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WO1998013183A1 - Noyau amovible utile dans un procede de moulage par injection et procede de fabrication d'un produit creux moule par injection - Google Patents

Noyau amovible utile dans un procede de moulage par injection et procede de fabrication d'un produit creux moule par injection Download PDF

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Publication number
WO1998013183A1
WO1998013183A1 PCT/NL1997/000537 NL9700537W WO9813183A1 WO 1998013183 A1 WO1998013183 A1 WO 1998013183A1 NL 9700537 W NL9700537 W NL 9700537W WO 9813183 A1 WO9813183 A1 WO 9813183A1
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WO
WIPO (PCT)
Prior art keywords
core
injection molding
cores
hollow
injection
Prior art date
Application number
PCT/NL1997/000537
Other languages
English (en)
Other versions
WO1998013183A9 (fr
Inventor
Andries Hanzen
Gerald Schennink
Arend Timmerije
Diane Pluimers
Original Assignee
Coöperatieve Verkoop- En Productievereniging Van Aardappelmeel En Derivaten Avebe B.A.
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Coöperatieve Verkoop- En Productievereniging Van Aardappelmeel En Derivaten Avebe B.A. filed Critical Coöperatieve Verkoop- En Productievereniging Van Aardappelmeel En Derivaten Avebe B.A.
Priority to AU44020/97A priority Critical patent/AU4402097A/en
Publication of WO1998013183A1 publication Critical patent/WO1998013183A1/fr
Publication of WO1998013183A9 publication Critical patent/WO1998013183A9/fr

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Classifications

    • 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
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17—Component parts, details or accessories; Auxiliary operations
    • B29C45/40—Removing or ejecting moulded articles
    • B29C45/44—Removing or ejecting moulded articles for undercut articles
    • B29C45/4457—Removing or ejecting moulded articles for undercut articles using fusible, soluble or destructible cores
    • 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
    • B29C33/00—Moulds or cores; Details thereof or accessories therefor
    • B29C33/44—Moulds or cores; Details thereof or accessories therefor with means for, or specially constructed to facilitate, the removal of articles, e.g. of undercut articles
    • B29C33/52—Moulds or cores; Details thereof or accessories therefor with means for, or specially constructed to facilitate, the removal of articles, e.g. of undercut articles soluble or fusible

