WO2020012358A1 - Récipients en polyéthylène résistant aux acides - Google Patents

Récipients en polyéthylène résistant aux acides Download PDF

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Publication number
WO2020012358A1
WO2020012358A1 PCT/IB2019/055842 IB2019055842W WO2020012358A1 WO 2020012358 A1 WO2020012358 A1 WO 2020012358A1 IB 2019055842 W IB2019055842 W IB 2019055842W WO 2020012358 A1 WO2020012358 A1 WO 2020012358A1
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Prior art keywords
ethylene copolymer
copolymer composition
primary antioxidant
antioxidant
ppm
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PCT/IB2019/055842
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English (en)
Inventor
Henry Hay
Derek Wasylenko
Tony Tikuisis
Gilbert Arnould
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Nova Chemicals (International) S.A.
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Priority to BR112021000483-1A priority Critical patent/BR112021000483A2/pt
Priority to MX2021000269A priority patent/MX2021000269A/es
Publication of WO2020012358A1 publication Critical patent/WO2020012358A1/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
    • 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
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/0008—Organic ingredients according to more than one of the "one dot" groups of C08K5/01 - C08K5/59
    • C08K5/005—Stabilisers against oxidation, heat, light, ozone
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/04—Oxygen-containing compounds
    • C08K5/13—Phenols; Phenolates
    • C08K5/134—Phenols containing ester groups
    • C08K5/1345—Carboxylic esters of phenolcarboxylic acids
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/16—Nitrogen-containing compounds
    • C08K5/32—Compounds containing nitrogen bound to oxygen
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/16—Nitrogen-containing compounds
    • C08K5/34—Heterocyclic compounds having nitrogen in the ring
    • C08K5/3412—Heterocyclic compounds having nitrogen in the ring having one nitrogen atom in the ring
    • C08K5/3432—Six-membered rings
    • C08K5/3435—Piperidines
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/16—Nitrogen-containing compounds
    • C08K5/34—Heterocyclic compounds having nitrogen in the ring
    • C08K5/3467—Heterocyclic compounds having nitrogen in the ring having more than two nitrogen atoms in the ring
    • C08K5/3477—Six-membered rings
    • C08K5/3492—Triazines
    • C08K5/34926—Triazines also containing heterocyclic groups other than triazine groups
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/49—Phosphorus-containing compounds
    • C08K5/51—Phosphorus bound to oxygen
    • C08K5/52—Phosphorus bound to oxygen only
    • C08K5/524—Esters of phosphorous acids, e.g. of H3PO3
    • C08K5/526—Esters of phosphorous acids, e.g. of H3PO3 with hydroxyaryl compounds

Definitions

  • This invention provides a rotomolded polyethylene container that is resistant to discoloration when contacted with sulfuric acid.
  • Rotational molding also known as rotomolding, is a well-known process which is widely used to produce hollow plastic parts such as gasoline containers, garbage cans, agricultural storage vessels, septic tanks and sporting goods such as kayaks.
  • the process is undertaken by loading a charge of finely divided plastic copolymer into the mold "shell", then rotating the mold (usually, on two axes) while heating it to a temperature above the melting point of the plastic copolymer.
  • the melted plastic flows through the mold cavity under the forces caused by the rotation of the apparatus.
  • the rotation continues for sufficient time to allow the molten plastic to cover the surface of the mold.
  • the mold is then cooled to permit the plastic to freeze into a solid.
  • the final stage of the molding cycle is the removal of the part from the rotomolding machine.
  • the time required to complete the molding cycle is a function of the bulk properties of the plastic which is being molded.
  • the plastic copolymer which is charged into the mold is preferably finely divided (i.e. ground into powder) and has a high bulk density and a narrow particle size distribution to facilitate the“free flow” of the copolymer.
  • the physical properties of the rotomolded part are influenced by the use of a proper molding cycle time with“undercooked” parts having poor strength properties and“overcooked” parts suffering from poor appearance (a “burnt” color) and/or a deterioration of strength properties. It is desirable to have a short molding cycle (so as to improve the productivity of the expensive rotomolding machinery) and a broad“processing window” (i.e. the rotomolding composition ideally provides“properly cooked” parts in a short period of time but does not become “overcooked” for an extended period of time).
