JPH09141657A - Removing method for film of resin base surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to form recyclable reclaimed resin by sufficiently removing the film formed on the resin base surface of a resin product without lowering resin physical properties. SOLUTION: The method for removing the film of resin base surface comprises the steps of introducing resin base having the film on the surface in a reaction vessel having an agitator, agitating it at 1.8m/sec of the rotating speed at the end of the agitating blade of the agitator at a lower temperature than the melting temperature of the base at 110 deg.C or lower in the presence of aqueous release liquid of the quantity for forming the same as or lower than the uppermost surface of the base laminated in the vessel, and bringing the surfaces of the bases into contact with each other to polish it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing a coating film on the surface of a resin substrate, and more particularly, it is possible to sufficiently remove the coating film on the surface of a resin substrate without deteriorating the physical properties of the resin constituting the resin substrate. Therefore, the present invention relates to a method for removing a coating, which allows a resin from which the coating has been removed to be a resin material that can be recycled for industrial use.

[0002]

2. Description of the Related Art Generally, resin molded products have advantages such as light weight and excellent impact resistance as compared with metal products and glass products, as well as low cost and easy molding process. It is used in automobiles, home appliances, household goods, and many other fields. In particular, in the automobile industry, the number of resin parts occupying the vehicle body tends to increase year by year in order to reduce the weight of the vehicle body.

Many of these resin products are painted in order to improve their scratch resistance, weather resistance and product aesthetics. As a paint used for this coating, a material that forms a three-dimensional crosslinked structure is often used in terms of the adhesiveness to a resin molded product and the performance of the coating film itself. However, a coating film made of these paints has a problem that, if the coating film needs to be peeled for some reason, it cannot be easily peeled because it has a strong crosslinked structure.

By the way, the technique of peeling off the coating film and removing it from the substrate is a resin base material of a resin molded product to be coated, when a defective coating process occurs, when an old coating film having deteriorated performance is replaced with a new coating film. It is an industrially important technology that is required in many industrial situations, such as when only reusing only.

The conventional methods for removing the coating film are roughly classified into a physical peeling method and a chemical peeling method. Among them, the method by physical peeling is a method of scraping the coating with sandpaper or the like. The method of chemical peeling is roughly divided into the following three methods. 1) A method using a release agent containing a chlorine-based solvent as a main component (JP-B-51-34238, JP-B-57-76065, and JP-A-59-117567). 2) A method using a release agent containing an organic substance as a main component (JP-A-50-109925, JP-A-1-289878, and JP-A-2-274775). 3) A method using a release agent containing an inorganic substance as a main component (JP-A Nos. 50-109925, 59-131674, and 61-162568). In addition, there is also a removal method using a release agent obtained by arbitrarily mixing the main components of the above-mentioned three types of release agents, and a release agent obtained by optionally mixing these with other components.

[0006]

However, in such a conventional method for removing a coating film, the removal of the coating film may be incomplete depending on the type and thickness of the coating film to be removed. When the resin product from which the film has been removed is reused for the same purpose again, if the removal of the film is incomplete, the physical properties of the product obtained will deteriorate.

The object of the present invention is to solve the above-mentioned problems of the prior art and to sufficiently remove the coating film formed on the surface of a resin substrate such as a resin product without deteriorating the physical properties of the resin. It is an object of the present invention to provide a method for removing a coating that can be used as a recycled resin that can be recycled.

[0008]

In order to solve the above-mentioned problems, the present invention provides a resin substrate having a film on its surface in a reaction vessel equipped with a stirrer in the presence of an aqueous stripper containing an alkaline substance. A method of removing a coating film on a surface of a resin substrate by stirring treatment, comprising: (A) an amount of an aqueous stripping solution having a liquid level which is the same as or lower than the uppermost surface of the resin substrates laminated in a reaction container. In the presence, (B) 110 ° C. or higher and a temperature lower than the melting temperature of the resin substrate, and (C) stirring is performed at a rotation speed of the tip of the stirring blade of the stirring device of 1.8 m / sec or more, It is intended to provide a method for removing a coating film on a surface of a resin substrate, which includes a step of bringing the surfaces of the resin substrate into contact with each other and polishing them.

The method for removing the film on the surface of the resin substrate of the present invention (hereinafter referred to as "the method of the present invention") will be described in detail below.

The method of the present invention is a method for removing a coating film formed on the surface of a resin substrate. The resin substrate from which the coating is removed is not particularly limited and may be made of any material. Further, the resin substrate may be filled and reinforced with glass fiber, carbon fiber, or inorganic powder.
In particular, the method of the present invention is effective as a method for removing a coating film on the surface of a substrate made of polyolefin. further,
Among the resin substrates made of polyolefin, the method of the present invention is particularly effective when applied to a resin substrate made of polypropylene, which has a high melting point and is difficult to dissolve in a solvent, among polyolefins.

