EP0239080A2 - Fibres élastomères, nappes fibreuses élastomères, nappes composites élastomères et composition apte à l'extrusion à base de copolymères d'éthylène-vinyle - Google Patents

Fibres élastomères, nappes fibreuses élastomères, nappes composites élastomères et composition apte à l'extrusion à base de copolymères d'éthylène-vinyle Download PDF

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EP0239080A2
EP0239080A2 EP87104343A EP87104343A EP0239080A2 EP 0239080 A2 EP0239080 A2 EP 0239080A2 EP 87104343 A EP87104343 A EP 87104343A EP 87104343 A EP87104343 A EP 87104343A EP 0239080 A2 EP0239080 A2 EP 0239080A2
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Prior art keywords
weight
fibers
copolymer
ethylene
elastomeric
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EP87104343A
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German (de)
English (en)
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Diego H. Daponte
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Kimberly Clark Corp
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Kimberly Clark Corp
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    • 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
    • D01F6/44—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from mixtures of polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds as major constituent with other polymers or low-molecular-weight compounds
    • D01F6/46—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from mixtures of polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds as major constituent with other polymers or low-molecular-weight compounds of polyolefins
    • 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
    • D01F6/28—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D01F6/30—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds comprising olefins as the major constituent
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/54—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by welding together the fibres, e.g. by partially melting or dissolving
    • D04H1/56—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by welding together the fibres, e.g. by partially melting or dissolving in association with fibre formation, e.g. immediately following extrusion of staple fibres

Definitions

  • the field of the present invention generally includes certain extrudable compositions and methods for forming the extrudable compositions into fibers, microfibers and fibrous nonwoven elastomeric webs formed therefrom.
  • melt-blowing techniques for forming very small diameter fibers, sometimes referred to as melt-blown fibers or microfibers, from thermoplastic resins are well known in the art.
  • melt-blown fibers or microfibers are well known in the art.
  • the production of fibers by melt-blowing is described in an article entitled "Superfine Thermoplastic Fibers", appearing in Industrial and Engineering Chemistry, Vol. 48, No. 8, pages 1342-1346. This article describes work done at the Naval Research Laboratories in Washington, D.C.
  • melt-blowing techniques include heating a thermoplastic fiber-forming resin to a molten state and extruding the molten resin through a plurality of linearly arranged small diameter capillaries that are formed in a die as molten threads.
  • the molten threads exit the die into a high velocity stream of gas, usually air, which may be maintained at an elevated temperature and which serves to attenuate the threads of molten resin to form fibers or, depending upon the degree of attenuation, microfibers having diameters less than the diameters of the capillaries of the die arrangement.
  • U.S. Patent 3,849,241 to Butin discloses the manufacture of nonwoven mats by melt-blowing and describes, at column 4, lines 57 et seq., the formation of melt-blown fibers having diameters of from about 0.5 ⁇ m to about 400 ⁇ m by extruding degraded fiber-forming molten thermoplastic polymer. resins as molten threads into an attenuating gas stream. Also disclosed is the fact that the diameters of the attenuated fibers will decrease as the flow of the attenuating gas through the gas outlets, which are located on either side of the die capillaries, increases.
  • the extruded molten threads even after attenuation by the gas into fibers, remain essentially continuous with little or no fiber breakage and that fibers produced in such an arrangement have diameters of, preferably, from about 8 ⁇ m to 50 ⁇ m.
  • the fiber-forming thermoplastic polymer resins Prior to extrusion the fiber-forming thermoplastic polymer resins are subjected to controlled thermal and oxidative degradation at temperatures ranging from about 550OF to about 900° F, that is, from about 288° C to about 482°C, preferably from about 600°F to 750°F, that is, from about 316°C to about 399°C, to effect a requisite degradation of the resin to reduce the viscosity of the fiber-forming resin.
  • Typical fiber-forming thermoplastic resins are listed at column 4, lines 35 et seq. and commercially useful resin throughput rates are stated to be from about 0.07 to 5 grams per minute per die extrusion capillary, preferably at least 1 gram per minute per die extrusion capillary.
  • thermoplastic polymers are amenable to the melt-blowing process, while others do not seem to be. As is reported in Tappi, The Journal of the Technical Association of the Pulp and Paper Industry, Vol. 56, pages 74-77 (April 1973), a good deal of work has been done with the melt-blowing of polypropylene. Nonwoven webs made from polypropylene microfibers are said to be soft and drapeable.
  • Other polymers that have been evaluated for use in melt-blowing include polyethylene, nylon 6, nylon 11, certain polycarbonates, polyesters of the kind useful as hot-melt adhesives, polyethylene terephthalate, poly(4-methylpentene-l), poly(tetramethylene terephthalate), and polystyrene.
  • the Tappi article reports the properties of nonwoven webs made from melt-blown fibers of these materials.
  • the article also reports that attempts have been made to melt-blow polysulfone, nylon 4, and polyphenylene oxide, without achieving acceptable operation in short screening trials.
  • the Tappi article also reports that blends of certain resins can be made up for melt-blowing. Thus, pellets of polypropylene and nylon 6 were mixed together, then melt-blown, to produce webs made from blends of these two materials.
  • the invention provides elastomeric fibers obtainable by melt-blowing according to the independent claims 1, 2 and 8 and their corresponding dependent claims.
  • the invention also provides fibrous nonwoven coherent elastomeric webs comprising said elastomeric fibers according to claim 11.
  • the invention provides composite elastomeric webs according to the independent claims 12, 18, 19 and 20 and their corresponding dependent claims as well as an extrudable composition as described in claim 26.
  • copolymers of ethylene can in fact be successfully melt-blown into elastomeric fibers or microfibers by judicious selection of materials and processing conditions.
  • the useful copolymers are those of ethylene with at least one vinyl monomer selected from the group including vinyl ester monomers, unsaturated aliphatic monocarboxylic acids and alkyl esters of these monocarboxylic acids, where the amount of vinyl monomer is sufficient to impart elasticity to the melt-blown fibers.
  • Exemplary copolymers are those of ethylene with vinyl acetate (EVA) having a melt index in the range from 32 to 500 grams per ten minutes, when measured in accordance with ASTM D-1238 at condition E, and including from about 10% by weight to about 50% by weight of vinyl acetate monomer, more specifically from about 18% to about 36% by weight of vinyl acetate monomer, and most specifically from about 26% to about 30% by weight of vinyl acetate monomer.
  • EVA vinyl acetate
  • the amount of monomer contained besides ethylene is generally from about 10% to about 50% by weight of the copolymer.
  • Copolymer materials of this type contribute pendent groups to the polyethylene backbone, and it has been observed that about 10% by weight of the component other than ethylene is needed to impart desired elastomeric properties to the products produced.
  • the elastomeric fibers or microfibers of the present invention can be coformed with one or more type of secondary fibers to form a composite elastomeric web.
  • the secondary fiber may be used in an amount greater than 0% by weight up to about 80% by weight of the composite coformed material. Wood pulp fibers are particularly preferred as a secondary fiber because of low cost, high absorbency and retention of satisfactory tactile properties.
  • an extrudable blend can be prepared from (a) at least about 10% by weight of a copolymer of ethylene and at least one vinyl monomer selected from the group including vinyl ester monomers, unsaturated aliphatic monocarboxylic acids and alkyl esters of these monocarboxylic acids, wherein the amount of vinyl monomer in the copolymer is sufficient to impart elasticity to the melt-blown fibers and (b) at least one modifying polymer.
  • the modifying polymer is a compatible polymer, which may for example be one formed from a monomer having olefinic unsaturation, and is used in an amount of greater than 0% by weight up to about 90% by weight of the blend.
  • One of the valuable properties of fibers and microfibers and the nonwoven webs produced in accordance with the invention is that of being elastomeric. Webs produced in accordance with the invention thus are stretchable and recover to substantially their original unstretched dimensions when the stretching force is released. They also become tacky at moderately elevated temperatures and their adhesive properties provide added utility.
  • the modifying polymer is employed to enhance the extrudability and fiber-forming characteristics of the copolymer. However, it may also be selected because of the properties that it imparts to the fibers, microfibers and/or to the nonwoven web formed from the fibers and/or microfibers.
  • Fibers or microfibers are tactically acceptable, soft, and cloth-like elastomeric nonwoven fabrics.
  • the fibers or microfibers are formed from an extrudable composition that is a mixture of a copolymer of ethylene and vinyl acetate along with one or more polyolefins.
  • the polyolefin or polyolefins modify the hand of the web so that a web of such material is tactically acceptable, and at the same time, the polyolefin or polyolefins may be present in an amount that does not undesirably affect strength and stretch properties.
  • the modifying polymer may be a polyolefin selected from the group including at least one polymer selected from the group including polyethylene, polypropylene, polybutene, ethylene copolymers (generally other than those with vinyl acetate), propylene copolymers, butene copolymers or blends of two or more of these materials. If the modifying polymer is polyethylene it may be a linear low density polyethylene.