  • the properties of the rotomolded part are affected by the molecular structure of the polymer used to prepare the part. Physical properties of importance include stiffness (as indicated by the modulus of the part), environmental stress crack resistance (or“ESCR”), impact resistance and resistance to warpage.
  • stiffness as indicated by the modulus of the part
  • ESCR environmental stress crack resistance
  • Thermoplastic ethylene copolymer is a commonly used plastic copolymer for the manufacture of rotomolded parts.
  • Conventional ethylene copolymer (which is generally prepared by the copolymerization of ethylene with a C 4 to 10 alpha olefin in the presence of a chromium catalyst or a Ziegler Natta catalyst) is typically used.
  • the alpha olefin comonomer produces“short chain branches” (SCB) in the copolymer. These SCB reduce the crystallinity of the copolymer (in comparison to a linear ethylene
  • homogeneous ethylene copolymers have become commercially available. These homogenous copolymers have a uniform (or narrow) molecular weight distribution and a uniform comonomer distribution. This, in turn, causes the homogeneous copolymers to have a well-defined melting point (in comparison to the heterogeneous copolymers which have a melting point "range” or even multiple melting points).
  • One embodiment of this invention provides a method for improving the discoloration resistance of a rotational molded polyethylene container that is contacted with concentrated sulfuric acid, said method comprising the steps of:
  • A.1 a hindered phenolic primary antioxidant
  • At least one hindered phenolic primary antioxidant (especially from 300 to 1500 ppm of at least one hindered phenolic primary antioxidant);
  • At least one hydroxylamine primary antioxidant (especially from 100 to 1000 ppm);
  • At least one phosphite secondary antioxidant especially from 500 to 2000 ppm
  • At least one hindered amine light stabilizer especially from 500 to 5000 ppm
  • stabilized ethylene copolymer composition simply refers to a composition that contains the ethylene copolymer composition plus the“additive package” (that serves to stabilize the ethylene copolymer composition).
  • Rotational molding technology is well known and is described in the literature. Reference may be made to United States Patent (USP) 5,530,055 (Needham), for further details concerning the operation of a rotomolding process.
  • USP United States Patent
  • Two important process conditions to define a rotomolding process are the molding temperature and “cook” time (or heated molding time). A temperature of from 230 to 350°C and a heated molding time of from 10 to 60 minutes are suitable for this invention.
  • Ethylene copolymer compositions for use in this invention may be partially characterized by density and melt flow characteristics.
  • the density range is from 0.93 to 0.95 grams per cubic centimeter (especially 0.935 to 0.945) and the melt index (“I2”, as determined by ASTM D-1238, using a 2.16 kilogram load at a temperature of 190°C) is from 1 to 10 grams per 10 minutes (preferably 2 to 8).
  • Melt index might be regarded as an indicator of molecular weight, though an inverse relationship between the two exists. That is, as the molecular weight of the polymer increases, the flow index (I2) decreases.
  • ethylene copolymer is meant to refer to a copolymer of ethylene with at least one alpha olefin monomer containing from 3 to 10 carbon atoms.
  • ethylene homopolymers are excluded but terpolymers are included.
  • the physical properties of such ethylene copolymers are influenced by their molecular weight, molecular weight distribution, comonomer content and comonomer distribution. It is well known that the use of such comonomers produces copolymers that generally have decreased density and crystallinity as the amount of incorporated comonomer increases.
  • the ethylene copolymers used in this invention may be either heterogenous copolymers or homogeneous copolymers as explained below. Heteroaenous Ethylene Copolymers (or“Heterogeneous Copolymers”)
  • Conventional (heterogeneous) ethylene copolymers which are prepared with a conventional Ziegler-Natta (Z/N) catalyst generally have a comparatively broad molecular weight distribution (as defined by dividing weight average molecular weight, Mw, by number average molecular weight, Mn - i.e. molecular weight distribution equals Mw/Mn) and a broad comonomer distribution.
  • copolymers typically contain at least three distinct polymer fractions, namely a small amount (generally less than 5 weight %) of a low molecular weight, high comonomer content material (also known as“wax”); a significant fraction (15 to 25 weight %) of material having a very high molecular weight and a low comonomer content (also known as“homopolymer”); with the remainder of the copolymer being of intermediate density and molecular weight.
