JP4558306B2 - Surface modification method and resin material modified by the surface modification method - Google Patents

Description

The present invention relates to a surface modification method for modifying the surface of a resin sheet or resin film that is difficult to adhere to an adhesive to make it easy to adhere, and in particular, a resin material such as polypropylene and an instantaneous adhesive. a surface modification method capable of improving the adhesion between relates to a resin material in which surface-modified in the process.

  Conventionally, as this type of surface modification method, there is an atmospheric pressure plasma surface treatment method described in Patent Document 1. In this treatment method, a gas is introduced into a plasma reactor having a dielectric-covered electrode in which a solid dielectric is disposed on the surface of at least one of the opposing electrodes, and plasma excitation is performed under atmospheric pressure. A surface treatment method for performing a surface treatment of an object to be processed located between electrodes to be introduced is characterized in that a gas to be introduced is a gas composition consisting essentially of argon and helium and / or acetone. In this plasma processing apparatus, a polypropylene base material is plasma-treated in a pressure environment near atmospheric pressure using argon and helium to impart hydrophilicity.

  In addition, as a treatment by corona discharge, the method for corona discharge treatment of a synthetic resin molded article described in Patent Document 2 is that a synthetic resin molded article is applied under a smaller effective output due to a smaller peak current and a larger peak voltage. In this case, corona discharge is performed, and discharge treatment is performed using air (so-called nitrogen and oxygen) as a processing gas.

JP-A-4-74525 JP-A-10-259261

  By the way, the atmospheric pressure plasma surface treatment method described in Patent Document 1 can impart hydrophilicity to polypropylene, but its level is low and bonding with an adhesive is weak. Further, the corona discharge treatment method described in Patent Document 2 has a problem that adhesiveness with the instantaneous adhesive is low, the change with time is large, and the adhesive strength over a long period is low. Furthermore, the method of corona discharge treatment under atmospheric pressure to oxidize the surface has a problem that durable hydrophilicity cannot be obtained because the surface treatment is very local. Therefore, primer treatment is indispensable for bending containers using polypropylene sheets.

The present invention has been made in view of such problems, and the object of the present invention is to adhere to an adhesive, particularly a resin material that is difficult to adhere to a cyanoacrylate-based instantaneous adhesive. An object of the present invention is to provide a surface modification method capable of performing a surface modification treatment with excellent properties. Moreover, it is providing the resin material processed with the said surface modification method .

In order to achieve the above object, the surface modification method according to the present invention is a method in which a resin material formed from a polypropylene resin that is hardly adhesive to a cyanoacrylate-based instantaneous adhesive is subjected to plasma treatment near atmospheric pressure, Plasma treatment is performed in a treatment gas containing nitrogen and ammonia by a method of modifying the surface, and easy adhesion is imparted by setting the ammonia concentration in the treatment gas to 0.1 to 15 vol%. It is characterized by. Moreover, as a resin material, a resin sheet, a resin film, a resin molded product of various shapes, etc. are applicable.

  The surface modification method of the present invention configured as described above is easy to perform, for example, by subjecting the surface of a resin material such as a polypropylene resin molded product or a polypropylene sheet to plasma treatment and introducing a polar group to the surface of the resin material. In order to impart adhesiveness, for example, when bonding is performed using a cyanoacrylate-based instantaneous adhesive, the adhesive strength is high, and the adhesive state can be stabilized over a long period of time. By this surface modification method, it is possible to manufacture an adhesive body in which a resin material and a homogeneous material or another member are firmly bonded with an instantaneous adhesive.

In the surface modification method described above, the ammonia concentration in the processing gas is 0.1 to 15 vol% , and the remainder is an inert gas such as nitrogen or argon. In particular, the ammonia concentration is preferably set to 0.5 to 5 vol%. By setting the ammonia concentration in this way, the discharge between the opposing electrodes can be stabilized, the plasma state is stabilized, the polar groups introduced to the surface become uniform, and the easy adhesion of the resin material is made uniform. can do.

