JP2000119591A - Primer composition for polyolefin-based resin and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a primer composition excellent in gasohol resistance and adhesiveness in coating of polyolefin-based resin molded products and provide a method for producing the primer composition. SOLUTION: This primer composition for polyolefin-based resins comprises a carboxyl group-containing chlorinated polyolefin (II) obtained by carrying out chlorination reaction of a carboxyl group-containing polyolefin (I) between a temperature at which the carboxyl group-containing polyolefin (I) begins to deposit into a chlorinated solvent and a temperature higher by 1-15 deg.C than the above temperature by completely dissolving the carbonyl group-containing polyolefin (I) into a chlorination reaction solvent under heating and then cooling the solution in a carboxyl group-containing polyolefin (II) obtained by chlorinating a carboxyl group-containing polyolefin (I) obtained by grafting 1-10 wt.% at least one kind of unsaturated carboxylic acid monomer selected from a carboxylic acid and/or carboxylic anhydride onto a polyolefin until chlorine content becomes 10-30 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a polyolefin resin, for example, polypropylene, polyethylene, ethylene-
The present invention relates to a primer composition used for the purpose of protecting or cosmetically protecting a propylene copolymer, an ethylene-propylene-diene copolymer or the like, and more particularly, to a primer composition used for painting a polyolefin resin molded article.

[0002]

2. Description of the Related Art In recent years, plastics have many advantages such as high productivity, wide design freedom, light weight, rust prevention and impact resistance. It is often used as a material for such applications.
In particular, polyolefin resin is inexpensive and moldable,
It has many excellent properties such as chemical resistance, heat resistance, water resistance, and good electrical properties, and is widely used as an industrial material. It is one of the materials whose demand is expected to grow in the future. is there. However, polyolefin resins are different from polar synthetic resins, such as polyurethane resins, polyamide resins, acrylic resins, and polyester resins, in that they are non-polar and crystalline, and are difficult to paint and adhere. Having.

[0003] For coating and bonding of such a hardly adherent polyolefin resin, a low chlorinated polyolefin having a strong adhesive force to the polyolefin resin has been conventionally used as a binder resin.

[0004] For example, JP-A-57-36128, JP-A-59-166
No. 534, JP-B-63-36624 and the like have a chlorine content of 5 containing carboxylic acid and / or carboxylic anhydride.
Up to 50% of low-chlorinated polypropylene or low-chlorinated propylene-α-olefin copolymer has been proposed as a coating primer or a binder resin for coating polyolefin-based molded products.

[0005] Further, a composition obtained by further chlorinating a modified copolymer obtained by graft copolymerizing a styrene / conjugated diene block copolymer with an α, β-unsaturated vinyl monomer having a hydroxyl group, as an essential component. (Japanese Unexamined Patent Publication No.
No. -25405), a composition containing a chlorinated product of a graft-modified styrene-isoprene-block copolymer as an essential component (JP-A-5-25404), propylene / ethylene / α
A composition comprising a chlorinated product of a graft-modified olefin random copolymer as an essential component (Japanese Patent Application Laid-Open No. 5-112750,
Japanese Patent Application Laid-Open No. H5-112751) has also been proposed.

[0006] However, although these compositions show good adhesion to poorly adherent polyolefins, they have a "gasohol resistance test" which is a measure of solvent resistance, that is, they are used for regular gasoline such as methanol and ethanol. The test method is extremely inferior in a test method for determining whether or not the solvent resistance is good by the time until the coating film is peeled off by dipping the coated plate in a gasoline / alcohol mixture (gasohol) containing 10% of a low alcohol.

The method of crosslinking a carboxyl group-containing chlorinated polyolefin with an epoxy resin, which is disclosed in JP-B-63-50381, JP-B-01-16414, JP-A-8-100032, etc., uses regular gasoline. It is excellent in so-called gasoline resistance in which only gas is immersed, but inferior in gasohol resistance.

Further, a composition containing a modified chlorinated polyolefin obtained by reacting a carboxyl group-containing chlorinated polyolefin with a low molecular weight diol or a low molecular weight compound having a hydroxyl group and an amino group (JP-A-7-247381) JP-A-10-158447) and a composition obtained by mixing a carboxyl group-containing chlorinated polyolefin with an acrylic-modified chlorinated polyolefin modified with acrylic having a glass transition point of 60 ° C. or higher (JP-A-10-158447). For example, there is a description that gasohol resistance is excellent, but none of them can be said to satisfy gasohol resistance.

