阅读说明：本技术 制造柔性织物接触紧固件 (Making flexible fabric touch fasteners ) 是由 S.R.阿拉塔 G.K.科潘斯基 于 2020-02-28 设计创作，主要内容包括：制造凸型接触紧固件产品(20)的方法,在该方法中,剪切从柔性织物(70)的侧面延伸的纤维圈(40)的远侧部分,以从柔性织物(70)的侧面延伸的纤维代替剪切的纤维圈,使纤维延伸到各自的自由远端,同时使从织物(70)的侧面延伸的其它纤维圈(40)保持完好,然后用由直线式能量源提供的能量加热远端,使得远端的树脂流动以在延伸的纤维(36)上形成扩大头部(74),同时使至少一部分其它纤维圈(40)保持完好。一种凸型接触紧固件产品(20)包括：具有宽大侧面的柔性织物基底(70)；从基底(70)的宽大侧面延伸的纤维。所述纤维形成两层纤维圈(40),每个纤维圈(40)在两个隔开的点从基底(70)延伸；以及从基底(70)延伸到与基底(70)隔开的相应远侧纤维端的纤维段(36)。每个远侧纤维端形成纤维树脂的扩大头部(74),以钩住其它纤维。(A method of making a male touch fastener product (20) in which a distal portion of a loop of fibers (40) extending from a side of a flexible fabric (70) is sheared to replace the sheared loop of fibers with fibers extending from the side of the flexible fabric (70), extending the fibers to respective free distal ends while leaving other loops of fibers (40) extending from the side of the fabric (70) intact, and then the distal ends are heated with energy provided by an inline energy source such that resin at the distal ends flows to form enlarged heads (74) on the extending fibers (36) while leaving at least a portion of the other loops of fibers (40) intact. A male touch fastener product (20) comprising: a flexible fabric substrate (70) having a broad side; fibers extending from the broad sides of the substrate (70). The fibres forming two layers of fibrous loops (40), each fibrous loop (40) extending from the base (70) at two spaced apart points; and fiber segments (36) extending from the base (70) to respective distal fiber ends spaced from the base (70). Each distal fiber end forms an enlarged head (74) of fiber resin to hook over the other fibers.)

1. A male touch fastener product comprising:

a flexible fabric substrate having a broad side; and

fibers forming loops of fibers, each loop of fibers being joined at two spaced apart points in the substrate; and

a fiber segment extending from the base to respective distal fiber ends spaced from the base, each distal fiber end forming an enlarged head of fiber resin to hook over other fibers;

wherein the number of fiber loops is at least one sixteenth of the fiber segments.

2. The product of claim 1 wherein the number of fiber loops is at least one-eighth of the fiber segments.

3. The product of claim 1 or 2, wherein the substrate comprises or is a nonwoven material.

4. The product of claim 3 wherein the fibers comprise staple fibers that are needle punched into the nonwoven material.

5. The product of any of claims 3 or 4, wherein the nonwoven material has a flexible adhesive layer, particularly wherein the adhesive layer is disposed on a side opposite the broadside, more particularly wherein the fibers pass through the adhesive layer.

6. The product of any of claims 1-5, wherein the fabric substrate comprises a woven substrate and/or a knitted substrate.

7. The product of any of claims 1 to 6, wherein the total weight of the product is from 40 to 60 grams per square meter, in particular the total weight thereof is from 60 to 80 grams per square meter.

8. The product of any of claims 1-7, wherein the flexible fabric substrate and the fibers collectively have a basis weight of 50 to 90 grams per square meter.

9. The product of any one of claims 1 to 8, wherein the diameter of the fibers is 20 to 40 microns and/or the titer of the fibers is 6 to 10.

10. The product of any of claims 1 to 9, wherein the fibers are drawn amorphous polymers and/or wherein the fibers are bicomponent fibers, in particular having a polypropylene core and a polyethylene sheath.

11. The product of any of claims 1-10, wherein the transverse dimension of the enlarged head is 2.5 to 6.0 times the fiber diameter.

12. The product of any of claims 1 to 11, wherein at least a portion of the fiber loops extend from the broad side of the base to a height greater than an average height of the enlarged heads of the fiber segments, particularly wherein at least a majority of the enlarged heads are located within a top layer defined by the fiber loops.

13. A product as claimed in any of claims 1 to 12 wherein the loops are engageable by the enlarged head to form a releasable fastening when the product is engaged with itself.

Technical Field

The present invention relates to fabric touch fasteners and methods of making the same, and more particularly to a flexible fabric touch fastener having a particularly soft surface feel.

Background

Touch fasteners have complementary surfaces that are joined together by making a large number of engagements between corresponding discrete features on both surfaces, respectively, to achieve a fastening, which is typically a releasable fastening. This is in contrast to adhesive fastening, where two broad surfaces engage each other, but not by engagement of discrete features. The most common form of touch fastener achieves fastening by engaging discrete male fastener element regions with discrete female fastener element regions, such as hook-and-loop engagement. The male fastener elements may be configured as stems with enlarged heads that hook onto discrete female fastener elements in the form of fibers that are secured at two points to form engageable fiber segments, such as a nonwoven material. Touch fasteners can be used in disposable garments and durable garments, and the like. The fastening performance of touch fasteners is typically measured in terms of peel strength and shear strength. It is desirable to produce touch fasteners with sufficient performance to secure two items together for a particular application while making the two mating surfaces as soft as possible.

