US2827661A - Apparatus for the production of artificial cellulose sponge - Google Patents

Description

March 25, 1958 R. S. VON KOHORN APEARATUS FOR THE PRODUCTION OF ARTIFICIAL CELLULOSE SPONGE Filed April 26, 1955 /A/ VENTOR ea/Pb 5 Von Ko iar United States Patent APPARATUS FGR THE PRODUCTION OF ARTIFICIAL CELLULOSE SPONGE Ralph S. Von Kohorn, New York, N. Y.

Application April 26, 1955, Serial No. 503,964

3 Claims. (Cl. 18-12) The present invention relates to an improved apparatus for the production of artificial sponge and it relates more particularly to an improved apparatus for the continuous manufacture of artificial cellulose sponge by the viscose method.

Heretofore, artificial sponge of regenerated cellulose produced by the viscose method has been manufactured by the batch system although there have been proposed methods for producing such sponge masses in a continuous manner. However, due to many physical and chemical drawbacks which are characteristic of these proposed continuous systems they have not been commercially adopted. Although artificial cellulose sponge has been produced in other simple shapes they are generally formed as rectangular blocks which are then cut to the desired shape. Where complex shapes are desired either correspondingly complex molds are required and the cost of such molds are generally prohibitive or the shapes must be cut from the simple blocks with the necessary attendant waste.

The methods now generally employed in the production of regenerated cellulose sponges include the steps of thoroughly admixing a relatively green viscose, a pore forming substance such as pellets or crystals of sodium sulphate decahydrate of a predetermined range of sizes and reinforcing fibers of suitable length such as cotton, rayon, flax, jute, hemp, nylon, or other fibers. The mixture is then deposited into molds of the desired shape, usually of rectangular configuration and is coagulated and the cellulose substantially regenerated. This has been accomplished by means of hot acid or salt solutions such as of sodium sulphate, by steam at usually greater atmospheric pressure or by heat generated internally of the mass by the passage of an electrical current therethrough. During the coagulation of the sponge mass the Glauber salt pore former is liquified and either partially or substantially drains from the forms during coagulation or is drained from the sponge mass following coagulation and separation from the forms. This coagulated sponge mass is then dried and cut to the desired shapes and sizes. None of the above methods readily lend themselves to the economic or continuous production of sponges, particularly of sponges having complex shapes. As set forth previously such production requires either expensive molds or involves large amounts of waste of time and material.

it is therefore a principal object of the present invention to provide an improved apparatus for the production of artificial sponge.

Still another object of the present invention is to provide an improved apparatus for the continuous production of artificial sponge which apparatus is simple, economical and highly flexible and results in a superior uniform product.

A further object of the present invention is to provide an improved apparatus for the continuous production of artificial sponge of intricate transverse cross section which apparatus is readily and simply adjustable to produce sponges of difierent desired cross sections.

The above and other objects of the present invention will become apparent from a reading of the following description taken in conjunction with the accompanying drawing wherein:

Figure 1 is a front sectional view of the present improved apparatus;

Figure 2 is a sectional view taken along line 2-2 of Figure 1; and

Figures 3-6 are horizontal plan views of improved electrodes which may be employed to advantage with the present apparatus.

The present invention broadly contemplates the production of artificial cellulose sponge in a continuous manner comprising extruding a sponge forming mass including viscose and a pore forming substance to form a substantially continuous body, advancing said body along a predetermined path and applying an electrical difference in potential to said advancing body along said predetermined path whereby to pass an electric current through said body and coagulate said viscose. In accordance with a preferred embodiment, the sponge forming mass is extended through a heated die to form a skin thereby effecting a coherent body of said mass. Thereafter, an alternating current is passed through the advancing body by transporting the body along longitudinally spaced electrodes which are alternately connected to the oppossite terminals of a source of alternating voltage to coagulate the viscose. The coagulated body is then passed through a hot solution of sodium sulphate through squeeze rolls and then through counter-current flowing hot water bath with successive squeezings. The resulting sponge may then be further treated and dried and cut. A preferred form of apparatus for producing the improved process includes an extrusion device having a heated downwardly facing extrusion die at its discharge end. Below the extrusion die and in alignment therewith are a plurality of electrodes having apertures of greater cross section than the extrusion opening in the die and provided with a multiplicity of flexible metal fingers extending inwardly from the edge of the electrode aperture. The extended mass is contacted by the sets of fingers of successive electrodes which are in turn alternately connected to opposite terminals of an alternating voltage source to produce a current through the mass and coagulated as aforesaid. The electrodes may be so shaped and disposed as to contact the continuous body at alternately opposite longitudinally spaced zones.

