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WO2012138265A1 - Substance hautement purifiée comprenant une résine expansée d'acide polylactique - Google Patents

Substance hautement purifiée comprenant une résine expansée d'acide polylactique Download PDF

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Publication number
WO2012138265A1
WO2012138265A1 PCT/SE2011/050394 SE2011050394W WO2012138265A1 WO 2012138265 A1 WO2012138265 A1 WO 2012138265A1 SE 2011050394 W SE2011050394 W SE 2011050394W WO 2012138265 A1 WO2012138265 A1 WO 2012138265A1
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WIPO (PCT)
Prior art keywords
pla
liquid
beads
temperature
extraction
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PCT/SE2011/050394
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English (en)
Inventor
Ulrika ANDREASSON
Tomas GERDSDORFF
Kent Malmgren
Original Assignee
Sca Packaging Sweden Ab
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Publication date
Application filed by Sca Packaging Sweden Ab filed Critical Sca Packaging Sweden Ab
Priority to PCT/SE2011/050394 priority Critical patent/WO2012138265A1/fr
Publication of WO2012138265A1 publication Critical patent/WO2012138265A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/16—Making expandable particles
    • C08J9/18—Making expandable particles by impregnating polymer particles with the blowing agent
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D11/00—Solvent extraction
    • B01D11/02—Solvent extraction of solids
    • B01D11/0292—Treatment of the solvent
    • B01D11/0296—Condensation of solvent vapours
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
    • C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
    • C08G63/06—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from hydroxycarboxylic acids
    • C08G63/08—Lactones or lactides
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
    • C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
    • C08J9/122—Hydrogen, oxygen, CO2, nitrogen or noble gases
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
    • C08J2367/04—Polyesters derived from hydroxy carboxylic acids, e.g. lactones

Definitions

  • the present invention relates to a material comprising expanded polylactic acid (PLA) resin.
  • PVA resin foams for use in packaging applications, since such polymers are bio-derived and bio-degradable. These foams have good performance and are economic, and are often preferred over petroleum-derived foams such as polystyrene foam, due to increasing environmental awareness and consumer demands.
  • Carbon dioxide is a useful blowing agent for PLA foams, being an environmentally friendly blowing agent without any ozone depletion potential.
  • Some processes that use carbon dioxide as a blowing agent involve foaming and moulding, and PLA resin beads impregnated with carbon dioxide may then be used. Such processes generally involve impregnating the beads with gaseous or supercritical C0 2 , pre- expanding the impregnated beads, resting and sometimes treating the pre- expanded beads, before re-impregnating them with more C0 2 or another blowing agent and further expanding and fusing them in a mould, see e.g. EP 1 378 538.
  • Another known process involving impregnation of PLA resin beads with carbon dioxide is disclosed in WO 2008/093284.
  • packaging foam material does not contain any undesired substances, to avoid any possible transfer of extractives from the packaging foam to the package contents.
  • An object of the present invention is to provide a foamed PLA material with very high purity useful for packaging application.
  • the present invention thus relates to a material comprising expanded polylactic acid (PLA) resin that comprises a total amount of extractives of 0-0,035 % by weight, calculated on the total weight of PLA, said extractives being substances that can be extracted from PLA with diethyl ether as extraction medium according to the method of determination of extractives in PLA as described in the description of this patent application.
  • PLA expanded polylactic acid
  • This material can be used for example in packaging applications, especially for packaging of foodstuff.
  • Said extractives may comprise oligomers of lactic acid of which lactide is 0-0,020 % by weight, calculated on the total weight of PLA.
  • the above material is obtainable by a process in which PLA beads are subject to a liquid C0 2 " treatment, which involves impregnation and extraction with liquid C0 2 .
