Polyethylene compositions for blow molding, comprising recyclate polyethylene

Abstract

The present disclosure relates to a polyethylene composition particularly suited for blow molding, comprising: A) from 99.5% to 94% by weight of a recyclate polyethylene component; and B) from 0.5% to 6% by weight of a polypropylene composition comprising from 8% to 30% by weight of a propylene polymer fraction (a) and from 70% to 92% by weight of a polymer fraction (b) comprising one or more copolymer(s) of ethylene containing an amount of units deriving from ethylene equal to or lower than 40% by weight, wherein the polymer fraction (b) comprises a fraction soluble in xylene at 25°C equal to or greater than 60% by weight.

Description

Basell Polyolefine GmbH FE7784-WO-P1POLYETHYLENE COMPOSITIONS FOR BLOW MOLDING, COMPRISINGRECYCLATE POLYETHYLENEFIELD OF THE INVENTION

[0001] The present disclosure relates to polyethylene compositions containing recyclate polyethylene, that can be advantageously used for the production of blow molded articles.BACKGROUND OF THE INVENTION

[0002] Polyethylene is increasingly consumed in large amounts for many applications, including packaging for food and other goods, fibers, and a great variety of manufactured articles. However the said massive use of polyethylene is creating large volumes of waste materials.

[0003] Increasing amounts of said waste materials are presently collected in form of recy elates.

[0004] The term “recyclate” is currently used in the plastic industry to designate secondary raw materials that have been obtained through the recovery of waste and are suitable for the manufacture of products.

[0005] Plastic recyclates, including polyethylene recyclates, are basically divided into two categories: recyclates from end-user waste, called Post Consumer Recyclate (PCR); or recyclates from industrial waste, called Post Industrial Recyclate (PIR).

[0006] With regard to polyethylene recyclates, the recycling market offers a big variety of PCR and PIR, in terms of composition and quality. Most of these are mixtures mainly coming from streams of flexible packaging.

[0007] An important recycling route for said recyclate materials is represented by the so called “mechanical recycling”, which can be defined as a material reprocessing into plastic items after a reworking step, generally carried out by regrinding or repelletising.

[0008] However, a serious obstacle playing against the growth of mechanical recycling of polyethylene is represented by the low quality, in terms of processabilty and in particular of mechanical properties, of the reworked material, strongly limiting the potential value of recycledBasell Polyolefine GmbH FE7784-WO-P1 polyethylene in many important applications, like packaging.

[0009] In particular, the presence of propylene polymers as contaminants in polyethylene recyclates decreases the weld strength of the welding lines in blow molded articles.

[0010] Moreover, the optimal swell ratio values required in the blow molding process to obtain articles with controlled, uniform wall thickness, is not easily obtained with polyethylene recyclates.

[0011] Hence, one of the big challenges and an hopefully an alternative to the downcycling of said recyclates is of enabling to enhance the performances of the mixtures, to find some outlets in important markets.

[0012] For instance, according to W02007071494A1 the mechanical, and in particular the tensile properties of waste polyolefin materials are improved by adding specific kinds of heterophasic compositions.

[0013] It has now unexpectedly been found that blow molded articles with valuable mechanical properties, in particular weld strength and ESCR, are easily obtained, using conventional blow molding techniques and conditions, from polyethylene compositions comprising recyclate polyethylene and a polypropylene composition having properly selected features.SUMMARY OF THE INVENTION

[0014] Thus the present disclosure provides a polyethylene composition comprising:A) from 99.5% to 94% by weight, preferably from 99% to 94% by weight, of a recyclate polyethylene component containing not less than 80% by weight, preferably not less than 90% by weight, more preferably not less than 95% by weight, with respect to the weight of A), of waste polyethylene containing from 0% to 20% by weight, in particular from 1% to 15% by weight of polypropylene, with respect to the total weight of the waste polyethylene;B) from 0.5% to 6% by weight, preferably from 1% to 6% by weight, of a polypropylene composition comprising:- from 8% to 30% by weight, preferably from 13% to 27% by weight, more preferably from 15% to 25% by weight of a polymer fraction (a)Basell Polyolefine GmbH FE7784-WO-P1 comprising a propylene polymer selected from a propylene homopolymer, a propylene copolymer and combinations thereof, the propylene copolymer containing up to and including 10.0% by weight, based on the weight of the copolymer, of units derived from a comonomer selected from ethylene, a CH2=CHR alpha-olefin, where R is an alkyl radical, linear or branched, or an aryl radical, having from 2 to 8 carbon atoms, and combinations thereof, the polymer fraction (a) having solubility in xylene at 25°C XS(a) equal to or lower than 10.0% by weight, based on the weight of the polymer fraction (a); and- from 70% to 92% by weight, preferably from 73% to 87% by weight, more preferably from 75% to 85% by weight, of a polymer fraction (b) comprising one or more copolymer(s) of ethylene with a comonomer independently selected from a CH2=CHR alpha-olefin, where R is an alkyl radical, linear or branched, or an aryl radical, having from 1 to 8 carbon atoms, and combinations thereof, said copolymer or copolymers containing an amount of units deriving from ethylene equal to or lower than 40% by weight, based on the weight of the respective copolymer, and wherein the polymer fraction (b) comprises a fraction soluble in xylene at 25°C equal to or greater than 60% by weight, based on the weight of the polymer fraction (b); wherein the amounts of A) and B) are referred to the total weight of A) + B) and the amounts of a) and b) are referred to the total weight of a) + b).

[0015] The present composition provides final articles with valuable mechanical properties even when the recy elate polyethylene A) contains the said amounts of polypropylene.DETAILED DESCRIPTION OF THE INVENTION

[0016] The preferred upper limit of waste polyethylene in A) is of 100% by weight with respect to the weight of A) in all cases.

[0017] The said polypropylene which can be present in A) is typically waste polypropylene as well.

[0018] The expression “recyclate polyethylene” as used herein for component A), meansBasell Polyolefine GmbH FE7784-WO-P1 the previously said Post Consumer Recyclate (“PCR”) polyethylene and / or Post Industrial Recyclate (“PIR”) polyethylene. As previously mentioned, the PCR polyethylene is derived from an end product that has completed its life cycle as a consumer item and would otherwise be disposed of as waste.

