WO1997032707A1 - Molding products - Google Patents

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Publication number
WO1997032707A1
WO1997032707A1 PCT/US1997/003366 US9703366W WO9732707A1 WO 1997032707 A1 WO1997032707 A1 WO 1997032707A1 US 9703366 W US9703366 W US 9703366W WO 9732707 A1 WO9732707 A1 WO 9732707A1
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WO
WIPO (PCT)
Prior art keywords
period
time
mold
polyethylene
inch
Prior art date
Application number
PCT/US1997/003366
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English (en)
French (fr)
Inventor
Burdette Lee Joesten
Original Assignee
Mobil Oil Corporation
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 Mobil Oil Corporation filed Critical Mobil Oil Corporation
Priority to EP97908009A priority Critical patent/EP0885104A1/en
Priority to JP9531891A priority patent/JP2000506088A/ja
Priority to CA002247916A priority patent/CA2247916C/en
Priority to AU19862/97A priority patent/AU703420B2/en
Publication of WO1997032707A1 publication Critical patent/WO1997032707A1/en

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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
    • B29C41/003—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
    • 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
    • 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
    • B29C2791/001—Shaping in several steps

Definitions

  • the invention relates to rotational molding and articles of manufacture produced thereby.
  • Articles of manufacture are produced from ethylene polymers or copolymers, which over an extended range of molding temperatures and times, exhibit ductility at impact.
  • Rotational molding is frequently the only practical technique for producing very large molded parts. Rotational molding is used to fabricate large tanks, up to 10 m 3 (greater than 2600 gallons) , complex hollow-shaped objects for which injection molding is not feasible, hollow spheres, large pipe, and similar objects.
  • Resins suitable for rotational molding applications must display relatively low melt viscosity in order to replicate the mold surface faithfully. At the same time, many applications require excellent stress crack resistance.
  • Resins that meet these requirements display a moderately high melt index and narrow molecular weight distribution.
  • a rotational molding hollow mold is charged with resin in the form of a powder.
  • the powder is made by pulverizing pellets where the pellets are made by hot compounding an as- synthesized composition which is dry and solvent-free and comprises spherical particles, which have an average particle size of 0.015 to 0.035 inches, and a settled bulk density of from 25 to 36 lb/ft 3 , and which is a linear polymer or copolymer of ethylene and an alpha olefin, a MFR of 15 to 20, and a Vi ⁇ /VL n of from about 2.5 to about 3.0, wherein the copolymer is further characterized by an HI(I 2 ) of 0.1 to 6.0.
  • the mold is then transferred into an oven and rotated, preferably about two axes, to distribute the powder uniformly over the hot surface of the mold.
  • the heating cycle is continued until all of the powder has melted and formed a thick, continuous layer within the mold.
  • the mold is then removed from the oven and cooled until the resin has fully solidified, then the part is removed.
  • the resin products may contain any of various additives conventionally added to polymer compositions such as lubricants, microtalc, stabilizer, antioxidants, compatibilizers, pigments, etc. These reagents can be employed to stabilize the products against oxidation.
  • additive packages comprising 400-1200 ppm hindered phenol(s); 400-2000 ppm phosphites; 1000 to 3000 ppm UV stabilizers; and 250-1000 ppm stearates, can be incorporated during pelletization.
  • Rotational molding is sometimes denoted as "rotomolding" in this disclosure.
  • Rotational molding of polyethylene comprises a process in which a mold is charged with polyethylene powder, and, while rotating about two axes, is placed in a hot oven long enough for the powder to melt and take the shape of the mold; thereafter the mold is removed from the oven and cooled until the molten polyethylene solidifies, and then the solidified part is removed from the mold. Unlike other molding process, no pressure is involved in rotomolding.
