KR100241267B1 - Method for recycling resin covered with thermoset paint - Google Patents

Abstract

The present invention relates to a method for peeling a thermosetting polymer coating film coated on plastic, and more particularly, in the presence of an inorganic acetate catalyst or an alkali catalyst, ethylene glycol, diethylene glycol, 1,2-propane diol, 1,3- A method for peeling a thermosetting polymer coating film coated on a plastic in which the thermosetting paint is immersed in a plastic resin coated with a thermosetting paint in a glycol selected from the group consisting of propane diol and dipropylene glycol for 1 to 30 minutes will be.

Description

Peeling method of thermosetting polymer coating coated on plastic

The present invention relates to a method for peeling a thermosetting polymer coating film coated on plastic, and more particularly, to a method for efficiently peeling a coating film by a simple chemical treatment of a thermosetting polymer coating film coated on a plastic surface.

Among the various components used in automobiles, home appliances, daily necessities and other fields, a considerable amount is used to paint the surface of the plastic resin. Paints used for painting plastics are mostly used thermosetting paints because of their coating properties and adhesion to the plastic resin as the adherend. Since the coating film applied on the surface of the plastic resin is mainly a thermosetting paint, it is almost impossible to recycle the plastic resin used as the base material by the simple melt processing method unless it is removed.

Therefore, a great deal of research is being conducted to overcome this problem, the core of which is an efficient peeling technology of the coating film. There are two main methods of peeling the coating film, physical method and chemical method. Among these two methods, the physical method is scraping with sand paper, etc., and this method has not been industrialized at present due to the removal rate and economic efficiency of the film.

Peeling of the film by a chemical method is theoretically possible to achieve perfect film separation if the method is perfect. Therefore, a lot of research has been conducted on the coating film separation method by the chemical method, the important results are as follows.

1) A method of using a peeling liquid containing a chlorine solvent as a main component (JP-A 51-34238, 57-76065, and 59-117567). 2) A method of using a peeling liquid containing organic substances as a main component (Japanese Patent Laid-Open No. 50-109925, Japanese Patent Laid-Open No. 1-289878, and Japanese Patent Laid-Open No. 2-274775). 3) A method of using a stripping solution containing inorganic substances as a main component (Japanese Patent Laid-Open Nos. 50-109925, 59-131674, and 61-162568).

However, these methods have not been put to practical use due to problems such as incomplete peeling of the coating film depending on the type and thickness of the coating film to be removed. And here are some other ways:

4) 0.01 to 1 wt% of a coating film decomposition accelerator comprising one or two or more kinds of Lewis acid, alkali hydroxide, alkaline earth metal hydroxide, amine, metal phosphate salt, diethanol amine such as tin chloride, and the like is added to the polypropylene composite. And a method of thermally decomposing the coating film at 200 ° C. to regenerate the polypropylene composite (Japanese Patent Application Laid-Open No. 5-200749). However, the above method has a problem in that the film decomposition accelerator is left in the plastic resin and the quality of the recycled resin is lowered.

5) 0.5 to 50 wt% of organic or inorganic coating film decomposition accelerator containing 0.001 to 3 wt% of bismuth, lead, tin, etc., with respect to 10 wt% of the plastic molded body, by crushing the coated plastic molded article and melt-kneading it in the melter. A method of regenerating a coated plastic molded body by mixing with water and contacting it for 0.5 to 5 minutes at 200 to 320 ° C (Japanese Patent Laid-Open No. 6-198652) has been introduced. However, the method has a disadvantage in that the peeling effect of the coating film is low, and the use of the recycled plastic resin is limited because bismuth, lead, and tin remain in the recycled resin.

6) After crushing the painted plastic molded product to a certain size, the crushed material is fed into a screw-type extruder and kneaded while supplying water, aqueous alkali solution or alcohol to exhaust the decomposition gas and vaporized water of the coating film to recover recycled plastic. The method (Japanese Patent Laid-Open No. 6-23748) is disclosed. This method also lowers the physical properties of the recovered recycled plastic due to the presence of alkali in the recycled plastic resin. On the other hand, if the amount of alkali used is reduced, the peeling effect of a coating film will fall.

