CA2107018A1 - Production of foamed polylactide injection moldings of high strength and rigidity - Google Patents
Production of foamed polylactide injection moldings of high strength and rigidityInfo
- Publication number
- CA2107018A1 CA2107018A1 CA002107018A CA2107018A CA2107018A1 CA 2107018 A1 CA2107018 A1 CA 2107018A1 CA 002107018 A CA002107018 A CA 002107018A CA 2107018 A CA2107018 A CA 2107018A CA 2107018 A1 CA2107018 A1 CA 2107018A1
- Authority
- CA
- Canada
- Prior art keywords
- polylactide
- solvent
- melt
- melting point
- mold
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 229920000747 poly(lactic acid) Polymers 0.000 title claims abstract description 20
- 238000001746 injection moulding Methods 0.000 title claims abstract description 10
- 238000004519 manufacturing process Methods 0.000 title description 3
- 239000002904 solvent Substances 0.000 claims abstract description 15
- 238000002844 melting Methods 0.000 claims abstract description 14
- 230000008018 melting Effects 0.000 claims abstract description 14
- 238000000034 method Methods 0.000 claims abstract description 11
- 238000000465 moulding Methods 0.000 claims description 8
- 239000003960 organic solvent Substances 0.000 claims description 5
- 238000009835 boiling Methods 0.000 claims description 2
- 239000011521 glass Substances 0.000 abstract description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 12
- 239000008187 granular material Substances 0.000 description 9
- 239000000155 melt Substances 0.000 description 7
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 6
- 229910052757 nitrogen Inorganic materials 0.000 description 6
- 239000004604 Blowing Agent Substances 0.000 description 5
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 description 4
- JJTUDXZGHPGLLC-UHFFFAOYSA-N lactide Chemical compound CC1OC(=O)C(C)OC1=O JJTUDXZGHPGLLC-UHFFFAOYSA-N 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 238000001816 cooling Methods 0.000 description 3
- 238000005187 foaming Methods 0.000 description 3
- 239000002667 nucleating agent Substances 0.000 description 3
- 229920001169 thermoplastic Polymers 0.000 description 3
- 239000004416 thermosoftening plastic Substances 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- HEDRZPFGACZZDS-UHFFFAOYSA-N Chloroform Chemical compound ClC(Cl)Cl HEDRZPFGACZZDS-UHFFFAOYSA-N 0.000 description 2
- XBDQKXXYIPTUBI-UHFFFAOYSA-M Propionate Chemical compound CCC([O-])=O XBDQKXXYIPTUBI-UHFFFAOYSA-M 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 238000002425 crystallisation Methods 0.000 description 2
- 230000008025 crystallization Effects 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 229920001519 homopolymer Polymers 0.000 description 2
- 238000004898 kneading Methods 0.000 description 2
- 239000004310 lactic acid Substances 0.000 description 2
- 229960000448 lactic acid Drugs 0.000 description 2
- 235000014655 lactic acid Nutrition 0.000 description 2
- TZIHFWKZFHZASV-UHFFFAOYSA-N methyl formate Chemical compound COC=O TZIHFWKZFHZASV-UHFFFAOYSA-N 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000000454 talc Substances 0.000 description 2
- 229910052623 talc Inorganic materials 0.000 description 2
- RYHBNJHYFVUHQT-UHFFFAOYSA-N 1,4-Dioxane Chemical compound C1COCCO1 RYHBNJHYFVUHQT-UHFFFAOYSA-N 0.000 description 1
- JJTUDXZGHPGLLC-IMJSIDKUSA-N 4511-42-6 Chemical compound C[C@@H]1OC(=O)[C@H](C)OC1=O JJTUDXZGHPGLLC-IMJSIDKUSA-N 0.000 description 1
- 239000002028 Biomass Substances 0.000 description 1
- 239000002841 Lewis acid Substances 0.000 description 1
- 241001077660 Molo Species 0.000 description 1
- KXKVLQRXCPHEJC-UHFFFAOYSA-N acetic acid trimethyl ester Natural products COC(C)=O KXKVLQRXCPHEJC-UHFFFAOYSA-N 0.000 description 1
- 229940023032 activated charcoal Drugs 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 150000001721 carbon Chemical group 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 229960001701 chloroform Drugs 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- 230000006837 decompression Effects 0.000 description 1
