Process for producing degradable fiber and films and articles made therefrom

Abstract

A process is disclosed for producing fibers and films from biodegradable polymers. The polymer composition used to form the fibers and films, for instance, can contain a polyhydroxyalkanoate polymer. In accordance with the present disclosure, during formation of the fiber and film, the fiber and film is fed into an accumulation zone that promotes crystallization of the biodegradable polymer for increasing strength and improving the processability of the article.

Description

[0001] PROCESS FOR PRODUCING DEGRADABLE FIBER AND FILMS AND ARTICLES MADE THEREFROM

[0002] CROSS-REFERENCE TO RELATED APPLICATION

[0003] The present application is related and has right of priority to U.S. Provisional Patent Application No. 63 / 688,942 filed on August 30, 2024, which is incorporated by reference in its entireties for all purposes.

[0004] BACKGROUND

[0005] Various attempts have been made to form fibers, nonwoven webs, and films from biodegradable polymers. Various problems have been encountered, however, in being able to form fibers and films from biodegradable polymers, such as polylactic acid polymers and polyhydroxyalkanoate polymers.

[0006] For example, many biodegradable polymers experience a very slow crystallization rate. The crystallization rate of these polymers, for instance, can be much slower than conventional fossil-based polymers, such as polypropylene. The slow crystallization rate can lead to the formation of articles with low strength and a “sticky’’ surface feature. In addition, articles, such as fibers and films, made from biodegradable polymers typically exhibit low elongations that are not acceptable in certain applications.

[0007] In view of the above problems, in the past, biodegradable polymers have been combined with other components, such as other polymers including plasticizers, in order to not only make it easier to process the polymers but also to produce articles with better mechanical properties. For instance, U.S. Patent No. 8,598,404, U.S. Patent No. 8,936,740, U.S. Patent No. 9,056,967, U.S. Patent No. 10,718,069, and U.S. Patent No. 11 ,236,443, which are all incorporated herein by reference, disclose combining a biodegradable polymer with other components in forming various articles including fibers and films.

[0008] Although the above polymer compositions and related processes for forming articles have made great advances in the art, further improvements are needed. In particular, enhancements are needed in developing techniques and processes for further improving not only the processability of biodegradable polymers but also improving the resulting mechanical properties of articles made from the polymers. For example, a need exists for fibers and films made from biodegradable polymers with improved mechanical properties, such as strength and / or elongation.

[0009] SUMMARY

[0010] In general, the present disclosure is directed to a process for producing articles, such as fibers and films, from a biodegradable polymer. The biodegradable polymer, for instance, may comprise a polyhydroxyalkanoate polymer. In accordance with the present disclosure, the biodegradable polymer composition is heated to a molten state and fed to a process in a manner that permits the polyhydroxyalkanoate to crystallize in a manner that produces articles with greater mechanical properties.

[0011] For example, in one embodiment, the present disclosure is directed to a process for forming a fiber or film. The process includes extruding a molten thermoplastic composition through a die to form a continuous fiber or film. The thermoplastic composition contains a polyhydroxyalkanoate. In accordance with the present disclosure, the continuous fiber or film is fed through an accumulation zone for a period of time that causes the polyhydroxyalkanoate polymer to at least partially crystallize. For instance, the continuous fiber or film can remain in the accumulation zone for an amount of time of from about 0.5 seconds to about 80 seconds, such as from about 1 second to about 30 seconds. After exiting the accumulation zone, the fiber or film can optionally be drawn. For instance, the fiber or film can be drawn so as to achieve a draw ratio of greater than about 10:1 , such as greater than about 50:1 , such as greater than about 100:1 , and less than about 7,500:1, such as less than about 5,000:1 . The drawn fiber or film can then optionally be wound into a roll for later processing. In one aspect, between the accumulation zone or the draw zone (when present) and the winding roll, the fiber or film is relaxed by greater than about 5%, such as greater than about 10%, such as greater than about 15% and less than about 30%, such as less than about 25%, such as less than about 20% in the machine or length direction (a reverse draw). The reverse draw can help to wind the material in a way that promotes easier unwinding later (e.g., reduces blocking, etc.).

[0012] In one embodiment, the process is used to produce fibers. For example, the die can be configured to form multiple filaments that are brought together and fed through the accumulation zone. The formed fibers, in one embodiment, can be cut so as to form staple fibers. The fibers can have a size of less than about 100 denier, such as less than about 50 denier, such as less than about 30 denier, such as less than about 25 denier, such as less than about 20 denier, such as less than about 15 denier, such as less than about 10 denier, such as less than about 8 denier, such as less than about 5 denier, such as less than about 3 denier, and greater than about 0.5 denier, such as greater than about 1 denier. When formed into staple fibers, the staple fibers can have an average length of greater than about 3 mm, such as greater than about 5 mm, such as greater than about 7 mm, and less than about 60 mm, such as less than about 40 mm, such as less than about 20 mm. The fibers can have a fiber tenacity of from about 0.2 gf to about 10 gf per denier, such as greater than about 1 gf per denier, such as greater than about 4 gf per denier.

[0013] When forming fibers, the fibers can be formed into a nonwoven web. In one aspect, the fibers can be used to form a carded web. In an alternative embodiment, the process can be used to form a continuous film. The film, for instance, can have a thickness of less than about 50 microns.

[0014] The accumulation zone contained in the process of the present disclosure can be any mechanism or technique for promoting crystallization of the polyhydroxyalkanoate polymer. In one aspect, the accumulation zone can comprise a plurality of opposing guide rolls. The fiber or film can extend back and forth between the guide rolls for promoting crystallization. In one aspect, the fiber or film is not substantially drawn within the accumulation zone. For instance, in the accumulation zone, the fiber or film can be stretched less than about 50%, such as less than about 20%, such as less than about 10%, such as less than about 5%, such as less than about 1%. After exiting the accumulation zone, the fiber or film can be drawn. In one embodiment, the fiber or film can also be annealed and / or subjected to a heat treatment while being drawn or after being drawn.

