JPH09310041A - Composition for fluororesin coating material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition comprising a fluorine-containing copolymer containing hydroxyl group and having a specific molecular weight and a polyester polol having a specific molecular weight, excellent in processability, impact resistance, flexibility and solvent resistance and useful as a coating material for precoat metal, etc. SOLUTION: This composition consists essentially of (A) a fluorine-containing copolymer having 1000-10000 number-average molecular weight and hydroxyl group and (B) a polyester polyol having <=2000 number-average molecular weight and contains the components A and B so that a weight ratio of the components A/B becomes (95/5) to (50/50). Furthermore, the component A comprises (i) preferably 30-60mol% fluoroolefin monomer, (ii) preferably 3-30mol% hydroxy group-containing α,β-ethylenically unsaturated monomer and (iii) preferably 10-67mol% other radically polymerizable monomer. The component B is preferably a compound containing a cycloalkyl group.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a composition for a fluororesin coating which is excellent in processability, impact resistance, flexibility and solvent resistance.

[0002]

2. Description of the Related Art Conventionally, as a fluororesin paint having excellent workability and impact resistance, a paint composition (hereinafter referred to as PVdF type paint) in which an acrylic resin is blended with a polyvinylidene fluoride fluororesin has been used. However, this PVdF type coating composition has a problem in glossiness of a dried coating film, and its application is limited because it does not form a coating film at room temperature. On the other hand, by adding a curing agent such as isocyanate or melamine to a solvent-soluble fluorine-containing copolymer containing a hydroxyl group, it becomes possible to cure at room temperature and bake, so that a coating composition with high gloss and excellent durability (Hereinafter, referred to as solution type fluorine coating) can be used in JP-A-3-231906 and JP-A-57-34.
It is known from Japanese Patent Publication No. 107. However, since this solution type fluorine coating material is inferior in workability and impact resistance, it cannot be applied to applications requiring flexibility such as precoated metal. Further, in order to improve the processability and impact resistance of the solution type fluorine coating, improvements such as a method of lowering the glass transition temperature of the fluorine-containing copolymer and a method of increasing the molecular weight of the fluorine-containing copolymer are carried out. ing. However, when the glass transition temperature is lowered, problems such as a decrease in coating film hardness and residual tackiness on the coating film surface occur, and when the molecular weight is increased, the viscosity of the coating composition increases. Since it becomes high, it is necessary to use a large amount of a volatile organic compound at the time of use, and as a result, a VOC (volatile organic compound) subject to regulation is often generated, which is an environmental problem.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a composition for a fluororesin coating which is excellent in workability and impact resistance, and is excellent in flexibility, solvent resistance and working environment. .

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a coating composition comprising a fluorine-containing copolymer having a specific molecular weight containing a hydroxyl group and a polyester polyol having a specific molecular weight. It was found that the composition for use not only excels in processability and impact resistance but also provides a coating film excellent in flexibility and solvent resistance, and has completed the present invention. That is, the present invention mainly comprises a fluorine-containing copolymer having a number average molecular weight of 1,000 to 10,000 and a hydroxyl group and a polyester polyol having a number average molecular weight of 2000 or less, and the fluorine-containing copolymer / the polyester The weight ratio of the polyol is 95
It is a composition for fluororesin coatings of / 5 to 50/50.

Hereinafter, the present invention will be described in more detail. The fluorine-containing copolymer in the present invention can be used without particular limitation as long as it contains a hydroxyl group.
Those composed of (a) a fluoroolefin monomer, (b) an α, β-ethylenically unsaturated monomer having a hydroxyl group, and (c) another radically polymerizable monomer are preferable. Examples of the (a) fluoroolefin monomer include vinyl fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, and hexafluoropropylene. From the viewpoint of polymerization reactivity, tetrafluoro Ethylene, chlorotrifluoroethylene and hexafluoropropylene are preferred, with chlorotrifluoroethylene being especially preferred. Also, two or more of these may be used in combination. The preferred amount of fluoroolefin monomer is 30 to 60 mol% based on the total amount of all constitutional units, and 30 mol%
If it is less than 6, weather resistance may be a problem, while 6
If it exceeds 0 mol%, the solubility in a solvent may decrease.

