MXPA98000068A - Fibers of multicomponent and non-woven degradable in a - Google Patents

Abstract

The present invention relates to multicomponent fibers wherein at least one component will allow the joining of the fibers to themselves and other types of fibers and wherein the same first component is also degradable in an aqueous medium. Such fibers can be used as a component in such end-use products such as health-care and medical articles, cleaners and absorbent articles for personal care.

Description

FIBERS OF MULTICOMPONENT AND NON-WOVEN DEGRADABLE IN WATER FIELD OF THE INVENTION The present invention is directed to multicomponent fibers. More particularly, the present invention is directed to multicomponent fibers including bicomponent fibers which have at least one component which will allow the bonding of the fibers to themselves and other types of fibers and wherein the same component is also degradable in an aqueous medium. Such fibers can be used to form fibrous nonwoven fabrics and can be used as components in such end products including, but not limited to, medical and health care articles, cleaners and absorbent articles for personal care such as diapers, training pants, incontinence garments, sanitary napkins, bandages and the like.

BACKGROUND OF THE INVENTION The disposal of solid waste has become an increasing problem throughout the world. As fill-up areas continue to fill, there has been an increased demand for a reduction in the source of disposable material, the incorporation of more recyclable components into disposable products, and the design of products which can be disposed of by other means. to the incorporation within solid waste disposal facilities such as filling fields.

One area of product that received particular attention with respect to the disposition of solid waste is that of disposable diapers. Most diapers in the United States of America are disposed of in landfills. Other proposed disposal methods have included making all or part of the drainable diapers in public drainage systems and / or making their components more compatible with evolving fertilizer and biometalization techniques.

Diapers and almost all personal care products include a body-side cover, an absorbent core and some type of outer cover to protect the wearer's clothes from getting dirty. Most of the side-to-body covers and outer covers are made of fibrous non-woven fabrics and / or films that are made of thermoplastic polymers such as polyolefins and polyesters. These parts of the product and diapers especially usually have to have a fairly high degree of integrity so that they remain intact during use. This same integrity, however, makes disposal much more difficult, for example, through drainage in a toilet. Consequently, there is a need for materials, components and product designs which make such disposable articles as absorbent personal care products more compatible with alternative waste techniques such as toilet drain, composting and biometalization.

SYNTHESIS OF THE INVENTION The present invention is directed to a multicomponent fiber which includes a first component, at least a second component and optionally more components if desired. The first component forms an exposed surface on at least a part of the fiber. The first component is water degradable and can be made from a wide variety of water degradable polymers including, for example, poly (vinyl alcohol) and sulfonated polyester. The second component can be made of a thermoplastic fiber forming polymer which is capable of being extruded through, for example, the bicomponent fiber forming equipment. Examples of such polymers include, but are not limited to polyolefins and polyesters. If desired, the second component can also be made from a polymer which is degradable in water even though it will generally be more advantageous if the second polymer degrades at a rate which is slower than the rate of degradation of the first component. Multicomponent fibers such as bicomponent fibers can be extruded in a number of ways including, but not limited to concentric and eccentric sheath / core configurations and side-by-side configurations. If desired, the additional components can also be incorporated into the multicomponent fibers according to the present invention including other polymers and / or additives.

The multicomponent fibers according to the present invention can be used to form the fibrous non-woven fabrics using heat and / or pressure to join the fibers together using the first component as the binding agent. The fabrics can be completely formed of fibers according to the present invention or they can be mixed with other fibers. Once the fabrics have been formed these can be used to form all or a part of a number of end-use products including, but not limited to, absorbent articles for personal care.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional view of a sheath / concentric core bicomponent fiber according to the present invention.

Figure 2 is a cross-sectional view of an eccentric sheath / bicomponent core fiber according to the present invention.

