Biodegradable polymer blends

Abstract

A polymer composition containing at least one biodegradable polymer in combination with a small amount of a non-biodegradable polymer for providing strength and improving processability is disclosed. At least one degradation aid is included in the polymer composition for accelerating the rate of degradation of the non-biodegradable polymer. The polymer composition is particularly suitable for producing fibers and films.

Description

Background Art

[0001] The attempt of forming nonwoven web by biodegradable polymer has been carried out many times.Although the fiber prepared by biodegradable polymer is known, some problems have been encountered when using such fiber.For example, polylactic acid (" PLA ") is one of the most common biodegradable and sustainable (renewable) polymers for forming nonwoven web.Unfortunately, due to the high glass transition temperature and slow crystallization rate of polylactic acid, PLA nonwoven web has low bonding flexibility and high roughness usually.Then, the PLA nonwoven web of thermal bonding usually shows low elongation, which is unacceptable in some applications (such as in absorbent articles).Equally, although polylactic acid can withstand high draw ratio, it needs high level of stretching energy to realize the crystallization required for overcoming thermal shrinkage.

[0002] In addition to PLA, polymer fibers and other components are also formed from polyhydroxyalkanoate ("PHA") polymers. However, PHA polymers have many of the same disadvantages as PLA. In addition, PHA molded articles often lack the strength for many processes and end uses.

[0003] To improve strength and processability, biodegradable polymers have been combined with other polymers, such as polyolefins. However, the introduction of polyolefin polymers into polymer blends can adversely affect the biodegradability of the resulting product. For example, biodegradable polymers can rapidly decompose after use, potentially leaving behind microplastics formed from the polyolefin.

[0004] In view of the foregoing, there is a need for polymer blends containing biodegradable polymers with enhanced biodegradation rates. There is also a need for polymer blends that are well suited for the production of fibers and films, which are biodegradable and have good mechanical strength and processing properties. Summary of the Invention

[0005] In general, the present disclosure relates to polymer blends containing at least one biodegradable polymer, such as a biodegradable polyester polymer, in combination with a small amount of a non-biodegradable polymer, such as a polyester polymer or a polyolefin polymer, to provide enhanced strength or improved processability. In one aspect, the biodegradable polymer forms a polymer matrix, and the non-biodegradable polymer forms discrete domains dispersed within a continuous phase of the polymer matrix. According to the present disclosure, the polymer blend also contains an additive that promotes degradation of the non-biodegradable polymer.

[0006] For example, in one embodiment, the present disclosure relates to a polymer composition containing a biodegradable polyester polymer, which is present in the polymer composition in an amount greater than about 40% by weight, such as greater than about 50% by weight, such as greater than about 60% by weight, such as greater than about 70% by weight. The polymer composition also contains a polymer strength enhancer. The polymer strength enhancer can include polyolefins, polyalkylene terephthalates, or mixtures thereof. The polymer strength enhancer can be present in a relatively small amount. For example, the polymer strength enhancer can be present in the polymer composition in an amount less than about 25% by weight, such as less than about 15% by weight, such as less than about 10% by weight, such as less than about 8% by weight, such as less than about 5% by weight. One or more polymer strength enhancers are typically present in the polymer composition in an amount greater than about 0.25% by weight, such as greater than about 0.5% by weight. The polymer composition of the present disclosure also contains at least one prodegradant. At least one prodegradant accelerates the degradation rate of the polymer strength enhancer.

[0007] Various prodegradants can be introduced into the polymer composition. In one aspect, at least one prodegradant comprises a transition metal compound. The transition metal compound can comprise an iron salt, a manganese salt or a copper salt, such as a salt of a carboxylic acid. In a specific embodiment, the transition metal compound comprises ferric stearate, manganese stearate, copper stearate or a mixture thereof. One or more transition metal compounds can be present in the polymer composition typically in an amount of about 0.08 wt % to about 0.5 wt %.

[0008] The prodegradant may also include an unsaturated carboxylic acid having a carbon chain length of about 12 to about 26 carbon atoms, or may include an ester, anhydride, or amide of the carboxylic acid. The unsaturated carboxylic acid or its ester, anhydride, or amide may be present in the polymer composition in an amount of about 0.01% to about 0.2% by weight, and may be present alone or in combination with one or more transition metal compounds.

[0009] Other prodegradants that may be present in the polymer composition include sugars (such as starch), calcium oxide, calcium carbonate, or mixtures thereof. Still other prodegradants may include furanone compounds, glutaric acid, hexadecenoic acid compounds, or mixtures thereof.

[0010] In one aspect, the strength enhancer comprises a polyolefin. The polyolefin can be a propylene homopolymer, a propylene / alpha olefin copolymer, or a combination thereof. The polyolefin can also be an ethylene homopolymer, an ethylene copolymer, an ethylene / alpha olefin copolymer, or a combination thereof. In yet another aspect, the polymer strength enhancer can comprise a polyalkylene terephthalate. The polyalkylene terephthalate can comprise polyethylene terephthalate.

[0011] A variety of different biodegradable polyester polymers can be introduced into the polymer composition. In one embodiment, the biodegradable polyester polymer comprises polyhydroxyalkanoate. For example, in one aspect, the biodegradable polymer can comprise polyhydroxybutyrate.

[0012] In an alternative embodiment, the biodegradable polymer may include polylactic acid. For example, polylactic acid may be present in combination with polyhydroxyalkanoate.

[0013] The polymer composition may also contain various other additives. For example, in one embodiment, the polymer composition may also contain fillers. For example, the filler may include clay particles, such as diatomaceous earth. The filler particles may be present in the polymer composition in an amount of less than about 5% by weight, such as less than about 4% by weight, such as less than about 3% by weight.

[0014] The present disclosure also relates to fibers formed from polymer compositions. The fibers can be manufactured in any suitable manner and can include continuous fibers or discontinuous fibers (including staple fibers). In one aspect, the fibers can include meltblown fibers or spunbond fibers. The fibers can be single-component fibers manufactured entirely from a polymer composition, or can include multicomponent fibers, such as bicomponent fibers. For example, in one aspect, a bicomponent fiber can include a sheath polymer surrounding a core polymer. The core polymer can be manufactured from a polymer composition of the present disclosure. In another aspect, the sheath polymer can be manufactured entirely from one or more biodegradable polymers. For example, the sheath polymer can be manufactured from polyhydroxyalkanoate, polylactic acid, or a mixture thereof.

[0015] In yet another aspect, the present disclosure relates to a nonwoven web comprising a plurality of fibers formed according to the present disclosure. For example, the nonwoven web can be a spunbond web or a meltblown web.

[0016] Other features and aspects of the disclosure are discussed in greater detail below. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The full and enabling disclosure of the present disclosure is more particularly set forth in the remainder of the specification and with reference to the accompanying drawings, in which:

[0018] Figure 1 is a schematic diagram of a method that can be used in accordance with one embodiment of the present disclosure to form fibers; and

[0019] Figure 2 is one embodiment of a fiber that can be made according to the present disclosure.

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

[0021] definition

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

[0023] As used herein, the term "fiber" refers to an elongated extrudate formed by passing a polymer through a forming orifice (such as a die). Unless otherwise indicated, the term "fiber" includes both discontinuous fibers having a certain length and substantially continuous filaments. Substantially continuous filaments can, for example, 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 are added to obtain color, antistatic properties, lubricity, hydrophilicity, liquid repellency, etc.

[0025] As used herein, the term "multicomponent" refers to a fiber (e.g., a bicomponent fiber) formed from at least two polymers extruded from a separate extruder. The polymers are arranged in substantially constant, different zones throughout the cross section of the fiber. The components can be arranged into any desired configuration, such as a skin-core configuration, a side-by-side configuration, a segmented pie configuration, an island-in-the-sea configuration, etc. Various methods for forming multicomponent fibers are described in U.S. Patents 4,789,592 to Taniguchi et al., 5,336,552 to Strack et al., 5,108,820 to Kaneko et al., 4,795,668 to Kruege et al., 5,382,400 to Pike et al., 5,336,552 to Strack et al., and 6,200,669 to Marmon et al., which are incorporated herein by reference in their entirety for all purposes. Multicomponent fibers having various irregular shapes can also be formed, such as described in U.S. Patents 5,277,976 to Hogle et al., 5,162,074 to Hills, 5,466,410 to Hills, 5,069,970 to Largman et al., and 5,057,368 to Largman et al., the entireties of which are incorporated herein by reference for all purposes.

