JPH10249270A - Method for peeling coating film on resin molded body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To completely and highly efficiently peel a coating film out of a resin molded body without requiring complicated process and stirring work at low cost by immersing the resin molded body bearing the coating film on the surface and a presser-type cover while keeping the presser-type cover on the coating in a peeling liquid and carrying out heating treatment. SOLUTION: In the case that a peeling treatment of a coating film formed on a resin used as a material for bumpers of automobiles is carried out, molded body 2 pulverized into granules is put in an autoclave 4 filled with a liquid 3 for peeling the coating film and a presser type cover 1 having a large number of air ventilation holes 5 is put on the body 2. Surfactant-containing aqueous solutions, liquids only consisting of a surfactant, oils containing surfactants, etc., are examples for the liquid 3 for peeling the coating film. The coating film on the surface of the molded body 2 is peeled by heating in the autoclave 4 and after the heating treatment, the presser type cover 1 is pulled up and the liquid in which the molded body 2 is immersed is stirred to promote peeling of the coating film and completely separate the coating film from the resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for peeling a coating film formed on a resin surface of a resin molded product. In particular, coatings applied to improve the weather resistance and decorative properties of resins such as polypropylene used as materials for automobile bumpers and grilles are difficult to peel off from the resin, which is an obstacle in recycling the resin. Because,
A method for easily removing such a coating film is provided.

[0002]

2. Description of the Related Art Reusing a resin with a coating film has the following problems: (1) particulate matter derived from a coating film having various colors is scattered in the resin; As a result, the appearance of the recycled molded product deteriorates,
(2) The surface of the recycled molded article is roughened by the particulate matter derived from the coating film, and the gloss is reduced. (3) The notch effect caused by the particulate matter derived from the coating film in the recycled molded article (4)
There are problems such as the inability to use recycled materials in parts where high physical properties (such as strength) are required among automotive parts. In particular, regarding physical properties, it is known that the impact resistance (Izod impact value) is reduced to about 50% and the tensile elongation at break is reduced to about 30% as compared with the virgin material.

[0003] Therefore, a technique for peeling a coating film from the surface of a resin molded article has been studied. For example, a melt filtration method, a blast method, a hydrolysis method, an organic solvent method, an alcohol / organic salt method and the like have been studied as a method of peeling a coating film.

[0004] In the melt filtration method, a resin having a coating film is heated and melted, and the resin in a liquid state and the coating film remaining in a solid state are formed.
This is a method of separating by filtering through a wire net. This method has a drawback of low efficiency because the wire mesh is easily clogged.

[0005] The blast method is a method in which the surface of a coating film is subjected to impact with a liquid or water injected at a high speed and a high pressure, and at the same time, is ground to remove the coating film. This method has the drawbacks that the peeling efficiency is low and that peeling is difficult if the surface of the object has irregularities.

The hydrolysis method is a method in which a resin with a coating film is poured into a high-temperature acid or alkali aqueous solution, and the thermosetting resin coating film is hydrolyzed and removed using the acid or alkali as a catalyst. This method has drawbacks such as the necessity of an acid or alkali neutralization step. JP-A-5-18502
Japanese Patent Application Publication No. 4 (1999) -114 discloses a technique in which a polyurethane-based coating film is immersed in a heated methanol-sodium hydroxide saturated solution to stir the whole.

[0007] The organic solvent method is a method in which a coating film is peeled by swelling the coating film in an organic solvent to break an adhesive interface. This method requires a step of recovering the organic solvent, and has problems such as the organic solvent remaining in the recycled material.

The alcohol / organic salt method is a method in which a coating film is put into a coating film decomposing agent composed of water, ethanol, and an organic salt, and is chemically decomposed and removed using organic salt ions as a catalyst. The target coating film is a melamine resin. This method
There are problems such as the necessity of a step of recovering the decomposing agent.

