CN1349570A - 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

stretchable nonwoven material

Background of the invention

technical field

The present invention relates to a nonwoven material that exhibits elastomeric properties although it does not contain thermoplastic elastomers or rubber. More specifically, the present invention relates to a nonwoven material that can be stretched in the machine direction and/or in the transverse direction without the use of thermoplastic elastomers or rubber. The nonwoven material, when stretched up to about 30%, exhibits elastic recovery in both the machine and cross directions. The material is especially suitable for use in personal care absorbent articles such as diapers, training pants and adult incontinence garments.

Description of prior art

Absorbent personal care articles such as sanitary napkins, disposable diapers, incontinence pads and the like are in widespread use and much effort has been made to improve the effectiveness and function of such articles. Previously thick and flat personal care products that failed to conform to the shape of the human body and remain conformal to the movement of the user have largely given way to resilient conformal, three-dimensional, body-shaping products.

A nonwoven web is defined as a web having a structure of individual fibers or threads laid across, rather than in a regular or identifiable pattern as in knitted fabrics. Nonwoven webs can be formed by a variety of methods, such as meltblowing, spunbonding, and bonded carded webs. Typically, according to these methods, fibers are deposited onto a forming wire or belt to form a web. The nonwoven web has a tendency to shrink when it is heated after formation. Shrinkage of nonwoven webs is considered undesirable because it often results in non-uniform webs. See, for example, U.S. Patent 5,382,400 and U.S. Patent 5,418,045, both to Pike et al., which disclose a method of making polymeric nonwovens in which continuous melt-spun multicomponent polymeric tows are polymerized in the continuous melt-spun multicomponent The tow is crimped before being formed into a nonwoven web, thereby greatly reducing shrinkage and making a substantially stable and uniform nonwoven web.

It is clear, however, that diapers, training pants, and incontinence garments made from substantially stable, uniform nonwoven webs may not remain conformable to the activities of the wearer, thereby reducing the comfort of the article and possibly compromising its function. As noted above, this problem has heretofore been addressed by the use of resiliently conformal, three-dimensional, body-shaped articles as well as articles employing elastic films.

Summary of the invention

It is an object of the present invention to provide an elastic nonwoven web.

Another object of the present invention is to provide a nonwoven web material which is elastic without using any thermoplastic elastomer or rubber.

The above and other objects of the present invention are achieved by a stretchable nonwoven material comprising a nonwoven web comprising a plurality of bicomponent fibers comprising polyester and a second polymer, said The nonwoven web is pattern bonded or point bonded after it is formed and then heated. Polyesters suitable for use in the present invention may be any polyester which shrinks upon heating, and according to a particularly preferred embodiment, the polyester is ethylene terephthalate (PET). The second polymer is a polymer that does not shrink as much as polyester after heating, and is preferably polyolefin or polyamide. The resulting stretchable nonwoven material can be stretched up to about 130% of its unbiased length in the machine and/or transverse directions. After the biasing force is removed, the nonwoven material exhibits elastic recovery in both the machine and transverse directions, thereby returning substantially to its original dimensions. Depending on the polyester and the second polymer used to make the fiber, the fiber can be split.

Brief description of the drawings

These and other objects and features of the present invention will be better understood after studying the following detailed description and referring to the accompanying drawings, which are:

Fig. 1 is a schematic diagram of a production line for producing the stretchable nonwoven material of the present invention; and

Figure 2 is a table showing the results achieved with materials produced by the method of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

definition

The term "stretchable" as used herein refers to a material that, when subjected to a biasing force, can stretch to an elongated biased length and will return (recover) to its elongated length when the stretching, elongating force is removed. At least 50%. A hypothetical example is that a 1-inch sample of a material stretchable to at least 1.50 inches (50% elongation) will recover to no more than 1.25 (50% recovery) inches after being stretched to 1.50 inches and released. length.

As used herein, the term "nonwoven web" or "nonwoven material" refers to a material that is composed of individual fibers or threads that are crosslaid rather than in a regular or identifiable pattern as in knitted fabrics and fibrillated films. The fiber mesh that constitutes the structure. Nonwoven webs or materials can be formed by a variety of methods, such as meltblowing, spunbonding, and bonded carded webs. The basis weight of a nonwoven web or material is usually expressed in ounces of material per square yard (osy) or grams per square meter (gsm); usable fiber diameters are usually expressed in microns. (Note: To convert the osy value to gsm value, multiply the osy value by 33.91.)