  • the process may preferably comprise the following steps: subjecting PLA resin beads to a liquid C0 2 treatment, which involves impregnation and extraction comprising at least one impregnation and extraction step, in which the PLA resin beads are brought into contact with 0,01 -1000 kg pure liquid C0 2 /kg PLA, preferably 2-20 kg liquid C0 2 /kg PLA, in a reactor for a predetermined time period, at a temperature and pressure that prevents the beads from sticking together and foaming; and a portion of the liquid C0 2 is drained from the PLA beads after completion of the impregnation and extraction step, at a temperature that prevents the beads from sticking together and foaming, and at which the C0 2 is in liquid form, while leaving at least 0,01 kg liquid C0 2 /kg PLA, preferably 0,01 -1 kg liquid C0 2 /kg PLA in the reactor containing the PLA resin beads; followed by evacuation of C0 2 gas from the reactor so as to decrease the pressure to ambient pressure, whereby the remaining liquid C0 2 is evaporated, thereby decreasing
  • the liquid C0 2 treatment involving impregnation and extraction may alternatively comprise impregnation and extraction in a continuous process, wherein PLA resin beads are held in a reactor, in which the PLA resin beads are brought into contact with liquid C0 2 for a predetermined time period, at a temperature that prevents the beads from sticking together and foaming, and at which the C0 2 is in liquid form, and pure liquid C0 2 is continuously fed at one end of the reactor, and is drained from another end of the reactor; and wherein a portion of the liquid C0 2 is drained from the PLA beads upon completion of the impregnation and extraction, at a temperature that prevents the beads from sticking together and foaming, and at which the C0 2 is in liquid form, while leaving at least 0,01 kg liquid C0 2 /kg PLA, preferably 0,01 -1 kg liquid C0 2 /kg PLA in the reactor containing the PLA resin beads; followed by evacuation of C0 2 gas from the reactor so as to decrease the pressure to ambient pressure, whereby the remaining liquid C0 2 is
  • the impregnation and extraction step may preferably comprise 2 or more successive steps, wherein the PLA resin beads are brought into contact with pure liquid C0 2 in each successive step for a predetermined time period at a temperature and pressure that prevents the beads from sticking together and foaming, and wherein at least a portion of the liquid C0 2 is drained from the PLA beads at the end of each step, at a temperature that prevents the beads from sticking together and foaming, and at which the C0 2 is in liquid form.
  • the PLA beads are impregnated and extracted with liquid C0 2 advantageously at a pressure of above 1 MPa, preferably 4,5-8 MPa.
  • the PLA beads are impregnated and extracted with liquid C0 2 at a temperature suitably above -50 °C, but below the glass transition temperature of PLA at the pressure used, preferably -10 to +15 °C, for 10 to 240 minutes, preferably 30 to 90 minutes.
  • the PLA beads are impregnated and extracted with liquid C0 2 that may contain additives such as coloring agents, anti-static agents, flame retardants, adhesives.
  • the PLA resin beads may comprise 50-100% by weight of PLA, preferably 80-100% by weight.
  • the PLA is preferably amorphous PLA.
  • the material of the invention may further comprise one or more of fillers, reinforcing agents, coloring agents.
  • Figure 1 shows a schematic view of a system, useful for performing impregnation and purification of PLA resin beads.
  • Figure 2 shows a schematic view of a system, similar to the one of Figure 1 , and which includes a pump.
  • the material of the present invention is an expanded polylactic acid (PLA) resin having a total content of extractives of 0-0,035 % by weight, calculated on the total weight of PLA, said extractives being substances that can be extracted from PLA with diethyl ether as extraction medium according to the method of determination of extractives in PLA as described in the description of this patent application.
  • the extractives comprise oligomers of lactic acid, of which lactide is 0-0,020 % by weight, calculated on the total weight of PLA.
  • the material may be obtained by a process utilizing C0 2 as blowing agent, and in which PLA beads are subject to an a liquid C0 2 treatment, which involves impregnation and extraction with liquid C0 2 , which preferably includes at least one impregnation and extraction step, and draining of the C0 2 in liquid form.
  • the process may further include conditioning and pre-expanding the PLA beads, before increasing the temperature to a fusing temperature to allow moulding of the PLA beads.
  • extracttables refers to substances that are extracted from PLA during impregnation with carbon dioxide.
  • extractives refers to substances that can be extracted from PLA with diethyl ether as extraction medium according to the method of determination of extractives in PLA as described in the description of this patent application.
  • Additives or coating materials can be added to the PLA resin beads during impregnation and extraction. Accordingly, by means of the present invention various functionalities can effectively be added to the material, since impregnation, extraction and addition of additives can be performed in one process, without any need for additional process steps.
  • Polylactic acid or PLA is a polymer or copolymer comprising lactic acid monomer units.
  • references to polylactic acid includes crystalline and amorphous polymers and mixtures thereof.
  • the PLA resin beads may comprise about 50-100 % by weight of PLA.
