KR20070098877A - Polyolefinic compositions having good whitening resistance - Google Patents

Abstract

A polypropylene composition comprising (per cent by weight) (a) 50-77% of a crystalline propylene polymer having an amount of isotactic pentads (mmmm), measured by 13C-MNR on the fraction insoluble in xylene at 25°C, higher than 97.5 molar % and a polydispersity index ranging from 4 to 10; (b) 13-28% of an elastomeric copolymer of ethylene and propylene, the copolymer having an amount of recurring units deriving from ethylene ranging from 30 to 70% and being partially soluble in xylene at ambient temperature, the polymer fraction soluble in xylene at ambient temperature having an intrinsic viscosity value ranging from 2 to 4 dl/g; and (c) 10-22% of polyethylene having an intrinsic viscosity value ranging from 1 to 3 dl/g, in said composition component (b) plus component (c) being in amounts of at least 25 wt%. The polymer composition exhibits good impact resistant, whitening resistance and relatively low stiffness.

Description

Polyolefin composition with good whitening resistance {POLYOLEFINIC COMPOSITIONS HAVING GOOD WHITENING RESISTANCE}

The present invention relates to a polyolefin composition having good whitening resistance properties and impact resistance.

The polyolefin compositions according to the invention find application in the automotive sector, in particular in bumpers and interior trims, luggage and household goods.

As is known, isotactic polypropylene has been endowed with exceptionally good combinations of properties, but at relatively low temperatures is affected by the disadvantage of having insufficient impact resistance.

According to the teachings of the prior art, the addition of rubber and polyethylene to polypropylene can eliminate these drawbacks and maintain whitening resistance without severely affecting other polymer properties.

For example, US Pat. No. 4,245,062 discloses a process for preparing blends of polypropylene and two other propylene-ethylene copolymers, one of which forms a substantially rubbery phase. The propylene polymer thus obtained has good impact resistance at low temperatures.

European patent application 86300 relates to a so-called "impact polypropylene composition", in which a polypropylene block copolymer with improved impact resistance and high stiffness is disclosed.

US Pat. No. 4,521,566 discloses polypropylene compositions having the following composition:

74 to 91% of crystalline isotactic polypropylene,

6.7 to 19% of an amorphous copolymerizable fraction of ethylene and propylene, and

1.5 to 8.5% of crystalline polyethylene (containing 50 to 98% by weight of ethylene and exhibiting a crystalline polyethylene form).

The composition shows quite high stiffness and good impact resistance, but the resistance to whitening is not as high as desired.

US Pat. No. 4,473,687 discloses polypropylene molding compositions consisting of polypropylene, ethylene-propylene copolymers and polyethylene having different properties, which have high hardness and increased impact strength.

US Pat. No. 4,734,459 discloses polypropylene compositions with good whitening resistance. As taught in this prior art document, whitening resistance can be improved by replacing ethylene-propylene copolymer rubber with ethylene-butene-1 copolymer rubber.

It has now been surprisingly found that by preparing polypropylene compositions having different proportions between polymer components exhibiting specific properties, polypropylene compositions can be obtained that are simultaneously endowed with relatively low stiffness, high impact resistance and high whitening resistance.

Accordingly, embodiments of the present invention consist of polypropylene compositions containing the following (% by weight):

a) 50~77%, and preferably 50-70% of a crystalline propylene polymer and under: the content of isotactic pentads (mmmm) measured at 25 ℃ in the xylene insoluble fraction by ¹³ C-NMR 97.5 Greater than mole%, polydispersity in the range of 4 to 10, preferably 5 to 10, more preferably 5.5 to 10;

b) an elastomeric copolymer of ethylene and propylene in an amount of from 13 to 28%, preferably greater than 15% to 28%: said copolymer is repeat derived from ethylene in an amount ranging from 30 to 70%, preferably 35 to 60% The polymer fraction having a unit, partially soluble in xylene at ambient temperature, and partially soluble in xylene at ambient temperature, has an intrinsic viscosity value in the range of 2 to 4 dl / g;

c) from 10% to 22%, preferably from 10% to 20% of polyethylene: having an intrinsic viscosity value in the range of 1 to 3 dl / g and optionally comprising repeating units derived from propylene in an amount of less than 10%.