[0026] As used herein, the term "nonwoven web" refers to a web having a structure of individual fibers that are randomly but not sandwiched in an identifiable manner (as in a knitted fabric). Nonwoven webs include, for example, meltblown webs, spunbond webs, carded webs, wet-laid webs, air-laid webs, coform webs, hydroentangled webs, and the like. The basis weight of a nonwoven web can 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 formed by a process in which a molten thermoplastic material is extruded as molten fibers through a plurality of thin, usually circular die capillaries into a converging high-velocity gas (e.g., air) stream that reduces the diameter of the fibers of the molten thermoplastic material to a microfiber diameter. Thereafter, the meltblown fibers are carried by the high-velocity gas stream and deposited on a collecting surface to form a web of randomly dispersed meltblown fibers. This process is disclosed, for example, in U.S. Patents 3,849,241 to Butin et al., 4,307,143 to Meitner et al., and 4,707,398 to Wisneski et al., which are incorporated herein by reference in their entirety for all purposes. The meltblown fibers may be substantially continuous or discontinuous and may be substantially tacky when deposited onto a collecting surface.

[0028] As used herein, the term "spunbond" web or layer generally refers to a nonwoven web containing substantially continuous filaments of small diameter. The filaments are formed by extruding molten thermoplastic material from a plurality of fine, generally circular capillaries of a spinneret having the diameter of the extruded filaments and then rapidly attenuating 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. Patents 4,340,563 to Appel et al., 3,692,618 to Dorschner et al., 3,802,817 to Matsuki et al., 3,338,992 to Kinney, 3,341,394 to Kinney, 3,502,763 to Hartman, 3,502,538 to Levy, 3,542,615 to Dobo et al., and 5,382,400 to Pike et al., which are incorporated herein by reference in their entirety for all purposes.

[0029] Spunbond filaments are generally non-tacky when deposited onto a collecting surface.Spunbond filaments sometimes have diameters of less than about 40 microns and typically range from about 5 to about 20 microns.

[0030] The tensile properties of the fiber can be measured according to the following procedure. A single fiber specimen is cut short (e.g., with scissors) into 38 mm lengths and placed separately on a black velvet cloth. Ten to 15 fiber specimens are collected in this manner. The fiber specimens are then mounted in a substantially vertical position on a rectangular paper frame having an outer dimension of 51 mm × 51 mm and an inner dimension of 25 mm × 25 mm. The ends of each fiber specimen are operably attached to the paper frame by carefully securing the fiber ends to the sides of the paper frame with tape. The outer, relatively shorter fiber cross-sectional dimensions of each fiber specimen are then measured using a conventional laboratory microscope, which is appropriately calibrated and set to 40× magnification. The fiber cross-sectional dimensions are recorded as the diameter of each fiber specimen. The paper frame helps to secure the ends of the sample fiber specimens in the upper and lower clamps of a constant rate extension tensile testing machine in a manner that avoids excessive damage to the fiber specimens.

[0031] A constant rate extension tensile testing machine and an appropriate load cell are used for the test. The load cell (e.g., 10N) is selected so that the test value falls within 10% to 90% of the full-scale load. The tensile testing machine (i.e., MTSSYNERGY 200) and the load cell are from MTS Systems Corporation, Eden Prairie, Mich. The fiber specimen in the paper frame assembly is then mounted between the clamps of the tensile testing machine so that the end of the fiber can be operably held by the clamps of the tensile testing machine. The side of the paper frame extending parallel to the fiber length is then cut off or otherwise separated so that the tensile testing machine only applies a test force to the fiber. The fiber is then subjected to a tensile test at a draw rate and a clamp speed of 12 inches per minute. The data obtained are analyzed by the following test setup using the TESTWORKS 4 software program from MTS Corporation:

[0032]

[0033]

[0034] Tenacity values ​​are reported in grams-force per denier. Peak elongation (percent strain at break) was also measured. DETAILED DESCRIPTION

[0035] Those skilled in the art will appreciate that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of the disclosure.

[0036] Generally speaking, the present disclosure relates to a polymer blend that is not only easy to process and has excellent physical properties, but also has excellent biodegradability. The main component of the polymer blend is one or more biodegradable polymers. For example, the biodegradable polymer may include at least one polyhydroxyalkanoate. Alternatively, the polymer blend may contain polylactic acid alone or a combination of polylactic acid and one or more polyhydroxyalkanoates. At least one biodegradable polymer is combined with a polymer strength enhancer. The polymer strength enhancer may include a non-biodegradable polymer that can enhance the strength characteristics of at least one biodegradable polymer and / or improve the processing of the polymer, thereby producing improved mechanical properties. For example, the polymer strength enhancer may include a polyolefin or polyester, such as polyethylene terephthalate. For example, the polymer strength enhancer can provide performance enhancement for one or more mechanical properties of the biodegradable polymer, which can occur due to rapid crystallization of the polymer strength enhancer, which is optionally coupled to the backbone of the strength-enhancing polymer chain. Particularly advantageously, it has been found that significantly improved results can be achieved by only including a small amount of the polymer strength enhancer in the polymer composition. For example, polymeric strength enhancers can double or even triple the tensile strength of an article (eg, fiber) formed from the polymer blend.

[0037] According to the present disclosure, the polymer composition also contains at least one prodegradant that accelerates the degradation rate of the polymer strength enhancer. For example, when the polymer composition formed by the polymer blend is processed and degraded, the prodegradant significantly increases the biodegradation rate of the polymer strength enhancer to prevent the formation of microplastics. For example, the prodegradant can be used as an initiator to biodegrade the domain composed of the polymer strength enhancer contained in the polymer composition at a rate comparable to the biodegradable polymer contained in the blend.

[0038] As described above, the polymer composition contains at least one biodegradable polymer. In one aspect, the biodegradable polymer can be a biodegradable polyester polymer, such as an aliphatic or aromatic polyester. The biodegradable polyester polymer can be one or more polyhydroxyalkanoates (PHA), such as poly-3-hydroxybutyrate (PHB), poly-3-hydroxyvalerate (PHV), poly-3-hydroxybutyrate-to-4-hydroxybutyrate, poly-3-hydroxybutyrate-to-3-hydroxyvalerate copolymer (PHBV), poly-3-hydroxybutyrate-to-3-hydroxyhexanoate, poly-3-hydroxybutyrate-to-3-hydroxyoctanoate, poly-3-hydroxybutyrate-to-3-hydroxydecanoate, poly-3-hydroxybutyrate-to-3-hydroxyoctadecanoate and mixtures thereof.

[0039] Other examples of suitable biodegradable aliphatic polyesters include polycaprolactone, polyesteramides, modified polyethylene terephthalate, polylactic acid (PLA) and its copolymers, polylactic acid-based terpolymers, polyglycolic acid, polyalkylene carbonates (such as polyethylene carbonate), and succinate-based aliphatic polymers (e.g., polybutylene succinate, polybutylene succinate adipate, polyethylene succinate, etc.).

[0040] Biodegradable polymers can also include aromatic polyesters and modified aromatic polyesters, and aliphatic-aromatic copolyesters. In a specific embodiment, the biodegradable polyester is an aliphatic-aromatic copolyester (e.g., block aliphatic-aromatic copolyesters, random aliphatic-aromatic copolyesters, grafted aliphatic-aromatic copolyesters, etc.). Aliphatic-aromatic copolyesters can be synthesized using any known technology, such as synthesized by the polycondensation of polyols with aliphatic and aromatic dicarboxylic acids or their anhydrides. Polyols can be substituted or unsubstituted, straight or branched polyols selected from polyols containing 2 to about 12 carbon atoms and polyalkylene ether glycols containing 2 to 8 carbon atoms. Examples of polyols that can be used include, but are not limited to, ethylene glycol, diethylene glycol, propylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 2,2-dimethyl-1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,5-pentanediol, 1,6-hexanediol, polyethylene glycol, diethylene glycol, 2,2,4-trimethyl-1,6-hexanediol, thiodiglycol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, cyclopentanediol, triethylene glycol, and tetraethylene glycol. Preferred polyols include 1,4-butanediol; 1,3-propylene glycol; ethylene glycol; 1,6-hexanediol; diethylene glycol; and 1,4-cyclohexanedimethanol.

