JPH083513A - Coating composition - Google Patents

Abstract

PURPOSE:To improve the adhesion of a coating film to a plastic material, especially polypropylene resin and obviate the use of a primer. CONSTITUTION:A coating material containing a thermosetting resin such as an acrylic-melamine resin as a binder is incorporated with a terpene polymer modified with a hydroxyl-containing compound such as phenol and the composition of the mixture is controlled to get a baked and dried coating film having a glass transition point (Tg) of <=40 deg.C The modified terpene polymer can be added generally at a ratio of 3-30 pts.wt. based on 100 pts. wt. of the thermosetting resin binder.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a coating composition, and more particularly to a coating composition suitable for coating plastic products.

[0002]

2. Description of the Related Art Conventionally, plastic materials such as polypropylene resin have been used for many interior and exterior parts of automobiles such as bumpers, fender aprons and glove boxes. And for such plastic products,
Painting is often applied for the purpose of protection and ensuring design.

However, a coating film is generally hard to adhere to the plastic surface, and particularly polypropylene resin is easy to crystallize and has a large self-cohesive force, so that the adhesion of the coating film is higher than that of other plastic materials. Inferior Therefore, in order to improve the adhesion of the coating film, it is also known to perform surface treatment such as acid etching treatment with chromic acid immersion liquid, plasma treatment, gas flame treatment, etc. prior to coating. Requires special processing equipment for that purpose.

Therefore, for coating plastic products such as polypropylene resin, it is general to use a primer having good adhesiveness to the plastic, which is applied and then the coating is applied. As the primer, for example, in the case of a polypropylene resin, a chlorinated polyolefin resin such as chlorinated polypropylene or an isocyanate primer is generally used.

Incidentally, there is also known a paint capable of forming a coating film having good adhesion on the plastic surface without using a primer. For example, JP-A-58-136627 discloses that
As a coating composition for polypropylene resin, there is disclosed a composition in which a chlorinated polypropylene resin is used as a resin binder, and a terpene phenol copolymer is further added to the resin composition in order to improve image clarity.

[0006]

However, although the paint using a chlorinated polyolefin resin as a resin binder has good adhesion to plastics, especially polypropylene resin, the coating film formed by this method has the problem that the entire coating film is separated by the chlorine ions generated separately. It was deteriorated and tended to be inferior in weather resistance. This tendency is the same even when a chlorinated polyolefin resin is used as a primer, and the weather resistance of the coating film overcoated with this may decrease.

Therefore, when the weather resistance of the coating film is important, a primer other than a chlorinated polyolefin resin may be used for coating plastics, particularly polypropylene resin products. In any case, however, painting the primer requires man-hours and material cost for that purpose, and improvement thereof has been demanded.

Therefore, an object of the present invention is to provide a coating composition capable of forming a coating film having good adhesion to a plastic material, particularly a polypropylene resin, without using a primer. .

[0009]

Means for Solving the Problems The present inventors have added a terpene polymer modified with a hydroxyl group-containing compound such as phenol to a coating composition containing a thermosetting resin as a binder, and adjusting the composition thereof, and after baking and drying. It was found and confirmed that the above problems can be advantageously solved by making the glass transition point (Tg) of the formed coating film appropriate.

That is, the coating composition according to the present invention contains a thermosetting resin binder and a hydroxyl group-containing compound-modified terpene polymer, and has a glass transition point (Tg) of 40 ° C. or less after baking and drying. Is what is.

The coating composition according to the present invention will be described in more detail below.

As the thermosetting resin binder, any of those commonly used as a resin binder for thermosetting paints such as acrylic-melamine type and polyester-melamine type can be used, and it can be cured by ultraviolet rays. A resin binder or the like can also be used. And, such a resin binder generally comprises a hydroxyl group-containing resin containing two or more hydroxyl groups in one molecule and a curing agent such as an amino resin or a polyisocyanate compound, and the hydroxyl group-containing resin contains a hydroxyl group. Examples of the acrylic resin, polyester resin, alkyd resin, epoxy resin, silicone resin, fluorine resin, amide resin, urethane resin, polyether resin, etc. These hydroxyl group-containing resins can be used alone or in combination of two or more thereof, and among these, preferred are hydroxyl group-containing acrylic resin and polyester resin.

