In-SITU nucleated polypropylene

Abstract

The invention relates to process for producing a nucleated polypropylene, comprising the steps of: (i) supplying a reaction stream comprising vinyl cycloalkane into a first reactor; (ii) polymerizing the vinyl cycloalkane in presence of a catalyst system to obtain a product stream, wherein the product stream comprises polyvinyl cycloalkane, unreacted vinyl cycloalkane, and the catalyst system; (iii) supplying the product stream into a second polymerization reactor containing propylene; and (iv) polymerizing the propylene in presence of the product stream and hydrogen to obtain the nucleated polypropylene; The mass ratio of the polyvinyl cycloalkane to the unreacted vinyl cycloalkane present in the product stream is ≤ 0.5. The invention further relates to the nucleated polypropylene obtained from the process and having suitable optical clarity and tensile strength.

Description

24POLY0067-WO-ORD1IN-SITU NUCLEATED POLYPROPYLENEFIELD OF INVENTION

[0001] The invention relates to a process of producing in-situ nucleated polypropylene and to the nucleated polypropylene so produced.BACKGROUND

[0002] Polypropylene such as isotactic polypropylene is a synthetic resin which has high rigidity and mechanical strength but in general has slow rate of crystallization. In particular, polypropylene polymer properties such as clarity and haze, flexural & tensile properties can be greatly affected by the degree of crystallinity and the size of the spherulitic crystallites as well as the balance of crystalline and amorphous domain. At increasing cooling rates, the nucleation rate increases and spherulitic size decreases leading to enhanced polymer clarity at the cost of reduced tensile properties. Further, in certain other situations owing to the formation of relatively large spherulites, molded articles of the polymer have inferior transparency thereby affecting its commercial value.

[0003] In the past nucleating agents have been used to improve the crystallinity and transparency of polypropylene by adding these to the polypropylene resin during the compounding or molding step. For example, it is known that when an aluminum or sodium salt of an aromatic carboxylic acid (Japanese Laid-open Patent Publication No. 80329 / 1983) is added as a nucleating agent to a polypropylene resin, such a nucleating agent improves both transparency and crystallinity of the resin. However, it has been observed in certain situations, these nucleating agents may leach out from the resin during further processing or storage of the resin product and may contaminate the polymer product itself. Such contamination may in turn invite regulatory hurdles. In addition, due to inefficient mixing of the nucleating agent in the molten polymer phase during compounding, typically high amounts of the nucleating agent are required.

[0004] Previously, in-situ nucleating agents have also been used to address both the issue of leaching as well as non-homogeneous distribution while improving clarity of the polymer product. Such in situ nucleating agents are introduced during the stage of polymerization / pre- polymerization rather than separately compounding the resin with nucleating agents once the polypropylene polymer is formed. The use of in-situ nucleating agents helps in improving process24POLY0067-WO-ORD2 efficiency through improved dispersion inside the polypropylene matrix and ultimately reducing material costs of the nucleating agent.

[0005] For example, polymerized vinyl compound have been used as in-situ nucleating agent in preparing polypropylene as described in the patent US6437063. However, the catalyst system that is used for the polymerization of both the propylene and the vinyl monomer must be chosen carefully as the presence of both polymerized and especially unreacted vinyl compound during the propylene polymerization may adversely affect catalyst performance, crystallinity and the stereoregularity of the resultant polypropylene product. WO 2018 / 011165 describes solid catalyst particles comprising a Ziegler-Natta catalyst and a polymeric nucleating agent such as VCH / PVCH. However, the patent does not address the requirement of improving optical properties of a polypropylene compound.

[0006] In the past, multistage polymerization process has been explored involving a prepolymerization process in a first reactor followed by a polymerization process in a second reactor. However, in such multi-stage polymerization process, the catalyst slurry from the first reactor either needs to be washed to remove any unreacted monomer or have near complete conversion of monomer to polymer prior to introducing the catalyst slurry in the second reactor for propylene polymerization. However, in such a process the washing of the catalyst may not only reduce process efficiency but also in certain situations reduce catalyst efficiency in subsequent polymerization steps.

[0007] Accordingly, it is an objective of the present invention to provide for a process of producing a nucleated polypropylene having excellent clarity while maintaining suitable tensile property and isotacticity without the need of washing the catalyst slurry. It is yet another objective of the present invention to provide for a process of preparing polypropylene using an in-situ nucleating agent and using a suitable polymerization catalyst without adversely affecting catalyst performance and the stereoregularity (isotacticity) of the resultant polypropylene product.DESCRIPTION

[0008] Accordingly, the one or more objectives of the present invention is achieved by a process for producing a nucleated polypropylene, comprising the steps of:(i) supplying a reaction stream comprising vinyl cycloalkane having at least 6 carbon atoms, into a first reactor;24POLY0067-WO-ORD3(ii) polymerizing the vinyl cycloalkane in presence of a catalyst system to obtain a product stream, wherein the product stream comprises polyvinyl cycloalkane, unreacted vinyl cycloalkane, and the catalyst system;(iii) supplying the product stream into a second polymerization reactor containing propylene; and(iv) polymerizing the propylene in presence of the product stream and hydrogen to obtain the nucleated polypropylene; wherein the weight ratio of the polyvinyl cycloalkane to the unreacted vinyl cycloalkane present in the product stream is > 0 and < 0.5; and wherein the catalyst system comprises a procatalyst comprising at least one internal electron donor represented by any one of Formula I or Formula II:• wherein for Formula I each R90group is independently a substituted or an unsubstituted aromatic group; R91, R92, R93, R94, R95, and R96are each independently selected from a hydrogen or a linear, branched or cyclic hydrocarbyl group selected from alkyl, alkenyl, aryl, aralkyl, or alkylaryl groups, and one or more combinations thereof; R97is a hydrogen or a linear, branched or cyclic hydrocarbyl group selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; N is a nitrogen atom; O is an oxygen atom; and C is a carbon atom;• wherein for Formula II: R81, R82, R83, R84, R85, and R86are the same or different and are independently hydrogen or a linear, branched or cyclic hydrocarbyl group selected from alkyl, alkenyl, aryl, aralkyl, or alkylaryl groups, and one or more combinations thereof; R87is a hydrogen or a linear, branched or cyclic24POLYOQ67-WO-ORD4 hydrocarbyl group, selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; each R80group is independently a linear, branched or cyclic hydrocarbyl group selected from alkyl, alkenyl, aryl, aralkyl, or alkylaryl groups, and one or more combinations thereof; N is nitrogen atom; O is oxygen atom; and C is carbon atom.