Figure 3 is a cross-sectional view of a side-by-side bicomponent fiber according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to multicomponent fibers such as a bicomponent fiber which includes a first component and a second component. For purposes of illustration only, the present invention will be described in relation to a bicomponent fiber. It should be understood, however, that the scope of the invention is intended to encompass the fibers with two or more components and thus be "multicomponent" fibers. The first component provides at least two functions. First, it provides an exposed part on the surface of the bicomponent fiber which will allow the thermal bonding of the fiber to other fibers that may be the same or different from the fibers of the present invention. Second, the first component of the bicomponent fiber of the present invention must be biodegradable when placed in an aqueous medium. As a result of this, the bicomponent fiber of the present invention can be used to form the thermally bonded fibrous nonwoven fibers. Then, when the fabric is exposed to an aqueous medium such as water in a toilet bowl, the fiber to fiber bond caused by the first component will be degraded to a sufficient degree so that the fiber to fiber bonds will break causing so that the fibrous nonwoven fabric loses its integrity and breaks into small pieces or individual fibers.

The second component is another fiber-forming polymer which is less degradable in an aqueous medium when compared to the first component or can be totally non-degradable. Generally, the purpose of the second component will be to provide rigidity to the fiber and thus to the resulting non-woven fabric. - - - Referring to Figures 1 to 3, the bicomponent fibers 10 according to the present invention will have two or more components including a first component 12 and a second component 14 with the first component being "degradable in water". By this it is meant that when the first component 12 of the bicomponent fiber 10 is exposed to an aqueous liquid, including water such as that found in the toilet bowl or an aqueous mixture which may have an added buffer, components alkaline or acidic or complexing, the bond formed between the fibers by the first component will be sufficiently weakened so that the fibers will begin to break and separate by themselves or if necessary with agitation. To effect bonding, the first component 12 has a melting or softening temperature lower than the melting or softening temperature of the second component. In addition, as shown by Figures 1 to 3, the first component forms at least a portion of the exposed surface of the fiber 10, usually along the longitudinal axis of the fiber 10. The cross sections of fiber which provide such exposed surface for the first component include, but are not limited to a concentric sheath / core configuration as shown in Figure 1, an eccentric sheath / core configuration as shown in Figure 2, and a side-by-side configuration as shown in FIG. Figure 3. As a result of this, the first component serves as the joining means for "joining the fibers together while the second component provides the structural rigidity to the fiber and the resulting non-woven fabric.

The second component 14 is a polymer which has a melting or softening temperature higher than that of the first component 12 so that the thermal bond is used to join the bicomponent fibers together. The first bicomponent 12 are the primary means for effecting the interfiber connection. To achieve this, it is generally desirable that the second component has a melting / softening temperature which is at least 10 ° C higher than the melting / softening temperature of the first component 12. The polymer or the polymer blends which are relatively crystalline in nature will have a specific melting temperature or a very narrow melting temperature range. Other polymers are more amorphous and therefore will melt or soften over a wider temperature range. For polymers which are relatively crystalline, the melting temperature can be determined using differential examination calorimetry (DSC) according to ASTM Test Method E-794-85. For polymers which are more amorphous, the softening temperature or the temperature range for the particular polymer, copolymer or mixture can be determined using Test Method ASTM (Vicat) D-1525 (1993). Therefore, by choosing the polymers to make the first and second components, the highest end of the softening melt temperature range of the first component 12 must be at least 10oc lower than the lower end of the temperature range. of softening melt for the second component 14. As a result of this, when the joining of the bicomponent fibers is carried out, most of the interfiber bonds will be through the first component and not the second component, as long as the conditions / bonding temperature do not fall within the melting temperature range of the second component. Examples of the polymers which are commonly used as the core or second component include, but are not limited to polyesters and polyolefins, such as polyethylene and polypropylene. Another factor for selecting the second component 14 is that it is sufficiently compatible with the first component from an adhesion point of view so that the two components do not unduly separate from each other once the fiber 10 has formed. This is especially true with respect to the side-by-side fiber configuration where there is little or no encapsulation of one component on the other as is the case with the concentric and eccentric sheath / core fiber configurations.

Typically, the material chosen to form the first component 12 will be more expensive than the second component 14. As a result of this, it is generally desirable to use as little of the first component when fiber is formed as possible to reduce costs. To further reduce costs it may be desirable to use other lower cost fibers within the woven non-fibrous fabric incorporating bicomponent fibers according to the present invention.

Accordingly, when the fibers are mixed, the fibers should be selected so that the first component of the bicomponent fiber according to the present invention will have the lowest melting / softening point of all the fiber polymers that are being used in the nonwoven.