7) The waste polypropylene bumper cover for automobiles was pulverized to a size of 4 to 5 mm, immersed in a mixed solution of a glycol compound, lithium hydroxide and water, treated at 140 to 160 ° C. for 15 to 20 minutes, and then dehydrated in a centrifuge. Thereafter, a method of regenerating plastic resin by melt kneading (Korean Patent Publication No. 96-37238) is disclosed. However, the method has a disadvantage in that the peeling effect of the coating film is low and the use of the recycled plastic resin is limited.

In addition to the Republic of Korea Patent Publication No. 96-37238, a lot of methods for recycling the waste plastic bumper for automobiles have been introduced, but the economical method has not yet been established that the recycled plastic resin has good mechanical properties. That is, it is not economical due to low peeling effect of coating film, low processing ability, or at the same time to solve the problems such as deterioration of physical properties of plastic resin recycled during coating film peeling process or toxicity or environmental pollution of liquid used to treat. There is no way of doing this yet. Therefore, the recycling of waste bumpers is still a big concern in the automotive industry.

In order to solve this problem, the present inventors regenerate a product coated with a thermosetting polymer, for example, a vehicle bumper cover to recycle a polypropylene composite used therein, and then use it as an automobile bumper material or other high value-added material. As a result of intensive research on a more efficient method, depolymerization of a coating film used for a bumper cover for a car to glycol in the presence of a catalyst does not impair the physical properties of the polypropylene composite used for the bumper and the coating film is hardly applied for 2 to 20 minutes. It has been found that the peelable polypropylene composite can be melted and kneaded to be utilized as a bumper material or other material for automobiles, and the present invention has been completed based on this.

Accordingly, it is an object of the present invention to provide a method capable of efficiently peeling a coating film by a simple chemical treatment of the thermosetting polymer coating film applied to a plastic surface.

Another object of the present invention is to crush and melt kneaded plastic material removed by the above method and to recycle the recycled plastic resin with a single or virgin polypropylene composite as a material for automobile bumpers or other materials To provide.

The method of the present invention for achieving the above object is selected from the group consisting of ethylene glycol, diethylene glycol, 1,2-propane diol, 1,3-propane diol and dipropylene glycol in the presence of an inorganic acetate catalyst or an alkali catalyst. It consists of immersing the plastic resin coated with a thermosetting paint on glycol at 120 to 165 캜 for 1 to 30 minutes to peel off the thermosetting paint.

Hereinafter, the present invention will be described in more detail.

The present invention relates to a method for recycling a plastic resin coated with a thermosetting paint. Hereinafter, a representative example of the plastic resin will be described with reference to the automobile bumper cover, but the present invention is not limited thereto.

The structure of the bumper cover for an automobile is based on a polypropylene composite (a thermoplastic rubber compounded in polypropylene, which is about 3 to 5 mm thick), which is used as a base material. And on the polypropylene composite (hereinafter referred to as "PP substrate") to increase the paintability of the coating on the PP substrate, the primer (Primer) is mainly 5 ~ 30 chlorinated polyethylene (hereinafter referred to as CPE: Chlorinated Polyethylene) It is coated with a micrometer, and about 30 micrometers of a thermosetting paint is coated on it.

There are various kinds of paints used for painting, but all of them are thermosetting polymers, which are three-dimensional network structures. Initially, melamine and polyurethane type paints were used. Currently, however, polyurethane-ester-acrylic copolymers are mainly used in which the chemical basic structures of polyurethanes, esters and acrylics are copolymerized. Other or different structures may be added.

In the present invention, the chemical structure of the paints used for the coating of automobile bumpers decomposed polyester and polyurethane structures by glycol depolymerization, especially in the presence of specific catalysts.