Reference is now made to the drawings which illustrates a preferred embodiment of the present invention which may be employed in practicing the present improved method and in which numeral 10 generally designates an extrusion device of the worm advancing type. More particularly the extrusion device 10 includes a funnel-shaped casing 11 having a vertical conical passageway 12 of circular cross section, the passageway 12 having axially supported therein a rotatable helical worm 13, the peripheral edges of which are of progressively smaller diameter, so as to substantially conform to the shape of the abutting wall of the passageway 12. The worm 13 which is suitably supported by means of hearings or bushings not shown and is connected by way of a shaft 14 through a right-angle gear reduction box 16 to an electric motor 17. The upper opening of the passageway 12 is connected to the discharge opening of the suitable hopper 18, the shaft 14 passing through the hopper 18 to the gear reduction box 16. Furthermore, the casing 11 is provided with a surrounding jacket 19 having inlet and outlet conduits 20 and 21 respectively, to permit the circulation of a cooling medium through the jacket such as, .for'example, cold water, brine, etc. to inhibit any reaction from occurring in this portion of the casing as will be hereinafter set forth. Secured to the lower face of the casing 11 is an extrusion die 22 formed preferably of a heat conducting material such as metal and having an extrusion aperture-23,assumingany desired shape, in accordance with the desired end product and having its maximum cross sectional dimensions less than the corresponding dimensions of the lower opening of the vertical passageway 12. The inner face of' the extruding 'die 22 is highly polished or preferably coated with a non-wetting material'having arelative'ly high softening point such as, for example, polytetrafluorethylene or .polymonochlorotrifluorethylene. Where a .coa-tiuglas aforesaid'is employed on the inner face of the extrusion die 22 the upper part .of the ;die is'uncoatedso that .theba-re metal is exposedand this is in turn electrically connected to ground. The extrusion die 22 is suit-ably heatedsuch as by an electrical :heating element 24 which is connected to a suitable source of current or ;by means of any other heating from ground. The electrodes 27, on the other hand, are 7 likewise mounted on a'suita'ble support 29 and are electrically connected to each other and to ground as is the extrusion die 22. The electrodes 26 are connected to one terminal of a suitable source of alternating current, the other terminal of which is grounded.

Although any suitable type of electrodes may be employed for the electrodes 26 and 27, those illustrated in Figures 3 to 6 of the drawing are highly preferred and highly versatile and flexible. For example, the electrode illustrated in Figure3 of the drawing may 'be used for both the electrodes 26 and 27 and consists preferably of a plate '30 formed of metal or other suitable conducting material, having an aperture 32 formed therein which is similar in outline to the extrusion aperture of the die 22 but of greater dimensions. Mounted on the plate 30 and projecting inwardly from the edge of the aperture 32 are a plurality of flexible Wire fingers 33 which are preferably of equal length and substantially cover the area defined by the aperture 32. Thus when the extruded material travels downwardly through the opening 32 in the electrode 30, the fingers 33 are forced downwardly and outwardly, but because of their resilience press against the extruded material and effect good electrical contact therewith. It should be noted that the fingers 33 are of such resiliency and dimensions as to produce a good electrical contact with the extruded mass, with no or a minimum distortion thereof. In Figure 4 of the drawing there is illustrated an alternative electrode .34 likewise formed of metal .or other suitable material and wherein there is formed .an aperture 36 of substantially circular cross section. This permits the use of the electrode 36 with different extrusion shaped dies 22 as long as the diameter of the opening 36 is greater than the maximum dimension of the extrusion die aperture. provided a plurality of resilient metal wire fingers 37 projecting inwardly from the edge of the aperture 36 and extending to-a point close to the center of the aperture 36. The operation of the electrode 34 is similar to that of the electrode 30. Where it is desired to effect an electric field produced in the extruded mass which is different from that effected by the'ele ctrodes illustrated in Figures 2 and 3 of the drawing, the alternate electrodes 26 may assume the configuration-of the electrode 38 illustrated in Figure :5 ofthe drawings, whereas the electrodes 27 may assume the configuration of electrode 39 illustrated in Figure 6 of thedrawing :or vice .versa. The electrodes 38v are :so' shaped and disposed as to electrically contact There is here similarly ...2,s2 7,ee1 p a. i