[0041] Representative aliphatic dicarboxylic acids that can be used include substituted or unsubstituted, linear or branched non-aromatic dicarboxylic acids selected from aliphatic dicarboxylic acids containing 1 to about 10 carbon atoms and their derivatives. Non-limiting examples of aliphatic dicarboxylic acids include malonic acid, malic acid, succinic acid, oxalic acid, glutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, fumaric acid, 2,2-dimethylglutaric acid, suberic acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, diglycolic acid, itaconic acid, maleic acid and 2,5-norbornanedicarboxylic acid. Representative aromatic dicarboxylic acids that can be used include substituted and unsubstituted, linear or branched aromatic dicarboxylic acids selected from aromatic dicarboxylic acids containing 1 to about 6 carbon atoms and their derivatives. Non-limiting examples of aromatic dicarboxylic acids include terephthalic acid, dimethyl terephthalate, isophthalic acid, dimethyl isophthalate, 2,6-naphthalene dicarboxylic acid, dimethyl 2,6-naphthalene dicarboxylate, 2,7-naphthalene dicarboxylic acid, dimethyl 2,7-naphthalene dicarboxylate, 3,4'-diphenyl oxide dicarboxylic acid, dimethyl 3,4'-diphenyl oxide dicarboxylate, 4,4'-diphenyl oxide dicarboxylic acid, dimethyl 4,4'-diphenyl oxide dicarboxylate, 3,4'-diphenyl sulfide dicarboxylic acid, dimethyl 3,4'-diphenyl sulfide dicarboxylate, 4,4'-diphenyl sulfide dicarboxylic acid, 4,4'-diphenyl oxide ... -dimethyl diphenyl sulfide dicarboxylate, 3,4'-diphenylsulfone dicarboxylic acid, dimethyl 3,4'-diphenylsulfone dicarboxylate, 4,4'-diphenylsulfone dicarboxylic acid, dimethyl 4,4'-diphenylsulfone dicarboxylate, 3,4'-benzophenone dicarboxylic acid, dimethyl 3,4'-benzophenone dicarboxylate, 4,4'-benzophenone dicarboxylic acid, dimethyl 4,4'-benzophenone dicarboxylate, 1,4-naphthalene dicarboxylic acid, dimethyl 1,4-naphthalene dicarboxylate, 4,4'-methylenebis(benzoic acid), dimethyl 4,4'-methylenebis(benzoic acid), and the like, and mixtures thereof.

[0042] The polymerization can be catalyzed by a catalyst, such as a titanium-based catalyst (e.g., tetraisopropyl titanate, tetraisopropoxy titanium, dibutoxydiacetoacetoxy titanium, or tetrabutyl titanate). If desired, a diisocyanate chain extender can be reacted with the copolyester to increase the molecular weight of the copolyester. Representative diisocyanates can include toluene 2,4-diisocyanate, toluene 2,6-diisocyanate, 2,4'-diphenylmethane diisocyanate, naphthalene-1,5-diisocyanate, meta-xylylenediisocyanate, hexamethylene diisocyanate ("HMDI"), isophorone diisocyanate, and methylenebis(2-isocyanatocyclohexane). Trifunctional isocyanate compounds containing isocyanurate and / or biurea groups having a functionality of not less than three can also be used, or triisocyanates or polyisocyanates can be used to partially replace the diisocyanate compounds. A preferred diisocyanate is hexamethylene diisocyanate. The amount of chain extender employed is generally from about 0.3 wt% to about 3.5 wt%, and in some embodiments, from about 0.5 wt% to about 2.5 wt%, based on the total weight percentage of the polymer.

[0043] Copolyesters can be linear polymers, or long-chain branched polymers. Long-chain branched polymers are generally prepared using low molecular weight branching agents (such as polyols, polycarboxylic acids, hydroxy acids, etc.). Representative low molecular weight polyols that can be used as branching agents include glycerol, trimethylolpropane, trimethylolethane, polyether triols, 1,2,4-butanetriol, pentaerythritol, 1,2,6-hexanetriol, sorbitol, 1,1,4,4-tetrakis (hydroxymethyl) cyclohexane, tris (2-hydroxyethyl) isocyanurate and dipentaerythritol. Representative high molecular weight polyols (molecular weight of 400 to 3000) that can be used as branching agents include triols derived by the condensation of alkylene oxides (such as ethylene oxide and propylene oxide) with polyol initiators having 2 to 3 carbons. Representative polycarboxylic acids that can be used as branching agents include trimesic acid, trimellitic acid (1,2,4-benzenetricarboxylic acid) and anhydride, trimesic acid (1,3,5-benzenetricarboxylic acid), pyromellitic acid and anhydride, benzene tetracarboxylic acid, benzophenone tetracarboxylic acid, 1,1,2,2-ethane-tetracarboxylic acid, 1,1,2-ethanetricarboxylic acid, 1,3,5-pentanetricarboxylic acid and 1,2,3,4-cyclopentanetetracarboxylic acid. Representative hydroxy acids that can be used as branching agents include malic acid, citric acid, tartaric acid, 3-hydroxyglutaric acid, mucic acid, trihydroxyglutaric acid, 4-carboxyphthalic anhydride, hydroxyisophthalic acid and 4-(β-hydroxyethyl)phthalic acid. Such hydroxy acids contain a combination of 3 or more hydroxyl groups and carboxyl groups. Particularly preferred branching agents include trimellitic acid, trimesic acid, pentaerythritol, trimethylolpropane, and 1,2,4-butanetriol.

[0044] The aromatic dicarboxylic acid monomer component can be present in the copolyester in an amount of from about 10 mol % to about 40 mol %, in some embodiments, from about 15 mol % to about 35 mol %, and in some embodiments, from about 15 mol % to about 30 mol %. Similarly, the aliphatic dicarboxylic acid monomer component can be present in the copolyester in an amount of from about 15 mol % to about 45 mol %, in some embodiments, from about 20 mol % to about 40 mol %, and in some embodiments, from about 25 mol % to about 35 mol %. The polyol monomer component can also be present in the aliphatic-aromatic copolyester in an amount of from about 30 mol % to about 65 mol %, in some embodiments, from about 40 mol % to about 50 mol %, and in some embodiments, from about 45 mol % to about 55 mol %.

[0045] As described above, in one aspect, the biodegradable polyester polymer comprises a single polyhydroxyalkanoate or a combination of a polyhydroxyalkanoate and polylactic acid. For example, the polyhydroxyalkanoate can be polyhydroxybutyrate. In one embodiment, a blend of different polyhydroxyalkanoates can be introduced into the polymer composition.

[0046] Polylactic acid can generally be derived from monomeric units of any isomer of lactic acid, such as left-lactic acid ("L-lactic acid"), right-lactic acid ("D-lactic acid"), meso-lactic acid, or mixtures thereof. Monomeric units can also be formed from the anhydrides of any isomers of lactic acid, including L-lactide, D-lactide, meso-lactide, or mixtures thereof. Cyclic dimers of such lactic acid and / or lactide can also be employed. Any known polymerization method, such as polycondensation or ring-opening polymerization, can be used to polymerize lactic acid. Small amounts of chain extenders (e.g., diisocyanate compounds, epoxy compounds, or acid anhydrides) can be employed. Polylactic acid can be a homopolymer or a copolymer, such as those containing monomeric units derived from L-lactic acid and monomeric units derived from D-lactic acid. Although not required, the content ratio of one of the monomer units derived from L-lactic acid and the monomer units derived from D-lactic acid is preferably about 85 mol% or higher, in some embodiments from about 90 mol% or higher, and in some embodiments from about 95 mol% or higher. A plurality of polylactic acids may be blended at any percentage, each having a different ratio of the monomer units derived from L-lactic acid to the monomer units derived from D-lactic acid.

[0047] In a particular embodiment, the polylactic acid has the following general structure:

[0048]

[0049] Biodegradable polyesters typically have a melting point of about 140° C. to about 260° C., in some embodiments, about 150° C. to about 250° C., and in some embodiments, about 160° C. to about 220° C. Such biodegradable polyesters are useful in that they biodegrade at a rapid rate. The glass transition temperature (“T”) of polylactic acid is about 100° C. to about 250° C. g ”) can be relatively high, such as from about 40°C to about 80°C, in some embodiments, from about 50°C to about 80°C, and in some embodiments, from about 55°C to about 65°C. As discussed in more detail above, melting temperatures and glass transition temperatures can be determined using differential scanning calorimetry (“DSC”) according to ASTM D-3417.

