JPH07149932A - Cleaning method for polyolefin resin molding - Google Patents

Abstract

PURPOSE:To provide a cleaning method by which a polyolefin resin molding can be cleaned without leaving water drops behind on the surface of the molding after cleaned with water and can be dried in a short time. CONSTITUTION:The step of bringing a polyolefin resin molding cleaned with water into contact with an aq. soln. of a nonionic surfactant is inserted into between the water cleaning step for cleaning the molding with water and the water-draining and drying step. The surfactant is a sec. or tert. higher alcohol surfactant and is contained in the aq. soln. in a concn. of 300-3,000ppm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a polyolefin resin molded article used for automobile bumpers and the like.

[0002]

2. Description of the Related Art Conventionally, urethane bumpers molded by RIM molding or the like have been used for automobile bumpers, but recently, polyolefin resin molded products such as polyethylene and polypropylene, which are low in price and excellent in moldability, have been used. It has become so.

The large-sized polyolefin resin molded articles used for the bumpers of automobiles and the like are generally coated on the surface thereof, but JP-A-3-4970 discloses the polyolefin resin molding. In order to electrostatically coat a product with a metal part of a body at the same time, a technique is disclosed in which, as a pretreatment, etching is performed, followed by washing with water, and a conductive cationic surfactant is applied to conduct a conductive treatment.
When the polyolefin resin molded product is washed with water as described above, it must be drained and dried before applying the conductive cationic surfactant.

However, unlike the urethane resin molded product, the surface of the polyolefin resin molded product is poor in hydrophilicity, so that it takes 10 to 20 minutes for the water to be dried and the water adhering to the surface becomes water droplets. Therefore, after the water droplets are condensed and dried, the ions contained in the water droplets remain on the surface of the polyolefin-based resin molded product, which is likely to cause defects such as blisters (blisters) after coating. is there.

[0005]

DISCLOSURE OF THE INVENTION The present invention eliminates such inconveniences, and after the polyolefin-based resin molded article is washed with water, water drops do not adhere to the surface of the polyolefin-based resin molded article and can be dried in a short time. It is an object of the present invention to provide a possible cleaning method.

[0006]

In order to achieve the above object, a method for cleaning a polyolefin resin molded article of the present invention comprises a step of washing the polyolefin resin molded article with water, and a polyolefin washed in the water washing step. In a cleaning method having a drying step of draining and drying the resin-based molded article, between the water-washing step and the drying step, a nonionic surfactant aqueous solution is added to the polyolefin-based resin-molded article washed in the water-washing step. The method is characterized by comprising a step of contacting a surfactant for contact.

Examples of the nonionic surfactant include higher alcohol nonionic surfactants, nonylphenol nonionic surfactants, polynuclear phenol nonionic surfactants, and the like. Due to the fact that the effect of improving the hydrophilicity of the surface of the resin-based molded article is stable regardless of the concentration, has an excellent affinity for paints, is easily biodegradable, and is easy to treat wastewater. Second or third higher alcohol-based nonionic surfactants are particularly suitable.

The second or third higher alcohol nonionic surfactant preferably has an HLB value of about 12 to 14 because it has an intermediate value between hydrophilicity and lipophilicity. For example, R (OC) ₂ H ₄ ) _n OH is a surfactant represented by the general formula. In the above general formula, R represents a second or third alkyl group having 6 to 18 carbon atoms, and n is 6 to 21.

The nonionic surfactant aqueous solution is 30
Used in concentrations ranging from 0 to 3000 ppm. When the concentration of the aqueous solution of the nonionic surfactant is less than 300 ppm, sufficient hydrophilicity cannot be obtained on the surface of the polyolefin resin molded article, and when it exceeds 3000 ppm, the coating film performance after coating may be adversely affected.

In order to improve the hydrophilicity of the surface of the polyolefin resin molded article, a lower alcohol organic solvent such as methanol or ethanol, or a nonionic surfactant such as a cationic or anionic surfactant is used. Although lower alcohol organic solvents have strong volatility, they dry quickly and the time required to maintain the entire surface of the polyolefin resin molded product in a hydrophilic state is short and there is a risk of explosion or fire. Since non-ionic surfactants easily adsorb water, blisters are likely to occur after coating.

[0011]

According to the cleaning method of the present invention, the hydrophilicity of the surface of the polyolefin resin molded product is improved by bringing the non-ionic surfactant aqueous solution into contact with the polyolefin resin molded product after washing with water. The water adhering to the surface of the polyolefin resin molded product is easily removed. Therefore, the drying time of the water-washed polyolefin-based resin molded product can be shortened, and the inconvenience of the post-process due to the remaining water droplets can be prevented.

