JP2010260937A - Clear-coating composition and coated article comprising the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a clear-coating composition having flexibility, without damaging the visual recognizing property of a coated article and also capable of enduring impact and the change of shape of the coated article for a long period of time, and the coated article comprising of the same. <P>SOLUTION: This clear-coating composition contains a resin composition containing a fluorine resin containing a hydroxy group and an isocyanate-based curing agent, a fluorine-based surfactant, an ultraviolet absorber, an organosilicate compound and solvent, and the isocyanate-based curing agent is a reaction product obtained by urethane-bonding (A) an isocyanate compound with (B) a lactone-based polyol, and having 1,000 to 10,000 weight-average molecular weight. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a clear coating composition and a coated article comprising the same.

  Structures that have been exposed to the outdoors for a long period of time will be damaged when they come into contact with automobiles, etc., and will deteriorate due to changes in shape, and will also be contaminated by automobile exhaust gas, dust, etc. Deteriorates over time. Especially, the road sign pillars installed in the median strip of the road are liable to be cracked by the impact at the time of contact with the automobile, and the surface is easily cracked as a result of being temporarily bent. In addition, since contaminants contained in the exhaust gas of automobiles adhere to the surface, the appearance of the outdoor structure is particularly deteriorated. However, the road sign pillar needs to alert the driver of the car by the color it has during the day and by the retroreflective reflective sheet attached to the surface at night. Therefore, the function of maintaining the appearance, that is, the visibility is important.

  2. Description of the Related Art Conventionally, a technique for applying a transparent clear coating to an outdoor structure in order to prevent contamination by exhaust gas or dust or deterioration due to ultraviolet rays has been known. For example, Patent Document 1 proposes a clear coating composition that can be applied in one coat and one bake and has high transparency.

  In addition, Patent Document 2 proposes a road sign post in which a photocatalytic film having a self-cleaning property is attached to the surface of a reflective sheet in order to prevent adhesion of dirt to the reflective sheet and maintain its function for a long period of time. .

Japanese Patent Laid-Open No. 2007-217514 Japanese Patent No. 4113019

  However, there has been no clear coating composition having flexibility that can withstand impacts and changes in the shape of an object to be coated while maintaining high transparency, adhesion to a substrate, and contamination prevention function. For this reason, it has not been possible to suppress the occurrence of cracks and wrinkles in the coating film due to impacts caused by contact with automobiles and the change in the shape of the object. When a crack occurs in the coating film, dirt enters from there, and there is also a problem that the anti-staining function of the coating film decreases. In particular, although visibility is important for road sign pillars, the change in shape and the degree of contamination are so remarkable that methods other than replacing with new sign pillars, such as a transparent coating film on the surface, etc. No attempt has been made to form and maintain visibility.

  The present invention has been made in view of the above problems, and has excellent transparency, weather resistance and adhesion to a substrate, and has a high anti-contamination function. It is an object of the present invention to provide a clear coating composition having flexibility and capable of withstanding impacts and changes in the shape of an object to be coated, and a coated article comprising the same.

  The clear coating composition of the present invention comprises a resin composition containing a hydroxyl group-containing fluororesin and an isocyanate curing agent, a fluorosurfactant, an ultraviolet absorber, an organosilicate compound, and a solvent. The isocyanate curing agent is a reaction product having a weight average molecular weight of 1,000 to 10,000 in which an isocyanate compound (A) and a lactone polyol (B) are urethane-bonded. .

（式中、ｎは１〜５の整数である）で表される化合物、一般式（３）：

（式中、ｎは炭素数１〜５の整数である）で表される化合物、一般式（４）：

（式中、Ｒ¹は炭素数３〜８の３価アルコールであり、ｎは１〜５の整数である）で表される化合物、一般式（５）：

（式中、ｎは１〜５の整数である）で表される化合物、および一般式（６）：

（式中、Ｒ²は炭素数１〜１０のアルキル基であり、ｎは１〜５の整数である）で表される化合物よりなる群から選ばれる少なくとも１種以上であり、
ラクトン系ポリオール（Ｂ）が、一般式（７）：

（式中、Ｒ³は炭素数２〜６の２価アルコールであり、ｍおよびｎはそれぞれ同じかまたは異なる１〜１０の整数であり、ｘおよびｙはそれぞれ同じかまたは異なる３、４または５の整数である）で表される化合物および／または一般式（８）：

（式中、Ｒ⁴は炭素数３〜８の３価アルコールであり、Ｌ、ｍおよびｎはそれぞれ同じかまたは異なる１〜８の整数であり、ｘ、ｙおよびｚはそれぞれ同じかまたは異なる３、４または５の整数である）で表される化合物であることが好ましい。 The isocyanate compound (A) is represented by the general formula (1):
ONC- (CH _{2) 6} -NCO
A compound represented by the general formula (2):

(Wherein n is an integer of 1 to 5), general formula (3):

(Wherein n is an integer having 1 to 5 carbon atoms), general formula (4):

(Wherein R ¹ is a trihydric alcohol having 3 to 8 carbon atoms and n is an integer of 1 to 5), general formula (5):

(Wherein n is an integer of 1 to 5), and general formula (6):

(Wherein R ² is an alkyl group having 1 to 10 carbon atoms and n is an integer of 1 to 5), and is at least one selected from the group consisting of compounds represented by:
The lactone polyol (B) is represented by the general formula (7):

(Wherein R ³ is a dihydric alcohol having 2 to 6 carbon atoms, m and n are the same or different integers of 1 to 10, and x and y are the same or different 3, 4 or 5 respectively. And / or the general formula (8):

Wherein R ⁴ is a trihydric alcohol having 3 to 8 carbon atoms, L, m and n are the same or different integers of 1 to 8, and x, y and z are the same or different 3 4 or an integer of 5).

