EP0702732A1

EP0702732A1 - Spandex containing barium sulfate

Info

Publication number: EP0702732A1
Application number: EP94916808A
Authority: EP
Inventors: Howard Wayne Jacobson; Charles William Goodrich
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1993-06-11
Filing date: 1994-05-25
Publication date: 1996-03-27
Anticipated expiration: 2014-05-25
Also published as: DE69412824T2; DE69412824D1; EP0702732B1; JPH08511585A; TW316931B; KR19990037960A; BR9407074A; WO1994029499A1; JP3279569B2; KR100245846B1

Abstract

Dry-spun spandex having a silicone oil finish on its surface and barium sulfate of low isoelectric point (0-4) dispersed in its volume have highly roughened surfaces and advantageously low tackiness.

Description

TITLE Spandex Containing Barium Sulfate BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to spandex in which particles of barium sulfate are dispersed. More particularly, the invention concerns an improvement in such a spandex wherein the spandex has a roughened surface and the barium sulfate particles have a very low isoelectric point. The invention also concerns a process for producing such spandex. The presence of the barium sulphate particles of low isoelectric point in the spandex provides unexpected and advantageous reductions in the tackiness of the spandex and improvements in the process for producing the spandex.

Description of the Prior Art

Spandex is known to exhibit considerable tackiness compared to conventional non-elastomeric textile fibers. The filaments tend to stick to various surfaces and to each other, especially when wound up on a bobbin.

Tackiness can cause excessive unwinding tension (referred to hereinafter as "take-off tension") as well as frequent, large transients in the tension as the spandex is unwound from the package. Excessive take-off tensions and transients can cause yarn breaks during handling, fabric defects and other manufacturing difficulties, especially in making of knit fabrics.

To reduce spandex tackiness, lubricating finishes are applied to spandex yarn and/or special agents are dispersed within the spandex. Examples of such lubricating finishes include (a) metallic soaps dispersed in textile oils, such as those disclosed by Yuk, United States Patent 3,039,895, and (b) polyalkylsiloxanes, such as those disclosed by Chandler, U.S. Patent 3,296,063. The dispersion of certain metal soaps (e.g., stearates of calcium, magnesium or lithium) within the spandex for tackiness reduction is disclosed by Hanzel et al, U.S. Patent 4,296,174. Further reductions in the tackiness of the spandex would improve its handling characteristics, make its production more economical and enhance its utilization in various fabrics.

Though not noted for decreasing tackiness, barium sulfate, among many other inert inorganic materials, has been disclosed for use in spandex, by for example, Bell et al U.S. Patent 3,386,942 and Imai et al, U.S. Patent 4,525,420. Barium sulfate is available commercially in several forms, purities and grades. Applicant now has found that the tackiness characteristics of the spandex can be modified very favorably by dispersing in the spandex particular barium sulfate particles having specific isoelectric properties.

SUMMARY OF THE INVENTION The present invention provides an improved spandex of the type that has a lubricating finish on its surface and barium sulfate particles dispersed within its volume. In accordance with the improvement of the invention, to reduce tackiness of the spandex, the barium sulfate particles have an isoelectric point in the range of 0 to 4, preferably in the range of 0.5 to 3. Typically, the barium sulfate particles amount to in the range of 0.3 to 5%, preferably 1 to 3%, of the weight of the spandex. The spandex containing the barium sulfate has a surface roughness parameter (defined hereinafter) of at least 75, preferably in the range of 100 to 200. Preferably, the average pore size is in the range of 10 to 30 Angstroms and the BET surface area is in the range of 1 to 5 m²/g. In another embodiment of the invention, the spandex contains titanium dioxide particles amounting to in the range of 1 to 5% of the total weight of the spandex and the lubricating finish is a polysiloxane amounting to in the range of 1 to 6% by weight of the spandex. In still another embodiment of the invention, the yarn is wound up on a cylindrical member to form a yarn supply package of low tackiness.

The invention also provides an improved process for dry-spinning spandex, wherein a solution of a segmented polyurethane polymer in an organic solvent is mixed with additives and then dry-spun into filaments. The improvement comprises at least one additive being barium sulfate having an isoelectric point in the range of 0 to 4.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The invention is further illustrated by the following description of preferred embodiments. These are included for the purposes of illustration and are not intended to limit the scope of the invention, which is defined by the appended claims. As used herein, the term "spandex" has its usual definition; that is, a manufactured fiber in which the fiber-forming substance is a long chain synthetic polymer composed of at least 85% by weight of a segmented polyurethane. The term "fiber" includes in its meaning staple fibers and continuous filaments.

