Patent Description:
In recent years, demand for chemical resistance of primer paints used for forming paint films on automobile bumpers etc. has been increasing. To satisfy such demand, various proposals have been made. In addition, high reliability is required for weather resistance when primer paints are used in harsh environments, such as outdoors, for a long period of time.

PTL <NUM>, for example, discloses a primer paint formulation using an acid-modified chlorinated polyolefin and a dispersion resin.

PTL <NUM> discloses an aqueous paint formulation using an acid-modified polyolefin and a coumarone resin or indene resin.

Furthermore, PTL <NUM> (<CIT>) discloses an aqueous dispersion mixture comprising: an aqueous dispersion (A) that comprises a crystalline polyolefin (a) as a dispersoid thereof; an aqueous dispersion (B) that comprises a crystalline polyurethane (b) as a dispersoid thereof; and an aqueous dispersion (C) that comprises a non-crystalline polyurethane (c) as a dispersoid thereof. PTL <NUM> (<CIT>) relates to a spray dried polyolefin elastomer powder for rotational molding processes. PTL <NUM> (<CIT> )discloses an acid-modified polyolefin obtained by a graft modification of a polyolefin resin (A) such that an unsaturated carboxylic acid derivative and/or its anhydride (B) and an N-substituted maleimide (C) are incorporated in amounts of <NUM> to <NUM> wt. % and <NUM> to <NUM> wt. %, respectively, the wt. %'s being based on the polyolefin resin, and having a weight average molecular weight of <NUM>,<NUM> to <NUM>,<NUM>. PTL <NUM> (<CIT>) provides a modified polyolefin resin graft modified with unsaturated polycarboxylic acid or its derivative (A) and (meth)acrylic ester (B) represented by a specific general formula, with contents of (A) and (B) of <NUM> to <NUM>% by weight and <NUM> to <NUM>% by weight, respectively, with a weight average molecular weight of <NUM>,<NUM> to <NUM>,<NUM>. PTL <NUM> (<CIT>) relates to a coating agent which is characterized as containing an olefin polymer (A) that has a heat of fusion of <NUM>-<NUM> J/g, and a weight-average molecular weight (Mw) of <NUM> x <NUM><NUM> to <NUM> x <NUM><NUM>; a hydrocarbon-based synthetic oil (B) that has a defined kinematic viscosity; and a tackifier (C) that has an acid value of at least <NUM> and a weight -average molecular weight (Mw) of <NUM> x <NUM><NUM> to <NUM> x <NUM><NUM>. PTL <NUM> (<CIT>) discloses a coating agent containing (A) an olefin polymer having a heat of fusion as measured in accordance with JIS K <NUM> in the range from <NUM> to <NUM> J/g and a weight-average molecular weight (Mw) of <NUM> x <NUM><NUM> to <NUM>,<NUM> x <NUM><NUM> and (B) a semisolid hydrocarbon having a kinematic viscosity at <NUM> of <NUM>,<NUM> to <NUM>,<NUM><NUM>/s.

However, the primer paint formulation disclosed in PTL <NUM> uses an acid-modified chlorinated polyolefin as a primer resin component, which is environmentally problematic, and does not exhibit sufficient chemical resistance. Further, the composition disclosed in PTL <NUM> is an aqueous dispersion, and does not have sufficient water resistance and chemical resistance. Moreover, tackifiers having many double bonds, such as coumarone resins or indene resins, do not have sufficient weather resistance.

An object of the present invention is to provide a paint formulation that is used as a primer of a polypropylene substrate for an automobile bumper etc., and that has excellent adhesion, water resistance, and chemical resistance, such as gasohol resistance and fuel resistance, as well as good paint storage stability and weather resistance, compared to conventional bumper primers.

The present inventors conducted extensive research to solve the above problems, and consequently found that by mixing an acid-modified polyolefin having crystallinity and a specific tackifier, a paint film having excellent adhesion and chemical resistance, as well as good paint storage stability and weather resistance, can be obtained. The present invention was thus accomplished.

Specifically, the present invention includes the following.

A paint formulation comprising an acid-modified polyolefin (A) and a tackifier (B), and satisfying the following (a) and (b):.

The paint formulation preferably comprises a hydrocarbon-based solvent (C), the hydrocarbon-based solvent (C) is preferably contained in an amount of <NUM> to <NUM> parts by mass per <NUM> parts by mass of the acid-modified polyolefin (A), and the paint formulation preferably comprises at least one of an ester-based solvent (D1) or a ketone-based solvent (D2).

