Polypropylene sheet

Abstract

Polypropylene sheets exhibiting an advantageous combination of optical and mechanical properties are particularly suitable for thermoforming.

Description

Technical Field

[0001] The present invention relates to a polypropylene sheet, particularly suitable for thermoforming, which exhibits an advantageous combination of optical and mechanical properties. Background Art

[0002] Polymers are widely used in daily life, including polypropylene (PP), polyethylene (PE), polystyrene (PS), etc., but while human society enjoys the convenience brought by plastic products, it also generates a lot of waste. This has put some pressure on society to find sustainable solutions. Obviously, material diversity will lead to mixed plastic waste, which will cause problems for reuse and recycling. PS is widely used in thermoforming (TF) applications of cups and trays. However, it is known that PS is not miscible with PP and PE, so it is feasible to replace PS with PP to reduce diversity. In addition, PS has poor mechanical properties and the monomer has some HSE (health-safety-economy) problems. Therefore, it would be useful to provide a solution with an advantageous combination of optics, stiffness and impact.

[0003] There are three main types of PP currently used in the thermoforming market segment (e.g. for food packaging): PP homopolymer, PP random copolymer and heterophasic PP copolymer.

[0004] Propylene homopolymers are characterized by high stiffness, especially when they are α-nucleated. A disadvantage of polypropylene homopolymers is low impact strength, which leads to a restriction in the application temperature range. Polypropylene random copolymers are characterized by good optical properties, especially high transparency, but also low stiffness and low impact strength at low temperatures. Heterophasic propylene copolymers have good impact strength over a wide temperature range, but usually heterophasic copolymers have low transparency, i.e. high haze and low clarity.

[0005] Several patents have been filed in this field.

[0006] For example, EP 2582732 claims a nucleated thermoformed article comprising a propylene homopolymer comprising a substituted 1,2-phenylene dibenzoate selected from 3-methyl-5-tert-butyl-1,2-phenylene dibenzoate and 3,5-diisopropyl-1,2-phenylene dibenzoate; the thermoformed article having a haze value of 1% to 10% measured according to ASTM D 1003. The claim states that the PP itself is a propylene homopolymer having a polydispersity index of greater than 5.0 to 10.0, which is typical for unimodal or bimodal Ziegler-Natta (ZN) catalyzed grades. The patent is silent on clarity and dart impact, and it is known that PP with such a high polydispersity can lead to stability problems in film or sheet processing.

[0007] WO 2004 / 055101 discloses a heterophasic polypropylene composition, particularly suitable for forming a flat film for thermoforming. In order to improve the transparency of the heterophasic polypropylene composition, it is proposed to use an α-nucleating agent, in particular selected from low molecular weight compounds, such as phosphate-derived nucleating agents and sorbitol-derived nucleating agents. Other suitable nucleating agents disclosed in the above-mentioned international patent application are metal salts of aromatic carboxylic acids and metal salts of aliphatic carboxylic acids, inorganic compounds (such as talcum), and vinyl cyclohexane polymers. Although the haze achieved is significantly better than that of ordinary heterophasic copolymers, the transparency is still not enough to replace, for example, polystyrene.

[0008] In order to avoid the use of expensive low molecular weight nucleating agents (e.g. sorbitol derived nucleating agents) without sacrificing the requirement for transparency, EP 1801156 proposes to add low density ethylene copolymers to heterophasic polypropylene compositions. In addition, a polymeric nucleating agent is also added. The composition is suitable for thermoforming and thin wall packaging and has good transparency. The example composition shows improved ductility, but the haze is still quite undesirable.

[0009] Although much development work has been done in this area, further improvements are needed to design materials that provide improved and advantageous combinations of beneficial optical properties (such as low haze and high clarity) along with high stiffness and impact resistance.

[0010] The present invention is based on the discovery that the above discussed needs for thermoforming applications can be achieved through specific design of metallocene-catalyzed polypropylene random copolymers. Summary of the invention

[0011] Therefore, the present invention relates to a polypropylene sheet, the polypropylene sheet comprising:

[0012] Metallocene-catalyzed propylene-C4-C 12 -α-olefin random copolymer, the propylene-C4-C 12 -α-olefin random copolymers having:

[0013] a-1) Propylene-C4-C 12 Based on the total weight of the random α-olefin copolymer, 1.0 to 6.0 wt% of C4-C 12 -α-olefin content;

[0014] a-2) MFR2 of 2.0 to 20.0 g / 10 min (230° C., 2.16 kg, ISO 1133);

[0015] a-3) a melting temperature Tm (DSC) of 125°C to 150°C; and

[0016] a-4) an amount of xylene cold solubles (XCS) of 0.3 to 2.5 wt% (measured at 25° C. according to ISO 16152:2005);

[0017] The thickness of the sheet is 100 to 1000 μm, and the sheet contains at least 90.0 wt% of propylene-C4-C 12 -α-olefin random copolymer.

[0018] Unexpectedly, it has been discovered that such sheets have an optimized or improved balance between optical properties, stiffness, and toughness (ie, dart drop impact).

[0019] The propylene-C2-C 12 The following preferred embodiments, properties and subgroups (including preferred ranges thereof) of the propylene-C2-C-olefin random copolymers and sheets are independently generalizable and thus can be used in any order or combination to further define the propylene-C2-C-olefin random copolymers and sheets of the present invention. 12 - Preferred embodiments of α-olefin random copolymers and sheets. DETAILED DESCRIPTION

[0020] Propylene-C4-C 12 -α-Olefin random copolymer

[0021] Propylene-C4-C 12 -α-olefin random copolymer comonomer is selected from C4-C 12 -α-olefins, preferably selected from C4-C 10 -α-olefins, more preferably selected from C4-C8-α-olefins, especially selected from 1-butene (C4) and 1-hexene (C6). Even more preferably, the comonomer is 1-hexene.

[0022] Propylene-C4-C 12 -α-olefin random copolymer is based on the total weight of propylene-C4-C 12 The comonomer content of the random α-olefin copolymer is from 1.0 to 6.0 wt%, preferably from 1.5 to 5.0 wt%, more preferably from 1.8 to 4.5 wt%, still more preferably from 2.0 to 4.2 wt%, even more preferably from 2.4 to 4.0 wt%.

[0023] Propylene-C4-C 12 The MFR2 (230°C, 2.16 kg, ISO 1133) of the α-olefin random copolymer is 1.0 to 20.0 g / 10 min, preferably 1.5 to 15.0 g / 10 min, more preferably 2.0 to 12.0 g / 10 min, still more preferably 3.0 to 10.0 g / 10 min, even more preferably 4.0 to 8.0 g / 10 min.

[0024] Propylene-C4-C 12 The melting temperature Tm of the α-olefin random copolymer is from 125°C to 150°C, preferably from 128°C to 145°C, more preferably from 130°C to 143°C.

[0025] Propylene-C4-C 12 The α-olefin random copolymer also has a xylene cold soluble (XCS) amount (measured at 25° C. according to ISO 16152:2005) of 0.3 to 2.5 wt%, preferably 0.4 to 2.0 wt%, more preferably 0.5 to 1.8 wt%.

