JP3343426B2 - 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
A method of spraying a blast material made of a melamine resin described in JP-A-62079, a method of dipping in a heated methanol-sodium hydroxide saturated solution described in JP-A-5-185024, a method of peeling paint by a hydrojet, and the like are known. ing. 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. JP-A-5-
As described in Japanese Patent No. 185045, it is also known to use a stripping solution containing methylene chloride, formic acid, and a nonionic surfactant for stripping paint adhered in a paint pipe. 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. In addition, formic acid has a relatively high flammability and has a problem in handling safety.

[0003] Also, Japanese Patent Application Laid-Open No. 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.

[0004]

DISCLOSURE OF THE INVENTION The present invention relates to a resin made of a resin which has good paint peeling effect, low flammability, excellent safety, almost odorless, good workability, and excellent economy. Provide bumper paint stripper.

[0005]

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, a coating stripper containing γ-butyrolactone (hereinafter sometimes abbreviated as GBL) and oxalic acid has a good coating stripping effect, low flammability, excellent safety, and odorlessness. The inventors have found that the present invention has been completed.

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

[0007] The coating stripping solution containing GBL and oxalic acid of the present invention enables coating stripping of a resin bumper in a short period of time under mild conditions, and does not deteriorate the resin. Since the coating stripper of the present invention has a high flash point and oxalic acid is a solid at room temperature, it is very excellent in terms of safety and workability. 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. In addition, a solution obtained by diluting oxalic acid with water in order to eliminate flammability has no peeling power, whereas the stripping solution of the present invention has an advantage of having a good peeling power.

[0008] In the coating stripper of the resin bumper of the present invention, the compounding ratio of GBL and oxalic acid is preferably GBL
Oxalic acid is 40 to 5 parts by weight with respect to 60 to 95 parts by weight, and particularly preferably 35 to 20 parts by weight of oxalic acid with respect to 65 to 80 parts by weight of GBL. If the GBL is more than 95 parts by weight and the amount of oxalic acid is less than 5 parts by weight, the peeling force of the coating remover is undesirably low. If GBL is less than 60 parts by weight and oxalic acid exceeds 40 parts by weight, oxalic acid is converted to GB.
The entire amount cannot be dissolved in L and handling becomes inconvenient, and there is a risk of ignition, which is not preferable in terms of safety.

It is preferable to add water to the coating stripper of the resin bumper of the present invention, because it can be made less flammable or can lose flammability. A solution obtained by adding water to oxalic acid in order to extinguish the flammability of oxalic acid has no paint peeling force. Also, GB
Even if only L is used, there is no paint peeling force. The coating stripping solution containing oxalic acid, GBL and water of the present invention has both the effects of good coating stripping power and reduced flammability that could not be achieved with oxalic acid and water or GBL alone as described above. It has the feature of having both. Where GBL,
The mixing ratio of oxalic acid and water is preferably GBL50-9.
5 parts by weight, 5-40 parts by weight of oxalic acid and 0-30 parts by weight of water, the total of which is 100 parts by weight. More preferably, GBL is 50 to 80 parts by weight, oxalic acid is 10 to 30 parts by weight, and water is 5 to 30 parts by weight, and the total is 100 parts by weight.

The resin bumper to which the coating stripper of the present invention is used includes, 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), inorganic filler (such as talc) and the like.

The resin bumper to which the coating stripping solution of the present invention is applied is obtained by coating a bumper. 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 paint stripper of the present invention is used to strip paint from a resin bumper will be described below.

First, the coated resin bumper is pulverized so that the average particle diameter 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 110 ° C, particularly 50 to 90 ° C. When the temperature is lower than 30 ° C, the stripping rate is low, and when the temperature exceeds 110 ° C, the resin deteriorates. The physical properties may be reduced, which is not preferable. Also,
With a coating stripper containing three components of GBL, oxalic acid and water, it is not preferable if the temperature of the stripper is 90 ° C. or higher, because the evaporation of water becomes severe. The time for performing the coating peeling is preferably from 3 minutes to 2 hours, particularly from 5 to 30 minutes. If the time is less than 3 minutes, a sufficient peeling effect may not be obtained in many cases. It is not preferable because it is small.
Also, after coating film peeling, in order to refine the peeled coating film,
It is preferable to continue stirring or shaking for preferably 2 minutes to 1 hour, particularly preferably 5 to 30 minutes. 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 resin bumper. If the amount is less than 1 liter, the efficiency of separating the resin decreases, which is not preferable.

After the coating is stripped, the resin is separated by allowing the stripping solution to stand 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. The upper limit of the standing time is
Generally, about 10 minutes is sufficient, 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.

The resin recovered as described above 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,
A titania-based white paint (trademark, Flexen 105, manufactured by Nippon Paint Co., Ltd.) is applied to the surface of a bumper produced from a composition comprising an ethylene-propylene copolymer rubber and talc, and the baked paint bumper is crushed ( (Made by Korai Co., Ltd.) at room temperature to an average diameter of about 5 mm. Subsequently, it 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 provided as a sample for a peeling test.

Stripper 100 obtained by dissolving 25 grams of oxalic anhydride in 75 grams of γ-butyrolactone (GBL)
After heating the gram to 50 ° C.,
0 grams were added and rocked at 50 ° C. using a shaker with an oil bath. Almost all of the coating film was peeled off and settled in the solution in 5 minutes, partially in 2 hours. 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 15 minutes, and the liquid became a white suspended state. When the rocking was stopped and the mixture was allowed to stand for 10 minutes, the cloudy substance precipitated and the stripping solution returned to colorless and transparent.