Disclosure of Invention

Aspects of the invention feature a method of making a touch fastener of the male type product in which a distal portion of a loop of fiber extending from a side of a flexible fabric is sheared to replace the sheared loop of fiber with fiber extending from the side of the flexible fabric, extending the fiber to respective free distal ends while leaving other loops of fiber extending from the side of the fabric intact, and then heating the distal ends with energy provided by an inline energy source such that resin at the distal ends flows to form enlarged heads on the extended fiber while leaving at least a portion of the other loops of fiber intact.

"inline energy source" refers to an energy source that emits energy from a very thin line (e.g., a laser beam or a high temperature wire), as opposed to an iron or oven, etc.

Loops of fibers "extending from the side of the substrate" refer to loops of fibers that may generally lie in the plane of the side of the fabric but extend at the cut point, as well as loops of fibers that extend from the side of the fabric in an unloaded state.

According to one aspect of the method of the invention, the sheared fiber loops are fibers having a denier of less than about 10, preferably greater than 5.

According to another aspect of the method of the present invention, the shearing and heating leaves at least 10% (preferably at least 20%; more preferably at least 30%) of the loops of fibers extending from the sides of the flexible web intact prior to shearing.

According to yet another aspect of the method of the present invention, the flexible web has headed fibers and loops of functional fibers extending from the sides of the flexible web as a result of the shearing and heating. Preferably the flexible fabric has more headed fibers than loops of functional fibers extending from the sides of the flexible fabric. "functional loops" means loops that do not lay flat on the fabric surface, but rather extend away from the surface, thereby forming a gap between the fabric surface and the distal portion of the loop to form a portion of a compliant loop layer on one side of the fabric and/or to receive a hooking member to effect releasable fastening.

According to yet another aspect of the method of the present invention, at least some of the enlarged heads are closer to the side of the flexible fabric than portions of intact loops of fiber.

Aspects of the methods of the invention can include one or more of the following features.

In some embodiments, the sheared fiber loops are fibers having a diameter of less than about 50 microns, preferably between 20 and 40 microns.

In some examples, the enlarged head has a transverse dimension that is 2.5 to 6.0 times another dimension of the fiber (e.g., fiber diameter).

In some cases, the fabric comprises (or is) a needle punched nonwoven. In some cases, the fabric comprises (or is) an air-laid nonwoven material. For some applications, the basis weight of the nonwoven material is from 40 to 60 grams per square meter (GSM). For certain other applications, the basis weight of the nonwoven material is 60 to 80 GSM.

In some cases, shearing the fibers includes shearing staple fibers that are needle-punched into the nonwoven material. The nonwoven material may have a flexible adhesive layer, for example, disposed on the side opposite the loops or through which the loops pass. The adhesive layer may be or comprise a film.

Preferably the fibers are made from a drawn amorphous polymer (e.g., polypropylene). In some cases, the fibers are bicomponent fibers, such as fibers having a polypropylene core and a polyethylene sheath.

In some examples, the method includes forming a flexible fabric by needling a fibrous batt prior to cutting the distal portion of the fibrous loops. For example, the batt of fibers may be needled into the nonwoven fabric from one side of the nonwoven fabric, forming loops of fibers on the other side of the nonwoven fabric.

In some cases, the loops of fibers to be cut extend 6 to 10 millimeters from the sides of the flexible fabric prior to cutting.

In some embodiments, shearing the distal portion of the fiber loop includes training a flexible fabric around a rotary shears and a shear presenting beam near the cutting anvil such that the fiber loop is engaged by the rotary shears and sheared against the cutting anvil (e.g., when bent around an edge of the presenting beam). Generally, the flexible fabric should have additional loops of fibers extending from the sides of the flexible fabric and not sheared against the cutting anvil.

In some cases, the fiber loops are sheared in two successive stages, some by a first shearer and others by a second shearer downstream of the first shearer.

The method may include brushing the surface of the flexible fabric to increase the height of the fiber loops prior to shearing the fiber loops. The method may further comprise unwinding the flexible fabric from a roll of flexible fabric prior to brushing the surface.

In some embodiments, the inline energy source is a distally directed energy beam. For example, the energy beam may be a laser. Preferably the direction of the energy beam is non-parallel to the longitudinal axis of the heat presenting shaft about which the flexible fabric is trained during heating.

In some examples, the energy beam extends from a position that is in a cross direction of the width of the fabric during heating. Preferably the method comprises adjusting the focus of the beam to coincide with the point of the energy beam closest to the flexible fabric.

In some cases, heating the distal end involves engaging the distal end with a plurality of different energy beams engaging different distal ends. For example, the plurality of different energy beams may be directed along respective widths of the flexible fabric to heat the distal end. By varying the angle of each energy beam relative to the flexible web, the plurality of energy beams can be constantly redirected to traverse a respective width of the flexible web. Preferably the method further comprises continuously varying the focus of each energy beam to align with the energy beam spot closest to the flexible fabric.