The hydroxyl group-containing acrylic resin can be obtained by copolymerizing a hydroxyl group-containing vinyl monomer with another vinyl monomer and has a number average molecular weight of 1,000 to 1,500.
0, a hydroxyl value of 50 to 200, and an acid value of about 5 to 50 are generally preferable. Here, as the hydroxyl group-containing vinyl monomer, acrylic acid such as 2-hydroxyethyl acrylate and hydroxypropyl methacrylate, hydroxyalkyl esters of methacrylic acid having 2 to 24 carbon atoms, N-methylol acrylamide, N-dihydroxyethyl methacryl Examples thereof include acrylic acid such as amide, and hydroxyalkydamides having 1 to 12 carbon atoms such as methacrylic acid. These hydroxyl group-containing vinyl monomers can be used alone or in appropriate combination. Further, as other vinyl monomers, acrylic acid such as isobutyl acrylate has 1 to 24 carbon atoms.
Alkyl esters of methacrylic acid such as n-butyl methacrylate, etc., having 1 to 24 carbon atoms,
Acrylic acid, methacrylic acid, maleic acid, carboxyl group-containing vinyl monomers such as fumaric acid, glycidyl group-containing vinyl monomers such as glycidyl methacrylate, styrene,
Examples include vinyltoluene and the like. These vinyl monomers may be used alone or in combination of two or more kinds.

The hydroxyl group-containing polyester resin is an ester reaction product of a polyhydric alcohol and a polybasic acid or an anhydride thereof, and has a residual hydroxyl group in the molecule, and its number average molecular weight is 200 to 10,000, and the hydroxyl value is Is 50 ~
It is generally preferable that the acid value is 350 and the acid value is about 5 to 50. As the polyhydric alcohol for forming the hydroxyl group-containing polyester resin, ethylene glycol, propylene glycol, 1,6-hexanediol, diethylene glycol, glycerin, pentaerythritol, etc. are used alone or in combination. be able to. As the polybasic acid or its anhydride, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid,
Tetrahydrophthalic anhydride, succinic acid, maleic anhydride, fumaric acid, trimellitic anhydride, etc. can be used similarly. Then, these polyhydric alcohols and polybasic acids or their anhydrides can generally be reacted such that the hydroxyl groups and the carboxyl groups are in a molar ratio of 1.2 to 1.8.

As the curing agent for these hydroxyl group-containing resins, any of those generally used as this type of curing agent can be used. Examples include amino resins such as melamine resins and urea resins, and polyisocyanates. A compound etc. can be mentioned. Here, as the amino resin, a methylolated amino resin obtained by the reaction of an amino component such as melamine, urea or dicyandiamide with an aldehyde such as formaldehyde or benzaldehyde, or this methylolated amino resin is ethyl alcohol or 2-ethylhexanol. Alkyl etherified amino resins etherified with a suitable alcohol such as can be used. Among these, butyl etherified melamine resin is the most representative. As the polyisocyanate compound, hexamethylene diisocyanate (HD
I), aliphatic diisocyanates such as trimethylhexamethylene diisocyanate, cycloaliphatic diisocyanates such as isophorone diisocyanate (IPDI), 4,
Diisocyanate itself such as aromatic diisocyanate such as 4'-diphenylmethane diisocyanate, m- or p-xylylene diisocyanate, or an adduct of these diisocyanate with polyhydric alcohol, low molecular weight polyester resin or the like, or polymer of diisocyanate Etc. Further, these isocyanate compounds can be used after being blocked with a blocking agent.

Further, in the coating composition of the present invention, a hydroxyl group-containing compound-modified terpene polymer is an essential component.
This hydroxyl group-containing compound-modified terpene polymer is a terpene polymer such as limonene, dipentene, α-pinene, β-pinene, phenol, phenols such as cresol,
Alternatively, it is modified with a hydroxyl group-containing compound such as alcohols. And its molecular weight is generally 500-100.
It is preferably in the range of about 0. If the molecular weight is too large, the compatibility with the resin binder in the coating composition becomes insufficient, and if the molecular weight is too small, the adhesiveness tends to be insufficient. Further, this hydroxyl group-containing compound modified terpene polymer, if the addition amount is too small,
Practically sufficient adhesiveness cannot be obtained, and if it is too large, the hardness of the formed coating film tends to be insufficient. For this reason, the amount of addition is generally preferably 3 to 30 parts by weight with respect to 100 parts by weight of the resin binder. However, this is not limiting and more formulations are possible.

