JPH10204195A - Method for modifying surface of polypropylene resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hydrophilize the surface of a polypropylene resin within a short time with a simple equipment to thereby making the surface easily coatable or bondable. SOLUTION: Prior to the fluorination, a cylinder 6 is evacuated, and is filled with a fluorine gas having a purity of 99% or higher to a specified pressure and then filled with a nitrogen gas to adjust the fluorine concentration to 1.0vol.%. On the other hand, a case made by injection molding a polypropylene resin and having a specified box shape is introduced into a pressure-resistant vacuum chamber 1 and mounted on a table 14. The chamber is then evacuated to a degree of vacuum of 200-300Pa by exhaustion from a vent 4 and a fluorine gas having a specified concentration of 1.0vol.% is introduced from the cylinder 6. The case 20 is left standing in the fluorine gas atmosphere for 5-7min after the fluorine gas is introduced to hydrophilize the surface of the polypropylene resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coating or bonding a surface of a processed product or a molded product formed to a predetermined size by extrusion or injection molding using a polypropylene resin. The present invention relates to a surface modification method for improving the adhesiveness of a coated film after coating and for improving the adhesive strength.

[0002]

2. Description of the Related Art Polypropylene resin is a general-purpose plastic material which is widely used in daily necessities and industrial materials, particularly in automobile parts, electric appliances and computer products. This polypropylene resin has extremely low surface polarity, has poor wettability to water, and exhibits water repellency, so that coating, plating and bonding as secondary processing were extremely difficult.

For this reason, surface modification has been conventionally performed by performing various surface treatments as pretreatments for painting, plating and bonding work. In particular, as described above, polypropylene resin has a wide field of application as a molded product for components, and therefore, the development of a simple and effective surface modification method is required.
It has been demanded that painting and bonding be easily performed.

[0004] In response to such demands, in the field of painting and bonding, modification of polypropylene resin itself, that is, property modification of the resin by copolymerization or polymer blending, or ultraviolet irradiation treatment or plasma pretreatment as painting pretreatment. The adhesion or the adhesion strength of the coating film is improved by a treatment or a treatment method such as application of a primer or ozone oxidation.

[0005]

However, these treatment methods have problems such as high equipment costs, environmental measures, especially the destruction of the ozone layer and many problems in the working environment, and furthermore, the treatment time is too long. was there. The present invention
In view of such circumstances, the purpose is to make the surface of a polypropylene resin having a very low surface polarity hydrophilic in a short period of time using simple equipment to facilitate coating and adhesion. It is to provide a reforming method.

[0006]

The object of the present invention is to provide a method for modifying the surface of a polypropylene resin, wherein the surface of the polypropylene resin is fluorinated with a dilute fluorine concentration gas to render the surface hydrophilic. A method for modifying the surface of a resin. The fluorination treatment used here is desirably performed by leaving it in a normal temperature atmosphere at a degree of vacuum of 200 to 300 Pa and a fluorine concentration of 0.5 to 2.0% for 1 to 10 minutes.

[0007]

According to the present invention, by fluorinating the surface of a polypropylene resin having a very small polar force component,
Dipolar or polarizable functional groups can be formed on the polypropylene resin surface. That is, a bond between -CF-CF- and -C-CF- is formed on the surface of the polypropylene resin, and a functional group is formed by replacing a hydrogen atom of an existing R-group (-CH3-) on the surface of the polypropylene resin. It is considered to be. By the way, since fluorine atoms tend to attract electrons, in the bond between -CF-CF- and -C-CF-, atoms are attracted by fluorine atoms to polarize the surface of the polypropylene resin, thereby increasing wettability. It seems to improve.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method for modifying the surface of a polypropylene resin according to the present invention will be described in detail below. First,
A fluorine gas having a purity of 99% or more is put in a vacuumed stainless steel cylinder, and then a nitrogen gas is press-fitted thereinto, and a fluorine gas whose concentration has been adjusted in advance so that the fluorine concentration in the cylinder becomes 0.5 to 2.0 Vol% is obtained. prepare. Next, the polypropylene resin molded product / processed product is placed in a pressure-resistant vacuum chamber, and then vacuumed to 200 to 300 Pa. Thereafter, the fluorine gas previously adjusted to a predetermined concentration of 0.5 to 2.0 Vol% is introduced from a cylinder. After sealing the fluorine gas, it is left for 1 to 10 minutes to make the surface of the polypropylene resin molded product or processed product hydrophilic.

Immediately after the lapse of a predetermined processing time, nitrogen gas is introduced and fluorine gas is purged. After evacuating, the fluorinated polypropylene resin molded product / processed product is taken out and painted. The fluorine-treated polypropylene resin surface does not require any treatment such as primer coating, which is a normal coating process, or any solvent treatment, and a thin film with good adhesion can be obtained by directly applying the enamel paint only once. be able to. In addition, since the surface of the polypropylene resin is made hydrophilic, good adhesive strength can be obtained for all kinds of adhesives not only in painting but also in bonding.