[0019] Said PCR polyethylene includes polyethylene materials that have been collected in commercial and residential recycling programs, including flexible packaging (cast film, blown film and BOPP film), rigid packaging, blow molded bottles and injection molded containers.

[0020] The PIR polyethylene is derived from plastic scrap that is generated as waste from an industrial process.

[0021] Usually, through a step of separation from other polymers possibly present, different types of recyclate polyethylene A) are obtained.

[0022] All kinds of polyethylene (ethylene homopolymers or copolymers) and polypropylene (propylene homopolymers or copolymers) can be present in the recyclate polyethylene component A). In particular, it can comprise one or more polymer materials selected from HDPE (High Density Polyethylene, typically having a density from 0.935 to 0.970 g / cm3, in particular from 0.935 to 0.965 g / cm3), MDPE and LLDPE (Medium Density and Linear Low Density Polyethylene, typically having a density from 0.915 to 0.934 g / cm3), VLDPE (Very Low Density Polyethylene, typically having a density from 0.900 to 0.914 g / cm3), and LDPE (Low Density Polyethylene, typically having a density 0.914 to 0.935 g / cm3).

[0023] While the HDPE and LDPE can be either homopolymers or copolymers of ethylene,MDPE, LLDPE and VLDPE are copolymers.

[0024] In MDPE, LLDPE and VLDPE copolymers, the comonomers are generally selected from propylene and higher alpha-olefins, in particular C4-C10 alpha-olefins having the general formula CH2=CHR wherein R is an alkyl radical, linear or branched, or an aryl radical, having from 2 to 8 carbon atoms.

[0025] Specific examples of C4-C10 alpha-olefins are butene- 1, pentene- 1, 4- methylpentene-1, hexene- 1 and octene- 1.

[0026] Examples of LDPE copolymers include ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, ethylene-acrylate copolymers, ethylene-methacrylate copolymers and ethylene-alpha-olefin copolymers, where preferred examples of alpha-olefins are propylene and the above reported C4-C10 alpha-olefins.Basell Polyolefine GmbH FE7784-WO-P1

[0027] The amount of comonomers in the ethylene copolymers may be from 1 to 40% by weight, in particular from 2 to 35% by weight, referred to the weight of the concerned copolymer.

[0028] The polypropylene fraction can comprise one or more polymer materials selected from homopolymers, copolymers and heterophasic copolymers. In particular it can comprise one or more propylene polymer materials selected from the following:I) isotactic or mainly isotactic propylene homopolymers;II) random copolymers of propylene with ethylene and / or C4-C10 alpha-olefins, wherein the total comonomer content ranges from 0.05% to 20% by weight, or mixtures of said copolymers with isotactic or mainly isotactic propylene homopolymers;III) heterophasic copolymers comprising a propylene homopolymer and / or one of the copolymers of item II), and an elastomeric fraction comprising copolymers of ethylene with propylene and / or a C4-C10 alpha-olefin, optionally containing minor amounts of a diene, such as butadiene, 1,4-hexadiene, 1,5-hexadiene, ethylidene-1 -norbornene.

[0029] Preferred examples of C4-C10 alpha-olefins are the same as reported above.

[0030] The said HDPE, MDPE, LLDPE, VLDPE and propylene polymers described herein are well known in the art and are prepared with low pressure polymerization in the presence of a Ziegler-Natta, or a single site, or a chromium polymerization catalyst.

[0031] The said LDPE is well known in the art as well and is prepared with high pressure polymerization in the presence of a radical initiator, like an organic peroxide or oxygen.

[0032] Other polymeric materials that can be present as impurities in the recyclate polyethylene component A) are polystyrene, ethylene vinyl acetate copolymers, polyethylene terephthalate.

[0033] Other impurities that can be present in the recyclate polyethylene component A) are metals (in particular Al), fillers and pigments.

[0034] Preferably, the recyclate polyethylene A) is a high density polyethylene (HDPE), containing from 0% to 20% by weight, in particular from 1% to 15% by weight of polypropylene, as previously said.

[0035] It has preferably a density of from 0.940 g / cm3to 0.965 g / cm3.Basell Polyolefine GmbH FE7784-WO-P1

[0036] The MIF of the recy elate polyethylene A) is preferably from 1 to 100 g / 10 min., more preferably from 5 to 60 g / 10 min., where where MIF is the melt flow index at 190°C with a load of 21.6 kg, determined according to ISO 1133-1 2012-03.

[0037] The MIP of the recyclate polyethylene A) is preferably from 0.5 to 10 g / 10 min., more preferably from 1 to 5 g / 10 min., where where MIP is the melt flow index at 190°C with a load of 5 kg, determined according to ISO 1133-1 2012-03.

[0038] The MIE of the recyclate polyethylene A) is preferably from 0.1 to 10 g / 10 min., more preferably from 0.2 to 5 g / 10 min., where where MIE is the melt flow index at 190°C with a load of 2.16 kg, determined according to ISO 1133-1 2012-03.

[0039] The swell ratio of the recyclate polyethylene A) is preferably of from 130% to 190%.

[0040] The stress crack resistance, measured by FNCT 6 MPa / 50°C, of the recyclate polyethylene A) is preferably equal to or higher than 2 hours, in particular from 2 to 15 hours.

[0041] The recyclate polyethylene A) is available on the market.

[0042] An example is represented by the grade sold by LyondellBasell Industries under the tradename CirculenRecover HD5603 Grey.

[0043] Another example is represented by the grade sold by LyondellBasell Industries under the tradename CirculenRecover HD5404 Grey.

[0044] In general, the term “copolymer” is meant to include also polymers containing more than one kind of comonomers, such as terpolymers.

[0045] The component B) is preferably a virgin polymer.

[0046] The expression “virgin polymer” means that it is a polymer which has not been subjected to any process for production of finished articles, for instance packaging films, pipes, bottles, containers, or semi-finished articles, like fibers or sheets for thermoforming.

[0047] Thus the virgin polymer has not been subjected to post- product! on working, except for possible pelletization, which is still considered part of the polymer production process.

[0048] Preferably the said polymer fraction (b) of the polypropylene composition B) comprises a first and a second copolymer of ethylene wherein the difference in the amount of units deriving from ethylene of the first and the second ethylene copolymer is greater than 1.0% by weight.Basell Polyolefine GmbH FE7784-WO-P1

[0049] Specific examples of CH2=CHR alpha-olefins in the polymer fraction (a) of the polypropylene composition B) are butene- 1, pentene- 1, 4-methylpentene-l, hexene- 1 and octene- 1. Preferred comonomers in said fraction (a) are ethylene and butene- 1, in particular ethylene.