[0009]

SUMMARY OF THE INVENTION The present invention provides a primer composition having improved gasohol resistance and adhesion, which is used for coating a molded article or sheet of a polyolefin resin. .

[0010]

According to the present invention, there is provided a primer composition comprising 1 to 10% by weight of at least one unsaturated carboxylic acid monomer selected from carboxylic acids and / or carboxylic anhydrides. The carboxyl group-containing polyolefin (I) which has been graft-copolymerized is a carboxyl group-containing chlorinated polyolefin (II) having a chlorine content of 10 to 30% by weight, and the reaction condition for chlorination is chlorination. The carboxyl group-containing polyolefin (I) is completely dissolved in the reaction solvent by heating and then gradually cooled to obtain the carboxyl group-containing polyolefin (I).
Is a carboxyl group-containing chlorinated polyolefin (II) obtained from a chlorination reaction at a temperature of 1 to 15 ° C. higher than a temperature at which chlorination begins to precipitate in a chlorinated solvent.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The carboxyl group-containing polyolefin (I) obtained by graft copolymerizing an unsaturated carboxylic acid according to the present invention is prepared by melting a polyolefin by heat and, if necessary, reducing or decomposing by thermal decomposition. It can be obtained by graft polymerization of 1 to 10% by weight of an unsaturated carboxylic acid monomer of carboxylic acid and / or carboxylic acid anhydride in the presence of a radical generator in a formula or a continuous formula.

As the raw material polyolefin, crystalline polypropylene, amorphous polypropylene, propylene-α-olefin copolymer and the like can be used alone or in combination of two or more. From the viewpoint, a weight-average molecular weight is 10,000 to 150,000 crystalline polypropylene and / or a propylene-α-olefin copolymer containing 70 to 97 mol% of a propylene component, wherein the α-olefin unit is, for example, ethylene, 1-butene. , 1-pentene, 4-methyl-1-pentene, 3-methyl-1-pentene and 1-hexene are preferably at least one α-olefin having 2 or 4 to 6 carbon atoms. If the weight-average molecular weight of the raw material polyolefin is less than 10,000 or the propylene component is less than 70 mol%, adhesion to polyolefin resin and gasohol resistance deteriorate, and if the weight-average molecular weight exceeds 150,000, it is applied by air spray or the like. It is not preferable because the primer is not atomized at the time of processing and the appearance of the coated surface is impaired. Also, propylene-α
-When the carbon number of the α-olefin of the olefin copolymer exceeds 6, the adhesion to the polypropylene resin becomes poor.

Examples of the unsaturated carboxylic acid monomer that can be used for introducing a carboxyl group include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, itaconic anhydride, aconitic acid, aconitic anhydride and the like. The graft copolymerization amount is preferably 1 to 10% by weight based on the polyolefin. If it is less than 1%, the adhesion to the top coat is poor, and if it exceeds 10%, the adhesion to the polyolefin resin is poor.

As the radical generator used in the graft copolymerization reaction, for example, di-tert-butyl peroxide, te
peroxides such as rt-butyl hydroperoxide, dicumyl peroxide, benzoyl peroxide, tert-butyl peroxide benzoate, methyl ethyl ketone peroxide, di-tert-butyl dipar-phthalate and azobisisobutyronitrile And azonitriles such as

[0015] The carboxyl group-containing chlorinated polyolefin (II) used in the present invention is obtained by converting a carboxyl group-containing polyolefin (I) obtained by graft copolymerizing an unsaturated carboxylic acid with a chlorination reaction solvent such as chloroform, carbon tetrachloride, tetrachloroethylene. , Tetrachloroethane, etc., and then gradually cooled to a temperature between 1 and 15 ° C. higher than the temperature at which the carboxyl group-containing polyolefin (I) starts to precipitate in the chlorinated solvent. It can be obtained by blowing chlorine gas under pressure or normal pressure in the presence of such a radical generator or under irradiation of ultraviolet rays.