- 239000007857 degradation product Substances 0.000 description 1
- 238000006471 dimerization reaction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 230000007717 exclusion Effects 0.000 description 1
- 238000000855 fermentation Methods 0.000 description 1
- 230000004151 fermentation Effects 0.000 description 1
- 239000006260 foam Substances 0.000 description 1
- WBJINCZRORDGAQ-UHFFFAOYSA-N formic acid ethyl ester Natural products CCOC=O WBJINCZRORDGAQ-UHFFFAOYSA-N 0.000 description 1
- 230000009477 glass transition Effects 0.000 description 1
- 229940090044 injection Drugs 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 150000007517 lewis acids Chemical class 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000012803 melt mixture Substances 0.000 description 1
- 239000012778 molding material Substances 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- YKYONYBAUNKHLG-UHFFFAOYSA-N n-Propyl acetate Natural products CCCOC(C)=O YKYONYBAUNKHLG-UHFFFAOYSA-N 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 229920001432 poly(L-lactide) Polymers 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 229940090181 propyl acetate Drugs 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000011877 solvent mixture Substances 0.000 description 1
- NQPDZGIKBAWPEJ-UHFFFAOYSA-N valeric acid Chemical compound CCCCC(O)=O NQPDZGIKBAWPEJ-UHFFFAOYSA-N 0.000 description 1
- 238000013022 venting Methods 0.000 description 1
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
- C08J9/04—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
- C08J9/14—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 organic
- C08J9/142—Compounds containing oxygen but no halogen atom
-
- 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
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/34—Auxiliary operations
- B29C44/3415—Heating or cooling
- B29C44/3419—Quick cooling
-
- 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
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/34—Auxiliary operations
- B29C44/36—Feeding the material to be shaped
- B29C44/38—Feeding the material to be shaped into a closed space, i.e. to make articles of definite length
- B29C44/42—Feeding the material to be shaped into a closed space, i.e. to make articles of definite length using pressure difference, e.g. by injection or by vacuum
-
- 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
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/34—Auxiliary operations
- B29C44/36—Feeding the material to be shaped
- B29C44/38—Feeding the material to be shaped into a closed space, i.e. to make articles of definite length
- B29C44/44—Feeding the material to be shaped into a closed space, i.e. to make articles of definite length in solid form
- B29C44/445—Feeding the material to be shaped into a closed space, i.e. to make articles of definite length in solid form in the form of expandable granules, particles or beads
-
- 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
Abstract
Abstract of the Disclosure: In a process for injection molding foamed parts of polylactide, the polylactide melt contains solvent and cools to below the melting point during the expansion in the mold and is expanded in the temperature range between the glass softening point and the melting point.
Description
2:~0701 8 o.z. 0050/43623 Production of foamed polylactide inlection moldinqs of hiqh strength and rigidlty Poly-L-lactide, poly-D-lactide and copolymers thereof are biodegradable polym~rsO Rotting of these polymers does not form any degradation products which are foreign to nature, but instead only biomass and carbon dioxide. Due to this behavior, polylactides have great potential for increased use, particularly in the packag-ing sector.
There is no need for return for recycling purpos-e~ with inconvenient collection, cleaning, sorting and melting - all energy-consuming procedures which produce environmental pollution and an increase in traffic.
From the raw material~ point of view, poly-lactide3 are produced entirely from renewable sourceR.