[0009]

As described above, the conventional techniques have problems such as low efficiency, complicated processes, concerns about safety of chemicals used, necessity of drainage treatment, and high cost. Yes, it has not yet been put to practical use. On the other hand, in Japanese Patent Application No. 9-34539 filed earlier by the present applicant, a part of the resin molded body is protruded above the liquid surface by immersing the coarsely ground resin molded body in a liquid and stirring the resin molded body. To prevent it from being left untreated. Therefore, an object of the present invention is to provide a coating film that is highly efficient and low cost, does not require complicated steps, and can completely treat a resin molded body without stirring, as compared with the prior art. To provide a method for peeling off.

[0010]

According to a first aspect of the present invention, there is provided a method of peeling a coating film of a resin molded product, comprising: removing a resin molded product having a coating film on a surface thereof; It is characterized in that it is immersed so that the drop lid is on the upper side and then heat-treated. According to a second aspect of the present invention, in the method for removing a coating film of a resin molded body, the drop lid further has an air hole. According to a third aspect of the present invention, the method of the present invention is further characterized in that the drop lid has a convexly curved shape.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION As a material (resin) of a resin molded body used in the present invention, for example, modified polypropylene,
An olefin-based thermoplastic elastomer can be used. Among them, the modified polypropylene is obtained, for example, by modifying polypropylene with an ethylene propylene diene terpolymer (EPDM), and the olefin-based thermoplastic elastomer has a hard segment made of polyethylene or polypropylene, and a soft segment made of EPDM. It is a thermoplastic elastomer.

Examples of the coating film include urethane paint. Specifically, an acid-modified chlorinated polyolefin-based undercoat and a polyurethane-based overcoat are separately applied to the surface of a polyolefin-based resin molded article in multiple layers. Examples of the coating material include a coating material obtained by blending or chemically bonding two components of an undercoat / polyurethane-based paint. Further, melamine, alkyd, water-based paint or the like may be applied as a top coat. The thickness of the coating film is arbitrary, but is generally about 30 to 50 μm.
m. For example, when urethane paint is applied to a bumper of an automobile, the thickness is about 30 μm.

The drop lid used in the present invention is for preventing a resin molded product having a specific gravity smaller than that of water from protruding above the liquid surface and preventing the protruding portion from being treated with the liquid for peeling the coating film. Things. By submerging the resin molded article in the liquid containing the resin molded article, the resin molded article can be completely submerged in the liquid. The drop lid has a shape conforming to the cross section of a heating vessel such as an autoclave, preferably,
The shape is such that a gap of about 2 to 5 mm is formed between the autoclave and the wall surface during use. If the gap is too small, the drop lid may expand during heating, and may not be removable from the heating container. Conversely, if the gap is too large, the resin molded body may pass through the gap and move to the liquid level.

The drop lid is preferably formed into a convexly curved shape, and is immersed in a liquid in a heating container with the convex portion facing upward when used. By making the shape curved in a convex shape, the resin molded body can be dropped and collected at the center of the lid. When using a flat drop lid, or when using a convex curved drop lid with the convex part down, the molded resin passes through the gap between the drop lid and the autoclave wall surface, It may move to the liquid level.

[0015] The drop lid is preferably provided with at least one air vent hole. In particular, in the case where a drop lid that is convexly curved is used, if there is no air vent hole, when immersed in the liquid in the heating container, air will stay under the drop lid. The diameter of the air vent is usually 2
About 5 mm.

As the material of the dropping lid, a material that does not denature or deform at a heating temperature of 120 ° C. or more, preferably 150 ° C., which is the heating temperature in the present invention, and that is not deteriorated by the liquid for peeling off the coating film used in the present invention. Used. For example, various metals, ceramics, enamels, resins, and the like. The specific gravity of the dropping lid is preferably larger than the specific gravity of the liquid in order to naturally sink the dropping lid into the liquid for removing the coating film. If the specific gravity is smaller than the liquid, it is necessary to attach a weight to the dropping lid.

FIG. 1 shows an autoclave 4 in which a dropping lid 1 is filled with a molded product 2 crushed into granules and a liquid 3 for peeling a coating film.
Shows the state immediately after being put inside. The drop lid 1 is provided with an air bleed hole 5, and air entrained when submerged in the liquid 3 passes through the air bleed hole 5 and emerges as air bubbles 6.

