JPH0788969A - Surface modifying method of polyolefin resin form - Google Patents

Abstract

PURPOSE:To modify the surface of a resin form easily and uniformly to adhere a coating film layer onto the surface thereof strongly and contrive the reduction of a cost. CONSTITUTION:A surface modifying device is provided with an air supplying device 11, an oxygen supplying device 12, a control box 13 for controlling mixture, a hot-air generator 14 and an exhausting device 15. Heat etching treatment is applied on the surface of a side mole main body 2 to form a coating film layer on the surface of the same. Hot-air can be contacted with the whole surface of the decorative surface of the side mole main body 2 even when the same main body 2 has any configuration. Accordingly, polarizing reaction is effected on respective surfaces uniformly whereby reaction mottle will hardly generated in respective places whereby the coating film layer, formed on the surface, is fixed strongly and uniformly. On the other hand, the facility is not necessitated to have explosion-proof specification whereby modifying process can be introduced into one series of coating process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for modifying the surface of a polyolefin resin molded product having a relatively small surface polarity such as polypropylene.

[0002]

2. Description of the Related Art Conventionally, when a polyolefin resin molding having a relatively small surface polarity represented by polypropylene is subjected to secondary processing such as painting, the surface of the resin molding is first cleaned and etched with a solvent such as trichloroethane. Be seen. Next, the surface is coated with a primer,
Further, a top coat film layer is formed on the surface. Here, the above-mentioned etching substantially increases the surface area of the resin molded product and forms irregularities on the surface. Therefore, the primer layer formed on the surface of the resin molded product (or the directly-applied top coat film layer) is relatively strongly bonded to the surface of the molded product.

However, the use of trichloroethane has come to be restricted as a part of recent environmental protection measures. For this reason, new surface reforming means in place of trichloroethane have been required, and various research and development have been conducted on the reforming means. As one of the means, there is a reforming means called frame processing.

This treatment is a treatment method in which a flame is directly applied to the surface of a resin molded product to oxidize the surface of the molded product. According to this treatment, the surface of the resin product having a low polarity is oxidized (a carbonyl group or the like is formed) and the polarity is enhanced. Therefore, it is possible to increase the bonding strength of the primer layer to the surface of the surface without using trichloroethane.

[0005]

However, in the above-mentioned prior art, the flame was directly applied to the surface of the resin molded product. Therefore, the temperature distribution varies depending on the location, and it is difficult to uniformly modify the entire surface of the resin molded product. That is, to uniformly modify the surface, the flame must be applied uniformly to all surfaces and for each surface only at the same time. Therefore, if the resin molded product has a complicated uneven shape, all surfaces of the resin molded product cannot be uniformly modified unless the resin molded product or the flame is appropriately moved. As a result, it was very difficult to apply a uniform coating.

Further, in the above-mentioned prior art, since flames are used, it is necessary to use explosion-proof specifications in order to make the processing equipment itself safe. Therefore, the equipment cost has risen remarkably.

Furthermore, since flames are used as in the above case, it was not possible to introduce a flame treatment step during a series of painting steps for safety reasons. As a result, a separate process called a frame processing process is required, resulting in a further increase in cost.

The present invention has been made to solve the above-mentioned problems, and its object is to polarize and modify the surface of a polyolefin resin molded product without using an organic solvent and to mold the resin molded product. Provided is a method for surface-modifying a polyolefin resin molded product, which can easily and uniformly modify the surface, thereby firmly adhering a coating layer to the surface, and further reduce the cost. To do.

[0009]

In order to achieve the above-mentioned object, the present invention exposes a polyolefin resin molded article to be coated in a hot air atmosphere to modify the surface of the polyolefin resin molded article. The gist is a method for modifying the surface of a polyolefin resin molded article, which is characterized in that

Here, the temperature of the hot air is 80 ° C. or higher and 140 ° C.
It is desirable to be less than. If the temperature is lower than 80 ° C, the modifying effect may not be sufficiently obtained. At 140 ° C or higher, the molded product may be deformed. The exposure time to the hot air varies depending on the temperature of the hot air, but is usually 3 seconds or more 30
It is desirable to be less than a second. If it is less than 3 seconds, the modifying effect by the part of the molded product tends to vary, and if it is more than 30 seconds, not only the work efficiency is deteriorated, but also the molded product may be deformed.