  • modifying polymers include ABA' block copolymers, where A and A' are each a thermoplastic endblock that includes a styrenic moiety and where B is an elastomeric poly(ethylene-butene) midblock.
  • the extrudable blend usually includes from at least about 10% by weight of the ethylene/vinyl copolymer and from greater than 0% by weight to about 90% by weight of the modifying polymer.
  • the extrudable blend may include from about 10% by weight to about 95% by weight of ethylene/vinyl copolymer and from about 5% by weight to about 90% by weight of the modifying polymer.
  • the blend may include from about 20% by weight to about 95% by weight of the ethylene/vinyl copolymer and from about 5% by weight to about 80% by weight of the modifying polymer.
  • the blend may include from about 30% by weight to about 90% by weight of the ethylene/vinyl copolymer and from about 10% by weight to about 70% by weight of the modifying polymer. More specifically, the blend may include from about 50% by weight to about 90% by weight of the ethylene/vinyl copolymer and from about 10% by weight to about 50% by weight of the modifying polymer. Even more specifically, the blend may be composed of from at least about 50% by weight to about 70% by weight of the ethylene/vinyl copolymer and from at least about 30% by weight to about 50% by weight of the modifying polymer.
  • One preferred blend includes about 60% by weight of the ethylene/vinyl copolymer and about 40% by weight of the modifying polymer.
  • the extrudable blend is extruded at an effective combination of elevated pressure and elevated temperature conditions. These conditions will vary depending on the modifying polymer utilized. For example, the extrudable blend should be extruded or otherwise formed at a temperature of at least about 380°F (193°C), for example about 460°F (238°C), if the extrudable blend includes a copolymer of ethylene and vinyl acetate and the modifying polymer is polyethylene, polypropylene, or a mixture of the two.
  • the blends are generally extrudable at or above the above-defined temperatures at elevated pressures within the die.
  • a pressure of no more than about 20.7 bar (G) 300 pounds per square inch, gauge
  • pressures of from about 1.4 bar (G) (20 pounds per square inch, gauge) to about 17.2 bar (G) (250 pounds per square inch, gauge) are often adequate.
  • the blends are generally extrudable within the above-defined temperature ranges at pressures of from about 3.44 bar (G) (50 pounds per square inch, gauge), to about 17.2 bar (G) (250 pounds per square inch, gauge), for example, from about 8.6 bar (G) ( 125 pounds per square inch, gauge), to about 15.5 bar (G) (225 pounds per square inch, gauge).
  • G 3.44 bar
  • G 17.2 bar
  • G 250 pounds per square inch, gauge
  • G 125 pounds per square inch, gauge
  • 15.5 bar G
  • higher elevated pressures can be utilized with other die designs having a lower number of capillaries per 2.54 cm (inch) of die, but generally speaking, lower production rates result.
  • An ethylene vinyl acetate copolymer with a very high melt index and a high content of vinyl acetate can be expected to be very low in viscosity and somewhat difficult to process unless blended with a polyolefin, preferably polypropylene.
  • a polyolefin preferably polypropylene.
  • an ethylene vinyl acetate copolymer having about 21% to 40% by weight vinyl acetate content, and a melt index in the range of from about 100 to 300 grams per ten minutes when measured in accordance with ASTM D-1238, condition E will facilitate processing.
  • those skilled in the art will be able to make the necessary adjustments to practice the invention on particular equipment and with particular copolymers or copolymer blends.
  • the extrudable blends of the present invention are usually extrudable at satisfactory throughput rates. Such rates may be attributable to the presence of the modifying polymer additive in the extrudable blend, to form blends of suitable viscosity, where the copolymer is, for example, an ethylene vinyl acetate copolymer having a low melt index and high viscosity. A reduced viscosity proportionally reduces the die pressure if all other parameters remain the same.
  • the viscosity of the extrudable blends should generally be less than about 50 Pa•s (500 poise) when extruded at the above-defined elevated temperature and elevated pressure ranges.
  • the viscosity of the extrudable blend is from about 10 Pa•s (100 poise) to about 20 Pa s (200 poise) when extruded at the above-identified elevated temperature and elevated pressure conditions.
  • the modifying polymer may reduce or increase the viscosity of the blend, as compared to the viscosity of the copolymer, so that the extrudable blend is extrudable within the above-identified elevated temperature and elevated pressure ranges. Reduction or increase will depend on the ethylene/vinyl copolymer and modifying polymer selected for use.
  • the extrudable blend may be formed into a variety of products such as, for example, fibrous nonwoven elastomeric webs formed from elastomeric microfibers with an average diameter of not greater than about 100 ⁇ m, and having an average basis weight of not more than about 300 grams per square meter, or more specifically, an average basis weight of from about 17 g/m 2 (0.5 oz. per square yard) to about 3390 g/m 2 (100 oz. per square yard) or more; for example, an average basis weight of from about 34 g/m 2 (1 ounce per square yard) to about 339 g/m 2 (10 ounces per square yard).
  • the fibrous nonwoven elastomeric web may be formed by melt-blowing the extrudable composition at an effective combination of elevated temperature and elevated pressure conditions.
  • the extrudable blend may be extruded at a rate of from at least about 0.02 gram per capillary per minute to about 1.7 or more grams per capillary per minute, for example, from at least about 0.1 gram per capillary per minute to about 1.25 grams per capillary per minute, more specifically, from at least about 0.3 gram per capillary per minute to about 1.1 grams per capillary per minute, through a die having a plurality of small diameter extrusion capillaries as molten threads into a gas stream which attenuates the molten threads to provide a gas-borne stream of fibers or microfibers. These fibers or microfibers may be collected and formed into a fibrous nonwoven elastomeric web.
  • the attenuating gas stream may be applied to the molten threads at a temperature of from at least about 121.1°C (250°F) to about 260°C (500°F), and preferably from about 138°C (280°F) to about 232°C (450°F), and at a pressure of from at least about 0.034 bar (G) (0.5 pound per square inch,gauge) to about 1.38 bar (G) (20 pounds per square inch, gauge), for example, from at least about 0.07 bar (G) (1 pound per square inch, gauge), to about 0.7 bar (G) (10 pounds per square inch, gauge).
  • the attenuating gas stream may be air or an inert, non-oxidizing gas stream such as, for example, a stream of nitrogen gas. Temperatures above about 232°C (450°F) are to be avoided if the ethylene/vinyl copolymer is an ethylene vinyl acetate copolymer which begins to degrade at about 232°C (450°F).
  • the velocity and temperature of the thread-attenuating gas stream is adjusted so that the fibers are collected as substantially continuous fibers having diameters of from about ten (10) ⁇ m to about sixty (60) um, for example, from at least about ten (10) ⁇ m to about forty (40) ⁇ m.
  • copolymer without any preceding modifying term, is used herein as a form of abbreviation. It refers to a copolymer of ethylene and at least one other vinyl monomer selected from the group consisting of vinyl ester monomers, and unsaturated aliphatic monocarboxylic acids and alkyl esters of said monocarboxylic acids.
  • the preferred copolymer is a copolymer of ethylene and vinyl acetate having a melt index in the range from 32 to 500 grams per 10 minutes when measured in accordance with ASTM-D 1238, condition E (2,160 gram load at 190°C) and comprising from about 10% to about 50% by weight of vinyl acetate.
  • modifying polymer is employed to refer to a material that is added to the copolymer to modify the properties of the product. Sometimes, the modifying polymer is added for the purpose of reducing viscosity at the extrusion orifices, that is, at the capillaries in the die head. More generally, however, the modifying polymer may be added to impart unique attributes to fibers or microfibers formed from the blend, or to enhance one or more desirable properties already present.
  • compatible is used to refer to the relationship of one polymeric material to another with respect to the extrusion process and extrudates.
  • two different polymeric materials must have similar rheological behavior, they must form a generally homogeneous melt.
  • a compatible polymer is one which when mixed with the copolymer and subjected to an effective combination of elevated temperature and elevated pressure conditions can be extruded and melt-blown to form fibers or microfibers.
  • coforming is well understood in the art. It is used to refer to the incorporation of at least one type of secondary fibrous material into a stream of fibers or microfibers.
  • the fibers or microfibers may still be tacky or molten, so that upon contact, the secondary fibers bond to the fibers or microfibers or the fibers or microfibers may be completely cooled so that joining of the secondary fibers to the elastomeric fibers or microfibers is limited to physical entangling.
  • elastic and “elastomeric” are used interchangeably herein to define any material that, upon application of a biasing force, is stretchable to a stretched, biased elongated length which is at least about 125 percent, that is about one and one-quarter times, its relaxed, unbiased length, and which will recover at least 40 percent of its elongation upon release of the stretching, elongating force.
  • a hypothetical example which would satisfy this definition of an elastomeric material would be a 2.54 cm (one (1) inch) sample of a material which is elongatable to at least 3.18 cm (1.25 inches) and which, upon being elongated to 3.18 cm (1.25 inches) and released, will recover to a length of not more than 2.92 cm (1.15 inches).
