Highly ductile, high modulus, phthalate-free impact propylene copolymer

Abstract

The present invention provides a phthalate-free impact polypropylene copolymer and a method for its preparation that is produced directly from a polymerization reactor system without the incorporation of additional components that significantly alter the physical properties of the resulting polymer. The copolymer according to the present invention has both low temperature ductility and a high flexural modulus, and the polymer is produced in the presence of a phthalate-free ZN catalyst containing a urea component.

Description

[Technical Field]

[0001]

[0001] The present invention relates to phthalate-free impact propylene copolymer compositions and methods for their preparation. More specifically, the present invention relates to phthalate-free polypropylene copolymers having low temperature impact ductility and high flexural modulus. Polymers made according to the present invention possess physical properties previously achievable only through post-reactor processing steps, typically involving blending with other polymeric materials. The compositions obtained according to the present invention are further characterized by an excellent impact / stiffness balance. [Background technology]

[0002] Impact-resistant propylene polymer compositions are very well known in the art. They typically consist of a relatively crystalline propylene polymer fraction and a relatively low-crystalline copolymer fraction. The relatively crystalline fraction is generally a propylene homopolymer characterized by high isotacticity. The relatively low-crystalline fraction is generally a propylene copolymer, particularly a propylene-ethylene copolymer having an ethylene content ranging from 15 to 75% by weight. Prior art compositions can be prepared by several methods, including mechanical blending of the two polymer components. However, the preferred method is in-reactor preparation by a series of polymerization steps carried out in one or two reactors. Typically, in the first stage, propylene is homopolymerized or copolymerized with small amounts of other olefins to produce a highly crystalline fraction, and in the second stage, the reaction mixture contains a higher amount of olefin comonomer. This method is primarily used industrially and is preferably carried out in two different reactors, which can operate according to the same or different polymerization techniques. In particular, the first stage can be carried out in a liquid phase reactor or a gas phase reactor, while the second stage is usually carried out in a gas phase reactor to avoid dissolution of the low crystalline fraction in the reaction bath.

[0003] In this prior art process, the performance of the catalyst is crucial. Indeed, the catalyst system must be capable of producing a highly isotactic propylene (co)polymer in the first stage, and a copolymer in the second stage in which the olefin comonomer units are well distributed along and between the polymer chains in order to obtain a low-crystalline copolymer that imparts impact resistance to the polymer composition. This requires a high polymerization activity, since it is crucial to have sufficient activity in the second stage of the (co)polymerization to maintain an acceptable level of plant productivity. Due to the fact that there are multiple polymerization steps and that a certain weight balance must be maintained between the two polymer fractions, the catalyst must be able to maintain the required level of reactivity in the second, gas-phase polymerization step. This is crucial, since reactivity in the gas phase is related to the amount of low-crystalline copolymer and, therefore, the amount of crystalline polymer matrix for a given balance of properties. If the reactivity in the gas phase is too low, the productivity of the first polymerization stage must be reduced to achieve the compositional target.

[0004]

[0004] Therefore, it is desirable to have a catalyst with improved second-stage gas-phase reactivity. Numerous attempts have been made to produce high-impact propylene polymers. For example, U.S. Patent No. 7,348,381 disclosed polyolefins with high flexural modulus and low-temperature ductility produced by catalysts containing phthalate and 1,3-diether internal donors. U.S. Patent Application Publication No. 2010 / 0016510 disclosed heterophasic polypropylene (co)polymers with high melt flow and good hardness.

[0005]

[0005] Meanwhile, due to environmental safety concerns, there has been an increasing demand for phthalate-free polypropylene (co)polymers. U.S. Patent Nos. 9,068,928 and 9,068,029 disclose impact-resistant propylene polymers produced by phthalate-free catalysts containing internal donors, including magnesium halides, titanium compounds with succinic acid, and 1,3-diethers as internal donors.

