US3806572A

US3806572A - Production of asbestos products

Info

Publication number: US3806572A
Application number: US00183327A
Authority: US
Inventors: J Trainor; J Orzechowski
Original assignee: Raybestos Manhattan Inc
Current assignee: RM INDUSTRIAL PRODUCTS COMPANY Inc
Priority date: 1969-09-10
Filing date: 1971-09-24
Publication date: 1974-04-23
Anticipated expiration: 1991-04-23

Abstract

Asbestos yarn having superior strength and uniformity is produced in a continuous process by disposing a plurality of stationary nozzles fed with asbestos dispersion within a coagulating bath to form a plurality of individual strands. The strands are continuously pulled through the coagulating bath away from the nozzles and are substantially elongated during the initial stages of progressive coagulation. The individual strands are then combined, removed from the bath and passed through a zone of low tension wherein the final stages of coagulation can take place; whereafter the combined strands can be withdrawn as a single end under tension, for example by pot spinning.

Description

[ Apr. 23, 1974 United States Patent [191 Trainor et al. I

[ PRODUCTION OF ASBESTOS PRODUCTS [75] Inventors: James T. Trainor, Shelton; John F.

2/1961 Wilke et al.

11/1969 Wilke et a].

1/1972 Donaldson et al........

7/1972 Orzechowski et al.

m I e k a v O N 9 6 9 l. 7 8 l. 3 5 3 Primary Examiner-Jay H. Woo

Attorney, Agent, or Firm-Gary, Juettner, Pigott & Cullinan [22] Filed: 'Sept. 24, 1971 [211 App]. No.: 183,327

Related US. Application Data Continuation-in-part of Ser. No. 856,716, Sept. 10, 1969, abandoned.

[57] ABSTRACT Asbestos yarn having superior strength and uniformity is produced in a continuous process by disposing a plurality of stationary nozzles fed with asbestos dispersion within a coagulating bath to form a plurality of individual strands. The strands are continuously pulled through the coagulating bath away from the nozzles and are substantially elongated during the initial stages 8M M 6 8 H/S 7 0 5 1 8 2 O loo D ,5 .00 1F 810 5 HMUW; 76121 523,8 4. 3 0 4 0 1 1 .4 4 6 M m2 m n .c r n a n .e H m L C l0 5 m n U IF U Hwm w 55 of progressive coagulation. The individual strands are References Cited then combined, removed from the bath and passed UNITED STATES PATENTS through a zone of low tension wherein the final stages of coagulation can take place; whereafter the combined strands can be withdrawn as' a-single end under tension, for example by pot spinning.

mgrm1nme 23 :974 3,806; 572

sum 2 OF 2 1 PRODUCTION OF ASBESTOS PRODUCTS CROSS REFERENCE This application is a continuation-in-part of our copending application Ser. No. 856,716, filed Sept. 10, 1969, and now abandoned.

BACKGROUND OF THE INVENTION This invention relates to improvements in a process for producing asbestos products from an asbestos dispersion and more particularly to a process wherein the dispersion is fed through a stationary orifice disposed within a coagulating bath to produce a continuous as-' bestos strand.

Various recent proposals have been made relating to the production of asbestos products from an asbestos dispersion. The development of an economical commercial liquid or wet process is important in order to eliminate many potential health hazards inherrent in exposure of personnel to asbestos dust generated in the conventional dry processing of asbestos.

The patents to Wilke et al. 2,972,221 and Novak et al. 3,453,818 disclose the production of yarn from an asbestos dispersion by extruding the dispersion through a stationary nozzle into a coagulating bath. In Wilke et al., the dispersion is immediately coagulated and removed for further processing. In Novak et al., the extrudate is somewhat stretched during coagulation by flowing the coagulating liquid away from the extrusion nozzle. The use of liquid flow to elongate the extruded strand is unsatisfactory, however, because a nonuniform flow of coagulating liquid will produce an uneven strand, and the degree of elongation cannot be sufficiently controlled. Another drawback of these prior art methods is that the resulting wet strand or yarn is normally too weak to permit continuous collection in a package suitable for subsequent textile processing. Textile collection methods require the application of tension to the wet yarn, which the yarns of Wilke and Novak could not tolerate.

