KR20020040917A - Methods for preparing soft and elastic biodegradable polyhydroxyalkanoate copolymer compositions and polymer products comprising such compositions - Google Patents

Abstract

The present invention relates to soft and elastic polymeric articles obtained by stretching compositions containing biodegradable polyhydroxyalkanoate copolymers comprising at least two randomly repeating monomer units. The first randomly repeating monomer unit has the structure of formula (I):

[Formula I]

[Wherein, R ¹ is H or C1 or C2 alkyl and n is 1 or 2].

The second randomly repeating monomeric unit is different from the first randomly repeating monomeric unit and has the structure of Formula II:

[Formula II]

[Wherein m is 2 to about 9].

At least about 70 mole% of the copolymer contains randomly repeating monomer units having the first randomly repeating monomer unit structure of formula (I). The polymeric article of the present invention is advantageous in that it exhibits a combination of ductility and elasticity while maintaining strength.

Description

METHOD FOR PREPARING SOFT AND ELASTIC BIODEGRADABLE POLYHYDROXYALKANOATE COPOLYMER COMPOSITIONS AND POLYMER PRODUCTS COMPRISING SUCH COMPOSITIONS

In view of reducing the volume of solid waste generated by consumers every year, products formed from biodegradable polymers and biodegradable polymers are becoming increasingly important.

In the past, biodegradability and physical properties of various polyhydroxyalkanoates have been studied. Polyhydroxyalkanoates are polyester compounds produced by various microorganisms such as, for example, bacteria and algae. Polyhydroxyalkanoates have attracted general attention because of their biodegradability, but their practical use as plastic materials has been limited by their thermal instability. For example, poly-3-hydroxybutyrate (PHB) is a natural energy storage product of bacteria and algae and exists as individual granules in the cytoplasm. PHB is thermoplastic and has a high degree of crystallinity and a well defined melting temperature of about 180 ° C. Unfortunately, PHB is unstable and decomposes at elevated temperatures near its melting temperature. Because of this thermal instability, the commercial application of PHB has been extremely limited.

Other polyhydroxyalkanoates such as poly (3-hydroxybutyrate-co-3-hydroxyvalericate) (PHBV) have also been studied. Examples of PHB homopolymers and PHBV copolymers are described in Holmes et al., US Pat. Nos. 4,393,167 and 4,880,59, and PHBV copolymers are available from Monsanto under the trade name BIOPOL. Unfortunately, polyhydroxyalkanoates such as PHB and PHBV are difficult to process into films for use in various applications. As discussed above, the thermal instability of the PHB makes such processing almost impossible. In addition, the slow crystallization rate and flow properties of PHB and PHBV make film processing difficult. PHBV copolymers are typically prepared with valerate content in the range of about 5 to about 24 mole percent. Increasing the valerate content reduces the melting temperature of the polymer. However, because of the relatively small change in crystallinity, PHBV films are frequently stiff and brittle for many applications.

Improved biodegradable copolymers are disclosed by Noda, for example, in US Pat. Nos. 5,498,692, 5,536,564, 5,602,227 and 5,685,756. The biodegradable copolymer of Noda contains two or more randomly repeating monomer units (RRMU), wherein the first RRMU is of the structure [-O-CH (R ¹ )-(CH ₂ ) _n -C (O ), Wherein R ¹ is H or C1 or C2 alkyl, n is 1 or 2, and the second RRMU has the structure [-O-CH (R ² ) -CH ₂ -C ( O)-], wherein R ² is C4-C19 alkyl or alkenyl, and at least 50% of the RRMUs have a first RRMU structure. These copolymers are advantageous in that they are biodegradable and exhibit a good combination of physical properties that allow them to be processed into films, sheets, fibers, foams, molded articles, nonwoven fabrics, and the like, and provide a variety of useful articles. However, these copolymers are not soft and elastic while maintaining their strength when they are in their original unstretched state.

Polyhydroxyalkanoate (PHA) copolymers essentially composed of repeating units having relatively long alkyl pendant groups of 3 to 9 carbon atoms, such as polyhydroxyoctanoate, exhibit ductile and rubbery elasticity with several levels of strength. It is known to represent (see, eg, KD Gagnon, RW Lenz, RJ Farris and RC Fuller, Macromolecules, vol. 25, pp. 3723-3728, 1992). However, the usefulness of flexible and elastic products made from such PHA copolymers is disappointingly limited by the low melting temperature around 60 ° C. The dimensional stability of the product is endangered even at summer warehouse temperatures, which can exceed 80 ° C. Thus, biodegradable ductile and elastic products made from polymers having a high melting temperature range are desirable.

It is often desirable to stretch thermoplastic polymers to change their physical properties. Unfortunately, PHB and PHBV form brittle products that are typically split even when taken only to a very small degree. Various methods have been attempted, for example, as disclosed in Holmes, U.S. Pat. No. 4,537,738 and Barham et al., U.S. Pat. Has been. Additional methods are described in Safta European Reference EP 736,563 A1, the Institute of Physical and Chemical Research European Reference EP 849,311 A2, the Waldock WO reference 97/22459, Kusaka et al., Pure Appl. Chem., 834 (2): 319-335 (1998) and Yamamoto et al., Intern. Polymer Processing XII, (1997) 1: 29-37. However, these methods have not been particularly successful in providing a means for easily forming an elongated product having a specific combination of desired properties. In particular, the prior art does not provide polymer products having ductility and elasticity while maintaining strength.

