MXPA99006058A - Improved composite elastic material and process for producing the same - Google Patents

Abstract

The present invention relates to dimensionally stable and/or latent composite elastic laminate materials. The method of manufacturing the composite elastic laminate materials includes providing a polymeric material having a first length, stretching the polymeric material to a second length and bonding at least one non-woven facing to the polymeric material in a calender consisting of two smooth-surfaced rolls, such that the elastic component is not damaged or preconditioned to damage during the use of the personal care articlein which the composite elastic material is used.

Description

ELASTIC COMPOSITE MATERIAL IMPROVED AND PROCESS FOR THE PRODUCTION OF THE SAME FIELD OF THE INVENTION The present invention relates to a composite elastic material having improved tension relaxation and improved dimensional stability. This invention also relates to a method for manufacturing composite elastic materials that are dimensionally stable and latent and that have improved stress relieving.

BACKGROUND OF THE INVENTION The present invention relates to a latent and / or dimensionally stable composite elastic material having improved strain relief and improved crimping resistance and laminations thereof. The present invention also relates to a method for manufacturing the same.

As used herein, the term "composite elastic material" refers to a multilayer or multi-component elastic material in which a layer is elastic. A composite elastic material that is "dimensionally stable" is one that retains its dimensions, for example, the length and width, under the actual conditions of use. The conditions of use generally involve body temperature, humidity and heat. A "latent elastic laminate material" refers to a laminated material having an elastic component that is dormant but can be acted at will, usually using a stimulus such as heat. In other words, a latent elastic laminate material will become elastic when acted.

The term "tension relaxation" is defined as the load required to sustain a constant elongation over a period of time. The term "drag" is defined as the loss of shape or dimension of an article due to some irreversible flow or a structural break under a constant force or load. There are two kinds of drag: (1) independent of the time in which the shape changes due to irreversible flow or structural breakage under constant force or load and does not recover when the force is removed; and (2) dependent on the time in which one of the forms recovers when the force is removed.

The composite elastic materials and the laminates thereof have a wide variety of uses, especially in the areas of absorbent articles and disposable articles. As used herein, the term "absorbent articles" refers to devices which absorb and contain exudates from the body and, more specifically, refer to devices that are placed against or in proximity to the user's body to absorb and contain the various exudates discharged from the body. The term "absorbent articles" is intended to include diapers, underpants, absorbent underpants, incontinence products, and the like. The term "disposable" was used herein to describe the absorbent articles and is not intended to be washed or otherwise restored or reused as an absorbent article.

Generally, the composite elastic material is a continuous filament type structure in which a layer of elastic, generally parallel and continuous filaments are attached to at least one face layer using a heated calender roll and an anvil roller. Continuous filament laminates are described in U.S. Patent No. 5,366,793 issued to Fitts, Jr. and others and in U.S. Patent No. 5,385,775 issued to Wright, both of which are incorporated here by reference in its entirety.

Typically, the calender roll is patterned in some manner so that the resulting laminate is not bonded through its entire surface. The anvil roller can also have a pattern if desired. The maximum joint point surface area for a given surface area on one side of the laminate will generally not exceed about 50% of the total surface area. Typically, the area bonding percentage varies from about 10% to about 30% of the area of the laminate. Such a process is described, for example, in U.S. Patent No. 5,385,775 issued to Wright and in U.S. Patent No. 4,041,203 to Broc-k and others both of which are incorporated herein. by reference in its entirety.

A disadvantage of this rolling method is that the patterned rolls severely damage the elastic filaments. The damage to the elastic filaments affects the elastic properties, and therefore, the operation of the composite elastic material and the laminates thereof by causing the fibers to break during use at room temperature and under stretched conditions.

There is therefore a need for a method of manufacturing a composite elastic material that is dimensionally stable. Additionally, there is a need for a method of manufacturing a composite elastic material without damaging the polymer threads during the manufacturing process.