Examples of the α, β-ethylenically unsaturated monomer having a hydroxyl group (b) include 2-hydroxyethyl crotonate, 4-hydroxybutyl crotonate and 2
Hydroxyalkyl crotonates such as hydroxypropyl crotonate; hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate and 2-hydroxypropyl acrylate; 2-hydroxyethyl vinyl ether, 4
-Hydroxybutyl vinyl ethers and hydroxyalkyl vinyl ethers such as 6-hydroxyhexyl vinyl ether. Preferred are 2-chodroxyethyl crotonate, 2-hydroxyethyl acrylate and 4-hydroxybutyl vinyl ether.

The preferable proportion of the α, β-ethylenically unsaturated monomer having a hydroxyl group is 3 to 30 mol% based on the total amount of all the monomers, and when it is less than 3 mol%, the fluorine-containing copolymer is present. And the curing reaction of the curing agent is insufficient, and the solvent resistance and mechanical strength of the resulting coating film may be reduced.
If it exceeds 30 mol%, the weather resistance may decrease.

As the other radically polymerizable monomer (c), vinyl carboxylate and vinyl ether are preferable. As the carboxylic acid vinyl ester,
Aliphatic vinyl esters such as vinyl propionate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate and vinyl versatate; vinyl cyclohexanecarboxylate and 4-t -Vinyl cycloalkanecarboxylates such as vinyl butylcyclohexanecarboxylate, vinyl benzoates and aromatic vinyl carboxylates such as p-tert-butyl vinyl benzoate.

Examples of the vinyl ether include alkyl vinyl ethers such as ethyl vinyl ether and butyl vinyl ether; and cycloalkyl vinyl ethers such as cyclohexyl vinyl ether. The proportion of these monomer units in the fluorocopolymer is preferably 10 to 67 mol%.

Further, in order to improve the pigment dispersibility,
The unsaturated carboxylic acid such as crotonic acid can be used in a proportion of 5 mol% or less based on the total amount of the constituent units of the fluorinated copolymer.

The molecular weight of the fluorinated copolymer is 1,000 to 10,000, preferably 2,000 to 10,000 in terms of polystyrene equivalent number average molecular weight measured by gel permeation chromatography (hereinafter referred to as GPC).
It is 8000. The number average molecular weight of the fluorocopolymer is 1
If it is less than 000, the mechanical strength of the coating film obtained will be poor, while if it exceeds 10,000, the compatibility with the polyester polyol will be reduced and the appearance state and solvent resistance of the coating film obtained will be poor.

The polyester polyol in the present invention is a special polyester resin having two or more hydroxyl groups in the molecule, unlike a general polyester resin having one hydroxyl group in the molecule, and these are polyhydric alcohols. Can be produced by a condensation reaction of a polycarboxylic acid and the like, and various commercially available products can be used. Among them, from the viewpoint of compatibility with the fluorocopolymer, the molecular weight of the polyester polyol is preferably one having a polystyrene-reduced number average molecular weight of 2000 or less measured by GPC. Specific examples of the polyester polyols include CLAPOL P-510, P-1010 and F-1010 [trade names: all manufactured by Kuraray Co., Ltd.] and FLEXORE.
Z-188, 148 and XP-171-90 [trade name: all manufactured by KING INDUSTRIES] or the like. In the present invention, when a general polyester resin having one hydroxyl group in the molecule is mixed with a fluorinated copolymer, the compatibility with the fluorinated copolymer is poor, so that when a coating film is formed, While separation of the two components occurs and functions such as flexibility and solvent resistance cannot be expressed,
When a polyester polyol having a hydroxyl group at both ends is mixed, the compatibility between the two is excellent and functions such as flexibility and solvent resistance are exhibited.

