CN1503824A - Polyhydroxyalkanoate Processing Using Nucleating Agents and Plasticizers - Google Patents

Abstract

The present invention relates to polyhydroxyalkanoate copolymer compositions which can be easily and rapidly processed into extrusions, moldings and film-based products. More specifically, the present invention relates to the melt processing of polyhydroxyalkanoates containing novel combinations of nucleating agents and plasticizers for increased crystallization rates resulting in improved processability.

Description

Polyhydroxyalkanoate Processing Using Nucleating Agents and Plasticizers

technical field

This invention relates to the field of polyhydroxyalkanoate polymers, articles made therefrom, and melt processing methods. More specifically, the present invention relates to melts of polyhydroxyalkanoates containing novel combinations of nucleating agents and plasticizers for increased chain mobility, crystallization rate with the aim of improving processability in conventional melt processes. body processing and cast film extrusion.

Background technique

Polyhydroxyalkanoates (PHA) and other thermoplastic polyesters represent potential raw materials for countless useful products. Examples include melt-spun fibers that can be used to produce nonwovens for medical gowns and face shields, blown and cast films for compostable grocery and garbage bags, injection molded bottles for health and personal care products, and biodegradable / Extrusion coating on paper/board for compostable fast food containers. In the process of producing PHA products, it is important to achieve economically desirable line speeds, cycle times, and other processing parameters.

Polyhydroxyalkanoate copolymers, at least in part due to the extremely slow crystallization rate of their crystalline domains, are extremely viscous when melt processed. This sticky or "sticky" behavior renders the polymer incapable of being processed through any melt processing equipment, including extrusion, compounding, film and fiber operations. Unmodified polymers have a strong tendency to stick to all mechanical parts, regardless of the material of construction. The polymer also has a strong tendency to self-adhesive and stick to human skin when touched. From a few minutes to a few hours, this stickiness or stickiness will gradually disappear. However, this time frame is significantly long for any conventional processing technique, which generally requires the polymer to become tack-free in the range of a few seconds.

Previous work has shown that the addition of crystallization nucleating agents to some compositions of polyhydroxyalkanoate copolymers increases the rate of crystallization to the point where melt processability is acceptable. In addition, such nucleating agents sometimes improve the physical and mechanical properties of processed articles. Customary nucleating agents include, for example, talc, micronized mica, calcium carbonate, boron nitride (see for example EP 0291024) and ammonium chloride (see for example WO 9119759).

US 5,296,521 describes polyester compositions having increased crystallization rates, comprising a thermoplastic polyester resin and 0.5 to about 5 wt% of a nucleating agent of formula RO[P(O)(Ph)(CH ₂ ) _m O]nH, formula wherein R is an alkali metal or alkaline earth metal; m is 1, 2, or 3; n is an average value within the range of 1-5. The nucleating agent may optionally be mixed with its acid or ester form as long as at least 50 mole percent of the nucleating agent is in the salt form. The nucleating agent is preferably in the form of a sodium salt (eg, hydroxymethylphenylphosphonic acid sodium salt or oligomethylenephenylphosphonic acid sodium salt).

US 4,536,531 describes the use of carboxylates of metals of Groups I and II of the Periodic Table of the Elements as nucleating agents for polyesters and lists aliphatic monocarboxylic acids such as acetic acid, propionic acid, hexanoic acid, palmitic acid, hard Metal salts of fatty, oleic, behenic and montanic acids. Suitable metals are sodium, potassium, lithium, magnesium, calcium, barium and zinc. In these carboxylates, it is not necessary that all of the carboxyl groups are converted into salt form, but a part of the carboxyl groups may be in salt form and the remaining groups may be in free acid or ester form.

Several references disclose the use of organophosphorus compounds as nucleating agents. US 5,061,743 discloses a preferred polyhydroxyalkanoate nucleating agent made by dry blending cyclohexylphosphonic acid and zinc stearate with polyhydroxybutyrate covalerate. The nucleating agent is disclosed as being particularly advantageous for the nucleation of polyhydroxybutyrate covalerate with a high hydroxyvalerate content. WO 9905208 discloses that organophosphorus compounds having at least two phosphonic acid moieties can be used as nucleating agents for polyhydroxyalkanoates and other thermoplastic polyesters.

