JP2861023B2 - Fluororesin composition for aqueous coating - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel and useful fluororesin composition for aqueous coating. More specifically, the present invention provides a carboxyl group-containing fluororesin having a relatively high acid value,
By mixing with a fluororesin having a relatively low acid value and dispersing it in an aqueous medium, it is possible to form a coating film having excellent weather resistance, and it is extremely excellent in dispersion stability. The present invention relates to a highly practical fluororesin composition for aqueous coating.

(Prior Art) Conventionally, various synthetic resin paints have been developed for the purpose of surface protection and appearance. Fluororesin paints have recently received particular attention as having long-term weather resistance. The fluororesin paint is composed of a fluororesin, a pigment, various additives, and an organic solvent. In the configuration of this conventional fluororesin,
Since organic solvents are used as the medium, the solvent evaporates in the working atmosphere, deteriorating the working environment, impairing the safety of humans such as solvent poisoning of workers, polluting the atmosphere, and being a flammable solvent. There was always a risk of fire and explosion.

In order to solve such a problem, a method of synthesizing a fluororesin by emulsion polymerization using an emulsifier is known (JP-A-55-25412). However, in this method, it is difficult to use a large amount of a highly polar monomer in order to carry out the emulsion polymerization reaction in water, and the resulting emulsion has a problem in film-forming properties, and also has a water-resistant property due to the remaining emulsifier. sex,
It has the drawback that it is inferior in corrosion resistance, adhesion and the like, and also has a problem in storage stability.

As a means for solving such disadvantages of the fluororesin emulsion, a method of dispersing the fluororesin using a water-soluble resin such as a water-soluble acrylic resin, a water-soluble alkyd resin, or a water-soluble maleated oil has been proposed (particularly). 62-1587
No. 66).

(Problems to be Solved by the Invention) However, according to this method, the compatibility between the fluororesin and the various water-soluble resins is not sufficient, and there is a problem that the resin film becomes turbid and the coating film has poor gloss. There is also a problem that the excellent characteristics of the fluororesin are lost depending on the amount of the resin used.

Thus, regarding the aqueous conversion of the fluororesin, various
At present, although it has been examined and proposed, it has not yet been fully satisfactory.

However, the present inventors have conducted intensive studies in order to solve the various problems in the above-described prior art, and as a result, a resin having a relatively high acid value, that is, a resin having an acid value not less than a predetermined value, A fluororesin having a group and a piece, basically, a fluororesin having a relatively low acid value or no acid value are mixed at a predetermined ratio, and this is mixed with an aqueous medium. In addition, by dispersing, in order to find that a carboxyl group-containing fluororesin excellent in various performances can be obtained efficiently, here,
The present invention has been completed.

Therefore, the object of the present invention is to provide, among other things, excellent water dispersibility and storage stability, good chroma and transparency, and excellent adhesion to a substrate. In order to provide an extremely practical aqueous coating fluororesin composition, which can provide a film that does not change the properties of the coating film such as water resistance and weather resistance, as well as the solvent-based fluororesin. is there.

(Means for Solving the Problems) In order to achieve the above object, a fluororesin composition for aqueous coating of the present invention comprises a carboxyl group-containing fluororesin having an acid value (solid content) of 5 or more, and an acid value ( And a fluororesin having a solid content of 2 or less at a solid content ratio of 3:97 to 70:30 and dispersed in an aqueous medium.

The amount of the carboxyl group-containing fluororesin having an acid value (solid content) of 5 or more is preferably in the range of 3 to 70% by weight,
Further, a range of 10 to 50% by weight is particularly preferred. If the amount does not reach 3% by weight, the dispersion stability of the fluororesin composition of the present invention in an aqueous medium becomes poor, which is not preferable.
Further, even if this amount exceeds 70%, no improvement in the dispersing effect due to it is recognized.

