MXPA01011064A - Stretchable nonwoven material. - Google Patents

Abstract

A stretchable nonwoven material including a nonwoven web comprising a plurality of bicomponent fibers comprising a polyester and a second polymer, said nonwoven web having been pattern-bonded or point-bonded followed by heating after forming. The second polymer is preferably a polyolefin, such as polyethylene or polypropylene.

Description

STRETCHED NON-WOVEN MATERIAL BACKGROUND OF THE INVENTION Field of the Invention This invention relates to a non-woven material which exhibits elastomeric properties even when it does not contain rubbers or thermoplastic elastomers. More particularly, this invention relates to a non-woven material that is stretchable in a machine direction and / or in a transverse direction without the use of rubber or thermoplastic elastomers. The non-woven material exhibits an elastic recovery in both the machine direction and the transverse direction when stretched to about 30%. The material is particularly suitable for use in absorbent articles for personal care such as diapers, training pants and adult incontinence garments.

Description of Previous Art Absorbent personal care items such as sanitary napkins, disposable diapers, incontinent care pads and the like are widely used, and much effort has been expended to improve the effectiveness and functions of these items. Flat and thick personal care items from the past that do not conform to the shape of the human body and that do not conform to the litÉ # f? iít-iitt? piirttt? iira 'rí? rt .- »-------- ^ i --- i-- ...- .., - ..-- .-. ---..... user movements have been replaced for the most part by articles shaped to the body, three-dimensional and elastically conformant.

Non-woven fabrics are defined as fabrics having a structure of individual fibers or yarns which are interlocked, but not in a regular or identifiable manner, as in a woven fabric. Non-woven fabrics can be formed by many processes such as, for example, meltblowing processes, spinning processes, and carded and bonded weaving processes. Typically, the fibers of these processes are deposited on a wire or forming band for tissue formation. When subjected to heat after tissue formation, there is a tendency for the non-woven fabric to shrink. The shrinkage of the non-woven fabric is considered to be disadvantageous in the sense that it generally results in non-uniformity of the fabric. See, for example, U.S. Patent Nos. 5,382,400 and 5,418,045, both issued to Pike et al., Which teach a process for making nonwoven polymeric fabrics wherein the polymeric filaments of multiple components bonded with spinning and continuous are crimped. before the multi-component and continuous filaments are formed into a non-woven fabric, resulting in an essential reduction in shrinkage and in an essentially stable and uniform non-woven fabric.

It will be evident, however, that diapers, training underpants and incontinence garments made of essentially stable uniform nonwoven fabrics may not conform to the user's movement, may reduce the comfort and possibly the functionality of the articles. To date, as indicated above, the subject has been focused on three-dimensional body-shaped articles that conform elastically as well as articles that employ elastic films.

SYNTHESIS OF THE INVENTION It is an object of this invention to provide a non-woven fabric material which exhibits elastic properties.

It is another object of this invention to provide a non-woven fabric material which exhibits elastic properties and which does not employ any rubbers or thermoplastic elastomers.

These and other objects of this invention are treated by a stretchable nonwoven material comprising a non-woven fabric which in turn comprises a plurality of bicomponent fibers comprising a polyester and a second polymer, said non-woven fabric, after forming of it, has been patterned or knitted together and then heated.

Polyesters suitable for use in this invention are any polyesters which shrink when heated. According to a particularly preferred embodiment, the polyester is polyethylene terephthalate (PET). The second polymer is one which does not shrink as much as the polyester with heating, preferably a polyolefin or a polyamide. The resulting stretchable nonwoven material is stretchable to about 130% of its length not pressed in the machine direction and / or in the cross machine direction. With the release of the pressing force, the non-woven material exhibits an elastic recovery in both the machine direction and the transverse direction, essentially returning to its original dimensions. Depending on the polyester and the second polymer used to form the fibers, the fibers can be made to split.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects and features of this invention will be better understood from the following detailed description taken in conjunction with the drawings in which: Figure 1 is a schematic diagram of a process line for producing a stretchable nonwoven material according to the invention; Y Figure 2 is a table showing the results obtained from materials produced according to the method of this invention.