  • the time which the mold must be kept in the oven depends on the oven temperature, on the amount of resin in the mold and on the resin properties. Oven temperatures range from 500° to 700°F. The time in the oven decreases as the temperature increases and can range from a few hours at 500°F to a few minutes at 700°F. For a given oven temperature, the mold must be kept in the oven for a longer time as the amount of powder in the mold increases. As the amount of powder that is placed in the mold increases, the wall thickness of the part increases.
  • the time which the mold must be kept in the oven depends on characteristics of the specific resin.
  • Current commercial rotational molding resins generally have a relatively narrow range of molding times where parts have good mechanical integrity without excessive degradation. For example, a commercial resin could require that the mold be kept in the oven between 17 h and 18*5 minutes to make a good part with 1/8" wall thickness at 550°F. For longer or shorter times, the part could have unacceptable properties.
  • An alternative resin would be particularly desirable for rotational molding if it could form a good part (1) in much less than 17 ⁇ minutes or (2) over more than a 1 minute range of times.
  • the resins made with metallocene catalyst used in this invention form ductile articles when rotationally molded either for shorter times or over broader range of times than that which is required to rotationally mold ductile articles from resins that have similar density and melt index but are not made with metallocene catalyst. Accordingly, the process of this invention allows greater process flexibility in the production of articles of manufacture by rotational molding, or rotomolding, which exhibit mechanical integrity or impact resistance.
  • the article is characterized as having good impact resistance if it cannot be broken easily by striking it, for example, with a hammer or by letting an object fall on it.
  • impact resistance is determined by dropping a dart on the article or on a section taken from the article. If the falling dart has enough energy to pierce the article and if the deformation is localized around the tip of the dart, the failure is described as ductile. Ductile failures indicate that the article was molded well. If the falling dart causes the article to crack in many directions away from the point of impact, the failure is described as brittle. Brittle failures indicate that the article was not left in the oven long enough (undercure) or that it was left in the oven too long (overcure) .
  • the impact resistance can be quantified from the dart weight and drop height which cause failure.
  • the products of rotational molding in accordance with the invention exhibit ductility during impact. Specifically, when subjected to dart drop impact sufficient to pierce the wall of the rotational molded articles, the material of the wall will not shatter (like glass on impact.)
  • the articles of manufacture herein are hollow with wall thicknesses ranging from 3/32" to 1" preferably ranging from 1/8" to 1/2" preferably ranging from 3/16" to 3/8". Products which can be made this way include rotationally molded plastics which are hollow parts. With rotomolding, parts can be molded economically in a variety of shapes and sizes, many of them impossible to produce by any other process.
  • Common rotationally molded products include shipping drums, storage tanks and receptacles, material handling bins, fuel tanks and housings. Consumer products include furniture, light globes, toys, surfboards, and a marine accessories.
  • Storage containers include, for example, tanks for storage of solvent (nylon) ; high purity chemicals (PDVE) , general storage (HDPE) and aggressive chemicals (XLPE) , tanks for may applications, portable tanks, closed- dome tanks, agricultural and chemical storage tanks, 500 gallon septic tank, toys such as carousel horse, toys storage container, spring horse, see-saw , rocking horse, picnic table, play balls, wading pool, hopalong rider bounce toys, motorcycle fairings and saddle bags, hockey game base, camper top, video game housing, swimming pool filter.
  • solvent nylon
  • PDVE high purity chemicals
  • HDPE general storage
  • XLPE aggressive chemicals
  • the polyethylene preferably polyethylene copolymers described below, have a wide range of molding times at which parts are ductile during impact failure. Molders have the opportunity to use shorter molding cycles. Molders who tend to use less than optimum molding conditions for resins with a narrow operational molding window could observe improved properties and improved quality by using resin with a wide molding latitude.
  • the resin described below for use in the invention is also capable of providing a wide molding cycle latitude.
  • the polyethylene resin, preferably a copolymer, which is used herein is produced, catalytically, in the gas phase fluid bed is retrieved as a powder. Additives for stabilization are incorporated with the reactor powder during pelletization, the polyethylene pellets are subjected to grinding prior to rotational molding.