[0026] In addition, propylene-C4-C 12 The crystallization temperature Tc of the α-olefin random copolymer is 90°C to 105°C, preferably 92°C to 103°C.

[0027] In addition, propylene-C4-C 12 - The Mw / Mn value of the α-olefin random copolymer measured by GPC, which represents the breadth of the molecular weight distribution (MWD), is from 1.5 to 5.0, preferably from 2.0 to 4.5, and more preferably from 2.5 to 4.0.

[0028] The above propylene-C4-C 12 -α-olefin random copolymers are obtained in the presence of metallocene catalysts.

[0029] Therefore, the term "metallocene-catalyzed propylene-C4-C 12 "-α-olefin random copolymer" means that the polymer is prepared in the presence of a metallocene catalyst.

[0030] The metallocene catalyst may be a supported catalyst using a conventional support or may be free of an external support. Free of an external support means that the catalyst does not contain an external support such as an inorganic support (eg, silica or alumina) or an organic polymer support material.

[0031] Preferably, the metallocene catalyst comprises:

[0032] (i) Complex of formula (I):

[0033]

[0034] Each X is independently a σ-donor ligand;

[0035] L is a divalent bridge selected from -R'2C-, -R'2C-CR'2-, -R'2Si-, -R'2Si-SiR'2- and -R'2Ge-, wherein each R' is independently a hydrogen atom or a C1-C2-containing heteroatom (Groups 14-16 of the Periodic Table of Elements) or a fluorine atom. 20- a hydrocarbon group, or alternatively two R' groups may together form a ring;

[0036] Each R 1 are independently identical or different and are hydrogen, linear or branched C1-C6-alkyl, C 7-20 Aralkyl, C 7-20 Alkyl or C 6-20 Aryl or OY group, where Y is C 1-10 Hydrocarbon; Optionally, two adjacent R 1 The groups may be part of a ring containing the phenyl carbon to which they are bonded;

[0037] Each R 2 are independently the same or may be different and are CH2-R 8 Group, where R 8 is hydrogen or a straight or branched chain C 1-6 -alkyl, C 3-8 Cycloalkyl, C 6-10 Aryl;

[0038] R 3 is a straight-chain or branched C1-C6-alkyl, C 7-20 Aralkyl, C 7-20 Alkyl or C6-C 20 Aryl;

[0039] R 4 is C(R 9 )3 groups, R 9 is a linear or branched C1-C6 alkyl group;

[0040] R 5 is hydrogen or aliphatic C1-C 20 A hydrocarbon group, optionally containing one or more heteroatoms from Groups 14 to 16 of the Periodic Table of Elements;

[0041] R 6 is hydrogen or aliphatic C1-C 20 A hydrocarbon group optionally containing one or more heteroatoms from Groups 14 to 16 of the Periodic Table of the Elements; or

[0042] R 5 and R 6 can form a five-membered saturated carbon ring, which may be optionally substituted by n R 10 Group substitution, n is 0 to 4;

[0043] Each R 10 Same or different, can be C1-C 20 A hydrocarbon group, or a C1-C ... 20 Hydrocarbon.

[0044] R 7 is H, or linear or branched C1-C6-alkyl, or optionally substituted by 1 to 3 R 1 C6-C 20 aryl or heteroaryl;

[0045] (ii) a cocatalyst system comprising a boron-containing cocatalyst and / or an aluminoxane cocatalyst, and

[0046] (iii) Optional silica support.

[0047] Each X is independently a σ-donating ligand, and thus each X may be the same or different, and is preferably a hydrogen atom, a halogen atom, a linear or branched, cyclic or non-cyclic C 1-20 -alkyl or C 1-20 -alkoxy, C 6-20 -Aryl, C 7-20 -Alkaryl or C 7-20 - Arylalkyl; optionally containing one or more heteroatoms from Groups 14 to 16 of the Periodic Table.

[0048] The term "C 1-20 "Hydrocarbon" includes C 1-20 -alkyl, C 2-20 -Alkenyl, C 2-20 -Alkynyl, C 3-20 -cycloalkyl, C 3-20 -cycloalkenyl, C 6-20 -Aryl, C 7-20 -Alkaryl or C 7-20 - aralkyl, including mixtures of these groups, such as cycloalkyl substituted by alkyl. Straight-chain and branched hydrocarbon groups cannot contain cyclic units. Aliphatic hydrocarbon groups cannot contain aromatic rings.

[0049] Unless otherwise stated, the preferred C 1-20 The hydrocarbon group is C 1-20 Alkyl, C 4-20 Cycloalkyl, C 5-20 Cycloalkyl-alkyl, C 7-20 Alkyl, C 7-20 Arylalkyl or C 6-20 Aryl, especially C 1-10 Alkyl, C 6-10 Aryl or C 7-12 Arylalkyl, such as C 1-8 The most particularly preferred hydrocarbon groups are methyl, ethyl, propyl, isopropyl, tert-butyl, isobutyl, C 5-6 cycloalkyl, cyclohexylmethyl, phenyl or benzyl.

[0050] The term "halogen" includes fluoro, chloro, bromo and iodo, in particular chloro or fluoro when referring to the complex definition.

[0051] Any group containing "one or more heteroatoms belonging to Groups 14 to 16 of the Periodic Table of Elements" preferably refers to O, S or N. The N group can be represented by -NH- or -NR"-, wherein R" is C1-C 10 Alkyl. For example, there may be 1 to 4 heteroatoms. A group containing one or more heteroatoms belonging to Groups 14 to 16 of the Periodic Table of the Elements may also be an alkoxy group, for example C1-C 10 -alkoxy.

[0052] For example, WO 2019179959 describes a method for preparing propylene-C4-C 12 - Preferred complexes of random copolymers of α-olefins.

[0053] A more preferred complex is a complex of formula (II)

[0054]

[0055] In the formula, each R 1 are independently identical or different and are hydrogen or linear or branched C1-C6-alkyl, at least one R on each phenyl group 1 It is not hydrogen;

[0056] R' is C 1-10 Hydrocarbyl, preferably C 1-4 A hydrocarbon group, more preferably a methyl group; and

[0057] X is independently a hydrogen atom, a halogen atom, C 1-6 Alkoxy, C 1-6 Alkyl, phenyl or benzyl.

[0058] Most preferably, X is chlorine, benzyl or methyl. Preferably, the two X groups are the same. Most preferably, two chlorines, two methyls or two benzyls, especially two chlorines.

[0059] Specific preferred metallocene catalyst complexes of the present invention include:

[0060] Racemic-trans-dimethylsilanediyl[2-methyl-4,8-bis(4'-tert-butylphenyl)-1,5,6,7-tetrahydro-s-indacen-1-yl][2-methyl-4-(3',5'-dimethyl-phenyl)-5-methoxy-6-tert-butylinden-1-yl]zirconium dichloride

[0061] Racemic-trans-dimethylsilanediyl[2-methyl-4,8-bis-(3',5'-dimethylphenyl)-1,5,6,7-tetrahydro-s-indacene-1-yl][2-methyl-4-(3',5'-dimethyl-phenyl)-5-methoxy-6-tert-butylindene-1-yl]zirconium dichloride

[0062] Racemic-trans-dimethylsilanediyl[2-methyl-4,8-bis-(3',5'-dimethylphenyl)-1,5,6,7-tetrahydro-s-indacene-1-yl][2-methyl-4-(3',5'-di-tert-butyl-phenyl)-5-methoxy-6-tert-butylindene-1-yl]zirconium dichloride

[0063] or its corresponding dimethyl zirconium analogue.