（式中、Ｒ⁵〜Ｒ⁸はそれぞれ同じかまたは異なる炭素数１〜４のアルキル基であり、ｎは１０より大きく３０以下の整数である）で表される化合物であることが好ましい。 Further, the organosilicate compound has the general formula (9):

(Wherein R ^{5 to} R ⁸ are the same or different alkyl groups having 1 to 4 carbon atoms, and n is an integer greater than 10 and 30 or less).

  Moreover, it is preferable that 1-15 weight part polyester polyol is further included per 100 weight part of resin solid content of the said resin composition.

  The coated article of the present invention is characterized by having a coating film made of a clear coating composition on its substrate.

  The road sign pillar of the present invention is characterized in that a coating film made of a clear coating composition is formed so as to cover the surface thereof.

  According to the clear coating composition of the present invention, it has excellent transparency, weather resistance and adhesion to a substrate, and has a high anti-contamination function, so that it can maintain visibility over a long period of time and has high flexibility. Even if the shape of the paint is greatly changed, cracks and wrinkles are less likely to occur.

  In addition, a coated product having a coating film comprising the clear coating composition of the present invention on a substrate is less likely to be contaminated with dirt such as exhaust gas even when exposed to the outdoors for a long period of time. Even when the shape of the film changes, cracks and wrinkles are unlikely to occur in the coating film, so that excellent visibility can be maintained for a long time.

It is a front view of the road sign pillar of this invention. It is a schematic diagram of the partial cross section in the II-II line of FIG. 2 is a graph showing the relationship between tensile strength and elongation in Example 1. FIG. 4 is a graph showing the relationship between tensile strength and elongation in Example 2. 6 is a graph showing the relationship between tensile strength and elongation in Example 3. 6 is a graph showing the relationship between tensile strength and elongation in Example 4. 10 is a graph showing the relationship between tensile strength and elongation in Example 5. It is the graph which showed the relationship between the tensile strength and elongation amount in a comparative example. It is explanatory drawing of the running test by the Example of this invention, Comprising: (a) is the figure which showed the state which the jig | tool contacted the road sign pillar, (b) is a jig | tool pushing and bending a road sign pillar. (C) is the figure which showed the state which the jig | tool passed the road sign pillar.

<Resin composition>
The resin composition used in the present invention is a main component of the clear coating composition, and contains a hydroxyl group-containing fluororesin and an isocyanate curing agent.

(Hydroxyl-containing fluororesin)
The hydroxyl group-containing fluororesin is obtained by introducing a hydroxyl group into the fluororesin. The method for introducing a hydroxyl group is not particularly limited, and examples thereof include a method of copolymerizing a hydroxyl group-containing monomer when polymerizing a fluoroolefin.

As the fluoroolefin, the general formula (10):
R ⁹ R ¹⁰ C = CFR ¹¹
(Wherein R ^{9 to} R ¹¹ are the same or different and each represents a hydrogen atom, a fluorine atom, a chlorine atom, a monovalent alkyl group or a monovalent fluoroalkyl group). be able to.

  Examples of the monovalent alkyl group include alkyl groups having 1 to 10 carbon atoms such as a methyl group, an ethyl group, a propyl group, and a butyl group. Examples of the monovalent fluoroalkyl group include a fluoroalkyl group in which one or more hydrogen atoms in the alkyl group are substituted with a fluorine atom.

  Specific examples of the monomer represented by the general formula (10) include vinyl fluoride, vinylidene fluoride, chlorotrifluoroethylene, and tetrafluoroethylene.

  The monomer other than the fluoroolefin and the hydroxyl group-containing monomer is not particularly limited, and a monomer that can be copolymerized with the fluoroolefin and the hydroxyl group-containing monomer can be used. For example, α-olefins such as ethylene, propylene, isobutene and 1-butene; vinyl ethers such as ethyl vinyl ether, isobutyl vinyl ether, butyl vinyl ether and cyclohexyl vinyl ether; vinyl acetate, vinyl lactate, vinyl butyrate, vinyl isobutyrate and vinyl caproate Fatty acid vinyl esters such as vinyl pivalate and vinyl caprylate; fatty acid isopropenyl esters such as isopropenyl acetate and isopropenyl propionate, methyl (meth) acrylate, ethyl (meth) acrylate, and (meth) acrylic Propyl acid, isopropyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, lauryl (meth) acrylate, (meth) acrylate Alkyl (carbon number 1 to 18) ester of (meth) acrylic acid such as rohexyl; Ethylenically unsaturated carboxylic acid such as acrylic acid and methacrylic acid; Vinyl aromatic monomer such as styrene, α-methylstyrene, vinyltoluene; Acrylic Examples thereof include amide compounds of acid or methacrylic acid and derivatives thereof; acrylonitrile, methacrylonitrile, etc., or those in which one or more hydrogen atoms in these monomers are substituted with fluorine atoms.

  Among these, if the copolymerization ratio of the fluoroolefin is too small, excellent weather resistance tends to be not obtained, and if the copolymerization ratio of the fluoroolefin is too large, the solubility in a solvent is lowered. It is preferably a fluoroolefin-vinyl ether copolymer containing 20 to 80% by weight of olefin units and 80 to 20% by weight of vinyl ether units, 40 to 70% by weight of fluoroolefin units, and 60 to 30% by weight of vinyl ether units. % Of fluoroolefin-vinyl ether copolymer is more preferred.

  Hydroxyl-containing monomers introduced into the fluororesin include hydroxyalkyl vinyl ethers such as hydroxyethyl vinyl ether, hydroxypropyl vinyl ether, hydroxybutyl vinyl ether and hydroxypentyl vinyl ether, ethylene glycol monoallyl ether, diethylene glycol monoallyl ether, triethylene glycol monoallyl Examples thereof include hydroxyallyl ethers such as ether, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and hydroxypropyl methacrylate.

