WO2008115980A1 - Bouteille en poly(lactide) moulé par injection-étirage-soufflage et procédé de celle-ci - Google Patents

Bouteille en poly(lactide) moulé par injection-étirage-soufflage et procédé de celle-ci Download PDF

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Publication number
WO2008115980A1
WO2008115980A1 PCT/US2008/057478 US2008057478W WO2008115980A1 WO 2008115980 A1 WO2008115980 A1 WO 2008115980A1 US 2008057478 W US2008057478 W US 2008057478W WO 2008115980 A1 WO2008115980 A1 WO 2008115980A1
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Prior art keywords
molded container
blow molding
stretch blow
conditioning
preform
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PCT/US2008/057478
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English (en)
Inventor
Jim Lunt
Pat Gruber
Greg Roda
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Green Harvest Technologoes, Llc
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Application filed by Green Harvest Technologoes, Llc filed Critical Green Harvest Technologoes, Llc
Priority to EP08732470A priority Critical patent/EP2134765A4/fr
Publication of WO2008115980A1 publication Critical patent/WO2008115980A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
    • C08L67/04—Polyesters derived from hydroxycarboxylic acids, e.g. lactones
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
    • B29C49/42—Component parts, details or accessories; Auxiliary operations
    • B29C49/64—Heating or cooling preforms, parisons or blown articles
    • B29C49/6409—Thermal conditioning of preforms
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
    • B29C49/42—Component parts, details or accessories; Auxiliary operations
    • B29C49/64—Heating or cooling preforms, parisons or blown articles
    • B29C49/6409—Thermal conditioning of preforms
    • B29C49/6418—Heating of preforms
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
    • B29C49/02—Combined blow-moulding and manufacture of the preform or the parison
    • B29C2049/023—Combined blow-moulding and manufacture of the preform or the parison using inherent heat of the preform, i.e. 1 step blow moulding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
    • B29C49/42—Component parts, details or accessories; Auxiliary operations
    • B29C49/78—Measuring, controlling or regulating
    • B29C49/783—Measuring, controlling or regulating blowing pressure
    • B29C2049/7831—Measuring, controlling or regulating blowing pressure characterised by pressure values or ranges
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2949/00—Indexing scheme relating to blow-moulding
    • B29C2949/07—Preforms or parisons characterised by their configuration
    • B29C2949/0715—Preforms or parisons characterised by their configuration the preform having one end closed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2949/00—Indexing scheme relating to blow-moulding
    • B29C2949/07—Preforms or parisons characterised by their configuration
    • B29C2949/081—Specified dimensions, e.g. values or ranges
    • B29C2949/0811—Wall thickness
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2949/00—Indexing scheme relating to blow-moulding
    • B29C2949/20—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer
    • B29C2949/22—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer at neck portion
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2949/00—Indexing scheme relating to blow-moulding
    • B29C2949/20—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer
    • B29C2949/24—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer at flange portion
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2949/00—Indexing scheme relating to blow-moulding
    • B29C2949/20—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer
    • B29C2949/26—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer at body portion
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2949/00—Indexing scheme relating to blow-moulding
    • B29C2949/20—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer
    • B29C2949/28—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer at bottom portion
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2949/00—Indexing scheme relating to blow-moulding
    • B29C2949/30—Preforms or parisons made of several components
    • B29C2949/3024—Preforms or parisons made of several components characterised by the number of components or by the manufacturing technique
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2949/00—Indexing scheme relating to blow-moulding
    • B29C2949/30—Preforms or parisons made of several components
    • B29C2949/3032—Preforms or parisons made of several components having components being injected
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
    • B29C49/02—Combined blow-moulding and manufacture of the preform or the parison
    • B29C49/06—Injection blow-moulding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
    • B29C49/08—Biaxial stretching during blow-moulding
    • B29C49/10—Biaxial stretching during blow-moulding using mechanical means for prestretching
    • B29C49/12—Stretching rods