one side of the extruded mass whereas the electrodes '39 are so shaped and disposed as to contact the other side of extruded mass. The electrode 38 has an opening 40 formed therein and is provided with the resilient metal wire fingers 41 which covers an area extending only to the right side of the middle point of the electrode 38.

The electrode 39 is provided with an opening 42 which.

is provided with resilient metal wire fingers 43 which covers an area on the left side of the center of the electrode 39. It is obvious that either of these electrodes can be used since, if they are symmetrically shaped, they may be reversed where the fingersare co-planar with the plate forming these electrodes. i

Directly below the electrodes 26 and 27 is a longitudinally extending trough 50 which is electrically grounded and which is provided with heating coils to permit main taining a solution 52 contained in the trough at an elevated temperature. A pair of longitudinally spaced roller guides '53 which can be raised and lowered for threading of sponge are positioned in the lower part of the trough 50 and directly above the trough at the discharge end thereof is a pair of squeeze rolls 54. An outlet 56 at the feed end of the trough 50 permits the removal of excess solution from the trough .50. Following the trough 50 is a second longitudinal trough57 having a plurality of longitudinally spaced pairs of squeeze rolls disposed adjacent to the base of the trough 57 which can be raised and lowered for threading of sponge. A guide roll ""59 is disposed above the feed end of the trough 57 and a pair 7 of squeeze rolls 60 is disposed above the discharge end of the trough .57. Furthermore, an inlet conduct 61 viscose is prepared by methods well-known in the in-' dustry. For example-sheets of pulp are steeped :for approximately 9.0 minutes at about 20 C..-in a caustic solution of approximately 18% concentration for aperiod of about minutes. Excess liquor is expressed from the resulting alkali cellulose until the weight of the alkali cellulose is approximately two and a half to three times the weight of the dry cellulose present. The alkali cellulose is then shredded undercooled conditions and the shredded alkali'cellulose is immediately admixed with CS in a ratio of approximately 5 parts alkali cellulose to one. part CS and tumbled until the result is a uniform cellulose xanthate. This cellulose x-anthate is then dissolved in a weak caustic solution to produce a viscose containing approximately 8.5% cellulose and 5% sodium hydrate.

The resulting viscose is' permitted to ripen for about 3 to 4 hours and is then introduced intoa kneaderto which is added a pore forming salt, preferably sodium sulfate decahydrate (Glauber salt) and if desired, a suitable dyestulf. The Glauber salt is preferably of a crystal size ranging properly proportioned approximately between 1 and 8 mm. After the Glauber salts have been thoroughly mixed with the viscose there is added a cut fiber such as jute, hemp, cotton, nylon or the like, having a staple length of approximately 4 to 15 mm., and a mixing operation continued until the fibers are thoroughly distributed throughout the mass. During the mixing operation it isimportant that the temperature of the mass is not unduly raised whereby to cause dissolution of the pels the mass through the passageway 12 extruding it through the opening 23 in the extrusion device 22. A liquid cooling medium is passed through the jacket 19 by way of the conduit 20 and 21 whereby to prevent and inhibit the coagulation of the sponge mass as it passes through the conical portion of the passageway 12. However, as the sponge forming mass passes through the aperture 23 in the extrusion die 22, the surface of the mass is coagulated, as a result of the heat applied thereto by the walls of the extrusion die 22 to form a skin. This skin is sufiicient to maintain the extruded mass in the substantially coherent form. As the mass passes in its downward travel through the electrodes 26 and 27, electrical cont-act is effected between the electrodes 26 and 27 and the extruded mass by means of the fingers protruding from the electrodes. The electrodes being alternately connected to the different terminals of the source alternating current, such current passes through the interior of the sponge forming mass raising the temperature and rapidly coagulating said mass to form the sponge mass, dissolving the crystals thus forming pores. It should be noted that the voltage, spacing of the electrodes and extrusion speeds are so adjusted that complete coagulation is effected by the time the extruded mass leaves the trough 50. It has been found that a 60 cycle voltage of the order of between 110 and 220 volts is highly satisfactory. It should be noted that with some sponge shapes it may be desirable to employ the electrodes 38 or 39 illustrated in Figures 5 and 6 of the drawings. In the latter event the current would flow along substantially diagonal lines along and across the extended sponge mass between successive electrodes so that the current flow lines assume a zigzag shape. The substantially coagula-ted sponge mass then passes through the solution 52 contained in the trough 50, which solution is preferably sodium sulfate, maintained in a temperature of about 90 to 100 C. The sponge mass upon leaving the trough 50 passes between squeeze rolls 54 so as to express most of the pore forming salt, that is, Glauber salt from the mass which then drops into the trough 50. The excess liquor from the trough 50 is continuously drawn and water is added to maintain the desired concentration. The Gl-auber salt dissolved in the liquor which is drawn from the trough 52 is recovered and reused.