Although many of these compounds have shown effectiveness in increasing the nucleation density of polyhydroxyalkanoates and thereby increasing the rate of crystallization, certain disadvantages have been associated with their use. For example, the dispersion of particulate nucleating agents is problematic because agglomeration tends to occur during processing, which creates stress concentrations and non-uniform areas in molding. Furthermore, nucleating agents like boron nitride have been found to act as pigments in some cases, especially in films and injection molded articles, resulting in opaque products where transparent products are generally desired. Furthermore, some nucleating agent systems include components that may be environmentally and toxicologically undesirable.

Furthermore, the polymers of the previous references tend to be copolymers that do not contain comonomers effective to increase the amorphous character of the polymer or reduce its rate of crystallization. The resulting polymers tend to be brittle and lead to undesirable properties. Polyhydroxyalkanoate copolymers containing more modifying comonomers that result in a significant amount of amorphous phase tend to be more desirable polymers because they exhibit high levels of toughness and resiliency. However, the presence of a large amount of amorphous phase in these polymers is not conducive to good crystal formation or fast crystallization rates. Furthermore, the addition of nucleating agents to these polymers generally does not increase the number of crystals or the rate of crystallization sufficiently to make melt processing of these polymers feasible. Therefore, there is currently a need for benign and cost-effective nucleating agent systems that allow the production of polyhydroxyalkanoate resins with moderate to high crystallinity, excellent moldability, mechanical strength and dimensional stability.

Accordingly, the problem to be solved was to provide a polymer composition which yields a tough and flexible polyhydroxyalkanoate which can be easily and rapidly processed into film-based products. Another object of the present invention is to provide a continuous melt extrusion process for these polyhydroxyalkanoates. Still another object of the present invention is to provide a continuous cast film production method using these polyhydroxyalkanoates.

Contents of the invention

The present invention provides a polyhydroxyalkanoate copolymer composition that can be processed into film-based products, extruded and molded products, and coatings, comprising: (a) a polyhydroxyalkanoate copolymer, (b) a nucleating agent, and (c) a plasticizer; and a method of making the composition.

In a preferred embodiment, a unique combination of either poly-3-hydroxy(butyrate-co-caprylate) or poly-3-hydroxy(butyrate-co-caproate) is combined with polyhydroxybutyrate ( nucleating agent) and either methyl laurate or dibutyl maleate (plasticizer).

Detailed ways

The applicant et al. have addressed this problem by providing polyhydroxyalkanoate ("PHA") copolymers with a combination of nucleating agents and plasticizers. The addition of this nucleating agent and plasticizer to the PHA copolymer enables the crystallization process to occur within a time frame that enables practical melt processing. The present invention is applicable wherever it is desired to increase the rate of crystallization. Specifically, the nucleating and plasticizing agents are used to improve PHA and other thermoplastic polyester products by reducing the cycle time typically required for film, extrusion and molding, and coating production. produced.

Throughout this disclosure, a number of terms and abbreviations are used. The following definitions are provided.

"Poly(3-hydroxybutyrate co-3-hydroxyoctanoate)", also known as "poly-3-hydroxy(butyrate co-octanoate)", abbreviated as P3HBO.

"Poly(3-hydroxybutyrate co-3-hydroxyhexanoate)", also known as "poly-3-hydroxy(butyrate co-hexanoate)", abbreviated as P3HBH.

"Polyhydroxyalkanoate" is abbreviated as PHA.

"Polyhydroxybutyrate" is abbreviated as PHB.

polyhydroxyalkanoate

The polyhydroxyalkanoates ("PHA") of the present invention include naturally derived polymers such as polyhydroxybutyrate (PHB), including homopolymers of 3-hydroxybutyrate and 4-hydroxybutyrate. They also include copolymers of PHB with hydroxyacids, for example, copolymers of PHB with 3-hydroxyhexanoate, 3-hydroxyoctanoate, or longer chain hydroxyacids (e.g., _C9 - _C12 hydroxyacids), and its copolymers. The PHAs of the present invention may also be synthetically derived from hydroxycarboxylic acids. Further, the PHA can also have predominantly R(-) configuration, predominantly S(+) configuration, or random, block, or other combinations of R(-) and S(+) configurations. As will be understood by those skilled in the art, the R(-) and S(+) isomers refer to the ability of each repeat unit of the polymer to rotate plane polarized light in a counterclockwise or clockwise direction, respectively. Racemic copolymers consist of both R(-) and S(+) repeat units within the polymer, which units can be arranged in any combination including random or block configurations.