The glycols used for the depolymerization according to the present invention are ethylene glycol (EG), diethylene glycol (DEG), 1,2-propane diol (PG), 1,3-propane diol (trimethylene glycol), dipropylene glycol (DPG) , 1,4-butanediol, 1,3-butanediol, 1,2-butanediol, neopentyl glycol, 1,5-pentanediol, hexylene glycol, bisphenol A, 2,2-di (4-hydroxy propoxy phenyl Dihydric alcohols such as propane, 2,2-di (4-hydroxyethoxyphenyl) propane, or trivalent or higher glycols such as glycerin, trihydroxy methylpropane, trimethylol ethane and pentaerythritol. Preferably ethylene glycol (EG), diethylene glycol (DEG), 1,2-propane diol (PG), 1,3-propane diol or dipropylene glycol (DPG), more preferably 1,2- Propane diol (PG).

In addition, the catalyst used in the depolymerization reaction according to the present invention includes, for example, sodium catalyst, sodium bicarbonate, calcium hydroxide, barium hydroxide, potassium hydroxide, sodium hydroxide or lithium hydroxide as an alkali catalyst, acetic acid which is a carboxylic acid catalyst as an acid catalyst. , Formic acid, propionic acid, butyric acid and benzoic acid, and are inorganic acetate catalysts such as magnesium acetate, lead acetate, calcium acetate, potassium acetate, and zinc acetate. acetate, sodium acetate, silver acatate, ammonium acetate, copper acetate, etc., and the Lewis acid catalyst includes zinc chloride, iron chloride, aluminum chloride, mercury chloride, and the like. One or two or more mixtures selected from the group consisting of these catalysts There is this. Preferably it is an inorganic acetate catalyst or an alkali catalyst.

The amount of catalyst used for glycol depolymerization of the paint used for coating the plastic resin is in the range of 0.01 to 5 parts by weight based on 100 parts by weight of glycol. At this time, when the amount of the catalyst is less than 0.01 parts by weight, the peeling effect of the coating film is lowered, and when it exceeds 5 parts by weight, there is a disadvantage that the economy is inferior to the amount of the added catalyst. On the other hand, when an inorganic acetate catalyst is used, acetic acid may be decomposed during the glycol depolymerization reaction, so that the catalyst may be supplemented during the reaction.

The reaction mixture consisting of the components and the amount was introduced into a reactor equipped with a cooler, and then inside the reactor at a reaction temperature of 120 to 165 ° C, preferably 133 to 155 ° C, while stirring the reaction mixture with an appropriate stirrer under a nitrogen atmosphere. Raise the temperature. At this time, if the reaction temperature is less than 120 ℃ depolymerization reaction does not proceed well. After satisfying the conditions of the reactor, a plastic resin coated with a PP base material, for example, an automobile bumper cover is cut into a suitable size or put into the reactor, and glycol and chemicals of polyurethane and ester in the coating component are chemically It depolymerizes and gold is formed in a coating film. Glycol penetrates through the gold thus generated and physically pushes the coating to separate the coating. This is because the CPE is in physical bond with the coating film. That is, when glycol is infiltrated between the CPE and the coating film where gold is generated due to a slight decomposition by the depolymerization of glycol, it is possible to physically separate the coating film and the CPE having a relatively weak bonding force than that of the PP substrate and the CPE. Therefore, at the reaction temperature of the present invention, the coating film can be easily separated without being degraded. In addition, the reaction is preferably carried out within the shortest time possible, that is, for 1 to 30 minutes, since it is possible to minimize deformation of the PP substrate and reduction of physical properties.

If the surface of the coating film is rubbed with a sandpaper or scratched with another device before the reaction under the above conditions, the reaction may be more easily peeled off, and also withstands the reaction temperature when depolymerizing the coating film in the reactor. The surface of the coating film may be rubbed with a brush attached to a material that may be attached to the surface of the coating film, or an ultrasonic wave may be generated in the reaction solution so that the coating film may be more easily peeled off.

The PP substrate having completely removed the coating film is washed once with water and then dried, crushed and melt-extruded to prepare pellets. The recycled PP substrate thus prepared may be recycled as a bumper cover for automobiles, even though the CPE is attached, and may be branded alone or with a virgin PP substrate at a predetermined mixing ratio.

