US 3190718 A
Description (OCR text may contain errors)
' United States Patent PRGCESS 0F HEAT TREATING A TGW @F POLY- ESTER FEAMEN'EE 'Wlillld UNDER TENdilflN T l MQDEFY THE PRGPERTEES THEREOF Werner A. P. choeneherg and William D. Parirey, Charlotte, Nil, assignors to Ceianese Corporation of America, New York, N.Y., a corporation of Delaware No Drawing. Filed Apr. 23, 1960, er. No. 25,249 18 Claims. (Cl. 8-==-l30.1)
The present invention relates to a novel process for improving the properties of polyester filamentary material.
While polyester filamentary material has many desirable properties, it sufiers from a proneness to pilling. it also suffers from poor dyeability sometimes so proncunced that even with carriers and/or accelerants dyeing is very slow. This slow dyeing limits the dyeing processes and types of blends which may be employed.
It is accordingly an object of the present invention to modify the properties of polyester filamentary material so as to render it more readily dyeable.
it is a further object of the invention to improve the pilling performance of polyester filamentary material.
()ther objects and advantages of the invention will be come apparent from the following detailed description and claims wherein all parts are by weight unless otherwise specified.
in accordance with one aspect of the invention a treating agent is applied to a tow of polyester filaments, advantageously as an aqueous solution although it may be undiluted or suspended or dissolved in other media.
For the purposes of this invention the expression polyester-treating agent is defined as follows: The substance being tested is dissolved to a 25% concentration in a volatile solvent which is inert to it and the polyethylene terephthalate, e.g., water or alcohol The solution is padded to a pick-up of 40%, i.e., an add-on of 10%, on a tow of 3 denier polyethylene terephthalate filaments of inherent viscosity of 0.64 (as determined at 25 C. at 0.1% concentration in 10/7 phenol/2,4,6-trichlorophenol) which were previously drawn at a ratio of 4.421 in steam and stabilized at 275 F. in relaxed condition. The padded tow is dried in air until the solvent content is less than 10% of the dry tow weight. The tow is placed on a metal plate at 450 F. and a second plate at 450 F. is placed on the tow. After 10 seconds the tow is removed from the plates and dyed for 1 hour at 200 F. in 100 times its weight of a 5% dispersion in water of Latyl Cerise B which is designated as Disperse Red 59 in Part I of the Second Edition of the Colour Index. The starting tow picks up about 0.3% of dye. If, after the treatment just described, the tow picks up at least 0.4% and preferably at least 0.6% by weight of dye, the test substance is a treating agent as employed herein.
In practicing the invention, the treating agent is preferably applied at about room temperature although higher or lower temperatures may be employed, elevated temperatures facilitating penetration into the individual fibers. Wetting agents may also be presenuif desired. Advantageously the application of treating agent and further processing thereof may be effected continuously directly following formation of the tow.
While treating agents such as lower alkyl phosphates, e.g., triethyl phosphate, improve the properties of the polyester, the treating agent is advantageously a hydroxylated organic compound, e.g., diacetone alcohol, diacetin (glycerine diacetate), monoethanolamine, alkylene glycol ethers such as butyl carbitol, and the like, and preferably a polyhydric alcohol such as a polyhydroxyalkyl amine or a polyalkylene glycol, or an ether or ester thereof, e.g., the mono hydrochloric acid ester of 9" polyethylene glycol having the formula H(C H O) Cl.
Advantageously the treating agent is of low volatility,
e.g., its boiling point at atmospheric pressure exceeds about 450 B, so that it will not be lost during subsequent drying, if effected, or during a subsequent heat treatment. For example, polyethylene glycol 600 (average molecular weight of 600), one of the preferred materials, has a boiling point well in excess of 450 F. In contrast, a related material, such as polyethylene glycol 200, is much more volatile and when used in a process operating at atmospheric pressure tends to volatilize to such an extent during high temperature heat treatment that little if any improvement is obtained. It will be understood that while it is most advantageous to carry out the heat treatment at atmospheric pressure, one may also use superatmospheric pressures which will retain more volatile agents, although the use of such pressures will increase the cost and difiiculty of treatment.