In some embodiments, the energy beam is pulsed to define alternating energy beam on periods and energy beam off periods. For example, the energy beam may be pulsed with a duty cycle selected such that a desired proportion of the distal end is heated.

The method may further include directing a flow of air through the optical component from which the energy beam is emitted distally while heating the distal end.

In some examples, the linear energy source is a heated wire. Preferably the wires extend parallel to the longitudinal axis of the heat presentation shaft such that the wires heat the sheared ends in a very narrow transverse region of the fabric, preferably while the fabric is supported on the heat presentation shaft.

Heating the distal end preferably involves training the flexible fabric about a heat presentation axis with the distal end radially outward while heating the distal end by a linear energy source. The inline energy source should be spaced a distance from the heat presentation roll such that the substrate of the flexible fabric is not permanently altered by the inline energy source.

In some embodiments, the method includes engaging a surface of the flexible fabric with an air flow having sufficient energy to deflect the fiber loops during or after heating the distal end to help redistribute the fiber loops and heated ends such that at least a number or a majority of the enlarged heads are within the compliant pad formed by the fiber loops.

The method may further include compressing the sheared fiber loop and the intact fiber loop after heating the distal end. Compressing the sheared fiber loops and intact fiber loops may include forming the product into a roll in which the sheared fiber loops and intact fiber loops are pressed against the other side of the touch fastener product.

In some embodiments, the method is formed as a continuous process to produce a longitudinally continuous, unitary sheet of fastener product. In some cases, the method further comprises winding the resulting sheet material to form a roll.

Some other aspects of the invention feature a male touch fastener product that includes: a flexible fabric substrate having one broad side; fibers forming two layers of fiber loops, each fiber loop being connected to other fibers at two spaced apart points in the substrate; and fiber segments extending from the substrate to respective distal fiber ends spaced from the substrate. Each distal fiber end forms an enlarged head of fiber resin to hook over the other fibers. "fiber loops" refers to fiber segments generally located on the surface of the substrate and exposed for bonding, as well as fiber loops that are raised above the broad side of the fabric substrate.

According to one aspect of the product according to the invention, the number of fibre loops is at least one sixteenth (preferably at least one eighth) of the fibre length.

In accordance with another aspect of the product of the present invention, the fiber diameter of the fiber segments is less than about 50 microns, and the enlarged head of each fiber segment has a transverse width that is at least 2.5 times the transverse width (e.g., diameter) of the fiber segment.

Another aspect of the invention features a male touch fastener product that includes: a flexible fabric substrate having one broad side; forming two layers of fibrous loops to form a mat of compliant fibrous loops of defined thickness, each fibrous loop being connected at two spaced apart points in the substrate; and fiber segments extending from the substrate to respective distal fiber ends spaced from the substrate. Each distal fiber end forms an enlarged head of fiber resin to hook over the other fibers. At least a portion of the enlarged head is located within the thickness of the compliant fibrous loop mat.

Aspects of the inventive product may include one or more of the following features.

In some examples, the substrate comprises (or is) a nonwoven material. The fibers may be staple fibers that are needle-punched into the nonwoven material.

In some cases, the nonwoven material has a flexible adhesive layer that can be disposed on the side opposite the broadside or through which the fibers can pass. The adhesive layer may, for example, have or comprise a film.

In some other examples, the fabric substrate comprises a woven substrate or a knitted substrate.

In some examples, the total weight of the product is 40 to 60 grams per square meter, or 60 to 80 grams per square meter. In some cases, the flexible fabric substrate and the fibers collectively have a basis weight of 50 to 90 GSM.

In some embodiments, the diameter of the fibers is 20 to 40 microns.

In some cases, the denier of the fiber is 6 to 10.

The fibers are preferably made of a drawn amorphous polymer (e.g., polypropylene). In some cases, the fibers are bicomponent fibers, such as fibers having a polypropylene core and a polyethylene sheath.

The transverse dimension of the enlarged head is preferably 2.5 to 6.0 times the transverse dimension of the fibre.

The height at which at least a portion of the fiber loops extend from the broad side of the base is preferably greater than the average height of the enlarged heads of the fiber segments. Preferably at least the majority of the enlarged head is located within the protruding layer defined by the fibrous loop.

In some embodiments, the loops of fibers may be engaged by the enlarged head, thereby forming a releasable fastening when the product is engaged with itself.

Aspects of the present invention may provide a fastening fabric having very small headed fibers dispersed in a fiber field that provide a softer-to-touch surface, but are capable of hooking into a suitably configured microfiber fabric to form a releasable fastening. The fastening fabric may be made from a less expensive, lightweight nonwoven material through a series of shearing and heating steps that form small ends on some fibers while leaving other loops intact to provide a soft touch. The process of making the fastening fabric may be carried out on a continuous production line to which the raw material is fed from a feed roll, from which the finished product is wound into rolls. The process can even be carried out on a continuous line where the staple fiber batt is first formed from a bale opener or a fiber carding machine.

The fine denier of the drawn fibers forming the head is advantageous in maintaining the softness of the fabric and allowing the head to be formed very quickly under the energy of an energy beam or local heat source without deforming the rest of the fibers. Shearing before head formation helps to form a more uniform head to improve fastening performance and maintain flexibility.