On the other hand, the present invention is characterized by the most efficient reaction system used for glycol depolymerization of a polyurethane-ester-acrylic copolymer used as a paint for automobile bumper covers. Therefore, lowering the reaction temperature and shortening the reaction time in the reaction system of the present invention has a very important meaning in separating the coating film of the automobile bumper. When the reaction temperature exceeds 165 ° C, the substrate of the bumper is thermally deformed and reacts at a high temperature for a long time. In this case, the PP substrate used for the bumper is thermally decomposed due to economic problems, resulting in a decrease in molecular weight and consequent deterioration of physical properties. In particular, the PP substrate used as an automobile bumper cover is a polyolefin-based elastomer is mixed in the PP, so when the reaction temperature exceeds 165 ℃ during the glycol reaction, the PP substrate used in the automobile bumper heat deformation occurs. In addition, at a reaction temperature of 170 ° C. or higher, decomposition of the peeled coating film proceeds with the glycol, causing the peeled coating film to stick to the automobile bumper again. This causes a difficult problem in the process of peeling off the coating film, in particular, removing the coating film and then physically removing the coating film. In addition, if the reaction is carried out at 165 ° C. for 30 minutes or more, the covalent bond of PP or elastomer is broken, thereby reducing the molecular weight of the polymer used for the PP substrate, which ultimately results in a decrease in the mechanical properties of the polymer.

Therefore, in plastic products coated with a thermosetting polyurethane-ester-acrylic copolymer paint, in particular, recycling of the PP-based glycol depolymerization method used in automobile bumpers is the key, as long as the reaction temperature can be lowered below 165 ° C. If possible, the reaction time should also be shortened as much as possible. To achieve this, an appropriate reaction system, ie catalyst and glycol, must be selected.

However, different automakers also have different reaction systems, depending on the color of the paint, even for the same automaker. This is because the composition of the paint used is slightly different. This trend is illustrated in the examples.

On the other hand, after being used for the reaction, the waste glycol can be distilled at the boiling point to recover the unreacted glycol in a pure state and reuse.

According to a preferred embodiment of the present invention, experiments with regard to whether a common automobile company and various color peelings of the film can be achieved in common, and glycol reacts with PG or DEG and the catalyst reacts with ammonium acetate. The system is the most efficient. In the reaction system, the peeling of the coating film took about 5 to 10 minutes between the reaction temperatures of about 130 to 150 ° C., but the results were slightly different depending on the company and the color. In about 10 minutes (Hyundai, Daewoo products within 5 minutes, and Samsung products in 10 minutes) and at 130 ℃, Hyundai and Daewoo products took about 17 minutes. Therefore, in this reaction system, the coating film can be peeled off within 10 minutes depending on the coating of various bumpers at reaction temperatures between 133 and 155 ° C. The peeled coating film was washed, dried, crushed, melt-mixed, and measured, and the physical properties thereof were almost the same as those of the pure PP substrate, and the molecular weight values were almost the same.

Hereinafter, the present invention will be described in more detail with reference to examples, but the scope of the present invention is not limited only to the following examples.

Example 1

100 g of ethylene glycol, 0.5 g of sodium acetate, and 0.5 g of zinc acetic acid were added to a reactor equipped with a cooler, and the inside of the reactor was replaced with nitrogen, and the temperature of the reactor was raised to 150 ° C. Under these reaction conditions, the car bumper cover (Samsung Automotive Products Purple) was cut to an appropriate size and then put into the reactor, and the coating film was peeled off in 8 minutes, which was washed with water to obtain a pure PP substrate.

Example 2

Under the same conditions as in Example 1, 1 g of sodium acetic acid was added instead of 0.5 g of sodium acetic acid and 0.5 g of zinc acetic acid, and the reaction temperature was 160 ° C.

Example 3

The coating film was peeled off after 5 minutes under the same conditions as in Example 2 but the reaction temperature was 165 ℃.