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
    • B29C49/42—Component parts, details or accessories; Auxiliary operations
    • B29C49/64—Heating or cooling preforms, parisons or blown articles
    • B29C49/6409—Thermal conditioning of preforms
    • B29C49/6427—Cooling of preforms
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
    • B29C49/42—Component parts, details or accessories; Auxiliary operations
    • B29C49/64—Heating or cooling preforms, parisons or blown articles
    • B29C49/6604—Thermal conditioning of the blown article
    • B29C49/6605—Heating the article, e.g. for hot fill
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
    • B29C49/42—Component parts, details or accessories; Auxiliary operations
    • B29C49/64—Heating or cooling preforms, parisons or blown articles
    • B29C49/6604—Thermal conditioning of the blown article
    • B29C49/6605—Heating the article, e.g. for hot fill
    • B29C49/66055—Heating the article, e.g. for hot fill using special pressurizing during the heating, e.g. in order to control the shrinking
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2995/00—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds
    • B29K2995/0037—Other properties
    • B29K2995/0059—Degradable
    • B29K2995/006—Bio-degradable, e.g. bioabsorbable, bioresorbable or bioerodible
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2031/00—Other particular articles
    • B29L2031/712—Containers; Packaging elements or accessories, Packages
    • B29L2031/7158—Bottles

Definitions

  • aspects of the present invention relate to the use of polylactide resin (PLA) in an injection stretch blow molding process to manufacture durable and relatively thick- walled containers suitable for repeated use.
  • aspects of the present invention relate to PLA bottles produced using the processes described herein.
  • Containers such as water bottles are often molded from thermoplastic resins such as polypropylene, PVC, PET and polycarbonate.
  • Polycarbonate in particular, is the material of choice for clear and durable thick walled drinking containers used for non-carbonated drinks. Such containers are often used by outdoor sporting enthusiasts and for baby bottles.
  • the advantages of polycarbonate include high clarity, high impact resistance and non retention of odors.
  • Drawbacks of polycarbonate include the fact that it is produced from non renewable resources and is thus difficult to dispose of at the end of its useful life.
  • concerns have surfaced regarding the effects on human health due to potential leaching of residual monomers during contact with liquids.
  • Polylactide resins also known as Polylactic acid or PLA
  • PLA is produced from annually renewable resources such as corn or sugar beet.
  • PLA is easily composted to produce carbon dioxide and water.
  • U.S. Patent No. 5,409,751 the details of which are incorporated into the present disclosure by reference, describes such a process.
  • the process described in U.S. Patent No. 5,409,751 involves first forming a preform, or "plug", which is hollow and has dimensions far smaller than that of the final container.
  • the preform is molded into a container by inserting it into a mold, and stretching it both axially (i.e. along its length) and radially.
  • the axial stretching is done mechanically by inserting a pusher rod into the preform and mechanically extending it towards the bottom of the mold. Radial stretching is accomplished by injecting a compressed gas into the plug, thereby forcing the resin outward to contact the interior surface of the mold. Typically, a preliminary radial stretch is preformed by injecting a first increment of gas. This makes room for the stretcher rod, which can then be inserted. The preform is then stretched and immediately afterward is blown with more gas to complete the blow molding operation. [0005] ISBM processes are generally divided into two main types. The first is a one- step process, in which the preform is molded, conditioned, and then transferred to the stretch blow molding operation before the preform has cooled below its softening temperature.
  • the second type of ISBM process is a two-step process in which the preform is prepared ahead of time and stored for later use.
  • the preform is reheated prior to the initiation of the stretch blow molding step.
  • the two-step process has the advantage of faster cycle times, as the stretch blow molding step does not depend on the slower injection molding operation to be completed.
  • the two-step process presents the problem of reheating the preform to the stretch blow molding temperature. This is usually done using infrared heating, which provides radiant energy to the outside of the preform. It is sometimes difficult to heat the preform uniformly using this technique and unless done carefully, a large temperature gradient can exist from the outside of the preform to the center. Conditions usually must be selected carefully to heat the interior of the preform to a suitable molding temperature without overheating the outside. The result is that the two-step process usually has a smaller operating window than the one-step process.