[0009] The term polypropylene as used herein includes polypropylene homopolymer, propylene-alpha olefin copolymer such as propylene-ethylene copolymer, heterophasic polypropylene containing polypropylene matrix and propylene-alpha olefin copolymer dispersed on the matrix. Preferably the polypropylene is a polypropylene homopolymer.

[0010] Advantageously, the process of the present invention resulted in the production of an a-nucleated polypropylene with increased crystallization temperature, improved optical clarity and no negative impact on stereoregularity (minimal change in isotacticity) or tensile strength. As a further advantage, in accordance with the present inventive process, the catalyst slurry or the product stream from the first reactor is not washed or modified before being introduced the stream into the second reactor.

[0011] In addition, as the vinyl cycloalkane is added in the pre-polymerization reactor, the polyvinyl cycloalkane once formed is better dispersed as it is formed in-situ in the prepolymerization reactor. On the other hand, if the vinyl cycloalkane or polyvinyl cycloalkane were to be added in the post polymerization process step such as an extruder, the vinyl cycloalkane or polyvinyl cycloalkane may not be homogenously dispersed to the same extent as described in the present invention where VCH is added in the first reactor. Accordingly, in an aspect of the invention, the process of the present invention, involves no additional nucleating agent being added to the nucleated polypropylene once it is formed.

[0012] Preferably, the nucleated polypropylene has a total luminous transmittance of > 85 %, preferably > 90 %, preferably > 92 % as determined in accordance with ISO 13468, preferably the total luminous transmittance is measured on an injection molded sample having the dimension 40 x 40 x 1 mm or with a sample having thickness of 1 mm; and / or a tensile modulus of > 2000 and < 10000 MPa as determined in accordance with ISO 527-2 / 5A.

[0013] As a further advantage, the use of the vinyl cycloalkane imparts suitable degree of crystallinity in the nucleated polypropylene that is obtained. The degree of crystallinity may be24POLY0067-WO-ORD5 evidenced from the increase in the temperature of crystallinity compared to a polypropylene compound that is free of polyvinyl cycloalkane or any nucleating agent.

[0014] For example, the nucleated polypropylene has a crystallization temperature ATCof > 8°C, preferably > 9°C compared to the crystallization temperature Tcof an identical polypropylene compound that is free of polyvinyl cycloalkane.

[0015] Preferably the nucleated polypropylene has a crystallization temperature Tcin the range of > 120°C and < 140 °C; and a peak melt temperature Tmof > 155°C and < 170 °C, wherein the crystallization temperature Tcand the peak melt temperature Tmof the nucleated polypropylene is determined using Differential Scanning Calorimetry (DSC) with a first heating at a temperature between -90°C to 230°C @ 10°C / min (3 min hold at the end temperature) and a cooling of 230°C to -90°C @ 10°C / min at a heating and a cooling rate of 10°C / min for a 3-5 mg sample, using a nitrogen purge gas at flow rate of 50 ± 5 mL / min, followed by a second heating and cooling cycle identical to the first heating and cooling cycle, with crystallization temperature, Tc, determined from the cooling cycle whereas the melting temperature, Tm, was taken from the second heating step.Catalyst System

[0016] The catalyst system comprises a transition metal-containing solid catalyst compound (also typically referred to as a procatalyst); an organometallic compound (also typically referred to as a co-catalyst) and optionally one or more electron donor compounds (e.g. external electron donors). The transition metal-containing solid catalyst compound comprises a transition metal halide (e.g. titanium halide, chromium halide, hafnium halide, zirconium halide, vanadium halide) supported on a metal or metalloid compound (e.g. a magnesium compound or a silica compound). An overview of such catalyst types is for example given by T. Pullukat and R. Hoff in Catal. Rev. - Sci. Eng. 41, vol. 3 and 4, 389-438, 1999.

[0017] Preferably, the procatalyst comprises at least one internal electron donor represented by Formula I:24POLY0067-WO-ORD6

[0018] , with the substituents R90to R97are as defined herein.

[0019] Preferably, the procatalyst comprises the internal donor represented by the formula:

[0020] The term “procatalysf ’ as used herein means a component of a catalyst composition generally comprising a solid support, a transition metal-containing catalytic species and optionally one or more internal donor.

[0021] The procatalyst may comprise titanium supported on a solid magnesium-containing support, and wherein the procatalyst comprises in wt.% based on the total weight of the procatalyst: magnesium: from 13 to 24, preferably from 14 to 22; titanium: from 1 to 5, preferably froml.5 to 4.

[0022] Preferably, the catalyst system comprises a co-catalyst selected from triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, diisobutylaluminum hydride and dihexylaluminum hydride, preferably the co-catalyst is tri ethyl aluminium .