Thus, it is advantageous to obtain a biodegradable polymeric product having the desired combination of ductile and elastic properties that enable the use of the product in a wide range of applications.

[Overview of invention]

It is therefore an object of the present invention to provide novel products and methods that overcome the disadvantages of the prior art. It is an object of the present invention to provide a polymeric article formed from a composition containing a biodegradable polymer. It is also an object of the present invention to provide a polymeric article exhibiting an advantageous combination of properties. A more specific object of the present invention is to provide a biodegradable polymer product exhibiting ductility and elasticity while maintaining strength. Another object of the present invention is to provide a method for easily forming the products. In addition, it is an object of the present invention to provide articles comprising said polymeric article.

These and additional objects and advantages are provided by the products and methods of the present invention. In one embodiment, the present invention relates to a polymeric product obtained by stretching a composition containing a biodegradable polyhydroxyalkanoate copolymer. Biodegradable polyhydroxyalkanoate copolymers contain two or more randomly repeating monomer units (RRMU). The first RRMU has the structure of Formula I:

[Wherein, R ¹ is H or C1 or C2 alkyl and n is 1 or 2].

The second RRMU is different from the first RRMU and has a structure of Formula II:

[Wherein m is 2 to about 9].

At least about 70 mol% of the copolymer contains RRMUs having the first RRMU structure of Formula (I). Suitable polymeric articles include, but are not limited to, films, sheets, fibers, nonwovens, and articles formed by combining a plurality of fibers (eg, nonwoven sheets, etc.). The polymeric article of the present invention is advantageous in that it exhibits a combination of ductility and elasticity while maintaining strength.

In another embodiment, the present invention is directed to a method of forming an improved biodegradable polymeric article. The method comprises stretching a composition containing a biodegradable polyhydroxyalkanoate copolymer at a temperature above the glass transition temperature T _{g of the} composition and below the melting temperature T _m of the composition. The biodegradable polyhydroxyalkanoate copolymer contains two or more RRMUs, where the first RRMU has the structure of Formula I, the second RRMU is different from the first RRMU and has the structure of Formula II. , All as defined above, wherein at least about 70 mol% of the copolymer contains an RRMU having the structure of the first RRMU of Formula (I). Conveniently, conventional solid state stretching can be used. Thus, the process of the present invention provides a stretched polymer article that includes relatively easy steps and has an advantageous combination of physical properties, compared to many of the cumbersome methods of the prior art for making stretched polymer articles.

These and additional objects and advantages will be understood in more detail in light of the following detailed description.

The present invention relates to polymeric products obtained by stretching compositions containing biodegradable polyhydroxyalkanoate copolymers, including but not limited to films, fibers, nonwovens, and sheets. The article exhibits a preferred combination of ductility and elasticity while maintaining strength. The products are useful for a variety of biodegradable articles, including diaper topsheets, diaper backsheets, garbage bags, food packaging, disposable garments, and the like.

Without being bound by theory, it is believed to some extent that the stretching method is to orient the copolymer chain of the product according to the invention. The stretched polymeric articles of the present invention exhibit an unexpectedly advantageous combination of physical properties, in particular exhibiting ductility and elasticity while maintaining strength. In particular, the stretched polymeric articles of the invention are compared to unstretched articles of the same composition, for example, by higher strengths measured by higher tensile stress at break, and by lower tensile modulus, for example. Higher ductility all. This combination of properties is a very unintended consequence of stretching. Typically, stretch processing results in a stronger and more rigid (less soft) product, rather than being stronger and softer. For example, for fibers, MSM Mark is described in Polymer Science Dictionary , Elsevier Applied Science, New York (1989), p. 295, "drawn or spun fibers are slowly oriented along their length to enhance strength and stiffness in this direction due to uniaxial orientation," LE Nielson and RF Landel [295]. Mechanical Properties of Polymers and Composites , 2nd Edition, Marcel Dekker, Inc., New York (1994), p. 116, "Many oriented fibers have a Young's modulus of approximately one order of magnitude greater than that of an unoriented polymer." For films, Nielson and Landel (p. 116) also note that "biaxially oriented films made by stretching in two mutually perpendicular directions have reduced creep and stress relaxation compared to unoriented materials. Part of the effect is due to the increased coefficient. "

The products exhibit good elasticity in that they can recover quickly when strain or pressure are removed. In a preferred embodiment, the elasticity represented by the present products is the springy that the products easily respond to the applied stress and quickly return to their original form after release of the strain stress. This elastic behavior exhibited by the preferred product according to the invention can be similar to that of vulcanized rubber and certain synthetic thermoplastic elastomers. However, the product also exhibits high strength and creep resistance, such that the product is not affected by immature deformation at low stresses and sagging when used. The products of the present invention also exhibit good ductility in that they can be bent, twisted or folded without breaking. In a preferred embodiment, the ductility involves a flexible property that allows the material to bend, twist or fold easily without any indication of damage. Thus, the product is highly oriented, exhibiting enhanced flexibility or drape, i.e., flexibility and resilience at small deformations, providing that the product fits more easily around the object and fits more comfortably. It can exhibit high strength at large deformations, which are generally surpassed only by modified materials. In addition, the product does not exhibit the tack associated with many conventional elastomers without the use of other antiblocking agents or powders, which may negatively interact or affect performance in the desired application. Importantly, the product is biodegradable.