[0015] The polyhydroxyalkanoate polymer contained in the polymer composition can have a melting point of less than about 190°C, such as less than about 170°C, such as less than about 160°C, such as less than about 155°C, and greater than about 120°C, such as greater than about 130°C. The polyhydroxyalkanoate can display a melt flow rate of less than about 100 g / 10 min, such as less than about 60 g / 10 min, such as less than about 50 g / 10 min, and greater than about 5 g / 10 min, such as greater than about 15 g / 10 min, such as greater than about 20 g / 10 min, such as greater than about 25 g / 10 min, when tested according to ASTM Test D1238-E at a load of 2.16 kg and at a temperature of 190°C. The polyhydroxyalkanoate polymer can display a relative viscosity when tested according to ASTM Test D4603 (0.5% by weight in solvent) of from about 1 .5 to about 3.5, such as from about 2 to about 3.

[0016] The thermoplastic polymer composition can contain various other components in addition to the polyhydroxyalkanoate polymer. In one aspect, the polyhydroxyalkanoate polymer is present in the polymer composition in an amount greater than about 50% by weight, such as in an amount greater than about 60% by weight, such as in an amount greater than about 70% by weight, such as in an amount greater than about 80% by weight, such as in an amount greater than about 90% by weight. In one aspect, the polymer composition can contain a second polymer, such as a second biodegradable polymer. The second polymer, for instance, may comprise a polycaprolactone, a polyesteramide, a polylactic acid, a polyglycolic acid, a polyalkylene carbonate, a poly-3- hydroxyvalerate, a polybutylene succinate, a polybutylene succinate adipate, a polyethylene succinate, a polybutylene adipate terephthalate, a polyethylene adipate terephthalate, a polyethylene adipate isophthalate, a polybutylene adipate isophthalate, or mixtures thereof. In one particular embodiment, the polyhydroxyalkanoate polymer is combined with a polybutylene adipate terephthalate polymer. Alternatively, the polymer composition can contain fillers and / or plasticizers. Other features and aspects of the present disclosure are discussed in greater detail below.

[0017] BRIEF DESCRIPTION OF THE DRAWINGS

[0018] A full and enabling disclosure of the present disclosure is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which:

[0019] Figure 1 is one embodiment of a process for producing fibers or films in accordance with the present disclosure.

[0020] Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present invention.

[0021] DEFINITIONS

[0022] As used herein, the term “biodegradable" or “biodegradable polymer” generally refers to a material that degrades from the action of naturally occurring microorganisms, such as bacteria, fungi, and algae; environmental heat; moisture; or other environmental factors. The biodegradability of a material may be determined using ASTM Test Method 5338.92.

[0023] As used herein, the term “fibers” refer to elongated extrudates formed by passing a polymer through a forming orifice such as a die. Unless noted otherwise, the term “fibers” includes both discontinuous fibers having a definite length and substantially continuous filaments. Substantially filaments may, for instance, have a length much greater than their diameter, such as a length to diameter ratio (“aspect ratio”) greater than about 15,000 to 1 , and in some cases, greater than about 50,000 to 1.

[0024] As used herein, the term “monocomponent” refers to fibers formed from one polymer. Of course, this does not exclude fibers to which additives have been added for color, anti-static properties, lubrication, hydrophilicity, liquid repellency, etc.

[0025] As used herein, the term “multicomponent” refers to fibers formed from at least two polymers (e.g., bicomponent fibers) that are extruded from separate extruders. The polymers are arranged in substantially constantly positioned distinct zones across the cross-section of the fibers. The components may be arranged in any desired configuration, such as sheath-core, side-by-side, segmented pie, island-in-the-sea, and so forth. Various methods for forming multicomponent fibers are described in U.S. Pat. No. 4,789,592 to Taniguchi et al. and U.S. Pat. No. 5,336,552 to Strack et al., U.S. Pat. No. 5,108,820 to Kaneko, et al., U.S. Pat. No. 4,795,668 to Kruege, et al., U.S. Pat. No. 5,382,400 to Pike, et al., U.S. Pat. No. 5,336,552 to Strack, et al., and U.S. Pat. No. 6,200,669 to Marmon, et al., which are incorporated herein in their entirety by reference thereto for all purposes. Multicomponent fibers having various irregular shapes may also be formed, such as described in U.S. Pat. No. 5,277,976 to Hogle, et al., U.S. Pat. No. 5,162,074 to Hills, U.S. Pat. No. 5,466,410 to Hills, U.S. Pat. No. 5,069,970 to Largman, et al., and U.S. Pat. No. 5,057,368 to Largman, et al., which are incorporated herein in their entirety by reference thereto for all purposes.

[0026] As used herein, the term “nonwoven web” refers to a web having a structure of individual fibers that are randomly interlaid, not in an identifiable manner as in a knitted fabric. Nonwoven webs include, for example, meltblown webs, spunbond webs, carded webs, wet-laid webs, airlaid webs, coform webs, hydraulically entangled webs, etc. The basis weight of the nonwoven web may generally vary, but is typically from about 5 grams per square meter (“gsm”) to 200 gsm, in some embodiments from about 10 gsm to about 150 gsm, and in some embodiments, from about 15 gsm to about 100 gsm.

[0027] As used herein, the term “meltblown” web or layer generally refers to a nonwoven web that is formed by a process in which a molten thermoplastic material is extruded through a plurality of fine, usually circular, die capillaries as molten fibers into converging high velocity gas (e.g. , air) streams that attenuate the fibers of molten thermoplastic material to reduce their diameter, which may be to microfiber diameter. 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. Such a process is disclosed, for example, in U.S. Pat. No. 3,849,241 to Butin, et al.; U.S. Pat. No. 4,307,143 to Meitner, et al.; and U.S. Pat. No. 4,707,398 to Wisneski, et al., which are incorporated herein in their entirety by reference thereto for all purposes. Meltblown fibers may be substantially continuous or discontinuous, and are generally tacky when deposited onto a collecting surface.