A preferred example of the polyhydroxyalkanoate copolymer used in the present invention is poly-3-hydroxy(butyrate co-octanoate) (y=3) (P3HBO)

R = CH ₃ (CH ₂ ) _y where y = 0-11 and poly-3-hydroxy(butyrate cohexanoate) (y = 1) (P3HBH). These block copolymers have the generalized structures shown below.

    m＝0.7-0.97 and n＝0.3-0.03, where m+n＝1.0

In general, block copolymers with a variety of different structures can be prepared. For example, an AB diblock copolymer has a block of polymer A segments coupled to a block of B polymer segments. ABA triblock copolymers have a block of B segments coupled to a block of A segments at each of their ends. -(AB) _n -Multi-block copolymers having alternating sequences of A and B segments, where n is a positive integer greater than one. Particularly preferred are random block copolymers in which the PHB segment comprises from 85 to about 95% by weight of the copolymer. For use in the present invention, the weight average molecular weight of PHA is about 600,000 to more than 1,000,000; the number average molecular weight is in the range of about 280,000 to 500,000 g/mol.

PHAs are generally difficult to process into films, fibers, monofilaments, rods, tubing or other forms with physical integrity using conventional melt processes. Conventional melt processes include continuous melt extrusion processes, cast film extrusion processes, blown film extrusion processes, melt spinning processes, and others that are generally known in the art. "Polymer that is difficult to melt process" means that the polymer exhibits an effective melt strength and/or solidification time that detracts from the ability to form a product with physical integrity by conventional melt extrusion processes.

"Effective melt strength" refers to the resistance of a molten polymer to sag to a desired dimension such as thickness (in the case of films) or diameter or denier (in the case of fibers or monofilaments). A polymer with low effective melt strength cannot withstand the minimum strain required to stretch the polymer melt to the desired dimensions. For example, the polymeric material may exhibit instabilities such as fracture, sag or draw resonance. The resulting product is often highly heterogeneous in physical integrity.

"Set time" means the period of time required for the molten polymeric material to achieve a substantially tack-free or tack-free physical state under a given set of process conditions. Cure time is important because blocking may occur if the polymer is not cured for an appropriate amount of time during processing. Thus, polymeric materials with residual tack may stick to themselves and/or to processing equipment even after cooling to room temperature or below. Such residual stickiness may limit the rate at which the product can be processed or prevent the product from being collected in a form of proper quality.

Cure time is affected by polymer material as well as processing equipment and conditions. Generally speaking, under customary process conditions, the curing time should be on the order of seconds. Such conditions typically include temperatures ranging from chill roll temperatures such as those known in the art to the melt temperature of the material being processed, which can be as high as about 150°C (preferably 120-135°C). In general, longer process cycle times (eg, from melt extrusion point to collection coiling point) tend to accommodate longer solidification times.

"Tacky" or "sticky" are known in the art and refer to stickiness or the amount of stickiness. Sticking is generally a subjective measurement of touching the film surface with a finger. A surface is "sticky" if it is "sticky" or sticky. Stickiness can be measured subjectively with the aid of many scales, but to illustrate the concept, consider flypaper to be the high point on the scale, and ^Teflon® sheets (polytetrafluoroethylene) (available from EI du Pont de Nemours and Company, Wilmington, DE) was not sticky. For the purposes of this invention, tack is measured subjectively by a single operator after pressing a film of an appropriate polymer blend five times between two sheets of Teflon ^(R) coated aluminum foil. After the fifth press, the sample film was allowed to cool at room temperature for 10 seconds and the relative force required to initially separate the film from the ^Teflon sheet was noted. In addition, the force required to peel the film from itself after folding on itself, as well as the force required to peel the polymer from the operator's glove, was also monitored subjectively. A "no stick" result was recorded when no appreciable additional force was required to remove the film from the Teflon( ^R) sheet or from itself after folding. A subjective grading scale of "slightly tacky" to "moderately tacky" indicates that greater force is required in each category to pull the film away from the Teflon ^(R) sheet and from itself, respectively. The "sticky" category indicates that the film was extremely difficult to remove from the Teflon ^(R) sheet when cooled at a standard time of 10 seconds, and was virtually impossible to separate from itself after folding.

