WO2008093215A1

WO2008093215A1 - Primers and a method of coating in which they are used

Info

Publication number: WO2008093215A1
Application number: PCT/IB2008/000203
Authority: WO
Inventors: Toshiya Kitamura
Original assignee: Basf Coatings Japan Ltd.
Priority date: 2007-01-29
Filing date: 2008-01-28
Publication date: 2008-08-07
Also published as: JP2008184523A

Abstract

To provide a primer which has excellent adhesion on a plastic base material, and with which the inter- layer adhesion with the paint film which forms the base on recoating (repainting) is excellent, and a method of coating in which this primer is used. [Means of Resolution] A primer which is characterized in that it contains (A) chlorinated polyolefin resin which has a chlorine content of from 5 to 50 mass% and a weight average molecular weight of from 1,000 to 100,000, (B) diol which has a weight average molecular weight of from 120 to 1,000 and (C) hardening catalyst, and in that the proportions with respect to the mass of the resin solid fraction of the (A) component in which these components are included are from 0.5 to 12 mass% of the (B) component and from 0.01 to 1.5 mass% of the (C) component.

Description

Primers and a method of coating in which they are used

Specification [Technical Field] [0001]

The invention concerns primers which have excellent adhesion on plastic base materials and especially polyolefin base materials, and which have excellent adhesion with the surface paint film when recoating (repainting) without sanding, and a method of coating in which these primers are used. [0002]

Polyolefin moldings are often used as parts of automobile outer panels and domestic electrical goods for example and more recently recycled polyolefin moldings have been reused. A primer which contains a chlorinated polyolefin is used in those cases where a two-liquid type top-coat paint which includes a polyisocyanate compound is used as the top-coat paint of a polyolefin molding in order to improve the adhesion of the top-coat paint film on the polyolefin molding. However, there is a problem in that the adhesion with the polyolefin base material is inadequate in cases where recycled rubber products (such as styrene/butadiene rubber, isoprene rubber and the like) which have been included in polyolefin moldings and polyolefin moldings to which only a small amount of or no hydroxyl group containing polyolefin has been added are reused. [0003]

Furthermore, in those cases where repair-coating is carried out after a primer and a top-coat paint have been coated on a polyolefin molding, the paint film has generally been sanded to remove dirt and marks and then this part has been repainted (recoated) with primer and top-coat paint. At this time the recoating with primer and top-coat paint can be carried out on a paint film which has not been ground (unsanded) without grinding the paint film which is to be repaired. In such a case there is a problem in that the inter-layer adhesion of the under-layer paint film and the recoated primer is inadequate . [0004]

Paint compositions which have as essential components (A) chlorinated polyolefin resin which has a chlorine content of from 10 to 50 mass%, (B) acrylic modified chlorinated polyolefin resin, (C) acrylic resin and/or polyester resin of weight average molecular weight from 2,000 to 50,000 and hydroxyl group value from 10 to 90 mgKOH/g and (D) isocyanate compound in which the ratio of the isocyanate equivalent and the hydroxyl group equivalent [Isocyanate Equ. ]/ [Hydroxyl Group Equ.] is from 0.5/1.0 to 1.2/1.0 and in which, of the total mass (solid fractions) of the (A) , (B) and (C) components, the (A) component accounts for from 3 to 20 mass%, the (B) component accounts for from 5 to 40 mass% and the (C) component accounts for from 40 to 92 mass% are known as two-liquid type paint compositions which have an excellent high gloss appearance, weather resistance, solvent resistance and coating operability and provide excellent adhesion on being coated directly without the application of a primer on polyolefin moldings with which adhesion is difficult to achieve (for example, see Patent Citation 1) . However, since these combine the function of a primer and the function of a top-coat paint the adhesion with polyolefin base material moldings is inadequate and, furthermore, there is a problem with the pot-life of these two-liquid type paints . [0005]

Furthermore, resin compositions for coating purposes which have good adhesion on polyolefin base materials which are characterized in that they include as essential components (1) polymer which has acetoacetoxy groups in a side chain which has been obtained by polymerizing or copolymerizing an acetoacetoxy group containing monomers with other copolymerizable monomers, as required, in the presence of from 5 to 50 parts by weight of a chlorinated polyolefin resin of chlorine content from 15 to 50 wt% and (2) isocyanate compound are known as resin compositions for coating purposes with which paint films which have excellent adhesion, hot water resistance and gasoline resistance as well as excellent paint storage stability can be formed and which can be coated directly without the need for any pre-treatment such as coating with primer etc. on polyolefin base material moldings (for example, see Patent Citation 2) . However, these resin compositions for coating purposes are two-liquid type paints and there are problems with the pot-life. [0006]

Furthermore, a primer for use on plastics which is characterized in that it contains (A) chlorinated polyolefin which has a chlorine content of from 16 to 22 wt% and which is of molecular weight from 30,000 to 120,000, (B)- blocked polyisocyanate where an isocyanurate-type aliphatic and/or alicyclic polyisocyanate has been blocked with malonic acid di- alkyl ester and acetoacetic acid ester and (C) polyol resin is known as a primer for use on plastics which has excellent adhesion on polyolefin base material moldings and excellent recoat adhesion on paint films (for example, see Patent Citation 3) . However, although the adhesion is good when the polyolefin-based base material molding or paint film has been sanded, there is a problem in that the recoat adhesion is inadequate in the absence of sanding. [ 0007 ]