[0028] As used herein, the term “spunbond” web or layer generally refers to a nonwoven web containing small diameter substantially continuous filaments. The filaments are formed by extruding a molten thermoplastic material from a plurality of fine, usually circular, capillaries of a spinnerette with the diameter of the extruded filaments then being rapidly reduced as by, for example, eductive drawing and / or other well-known spunbonding mechanisms. The production of spunbond webs is described and illustrated, for example, in U.S. Pat. No. 4,340,563 to Appel, et al., U.S. Pat. No. 3,692,618 to Dorschner, et al., U.S. Pat. No. 3,802,817 to Matsuki, et al., U.S. Pat. No. 3,338,992 to Kinney, U.S. Pat. No. 3,341 ,394 to Kinney, U.S. Pat. No. 3,502,763 to Hartman, U.S. Pat. No. 3,502,538 to Levy, U.S. Pat. No. 3,542,615 to Dobo, et al., and U.S. Pat. No. 5,382,400 to Pike, et al., which are incorporated herein in their entirety by reference thereto for all purposes. Spunbond filaments are generally not tacky when they are deposited onto a collecting surface. Spunbond filaments may sometimes have diameters less than about 40 micrometers, and are often between about 5 to about 20 micrometers.

[0029] The term “machine direction” or “MD” as used herein with respect to a fiber, a film, or a nonwoven web, means the direction parallel to the predominant direction of movement of the article through its manufacturing line and can also refer to the length direction.

[0030] The term “cross machine direction” or “CD” when used herein with respect to a fiber, a film, or a nonwoven web, means the direction perpendicular to the predominant direction of movement of the articles through its manufacturing line and can also be referred to as the width direction.

[0031] As used herein, an “absorbent article” refers to an article that is capable of absorbing water or other fluids. Examples of some absorbent articles include, but are not limited to, personal care absorbent articles, such as diapers, training pants, absorbent underpants, incontinence articles, feminine hygiene products (e.g., sanitary napkins), swimwear, baby wipes, mitt wipes, and the like; medical absorbent articles, such as garments, fenestration materials, underpads, bed pads, bandages, absorbent drapes, and medical wipes; food service wipers; clothing articles; pouches, and so forth.

[0032] As used herein, the term “carded web” refers to a web made from staple fibers that are sent through a combing or carding unit, which separates or breaks apart and aligns the stable fibers in the machine direction to form a generally machine direction-oriented fibrous nonwoven web. The fibers can be supplied to the process in bales and placed in an opener / blender or picker, which separates the fibers prior to the carding unit. Once formed, the web may be bonded by one or more known methods including by being thermally bonded or ultrasonically bonded.

[0033] DETAILED DESCRIPTION

[0034] It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only and is not intended as limiting the broader aspects of the present disclosure.

[0035] In general, the present disclosure is directed to a process for producing articles, such as fibers, films, and nonwoven webs from one or more biodegradable polymers. In one embodiment, the biodegradable polymer can be a polyhydroxyalkanoate (PHA) polymer. Polyhydroxyalkanoate polymers, for instance, have excellent end-of-life properties and are biodegradable, such as marine degradable. Unlike other biodegradable polymers such as regenerated cellulose, polyhydroxyalkanoate polymers can be processed using thermoplastic polymer extrusion equipment. Polyhydroxyalkanoate polymers, however, have a slow crystallization rate and tend to produce articles, such as fibers and films, that have lower tensile strength and can be characteristically sticky.

[0036] In accordance with the present disclosure, however, the polyhydroxyalkanoate polymer is melt processed in a manner that promotes crystallization without causing a decrease in mechanical properties. To the contrary, fibers and films made according to the present disclosure can have enhanced mechanical properties, including an enhanced tensile strength. Of particular advantage, the polyhydroxyalkanoate polymer can crystallize during the process without having to add additives or other components used in the past, such as nucleating agents and the like, which can not only frustrate the biodegradation properties of the polymer but can also have other adverse consequences on the resulting articles that are formed.

[0037] In accordance with the present disclosure, when producing articles, such as continuous fibers or films, the polyhydroxyalkanoate polymer is heated to form a molten composition that is then fed through a die. In the die, the polymer composition is shaped into an article, such as a film or fiber. Prior to drawing and cooling the formed article, the article is fed to an accumulation zone. The article is maintained in an accumulation zone for a time sufficient for the polyhydroxy alkanoate polymer to crystallize. In one aspect, the article is maintained in the accumulation zone without substantially drawing the article. The accumulation zone, for instance, can comprise one or more large rolls over which the article travels or can comprise a series of guide rolls in which the article passes through in a back and forth manner. In one aspect, for instance, the accumulation zone represents an increased path length that allows the polymer to crystallize while still continuously feeding the formed article into the process for producing the continuous fiber or film. After exiting the accumulation zone, in one embodiment, the article, such as the fiber or film, can optionally be drawn. It was discovered that allowing for crystallization of the polymer enables a higher draw allowing for the production of finer fibers or thinner films having greater strength properties.

[0038] Thermoplastic Composition

[0039] The thermoplastic polymer composition used to form articles in accordance with the present disclosure generally contains one or more biodegradable polymers. In one aspect, the biodegradable polymer comprises a polyhydroxyalkanoate polymer. Poly hydroxy alkanoate polymers are generally semi-crystalline, thermoplastic polyester polymers that can either be produced by synthetic methods or by a variety of microorganisms, such as bacteria or algae. The latter typically produce optically pure materials.

[0040] Some of the key characteristics of polyhydroxyalkanoate polymers is that the polymers are biodegradable meaning that they can be broken down by natural biological processes. Thus, the polymers are environmentally friendly and sustainable. In addition, polyhydroxyalkanoate polymers are biocompatible. In particular, polyhydroxyalkanoate polymers are compatible with living tissues making them suitable for medical applications and for producing absorbent articles and other products intended to contact a wearer or patient.