The total resin acid value (solid content) is preferably from 1 to 80, particularly preferably from 5 to 40. If the acid value is less than 1, the dispersibility and stability will be poor, and if it exceeds 80, the water resistance and alkali resistance of the resulting film will decrease. The value of the total resin acid value (solid content) is, of course, adjusted so as to be derived from a carboxyl group-containing fluororesin having an acid value (solid content) of 5 or more.

As the carboxyl group-containing fluororesin having an acid value (solid content) of 5 or more used in the present invention, for example, a carboxyl group-containing vinyl monomer and a modified fluororesin with another vinyl monomer can be used. This vinyl-modified fluororesin is, for example, (a) a hydroxyl-containing fluororesin 90-
99.9% by weight and an acid anhydride having a reactive unsaturated double bond
Polymerization of 40 to 95 parts by weight of a vinyl group-containing reaction product obtained by reacting 0.1 to 10% by weight with (b) 5 to 60 parts by weight of a polymerizable vinyl monomer containing a carboxyl group-containing vinyl monomer It can be produced by performing a copolymerization reaction in the presence of an agent.

As the hydroxyl group-containing fluororesin used in the above-mentioned production method, any conventionally known ones can be used.For example, a fluoroolefin and a hydroxyl group-containing monomer or a monomer having a group convertible to a hydroxyl group by hydrolysis or the like can be used. What is obtained as an essential component by further copolymerizing another vinyl monomer is used.

As the fluoroolefin, vinyl fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, bromotrifluoroethylene, pentafluoropropylene, hexafluoropropylene, or trifluoromethyl trifluorovinyl ether, pentafluoro Typical examples thereof include perfluoroalkyl perfluorovinyl ether such as ethyl trifluorovinyl ether or heptafluoropropyl trifluorovinyl ether, and particularly, tetrafluoroethylene, vinylidene fluoride, chlorotrifluoroethylene, or hexafluoroethylene. The use of propylene is preferred. These fluoroolefin monomers may be used alone or in combination of two or more.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 3-hydroxybutyl vinyl ether, 2-hydroxy-2-methylpropyl vinyl ether, and 5-hydroxypentyl. Vinyl ether, 6
Vinyl ethers containing a hydroxyl group such as -hydroxyhexyl vinyl ether are preferably used.

Monomers having a group that can be converted to a hydroxyl group by hydrolysis or the like include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinylmethyldiethoxysilane, vinyltris (β-methoxyethoxy) silane, and allyltrimethoxysilane , Trimethoxysilylethyl vinyl ether, methyldimethoxysilylethylvinylether, trimethoxysilylpropylvinylether, triethoxysilylpropylvinylether, methyldimethoxysilylpropylvinylether, γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxy Monomers containing a hydrolyzable silyl group such as propyltriethoxysilane and γ- (meth) acryloyloxypropylmethyldimethoxysilane It can be given over.

Other monomers include alkyl vinyl ethers or substituted alkyl vinyl ethers, cycloalkyl vinyl ethers, carboxylic acid vinyl esters,
Representative examples include α-olefins, various halogenated olefins other than fluoroolefins, aromatic vinyl compounds, methacrylates, acrylates, and the like.

Further, as a preferable example of the hydroxyl group-containing fluororesin, for example, "Fluonate K-700" manufactured by Dainippon Ink and Chemicals, Inc. can be mentioned.

As the acid anhydride having a reactive unsaturated double bond, any acid anhydride having a reactive unsaturated double bond can be used, but acrylic acid anhydride and / or methacrylic anhydride are particularly preferably used.

The use ratio of the hydroxyl group-containing fluororesin and the acid anhydride having a reactive unsaturated double bond is 90:10 to 99.9: 0 by weight.
A range of 1 is preferred, and a range of 95: 5 to 99.8: 0.2 is particularly preferred.

The use ratio of the acid anhydride having a reactive unsaturated double bond is
If the amount does not reach 0.1% by weight, the dispersion stability of the carboxyl group-containing modified polymer in the aqueous medium tends to be inferior, which is not preferable. If the proportion of the acid anhydride having a reactive unsaturated double bond exceeds 10% by weight, the carboxyl group-modified polymer tends to have a high molecular weight during polymerization and tends to gel, which is not preferable.