One or more embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

Drawings

FIG. 1 is a plan view of a manufacturing system and method for making a male fabric touch fastener;

FIG. 2 is an enlarged view of a shearing station of the system of FIG. 1;

FIG. 3 illustrates the cutting of a fiber loop fabric;

FIG. 4 is a plan view of the head forming station;

FIG. 5 is a perspective view of a portion of the station of FIG. 4, showing heating of the distal end of the fiber to form a head;

FIG. 6 illustrates the use of multiple laser beams to scan the respective widths of the fabric to heat the distal ends of the fibers;

FIG. 7 illustrates the use of high temperature wire to heat shear the distal end of the fiber;

FIG. 8 is a schematic side view of a male fabric touch fastener;

FIGS. 9-12 are photomicrographs of a male fabric touch fastener;

FIGS. 10-12 illustrate the engagement with the microfiber coil material;

FIG. 13 is a side view of a test for determining the number of fiber loops and heads in a given area;

FIG. 14 is an exemplary image of a test area showing comb teeth passing through the fiber circle field;

15A-C illustrate in sequence a method of making fastener material from an airlaid nonwoven material.

Like reference symbols in the various drawings indicate like elements.

Detailed Description

Referring initially to FIG. 1, an apparatus 10 for making fastener material has a shearing station 12 and a head forming station 14, both of which operate sequentially and continuously. The flexible web 16 is fed from the feed roll 18 to a shearing station and, after leaving the head forming station, the fastener material 20 is wound onto a take-up roll 22 for storage or transport.

The flexible fabric 16 fed into the apparatus 10 may be a nonwoven material produced by needling a loose staple fiber batt to form loops of fibers on the side of the batt opposite the needled side. The height and density of the fiber loops can be controlled by adjusting the needling density and the needling depth. More information on suitable methods of making such nonwoven materials and the resulting structures thereof can be found in U.S. patent 9,790,626, the contents of which are incorporated herein by reference. In creating a nonwoven material for the flexible fabric 16, it is preferred to use a needle depth of at least 7 to 8 millimeters to form the loops of fibers to be cut. The fabric may be needled with different penetration depths to produce long fiber loops to be sheared and short fiber loops that remain intact during shearing of the long fiber loops. The higher the needling density, the more loops of fibers are formed. Larger needles also form more loops of fibers. For example, a 36 gauge needle has a larger jaw than a 40 gauge needle and will therefore "grab" more fiber and pull it down into the brush. For example, the inventors have found that useful products can be made from needled fiber batts using 36 gauge needles at a needling density of 83 needles per square centimeter, while similar performance can be obtained using 40 gauge needles requiring needling at a needling density of 137 needles per square centimeter. If the needling density is too low, the number of loops of fibers sheared and formed into the head may be insufficient, and thus fastening performance may be insufficient. If the needling density is too high, adjacent fibers may fuse together during head formation, thereby possibly reducing fastening performance. In addition, over needling the fibrous batt may result in too little fiber remaining on the back of the product, which may reduce tear resistance and increase the amount of fiber draw during the release process. The optimum needling density will vary depending upon the particular application, but as an example, a carded web of about 70 grams per square meter (GSM) can be needled with a needling density of about 59 to 88 needles per square centimeter.

The nonwoven material may be composed entirely of staple fibers, wherein the staple fibers form loops and a base of the material. Alternatively, the nonwoven material may be formed by needling staple fibers into a preformed nonwoven scrim, or by adding a layer of film or scrim to the needled fibrous batt prior to the non-fibrous loop side of the molten material to provide more structure and improve tear resistance. For example, two layers of 25GSM carded staple fibers can be needled into a 17GSM polypropylene spunbond nonwoven material and then the non-loop side heated with a 390 ° f iron for 20 seconds to melt the fibers on the side opposite the loops. In another example, a 40GSM carded web was needled into a 20GSM spunbond web using a 36 gauge needle at a density of 83 needles per square centimeter, and then heated on the non-loop side with a 390 ° f iron for 20 seconds. As discussed in more detail below, the fibers or filaments to be cut and formed into a head are preferably made of a drawn polypropylene resin.

The inventors have found that the elastic stretch properties in the machine and cross directions of products made by needling fibers into one scrim are much higher than products made entirely of staple fibers, or products made by needling fibers into one scrim and then adding a second scrim on top of the needled fibers before heating. Generally, the larger the needle, the stronger the elastic stretchability of the product. In addition, the higher the needling density, the greater the elastic stretchability of the product. For many applications, elastic stretchability is a desirable characteristic because it enhances the feeling of softness/flexibility. Furthermore, if the product is used on a stretchable substrate (e.g., ears of a diaper) and the substrate is partially stretched when engaged with loops of fibers, the release of the stretch may create shear loads at the engagement, thereby increasing the fastening strength against peel loads.

In producing a product by needling a single scrim, the larger the needles used and/or the higher the needling density, the more light/soft the product is. This is because the number of "open areas" created by larger needles and/or higher needling density is increased. Of course, tear resistance/performance decreases with increasing open area.