Further, in the cleaning method of the present invention, by using the second or third higher alcohol surfactant as the nonionic surfactant, excellent paint adhesion can be obtained when coating is performed in a later step. Is obtained.

When the concentration of the nonionic surfactant aqueous solution is in the range of 300 to 3000 ppm, the water adhering to the surface of the polyolefin resin molded product after washing with water can be easily removed. .

[0014]

Next, the method for cleaning a polyolefin resin molded article of the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 is an explanatory view of a method for cleaning a polyolefin resin molded article of this example, and FIGS. 2 to 5 show HLB values and concentrations of various nonionic surfactants and hydrophilicity of the surface of the polyolefin resin molded article. It is a graph which shows the relationship with the effect which improves.

In the cleaning method of this embodiment, first, as shown in FIG.
As shown, the polypropylene resin bumper 1 is immersed in the etching solution 2 for etching, and then the water-based cleaning solution 4 is sprayed from the spray 3 as shown in FIG. The aqueous cleaning solution 4 may contain a detergent.

Next, as shown in FIG. 1 (c), the washed poly is washed with water.
Spray the propylene resin bumper 1 from the spray 5 to the second
Rucol-based nonionic surfactant ((CH₃)₂CH
(CH ₂)₃(OC₂H_Four)₆OH) aqueous solution (concentration 15
(00 ppm) 6 by spraying
The bumper 1 made of ren resin is brought into contact with the aqueous surfactant solution 6
It The aqueous surfactant solution 6 is stored in the receiving tank 7, and the circulating po
Pump 8 circulates to spray 5 via conduit 9.
In doing so, the concentration of the aqueous surfactant solution 6 is
It can be controlled by conductivity, for example 1500pp
The control value is 20 μS / cm, which is the electric conductivity corresponding to m.
To set.

Next, as shown in FIG. 1D, the polypropylene resin bumper 1 is blown with air from the air spray 10. Since the polypropylene resin bumper 1 is in contact with the surfactant aqueous solution 6, the hydrophilicity of the surface is improved, and the water adhering to the surface of the polypropylene resin bumper 1 is easily removed by the air blow. , Water drops do not remain. In this embodiment, the polypropylene resin bumper 1 is obtained by performing the air blowing for 45 seconds.
The water adhering to the surface of was completely removed without leaving any liquid pool in the recesses such as the winkers.

Next, as shown in FIG. 1 (e), the polypropylene resin bumper 1 is dried at 80 ° C. for 5 minutes by using the heater 11 to complete the pretreatment of coating. In this example, the polypropylene resin bumper 1 could be dried in about 6 minutes including the air blow. In addition, since the polypropylene resin bumper 1 washed as described above has the water droplets completely removed in the drying step, ions and the like in the water droplets do not remain, and excellent paint adhesion in the coating step is achieved. Sex was obtained.

When the polyolefin resin molded product does not have a recess such as a winker part, the air blow shown in FIG. 1 (d) is omitted and the drying shown in FIG. 1 (e) is performed at 80 ° C. for about 5 minutes. May be.

Although the second higher alcohol-based nonionic surfactant is used as the nonionic surfactant in the above-mentioned embodiment, the third higher alcohol-based nonionic surfactant may be used. The same effect can be obtained. Further, other nonionic surfactants such as the first higher alcohol nonionic surfactant, nonylphenol nonionic surfactant, polynuclear phenol nonionic surfactant and the like may be used.

Next, HLB of various nonionic surfactants
The relationship between the value and the concentration and the effect of improving the hydrophilicity of the surface of the polyolefin resin molded product will be described.

In order to investigate the above relationship, a second higher alcohol-based nonionic surfactant, a first higher alcohol-based nonionic surfactant, a nonylphenol-based nonionic surfactant, and a polynuclear phenol-based nonionic surfactant. Activator 4
Three kinds of surfactants each having a different HLB value were prepared, and the polypropylene resin molded product was immersed in an aqueous solution at 20 ° C. in which the concentration of each surfactant was changed. Then, 30 seconds after the polypropylene resin molded product was taken out of the aqueous surfactant solution, the ratio of the area of the surface of the polypropylene resin molded product wet with water was measured. The results are shown in FIGS. 2 to 5.

