORATION]
After charging 10 g, 245 g of vinyl caproate (hereinafter referred to as VCp), 45 g of versatic vinyl acid [Shell Chemical Co., Ltd., Veova 9; hereinafter referred to as VV-9] 45 g, crotonic acid (hereinafter referred to as CRA) 64 g and crotonic acid 32 g of 2-hydroxyethyl (hereinafter referred to as HEC) was charged. Next, the atmosphere was replaced with nitrogen and deaeration under reduced pressure was performed, and 230 g of chlorotrifluoroethylene (hereinafter referred to as CTFE) was introduced. The molar ratio of each charged monomer is CTFE / V
Cp / VV-9 / CRA / HEC = 40/35/5/1
It is 5/5. Subsequently, the temperature was gradually raised and polymerization was carried out at 64 ° C. for 10 hours, then unreacted CTFE was removed and the autoclave was opened to obtain a solution of the fluorinated copolymer (A-1). The resulting polymer solution was heated under reduced pressure and dried to obtain a pale yellow solid resin.

The acid value of the obtained fluorocopolymer is 56.
mgKOH / g, hydroxyl value is 16 mgKOH / g,
The polystyrene reduced number average molecular weight was 10,000 and the weight average molecular weight was 39,000. Further, the fluorine content by the alizarin complexon method is 15% by weight,
The glass transition temperature by DSC was 8 ° C. The ratio of each monomer unit in the fluorine-containing copolymer is CTFE / VCp.
/ VV-9 / CRA / HEC = 35/45/6/10 /
4 mol% (CTFE is more
A was determined from the acid value and HEC was determined from the hydroxyl value, and the ratio of VCp and VV-9 was determined from the NMR spectrum).

B. Preparation of Aqueous Resin Dispersion (B-1) In a 1000 cc reactor equipped with a stirrer, 100 g of the fluorinated copolymer (A-1) and 80.6 g of isopropanol (hereinafter referred to as IPA), methyl ethyl ketone (hereinafter referred to as M
20.1 g (referred to as EK) was added and dissolved while stirring.
Next, Toto Kasei Co., Ltd. aliphatic epoxy compound ST-
3000 (epoxy equivalent 230) 6.9 g (0.3 equivalent to the amount of carboxyl group in the fluorine-containing copolymer) was added,
After heating to 70 ° C., 6.2 g of dimethylethanolamine (hereinafter referred to as DMEA) was added. After reacting for 2 hours, it was cooled to 50 ° C., and 15 g of amino resin [CYMELL 303 manufactured by Mitsui Toatsu Chemicals, Inc.] and DMEA2.
7 g was added. While stirring the solution obtained by the above operation, 486 g of ion-exchanged water was added from the dropping funnel at 40
The solution was added dropwise to the solution over minutes to obtain an aqueous resin dispersion having a solid content of 20% by weight. The obtained aqueous resin dispersion was transferred to an evaporator, 240 g of the solvent was distilled off, 10 g of n-butanol was added, and the solid content concentration was adjusted with ion-exchanged water to obtain an aqueous resin having a solid content concentration of 30% by weight. A dispersion (B-1) was obtained. The resulting dispersion had excellent dispersion stability and maintained a good dispersion state for 3 months or more.

Example 2 a. Synthesis of Fluorine-Containing Copolymer (A-2) Same as in Example 1 except that the monomer charging ratio was CTFE / vinyl pivalate (hereinafter referred to as VPV) / CRA = 50/30/20 mol%. Depending on the operation, CTFE /
A fluorinated copolymer (A-2) having a composition of VPV / CRA = 43/41/16 mol% was obtained. This copolymer has an acid value of 77, a number average molecular weight of 6,400 and a weight average molecular weight of 1,450.
0, a fluorine content of 21% and a glass transition temperature of 45 ° C. b. Preparation of Aqueous Resin Dispersion (B-2) An aqueous resin dispersion (B-2) having a solid content of 30% by weight was prepared in the same manner as in Example 1 except that the fluorinated copolymer (A-2) was used. Was prepared. The resulting dispersion had excellent dispersion stability and maintained a good dispersion state for 3 months or more.

