EP1140453A1 - Procede de moulage rotatif et appareil correspondant - Google Patents

Procede de moulage rotatif et appareil correspondant

Info

Publication number
EP1140453A1
EP1140453A1 EP99961253A EP99961253A EP1140453A1 EP 1140453 A1 EP1140453 A1 EP 1140453A1 EP 99961253 A EP99961253 A EP 99961253A EP 99961253 A EP99961253 A EP 99961253A EP 1140453 A1 EP1140453 A1 EP 1140453A1
Authority
EP
European Patent Office
Prior art keywords
mould
activator
polymer
polymerisation
thermoplastic
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.)
Withdrawn
Application number
EP99961253A
Other languages
German (de)
English (en)
Inventor
Adrian Murtagh
Patrick Joseph Feerick
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Kingspan Research and Developments Ltd
Original Assignee
Kingspan Research and Developments Ltd
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 Kingspan Research and Developments Ltd filed Critical Kingspan Research and Developments Ltd
Publication of EP1140453A1 publication Critical patent/EP1140453A1/fr
Withdrawn legal-status Critical Current

Links

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
    • B29C41/00—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor
    • B29C41/02—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor for making articles of definite length, i.e. discrete articles
    • B29C41/04—Rotational or centrifugal casting, i.e. coating the inside of a mould by rotating the mould
    • 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
    • B29C41/00—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor
    • B29C41/003—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor characterised by the choice of material
    • 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
    • B29C2791/00—Shaping characteristics in general
    • B29C2791/004—Shaping under special conditions
    • B29C2791/005—Using a particular environment, e.g. sterile fluids other than air
    • 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
    • B29C31/00—Handling, e.g. feeding of the material to be shaped, storage of plastics material before moulding; Automation, i.e. automated handling lines in plastics processing plants, e.g. using manipulators or robots
    • B29C31/04—Feeding of the material to be moulded, e.g. into a mould cavity
    • B29C31/06—Feeding of the material to be moulded, e.g. into a mould cavity in measured doses, e.g. by weighting
    • 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
    • B29C41/00—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor
    • B29C41/02—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor for making articles of definite length, i.e. discrete articles
    • B29C41/04—Rotational or centrifugal casting, i.e. coating the inside of a mould by rotating the mould
    • B29C41/06—Rotational or centrifugal casting, i.e. coating the inside of a mould by rotating the mould about two or more axes
    • 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
    • B29K2077/00—Use of PA, i.e. polyamides, e.g. polyesteramides or derivatives thereof, as moulding material
    • 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
    • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
    • B29K2105/0002—Condition, form or state of moulded material or of the material to be shaped monomers or prepolymers