The coating composition of the present invention contains a pigment, an ultraviolet absorber, an antioxidant, and
Etc. can be blended appropriately.

Examples of the pigment include organic pigments and inorganic pigments. Examples of the organic pigments include azo-based and phthalocyanine-based pigments or dyes, and the inorganic pigments include titanium dioxide, iron oxide, red iron oxide, and other inorganic pigments, barium sulfate, talc, and extender pigments such as mica. , Carbon black such as carbon black, metallic powder, and the like. These pigments may be used either individually or in combination of two or more.

As the ultraviolet absorber, benzotriazole compounds such as 2- (2'-hydroxy-5'-methyl-phenyl) benzotriazole, benzophenone compounds such as 2,4-dihydroxybenzophenone, acrylate compounds such as diphenyl acrylate. Compounds, salicylate compounds such as p-octyl-phenyl salicylate,
Other compounds such as 2-hydroxy-naphthophenone and nickel-bisoctylphenyl sulfide may be mentioned, and these may be used alone or in combination of two or more.

This UV absorber can be used alone, but preferably it can be used in combination with an antioxidant. Examples of antioxidants include hindered amine-based compounds such as bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, phenol-based compounds, and sulfide-based compounds.

In addition, surface modifiers such as silicone and other organic polymers, anti-sagging agents such as silica fine powder, thickeners and the like can be appropriately used as required.

The coating composition of the present invention comprises the above-mentioned materials. Here, this coating composition has a glass transition point (Tg) of 4 after baking and curing.
It is necessary to be 0 ° C or lower. That is, when the glass transition point (Tg) of the coating film exceeds 40 ° C., the physical properties of the coating film are close to those of glass and are brittle like glass, so they are vulnerable to external stress and fracture such as cracks occurs. As a result, sufficient adhesion to the plastic material cannot be obtained. On the other hand, the glass transition point (T
When g) is 40 ° C. or less, the physical properties are similar to rubber, it has flexibility like rubber, and the strain rate increases, so it is strong against external stress and breaks cracks and the like. Is less likely to occur. Therefore, good adhesion to the plastic material can be ensured.

Therefore, the composition of each component forming the coating composition of the present invention is adjusted so that the glass transition point (Tg) of the formed coating film is 40 ° C. or lower. In general, the glass transition point (Tg) of the coating film tends to be higher as the blending amount of the curing agent of the thermosetting resin binder is larger and as the blending amount of the pigment is larger. As the amount of the pigment is small and the amount of the hydroxyl group-containing compound-modified terpene polymer is large, the glass transition point (Tg) of the coating film tends to be low. Therefore, setting the glass transition point (Tg) of the formed coating film at 40 ° C. or lower is effective for curing
It can be carried out by appropriately adjusting the compounding ratio of the hydroxyl group-containing compound-modified terpene polymer, pigment and the like.

The above-mentioned coating composition of the present invention can be applied to a suitable viscosity by a solvent or the like and applied by an appropriate coating means such as spray coating. In addition, the coating film of the applied paint is baked and cured by setting and the like and then heating it at a temperature suitable for curing it.

[0025]

The coating composition according to the present invention contains a hydroxyl group-containing compound-modified terpene polymer, so that it is possible to obtain excellent adhesion to plastics, especially polypropylene resin, as will be seen from the examples below. It is considered that this is because the hydroxyl group-containing compound-modified terpene polymer itself has excellent adhesiveness and, in addition, enhances the wettability of the coating material to the plastic surface. Along with that, since the glass transition point (Tg) of the formed coating film is 40 ° C. or lower, the physical properties of the coating film are close to those of rubber, the flexibility is excellent, and the strain rate is large. Since it is resistant to stress or deformation from the surface and is unlikely to break such as cracks, excellent adhesion to the plastic surface can be obtained. Therefore, the plastic surface can be coated without using a primer.