As used herein, the term “copolymer” refers to both polymers having two different repeat units in the chain and polymers having at least two different repeat units, such as terpolymers. "Ambient temperature" means that the temperature in it is about 25 degreeC. “Crystalline propylene polymer” means a propylene polymer having an isotactic pentad (mmmm) content of greater than 70 mol%, measured by ¹³ C-NMR, in a fraction insoluble in xylene at 25 ° C .; By "elastic" polymer is meant a polymer having a solubility in xylene at ambient temperature of greater than 50% by weight.

The combined amount of component (b) and component (c) in the composition is typically at least 25% by weight, preferably at least 30% by weight and the total amount of copolymerized ethylene is at least 17% by weight, preferably at least 20% by weight. .

The melt flow rate value in the composition is typically 10-30 g / 10 minutes, preferably 10-20 g / 10 minutes.

The content of the elastic copolymer (b) in the composition is equal to or higher than the polyethylene (c), preferably the weight ratio of the copolymer (b) and the polyethylene (c) is at least 1.2.

Typically, the flexural modulus values in the compositions of the present invention are at least 800 MPa, preferably 850 to 1250 MPa, and the stress-whitening resistance values are caused by rams falling at a height of 30 cm. Corresponds to the diameter of the bleaching area of 1.50 cm or less and the diameter of the bleaching area of 0.80 cm or less caused by ram crashed at 5 cm height, the Izod impact resistance value is greater than 16 kJ / m ² at 23 ° C., and 0 ° C. Greater than 10 kJ / m ² .

The crystalline propylene polymer (a) is selected from propylene homopolymers and propylene copolymers containing up to 3% by weight of ethylene or C ₄ -C ₁₀ α-olefins or combinations thereof. Particular preference is given to polypropylene homopolymers.

은 7.5 초과, 특히 8 내지 20, 보다 바람직하게는 12 내지 18 이다.Typically, the molecular weight distribution of the crystalline propylene polymer (a) expressed as the ratio between the weight average molecular weight and the number average molecular weight measured by GPC, ie

Is greater than 7.5, in particular 8 to 20, more preferably 12 to 18.

의 값은 3.5 이상, 바람직하게 3.5 내지 9 이다.Typically, the z mean molecular weight to weight average molecular weight ratio measured by GPC of the crystalline propylene polymer (a), ie

The value of is 3.5 or more, preferably 3.5 to 9.

The elastic ethylene-propylene copolymer (b) optionally contains diene. If present, the amount of diene is typically in the range of 0.5 to 10% by weight relative to the weight of copolymer (b). The diene may be conjugated or nonconjugated, for example selected from butadiene, 1,4-hexadiene, 1,5-hexadiene and ethylidene-norbornene-1.

Copolymer (b) represents a fraction insoluble in xylene at ambient temperature, typically in an amount of less than 45% by weight, preferably up to 20% by weight. The xylene-insoluble polymer fraction of the copolymer (b) reaches ethylene and the amount of ethylene is typically greater than 55% by weight.

Polyethylene (c) is selected from crystalline or semicrystalline, ethylene homopolymers or ethylene-propylene copolymers with an average content of comonomers of less than 10% by weight. The intrinsic viscosity value of polyethylene (c) is preferably in the range of 1.2 to 2 dl / g.

The composition of the present invention is obtained by a continuous copolymerization method.

Accordingly, the present invention also relates to a process for preparing a polyolefin composition as described above, wherein the process comprises at least three successive polymerization stages, each subsequent polymerization of the polymeric material formed in the immediately preceding polymerization reaction stage. Is carried out in the presence, wherein the polymerization of the crystalline polymer (a) is carried out in one or more stages, followed by copolymerization of the mixture of ethylene and propylene (and any dienes) to the elastomer (b) and finally in ethylene The polymerization step to polyethylene (c) is carried out. The polymerization step can be carried out in the presence of a stereoselective Ziegler-Natta catalyst.

