WO1995015245A1 - Conduite moulee par centrifugation - Google Patents

Conduite moulee par centrifugation Download PDF

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Publication number
WO1995015245A1
WO1995015245A1 PCT/US1993/011626 US9311626W WO9515245A1 WO 1995015245 A1 WO1995015245 A1 WO 1995015245A1 US 9311626 W US9311626 W US 9311626W WO 9515245 A1 WO9515245 A1 WO 9515245A1
Authority
WO
WIPO (PCT)
Prior art keywords
pipe
bulk
cylindrical mold
inches
mold
Prior art date
Application number
PCT/US1993/011626
Other languages
English (en)
Inventor
Charles S. Woodson
Michael James Darnall
Norman A. Deumite
Original Assignee
Pti/End-Corr, Inc.
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
Priority to US07/679,862 priority Critical patent/US5266370A/en
Priority claimed from US07/679,862 external-priority patent/US5266370A/en
Application filed by Pti/End-Corr, Inc. filed Critical Pti/End-Corr, Inc.
Priority to PCT/US1993/011626 priority patent/WO1995015245A1/fr
Publication of WO1995015245A1 publication Critical patent/WO1995015245A1/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
    • 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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
    • F16L9/00—Rigid pipes
    • F16L9/12—Rigid pipes of plastics with or without reinforcement