SYNTHESIS OF THE INVENTION The present invention provides a process for producing a latent and / or dimensionally stable elastic laminate. The process includes the steps of providing a polymeric material having a first length, stretching the polymeric material to a second length and joining at least one non-woven face to the polymeric material in a calender having two smooth surface rollers in order to reduce the damage to the structure of the elastic material. The present invention also provides a process wherein 100% of the surface area of the roller makes contact with the elastic # material. The present invention therefore produces a unique composite elastic material that has minimal to negligible damage to the polymeric material by calendering a polymeric material and at least one non-woven face between the smooth surface rolls.

The process of the present invention not only overcomes the problems of the prior art, but also provides several advantages. These include: (1) a substantial improvement in the performance of the resulting laminate through dimensional stability; (2) a loss of load reduced with time under conditions of actual use; (3) a possible cost reduction through the use of a lower amount of elastic material in the final laminate; (4) the production of heat shrinkable and / or latent materials; and (5) the use in the laminate resulting from the full potential of the elastic polymer. The present invention also provides a method of manufacturing a low cost elastic nonwoven material.

The composite elastic laminate materials produced in accordance with the present invention can be used as elastic components for personal care absorbent articles such as, for example, on the side panels of diapers and training underpants. These can also be used in the leg elastic and diaper packing, underpants, incontinence devices and the like.

The foregoing and other features and advantages of the present invention will be apparent from the following detailed description of the currently preferred embodiments, when read in conjunction with the accompanying examples.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic drawing of the process for forming a composite elastic material according to the present invention.

Figure 2 is a perspective view of an example disposable garment, in this case, training underpants, which use the laminated material made according to the present invention.

Figure 3 is a graph of tension relieving modulus versus time determined during stress relieving test of a composite elastic laminate produced using a patterned roller and testing a composite elastic laminate produced using two smooth rollers .

DETAILED DESCRIPTION OF THE PREFERRED INCORPORATIONS The present invention is directed to a dimensionally stable composite elastic material and to the laminates thereof having improved strain relief and improved drag resistance. The present invention also relates to a method for forming composite elastic laminate materials which are dimensionally stable and latent and which have improved stress relieving properties.

Referring now to the drawings in which the like reference numbers represent the same or an equivalent structure and, in particular, to Figure 1 of the drawings, there is illustrated in point 10 a process for forming a composite elastic material using a calendering of smooth roller.

According to the present invention, an elastic fabric 12 is unwound from a supply roll 14 and moves in the direction indicated by the arrow associated therewith as the supply roll 14 rotates in the direction of the arrows associated therewith. . The physical structure of the elastic fabric 12 can be a film, a nonwoven or yarns. The elastic fabric 12 passes through the pressure point 16 of the S-roll arrangement formed by the stack rollers 20 and 22.

The elastic fabric 12 can also be formed in a continuous process such as, for example, the process described below, and passed through the pressure point 16 without first being stored on a supply roll.

A first recoverable layer 24 is unwound from a supply roll 26 and moves in the direction indicated by the arrow associated therewith as the supply roll 26 rotates in the direction of the arrows associated therewith. A second foldable layer 28 is unwound from a second supply roll 30 and moves in the direction indicated by the arrow associated therewith as the supply roll 30 rotates in the direction of the arrows associated therewith. The first fold 24 and second layer folded layer 28 pass through the pressure point 32 of the calender roll 34 formed by the calender roll 36 and 38. The first folding layer 24 and / or the second folding layer 28 may be formed by extrusion processes such as, for example, meltblowing processes, spin bonding processes or film extrusion processes and pass directly through pressure point 32 without first being stored on a supply roll .