[Patent Citation 1]

Japanese Unexamined Patent Application Laid Open

2005-139336

[Patent Citation 2]

Japanese Unexamined Patent Application Laid Open H8-311397

[Patent Citation 3]

Japanese Unexamined Patent Application Laid Open 2002-121462

[Disclosure of the Invention]

[Problems to be Resolved by the Invention]

[0008]

The present invention is intended to provide primers which have excellent adhesion on plastic base materials, and especially on polyolefin base materials, and which have excellent inter-layer adhesion with underlying paint films, and especially urethane resin- based top-coat paint films, on recoating (repainting) , and to provide a method of coating in which these primers are used.

[Means of Resolving These Problems]

[0009]

As a result of thorough research carried out with a view to resolving the abovementioned problems, the inventors have discovered that by adding a low molecular weight diol and a hardening catalyst to a composition which contains a specified chlorinated polyolefin resin the recoat adhesion on a molding comprising a plastic base material such as a polyolefin base material or a paint film is greatly improved, and the invention is based upon this discovery. [0010]

That is to say, the present invention provides a primer which is characterized in that it contains (A) chlorinated polyolefin resin which has a chlorine content of from 5 to 50 mass% and a weight average molecular weight of from 1,000 to 100,000, (B) diol which has a weight average molecular weight of from 120 to 1,000 and (C) hardening catalyst, and in that the proportions with respect to the mass of the resin solid fraction of the (A) component in which these components are included are from 0.5 to 12 mass% of the (B) component and from 0.01 to 1.5 mass% of the (C) component . [0011]

Furthermore, the present invention also provides a method for coating plastic moldings which is characterized in that the abovementioned primer and a top-coat paint are coated sequentially on the plastic molding, baked and hardened and a top-coat paint film is formed.

Furthermore, the present invention also provides a method for coating plastic moldings which is characterized in that the abovementioned primer and a top-coat paint are coated sequentially on the plastic molding, baked and hardened and then the abovementioned primer and a top-coat paint are coated sequentially on the top-coat paint film, baked and hardened.

Furthermore, the present invention provides a method for coating moldings which is characterized in that the abovementioned primer and a top-coat paint are coated sequentially, baked and hardened on the top-coat paint film of a molding on which a top-coat paint has been coated and hardened. [0012]

Furthermore, the present invention also provides a method for coating a molding in which, in the abovementioned methods for coating a molding, the topcoat paint is a two-liquid type urethane resin paint of the one-coat type.

Furthermore, the present invention also provides a

I method for coating a molding in which, in the abovementioned methods for coating a molding, the topcoat paint comprises two layers, namely a base-coat paint film and a clear paint film, and at least the clear paint is a two-liquid type urethane resin paint.

Furthermore, the present invention also provides a method for coating a molding in which, in the abovementioned methods for coating a molding, the topcoat paint comprises three layers, namely a colored base-coat paint film, a pearl base-coat paint film and a clear paint film, and at least the clear paint is a two-liquid type urethane resin paint. [Effect of the Invention]

[0013]

By using a primer of this invention it is possible to obtain paint films which have excellent adhesion of the primer paint film on a plastic base material, and especially a polyolefin base material, and paint films which have excellent inter-layer adhesion of the primer paint film with a urethane resin-based top-coat paint film which forms the base when recoating (repainting) .

[Embodiment of the Invention]

[0014]

The (A) component chlorinated polyolefin resin which is used in the invention has a chlorine content of from 5 to 50 mass%, preferably of from 15 to 35 mass%, and most desirably of from 18 to 25 mass% . In those cases where the chlorine content exceeds 50 mass% the adhesion with a plastic base material, and especially a polyolefin base material, or a paint film is poor, and in those cases where the chlorine content is less than 5 mass% the solubility in solvents is reduced and problems arise with storage stability.

[0015]

Furthermore, the weight average molecular weight of the (A) component chlorinated polyolefin resin is from 1,000 to 100,000, preferably from 5,000 to 90,000, and most desirably from 10,000 to 80,000. If the weight average molecular weight exceeds 100,000 then problems arise in that the coating operability becomes poor, and in those cases where it is less than 1,000 the resin itself lacks cohesive strength and so a problem arises in that a normal paint film cannot be obtained.

Resins where a polymer resin which has a polyolefin resin as the main skeleton has been modified with chlorine can be cited as examples of the (A) component chlorinated polyolefin resin. As well as polyethylene resins, polypropylene resins and the like, modified polyolefin resins which have been modified with maleic anhydride or the like, and polyolefin-based polymer compounds which have hydroxyl groups, carboxyl groups, methacryloyl groups, acryloyl groups or epoxy groups, for example, at the ends of the molecules or in the molecular chains can also be cited as examples of the polyolefin resin. [0016]

Actual examples of the (A) component chlorinated polyolefin resin include chlorinated polyethylene resins, chlorinated polypropylene resins, chlorinated ethylene/propylene copolymers, chlorinated ethylene/ vinyl acetate copolymers and modified resins where acid anhydrides such as maleic anhydride and the like have been copolymerized in these chlorinated polyolefin resins .