  • Many elastic materials may be stretched by much more than 25 percent of their relaxed length and many of these will recover to substantially their original relaxed length upon release of the stretching, elongating force. This latter class of materials is generally preferred for purpose of the present invention.
  • melt flow is the amount (usually in grams per 10 minutes or decigrams per minute) of a material which can be forced through a given orifice under a specified pressure and at a given temperature. The value should be determined in accordance with ASTM D 1238.
  • melt index refers to the value obtained in accordance with condition E of ASTM D 1238 (190°C and 2,160 gram load) and modified as follows:
  • the term "recover” refers to a contraction of a stretched material upon termination of a biasing force following stretching of the material by application of the biasing force. For example, if a material having a relaxed, unbiased length of 2.54 cm (one (1) inch) were elongated 50% by stretching to a length of 3.81 cm (one and one-half (1.5) inches), the material would have been elongated 50% and would have a stretched length that is 150% of its relaxed length. If this exemplary stretched material contracted, that is, recovered to a length of 2.79 cm (one and one-tenth (1.1) inches) after release of the biasing and stretching force, the material would have re - covered 80 percent (1.02 cm (0.4 inch)) of its elongation.
  • microfibers is used herein to refer to small diameter fibers having an average diameter not greater than about 100 ⁇ m. For example, having an average diameter in the range from about 0.5 pm to about 50 ⁇ m, more specifically having an average diameter of from about ' 4 ⁇ m to about 40 ⁇ m.
  • nonwoven web means a web of material which has been formed without the use of a weaving process.
  • a nonwoven web has a structure of individual fibers or threads which are interlaid, but not in an identifiable, repeating manner.
  • Nonwoven webs in the past have been formed by a variety of processes such as, for example, melt-blowing processes, spun-bonding processes and staple fiber carding processes.
  • polymer or “polymer resin” as used herein generally include, but are not limited to, homopolymers, copolymers, such as, for example, block, graft, random and alternating copolymers, terpolymers, etc., and blends and modifications thereof.
  • polymer or “polymer resin” shall include all possible geometrical, i.e., stereo configurations of the material. These configurations include, but are not limited to, isotactic, syndiotactic and random symmetries.
  • an "inert" attenuating gas is a non-oxidizing gas which does not degrade the material being melt-blown.
  • the term "consisting essentially of” does not exclude the presence of additional materials which do not significantly affect the elastic properties and characteristics of a given polymeric composition.
  • Exemplary materials of this- sort would include, without limitation, pigments, antioxidants, stabilizers, surfactants, waxes, flow promoters_, solid solvents, particulates and materials added to enhance processability of the composition.
  • the ethylene/vinyl copolymers of the present invention have broad application in the formation of elastomeric materials such as elastomeric fibers which may be formed into elastomeric webs or other products, by suitable methods such as, for example, extrusion or molding processes.
  • a preferred method for forming the fibers or microfibers is to melt-blow fibers to form a fibrous nonwoven elastomeric web.
  • Melt-blowing processes generally involve extruding a thermoplastic polymer resin through a plurality of small diameter capillaries of a melt-blowing die as molten threads into a heated gas stream which is flowing generally in the same direction as that, of the extruded threads so that the extruded threads are attenuated, i.e., drawn or extended, to reduce their diameters to fiber or microfiber size.
  • the thus-formed fibers are then borne away from the vicinity of the die by the gas stream.
  • the gas stream is directed onto a foraminous member, such as a screen belt or a screen drum which is moving over a vacuum box, so that the gas-borne fibers impinge upon and are collected on the surface of the foraminous member and form a cohesive fibrous nonwoven web.
  • a foraminous member such as a screen belt or a screen drum which is moving over a vacuum box
  • Melt-blowing dies usually extend across the foraminous collecting member in a direction which is substantially transverse to the direction of movement of the collecting surface.
  • the die includes a plurality of small diameter capillaries arranged linearly along the transverse extent of the die with the transverse extent of the die being approximately as long as the desired width of the fibrous nonwoven web which is to be produced. That is, the transverse dimension of the die is the dimension which is defined by the linear array of die capillaries.
  • the diameter of the capillaries will be on the order of from about 0.025 cm (0.01 inch) to about 0.051 cm (0.02 inch), for example, from about 0.037 cm (0.0145 inch) to about 0.046 cm (0.018 inch).
  • capillaries From about 5 to about 50 such capillaries will be provided per linear 2.54 cm (inch) of die face.
  • the length of the capillaries will be from about 0.127 cm (0.05 inch) to about 0.508 cm (0.20 inch), for example, about 0.287 cm (0.113 inch) to about 3.556 cm (0.14 inch) long.
  • a melt-blowing die can extend from about 76.2 cm (30 inches) to about 152.4 cm (60 inches) or more in the transverse direction.
  • melt-blowing copolymers of ethylene and vinyl acetate in the absence of any modifying polymer, a copolymer having a melt index in the range of from about 32 to about 500 grams per ten minutes and comprising from about 10% to about 50% by weight of vinyl acetate may be utilized.
  • a copolymer having a melt index in the range of from about 32 to about 500 grams per ten minutes and comprising from about 10% to about 50% by weight of vinyl acetate may be utilized.
  • an ethylene vinyl acetate copolymer having a melt index of from about 50 to 300 grams per 10 minutes and from about 21% by weight to about 40% by weight of vinyl acetate monomer is desired for facilitated processing.
  • the melt index is less than about 32 grams per ten minutes the ethylene-vinyl acetate exhibits a high viscosity during melt-blowing.
  • the copolymer exhibits a very low viscosity during melt-blowing.
  • the use of a modifying copolymer is not essential for melt-blowing the copolymer.
  • some modifying polymer may be useful for adjusting viscosity values.
  • Ethylene vinyl acetate copolymers are characterized by both their melt index and their percentage of vinyl acetate. In some cases, a melt index as low as 20 grams per ten minutes probably could be used, but would be expected to require such special precautions and treatment as not to be feasible for commercial processes under present conditions and with existing equipment. Exemplary melt index ranges for the ethylene vinyl acetate copolymer are from about 50 to 200 grams per ten minutes, more specifically from about 150 to 200 grams per ten minutes.
  • the copolymer is readily commercially available. Generally, the percentage of vinyl acetate in commercial products is from about 6% to about 70%, depending upon the properties desired and the application intended. When the percentage of vinyl acetate is above about 40%, processing is difficult. For developing elastomeric properties in fibers or microfibers, and in nonwoven coherent webs made from these fibers or microfibers, it is believed that the ethylene vinyl acetate copolymer should contain at least about 10% by weight of vinyl acetate monomer. Generally, the vinyl acetate content should not exceed about 50% by weight for present purposes, because at contents above about 50%, the viscosity of the copolymer is very low and processing difficulties are encountered.
  • the percentage of vinyl acetate therefore may be in the range from about 10% by weight to about 50% by weight, a specific range is 18% by weight to 36% by weight, and a more specific range is about 26% by weight to 30% by weight, with an even more specific value being about 28% by weight.
  • melt-blown fibers can be formed from a copolymer of ethylene and at least one vinyl monomer selected from the group including vinyl ester monomers, unsaturated aliphatic monocarboxylic acids and alkyl esters of said monocarboxylic acids, wherein the amount of vinyl monomer in said copolymer is sufficient to impart elasticity to the fibers formed therefrom.
  • the ethylene/vinyl copolymer embraces a spectrum of materials including the copolymers of ethylene and vinyl acetate, ethylene and ethyl acrylate, ethylene and methyl acrylate, ethylene and methyl methacrylate, and the like. It is also possible to use mixtures of these copolymeric materials to achieve particular properties in the melt-blown fibers and in the webs formed therefrom.
  • Blending of the copolymer with a modifying polymer is often not necessary for viscosity adjustment purposes. However, when the melt index of the selected -copolymer is low, blending may be desirable to facilitate extrusion. Also, blending may be desirable even where not mandated to control viscosity, in order to develop particular properties in the resulting fibers or microfibers.
  • the modifying polymer selected should be one which, when blended with the copolymer, and subjected to an effective combination of elevated temperature and elevated pressure conditions, is adapted to be extruded, in blended form, with the copolymer.
  • Suitable modifying polymers may be polyolefin materials selected from the group including polypropylene, polyethylene, polybutene, including ethylene copolymers, propylene copolymers and butene copolymers. If the modifying polymer is polyethylene it may be a linear low density polyethylene. Blends of two or more of the polyolefins may be utilized.
  • One polyethylene may be obtained from U.S.I. Chemical Company under the trade designation Petrothene Na601 (also referred to herein as PE Na601).
  • a preferred polyethylene is that used in Example V, below.
  • a preferred polypropylene may be obtained from The Exxon Chemical Co. under the trade designation PP 3145.
  • the Na601 is a low molecular weight, low density polyethylene for application in the areas of hot melt adhesives and coatings.