[0064] The ligands required for forming the complexes and catalysts of the present invention can be synthesized by any process, and experienced organic chemists can design various synthesis schemes to make the necessary ligand materials. For example, WO2007 / 116034 discloses the necessary chemical knowledge. Synthesis schemes can also be generally found in WO2002 / 02576, WO2011 / 135004, WO2012 / 084961, WO2012 / 001052, WO2011 / 076780, WO2015 / 158790 and WO2018 / 122134. The embodiments also provide sufficient guidance for the technician.

[0065] Catalyst

[0066] In order to form an active catalytic species, it is usually necessary to employ a promoter known in the art.

[0067] According to the present invention, a cocatalyst system comprising a boron-containing cocatalyst and / or an aluminoxane cocatalyst is used in combination with the metallocene catalyst complex defined above.

[0068] The aluminoxane cocatalyst may be a catalyst having formula (III):

[0069]

[0070] In the formula, n is usually 6 to 20, and R has the following meanings.

[0071] Aluminoxanes are formed when organoaluminum compounds are partially hydrolyzed, such as those having the formula AlR3, AlR2Y, and Al2R3Y3, where R can be, for example, C1-C 10 Alkyl (preferably C1-C5 alkyl) or C 3-10 Cycloalkyl, C7-C 12Aralkyl or alkaryl and / or phenyl or naphthyl, wherein Y can be hydrogen, halogen (preferably chlorine or bromine) or C1-C 10 Alkoxy (preferably methoxy or ethoxy). The resulting oxygen-containing aluminoxane is usually not a pure compound but a mixture of oligomers of formula (III).

[0072] The preferred aluminoxane is methylaluminoxane (MAO).Since the aluminoxanes used as cocatalysts according to the invention are not pure compounds due to the way they are prepared, the molar concentrations of the aluminoxane solutions hereinafter are based on their aluminum content.

[0073] According to the present invention, a boron-containing cocatalyst may also be used instead of the aluminoxane cocatalyst, or the aluminoxane cocatalyst may be used in combination with the boron-containing cocatalyst.

[0074] Those skilled in the art will appreciate that in the case of a boron-based cocatalyst, the complex is typically pre-alkylated by reacting it with an alkyl aluminum compound such as TIBA. This process is well known and any suitable aluminum alkyl may be used, such as Al(C 1-6 -alkyl) 3. Preferred alkylaluminum compounds are triethylaluminum, triisobutylaluminum, triisohexylaluminum, tri-n-octylaluminum and triisooctylaluminum.

[0075] Alternatively, when a borate cocatalyst is used, the metallocene catalyst complex is in its alkylated form, ie, for example, a dimethyl or dibenzyl metallocene catalyst complex may be used.

[0076] Boron-based promoters of interest include those of formula (IV):

[0077] BY3(IV)

[0078] In the formula, Y is the same or different and is a hydrogen atom, an alkyl group (having 1 to about 20 carbon atoms), an aryl group (having 6 to about 15 carbon atoms), an alkaryl group, an aralkyl group, a halogenated alkyl group or a halogenated aryl group (each having 1 to 10 carbon atoms in the alkyl group or 6 to 20 carbon atoms in the aryl group and having fluorine, chlorine, bromine or iodine). Preferred examples of Y are a methyl group, a propyl group, an isopropyl group, an isobutyl group or a trifluoromethyl group, an unsaturated group such as an aryl group or a halogenated aryl group such as a phenyl group, a tolyl group, a benzyl group, a p-fluorophenyl group, a 3,5-difluorophenyl group, a pentachlorophenyl group, a pentafluorophenyl group, a 3,4,5-trifluorophenyl group and a 3,5-bis(trifluoromethyl)phenyl group. Preferred are trifluoroborane, triphenylborane, tri(4-fluorophenyl)borane, tri(3,5-difluorophenyl)borane, tri(4-fluoromethylphenyl)borane, tri(2,4,6-trifluorophenyl)borane, tri(pentafluorophenyl)borane, tri(tolyl)borane, tri(3,5-dimethyl-phenyl)borane, tri(3,5-difluorophenyl)borane and / or tri(3,4,5-trifluorophenyl)borane. Particularly preferred is tri(pentafluorophenyl)borane.

[0079] However, it is preferred to use borates, i.e. 3+ Ionic compounds. Such ionic promoters preferably contain non-coordinating anions, such as tetrakis(pentafluorophenyl)borate and tetraphenylborate. Suitable counterions are protonated amines or aniline derivatives, such as methylammonium, aniline, dimethylammonium, diethylammonium, N-methylaniline, diphenylammonium, N,N-dimethylaniline, trimethylammonium, triethylammonium, tri-n-butylammonium, methyldiphenylammonium, pyridinium, p-bromo-N,N-dimethylaniline or p-nitro-N,N-dimethylaniline.

[0080] Preferred ionic compounds that can be used according to the present invention include triethylammonium tetra(phenyl)borate, tributylammonium tetra(phenyl)borate, trimethylammonium tetra(tolyl)borate, tributylammonium tetra(tolyl)borate, tributylammonium tetra(pentafluorophenyl)borate, tripropylammonium tetra(dimethylphenyl)borate, tributylammonium tetra(trifluoromethylphenyl)borate, tributylammonium tetra(4-fluorophenyl)borate, N,N-dimethylcyclohexylammonium tetra(pentafluorophenyl)borate, N,N-dimethylbenzylammonium tetra(pentafluorophenyl)borate, N,N-dimethylanilammonium tetrakis(phenyl)borate, N,N-diethylaniliniumtetrakis(phenyl)borate, N,N-dimethylaniliniumtetrakis(pentafluorophenyl)borate, N,N-di(propyl)ammoniumtetrakis(pentafluorophenyl)borate, di(cyclohexyl)ammoniumtetrakis(pentafluorophenyl)borate, triphenylphosphoniumtetrakis(phenyl)borate, triethylphosphoniumtetrakis(phenyl)borate, diphenylphosphoniumtetrakis(phenyl)borate, tri(methylphenyl)phosphoniumtetrakis(phenyl)borate, tri(dimethylphenyl)phosphoniumtetrakis(phenyl)borate, triphenylcarboniumtetrakis(pentafluorophenyl)borate or ferroceniumtetrakis(pentafluorophenyl)borate.

[0081] Preferred are triphenylcarbonium tetrakis(pentafluorophenyl)borate, N,N-dimethylcyclohexylammonium tetrakis(pentafluorophenyl)borate or N,N-dimethylbenzylammonium tetrakis(pentafluorophenyl)borate.