[0023] Preferably, the catalyst system comprises an external electron donor selected from benzoic acid esters, 1,3-diethers, alkylamino-alkoxysilanes, alkyl-alkoxysilanes, imidosilanes, and alkylimidosilanes. Preferably wherein the external electron donor is an alkyl-alkoxysilane. Preferably wherein the external electron donor is any one of cyclohexylmethyldimethoxysilane, diisobutyldimethoxysilane or diisopropyldimethoxysilane.24POLY0067-WO-ORD7

[0024] The procatalyst may be prepared by a process involving the step of contacting a magnesium-containing support with a halogen-containing titanium compound and an internal electron donor.Preparing the procatalyst

[0025] In particular, the process may involve the steps of step (i) contacting a compound R4zMg X42-z with an alkoxy- or aryloxy-containing silane compound to obtain a first intermediate reaction product, being a solid Mg(OR1)xX12-x, wherein: R4and R1are each a linear, branched or a cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxy carbonyl or alkylaryl groups, and one or more combinations thereof. The hydrocarbyl group may be substituted or unsubstituted and may contain one or more heteroatoms and preferably has from 1 to 20 carbon atoms.

[0026] Preferably R4is phenyl or butyl; X4and X1are each independently selected from the group consisting of fluoride (F-), chloride (CI-), bromide (Br-) or iodide (I-), preferably chloride; z is in a range of larger than 0 and smaller than 2, being 0 < z < 2; x is in a range of larger than 0 and smaller than 2, being 0 < x < 2.

[0027] Step (ii) optionally, in an aspect of the invention, the process may further comprise the step of contacting the first intermediate reaction product obtained in step (i) with at least one activating compound selected from the group formed by activating electron donors and metal alkoxide compounds of formula M1(OR2)v-w(OR3)w or M2(OR2)v-w(R3)w, to obtain a second intermediate product; wherein: M1is a metal selected from the group consisting of Ti, Zr, Hf, Al or Si; M2is a metal being Si; v is the valency of M1or M2; w is smaller than v; R2and R3are each a linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof. The hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms, and preferably has from 1 to 20 carbon atoms; and(iii) contacting the first or second intermediate reaction product, obtained respectively in step i) or (ii), with a halogen-containing Ti-compound and the internal electron.

[0028] Preferably, in step (ii) the first intermediate reaction product obtained in step (i) is contacted with two activating compounds, being an alcohol, preferably ethanol, as activating24POLY0067-WO-ORD8 electron donor, and a titanium tetraalkoxide, preferably titanium tetraethoxide, as metal alkoxide compounds of formula M1(OR2)v-w(OR3)w wherein M1= Ti, v = 4, w = 0 and R2= ethyl.

[0029] Preferably the activator is selected from the group consisting of benzamides, alkylbenzoates, and mono-esters is used.

[0030] Preferably, the activator is selected from the group consisting of ethyl acetate, amyl acetate, butyl acetate, ethyl acrylate, methyl methacrylate, and isobutyl methacrylate, benzamide, methylbenzamide, N,N-dimethylbenzamide, methylbenzoate, ethylbenzoate, n-propylbenzoate, iso-propylbenzoate, n-butylbenzoate, 2-butylbenzoate, and t-butylbenzoate, more preferably ethyl benzoate.

[0031] In some embodiments of the invention, the catalyst may be prepared by the process as described in W02014001257 under Pg 22-Pg 27 of the patent application.Polymerization of vinyl cycloalkane (Pre-polymerization Step)

[0032] In an aspect of the invention, the poly(vinyl cycloalkane), preferably isotactic poly(vinyl cycloalkane), is used as an in-situ nucleating agent i.e the vinyl cycloalkane is prepolymerized prior to the process of preparing the polypropylene. Preferably, the vinyl cycloalkane is selected from vinyl cyclobutane, vinyl cyclopentane, vinyl-3 -methyl cyclopentane, vinyl cyclohexane, vinyl-2-methyl cyclohexane, vinyl-3 -methyl cyclohexane, vinyl norbornane and mixtures thereof.

[0033] Preferably, the vinyl cycloalkane is vinyl cyclohexane and the polyvinyl cycloalkane is polyvinyl cyclohexane (PVCH).

[0034] The first reactor may for example is a pre-polymerization reactor. In some embodiments of the invention, the reaction stream comprises vinyl cycloalkane having at least 6 carbon and the catalyst system. Alternatively, the catalyst system is fed separately into the first reactor.

[0035] Preferably, polymerization of the vinyl cycloalkane is a process of homopolymerization of the vinyl cycloalkane or copolymerization thereof with a small amount (i.e., up to 20 mole.% per mole of the vinyl cycloalkane) of another vinyl cyloalkane or with an a- olefin such as ethylene, propylene or butene. Preferably, the polymerization of the vinyl cycloalkane is a process of homopolymerization of the vinyl cycloalkane.24POLY0067-WO-ORD9

[0036] The polymerization of vinyl cycloalkane may be carried out in presence of solvents.Suitable polymerization solvents include vinyl cycloalkane monomers such as vinyl cyclobutane, vinyl cyclopentane, vinyl-3 -methyl cyclopentane, vinyl cyclohexane, vinyl-2-m ethyl cyclohexane, vinyl-3 -methyl cyclohexane, vinyl norbornane and hydrocarbons such as butane, hexane, heptane, 2,2,4,6,6-pentamethylheptane, benzene, isododecane and toluene.

[0037] Preferably, the polymerization of the vinyl cycloalkane in the first reactor is carried out at any temperature between > 20 °C and < 100°C, preferably between > 20 °C and < 80°C, preferably > 50 °C and < 70°C; and at any pressure between > 0.1 MPa and < 5.0 MPa, preferably between > 0.1 MPa and < 3.0 MPa, preferably between > 0.1 MPa and < 0.3 MPa. There is no particular limitation on the amount of the vinyl cycloalkane that may be polymerized per gram of the catalyst system that is used, but preferably it is 0.1 to 25 g, more preferably 0.1 to 15 g.

[0038] Preferably, the weight ratio of vinyl cycloalkane to the catalyst system present in the first reactor ranges between > 0.1 : 1 and < 10: 1, preferably wherein the weight ratio of vinyl cycloalkane to the catalyst system is 1.1 : 1, preferably 1 : 1.