[0050] The said polymer fraction (a) of the polypropylene composition B) preferably has at least one, more preferably all, the following features:- comprises a propylene copolymer containing from 0.5% to 10.0% by weight, preferably from 1.0% to 8.0% by weight, more preferably from 2.5% to 5.0% by weight, based on the weight of the fraction (a), of a comonomer selected from ethylene, the said CH2=CHR alpha-olefin, where R is an alkyl radical, linear or branched, or an aryl radical, having from 2 to 8 carbon atoms, and combinations thereof; and / or- has solubility in xylene at 25°C XS(a) ranging from 0.5% to 10.0% by weight, preferably from 2.0% to 8.0% by weight, based on the weight of the polymer fraction (a); and / or- MIL(a) from 1 to 20 g / lOmin, preferably from 2 to 15 g / lOmin and especially from 3 to 12 g / 10min., where MIL is the melt flow index at 230°C with a load of 2.16 kg, determined according to ISO 1133-1 2012-03.

[0051] Specific examples of CH2=CHR alpha-olefins in the polymer fraction (b) of the polypropylene composition B) are propylene, butene- 1, pentene- 1, 4-methylpentene-l, hexene- 1 and octene- 1. Preferred comonomers in said fraction (a) are propylene and butene- 1, in particular propylene.

[0052] In a specific embodiment, the said polymer fraction (b) of the polypropylene composition B) is further characterized by one or more of the following features:- the first and the second copolymer of ethylene are a copolymer of ethylene with a comonomer independently selected from propylene, butene- 1, hexene- 1, 3 -methyl- 1 -pentene, octene- 1 and combinations thereof, propylene being the most preferred; and / or- the first and the second ethylene copolymer are copolymers of ethylene with the same comonomer, propylene being the most preferred; and / or- the first copolymer of ethylene contains an amount of units deriving from ethylene ranging from 15% to 32% by weight, preferably from 20% to 30% by weight, based on the weight of the first copolymer; and / or- the second copolymer of ethylene contains an amount of units derived from ethylene ranging from 32%% to 40% by weight, based on the weight of the second copolymer; and / orBasell Polyolefine GmbH FE7784-WO-P1- the weight ratio of the first copolymer of ethylene to the second copolymer of ethylene ranges from 1:5 to 5:1, preferably from 1:1 to 3: 1; and / or- has a fraction soluble in xylene at 25 °C equal to or greater than 60% by weight, preferably ranging from 60% to 95% by weight, more preferably from 70% to 90% by weight, based on the weight of the polymer fraction (b).- at least one copolymer of ethylene optionally contains from 0.1% to 10.0% by weight, based on the weight of the polymer fraction (b), of units deriving from a diene preferably selected from the group consisting of butadiene, 1,4-hexadiene, 1,5-hexadiene, ethylidene-l-norbonene and combinations thereof.

[0053] In a further specific embodiment, the polypropylene composition B) preferably has at least one, more preferably all, of the following features:- a total ethylene content C2(B) ranging from 15.0% to 40.0% by weight, more preferably from 20.0% to 35.0% by weight and especially from 23.0% to 30.0% by weight, based on the sum of the weights of fraction (a) and fraction (b); and / or- MIL(B) of 1.2 g / 10 min. or lower, in particular from 0.02 to 1.2 g / 10min., or from 0.05 to 1.0 g / 10min.; and / or- has solubility in xylene at 25°C XS(B) of at most 95% by weight, preferably from 65% to 85% by weight, still preferably from 70% to 80% by weight, based on the sum of the weights of fraction (a) and fraction (b); and / or- an intrinsic viscosity of the fraction soluble in xylene at 25°C XSIV(B) ranging from 2.5 to 6.5 dl / g, preferably from 3.0 to 6.0 dl / g, the intrinsic viscosity being determined in tetrahydronaphthalene at 135°C; and / or- flexural modulus (ISO 178:2010) equal to or lower than 80 MPa, preferably equal to or lower than 60 MPa, more preferably ranging from 30 to 80 MPa, most preferably from 35 to 60 MPa; and / or- strength at break (ISO 178:2010) equal to or lower than 15 MPa, preferably ranging from 7.0 to 15.0, more preferably from 8.5 to 12.0 MPa; and / or- elongation at break (ISO 178:2010) equal to or higher than 400%, preferably ranging from 400% to 650%, more preferably from 450% to 600%; and / or- tensile modulus on film (ISO 527-3) equal to or lower than 80 MPa, preferably equal to or lower than 60 MPa, more preferably ranging from 30 to 60 MPa, in MD and ID; and / orBasell Polyolefine GmbH FE7784-WO-P1- tensile strength at break on film (ISO 527-1,-2) ranging from 5 to 20 MPa, more preferably from 10 to 16 MPa in MD and ID; and / or- elongation at break on film (ISO 527-1,-2) equal to or greater than 600%, preferably ranging from 600% to 850%, more preferably from 700% to 800%, in MD and TD; and / or- Shore A (ISO 868, 15 sec) equal to or lower than 90, preferably equal to or lower than 85, like ranging from 60 to 85; and / or- Shore D (ISO 868, 15 sec) equal to or lower than 30, preferably equal to or lower than 25, in particular ranging from 5 to 25, more preferably from 10 to 20; and / or- Charpy impact strength, notched at -40°C (ISO 179-1:2010 eA) ranging from 4.0 to 8.0 KJ / m2.

[0054] In a further embodiment the polypropylene composition B) may also comprise additives such as stabilizers, antioxidants, nucleating agents, fillers, reinforcements, or pigments to further enhance specific properties or achieve desired characteristics, without deviating from the spirit and scope of the present application.

[0055] The polypropylene composition B) may be prepared by polymerization in sequential polymerization stages, with each subsequent polymerization being conducted in the presence of the polymeric material formed in the immediately preceding polymerization reaction.