The tow advantageosuly comprises a bundle of more than about 100 continuous filaments and preferably more than about 50,000 filaments.
fully the process will be rendered less economical. The denier per filament may be 0.5 or less and may range upward to 50 or more. The polyester filamentary material comprises a linear polyester wherein the preponderance of polymer linkages are ester. While some or all of the monomeric units may be hydroxycarboxylic acids such as glycolic acid, preferably the monomeric units are dicarboxylic acids and dihydric alcohols. The dicarboxylic acids may be aliphatic and/or substituted but preferably they comprise aromatic dicarboxylic acids such as phthalic, isophthalic and especially terephthalic acid. A small proportion of sulfonic acid or other dyeattracting functional groups may be present, if desired. The dihydric alcohols of the polyesters are preferably lower alkylene glycols such as ethylene glycol although polyalkylene glycols or other dihydric alcohols such as dimethylal cyclohexane or the like may be employed. As with the dicarboxylic acid, the dihydric alcohol may contain dye-receptive functional groups. The inherent viscosity in filaments of the polyester as determined at 78 F. at 0.1% concentration, in 10/7 phenol/2,4,6-trichlorophenol advantageously exceeds about 0.3 and preferably exceeds about 0.6. The invention greatest advantage with polyesters which are diflicult to dye and suffer from pilling, e.g., polyethylene terephthalate having an intrinsic viscosity in excess of 0.6, and the invention will be further described with reference thereto.
The application to the tow of the treating agent is advantageously elfected by padding a continuously running tow although spraying, immersion, or-other techniques whidh ensure a substantially uniform deposit of the treating agent on the filament surfaces may also be employed. When the treating agent is a poly-hydroxyalkyl amine such as triethanolamine it is advantageously employed at a concentration in water of about 1 to 30% and preferably about 5 to 10% since higher concentrations do not result in proportionately greater improvement. It is applied to an add-on of about 0.5 to 100% and pref rably about 1 to 10% of triethanolarnine on polyester Weight. When the treating agent is applied as a solution the concentration and pick-up of solution by the tow will of course be adjusted to arrive at the desired ultimate add-on. a
When a polyalkylene glycol or an ether or ester thereof is used such as polyethylene glycol, advantageously it is employed at a concentration in water of about 5 to 80% and preferably about 10 to 30%. A concentration of about 20% of polyethylene glycol of molecular Weight 600 is especially useful since due to its low viscosity the pick- While bundles of feW' filaments and even monofilaments can be treated successshows its up of solution on weight of fiber is low while the improving action is high. The add-on of polyethylene glycol generally ranges from about 1 to 100% and preferably about 5 to of the polyester weight. The average molecular weight of the polyethylene glycol generally ranges from about 350 to 15,000 and preferably from about 500 to 1000 for maximum improvement and ease of processing. Other poly-lower alkylene glycols and their derivatives give comparable improvements.
The pH of the solution of treating agent may range from about-2 0t 12 or even more widely but preferably is approximately neutral, e.g., about 6 to 8.
7 If the tow is undrawn it is especially desirable that any water, or other solvent for the treating agent, which may be on the tow is removed, as by drying, prior to the heat treatment; the drying can be carried out before, after or simultaneously with a drawing operation. Even if the tow hasbeen drawn prior to application of aqueous treating agent it is desirable, though not essential, that it be dried plror to heat treament. Conveniently the drying is carried out continuously following padding. Advantageously drying is effected without tension, i.e., permitting free shrinkage. If the tow is undrawn advantageously drying is effected below about 250 F. using hot air rather than ahot contact surface. If the tow has not previously been drawn it should now be drawn, preferably under conditions which induce crystallization. The presence of the treating agent facilitates drawing.
In accordance with a preferred embodiment of the invention the tow is then subjected to heat treatment while under tension, preferably with all filaments under substantially equal tension. The tension should extend to all portions of the tow being heat treated as contrasted, for ex ample, with ordinary woven fabric in which tension applied at the fabric edges will not be transmitted to the center because of the weave. The use of tension surprisingly avoids coalescence between adjacent filaments which sometimes occurs during identical heat treatments but in the absence of tension. Thetension also prevents excessive loss of tenacity, production of material having nonuniform physical properties and excessive uncontrolled shrinkage with attendant denier increase. The tension can be just sufficient to prevent significant shrinkage or it can be if such magnitude as to produce drawing, e.g., to stretch the tow by about 1 to 40% and preferably by about 15 to 25%. For example, tow which was drawn prior to ap plication of treating agent may be permitted to shrink as much as about 5% during heat treatment; even when shrinking the tow is under considerable tension since it would shrink about if untensioned.
