WO1998045338A1

WO1998045338A1 - Modification of polymer molecular weight distribution by using mixed silane systems in high activity polymerization catalysts

Info

Publication number: WO1998045338A1
Application number: PCT/US1998/006783
Authority: WO
Inventors: Chung-Ping Cheng; Paul D. Smith
Original assignee: Engelhard Corporation
Priority date: 1997-04-07
Filing date: 1998-04-06
Publication date: 1998-10-15
Also published as: AU6952698A

Abstract

A catalyst system for use in olefinic polymerization and copolymerization comprising components (A, B and C). Catalyst system component (A) comprises titanium, magnesium, halogen, electron donor atoms. Component (B) is an organic aluminum compound. Component (C) is a mixture of two or more organic silicon compounds. Preferred-component (C) is a mixture of cyclohexylmethyldimethoxysilane/dicyclopenthyldimethoxysilane. The catalyst system is advantageous because it combines the very high activity of modern polymerization catalysts with the broader molecular weight distribution of older titanium trichloride catalysts. Broader molecular weight distributions are desirable for certain applications such as BOPP film and HCPP (high crystallinity polypropylene).

Description

MODIFICATION OF POLYMER MOLECULAR WEIGHT DISTRIBUTION BY USING MIXED SILANE SYSTEMS IN HIGH ACTIVITY POLYMERIZATION CATALYSTS

Field of the Invention The present invention relates generally to polymerization or copolymerization catalyst compositions and processes wherein mixed silanes are used to modify the molecular weight distribution of the resultant polymer.

Background of the Invention

Many of the recent efforts in the field of polymerization catalysis have been directed toward improvement of catalytic activity. Such prior art improvements, however, have often come at the expense of other catalytic characteristics. High activity polypropylene catalysts generally consist of a solid, comprised of magnesium dichloride and titanium tetrachloride, along with some amount of a complexed organic electron donor such as a phthalate ester. In the polymerization of propylene, the solid catalyst component is normally used in conjunction with a) an aluminum alkyl, and b) an organic silane. Catalyst systems of this type differ from the earlier generation titanium trichloride catalyst in several aspects, one being the breadth of the resultant polymer molecular weight distribution (MWD).

The molecular weight distribution of polymers affect many of the polymer's physical characteristics. For example, polypropylenes used in making BOPP (Biaxially Oriented

Polypropylene) films must have a relatively broad molecular weight distribution. The broad

MWD is important in giving the polymer sufficient strength so it will not easily tear when stretched. This is important in the application of the polymer as well as in processing the polymer. The higher strength also allows the processing equipment that stretches the polymer into a film to run faster without film breakage. Traditionally, older first and second-generation Ziegler-Natta titanium trichloride catalysts yielded polypropylene with a MWD in the range of 8 to 10 (as measured by MJM,, using GPC). This range has been found to be suitable for making BOPP films.

Polypropylene produced using more recent 3^rd and 4^th generation high activity catalysts gives polymers with a MJM_ of 4 to 5. Experience has shown this type of polymer to be unsuitable for manufacturing BOPP films. For example, U. S. Letters Patent Nos. 4,794,983 and 4,861,847 describe a solid, high efficiency catalyst consisting of magnesium dihalide, titanium halide, an electron donor, an organic phosphorous ester, an organic epoxy compound, an aluminum alkyl, and a single organic silane.

The silane component in prior catalyst systems, in conjunction with high activity co- catalysts, is used to control polymer isotacticity. Traditionally, only one type of silane compound is used and the isotacticity is controlled by varying the amount of silane used in the polymerization. Polymers obtained with this type of catalyst system typically have narrower molecular weight distributions compared to older catalyst systems. Broader molecular weight distributions are desirable for certain applications such as BOPP film and HCPP (high crystallinity polypropylene).

Previously, to produce polymers with a broad MWD, a traditional titanium trichloride catalyst system is used. The disadvantage or the traditional catalyst system is the low catalyst activity obtained. High activity catalysts normally give much narrower MWD and, thus, are not suitable for applications such as BOPP film and HCPP. The present invention, however, allows the production of polymers using high activity catalysts and produces polymers with the broad MWD desirable for producing such product grades.