[0056] Preferably, the polymer fraction (a) is prepared in a first polymerization stage and the polymer fraction (b) is prepared in a second polymerization stage, each stage being carried out in the presence of the polymeric material prepared in the immediately preceding polymerization stage. The polymerization stage to prepare the polymer fraction (a) is carried out in at least one polymerization reactor and the polymerization stage to produce the polymer fraction (b) is carried out in at least one polymerization reactor, or in at least two polymerization reactors when containing at least a first and a second copolymer of ethylene. The amount of polymer fraction (a) and of polymer fraction (b) correspond to the split between the polymerization stages, and the amount of the first and the second ethylene copolymer of polymer fraction (b), when present, correspond to the split between the respective polymerization reactors.

[0057] The polymerization stages are preferably carried out in the presence of a Ziegler- Natta catalyst. According to a preferred embodiment, all the polymerization stages are carried out in the presence of a catalyst comprising the product of the reaction between: i) a solid catalyst component comprising Ti, Mg, Cl, and at least an internal electron donor compound;Basell Polyolefine GmbH FE7784-WO-P1 ii) an alkylaluminum compound and, iii) an external electron-donor compound selected from aromatic acid esters, such as alkyl benzoates, and silicon compounds containing at least one Si-OR bond, where R is a hydrocarbon radical, wherein silicon compounds are particularly preferred.

[0058] The internal donor is preferably selected from the esters of mono or dicarboxylic organic acids such as benzoates, malonates, phthalates, like phthalic acid esters, such as diisobutyl, dioctyl and diphenyl phthalate and benzyl-butyl phthalate, and certain succinates. Examples of internal donors are described in US4,522,930, EP045977A2 and international patent applications WOOO / 63261 and W001 / 57099.

[0059] Further, particularly suitable internal electron donor compound are 1,3-diethers of formula

[0060] wherein R1and Rn, the same or different from each other, are Cl -Cl 8 alkyl, C3- C18 cycloalkyl or C7-C18 aryl radicals; R111and RIV, the same or different from each other, are Cl - C4 alkyl radicals; or are the 1,3-diethers in which the carbon atom in position 2 belongs to a cyclic or polycyclic structure made up of from 5 to 7 carbon atoms and containing two or three unsaturations. Ethers of this type are described in EP361493 and EP728769.

[0061] Representative examples of said dieters are 2-methyl-2-isopropyl-l,3- dimethoxypropane, 2,2-diisobutyl- 1 ,3-dimethoxypropane, 2-isopropyl-2-cyclopentyl-l ,3- dimethoxypropane, 2-isopropyl-2-isoamyl-l,3-dimethoxypropane, and 9,9- bis(methoxymethyl)fluorene.

[0062] The particles of solid component (i) may have substantially spherical morphology and average diameter ranging between 5 and 150pm, preferably from 20 to 100pm and more preferably from 30 to 90pm. As particles having substantially spherical morphology, those are meant wherein the ratio between the greater axis and the smaller axis is equal to or lower than 1.5 and preferably lower than 1.3.

[0063] According to one method, the solid catalyst component (i) can be prepared by reacting a titanium compound of formula Ti(OR)q-yXy, where q is the valence of titanium and y is a number between 1 and q, preferably TiCh, with a magnesium chloride deriving from an adductBasell Polyolefine GmbH FE7784-WO-P1 of formula MgCh^pROH, where p is a number between 0.1 and 6, preferably from 2 to 3.5, and R is a hydrocarbon radical having 1-18 carbon atoms. The adduct can be suitably prepared in spherical form by mixing alcohol and magnesium chloride, operating under stirring conditions at the melting temperature of the adduct (100°-130°C). Then, the adduct is mixed with an inert hydrocarbon immiscible with the adduct thereby creating an emulsion which is quickly quenched causing the solidification of the adduct in form of spherical particles. Examples of spherical adducts prepared according to this procedure are described in USP4,399,054 and US4,469,648. The so obtained adduct can be directly reacted with Ti compound or it can be previously subjected to thermal controlled dealcoholation (80°-130°C) so as to obtain an adduct in which the number of moles of alcohol is of lower than 3, preferably between 0.1 and 2.5. The reaction with the Ti compound can be carried out by suspending the adduct (dealcoholated or as such) in cold TiCh; the mixture is heated up to 80°-130°C and kept at this temperature for 0.5-2 hours. The treatment with TiCh can be carried out one or more times. The electron donor compound can be added in the desired ratios during the treatment with TiCk

[0064] The alkyl-Al compound (ii) is preferably chosen among the trialkyl aluminum compounds such as for example triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, tri- n-hexylaluminum, tri-n-octylaluminum. It is also possible to use alkylaluminum halides, alkylaluminum hydrides or alkylaluminum sesquichlorides, such as AlEt2Cl and AhEtsCh, possibly in mixture with the above cited trialkylaluminums. The Al / Ti ratio is higher than 1 and may preferably range between 50 and 2000.

[0065] Preferably, the external donor (iii) is a silicon compound having the general formula (R7)a(R8)bSi(OR9)c, where a and b are integers from 0 to 2, c is an integer from 1 to 4 and the sum (a+b+c) is 4; R7, R8, and R9, are alkyl, cycloalkyl or aryl radicals with 1-18 carbon atoms optionally containing heteroatoms.

[0066] Particularly preferred are the silicon compounds (iii) in which a is 1, b is 1, c is 2, at least one of R7and R8is selected from branched alkyl, cycloalkyl or aryl groups with 3-10 carbon atoms optionally containing heteroatoms and R9is a Ci-Cio alkyl group, in particular methyl. Examples of such preferred silicon compounds are methylcyclohexyldimethoxysilane, diphenyldimethoxysilane, methyl-t-butyldimethoxysilane, dicyclopentyldimethoxysilane, diisopropyldimethoxysilane, (2-ethylpiperidinyl)t-butyldimethoxysilane, (2- ethylpiperidinyl)thexyldimethoxysilane, (3,3,3-trifluoro-n-propyl)(2-Basell Polyolefine GmbH FE7784-WO-P1 ethylpiperidinyl)dimethoxysilane, methyl(3,3,3-trifluoro-n-propyl)dimethoxysilane. Moreover, are also preferred the silicon compounds in which a is 0, c is 3, R8is a branched alkyl or cycloalkyl group, optionally containing heteroatoms, and R9is methyl. Examples of such preferred silicon compounds are cyclohexyltrimethoxysilane, t-butyltrimethoxysilane and thexyltrimethoxysilane.