The elastic fabric 12 passes through the pressure point 16 of the roll arrangement at S 18 in a reverse path at S as indicated by the rotation direction arrows associated with the stack rolls 20 and 22. From the arrangement of S-roll 18, the elastic fabric 12 passes through pressure point 32 formed by the calendering roll arrangement 34. Additional S-roll arrangements (not shown) can be introduced between the roller arrangement S 18 and the calendering roll arrangement 34 to stabilize the stretched material and to control the amount of stretch. Because the peripheral linear speed of rollers under roller S 18 is controlled to be less than the peripheral linear speed of rollers arrangement calendering roller 34, the stretch fabric 12 is tensioned between the fixing roller S 18 and the pressure point of the calendering roll arrangement 34. Importantly, the filaments of the elastic yarn-like fabric 12 must run along the direction in which the film is stretched so that the filaments can provide the filaments. desired stretch properties in the finished composite. By adjusting the difference in the speeds of the rollers, the elastic fabric 12 is tensioned so that it is stretched by a desired amount and held in such a stretched condition while the first recoverable layer 24 and the second recoverable layer 28 are joined together. to the elastic fabric 12 during its passage through the calendering rollers 36 and 38 to form a composite elastic material 40. The surfaces of the calendering rolls 36 and 38 are smooth and without pattern. Therefore, the bonded area of the composite elastic material 40 is 100% due to the fact that the calendering rollers have a smooth surface.

Preferably, the stretched length of the polymeric material is at least about 50% of the original length. Preferably, the stretched length is up to about 95% of the final elongation of the elastomer. It should be noted that different elastomers have different elongations. Even more preferably, the stretched length should be in the range of about 200% to about 600% where the elongation percent is defined according to the following formula: final length - initial length x 100% initial length Referring again to Figure 1, the composite elastic material 40 relaxes immediately with the release of the tensioning force provided by the roller arrangement S 18 in the joining roller arrangement 34, so that the first recoverable layer 24 and the second The recoverable layer 28 is folded into the composite elastic material 40. Preferably, a permanent elongation length of from about 1.5 times the original length is retained after the stretched film is allowed to relax.

The composite elastic material 40 is then wound onto a winder 42. The composite elastic material 40 can be wound under tension or without tension. If rolled without tension, the composite elastic material will be stored in the roll in its non-stretched state so that the material can be stretched at any time. If rolled with tension, the composite elastic material is stored in a stretched condition. The elastic properties of the material stored in the stretched condition can be reactivated using heat or other conditions. Alternatively, the composite elastic material 40 may continue in line for further processing or conversion (not shown).

The polymeric materials that are useful in the formation of elastic tissue 12 are generally known as "elastomer". An elastomer is an elastic rubber material capable of stretching to seven times its original relaxed length and which tends to fully recover its elongation with the release of the pressing and stretching force. As used herein, the term "recover" refers to a contraction of a stretched material with the termination of the pressing force after stretching of the material by the application of a pressing force. Examples of these materials are indexed as "elastomers" in the work of Bradley and other Materials Handbook, pages 284-290 (McGraw-Hill, Inc. 1991), incorporated herein by reference.

The elastomers useful in the present invention may be selected from the group consisting of elastomeric thermoplastic polymers. The physical structure of the elastomer can be yarns, a melted or blown film, crimped any fiber non-woven fabric of a desired thermoplastic polymer or a combination thereof.

Suitable elastomeric thermoplastic polymers include styrene block copolymers such as, for example, those available under the trademark KRATON® from Shell Chemical Company of Houston, Texas. KRATON® block copolymers are available in several different formulas, a number of which are identified in US Pat. Nos. 4,663,220; 4,323,534; 4,834,738; 5,093,422 and 5,304,599 which are incorporated herein by reference.

Other exemplary elastomeric materials that may be used include polyurethane elastomeric materials such as, for example, those available under the PELLATHANE® brand from Dow Chemical Company, of Midland, Michigan or under the trademark ESTAÑE® of B.F. Goodrich & Company of Akron, Ohio or under the MORTHANE® brand of Morton Thiokol Corporation; polyester elastomeric materials such as, for example, those available under the trade designation HYTREL from E. I. Dupont de Nemours & Company of Wilmington, Delaware, and those known as ARNITEL® that were previously available from Akzo Plastics of Arnhem, The Netherlands and now available from DSM of Sittard, The Netherlands; and polymers of the metallocene-based catalysts which are available under the name ENGAGE® from the Dow Chemical Company of Midland, Michigan for polymers based on polyethylene and Exxon Chemical Company of Baytown, Texas under the trade name ACHIEVE® for polymers based on polypropylene and EXACT® and EXCEED® for polymers based on polyethylene.