Definitions

  • the invention relates to rotational moulding.
  • Rotomoulding is an inexpensive process that is widely used for manufacturing hollow plastics components.
  • a polymer resin in a powder form is introduced into a hollow mould which is heated externally in a large oven.
  • the mould is biaxially rotated as the powder sinters and the plastic coats the interior surface of the mould relatively evenly, typically to a thickness greater than 3 mm.
  • Such conventional rotomoulding has the advantages of relatively low capital equipment costs, inexpensive tooling as there is no pressure applied, and allows large volume complex shapes to be easily moulded.
  • thermoplastic materials have become available which have potential advantages of improved mechanical strength, toughness, low water absorption, high softening temperature and relatively low cost.
  • thermoplastics melt in the mould According to the invention there is provided a method of rotomoulding comprising the step of forming a reactant thermoplastics melt in the mould.
  • the reactant thermoplastics melt comprises a mixture of a thermoplastic pre-polymer and a polymerisation activator.
  • thermoplastics pre-polymer and the polymerisation activator may be mixed in the mould.
  • thermoplastics pre-polymer and the polymerisation activator are mixed prior to delivery into a mould.
  • the mixing and preferably also the moulding is carried out under an inert atmosphere.
  • the inert atmosphere is typically a nitrogen atmosphere.
  • the pre-polymer and polymerisation activator are mixed to form a pre-mix which is stored in a holding container prior to delivery into the mould.
  • the mixture is added to the mould at ambient temperature conditions.
  • the mixture is introduced into the mould under an inert atmosphere.
  • the mould is heated to polymerisation temperature.
  • the mould is rotated, usually biaxially, typically at a speed of greater than 5 r.p.m.
  • the method comprises the steps of: - delivering a thermoplastics pre-polymer into the mould; and
  • thermoplastic pre-polymer in the mould introducing a polymerisation activator to the thermoplastic pre-polymer in the mould.
  • the polymerisation activator may be introduced into the mould separately from the pre-polymer.
  • the polymerisation activator may be injected into the mould to form a reactant melt in the mould.
  • thermoplastic pre-polymer placing the thermoplastic pre-polymer in a mould
  • the method comprises the steps of: -
  • thermoplastic pre-polymer placing thermoplastic pre-polymer in a mould
  • the mould is pre-heated to a temperature of from ambient temperature to 170°C, preferably to a temperature of approximately 170°C.
  • the mould after injection of the activator, is further heated to a temperature of from 170°C to 205°C over a period of from 5 to 10 minutes.
  • the mould is further heated to a temperature of about 200°C over a period of about 10 minutes to ensure complete polymerisation.
  • the activator line is purged after injection of the activator.
  • the method includes the step of rotating the mould during preheating.
  • the method includes the step of rotating the mould after injection of the activator to dissolve or disperse the activator in the preheated melt.
  • the mould is preferably rotated biaxially after dispersion of the activator in the melt.
  • the biaxial rotation is usually at a speed of greater than 5 rpm.
  • thermoplastic is selected from one or more of PBT, ABS, acrylic, polycarbonate, lactam, mixtures, blends or copolymers thereof.
  • thermoplastic is a lactam material.
  • activator is preferably an activator for producing an ionically polymerised lactam.
  • the lactam is lactam-12.
  • the invention also provides a rotomoulding apparatus including a mould having an injector means for injecting an activator into the mould for in-mould reactive moulding.
  • the apparatus includes a flush means for flushing the injector after injection of the activator into the mould.
  • the mould used in the method of the invention has integral mould heating and cooling means.
  • the rotation speeds during rotomoulding may be changed from an initially high speed when the liquid has a low viscosity to lower speeds as the viscosity of the matrix within the mould increases.
  • Nitrogen flush is maintained throughout to ensure polymerisation and to reduce oxidation and material degradation.
  • the invention further provides a rotomoulded article whenever produced using the apparatus and/or method of the invention.
  • Figs 1 to 5 are schematic views illustrating the various steps in a process According to one embodiment of the invention.
  • Figs 6 to 11 are schematic views illustrating steps in a process according to another embodiment of the invention. Detailed Description
  • the method and apparatus for rotomoulding used in the invention employs a system with improved control of the mould temperature. This facilitates a high level of repeatability and traceability.
  • a gimbal-type aluminium framed biaxial rotomoulding machine may be used to provide full biaxial rotation.
  • the mould may be heated by infra-red.
  • a composite tool with embedded heating wires and cooling channels may be used.
  • One such system is described in WO-A-961496.
  • a reactant thermoplastics melt is formed in the mould rather than outside the mould.
  • This has processing advantages especially in overcoming difficulties in handling the separate monomeric and activator materials. In this case they are kept separate and are only mixed in the mould so that in mould polymerisation of the material takes place. This is easy to control because the material can be kept in motion in the mould and the temperature is readily controlled in the mould. Thus, an even and reproducible polymerisation and moulding can be achieved.