In another example shown in fig. 15A-15C, the flexible web 16 from which the fastener material is produced is an air-laid nonwoven. To produce such a flexible fabric, staple fibers are made into a carded web by air-laying. Due to the nature of the airlaid process, the fibers are randomly oriented. The fibrous batt is then bonded so that at least a number of the locations in the web where the discrete fibers touch or cross fuse together to form fusion points 100. Such fusing can be accomplished, for example, by passing the fabric through an oven or applying an adhesive and setting the fabric. After the fusing process, the resulting flexible fabric is a stable, homogeneous product, preferably having equal web strength in all directions, and its inherent properties when compressed provide some resistance to compression and elasticity.

The fusion points 100 connect the fibers of the entire web and the segments of the fibers joining the fusion points define hook-engageable loops 101 of the fibers. The loops 101 are distributed substantially uniformly throughout the web.

In addition, if the web is bonded to a rough, textured tape or web, the bonding process can impart a three-dimensional texture to the web. The bonding may be an embossing process, for example leaving areas of high protruding layer surrounded by a bonding border. Providing the final fastening surface with a three-dimensional profile can facilitate engagement and retention of the fibers during use. The bonding process may also be used to attach another layer of nonwoven, film or scrim to one side of the fabric.

The flexible fabric, preferably made by an airlaid process, is made of polypropylene fibers having a denier of 7 to 30 and the final weight of the fabric is preferably 25 to 250 GSM. The fibers may have a uniform circular cross-section, may be hollow, and may have a non-circular cross-section. In some cases, the fibers are bicomponent fibers, in which case the sheath of the fibers may form an adhesive layer that fuses the fibers at the point of fusion. The flexible fabric may be formed from a mixture of different fibers exhibiting different properties.

In addition, a plurality of airlaid fiber batts having similar or different configurations may be fused together to form the flexible fabric 16.

Referring next to fig. 2 and 3, the flexible web 16 enters the shear station 12 where it is guided by two idler pulleys 26a and 26b onto a stationary shear presentation beam 24. The fabric passes around the small radius edge 28 of the shear presenting beam 24 at an acute angle, causing the fiber loops in this region to rise high from the surface. The upper edge of the shear presenting beam 24 is aligned with the rotary shears 30 and the cutting anvil 32 so that the top of the tall fibre loop 34 of the curved fabric is engaged by the blades of the rotary shears and sheared against the cutting anvil. The cutting operation is most effective in the cocked state of the fiber loops because it ensures that a greater number of fiber loops 34 are cut and to a similar height.

The rotary cutter is a helical blade that cuts against a cutting anvil, rotating at a surface speed much higher than the fabric advancement speed, and cuts the taller fiber loop 34 into upstanding fiber segments 36. The sheared pieces 38 of fiber are collected by a vacuum system (not shown). Because not all loops are of the same height, the shorter loops 40 are not affected by the shearing process and remain intact throughout the shearing station. The height at which the loop of fibre is cut is adjusted by moving the shear-presenting beam 24 up and down relative to the rotary cutter and cutting anvil. Raising the shear presenting beam results in shorter standing fibres, while lowering the shear presenting beam results in longer standing fibres. At higher line speeds, two or more rotary cutters may be arranged in sequence to perform two or more cutting operations.

In the case where the flexible fabric 16 is an airlaid product as shown in fig. 15a, the cut product may resemble the image shown in fig. 15b, where the hook engaging features of the surface cut height have been cut, while the hook engaging features below the cut height remain intact, now resembling standing fibers 102.

Referring again to FIG. 1, after exiting the shearing station 12, the sheared web 42 enters the head forming station 14 where the distal ends of the sheared fibers are heated to form the fastener heads. Whereas the head forming process melts the ends of the sheared fibers, it appears to be redundant to shear the fibers prior to heating the fibers. However, the inventors have found that shearing prior to heating significantly improves performance and softness, in part because it aids in the formation of unique mushroom heads and minimizes excess resin flow during the heating stage. Omitting the shearing step may result in fewer useful mushroom heads and less blurring of resin nodules connecting the fibers. The cutting and heating may be performed on a continuous line, as shown in fig. 1, or the cut web 42 may be wound into a roll for subsequent head forming.

In the case where the cut web 42 is an airlaid product, as shown in fig. 15b, after the head is formed, the cut web 42 can be similar to fig. 15c, where the upstanding fibers 102 have been heated to form fastener heads 103.

Fig. 4 and 5 show the same head forming station 14 as fig. 1, but configured as a separate station to which the previously cut fabric 42 is fed from a feed roll 44. The material in fig. 4 and 5 moves from right to left rather than proceeding from left to right as in fig. 1. The cut web 42 is wound on the heated presenting shaft 46 by two idlers 48a and 48b and advanced by two nips 50a and 50 b. The use of two nips ensures that the material is constantly pushed forward even in the event of slippage at one of the nips. The nip pressure can be controlled by a lighter spring or hydraulic/pneumatic control to avoid over-squeezing the finished product.