  • U.S.I. has also stated that the Na601 has the following nominal values: (1) a Brookfield Viscosity, Pa-s (cP) at 150°C of 8.5 (8500) and at 190°C of 3.3 (3300) when measured in accordance with ASTM D 3236; (2) a density of 0.903 grams per cubic centimeter when measured in accordance with AST M D 1505; (3) an equivalent Melt index of 2000 grams per 10 minutes when measured in accordance with ASTM D 1238; (4) a ring and ball softening point of 102°C when measured in accordance with ASTM E 28; (5) a tensile of 58.6 bar (850 pounds per square inch) when measured in accordance with ASTM D 638; (6) an elongation of 90% when measured in accordance with ASTM D 638; (7) a modulus of
  • the Na601 is believed to have a number average molecular weight (Mn) of about 4600; a weight average molecular weight (Mw) of about 22,400 and a Z average molecular weight (MZ) of about 83,300.
  • the polydispersity (Mw/Mn) of the Na601 is about 4.87.
  • Mn is calculated by the formula: Mw is calculated by the formula: Mz is calculated by the formula:
  • Typical characteristics of the Exxon PP 3145 polypropylene as stated by Exxon are a density of about 0.910 grams per cubic centimeter measured in accordance with ASTM D 792. A melt-flow rate obtained in accordance with ASTM D 1238, Condition L, of about 300 grams per ten (10) minutes.
  • the PP 3145 is believed to have a number average molecular weight (Mn) of about 43,580; a weight average molecular weight (Mw) of about 124,400 and a Z average weight (Mz) of about 255,600.
  • the polydispersity of the PP 3145 (Mw/Mn) is about 2.85.
  • the modifying polymer may also be an ABA' block copolymer, for example one of the kind sold under the trademark KRATON G by the Shell Chemical Company.
  • a and A' are each a thermoplastic polymer endblock that includes a styrenic moiety
  • B is an elastomeric poly(ethylene-butene) midblock.
  • the ABA' block copolymer resin must be one which is free of polymer segments which chain scission or which crosslink at the temperatures utilized by the process of the present invention, because such materials will either tend to plug up the small diameter capillaries through which the molten extrudable composition must be extruded or will degrade and form unsatisfactory product.
  • the neat copolymer may be extruded through the die capillaries at a temperature of at least about 116°C (240°F). If polyethylene and/or polypropylene is utilized as a modifying polymer the blend may be extruded through the die capillaries at a temperature in the range of from at least about 138 0 C (280°F). For example, from about 204°C (400 °F) to about 260°C (500°F).
  • the blend usually includes from at least about 10% by weight to about 95% by weight of the copolymer and from about 5% by weight to about 90% by weight of the modifying polymer.
  • the blend may include from about 20% by weight to about 95% by weight of the ethylene/vinyl copolymer and from about 5% by weight to about 80% by weight of the modifying polymer, more specifically from about 30% by weight to about 90% by weight of the ethylene/vinyl copolymer and from about 10% by weight to about 70% by weight of the modifying polymer.
  • the blend may include from about 50% by weight to about 90% by weight of the ethylene/vinyl copolymer and from about 10% by weight to about 50% by weight of the modifying polymer.
  • the blend may include from about 50% by weight to about 70% by weight of the ethylene/vinyl copolymer with from about 30% by weight to about 50% by weight of the modifying polymer.
  • One blend includes about 60% by weight of the ethylene/vinyl copolymer and about 40% by weight of the modifying polymer.
  • the temperature of the blend is elevated within the extruder 12 by a conventional heating arrangement (not shown) to melt the blend.
  • Pressure is applied to the blend by the pressure-applying action of a turning screw (not shown), located within the extruder, to form the blend into an extrudable composition.
  • the blend is heated to a temperature of at least about 1380C (2800F) for example at least about 204°C (400°F), if polyethylene or polypropylene is utilized as the modifying polymer in the blend.
  • the extrudable composition is then forwarded by the pressure applying action of the turning screw to a melt-blowing die 14.
  • the elevated temperature of the extrudable composition is maintained in the melt-blowing die 14 by a conventional heating arrangement (not shown).
  • the die 14 generally extends a distance about equal to the width 16 of the nonwoven web 18 which is to be formed by the process.
  • the combination of elevated temperature and elevated pressure conditions which effect extrusion of the composition will vary over wide ranges. For example, at higher elevated temperatures, lower elevated pressures will result in satisfactory extrusion rates and, at higher elevated pressures of extrusion, lower elevated temperatures will effect satisfactory extrusion rates.
  • FIGs 3 and 4 best illustrate the melt-blowing die 14.
  • An extrusion slot 20 receives the extrudable blend from the extruder 12. The extrudable blend then passes through the extrusion slot 20 and through a plurality of small diameter capillaries 22, which exit the die 14 in a linear arrangement, best illustrated in Figure 2, extending across the tip 24 of the die 14, to emerge from the capillaries 22 as molten threads 26.
  • the extrudable blend is extrudable within the above-defined temperature ranges, through the small diameter capillaries, that is, within the die tip, at pressures as applied by the turning screw of the extruder 12, of no more than about 20.7 bar (G) (300 pounds per square inch, gauge).
  • usefule pressures include those from about 1.4 bar (G) (20 pounds per square inch, gauge), to about 17.2 bar (G) (250 pounds per square inch, gauge), and more specifically, pressures of from about 3.44 bar (G) (50 pounds per square inch, gauge), to about 17.2 bar (G) (250 pounds per square inch, gauge), even more specifically from about 8.6 bar (G) (125 pounds per square inch, gauge), to about 15.5 bar (G) (225 pounds per square inch, gauge). Pressures in excess of 20.7 bar ( G ) (300 pounds per square inch, gauge), may rupture or break some dies 14.
  • the extrudable blend is discharged through the capillaries 22 of the die 14 at a rate of from at least about 0.02 gram per capillary per minute to about 1.7 or more grams per capillary per minute, for example, from at least about 0.1 gram per capillary per minute to about 1.25 grams per capillary per minute, and more specifically, from at least about 0.3 gram per capillary per minute to about 1.1 grams per capillary per minute.
  • the die 14 also includes attenuating gas inlets 28 and 30 which are provided with heated, pressurized attenuating gas (not shown) by attenuating gas sources 32 and 34 ( Figure 1).
  • the heated, pressurized attenuating gas enters the die 14 at the inlets 28 and 30 and follows the path generally designated by the arrows 36 and 38 in Figures 3 and 4 through two chambers 40 and 42 and on through to narrow passageways or gaps 44 and 46, respectively, so as to contact the extruded threads 26 ( Figure 1) as they exit the capillaries 22 of the die 14.
  • the chambers 40 and 42 are designed so that the heated attenuating gas exits the chambers 40 and 42 and passes through the gas passages 44 and 46 to form a stream (not shown)of attenuating gas which exits the die 14.
  • the temperature and pressure of the heated stream of attenuating gas can vary widely, depending on the particular equipment being used.
  • the heated attenuating gas can be applied at a temperature of from about 121°C (250°F) to about 260°C.(500°F), more specifically, from about 138°C (280°F) to about 232°C (450°F), at a pressure of from about 0.034 bar (G) (0.5 pound per square inch, gauge), to about 1.38 bar (G) (20 pounds per square inch, gauge), more specifically, from about 0.07 bar (G) (1 pound per square inch, gauge), to about 0.7 bar (G) (10 pounds per square inch, gauge).
  • air plates 48 and 50 which, in conjunction with a die tip portion 52 of the die 14, define the chambers 40 and 42 and the passageways 44 and 46, may be adjusted relative to the die tip portion 52 to widen or narrow the width 54 ⁇ of the attenuating gas passageways 44 and 46 so that the volume of attenuating gas passing through the air passageways 44 and 46 during a given time period can be adjusted without varying the velocity of the attenuating gas.
  • the air plates 48 and 50 can also be adjusted upwardly and downwardly to effect a "recessed" die 'tip configuration ( Figure 3) or a positive die tip "stick-out" configuration ( Figure 4) as discussed in detail below.
  • Attenuating gas pressures of less than about 1.38 bar (G) (20 pounds per square inch, gauge), in conjunction with air passageway widths, which are usually the same, of no greater than about 0.51 cm (0.20 inch).
  • G 1.38 bar
  • air passageway widths which are usually the same, of no greater than about 0.51 cm (0.20 inch).
  • Lower attenuating gas velocities and wider air passageway gaps are generally preferred if substantially continuous fibers or microfibers are to be produced.
  • the die tip 52 is formed at an angle preferably bisected by the capillaries 22.
  • the air plates are arranged so that respective surfaces 48'-50' inside chambers 40 and 42 define an angle ⁇ preferably bisected by capillaries 22.
  • the two streams of attenuating gas converge to form a stream of gas which entrains and attenuates the molten threads 26, as they exit the linearly arranged capillaries 22 into fibers or, depending upon the degree of attenuation, microfibers 26 of a small diameter, to a diameter less than the diameter of the capillaries 22.