Furthermore, a commercial product can be used for the (A) component chlorinated polyolefin resin. Examples of such commercial products include Superclon 773H, Superclon 882, Superclon 892L, Superclon 832L, Superclon E (produced by the Nippon Seishi Chemical Co.), Hardren 14 LLB, Hardren CY9122, Hardren HM-21 and Hardren 13-MLJ (produced by the Toyo Kasei Kogyo Co.). [0017]

The (B) component diol which is used in the invention fulfills the role of improving the ability of the chlorinated polyolefin resin to wet a plastic material and, when recoating, it fulfills the role of heightening the ability to wet the top-coat layer, and especially a urethane resin-based top-coat paint film, which forms the base, and heightens adhesion. In those cases where unreacted isocyanate compound remains in the vicinity of the interface with the primer in a urethane resin-based top-coat paint film which forms the lower layer which is in contact with the primer, the low molecular weight diol, simply on the basis of its high mobility, migrates in the primer paint film to the vicinity of the interface and there is great potential for it to react with the unreacted isocyanate compound and it is thought that this has a pronounced effect which improves the inter-layer adhesion between the primer paint film and the top-coat paint film on recoating. [0018]

The weight average molecular weight of the (B) component diol is from 120 to 1,000, and preferably from 120 to 800. In those cases where the weight average molecular weight of the (B) component diol is less than 120 the storage stability of the primer is reduced due to reduced solubility in the main aromatic based solvent, and this is undesirable. In those cases where the weight average molecular weight exceeds 1,000 no improving effect on the adhesion on the top-coat paint film, and especially a urethane resin-based topcoat paint film, of the lower layer is observed.

Actual examples of the (B) component low molecular weight diol include dipropylene glycol, triethylene glycol, hydrogenated bisphenol A and the like. Furthermore, diols which are the reaction products of dibasic acids and an excess of a diol, and lactone such as caprolactone adducts with these diols and the like can also be used as the (B) component low molecular weight diol . Actual examples of the diols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butanediol, neopentyl glycol, pentanediol, hexanediol, heptanediol, octanediol, butylethylpropanediol, cyclohexanediol, cyclohexanedimethanol and phenyldimethanol . Examples of the dibasic acids include malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azeleic acid, sebacic acid, terephthalic acid, isophthalic acid, hexahydroterephthalic acid, maleic acid, fumaric acid and the like, and the acid anhydrides of these dibasic acids. Furthermore, they may also be modified with monoglycidyl compounds such as butyl glycidyl ether, 2-ethylhexyl glycidyl ether, sec-butylphenol glycidyl ether, neodecanoic acid glycidyl ester and the like which include a mono- glycidyl group. [0019]

In this invention, the proportion of the (B) component included is from 0.5 to 12 mass%, preferably from 1 to 10 mass%, and most desirably from 1.5 to 8 mass%, with respect to the mass of the (A) component resin solid fraction. If the proportion of the (B) component included is less than 0.5 mass% then the adhesion of the primer paint film on the top-coat paint film, and especially a urethane resin-based top-coat paint film, which forms the base is inadequate, and in those cases where it exceeds 12 mass% the storage stability of the primer falls as the compatibility with the main chlorinated polyolefin resin which forms the (A) component falls, and this is undesirable.

Moreover, the proportion of the (B) component included is the proportion of the effective component of the (B) component included, and here the effective component means in those cases where it has been diluted with a solvent or the like the component not including the solvent or the like.

Furthermore, the resin solid fraction signifies the residual fraction on heating measured with the method described in JIS K5601-1-2. [ 0020 ]

The (C) component hardening catalyst which is used in the invention should be a catalyst which promotes the reaction of the (B) component diol with the reactive component which is included in the top-coat paint film which forms the base and in particular it is preferably a catalyst which is used in urethane resins. In those cases where the top-coat paint film which forms the base is a urethane resin-based paint film the reaction of the hydroxyl groups of the primer layer of the recoat with the unreacted isocyanate of the urethane resin-based top-coat paint film which forms the base is promoted and the adhesion at the time of un-sanded recoating is improved.

[0021]

In practical terms, the (C) component hardening catalyst is, for example, a tin compound or a zinc compound. Examples of tin compounds include tin halides such as tin chloride and tin bromide, and organo-tin compounds such as dibutyltin diacetate and dibutyltin dilaurate and the like, and examples of zinc compounds include zinc halides such as zinc chloride and zinc bromide and zinc salts of organic acids such as zinc octylate, zinc laurate and the like. One type of tin compound or zinc compound, or a combination of two or more types, may be used for the hardening reaction catalyst, and other hardening reaction catalysts may be used conjointly. [ 0022 ]

In this invention the proportion of the (C) component included is from 0.01 to 1.5 mass%, preferably from 0.02 to 1.0 mass%, and most desirably from 0.05 to 0.8 mass% with respect to the mass of the (A) component resin solid fraction. If the proportion of the (C) component is less than 0.01 mass% then the promoting effect on the hardening reaction is not realized satisfactorily, and in those cases where it exceeds 1.5 mass% a reduction in the recoat adhesion thought to be due to excessive hardening of the paint film arises, and this is undesirable.

