Closed cell foams including poly-4-hydroxybutyrate and copolymers thereof

Patent metadata

Field	Value
Publication number	US-10689498-B2
Application number	US-201414464099-A
Country	US
Kind code	B2
Filing date	Aug 20, 2014
Priority date	Aug 20, 2013
Publication date	Jun 23, 2020
Grant date	Jun 23, 2020

Abstract

Methods to produce substantially closed cell foams with densities less than 0.75 g/cm 3 , and more preferably less than 0.5 g/cm 3 , without substantial loss of the polymer's weight average molecular weight, have been developed. The closed cells foams have an open cell content of generally less than 50%, and more preferably an open cell content of less than 20%, and the cells have a maximum diameter of less than 5 mm. The foam may include poly-4-hydroxybutyrate or a copolymer thereof. Preferably, the foam is derived by heating a foam polymer formula to a temperature above the melt temperature of the polymer to form a melt polymer system, adding a blowing agent to produce a foamable melt, extruding the foamable melt through a die to a lower pressure to cause foaming, cooling of the foam, and solidification of the foam. These foam structures can be used for fabrication of medical products.

First claim

We claim:

1. A foam composition comprising poly-4-hydroxybutyrate (P4HB) homopolymer, wherein the foam comprises closed cells as measured by ASTM D6226-10, and wherein the foam has an open cell content of less than 50%, and wherein the P4HB homopolymer is not crosslinked.

2. The composition of claim 1 wherein the foam has a density of less than 0.75 g/cm 3 .

3. The composition of claim 1 wherein the cells of the foam have a maximum diameter of less than 5 mm.

4. The composition of claim 1 wherein the weight average molecular weight of the poly-4-hydroxybutyrate homopolymer decreases less than 25% during the processing of the polymer into a cell foam comprising closed cells.

5. The composition of claim 1 further comprising one or more of the following: nucleating agent, plasticizing agent, surfactant, thermoplastic elastomer, foaming aid, dye, bioactive agent, contrast agent, radiopaque agent, radioactive marker, radioactive substance, resorbable polymer, and non-degradable polymer.

6. The composition of claim 5 wherein the foam comprises one or more of the following: 0.1-5% by weight of the nucleating agent, 0.5-20% by weight of the plasticizing agent, 1-20% by weight of the surfactant, and up to 0.5% by weight of the dye.

7. The composition of claim 5 wherein the foam comprises one or more resorbable polymers comprising poly(lactide); poly(glycolide); poly(lactide-co-glycolide); poly(lactic acid); poly(glycolic acid); poly(lactic acid-co-glycolic acid); polycaprolactone; poly(orthoester); polyanhydride; poly(phosphazene); polyhydroxyalkanoates; poly-3-hydroxybutyrate; poly-3-hydroxybutyrate-co-3-hydroxyvalerate; synthetically or biologically prepared polyester; polyester with one or more of the following monomeric units: glycolic, lactic; trimethylene carbonate, p-dioxanone, or e-caprolactone; poly(lactide-co-caprolactone); polycarbonate; tyrosine polycarbonate; polyamide; synthetic or natural polyamide, polypeptide, poly(amino acid); polyesteramide; poly(dioxanone); poly(alkylene alkylate); polyether; polyethylene glycol; polyethylene oxide; polyvinyl pyrrolidone; polyurethane; polyetherester; polyacetal; polycyanoacrylate; poly(oxyethylene)/poly(oxypropylene) copolymer; polyacetal, polyketal; polyphosphate; phosphorous-containing polymer; polyphosphoester; polyalkylene oxalate; polyalkylene succinate; poly(maleic acid); chitin; chitosan; modified chitosan; hyaluronic acid and derivatives thereof; hydrophilic or water soluble polymer.

8. The composition of claim 1 wherein the closed cells contain a blowing agent.

9. The composition of claim 8 wherein the blowing agent is one or more of the following: nitrogen, carbon dioxide, air, argon, helium, methane, ethane, propane, butanes, hexanes, and a halogenated hydrocarbon.

10. A composition according to claim 1 wherein the poly-4-hydroxybutyrate homopolymer has a weight average molecular weight greater than 50 kDa relative to polystyrene.

11. A method for preparing the composition of claim 1 by using melt-foaming wherein the method comprises the following steps: (i) preparing a foam polymer formula comprising poly-4-hydroxybutyrate homopolymer, (ii) heating the foam polymer formula to create a polymer melt in an extruder, (iii) introducing a blowing agent to the polymer melt, and (iv) cooling and extruding the foamable melt to form a substantially closed cell foam.

12. The method of claim 11 wherein (i) the moisture content of the foam polymer formula is less than 0.03% by weight, (ii) a temperature of 150-260° C. is used to melt the foam polymer formula, and (iii) the amount of blowing agent introduced to the polymer melt is 1-10% by weight.

13. The foam of claim 1 , wherein the foam is made from a P4HB homopolymer by a polymer foaming process, wherein the process does not include a crosslinking agent.

Assignees

• Tepha Inc

Inventors

• Connelly Dennis
• Felix Fabio
• Martin David P
• Montcrieff Jon
• Rizk Said
• Williams Simon F

Classifications

• C08J2205/052

  Closed cells, i.e. more than 50% of the pores are closed · CPC title

• C08J2203/08

  Supercritical fluid · CPC title

• C08J2207/10

  Medical applications, e.g. biocompatible scaffolds · CPC title

• C08J2203/06

  CO2, N2 or noble gases · CPC title

• C08L2203/02

  for biomedical use · CPC title