FI80078B - NEW SYNTHETIC DISPENSERS OF FIBER. - Google Patents

Abstract

Water-dispersible polyester fiber of cruciform cross-section to promote dispersibility, and so better uniformity, more opacity, good permeability and an attractive flannel-like hand to the resulting wet-laid fabrics.

Description

! 80078

TECHNICAL FIELD This invention relates to a novel water-dispersible synthetic polymeric fiber, in particular poly (ethylene terephthalate) fiber, and its manufacture.

Background of the invention

In recent years, there has been a growing interest in water-dispersible, synthetic fibers, especially poly-10 polyester. Such water-dispersible fiber is used in a variety of nonwoven applications, including papermaking and wet-laid nonwovens, sometimes as part of a blend, often in combination with large amounts of wood pulp or fiberglass, but also in applications requiring only polyester fiber, i. unmixed with other fibers. This use, and its requirements, are completely different from the previous, more conventional use as tow or staple fiber for textile yarns, which yarns are eventually used in woven or knitted fabrics, due to the need to disperse this fiber in water instead of turning it into yarns, e.g. , e.g., in a wood-wool system. This requirement for water dispersibility is the requirement that distinguishes the subject matter of the invention from prior art, more conventional polyester staple fibers.

Most such water-dispersible polyester fibers are poly (ethylene terephthalate) and are made essentially in the same general manner as conventional polyester staple fibers, except that most water-dispersible fibers are not crimped, while any polyester staple fiber intended for use in textiles is in the form of a tow, before being converted into staple fiber. Thus, water-dispersible fibers are generally made by melt-spinning polyester filaments, combining the filaments into 2,878 tows, drawing, adding a suitable coating to improve water-dispersing properties, generally in the same manner as coating is added with conventional textile filaments or then, usually without air. slightly wavy in some cases to provide additional volume and a three-dimensional matrix), by converting the tow to staple fiber. Some prior polyester fibers have been made in a non-crimped form (e.g., for use in dummies) in chicken lint fabrics, but water dispersibility is not necessary for such use.

Polyester fibers are inherently hydrophobic, so it is necessary to apply a coating suitable for polyester, as disclosed in U.S. Patent No. 15,400,083 to Ring et al., U.S. Patent Nos. 4,137,181, 4,179,543, and 4,294 to Hawkins. 883 and Viscose Suisse GB Patent No. 958,350 to overcome the inherent hydrophobic nature of the polyester fiber without generating foam or causing the fibers to flocculate. This coating 20 distinguishes the water-dispersible polyester fiber from conventional polyester staple fiber, more than any characteristic of the polyester itself or its shape, such as cross-sectional area. To date, as is known, the cross-section of all commercial water-dispersible polyester fibers has been circular. In particular, the cross-section of several commercial polyester staple fibers has generally been round, as this has been advantageous.

Although, to date, most synthetic, polymeric, water-dispersible fibers have been formed from polyester, which is preferred and widely available, increasing amounts of polyolefins and polyamides have begun to be used in water-dispersible fibers, so the invention is not limited to polyesters but includes other synthetic polymers.

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SUMMARY OF THE INVENTION

The invention relates to a synthetic polymeric fiber, in particular a polyester fiber and in particular to a poly (ethylene tephthalate) fiber, which is made water-dispersible by a coating which promotes water-dispersibility.

The polymer fiber according to the invention is characterized in that the cross-section of the fibers is cross-shaped.

The cross-shaped cross-section has heretofore been used in other polyester fibers, as described herein. With the exception of the cross-section, the water-dispersible fiber of the invention may be approximately similar to prior water-dispersible polyester or other synthetic polymeric fibers, although the advantages described below may allow for additional applications. The invention is described below with particular reference to polyester fiber, although it should be noted that other synthetic polymers such as polyamides and polyolefins may also be used.

The fibers of the invention can be conventionally prepared by melt spinning and drawing filaments of suitable denier and applying a suitable coating to them to improve the water dispersion properties. The filaments are then generally cut into staple fibers of the desired length according to the intended end use.

The use of a cross-sectional area in the water-dispersible fibers of the invention has surprisingly been found to promote dispersibility when compared to a circular cross-section, and this improves the uniformity of the resulting wet-webed fibers, such as opaque, good permeability and pleasant permeability.

Brief description of the drawings

Figure 1 shows a cross-shaped cross-section with a stylized fiber according to the invention.

Figure 2 shows a typical spinneret nozzle for spinning filaments according to the invention.