Resin material of the present invention is a resin material, characterized in that modified with the surface modification process. The resin material modified in this way has a polar group introduced by the surface modification method described above to impart easy adhesion, and the same material or between this resin material and another resin material, metal, etc. for possible bonding a member and an instant adhesive, the adhesive strength is high, long term over and can be stabilized, the quality of the adhesive body can be stabilized. In particular, a cyanoacrylate instant adhesive with a polypropylene resin material adhered is suitable. The resin material surface modified with the surface modification method, and is easily printed or painted with ink or paint, the thus formed coated body, long-term adhesion of the ink or paint is rather high It is possible to improve durability without peeling.

As described above, according to the present invention, a resin material formed from a polypropylene resin can be bonded with a cyanoacrylate instantaneous adhesive with high adhesive strength. Moreover, since the adhesive strength is stable over a long period of time without performing primer treatment, the quality of the bonded body bonded with the instantaneous adhesive can be stabilized. In addition, a coated body obtained by printing or painting the surface of the resin material modified by the surface modification method of the present invention with ink or paint has high adhesion and can improve durability.

Hereinafter, an embodiment of a surface modification method according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram of a main part of a glow discharge plasma processing apparatus as a surface processing apparatus used in the surface modification method according to the present embodiment. In FIG. 1, a glow discharge plasma processing apparatus (hereinafter referred to as a plasma processing apparatus) 1 uses a polypropylene resin (hereinafter referred to as PP) sheet as a resin material for surface modification treatment, and has, for example, OH, COOH, A polar group such as NH ₂ is introduced to impart hydrophilicity and easy adhesion.

  The plasma processing apparatus 1 includes a roll-shaped electrode 2 that conveys a PP sheet, and a curved electrode 3 having a partial arc-shaped concave arc electrode surface 3a facing the convex arc electrode surface 2a of the roll-shaped electrode, The convex arc electrode surface 2a of the roll electrode 2 and the concave arc electrode surface 3a of the curved electrode 3 are opposed to each other with a uniform interval to form a discharge space 4. A solid dielectric layer is formed on the electrode surfaces 2 a and 3 a of the roll electrode 2 and the curved electrode 3 that form the discharge space 4. The solid dielectric may be formed on at least one opposing surface, and a thin film such as alumina is suitable.

  The roll electrode 2 can be rotated at an arbitrary rotation speed by a rotating means (not shown), and in the case of the PP sheet 5 as a resin material subjected to the surface modification treatment, the PP sheet 5 is brought into close contact with the roll electrode 2. It is possible to carry out processing while carrying it. That is, the PP sheet 5 is supplied from the unwinding roll 5a, enters the discharge space 4, is processed in the discharge space, and is wound up by the winding roll 5b. The PP sheet 5 may be in close contact with the roll-shaped electrode 2, for example, by forming a suction hole on the surface of the roll-shaped electrode so as to be attracted by negative pressure, or by charging static electricity. It may be adsorbed.

  The roll electrode 2 and the curved electrode 3 are accommodated in a container 6, in which a gas introduction container 7 is installed on the inlet side of the discharge space 4 and a gas discharge container 8 is installed on the outlet side of the discharge space 4. Has been. The gas introduction container 7 is supplied with a treatment gas containing ammonia as a treatment gas for the discharge plasma treatment from the gas cylinder 9, collects the gas used for the treatment in the gas discharge container 8, and discards it in a collection container (not shown). It is configured as follows. Accordingly, the surface of the PP sheet 5 is modified by generating discharge plasma in the processing gas. As the processing gas, a mixture of ammonia and an inert gas such as nitrogen or argon is used.

