JPH07157697A - Paint remover - Google Patents

Abstract

PURPOSE:To obtain a paint remover for a resin bumper having an excellent effect of removing a coating film, low flammability, excellent safety and economic profitability by mixing gamma-butyrolactone with formic acid. CONSTITUTION:gamma-Butyrolactone is mixed with formic acid to obtain the objective remover. The mixing ratio is suitably such that 10-95 pts.wt. gamma-butyrolactone and 90-5 pts.wt. formic acid are used. It is desirable in view point of the diffucult flammability that water is added to this remover to obtain 100 pts.wt. remover comprising 10-70 pts.wt. gamma-butyrolactone, 20-65 pts.wt. formic acid and 10-30 pts.wt. water. The method for removing a coating film from a resin bumper with the remover comprises crushing the bumper, dipping the same in the remover, agitating the mixture to remove the coating film, setting the removed film by leaving the mixture still after the removal of the film, and floating the resin from which the film has been removed on the surface of the remover to recover and recycle the same.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paint remover, and more particularly to a paint remover used for a resin bumper.

[0002]

2. Description of the Related Art Conventionally, as a method for removing paint from a bumper, Japanese Patent Laid-Open Nos. 5-115810 and 5-115811 have been used.
Method using a surfactant described in Japanese Patent Laid-Open No. 5-1
A method for injecting a blast material made of a melamine resin described in JP-A-62079, a method for immersing in a saturated sodium hydroxide saturated solution of methanol described in JP-A-5-185024, and a method for removing paint by hydrojet are known. There is. However, the treatment with a surfactant or an alkaline solution is not preferable in terms of economical efficiency because the cost of waste liquid treatment is high. The method using blast treatment or hydrojet is not preferable in terms of cost because the cost of the apparatus and its maintenance is high.

Use of a stripping solution containing methylene chloride, formic acid, and a nonionic surfactant for stripping the coating material adhering to the inside of the coating piping, as described in JP-A-5-185045. Is also known. However, methylene chloride is a substance that destroys the ozone layer, and its production will be banned in the near future, and a substitute is required. Furthermore, methylene chloride is highly toxic and prevents water pollution, so its regulations are strict.

Further, Japanese Patent Laid-Open No. 5-78608 discloses that
A coating stripping method using an ester of (methyl) benzyl alcohol, a system containing the alcohol and formic acid as a general coating stripping solution is described. However, the paint peeling effect was low, and it was not sufficient yet.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a paint remover for a resin bumper which has a good paint peeling effect, a low flammability, an excellent safety and an excellent economical efficiency. .

[0006]

Means for Solving the Problems The present inventors have made various studies in order to solve many drawbacks of the above-mentioned various paint stripping methods. As a result, it was found that a coating stripping solution containing γ-butyrolactone (hereinafter sometimes abbreviated as GBL) and formic acid has a good coating stripping effect and low flammability and excellent safety. Has been completed.

That is, the subject matter of the present invention is a coating stripper for a resin bumper characterized by containing γ-butyrolactone and formic acid.

The coating stripper containing GBL and formic acid of the present invention enables coating stripping of a resin bumper in a short time under mild conditions and does not deteriorate the resin. The paint stripping solution of the present invention has a high flash point and is very excellent in terms of safety. Further, in the stripping solution, the resin floats and the coating film after stripping settles, so that separation is easy if desired. Further, unlike the surfactant and the alkaline solution, the stripping solution has an advantage that it can be regenerated by distillation. Further, it has an advantage that the peeling force is large as compared with a solution in which formic acid is diluted with water.

In the resin bumper coating stripper of the present invention, the blending ratio of GBL and formic acid is preferably GBL10.
To 95 parts by weight, 90 to 5 parts by weight of formic acid, particularly preferably 10 to 75 parts by weight of GBL to 9 parts of formic acid.
It is 0 to 25 parts by weight. If the GBL exceeds 95 parts by weight and the formic acid is less than 5 parts by weight, the peeling force of the coating stripping solution becomes low, which is not preferable. Even if GBL is less than 10 parts by weight and formic acid exceeds 90 parts by weight, there is no particular improvement in the peeling force of the coating remover,
In addition, there is a risk of ignition, and especially when peeling is performed at a high temperature, the risk becomes high, which is not preferable in terms of safety.