The stretched polymeric product is formed from a composition containing a biodegradable polyhydroxyalkanoate copolymer containing two or more RRMUs. The first RRMU has the structure of formula I:

[Formula I]

[Wherein, R ¹ is H or C1 or C2 alkyl and n is 1 or 2].

In a preferred embodiment, R ¹ is a methyl group (CH ₃ ), so the first RRMU has the structure

[Wherein n is 1 or 2].

In a more preferred embodiment of the first RRMU, R ¹ is methyl and n is 1, so the polyhydroxyalkanoate copolymer contains 3-hydroxybutyrate units.

The second RRMU contained in the biodegradable polyhydroxyalkanoate copolymer is different from the first RRMU and has the structure of Formula II:

[Formula II]

[Wherein m is 2 to about 9].

In general, in the RRMU of Formula II, the length of (CH ₂ ) _m will to some extent affect the reduction in the overall crystallinity of the copolymer. In a preferred embodiment, m is from 2 to about 9, more preferably from about 2 to about 5. In a more preferred embodiment, m is about 3.

In order to obtain an advantageous combination of physical properties represented by the stretched polymeric product of the present invention, while maintaining the biodegradability of the polyhydroxyalkanoate copolymer, at least about 70 mole% of the copolymer is selected from the It contains RRMUs having the structure of RRMUs. Suitably, the molar ratio of first RRMU to second RRMU in the copolymer ranges from about 70:30 to about 98: 2. More preferably, the molar ratio is in the range of about 75:25 to about 95: 5, and even more preferably, the molar ratio is in the range of about 80:20 to about 90:10. As a result, the polyhydroxyalkanoate copolymer suitably has a number average molecular weight of greater than about 150,000 g / mole. Without being bound by theory, it is believed that the combination of the chain length of the second RRMU and the molar amount indicated sufficiently reduces the crystallinity of the first RRMU, forming a copolymer having desirable physical properties.

In further embodiments of the polyhydroxyalkanoate copolymer used in the composition, one or more additional RRMUs may be contained. Suitably, the additional RRMU may have a structure of formula III:

[Wherein, R ³ is H or a C1-C19 alkyl or alkenyl group, p is 1 or 2].

However, the additional RRMUs are not the same as the first and second RRMUs.

Biodegradable polyhydroxyalkanoate copolymers are for example chemically or biologically based as disclosed in U.S. Patent 5,618,855 to Noda and U.S. Patent 5,942,597 to Noda et al., Both of which are incorporated herein by reference. It can be synthesized by the method.

The composition preferably contains more than about 50% by weight of the biodegradable polyhydroxyalkanoate copolymer, wherein the copolymer is preferably present as a continuous phase in the composition. In one embodiment, the composition may contain only polyhydroxyalkanoate copolymer as the polymerizable component, while in other embodiments, one or more additional polymers or copolymers may be polyhydroxyalkanoate copolymers. It may be contained in combination with. For example, the composition may be a combination of two or more of such biodegradable polyhydroxyalkanoate copolymers, a combination of biodegradable polyhydroxyalkanoate copolymers as defined herein, and other polyhydroxyalkanoate Copolymers and / or additional polymerization components such as additional polyester components and the like. In such embodiments, the biodegradable polyhydroxyalkanoate copolymer preferably comprises at least about 50% by weight, more preferably at least about 60% by weight, even more preferably at least about 75% by weight in the composition.

The composition may additionally contain various nonpolymerizable components including nucleating agents, antiblocking agents, antistatic agents, slipping agents, preheat stabilizers, antioxidants, preliminary oxidation additives, pigments, fillers and the like. Typically, these additives can be used in conventional amounts, although such additives are not required in the composition to obtain an advantageous combination of ductility, elasticity and strength. In addition, one or more plasticizers may be used in the composition in conventional amounts, although plasticizers are not typically required to obtain advantageous combinations of the properties discussed above.

While maintaining strength, the upper limit of the use temperature of biodegradable polymeric articles exhibiting a desirable combination of ductility and elasticity can be substantially higher than room temperature because of the relatively high melting temperatures of the polymers used to make such articles. Preferably the upper limit of the use temperature of the product may exceed 80 ° C., more preferably 100 ° C., even more preferably 120 ° C. without melting or becoming excessively soft.