[0050] The biodegradable polyesters typically have a number average molecular weight ("M") in the range of about 40,000 g / mole to about 160,000 g / mole, in some embodiments, about 50,000 g / mole to about 140,000 g / mole, and in some embodiments, about 80,000 g / mole to about 120,000 g / mole. n Likewise, the polymers also typically have a weight average molecular weight ("M") in the range of from about 80,000 g / mole to about 200,000 g / mole, in some embodiments, from about 100,000 g / mole to about 180,000 g / mole, and in some embodiments, from about 110,000 g / mole to about 160,000 g / mole. w The ratio of weight average molecular weight to number average molecular weight ("M w / M n ”), i.e., the “polydispersity index” is also relatively low. For example, the polydispersity index typically ranges from about 1.0 to about 3.0, in some embodiments from about 1.1 to about 2.0, and in some embodiments from about 1.2 to about 1.8. The weight average molecular weight and number average molecular weight can be determined by methods known to those skilled in the art.

[0051] As at a temperature of 190°C and 1000 seconds -1 The biodegradable polyester may also have an apparent viscosity of about 50 Pascal seconds to about 600 Pascal seconds (Pa·s), in some embodiments, about 100 Pa·s to about 500 Pa·s, and in some embodiments, about 200 Pa·s to about 400 Pa·s, as measured at a shear rate of 1000 rpm. The biodegradable polyester may also have a melt flow rate (on a dry basis) in the range of about 0.1 g / 10 min to about 40 g / 10 min, in some embodiments, about 0.5 g / 10 min to about 20 g / 10 min, and in some embodiments, about 5 g / 10 min to about 15 g / 10 min, when measured under a load of 2160 g and at 190° C.

[0052] One or more biodegradable polymers, such as one or more biodegradable polyester polymers, can be included in the polymer composition with the amount being enough to form a continuous phase.For example, one or more biodegradable polymers can be greater than the amount of about 40 % by weight, such as with the amount greater than about 45 % by weight, such as with the amount greater than about 50 % by weight, such as with the amount greater than about 55 % by weight, such as with the amount greater than about 60 % by weight, such as with the amount greater than about 65 % by weight, such as with the amount greater than about 70 % by weight, such as with the amount greater than about 75 % by weight, such as with the amount greater than about 80 % by weight, such as with the amount greater than about 85 % by weight, such as with the amount greater than about 90 % by weight, such as with the amount greater than about 95 % by weight and be present in the polymer composition. One or more biodegradable polymers can usually be less than about 99.9 % by weight, such as less than about 98 % by weight, such as less than about 95 % by weight and be present in the polymer composition.

[0053] Polymer compositions of the present disclosure also contain polymer strength reinforcing agents. Due to the polymer properties of the polymer strength reinforcing agents, it has a relatively high molecular weight, which can contribute to improving the melt strength and stability of the thermoplastic composition. The polymer strength reinforcing agents may not be miscible with one or more biodegradable polymers usually. In this way, the polymer strength reinforcing agents can be dispersed in the continuous phase of one or more biodegradable polymers as discrete phase domains. The discrete domains can absorb the energy generated by the stress applied during the elongation of the composition during the drawing-off, which increases the overall toughness and strength of the fiber or film obtained. Although polymers are usually immiscible, polymer strength reinforcing agents with solubility parameters relatively similar to one or more biodegradable polymers can be selected. This usually improves the interfacial adhesion and physical interaction of the boundary of the discrete phase and the continuous phase, and thus reduces the possibility of fracture of the composition when stretched.

[0054] The polymeric strength enhancing agent may be selected to have a melt flow rate (or viscosity) to ensure that the discrete domains can be adequately maintained. In this regard, the ratio of the melt flow rate of the polymeric strength enhancing agent to the melt flow rate of the one or more biodegradable polymers may be from about 0.2 to about 8, in some embodiments, from about 0.5 to about 6, and in some embodiments, from about 1 to about 5. The polymeric strength enhancing agent may, for example, have a melt flow rate of from about 0.1 grams per 10 minutes to about 250 grams per 10 minutes, in some embodiments, from about 0.5 grams per 10 minutes to about 200 grams per 10 minutes, and in some embodiments, from about 5 grams per 10 minutes to about 150 grams per 10 minutes when measured at 190° C. under a load of 2160 grams.

[0055] In addition to the above-mentioned character, the mechanical characteristics of polymer strength reinforcing agent are usually also selected to increase to realize required intensity (comprising fiber toughness).For example, when the blend of one or more biodegradable polymers and polymer strength reinforcing agent is stretched during fiber drafting, due to the stress concentration produced by the difference of the elastic modulus of polymer strength reinforcing agent and one or more biodegradable polymers, shearing and / or plastic yield zone can be caused in and around the discrete phase domain. Larger stress concentration has promoted stronger local plastic flow in the domain, and this makes these domains become significantly elongated during fiber drafting. The domains of these elongations make composition show more pliable and soft behavior than other compositions. In order to strengthen stress concentration, select to compare the polymer strength reinforcing agent with relatively low Young's modulus of elasticity with one or more biodegradable polymers.

[0056] To impart the desired increase in strength, the polymeric strength enhancer may also exhibit a peak elongation (i.e., the percentage of elongation of the polymer at its peak load) greater than that of the biodegradable polyester polymer. For example, the polymeric strength enhancers of the present invention may exhibit a peak elongation of about 50% or greater, in some embodiments, about 100% or greater, in some embodiments, from about 100% to about 2000%, and in some embodiments, from about 250% to about 1500%.

[0057] While a variety of polymeric strength enhancers having the properties identified above may be employed, particularly suitable examples of such polymers may include, for example, polyolefins (e.g., polyethylene, polypropylene, polybutylene, etc.); polytetrafluoroethylene; polyesters (e.g., recycled polyester, polyethylene terephthalate, etc.); polyvinyl acetates (e.g., poly(ethylene vinyl acetate), polyvinyl chloride acetate, etc.); polyvinyl alcohols (e.g., polyvinyl alcohol, poly(ethylene vinyl alcohol)), etc.); polyvinyl butyral; acrylic resins (e.g., polyacrylates, polymethacrylates, polymethyl methacrylate, etc.); polyamides (e.g., nylon); polyvinyl chloride; polyvinylidene chloride; polystyrene; polyurethane; etc. For example, suitable polyolefins may include ethylene polymers (e.g., low-density polyethylene ("LDPE"), high-density polyethylene ("HDPE"), linear low-density polyethylene ("LLDPE"), etc.), propylene homopolymers (e.g., syndiotactic homopolymers, atactic homopolymers, isotactic homopolymers, etc.), propylene copolymers, etc.

[0058] In a particular embodiment, the polymer is a propylene polymer, such as a homopolypropylene or a propylene copolymer. The propylene polymer can be formed, for example, from a substantially isotactic polypropylene homopolymer or a copolymer containing equal to or less than about 10% by weight of other monomers (i.e., at least about 90% by weight of propylene). Such homopolymers can have a melting point of about 160° C. to about 170° C.

[0059] In yet another embodiment, the polyolefin may be ethylene or propylene with another α-olefin (such as C3-C 20 α-olefins or C3-C 12 Copolymers of α-olefins). Specific examples of suitable α-olefins include 1-butene; 3-methyl-1-butene; 3,3-dimethyl-1-butene; 1-pentene; 1-pentene having one or more methyl, ethyl or propyl substituents; 1-hexene having one or more methyl, ethyl or propyl substituents; 1-heptene having one or more methyl, ethyl or propyl substituents; 1-octene having one or more methyl, ethyl or propyl substituents; 1-nonene having one or more methyl, ethyl or propyl substituents; 1-decene substituted with ethyl, methyl or dimethyl; 1-dodecene and styrene. Particularly desirable α-olefin comonomers are 1-butene, 1-hexene and 1-octene. The ethylene or propylene content of such copolymers may be from about 60 mol % to about 99 mol %, in some embodiments from about 80 mol % to about 98.5 mol % and in some embodiments from about 87 mol % to about 97.5 mol %. The alpha-olefin content may likewise range from about 1 mole % to about 40 mole %, in some embodiments from about 1.5 mole % to about 15 mole %, and in some embodiments from about 2.5 mole % to about 13 mole %.