DESCRIPTION OF PREFERRED INCORPORATIONS Definitions The term "stretchable" is used herein to mean any material which, with the application of a pressing force, is stretchable, to a pressed and stretched length and which will recover at least 50% of its elongation with the release of the lengthening force and stretcher. A hypothetical example will be a one-inch sample of a material which is stretchable to at least 1.50 inches (50% elongation) and which, when lengthened to 1.50 inches and when released, will recover to a length of no more than 1.25 inches (50% recovery).

As used herein, the term "non-woven fabric" or "nonwoven material" means a fabric having a structure of individual fibers or threads which are interlocked, but not in a regular or identifiable manner, such as in a fabric or films woven that have fibrillated. Fabrics or non-woven materials have been formed from many processes such as, for example, meltblowing processes, spinning processes, and carded and bonded weaving processes.

The basis weight of the non-woven materials or fabrics is usually expressed in ounces of material per square yard (osy) or grams per square meter (gsm) and the fiber diameters are usually expressed in microns. (Note that to convert from ounces per square yard to grams per square meter multiply ounces per square yard by 33.91).

As used herein, the term "spunbonded fibers" refers to fibers of small diameter which are formed by extruding the molten thermoplastic material as filaments from a plurality of thin, usually circular, capillary vessels of a spinner with a diameter of the extruded filaments being rapidly reduced as taught, for example, by the patents of the United States of America numbers 4,340,563 granted to Appel et al., and 3,692,618 granted to Dorschner et al., 3,802,817 granted to Matsuki et al., 3,338,992 and 3,341,394 granted to Kinney, 3,502,763 granted to Hartman, 3,502,538 granted to Levy, and 3,542,615 granted to Dobo and others. Spunbonded fibers are cooled and are generally non-tacky when they are deposited on a collecting surface. Spunbonded fibers are generally continuous and have average diameters greater than 7 microns, more particularly, between about 10 and 35 microns. As used herein the term "melt blown fibers" refers to fibers formed by extruding a molten thermoplastic material through a plurality of matrix capillary vessels, usually circular and thin like strands or filaments fused into high velocity and converging gas streams (eg air streams) which attenuate the filaments of molten thermoplastic material for reduce its diameter, which can be to a microfiber diameter. Then, the meltblown fibers are carried by the high velocity gas stream and are deposited on a harvester surface to form a meltblown fabric and randomly dispersed. Such a process is described, for example, by the United States of America patent number 3,849,241 granted to Butin. Melt-blown fibers are microfibers which may be continuous or discontinuous, are generally smaller than 10 microns in average diameter and are generally sticky when deposited on a collecting surface.

As used herein, the term "carded and bonded fabric" refers to fabrics made of basic fibers which are sent through a combing or carding unit, which breaks apart and aligns the basic fibers in the direction of the machine to form a fibrous nonwoven fabric generally oriented in the machine direction. Such fibers are usually purchased in bales which are placed in a shredder which separates the fibers before the carding unit. Once the tissue is formed, it is then joined by one or more of the various known joining methods.

As used herein, the term "microfibers" refers to fibers of small diameter having an average diameter of no more than about 75 microns. For example, they have an average diameter of from about 0.5 microns to about 50 microns, or more particularly, having an average diameter of from about 2 microns to about 40 microns. Another frequently used expression of fiber diameter is denier, which is defined as grams per 9,000 meters of a fiber and can be calculated as a fiber diameter in square microns, multiplied by the density in grams per cubic centimeter, multiplied by 0.00707. A lower denier indicates a finer fiber and a higher denier indicates a thicker or heavier fiber. For example, a diameter of polypropylene fiber given as 15 microns can be converted to denier by placing the square, multiplying the results by 0.89 g / cc and multiplying by 0.00707. Therefore, a 15 micron polypropylene fiber has a denier of about 1.42. Outside the United States of America, the unit of measurement is most commonly the "tex" which is defined as grams per kilometer of fiber. The tex can be calculated as denier / 9.