[0006]

[0006] Recently, commonly owned and co-pending U.S. Patent Application Publication No. 2021 / 0101211, which is incorporated by reference in its entirety, discloses a phthalate-free catalyst component for propylene polymers produced by contacting magnesium ethoxide with titanium halides in the presence of internal donors including urea, carbonate ethers, and 1,3-diethers, producing polymers with high flexural modulus and high melt flow, but does not teach or describe the preparation of phthalate-free impact resistant propylene (co)polymers. Summary of the Invention

[0007]

[0007] The present invention provides a phthalate-free propylene impact (co)polymer composition having low temperature impact ductility and high flexural modulus, wherein the preparation of the copolymer is carried out in the presence of a phthalate-free catalyst system comprising (a) a phthalate-free catalyst component obtained by contacting a magnesium halide, a titanium compound having at least a Ti-halogen bond, and one or more electron donor compounds including urea, carbonate ethers and 1,3-diethers, (b) an alkylaluminum compound, and optionally (c) an external electron donor compound.

[0008] The one or more urea-containing electron donor compounds are preferably represented by Formula I:

[0009] [ka]

[0010] where R 1 , R 2 , R 3 , and R 4R may be the same or different and are independently selected from hydrogen, an aliphatic hydrocarbon group having 1 to 20 carbon atoms, an alicyclic hydrocarbon group having 3 to 20 carbon atoms, an aromatic hydrocarbon group having 6 to 20 carbon atoms, or a heteroatom containing hydrocarbon group of 1 to 20 carbon atoms. 1 , R 2 , R 3 , and R 4 Two or more of may be joined to form one or more saturated or unsaturated monocyclic or polycyclic rings.

[0011]

[0009] A method for producing phthalate-free propylene impact (co)polymers comprises the following steps: (1) first producing a propylene (co)polymer having at least 85% by weight insoluble matter in xylene at 25°C in a gas phase or bulk propylene liquid phase reactor, optionally in the presence of ethylene; and (2) in the next step, carrying out polymerization in the gas phase in the presence of a mixture of propylene and ethylene to produce a propylene impact copolymer. DETAILED DESCRIPTION OF THE INVENTION

[0012] In a preferred embodiment of the present invention, a polypropylene impact (co)polymer is produced using a catalyst system comprising a phthalate-free Ziegler-Natta (ZN) catalyst component (a), an alkylaluminum component (b), and optionally an external electron donor component (c). The phthalate-free ZN catalyst component (a) is produced using well-known techniques by contacting titanium chloride with magnesium ethoxide in the presence of an internal electron donor comprising a 1,3-diether, a carbonate ether, and a urea compound.

[0013] The one or more urea-containing electron donor compounds are preferably of formula I:

[0014] [ka]

[0015] where R 1 , R 2 , R 3 , and R 4 R may be the same or different and are independently selected from hydrogen, an aliphatic hydrocarbon group having 1 to 20 carbon atoms, an alicyclic hydrocarbon group having 3 to 20 carbon atoms, an aromatic hydrocarbon group having 6 to 20 carbon atoms, or a heteroatom containing hydrocarbon group of 1 to 20 carbon atoms. 1 , R 2 , R 3 , and R 4 Two or more of may be joined to form one or more saturated or unsaturated monocyclic or polycyclic rings.

