JPH08324576A - Method for protecting surface of resin container and coating used therefor - Google Patents

Abstract

PURPOSE: To achieve a simple and remarkable weathering-performance improvement, by forming a surface protective layer on the external layer of a polyolefin resin container. CONSTITUTION: The entire surface of the external layer of a polyolefin resin container is coated with a chlorinated-polyolefin resin coating or/and a chlorinated-polyolefin modified-acrylic resin coating or/and an acrylic modified- chlorinated-polyolefin resin coating, each containing one or more additives selected from among an ultraviolet absorber, a light-resisting stabilizer, and an antioxidant. The coating is dried or hardened, and thus a protective layer consisting of a film of the coating is formed on the surface of a container.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for protecting the surface of a resin-made container, and more particularly to forming a coating layer having excellent weather resistance on the outer surface layer of a polyolefin-based resin container immediately after molding. The present invention relates to a method for preventing surface deterioration by means of the above, and a paint for protecting the surface of a resin container used therefor.

[0002]

2. Description of the Related Art Used in plastic containers that have been used in many fields, such as plastic (resin) containers used for the transportation and storage of beer, carbonated drinks, fruit juice drinks, milk and other glass bottles. From the required physical properties, polyolefin resins such as polyethylene and polypropylene, impact-resistant polystyrene resins, ABS resins, methacrylic resins and the like are used for the resin to be obtained, but from the viewpoint of physical properties such as strength, appearance and price, A polyolefin resin such as polyethylene or polypropylene in which a pigment is kneaded and colored is widely used, and a resin produced by injection molding is generally used. These resin containers are usually printed with the company name, product name, design, etc. of each maker, and epoxy- or urethane-based silk screen ink is usually used for the printing. .

[0003] Usually, the resin container is collected and repeatedly used in the market, and it is estimated that its strength life is 20 years or more from the characteristics of the resin forming the container. Such resin containers that are repeatedly used over a long period of time are often stored outdoors, and their surfaces are exposed to sunlight and wind and rain, which causes severe discoloration and surface deterioration of the resin surface layer and printed film. . As a result, the appearance was significantly impaired and the commercial value was reduced.

Conventionally, a resin container whose surface has been remarkably deteriorated and its appearance has been deteriorated is discarded, and a resin container which can be used for 20 years or more from the viewpoint of mechanical strength is actually used only for its useful life or less. It was not possible to do it and it was not economical. Further, in order to impart weather resistance to these resin containers, the resin material forming the containers contains an ultraviolet absorber, an antioxidant, etc.,
There is a limit to the blending amount in terms of ensuring the quality of the molded product and cost, and there is a limit to improving the weather resistance.

To solve such a problem, Japanese Patent Laid-Open No. 01-58
Japanese Patent No. 662 discloses a method of repairing a container by removing a deteriorated surface layer of the container, then applying a colored paint and curing the paint. According to this method
Although it is sufficiently usable in terms of mechanical strength, it is possible to add commercial value again by repairing the surface of a resin container whose surface has deteriorated significantly. However, such a method is merely a method for repairing a deteriorated one, and is not a fundamental solution to the surface deterioration itself of the container.

[0006]

In view of the above problems, the present invention fundamentally solves the surface deterioration of the resin container. That is, an object of the present invention is to provide a method for preventing surface deterioration of a polyolefin resin container, improving the weather resistance of the resin container, and dramatically improving the service life. In addition,
To provide a method capable of economically preventing this surface deterioration, and to provide a paint capable of forming a coating layer having excellent weather resistance for preventing the surface deterioration of a resin container used in the method. It is in.

[0007]

Means for Solving the Problems As a result of intensive studies, the inventors of the present invention have excellent weather resistance on the outer surface layer of a polyolefin resin container before the surface of the resin container is deteriorated, that is, immediately after molding. It has been found that it is possible to dramatically improve the service life of the resin container by applying a paint to form a surface protective layer,
The present invention has been completed. Furthermore, the present invention forms a surface protective layer containing an expensive ultraviolet absorber, antioxidant, etc. (hereinafter abbreviated as "additive") so that these additives can be added to the entire resin constituting a conventional molded article. Compared with the case of containing, it has succeeded in effectively preventing surface deterioration with a small amount of additive, and has achieved a great effect in terms of economic efficiency, resource saving and energy saving. Is.