  • a small amount generally less than 5 weight
  • high comonomer content material also known as“wax”
  • a significant fraction 15 to 25 weight
  • material having a very high molecular weight and a low comonomer content also known as“homopolymer”
  • the“wax” fraction may limit the use of these interpolymers in applications which come into contact with food and the “homopolymer” fraction is often associated with the poor impact resistance of goods made with these interpolymers.
  • these heterogeneous copolymers have a molecular weight distribution, Mw/Mn, of greater than 3.0.
  • these copolymers can also have good Environmental Stress Crack Resistance (ESCR) and are suitable for use in this invention.
  • the resulting parts are prone to warpage.
  • the rotomolded parts prepared from homogeneous copolymers have poor stiffness in comparison to parts prepared from Z/N copolymers.
  • the well-defined melting point of the homogeneous copolymers may also assist with the fabrication of custom parts (in which thin molds with irregular shapes must be filled within tight tolerances).
  • the warpage problem may be mitigated by using ethylene copolymer compositions that may contain at least two ethylene copolymer blend components. Each of these components may be prepared by the copolymerization of ethylene with a C 4t0 2o alpha olefin in the presence of a catalyst system which produces homogenous copolymers (i.e. as above, polymers with a narrow molecular weight distribution and narrow composition distribution).
  • Exemplary catalyst systems include the vanadium catalyst system disclosed in USP 3,645,992 (Elston),“metallocene” catalysts (as disclosed, for example, in USP 5,324,800),“constrained geometry” catalysts (as disclosed, for example, in USP 5,064,802 Stevens et al.) and the phosphinimine catalyst systems described in the USP 6,372,864 (Brown et al.).
  • the blend components may be prepared as distinct polymers in separate polymerization reactions and then blended together to provide the present
  • compositions comprising blend components.
  • the blend components may be blended using conventional additives.
  • mixing/blending equipment such as a single or twin sinew extruder; and internal batch mixer such as a BANBURYTM mixer; or a continuous mixer such as a FARRELTM mixer.
  • the mixing time and temperatures may be readily optimized by those skilled in the art without undue experimentation. As a guideline, mixing temperatures of from 150 to 250°C are suitable and mixing times of 1 -10 minutes may provide satisfactory results.
  • the blend components may be prepared in a multiple reactor polymerization system.
  • Homogenous copolymers as described above are suitable for use in the present invention.
  • each blend component is a copolymer of ethylene with C 4 to 8 alpha olefin such as butene-1 , pentene-1 , 4-methyl-1 -pentene, hexene-1 or octene-1 ; with hexene-1 and octene-1 being most preferred.
  • Rotomolding compositions conventionally contain an additive package to protect the polymer from decomposing during the processing and/or exposure to the elements and to improve processing cycle times and windows.
  • the additives may be incorporated into the compositions using mixing equipment such as an extruder, or internal batch mixer (also known as a BANBURY mixer).
  • the additive may be added“neat” (i.e. directly to the copolymer); as a “masterbatch” (i.e. by premixing the additives with a small amount of polyethylene which is subsequently mixed with the bulk of the composition); or as“preblends” (i.e. mixtures of the additives).
  • the additive system of this invention includes at least one Hindered Amine Light Stabilizers (or“HALS”); at least one secondary antioxidant that is preferably a phosphite or phosphonite (especially a diphosphite as illustrated in the examples); and at least two“primary” antioxidants, namely a hindered phenol and a hydroxyl amine.
  • HALS Hindered Amine Light Stabilizers
  • secondary antioxidant that is preferably a phosphite or phosphonite (especially a diphosphite as illustrated in the examples)
  • at least two“primary” antioxidants namely a hindered phenol and a hydroxyl amine.
  • the additive package used in the present invention must contain at least four components, namely 1 ) a first primary antioxidant (Part 1 , below); 2) a second primary antioxidant (Part 1 ); 3) a secondary antioxidant (Part 2); and 4) a hindered amine light stabilizer (Part 3).
  • Part 1 a first primary antioxidant
  • Part 1 a second primary antioxidant
  • Part 2 a secondary antioxidant
  • Part 3 a hindered amine light stabilizer
  • primary antioxidant refers to a molecule which is capable of quenching free radicals in a polyethylene matrix.
  • primary antioxidants include hindered phenols, hydroxylamines, amine oxides and lactones.