Best results are achieved when the tow is flattened out while being heat treated so that even though some filaments may overlap one another all are sufficiently close to the heating agent to be acted upon to the same degree, i.e., so that each filament is uniformly heat treated along its length and all are similarly treated. The flattening of the tow can be achieved by passing it between spaced pairs of rolls with little or no space between the rolls of each pair. It can also be effected by passage about a roll or curved plate. The heating agent may be hot air or a heated contact surface such as hot cans or a plate which also serves to'effect the tow flattening. Other ways in which heat treatment can be effected include passage through molten metal or. other inert fluid at suitable temperatures. Preferably, however, the heating agent comprises one or a pair of opposedhot plates spaced only a short distance from the running tow, heat transfer being effected primarily by radiation and somewhat by convection; this type of heat treating apparatus permits the shortest treatment time and allows he greatest amount of stretch and improvement in pillresistance for a given degree of improvement in dyeability.
The heat treatment is carried out for a time sufficient to bring the tow temperature to about 390 to 430 F.,
when working with the preferred treating agents. The temperature of the heat source will of course be somewhat higher, the exact temperature dilfcrential depending upon the time and type of heating. The time during which the tow temperature exceeds 390 F. should be as short as possible, e.g., less than a minute. When using spaced hot plates, for example, a dwell time of 5 seconds or less has proven sufficient. Excessive time and/ or temperature of the heat treatment may result in degradation, embrittlement and weakening of the filaments, and in coalescence of the filaments where they contact one another.
Following completion of the heat treatment the tow may be scoured or solvent-extracted to recover the treating agent or the agent may be left on. In either event the improved dyeability is not impaired. Subsequent setting treatments such as pleat setting or heat treatment will not reduce the dyeability of the product.
While not wishing to be bound thereby, it is believed that the individual fibers of the novel product are each made up of a network of crystalline regions in which network there are localized highly porous non-crystalline regions of lower density than the non-crystalline regions of a material treated identically except for the absence of treating agent. These non-crystalline regions of the novel product are more accessible to dyes. This structure is produced by having the treating agent present prior to and during crystallization. The treating agent is believed to solvate the polar sites for intermolecular attraction and thereby to permit greater mobility of the chain segments which may be responsible for easier and perhaps greater crystallization. As crystallization proceeds the treating agent is squeezed out of the crystalline regions into the non-crystalline or amorphous regions which are less dense especially in view of the localized high concentration of treating agent. This lower density is responsible for greater mobility of the non-crystalline sections of the molecules in the amorphous regions as evidenced by a reducton in the glass transition temperature of the product as compared with a water-treated control. This reduced density, or greater porosity, enhanced by the further increase in porosity when the treating agent is washed out as in scouring or dyeing, renders the filaments more accessible for inward diffusion of dye.
The polyethylene glycol, tension-heat treated product is characterized by a higher moisture regain than a oncedrawn tow which has not been treated with polyethylene glycol. As yet no chemical changes have been noted by infrared analysis nor have extraction tests indicated the presence of any free polyethylene glycol. A caustic or soda ash boil of the novel product produces a somewhat greater weight loss than similar boiling of other, convent1onal polyesters. The novel product is degraded to a somewhat greater extent by ultraviolet light than a control treated identically except that the pad liquor applied to the tow was water rather than aqueous polyethylene glycol, forexample.