  • Granules/pellets of lactam-12 are first placed in a mould 1 at room temperature.
  • the mould 1 is then pre-heated to approximately 170°C to melt the lactam-12.
  • the mould is preferably rotated during pre-heating to maximise exposure of pellets to the hot surface of the mould.
  • a polymerisation activator is then injected directly into the mould through an atomiser/injector 2 fitted with a Nitrogen purge.
  • the activator is efficiently dispersed into the molten lactam-12 and in- mould polymerisation is initiated.
  • the mould is preferably rotated around one or two axes on introduction of the activator to efficiently dissolve or disperse the activator in the melt.
  • the activator may be introduced using a piston driven pneumatic actuator or a dosing pump with a separate reservoir mounted on the moulding machine. This facilitates controlled delivery of activator, on demand.
  • An atomiser head forms a fine mist of activator droplets for rapid mixing.
  • the temperature of the mould is increased to about 200°C over a period of about 10 minutes to complete the polymerisation process.
  • the material evenly adheres to the mould forming a moulded article 3 of desired thickness, especially thin walled articles.
  • the lactam and activator are easily handled.
  • the reactive rotational moulding technique is more easily controlled, is faster, can produce a wider range of moulded articles, especially thin walled articles, and lends itself to automation leading to at lest semi-continuous operation.
  • An inert atmosphere for example provided by nitrogen, is provided in the cavity of the mould to exclude moisture.
  • Re-fillable supply cylinders may be mounted to the mould by a system of valves and regulators to control the flow of gas into the mould.
  • a pre -weighed amount of lauralactam pellets (the monomer form of Nylon- 12) is placed within the mould 1 e.g. 1.25 kg.
  • a pre-weighed amount of liquid activator is dispensed into a syringe container and placed in the mounting fixture on the mould.
  • the amount is typically 1.5% by weight of the pre-defined weight of lauralactam pellets being processed e.g. 18.75 ml for 1.25 kg of lauralactam.
  • the mould breather device encompassing nitrogen flush tube activator dispensing needle, atomiser head and breather exhaust is inserted into the mould.
  • N 2 flush is provided for the activator dispensing system to maintain an N 2 atmosphere in the mould and to purge all the activator from the dispensing system after dispensing.
  • the mould is closed to form a water-tight seal between both halves.
  • a nitrogen flush maintains a slight positive pressure (0.05 bar) within the mould of nitrogen gas. This is to (a) purge any air/ moisture within the mould which could adversely affect polymerisation, (b) keep the atomiser head free of any condensed lactam material and, c) to clean atomiser head after injection of activator.
  • the heating cycle commences which heats the mould using embedded resistance heating wires.
  • the mould heats to a typical set point temperature of 170°C
  • the lactam pellets also heat up and begin to melt.
  • a large surface area of the mould improves heat transfer and reduces the time required for complete melting of the pellets. Rotation of the mould during pre-heating also ensures uniform and efficient melting of the pellets.
  • a slow rotation speed of typically 3 rpm on the major axis, 3 rpm on the minor axis is used to distribute the pellets on the inside of the mould as illustrated in Fig. 2.
  • the lactam pellets have fully melted out to form a liquid with a viscosity similar to that of water.
  • the rotomoulding machine comes to a halt in the vertical plane.
  • the rotation speed in the horizontal is increased to promote shearing motion of the liquid , which now forms a pool on the bottom of the mould.
  • a pneumatic ram is triggered which forces the liquid activator out through a syringe, through the dispensing needle and atomiser head and into the mould.
  • the force applied is regulated by the speed of the ram pushing the syringe.
  • the atomiser head causes the activator to disperse into a cone of minute droplets which drop over the surface of the liquid pool.
  • the combination of the fine activator droplets and the motion of the liquid mean that intimate mixing occurs almost immediately and does not give the activator time to coalesce on the surface of the mould.
  • the injection time is in the order of 10-15 seconds.
  • the nitrogen flush is used to clean the dispensing needle and atomiser head of any remaining liquid activator.
  • Biaxial rotation re-commences after the activator is injected at a speed of typically greater than 5 rpm on the major and minor axes. This is to create the conditions for the phenomenon of solid body rotation of the molten mass. As the viscosity increases on polymerisation, the speed of rotation may be reduced to maintain solid body rotation and to reduce centrifugal effects and uneven thickness build up.
  • the mould set point temperature is increased to 205°C (typical value, internal face temperature). This takes approximately 5-7 minutes to achieve. The higher temperature is required to reduce the time for polymerisation. After a sufficient period of time (typically 5-7 minutes to reach temperature, 10 minutes at temperature), the rotation speeds of both axes are reduced by a factor of 50% (typically). This is to account for the rapidly increasing viscosity of the nylon- 12 material within the mould. After another 5 minutes, the heaters are turned off and forced air convection cooling commences.
  • 205°C typically value, internal face temperature
  • Cooling takes approximately 15 minutes to reduce the temperature from 205°C to part removal temperature (typically 80°C).
  • the mould can them be opened, the breather device withdrawn and the moulded nylon-12 part removed.
