JPS5942693B2 - Surface treatment method for polyolefin molded products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for improving paint adhesion of polyolefin molded articles.

Molded products made of crystalline polyolefin have low polarity and poor adhesion with general paints, so it is known that the surface of polyolefin molded products is treated in advance by chromic acid treatment, flame treatment, solvent treatment, etc. .

However, it is not preferable to use complicated treatments or corrosive chemicals, and a simple method with excellent paint adhesion is desirable.

The present applicant has already filed in Japanese Patent Application Laid-Open No. 48-20844 a method of immersing a polyolefin molded article in a treatment liquid consisting of a halogen hydrocarbon solution or suspension of rubber or an addition polymer resin having a polar group. This method has been applied to molded products of polyethylene, polypropylene, etc., and is used for miscellaneous goods, containers, automobile parts, fibers, nonwoven fabrics, etc. as molded products with excellent paint adhesion.

However, depending on the conditions, the primer layer formed on the surface of these molded products may become sticky or uneven in thickness, and the smoothness of the coating film after coating may not be desirable.

Furthermore, depending on the intended use of the molded article, it may be used outdoors, and a coating film that has excellent properties in terms of durable adhesion is also desired. The present invention aims to provide a coated polyolefin molded product with excellent coating film smoothness and particularly improved durable adhesion, and relates to a method for surface treatment of polyolefin molded products.

That is, the present invention relates to modified ethylene-α- which is partially or completely graft-polymerized with an unsaturated carboxylic acid or its anhydride.
A mixture consisting of 20 to 95% by weight of olefin copolymer (A) and 5% by weight of ethylene-α-olefin-diolefin copolymer rubber Q3) is mixed with 1 part organic solvent.
The present invention relates to a method for surface treatment of a polyolefin molded product, which comprises treating the surface of the polyolefin molded product with a treatment liquid prepared by dissolving 0.00CC in a proportion of 0.1 to 57% to form a primer layer.

The polyolefin molded article to which this invention is applied can be molded by various melt molding methods, and various polyolefin raw materials can be used.

Specifically, high-pressure polyethylene, medium-low pressure polyethylene, polypropylene, poly-4-methyl-pentene-1,
Examples of copolymers include ethylene-propylene copolymers, ethylene-butene copolymers, propylene-butene copolymers, and mixtures thereof. These polyolefins
The adhesion of the paint is particularly good when it contains inorganic fillers such as talc, zinc white, glass fiber, titanium white, magnesium sulfate, and the like. The polyolefin may contain additives such as stabilizers, ultraviolet absorbers, and hydrochloric acid absorbers.

The stabilizer preferably used is 2,6-di-tert-butyl-
4-Methylphenol, tetra-scratch [methylene (3,5
-di-tert-butyl-4-hydroxyhydrocinnamate)
] Methane, metaotatadecyl-3-(e-hydroxy-3,5-di-tert-butylphenyl)propionate, 2
, 27-methylenebis(4-methyl-6-tert-butylphenol), 4,e-butylidenebis(3-methyl-6-tert-butylphenol), 4,E-thiobis(3-methyl-6-tert-butylphenol) , 2la 2-thiobis(
4-methyl-6-tert-butylphenol). 1, 3,
5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, 1,3,
Phenol-based stabilizers such as 5-tris(2-methyl-4-hydroxy-5-tert-butylphenol)butane, sulfur-based stabilizers such as dilaurylthiodipropionate and distearylthiodipropionate, and tridecyl phosphatide. Phosphate, trinonylphenyl phosphite, and other phosphorus stabilizers. Preferably used UV absorbers are 2-hydroxy 4-oxybenzophenone, 2-
These include ethylhexyl-2-cyano-3,3-diphenyl acrylate and paraoctylphenyl salicylate. Further, preferably used hydrochloric acid absorbents include calcium stearate and the like. The treatment liquid used for surface treatment of polyolefin molded products is a modified ethylene-α-olefin copolymer (4) in which part or all of an unsaturated carboxylic acid or its anhydride is graft-polymerized, and an ethylene-α-olefin copolymer (4). It is used by dissolving a mixture consisting of olefin copolymer rubber (]3) in an organic solvent.

The ethylene α-olefin copolymer used as a raw material for graft polymerization contains ethylene, propylene, and butene-1.
, benzene-1, 4-methylbenzene-1, etc., and a copolymer containing 25 to 90 mol%, preferably 35 to 85 mol% of ethylene units. It is. Among these, ethylene-propylene copolymers and ethylene-butene copolymers are preferably used, and ethylene-propylene copolymers are particularly preferred. Monomer grafted onto the ethylene-α-olefin copolymer (hereinafter referred to as graft monomer)
For this, one or more unsaturated carboxylic acids or anhydrides thereof are used, and preferred examples include acrylic acid,
Examples include methacrylic acid, maleic acid, fumaric acid, itaconic acid, maleic anhydride, and maleic anhydride is particularly suitable.