The novel products are characterized by improved pilling resistance. For example, the product when blended 55/45 with wool, woven into a tropical worsted construction and sheared once exhibits a pilling rating of 4 (slight) on the Random Tumble Filling Tester (ASTMD1375). This improved pilllng resistance is believed due to the low loop toughness e.g. below about 0.4 and preferably below about 0.25 gram per denier. Nonetheless the filaments often have .a high (straight) tenacity, at least about 4 and preferably at least about 5 grams per denier, and a high (Straight) elongation, at least about 12%, and preferably at least about 15%. While some commercial polyesters also exhibit low loop toughness, this is usually accomplished only at sacrifice of straight properties. Loop toughness is one half the product of loop tenacity and loop elongation, measured on 3 denier sample at a gauge length of 1 inch and a rate of cross-head travel of 0.6 inch shrinkage in per minute. Whereas convention-a1 polyester filaments which have been highly drawn to develop high ten-acities generally tend to be dyeable only with difficul-ty employing a carrier or accelerant, the novel filaments in spite of their high tenacities are readily dyeable without accelerant or carrier which has little or no eifect on their dyeability. As employed herein, the expression readily dyeable has reference to the ability of the polyester to uniformly and deeply, rather than merely being ring dyed,- as can be determined by dyeing for 3 hours at 95 C. in a carrier-free bath containing 3% on fiber weight of Polyester Blue B.L.F. which has the formula OH (H) OH at a liquorratio of :11. Moreover, the abrasion resistance of the novelproducts compares favorably with conventional polyesters as contrasted with polyesters which have been modified otherwise than in accordance with the present invention to improve dyea'bility.
The invention will be further described in the following illustrative examples:
Example I A tow made up of 75,000 continuous filaments of polyethylene terephthalate averaging about 3 denier per fil, 4.6 grams tow having previously been stretched at a draw ratio of 4.41:1 while moving past a jet of steam at 220 F. and stabilized at 275 F, is run continuously at the rate of 50 feet per minute through a trough containing a 20% by Weight aqueous solution of polyethylene glycol (average molecular weight of 600) at room temperature. The tow is squeezed to a liquid pick up of based on its dry weight. The tow is run in relaxed condition through an oven where in 5 minutes it is dried by hot air at 300 F. to 9% add-on on the tow dry weight. If the treating agent is removed at this stage, as by washing with water or the like, the tow will behave as though never treated. Even if the treating agent is not washed off, the tow at this stage will dye just as though the treating agent had been added to a conventional dyebath, i.e., there may be a slight accelerant action but it will nowwhere approach the improvements produced by further treatment as set forth hereinafter.
Specifically, col is pulled through a hot air zone maintained at about 445 F. (a peak tow temperature of about 425 F.) the dwell time being 35 seconds. The rolls which feed the tow to the hot air zone are braked sufiicien-tly to allow only 3% the tow length. The tow is scoured at 180 F. with 0.5% aqueous solution of a non-ionic surface active agent such as Triton X 100, (an alkylaryl polyether alcohol) and dried on an apron at 250 As compared with the starting material, the tow processed as described retains its tenacity while its elongation is about halved. The loop physicals of the filaments are reduced from initial values of 4.1 grams per denier and 37% elongation to 2.9 grams per denier and 14% elongation; the modulus, however, is increased from 31 to grams per denier. Filaments produced identically, except that they are free to relax during heat treatment, increase 20% in denier, exhibit a tenacity of 1.84 grams per denier, an elongation of 28.6%, a modulus of 31.7 grams per denier, a loop tenacity of -1.7 grams per denier and a loop elongation of 25.3%. I
The novel tow isstufiing box crimped and cut into a loose mass of staple fibers whch are blended with wool to produce a /45 by weight polyester/wool yarn. No static problem is encountered with the polyester staple the dry tow carrying the polyethylene glybe dyed rapidly,
per denier tenacity and 45% elongation, the
about driven cans in flattened condition heat set since the fiber is already stabilized.)
fibers even without application of an anti-static agent.
The yarn is woven into a tropical worsted construction which is prepared for dyeing in conventional manner, e.g., by crabbing, scouring, carbonizing, dyeing, drying, shearing, pressing and decatizing. (The fabric need not be The fabric is dyed in a dye beck at 95 C. for 3 hours employing in a liquor ratio of 30:1 a bath containing 0.5 gram per liter of Tamol N (neutral sodium salt of a complex condensed aryl organic acid) as dispersing agent, 3% on fabric weight of Polyester Blue B.L.-F., 1% on fabric weight of C-ibalan Blue BL (1958 Colour Index No. 15075) and 3% on fabric weight of ammonium acetate. The fabric is rinsed in warm water, washed for 20 minutes at 140 F. with water containing 0.5 gram per liter of soap and 0.5 grant per liter of Tamol N, rinsed in warm water, rinsed in cold water, and dried. The fabric shrinks about 3% in dyeing, which is much less than a similar control fabric wherein the polyester fibers did not receive the polyethylene glycol and heat treatments. The fabric is uniformly dyed a dark blue with good wet-and lightfastness, with good resistance to dry-cleaning solvents and with good penetration as evidenced by uniform distribution or" the dye throughout the cross-section of the polyester fibers. The control fabric is dyed only a light shade, with the dye concentrated near he surface rather than throughout the polyester fiber; it is of poor wetand lightfastness. If the control fabric is dyed using an accelerant and a 3-bath system in an effort to approximate the advantages achieved by l-bath dyeing of this novel material, the
' Wool will be stained by polyester dye and dulled to a greater degree than in the novel fabric wherein the polyester fibers have so great an affinity for their dyes.