[0060] Exemplary olefin copolymers useful in the present invention include those which may be referred to as EXACT TM Ethylene-based copolymers available from ExxonMobil Chemical Company, Houston, Tex. Other suitable ethylene copolymers are available under the name ENGAGE TM 、AFFINITY TM 、DOWLEX TM (LLDPE) and ATTANE TM (ULDPE) is available from Dow Chemical Company, Midland, Mich. Other suitable ethylene polymers are described in U.S. Patents 4,937,299 to Ewen et al., 5,218,071 to Tsutsui et al., 5,272,236 to Lai et al., and 5,278,272 to Lai et al., which are incorporated herein by reference in their entirety for all purposes. Suitable propylene copolymers are available under the designation VISTAMAXX TM Obtained from ExxonMobil Chemical Co., Houston, Tex.; under the name FINA TM(e.g., 8573) were obtained from Atofina Chemicals of Feluy, Belgium; TM Available from Mitsui Petrochemical Industries and marketed as VERSIFY TM Available from Dow Chemical Co., Midland, Mich. Other examples of suitable propylene polymers are described in US Patent 6,500,563 to Datta et al., US Patent 5,539,056 to Yang et al., and US Patent 5,596,052 to Resconi et al., which are incorporated herein by reference in their entirety for all purposes.

[0061] Any of a variety of known technologies can be used to form olefin copolymers generally.For example, olefin polymers can be formed using free radicals or coordination catalysts (for example, Ziegler-Natta).Preferably, olefin polymers are formed by single-site coordination catalysts such as metallocene catalysts.Such catalyst systems produce such ethylene copolymers, wherein comonomers are randomly distributed in the molecular chain and are evenly distributed in the parts of different molecular weights.Metallocene-catalyzed polyolefins are for example described in the United States Patent (USP) 5,571,619, the United States Patent (USP) 5,322,728, the United States Patent (USP) 5,472,775, the United States Patent (USP) 5,272,236, the United States Patent (USP) 6,090,325, the United States Patent (USP) 6,090,325, the United States Patent (USP) 6,090,325, the United States Patent (USP) 5,571,619, the United States Patent (USP) 5,322,728, the United States Patent (USP) 5,322,728, the United States Patent (USP) 5,472,775, the United States Patent (USP) 5,272,236, the United States Patent (USP) 6,090,325 ... The example of metallocene catalyst comprises bis(n-butylcyclopentadienyl) titanium dichloride, bis(n-butylcyclopentadienyl) zirconium dichloride, bis(cyclopentadienyl) scandium chloride, bis(indenyl) zirconium dichloride, bis(methylcyclopentadienyl) titanium dichloride, bis(methylcyclopentadienyl) zirconium dichloride, cobaltocene, cyclopentadienyl titanium trichloride, ferrocene, hafnocene dichloride, isopropyl(cyclopentadienyl-1-fluorenyl) zirconium dichloride, molybdenum dichloride, nickelocene, silver dichloride, ruthenocene, titanocene dichloride, hydrogen chloride zirconocene, zirconocene dichloride etc.The polymer made with metallocene catalyst has narrow molecular weight range conventionally.For example, the polymer of metallocene catalysis can have polydispersity value (M) below 4. w / M n ), controlled short-chain branching distribution, and controlled isotacticity.

[0062] One or more polymer strength enhancers can be typically present in the polymer composition in an amount of about 0.1 % by weight to about 25 % by weight (including all 0.1 % by weight increments therebetween). However, for many applications, it is only necessary to introduce a small amount of one or more polymer strength enhancers into the polymer composition to significantly improve mechanical properties, melt strength or processing characteristics. For example, one or more polymer strength enhancers can be present in the polymer composition in an amount less than about 20 % by weight, such as less than about 15 % by weight, such as less than about 12 % by weight, such as less than about 10 % by weight, such as less than about 8 % by weight, such as less than about 6 % by weight, such as less than about 5 % by weight, such as less than about 4 % by weight, such as less than about 3 % by weight, such as even less than about 2 % by weight. One or more polymer strength enhancers may be present in the polymer composition in an amount greater than about 0.25 wt%, such as greater than about 0.5 wt%, such as greater than about 0.75 wt%, such as greater than about 1 wt%.

[0063] According to the present disclosure, the polymer composition further contains at least one prodegradant. The at least one prodegradant is selected to accelerate the degradation rate of the polymer strength enhancer. Various prodegradants can be introduced into the polymer composition of the present disclosure. For example, the prodegradant can be selected based on the amount of polymer strength enhancer introduced into the composition and / or the amount of polymer strength enhancer present. In one aspect, the polymer composition contains at least two prodegradants, such as at least three prodegradants, such as at least four prodegradants.

[0064] In one aspect, the prodegradant can be a transition metal compound. For example, the polymer composition can contain at least one transition metal compound, such as at least two transition metal compounds, such as at least three transition metal compounds and generally less than about ten transition metal compounds.

[0065] The following description uses the term transition metal to refer to any of the metal elements in Groups IVB to VIII, IB and IIB, or Groups 4 to 12 of the Periodic Table of the Elements. Preferred transition metals are iron, manganese, copper, cobalt, and cerium, preferably wherein the iron is in the +3 oxidation state and wherein the copper is in the +2 oxidation state. These compounds catalyze degradation.

[0066] When two or more transition metal compounds are present, they may be selected from iron compounds, manganese compounds, copper compounds, cobalt compounds and cerium compounds, and the transition metals in the two or more transition metal compounds are different. Preferably, the two or more transition metal compounds are selected from iron compounds, manganese compounds, copper compounds, cobalt compounds and cerium compounds, and the transition metals in the two or more transition metal compounds are different. In one aspect, the transition metals in the two or more transition metal compounds include iron, manganese and copper; or manganese and copper; or iron and manganese.

[0067] The temperature of a polymer composition and its exposure to light can also affect its degradation rate. Iron is a more effective photocatalyst, while manganese is a more effective thermal catalyst for the degradation process. Therefore, the degradation rate can be adjusted using transition metal components based on the expected exposure to heat and light for a particular product.

[0068] The ligand of the metal compound may be an inorganic ligand and / or a saturated organic ligand. Preferably, the ligand of the metal compound does not contain a monounsaturated or polyunsaturated C14-C24 carboxylic acid, or an ester, anhydride or amide thereof.

[0069] The transition metal compound can include a portion selected from stearate, carboxylate, acetylacetonate, triazacyclononane, or a combination of two or more thereof. In one aspect, the transition metal compound includes stearate and can be present in a weight ratio of 4:1 to 8:1 of ferrous stearate and manganese stearate to cupric stearate. For example, the transition metal compound can be present in a ratio of 4:1 to 8:1 of ferrous stearate and manganese stearate to cupric stearate.

[0070] One or more transition metal compounds can be with relatively small amounts, such as being present in polymer composition in an amount less than about 1 % by weight. For example, one or more transition metal compounds can be with the amount less than about 0.8 % by weight, such as being less than about 0.5 % by weight, such as being less than about 0.4 % by weight, such as being present in polymer composition in an amount less than about 0.3 % by weight. One or more transition metal compounds can usually be with the amount greater than about 0.08 % by weight, such as being greater than about 0.1 % by weight, such as being present in polymer composition in an amount greater than about 0.12 % by weight.

[0071] As an alternative to or in addition to one or more transition metal compounds, the polymer composition may also contain a ligand selected from amines, imines, amides, phosphites, phosphines, carbenes and mixtures thereof. Such ligands are particularly suitable for use with transition metal compounds.

[0072] Another prodegradant that may be present in the polymer composition is a carboxylic acid, particularly an unsaturated carboxylic acid having a carbon chain length of about 12 carbon atoms to about 26 carbon atoms. The prodegradant may also be an ester, anhydride, or amide of a carboxylic acid.

[0073] The following description uses the term carboxylic acid to refer to a range of molecules containing a carboxylic acid-(COOH) moiety. Carboxylic acids can be monounsaturated or polyunsaturated and have a carbon backbone containing 14 to 24 carbon atoms, meaning that they have at least one double bond in their carbon backbone. The carbon backbone of a carboxylic acid can be linear, branched, or aromatic. Preferably, the monounsaturated or polyunsaturated carboxylic acid is C 16 -C 20 Carboxylic acids. Preferred carboxylic acids are oleic acid, linoleic acid, and cinnamic acid, and most preferably, the carboxylic acid is oleic acid.

[0074] Alternatively, the degradable polymer composition comprises a monounsaturated or polyunsaturated C 14 -C 24 Esters, anhydrides or amides of carboxylic acids.

[0075] The carboxylic acids or their esters, anhydrides or amides are preferably "free" or "non-coordinating", that is to say they do not form part of the transition metal compound.

