US2906367A

US2906367A - De-gasifying liquids

Info

Publication number: US2906367A
Application number: US621079A
Authority: US
Inventors: Charles D Vandenburgh
Original assignee: American Viscose Corp
Current assignee: Akzo Nobel UK PLC
Priority date: 1956-11-08
Filing date: 1956-11-08
Publication date: 1959-09-29
Anticipated expiration: 1976-09-29

Description

Sept. 29, 1959 Filed Nov. 8. 1956 C. D. YANDENBURGH DE-GASIFYING LIQUIDS 2 Sheets-Sheet 1 Sept. 29, 1959 C. D. VANDENBURG H DE-GASIFYING LIQUIDS 2 Sheets-Sheet 2' Filed Ndv. 8. 1956 Uni? t tes Patent DE-GASIFYING LIQUIDS Charles D. 'Vandenburgh, Wallingford, Pa., assignor to American Viscose Corporation, Philadelphia, Pa., a corporation of Delaware Application'N'ovember 8, 1956, Serial No. 621,079

"15 Claims. (Cl. 183-25) be discussed with specific reference to the 'd'e-gasif-ying.

ofviscose.

In'the production of articles such as yarn and pellicular structures from viscose compositions, it is necessary to remove the air or other gases from the composition before spinning the yarn or casting the film. If this air is not removed, the air bubbles pass through the extrusion orifices, causing broken filaments during the spinning; or in the case of films, bubbles or holes will be formed in the film itself. 7

Air is present in viscose in two forms; that is, as occluded air which appears as bubbles, and dissolved air which develops bubbles during spinning. If a body of viscose is subjected to a vacuum, the bubbles present become larger becauseof the decreased pressureand thus tend to rise more rapidly to the surface. The dissolved air forms bubbles and gradually comes out of solution at the surface of the viscose. These actions, of course,

occur more rapidly the thinner the viscose layer becomes.

A number of methods have been proposed and used to remove the air from viscose compositions. In the most common methods, the viscose is subjected to a high vacuum during its ripening process or is kneaded or spread in a thin film while maintained in an evacuated area. I

There are a number of disadvantages in the above prior art processes, one of the most critical being the extended period of treatment required to remove all or substantially all of the entrapped air. While the occluded air is difiicult to remove completely, it is even more :diificult to remove a substantial part of the dissolved air.

In cases where it is desired to spin a high salt index viscose, the time necessary for removing the air is sometimes so long that the desired salt index is passed before the air is removed.

The primary disadvantage of the presently used continuous methods for removing gases from viscose 'is that "stagnant zones are formed, due in most cases to the construction of the apparatus. This stagnant material contaminates the spinning fluid and thereby affects the quality of the yarn. This result is readily seen in the spinning of viscose which, when containing stagnant material, becomes over-ripe and gels. As the gels build up, they frequently break out into the main stream of spinning fluid, contaminating the spinning fluid with overripe gels and resulting in filtering difficulties and poor yarn. In prior art methods of removing gases where the viscose is spread as a thin film in a container, such stagnant Zones result through the formation of skins on the walls of the apparatus itself. This is due in part to the fact that when a stream of viscose flows down a 2 container wall thattpar't of the stream adjacent the wall will have a tendency to cling to the wall, while the :outer part of the stream .passes freely over this clinging .film.

It is an object of this invention to provide an improved process and apparatus for continuously removing occluded and dissolved air or other gases from liquids.

It is a further object of this invention to provide an improved process and apparatus for the continuous :degasifying of viscose.

It is another object of this invention to provide a process and apparatus which will efiect removal of gases from viscose at a more rapid rate than heretofore possible.

It is still another object of the present invention to provide a process and apparatus for removing air from viscose without forming stagnant flow areas.

Other objects and the advantages of this invention will appear hereinafter.

The objects of this invention are accomplished in general by continuously flowing viscose in a thin layer or film of substantially uniform thickness onto a moving surface, subjecting the thin film to a sub-atmospheric pressure to de-gasify the viscose, removing the de-gasified film from the moving surface, and finally withdrawing the de-gasified viscose from the sub-atmospheric pressure zone.

