JP3343425B2 - Paint stripper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, as a method for removing paint from a bumper, Japanese Patent Application Laid-Open Nos. 5-115810 and 5-115581
Using surfactant described in Japanese Patent Application Laid-Open No. 5-1
The method of spraying a blast material made of a melamine resin described in JP-A-62079, the method of dipping in a heated methanol-sodium hydroxide saturated solution described in JP-A-5-185024, and the method of peeling off a coating by hydrojet are known. I have. However, the treatment with a surfactant or an alkali solution is not preferable from the viewpoint of cost because the cost of waste liquid treatment is high. The method using blasting or hydrojet is not preferable from the viewpoint of cost because the cost of the apparatus and its maintenance is high.

As described in Japanese Patent Application Laid-Open No. 5-185045, a stripping solution containing methylene chloride, formic acid, and a nonionic surfactant is used to strip paint adhered to paint pipes. Is also known. However, methylene chloride is expected to be banned in the near future as a substance that destroys the ozone layer, and alternatives are needed. Further, methylene chloride is highly toxic, and its regulations are strict in order to prevent water pollution.

Japanese Patent Laid-Open Publication No. Hei 5-78608 discloses that
A paint stripping method using a system containing an ester of (methyl) benzyl alcohol, the same alcohol and formic acid as a general paint stripper is described. However, the paint peeling effect was low and could not be said to be sufficient yet.

[0005]

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

[0006]

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

[0007] That is, the gist of the present invention resides in a coating stripping solution for a resin bumper containing γ-butyrolactone and formic acid.

The coating stripping solution containing GBL and formic acid of the present invention enables coating stripping of a resin bumper within a short period of time under mild conditions, and does not deteriorate the resin. The coating stripping solution of the present invention has a high flash point and is extremely excellent in terms of safety. Further, in the stripping solution, the resin floats and the coating film after stripping settles, so that separation can be easily performed if desired. Also, unlike a surfactant or an alkaline solution, the stripping solution has an advantage that it can be regenerated by distillation. It also has the advantage that the peeling force is greater than a solution obtained by diluting formic acid with water.

[0009] In the coating stripping solution of the resin bumper of the present invention, the compounding ratio of GBL and formic acid is preferably GBL 10
90 to 5 parts by weight of formic acid with respect to 95 to 95 parts by weight, particularly preferably 10 to 75 parts by weight of GBL with 9 parts of formic acid.
0 to 25 parts by weight. If the GBL is more than 95 parts by weight and the formic acid is less than 5 parts by weight, the peeling force of the coating remover is undesirably low. 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 danger of ignition, and particularly in the case of peeling at a high temperature, the danger increases, which is not preferable in terms of safety.

[0010] It is preferable to further add water to the coating stripper of the resin bumper of the present invention because it can be made inflammable. The compounding 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 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 exceeds 1, the peeling force will decrease. Can not be eliminated. Therefore, it is preferable to determine the compounding ratio of GBL, formic acid, and water in consideration of the above respective characteristics.

The resin bumper to which the coating stripping solution of the present invention is used is, for example, a polypropylene resin bumper. The polypropylene resin forming the bumper is mainly composed of a polymer mainly composed of propylene, and is usually blended with other polyolefins, thermoplastic elastomers and various fillers, etc., in a homopolymer or copolymer of propylene. A composition. As the polymer mainly composed of propylene,
Not limited to propylene homopolymer, but also includes block or random copolymers 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 inorganic fillers (such as talc).

A resin bumper to which the coating stripping solution of the present invention is applied is one in which the bumper is coated. The coating of the bumper is preferably performed by performing a surface treatment such as a plasma treatment, and then forming a primer layer, an intermediate coating layer, an overcoating layer, and the like by an ordinary method, followed by baking. The paint is not particularly limited, but usually includes ordinary automotive paints such as urethane resins, melamine resins, two-part curable epoxy resins, and aminoacrylic resins.