If the chlorination reaction temperature is lower than the temperature at which the carboxyl group-containing polyolefin (I) is precipitated plus 1 ° C., insolubles are generated in the chlorination reaction product, and gasohol resistance is deteriorated. The chlorination reaction temperature is higher than the temperature at which the carboxyl group-containing polyolefin (I) precipitates by 15
If the temperature is higher than ℃, the gasohol resistance is deteriorated, which is not preferable.

The chlorine content of the carboxyl group-containing chlorinated polyolefin (II) used in the present invention is preferably from 10 to 30% by weight. If the chlorine content is less than 10% by weight, the solubility in organic solvents such as toluene and xylene is inferior, so that a uniform solution cannot be obtained. If the chlorine content exceeds 30% by weight, the adhesion to the polyolefin resin and the gasohol resistance deteriorate, which is not preferable.

A chlorinated resin such as a carboxyl group-containing chlorinated polyolefin (II) obtained by the above-mentioned method is conventionally used by adding an epoxy compound as a stabilizer. Although the epoxy compound is not particularly limited, those that are compatible with the chlorinated resin are preferable, and the epoxy equivalent is 100 to 500.
Epoxy compounds having at least one epoxy group in one molecule can be exemplified.

For example, epoxidized soybean oil and epoxidized linseed oil obtained by epoxidizing a natural vegetable oil having an unsaturated group with a peracid such as peracetic acid. Also, oleic acid, tall oil fatty acids,
Epoxidized fatty acid esters obtained by epoxidizing unsaturated fatty acids such as soybean oil fatty acids. Epoxidized alicyclic compounds represented by epoxidized tetrahydrophthalate. Bisphenol A or polyhydric alcohol condensed with epichlorohydrin, for example, bisphenol A glycidyl ether, ethylene glycol glycidyl ether, propylene glycol glycidyl ether, glycerol polyglycidyl ether, sorbitol polyglycidyl ether and the like are exemplified. Also, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, decyl glycidyl ether, stearyl glycidyl ether, allyl glycidyl ether, phenyl glycidyl ether, sec-butyl phenyl glycidyl ether, tert-butyl phenyl glycidyl ether, phenol-polyethylene oxide glycidyl ether, etc. And monoepoxy compounds represented by In addition, calcium stearate used as a stabilizer for polyvinyl chloride resin, metal soaps such as lead stearate, organic metal compounds such as dibutyltin dilaurate, dibutyltin malate, and hydrotalcite compounds can also be used. May be used in combination.

The carboxyl group-containing chlorinated polyolefin (II) obtained by the above-mentioned method is obtained by removing the chlorinated solvent after completion of the chlorination reaction, and removing aromatic solvents such as toluene and xylene which are good solvents. Solvents are substituted with alicyclic hydrocarbons such as cyclohexane and methylcyclohexane, and a stabilizer such as an epoxy compound is used.

After completion of the chlorination reaction, after removing hydrochloric acid in the chlorination reaction solvent such as chloroform, an epoxy compound or the like is added as a stabilizer, and the screw shaft has a vent provided with a suction part for desolvation. It may be supplied to an extruder, solidified, and then dissolved in a solvent such as toluene. The method of solidification uses a known method already known, for example, an extruder with a vent equipped with a submerged cut pelletizer at the outlet of the extruder, an extruder with a vent, a pelletizer for cutting a strand-like resin, and the like. Can be implemented.

[0022] The carboxyl group-containing chlorinated polyolefin (II) used in the present invention can be used as it is by coating directly in the form of a clear varnish or by spray coating.
Add titanium dioxide, carbon black, aluminum paste, coloring pigment, etc., and if necessary, add other additives such as UV absorbers, antioxidants, pigment settling inhibitors, and knead them to form a base coat of metallic specification. Can be used.

The chlorinated polyolefin (II) containing a carboxyl group alone exhibits well-balanced coating film properties. However, if necessary, an alkyd resin, an acrylic resin, a polyacryl polyol, a polyester resin, a polyester polyol, a poly An ether resin, a polyether polyol, a polyurethane resin, an epoxy resin or the like may be added for use.