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Description of the invention

As discussed above, the cross-shaped cross-section has already been used in more conventional polyester staple fibers spun into filaments and drawn, cut, converted into spun yarn, and used in woven or knitted fabrics. Such fibers did not have the water-dispersible properties required by this invention. Accordingly, cross-sectional polyester filaments are already known from Lehmicken 10 U.S. Patent No. 2,945,739, which discloses a process for melt-spinning polyamide and polyester filaments having, inter alia, a cross-sectional surface, and a method for woven and knitted fabrics of U.S. staple fibers. U.S. Patent No. 15,324,669, which discloses a method of making a multifilament yarn from polyester filaments having a different cross-section, including a cross-shaped cross-section. Oriented polyester filaments having a non-circular cross-section are described in Frankfort et al., U.S. Patent Nos. 4,134,882 and 4,195,051, prepared by spinning at a very high speed (6000 μm, 5684 m / min), such as high speeds could be used to make oriented, cross-sectional polyester filaments as a substrate to which a suitable coating is applied to improve the water dispersion properties, and thus a water-dispersible fiber according to the invention is obtained. Nothing in this field relates to the scope of the present invention. However, filamentary polyester substrates for making the water-dispersible fiber of the invention 30 can be prepared by the methods described therein or their suitable applications or by other known methods for making non-circular polyester filaments.

Previous references in the art show parameters 35 for a cross-shaped cross-section, and Figure 1 is substantially as shown therein.

The manufacture of polyester staple fiber is otherwise conventional, including melt spinning of the polymer into filaments, spinning of the filaments into tow, drawing of the tow, and application of a suitable coating to improve water dispersion properties. If slight shrinkage is desired, the drawn filaments are usually polished.

The choice of a suitable coating is important to improve water dispersibility, and in general such a pin-10 weave is required more than corresponding masses of fiber having a circular cross-section and the same dpf (denier filament) due to the large surface area surrounding the cross-shaped cross-section. It is especially important to achieve good lubrication properties of the interfaces. Therefore, an ethoxylated coating is preferred.

Suitable coatings are disclosed in Hawkins U.S. Patent Nos. 4,137,181, 4,179,543 and 4,294,884 and also in related U.S. Patent Application No. 721,334, which is incorporated herein by reference in the names of Issum and Schlu-20 ter. disclosing a synthetic copolyester of poly (ethylene terephthalate) units and groups derived from poly (oxyalkylene) poly (oxyalkylene) glycol having an average molecular weight of 300-6000, as disclosed, e.g., in McIntyren et al. U.S. Patent Nos. 3,416,952, 3,557,039 and 3,619,269; other useful block copolyesters are disclosed in Raynolds U.S. Patent 3,981,807; all of these publications are incorporated herein by reference.

Such a polyester fiber is generally made in the form of a continuous, filamentous, non-curled tow, or if a particularly large volume is required, and a more three-dimensional matrix, the filaments can be made slightly wavy by a mild, crimped process, and uncurled or slightly curled, filaments are cut. to form a water-dispersible fiber 6,80078, which fiber is generally sold in bales or other staple fiber packages. Suitable cutting lengths are generally about 5 to 90 mm (1/4 to 3 inches), usually up to 60 mm (2 to 1/2 inch) 5 and the length / diameter (L / D) ratio is about 150: 1. 2000: 1, being an advantage of the invention, that good properties have been achieved with the preferred water-dispersible fiber of the invention having a higher L / D ratio than has been found satisfactory with previous water-dispersed wool fibers. For example, machine manufacturers have generally recommended that the L / D ratio should not exceed 500: 1, and many users have even considered this figure to be unrealistically high. A suitable denier per filament is generally about 0.520. The coating is generally present at about 0.04-1.0% by weight of the fiber (0WF%), which is an advantage if smaller amounts can generally be used compared to those previously considered satisfactory.

The invention relates to a process for producing a polyester fiber 20 made water-dispersible by a water-dispersible coating, melt-spinning the polyester into filaments, drawing a tow and cutting the filaments to produce water-dispersible polyester fibers.

The process according to the invention is characterized in that the polyester is melt-spun into cross-sectional filaments, that the filaments are coated with a segmented synthetic copolyester consisting of repeating units of poly (ethylene terephthalate) and poly (oxyalkylene) oxyalkylene) glycol having an average molecular weight of 300-6000 and that the coated filaments are cut into a fiber having a cut length of about 5-90 mm.

35 The coating is cured on the surface of the filaments

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7,80078 by heating the coated filament, or the resulting staple fibers, if desired, to a temperature of about 100-190 ° C to improve durability.