As used herein, the term "spunbond fibers" refers to a class of small diameter fibers formed by extruding molten thermoplastic material into tows from a plurality of fine, usually circular spinneret holes in a spinnerette, Subsequently, the diameter of the extruded strands is rapidly attenuated by methods such as in U.S. Patents 4,340,563 to Appel et al. and 3,692,618 to Dorschner et al., 3,802,817 to Matsuki et al., 3,802,817 to Kinney et al. US Patents 3,338,992 and 3,341,394, US Patent 3,502,763 to Hartmann, US Patent 3,502,538 to Levy, US Patent 3,542,615 to Dobo et al. Spunbond fibers are generally non-tacky when deposited onto a collecting surface after quenching. Spunbond fibers are generally continuous and have an average diameter greater than 7 μm, especially about 10 to 35 μm.

As used herein, the term "meltblown fibers" refers to fibers formed by extruding molten thermoplastic material in the form of molten strands or tows from a plurality of fine, usually circular spinneret holes to gradually convergent In a high-velocity gas stream (such as an air stream), the gas stream attenuates the molten thermoplastic material strands to a small diameter, which may be as small as the diameter range of microfibers. The molten fibers are then entrained by the high-velocity air stream and deposited on a collection surface to form a web of randomly distributed meltblown fibers. Such methods are disclosed, for example, in US Patent 3,849,241 to Buntin. Meltblown fibers are microfibers, which may be continuous or discontinuous, generally have an average diameter of less than about 10 μm, and are generally tacky when deposited onto a collecting surface.

As used herein, the term "bonded carded web" refers to a web made of staple fibers that, during manufacture, are passed through a comber or carding device that separates the staple fibers and separates them along the aligned along the machine direction, thereby forming a nonwoven web composed of fibers generally oriented along the machine direction. The fibers are purchased in bales and placed on a picker to separate the fibers before being fed to the carding unit. Once formed, the web is subsequently bonded by one or more of several known bonding methods.

As used herein, the term "microfiber" refers to a small-diameter fiber having an average diameter of not greater than about 75 μm, such as an average diameter of about 0.5 μm to about 50 μm, or more specifically, a microfiber may have an average diameter of about 2 μm to about 40 μm. diameter. Another often-used expression of fiber diameter is denier, which is defined as grams per 9000 meters of fiber and can be squared based on the fiber diameter expressed in μm, multiplied by the density in g/cc, multiplied by Calculated at 0.00707. Lower deniers indicate thinner fibers; higher deniers indicate thicker or heavier fibers. For example, it is known that the diameter of polypropylene fiber is 15 μm, to convert it to denier, it can be squared, multiplied by 0.89g/cc, and then multiplied by 0.00707. Thus, a 15 μm polypropylene fiber has a denier of about 1.42. Outside the United States, the common unit of measurement is "tex," which is defined as grams per kilometer of fiber. The tex can be calculated as denier/9.

The term "polymer" as used herein generally includes, but is not limited to: homopolymers; copolymers, such as block, graft, random and alternating copolymers, terpolymers, etc.; a transformative form. Furthermore, unless specifically defined otherwise, the term "polymer" shall cover all possible molecular geometries of the material. These configurations include, but are not limited to, isotactic, syndiotactic and atactic symmetric configurations.

As used herein, the term "personal care product" refers to diapers, training pants, absorbent underpants, adult incontinence products, and feminine hygiene products.

As used herein, the term "bicomponent fiber" refers to at least two polymers extruded from separate extruders but spun together to form the same fiber. Bicomponent fibers are also sometimes called conjugate fibers or multicomponent fibers. The polymers are arranged in substantially fixed, well-defined regions across the cross-section of the bicomponent fiber and extend continuously along the entire length of the bicomponent fiber. The configuration (section arrangement) of such bicomponent fibers may be, for example, a sheath/core arrangement in which one polymer is surrounded by another, or may be side-by-side, fanned out, or " Sea-island" arrangement. Bicomponent fibers are disclosed in US Patent 5,108,820 to Kaneko et al., US Patent 4,795,668 to Krueger et al., US Patent 5,540,992 to Marcher et al., and US Patent 5,336,552 to Strack et al. Bicomponent fibers are also disclosed in US Patent 5,382,400 to Pike et al. For bicomponent fibers, the polymers may be present in a ratio of 75/25, 50/50, 25/75 or any other desired ratio.

