KR20080007583A - Elastic laminates and process for producing same - Google Patents

Abstract

A method is provided for producing elastic composite laminates. The laminates contain elastic filaments that are stretched and laminated to at least one facing material. The continuous filaments are laminated to the facing material using a starved slot coat process. The starved slot coat process provides various benefits and advantages including the production of laminates having improved properties.

Description

ELASTIC LAMINATION AND MANUFACTURING METHOD THEREOF {ELASTIC LAMINATES AND PROCESS FOR PRODUCING SAME}

Articles that require some degree of elasticity have been made by combining elastic materials with inelastic or less elastic materials through various lamination processes. Often, such composite laminate articles are stretchable due to the presence of the elastic material and the particular manner in which the elastic and inelastic materials are bonded together during the lamination process.

Typically, such stretchable laminates are formed by bonding the inelastic material to the elastic material while the elastic material or sheet is in the stretched state. After bonding of these materials, allowing the laminated article to be subsequently relaxed causes gathering of inelastic components in the spaces between the bonding sites on the elastic sheet. The resulting laminate article is then stretchable to the extent that the nonelastic materials gathered between the bonding locations can stretch the elastic material. Examples of composite laminate articles and materials of these types are described in US Pat. Nos. 4,720,415 and 5,385,775, each of which is incorporated herein by reference.

In some stretchable laminate articles, the elastic strands of the continuous filaments are bonded to the relatively inelastic sheet material while the elastic strands are in the stretched state. Such elastic continuous filaments may, in certain articles, be sandwiched between two or more relatively non-elastic sheets. The relatively inelastic sheet may comprise a nonwoven web formed by meltblowing or spunbonding of various polymers. Examples of such laminates are all described in US Pat. No. 5,385,775, which is incorporated herein by reference; In US Pat. No. 6,057,024; And US published patent application U.S. 2002/0104608.

As indicated in the '775 patent, elastic continuous filaments may be extruded onto a sheet of horizontally moving material. The continuous filaments are extruded directly onto the material to which they bind from above the horizontal plane of the sheet material. The '024 patent discloses another embodiment in which the continuous filaments are extruded vertically in the downward direction. When the filaments are extruded downwards, the filaments are stretched and then laminated to one or more sheet materials.

In many past embodiments, adhesives have been used to bond the elastic strands of continuous filaments to the sheet material. For example, in one embodiment, the adhesive is sprayed onto the sheet material prior to contacting the filaments. However, spraying the adhesive material onto the sheet material can have some disadvantages in various applications. For example, spraying devices can be difficult to control, especially at high machine speeds and at low application rates, which can lead to over-application of the adhesive or to uneven coating of the adhesive onto the sheet material. In fact, overspray of the hot melt adhesive during the spraying process can cause filament breakage and mechanical shutdown. In addition, since the adhesive must travel a certain distance before contacting the sheet material, the adhesive may experience loss of adhesion before contacting the sheet material.

In view of the above, there is a current need for an improved method for applying adhesive material between stretched elastic filaments and nonwoven facings. There is also a need for elastic composite laminates having improved properties due to the manner in which the adhesive is applied.

Summary of the Invention

In general, the present invention relates to a composite elastic material comprising a plurality of elastic continuous filaments bonded to one or more nonwoven webs. The nonwoven web is laminated to the continuous filament when the filament is in the stretched state. Thus, when the filament is relaxed, the nonwoven web is gathered such that the entire composite is stretchable in at least one direction.

The present invention more specifically relates to a method of applying an adhesive material between an elastic continuous filament and a nonwoven web and relates to a composite nonwoven material produced by this method. The adhesive material is applied to the nonwoven web using a "starved" slot coating process, where the adhesive is released on the nonwoven web through a slot extrusion die to form a discontinuous coating. Discontinuous coatings contain amorphous elements of an adhesive material. The adhesive material is applied to the surface of the nonwoven web in a substantially uniform manner in terms of amount per unit area.

The lack of material coat process provides various benefits and advantages. For example, the process allows control over the positioning of the adhesive on the nonwoven web. In addition, the inventors have found that this process provides a very efficient use of the adhesive. In particular, even when the elastic filaments are in the stretched state, a relatively small amount of adhesive is used to firmly bond the elastic continuous filaments to the nonwoven web. Unexpectedly, the inventors have also found that this process produces a composite nonwoven material with reduced porosity when compared to similar composites prepared by spraying an adhesive onto a nonwoven web. Relatively low porosity when the composite material is used to construct a variety of articles, such as when incorporated into absorbent garments, including diapers, training pants, swimwear, adult incontinence products, feminine hygiene products, bandages and medical drapes. It offers several benefits.

For example, in one particular embodiment, the present invention relates to a method of making a composite nonwoven material. The method includes extruding continuous filaments. The filament includes an elastomeric material. Elastomeric materials can include, for example, elastic polyesters, elastic polyurethanes, elastic polyamides, elastic copolymers of ethylene and one or more vinyl monomers, elastic metallocene-catalyzed polyolefins, and elastic block copolymers. .

Once formed, the elastic continuous filaments are stretched and then laminated to the first side of the nonwoven web. In order to bond the stretched laminate to the nonwoven web, an adhesive material is applied to the nonwoven web from a slot extrusion die. The adhesive material forms a discontinuous coating that includes an amorphous element of the adhesive material. The adhesive material may be applied to the first side of the nonwoven web in an amount of less than about 4.4 gsm, for example from about 0.5 gsm to about 3 gsm. The adhesive material may include, for example, styrenic block copolymers, amorphous polyalphaolefins or random copolymers of polyolefins. In addition to the above, any suitable hot melt adhesive may be applied in accordance with the teachings of the present invention.