As an acid anhydride having this reactive unsaturated double bond,
For example, when reacted using methacrylic anhydride, A reactant containing a vinyl group represented by the formula is obtained.

The polymerizable vinyl monomer used for the copolymerization reaction with the vinyl group-containing reactant is a polymerizable vinyl monomer containing a carboxyl group-containing vinyl monomer. The content of the carboxyl group-containing vinyl monomer is not particularly limited, but is preferably at least about 5% by weight. If the content of the carboxyl group-containing vinyl monomer is too small, the dispersion stability of the resin in the aqueous medium, the adhesion of the coated film to metal, and the solvent resistance tend to deteriorate, which is not preferable.

Examples of the carboxyl group-containing vinyl monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, and fumaric acid.

Other vinyl monomers include, for example, styrene monomers such as styrene, vinyl toluene, 2-methylstyrene, t-butylstyrene, chlorostyrene; methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, Acrylates such as isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, decyl acrylate, dodecyl acrylate; methyl methacrylate; Propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, n-hexyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, decyl methacrylate, dode methacrylate Methacrylic esters such as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate and hydroxypropyl methacrylate; N-methylol (meth) acrylamide, N-butoxymethyl (meth) ) N-substituted (meth) acrylic monomers such as acrylamide. Also, vinyl acetate, vinyl carboxylate such as vinyl propionate, vinyl butyrate, vinyl caproate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl benzoate, or methyl, ethyl, n-propyl, isopropyl, n Vinyl ethers having an alkyl group such as -butyl, isobutyl, t-butyl, isoamyl, n-hexyl, n-octyl, 2-ethylhexyl or a substituent-containing alkyl group such as hydroxyethyl, hydroxybutyl and the like.

As described above, the vinyl-modified fluororesin is produced by solution-polymerizing the vinyl-containing reactant and the polymerizable vinyl monomer.

The usage ratio of the vinyl group-containing reactant and the polymerizable vinyl monomer is preferably in the range of 40:60 to 95: 5 by weight. If the use ratio of the vinyl group-containing reactant is less than 40% by weight, it is not preferable because various characteristics of the fluorocopolymer cannot be utilized. If the proportion of the vinyl group-containing reactant exceeds 95% by weight, the carboxyl group-containing modified polymer tends to be less susceptible to self-emulsification, which is not preferred.

Examples of the polymerization initiator used for the copolymerization reaction between the vinyl group-containing reactant and the polymerizable vinyl monomer include a common radical polymerization initiator such as azobisisobutyronitrile and benzoyl peroxide.

Examples of the organic solvent used in the copolymerization reaction include alcohols such as methanol, ethanol, propanol and butanol; ether alcohols such as methyl cellosolve, ethyl cellosolve, propyl cellosolve, butyl cellosolve, methyl carbitol and ethyl carbitol;
Examples include ketones such as methyl ethyl ketone and diisobutyl ketone, and aromatic hydrocarbons such as toluene.

The acid value of the resin solid content of the copolymer of the vinyl group-containing fluororesin and the polymerizable vinyl monomer is in the range of 5-150, particularly 10-8.
It is preferred that the value be in the range of 0. When the resin solid content acid value is 5 or less, dispersibility becomes poor, and when it is 150 or more, water resistance tends to decrease, which is not preferable.

As the fluororesin having an acid value (solid content) of 2 or less used in the present invention, for example, Fluoronate K-70
0 (manufactured by Dainippon Ink and Chemicals, Inc., for clear), Fluoronate K-701 (same as for colored enamel), Fluorate K-600 (same as lacquer type fluororesin hard type), Fluorate K-601 (same as above) Lacquer type fluororesin soft type) and the like can be used.