  • the preform is generally heated to a temperature at which the preform becomes soft enough to be stretched and blown. This temperature is generally above the glass transition temperature (Tg) of the PLA resin. A preferred temperature is from about 70 to about 120° C. and a more preferred temperature is from about 80 to about 100° C. The transition temperature is dependent upon the specific PLA resin being used. In order to help obtain a more uniform temperature gradient across the preform, the preform may be maintained at the aforementioned temperatures for a short period to allow the temperature to equilibrate.
  • Mold temperatures in the two-step process are generally below the glass transition temperature of the PLA resin, such as from about 30 to about 60° C, especially from about 35 to about 55° C. Sections of the mold such as the base where a greater wall thickness is desired may be maintained at even lower temperatures, such as from about 0 to about 35° C, especially from about 5 to about 20° C.
  • the preform from the injection molding process is transferred to the stretch blow molding step while the preform is still at a temperature at which the preform becomes soft enough to be stretched and blown, again preferably above the Tg of the resin, such as from about 80 to about 120° C, especially from about 80 to about 110° C.
  • the preform may be held at that temperature for a short period prior to molding to allow it to equilibrate at that temperature.
  • the mold temperature in the one-step process may be above or below the Tg of the PLA resin. In the so-called "cold mold” process, mold temperatures are similar to those used in the two-step process.
  • the mold temperature is maintained somewhat above the Tg of the resin, such as from about 65 to about 100° C.
  • the molded part may be held in the mold under pressure for a short period after the molding is completed to allow the resin to develop additional crystallinity and relax residual stresses in the amorphous phase (commonly referred to as heat setting).
  • the heat setting tends to improve the dimensional stability and heat resistance of the molded container while still maintaining good clarity.
  • Heat setting processes may also be used in the two-step process, but are used less often in that case because the heat setting process tends to increase cycle times.
  • Blowing gas pressures in either the one-step or two-step processes typically range from about 5 to about 50 bar (about 0.5 to about 5 MPa), such as from about 8 to about 45 bar (about 0.8 to about 4.5 MPa). It is common to use a lower pressure injection of gas in the preliminary radial stretch, followed by a higher pressure injection to complete the blowing process. ISBM processes can further be defined as either a single blow process, where the preform is stretched to its final shape in a single blowing process, or a double blow process, where the perform is first blown followed by a second blow process using the previously formed bottle.
  • Nalgene ® is one of the registered trademarks of Nalge Nunc International, or its subsidiaries.
  • One of Nalge's major products is a line of clear plastic drinking water bottles of various size marketed to outdoor enthusiasts. Produced from polycarbonate by an Injection Stretch Blow Molding Process (ISBM), the key properties of these bottles are high impact resistance and resistance to staining. In addition, they do not retain odors, are capable of withstanding sub-freezing to boiling temperatures, are dishwasher safe away from the heating element, and can withstand temperature ranges of 135°C/275°F to -135°C/-21 FF. These properties make the Nalge bottles, and others formed from a similar polycarbonate, appealing to consumers who need a durable and reusable bottle for various activities.
  • ISBM Injection Stretch Blow Molding Process
  • the polycarbonate material these bottles are formed from is an amorphous polymer with a glass transition temperature of approximately 148°C.
  • the material has high toughness, transparency and very low moisture absorption as additional positive attributes for this market.
  • these polycarbonate bottles have several negative attributes including that they are derived from non-renewable oil based resources, have high melt processing temperatures of approx 200C, and have a relatively high material cost.
  • Polycarbonate bottles such as the clear Nalgene ® type found in many outdoor sporting goods retail stores, are typically made by one or more of the same injection stretch blow molding process known and described above.
  • PLA products have high MVTR and high oxygen and carbon dioxide transmission rates which exclude PLA bottles from the longer life beverage/drinks bottle applications and carbonated soft drinks markets.
  • properties of PLA for the short shelf life, more durable non-carbonated market segment presently occupied by polycarbonate Nalgene ® - type bottles hold significant potential to meet the functional requirements of this market segment.
  • PLA has superior oxygen and carbon dioxide permeability although, as already noted, the carbon dioxide permeability of both polymers makes both unsuitable for the carbonated drinks market
  • An injection stretch blow molding process for making containers from a polylactic acid resin.