  • the PLA may comprise amorphous PLA or a blend of amorphous PLA and crystalline PLA. Preferred blends comprise at least about 50 % by weight of amorphous PLA and about 0-50 % by weight of crystalline PLA.
  • the lactic acid in the resin beads may comprise one or more lactic acid isomers including L-lactic acid, D-lactic acid or DL-lactic acid.
  • the lactic acid is preferably L-lactic acid.
  • the PLA may be produced industrially by polymerisation of lactic acid obtained by the bacterial fermentation of biomass such as beet, sugarcane, cornstarch or milk products.
  • PLA resin beads can be impregnated without any pre- treatment using liquid C0 2 .
  • Amorphous, crystalline, and amorphous-crystalline blends may be used but results with highly crystalline grades are sometimes of lesser quality at the preferred pressure and temperature ranges.
  • Reference to resin "beads" is intended to mean the crude resin material (often in the form of pellets) obtained from manufacturers and the terms beads, granules and pellets may be used interchangeably.
  • the beads may also be in the form of fibres. Beads may be resized by extrusion and pelletizing of the commercially available material using known techniques.
  • the present invention is based on the use of liquid C0 2 for the impregnation of PLA.
  • liquid C0 2 impregnation the PLA beads have little tendency to stick to each other, especially when using sub-cooled liquid C0 2 , i.e. liquid C0 2 at higher pressure than equilibrium pressure at a given temperature.
  • Liquid C0 2 impregnation requires moderate temperature and pressure.
  • the impregnated beads do not stick together and after releasing the pressure from the impregnation reactor they can be handled as a bulk commodity.
  • PLA resin beads are subjected to a liquid C0 2 treatment, which involves impregnation and extraction.
  • the liquid C0 2 treatment comprises at least one impregnation and extraction step, in which the PLA resin beads are brought into contact with 0,01 -1000 kg pure liquid C0 2 /kg PLA in a reactor for a predetermined time period, at a temperature and pressure that prevents the beads from sticking together and foaming.
  • C0 2 is impregnated into the PLA resin beads, and at the same time extractable substances are dissolved into the liquid C0 2 .
  • a portion of the liquid C0 2 is drained from the PLA beads, at a temperature that prevents the beads from sticking together and foaming, and at which the C0 2 is in liquid form, while leaving at least 0,01 kg liquid C0 2 /kg PLA, preferably 0,01 -1 kg liquid C0 2 /kg PLA in the reactor containing the PLA resin beads.
  • evacuation of C0 2 gas from the reactor is performed so as to decrease the pressure to ambient pressure, whereby the remaining liquid C0 2 is evaporated, thereby decreasing the temperature so as to prevent foaming at ambient pressure.
  • liquid C0 2 is effective in extracting undesired substances from the PLA.
  • the C0 2 is drained from the reactor in liquid form, the substances extracted from the PLA beads are effectively removed.
  • the temperature of the beads is kept low to prevent foaming when the pressure is decreased to ambient pressure at the end of the process.
  • the impregnation and extraction step preferably comprises 2 or more successive steps, wherein the PLA resin beads are brought into contact with pure liquid C0 2 in each successive step for a predetermined time period at a temperature and pressure that prevents the beads from sticking together and foaming.
  • a part of the total impregnation is obtained.
  • the following steps continue the impregnation and the PLA resin beads are extracted with liquid C0 2 , each time further lowering the content of extractable substances in the PLA resin beads.
  • At the end of each successive step at least a portion of the liquid C0 2 is drained from the PLA beads, at a temperature that prevents the beads from sticking together and foaming, and at which the C0 2 is in liquid form.
  • the liquid C0 2 treatment, involving impregnation and extraction treatment may be carried out in a batch process or in a continuous process.
  • the PLA resin beads are held in a reactor to which an amount of liquid C0 2 is added, and after a certain time period the liquid C0 2 is drained from the reactor, while substantially maintaining the pressure. A new amount of pure liquid C0 2 is then added to the reactor at the same pressure. After completion of the last impregnation and extraction step, a portion of the liquid C0 2 is drained from the PLA beads, and a smaller amount of liquid C0 2 is left in the reactor. As said above, the remaining liquid C0 2 is evaporated when C0 2 gas is evacuated from the reactor and the temperature is thereby decreased so as to prevent sticking together and foaming at ambient pressure.