The collapsible layers, or covers, 24 and 28 can be made of fibrous nonwoven materials such as, for example, fabrics bonded with spinning or blown fabrics with melting. A non-woven fabric, as described herein, means a fabric having a structure of individual fibers or threads that are interlocked, but not in a repetitive and identifiable manner. A plurality of fibrous nonwoven covers 24 and 28, as shown in Figure 1, may also be used depending on the basis weight of the nonwoven material used.

The recoverable layers 24 and 28 can be formed by a variety of processes including, but not limited to, meltblowing and spin bonding processes. Melt-blown fibers are fibers formed by extruding a melted thermoplastic material through a plurality of usually circular and thin capillaries of a meltblown matrix such as melted threads or filaments into gas streams (eg, air). ) usually hot and high-speed converging which are flowing in the same direction as the extruded filaments or filaments of the melted thermoplastic material so that the extruded yarns or filaments are attenuated, for example, pulled or stretched to reduce their diameter. The yarns or filaments can be attenuated to a microfiber diameter which means that the yarns or filaments have an average diameter of no more than about 75 microns, generally from about 0.5 microns to about 50 microns, and more particularly from about 50 microns. around 2 microns to around 40 microns. Then, the meltblown fibers are carried by the gas stream at high speed and are deposited on a collector surface to form a fabric of melt blown fibers and discarded at random. The meltblowing process is well known and is described in several patents and publications including the Naval Research Laboratory Report 4364, "Manufacturing of Superfine Organic Fibers" by B.A. Wendt, E.L. Boone and D.D. Foharty; the Marine Research Laboratory Report 5265, "Improved Device for the Formation of Superfine Thermoplastic Fibers" by K.D. Lawrence, R.T. Lukas and J.A. Young; U.S. Patent No. 3,676,242 issued to Prentice; and U.S. Patent No. 3,849,241 issued to Butin et al. The above references are incorporated herein by their mention in their entirety. Melt-blown fibers are microfibers which may be continuous or discontinuous, are generally smaller than 10 microns in average diameter and are generally sticky when deposited on a collecting surface.

Spunbonded fibers are small diameter fibers that are formulated by extruding a melted thermoplastic material as filaments from a plurality of usually circular and thin capillaries of a spinner with the diameter of the extruded filaments then being rapidly reduced such as, for example, by pulling eductive or non-eductive fluid or other well-known spinning bonding mechanisms. The production of non-woven fabrics bonded with yarn is illustrated in the patents such as, for example, US Pat. Nos. 4,340,563 issued to Appel et al .; 3,802,817 awarded to Matsuki and others; 3,692,618 issued to Dorschner and others; 3,542,615 granted to Dobo; 3,502,763 awarded to hartmap; 3,502,538 awarded to Peterson; US Pat. Nos. 3,341,394 and 3,338,992 issued to Kinney; 3,276,944 issued to Levy, and Canadian patent No. 803,714 granted to Harmon. The descriptions of these patents are included herein by reference in their entirety. Spunbonded fibers are generally non-tacky when deposited on the collector surface. Spunbonded fibers are generally continuous and have average diameters (from a sample of at least 10) larger than 7 microns, and more particularly, from about 10 microns to about 20 microns.

Preferably, the non-woven recoverable layers comprise spunbonded fibers. For most uses, the total weight of the yarn bonded face material is about 0.4 ounces per square yard.

Various techniques have been employed to secure the elastic fabric 12 and the non-woven faces 24 and 28 such as, for example, with adhesive bonding. In the bonding of adhesive, an adhesive such as a pressure sensitive adhesive and hot melt was applied between the polymeric material and the face to join the polymeric material and the face together. The adhesive can be applied by, for example, melt spraying, printing or melt blowing. Various types of adhesives are available, including those produced from amorphous polyolefins, ethylene vinyl acetate hot melt adhesives and KRATON® brand adhesives available from Shell Chemical Company of Houston, Texas.

The resulting composite elastic material 40 has elastic properties identical to those of the pure polymeric material. The resulting laminate material does not suffer loss of elasticity and provides a better conformation to the body than laminated materials produced using one or more pattern calendering rolls. The filaments in the laminated materials of the present invention are also less likely to break.