  Next, as an example of a power supply circuit for applying a pulse electric field to the plasma processing apparatus 1, a power supply circuit 10 will be described with reference to the block diagram of FIG. The power supply circuit 10 includes a pulse oscillation circuit 11 that outputs a pulse signal having a predetermined frequency, a switching inverter circuit 12 to which the pulse signal is input, a + DC power supply circuit 13 that supplies a positive power source and a negative power source to the switching inverter circuit, and − A DC power supply circuit 14, and an output signal from the switching inverter circuit 12 is amplified by a step-up transformer 15 and output from one output terminal 16, and the other output terminal is grounded. For example, the output terminal 16 is connected to the upper curved electrode 3 of the plasma processing apparatus 1 of FIG. 1, and the lower roll electrode 2 is grounded. Thus, the curved electrode 3 constitutes a hot electrode, the roll electrode 2 constitutes a ground electrode, and a pulse electric field is applied to the discharge space 4.

In the plasma processing apparatus 1 of this embodiment, the processing is preferably performed under a pressure near atmospheric pressure. The pressure near atmospheric pressure is a pressure of 100 to 800 Torr (about 1.333 × 10 ^{4 to} 10.664 × 10 ⁴ Pa), and is actually easy to adjust the pressure and used for the discharge plasma treatment. A pressure of 700 to 780 Torr (about 9.331 × 10 ^{4 to} 10.9797 × 10 ⁴ Pa) is preferable because the apparatus is simple. Further, when the surface of the PP sheet 5 which is a resin material to be surface-modified is activated by bringing the discharge plasma into contact therewith, the resin material may be heated or cooled, and may be cooled to room temperature. May be kept.

  The time required for the discharge plasma treatment is appropriately set depending on the magnitude of the applied voltage applied to the discharge space 4, the ratio and flow rate of the processing gas used, the resin material to be processed, the use, and the like. Due to the discharge plasma treatment, the processing gas containing ammonia reacts with the PP sheet 5 which is a resin material, so that polar groups are introduced on the surface of the PP sheet 5, and the surface of the PP sheet 5 is modified to facilitate adhesion. Can be granted. Since the PP sheet 5 is processed at a portion in contact with the discharge plasma generated in the discharge space 4, only the upper surface of the PP sheet 5 is modified in the plasma processing apparatus 1 of this embodiment.

  In the plasma processing apparatus 1 of this embodiment, the roll-shaped electrode 2 is rotated at the same speed as that of the PP sheet 5, and the process gas also moves along with the rotation of the roll-shaped electrode 2. However, it can be performed stably, the plasma state is stable, and the reforming process becomes uniform. Moreover, since discharge plasma is generated along the roll electrode 2, the discharge state is stabilized and the occurrence of arc discharge can be prevented. And since PP sheet 5 can be processed continuously, processing time can be shortened and efficiency can be improved.

According to the surface modification method by plasma treatment of the present invention configured as described above, when an instantaneous adhesive mainly composed of cyanoacrylate is applied to the surface of the modified PP sheet 5, PP The adsorbed water on the surface of the sheet 5 diffuses into the adhesive to form monomeric zwitterions, and anionic polymerization begins, curing and bonding. In this anionic polymerization, it is considered that weak bases such as water and amines (N, N-dimethylformaldehyde, trimethylamine, etc.) and metal ions promote the polymerization. Here, when the plasma treatment of NH ₃ is performed on the PP sheet 5, weak bases such as amide groups are formed to promote polymerization, and moisture in the air is adsorbed on the surface of the resin material by the polar groups. It is considered that anionic polymerization is promoted by being trapped and cured and adhered.

  In the surface modification method of the present invention, the surface modification treatment was performed by flowing a treatment gas under the plasma treatment conditions A and B shown in Table 1, and Examples 1 and 2 and Comparative Examples 1 and 2 as shown in Table 2 were performed. The result was obtained. As the processing gas, ammonia gas was flowed at a flow rate of 1 L / min, and nitrogen gas was flowed at flow rates of 16 L / min and 34 L / min, so that the ammonia concentration was 2.86 vol% and 5.88 vol%.