Following the squeeze rolls 54 the sponge mass passes over a guide roll 59 into a trough 57 through a purifying solution, for example water, is flowed countercurrent to the travel of the sponge mass through the trough 57. Moreover, as the sponge mass travels through the trough 57 it passes through successive pairs of squeeze rolls 58 which can be raised and lowered where it is sequentially compressed and released to accelerate the treatment of the sponge mass. Upon leaving the trough 57 the sponge mass passes through the squeeze roll 60 and then may be further treated, dried and cut as earlier set forth.

While there has been described and illustrated preferred embodiments of the present invention, it is apparent that numerous alterations and omissions may be made without departing from the spirit thereof. For example, the spacing between the electrodes 26 and 27 may vary as well as the potentials applied to these electrodes so that the rate of feed of energy to the sponge forming mass may diminish as the temperature thereof increases.

What is claimed is:

1. An improved apparatus for the production of artifical cellulose sponge in a continuous manner, comprising an extrusion device including a die having a downwardly directed extrusion aperture of predetermined outline, an electrode disposed below and spaced from said die and having an opening formed therein of greater corresponding dimensions than said extrusion aperture and in substantially vertical alignment therewith, a plurality of flexible finger elements formed of a conducting material connected to said electrode and directed inwardly relative to said opening, and intersecting the vertical projection of said extrusion aperture, and means for applying a diiference in electrical potential between said electrode and said die.

2. An improved apparatus in accordance with claim 1, including means for heating said die.

3. An improved apparatus in accordance with claim 1, including a plurality of said finger element carrying electrodes in spaced vertical alignment, and means for applying a difierence in electrical potential between successive electrodes.

References Cited in the file of this patent UNITED STATES PATENTS 2,011,160 Plepp Aug. 13, 1935 2,133,810 Craigue Oct. 18, 1938 2,450,457 Te Grotenhuis Oct. 5, 1948 2,665,450 Lindquist Jan. 12, 1954 2,712,154 Lindquist July 5, 1955

Claims (1)

1. AN IMPROVED APPRATUS FOR THE PRODUCTION OF ARTIFICAL CELLULOSE SPONGE IN A CONTINUOOUS MANNER, COMPRISING AN EXTRUSION DEVICE INCLUDING A DIE HAVING A DOWNWARDLY DIRECTED EXTRUSION APERTURE OF PREDETERMINED OUTLINE, AN ELECTRODE DISPOSED BELOW AND SPACED FROM SAID DIE AND HAVING AN OPENING FORMED THEREIN OF GREATER CORRESPONDING DIMENSIONS THAN SAID EXTRUSION APERATURE AND IN SUBSTANTIALLY VERTICAL ALIGNMENT THEREWITH, A PLURALITY OF FLEXIBLE FINGER ELEMENTS FORMED OF A CONDUCTING MATERIAL CONNECTED TO SAID ELECTRODE AND DIRECTED INWARDLY RELATIVE TO SAID OPENING, AND INTERSECTING THE VERTICAL PROJECTION OF SAID EXTRUSION APERATURE, AND MEANS FOR APPLYING A DIFFERENCE IN ELECTRICAL POTENTIAL BETWEEN SAID ELECTRODE AND SAID DIE.

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