JPH0257832B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to coating compositions, and more particularly to room temperature curable coating compositions. Paints are applied in a liquid state, lose their fluidity and tackiness when dried, and form a coating film using various film-forming mechanisms. Although there are paints that form coatings through evaporation drying, cooling drying, or oxidative polymerization, coatings formed through polycondensation generally exhibit superior properties, so the demand for coatings with such drying mechanisms is increasing. There is. One method for polycondensation is heating, that is, baking drying, but it requires a heating device and is difficult to carry out on-site, and from an energy-saving perspective, There is a demand for paints that can be cured. Room-temperature curing paints include two-component paints that are used by mixing curing agent components such as isocyanate immediately before use, and paints that react and condense in the presence of moisture, or that cause a catalytic effect in the presence of moisture. There are moisture-curing types that cure, and one-component radiation-polymerizing types that generate radicals and polymerize by irradiation with radiation such as gamma rays, electron beams, and ultraviolet rays. Two-component room-temperature curing paints can form a tough coating film, but their major drawbacks are that the pot life of the curing agent mixture is short and the curing process must be complicated each time it is used. Furthermore, moisture-curing one-component room-temperature curing paints have a small curing reaction and a small curing density, and cannot form a sufficiently tough coating film. Furthermore, radiation-polymerized paints have the disadvantage that they require complicated equipment and are difficult to apply on-site. The object of the present invention is to be able to form a coating film with a strong three-dimensional network structure and excellent properties at room temperature,
An object of the present invention is to provide a one-component room-temperature curing coating composition that can be stored for a long period of time. The coating composition according to the present invention is a coating composition containing a synthetic resin, a curing agent, and an organic solvent, in which the synthetic resin is a fluororesin having a hydroxyl group or an acrylic resin having a hydroxyl group,
The curing agent is a metal alkoxide selected from titanium and silicon, the organic solvent contains 5% by weight or more of alcohol, and the amount of the metal alkoxide is equal to or greater than the alkoxyl of the metal alkoxide per mole of the hydroxyl group of the synthetic resin. The molar equivalent of the group is
A coating composition characterized in that the amount is 0.1 to 10 molar equivalents. In a preferred embodiment of the coating composition according to the present invention, the alkoxyl group of the metal alkoxide has 1 to 12 carbon atoms, more preferably 3 to 8 carbon atoms,
In another preferred embodiment, the alcohol content of the organic solvent is 10% by weight or more, and in another preferred embodiment, the alcohol has 1 carbon number.
-8 alcohols, more preferably 1-4 alcohols. The synthetic resin in the composition of the present invention is a fluororesin having a hydroxyl group or an acrylic resin having a hydroxyl group. Examples of acrylic resins having hydroxyl groups include acrylic resins that are polymers of acrylic acid esters containing hydroxyl group-containing acrylates or methacrylates such as hydroxyethyl acrylate as an essential component. These acrylic resins having hydroxyl groups include 2-hydroxyethyl acrylate and ethyl acrylate.
By radical polymerizing 89.2 moles, the OH value was 50.
It can be manufactured by a method such as obtaining an acrylic resin. Here are a few examples of methods for producing fluororesins having hydroxyl groups. By copolymerizing a fluoroolefin such as tetrafluoroethylene or chlorotrifluoroethylene with vinyl alcohol, hydroxyalkyl vinyl ether, or hydroxyalkyloxyalkyl vinyl ether, a fluorine containing hydroxyl group that can be used as a raw material for the coating composition of the present invention is produced. Resin is obtained. Example 1 CF ₂ = CF ₂ /CH ₂ = CH-CH ₂ OH 35.1 mol 64.9 mol Example 2 CF ₂ = CF ₂ /CH ₂ = CH-O-C ₄ H ₈ OH 51 mol 49 mol Furthermore, polyfunctional fluorine-containing compounds containing the following hydroxyl groups