The polymeric product may be in any physical form and typically include a product from a stretched film, sheet, fiber or nonwoven or a stretched film, sheet, fiber or nonwoven. For example, the stretched nonwoven product may be spunbonding, melt blowing, air-laying, carding, hydroentangling, or a combination of the foregoing. It can be produced by stretching a nonwoven structure made by conventional means, wherein the nonwoven is joined by any means known in the art, including but not limited to thermal, mechanical, chemical or adhesive bonds. Can be. Alternatively, the plurality of drawn fibers can be combined to form a nonwoven that can exhibit similar ductility, elasticity, and strength properties to the above approach. In addition, the stretched polymeric product need not be limited to single component structures such as, for example, monolayer films or single yarn fibers. Stretched polymer products include (1) side-side, sheath-core, multiple-segments, island-in-the-sea and matrix-fibrils Fibers or nonwovens having a morphology, (2) coextruded films or sheets constituting two or more layers, (3) films / fibers, sheets / fibers, films / nonwovens, or sheet / nonwoven composites, Or (4) a combination of 1-3, so long as the PHA copolymer (s) comprise at least 50%, more preferably at least about 60%, even more preferably at least about 75% by weight of the composition. Various multicomponent products may also be included, without being limited thereto. In addition, those skilled in the art have reviewed Polymer Blends and Alloys , MJ Folkes and PS Hope (editor), Chapman & Hall, New York (1993), and Plastics Films , 2nd edition, JH Briston, Longman Inc., New York (1983). It will be appreciated that the levels of elasticity, strength and ductility exhibited by the stretched multicomponent polymer product may be affected by the particular morphology and arrangement, as described in part in the text.

The stretched polymeric article can be conveniently formed by conventional solid state stretching techniques in which the composition is stretched at temperatures above the glass transition temperature T _g of the composition and below the melting point T _{m of the} composition. Preferably, the product is obtained by stretching the composition in solid state at a temperature above at least 20 ° C. (T _g + 20 ° C.) of the glass transition temperature of the composition and at a temperature below at least 20 ° C. (T _m -20 ° C.) of the melting temperature. do. The glass transition temperature of the polyhydroxyalkanoate copolymers used in the compositions of the present invention is generally below room temperature, ie, below about 25 ° C. Generally, the melting temperature of the copolymer is above about 100 ° C.

Those skilled in the art will appreciate that the levels of elasticity, strength and ductility, including the elastic properties exhibited by the stretched product, are not only at the stretching temperature, but also at the stretching speed and extent, whether the stretching is performed at a constant velocity or shift of displacement, deformation or stress, In the stretched form, film, sheet, or nonwoven fabric, whether the stretching is uniaxial or biaxial, if biaxial, may be influenced by whether the stretching step is performed continuously, simultaneously or by a combination thereof. Will understand. Stretching can be carried out at displacement, deformation or stress of constant velocity or shift according to techniques known in the art, see for example JH Briston, Plastics Films , Second Edition, Longman Inc., New York (1983), pp. 83-85 tenter framing method for films, sheets and nonwovens as described in, or by JE McIntyre and MJ Denton, Concise Encyclopedia of Polymer Science and Engineering , John Wiley & Sons, New York (1990) ) pp. 390, 391 and 395 there is a spinning operation using a roll of rolls or filament for fiber products such as described. In addition, for films, sheets and nonwovens, the stretching can be carried out uniformly across the form, for example, as achieved by the tenter framing method, or for example with the areas remaining substantially unstretched. It may be performed incrementally across the shape, such as in ring rolling operations such as those described in US Pat. Nos. 4,116,892 and 5,296,184, where elongated alternating parallel regions coexist. Additionally, for blowing films and sheets, stretching is described in JH Briston, Plastics Films , 2nd Edition, Longman Inc., New York (1983), p. 85 may be performed by a double or tubular bubble method. Furthermore, depending on the intended use, the stretching of the films, sheets and nonwovens can be carried out uniaxially or biaxially, in which case the stretching step is carried out continuously, simultaneously or in any combination thereof according to techniques known in the art Can be performed. All of the methods described above, including uniform stretching methods for stretched films, sheets, and nonwovens, as well as incremental stretching methods, can be used and are within the scope of the present invention.

The degree of stretching must exceed the yield point or neck point in stretching in at least one direction while remaining below the breakpoint in all stretching directions. Preferably, the product is in one or more directions with more than about 50% of deformation from its initial unstretched state, more preferably with more than about 100% of deformation from its initial unstretched state. Obtained by stretching the composition in one or more directions. In a more preferred embodiment, the article is in one or more directions, more preferably from about 300% to about 300% from its initial unstretched state from its initial unstretched state. Obtained by stretching the composition in one or more directions to a degree of deformation in the range of 1000%. In addition, those skilled in the art will further understand that the effective deformation in each stretching direction depends on the deformation method and geometry. For example, in a uniform stretching method such as fiber spinning, the effective strain is determined by the drawdown ratio, which is the ratio of the speed of the fiber exiting the pod or draw roll divided by the speed of the fiber entering the pod or draw roll. It is proportional to the total change in sample length. Conversely, in incremental stretching methods such as, for example, ring rolling, the effective strain is determined by the draw ratio in each draw or gauge region, such as disclosed in U.S. Patent No. 4,116,892, referenced above, which is generally It is not proportional to the total change in sample length but is proportional to the local change in length within each draw region.

In general, once stretching is complete, the stretched polymeric article may be cooled below its glass transition temperature, or the stretched form may be at temperatures above the glass transition temperature of the composition and below the melting temperature of the composition, typically about A heat-fixing step can be carried out which is annealed under deformation in the range of T _g + 20 ° C. to about T _m -20 ° C.