It is preferable that water is further added to the resin bumper coating stripping solution of the present invention because it can be made incombustible. The blending ratio of GBL, formic acid and water is preferably 10 to 70 parts by weight of GBL, 20 to 65 parts by weight of formic acid and 10 to 30 parts by weight of water, and the total thereof is 100 parts by weight. Here, the weight ratio of water is particularly preferably 0.23 to 1 with respect to formic acid and 0.1 or more with respect to GBL. If the compounding ratio is less than 0.23 with respect to formic acid, the flammability of formic acid cannot be eliminated, and if it is more than 1 the peeling force is reduced, and with less than 0.1 against GBL the flammability of GBL. Can't be lost. Therefore, it is preferable to determine the compounding ratio of GBL, formic acid, and water in consideration of the above-mentioned characteristics.

Examples of the resin bumper in which the coating stripper of the present invention is used include polypropylene resin bumpers. The polypropylene resin forming the bumper is mainly composed of a polymer containing propylene as a main component. Usually, a homopolymer or copolymer of propylene is blended with other polyolefins, thermoplastic elastomers and various fillers. It is a composition. As the polymer mainly composed of propylene,
Not only a propylene homopolymer but also a block or random copolymer with other α-olefins such as ethylene. In the case of a copolymer, a propylene-ethylene block copolymer is usually used. Other components to be added to the polypropylene resin include polyethylene, ethylene-propylene copolymer rubber (EPR), ethylene-propylene-diene copolymer rubber (EPDM), ethylene-
Butene copolymer rubber (EBR) and an inorganic filler (talc etc.) are mentioned.

The resin bumper in which the coating stripper of the present invention is used is a bumper coated with paint. The bumper is preferably applied by surface treatment such as plasma treatment, followed by forming a primer layer, an intermediate coat layer, an overcoat layer and the like by a usual method and baking. The coating material is not particularly limited, but usually, an ordinary automotive coating material such as urethane resin, melamine resin, two-component curing type epoxy resin, amino acrylic resin, etc. may be mentioned.

Next, an example of performing the paint peeling of the resin bumper using the paint peeling liquid of the present invention is shown below.

First, the coated resin bumper is pulverized to have an average particle size of preferably 0.1 to 10 mm. By pulverizing in this way, the coating stripping liquid easily enters the gap between the coating film and the resin, which is preferable. The crushing may be performed by a mechanical crusher such as a crusher.
If the average particle size of the crushed resin exceeds 10 mm, the removal rate of the coating film becomes low, while if it is less than 0.1 mm, the removal rate of the coating film cannot be improved significantly and only the cost increases. Is not preferable.

The above grinding can be carried out at room temperature,
It is preferable to cool in order to suppress the temperature rise due to pulverization. As the cooling method, it is possible to use cooling with dry ice, liquid nitrogen, or the like in the case of intense heat generation, in addition to cooling with normal water. Alternatively, it can be frozen and pulverized using dry ice or liquid nitrogen. The pulverization does not have to be performed in one step, and may be performed in two or more steps so that the resin finally has a desired average particle size. In particular, when a resin having a small average particle size is obtained, it is preferable to reduce the particle size stepwise by a plurality of crushing steps.