FIGS. 2 and 3 show examples of drop lids. FIG. 2 shows an example of a resin drop cover, in which a large number of air vent holes 8 are formed in a drop cover 7 formed into a convexly curved shape. FIG. 3 shows an example of a metal drop lid. A drop lid 10 formed by overlapping a plurality of curved metal plates 9 is provided with a large number of air vent holes 11.
Further, by sliding the metal plate 9, the diameter of the drop lid 10 can be changed.

The liquid for removing a coating film used in the present invention is as follows:
What is necessary is just to be able to swell or dissolve the resin of the resin molded body without being corroded. Preferably, the liquid has a boiling point of 100 ° C. or higher at normal pressure and does not denature even at a high temperature of 180 ° C. Further, when a liquid having a specific gravity between the resin and the coating film is used as the liquid for peeling the coating film, the resin floats up and the coating film sinks down only by stirring the liquid after peeling the coating film. Then, the two naturally separate.

Examples of the liquid for removing the coating film include an aqueous solution containing a surfactant, a liquid containing only a surfactant, an oil containing a surfactant, and a liquid containing an oil.

As the aqueous solution containing a surfactant, for example, when a coating film made of a urethane paint is peeled off, a polyoxyalkylene alkyl ether, a polyoxyalkylene alkyl aryl ether, or a phosphoric acid ester or a sulfate thereof is used as a main component. And 0.00
Aqueous solution having a concentration of 1% by weight or more, polyoxyethylene alkyl ester such as polyoxyethylene laurate (HL
B is as low as about 9.5) 0.00
An aqueous solution having a concentration of 1% by weight or more is preferably used.
The surfactant is selected according to the type of the coating film.

The above polyoxyalkylene alkyl ether or polyoxyalkylene alkylaryl ether has a chemical formula of RO (CH ₂ CH ₂ O) _n H (R is an alkyl or alkylaryl group having 1 to 20 carbon atoms in the alkyl, n is an integer of 1 to 10.) The chemical formula of the phosphate ester of the polyoxyalkylene alkyl (or alkylaryl) ether is represented by R
_{O (CH 2 CH 2 O)} n PO (OR ') is (OH) (R is an alkyl or alkyl aryl group having carbon atoms in the alkyl is 1 to 20, n is an integer of 1 to 10, R' is Represented by a hydrogen atom or R (CH ₂ CH ₂ O) _n .)
It is represented by The chemical formula of the polyoxyalkylene alkyl (or alkylaryl) ether sulfate is represented by RO (CH ₂ CH ₂ O) _n SO ₂ (OR ′) (R is an alkyl or alkylaryl group having 1 to 20 carbon atoms of alkyl. and a, n is an integer of from 1 to 10, R 'is represented by a hydrogen atom or _{R (CH 2 CH 2 O)} n.)
It is represented by

Examples of the phosphoric acid ester of polyoxyalkylene alkylphenyl ether include “Plysurf A”
210G "(manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and a mixture of polyoxyethylene alkyl ether and sodium sulfate of alkyl ether is" Natera "
(Lion Oil & Fats Co., Ltd.), the sulfate of polyoxyethylene lauryl ether is "more"
(Manufactured by Kao Corporation) and are commercially available.
Note that the above “Natella” contains water and therefore cannot be used in a mixture with oil. Polyoxyethylene laurate (HLB: 9.5) is commercially available under the trade name “Nissan Nonion L-2”.

The concentration of the surfactant in the aqueous solution is 0.00
It is about 1 to 10% by weight, preferably 0.01 to 3% by weight. If the amount is less than 0.001% by weight, the processing time required for peeling off the coating film increases, resulting in inefficiency. If it exceeds 10% by weight, the peeling effect is almost the same as that of 10% by weight, but the cost increases and the burden of drainage treatment also increases.

As the liquid containing a surfactant, for example, when a coating film made of a urethane paint is peeled off, a phosphoric acid ester of polyoxyalkylene alkylphenyl ether is preferably used.