Nucleating agent

"Nucleants" (or nucleating agents) are compounds used to artificially introduce nucleation sites for the crystallization of polyhydroxyalkanoates from the molten state. One description is given in US Patent No. 5,534,616 (beginning at column 1, line 36). This article is listed as a reference in this article. The nucleating agent helps to compensate for the slow crystallization rate of many PHAs due to their low nucleation density. A preferred amount of nucleating agent in the composition is from about 1% to about 10%, based on the total weight of the composition. The nucleating agent in the preferred compositions is polyhydroxybutyrate and is present in a range of from about 0.005% to about 20%, more preferably from about 0.05% to about 10%, based on the total weight of the composition , preferably in an amount of about 0.5% to about 5%.

plasticizer

In the compositions of the present invention, plasticizers are used to improve the mechanical properties of the formed product and to improve the processability of the composition. In general, plasticizers tend to reduce the modulus and tensile strength of the polymer product, and increase its ultimate elongation, impact strength, and tear strength. The plasticizer can also be used to lower the melting point of the composition to enable melt processing at lower temperatures. In the present invention, the plasticizer is used to lower the glass transition temperature, thereby being an aid in increasing the speed of reaching a non-tacky product.

External plasticizers known in the art include glycerin, ethylene glycol, and low molecular weight polyethylene glycols. Preferred plasticizers for the PHAs considered include dioctyl bis(2-ethylhexyl)maleate, paraffin, dodecanol, olive oil, soybean oil, polytetramethylene glycol, methyl oleate, ester, n-propyl oleate, tetrahydrofurfuryl oleate, epoxidized linseed oil, 2-ethylhexyl epoxy resinate, triacetin, methyl linoleate, difumarate Butyl ester, Methyl ricinoleate, Acetyl tri-n-butyl citrate, Acetyl triethyl citrate, Tri-n-butyl citrate, Triethyl citrate, Dimer acid bis(2-hydroxy ethyl ricinoleate), butyl ricinoleate, triglyceride (acetyl ricinoleate), methyl ricinoleate, acetyl ricinoleate n-butyl, propylene glycol ricinoleate, diethyl succinate, hexadiene diisobutyl azelate, dimethyl azelate, di(n-hexyl) azelate and tributyl phosphate. The best plasticizers for PHAs considered included methyl laurate and di-n-butyl maleate. Preferred amounts of plasticizer in the composition are from about 5% to about 35%, more preferably from about 12% to about 20%, by weight of the composition.

melt extrusion method

The extrusions and moldings of the invention are produced using customary melt extrusion methods. Such melt extrusion processes involve blending of the individual polymer components followed by extrusion of the blend. In a preferred embodiment, the strands of PHA polymer are extruded through a die plate at a temperature of about 120-160°C, more preferably 130-145°C, into a water bath having a temperature of about 30-40°C.

In a preferred melt extrusion process of the present invention, pellets of the individual polymer components are first prepared. The PHA nucleating agent and plasticizer can be dry blended first and then melt mixed in the film extruder itself. Alternatively, if insufficient mixing occurs in the melt extruder, the components can be dry blended first, then mixed in a pre-compounding extruder and subsequently extruded in a film melt previously made into pellets.

The PHA films of the present invention can be processed by conventional methods and used to produce single or multilayer films on conventional film making equipment. The cast or blown film extrusion process used to make the PHA films of the present invention is more fully described in U.S. Patent No. 6,027,787, by Allan A. Griff, Plastics Extrusion Technology-2nd Ed., incorporated herein by reference. Also described in Nostrand Reinhold, 1976). In a preferred embodiment, the PHA polymer continuous film is extruded at about 120 to 160°C, more preferably 120 to 140°C, onto rolls having a temperature of about 30 to 45°C, more preferably about 40°C .

"Film" means a continuous piece of extruded material having a high length/thickness ratio and an aspect/thickness ratio. While there is no requirement for an exact upper or lower thickness limit, preferred film thicknesses of the present invention are from about 0.05 to about 50 mils, more preferably from about 0.5 to about 15 mils. The films of the present invention may comprise one, two or more layers.

The PHA compositions of the present invention may also be manufactured into certain selected shapes using conventional injection molding techniques.

Example

The invention is further defined by the following examples. It should be understood that these Examples, while indicating preferred embodiments of the invention, are given by way of illustration only. From the above discussion and these Examples, one skilled in the art can ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.

The meanings of the abbreviations are as follows: "h" means hours, "min" means minutes, "sec" means seconds, "d" means days, "mL" means milliliters, "L" means liters, "ft" means feet, " lb" means pounds, and "g" means grams.

general method

Poly-3-hydroxy(butyrate-co-octanoate) (P3HBO) was purchased from Procter & Gamble (Cincinnati, Ohio, USA). Poly-3-hydroxy(butyrate-cohexanoate) (P3HBH) was purchased from Procter & Gamble (Cincinnati, Ohio, USA), Jiangmen Biotechnology Development Center, and Tsinghua University (China). PHB was supplied by Aldrich Chemical Company (St. Louis, MO).