As used herein, the term "polymer" generally includes, but is not limited to, homopolymers, - -M'itj- ^ riffH8 ** ^ * ^ *** - ^ * '"-" ^ ~ -M - M - «-_ M --- ^ - J- ^ l *« ._ j? ^ J? The present invention is also directed to the use of copolymers, such as, for example, block, graft, random and alternating copolymers, terpolymers, etc., and mixtures and modifications thereof. In addition, unless specifically limited in another way, the term "polymer" also includes all possible geometric configurations of the material. These configurations include, but are not limited to, isotactic, syndiotactic, atactic and random symmetries.

As used herein, the term "personal care product" means disposable diapers, training underpants, absorbent undergarments, adult incontinence products, and women's hygiene products.

As used herein the term "bicomponent fibers" refers to fibers which have been formed from at least two polymers extruded from separate extruders but spun together to form a fiber. The bicomponent fibers are also sometimes referred to as conjugated fibers or multi-component fibers. The polymers are arranged in different zones placed essentially constant across the cross sections of the bicomponent fibers and extend continuously along the length of the bicomponent fibers. The configuration of such bicomponent fiber can be, for example, a sheath / core arrangement where one polymer is surrounded by another, or can be ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^^^^^^^^^^^^^^^^^^^^^^^^ ^ £ ^ be a side-by-side arrangement, a cake arrangement or an arrangement of "islands in the sea" type. The bicomponent fibers are taught in the patents of the United States of America number 5,108,820 granted to Kaneko and others, 4,795,668 granted to Krueger and others, 5,540,992 granted to Marcher and others, and 5,336,552 granted to Strack and others. The bicomponent fibers are also shown by U.S. Patent No. 5,382,400 issued to Pike et al. For the two component fibers, the polymers may be present in proportions of 75/25, 50/50, 25/75 or any other desired ratio.

As used herein, the term "machine direction" or "MD" means the length of a fabric in the direction in which it is produced. The term "cross machine direction" or "CD" means the width of the fabric, that is, an address generally perpendicular to the machine direction.

As used herein, the term "consisting essentially of" does not exclude the presence of additional materials which do not significantly affect the desired characteristics of a given composition or product. Example materials of this class include, without limitation, pigments, antioxidants, stabilizers, surfactants, waxes, flow promoters, solvents, particles, and materials.

»A-j ---». Il. j.-t ^ *, aggregates to increase the processing of the composition.

The invention described herein is a nonwoven material exhibiting elastomeric properties even when it does not contain rubbers or thermoplastic elastomers. The material comprises a non-woven fabric made of bicomponent fibers containing a polyester and a second polymer, such as polyethylene. When the fabric is knitted or bonded and exposed to a heating process after having When joined, it shrinks, resulting in a nonwoven material exhibiting elastic recovery in both the machine direction and the transverse direction when stretched to about 30%. The non-woven fabric is preferably heated to a temperature of at least about 220 degrees F.

The amount of stretch and recovery is adjustable by varying the "shrinkage" temperature, and / or the bond area and / or the polyester content. In addition, the amount of shrinkage increases with increasing the basis weight of the non-woven fabric. Figure 1 is a schematic diagram of a process line for producing a stretchable nonwoven material according to this invention. Process line 10 is arranged to produce continuous bicomponent filaments.

The process line 10 includes a pair of extruders 12a and 12b for separately extruding a polymer component A, a _-- i ----------- H______ - '^ EfeáaJtei-M-MÉ - S- aEv-¿- - - ¿¿^ - ¿^ polyester in the present case, and a polymer component B, for example a polyolefin. The polymer A is fed to a respective extruder 12a from a first hopper 14a and the polymer component B is fed to the respective extruder 11b from a second hopper 14b. The polymer components A and B are fed from the extruders 12a and 12b through the respective polymer conduits 16a and 16b to a spinning organ 18. The spinning organs are not well known to those skilled in the art and therefore not they will be described in detail here. Generally, spinner 18 includes a box containing a spin pack which includes a plurality of plates stacked one on top of the other with an aperture pattern arranged to create flow paths to direct polymer A and polymer B separately through of the spinner organ. The spinner member 18 has the openings arranged in one or more rows. The openings of the spinning member form a curtain of filaments that extends downwardly when the polymers are extruded through the spinning organ. For the purposes of the present invention, the spinner 18 is arranged so as to form bicomponent filaments wherein both polymer A and polymer B are placed on a part of the surface thereof. Such bicomponent filaments include side-by-side arrays, cake arrays, and arrays of several lobes in which one of the polymers forms at least a portion of the lobes, whose lobes are positioned at a distance from each other, and the Í > &? m.? Mk ** lmí ~. , ~ -... ^ .--. ^ ---., ..., - ..m,., - »^ ..._ ,. * .... -.- * ,, * - _ »__» ^ -.-- h _ »- i_ > ?? The second polymer is placed centrally, at least a part of the surface of which can be seen in the area between the lobes.