  • the PLA beads may be placed in a rotating drum during the impregnation and extraction step. When gas is evacuated from the drum, the cold liquid C0 2 is distributed evenly in the PLA material, which gives a thorough and even cooling of the PLA beads.
  • the PLA resin beads When carrying out the liquid C0 2 treatment in a continuous process the PLA resin beads are held in a reactor, in which the PLA resin beads are brought into contact with liquid C0 2 for a predetermined time period, at a temperature that prevents the beads from sticking together and foaming, and at which the C0 2 is in liquid form. Pure liquid C0 2 is continuously fed at one end of the reactor, and the liquid C0 2 is continuously drained from another end of the reactor, so that the liquid C0 2 flows through the reactor.
  • the reactor is dimensioned so that the time of contact between the PLA resin beads and the liquid C0 2 is sufficient to achieve the desired impregnation and extraction.
  • the PLA beads may be placed in a rotating drum during the impregnation and extraction step. When gas is evacuated from the drum, the cold liquid C0 2 is distributed evenly in the PLA material, which gives a thorough and even cooling of the PLA beads.
  • the pressure and temperature during the impregnation and extraction are chosen so as to prevent the PLA resin beads from sticking together and foaming, and to provide the C0 2 in liquid phase.
  • the impregnation and extraction may be performed at a pressure above 1 MPa, to ensure that the C0 2 can be present in liquid phase in a workable temperature range, and to avoid formation of solid C0 2 . More preferably the pressure during impregnation and extraction is 4,5-8 MPa, so as to provide conditions under which C0 2 can be in liquid phase at temperatures around 0 °C, and which leads to reasonable treatment time.
  • the temperature of the impregnation and the extraction is advantageously performed at above -50 °C to ensure liquid phase C0 2 during the treatment, but below the glass transition temperature of PLA at the C0 2 pressure used to avoid the PLA beads from sticking together.
  • the temperature of the impregnation and the extraction is more preferably -10 to +15 °C, in order to achieve reasonable treatment time and ensures that C0 2 is liquid at the pressure chosen in the range of 4,5-8 MPa.
  • the total amount of liquid C0 2 used in the liquid C0 2 treatment is advantageously in the range of 2-20 kg C0 2 /kg PLA.
  • the liquid C0 2 drained from the impregnation and extraction may be transferred to a recovery equipment, in which the C0 2 is recovered by separation of extractives from the C0 2 by distillation.
  • the recovered C0 2 may then be recycled to an impregnation and extraction step of PLA resin beads. Accordingly, the C0 2 can be recirculated in a closed circuit, which is advantageous from both an environmental and an economical point of view.
  • the PLA resin beads are placed the reactor (a pressure vessel) under impregnation pressure and temperature, and liquid C0 2 is then added to the reactor until the PLA resin beads are at least partially submerged, or if a rotating drum is used, until the amount of liquid C0 2 is sufficient to wet the PLA beads.
  • the PLA resin beads are left in contact with the liquid C0 2 for a predetermined time, preferably 10 to 240 minutes, to achieve sufficient C0 2 content and at the same time avoid unnecessary treatment time in order to save costs.
  • Achieving equilibrium takes approximately 30-90 minutes when using PLA Ingeo 4060DTM (NatureWorks LLC, USA), a commonly available commercial amorphous grade but may take longer or shorter depending on the size of the beads and the grade and composition of the beads. After substantially achieving equilibrium at the preferred temperature and pressure ranges, the beads comprise about 18-35 % C0 2 by weight. When using PLA Ingeo 4060DTM and C0 2 at 6 MPa and 10 °C equilibrium results in the beads having around 30 % by weight C0 2 .
  • the impregnated and extracted PLA resin beads are stored in a freezer until C0 2 is desorbed and dispersed evenly throughout the impregnated bead, and leads to even foaming and good cell structure. Pre-expansion is conducted at different temperatures and for different times according to the individual foaming characteristics of impregnated beads which in turn depends on blend and C0 2 content and the differences in minimum foaming temperatures that are the consequence of these factors.
  • the pre- expansion is conducted at temperatures ranging from 50 °C to 90 °C at ambient pressure and more preferably commercially available amorphous PLA beads having been impregnated to about 30 % by weight C0 2 , refrigerated until the C0 2 percentage reduces to 5-18 %, and pre-expanded at 50-75 °C.