  • the process comprises molding the polylactic acid resin into a perform, applying heat to the perform, stretching and blowing the perform in axial and radial dimensions in order to form a preliminary molded container, and conditioning the molded container.
  • Another aspect of the present invention includes an injection stretch blow molding process for making containers from a polylactic acid resin.
  • the process comprises molding the polylactic acid resin into a perform, applying heat to the perform, stretching and blowing the perform in axial and radial dimensions in order to form a preliminary molded container, conditioning the molded container pursuant to a first conditioning method, conditioning the molded container pursuant to a second conditioning method, and stretching and blowing the molded container in order to form a final molded container.
  • Relatively rigid bottles constructed in accordance with one or more processes disclosed herein are also contemplated.
  • FIG. 1 is a schematic diagram/flow chart of a single blow ISBM process
  • FIG. 2 is a schematic diagram/flow chart of a double-blow ISBM process
  • FIG. 3 is a drawing showing the details of a representative PLA bottle produced pursuant to one or more of the processes described herein.
  • aspects of the present invention relate to ISBM manufacturing processes for producing relatively thick walled containers from a PLA resin wherein (1) the PLA is a copolymer having repeating L and D lactic acid units in which either the L or D units are the predominant repeating units and the predominant repeating units constitute 90 to 99.5% of the lactic acid repeating units; (2) the product of axial and radial stretch ratios is from about 3 to about 17.5; and (3) where the wall thickness of the final container is from about 30 to about 80 mils, although wall thicknesses greater than 80 mils are also contemplated in some embodiments.
  • PLA polymers are already in the marketplace for single use, short shelf applications such as non carbonated water sold through retail stores. Because of their low wall thicknesses (10-12 mil), which leads to low durability, poor impact performance, and low temperature performance (130°F/55°C), these single use products will not meet the demands of the outdoor multiple use sporting goods market. It has been shown in connection with aspects of the present invention that these issues can be overcome by the use of various heat-setting techniques and modifications to ISBM processes.
  • the ISBM process in accordance with aspects of the present invention can be either a one or two step process as described more fully below and can utilize either a single blow or a multiple blow process. While not specifically required, in preferred embodiments, a double blow process has been shown to yield desirable results. It should be noted that while some embodiments within the specification might be referred to as preferred, this language is not intended to limit the scope of the claims to these specific embodiments, unless specifically indicated in the specification and claims. The claims are meant to encompass the broadest interpretation that is consistent with the plain meaning of the terms as confirmed by the specification.
  • PLA resin within the processing guidelines and specific manufacturing specifications stated below and as set forth in the appended claims, allows for containers to be produced through an ISBM process that have controlled crystallinity, good clarity, good impact performance, and increased thermal stability over previously produced PLA containers.
  • thick walled containers in accordance with aspects of the present invention are made using an injection stretch molding (ISBM) process.
  • ISBM processes are well known, being described for example in U.S Patent No. 5,409,751, the details of which are incorporated into the present disclosure by reference in their entirety, and further described in Figure 1.
  • the generalized ISBM process 100 involves first forming a preform or "plug" at step 102 which is hollow and whose dimensions are a fraction of those of the final container.
  • the perform geometry is specifically designed to produce a container of a determined geometry.
  • the preform can be formed, conditioned, and transferred to the stretch blow molding operation before the preform is cooled below its softening temperature at step 104.
  • This process is commonly referred to as a "one step” process since the perform is prepared and blown into a container in a single step, prior to the perform cooling.
  • the preform is allowed to cool below its softening point and can then be stored for use at a later time at step 103.
  • the preform is then reheated to carry out the stretch blow molding process when needed at step 104.
  • This process is commonly referred to as a "two-step” process.
  • Conditioning step 106 may be carried out depending on the specific application. After any such conditioning, the finished bottled is ejected from the processing machine at step 108
  • the two step process is most often employed for the manufacture of thick walled durable containers such as the Nalgene-type bottles described above.
  • the two- step process has the advantage of faster cycle times since the stretch molding process step does not depend on the slower preform injection molding process. Additionally, for the production of thick walled containers the preform temperature can be accurately controlled to allow even material distribution and stress distribution in the final part, thereby providing the required durability and robustness required.