Definitions

  • This invention relates to a centrifugally cast pipe comprised of bulk polymerized polymers. It is conventional to centrifugally cast thermosetting and thermoplastic resins to form pipes of diameters within the range of 1-12 inches. See U.S. Patent Nos. 3,988,412, 3,816,582, 3,718,161 and 2,887,728.
  • the pipes formed are generally of a thickness wherein reinforcement with fibers such as fiber glass is desired.
  • a centrifugally cast plastic pipe with smooth inner and outer surfaces which is comprised of bulk polymerized monomers can be obtained by introducing a reactive formulation of bulk polymerizable monomers having a gel time which ranges from about 20 seconds to 12 minutes into a cylindrical mold, spinning the reactive formulation within the cylindrical mold to obtain the cylindrical dimensions of the pipe, pressurizing the cylindrical mold with a gas to a pressure greater than 1 atmosphere for a period sufficient to allow the reactive formulation of bulk polymerizable monomers to complete the reaction exotherm and removing the pipe from the mold when polymerization is complete.
  • the present invention utilizes polymers obtained by bulk polymerization. These polymers are formed within the mold during the centrifugal casting process. While any polymer produced by bulk polymerization is suitable for this invention, those which can be obtained from a reactive monomer formulation that completely cures in less than 1 hour are preferred. This provides short molding cycles when manufacturing the pipe.
  • bulk polymerization refers to polymerization in the substantial absence of a solvent or diluent, wherein a catalyst or curing agent is dissolved within the monomer itself and polymerization yields a solid finished article substantially in final form.
  • the bulk polymerization poly ⁇ mer exhibit high temperature and chemical resistance as well as high strength and high impact resistance.
  • Poly- carbonates and polycycloolefins are examples of such polymers.
  • Bulk polymerized polycycloolefins are preferred and the preferred polymers within this group comprise di- cyclopentadiene monomers.
  • Commercially available two component formulations which comprise bulk polymerizable monomers are Telene ® , produced by the B.F. Goodrich Company.
  • Another commercially available formulation is Metton ® , produced by Hercules, Inc.
  • Examples of monom aers known in the art include nor ⁇ bornene, dicyclopentadiene, ethylidenenorbornene, nor- bornidiene, dihydrodicyclopentadiene, trimers of cyclo- pentadiene, tetramers of cyclopentadiene, tetracyclo- dodecene, methyltetracyclododecene, methylnorbornene, ethylnorbornene, dimethylnorbornene and similar derivatives. These and other monomers are described by Minchak in U.S. Patent Nos. 4,380,617 and 4,426,502.
  • Preferred monomer formulations are those suitable for reaction injection molding (RIM) techniques and resin transfer moldings (RTM) which are forms of bulk polymerization which occur in a closed mold.
  • RIM and RTM differ from the thermoplastic injection molding in that lower pressures are used and lower temperatures are used.
  • the primary distinction between injection molding and RIM/RTM is in the fact that a chemical reaction takes place to transform a monomer to a polymeric state.
  • the reactive formulations preferably have a gel time in the range of 20 seconds to 12 minutes at about 4(5*C.
  • the preferred values within this range depend on the size of the pipe and whether it contains reinforcement. For some applications, longer gel times in excess of 10 minutes at 40°C are desired.
  • the gel time is the time at which the viscosity of the formulation increases to a point where it is difficult to shape the cylinder within the centrifugal mold, i.e., the mold cannot be filled without knit lines or other defects.
  • the time to exotherm is the point at which the formulation increases rapidly in temperature because of the heat of polymerization.
  • the reactive monomer formulation contains a curing agent or catalyst which is activated to initiate polymerization.
  • the catalyst may be activated simultaneously with its formation in preparing the reactive monomer formulation by combining two catalyst components just prior to use. Alternatively, a complete catalyst may be dissolved within the monomer and activated by means such as heat or UV radiation.
  • Suitable two component catalysts for the formation of polycycloolefins are described by Minchak in U.S. Patents 4,426,502 and 4,380,617, Khasat et al. in U.S. Patent 4,835,230, Nelson in U.S. 4,897,456 and Martin in U.S. 4,918,039.
  • the formulation may contain conventional additives used to enhance the polymerization reaction as well as additives which enhance the properties of the resultant plastic pipe. Blowing agents may be introduced into the formulation to generate a foam core when activated by the heat of reaction. It may also be desirable to introduce fiber reinforcement for certain applications. Fill ⁇ rs may also be desirable to reduce material costs or enhance the properties of the pipe.
  • the plastic pipe of the present invention is obtained by introducing a reactive monomer formulation of bulk polymerizable monomers into a cylindrical mold which is preferably spinning within a casting machine (caster) , particularly where reinforcement is used.
  • the reactive monomer formulation catalyst is derived from two components, it is preferable to premix these components before addition to the cylindrical mold.
  • the reactive formulation preferably has a gel time at 40°C within the preferred range given above.
  • the reactive monomer formulation has a time to exotherm in less than 1 hour, preferably less than 20 minutes. It is desirable for the exotherm to be short in duration and small magnitude. This allows flexibility in the equipment utilized. In addition, it allows for short mold cycle times.
  • the mold cycle times range from 6-40 minutes, most preferably from 6-12 minutes.
  • the mold is pressurized with a gas to an internal pressure greater than 1 atmosphere, preferably, greater than 10 psi and most preferably, within the range of 20-60 psi. The pressure is maintained until the exotherm is complete, i.e., the temperature of the reactive monomer formulation starts to decrease.
  • an inert gas such as nitrogen
  • a gas which will react with the unsaturated carbons in the polymer such as fluorine
  • fluorine the interior surface of the pipe will be modified in that the fluorine incorporates into the polymers formed.
  • halog ⁇ n gases such as chlorine and bromine are also suitable.
  • This modification will enhance the chemical resistance of the pipe formed by providing a surface layer with properties that resemble a corrosion resistant fluorinated surface material.
  • the cylindrical mold is spun to shape the reactive monomer formulation into the cylindrical dimensions defined by the mold, i.e., the outer diameter of the pipe and its length.
  • the inner diameter of the pipe- is determined by the amount of reactive formulation introduced to the mold.
  • the mold is spun under pressure until the reaction exotherm is complete. Preferably, spinning is continued until the pipe is ready to be removed from the mold. The additional spinning is continued at atmospheric pressure, preferably by venting the mold. The pipe formed is removed from the cylindrical mold once polymerization is complete.
  • the pipe formed will have smooth inner and outer surfaces. Smooth inner surfaces are obtained because the pressurization prevents entrapped gas from escaping from the reactive monomer formulation during reaction.
  • the number of voids in the inner surface are as few as the number of voids in the outer surface.
  • Such a pipe is substantially uniform in composition and any voids should not be the result of bubble formation.
  • the inner surface has less than one void per square inch. Most preferably, the inner surface has no visible voids.
  • the plastic pipe of this invention can vary widely in length. Preferred lengths are from about 4-20 feet.
  • the pipes of this invention can also vary widely in wall thickness as well. Thicknesses ranging from 1/8 inch to 3 inches are suitable in that the reactive formulation can be easily distributed since it is low in viscosity and heat need not be introduced to initiate the polymerization.
  • the inner surface need not be uniform in diameter since the pipe couplings and connectors can be adapted to fit the uniform outer diameter.
  • the pipes of this invention can also range widely in diameter.
  • the pipes have a uniform outer diameter defined by the cylindrical mold. This can range from 1 inch to 12 feet. Pipes of a diameter outside of this range are also possible with the appropriate equipment.
  • the diameter of the pipe is limited by the viscosity of the reactive formulation and the rpm of the molding machine.
  • an rpm in the range of 800-2,000 is preferred and is most preferably about 400-900 if non-reinforced, and 1,500-2,000 if reinforced, particularly for formulations comprised of dicyclopentadiene monomers.
  • the optimum rpm will vary with the formulation, its viscosity, the size of the desired pipe and whether reinforcement is used.
  • a centrifugal pipe caster fitted with a cylindrical mold about 4 feet long with a 4 inch inner diameter is used in this example.
  • the cylindrical mold is fitted with end caps that provide a gas tight seal. Swivel feeds are incorporated into each end cap. One feeds the reactive monomer formulation, the other feeds a gas.
  • the cylindrical mold is spun at about 850 rpm.
  • the two " component reactive monomer solution of bulk polymeri-zable monomer (trade designation TELENE ® sold by the B.F. Goodrich Co.) is mixed and fed into the spinning cylindrical mold from a reaction injection molding machine at a continuous rate of about 0.4 lbs. per second at a injection pressure of 1,050 psi.
  • the total shot time was about 16.85 seconds.
  • the amount of material fed into the cylindrical mold is enough to provide a 1/4 inch wall.
  • the reaction injection molding machine mixes components A and B of the TELENE ® formulation. There is no pressure in the mold while feeding the reactive monomer formulation into a mold through the end caps; however, after the material is introduced, the mold is pressurized to 30 psi nitrogen through the opposing end cap. The reactive formulation experiences exotherm at about 2 minutes, 48 seconds. The caster is then stopped at 10 minutes, 12 seconds, the nitrogen pressure released and the interior of the mold is left open to the atmosphere by removing the end caps. The caster is started up again after about 2 minutes with the interior of the cylindrical mold is vented into the atmosphere. The caster is stopped after about 20 minutes from the initial feeding of the reactive monomer formulation and the pipe is separated from the mold. No holes appear on the outside surface and few, if any, very tiny holes are found on the inside surface.
  • a reactive formulation of TELENE ® is fed into the cylindrical mold, spinning at about 850 rpm.
  • the total shot time is 16.85 seconds at a rate of about 0.4 pounds per second with an injection pressure of '1,050 psi.
  • Enough material is fed to the cylindrical mold, to provide a 1/4 inch wall thickness.
  • the reactive formulation exotherms at about 3 minutes, 20 seconds, and after about 10 minutes, the caster is stopped and the interior of the cylindrical mold was vented to the atmosphere by removing the end caps.
  • the caster is started back up after about 2 minutes with the cylindrical mold still vented to the atmosphere.
  • the caster is stopped after 15 minutes, 20 seconds from the initial feeding of the reactive monomer formulation.
  • the part is removed from the mold shortly thereafter. Small holes are detected on the outside surface and large air bubbles or voids are detected on the inside surface.