It is therefore desirable to provide a high speed method of producing asbestos yarn having sufficient wet strength to enable collection under tension, such as by pot spinning. Since the strength of the yarn is greatly dependent upon proper alignment of the asbestos fibers, it is also desirable that the fibers in the wet yarn be aligned in a direction parallel to the axis of the yarn. This result is not easily achieved by the aforesaid prior art methods. Fine c'ut yarns produced by these methods are too weak and are non-uniform. Heavier cut yarns have too large a cross section to permit complete penetration of coagulant within a reasonable time (cut yards 100 per pound). As a result, the heavier yarn must be produced at lower speeds and proper fiber alignment is not achieved. In addition, since asbestos dispersions are non-uniform and contain relatively large unopened fiber bundles, the strands produced by these methods contain undesirable irregularities or weak spots.

A later Wilke patent 3,475,894 attempted to overcome the above problems by abandoning the use of stationary nozzles in favor of driven rollers. Aprimary drawback of this method is that defects, such as splints, clots, rock, etc., are forced into the extrudate and cause irregularities and weak spots. In addition, this method does not achieve maximum fiber alignment in the wet coagulated product.

BRIEF DESCRIPTION OF THE INVENTION In accordance with the present invention, the above shortcomings are overcome by providing a high speed method of and apparatus for producing a wet yarn. having a high degree of fiber alignment and strength. The superior product is achieved by (i) flowing asbestos dispersion through a plurality of confined nozzles disposed within a coagulating bath, in order to produce a plurality of spaced strands; (ii) exerting a positive and constant tractive force on the individual strands during progressive coagulation thereof in order to uniformly elongate the strands in excess of 300 percent and preferably at least 400 percent, which results in maximum fiber alignment and maximum coagulant penetration in each strand; (iii) passing the wet strands through a zone of little or no tension until coagulation is complete; (iv) combining the individual strands into a single yarn in the absence of tension; and (v) withdrawing the multiply yarn under tension, preferably by pot spinning.

Multi-ply yarns produced by the above method exhibit substantially greater tensile strength in comparison with a single strand of the same cut and may be produced and collected at much higher speeds and over a wider range of cuts. Fiber orientation and coagulant penetration are optimized by the controlled drawing and stretching of a group of relatively fine strands during the initial stages of coagulation; the strands are then combined in the final stages of coagulation in the form of a multi-ply yarn having a tensile strength greatly in excess of a single strand of the same cut, thereby enabling further immediate processing under tension,

such as pot spinning.

THE DRAWINGS FIG. 1 is a perspective view of the apparatus employed in connection with the presently described process; and

FIG. 2 is an elevational view, partly in section, of the apparatus shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT The process of the present invention utilizes asbestos dispersions such as those described in U.S. Pat. Nos. 2,626,213 and 2,772,157. The raw asbestos, typically chrysotile fiber, is dispersed into the form of aqueous colloid with the addition of a suitable dispersant. One type of a satisfactory dispersant is a fatty acid soap added in an amount of about 15 percent to 35 percent by weight, although any of the other known dispersants may be employed if capable of being chemically solidified or precipitated into water insoluble compounds.

The asbestos dispersion is prepared in a mixer of the type that produces minimum shearing action and therefore minimum loss of fiber length. A conventional hydrapulper employed in paper making or other vessel equipped with vertical cylindrical mixing bars is suitable for this purpose. As described in U.S. Pat. No. 3,035,698, the dispersion is also preferably filtered or otherwise refined to remove as much foreign matter, splints and large fiber bundles as possible and adjusted to a fiber content of from about 0.5 percent to about 10 percent, although the preferred fiber content is in the order of about 2 percent.

Although not required or necessary to the process, suitable binders or other additives may be incorporated into the dispersion prior to extrusion, as determined by special properties that may be required in the final product. In addition, other organic or inorganic fibers may be added,-as well as water soluble dyes.

As shown in the Figures, the dispersion is fed under low hydrostatic head to a plurality of confined orifice nozzles disposed in a coagulating bath, and the formed dispersion issuing into the bath is rapidly pulled away or drawn from the nozzles in the form of a plurality of individual strands as coagulation progresses. A container of dispersion is 'held by a stand 12 above the area of extrusion and feeds via one or more tubes 14 into secondary containers 16 mounted for vertical adjustment on the stand. The secondary containers 16 may thus be vertically adjusted to regulate the amount of head at the point of extrusion. A plurality. of tubes 18 extend generally downward from the secondary containers, and each terminates in an extrusion nozzle 20. lt should be noted that separate feeding of each of the nozzles is important in order to prevent the longer asbestos fibers from clogging between adjacent nozzles, and also to aid in orientation of the fibers longitudinally of the respective strands.