Fermentation give~ a 10 to 15% strength lacticacid, which is concentrated to give pure lactic acid, from which, with elimination of water and dimerization, lactide is prepared as a polymerizable monomer. In the presence of Lewis acids, L-lactide, D-lactide, DL-lactide and mixtures thereof are ring-opened to give high-molecu-lar-weight products and polymeriæed~with retention of tha a~ymmetric carbon atom. ~he homopolymeric D- and L-lactides have melting point~ of around 180C, the modulus o~ ela~ticity intention at room temperature is 3500-4000 N/mm2, the tensile ~trength i9 60-70 N/mm2, and the weight average molecular weight is from 50,000 to 200,000 g/molO The gla~s ~oftening point is 50C.
Although polylactide~ have all these properties which are very advantageous for polymeric materials, they have a particular disadvantage for proces~ing: they cry~tallize 30 slowly that, in particular during injec-tion molding, very long cooling times o up to ~everal minutes are necessary to obtain par~ially crystalline moldings having heat deflection temperatures above the glass transition temperature.
It i9 an object of the present invention to find 21~7018 - 2 - O.z. 0050/43623 proces~ing conditions for polylactides which do not have the disadvantage of slow crystallization and give mold-ings of high ~trength, rigidity and heat deflection temperature which can be processed rapidly.
We have found that thi~ object i~ achieved by the features of claims 1 to 5, since the disadvantage of slow cry~tallization is utilized and turned into an outright advantage by injecting the melt into a mold and subject-ing it therein to multiaxial expansion under the effect of a blowing agent at a temperature between the glass ~oftening point and the melting point, the polylactide being oriented and predominantly cry~tallizing.
This procedure differs essentially from the process of the prior art for the production of injection moldings foamed using blowing agents; in the latter, blowing agents, preferably a~odicarboxamides, are admixed usually as a powder, with the thermoplastic to be pro-ce~sed. The thermoplastic granules treated in this way are melted in the barrel of an inject:ion-molding machine, during which the blowing agent decomposes, eliminating nitrogen. Application of a high back pressure of up to 1500 bar at the no~zle keeps the nitrogen in the melt and prevents decompression. Finally, an amount of the melt/nitrogen mixture corresponding to a fraction of the mold volume is injected into the relatively cold mold, which is under atmo~pheric pre~ure, where the nitrogen expands the melt, giving a foamed molding, u~ually with a compact outer skinO
In order to produce a homogeneous foam structure, the thermoplastic is treated with up to 0.5~ of a hetero-geneous nucleating agent such as talc which nucleates the foaming process.
In contrast to the process according to the invention, the expansion iR alway~ carried out at a temperature above the melting point, since the expanding melt cools so slowly, due to its relatively low thermal condu~tivity, that the foaming operation has already 2107~1~
There is no need for return for recycling purpos-e~ with inconvenient collection, cleaning, sorting and melting - all energy-consuming procedures which produce environmental pollution and an increase in traffic.
From the raw material~ point of view, poly-lactide3 are produced entirely from renewable sourceR.
Fermentation give~ a 10 to 15% strength lacticacid, which is concentrated to give pure lactic acid, from which, with elimination of water and dimerization, lactide is prepared as a polymerizable monomer. In the presence of Lewis acids, L-lactide, D-lactide, DL-lactide and mixtures thereof are ring-opened to give high-molecu-lar-weight products and polymeriæed~with retention of tha a~ymmetric carbon atom. ~he homopolymeric D- and L-lactides have melting point~ of around 180C, the modulus o~ ela~ticity intention at room temperature is 3500-4000 N/mm2, the tensile ~trength i9 60-70 N/mm2, and the weight average molecular weight is from 50,000 to 200,000 g/molO The gla~s ~oftening point is 50C.
Although polylactide~ have all these properties which are very advantageous for polymeric materials, they have a particular disadvantage for proces~ing: they cry~tallize 30 slowly that, in particular during injec-tion molding, very long cooling times o up to ~everal minutes are necessary to obtain par~ially crystalline moldings having heat deflection temperatures above the glass transition temperature.
It i9 an object of the present invention to find 21~7018 - 2 - O.z. 0050/43623 proces~ing conditions for polylactides which do not have the disadvantage of slow crystallization and give mold-ings of high ~trength, rigidity and heat deflection temperature which can be processed rapidly.