[0041] Polyhydroxyalkanoate polymers come in various different forms. For instance, there are short chain length polyhydroxyalkanoate polymers that are formed from monomers with three to five carbon atoms such as polyhydroxybutyrate. There are also medium chain length polyhydroxyalkanoate polymers formed from monomers with from about six to about 14 carbon atoms, such as polyhydroxyhexanoate. Polyhydroxyalkanoates include various different homopolymers and copolymers which can all be used in the process of the present disclosure. In addition, the polymer composition of the present disclosure used to produce various articles, such as fibers and films, can be produced from a single polyhydroxyalkanoate polymer or from a blend of polyhydroxyalkanoate polymers.

[0042] Various different polyhydroxyalkanoate homopolymers exist. The most common PHA homopolymers include poly(3-hydroxybutyrate) (PHB) (made up of 3-hydroxybutyrate monomers); poly(4-hydroxybutyrate) (P4HB) (composed of 4-hydroxybutyrate monomers); poly(3-hydroxyvalerate) (PHV) (composed of 3-hydroxyvalerate monomers); and poly(3-hydroxyhexanoate) (PHHx) (made of 3-hydroxyhexanoate monomers).

[0043] PHA copolymers can be made up of two or more different types of monomers. These copolymers can exhibit a range of properties by varying the ratio and type of monomers used. PHA copolymers include poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) (made of 3-hydroxybutyrate and 3-hydroxyvalerate monomers); poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) (composed of 3-hydroxybutyrate and 3-hydroxyhexanoate monomers); poly(3-hydroxybutyrate-co-4- hydroxybutyrate) (P3HB4HB) (contains 3-hydroxybutyrate and 4-hydroxybutyrate monomers); poly(3- hydroxybutyrate-co-3-hydroxydecanoate) (PHBHD) (composed of 3-hydroxybutyrate and 3- hydroxydecanoate monomers); poly(3-hydroxybutyrate-co-3-hydroxyoctanoate) (PHBO) (composed of 3-hydroxybutyrate and 3-hydroxyoctanoate monomers); poly(3-hydroxybutyrate-co-3- hydroxyheptanoate) (PHBH) (made of 3-hydroxybutyrate and 3-hydroxyheptanoate monomers); poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-4-hydroxybutyrate) (PHBV4HB) (comprised of 3- hydroxybutyrate, 3-hydroxyvalerate, and 4-hydroxybutyrate monomers); and poly(3-hydroxybutyrate- co-3-hydroxyhexanoate-co-3-hydroxydecanoate) (PHBHHxHD) (made of 3-hydroxybutyrate, 3- hydroxyhexanoate, and 3-hydroxydecanoate monomers).

[0044] In one aspect, the polyhydroxyalkanoate polymer or polymers contained in the polymer composition of the present disclosure have controlled crystalline or amorphous properties. For instance, the polyhydroxyalkanoate polymer for use in the present disclosure can be substantially amorphous (greater than 50% by weight), substantially crystalline (greater than 50% by weight), or can comprise a mixture of both.

[0045] Various techniques can be used to produce polyhydroxyalkanoate polymers that are substantially amorphous. Producing amorphous polyhydroxyalkanoate polymers can be done through controlling the process of producing the polymers. For instance, the amorphous portion of the polymer can be increased through using particular types of microorganisms to produce the polymer, through extraction, and through various post-processing techniques. For instance, producing polyhydroxyalkanoate polymers from microorganisms such as Cupriavidus nectaor or Ralstonia eutropha can be used to produce polymers with more amorphous content.

[0046] In addition, various techniques can be used during fermentation to increase the amorphous content of the polymer. For instance, the selected microorganisms can be grown in a nutrient-rich medium. In addition, the polymer can be grown while limiting specific nutrients in the environment including nitrogen, phosphorus, or oxygen. In addition, an excess of a carbon source can assist in increasing the amorphous content of the polymer.

[0047] When collecting and purifying the polymer, various other steps can be used to control the amorphous and / or crystalline content of the polymer. For instance, rapidly cooling the extracted polyhydroxyalkanoate polymer can avoid crystallization. In one aspect, for instance, the polymer can be quenched in liquid nitrogen or using a cooling bath.

[0048] Amorphous and crystalline polyhydroxy alkanoate polymers may be used to produce the polymer composition of the present disclosure. In one aspect, however, a polymer is used having a greater amorphous content which facilitates initial formation of the article. In accordance with the present disclosure, however, the article is maintained in an accumulation zone that allows the polymer to crystallize for increasing and improving the mechanical properties of the article.

[0049] The polyhydroxyalkanoate polymer of the present disclosure generally has a melting point of from about 120°C to about 190°C. In one aspect, the melting point can be relatively low. For instance, the melting point can be less than about 170°C, such as less than about 160°C, such as less than about 155°C, and greater than about 125°C, such as greater than about 130°C. The polyhydroxyalkanoate polymer can also have a relatively high melt flow rate. The melt flow rate, for instance, can be greater than about 5 g / 10 min, such as greater than about 15 g / 10 min, such as greater than about 20 g / 10 min, such as greater than about 25 g / 10 min. The melt flow rate is generally less than about 100 g / 10 min, such as less than about 60 g / 10 min, such as less than about 50 g / 10 min, such as less than about 40 g / 10 min, such as less than about 35 g / 10 min, such as less than about 30 g / 10 min.

[0050] When tested in a 0.5% by weight solvent, the polyhydroxyalkanoate polymer can display a relative viscosity of from about 1 .5 to about 3.5, such as from about 2 to about 3. Relative viscosity can be measured according to ASTM Test D4603.