The acid-modified polyolefin (A) preferably has an acid value of <NUM> to <NUM> mgKOH/g-resin, and preferably has a weight average molecular weight of <NUM>,<NUM> to <NUM>,<NUM>.

The paint formulation preferably further comprises an alcohol-based solvent (E).

A primer paint for a polyolefin substrate, comprising the paint formulation according to the invention.

According to the present invention, a paint formulation that has good storage stability and weather resistance, and that is capable of forming a paint film having excellent water resistance, chemical resistance such as gasohol resistance and fuel resistance, and adhesion can be obtained.

Embodiments of the present invention are described in detail below.

The acid-modified polyolefin (A) used in the present invention is obtained by grafting at least one of polyethylene, polypropylene, and a propylene-α-olefin copolymer with at least one of α,β-unsaturated carboxylic acid and acid anhydride thereof.

Examples of α-olefins include those having two or more carbon atoms. Specific examples include ethylene, propylene, <NUM>-butene, <NUM>-methyl-<NUM>-propene, <NUM>-methyl-<NUM>-butene, <NUM>-methyl-<NUM>-butene, <NUM>-hexene, <NUM>-ethyl-<NUM>-butene, <NUM>,<NUM>-dimethyl-<NUM>-butene, <NUM>-methyl-<NUM>-pentene, <NUM>-methyl-<NUM>-pentene, <NUM>-methyl-<NUM>-pentene, <NUM>,<NUM>-dimethyl-<NUM>-butene, <NUM>-heptene, methyl-<NUM>-hexene, dimethyl-<NUM>-pentene, ethyl-<NUM>-pentene, trimethyl-<NUM>-butene, methylethyl-<NUM>-butene, <NUM>-octene, methyl-<NUM>-pentene, ethyl-<NUM>-hexene, dimethyl-<NUM>-hexene, propyl-<NUM>-heptene, methylethyl-<NUM>-heptene, trimethyl-<NUM>-pentene, propyl-<NUM>-pentene, diethyl-<NUM>-butene, <NUM>-nonen, <NUM>-decene, <NUM>-undecene, and <NUM>-dodecene. One or two or more of these α-olefins can be polymerized to obtain an α-olefin polymer or copolymer.

The propylene-α-olefin copolymer mainly comprises propylene that is copolymerized with an α-olefin. Examples of α-olefins include ethylene, <NUM>-butene, <NUM>-heptene, <NUM>-octene, <NUM>-methyl-<NUM>-pentene, vinyl acetate, and the like, which can be used singly or in a combination of two or more. Preferred among these α-olefins are ethylene and <NUM>-butene. Although the proportion of the propylene component and the α-olefin component in the propylene-α-olefin copolymer is not limited, the amount of propylene component is preferably <NUM> mol% or more, and more preferably <NUM> mol% or more. When the amount of ethylene component in the propylene-α-olefin copolymer is <NUM> mol% or less, the paint formulation of the present invention shows good adhesion, chemical resistance, and paint storage stability. Further, even when the amount of ethylene component is <NUM> mol% or less, the paint formulation of the present invention shows sufficient adhesion, chemical resistance, and paint storage stability. An amount of ethylene component of <NUM> mol% or less also poses no problem.

The acid-modification of the acid-modified polyolefin (A) is preferably polymerization of an acid functional group. As the acid functional group, at least one of α,β-unsaturated carboxylic acid and a derivative thereof can be used, and the derivative of α,β-unsaturated carboxylic acid is preferably acid anhydride. Examples of at least one of α,β-unsaturated carboxylic acid and acid anhydride thereof include maleic acid, itaconic acid, citraconic acid, and acid anhydride thereof. Among these, acid anhydride is preferred, and maleic acid anhydride is more preferred. Specific examples include acid-modified polypropylene, acid-modified propylene-ethylene copolymers, acid-modified propylene-butene copolymers, acid-modified propylene-ethylene-butene copolymers, and the like. These acid-modified polyolefins can be used singly or in a combination of two or more.

The weight average molecular weight (Mw) of the acid-modified polyolefin (A) is preferably within the range of <NUM>,<NUM> to <NUM>,<NUM>, more preferably <NUM>,<NUM> to <NUM>,<NUM>, and even more preferably <NUM>,<NUM> to <NUM>,<NUM>. When the weight average molecular weight (Mw) is <NUM>,<NUM> or more, good chemical resistance is obtained. In contrast, when the weight average molecular weight (Mw) is <NUM>,<NUM> or less, good paint storage stability is obtained.