Moreover, the proportion of the (C) component included is the proportion of the effective component of the (C) component which is included and the effective component in cases where it has been diluted with a solvent or the like signifies the component not including the solvent or the like. [0023]

Liquid epoxy resins of low molecular weight, color pigments, true pigments, organic solvents and various types of additive can also be used, as required, in a primer of this invention. Examples of color pigments include organic pigments such as the azo-lake based pigments, phthalocyanine pigments, indigo-based pigments, perynone-based pigments, perylene-based pigments, quinophthalone-based pigments, dioxazine- based pigments, quinacridone-based pigments and the like and inorganic pigments such as chrome yellow, yellow iron oxide, red iron oxide, titanium dioxide and the like. The true pigments include kaolin, talc and the like. [0024]

Furthermore, no particular limitation is imposed upon the organic solvent provided that the various components can be dissolved therein. Examples include aliphatic hydrocarbons such as n-hexane, n-heptane and n-octane, aromatic hydrocarbons such as benzene, toluene and xylene, halogenated hydrocarbons such as chloroform and carbon tetrachloride, ethers such as dibutyl ether, tetrahydrofuran and 1,4-dioxane, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, and esters such as ethyl acetate, n-propyl acetate and n-butyl acetate. One of these solvents may be used, or a combination of two or more types can be used. No particular limitations are placed on the method of compounding the various components or the method of adding luster pigments, color pigments, organic solvents and the various types of additive and resin and a variety of methods can be used, and the order of mixing and the addition order can also be varied. [0025]

Coating with a coating machine as generally used, such as a machine of the air spray, airless spray, electrostatic air spray, flow-coating or dip-coating type for example, or with a brush after adjusting the primer to the desired viscosity by warming and adding organic solvent, as required, can be used as a suitable method of coating in which a primer of this invention is used, but air spray coating is preferred. The dry paint film thickness of the primer paint film is preferably of from 2 to 15 μm and most desirably of from 4 to 10 μm. [0026]

After coating a primer of this invention the topcoat paint is preferably coated wet-on-wet without baking the primer. The top-coat paint may be a paint of the one-coat type, the two-coat type or the three- coat type, and a two-liquid type urethane resin paint is preferred for the paint which forms the uppermost paint film layer. No particular limitation is imposed upon the urethane resin-based top-coat paint, but it should be such that the paint film is formed by the reaction between a polyol and an isocyanate compound. [0027]

The top-coat paints of the one-coat type may be solid paints or paints which have a metallic tone. The dry paint film thickness of the top-coat paint is preferably from 15 to 40 μm, and most desirably from 20 to 35 μm. The two-coat type paints are generally combinations of a colored base-coat paint or a pearlescent base-coat paint, such as a metallic base- coat paint, and a clear paint, and the dry paint film thickness of the base-coat paint is preferably from 10 to 20 μm and the dry film thickness of the clear paint is preferably from 20 to 40 μm, and most desirably from 25 to 35 μm. The three-coat type paints are generally combinations of a colored base-coat paint, a pearlescent base-coat paint and a clear paint, and the dry paint film thickness of the colored base-coat paint is preferably from 5 to 15 μm, the dry film thickness of the pearlescent base-coat paint is preferably from 5 to 15 μm, and the dry film thickness of the clear paint is preferably from 20 to 40 μm, and most desirably from 25 to 35 μm. In those cases where these paints are over-painted they are preferably all painted wet-on-wet in the unhardened state . [0028]

Baking and drying conditions for a urethane resin- based top-coat paint of from 5 minutes to 3 days at from 20 to 150ºC are preferred, and conditions of from 10 to 30 minutes at from 80 to 140ºC are more desirable.

The moldings which are coated with a primer of this invention may be, for example, moldings comprising polyolefin base materials such as polyethylene and polypropylene, and plastic base materials which include polyolefins . Moreover, the primer can also be used on moldings comprising plastic base materials such as ABS resin, PC resin, nylon and the like. [ 0029 ]

Recoating (repainting) in this invention includes, for example, methods in which a primer of this invention and a top-coat paint are coated sequentially and baked and hardened on a molding on which a top-coat paint has been coated and hardened to form a top-coat paint film, and methods in which recoating is carried out in those cases where dust has been deposited or there is failure of the paint film after a primer of this invention and a top-coat paint have been coated sequentially and baked and hardened on a plastic molding. In this case said primer is coated again after removing the dust and without sanding the whole top-coat paint film and the primer and the top-coat paint should be coated sequentially and baked in essentially the same way as on the first occasion. Furthermore, recoating (repainting) can be carried out even if part of the top-coat paint film which forms the base has peeled away, and a paint film which has excellent adhesion can be obtained by coating the primer and top-coat paint sequentially and baking. [0030]