[0082] Surprisingly, it has been found that certain boron promoters are particularly preferred. Thus, preferred borates for use in the present invention contain trityl ions. Thus, it is particularly preferred to use N,N-dimethylammonium-tetrapentafluorophenyl borate and Ph3CB(PhF5)4 and the like.

[0083] According to the present invention, preferred cocatalysts are aluminoxanes, more preferably methylaluminoxane, combinations of aluminoxanes with alkylaluminum, boron or borate cocatalysts, and combinations of aluminoxanes with boron-based cocatalysts.

[0084] Suitable amounts of promoters are known to the skilled person.

[0085] The molar ratio of boron to the metal ion of the metallocene may be 0.5:1 to 10:1 mol / mol, preferably 1:1 to 10:1, and especially 1:1 to 5:1 mol / mol.

[0086] The molar ratio of Al in the aluminoxane to the metal ion of the metallocene may be 1:1 to 2000:1 mol / mol, preferably 10:1 to 1000:1, and more preferably 50:1 to 500:1 mol / mol.

[0087] The catalyst can be used in supported or unsupported form, preferably in supported form. The particulate support material used is preferably an organic or inorganic material, for example silicon dioxide, aluminum oxide or zirconium oxide or a mixed oxide (for example silicon dioxide-alumina), in particular silicon dioxide, aluminum oxide or silicon dioxide-alumina. Preference is given to using a silicon dioxide support. The skilled person is aware of the procedures required for supporting the metallocene catalyst.

[0088] Particularly preferably, the support is a porous material so that the complex can be loaded into the pores of the support, for example using methods similar to those described in WO 94 / 14856 (Mobil), WO 95 / 12622 (Borealis) and WO 2006 / 097497.

[0089] The average particle size of the silica support may typically be from 10 to 100 μm. However, it has been found that particular advantages are obtained if the average particle size of the support is from 15 to 80 μm, preferably from 18 to 50 μm.

[0090] The silica support may have an average pore size of 10 to 100 nm and a pore volume of 1 to 3 mL / g.

[0091] Examples of suitable support materials are ES757 produced and sold by PQ, Sylopol 948 produced and sold by Grace, or SUNSPERA DM-L-303 silica produced by AGC Technologies. Before use in catalyst preparation, the support may optionally be calcined to achieve an optimal silanol group content.

[0092] The use of these vectors is routine in the art.

[0093] Propylene-C4-C 12The α-olefin random copolymer can be produced in a single polymerization step comprising a single polymerization reactor (R1) or in a sequential polymerization process comprising at least two polymerization reactors (R1) and (R2), wherein in the first polymerization reactor (R1) a first propylene copolymer fraction (R-PP1) is produced which is subsequently transferred to the second polymerization reactor (R2). In the second polymerization reactor (R2) the second propylene copolymer fraction (R-PP2) is produced in the presence of the first propylene copolymer fraction (R-PP1).

[0094] Applicable to the production of propylene-C4-C 12 The polymerization process of the random α-olefin copolymers generally comprises one or two polymerization stages, each of which can be carried out in solution, slurry, fluidized bed, bulk or gas phase.

[0095] The term "polymerization reactor" shall mean that the main polymerization takes place. Thus, if the process consists of one or two polymerization reactors, this definition does not exclude the option that the overall system comprises a prepolymerization step, for example in a prepolymerization reactor. The term "consisting of" is a closed expression only with respect to the main polymerization reactor.

[0096] The term "sequential polymerization process" refers to the process of propylene-C2-C 12 -α-olefin random copolymer is produced in at least two reactors connected in series. Accordingly, this polymerization system comprises at least a first polymerization reactor (R1) and a second polymerization reactor (R2), and optionally a third polymerization reactor (R3).

[0097] The first (i.e. single) polymerization reactor (R1) is preferably a slurry reactor and can be any continuous or simple stirred batch reactor or a loop reactor operating in bulk or slurry. Bulk refers to polymerization in a reaction medium comprising at least 60% (w / w) monomers. According to the present invention, the slurry reactor is preferably a (bulk) loop reactor.

[0098] In the case of adopting a "sequential polymerization process", the second polymerization reactor (R2) and the optional third polymerization reactor (R3) are gas phase reactors (GPR), i.e., a first gas phase reactor (GPR1) and a second gas phase reactor (GPR2). The gas phase reactor (GPR) according to the present invention is preferably a fluidized bed reactor, a fast fluidized bed reactor or a settled bed reactor or any combination thereof.

[0099] A preferred multi-stage process is a "loop-gas phase" process, such as the one developed by Borealis (called Technology), for example, is described in the following patent literature: for example EP 0 887 379, WO 92 / 12182, WO 2004 / 000899, WO 2004 / 111095, WO 99 / 24478, WO 99 / 24479 or WO 00 / 68315.

[0100] Another suitable slurry-gas phase process is Basell's Craftsmanship.

[0101] Taking into account the comonomer content and / or MFR2, propylene-C4-C 12 The random α-olefin copolymer may be unimodal or multimodal, such as bimodal.

[0102] If propylene-C4-C 12 The random α-olefin copolymer is unimodal and is preferably produced in a single polymerization step in the polymerization reactor (R1). 12 -α-olefin random copolymers can also be produced in a sequential polymerization process using the same polymerization conditions in all reactors.

[0103] If propylene-C4-C 12 The random α-olefin copolymers are multimodal and are preferably produced in a sequential polymerization process using different polymerization conditions (comonomer amount, hydrogen amount, etc.) in the reactors.

[0104] Preferably, the propylene-C4-C 12 - The α-olefin random copolymer is bimodal, in particular taking into account the MFR and / or the comonomer content, for example the 1-hexene content.

[0105] In this case, propylene-C4-C 12 The α-olefin random copolymer comprises two polymer fractions (R-PP1) and (R-PP2).

[0106] Preferably, propylene-C4-C 12 -α-olefin random copolymer is composed of:

[0107] 25.0 to 50.0 wt%, preferably 30.0 to 48.0 wt%, more preferably 35.0 to 45.0 wt% of a polymer fraction (R-PP1), said polymer fraction (R-PP1) having:

[0108] (i) 0.5 to 5.0 wt%, preferably 0.8 to 4.0 wt%, more preferably 1.0 to 3.0 wt% of C4-C 12 - alpha-olefin content; and

[0109] (ii) a melt flow rate MFR2 (230°C / 2.16kg) measured according to ISO 1133 of 2.0 to 10.0 g / 10 min, preferably 3.0 to 9.0 g / 10 min; and

[0110] 50.0 to 75.0 wt%, preferably 52.0 to 70.0 wt%, more preferably 55.0 to 65.0 wt% of a polymer fraction (R-PP2), the polymer fraction (R-PP2) having:

[0111] (i) 3.2 to 10.0 wt%, preferably 3.4 to 8.0 wt%, more preferably 3.6 to 7.5 wt% of C4-C 12 - alpha-olefin content; and

[0112] (ii) a melt flow rate MFR2 (230°C / 2.16kg) measured according to ISO 1133 of 1.0 to 20.0 g / 10 min, preferably 3.0 to 15.0 g / 10 min, more preferably 5.0 to 10.0 g / 10 min;

[0113] Among them, the C4-C 12 -α-olefin content higher than C4-C 12 -α-olefin content.