[0076] When the degradable polymer composition comprises monounsaturated or polyunsaturated C 14 -C 24 When the ester of a carboxylic acid is prepared, the alcohol component preferably comprises C1-C 30 Alcohol, more preferably a saturated straight chain C1-C 30 alcohol.

[0077] When the degradable polymer composition comprises monounsaturated or polyunsaturated C 14 -C 24 When the anhydride of a carboxylic acid is used, the anhydride may be symmetrical or asymmetrical. The second carboxylic acid component preferably comprises C1-C 30 Carboxylic acid, more preferably a saturated straight chain C1-C 30 carboxylic acid.

[0078] When the degradable polymer composition comprises monounsaturated or polyunsaturated C 14 -C 24 When the amide is an amide of a carboxylic acid, the amide may be a primary amide, a secondary amide or a tertiary amide. When a secondary amide or a tertiary amide is present, each of the carbon chains preferably contains 1 to 30 carbon atoms, more preferably each carbon chain is C1-C 30 Alkyl group.

[0079] Unless otherwise indicated, when a feature of a carboxylic acid is discussed in this specification, the carboxylic acid is also intended to encompass the ester, anhydride or amide of the carboxylic acid.

[0080] Without wishing to be bound by theory, it is believed that the monounsaturated or polyunsaturated C 14 -C 24 Carboxylic acids undergo auto-oxidation to produce peroxides that can attack the carbon-carbon bonds of the polymer chain, making the polymer susceptible to normal degradation processes. The presence of transition metals catalyzes auto-oxidation, thereby increasing the degradation rate of the polymer composition.

[0081] The carboxylic acid or its ester, anhydride or amide can be present in the polymer composition typically in an amount of less than about 0.5 wt %, such as less than about 0.2 wt %, such as less than about 0.16 wt %, such as less than about 0.14 wt %. The carboxylic acid or its ester, anhydride or amide can be present in an amount of greater than about 0.01 wt %, such as greater than about 0.05 wt %, such as greater than about 0.09 wt %, such as greater than about 0.11 wt %.

[0082] In another embodiment, the prodegradant may include a sugar (including starch). Examples of sugars that can be introduced into the composition include, but are not limited to, galactose, galactonate, succinate, malate, aspartate, serine, fumarate, ribose, pyruvate, oxalacetate, and other L- and D-sugar structures, but are not limited thereto. In one embodiment, the sugar is non-esterified starch.

[0083] In one embodiment, starch can be a dry starch. For example, starch can be a polysaccharide composed of the glucose units connected by glycosidic bonds. Sugar (comprising one or more starches) can be present in the polymer composition with the amount of about 0.1 % by weight to about 18 % by weight (comprising all 0.1 % by weight increments between them). For example, sugar or starch can be with the amount greater than about 0.1 % by weight, such as with the amount greater than about 0.5 % by weight, such as with the amount greater than about 1 % by weight, such as with the amount greater than about 1.5 % by weight, and usually with the amount less than about 10 % by weight, such as with the amount less than about 8 % by weight, such as with the amount less than about 5 % by weight. Sugar (comprising starch) is particularly suitable for being used in combination with other prodegradants.

[0084] In another embodiment, the degradation aid can be a calcium salt. For example, the calcium salt can be calcium carbonate, calcium oxide or their mixture. The introducing of the calcium salt can also improve the processing characteristics of the polymer composition except accelerating the degradation rate of the polymer strength reinforcing agent. One or more calcium salts can usually be less than the amount of about 3 % by weight, such as less than the amount of about 2 % by weight, such as less than the amount of about 1.5 % by weight, and usually with the amount greater than about 0.1 % by weight, such as being present in the polymer composition with the amount greater than about 0.5 % by weight.

[0085] In another aspect, the prodegradant can be one or more furanones. Some furanones can serve as attractants for bacteria. Suitable furanones can include, but are not limited to, 3,5-dimethylpentenyl (dimethylyentenyl)-dihydro-2 (3H) furanone isomer mixtures, emoxyfurane, and N-acyl homoserine lactone. Bacteria that are shown to be attracted by the furanones compounds listed above include, but are not limited to, C. violaceum. One or more furanones can be present in the polymer composition in an amount less than about 3% by weight, such as in an amount less than about 1.5% by weight, such as in an amount less than about 0.5% by weight, such as in an amount less than about 0.2% by weight. One or more furanones can typically be present in the polymer composition in an amount greater than about 0.001% by weight, such as in an amount greater than about 0.01% by weight, such as in an amount greater than about 0.1% by weight.

[0086] Other degradation agents that can be introduced into the composition include furanone compounds, glutaric acid, hexadecanoic acid compounds or their mixtures. For example, the glutaric acid compound can be propyl glutaric acid. Each degradation agent in the above-mentioned degradation agent can be present in the polymer composition in an amount less than about 4 % by weight, such as less than about 2 % by weight, such as less than about 1 % by weight, such as less than about 0.5 % by weight. Each degradation agent in the above-mentioned degradation agent can usually be present in the polymer composition in an amount greater than about 0.001 % by weight, such as greater than about 0.01 % by weight, such as greater than about 0.1 % by weight.

[0087] In one embodiment, the polymer composition may include at least one, such as at least two, transition metal compounds in combination with at least one other prodegradant. For example, the other prodegradant may be a carboxylic acid, or an ester, anhydride, or amide thereof, alone or in combination with starch and / or a calcium salt.

[0088] An advantageous aspect of the present disclosure is that good mechanical properties (e.g., elongation) can be provided without the need for conventional plasticizers (such as alkane diols). Therefore, thermoplastic compositions of the present invention can be substantially free of such plasticizers. However, it should be understood that plasticizers can be used in certain embodiments. However, when adopting plasticizers, plasticizers are generally present in an amount less than about 10% by weight of the thermoplastic composition, in some embodiments, in an amount of about 0.1% by weight to about 5% by weight of the thermoplastic composition, and in some embodiments, in an amount of about 0.2% by weight to about 2% by weight of the thermoplastic composition.

[0089] Of course, for a variety of different reasons, other ingredients can also be used. For example, usable materials include, but are not limited to, catalysts, pigments, antioxidants, stabilizers, surfactants, waxes, flow promoters, solid solvents, nucleating agents (e.g., titanium dioxide, calcium carbonate, etc.), particles, and other materials added to enhance the processability of the thermoplastic composition. When adopted, it is generally desirable to minimize the amount of these additional ingredients to ensure optimal compatibility and cost-effectiveness. Therefore, for example, it is generally desirable that these ingredients account for less than about 10% by weight of the thermoplastic composition, in some embodiments, less than about 8% by weight of the thermoplastic composition, and in some embodiments, less than about 5% by weight of the thermoplastic composition.

[0090] In one embodiment, the polymer composition can contain a swelling agent (including fillers). For example, the filler can include clay particles. The clay particles can have an average particle size generally less than about 15 microns, such as less than about 10 microns, such as less than about 5 microns, and generally greater than about 0.001 microns. In one embodiment, the clay particles can be nanoparticles with a particle size less than about 1 micron, such as less than about 0.8 microns, such as less than about 0.6 microns. Generally speaking, any suitable clay can be introduced into the polymer composition. In one embodiment, the clay particles can include diatomaceous earth. The swelling agent can be selected from, but not limited to, natural fibers, cultured colloids, organoleptic compounds, cyclodextrins, or mixtures thereof. The swelling agent or filler can be present in the polymer composition in an amount less than about 12 wt %, such as in an amount less than about 5 wt %, such as in an amount less than about 3 wt %, such as in an amount less than about 2 wt %. The swelling agent or filler can be present in the polymer composition in an amount generally greater than about 0.5 wt %, such as in an amount greater than about 1 wt %, such as in an amount greater than about 2 wt %.

[0091] When forming a polymer article from a polymer composition of the present disclosure, one or more biodegradable polyester polymers, one or more polymer strength enhancers and one or more degradation aids are melt blended together. In one embodiment, one or more degradation aids can be introduced into the polymer composition in a compounded form as a masterbatch. For example, one or more degradation aids can be combined with a carrier polymer to form a masterbatch, and then the masterbatch is combined with one or more biodegradable polyester polymers and one or more polymer strength enhancers. For example, the carrier polymer can include a biodegradable polyester polymer or a polymer strength enhancer polymer. For example, the carrier polymer can include a polyolefin, such as polypropylene or polyethylene. One or more degradation aids can be present in the masterbatch in an amount less than about 20% by weight, such as in an amount less than about 10% by weight, such as in an amount less than about 3% by weight, and generally in an amount greater than about 0.1% by weight, such as in an amount greater than about 0.2% by weight.