During application of the adhesive material to the nonwoven web, the nonwoven web may be configured to be able to contact and slide against a slot on a slot extrusion die. The adhesive material may be in contact with the web at a viscosity of 500 cp to about 50,000 cp, for example about 2,000 cp to about 20,000 cp. The temperature of the adhesive can vary depending on the specific adhesive material used. In one embodiment, for example, the application temperature of the adhesive can be from about 320 ° F. to about 350 ° F.

In one embodiment, the method may further comprise laminating the elastic continuous filament to the second nonwoven web. For example, the continuous filament may be located between the first nonwoven web and the second nonwoven web. The second nonwoven web can be laminated to continuous filaments using an adhesive material as described above.

The nonwoven web laminated to the elastic continuous filament can vary depending on the particular application and the desired result. Nonwoven webs may include, for example, meltblown webs, spunbond webs, bonded carded webs, and the like. For example, in one embodiment, the nonwoven web comprises a spunbond web having a basis weight of about 7 gsm to about 100 gsm, for example about 10 gsm to about 20 gsm.

Other features and aspects of the present invention are discussed in more detail below.

It is described in more detail in the remainder of the specification, including references to figures accompanying the complete and empowering disclosure of the invention, including its best mode for those skilled in the art.

1 is a perspective view of one embodiment of a method for producing a composite nonwoven material according to the present invention.

FIG. 2 is a side view of the process and system illustrated in FIG. 1.

3 is a partial view of an extrusion surface for an exemplary extruder head for extruding elastic continuous filaments.

4 is an enlarged view of a portion of the surface illustrated in FIG. 3.

5 is a side view of another known embodiment that may be used to form the composite nonwoven material according to the present invention.

6 is a plan view of one embodiment of a method and system for applying an adhesive material to a nonwoven web for use in the method of the present invention.

7 is a perspective view of one embodiment of a slot extrusion die head that may be used in the process of the present invention.

Repeat use of reference characters in the present specification and drawings is intended to represent the same or similar features and elements of the present invention.

<Definition>

As used herein, the term "continuous filament" refers to a strand of polymeric filaments that are formed continuously. Such filaments will typically be formed by extruding molten material through a die head having a particular type and arrangement of capillary holes therein.

As used herein, the term “elastic” or “elasticized” extends the material to at least about 60% (ie to an elongated biased length that is at least about 160% of its relaxed unbiased length) upon application of a biasing force. And a material that is elastic, upon release of the stretching force, the material recovers at least 55% of its elongation. A hypothetical example of an elastic material is a 1 inch sample of material that can extend to at least 1.60 inches and that, when released, will recover to a length of no greater than 1.27 inches. Many elastic materials may extend by greater than 60% (ie, greater than 160% of their relaxed length). For example, some elastic materials may extend 100% or more, many of which recover substantially to their initial relaxed length upon release of the stretching force, for example within 105% of its original relaxed length. Done.

The term "composite nonwoven", "composite nonwoven", "laminate" or "nonwoven laminate" as used herein refers to a material having at least one elastic material connected to at least one sheet material, unless otherwise defined. In most embodiments, such laminates or composite fabrics will have a gatherable layer bonded to an elastic layer or material such that the gatherable layer can be gathered between bonding locations. As described herein, the composite elastic laminate can be stretched to such an extent that the gatherable material gathered between the bonding locations can extend the elastic material. Composite elastic laminates of this type are disclosed, for example, in US Pat. No. 4,720,415 to Vander Wielen et al., Which is hereby incorporated by reference in its entirety herein.

As used herein, the term "nonwoven web" refers to a web that has the structure of individual fibers or yarns interposed, but not in an identifiable, repeating manner. Nonwoven webs have been produced in the past by various methods such as, for example, meltblowing methods, spunbonding methods, and bonded carded web methods.

As used herein, the term “meltblown fibers” allows the molten thermoplastic material to be microfiber diameter by tapering the filaments of the molten thermoplastic material and reducing their diameter through a plurality of fine, generally circular die capillaries. Fiber produced by extruding as molten thermoplastic or filament into a high velocity gas (eg air) stream. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly dispersed meltblown fibers. One such method is disclosed, for example, in US Pat. No. 3,849,241 to Butin et al., Which is hereby incorporated by reference in its entirety.

As used herein, the term “spunbonded fiber” refers to a molten thermoplastic material that is generally circular such that the diameter of the extruded filament is then drastically reduced, such as by deductive stretching or other known spunbonding mechanisms. A small diameter fiber made by extruding as filaments from a plurality of fine capillaries. The manufacture of spun-bonded nonwoven webs is illustrated, for example, in patents such as US Pat. No. 4,340,563 to Appel et al. And US Pat. No. 3,692,618 to Dorschner et al. The contents of these patents are herein incorporated by reference in their entirety.

It should be understood by those skilled in the art that this discussion is not intended to limit the broader aspects of the present invention merely to illustrate exemplary embodiments.

The present invention generally relates to a method of making a composite elastic nonwoven material and to the material itself. More specifically, the present invention relates to a material short slot coat process for applying an adhesive to a facing material for laminating the facing material to a plurality of stretched filaments. Through this process, the adhesive was found to firmly bond the elastic filaments in the stretched state to the facing material. Once relaxed, the facing material forms a stretch bonded laminate having elastic properties in one or more directions.

In one embodiment, during the low material slot coat process, the facing material contacts the slot of the slot extrusion die (or “slot die”) when the adhesive is applied to the facing. The adhesive is applied to the facing in relatively small amounts to form a discontinuous coating on the nonwoven material. Even at relatively low adhesive application rates, the process has been found to bind the elastic filaments tightly to the facing without the problem of two layers.