Unlike the prior catalyst systems, in the present invention a mixture of at least two different silanes is used to obtain polymers with MWD similar to those of the older generation catalysts. In the present invention, the silanes are selected based on their hydrogen response.

Preferably, the two different silanes used in the combination should have sufficiently different hydrogen response so as to achieve the desired MWD broadening effect. The choice of silanes in the present invention allows one to tailor the MWD to the desired level. This method of MWD control is applicable to other α-olefin polymerization catalysts which utilize silanes for isotacticity control. If the hydrogen response of the two different silanes is similar, no broadening of the MWD is possible, because the polymer made from the two different silanes will merely have the same MWD. If the hydrogen response of the two different silanes is too dissimilar, a polymer with a bi-modal MWD is obtained, and often this is undesirable.

Preferably, the silane mixture comprises a first organic silane compound, characterized in that, when said first silane is used for polymerization in the absence of any other silanes, the slope of the line fitted to a plot of the amount of hydrogen used in the polymerization (X-axis) v. resultant polymer melt flow rate (Y-axis) is between 2.5 and 5.0, preferably 3.25 to 3.75; and a second organic silane compound, characterized in that, when said second silane is used for polymerization in the absence of any other silanes, the slope of the line fitted to a plot of the amount of hydrogen used in the polymerization (X-axis) v. resultant polymer melt flow rate (Y- axis) is between 0 and 1.5, preferably 0.5 to 1.0 (see Fig. 2).

Various mixtures of specific silanes have been used in different ways for different purposes. U.S. Patent 5,100,981 describes the use of a mixture of cyclohexylmethyldimethoxy- silane (CMDMS) and phenyltriethoxysilane to narrow a polymer's molecular weight distribution (MWD). They do not attempt to use any other combinations of mixed silanes nor do they attempt to use mixed silanes to create a polymer with a broad MWD. Published PCT application WO 95/21203 describes the use of a two-stage reaction, first using a weak silane, then at the second stage, adding a dominating silane. This two-stage reaction is used to create a polymer that has the characteristics of a polymer created using the dominant silane, but with a slightly broader MWD. The present invention does not use a weak/dominant silane system like the one disclosed in this patent. Additionally, the catalytic composition of the present invention has a higher catalytic efficiency and gives polymer with a broader molecular weight distribution.

European Patent 0385765 A2 describes the use of two electron donors, (a) and (b), with very different independent MFR values, such that log|MFRJMFRJ > 1.5. The current invention uses a novel mixture of silanes having a loglMFRJMFRJ value well below 1.5. Additionally, the catalytic composition of the present invention exhibits a higher catalytic efficiency and provides a polymer with a broader molecular weight distribution.

Japanese Patent 2-170803 describes a catalyst comprising an organic silicon compound, of the formula R_Si(OR')_4.„, and an ethylsilicate. The present invention has a unique catalytic composition and does not use ethylsilicates as required by this patent. The efficiency of the present catalyst is also greater than 270% higher.

Japanese Patents 4-117411 and 4-117412 describe a catalyst comprising a mixture of a dimethoxysilane and an alkoxysilane to produce a polymer with a broad MWD. The unique catalytic composition of the present invention does not use alkoxysilanes, as they are defined and required in these patents. Additionally, the present invention exhibits substantially higher catalyst efficiency.

Japanese Patent 4-136006 describes a catalyst comprising a di-branched-alkyldialkoxy- silane and a cycloalkylalkyldialkoxysilane. The present invention does not use the required di- branched-alkyldialkoxy silanes and has a different catalytic composition providing a more desirable molecular weight distribution.

Japanese Patent 4-239008 describes a catalyst comprising at least a di- or trialkoxysilane and a branched alkoxysilane. The most relevant example uses cyclohexylmethyldimethoxysilane and triisopropoxymethylsilane. The present invention does not use the same silane combinations as those disclosed in this patent. Additionally, the catalytic composition of the present invention provides polymer with a more desirable molecular weight distribution.