The composition ratio of the fluorocopolymer and the polyester polyol in the present invention is 95/5 by weight.
50/50, preferably 90/10 to 60/40. When the proportion of the polyester polyol is less than 5% by weight based on the total amount of the fluorocopolymer and the polyester polyol, the flexibility of the obtained coating film is poor, while
When it exceeds 50% by weight, the compatibility with the fluorine-containing copolymer decreases, and the resulting coating film has poor solvent resistance and weather resistance.

It is desirable to mix an organic solvent, a curing agent and a curing accelerator into the fluororesin coating composition of the present invention, if necessary. Examples of the organic solvent include aromatic hydrocarbons such as toluene, xylene, ethylbenzene and alkyl polysubstituted benzene; ketone compounds such as methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone and cyclohexanone; ethyl acetate, butyl acetate, amyl acetate and dibasic acid. Ester compounds such as diesters; cyclic ethers such as tetrahydrofuran and dioxane; glycol ethers such as ethylene glycol monoethyl ether and ethylene glycol monobutyl ether; glycol ether acetates such as ethylene glycol monomethyl ether acetate and ethylene glycol monoethyl ether acetate; And alcohols such as isopropanol and butanol.

Examples of the curing agent include polyisocyanates, blocked isocyanates, urea resins, melamine resins, benzoguanamine resins, phenol resins and polycarboxylic acids which are reactive with hydroxyl groups. Further, together with the above curing agent, dibutyltin dilaurate and p-
A curing accelerator such as toluene sulfonic acid may be used together.

The composition for a fluororesin coating material of the present invention can be used as a clear coating material, but it can also be used as a coloring coating material in which a coloring pigment usually used in a coating material is dispersed. Preferred pigments include, for example, inorganic pigments such as titanium oxide, red iron oxide and calcined pigments, and organic pigments such as phthalocyanine blue, quinacridone red, isoindolinone and carbon black. The dispersion of the pigment can be performed by using a dispersing machine such as a ball mill, a sand mill, a roll mill, a paint shaker and a disper. In addition, wetting agents, dispersants, anti-sagging agents, thickening agents, anti-settling agents, anti-separation agents, defoaming agents, leveling agents, anti-repellent agents, anti-skin agents, slip agents, matting agents as required. Agents and coating additives such as silane coupling agents; UV absorbers such as benzophenone-based and benzotriazole-based, and hindered phenol-based and hindered amine-based antioxidants can be added. Further, an acrylic resin and a polyester resin which are compatible with the fluorine-containing copolymer and the polyester polyol may be blended.

The fluorine coating composition of the present invention can be applied to metal, plastic, wood, paper, cement-based substrates, etc. by spray coating, roll coater or brush coating. Specific examples of the metal include stainless steel, aluminum and zinc steel plate, and specific examples of the plastic include ABS, FRP, PC and hard PV.
C, Bakelite, epoxy, polyacrylic, polyurethane and the like. Further, examples of the cement-based base material include mortar and exposed concrete.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

Example 1 The following copolymer composition was used, and the polystyrene-equivalent number average molecular weight (hereinafter referred to as Mn) measured by GPC under the following conditions was 4500 and the hydroxyl value (hereinafter referred to as OH).
V) is 65 mgKOH / resin g and the glass transition temperature (hereinafter referred to as Tg) is 25 ° C., and the fluorine-containing copolymer A is mixed with each component of Table 1 below by a paint conditioner. The indicated curing agent and curing accelerator were added to obtain a coating composition. -Structural unit of the fluorinated copolymer A: chlorotrifluoroethylene / vinyl pivalate / vinyl versatic acid / vinyl caproate / 2-hydroxyethyl crotonic acid = 47/3/16/21/13 (mol%)- GPC measurement conditions (same for other examples and comparative examples) Device: high performance liquid chromatography [manufactured by Tosoh Corporation] Column: G5000HXL, GMHXL-L [manufactured by Tosoh Corporation] Detector: RI measurement temperature : 40 ° C Eluent: Tetrahydrofuran Flow rate: 1.0 ml / min

The coating composition obtained above was coated on a chromate-treated aluminum plate (thickness: 0.6 mm) using a bar coater and cured at room temperature for 1 week (dry film thickness: 25 μm).
After m), the following physical properties of the obtained coating film were measured.