[0067] The external electron donor compound (iii) is used in such an amount to give a molar ratio between the organoaluminum compound and said external electron donor compound (iii) of from 0.1 to 200, preferably from 1 to 100 and more preferably from 3 to 50.

[0068] Examples of polymerization processes for the preparation of said compositions can be found in EP472946A, the relevant part of which is incorporated herein by reference.

[0069] All the polymerization stages preferably occur in gas phase. The reaction temperature in the polymerization stage for the preparation of the polymer fraction (a) and in the preparation of the copolymer fraction (b) can be the same or different, and is preferably from 40° to 90°C; more preferably, the reaction temperature ranges from 50° to 80°C in the preparation of the fraction (a), and from 40° to 80°C for the preparation of components (b). The pressure of the polymerization stages to prepare the fractions (a) and (b), is from 5 to 30bar in gas phase. The residence times relative to the two stages depend on the desired ratio between the fractions (a) and (b), and can usually range from 15 minutes to 8 hours. Conventional molecular weight regulators known in the art, such as chain transfer agents (e.g. hydrogen or ZnEt2), may be used.

[0070] If needed, the final composition comprising (a)+(b) can be subject to a chemical treatment with organic peroxides in order to lower the average molecular weight and increase the melt flow rate up to the value of MFR(B).

[0071] The present polyethylene composition may comprise conventional additives. Examples of these additives are heat stabilizers, antioxidants, UV absorbers, light stabilizers, metal deactivators, compounds which destroy peroxide, and basic co-stabilizers, preferably in amounts of from 0.05% to 10 % by weight, more preferably from 0.05% to 5% by weight, based on the total weight of the polyethylene composition.

[0072] The present polyethylene composition may also comprise fillers, reinforcing agents, plasticizers, lubricants, emulsifiers, pigments, optical brighteners, flame retardants, antistatic agents, blowing agents, or a combination of these, preferably in total amounts of from 1 to 50% by weight, based on the total weight of the polyethylene composition.Basell Polyolefine GmbH FE7784-WO-P1

[0073] Preferably the present polyethylene composition has density from 0.945 to 0.962 g / cm3, more preferably from 0.950 to 0.960 g / cm3.

[0074] The MIE of the present polyethylene composition is preferably from 0.05 to 5 g / 10 min., more preferably from 0.1 to 1 g / 10 min., most preferably from 0.1 to 0.5 g / 10 min.

[0075] The present polyethylene composition is obtainable by melting and mixing the components, and the mixing is effected in a mixing apparatus at temperatures generally of from 160 to 250°C.

[0076] Any known apparatus and technology can be used for this purpose.

[0077] Useful melt-mixing apparatus in this context are in particular extruders or kneaders, and particular preference is given to twin-screw extruders. It is also possible to premix the components at room temperature in a mixing apparatus.

[0078] As previously said, the present polyethylene composition can be advantageously used for producing blow molded articles.

[0079] In particular, the present polyethylene composition has particularly good suitability for production of small blow moldings.

[0080] Preferred examples of small blow moldings are those having a capacity from 250 to 5000 ml, like small containers, canisters and bottles.

[0081] In fact the present polyethylene composition is preferably characterized, in addition to an improved weld line quality, in particular the weld strength, by an environmental stress crack resistance, measured by FNCT 6 MPa / 50°C, equal to or higher than 15h, more preferably equal to or higher than 18h, in particular from 15 to 5 Oh or from 18 to 5 Oh.

[0082] The swell ratio of the present polyethylene composition is preferably from 130% to 180%.

[0083] The Charpy aCN fracture toughness at -30°C of the present polyethylene composition is preferably from 3 to 10 kJ / m2.

[0084] The details of the test methods are given in the examples.

[0085] The blow-molding process is generally carried out by first plastifying the polyethylene composition in an extruder at temperatures in the range from 180 to 250°C and then extruding it through a die into a blow mold, where it is cooled.Basell Polyolefine GmbH FE7784-WO-P1

[0086] Hence the present disclosure also relates to use of the present polypropylene composition B) for improving the weld line quality, in particular the weld strength, of blow molded articles obtained from the present polyethylene composition.EXAMPLES

[0087] The practice and advantages of the various embodiments, compositions and methods as provided herein are disclosed below in the following examples. These examples are illustrative only, and are not intended to limit the scope of the appended claims in any manner whatsoever.

[0088] The following analytical methods are used to characterize the polymer compositions.

[0089] Melt flow index

[0090] Determined according to to ISO 1133-1 2012-03 at with the specified temperature and load.

[0091] Density

[0092] Determined according to ISO 1183-1 :2012 at 23°C.

[0093] Swell ratio

[0094] The Swell-ratio of the studied polymers was measured utilizing a capillary rheometer, Gbttfert Rheotester2000 and Rheograph25, at T = 190°C, equipped with a commercial 30 / 2 / 2 / 20 die (total length 30 mm, Active length=2 mm, diameter = 2 mm, L / D=2 / 2 and 20° entrance angle) and an optical device (laser-diod from Gbttfert) for measuring the extruded strand thickness. Sample was molten in the capillary barrel atl90°C for 6 min and extruded with a piston velocity corresponding to a resulting shear- rate at the die of 1440 s'1.

[0095] The extrudate was cut (by an automatic cutting device from Gbttfert) at a distance of 150 mm from the die-exit, at the moment the piston reached a position of 96 mm from the dieinlet. The extrudate diameter was measured with the laser-diod at a distance of 78 mm from the die-exit, as a function of time. The maximum value corresponds to the Dextrudate. The swell-ratio is determined from the calculation:SR = (Dextrudate-Ddie)100% / Ddie where Ddie is the corresponding diameter at the die exit, measured with the laser-diod.Basell Polyolefine GmbH FE7784-WO-P1

[0096] Environmental stress cracking resistance according to full notch creep test (FNCT)

[0097] The environmental stress cracking resistance of polymer samples was determined in accordance to international standard ISO 16770 (FNCT) in aqueous surfactant solution. From the polymer sample a compression moulded 10 mm thick sheet has been prepared. The bars with squared cross section (10x10x100 mm) were notched using a razor blade on four sides perpendicularly to the stress direction. A notching device described in M. Fleissner in Kunststoffe 77 (1987), pp. 45 was used for the sharp notch with a depth of 1.6 mm.