Japanese Patent 6-248019 describes a catalyst comprising at least two silane compounds. The most relevant example uses cyclopentylethyldimethoxysilane and 0-phenethylmethyl- dimethoxysilane. The current invention does not use the silane mixtures disclosed in this patent. Additionally, the present invention has a catalytic composition that provides significantly higher catalyst efficiency and gives a polymer with a more desirable melt flow index.

Japanese Patent 6-298835 describes a catalyst comprising component obtained by reacting a Ti/Mg Hal compound with two silicon compounds. The most relevant example discloses the use of dicyclopentyldimethoxysilane and tert-butyldiethoxysilane. The present invention uses a different catalytic composition and silane system with a substantially higher (>600%) catalyst efficiency to give polymer with a more desirable melt flow index and a higher molecular weight distribution.

Japanese Patent 6-145204 describes a catalyst comprising two silicon compounds. The most relevant example uses t-butyl-n-propyldimethoxysilane and t-butyldimethoxysilane. The present invention uses a different catalytic composition and silane system with a substantially higher (>500%) catalyst efficiency to give polymer with a more desirable melt flow index and a higher molecular weight distribution.

Japanese Patent 6-179513 describes a catalyst comprising two organic silicon compounds. The most relevant example uses cyclohexylmethyldimethoxysilane and ethyltriethoxysilane. The present invention uses a different catalytic composition and silane system with a higher catalyst efficiency.

Other references suggest, but do not disclose the use of multiple silanes. U.S. Patent 5,550,094 suggests the addition of "one or several organosilicon compounds" to form a catalyst. (Col. 3, 11. 64-65; Claim 2(ii)). The specification discloses the possible use of hydrocarbyl- substituted silanes, including aryl and alkyl substituted silanes, but excluding cycloalkylsilanes. U.S. Patent 5,258,345 suggests the use of "at least one silane" (Col. 2, 11. 37-47) in an invention that is attempting to achieve a bimodal MWD. However, there is no mention of cycloalkyl substituted silanes. U.S. Patent 5,489,634 suggests that "compounds of silicon may be used alone or more of them may be mixed or reacted for use." U.S. Patent 5,498,770 mentions the use of mixed asymmetric silanes (Col. 11, 11, 61-63), but does not refer directly to the use of mixed silanes when symmetric silanes are used. It does disclose the use of DCPDMS and CMDMS as individual symmetric silanes (Col. 5, 11. 41-43). U.S. Patent 5,547,912 discloses that "silicon compounds may be used independently or as admixture thereof (Col. 8, 11. 7-8). DCPDMS and CMDMS are disclosed as possible silanes. (Col. 8, 11. 1-3). U.S. Patent 4,990,478 mentions that "mixtures of silanes may be used," (Col. 2, 11. 24-25) but gives no reason why one would want to, such as to broaden the polymer MWD. There is no disclosure of any cycloalkyl substituted silanes. Summary of the Invention

Component (A) may be prepared in the same manner as set forth in Example 1 of U.S. Letters Patent Nos. 4,784,983 and/or 4,861,847. Alternatively, Component (A) may be prepared using a supported catalyst, such as a traditional ball-milled Ziegler-Natta catalyst.

Component (B) is an organic aluminum compound, having a general formula AIR_X₃._n, wherein R is hydrogen, or a hydrocarbon group having 1-20 carbon atoms, preferably an alkyl, aralkyl or aromatic group; X is halogen, preferably chlorine or bromine and n is an integer of from 1 to 3.

Examples of such compounds are triethyl aluminum, triisobutyl aluminum, trioctyl aluminum; hydrogenated alkyl aluminums, such as diethyl aluminum hydride, diisobutyl aluminum hydride; halogenated alkyl aluminums, such as diethyl aluminum chloride, diisobutyl aluminum chloride, ethyl aluminum sesquichloride, ethyl aluminum dichloride; with triethyl aluminum and triisobutyl aluminum being preferred.

The organic aluminum compound is used in the catalyst composition in such an amount that the mole ratio of aluminum to titanium in solid component (A) is about 5-5000 and preferably about 20-500.