Definitions

  • Removable core for use xn an injection molding process, and method for manufacturing a hollow injection molded product.
  • the invention resides in the field of molded products and particularly relates to a removable core for use in an injection molding process.
  • the invention further relates to a method for manufacturing hollow-walled injection molded products, at least injection molded products provided with hollow spaces.
  • cores are generally used, which must be removed after injection molding as completely as possible.
  • cores can be divided into two main categories, namely cores for repeated use and cores for single use.
  • Cores for repeated use may either be fixed in a mold or die or be detachable or removable so as to enable easier removal of the product from the mold or die.
  • This type of core is generally made of die steel and will normally last the whole service life of the die.
  • cores In a large number of embodiments, especially when complicatedly shaped cavities, e.g. highly undercut shapes, are to be provided in the product or when the cavity is not properly accessible for a core for repeated use, such cores cannot be used. For these embodiments the cores must be deformed or broken down to enable their removal .
  • This type of core is designated by the term "core for single use”.
  • the present invention relates to this type of core.
  • sand cores are generally used. These cores are formed out of sand-like material using water and additives and can be broken down after being circumjected with metal in a mold.
  • European patent application 0 466 419 describes sand cores in which starch is used as binder.
  • melt cores are chiefly manufactured from metal alloys melting at low temperatures.
  • Such cores which preferably have a melting point between about 90 and 200°C, may be composed of, e.g., combinations of tin, bismuth, lead, antimony and cadmium.
  • European patent application 0 433 000 The alloys, which are relatively expensive, are shaped into cores in a separate device. These cores are then placed or fixed in a die and circum ected with the desired material.
  • the cores are removed by melting, after which the core material can be reused.
  • This melting can be carried out, inter alia, by immersing the molded product in a hot medium, such as hot oil, polyhydric aliphatic alcohols, modified polyglycol ethers, silicones or alkaline solutions.
  • a hot medium such as hot oil, polyhydric aliphatic alcohols, modified polyglycol ethers, silicones or alkaline solutions.
  • salt cores For the manufacture of salt cores similar molding devices are required as necessary for the known sand cores.
  • the salt cores must be dried, and steps must be taken to limit as much as possible the corrosive and hygroscopic character of the employed salts. After circum ection of this core material, the salt is removed by dissolving in a suitable medium. The aim is to recycle the employed materials as completely as possible, but also when salt cores are used, compounds are released that are environmentally harmful.
  • An example of salt cores is described m French patent application 2 080 725.
  • French patent 1 100 359 describes cores for manufacturing hollow-walled products, which cores are based on the "lost wax” principle.
  • the term “wax” is very broadly defined in this publication and comprises all kinds of low- melting compounds, including gelatin, starch, alginate and methyl cellulose.
  • the cores are removed by means of a mild heating step.
  • Japanese publication 62-152713 teaches the use of a soluble core, such as a core of a neutral polysaccharide consisting of ⁇ -16 bonded maltotriose units.
  • a core for metal products is manufactured by subjecting a mixture of water- insoluble cellulose, water-soluble cellulose, oil or fat and water to a number of drying and heating steps. The core is removed by burning out.
  • German “Offenlegungsschrift” 18 07 193 relates to hollow-walled products and proposes a shaped core of a plastic material which is soluble or biodegradable or which can be removed by the action of heat. Suitable plastic materials are not specified.
  • the material must preferably be injection moldable, so that it better fits in with the technology, comprising process and devices, used for the manufacture of the desired hollow-walled end product.
  • the manufacture of, e.g., melting and salt cores requires special devices which are usually not present in an injection molding factory.
  • the object of the invention is to provide a moldable, removable material, which does not cause problems to environment and health and is preferably rapidly biodegradable for the manufacture of cores for creating cavities in the products to be injection molded. Besides, this material is preferably inexpensive. It is a further object of the invention to provide a method by which theses cores can be removed from the injection molded product as completely as possible.
  • the removable core according to the invention which is manufactured from a biodegradable, moldable material and contains a blowing agent.
  • the invention relates to a removable core of a biodegradable, moldable material containing a blowing agent, for use in an injection molding process for manufacturing a hollow-walled injection molded product.
  • the invention in a second aspect relates to a method for manufacturing a hollow-walled injection molded product, comprising injecting an injection molding material into a mold in which the core according to the invention, which core contains a blowing agent, is placed, and removing the core using the blowing agent present m the core.
  • the invention further relates to the use of a biodegradable, moldable material comprising a blowing agent as removable core in an injection molding process.