The fluororesin composition for aqueous coating of the present invention comprises (a) a carboxyl group-containing fluororesin having an acid value (solid content) of 5 or more, and (b) a fluororesin having an acid value (solid content) of 2 or less. , At a solid content ratio of 3:97 to 70:30, neutralizing at least a part of the carboxyl groups contained in the mixture with a basic compound, and then finely dispersing the mixture in water. Manufactured by

The basic compound used here is preferably ammonia or a volatile amine. Inorganic bases are not preferable because they tend to remain in the coating film and deteriorate water resistance.

Examples of the amine include alkylamines such as trimethylamine, triethylamine, and butylamine;
Alcohol amines such as dimethylaminoethanol, diethanolamine and aminomethylpropanol; morpholine and the like can be used. Further, polyamines such as ethylenediamine and diethylenetriamine can also be used.

In the present invention, the aqueous medium means water alone having at least 10% by weight of water or a mixture with a hydrophilic organic solvent. Examples of the hydrophilic organic solvent include alkyl alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol and isobutanol; methyl cellosolve, ethyl cellosolve, propyl cellosolve, butyl cellosolve, Glycol ethers such as hexyl cellosolve, methyl carbitol and ethyl carbitol; glycol ether esters such as methyl cellosolve acetate and ethyl cellosolve acetate; and dioxane, dimethylformamide, diacetone alcohol, tetrahydrofuran and the like can be used.

The fluororesin composition for aqueous coating of the present invention has very good dispersion stability. When it is necessary to further reduce the contained organic solvent, a solvent having a low boiling point such as acetone or methyl ethyl ketone, or a solvent azeotropic with water such as butanol or butyl cellosolve is used as a reaction solvent or a dispersing agent, and is used in an aqueous medium. By distilling the mixture at normal pressure or reduced pressure after dispersion, a fluororesin composition for aqueous coating containing a low organic solvent can be obtained stably and easily.

If necessary, a solvent, a surfactant and an antifoaming agent for improving coating properties can be added to the fluororesin composition for aqueous coating of the present invention. It is also possible to add an amino resin, a phenol resin, a blocked isocyanate or the like as a curing agent to the fluororesin composition for aqueous coating of the present invention.

The fluororesin composition for aqueous coating of the present invention can be used as a clear coating agent as it is, but can also be used as a paint containing a pigment or the like. In forming the coating, various devices used for forming a coating such as a ball mill, a paint shaker, a sand mill, a jet mill, a three-roll mill and a kneader can be used. At this time, pigment, dispersion stabilizer, viscosity modifier, leveling agent, anti-gelling agent,
An ultraviolet absorber or the like can be added.

As a coating method, a conventionally known method, that is, roll coating, electrodeposition coating, flow coating, spray coating, brush coating, or the like is used.

The fluororesin composition for aqueous coating of the present invention can be widely used at room temperature, from forced drying to baking using a curing agent such as melamine and blocked isocyanate.
It is preferable to use the baking conditions at 100 to 250 ° C. for 10 seconds to 30 minutes.

The fluororesin composition for aqueous coating of the present invention is excellent in workability, and has excellent surface hardness, gloss, and flexibility, and is mild to a coating film excellent in solvent resistance, stain resistance, and even weather resistance. It can be given under a variety of conditions and is useful not only as a baking paint for color steel plates, color aluminum plates, aluminum sashes and the like, but also as a normally dry paint that can be applied on site. The base material is iron, aluminum,
Steel or alloys thereof, for example, not only metals such as stainless steel and brass, but also inorganic materials such as glass, cement and concrete, FRP, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, nylon, acrylic, polyester, ethylene -It is also useful for coating plastics such as polyvinyl alcohol copolymer, vinyl chloride, vinylidene chloride, and polycarbonate, and organic materials such as wood, and is particularly useful as a top coat for objects having another base coat. These also include aluminum pool, exterior colored glass,
It is also useful in certain applications such as cement wallets.

(Examples) Hereinafter, the present invention will be described in more detail with reference to Examples, but it goes without saying that the present invention is not limited to the descriptions of these Examples. In the examples, “part” or “%”
Indicates “parts by weight” or “% by weight”, respectively.