[0092] All different types of molded articles can be made according to the present disclosure. However, the polymer composition is particularly suitable for forming fibers and films.

[0093] The fibers formed from the blended thermoplastic compositions can generally have any desired configuration, including single component and multicomponent (e.g., sheath-core configuration, side-by-side configuration, segmented pie configuration, island-in-the-sea configuration, etc.). In some embodiments, the fibers can include one or more additional polymers as their components (e.g., bicomponent) or ingredients (e.g., bicomponent) to further enhance strength and other mechanical properties. For example, the thermoplastic composition can form the sheath component of a sheath / core bicomponent fiber, while the additional polymer can form the core component, or vice versa. The additional polymer can be a thermoplastic polymer that is not generally considered to be biodegradable, such as polyolefins, e.g., polyethylene, polypropylene, polybutylene, etc.; polytetrafluoroethylene; polyesters, e.g., polyethylene terephthalate, etc.; polyvinyl acetate; polyvinyl chloride acetate; polyvinyl butyral; acrylic resins, e.g., polyacrylates, polymethacrylates, polymethyl methacrylates, etc.; polyamides, e.g., nylon; polyvinyl chloride; polyvinylidene chloride; polystyrene; polyvinyl alcohol; and polyurethane. More advantageously, however, the additional polymer is biodegradable, such as aliphatic polyesters such as polyesteramides, modified polyethylene terephthalate, polyglycolic acid, polyalkylene carbonates (such as polyethylene carbonate), polyhydroxyalkanoates (PHA), polyhydroxybutyrate (PHB), polyhydroxyvalerate (PHV), polyhydroxybutyrate-hydroxyvalerate copolymers (PHBV), and polycaprolactone, as well as succinate-based aliphatic polymers (e.g., polybutylene succinate, polybutylene succinate adipate, and polyethylene succinate); aromatic polyesters; or other aliphatic-aromatic copolyesters.

[0094] For example, see Figure 2 , shows a cross-sectional view of a bicomponent fiber 50. The bicomponent fiber 50 includes a core 52 surrounded by a sheath 54. In one embodiment, the core 52 can be formed from a polymer composition of the present disclosure. In another aspect, the sheath 54 can be made entirely of one or more biodegradable polymers, particularly one or more biodegradable polyester polymers (such as PHA).

[0095] According to the present invention, any one of the multiple methods can be used to form fiber.For example, thermoplastic composition described above can be extruded, quenched and drawn into the vertical channel of fiber drafting unit by spinneret.Once formed, fiber can be cut to form average fiber length at about 3 millimeters to about 80 millimeters, in some embodiments, about 4 millimeters to about 65 millimeters, and in some embodiments, about 5 millimeters to about 50 millimeters of staple fibers in the scope.Then staple fibers can be introduced into nonwoven web known in the art, such as bonding carded web, through-air bonded web.Fiber also can be deposited on porous surface to form nonwoven web.

[0096] For example, see Figure 1 , shows one embodiment of a method for forming fibers, such as spunbond fibers, in more detail. In this particular embodiment, a polymer blend is fed from a hopper 14 to an extruder 12. The blend may be provided to the hopper 14 using any conventional technique.

[0097] Extruder 12 is heated to a temperature sufficient to extrude molten polymer. The extruded composition is then passed through polymer conduit 16 to spinneret 18. For example, spinneret 18 can include a housing containing a spinning assembly having a plurality of plates stacked on each other and having an opening pattern arranged to produce a flow path for guiding the polymer components. Spinneret 18 also has openings arranged in one or more rows. These openings form a filament curtain that is extruded downward when the polymer is extruded therefrom. Method 10 also adopts a quench blower 20 positioned adjacent to the fiber curtain extending from spinneret 18. The air from quench blower 20 quenches the fibers extending from spinneret 18. The quench air can be imported from one side of the fiber curtain (e.g., Figure 1 as shown) or introduced from both sides of the fiber curtain.

[0098] After quenching, the fibers are drawn into a vertical channel of a fiber draw unit 22. Fiber draw units or aspirators for melt-spinning polymers are well known in the art. Fiber draw units suitable for use in the process of the present invention include linear fiber aspirators of the type shown in U.S. Patents 3,802,817 and 3,423,255, both of which are incorporated herein by reference in their entirety for all relevant purposes. The fiber draw unit 22 typically includes an elongated vertical channel through which fibers are drawn by suction air entering from the side of the channel and flowing downward through the channel. A heater or blower 24 supplies suction air to the fiber draw unit 22. The suction air draws the fibers and ambient air through the fiber draw unit 22. The flow of gas causes the fibers to be drawn or contracted, which increases the molecular orientation or crystallinity of the polymer forming the fibers. The fibers are deposited onto a godet 42 through the outlet opening of the fiber draw unit 22.

[0099] Due to the increased strength of the fibers of the present invention, high draw ratios can be used in the present invention without causing breakage. The draw ratio is the linear velocity of the fiber after being drawn (e.g., the linear velocity of the godet 42 or the porous surface (not shown)) divided by the linear velocity of the fiber after being extruded. For example, the draw ratio can be calculated in certain embodiments according to the following formula:

[0100] Stretch ratio = A / B

[0101] in,

[0102] A is the linear velocity of the fiber after it is drawn (i.e., the godet speed) and is measured directly; and

[0103] B is the linear velocity of the fiber after extrusion and can be calculated as follows:

[0104] Extruder linear fiber speed = C / (25*π*D*E 2 )

[0105] in,

[0106] C is the flux through a single hole (grams per minute);

[0107] D is the melt density of the polymer (grams per cubic centimeter); and

[0108] E is the diameter (in centimeters) of the orifice through which the fiber is extruded. In certain embodiments of the present invention, the draw ratio can be from about 200:1 to about 8500:1, in some embodiments, from about 500:1 to about 7500:1, and in some embodiments, from about 1000:1 to about 6000:1. If desired, the fibers collected on the godet roll 42 can optionally be subjected to additional in-line processing and / or conversion steps (not shown), as will be understood by those skilled in the art. For example, staple fibers can be formed by "cold drawing" the collected fibers to the desired diameter at a temperature below the softening temperature, followed by crimping, texturizing, and / or cutting the fibers to the desired fiber length.

[0109] The fiber of the present invention can also be formed into a coherent web structure by some means: the fiber is randomly deposited onto a forming surface (optionally with the aid of a vacuum), and then the resulting web is bonded using any known technology. For example, an annular porous forming surface can be positioned below the fiber drafting unit and receive the fiber from the outlet opening. A vacuum can be positioned below the forming surface to draft the fibers and consolidate the unbonded nonwoven web. Once formed, any conventional technology can be used to bond the nonwoven web, such as by an adhesive or in a spontaneous manner (for example, without applying an external adhesive, the fibers fuse and / or self-adhere). For example, spontaneous bonding can be achieved by contacting when the fibers are semi-molten or tacky. Suitable spontaneous bonding techniques can include ultrasonic bonding, thermal bonding, air-through bonding, hot rolling bonding, etc. For example, the web can be further bonded or embossed with a pattern by a thermomechanical process, in which the web is passed between a heated smooth anvil roll and a heated pattern roll. The pattern roll can have any elevated pattern that provides desired web properties or outward appearance. Advantageously, the patterned roller defines an elevated pattern that defines a plurality of bonding locations that define a bonding area between about 2% and 30% of the total area of ​​the roller. Exemplary bonding patterns include, for example, those described in U.S. Patents 3,855,046 to Hansen et al., 5,620,779 to Levy et al., 5,962,112 to Haynes et al., 6,093,665 to Sayovitz et al., and 428,267 to Romano et al., 390,708 to Brown, 418,305 to Zander et al., 384,508 to Zander et al., 384,819 to Zander et al., 358,035 to Zander et al., and 315,990 to Blenke et al., all of which are incorporated herein by reference in their entirety for all purposes.

[0110] In addition to spunbond webs, a variety of other nonwoven webs can also be formed by the thermoplastic composition according to the present invention, such as meltblown webs, bonded carded webs, wet-laid webs, air-laid webs, co-formed webs, and hydroentangled webs. For example, the thermoplastic composition can be extruded through a plurality of fine die capillaries into a converging high-speed gas (e.g., air) stream that reduces the fiber to reduce its diameter. After this, the meltblown fibers are carried by the high-speed air stream and deposited on a collecting surface to form a randomly dispersed meltblown fiber web. Alternatively, the polymer can be formed into a carded web by placing the fibers formed by the thermoplastic composition in bundles in a cotton cleaning machine that separates the fibers. Then, the fibers are sent to a combing or carding unit that further separates the fibers and aligns them in the machine direction, thereby forming a fiber nonwoven web oriented in the machine direction. Once formed, the nonwoven web can usually be stabilized by one or more known bonding techniques.