  • the gas-borne fibers 26 are blown, by the action of the attenuating gas, onto a collecting arrangement which, in the embodiment illustrated in Figure 1, is a foraminous endless belt 56 conventionally driven by rollers 57. Other foraminous arrangements such as a rotating drum arrangement may be utilized.
  • Figure 1 illustrates the formation of substantially continuous fibers 26 on the surface of the belt 56.
  • the fibers 26 can be formed in a substantially discontinuous fashion as illustrated in Figure 5 by adjusting the velocity of the attenuating gas, the temperature of the attenuating gas, and the volume of attenuating gas passing through the air passageways in a given time period.
  • the collecting arrangement may also include one or more vacuum boxes (not shown) located below the surface of the belt 56 and between the rollers 57.
  • the fibers 26 are collected as a fibrous nonwoven elastomeric web 18 on the surface of the belt 56 which is travelling in the direction indicated by the arrow 58 in Figure 1.
  • the vacuum boxes assist in retention of the fibers 26 on the surface of the belt 56.
  • the tip 24 of the die tip portion 52 of the melt-blowing die 14 is from about 10.2 cm (4 inches) to about 61.0 cm (24 inches) from the surface of the belt 56 upon which the fibers 26 are collected.
  • the thus-collected, entangled fibers 26 form a coherent, fibrous nonwoven elastomeric web 18 which may be removed from the belt 56 by a pair of pinch rollers 60 and 62 (Fig. 1) which may be designed to press the entangled fibers of the web 18 together to improve the integrity of the web 18. Thereafter, the web 18 may be transported by a conventional arrangement to a windup roll (not shown) for storage. Alternatively, the web 18 may be removed directly from the belt 56 by the windup roller.
  • the web 18 may be pattern-embossed as by ultrasonic embossing equipment. (not shown) or other embossing equipment such as, for example, the pressure nip formed between a heated calendar and anvil roll (not shown).
  • the melt-blowing die 14 includes a base portion 64 and a die tip portion 52 which generally centrally extends from the base portion 64.
  • the centrally located die tip portion 52 is inwardly tapered to a "knife-edge" point which forms the tip 24 of the die tip portion 52 of the die 14.
  • the base portion 64 and the die tip portion 52 are formed from a single block of metal which surrounds the extrusion slot 20 and the extrusion capillaries 22-
  • the die 14 also includes two air plates 48 and 50-, discussed above, which are secured by conventional means to the base portion 64 of the die 14.
  • the air plate 48 in conjunction with the die tip portion 52 of the die 14, defines the chamber 40 and the attenuating gas air passage or gap 44.
  • the air plate 50 in conjunction with the die tip portion 52, defines the chamber 42 and the air passageway or gap 46.
  • the air plates 48 and 50 terminate, respectively, in air plate lips 66 and 68.
  • the knife-edge point which forms the tip 24 of the die tip portion 52 of the die 14 is recessed inwardly of the plan formed by the air plate lips 66 and 68.
  • the perpendicular distance between the plane formed by the lips 66 and 68 and the tip 24 of the die tip portion 52 is sometimes referred to by those in the art as a "negative stick-out” or a "recessed" die tip configuration.
  • the tip of the die tip portion 52 of the die 14 is configured to protrude outwardly beyond the plane formed by the lips 66 and 68 of the air plates 48 and 50, as is illustrated in Figure 4, such a configuration is referred to by those in the art as a "positive stick-out" of the tip 24 of the die tip 52.
  • negative numbers are utilized with die tip 52 "stick-out" distances when the tip 24 of the die tip 52 is recessed with regard to the plane formed by the lips 66 and 68 of the air plates 48 and 50. If the tip 24 of the die tip 52 is configured so that it protrudes beyond the plane formed by the lips 66 and 68 of the air plates 48 and 50, the die tip "stick-out" distances are given in positive numbers.
  • Positive and negative die tip "stick-out” values are obtained by measuring the perpendicular distance between the plane formed by the lips 66 and 68 of the air plates 48 and 50 and the knife-edge point which forms the tip 24 of the die tip portion 52 of the die 14, in other words, the closest distance between the point 24 and the plane formed by the lips 66 and 68, as defined above.
  • air gap or width is the perpendicular, i.e., minimum, width 54 of either of the air passages 44 and 46. These widths are normally arranged to be identical.
  • Figure 5 illustrates another embodiment of the present invention where one or more types of secondary fibers 72 are distributed within or upon the stream of fibers or microfibers 26.
  • Distribution of the secondary fibers 72 within the stream of fibers 26 may be such that the secondary fibers 72 are generally uniformly distributed throughout the stream of fibers 26. This may be accomplished by merging a secondary gas stream (not shown) containing the secondary fibers 72 with the stream of fibers 26.
  • Apparatus for accomplishing this merger may include a conventional picker roll 74 arrangement which has a plurality of teeth 76 that are adapted to separate a mat, sheet or batt of secondary fibers 78 into the individual secondary fibers 72.
  • the mat, sheet or batt of secondary fibers 78 which is fed to the picker roll 74 may be of pulp fibers (if a two component mixture of fibers and secondary pulp fibers is desired), of staple fibers (if a two component mixture of fibers and secondary staple fibers is desired) or of both pulp fibers and staple fibers (if a three component mixture of polyetherester fibers, secondary staple fibers and secondary pulp fibers is desired).
  • the secondary fibers 72 are absorbent or superabsorbent fibers.
  • the secondary fibers 72 may generally be selected from the group including one or more polyester fibers, polyamide fibers, polyolefin fibers such as, for example, polyethylene fibers and polypropylene fibers, cellulosic derived fibers such as, for example, rayon fibers and wood pulp fibers, multi-component fibers such as, for example, sheath-core multi-component fibers or side-by-side multi-component fibers, natural fibers such as silk fibers, wool fibers or cotton fibers, electrically conductive fibers, absorbent fibers, superabsorbent fibers or blends of two or more of such secondary fibers. Other types of secondary fibers 72 as well as blends of two or more of other types of secondary fibers 72 may be utilized.
  • the secondary fibers 72 may be microfibers or the secondary fibers 72 may be macrofibers having an average diameter of from about 300 11m to about 1,000 ⁇ m.
  • the sheets, batts or mats 78 of secondary fibers 72 are fed to the picker roll 74 by a roller arrangement 80. After the teeth 76 of the picker roll 74 have separated the mat, sheet or batt of secondary fibers 78 into separate secondary fibers 72 the individual secondary fibers 72 are conveyed toward the stream of fibers or microfibers 26 through a nozzle 82.
  • a housing 84 encloses the picker roll 74 and provides a passageway or gap 86 between the housing 84 and the surface of the teeth 76 of the picker roll 74.
  • a gas (not shown), for example air, is supplied to the passageway or gap 86 between the surface of the picker roll 74 and the housing 84 by way of a gas duct 88.
  • the gas duct 88 may enter the passageway or gap 86 generally at the junction 90 of the nozzle 82 and the gap 86.
  • the gas is supplied in sufficient quantity to serve as a medium for conveying the secondary fibers 72 through the nozzle 82.
  • the gas supplied from the duct 88 also serves as an aid in removing the secondary fibers from the teeth 76 of the picker roll 74.
  • gas supplied through the duct 92 generally provides for removal of the secondary fibers 72 from the teeth 76 of the picker roll 74.
  • the gas may be supplied by any conventional arrangement such as, for example, an air blower (not shown).
  • the individual secondary fibers 72 are conveyed through the nozzle 82 at about the velocity at which the secondary fibers 72 leave the teeth 76 of the picker roll 74.
  • the secondary fibers 72 upon leaving the teeth 76 of the picker roll 74 and entering the nozzle 82, generally maintain their velocity in both magnitude and direction from the point where they left the teeth 76 of the picker roll 74.
  • Such an arrangement which is discussed in more detail in U.S. patent 4,100,324 to Anderson et al., hereby incorporated by reference, aids in substantially reducing fiber floccing.
  • the nozzle 82 may be positioned so that its longitudinal axis is substantially parallel to a plane which is tangent to the picker roll 74 at the junction 90 of the nozzle 82 with the passageway 86. As a result of this configuration, the velocity of the second ' ary fibers 72 is not substantially changed because of contact of the secondary fibers 72 with the walls of the nozzle 82.
  • the axis of the nozzle 82 may be adjusted appropriately to be aligned with the direction of secondary fiber 72 velocity at the point where the secondary fibers 72 disengage from the teeth 76 of the picker roll 74.
  • the disengagement of the secondary fibers 72 from the teeth 76 of the picker roll 74 may be assisted by application of a pressurized gas, i.e., air through duct 92.
  • the vertical distance 94 that the nozzle 82 is below the die tip 24 may be adjusted to vary the properties of the composite product 100. Variation of the horizontal distance 96 of the tip 98 of the nozzle 82 from the die tip 24 will also achieve variations in the final elastic composite product 100. The vertical distance 94 and the horizontal distance 96 values will also vary with the material being added to the fibers 26. The width of the nozzle 82 along the picker roll 74 and the length that the nozzle 82 extends from the picker roll 74 are also important in obtaining optimum distribution of the secondary fibers 72 throughout the stream of fibers 26. It is usually desirable for the length of the nozzle 82 to be as short as equipment design will allow.