[0114] Preferably, both fractions have the same comonomer type.

[0115] Further, fraction (R-PP1) is characterized in that the amount of xylene cold solubles (XCS) is from 0.3 to 3.0 wt%, preferably from 0.4 to 2.5 wt%, more preferably from 0.5 to 2.0 wt%. Further, fraction (R-PP2) is characterized in that the amount of xylene cold solubles (XCS) is from 0.3 to 3.0 wt%, preferably from 0.4 to 2.5 wt%, more preferably from 0.5 to 2.0 wt%.

[0116] The propylene-C4-C 12 -α-olefin random copolymers may contain up to 5.0 wt% additives (e.g., α-nucleating agents and antioxidants) as well as slip agents and anti-caking agents. Preferably, the content of additives (excluding α-nucleating agents) is less than 3.0 wt%, such as less than 1.0 wt%. Typically, the content of additives (excluding α-nucleating agents) is at least 0.1 wt%.

[0117] application

[0118] The present invention relates to a sheet material comprising the propylene-C4-C 12 -α-olefin random copolymer.

[0119] Such sheets according to the present invention have been found to exhibit an optimized or improved balance between optical properties, stiffness and toughness (ie dart drop impact).

[0120] Containing the above propylene-C4-C 12 The sheet of the α-olefin random copolymer preferably has a tensile modulus in the longitudinal and transverse directions measured on a 300 μm sheet (each 300 μm cast film) of 350 to 800 MPa, more preferably 380 to 750 MPa, even more preferably 400 to 720 MPa, for example 450 to 700 MPa.

[0121] In addition, the above-mentioned propylene-C4-C 12 The haze of such a sheet of -α-olefin random copolymer measured on a 300 μm sheet (each 300 μm cast film) is preferably 0.01% to less than 10.0%, preferably 0.05% to less than 7.5%, more preferably 0.10% to less than 5.0%, even more preferably 0.20% to less than 2.0%.

[0122] The sheet of the present invention preferably has a clarity of 80.0 to 100.0%, preferably 85.0 to 100.0%, more preferably 90.0 to 100.0%, even more preferably 95.0 to 100.0%, measured on a 300 μm sheet (each 300 μm cast film).

[0123] The sheet according to the present invention may also have a dart drop impact strength (DDI) of at least 1500 g to more than 1700 g, preferably 1600 g to more than 1700 g, measured on a 300 μm sheet (respectively 300 μm cast film) according to ASTM D1709 Method A. The upper limit of more than 1700 g is due to the upper limit of detection of the respective methods being 1700 g.

[0124] In a preferred embodiment, the sheet according to the present invention exhibits at least 2 of the above properties, more preferably at least 3 of the above properties, and most preferably all of the above 4 properties, namely haze, clarity, tensile modulus and DDI.

[0125] The thickness of the sheet according to the present invention is 100 to 1000 μm, preferably 200 to 800 μm, more preferably 250 to 500 μm.

[0126] The sheet according to the present invention comprises at least 90.0 wt%, preferably at least 95.0 wt%, more preferably at least 99.0 wt% of propylene-C4-C 12 -α-olefin random copolymer.

[0127] The sheet material according to the invention is particularly suitable for thermoforming, so the invention also relates to the use of the sheet material for producing thermoformed articles, and to thermoformed articles produced from the sheet material according to the invention.

[0128] As used herein, a "thermoformed article" is a thermoplastic sheet that is heated to at least its softening point and placed under pressure (positive and / or negative) along the contours of a mold. The thermoformed article is then removed from the mold after cooling to below its softening point. Non-limiting examples of thermoformed articles include trays, containers, and cups.

[0129] The sheet according to the invention can be produced by known techniques for producing thermoformed sheets. Examples are cast film technology or roll-stack technology.

[0130] Cast Film Technology

[0131] In the simplest technology for producing polymer films (respectively sheets), the molten copolymer is extruded through a slot die and fed by a (usually single-screw) extruder to a first cooled roll, the so-called chill roll. The solidified film from the first cooled roll is taken up by a second roll (nip roll or take-up roll) and fed to a winding device (after trimming the edges).

[0132] Only a very limited amount of orientation occurs in the film, which is determined by the ratio between die thickness and film thickness or the ratio between extrusion speed and take-up speed, respectively. Due to the technical simplicity, cast film technology is a very economical and easy-to-operate process.

[0133] Roller stack technology

[0134] The production of extruded sheets for thermoforming is usually carried out using a three-roll roll stack, where the thickness range is usually about 0.3 mm to about 2 mm. The roll stack comprises three rotating, hardened and highly polished rolls (typically 300-600 mm in diameter), preferably with independent temperature control and drive.

[0135] The purpose of the roll stack is to convert the polymer melt exiting the flat die into a solid polished sheet with a uniform and controlled morphology that can be subsequently processed. The roll stack is most commonly in a vertical configuration, although other configurations are used, and the sheet can pass either downward or upward over the roll stack. This specification is directed to vertical downward stack operation.

[0136] In the case of polypropylene, the molten polymer (usually at 210-240°C) is directed from the die into the gap between the rotating top and middle rolls, which is close to the die opening (+ / - 10%). The output of the extruder is adjusted so that a small and constant rolling bank of material is established between one of the rolls (preferably the top roll) and one surface of the polymer melt. The output of the extruder and the roll speed are adjusted to minimize any stretching and longitudinal orientation of the polymer melt. The polymer passes through the middle roll and enters the gap between the middle roll and the bottom roll. The temperature of the middle roll is adjusted so that good contact is maintained between the polymer and the rolls and the upper surface (outer surface) of the sheet is at the appropriate temperature under pressure between the middle roll and the bottom roll to provide a highly polished surface. Further cooling is carried out on the bottom roll and the sheet leaves the roll stack for subsequent operations - usually winding or direct in-line thermoforming.

[0137] The temperature of the rollers is a particularly critical factor in obtaining good quality thermoformed polypropylene sheets.

[0138] The optimum temperature depends on several factors, including the diameter of the rolls, the line speed, the sheet thickness and the type of polypropylene being processed.

[0139] Depending on these factors, the temperature of the rollers is usually within the following ranges:

[0140] Top roller: 20-50℃;

[0141] Middle roller: 20-80℃;

[0142] Bottom roller: 30-90℃.

[0143] The temperature of the top roll is usually lower than that of the middle roll, and the middle and bottom rolls usually have similar temperatures. Planar films produced with roll stack technology have low anisotropy in orientation and mechanical properties.

[0144] Experimental Section

[0145] 1. Methods

[0146] Xylene soluble fraction at room temperature (XCS, wt%): The amount of polymer soluble in xylene is determined at 25°C according to ISO 16152:2005.