In terms of adhesion to the polyolefin resin substrate, the acid value of the acid-modified polyolefin (A) is preferably within the range of <NUM> to <NUM> mgKOH/g-resin, and more preferably <NUM> to <NUM> mgKOH/g-resin. When the acid value is <NUM> mgKOH/g-resin or more, good paint storage stability is obtained. In contrast, when the acid value is <NUM> mgKOH/g-resin or less, excellent chemical resistance is obtained.

The acid-modified polyolefin (A) of the present invention is crystalline. Crystalline polyolefins are superior in adhesion and chemical resistance to amorphous polyolefins. Crystalline polyolefins refer to those that show a clear melting peak during heating from -<NUM> to <NUM> at <NUM>/min using a differential scanning calorimeter (DSC).

The melting point (Tm) of the acid-modified polyolefin (A) is preferably <NUM> or more, more preferably <NUM> or more, and even more preferably <NUM> or more. When the melting point is <NUM> or more, good adhesion and chemical resistance are obtained. The melting point is preferably <NUM> or less, more preferably <NUM> or less, and even more preferably <NUM> or less. When the melting point is <NUM> or less, good paint storage stability is obtained.

The heat enthalpy (ΔH) of the acid-modified polyolefin (A) is preferably <NUM> J/g or more, and more preferably <NUM> J/g or more. When the heat enthalpy (ΔH) is <NUM> J/g or more, good adhesion and chemical resistance are obtained. The heat enthalpy (ΔH) is preferably <NUM> J/g or less, and more preferably <NUM> J/g or less. When the heat enthalpy (ΔH) is <NUM> J/g or less, good paint storage stability is obtained.

It is preferable that the acid-modified polyolefin (A) is substantially not chlorinated. A substantially chlorinated acid-modified polyolefin (A) is environmentally problematic and may reduce chemical resistance. The expression "substantially not chlorinated" means that the chlorine content is preferably <NUM> wt% or less, more preferably <NUM> wt% or less, even more preferably <NUM> wt% or less, and particularly preferably <NUM> wt%.

The method for producing the acid-modified polyolefin (A) is not particularly limited. Examples of the method include a radical grafting reaction in which a radical species is formed in a polymer serving as a main chain, and unsaturated carboxylic acid and acid anhydride are graft-polymerized using the radical species as a polymerization starting point.

Examples of radical generators include, but are not limited to, organic peroxides, such as di-tert-butyl peroxyphthalate, tert-butyl hydroperoxide, dicumyl peroxide, benzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxy-<NUM>-ethylhexanoate, tert-butyl peroxypivalate, methyl ethyl ketone peroxide, di-tert-butyl peroxide, and lauroyl peroxide; azonitriles, such as azobisisobutyronitrile and azobisisopropionitrile; and the like. Of these, organic peroxides are preferably used.

The tackifier, also called a tackiness-imparting agent, is an additive added for the purpose of improving adhesive strength.

The tackifier is an amorphous oligomer, and is a thermoplastic resin that is liquid or solid at room temperature.

Examples include petroleum resin-based tackifiers, hydrocarbon resin-based tackifiers, rosin-based tackifiers, terpene-based tackifiers, and the like. In terms of weather resistance, hydrogenated versions of the above-mentioned tackifiers are preferred.

The double-bond equivalent of the tackifier is defined by the formula: double-bond equivalent = weight average molecular weight/number of double bonds in a molecule. Double bonds refer to unsaturated carbon bonds. Unsaturated carbon bonds in the aromatic ring count as double bonds. For example, benzene has <NUM> double bonds. In consideration of weather resistance, the tackifier (B) of the present invention has a double-bond equivalent of <NUM> or more, or contains no double bond. The double-bond equivalent is more preferably <NUM> or more, even more preferably <NUM> or more, and particularly preferably <NUM> or more. Because the double-bond equivalent is <NUM> or more, even if the composition of the present invention is applied as a paint to a substrate and exposed as a paint film to light or rain outdoors for a long period of time, the paint film tends to be less likely to discolor and particularly has good weather resistance. The upper limit is not particularly limited, but is preferably <NUM> or less in terms of storage stability. Double bond-free tackifiers are particularly preferably used in terms of weather resistance. The double-bond equivalent in the molecule can be adjusted, for example, by hydrogenation reaction. The tackifier (B) may contain a hydroxyl group or a carboxylic acid group. The molecular weight in this case is measured using weight average molecular weight, and the number of double bonds in the molecule is measured by nuclear magnetic resonance spectroscopy.