As previously mentioned, the first component must be a material which is thermally unible so as to be capable of forming fibrous non-woven fabrics. The first component must be degradable in water as previously delineated. Many polymers are degradable in water essentially such as tap water which typically has a pH in the range of about 6.5 to about 8.5. Therefore, fibrous non-woven fabrics are made using the bicomponent fibers degradable in water according to the present invention, then these will be more feasibly suitable for uses where they are exposed to very little or no water. Then, after use, these can be placed in water so that the pods can degrade and the non-woven fabric can break and separate. In other applications, the fibrous non-woven fabrics using the water degradable bicomponent fibers according to the present invention can be exposed to sufficient quantities of aqueous liquids during use, so that the first component will begin to degrade and prematurely break. Absorbent personal care items such as diapers, incontinence garments, training underpants, and moisture cleansers are examples of such products which may be subject to this problem. To solve or reduce this problem, polymers can be selected for the first component which are sensitive or degradable as a result of a pH change, a change in dissolved ion concentration and / or a change in temperature in the aqueous environment.

As described in more detail below, certain first component polymers are degradable in water only when exposed to sufficient amounts of water within a certain pH range. Outside of this range, these will not degrade. It is therefore possible to choose a first pH-sensitive polymer component which will be non-degradable in a liquid or aqueous liquids in a pH range, for example a pH of 3 to 5, but which will become degradable in a range pH of the water of the normal tap. See, for example, U.S. Patent No. 5,102,668 issued to Eichel et al., Which is incorporated herein by reference in its entirety.

Another mechanism which can be used to trigger the degradability in water is the sensitivity to the ion. Certain polymers contain acid-based components (R-COO) which are held together by a hydrogen bond. In the dry state, these polymers remain solid. In an aqueous solution which has a relatively high cation concentration such as urine, the polymer will remain relatively intact. However, when the same polymer is subsequently exposed to larger amounts of water with a reduced ion content, such as that found in the toilet bowl, the cation concentration will decrease and the hydrogen bonding will begin to break apart. . When this happens, the polymer itself will begin to break in the water. See, for example, U.S. Patent No. 4,419,403 to Varona, which is incorporated herein by reference in its entirety.

Still other means for making a polymer degradable in water is through the use of a change in temperature. Certain polymers exhibit a cloud point. As a result of this, these polymers will precipitate out of the solution at a particular temperature-cloud point. These polymers can be used to form fibers which are insoluble in water above a certain temperature but which become soluble and therefore degradable in water at a lower temperature. As a result of this, it is possible to select or mix a polymer which will not degrade in the fluids of the body, such as urine at or near the body temperature (37 © c) but which will degrade when It is placed in water at temperatures at or below room temperature (23 ° C). An example of such a polymer is a polyvinyl methyl ether which has a cloud point of 34 cc. When this polymer is exposed to body fluids such as urine at 37oC, it will not degrade since this temperature is above the turbidity point (34oC). However, if the polymer is placed in water at room temperature (23oc), the polymer will return to the solution when it is already exposed to water at a temperature below its cloud point. Consequently, the polymer will begin to degrade.

The first component polymers can be classified according to the means by which they are found to be stable in specific fluid environments. These environmental conditions are: low volume water body fluids, regulated pH conditions (such as are found in wet-cleaner storage solutions or buffer systems). High cationic resistance solutions (for example, baby or adult urine and menstrual fluids), and variable temperature conditions (for example, body temperature against room temperature or water from the coldest key).