[0147] Calculation of XCS and comonomer content of the second polymer fraction (R-PP2):

[0148] The comonomer content and XCS of the first polymer fraction (R-PP1) of the propylene-hexene random copolymer (A) can be determined directly on the sample taken after the first polymerization step, the above values ​​for the second polymer fraction (R-PP2) have to be calculated. For this purpose, the simple mixing law is used, giving the following formula:

[0149]

[0150] and

[0151]

[0152] In the formula,

[0153] w(R-PP1) is the weight fraction [wt%] of polymer fraction R-PP1;

[0154] w(R-PP2) is the weight fraction [wt%] of the polymer fraction R-PP2;

[0155] XCS(R-PP1) is the XCS content [wt%] of polymer fraction R-PP1;

[0156] XCS(A) is the XCS content [wt%] of the propylene-hexene random copolymer;

[0157] XCS(R-PP2) is the calculated XCS content of polymer fraction R-PP2 [wt %];

[0158] C6(R-PP1) is the 1-hexene content [wt%] of polymer fraction R-PP1;

[0159] C6(A) is the 1-hexene content [wt%] of the propylene-hexene random copolymer;

[0160] C6(R-PP2) is the calculated 1-hexene content [wt %] of polymer fraction R-PP2.

[0161] MFR2 (230°C) is measured according to ISO 1133 (230°C, 2.16 kg load).

[0162] The melt flow rate MFR2 of polypropylene is measured according to ISO 1133 15 (230°C, 2.16 kg load). MFR is an indicator of the flowability and processability of the polymer. The higher the melt flow rate, the lower the viscosity of the polymer.

[0163] Calculation of the melt flow rate MFR2 (230°C) of the polymer fraction (R-PP2):

[0164]

[0165] In the formula,

[0166] w(R-PP1) is the weight fraction [wt%] of polymer fraction R-PP1;

[0167] w(R-PP2) is the weight fraction [wt%] of the polymer fraction R-PP2;

[0168] MFR(R-PP1) is the melt flow rate MFR2 (230°C) [g / 10 min] of polymer fraction R-PP1;

[0169] MFR(A) is the melt flow rate MFR2 (230°C) [g / 10min] of the propylene-hexene random copolymer;

[0170] MFR(R-PP2) is the calculated melt flow rate MFR2 (230° C.) [g / 10 min] of polymer fraction R-PP2.

[0171] Comonomer determination: 1-hexene content - 13 C NMR spectroscopy

[0172] against 1 H and 13 C, quantitative analysis of the melt was recorded using a Bruker Advance III 500 NMR spectrometer at 500.13 MHz and 125.76 MHz, respectively. 13 C{ 1 H}NMR spectroscopy. 13All spectra were recorded using a C-optimized 7 mm magic angle spinning (MAS) probe at 180°C using nitrogen for all atmospheres. Approximately 200 mg of material was loaded into a 7 mm outer diameter zirconium oxide MAS rotor and spun at 4 kHz. This setting was chosen primarily for the high sensitivity required for rapid identification and accurate quantification (Klimke, K., Parkinson, M., Piel, C., Kaminsky, W., Spiess, H. W., Wilhelm, M., Macromol. Chem. Phys. 2006: 207: 382., Parkinson, M., Klimke, K., Spiess, H. W., Wilhelm, M., Macromol. Chem. Phys. 2007: 208: 2128., Castignolles, P., Graf, R., Parkinson, M., Wilhelm, M., Gaborieau, M., Polymer 50 (2009) 2373). The NOE with a short recycle delay of 3 s was performed using standard single pulse excitation (Klimke, K., Parkinson, M., Piel, C., Kaminsky, W., Spiess, H. W., Wilhelm, M., Macromol. Chem. Phys. 2006; 207: 382., Pollard, M., Klimke, K., Graf, R., Spiess, H. W., Wilhelm, M., Sperber, O., Piel, C., Kaminsky, W., Macromolecules 2004: 37: 813) and the RS-HEPT decoupling scheme (Filip, X., Tripon, C., Filip, C., J. Mag. Resn. 2005: 176, 239., Griffin, J. M., Tripon, C., Samoson, A., Filip, C. and Brown, S. P., Mag. Res. in ... Chem. 2007 45, S1, S198). A total of 16384 (16k) transient signals were collected for each spectrum.

[0173] Quantitative 13 C{ 1 H} NMR spectra were processed, integrated and relevant quantitative properties were determined from the integration. All chemical shifts were internally referenced to the methyl isotactic pentad (mmmm) at 21.85 ppm.

[0174] A characteristic signal corresponding to 1-hexene incorporation was observed and the comonomer content was quantified in the following manner.

[0175] The incorporation of 1-hexene in the PHP separation sequence was quantified using the integral of the αB4 site at 44.2 ppm as a ratio of the number of reported sites for each comonomer:

[0176] H=IαB4 / 2

[0177] The amount of 1-hexene incorporated in the PHHP double continuous sequence was quantified using the integral of the ααB4 site at 41.7 ppm as a ratio of the number of reported sites for each comonomer:

[0178] HH=2×IααB4

[0179] When a double continuous incorporation is observed, the incorporation of 1-hexene in the PHP separation sequence needs to be compensated due to the overlap of the signals αB4 and αB4B4 at 44.4 ppm:

[0180] H=(IαB4–2×IααB4) / 2

[0181] The total 1-hexene content was calculated based on the total amount of 1-hexene separated and continuously added:

[0182] H 总 =H+HH

[0183] When no sites indicating continuous incorporation were observed, the total 1-hexene comonomer content was calculated based solely on this amount:

[0184] H 总 =H

[0185] Characteristic signals indicative of regional 2,1-erythro defects were observed (Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253).

[0186] The presence of 2,1-erythro regiodefects was indicated by the presence of Pαβ (21e8) and Pαγ (21e6) methyl sites at 17.7 and 17.2 ppm, and was confirmed by other characteristic signals.

[0187] The total amount of secondary (2,1-erythro) inserted propylene was quantified based on the αα21e9 methylene site at 42.4 ppm:

[0188] P21=Iαα21e9

[0189] The total amount of primary (1,2-erythro) inserted propene is quantified based on the major Sαα methylene site at 46.7 ppm and compensating for the relative amounts of unaccounted 2,1-erythro, αB4, and ααB4B4 methylene units of propene (note that the H and HH counts for the hexene monomers in each sequence are not the sequence number):

[0190] P12=I S αα+2×P21+H+HH / 2

[0191] The total amount of propene was quantified as the sum of primary (1,2-erythro) and secondary (2,1-erythro) inserted propene:

[0192] P 总 =P12+P21=I S αα+3×Iαα21e9+(IαB4–2×IααB4) / 2+IααB4

[0193] Simplified to:

[0194] P 总 =I S αα+3×Iαα21e9+0.5×IαB4

[0195] The total mole fraction of 1-hexene in the polymer is then calculated as:

[0196] fH=H 总 / (H 总 +P 总 )

[0197] The complete integrated equation for the mole fraction of 1-hexene in the polymer is:

[0198] fH=(((IαΒ4–2×IααΒ4) / 2)+(2×IααΒ4)) / ((ISαα+3×Iαα21e9+0.5×IαB4)+((IαΒ4–2×IααΒ4) / 2)+(2×IααΒ4))

[0199] Simplified to:

[0200] fH=(IαΒ4 / 2+IααΒ4) / (ISαα+3×Iαα21e9+IαB4+IααB4)

[0201] The total comonomer incorporation of 1-hexene (in mole percent) was calculated from the mole fractions in the conventional manner:

[0202] H[mol%]=100×fH

[0203] The total comonomer incorporation of 1-hexene (in weight percent) was calculated from the mole fractions in the standard manner:

[0204] H[wt%]=100×(fH×84.16) / ((fH×84.16)+((1-fH)×42.08))

[0205] DSC analysis, melting temperature (Tm) and crystallization temperature (Tc)

[0206] 5 to 7 mg samples were measured using a TA Instrument Q2000 Differential Scanning Calorimeter (DSC). The DSC was run according to ISO 11357 / Part 3 / Method C2 in a heating / cooling / heating cycle with a scan rate of 10°C / min and a temperature range of -30°C to +225°C.