  • the core according to the invention after being circumjected with an injection moldable material, can be removed completely by activating the blowing agent in a known manner. Through this activation gases are formed, which expel the cores from the circumjected material and may or may not fragmentize the core.
  • the blowing agent must be compatible with the moldable material from which the core is manufactured and, if m a less degree, with the material provided around the core by means of injection molding. Furthermore, the blowing agent must be activated neither during the formation of the core nor during the step of circum ectmg the core with an injection moldable material. On the basis of this information, it is obvious to those skilled m the art t ⁇ select suitable blowing agents for different core materials and injection molding processes.
  • blowing agents such as sodium bicarbonate
  • this blowing agent is known to disintegrate at temperatures exceeding about 60°C, so that it is not suitable for being included m an injection moldable or extrudable material, for which injection molding or extrusion conditions are necessary which require a temperature of at least 60°C.
  • it can be suitably included in materials which are shaped into cores, e.g., by molding at lower temperatures.
  • the blowing agent present in the core is generally not activated, because the operating conditions (residence time, prevailing pressure, temperature transfer etc.) in the injection molding process do not initiate the decomposition reaction in the core.
  • the blowing agent is water.
  • This blowing agent can be activated by heating the injection molded product to the extent that steam arises from water. Preferably, this is done by heating the core with microwaves, e.g. generated with a microwave oven. Under the influence of the generated microwaves the water is heated and steam is formed. This causes the core to foam more or less out of the injection molded product, after which it can be easily removed.
  • microwaves e.g. generated with a microwave oven.
  • the core e.g. generated with a microwave oven.
  • steam e.g. generated with a microwave oven
  • moldable materials which, according to the invention, contain blowing agents or in which blowing agents can be included, are preferably biodegradable macromolecules, such as biodegradable polysaccharides, synthetically or fermentatively prepared biodegradable polyesters, such as polyhydroxyalkanoates and polyvinyl alcohols.
  • biodegradable macromolecules such as biodegradable polysaccharides, synthetically or fermentatively prepared biodegradable polyesters, such as polyhydroxyalkanoates and polyvinyl alcohols.
  • biodegradable macromolecules such as biodegradable polysaccharides, synthetically or fermentatively prepared biodegradable polyesters, such as polyhydroxyalkanoates and polyvinyl alcohols.
  • biodegradable macromolecules such as biodegradable polysaccharides, synthetically or fermentatively prepared biodegradable polyesters, such as polyhydroxyalkanoates and polyvinyl alcohols.
  • WO-A- 95/07170 refers to suitable classes of compounds.
  • the above materials are shaped into a core by known per se methods. This can be done, e.g., by molding, extruding and injection molding. As stated above, the moldable materials are preferably shaped into a core by injection molding.
  • the core is shaped from a moldable material, and preferably an injection moldable material, selected from the group consisting of starches, e.g. potato, wheat, maize or tapioca starch, celluloses, inulin, proteins, such as gluten and caseinates, as well as derivatives and/or mixtures thereof.
  • a moldable material e.g. potato, wheat, maize or tapioca starch
  • celluloses, inulin, proteins, such as gluten and caseinates as well as derivatives and/or mixtures thereof.
  • potato starch contains between 5 and 30 wt.%, and more usually between 10 and 20 wt . % water; tapioca starch between about 5 and 15 wt.% water; cellulose between about 7 and 13 wt.% water, and inulin about 10 wt.% water .
  • Suitable injection molding formulations of the above materials are known to those skilled in the art and are described, inter alia, in Dutch patent 1001036, in the brochure by Avebe on the product PARAGON 1 " 1 , in Kunststoff Magazine 8/9 (1996), 28-29, and in Kunststoffstof en Rubber 4 (1996) 21-23.
  • the starch and/or cellulose formulations may contain up to 25% additives, such as fillers, flow- improving agents etc., which are preferably also biodegradable .
  • the above injection moldable materials on the basis of starch, cellulose, inulin and proteins, which are used to form the above cores according to the invention, can be injection molded into products without collapse or shrinkage cavities.
  • the shaped cores can be solid without any problem, which positively influences the dimensional stability of the core. Furthermore, no thermal deformation of the core takes place during circumjection, because for a short period of time the thus shaped cores can excellently resist temperatures up to about 300°C, as may occur in the injection molding process.
  • this preferred core does not adhere to the material from which the final hollow-walled product is manuf ctured, which is particularly important to remove the filler from the injection molded product as completely as possible.
  • this type of cores can be excellently circumjected with materials known for injection molding uses, such as polyamides, polyesters and polyolefins, which may be fiber-reinforced, if required. These polymers are not limited to the water-insoluble polymers.
  • the injection moldable composition partly, e.g. between 10 and 30 wt.%, contains a starch hydrolysate. Such hydrolysates are obtained by partially decomposing native or modified starch by chemical or enzymatic hydrolysis to obtain a shorter-chain starch