Examples of coated objects which can be obtained with the method of coating of this invention include structural materials, metal products, plastic products, and rubber products . In more practical terms these include automobiles and automobile parts (for example bodies, bumpers, spoilers, mirrors, wheels and interior decorative parts, which are made of a variety of materials), metal sheets such as steel sheets, bicycles, bicycle parts, materials used on roads (for example guard rails, traffic signs, sound-deadening walls and the like) , materials used in tunnels (for example side wall panels and the like) , ships, railway rolling stock, aircraft, musical instruments, domestic electrical goods, building materials, containers, office accessories, sports accessories, toys and the like.

[Illustrative Examples] [0031]

The invention is described in more practical terms below by means of examples of production, illustrative examples and comparative examples. Moreover, the invention is not limited by these illustrative examples. While it is not indicated specifically, hereinafter the terms "parts" and "%" signify "parts by mass" and "mass%" respectively. Furthermore, in Tables 1 to 6 the units of the numerical values which indicate the amount of each component compounded are parts by mass.

Moreover, in the examples and comparative examples the evaluation of the various features was carried out using the methods outlined below. [0032]

<Method of Evaluating Paints and Paint Films> (Primer Storage Stability) The primer was stored for 10 days at 40ºC and its state was evaluated on the basis of the following criteria .

O: No abnormality observed D: Slight separation observed X: Pronounced separation observed [0033] (Primer Coating Operability)

The surface of a commercial black polypropylene plate (length 70 mm x width 150 mm x thickness 3 mm) was wiped with isopropyl alcohol and the dust and contamination which had been deposited on the sample for coating were removed. Then the viscosity of a primer shown in Table 2 or 3 was adjusted with xylene to a Ford cup #4 viscosity (20ºC) of 11 seconds and coated with an air sprayer and the coating operability was evaluated in accordance with the criteria indicated below.

O: No abnormality, coating was possible

X: Coating impossible due to coagulation of the paint, or a cobweb state arose during coating and normal coating was impossible [0034] (Adhesion of First Top-coat)

A top-coat paint of which the viscosity had been adjusted to a Ford cup #4 viscosity (25ºC) of 12 seconds with a diluting solvent (butyl acetate/xylene = 70/30 (ratio by mass) solvent mixture) was air spray coated wet-on-wet over a primer paint film which had been coated in such a way as to form a dry film thickness of from 6 to 8 μm on a commercial black polyolefin plate essentially as described above and left to stand for 5 minutes at room temperature and then dried by being maintained at 90ºC for 20 minutes. The coating was carried out wet-on-wet in all cases, including the two-coat and three-coat types, in such a way that the dry paint film thickness of the top-coat paint was 25 μm in the case of a one-coat paint, and in the case of the base paint of a two-coat type the dry paint film thickness was 15 μm, in the case of the colored base-coat paint of a three-coat type the dry paint film thickness was 10 μm and in the case of the pearl base-coat paint of a three-coat type the dry paint film thickness was 8 μm, and in the case of the clear paint the dry film thickness was 30 μm. For testing, the coated sheets obtained were left to stand for 60 minutes at room temperature and then 11 cuts were made with a cutter knife in the paint film in the length and width directions with a spacing of 2 mm to provide 100 squares, peeling was carried out with cellophane tape and the state of peeling was evaluated on the basis of the criteria indicated below. [0035]

O: No peeling of the paint film (100/100 expressed as remaining squares) D: Part of the paint film peeled off (from 90/100 to 99/100 expressed as remaining squares)

X: Peeling of the paint film (from 0/100 to 89/100 expressed as remaining squares)

In those cases where peeling of the paint film was observed the site of the peeling was confirmed as being between the base and the primer paint film or between the primer paint film and the top-coat paint film. [0036] (Adhesion of First Top-coat and Recoated Top-coat)

A top-coat paint of which the viscosity had been adjusted to a Ford cup #4 (25°C) viscosity of 12 seconds with a diluting solvent (butyl acetate/xylene = 70/30 (ratio by mass) solvent mixture) was air spray coated wet-on-wet over a primer paint film which had been coated in such a way as to become from 6 to 8 μm on a commercial black polyolefin plate essentially as described above and left to stand for 5 minutes at room temperature and then dried by being maintained at 100ºC for 40 minutes. The coating was carried out wet-on-wet in all cases, including the two- coat and three-coat types, in such a way that the dry paint film thickness of the top-coat paint was 25 μm in the case of a one-coat type paint, and in the case of the base paint of a two-coat type the dry paint film thickness was 15 μm, in the case of the colored base- coat paint of a three-coat type the dry paint film thickness was 10 μm and in the case of the pearl base- coat paint of a three-coat type the dry paint film thickness was 8 μm, and in the case of the clear paint the dry film thickness was 30 μm. The coated sheet was left to stand for 24 hours at room temperature and then the primer and top-coat paint were coated wet-on-wet with an air spray in essentially the same way as on the first occasion and left to stand for 5 minutes at room temperature and dried for 20 minutes at 80ºC.