  The number average molecular weight of the hydroxyl group-containing fluororesin is preferably 2,000 to 100,000, and more preferably 5,000 to 30,000. When the number average molecular weight is less than 2,000, durability of the coating film and retention of stain resistance tend to be reduced. When the number average molecular weight is more than 100,000, compatibility with the isocyanate curing agent is reduced. Storage stability tends to decrease.

  The hydroxyl value of the hydroxyl group-containing fluororesin is preferably 20 to 200 mgKOH / g, and more preferably 20 to 150 mgKOH / g. When the hydroxyl value is less than 20 mgKOH / g, the durability and stain resistance of the coating film tend to be lowered, and when it exceeds 200 mgKOH / g, the durability, water resistance and stain resistance of the coating film are lowered. Tend.

(Isocyanate curing agent)
The isocyanate curing agent is a reaction product containing an isocyanate compound (A) and a lactone polyol (B), in which the isocyanate group of the isocyanate compound (A) and the hydroxyl group of the lactone polyol (B) are urethane-bonded. . The number average molecular weight of this reaction product is 500 to 5,000, more preferably 1,000 to 2,500, and the weight average molecular weight is 1,000 to 10,000, more preferably 1,500 to 5 , 000. If the weight average molecular weight is less than 1,000, the flexibility of the coating composition tends to decrease, and if it exceeds 10,000, the tackiness tends to be too high.

または、一般式（１５）：

（上記一般式（１４）および（１５）中、Ａはイソシアネート化合物（Ａ）であり、Ｂはラクトン系ポリオール（Ｂ）であり、ＡとＢとはウレタン結合している）で表されることもできる。 In the isocyanate curing agent, the isocyanate compound (A) and the lactone polyol (B) include, for example, the general formula (11):
A-B-A
Or general formula (12):
A-B-A-B-A
Or, general formula (13):
A-B-A-B-A-B-A
(In the above general formulas (11), (12) and (13), A is an isocyanate compound (A), B is a lactone-based polyol (B), and A and B are urethane-bonded) expressed. When the lactone polyol (B) is a trivalent alcohol, the general formula (14):

Or, general formula (15):

(In the above general formulas (14) and (15), A is an isocyanate compound (A), B is a lactone polyol (B), and A and B are urethane-bonded). You can also.

  The isocyanate compound (A) contained in the isocyanate-based curing agent is not particularly limited, but is a bifunctional or higher functional isocyanate compound having two or more isocyanate groups because of excellent solvent resistance, weather resistance and stain resistance. It is preferable that As such an isocyanate compound (A), for example, isocyanate compounds such as tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, their dimers, trimers, or reaction products with water or alcohols Etc.

（式中、ｎは１〜５の整数である）で表される化合物、一般式（３）：

（式中、ｎは１〜５の整数である）で表される化合物、一般式（４）：

（式中、Ｒ¹は炭素数３〜８の３価アルコールであり、ｎは１〜５の整数である）で表される化合物、一般式（５）：

（式中、ｎは１〜５の整数である）で表される化合物、または一般式（６）：

（式中、Ｒ²は炭素数１〜１０のアルキル基であり、ｎは１〜５の整数である）で表される化合物であることがより好ましく、これらは単独または混合して用いることができる。 Among them, since the yellowing of the coating film is prevented and the weather resistance is excellent, the isocyanate compound (A) is represented by the general formula (1):
ONC- (CH _{2) 6} -NCO
A compound represented by the general formula (2):

(Wherein n is an integer of 1 to 5), general formula (3):

(Wherein n is an integer of 1 to 5), a general formula (4):

(Wherein R ¹ is a trihydric alcohol having 3 to 8 carbon atoms and n is an integer of 1 to 5), general formula (5):

(Wherein n is an integer of 1 to 5), or general formula (6):

(Wherein R ² is an alkyl group having 1 to 10 carbon atoms and n is an integer of 1 to 5), and these are preferably used alone or in combination. it can.

  Examples of the trivalent alcohol having 3 to 8 carbon atoms include glycerin, trioxyisobutane, 1,2,3-butanetriol, 1,2,3-pentanetriol, and 2-methyl-1,2,3-propanetriol. 2-methyl-2,3,4-butanetriol, 2-ethyl-1,2,3-butanetriol, 2,3,4-pentanetriol, 2,3,4-hexanetriol, 4-propyl-3 , 4,5-heptanetriol, 2,4-dimethyl-2,3,4-pentanetriol, pentamethylglycerin, pentaglycerin, 1,2,4-butanetriol, 1,2,4-pentanetriol, trimethylol Examples include ethane and trimethylolpropane.

  Examples of the alkyl group having 1 to 10 carbon atoms include methyl group, ethyl group, propyl group, n-butyl group, isobutyl group, n-pentyl group, isopentyl group, sec-pentyl group, tert-pentyl group, and n-hexyl group. , Isohexyl group, sec-hexyl group, tert-hexyl group, n-heptyl group, isoheptyl group, sec-heptyl group, tert-heptyl group, n-octyl group, isooctyl group, sec-octyl group, Examples thereof include a tert-octyl group, an n-nonyl group, an isononyl group, a sec-nonyl group, a tert-nonyl group, an n-decyl group, an isodecyl group, a sec-decyl group, and a tert-decyl group.

  The lactone polyol (B) contained in the isocyanate curing agent is for imparting flexibility to the clear coating composition. The molecular weight is not particularly limited, but it is preferably a divalent or trivalent alcohol having a molecular weight of 300 to 2,000 in consideration of the flexibility and crosslinkability of the coating film, and the molecular weight is 500 to 1, More preferably, it is 200.