The softening point of the tackifier (B) is not particularly limited. It is preferably <NUM> or more, and more preferably <NUM> to <NUM>, from the viewpoint of applicability to desired application usage, and good blending properties, coating properties, and adhesion.

The weight average molecular weight (Mw) of the tackifier (B) is <NUM> or more, more preferably <NUM> or more, and even more preferably <NUM> or more. Further, the weight average molecular weight (Mw) is <NUM> or less, more preferably <NUM> or less, even more preferably <NUM> or less, and particularly preferably <NUM> or less. When the weight average molecular weight (Mw) is <NUM> or more, the paint has good adhesion. In contrast, when the weight average molecular weight (Mw) is <NUM> or less, the paint tends to have good storage stability. The above range is also preferred even when the tackifier (B) does not contain a double bond.

The acid value of the tackifier (B) is not particularly limited. It is preferably <NUM> mgKOH/g-resin or less, and more preferably <NUM> mgKOH/g-resin or less. If the acid value exceeds the above value, the storage stability of the paint may be problematic. Although it is not limited thereto, the acid value is preferably <NUM> mgKOH/g-resin or more, and more preferably <NUM> mgKOH/g-resin or more, in terms of adhesion.

The hydroxy value of the tackifier (B) is not particularly limited, and it is preferably <NUM> mgKOH/g-resin or more, more preferably <NUM> mgKOH/g-resin, and even more preferably <NUM> mgKOH/g-resin or more. When the hydroxy value is equal to or more than the above value, the paint has good adhesion. The hydroxy value of the tackifier (B) is preferably <NUM> mgKOH/g-resin or less, more preferably <NUM> mgKOH/g-resin or less, and even more preferably <NUM> mgKOH/g-resin or less. When the hydroxy value is equal to or less than the above value, the paint has good storage stability.

The content of the tackifier (B) in the paint formulation of the present invention is <NUM> parts by mass or more, preferably <NUM> parts by mass or more. When the content of the tackifier (B) is <NUM> parts by mass or more, the paint has good storage stability. The content of the tackifier (B) is <NUM> parts by mass or less, preferably <NUM> parts by mass or less, even more preferably <NUM> parts by mass or less, and particularly preferably <NUM> parts by mass or less. When the content of the tackifier (B) is <NUM> parts by mass or less, good adhesion and chemical resistance are attained.

The paint formulation of the present invention may contain a pigment. Examples of pigments include titanium oxide, calcium carbonate, barium sulfate, talc, carbon black, and the like. Such pigments can be used singly or in a combination of two or more. The total amount of the pigment is preferably <NUM> to <NUM> parts by mass, and more preferably <NUM> to <NUM> parts by mass, per <NUM> parts by mass of the acid-modified polyolefin (A).

In the present invention, the paint formulation contains a hydrocarbon-based solvent (C), and may further contain at least one of an ester-based solvent (D1) or a ketone-based solvent (D2). The hydrocarbon-based solvent (C) is preferably contained in an amount of <NUM> parts by mass or more, more preferably <NUM> parts by mass or more, and even more preferably <NUM> parts by mass or more, per <NUM> parts by mass of the acid-modified polyolefin (A). The amount of the hydrocarbon-based solvent (C) is preferably <NUM> parts by mass or less, more preferably <NUM> parts by mass or less, and even more preferably <NUM> parts by mass or less. When the amount of the hydrocarbon-based solvent (C) is in the above range, excellent paint storage stability can be attained.

Examples of the hydrocarbon-based solvent (C) include aromatic hydrocarbon-based solvents, such as toluene, xylene, and Solvesso (registered trademark) <NUM>; aliphatic hydrocarbon-based solvents, such as hexane and heptane; and alicyclic hydrocarbon-based solvents, such as cyclohexane, cyclohexene, methylcyclohexane, and ethylcyclohexane. One or more of these solvents can be preferably used. Of these, xylene or cyclohexane is preferred. In particular, a combination of xylene, Solvesso (registered trademark) <NUM>, and cyclohexane is preferred.