[0026]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples.

<Examples 1 to 3> The coating composition of the present invention was embodied as a metallic coating material, and the composition shown in FIG.
~ 3 coating compositions were prepared.

As shown in FIG. 1, the metallic paints of Examples 1 to 3 include a thermosetting resin binder composed of an acrylic resin and a melamine resin which is a curing agent thereof, a phenol-modified terpene polymer, and an aluminum paste. Include,
In each example, the compounding amounts of components other than the aluminum paste are changed. That is, in Example 1, the acrylic resin 10
It is composed of 0 parts by weight, 40 parts by weight of melamine resin, 5 parts by weight of phenol-modified terpene polymer, and 10 parts by weight of aluminum paste. In Example 2, the amount of phenol-modified terpene polymer is increased to 10 parts by weight. . Further, in Example 3, the acrylic resin and the melamine resin of Example 1 were changed to 110 parts by weight and 30 parts by weight, respectively, and the amount of the melamine resin as the curing agent was reduced.

Here, the acrylic resin is a hydroxyl group-containing acrylic resin (Acridic A-345, manufactured by Dainippon Ink and Chemicals, Inc.), and the melamine resin is a butyl etherified melamine resin (Super Beckamine L-).
117-60 manufactured by Dainippon Ink and Chemicals, Inc. As the hydroxyl group-containing compound-modified terpene polymer, a phenol-modified terpene polymer (Mighty Ace
G-150 manufactured by Yasuhara Chemical Co., Ltd. was used.
As the metallic pigment, aluminum paste (Alpaste 7790N Toyo Aluminum Co., Ltd.) was used.

Specifically, the paint was prepared as follows. First, an acrylic resin and a phenol-modified terpene polymer were mixed in the above-mentioned composition, dispersed for 20 minutes with a paint shaker, and then a melamine resin and an aluminum paste were compounded. Then, using a mixed solvent consisting of 30 parts by volume of Solvesso 100 and 70 parts by volume of toluene, Ford Cup No. In 3, the viscosity was adjusted to 20 seconds (20 ° C.).

In this way, the coating compositions of Examples 1 to 3 which were metallic paints were prepared.

<Example 4> The coating composition of the present invention was embodied as a solid color coating material, and the coating composition of Example 4 was prepared with the composition shown in FIG.

The coating composition of this Example 4 was prepared according to Examples 1 to 1.
A titanium white pigment is used in place of the aluminum paste used as the pigment in the coating composition of 3 above, 100 parts by weight of acrylic resin, 40 parts by weight of melamine resin, 20 parts by weight of phenol-modified terpene polymer and titanium white pigment. Including 50 parts by weight, 0.2 parts by weight of the surface modifier is further added. Here, many pigments are used and many phenol-modified terpene polymers are blended.

The titanium white pigment is titanium dioxide (Taipec CR-95 manufactured by Ishihara Sangyo Co., Ltd.), and the surface modifier is a silicone-based surface modifier (BYK-
300 manufactured by Big Chemie).

The solid color paint of this Example 4 was specifically prepared as follows. First, the acrylic resin, the phenol-modified terpene polymer, and the titanium white pigment were mixed in the above-mentioned formulation, dispersed for 30 minutes with a paint shaker, and then the melamine resin and the surface conditioner were blended. Then, as in the first to third embodiments, this is the Solvesso 100.
Ford cup No. In 3, the viscosity was adjusted to 20 seconds (20 ° C.).

Thus, the coating composition of Example 4 as a solid color coating was prepared.

<Comparative Examples 1 to 3> Further, for comparison with the Examples, coating compositions of Comparative Examples 1 to 3 were prepared with the composition shown in FIG.

Comparative Examples 1 and 2 are metallic paints for comparison with Examples 1 to 3, Comparative Example 1 is the compound of Example 1 from which the phenol-modified terpene polymer has been removed, and Comparative Examples 2 added 5 parts by weight of phenol-modified terpene polymer, but 80 parts by weight of acrylic resin,
The amount of the melamine resin is 60 parts by weight, and the mixing ratio of the curing agent is increased.