[0039] Advantageously, the conversion of the vinyl cycloalkane may be adjusted to control the amount of polyvinyl cycloalkane that is formed. For example, the weight ratio of the polyvinyl cycloalkane to the unreacted vinyl cycloalkane present in the product stream may be > 0 and < 0.5. The term “unreacted vinyl cycloalkane” is the portion of vinyl cycloalkane introduced in the first reactor which did not convert to polyvinyl cycloalkane.

[0040] By limiting the extent of conversion from vinyl cycloalkane to polyvinyl cycloalkane, any risk of adverse catalytic performance and to the stereoregularity of the resultant polypropylene is greatly mitigated. In addition, the lower conversion of vinyl cycloalkane to polyvinyl cycloalkane influences a suitable balance in the formation of crystalline and amorphous domain in the final nucleated polypropylene product which in turn affects the optical and mechanical properties of the polymer.

[0041] Preferably, the weight ratio of the polyvinyl cycloalkane obtained in the first reactor to the vinyl cycloalkane supplied to the first reactor, ranges from > 0.05 and < 0.5, preferably > 0.1 and < 0.3.24POLY0067-WO-ORD10

[0042] In other words, it is preferred that the conversion of the vinyl cycloalkane to polyvinyl cycloalkane is at most 50%, preferably > 5% and < 50%, preferably > 10% and < 30%, with regard to the total amount of vinyl cycloalkane monomer fed to the first reactor.Propylene of polymerization in the second reactor

[0043] The polymerization of propylene may for example be carried out in presence of the product stream and hydrogen to obtain the nucleated polypropylene. The polymerization of propylene may be a homopolymerization or a co-polymerization process.

[0044] The product stream is the stream comprising the products obtained from the first reactor and comprises polyvinyl cycloalkane, unreacted vinyl cycloalkane, and the catalyst system. In other words, the polymerization of propylene is carried out in presence of the polyvinyl cycloalkane and the unreacted vinyl cycloalkane that is obtained from the first reactor.

[0045] In some embodiments of the invention, the catalyst system used for the polymerization of the vinyl cycloalkane monomer in the first reactor and the polymerization of propylene in the second reactor is identical.

[0046] The homo-polymerization of propylene or its copolymerization with ethylene may be carried out by any known polymerization methods, for example, by slurry polymerization in a hydrocarbon solvent such as hexanes or and heptane such as (2,2,4,6,6-pentamethylheptane) or isododecane, bulk polymerization in liquefied propylene, or gas-phase polymerization in a propylene gas, etc.

[0047] For the purpose of the present invention, “slurry reactor” designates any reactor, such as a continuous or simple batch stirred tank reactor or loop reactor, operating in bulk or slurry and in which the polymer forms in particulate form. “Bulk” means a polymerization in reaction medium that comprises at least 60 wt-% propylene monomer. According to a preferred embodiment, the slurry reactor comprises a bulk loop reactor. By “gas phase reactor” is meant any mechanically mixed or fluid bed reactor. The gas phase reactor may be a horizontal gas phase reactor or a vertical gas phase reactor. Preferably the gas phase reactor comprises a mechanically agitated fluid bed reactor with gas velocities of at least 0.2 m / sec.

[0048] Preferably, the polymerization of propylene in the second polymerization reactor is carried out at any temperature between > 50 °C and < 120 °C; and at any pressure between > 0.224POLY0067-WO-ORD11MPa and < 8.0 MPa, preferably > 3.0 MPa and < 8.0 MPa; and in the presence of hydrogen, wherein the molar mass ratio of hydrogen to propylene present in the second reactor prior to polymerization is > 0.01 and < 0.06.Nucleated Polypropylene product

[0049] In an aspect of the invention, the invention relates to a nucleated polypropylene, wherein the nucleated polypropylene comprises > 10.0 and < 2000 parts per million (ppm) by weight, preferably > 50.0 and < 100.0, parts per million by weight of polyvinyl cycloalkane; and wherein the nucleated polypropylene has total luminous transmittance of > 85 %, preferably > 90 %, preferably > 92 % as determined in accordance with ISO 13468, measured on an injection molded sample having the dimension 40 x 40 x 1 mm or with a sample having thickness of 1 mm; and a tensile modulus of > 2000 MPa and < 10000 MPa as determined in accordance with ISO 527-2 / 5A; and a change in isotacticity index (I. I.) of > 0 and < 0.5, where change in isotacticity index (LI.) is defined as isotacticity index (I. I.) of the nucleated polypropylene - isotacticity index (LI.) of an identical polypropylene polymer that is free of polyvinyl cycloalkane as a nucleating agent, where isotacticity index (LI.) is determined using13C NMR spectroscopy.

[0050] The presence of polyvinyl cycloalkane in the final product influences nucleation and crystallization properties of the final polypropylene polymer. The extent of conversion of the vinyl cycloalkane to polyvinyl cycloalkane in the first reactor influences the amount of polyvinyl cycloalkane in the final polypropylene product which in turn affect the nucleation and overall crystalline property of the polypropylene which in turn influences the optical and mechanical properties of the nucleated polypropylene. The lower conversion of vinyl cycloalkane to polyvinyl cycloalkane in the first reactor provides a suitable balance of amorphous and crystalline domain in the final polypropylene product.