[0016] Examples of 1,3-diether compounds include 2-(2-ethylhexyl)-1,3-dimethoxypropane, 2-isopropyl-1,3-dimethoxypropane, 2-butyl-1,3-dimethoxypropane, 2-sec-butyl-1,3-dimethoxypropane, 2-cyclohexyl-1,3-dimethoxypropane, 2-phenyl-1,3-dimethoxypropane, 2-tert-butyl-1,3-dimethoxypropane, 2-cumyl-1,3-dimethoxypropane, 2-(2-phenylethyl)-1,3-dimethoxypropane, 2,2-diethyl-1,3-diethoxypropane, 2,2-dicyclopentyl-1,3-dimethoxypropane, 2,2-dipropyl-1,3-diethoxypropane, 2,2-dibutyl-1,3-di Ethoxypropane, 2-methyl-2-ethyl-1,3-dimethoxypropane, 2-methyl-2-propyl-1,3-dimethoxypropane, 2-methyl-2-benzyl-1,3-dimethoxypropane, 2,2-diphenyl-1-dimethoxypropane, 2,2-dibenzyl-1,3-dimethoxypropane, 2-isopropyl-2-cyclopentyl-1,3-dimethoxypropane, 2,2-bis(cyclohexylmethyl)-1,3-dimethoxypropane, 2,2-diisobutyl-1,3-diethoxypropane, 2,2-diisobutyl-1,3-dibutoxypropane, 1,1-bis(methoxymethyl)-7-(3,3,3-trifluoropropyl)indene, 1,1-bis(methoxymethyl)-7-trimethylsilylindene;1,1-bis(methoxymethyl)-7-trifluoromethylindene, 1,1-bis(methoxymethyl)-4,7-dimethyl-4,5,6,7-tetrahydroindene, 1,1-bis(methoxymethyl)-7-methylindene, 1,1-bis(methoxymethyl)-1H-benzo[e]indene, 1,1-bis(methoxymethyl)-1H-2-methylbenzo[e]indene, 9,9-bis(methoxymethyl)fluorene, 9,9-bis(methoxymethyl)-2,3,6,7-tetramethylfluorene, 9,9-bis(methoxymethyl)-2,3,4,5,6,7-hexafluorofluorene, 9,9-bis(methoxymethyl)-2,3-benzofluorene , 9,9-bis(methoxymethyl)-2,3,6,7-dibenzofluorene, 9,9-bis(methoxymethyl)-2,7-diisopropylfluorene, 9,9-bis(methoxymethyl)-1,8-dichlorofluorene, 9,9-bis(methoxymethyl)-2,7-dicyclopentylfluorene, 9,9-bis(methoxymethyl)-1,8-difluorofluorene, 9,9-bis(methoxymethyl)-1,2,3,4-tetrahydrofluorene, 9,9-bis(methoxymethyl)-1,2,3,4,5,6,7,8-octahydrofluorene, and 9,9-bis(methoxymethyl)-4-tert-butylfluorene;

[0017]

[0013] Examples of carbonate ethers include, but are not limited to, (2-methoxyethyl)methyl carbonate, (2-ethoxyethyl)methyl carbonate, (2-propoxyethyl)methyl carbonate, (2-butoxyethyl)methyl carbonate, (2-(2-ethoxyethyloxy)ethyl)methyl carbonate, (2-benzyloxyethyl)methyl carbonate, (2-methoxypropyl)methyl carbonate, (2-ethoxypropyl)methyl carbonate, (2-methyl-2-methoxybutyl)methyl carbonate, (2-methyl-2-ethoxybutyl)methyl carbonate, (2-methyl-2-methoxypentyl)methyl carbonate, (2-methyl-2-ethoxypentyl)methyl carbonate, (1-phenyl-2-methoxypropyl)methyl carbonate, (2-methoxyethyl)ethyl carbonate, and (2-ethoxyethyl)ethyl carbonate.