The details of the invention will be better understood by reference to the following detailed description when taken in connection with the accompanying illustrations in which:

Figure 1 is a vertical sectional view of a de-gasifying apparatus in accordance withfthe present invention.

Figure 2 is a vertical sectional view of a modified de-gasifying apparatus taken along line 'HII of Figure 3.

Figure 3 is a side elevation of the apparatus shown in Figure 2.

Referring to Figure 1 of the drawing, the numeral '1 designates a device or hopper for feeding the viscose or other liquid to the surface of a continuously rotating film-carrying drum or roll 2. The hopper 1 is preferably adjustably mounted or suspended over the roll by any suitable means (not shown) for movement toward "and away from the roll 2 as the occasion may require.

The hopper l, as shown, comprises a substantially V-shaped trough having a blade 3 set into a recess formed in the lower portion of one of its walls. Cooperating with the blade 3 is a similar second blade 4 set into a recess formed in the outer surface of the opposite trough wall. The blades 3 and 4 are each provided with a plurality of adjusting screws 5 and 6 by which they may be moved towards or away from each 'other to regulate the stream of viscose flowing from the hopper so that the surface of the film-carrying roll-2 is only thinly coated with the viscose material. It will be noted that coated blades 3 and 4 project downwardly into the space below the hopper 1, and that the edges of both blades are spaced from the surface of roll 2. The numeral 7 designates a fluid-tight housing enclosing the roll 2 and the lower end of the hopper 1, with an outlet 8 being provided to facilitate evacuation of the chamber 9 by a vacuum pump 10. The hopper is secured to the housing 7 directly above the roll 2 and is connected with a viscose delivery conduit or feed line 11. The film-carrying roll 2 is rotated continuously by a motor and speed reduction unit 12 acting through an endless belt 13.

The level 14 in the viscose hopper 1 may be controlled by a float 15 carried by a movable rod 16, the latter of which acts through a rheostat 17, an electric motor 18. and a pump 19 to control the flow of viscose through the conduit 11. The rheostat 17 regulates the amount of electric current passing to the motor 18 from the power line A and thereby controls the motor speed. By main- 3 taining the proper level of viscose in the hopper 1, the viscose serves to seal the chamber 9 from the surrounding atmosphere. 7

As the hopper 1 is supplied with viscose, preferably in a continuous manner, and with the hopper blades 3 and 4 properly adjusted, a continuous viscose stream is delivered onto the surface of the rotating roll 2 in the form of a thin film 20. The roll 2 travels at such a speed as to prevent relative movement between the liquid film and the roll surface. In the chamber 9, which is continuously kept under the desired vacuum, any occluded or dissolved air is sucked out from the thin layer of viscose as it is carried by the roll 2 through an arcuate path usually less than a complete revolution. The film is then removed from the roll by means of a scraper or doctor blade 21, with care being taken to see that the doctor blade removes all the viscose from the roll surface.

As the thin viscose film is scraped or wiped from the roll 2, it drops as a substantially continuous film into a catch basin 22 from which it is discharged through a conduit 23. The rate of discharge may be controlled by a pump 24 operated by an electric motor 25 in the discharge line. This pump 24 may be regulated by a float 26 which is buoyantly supported on top of the collected viscose 27 and regulates a rheostat 28 through a rod 29 to thereby control the speed of the electric motor 25. The motor 25 is connected to the power line B through the rheostat 28. The level of liquid maintained in the catch basin is sufficient to provide an air lock so that the interior of the chamber is kept at sub-atmospheric pressure.

The doctor blade 21 is preferably pivotably supported at its mid-point 30 and resiliently wedged against the periphery of the roll 2 by the spring 31.

A second modification of apparatus 40 for carrying out the process is shown in Figures 2 and 3 and includes two

hollow calender rolls

41 and 42 mounted on shafts 43 and 44 for rotation in opposite directions, whereby liquid material, delivered as shown in Figure 2, is carried by and between the rolls as substantially continuous films. These rolls 41 and 42 are spaced apart slightly within the nip and may also be maintained at any desired temperature by circulating fluid into and through the interior of the rolls by means of hollow shafts 45 and 46, which extend through the bearings 43, 43a, 44 and 44a and project into the roll interiors.

