US3537135A - Spinning apparatus - Google Patents

Description

1970 J- SANTANGELO 3,537,135

SPINNING APPARATUS Filed Aug. 7, 1968 United States Patent 3,537,135 SPINNING APPARATUS Joseph Germano Santangelo, Morristown, N.J., assignor to Celanese Corporation, New York, N.Y., a corporation of Delaware Continuation-in-part of application Ser. No. 336,683,

Jan. 9, 1964. This application Aug. 7, 1968, Ser.

Int. Cl. D01d 3/00; D0115 3/02 US. Cl. 18-8 5 Claims ABSTRACT OF THE DISCLOSURE This application is a continuation-in-part of United States application Ser. No. 336,683, filed Jan. 9, 1964 and now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to a novel spinning process and a novel jet or spinneret used in such process.

In spinning a man-made fiber-forming material such as cellulose triacetate into filaments, a liquid comprising the polymer, i.e., a solution of the polymer in an appropriate solvent or a molten composition containing the material, is extruded through fine capillary orifices. While satisfactory products have been obtained with orifices having profiles heretofore used, the formation of these orifices is often difficult and costly and/ or their use in the spinning process results in various process disadvantages, e.g., the formation of excessive amounts of deposits in the orifices resulting in high pressure drops across the spinneret and necessitating the use of larger than desirable orifices which have a diverse effect on fiber properties, in starting up the process.

In dry spinning, since the filaments are not normally given an after-stretch, the major orientation imparted to the fiber takes place in the vicinity of the jet. Since fiber properties are related to the degree of orientation, it is desirable to have a detailed understanding of this mechanism.

The flow profile or velocity distribution of the fluid leaving the jet is a function of the orifice design. The pressure distribution throughout the orifice is also related to orifice design. If we assume that the major flow pattern, e.g., smooth flow lines vs. turbulence, is translated down to the smaller element, the molecule, then a smooth flow pattern through the orifice will orient the molecules along their major axis whereas turbulence would produce random non-oriented molecules.

An analysis of orifice design, as related to velocity and pressure distributions, shows that the flow lines are smooth and undisturbed over the continuous portion of the orifice. It was found that when the polymer flow meets an angle or other discontinuous surface, eddy currents and turbulence set in. This condition becomes worse as the velocity of the polymer through the orifice is increased. These conditions are not conducive to molecular orientation and disrupt molecular alignment. The correct rate of change of curvature eliminates this disruption and improves yarn properties and this same mechanism also contributes to a reduction in jet corrosion.

The ideal solution to the problem of turbulence is a jet with a smooth hyperbolic approach to the orifice. This design minimizes flow turbulence and produces greater orientation in the yarn. To produce pure hyperbolic holes in a spinneret would be extremely diflicult and impractical, but the novel technique developed by applicant is an excellent inexpensive approximation. Yarn tenacity, elongation and jet deposits are unexpectedly improved with a decrease in turbulence caused by a decrease in the orifice incidence angle. Therefore, the preferred jet des gn for both quality and productivity, especially with regard to jet deposits, combined a smooth hyperbolic approach and an incidence angle which approaches zero.

It is an object of this invention to provide a process for the formation of man-made fiber-forming materials such as cellulose triacetate into filaments using an improved spinning process.

It is a further object of this invention to provide a spinning process using a novel jet or spinneret whereby the problem of turbulence in spinning filaments is eliminated, as evidenced by a reduction in jet deposits, a reduction in pressure drop across the spinneret and the production of yarn having extremely high tensile properties.

It is a still further object of this invention to provide novel jets or spinnerets having a specified profile which may be produced using a relatively simple manufacturing operation. I

Other Objects will be apparent from the following detailed description and claims wherein all parts are by weight unless otherwise indicated.

DISCUSSION OF THE PRIOR ART The spinneret of this invention represents an improvement over the prior art spinneret disclosed in United States Pat. 3,210,451, to Manning, isued on Oct. 5, 1965, on an application filed on Dec. 1, 1960. This patent is ass gned to the assignee of the present application. In addition to the advantages of Mannings spinneret, applicants apparatus and process significantly reduce jet deposits which cause great pressure drops across the spinneret and allow the production of high tenacity and high elongation fibers by utilizing a smooth approach to the capillary. Jet deposits tend to form when there is a sharper line of demarcation between the smallest or first frustoconical section and the bottom cylinder or capillary.