The method of protecting the surface of the resin container of the present invention comprises a first step of subjecting the outer surface layer of the molded polyolefin resin container to a treatment for improving the wettability of the surface layer, On the entire surface of the surface layer, at least one resin selected from chlorinated polyolefin resin, chlorinated polyolefin-modified acrylic resin and acryl-modified chlorinated polyolefin resin is used as a coating main agent, and an ultraviolet absorber, a light resistance stabilizer and It is characterized by including a second step of applying a coating material containing at least one additive selected from antioxidants, and a third step of drying or curing the coating material. Further, in the method for protecting the surface of the resin container of the present invention according to claim 2, after the first step of performing the treatment for improving the wettability of the surface layer,
The method is characterized by including a step of printing a part or all of the surface layer. Furthermore, in the method for protecting the surface of the resin container of the present invention according to claim 3, the first step of performing a treatment for improving the wettability of the surface layer is performed after molding the polyolefin resin container. , Characterized by being performed immediately.

The paint for protecting the surface of the resin container of the present invention according to claim 4 is a paint used in a method for protecting the surface of the resin container, which is a chlorinated polyolefin resin or a chlorinated polyolefin-modified At least one resin selected from an acrylic resin and an acrylic modified chlorinated polyolefin resin is used as a paint main agent, and at least one additive selected from an ultraviolet absorber, a light stabilizer and an antioxidant is contained. Is characterized by.

The resin container used in the present invention is made of polyolefin resin such as polyethylene and polypropylene.
It is colored with a coloring agent such as a pigment and molded by an injection molding machine.

The method of the present invention will be described in detail below.
First, the outer surface layer of the polyolefin resin container manufactured by injection molding is subjected to a treatment for improving wettability. Since the polyolefin-based resin is low in orientation and crystalline, and has low adhesiveness to paints, etc., this first step is followed by ink used for silk screen printing, etc., which is optionally applied, and further, This is a step necessary for developing and improving the adhesion of the coating material applied to form the surface protective layer to the surface layer. Since the degree of treatment affects the weather resistance of the ink and paint, the wetting tension of the polyolefin resin surface layer is 40 dy.
Adjust to ne / cm or more, preferably 50 dyne / cm or more. The surface treatment method is not particularly limited as long as it is a method used for treating a polyolefin resin as long as it does not impair the physical properties of the resin, and a known chromic acid mixture treatment, flame treatment, plasma treatment, corona discharge treatment, etc. Can be applied. Further, if left for a long time after the molding of the container, dust, water, etc. may adhere to the surface layer, so this surface treatment is preferably performed immediately after molding the polyolefin resin container in terms of treatment efficiency.
Before the surface treatment, if desired, a pretreatment for removing organic substances such as a release agent and dust remaining on the surface of the container after molding, for example, a solvent such as alcohol or aromatic hydrocarbon, or a surface active agent. It is also possible to perform wiping with an agent or the like.

Next, if desired, a part or all of the surface layer of the container is subjected to printing for marking a company name, a product name, a design or the like. Examples of this printing include silk screen printing, inkjet printing, etc., which are not easily affected by surface irregularities,
Silk screen printing is preferable from the viewpoint of simplicity of the printing apparatus.

Then, on the entire surface of the outer surface layer of the container, at least one selected from a chlorinated polyolefin resin, a chlorinated polyolefin modified acrylic resin and an acrylic modified chlorinated polyolefin resin is used as a coating main agent,
A second step of applying a paint containing at least one additive selected from an ultraviolet absorber, a light stabilizer and an antioxidant is performed.

The paint used to form the surface protective layer in the present invention includes chlorinated polyolefin resins,
Ingredients such as additives such as UV absorbers, light stabilizers and antioxidants, organic solvents, etc. were added to the resin coating main agent selected from chlorinated polyolefin modified acrylic resin and acrylic modified chlorinated polyolefin resin. Further, known paint additives such as defoaming agents and antistatic agents can be blended and used as needed.

The chlorinated polyolefin resin used as the main component of the coating material applied to form the surface protective layer includes chlorinated polyethylene and chlorinated polypropylene, and the chlorinated polyolefin modified acrylic resin is chlorinated. Examples include polyethylene-modified acrylic resin and chlorinated polypropylene-modified acrylic resin. Examples of acryl-modified chlorinated polyolefin resins include acryl-modified chlorinated polyethylene-based resins and acryl-modified chlorinated polypropylene-based resins. It is known that these chlorinated polyolefin resins are excellent in weather resistance and adhesion to olefin resins as compared with unmodified polyolefin resins, and that their physical properties can be controlled by the degree of chlorination, For example, trade name Hitaroid TA-5
01 (manufactured by Hitachi Chemical Co., Ltd.), Supercron 814H, and Supercron 224H (above, manufactured by Nippon Paper Industries).