[0018] Examples of the urea compound represented by formula I include N,N,N',N'-tetramethylurea, N,N,N',N'-tetraethylurea, N,N,N,N'-tetrapropylurea, N,N,N'N'-tetrabutylurea, N,N,N'N'-tetrapentylurea, N,N,N',N'-tetrahexylurea, N,N,N',N'-tetra(cyclopropyl)urea, N,N,N',N'-tetra(cyclohexyl)urea, N,N,N',N'-tetraphenylurea, bis(butylene)urea, Urea, bis(pentylene)urea, N,N'-dimethylethyleneurea, N,N'-dimethylpropyleneurea, N,N'-dimethyl(2-(methylaza)propylene)urea, and N,N'-dimethyl(3-(methylaza)pentylene)urea, n-amyltriphenylurea, n-hexyltriphenylurea, n-octyltriphenylurea, n-decyltriphenylurea, n-octadecyltriphenylurea, n-butyltritolylurea, n-butyltrinaphthylurea, n -Hexyltrimethylurea, n-hexyltriethylurea, n-octyltrimethylurea, dihexyldimethylurea, dihexyldiethylurea, trihexylmethylurea, tetrahexylurea, n-butyltricyclohexylurea, t-butyltriphenylurea, 1,1-bis(p-biphenyl)-3-methyl-3-n-octadecylurea, 1,1-di-n-octadecyl-3-t-butyl-3-phenylurea; 1-p-biphenyl-1-methyl-3-n-octadecyl 1-methyl-1-n-octadecyl-3-p-biphenyl-3-o-tolylurea; m-terphenyl-tri-t-butylurea, 1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidinone, 1,3-dipropyl-2-imidazolidinone, 1,3-dibutyl-2-imidazolidinone, 1,3-dimethyl-3,4,5,6-tetrahydro-2-pyrimidinone, N,N-dimethyl-N,N,diphenylurea.

[0019] The alkylaluminum compound (b) is preferably selected from aluminum alkyls having the formula AlR3, where R is an alkyl having 1 to 8 carbon atoms, and the three R groups may be the same or different. Examples of suitable aluminum alkyls are trimethylaluminum (TMA), triethylaluminum (TEAL), and triisobutylaluminum (TIBAL). A preferred aluminum alkyl is TEAL.

[0020] Preferred external electron donor compounds have the formula R 1 R 2 Si(OR 3 ) a where a is an integer from 1 to 3, and R 1 , R 2 and R 3is an alkyl, cycloalkyl, or aryl radical having 1 to 18 carbon atoms, optionally containing heteroatoms. Particularly preferred external electron donor compounds are methylcyclohexyldimethoxysilane, diphenyldimethoxysilane, methyl-t-butyldimethoxysilane, dicyclopentyldimethoxysilane, 2-ethylpiperidinyl-2-t-butyldimethoxysilane, 1,1,1-trifluoropropyl-2-ethylpiperidinyl-dimethoxysilane, and 1,1,1-trifluoropropyl-methyl-dimethoxysilane. Silicon compounds include, but are not limited to, cyclohexylmethyldimethoxysilane, cyclohexylethyldimethoxysilane, isobutylisopropyldimethoxysilane, diphenyldimethoxysilane, isobutylisopropyldimethoxysilane, phenyltriethoxysilane, 3,3,3-trifluoropropylmethyldimethoxysilane, diisopropyldimethoxysilane, octylmethyldimethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, n-propyltrimethoxysilane, di-t-butyldimethoxysilane, cyclopentyl-1,1-dimethyl-2,2-dimethylethyldimethoxysilane; and diaminosilanes such as (RN)Si(OCH), (RN)Si(OCHCH), and (piperidinyl)Si(OCH). The preferred molar ratio of external donor to titanium in the ZN catalyst is about 5 to about 30, preferably about 8 to about 15, and most preferably about 10.

[0021] In the first polymerization step (1), the catalyst components (a), (b), and optionally (c) are fed to a polymerization vessel containing liquid or gaseous propylene in amounts such that the weight ratio (b) / (a) is in the range of 0.1 to 10. If compound (c) is present, the weight ratio (b) / (c) corresponds to the molar ratio described above. The first polymerization step can be carried out in either the gas or liquid phase. Gas-phase processes can be carried out in fixed-bed reactors, either fluidized or stirred, or in gas-phase reactors containing two interconnected polymerization zones, one operated under high-velocity fluidization conditions and the other in which the polymer flows by gravity. Liquid-phase processes can be carried out in either slurry, solution, or bulk (liquid monomer). Polymerization is generally carried out at temperatures between about 20°C and about 120°C, preferably between about 40°C and about 85°C. Hydrogen can be used as a molecular weight regulator.