SUMMARY OF THE INVENTION In accordance with one aspect of the invention, a fiberforming material, such as cellulose triacetate or cellulose secondary acetate, is formed into filaments by extruding a liquid comprising such material, e.g., a solution of such material in an appropriate solvent or a molten composition containing such material, through an orifice having a cylindrical portion communicating with the outlet face of the spinneret and three frusto-conical portions which are divergent toward the inlet side of the spinneret, with the apex angle of each frusto-conical portion being larger, the farther away it is from the cylindrical portion. Thus, if the frusto-conical portion adjacent to the cylindrical portion is termed the first 'frusto-conical portion, then the second frusto-conical portion adjacent to the first has an apex angle larger than that of the first and the third frustoconical portion adjacent to the second on the inlet side has an apex angle greater than that of the second.

The first frusto-conical portion, i.e., that communicating with the cylindrical portion preferably has an apex angle of less than about 17 degrees, e.g., 12 to 17 degrees, and most suitably in the range of 16 to 17 degrees; the second frusto-conical portion communicating with the first 'frustoconical portion preferably has an apex angle of at least 13 degrees greater than the apex angle of the first frustoconical portion and most suitably in the range of 25 to 35 degrees; and the third frusto-conical portion communicating with the second frusto-conical portion preferably has an apex angle of at least 30 degrees greater than that of the second frusto-conical portion and most suitably in the range of 60 to 65 degrees.

The use of an orifice having the above-described profile allows for an orifice size, e.g., expressed as diameter, of the cylindrical portion, which is smaller than usual. The use of smaller holes, e.g., as low as 0.025 mm., allows for the production of lower denier material, e.g., as low as 1 denier per filament, produced at a lower drawdown or spin draw ratio, defined as the ratio of the denier of the fiber-forming material being extruded to the denier of the taken-up material. This type of material is very desirable for certain uses, e.g., cigarette filters. Moreover, smaller holes with the concomitant employment of smaller draw down ratios also result in superior mechanical properties, e.g., tenacity and elongation.

The term cylindrical is employed herein for the jet face section of the orifice design since it connotes a generally regular cross-section,'as distinguished from the -i diameters of the remaining sections, but it is understood that such cross-section may be circular or any non-circular configuration conventional in this art such as triangular cross-sections, square cross-sections, Y cross-sections, I-

beam cross-sections, X cross-section, trilobal cross-sections the third frusto-conical portion is about 20 to 30 times the diameter of the cylindrical portion.

Preferable ranges of linear values for the dimensions of each portion of the orifice are as follows: about 0.025 to 0.50 mm., preferably about 0.025 to 0.060 mm. for the diameter of the cylindrical portion; about 0.0125 to 0.50

mm., preferably about 0.0125 to 0.060 mm. for the length of the cylindrical portion; about 0.030 to 0.040 mm. for the length of the first frusto-conical portion; about 0.1 to 0.23 mm. for the length of the second frusto-conical portion; and about 0.76 to 0.89 mm. (i.e., about 30 to 40 mils) for the third frusto-conical portion.

A particularly desirable spinneret of the type described a above is one having orifices each with a cylindrical portion having a circular cross-sectional diameter no greater than about 0.034 mm. and a length of about /2 times the diameter of the crosssection, a first frusto-conical portion hav- 'ing an apex angle of about 17 degrees and a length of about 1 times the diameter of the cylindrical portion, a second frusto-conical portion having an apex angle of about 30 degrees and a length of about 6 times the diameter of the cylindrical portion, and a third frusto-conical portion having an apex angle of about degrees and a length of about 22.5 times the diameter of the cylindrical portion, all the lengths being measured along the axis of the orifice.

The process is of particular value in the dry, spinning of v the third frusto-conical portion, the depth of such hole corresponding to the length desired for such third frustoconical portion. A drilling or countersinking tool having an angle corresponding to the second frusto-conicalpor tion, i.e., less than that of the first tool used, is then inserted into the hole and used to further drill a hole o an creased depth corresponding to the desired length of the second frusto conical"portion. A cylindrical tool is inserted into the hole and used to drill the' cylindrical portion of the orifice which extends entirely to the outlet face of the spinneret. Finally, a punch is used to form the first frusto-conical portion by pressing down the circle of intersection between the second frusto-conical portion and the cylindrical portion, using a punching tool with an angle corresponding to the desired first frusto-conical portion. After the first operation resulting in the formation of a cone-shaped hole including a part corresponding to the third frusto-conical'portion, the placing of each drilling tool-is simplified by the' fact that it need only be inserted into an already formed hole.

It can be seen that when using the above-described method, the relatively Weak drilling tools, i.e., the tool used to drill the cylindrical portion and the frusto-conical portions of smaller apex angles, are only employed to drill relatively small proportions of the total thickness of the spinneret plate. This has the effect of drastically reducing breakage of the drilling tools.