[0037]

For testing, the coated sheets obtained were left to stand for 60 minutes at room temperature and then 11 cuts were made with a cutter knife in the paint film in the length and width directions with a spacing of 2 mm to provide 100 squares, peeling was carried out with cellophane tape and the state of peeling was evaluated on the basis of the criteria indicated below. O: No peeling of the paint film (100/100 expressed as remaining squares)

D: Part of the paint film peeled off (from 90/100 to 99/100 expressed as remaining squares)

[0038]

Example of Resin Production 1 (Production of a Diol Resin Solution)

1, 6-Hexanediol (561 parts) and 347.1 parts of adipic acid were introduced into a glass flask of capacity 2 L which had been furnished with a thermometer and a stirrer and, after slowly raising the temperature to 140ºC, the temperature was raised to 190ºC over a period of 3 hours. The mixture was maintained at 190ºC for 2 hours and the esterification reaction proceeded, and then the temperature was raised to 210ºC over a period of 2 hours and the esterification was carried out until the resin acid value fell below 1. The resin so obtained was cooled, 91.9 parts of xylene were added and the diol resin

solution B-I of weight average molecular weight 330 and resin solid fraction 90 mass% was obtained.

[0039]

Examples of Resin Production 2 to 4 (Production of Diol

Resin Solutions)

Resin syntheses were carried out in the same way as in Example of Resin Production 1 with the raw materials shown in Table 1 and the diol resin solutions B-2 to B-4 shown in Table 1 were obtained. The raw material "Cardura E-10" in Table 1 is a mono-glycidyl ester of versatic acid (produced by the Japan Epoxy Resin Co . ) . [0040]

Table 1

[ 0041 ]

Example of Primer Production 1

Chlorinated polypropylene resin solution (trade name "Hardren CY9122", produced by the Toyo Kasei Kogyo Co., maleic anhydride modified chlorinated polypropylene resin, chlorine content 22 mass%, weight average molecular weight from 50,000 to 60,000, resin solid fraction 20%) (750 parts) , 99 parts of Typake CR-90 (titanium oxide, produced by the Ishihara Sangyo Co.), 0.1 part of pigment black FW200 beads (carbon black, produced by the Degussa Co.) and 0.9 part of TSY-I (yellow pigment, produced by the Toda Pigment Co.) were introduced into a dispersing container and dispersed until the particle size was less than 15 μm. On reaching the target particle size the dispersion was stopped, 5 parts of the diol B-I produced in Example of Resin Production 1, 0.9 part of dibutyltin dilaurate and 144.1 parts of xylene were added and stirred thoroughly and the primer P-I of Example of Primer Production 1 shown in Table 2 was obtained.

[0042]

Examples of Primer Production 2 to 16

The primers P-2 to P-16 shown in Tables 2 and 3 were obtained in the same way as in Example of Primer Production 1.

[00431

Table 2

[0044] Table 3

[ 0045 ]

The meanings of the abbreviations and trade names shown in the tables are indicated below.

1) Typake CR-90: Titanium oxide, produced by the Ishihara Sangyo Co.

2) Acicular Electrically Conductive Titanium Oxide: Electrically conductive titanium oxide-, produced by the Ishihara Sangyo Co.

3) Pigment Black FW200 Beads: Carbon black, produced by the Degussa Co.

4) PRINTEX L: Electrically conductive carbon black, produced by the Degussa Co.

5) TSY-I: Yellow pigment, produced by the Toda Pigment Co .

6) Hardren CY9122: Produced by the Toyo Kasei Kogyo Co., maleic anhydride modified chlorinated polypropylene resin, chlorine content 22 mass%, weight average molecular weight from 50,000 to 60,000, residue on heating 20 mass%.

[0046]

7) Superclon 892L: Produced by the Nippon Seishi Chemical Co., maleic anhydride modified chlorinated polypropylene resin, chlorine content 22 mass%, weight average molecular weight from 60,000 to 70,000, residue on heating 20 mass%.

8) Desmodure BL3175: Produced by the Sumitomo Beyer Urethane Co., HDI isocyanurate blocked with MEK oxime, NCO content 11.2 mass%, residue on heating 75 mass% . 9) Desmodure BL3272MPA: Produced by the Sumitomo Beyer Urethane Co., HDI isocyanurate blocked with D-caprolactam, NCO content 10.2 mass%, residue on heating 72 mass%.

10) Desmodure BL4265SN: Produced by the Sumitomo Beyer Urethane Co., IPDI isocyanurate blocked with MEK oxime, NCO content 8.9 mass%, residue on heating 65 mass%.