The nozzles 20 are immersed in a coagulating bath contained by an elongate vessel 22, and the drawing of the strands 24 is accomplished in substantially a horizontal plane, with a plurality of individual strands 24 being drawn through and away from the nozzles and within the bath during progressive coagulation. Horizontal drawing is important in that elongation or stretch of the strands maybe accurately and uniformly controlled, and the strands 24 are supported equally along their length Within the bath during progressive coagulation.

The nozzles 20 are located along a common transverse line and are tapered toward their ends. The taper-ed conf guration of the nozzles has been found to significantly improve fiber orientation and hence strength of the strand. The outlet orifices of the nozzles are circular and, are preferably equisizcd, with a diameter of from about 0.06 to 0.120 inches and preferably in the order of about 0.09 inches. Smaller orifice sizes may not be employed because of clogging problems, while larger orifice sizes do not impart the desired degree of fiber orientation to the extrudate and require excessive elongation to achieve a fine cut strand. Thus,

' the size of the orifice may not be varied greatly and is held relatively constant, irrespective of the desired size or cut of the final product. The number of nozzles is critical to the extent that at least three and preferably four or more should be employed to attain the desired strength characteristics in the resulting yarn. To obtain various cuts or sizes of yarn ends, from three to fifteen to twenty or more nozzles may be employed.

As described, the dispersion emanates from the tapered nozzles directly into the coagulating bath in the form of a plurality of spaced strands 24. The bath may comprise an aqueous solution containing any of the known coagulants, such as bior trivalent salts of a metal in weight concentrations of from about 1 to 25 percent, depending on the type and amount of dispersant employed. Means may alsobe provided to slightly agitate the bath and to circulate fresh coagulant as the available supply is depleted. In this manner, the polyvalent metal ions react with and precipitate the dispersant, thereby causing the dispersion to be broken and the fibers to become frictionally interlocked and bonded together in aligned fashion within a matrix of water insoluble soap.

Means are provided for pulling the strands away from the nozzles and for substantially stretching the individual strands to a constant and controlled degree during the initial stages of progressive coagulation. A pair of spaced cylindrical Godet rolls 26 and 28 are mounted for rotation beyond the end of the coagulating bath remote from the points of strand withdrawal. The

rolls

26 and 28 may be ridged on their outer surfaces to prevent slippage with the first roll 26 being located slightly above the level of the bath to allow some clearance be tween the strands 24 and the end of the vessel 22. A rod 30 or other suitable bearing surface may be located at the exit end of the bath transverse to the strands 24 in order to prevent undue friction thereon before coagulation is completed. The second roll 28 is mounted below and in a rearwardly spaced relationship from the first roll 26. Alternatively, the second roll 28 may be replaced by a stationary rod 32. i

The Godet rolls 26 and 28 are both driven by a suitable motor 29 at the same surface speed and in the same'direction as the direction of strand withdrawal.

The individual strands 24 are united or combined into a single yarn 24 at the exit end of the bath, and the multi-ply yarn is wrapped over and partially around the first Godet roll 26 and then over the second roll 28 and continuously around both rolls for several wraps. The free end of the yarn 24' is then fed downward under tension tangentially from the first roll 26 directly into the funnel 34 of a spinning pct 36, as will be hereinafter more fully described.

An important feature of the present invention is the degree of drawing and stretching that is achieved on the partially coagulated individual strands 24 between the nozzles 20 and the first Godet roll 26. The hydrostatic head on the viscous dispersion is maintained at a very low level, while the Godet rolls 26 and 28 rotate together at a relatively high speed. The net result is that the dispersion is uniformly pulled under a constant tractive force from the nozzles and substantially elongated during progressive coagulation. The tapering of the nozzles and the pulling action on the strand serves toinitially align the colloidal fibrils parallel to the axis of filament formation. The coagulant in the bath then fixes the fibers in aligned position as the strands are rapidly elongated, which causes increasingly greater surface area to be exposed to the coagulant and maintains the fibers in aligned position. In order to achieve complete penetration of coagulant, each of the strands is elongated at least to about lOOcut, although the strands may, if desired, be elongated in excess of 600 cut.

