JPS63110265A - Composition for coating - Google Patents

Abstract

PURPOSE:To obtain a fluorine-containing coating composition curable at normal temperature and giving a coating film having excellent weather resistance, by copolymerizing a perfluoroethylene with a specific hydroxyl-containing alkyl vinyl ether. CONSTITUTION:The objective composition containing a hydroxyl-containing fluorine compound copolymer having an intrinsic viscosity of 0.05-2.0dl/g measured in tetrahydrofuran at 30 deg.C in noncrosslinked state can be produced by copolymerizing (A) 40-60mol% tetrafluoroethylene and/or chlorotrifluoroethylene, (B) 5-40mol% hydroxyl-containing alkyl vinyl ether containing >=10mol% alkyl vinyl ether having secondary hydroxyl group and (C) 0-55mol% other monomer copolymerizable with the components A and B.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a composition for a fluorine-containing paint that can be cured at room temperature and provides a coating film with excellent weather resistance.

[Prior Art] As a coating composition that provides a coating film with excellent weather resistance, a coating composition containing a solvent-soluble hydroxyl group-containing fluorine-containing copolymer as an essential component is known. For example, JP-A-57-34
No. 107, JP-A No. 58-138862, etc., describe and compose a solvent-soluble fluorine-containing copolymer and a coating composition containing the fluorine-containing copolymer, which are essential components of a coating composition. ing.

Conventional fluorine-containing copolymers can be cured for about 3 days at room temperature and 10% at 60°C by adding an incyanate curing agent.
Sufficient curing can be achieved in about a minute. In addition, by blending a butylated melamine curing agent, etc., it is possible to
A cured coating film with some degree of solvent resistance can be obtained in about 10 minutes.

However, with conventional fluorine-containing copolymers, the crosslinking reaction occurs very quickly, so when heat curing is carried out, the solvent may not evaporate in time, resulting in so-called wrinkles, which may deteriorate the appearance of the coating film. there were. Furthermore, when a paint is formulated for curing at room temperature, the pot life may be short.

[Problems to be Solved by the Invention] The present invention solves problems such as armpits by appropriately adjusting the reaction rate between hydroxyl groups in a resin containing a hydroxyl group-containing fluorine-containing copolymer as a main component and a curing agent. The purpose of this invention is to provide a paint film with an excellent appearance or to provide a paint composition with a sufficient pot life.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, that is, at least one perhaloolefin selected from tetrafluoroethylene and chlorotrifluoroethylene 40- 60 mol% of hydroxyl group-containing alkyl vinyl ether, 5 to 40 mol% of hydroxyl group-containing alkyl vinyl ether, and 0 to 55 mol% of other comonomers copolymerizable with these as copolymerization components, At least 10 mol% of which is an alkyl vinyl ether teary having a secondary hydroxyl group, which has an intrinsic viscosity of 0.05 to 2 when measured in an uncrosslinked state at 30°C in tetrahydrofuran.
．． The present invention provides a coating composition comprising a hydroxyl group-containing fluorine-containing copolymer having a concentration of 0 dl/g.

In the hydroxyl group-containing fluorine-containing copolymer that is the composition of the present invention, the perhaloolefin is selected from tetrafluoroethylene and chlorotrifluoroethylene, but it is also possible to use both olefins in combination. The copolymerization ratio needs to be 40 to 60 mol%. If it is less than 40 mol%, the weather resistance, which is a characteristic of fluorine paints, will not be sufficient, and if it is more than 60 mol%, it will be difficult to dissolve in general paint solvents.

Examples of the hydroxyl group-containing alkyl vinyl ether include hydroxyethyl vinyl ether, hydroxypropyl vinyl ether, hydroxybutyl vinyl ether, cyclohexane dimetatool monovinyl ether, etc. In the coalescence, it is necessary that at least 10 mol % of these hydroxyl group-containing vinyl ethers have secondary hydroxyl groups.

Various compounds are employed as the vinyl ether having a secondary hydroxyl group. Preferably =CH2=CH general formula 〇(OH2). A compound H represented by CHC)13 is employed. Here, n is an integer of 1 or more, but if n is too large, it is not preferable because the coating becomes soft and the coating becomes sticky or easily stained.

Preferably n is an integer of 1-6. Furthermore, if n is small, the coating film tends to be not hard or brittle, but this is not a problem. Particularly preferably, n is an integer from 1 to 3. It is also possible to use vinyl ethers having secondary hydroxyl groups with different n's. As a vinyl ether having such a secondary hydroxyl group. Examples include 2-hydroxypropyl vinyl ether, 3-hydroxybutyl vinyl ether, 4-hydroxypentyl vinyl ether, and the like.

The copolymerization ratio of the hydroxyl group-containing alkyl vinyl ether is 5
-40 mol%, 8-30 mol%
A range of is preferred. If it is less than 5 mol %, a sufficient crosslinking density cannot be obtained, and the physical properties of the coating film, such as solvent resistance and surface hardness, deteriorate.