[0051] The property of nucleated polypropylene is influenced by the process of preparing the nucleated polypropylene in accordance with the invention. In an aspect of the invention, the invention relates to a nucleated polypropylene obtained from or obtainable by the process of the present invention, wherein the nucleated polypropylene comprises > 10.0 and < 2000 parts per million (ppm) by weight, preferably > 50.0 and < 100.0, parts per million (ppm) by weight of polyvinyl cycloalkane; and wherein the nucleated polypropylene has total luminous transmittance24POLY0067-WO-ORD12 of > 85 %, preferably > 90 %, preferably > 92 % as determined in accordance with ISO 13468, preferably the total luminous transmittance is measured on an injection molded sample having the dimension 40 x 40 x 1 mm or with a sample having thickness of 1 mm; and a tensile modulus of> 2000 MPa and < 10000 MPa as determined in accordance with ISO 527-2 / 5A; and a change in isotacticity index (LI.) of > 0 and < 0.5, where change in isotacticity index (LI.) is defined as isotacticity index (LI.) of the nucleated polypropylene - isotacticity index (LI.) of an identical polypropylene polymer that is free of polyvinyl cycloalkane as a nucleating agent, where isotacticity index (LI.) is determined using13C NMR spectroscopy.

[0052] In an aspect of the invention, the invention relates to a nucleated polypropylene obtained from or obtainable by the process of the present invention, wherein the nucleated polypropylene comprises > 10.0 and < 2000 parts per million (ppm) by weight, preferably > 50.0 and < 100.0, parts per million by weight of polyvinyl cycloalkane; and wherein the nucleated polypropylene has total luminous transmittance of > 85 %, preferably > 90 %, preferably > 92 % as determined in accordance with ISO 13468, measured on an injection molded sample having the dimension 40 x 40 x 1 mm or with a sample having thickness of 1 mm; and a tensile modulus of> 2000 MPa and < 10000 MPa as determined in accordance with ISO 527-2 / 5A; and a change in isotacticity index (LI.) of > 0 and < 0.5, where change in isotacticity index (LI.) is defined as isotacticity index (LI.) of the nucleated polypropylene - isotacticity index (LI.) of an identical polypropylene polymer that is free of polyvinyl cycloalkane as a nucleating agent, where isotacticity index (LI.) is determined using13C NMR spectroscopy.

[0053] The relationship “change in isotacticity index (LI.)” signifies that the difference in isotacticity index (LI.) of the nucleated polypropylene as obtained by the process of the present invention and that for a similar polypropylene that is free of polyvinyl cycloalkane as nucleating agent, is minimal. In other words, the incorporation of the polyvinyl cycloalkane to the polypropylene did not affect the stereochemistry or isotacticity of the resultant nucleated polypropylene.

[0054] In other words, change in isotacticity index (LI.) is the absolute difference of (isotacticity index (LI.) of the nucleated polypropylene) - (isotacticity index (LI.) of an identical polypropylene polymer that is free of polyvinyl cycloalkane as a nucleating agent).24POLY0067-WO-ORD13

[0055] Advantageously, the nucleated polypropylene may be used to prepare articles which require high optical transparency and tensile strength. For example, optical eye wear, packaging material, health care article, electronic goods. The article may comprise > 90.0 wt.%, > 96.0 wt.%, preferably 100.0 wt.% with regard to the total weight of the nucleated polypropylene.

[0056] Preferably in an aspect of the invention, the invention relates to an article comprising the nucleated polypropylene of the present invention, wherein the article comprises > 90.0 wt.%, with regard to the total weight of the article, of the nucleated polypropylene.

[0057] The invention will now be demonstrated with the following non-limiting examples.EXAMPLES

[0058] Purpose: To evaluate the tensile and optical performance of nucleated polypropylene obtained by the process of the present invention (IE1) in comparison to a polypropylene that is free of nucleating agent (CE). The comparative sample is a polypropylene homopolymer procured from SABIC. Vinyl cyclohexane (695-12-5) was used as the vinyl cycloalkane. The catalyst was obtained from SABIC.Catalyst system preparation: Step A) Butyl Grignard formation

[0059] A 1 .7 L stirred flask, fitted with a reflux condenser and a funnel, was filled with magnesium powder (40.0 g, 1 .65 mol). The flask was brought under nitrogen. The magnesium was dried at 80°C for 2 hours under nitrogen purge, after which dibutyl ether (200 ml), iodine (0.05 g) and n-chlorobutane (10 ml) were successively added and stirred at 120 rpm. The temperature was maintained at 80°C and a mixture of n-chlorobutane (146 ml) and dibutyl ether (1 180 ml) was slowly added over 3 hours. The reaction mixture was stirred for another 3 hours at 80°C. Then the stirring and heating were stopped and the small amount of solid material was allowed to settle for 24 hours. By decanting the colourless solution above the precipitate, a solution of butyl magnesium chloride with a concentration of 0.90 mol Mg / L was obtained.Step B) Preparation of the first intermediate reaction product

[0060] The solution of reaction product of step A (500 ml, 0.45 mol Mg) and 260 ml of a solution of tetraethoxy silane (TES) in dibutyl ether (DBE), (47 ml of TES and 213 ml of DBE), were cooled to 5°C, and then were fed simultaneously to a mixing device (minimixer) of 0.45 ml volume equipped with a stirrer and jacket. The minimixer was cooled to 5°C by means of cold water24POLY0067-WO-ORD14 circulating in the minimixer's jacket. The stirring speed in the minimixer was 1000 rpm. From the mixing device, the mixed components were directly dosed into a 1.3 liter reactor fitted with blade stirrer and containing 350 ml of dibutyl ether. The dosing temperature of the reactor was 35 °C and the dosing time was 360 min. The stirring speed in the reactor was 250 rpm at the beginning of dosing and was gradually increased up to 450 rpm at the end of dosing stage. On completion of the dosing, the reaction mixture was heated up to 60°C in 30 minutes and held at this temperature for 1 hour. Then the stirring was stopped and the solid substance was allowed to settle. The supernatant was removed by decanting. The solid substance was washed three times using with 700 ml of heptane at a reactor temperature of 50°C for three times. A pale yellow solid substance, reaction product B (the solid first intermediate reaction product; the support), was obtained upon drying with a nitrogen purge.Step C) Preparation of the activated supportStep Cl) first activation step