The total amount of the ester-based solvent (D1) and ketone-based solvent (D2) is preferably <NUM> parts by mass or more, and more preferably <NUM> parts by mass or more, per <NUM> parts by mass of the acid-modified polyolefin (A). The total amount of the ester-based solvent (D1) and ketone-based solvent (D2) is preferably <NUM> parts by mass or less, more preferably <NUM> parts by mass or less, and even more preferably <NUM> parts by mass or less. When the total amount of the ester-based solvent (D1) and ketone-based solvent (D2) is within the above range, excellent paint storage stability can be attained.

Examples of the ester-based solvent (D1) include methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, amyl acetate, and the like. Preferred among these is ethyl acetate. Examples of the ketone-based solvent (D2) include acetone, methyl ethyl ketone, methyl isobutyl ketone, and methyl amyl ketone. Preferred among these is methyl ethyl ketone. It is also possible to combine two or more members selected from the ester-based solvents (D1) and the ketone-based solvents (D2).

The paint formulation may further contain an alcohol-based solvent (E). Addition of the alcohol-based solvent (E) can further improve the storage stability of the paint. The amount of the alcohol-based solvent (E) when added is preferably <NUM> parts by mass or more, and more preferably <NUM> parts by mass or more, per <NUM> parts by mass of the acid-modified polyolefin (A). The amount of the alcohol-based solvent (E) is preferably <NUM> parts by mass or less, and more preferably <NUM> parts by mass or less. When the amount of the alcohol-based solvent (E) is within the above range, remarkably excellent paint storage stability can be attained. Examples of the alcohol-based solvent (E) include methanol, ethanol, normal propyl alcohol, isopropyl alcohol, normal butanol, isobutanol, <NUM>-butanol, and the like.

The paint formulation of the present invention comprises the acid-modified polyolefin (A) and tackifier (B). The paint formulation of the present invention can be obtained by dilution as needed.

It is preferable that the paint formulation of the present invention is substantially a solvent-based paint formulation. Specifically, the total of the hydrocarbon-based solvent (C), ester-based solvent (D1), ketone-based solvent (D2), and alcohol-based solvent (E) is preferably <NUM> mass% or more, more preferably <NUM> mass% or more, and even more preferably <NUM> mass% or more, when the total amount of the solvents contained in the paint formulation is <NUM> mass%. There is no problem when the total of these components is <NUM> mass%. The paint formulation of the present invention can exhibit excellent water resistance and chemical resistance because it is substantially a solvent-based paint formulation.

The viscosity of the paint formulation when applied is not particularly limited. It is within the range of <NUM> to <NUM> mPa·sec, and more preferably within the range of <NUM> to <NUM> mPa·sec because good application workability and finish appearance are attained.

The paint formulation proposed in the present invention may contain an acrylic resin, alkyd resin, urethane resin, and the like insofar as the effect of the present invention is not impaired.

The paint formulation of the present invention is useful as a primer for a polyolefin substrate. The polyolefin substrate is preferably a polypropylene substrate.

The present invention is described in more detail below with reference to Examples. However, the present invention is not limited to the Examples.

<NUM> parts by mass of propylene-butene copolymer polymerized with a metallocene catalyst (propylene component: <NUM> mol% and <NUM>-butene component: <NUM> mol%), <NUM> parts by mass of toluene, <NUM> parts by mass of maleic acid anhydride, and <NUM> parts by mass of di-tert-butyl peroxide were placed in a <NUM>-L autoclave. The mixture was heated to <NUM>, and then stirred for <NUM> hours. After cooling the resulting reaction mixture, the reaction mixture was poured into a container containing a large amount of methyl ethyl ketone, and the resin was precipitated. Then, the solution containing the resin was centrifuged to thereby separate and purify an acid-modified propylene-butene copolymer in which maleic acid anhydride was graft-polymerized, (poly)maleic acid anhydride, and low-molecular-weight substances. After drying under reduced pressure at <NUM> for <NUM> hours, an acid-modified propylene-butene copolymer (acid value: <NUM> mgKOH/g-resin, weight average molecular weight: <NUM>,<NUM>, Tm: <NUM>) was obtained. The acid-modified polyolefin produced by this production example was referred to as A-<NUM>.

An acid-modified propylene-butene copolymer (acid value: <NUM> mgKOH/g-resin, weight average molecular weight: <NUM>,<NUM>, Tm: <NUM>) was obtained in the same manner as in Production Example <NUM>, except that the amounts of maleic acid anhydride and di-tert-butyl peroxide were respectively changed to <NUM> parts by mass and <NUM> parts by mass. The acid-modified polyolefin produced by this production example was referred to as A-<NUM>.

