GB2080611A

GB2080611A - An apparatus for continuous treatment of a continuous-length material with low temperature plasma

Info

Publication number: GB2080611A
Application number: GB8118765A
Authority: GB
Original assignee: Shin Etsu Chemical Co Ltd; Hitachi Ltd; Toray Industries Inc
Current assignee: Shin Etsu Chemical Co Ltd; Hitachi Ltd; Toray Industries Inc
Priority date: 1980-06-21
Filing date: 1981-06-18
Publication date: 1982-02-03
Also published as: FR2485319B1; BE889306A; KR830006025A; DE3124280A1; AU7204681A; NO155990C; IT1136887B; AU547901B2; IT8122492A0; NO812087L; SU1039438A3; JPH0341496B2; NL8102964A; KR840000727B1; FR2485319A1; DK270081A; JPS5718737A; GB2080611B; NO155990B

Abstract

The apparatus comprises a plasma chamber 1 and a front and a rear preparatory vacuum chambers 8 and 9 which serve to introduce the film material F into and to lead the material out of he plasma chamber without permitting air intrusion into the plasma chamber from the atmosphere, wherein the vacuum chambers 8 and 9 are each divided into at least two (e.g. four) sealing chambers 8a-8d and 9a-9d, each being provided with a pair of opposing sealing rollers 10a-10d and 11a-11d. The low temperature plasma is generated in the plasma chamber by applying high frequency electric power to the drum-like rotatable cathode 4 and a plurality of rod-like anodes 5 surrounding the cathode and the film material F is led into the space between the cathode and the anodes in contact with the cathode to be transferred as the cathode rotates, with the aid of guide rollers 7. The electrodes and guide rollers are held on one of the side walls of the plasma chamber in cantilever fashion, the side wall being demountable and mountable upside down, and the other side wall is made a removable cover of the plasma chamber so as to facilitate film setting up and inspection or cleaning of the inside of the chamber. <IMAGE>

Description

SPECIFICATION An apparatus for continuous treatment of a continuous-length material with low temperature plasma The present invention relates to apparatus for continuous treatment of a continuous-length material such as a film of plastic, e.g. polyvinyl chloride resin, with low temperature plasma.

It is well known that, when a shaped article of a plastic, in particular, polyvinyl chloride resin, is subjected to a treatment with or exposed to low temperature plasma of certain gases, various beneficial improvements are obtained in the surface properties of the shaped article. Properties improved by the plasma treatment include decreased migration and bleeding of plasticizer contained in the shaped article, increased wettability of the surface with water, i.e. affinity to water, decreased accumulation of static electricity on the surface, less tendency toward blocking or adhesive sticking of surfaces, enhanced printability, anti-wear resistance, antiweathering resistance, decreased stain on the surface and the like.

Since the effect of the plasma treatment is limited to the surface properties, the most prominent advantages are obtained when the shaped article treated with plasma is in a thinly extended form such as a film of plastic. When a continuous length of material is desired to be treated with low temperature plasma on an industrial scale, however, no practically feasible apparatus has been available hitherto due to the difficult conditions of plasma generation - low temperature plasma can be generated by the application of high frequency electric power only in an atmosphere under reduced pressure of, for example, from 0.01 to 10 Torr.

Of course, there have been proposed several apparatuses for the plasma treatment of a continuous-length material not only in the form of a cut sheet but also as a roll in a batchwise process. When a continuous-length material such as a film in the form of a roll is treated in such an apparatus, the roll as a whole is accommodated in a plasma chamber and the chamber is evacuated to a desired reduced pressure suitable for plasma generation. Therefore, a plasticfilm containing a plasticizer, stabilizer or other relatively volatile additive ingredients cannot be free from denaturation in the plasma chamber due to the dissipation of the volatile ingredients.In addition, the air confined in the depth of the film roll is released bit by bit to the reduced pressure atmosphere in the plasma chamber so that a considerably long period of time is required before a desired reduced pressure is obtained in the plasma chamber, this pressure preferably being below 0.1 Torr. Furthermore, the gradual release of the air from the film roll is particularly detrimental when the oxygen in the air adversely affects the effectiveness of the plasma treatment giving rise to a very difficult problem.