According to a preferred embodiment, all the polymerization steps are carried out in the presence of a catalyst containing a trialkylaluminum compound, optionally an electron donor, a halide or halogen-alcolate of Ti and an electron-donor compound supported with anhydrous magnesium chloride. Catalysts having this property are known from the patent literature; Particularly advantageous are the catalysts described in USP 4,399,054 and EP-A-45 977. Other examples can be found in USP 4,472,524.

Preferably the polymerization catalyst is a Ziegler-Natta catalyst comprising a solid catalyst component comprising:

a) Mg, Ti and electron donors (internal donors),

b) alkylaluminum compounds, optionally (but preferably),

c) one or more electron-donor compounds (external donors).

The internal donor is preferably selected from esters of mono or dicarboxylic organic acids such as benzoate, malonate, phthalate and certain succinates. This is described in US Pat. No. 4,522,930, EP 45977, International Patent Applications WO 00/63261 and WO 01/57099. Phthalic acid esters and succinic acid esters are particularly suitable. Preference is given to alkylphthalates such as diisobutyl, dioctyl and diphenyl phthalate and benzyl-butyl phthalate.

Among the succinates, it is preferably selected from succinates of the general formula (I) or of the general formula (II):

[Formula I]

[Wherein, the same or different radicals R ₁ And R ₂ silver C ₁ -C ₂₀ linear or branched alkyl, alkenyl, cycloalkyl, aryl, arylalkyl or alkylaryl groups optionally containing heteroatoms; Radicals R ₃ to R _{6, which} are the same or different from each other, are hydrogen or a C ₁ -C ₂₀ linear or branched alkyl, alkenyl, cycloalkyl, aryl, arylalkyl or alkylaryl group optionally containing heteroatoms; The radicals R ₃ to R ₆ linked to the same carbon atom may be bonded to each other to form a ring, provided that when R ₃ to R ₅ are hydrogen at the same time, R ₆ is a primary branched, secondary having 3 to 20 carbon atoms. Or tertiary alkyl group, cycloalkyl, aryl, arylalkyl or alkylaryl group;

[Formula II]

[Wherein, the same or different radicals R ₁ And R ₂ Is a C ₁ -C ₂₀ linear or branched alkyl, alkenyl, cycloalkyl, aryl, arylalkyl or alkylaryl group optionally containing heteroatoms and is a radical R ₃ Is a linear alkyl group of 4 or more carbon atoms optionally containing heteroatoms;

Al-alkyl compounds used as cocatalysts are O or N atoms, or SO ₄ or Al-trialkyl comprising two or more Al atoms linked via a SO ₃ group, such as Al-triethyl, Al-triisobutyl, Al-tri-n-butyl, and linear or cyclic Al-alkyl compounds. Al-alkyl compounds are generally used in amounts having an Al / Ti ratio of 1 to 1000.

The external donor (c) may be the same or different than the succinate of formula (I) or (II). Suitable external electron-donor compounds include silicon compounds, ethers, esters such as phthalates, benzoates, and succinates, amines, heterocyclic compounds having structures other than those of formula (I) or (II) and especially 2,2, 6,6-tetramethylpiperidine, ketone and 1,3-dieter of general formula (III):

[Formula III]

^{Wherein the} same or different R ^I and R ^II are C ₁ -C ₁₈ alkyl, C ₃ -C ₁₈ cycloalkyl or C ₇ -C ₁₈ aryl radicals; R ^III and R ^IV is the same or different and is a C ₁ -C ₄ alkyl radical; Or the carbon atom in the 2 position is 1,3-dieter which belongs to a cyclic or polycyclic structure having 5, 6 or 7 carbon atoms and having 2 or 3 unsaturations.

Ethers of this type are described in European patent applications 361493 and 728769.

