Polylactic acid composition, foam molded article thereof and method of producing the same

• US 8,921,434 B2
• Filed: 03/29/2011
• Issued: 12/30/2014
• Est. Priority Date: 03/29/2010
• Status: Active Grant

• Current Assignee: Kazunori Tsuda, Kosuke Uchiyama
• Original Assignee: Kazunori Tsuda, Kosuke Uchiyama
• Inventors: Uchiyama, Kosuke, Tsuda, Kazunori, Suzuki, Tenya
• Primary Examiner(s): Gulakowski, Randy
• Assistant Examiner(s): WALES, CHRISTINA H
• Application Number:
  US13/636,223
• Publication Number:
  US 20130203877A1
• Time in Patent Office: 1,372 Days
• US Class Current: 521/79
• CPC Class Codes: B29C 44/3446 Feeding the blowing agent
• CPC Class Codes: B29C 44/586 with a cavity increasing in size during foaming
• CPC Class Codes: B29C 48/022 characterised by the choice of material
• CPC Class Codes: B29C 48/03 characterised by the shape of the extruded material at extrusion
• CPC Class Codes: B29C 48/37 Gear pumps
• CPC Class Codes: B29C 48/655 having three or more threads
• CPC Class Codes: B29C 48/76 Venting , drying means; Degassing means
• CPC Class Codes: B29K 2067/046 PLA, i.e. polylactic acid or polylactide
• CPC Class Codes: C08G 18/428 Lactides
• CPC Class Codes: C08G 18/6644 having at least three hydroxy groups
• CPC Class Codes: C08G 18/73 acyclic
• CPC Class Codes: C08G 2101/00 Manufacture of cellular products
• CPC Class Codes: C08G 63/08 Lactones or lactides
• CPC Class Codes: C08G 63/88 Post-polymerisation treatment
• CPC Class Codes: C08G 63/91 Polymers modified by chemical after-treatment
• CPC Class Codes: C08J 2201/024 Preparation or use of a blowing agent concentrate, i.e. masterbatch in a foamable composition
• CPC Class Codes: C08J 2201/026 Crosslinking before of after foaming
• CPC Class Codes: C08J 2201/03 Extrusion of the foamable blend
• CPC Class Codes: C08J 2203/08 Supercritical fluid
• CPC Class Codes: C08J 2367/04 Polyesters derived from hydroxy carboxylic acids, e.g. lactones C08J2367/06 takes precedence
• CPC Class Codes: C08J 3/24 : Crosslinking, e.g. vulcanising, of macromolecules mechanical aspects B29C35/00; crosslinking agents C08K
• CPC Class Codes: C08J 9/122 : Hydrogen, oxygen, CO2, nitrogen or noble gases
• CPC Class Codes: C08K 3/26 : Carbonates; Bicarbonates
• CPC Class Codes: C08K 3/34 : Silicon-containing compounds
• CPC Class Codes: C08K 5/29 : Compounds containing one or more carbon-to-nitrogen double bonds
• CPC Class Codes: C08L 67/04 : Polyesters derived from hydroxycarboxylic acids, e.g. lactones C08L67/06 takes precedence

Abstract

A polylactic acid composition is produced with an MI value of 0.05 or more and 5 or less, the MI value being measured at 190° C. under a load of 21.6 kg in accordance with JIS K7210 (ISO 1133). A polylactic acid is crosslinked with a polyisocyanate to generate a cross-linked polylactic acid, including a large cross-linked polylactic acid molecule which inhibits foaming. The cross-linked polylactic acid is mechanically grinded-by applying a shear force to decrease a molecular weight of the large cross-linked polylactic acid molecule. The amount of the polyisocyanate combined is 0.4 to 5% by weight based on the polylactic acid. The grinding is conducted in supercritical condition of an inert gas. A foam molded article is made from the polylactic acid composition.

Claims

1. A method of producing a polylactic acid composition with an MI value of 0.05 or more and 5 or less, the MI value being measured at 190°

C. under a load of 21.6 kg in accordance with JIS K7210 (ISO

     1133), comprising;

crosslinking a polylactic acid with a polyisocyanate to generate a cross-linked polylactic acid, including a large cross-linked polylactic acid molecule which inhibits foaming, and

mechanically grinding the cross-linked polylactic acid, by applying a shear force to decrease a molecular weight of the large cross-linked polylactic acid molecule, the amount of the polyisocyanate combined being 0.4 to 5% by weight based on the polylactic acid, the grinding being conducted in supercritical condition of an inert gas, the shear force being applied in an orifice portion having a slit or a sleeve from which the polylactic acid composition is extruded, by allowing the cross-linked polylactic acid to pass through the orifice portion, the temperature in the orifice portion being from 160 to 180°

C., and the pressure in the orifice portion being from 6 to 12 MPa.

2. The method according to claim 1, wherein a number average molecular weight in a polystyrene equivalent of the polylactic acid composition obtained by the grinding measured by GPC is less than 1.5 million.

3. The method according to claim 1, and selecting the polyisocyanate as one of triisocyanate, tetraisocyanate, diisocyanate, and any of the adduct forms of said polyisocyanates.

4. The method according to claim 1, and adding 0.5 to 5% by weight of calcium carbonate or talc particle.

5. The method according to claim 1, wherein the polylactic acid composition has a composition which does not contain high molecules having a molecular weight of 1.5 million or more in polystyrene equivalent.

6. The method according to claim 1, wherein the grinding is conducted in supercritical condition of nitrogen gas, or the mixed gas of nitrogen gas and methanol.

7. A method of producing a foam molded article of a polylactic acid composition with an MI value of 0.05 or more and 5 or less, the MI value being measured at 190°

C. under a load of 21.6 kg in accordance with JIS K7210 (ISO

     1133), comprising;

crosslinking a polylactic acid with a polyisocyanate to generate a cross-linked polylactic acid, including a large cross-linked polylactic acid molecule which inhibits foaming,

mechanically grinding the cross-linked polylactic acid, by applying a shear force to decrease a molecular weight of the large cross-linked polylactic acid molecule, the amount of the polyisocyanate combined being 0.4 to 5% by weight based on polylactic acid, the grinding being conducted in supercritical condition of an inert gas, the grinding being conducted by the use of a device equipped with an injection molding machine (B) or an extrusion molding machine (G), an orifice portion (S) having a slit or a sleeve in which the shear force is applied and from which the polylactic acid composition is extruded, and a foaming mold (P), in supercritical condition of a foaming gas in the orifice portion (S), the shear force being applied by allowing the cross-linked polylactic acid to pass through the orifice portion, the temperature in the orifice portion being from 160 to 180°

C., and the pressure in the orifice portion being from 6 to 12 Mpa, and

forming the foam molded article of the polylactic acid composition.

8. The method according to claim 7, wherein a number average molecular weight in a polystyrene equivalent of the polylactic acid composition obtained by the grinding measured by GPC is less than 1.5 million.

9. The method according to claim 7, and selecting the polyisocyanate as one of triisocyanate, tetraisocyanate, diisocyanate, and any of the adduct forms of said polyisocyanates.

10. The method according to claim 7, and adding 0.5 to 5% by weight of calcium carbonate or talc particle.

11. The method according to claim 7, wherein the polylactic acid composition has a composition which does not contain high molecules having a molecular weight of 1.5 million or more in polystyrene equivalent.

12. The method according to claim 7, wherein the grinding is conducted in supercritical condition of nitrogen gas, or the mixed gas of nitrogen gas and methanol.