（式中、Ｒ³は炭素数２〜６の２価アルコールであり、ｍおよびｎはそれぞれ同じかまたは異なる１〜１０の整数であり、ｘおよびｙはそれぞれ同じかまたは異なる３、４または５の整数である）で表される化合物、または一般式（８）：

（式中、Ｒ⁴は炭素数３〜８の３価アルコールであり、Ｌ、ｍおよびｎはそれぞれ同じかまたは異なる１〜８の整数であり、ｘ、ｙおよびｚはそれぞれ同じかまたは異なる３、４または５の整数である）で表される化合物であることがより好ましい。 Among these, since it is excellent in water resistance and elongation, the lactone polyol (B) is represented by the general formula (7):

(Wherein R ³ is a dihydric alcohol having 2 to 6 carbon atoms, m and n are the same or different integers of 1 to 10, and x and y are the same or different 3, 4 or 5 respectively. A compound represented by the general formula (8):

Wherein R ⁴ is a trihydric alcohol having 3 to 8 carbon atoms, L, m and n are the same or different integers of 1 to 8, and x, y and z are the same or different 3 4 or an integer of 5) is more preferable.

  Examples of the lactone-based polyol (B) of the general formulas (7) and (8) include polybutyrolactone polyol, polyvalerolactone polyol, and polycaprolactone polyol. Among these, it is particularly preferable to use a polycaprolactone polyol that is excellent in elongation and water resistance.

  Examples of the dihydric alcohol having 2 to 6 carbon atoms include ethylene glycol, propylene glycol, 1,4-butylene glycol, neopentyl glycol, 1,6-hexamethylene glycol, sorbite, and the like.

  Examples of the trihydric alcohol having 3 to 8 carbon atoms include glycerin, trioxyisobutane, 1,2,3-butanetriol, 1,2,3-pentanetriol, 2-methyl-1,2,3- Propanetriol, 2-methyl-2,3,4-butanetriol, 2-ethyl-1,2,3-butanetriol, 2,3,4-pentanetriol, 2,3,4-hexanetriol, 4-propyl -3,4,5-heptanetriol, 2,4-dimethyl-2,3,4-pentanetriol, pentamethylglycerin, pentaglycerin, 1,2,4-butanetriol, 1,2,4-pentanetriol, Examples thereof include trimethylolethane and trimethylolpropane.

  As a commercially available isocyanate curing agent in which the isocyanate compound (A) represented by the general formula (1) and the lactone polyol (B) represented by the general formula (7) or (8) are urethane-bonded. Duranate E402-90T (Asahi Kasei Chemicals Corporation) and Duranate E405-80T (Asahi Kasei Chemicals Corporation). In addition, a commercially available isocyanate curing agent in which the isocyanate compound (A) represented by the general formula (2) and the lactone polyol (B) represented by the general formula (7) or (8) are urethane-bonded. An example of the product is Death Module N3800 (manufactured by Sumika Bayer Urethane Co., Ltd.). Furthermore, although it is not a commercial item, the isocyanate compound (A) represented by the general formula (6) and the lactone-based polyol (B) represented by the general formula (7) or (8) are urethane-bonded. Examples of the isocyanate curing agent include HDI allophanate-based modified polyisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd.).

  The mixing ratio of the hydroxyl group-containing fluororesin and the isocyanate curing agent is preferably such that the isocyanate group of the isocyanate curing agent is 0.8 to 2.0 mol with respect to 1 mol of the hydroxyl group of the hydroxyl group-containing fluororesin. More preferably, it is -1.5 mol. If it is less than 0.8 mol, the coating film will be insufficiently cured, and the solvent resistance, stain resistance, weather resistance and the like will tend to be reduced. If it exceeds 2.0 mol, unreacted isocyanate groups will form. Residues in it tend to lower weatherability and stain resistance.

<Solvent>
The solvent used in the clear coating composition is not particularly limited, but preferably contains cyclohexanone and diisobutyl ketone. As a result, it is possible to coat a resin molded product such as a polyurethane resin or a polycarbonate resin, which has a low solvent resistance and generally does not have sufficient adhesion to a paint, without impairing high transparency with one coat and one bake. The content of cyclohexanone in the solvent is preferably 5 to 20% by weight, and more preferably 7 to 15% by weight. When the cyclohexanone is less than 5% by weight, the adhesion of the coating film to a resin or the like tends to be reduced. The content of diisobutyl ketone in the solvent is preferably 10 to 50% by weight, more preferably 15 to 40% by weight. Thereby, the clear coating composition can obtain high transparency.

  Solvents other than cyclohexanone and diisobutyl ketone include aromatic hydrocarbons such as toluene and xylene, saturated hydrocarbons such as n-hexane, n-heptane, n-octane and mineral spirits, methylene chloride, trichloroethylene, trichloroethane, Halogenated hydrocarbons such as chloroethylene, alkyl ethers such as ethyl ether and dipropyl ether, esters such as ethyl acetate, cellosolve acetate and butyl acetate, and ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone . Among these, from the viewpoint of solubility in the resin composition, ketones are preferable, and methyl isobutyl ketone is more preferable. In addition, in solvents other than cyclohexanone and diisobutyl ketone, when there are many aromatic hydrocarbons, halogenated hydrocarbons, esters, and ketones, there is a tendency that cracks, haze, whitening, etc. tend to occur on the surface of the coating, and saturation occurs. When there are many hydrocarbons, the solubility with respect to a resin composition becomes inadequate, and there exists a tendency for a uniform coating to become difficult to be obtained.

  The addition amount of the solvent other than cyclohexanone and diisobutyl ketone is not particularly limited as long as it is 100% by weight in total with cyclohexanone and diisobutyl ketone, but is 30 to 85% by weight in the solvent. It is preferably 35 to 70% by weight.

  The solubility parameter (hereinafter referred to as SP value) of cyclohexanone used for the solvent is 9.9. This value is for both hydroxyl group-containing fluororesin (SP value: 10.2) and polyurethane resin (SP value: 10-11), polycarbonate resin (SP value: 9.8) and the like used in the present invention. It has excellent solubility. Therefore, when coating on a resin substrate, cyclohexanone causes the substrate surface to swell / dissolve, and assists diffusion / dissolution of the resin composition in the coating composition into the substrate. Adhesion is improved.