Solid state stretching can be performed using any suitable apparatus known in the art as discussed above. The examples listed below describe the use of an Instron universal testing machine, but one of ordinary skill in the art will recognize other devices that may be used. The Instron or other stretching device used is preferably equipped with an environmental chamber to provide a thermally controlled stretching method. If used, it will be understood by those skilled in the art that the stretching conditions and the heating and cooling conditions may be determined as described herein depending upon the desired intended use application for the given composition.

Stretched articles of the invention are advantageous in exhibiting a good combination of ductility and elasticity while maintaining strength. More specifically, the stretched polymeric articles of the present invention, when compared to unstretched articles of the same composition, (1) higher strength measured by, for example, higher tensile stress at break, (2) eg Higher ductility measured by low Young's modulus, and (3) higher elasticity measured by higher percentage recovery after release of strain stress, for example. In a preferred embodiment, the stretched polymeric article has a tensile strength of greater than about 15 MPa, preferably greater than about 20 MPa, measured for example according to ASTM D882-97. Additionally, in preferred embodiments, the stretched polymeric article has a Young's modulus of less than about 400 MPa, more preferably less than about 300 MPa, even more preferably less than about 200 MPa, for example, measured according to ASTM D882-97 for the film. Has

The elasticity of the stretched product, in particular the springiness of the product, allows the product to recover substantially when the stretched product is elongated, for example, during use. Thus, in a preferred embodiment, the stretched polymeric article is less than about 65% of the article in less than about 15 seconds when the article is stretched to about 50% or less, for example, measured according to ASTM D5459-95 for the film. It exhibits elastic behavior that causes recovery. More preferably greater than about 75% recovery, even more preferably greater than about 85% recovery.

Stretched products include disposable eco-friendly packaging, outer packaging, absorbent articles including diaper / sanitary napkins / panty liners, nonwoven cores, and backsheets, stretched films including food and pallet packaging, agricultural films, mulch Films, balloons, skin packages, stretch packages, bags containing food and garbage bags, contraceptives containing condoms and pessaries, shrink wrap, synthetic paper, carpets, fishing lines, hospital gowns, gloves, plasters, wound bandages, It is useful for constructing a variety of biodegradable articles including agricultural use, including disposable garments including shirts and socks, disposable surgical drape, sutures, letter envelopes and roadside covers, flower bed covers, grass covers, and weed barriers.

The products and methods of the present invention will be further illustrated in the following examples. In the examples and throughout this specification, parts and percentages are by weight unless otherwise specified.

Example 1

This example illustrates the uniaxial stretching of a melt extrusion casting film according to the present invention. Specifically, the copolymer of 3-hydroxybutyrate and 11.1 mol% 6-hydroxyhexanoate (hereinafter PHBHH copolymer) is melt extruded into a cast film of varying thickness in the range of about 0.004 to about 0.005 inches. . A rectangular piece of about 1 x 4 inches is cut out of the film so that the long direction is parallel to the machine direction of manufacture. The individual pieces are placed on an Instron universal testing machine (Model 1122, Canton, Mass.), With the test gauge length of 1 inch so that the long direction is the takeover direction. Testing machine MTS Systems Corp., Research Triangle Park, Sintech ReNew TM 1122 / R upgrade package, the test control and analysis TestWorks ^TM V3.02 software, and a 200 lb _f high / low pressure from the grip for NC (grip, model S512 .01) and MTS Direct, Eden Prairie, Environmental Chambers from MN, Series 3710, to provide thermally controlled uniaxial stretching. For tests where the stretching temperature differs from room temperature, the test pieces are equilibrated for about 2-3 minutes before the start of the stretching method. Using a stretching temperature of about 60 ° C. and an initial strain of about 2 in / in-min, the film pieces of the PHBHH cast film can be extended by more than about 600% before breaking. In addition, the stretched pieces exhibit elastic behavior, i.e., when caught and pulled between the thumb and index finger of each hand of the technician, the film easily extends and quickly returns to its original length after release. This behavior illustrates that the PHBHH film composition is very flexible and the stretched PHBHH film composition is elastic.

Example 2

This example illustrates the uniaxial stretching of the melt spun fibers of the PHBHH copolymer according to the present invention. The PHBHH copolymer from Example 1 is melt spun into fibers having a diameter of about 4 mm. About 3 inches of test strands are cut from the PHBHH fibers. According to the stretching procedure described in Example 1, a stretching temperature of about 60 ° C. and an initial strain of about 2 in / in-min can be used to stretch the strands of PHBHH fibers by more than 400% before breaking. In addition, the stretched fiber strands exhibit elastic behavior, i.e., when caught and pulled between the thumb and index finger of each hand of the technician, the fiber easily extends and quickly returns to its original length after release. This behavior illustrates that the PHBHH fiber composition is very flexible and the stretched PHBHH fiber composition is elastic.