[0022] In the subsequent polymerization step, a propylene / ethylene impact copolymer is produced in a gas-phase reactor in the presence of propylene, ethylene, and the above-described catalyst system. The polymer produced is preferably a propylene impact copolymer containing 5 to 25% by weight of ethylene. The composition obtained according to the method of the present invention can be obtained as a reactor grade having a melt flow rate according to ISO 1133 (230°C, 2.16 kg) in the range of about 0.01 to about 100 g / 10 min, preferably about 0.1 to about 70 g / 10 min, and more preferably about 0.2 to about 60 g / 10 min. [Example]

[0023] Data for the propylene polymer materials was obtained according to the following method. Xylene-soluble fraction: 2.5 g of polymer and 250 mL of o-xylene are placed in a glass flask equipped with a refrigerator and a magnetic stirrer. The temperature is raised to the boiling point of the solvent over 30 minutes. The resulting solution is then stirred under reflux for another 30 minutes. The closed flask is then placed in an ice-water bath for 30 minutes, followed by a 25°C constant temperature water bath for another 30 minutes. The resulting solid is filtered through a simple filter paper, and the filtered liquid is divided into two 100 ml portions. One 100 ml portion of the filtered liquid is poured into a pre-weighed aluminum container and heated on a heating plate under a nitrogen stream to evaporate and remove the solvent. The container is then placed in an 80°C oven under vacuum until a constant weight is reached. The residue is weighed, and the percentage of xylene-soluble polymer is determined.

[0024] Heptane Insoluble Matter (% HI): The weight percent (wt%) of the residue of a polypropylene sample after extraction with boiling heptane for 8 hours. MFR (Melt Flow Rate): MFR was evaluated by a melt indexer in accordance with ASTM D1238 under the conditions of a total weight of 2.16 kg and 230° C. Sample mass: 5 grams.

[0025] Conditioning: Specimens are tested for tensile or flexural modulus within 40 to 96 hours according to ASTM D4101 section 12.1.5. Tensile strength at break: Test specimens are injection molded to ASTM tensile specimen type I with specimen dimensions of 165 mm total length, 13 mm narrow width, and 3.2 mm thickness. (Speed). Tensile strength was measured according to ASTM D638-10.

[0026] Flexural Modulus: Test specimens are injection molded into ASTM tensile specimens Type I using a type / center section with specimen dimensions of 127 mm x 13 mm x 3.2 mm. Flexural modulus determination is performed according to ASTM D790 Method 1, Procedure A, 1% Tangent (Speed) Method at 23±2°C and 50±10% RH.

[0027] Izod Impact Strength: Izod impact strength was measured according to ASTM D256.

[0027] Tg measurement of rubber phase: The glass transition temperature Tg of the rubber component was measured by dynamic mechanical thermal analysis (DMTA). The test was carried out using an RSA G2 instrument in a three-point bending configuration at a rate of 5°C / min and a frequency of 10 rad / s.

[0028] Low Temperature Ductility: Low temperature ductility was measured according to ASTM D3763-08.

[0029] Phthalate-free catalyst components The TFC catalyst used herein is a phthalate-free catalyst component that uses an internal donor comprising a 1,3-diether, a carbonate ether, and a urea compound in accordance with the specific teachings of the present invention and is manufactured by contract manufacturing in a commercial-scale reactor. Catalyst composition analysis showed 1-5 wt% Ti, 1-15 wt% diether, 1-15 wt% carbonate, and 0.5-10 wt% urea.

[0030] Continuous Gas Phase Polymerization - Preparation of Phthalate-Free C2 / C3 Impact Propylene Copolymers Polymerizations carried out in the presence of a catalyst system containing the TFC catalyst components, triethylaluminum, and an external silane donor are carried out in a continuous gas-phase mode in two reactors in series, equipped with a device for transferring the product from one reactor to the other. The first and second reactors are preferably gas-phase continuous reactors. Propylene homopolymer is prepared in the first gas-phase reactor, while ethylene / propylene copolymer is prepared in the second gas-phase reactor in the presence of propylene homopolymer from the first reactor. Hydrogen is used as a molecular weight regulator. The gas phase (propylene, ethylene, and hydrogen) is continuously analyzed by gas chromatography. At the end of the run, the product powder is discharged and dried under a nitrogen stream. The main polymerization conditions and analytical data for the polymers produced in the two reactors are summarized in Table 1.