We have found that thi~ object i~ achieved by the features of claims 1 to 5, since the disadvantage of slow cry~tallization is utilized and turned into an outright advantage by injecting the melt into a mold and subject-ing it therein to multiaxial expansion under the effect of a blowing agent at a temperature between the glass ~oftening point and the melting point, the polylactide being oriented and predominantly cry~tallizing.
This procedure differs essentially from the process of the prior art for the production of injection moldings foamed using blowing agents; in the latter, blowing agents, preferably a~odicarboxamides, are admixed usually as a powder, with the thermoplastic to be pro-ce~sed. The thermoplastic granules treated in this way are melted in the barrel of an inject:ion-molding machine, during which the blowing agent decomposes, eliminating nitrogen. Application of a high back pressure of up to 1500 bar at the no~zle keeps the nitrogen in the melt and prevents decompression. Finally, an amount of the melt/nitrogen mixture corresponding to a fraction of the mold volume is injected into the relatively cold mold, which is under atmo~pheric pre~ure, where the nitrogen expands the melt, giving a foamed molding, u~ually with a compact outer skinO
In order to produce a homogeneous foam structure, the thermoplastic is treated with up to 0.5~ of a hetero-geneous nucleating agent such as talc which nucleates the foaming process.
In contrast to the process according to the invention, the expansion iR alway~ carried out at a temperature above the melting point, since the expanding melt cools so slowly, due to its relatively low thermal condu~tivity, that the foaming operation has already 2107~1~
- 3 - o.Z~ OOS0/~3623 ceased, while the temperature in the interior of t.he molding is still above the melting point of the thermo-pla~tic.
The process according to the invention i~ de-scribed in greater detail below:
In one variant of the preparation of the injec tion-molding composition according to the invention, a polylactide melt is mixed with an organic solvent under the vapor pressure of the latter at from 185 to 215C in a gas-tight extruder with exclusion of atmospheric oxygen and moisture, the organic solvent forming a single-phase mixture with the polylactide melt. The boiling point of the solvent at atmospheric pressure is from 30 to 110C.
At the extruder outlet, the melt/solvent mixture i9 forced through dies by which a rotating blade is passed in the presence of water. The extrudate leaving the extruder is thereby immediately quenched and chopped off, so that expansion on transfer into the atmospheric-pressure zone is prevented. It is ladvantageous to cool the water to from 2 to 10C. Examples of suitable sol-vents are methyl formate, ethyl formate, methyl acetate, propyl acetate, dioxane and methyl ethyl ketone.
The solvent concentration i'3 from 10 to 30 parts by weight, preferably from 15 to 25 parts by weight, based on the parts by weight of polylactide making up the remainder to 100. The granules produced in this way are dried at room temperature in a stream of nitrogen, during which they crystallize and are prevented from sticking together.
In order to produce relatively small amounts of impregnated granules, it is also possible to introduce granules impregnated with nucleating agent into a mixer and to meter in the organic solvent at room temperature over the course of fxom ~ to 2 hours while the granules are agitated, the solvent being taken up by the poly-lactide granules and the polylactide cry tallizing.
The granules are fed to an injection-molding 21~7 ~1~
The process according to the invention i~ de-scribed in greater detail below:
In one variant of the preparation of the injec tion-molding composition according to the invention, a polylactide melt is mixed with an organic solvent under the vapor pressure of the latter at from 185 to 215C in a gas-tight extruder with exclusion of atmospheric oxygen and moisture, the organic solvent forming a single-phase mixture with the polylactide melt. The boiling point of the solvent at atmospheric pressure is from 30 to 110C.
At the extruder outlet, the melt/solvent mixture i9 forced through dies by which a rotating blade is passed in the presence of water. The extrudate leaving the extruder is thereby immediately quenched and chopped off, so that expansion on transfer into the atmospheric-pressure zone is prevented. It is ladvantageous to cool the water to from 2 to 10C. Examples of suitable sol-vents are methyl formate, ethyl formate, methyl acetate, propyl acetate, dioxane and methyl ethyl ketone.
