Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
  • D01F6/02—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D01F6/18—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds from polymers of unsaturated nitriles, e.g. polyacrylonitrile, polyvinylidene cyanide

Definitions

• acrylic fiber when used herein, means a fiber in which the fiber-forming substance is any long chain synthetic polymer composed of at least 35% by weight of acrylonitrile units
• fiber includes fibers of extreme or indefinite length (filaments) and fibers of short length (staple).
• yarn as used herein, means a strand of fibers and the term “tow” means a large strand of fibers without definite twist collected in loose rope-like form, usually held together by crimp. Tow is the form which most fiber reaches before being converted (e.g. cut) into staple.
• Acrylic fibers have the appearance and feel of wool and therefore, are widely used in socks where wool-like appearance and feel are important.
• commercially available acrylic fibers lack the level of flex fatigue and abrasion resistance properties that is required to provide socks having truly significant wear performance properties, for example, socks knitted from commercially available acrylic fibers tend to abrade (develop holes) in the toe and heel regions thereof within a relatively short period of time.
• This deficiency of acrylic fibers has been long recognized and much effort has been expended on the part of acrylic fiber producers to improve the flex fatigue and abrasion resistance properties of acrylic fibers.
• U.S. patent 3,932,577 This approach relates to the wet spinning of acrylic fibers and consists of adding a small amount of water (1 to 8%) to the spinning solutions used to prepare the fibers. Although this approach provides some improvement in abrasion resistance, there is still room for further improvement.
• acrylic fibers are provided that have superior abrasion resistance and flex fatigue properties.
• the fibers also have other desirable properties which in combination with their superior abrasion resistance and flex fatigue properties make the fibers particularly suitable and useful for commercial applications in fabrics where wear performance properties are important, such as socks, upholstery, and the like.
• the fibers are characterized in having a mercury density of greater than 1.0 gm/cc and an average flex fatigue parameter value (hereinafter defined) of at least -0.60 and, preferably, at least -0.40 and, more preferably, at least -0.30 and, most preferably, at least -0.11.
• the fibers also have a tenacity of at least 1.75 gpd and an average knot strength of at least 85% of the tenacity.
• Acrylic fibers having a mercury density (measured at atmospheric pressure) of 1.0 gm/cc or less inherently have voids which yield generally undesirable properties, such as lack of luster and dye uniformity.
• the fibers of this invention are particularly useful for sock and home furnishing end use applications where abrasion resistance and flex fatigue properties are important.
• acrylic fibers in yarn or tow form are converted into staple length fibers which in turn are converted into staple yarn for end use applications.
• Flex fatigue parameter values are determined by the Satec Test (hereinafter described in detail) using a Satec Tester machine made by the Satec Corporation, Grove City, Pennsylvania. Briefly, in conducting the test, a single fiber is pulled back and forth over a sharp blade until the fiber breaks (fails). One back and forth movement is a cycle. The cylces to fail (CTF) value is recorded along with the denier (d) value of the fiber and the aspect ratio (AR) value of the cross-section of the fiber. A plurality of fibers selected at random from a sample of fibers are tested.
• CTF cylces to fail
• the average flex fatigue parameter value is obtained by determining the FFP value for a plurality of samples selected at random.
• the aspect ratio is the ratio of the width of the fiber cross-section (x-axis) to the height of the fiber cross-section (y-axis) with the measurements being made where the width and the height are maximum values.
• the acrylic fibers of this invention may be prepared by a wet-spinning process comprising: (1) extruding a solution (dope) of an acrylic polymer in dimethylformamide (DMF) through a spinnerette nozzle immersed in an aqueous DMF coagulation bath (i.e. spinbath) maintained at temperatures between 10° and 90°C.
• a solution i.e. spinbath
• aqueous DMF coagulation bath i.e. spinbath
• the conditions under which the process is conducted are correlated to provide fibers having an average flex fatigue parameter value of at least - 0.6, a tenacity of at least 1.75 gpd and a knot strength corresponding to at least 85% of its tenacity.
• the spinbath is maintained at a temperature ranging from about 25 to 40°C.
• the temperature is reduced from about 25°C. or increased above about 40°C.
• the average flex fatigue parameter value of the resulting fibers tend to fall off.
• the spinning of the dope into filaments becomes a problem.