[0098] The load applied is calculated from tensile force divided by the initial ligament area. Ligament area is the remaining area = total cross-section area of specimen minus the notch area. For FNCT specimen: 10x10 mm2- 4 times of trapezoid notch area = 46.24 mm2(the remaining cross-section for the failure process / crack propagation). The test specimen was loaded with standard condition suggested by the ISO 16770 with constant load of 6 MPa at 50°C in a 2% (by weight) water solution of non-ionic surfactant ARKOPAL N100. Time until rupture of test specimen was detected.

[0099] Charpy aCN

[0100] Fracture toughness determination by an internal method on test bars measuring 10 x 10 x 80 mm which had been sawn out of a compression molded sheet with a thickness of 10 mm. Six of these test bars were notched in the center using a razor blade in the notching device mentioned above for FNCT. The notch depth was 1.6 mm. The measurement was carried out substantially in accordance with the Charpy measurement method in accordance with ISO 179-1, with modified test specimens and modified impact geometry (distance between supports). All test specimens were conditioned to the measurement temperature of -30°C over a period of from 2 to 3 hours. A test specimen was then placed without delay onto the support of a pendulum impact tester in accordance with ISO 179-1. The distance between the supports was 60 mm. The drop of the 2 J hammer was triggered, with the drop angle being set to 160°, the pendulum length to 225 mm and the impact velocity to 2.93 m / s. The fracture toughness value is expressed in kJ / m2and is given by the quotient of the impact energy consumed and the initial cross-sectional area at the notch, aCN. Only values for complete fracture and hinge fracture can be used here as the basis for a common meaning (see suggestion by ISO 179-1).

[0101] Welding quality (weld line strength)Basell Polyolefine GmbH FE7784-WO-P1

[0102] 22 g blow molded bottles with an internal volume of 310 ml and average wall thickness 0.8 mm were prepared with a W. Muller molding machine, model Blowtec BFB 1 / 4.

[0103] The machine parameters were:- Processing temperature: 200 °C;- Mold temperature: 12 °C;- Molding cycle time: 15 sec;- Blow pressure: 5 bar;- Throughput: 7Kg / h.

[0104] A bottom weld sample was cut from each of the so obtained bottles, after deflashing.The bottom weld samples were then bent twice manually and manual tear off was tried. The samples were classified “good” if they did not break along the weld, “bad” if they broke.

[0105] The measurements were carried out immediately after production of the bottles and after 24 hours from production of the bottles.

[0106] Comonomer content in ethylene polymers

[0107] The comonomer content was determined by means of IR in accordance with ASTM D 6248 98, using an FT-IR spectrometer Tensor 27 from Bruker, calibrated with a chemometric model for determining the comonomer content, for instance ethyl- side-chains in PE for butene- 1 as comonomer.

[0108] Comonomer content in propylene polymers

[0109] 13C NMR spectra are acquired on a Bruker AV-600 spectrometer equipped with cry oprobe, operating in the Fourier transform mode at 120°C. The samples are dissolved in 1, 1,2,2- tetrachloroethane-d2 at 120°C with a 8 % wt / v concentration. Each spectrum is acquired with a 90° pulse, and 15 seconds of delay between pulses and CPD to remove 1H-13C coupling. The spectrometer is operated at 160.91 MHz. The peak of the S88 carbon (nomenclature according to “Monomer Sequence Distribution in Ethylene-Propylene Rubber Measured by 13C NMR. 3. Use of Reaction Probability Mode” C. J. Carman, R. A. Harrington and C. E. Wilkes, Macromolecules, 1977, 10, 536) is used as an internal reference at 29.9 ppm. 512 transients are stored in 32K data points using a spectral window of 9000 Hz.

[0110] The assignments of the spectra, the evaluation of triad distribution and the composition are made according to Kakugo (“Carbon- 13 NMR determination of monomer sequence distribution in ethylene-propylene copolymers prepared with 8-titanium trichloride-Basell Polyolefine GmbH FE7784-WO-P1 diethylaluminum chloride” M. Kakugo, Y. Naito, K. Mizunuma and T. Miyatake, Macromolecules, 1982, 15, 1150) using the following equations:PPP = 100 Tpp / S PPE = 100 Tps / S EPE = 100 TWSPEP = 100 Spp / S PEE= 100 Sps / S EEE = 100 (0.25 Syg+0.5 S55) / SS = Tpp + Tps + Tss + Spp + Sps + 0.25 Syg + 0.5 SssThe molar content of ethylene and propylene is calculated from triads using the following equations: E mol = EEE + PEE + PEP[P]moZ = PPP + PPE + EPEThe weight percentage of ethylene content (E% wt) is calculated using the following equation:wherein[P] mol = the molar percentage of propylene content;MWE = molecular weights of ethyleneMWP = molecular weight of propylene.The total ethylene content C2(tot) and the ethylene content of component (A), C2(A), are measured; the ethylene content of component (B), C2(B), is calculated using the formula:C2(tot) = W(A)xC2(A) + W(B)xC2(B) wherein W(A) and W(B) are the relative amounts of components (A) and (B) (W(A)+W(B)=1).

[0111] Solubility in xylene at 25°C., XS

[0112] 2.5 g of polymer sample and 250 ml of xylene are introduced in a glass flask equipped with a refrigerator and a magnetic stirrer. The temperature is raised in 30 minutes up to 135°C. The obtained clear solution is kept under reflux and stirring for further 30 minutes. The solution is cooled in two stages. In the first stage, the temperature is lowered to 100°C in air for 10 to 15 minute under stirring. In the second stage, the flask is transferred to a thermostatically controlled water bath at 25°C for 30 minutes. The temperature is lowered to 25°C without stirring during the first 20 minutes and maintained at 25°C with stirring for the last 10 minutes. The formed solid is filtered on quick filtering paper (eg. Whatman filtering paper grade 4 or 541). 100 ml of the filtered solution (SI) is poured in a previously weighed aluminum container, which is heated to 140°C on a heating plate under nitrogen flow, to remove the solvent by evaporation. TheBasell Polyolefine GmbH FE7784-WO-P1 container is then kept on an oven at 80°C under vacuum until constant weight is reached. The amount of polymer soluble in xylene at 25°C is then calculated.