Various known methods can be employed to graft the graft monomer onto the ethylene-α-olefin copolymer.

For example, it is carried out by heating the ethylene-α-olefin copolymer and the grafting monomer at high temperature in the presence or absence of a solvent, with or without the addition of a radical initiator. A vinyl monomer such as styrene may be present during the reaction. The amount of the graft monomer grafted onto the ethylene-α-olefin copolymer (hereinafter referred to as grafting ratio) is preferably 10-4 to 10% by weight of the modified ethylene-α-olefin copolymer (4) after graft modification. It is preferably adjusted to a range of 10 to 2 to 5% by weight.

These modified ethylene-α-olefin copolymers (A)
Among these, those having a melt index (190°C) of 0.05 to 100, particularly 0.3 to 50 are preferably used.

When the melt index is small, a fryer layer with excellent paint adhesion can be obtained, but the solubility in organic solvents is also low, so the melt index (190°C) is 0.05.
It is preferable that it is above. Moreover, when it is larger than 100, the primer layer becomes sticky and has an uneven thickness. The ethylene-α-olefin-diolefin copolymer rubber (8), which is another component of the processing agent, is a copolymer of ethylene, the aforementioned α-olefin, and diolefin, and the diolefin includes isoprene and butadiene. , synchropentadiene, 1,4-pentadiene, 2-methyl-1,4-pentadiene, 1,4-hexadiene, divinylbenzene, alkylidenenorbornene such as methylidenenorbornene, ethylidenenorbornene, etc. There is no problem in using two or more types.

Among these, alkylidene norbornene and synchlopentadiene are preferred. The copolymer has 2 ethylene units.
5 to 85 mol%, preferably 30 to 80 mol%
It is. In addition, the content of diene monomers is 0.5 to 1
Preferably it is 0 mol%. The viscosity of these copolymer rubbers (6) (ML1+4, 100°C) is 10
300 to 300, particularly 30 to 200 is preferred.

In the present invention, a mixture consisting of 20 to 95% by weight of the modified ethylene-α-olefin copolymer (4) and 80 to 5% by weight of the ethylene-α-olefin-diolefin copolymer 8 is dissolved in an organic solvent. A processing agent that has been used is used.

Examples of organic solvents include aromatic hydrocarbons such as benzene, toluene, and xylene, aliphatic hydrocarbons such as hexane, heptane, octane, and decane, trichlorethylene, perchlorethylene, dichloroethylene, dichloroethane,
Chlorinated hydrocarbons such as chlorobenzene are used.

Modified ethylene-α-olefin copolymer (A
) and ethylene-α-olefin-diolefin copolymer rubber (g), the concentration of the mixture is preferably in the range of 0.1f to 57% of the organic solvent 100a.

If the concentration is less than 0.1y/100α, when a polyolefin molded product is sprayed, uneven coating will occur and the paint adhesion will vary greatly. Moreover, if it exceeds 57/100 CC, the formed primer layer becomes thick, becomes sticky and tends to have uneven thickness, and the smoothness after painting becomes poor. others,
A small amount of known pigment fillers, stabilizers, etc. may be added to the processing liquid to the extent that it does not contradict the purpose of the present invention.

Various known methods can be used to surface-treat polyolefin molded products, such as spraying, dipping, brushing, etc.

In particular, it is preferable to carry out a dipping treatment in which the polyolefin is immersed in the treatment liquid or a spraying treatment in which the treatment liquid is sprayed using a spray gun. After processing, the molded product is air-dried.
It is dried by a method such as forced drying by heating. The primer layer formed on the surface of the polyolefin molded product is 0.1
The film thickness is from μ to 5μ. A polyolefin molded article whose surface has been treated by the surface treatment method of the present invention is coated with a paint by a method such as electrostatic coating, spray coating, or brush coating.

These paints may be applied by applying a primer coat and then a top coat. There are no particular restrictions on the paint used, but if a coating film with particularly high paint adhesion is required, a solvent-based thermoplastic acrylic resin paint may be used. It is preferable to use a solvent type thermosetting acrylic resin paint, an acrylic modified alkyd resin, an epoxy resin paint, or a polyurethane paint. Polyolefin molded products coated with these coatings can be cured using conventional methods such as nichrome wire, infrared rays, or high-frequency heating, or the curing conditions may vary depending on the material of the polyolefin molded product, the properties of the paint on the shape, etc. You can decide accordingly.