  • the pre-expanded beads are promptly transferred into a mould and steam (or other heating providing a temperature higher than the pre-expansion temperature) is applied to further expand the beads and fuse them together in the mould.
  • a vacuum may also be applied before cooling and removal from the mould.
  • the mould is preferably adapted to produce a moulded product including moulded blocks and shaped moulded products, especially blocks adapted to form packing material and shaped moulded products in the form of packaging material or convenience items such as packaging and storage products.
  • Preferred convenience items include containers such as clamshell containers, pots, boxes, bowls, cups, plates and trays.
  • the material of the present invention is an expanded polylactic acid (PLA) resin which comprises a total amount of extractives of 0-0,035 % by weight.
  • the total amount of extractives is calculated based on the total weight of PLA, said extractives being substances that can be extracted from PLA with diethyl ether as extraction medium.
  • the total amount of extractives is determined by means of the following method, which accordingly is a method used to describe the quantitative determination of extractable compounds in PLA (polylactic acid).
  • 2.6-diethylnaphtalene (DiEN) is used as internal standard (ISTD). No correction is made to compensate for the individual extractives detector responses in relation to the internal standard.
  • standard solutions are prepared, said solutions being an internal standard stock solution (ISTDO) and an internal standard working solution (ISTD1 ).
  • the stock solution is prepared by dissolving 0.04 to 0.05 g of DiEN in 50 mL of acetone (99.9%).
  • the concentration of DiEN will be approximately 0.9 g/L. The true concentration is calculated.
  • the concentration of DiEN will be approximately 180 mg/L. The true concentration is calculated.
  • PLA beads are ground in a centrifugal mill (Retsch ZM1 ) under cooling with liquid nitrogen.
  • the sample is ground to a size of 0.5 mm.
  • An amount of approximately 1 g ground sample is put into a round bottom flask for reflux and 100 mL of diethyl ether is added (the true amount of PLA sample is noted).
  • a few anti-bumping granules are put into the round bottom flask.
  • the sample Before starting the reflux, the sample is standing for 5 minutes. The reflux is performed for 1 hour and the diethyl ether is thereafter collected and reduced to 10 mL and 10 ⁇ of ISTD 1 is added.
  • Carrier gas 0.7 mL/min of helium at a constant flow
  • Cis concentration of ISTD in sample extract (mg/L)
  • Example 2 Gas analysis performed for Example 2 below The followed procedure was applied for gas analysis (example 2). 5-hexen-1 -ol was used as internal standard, and a working solution was prepared by dissolving approximately 1 gram of 5-hexen-1 -ol in 250 mL methanol. The true concentration was calculated. From the working solution 2 ⁇ was injected into the gas-tight bag used in example 2. The bag was conditioned in room temperature for 1 hour before analysis. Solid phase microextraction (SPME) supplied with Carboxen 0,75 ⁇ absorption phase was inserted into the gas-tight bag. After the SPME phase has been exposed to the sampled gas for 30 minutes it was transferred to the GC-MS for analysis.
  • SPME Solid phase microextraction
  • Carrier gas 1 mL/min of helium at a constant flow
  • PLA beads were used without additional treatment, i.e. as commercially available.
  • PLA Ingeo 4060DTM (NatureWorks LLC, USA) as commercially available was extracted with diethyl ether according to the above described procedure for determining extractives in PLA, and analysed with GC-MS regarding extractable low molecular compounds. Among detected extractives, lactide was dominating followed by other lactic acid oligomers. The result is shown in Table 1.
  • Example 2 The aim of Example 2 was to determine extractable substances extracted from the PLA, which may not have been detected by the extraction with diethylether.
  • PLA Ingeo 4060D (NatureWorks LLC, USA) as commercially available was placed in an autoclave which was filled with liquid carbon dioxide and pressurised to 60 bars at 0-2 °C. The ratio by weight between PLA and carbon dioxide was 1/10.
  • liquid C0 2 was drained off and C0 2 was collected in a gas-tight bag (1 L, Tedlar, SKC). The gas-tight bag was carefully cleaned and checked for background before sample collection.
  • the C0 2 liquid level was allowed to decrease until the ratio by weight between PLA and C0 2 was 1/2.
  • the remaining liquid C0 2 was evaporated during the evacuation of C0 2 , thereby decreasing the temperature below Tg for PLA impregnated with C0 2 .