  • the linear copolymer products used herein contain 0.1 to 2 ppm of Zr.
  • the product has an average particle size of 0.015-0.035 inches, settled bulk density from 25 to 36 lb/ft 3 .
  • the particles have spherical shape and are relatively non- porous.
  • the density is greater than .900, generally greater than 0.930, preferably ranging from 0.935 to 0.945 g/cm 3 .
  • the narrow molecular weight distribution copolymers have been produced with MI of one (1) and less than 1, down to 0.01, and up to 10.
  • products used in the invention exhibit a MI value which can range from 1 to 7, and most preferably from 2 to 5.
  • the resins exhibit a melt flow ratio (MFR) range of 15 to 25, preferably from 15 to 20. In products of some of the Examples, the MFR ranges from 16 to 18. MFR is the ratio l 2 i/! 2 [wherein I 21 is measured in accordance with ASTM D-1238, Condition 190/21.6 and I 2 is measured in accordance with ASTM D-1238, Condition 190/2.16.]
  • Melting points of the products range from 95°C to 130°C. Furthermore, the hexane extractables content is very low, typically ranging from 0.3 to 1.0 wt.%.
  • the M exert/M n of these products ranges from about 2.0 to about 3.5 and from about 2.5 to about 3.0.
  • t is the weight average molecular weight and M n is the number average molecular weight, each of which is calculated from molecular weight distribution measured by GPC (gel permeation chro atography) .
  • Products have been produced with M w /M ⁇ lower than 2.5, in the range of 2.0 to 3.5 preferably in the range of 2 to 3.
  • the numerical value of I 10 /I 2 ⁇ 4.63 is less than M thread/M n .
  • I 2 , or melt index is measured in accordance with ASTM D-1238; and l 10 is measured in accordance with ASTM-D 1238, Condition 190/10.
  • the copolymers are produced with ethylene and optionally one or more C 3 -C 10 alpha-olefins, in accordance with the invention.
  • the copolymers contain at least 80 weight % ethylene units.
  • the comonomers used in the present invention preferably contain 3 to 8 carbon atoms.
  • Suitable alpha olefins include propylene, butene-1, pentene-1, hexene-1, 4- methylpentene-1, heptene-1 and octene-1.
  • the alpha-olefin comonomer is 1- butene, 1-hexene, and 1- octene.
  • the most preferred alpha olefin is hexene-1.
  • copolymers having two monomeric units are possible as well as terpolymers having three monomeric units.
  • Particular examples of such polymers include ethylene/1-butene copolymers, ethylene/1-hexene copolymers, ethylene/4-methyl- 1-pentene copolymers, ethylene/1-butene/l-hexene terpolymers, ethylene/propylene/1-hexene terpolymers and ethylene/propylene/1-butene terpolymers.
  • Hydrogen frequently used as a chain transfer agent in the polymerization reaction, is not necessary for the present invention. Any gas inert to the catalyst and reactants can also be present in the gas stream.
  • the product is dry and solvent-free and comprises spherical, non- porous particles, which has an average particle size of 0.015 to 0.035 inches and a settled bulk density of from 25 to 36 lb/ft 3 .
  • an operating temperature of 60° to 115°C is preferred, and a temperature of 75° to 95°C is most preferred.
  • the fluid bed reactor is operated at pressures of about 150 to 350 psi, with operation at the higher pressures in such ranges favoring heat transfer since an increase in pressure increases the unit volume heat capacity of the gas.
  • a "diluent" gas is employed with the comonomers. It is nonreactive under the conditions in the polymerization reactor.
  • the diluent gas can be nitrogen, argon, helium, methane, ethane, and the like.
  • the superficial gas velocity of the gaseous reaction mixture through the bed must exceed the minimum flow required for fluidization, and preferably is at least 0.2 feet per second above the minimum flow. Ordinarily the superficial gas velocity does not exceed 5.0 feet per second, and most usually no more than 2.5 feet per second is sufficient.