As the oil containing a surfactant, for example, when a coating film made of a urethane paint is peeled, an oil containing a phosphoric acid ester of polyoxyalkylene alkylphenyl ether or the like is preferably used. Silicon oil or the like can be used as the oil. Silicon oil is preferred because it is flame retardant.

[0027] Silicon oil has a flash point of 300
A material having a specific gravity of 0.960 to 0.970 at a temperature of not less than 0 ° C., stable to heat, and non-volatile is used. For example, a commercially available silicone oil such as “SRX-310” manufactured by Toray Industries, Inc. can be used. By mixing the surfactant in the oil, the oil adhering to the resin can be easily washed after the coating film is separated and separated. The concentration of the surfactant in the oil is preferably 0.5 to 100% by weight, more preferably 5 to 30% by weight. If the content is less than 0.5% by weight, it becomes difficult to remove oil adhering to the resin.

As the liquid consisting only of oil, the same oil as the oil used in the oil containing the above-mentioned surfactant is used.

In the method of the present invention, first, a compact of waste material (for example, a bumper of an automobile) is collected, and this is roughly crushed or cut to a size of 3 mm square or more. The molded article can be used as it is, but in this case, the coating film is cut in a mesh shape with a blade or a laser beam so as to be easily peeled off.

A liquid for peeling the coating film is prepared, and the liquid and the resin molded product are put into a heating container such as an autoclave, and then dropped from above and a lid is put. The drop lid is submerged in the liquid to prevent the resin molded body from floating on the liquid surface. The liquid for peeling the coating film is kept at a certain temperature or higher, and the resin molded body is heated. By this heat treatment, the coating film coated on the surface of the molded body is separated from the resin of the molded body.

When an aqueous solution containing a surfactant is used, the heating temperature is 105 to 180 ° C., preferably 120 to 180 ° C.
~ 160 ° C, more preferably 145 ~ 155 ° C,
The heating time is preferably from 10 to 90 minutes, more preferably from 15 to 40 minutes. At the time of heating, it is necessary to pressurize with an autoclave or the like.

When a liquid consisting of only a surfactant is used, the heating temperature is 30 to 180 ° C., preferably 50 to 1 ° C.
The temperature is 60 ° C, more preferably 70 to 100 ° C, and the heating time is 1 minute or more, preferably 5 to 150 minutes, more preferably 30 to 60 minutes. It can be heated at normal pressure, and no autoclave is required. It is not limited to the batch type, and continuous operation is possible.

When an oil containing a surfactant is used, the heating temperature is 30 to 180 ° C., preferably 70 to 1 ° C.
The temperature is 60 ° C., more preferably 140 to 155 ° C., and the heating time is 1 minute or more, preferably 5 to 150 minutes, more preferably 10 to 15 minutes. It can be heated at normal pressure, and no autoclave is required. It is not limited to the batch type, and continuous operation is possible.

When a liquid consisting only of oil is used, the heating temperature is 50 to 180 ° C., preferably 70 to 160 ° C.
° C, more preferably 140 to 155 ° C, and the heating time is 1 minute or more, preferably 1 to 150 minutes, more preferably 10 to 15 minutes. It can be heated at normal pressure, and no autoclave is required. It is not limited to the batch type, and continuous operation is possible.

After the heat treatment, the drop lid is pulled up, and the liquid containing the resin molded body is transferred in a heating container or another container, and stirred for 3 minutes or more, preferably 10 to 30 minutes. For example, a diameter of 5 to 5
A propeller of about 10 cm is installed, and it is rotated at normal temperature and normal pressure at a speed of 5 rpm or more, preferably 300 to 500 rpm. By the agitation, the resin moldings rub against each other and the peeling of the coating film is promoted, and the coating film is completely separated from the resin.