[0024]

The feature of the present invention is that a chlorinated polyolefin obtained by dissolving a polyolefin in a chlorinated solvent and performing a chlorination reaction at a temperature of 1 ° C. to 15 ° C. higher than the start of precipitation. Another object of the present invention is to obtain a primer composition for a polyolefin resin having good gasohol resistance. It is unknown why the chlorination reaction improves gasohol resistance, but the following literature (ENCYCLOPEDIA OF POLYMER SCIENCE
AND TECHNOLOGY, Vol. 6, p. 435) states the following. 1. When polyethylene is chlorinated in a solution state or at a temperature higher than the melting point, chlorine is randomly introduced into the molecule. (Chlorine is uniformly introduced into the molecule) 2. Chlorination of polyethylene in suspension or below its melting point produces segments with a high amount of chlorine introduced into the molecule and segments with no chlorine introduced. (Chlorine is introduced unevenly in the molecule) Thus, the arrangement of chlorine to be introduced differs depending on the state of the polyolefin before chlorination. Chlorination at a temperature slightly higher than that at which the polyolefin precipitates as in the present invention results in an arrangement of chlorine in the middle between 1 and 2 described above, for unknown reasons. It is thought that it has contributed to the improvement.

[0025]

EXAMPLES The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples.

(Production Example 1) 5 kg of crystalline polypropylene having a weight average molecular weight of 40,000 was placed in a three-necked flask equipped with a stirrer, a dropping funnel and a condenser for refluxing monomers, and kept constant at 180 ° C. It was completely melted in the hot water bath. The atmosphere in the flask was replaced with nitrogen, and 200 g of maleic anhydride was added thereto over about 5 minutes while stirring. Then, 20 g of di-t-butyl peroxide was dissolved in 50 ml of heptane, and the solution was dropped from the dropping funnel for about 30 minutes. I put it in.
At this time, the inside of the system was maintained at 180 ° C., and the reaction was further continued for 15 minutes. Then, while depressurizing the inside of the flask with an aspirator, unreacted maleic anhydride was removed over about 30 minutes, and an anhydride obtained by copolymerizing maleic anhydride was obtained. A maleic acid-modified polypropylene was obtained.

Next, 5 kg of this product was charged into a glass-lined reaction vessel, and 80 liters of chloroform was added. After sufficiently dissolving at 120 ° C. under a pressure of 4 kg / cm 2,
When the temperature was gradually cooled to 73 ° C., precipitation of polypropylene was observed. The temperature was raised again to 85 ° C., and chlorine gas was blown in from the bottom of the reaction vessel while maintaining this temperature while irradiating ultraviolet rays, and a chlorination reaction was carried out until the chlorine content reached 20% by weight. The solvent was distilled off and replaced with a mixed solvent of toluene / cyclohexane = 7/3 (wt), and Epicoat 828 (epoxy resin having a condensate of bisphenol A and epichlorohydrin and an epoxy equivalent of 184 to 194, manufactured by Shell Chemical Co., Ltd.) was used as a stabilizer. Was added to the solid content at 4% to adjust the concentration, thereby obtaining a carboxyl group-containing chlorinated polypropylene (A-1) in a 20% solid content toluene solution.

(Production Example 2) A propylene-butene-ethylene copolymer having a weight average molecular weight of 120,000, a propylene component of 75 mol%, and an ethylene component of 8 mol% (propylene-
5 kg of an α-olefin copolymer) was put into a three-necked flask equipped with a stirrer, a dropping funnel, and a condenser for refluxing the monomer, and was completely melted in a water bath kept constant at 180 ° C. The atmosphere in the flask was replaced with nitrogen, and 300 g of maleic anhydride was added over about 5 minutes while stirring.
Next, 30 g of dicumyl peroxide was dissolved in 50 ml of heptane, and the solution was introduced from a dropping funnel over about 30 minutes.
At this time, the inside of the system was maintained at 180 ° C., and the reaction was further continued for 15 minutes. Then, while depressurizing the inside of the flask with an aspirator, unreacted maleic anhydride was removed over about 30 minutes, and an anhydride obtained by copolymerizing maleic anhydride was obtained. A maleic acid-modified propylene-butene-ethylene copolymer was obtained.