Further, in the method of the present invention, the resin substrate from which the coating film is removed can be sufficiently abraded by the contact and collision of the resin substrates in the aqueous stripping solution by stirring, and it is industrially possible. From the viewpoint that a large amount of treatment is possible, a pulverized product or a granular product is preferable, and a particle size of 3 to 20 mm is particularly preferable.

The method of the present invention is effective as a method for removing a coating film formed on the surface of a resin substrate, particularly a cured coating film. As a cured coating peeled by the method of the present invention,
For example, apply a coating containing a thermosetting resin or a thermoplastic resin as a main component such as phenol resin-based paint, polyester resin-based paint, alkyd resin-based paint, acrylic resin-based paint, polyurethane resin-based paint, epoxy resin-based paint, etc. ,
A film formed by curing is included. This coating may be a coating made of a mixture containing a thermosetting resin and a thermoplastic resin, or a laminated coating having a plurality of coatings made of these thermosetting resins and / or thermoplastic resins. It may be. Further, the method of the present invention is suitable as a method for removing a coating film made of a resin containing a thermosetting resin as a main component such as an alkyd resin, an acrylic resin, and a polyester resin. In particular, the method of the present invention is suitable as a method for peeling off a cured film made of paint such as polyester urethane, polyester melamine, acrylic urethane, and acrylic melamine used for coating automobiles.

Further, in the method of the present invention, the cured coating film may be directly formed on the surface of the resin substrate, or may be formed on the surface of the resin substrate via the primer layer. This primer is not particularly limited and may be any primer used for forming a cured coating film on the surface of this type of resin substrate. Also,
The surface of the resin substrate improves adhesion to the cured coating film,
Surface treatment such as plasma treatment, flame treatment, and water blast may be applied.

The method of the present invention is also effective for removing the multi-layer coating formed by various paints. The thickness of the coating to be removed is not particularly limited, but a cured coating having a thickness of 200 μm or less is preferable, and further 10 to 100.
The one having a thickness of 30 μm is preferable, and the one having a thickness of 30 to 80 μm is particularly preferable.

The method of the present invention is a method of removing the coating film on the surface of the resin substrate by stirring the resin substrate in a reaction vessel equipped with a stirring device in the presence of an aqueous stripping solution. In this method, first, (A) a resin substrate and an aqueous stripping solution are put into a reaction vessel, and then a stirring process is performed. The resin substrate and the aqueous stripping solution may be charged into the reaction vessel at the same time, or either may be charged first, and the order of charging is not particularly limited.

The reaction vessel used for the stirring treatment is not particularly limited, and may be a tank type vessel equipped with a stirring device. In particular, an autoclave equipped with a stirrer is preferable because it becomes a pressurized state when treated at a high temperature.

The aqueous stripper used in the method of the present invention is an aqueous solution containing an alkaline substance. The alkaline substance is not particularly limited, and examples thereof include LiOH and NaO.
Examples thereof include inorganic alkaline substances such as H, KOH, Mg (OH) ₂ and Ca (OH) ₂ . These may be used alone or in combination of two or more. Among these, NaOH and KOH are preferable, and NaOH is more preferable.

The concentration of the alkaline substance in the aqueous stripper is
From the viewpoint that the coating film on the surface of the resin substrate can be sufficiently embrittled, the risk of handling is small, and the treatment of waste water is easy, the content is preferably 0.1% by weight or more, and more preferably 0.1% by weight. 1 to 5% by weight, particularly preferably 0.2 to 4% by weight.

In addition to the alkaline substance, the aqueous stripper may optionally contain other compounding agents. For example, a small amount, especially 50
It may be contained by weight% or less. Examples of the defoaming agent include silicone-based, alcohol-based and fatty acid-based defoaming agents, and examples of the surfactant include alkylbenzene sulfonic acid, dialkyl sulfosuccinic acid, and polyoxyethylene alkyl ether. Examples of amines include alkylamines such as triethylamine and alkanolamines such as monoethanolamine. Further, as the organic solvent, for example,
Examples thereof include those having good compatibility with water, such as methyl alcohol, 1-propyl alcohol, 2-propyl alcohol and t-butyl alcohol.

The amount of this aqueous stripping solution is introduced into the reaction container in an amount that forms a liquid surface which is the same as or lower than the uppermost surface of the resin substrates laminated in the reaction container. The amount of the aqueous stripper used is usually 0.3 to 1.2 with respect to the resin substrate.
The weight ratio is 0.5 to 1.2 times by weight. By reducing the amount of this aqueous stripper,
It is possible to improve the processing volume efficiency of the reaction container and reduce the waste liquid after the processing. 0.5 against the amount of resin substrate charged
When the weight ratio of the aqueous stripping solution is added, it is immersed to a height of about ½ of the resin substrate in the reaction vessel without stirring. When 1.2 weight ratio of the aqueous stripping solution to the charged amount of the resin substrate is added, the upper surface of the resin substrate and the surface of the aqueous stripping solution are almost the same surface without stirring, and the aqueous stripping solution is The resin substrate is immersed in the.