Example 3

This example illustrates the biaxial stretching of a PHBHH melt extruded cast film according to the present invention. At a temperature of about 60 ° C. and an initial strain of about 4 in / in-min, according to the procedure described in Example 1, the film piece of the PHBHH copolymer cast film of Example 1 is first drawn to about 150%. The stretched sample is then rotated 90 ° in the test machine such that the first stretching direction is perpendicular to the take-up direction. A second stretching of about 150% elongation is performed at a temperature of about 60 ° C. and an initial strain of about 4 in / in-min. The elasticity of the resulting biaxially oriented film is easily identified because the film quickly recovers to its original length after release of the strain force, simply by stretching the film by hand.

Example 4

This example compares the tensile properties of stretched and unstretched PHBHH melt extruded cast films. Specifically, the tensile properties of the pieces of stretched and unstretched PHBHH melt extruded cast films from Example 1 were measured using an Instron Universal Tester as described in Example 1 by the method outlined in ASTM D882-97. do. The drawn sample is produced at a draw temperature of about 60 ° C. and an initial strain of about 4.0 in / in-min. The stretched film is stronger, as evidenced by higher stresses at break, and softer as evidenced by Young's modulus, but less as evidenced by lower strain at break, as compared to the unstretched counterparts. Elongation is possible.

Example 5

This example illustrates the elastic recovery of the drawn PHBHH melt extrusion casting film according to the present invention. The elastic properties of the stretched PHBHH cast film from Example 1 are measured by defining the dimensional recovery exhibited by the film when stretched in an Instron universal tester as described in Example 1. The stretched film is stretched to a predefined elongation at room temperature with an initial strain of 1.0 in / in-min, and the reduction in strain is measured after the applied stress is removed and a relaxation time of about 10-15 seconds. Stretched PHBHH film pieces exhibit short term recovery from greater than about 85% to up to about 100% elongation. This behavior illustrates the long-range mechanical elasticity of the product according to the invention.

Example 6

This example illustrates an elastic and flexible bandage formed from a stretched PHBHH cast film according to the present invention. The stretched film is prepared from the PHBHH cast film of Example 1, wherein the stretching method is performed at a temperature of about 60 ° C. and an initial strain of about 4.0 in / in-min. A 0.75 × 3 inch piece of film is cut out of the drawn PHBHH film. A 0.75 × 1.0 inch absorbent pad is applied in length to the center of the piece, and a self-adhesive Velcro piece is attached to the end to form a bandage. The use of a band-aid on the index finger tends to bend the film easily and follow both the front and back and bending motion of the index finger without sagging.

Example 7

This example illustrates the fabrication of an elastic, soft nonwoven sheet from elongated PHBHH fibers according to the present invention. Nonwoven sheets are made from drawn PHBHH fibers. The melt spun PHBHH fibers are drawn at a temperature of about 60 ° C. and an initial strain of about 3.0 in / in-min as described in Example 2. Cut several stretched strands to 3 inches long, and cut two polytetrafluoroethylene (Teflon 10 mm thick, randomly placed between 6 × 6 inch sheets, and Carver the whole Place between the platens of the experimental oil press. The upper platen is preheated to a melting point of PHBHH defined by calorimetry above about 15 ° C. and has equally spaced spot bonding patterns of 25 1.0 mm diameter bonds per square inch. Sufficient pressure is applied to allow the bond spots to soften and fuse. The pressure is released and the nonwoven sheet is cooled to room temperature before removing the outer polytetrafluoroethylene sheet. The elasticity of the nonwoven sheet is easily identified because by simply stretching the film by hand, the film quickly returns to its original dimensions after the release of the applied strain.

Example 8

This example illustrates the uniaxial stretching and conventional tensile properties of conventional melt extrusion casting films. The melt extruded cast film is made of polycaprolactone (Tone). P787, Union Carbide,), Bionolle 1001 and 3001 (Showa Highpolymer Co., LTD., Tokyo, JP), Eastar 14766 (Eastman Chemical Company, Kingsport, TN), and BAK 1095 (Bayer Corporation, Pittsburgh, PA) As well as several biodegradable polymers, polypropylene (type 7300 KF, Millennium Petrochemicals, Cincinnati, OH), high density polyethylene (HDPE) (type LTPR059, Millennium Petrochemicals, Cincinnati, OH) and 50:50 weight ratio low density polyethylene (LDPE ): Made from several non-degradable polymers containing linear low density polyethylene (LLDPE) blends (types NA940000 and GA5010110, Millennium Petrochemicals, Cincinnati, OH, respectively). Following the sample preparation and stretching procedure described in Example 1, using a stretching temperature of about 25 ° C. and an initial strain of about 1.0 in / in-min, film pieces of various cast films can be extended to greater than 300% before breaking. have. The behavior is consistent with the flexible film composition.

The tensile properties of the drawn melt extruded cast film pieces are defined as described in Example 1 using an Instron Universal Tester, by the method outlined in ASTM 882-97. Orthopedic, various stretched films of the stretching method are stronger as evidenced by the higher stress at break, but more rigid as demonstrated by the higher Young's modulus, and more fracture at break compared to the unstretched counterparts. Less extensible as evidenced by low stress.