Example 1

Identification of "active" nucleating agent and plasticizer combinations

The screening of nucleating agent and plasticizer combinations was performed as follows: Melt blends of the nucleating agent PHB with a PHA especially either P3HBO or P3HBH were prepared by first tank mixing the appropriate amount of PHB and either P3HBO or P3HBH powder of. Generally, 1 wt% PHB (0.75g) was added to P3HBO (74.25g) polymer and 3 wt% PHB (2.25g) was added to P3HBH (72.75g) polymer. (The percentage of nucleating agent added was determined by the anti-stick performance in preliminary experiments.) After tank mixing the appropriate components, the powder was fed to a small 16mm PRISM twin-screw extruder set to a maximum temperature of 155°C. In the plastic machine. The polymer was melt extruded through a single hole 3/16 inch die onto a water cooled "nonstick" tape in a water bath. The polymer tends to stick to the belt, which is cut into 2-3 ft lengths and draped over a rack to allow time for crystallization to occur. After 20 min-1 hr, the polymer strands had crystallized enough to be cut manually with scissors or run through a blade cutter to produce small (2-8mm long) pellets. The pellets were then pressed into films under the following conditions: press temperature (140°C); pressure (1000 psi); time in the press (2 min); cooling temperature (25°C). The resulting film was then cut into 2-5 mm wide test strips to be used in the screening process.

Since no good mixing facilities are available for blending very small amounts of polymer and plasticizer, the following methodology was developed and followed to screen melt blends of polymer, nucleating agent and plasticizer. Add 0.4 g of the desired plasticizer to a small test tube. The test tube containing the plasticizer was placed in a Wood's metal bath heated to 160°C and held there for 10 minutes. After the plasticizer had preheated, 1.6 g of an appropriate PHA film strip containing the PHB nucleating agent (prepared as described above) was added to the test tube. The entire contents of the tube were then heated at 160°C for an additional 50 min. The tube was then removed from the heating bath and allowed to cool at room temperature for at least 1 h. The resulting polymer was removed from the test tube (breaking the test tube if necessary). The resulting polymer and any liquid contents were placed on a Teflon ^(R) coated aluminum foil sheet (available from EI du Pont de Nemours and Company, Wilmington, DE) and pressed into a film. The film is then removed from the sheet, folded upon itself, and pressed into a film again. The film pressing process was repeated 5 times to ensure good blending of the three components and to assess the effectiveness of the nucleant-plasticizer combination. Film processing conditions were generally as follows: press temperature (140° C.); press pressure (1000 psi); press time (2 min); cooling temperature (room temperature); cooling pressure (51b plate); and cooling time (10 sec). Immediately after the final film was pressed and cooled for 10 sec the sample was peeled from the Teflon ^(R) coated sheet and evaluated for adhesion to the Teflon ^(R) coated sheet, to itself, and to the operator's glove. If the sample exhibits no tack as defined herein to any of the surfaces to which it is exposed, it is given a "no tack" rating. All other grades indicate a certain level of stickiness. The sample was then swabbed of any remaining plasticizer and weighed. The percent plasticizer incorporation was determined by comparing the final polymer weight to the theoretical weight and back-calculating the plasticizer content, assuming only plasticizer loss. A sample is calculated as follows:

Added components:

1.6 g (nucleating agent + polymer) in film form

0.4g plasticizer

Total amount of components processed = 1.60g + 0.40g = 2.00g

Theoretical % of plasticizer=(0.40g/2.00g)×100%=20%

General example:

The actual final weight of the film = Xg

Assumed final weight of plasticizer = Xg-1.60g = Yg

Actual % of plasticizer=(Yg/Xg)×100%

Specific example:

Actual final weight of film = 1.86g

Assumed final weight of plasticizer = 1.86g - 1,60g = 0.26g

Actual % of plasticizer present = (0.26g/1.86g) x 100% = 14% It should be noted that in no case was the film produced below 1.60g, indicating that in all cases there was some Plasticizers are incorporated into the polymer.

Table 1 (Examples 1-44) summarizes the nucleating agent and plasticizer screens performed with both P3HBO and P3HBH, respectively, that showed tack-free results. Table 2 (Examples 45 to 60) summarizes comparative examples showing stickiness. The abbreviation Tg used in Table 1 and Table 2 stands for glass transition temperature (°C).

In general, for those samples that produced a "tack-free" grade, samples that entrapped more plasticizer tended to perform better than samples that entrapped less (shown even lower viscosity). Occasionally, tack was still evident when some films were cooled at room temperature. And when these same films were cooled at 65°C some of them showed no tack. These films were rated as non-tacky; however, they were considered inferior to those films that showed no tack after cooling at room temperature for 10 seconds. Samples showing rapid tack removal were considered candidates for melt processing via injection molding, film extrusion and fiber extrusion.