• the concentration of DMF in the spinbath be in the range of from 72% to 84%, by weight.
• DMF concentrations below about 72% the FFP values are low and fibers tend to break in the spinbath and at concentrations above about 84%, the fibers tend to fuse to one another in the spinbath. Filaments that are fused to one another ("married") snag on equipment during conversion of the fibers into staple, the processing of the staple into yarns and the knitting of such yarns into socks and other fabric.
• the filaments are dried by passing the tow under tension with a plurality of wraps over two or more heated rolls, the rolls being heated internally with steam to a surface temperature of about 150°C.
• the filaments in passing over the rolls change from an opaque (dull), uncollapsed filaments having a mercury density of less then 1.0 gm/cc to lusterous collapsed filaments having a mercury density greater than one and typically greater than 1.15 gm/cc.
• the uncollapsed filaments have pockets (voids in the polymer structure) filled with water or water and DMF. As the tow passes over the rolls, it becomes heated, water in the form of vapor is forced from the filaments and the filaments assume a collapsed structure.
• the collapsed filaments have a greater density than the uncollapsed filaments. Uncollapsed filaments lack dye uniformity due to voids and are more difficult to process, also due to the voids, than are the collapsed filaments.
• the dried collapsed filaments in tow form are then crimped, for example, by first passing the tow into contact with steam to preheat the tow and then passing the tow through a conventional stuffer box crimper using pressurized steam as the jetting fluid. The crimped tow is then piddled into a can. The tow then is preferably annealed by heating the tow in saturated steam at a temperature within 25°C.
• the tow after being stretched in boiling water is presteamed, crimped in a stuffer box and then dried, for example on a moving belt using superheated steam.
• the tow is dyed inline, neutralized and washed after being stretched in boiling water and prior to being presteamed.
• the acrylic fibers of the present invention are composed of a fiber-forming copolymer formed by reacting acrylonitrile with one or more vinyl monomers copolymerizable therewith.
• vinyl monomers are well-known in the art and include by way of example vinyl acetate, vinylpyridine, methylvinylpyridine, vinyl chloride, vinylidene chloride, methacrylate, methyl methacrylate, vinyl bromide, styrene and sodium sulphophenyl methallyl ether.
• the copolymer is composed from 85% to 98% by weight of acrylonitrile units (i.e. units).
• the processing conditions and acrylic polymers are selected to provide fibers having an average flex fatigue parameter value of at least -0.40 and, more preferably, -0.30, and most preferably, at least -0.11, tenacities of at least 2.0 gpd (e.g. in the 2.0 to 3.0 gpd range), knot strengths of at least 90% of their tenacities, a dye diffusion rate greater than 0.3 cm2/sec., and an elongation of at least about 25% and, preferably, in the range of 35% to 60%.
• Fibers of this invention prepared by the above wet-spinning process contain from 0.001 to 1.0% by weight of DMF.
• Fibers of this invention may be of any desired cross-section.
• the fibers will usually have a denier ranging from 1.5 to 4.0 and typically ranging from 2.0 to 3.0.
• Tows wet-spun in accordance with the above process are characterized in having substantially no married fibers.
• Flex fatigue parameter values and average flex fatigue parameter values are determined using a Satec Flex Tester machine.
• the machine has ten test stations.
• a single fiber (referred to as a "fiber specimen") is tested at each of the ten stations.
• a blade bar holds ten individual blades in a vertical position with the sharp edge of the blades pointed upwardly. Each edge is perpendicular to a post on a reciprocating arm of the tester.
• one end of the fiber is attached by means of a tab to the post and the other end is attached by means of a second tab to a test weight selected in accordance with the denier of the fiber specimen.
• the fiber specimen extends horizontally from the tab attached to the post over the blade edge associated therewith and then vertically down the back of the blade edge to the tab to which the weight is attached.
• the reciprocal arm moves back and forth approximately 2 cm. One cycle consists of one back and forth movement.
• a counter is associated with each station. When a fiber specimen fails (breaks) the test weight is caught in a split copper cup and completes a circuit to shut off the counter associated with that station.
• the fiber specimens are prepared as follows:
• Either of two blades may be used in conducting the test.
• a different set of weights is used with each blade.