The pulverized resin thus obtained is put into the stripping solution of the present invention and stirred or shaken to remove the coating. In addition, ultrasonic waves can be used, and it is preferable to use ultrasonic waves in combination with stirring or shaking because the peeling effect is further enhanced. In this case, the usage conditions of ultrasonic waves are, for example, 20 to 10
0 kHz and 10 to 200 W / l are preferable. The temperature of the stripping solution is preferably 30 to 90 ° C., particularly 40 to 70 ° C. When the temperature is lower than 30 ° C., the stripping rate is slow, and when the temperature exceeds 90 ° C., formic acid evaporates violently and the stripping solution concentration control becomes difficult. Is not preferable. The time for peeling off the coating is preferably 1 minute to 2 hours, particularly 2 to 30 minutes, and if it is less than 1 minute, a sufficient peeling effect is often not obtained, and if it exceeds 2 hours, the peeling effect is increased. It is not preferable because it is small. Further, after the coating film is peeled off, in order to make the peeled coating film finer, it is preferable to further continue stirring or shaking for 2 minutes to 1 hour, particularly preferably 5 to 30 minutes. When the coating film becomes finer, the physical properties of the regenerated molded product are not adversely affected even if it is mixed in the recovered resin to some extent. Moreover, even though it is fine, it quickly settles in the stripping solution that has been left standing, so that separation is easy. The coating stripper is preferably at least 1 liter per 1 kg of bumper. Below 1 liter,
This is not preferable because the efficiency of resin separation is reduced. After the coating film is peeled off, the resin is separated by allowing the peeling liquid to stand.
Upon standing, the peeled coating film precipitates and the peeling liquid becomes colorless and transparent. The resin with the coating film peeled off floats on the peeling liquid. The pulverized resin thus recovered has a paint removal rate of preferably 95% or more. The standing time is preferably 1 minute or more, and if it is less than 1 minute, the separation is not sufficient. The upper limit of the standing time is generally about 10 minutes, and even if the upper limit is exceeded, the sorted state is not particularly improved.

Next, the resin floating on the stripping solution is recovered and dried. The drying may be performed at about 80 to 120 ° C. For example, if it is carried out by a hopper dryer of an extruder or the like, it is possible to continuously perform drying and melt extrusion,
It can be recycled efficiently. The resin dried in this way is charged into a usual single-screw or twin-screw extruder,
Melt extrude. A screen mesh of preferably 40 to 800 mesh may be installed on the breaker plate portion at the tip of the cylinder of the extruder. The number of screen meshes installed is preferably 1 to 10. The melt extrusion is preferably carried out at 180 to 270 ° C, particularly preferably 200 to 250 ° C. In the above extrusion, if necessary, an antioxidant, an organic peroxide, a filler,
Additives such as a coloring agent and a foaming agent can be appropriately added.

As described above, the recovered resin can be reused for the production of bumpers or other molded articles. The regenerated bumper has very little deterioration in surface quality due to the coating film protruding on the bumper surface,
In addition, mechanical properties such as impact resistance and mechanical strength are not significantly deteriorated.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[0020]

【Example】

[0021]

Example 1 Propylene-ethylene block copolymer,
A titania-based white paint (trademark, Warexen 105, manufactured by Nippon Paint Co., Ltd.) was applied to the surface of a bumper manufactured from a composition comprising ethylene-propylene copolymer rubber and talc, and a baked bumper was crushed ( It was crushed to an average diameter of about 5 mm at room temperature using Kikurai Co., Ltd.). Then, it was crushed with a freeze crusher (manufactured by Alfred Fritsch Co., Ltd.) together with dry ice so as to have an average diameter of about 3 mm and subjected to a peeling test. After 50 g of formic acid (Kanto Chemical Co., Inc. special grade reagent, concentration 98.0% by weight or more) dissolved in 50 g of γ-butyrolactone (GBL), 100 g of a stripping solution was heated to 60 ° C., and then the stripping test sample 20 was prepared. Grams were added and rocked at 60 ° C. using a shaker with oil bath. 10 in 3 minutes
Almost all of the coating film peeled off in a minute and settled in the liquid. The sample from which the coating film was peeled off floated near the surface of the peeling liquid.
When the shaking was further continued, after about 10 minutes, the peeled coating film became completely fine and the liquid became a white suspension state. When the shaking was stopped and the mixture was allowed to stand for 30 minutes, white turbid matter was precipitated and the peeling solution returned to colorless and transparent.

[0022]

Examples 2 to 5 The weight ratio of GBL / formic acid is 25/7, respectively.
A peeling test was performed under the same conditions as in Example 1 except that the values were 5, 75/25, 90/10 and 95/5. In all cases, almost all the coating film peeled off and settled in the liquid in 10 minutes. As a result of visual observation, it was found that the peeling force of the peeling solution was slightly decreased as the weight ratio of GBL was increased.