  • the feed stream of gaseous monomer, with or without inert gaseous diluents, is fed into the reactor at a space time yield of 2 to 10 pounds/hour/cubic foot of bed volume.
  • the catalysts used to form the polyethylene resins preferably polyethylene copolymers, comprise a carrier, an aluminoxane and at least one metallocene.
  • the carrier material is a solid, particulate, porous, inorganic or organic materials, but preferably inorganic material, such as an oxide of silicon and/or of aluminum.
  • the carrier material is used in the form of a dry powder having an average particle size of from about 1 micron to about 250 microns, preferably from about 10 microns to about 150 microns. If necessary, the treated carrier material may be sieved to insure that the particles have an average particle size of preferably less than 150 microns. This is highly desirable in forming narrow molecular weight LLDPE, to reduce gels.
  • the surface area of the carrier is at least 3 square meters per gram (m 2 /gm) , and preferably at least 50 m 2 /gm up to 350 2 /qm. When the carrier is silica, it is heated to preferably 100° to about 850°C and most preferably at about 250°C.
  • the carrier material must have at least some active hydroxyl (OH) groups to produce the catalyst composition of this invention.
  • the carrier is silica which, prior to the use thereof in the first catalyst synthesis step, has been dehydrated by fluidizing it with nitrogen and heating at about 250°C for aproximately 4 hours to achieve a surface hydroxyl group concentration of about 1.8 millimoles per gram (mmols/gm) .
  • the silica of the most preferred embodiment is a high surface area, amorphous silica (surface area - 300 m 2 /gm ; pore volume of 1.65 cm 3 /gm) , and it is a material marketed under the tradenames of Davison 952- 1836, Davison 952 or Davison 955 by the Davison Chemical Division of W. R. Grace and Company.
  • the silica is in the form of spherical particles, e.g., as obtained by a spray- drying process.
  • all catalyst precursor components can be dissolved with aluminoxane and reacted with a carrier.
  • the carrier material is reacted with an aluminoxane solution, preferably methylaluminoxane, in a process described below.
  • the class of aluminoxanes comprises oligo eric linear and/or cyclic alkylaluminoxanes represented by the formula: R-(A1(R)-0) n -AlR 2 for oligomeric, linear aluminoxanes and (-Al(R)-0-) m for oligomeric cyclic aluminoxane wherein n is 1-40, preferably 10-20, m is 3-40, preferably 3- 20 and R is a C ⁇ Cg alkyl group and preferably methyl.
  • Methylaluminoxane (MAO) is a mixture of oligomers with a very wide distribution of molecular weights and usually with an average molecular weight of about 1000. MAO is typically kept in solution in toluene.
  • one of the controlling factors in the aluminoxane incorporation into the carrier material during catalyst synthesis is the pore volume of the silica.
  • the process of impregnating the carrier material is by infusion of the aluminoxane solution, without forming a slurry of the carrier material, such as silica, in the aluminoxane solution.
  • the volume of the solution of the aluminoxane is sufficient to fill the pores of the carrier material without forming a slurry in which the volume of the solution exceeds the pore volume of the silica; accordingly and preferably, the maximum volume of the aluminoxane solution is and does not exceed the total pore volume of the carrier material sample. That maximum volume of the aluminoxane solution insures that no slurry of silica is formed. Accordingly, if the pore volume of the carrier material is 1.65 cm 3 /g, then the volume of aluminoxane will be equal to or less than 1.65 cm 3 /gram of carrier material.
  • solvent may be removed from the aluminoxane impregnated pores of the carrier material by heating and/or under a positive pressure induced by an inert gas, such as nitrogen. If employed, the conditions in this step are controlled to reduce, if not to eliminate, agglomeration of impregnated carrier particles and/or crosslinking of the aluminoxane.
