JPH05345868A - Composition for primer - Google Patents

Abstract

PURPOSE:To obtain a composition for primer, comprising a graft copolymer prepared by reacting a specific polyolefin with a specified acrylic polymer and excellent in adhesion and coating properties. CONSTITUTION:This composition comprises a graft copolymer obtained by reacting (A) a polyolefin having carboxyl group or epoxy group in the molecular chain with (B) an acrylic polymer having primary or secondary amino group at the molecular terminal and 5000-70000 number-average molecular weight.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a primer composition containing a graft copolymer obtained by grafting an acrylic polymer onto a polyolefin having a carboxyl group or an epoxy group in its molecular chain.

[0002]

2. Description of the Related Art Polyolefin represented by polypropylene is widely used in place of a metal material because it is easy to mold and is lightweight. Further, although recycling of materials has become a major issue due to environmental problems, polypropylene has a high possibility of recycling, and therefore, there are more and more opportunities to be used by replacing it with other plastic materials. However, this polypropylene has a serious problem of poor paintability due to its molecular characteristics.

In the case of coating on polypropylene, it is common to perform a pretreatment such as corona discharge treatment and trichlene washing, and then apply a primer and then coat.

Pretreatments such as corona discharge treatment and trichlene cleaning require large-scale equipment, and there are many problems such as the use of harmful organic solvents. However, at present, it is impossible to ensure sufficient paintability by omitting this pretreatment and using only the primer.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a primer composition which is excellent in the adhesiveness of a paint even when it is not pretreated during the coating of polyolefin, especially polypropylene.

[0006]

According to the present invention, the above object is to provide a polyolefin having a carboxyl group or an epoxy group in its molecular chain, and a primary or secondary polyolefin at the molecular end.
Number average molecular weight 5,000 to 70,000 having a primary amino group
It is achieved by a primer composition containing a graft copolymer obtained by reacting with the acrylic polymer.

As the polyolefin containing a carboxyl group or an epoxy group in the molecular chain used in the present invention, maleic anhydride-added polyethylene, polypropylene; a carboxyl group-containing polyolefin such as a copolymer of ethylene and acrylic acid; Examples thereof include epoxy group-containing polyolefin such as a copolymer of ethylene and glycidyl methacrylate. Any of these polyolefins can be obtained by a known method.

The content of carboxyl group or epoxy group in these polyolefins is preferably in the range of 0.1 to 5 mol% with respect to the constituent monomer units. If the content is less than the above range, the efficiency of the grafting reaction described below becomes extremely low, and if it is too large, the adhesiveness when used as a primer is rather lowered, which is not preferable.

In the present invention, a carboxyl group or an epoxy group added to a polyolefin is reacted with an acrylic polymer having a number average molecular weight of 5,000 to 70,000 and having a primary or secondary amino group at the molecular end, and grafted. It is a copolymer. The amount of the acrylic polymer to be grafted is 90/1 in weight ratio with the modified block copolymer.
It is better to be in the range of 0 to 30/70. If the amount of the acrylic polymer is smaller than the above ratio, the adhesion with the coating material to be applied thereon will be insufficient, and conversely if it is greater than the above ratio, the adhesion with the polyolefin will be insufficient. ..

Acrylic polymers having a primary or secondary amino group at the molecular end include acrylic acid, acrylic acid esters such as methyl acrylate, ethyl acrylate and butyl acrylate, methacrylic acid, methyl methacrylate, One or more kinds of monomers selected from methacrylic acid esters such as ethyl methacrylate and butyl methacrylate are polymerized. Such a polymer can be obtained by polymerizing an acrylic monomer with a radical initiator in the presence of a compound having a thiol group and a primary or secondary amino group. Thiol group and primary or secondary
Examples of the compound having a primary amino group include aminomethanethiol, 2-aminoethanethiol, 3-aminopropanethiol, 4-aminobutanethiol and the like. Known radical initiators are used, and examples thereof include azo compounds such as azobisisobutyronitrile and organic peroxides such as benzoyl peroxide. The polymerization method is as follows. A compound having a thiol group and a primary or secondary amino group is added to an acrylic monomer, and a radical initiator is further added to perform polymerization, whereby an acrylic polymer having an amino group at a terminal is obtained. can get. At this time, it is preferable to use a solvent for the purpose of facilitating control of the reaction. As the solvent, aromatic hydrocarbons such as benzene and toluene, and acetic acid esters such as methyl acetate and ethyl acetate are preferably used.

The molecular weight of this acrylic polymer is 5,000.
Those in the range of up to 70,000 are used. Molecular weight is 50
If it is less than 00, the reaction is extremely difficult and the effect of improving the adhesiveness when used as a primer composition is poor. On the other hand, when the molecular weight exceeds 70,000, the efficiency of the reaction with the polyolefin containing a carboxyl group or an epoxy group becomes extremely low, the desired reaction product cannot be obtained, and the elasticity when used as a primer composition is also poor. It becomes sufficient and not preferable. From this viewpoint, the molecular weight of the acrylic polymer is more preferably in the range of 7,000 to 50,000.