The solvent concentration i'3 from 10 to 30 parts by weight, preferably from 15 to 25 parts by weight, based on the parts by weight of polylactide making up the remainder to 100. The granules produced in this way are dried at room temperature in a stream of nitrogen, during which they crystallize and are prevented from sticking together.
In order to produce relatively small amounts of impregnated granules, it is also possible to introduce granules impregnated with nucleating agent into a mixer and to meter in the organic solvent at room temperature over the course of fxom ~ to 2 hours while the granules are agitated, the solvent being taken up by the poly-lactide granules and the polylactide cry tallizing.
The granules are fed to an injection-molding 21~7 ~1~
- 4 - O.Z. 0050/~3623 machine which is set up for blowing agent-containing injection-molding material and are melted at from 160 to 200C. The solvent content cau~es a melting point depre -sion, allowing melting temperatures lower than 180C to be used.
After injection into the mold provided with narrow venting slits, the solvent expands the melt under its vapor pressure, the heat of evaporation required meaning that the expanding melt cools virtually adiabati-cally to below the melting point and is thu~ expanded atbelow the melting point. During thi , orientation and cry~tallization occur, giving the de~ired molding~ of high strength, high rigidity and high heat deflection temperature in short cycle times.
The heat of evaporation of the solvent must always be greater than the heat of fu~ion liberated during the crystallization, which, in the case of lactide homopolymers, is about 60 J/g.
At a heat capacity of the polylactide of about 1.2 J/g K and a heat capacity of the solvent of about 440 J/g K, a cooling of g or 31C is obtained in the mold if the proportion by weight of solvent i9 15 to 20%
respectively.
For industrial safety reason~, the feed hopper and the mold of the injection-molding machine are provid-ed with extra~tion, and the extracted organic solvent is absor~ed, for example, by means of an activated-charcoal filter or burnt in a burner flame.
EXAMPLE
In a twin-screw extruder with a ~crew diameter of 30 mm, 8.0 kg/h of polylactide having an intrinRic vi~co~ity of 1.68, mea~ured a~ a 0.1% solution in chloro-form at 25C, are metered in under argon in order to expel atmospheric oxygen and moisture, and are melt~d at 205C. The polylactide contain~ 0.4 part by weight of talc a~ nucleating agent for uniform foaming.
The screws are right-handed in the conveying ~1~7018 ~ S ~ O.Z. 0050/43623 direction. A right-handed melting zone i8 followed by a left-handed screw zone, causing the melt to be pressed tightly between the screws and the barrel and dynamically sealing the extruder at the feed end. The left-handed zone is followed by a right-handed conveying zone con-taining two kneading elements. Thi~ i~ followed by a further left-handed screw zone and a further right-hande~
conveying zone before the dies.
In the case of the first kneading element, 2.0 kg/h of methyl ethyl ketone are pumped via a piston metering pump into the right-handed conveying zone between the left-handed zones of restricted flow through a pressure valve set at 100 bar.
The melt mixed with solvent i9 forced through dies and choppsd off by a blade rotating under water at 4C directly in front of the die plateO
The wet granules obtained are dried in a dry stream of nitrogen at 25C, during which the polylactide crystallizes under the influence of the solvent.
The dried and crystallized granule~ are melted in an injection-molding machine at 175C and injected into a mold at 120C, sufficient melt being metered in to fill the mold to 1/3 of its volume. For a maximum molding wall thickness of 5 mm, a cooling time of 30 ~econds is sufficient to demold a rigid molding without sticking to the mold wall.
After injection into the mold provided with narrow venting slits, the solvent expands the melt under its vapor pressure, the heat of evaporation required meaning that the expanding melt cools virtually adiabati-cally to below the melting point and is thu~ expanded atbelow the melting point. During thi , orientation and cry~tallization occur, giving the de~ired molding~ of high strength, high rigidity and high heat deflection temperature in short cycle times.
The heat of evaporation of the solvent must always be greater than the heat of fu~ion liberated during the crystallization, which, in the case of lactide homopolymers, is about 60 J/g.