Further, Comparative Example 3 is a solid color paint, and the titanium white pigment in Example 4 was further increased to 80%.
It is a part by weight.

Then, the viscosity was adjusted by using a mixed solvent in the same manner as in Examples 1 to 4 to prepare coating compositions of Comparative Examples 1 to 3.

[Formation of coating film] A coating test was conducted on the coating compositions of Examples 1 to 4 and Comparative Examples 1 to 3 in order to evaluate their adhesion and the like. The glass transition point (Tg) was measured.

A polypropylene resin test plate was used for the coating test. Then, in the case of the metallic paints of Examples 1 to 3 and Comparative Examples 1 and 2, after the metallic paints were applied to the degreased test plate, the clear paint was applied wet-on-wet, and after setting, the temperature was changed. 12
The coated film was baked and dried by holding it at 0 ° C. for 30 minutes. In this way, a metallic coating film consisting of a metallic base coating film having a film thickness of 15 to 20 μm and a clear coating film having a film thickness of 25 to 30 μm was formed on the surface of the test plate.

The clear paint used here has the following composition.

[0044]

[Table 1]

Here, the acrylic resin, the melamine resin and the surface conditioner are the same as those used in the coating compositions of Examples and Comparative Examples, and a benzotriazole type ultraviolet absorber (Tinuvin 900 Ciba Geigy) is used as the ultraviolet absorber. And a hindered amine-based antioxidant (Sanol LS-292 Co., Ltd. Sankyo) was used as the antioxidant. In addition, this clear paint was mixed with a Ford cup No. 3 using a mixed solvent as in the case of Examples and Comparative Examples. Four
The viscosity was adjusted to 20 seconds (20 ° C.) and used.

Further, in the case of the solid color paints of Example 4 and Comparative Example 3, the solid color paints were similarly applied to a degreased polypropylene resin test plate, and after setting, at a temperature of 120 ° C. for 30 minutes. The coating film was baked and dried by holding it for a minute. As a result, a solid color coating film having a film thickness of 30 to 40 μm was formed on the surface of the test plate.

Then, Examples 1 to 4 thus formed
And about the coating film of the coating composition of Comparative Examples 1-3, the glass transition point (Tg) (degreeC) was measured using the dynamic viscoelasticity measuring device "Reovibron".

The measurement results are also shown in FIG. Then, as shown in FIG. 1, the glass transition point (Tg) of the coating film formed from the coating composition of Example 1 was 30 ° C. Similarly, Example 2 was 28 ° C., Example 3 was 27 ° C., Example 4 was 40 ° C., Comparative Example 1 was 34 ° C., Comparative Example 2 was 44 ° C.,
The temperature of Comparative Example 3 was 48 ° C.

[Evaluation Test] Then, with respect to the metallic coating film and the solid color coating film formed on the test plate of the polypropylene resin by the coating composition of Examples and Comparative Examples as described above, the initial adhesion, sharpness, Adhesion, appearance and weather resistance (excluding Comparative Examples 2 and 3) after the moisture resistance test were tested and evaluated.

Regarding the initial adhesion, a 1 mm cross-cut test was conducted 24 hours after the coating film was formed. In this 1 mm cross-cut test, the coating film formed on the test plate is cut parallel to each other at an interval of 1 mm vertically and horizontally using a cutter knife, and at this time, the cutter knife is used. The blade edge of (1) is kept at a constant angle in the range of 35 to 45 degrees with respect to the coated surface so that it penetrates the coating film and reaches the test plate. Then, the state of cross-shaped scratches appearing on the coated surface was observed, and the adhesion of the coating film was evaluated according to the following criteria. ◯: Each cut is thin and smooth on both sides, there is no peeling at the intersection of the cut and the square, and the area of the defect is less than 5% of the total square area. X: There is peeling at both sides of the cut and the intersection, and the area of the defective portion is 5% or more of the total square area.

Regarding the sharpness, an angle of 6 was measured with a specular gloss meter.
The 0 ° gloss value was measured and evaluated according to the following criteria. ◯: The gloss value is 85 or more. X: The gloss value is less than 85.