[0031] [Table 1]

[0032] As shown in Table 1, the impact propylene copolymers produced by the TFC catalyst of the present invention, while containing no phthalates in their composition, exhibit high flexural moduli of 889-965 MPa (129-140 kpsi), low temperature (-30°C) ductility at compositions of 26.1-27.3 wt% XS, and total ethylene % of 10.3-12.4%, which are comparable to propylene polymers containing phthalates in their composition.

Claims

1. 1. A phthalate-free impact polypropylene copolymer comprising a homopolymer portion and C2 / C3 rubber portions interspersed therein, the copolymer has a flexural modulus value in the range of about 827 to 1379 MPa (about 120 to 200 Kpsi); The copolymer has an instrumented impact ductility of 100% at −30° C. and 6.7 m / s; the copolymer has a C2 / C3 rubber content greater than 20 wt. %; The copolymer has a total ethylene content in the range of about 10 to 20 mole percent. Phthalate-free impact-resistant polypropylene copolymer.

2. 10. The copolymer of claim 1, wherein the copolymer has a flexural modulus in the range of about 827 to 1103 MPa (about 120 to 160 Kpsi).

3. 10. The copolymer of claim 1, wherein the copolymer has a C2 / C3 rubber content in the range of about 20-30 wt%.

4. 1. A method for producing a phthalate-free impact polypropylene copolymer comprising a homopolymer portion and a C2 / C3 rubber portion interspersed therein, comprising: a) polymerizing propylene in a first polymerization step in bulk or gas phase to produce a propylene homopolymer having at least 85% by weight insoluble matter in xylene at 25°C; and b) polymerizing ethylene and propylene in the presence of the propylene homopolymer from the first polymerization step in a second polymerization step to produce a phthalate-free impact polypropylene copolymer. Including, the copolymer has a flexural modulus value in the range of about 827 to 1379 MPa (about 120 to 200 Kpsi); The copolymer has an instrumented impact ductility of 100% at −30° C. and 6.7 m / s; the copolymer has a C2 / C3 rubber content greater than 20 wt. %; the copolymer has a total ethylene content in the range of about 10 to 20 mole percent; The second polymerization step is conducted in the presence of a phthalate-free Ziegler / Natta (Z / N) catalyst, the Z / N catalyst comprising a urea component represented by Formula I: 【Chemical 1】 In the formula, R １ , R ２ , R ３ , and R ４ may be the same or different and are independently hydrogen, an aliphatic hydrocarbon group having 1 to 20 carbon atoms, an alicyclic hydrocarbon group having 3 to 20 carbon atoms, an aromatic hydrocarbon group having 6 to 20 carbon atoms, or a heteroatom containing hydrocarbon group of 1 to 20 carbon atoms; R １ , R ２ , R ３ , and R ４ two or more of may be joined to form one or more saturated or unsaturated monocyclic or polycyclic rings; method.

5. 5. The process of claim 4, wherein the process is carried out in the presence of a catalyst system comprising: (a) a solid catalyst component prepared by contacting titanium chloride with a magnesium compound in the presence of an internal donor comprising a 1,3-diether compound, a urea compound, and a carbonate ether compound; (b) an aluminum alkyl; and optionally (c) an external electron donor compound.

6. 6. The method of claim 5, wherein the catalyst system comprises a 1,3-diether compound selected from the group consisting of 2,2-diisobutyl-1,3-dimethoxypropane, 2-isopropyl-2-isopentyl-1,3-dimethoxypropane, and 2,2-bis(cyclohexylmethyl)-1,3-dimethoxypropane.

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