Inorder to achieve rapid and complete penetration of the coagulant into the strands and to maintain the fibers in alignment for optimum strength, itzhas been found to be essential to provide a stretch or elongation factor on the strand in the bath in excess of 300 percent, and preferably in excess of 350 percent to 400 percent. Heretofore, it had not been appreciated or known that stretch factors of this magnitude could be achieved utilizing a dispersion containing only about 2 percent solids and maintain extrusion continuity suit- .able for a commercial process. By combining a positive and constant tractive force on the strands with a low head on the dispersion, we achieve substantially complete and rapid penetration of coagulant while greatly improving tensile strength.

The Godet rolls 26 and 28 (or the roll 26 and rod 32) serve several important functions. As mentioned, the rolls exert a constant and positive tractive force on the strands 24 during progressive coagulation in the space between the nozzles and roll 26, thereby resulting in maximum strand uniformity and strength. In addition, once the combined strands or multiply yarn is laid on the roll 26, the rolls, since they rotate at the same surface speed, cause little or no tension to be exerted on the newly formed and vulnerable yarn and therefore provide a quiescent or low tension zone within which the final stages of coagulation can take place. The dwell time of the multiply yarn on the rolls is sufficient to allow complete penetration of the coagulant; the number of wraps taken around the rolls is appropriately adjusted to provide the penetration time required. The Godet rolls 26 and 28, or the roll 26 and rod 32, also serve to slightly flex the yarn 24' during the final stages of coagulation and thus facilitate penetration of the coagulant into the center of the strand. The Godet rolls also serve to prevent bunching of the yarn and maintain the yarn in its stretched or elongated form.

As mentioned previously, the size or cut of the individual strands and hence the cut of the final yarn is regulated primarily by adjusting the head on the dispersion and by changing the speed of the Godet rolls, without making substantial changes in size of the nozzle orifice as previously discussed. The nozzle orifice must be maintained at a relatively large size as compared to conventional synthetic extrusion processes because of the non-uniformity peculiar to asbestos dispersions. In addition to colloidal fibrils, such dispersions normally contain larger unopened fibers and splints which would clog a nozzle having an orifice less than 0.06 inches in diameter. The unexpected ability to achieve high stretch ratios simultaneously on a plurality of filaments thus'compensates for the disability to decrease nozzle orifice size.

The yarn 24' is fed from the first Godet roll 26 directly into the funnel-shaped inlet 34 of a spinning pot 36, which comprises an upwardly open cylindrical container 38 rotatably driven by a suitable motor 40 at a speed in the order of 5,000 to 6,000 rpm. The funnelis reciprocated vertically along the rotation axis of the pot such that the yarn 24 is slightly twisted and uniformly collected along the side of the pot. Since the centrifugal force within the spinning pot causes consid-' erable tension to be exerted on the wet yarn, it is important that the yarn be completely coagulated, which is assured by the steps previously described. A fraction of the tension from the spinning pot is transferred to the last wrap of yarn around the Godet rolls, thereby slightly flattening the yarn against the surfaces of the rolls. In this manner, final penetration of the coagulant into the yarn is expedited and the yarn is conditioned for spinning. The use of the rod 32 instead of the second Godet roll 28 is beneficial in maximizing penetration because the yarn slides across the rod and is deflected or flexed at an acute angle.

A further important feature of the present invention is the merger of the coagulated strands 24 into a single yarn 24' in a zone of low tension and before significant tension is applied. Any irregularities or defects in the individual strands due to unavoidable non-uniformities in the dispersion are compensated for by the strength of the other strands in the group, thereby greatly increasing the overall strength of the yarn and decreasing the likelihood of breakage.

The cured yarn coming off the roll 26 to the spinning pot 36 is substantially non-elastic and has a moisture content in excess of percent and typically about percent. By virtue of the present invention, however, the multi-ply yarn also has a tensile strength in excess of 2 oz. and therefore can withstand the tension exerted by pot spinning at high speeds. The high strength of the wet yarn and rapid collection therefore allow for production rates easily in excess of 150 feet per minute, and at the same time the yarn is collected in a convenient package for subsequent processing pursuant to standard textile techniques.