[Formula] HOCH ₂ (CF ₂ ) _o CH ₂ OH A fluororesin containing a hydroxyl group can also be obtained by co-condensation of an epoxy compound such as glycidol and a polyfunctional fluorine-containing compound. Since the composition of the present invention uses a fluororesin or an acrylic resin, it is possible to obtain a coating film with excellent solvent resistance. The composition of the present invention contains a metal alkoxide selected from titanium and silicon as a hardening agent. It has been known for a long time that these metal alkoxides undergo a crosslinking reaction with the OH groups of polymers.
Furthermore, Ti chelate compounds such as di-1-propoxy, bis(acetylacetone) titanate, and di-n-butoxy bis(triethanolamine) titanate have been conventionally used as crosslinking agents in paints. Alkoxides of these metals react quickly, but
It has been known that paint compositions tend to gel. In the composition of the present invention, the problem of gelation is solved by using a large amount of alcohol as a solvent, as will be explained in detail later. The alkoxyl group of the metal alkoxide in the composition of the present invention has 1 to 12 carbon atoms, preferably 3 to 12 carbon atoms.
It is considered to be 8. Examples of titanium alkoxides include Ti(O·i-C ₃ H ₇ ) ₄ , Ti(O·n-C ₄ H ₉ ) ₄ ,
Examples include Ti[OCH ₂ CH (O ₂ H ₅ ) O ₄ H ₉ ] ₄ and the like. CH ₃ Si as an example of silicone alkoxide
(O·n-O ₄ H ₉ ) ₃ , CH ₃ Si(O·i-C ₃ H ₇ ) ₃ and the like. It is desirable that the valence of the metal forming the alkoxide is high; alkoxides of alkali metals and alkaline earth metals have poor water resistance, while metals such as iron are difficult to form into alkoxides. Metal alkoxides selected from titanium and silicon are more strongly crosslinked with synthetic resins than other metal alkoxides, forming a strong three-dimensional network structure, resulting in improved solvent resistance. It is considered that an excellent coating film can be obtained. The amount of metal alkoxide in the composition of the present invention is such that the molar equivalent of alkoxyl groups in the metal alkoxide is from 0.1 to 10, preferably from 0.5 to 5.0, per mole of hydroxyl groups in the synthetic resin. The content of hydroxyl groups in a synthetic resin is indicated by the hydroxyl value (OH value). The hydroxyl value (OH value) is the number of mg of KOH required to neutralize the acetic acid released by hydrolyzing the acetylated product obtained from 1 g of organic matter. Therefore, if you divide the OH value of the synthetic resin by 56108 mg (molecular weight of KOH),
The number of moles of OH in 1 g of synthetic resin is determined. On the other hand, since the metal alkoxide used generally has a clear structure, the molar equivalent of the alkoxyl group can be easily calculated. For example, 1g of synthetic resin with an OH value of 60 is
It will contain 60/56108=0.00107 moles of OH.
When Ti(OC ₄ H ₉ ) ₄ (molecular weight 340) is used as a curing agent, 1 g of Ti(OC 4 H 9 ) 4 contains 4/340=0.0118 mol of alkoxyl groups. Therefore, Ti has a molar equivalent of alkoxyl groups of 0.1, 0.5, 5.0, and 10 per mole of hydroxyl groups in the synthetic resin.
(OC ₄ H ₉ ) The amount of ₄ is each for 1 g of resin.
They are 0.0907g, 0.4535g, 4.535g, and 9.07g. One of the most important features of the composition of the present invention is that the organic solvent contains 5% by weight or more of alcohol. Metal alkoxides such as Ti and Si easily react with polymers having OH groups at room temperature, but if more than 5% by weight of low molecular weight alcohol is present in the solvent, the metal alkoxides and polymers will react during storage. It has been found that reaction-induced gelation can be suppressed. Moreover, when the alcohol as a solvent evaporates after painting, the metal alkoxide reacts with the polymer having OH groups, forming a strong three-dimensional network structure at room temperature. The alcohol content of the solvent is preferably as high as possible without impairing the solubility of the synthetic resin, and is preferably 10% by weight or more. In addition, it is appropriate that the number of carbon atoms in the alcohol is 1 to 8.
More preferably, it is 1-4. As the organic solvent used together with the alcohol, almost all solvents such as esters, ketones, aromatics, etc. can be freely selected in consideration of coatability and the like. Next, an example will be described. Example 1 Tetrafluoroethylene, isobutyl vinyl ether, and hydroxybutyl vinyl ether at 50:
By copolymerizing at a molar ratio of 40:10, the molecular weight is 40,000,
A fluororesin having hydroxyl groups with an OH value of 60 was obtained. A clear varnish of the coating composition according to the present invention was prepared by dissolving 50 g of this fluororesin and 10 g of tetrabutoxytitanium in an organic solvent consisting of 50 g of butanol and 50 g of xylene. Although this composition was kept at room temperature for 3 months, no thickening or gelation phenomena were observed. This composition was applied to an alodine-treated aluminum plate having a thickness of 0.8 mm using an applicator and left at room temperature for 3 days to form a clear coating film. The results of measuring the properties of the coating film were very good as shown in Table 1. This measurement method was based on JIS K5400.