[0011]

According to the above construction, the polyolefin resin molded product is exposed to the hot air atmosphere. This exposure to hot air firstly decomposes and removes the fragile bonding layer consisting of the low molecular weight component adhering to the surface of the polyolefin resin molded product. Here, when thermoplastic rubber is mixed in the polyolefin resin molded product, the fragile bonding layer is decomposed and removed, so that the concentration of the rubber on the surface side increases. For this reason, the polarity of the surface is increased, and the primer layer or the coating layer formed on the surface is bonded relatively firmly.

Secondly, due to the exposure to hot air, the surface portion of the polyolefin resin molded product is polarized. At this time, no matter what shape the polyolefin resin molded product has, the hot air can surely contact the entire surface of the resin molded product. Therefore, the polarization reaction is uniformly carried out on each surface of the resin molded product, and reaction spots at each location are unlikely to occur. Therefore, the primer layer or the coating layer formed on the surface is firmly and uniformly bonded.

Further, due to the exposure to hot air, thirdly, the dirt (hands, oil, etc.) adhering to the surface of the polyolefin resin molded product is evaporated or decomposed and removed. For this reason,
In some cases, it is possible to omit the cleaning step before the modification treatment.

In addition, the above-mentioned surface modification is only required to expose the molded product to hot air as a step before coating. Therefore, it is not necessary to spend a huge amount of money on equipment for the process. In addition, the exposing step can be introduced during a series of painting steps.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment embodying the present invention will now be described with reference to FIGS.
4 will be described in detail. (Polyolefin Resin Molded Product) First, in this embodiment, as shown in FIG. 2, the side molding 1 is embodied.
The side molding 1 has a substantially semi-cylindrical cross section and is formed in a long shape. The side molding 1 is composed of a side molding body 2 containing polypropylene as a main component, and a coating layer 3 applied and formed on the surface (design surface) thereof. More specifically, as the material of the side molding body 2, a material containing polypropylene as a main component and mixed with 20% to 50% of ethylene propylene rubber is used. The coating layer 3 is composed of a primer layer 4 and a top coating layer 5. However, the primer layer 4 may be omitted.

(Apparatus) Next, an apparatus used for surface modification will be described. As shown in FIG. 1, the surface reforming apparatus includes an air supply device 11, an oxygen supply device 12, a control box 13 for controlling the air-fuel mixture, a hot air generator 14 and an exhaust device 15.

Air supply device 11 and oxygen supply device 12
As its name implies, is a device for supplying air and oxygen to the control box 13, respectively. Also,
As shown in FIG. 4, in the control box 13,
An oxygen valve 16, a mixer 17, a controller (not shown), and the like are provided, and the oxygen concentration in the air-fuel mixture that is discharged can be adjusted appropriately. Further, the hot air generator 14 is provided with a heat source (not shown) and heats the air-fuel mixture sent from the control box 13 and blows it downward. In addition, the exhaust device 15 is provided above the hot air generator 14 and discharges excess hot air from the hot air generator 14 to the outside. In addition, the side molding 2 used for reforming is moved to the right in the figure by the belt conveyor 10.

(Modification Experiment) Next, in molding the side molding 1 as described above, with respect to the side molding main body 2,
Modification was carried out by various methods, and then the coating layer 3 was formed.
The modification method and the coating film forming method will be described below.

[Experiment A] First, the surface of the side molding body 2 after molding was wiped off with isopropyl alcohol (IPA), and thereafter, a heat etching (surface modification) treatment was carried out using the above surface modifying apparatus. Performed (experiment
No1). The treatment temperature at this time was 90 ° C., and the treatment time was 10 seconds. Also, only the one wiped with IPA was prepared (Experiment No. 2). Then, each surface was coated (Fujikura 2300TG: using an acrylic urethane-based paint) at 80 ° C. for 30 minutes without using a primer layer to form a top coating film layer 5. At that time, the peel strength of both of them and the peeling length at the time of washing with high pressure (at a water pressure of 70 kg / cm ² for 10 seconds) were measured. The results are shown in Table 1.