[0051] The polymer composition can contain one or more polyhydroxyalkanoate polymers generally in an amount greater than about 40% by weight, such as in an amount greater than about 50% by weight, such as in an amount greater than about 60% by weight, such as in an amount greater than about 70% by weight, such as in an amount greater than about 80% by weight. In one aspect, the polymer composition may only contain polyhydroxyalkanoate polymers and they can be present in the composition in an amount greater than about 85% by weight, such as in an amount greater than about 90% by weight, such as in an amount greater than about 95% by weight.

[0052] The polymer composition can contain various other components and additives. For instance, the polymer composition can contain a thermoplastic starch as disclosed in U.S. Patent No. 11 ,236,443, which is incorporated herein by reference.

[0053] Other additives and components that can be added include plasticizers and other polymers. Plasticizers that may be used include polyethylene glycol or a polycaprolactone. When present, plasticizers are typically included in an amount less than about 10% by weight, such as from about 0.1% by weight to about 5% by weight.

[0054] Of course, other ingredients may be utilized for a variety of different reasons. For instance, materials that may be used include, without limitation, catalysts, pigments, antioxidants, stabilizers, surfactants, waxes, flow promoters, solid solvents, compatibilizers, nucleating agents (e.g., titanium dioxide, calcium carbonate, etc.), particulates, and other materials added to enhance the processability of the thermoplastic composition. When utilized, it is normally desired that the amounts of these additional ingredients are minimized to ensure optimum compatibility and cost-effectiveness. Thus, for example, it is normally desired that such ingredients constitute less than about 10 wt. %, in some embodiments less than about 8 wt. %, and in some embodiments, less than about 5 wt. % of the thermoplastic composition.

[0055] It should also be understood that other components may be included in the thermoplastic composition. One such component that may be employed is an additional biodegradable polyester, including aliphatic polyesters, such as polycaprolactone, polyesteramides, modified polyethylene terephthalate, polylactic acid (PLA) and its copolymers, terpolymers based on polylactic acid, polyglycolic acid, polyalkylene carbonates (e.g., polyethylene carbonate), a second PHA such as poly- 3-hydroxybutyrate (PHB), poly-3-hydroxyvalerate (PHV), poly-3-hydroxybutyrate-co-4-hydroybutyrate, poly-3-hydroxybutyrate-co-3-hydroxyvalerate copolymers (PHBV), poly-3-hydroxybutyrate-co-3- hydroxyhexanoate, poly-3-hydroxybutyrate-co-3-hydroxyoctanoate, poly-3-hydroxybutyrate-co-3- hydroxydecanoate, poly-3-hydroxybutyrate-co-3-hydroxyoctadecanoate, and succinate-based aliphatic polymers (e.g., polybutylene succinate, polybutylene succinate adipate, polyethylene succinate, etc.); aliphatic-aromatic copolyesters (e.g., polybutylene adipate terephthalate, polyethylene adipate terephthalate, polyethylene adipate isophthalate, polybutylene adipate isophthalate, etc.), and so forth.

[0056] In one particular embodiment, a polyhydroxyalkanoate polymer is combined with a polybutylene adipate terephthalate polymer in producing articles in accordance with the present disclosure. When another or second biodegradable polymer is present in the polymer composition in addition to a polyhydroxyalkanoate polymer, the second biodegradable polymer can be present generally in an amount less than about 40% by weight, such as in an amount less than about 30% by weight, such as in an amount less than about 20% by weight, such as in an amount less than about 10% by weight, and in an amount greater than about 1 % by weight, such as in an amount greater than about 3% by weight, such as in an amount greater than about 5% by weight, such as in an amount greater than about 8% by weight, such as in an amount greater than about 10% by weight, such as in an amount greater than about 15% by weight.

[0057] Another component that can be present in the polymer composition is a filler. Fillers are particulates or other forms of material that may be added to the polymer composition that will not chemically interfere with the polymer and which may be uniformly dispersed throughout the polymer matrix. The filler can be used to enhance one or more properties. For instance, fillers can be used to increase the porosity of the film, change the color of the extruded article, change the opacity of the extruded article, or can influence one or more other physical properties. Suitable fillers that can be added to the polymer composition include calcium carbonate, magnesium oxide, a clay such as kaolin clay, mica, or the like. In one embodiment, the filler can have an average particle size of less than about 20 microns, such as less than about 15 microns, such as less than about 10 microns, such as less than about 8 microns, such as less than about 5 microns, such as less than about 2 microns, such as less than about 1 micron, and generally greater than about 0.01 microns. When present, a filler can be contained in the polymer composition in an amount greater than about 1% by weight, such as in an amount greater than about 2% by weight, such as in an amount greater than about 5% by weight, such as in an amount greater than about 8% by weight, such as in an amount greater than about 10% by weight, such as in an amount greater than about 15% by weight, and in an amount less than about 30% by weight, such as in an amount less than about 25% by weight, such as in an amount less than about 20% by weight, such as in an amount less than about 18% by weight, such as in an amount less than about 15% by weight.

[0058] Optionally, the polymer composition can contain a nucleating agent. The nucleating agent can comprise a compound having a melting point higher than the polyhydroxyalkanoate polymer. Examples of nucleating agents include inorganic substances such as boron nitride, titanium oxide, talc, layered silicate, calcium carbonate, and the like. Sugar alcohol compounds, polyvinyl alcohol, chitin, polyethylene oxide, and the like can also be used as nucleating agents. In still another embodiment, the nucleating agent can comprise a sorbitol or sorbitol-based derivative. Nucleating agents are generally present in minor amounts, such as in amounts less than about 3% by weight, such as in an amount less than about 2% by weight, such as in an amount less than about 1% by weight, and in an amount greater than about 0.1% by weight.

[0059] Fiber or Film Formation

[0060] As described above, fibers and films can be made according to the present disclosure. The films can comprise blown films or cast films. In particular, any suitable process can be used to produce the films as long as the process can accommodate an accumulation zone as described below for crystallizing the polyhydroxyalkanoate polymer.