【table】

[Table] Example 2 Acrylic resin (acrylic polyol, trade name Olester Q-161-45 manufactured by Mitsui Toatsu KK) (OH value 70)
A clear varnish was prepared using the following raw materials: 100g xylene 100g n-butanol 100g tetraisopropoxytitanium 25g.
Even when this varnish was left for three months, there was no change such as thickening or gelation. Apply this varnish on a glass plate with an applicator, leave it at room temperature for 3 days,
When the physical properties of the coating film were measured, the pencil hardness was HB and the xylene rub test was passed 200 times. Examples 3 and 4 Comparative Examples 1 and 2 Clear varnishes were prepared using the same amounts of the fluororesin and organic solvent used in Example 1 and changing only the curing agent as follows. Example 3 Methyltrimethoxysilane 10g Example 4 Tetrabutoxytitanium 15g Comparative Example 1 Tetrabutoxyzirconium 25g Comparative Example 2 Isopropoxyaluminum 10g Each clear varnish did not exhibit any changes such as thickening or gelation over 3 months. The coating was applied to an aluminum plate and a glass plate, and the physical properties of the coating film were measured. The results are shown in Table 2.

【table】

[Table] Comparative example 3 Alkyd resin (trade name Burnock D-120-50)
(OH value 60) 100g xylene 100g methanol 100g tetra(2-ethylhexyloxytitanium) 30g or more clear varnish was prepared from raw materials.
It is the same as Examples 1 to 4 that there is no change during storage. This varnish was applied onto a glass plate with an applicator, left at room temperature for 5 days, and the physical properties of the resulting transparent coating film were measured; it had a pencil hardness of HB and passed 50 xylol rub tests. Comparative Example 4 When a clear varnish was prepared using only xylene (100 g) without including butanol in the solvent in Example 1, the viscosity increased and gelation occurred in a few ten minutes, making it unusable as a paint. Comparative Example 5 In Example 1, when a varnish was prepared and applied using only fluororesin, butanol, and xylene without using tetrabutoxytitanium, the uncured coating had a xylol rub test of 10 times or less and a pencil hardness of 2B or less. Only a membrane was obtained. [Effects of the Invention] As described above, the coating composition of the present invention can be stored for a long period of time without causing changes such as thickening or gelling, and can be coated at room temperature without adding new additives. By drying the metal alkoxide and the OH group-containing polymer, it is possible to form a strong three-dimensional network structure, making it easy to paint. It is possible to obtain a coating film with different characteristics. Therefore, the coating composition according to the present invention has extremely high industrial utility value.

Claims (1)

[Scope of Claims] 1. A coating composition containing a synthetic resin, a curing agent, and an organic solvent, wherein the synthetic resin is a fluororesin having a hydroxyl group or an acrylic resin having a hydroxyl group, and the curing agent is a titanium and silicone resin. The organic solvent contains 5% by weight or more of alcohol, and the amount of the metal alkoxide is such that the molar equivalent of the alkoxyl group of the metal alkoxide is 0.1 per mole of the hydroxyl group of the synthetic resin. A coating composition characterized in that the amount is ~10. 2. The coating composition according to claim 1, wherein the alkoxyl group of the metal alkoxide has 1 to 12 carbon atoms, preferably 3 to 8 carbon atoms. 3 Alcohol content of the organic solvent is 10% by weight
The coating composition according to claim 1, which is the above. 4. The coating composition according to claim 1 or 4, wherein the alcohol is an alcohol having 1 to 8 carbon atoms.