[0016] As the ultraviolet absorber blended in the paint,
salicylic acid compounds such as p-octylphenyl salicylate,
Benzophenone-based compounds such as 2,4-dihydroxybenzophenone, 2 (2'-hydroxy-3'-tert-butyl-
Benzotriazoles such as 5'-methylphenyl) -5-chlorobenzotriazole, ethyl-2-cyano-
There are cyanoacrylate-based UV absorbers such as 3,3′-diphenyl acrylate and the like, and as the light resistance stabilizer, H such as TINUVIN 622LD (trade name: manufactured by Ciba-Geigy) is used.
There are hindered amine light stabilizers, which are generically referred to as ALS, and nickel complex salt ultraviolet stabilizers such as nickel bis (octylphenyl) sulfide. As for the blending amount of these, with respect to 100 parts by weight of the resin solid content which is the main component of the coating material,
It is preferably 0.1 to 3.0 parts by weight, and more preferably 0.5 to 1.0 parts by weight.

Further, as the antioxidant, 2,6-di-
tert-butyl-4-ethylphenol, 4,4'-butylidenebis (3-methyl-6-tert-butylphenol) and other phenolic compounds, amine compounds, dilauryl-3,
There are organic sulfur-based antioxidants such as 3′-thiodipropionate and phosphite-based antioxidants such as triphenylphosphite. The blending amount of the antioxidant is preferably 0.1 to 5.0 parts by weight, more preferably 0.5 to 5.0 parts by weight, relative to 100 parts by weight of the resin solid content which is the main coating material.
2.0 parts by weight. Regarding the blending amount of the above additives,
If it is less than 0.1 parts by weight, it is difficult to obtain the protective effect, and even if it is added in excess of the upper limit value, the protective effect is not improved,
Rather, a phenomenon such as so-called blooming in which the additive floats on the resin surface may occur, which is not preferable. Each of these ultraviolet absorbers, light stabilizers and antioxidants may be added alone, but only 2
It is preferable to combine at least three kinds of additives from the viewpoint of the effect, and it is particularly preferable to use three kinds of the ultraviolet absorber, the light stabilizer and the antioxidant in combination because the synergistic effect of improving the weather resistance is exhibited. Also, with respect to each of the ultraviolet absorber, the light resistance stabilizer and the antioxidant, only one kind may be used, or two or more kinds may be used in combination.

The organic solvent used for the coating material is
Ethyl acetate, methyl ethyl ketone, toluene, xylene, methyl isobutyl ketone, cellosolve acetate,
Examples thereof include ethyl cellosolve. It is possible to obtain the coating material for protecting the surface of the resin container according to the fourth aspect of the present invention, which is used in the method of the present invention, by mixing the above-mentioned compounding components by a conventional method. When these paints are applied to the method of the present invention, one kind of paint containing a single resin or a plurality of kinds of resins as a paint main component may be applied, or a chlorinated polyolefin resin paint and a chlorinated polyolefin modified compound which are separately blended. Two or more kinds of acrylic resin paints or acrylic modified chlorinated polyolefin resin paints may be mixed and applied.

The paint thus obtained can be applied to the surface of the container by a known method. Examples of the application method include spray application, flow coating, roll transfer, cloth or sponge. And the like. Alternatively, the container may be dipped in a paint bath for application. As the coating amount of this coating material, it is preferable to select an amount such that the coating film thickness after drying and curing is 1 to 50 μm. If the thickness of the coating film is less than 1 μm, the surface protection effect is insufficient, and if it exceeds 50 μm, improvement of the surface protection effect can hardly be expected, and conversely, problems such as sagging of the paint occur at the time of coating. It is easy to do and neither is preferable.

Next, a third step of drying the coating layer formed on the container surface layer is performed. In the present invention, examples of the method of drying or curing the coating material applied to the container surface include a method of leaving it at room temperature and naturally drying, and a method of blowing hot air to the extent that the resin is not deformed.
Since the surface protective layer is formed on the entire surface of the container by the dried and cured coating film, the polyolefin resin that composes the container and the ink used for printing are effectively protected from the influence of ultraviolet rays and the outside air. Therefore, it is possible to prevent a decrease in the commercial value of the container due to surface deterioration.

[0021]

The present invention will be described below with reference to examples, but the present invention is not limited thereto. In the following,% means% by weight unless otherwise specified.

[Preparation of paint] The materials shown in Table 1 were mixed and stirred at room temperature for 10 minutes to prepare a chlorinated polyolefin resin paint (paint 1), a chlorinated polyolefin-modified acrylic resin paint (paint 2), Acrylic modified chlorinated polyolefin resin paint (paint 3) and chlorinated polyolefin modified acrylic resin paint with different additives (paint 4
~ 6) were produced.