For convenience, in the discussion and examples that are presented below, the following abbreviations may be used for the accompanying term:

Poly(tetramethyleneether)glycol P04G Methylene-bis(4-phenylisocyanate) , also called p,p*-methylenediphenyldiisocyanate MDI Isocyanate end group NCO

Ethylenediamine EDA

2-methyl-l,5-diaminopentane MPMD N,N-dimethylacetamide solvent DMAc

Diethylamine DEA

1,3,5-tris(4-t-butyl-3-hydroxy-2,6-dimethyl- "Cyanox" benzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)trione 1790 antioxidant sold by American Cyanamid Copolymer of diisopropylaminoethyl "Methacrol" methacrylate and n-decylmethacrylate, 2138 also called DIPAM/DM Tenacity, dN/tex T

Elongation at break, % E Load power on first cycle, dN/tex

Load at 100% elongation LP-100

Load at 200% elongation LP-200

Unload power on fifth cycle, dN/tex

Unload at 100% elongation UP-100 Unload at 200% elongation UP-200

Over end take-off tension, centiNewtons OET

The chemical composition of a polymer of the spandex also may be abbreviated as illustrated by the following example, in which a polyurethaneurea made from poly(tetramethyleneether)glycol ("P04G") having a number average molecular weight of 1800, methylene-bis (4- phenylisocyanate) ("MDI") and a mixture of ethylene diamine ("EDA") and 2-methyl-l,5-diaminopentane ("MPMD") in a molar ratio of 90 to 10, is abbreviated as

PO4G(1800) :MDI:EDA/MPMD(90/10) . Note that colons are used to separate the monomers of the repeating units of the polymer, a slash (i.e., /) between the diamines indicates that the diamines are in a mixture and parenthetic numbers immediately following the glycol and diamine mixture respectively refer to the number average molecular weight of the glycol and the molar ratio of the diamines in the mixture. In accordance with the present invention, a spandex has dispersed within its volume barium sulfate particles having an isoelectric point in the range of 0 to 4, preferably 1 to 2.5. Conventional techniques are employed to add the particles to a polyurethane solution from which the spandex is to be dry spun. Generally, the barium sulfate amounts to 0.3 to 5%, preferably 1 to 3%, of the total weight of the spandex. The particles of barium sulfate may be coated with specific agents for special purposes. For example, the particles can be coated with antimicrobial compositions such as those disclosed by Jacobson et al in U.S. Patent 5,180,585. As long as the isoelectric point of the particles remains within the 0-to-4 range in accordance with the invention, the use of coatings on the barium sulfate does not detrimentally affect the spandex produced therewith, and such coated particles are intended to be included within the scope of the invention.

The barium sulfate particles suitable for use in the present invention are small. The average size of the du Pont de Nemours & Co. Typically, about 0.4 to 0.7 kilogram of spandex yarn is wound up on the cylindrical tube of such yarn supply packages.

The polymer of the spandex of the invention can contain conventional agents that are added for specific purposes, such as antioxidants, thermal stabilizers, UV stabilizers, pigments, dyes, lubricating agents and the like. Such agents are usually added to the solution of the polymer and become incorporated into the filaments during the dry spinning step.

The barium sulfate additive, in accordance with the present invention, can be incorporated into the filaments in the same manner as the other additives. The concentration of barium sulfate is typically in the range of 0.3 to 5% by weight of the spandex polymer. Although various types and grades of barium sulfate particles are known, such as barites or barytes ore, chemically pure barium sulfate, blanc fixe and the like, only barium sulfate having an isoelectric point in the range of 0 to 4 is suitable for use in the spandex of the invention.

Barium sulfate particles with an isoelectric point in the range of 1 to 2.5 are preferred.

The particular barium sulfate suited for use in the present invention represents a small fraction of all the barium sulfates that are available commercially. Natural barium sulfate, the mined ore (also known as "barite" or "barytes") , contains several colored impurities. Some of these impurities can be removed by beneficiation of the ore through washing, tabling, jigging or floatation. Although the mined barium sulfate contains various impurities, such barium sulfate often can be used directly for drilling muds, the largest known use for the ore. Finely ground barite is used as a filler or extender for paints. Barite for pigment usually is "bleached" by treatment with acid and often also with a reducing agent to remove colorizing compounds. Chemically pure barium sulfate is also available for chemical reaction purposes. Still another commercially available barium sulfate is precipitated barium sulfate, also known as blanc fixe.