The invention is further described in the following Example 5, in which all parts and percentages are by weight unless otherwise indicated and the OWF is calculated by "fiber mass" (solid). Reference is made to various measurements of wire properties, such as elongation properties (strength and elongation at break), which are measured by the methods described in U.S. Patent No. 4,134,882 to Frankfort et al. It will be appreciated that other conditions may be used, e.g., otherwise designed nozzles, as disclosed in the art.

Example 15 The following fibers, fiber A, a comparison of a circular cross-section, and fiber N, a cross-sectional fiber of the invention, were both spun from poly (ethylene terephthalate) having an intrinsic viscosity of 0.64 and containing 0.3% TiO 2: a dimmer.

Fiber A was spun at 1600 rpm (1462.4 m / min) into strands by conventional radial air quenching using a 900 hole spinner with round holes 0.015 inches (0.381 mm) in diameter and 0.030 inches (0.762 mm) in capillary thickness. At 270 ° C Blok-25, and the polymer throughput was 68.2 pounds / hour (about 30.96 kg / hour). The Denier number per filament was 3.67. Fiber A was then directed by passing through feed drums at 29.3 ypm (26.78 m / min), followed by a series of traction drums at 80.1 ypm (73.12 30 m / min) and conveyed by a conveyor belt with extraction drums at 80.1 ypm. (73.21 m / min). Between the feed drum sections, the filaments were treated at 45 ° C in a water bath. Between the feed and traction drums, the rope was sprayed with 98eC water. Between the draw and pull drums Levi-35 tetiln commercial water-dispersible coating (50/50 e 80078 mixture: potassium salt / tallow alcohol of lauryl alcohol mono- and diacid phosphate esters ethoxylated with 25 moles of ethylene oxide). The filaments were then released in an oven at 150 ° C for 6 minutes.

Fiber N was prepared in the same manner as fiber A, except that 625 filaments with a denier per filament of 3.22 dpf and a cross-sectional area were spun through capillaries as shown in Figure 2 at a block temperature of 273 ° C. and a through-going of 42.9 pounds / hour (19.48 kg / hour). Drum speeds in the trend were: feed drums, 32.1 ypm (39.34 m / min); 80.2 ypm (73.30 m / min) and 79.2 ypm (72.39 m / min), and a somewhat higher concentration of water-dispersible coating was used for approximately 57% of the cross-sectional area. to level the playing field.

The properties of the drawn, coated filaments are compared in Table 1.

table 1

20 sample A N

cross section round cross-shaped dpf 1.47 1.56 coatings 0WF (%) 0.4 0.44 boiling shrinkage (%) 1.0 0 25 dry heat shrinkage (196 ° C) (%) 2.45 3.6 tensile strength (g / d ) 4.5 4.8 Elongation at break (%) 42 26 Strength at 2% elongation (g / d) 0.93 0.93 30 Both types were cut to form water-dispersible fibers with a length of 1/4, 3 / 8, 1/2 and 3/4 inches (6.35 mm, 8.53 mm, 12.7 mm and 19.05 mm) and were tested on a Fourdrinier inclined wire. The fibers were dispersed for three minutes in a small pulp-35 mixer with a composition of 0.75% (kg of fiber per 100 kg of 9,80078 slurry or mixture in the mixer. The cylindrical pulp mixer was about 3 feet (0.915 m) in diameter and 6 feet (1, 83 m) The fibers were then mixed with crushed sulphite pulp 5 to form a 50% polymer blend and diluted to 0.1% composition in a 10 m3 storage tank, this raw material was further diluted to 0.0143% composition at the front of the machine to form 0.5 m wide, wet laid nonwoven fabric at a speed of 20 m / min at a speed of No. 10. An acrylic binder spray, Acronyl 240 D, was applied by spraying on the rest of the wire of a Fourdrinier machine and then cured in a through-air dryer at 150 ° C: The finished fabric weighed an average of 40 g / m2.

The quality of the dispersion can be assessed on the basis of the uniformity of the fabric made from a given sample. As the cut length increases, it is expected that the integrity of the fabric will suffer significantly. However, the use of a long fiber can have great advantages as the shear strength of the fabric 20 increases, for example. In practice, because of this, the fabric manufacturer generally wants to use the longest fiber that meets uniformity standards. Thus, a longer fiber with better or equal uniformity would be preferred.

The dispersion quality of fabrics made of fibers A and N was evaluated during machine production by observing the fabrics when dewatering was performed with Fourdri-Nier fabrics. The results of this comparison are shown in Table 2 and show good dispersion for the cross-shaped product despite its 57% larger surface area.