  Although the addition amount of a solvent is not specifically limited, It is preferable that it is 150-500 weight part per 100 weight part of resin solid content of a resin composition, and it is more preferable that it is 200-400 weight part. When the amount of the solvent added is less than 150 parts by weight, the smoothness of the coating film tends to decrease when the vertical surface of the object to be coated is applied by air spray or the like. The film thickness cannot be ensured during coating, and the weather resistance tends to decrease.

<Fluorosurfactant>
Fluorosurfactants include perfluoroalkyl-containing oligomers, perfluoroalkyl-containing polymers, polysiloxanes containing fluoroalkyl groups, perfluoroalkyl ethylene oxide adducts, perfluoroalkyl carboxylates, perfluoroalkyl phosphate esters, Examples thereof include perfluoroalkyltrimethylammonium salts and perfluoroalkylbetaines. Among these, it is more preferable to use a perfluoroalkyl-containing oligomer, a perfluoroalkyl-containing polymer, and a polysiloxane containing a fluoroalkyl group from the viewpoint of excellent compatibility with a resin and a solvent and a decrease in stain resistance. These can be used alone or in combination.

  Examples of the perfluoroalkyl-containing oligomer include MEGAFAC F-477 (manufactured by DIC Corporation), and examples of the perfluoroalkyl-containing polymer include Surflon S-393 (manufactured by Seimi Chemical Co., Ltd.). Examples of the polysiloxane containing an alkyl group include EFKA-3034 (manufactured by Ciba Japan Co., Ltd.).

  By using a fluorosurfactant, the surface tension of the coating composition can be reduced, and wettability to a polyurethane resin, a polycarbonate resin, or the like can be improved. As a result, sufficient adhesive strength can be obtained even when the content of cyclohexanone is 5 to 20% by weight, which is less than the conventionally used amount.

  The addition amount of the fluorosurfactant is preferably 0.01 to 1.0 part by weight and preferably 0.02 to 0.2 part by weight per 100 parts by weight of the resin solid content of the resin composition. More preferred. If the addition amount of the fluorosurfactant is less than 0.01 parts by weight, the wettability with respect to polyurethane resin, polycarbonate resin or the like tends to be lowered, and if it exceeds 1.0 parts by weight, the stain resistance tends to be lowered. is there.

<Ultraviolet absorber>
As UV absorbers, hydroxyphenyltriazine UV absorbers, benzophenone UV absorbers, benzotriazole UV absorbers, cerium oxide UV absorbers, cyanoacrylate UV absorbers, zinc oxide UV absorbers, oxalic acid Examples include anilide ultraviolet absorbers and titanium oxide ultraviolet absorbers. Among these, it is preferable to use a hydroxyphenyltriazine-based ultraviolet absorber that is excellent in heat resistance and ultraviolet absorption stability.

  Specific examples of the hydroxyphenyl triazine-based ultraviolet absorber include 2- (4,6-bis (2,4-dimethylphenyl) -1,3,5-triazin-2-yl) -5-hydroxyphenyl and oxirane [ Reaction product with (C10-C16 mainly C12-C13 alkyloxy) methyl] oxirane (trade name: Tinuvin 400, manufactured by Ciba Japan Co., Ltd.), 2- (2,4-dihydroxyphenyl) -4,6- Reaction product of bis- (2,4-dimethylphenyl) -1,3,5-triazine and (2-ethylhexyl) -glycidic acid ester (trade name: Tinuvin 405, manufactured by Ciba Japan Co., Ltd.), 2 , 4-Bis [2-hydroxy-4-butoxyphenyl] -6- (2,4-dibutoxyphenyl) -1,3,5-triazine (trade name: Tinuvin 46 Ciba Japan Co., Ltd.), 2- [4- (octyl-2-methylethanoate) oxy-2-hydroxyphenyl] -4,6- [bis (2,4-dimethylphenyl)]-1, 3,5-triazine (trade name: Tinuvin 479, manufactured by Ciba Japan Co., Ltd.), tris [2,4,6- [2- {4- (octyl-2-methylethanoate) oxy-2-hydroxyphenyl] }]-1,3,5-triazine (trade name: Tinuvin 777, manufactured by Ciba Japan Co., Ltd.) and the like.

  The addition amount of the ultraviolet absorber is preferably 1 to 20 parts by weight, more preferably 5 to 12 parts by weight, per 100 parts by weight of the resin solid content of the resin composition. If the amount is less than 1 part by weight, the weather resistance tends to decrease, and if it exceeds 20 parts by weight, the haze and stain resistance tend to decrease.

（式中、Ｒ⁵〜Ｒ⁸はそれぞれ同じかまたは異なる炭素数１〜４のアルキル基であり、ｎは１０より大きく３０以下の整数である）で表される化合物などをあげることができる。炭素数１〜４のアルキル基としては、メチル基、エチル基、プロピル基、ｎ−ブチル基、ｔ−ブチル基などをあげることができる。メチル基は最も高い反応性を示すが、安定性が低い。そのため、溶媒への溶解性と樹脂との相溶性のバランスをとるためにメチル基をブチル基もしくはエチル基などで部分置換することなどが好ましい。オルガノシリケート化合物を添加することで、塗装後の早い時期から塗膜表面は高い親水性を示す。その結果、自動車の排気ガスや塵埃などによる汚れの付着が抑えられ、長期間屋外に曝されて場合であっても、高い透明性、すなわち被塗装物の視認性を維持することができる。 <Organosilicate compound>
As the organosilicate compound, the general formula (6):

(Wherein, R ^{5 to} R ⁸ are the same or different alkyl groups having 1 to 4 carbon atoms, and n is an integer of greater than 10 and 30 or less). Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, a propyl group, an n-butyl group, and a t-butyl group. Methyl groups show the highest reactivity but are less stable. Therefore, in order to balance the solubility in the solvent and the compatibility with the resin, it is preferable to partially substitute the methyl group with a butyl group or an ethyl group. By adding an organosilicate compound, the surface of the coating film exhibits high hydrophilicity from an early stage after coating. As a result, adhesion of dirt due to automobile exhaust gas, dust, and the like can be suppressed, and high transparency, that is, visibility of an object to be coated can be maintained even when exposed to the outdoors for a long time.