Landscapes

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

Abstract

L'invention concerne une conduite en plastique moulée par centrifugation. Le plastique utilisé est un polymère dérivé de monomères polymérisés en masse. Un moule cylindrique sous pression permet d'avoir des surfaces interne et externe lisses. On peut réaliser ainsi des conduites avec une épaisseur de paroi allant de 1/8ème de pouce à 3 pouces et un diamètre externe de 1 pouce à 12 pieds.
PCT/US1993/011626 1991-04-03 1993-11-30 Conduite moulee par centrifugation WO1995015245A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US07/679,862 US5266370A (en) 1991-04-03 1991-04-03 Centrifugally cast pipe
PCT/US1993/011626 WO1995015245A1 (fr) 1991-04-03 1993-11-30 Conduite moulee par centrifugation

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US07/679,862 US5266370A (en) 1991-04-03 1991-04-03 Centrifugally cast pipe
PCT/US1993/011626 WO1995015245A1 (fr) 1991-04-03 1993-11-30 Conduite moulee par centrifugation

Publications (1)

Publication Number Publication Date
WO1995015245A1 true WO1995015245A1 (fr) 1995-06-08

Family

ID=26787145

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1993/011626 WO1995015245A1 (fr) 1991-04-03 1993-11-30 Conduite moulee par centrifugation

Country Status (1)

Country Link
WO (1) WO1995015245A1 (fr)

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2887728A (en) * 1954-05-14 1959-05-26 Reflin Co Method of centrifugally casting a pipe using thermoplastic and thermosetting resins
US3718161A (en) * 1971-06-23 1973-02-27 Youngstown Sheet And Tube Co Crack-resistant pipe
US4568501A (en) * 1983-05-23 1986-02-04 Ceskoslovenska Akademie Ved Method and apparatus with automatic feed means for centrifugally casting articles
US4705660A (en) * 1985-04-11 1987-11-10 Robert Demarle Method and apparatus for producing a pipe of fiber-reinforced, hardenable synthetic resin
US4808364A (en) * 1984-03-23 1989-02-28 Hercules Incorporated Rotational polymerization molding
US4918146A (en) * 1989-04-20 1990-04-17 Hercules Incorporated Surface modification of polycyclic cycloolefin polymers

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2887728A (en) * 1954-05-14 1959-05-26 Reflin Co Method of centrifugally casting a pipe using thermoplastic and thermosetting resins
US3718161A (en) * 1971-06-23 1973-02-27 Youngstown Sheet And Tube Co Crack-resistant pipe
US4568501A (en) * 1983-05-23 1986-02-04 Ceskoslovenska Akademie Ved Method and apparatus with automatic feed means for centrifugally casting articles
US4808364A (en) * 1984-03-23 1989-02-28 Hercules Incorporated Rotational polymerization molding
US4705660A (en) * 1985-04-11 1987-11-10 Robert Demarle Method and apparatus for producing a pipe of fiber-reinforced, hardenable synthetic resin
US4918146A (en) * 1989-04-20 1990-04-17 Hercules Incorporated Surface modification of polycyclic cycloolefin polymers

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