Table 2 Description of dispersion

Cutting length Round product Cross-shaped product 35 1/4 inch (6.35 mm) good dispersion good dispersion 10 80078 little chip defects little chip defects 3/8 inch (9.53 mm) some chip defects- good dispersion and, overall quality good fabric cover not so good than (opaque-5 1/4 inch for sale) 1/2 inch (12.7 mm) fairly good dispersion- normal dispersion sio 3/4 inch (19.05 mm) dispersion rod- very good ti bad dispersion 10 cover low

Standard physical properties were measured for a variety of fabrics at the Herty Foundation, Savannah, GA. Compared to fiber A at 100%, the following average properties were obtained for fiber N 15: air permeability, Gurley 112% opacity, ISO 2471 111% bulk volume, TAPPI 7410 om-83 and T411 om-83 118% tensile strength, TAPPI T494 om-81 100% 20 tensile elongation, TAPPI T494 om-81 85% shear strength, TAPPI T414 om-82 104%

Overall, product N showed advantages in such important areas as high permeability, opacity, bulk and shear strength compared to the equivalent 25 tensile strength control with little reduction in elasticity. The coverage advantage is important because less fiber can be used for nonwovens with similar performance characteristics, thus saving on material costs. Fabrics made from product N also have a pleasant flannel-30 slimy contact.

By using a suitable water-dispersible coating in a suitable amount, a fabric having a cross-shaped cross-section of the invention has been obtained into a fabric with surprisingly good dispersion uniformity and the properties shown. 35 In a theoretical analysis, water-dispersible fibers with a conventional circular cross-section of 80078 could have been expected to give a more uniform dispersion, and therefore a more uniform wet-laid fabric. This is because the surface energy required to disperse the fiber (or other product) 5 is: energy = (surface tension) x (dispersed surface area-non-dispersed surface area).

The non-dispersed fiber occurs as interconnected logs or dumplings with many hundreds of fibers, most of which are within the Block. Therefore, the undispersed surface area is almost non-existent compared to the dispersed one, and the energy term can be expressed approximated: energy = (surface tension) x (number of fibers) x (fiber surface area).

15 This energy term describes both the energy required to disperse the fiber and the free energy that promotes re-agglomeration. Therefore, for any given coating and dpf of the fiber, fibers with a lower surface area could be expected to provide a more uniform dispersion and thus a more uniform fabric.

The minimum surface area per unit weight of a given fiber occurs when the cross-section is circular, which could therefore be expected to be advantageous.

Surprisingly, however, these cross-shaped fibers, in spite of about 60% larger surface area, gave more uniform fabrics. Without limiting the invention to any theories, this may be the result of a hydrodynamic form of the fiber that can more efficiently use the available energy in the shear field of the mixer.

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Claims (9)

12 80078 Synthetic polymer fiber, in particular a polyester fiber and in particular a poly (ethylene terephthalate) fiber, which is made water-dispersible by a coating which promotes water-dispersibility, characterized in that the fibers have a cross-section. Polymer fiber according to Claim 1, characterized in that the coating is an ethoxylated, water-dispersible coating in an amount of about 0.04 to 1.0% by weight of the fiber. Polymer fiber according to Claim 2, characterized in that the coating consists essentially of a segmented copolyester of repeating units of poly (ethylene terephthalate) and poly (oxyalkylene) groups, which poly (oxyalkylene) groups are derived from poly (oxyalkylene) glycol with an average molecular weight of 300-5000. Polymer fiber according to one of Claims 1 to 3, characterized in that it is in the form of a package of cut fiber. Polymer fiber according to any one of claims 1 to 4, characterized in that it is substantially uncurled, has a cut length of about 5 to 90 mm, a length / diameter ratio of about 100: 1 to 2000: 1 and a denier number. is about 0.5-20. Polymer fibers according to Claim 1, characterized in that they are in the form of a continuous, filamentous, uncurled tow. 7. A method of making a polyester fiber which is made water-dispersible by a water-dispersible coating, melt-spinning the polyester into filaments, drawing a tow and cutting the filaments, characterized in that the polyester is melt-spun-crosslinked, consists of repeating units of poly (ethylene terephthalate) and poly (oxyalkylene) groups derived from poly (oxy-5-alkylene) glycol having an average molecular weight of 300-6000 and that the coated filaments are cut into a fiber of cut length is about 5-90 mm. Process according to Claim 7, characterized in that the filaments are coated with copolyester in an amount of 0.04 to 1.0%, based on the weight of the filaments. A method according to claim 8, characterized in that the coating is cured on the filaments by heating the coated filaments to 100-190 ° C. 14 80078