The spinning process causes from about two to five turns per inch to be imparted to the yarn, and also causes a majority of the excess water to be removed. The tension on the yarn between the Godet roll 26 and the pot 36 may vary, and the tension decreases as the quantity of yarn in the pot increases. This varying tension, however, is not imparted to the uncoagulated strands because of the presence of the Godet rolls 26 and 28, which serve to isolate the spinning stage tension from the stage of initial progressive coagulation and also from the low tension zone where coagulation is completed.

In order to illustrate the degree of improvement that the present method provides over the method of Novak et a]. U.S. Pat. No. 3,453,818, comparative tests were conducted on the apparatus herein described. The yarn was not collected in the spinning pot, however, but was withdrawn for testing. In comparing a single ply yarn of 70 cut with a four ply yarn of 70 cut (280 out per ply), it was found that the untwisted wet tensile strength of the single ply was about 1 to 2 ounces, whereas the four ply yarn of the same cut had a tensile strength of about 4 to 6 ounces. The production rates of the single strand yarn could not exceed 40 to 60 feet per minute because of frequent breakage problems, while the production rate of the four-ply yarn of the same cut could easily exceed 150 to 200 feet per minute.

From the foregoing, it will be appreciated that the present invention allows for the rapid production of asbestos yarn in a commercially feasible manner, since the. yarn must have a tensile strength in excess of two or three ounces to enable collection in a spinning pot, and since production speeds of less than feet per minute would not be economically feasible. The present invention thus allows for production at strengths and speeds in excess of these minimum criteria without detriment to the quality of the final product.

Having thus described the invention, what is claimed 1. A method for producing asbestos yarn from an asbestos dispersion that is subject to coagulation, comprising the steps of forming the dispersion into a plurality of individual strands, subjecting the strands to progressive coagulation while uniformly drawing the strands into an elongate form, continuously passing said strands through a zone of low tension until coagulation thereof is substantially complete, merging the strands into a multi-ply yarn, and continuously withdrawing said strands under tension from said zone of low tension, said zone of low tension serving to isolate the steps of yarn withdrawal from the step of strand formation.

2. The method of claim 1 wherein the strands are elongated during progressive coagulation in excess of 300 percent 3. The method of claim 1 wherein the strands are flexed in said zone of low tension.

4. A method for producing a uniform asbestos yarn of high tensile strength from a non-homogeneous asbestos dispersion, wherein the dispersion is passed through a nozzle into a coagulating bath to form a continuous strand, comprising the steps of flowing the dispersion under hydrostatic head through a plurality of nozzles within a coagulating bath to produce a plurality of individual spaced strands, exerting a constant and uniform pulling force on the progressively coagulating strands sufficient to elongate said strands in excess of 300 percent, continuously passing said elongated strands through a zone of low tension until coagulation thereof is substantially complete while maintaining said strands in their elongate form and while merging said strands together substantially in the absence of tension thereon, and continuously withdrawing the coagulated strands under tension by pot spinning from said zone of low tension.

'5. The method of claim 4 wherein the step of passing said strands through a zone of low tension comprises wrapping said strands several times around a pair of spaced rolls rotating at the same surface speed.

6. The method of claim 4 wherein the nozzles have an orifice of about 0.09 inches and said yarn is withdrawn in excess of feet per minute.

Claims

1. A method for producing asbestos yarn from an asbestos dispersion that is subject to coagulation, comprising the steps of forming the dispersion into a plurality of individual strands, subjecting the strands to progressive coagulation while uniformly drawing the strands into an elongate form, continuously passing said strands through a zone of low tension until coagulation thereof is substantially complete, merging the strands into a multi-ply yarn, and continuously withdrawing said strands under tension from said zone of low tension, said zone of low tension serving to isolate the steps of yarn withdrawal from the step of strand formation.

2. The method of claim 1 wherein the strands are elongated during progressive coagulation in excess of 300 percent.

3. The method of claim 1 wherein the strands are flexed in said zone of low tension.

5. The method of claim 4 wherein the step of passing said strands through a zone of low tension comprises wrapping said strands several times around a pair of spaced rolls rotating at the same surface speed.

6. The method of claim 4 wherein the nozzles have an orifice of about 0.09 inches and said yarn is withdrawn in excess of 150 feet per minute.