Next, 5 kg of this product was put into a glass-lined reaction vessel equipped with a stirrer, and 80 liters of chloroform was added. The mixture was sufficiently stirred and dissolved at 100 ° C. under a pressure of 3 kg / cm 2, and then gradually cooled. When the temperature reached 45 ° C., precipitation of polypropylene was observed. The temperature was raised again to 50 ° C., 5 g of azobisisobutyronitrile was added as a radical generator, and while maintaining this temperature, chlorine gas was blown in from the bottom of the reactor to chlorinate until the chlorine content became 12% by weight. The reaction was carried out, and chloroform as a solvent was distilled off with an evaporator, and the solvent was replaced with toluene. Epicoat 828 was added as a stabilizer at 4% to the solid content to adjust the concentration. Propylene-butene-ethylene copolymer (A-
2) was obtained.

(Production Example 3) Production Example except that a propylene-ethylene copolymer having a weight average molecular weight of 50,000, a propylene component of 94 mol%, and an ethylene component of 6 mol% was collected.
Maleic anhydride was copolymerized in the same manner as in Example 2 to obtain a maleic anhydride-modified propylene-ethylene copolymer. Next, 5 kg of this product was charged into a glass-lined reaction vessel equipped with a stirrer, and 80 liters of chloroform was added. The mixture was sufficiently dissolved at 110 ° C. under a pressure of 3 kg / cm 2, and then gradually cooled to 62 ° C. By the way, precipitation of polypropylene was observed. Raise the temperature again to 65 ° C,
5 azobisisobutyronitrile as radical generator
While maintaining this temperature, chlorine gas was blown in from the bottom of the reaction vessel to carry out a chlorination reaction until the chlorine content became 17% by weight, and chloroform as a solvent was distilled off by an evaporator. Butyl phenyl glycidyl ether (monoepoxy) was added at 5% to the solid content, and the remaining chloroform was completely removed by a vented extruder equipped with a vent port for distilling off under reduced pressure. A solid of an ethylene copolymer was obtained.

Next, this solid was dissolved in toluene to prepare a 20% solids concentration toluene solution (A-3).

(Production Example-4) The chlorination reaction of Production Example-1 was
The reaction was carried out in exactly the same manner as in Production Example 1 except that the reaction was carried out at 0 ° C., to obtain a carboxyl group-containing chlorinated polypropylene (B-1) in a 20% solids concentration toluene solution.

(Production Example-5) The chlorination reaction of Production Example-2 was carried out at 80
The reaction was carried out in exactly the same manner as in Production Example 2 except that the reaction was carried out at a temperature of 200 ° C. to obtain a carboxyl group-containing chlorinated propylene-butene-ethylene copolymer (B-2) in a 20% solids concentration toluene solution.

(Production Example-6) The chlorination reaction of Production Example-3 was carried out by 90
The reaction was carried out in exactly the same manner as in Production Example 3 except that the reaction was carried out at ℃, and a carboxyl group-containing chlorinated propylene-ethylene copolymer (B-3) in a 20% solids concentration toluene solution.
I got

(Examples 1-3 and Comparative Examples 1-3) 100 g of each of the carboxyl group-containing chlorinated polyolefins (A-1 to 3 and B-1 to 3) obtained in Production Examples 1 to 6 were taken.
13.2 g of titanium dioxide and 0.1 g of carbon black were added to each and kneaded for 1 hour with a sand grinder mill, and then 13-14 seconds / 2 with Ford Cup No. 4.
The viscosity was adjusted with xylene so as to be 0 ° C. to prepare a primer.

Next, this primer is spray-coated on a polypropylene plate washed with water so as to have a film thickness of 10 μm, and after a few minutes, a two-component curable urethane paint is coated with a film thickness of 30 to 40 μm.
And dried at room temperature for about 15 minutes, followed by forced drying at 80 ° C. for 30 minutes. After standing at room temperature for 3 days, the coating film was tested. Table 1 shows the test results of the coating films.

[0037]

[Table 1]

(Coating film test method) ○ Gasohol resistance Time in which a coated plate whose both ends are cut is immersed in a mixed gasoline of regular gasoline: ethanol = 9: 1 and peeled off about 2 mm from the end of the cut coated surface. Was determined. ○ Adhesiveness 100 cross-cuts are made on the painted surface to reach the substrate at 1 mm intervals, and a cellophane adhesive tape is adhered on top of the grid to obtain 18
It was peeled off in the direction of 0 ° and the number of remaining crosses was checked. ○ Warm water resistance The coated plate was immersed in warm water of 40 ° C. for 240 hours to examine the state of the coating film. In addition, a scratch (x mark) reaching the substrate was put on the coated surface, and a cellophane adhesive tape was adhered thereon, and the film was peeled off in the 180 ° direction to examine the adhesion of the coating film. O Humidity resistance The film was left in an atmosphere of 50 ° C and a relative humidity of 98% for 240 hours, and the state and adhesion of the coating film were examined in the same manner as in the case of warm water resistance.