  The addition amount of the organosilicate compound is preferably 1 to 30 parts by weight and more preferably 3 to 20 parts by weight per 100 parts by weight of the resin solid content of the resin composition. If the amount is less than 1 part by weight, the stain resistance tends to be reduced. If the amount exceeds 30 parts by weight, the coating film becomes hard, resulting in cracks and a decrease in compatibility with the resin composition. The film tends to become cloudy.

  A catalyst may be added for the purpose of promoting hydrolysis of the organosilicate compound. As the catalyst, a metal compound catalyst such as a metal chelate, a metal ester, or a metal alkoxide is used, and examples of the metal include aluminum, titanium, silicon, tin, and zinc. Specific examples include aluminum monoacetylacetonate bis (ethylacetoacetate) and aluminum tris (acetylacetonate).

  The addition amount of the catalyst is not particularly limited, but is preferably 0.1 to 20 parts by weight, more preferably 1 to 15 parts by weight per 100 parts by weight of the organosilicate compound.

<Polyester polyol>
A polyester polyol can be further added to the clear coating composition of the present invention. Thereby, the flexibility of the coating film can be increased, and the adhesion to the substrate can be improved. The polyester polyol is not particularly limited, but a polyester skeleton having a straight chain and a saturated aliphatic structure is preferable in terms of excellent weather resistance. Specifically, FLEXOREZ148 (manufactured by KING Industries CO.) Or FLEXOREZ188 (manufactured by KING Industries CO.) Can be used. The addition amount of the polyester polyol is preferably 1 to 15 parts by weight, more preferably 5 to 12 parts by weight per 100 parts by weight of the resin solid content of the resin composition.

  In the present invention, other materials usually used for coating compositions can be blended. Examples of other materials include plasticizers, color pigments, reflectors, surfactants, antifoaming agents, inorganic fillers, and curing catalysts.

<Method for producing coating composition>
The manufacturing method of the coating composition of this invention is not specifically limited, The manufacturing method of a well-known coating composition is employable. For example, a solution obtained by mixing and stirring a hydroxyl group-containing fluororesin, a solvent, a fluorine-based surfactant, an ultraviolet absorber, and the like, and an isocyanate-based curing agent, a solvent, an organosilicate compound, a catalyst, and the like are mixed and stirred uniformly. Each solution is prepared individually. A method of preparing these solutions and a viscosity adjusting solvent before coating can be used.

<Coated product comprising clear coating composition>
The object to be coated on which the clear coating composition of the present invention is applied is not particularly limited. As a substrate of the object to be coated, a resin molded article made of a synthetic resin such as an acrylic resin, a polycarbonate resin, a polyurethane resin, or a polyester resin, or paint molding Examples include steel plates, stainless steel, aluminum, brass, and chrome-plated steel materials. Also, the object to be painted is not particularly limited, and structures that are exposed to the outdoors for a long period of time, such as sound insulation walls installed on roads and railways, road sign pillars, automobile windows, exterior walls and windows such as buildings, signs, etc. Etc.

  In particular, the road sign pillars installed in the median strip of the roadway are alerted to the driver of the car by the retroreflective reflective sheet attached to the surface at night by the color that it has in the daytime. Visibility is important. Nevertheless, since the installation location is on the road, the frequency of contact with the automobile is high, and the surface is easily contaminated by substances contained in the exhaust gas of the automobile. The clear coating composition of the present invention can exert a remarkable effect on such a road sign pillar having a remarkable degree of deformation and contamination of the base material. FIG. 1 is a front view of a road sign pillar of the present invention, and FIG. 2 is a schematic diagram of a partial cross section taken along line II-II in FIG.

  Referring to FIG. 1, a retroreflective reflecting sheet 11 that reflects automobile light at night is wound around a road sign pillar 1. The clear coating composition of this invention is apply | coated there so that the road sign pillar 1 and the reflective sheet 11 may be covered with an air spray etc. there. FIG. 2 shows a state in which the clear coating composition is applied to the entire road sign pillar 1 including the reflection sheets 11a, 11b, and 11c. As a result, not only the road sign pillar 1 but also the reflection sheets 11a, 11b, and 11c are covered with the clear coating layer 12, and the visibility can be maintained for a long time not only in the daytime but also in the nighttime. The thickness of the clear coating layer 12 is not particularly limited, but is preferably 10 μm or more in order to enhance ultraviolet absorption, and 100 μm or less in order to maintain good adhesion to the substrate. Is preferable, and it is more preferable that it is 15-50 micrometers.

  Further, the clear coating layer 12 preferably has a contact angle with water of 60 ° or less, more preferably 50 ° or less, on the surface of the sunshine carbon arc lamp type weather resistance tester 500 hours. If it exceeds 60 °, the contamination resistance tends to decrease.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples.