In addition, if the content exceeds 40 mol%, the pot life of the paint will be short.
Problems such as thickening during storage occur, and the water resistance of the coating film also decreases. In addition, the proportion of secondary hydroxyl group-containing vinyl ether in the hydroxyl group-containing vinyl ether is 1
If it is less than 0 mol %, the curing rate as intended by the present invention cannot be controlled sufficiently, so it is preferable that 50 mol % or more is secondary.

The hydroxyl group-containing fluorine-containing copolymer in the present invention includes the above-mentioned 2
In addition to the components, other vinyl monomers copolymerizable with these may be copolymerized.

Such vinyl monomers are not subject to any restrictions as long as they copolymerize with perhaloolefins and hydroxyl group-containing alkyl vinyl ether monomers, but vinyl ether monomers, particularly ethyl vinyl ether, n-butyl vinyl ether, cyclohexyl Vinyl ether etc. are preferably employed. Furthermore, these monomers may be partially or completely fluorinated within the molecule. Moreover, these monomers can also have functional groups other than hydroxyl groups, such as epoxy groups and carboxyl groups.

The fluorine-containing copolymer having secondary hydroxyl groups, which is an essential component of the composition of the present invention, is mixed with the fluorine-containing copolymer having only primary hydroxyl groups when preparing the coating composition. In this case, the curing speed of the coating film can be appropriately set by adjusting the mixing ratio of both types.

The above copolymers can be produced by carrying out a copolymerization reaction by causing a polymerization initiator or a polymerization initiation source such as ionizing radiation to act on a monomer mixture of a predetermined ratio in the presence or absence of a polymerization medium. Manufacturable.

Here, as the polymerization initiator, water-soluble or oil-soluble ones can be used as appropriate depending on the polymerization type or polymerization medium. Specifically, the water-soluble initiator is
A redox initiator consisting of a persulfate such as potassium persulfate, hydrogen peroxide, or a combination of these with a reducing agent such as sodium bisulfite or sodium periosulfate, as well as small amounts of iron, ferrous salts, or silver nitrate. An inorganic initiator such as a system in which these compounds coexist, or a dibasic acid oxide such as disuccinic acid peroxide, diglutaric acid peroxide, monosuccinic acid peroxide, an organic initiator such as azobisisobutyramidine dihydrochloride, etc. As the oil-soluble initiator, t-butyl peroxyisobutyrate, t
Examples include peroxy ester type peroxides such as -butyl peroxyacetate, dialkyl peroxydicarbonates such as diisopropyl peroxydicarbonate, benzoyl peroxide, and azobisisobutyronitrile. The amount of the polymerization initiator used can be changed as appropriate depending on the type, copolymerization reaction conditions, etc., but it is usually 0.005 to 5% based on the total amount of monomers to be copolymerized.
Weight %, especially about 0.05 to 0.5 weight % is adopted.

In the above copolymerization reaction, the reaction format is not particularly limited, and bulk polymerization, suspension polymerization, emulsion polymerization, solution polymerization, etc. can be adopted, but the stability of the polymerization reaction operation and the separation of the produced copolymer can be improved. For ease of use, emulsion polymerization in an aqueous medium or alcohols such as t-butanol, esters,
Solution polymerization using a saturated halogenated hydrocarbon containing one or more fluorine atoms, an aromatic hydrocarbon such as xylene, etc. as a solvent is preferably employed.

In addition, when carrying out the copolymerization reaction in an aqueous medium, J
1! By adding a basic buffer, the pH value of the solution during polymerization is 4,
Preferably, it should not be less than 6.

Addition of a basic substance is also effective in solution polymerization. Moreover, it goes without saying that the method of the present invention can be carried out by a quarter-section, semi-continuous, or continuous operation.

In this copolymerization reaction, the copolymerization reaction temperature is -30°
The optimum value can be appropriately selected within the range of C to +150 °C depending on the polymerization initiation source, the type of polymerization medium, etc., but when the copolymerization reaction is carried out in an aqueous medium, the temperature is preferably 0 °C to +100 °C. A temperature of about 10°C to 90°C may be adopted. In addition, the reaction pressure can be selected as appropriate, but is usually 1 to 1
It is desirable to adopt 00Kg/cm2, especially about 2 to 50Kg/cm2.

In order to suppress the intrinsic viscosity of the resulting copolymer within the above range, it is preferable to use a reaction medium with a relatively large chain transfer constant or to carry out the copolymerization reaction in the presence of an appropriate chain transfer agent.