[0023]

Example 2 A peel test was carried out under the same conditions as in Example 1 except that the weight ratio of GBL / oxalic acid was 70/30 and the rocking was performed at 100 ° C. Almost all of the coating film was peeled off and settled in the liquid by rocking for 5 minutes.

[0024]

Example 3 30 grams of oxalic acid dihydrate was added to GBL7
100 g of a stripping solution dissolved in 0 g (composed of 21.4 parts by weight of oxalic acid (in terms of anhydride), 70.0 parts by weight of GBL and 8.6 parts by weight of water) was heated to 80 ° C. 20 g of the peel test sample prepared in 1 was added,
It rocked at 80 degreeC using the shaker with an oil bath. In 5 minutes, part of the coating film was peeled off and settled in the liquid in 10 minutes. The sample from which the coating film was peeled was floating near the surface of the peeling liquid. After further rocking for about 15 minutes in the same manner as in Example 1, the suspension was allowed to stand, and a cloudy substance precipitated, and the stripping solution returned to colorless and transparent.

[0025]

Examples 4 to 6 The weight ratio of GBL / oxalic acid / water was 85 / 10.7 / 4.3 and 66.6 / 23.8 / 9.5, respectively.
And Example 3 except that the values were 50 / 28.6 / 21.4 and 50 / 28.6 / 21.4.
A peel test was performed under the same conditions as those described above. In each case, almost all of the coating film was peeled off and settled in the liquid in 10 minutes.

[0026]

Example 7 A peeling test was performed under the same conditions as in Example 3 except that a method of vigorously stirring with a mechanical stirrer was used instead of shaking by a shaker. The coating film was almost completely removed in about 5 minutes.

[0027]

Example 8 A peeling test was carried out under the same conditions as in Example 3 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 was almost completely removed in about 6 minutes.

[0028]

Comparative Examples 1 and 2 The weight ratio of GBL / oxalic acid / water was 0 / 21.4 / 78.6 and 0 / 28.6 / as the stripping solution.
A peeling test was performed under the same conditions as in Example 3 except that 71.4 was used. In each case, the coating film did not peel off at all even when rocked for 2 hours.

[0029]

Comparative Example 3 A peeling test was carried out under the same conditions as in Example 1 except that a stripping solution having a weight ratio of methyl ethyl ketone / oxalic acid of 75/25 was used. Even after rocking for 2 hours, the coating film did not peel off at all.

[0030]

COMPARATIVE EXAMPLE 4 A peeling test was carried out under the same conditions as in Example 1 except that the weight ratio of methylcellosolve / oxalic acid was 75/25. Even after rocking for 2 hours, the coating film did not peel off at all.

[0031]

Comparative Example 5 A peeling test was performed under the same conditions as in Example 3 except that only GBL was used as the peeling solution. Even after rocking for 2 hours, the coating film did not peel off at all.

[0032]

Comparative Example 6 The weight ratio of GBL / acetic acid / water was 60/30 /
Except that the stripping liquid of No. 10 was used, the same operation as in Example 3 was performed. Even after rocking for 2 hours, the coating film hardly peeled off. Table 1 shows the above results.

[0033]

[Table 1] ：: Almost all of the coating film was peeled off. Δ: Part of the coating film was peeled off. X: The coating film was not peeled at all. * 1: Agitation by mechanical stirrer * 2: Use of ultrasonic cleaner * 3: Use of methyl ethyl ketone instead of GBL * 4: Use of methyl cellosolve instead of GBL * 5: Use of acetic acid instead of oxalic acid No. 2 is a stripping solution containing GBL and oxalic acid, and all showed good stripping properties. Examples 3 to 8
Is a case where three components of GBL / oxalic acid / water are blended. All were found to have good peelability. On the other hand, in Comparative Examples 1 and 2, oxalic acid was mixed with water, but neither of them had releasability. Comparative Examples 3 and 4 are cases in which an organic solvent other than GBL is used, but none of them has releasability. Comparative Example 5 is GBL
Was used, and no releasability was observed.

As described above, the stripping solution in which oxalic acid is mixed with water, methyl ethyl ketone, and methyl cellosolve has no releasability, and good releasability is obtained only when GBL is mixed with oxalic acid as in the present invention. I understood. Further, the stripping solution containing the three components of GBL / oxalic acid / water of the present invention exhibits good stripping properties, and GBL alone,
Alternatively, good peeling properties were obtained which could not be expected from the peeling properties of oxalic acid and water.

In Comparative Example 6, acetic acid was used instead of oxalic acid. It was found that acetic acid hardly produced a peeling effect.

[0036]

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

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-199898 (JP, A) JP-A-58-174456 (JP, A) JP-A-6-293899 (JP, A) JP-A-6-293899 65533 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C09D 9/00-9/04 C11D ^7/ 00-7/60

Claims (3)

(57) [Claims] 1. A coating stripper for a resin bumper, comprising γ-butyrolactone and oxalic acid. 2. The coating stripper according to claim 1, comprising 60 to 95 parts by weight of γ-butyrolactone and 40 to 5 parts by weight of oxalic acid. 3. 50 to 95 parts by weight of γ-butyrolactone,
The coating stripper according to claim 1, comprising 5 to 40 parts by weight of oxalic acid and 0 to 30 parts by weight of water, the total of which is 100 parts by weight.