In the past, elastic filaments have been laminated to the facing material by applying an adhesive onto the facing material, as disclosed in US patent application US 2002/0104608. However, the process of the present invention provides many benefits and advantages as compared to the adhesive spray process. For example, the slot coat process may enable two layers at higher line speeds and produce laminates with higher peel strength. Unexpectedly, the slot coat process also produces laminates with lower porosity, which makes the material easier to handle during later conversion processes. Lower laminate porosity is believed to be due to the fact that the adhesive is applied with a discontinuous coating that produces an amorphous element of the adhesive, in contrast to spray fibrosis, which produces fine fibers that may not have much resistance to air flow.

A material shortage slot coat adhesive process has been found to efficiently position the adhesive on the surface of the facing material. For example, the adhesive generally only covers the fibers of the facing material and does not crosslink void regions in the material. In the spraying process, on the other hand, the adhesive is applied everywhere on the support and typically gathers in the void regions on the facing. When gathered in the void regions, the adhesive does not substantially contribute to bonding the facing material to the elastic support.

In some applications, it has been found that the material short coat process is generally applied to the surface of the facing material only at substantially high points of the material and only on the fibers of the material, where the facing is the only location on the material that can be bonded to the elastic filaments. lost.

Another advantage of the process of the present invention over the spraying process is that no cooling or quenching of the adhesive occurs before the adhesive is attached onto the material because the adhesive is applied to the support as it is released from the slot extrusion die. For this reason, adhesives with higher or faster curing rates can be used.

In the past, slot coat processes have been disclosed in which slot dies have been used to meter adhesives to form laminates. For example, US Pat. No. 5,750,444 to Jarrell, which is incorporated herein by reference, discloses a method of making breathable laminates using slot dies. In the '444 patent, the adhesive is described as forming a porous random fibrous web. The adhesive is used to attach two or more porous webs, including woven or nonwoven materials, together to form a laminate that remains breathable even after applying the adhesive between the materials.

On the other hand, in the process of the present invention, a laminate is formed in which the elastic filaments are stretched and then bonded to the facing material. The shortage slot coat process of the present invention has found that stretched filaments can be properly bonded to the facing even with relatively low adhesive application amounts. It was also unexpectedly found that the slot coat process disclosed herein increased the porosity of the laminate compared to the spray process. As will be explained in more detail below, the increase in porosity facilitates handling of the laminate in later conversion processes.

1 and 2, one exemplary system and process for making a laminate in accordance with the present invention is illustrated. In the embodiment shown in FIG. 1, the system can be considered a vertical filament stack (hereinafter “VFL”) because the filaments are formed and stretched in a vertical arrangement. However, the system illustrated in FIGS. 1 and 2 is for illustration only. It should be understood that the process of the present invention may consist of a horizontal system in which the filaments are cooled and stretched in the horizontal direction. For example, one embodiment of a horizontal system is illustrated in FIGS. 1 and 2 of US Pat. No. 6,057,024, which is incorporated herein by reference.

However, as shown in FIG. 1, the VFL system 11 is configured vertically. An extruder 15 is mounted onto the chilled positioning roller 12 at an angle inclined downward from the die to extrude the continuous molten filaments 14. The chilled positioning roller 12 ensures proper alignment over the rest of the system when unfolding the filaments. As the filaments move over the surface of the chilled positioning roller 12, they cool and solidify as they move towards the chilled roller 13 and over their chilled surface. The filaments are then downward in the "s-shaped" direction of travel to roller 16 and then across the surface of roller 17, between roller 18 and between nip roller 19 and nip roller 20. Move to the formed nip.

The continuous filaments 14 formed in this process may have any desired form. For example, in one embodiment, the filaments can have a shape similar to a ribbon. For example, the filaments can have a width of about 0.5 mm to about 1.5 mm in the unstretched state. The filaments all generally extend in the same direction and are generally parallel to each other. The actual number of continuous filaments used in any particular process may vary depending on the particular properties desired for the final product. For example, the array of filaments may be more than about 100 strands in total, for example more than about 200 distinct strands. For example, in one embodiment, the array of filaments can be as many as 2600 separate strands from about 200 distinct strands. However, larger or smaller number of strands are also possible.

As shown in FIG. 1, the extruder 15 may be positioned relative to the first roller 12 such that the continuous filaments may meet the first roller at a predetermined angle. In some embodiments, the angled or inclined orientation provides the opportunity for the filaments to be released from the die to the roll contact at an angle, resulting in improved radiation, more efficient energy transfer, and generally longer die life. This configuration allows the filament to be released from the die and contact the contacts on the roll surface along a relatively straight path. The angle between the die exit of the extruder and the vertical axis may be as few degrees or as great as 90 °. For example, the angle may be about 20 °, about 35 °, or about 45 ° away from the vertical.

Continuous filaments can be combined with various types of facings in the nip. Facings may include, for example, nonwovens, wovens, such as knits, films, laminates, and the like. In the embodiment depicted in FIG. 1, the first nonwoven spunbond facing 22 and the second nonwoven spunbond facing 24 are combined on opposing surfaces of continuous filaments to form a bonded laminate 25. In some embodiments, only one facing may be used, while in other embodiments it is possible to combine the elastic continuous filaments with three, four or more layers of facing material.

The bonding of the facings to the continuous filaments is typically done by using an adhesive material. According to the invention, the adhesive is applied to the facing using a slot extrusion die. For example, as shown in FIGS. 1 and 2, the first slot extrusion die 23 applies adhesive to the nonwoven material 22, while the second slot extrusion die 53 applies the adhesive to the nonwoven material 24. Apply to As illustrated, when the adhesive is metered onto the nonwoven material, the nonwoven material 22 is in contact with the slot extrusion die 23 while the nonwoven web 24 is in contact with the slot extrusion die 53. To ensure proper contact, for example, pressure rollers 60 and 62 are used.

In one embodiment, the amount of adhesive applied to the nonwoven material can be relatively small. In fact, the amount of adhesive is so low that this process can be referred to as a "lack of material" slot coat process. For example, in one embodiment, the adhesive is applied to each nonwoven material in an amount of less than about 4.4 gsm, such as from about 0.5 gsm to about 3 gsm, for example from about 0.8 gsm to about 2.5 gsm.