In order to obtain reproducible effects in the treatment of a continuous-length material such as a plastic film with low temperature plasma generated by the application of a high frequency electric power supply at a frequency of several kHz to several hundreds of MHz in a selected plasma gas under a pressure of 0.01 to 10 Torr, it is essential that the pressure of the plasma atmosphere is kept constant throughout the treatment and that gases other than the selected plasma gas are excluded from the plasma atmosphere as completely as possible. A film roll placed in a plasma chamber is necessarily accompanied by these very difficult problems.

Ways were therefore sought of providing an apparatus for the continuous treatment of a continuous-length material such as a plastic film in roll form with low temperature plasma which is free from the above described problems in the prior art apparatuses and procedures. In the apparatus, of the invention as hereinafter described in detail no roll of the continuous-length material is necessarily placed in the plasma chamber. The apparatus utilizes air-to-air transfer of the continuous-length material and the material as unrolled is transferred into and then out of a plasma chamber and the material after the plasma treatment in the plasma chamber is continuously rolled up in a roll.

The apparatus according to the invention for continuous treatment of a material of continuous length with low temperature plasma of a plasma gas at reduced pressure comprises (a) at least one plasma chamber having a front opening and a rear opening in the front and the rear walls, respectively, for transferring the material therethrough, (b) a cathode or a grounded electrode in a form of a drum mounted in the plasma chamber and supported by a shaft and rotatable around the axis thereof, which axis is perpendicular to the direction connecting the front and the rear openings of the plasma chamber, (c) at least one rod-like anode or power electrode mounted in the plasma chamber axially parallel with the cathode, (d) a front preparatory vacuum chamber connected at one end to the front opening of the plasma chamber air-tightly and opening at the other end to the atmosphere so that the continuous-length material can be transferred therethrough into the plasma chamber and divided into at least two sealing chambers, each sealing chamber being provided with a pairofverticallyfacing sealing rollers, (e) a rear preparatory vacuum chamber connected at one end to the rear opening of the plasma chamber air-tightly and opening at the other end to the atmosphere so that the continuous-length material can be transferred therethrough out of the plasma chamber and divided into at least two sealing chambers, each sealing chamber being provided with a pair of vertically facing sealing rollers, (f) means for evacuating the plasma chamber and the preparatory vacuum chambers, (g) means for supplying high-frequency electric power to the cathode and the anode, and (h) means for concurrently rotating the cathode and the sealing rollers.

Preferred embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figures 1 and 2 are each a schematic illustration of the cross sectional side view and the plan view, respectively, of one embodiment of the apparatus.

Figure 3 is a schematic illustration of an enlarged axial cross sectional view of the plasma chamber.

Figure 4 is a schematic illustration of the side view of the apparatus modified by increasing the number of the plasma chambers to two and connecting them in series.

In the Figures, the plasma chamber 1, which itself is shaped in a drum-like form to withstand evacuation inside, has a front opening 2 and a rear opening 3 in its front and rear side walls, respectiely. These openings 2,3 are each in a form of a narrow slit of a width and a height sufficient not to contact the running continuous-length material F.

In the plasma chamber 1,the low temperature plasma is generated by applying a high frequency electric voltage between the cathode 4 and the anodes 5 which are provided, if desired, with cooling means. The cathode 4 is in the form of a drum which is supported by the horizontal shaft 6 shown in Figure 3 (which is an axial cross sectional view of the plasma chamber 1) and rotatable around its axis.

The cathode 4 is preferably made of a metallic material.

The apparatus shown in Figures 1 and 2 is provided with a plural number of anodes 5 but sometimes a single anode 5 may be sufficient to obtain the desired plasma treatment effect. Each of the anodes 5 is in the form of a rod and fixedly supported on the side wall 30 of the plasma chamber 1 in a disposition axially parallel with the drum-like rotatable cathode 4 so as to keep a uniform distance from the surface of the cathode over its length.

When a plurality of anodes 5 are installed in the plasma chamber 1, all of the anodes 5 have approximately the same distance from the surface of the cathode 4 so that uniformity of the electric field and, consequently, uniformity of the intensity of the low temperature plasma, is ensured in the space formed by the surface of the cathode 4 and the cage-like assembly of the anodes 4. Usually these anodes 5 are connected to a common power terminal of a high frequency generator (not shown in the Figures) and the cathode 4 is connected to the grounded terminal of the generator.