  As the PP sheet 5, a transparent PP sheet “Super Pure Array” (SG-240TN T = 0.3 mm) manufactured by Idemitsu Unitech Co., Ltd. is used. In Examples 1 and 2 and Comparative Example 1, it is used as untreated. In Comparative Example 2, corona discharge treatment was performed. As the electrode, AL203 manufactured by Tokaro, and one having nitroflon tape were used. The electrode surfaces 2a and 3a of the opposing electrodes 2 and 3 were coated with alumina as a solid dielectric layer, and the distance between the electrodes was set to 1.8 mm. A DC voltage of 210 to 230 V was applied to the DC power supply of the power supply circuit 10 that generates a pulsed electric field, and a pulsed electric field with a frequency of 10 kHz and Vpp 16.09 kV was applied between the electrodes to perform a discharge plasma treatment for 30 seconds.

  In Example 1, plasma processing was performed under the processing condition A in which ammonia gas was flowed at a flow rate of 1 L / min and nitrogen gas was flowed at a flow rate of 34 L / min to make the ammonia concentration 2.86 vol%. In Example 2, plasma treatment was performed under the treatment condition B in which ammonia gas was flowed at a flow rate of 1 L / min and nitrogen gas was flowed at a flow rate of 16 L / min to set the ammonia concentration to 5.88 vol%. In contrast, in Comparative Example 1, the untreated PP sheet was not subjected to plasma treatment, and in Comparative Example 2, only the corona treatment was performed, and the plasma treatment was not performed.

  When the water contact angles of the PP sheets of Examples 1 and 2 and the PP sheets of Comparative Examples 1 and 2 were measured, Examples 1 and 2 were 51.4 degrees and 50.5 degrees, respectively. In Comparative Examples 1 and 2, they were 101.6 degrees and 72.8 degrees, respectively. The plasma-treated surfaces of the PP sheets of Examples 1 and 2 and Comparative Examples 1 and 2 were overlapped, and bonded and bonded using MC-1 manufactured by Arteco Co., Ltd., a cyanoacrylate instantaneous adhesive as the instantaneous adhesive. A body (not shown) was constructed, and the adhesive portion was peeled off to determine the adhesive strength. The adhesive strengths of Examples 1 and 2 were strong enough to cause material destruction of the base material. This characteristic was maintained even after 4 months. The adhesive strengths of Comparative Example 1 and Comparative Example 2 were so weak that they easily peeled off at the substrate-adhesive interface.

  The change with time of the hydrophilicity of the PP sheet 5 of Example 2 whose surface has been modified as described above will be described with reference to FIG. In FIG. 3, the horizontal axis represents the number of days elapsed, and the vertical axis represents the contact angle of water. As experimental data, the contact angle immediately after the treatment was 47.5 degrees, 50.3 degrees after 1 day, 49.4 degrees after 2 days, 49.5 degrees after 3 days, and 49.3 degrees after 8 days. 14 days later, 47.2 degrees after 17 days, 50.3 degrees after 17 days, 49.6 degrees after 30 days, 48.5 degrees after 45 days, and 46.5 degrees after 60 days. It is expressed that there is. FIG. 3 shows, as an example, the change over time in hydrophilicity of Example 2 shown in Table 2. Also in Example 1, the result that the change over time in hydrophilicity was similarly small was obtained.

Another effect of the surface modification method of the present invention is to improve the adhesion of the coating film when the modified resin material surface is printed or painted with ink or paint. Various UV curable offset inks (FD Carton ACE GT (for paper), FD O New PT (for PET), FD O New from Toyo Ink Mfg. Co., Ltd. were used for the PP sheets of Example 2, Comparative Example 1 and Comparative Example 2. KR2 (for PP)), and the adhesion was evaluated by a cello tape (registered trademark) peel test method. The results are shown in Table 3. In Example 2, the adhesion without any practical problems was shown for all the inks, whereas in the comparative example, the range of the ink with which sufficient adhesion was obtained was extremely limited. It was confirmed that the improvement in adhesion by the method was great.