  • solvent can be removed by evaporation effected at relatively low elevated temperatures of above about 40° and below about 50°C. Although solvent can be removed by evaporation at relatively higher temperatures than that defined by the range above 40° and below about 50°C, very short heating times schedules must be employed.
  • the metallocene is added to the solution of the aluminoxane prior to reacting the carrier with the solution.
  • the maximum volume of the aluminoxane solution also including the metallocene is the total pore volume of the carrier material sample.
  • the mole ratio of aluminoxane provided aluminum, expressed as Al, to metallocene metal expressed as M (e.g. Zr) ranges from 50 to 500, preferably 75 to 300, and most preferably 100 to 200.
  • An added advantage of the present invention is that this Al:Zr ratio can be directly controlled.
  • the aluminoxane and metallocene compound are mixed together at a temperature of 20" to 80°C, for 0.1 to 6.0 hours, prior to reaction with the carrier.
  • the solvent for the metallocene and aluminoxane can be appro-priate solvents, such as aromatic hydrocarbons, halogenated hydrocarbon or halogenated aromatic hydrocarbons, preferably toluene.
  • the metallocene compound has the formula Cp m MA n B p in which Cp is an unsubstituted or substituted cyclopenta-dienyl group, M is zirconium or hafnium and A and B belong to the group including a halogen atom, hydrogen or an alkyl group.
  • the preferred transition metal atom M is zirconium.
  • the Cp group is an unsubstituted, a mono- or a polysubstituted cyclopenta-dienyl group.
  • the substituents on the cyclopentadienyl group can be preferably straight-chain or branched Ci-Cg alkyl groups.
  • the cyclopentadienyl group can be also a part of a bicyclic or a tricyclic moiety such as indenyl, tetrahydroindenyl, fluorenyl or a partially hydrogenated fluorenyl group, as well as a part of a substituted bicyclic or tricyclic moiety.
  • the cyclopentadienyl groups can be also bridged by polymethylene or dialkylsilane groups, such as -CH 2 -, -CH 2 -CH 2 -, -CR'R"- and -CR'R"-CR'R"- where R « and R" are short alkyl groups or hydrogen, -Si(CH 3 ) 2 -, Si(CH 3 ) 2 -CH 2 - CH 2 -Si(CH 3 ) 2 - and similar bridge groups.
  • a and B substituents in the above formula of the metallocene compound are halogen atoms, they belong to the group of fluorine, chlorine, bromine or iodine. If the substituents A and B in the above formula of the metallocene compound are alkyl or aromatic groups, they are preferably straight-chain or branched alkyl groups, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-pentyl, n-hexyl or n-octyl.
  • Suitable metallocene compounds include bis(cyclopentadienyl)metal dihalides, bis(cyclopentadienyl)metal hydridohalides, bis(cyclopentadienyl)metal monoalkyl monohalides, bis(cyclopentadienyl)metal dialkyls and bis(indenyl)metal dihalides wherein the metal is titanium, zirconium or hafnium, halide groups are preferably chlorine and the alkyl groups are Cj-Cg alkyls.
  • metallocenes include bis(cyclopentadienyl)zirconium dichloride, bis(cyclopentadienyl)hafnium dichloride, bis(cyclopentadienyl)zirconium dimethyl, bis(cyclopentadienyl) afnium dimethyl, bis(cyclopentadienyl)zirconium hydridochloride, bis(cyclopentadienyl)hafnium hydridochloride, bis(pentamethylcyclopentadienyl)zirconium dichloride, bis(pentamethylcyclopentadienyl)hafnium dichloride, bis(n- butylcyclopentadienyl)zirconium dichloride, bis(iso- butylcyclopentadienyl) zirconium dichloride, cyclopentadienyl-zirconium trichloride, bis(inden
  • the metallocene compounds utilized within the embodiment of this art can be used as crystalline solids, as solutions in aromatic hydrocarbons or in a supported form.
  • the catalyst comprising a metallocene compound and an aluminoxane in particulate form is fed to the fluid bed reactor for gas phase polymerizations and copolymerizations of ethylene and higher alpha olefins.