Referring to Table I, examples of the first component polymers that are stable in low water volume solution environments (eg, pantyliners, lightweight incontinence products and cleaners for baby or adult), can be polyamides NP2068 , NP2074 or NP2120 as supplied by HB Fuller Company of Vadnais Heights, Minnesota. Fuller materials are aliphatic polyamides which are completely soluble in cold water and are processed in fiber yarn very similar to low density polyethylene. Other polymers capable of degrading in aqueous mixtures or tap water are the polyvinyl alcohol graft copolymers supplied by Nippon Synthetic Chemical Co., Ltd. of Osaka, Japan, encoded Ecomaty AX2000, AX10000 and AX-300G. Nippon polymers are soluble in cold water but somewhat slower in their solubility rate than the more complete polymers. Still another first component polymer can be a polyether blockair, encoded Pebax MX1074, supplied by Atochem (USA) located in Philadelphia, Pennsylvania. The Pebax MX1074 polymer is composed of epsilon-caprolactam (Nylon 12) and tetramethylene glycol monomers. These monomers are polymerized to make a series of polyether block amide copolymers. The Pebax polymer is not soluble in water but is swellable in water, and therefore it can also be used in an environment of superior water volume as well. The Fuller polymers can be matched to a second component polymer (core) with a softening melt temperature of at least about 10 ° C higher, as would be the case with polypropylene. The Nippon or Atochem polymers can be matched with the second higher melt temperature range component polymer such as polypropylene or poly (butylene terephthalate).

TABLE I SHEATH POLYMERS FOR BICOMPONENT FIBERS Polymer Type Temperature Melt Flow * DSC Softening Polymer or Viscosity (Range) Matched Nucleus H. B. Fuller 410 Pa.s 142oC-158oC Polypropylene Code NP-2120 ®204oc H. B. Fuller 95 Pa.s 128oC-145oC Polypropylene Code NP-2068 @ 204oC H. B. Fuller 290 Pa.s 133 ° C-145oC Polypropylene Code NP-2074 ®204oc ATOCHEM MF - 1-3 158oC Polybutyl-PEBAX MX1074 terephthalate Nippon-Gohsei MFR = 100 180oC Polybutyl-ECOMATY AX10000 terephthalate Findley mix 200 Pa.s 117oC Polyethylene N-10, Ester ® 140 ° C acrylate / methacrylic or acrylic acid Findley mix 370 Pa.s 131oC Polyethylene H-10, Ester © 160OC acrylate / methacrylic or acrylic Mixture Findley 30 Pa.s X-10, ® 190 ° C acrylate / methacrylic or acrylic acid Eastman Code 300 Pa.s 120oC-130 ° C Polyethylene AQ38S © 200 ° C * ASTMD Test Method D-1238-906 (load from 2.16 kg to 190oc for the polyethylene) The first component polymers which are stable in a specific pH range, for example at a pH of 3-5, can be copolymers of methacrylic or acrylic acid / acrylate ester and mixtures encoded N-10, H-10 or X-10 as supplied by Findley Adhesives, Inc., of Milwaukee, Wisconsin. Findley materials are stable to the pH conditions of the body (or when cushioned against body fluids), but can break quickly in the toilet water during the draining process (excess water) creating both the pH towards the neutral. Findley polymers can be matched with a second higher temperature melt temperature component component such as polyethylene or polypropylene.

The first component polymers that are stable in high cation concentration solution environments (eg, baby or adult urine and menstrual fluids) can be sulfonated polyesters encoded AQ29, AQ38, or AQ55 as supplied by Eastman Chemical Company , of Kingsport, Tennessee. The Eastman AQ38 polymer is composed of 89 mole percent isophthalic acid, 11 mole percent sodium sulfoisophthalic acid, 78 mole percent diethylene glycol and 22 mole percent 1,4-cyclohexanedimethanol.

It has a nominal molecular weight of 14,000 Daltons, an acid number less than two, a hydroxyl number of less than 10, and a glass transition temperature of 38oC. Other examples may be mixtures of polyvinyl alcohol or copolymers of poly (vinyl alcohol) mixed with polyacrylic acid or. methacrylic, or polyvinylmethylether mixed with polyacrylic or methacrylic acid. Eastman polymers are stable in those of high cationic solution environments, but they will break down rapidly in the toilet water during the draining process (excess water) thus reducing the concentration of non-cation. The Eastman polymers can be matched with a non-second component polymer of higher melt temperature range such as polyethylene. The first component polymers that are stable to the temperature conditions of the body (this is at a temperature of 37 ° C) can be any polymer that exhibits a "cloud point" at or near the body temperature. The turbidity point or the solubility temperature n. Inverse is a useful property to "trigger" a change in the physical state such as solubility in water. For example, the polyvinyl methyl ether has a turbidity point temperature of 34 ° C above which it is no longer soluble in water, but at room temperature (almost 23 ° C) it is completely degradable in water. Mixtures of polyvinyl methyl ether can be considered in also. The polyvinyl methyl ether can be matched with the second polymer polymers of higher melting temperature range component such as polyethylene.