[0111] Nonwoven laminates can also be formed, wherein one or more layers are formed by thermoplastic compositions. For example, the nonwoven web of one layer can be a spunbond web containing a thermoplastic composition, and the nonwoven web of another layer comprises a thermoplastic composition, other biodegradable polymers and / or any other polymer (for example, polyolefin). In one embodiment, the nonwoven laminate comprises a meltblown layer positioned between two spunbond layers to form a spunbond / meltblown / spunbond ("SMS") laminate. If desired, the spunbond layer can be formed by thermoplastic compositions. The meltblown layer can be formed by thermoplastic compositions, other biodegradable polymers and / or any other polymer (for example, polyolefin). Various techniques for forming SMS laminates are described in U.S. Patent Nos. 4,041,203 to Brock et al., 5,213,881 to Timmons et al., 5,464,688 to Timmons et al., 4,374,888 to Bornslaeger et al., 5,169,706 to Collier et al., 4,766,029 to Brock et al., and U.S. Patent Application Publication No. 2004 / 0002273 to Fitting et al., all of which are incorporated herein by reference in their entirety for all purposes. Of course, the nonwoven laminate can have other configurations and have any desired number of meltblown and spunbond layers, such as spunbond / meltblown / meltblown / spunbond laminates ("SMMS"), spunbond / meltblown laminates ("SM"), etc. While the basis weight of the nonwoven laminate can be tailored for the desired application, it generally ranges from about 10 grams per square meter to about 300 grams per square meter ("gsm"), in some embodiments, from about 25 gsm to about 200 gsm, and in some embodiments, from about 40 gsm to about 150 gsm.

[0112] If desired, nonwoven web or laminate can be subjected to various treatments to impart required characteristics. For example, the net can be treated with liquid repellency additives, antistatic agents, surfactants, colorants, antifog agents, fluoride blood (fluorochemical blood) or alcohol repellent (alcohol repellent), lubricants and / or antimicrobial agents. In addition, the net can be subjected to electret treatment, which imparts electrostatic charge to improve filtration efficiency. Electric charge can include a positive charge or negative charge layer captured at or near the polymer surface, or a charge cloud stored in the polymer bulk. Electric charge can also include a polarized charge frozen in the alignment of the dipole of the molecule. Making fabrics accept the technology of electret treatment is well known to those skilled in the art. The example of such technology includes but is not limited to heat, liquid contact, electron beam and corona discharge technology. In a specific embodiment, electret treatment is a corona discharge technology, which relates to making laminates accept a pair of electric fields with opposite polarities. Other methods for forming electret materials are described in U.S. Patents 4,215,682 to Kubik et al., 4,375,718 to Wadsworth, 4,592,815 to Nakao, 4,874,659 to Ando, ​​5,401,446 to Tsai et al., 5,883,026 to Reader et al., 5,908,598 to Rousseau et al., and 6,365,088 to Knight et al., which are incorporated herein by reference in their entirety for all purposes.

[0113] Nonwoven webs can be used in a variety of applications. For example, nonwoven webs can be incorporated into "absorbent articles" that can absorb 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 products, feminine hygiene products (e.g., sanitary napkins), swimsuits, baby wipes, mitt wipes, and the like; medical absorbent articles such as clothing, fenestration materials, padding, mattresses, bandages, absorbent drapes, and medical wipes; food service tissues; clothing products; pockets, and the like. The materials and methods for forming such articles are well known to those skilled in the art. For example, absorbent articles typically include a substantially liquid-impermeable layer (e.g., an outer cover), a liquid-permeable layer (e.g., a body-side liner, a surge layer, and the like), and an absorbent core. For example, in one embodiment, a nonwoven web formed according to the present invention can be used to form the outer cover of an absorbent article. If desired, the nonwoven web can be laminated to a vapor-permeable or vapor-impermeable liquid-impermeable film.

[0114] These and other modifications and variations of the present invention may be practiced by those skilled in the art without departing from the spirit and scope of the present invention as more particularly described in the appended claims. Furthermore, it should be understood that aspects of the various embodiments may be interchanged in whole or in part. Furthermore, it will be appreciated by those skilled in the art that the foregoing description is by way of example only and is not intended to limit the present invention as further described in such appended claims.

Claims

1. A polymer composition comprising: a biodegradable polyester polymer, said biodegradable polyester polymer being present in said polymer composition in an amount greater than about 40% by weight; a polymeric strength enhancer comprising a polyolefin, a polyalkylene terephthalate, or a mixture thereof; and At least one prodegradant, the at least one prodegradant accelerating the degradation rate of the polymer strength enhancing agent.

2. The polymer composition of claim 1, wherein the at least one prodegradant comprises a transition metal compound.

3. The polymer composition of claim 2, wherein the transition metal compound comprises an iron salt, a manganese salt, or a copper salt of a carboxylic acid.

4. The polymer composition of claim 3, wherein the transition metal compound comprises iron stearate, manganese stearate, copper stearate, or a mixture thereof.

5. The polymer composition of any of the preceding claims, wherein the at least one prodegradant comprises a total amount of about 0.08 wt% to about 0.5 wt% of two or more transition metal compounds.

6. The polymer composition of any one of the preceding claims, wherein the at least one prodegradant comprises an unsaturated carboxylic acid having a carbon chain length of about 12 carbon atoms to about 26 carbon atoms, or an ester, anhydride, or amide thereof.

7. The polymer composition of claim 6, wherein the unsaturated carboxylic acid having a carbon chain length of about 12 carbon atoms to about 26 carbon atoms, or an ester, anhydride or amide thereof is present in the polymer composition in an amount of about 0.01 wt % to about 0.2 wt %.

8. The polymer composition according to any one of the preceding claims, wherein the at least one prodegradant comprises a sugar, such as starch.

9. The polymer composition of any one of the preceding claims, wherein the at least one prodegradant comprises calcium oxide, calcium carbonate, or a mixture thereof.

10. The polymer composition of any one of the preceding claims, wherein the at least one prodegradant comprises a furanone compound, glutaric acid, a hexadecenoic acid compound, or a mixture thereof.

11. The polymer composition of any one of the preceding claims, wherein the strength enhancer comprises a polyolefin.

12. The polymer composition of claim 11, wherein the polyolefin is a propylene homopolymer, a propylene / α-olefin copolymer, an ethylene / α-olefin copolymer, or a combination thereof.

13. The polymer composition of claim 11, wherein the polyolefin is an ethylene homopolymer, an ethylene copolymer, or a combination thereof.

14. The polymer composition of any one of the preceding claims, wherein the polymeric strength enhancer comprises a polyalkylene terephthalate comprising polyethylene terephthalate.

15. The polymer composition of any one of the preceding claims, wherein the polymer strength enhancer comprises from about 0.25 wt% to about 25 wt%, such as from about 0.5 wt% to about 8 wt%, such as from about 0.5 wt% to about 5 wt% of the polymer composition.

16. The polymer composition of any one of claims 1 to 15, wherein the biodegradable polyester polymer comprises a polyhydroxyalkanoate.

17. The polymer composition of claim 17, wherein the biodegradable polyester polymer comprises polyhydroxybutyrate.

18. The polymer composition of any preceding claim, wherein the biodegradable polyester polymer comprises polylactic acid.

19. The polymer composition of any one of the preceding claims, wherein the polymer composition further comprises a filler.

20. The polymer composition of claim 19, wherein the filler comprises clay particles.

21. The polymer composition of claim 19 or claim 20, wherein the filler comprises diatomaceous earth.

22. A fiber formed from the polymer composition of any preceding claim.

23. The fiber of claim 22, wherein the fiber comprises meltblown fibers or spunbond fibers.

24. A fiber according to claim 22 or claim 23, wherein the fiber is a bicomponent fiber comprising a sheath polymer surrounding a core polymer.

25. The fiber of claim 24, wherein the sheath polymer comprises a biodegradable polyester polymer and the core polymer comprises the polymer composition of any one of claims 1 to 18.

26. A nonwoven web comprising a plurality of fibers according to any one of claims 22 to 25.

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