  • Polyethylene having a 6.0 melt index, 16 melt-flow-ratio and 0.936 density was produced with a metallocene catalyst and hexene comonomer in a gas phase reactor.
  • Conditions for the pilot plant Rxl were:
  • the metallocene produced polyethylene was (1) melt compounded on a 25-pound Banbury mixer with 750 ppm Irganox 1010, 400 ppm Irgafos 168, 500 ppm Calcium Stearate and 2000 ppm Tinuvin 622 and (2) pulverized on a semi-works scale Wedco pulverizing mill.
  • commercial as-polymerized polyethylene particles (Mobil 3559B-M4HN) were selected having a 6 melt index, 25 melt- flow-ratio and 0.936 density.
  • the commercial polyethylene particles were melt compounded on the same equipment with the same additives as the metallocene catalyzed polyethylene. Both polyethylenes were pulverized on the same semi-works scale Wedco pulverizing mill.
  • the powders from the commercial polyethylene and from the metallocene catalyzed polyethylene were molded side-by- side in a rotating twin-cube mold at 550°F and each of several molding times from 12 to 20 minutes.
  • the molds were charged with 8 1/4 pounds of polyethylene powder, which produced walls approximately 1/8 inch thick.
  • Example 2 Polyethylene having a 3.8-4.4 melt index, 16 melt-flow- ratio and 0.936 density was produced with a metallocene catalyst and hexene comonomer in a gas phase reactor. Conditions for the pilot plant Rxl were:
  • the metallocene catalyzed polyethylene was (1) melt compounded on a 25-pound Banbury mixer with 750 ppm Irganox 1010, 400 ppm Irgafos 168, 500 ppm Calcium Stearate and 2000 ppm Tinuvin 622 and (2) pulverized on a semi-works scale Wedco pulverizing mill.
  • commercial polyethylene pellets Mobil NRA-235, were selected having a 5 melt index, 24 melt-flow-ratio and 0.939 density and containing the same additives as the metallocene catalyzed polyethylene.
  • the commercial pellets were pulverized on the same semi-works scale Wedco pulverizing mill.
  • the powders from the commercial polyethylene pellets and from the metallocene catalyzed polyethylene were molded side- by-side in a rotating twin-cube mold at 550°F at each of three molding times with increasing amounts of resin being charged to the mold for each molding time.
  • the mold was charged with 8 1/4 pounds and the wall thickness was approximately 1/8 inch.
  • the mold was charged with 16 and 24 pounds which produced walls approximately 1/4 and 3/8 inch thick respectively.
  • Example 3 Polyethylene having a 3.2-3.8 melt index, 17 melt-flow- ratio and 0.939 density was produced with a metallocene catalyst and hexene comonomer in a gas phase reactor. Conditions for the pilot plant Rx2 were:
  • the metallocene catalyzed polyethylene was (1) melt compounded on a 25-pound Banbury mixer with 750 ppm Irganox 1010, 400 ppm Irgafos 168, 500 ppm Calcium Stearate and 2000 ppm Tinuvin 622 and (2) pulverized on a Wedco pulverizing mill.
  • a commercial polyethylene powder, Mobil HRP-134 was selected having a 3.4 melt index, 24 melt-flow-ratio and 0.939 density and containing the same additives as the metallocene catalyzed polyethylene.
  • the polyethylene powder from the metallocene catalyst and the commercial powder were molded side-by-side in a rotating twin-cube mold at 550°F at each of several molding times from 17 to 25 minutes. Each cube was charged with 16 pounds of polyethylene powder, which produced a wall thickness of approximately 1/4 inch.