As used herein, the term "machine direction" or "MD" refers to the direction along which the fabric is produced, ie, the length of the fabric. The term "cross-machine direction" or "CD" refers to the width of the fabric, ie, the direction approximately perpendicular to the MD.

The term "consisting essentially of" as used herein does not exclude the presence of additional materials which do not significantly affect the desired properties of a given composition or product. Such exemplary materials would include, but are not limited to, pigments, antioxidants, stabilizers, surfactants, waxes, flow promoters, solvents, pellets, and materials added to improve the processability of the composition.

The invention disclosed herein is a nonwoven material that exhibits elastomeric properties but does not contain thermoplastic elastomers or rubber. The material comprises a nonwoven web composed of bicomponent fibers comprising polyester and a second polymer such as polyethylene. When the web is pattern bonded or point-bonded and then subjected to heat treatment after bonding, it shrinks, causing the resulting nonwoven material to exhibit longitudinal and Lateral elastic recovery. The nonwoven web is preferably heated to a temperature of at least about 220°F. The amount of stretch and recovery can be adjusted by varying the "shrink" temperature and/or bond area and/or polyester content. Additionally, the amount of shrinkage increases as the basis weight of the nonwoven web increases.

Fig. 1 is a schematic diagram of a production line for producing the stretchable nonwoven material of the present invention. Line 10 is arranged to produce bicomponent continuous filaments. Line 10 includes a pair of extruders 12a and 12b for extruding polymer component A, in this example polyester, and polymer component B, such as polyolefin, respectively. Polymer A is fed from the first hopper 14a to the corresponding extruder 12a, and polymer B is fed from the second hopper 14b to the corresponding extruder 12b. Polymer components A and B are fed from extruders 12a and 12b to spinneret 18 through respective polymer conduits 16a and 16b. Spinnerets are well known to those skilled in the art and will therefore not be described in detail here. Broadly speaking, the spinneret 18 comprises a housing enclosing a spin pack comprising successively superimposed plates with arrays of openings arranged to direct polymer A and polymer B to flow separately from each other through the spinneret. flow path. The spinneret 18 has holes arranged in one or more rows. These spinneret holes form a downwardly extending curtain of filaments as the polymer is extruded through the spinneret. For the purposes of the present invention, the spinneret 18 is arranged in a configuration suitable for producing bicomponent filaments in which both polymer A and polymer B are disposed on a portion of the filament surface. Such bicomponent filaments include side-by-side arrangements, fan-shaped arrangements and multi-lobal arrangements, in which one polymer forms at least some of the leaves spaced apart from each other and a second polymer forms In the center, at least part of its surface is visible from the area between the blades.

The production line 10 also includes a quench fan 20 arranged adjacent to the silk curtain extending from the spinneret 18 . Air exits the quench blower 20 to quench the filaments extending from the spinnerette 18.

A fiber drafting unit or aspirator 22 is located below the spinneret 18 for receiving the quenched tow. Fiber draw units or aspirators used in polymer melt spinning processes are well known to those skilled in the art. Fiber drafting units suitable for use in the process include (straight) linear fiber aspirators of the type shown in U.S. Patent 3,802,817 and ejector guns of the type shown in U.S. Patents 3,692,618 and 3,423,266, which are incorporated herein The published content is accepted as a reference.

Broadly speaking, the fiber drafting unit 22 comprises an elongated vertical passage through which the tow is drawn, and suction air enters from the side of the passage and flows downwardly through the passage. The heater 24 supplies hot suction air to the fiber drafting unit 22 . The hot suction air draws in the tow and ambient air as it flows through the fiber drafting unit 22 .

An annular perforated forming surface 26 is located below the fiber drafting unit 22 and receives the continuous tow from the exit of the fiber drafting unit 22 . The forming surface 26 moves around guide rollers. A vacuum 30 located below the forming surface 26 draws the tow deposited on the forming surface against the forming surface.