[0113] In the polypropylene composition B) the values of XS(B), which is the total XS and of XS(a), which is the XS of the polymer fraction (a), are experimentally determined via the above procedure.

[0114] XS(b), which is the XS value of the polymer fraction (b), can be consequently calculated from the following:XS(B) = W(a) x XS(a) + W(b) x XS(b)

[0115] wherein W(a) and W(b) are the relative amounts of fractions (a) and (b) respectively, and W(a)+ W(b)=l .

[0116] Intrinsic viscosity of the xylene soluble fraction

[0117] To calculate the value of the intrinsic viscosity IV, the flow time of a polymer solution is compared with the flow time of the solvent (THN). A glass capillary viscometer of Ubbelohde type is used. The oven temperature is adjusted to 135°C. Before starting the measurement of the solvent flow time tO the temperature must be stable (135° ± 0.2°C). Sample meniscus detection for the viscometer is performed by a photoelectric device.Sample preparation: 100 ml of the filtered solution (SI) is poured in a beaker and 200 ml of acetone are added under vigorous stirring. Precipitation of insoluble fraction must be complete as evidenced by a clear solid-solution separation. The suspension is filtered on a weighed metallic screen (200 mesh), the beaker is rinsed and the precipitate is washed with acetone so that the o-xylene is completely removed. The precipitate is dried in a vacuum oven at 70°C until a constant weight is reached. 0.05g of precipitate are weighted and dissolved in 50ml of tetrahydronaphthalene (THN) at a temperature of 135°C. The efflux time t of the sample solution is measured and converted into a value of intrinsic viscosity [r|] using Huggins' equation (Huggins, M.L., J. Am. Chem. Soc. 1942, 64, 11, 2716-2718) and the following data:- concentration (g / dl) of the sample;- the density of the solvent at a temperature of 135°C;- the flow time tO of the solvent at a temperature of 135°C on the same viscometer.One single polymer solution is used to determine [r|] .Basell Polyolefine GmbH FE7784-WO-P1

[0118] Polypropylene content

[0119] 13C NMR spectra were acquired on a Bruker AV-600 spectrometer equipped with cry oprobe, operating at 160.91 MHz in the Fourier transform mode at 120°C.

[0120] The peak of the CH2ethylene was used as internal reference at 29.9 ppm. The samples were dissolved in 1 , 1 ,2,2-tetrachloroethane-<72 at 120°C with a 8 % wt / v concentration. Each spectrum was acquired with a 90° pulse, 15 seconds of delay between pulses and CPD to removeJH-13C coupling. 512 transients were stored in 32K data points using a spectral window of 9000 Hz.

[0121] Molar composition was obtained according to the following using peak areas (table 1):P = 100 A3 / SE = 0.5100 A2 / SWhere S = 0.5A2+A3

[0122] Molar content was transformed in weight using monomers molecular weight.Table 1 : Assignment of PP / PE mixtures

[0123] Example 1 and Comparative Example 1

[0124] The commercial grade CirculenRecover ® HD5603 Grey, sold by LyodellBasell Industries, was used as recyclate polyethylene component A).

[0125] CirculenRecover ® HD5603 Grey is a PCRHDPE, containing around 9% by weight of propylene polymer(s) with respect to the total weight, having the properties reported in Table 2 below, where it is identified as 5603.Basell Polyolefine GmbH FE7784-WO-P1Table 2

[0126] The polypropylene composition B) was prepared in in a series of three gas phase reactors (GPR), namely GPR1, GPR2 and GPR3, equipped with devices to transfer the product from one reactor to the one immediately next to it, according to the procedure reported in example 2 of EP1279699A1, using a Ziegler-Natta catalyst system comprising:- a titanium solid catalyst component prepared with the procedure described in EP395083, Example 3, using diisobutyl phthalate as internal donor,- triethylaluminum (TEAL) as cocatalyst; and- dicyclopentyldimethoxysilane (DCPMS) as external donor, with a TEAL / DCPMS weight ratio of 5.

[0127] The characterization and specific polymerization conditions are reported in Table 3 below.Basell Polyolefine GmbH FE7784-WO-P1Table 3Basell Polyolefine GmbH FE7784-WO-P1

[0128] Other properties of the polypropylene composition B) are reported in Table 3b below.Table 3b

[0129] The polyethylene composition of Example 1 was obtained by blending 95% by weight of said polyethylene component A) with 5% by weight of said polypropylene composition B).Basell Polyolefine GmbH FE7784-WO-P1

[0130] The polyethylene composition of Comparison Example 1 was obtained by blending 93% by weight of said polyethylene component A) with 7% by weight of said polypropylene composition B).

[0131] The polyethylene compositions of the said examples were prepared by blending the said components in a twin-screw extruder Leistritz ZSE 27 MAXX 44D operating at 250 rpm, with temperatures of 230°C (first barrel) and 250 °C (second to 10thbarrel and die)

[0132] The properties of the final compositions so obtained are reported in Table 4 below.Table 4

Claims

Basell Polyolefine GmbH FE7784-WO-P1CLAIMSWhat is claimed is:

1. A polyethylene composition comprising:A) from 99.5% to 94% by weight, preferably from 99% to 94% by weight, of a recyclate polyethylene component containing not less than 80% by weight, preferably not less than 90% by weight, more preferably not less than 95% by weight, with respect to the weight of A), of waste polyethylene containing from 0% to 20% by weight, in particular from 1% to 15% by weight of polypropylene, with respect to the total weight of the waste polyethylene;B) from 0.5% to 6% by weight, preferably from 1% to 6% by weight, of a polypropylene composition comprising:- from 8% to 30% by weight, preferably from 13% to 27% by weight, more preferably from 15% to 25% by weight of a polymer fraction (a) comprising a propylene polymer selected from a propylene homopolymer, a propylene copolymer and combinations thereof, the propylene copolymer containing up to and including 10.0% by weight, based on the weight of the copolymer, of units derived from a comonomer selected from ethylene, a CH2=CHR alpha-olefin, where R is an alkyl radical, linear or branched, or an aryl radical, having from 2 to 8 carbon atoms, and combinations thereof, the polymer fraction (a) having solubility in xylene at 25°C XS(a) equal to or lower than 10.0% by weight, based on the weight of the polymer fraction (a); and- from 70% to 92% by weight, preferably from 73% to 87% by weight, more preferably from 75% to 85% by weight, of a polymer fraction (b) comprising one or more copolymer(s) of ethylene with a comonomer independently selected from a CH2=CHR alpha-olefin, where R is an alkyl radical, linear or branched, or an aryl radical, having from 1 to 8 carbon atoms, andBasell Polyolefine GmbH FE7784-WO-P1 combinations thereof, said copolymer or copolymers containing an amount of units deriving from ethylene equal to or lower than 40% by weight, based on the weight of the respective copolymer, and wherein the polymer fraction (b) comprises a fraction soluble in xylene at 25°C equal to or greater than 60% by weight, based on the weight of the polymer fraction (b); wherein the amounts of A) and B) are referred to the total weight of A) + B) and the amounts of a) and b) are referred to the total weight of a) + b).