The process line 10 also includes a cooling blower 20 positioned on one side of the curtain of filaments extending from the spinner member 18. The air from the cooling air blower 20 cools the filaments extending from the spinner member. 18 A vacuum cleaner or fiber pulling unit 22 is placed below the spinner member 18 and receives the cooled filaments. Vacuum cleaners or fiber pulling units for use in melt spinning polymers are well known to those skilled in the art. Fiber pulling units suitable for use in the process include a linear fiber vacuum cleaner of the type shown in U.S. Patent No. 3,802,817 and eductive guns of the type shown in U.S. Pat. Nos. 3,692,618 and 3,423,266, the descriptions of which are incorporated herein by reference.

Generally described, the fiber pull unit 22 includes an elongated vertical conduit through which the filaments are pulled, sucking in the air entering from the sides of the conduit and flowing down through the conduit. ii _-.- ft-tt? irri. ^ .... ^ - ^ .. a ^^^^^ - »^ ,,,. ^ -, ..,,, rtiüiti The heater 24 supplies the hot suction air to the fiber pulling unit 22. The hot suction air pulls the filaments and ambient air through the fiber pull unit 22.

An endless perforated forming surface 26 is positioned below the fiber pulling unit 22 and receives the continuous filaments from the outlet opening of the fiber pulling unit 22. The forming surface 26 travels around the guide rollers 28. A vacuum 30 placed below the forming surface 26 where the filaments are deposited pulls the filaments against the forming surface.

The process line 10 further comprises a compression roller 32 which, together with the forward part of the guide rollers 28, receives the fabric as it is cut out of the forming surface 26. In addition, the process line 10 includes an apparatus attachment such as a pattern joint or a thermal point union 34.

The thermal point joint involves passing a fabric or fabric of fibers that are to be joined between an anvil roller and a heated calender roll. The calendering roll usually has, although not always, a pattern in some way so that the entire fabric is not attached to it through its entire surface.As a result of this, several patterns have been developed for the Calendering rolls for functional reasons as well as for aesthetic reasons An example of a pattern has points and is the Hansen Pennings 5 or "H &P" pattern with a bound area of about 30% with about 200 joints per square inch as US Pat. No. 3,855,046 issued to Hansen &Pennings is taught The H &P pattern has bolt or square dot joining areas where each bolt has a lateral dimension of 10 0.038 inches (0.965 millimeters), a gap of 0.070 inches (1,778 millimeters) between the bolts, and a bond depth of 0.023 inches (0.584 millimeters). The resulting pattern has a bound area of about 29.5%. Another typical point union pattern is the Hansen pattern attached and 15 expanded Pennings or "EHP" which produces a 15% joint area with a square bolt that has a side dimension of 0.037 inches (0.94 millimeters), a bolt spacing of 0.097 inches (2.464 millimeters) and a depth of 0.039 inches (0.991 millimeters). Another typical point union pattern 20 designated "714" has square point joining areas where each bolt has a side dimension of 0.023 inches, a gap of 0.062 inches (1,575 mm) between the bolts, and a joint depth of 0.033 inches (0.838 mm). The resulting pattern has a bound area of around 15%. Yet Another common pattern is the star pattern in C which has a bound area of about 16.9%. The star pattern in C B ^^ yi? S ^^^^^ j ^ jjg ^^ gijj ^^^^ g ^ gg ^^ j ^^^^^^^ g ^^^ jgy ^ j ^^^^^^^^^ ^^^^^^^^^^^^^^^^^ has a bar design in the transverse direction or "corduroy" interrupted by shooting stars. Other common patterns include a diamond pattern with repetitive and slightly off-center diamonds and a woven wire pattern that looks like the name suggests, like a window grate.