  • the impregnated beads were stored at -19 °C over night and thereafter pre- expanded in hot water.
  • a mould was filled with pre-expanded beads and moulded by applying steam mixed with air. Extractable substances in the gas phase were analysed according to the gas analysis procedure as described above. Lactide was dominating followed by other lactic acid oligomers.
  • Example 3 The aim of Example 3 was to determine substances extracted from the PLA, which may not have been detected by the extraction with diethyl ether, by a method different to the one used in Example 2.
  • PLA Ingeo 4060DTM (NatureWorks LLC, USA) as commercially available was placed in an autoclave which was filled with liquid carbon dioxide (PLA/C0 2 ; 1/10 by weight) and pressurised to 50 bars at 0 °C. After 80 minutes, the liquid phase C0 2 was removed by evaporation and the pressure released. Substances released from PLA during impregnation were collected from the reactor chamber by extraction of the reactor with acetone, and analysed with GC-MS.
  • PLA/C0 2 liquid carbon dioxide
  • PLA Ingeo 4060DTM (NatureWor s LLC, USA) as commercially available was placed in an autoclave and treated with liquid carbon dioxide (PLA C0 2 , 1/100 by weight) at 53 bars at 0°C for 90 minutes. The liquid phase was drained off until the ratio by weight between PLA and C0 2 was 1/20 and the remaining liquid C0 2 was evaporated during evacuation of C0 2 gas in order to lower the temperature below Tg for C0 2 impregnated PLA.
  • PVA C0 2 liquid carbon dioxide
  • the remaining low molecular substances in the purified PLA was determined by extraction with diethyl ether according to the above described method and analysed with GC-MS. Detected substances were lactide and other lactic acid oligomers. The result is shown in Table 1.
  • the impregnated beads were also stored, pre-expanded, foamed and moulded according to the method described in example 2.
  • Example 5 liquid C0 2 drained off (2 impregnation and extraction steps)
  • PLA Ingeo 4060DTM (NatureWorks LLC, USA) as commercially available was placed in an autoclave and treated with liquid carbon dioxide (PLA/C0 2 ; 1/100 by weight) at 53 bars at 0 °C for 90 minutes. The liquid phase was drained off until the ratio by weight between PLA and C0 2 was 1/20. A second treatment in which pure liquid C0 2 was added at 53 bars was done at 53 bars, -5-0 °C for 90 minutes. The liquid phase was drained off until the ratio by weight between PLA and C0 2 was 1/20 and the remaining liquid C0 2 was evaporated during evacuation of C0 2 gas in order to lower the temperature below Tg for C0 2 impregnated PLA. .
  • the remaining low molecular substances in the purified PLA were determined by extraction with diethyl ether according to the described method and analysed with GC-MS. Detected substances was lactide and other lactic acid oligomers. The result is shown in Table 1 .
  • Example 6 liquid C0 2 drained off (3 impregnation and extraction steps)
  • PLA Ingeo 4060DTM (NatureWorks LLC, USA) as commercially available was placed in an autoclave.
  • PLA was treated with liquid carbon dioxide (PLA/C02, 1/100 by weight) at 53 bars, 0 °C for 90 minutes.
  • the liquid phase was drained off until the ratio by weight between PLA and C0 2 was 1/20.
  • the procedure was repeated with pure liquid C0 2 two more times.
  • the liquid phase was drained off until the ratio by weight between PLA and C0 2 was 1/20 and the remaining liquid C0 2 was evaporated during evacuation of C0 2 gas in order to lower the temperature below Tg for C0 2 impregnated PLA.
  • Table 1 The result is shown in Table 1 .
  • the remaining low molecular substances in the purified PLA were determined by extraction with diethyl ether according to the described method and analysed with GC-MS. Detected substances were lactide and other lactic acid oligomers.
  • PLA Ingeo 4060DTM (NatureWor s LLC, USA) as commercially available was placed in an autoclave. PLA was treated with liquid carbon dioxide (PLA/C02, 1/100 by weight) at 53 bars, 0 °C for 90 minutes. The liquid phase was drained off until the ratio by weight between PLA and C0 2 was 1/20. The procedure was repeated with pure liquid C0 2 three times. The liquid phase was drained off until the ratio by weight between PLA and C0 2 was 1/20 and the remaining liquid C0 2 was evaporated during evacuation of C0 2 gas in order to lower the temperature below Tg for C0 2 impregnated PLA. The result is shown in Table 1 .