6 particles is typically in the range of 0.5 to 3 microns, with the largest particles (i.e., not more than 2% of the particle size distribution) being greater than 25 microns, preferably no greater than 15 microns. Conventional polymers used for preparing spandex by dry spinning are suitable for the spandex of the present invention. These typically are prepared by known processes in which a polyether-based glycol or polyester- based glycol is reacted with a diisocyanate to form an isocyanate-capped glycol which is then reacted with diamine chain extender to form the segmented polyurethane polymer. Usually, the polymer is dissovled in an inert organic solvent, such as dimethylacetamide (DMAc) , dimethylformamide, N-methyl pyrrolidone or the like. Generally, the pH of the polymer solution is in the range of 9 to 12. As a result of the low isoelectric point (i.e., 0 to 4) of the barium sulfate particles for use in the invention, the particles are very well dispersed within the solution and subsequently within the spandex. The polymer solution is dry-spun in conventional equipment through orifices into a shaft. Heated inert gas passes through the shaft to assist solvent evaporation from the surface of the formed filament as the filament passes through the shaft. Filaments from multiple orifices are twisted together to form a multi-filament yarn. Lubricant can be deposited on the surface of the filaments by a conventional finish roll or by being co-spun with the filaments from the polymer solution. Thereafter, the thusly dry-spun filaments (i.e., spandex) are wound up on a cylindrical member to form a yarn supply package (e.g., a pirn, bobbin, cake) .

Conventional spandex filaments (i.e., not containing the special barium sulfate particles in accordance with the invention) are quite tacky. Polyether-based spandex usually is more tacky than polyester-based spandex. Clear spandex, derived from polyether glycols is the tackiest.

Commercial spandex yarns are well known. For example, "LYCRA" spandex is manufactured and sold by E. I. Blanc fixe, usually is prepared by mixing aqueous solutions of barium sulfide and sodium sulfate under controlled conditions in order to produce a precipitate of uniform particles of pigmentary fineness. Of all the barium sulfate particles commercially available, only particles having an isoelectric point of no greater than about 4 (e.g., some of the blanc fixe grades) were found suitable for use in the present invention. These particular blanc fixe particles were unexpectedly better than all the others in reducing the tackiness of dry-spun spandex and in providing more efficient operation of the dry-spinning process. With regard to the process, when barium sulfate particles having isoelectric points in accordance with the invention were employed, the barium sulfate particles were well dispersed and did not form agglomerates in the polymer solution; screens and filters operated longer before needing shutdown and cleaning; and even more surprisingly, the solvent content of the filaments leaving the spin shaft was decreased. In addition, spandex yarns containing barium sulfate particles of 0-4 isoelectric point, when wound up into yarn supply packages, permitted satisfactory removal of all the yarn from the package. In contrast, conventional spandex yarn packages having no barium sulfate particles in the filaments usually cannot be totally removed from the package. The portion of the wound-up yarn that is closest to the central cylindrical member of the yarn package usually can not be removed satisfactorily from the package, which results in about 6% of the total yarn in the package being wasted.

The following table lists the isoelectric point and particle size determined for a selected group of commercial barium sulfates. Size of Particles

1staelectric (microns)

Barium sulfate Point Averacre Rancfe

Blanc fixe*

Micro grade 1.0 0.7 0.3-2.5

F grade 1.4 3.0 0.3-5

N grade 10 1.0 0.4-20

N grade with flame- retardent coating 10 n nm

Certified chemically pure B68-500+ 9 3.7 2-7.5

Notes: * manufactured and sold by Sachtleben of

Duisberg-Hamburg, Germany

+ sold by Fisher Scientific of Pittsburgh, Pa. nm = no measurement made The above-listed "Micro grade" and "F Grade" commercial blanc fixe from Sachtleben, each having an isoelectric point well below 4, are barium sulfates that are suitable for use in the present invention.