Referring to fig. 5, the head forming station 14 includes a laser 52 that emits a beam 54 spaced from the surface of the heat presentation shaft 46 to rapidly heat the ends of the sheared fibers to form the mushroom head. This occurs at the location where the beam is closest to the axis 56 of the heat presentation shaft 46, where the beam axis is only a distance D from the surface of the shaft_L(e.g., 0.15 to 2.5 millimeters). In this example, the laser remains on as the fabric advances, and the laser moves back and forth across the fabric along the rod 60 between the laser travel stops 58a and 58 b. The advance of the fabric may be halted while the laser is traveling between its stops, or the fabric may be kept advanced while the laser is moving so that the path of travel of the laser is at an angle to the longitudinal direction of the fabric. If the web is kept advanced during laser traversing, the fiber distal ends are affected by the laser over discrete web lengths to form mushroom heads, and by varying the advance step between laser strokes, the overall fastening performance can be varied. The width of the laser beam is shown in exaggerated form in fig. 5 to show that the beam is controlled to have its focal point 62 aligned with the height of the axis 56 of the heat presenting shaft. The spot where the beam power is most concentrated and preferably coincides with the position where the fiber end is closest to the beam. The beam diverges after passing through the fabric until it is incident on the beam stop 64.

There are several parameters that can be adjusted during laser heating:

cutting distance: this parameter controls the step size of the advancement of the web between laser passes and thus the degree of tightness between adjacent passes. If the adjacent runs are too close together, excessive heat may deform the mushroom head and/or cause the resin of adjacent fibers to fuse together. If the adjacent strokes are too far apart, the fastening performance may be degraded.

Laser cutting height: this parameter controls the distance of the laser beam 54 from the fabric (from distance D)_LCorrelated). If the laser is closer to the tangent region, the upstanding fiber will be laser cut an additional amount before the mushroom head is formed. If the distance is too close, the fibers will melt severely and the backing of the web will partially melt or deteriorate. If the laser beam is positioned too far away, the fiber may not receive enough heat to adequately form the mushroom head (if formed). Ideally, most headed fibers are headed by a laser beam rather than being cut by a laser beam.

Laser focusing: this parameter controls the position of the laser focal point 62 along the beam axis relative to the heat presentation axis.

Laser speed: this parameter controls the speed at which laser 52 travels back and forth between laser travel stops 58a and 58 b.

Laser power: this parameter controls the power/intensity of the laser beam. In this example, a 75 watt carbon dioxide laser operates at 20% power (achieving 15 watt effective beam power), but the optimum laser power is a function of the fiber material and structure, as well as other process parameters. In comparison, at a given line speed and laser speed, a hollow polypropylene fiber of denier about 7 would rapidly form a mushroom head under such a laser when the laser is set to 11% to 20% power, while in a similar process a solid polypropylene fiber of the same denier would tend to rapidly form a mushroom head under a laser power set to 2% to 11%, but at a power exceeding 11% the head begins to become globular or elongated.

Laser pulse frequency: the laser may be operated in a pulsed mode to control the frequency at which the laser beam appears near the end of the sheared fiber. In the event that it is desired to reduce the fastening strength or further enhance the softness sensation, the laser can be operated at a lower duty cycle.

At higher line speeds (e.g., up to 30 m/min), it may be necessary to use multiple lasers simultaneously to form the desired number of heads on a wide fabric. Such lasers may each be arranged to impinge only a small portion of the width of the fabric and may be spaced apart along the machine direction.

Alternatively, one or more of the lasers 52 may be held stationary and may be equipped with dynamic optics that sweep their beams across the respective width of the fabric at an angle α, as shown in FIG. 6. In this example, two lasers are shown, each running along half the entire fabric width. The optics of each laser are preferably configured to change the focus of its beam during scanning so that the focus remains more or less aligned with the point closest to the fabric surface. Air nozzles 66 (only one shown) continuously direct a flow of compressed air toward each laser optic to keep the optics free of debris and contaminants. Referring again to fig. 1, after the laser machining process, a separate air nozzle 66 may blow air into the web to help redistribute the headed fibers within the protruding layers of uncut fiber loops on the fabric surface. Nips 50a and 50b also assist in pushing the fibers with the mushroom heads down into the remaining fiber loops after the heads are formed.

Referring again to FIG. 4, in addition to a laser beam, a highly localized energy source may be used to form the end of the sheared optical fiber into a head. For example, a very hot wire 68 may be arranged to extend parallel to the axis of the heat presentation roll 46, at a suitable spacing from the surface of the roll, so that the radiant heat from the wire is sufficient to melt the ends of the sheared fibers without damaging the shorter loop of fibers or the base of the fabric. Cooling the presentation rolls also helps to reduce the thermal impact (from the laser or high temperature wire) on the fabric substrate and shorter fiber loops. The heat presentation roll 46 may also be stationary and configured with a small radius tip (like the edge of the shear presentation beam 24 of fig. 3) protruding toward the heated area so that the end of the shear protrudes from the fabric substrate as far as possible for heating.

The shearing and heating may be performed in close proximity. For example, fig. 7 shows high temperature wire 68 disposed downstream proximate the shearing location and arranged to heat and form the ends of the sheared fibers into a head while the fabric is still supported on shear presenting beams 24. In this way, the fabric that is released from the shear feed beam is essentially already finished and ready to be wound into rolls for transport.