The comparison of the tensile properties of the stretched PHBHH film from Example 4 with the tensile properties of the stretched film from this example indicates that the PHBHH film is softer than the stretched film formed from conventional compositions. In fact, the stretching method enhances the ductility of the PHBHH film as evidenced by the decrease in Young's modulus, while the conventional compositions all exhibit an increase in stiffness as evidenced by an increase in Young's modulus. In all cases, the stretched film shows some level of recovery from small extension strains; This makes it more difficult to extend the stretched film formed from the conventional composition beyond the relatively low elongation compared to the stretched film according to the present invention. For example, a 10 lb draw force or equally 35 MPA stress on a 0.002 inch thickness of a 1 inch wide piece of film results in an immediate 45% extension to the drawn PHBHH film, while a stretched film formed from a conventional composition At most immediately results in an 8% extension.

Example 9

This example illustrates the fabrication of a nonwoven sheet using a melt blown method. Specifically, the PHBHH copolymer of Example 1 is fed to an extruder which gradually melts the polymer as the polymer is fed to a melt blown die. The die is oriented linearly in the cross machine direction, metering the polymer into a balancing channel narrowed to a spinneret of several holes per linear inch. At the exit point, the polymer strands are tapered by heated high velocity air. The fibers formed are continuous and extremely fine and are blown on a moving collector screen to form a nonwoven structure. The fabric is thermally bonded by passing the fabric through a two-roll stainless steel stack roll, and on one of the fabrics there are about 25 1.0 mm diameter bond spot bonding patterns per square inch. The stack roll is preheated above about 15 ° C. of the melting point of the PHBHH composition defined by calorimetry, and when the foam passes through the stack roll, sufficient pressure is applied to the fabric to soften and fuse the spot bonds. The lack of elasticity is easily discernible by simply stretching the nonwoven by hand, since the fabric is not easily stretched and does not recover to its original dimensions after release of the applied strain.

Example 10

This example illustrates the fabrication of an elastic nonwoven sheet from a molten blown nonwoven. A rectangular piece of about 1 × 4 inch is cut out of the bonded PHBHH fabric described in Example 9 so that the long direction is parallel to the machine direction of manufacture. According to the stretching procedure described in Example 1, an elongated piece of PHBHH nonwoven can be produced using a stretching temperature of about 60 ° C. and an initial strain of about 1.0 in / in-min. The elasticity of the stretched nonwoven sheet is easily discernible, even by simply stretching the sheet by hand, because the sheet is easily stretched and quickly recovered to its original dimensions after releasing the applied deformation. Comparison of this behavior with that of Example 7 indicates that similar nonwoven products of similar elasticity can be made by stretching nonwoven sheets produced using conventional means or by making nonwoven sheets from the drawn fibers.

Example 11

This example illustrates the fabrication of a flexible film product by incrementally stretching a PHBHH film in a ring rolling operation according to US Pat. No. 4,116,892. The melt extruded PHBHH cast film of Example 1 is introduced in the machine direction of production through a pair of grooved rolls preheated to a temperature of about 60 ° C. The grooves are perpendicular to the machine direction of the film, have a sinusoidal shape approximately 3 mm deep and 3 mm spaced, making a pull rate of about 2. When the film is stretched to match the shape of the grooves, the eight groove ends simultaneously fill the film. The film is introduced into a nip of fine rolls with intermeshing grooves rotating at about 2 RPM, created at a feed rate of approximately 2 feet per minute, and wound at about 4 feet per minute. The film has a relatively transparent line with an opaque portion uninterrupted at about 3 mm intervals, corresponding to the contact point or stretched area. The elasticity of the ring rolled PHBHH film is easily discerned in the direction parallel to the machine direction, even by simply stretching the sheet by hand, since the sheet is easily stretched and quickly recovered to its original dimensions after releasing the applied deformation. In contrast, stretching the film in a direction perpendicular to the machine direction does not exhibit any apparent elasticity or elasticity since the sheet is not easily stretched and does not recover to its original dimensions after release of the applied strain. This example illustrates that a ring rolling operation can impose uniaxial or directional elastic behavior on a preferred film product. This approach is also applicable to preferred sheet and nonwoven products.

Example 12

This example illustrates the production of a stretched film product by stretching the film of Bionolle 3001 (Showa Highpolymer Co., LTD., Tokyo, JP) incrementally by a ring rolling operation. Specifically, about 0.002 inches of Bionolle 3001 melt extruded cast film was ring rolled according to the procedure described in Example 11, using a grooved roll at a temperature of about 25 ° C. The lack of elasticity is easy because, in the direction parallel and perpendicular to the machine direction of manufacture, the film is not easily elongated and simply does not recover to its original dimensions after release of the applied strain, even by stretching the ring rolled film product by hand. Are identified. In fact, ring rolling operation permanently deforms the Bionolle 3001 film in the machine direction.