The cylindrical portion of the orifice may be punched rather than drilled, in which. case such section may have, in addition to a circular cross-section, cross-sections of other shapes, such as a triangular cross-section, a'square crosssection, etc., depending upon the shape of the punching tool.

Contemplated under this invention are spinnerets having plates with thicknesses up to about 7.62 mm., i.e., about 300 mils. However, to avoid an unduly large amount of breakage of drillingand/or punching tools, particularly when the spinneret is to be' used in a dry spinning process, a plate having a relatively small thickness is suitably used, e.g no greater than about 1.016 mm., i.e., about 40 mils, and most suitably in the range-of about 0.635 to 1.016 mm., i.e. about 25 to 40 mils. Moreover, the use of a spinneret plate of small thickness has the further advantages that it results in lower pressure drop across the spinneret plate making spinning easier and reduces the chance of blockage of the orifice.

As mentioned previously, the process of this invention is particularly useful in the dry spinning of cellulose esters, such as the spinning of cellulose triacetate from solution in a solvent comprising a major proportion of a halogenated hydrocarbon. The process may be suitably carried out using fairly high spinning speeds using 100 to 1000 meters per minute to produce filaments having a denier in the range, forfexample, of 1 to 10 denier per filament. However, deniers outside of this range may also be obtainedl'" Asemployed herein, cellulose triacetate has reference to cellulose acetate having fewer than about 0.29 and preferably fewer than about 0.12 free hydroxyl group per anhydroglucose unit of vthe cellulose molecule, i.e., an acetyl value calculated as combined acetic acid by weight of at least about 59 percent and preferably at least about 61 percent. 1 7 r 1 Advantageously, its intrinsic viscosity, ranges from about 1.5 to 2.5 and is preferably about 2,and it is present in the dope to a concentration ranging from about 20 to 25 percent. Inplace of methylene chloride, the dope ,solvent may comprise other halogenatedlower alkanes 'suchvas ethylene dichloride or propylene chloride. Advantageously, up to about 15 percent by weight of the dope solvent comprises -a l0wer 'alkanol such as methanol, ,ethanol, isopropanol, etc. The preferred dope solvent is methylene chloride-methanol in the proportions of about -10byweight. Q v i v The process of thisinventionis also especially useful in the dry spinningfof cellulose secondary acetate from solution in a solventflsuch'as acetone. Cellulose secondary acetate, as employed herein, has reference to cellulose acetate having an acetyl value in the range from 54 to '56percent, preferably between 54 and 55 percent, calculatedascombined acetic acid.' I 1 BRIEF DESCRIPTION OF THE DRAWINGS The invention may be further illustrated with reference to the accompanying drawing wherein:

FIG. 1 is a plane view of a section of a spinneret used in accordance with this invention with the orifices arranged in a circle around the periphery of the spinneret plate and their size exaggerated to indicate their appearance;

FIG. 2 is a sectional view showing the profile of the contemplated orifices; and

FIG. 3 is a schematic illustration of a dry spinning operation.

Referring now more particularly to the drawing, FIG. 1 shows a spinneret or jet plate 10 as viewed from the inlet side with orifices 11 each of which has the appearance of four concentric circles corresponding to the largest diameter of the orifice at the inlet face of the plate and the circles of intersection of the various frusto-conical portions and the cylindrical portion, at the outlet side of the spinneret plate.

As shown in FIG. 2 illustrating the profile of the contemplated orifice of spinneret 10, the wall of the cylindrical portion is indicated at 13 with numerals 14, 15 and 16 identifying the walls of the first, second, and third frusto-conical portions of the orifices respectively.

' In FIG. 3 there is shown a dry spinning cabinet 17 to which dope is supplied through a pipe 18, being extruded through the spinneret 10 of FIGS. 1 and 2. Hot air is admitted to the cabinet 17 at 19 and is exhausted at 20 along with vapors of the dope solvent. The filaments 21 leaving spinneret 10 pass about a guide 22 and leave the cabinet at 23 being pulled as a yarn 24 by draw rolls 25. The yarn 24 passes through a guide 26 and is twisted and taken up on a bobbin 27 by a conventional collector such as ring spinner-28.

In addition to the fact that smaller orifices may be used in carrying out the process with the advantages described above, the process of this invention results in the formation of substantially. less jet deposits than when various other orifice shapes are used, particularly in the case of the dry spinning of cellulose triacetate from solution in a solvent comprising a major proportion of a halogenated hydrocarbon. Moreover, the employment of the orifice profile of this invention results in considerably longer jet life, a more uniform filamentary product (e.g., in terms of cross-section) with better properties, e.g., of

6 are employed with more conventional orifice designs. Improved dyeing properties may also be obtained.