An embodiment of the present invention will be described below in detail with reference to FIG. In the figure, 1 is a pressure-resistant vacuum chamber, 2 is a chamber main body, 3 is a lid provided at the upper opening of the main body 2 so as to be opened and closed, 4 is an exhaust port connected to a vacuum pump (not shown), and 5 is A first intake port connected to a stainless steel cylinder 6 filled with fluorine gas through a pipe 7, and a second intake port 8 connected to a stainless steel cylinder 9 filled with nitrogen gas through a pipe 10. 7 and 10 are provided with valves 11 and 12 for opening and closing the pipeline.

In the chamber main body 2, a table 14 is integrally provided on a column 13 standing upright on the bottom surface of the main body 2, and a box-shaped case made of a polypropylene resin as an object to be processed is provided on the table 14. 20 is placed. A method for fluorinating the surface of the polypropylene resin using the fluorination apparatus configured as described above will be described.

Prior to the fluorination treatment, the cylinder 6 is evacuated, and a predetermined amount of fluorine gas having a purity of 99% or more is injected thereinto.
ol%. On the other hand, a case 20 injection-molded into a box-shaped predetermined shape using a polypropylene resin (UBE Polypro Grade J609H manufactured by Ube Industries, Ltd.) is placed in the pressure-resistant vacuum chamber 1 and placed on the table 14. Thereafter, the inside of the chamber 1 is vacuumed to 200 to 300P.
After exhausting from the exhaust port 4 until a
Fluorine gas adjusted to ol% is introduced from the cylinder 6.
The case 20 is left in a fluorine gas atmosphere for 5 to 7 minutes after the introduction of the fluorine gas, and the surface is modified by hydrophilizing the surface of the polypropylene resin.

Immediately after the lapse of a predetermined time, the nitrogen gas cylinder 9
, A fluorine gas is purged to an inert substance, and the vacuum of the chamber 1 is released. afterwards,
Open the lid 3 and the polypropylene resin case 20 to be treated.
Take out. At this time, care must be taken so that stains such as fingerprints do not adhere to the surface of the case 20 to be coated. The case 20 taken out of the chamber 1 is immediately painted. Coating is performed by a usual method, but no pre-treatment such as pre-coating treatment such as primer coating and solvent wiping is required.
Enamel is directly applied to the surface treated with fluorine gas.

The enamel was treated at room temperature using a one-pack type paint (Polynal No. 350 manufactured by Ohashi Chemical Co., Ltd.) containing acrylic resin and a special polyolefin resin as main components at room temperature. 60 parts (weight) of thinner is added to 100 parts of the enamel, and the paint viscosity is adjusted to 12 to 15 seconds (Ford Cup No. 4), applied once with a spray gun (approximately 20 μm of coating film), and at room temperature. It was left for 24 hours. Then, in order to check the adhesion between the polypropylene and the coating film, a 1 mm square 100EA (gap interval 1 m
m, squares 100) were formed, and adhesion of the coating film was confirmed.
As a result, good adhesion of 0/100 (defect cross-cut / cross-cut) was obtained (JISK5400 8.5 cross-cut adhesion test).

Furthermore, in order to set the fluorination treatment conditions (fluorine concentration and treatment time) at which the best adhesion to the coating film is obtained, the specimen is 100 × 100 × 5 mm in thickness.
An adhesion test was carried out using a polypropylene resin (UBE Polypro Grade 609H manufactured by Ube Industries, Ltd.) of 5 sheets per condition, coating with the same method as in the above example, changing the fluorine concentration and the processing time. As a result, the results shown in the following table were obtained.

[Table 1] As is apparent from the experimental results, the fluorination treatment conditions were a fluorine concentration of 0.5 to 2.0 VOL%, a treatment time of 1
-10 minutes was most appropriate.

[0016]

According to the present invention, when a polypropylene resin is used for painting or bonding on a polypropylene surface of a processed product or a molded product formed to a predetermined size by extrusion or injection molding, the polypropylene surface is made hydrophilic. In order to improve the adhesion of the coated film after coating, the surface of the polypropylene resin can be fluorinated with a dilute fluorine concentration gas at room temperature to make the surface hydrophilic, Adhesion or adhesive strength can be increased. Further, since a molded product or a processed product is simply placed in a fluorine atmosphere of a predetermined concentration, fluorination treatment can be easily performed even if the shape is complicated. Therefore, the number of work steps is reduced, productivity is improved, and cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus used for a method for modifying the surface of a polypropylene resin according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Chamber 2 Main body 3 Lid 4 Exhaust port 5 First intake port 6 Fluorine gas cylinder 7.10 Piping 8 Second intake port 9 Nitrogen gas cylinder 11.12 Valve 14 Table 20 Case to be treated

Claims (2)

[Claims] 1. A method for modifying the surface of a polypropylene resin, wherein the surface of the polypropylene resin is fluorinated with a dilute fluorine concentration gas to render the surface hydrophilic. 2. The method according to claim 1, wherein the fluorination treatment is performed at a degree of vacuum of 200 to 3
The method for modifying the surface of a polypropylene resin according to claim 1, wherein the method is carried out by leaving it in a normal temperature atmosphere at 00 Pa and a fluorine concentration of 0.5 to 2.0% for 1 to 10 minutes.