Example 2

Continuous melt extrusion of poly-3-hydroxy(butyrate-cohexanoate) into strands and in-line pelletizing Demonstration

Component Blending (Dibutyl Maleate Plasticizer): To a 35 gallon fiber spinner pack was added 15088.6 grams of powdered P3HBH and 588.5 grams of powdered PHB. To this powder mixture, 3923.0 g of dibutyl maleate was slowly added at such a rate that the liquid plasticizer was immediately absorbed into the powder. The fiber spinner assembly was then tumble mixed for 6 hours on a polished tumbler to ensure good mixing.

Extrusion and pelletizing of polymer strands (di-n-butyl maleate plasticizer): After tank blending of the polymer components as described above, the resulting mixture was fed at a rate of approximately 10 lb/h into a In a 30mm twin-screw extruder. The extruder temperature is set to maintain a gradient barrel temperature of 120°C to 160°C. Screw RPM was maintained at 100. The resulting molten polymer was extruded through a 3/16 inch die into a 12 foot long tank maintained at a temperature of 34°C to 38°C. The polymer was cut and fed into a Conair polymer cutter at a rate of 6-8 ft/min, collecting a total of 40.9 lbs of pellets.

The resulting polymer strands exhibited some viscous behavior within the first 6 feet of the quench tank. After the wire becomes tack-free in the tank, the polymer exhibits tack-free behavior at any time during the processing operation or in subsequent processing operations.

Example 3

Continuous melt extrusion of poly-3-hydroxy(butyrate-cohexanoate) into strands and in-line pelletizing Demonstration

Blending and extrusion of polymer strands and pelletizing (methyl laurate plasticizer): in a method similar to that described in Example 2 for the polymer blended with di-n-butyl maleate In the process, the following components were blended: 11,793g P3HBH, 459.5g PHB, and 3063g methyl laurate. The resulting mixture was then fed to a 30 mm extruder as previously described, set to maintain a gradient barrel temperature of 120°C to 160°C. The screw RPM was maintained at 100 and the polymer was extruded through a 3/16 inch die into a 12 foot tank maintained at 34°C-38°C. The polymer was cut with a Conair polymer cutter at approximately 12 ft/min. The polymer quench time (time at which no further stickiness was observed) was approximately 25 sec. A total of approximately 32 lbs of non-tacky pellets were collected. It is noted that methyl laurate promotes a faster quench time, allowing faster cutting speeds.

Example 4

Continuous use of poly-3-hydroxy(butyrate-cohexanoate) and methyl laurate plasticizers Demonstration of cast film production

The P3HBH pellets prepared in the previous example, plasticized with methyl laurate and nucleated with PHB, were fed to a gradient machine equipped with a 14 inch film die and set to maintain a temperature between 140°C and 120°C barrel/die temperature in a single-screw extruder. The resulting polymer extrudate was cast onto a 12 inch diameter stainless steel roll set at a temperature of 40°C. The extruded film was taken up onto chill rolls and then onto wrapping rolls at speeds ranging from 2 ft/min to 13 ft/min to produce films having thicknesses ranging from 1 mil to 10 mils. The film exhibited no tack and the properties listed in Table 3 below (determined in accordance with ASTM D 882-95a - Standard Test Method for Tensile Properties of Thin Plastic Sheets):

table 3 direction Thickness (mil) Young's modulus (MPa) Fracture strain (%) Fracture stress (MPa) Toughness (J/in ³ ) portrait 1.7 187 562 10.3 745 horizontal 1.7 147 524 8.2 623