<NUM> parts by mass of A-<NUM>, <NUM> parts by mass of cyclohexane, and <NUM> parts by mass of xylene were placed in a <NUM>-mL four-necked flask equipped with a water-cooled reflux condenser and a stirrer. The mixture was heated to <NUM> while stirring, and stirring was continued for <NUM> hour to thereby obtain an A-<NUM> solution.

In the same manner as the A-<NUM> solution, A-<NUM> to A-<NUM> solutions were obtained by dissolving A-<NUM> to A-<NUM>.

<NUM> parts by mass of an amorphous chlorinated polyolefin (A-<NUM>) having a weight average molecular weight of <NUM>,<NUM> and a chlorine content of <NUM> wt%, <NUM> parts by mass of cyclohexane, and <NUM> parts by mass of butyl acetate were placed in a <NUM>-ml four-necked flask equipped with a water-cooled reflux condenser and a stirrer. The mixture was heated to <NUM> while stirring, and stirring was continued for <NUM> hour to thereby obtain an A-<NUM> solution.

<NUM> parts by mass of a rosin-based tackifier (B1-<NUM>) having a weight average molecular weight of <NUM>, a softening point of <NUM>, a hydroxy value of <NUM> mgKOH/g-resin, an acid value of <NUM> mgKOH/g-resin or less, and a double-bond equivalent of <NUM>, <NUM> parts by mass of Solvesso (registered trademark) <NUM>, and <NUM> parts by mass of cyclohexane were placed in a <NUM>-ml four-necked flask equipped with a water-cooled reflux condenser and a stirrer. The mixture was stirred at room temperature for <NUM> hours to thereby obtain a B1-<NUM> solution.

<NUM> parts by mass of a rosin-based tackifier (B1-<NUM>) having a weight average molecular weight of <NUM>, a softening point of <NUM>, a hydroxy value of <NUM> mgKOH/g-resin, an acid value of <NUM> mgKOH/g-resin or less, and a double-bond equivalent of <NUM>, <NUM> parts by mass of Solvesso <NUM>, and <NUM> parts by mass of cyclohexane were placed in a <NUM>-ml four-necked flask equipped with a water-cooled reflux condenser and a stirrer. The mixture was stirred at room temperature for <NUM> hours to thereby obtain a B1-<NUM> solution.

<NUM> parts by mass of a terpene-based tackifier (B1-<NUM>) having a weight average molecular weight of <NUM>, a softening point of <NUM>, a hydroxy value of <NUM> mgKOH/g-resin, an acid value of <NUM> mgKOH/g-resin or less, and a double-bond equivalent of <NUM>, <NUM> parts by mass of Solvesso <NUM>, and <NUM> parts by mass of cyclohexane were placed in a <NUM>-ml four-necked flask equipped with a water-cooled reflux condenser and a stirrer. The mixture was stirred at room temperature for <NUM> hours to thereby obtain a B1-<NUM> solution.

<NUM> parts by mass of a double bond-free rosin-based tackifier (B1-<NUM>) having a weight average molecular weight of <NUM>, a softening point of <NUM>, a hydroxy value of <NUM> mgKOH/g-resin, and an acid value of <NUM> mgKOH/g-resin or less, <NUM> parts by mass of Solvesso <NUM>, and <NUM> parts by mass of cyclohexane were placed in a <NUM>-ml four-necked flask equipped with a water-cooled reflux condenser and a stirrer. The mixture was stirred at room temperature for <NUM> hours to thereby obtain a B1-<NUM> solution.

<NUM> parts by mass of a rosin-based tackifier (B2-<NUM>) having a weight average molecular weight of <NUM>, a softening point of <NUM>, a hydroxy value of <NUM> mgKOH/g-resin, an acid value of <NUM> mgKOH/g-resin or less, and a double-bond equivalent of <NUM>, <NUM> parts by mass of Solvesso <NUM>, and <NUM> parts by mass of cyclohexane were placed in a <NUM>-ml four-necked flask equipped with a water-cooled reflux condenser and a stirrer. The mixture was stirred at room temperature for <NUM> hours to thereby obtain a B2-<NUM> solution.

<NUM> parts by mass of a terpene-based tackifier (B2-<NUM>) having a weight average molecular weight of <NUM>, a softening point of <NUM>, a hydroxy value of <NUM> mgKOH/g-resin, an acid value of <NUM> mgKOH/g-resin or less, and a double-bond equivalent of <NUM>, <NUM> parts by mass of Solvesso <NUM>, and <NUM> parts by mass of cyclohexane were placed in a <NUM>-ml four-necked flask equipped with a water-cooled reflux condenser and a stirrer. The mixture was stirred at room temperature for <NUM> hours to thereby obtain a B2-<NUM> solution.