2. The polyethylene composition of claim 1 , wherein the polymer fraction (b) of the polypropylene composition B) comprises a first and a second copolymer of ethylene wherein the difference in the amount of units deriving from ethylene of the first and the second ethylene copolymer is greater than 1.0% by weight.

3. The polyethylene composition of claim 1 or 2, wherein the recy elate polyethylene component A) has a density from 0.940 g / cm3to 0.965 g / cm3.

4. The polyethylene composition of claim 1 or 2, wherein the recyclate polyethylene component A) has MIP from 0.5 to 10 g / 10 min., preferably from 1 to 5 g / 10 min., and / or MIE from 0.1 to 10 g / 10 min., preferably from 0.2 to 5 g / 10 min., where MIP is the melt flow index at 190°C with a load of 5 kg and MIE is the melt flow index at 190°C with a load of 2.16 kg, both determined according to ISO 1133-1 2012-03.

5. The polyethylene composition of claim 1 or 2, wherein the recyclate polyethylene component A) has a swell ratio of from 130% to 190%.

6. The polyethylene composition of claim 1 or 2, wherein the polypropylene composition B) has a MIL of 1.2 g / 10 min. or lower, in particular from 0.02 to 1.2 g / 10min., or from 0.05 to 1.0 g / 10min., where MIL is the melt flow index at 230°C with a load of 2.16 kg, determined according to ISO 1133-1 2012-03.

7. The polyethylene composition of claim 1 or 2, wherein the polypropylene composition B) has one or more of the following features:Basell Polyolefine GmbH FE7784-WO-P1- a total ethylene content C2(B) ranging from 15.0% to 40.0% by weight, preferably from 20.0% to 35.0% by weight and especially from 23.0% to 30.0% by weight, based on the sum of the weights of fraction (a) and fraction (b); and / or- solubility in xylene at 25°C XS(B) of at most 95% by weight, preferably from 65% to 85% by weight, still preferably from 70% to 80% by weight, based on the sum of the weights of fraction (a) and fraction (b); and / or- an intrinsic viscosity of the fraction soluble in xylene at 25°C XSIV(B) ranging from 2.5 to 6.5 dl / g, preferably from 3.0 to 6.0 dl / g, the intrinsic viscosity being determined in tetrahydronaphthalene at 135°C.

8. The polyethylene composition of claim 1 or 2, wherein the polymer fraction (b) of the polypropylene composition B) is further characterized by one or more of the following features:- the first copolymer of ethylene contains an amount of units deriving from ethylene ranging from 15% to 32% by weight, preferably from 20% to 30% by weight, based on the weight of the first copolymer; and / or- the second copolymer of ethylene contains an amount of units derived from ethylene ranging from 32%% to 40% by weight, based on the weight of the second copolymer; and / or- the weight ratio of the first copolymer of ethylene to the second copolymer of ethylene ranges from 1:5 to 5: 1, preferably from 1 : 1 to 3: 1; and / or- has a fraction soluble in xylene at 25°C equal to or greater than 60% by weight, preferably ranging from 60% to 98% by weight, more preferably from 70% to 95% by weight, based on the weight of the polymer fraction (b).

9. Manufactured article comprising the polyethylene composition of claim 1.

10. The manufactured article of claim 9, in form of a blow molded article, in particular a small blow molded article having a capacity from 250 to 5000 ml.Basell Polyolefine GmbH FE7784-WO-P111. Use, for improving the weld line quality, in particular the weld strength, of blow molded articles, of a polypropylene composition B) comprising:- from 8% to 30% by weight, preferably from 13% to 27% by weight, more preferably from 15% to 25% by weight of a polymer fraction (a) comprising a propylene polymer selected from a propylene homopolymer, a propylene copolymer and combinations thereof, the propylene copolymer containing up to and including 10.0% by weight, based on the weight of the copolymer, of units derived from a comonomer selected from ethylene, a CH2=CHR alpha-olefin, where R is an alkyl radical, linear or branched, or an aryl radical, having from 2 to 8 carbon atoms, and combinations thereof, the polymer fraction (a) having solubility in xylene at 25°C XS(a) equal to or lower than 10.0% by weight, based on the weight of the polymer fraction (a); and- from 70% to 92% by weight, preferably from 73% to 87% by weight, more preferably from 75% to 85% by weight, of a polymer fraction (b) comprising one or more copolymer(s) of ethylene with a comonomer independently selected from a CH2=CHR alpha-olefin, where R is an alkyl radical, linear or branched, or an aryl radical, having from 1 to 8 carbon atoms, and combinations thereof, said copolymer or copolymers containing an amount of units deriving from ethylene equal to or lower than 40% by weight, based on the weight of the respective copolymer, and wherein the polymer fraction (b) comprises a fraction soluble in xylene at 25 °C equal to or greater than 60% by weight, based on the weight of the polymer fraction (b); wherein the amounts of a) and b) are referred to the total weight of a) + b) and wherein the blow molded articles are obtained from a polyethylene composition comprising:- from 99.5% to 94% by weight, preferably from 99% to 94% by weight, of a recy elate polyethylene component A) containing not less than 80% by weight, preferably not less than 90% by weight, more preferably not less than 95% by weight, with respect to the weight of A), of waste polyethylene containing from 0% to 20% by weight, in particular from 1% to 15% by weight of polypropylene, with respect to the total weight of the waste polyethylene;Basell Polyolefine GmbH FE7784-WO-P1- from 0.5% to 6% by weight, preferably from 1% to 6% by weight, of said polypropylene composition B); the said amounts of A) and B) being referred to the total weight of A) + B).

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