[0020]

[Table 1]

As shown in Table 1, when the heat etching treatment is carried out, the peel strength is higher than that in the case where the heat etching treatment is not carried out, and moreover, it is difficult to be peeled off even by washing at high pressure. .

[Experiment B] Next, the same treatment as in the case of Experiment No. 1 was performed (treatment time: 10 seconds), and at this time, only the heat etching treatment temperature was 60 ° C., 80 ° C., 100, 1
Various changes were made to 20 ° C and 140 ° C. And the coating film adhesion at that time, peel strength, the presence or absence of peeling during high-pressure cleaning,
The appearance quality was examined. The results at that time are shown in Table 2. However, the coating film adhesion is represented by the results of the goose eye peel test. In this test, the coating film layer 3 is provided with notches in a notch pattern, the number of which is 100, and a tape is adhered to the notch and peeled off. This was repeated 10 times for each sample, and those without any peeling were regarded as no peeling (“◯” in the table). Further, for example, when two of 100 sheets are peeled off by the first peeling, it is expressed as “2 / 100-1”, and when 4 sheets of 100 sheets are peeled off for the first time by the third peeling. Is "4
/ 100-3 ".

[0023]

[Table 2]

As shown in Table 2, when the heat etching temperature is 80 ° C. to 120 ° C., it has a strong coating film adhesion (including peel strength and high pressure cleaning resistance) and also has an appearance quality. It turns out that it is good. On the other hand, when the heat etching temperature is 60 ° C., the coating film adhesion (including peel strength and high pressure cleaning resistance) is low. This is probably due to insufficient surface oxidation as the temperature was too low. On the other hand, when the heat etching temperature is 140 ° C., the coating film adhesion (including peel strength and high pressure cleaning resistance) is excellent, but heat causes unevenness on the surface of the resin molded product,
The appearance quality has deteriorated.

[Experiment C] Next, the same treatment as in Experiment No. 1 was performed (heat etching treatment temperature: 100 ° C.).
℃), at this time, heat etching treatment time only 1
Seconds, 3 seconds, 5 seconds, 10 seconds, 20 seconds, 30 seconds, 35 seconds were variously changed. Then, the coating film adhesion at that time, the peel strength, the presence or absence of peeling during high pressure cleaning, and the appearance quality were examined. The results at that time are shown in Table 3.

[0026]

[Table 3]

As shown in Table 3, when the heat etching time is from 3 seconds to 30 seconds, the coating film has a strong adherence (including peel strength and high-pressure washing resistance) and the appearance quality is also high. It turns out that it is good. On the other hand, when the heat etching time is 1 second, the coating film adhesion (peel strength,
(Including high-pressure washing resistance) is low. This is probably due to insufficient surface polarization as the treatment time was too short. On the other hand, when the heat etching time is 35 seconds, although the coating film adhesion (including peel strength and high-pressure cleaning property) is excellent, heat causes unevenness on the surface of the resin molded product, resulting in appearance quality. Has dropped.

[Experiment D] Next, the following experiment was conducted in order to confirm the effect on dirt and the like. That is, instead of wiping the surface of the side molding body 2 with IPA, apply hand dust, grease, a rust inhibitor (mineral oil), and a release agent (vegetable oil / fat type) to the surface of the side molding body 2, respectively. Each of them was prepared with or without heat etching treatment. The conditions of the heat etching treatment were a treatment temperature of 90 ° C. and a treatment time of 10 seconds. Thereafter, a primer (chlorinated polypropylene type) was applied to each of them to form a primer layer 4, and a top coat (2 coat type) treatment was performed to form a top coat layer 5. Then, the coating film adhesion of each sample was examined. The results are shown in Table 4.