Synthesis Example 1 First Step: Introduction of Vinyl Group into Fluororesin Fluonate K-700 200.0 parts Methacrylic anhydride 4.0 parts Triethylamine 0.5 parts (In the above composition, Fluonate K-700 is Dainippon Ink Chemical A hydroxyl group-containing fluororesin manufactured by Kogyo Co., Ltd., having a non-volatile content of 50% and a solid content hydroxyl value of 48.) A 4-neck flask purged with nitrogen gas is charged and heated to 80 ° C. while stirring the contents. At the same temperature, 2
By stirring for a time, a vinyl group-containing reactant was obtained.

Second step: Synthesis of vinyl-modified fluororesin The above vinyl group-containing fluororesin ... 204.5 parts Isopropanol ... 117 parts Methacrylic acid ... 7.0 parts n-butyl methacrylate ... 32 parts Perbutyl-O ... 2 parts (the above composition In the above, perbutyl-O is t-butyl peroxy-2-ethylhexanate (radical polymerization initiator) manufactured by NOF Corporation.),, And, and after uniformly mixed, Charge 100 parts into a four-necked flask purged with nitrogen gas.
The mixture was heated to 0 ° C., the remaining mixture was gradually added dropwise over 4 hours while maintaining the temperature, and the mixture was further stirred at the same temperature for 4 hours to obtain a vinyl-modified fluororesin.

 The properties of this composite were measured and are shown in Table 1.

Synthesis Example 2 20 parts of methacrylic acid and 24 parts of n-butyl methacrylate
And a vinyl-modified fluororesin was obtained in the same manner as in Synthesis Example 1 except that 20 parts of methyl methacrylate was newly added. The properties of this composite were measured and are shown in Table 1.

Synthesis Example 3 A vinyl-modified fluororesin was obtained in the same manner as in Example 1, except that 8 parts of methacrylic anhydride, 88 parts of methacrylic acid, and 4 parts of n-butyl methacrylate were used. The properties of this composite were measured and are shown in Table 1.

Example 1 75 parts of vinyl-modified fluororesin of Synthesis Example 1 (solid content: 30 parts)
And Fluorate K-700 (Dainippon Ink Chemical Industry Co., Ltd.)
140 parts (solid content: 70 parts) of a hydroxyl group-containing fluororesin was charged into a four-necked flask purged with nitrogen gas, and the contents were heated to 60 ° C. while stirring, and triethylamine was added to the flask at the same temperature.
After adding 2 parts and uniformly mixing, 150 parts of ion-exchanged water was added dropwise over 30 minutes to obtain an aqueous dispersion. The obtained dispersion was further concentrated under reduced pressure to obtain an aqueous coating fluororesin composition having the properties shown in Table 2.

Example 2 62.5 parts of the vinyl-modified fluororesin of Synthesis Example 2 (solid content: 25
Parts) and 150 parts (solid content: 75 parts) of Fluorate K-600 (manufactured by Dainippon Ink and Chemicals, Inc., lacquer type fluororesin hard type), and 3.8 parts of triethylamine was added. A dispersion was obtained. The obtained dispersion was further concentrated under reduced pressure to obtain an aqueous coating fluororesin composition having the properties shown in Table 2.

Example 3 125 parts of the vinyl-modified fluororesin of Synthesis Example 2 (solid content: 50
Parts) and 100 parts of fluorate K-600 (a lacquer type fluororesin hard type, manufactured by Dainippon Ink and Chemicals, Inc.) (solids content: 50 parts), and 7.5 parts of triethylamine was added. A dispersion was obtained. The obtained dispersion was further concentrated under reduced pressure to obtain an aqueous coating fluororesin composition having the properties shown in Table 2.

Comparative Example 1 5 parts of vinyl-modified fluororesin of Synthesis Example 1 (2 parts of solid content)
And Fluorate K-700 (Dainippon Ink Chemical Industry Co., Ltd.)
An aqueous dispersion was obtained in the same manner as in Example 1 by using 196 parts (manufactured and manufactured, hydroxyl group-containing fluororesin) (solid content: 95 parts) and adding 0.4 part of triethylamine. The obtained dispersion was further concentrated under reduced pressure to obtain an aqueous coating fluororesin composition having the properties shown in Table 2.