[0207] The crystallization temperature and the heat of crystallization (Hc) are determined by the cooling step, while the melting temperature and the heat of fusion (Hf) are determined by the second heating step.

[0208] GPC: Molecular weight mean, molecular weight distribution and polydispersity index (Mn, Mw and Mw / Mn)

[0209] The molecular weight mean (Mw and Mn), molecular weight distribution (MWD) and its breadth (described by the polydispersity Mw / Mn, where Mn is the number average molecular weight and Mw is the weight average molecular weight) were determined by gel permeation chromatography (GPC) according to ISO 16014-1:2003, ISO 16014-2:2003, ISO 16014-4:2003 and ASTM D 6474-12. A high temperature GPC instrument equipped with an infrared (IR) detector (IR4 or IR5 from PolymerChar (Valencia, Spain)) or a differential refractometer (RI) from Agilent Technologies equipped with 3× Agilent-PLgelOlexis columns and 1× Agilent-PLgel Olexis Guard columns was used. As solvent and mobile phase, 1,2,4-trichlorobenzene (TCB) stabilized with 250 mg / L 2,6-di-tert-butyl-4-methylphenol was used. The chromatographic system was operated at 160°C and a constant flow rate of 1 mL / min. 200 μL of sample solution was injected for each analysis. Data collection was performed using Agilent Cirrus software version 3.3 or PolymerChar GPC-IR control software.

[0210] Haze and clarity were measured according to ASTM D1003-00 on 300 μm thick cast films produced on a single layer cast film line (melt temperature 220°C, chill roll temperature 20°C).

[0211] Tensile modulus

[0212] The tensile modulus in the longitudinal and transverse directions was determined according to ISO 527-3 at 23° C. on 300 μm cast films produced as described below. The test was carried out at a crosshead speed of 1 mm / min.

[0213] Dart Drop Intensity (DDI)

[0214] Dart drop is measured using ASTM D1709 Method A (alternative test technique) from a 300 μm cast film produced as shown below. A dart with a hemispherical head of 38 mm diameter is dropped from a height of 0.66 m onto the film clamped over an orifice. Multiple consecutive groups of 20 specimens are tested. One weight is used per group, increasing (or decreasing) the weight from group to group in uniform increments. The weight that causes 50% of the specimens to fail is calculated and reported.

[0215] The 300μm sheet was produced on a Collin cast film line equipped with a pilot-scale extruder with a diameter of 30mm and a L / D of 30, running with a multi-purpose screw suitable for PP and PE processing, with a maximum production capacity of 15kg / h. The attached cast film die has a width of 300mm, a die gap of 0.5mm to 1mm, and is equipped with an air knife. The cooling roll (commonly known as the chill roll) and the auxiliary roll are both 350mm wide and 144mm in diameter, followed by a conventional winder. The die gap is set to 1.0mm using drawdown to achieve a final 300μm thick film, and both the cooling roll and the auxiliary roll are set to 20°C.

[0216] 2. Example

[0217] Preparation of Propylene-1-Hexene Random Copolymer

[0218] Catalyst: Synthesis of Metallocene

[0219] The metallocene complex (metallocene MC-2) has been produced as described for MC-2 in WO2019 / 179959.

[0220]

[0221] Preparation of MAO-silica carrier

[0222] A steel reactor equipped with a mechanical stirrer and a filter screen was purged with nitrogen and the reactor temperature was set to 20°C. 5.0 kg of silica grade DM-L-303 (5.0 kg) pre-calcined at 600°C from AGC Technology was then added from the feed bucket, and then carefully pressurized and depressurized with nitrogen using a manual valve. Toluene (22 kg) was then added. The mixture was stirred for 15 minutes. A toluene solution (9.0 kg) of 30 wt% MAO from Lanxess was then added through the feed line at the top of the reactor within 70 minutes. The reaction mixture was then heated to 90°C and stirred at 90°C for another 2 hours. The slurry was allowed to settle and the mother liquor was filtered out. The catalyst was washed twice with toluene (22 kg) at 90°C, followed by settling and filtering. The reactor was cooled to 60°C and the solid was washed with heptane (22.2 kg). Finally, the SiO2 treated with MAO was dried at 60°C for 2 hours under a nitrogen stream and then stirred and dried for 5 hours under vacuum (-0.5 bar). The MAO treated support was collected as a free flowing white powder and found to contain 12.2 wt% Al.

[0223] Preparation of Catalyst System 1 (ICS1) Catalyst of the Invention

[0224] A 30 wt % MAO toluene solution (0.7 kg) was added to a steel nitrogen-sealed reactor via a burette at 20° C. Toluene (5.4 kg) was then added under stirring. Metallocene MC-2 (93 g) was added from a metal cylinder and then rinsed with 1 kg of toluene. The mixture was stirred for 60 minutes at 20° C. Trityl tetrakis (pentafluorophenyl) borate (91 g) was then added from a metal cylinder and subsequently rinsed with 1 kg of toluene. The mixture was stirred at room temperature for 1 hour. The resulting solution was added to the stirred cake of the MAO-silica support prepared as described above within 1 hour. The cake was left for 12 hours and then dried for 2 hours at 60° C. under a stream of N2 and dried for another 5 hours under vacuum (-0.5 bar) under stirring.

[0225] The dried catalyst (in the form of a pink free-flowing powder) was sampled and contained 13.9% Al and 0.11% Zr.

[0226] Propylene-1-hexene random copolymer The product was produced in a pilot plant with a prepolymerization reactor and a slurry loop reactor.