The continuous-length material F introduced into the plasma chamber 1 at the front opening 2 is brought into direct contact with the surface of the rotating cathode 4 by a set of guide rollers 7 and led to the rear opening 3 by another set of guide rollers 7 so that the surface of the material F not in contact with the surface of the cathode 4 is continuously exposed to the lowtemperaure plasma generated in the space between the cathode 4 and the anodes 5 as the cathode 4 is rotated.

In order to ensure vacuum-tightness of the plasma chamber 1 at the front and the rear openings 2, 3, each of the openings 2, 3 is connected to a front preparatory vacuum chamber 8 or a rear preparatory vacuum chamber 9, respectively, which serves to introduce the continuous-length material F into orto take the material F out of the plasma chambers without permitting the atmospheric air to enter the plasma chamber 1. The front and the rear preparatory vacuum chambers 8, 9 are connected air-tightly to the front and the rear openings 2, 3, respectively, of the plasma chamber 1 and each of the preparatory vacuum chambers 8, 9 is divided or partitioned into at least two sealing chambers 8a, 8b, 8c, ...... or 9a, 9b, 9c , respectively.The embodiment shown in Figures 1 and 2 has four sealing chambers in each of the preparatory vacuum chambers 8,9.

Each of the sealing chambers 8a, 8b, ...... and 9a, 9b is provided therein with a pair of-sealing rollers 1 Oa, 1Ob, Ob, and 11 a, 1 b, , respectively, and the continuous-length material F introduced Into the plasma chamber 1 is pinched by the pairs of sealing rollers 10a, 10b,... in the front preparatory vacuum chamber 8 and, after being subjected to the plasma treatment in the plasma chamber 1 as mentioned above, led out of the plasma chamber 1 into the atmospheric air through the rear preparatory vacuum chamber 9 where it is pinched bythe pairs of the sealing rollers 1 lea, 1 1b The sealing chambers are designed not to permitthe airto enter the plasma chamber 1 although the pressure in a sealing chamber further from the plasma chamber is higher than in the adjacent sealing chamber closer to the plasma chamber 1. In the Figures, the pressures in the outermost sealing chambers 8a and 9d are approximately equal to the atmospheric pressure and the pressures in the innermost sealing chambers 1 Od and 11 a are also approximately equal to the pressure in the plasma chamber 1.In this manner, the continuous-length material F drawn out of the roll 12 is continuously treated with the low temperature plasma in the plasma chamber 1 Bnd thereafter rolled up on the roll 13 by air-to-airtransfer.

The plasma chamber 1 and the sealing chambers in the preparatory vacuum chambers 8, 9 are evacuated each with a separate vacuumpump.

However, it is convenient that the sealing chambers in the front and rear preparatory vacuum chambers 8, 9 positioned at the same distlance orn the same order as counted from the plasma chamber 1, for example, the sealing chambers 8a and 9d, 8b and 9c, and 8c and 9b are combined in twos and the sealing chambers of each of the thus combined pairs are connected to one and the same vacuum pump since the pressures in the sealing chambers positioned at the symmetrical positions relative to the plasma chamber 1 are approximately equal.As is shown in Figure 2, the plasma chamber 1, the sealing chambers 8c and 9b paired together,-8b and 9c paired together, and 8a and 9d paired together are evacu atedwiththevacuum pumps 14,15,16and17, respectively, through the vacuum lines 18, 19, 20 and 21, respectively.