At this low impregnation amount, the adhesive does not completely coat the nonwoven material. Instead, the adhesive forms a discontinuous coating. For example, in one embodiment, the adhesive can form an amorphous element located on the surface of the nonwoven material. Particularly advantageously, the adhesive is adapted to be applied to the nonwoven web at the ridges on the web, which are mainly locations where the web can engage the elastic filaments 14. More specifically, the adhesive tends to coat the top surface of the fibers on the web and does not collect or crosslink in void areas in the web. Therefore, little adhesive is wasted in producing the maximum adhesion efficiency.

However, it should be understood that although the adhesive forms a discontinuous coating, the adhesive is applied in a substantially uniform manner on the surface of the nonwoven material in terms of amount per unit area.

In general, any suitable slot extrusion die may be used in the process of the present invention. For example, in one embodiment, a slot extrusion die commercially available from Nordson Corporation, Wesley Lake, Ohio may be used. One example of a Nordson slot extrusion die is disclosed in US Pat. No. 5,750,444, which is incorporated herein by reference.

For purposes of illustration only, one embodiment of a slot extrusion die system is illustrated in FIGS. 6 and 7. As shown in FIG. 6, the system includes a foldable feed 64 for receiving the adhesive material. The adhesive supply may comprise a reservoir, may comprise a heated reservoir, or may comprise an extruder as specifically shown in FIG. 6. Adhesive supply 64 supplies adhesive material to line 66 to multiple metering stations 68. The metering station 68 is connected to the slot extrusion die 23 for applying the adhesive material to the nonwoven material 22. More specifically, the weighing station 68 is connected to a plurality of lines 70A, 70B, 70C, 70D, 70E, 70F, 70G, 70H, 70I, 70J and 70K. The metering station 68 may, for example, be configured to supply adhesive to each line in fluid communication with the slot extrusion die head 23. However, it should be understood that more or fewer lines may be supplied between the metering station 68 and the slot extrusion die 23.

In one embodiment, the plurality of metering stations 68 may include a pumping device located in relation to each of the lines 70A- 70K. In this way, each line can be operated independently of one another. Thus, the amount of adhesive flowing through each line can vary from line to line. However, in other embodiments, each line may be supplied with an equal amount of adhesive.

In one embodiment, instead of containing a pumping device, it is fed directly to each line from a screw extruder.

Referring to FIG. 7, there is shown a perspective view of a slot extrusion die 23, with a portion cut away for the purpose of illustrating the interior of the extruder. Slot extrusion die 23 includes a slot 72 through which adhesive material is discharged. In one embodiment, the slot 72 is supplied by a plurality of segments 74. Each segment 74 may be connected to a corresponding line 70A-70K, for example. By having multiple segments 74, the amount of adhesive dispensed from each location on the slot extrusion die can vary. In addition, the effective width of the slot 72 can be changed by turning on or off the outer line.

In general, any suitable adhesive material may be metered onto the nonwoven material in accordance with the present invention. In general, the adhesive may be, for example, a hot melt adhesive that is heated before being applied to the nonwoven material. The adhesive may have a viscosity exiting the slot extrusion die from about 500 cp to about 50,000 cp, for example from about 2,000 cp to about 20,000 cp. The temperature of the adhesive can vary depending on the adhesive used. However, in one embodiment, the adhesive may be heated to a temperature of about 250 ° F. to about 400 ° F., for example about 320 ° F. to about 350 ° F.

Particular adhesives that can be used in the present invention include various block copolymers, such as styrene block copolymers. Such block copolymers include, for example, styrene-isoprene-styrene block copolymers, styrene-ethylene-butylene-styrene block copolymers, styrene-butadiene-styrene block copolymers, and the like.

In other embodiments, the adhesive material may comprise a random copolymer of polyolefins. The polyolefin may for example be polyethylene or polypropylene.

In another embodiment, amorphous polyalphaolefins can be used. In another embodiment, metallocene-catalyzed elastomeric resins such as polyethylene or polypropylene resins can be used.

Commercially available adhesive materials can be obtained from Bostik, Inc., from Dow Chemical Company, and from various other commercial sources. In some embodiments, the adhesive material may need to be heated before being applied to the nonwoven material. The adhesive can be heated to a temperature, for example, above 100 ° F., for example from about 200 ° F. to about 400 ° F. In some embodiments, the adhesive may be blended with tackifiers or, optionally, with other elastomers.

After the adhesive material is applied to the nonwoven webs 22 and 24, the web is laminated to the elastic filaments 14 while the filaments are in the stretched state. As shown in FIG. 1, a winding roll 21 can be used to receive and wound a bonded nonwoven material / continuous filament / nonwoven material laminate 25 for storage.

2 illustrates a side view of a VFL assembly that includes a support frame 26 to which various components of the system are secured thereon. Reference numerals are used to consistently represent like parts in various figures throughout the drawings. As shown in FIG. 2, the first outer facing roll 27 and the second outer facing roll 28 provide the desired facings 22 and 24 to the assembly. The support strut 29 holds the nip roller 20 in place. Rollers that deliver continuous filaments down to the nip can be seen in a side view, in which the filaments are combined with the facing to form a bonded laminate.

The construction of the continuous filament 14 will now be described in more detail, including the way in which the filaments are stretched before being joined to the nonwoven facing. As shown in Figures 1 and 2, the elastomeric material is extruded through the die head to form the first filament.