Preferred electron-donor compounds that can be used as external donors include silicon compounds having at least one Si-OR (where R is a hydrocarbon radical) bond. Particularly preferred external donor compound series are those of the silicon compounds of the formula R _a ⁷ R _b ⁸ Si (OR ⁹ ) _c , where a and b are integers from 0 to 2, c is an integer from 1 to 3, a + b + c) is 4; R ⁷ , R ⁸ and R ⁹ are C ₁ -C ₁₈ hydrocarbon groups optionally containing heteroatoms. Especially preferably, it is a silicon compound in which a is 1, b is 1, c is 2, and R ⁷ And ^At least one of R ⁸ is selected from branched alkyl, alkenyl, alkylene, cycloalkyl or aryl groups of 3 to 10 carbon atoms optionally containing hetero atoms, and R ⁹ is C ₁ -C ₁₀ Alkyl groups, especially methyl. Examples of such a preferred silicon compound include cyclohexyltrimethoxysilane, t-butyltrimethoxysilane, t-hexyltrimethoxysilane, cyclohexylmethyldimethoxysilane, 3,3,3-trifluoropropyl-2 -Ethylpiperidyl-dimethoxysilane, diphenyldimethoxysilane, methyl-t-butyldimethoxysilane, dicyclopentyldimethoxysilane, 2-ethylpiperidinyl-2-t-butyldimethoxysilane, (1 , 1,1-trifluoro-2-propyl) -methyldimethoxysilane and (1,1,1-trifluoro-2-propyl) -2-ethylpiperidinyldimethoxysilane. Furthermore, a is 0, c is 3, R ⁸ is branched alkyl or cycloalkyl optionally containing heteroatoms, R ⁹ Also preferred are silicon compounds wherein methyl is methyl. Particularly preferred examples of silicon compounds include (tert-butyl) ₂ Si (OCH ₃ ) ₂ , (cyclohexyl) (methyl) Si (OCH ₃ ) ₂ , (phenyl) ₂ Si (OCH ₃ ) ₂ and (Cyclopentyl) ₂ Si (OCH ₃ ) ₂ .

Preferably, the electron donor compound (c) is used in an amount such that the molar ratio between the organoaluminum compound and the electron donor compound (c) is 0.1 to 500, more preferably 1 to 300, in particular 3 to 100.

As mentioned above, the solid catalyst component includes Ti, Mg and halogen in addition to the electron donor. In particular, the catalyst component comprises a titanium compound having at least one Ti-halogen bond and the aforementioned Mg halide supported electron donor compound. Magnesium halides are preferably MgCl ₂ in active form, which is known in the patent literature as a support for Ziegler-Natta catalysts. Patents USP 4,298,718 and USP 4,495,338 describe for the first time the use of such compounds in Ziegler-Natta catalysis. In this patent, the active form of magnesium dihalide, which is used as a support or known carrier of the catalyst component for olefin polymerization, in the X-ray spectrum, the intensity of the strongest diffraction line appearing in the spectrum of the inactive halide is reduced, and the position of the maximum intensity is It is known to be replaced by halo converted to smaller angles rather than stronger lines.

Preferred titanium compounds are TiCl ₄ And TiCl ₃ ego; Further also Ti-halo of the formula Ti (OR) n-yXy, where n is the valence of titanium, y is a number between 1 and n, X is a halogen, and R is a hydrocarbon radical of 1 to 10 carbon atoms. Alcoholates can be used.

The preparation of the solid catalyst component can be carried out according to various methods known and described in the art.

According to a preferred method, the solid catalyst component comprises a titanium compound of formula Ti (OR) n-yXy, wherein n is the valence of titanium and y is a number between 1 and n, preferably TiCl _4. It can be prepared by reaction with magnesium chloride derived from an adduct of _{2 ·} pROH, wherein p is a number between 0.1 and 6, preferably between 2 and 3.5, and R is a hydrocarbon radical having 1 to 18 carbon atoms. The adduct can be suitably prepared in spherical form by mixing the alcohol with magnesium chloride in the presence of an incompatible hydrocarbon which is immiscible with the adduct and stirring under conditions of melting temperature of the adduct (100-130 ° C.). The emulsion is then quickly stopped to allow the adduct to solidify into spherical particles.