  • the remaining low molecular substances in the purified PLA were determined by extraction with diethyl ether according to the described method and analysed with GC-MS. Detected substances were lactide and other lactic acid oligomers.
  • Table 1 shows that three impregnation and extraction steps may be sufficient to decrease the amount of extractives to a reasonable level, which is considerably lower than the initial levels in the PLA material.
  • PLA Nature Works Ingeo 4060D, re-extruded to beads with the appropriate size of 1 ,5 x1 ,5 mm, was placed in an autoclave together with a cotton bag containing, the colouring agent 1 ,4-diamino anthraquinone (Sigma-Aldrich) 0,4% by weight PLA .
  • Liquid C0 2 was added at 47 bars and 0-1 °C until the ratio by weight between PLA and C0 2 was 1/10 .
  • After 90 minutes treatment liquid C0 2 was drained off until the ratio by weight between PLA and C0 2 was 1/2, and the remaining liquid C0 2 was evaporated during evacuation of C0 2 gas in order to lower the temperature below Tg for C0 2 impregnated PLA.
  • Purple PLA pellets were collected from the reactor. After storage at -19 °C, the impregnated beads were foamed and moulded according to the method described in example 2. The foam was light purple.
  • Figure 1 shows a schematic view of a system for performing a process including the method of impregnating and purifying PLA resin.
  • an extraction chamber 1 is loaded with PLA resin beads through an inlet 2.
  • the extraction chamber may be a reactor in the form of an autoclave or any other vessel that may be pressurised. Air present in the extraction chamber 1 is evacuated by means of a vacuum pump.
  • C0 2 gas is supplied to the extraction chamber 1 from a C0 2 storage tank 3, so as to pressurize the extraction chamber 1 to approximately 6 MPa with C02 gas.
  • Sensors in the system monitor the level of C0 2 in the storage tank 3, and additional C0 2 is added to the extraction chamber 1 from a storage tank 3_from an external source (not shown in figure 1 ) if necessary.
  • the pressures in the extraction chamber 1 and the storage tank 3 are balanced to a pressure P0.
  • Liquid C0 2 is added from the storage tank 3 to the extraction chamber 1 at the pressure P0, and the temperature TO, by means of a compressor, which sucks gas from extraction chamber 1 and pushes out liquid C0 2 from the bottom of the storage tank 3 by adding it to the top.
  • additives for coating or impregnating into the PLA material can be added to the liquid C0 2 .
  • the temperature in the extraction chamber 1 is decreased by evaporation of liquid C0 2 to a pressure P1 and temperature T1 .
  • C0 2 gas is taken from the storage tank 3 by the compressor and is supplied at the top of the extraction chamber 1 to a pressure P2 at a temperature T1 , thereby achieving a subcooling of the liquid C0 2 , thus preventing the PLA resin beads from sticking together.
  • the temperature T1 should be below the glass transition temperature Tg of PLA for the actual C0 2 pressure.
  • Evaporation and addition of C0 2 gas so as to achieve subcooling of the liquid C0 2 is repeated as often as necessary to maintain the desired conditions in the extraction chamber 1 .
  • the pressures between the extraction chamber 1 and the distiller tank 4 are balanced, and liquid C0 2 is drained off from the extraction chamber to the distiller tank 4.
  • the impregnation and extraction phase may be repeated several times, as desired.
  • Liquid C0 2 received in the distiller tank 4 comprises extractable substances originating from the PLA resin beads.
  • the C0 2 is separated from these extractable substances by distillation, and the pure C0 2 thereby obtained is recycled to the storage tank 1 .
  • the extractable substances remain at the bottom of the distiller tank
  • the above system relates to a batch process. However, the process may as well be performed continuously, and the system is then adapted thereto.
  • FIG. 2 shows a schematic view of a system for performing a process including the method of impregnating and purifying PLA resin.
  • an extraction chamber 1 is loaded with PLA resin beads through an inlet 2.
  • the extraction chamber may be a reactor in the form of an autoclave or any other vessel that may be pressurized. Air present in the extraction chamber 1 is evacuated by means of a vacuum pump.
  • C0 2 gas is supplied to the extraction chamber 1 from a C0 2 storage tank 3, so as to pressurize the extraction chamber 1 to approximately 6 MPa with C0 2 gas.