When polymer solutions containing barium sulfate particles in accordance with the invention were dry spun through orifices, the filaments acquired roughened surfaces. The present inventors theorize that the surface roughness plays an important role in retaining lubricant on the surface of the spun filament and maintaining low tackiness. Though the invention is not intended to be limited by the theory, the inventors believe that the small pores of the roughness permit the surface lubricant to be retained in place and not be lost from the surface. The inventors noted that in tests in which spandex samples of the invention were heated at 10°C per minute, a silicone oil surface lubricant showed no signs of being removed until a temperature of about 320°C was reached. In contrast, tests of similar spandex samples not of the invention (i.e., not having barium sulfate of the desired isoelectric point and accompanying surface roughness) indicated that silicone oil was evolved from the filament surfaces when the temperature reached only 120°C. When the "roughness parameter" (defined hereinafter) of the filaments is greater than about 75, and preferably in the range of 100 to 200, the surface lubricant apparently is held firmly on the surface of the filament and provides the filament with decreased tackiness. The following test procedures are used for measuring various characteristics of the spandex described above and in the Examples below.

Isoelectric point determinations are made with conventional instruments. The isoelectric point is defined as the concentration of hydrogen ions and other ions, usually expressed as a pH, at which the particles have no net charge and the zeta potential is zero. The procedure is as follows. A 20-gram sample of barium sulfate powder in 200ml of a 0.001N potassium nitrate is titrated with 3M potassium hydroxide or 2M nitric acid (depending on whether acid or base is needed for the titration) . Prior to the titration, the sample is thoroughly dispersed in the liquid by means of a sonic mixer, a Sonicator Model W-385, sold by Heat Systems- Ultrasonics Corp. of Farmingdale, New York. The titration is performed with the sample being stirred constantly. A potentiometric titration meter, an ESA-8000 System Model MBS-8000, sold by Matec Applied Science, Inc. of Hopkinton, Mass., was employed for the titration. To measure sizes of barium sulfate particles, a laser light scattering instrument is used. For the values reported herein, the instrument was a Micro-Trac FRA (full range analyzer) , sold by Leeds & Northrup of St. Petersburg, Fla. Sonically dispersed samples are employed. Each sample consists of 0.8 to 2.0 grams of the particles in 80 ml of deionized water which containes 10 drops of "Darvon C" dispersant, sold by R. T. Vanderbilt Chemical of Norwalk, Conn. At least three samples of each material are analyzed to obtain average particle size and particle size distributions.

Surface roughness is characterized herein by a "Roughness Parameter", R, which is defined as

R = 1000 (A)/(P) wherein A is the BET surface area in square meters/gram and P is the average pore size in Angstroms. The surface area of spandex is determined from nitrogen adsorption measurements in accordance with the method of Baunner, Emmet and Teller (BET) . The measurements are made with a Model 2100 Surface Area and Pore Volume Analyzer sold by Micromeritics Instruments Corp. of Norcross, Georgia. To prepare the test samples, the filaments are conditioned for about 10 hours under a vacuum of about 0.025 mm of mercury while at a temperature of about 120°C. During the testing the instrument automatically measures at least 21 points during each adsorption-desorption cycle. From these data, the BET surface area A, individual pore sizes, and average pore size, P, are calculated. The surface roughness parameter, R, of the spandex is then computed by the formula given above.

To determine the temperatures at which silicone lubricating oil is released from a spandex surface, a thermogravimetric analyzer is employed to raise the temperature of spandex samples at a rate of 10°C per minute, with the sample being flushed by a 100-cc/min flow of nitrogen. The flushed gas is passed to a Fourier Transform Infra-red Analyzer. The time at which the infra-red analyzer detects the presence of silicone oil in the nitrogen gas is correlated with the temperature of the sample when the oil is evolved from the sample.

Over-end take-off tension, a measure of the tackiness of a spandex yarn, is determined in accordance with the procedure disclosed in Hanzel et al, United States Patent 4,296,174, column 4, lines 20-45, with reference to Figure 6 of the patent, which disclosure is hereby incorporated by reference. In accordance with this technique, measurement is made of the average tension required to remove a 183-meter sample of spandex yarn from a supply package of the yarn at a delivery rate of 45.7 meters per minute.

Strength and elastic properties of the spandex are measured in accordance with the general method of ASTM D 2731-72. Three filaments, a 2-inch (5-cm) gauge length and a zero-to-300% elongation cycle are used for each of the measurements. The samples are cycled five times at an constant elongation rate of 800% per minute and then held at the 300% extension for half a minute after the fifth extension. "Load power" is reported herein in deciNewtons/tex and is the stress measured at a given extension during the first load cycle. "Unload Power" is reported herein in deciNewtons/tex and is the stress measured at a given extension during the fifth unload cycle. Percent elongation at break is measured on the sixth extension cycle. Percent set also is measured on samples that have been subjected to five 0-300% elongation-and-relaxation cycles. The percent set ("% S") is then calculated as % S = 100(Lf - L₀)/L₀, where L₀ and Lf are respectively the filament length, when held straight without tension, before and after the five elongation/relaxation cycles.