<Isocyanate curing agent>
Isocyanate-based curing agent A (trade name: Duranate E402-90T, manufactured by Asahi Kasei Chemicals Corporation, weight average molecular weight: about 1,500, resin solid content: 90% by weight (solvent: toluene), NCO content: 8.5 weight%)
Isocyanate-based curing agent B (trade name: Duranate E405-80T, manufactured by Asahi Kasei Chemicals Corporation, weight average molecular weight: about 1,500, resin solid content: 80% by weight (solvent: toluene), NCO content: 7.1 weight%)
Isocyanate-based curing agent C (modified polyisocyanate based on HDI allophanate, isocyanate compound (A) represented by general formula (6) and lactone-based polyol (B) represented by general formula (7) or general formula (8)) And urethane-bonded reaction product, manufactured by Nippon Polyurethane Industry Co., Ltd., molecular weight: about 1,500, NCO content: 8.9% by weight)
Isocyanate-based curing agent D (trade name: Desmodur N3800, manufactured by Sumika Bayer Urethane Co., Ltd., number average molecular weight: 1,000 to 1,500, weight average molecular weight: 1,500 to 2,000, resin solid content: (100% by weight, NCO content: 11.0% by weight)
Isocyanate-based curing agent E (trade name: Coronate HX, manufactured by Nippon Polyurethane Industry Co., Ltd., resin solid content: 100% by weight, NCO content: 21.3% by weight)

<Fluorine resin>
Lumiflon LF200F (Asahi Glass Co., Ltd., number average molecular weight: 12,000, resin solid content: 100% by weight, hydroxyl value: 52 KOH / g)

<Polyester polyol>
Polyester polyol 1 (trade name: FLEXOREZ188, manufactured by KING Industries CO., Resin solid content: 100% by weight, hydroxyl value: 230 KOH / g)
Polyester polyol 2 (trade name: FLEXOREZ148, manufactured by KING Industries CO., Resin solid content: 100% by weight, hydroxyl value: 235 KOH / g)

<Fluorosurfactant>
EFKA-3034 (manufactured by Ciba Japan)

<Ultraviolet absorber>
Tinuvin 400 (manufactured by Ciba Japan, 2- (4,6-bis (2,4-dimethylphenyl) -1,3,5-triazin-2-yl) -5-hydroxyphenyl and oxirane [(C10 Reaction product with -C16 mainly C12-C13 alkyloxy) methyl] oxirane)

<Organosilicate compound>
MKC silicate MS58B30 (Mitsubishi Chemical Co., Ltd., methyl silicate condensate in which the methyl group is partially substituted with a butyl group, average degree of condensation≈15)

<Catalyst>
Aluminum monoacetylacetonate bis (ethylacetoacetate) (trade name: Aluminum Chelate D, manufactured by Kawaken Fine Chemical Co., Ltd.)

Examples 1 to 5 and Comparative Examples Coating compositions of Examples 1 to 5 and Comparative Examples were obtained with the formulations shown in Table 1. In the examples and comparative examples, the mixing ratio of the hydroxyl group-containing fluororesin and the isocyanate curing agent was 1.1 mol of the isocyanate group of the isocyanate curing agent with respect to 1 mol of the hydroxyl group of the hydroxyl group-containing fluororesin. .

<Tensile test>
The obtained coating composition was applied to the surface of a tin plate, and a clear coating film was formed with a target thickness of 100 μm. The coating film was separated from the tin plate and cut into a dumbbell shape No. 2 to prepare a test piece. Using this test piece, the elongation was measured according to JIS K6251. The measurement conditions were a tensile speed of 20 mm / min and a measurement temperature of 23 ° C. The growth rate (%) is
EB = (L1-L0) / L0 × 100
Sought by. Here, EB is the elongation rate (%) at the time of cutting, L0 is the distance between marked lines (20 mm), and L1 is the distance between marked lines at the time of cutting. EB measurement results are shown in Table 2, and the relationship between tensile strength and elongation is shown in FIGS.

<Physical property test>
The obtained coating composition was applied to a polyurethane resin molded plate by air spray so that the film thickness after drying was 20 μm, allowed to stand at room temperature for 15 minutes, and then dried at 80 ° C. for 1 hour to produce a coated plate. did. Using the obtained coated plate, the following adhesion, adhesion after boiling water test, and water contact angle after acid immersion were measured. Moreover, the water contact angle was measured after acid immersion using an unpainted polyurethane resin molded plate as a reference example. The results are shown in Table 2.

(Adhesiveness)
The obtained coated plate was evaluated by a cross cut tape test (cut interval 1 mm, square 100) according to JIS K5600-5-6. The denominator is the measured power, and the numerator is the power that was not peeled off.

(Adhesion after boiling water test)
The obtained coated plate was immersed in boiling water for 1 hour, and then evaluated by a cross-cut tape test (cut interval 1 mm, square 100) according to JIS K5600-5-6. The denominator is the measured power, and the numerator is the power that was not peeled off.

(Water contact angle after acid immersion)
The obtained coated plate was immersed in a 0.1N nitric acid aqueous solution at 60 ° C. for 24 hours, and then measured 30 seconds after droplet formation using a CA-X type contact angle meter (manufactured by Kyowa Interface Science Co., Ltd.). went. The lower the water contact angle, the more hydrophilic the coating film surface is.

<Running test>
After coating the obtained coating composition on a road sign post made of polyurethane resin (diameter 8 cm, height 65 cm) by air spray so that the film thickness after drying is 20 μm, the lower part of the road sign post is outdoors Fixed to the ground. A running test machine having a bumper-shaped steel jig 2 attached so that the height from the ground is 23 cm is prepared, and the jig 2 comes into contact with the road sign pillar 1 fixed to the ground (FIG. 9). (A)), the road sign pillar 1 was subjected to a running test so that the road sign pillar 1 was pushed and bent ((b) in FIG. 9) and passed ((c) in FIG. 9). The set speed of the running test machine was 40 km / h. The outside temperature was 27 ° C. After the running test was repeated 80 times, the coating on the part A (bumper impact part) of the road sign pillar 1 that the jig 2 touched and the parts B and C (bent part) where the road sign pillar 1 was bent by the running The cracks of the film were visually observed and evaluated according to the following criteria. The results are shown in Table 2.
◎ ・ ・ ・ There are no cracks in the coating film.
○ 1 to 9 cracks are in the coating film.
Δ: Ten or more cracks are present in the coating film.
X: There are 10 or more cracks in the coating film, and there is a part where the coating film is floating.