[0061] The film, for instance, can be formed having a thickness of up to about 50 microns. The film, for instance, can have a basis weight, in one aspect, of from about 50 gsm to about 70 gsm, such as from about 25 gsm to about 40 gsm. The film can comprise a single layer film or can comprise a coextruded film.

[0062] Fibers formed from the reacted thermoplastic composition may generally have any desired configuration, including monocomponent and multicomponent (e.g., sheath-core configuration, side-by- side configuration, segmented pie configuration, island-in-the-sea configuration, and so forth). In some embodiments, the fibers may contain one or more additional polymers as a component (e.g., bicomponent) or constituent (e.g., biconstituent) to further enhance strength and other mechanical properties. For instance, the thermoplastic composition may form a sheath component of a sheath / core bicomponent fiber, while an additional polymer may form the core component, or vice versa. The additional polymer may be a thermoplastic polymer that is not generally considered biodegradable, such as polyolefins, e.g., polyethylene, polypropylene, polybutylene, and so forth; polyesters, e.g., polyethylene terephthalate, and so forth; polyvinyl acetate; polyvinyl chloride acetate; polyvinyl butyral; acrylic resins, e.g., polyacrylate, polymethylacrylate, polymethylmethacrylate, and so forth; polyamides, e.g., nylon; polyvinyl chloride; polyvinylidene chloride; polystyrene; polyvinyl alcohol; and polyurethanes. More desirably, however, the additional polymer is biodegradable, such as aliphatic polyesters, such as polyesteramides, modified polyethylene terephthalate, polyglycolic acid, polyalkylene carbonates (such as polyethylene carbonate), other polyhydroxyalkanoates (PHA), polyhydroxybutyrates (PHB), polyhydroxyvalerates (PHV), polyhydroxybutyrate-hydroxyvalerate copolymers (PHBV), and polycaprolactone, and succinate-based aliphatic polymers (e.g., polybutylene succinate, polybutylene succinate adipate, and polyethylene succinate); aromatic polyesters; or other aliphatic-aromatic copolyesters.

[0063] Any of a variety of processes may be used to form fibers in accordance with the present disclosure as long as the process can include an accumulation zone for crystallizing the polyhydroxyalkanoate polymer. In one aspect, the polymer composition containing the polyhydroxyalkanoate polymer may be extruded through a spinneret, optionally quenched, fed through an accumulation zone and then fed into a draw zone for drawing the fiber. In one aspect, multiple filaments can be formed, combined together, and then wound onto a spool. Optionally, the fibers can be cut to form staple fibers having an average fiber length in the range of from about 3 mm to about 80 mm. For instance, the staple fibers can have an average length of greater than about 4 mm, such as greater than about 5 mm, and less than about 65 mm, such as less than about 60 mm, such as less than about 50 mm, such as less than about 40 mm, such as less than about 30 mm, such as less than about 25 mm, such as less than about 20 mm, such as less than about 15 mm, such as less than about 12 mm, such as less than about 10 mm, such as less than about 8 mm. The staple fibers may then be incorporated into a nonwoven web such as a bonded carded web.

[0064] In one embodiment, in order to form fibers or films in accordance with the present disclosure, a polymer composition containing a polyhydroxyalkanoate polymer can be formulated and optionally compounded with various other components including a second biodegradable polymer and / or a filler. The polymer composition can be fed to an extruder from a hopper. The polymer composition may be provided to the hopper using any conventional equipment or technique. The polymer composition can be in the form of pellets, flakes, or a powder. The polymer composition is then fed to a die and extruded into a particular shape.

[0065] For instance, for purposes of illustration, FIG. 1 illustrates one embodiment of forming fibers in accordance with the present disclosure. As shown, the heated and molten polymer composition can be fed to a die or spinneret 18. For instance, the spinneret 18 may include a housing containing a spin pack having a plurality of plates stacked one on top of each other and having a pattern of openings arranged to create flow paths for directing the polymer composition. The spinneret 18 can also have openings arranged in one or more rows. The openings form a downwardly extruding curtain of filaments 20.

[0066] Not shown in FIG. 1 , the process may also employ a quench blower positioned adjacent the curtain of filaments 20 extending from the spinneret 18. Air from the quench air blower can quench the fibers extending from the spinneret 18. The quench air may be directed from one side of the fiber curtain or from both sides.

[0067] Quenching the filaments 20, however, is optional. For instance, in some embodiments, the process may not include a quenching step. When a quenching step is employed, the quench is conducted in a way that controls the temperature of the filaments 20 in a manner that can further promote crystallization downstream.

[0068] As shown in FIG. 1 , in accordance with the present disclosure, the formed filaments 20 are brought together and fed through an accumulation zone 22. The accumulation zone 22 comprises any suitable machinery or equipment that can increase the travel path of the fibers 20 for allowing the fibers 20 to crystallize. In the embodiment illustrated in FIG. 1 , the process includes a first column of guide rolls 24 and a second column of guide rolls 26. As shown, the fibers 20 pass back and forth between the first column of guide rolls 24 and the second column of guide rolls 26. In this manner, the fibers 20 remain in the accumulation zone 22 for a period of time sufficient for the polyhydroxyalkanoate polymer to at least partially crystallize prior to being fed to a draw zone 30.

[0069] In the embodiment illustrated in FIG. 1 , the accumulation zone 22 includes a first set of guide rolls 24 spaced from a second set of guide rolls 26 that creates a significant path length for the fibers 20. In another embodiment, large diameter rolls can be placed in the process and the fibers 20 can travel over the surface of the rolls. For instance, traveling over the surface of the large diameter rolls creates a long travel path for the fibers 20 prior to entering the draw zone 30.

[0070] The amount of time the fibers 20 remain in the accumulation zone 22 can depend upon various factors, such as the type of polyhydroxyalkanoate polymers contained in the polymer composition. As described above, the fibers 20 remain in the accumulation zone 22 in an amount of time sufficient for the polyhydroxyalkanoate polymer to at least partially crystallize. For instance, the polyhydroxyalkanoate polymer can remain in the accumulation zone 22 for a period of time sufficient for the polyhydroxyalkanoate polymer to crystallize at least about 50%, such as at least about 60%, such as at least about 70%, such as at least about 80%.