EXAMPLES The following examples describe preferred embodiments of the invention. These are presented for illustrative purposes and are not intended to limit the scope of the invention, which scope is defined by the appended claims. The results reported in these examples are believed to be representative but do not constitute all the runs involving the indicated ingredients. In the examples, samples of the invention are designated with Arabic numerals and comparison samples are designated with upper case letters.

Each of the samples of the invention described in the examples are prepared with a commercial spandex,

"Lycra" Type 146C, to which 1.5% barium sulfate is added. For comparison samples, the barium sulfate is omitted or the barium sulfate has an isoelectric point outside the range required by the invention. For each sample, the polymer for the spandex is made from a capped glycol, which was the reaction product of P04G and MDI prepared with a capping ratio (i.e., the molar ratio of MDI to P04G) of 1.63 and having an NCO content of 2.40%. The capped glycol is chain extended with a 90/10 diamine mixture of EDA/MPMD. DEA is employed as a chain terminator. The polymer is dissolved in DMAc to provide a solution having 36.8% solids. Additives consisting of 1.5% "Cyanox"-1790 antioxidant, 2% "Methacrol"-2138, and 0.6% silicone oil (based on the weight of the polymer) are added to the solution.

The solution described in the preceding paragraph is dry spun into 4-coalesced-filament 44-dtex yarns (or 2- filament 22-dtex yarns) in a conventional apparatus. The solution is metered through spinneret orifices into a spin shaft, in which the thusly spun solution forms filaments and DMAc solvent evaporates from the filament. A co- current flow of nitrogen gas is supplied to the shaft at a temperature of 420°C, which results in a temperature of 220°C at the half-way point through the shaft. The DMAc gas exits through a pipe in a side wall near the bottom of the shaft. The filaments are false-twisted by jets at the bottom of the shaft to cause groups of filaments to coalesce into single threadlines. A counter current flow of nitrogen, which is supplied at 135°C near the bottom of the shaft, combines with the exiting DMAc. The coalesced multi-filament threadlines exit through the bottom of the shaft. A silicone oil finish lubricant is applied to the threadlines by a kiss roll applicator, to provide an add- on of about 3.5% based on the weight of the threadline.

Unless indicated otherwise, the yarn is then wound up at a speed of about 840 meters per minute.

Barium sulfate is added to the polymer solution as follows. An 11.4% solution of polymer in DMAc is made by diluting 450 parts of polymer solution in 1000 parts of DMAc and then adding 1050 parts (by weight) of barium sulfate particles to the dilute solution while providing thorough mixing. The resulting slurry is then passed through a sandgrinder to break up any agglomerates that had possibly formed. The concentration of the barium sulfate in the slurry is 42%. The barium sulfate slurry is then metered to the polymer solution that already contains the other additives at a rate selected to provide a 1.5% concentration of barium sulfate in the polymer

(based on total weight of polymer) .

Example I

This example shows the effects of isoelectric point of the barium sulfate additive on the surface roughness of the spandex that is produced. Seven 44-dtex samples are prepared by the above-described procedures.

Two samples (Samples 1 and 2) are in accordance with the invention and five samples (Comparison Samples A, B, C, D and E) are outside the invention. All samples are prepared in the same manner, except as otherwise noted in

Table 1, which summarizes some of the properties of the spandex thusly produced.

Table 1 d S R

Sample BaS0 IEP A m-^ q lOOOS/d

1 1.5 1.0 28 3.9 139

2 1.5 1.0 13 2.2 169

A 1.5 10 56 0.31 5.6

B 1.5 9 72 0.13 1.8

C 0 nm 44 0.8 18

D 0 nm 53 0.16 3.0

E 0 nm 70 0.11 1.6

Notes:

IEP = isoelectric point d — average pore size in Angstroms S = BET surface area, square meters per gram R = roughness parameter Samples 1 and 2 are prepared with Sachtleben Micro-grade blanc fixe. Comparison Sample A is prepared with Sachtleben N-Grade blanc fixe and Comparison Sample B, with Fisher Scientific certified pure barium sulfate. Comparison Samples C, D, and E are prepared with no barium sulfate additive; D is wound up at 640 meters/min and E, at 914 meters/min.