  Next, another example of the glow discharge plasma processing apparatus will be described in detail with reference to FIG. FIG. 4 is a block diagram showing the main part of another example of a glow discharge plasma processing apparatus for performing the surface modification method according to the present invention. This embodiment is characterized in that a PP sheet as an object to be processed is transported in a plane with respect to the glow discharge plasma processing apparatus 1 of the above-described example. Other substantially equivalent configurations are denoted by the same reference numerals, and detailed description thereof is omitted.

  In FIG. 4, in the glow discharge plasma processing apparatus 20, the upper and lower electrodes 21 and 22 that face each other have a flat upper surface and lower surface, and the discharge space 23 is formed flat. A solid dielectric layer is formed on at least one surface of the opposing electrodes. In this example, alumina coating layers 21 a and 22 a are formed on the opposing surfaces of the upper and lower electrodes 21 and 22. A pulse electric field is applied to the upper electrode 21 from the power supply circuit 10, and the lower electrode 22 is grounded. In this example, the PP sheet 5 is supplied from the unwinding roll 5a to the discharge space 23 and wound up by the winding roll 5b, and is moved in a plane in contact with the lower electrode 22. A processing gas is supplied to the discharge space 23 from the gas introduction container 24 and is collected in the gas discharge container 25.

  Also in the glow discharge plasma processing apparatus 20 of this example, ammonia gas is flowed under the plasma processing conditions A and B shown in Table 1, and a pulse electric field is applied to the upper and lower electrodes 21 and 22 facing each other in the power supply circuit 10 shown in FIG. Then, by generating glow discharge in the discharge space 23, a polar group can be introduced into the surface of the PP sheet 5 similarly to the plasma processing apparatus 1 shown in FIG. Could be applied. An instantaneous adhesive was applied to the surface-modified PP sheet and firmly adhered to other members (not shown) to obtain an integrated adhesive body (not shown). This adhesive was also strongly bonded and had a high peel strength.

  Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention described in the claims. Design changes can be made. For example, although nitrogen is shown as an example of a gas that flows simultaneously with ammonia gas, an inert gas such as argon may be flowed. In addition, as a processing configuration, multistage processing using a plurality of electrodes and simultaneous double-side processing can be performed.

  In addition, as an example of the resin material to be subjected to the surface modification treatment, an example in which the resin sheet is continuously supplied from a roll wound with a resin sheet has been shown. However, for example, a plate-like resin material is conveyed and supplied by a belt conveyor. May be. Further, the pulse electric field applied to the electrode can be an appropriate waveform such as an impulse type, a rectangular wave type, a modulation wave type, etc., and a so-called single-wave shape in which a voltage is applied to either the positive or negative polarity side. The waveform may be used.

The principal part block diagram of a glow discharge plasma processing apparatus as a surface processing apparatus which performs one Embodiment of the surface modification method which concerns on this invention. The block diagram of the power supply circuit which applies a pulse electric field to the processing apparatus of FIG. The graph which shows the time-dependent change of the hydrophilic property of Example 2 of Table 2. FIG. The principal part block diagram of the other example of a glow discharge plasma processing apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,20: Glow discharge plasma processing apparatus, 2: Roll-shaped electrode (earth electrode), 3: Curved electrode (hot electrode), 2a, 3a, 21a, 22a: Electrode surface (solid dielectric layer), 4, 23: Discharge space, 5: PP sheet (resin material), 7, 24: Gas introduction container, 8, 25: Gas discharge container, 9: Gas cylinder (processing gas), 10: Power supply circuit, 21, 22: Electrode

Claims (2)

A method of modifying a surface of a resin material formed from a polypropylene resin that is difficult to adhere to a cyanoacrylate-based instantaneous adhesive by plasma treatment under the vicinity of atmospheric pressure,
The plasma treatment is performed in a processing gas containing nitrogen and ammonia, and the ammonia concentration in the processing gas is set to 0.1 to 15 vol%.   A resin material modified by the surface modification method according to claim 1.

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