4 depicts an exemplary extruder die head 30 with capillary holes 31. In FIG. 5, an enlarged view of the die head is depicted. The pattern and diameter of the capillary holes on the extruder die head can be varied to provide filaments that form the fabric with the correct elastic geometry with appropriate spacing without the need for expensive combs and the like. The distances d1 (distance between the centers of the capillary hole rows), d2 (distance between successive diagonal capillary hole centers on opposite rows) and d3 (distance between successive capillary hole centers in the same row) It may vary depending on the specific features desired. For example, various hole densities can be used in the process of the present invention. In the 12-filament / inch example, the distance d1 between the centerlines of the die holes may be approximately 2.12 millimeters. When a hole density of 18-filament / inch is used, the distance d1 between die hole centerlines is approximately 1.41 mm.

The rollers carrying the continuous filaments are positioned and operate so that they can be stretched as the continuous filaments flow vertically through the lamination system. When many rollers are used, each successive roller rotates in a direction opposite to the previous roller so that the strands of the continuous filament can cross from one roller to another. In addition, the speed of each successive roller can be varied from previous rollers to achieve the desired stretching and stretching properties. For example, any particular roller may operate between 1 and 10 times the speed of any previous roller and above. Typically, separate controllers, such as servomotors or turner drives, can be used to enable individual speed control for each roll and drive each individual roll. As the speed changes, successive rollers can rotate at higher speeds to stretch or stretch them as the strands move downward in a vertical process. In addition, continuous filaments ultimately decrease to fiber sizes of approximately 0.008 to 0.040 in diameter and in some cases approximately 0.015 to 0.020 in diameter.

The number of separate rollers used to transport the continuous filaments to the mating position can vary depending on the particular properties desired for the final product. In one specific embodiment, four or more rollers may be used, namely a first chilled (or positioning) roller, a second chilled roller, a third unchilled roller and a fourth unchilled roller. In other embodiments, only two chilled rollers may be needed before the continuous filaments are fed to the stacker portion of the system that couples the spunbond facing (s) to the continuous filaments in the roller nip.

In certain embodiments, the rollers may be plasma coated to provide good peeling properties. In other embodiments, the rollers may additionally be grooved or channeled to ensure that the extruded continuous filaments ensure proper spacing between individual filaments as the filaments pass over the surface of the roll and flow through the system. Can be. In some embodiments, a smooth roll can be used for one or all of the rolls. When plasma-coated rolls are used, continuous filaments do not slip as much as they pass over uncoated smooth rolls. Plasma-coating catches the strands to promote increased uniformity of distance between the continuous filament strands.

As shown, either or both of the rollers may be cooled to quench or cure them faster as the continuous filaments progress through the process. The chilled roll may be cooled to a controlled temperature between about 45 ° F. and about 60 ° F. (typically about 45 ° F. or about 50 ° F.). Simultaneous quenching and stretching can be optimized according to the specific stretch characteristics desired for the final product.

In one specific embodiment, a series of rollers (or rollers) can be enclosed in a closed tower structure and conditioned air can be used to control the cooling effect of the rollers. For example, chill rolls may be cooled to 50 ° F. or lower than controlled dew point. In this case, the temperature at which the roll is cooled may be significantly lower than 50 ° F., but in a conditioned air environment the roll may be kept at 50 ° F.

Various other mechanisms can be used to quench the continuous filaments. For example, outside air may be forced onto the fiber to control the curing of the fiber. In other embodiments, a large roll can be used as long as it has sufficient surface area to quench the fibers.

Maintaining a particular roller speed allows an appropriate amount of elastic stretch to allow the pucker to form the final laminate. The chilled positioning roller 12 usually rotates at a surface speed in the range of about 3-10 feet / minute (“fpm”), while the first vertically located chilled roller rotates at about 5 to about 15 fpm. The next roller rotates at about 7 to about 18 fpm, while the last roller rotates at a speed of about 12 to about 100 fpm when applied and used. These ranges are approximate and may vary depending on the conditions desired and the final product shape.

In one particular method, the first roll is at approximately 5 fpm; The second roll is approximately 6 fpm; The third roll is approximately 11 fpm; And the fourth roll can rotate at approximately 26 fpm. Another embodiment includes a first roll speed of 10 fpm; Second roll speed of 20 fpm; A third roll speed of 40 fpm; And a fourth roll speed of 80 fpm. In this embodiment, the speed of the nip rollers is approximately 75 fpm. In further embodiments, the speed of the first chill roll may be approximately 400 fpm; The speed of subsequent rolls may be approximately 750 fpm to stretch continuous filaments; The speed of the composite material formed at the nip roller can be approximately 1500 fpm; The winding roller speed (to allow for relaxation, thus allowing gathering of the spunbond facing) can be approximately 700 fpm.

After passing and stretching through a series of rollers, the continuous filaments are then bonded to the nonwoven materials 22 and 24 using a slot extrusion die as described above. Nonwoven materials 22 and 24 may be any suitable web or laminate, including meltblown nonwoven webs, spunbond nonwoven webs, carded webs or even woven webs. In one particular embodiment, polypropylene spunbond facings having a basis weight of approximately 0.4 oz / yd ² may be used.

The system uses nip rolls 19 and 20 to apply pressure to the adhesive-coated facing and continuous filaments resulting in the necessary lamination. The outer facing is joined with continuous filaments at quite high surface pressures, which can be between about 20 and 300 pounds per straight inch ("pli"). Representative bonding pressures may be about 50 pli or about 100 pli.

A combiner or nip roll (sometimes referred to as a "laminator") section of the lamination apparatus performs the primary stretching on the continuous filaments. The speed ratio of the combiner or nip roll to chilled roll can vary, in most cases from about 2: 1 to 8: 1 and in some cases about 4: 1 to 6: 1.

The facing (s) are bonded to the continuous filaments to form a spunbond / elastomer continuous filament / spunbond laminate, which then allows the laminate to relax to shrink in an unstretched or less stretched state. The laminate is then wound onto a winding roll 21 via a surface driven winder. The speed ratio of the winder to the combiner roller causes the stretched continuous filament to relax and the laminate to shrink to a gathered state when the laminate is wound on the roll. For example, the winder roll speed relative to the combiner roll speed can be about 0.3 to about 1.0, and can be about 0.5 to 1.0. Shrinkage of the continuous filaments creates a gathered stretchable laminate article in which the outer facing (s) are gathered between the bond points.