Examples of spherical adducts prepared according to this process are described in USP 4,399,054 and USP 4,469,648. The adduct thus obtained is reacted directly with the Ti compound or firstly subjected to heat-controlled dealcoholization (80-130 ° C.) to obtain an adduct having a molar number of alcohols generally less than 3, preferably between 0.1 and 2.5. do. Reaction with the Ti compound suspends the adduct (dealcoholized or as such) in cold TiCl ₄ (generally 0 ° C.); The mixture is heated to 80-130 ° C. and maintained at this temperature for 0.5-2 hours. Such TiCl ₄ The treatment can be performed one or more times. The electron donating compound (s) is TiCl ₄ It can be added during the treatment.

Regardless of the preparation method used, the final content of the electron donor compound (s) is preferably from 0.01 to 1, more preferably from 0.05 to 0.5, molar ratio to MgCl ₂ .

Such catalyst components and catalysts are described in WO 00/63261 and WO 01/57099.

The catalyst can be contacted in advance with a small amount of olefin (prepolymerisation), maintaining the suspension of the catalyst in a hydrocarbon solvent and polymerizing at temperatures from room temperature to 60 ° C. to prepare the polymer in 0.5 to 3 times the catalyst. This operation can be carried out in a liquid monomer, in which case the polymer is produced in 1000 times the catalyst weight.

By using the above-mentioned catalyst, the polyolefin composition is obtained in the form of spheroidal particles having an average diameter of about 250 to 7,000 microns and a flowability and bulk density (compressed) of less than 30 seconds are greater than 0.4 g / mL.

The polymerization step can be carried out in liquid phase, gas phase or liquid-gas phase. Preferably, the polymerization of the crystalline polymer fraction (a) is carried out in a liquid monomer (eg using liquid propylene as the diluent), while the copolymerization steps of the elastomeric copolymer (b) and polyethylene (c) are carried out in gas phase. Alternatively, all three successive polymerization stages are carried out in gas phase.

The reaction temperature in the polymerization step for the preparation of the crystalline polymer (a) and for the preparation of the elastic copolymer (b) and the polyethylene (c) may be the same or different, preferably from 40 to 100 ° C; More preferably, it is 50-80 degreeC in manufacture of a polymer (a), and 50-90 degreeC in manufacture of a polymer component (b) and (c).

If the polymerization step for preparing the polymer (a) is carried out in a liquid monomer, its pressure competes with the vapor pressure of the liquid propylene at the operating temperature used, which is via the vapor pressure of the small amount of inert diluent used to feed the catalyst. , Through the overpressure of the optical monomer, and through hydrogen used as molecular weight modifier. The polymerization pressure is preferably in the range from 33 to 43 bar if carried out in the liquid phase and from 5 to 30 bar if carried out in the gas phase. The residence time for the two stages depends on the required ratio between the polymers (a) and (b) and (c), which can mainly range from 15 minutes to 8 hours. Conventional molecular weight regulators known in the art such as chain transfer agents (eg hydrogen or ZnEt ₂ ) can be used.

Conventional additives, fillers and pigments mainly used in olefin polymers can be added, such as nucleating agents, extender oils, mineral fillers and other organic and inorganic pigments. In particular, addition of inorganic fillers such as talc, calcium carbonate and mineral fibers can also achieve some improvement in flexural modulus and some mechanical properties such as HDT. Talc also has a nucleating effect.

The nucleating agent is preferably added to the composition of the present invention in the range of 0.05 to 2% by weight, more preferably 0.1 to 1% by weight relative to the total weight.

Specifically, the following examples are presented, which are intended to illustrate the invention without limitation.

The following assay was used to determine the properties reported in the description and in the examples.

Ethylene : by IR spectroscopy

Fraction soluble and insoluble in xylene at 25 ° C . : 2.5 g of polymer is dissolved in 250 mL of xylene while stirring at 135 ° C. After 20 minutes, the solution is allowed to cool to 25 ° C while stirring continuously, and then left for 30 minutes. The precipitate is filtered through filter paper, the solution is evaporated in a nitrogen stream and dried under vacuum at 80 ° C. until the residue reaches a constant weight. And the weight% of the polymer which is soluble and insoluble at room temperature (25 degreeC) is calculated.

Intrinsic viscosity [η] : Measured in 135 ° C tetrahydronaphthalene.