Line 10 also includes compaction rolls 32 which, in conjunction with forwardmost guide rolls 28, receive the web as it is pulled from forming surface 26. In addition, the production line 10 also includes bonding equipment 34, such as pattern bonding or thermal point bonding.

Thermal point bonding involves passing the nonwoven or web to be bonded between a heated calender roll (or embossing roll) and an anvil roll. Embossing rolls are usually, though not always, patterned in some way so that the nonwoven is not bonded along its entire surface. Thus, various patterns for rolls have been developed for functional as well as aesthetic reasons. An example of a pattern comprising many points is the Hansen Pennings or "H&P" pattern with a bond area of about 30% and about 200 bond points per square inch as described in U.S. Patent 3,855,046 to Hansen and Pennings . The H&P pattern has square-shaped dot or pin bond areas, where each pin has a side dimension of 0.038 inches (0.965 mm), a pin-to-pin spacing of 0.070 inches (1.778 mm), and a bond depth of 0.023 inches (0.584mm). The pattern formed had a bonded area of about 29.5%. Another typical point bonding pattern is the Extended Hansen and Pennings, or "EHP" bonding pattern, which produces a 15% bonded area with a square needle side dimension of 0.037 inches (0.94mm). The pitch is 0.097 inches (2.464mm), and the depth is 0.039 inches (0.991mm). Another typical point bond pattern called "714" has a square pin bond area where each pin has a side dimension of 0.023 inches, a pin-to-pin spacing of 0.062 inches (1.575 mm), and a bond depth of 0.033 inches. inches (0.838mm). The resulting pattern had a bonded area of about 15%. Yet another commonly used pattern is the C-Star pattern, which has a bond area of about 16.9%. The C-Star pattern features horizontal stripes or a "corduroy" pattern interrupted by glittering stars. Other common patterns include argyle, which has repeating and slightly offset diamonds, and wavy lines, which look like the name suggests, like window screens.

Downstream of the thermal point bonding roll 34 is a hot air knife 36, or some other heating method, such as an oven, for heating the web to the desired temperature. A traditional hot air knife consists of a mandrel with a slot through which a jet of hot air is continuously ejected onto the surface of the nonwoven web. Such a hot air knife is disclosed, for example, in US Patent 4,567,796 to Kloehn et al. Alternatively, if the material can be washed, it is washed and dried at high temperature to achieve the desired shrinkage.

As noted above, the nonwoven web used to make the nonwoven material of the present invention comprises a plurality of bicomponent fibers which in turn contain polyester and a second polymer, such as polyethylene. Although any heat-shrinkable polyester may be used, in a particularly preferred embodiment of the invention the polyester is polyethylene terephthalate. The second polymer constituting the bicomponent fiber is a polymer selected from 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 particular choice of polyester and second polymer used to form the bicomponent fibers, the fibers can be made splittable, thereby increasing the softness of the nonwoven material produced from them. Splitting of the fibers can be accomplished by any mechanical, thermal or chemical means. Furthermore, although splitting of the bicomponent fibers is not required for shrinkage of the nonwoven web during forming and elastic recovery of the resulting nonwoven web, it can increase the elastomeric properties of the material.

According to a preferred embodiment of the present invention, the bicomponent filaments comprise from about 40% to about 90% by weight polyester (PET). According to a particularly preferred embodiment of the present invention, the bicomponent filaments comprise from about 55% to about 65% by weight polyester.

The stretchable nonwoven material of the present invention according to one embodiment of the present invention comprises bicomponent filaments produced in a bonded carded web process. According to a particularly preferred embodiment, the bicomponent filaments used to produce the nonwoven web are spunbonded.