[0039]

According to the results in Table 1, as shown in Examples 1 to 3, those in which the maleic anhydride-modified polyolefin was chlorinated at a temperature 1 to 15 ° C. higher than the temperature at which the polyolefin was precipitated in the chlorinated solvent were obtained. Excellent gasohol resistance and other physical properties.

On the other hand, when the maleic anhydride-modified polyolefin is subjected to a chlorination reaction at a temperature exceeding 15 ° C. from the temperature at which the polyolefin is precipitated in the chlorination solvent, as in Comparative Examples 1 to 3, the gasohol resistance is significantly deteriorated. , Adhesion, warm water resistance and moisture resistance are slightly inferior. This shows that the primer composition of the present invention is useful for polyolefin resin molded products.

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Keiji Urata 2-8-1 Iida-cho, Iwakuni-shi, Yamaguchi Prefecture Nippon Paper Industries Co., Ltd. Chemical Development Laboratory F-term (reference) 4J011 AA05 AB01 AB02 BA04 BB10 HA03 HB11 HB24 4J038 CB171 CB172 CP031 CP032 CP041 CP042 GA06 MA14 NA04 NA08 NA12 PB04 PB05 PB07 PB09 PC08 4J100 AA02Q AA03P AA04Q AA07Q AA16Q AA17Q AA18Q AJ02R AJ08R AJ09R AK31R AK32R BB01H03 HE03 HA21

Claims (4)

[Claims] 1. A carboxyl group-containing polyolefin (I) obtained by graft copolymerizing 1 to 10% by weight of at least one unsaturated carboxylic acid monomer selected from carboxylic acids and / or carboxylic acid anhydrides, has a chlorine content of 10-30
A carboxyl group-containing chlorinated polyolefin (II) chlorinated to a weight percent, wherein the reaction conditions for chlorination are:
By completely heating and dissolving the carboxyl group-containing polyolefin (I) in the chlorination reaction solvent and then gradually cooling it, it is 1 to 15 ° C. higher than the temperature at which the carboxyl group-containing polyolefin (I) starts to precipitate in the chlorination solvent. A primer composition for a polyolefin-based resin comprising a carboxyl group-containing chlorinated polyolefin (II) obtained by a chlorination reaction at a temperature. 2. A crystalline polypropylene having a weight average molecular weight of 10,000 to 150,000 and / or a weight average molecular weight of 10,000 to 15
2. A propylene-.alpha.-olefin copolymer containing 0.007 and 70 to 97 mol% of a propylene component, wherein a polyolefin having .alpha.-olefin having 2 or 4 to 6 carbon atoms is used as a starting material. A primer composition for a polyolefin resin. 3. A chlorination reaction solvent for a carboxyl group-containing polyolefin (I) graft-copolymerized with 1 to 10% by weight of at least one unsaturated carboxylic acid monomer selected from carboxylic acids and / or carboxylic anhydrides. After heating and dissolving completely, the mixture was gradually cooled, and the chlorine content was 10 to 3 ° C. at a temperature 1 to 15 ° C. higher than the temperature at which the carboxyl group-containing polyolefin (I) started to precipitate in the chlorinated solvent.
A method for producing a primer composition for a polyolefin-based resin comprising a carboxyl group-containing chlorinated polyolefin (II), which is chlorinated to 0% by weight. 4. A crystalline polypropylene having a weight average molecular weight of 10,000 to 150,000 and / or a weight average molecular weight of 10,000 to 15
4. A propylene-.alpha.-olefin copolymer containing 0.007 and 70 to 97 mol% of a propylene component, wherein a polyolefin having .alpha.-olefin having 2 or 4 to 6 carbon atoms is used as a starting material. A method for producing a primer composition for a polyolefin resin.