[0071] The amount of time that the fibers 20 are in the accumulation zone can be relatively short while producing significant improvements in the product. The amount of time the fibers 20 are in the accumulation zone can depend on many factors including the amorphous nature of the polymer, the size of the fibers, the temperature of the polymer, and the like. In one aspect, the fibers 20 can remain in the accumulation zone 22 for a dwell time of at least about 0.5 second, such as at least about 1 second, such as at least about 2 seconds, such as at least about 3 seconds, such as at least about 4 seconds, such as at least about 5 seconds, such as at least about 6 seconds, such as at least about 7 seconds, such as at least about 8 seconds, such as at least about 9 seconds, such as at least about 10 seconds, and in an amount of time of less than about 80 seconds, such as less than about 60 seconds, such as less than about 40 seconds, such as less than about 30 seconds, such as less than about 20 seconds, such as less than about 15 seconds, such as less than about 12 seconds. While in the accumulation zone 22, the fibers 20 can remain at a temperature near the softening point of the polymer composition.

[0072] Although the fibers can optionally be drawn within the accumulation zone 22, in one embodiment, the accumulation zone 22 does not substantially draw the fibers 20. For instance, the fibers 20 can be drawn in an amount less than about 50%, such as less than about 40%, such as less than about 30%, such as less than about 20%, such as less than about 10%, such as less than about 5%, such as less than about 2% (percent increase in the length or machine direction).

[0073] As shown in FIG. 1 , from the accumulation zone 22, the fibers 20 can optionally be fed to a draw zone 30 for drawing the fibers. From the draw zone 30, the fibers 20 can be wound onto a roll 40. Once wound on the roll 40, the fibers can be fed to another process for producing various different articles. In one embodiment, for instance, the fibers can be cut into staple fibers and then fed to a process for producing nonwoven webs.

[0074] In the draw zone 30, the fibers are stretched and elongated in the machine direction by being fed around a number of draw rolls 32. In order to draw the fibers 20, for instance, the winding roll 40 can wind at a greater speed than the speed at which the fibers 20 are fed to the draw zone 30. For instance, the speed of the draw rolls 32 can be controlled in order to control the amount the fibers are drawn.

[0075] In the embodiment illustrated in FIG. 1 , the fibers 20 are drawn using the draw rolls 32. Alternatively, various other fiber drawing units or aspirators can be used. In an alternative embodiment, for instance, the fiber draw zone 30 can include a fiber draw device that includes an elongated passage through which the fibers are drawn by aspirating air entering from the sides of the passage and flowing downwardly through the passage. A heater or blower can supply the aspirating air to the fiber draw device.

[0076] It was discovered in accordance with the present disclosure that the accumulation zone 22 can greatly increase the strength of fibers or films made according to the process of the present disclosure. Due to the increase in strength, higher draw ratios may be employed. The draw ratio, for instance, is the ratio of the linear speed of the fibers after drawing divided by the linear speed of the fibers entering the draw zone 30.

[0077] The amount that articles are drawn in accordance with the present disclosure can vary depending upon the particular application and the desired result. For instance, the amount the article is drawn within the draw zone 30 can depend on whether fibers or films are being formed and the polymer composition being used. The draw ratio, for instance, can be from about 2:1 to about 7,500:1 . In certain applications, for instance, the draw ratio can be from about 3:1 to about 20:1 . In other embodiments, however, higher draw ratios can be used. For instance, the draw ratio can be greater than about 10:1 , such as greater than about 30:1 , such as greater than about 50:1 , such as greater than about 70:1 , such as greater than about 100:1 , and less than about 5,000:1 , such as less than about 3,000:1 , such as less than about 2,000:1 , such as less than about 1 ,000:1 , such as less than about 500:1 , such as less than about 300:1 , such as less than about 200:1.

[0078] When forming fibers, the fibers can be drawn in an amount sufficient to achieve a desired fiber size. For instance, the fibers produced according to the process as shown in FIG. 1 can have a size of less than about 100 denier, such as less than about 50 denier, such as less than about 30 denier, such as less than about 25 denier, such as less than about 20 denier, such as less than about 15 denier, such as less than about 10 denier, such as less than about 8 denier, such as less than about 5 denier, such as less than about 3 denier, such as less than about 2 denier, such as even less than about 1 denier. The size of the fibers can be greater than about 0.5 denier, such as greater than about 1 denier, such as greater than about 3 denier, such as greater than about 5 denier, such as greater than about 10 denier.

[0079] In one aspect, between the accumulation zone 22 or the draw zone 30 (when present) and the winding roll 40, the fiber or film can be relaxed by greater than about 5%, such as greater than about 10%, such as greater than about 15% and less than about 30%, such as less than about 25%, such as less than about 20% in the machine or length direction (a reverse draw). This can be accomplished by winding the fibers at a reduced speed in relation to the speed of the fibers moving through the process. The reverse draw can help to wind the material in a way that promotes easier unwinding later (e.g., reduces blocking, etc.).

[0080] The process as shown in FIG. 1 is provided for exemplary purposes only and it should be understood that various other process steps can be incorporated into the method of making fibers and films. In one embodiment, for instance, the process can include a heat treating or annealing zone prior to winding the fiber or film onto the roll 40.

[0081] Fibers and films made according to the present disclosure have been found to have excellent strength properties. In addition, the polymer composition can contain primarily polyhydroxyalkanoate polymers without producing articles having a sticky surface characteristic.