The overall basis weight of the laminate may vary, but in some applications is about 2 to about 4 ounces per square yard (oz / yd ² ). In one particular embodiment, the basis weight is about 2.85 to about 3.2 oz / yd ² .

Various types of compositions and various process conditions can be used to form elastic continuous filaments. For example, the Kraton (Kraton) can be supplied to ^® brand elastomer, in an extruder in which the polymer is melted at about 260 to 460 ℉ ℉ and Der temperature of about 385 ℉ in certain cases. In other embodiments, depending on the specific polymer used. Melting temperatures can be approximately 470 ° F. to 480 ° F. The polymer is then extruded into discrete continuous filaments generally downwardly through a predetermined number of openings in the die head at a pressure of approximately 300 to 4000 psi (typically about 1500 to about 2000 psi). As described below, various die hole shapes can be used in the present invention.

One particular group of polymers that can be used in the present invention is the polymers of the Kraton ^® G series (now Kraton Products US-L.C.) Distributed by Shell Chemical Company. Available from LLC). Various Kraton ^® polymers can be used.

However, the present invention is not limited to these or any specific polymers or materials that form continuous filaments therefrom. For example, various materials may be used including the following: polypropylene, polyethylene, polyester, polyethylene terephthalate, polybutane, polymethyldentene, ethylene propylene copolymer, polyamide, tetrablock polymer, styrenic block Copolymers, polyhexamethylene adipamide, poly- (oc-caproamide), polyhexamethylene sebacamide, polyvinyl, polystyrene, polyurethanes, thermoplastic polymers, polytrifluorochloroethylene, ethylene vinyl acetate polymers, poly Ether esters, polyurethanes, polyurethane elastomer resins, polyamide elastomer resins, polyamides, viscoelastic hot melt pressure sensitive adhesives, cotton, rayon, hemp and nylon. In addition, the materials can be used to extrude single-constituent, bi-constituent and bi-component filaments that are within the scope of the presently described invention.

Other exemplary elastomeric materials that can be used are polyurethane elastomeric materials, such as B.F. Those available under the trade name ESTANE from BF Goodrich & Co., polyamide elastomeric materials, for example those under the trade name PEBAX from Rilsan Company And polyester elastomeric materials such as E.I. Including those available under the trade name HYTREL from DuPont De Nemours & Company.

However, the present invention is not limited to only such elastomeric materials. For example, various latent elastic materials, such as Arnitel-brand polymers, can be used to provide the resilient properties necessary for continuous filaments.

Likewise, the above-mentioned materials and other materials can be used to form the outer facing of the laminates now described. In particular, webs formed from elastomeric or non-elastomeric fibers may be used. Various polyester elastic materials are disclosed, for example, in US Pat. No. 4,741,949 to Morman et al., Which is incorporated herein by reference in its entirety. Other useful elastomeric polymers also include, for example, elastomeric copolymers of ethylene and one or more vinyl monomers such as vinyl acetate, unsaturated aliphatic monocarboxylic acids, and esters of these monocarboxylic acids. Elastic copolymers and the formation of elastomeric fibers from these elastic copolymers are disclosed in US Pat. No. 4,803,117, which is also incorporated herein by reference in its entirety.

Various processing aids may also be added to the elastomeric polymers used in the present invention. For example, polyolefins can be blended with elastomeric polymers (eg, A-B-A elastomeric block copolymers) to improve processability of the composition. The polyolefin must be extrudable in blended form with the elastomeric polymer when so blended to receive the proper combination of elevated pressure and elevated temperature conditions. Useful blended polyolefin materials include, for example, polyethylene, polypropylene and polybutenes such as ethylene copolymers, propylene copolymers and butene copolymers. Particularly useful polyethylene is U.S.I. Obtainable under the tradename Petrorothene NA601 (also referred to herein as PE NA 601 and polyethylene NA 601) from U.S.I.Chemical Company. Two or more polyolefins may be used. Extrudeable blends of elastomeric polymers and polyolefins are disclosed, for example, in US Pat. No. 4,663,220, which is incorporated herein by reference in its entirety.

5, another embodiment of a process for making a laminate in accordance with the present invention is shown. However, as mentioned above, horizontally configured systems are equally applicable to the present invention.

As shown in FIG. 5, an extruder 115 is mounted onto chilled positioning roller 112 at an angle inclined downward from the die to extrude continuous molten filaments 114. Chill positioning roller 112 ensures proper alignment over the rest of the system when unfolding the filaments. As the filaments move over the surface of the chilled positioning roller 112, they cool and solidify as they move towards the chilled roller 113 and over their chilled surface. The filaments then move downwards towards the stacker zone of the system comprising a nip formed between the nip roller 119 and the nip roller 120.

Continuous filaments can be combined with various types of facings in the nip. In the embodiment depicted in FIG. 5, the first nonwoven spunbond facing 122 and the second nonwoven spunbond facing 124 are combined on opposing surfaces of continuous filaments to form a bonded laminate 125.

According to the present invention, the adhesive material is applied to the facing 122 using the slot extrusion die 123, while the adhesive material is applied to the spunbond facing 124 using the slot extrusion die 153.

In the embodiment illustrated in FIG. 5, only two chill rolls are used in contrast to the larger number of chill rolls shown in FIG. 1.