[0061] In inert nitrogen atmosphere at 20°C in a 1000 ml glass flask equipped with a mechanical agitator was filled with 50 g of reaction product B, dispersed in 500 ml of heptane and stirred at 250 rpm. Subsequently, a solution of 2.7 ml ethanol (EtOH / Mg=0.1) in 20 ml heptane was dosed under stirring during 1 hour. After keeping the reaction mixture at 20°C for 30 minutes, a solution of 9.5 ml titanium tetraethoxide (TET / Mg=0.1) in 20 ml of heptane was added for 1 hour. The slurry was slowly allowed to warm up to 30°C over 30 minutes and held at that temperature for another 2 hours. Finally, the supernatant liquid was decanted from the solid reaction (partly activated support) which was washed once with 500 ml of heptane at 30°C and dried using a nitrogen purge.Step C2) second activation step

[0062] In inert nitrogen atmosphere at 25°C in a 1000 ml glass flask equipped with a mechanical agitator was filled with 50 g of partly activated support obtained in step Cl dispersed in 500 ml of heptane and stirred at 250 rpm. Subsequently, a solution of 6.3 ml ethanol (EtOH / Mg=0.3), 20.8 ml of toluene and 37.5 ml of heptane was dosed at 25°C under stirring during 1 hour. The slurry was slowly allowed to warm up to 30°C over 30 minutes and held at that temperature for another 3 hours. Finally, the supernatant liquid was decanted from the solid reaction24POLY0067-WO-ORD15 product (second intermediate reaction product; activated support) which was washed once with 500 ml of heptane at 25°C and dried using a nitrogen purge.

[0063] Step D) Preparation of the procatalystStage I of procatalyst preparation

[0064] A 300 ml reactor-filter flask was brought under nitrogen and 125 mL of titanium tetrachloride was added, then 5.5 g of activated support obtained in step C2 in 15 ml of heptane was added to the reactor. The contents of the reactor were stirred for 60 minutes at room 25°C. Then, 0.83 ml of ethylbenzoate, EB (EB / Mg=0.30 molar ratio) in 4 ml of chlorobenzene was added to the reactor in 30 minutes. Temperature of reaction mixture was increased to 105°C and then the reaction mixture was stirred at 105°C for 90 minutes. The contents of the flask were filtered, after which the solid product was washed with chlorobenzene (125 ml) at 100 to 105°C for 20 minutes. Then, the contents of the flask were filtered.

[0065] Stage II of procatalyst preparation

[0066] A mixture of titanium tetrachloride (62.5 ml) and chlorobenzene (62.5 ml) was added to the reactor. Then, 0.438 g of the internal donor (ID / Mg = 0.03) in 4 ml of chlorobenzene was added to the reactor in 10 minutes. The reaction mixture was stirred at 105°C for 60 minutes. Then, the contents of the flask were filtered.

[0067] Stage III of procatalyst preparation

[0068] A mixture of titanium tetrachloride (62.5 ml) and chlorobenzene (62.5 ml) was added to the reactor. Then, 0.438 g of the internal donor (ID / Mg = 0.03) in 4 ml of chlorobenzene was added to the reactor in 10 minutes. The reaction mixture was stirred at 105°C for 60 minutes. Then, the contents of the flask were filtered.

[0069] Stage IV of procatalyst preparation

[0070] A mixture of titanium tetrachloride (62.5 ml) and chlorobenzene (62.5 ml) was added to the reactor. Then, 0.438 g of the internal donor (ID / Mg = 0.03) in 4 ml of chlorobenzene was added to the reactor in 10 minutes. The reaction mixture was stirred at 105°C for 30 minutes. Then, the contents of the flask were filtered.Work up of procatalyst preparation

[0071] The solid product obtained was washed five times with 125 ml of heptane starting at 60°C with 5 minutes stirring per wash prior to filtration. The temperature was gradually reduced24POLY0067-WO-ORD16 from 60 to 25°C during the washings. Finally, the solid product obtained was dried using a nitrogen purge at a temperature of 25°C for 2 hours.

[0072] Vinyl cyclohexane (VCH) polymerization - To a vial containing 35.8 uL of TEA1 (co-catalyst) and 4.525 mL of isododecane was added 270 uL of 0.2 M diisobutyldimethoxysilane (external donor) in isododecane. After 10 minutes, this mixture was added to a glass vial containing 100 mg of the catalyst powder consisting of 2.6% titanium by weight and 19.0 wt.% of Magnesium, and a mixture of ethyl benzoate (activator) and internal donor (ID). The internal donor (ID) used was:

[0073] After occasional stirring for 20 minutes, 124.2 uL of VCH (aimed at 1 g VCH per g catalyst) was added to the vial before loading it into an autoclave kept at 20 °C. The autoclave (first reactor) was brought to 70 °C over 30 minutes while stirring at 200 rpm then maintained at these conditions for 24 hours. The VCH conversion was estimated to be 20% meaning 0.2 g PVCH / g catalyst based on a separate prepolymerization run. This was followed by isolating the PVCH product after quenching, washing and drying. The product stream from the autoclave comprising the pre-polymerized catalyst slurry, residual VCH monomer (unreacted VCH) was used fed into the second reactor for the propylene polymerization step.

[0074] VCH Conversion Estimation” - A separate VCH polymerization run using conditions as described above, which was conducted where instead of using the pre-polymerized catalyst slurry in a subsequent propylene homo-polymerization run, the entire pre-polymerized catalyst slurry was first quenched with isopropanol and then filtered and washed several times with isopropanol. Finally, the prepolymer was dried at 80 °C under vacuo overnight and the prepolymer mass was determined the following day using a weight balance to calculate the VCH conversion in units of g VCH per g catalyst based on the mass balance.