[0023]

Example 6 A peeling test was performed in the same manner as in Example 1 except that a method of vigorously stirring with a mechanical stirrer was used instead of rocking with a shaker. The coating film peeled off almost completely in about 7 minutes.

[0024]

Example 7 A peeling test was performed in the same manner as in Example 1 except that an ultrasonic cleaner (oscillation frequency 28 kHz, oscillation output 80 W / l) was used instead of shaking by a shaker. The coating film peeled off almost completely in about 5 minutes.

[0025]

[Comparative Example 1] As a stripping solution, the weight ratio of water / formic acid is 50/5.
A peeling test was carried out under the same conditions as in Example 1 except that 0 was used. Only a part of the coating film was peeled off in 10 minutes, and it took about 30 minutes to peel the coating film almost completely.

[0026]

Comparative Example 2 Example 1 except that a stripping solution having a methyl ethyl ketone / formic acid weight ratio of 50/50 was used.
A peeling test was performed under the same conditions as above. The coating film did not peel off at all for 5 minutes, and almost all peeled off at 10 minutes.

[0027]

[Comparative Example 3] A peeling test was carried out under the same conditions as in Example 1 except that a weight ratio of methylcellosolve / formic acid of 50/50 was used as a peeling liquid. Only a part of the coating film was peeled off in 10 minutes, and it took about 30 minutes to completely peel the coating film.

[0028]

[Comparative Example 4] As a stripping solution, the weight ratio of GBL / acetic acid was 6
A peeling test was performed under the same conditions as in Example 1 except that 0/40 was used. Even after shaking for 2 hours, the coating film was scarcely peeled off.

[0029]

[Comparative Example 5] As a stripping solution, the weight ratio of water / sulfuric acid was 50 /.
A peeling test was carried out under the same conditions as in Example 1 except that 50 was used. The coating film was not peeled at all even after shaking for 30 minutes.

[0030]

Comparative Example 6 As a stripping solution, the weight ratio of water / phosphoric acid is 50.
A peeling test was carried out under the same conditions as in Example 1 except that the one of / 50 was used. The coating film was not peeled at all even after shaking for 30 minutes.

As described above in Examples 1 to 7, G
The stripping solution of the present invention containing BL and formic acid showed a good stripping effect. Comparative Example 1 is a case of using water instead of GBL, but the peeling effect is inferior to that of Example 1. Comparative Examples 2 and 3 are cases in which an organic solvent other than GBL was used, but in both cases, the peeling effect was inferior to that in Example 1, and G
BL has been found to be a particularly good solvent. Comparative Example 4
Nos. 6 to 6 use other acids than formic acid, but it was found that there was almost no peeling effect.

[0032]

Examples 8 to 16 GBLs shown in Table 1 as stripping solutions
Example 1 except that a compounding ratio of / formic acid / water was used.
A peeling test was performed under the same conditions as above. Example 8 was completely peeled off by rocking for 5 minutes, and Examples 9 to 11 and 13 to 15
In each case, they were completely peeled off by shaking for 10 minutes. Also,
Other Examples 12 and 16 were completely peeled off by shaking for about 30 minutes.

[0033]

[Table 1]

[0034]

EFFECTS OF THE INVENTION The coating stripper for resin bumpers of the present invention has a good coating stripping effect and also has low flammability and excellent safety. Further, since it is excellent in economical efficiency, it is extremely useful industrially.

Claims (3)

[Claims] 1. A paint remover for a resin bumper, which contains γ-butyrolactone and formic acid. 2. The paint stripper according to claim 1, which contains 10 to 95 parts by weight of γ-butyrolactone and 90 to 5 parts by weight of formic acid. 3. γ-butyrolactone 10 to 70 parts by weight,
The coating stripper according to claim 1, comprising 20 to 65 parts by weight of formic acid, and further 10 to 30 parts by weight of water, and the total of these is 100 parts by weight.