JPH0242663B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a coated body using polyolefin as a coating material.

Conventionally, for example, protecting the surface of metal products,
Painting with polyolefin is carried out for purposes such as corrosion prevention, but at this time it is necessary to use a primer to ensure sufficient adhesion strength between the polyolefin paint film, such as a polyethylene paint film, and the object to be coated. It is said that For example, it is known to use a mixture of epoxy urethane resin, epoxy resin, and curing agent as a primer, and to use an aqueous solution of an organic polymer such as polyacrylic acid or polyvinyl alcohol as a primer. However, the adhesion with the polyethylene paint film is not sufficient, and the latter also has similar problems.For this reason, when painting with polyolefin, a method of forcibly oxidizing the polyethylene etc. at a temperature of approximately 280°C has been adopted. However, in this case, due to oxidative deterioration of polyethylene, etc., the quality of the tap water that is passed through, for example, in the inner coating of water pipes, tends to deteriorate, and since the primer is hydrophilic, There are problems with long-term water resistance.

In view of the above-mentioned current situation, the present invention has been made for the purpose of providing a method for manufacturing a coated body coated with polyolefin, which has excellent paint film adhesion and water resistance. The gist is a molecular weight that has two or more carboxyl groups in one molecule, including at least both ends.
A mixture of a 500 to 5000 diene polymer or its hydrogenated product and a polyfunctional epoxy compound is dissolved in an organic solvent and applied as a primer layer to the object to be coated, and after the primer layer is heat-treated, the primer layer is A method for producing a polyolefin-coated body is provided, which comprises coating a polyolefin-coated body on top of the polyolefin coating.

In the present invention, a diene polymer having two or more carboxyl groups or a hydrogenated product thereof is used so that one molecule includes at least both ends thereof, and this carboxyl group-terminated polymer is
Obtained by reacting a diene polymer having two or more hydroxyl groups at the terminal or its hydrogenated product with a polyhydric carboxylic acid such as maleic acid, fumaric acid, itaconic acid, phthalic acid, or its acid anhydride. However, in addition to this method, 1,3-butadiene, isoprene, 1,3-pentadiene, 2,
It can also be obtained by polymerizing a conjugated diene monomer such as 3-dimethylbutadiene or chloroprene using a dithiodicarboxylic acid such as dithiodiglycolic acid as a chain transfer agent, and introducing a carboxyl group at the end of the polymer. I can do it. The molecular weight of the carboxyl group-containing diene polymer needs to be within the range of 500 to 5,000.

The above-mentioned diene polymer having two or more hydroxyl groups at the terminal includes the above-mentioned conjugated diene system alone or mixed with a vinyl monomer such as styrene, acrylic monomer, vinyl pyridine, etc.
It can be easily obtained by polymerization using an initiator for hydrogen peroxide or an azobisisonitrile initiator having a hydroxyl group, and this method mainly uses 1,
A 4-polydiene type product is obtained. In addition, when a vinyl monomer is mixed in the above, it is usually advisable to mix the vinyl monomer in an amount of 50% or less, more preferably 20% or less of the mixed monomer. The above hydroxyl group-terminated diene polymer can also be obtained by reacting a living diene polymer with an epoxy compound such as halogeno alkylene oxide and then treating it with protonic acid. A 1,2-polydiene type product is obtained. Further, the hydrogenated product of the above-mentioned hydroxyl group-terminated diene polymer can be used to convert the diene polymer into nickel,
It can be obtained by hydrogenation using a hydrogenation catalyst such as a cobalt or rhodium catalyst.

Next, the polyfunctional epoxy compound used in the present invention refers to a compound containing two or more epoxy groups in the molecule, and usually includes epichlorohydrin and 2,2-bis(4'-oxyphenyl)propane (abbreviated as bisphenol A). The following general formula with A reaction product represented by is used, and n in the formula is 1
~12 are preferably used.

Further, in place of the bisphenol A, an initial condensate of phenol and formaldehyde is preferably used.

In the present invention, a primer layer is formed by applying a mixture of the carboxyl group-containing diene polymer and the polyfunctional epoxy compound to an object to be coated such as a metal molding. The mixing ratio with the polyfunctional epoxy compound is determined by the molar ratio of carboxyl groups to epoxy groups.
It is preferable to add them together so that the molar ratio is in the range of 0.8 to 1.2, and more preferably so that the molar ratio is 1:1. Furthermore, it is preferable that the thickness of the primer layer is 50μ or less, as the thinner the layer, the better the adhesion strength of the painted body.
More preferably, the coating thickness is 20μ or less.

Further, fillers such as carbon black, calcium carbonate, titanium dioxide, chalk, clay, silica, colorants, antioxidants, ultraviolet absorbers, etc. may be added to the primer as necessary.
Further, when the object to be coated is a metal product such as iron, it is also possible to obtain a rust preventive effect by adding a rust preventive material such as a metal powder such as zinc or a metal oxide such as red iron oxide.

However, the pot life of the primer used in the present invention is usually 10 days or more at room temperature, which is significantly longer than the pot life of about 2 days for conventional urethane primers. It has excellent workability.

Spray the above-mentioned primer dissolved in an appropriate organic solvent such as xylene with a spray gun, and dry.
After painting, it is usually heated to 180℃ or higher. By heating, the functional groups of the resin components in the primer react with each other and crosslink, forming a primer layer with excellent heat resistance and water resistance.

A paint made of polyolefin such as polyethylene is applied on top of the primer layer.
For this coating, an appropriate coating method such as a powder coating method may be employed.