  • the present invention must use both a hindered phenol (See 1 .1 and 1.4, below) and a hydroxylamine (1 .5 below) - i.e. two primary antioxidants are required. Other primary antioxidants may optionally be included. Exemplary primary antioxidants are described in more detail in section 1 below.
  • 2,6-di-tert-butyl-4-methylphenol 2-tert-butyl-4,6-dimethylphenol; 2,6-di-tert-butyl-4-ethylphenol; 2,6-di-tert-butyl-4-n-butylphenol; 2,6-di-tert-butyl- 4isobutylphenol; 2,6-dicyclopentyl-4-methylphenol; 2-(.alpha.-methylcyclohexyl)-4,6 dimethylphenol; 2,6-di-octadecyl-4-methylphenol; 2,4,6,-tricyclohexyphenol; 2,6-di-tert- butyl-4-methoxymethylphenol, Octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)- propionate (e.g.,
  • IRGANOX ® 1076 from BASF
  • pentaerythritol tetrakis(3-(5-di-tert- butyl-4-hydroxyphenol)propionate) e.g. IRGANOX ® 1010, from BASF
  • 1 ,3,5- tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1 ,3,5-triazine-2,4,6(1 H,3H,5H)-trione e.g.
  • 2,6di-tert-butyl-4-methoxyphenol 2,5-di-tert-butylhydroquinone; 2,5-di-tert-amyl-hydroquinone; and 2,6diphenyl-4-octadecyloxyphenol.
  • the analogous amine oxides as disclosed in USP 5,844,029,
  • secondary antioxidant refers to an additive that is used to scavenge peroxides. Examples include triphenyl phosphite; diphenylalkyl phosphates;
  • phenyldialkyl phosphates tris(nonyl-phenyl)phosphite; trilauryl phosphite; trioctadecyl phosphite; distearyl pentaerythritol diphosphite; tris(2,4-di-tert-butylphenyl)phosphite (e.g.
  • IRGASTAB ® 168 from BASF
  • diisodecyl pentaerythritol diphosphite 2,4,6-tri-tert- butylphenyl-2-butyl-2-ethyl-1 ,3-propanediol phosphite
  • tetrakis(2,4-di- tert-butylphenyl)4,4'-biphenylene and bis (2,4-dicumylphenyl) pentaerythritol diphosphite e.g. DOVERPHOS ® S-9228, from Dover Chemicals
  • sulfur e.g. DOVERPHOS ® S-9228
  • Phosphorus compounds are preferred, especially the phosphites and phosphonites.
  • a combination of more than one secondary antioxidant may be used.
  • diphosphite especially DOVERPHOS ® S-9228
  • monophosphite especially IRGAFOS ® 168
  • the preferred amount of secondary antioxidant is from 100 to 3000 ppm.
  • a hindered amine light stabilizer has a hindered amine functional group (which is preferably a tetramethyl piperidine group) together with an organic“structure” or“backbone” that is used to deliver the functional group to the polymer that is being stabilized.
  • the number average molecular weight (Mn) of these HALS structures typically range from about 600 to about 15,000. HALS are well known items of commerce and are readily available from such suppliers as Ciba Specialty Chemicals and Cytec Incorporated.
  • HALS include bis (2,2,6,6-tetramethylpiperidyl)-sebacate; bis-5 (1 ,2,2,6,6-pentamethylpiperidyl)-sebacate; n-butyl-3,5-di-tert-butyl-4-hydroxybenzyl malonic acid bis(1 ,2,2,6,6,-pentamethylpiperidyl)ester; condensation product of 1 - hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxy-piperidine and succinic acid; condensation product of N,N'-(2,2,6,6-tetramethylpiperidyl)-hexamethylendiamine and 4-tert- octylamino-2,6-dichloro-1 ,3,5-s-triazine; tris-(2,2,6,6-tetramethylpiperidyl)- nitrilotriacetate, tetrakis-(2,2,6,6-tetramethyl-4-piperidyl)
  • HALS Hindered Amines Light Stabilizers
  • carboxylic acid 2 2,6,6- tetramethyl piperidinol esters (e.g. TINUUIN ® 622, form BASF and CYASORB ® UV- 3346 from Cytec).