  • Figure 2 describes such a process 200.
  • a preform is prepared at 202 and reheated and/or conditioned.
  • the preform is rotated during this process to ensure a consistent reheat.
  • a primary blow-molding step 204 the reheated preforms are stretch blown in a primary stretch blow mold.
  • a first conditioning step 206 heat setting or some other type conditioning is achieved. Heat setting can be performed through, for example, a direct contact procedure.
  • a second conditioning step 208 is applied, for example heat processing in an oven or other contained environment.
  • the bottle undergoes a final blow-molding step 210 in which the bottle takes its final form prior to being ejected from the processing equipment 212.
  • Various modifications to one or more of the above double-blow process are known in order to fine tune the resulting bottle.
  • the controlled reheating of the preform and the subsequent stretch blow molding step are also highly dependent on the grade of PLA resin utilized.
  • the three significant resin variables are: 1) molecular wt, 2) viscosity versus temperature, and 3) enantiomeric ratio (L to D ratio). All three variables must be carefully selected and controlled to enable a practical processing window for the manufacture of thick walled containers. The correct selection of the resin grade is also essential if high clarity is also required in the final part. Examples of enantiomeric ratio, extensional viscocity and molecular weight information can be found, for example, in PCT Patent Application publication No. WO2006/002409 assigned to Nature Works LLC. The details of this reference are hereby incorporated into the present disclosure by reference in its entirety.
  • Mold temperatures in a two-step process are generally held below the glass transition temperature of the PLA resin, typically from about 30-60° centigrade and most preferably in the 35-55° centigrade range.
  • the mold temperature may be raised to 65-100 °C and the molded part held under controlled pressure for a short period of time. This allows stress relief and increased crystallinity to develop while maintaining the clarity in the part.
  • 0.5 liter bottles were prepared from specific PLA resins in a two-step ISBM process as follows.
  • Preforms having a weight of 100-180 gms were prepared via injection molding by heating the resin to a temperature of 200-220° and injecting the resin into a preform mold specifically designed for PLA and the final container dimensions.
  • Such a perform design takes into account the different extensional viscosity properties of PLA compared to other polymers.
  • the molding conditions were optimized to produce performs with even wall thickness, minimal part stress and clear parts free of haze.
  • the preforms were cooled to room temperature before stretch blow molding in a separate step. Stretch blow molding was accomplished using a typical stretch blow molding machine used for PET or PC bottles at cycles of up to 2000 bottles/ hour.
  • the PLA resins used were 1) a first copolymer of 96% L and 4% D having a relative number average molecular wt of above 100,000, and 2) a second copolymer of 98.4% L and 1.6% D having a relative molecular wt. of above 100,000.
  • the perform weight can be in the range of 100-180 gms.
  • the above example may be performed via a one-step process, where the conditioning step is eliminated.
  • Double blow molding process (200 0 F mold temperature for both passes)
  • Thermal Stability Six (6) bottles, from sets 1-10 listed above, were tested for thermal stability at 15O 0 F. The diameters, height and volume of each bottle were measured before placing the empty bottles in an oven at 15O 0 F for 24 hours. Once the bottles were removed from the oven and cooled to room temperature, they were re- measured. The difference of these measurements was reported as a percent change. If the bottles showed excessive shrinkage at the 15O 0 F storage temperature, the oven temperature was reduced in 1O 0 F increments for the storage until acceptable shrinkage was observed.
  • Crystallinity via DSC The crystallinity in the center of the panel area of the bottle was measured for sets 1-10. The crystallinity was also be measured in the base of sets 2, 10, and 11. Finally, the crystallinity was measured in the finish for sets 2 and 10.
  • Injection Molding The PLA resins in the previous example were dried overnight at 176°F to achieve a moisture level below 250 ppm prior to injection molding. Once dry, the appropriate amount of Colormatrix 80-740-2 reheat toner was added to an aluminized mylar bag, then purged with nitrogen and sealed. The aluminized Mylarbags were then placed on a tumbler for 10-15 minutes to allow an even distribution of material. The resin samples were injection molded on an Arburg 420M reciprocating screw injection molding machine using a 4Og preform tool designed to blow mold into a thick- walled 18oz Boston round container. The following table summarizes the injection molding conditions used for this trial. Approximately 300 preforms were produced using these conditions.