[0023]

[Table 1]

Next, a bottled beer container made of polypropylene was molded by an injection molding machine, and immediately the outer surface layer of the beer container was subjected to flame treatment so that the surface wetting tension was 50 dyne / cm or more. Thereafter, a silk screen printing for clearly indicating the company name and the product name was applied to a part of the outer surface layer of the beer container using urethane type silk screen ink. Then, Table 1 above
The coating thickness after drying the paint produced according to the formulation of
The outer surface layer of the container was evenly coated with an air spray gun so as to have a thickness of 10 μm, and dried in hot air at 80 ° C. for 5 minutes. From the container on which the surface protective layer obtained by the method of the present invention is formed as described above, 7 cm × 14
A test plate of cm was cut out so as to include a portion subjected to silk screen printing, and the product coated with the paint 1 was designated as the product 1 of the present invention. did. Further, a 7 cm × 14 cm test plate was similarly cut out from the same container (unpainted) on which no paint was applied, to give a comparative product. The test plates of the present invention products 1 to 6 and the comparative product were subjected to an accelerated weathering test using a sunshine weather meter, and various performances were evaluated according to the following evaluation criteria by a resin surface layer (hereinafter referred to as PP surface) and The silk screen printed portion (hereinafter referred to as the printed surface) was evaluated. The test results are shown in Tables 2 and 3 below.

Evaluation criteria (appearance evaluation of PP surface) 5 --- No abnormal appearance 4 ---- Slight discoloration is recognized 3 ---- Discoloration is recognized 2 --- Intermediate between 3 and 1 1- ──Significant discoloration (appearance evaluation of the printing surface) 5─── No abnormal appearance 4 ─── Ink choking or slight discoloration 3 ─── Ink choking or discoloration 2 ─ ── Between 3 and 1 1 ─── Marking or fading of ink is remarkable

[0026]

[Table 2]

[0027]

[Table 3]

As is clear from the results shown in Tables 2 and 3, the polypropylene bottle beer container of the present invention having the surface protective layer formed by the method of the present invention is a conventional container having no surface protective layer. It was found that the weather resistance performance was dramatically improved in both the resin surface layer and the printed portion, compared with. Further, as a result of observing the product of the present invention during the test period, almost no change was observed in the coating film portion as the surface protective layer. On the other hand, the bottled beer container of the comparative product which does not form the surface protective layer of the present invention, the appearance is impaired as the light irradiation time becomes longer, and in particular,
It was found that the print surface was significantly deteriorated.

[0029]

According to the method of protecting the surface of the resin container of the present invention, there is an excellent effect that the weather resistance of the resin container can be improved. Furthermore, since the usable life of the resin container can be effectively extended with a small amount of the additive, the present invention is particularly useful in terms of economical efficiency and energy saving. Further, the coating material for protecting the surface of the resin container of the present invention can form a film having excellent weather resistance, and has an effect that it can be suitably used in the above method.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Ankichi Ogasawara 2-3-13 Kyobashi, Chuo-ku, Tokyo Toyo Ink Manufacturing Co., Ltd. (72) Inventor Yuichi Takaishi 2-10-1, Shinkawa, Chuo-ku, Tokyo Kirin Brewery Co., Ltd. Ceremony Company (72) Inventor Fumio Otsuka No. 1 Nobezawa, Kaisei-cho, Ashigarakami-gun, Kanagawa Meiji Rubber Kasei Kanagawa Plant

Claims (4)

[Claims] 1. A first step of subjecting an outer surface layer of a molded polyolefin resin container to a treatment for improving the wettability of the surface layer, and a chlorinated polyolefin resin on the entire surface layer. , At least one resin selected from chlorinated polyolefin-modified acrylic resin and acrylic modified chlorinated polyolefin-based resin as a paint main agent, and at least one addition selected from ultraviolet absorbers, light stabilizers and antioxidants A method for protecting the surface of a resin container, comprising: a second step of applying a paint containing an agent; and a third step of drying or curing the paint. 2. The method according to claim 1, further comprising a step of printing a part or all of the surface layer after the first step of performing a treatment for improving the wettability of the surface layer. How to protect the surface of a plastic container. 3. The first step of applying a treatment for improving the wettability of the surface layer is performed immediately after the molding of the polyolefin resin container.
A method for protecting the surface of the resin container described. 4. The coating material used in the method according to claim 1, wherein at least one resin selected from a chlorinated polyolefin resin, a chlorinated polyolefin-modified acrylic resin, and an acrylic modified chlorinated polyolefin-based resin is used as a main coating material. A paint for protecting the surface of a resin container, which is a paint containing at least one additive selected from an ultraviolet absorber, a light stabilizer and an antioxidant.