As is mentioned above, the continuous-length material F is drawn out from the starting roller 1-2 and rolled up on the roller 13 using ài,r-to-airtransfer via the front preparatory vacuum chamber 8, plasma chamber 1 and rear preparatoryvacuum chamber9 with the aid of the tension roll - 22-ari'd 23. The transfer of the material Fthrou ia. aratusis.

controlled by the synchronized rotation of the drum- like cathode 4 and the sealing rollers 10a, a, etc. in the preparatory vacuum chambers 8, 9. The synchronized rotation of the cathode and these rollers is essential for the smooth transfer of the film material F through the apparatus. In order to ensure the concurrent rotation of the cathode and the sealing rollers 10a, 1 1a, etc. as well as the roll-up roller 13, they are driven by a common line shaft 24 rotated by a motor 25 with transmissions 26 for the sealing rollers in the front preparatory vacuum chamber 8, 27 for the cathode 4 in the plasma chamber 1,28 for the sealing rollers in the rear preparatory vacuum chamber 9 and 29 for the roll-up roller 13.No driving power is supplied to the starting roller 12 and the tension rollers 22 and 23 since they are rotated passively. The starting roller 12 may be omitted when the apparatus for the plasma treatment is immediately downstream of a manufacuring facility such as, for example, a calendering machine, extruder machine and the like for a plastic film and a loom for a woven cloth and the material as manufactured in the machine is directly introduced into the front preparatory vacuum chamber 8.

Figure 3 schematically illustrates an enlarged axial cross sectional view of the plasma chamber 1 with the drum-like cathode 4, the anodes 5 and the guide rollers 7 installed therein. The shaft 6 supporting the cathode 4 is mounted in cantilever fashion on one of the side walls 30 by means of a mechanical seal 31 so as to be rotatable vacuum-tightly. Each of the anodes 5 penetrates the side wall 30 and is electrically insulated with an insulator 32 but the guide rollers 7 may be confined within the chamber. It should be noted that, as is shown in Figure 3, the cathode 4, anodes 5 and guide rollers 7 are all held on one side wall 30 in cantilever fashion and the other side wall 33 is freed from the duty of supporting the cathode 4, etc. Instead, the side wall 33 is made as a removable cover with a vacuum-tightly sealed flange 33a.The vacuum line 28 for evacuating the plasma chamber 1 opens into the bottom of the chamber 1.

The above described function of the side walls 30 and 33 is very advantageous since the side wall or the removable cover 33 can be removed to facilitate setting up of the leading end of the continuouslength material F through the plasma chamber 1 as well as inspection and cleaning of the inside of the plasma chamber 1 including the electrodes 4, 5 and guide rollers 7 so that very high working efficiency is obtained.

Furthermore, the side wall 30 holding the electrodes 4, 5 and the guide rollers 7 is designed so as that it can be mounted on the body of the plasma chamber 1 upside down, i.e. rotated through 180 C, with the relative arrangement of the electrodes and the guide rollers unchanged. This design of the side wall 30 is advantageous when successive treatments of the top and bottom surfaces of a continuouslength material with low temperature plasma are desired using two plasma chambers of the same design connected in series.

Figure 4 illustrates schematically such an arrangement of the apparatus in side view, in which two plasma chambers la and 1b are connected in series at the rear opening 3a of the first plasma chamber 1 a and the front opening 2b of the second plasma chamber 1 b with the front and the rear preparatory vacuum chambers 8 and 9 connected to the former and the latter, respectively, as described before. The plasma chambers 1 a and 1 b can be constructed in just the same way but the inside walls supporting the respective electrodes and the guide rollers are mounted on the respective bodies of the chambers in the reverse direction relative to each other.In other words, the side wall of the second plasma chamber 1 b is in an upside down disposition with respect to the side wall of the first plasma chamber 1 a so that the continuous-length material F running through these chambers 1 a and 1 b is first exposed to the plasma atmosphere on one surface thereof in the first chamber 1a and then introduced into the second chamber 1 b where the other surface of the material F is exposed to the plasma atmosphere. In this manner, the material F can be treated with low temperature plasma on both surfaces in a single continuous run so that a great improvement is obtained in the working efficiency.

When the effect of the plasma treatment is desired only on one surface of the continuous-length material, it is of course possible that the side walls of the two plasma chambers 1 a and 1 are mounted on the bodies of the respective chambers at the same direction so that the material F exposed to the plasma atmosphere on one surface in the first plasma chamber 1 a is exposed to the plasma atmosphere on the same surface in the second plasma chamber 1b resulting in a doubled exposure time to the plasma atmosphere. Alternatively, the velocity of the film transfer through the plasma chambers can be doubled when the effect of the exposure to plasma, which is assumedly proportionalto the time of exposure to plasma atmosphere, desired in a single pass is the same.Therefore, the efficiency of the plasma treatment can be increased by increasing only the number of the plasma chambers with a pair of the front and the rear preparatory vacuum chambers connected to the foremost and rearmost ones, respectively, of the serial combination of the plasma chambers. The number of the plasma chambers is of course not limited to two but may be three or more according to the desired working efficiency with correspondingly increased velocity of transfer of the continuouslength material through the plasma chambers.

The apparatus is applicable to a variety of materials, mainly organic, of a continuous length. The materials include plastic films of polyvinyl chloride, polyethylene, nylon, polyester, cellulose acetate and the like, sheets of natural and synthetic rubbers and webs, i.e. woven, non-woven and knit fabrics of natural and synthetic fibers as well as wood veniers, papers and combinations thereof.

As will be understood from the above given description, the apparatus of the invention for the continuous treatment of a continuous-length material with low temperature plasma is very advantageous in the high efficiency of the plasma treatment therewith as well as in the versatility of the apparatus which is capable of complying with a diversity of requirements according to the con tinuous-length material under treatment and the desired nature of the effects of the plasma treatment.

Claims

1. An apparatus for continuous treatment of a material of continuous length with low temperature plasma of a plasma gas at reduced pressure which comprises (a) at least one plasma chamber having a front opening and a rear opening in the front and the rear walls, respectively, for transferring the continuouslength material therethrough, (b) a cathode in the form of a drum mounted in the plasma chamber and supported by a shaft and rotatable around the axis thereof, which axis is perpendicular to the direction connecting the front and the rear openings of the plasma chamber, (c) at least one rod-like anode mounted in the plasma chamber axially parallel with the cathode (d) a front preparatory vacuum chamber connected at one end to the front opening of the plasma chamber air-tightly and opening at the other end to the atmosphere so that the continuous-length material can be transferred therethrough into the plasma chamber and divided into at least two sealing chamber, each sealing chamber being provided with a pair of vertically facing sealing rollers, (e) a rear preparatory vacuum chamber connected at one end to the rear opening of the plasma chamber air-tightly and opening at the other end to the atmosphere so as that the continuous-length material can be transferred therethrough out of the plasma chamber and divided into at least two sealing chambers, each sealing chamber being provided with a pair of vertically facing sealing rollers, (f) means for evacuating the plasma chamber and the preparatory vacuum chambers, (g) means for supplying high-frequency electric power to the cathode and the anode, and (h) means for concurrently rotating the cathode, the sealing rollers and a roll-up roller.

2. The apparatus as claimed in claim 1 which further comprises at least one guide roller mounted in the plasma chamber for guiding the continuouslength material to be contacted with the surface of the cathode.

3. The apparatus as claimed in claim 2 wherein the cathode, the anode and the guide roller are carried by one of the side walls of the plasma chamber in cantilever fashion, the other sidewall of the plasma chamber being a removable cover of the plasma chamber.

4. The apparatus as claimed in claim 3 wherein the side wall of the plasma chamber holding the cathode, the anode and the guide roller together is demountabie and mountable upside down.

5. The apparatus as claimed in any preceding claim wherein the means for evacuating the plasma chamber and the preparatory vacuum chambers iscomposed of a plurality of vacuum lines each connecting eitherthe plasma chamber or one ofthe pairs of the sealing chambers, each pair being a combination of the sealing chambers in the front and the rear preparatory vacuum chambers positioned at the symmetrical positions relativeta the plasma chamber, and a respective vacuum pump.

6. The apparatus as claimed in any preceding claim wherein the means for concurrently rotating the cathode, the sealing rollers and the roll-up roller comprises a motor, a line shaft driven by the motor and transmissions for transmitting the driving power from the line shaft to the cathode, the sealing rollers and the roll-up roller.

7. The apparatus as claimed in claim'4compns- ing two plasma chambers connected to each other in series, of which the cathode, anode and guide rollers in the second plasma chamber are upside down with respect to the cathode, anode and guide rollers in the first plasma chamber.

8. An apparatus for continuous; treatment of a material of continuous length with lwtenlperabure plasma of a plasma gas at reduced pressure, sub stantially as hereinbefore described with reference to Figures 1 - 3 or'Figure 4 of the accompanying drawings.