Whatever localized heating source is employed, it is preferred that the heating occur under the following conditions: this condition causes the resin of the sheared fiber ends to flow and retract, forming a mushroom head having a substantially hemispherical upper surface and a flat lower surface that overhangs all sides of the fiber and is generally perpendicular to the fiber. Polypropylene may be in the form of drawn fibers and is known to form mushroom heads when the cut ends melt, but other drawn amorphous polymer fibers may behave similarly. Theoretically, the pre-draw diameter of the fiber is the upper size limit of the mushroom head that can be effectively formed.

A number of fiber and process parameters can affect the shape and size of the resulting head, and optimization of the desired shape for a particular application may require changing one or more parameters. In theory, the hollow fiber cross-section improves head formation over a wide range of velocities and temperatures, as the voids in the middle of the fiber provide space for the inflow of excess material during head formation. A smaller fiber draw ratio may allow the fiber to more quickly transform into an elongated or spherical shape. For some applications, Bicomponent (BICO) fibers having a polypropylene core and a polyethylene sheath facilitate head formation and fiber fusion in the fabric substrate at lower temperatures and/or faster line speeds. With such BICO fibers, the polyethylene sheath is preferably thin so as not to significantly inhibit the ability of the polypropylene core to flow into a mushroom shape. For other applications, mixtures of fibers and resins of different denier may be used.

An example of a suitable polypropylene fiber is the product manufactured by IFG Asota GmbH under the designation CL-10, which is a 6 denier solid fiber with low melting energy. There was also a 17 denier homogeneous fiber of the same name. The nonwoven fabric may be made entirely of such fibers and then used in the above-described process.

Another suitable fiber is a 7 denier hollow core polypropylene fiber manufactured by FiberVision under the designation T-118.

Mixtures of fibers may also be used. For example, one suitable blend consists of 80% by weight of T-118 and 20% of 6 denier CL-10. Another suitable blend consists of 50% by weight 6 denier CL-10 and 50% 17 denier CL-10. Another suitable blend consists of 80% by weight of 17 denier CL-10 and 20% of 6 denier CL-10.

The use of fiber blends made from different resins is also beneficial for performance and processing. For example, a blend of 80% by weight of 17 denier CL-10 and 20% of 17 denier polyethylene staple fibers may be used.

Referring next to FIG. 8, a male touch fastener product 20 includes: a flexible fabric substrate 70 having one broad side 72; fibers extending from the broad side of the substrate, the fibers forming loops of fibers 40, each loop extending from the substrate at two spaced apart points; and fiber segments 36 extending from the base 70 to respective distal fiber ends spaced from the base. Each distal fiber end forms an enlarged head 74 of fiber resin to hook over the other fibers. As schematically shown in the drawings, the heads 74 are generally spaced from the nonwoven substrate, but at least a majority of the heads are within the projecting layers formed by the unbroken loops 40. Neither the fiber loops 40 nor the fiber segments 36 are straight. The fibrous loop backing layer 40 is sufficiently dense and the headed fibers are sufficiently fine and soft so that the overall product provides a particularly soft feel to the human skin. The fabric substrate shown in the drawings is a nonwoven material that may be formed by needling a staple fiber batt to form a coherent substrate and extended loops of fibers. The longer loops of fibers forming the fiber section 36 may be formed by piercing the larger denier fibers into the brush mat and then introducing the smaller denier fibers and needling them to a shallower penetration depth. An optional backing or adhesive layer 76 is shown in phantom on the other side of the substrate. The fibers forming the fiber loops may alternatively be formed by needling the fibers from the substrate into a support film or scrim 78, as shown by the similar dashed lines on the fiber loop side of the substrate. Such a support scrim may itself have loops of fibers 40 left behind after shearing. While the product 20 shown in fig. 8 is configured to releasably engage a loop fastener material having fine fiber loops, it may also be used for self-engaging fastening, wherein the headed fiber segments 36 of one mating fabric surface releasably engage loops 40 of the other surface (or, in the case of folding over on itself, loops 40 of the same surface), or vice versa. In this case, the fibers forming the male (headed) fiber sections (e.g., formed by the higher fiber loops during shearing) preferably have a higher titer than the fiber loops 40 (e.g., formed by the shorter fiber loops during shearing).

Alternatively, the fabric substrate 70 may be a knitted or woven fiber loop fastener fabric. The preferred knitted/woven fibrous loop material should have a less dense array of upstanding monofilament polypropylene fibers. Such products may have a wide range of applications, particularly in the apparel industry.

The male touch fastener products discussed above can be formed to releasably engage with conventional microfiber cloth fibrous loop materials. One suitable fibrous loop material is made from 5 dtex by 64 mm polypropylene/polyester hollow splittable fibers (segmented pie construction) which is a product manufactured by fibervision under the designation PTS 850. After splitting, the split fibers produced had a diameter of 3.4 to 8.9 microns. Splitting was accomplished by needling using Groz-Beckert's 46 gauge crown needle. To aid in fusing, approximately 30 wt% of the CL-10 binder fibers described above were mixed prior to carding, needling, and fusing. The resulting material is well-engaged with male touch fastener products made from T-118 fibers as described above, with some mushrooms engaging multiple splittable fibers at a time.