From FIG. 2, in the case of the second higher alcohol type nonionic surfactant, HLB12 and HLB13.
In the case of No. 5, when the concentration is 300 ppm or more, the entire surface of the polypropylene resin molded product is wet with water, and it is clear that an excellent effect can be obtained in improving the hydrophilicity of the surface of the polypropylene resin molded product. . The third
The higher alcohol-based nonionic surfactant also exhibits the same tendency as the second higher alcohol-based nonionic surfactant.

Further, as shown in FIG. 3, in the case of the first higher alcohol nonionic surfactant, the effect of improving the hydrophilicity of the surface of the polypropylene resin molded product varies depending on the concentration depending on the HLB value. It may come out.

Further, as shown in FIG. 4, in the case of the nonylphenol-based nonionic surfactant, the same effect as that of the second higher alcohol-based nonionic surfactant can be obtained. However, nonylphenol-based nonionic surfactants have a low affinity for paints and may repel paints during painting, and are difficult to biodegrade, so proper wastewater treatment is required.

Further, as shown in FIG. 5, in the case of the polynuclear phenol-based nonionic surfactant, HLB 9.8 has substantially the same effect as that of the second higher alcohol-based nonionic surfactant. Although it can be obtained, its effect varies greatly depending on the HLB value and is difficult to manage.

Therefore, it is clear that among the various nonionic surfactants, the second or third higher alcohol nonionic surfactant is particularly suitable for the present invention.
In addition, the concentration of the aqueous solution of each of the above nonionic surfactants is 3
If it exceeds 000 ppm, it may adversely affect the coating film.

[0028]

As is clear from the above, according to the cleaning method of the present invention, the polyolefin resin molded article after being washed with water is brought into contact with an aqueous solution of a nonionic surfactant to form the polyolefin resin molded article. Since the water adhering to the surface of the product is easily removed, it is possible to shorten the drying time of the washed polyolefin resin molded product and prevent the inconvenience of the post-process due to the residual water droplets.

Further, in the cleaning method of the present invention, by using the second or third higher alcohol-based surfactant as the nonionic surfactant, excellent paint adhesion can be obtained when coating is performed in a later step. Can be obtained.

By adjusting the concentration of the nonionic surfactant aqueous solution in the range of 300 to 3000 ppm, water adhering to the surface of the polyolefin resin molded product after washing with water can be more easily removed. be able to.

[Brief description of drawings]

FIG. 1 is an explanatory view of a method for cleaning a polyolefin resin molded product according to the present invention.

FIG. 2 is a graph showing the relationship between the HLB value and concentration of a second higher alcohol-based nonionic surfactant and the effect of improving the hydrophilicity of the surface of a polyolefin resin molded product.

FIG. 3 is a graph showing the relationship between the HLB value and concentration of the first higher alcohol-based nonionic surfactant and the effect of improving the hydrophilicity of the surface of the polyolefin resin molded product.

FIG. 4 H of nonylphenol-based nonionic surfactant
The graph which shows the relationship between LB value and concentration, and the effect which improves the hydrophilicity of the surface of a polyolefin resin molded product.

FIG. 5: HL of polynuclear phenol-based nonionic surfactant
The graph which shows the relationship between B value and concentration, and the effect which improves the hydrophilicity of the surface of a polyolefin resin molded product.

[Explanation of symbols]

1 ... Polyolefin resin molded product, 4 ... Water-based cleaning liquid, 6
… Surfactant aqueous solution.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Daizo Shiga 1-10-1 Shin-Sayama, Sayama-shi, Saitama Prefecture Honda Engineering Co., Ltd. (72) Inventor Kazuto Iiyama 1-10 Shin-Sayama, Sayama-shi, Saitama Prefecture 1 Within Honda Engineering Co., Ltd.

Claims (3)

[Claims] 1. A washing method comprising a water washing step of washing a polyolefin resin molded article with water, and a drying step of draining and drying the polyolefin resin molded article washed in the water washing step, the washing step and the drying step A method for cleaning a polyolefin resin molded article, characterized by comprising a surfactant contact step of bringing a nonionic surfactant aqueous solution into contact with the polyolefin resin molded article washed in the water washing step. 2. The method for cleaning a polyolefin resin molded article according to claim 1, wherein the nonionic surfactant is a second or third higher alcohol surfactant. 3. The method for cleaning a polyolefin resin molded article according to claim 1, wherein the concentration of the nonionic surfactant aqueous solution is in the range of 300 to 3000 ppm.