When examined for tackiness, only Samples 1 and 2, containing barium sulfate in accordance with the invention, show large improvements over the tackiness of the samples without any barium sulfate. The samples with barium sulfate of high isoelectric point and low roughness parameters show no significant improvement over the spandex containing no barium sulfate. Quantitative measurements of the take-off tension of various yarns are shown in the next two examples. Example II

Physical properties of 44-dtex spandex yarns produced by the procedures described above and containing 1.5% micro-grade blanc fixe in accordance with the invention are compared with similarly made yarns having no barium sulfate in them. Table II summarizes the data.

Table II

Sample 3 Comparison F

%E, break elongation 476 483

Tenacity, deciNewton/tex 0.78 0.81 Power, centiNewton/tex First cycle load LP-100 0.083 0.084

LP-200 0.171 0.170 Fifth cycle unload

UP-100 0.015 0.015

UP-200 0.024 0.023 Set, % 24.2 23.2

Samples identical to Sample 3 and Comparison Sample F are prepared except that corresponding Samples 4 and G are 2-filament 22-dtex spandex yarns. The over-end take-off tension (OET) is measured for wound up yarns of Sample 4 and Comparison Sample G, immediately after spinning and then after 2 weeks, 4 weeks and 8 weeks of storage. Table III summarizes the results. Table III

Time after spinning OET, centiNewtons and winding up. weeks Sample G Sample 4 0 0.116 0.095

2 0.275 0.101

4 0.391 0.101

8 0.444 0.203

Note that the take-off tension of Comparison Sample G increases to about four times its initial value while that of Sample 4 of the invention only doubles its initial value. Note also that the take-off tension of fresh yarn of the invention is already about 20% lower than that of the comparison sample. Three additional samples are made with spandex yarns of 44 dtex; namely, Sample 5 of the invention containing 1.5% Micro grade blanc fixe, Comparison Sample H containing no barium sulfate, and Comparison Sample I containing 1.5% of certified pure (Fisher Scientific) barium sulfate. Bobbins of these samples were aged for 16 hours in an oven maintained at a temperature of 52°C after which the bobbins were permitted to remain at room temperature for another 24 hours before being subjected to over-end take-off tension tests. Tension-test results are summarized in the following table.

Table IV Sample Barium sulfate type OET,centiNewtons 5 1.5% micro-grade 0.344

H none 0.652 I 1.5% certified pure 0.550

Example III

In this example, two bobbins of 44-dtex spandex yarns are made by the procedures of Example I, but with 2 weight percent of titanium dioxide dispersed therein, and then tested for over-end take-off tension after 8 weeks of room-temperature storage. Sample 6 contains 1.5% of micro-grade barium sulfate and is of the invention. Comparison Sample J contains no barium sulfate and is outside the invention. The measured OET for Sample 6 of the invention was 0.141 centiNewtons versus 0.380 cN for Comparison for sample J.

Claims

WE CLAIM:

1. An improved spandex having a lubricating finish on its surface and barium sulfate particles dispersed within its volume, the improvement comprising, to reduce spandex tackiness, the barium sulfate particles have an isoelectric point in the range of 0 to 4.

2. An improved spandex of claim 1 wherein the barium sulfate particles amount to 0.3 to 5% of the weight of the spandex and the isoelectric point is in the range of 0.5 to 3.

3. An improved spandex having a lubricating finish on its surface and barium sulfate particles dispersed within its volume, the improvement comprising, to reduce spandex tackiness, the spandex has surface roughness parameter of at least 75.

4. An improved spandex of claim 3 wherein the barium sulfate amounts to 0.3 to 5% of the weight of the spandex, the surface roughness parameter is in the range of 100 to 200, and the barium sulfate particles have an isoelectric point in the range of 0 to 4.

5. An improved spandex of any one of claims 1 through 4, wherein the spandex has an average pore size in the range of 10 to 30 Angstroms and a BET surface area in the range of 1 to 5 m²/g.

6. An improved spandex of claim 5, wherein the spandex contains titanium dioxide particles amounting to in the range of 1 to 5% of the total weight of the spandex and the lubricating finish is a polysiloxane amounting to in the range of 1 to 6% by weight of the spandex.

7. An improved spandex of any one of claims 1 through 4 wound up on a cylindrical member to form a yarn supply package of low tackiness.

8. An improved process for dry-spinning spandex, wherein a solution of a segmented polyurethane polymer in an organic solvent is mixed with additives and then dry- spun into filaments, the improvement comprising at least one additive being barium sulfate having an isoelectric point in the range of 0 to 4.