• the specification for the blades and weights are as follows:
• Blade No. 1 was made by Satec Corporation and Blade No. 2 was made by Valenite Corporation, 3100 Stephenson Highway, Madison Heights, Michigan 48071, under the designation Grade VC2, No. BJ, Style SPC 322. These blades or equivalent blades may be used in conducting the test.
• the radius of curvature given above for each type of blade represents the average of the radius of curvatures of the ten blades on the machine during testing. If the average radius of curvature is different from that specified above, one or more of the blades must be replaced with different blades so as to attain the specified average.
• the averaged (CTF) value for the thirty fiber specimens is multiplied by 1.8398 before calculation of the flex fatigue parameter (FFP).
• the average flex fatigue parameter value is the average of the flex fatigue parameter values of fifteen fiber samples, each determined as described above, where the fifteen fiber samples are selected at random.
• the above formula defines a straight line having a y-axis intercept when x is zero corresponding to FFP, where in the formula y is "1n (CTF)" and x is 7(AR 0.73 /dpf) 0.5 .
• y is "1n (CTF)"
• x is 7(AR 0.73 /dpf) 0.5 .
• All fibers of the invention described in the examples are collapsed fibers having a mercury density greater than 1.0g/cc.
• percentages are weight percentages except in those instances where the shrinkage or elongation of a fiber is given. In those instances, percentages represent changes in the length of the fibers.
• This example illustrates the preparation of acrylic fibers of the present invention and also the effect of varying the spinbath temperature on the tensile properties and flex fatigue parameter values of such fibers.
• a spinning dope (25% polymer) was prepared by dissolving a 50/50 mixture of 2500 g of an acrylic polymer (I) containing 92.5% acrylonitrile (AN) and 7.5% vinyl acetate (VA) and 2500 g of an acrylic polymer (II) containing 92.1% AN and 7.3% VA and .6% of sodium sulfophenyl methally ether (SPME) in 15,000 g of dimethyl formamide (DMF).
• a 1000 hole spinneret was used; the spinneret had ellipitcal spinneret capillaries (2/1 ellipse) with a cross-sectional area corresponding to that occupied by a round capillary with a 3.109 mil (0.079 mm) diameter.
• the dope was extruded through this spinneret at a 100°C dope temperature into a spinbath containing a DMF/water mixture of 78% DMF at a temperature ranging from 25 to 40°C.
• the resulting fiber bundle was withdrawn from the spinbath at a linear speed of 20 fpm (6.1 mpm) with a theroretical jet stretch of 0.9x by a first set of rolls, washed on these rolls, then stretched 6x in boiling water (cascade stretch) between the first and second set of rolls, washed thoroughly on the second set of rolls, then dried after application of finish on a set of drying rolls heated to 150°C.
• the fiber bundle was wound up on a winder bobbin at a spinning speed of 120 fpm (36.6 mpm).
• the fiber bundle was then annealed in pressurized steam at a pressure of 35 psi and an annealing shrinkage of about 30%.
• the resulting annealed fibers had the following tensile properties:
• the fiber samples of the invention had dye half-times of less than 10 minutes, whereas that for Orlon 42 was more than 50 minutes.
• This example illustrates the effect of using different annealing pressures/shrinkages and different annealing methods on tensile properties and flex fatigue parameter values of fibers of this invention.
• a dope was prepared and spun as described in Example I.
• the spinneret used had 1000 spinneret capillaries of a dogbone shape (aspect ratio: 2.5) with a cross-sectional area equivalent to a 3.25 mil (0.083 mm) diameter round hole.
• Two of the samples were conventionally annealed to 30 and 20% annealing shrinkage, respectively.
• the third sample was prepared by collecting the fibers bundle after the wet stretch, but before the drying step, and then drying/annealing the fiber bundle by subjecting it to dry air at 140°C for 30. min.
• This example illustrates the results obtainable from a different polymer blend and through the use of atmospheric pressure super-heated steam (SHS) as a means of annealing.
• SHS atmospheric pressure super-heated steam
• a 25% polymer dope was prepared in DMF from a 98.2/1.8 blend of acrylic polymer I and a copolymer containing 68% acrylonitrile, 25.4% styrene, and 16.6% sodium styrene sulfonate.
• the dope was spun similar to Example I through a 1000 hole spinneret with dogbone shaped spinneret capillaries (aspect ratio: 3.5) of a cross-sectional area equivalent to a 3.79 mil diameter round hole.