[0075] Propylene polymerization To a 10L stirred tank reactor (second reactor) equipped with a bladed stirrer and baffles, 5 L of hexane was added at room temperature together with 5.0 mL of a 1.825 M triethylaluminium solution (cocatalyst) in hexane and 2.3 mL of a 0.201 M24POLY0067-WO-ORD17 diisobutyldimethoxysilane (external donor) solution in hexane. The reactor was subsequently purged with a flow of propylene and hydrogen at a molar ratio of 0.05 for 5 minutes followed by heating the reactor to 70 °C under the same flow until a pressure of 6 bar is reached. At this point the hydrogen supply is closed and the VCH prepolymerized catalyst slurry in isododecane was injected into the second reactor, which was obtained in the pre-polymerization reactor (first reactor). The external donor used was identical to that for VCH prepolymerization.

[0076] Reactor pressure was maintained at 6.0 bar with propylene feed for 60 minutes after catalyst injection after which the propylene feed was stopped, reactor overpressure was removed and reactor contents were cooled down to 25 °C. The polymer slurry was then directly fed to a filter to remove diluent followed by drying the polymer powders for 6 hours in an oven at 50 °C and reduced pressure.

[0077] Comparative example 1 - The polypropylene for the comparative example 1, was prepared by utilizing the same catalyst as used in the inventive example, vinylcyclohexane prepolymerization step above except that vinylcyclohexane was not added in the prepolymerization step. Instead, the same mass amount of catalyst in isododecane was added directly to the second reactor under the identical polymerization conditions to obtain a non-nucleated homopolymer of polypropylene.

[0078] Compounding and Injection Molding Both the Inventive example 1 (i.ePVCH in-situ nucleated) and the comparative example 1 i.e non-nucleated polypropylene powders were compounded in a Pl 1 micro compounder using a basic additive package consisting of 1000 ppm Irganox 1010, 1000 ppm Irgafos 168 and 500 ppm Calcium stearate. The thus obtained granulates were then processed using a Babyplast injection molding machine to obtain the samples used for material evaluation.

[0079] Results: The results from the polymerization is as given below:Table 124POLYOQ67-WO-ORD

[0080] As can be determined from Table 1 above, the crystallization temperature, Tc, from the PVCH nucleated polypropylene sample was 10 °C higher than that of the comparative, nonnucleated polypropylene sample and in addition, the isotacticity of the PVCH nucleated polypropylene powder showed no decrease in stereoselectivity despite the propylene polymerization being carried out in presence of large amount of unreacted VCH monomer after the pre-polymerization step. The inventive process clearly demonstrated the benefits of producing polypropylene with excellent optical clarity while maintaining the required tensile property without the need of washing the catalyst slurry.

[0081] Test methods: The following test methods were used:

[0082] 13C-NMR - Polymer samples were dissolved at 130 °C in C2D2CI4 containing 2,6-Di-tert-butyl-p-cresol as stabilizer. The NMR spectra were recorded on a Bruker Avance500 spectrometer equipped with a cryogenically cooled probe head operating at 125°C. The isotacticity index (LI.) value was based on the occurrence (%) of the mmmm pentads.

[0083] Differential Scanning Calorimetry (DSC) - DSC measurements were performed using a TA Discovery DSC 250. All measurements were performed under a flow of nitrogen to avoid polymer degradation. The methodology consists of a first heating step from -90 °C to 230 °C with a 10 °C / min ramp and 3 minute hold time at end temperature followed by a cooling cycle back to -90 °C and a second heating step to 230 °C with the same ramp used. The crystallization temperature, Tc, was determined from the cooling cycle whereas the melting temperature, Tm, was taken from the second heating step.

[0084] The polymer samples were measured as 40 x 40 x 1 mm thick plaques obtained from injection molding and according to ISO 13468. Each sample was measured 4 times and the average clarity value is reported.

Claims

POLY0067-WO-ORD19CLAIMS1. A process for producing a nucleated polypropylene, comprising the steps of:(i) supplying a reaction stream comprising vinyl cycloalkane having at least 6 carbon atoms, into a first reactor;(ii) polymerizing the vinyl cycloalkane in presence of a catalyst system to obtain a product stream, wherein the product stream comprises polyvinyl cycloalkane, unreacted vinyl cycloalkane, and the catalyst system;(iii) supplying the product stream into a second polymerization reactor containing propylene; and(iv) polymerizing the propylene in presence of the product stream and hydrogen to obtain the nucleated polypropylene; and wherein the weight ratio of the polyvinyl cycloalkane to the unreacted vinyl cycloalkane present in the product stream is > 0 and < 0.5; and wherein the catalyst system comprises a procatalyst comprising at least one internal electron donor represented by any one of the Formula I or Formula II:wherein for Formula I each R90group is independently a substituted or an unsubstituted aromatic group; R91, R92, R93, R94, R95, and R96are each independently selected from a hydrogen or a linear, branched or cyclic hydrocarbyl group selected from alkyl, alkenyl, aryl, aralkyl, or alkylaryl groups, and one or more combinations thereof; R97is a hydrogen or a linear, branched or cyclic hydrocarbyl group selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; N is a nitrogen atom; O is an oxygen atom; and C is a carbon atom; andPOLY0067-WO-ORD20 wherein for Formula II: R81, R82, R83, R84, R85, and R86are the same or different and are independently hydrogen or a linear, branched or cyclic hydrocarbyl group selected from alkyl, alkenyl, aryl, aralkyl, or alkylaryl groups, and one or more combinations thereof; R87is a hydrogen or a linear, branched or cyclic hydrocarbyl group, selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; each R80group is independently a linear, branched or cyclic hydrocarbyl group selected from alkyl, alkenyl, aryl, aralkyl, or alkylaryl groups, and one or more combinations thereof; N is nitrogen atom; O is oxygen atom; and C is carbon atom.