The tension relaxation of the resulting composite elastic material 40 is at least about one pound per square inch less than the tension relaxation of a standard and thermally bonded material of similar composition at that time of about 8 hours. Preferably, the tension relaxation is about 2 pounds per square inch less than that of the pattern bonded material at a time of about 8 hours.

Referring now to Figure 2, there is illustrated a disposable garment 50 incorporating an elastic laminate made in accordance with the present invention. Although the training underpants are shown in Figure 2, it will be understood that the use of the elastic laminate produced according to the present invention is not limited to such articles and may also be used in a wide variety of applications including, but not limited to. to diapers, incontinence devices and the like.

Referring again to Figure 2, the disposable garment 50 includes the waste containment section 52 and two side panels 54 and 56 defining a waist opening 58 and a pair of leg openings 60 and 62. Figure 2 illustrates the garment disposable 50 fitted on a user's torso 64 in dotted lines. The side panel 54 includes the stretchable side member 66 and the stretchable side member 68 connecting the immediate member 70 which is made of a non-stretchable material. Similarly, the side panel 56 includes the stretchable side member 72 and the stretchable side member 74 connecting the intermediate member 76 which is made of a non-stretchable material. The disposable garment 50 also includes the front waist elastic member 78 and the rear waist elastic member 80 to provide additional elasticity along the waist opening 58. The leg elastics 82 are provided with a waist containment section. 52 between the side panels 54 and 56.

The composite elastic material of the present invention can be used to form various parts of the disposable garment 50 and particularly, the side panels 54 and 56.

The laminate material can also be used and the leg elastics 82 of the disposable garment 50.

EXAMPLES A composite elastic material was made using two smooth surface calendering rollers according to the present invention. A control material was made using the pattern rollers according to the prior art process. Both materials were made from the same polymer mixture.

Stress Relaxation The strain relief of the inventive and control samples was measured on a Sintech 1 / S voltage test frame available from Sintech, Inc., of Stoghton, Massachusetts. The sample size was about 3 inches wide and 7 inches long. Each specimen was gripped between the jaws of the grip at a grip distance of 3 inches. Each sample and grip accessories were enclosed in an environmental chamber and balanced at IOOOF for 3 minutes. Each sample was then stretched to a final constant elongation of 4.5 inches (50% elongation) to a head displacement in the transverse direction of 20 inches per minute. The load required to maintain 50% elongation as a function of time was monitored for 8 hours for each sample.

Sintech 1 / S system data was reduced by calculating the engineering tension (pounds per square inch, or psi) of a knowledge of the area in initial cross section of each sample. Tension, or elongation, was calculated from the initial distance of grip to grip and constant elongation. The proportion of stress and effort gives the stress relaxation module (pounds per square inch). These data were used to generate the stress relieving modulus against the time curve for the composite elastic laminates of control and of the invention. Figure 3 is a graph showing the stress relaxation modulus against the time curves of the composite elastic laminate produced using a pattern roll (A) and the composite elastic laminate produced using two smooth rolls (B).

The resulting data can be adjusted to the following force-law model to obtain the exponent, m: (st = 0.l min.) (t "m) where s is tension, t is time and m represents how fast the material loses its charge, or elastic properties. Table 1 shows the rate of actual head loss, or tilt, as calculated using the formula described above and the actual head loss in 8 hours at IOOOF. As can be seen from the table, the use of smooth calendering rolls decreases the magnitudes of the inclination and the percent of load loss favorably.

TABLE 1 Of course, it should be understood that a wide range of changes and modifications can be made to the incorporations described above. It is therefore intended that the foregoing description should illustrate rather than limit this invention and that it is the following clauses, including all equivalents, that define this invention.

Claims (28)

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

1. A process for producing dimensionally stable composite elastic laminates comprising: providing a polymeric material having a first length; stretching said polymeric material to a second length; Y joining at least one face to said polymeric material in a calendering consisting of two smooth surface rollers.

2. The process as claimed in clause 1, characterized in that said polymeric material is selected from the group consisting of elastomeric thermoplastic polymers.