Analytical measurement and evaluation of the thus-obtained acid-modified polyolefins were performed in the following manner.

The acid value (mgKOH/g-resin) of the acid-modified polyolefin (A) in the present invention is a value calculated by FT-IR (produced by Shimadzu Corporation, FT-IR8200PC) from the following formula using coefficient (f) obtained from a calibration curve prepared with a chloroform solution of maleic acid anhydride (produced by Tokyo Chemical Industry Co. ), and absorbance (I) of the elastic peak (<NUM>-<NUM>) of a carbonyl (C=O) bond of succinic anhydride in an acid-modified polyolefin solution.

The acid value of the tackifier (B) was measured according to JIS K <NUM>-<NUM>-<NUM>:<NUM> (ISO <NUM>:<NUM>).

The weight average molecular weight of the acid-modified polyolefin (A) in the present invention is a value measured by an Alliance e2695 gel permeation chromatograph (hereinafter "GPC"; standard substance: polystyrene resin, mobile phase: tetrahydrofuran, column: Shodex KF-<NUM> + KF-<NUM>, column temperature: <NUM>, flow rate: <NUM>/min, detector: photodiode array detector (wavelength <NUM> = ultraviolet light)) produced by Nihon Waters K.

The weight average molecular weight of the tackifier (B) in the present invention was determined by GPC measurement. The measurement was carried out under the following conditions. Then, the number average molecular weight (Mn) and weight average molecular weight (Mw) were determined from a calibration curve using commercially available monodispersed standard polystyrene. The value was measured using device: GPC HLC-<NUM> (produced by Tosoh Corporation), solvent: tetrahydrofuran, column: TSKgel G7000x1, TSKgel G4000x2, TSKgel G2000x1 (all produced by Tosoh Corporation), flow rate: <NUM>/min, sample: <NUM>/mL tetrahydrofuran solution at room temperature, and detector: photodiode array detector (wavelength: <NUM> = ultraviolet light).

The melting point of the acid-modified polyolefin (A) in the present invention is a value measured by a differential scanning calorimeter (hereinafter "DSC," Q-<NUM>, produced by TA Instruments Japan Inc. ) from the top temperature of the melting peak when melting by heating at a rate of <NUM>/min and resinification by cooling are performed, and melting by heating is again performed.

The softening point of the tackifier (B) in the present invention was measured according to JIS K <NUM> (<NUM>).

The paint formulation shown in Example <NUM> was produced in the following manner. <NUM> parts by mass of xylene and a pigment having the mass ratio shown in Table <NUM> were added to <NUM> parts by mass of the A-<NUM> solution (A-<NUM>, <NUM> parts by mass), and the mixture was dispersed using a bead mill until the size evaluated by a grindometer became <NUM> or less, thus obtaining a pigment dispersion. The B-<NUM> solution was added to the pigment dispersion (A-<NUM>, <NUM> parts by mass) in a manner such that the amount of B-<NUM> was <NUM> parts by mass. Subsequently, the mixture was mixed with <NUM> parts by mass of cyclohexane and <NUM> parts by mass of methyl ethyl ketone, thus obtaining the paint formulation shown in Example <NUM>.

The acid-modified polyolefin (A), tackifier (B), hydrocarbon-based solvent (C), ester-based solvent (D1), ketone-based solvent (D2), and alcohol-based solvent (E) were mixed in the proportion shown in Table <NUM>. Except for the proportion, the components were mixed in the same manner as in Example <NUM> to obtain the paint formulations shown in Examples <NUM> to <NUM>. The ester-based solvent (D1), ketone-based solvent (D2), and alcohol-based solvent (E) were added to a pigment dispersion.

The acid-modified polyolefin (A), tackifier (B), hydrocarbon-based solvent (C), ester-based solvent (D1), ketone-based solvent (D2), and alcohol-based solvent (E) were mixed in the proportion shown in Table <NUM>. Except for the proportion, the components were mixed in the same manner as in Example <NUM> to obtain the paint formulations shown in Comparative Examples <NUM> to <NUM>. The ester-based solvent (D1), ketone-based solvent (D2), and alcohol-based solvent (E) were added to a pigment dispersion.

The paint stability of the paint formulations produced in the Examples and Comparative Examples was evaluated for the following items. Tables <NUM> and <NUM> show the results.