Example 4

Under the same conditions as in Example 2, potassium acetic acid was used instead of sodium acetic acid, and the reaction temperature was 160 ° C.

Comparative Example 1

Under the same conditions as in Example 4, but the reaction temperature was 170 ℃ experiments as a result of melting the substrate of the bumper also occurred. Therefore, raising reaction temperature to 170 degreeC or more has a coating film problem. However, in case of Daewoo or Hyundai, which is inferred to have a relatively low content of elastomer other than Samsung Motor Company used in Example 5, the heat deformation temperature rises to about 180 ° C.

Example 5

Under the same conditions as in Example 2, lead acetic acid was used instead of sodium acetic acid, and the reaction temperature was 157 ° C.

Example 6

Under the same conditions as in Example 2, silver acetic acid was used instead of sodium acetic acid, and the reaction temperature was 158 ° C.

Example 7

Under the same conditions as in Example 2, zinc acetic acid was used instead of sodium acetic acid, and the reaction temperature was 142 to 144 ° C., and the experiments were conducted on Samsung automobile products (dark gray), Hyundai automobile products (white), and Daewoo automobile products (grey). As a result, the bumpers of Hyundai Motor and Daewoo Motors were peeled off within the reactor after 6 to 10 minutes, but Samsung's products were difficult to peel off.

Example 8

Under the same conditions as in Example 7, the experiment was carried out at a reaction temperature of 154 ° C., and after 8 minutes, the coating was peeled off.

Example 9

Ammonium acetic acid was used instead of sodium acetic acid under the same conditions as in Example 2, and the reaction temperature was 154 ° C., and the coating film was peeled off after 5 minutes.

Example 10

The coating film was peeled off after 10 minutes under the same conditions as in Example 9 except that the reaction temperature was 150 ° C.

Example 11

Under the same conditions as in Example 2, sodium hydroxide, which is an alkali catalyst, was used instead of sodium acetic acid, and the reaction temperature was 165 ° C.

Example 12

The coating film was peeled off after 10 minutes under the same conditions as in Example 11 except that the reaction temperature was 160 ° C.

Example 13

Under the same conditions as in Example 2, but instead of sodium acetic acid, an alkali catalyst, barium hydroxide, was used, and the reaction temperature was 150 ° C.

Example 14

Under the same conditions as in Example 2, but instead of sodium acetic acid, an alkali catalyst potassium hydroxide was used, and the reaction temperature was 160 ° C.

Example 15

Under the same conditions as in Example 2, but instead of sodium acetic acid, an alkali catalyst calcium hydroxide was used, and the reaction temperature was 160 ° C.

Example 16

Under the same conditions as in Example 1, propylene glycol was used instead of ethylene glycol, and as the catalyst, 0.5 g of sodium acetate and 1 g of zinc acetic acid were added instead of 0.5 g of zinc acetate, and the reaction temperature was maintained at about 142 to 145 ° C. As a result, in the case of Hyundai automobile products (white paint), the coating film was peeled off in about 1 minute and fell off into the reaction solution. In this case, unlike in the case of Examples 1 to 15, a separate step for peeling the coating film after the reaction was omitted, but only washed with water and dried to regenerate. However, in the case of Daewoo Motors (Gray Paint) and Samsung Motors (Dark Grey), decomposition reactions such as cracking of the coating film occurred after 10 minutes, but the coating film was not peeled off in the reactor.

Example 17

Under the same conditions as in Example 16, 1 g of ammonium acetic acid was added as a catalyst, and the reaction was performed while changing the reaction temperature from about 130 ° C. to 155 ° C. to obtain the following experimental results. First, in the case of Hyundai automobile products (white paint), the coating film was peeled off in about 1 minute at the reaction temperature of 155 ℃, and the film fell off into the reaction liquid.The film was peeled off in 5 minutes even when the reaction temperature was reduced to about 135 ℃. Away from myself. Therefore, in this case, as in Example 16, a separate process for peeling the coating film after the reaction was omitted, but only washed with water and dried to regenerate. In the case of Daewoo Automotive Products (Gray Paint), the coating film was peeled off in 2 minutes at 155 ℃ and 5 minutes at 135 ℃. After 3 minutes, the coating film was peeled off at 145 ° C. for 10 minutes, and then fell off into the reaction solution.