  • an injection molding material is injected into a mold in which a core according to the invention is placed, in fact in an analogous manner as for the known processes using melting cores, salt cores and dissolving cores.
  • injection molding technologies such as multi-component injection molding.
  • thermoplastic starch which optionally contains sodium bicarbonate molded bodies were manufactured by injection molding.
  • the compositions from which the molded bodies are shaped are specified in Table 1. Table 1
  • Thermoplastic starch sodium bicarbonate (wt.%) 1
  • thermoplastic starch 1 based on the weight of the thermoplastic starch.
  • thermoplastic starch had a glass transition temperature of about 80°C, which temperature is far above the mold temperature during injection molding.
  • the cores were circumjected with pre-dried polyamide
  • Example 1 was repeated using a core of polyhydroxyalkanoate (Biopol; Monsanto). This material contains neither water nor any other blowing agent . Injection molding of more thick-walled cores was found to be difficult, because Biopol slowly crystallizes. The cycle times during injection molding were longer as compared to the thermoplastic starch according to Example 1.
  • the core could hardly be removed using microwaves. No foaming occurred; the material became soft and weak.
  • Example 1 was repeated using polyvinyl alcohol (Mowiol 28-99; Hoechst) . This material had to be dried before it could be processed by injection molding; it contained neither water nor any other blowing agent . Removal of the core using microwaves with water functioning as blowing agent gave a soft, sticky foam. The removal of this foam proceeded with a little more difficulty than with the dry, hard starch foam.
  • polyvinyl alcohol Movityl 28-99; Hoechst
  • Composition 1 Paragon IM 1010 (Avebe, The Netherlands); Composition 2: Paragon IM 1010 (82.4 wt.%)
  • Composition 3 Paragon IM 1010 (76.1 wt.%)
  • Polyamide, glass-filled 30% (BKV-30; processing temperature 260°C; glass transition temperature 50°C; optically not transparent) .
  • composition 4 By injection molding of composition 4 at a temperature of 145°C and a mold temperature of 25°C a core was obtained.
  • This core was circumjected with styrene- acrylonitrile at a temperature of 220°C and a mold temperature of 30°C.
  • the core was foamed out by heating the product in a microwave oven for 1 minute at a power of 700 W. The core could be manually withdrawn from the product.
  • composition 4 By injection molding of composition 4 at a temperature of 145°C and a mold temperature of 25°C a core was obtained.
  • This core was circumjected with polycarbonate at a temperature of 300°C and a mold temperature of 80°C.
  • the core was foamed out by heating the product in a microwave oven for 1 minute at a power of 700 W. The core could be manually withdrawn from the product.
  • composition 4 By injection molding of composition 4 at a temperature of 145°C and a mold temperature of 25°C a core was obtained.
  • This core was circumjected with glass-filled polyamide at a temperature of 260°C and a mold temperature of 20°C.
  • the core was foamed out by heating the product in a microwave oven for 1 minute at a power of 700 W. The core could be manually withdrawn from the product.
  • Example 4d By injection molding of composition 1 at a temperature of 145°C and a mold temperature of 25°C a core was obtained. This core was circumjected with styrene- acrylonitrile at a temperature of 220°C and a mold temperature of 30°C. The core was foamed out by heating the product in a microwave oven for 1 minute at a power of 700 W. The core could be manually withdrawn from the product.
  • composition 2 By injection molding of composition 2 at a temperature of 145°C and a mold temperature of 25°C a core was obtained.
  • This core was circumjected with polycarbonate at a temperature of 300°C and a mold temperature of 80°C.
  • the core was foamed out by heating the product in a microwave oven for 1 minute at a power of 700 W. The core could be manually withdrawn from the product.
  • composition 3 By injection molding of composition 3 at a temperature of 145°C and a mold temperature of 25°C a core was obtained.
  • This core was circumjected with glass- filled polyamide at a temperature of 260°C and a mold temperature of 20°C.
  • the core was foamed out by heating the product in a microwave oven for 1 minute at a power of 700 W. The core could be manually withdrawn from the product.
  • Example 4g (equation) By injection molding of composition 4 at a temperature of 145°C and a mold temperature of 25°C a core was obtained. This core was circumjected with styrene-acrylonitrile at a temperature of 220°C and a mold temperature of 30°C. The circumjected core was placed in hot water. The core slowly dissolved; not all the core was removed.
  • composition 4 By injection molding of composition 4 at a temperature of 145°C and a mold temperature of 25°C a core was obtained.
  • This core was circumjected with styrene- acrylonitrile at a temperature of 220°C and a mold temperature of 30°C.
  • the circumjected core was placed in an aqueous ⁇ -amylase solution of 70°C. Although dissolving proceeded a little more rapidly than in Example 4g, not all the starch was dissolved yet after 24 hours.
  • composition 4 By injection molding of composition 4 at a temperature of 145°C and a mold temperature of 25°C a core was obtained.
  • This core was circumjected with styrene- acrylonitrile at a temperature of 220°C and a mold temperature of 30°C.
  • the circumjected core was subjected to an ultrasonic pulverization treatment. The core melted and burned locally.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Moulds For Moulding Plastics Or The Like (AREA)
  • Injection Moulding Of Plastics Or The Like (AREA)