  • Example 4 Polyethylene having a 2.6 melt index, 16 melt-flow-ratio and 0.939 density was produced with a metallocene catalyst and hexene comonomer in a gas phase reactor. Conditions for the pilot plant Rx2 were:
  • the metallocene catalyzed polyethylene was (1) melt compounded on a 25-pound Banbury mixer with 750 ppm Irganox 1010, 400 ppm Irgafos 168, 500 ppm Calcium Stearate and 2000 ppm Tinuvin 622 and (2) pulverized on a Wedco pulverizing mill.
  • a commercial polyethylene powder, Mobil HRP-134 was selected having a 2.9 melt index, 24 melt-flow-ratio and 0.939 density and containing the same additives as the metallocene catalyzed polyethylene.
  • the polyethylene powder from the metallocene catalyst and the commercial powder were molded side-by-side in a rotating twin-cube mold at 550°F at each of several molding times from 16 to 20 minutes. Each cube was charged with 8 1/4 pounds of polyethylene powder, which produced a wall thickness of approximately 1/8 inch.
  • the polyethylene from the metallocene catalyst had a mean failure energy ranging from 52 to 68 ft-lbs for molding times from 16 to 19 minutes, and the failures were ductile.
  • the commercial polyethylene had 90-100% ductile failures with mean failure energy of 39-56 ft-lbs at molding times of 17-19 minutes. For molding time of 16 minutes, the commercial polyethylene had 80% brittle failures. For molding time of 20 minutes, both types of polyethylene had 100% brittle failures.
  • Density ASTM D-1505 - a plaque is made and conditioned not less than 40 hours at
  • the catalyst has the following analysis:

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Moulding By Coating Moulds (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
  • Transition And Organic Metals Composition Catalysts For Addition Polymerization (AREA)
PCT/US1997/003366 1996-03-04 1997-03-04 Molding products WO1997032707A1 (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
EP97908009A EP0885104A1 (en) 1996-03-04 1997-03-04 Molding products
JP9531891A JP2000506088A (ja) 1996-03-04 1997-03-04 成形製品
CA002247916A CA2247916C (en) 1996-03-04 1997-03-04 Molding products
AU19862/97A AU703420B2 (en) 1996-03-04 1997-03-04 Molding products

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US60647396A 1996-03-04 1996-03-04
US08/606,473 1996-03-04

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EP (1) EP0885104A1 (enrdf_load_stackoverflow)
JP (1) JP2000506088A (enrdf_load_stackoverflow)
KR (1) KR19990087479A (enrdf_load_stackoverflow)
AU (1) AU703420B2 (enrdf_load_stackoverflow)
CA (1) CA2247916C (enrdf_load_stackoverflow)
WO (1) WO1997032707A1 (enrdf_load_stackoverflow)

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EP1273415A3 (en) * 2001-07-07 2003-03-05 Gordon Ellis & Co. Moulded articles and methods of producing moulded articles
WO2003091294A1 (en) * 2002-04-26 2003-11-06 Atofina Research Rotomoulded articles prepared with polyethylene
EP1428841A1 (en) * 2002-12-12 2004-06-16 ATOFINA Research Rotomoulded articles with dimensional stability
WO2005009714A1 (en) * 2003-07-24 2005-02-03 Nova Chemicals (International) S.A. Rotomolding process with reduced cycle times
US7074468B2 (en) * 2000-10-13 2006-07-11 Borealis Technology Oy Fuel tanks
US8486323B2 (en) 2009-08-28 2013-07-16 Dow Global Technologies Llc Rotational molded articles, and method of making the same

Families Citing this family (1)

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EP1409245B1 (en) * 2001-07-04 2006-08-23 Total Petrochemicals Research Feluy Glossy tubes and pipes

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EP0885104A4 (enrdf_load_stackoverflow) 1999-01-27
CA2247916A1 (en) 1997-09-12
JP2000506088A (ja) 2000-05-23
CA2247916C (en) 2006-01-24
EP0885104A1 (en) 1998-12-23
AU1986297A (en) 1997-09-22
AU703420B2 (en) 1999-03-25
KR19990087479A (ko) 1999-12-27

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