The rolls are completely surrounded by a fluid-tight housing or chamber 48 which fits snugly against the roll ends so that all the liquid material placed on the rolls will pass therebetween. The liquid material to be treated is carried to the top of the chamber by a conduit 49, so located that the material drops from the conduit to the space 50 between the rolls. The material is squeezed as it passes between the rolls, which are continuously rotating in opposite directions, and thus a film is formed on the surface of both rolls to expose the maximum amount of area of the material to the sub-atmospheric pressure in the chamber 48 which is maintained in an evacuated condition by means of a pump 53 and outlet 65.

The films are completely removed from the rolls by doctor blades 54 and 55 which extend the whole length of the rolls and are forced thereagainst by springs 56 and 57. The material is scraped from the rolls and collected in a catch basin 58, shown as forming a part of the housing 48, and is passed out of the chamber through a conduit 59 extending through the base of the chamber itself. The catch basin may be a separate part not integral with the housing 48, if desired. In this last-described apparatus the space 50 between the

rolls

41 and 42 forms a hopper. If desired, however, the hopper may be in the form as shown in Figure 1. The

rolls

41 and 42 are continuously rotated by motors 60 and 61 which act through sprocket drive systems of which

sprocket chains

62 and 63 are drive-transmitting members. Con trol of the input and the output of viscose to the apparatus 40 is effected through a float control and pumping system as shown in Figure 1. The performance of the apparatus may be varied also by controlling the vacuum at different levels, varying the clearance in nip of the rolls, and/ or varying the speed of rotation of the roll surfaces.

The length of time the film remains on the rolls will depend upon the length of time that is desired to subject the film to the sub-atmospheric pressure. Any length of time less than a full revolution of the rolls may be used. This last-described modification has the advantage over the preceding modification in that the viscose is also homogenized during the de-gasification.

While the apparatus of the present invention has been described in terms of its use in de-gasifying viscose, it is understood that it is not limited thereto and that it may be used to treat other viscous liquids, such as solutions of cellulose derivatives; vinyl compounds including polyvinyl acetates, polyvinyl alcohols, polyvinyl acetals, etc.; resins either synthetic or natural including rosin, dammar, alkyd, etc.; and synthetic linear polymeric materials including polyamides, polyesters and the like.

By the use of the process and apparatus of the present invention, numerous advantages in the de-gasifying of liquids are obtained. Due to the continuous and positive propulsion of a liquid through the apparatus a liquid may be de-gasified very effectively at a high rate. Moreover the equipment is simple in construction and operation and less space is usually needed for the present apparatus than for any of the apparatus that have been used in the past.

Since it is obvious that many changes and modifications can be made in the above-described process and apparatus without departing from the nature and spirit of the invention, it is to be understood that the invention is not to be limited to the above-described details except as set forth in the appended claims.

I claim:

1. Apparatus for de-gasifying liquids including a closed chamber having liquid inlet and outlet means adjacent its upper and lower portions, respectively, means for maintaining the interior of said chamber at sub-atmospheric pressure, movable means disposed within said chamber and having a liquid receiving surface located adjacent to said liquid inlet, means for moving said last-mentioned means relative to said inlet whereby the liquid is received on said surface as a thin film and is carried thereby to a discharge area removed from said liquid inlet, and means engaging with said surface for removing the liquid therefrom as a substantially continuous liquid film which is collected adjacent said liquid outlet.

2. Apparatus as defined in claim 1, wherein the movable means is a pair of spaced rolls disposed in side-byside relationship and rotatable toward each other for advancing a relatively thin sheet of liquid through the space therebetween.

3. A method for de-gasifying a liquid including the steps of maintaining a thin substantially continuous liquid film on a moving surface which supports and advances the liquid film in a predetermined direction, subjecting the substantially continuous liquid film during its advancement to sub-atmospheric pressure to remove gases therefrom, and thereafter removing the de-gasified liquid from the moving surface as a substantially continuous film.