  • Such amines include hydroxylamines derived from hindered amines, such as di(1 -hydroxy-2, 2,6, 6-tetramethylpiperidin-4-yl) sebacate; 1 -hydroxy 2,2,6,6-tetramethyl-4-benzoxypiperidine; 1 -hydroxy-2, 2,6, 6-tetramethyl-4-(3,5-di-tert- butyl-4-hydroxy hydrocinnamoyloxy)-piperdine; and N-(1 -hydroxy-2, 2,6, 6-tetramethyl- piperidin-4-yl)-epsiloncaprolactam.
  • hindered amines such as di(1 -hydroxy-2, 2,6, 6-tetramethylpiperidin-4-yl) sebacate; 1 -hydroxy 2,2,6,6-tetramethyl-4-benzoxypiperidine; 1 -hydroxy-2, 2,6, 6-tetramethyl-4-(3,5-di-tert- butyl-4-hydroxy hydrocinnamoyloxy)-piper
  • HALS for use in the present invention are disclosed in USP 5,037,870 and USP 5,134,181 , the disclosures of which are incorporated herein by reference.
  • the preferred amount of HALS is from 300 to 3000 ppm.
  • ZnO is widely used as a polyolefin additive. Any of the commercially available ZnO products which are presently used in polyolefins are potentially suitable for use in the present invention.
  • Preferred zinc oxide is prepared by the so called“French Process” and has a mean particle size of less than 1 micron.
  • ZnO sold under the trademark“KADOX 911” is suitable. Representative physical properties of KADOX 91 1 ZnO are reported by the manufacturer as: a) mean particle size: 0.12 microns and b) surface area: 9.0 m 2 /g.
  • copper salts in combination with iodides and/or phosphorus compounds and salts of divalent manganese for example, copper salts in combination with iodides and/or phosphorus compounds and salts of divalent manganese.
  • melamine for example, melamine; polyvinylpyrrolidone; dicyandiamide; triallyl cyanurate; urea derivatives; hydrazine derivatives; amines; polyamides; polyurethanes; alkali metal salts and alkaline earth metal salts of higher fatty acids, for example, Ca stearate, calcium stearoyl lactate, calcium lactate, Zn stearate, Mg stearate, Na ricinoleate and K palmitate; antimony pyrocatecholate or zinc pyrocatecholate, including neutralizers such as hydrotalcites and synthetic hydrotalcites; and Li, Na, Mg, Ca, Al hydroxy carbonates.
  • Ca stearate calcium stearoyl lactate, calcium lactate, Zn stearate, Mg stearate, Na ricinoleate and K palmitate
  • antimony pyrocatecholate or zinc pyrocatecholate including neutralizers such as hydrotalcites
  • Nucleating agents may improve stiffness of the rotomolded part.
  • calcium carbonate For example, calcium carbonate; silicates; glass fibers; asbestos; talc; kaolin; mica; barium sulfate; metal oxides and hydroxides; carbon black and graphite.
  • plasticizers for example, plasticizers; UV absorbers; epoxidized vegetable oils, such as epoxidized soybean oils; lubricants; emulsifiers; pigments; optical brighteners; flame proofing agents; anti-static agents; blowing agents and thiosynergists, such as dilaurythiodipropionate or distearylthiodipropionate.
  • Crosslinkable rotomolded parts are contemplated. As disclosed in USP
  • 5,367,025 (Needham) crosslinking agents may include a combination of organic peroxide initiator and a crosslinking co-agent.
  • dialkyl peroxides used include 2,5-dimethyl-2,5-di(t-butylperoxy)hexane or alpha, alpha'-bis(t- butylperoxy)diisopropylbenzene or those disclosed in USP 3,214,422.
  • Co-agents used by those experienced in the art of crosslinking polyethylene include triallyl cyanurate, triallyl isocyanurate, triallyl trimellitate, trimethololpropane trimethacrylate and related monomers.
  • SSC single site catalyst copolymer
  • SSC1 had a melt index, I2, of 1.7 g/10 minutes and a density of 0.945 g/cc.
  • SSC1 is further characterized by being a blend of two ethylene- octene blend components and was prepared in accordance with the teachings of U.S. Patent 7,201 ,864 (Weber et al.).
  • ethylene copolymers were blended with the additive packages described in Table 1 and ground into fine powder for the preparation of rotomolded parts.