In the method of the present invention, a resin substrate is placed in a reaction vessel, an aqueous stripping solution is placed therein, and a stirring treatment is carried out so that the surfaces of the resin substrate are brought into contact with or collided with each other so as to polish each other. This stirring treatment is preferably carried out in the aqueous stripping solution at a tip speed of the stirring blade of the stirrer of 1.8 m / sec or more, preferably 3 m / sec or more, more preferably 4 m / sec or more. The diameter and shape of the stirring blade of the stirring device are not particularly limited as long as they can uniformly stir the resin substrate, and examples thereof include paddle type, turbine type and propeller type blades.

In this stirring treatment, the temperature is 110 ° C. or higher, preferably 140 ° C. or higher and lower than the melting temperature of the resin substrate. For example, the temperature for treating the resin substrate made of polyolefin is 110 to 170 ° C. Yes,
Preferably 150 to 170 ° C., more preferably 150.
１６０160 ° C. Further, the treatment time may be appropriately selected according to the type and thickness of the cured coating, the shape and size of the resin substrate, the treatment temperature, and the like. Usually, it is about 10 minutes to 2 hours, preferably about 30 minutes to 1 hour.

In the method of the present invention, particularly, the aqueous stripping solution is NaOH or KOH, the concentration of the aqueous stripping solution is 0.2 to 4% by weight, and the treatment with the aqueous stripping solution melts the substrate. The method of removing the coating is preferably a stirring treatment at a temperature lower than the temperature to be applied and higher than 140 ° C., for example, a temperature of 150 ° C. to 170 ° C.

In the method of the present invention, the resin substrate is agitated with an aqueous stripping solution to peel off the cured coating, and then a cleaning device is used to remove the residue of the coating adhering to the surface of the resin substrate. Good.

[0025]

In the conventional method, the aqueous stripping solution is generally agitated while the pulverized product of the resin substrate having the coating film is sufficiently immersed. As described above, when the pulverized product is stirred with a sufficiently dipping amount of the aqueous stripping solution, the coating partially remains on the resin substrate, whereas in the method of the present invention, the pulverized product is treated more effectively than the aqueous stripping solution. The coating can be sufficiently removed by performing stirring treatment in a sufficiently immersed state. If this is agitated with insufficient immersion, the contact and collision of the pulverized products will increase,
It is considered that the coating film on the surface of the resin substrate is scraped off, peeled off, and removed.

[0026]

EXAMPLES The present invention will be specifically described below with reference to examples of the present invention and comparative examples, but the present invention is not limited to these examples.

(Examples 1 to 4 and Comparative Examples 1 to 3) "Preparation of coating sample" In each example, polypropylene containing 0.5% by weight of carbon black (manufactured by Mitsui Petrochemical Industry Co., Ltd., trade name: High pole X440, below, P
(Abbreviated as P) was subjected to injection molding to prepare a square plate having a thickness of 3 mm. The square plate was treated by exposing it to 1,1,1-tochloroethane vapor for 30 seconds, and then left at room temperature for 30 minutes to dry. Next, using an air spray gun, a primer (UNISTOL P-801 manufactured by Mitsui Petrochemical Industry Co., Ltd.) was applied to the surface of the square plate so that the primer film thickness after drying was about 10 μm. After that, setting was performed at room temperature for 10 minutes. After that, on the primer film of the square plate, one-pack type acrylic melamine paint which is a thermosetting paint (Kansai Paint Co., Ltd., Soflex # 1200)
Was applied using an air spray gun (discharge pressure 1 kg / cm ² ) so that the film thickness of the curable coating film was 40 to 50 μm, and the setting was performed for 10 minutes. Then 120
The coating film was cured by heating at 30 ° C. for 30 minutes to obtain a coated sample in which a curable coating film was formed on the surface of a square plate made of PP via a primer film.

"Removal of coating film from coated sample" The obtained coated sample was crushed into chips of about 5 mm square to obtain sample chips. Next, the aqueous stripping solution and the sample chip were put into a pressure reactor equipped with a stirrer at a charge weight ratio shown in Table 1 or Table 2, and
Alternatively, stirring treatment was performed under the conditions shown in Table 2. Then, after cooling to room temperature and washing the sample chip with water to remove the stripping solution,
Dried.

"Evaluation of effect of removing coating film" With respect to the sample chip from which the above coating film was removed, the following respective tests were carried out on the assumption that the treated sample chip is used for an automobile bumper. The results are shown in Table 1 or Table 2.