The pilli-ng resistance of the novel fabric after two shearings, as measured by the Random Tumble Pilling Tester (ASTM-D1375), is 2-3 units higher than the control fabric.
Example H Substantia'llyidentical results are achieved if 'Example I is repeated with the sole difference being that the heat treatment is effected by passing the tow over a series of hot cans heated internally to produce a surfa'cetemperature of about 450 F., the duration of treatment being 3, seconds.
Example 111 Polyethylene terephthalate having an intrinsicviscosity of 0.67 is melt spun at 285 C. in conventional manner to produce an undrawn tow of 35,000 total denier. The filaments are padded with 20% aqueous solution of polyethylene glycol 600 at F, expressed to a liquid pick up of 30% by weight and dried relaxed in loop form in a hot air oven at 180 F. for 10 minutes, whereupon they shrink about 15%. The filaments are then stretched by draw rolls at a 4.9:1 draw ratio, stretching being eir'ected while the filaments pass between a pair of spaced plates maintained at 250 F. T he plates are spaced sutficiently so that the filaments do not directly contact the plates; the speed of the tow is such that the residence time between the plates is 1.3 seconds. The tow is then drawn at a ratio of 1.31:1 between another pair of plates maintained at 450 F., the residence time or" the tow in this drawing'being 1.5 seconds. The tow is passed successively through two baths of water at 175 F. containing 0.5 by weightof Triton X to wash out the polyethylene glycol, dried and processed into crimped staple on the Pacific converter. grams per denier tenacity, 16.7% elongation, a modulus of 74 grams per denier, a loop tenacity of 2.19 grams per denier and a loop elongation of 8.7%; control filaments produced identically except for omission of the application of polyethylene. glycol and drying aver-age 5.58 grams per denier tenacity, 12.6% elongation, at modulus of 53.3 grams per denier, a loop tenacity of 3.44 grams per denier and a loop elongation of 11.6%. Following dyeing with 1,S-dihydroxy-4-phenylamino-5-nitro anthraquinone the product possesses substantially the same properties as that of Example I.
Example IV Somewhat similar improvements are achieved if in the process of Example 111 the polyethylene glycol solution is replaced by:
(a) A aqueous solution of triethanolamine, the tow being padded to a liquid pick-up of 25%;
(b) A aqueous solution of polypropylene glycol 425, the tow being padded to a liquid pick-up of 33%;
(c) A 20% aqueous solution of polyethylene glycol chloride 210 (approximately H(C H O)4Cl), the tow being padded to a liquid pick-up of 33 (d) A 20% aqueous solution of polyethylene glycol chloride 610 (approximately H(C H O) Cl), the tow being padded to a liquid pick-up of 33%;
(e) A 20% aqueous solution of diacetin, the tow being padded to a liquid pick-up of 30%;
(f) A aqueous solution of diacetone alcohol, the tow being padded :to a liquid pick-up of or (g) A 25% aqueous solution of triethyl phosphate, the tow being padded to a liquid pick-up of 30%.
Example V A 175 filament tow produced and padded as in Example III is drawn at a ratio of 5:1 at 250 F. using a pair of spaced hot plates, the drawing temperature drying the tow. The tow is then drawn at a ratio of 1.321 with a residence time of 1.52 seconds between spaced plates at 450 F. surface temperature. The tow is then broken into staple length fibers to produce a sliver which is stufi'ing box crimped.