Abstract

L'invention concerne un noyau amovible, en matériau biodégradable et apte au moulage, que l'on utilise dans un procédé de moulage par injection servant à fabriquer un produit à parois creuses, moulé par injection. L'invention concerne encore un procédé de fabrication d'un tel produit, consistant à injecter une matière de moulage dans un moule dans lequel on a placé le noyau de l'invention, puis à retirer ce noyau. En outre, l'invention concerne l'utilisation d'un matériau biodégradable et apte au moulage en tant que noyau amovible placé dans un produit moulé par injection.
PCT/NL1997/000537 1996-09-25 1997-09-25 Noyau amovible utile dans un procede de moulage par injection et procede de fabrication d'un produit creux moule par injection WO1998013183A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU44020/97A AU4402097A (en) 1996-09-25 1997-09-25 Removable core for use in an injection molding process, and method for manufacturing a hollow injection molded product

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL1004109A NL1004109C2 (nl) 1996-09-25 1996-09-25 Verwijderbare kern ten gebruike in gietproducten.
NL1004109 1996-09-25

Publications (2)

Publication Number Publication Date
WO1998013183A1 true WO1998013183A1 (fr) 1998-04-02
WO1998013183A9 WO1998013183A9 (fr) 1998-08-13

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Country Status (3)

Country Link
AU (1) AU4402097A (fr)
NL (1) NL1004109C2 (fr)
WO (1) WO1998013183A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0916464A2 (fr) * 1997-11-12 1999-05-19 Sakura Rubber Co., Ltd. Procédé de fabrication d'une structure par l'utilisation d'un moule biodégradable
EP1695805A1 (fr) * 2005-02-26 2006-08-30 Bayerische Motorenwerke Aktiengesellschaft Noyau de moule dispersible dans l'eau pour produire des objets creux renforcés par des fibres

Citations (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB709824A (en) * 1951-08-20 1954-06-02 Geoffrey Ronald Christian Improved method for joining the ends of pipes of polythene or other thermoplastic material
FR1100359A (fr) * 1954-03-01 1955-09-20 Procédé de fabrication d'objets creux en matières plastiques et en particulier en plastique renforcé
FR1576804A (fr) * 1967-08-04 1969-08-01
DE1807193A1 (de) * 1968-11-06 1970-05-27 Guenter Geschke Formkern und Verfahren zum Spritzen,Giessen,Pressen od.dgl. von Formteilen
FR2080725A1 (fr) * 1970-02-24 1971-11-19 Libbey Owens Ford Glass Co
US4123582A (en) * 1973-06-13 1978-10-31 Goodyear Aerospace Corporation Building form for molded articles having a urethane coating
GB2092694A (en) * 1981-02-06 1982-08-18 Penn Eng & Mfg Corp Preventing solder entering screw threads
JPS62152713A (ja) * 1985-12-26 1987-07-07 Canon Inc アンダカツトとなる形状を有する樹脂成形体の製造方法
EP0376201A1 (fr) * 1988-12-30 1990-07-04 National Starch and Chemical Investment Holding Corporation Produits faconnés qui sont biodégradables et procédé pour leur préparation
EP0466419A2 (fr) * 1990-07-11 1992-01-15 Advanced Plastics Partnership Enlèvement de noyaux de produits moulés
DE4202878A1 (de) * 1992-02-01 1993-08-05 Alfred Eigen Verfahren zur herstellung von hohlkoerperformteilen
JPH05337594A (ja) * 1992-05-19 1993-12-21 Mitsubishi Materials Corp 中空金属物品製造用中子およびそれを用いた中空金属物品の製造方法
EP0634261A1 (fr) * 1993-07-13 1995-01-18 SUZUKI SOGYO Co., Ltd. Mousse biodégradable et procédé et dispositif pour sa mise en oeuvre
WO1995007170A1 (fr) * 1993-09-06 1995-03-16 Minnesota Mining And Manufacturing Company Moulage perdu