As mentioned above, the use of the lack of material slot coat extrusion process provides various advantages. For example, it has unexpectedly been found that a material shortage slot coat process reduces the porosity of the resulting laminate, even with relatively low adhesive application amounts. For example, a laminate as shown in FIG. 1 may be made with an air permeability of less than about 400 cfm / ft ² , for example less than about 350 cfm / ft ² , in one embodiment about 300 cfm / ft ^2. May be less than. In another embodiment, the air permeability of the laminate may be less than about 250 cfm / ft ² , for example less than about 230 cfm / ft ² . For laminates containing only a single facing material laminated to continuous filaments, the air permeability can be less than about 300 cfm / ft ² . For example, specifically in applications where the facing comprises a spunbond web, the air permeability of the composite material may be less than about 250 cfm / ft ² , for example less than about 230 cfm / ft ² .

Having a low porosity facilitates handling of the material in later conversion processes. For example, the laminate is well suited for use in the construction of absorbent articles such as diapers. During manufacture of the diaper, the elastic laminate typically needs to be cut, manipulated and bonded in place. During these process steps, vacuum is often used to transport and move the material. The reduction in the porosity of the material promotes the ability to manipulate the material using vacuum or suction. Ultimately, the materials produced according to the invention can be processed at higher machine speeds to significantly increase yield.

The invention will be better understood with reference to the following examples.

Test procedure

During the examples which follow, the following tests were performed on the prepared samples.

Porosity was measured using process number STM 3801. Porosity was measured using a Frazier air permeability tester. Units are cubic feet per minute per square foot (cfm / ft ² ).

Elongation was measured using process number STM 529-W. Elongation can be tested using any suitable test apparatus, such as those available from Syntech Corporation of North Carolina Cary or Instron Corporation of Canton, Massachusetts.

In the peel test , the laminate was tested for the amount of force required to pull the layers of the laminate apart. Peel strength was measured using test process number STM 751-W. Any suitable tensile test apparatus can be used to perform this procedure.

Example  One

The following examples were performed to determine the effect of the slot coat extrusion process on the porosity of the nonwoven laminate.

In this example, two spunbond webs were laminated together. The spunbond web used was made of polypropylene and had a basis weight of 0.42 osy.

Nine samples were prepared and tested. In the first three samples, between spunbond webs using a uniform fiber depositor (“UFD”) available under the designation Dynafiber ^™ UFD nozzle from ITW Dynatec, Hendersonville, Tennessee. The adhesive was sprayed. The adhesive used with the spray device was adhesive number H2808-07 obtained from Bostik, Inc., and is a SIS-based adhesive. This particular adhesive is very suitable for use in the spraying process.

When spraying the adhesive between the spunbond webs, two different fiber depositors located adjacent to each web were used.

In the remaining six samples prepared, the spunbond webs were laminated together using a slot extrusion die. Specifically, the slot extrusion die was model number BC62 obtained from Nordson Corporation. The slot on the slot extrusion die had a 0.15 inch gap and was 20 inches wide.

The adhesive used with the slot extrusion die was HX9375-01 from Bostik, Inc., which is a polyolefin copolymer blend. This particular adhesive is rather rigid and therefore does not always produce a uniform spray pattern. This adhesive is very suitable for use with slot extrusion dies.

The adhesive was heated prior to application to the nonwoven web using a slot extrusion die. In Sample Nos. 4 and 5 below, the extruder was heated to a temperature of about 340 ° F. to about 345 ° F. However, in the remaining samples, the extruder was heated to a temperature of about 355 ° F. to about 360 ° F.

The adhesive impregnation amount was the same for both the spraying process and the slot extrusion die process and ranged from 1 gsm to 3 gsm.

The following results were obtained:

Example number Application method Adh Head # 1 GSM Adh Head # 2 GSM Glue Amount GSM Nip Pressure PLI Nip Speed FPM Porosity CFM One Spray 0.5 0.5 One 100 1000 474 2 Spray One One 2 100 1000 424 3 Spray 1.5 1.5 3 100 1000 429 4 Slot coat One n / a One 40 1000 430 5 Slot coat 2 n / a 2 40 1000 433 6 Slot coat 3 n / a 3 40 1000 407 7 Slot coat One n / a One 40 1000 391 8 Slot coat 2 n / a 2 40 1000 339 9 Slot coat 3 n / a 3 40 1000 320

As indicated above, laminates made using slot extrusion dies had lower porosity than laminates made using spray equipment.

Example  2

In this example, elastic laminates were prepared in accordance with the present invention and tested for various properties. To prepare the laminate, a process similar to that illustrated in FIG. 5 was used. Specifically, a VFL process containing two chill rolls was used. The laminates produced included two layers of material, spunbond facings attached to continuous elastic filaments.

The facing included a polypropylene spunbond web with a basis weight of 0.4 osy.

Elastic continuous filaments were made from elastomeric block copolymers. Specifically, elastic filaments were prepared using Kraton G2838 polymers available from Kraton Products.

The same two adhesives described in Example 1 were applied to the spunbond facing to make different samples. Specifically, in the first five samples, adhesive HX9375-01 available from Bostik, Inc. was used, while in the remaining seven samples, adhesive number H2808-07, also obtained from Bostik, Inc., was used. The adhesive was applied to the spunbond web in an amount of 1.5 gsm to 2.5 gsm. The elastic filaments were stretched 5,6% when laminated and attached to a 10 gsm basis weight spunbond web. The temperature of the adhesive varied with the sample.

In one sample of sample number 12 below, the adhesive was applied using the uniform fiber depositor described in Example 1 for comparison purposes.