Comparative Example 2 125 parts of the vinyl-modified fluororesin of Synthesis Example 3 (solid content 50
Parts) and 100 parts of fluorate K-600 (manufactured by Dainippon Ink and Chemicals, Inc., lacquer type fluororesin hard type) (50 parts of solid content), and 20 parts of triethylamine was added.
An aqueous dispersion was obtained in the same manner as in Example 1. The obtained dispersion was further concentrated under reduced pressure to obtain an aqueous coating fluororesin composition having the properties shown in Table 2.

As is clear from Table 2, Examples 1 to 3 all had good dispersibility and stability.

Comparative Example 1 was a case where the amount of the carboxyl group-containing fluororesin used was small and the acid value of the total resin solid content was low, but the dispersion state and stability were poor.

Comparative Example 2 is a case where the acid value of the total resin solid content is high. In this case, the dispersion state and the stability are good, but as shown in Table 3, the alkali resistance in the state of the coating film,
The water resistance was poor and the accelerated weather resistance was poor.

Test Example The coating properties of the compositions obtained in Examples 2 and 3 and Comparative Example 2 were measured, and the results are shown in Table 3. In addition, the coating film performance using the solvent-based fluororesin fluorate K-600 (product of Dainippon Ink and Chemicals, Inc.) is shown as Comparative Example 3.

Test conditions Pigment: R-TiO ₂ [CR-93 Ishihara Sangyo Co., Ltd.] PWC 35% Base material: Zinc phosphate treated steel sheet Bonde # 144 treated dull 0.6
mm thickness Painting: Air spray (Ford Cup No.4RT13 ~ 14sec dull steel plate) Painting: Air spray (In Table 3, the performance evaluation was ◎ (no abnormality), ○
(Good), Δ (poor), × (poor). The measurement conditions for the accelerated weathering resistance are as follows.

Test equipment: Dew panel light control weather meter (manufactured by Suga Test Instruments Co., Ltd.) Conditions: UV irradiation 70 ° C. × 8Hr, Wet 50 ° C. × 4Hr Pigment used: Taipaque CR-93, PWC 35%) Thus, it was found that the coating film performance of the fluororesin composition for aqueous coating of the present invention was equivalent to that of the solvent fluororesin (Fluonate K-600) and was excellent.

(Effects of the Invention) As is clear from the above description, the fluororesin composition for aqueous coating according to the present invention is particularly excellent in water dispersibility, storage stability, etc., The transparency is also good, the adhesion to the substrate is also excellent, and the coating properties such as water resistance and weather resistance also bring about a coating that is almost the same as the solvent-based fluororesin. This has a particularly remarkable effect.

Due to the achievement of such excellent effects, the fluororesin composition for aqueous coating according to the present invention is particularly suitable as a paint for exterior use.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C09D 127/12 C08L 27/12

Claims (4)

(57) [Claims] 1. A solid content ratio of (a) a carboxyl group-containing fluororesin having an acid value (solid content) of 5 or more and (b) a fluororesin having an acid value (solid content) of 2 or less, 3: 97-70: 3
A fluorine resin composition for aqueous coating, which is mixed at a ratio of 0 and dispersed in an aqueous medium. 2. A solid content ratio of (a) a carboxyl group-containing fluororesin having an acid value (solid content) of 5 or more and (b) a fluororesin having an acid value (solid content) of 2 or less, 3: 97-70: 3
Mixing at a ratio of 0, at least a part of the carboxyl groups contained in the mixture is neutralized with a basic compound, and then the mixture is finely dispersed in water,
A fluororesin composition for aqueous coating. 3. An acid value (solid content) of all the resins is from 1 to 80.
The fluororesin composition for aqueous coating according to claim 1 or 2. 4. The fluororesin composition for aqueous coating according to any one of claims 1 to 3, wherein the composition is used as an exterior coating.