Next, an example in which the coating stripper of the present invention is used to strip the coating of the resin bumper will be described below.

First, the coated resin bumper is pulverized so that the average particle size is preferably 0.1 to 10 mm. Such pulverization is preferable because the coating stripping liquid easily enters the gap between the coating film and the resin. The pulverization may be performed by a mechanical pulverizer such as a crusher.
When the average particle size of the pulverized resin exceeds 10 mm, the removal rate of the coating film is low. On the other hand, when the average particle size is less than 0.1 mm, the removal rate of the coating film cannot be particularly improved, and only the cost increases. Is not preferred.

The above grinding can be performed at room temperature,
It is preferable to cool in order to suppress a rise in temperature due to pulverization. As the cooling method, besides the usual cooling with water, when heat generation is severe, cooling with dry ice, liquid nitrogen or the like can be used. Alternatively, it can be frozen and pulverized using dry ice or liquid nitrogen. The pulverization does not need 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 diameter is obtained, it is preferable to gradually reduce the particle diameter by a plurality of pulverizing steps.

The pulverized resin thus obtained is placed in the stripping solution of the present invention, and the coating is stripped by stirring or shaking. In addition, ultrasonic waves can be used, and it is preferable to use a combination with stirring or shaking because the peeling effect is further increased. In this case, the use condition of the ultrasonic wave is, 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. If the temperature is lower than 30 ° C, the stripping rate is slow. Is not preferred. The time for performing the coating peeling 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. It is not preferable because it is small. Further, after the coating film is peeled, it is preferable to further continue stirring or shaking for preferably 2 minutes to 1 hour, particularly preferably 5 to 30 minutes, in order to make the peeled coating film finer. When the coating film becomes finer, even if it is mixed into the recovered resin to some extent, it does not adversely affect the physical properties of the recycled molded product. Moreover, although it is fine, it sediments quickly in the standing stripping solution, so that separation is easy. The coating stripper is preferably at least 1 liter per 1 kg of bumper. For less than 1 liter,
It is not preferable because the efficiency of resin separation decreases. After the coating is stripped, the resin is separated by leaving the stripping solution still.
Upon standing, the peeled coating film precipitates and the peeling liquid becomes colorless and transparent. The resin from which the coating has been stripped floats on the stripping solution. 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 less than 1 minute, separation is not sufficient. Generally, the upper limit of the standing time is about 10 minutes, and if it exceeds this, the separation state is not particularly improved.

Next, the resin floating on the stripper is recovered and dried. Drying may be performed at about 80 to 120 ° C. For example, if performed by a hopper dryer or the like of an extruder, drying and melt extrusion can be performed continuously,
It can be recycled efficiently. The resin dried in this way is put into a normal single-screw or twin-screw extruder,
Melt extrusion. A screen mesh of preferably 40 to 800 mesh may be provided at the breaker plate portion at the tip of the cylinder of the extruder. The number of screen meshes to be installed is preferably from 1 to 10. The melt extrusion is preferably performed at 180 to 270 ° C, particularly preferably at 200 to 250 ° C. In addition, at the time of 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 compounded.

As described above, the recovered resin can be used again for producing bumpers or other molded products. Recycled bumpers have very little deterioration in surface properties due to the coating film emerging on the bumper surface,
Also, there is little decrease in mechanical properties such as impact resistance and mechanical strength.