  • the length is usually limited to a minimum length which is generally equal to the radius of the picker roll 74.
  • the width of the nozzle 82 should not exceed the width of the sheets, batts or mats 78 that are being fed to the picker roll 74.
  • the picker roll 74 may be replaced by a conventional particulate injection system to form a composite nonwoven web product 100 containing various secondary particulates.
  • a combination of both secondary particulates and secondary fibers could be added to the fibers 26 prior to formation of the composite product 100 if a conventional particulate injection system was added to the left side of the system illustrated in Figure 5.
  • Figure 5 further illustrates that the gas stream carrying the secondary fibers 72 is moving in a direction which is generally perpendicular to the direction of movement of the stream of fibers 26 at the point of merger of the two streams. Other angles of merger of the two streams may be utilized.
  • the velocity of the gas stream of secondary fibers 72 is usually adjusted so that it is less than the velocity of the stream of fibers 26. This allows the streams, upon merger and integration thereof to flow in substantially the same direction as that of the stream of fibers 26. Indeed, the merger of the two streams may be accomplished in a manner which is somewhat like an aspirating effect where the stream of secondary fibers 72 is drawn into the stream of fibers 26.
  • the velocity difference between the two gas streams may be such that the secondary fibers 72 are integrated- into the fibers 26 in a turbulent manner so that the secondary fibers 72 become substantially thoroughly and uniformly mixed throughout the fibers 26.
  • the gas stream which entrains and attenuates the stream of fibers 26 should have a comparatively high initial velocity, for example from about 60.96 m (200 feet) to over 304.8 m/s (1,000 feet per second), and the stream of gas which carries the secondary fibers 72 should have a comparatively low initial velocity, for example from about 15.24 (50) to about 60.96 m/s (200 feet per second).
  • a composite stream 102 of fibers 26 and secondary fibers 72 is formed. If the fibers 26 are still semi-molten and tacky at the time of incorporation of the secondary fibers 72 into the fibers 26, the secondary fibers 72 are not only mechanically entangled within the coherent matrix formed by the fibers 26 but may also be thermally bonded or joined to the fibers 26.
  • a collecting device is located in the path of the composite stream 102.
  • the collecting device may be the endless belt 56 of Figure 1.
  • the belt 56 is usually porous and a conventional vacuum arrangement (not shown) which assists in retaining the composite stream 102 on the external surface of the belt 56 is usually present.
  • Other collecting devices are well known to those of skill in the art and may be utilized in place of the endless belt 56. For example, a porous rotating drum arrangement could be utilized.
  • the composite elastic nonwoven web 88 is removed from the screen by the action of rollers (not shown) such as rollers 60 and 62 shown in Figure 1.
  • particulate materials may be substituted for the secondary fibers 72.
  • the elastic nonwoven web 88 may have both secondary fibers 64 and particulate materials incorporated into the coherent matrix of polyetherester fibers.
  • the web can include (1) from at least about 20% by weight of a fibrous nonwoven elastic web of microfibers as defined herein, and (2) from greater than 0% by weight to about 80% by weight of at least one secondary fiber generally uniformly distributed throughout the fibrous nonwoven elastomeric web.
  • the material from which the microfibers are formed may be any of the melt-blown materials contemplated by the present invention.
  • the microfibers may be formed from copolymers of ethylene with vinyl acetate, acrylic acid, methacrylic acid, ethyl acrylate, methyl methacrylate, and mixtures of these.
  • the microfibers may also be formed from blends of copolymer with modifying polymer, which preferably is one or more of the polyolefins within any one of the above-mentioned blend ranges.
  • the secondary fibers can form from about 30% by weight to about 70% by weight of the coformed web and even more specifically, the secondary fibers can form from about 50% by weight to about 70% by weight of the coformed web.
  • melt-blowing die extruders and configurations were utilized or contemplated for use in a variety of combinations to illustrate the broad applicability of the present invention.
  • Specific details of melt-blowing dies that have been used or that are proposed for use are, for ease of reference, tabulated in Table II below:
  • Melt-blowing dies i3 and #4 are high pressure dies.
  • the apparatus employed is experimental equipment designed for screening. and small-scale production.
  • the EVA copolymer selected had a nominal melt index of 500 at 190°C and contained 28% by weight of vinyl acetate.
  • the die was of Japanese manufacture.
  • the extruder was a Prodex extruder with three zones for which the temperature could be set and adjusted, and the actual temperature could be observed.
  • the die head had 20 holes per 2.54 cm (inch).
  • the diameter of thenose piece holes was 0.38 mm.
  • the die head was supplied with hot air from a furnace. Air temperature measurement was possible at the furnace and also at different locations in the die head. The temperature of the die head could also be measured in several places.
  • the settings on the equipment for these production runs were as follows.
  • the three zones of the extruder, from its inlet end to its discharge end, were set. at 320°F, 360°F, and 380°F, respectively (160°C, 182°C, and 193°C, respectively). Actual readings during operation were generally within 0.5°C (1°F) of the settings.
  • the screw in the extruder was operated at 39.3 rpm. Since frictional heat is generated during the extrusion process, the temperature of the resin as measured near the discharge end of the extruder was 404°F (207°C). The furnace for heating the attenuating air was set for 370°F (188°C), and in actual operation was observed to attain a temperature of 375°F (191°C). Because of heat losses, the temperature of the air in the die head was generally in the range from about 340°F to about 348°F (171°C to 176°C). The die temperature was set to be about 400°F (204°C), and in operation, this temperature was attained with very minor differences between different parts of the die head. The back pressure on the extruder during operation was about 16.9 bar (245 psi).
  • microfibers from the EVA copolymer specifically identified in this Example.
  • the microfibers were discharged and during their path of travel to the collector surface, they were quenched with a light water spray that cooled the microfibers.
  • a cohesive nonwoven web was formed on the surface of the collector.
  • the microfibers retained sufficient tack to become cohesive (self-bonded).
  • the basis weight of the nonwoven web produced in run A was 3.6 g/m 2 (3.0 grams per square yard).
  • run B where the difference from run A was in the setting of the distance from the die head to the collector surface at 29.85 cm (11.75 inches), the basis weight was nominally 3.6 g/m 2 (3.56 actual) (3.0 (2.98 actual) grams per square yard), and as measured was 3.30 g/m 2 (2.76 grams per square yard).
  • run C the die collector distance, i.e., the distance from the die head to the collector surface, remained the same as in run B at 29.85 cm (11.75 inches), but the linear speed of the collector surface was adjusted to 76.2 cm/min. (30 inches per minute).
  • the basis weight for the cohesive nonwoven web formed was a nominal 33.91 g/m 2 (1.0 ounce per square yard), and as actually measured, was 37.29 g/m 2 (1.1 ounces per square yard).
  • Example II Different equipment was used from that in Example I, and under operating conditions as described below.
  • the EVA copolymer employed had a melt index (nominal) of 200 at 190°C and contained 28% by weight of vinyl acetate. The molten material could therefore be expected to be more viscous than the copolymer used in Example I, and in fact, it was.
  • the extruder had five permissible temperature settings. The settings during operation were: 250°F (66°C); 190°F (88°C); 300°F (149°C); 370°F (188°C); 400° F (204°C). The highest temperature was at the discharge end of the extruder. Toward the end of the run,.-the initial temperature settings were adjusted, without a significant change in the process or product.
  • the cohesive nonwoven web produced was taken off in two rolls. The characteristics are reported in Table IV below.
  • the data in this Example are actual data from actual production, but some of the values reported fluctuated during the course of the run.
  • the particular copolymer of ethylene and vinyl acetate selected for this run had a nominal melt index of 200 at 190°C, and contained 28% by weight of vinyl acetate.
  • the polyethylene was a linear low density polyethylene.
  • melt temperature refers to the temperature of the molten blend just before leaving the extruder.
  • pipe temperature refers to the temperature in the pipe that is shown in Figure 1 connecting the discharge end of the extruder with the inlet manifold of the die head.
  • die temperature refers to the temperature of the molten blend or resin as measured within the die head prior to extrusion.
  • Webs produced from these microfibers had good hand, were soft, cloth-like, and tactically acceptable.
  • the webs retained an elastomeric character and had good stretching properties.
  • Microfibers were prepared by melt-blowing several different blends of a copolymer of ethylene and vinyl acetate with polypropylene. For process comparison purposes, a run was also made with the copolymer alone. Since its properties were already known, they were not observed and recorded.
  • the ethylene-vinyl acetate copolymer had a nominal melt index of 200 at 190°C, and contained 28% by weight of vinyl acetate.
  • the polypropylene was a commercial product sold as Exxon PP 3145, having a nominal melt flow rate of 300.