[0227] Table 1: Propylene-1-hexene random copolymer (PHC)

[0228] PHC-1 PHC-2 Prepolymerization temperature ℃ 25 25 pressure kPa 5111 5123 Catalyst feed g / h 8.5 6.0 <![CDATA[H2 feed]]> g / h 0.10 0.10 Ring type (reactor 1) temperature ℃ 65 65 pressure kPa 5056 5061 <![CDATA[H2 / C3 ratio]]> mol / kmol 0.08 0.08 <![CDATA[C6 / C3 ratio]]> mol / kmol 45.9 44.4 Liquid residence time H 0.37 0.37 Loop Reactor Split wt% 43 39 <![CDATA[MFR2 of the loop reactor fraction*]]> g / 10min 5.3 6.6 <![CDATA[C6 content of the loop reactor fraction*]]> wt% 1.3 1.2 XCS* of loop reactor fraction wt% 1.4 1.3 GPR (reactor 2) temperature ℃ 80 80 pressure kPa 2400 2400 <![CDATA[H2 / C3 ratio]]> mol / kmol 1.1 1.2 <![CDATA[C6 / C3 ratio]]> mol / kmol 6.6 5.1 Polymer residence time H 2.7 3.6 GPR Reactor Split wt% 57 61 <![CDATA[C6 content of GPR fraction**]]> wt% 5.5 3.7 MFR of GPR fraction** g / 10min 8.6 8.0 XCS of GPR fraction** wt% 1.2 0.7 Polymer properties XCS wt% 1.3 0.9 <![CDATA[MFR2]]> g / 10min 7.0 6.6 <![CDATA[C6 content]]> wt% 3.7 2.7 Mw / Mn(GPC) - 2.9 2.9 Tm ℃ 140 137 Tc ℃ 96 101

[0229] *R-PP1, **R-PP2

[0230] Composition:

[0231] Propylene-1-hexene random copolymers PHC-1 and PHC-2 were compounded with 0.15 wt% of an antioxidant (Irganox B215FF, from BASF AG, Germany), 0.05 wt% of calcium stearate (CAS No. 1592-23-0, purchased from Faci, Italy) at 220°C in a co-rotating twin-screw extruder Coperion TSE 16, wherein Irganox B215FF is a 1:2 mixture of pentaerythritol tetrakis(3-(3',5'-di-tert-butyl-4-hydroxyphenyl) propionate (CAS No. 6683-19-8) and tris(2,4-di-tert-butylphenyl) phosphite (CAS No. 31570-04-4).

[0232] As comparative example CE1, a polypropylene homopolymer HD601CF from Borealis was used. This polymer was based on a conventional fourth generation Ziegler-Natta type catalyst and had an XCS content of 3.6 wt%, a polydispersity Mw / Mn of 5.0, a melting point Tm (DSC) of 165°C and an MFR2 of 8.0 g / 10 min. As comparative example CE2, a propylene-ethylene random copolymer RD204CF from Borealis was used. This polymer was a visbreaking grade with an ethylene content of 2.2 wt%, based on a conventional fourth generation Ziegler-Natta type catalyst and had an XCS content of 4.0 wt%, a polydispersity Mw / Mn of 3.2, a melting point Tm (DSC) of 153°C and an MFR2 of 8.0 g / 10 min.

[0233] Table 2: Examples and Comparative Examples

[0234]

[0235] As can be clearly seen from the above table, the sheet according to the invention is characterized by an advantageous combination of good optical properties, high tensile modulus and high impact strength (DDI).

Claims

1. A polypropylene sheet, comprising: Metallocene-catalyzed propylene-C4-C 12 -α-olefin random copolymer, the propylene-C4-C 12 -α-olefin random copolymers having: a-1) Propylene-C4-C 12 Based on the total weight of the random α-olefin copolymer, 1.0 to 6.0 wt% of C4-C 12 -α-olefin content; a-2) an MFR2 of 2.0 to 20.0 g / 10 min measured at 230° C. and 2.16 kg load according to ISO 1133; a-3) a melting temperature Tm of 125°C to 150°C as measured by DSC; and a-4) an amount of xylene cold solubles XCS of 0.3 to 2.5 wt% measured at 25°C according to ISO 16152:2005; in, The sheet has a thickness of 100 to 1000 μm and contains at least 90.0 wt% of propylene-C4-C 12 -α-olefin random copolymer.

2. The polypropylene sheet according to claim 1, wherein The propylene-C4-C 12 -α-olefin random copolymer comonomer is selected from C4-C 10 -α-olefins.

3. The polypropylene sheet according to claim 1 or 2, wherein: The propylene-C4-C 12 -α-olefin random copolymers having: 1.5 to 5.0 wt% C4-C 12 - alpha-olefin content; and / or An MFR2 of 2.0 to 12.0 g / 10 min measured at 230°C and 2.16 kg load according to ISO 1133; and / or a melting temperature Tm of 128°C to 145°C; and / or Xylene cold solubles, XCS, amount of 0.4 to 2.0 wt%, measured at 25°C according to ISO 16152:2005.

4. The polypropylene sheet according to claim 1 or 2, wherein The propylene-C4-C 12 The -α-olefin random copolymer also has a crystallization temperature of 90°C to 105°C.

5. The polypropylene sheet according to claim 1 or 2, wherein: The propylene-C4-C 12 -α-olefin random copolymers are composed of: 25.0 to 50.0 wt. % of a polymer fraction R-PP1 having: (i) 0.5 to 5.0 wt% C4-C 12 - alpha-olefin content; and (ii) a melt flow rate MFR2 of 2.0 to 10.0 g / 10 min, measured at 230° C. and 2.16 kg load according to ISO 1133; and 50.0 to 75.0 wt. % of a polymer fraction R-PP2 having: (i) 3.2 to 10.0 wt% C4-C 12 - alpha-olefin content; and (ii) a melt flow rate MFR2 of 1.0 to 20.0 g / 10 min, measured at 230° C. and 2.16 kg load according to ISO 1133; Wherein, the C4-C 12 - an α-olefin content higher than that of the C4-C 12 -α-olefin content.

6. The polypropylene sheet according to claim 5, wherein The amount of xylene cold solubles XCS of fraction R-PP1 is from 0.3 to 3.0 wt %; the amount of xylene cold solubles XCS of fraction R-PP2 is from 0.3 to 3.0 wt %.

7. The polypropylene sheet according to claim 1 or 2, wherein: The propylene-C4-C 12 - The Mw / Mn value of the α-olefin random copolymer is from 1.5 to 5.

0.

8. The polypropylene sheet according to claim 1 or 2, wherein: The sheet comprises at least 95.0 wt% of the propylene-C4-C 12 -α-olefin random copolymer.

9. The polypropylene sheet according to claim 1 or 2, wherein: The sheet has a tensile modulus in the machine and transverse directions of 350 to 800 MPa, measured according to ISO 527 at 23°C on a 300 μm cast film.

10. The polypropylene sheet according to claim 1 or 2, wherein: The sheet has a haze of 0.01% to less than 10.0% as measured on a 300 μm cast film according to ASTM D1003-00.

11. The polypropylene sheet according to claim 1 or 2, wherein: The sheet has a clarity of 80.0 to 100.0% as measured on a 300 μm cast film according to ASTM D1003-00.

12. The polypropylene sheet according to claim 1 or 2, wherein: The sheet has a dart drop impact strength DDI of at least 1500 g to over 1700 g measured according to ASTM D1709 Method A on a 300 μm cast film, wherein the upper limit of over 1700 g is due to the upper detection limit of the method being 1700 g.

13. The polypropylene sheet according to claim 1 or 2, wherein: The sheet exhibits at least two properties selected from the group consisting of haze, clarity, tensile modulus and DDI as defined in claims 9-12.

14. Use of the polypropylene sheet according to any one of claims 1 to 13 in the production of thermoformed articles.

15. A thermoformed article made from the polypropylene sheet according to any one of claims 1 to 13.

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