The methods for making bicomponent fibers are well known and do not need to be described in detail here. To form a bicomponent fiber, generally two polymers are extruded separately and fed into a polymer distribution system wherein the polymers are introduced into a segmented spinning organ plate. The polymers follow the separate paths to the fiber spinning organ and combine into a spinner organ orifice which comprises either two concentric circular holes thereby providing a sheath / core type fiber or a circular spinner organ orifice divided to a along a diameter in two parts to provide a type fiber side by side. The combined polymer filament is then cooled, solidified and pulled, generally by means of a mechanical roller system, such as an intermediate filament diameter and collected. Subsequently, the filament is "cold drawn" at a temperature below its softening temperature to the desired finished fiber diameter and is curled / textured and cut into a desirable fiber length. The bicomponent fibers can be cut into relatively short lengths such as short fibers which generally have stretches in the range of 25 to 51 millimeters (mm) and short fibers which are even shorter and generally have stretches of less than 18 millimeters . See, for example, U.S. Patent No. 4,789,592 issued to Taniguchi et al. And U.S. Patent No. 5,336,552 to Strack et al., Both of which are hereby incorporated by reference in their entirety.

The fibrous non-woven fabrics can be made entirely of fibers of the present invention or can be mixed with other fibers. The length of the fibers will depend on the particular end use. Where the fibers will degrade in the water, for example, in a toilet, it is advantageous that the fiber lengths remain at or below about 15 millimeters (mm).

The water degradable bicomponent fibers of the present invention can be used to form fibrous nonwoven fabrics for a number of uses. As a result of this, the examples listed herein should not be considered as a limitation as to the scope of the present invention.

Absorbent articles for personal care include such items as diapers, training pants, feminine hygiene products such as sanitary napkins, panty liners and plugs, garments and incontinence devices, bandages and the like . The most basic design of all those items typically includes a body-side liner, an outer shell and an absorbent core placed between the body-side liner and the outer shell. Generally the body side liner and the outer cover are sealed around their peripheries as to encapsulate the absorbent core and thus make it possible to trap and retain any fluids contained within the absorbent core. Depending on the design of the absorbent article for personal personal care, other components may be included. Therefore, the product may include such things as elastic side diapers, fluid containment flaps, fastening devices and other layers of fluid transfer or retention materials. Where appropriate, fibrous non-woven fabrics incorporate such water degradable bicomponent fibers that can be used to form all or a portion of the above components.

Other potential uses for fibers and non-woven fabrics according to the present invention include, but are not limited to, wet and dry cleansers, clothing articles and other compounds or non-wovens where a degradable characteristic may be advantageous. Water.

Having thus described the various parameters of the present invention, various samples of water-degradable bicomponent fibers and non-woven fabrics were made.

EXAMPLE I In Example I a degradable bicomponent fiber was made into sheath / core water using a core of high density polyethylene and a sulfonated polyester sheath in a weight ratio of 50/50. The core polymer was NCPE 1961 a high density polyethylene from Neste Oy, Espoo, Finland with a melting temperature range of 140-150oc. The sheath polymer was a sulfonated polyester AQ38S from the Eastman Chemical Company of Kingsport, Tennessee with a melting temperature range of 120-130 ° C. The fibers were produced using a bicomponent fiber line, at a fiber diameter Initially, 6 decitex (dtex) were then cold drawn at a pulling temperature of 50 to 60 cc to a final diameter of 4 decitex.The fibers were mechanically crimped in a filler box and cut to a length of 6 cm. A pure spinning of iso-propyl myristate was also used.