2. The process of claim 1, wherein the procatalyst comprises at least one internal electron donor represented by Formula I:Rgi R92, with the substituents R90to R97are as defined herein.

3. The process according to any one of claims 1-2, wherein the procatalyst comprises the internal donor represented by the formula:

4. The process according to any one of claims 1-3, wherein the procatalyst comprises titanium supported on a solid magnesium-containing support, and wherein the procatalyst comprises in wt.% based on the total weight of the procatalyst: magnesium: from 13 to 24, preferably from 14 to 22; titanium: from 1 to 5, preferably froml.5 to 4.POLY0067-WO-ORD215. The process according to any one of claims 1-4, wherein the catalyst system comprises a co-catalyst selected from triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, di-isobutylaluminum hydride and dihexylaluminum hydride, preferably the co-catalyst is triethylaluminium.

6. The process according to any one of claims 1-5, wherein the catalyst system comprises an external electron donor selected from benzoic acid esters, 1,3-diethers, alkylaminoalkoxysilanes, alkyl-alkoxysilane, imidosilanes, and alkylimidosilanes, preferably wherein the external electron donor is an alkyl-alkoxysilane, preferably wherein the external electron donor is any one of cyclohexylmethyldimethoxy silane, diisobutyldimethoxy silane or diisopropyldimethoxysilane.

7. The process according to any one of claims 1-6, wherein the vinyl cycloalkane is selected from vinyl cyclobutane, vinyl cyclopentane, vinyl-3 -methyl cyclopentane, vinyl cyclohexane, vinyl-2-m ethyl cyclohexane, vinyl-3 -methyl cyclohexane, vinyl norbornane and mixtures thereof.

8. The process according to any one of claims 1-7, wherein the vinyl cycloalkane is vinyl cyclohexane and the polyvinyl cycloalkane is polyvinyl cyclohexane (PVCH).

9. The process according to any one of claims 1-8, wherein the weight ratio of the polyvinyl cycloalkane obtained in the first reactor to the vinyl cycloalkane supplied to the first reactor, ranges from > 0.05 and < 0.5, preferably > 0.1 and < 0.3.

10. The process according to any one of claims 1-9, wherein the polymerization of vinyl cycloalkane in the first reactor is carried out at any temperature between > 20 °C and < 100°C, preferably between > 20 °C and < 80°C, preferably > 50 °C and < 70°C; and at anyPOLYOQ67-WO-ORD22 pressure between > 0.1 MPa and < 5.0 MPa, preferably between > 0.1 MPa and < 3.0 MPa, preferably between > 0.1 MPa and < 0.3 MPa.

11. The process according to any one of claims 1-10, wherein the polymerization of propylene in the second polymerization reactor is carried out at any temperature between > 50 °C and < 120 °C; and at any pressure between > 0.2 MPa and < 8.0 MPa, preferably > 3.0 MPa and < 8.0 MPa; and in the presence of hydrogen, wherein the molar mass ratio of hydrogen to propylene present in the second reactor prior to polymerization is > 0.01 and < 0.06.

12. The process according to any one of claims 1-11, wherein the nucleated polypropylene has a total luminous transmittance of > 85 %, preferably > 90 %, preferably > 92 % as determined in accordance with ISO 13468, preferably measured on an injection molded sample having the dimension 40 x 40 x 1 mm or with a sample having thickness of 1 mm; and / or a tensile modulus of > 2000 MPa and < 10000 MPa as determined in accordance with ISO 527-2 / 5 A.

13. The process according to any one of claims 1-12, wherein the nucleated polypropylene has a crystallization temperature ATC> 8°C, preferably > 9°C compared to the crystallization temperature Tcof an identical polypropylene compound that is free of polyvinyl cycloalkane, preferably wherein the nucleated polypropylene has a crystallization temperature Tcin the range of > 120°C and < 140 °C; and a peak melt temperature Tmof > 155°C and < 170 °C, wherein the crystallization temperature Tcand the peak melt temperature Tmof the nucleated polypropylene is determined using Differential Scanning Calorimetry (DSC) with a first heating at a temperature between -90°C to 230°C @ 10°C / min (3 min hold at the end temperature) and a cooling of 230°C to -90°C @ 10°C / min at a heating and a cooling rate of 10°C / min for a 3-5 mg sample, using a nitrogen purge gas at flow rate of 50 ± 5 mL / min, followed by a second heating and cooling cycle identical to the first heating and cooling cycle, with crystallization temperature, Tc, determined fromPOLY0067-WO-ORD23 the cooling cycle whereas the melting temperature, Tm, was taken from the second heating step.

14. A nucleated polypropylene obtained from or obtainable by the process as claimed in any one of claims 1-13, wherein the nucleated polypropylene comprises > 10.0 and < 2000 parts per million (ppm) by weight, preferably > 50.0 and < 100.0, parts per million by weight of polyvinyl cycloalkane; and wherein the nucleated polypropylene has total luminous transmittance of > 85 %, preferably > 90 %, preferably > 92 % as determined in accordance with ISO 13468, preferably the total luminous transmittance is measured on an injection molded sample having the dimension 40 x 40 x 1 mm or with a sample having thickness of 1 mm; and a tensile modulus of > 2000 MPa and < 10000 MPa as determined in accordance with ISO 527-2 / 5A; and a change in isotacticity index (I. I.) of > 0 and < 0.5, where change in isotacticity index (I. I.) is defined as isotacticity index (I. I.) of the nucleated polypropylene - isotacticity index (I. I.) of an identical polypropylene polymer that is free of polyvinyl cycloalkane as a nucleating agent, where isotacticity index (LI.) is determined using13C NMR spectroscopy.

15. An article comprising the nucleated polypropylene according to claim 14, wherein the article comprises > 90.0 wt.%, with regard to the total weight of the article, of the nucleated polypropylene.

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