Example VI A commercial polyethylene terephthala-te tow which has been drawn in steam at a draw ratio of about 5:1 to a tenacity of about 5 grams per denier and then stabilized in relaxed condition at 275 F. is padded with a 20% aqueous solution of polyethylene glycol 600 to a pick-up of about dried for 3 minutes at 320 F. while relaxed, limited to about 3% shrinkage while held for 3 seconds between spaced plates maintained at 450 F., cooled and processed into sliver on the Pacific converter.
It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of our invention.
Having described our invention what we desire to secure by Letters Patent is:
1. The processe which comprises heat treating under tension a tow of polyester filaments carrying substantially uniformly on the surfaces thereof a member selected from the group consisting of a polyalkylene glycol, an ether of a polyalkylene glycol, an ester of a polyalkylene glycol, an ether of an alkylene glycol, diacetone alcohol, diacetin, an alkanol-amine and a lower alkyl phosphate.
2. The process which comprises impregnating a polyester tow with an aqueous solution of a member selected from the group consisting of a polyalkylene glycol, an ether of a polyalkylene glycol, an ester of a polyalkylene glycol, an ether of an alkylene glycol, diacetone alcohol, diacetin, an alkanolamine and a lower alkyl phosphate, drying said tow and heat treating said tow above 390 F. while placed under tension at least sufficient to prevent shrinkage from going above 5%.
3. The process set forth in claim 2, wherein said solution comprises about 5 to 80% polyethylene glycol.
4. The process set forth in claim 2, wherein said solution comprises about 1 to 30% tniethanolamine.
5. The process set forth in claim 2, wherein the heat treatment is effected at a temperature of about 390 to 430 F. with the tow above 390 F. for less than about 1 minute.
a polyester tow with a 5 to solution of polyethylene glycol in water to an add-on of about 1 to 100% of the dry weight of the tow, the polyethylene glycol having an average molecular weight of about 350 to 15,000, drying the tow and heat treating the tow while under tension to a temperature of about 390 to 430 F. with the tow above 390 F. for less than about 1 minute.
10. The process which comprises crystallizing under tension a tow of polyester filaments carrying substantially uniformly on the surfaces thereof at least about 1% by weight of polyethylene glycol.
11. A polyester tow carrying substantially uniformly on the filament surfaces at least about 0.5% by weight of triethanolamine.
12. A polyester tow carrying substantially uniformly on the filament surfaces at least about 1% by weight of polyethylene glycol having an average molecular weight of about 350 to 15,000.
1 3. A bundle of polyester filaments made up of a network of crystalline reg-ions in which network there are localized highly porous non-crystalline regions of lower density than said crystalline regions, said filaments being resistant to pilling and readily dyeable as indicated by the'ability to be dyed rapidly, uniformly and deeply rather then merely ring dyed after they are dyed for 3 hours at C. in a carrier-free bath containing 3% on fiber weight of a dye having the formula II I N05 0 NHCsI'Is at a liquor ratio of 30:1.
14. A loose mass of readily dyeable, pilling-resistant polyester staple fibers each made up of a network of crystalline regions in which network there are localized highly porous non-crystalline regions of lower density than said crystalline regions, said filaments being readily dyeable and resistant to pilling.
15. Polyester filamentary material having a loop toughness of less than about 0.4 gram per denier, a straight tenacity of at least about 4 grams per denier and a straight elongation of at least about 12%.
16. Readily dyeable polyethylene terephthalate filamentary material having a loop toughness of less than about 0.25 gram per denier, a straight tenacity of at least about 4 grams per denier and a straight elongation of at least 12%.
17. A process comprising forming the product of claim 2 into a fabric and dyeing said fabric.
18. The process which comprises continuously flattening a tow of more than polyester filaments, placing said tow under tension sufiicient to prevent shrinkage of the filaments from going above 5%, and heat treating said tow at a temperature above 390 F. while it is under said tension in said flattened condition, said filaments carrying substantially uniformly on the surfaces thereof a treating agent having a boiling point at atmospheric pressure whichexceeds about 450 F. and selected from the group consisting of a polyalkylene glycol, an ether of a polyalkylene glycol, an ester of a polyalkylene glycol, an ether of an alkylene glycol, diacetone alcohol, diacetin, an alkanolamine and a lower alkyl phosphate.
(References on following page) References Cited by the Examiner UNITED STATES PATENTS Shivers. Meckienburgh et a1. Sbiggel. Hermes.
Salem et a1.