  • FIG. 6 there is illustrated another method of rotomoulding according to the invention.
  • Granules 10 of a thermoplastic material such as the lactam material described above are in this case mixed with a polymerisation activator 11 in a premix vessel 12.
  • the vessel 12 is a sealed vessel with a suitable mixer 13 for mixing the activator 11 and thermoplastics 10 under an inert atmosphere.
  • the vessel 12 has a bottom outlet closed by a valve 15, in this case a flap valve.
  • the premix thus formed is loaded into containers such as a bag 16 (Fig 7) under an inert atmosphere.
  • the bag of premixed material is sealed and may be stored until required.
  • a mould 20 When it is desired to mould a product using the premix a mould 20 is opened and under an inert atmosphere and at room temperature the premix is introduced into the mould 20. If desired, the premix is rotated biaxially in the mould (Fig. 9) and - li the temperature of the mould 20 is increased to polymerise the thermoplastic mixture. Typically the temperature is increased by heating the mould walls by imbedded resistance wires to achieve about 205°C on the internal face of the mould. This takes about 10 minutes.
  • biaxial rotation continues at a speed of typically greater than 5 rpm on the major and minor axes. This is to create the conditions for the phenomenon of solid body rotation of the molten mass. As the viscosity increases on polymerisation, the speed of rotation may be reduced to maintain solid body rotation and to reduce centrifugal effects and uneven thickness build up.
  • Cooling takes approximately 15 minutes to reduce the temperature from 205°C to part removal temperature (typically 80°C).
  • the mould 20 can then be opened, the breather device withdrawn and a moulded part 21 removed.
  • the process described with reference to Figs 6 to 11 is particularly advantageous as the premix is formed before being introduced into the mould.
  • the introduction into the mould can be carried out at ambient conditions.
  • the premix is readily prepared and can be stored under an inert atmosphere.
  • the invention provides an integrated process and apparatus for at least semi- continuous rotomoulding. Multiple moulds may be provided on a single machine. If desired, a number of separate moulds may be arranged at separate stations for delivery of pre-polymer material.
  • the stations may, for example, be arranged around a central dispensing unit or may be arranged in-line.
  • a control system may be operated to deliver the pre-polymer material on demand by the individual rotomoulding stations.
  • initial rotation speeds may be relatively high to ensure that a skin of uniform thickness is formed in the mould cavity before the viscosity increases, on polymerisation.
  • This has the advantage that potentially thin walled products may be readily rotationally moulded.
  • the moulding machine technology used allows the injection of other material into the mould cavity after the outer skin has formed.
  • polyethylene foam may be injected into the mould cavity.
  • the low viscosity of the lactam facilitates the forming of very fine details, such as screw threads and the like.
  • Internal pressurisation and/or forced circulation of cooled air/ N 2 to improve cooling efficiency is preferably maintained during cooling to reduce adverse warpage and shrinkage effects.
  • a batch of 1kg lactam is placed in a container and a vacuum is applied.
  • An inert atmosphere is introduced by nitrogen.
  • the container is opened while maintaining the inert atmosphere and an amount of about 15g of an activator which is typically in a liquid form is added.
  • the container is closed and the contents are mechanically agitated to disperse the activator in the lactam.
  • the premix thus formed can be stored indefinitely in an inert atmosphere.
  • the prepared premix is dispersed into the mould, air is purged from the mould and the moulding process is carried out as described above.
  • the premix may include a filler which may be present in an amount of from 10 to 70% by volume.
  • the filler may be of a ceramic material, glass, talc or any suitable inert material. It may be in the form of particulates, microbeads, microspheres or fibres.
  • the filler is added to the premix under an inert atmosphere.
  • the advantages of using such fillers are lower costs, enhanced properties and improved processing.
  • the fillers increase viscosity and reduce flow instability on flow allowing for more even wall thicknesses.
  • Fillers in formulations for rotational moulding can be accommodated because, in addition to the premixing described above the rotational moulding process mixes and agitates the filler during processing to ensure homogenous distribution of the fillers in the final product.
  • the use of a large hollow cavity facilitates the placement of materials with a relatively large bulk density into the mould to produce higher density material than with more conventional moulding where the entire cavity is filled with the material.
  • Using filler materials generally involves increasing the processing temperatures by typically 10°C, depending on the type of and amount of filler used.
  • thermoplastic material any suitable thermoplastic material.
  • the material is a lactam-based prepolymer.
  • a prepolymer may be laurylactam (Nylon 12), caprolactam (Nylon 6) or a blend of both at different ratios dependent on the final properties desired. In some cases a lower viscosity melt is obtained using such blends which is generally preferable if there are added fillers.
  • the thermoplastic may also include or comprise one or more of PBT, ABS, acrylic, polycarbonate, lactam, mixture, blends or copolymers thereof.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Moulding By Coating Moulds (AREA)