Table 1 Example number Composition (+ nucleating agent) plasticizer WT% Plasticizer film quality 1 PHBO/PHB (99:1) Di(2-ethylhexyl)dioctyl maleate 12 non sticky 2 PHBO/PHB (99:1) paraffin 3.6 non sticky 3 PHBO/PHB (99:1) Dodecanol 7 non sticky 4 PHBO/PHB (99:1) Polyethylene glycol 600 7 non sticky 5 PHBO/PHB (99:1) polyethylene glycol 8000 11 non sticky 6 PHBO/PHB (99:1) olive oil 2.4 non sticky 7 PHBO/PHB (99:1) Soybean oil 4.8 non sticky 8 PHBO/PHB (99:1) TERETHANE 650 14 non sticky 9 PHBO/PHB (99:1) methyl oleate 14 non sticky 10 PHBO/PHB (99:1) n-propyl oleate 12 non sticky 11 PHBO/PHB (99:1) tetrahydrofurfuryl oleate 13 non sticky 12 PHBO/PHB (99:1) Epoxidized Linseed Oil 9 non sticky 13 PHBO/PHB (99:1) 2-Ethylhexyl Epoxy Resinate 11 non sticky 14 PHBO/PHB (99:1) Dibutyl fumarate 20 non sticky 15 PHBO/PHB (99:1) Triacetin 18 non sticky 16 PHBO/PHB (99:1) Methyl laurate 12 non sticky Example number Composition (+ nucleating agent) plasticizer WT% Plasticizer film quality 17 PHBO/PHB (99:1) Methyl Linoleate, 75% 9 non sticky 18 PHBO/PHB (99:1) Di-n-butyl maleate 17 non sticky 19 PHBO/PHB (99:1) Methyl acetyl ricinoleate 11 very good 20 PHBO/PHB (99:1) Acetyl Tris(n-Butyl Citrate) 19 very little stickiness twenty one PHBO/PHB (99:1) Acetyl triethyl citrate 20 very little stickiness twenty two PHBO/PHB (99:1) tri-n-butyl citrate 20 very little stickiness twenty three PHBO/PHB (99:1) triethyl citrate 20 very little stickiness twenty four PHBO/PHB (99:1) Dimer acid bis(2-ethylhexyl) 7 very little stickiness 25 PHBO/PHB (99:1) Butyl ricinoleate 19 qualified 26 PHBO/PHB (99:1) Triglycerides (Acetyl Ricinoleate) 6 qualified 27 PHBO/PHB (99:1) Methyl ricinoleate 18 qualified 28 PHBO/PHB (99:1) N-Butyl Acetyl Ricinoleate 13 qualified 29 PHBO/PHB (99:1) Propylene glycol ricinoleate 17 qualified 30 (control) PHBO/PHB (99:1) high viscosity 31 PHBH/PHB (97:3) paraffin 2.4 non sticky 32 PHBH/PHB (97:3) Dodecanol 8 non sticky 33 PHBH/PHB (97:3) Dibutyl fumarate 17 non stick 34 PHBH/PHB (97:3) Methyl laurate 18 non stick Example number Composition (+ nucleating agent) plasticizer WT% Plasticizer film quality 35 PHBH/PHB (97:3) Methyl linoleate 17 non stick 36 PHBH/PHB (97:3) Di-n-butyl maleate 19 non stick 37 PHBH/PHB (97:3) Methyl ricinoleate 18 non stick 38 PHBH/PHB (97:3) Diethyl succinate 17 non stick 39 PHBH/PHB (97:3) Diisobutyl adipate 19 non stick 40 PHBH/PHB (97:3) Dimethyl azelate 19 non stick 41 PHBH/PHB (97:3) Di-n-hexyl azelate 17 non stick 42 PHBH/PHB (97:3) tributyl phosphate 20 non stick 43 PHBH/PHB (97:3) Dioctyl bis(2-ethylhexyl)maleate 17 qualified 44 PHBH/PHB (97:3) TERETHANE 650 15 qualified

Table 2 Example number Composition (+ nucleating agent) plasticizer WT% Plasticizer film quality 45 PHBO-Control stick 46 PHBH-control stick 47 PHBH/PHB (97:3) stick 48 PHBO/PHB (97:3) stick Example number Composition (+ nucleating agent) plasticizer WT% Plasticizer film quality 49 PHBO/microcrystalline cellulose (97:3) Sticky - easy to remove from ^Teflon® when hot, becomes sticky as it cools 50 PHBO/NUCREL 1214 (95:5) stick 51 PHBO/paraffin (95:5) worse than the control group 52 PHBO/PO2G (95:5) stick 53 PHBO/polyethylene glycol 8000 (97:3) slightly sticky 54 PHBO/polylactic acid (97:3) stick 55 PHBO/SURLYN 8020 (95:5) stick 56 PHBH/PHB (97:3) Butyl oleate 8 stick 57 PHBH/PHB (97:3) Bis(tridecyl) adipate 15 slightly sticky 58 PHBH/PHB (97:3) Dodecanol 8 slightly sticky 59 PHBH/PHB (97:3) Epoxidized Linseed Oil 13 slightly sticky 60 PHBH/PHB (97:3) olive oil 2 slightly sticky 61 PHBH/PHB (97:3) Soybean oil 3 stick 62 PHBH/PHB (97:3) triethyl citrate 18 stick 63 PHBO/PHB (99:1) Chloroparaffins 50% Cl 9 stick 64 PHBO/PHB (99:1) n-Butyl stearate 6 a bit sticky