[0029]

[Table 4]

As shown in Table 4, even if stains such as hand dust, grease, rust preventives and release agents are applied, good coating adhesion can be obtained by the heat etching treatment of this embodiment. I understand. On the other hand, when the heat etching treatment is not carried out, it can be seen that the adhesion of the coating film is low if various stains are present.

As described above, according to this embodiment,
Side molding body 2 as a polyolefin resin molding
Is exposed to the hot air atmosphere by the heat etching treatment. By this exposure to hot air, first, the fragile bonding layer composed of the low molecular weight component adhering to the surface of the polyolefin resin molded product is decomposed and removed. Here, when a thermoplastic rubber such as ethylene-propylene rubber is mixed in polypropylene as in this example, the concentration of the rubber on the surface side is decomposed and removed by degrading and removing the fragile bonding layer. Becomes higher. For this reason, the polarity of the surface is increased, and the primer layer 4 or the top coat film layer 5 formed on the surface is bonded relatively firmly.

Secondly, due to the exposure to hot air, the surface portion of the side molding body 2 is polarized. At this time,
Regardless of the shape of the polyolefin resin molded product, the hot air can surely come into contact with the entire design surface of the side molding body. Therefore, the polarization reaction is uniformly carried out on each surface of the resin molded product, and reaction spots at each location are unlikely to occur. Therefore, the primer layer 4 or the top coating film layer 5 formed on the surface is firmly and uniformly bonded. Therefore, according to the present embodiment, the surface of the resin molded product can be easily and uniformly modified without using an organic solvent such as trichloroethane, and thus the coating layer 3 can be firmly formed on the surface. Can be attached.

Further, due to the exposure to the hot air, the dirt (hands, oil, etc.) attached to the surface of the side molding body 2 is evaporated or decomposed and removed. Therefore, in some cases, it is possible to omit the cleaning step before the modification treatment.

In addition, the above surface modification may be performed by exposing the molded product to hot air as a step before coating. Therefore, it is not necessary to spend a huge amount of money on equipment for the process. In addition, the exposing step can be introduced during a series of painting steps. Therefore, from the above, it is possible to reduce the cost for the modification and the formation of the coating layer 3.

The present invention is not limited to the above-described embodiment, but may be implemented as follows with a part of the structure appropriately changed without departing from the spirit of the invention. (1) In the above-described embodiment, the case where the air-fuel mixture of air and oxygen is sent to the hot air generator 14 is embodied, but it is also possible to send only air.

(2) In the above embodiment, polypropylene mixed with ethylene-propylene rubber was used as the material of the polyolefin resin molded product, but if the material is mainly composed of polyolefin, the resin molded product made of polyethylene is used. It goes without saying that it can also be applied to the surface modification of any object. The shape may be any shape.

(3) In the above embodiment, the present invention is embodied in the side molding 1 as the resin product finally obtained, but it may be embodied in a resin product other than the side molding 1. (4) As described above, the coating layer 3 may be composed of the primer layer 4 and the top coating layer 5, or may be composed of only the top coating layer 5.

[0038]

As described in detail above, according to the method for modifying the surface of a polyolefin resin molded product of the present invention, it is possible to polarize and modify the surface of the polyolefin resin molded product without using an organic solvent. The surface of the resin molding can be easily
In addition, it has an excellent effect that it can be uniformly modified so that the coating layer can be firmly adhered to the surface thereof, and that the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic view showing an apparatus used for surface modification in one embodiment embodying the surface modification method of the present invention.

FIG. 2 is a perspective view showing a side molding according to an embodiment.

FIG. 3 is a cross-sectional view showing a side molding according to an embodiment.

FIG. 4 is a schematic diagram for explaining an internal configuration of a control box in one embodiment.

[Explanation of symbols]

 2 ... Side molding body as resin molding

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Sekiya No. 1 Nagahata Ochiai, Kasuga-cho, Nishikasugai-gun, Aichi Toyoda Gosei Co., Ltd. Toyoda Gosei Co., Ltd.

Claims (1)

[Claims] 1. A polyolefin resin molded product characterized by exposing the polyolefin resin molded product (2) to be coated to a hot air atmosphere to modify the surface of the polyolefin resin molded product (2). Surface modification method.