Abstract

Selon cette invention, un procédé de moulage rotatif consiste à créer de la matière fondue thermoplastique réactive dans un moule (1, 20). La matière fondue thermoplastique réactive comprend un mélange d'un prépolymère thermoplastique tel que lactame (12) et un activateur de polymérisation. Le prépolymère et l'activateur peuvent être mélangés dans le moule sous atmosphère inerte; on peut aussi former le prémélange du prépolymère et de l'activateur avant de le diriger dans le moule (1). Le prémélange peut être stocké sous atmosphère inerte dans un récipient scellé tel qu'un sac (16) qui peut servir à le distribuer dans un moule (20) à température ambiante. En variante, on peut former de la matière fondue réactive dans le moule (1) en y acheminant le prépolymère puis en y injectant un activateur de polymérisation.
EP99961253A 1998-12-23 1999-12-23 Procede de moulage rotatif et appareil correspondant Withdrawn EP1140453A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
IE981100 1998-12-23
IE981100 1998-12-23
PCT/IE1999/000144 WO2000038897A1 (fr) 1998-12-23 1999-12-23 Procede de moulage rotatif et appareil correspondant

Publications (1)

Publication Number Publication Date
EP1140453A1 true EP1140453A1 (fr) 2001-10-10

Family

ID=11041970

Family Applications (1)

Application Number Title Priority Date Filing Date
EP99961253A Withdrawn EP1140453A1 (fr) 1998-12-23 1999-12-23 Procede de moulage rotatif et appareil correspondant

Country Status (3)

Country Link
EP (1) EP1140453A1 (fr)
AU (1) AU1794600A (fr)
WO (1) WO2000038897A1 (fr)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2856625B1 (fr) * 2003-06-27 2005-09-23 Rhodia Engineering Plastics Sa Fabrication d'articles par rotomoulage
FR2871091B1 (fr) * 2004-06-03 2008-01-18 Commissariat Energie Atomique Procede de fabrication d'une vitesse d'etancheite d'un reservoir de type iv et reservoir de type iv
CN113561387A (zh) * 2021-07-07 2021-10-29 浙江飞友康体设备有限公司 一种儿童滑梯部件滚塑装置及其工艺
CN115246189A (zh) * 2022-06-29 2022-10-28 浙江瑞堂塑料科技股份有限公司 一种带除氧功能的通气管

Family Cites Families (8)

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Publication number Priority date Publication date Assignee Title
BE635595A (fr) * 1962-08-03
FR1519947A (fr) * 1966-03-29 1968-04-05 Allied Chem Procédé de moulage d'objets creux de grandes dimensions en epsilon-caprolactame, dans des moules tournants
DE1795358A1 (de) * 1968-09-19 1972-01-05 Basf Ag Verfahren und Vorrichtung zum Herstellen von Formkoerpern aus Polyamiden
DE2057709A1 (de) * 1970-11-17 1972-05-31 Mannesmann Ag Behaelter oder Rohre aus Kunststoff zum Lagern bzw. zum Transport von Fluessigkeiten,Pasten oder rieselfaehigen Schuettguetern
CH544785A (de) * 1971-02-11 1973-11-30 Inventa Ag Verfahren zur Herstellung von Formkörpern aus Polyamiden oder Copolyamiden
DE3406148A1 (de) * 1984-02-21 1985-09-05 Philips Patentverwaltung Gmbh, 2000 Hamburg Verfahren zur herstellung von rohrfoermigen koerpern und vorrichtung zur durchfuehrung des verfahrens
US4671753A (en) * 1985-08-19 1987-06-09 Payne Leroy Apparatus for molding
DE3818762A1 (de) * 1988-06-02 1989-12-07 Bayer Ag Verfahren zur herstellung von duromeren kunststoffkoerpern mit inhomogener, dreidimensionaler brechungsindexverteilung

Non-Patent Citations (1)

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Title
See references of WO0038897A1 *

Also Published As

Publication number Publication date
AU1794600A (en) 2000-07-31
WO2000038897A1 (fr) 2000-07-06

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