The reaction between the polyolefin containing a carboxyl group or epoxy group and the acrylic polymer may be carried out by mixing and heating both in a solution state or by heating both in a solid state while heating. In the case of reacting in a solution state, it is easy to dissolve both in a solvent such as benzene, an aromatic hydrocarbon such as toluene, an acetic acid ester such as methyl acetate or ethyl acetate, and heat at a temperature of 50 to 200 ° C. Can be reacted to. The reaction in the solid phase is carried out by stirring and mixing the block copolymer and maleic anhydride under heating using a closed mixer such as a kneader or a Banbury mixer or a single-screw or twin-screw extruder. .. The temperature during the reaction is 80 to 250 ° C., and the reaction time is 0.1 to 20 minutes.

The resulting graft copolymer is dissolved in an organic solvent and used in the form of a solution as a primer composition. The solvent used at this time is not particularly limited, but aromatic hydrocarbons such as toluene and xylene, acetic acid esters such as methyl acetate and ethyl acetate, methyl ethyl ketone, ketones with methyl isobutyl ketone, cellosolves, etc. As a typical example. Further, in some cases, a halogen-based solvent such as carbon tetrachloride or dichloroethane can be used.

In addition to the graft copolymer as an essential component, the composition of the present invention may contain various compounds as required. Examples thereof include various tackifiers such as rosin, vinylene polymer, petroleum resin, chlorinated polyethylene, polypropylene, etc., and styrene block copolymer with maleic anhydride added.

The primer composition of the present invention can be suitably used as a primer for polyolefin such as polypropylene, and also as a primer for various plastics such as polystyrene and ABS resin as well as metals such as iron and aluminum. It can be preferably used.

[0016]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 350 ml of ethyl acetate, 6 g of 2-aminoethylthiol, 200 g of methyl methacrylate monomer were placed in a pressure resistant reactor.
By adding 10 g of azobisisobutyronitrile as an initiator and polymerizing at 70 ° C., the molecular weight was 37600.
Thus, a methyl methacrylate polymer having an average of 1.01 primary amino groups at the terminal was obtained. Graft copolymer (I) was prepared by kneading 15 g of this methyl methacrylate polymer and 35 g of polypropylene having 1.2 mol% of maleic anhydride added per monomer unit at 200 ° C. for 7 minutes. Got

The obtained graft copolymer was dissolved in toluene so that the concentration of solid content was 10 wt% to obtain a primer composition. This is applied to an untreated polypropylene sheet so as to have a thickness of 10 μm and dried, then coated with an acrylic paint and the paint is dried. Then, a sharp cutter is applied to the coating film to cut 100 pieces vertically and horizontally. A cross-cut test in which 11 cuts are made so that a square is formed, and a commercially available cellophane tape is stuck on this, and when this tape is peeled off, the adhesiveness is evaluated depending on how many 100 squares remain. The adhesiveness was evaluated by.

The results are shown in Table 1, which shows that it has excellent adhesion.

Acrylic paint was applied and the adhesion was evaluated in the same manner as in Example 1 except that the primer was applied.
In this case, the paint does not adhere at all, as shown by the result shown in FIG.

Example 2 Polymerization was carried out in the same manner as in Example 1 except that the amounts of the initiator and 2-aminoethylthiol were changed.
1,500, a methyl methacrylate polymer having 0.98 primary amino groups added per molecule was obtained. 25 g of the obtained methyl methacrylate polymer and 25 g of polyethylene containing 1.6 mol% of epoxy groups were kneaded at 200 ° C. for 7 minutes to obtain a graft copolymer (II).

Using the copolymer thus obtained, the performance as a primer was evaluated in the same manner as in Examples. As shown in Table 1, the results show that the copolymer has excellent performance.

Example 3 Polymerization was carried out in the same manner as in Example 1 except that the amounts of the initiator and 2-aminoethylthiol were changed to give a polymer having a molecular weight of 4
5500, a methyl methacrylate polymer having 0.96 primary amino groups added per molecule was obtained. Polyethylene 35 in which 35 g of the obtained methyl methacrylate polymer and 0.9 mol% of maleic anhydride were added per monomer unit
200 g with Brabender Plasticorder
The mixture was kneaded for 7 minutes to obtain a graft copolymer (III).

Using the copolymer thus obtained, the performance as a primer was evaluated in the same manner as in the Examples. As shown in Table 1, it can be seen that the copolymer has excellent performance.

[0025]

[Table 1]

EFFECTS OF THE INVENTION According to the present invention, there is provided a primer composition which exhibits excellent adhesion when a coating is applied to a polyolefin without any particular pretreatment.

Claims (1)

[Claims] 1. A polyolefin having a carboxyl group or an epoxy group in its molecular chain and a number average molecular weight of 5,000 to 7 having a primary or secondary amino group at the molecular end.
A composition for a primer, which comprises a graft copolymer obtained by reacting with 0000 of an acrylic polymer.