Finally, the process of the invention using the distinct orifice shape as described above may be started up much more easily than other spinning processes, and makes possible the employment of higher spinning speeds without deterioration of filament properties.

The following example further illustrates the invention:

Example I A 22 weight percent solution of fiber-forming cellulose triacetate having an acetyl value of 61.5 percent by weight calculated as combined acetic acid in a solvent mixture consisting of 91 percent of methylene chloride and 9 percent of methanol was extruded through a chromium plated stainless steel spinneret with a plate having a thickness of 1.016 mm. and with 5 orifices arranged in a circle" each with a profile as indicated in FIG. 2. Cylindrical portion 13 of each orifice had a circular cross-section with a diameter of 0.034 mm. and a length of 0.018 mm. First frusto-conical portion 15 had an apex angle 17 degrees and a length of 0.035 mm.; second frusto-conical portion 16 had an apex angle of 30 degrees and a length of 0.20 mm.; and third frusto-conical portion 17 had an apex angle of degrees and a length of 0.762 mm., each of the lengths being measured along the axis of the orifice. The resulting filaments passed through air in a spinning cabinet at 35 degrees centigrade and were taken up on a bobbin at a linear speed of 500 meters per minute after being withdrawn from the spinning cabinet. The yarn had a denier of 3.75 d.p.f., a tenacity of 1.35 grams per denier and an elongation of 35 percent.

After 24 hours of continuous operation from the time that the spinneret was installed, the jet deposits resulted in a reduction in orifice area equal to only 1.7 percent of the total due to deposited material when observed at 400 magnification. This represents a substantially smaller formation of jet deposits than is obtained when orifices of more conventional profile are used.

Example II A 22 weight percent solution of fiber-forming cellulose triacetate having an acetyl value of 61.5 weight percent was extruded through the chromium plated stainless steel spinneret of Example I utilizing the procedure of Example I. The resulting filaments pass through air in a spinning cabinet at 40 degrees centigrade and were taken up on a bobbin at a linear speed of 350 meters per minute after being withdrawn from the spinning cabinet.

A 22 weight percent solution of fiber-forming cellulose triacetate having an acetyl value of 61.5 percent was extruded according to the procedure of the example of US. Pat. 3,210,451, Manning, utilizing the spinneret disclosed therein. The resulting filaments were passed through air in a spinning cabinet at 40 degrees centigrade and were taken up on a bobbin at a linear speed of 350 meters per minute after being withdrawn from the spinning cabinet.

Table I below shows the comparative jet deposit ratings of spinnerets utilized for long periods of time in the process of this invention and the prior art process and tenacity and elongation that is the case when spinnerets 60 jet of US. Pat. 3,210,451:

TABLE I Prior art jet-plated Jet of this inventionplated Spinning Percent Spinning Percent time hrs. deposits time, hrs. deposits 400x) 400x) As received, average 4. As received, average 3. 10 Average 1 2. 60 Average 1 1. 40

1 Boiled 3 hrs. in methylene chloride.

Cellulose triacetate filaments extruded according to the foregoing procedures was put on cones and beams and data collected for a period of six months. Data comparingefliciency and tensile properties of filaments ex-' truded utilizing the Manning spinneret with filaments utilizing the spinneret and process of this invention are shown in Table II belowr Fiber-forming cellulose triacetate was extruded according to the procedure of Example I utilizing unplated stainless steel spinnerets having the dimensions of the spinneret of Example I. The resulting filaments were passed through air in a spinning cabinet at degrees centigrade and were taken up on a bobbin at a linear speed of 500 meters per minute after being withdrawn from the spinning cabinet.

Cellulose triacetate wasextruded according to the pro cedure of the example of US. Pat. 3,210,451, Manning, utilizing an unplated spinneret having the dimensions of the spinneret of the said example. The resulting filaments were passed through air in a spinning cabinet at 25 degrees centigrade and were taken up on a bobbin at a linear speed of 500 meters per minute after being withdrawn from the spinning cabinet.

A comparison of the jet deposit data for jets run to 24 hours utilizing the process of this invention and the prior art process and jet of U.S. Pat. 3,210,451 is shown in Table HI below:

TABLE III Percent deposits Jet (1-inchX5-holeX0.032 mm.) Jet A J et B Average EXAMPLE IV 49.0 percent.