Claims (25)

1. A polyhydroxyalkanoate polymer composition with reduced tack, comprising (a) a polyhydroxyalkanoate copolymer, (b) a nucleating agent, and (c) A plasticizer. 2. A polyhydroxyalkanoate polymer composition with reduced tack, comprising (a) 55-94% polyhydroxyalkanoate copolymer, (b) 1 to 10% nucleating agent, and (c) 5-35% plasticizer. 3. The polyhydroxyalkanoate polymer composition of claim 1, Formula I R=CH ₃ (CH ₂ ) _y where y=0-11 Wherein, the polyhydroxyalkanoate copolymer is selected from compounds represented by formula I, wherein m=0.7-0.97, n=0.3-0.03, and m+n=1.0. 4. The polyhydroxyalkanoate polymer composition of claim 1, wherein the polyhydroxyalkanoate copolymer is selected from the group consisting of poly-3-hydroxy(butyrate co-caprylate) and poly-3-hydroxy (butyrate co-hexanoate) group. 5. The polyhydroxyalkanoate polymer composition of claim 1, wherein the nucleating agent is polyhydroxybutyrate. 6. The polyhydroxyalkanoate polymer composition of claim 1, wherein the nucleating agent is selected from the group consisting of talc, micronized mica, calcium carbonate, boron nitride, ammonium chloride, sodium salt, and A group consisting of carboxylates of Group I and Group II metals. 7. The polyhydroxyalkanoate polymer composition of claim 1, wherein the plasticizer is selected from the group consisting of di-n-butyl maleate, methyl laurate, dibutyl fumarate , Di(2-ethylhexyl)dioctyl maleate, paraffin, lauryl alcohol, olive oil, soybean oil, polytetramethylene glycol, methyl oleate, n-propyl oleate, oleic acid Tetrahydrofurfuryl, Epoxidized Linseed Oil, 2-Ethylhexyl Epoxy Resinate, Triacetin, Methyl Linoleate, Dibutyl Fumarate, Methyl Acetyl Ricinoleate , Acetyl tri-n-butyl citrate, Acetyl triethyl citrate, Tri-n-butyl citrate, Triethyl citrate, Dimer acid bis(2-hydroxyethyl), Ricinoleic acid butyl ester, Triglycerol tri(acetyl ricinoleate), methyl ricinoleate, n-butyl acetyl ricinoleate, propylene glycol ricinoleate, diethyl succinate, diisobutyl adipate, diazela methyl ester, di-n-hexyl azelate and tributyl phosphate. 8. A method for improving the processability of a polyhydroxyalkanoate polymer composition by reducing viscosity, the method comprising contacting the polyhydroxyalkanoate polymer with a nucleating agent and a plasticizer to form a A step of a polyhydroxyalkanoate polymer composition. 9. The method according to claim 8, further comprising the step of extruding the polyhydroxyalkanoate polymer composition. 10. The method according to claim 9, further comprising the step of pelletizing the extruded polyhydroxyalkanoate polymer composition. 11. The method according to claim 10, further comprising the step of extruding the pelletized polyhydroxyalkanoate polymer composition. 12. The method according to claim 10, wherein the polyhydroxyalkanoate polymer composition is extruded by a compounding extruder. 13. An extrusion comprising the polyhydroxyalkanoate polymer composition of claim 1. 14. Extrusions according to claim 13 in the form of fibres, monofilaments, rods, tubes or cast films. 15. The cast film of claim 14 having a film thickness of from about 0.05 to about 50 mils. 16. The cast film of claim 14 having a film thickness of from about 0.10 to about 15 mils. 17. Extrusions produced by the method of claim 8. 18. An extrusion produced by the method of claim 9. 19. An extrusion produced by the method of claim 11. 20. An extrusion produced by the method of claim 12. 21. Extrusions in the form of fibers, monofilaments, rods, tubes or cast films produced by the method of claim 8. 22. Extrusions in the form of fibers, monofilaments, rods, tubes or cast films produced by the method of claim 9. 23. Extrusions produced by the method of claim 11 in the form of fibers, monofilaments, rods, tubes or cast films. 24. Extrusions in the form of fibers, monofilaments, rods, tubes or cast films produced by the method of claim 12. 25. An injection molded article comprising the polyhydroxyalkanoate polymer composition of claim 1.