Once the fibers had formed, then they were placed by air at a 50/50 weight ratio based on the total weight of the fabric, the fibrous nonwoven fabric having a basis weight of 25 to 30 grams per square meter (gsm) in combination with one of three other fibers of 1.7 decitex by 6 mm. The three other fibers included a polyester fiber from Dupont Fiber Company of Wilmington, Delaware, a polyester fiber from EMS Grilon of Domat / Ems, Switzerland and a fiber ratio from Courtaulds, Ltd. of Coventry, England. All three fabrics were joined using a two step joining process. In the first step for water degradable bicomponent fiber fabric / mixed rayon, the fibers were bonded through air at a temperature of 132 ° C followed by a point bond in a pair of pattern bonding rolls with a binding area of about 15 percent at a temperature of 90 ° C. The polyester mixed water degradable fiber fabrics were bonded at the same temperatures but the bonding of the fabric containing the Dupont polyester fibers could not be perfect due to the excessive shrinkage of the polyester fibers. The fibers of the other two fabrics that were bonded, formed fiber-to-fiber bonds through the sulfonated polyester sheath component. When the fabrics were placed in water at room temperature and shaken, the fiber bonds degraded and the fabrics broke.

EXAMPLE II In Example II, a second degradable fiber was formed in sheath / core water using a core made of polybutylene terephthalate polymer Vestodur 1000 from Hulls, GmbH, a subsidiary of Veba AG of Duesseldorf, Germany. PBT polymer had a melting temperature of 250oc. The degradable pod in water was made of AX2000 poly (vinyl alcohol) from Nippon Synthetic Chemical Company, Ltd. of Osaka, Japan. This had a melting temperature of 225 ° C. As with the fibers of Example I, the proportion by weight of sheath polymer / core was 50/50. The fibers were initially pulled at 14 decitex and then pulled cold at 5 decitex at a temperature of 130oC. After forming, the fibers were mechanically crimped and cut to a length of 6 mm. The same spin finish of iso-propyl myristate was used on the fibers.

The water degradable sheath / core bicomponent fibers were again blended with the same polyester fibers E s Grilon and Courtauld rayon fibers used in Example I in a 50/50 weight percent polyester and fiber blend of bicomponent and rayon / bicomponent fibers. The two fabrics placed by air had base weights between 25 and 50 grams per square meter. The union of the two fabrics was not successful due to the limitations of the equipment. Despite this, the polyvinyl alcohol sheaths of the bicomponent fibers degraded and became viscous when placed in water.

Having thus described the invention in detail, it should be evident that various changes and modifications may be made to the present invention without departing from the spirit and scope of the following clauses.

Claims (15)

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

1. A multicomponent fiber comprising: a first component and at least a second component, said second component comprises a thermoplastic polymer, said first component forms an exposed surface on at least a part of said fiber, said first component comprises a heat-able polymer, said first component further comprises a water dispersible polymer which remains stable in the presence of high cationic solutions and is dispersed in low cationic solutions.

2. The multicomponent fiber as claimed in clause 1, characterized in that said fiber has a sheath / core configuration, said first component forms said sheath.

3. The multicomponent fiber as claimed in clause 1, characterized in that said fiber has a side-by-side configuration.

4. The multicomponent fiber as claimed in clause 1, characterized in that said second component is a thermoplastic fiber forming polymer.

5. The multicomponent fiber as claimed in clause 4, characterized in that said thermoplastic fiber forming polymer is a polyolefin.

6. The multicomponent fiber as claimed in clause 4, characterized in that said thermoplastic fiber forming polymer is a polyester.

7. A non-woven fabric comprising a plurality of fibers, at least a portion of said plurality of fibers comprises the multicomponent fibers as claimed in clause 1.

8. An absorbent article for personal care which includes a non-woven fabric as claimed in clause 7.

9. A cleaner that includes a non-woven fabric as claimed in clause 7.

10. A diaper that includes a non-woven fabric as claimed in clause 7.

11. A training pant that includes a non-woven fabric as claimed in clause 7.

12. An incontinence garment that includes a non-woven fabric as claimed in clause 7.

13. A sanitary napkin that includes a non-woven fabric as claimed in clause 7.

14. A pant liner that includes a non-woven fabric as claimed in clause 7.

15. A bandage that includes a non-woven fabric as claimed in clause 7. SUMMARY Multicomponent fibers are described herein wherein at least one component will allow the binding of the fibers to themselves and other types of fibers and wherein the same first component is also degradable in an aqueous medium. Such fibers can be used to form fibrous non-woven fabrics which can be used as a component in such end-use products such as health-care and medical articles, cleansers and absorbent articles for personal care.