  • the equipment used was generally similar to that used in Example 2.
  • the production runs were each of an initial quantity of 45.36 kg (100 pounds) of resin.
  • the rate of throughput through the die head was on the order of 0.18-0.36 kg/cm/h (1-2 pounds per inch per hour).
  • the operators were instructed to run with an extruder profile in the range from 177°C (350°F) to 216°C (420°F), a pipe temperature of about 216°C (420°F), a temperature in the die head of about 221°C (430°F), and an attenuating air temperature of about 204°C (400°F).
  • the die collector distance was to be set from 30.48 cm (12 inches) to 38.1 cm (15 inches).
  • the nonwoven web products produced in these runs had highly desirable tactile properties. The hand was good, and the web was strong.
  • the "Frazier" tests reported in this Example and in the previous Example reflect permeability and suitability for use in certain applications such as, for example, filtration, liquid-solid separation devices, and the like.
  • the polypropylene content imparts toughness and resistance to flexing fatigue, while the copolymer content of ethylene-vinyl acetate copolymer imparts smoothness, softness, and toughness.
  • Nonwoven Webs Produced From Microfibers of Ethylene-Vinyl Acetate Copolymer Blended with Polypropylene and Polyethylene
  • the copolymer of ethylene and vinyl acetate used was a commercially available product sold by Exxon Chemical Company under the trademark and grade designation, M-11948-077-0.04. This resin had a nominal melt index of 200 at 190°C, and an actual melt index of about 160. Its density was 0.950 grams per cubic centimeter, and the vinyl acetate content was 28.0% by weight.
  • the polypropylene was also a product of Exxon Chemical Company, sold under the designation, Polypropylene 3145. It had a density of about 0.910 grams per cubic centimeter when measured in accordance with ASTM D 792. It had a melt flow rate obtained in accordance with ASTM D 1238, Condition L, of about 300 grams per 10 minutes, a number average molecular weight (Mn) of about 43,580, a weight average molecular weight (Mw) of about 124,400, a Z average molecular weight (Mz) of about 255,600, and a polydispersity (Mw/Mn) of about 2.85.
  • Mn number average molecular weight
  • Mw weight average molecular weight
  • Mz Z average molecular weight
  • Mw/Mn polydispersity
  • the polyethylene employed was a linear low-density polyethylene obtained from the Exxon Chemical Company under the designation, LPX 61. It had a density of about 0.930 grams per cubic centimeter when measured in accordance with ASTM D 1505. It had a melt index of 105 at 190°C in accordance with ASTM 1238.
  • the number average molecular weight (Mn) was about 10,500, the weight average molecular weight (Mw) about 30,500, the Z average molecular weight (Mz) about 62,000, and the polydispersity (Mw/Mn) about 2.9.
  • polypropylene is identified by the abbreviation "PP”; polyethylene by the designation “PE”, and the copolymer of ethylene and vinyl acetate by the designation "EVA”.
  • PP polypropylene
  • PE polyethylene
  • EVA copolymer of ethylene and vinyl acetate
  • the proportions are by resin weight. In each case, they represent pellets of the respective resins placed in the hopper of apparatus similar to that shown in Figure 1 of the drawings, after being dry blended.
  • the equipment used in producing the microfibers was similar to that used in
  • All three nonwoven webs produced by the three different fiber blends had properties somewhat different from each other. All were tactically acceptable, soft and cloth-like. All had strength and stretch properties that were quite acceptable. The webs had tactile characteristics resembling those of polypropylene or polyethylene, but each of these nonwoven webs had recoverable stretch characteristics.
  • the two entries for the temperature of the attenuating air are those of the two plenum chambers respectively.
  • the ethylene-vinyl acetate used in this Example was purchased from Exxon Chemical Company at a nominal melt index of 200 at 190°C and containing 28% by weight of vinyl acetate.
  • a fibrous, nonwoven elastic coformed web was formed by utilizing the techniques illustrated in Figure 5 to combine wood pulp fibers with melt-blown fibers formed from the copolymer of ethylene and vinyl acetate.
  • melt-blowing of the copolymer was accomplished by extruding the the copolymer from a 3.81 cm (one and one-half inch) Johnson extruder and through a melt-blowing die having 15 extrusion capillaries per linear 2.54 cm (inch) of die tip. That is, melt-blowing system Al, as defined above, was utilized.
  • the capillaries in the die head each had a diameter of about 0.045 cm (0.018 inch) and a length of about 0.355 cm (0.14 inch).
  • the copolymer was extruded through the capillaries at a rate of about 1.8 grams per capillary per minute under the operating conditions that are summarized in Table VIII below.
  • the extrusion pressure exerted upon the copolymer in the die tip is reported as the "die pressure”.
  • the die tip configuration was adjusted so that it was recessed about 0.228 cm (0.090 inch) (-0.228 cm (-0.090)die tip stick-out) from the plane of the external surfaces of the lips of the air plates that form the attenuating air passageways on either side of the row of capillaries.
  • the air plates were adjusted so that the two attenuating air passages, one on each side of the extrusion capillaries, formed passageways having air gaps, i.e., widths, of about 0.170 cm (0.067 inch).
  • the air passageway or gap configuration utilized in this Example differed slightly from the configuration that is illustrated in Figure 3 in that the angle formed by the die tip portion 52, that is, the angle which the capillaries 22 bisect is 90°, and the angle is less than 90°, and therefore, the air gaps 44 and 46 are wider near the tip 24 of the die tip 52 than at the areas 40 and 42.
  • the air gaps 44 and 46 of this die configuration widen as opposed to narrow, as the attenuating air progresses (as indicated by the arrows 36 and 38).
  • melt-blown fibers were blown to a forming screen that was approximately 27.94 cm (12 inches) from the die tip.
  • dry wood pulp fibers having lengths of 0.635 to 1.27 cm (1/4 to 1/2 inch) were incorporated into the stream of melt-blown microfibers prior to the deposition of these microfibers upon the forming screen.
  • the wood pulp fibers were fed to a picker roll rotating at a rate of about 3,000 rpm, and fiber transporting air was supplied to the picker roll at a pressure of about 0.41 bar (G) (6 psig).
  • G 0.41 bar
  • the distance between the nozzle of the coforming apparatus and the streams of melt-blown fibers was not actually measured, but is believed to have been about 5.08 cm (two inches) below the die tip of the melt-blowing die, and about 5.08 cm (two inches) back from the die tip of the melt-blowing die.
  • This procedure provided a fibrous, nonwoven elastomeric web having a width in the cross-machine direction of about 50.8 cm (20 inches).
  • the web was composed of a blend having the composition indicated in Table VIII below for the two respective runs.
  • the cohesive, nonwoven coformed fibrous webs produced in these runs were characterized by very high absorbency for both oil and water, compared to copolymer webs in which wood pulp fiber was not incorporated.
  • the wood pulp fiber is an extremely inexpensive material at present, so that good web properties were attained at relatively low cost.
  • the webs had good hand.
  • the web produced from run A had good tactile characteristics.
  • the web produced from run B had a somewhat rough feel because of the relatively large amount of wood pulp fibers. Both webs were elastic and exhibited good recovery properties after being stretched. Both webs were therefore good candidates for the intercalary layer in a three-layer laminate, where the two outer layers were selected for strength and abrasion resistance, for example. Examples of such outer layers might be spun-bonded polyethylene and spun-bonded polypropylene, or spun-bcnded fibers from mixtures of these two polyolefins, or a random copolymer of both.
  • Example 2 Using the techniques generally described in Example 1, three additional runs were made to make microfibers and nonwoven cohesive elastomeric webs from ethylene-vinyl acetate copolymer.
  • This particular copolymer was purchased from Exxon Chemical Company, under the designation LD-763. It had a nominal melt index at 190°C of 50, and contained 28% by weight of vinyl acetate.
  • Other web properties are summarized in Table IX below, along with the properties of a web made from a somewhat different copolymer having a nominal melt index at 190°C of 160, and containing 28% by weight of vinyl acetate.
  • the web produced from this copolymer had a basis weight of 84.76g/m 2 (2.5 ounces per square yard).
  • run D could be operated at lower extrusion pressures than runs A, B and C.
  • the nonwoven elastomeric fibers, microfibers and webs of the present invention find widespread application in providing elasticized fabrics and fabric components.
  • the webs may be used by themselves, or they may be bonded to other materials.
  • Potential uses include disposable garments and articles, by which is meant garments and articles designed to be discarded after one or a few uses rather than being repeatedly laundered and reused.
  • Nonwoven webs made in accordance with the present invention are useful per se as wiping cloths because of their good absorbency. This is particularly the case with coformed webs where the secondary fiber is wood pulp fiber.