): 1,2,4-트리클로로벤젠 중에서 겔 투과 크로마토그래피 (GPC) 를 이용하여 측정한다.-Molecular weight (

): Measured using gel permeation chromatography (GPC) in 1,2,4-trichlorobenzene.

Isotactic Determination of pentad content : 50 mg of each xylene insoluble fraction was dissolved in 0.5 mL of C ₂ D ₂ Cl ₄ . ¹³ C-NMR spectra were obtained on Bruker DPX-400 (100.61 Mhz, 90 ° pulses, 12 sec delay between pulses). About 3000 transients were stored in each spectrum; mmmm pentad peak (21.8 ppm) was used as reference. Microstructure analysis was performed as described in the literature (Polymer, 1984, 25, 1640, Inoue Y. et al., And Polymer, 1994, 35, 339, Chujo R. et al.).

Polydispersity : Measure the molecular weight distribution of the polymer. In order to measure the PI value, the elastic modulus separation, for example, at a loss modulus value of 500 Pa, was carried out at 0.01 rad / sec. Measure at the frequency increasing up to / sec. The PI can be derived from the elastic modulus separation value by the following equation:

,

,

Elastic modulus separation (MS) is defined as follows:

[Wherein G 'is storage modulus and G' 'is loss modulus].

Melt flow rate : measured according to ISO method 1133 (230 ° C., 2.16 kg).

Flexural modulus : measured according to ISO method 178.

-Izod impact resistance : measured according to ISO method 180 / 1A.

- breaking (break) energy is determined in accordance with the internal MA 17324 method. The same test specimen and test method as the soft / brittle transition temperature (described below) measurement method were used, in which case the energy required to break the sample was measured at -20 ° C.

Stress-whitening resistance: Resistance to whitening is measured by impacting a ram with a small disc of predetermined weight made from the polymer to be tested. Record the minimum height (h) up to the maximum height allowed by the instrument required to achieve the bleaching phenomenon, and the width (diameter) of the bleached range.

Example  1 to 3

In a plant operating continuously according to the mixed liquid-gas polymerization technique, a run was performed under the conditions specified in Table 1.

The polymerization is carried out in a series of three reactors equipped with a device to transport the product from one reactor to the next in the presence of a catalyst system.

Preparation of Solid Catalyst Components

Into a 500 mL four-necked round flask purged with nitrogen, 250 mL of TiCl ₄ was introduced at 0 ° C. With stirring, 10.0 g of microspheres MgCl ₂ .9 C ₂ H ₅ OH (prepared according to the method described in example 2 of USP 4,399,054, except that it was operated at 3000 rpm instead of 10000 rpm) and 9.1 mmol of di Ethyl 2,3- (diisopropyl) succinate is added. The temperature is raised to 100 ° C. and maintained for 120 minutes. After stirring is stopped, the solid product is allowed to settle and the supernatant is removed with siphon. Then 250 mL of fresh TiCl ₄ is added. The mixture is allowed to react at 120 ° C. for 60 minutes, and then the supernatant is removed with a siphon. The solid was washed 6 times (6 × 100 mL) with anhydrous hexane at 60 ° C.

Catalytic System and Prepolymerization Treatment

The solid catalyst component described above was contacted with aluminum triethyl (TEAL) and dicyclopentyldimethoxysilane (DCPMS) as an external electron donating component for 24 minutes at 12 ° C. The weight ratio between TEAL and the solid catalyst component and the weight ratio between TEAL and DCPMS are shown in Table 1.

Next, prior to introduction into the first polymerization reactor, the catalyst system is prepolymerized while maintaining suspension for about 5 minutes at 20 ° C. in liquid propylene.

polymerization

The polymerization run is carried out continuously in a series of three reactors equipped with a device to transport the product from one reactor to the next. The first reactor is a liquid phase reactor and the second and third reactors are fluid bed gas phase reactors. Polymer (a) is produced in the first reactor, while polymers (b) and (c) are produced in the second and third reactors, respectively. Temperature and pressure remain constant throughout the reaction. Hydrogen is used as molecular weight regulator.