3. The process as claimed in clause 2, characterized in that said elastomeric thermoplastic polymer is selected from the group comprising block copolymers, polyurethanes, polyesters and metallocene-based catalyst polymers.

4. The process as claimed in clause 3, characterized in that said elastomeric thermoplastic polymer is a block copolymer.

5. The process as claimed in clause 3, characterized in that said elastomeric thermoplastic polymer is polyurethane.

6. The process as claimed in clause 3, characterized in that said elastomeric thermoplastic polymer is polyester.

7. The process as claimed in clause 3, characterized in that said elastomeric thermoplastic polymer is a catalyst polymer based on metallocene.

8. The process as claimed in clause 1, characterized in that said second length of said polymeric material is achieved at least 50% of said first length.

9. The process as claimed in clause 1, characterized in that the elongation percentage of said polymeric material is from about 200% to about 600%.

10. The process as claimed in clause 1, characterized in that said face is a fibrous non-woven fabric.

11. The process as claimed in clause 10, characterized in that said fibrous nonwoven fabric comprises a fabric of blown fibers with melting.

12. The process as claimed in clause 10, characterized in that said fibrous nonwoven fabric comprises a fabric of fibers joined with spinning.

13. The process as claimed in clause 12, characterized in that the basis weight of said fibrous non-woven fabric is about 0.4 ounces per square yard.

14. The process as claimed in clause 1, characterized in that said polymeric material is attached to said face with an adhesive.

15. A process for producing latent elastic and / or dimensionally stable laminated materials comprising: providing a polymeric material having a first length; stretching said polymeric material to a second length; apply a single-sided adhesive; Y joining said face to said polymeric material in a calender consisting of two smooth surface rollers.

16. The process as claimed in clause 15, characterized in that said adhesive is a hot-melt pressure-sensitive adhesive.

17. The process as claimed in clause 15, characterized in that said polymeric material is selected from the group consisting of elastomeric thermoplastic polymers.

18. The process as claimed in clause 17, characterized in that said elastomeric thermoplastic polymer is selected from the group comprising block copolymers, polyurethanes, polyesters and metallocene-based catalyst polymers.

19. The process as claimed in clause 17, characterized in that said face is a fibrous non-woven fabric.

20. The process as claimed in clause 19, characterized in that said fibrous nonwoven fabric comprises a fabric of blown fibers with melting.

21. The process as claimed in clause 19, characterized in that said fibrous nonwoven fabric comprises a fabric of fibers joined with spinning.

22. A dimensionally stable composite elastic material comprising a polymeric material and a fibrous nonwoven face wherein said composite elastic material has a tension relaxation of at least about 1 pound per square inch less than the tension relaxation of a bonded material with similar composition pattern at a time of about eight hours.

23. The dimensionally stable composite elastic material as claimed in clause 22, characterized in that said composite elastic material has a tension relaxation of at least about 2 pounds per square inch less than the stress relieving of the bonding material with pattern is similar to the composition at a time of about eight hours.

24. A disposable personal care absorbent article comprising a liquid permeable liner and an outer cover with an absorbent core positioned therebetween, wherein said outer cover is formed so that the tension relaxation is at least about 1 pound per square inch less than the tension relaxation of a material bonded with standard? e composition similar to the time of about eight hours.

25. The disposable absorbent article as claimed in clause 24, characterized in that the outer cover of said article is formed so that the tension relaxation is at least about 2 pounds per square inch less than the tension relieving of a material joined with a pattern of similar composition at the time of about eight hours.

26. The disposable absorbent article as claimed in clause 24, characterized in that said article is a diaper.

27. The disposable absorbent article as claimed in clause 24, characterized in that said article is a training underpants.

28. The disposable absorbent article as claimed in clause 24, characterized in that said article is a garment for adult incontinence. E S U M E N The present invention relates to latent elastic composite and / or dimensionally stable composite materials. The manufacturing method of composite elastic laminate materials includes providing a polymeric material having a first length, stretching the polymeric material to a second length and joining at least one non-woven face to polymeric material in a calendering consisting of two rolls of soft surface, so that the elastic component is not damaged or is not preconditioned for damage during the use of the personal care item in which the composite elastic material is used.