  • the compounded copolymer used in experiment 2 was conventional polyethylene ZN1 and contained 300 ppm of primary antioxidant; 1200 ppm of secondary antioxidant (IRGAFOS 168) and 200 ppm of HALS. This composition is comparative because it does not contain hydroxylamine.
  • Rotomolded parts were then prepared in a rotational molding machine sold under the tradename Rotospeed RS3-160 by Ferry Industries Inc.
  • the machine has two arms which rotate about a central axis.
  • Each arm is fitted with a plate which rotates on an axis that is roughly perpendicular to the axis of rotation of the arm.
  • Each plate is fitted with three cast aluminum molds that produce plastic cubes having dimensions of 12.5 inches (31 .8 cm) x 12.5 inches x 12.5 inches.
  • These molds produce parts having a nominal thickness of about 0.25 inches (0.64 cm) when initially filled with a standard charge of about 3.7 kg of ethylene copolymer.
  • a gas fired furnace which is capable of providing 2 million British thermal units (Btu) per hour is used to provide hot air that is circulated about the molds by a fan.
  • the temperature within the enclosed oven is typically maintained at a temperature of between 230°C (446°F) and 350°C (662°F) for specified periods of time while the machine rotates the arms (typically, at about 8 revolutions per minute (rpm) and the plate (typically, at about 2 rpm).
  • the compositions shown in Table 1 were“cooked” for a molding cycle of 40 minutes with an oven temperature of 440°F.
  • The“cooked parts” are then cooled by opening the oven. Water spray may also be used to facilitate cooling. “Cook times”, rotation speed, temperatures and cooling cycles are computer controlled with appropriate software which also includes a data acquisition system.
  • Test plaques were cut from the molded cubes. The plaques were exposed to concentrated sulfuric acid (98% H 2 S0 4 ) at 70°C. (As used herein, the term
  • concentrated sulfuric acid refers to a liquid that contains from about 95 to 99% sulfuric acid by weight. In general,“concentrated sulfuric acid” in commercial use contains about 98% sulfuric acid.)
  • the comparative compositions discolored after contact with the concentrated sulfuric acid.
  • the following color scale is used to describe increasing levels of discoloration.
  • compositions of this example were severely discolored (to black, number 4 on the above scale) after contact with concentrated sulfuric acid at 70°C for 8 days.
  • Table 2 The formulations shown in Table 2 were used in this example.
  • the rotational molding procedures were similar to those described above except that the molding time was reduced to 34 minutes and the temperature was increased to 480°F.
  • Test plaques were cut from the molded cubes and exposed to concentrated sulfuric acid (98 weight% H 2 S0 4 ) at 70°C for the times shown in Table 3. Color values are also presented in Table 3.
  • Table 3 illustrate that the composition that was prepared with the two different primary antioxidants (namely a phenolic and a hydroxylamine) has improved resistance to discoloration.
  • composition of experiment 10 also contained 450 ppm of zinc stearate.
  • compositions of experiments 1 1 -13 also contained 750 ppm of zinc oxide.
  • a rotomolded part is prepared with a high performance additive package that contains two different primary antioxidants.
  • the part is especially suitable for the storage of sulfuric acid.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Compositions Of Macromolecular Compounds (AREA)
  • Anti-Oxidant Or Stabilizer Compositions (AREA)
  • Moulding By Coating Moulds (AREA)

Abstract

Des récipients en polyéthylène rotomoulés qui sont utilisés pour stocker de l'acide sulfurique peuvent être décolorés sur la surface intérieure qui est en contact avec l'acide. Ce problème est atténué par l'utilisation d'un ensemble d'additifs qui contient deux antioxydants primaires.
PCT/IB2019/055842 2018-07-12 2019-07-09 Récipients en polyéthylène résistant aux acides WO2020012358A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
BR112021000483-1A BR112021000483A2 (pt) 2018-07-12 2019-07-09 Recipientes de polietileno resistentes a ácido
MX2021000269A MX2021000269A (es) 2018-07-12 2019-07-09 Recipientes de polietileno resistentes a los acidos.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CA3011044A CA3011044A1 (fr) 2018-07-12 2018-07-12 Contenants de polyethylene resistant aux acides
CA3011044 2018-07-12

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WO2020012358A1 true WO2020012358A1 (fr) 2020-01-16

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