At a heat capacity of the polylactide of about 1.2 J/g K and a heat capacity of the solvent of about 440 J/g K, a cooling of g or 31C is obtained in the mold if the proportion by weight of solvent i9 15 to 20%
respectively.
For industrial safety reason~, the feed hopper and the mold of the injection-molding machine are provid-ed with extra~tion, and the extracted organic solvent is absor~ed, for example, by means of an activated-charcoal filter or burnt in a burner flame.
EXAMPLE
In a twin-screw extruder with a ~crew diameter of 30 mm, 8.0 kg/h of polylactide having an intrinRic vi~co~ity of 1.68, mea~ured a~ a 0.1% solution in chloro-form at 25C, are metered in under argon in order to expel atmospheric oxygen and moisture, and are melt~d at 205C. The polylactide contain~ 0.4 part by weight of talc a~ nucleating agent for uniform foaming.
The screws are right-handed in the conveying ~1~7018 ~ S ~ O.Z. 0050/43623 direction. A right-handed melting zone i8 followed by a left-handed screw zone, causing the melt to be pressed tightly between the screws and the barrel and dynamically sealing the extruder at the feed end. The left-handed zone is followed by a right-handed conveying zone con-taining two kneading elements. Thi~ i~ followed by a further left-handed screw zone and a further right-hande~
conveying zone before the dies.
In the case of the first kneading element, 2.0 kg/h of methyl ethyl ketone are pumped via a piston metering pump into the right-handed conveying zone between the left-handed zones of restricted flow through a pressure valve set at 100 bar.
The melt mixed with solvent i9 forced through dies and choppsd off by a blade rotating under water at 4C directly in front of the die plateO
The wet granules obtained are dried in a dry stream of nitrogen at 25C, during which the polylactide crystallizes under the influence of the solvent.
The dried and crystallized granule~ are melted in an injection-molding machine at 175C and injected into a mold at 120C, sufficient melt being metered in to fill the mold to 1/3 of its volume. For a maximum molding wall thickness of 5 mm, a cooling time of 30 ~econds is sufficient to demold a rigid molding without sticking to the mold wall.
Claims (5)
1. A process for injection molding of foamed parts of polylactide, wherein the polylactide melt contains solvent and cools to below the melting point during expansion in the mold and is expanded in the temperature range between the glas softening point and the melting point.
2. A process as claimed in claim 1, wherein the proportion of organic solvent in the polylactide is from 10 to 30% by weight, preferably from 15 to 25% by weight.
3. A process as claimed in claim 1, wherein the boiling point of the solvent employed is from 30 to 110°C
at atmospheric pressure.
at atmospheric pressure.
4. A process as claimed in claim 1, wherein the solvent employed is miscible with the polylactide melt to form a single phase.
