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
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/30—Extrusion nozzles or dies
  • B29C48/3001—Extrusion nozzles or dies characterised by the material or their manufacturing process
  • B29C48/3003—Materials, coating or lining therefor
• • 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
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
  • B29C48/09—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
• • 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
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
  • B29C48/09—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
  • B29C48/10—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels flexible, e.g. blown foils
• • 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
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
  • B29C48/06—Rod-shaped

Definitions

• IPC 7 B29C 33/56, B28C 47/00, B29C 47/12, B29C 49/00
• the present invention generally relates to the processing of thermoplastic polymers by extrusion. More particularly the present invention relates to the manufacture of blown films, tubes, and wire coatings having a good surface appearance. In a more specific aspect, the invention relates to a process of thermoplastic polymers (e.g. polyolefins), which have a narrow molecular weight distribution. The invention further relates to a die design which provides a high rate of defect free extrusion of the molten plastics.
• additives for use as processing aids to obtain melt fracture reduction in extrudates [10,11] are expensive and the added cost, depending on the required concentration, may be prohibitive in resins, such as granular LLDPE, intended for commodity applications. Also additives influence the rheological properties of the base resin. In excess amounts they may adversely affect critical film properties including gloss, transparency, blocking and heat sealability characteristics of the product.
• Coating the die land area with substances which reduce or enhance the adhesion of the polymer material to the die land surfaces [18,19] eliminate surface melt fracturing at higher extrusion rates.
• substances which reduce or enhance the adhesion of the polymer material to the die land surfaces For example the use of brass or a composition containing about 80% to 99% nickel and about 1% to 20% phosphorous give better results as compared to common stainless steel.
• the use of thin coatings from fluorinated polymers as well as the use of PTFE for the die land area makes it possible to enlarge the rate of defect free extrusion up to 3.5 times.
• the invention also resides in an apparatus for processing of thermoplastic polymers including a bin feeder, heaters, press extruder, and a die, preferably an annular die, said die having a die land region defining opposing surfaces, the improvement wherein at least one of said opposing surfaces in area adjacent to the die orifice is coated with an elastic material.
• both opposing surfaces in area adjacent to the die orifice are coated with an elastic material comprising elastomers selected from the group consisting of: Hydrogenated Nitrile Rubber, Fluorinated Hydrocarbon Elastomers, Perfluorinated Elastomers, Silicone Elastomers, and Fluorosilicone Elastomers.
• elastomers selected from the group consisting of: Hydrogenated Nitrile Rubber, Fluorinated Hydrocarbon Elastomers, Perfluorinated Elastomers, Silicone Elastomers, and Fluorosilicone Elastomers.
• Silicon Rubber which is designed to work at elevated temperatures includes a filler, a heat resistance improver, etc. .
• the heat resistance improver may include, e.g., carbon black, graphite, fluorinated carbon, and iron oxide.
• the filler is mostly a silica-based inorganic filler, e.g. silica fume, but in accordance with our invention the rubber composition could include micro-powder of a low surface energy filler selected from the group of fluorinated polymers, Boron Nitrate having hexagonal crystal form, graphite, molybdenum disulfide, tungsten disulfide, talc in total amount of about 0,1 to about 80 wt. %.
• the rubber coatings were produced by potting a one component silicone rubber "Ceresit” from Henkel KGaA (maximum working temperature is 315°C) [30] or by potting a two component silicone rubber "RTN-ME 622A” from Wacker-Chemie GmbH [31]. The coatings were vulcanized by heating at 150°C.
• the rubber rings for the die design in Fig. IC were cut from silicon rubber or fluorinated rubber (Viton) tubes with 6 mm inner diameter. The rings were glued inside the metal frame and closed from the entrance side by diaphragms of 5 mm diameter.
• the extrusion rate was gradually increased from 0.1 to 250 mm per sec.
• the flow curve for the case of a tubular brass die of the conventional design (Fig. 1A, length - 24 mm, diameter - 6 mm, temperature of extrusion - 145°C) is presented in Fig. 4 by a continuous line.
• Fig. 1A length - 24 mm, diameter - 6 mm, temperature of extrusion - 145°C
• the experiments were performed with LLDPE, and the results therefore may contribute to an improvement of extrusion of thermoplastic polymers, which have a narrow molecular weight distribution. Especially the results may have an impact on the improvement of polymer processing in tubular film blowing , injection molding, fiber spinning, as well as on measurements of viscosity values in rheometers.

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

Applications Claiming Priority (3)

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• 2003
  • 2003-02-28 DE DE10308909A patent/DE10308909A1/de not_active Withdrawn
• 2004
  • 2004-02-23 EP EP04713535A patent/EP1606095A2/de not_active Withdrawn
  • 2004-02-23 WO PCT/EP2004/001772 patent/WO2004076151A2/en not_active Ceased

Non-Patent Citations (1)

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