EP87104343A 1986-03-24 1987-03-24 Fibres élastomères, nappes fibreuses élastomères, nappes composites élastomères et composition apte à l'extrusion à base de copolymères d'éthylène-vinyle Withdrawn EP0239080A2 (fr)

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Cited By (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0261921A2 (fr) * 1986-09-22 1988-03-30 Exxon Chemical Patents Inc. Tissus de fils préparés par filage éclair
EP0311860A2 (fr) * 1987-10-02 1989-04-19 Unitika Ltd. Non-tissé fabriqué à partir de filaments soudables à chaud
EP0333209A2 (fr) * 1988-03-18 1989-09-20 Kimberly-Clark Corporation Matériau élastomérique en feuille, en fibres non tissées, et procédé pour le fabriquer
EP0333212A2 (fr) * 1988-03-18 1989-09-20 Kimberly-Clark Corporation Etoffe non tissée élastomérique, et procédé pour la fabriquer
WO1990003464A2 (fr) * 1988-09-23 1990-04-05 Kimberly-Clark Corporation Materiau composite elastique unit par etranglement
EP0333210A3 (en) * 1988-03-18 1990-04-25 Kimberly-Clark Corporation Bonded nonwoven material, method and apparatus for producing the same
EP0432763A1 (fr) * 1989-12-15 1991-06-19 Kimberly-Clark Corporation Matériau composite élastique avec étirabilité multidirectionnelle ainsi que sa méthode de production
EP0432755A1 (fr) * 1989-12-15 1991-06-19 Kimberly-Clark Corporation Matériau composite élastique avec étirabilité multidirectionnelle ainsi que sa méthode de production
EP0452727A1 (fr) * 1990-03-30 1991-10-23 Kimberly-Clark Corporation Matériau composite extensible, et procédé de formation pour le recouvrement et son utilisation
FR2680963A1 (fr) * 1991-09-10 1993-03-12 Silver Plastics Gmbh Co Kg Chiffon a poussiere et pour essuyage, a base de polyolefines.
US5226992A (en) * 1988-09-23 1993-07-13 Kimberly-Clark Corporation Process for forming a composite elastic necked-bonded material
EP0560384A1 (fr) * 1992-03-12 1993-09-15 Kimberly-Clark Corporation Tissu en élastomère métallisé et procédé pour sa fabrication
EP0582569A1 (fr) * 1991-03-20 1994-02-16 Reinhardt Nils Sabee Tissu elastifie a filaments continus et procede de fabrication
US5316837A (en) * 1993-03-09 1994-05-31 Kimberly-Clark Corporation Stretchable metallized nonwoven web of non-elastomeric thermoplastic polymer fibers and process to make the same
US5514470A (en) * 1988-09-23 1996-05-07 Kimberly-Clark Corporation Composite elastic necked-bonded material
US5599585A (en) * 1992-03-12 1997-02-04 Kimberly-Clark Corporation Process to make an elastomeric metallized fabric
US5656355A (en) * 1992-03-12 1997-08-12 Kimberly-Clark Corporation Multilayer elastic metallized material
US5985193A (en) * 1996-03-29 1999-11-16 Fiberco., Inc. Process of making polypropylene fibers
US6387471B1 (en) 1999-03-31 2002-05-14 Kimberly-Clark Worldwide, Inc. Creep resistant composite elastic material with improved aesthetics, dimensional stability and inherent latency and method of producing same
US6458726B1 (en) 1996-03-29 2002-10-01 Fiberco, Inc. Polypropylene fibers and items made therefrom
US6547915B2 (en) 1999-04-15 2003-04-15 Kimberly-Clark Worldwide, Inc. Creep resistant composite elastic material with improved aesthetics, dimensional stability and inherent latency and method of producing same
US7923505B2 (en) 2002-07-02 2011-04-12 Kimberly-Clark Worldwide, Inc. High-viscosity elastomeric adhesive composition
US8043984B2 (en) 2003-12-31 2011-10-25 Kimberly-Clark Worldwide, Inc. Single sided stretch bonded laminates, and methods of making same

Cited By (33)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0261921A3 (en) * 1986-09-22 1990-03-21 Exxon Chemical Patents Inc. Low viscosity ethylene acrylic copolymers for nonwovens
EP0261921A2 (fr) * 1986-09-22 1988-03-30 Exxon Chemical Patents Inc. Tissus de fils préparés par filage éclair
EP0311860A3 (en) * 1987-10-02 1990-07-04 Unitika Ltd. Heat-bondable filament and nonwoven fabric made of said filament
EP0311860A2 (fr) * 1987-10-02 1989-04-19 Unitika Ltd. Non-tissé fabriqué à partir de filaments soudables à chaud
EP0333209A2 (fr) * 1988-03-18 1989-09-20 Kimberly-Clark Corporation Matériau élastomérique en feuille, en fibres non tissées, et procédé pour le fabriquer
EP0333212A2 (fr) * 1988-03-18 1989-09-20 Kimberly-Clark Corporation Etoffe non tissée élastomérique, et procédé pour la fabriquer
US4970104A (en) * 1988-03-18 1990-11-13 Kimberly-Clark Corporation Nonwoven material subjected to hydraulic jet treatment in spots
EP0333212A3 (en) * 1988-03-18 1990-04-25 Kimberly-Clark Corporation Nonwoven elastomeric web and method of forming the same
EP0333210A3 (en) * 1988-03-18 1990-04-25 Kimberly-Clark Corporation Bonded nonwoven material, method and apparatus for producing the same
EP0333209A3 (en) * 1988-03-18 1990-05-02 Kimberly-Clark Corporation Nonwoven fibrous elastomeric web material and method of formation thereof
US5514470A (en) * 1988-09-23 1996-05-07 Kimberly-Clark Corporation Composite elastic necked-bonded material
US5226992A (en) * 1988-09-23 1993-07-13 Kimberly-Clark Corporation Process for forming a composite elastic necked-bonded material
WO1990003464A3 (fr) * 1988-09-23 1990-04-19 Kimberly Clark Co Materiau composite elastique unit par etranglement
WO1990003464A2 (fr) * 1988-09-23 1990-04-05 Kimberly-Clark Corporation Materiau composite elastique unit par etranglement
US5336545A (en) * 1988-09-23 1994-08-09 Kimberly-Clark Corporation Composite elastic necked-bonded material
EP0432763A1 (fr) * 1989-12-15 1991-06-19 Kimberly-Clark Corporation Matériau composite élastique avec étirabilité multidirectionnelle ainsi que sa méthode de production
EP0432755A1 (fr) * 1989-12-15 1991-06-19 Kimberly-Clark Corporation Matériau composite élastique avec étirabilité multidirectionnelle ainsi que sa méthode de production
US5116662A (en) * 1989-12-15 1992-05-26 Kimberly-Clark Corporation Multi-direction stretch composite elastic material
EP0452727A1 (fr) * 1990-03-30 1991-10-23 Kimberly-Clark Corporation Matériau composite extensible, et procédé de formation pour le recouvrement et son utilisation
EP0582569A4 (fr) * 1991-03-20 1995-02-01 Reinhardt Nils Sabee Tissu elastifie a filaments continus et procede de fabrication.
EP0582569A1 (fr) * 1991-03-20 1994-02-16 Reinhardt Nils Sabee Tissu elastifie a filaments continus et procede de fabrication
FR2680963A1 (fr) * 1991-09-10 1993-03-12 Silver Plastics Gmbh Co Kg Chiffon a poussiere et pour essuyage, a base de polyolefines.
EP0531961A1 (fr) * 1991-09-10 1993-03-17 Gizeh Spuntec Vliesstoffe GmbH Chiffon à base de polyoléfines
US5656355A (en) * 1992-03-12 1997-08-12 Kimberly-Clark Corporation Multilayer elastic metallized material
US5599585A (en) * 1992-03-12 1997-02-04 Kimberly-Clark Corporation Process to make an elastomeric metallized fabric
EP0560384A1 (fr) * 1992-03-12 1993-09-15 Kimberly-Clark Corporation Tissu en élastomère métallisé et procédé pour sa fabrication
US5316837A (en) * 1993-03-09 1994-05-31 Kimberly-Clark Corporation Stretchable metallized nonwoven web of non-elastomeric thermoplastic polymer fibers and process to make the same
US5985193A (en) * 1996-03-29 1999-11-16 Fiberco., Inc. Process of making polypropylene fibers
US6458726B1 (en) 1996-03-29 2002-10-01 Fiberco, Inc. Polypropylene fibers and items made therefrom
US6387471B1 (en) 1999-03-31 2002-05-14 Kimberly-Clark Worldwide, Inc. Creep resistant composite elastic material with improved aesthetics, dimensional stability and inherent latency and method of producing same
US6547915B2 (en) 1999-04-15 2003-04-15 Kimberly-Clark Worldwide, Inc. Creep resistant composite elastic material with improved aesthetics, dimensional stability and inherent latency and method of producing same
US7923505B2 (en) 2002-07-02 2011-04-12 Kimberly-Clark Worldwide, Inc. High-viscosity elastomeric adhesive composition
US8043984B2 (en) 2003-12-31 2011-10-25 Kimberly-Clark Worldwide, Inc. Single sided stretch bonded laminates, and methods of making same

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