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,
Ethylene - propylene copolymer rubber and titania-based white paint on the surface of the bumper made from a composition consisting of talc (trademark, off veteran 105, manufactured by Nippon Paint Co., Ltd.) was applied to pulverizer painted bumper baked It was pulverized to an average diameter of about 5 mm at room temperature using (made by Korai Co., Ltd.). Subsequently, the mixture was pulverized with a dry pulverizer (manufactured by Alfred Fritsch Co., Ltd.) so as to have an average diameter of about 3 mm together with dry ice, and subjected to a peeling test. After heating 100 g of a stripping solution prepared by dissolving 50 g of formic acid (Kanto Chemical Co., Ltd., reagent grade, concentration: 98.0% by weight or more) in 50 g of γ-butyrolactone (GBL) to 60 ° C., Grams were added and rocked at 60 ° C. using a shaker with an oil bath. 10 minutes in 3 minutes
In a minute, almost all of the coating film was peeled off and settled in the liquid. The sample from which the coating film was peeled was floating near the surface of the peeling liquid.
When the rocking was further continued, the peeled coating film became completely fine after about 10 minutes, and the liquid became a white suspended state. When the rocking was stopped and the mixture was allowed to stand for 30 minutes, the cloudy substance precipitated and the stripping solution returned to colorless and transparent.

[0022]

Examples 2 to 5 The weight ratio of GBL / formic acid was 25/7, respectively.
The peel test was carried out under the same conditions as in Example 1 except that 5, 75/25, 90/10 and 95/5 were used. In each case, almost all of the coating film was peeled off and settled in the liquid in 10 minutes. As a result of visual observation, it was found that when the weight ratio of GBL was increased, the peeling force of the peeling liquid was slightly reduced.

[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 shaking with a shaker. The coating film was almost completely removed in about 7 minutes.

[0024]

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

[0025]

Comparative Example 1 Water / formic acid weight ratio of 50/5 was used as a stripping solution.
A peeling test was performed under the same conditions as in Example 1 except that 0 was used. In 10 minutes, only a part of the coating film was peeled off, and it took about 30 minutes to peel the coating film almost completely.

[0026]

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

[0027]

COMPARATIVE EXAMPLE 3 A peeling test was carried out under the same conditions as in Example 1 except that a peeling solution having a weight ratio of methylcellosolve / formic acid of 50/50 was used. In 10 minutes, only a part of the coating film was peeled, 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 carried out under the same conditions as in Example 1 except that 0/40 was used. Even after rocking for 2 hours, the coating film hardly peeled off.

[0029]

Comparative Example 5 The water / sulfuric acid weight ratio was 50 /
A peeling test was performed under the same conditions as in Example 1 except that 50 were used. Even after rocking for 30 minutes, the coating film did not peel off at all.

[0030]

Comparative Example 6 A water / phosphoric acid weight ratio of 50 was used as a stripping solution.
A peeling test was performed under the same conditions as in Example 1 except that a test piece of / 50 was used. Even after rocking for 30 minutes, the coating film did not peel off at all.

As described 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 where water was used instead of GBL, but the peeling effect was inferior to Example 1. Comparative Examples 2 and 3 are cases in which an organic solvent other than GBL was used.
BL was found to be a particularly good solvent. Comparative Example 4
Nos. 6 to 6 used an acid other than formic acid, and it was found that there was almost no peeling effect.

[0032]

Examples 8 to 16 Each of the GBLs shown in Table 1 was used as a stripping solution.
Example 1 except that a mixture having a mixing ratio of formic acid / formic acid / water was used.
A peel test was performed under the same conditions as those described above. Example 8 was completely peeled off by rocking for 5 minutes, while Examples 9 to 11 and 13 to 15
Was completely peeled off by rocking for 10 minutes. Also,
The other Examples 12 and 16 were completely peeled off by rocking for about 30 minutes.

[0033]

[Table 1]

[0034]

The coating stripping solution for the resin bumper of the present invention has a good coating stripping effect and low flammability and excellent safety. In addition, it is extremely useful industrially because of its excellent economic efficiency.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-185045 (JP, A) JP-A-5-156185 (JP, A) JP-A-58-199898 (JP, A) JP-A-58-1998 174456 (JP, A) JP-A-6-293899 (JP, A) JP-A-6-65533 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C09D 9 / 00-9 / 40 C11D 7/00-7/60

Claims (3)

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