(Preparation of Test Pieces) The sample chips after the above treatment were subjected to injection molding at a molding temperature of 200 ° C. to prepare the following test pieces for a tensile test high-speed surface impact strength test, and subjected to the respective tests. did.

(1) Tensile Test (Tensile Yield Strength, Tensile Elongation at Break) A test piece subjected to JIS K7113 was tested at 23 ° C.
Was measured.

(2) High-speed surface impact strength A disk having a thickness of 1.6 mm and a diameter of 100 mm was formed by injection molding. Using a high-speed impact tester manufactured by Orientec Co., Ltd., this disc was placed on a table having a pilot hole with a diameter of 60 mm, and then the disc was 25 mm in diameter at a speed of 2.5 m / sec.
Punching was performed with a (1 inch) falling weight, and the breaking energy (J, joule) was determined. If the impact strength is insufficient, the bumper will be damaged at the time of a light collision, and the vehicle body will be damaged or the scattered resin pieces will cause a secondary disaster. To prevent this, the breaking energy is 15 (J) joules or more, and the breaking state is Is required to be ductile fracture. The broken state was evaluated according to the following criteria. 5D: 5 out of 5 test pieces were ductile fracture 4D 1B: 4 out of 5 test pieces were ductile fracture, 1 was brittle fracture 5B: 5 out of 5 specimens were brittle fracture

(Preparation of bumper for automobile) Using the sample chip after the above treatment, a bumper having a shape shown in a perspective view in FIG. 1 was molded at a resin temperature of 250 ° C. using a 2000 ton injection molding machine. (3) Appearance evaluation of molded bumper The appearance of the molded bumper was visually observed and evaluated according to the following criteria. Criteria for evaluation judgment ○ In addition to rough spots on the bumper surface due to residual paint, irregularities, swelling, deformation, warp, sink marks, uneven gloss, silver marks, etc. The defects are not noticeable. × The bumper appearance is not noticeable or glossy.

(4) Bumper molded article collision test (Test method) A bumper is attached to a truck or an actual vehicle, and the bumper is hit with a pendulum type impact object (corresponding to vehicle weight) in an atmosphere of normal temperature and -30 ° C. (Evaluation method) Room temperature bumper deformation amount: 60 mm as dent amount due to impact
Less than ◯, and 60 mm or more as x. Impact resistance at −30 ° C .: those that do not break are ◯ and those that break are x.

(5) Comprehensive Evaluation of Bumper Molded Product In the appearance evaluation or the impact test, a product having x of 1 or more was evaluated as x (impossible).

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

According to the method of the present invention, a coating film formed on the surface of a resin substrate such as a resin product can be sufficiently removed without lowering the physical properties of the resin and can be recycled for industrial use. It can be a recycled resin.

[Brief description of the drawings]

FIG. 1 is a perspective view showing the appearance of bumpers prototyped in Examples and Comparative Examples.

Claims (8)

[Claims] 1. A method for removing a coating film on the surface of a resin substrate by stirring the resin substrate having a coating film on the surface thereof in a reaction vessel equipped with a stirring device in the presence of an aqueous stripping solution containing an alkaline substance. , (A) in the presence of an amount of an aqueous stripping solution that is the same as or lower than the uppermost surface of the resin substrate laminated in the reaction container, (B) is 110 ° C. or higher, and the resin substrate is At a temperature lower than the melting temperature of (1) and at a rotational speed of the stirring blade tip of the stirring device of 1.8 m / sec or more, and (C) includes a step of bringing the surfaces of the resin bases into contact with each other and polishing each other. A method for removing a coating film on the surface of a resin substrate. 2. The method for removing a coating film on the surface of a resin substrate according to claim 1, wherein 0.3 to 1.2 times by weight of an aqueous stripping solution is added to the resin substrate having a coating film on the surface. 3. The method for removing a coating film on a surface of a resin substrate according to claim 1, wherein the resin substrate having a coating film on the surface is a pulverized product. 4. The aqueous stripper contains an alkaline substance of 0.
The method for removing a coating film on the surface of a resin substrate according to claim 1, wherein the coating film contains 2 to 4% by weight. 5. The method for removing a coating film on a surface of a resin substrate according to claim 1, wherein the aqueous stripping solution contains NaOH and / or KOH. 6. The stirring treatment is performed at 140 ° C. or higher,
The method for removing a coating film on the surface of a resin substrate according to claim 1, which is performed at a temperature lower than the melting temperature of the resin substrate. 7. The resin substrate surface according to claim 1, wherein the coating film is a coating film having a single or multi-layered structure containing at least one resin selected from thermosetting resins and thermoplastic resins as a main component. How to remove the coating. 8. The removal of the coating film on the surface of the resin substrate according to claim 7, wherein the thermosetting resin is a resin whose main component is at least one selected from alkyd resins, acrylic resins and polyester resins. Method.