The viscosity (flow time) of the paint formulations produced in the Examples and Comparative Examples was measured by a Ford cup. The paint formulations were allowed to stand at -<NUM> and <NUM> for <NUM> days to evaluate the appearance and viscosity of each paint formulation. The viscosity was measured by a Ford cup (No. <NUM>, <NUM>). Evaluation criteria:.

<NUM> parts by mass of a paint formulation obtained in the Example or Comparative Example, <NUM> parts by mass of Solvesso <NUM>, and <NUM> parts by mass of toluene were mixed to adjust the solvent composition to that when applied. Hereinbelow, the adjusted paint formulations are referred to as diluted paint formulations.

A polypropylene substrate was degreased with isopropyl alcohol to make a test sheet. The diluted paint formulation produced as above was applied by spraying to the test sheet to a dry film thickness of <NUM> µm. As a colored base paint, Retan (registered trademark) PG white (tradename, produced by Kansai Paint Co. ) was applied by spraying to the diluted paint formulation side of the test sheet to a dry film thickness of <NUM> µm. Heating was then performed in an oven at <NUM> for <NUM> minutes, thereby obtaining a test piece including a laminated paint film. Various paint film performance tests described below were performed on the test piece.

Test pieces produced as above were evaluated for the following items. Tables <NUM> and <NUM> show the results.

Cross-cuts reaching the substrate of each test piece were made using a cutter knife to form a grid of <NUM> squares (<NUM> x <NUM>). Adhesive cellophane tape was applied to the surface of the grid portion, and the tape was peeled off rapidly at <NUM>. Then, the number of squares of the paint film remaining was checked.

After each test piece was immersed in hot water at <NUM> for <NUM> days, the surface of the paint film was observed. Evaluation criteria:.

Each test piece was immersed in a test solution having a weight ratio of gasoline/ethanol = <NUM>/<NUM> at <NUM>, and the coating surface conditions such as blistering and peeling after <NUM> minutes were observed and evaluated according to the following criteria.

Blistering with a diameter of less than <NUM> means that the maximum diameter of a blister on the coating surface is less than <NUM>.

A test solution was prepared based on an alcohol-added fuel solution for test designated by ISO1817. The test solution comprises <NUM> mass% of <NUM>,<NUM>,<NUM>-trimethylpentane, <NUM> mass% of toluene, <NUM> mass% of diisobutylene, <NUM> mass% of methanol, <NUM> mass% of ethanol, <NUM> mass% of water, and <NUM> ppm of formic acid. The test piece was immersed in the test solution at <NUM> for <NUM> minutes. Thereafter, the test piece was dried by heating in an oven at <NUM> for <NUM> minutes, and cross-cuts reaching the substrate of each test piece were made using a cutter knife to form a grid of <NUM> squares (<NUM> x <NUM>). Adhesive cellophane tape was applied to the surface of the grid portion, and the tape was peeled off rapidly at <NUM>. Then, the number of squares of the paint film remaining was checked.

The paint film of the test piece produced was subjected to an accelerated weather resistance test using a Sunshine Weather Meter (Suga Test Instruments Co. The test was carried out under the following conditions: irradiation temperature: <NUM>±<NUM>, humidity: <NUM>±<NUM>%, sample surface irradiance: <NUM> W/m<NUM>, light wavelength range: <NUM> to <NUM>, irradiation time: <NUM> hours, and rainfall conditions: raining for <NUM> minutes with a <NUM>-minute cycle.

Claim 1:
A paint formulation comprising an acid-modified polyolefin (A) and a tackifier (B), and satisfying the following (a) and (b):
(a) the acid-modified polyolefin (A) has crystallinity; and
(b) the tackifier (B) has a double-bond equivalent of <NUM> or more, as defined by the formula: double-bond equivalent = weight average molecular weight/number of double bonds in a molecule, or contains no double bond,
wherein the acid-modified polyolefin (A) is a grafted product of at least one of polyethylene, polypropylene, and a propylene-α-olefin copolymer with at least one of α,β-unsaturated carboxylic acid and acid anhydride thereof,
wherein the tackifier (B) is an amorphous oligomer having a weight average molecular weight of <NUM> or more and <NUM> or less, and is a thermoplastic resin that is liquid or solid at room temperature, and
wherein the tackifier (B) is contained in an amount of <NUM> to <NUM> parts by mass per <NUM> parts by mass of the acid-modified polyolefin (A).