The composition of the present invention preferably contains a curing agent or is mixed with a curing agent to be cured. Such curing agents include:
It is important to use a polyfunctional compound that is reactive with the hydroxyl group contained in the copolymer as a curing site. Examples of such curing agents include heat-curable ones such as melamine curing agents, urea resin curing agents, polybasic acid curing agents, and block polyvalent incyanates, which are used in ordinary thermosetting acrylic paints. . Examples of the melamine curing agent include butylated melamine, methylated melamine, epoxy-modified melamine, and 0 to B depending on the application.
Various degrees of modification can be used, and the degree of self-condensation can also be selected as appropriate. Examples of the urea resin include methylated urea, butylated urea, and the like. Further, as the polybasic acid curing agent, long-chain aliphatic dicarboxylic acids, aromatic polycarboxylic acids, or their anhydrides are useful. As the block polyvalent incyanates, block compounds of the polyvalent incyanates described below are suitable. When using melamine or urea hardeners, curing can be accelerated by adding an acidic catalyst.

As the curing agent in the present invention, it is also possible to use a room temperature curing type such as polyvalent incyanates. Examples of polyvalent incyanates include non-yellowing diisocyanates such as hexamethylene diisocyanate and inphorone diisocyanate. and adducts thereof are particularly useful. When curing at room temperature using isocyanates,
It is also possible to accelerate curing by adding a curing catalyst such as dibutyltin dilaurate.

It is preferable that the composition of the present invention contains a solvent for reasons such as ease of coating work. As such a solvent, various solvents can be used, including aromatic hydrocarbons such as xylene and toluene. In addition to alcohols such as , n-butanol, esters such as butyl acetate, ketones such as methyl isobutyl ketone, and glycol ethers such as ethyl cellosolve, various thinners from Ichihara can also be used. It is also possible to use them by mixing them in different proportions. It is desirable to select such an organic solvent as appropriate, taking into account the condition of the object to be coated, the evaporation rate, the working environment, etc.

When preparing the coating composition of the present invention, a ball mill,
Various equipment commonly used for making paints can be used, such as a paint shaker, sand mill, jet mill, Miki roll, and kneader. At this time, pigments, dispersion stabilizers, viscosity modifiers, leveling agents, gelling inhibitors, ultraviolet absorbers, etc. can also be added.

When the coating composition of the present invention is used as a heat-curable so-called baking coating, a curing agent such as melamine, urea resin, polybasic acid or its anhydride, block polyvalent incyanate, etc. is also added at the same time during the above formulation. mixed, −
Used as a liquid paint.

On the other hand, when used as a cold-curable coating material using non-blocking polyvalent incyanates, etc., the curing agent components are prepared separately and a two-component coating material is prepared.

[Example] Examples 1 to 4 and Comparative Examples 1 to 3 Using the fluorine-containing copolymers A-1 to A-5 shown in Table 1, the fluorine-containing copolymers A-1 to A-5 shown in Table 2 (however, the numbers in the table Paint compositions B-1 to B-7 shown in (parts by weight) were prepared.

Next, using an applicator, apply the L group acid to an aluminum plate that has been treated with alodine to a dry film thickness of 20 to 30μ, and heat it at 140°C for 1° to coat it. A membrane was created.

(1) The solvent resistance and surface properties of the resulting coating films were evaluated by a pheasant roll rubbing test and visual inspection, respectively, and the results are shown in Table 3.

1) Wealth Table 3 Pheasant roll rubbing test O: 300 times or more, Q
: 200,300 times, X: 200 times”Surface texture
O: No armpits, craters, etc., Δ: Fairly low Examples 5 to 7 and Comparative Examples 4 to 5 Coating compositions B-8 to B-12 shown in the table (the proportions in the table are parts by weight) were prepared, and the gelation time at room temperature was measured.

Table 4 Hardening agent: Incyanate hardening agent (product name “Coronet”)
Catalyst Nijibutyltin dilaurate Solvent: Xylene [Effects of the invention] The composition of the present invention is a solvent-soluble hydroxyl group-containing fluorine-containing copolymer-containing coating composition that can be used for crosslinking reactions. It has the effect of slowing down the speed appropriately, providing a coating film that satisfies both excellent surface properties and sufficient crosslinking density in the case of heat curing, and extending the pot life in the case of room temperature curing.

Claims (1)

[Scope of Claims] 1) 40 to 60 mol% of at least one perhaloolefin selected from tetrafluoroethylene and chlorotrifluoroethylene, 5 to 40 mol% of a hydroxyl group-containing alkyl vinyl ether, and others copolymerizable with these. A copolymer containing 0 to 55 mol% of the monomers as a copolymerization component, in which at least 10 mol% of the hydroxyl group-containing alkyl vinyl ether is an alkyl vinyl ether having a secondary hydroxyl group, and is in an uncrosslinked state. The intrinsic viscosity measured at 30°C in tetrahydrofuran is 0.05 to 2.0 d.
A coating composition comprising a hydroxyl group-containing fluorine copolymer having a hydroxyl group content of 1/g. 2) The alkyl vinyl ether having a secondary hydroxyl group is
The composition according to claim 1, which has a structure represented by the following formula. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, n = 1 to 3
integer)