Example

Figure 2 is a summary of data collected from stretchable nonwovens produced by the method of the present invention. The data presented correspond to five sample materials, sample numbers 1-5, produced with side-by-side bicomponent fibers of PET and linear low density polyethylene. Two sets of data are given for each sample - machine direction (MD) stretchability and cross direction (CD) stretchability. The preparation process conditions of these samples are as follows:

polymer:

PET＝ Ticona EKX-183

LLDPE＝Dow 6811A

HDPE＝ Dow 25455

Aperture = 0.6mm

Throughput = 0.6ghm (g/hole/min)

Melting temperature = 525°

Quench Air Temperature = 61°F

Polymer ratio = 50/50 (volume) or 59/41 PET/PE (weight)

Bonding pattern = see individual examples (5% and 10% helix, and HP)

Data are also given for a 16-lobe fan (orange segment) array splittable bicomponent fibrous nonwoven web, Example 6. In this example, bicomponent fibers were produced from PET and high density polyethylene (HDPE).

Although in the foregoing description the invention has been described in connection with certain preferred embodiments and numerous details have been given for purposes of illustration, it will be clear to those skilled in the art that additional embodiments can be derived and that herein Certain of the details described may be varied considerably and still without departing from the basic principles of the invention.

Claims (23)

1. Stretchable nonwoven material, it comprises:

A kind of nonwoven web, this fibre web comprise the bicomponent fiber that contains polyester and the 2nd polymer in a large number, and described nonwoven web heats then through being selected from that decorative pattern is bonding, point is bonding and the method for combination bonding.

2. according to the Stretchable nonwoven material of claim 1, wherein said polyester is the polyester of heating after-contraction.

3. according to the Stretchable nonwoven material of claim 2, wherein said the 2nd polymer is the polymer of heating after-contraction degree less than described polyester.

4. according to the Stretchable nonwoven material of claim 2, wherein said polyester is a polyethylene terephthalate.

5. according to the Stretchable nonwoven material of claim 1, being configured as of wherein said bicomponent fiber, described polyester and described the 2nd polymer all are present on the surface of described fiber.

6. according to the Stretchable nonwoven material of claim 5, one of arranged side by side, leafy and fan-shaped array of being configured as of wherein said bicomponent fiber.

7. according to the Stretchable nonwoven material of claim 1, wherein said polyester accounts for about 20～about 90% of described bicomponent fiber weight.

8. according to the Stretchable nonwoven material of claim 1, wherein said polyester accounts for about 40～about 65% of described bicomponent fiber weight.

9. according to the Stretchable nonwoven material of claim 1, wherein said bicomponent fiber is a spun-bonded fibre.

10. according to the Stretchable nonwoven material of claim 1, wherein said the 2nd polymer is the polymer that is selected from polyolefin and polyamide.

11. according to the Stretchable nonwoven material of claim 10, wherein said the 2nd polymer is selected from polyethylene, polypropylene and nylon.

12. according to the Stretchable nonwoven material of claim 1, wherein said bicomponent fiber is fissionable.

13. a method of producing Stretchable nonwoven material, this method comprises the following steps:

With a large amount of bicomponent fiber shaping nonwoven webs, described bicomponent fiber comprises polyester and the 2nd polymer;

Employing is selected from the bonding described nonwoven web of method that decorative pattern is bonding, point is bonding and make up; And

With described nonwoven web heating, thereby form Stretchable nonwoven web.

14. according to the method for claim 13, wherein said polyester is a polyethylene terephthalate.

15. according to the method for claim 13, wherein said the 2nd polymer is the polymer that is selected from polyolefin and polyamide.

16. according to the method for claim 13, wherein said bicomponent fiber is a spun-bonded fibre.

17. according to the method for claim 13, wherein said polyester accounts for about 20～about 90% of described bicomponent fiber weight.

18. according to the method for claim 13, wherein said polyester accounts for about 40～about 65% of described bicomponent fiber weight.

19. according to the method for claim 13, being configured as of wherein said bicomponent fiber, described polyester and described the 2nd polymer all are present on the surface of described fiber.

20. according to the method for claim 19, one of arranged side by side, leafy and fan-shaped array of being configured as of wherein said bicomponent fiber.

21. according to the method for claim 15, wherein said polyolefin is selected from polyethylene and polypropylene.

22. according to the method for claim 15, wherein said polyamide is a nylon.

23. a personal care product, it comprises:

A kind of nonwoven web, this fibre web comprise the bicomponent fiber that contains polyester and the 2nd polymer in a large number, and described nonwoven web heats after shaping then through being selected from that decorative pattern is bonding, point is bonding and the method for combination bonding.

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