[0082] One parameter that is indicative of fiber strength is tenacity. Tenacity indicates the tensile strength of a fiber expressed as force per unit linear density. Fibers of the present disclosure, for instance, can display a tenacity of greater than about 0.2 gf, such as greater than about 0.4 gf, such as greater than about 0.6 gf, such as greater than about 0.8 gf, such as greater than about 1 gf, such as greater than about 1 .2 gf, such as greater than about 1 .5 gf, such as greater than about 2 gf, such as greater than about 2.5 gf, such as greater than about 3 gf, and less than about 20 gf, such as less than about 15 gf, such as less than about 10 gf.

[0083] When the process of the present disclosure is used to form fibers, the fibers can then be used to produce all different types of nonwoven webs. The webs, for instance, can be carded webs including bonded carded webs, can be incorporated into wet-laid webs, air-laid webs, coform webs, hydraulically entangled webs, and the like. It is also believed that the process of the present disclosure can be used to form spunbond webs and meltblown webs by incorporating an accumulation zone into the process prior to the fibers being deposited onto a foraminous surface. Nonwoven webs made according to the present disclosure can be bonded using any suitable technique such as using an adhesive or through thermal bonding, through-air bonding, calender bonding, ultrasonic bonding, and the like. In one aspect, the nonwoven web can be embossed with a pattern by passing the nonwoven web between a heated smooth anvil roll and a heated pattern roll. Fibers and films made according to the present disclosure can be used to produce all different types of end use products. The end use product, for instance, can comprise an absorbent article. The fibers, for instance, can be used to produce nonwoven webs for incorporation into the articles. The films, on the other hand, can also be used to form a layer within the articles.

[0084] These and other modifications and variations to the present invention may be practiced by those of ordinary skill in the art, without departing from the spirit and scope of the present invention, which is more particularly set forth in the appended claims. In addition, it should be understood that aspects of the various embodiments may be interchanged both in whole or in part. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention so further described in such appended claims.

Claims

What Is Claimed:1 . A process for forming fibers or a film comprising: extruding a molten thermoplastic composition through a die to form a continuous fiber or film, the thermoplastic composition comprising a polyhydroxyalkanoate; feeding the continuous fiber or film through an accumulation zone for a period of time that causes the polyhydroxyalkanoate to at least partially crystallize; and thereafter drawing the fiber or film.

2. A process as defined in claim 1 , wherein the continuous fiber or film remains in the accumulation zone for a period of time of from about 0.5 seconds to about 80 seconds, such as from about 2 seconds to about 30 seconds.

3. A process as defined in claim 1 , wherein the fiber or film is not substantially drawn in the accumulation zone.

4. A process as defined in claim 1 , wherein the drawn fiber or film is wound into a roll at a reverse draw.

5. A process as defined in claim 1 , wherein the process is used to produce the fiber and wherein the fiber is periodically cut to produce staple fibers.

6. A process as defined in claim 1 , wherein the molten thermoplastic composition is extruded to form multiple filaments that are then brought together and fed to the accumulation zone.

7. A process as defined in claim 1 , wherein the thermoplastic composition contains a second polymer, the second polymer comprising a polycaprolactone, a polyesteramide, a polylactic acid, a polyglycolic acid, a polyalkylene carbonate, a poly-3-hydroxyvalerate, a polybutylene succinate, a polybutylene succinate adipate, a polyethylene succinate, a polybutylene adipate terephthalate, a polyethylene adipate terephthalate, a polyethylene adipate isophthalate, a polybutylene adipate isophthalate, or mixtures thereof.

8. A process as defined in claim 1 , wherein the polyhydroxyalkanoate displays a melting point of less than about 190°C, such as less than about 170°C, such as less than about 160°C, such as less than about 155°C, and greater than about 120°C, such as greater than about 130°C.

9. A process as defined in claim 1 , wherein the polyhydroxyalkanoate displays a melt flow rate of less than about 100 g / 10 min, such as less than about 50 g / 10 min, and greater than about 5 g / 10 min, such as greater than about 15 g / 10 min, when tested according to ASTM Test D1238-E at a load of 2.16 kg and at a temperature of 190°C.

10. A process as defined in claim 1 , wherein the polyhydroxyalkanoate displays a relative viscosity of from about 1 .5 to about 3.5, such as from about 2 to about 3, when tested according to ASTM Test D4603 in a 0.5% by weight solution.

11. A process as defined in claim 1 , wherein the process is used to produce a fiber and wherein the fiber has a tenacity of from about 0.2 gf per denier to about 10 gf per denier.

12. A process as defined in claim 1 , wherein the process is used to produce a fiber, the fiber having a size of less than about 100 denier, such as less than about 50 denier, such as less than about 30 denier, such as less than about 25 denier, such as less than about 20 denier, such as less than about 15 denier, such as less than about 10 denier, such as less than about 8 denier, such as less than about 5 denier, such as less than about 3 denier, and greater than about 0.5 denier, such as greater than about 1 denier.

13. A process as defined in claim 5, wherein the staple fibers have an average fiber length of greater than about 3 mm, such as greater than about 5 mm, such as greater than about 7 mm, and less than about 60 mm, such as less than about 40 mm, such as less than about 20 mm.

14. A process as defined in claim 1 , wherein the thermoplastic composition further contains polybutylene adipate terephthalate.

15. A process as defined in claim 1 , wherein the fiber or film is drawn so as to achieve a draw ratio of greater than about 4:1 , such as greater than about 50:1 , such as greater than about 100:1 , and less than about 7,500:1 , such as less than about 5,000:1.

16. A process as defined in claim 1 , wherein the accumulation zone comprises a plurality of opposing guide rolls, and wherein the fiber or film extends back and forth through the guide rolls.

17. A process as defined in claim 1 , further comprising the step of annealing or heat treating the fiber or film during or after being drawn.

18. A process as defined in claim 1 , wherein the fiber or film comprises the film.

19. A process as defined in claim 18, wherein the film has a thickness of less than about 50 microns.

20. A process as defined in claim 5, further comprising the step of forming a nonwoven web from the fibers.21 . A process as defined in claim 20, wherein the nonwoven web comprises a carded web.

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