Downstream of the thermal point bonding rolls 34 is a hot air knife 36, or some other heating processes, such as a furnace, to heat the fabric to a desired temperature. A conventional hot air blade includes a mandrel with a groove that blows a jet of hot air to the surface of the non-woven fabric. Such hot air blades are shown, for example, by U.S. Patent No. 4,567,796 issued to Kloehn et al. Alternatively, the material can be washed, and it is washed and dried at elevated temperatures to obtain the desired shrinkage.

As previously indicated, the nonwoven fabric used to make the nonwoven material of this invention comprises a plurality of bicomponent fibers containing a polyester and a second polymer, such as polyethylene. While any polyester that shrinks upon heating can be used, according to a particularly preferred embodiment, the polyester is polyethylene terephthalate. The second polymer comprising the bicomponent fibers is a polymer selected from the group consisting of polyolefins and polyamides. Particularly preferred polyolefins are polyethylene and polypropylene. Suitable polyamides include, but are not limited to, nylon 6, nylon 6/6, nylon 10, nylon 12, and the like.

Depending on the selection of the polyester and the second polymer used to form the bicomponent fibers, the fibers can be made divisible, thereby increasing the softness of the nonwoven materials produced therefrom. These fibers can be divided by any number of mechanical, thermal or chemical means. And, although the division of the bicomponent fibers is not required for the shrinkage of the non-woven fabric during the formation and for the elastomeric recovery of the formed nonwoven fabric, this may increase the elastomeric characteristics of the material.

According to a preferred embodiment of this invention, the bicomponent filament comprises a range of about 40% by weight to about 90% by weight of polyester (PET). According to a particularly preferred embodiment of this invention, the bicomponent filament comprises in a range of about 55% by weight to about 65% by weight of polyester.

The stretchable nonwoven material of this invention according to an embodiment of said invention comprises bicomponent filaments which are produced by means of a bonded and carded tissue process. According to a particularly preferred embodiment, the bicomponent filaments used to produce the non-woven fabric are spin-bonded.

E j e m p l o s Figure 2 is a summary of data collected in relation to stretchable nonwovens produced according to the method of this invention. Data are presented for five sample materials produced from side-by-side bicomponent fibers of polyester and linear low density polyethylene, samples numbered 1-5. Two sets of data are presented for each sample - stretchability in the direction of the machine (MD) and stretchability in the transverse direction (CD). The process conditions for the preparation of these samples were as follows: Polymers: Polyethylene = Ticona EKX-183 Linear Low Density Polyethylene = Dow 6811A High Density Polyethylene = Dow 25455 Hole Diameter = 0.6 mm J? ? H Production = 0.6 ghm Fusion Temperature = 525 ° Cooling Air Temperature = 61 ° F Polymer Ratio = 50/50 (by volume) or 59/41 PET / PE (by weight) Bonding Pattern = See examples (spirals of 5% and 10%, and HP) The data for a non-woven fabric of bicomponent fibers configured in the form of a 16-piece splittable cake, shows 6, are also presented. In this case the bicomponent fibers were produced from polyethylene and high density polyethylene (HDPE).

Although the foregoing description of this invention has been made in relation to certain preferred embodiments thereof, and many details have been established for the purpose of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional incorporations. and that certain of the details described herein can be considerably varied without departing from the basic principles of the invention. Í? É ^^^ M ^^^^^ £ tí ^^? Jg ^^? T ^^ ta ^^ i ^^^^^ * t¡ ^ _ ¡^^^^^ f -: .. " .- -, -. »? Fa» _ < _taM. > -A «_i? - -un --'-..-

Claims (23)

R E I V I N D I C A C I O N S

1. A stretchable nonwoven material comprising: a nonwoven fabric comprising a plurality of bicomponent fibers comprising a polyester and a second polymer, said nonwoven fabric being joined by a method selected from the group consisting of pattern bonding, knit bonding and combinations thereof and then it has warmed up.