4. A method for de-gasifying a liquid comprising delivering the liquid into an enclosed region maintained at sub-atmospheric pressure, feeding a thin relatively wide stream of liquid onto a continuously advancing surface supported within said region to form a substantially continuous film thereon, maintaining said sub-atmospheric pressure by suction to remove gases from the film concomitantly with its advancement, and removing the degasified liquid from the surface as a substantially continuous film.

5. A method of de-gasifying a liquid comprising delivering the liquid into an enclosed region maintained at sub-atmospheric pressure, feeding the liquid into the nip formed between a pair of parallel rolls spaced slightly from each other, rotating the rolls in opposite directions to squeeze the liquid and obtain a thin substantially continuous film of the same on the periphery of each roll, and stripping the liquid films from the roll peripheries after the films have been carried through an angular travel less than a full revolution from the nip.

6. Apparatus for de-gasifying liquids including a closed chamber having liquid inlet and outlet means adjacent its upper and lower portions, respectively, means for maintaining the interior of said chamber at sub-atmospheric pressure, at least one roll disposed within said chamber with its periphery in position to receive liquid delivered through said inlet, means for rotating said roll whereby the liquid is received on the periphery of the roll as a thin film and is carried thereby to a discharge area removed from said liquid inlet, and means engaging with the periphery of the roll for removing the liquid therefrom as a substantially continuous film which is collected adjacent said liquid outlet.

7. Apparatus as defined in claim 6 further including means for controlling the temperature of the roll periphery.

8. Apparatus for de-gasifying liquids including a closed chamber, a hopper mounted adjacent the upper portion of the chamber and provided with a discharge opening in its lower portion, a liquid inlet opening into said hopper, a liquid outlet adjacent the lower portion of the chamber, means for maintaining the interior of said cham ber at sub-atmospheric pressure, cooperating blades disposed adjacent to said hopper discharge opening, said blades being adjustable to control the discharge of liquid from said opening as a thin liquid stream, movable means disposed within said chamber and having a liquid receiving surface located adjacent to said hopper discharge opening, means for moving said last-mentioned means relative to said inlet whereby the liquid stream is received on said surface as a thin film and is carried thereby to a discharge area removed from said liquid inlet, and means for removing the liquid from said surface as a substantially continuous film which is collected adjacent said liquid outlet. 1

9. Apparatus as defined in claim 8 wherein said lastmentioned means includes a blade engaging with said surface and serving to wipe the liquid therefrom as substantially continuous film as said surface is moved relative thereto.

10. Apparatus as defined in claim 8 wherein said movable means includes a single rotatable roll disposed below said hopper discharge opening, with the roll axis extending substantially parallel and in alignment therewith.

11. Apparatus as defined in claim 10 wherein said lastmentioned means includes a blade engaging with the periphery of the roll and serving to wipe the liquid therefrom as a substantially continuous film as the roll is rotated.

12. Apparatus as defined in claim 8 in which said hopper includes a pair of inclined walls diverging at their upper ends and spaced apart at their lower ends to provide said discharge opening, and a top wall extending between the upper ends of said inclined walls, and wherein said blades are adjustably mounted on said inclined walls and project into the area adjacent said discharge opening.

13. Apparatus for de-gasifying liquids including a closed chamber having liquid inlet and outlet openings adjacent its upper and lower portions, means for maintaining the interior of said chamber at sub-atmospheric pressure, a pair of spaced parallel rolls disposed within said chamber and below said inlet, in position for receiving the liquid delivered therethrough, means for rotating said rolls in opposite directions to'carry a thin film of liquid on their peripheries to positions remote from said inlet, and a blade engaging with the periphery of each said rolls for removing the liquid therefrom as a substantially continuous film as said rolls are rotated.

14. A method as defined in claim 4 in which said surface is advanced at a rate sufiicient to prevent flow of said liquid film relative thereto.

15. A method as defined in claim 5 in which said rolls are rotated at a rate sufiicient to prevent flow of said liquid film relative to the peripheries of the rolls.

References Cited in the file of this patent UNITED STATES PATENTS 405,674 Morse June 18, 1889 1,156,096 Price Oct. 12, 1915 2,039,708 Crouch et al. May 5, 1936 2,064,650 Emanueli Dec. 15, 1936 2,271,401 Sainty Jan. 27, 1942 2,684,728 Malm July 27, 1954