  • the blow mold set point temperature was 16O 0 F. Approximately 10 bottles were produced at this condition. Next, the blow mold set point temperature was increased in 5-20° F increments until acceptable bottles could not be produced. 10 bottles were collected at each blow molding interval and tested for color, crystallinity and thermal stability. Bottles were first blown under heat set conditions, increasing mold temperatures by 10° F until an acceptable bottle could no longer be produced. The highest mold temperature that could be used to produce bottles was 22O 0 F. One bottle from each of these blow molding conditions was placed into an oven overnight at 15O 0 F. These bottles were visually inspected the following morning. Observation indicated that bottles that were blown using a 200° F set point temperature appeared to shrink and deform the least.
  • the mold temperature of the base was increased in increments of 10° F until the base of the bottle began to roll out. Once this temperature was determined, it was reduced 10° F to produce 50 samples for the double blow process.
  • These bottles were then passed through the blow molder oven in order to shrink the bottle and relax the existing stress in the bottle's sidewall. Since wall thickness of the bottles is thin compared to the preforms, less heat was required to reheat the bottles compared to the preforms. To achieve this, one of the oven banks was turned off and the blow molder's speed was increased. Blow molding conditions were further optimized to produce a double blown container with the best distribution that could be achieved.
  • Color/Haze Results The sidewall of 1 bottle from each of the blow molding conditions was measured for color and haze. Measurements were made in two locations of the panel, the upper and lower panel. In general, the amount of haze in the upper panel was greater than in the lower panel of the same condition, and as the mold set point temperature was increased the amount of haze increased.
  • DSC Results Differential scanning calorimetry was performed on these bottles at a few different locations on the bottle to understand the effect that mold temperature has on the crystallinity of the bottles. As the mold set point temperature increases the ⁇ Hc decreases, the ⁇ Hc at 22O 0 F mold temperature and after double blowing. To understand the effect of base temperature on the base crystallinity a DSC was also run on the double blown bottles, bottles molded at 22O 0 F (65 0 F base, used as reference), and bottles blown using a HO 0 F base temperature were run. The ⁇ Hc of the HO 0 F was slightly lower than the 65 0 F. The ⁇ Hfwas similar for these two measurements. There was not a crystallization peak to measure for the double blown sample. To verify that the double blow process was not changing the thermal characteristics of the finish, DSCs were performed on the finish from a double blown bottle and the finish from a first pass bottle.
  • the thermal stability of the containers improves as the blow mold temperature increases and if the bottles are double blown.
  • the main shrinkage is in the base of the bottles and the thinner portions of the sidewall, however there are small amounts of deformation in the thicker portions of the sidewall.
  • the haze and DSC results are consistent with increasing crystallinity with increasing blow mold temperature.
  • Preform Design A preform and tooling based on the target stretch ratios of 3-4 hoop stretch and >2 axial stretch ratio to produce a container thickness of 0.030" was designed. This preform design allows for more orientation in the base area, which leads to improved drop impact performance.
  • finish and base areas are not heated during the blowing process and remain amorphous.
  • Blow Molding - Nature Works 7032 preforms (See example 2 above) were blow molded using a Sidel SBO 1/2 blow molding machine with mold temperatures set at 45 0 F. Initially the optimized blow molding conditions from the previous trial were attempted. At these conditions, the bottles were hazier in the neck area than they were in the previous trial and the material distribution was slightly different. The blow molding oven heating profile was then adjusted in an attempt to produce bottles with the same appearance and material distribution. During processing the sidewall
  • Bottles were produced for testing at two conditions; the table below summarizes the conditions used.
  • the PLA resin was dried at 176°F for 4 hours to remove moisture prior to injection molding.
  • the resin samples were injection molded on an Arburg 420M reciprocating screw injection molding machine using a 40.2 ⁇ 0.5g preform tooling.
  • An injection molding process was optimized to achieve a clear part at the lowest possible injection molding temperatures and mildest conditions. Following are the preform molding conditions.