[0047]

Example of Top-coat Paint Production 1 (Two-liquid type urethane resin paint for one-coat purposes)

Acrylic resin LB-9020 (produced by the BASF Coatings Japan Co., residue on heating 55 mass%, hydroxyl group value 56 mgKOH/g) (45.5 parts), 24 parts of Typake CR-90 (titanium oxide, produced by the Ishihara Sangyo Co.), 0.1 part of Pigment Black FW200 beads (carbon black, produced by the Degussa Co, ) and 0.6 part of TSY-I (yellow pigment, produced by the Toda Pigment Co.) were introduced into a dispersing container and dispersed until the particle size was less than 10 μm. On reaching the target particle size the dispersion was stopped and 0.2 part of the surface controlling agent Modaflow (produced by the Monsanto Co., acrylic copolymer, residue on heating 100 mass%) , 10 parts of xylene and 13.2 parts of butyl acetate were added and stirred thoroughly in a Disper to prepare the uniform main component of the two-liquid top-coat paint T-I for one-coat purposes. Sumidure N75 (produced by the Sumitomo Beyer Co., polyisocyanate resin, residue on heating 75%, NCO content 16.5 mass%) was used as the hardening agent and this was mixed in the proportions of 93.6 parts of the main component and 6.4 parts of the hardening agent and stirred until the mixture was uniform immediately before coating and then used. [0048]

Example 2 of Top-coat Paint Production (Base-coat paint for two-coat purposes)

Acrylic resin LB-9020 (produced by the BASF Coatings Japan Co., residue on heating 55 mass%, hydroxyl group value 56 mgKOH/g) (45.5 parts), 6 parts of the rheology control agent LC-0988 (produced by the BASF Coatings Japan Co., inorganic-based, residue on heating 10 mass%) , 2.5 parts of the aluminum flake pigment Alpaste TCR3040 (trade name, produced by the Toyo Aluminum Co., residue on heating 80 mass%, average particle diameter (D₅₀) 17 μm, average thickness 0.8 μm) , 3 parts of Alpaste 6340NS (trade name, produced by the Toyo Aluminum Co., residue on heating 71 mass%, average particle diameter (D₅₀) 13 μm, average thickness 0.29 μm) , 3.3 parts of Desmodure BL3175 (trade name, produced by the Sumitomo Beyer Urethane Co., HDI isocyanurate blocked with MEK oxime, NCO content 11.2 mass%, residue of heating 75 mass%) , 0.2 part of the surface control agent Modaflow (produced by the Monsanto Co., acrylic copolymer, residue on heating 100 mass%) , 10 parts of xylene and 29.5 parts of butyl acetate were mixed together and stirred for 10 minutes in a Disper to provide a uniform mixture and prepare the one-liquid type metallic base-coat paint for two- coat purposes T-2.

[0049]

Examples of Top-coat Paint Production 3 and 4 (Base- coat paints for two-coat purposes)

The one-liquid type metallic base-coat paints for two-coat purposes T-3 and T-4 shown in Table 4 were prepared in the same way as in Example of Top-coat Paint Production 2.

[0050]

Example of Top-coat Paint Production 5 (Base-coat paint for two-coat purposes)

The main component of the two-liquid type metallic base-coat paint for two-coat purposes T-5 was prepared by mixing the raw materials shown in Table 4 except for the Sumidure N75 and stirring uniformly in the same way as in Example of Top-coat Paint Production 2. Sumidure N75 as the hardening agent was mixed in the proportions of 96.5 parts of the main component and 3.5 parts of hardening agent immediately before coating, stirred until uniform and used.

[0051]

Example of Top-coat Paint Production 6 (Colored base- coat paint for three-coat purposes)

The main component of a two-liquid type colored base-coat paint for three-coat purposes T-6 was prepared by dispersing the pigment shown in Table 4 and adding the raw materials except for the Sumidure N75 in the same way as in Example of Top-coat Paint Production 1 and stirring uniformly. Sumidure N75 as the hardening agent was mixed in the proportions of 96.5 parts of the main component and 3.5 parts of hardening agent immediately before coating, stirred until uniform and used.

[0052]

Example of Top-coat Paint Production 7 (Colored base- coat paint for three-coat purposes)

The pigment shown in Table 4 was dispersed and the remaining raw materials were added and stirred uniformly in the same way as in Example of Top-coat Paint Production 6 to prepare the one-liquid type colored base-coat paint for three-coat purposes T-7.

[0053]

Table 4

[ 0054 ]

Example of Top-coat Paint Production 8 (Pearl base-coat paint for three-coat purposes)

The main component of the two-liquid type pearl base-coat paint for three-coat purposes T-8 was prepared in the same way as in Example of Top-coat Paint Production 5 except that the aluminum pigment was replaced with a peal pigment. Sumidure N-75 as the hardening agent was mixed in the proportions of 96.5 parts of the main component and 3.5 parts of hardening agent immediately before coating, stirred until uniform and used.

[0055]

Example of Top-coat Paint Production 9 (Pearl base-coat paint for three-coat purposes)

The one-liquid type pearl base-coat paint for three-coat purposes T-9 was prepared in the same way as in Example of Top-coat Paint Production 2 except that the aluminum pigment was replaced with peal pigment.