<Accelerated weather resistance test>
The obtained coating composition was applied to a polyurethane resin molded plate by air spray so that the film thickness after drying was 20 μm, allowed to stand at room temperature for 15 minutes, and then dried at 80 ° C. for 1 hour to produce a coated plate. did. While observing the appearance after 500 hours and 2000 hours of the prepared coated plate and uncoated polyurethane resin molded plate (reference example) with a sunshine carbon arc lamp type weather resistance tester (manufactured by Suga Test Instruments Co., Ltd.) At the start of the test (initial stage), the water contact angle was measured after 500 hours and 2000 hours. Appearance and water contact angle were evaluated by the following methods. The results are shown in Table 2.

(appearance)
The appearance was visually observed and evaluated according to the following criteria.
No abnormality ... No change was observed compared to the beginning of the test.
Discoloration: Discoloration was observed.

(Water contact angle)
The obtained coated plate was measured 30 seconds after the droplet formation using a CA-X type contact angle meter (manufactured by Kyowa Interface Science Co., Ltd.). The lower the water contact angle, the more hydrophilic the coating film surface is.

<Outdoor exposure test>
The obtained coating composition was applied to a polyurethane resin molded plate by air spray so that the film thickness after drying was 20 μm, allowed to stand at room temperature for 15 minutes, and then dried at 80 ° C. for 1 hour to produce a coated plate. did. The prepared coated plate and unpainted polyurethane resin molded plate (reference example) are placed on an outdoor 45 ° south-facing exposure table, exposed to the outdoors for 186 days, and then visually observed for the degree of contamination and at the start of the test ( The water contact angle was measured after 186 days. The degree of contamination was evaluated by the following method. The water contact angle was measured by the same method as described above. The results are shown in Table 2.

(Degree of dirt)
The degree of contamination was visually observed and evaluated according to the following criteria.
A: Good with almost no dirt.
○: Good with little contamination.
Δ: Dirt is observed.
X: Dirt is remarkable.

  As is clear from Table 2 and FIGS. 3 to 8, the clear coating composition of the present invention using an isocyanate curing agent in which a specific isocyanate compound (A) and a lactone polyol (B) are urethane-bonded is used as a base material. It can be seen that the elongation rate (125 to 190%) in the tensile test was improved more than twice compared with the comparative example (elongation rate: 60%) while having high adhesion to the surface. Further, as is apparent from the results of the running test, it can be seen that the coating film made of the clear coating composition of the present invention did not crack at all even when the object to be coated was bent repeatedly. Furthermore, it can be seen that the object to which the clear coating composition of the present invention was applied did not change its appearance and did not adhere to dirt over a long period of time. Furthermore, it can be seen that by adding polyester polyol to the coating composition, the elongation rate in the tensile test is increased, and thus the flexibility of the coating film is improved. From the above, it can be seen that the clear coating composition of the present invention has high flexibility while having high transparency, adhesion to a substrate, and contamination prevention function.

  According to the clear coating composition of the present invention, it has excellent transparency, weather resistance and adhesion to a substrate, and has a high anti-contamination function, so that it can maintain visibility over a long period of time and has high flexibility. Even if the shape of the paint is greatly changed, cracks and wrinkles are less likely to occur. Therefore, for example, it can be suitably used for sound insulation walls, road sign pillars, windows for automobiles, exterior walls and windows for buildings, and signboards installed on roads and railways.

1 Road Sign Pillar 11, 11a, 11b, 11c Reflective Sheet 12 Clear Coating Layer

Claims (6)

A clear coating composition comprising a resin composition containing a hydroxyl group-containing fluororesin and an isocyanate curing agent, a fluorosurfactant, an ultraviolet absorber, an organosilicate compound, and a solvent,
A clear coating composition in which the isocyanate curing agent is a reaction product having a weight average molecular weight of 1,000 to 10,000 in which an isocyanate compound (A) and a lactone polyol (B) are urethane-bonded. Isocyanate compound (A) is represented by the general formula (1):
ONC- (CH _{2) 6} -NCO
A compound represented by the general formula (2):

(Wherein n is an integer of 1 to 5), general formula (3):

(Wherein n is an integer of 1 to 5), a general formula (4):

(Wherein R ¹ is a trihydric alcohol having 3 to 8 carbon atoms and n is an integer of 1 to 5), general formula (5):

(Wherein n is an integer of 1 to 5), and general formula (6):

(Wherein R ² is an alkyl group having 1 to 10 carbon atoms and n is an integer of 1 to 5), and is at least one selected from the group consisting of compounds represented by:
The lactone polyol (B) is represented by the general formula (7):

(Wherein R ³ is a dihydric alcohol having 2 to 6 carbon atoms, m and n are the same or different integers of 1 to 10, and x and y are the same or different 3, 4 or 5 respectively. And / or the general formula (8):

Wherein R ⁴ is a trihydric alcohol having 3 to 8 carbon atoms, L, m and n are the same or different integers of 1 to 8, and x, y and z are the same or different 3 The clear coating composition according to claim 1, which is a compound represented by (4 or 5). The organosilicate compound has the general formula (9):

3. wherein R ^{5 to} R ⁸ are the same or different alkyl groups having 1 to 4 carbon atoms, and n is an integer of greater than 10 and 30 or less. The clear coating composition as described.   The clear coating composition according to any one of claims 1 to 3, further comprising 1 to 15 parts by weight of a polyester polyol per 100 parts by weight of resin solid content of the resin composition.   A coated product comprising a coating film comprising the clear coating composition according to claim 1 on a substrate.   A road sign pillar formed by forming a coating film comprising the clear coating composition according to any one of claims 1 to 4 so as to cover the surface thereof.

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