• the fibers were spun with a 1.45 theoretical jet stretch in a spinbath of 78% DMF/22% water at 30°C.
• the resulting fibers had the following properties after pressurized steam annealing (34psi, 28% annealing shrinkage):
• a 25% polymer dope was prepared in DMF from an acrylic copolymer (polymer III) containing 93.5% AN 6.2% VA and .3% SPME.
• the dope was spun similar to Example I with a jet stretch of 1.92 through a 1000 hole spinneret with capillaries shaped like a rectangle, capped at both ends with semicircles, having an aspect ratio of 3.0 and a cross-sectional area equivalent to that of a 4.7 mil (0.119 mm) diameter round hole.
• the fiber samples had the following properties:
• a fiber spun and annealed similarly to sample 2 had a knot tenacity of 2.5 g/den, a 98% retention of straight tenacity, and a knot elongation of 43.1%, a 95% retention.
• This example illustrates the effect of using DMF versus that of using dimethyacetamide (DMAc) on the tensile properties and FFP values of wet spun acrylic fibers.
• DMAc dimethyacetamide
• This example demonstrates the advantage of using DMF at high concentrations in the spinbath. (60% is typical of conventional acrylic wet-spinning operations.
• a dope was prepared from a 50/50 blend of polymers I and II in DMF. Fiber samples were spun and annealed as in Example I. Spinbath temperature for samples 1-2: 35°C, 3-4: 25°C. Results obtained are given in Table 6.
• This example illustrates that a fiber sample spun into high concentrations of DMF in the spinbath has high flex fatigue/abrasion properties even without being annealed.
• a 25% polymer dope of acrylic polymer I was spun through a 1000 hole spinneret with spinneret capillaries as described in example IV into a 80% DMF spinbath at 25°C; the dope contained 2% water.
• the resulting filament bundle was subjected to 1.73x jet stretch, a 6x wet stretch and a subsequent relaxation of 13% in boiling water before being dried on rolls in a conventional manner.
• the filament bundle was crimped in a stuffer box crimper.
• the crimped fibers had the following properties:
• the crimped fiber had the following Satec properties:
• the tow obtained was converted to spun yarn by use of the Seydel stretch breaking process followed by conventional yarn spinning.
• the yarn was converted to crew socks which were subjected to a wear test using a 180 member test panel; socks made from Orlon 42 and Acrilan S-16 yarns were included in the wear test as controls.
• the following results were obtained on the annealed filaments before conversion to spun yarn:
• the invention sample and Orlon 42 had dye half-times of 9.3 and 39.1 minutes, respectively.
• This example shows the effect of using a high concentration of dimethylacetamide (DMAc) instead of DMF in the coagulation bath on the processability and tensile properties of the resulting tow.
• DMAc dimethylacetamide
• Example 2 Two tows consisting of 32,000 fibers were prepared as described in Example 1, except one tow (Control) was prepared utilizing a coagulation bath consisting of 78% DMAc/22% H2O and the other tow (Invention) was prepared utilizing a coagulation bath consisting of 75% DMF/25% H2O.
• the spinning performance of each tow was observed.
• the tow coagulated using DMF as the solvent was substantially free from married fibers, whereas the tow coagulated in DMAc contained numerous married fibers.
• Mercury density of the fibers is measured by immersing a dry weighed sample of the fibers in mercury in a pycnometer of known volume.
• the volume of mercury displaced by the sample (equal to the sample volume) is calculated from : the density of mercury, the weight of mercury and pycnometer, and the weight of the pycnometer with mercury and sample. Then the "mercury density" of the sample is calculated as the ratio of the sample weight to the sample volume.

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• Health & Medical Sciences (AREA)
• Toxicology (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Artificial Filaments (AREA)
• Socks And Pantyhose (AREA)
• Yarns And Mechanical Finishing Of Yarns Or Ropes (AREA)

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• 1987
  • 1987-04-02 JP JP8219987A patent/JPS62238813A/ja active Pending
  • 1987-04-02 EP EP87870043A patent/EP0244388A3/fr not_active Withdrawn
  • 1987-04-02 CA CA000533736A patent/CA1286071C/fr not_active Expired - Lifetime

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