2. A stretchable nonwoven material as claimed in clause 1, characterized in that said polyester is a polyester that shrinks upon being heated.

3. A stretchable nonwoven material as claimed in clause 2, characterized in that said second polymer is a polymer that shrinks less than said polyester when heated.

4. A stretchable nonwoven material as claimed in clause 2, characterized in that said polyester is polyethylene terephthalate.

5. A stretchable nonwoven material as claimed in clause 1, characterized in that said bicomponent fibers are configured so that both the polyester and the second polymer are present on a surface of said fibers.

6. A stretchable nonwoven material as claimed in clause 5, characterized in that said bicomponent fibers are configured as a side-by-side, multi-lobed and pastel arrangement.

7. A stretchable nonwoven material as claimed in clause 1, characterized in that said polyester comprises a range from about 20% to about 90% by weight of said bicomponent fibers.

8. A stretchable nonwoven material as claimed in clause 1, characterized in that said polyester comprises a range from about 40% by weight to about 65% by weight of said bicomponent fibers.

9. A stretchable nonwoven material as claimed in clause 1, characterized in that said bicomponent fibers are linked with spinning.

10. A stretchable nonwoven material as claimed in clause 1, characterized in that said second polymer is a polymer selected from the group consisting of polyolefins and polyamides.

11. A stretchable nonwoven material as claimed in clause 10, characterized in that said second polymer is selected from the group consisting of polyethylene, polypropylene, and nylon.

12. A stretchable nonwoven material as claimed in clause 1, characterized in that said bicomponent fibers are divisible.

13. A method for producing a stretchable nonwoven material comprising the steps of: forming a nonwoven fabric using a plurality of bicomponent fibers, said bicomponent fibers comprise a polyester and a second polymer; joining said nonwoven fabric using a method selected from the group consisting of pattern bonding, point bonding and combinations thereof; and heating said nonwoven fabric, resulting in a stretchable non-woven fabric.

14. A method as claimed in clause 13, characterized in that said polyester is polyethylene terephthalate.

15. A method as claimed in clause 13, characterized in that said second polymer is a polymer selected from the group consisting of polyolefins and polyamides.

16. A method as claimed in clause 13, characterized in that said bicomponent fibers are linked with spinning.

17. A method as claimed in clause 13, characterized in that said polyester comprises a range from about 20% by weight to about 90% by weight of said bicomponent fibers.

18. A method as claimed in clause 13, characterized in that said polyester comprises a range of about 40% by weight to about 65% by weight of said bicomponent fibers.

19. A method as claimed in clause 13, characterized in that said bicomponent fibers are configured so that both the polyester and said second polymer are present on a surface of said fibers.

20. A method as claimed in ---., at .---. A, -i-- «.-- ... j-dfcL, .." SfcM-fffl, clause 19, characterized in that said bicomponent fibers are configured in a side-by-side, multi-lobed and pastel arrangement.

21. A method as claimed in clause 15, characterized in that said polyolefin is selected from the group consisting of polyethylene and polypropylene.

22. A method as claimed in clause 15, characterized in that said polyamide is nylon.

23. An article for personal care that includes: a non-woven fabric comprising a plurality of bicomponent fibers comprising a polyester and a second polymer, said non-woven fabric being joined by a method selected from the group consisting of a pattern bond, a point bond and combinations thereof. and then heated after the training. Í! Tf-tTttH rr? I? F '* ^ - "- r-fiír rr ~ * ~ ^ * ^^^ - * - ^ - < ^ - ^^^. ~ ^ * ^ ~ ^ * ^ ~, *. * «. * ^ > > ~. > -.-_ > .. - -É-É t 'SUMMARY A stretchable nonwoven material including a nonwoven fabric comprising a plurality of bicomponent fibers which in turn comprise a polyester and a second polymer, said nonwoven fabric has been patterned or knit joined followed by heating after forming, the second polymer is preferably a polyolefin, such as a polyethylene or a polypropylene. ~ mm8M ~ ¿.- H¡m * i ~ k ??? ~? * ». * ~ * í ~ * ...-Jfe .. * my ii-táiiHrt