Example 13

This example illustrates the fabrication of a shrinkable film product by incrementally stretching a multilayer film in a ring rolling operation. Specifically, the PHBHH copolymer of Example 1 was coextruded with the Bionolle 3001 resin of Example 12 into a two-layer cast film article having a thickness of about 0.002 inches for the PHBHH layer and about 0.001 inches for the Bionolle 3001 layer. The PHBHH / Bionolle film is then ring rolled using a grooved roll at a temperature of about 60 ° C. according to the procedure described in Example 11. The ring rolling operation results in a shrinkable film product in which the PHBHH layer is elastic as described in Example 11, and the Bionolle 3001 layer is inelastic and permanently deformed as described in Example 12, wherein the Bionolle layer is applied Upon release of the deformation, wrinkles and pleats form due to PHBHH layer shrinkage. In addition, the Bionolle layer limits the extent to which the article can elastically extend to at least the initial stretch point.

Example 14

This example illustrates the fabrication of disposable infant diapers, with the listed dimensions ranged for use by children of 6-10 kg in size. The dimensions can be modified proportionally for children of different sizes or for adult incontinence pants according to standard practice.

1. Backsheet: 0.020-0.038 mm film composed of PHBHH copolymer from Example 1; 33 cm wide at the highest and lowest points; Internally notched on both sides with a width of 28.5 cm at center; Length 50.2 cm.

2. Topsheet: carded and heat bonded staple-length polypropylene fibers (Hercules Type 151 Polypropylene); 33 cm wide at the highest and lowest points; Internally notched on both sides with a width of 28.5 cm at center; Length 50.2 cm.

3. Absorbent core: 28.6 g of cellulose wood pulp and 4.9 g of absorbent gelling material particles (polyacrylates available from Nippon Shokubai); 8.4 mm thick, calendered; 28.6 cm wide at the highest and lowest points; Internally notched on both sides with a width of 10.2 cm at center; Length 44.5 cm.

4. Elastic leg bands: four individual rubber straps (two per side); 4.77 cm in width; Length 37 cm; Thickness 0.178 mm (all the above dimensions are in the relaxed state).

Diapers are manufactured in a standard manner by placing and adhering the core material covered with the topsheet on the backsheet.

Elastic bands ("inner" or "outer", meaning each corresponding to the closest and distal band from the core) are stretched to about 50.2 cm and topsheet / back along each longitudinal side of the core (two bands per face). Place between sheets. The inner band along each side is disposed about 55 mm (measured from the inner edge of the elastic band) from the narrowest width of the core. This provides a spacing element along each side of the diaper which includes a flexible topsheet / backsheet material between the elastic and curved edges of the interior of the core. The inner bands are glued down along their length in the stretched state. The outer bands are located about 13 mm from the inner bands and are glued down along their length in the stretched state. The topsheet / backsheet combination is flexible, and the band bonded below shrinks to elasticize the sides of the diaper.

Example 15

The diaper of Example 14 is modified by replacing the elastic leg band with the flexible PHBHH film product described in Example 1.

Example 16

The diaper of Example 14 is modified by replacing the elastic leg band with the shrinkable film product described in Example 13.

The above-listed embodiments and examples are provided for illustrative purposes only and are not intended to limit the scope of the following claims. Further embodiments of the invention, and the advantages provided thereby, will be apparent to those skilled in the art and are within the scope of the claims.

Claims (10)

A polymeric product obtained by stretching a composition characterized by a biodegradable polyhydroxyalkanoate copolymer containing at least two randomly repeating monomer units, The first randomly repeating monomer unit has the structure of Formula I: [Formula I] [Wherein, R ¹ is H or C1 or C2 alkyl, preferably R ¹ is C1 alkyl, n is 1 or 2, preferably n is 1; The second randomly repeating monomeric unit is different from the first randomly repeating monomeric unit and has the structure of Formula II: [Formula II] [Wherein m is 2 to 9, preferably m is 2 to 5, more preferably m is 3], And at least about 70 mole% of the copolymer is further characterized in that the randomly repeating monomeric units having the structure (I) of the first randomly repeating monomeric units are preferably the first randomly repeating Monomer units: A polymer product comprising a molar ratio of second randomly repeating monomer units in the range of 70:30 to 98: 2, more preferably 75:25 to 95: 5. The polymeric article of claim 1, wherein the article is obtained by stretching the composition at a temperature above the glass transition temperature T _{g of the} composition and below the melting temperature T _m of the composition. The product according to claim 1 or 2, wherein the article has a strain of greater than 50% from the initial unstretched state, preferably a strain range of 200% to 1500% from the initial unstretched state, more preferably Is obtained by stretching the composition in a deformation range of 300% to 1000% from the initial unstretched state. The polymer product according to any one of claims 1 to 3, wherein the biodegradable polyhydroxyalkanoate copolymer has a number average molecular weight of more than 150,000 g / mol. The polymer product according to any one of claims 1 to 4, wherein the composition contains at least 50% by weight of biodegradable polyhydroxyalkanoate copolymer. The polymer product according to claim 1, wherein the product is in the form of a film. The polymer product according to claim 6, wherein the film is uniaxially or biaxially stretched. 7. The polymeric product of claim 6, wherein the film is stretched by ring rolling. 6. The polymeric article of claim 1 wherein the article is in the form of a fiber or nonwoven sheet. 7. 10. The product according to any one of the preceding claims, wherein the product exhibits an elastic behavior that recovers to at least 65% when the product is stretched by 50%, preferably when the product is stretched by 50%. A polymer product, characterized by exhibiting elastic behavior recovering by more than%.