Example 3 ST-3000 manufactured by Tohto Kasei Co., Ltd. in the step of making an aqueous dispersion using the fluorocopolymer (A-2).
Example 1 except that the amount was 13.8 g and the IPA was 87.5 g.
The same operation as above was performed to prepare an aqueous resin dispersion (B-3) having a solid content of 30% by weight. The dispersion stability of the obtained dispersion was as good as the dispersion of each of the above examples.

Comparative Example 1 100 g of the fluorinated copolymer (A-2) of Example 2 and 10 g of Cymel 303 were dissolved in 110 g of IPA,
To this solution was added 12 g of DMAE in an amount to completely neutralize the carboxyl groups in the copolymer of A-2. While stirring the obtained solution, 500 g of water was added dropwise to the solution, but the resin component remained dissolved and an aqueous dispersion could not be obtained.

Comparative Example 2 In the step of forming an aqueous dispersion using the fluorine-containing copolymer (A-1) of Example 1, ST manufactured by Tohto Kasei Co., Ltd.
-300; 13.8 g and IPA; 87.5 g except using all, operating in the same manner as in Example 1, solid content 30.
A wt% aqueous resin dispersion (B-4) was obtained.

Reference Example The aqueous resin dispersions obtained in Examples 1 to 3 and Comparative Example 2 were applied on an aluminum plate so that the dry coating film had a thickness of 20 μ, and then in an electric oven. Temperature 180
The film was baked at 30 ° C. for 30 minutes and the performance of the resulting coating film was evaluated. The results are shown in Table 1.

[0025]

[Table 1] Adhesion test; JIS. According to K5400. Boiling water resistance test 1; Adhesion after 1 hour of hot water treatment Boiling water resistance test 2; Adhesion after 3 hours of hot water treatment Salt water resistance test; JIS. According to K5400 (immersion for 1 month at room temperature). Accelerated weathering test; QUV accelerated weathering tester 60 degree gloss retention rate after 1500 hours

[0026]

INDUSTRIAL APPLICABILITY In the present invention, a carboxylic acid vinyl ester or a hydroxyl group-containing monomer used together with a fluoroolefin is used as a constituent monomer of a fluorine-containing copolymer which forms an aqueous resin dispersion without being made into an aqueous solution. The type and amount of the copolymerizable monomer such as the polymer can be selected in a wide range, and according to the present invention, the aqueous fluoropolymer copolymer having the optimum configuration for expressing a wide variety of target coating film physical properties is obtained. It becomes possible to make a resin dispersion. Furthermore, as is clear from the comparison between the above-mentioned Examples and Comparative Examples, the coating film obtained from the aqueous resin dispersion of the present invention does not adopt a method of reacting an aliphatic epoxy compound, but simply contains an appropriate amount of a carboxyl group. Water resistance is superior to that of a coating film formed from an aqueous resin dispersion obtained by neutralizing the fluorine-containing copolymer with an alkali.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location C09D 163/00 PJM 8830-4J (72) Inventor Akito Iida 1 Funami-cho, Minato-ku, Nagoya, Aichi Prefecture No. 1 Toagosei Chemical Industry Co., Ltd. Nagoya Research Institute (72) Inventor Akio Otera No. 1 Funamicho, Minato-ku, Aichi Prefecture Nagoya City Toagosei Chemical Industry Co., Ltd. Nagoya Research Institute

Claims (1)

[Claims] 1. Based on the total amount of all monomer units,
(A) Fluoroolefin monomer unit 15 to 60 mol%, (b) Monocarboxylic acid vinyl ester monomer unit 2
0-78 mol%, (c) crotonic acid monomer unit 7-30
Mol% and (d) 0 to 3 other copolymerizable monomer units
It is composed of 0 mol% of each unit and has a number average molecular weight of 5
Of the reaction product of 000 or more fluorine-containing copolymers and an aliphatic epoxy compound, wherein a part or all of the carboxyl groups in the reaction product are neutralized with a basic compound Aqueous resin dispersion for use.