The gas phase (propylene, ethylene and hydrogen) is analyzed continuously via gas chromatography. At the end of the run the powder is drained and dried under nitrogen flow. The polymer particles are then introduced into an extruder, where they are mixed with nucleated with 8500 ppm talc, 1500 ppm Irganox B 215 (made of 1 part Irganox 1010 and 2 parts Irgafos 168) and 500 ppm Ca stearate. ) To obtain a composition. Irganox 1010 is pentaerythritol tetrakis 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propanoate, while Irgafos 168 is tris (2,4-di-tert-butylphenyl ) Phosphite and both are commercially available from Ciba-Geigy. The polymer particles were extruded through a twin screw extruder under a nitrogen atmosphere, with a rotational speed of 250 rpm and a melting temperature of 200-250 ° C.

Example  4

Example 1 is repeated except that the catalyst component is replaced with a catalyst component containing diisobutyl phthalate instead of diethyl 2,3- (diisopropyl) succinate and the crystalline homopolymer in two steps Prepared. Both steps were performed in a liquid phase reactor.

Comparative example  1 (1c)

Example 4 was repeated except that no polymerization was carried out in the second liquid phase reactor and no polymerization of ethylene to crystalline polyethylene was carried out, but the elastic ethylene-propylene copolymer rubber was prepared in the first and second gas phase reactors. It was.

Comparative example  2 (2c)

Example 4 was repeated except that polymerization of ethylene to crystalline polyethylene was not performed, but the elastic ethylene-propylene copolymer rubber was prepared in the first and second gas phase reactors.

Polymerization process Example One 2 3 4 1c 2c TEAL / solid catalyst component weight ratio 9 16 9 13 10 9 TEAL / DCPMS weight ratio 4 5 6 2.7 5 2.3 First liquid phase reactor Polymerization temperature, ℃ 69 68 70 67 70 67 Pressure, bar 39 39 39 41 39.5 40 Residence time, minutes 59 50 63 52 62 32 H ₂ bulk, mol ppm 7,400 9,600 6,900 7,980 6,700 10,000 Second liquid phase reactor Polymerization temperature, ℃ - - - 67 - 67 Pressure, bar - - - 41 - 40 Residence time, minutes - - - 35 - 26 H ₂ bulk, mol ppm - - - 7,300 - 9,800 First gas phase reactor Polymerization temperature, ℃ 80 80 80 85 80 80 Pressure, bar 16 16 17 15 15 15 Residence time, minutes 33 23 18 24 15 13 ^{_{C 2 - / (C 2 -}} + C 3 -),% 0.23 0.24 0.27 0.29 0.36 0.23 H ₂ / C ₂ ^- ,% 0.069 0.046 0.049 0.071 0.053 0.055 Second gas phase reactor Polymerization temperature, ℃ 83 85 100 90 80 80 Pressure, bar 17 18 15 15 20.8 19 Residence time, minutes 37 33 14 22 27 23 ^{_{C 2 - / (C 2 -}} + C 3 -),% 0.98 0.98 0.99 0.99 0.36 0.23 H ₂ / C ₂ ^- ,% 0.65 0.695 0.297 0.4 0.050 0.053 Note: H ₂ bulk = hydrogen concentration in liquid monomers; C ₂ ^- = ethylene; C ₃ ^- = propylene

The amounts of components (a) to (c) and the aspects of each component in the polymer composition thus obtained are shown in Table 2.

Composition analysis Example One 2 3 4 1c 2c Crystalline Propylene Homopolymer Homopolymer Content, Weight% 61.7 64.2 61 63 68 70 MFR, g / 10 min 59 71 71 53 69 80 Polydispersity 5.7 5.7 5.7 4.9 5 5.7