Since the method for manufacturing a polyolefin-coated body of the present invention has the above-described structure, it exhibits excellent effects as listed below.

Since the molecular weight of the diene polymer or its hydrogenated product is 500 to 5000, the mixture of the polymer and the polyfunctional epoxy compound can be dissolved in an organic solvent at room temperature, and the mixture can be used as a primer. It becomes easier to apply the coating as a layer to the object to be coated.

By heat-treating the applied primer layer, the functional groups of the mixture of diene polymer and polyfunctional epoxy compound react and crosslink, forming a primer layer with excellent heat resistance and water resistance. Ru.

A resin component that forms a primer layer by reacting carboxyl groups present at least at both ends in one molecule of a diene polymer or its hydrogenated product with an epoxy group contained in a polyfunctional epoxy compound by heating. has polar groups uniformly formed at predetermined intervals in the molecular chain in one molecule,
Strong adhesion with objects to be coated such as metal products.

The primer layer after heat treatment has a chemical structure in which the molecular structure between the polar groups has excellent adhesion strength to the polyolefin coating, and it also has a chemical structure that has excellent adhesion strength to the polyolefin coating and the object to be coated. This results in excellent adhesion strength.

The present invention will be described above based on examples.

Example 1 600 g of hydroxypolybutadiene having a number average molecular weight of 2800 and a hydroxyl value of 47 was dissolved in dehydrated toluene and reacted with 50 g of maleic anhydride at 110° C. for 5 hours in an argon stream. After the reaction was completed, toluene was distilled off to obtain 650 g of polybutadiene having carboxyl groups at the ends and having an acid value of 43 mg KOH/g.

Next, a steel pipe with a nominal diameter of 15 mm and a total length of 5,500 mm is pickled to completely remove scale, treated with zinc phosphate,
(4.2 g/m ² ), and on the inner surface of the steel pipe, 100 g of the polybutadiene obtained above with terminal carboxyl groups and bisphenol type epoxy (trade name Epicote 828, epoxy equivalent 190) were prepared.
A primer prepared by dissolving 13.6 g in 200 g of xylene was applied with a spray gun and dried at 250° C. for 5 minutes. The average film thickness of the primer at this time is
It was 10μ. After that, this steel pipe was heated to 250℃ in air.
A mixed fluid of air and low-density polyethylene powder with a melt index of 10 g/10 minutes is passed through the inner surface of the steel pipe to melt and bond for about 10 minutes, resulting in a thick film on the inner wall surface of the pipe.
A 900-1000μ polyethylene coating was formed.

The adhesion strength of this steel pipe coating at 25℃ is
It showed 9.0Kg/cm by 180° peeling method. The polyethylene coated steel pipe was cut into appropriate lengths and immersed in hot water at 50°C for 210 days, and then the adhesion was measured in the same manner as above.The adhesion was almost the same as before immersion, and the steel pipe No peeling of the coating from the end face was observed.

Example 2 300 g of hydroxypolybutadiene hydride (iodine value 0.5) obtained by adding hydrogen to hydroxypolybutadiene having a number average molecular weight of 2800 and a hydroxyl value of 47 was treated with maleic anhydride in the same manner as in Example 1. A terminal half-esterified hydrogenated polybutadiene having an acid value of 43 was obtained. This polymer 100
A primer obtained by dissolving 14g of g and bisphenol type epoxy (trade name Epicote 828) in 200g of xylene was applied to the pickled acid board surface,
It was dried at 180°C for 10 minutes. The average thickness of the primer layer was 50μ. Next, this steel pipe was preheated to 250℃ on a hot plate, and powder coated with the same polyethylene as in Example 1 to a film thickness of 900 to 1000μ.
A film was formed. The adhesion strength of this steel plate coating is 10mm.
The width was 11.0 kg/cm by 180° peeling method. Also 50℃
After 210 days of immersion in warm water, the adhesion was almost the same as before immersion, and no peeling of the film was observed from the incisions made before immersion.

Comparative Example 1 Using a primer consisting of 100 g of bisphenol type epoxy (trade name Epicote 828) and 30 g of phthalic anhydride as an epoxy primer, the primer was applied on a steel plate in the same manner as in Example 2 (average film thickness 50μ) and polyethylene powder was applied. Body painting (film thickness 900
~1000μ) and the adhesion force was measured in the same manner as in Example 2, and the adhesion force was 0.5 to 1.0 Kg/cm.

Comparative Example 2 A steel pipe with a nominal diameter of 15 m/m was pickled, treated with zinc phosphate, ethylene-vinyl acetate copolymer powder was attached to the inner surface of the steel pipe, and then heat-melted and bonded to reduce the film thickness.
A 150μ primer layer was formed.

Next, a film thickness was applied to the inner surface of the steel pipe in the same manner as in Example 1.
A polyethylene film having a thickness of 900 to 1000 μm was formed, and the adhesion was measured in the same manner as in Example 1. The adhesion is
It was 6.0Kg/cm. In addition, the adhesion strength after 210 days immersion in hot water is less than 2 kg/cm, and the adhesion strength is less than 2 kg/cm from the end of the steel pipe.
The film was peeled off over a distance of m/m, and rust had developed in that area.

Claims (1)

[Claims] 1 Molecular weight 500 with two or more carboxyl groups in one molecule, including at least both ends
A mixture of ~5000 diene polymer or its hydrogenated product and a polyfunctional epoxy compound is dissolved in an organic solvent and applied as a primer layer to the object to be painted,
A method for producing a polyolefin-coated body, which comprises applying a paint made of polyolefin on the primer layer after heat-treating the primer layer.