5. A molding produced as claimed in claim 1.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE4234620A DE4234620A1 (en) | 1992-10-14 | 1992-10-14 | Process for the production of foamed polylactide injection molded parts with high strength and rigidity |
| DEP4234620.7 | 1992-10-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2107018A1 true CA2107018A1 (en) | 1994-04-15 |
Family
ID=6470438
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002107018A Abandoned CA2107018A1 (en) | 1992-10-14 | 1993-09-27 | Production of foamed polylactide injection moldings of high strength and rigidity |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US5422053A (en) |
| EP (1) | EP0592911A1 (en) |
| JP (1) | JPH06190853A (en) |
| CA (1) | CA2107018A1 (en) |
| DE (1) | DE4234620A1 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3937727B2 (en) | 1997-10-29 | 2007-06-27 | 株式会社カネカ | Resin composition for foam having biodegradability |
| US8309619B2 (en) | 2004-09-03 | 2012-11-13 | Pactiv LLC | Reduced-VOC and non-VOC blowing agents for making expanded and extruded thermoplastic foams |
| JP5388584B2 (en) * | 2006-02-22 | 2014-01-15 | パクティヴ・エルエルシー | Expanded and extruded polyolefin foam produced using a blowing agent based on methyl formate |
| US7977397B2 (en) * | 2006-12-14 | 2011-07-12 | Pactiv Corporation | Polymer blends of biodegradable or bio-based and synthetic polymers and foams thereof |
| PL2089460T3 (en) * | 2006-12-14 | 2012-02-29 | Pactiv Corp | Expanded and extruded biodegradable and reduced emission foams made with methyl formate-based blowing agents |
| US8722754B2 (en) * | 2008-04-30 | 2014-05-13 | Natureworks Llc | Extruded foams made with polylactides that have high molecular weights and high intrinsic viscosities |
Family Cites Families (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1964748B2 (en) * | 1969-12-24 | 1973-12-13 | Chemische Werke Huels Ag, 4370 Marl | Process for the production of thermoplastic foam plastic molding by the injection molding process |
| DE2855182A1 (en) * | 1978-12-20 | 1980-06-26 | Owens Illinois Inc | Controlling crystallisation of injected thermoplastic materials - by the application of different pressure sequences during cooling |
| JPS6096419A (en) * | 1983-10-31 | 1985-05-30 | Japan Styrene Paper Co Ltd | Manufacture of injection foamed molded body |
| DE3428640A1 (en) * | 1984-08-03 | 1986-02-06 | Akzo Gmbh, 5600 Wuppertal | MICROPOROUS, POWDER-SHAPED POLYLACTIDES |
| US4766182A (en) * | 1986-12-22 | 1988-08-23 | E. I. Du Pont De Nemours And Company | Polylactide compositions |
| US4719246A (en) * | 1986-12-22 | 1988-01-12 | E. I. Du Pont De Nemours And Company | Polylactide compositions |
| WO1988010260A1 (en) * | 1987-06-16 | 1988-12-29 | Boehringer Ingelheim Kg | ''meso-lactide'' and process for manufacturing it |
| US4902515A (en) * | 1988-04-28 | 1990-02-20 | E. I. Dupont De Nemours And Company | Polylactide compositions |
| EP0428620B1 (en) * | 1988-08-08 | 1999-03-03 | Biopak Technology, Ltd. | A method of plasticizing lactide polymers. |
| US5290494A (en) * | 1990-03-05 | 1994-03-01 | Board Of Regents, The University Of Texas System | Process of making a resorbable implantation device |
| DE4007882C2 (en) * | 1990-03-13 | 1994-03-10 | Boehringer Ingelheim Kg | Use of polyglycolic acid and its derivatives as nucleating agents |
| US5102983A (en) * | 1990-04-02 | 1992-04-07 | United States Surgical Corporation | Process for preparing foamed, bioabsorbable polymer particles |
| JPH05508669A (en) * | 1990-07-16 | 1993-12-02 | イー・アイ・デユポン・ドウ・ヌムール・アンド・カンパニー | degradable foam material |
| CA2064410A1 (en) * | 1991-04-01 | 1992-10-02 | Masanobu Ajioka | Degradable foam and use of same |
| CA2057668A1 (en) * | 1991-12-13 | 1993-06-14 | Speros P. Nemphos | Degradable foam |
| US5210108A (en) * | 1992-07-29 | 1993-05-11 | E. I. Du Pont De Nemours And Company | Degradable foam materials |
-
1992
- 1992-10-14 DE DE4234620A patent/DE4234620A1/en not_active Withdrawn
-
1993
- 1993-09-27 CA CA002107018A patent/CA2107018A1/en not_active Abandoned
- 1993-10-04 EP EP93115984A patent/EP0592911A1/en not_active Withdrawn
- 1993-10-08 JP JP5252964A patent/JPH06190853A/en not_active Withdrawn
- 1993-10-13 US US08/135,334 patent/US5422053A/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| US5422053A (en) | 1995-06-06 |
| EP0592911A1 (en) | 1994-04-20 |
| JPH06190853A (en) | 1994-07-12 |
| DE4234620A1 (en) | 1994-04-21 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |