NL8102964A - DEVICE FOR CONTINUOUSLY TREATMENT OF LONG-TERM FILM MATERIAL WITH LOW TEMPERATURE PLASMA. - Google Patents

Description

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Device for continuous treatment of elongated film material with low temperature plasma

The invention relates to an apparatus for continuously treating a continuous web of material such as a film of a plastic, for example polyvinyl chloride resin, with low! temperature plasma.

It is known that when a molded plastic article, in particular polyvinyl chloride resin, is subjected to a treatment or exposed to low temperature plasma of certain gases, several advantageous improvements are obtained in the surface properties of the molded precursor. 10 throw. Several of the properties improved by the plasma treatment include the reduced migration and outflow of plasticizer present in the molded article, increased wetting. surface surface with water, ie affinity with water, reduced static electricity accumulation on the surface, less tendency to block or stick the surfaces, increased printability, wear resistance, resistance! | against weathering, reduced ugly spots on the surface and the like. j

Since the effect of the plasma treatment is limited to the surface properties, the most important advantages are obtained when the plasma treated molded article is thin and elongated like continuous length film material treated; should be used with low temperature plasma on an industrial scale, however, no practically useful device is available due to the difficulties in generating plasma because low temperature plasma can be generated by applying high-frequency electric current only in an atmosphere of reduced pressure, for example, 0 , 01 to 10 Torr.

Of course, various devices have been proposed for plasma-treating elongated material, not only in the form of a cut sheet, but also as a film roll in a batch; ! , i I wise process. When elongated material such as a film in the i I | 8102964-2 - In the form of a roll in such a device, the entire roll is placed in a plasma chamber and the chamber is evacuated to the desired reduced pressure useful for plasma generation. Therefore, a plastic film containing a plasticizer, a stabilizer or other relatively airy added ingredients cannot be free from denaturation in the plasma chamber due to the escape of the volatile ingredients. In addition, the air trapped in the depth of the film roll is released bit by bit into the atmosphere with reduced pressure in the plastic chamber so that a considerably longer period of time is required before the desired reduced pressure is obtained in the plasma chamber, preferably below 0.1 Torr. In addition, the gradual release of air from the film roll is particularly harmful when the oxygen in the air adversely affects the efficiency of the plasma treatment, giving rise to a very difficult and fatal problem which is hardly solved.

To obtain reproducible effects by treating an elongated material such as a low temperature plasma plastic film generated by applying a high frequency electric current supplied at a frequency of several kHz to several hundred MHz in a given plasma gas under a pressure of 0.01 to 10 Torr, it is essential that the pressure of the plasma atmosphere is kept constant during the treatment and that gases other than the selected plasma gas are excluded from the plasma aimos: so complete if possible. A film roll disposed in a plasma chamber is necessarily accompanied by this i | very difficult problems.

It is therefore an object of the invention to provide an apparatus for continuously treating an elongated material such as a roll of film of one; plastic with low temperature plasma which is free from the above-described problems with known devices and processes. j In the invented device, no roll of elongated material is placed in the plasma chamber. The device uses air j to transfer air from the elongated material which is transferred in uncoiled condition into and then out of a plasma chamber and 81 02 9 6 4 r 3 - j the material is continuously rolled up into a roll after the plasma treatment in the plasma chamber . j

The invented apparatus for continuously treating a low temperature plasma continuous film 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 back walls for the passage of | the film material, | b) a cathode or grounded electrode in the form of a drum 10 disposed in the plasma chamber and supported by an axis and rotatable about its axis, the axis being perpendicular to the direction between the front and rear openings of the plasma chamber, jc) At least one rod-shaped anode or current electrode disposed in the plasma chamber axially parallel to the cathode in the form of the drum, d) a front preparatory vacuum chamber connected at one end to the front opening of the plasma chamber airtight and at the other end into the atmosphere so that the elongated material can be passed therethrough in the plasma chamber and divided into at least two sealing chambers, each sealing chamber having a pair of sealing rollers arranged vertically with respect to each other, e) a rear preparatory vacuum chamber which is connected at one end to the rear opening of the plasma chamber in an airtight manner and each opens to the atmosphere at the other end so that the elongated material can be passed therethrough from the plasma chamber and divided into at least two sealing chambers with each | sealing chamber is provided with a pair of vertically opposite sealing rollers, means for evacuating the plasma chamber and the preparatory vacuum chambers, means for supplying high-frequency electric current to the anode and cathode, and j | The means for synchronously rotating the cathode in the form of a drum and the sealing rollers. j 81 02 9 6 4 -4-

Figures 1 and 2 each schematically show, in cross section j, a side view and a top view of the device.

! Fig. 3 schematically shows an enlarged cross-section along the axis of the plasma chamber.

FIG. 4 schematically shows the side view of the invented j | | device which has been modified by increasing the number of plasma chambers to two connected in series.

In the following, the invented device is described with respect to the accompanying drawing. Figures 1 and 2 schematically show a side view and j a top view of a typical embodiment of the device.

According to this figure, the plasma chamber 1, which itself is truss-shaped to withstand internal evacuation, is provided with a front opening 2 and a rear opening 3 on the front and rear side walls of the truncated plasma chamber 1.

These openings 2 and 3 each have the shape of a narrow slit of sufficient width and height not to come into contact with the traveling elongated material F.

In the plasma chamber 1, low temperature plasma is generated by applying a high-frequency electric current between the cathode 4 and the anodes 5, which can be provided with cooling means if desired. The cathode 4 has the shape of a truss drum carried by a horizontal axis 6 according to | Figure 3 which is an axial section of the plasma chamber 1, | the drum being rotatable about its axis. The cathode 4 is preferably made of a metal material.

The device of Figures 1 and 2 is provided with a large number of anodes 5, but sometimes a single anode 5 may be sufficient to obtain the desired effect of the plasma treatment. Each anode 5 has the shape of a bar and is | fixedly attached to the side wall 30 of the plasma chamber 1. In a position axially parallel to the truss-shaped, rotatable cathode 4 to maintain an even distance from the surface of the cathode over its length. When a large number of anodes 5 are set up in chamber 1, all anodes 5 have approximately the same | distance from the surfaces of the cathode 4 so that the

j I

The electric field or, as a result, uniformity of the intensity of the lower temperature plasma is ensured by the space formed by the surface of the cathode 4 and the cage-shaped system of the anode 4. These anodes 5 | are connected to a common terminal of an I high frequency generator (not shown) and the cathode 4 is connected to the ground terminal of the generator.

The elongated material F, which has been introduced into the plasma chamber 11 at the front opening 2, is brought into direct contact with the surface of the rotating cathode 4 by guiding through a set of guide rollers 7 and passed to the rear opening 3 by also guiding through a other set of guide rollers 7 so that the surface of the material F that does not come into contact j

with the surface of the cathode 4 being exposed to the low temperature plasma generated in the space between the cathode 4 and the. anode 5 continuously while the cathode 4 is being rotated. I.

To ensure 20 cm vacuum tightness of the plasma chamber 1 to the front opening 2 and the rear opening 3, each of these openings is connected to a front preparatory vacuum chamber 8 or a rear preparatory vacuum chamber 9, which respectively serve to introduce the material F 25 into the plasma chamber 1 or the film material F from the plasma chamber 1 without allowing atmospheric air to enter the plasma chamber 1. The front and rear preparatory 'i i | vacuum chambers 8 and 9 are airtightly connected to the front opening j | 2 and the rear opening 3 of the plasma sump 1 and each of the front j | 30 cleaning vacuum chambers 8 and 9 are divided by partitions in at least 1 y. Two sealing chambers 8a, 8b, 8c etc. or 9a, 9b, 9e_ etc. The model according to! Figures 1 and 2 have four sealing chambers in each of the | . preparatory vacuum chambers 8 and 9.

! . . . Each of the sealing chambers 8a, 8b etc. or 9a, 9b etc. is! I ':

j. 35 provided with a pair of sealing rollers 10a, 10b, etc. and 11a, 11b, etc. I

and the film material F is introduced into the plasma chamber 1 and squeezed by the pairs of sealing rollers 10, 10b etc. into the front preparatory vacuum chamber 8 and, after being subjected to the plasma treatment in the plasma chamber 1 the plasma chamber 1! | fed into the atmospheric air through the rear preparatory vacuum chamber 9, the film also being squeezed by the pairs of sealing rollers 11a, 11b, etc. It goes without saying that the sealing ji, - i | chambers are designed not to allow air to enter the plasma chamber 1 although the pressure in a sealing chamber is higher than in the neighboring sealing chamber which is located closer to the plasma chamber 1. In the drawing, the pressures of the outer sealing chambers 8a and 9d are approximately equal to the atmospheric pressure and the pressures in the inner sealing chambers 10d and 11a are also approximately equal to the pressure in the plasma chamber 1. In this way, the material F is pulled from the roll 12, continuously treated with low temperature plasma in the plasma chamber 1 and then rolled up on the roll 13 with continuous movement of the outside air to the outside air.

It goes without saying that the plasma chamber 1 and the sealing chambers in the preparatory vacuum chambers 8 and 9 are each evacuated with a separate vacuum pump. An easy way in this case, however, is that the sealing chambers in the front and rear preparatory vacuum chambers 8 and 9, which are spaced or in the same order from the plasma, for example, the sealing chambers 8a and 9d or 8b and 9c-9b with its twos are combined and the sealing chambers of each of the pairs thus combined are connected to one and the same vacuum pump since the pressures in the sealing chambers located symmetrically with respect to the plasma chamber 1 are approximately equal. As shown in Figure 2, the plasma chamber 1, the sealing chambers 8c and 9b are paired, 8b I 30 and 9c paired and 8a and 9d are evacuated in pairs with the vacuum pumps 14, 15, 16 and 17 via vacuum lines 18, 19, 20 and 21 . | As noted above, the elongated material F is subtracted from the outgoing roll 12 and rolled up in the roll j 13 when transferring from the outside air to the outside air through the front preparatory vacuum chamber 8, the plasma chamber 1 and the 81 02 9 6 4 -7- rear preparatory vacuum chamber 9 with tension rollers 22 and 23. j The transport of the film material F through the device is controlled by synchronous rotation of the drum-shaped cathode 4! j and the sealing rollers 10a, 11a, etc. in the preparatory vacuum chambers 8 and 9. The synchronized rotation of the cathode and j; these rollers are very essential for the uniform transport of the film material F through the device. To ensure synchronous rotation of the cathode and the sealing rollers 10a, 11a, etc., as well as the take-up reel 13, they are driven by a common drive shaft 24 by a motor 25 with drive rollers 26 in the front preparatory rollers. vacuum chamber 8, drives 27 for the cathode 4 in the plasma chamber 1 and drives 28 for the sealing rollers in the rear preparatory vacuum chamber 9 and drives 29 for the take-up reel 15, No driving force is supplied to the output roller 12 and the tension rollers 22 and 23 as they are rotated passively. It goes without saying that the initial roll 12 can be omitted when the invented plasma treatment device is immediately downstream of film making devices 20 such as a calender machine, extruder, and the like, for a plastic film and a fabric weaving chair. machine-made material is immediately fed into the front preparatory vacuum chamber 8.

Figure 3 schematically shows on an enlarged scale an axial cross-section of the plasma cutter 1 with the drum-shaped cathode 4, the anodes 5 and the guide rollers 7 arranged therein. The shaft 6 carrying the cathode 4 is cantilevered in one of the side walls 30 fitted by means of a mechanical seal 31 and each of the anodes 5 protrudes into the side wall 30 and is electrically insulated by the insulator 32 while the guide rollers 7 are within the room. It is noted that according to figure 3 | the cathode 4, the anodes 5 and the guide rollers 7 are all attached on one side wall 30 in a cantilevered manner and the other side wall I 35 33 is free from the task of carrying the cathode 4 etc. In; Instead, side wall 33 is constructed as a removable one; lid with a vacuum sealing flange 33a. A vacuum line 18 j for evacuating the plasma chamber 1 leads from the bottom j of the chamber 1. j 5 The above-described work distribution of the side walls j | 30 and 33 is of great advantage since the sidewall or!

the removable cover 33 can be removed to facilitate initial adjustment of the front end of the I

material F through the plasma chamber 1 as well as for inspecting and cleaning the inside of the plasma chamber 1 including the electrodes 4 and 5 and the guide rollers 7 so that a very high working efficiency is obtained in the invented device.

In addition, the side wall 30 carrying the electrodes 4 and 5 and the guide rollers 7 is designed such that this side wall 15 can be mounted upside down on the body of the plasma chamber 1, i.e. rotated through 180 °, with the mutual arrangement of the electrodes and the guide rollers are unchanged. This embodiment of side wall 30 is advantageous when successive treatment of the top and bottom of a material by low temperature plasma is desired. by using two plasma chambers of the same design and arranged in series.

Figure 4 schematically shows such an arrangement of the invented device in side view, in which two plasma chambers 25a and 1b are arranged in series, the rear opening 3a of the first plasma chamber 1a and the front opening 2b of the second plasma chamber 1b being connected to each other and wherein the front and rear preparatory vacuum chambers 8 and 9 are respectively connected to the front plasma chamber 1a and the rear plasma chamber 30 Ib. The plasma chambers 1a and 1b can be of the same design; are constructed, but the side walls of these chambers for carrying the electrodes and guide rollers involved are mounted on the respective bodies of the chambers in inverse position to each other. In other words, the side wall of the second plasma chamber 1b is upside down relative to the! 8102964 -9- side wall of the first plasma chamber 1a so that the material F which is passed through these chambers 1a and 1b is first exposed in the plasma atmosphere to one surface in the first chamber 1a and then is fed into the second chamber 1b where the other surface of material F is exposed to the plasma atmosphere. In this way, the material F can be treated on both surfaces with low temperature plasma in a single continuous operation so that a great improvement in working efficiency is obtained. j 10 When the effect of the plasma treatment is only | is desired on one surface of the material, it is obvious that the sidewalls of both plasma chambers 1a and 1b are similarly applied to the bodies of the chambers concerned so that the film material F is exposed to the plasma atmosphere on the one surface in the first plasma chamber 1a and is exposed to the plasma atmosphere on the same surface in the second plasma chamber 1b resulting in; a double duration of exposure to the plasma atmosphere. Conversely, the speed of film transport through the plasma chambers j 20 can be doubled when the effect of exposure to | plasma, which is assumed to be proportional to the time of exposure to the plasma atmosphere, if desired in a single pass is the same. As a result, the efficiency of; the plasma treatment are increased by only increasing the number of plasma chambers, with only a few anterior and posterior preparatory vacuum chambers connected to the anterior and posterior of a combination in series of plasma i | Rooms. The number of plasma chambers is of course not limited j | up to two but may be three or more depending on the desired operating efficiency at a correspondingly increased rate of material transport through the plasma chambers.

i j | The invention is applicable to various, mainly organic, elongated materials, such as plastic films such as polivenyl chloride, polyethylene, nylon, polyester,

i 35 Cellulose acetate or sheets of natural or synthetic rubber I and woven, non-woven and knitted fabrics of natural or I

8102964 -10- synthetic fibers or wood visor, paper and combinations thereof. | As can be seen from the foregoing, the invented device for the continuous treatment of elongated material with low temperature plasma is of great advantage due to the high efficiency of the plasma treatment as well as due to the great adaptability of the device which is capable of meet different requirements according to the material of the material to be treated and the desired nature of the effects of the plasma treatment. | 10 j i i t j j j 1 8102964 i

Claims (7)

A device for continuously treating a continuous strip of low temperature plasma material of a plasma gas at reduced pressure, characterized by: | I a) at least one plasma chamber with a front opening and! 5 a rear opening in the front wall and rear wall I for transporting the strip therethrough, b) a cathode in the form of a drum arranged i! in the plasma chamber and carried by an axis and rotatable about its axis, the axis being perpendicular to the line 10 between the front opening and the rear opening of the plasma chamber, c) at least one rod-shaped anode arranged in the plasma chamber axially parallel to the drum-shaped cathode , d) a front preparatory vacuum chamber which is hermetically connected at one end to the front opening of the plasma chamber and which opens at the other end into the atmosphere so that the strip can be passed through it in the plasma chamber, wherein the. vacuum chamber is divided into at least two sealing chambers, each of which is provided with two vertically opposite sealing rollers, 20 e), a rear preparatory vacuum chamber which is air-tight at one end to the rear opening of the plasma chamber and which opens at the other end to the atmosphere so that the strip can be passed therethrough from the plasma chamber, the rear vacuum chamber being divided into at least sealing chambers each comprising one pair of vertically opposed sealing rollers, means for evacuation, of the plasma chamber and the preparatory vacuum chambers! g) means for supplying high-frequency electric current to the cathode and anode and means for synchronously rotating the trunnion-shaped cathode and the sealing rollers and the take-up reel. ' Device according to claim 1, characterized by at least 1! one guide roller fitted in the plasma chamber to guide the j: 'i I .................................. ..............................._ _....... .......... .................................................. ...... j 81 02 9 6 4 -12- • 4 * strip which should come into contact with the cathode surface for ± one. 3. Device according to claim 2, characterized in that the cathode, the anode and the guide roller are arranged together on one of the side walls of the plasma chamber in a cantilevered manner, the other side wall of the plasma chamber being in a cantilevered manner. removable lid is from the plasma chamber. Device according to claim 3, characterized in that the - side wall of the plasma chamber containing the cathode, the anode and the I! | 1. Carrying guide roller, can be dismantled and mounted upside down. | i: Device as claimed in claim 1, characterized in that the means for evacuating the plasma chamber and the vacuum chamber preparatory j consist of a number of vacuum lines j | each of which is connected to either the plasma chamber or one of! 15 the pairs of sealing chambers, each pair of sealing chambers being a combination of the sealing chambers and the front and rear preparatory vacuum chambers located symmetrically! relative to the plasma chamber and a concerned vacuum pump. | i 6. Device according to claim 1, characterized in that the means for synchronous rotation of the cathode, the sealing rollers and the take-up reel consist of a motor, a drive shaft driven by the motor and drives for transferring driving force from the drive shaft on the cathode and the sealing rollers and the take-up reel. 25 Device according to claim 4, characterized by two plasma chambers connected in series, the cathode, anode and guide rollers in the second plasma chambers upside down! | are arranged with respect to the cathode, anode and guide rollers | in the first plasma chamber. I 30 I 1 | I 81 02 9 6 4! ;