[0056]

Example of Top-coat Paint Production 10 (Clear paint)

The surface control agent Modaflow (0.2 part) and 4.8 parts of butyl acetate were mixed with 80 parts of the acrylic resin LB-9040 (produced by the BASF Coatings Japan Co., residue on heating 55 mass%, hydroxyl group value 78 mgKOH/g) and stirred for 10 minutes in a Disper to prepare the uniform main component of the two-liquid type clear paint T-10. Sumidure N-75 as the hardening agent was mixed in the proportions of 85 parts of the main component and 15 parts of hardening agent immediately before coating, stirred until uniform and used. [0057]

Table 5

[ 0058 ]

11) Iriodin 103WNT: (Produced by the Merck Co., mica pigment)

12) Alpaste TCR3040: Aluminum pigment produced by the Toyo Aluminum Co., residue on heating 80 mass%, average particle diameter (D₅₀) 17 μm

13) Alpaste 6340NS (Aluminum pigment produced by the Toyo Aluminum Co., residue on heating 71 mass%, average particle diameter (D₅₀) 13 μm)

14) Sumidure N-75: Produced by the Sumitomo Bayer Urethane Co., polyisocyanate resin, residue on heating 75%, NCO content 16.5 mass%

15) Yuban 122: Produced by the Mitsui Kagaku Co., butylated melamine resin, residue on heating 60 mass%

16) Modaflow: Produced by the Monsanto Co., acrylic copolymer, residue on heating 100 mass%

[0059]

(Example 1)

Using P-I as the primer and T-I as the top-coat paint, tests were carried out in respect of the primer storage stability, the primer coating operability, the adhesion of the first top-coat after coating with the top-coat paint and the adhesion of the recoated topcoat paint on the first top-coat paint on the basis of the methods for the evaluation of paints and paint films described above, and the results of the evaluations are shown in Table 5.

[0060]

(Examples 2 to 12)

Tests were carried out essentially in the same way as in Example 1 except that the top-coat paint was replaced with the combination shown in Table 5, and the results of the evaluations are shown in Table 5. (Comparative Examples 1 to 9)

Tests were carried out essentially in the same way as in Example 1 except that the top-coat paint was replaced with the combination shown in Table 6, and the results of the evaluations are shown in Table 6. [0061]

Table 6

[0062] <Conclusion>

As shown by Examples 1 to 12 in Table 5, provided that they are within the scope of the invention indicated in the scope of the patent claims, the primers of the present invention have excellent storage stability and coating operability, the adhesion of the first top-coat paint film is excellent and, furthermore, it is possible to obtain paint films where there is excellent adhesion of a recoated paint film. Moreover, Examples 8 to 12 in Table 5 had somewhat reduced adhesion of a recoat paint film, but this was of a level which was not a problem in practical terms.

However, in those cases where the (B) component was outside the scope of the patent claims, as shown in Comparative Example 1, problems arose with the coating operability and storage stability of the primer, and as shown in Comparative Example 2 and Comparative Example 4 the recoat adhesion was unsatisfactory. If the (C) component is outside the scope of the patent claims then the recoat adhesion becomes unsatisfactory, as shown in Comparative Example 3.

On the basis of the results indicated above, with a primer of this invention it is possible to obtain excellent primer storage stability and coating operability, and to obtain coated objects where there is excellent adhesion of the first top-coat paint film and excellent recoat adhesion.

Claims

[Claim 1]

A primer, characterized in that it contains (A) chlorinated polyolefin resin which has a chlorine content of from 5 to 50 mass% and a weight average molecular weight of from 1,000 to 100,000, (B) diol which has a weight average molecular weight of from 120 to 1,000 and (C) hardening catalyst, and in that the proportions with respect to the mass of the resin solid fraction of the (A) component in which these components are included are from 0.5 to 12 mass% of the (B) component and from 0.01 to 1.5 mass% of the (C) component . [Claim 2]

A method for coating plastic moldings, characterized in that a primer according to claim 1 and a top-coat paint are coated sequentially on the plastic molding, baked and hardened and a top-coat paint film is formed. [Claim 3]

A method for coating plastic moldings, characterized in that a primer according to claim 1 and a top-coat paint are coated sequentially on the plastic molding, baked and hardened and then a primer according to claim 1 and a top-coat paint are coated sequentially on the top-coat paint film, baked and hardened. [Claim 4 ]

A method for coating moldings, characterized in that a primer according to claim 1 and a top-coat paint are coated sequentially, baked and hardened on the topcoat paint film of a molding on which a top-coat paint has been coated and hardened. [Claim 5]

The method for coating moldings disclosed in any of claims 2 to 4 in which the top-coat paint is a two- liquid type urethane resin paint of the one-coat type. [Claim 6]

The method for coating moldings disclosed in any of claims 2 to 4 in which the top-coat paint comprises two layers, namely a base-coat paint film and a clear paint film, and at least the clear paint is a two- liquid type urethane resin paint. [Claim 7]

The method for coating moldings disclosed in any of claims 2 to 4 in which the top-coat paint comprises three layers, namely a colored base-coat paint film, a pearl base-coat paint film and a clear paint film, and at least the clear paint is a two-liquid type urethane resin paint.