Example 18

Under the same conditions as in Example 17 but adding 1 g of ammonium acetic acid and reacting at 130 ° C., the coating film was peeled off in 5 minutes in the case of a modern automobile product (white). In the case of), the coating film was peeled off between 5 minutes and 10 minutes, and then fell into the reaction solution. However, in the case of Samsung Motor Company (dark gray), the coating did not peel off.

Example 19

Under the same conditions as in Example 17, 1 g of sodium acetic acid was added instead of ammonium acetic acid to react at a temperature of 140 ° C. to 145 ° C., and as a result, the coating film was peeled off in 10 minutes in the case of Hyundai automobile products (white) and Daewoo automobile products (grey). And fell off into the reaction solution. However, in the case of Samsung Motor Company (dark gray), the coating did not peel off.

Example 20

According to the present invention, a PP substrate having a peeled coating film was melted and mixed with a pure PP substrate in a weight ratio of 1: 1 to prepare a specimen of regenerated PP, and this was compared with the specimen of the pure PP substrate and the difference in workability and physical properties. Described.

Item MFI (g / 10min) Tensile strength (kgf / cm ² ) % Elongation Flexural Strength (kgf / cm ² ) -30 ℃ Izod strength (kgfcm / cm) Shrinkage (%) I'm after Pure PP base material 11.8 168 500 ↑ 9,400 5.6 1.14 1.49 Recycled PP base material 11.7 163 500 ↑ 9,500 5.7 1.09 1.41

As can be seen in Table 1, the MFI (Melt Flow Index: Melt Flow Index) for the processability was found to be almost similar to 11.8 for pure PP substrate and 11.7 for recycled PP substrate. In addition, mechanical properties such as tensile strength, elongation, flexural strength, -30 ° C Izod strength, and shrinkage rate showed almost similar values, so the recycling of the PP base material peeled off by the present invention is considered to be no problem. .

As described above, the peeling of the thermosetting coating film by the depolymerization method using glycol used in the present invention enables almost perfect peeling with a very high removal efficiency of the coating film than the methods previously introduced. And the use of the reaction liquid required for peeling a coating film is very small. In addition, after use in the reaction, the waste glycol is distilled at the boiling point to recover the unreacted glycol in a pure state, and reused. It is a very simple and economic way. In addition, the glycol used for peeling the coating film in the present invention is less toxic or harmless to the human body than the existing techniques and excellent in environmental safety. In addition, the price is cheaper than the material used in the existing invention and the economics are very high.

Claims (5)

In the presence of an inorganic acetate catalyst or an alkali catalyst, a plastic resin coated with a thermosetting paint is coated on a glycol selected from the group consisting of ethylene glycol, diethylene glycol, 1,2-propane diol, 1,3-propane diol and dipropylene glycol. A method of peeling a thermosetting polymer coating film coated on plastic, characterized in that the thermosetting paint is peeled off by immersing at 1 to 30 minutes at 165 ° C. The method of claim 1, wherein the inorganic acetate catalyst is one or more selected from the group consisting of magnesium acetate, lead acetate, calcium acetate, potassium acetate, zinc acetate, sodium acetate, silver acetate, ammonium acetate and copper acetate A method of peeling a thermosetting polymer coating film coated on plastic. The thermosetting polymer coating film of claim 1, wherein the alkali catalyst is selected from the group consisting of sodium carbonate, sodium bicarbonate, calcium hydroxide, barium hydroxide, potassium hydroxide, sodium hydroxide and lithium hydroxide. Peeling method. The method of claim 1, wherein the catalyst is used in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of glycol. The method of claim 1, wherein the plastic resin is a waste bumper cover for an automobile.