  • Drop Impact Testing To determine the drop impact strength of the containers, bottles were filled with 18oz. of water, refrigerated for 24 hrs to 4O 0 F and dropped vertically onto a flat marble platform. A Bruceton staircase method was used to determine the average failure height starting from an initial height of 60 inches using increments of 6 inches. For this method, 21 bottles were dropped. Failure is defined as any leakage of contents not resulting from closure failure. For the 7032 bottles, no failures were observed during the testing. The results are contained in the following table, including those from the previous drop impact testing with the Nalgene® bottles.
  • Container Color Testing Six bottles from the optimized conditions for each material were evaluated for preform color in L*a*b* (CIELAB) color space according to ASTM D 1003-61 using a Minolta Color meter. Preforms were cut in half and then
  • Figures 3A-3C show an exemplary embodiment of a PLA bottle 300 produced according to one or more of the manufacturing methods described above. It should be understood that the example of Figure 3 is just that, an example, an many variations to the size, dimensions, appearance, and look of the example in Figure 3 are contemplated by the scope of the present disclosure and invention.
  • the PLA resin may be selected from the class of polyhydroxy alkanoates.
  • the polylactic acid polymer may be (a) a copolymer having repeating L and D lactic acid units in which either the L or D lactic acid units are the predominant units or (b) a blend of such copolymers wherein the predominant repeating units in the copolymer or blend constitute 90-99.5% of the lactic acid enantiomer repeating units in the PLA resin or blend.
  • the containers are clear containers capable of passing the industry standards for durable containers.
  • the containers do not have extractable levels that are suspected or known to have any affect on human health.
  • the renewable resource based thermoplastic resin has sufficient molecular wt. melt strength and viscosity to successfully produce a durable thick walled container.
  • the container has sufficient stress induced and quiescent crystallinity to produce a heat stable and impact resistant container capable of meeting the industry performance standards for Polycarbonate bottles.
  • the PLA resin has a number average molecular wt of 80000-150000 as measured by gel permeation chromatography using a polystyrene standard.
  • 92-99% of the lactic acid enantiomer repeating units in the PLA are of the predominant lactic acid enantiomer.
  • the formed container has sufficient stress induced and quiescent crystallinity to produce a heat stable and impact resistant container capable of meeting the industry performance standards for Polycarbonate bottles

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  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Blow-Moulding Or Thermoforming Of Plastics Or The Like (AREA)

Abstract

L'invention concerne un procédé de moulage par injection-étirage-soufflage pour fabriquer des contenants à partir d'une résine de poly(acide lactique). Dans un aspect, le procédé comprend le moulage de la résine de poly(acide lactique) en une préforme, l'application de la chaleur à la préforme, l'étirage et le soufflage de la préforme dans les directions axiale et radiale afin de former un contenant moulé préliminaire, le conditionnement du contenant moulé conformément à un premier procédé de conditionnement, le conditionnement du contenant moulé conformément à un second procédé de conditionnement, ainsi que l'étirage et le soufflage du contenant moulé afin de former un contenant moulé final. Des bouteilles relativement rigides construites selon un ou plusieurs procédés révélés ici sont également envisagées.
PCT/US2008/057478 2007-03-20 2008-03-19 Bouteille en poly(lactide) moulé par injection-étirage-soufflage et procédé de celle-ci WO2008115980A1 (fr)

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EP08732470A EP2134765A4 (fr) 2007-03-20 2008-03-19 Bouteille en poly(lactide) moulé par injection-étirage-soufflage et procédé de celle-ci

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US89577607P 2007-03-20 2007-03-20
US60/895,776 2007-03-20
US12/050,830 2008-03-18
US12/050,830 US20080230954A1 (en) 2007-03-20 2008-03-18 Injection Stretch Blow Molded Polylactide Bottle and Process For Making Same

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WO2010065020A1 (fr) * 2008-12-05 2010-06-10 Primo To Go, LLC Préforme pour moulage par soufflage d’une bouteille à partir d’une biorésine
US20100143625A1 (en) * 2008-12-05 2010-06-10 Primo To Go, LLC Preform for blow molding a bottle from bioresin
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