Regarding the adhesion after the humidity resistance test, the coated test plate was left in an atmosphere having a temperature of 50 ° C. and a humidity of 95% for 100 hours to perform the humidity resistance test, and then the above-mentioned 1 mm crosscut test was performed. Then, the adhesion of the coating film after the moisture resistance test was evaluated according to the same criteria as the case of the initial adhesion.

The appearance of the coating film after the moisture resistance test was observed for blistering, discoloration, etc., and evaluated according to the following criteria. ○: No abnormality. X: Occurrence of blister, discoloration, etc.

For accelerated weather resistance, the accelerated weather resistance tester S
An 800-hour accelerated weathering test was performed using WOM, and the presence or absence of discoloration of the coating film was visually observed and evaluated according to the following criteria. ◯: No abnormality is recognized. X: Discoloration is recognized.

The ΔE value of the coating film after the accelerated weathering test was measured using a colorimeter.

Regarding the weather resistance, only in the case of Comparative Example 1, a chlorinated polyolefin-based primer was used to undercoat this and then a coating film was formed.

<Evaluation Test Results> The results of the above evaluation tests are also shown in FIG.

As shown in FIG. 1, it contains a phenol-modified terpene polymer and also has a glass transition point (T
The coating compositions of Examples 1 to 4, in which g) is 40 ° C. or lower,
Good results were obtained with respect to initial adhesion, image clarity (gloss), adhesion and appearance after a humidity resistance test, and weather resistance.

On the other hand, the coating composition of Comparative Example 1 in which the phenol-modified terpene polymer was not blended had good image clarity, but the adhesiveness of the coating film to the polypropylene resin was inferior to the initial adhesiveness. It wasn't enough. Further, also in the coating compositions of Comparative Examples 2 and 3, although the phenol-modified terpene polymer was blended, the glass transition point (Tg) of the formed coating film was 40 ° C.
And the adhesiveness was not sufficient.

As shown in the results of the weather resistance test of Comparative Example 1, when a chlorinated polyolefin-based primer was used, the coating film tended to be discolored.

From the results of this evaluation test, a terpene polymer modified with a hydroxyl group-containing compound such as phenol was added to the coating composition, and the glass transition point (Tg) of the coating film formed was 40 ° C. or lower. By using, even without using a chlorinated polyolefin type primer,
It can be seen that a coating film having excellent adhesion to a plastic material, particularly a polypropylene resin, can be formed.

In the above description, examples in which the coating composition of the present invention is embodied as a metallic coating and a solid color coating have been described. It can be embodied as various kinds of paints such as paints for household use. Further, although the coating composition of the present invention is particularly suitable for coating the surface of plastics such as polypropylene resin, it can be applied to the coating of surfaces other than plastics such as metal.

[0063]

As described above, the coating composition according to the present invention contains a thermosetting resin binder and a hydroxyl group-containing compound-modified terpene polymer, and has a glass transition point (Tg) after baking and drying. ) Is 40 ° C. or lower.

Therefore, since the hydroxyl group-containing compound-modified terpene polymer is added and the glass transition point (Tg) of the coating film after baking and drying is kept at 40 ° C. or lower, it is suitable for plastic materials, particularly polypropylene resin. A coating film having good adhesion can be formed.
Therefore, since it is not necessary to use a primer as in the conventional case, the primer coating process can be omitted, and the man-hour and material cost required for this can be reduced. Further, unlike the case where a chlorinated polyolefin-based primer is used, the weather resistance of the coating film does not deteriorate. Furthermore, since it is not necessary to use a chlorinated resin as the resin binder, a coating film having excellent weather resistance can be formed.

[Brief description of drawings]

FIG. 1 shows the composition of coating compositions of Examples and Comparative Examples of the present invention, and the glass transition point (Tg) of the coating film formed,
It is a table which shows the result of an evaluation test.

Claims (1)

[Claims] 1. A coating composition comprising a thermosetting resin binder and a hydroxyl group-containing compound-modified terpene polymer, and having a glass transition point (Tg) of 40 ° C. or lower after baking and drying. Stuff.