The coating film of the polyolefin molded article obtained by the surface treatment method of the present invention has excellent smoothness and, in particular, the durable adhesion of the coating film is improved.

This effect can be achieved by using the above-mentioned modified ethylene-α-olefin copolymer (A) and ethylene-α-olefin-diolefin copolymer rubber (6) in combination.

That is, modified ethylene-α-olefin copolymer (A
) alone or only ethylene-α-olefin-diolefin copolymer rubber (g) can improve the adhesion of the coating film to some extent, but the durable adhesion is insufficient. Furthermore, when only the modified ethylene-α-olefin copolymer (4) is used, reducing the melt index improves coating film adhesion, but due to its poor solubility in hydrocarbon solvents, It is difficult to make a single layer of fryer uniform, resulting in large variations in coating film adhesion.

However, if this and ethylene-α-olefin-diolefin copolymer rubber 8 are used together, even if the melt index of the modified ethylene-α-olefin copolymer (A) is small, a uniform primer layer can be formed. can be obtained. Examples are shown below.

Examples 1 to 4 and Comparative Examples 1 to 4 Modified ethylene-propylene copolymer graft-polymerized with maleic anhydride (ethylene units 80 mol%, melt index (190°C) 5, graft ratio of maleic anhydride 2% by weight) , hereinafter abbreviated as MEPR) and ethylene-propylene-ethylidenenorbornene copolymer rubber (65 mol % ethylene units, ML1+4=40, hereinafter abbreviated as EPDM) in various ratios was mixed with 1 part of toluene.
00cc to prepare a processing solution.

A sheet (50wn x 50Wff1) was prepared using polypropylene (Mitsui Petrochemical Polypropylene J43O).
X(1Wf1) was obtained by injection molding.

Each sheet was spray coated with the above treatment and then left to dry. Each sheet surface-treated in this way was spray coated with acrylic resin paint (Acryk 1000 manufactured by Kansai Paint Co., Ltd.) diluted approximately 1:1 with thinner, and placed in an air oven at 80°C for 30 minutes. Heat curing was performed by heating for 1 minute.

Next, to test the adhesion of each painted sheet,
Initial adhesion was evaluated by a peel test after each sheet was left at room temperature for 24 hours, and durable adhesion was evaluated by a peel test after being left in hot water at 40° C. for 240 hours.

The peel test was conducted using the following method. The results are shown in Table 1.
[Peeling test] Using a knife, make stripes at 1-audio intervals in all directions on the painted surface of the sheet.
100 substrate stitches were made, adhesive tape (Nichiban Cello Tape) was applied thereon, and adhesion was tested based on the number of substrate stitches that remained when the adhesive tape was peeled off.

Examples 5 to 11 and Comparative Example 5 Adhesion was investigated in cases where the grafting ratio of maleic anhydride to the modified ethylene-propylene copolymer was varied.

That is, 30% by weight of a modified ethylene-propylene copolymer obtained by graft polymerizing maleic anhydride in various proportions to an ethylene-propylene copolymer (80 mol% ethylene units, melt index (190°C) 28). % and ethylene-propylene-synchropentadiene copolymer rubber (ethylene units 70 mol%, ML, +4 = 33
) was added to 100% of toluene.
It was dissolved in CJC to prepare a treatment liquid.

Table 2 shows the results of evaluating the initial adhesion and durable adhesion using each of these treatment solutions in the same manner as in Example 1.

Claims (1)

[Scope of Claims] 1 20 to 95% by weight of a modified ethylene-α-olefin copolymer (A) obtained by graft polymerization of a partially or wholly unsaturated carboxylic acid or its anhydride and ethylene-α
- Olefin-diolefin copolymer rubber (B) A mixture consisting of 80 to 5% by weight was mixed with 100 c. of an organic solvent. c.
1. A method for surface treatment of a polyolefin molded article, which comprises treating the surface of the polyolefin molded article with a treatment liquid dissolved in a proportion of 0.1 to 5 g to form a primer layer. 2 The modified ethylene-α-olefin copolymer (A) obtained by graft polymerization of a partially or wholly unsaturated carboxylic acid or its anhydride is an ethylene-propylene copolymer obtained by graft polymerization of maleic anhydride. Range 1
Treatment method described in section. 3. The treatment method according to claim 1 or 2, wherein the grafting rate of the unsaturated carboxylic acid or its anhydride is 10^-^4 to 10% by weight. 4. A patent claim characterized in that the ethylene-α-olefin-diolefin copolymer rubber (B) is an ethylene-propylene-dicyclopentadiene copolymer rubber or an ethylene-propylene-alkylidene norbornene copolymer rubber. The treatment method described in Scope 1.