The following results were obtained:

Example number glue Extruder temperature ℉ Glue Amount GSM Nip Pressure PLI Nip Speed FPM Stretch at break (2000 grams)% Load Gram at 50% Porosity CFM Exfoliation CD gram One HX9375-01 345 1.5 100 800 266 328 239 1665 2 HX9375-01 345 2.0 100 800 265 317 245 2352 3 HX9375-01 365 1.5 100 800 282 330 237 1855 4 HX9375-01 365 2.0 100 800 266 322 224 2248 5 HX9375-01 365 2.5 100 800 252 319 238 3305 6 H2808-07 345 1.5 100 800 295 292 254 443 7 H2808-07 345 2.0 100 800 294 307 241 479 8 H2808-07 345 2.0 100 800 284 306 226 517 9 H2808-07 365 1.5 100 800 294 305 250 571 10 H2808-07 365 2.0 100 800 302 312 245 603 11 H2808-07 365 2.5 100 800 298 315 238 550 12 (control) H2808-07 365 2.5 (use spray device 100 800 265 298 266 2981

As indicated above, the samples prepared according to the present invention had much lower porosity compared to the control sample. As shown in the table above, the peel strength of samples made with H2808-07 adhesive was generally less than the peel strength of laminates made with HX9375-01 adhesive. As described in Example 1 above, the HX9375-01 adhesive is more suitable for use with a slot extrusion die.

These and other modifications and changes to the present invention can be made by those skilled in the art without departing from the spirit and scope of the present invention, which is described in more detail in the appended claims. In addition, it should be understood that each aspect of the various embodiments may be interchanged both in whole or in part. Moreover, one of ordinary skill in the art will recognize that the above description is for illustrative purposes only and is not intended to limit the invention as further described in the appended claims.

Claims (20)

Elastic continuous filaments comprising elastomeric material, generally extending in the same direction; A nonwoven web having a first side and a second side; And an adhesive material for bonding the elastic continuous filament to the first side of the nonwoven web, At this time, the first side of the nonwoven web is laminated to the elastic continuous filament, the elastic continuous filament is laminated to the nonwoven web in a stretched state so that the nonwoven web is gathered when the elastic continuous filament is relaxed, and the adhesive material is A composite elastic material comprising a discontinuous coating comprising an amorphous element of an adhesive material on the first side of the nonwoven web and present on the nonwoven web in an amount of less than about 4.4 gsm, for example from about 0.8 gsm to about 3 gsm. . The composite elastic material of claim 1, wherein the adhesive material comprises a styrenic block copolymer, a random copolymer of polyolefin, an amorphous polyalphaolefin, or a mixture thereof. The composite elastic material of claim 1, wherein the adhesive material comprises a hot melt adhesive. The nonwoven web of claim 1, further comprising: a second nonwoven web having a first side and a second side; And an adhesive material for bonding the elastic continuous filament to the first side of the second nonwoven web, At this time, a first side of the second nonwoven web is laminated to the elastic continuous filament such that the elastic continuous filament is positioned between the first nonwoven web and the second nonwoven web, and the adhesive material is the first of the second nonwoven web. A composite elastic material comprising a discontinuous coating comprising an amorphous element of an adhesive material on a side and present on the first side of the second nonwoven web in an amount of less than about 4.4 gsm. The composite elastic material of claim 1, wherein the nonwoven web comprises a spunbond web having a basis weight of about 10 gsm to about 20 gsm. The elastomeric material according to any one of claims 1 to 5, wherein the elastomeric material used to form the continuous filaments is made of an elastic polyester, an elastic polyurethane, an elastic polyamide, an elastic copolymer of ethylene and at least one vinyl monomer, or an elastic metal. A composite elastic material comprising an elastomer selected from the group consisting of sen-catalyzed polyolefins, and elastic block copolymers. The composite elastic material of claim 1, having an air permeability of less than about 350 cfm / ft ² . 8. The composite elastic material of claim 1, wherein the adhesive material is present on the first side of the nonwoven web in a substantially uniform manner in terms of quantity per unit area. 9. The composite elastic material of claim 1, comprising only two layers, including a nonwoven web comprising a spunbond web and a layer of continuous filaments, and having an air permeability of less than about 400 cfm / ft ^2. . The composite elastic material of claim 1, wherein the adhesive only coats the surface fibers of the nonwoven web and is not detectably deposited in any pores on the nonwoven web. Extruding a continuous filament comprising an elastomeric material; Stretching the continuous filament; Applying the adhesive material from the slot extrusion die to the first side of the facing material to form a discontinuous coating comprising an amorphous element of the adhesive material; And A method of making a composite material as claimed in claim 1, comprising laminating a continuous filament stretched to the first side of the facing material after the adhesive material has been applied. The method of claim 11, further comprising: applying an adhesive material from the slot extruder to the first face of the second facing material; And The stretched continuous filaments are laminated to the first face of the second facing material such that the stretched continuous filaments are positioned between the first facing material and the second facing material to form a composite material having a porosity of less than about 300 cfm / ft ^2. Further comprising the step of: The method of claim 12, wherein the first facing material and the second facing material comprise a spunbond web. 14. The method of any one of claims 11 to 13, wherein the slot extrusion die defines a slot from which adhesive material is released and wherein the first face of the facing material contacts the slot when the adhesive material is applied to the facing material. Way. The method of claim 11, wherein the adhesive materials have a viscosity of about 500 cp to about 50,000 cp when they are applied to the first side of the facing material. The method of claim 11, wherein the continuous filaments move vertically downwards as they are formed and laminated to the first facing material. The method of claim 11, further comprising the step of relaxing the composite nonwoven material after the continuous filaments have been laminated to the facing material. The method according to any one of claims 11 to 17, Applying the adhesive material from the slot extrusion die to the first face of the second facing material to form a discontinuous coating comprising an amorphous element of the adhesive material, and After the adhesive material is applied to the second facing material, the stretched continuous filaments are laminated to the first face of the second facing material such that the stretched continuous filaments are positioned between the first facing material and the second facing material. Forming steps How to further include. 19. The method of any one of claims 11 to 18, wherein the continuous filaments are stretched by being transported on one or more rollers. 20. The method of any one of claims 11 to 19, wherein the facing material comprises a nonwoven web having a basis weight of about 0.2 osy to about 1.5 osy.

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