FIG. 9 shows a male touch fastener product made from Beulieu fabrics International at 6.7 dtex (about 35 micron diameter) x 40 mm BICO polyethylene/polypropylene solid fibers (polypropylene core, polyethylene sheath, 50/50 ratio). The heads formed from these fibers by laser head forming have a head/stem diameter ratio of about 2.7:1, but the heads do not form mushroom well, possibly because the polyethylene material in the skin is too much, or is stretched relatively little. Although the head shape is not uniform, a degree of engagement with the microfiber fabric is achieved.

Figure 10 shows a head formed by laser heating the fibre end of a non-woven material formed from fibervision T-1187 denier (approximately 30 micron diameter) x 48 mm polypropylene hollow fibres, which can be engaged with a conventional commercially available microfibre material (in this case a microfibre wipe). The head/stem ratio of well-formed mushroom heads is 3.5:1 to 4.5: 1.

FIGS. 11 and 12 show a male touch fastener product made of IFG Asota Lv-10D-64.5 dtex (about 24 micron diameter) by 75 mm polypropylene solid fiber that can be joined with the common commercially available microfiber coil material of FIG. 10. The mushroom head with good shape has a head/stem diameter ratio of 3.6:1 to 6:1, and can be well jointed with the low-titer fiber ring. As shown in FIG. 12, the mushroom head material is sufficiently compliant to enable the fiber of the fiber loop to be caught and bite into the protruding portion of the mushroom head, thereby increasing the retention of the fiber loop and improving the fastening performance.

Another example (not shown) is produced using the shear and laser heating processes described above, but on a knitted material formed from monofilament yarns. The loops of knitted fabric are coated to maintain them in an upright position for shearing. The monofilament yarns are comprised of polyester. Each yarn had a diameter of 60 microns (35 denier). The knitted product had a basis weight of 345GSM, the loops were upright, had a substantially uniform height of 2.5 mm, and the knitted base had a thickness of 0.33 mm prior to cutting. In this case, substantially all of the loops of fibers are sheared during the shearing process, so that only the cut upstanding fibers remain after shearing, and the ends of substantially all of the upstanding fibers are melted during the head forming process. The resulting head is generally spherical, rather than mushroom-shaped, due primarily to the composition of the polyester fibers. To form a mushroom head, such a knit precursor material may be formed from polypropylene yarn having a high stretch ratio (similar to that of T-118, LV-10 or CL-10 staple fibers).

The parameters required to determine the relative number of loops and heads in a given fabric area are determined by the following procedure:

for knitted and woven materials having a pile formed from an ordered array of fiber loops, the fiber loops may be optically counted in a given area and scaled up as desired. The size of the region analyzed should take into account any changes in pile structure caused by the repeating pile pattern. The mushroom heads formed at the ends of the fiber segments can be similarly counted optically.

For nonwoven and other similar fabrics, counting loops requires a statistical test in which a defined comb is inserted transversely through the thickness of the loop layer and the number of loops traversing at least one tooth of the comb is then also counted optically. First, a sample of the fabric product was mounted to a flat rigid block using a strong adhesive tape. The comb is similarly mounted with the teeth extending horizontally so that when the comb is moved towards the mounted fabric, the parallel equidistant teeth extend into the space between the fabric substrate and the distal edge of the projecting layer with the centre line of the teeth just above the mid-point of the projecting layer of fabric, as shown in figure 13. The comb had a tooth width of 513 microns, a tooth spacing of 335 microns and a tooth length of 7.5 mm. Each comb tooth had a cone angle of 26 degrees and a tip radius of 42 microns. Such a Comb may be a Pro Brow Comb manufactured by Sephora under part number 21-P313039. As the comb extends into the loop layer of fibre in a direction corresponding to the machine or processing direction of the sample, magnified images are taken in at least five non-overlapping regions across the teeth spaced from the ends of the teeth and the edge of the fabric. For the above-described nonwoven material, a 4 mm x 4 mm area was used. An example of such an image taken with a Scanning Electron Microscope (SEM) is shown in fig. 14, where the SEM is focused at the middle face of the comb teeth. Very thin conductive materials (e.g., gold) can be sputter coated onto the fiber surfaces of the fabric if desired for better viewing of individual fibers using SEM. A comb is then inserted into the fiber loop of another portion of the sample, but this time in a direction perpendicular to the direction of processing or handling of the sample, and another set of at least five images is taken. For each image, the number of discrete fiber/comb tooth intersections (fibers extending completely over at least one comb tooth in the image area and through the space between two comb teeth) is determined by visual observation as the number of fiber loops or functional loops. The number of such fibre heads visible above or between the teeth of the comb is counted in the image area as the number of mushroom heads. These values were averaged based on the number of images analyzed and at least five test samples.

To determine the percentage of fiber loops that remain intact during the shearing and heating process, the number of fiber loops counted is divided by the sum of the number of fiber loops counted and half of the head counted and then multiplied by 100.

The focus of the microscope can be adjusted so that each mushroom head is in focus to determine its relative depth within the field of view to determine whether a particular mushroom head is below the upper or distal fibrous ring portion of the sample.

While several examples have been described for purposes of illustration, the foregoing description is not intended to limit the scope of the invention, which is defined solely by the scope of the following claims. Other examples and other modifications are possible within the scope of the appended claims.