  • Sensors in the system monitor the level of C0 2 in the storage tank 3, and additional C0 2 is added to the extraction chamber 1 from an external source if necessary.
  • the setpoint temperature is maintained using a cooling unit.
  • the pump is used to maintain the setpoint pressure in the extraction chamber during the extraction/impregnation.
  • the PLA particles are rotated in a drum in the extraction chamber 1.
  • the C0 2 in the extraction chamber 1 is drained to the distiller tank 4 after a predetermined time. New C0 2 is added from the storage tank 3 to the extraction chamber 1 while C0 2 in the distiller tank 4 is distilled and transported to storage tank 3 while extraction/impregnation of PLA occurs in the extraction chamber 1 in the same way as in the first bath.
  • the number of C0 2 baths can vary depending on purity level of the PLA. In any of the baths an additive can be added to the extraction chamber 1 to modify the properties of the PLA.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)

Abstract

La présente invention concerne une substance comprenant une résine expansée d'acide polylactique (PLA) contenant une quantité totale de produits d'extraction allant de 0 à 0,035 % en poids, comme calculé sur la base du poids total de PLA, lesdits produits d'extraction étant des substances pouvant être extraites du PLA en utilisant, comme produit d'extraction, de l'éther diéthylique, selon le procédé de détermination des produits d'extraction du PLA décrit dans la description de la présente demande de brevet.
PCT/SE2011/050394 2011-04-04 2011-04-04 Substance hautement purifiée comprenant une résine expansée d'acide polylactique WO2012138265A1 (fr)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014037889A1 (fr) * 2012-09-05 2014-03-13 Biopolymer Network Limited Fabrication de mousses d'acide polylactique au moyen de dioxyde de carbone liquide

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Publication number Priority date Publication date Assignee Title
US5049328A (en) * 1990-07-02 1991-09-17 Arco Chemical Technology, Inc. Purification, impregnation and foaming of polymer particles with carbon dioxide
WO2008045516A1 (fr) * 2006-10-11 2008-04-17 Qlt Usa, Inc. Préparation par extraction avec un fluide supercritique de polyesters biodégradables ayant des propriétés de faible pic de libération immédiate
WO2008093284A1 (fr) * 2007-01-30 2008-08-07 Biopolymer Network Limited Procédés de fabrication de mousses en acide polylactique
US20080269449A1 (en) * 2007-01-23 2008-10-30 Ferro Pfanstiehl Laboratories, Inc. Methods for the purification of polymers
WO2010053242A1 (fr) * 2008-11-07 2010-05-14 Samyang Corporation Acide polylactique extrêmement pur ou son dérivé, son sel et méthode de purification associée

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Publication number Priority date Publication date Assignee Title
US5049328A (en) * 1990-07-02 1991-09-17 Arco Chemical Technology, Inc. Purification, impregnation and foaming of polymer particles with carbon dioxide
WO2008045516A1 (fr) * 2006-10-11 2008-04-17 Qlt Usa, Inc. Préparation par extraction avec un fluide supercritique de polyesters biodégradables ayant des propriétés de faible pic de libération immédiate
US20080269449A1 (en) * 2007-01-23 2008-10-30 Ferro Pfanstiehl Laboratories, Inc. Methods for the purification of polymers
WO2008093284A1 (fr) * 2007-01-30 2008-08-07 Biopolymer Network Limited Procédés de fabrication de mousses en acide polylactique
WO2010053242A1 (fr) * 2008-11-07 2010-05-14 Samyang Corporation Acide polylactique extrêmement pur ou son dérivé, son sel et méthode de purification associée

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KOEGLER, W.S. ET AL.: "Carbon Dioxide Extraction of Residual Chloroform from Biodegradable Polymers", JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, vol. 63, no. 5, August 2002 (2002-08-01), pages 567 - 576, XP002602824, DOI: doi:10.1002/JBM.10209 *
PACK, J.W. ET AL.: "Ring-Opening Polymerization of L-Lactide and Preparation of Its Microsphere in Supercritical Fluids", MACROMOLECULAR BIOSCIENCE, vol. 4, no. 3, March 2004 (2004-03-01), pages 340 - 345 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014037889A1 (fr) * 2012-09-05 2014-03-13 Biopolymer Network Limited Fabrication de mousses d'acide polylactique au moyen de dioxyde de carbone liquide

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