. A 22 weight percent solution of fiber-forming cellulose triacetate having an acetyl value of 61.5 percent by weight calculated as combined acetic acid in a solvent mixture consisting of 91 percent of methylene chloride and 9 percent of methanol was extruded through an unplated stainless steel spinneret at a jet facetemperature of 80 degrees centigrade. The spinneret having a plate with a thickness of 1.016 mm. and with 20 orifices arranged in a circle each with a profile as indicated in FIG. 2. Cylindrical portion 13 of each orifice had a circular crosssection with a diameter "of 0.028 mm. and a length of 0.018 mm. First frusto-conical portion 15 had an apex angle 17 degrees and a length of 0.035 mm.; second frusto-conical portion 16 had an apex angle of 30 degrees and a length of 0.20 mm.; and third frusto-conical portion 17 had an apex angle of 60 degrees and a length of 0.762 mm., each of the lengths being measured along the axis of the orifice. The resulting filaments passed through a 12-foot updraft in a spinning cabinet at,35

of 1.33 grams per denier and an averageelongation of TABLE IV Elongation, percent Bobbin N0.

Denier Tenacity, g./d.

Average Spinning speeds in excess of 1000 meters per minute are easily achieved utilizing the process and spinneret of this invention. In addition, the life of the spinneret in use ranges from about 1000 to 1500 hours, as compared with a useful life of 600 hours for the prior artManning spinneret.

The embodiments of the invention in which an exclusive property or privilege is claimed 'as defined asfollowsi 1. A spinneret having at least one orifice including a cylindrical portion at its outlet end, a first frusto-conical portion connecting with said cylindrical portion, a second frusto-conical portion connecting with said first frustoconical portion and having a larger apex angle than said first frusto-conical portion, and a third frusto-conical por-, tion connecting with said second frusto-conical portion and having an apex angle larger than'that of said second frusto-conical portion, each of said .frusto-conical portions being divergent toward the inlet end of said orifice.

2. A spinneret having at least one orifice with a shape including a cylindrical portion at the outlet end of said orifice, a first frusto-conical portion connecting with said cylindrical portion, a second frusto-conical portion connecting with said first frusto-conical portion and having an apex angle of at least about 13 degrees greater than that of said first frusto-conical portionand a third frustoconical portion connecting with said second frusto-conical portion and having an apex angle of at least about 30 degrees greater than that of said second frusto-conical portion, each of the frusto-conical portions beingdivergent towardthe inlet end of said orifice.

3. The spinneret of claim 2 wherein said orifice is up to about 1.016 mm. long and said cylindrical portion is a right circular cylinder and has a diameter area of less than about 0.060 mm.

4. A spinneret having at least one orifice up to about 1.016 mm. long, said orifice having a cylindrical portion at its downstream end with a diameter up to about 0.060 mm. and a length in the range of about /2 to 1% times its diameter, a first frusto-conical portion connecting with said cylindrical portion and having an apex angle in the range of about 12 to 17 degrees, and a length in the range of about /2 to 1 times the diameter of said cylindrical portion, a second frusto-conical portion connecting with said first frusto-conical portion and having an apex angle 1 of at least about 13 degrees larger than that of said first frusto-conical portion and a length in the range of about 3 to 8 times the diameter of said cylindrical portion and degrees centigrade and were taken up on a bobbin at a linear speed of 300 meters perminute after being withdrawn from the spinning cabinet. The yarn was wound onto one pound packages'and had an average tenacity a third frusto-conical portion connecting with said second frusto-conical portion and having an apex angle of at least about 30 degrees larger thanthat of said second .frusto-conical portion and a length of about 20 to 30 5. A spinneret having at least one Orifice including a cylindrical portion at the outlet end of said orifice having a diameter no greater than 0.034 mm. and a length of about /2 times the diameter of said cylindrical portion, a first frusto-conical portion connecting with said cylindrical portion and having an apex angle of about 17 degrees and a length of about 1 times the diameter of said cylindrical portion, a second frusto-conical portion connecting with said first frusto-conical portion and having an apex angle of about 30 degrees and a length of about 6.0 times the diameter of said cylindrical portion, and a third frusto-conical portion connecting with said second frusto-conical section and having an apex angle of about 60 degrees and a length of about 22.4 times the diameter of said cylindrical portion, each of said frusto-conical portions being divergent toward the inlet end of said orifice.

References Cited UNITED STATES PATENTS 2,742,667 4/1956 Clouzean et a1. 18-855 2,839,783 6/1958 De Wolfe 18855 5 3,006,026 10/1961 Martin et a1. 18855 3,197,812 8/1965 Dietzsch et a1.

FOREIGN PATENTS 628,008 11/ 1961 Italy.

10 JULIUS FROME, Primary Examiner I. H. WOO, Assistant Examiner US. Cl. X.R. 15 264204

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