비율

ratio 15.3 15.3 15.3 10.4 8.9 10.9

ratio 7.3 7.3 7.3 4.2 4.4 7.7 Pentad content, mol% 98.4 98.4 98.4 98.4 98.6 98 Xylene soluble fraction, weight percent 2 2 2 1.9 2.0 2.5 Proylene -Ethylene copolymer Copolymer content, weight% 23.3 23.7 23 23 32 30 Ethylene Content in EPR, Weight% 39 39 40 40 47 42 Intrinsic viscosity [η] of xylene soluble fraction 13, dl / g 2.5 ⁽¹⁾ 2.9 ⁽¹⁾ 3.1 ⁽¹⁾ 3.1 ⁽¹⁾ 2.98 ⁽²⁾ 2.96 ⁽²⁾ Xylene soluble fraction, weight percent 25.7 ⁽¹⁾ 25.3 ⁽¹⁾ 25.7 ⁽¹⁾ 25.7 ⁽¹⁾ - Polyethylene Polyethylene content,% by weight 15 12.1 16 13 0 0 Ethylene Content in PE, Weight% 100 100 100 100 - - Intrinsic viscosity [η], dl / g 1.65 1.67 - 1.75 - Note: EPR: elastomeric ethylene-propylene copolymer rubber; PE: crystalline polyethylene ⁽¹⁾ Value measured on polymer composition prepared in the first and second reactors ⁽²⁾ Value measured on polymer composition prepared in the first, second and third reactors

The aspect of the final composition and the properties of the entire composition are reported in Tables 3 and 4, respectively.

Final composition Example One 2 3 4 1c 2c Ethylene Content, Weight% 23.8 22.1 25.2 22.3 15.1 12.5 Xylene soluble fraction, weight percent 22.8 21.1 22.5 22.2 28.2 28.1 Intrinsic viscosity [η] of xylene soluble fraction, dl / g 2.5 2.9 3.1 2.5 2.98 2.96 EPR / PE weight ratio 1.5 1.9 1.4 1.8 - -

Characteristics of the whole composition Examples and Comparative Examples One 2 3 4 1c 2c MFR, g / 10 min 15 15 12.2 13.9 14.3 14.7 Flexural Modulus, MPa 968 1075 1150 895 988 1150 Izod impact resistance, kJ / m ² At 23 ℃ 42.5 39 39 49.9 17.2 13 At 0 ℃ 12.1 11.8 11.8 16.7 11.5 9.3 At -20 ℃ 7.1 9.1 9.1 9.2 9.2 7.5 Whitening resistance: Diameter of whitening area (cm) due to ram falling from marked height 5 cm high 60 70 70 60 90 120 10 cm high 80 100 100 90 110 140 20 cm height 120 110 110 110 140 150 30 cm height 130 130 130 120 170 160 76 cm height 160 160 160 150 190 200

The data in the examples show improved whitening resistance, good Izod impact resistance and relatively low stiffness under the conditions according to the invention.

Claims (6)

Polypropylene composition containing the following (% by weight): a) 50-77% crystalline propylene polymer: the content of isotactic pentad (mmmm) measured by ¹³ C-NMR in fractions insoluble in xylene at 25 ° C is greater than 97.5 mol%, and the polydispersity is 4 In the range from 10 to 10; b) 13 to 28% of an elastomeric copolymer of ethylene and propylene: the copolymer has repeating units derived from ethylene in an amount ranging from 30 to 70%, partially soluble in xylene at ambient temperature, and at ambient temperature The polymer fraction partially soluble in xylene has an intrinsic viscosity value in the range of 2 to 4 dl / g; c) 10-22% polyethylene: having an intrinsic viscosity value in the range of 1-3 dl / g; At this time, the combined amount of the composition component (b) and component (c) is 25% by weight or more. The polypropylene composition according to claim 1, wherein the crystalline polymer (a) is a propylene homopolymer in a content range of 50% to less than 70%. The polypropylene composition according to claim 1, wherein the content of the elastic copolymer (b) is in the range of more than 15% by weight to 28% by weight. The polypropylene composition according to claim 1, wherein the content of polyethylene (c) is in the range of 10% to 20% by weight. The polypropylene composition of claim 1, wherein the total content of copolymerized ethylene is at least 17% by weight. A process for the preparation of the polypropylene composition of claim 1, wherein the process comprises at least three successive polymerization steps, wherein the crystalline polymer (a), the elastomer (b) and the polyethylene (c) are each successive steps. Wherein each step except the first step is operated in the presence of the polymeric material and catalyst used in the previous polymerization step.