(Test item and test method) 1) Gloss value: 60 ° -60 according to JIS-K5400
The gloss value was measured. 2) Flexibility: A coated aluminum plate was bent, an aluminum plate having a thickness of 0.6 mm was sandwiched, and bent with a vise. 3) Solvent resistance: Using a rubbing tester manufactured by Taihei Rika Kogyo Co., Ltd., a felt soaked with methyl ethyl ketone was used for 1 k.
The appearance of the coating film was evaluated after rubbing the coating film 100 times with a load of g. ◯: No rubbing mark, Δ: Rubbing mark, ×: Scratch 4) Weather resistance: Sunshine weather meter test (JI
The gloss retention after 2000 hours was measured with S-K5400).

[0021]

Example 2 It has the following copolymer composition and Mn of 650.
0, OHV is 55 mg KOH / resin g and Tg is 25
Fluorine-containing copolymer B having a temperature of 0 ° C. was used and mixed with each component shown in Table 1 below by a paint conditioner, and then a curing agent and a curing accelerator shown in Table 1 below were added to obtain a coating composition. -Structural unit of the fluorinated copolymer B: chlorotrifluoroethylene / vinyl versatic acid / vinyl caproate / 2-hydroxyethyl crotonic acid = 48/30/11
/ 11 (mol%) Furthermore, the physical properties of the coating film obtained in the same manner as in Example 1 were measured, and the results are shown in Table 1 below.

[0022]

Comparative Example 1 A coating film obtained in the same manner as in Example 1 except that the polyester polyol was not blended was used.
Physical properties were measured in the same manner as above, and the results are shown in Table 1 below.

[0023]

[Comparative Example 2] It has the following copolymer composition and Mn of 1500.
0, OHV is 52 mg KOH / resin g and Tg is 28
Fluorine-containing copolymer C having a temperature of 0 ° C. was used and mixed with each component shown in Table 1 below by a paint conditioner, and further a curing agent and a curing accelerator shown in Table 1 below were added to obtain a coating composition. -Structural unit of the fluorinated copolymer C: chlorotrifluoroethylene / vinyl versatic acid / ethyl vinyl ether / 4-hydroxybutyl vinyl ether = 50/2
8/12/10 (mol%) Furthermore, the physical properties of the coating film obtained by the same method as in Example 1 were measured, and the results are shown in Table 1 below.

[0024]

[Table 1]

The polyester polyol, titanium oxide, curing agent and curing catalyst in Table 1 are as follows. -Polyester polyol: FLEXOREZ-188 (trade name: manufactured by KING INDUSTRIES) Number average molecular weight: 488 (polystyrene conversion) -Titanium oxide: CR97 (trade name: manufactured by Ishihara Sangyo Co., Ltd.)-Curing agent: Coronate HX [trade name] : Nippon Polyurethane Industry Co., Ltd.]-Curing catalyst: dibutyltin dilaurate

[0026]

According to the composition for a fluororesin coating of the present invention, a coating film having excellent processability, impact resistance, flexibility and solvent resistance can be obtained, and can be used, for example, in coating materials such as precoated metal. .

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryusei Nishio 1-14-1 Nishishimbashi, Minato-ku, Tokyo Toagosei Co., Ltd.

Claims (3)

[Claims] 1. A fluorine-containing copolymer having a number average molecular weight of 1,000 to 10,000 and a hydroxyl group-containing copolymer and a polyester polyol having a number average molecular weight of 2,000 or less as a main component. The composition for fluororesin coating material having a weight ratio of 95/5 to 50/50. 2. A fluorine-containing copolymer comprising (a) a fluoroolefin monomer, (b) an α, β-ethylenically unsaturated monomer having a hydroxyl group, and (c) another radically polymerizable monomer. Based on the total amount thereof, the above (a)
Units based on: 30-60 mol%, units based on (b): 3-30 mol% and units based on (c): 10
The fluororesin coating composition according to claim 1, which is 67 mol%. 3. The fluororesin coating composition according to claim 1 or 2, wherein the polyester polyol is a compound containing a cycloalkyl group.