Patent Citations (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB709824A (en) * 1951-08-20 1954-06-02 Geoffrey Ronald Christian Improved method for joining the ends of pipes of polythene or other thermoplastic material
FR1100359A (fr) * 1954-03-01 1955-09-20 Procédé de fabrication d'objets creux en matières plastiques et en particulier en plastique renforcé
FR1576804A (fr) * 1967-08-04 1969-08-01
DE1807193A1 (de) * 1968-11-06 1970-05-27 Guenter Geschke Formkern und Verfahren zum Spritzen,Giessen,Pressen od.dgl. von Formteilen
FR2080725A1 (fr) * 1970-02-24 1971-11-19 Libbey Owens Ford Glass Co
US4123582A (en) * 1973-06-13 1978-10-31 Goodyear Aerospace Corporation Building form for molded articles having a urethane coating
GB2092694A (en) * 1981-02-06 1982-08-18 Penn Eng & Mfg Corp Preventing solder entering screw threads
JPS62152713A (ja) * 1985-12-26 1987-07-07 Canon Inc アンダカツトとなる形状を有する樹脂成形体の製造方法
EP0376201A1 (fr) * 1988-12-30 1990-07-04 National Starch and Chemical Investment Holding Corporation Produits faconnés qui sont biodégradables et procédé pour leur préparation
EP0466419A2 (fr) * 1990-07-11 1992-01-15 Advanced Plastics Partnership Enlèvement de noyaux de produits moulés
DE4202878A1 (de) * 1992-02-01 1993-08-05 Alfred Eigen Verfahren zur herstellung von hohlkoerperformteilen
JPH05337594A (ja) * 1992-05-19 1993-12-21 Mitsubishi Materials Corp 中空金属物品製造用中子およびそれを用いた中空金属物品の製造方法
EP0634261A1 (fr) * 1993-07-13 1995-01-18 SUZUKI SOGYO Co., Ltd. Mousse biodégradable et procédé et dispositif pour sa mise en oeuvre
WO1995007170A1 (fr) * 1993-09-06 1995-03-16 Minnesota Mining And Manufacturing Company Moulage perdu

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* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 011, no. 385 (M - 651) 16 December 1987 (1987-12-16) *
PATENT ABSTRACTS OF JAPAN vol. 018, no. 168 (M - 1580) 22 March 1994 (1994-03-22) *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0916464A2 (fr) * 1997-11-12 1999-05-19 Sakura Rubber Co., Ltd. Procédé de fabrication d'une structure par l'utilisation d'un moule biodégradable
EP0916464A3 (fr) * 1997-11-12 2000-02-23 Sakura Rubber Co., Ltd. Procédé de fabrication d'une structure par l'utilisation d'un moule biodégradable
US6350337B1 (en) 1997-11-12 2002-02-26 Sakura Rubber Co., Ltd. Method of manufacturing structure by using biodegradable mold
US6666941B2 (en) 1997-11-12 2003-12-23 Sakura Rubber Co. Ltd. Method of manufacturing ribbed structure by using biodegradable mold
EP1695805A1 (fr) * 2005-02-26 2006-08-30 Bayerische Motorenwerke Aktiengesellschaft Noyau de moule dispersible dans l'eau pour produire des objets creux renforcés par des fibres

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Publication number Publication date
NL1004109C2 (nl) 1998-03-26
AU4402097A (en) 1998-04-17

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