When a liquid having a specific gravity between the resin and the coating film is used as the liquid for peeling off the coating film, the resin having a lower specific gravity than the liquid floats above the liquid when left still after the stirring process, and Since the coating film having a large specific gravity sinks below the liquid, the two can be separated without any special operation. After natural cooling, the resin and the coating film are each recovered. In the case of using a liquid containing a surfactant, if the temperature of the surfactant is too low during the resin recovery, the viscosity increases and it is difficult to recover the resin. Therefore, it is preferable to recover the resin at 50 ° C. or higher.

The recovered resin is washed with water and then dried. The dried resin is melted, extruded and cut, and pelletized as a raw material for recycling. By the above operation, the coating film can be peeled almost 100%.

[0038]

EXAMPLES A polypropylene bumper (resin made of modified polypropylene coated with a urethane paint) obtained by grinding 1000 g of waste material of an automobile and grinding it to a diameter of about 5 mm was used as a "Plysurf A210G" (trade name, Daiichi Kogyo Co., Ltd.). Pharmaceutical Co., Ltd.)
Into an autoclave together with 1500 ml of a 1% aqueous solution, and from the aqueous solution, a number of vent holes made of a convexly curved metal having a diameter of 6 mm smaller than the inner diameter of the autoclave (about 18.2 cm). Was immersed in the aqueous solution with the convex portion facing upward. Then, it heated at 123 degreeC for 90 minutes, and peeled off the coating film.

Next, the aqueous solution and the resin molded product were separated by a diameter of 7 cm.
Transfer to a stirring vessel having a stirrer of
Minutes. After stirring, the mixture was allowed to stand, and the resin floating above the aqueous solution and the coating film sinking below the aqueous solution were collected.
The recovered resin was dried, melted, extruded and cut into pellets. Table 1 shows the physical properties of the molded article using the pellets.

[0040]

[Table 1]

[0041] The pulverized waste bumper used in Comparative Example Example, it is,
The pellets were melted and pelletized, and a molded article was produced using the pellets. Table 1 shows the physical properties of the obtained molded article.

Reference Example A molded article was produced using the modified polypropylene (virgin material) used as a bumper raw material in the examples. Table 1 shows the physical properties of the obtained molded article. The numerical values in Table 1 are relative values when the reference example is set to 100, excluding the tensile elongation at break. These tests were performed according to the following methods. Specific gravity (JIS K7112-80, ISO 1183-
87); melt flow rate (JIS K7210-9)
5, ISO 1133-91); Tensile test (JIS K
7161-94, JIS K7113-95, ISO
527 / 1-93); Bending test (JIS K7171-
1994, JIS K7203-1995, ISO 1
78-93); Izod impact test (JIS K711)
1-84, ISO 180-93); Deflection temperature under load test (JIS K7207-95, ISO 75-9)
3).

[0043]

According to the method of the present invention, there is no need for stirring when heating to remove the coating film, and no complicated heating device is required. Further, the coating film on the surface of the resin molded article can be peeled off with high efficiency and low cost by the method of the present invention.

[Brief description of the drawings]

FIG. 1 is a view showing a state in which a drop lid is immersed in a liquid for peeling a coating film in a method of the present invention.

FIG. 2 is a diagram showing an example of a drop lid used in the present invention.

FIG. 3 is a diagram showing an example of a drop lid used in the present invention.

[Explanation of symbols]

 1, 7, 10 Drop lid 2 Resin molded body 3 Liquid for removing coating film 4 Autoclave 5, 8, 11 Air vent hole 6 Air bubble 9 Metal plate

──────────────────────────────────────────────────の Continuation of front page (51) Int.Cl. ⁶ Identification code FI B09B 3/00 C08J 7/00 301 B29B 17/00 ZAB 11/18 ZAB C08J 7/00 301 B09B 3/00 ZAB 11/18 ZAB 304P // B29K 105: 26

Claims (3)

[Claims] 1. A resin molded article having a coating film on its surface and a drop lid are immersed in a liquid for peeling the coating film so that the drop lid faces upward, and heat-treated. A method for removing a coating film of a resin molded body. 2. The method according to claim 1, wherein the drop lid has an air hole. 3. The method according to claim 1, wherein the drop lid has a convexly curved shape.