Component (C) is a mixture of organic silane compounds such that the difference in the hydrogen response between the two is optimal for broadening the molecular weight distribution (MWD) of the resultant polymer. The most preferred silane mixture is a 60:40 molar ratio of CMDMS (cyclohexylmethyldimethoxysilane) and DCPDMS (dicyclopentyldimethoxysilane). In addition to the preferred silane mixture, other mixtures of silanes are possible. Other silane mixtures that are useful for this invention comprise a first organic silane compound, characterized in that, when said first silane is used for polymerization in the absence of any other silanes, the slope of the line fitted to a plot of the amount of hydrogen used in the polymerization (X-axis) v. resultant polymer melt flow rate (Y-axis) is between 2.5 and 5.0, preferably 3.25 to 3.75; and a second organic silane compound, characterized in that, when said second silane is used for polymerization in the absence of any other silanes, the slope of the line fitted to a plot of the amount of hydrogen used in the polymerization (X-axis) v. resultant polymer melt flow rate (Y- axis) is between 0 and 1.5, preferably 0.5 to 1.0 (see Fig. 2).

The organic silane compound is used in the catalyst composition in such an amount that the mole ratio of the organic aluminum compound to the organic silicon compounds is about 1 to 100, preferably 5 to 80. In general, component (C) is added in the polymerization of propylene either as a mixture or successively.

It is suitable to employ the catalyst system of the present invention in the polymerization of α-olefins, e.g. ethylene, propylene, 1-butylene, 4-methyl-l-pentene, 1-hexylene, 1-octylene, and the like. Homopolymerization as well as static copolymerization and block copolymerization of these olefins can be carried out using the catalyst system of the present invention. Conjugated diene or nonconjugated diene can be selected as a monomer for copolymerization.

Detailed Description of the Preferred Embodiment A standard 3 liter reactor was employed to run Examples 1 through 5 set forth below. In general, the prepolymerized catalyst mixture was charged at ca. 55 °C against a gaseous propylene stream into the polymerization reactor with precharged solvent and the balance of the triethyl aluminum (TEA1) and electron donor. Subsequently, the reactor is closed, hydrogen added and temperature and pressure set to final values (70 °C, 1.0 MPa) within about 5 minutes. Polymerization was conducted for 2 hours. Catalyst activity and reaction diluent solubles (RDS) were determined for each polymerization run.

Turning now to Figure 1, therein is disclosed the polymerization apparatus 10 used in the performance of the test runs described in Examples 1 to 5, including the following: 20 3 L jacketed stainless steel reactor, 30 two pitched-blade impeller, 40 glass vessel for stripping solvent, 50 circulating water bath, 60 radiant heater, 70 mercury manostat for nitrogen-actuated siphoning of solvent into reactor, 80 propylene storage vessel located on balance plate, 90 pressure controller, 100 pressure indicator, 110 pressure indicator and controller, 120 pressure indicator, recorder and controller, and a 130 weight indicator.

The catalyst system of the present invention was used in preparing the following Examples 1 through 5 below.

Example 1 1. Preparation of a solid catalyst Component (A):

Anhydrous magnesium chloride (13.2 g, 0.140 mol), toluene (225 ml), epoxychloro- propane (24.3 g, 0.260 mol) and tributyl phosphate (21.2 g, 0.0780 mol) were introduced into a reactor which had thoroughly been purged with highly purified nitrogen. The temperature was raised to 50 °C with stirring, and the mixture was then maintained at this temperature for 2 hours, while the solids dissolved completely. Phthalic anhydride (3.2 g, 0.021 mol) was added to the solution, and then the solution was maintained for 2 additional hours at 50 °C. The solution was then cooled to -28 °C. Titanium tetrachloride (151 ml, 1.37 mol) was added drop-wise over the course of 1 hour. The solution was heated to 80 °C over the course of 2 hours, while a solid product precipitated. Dibutyl phthalate (5.0 ml, 0.018 mol) was added and the mixture was maintained at the temperature of 80 °C for 1 hour.

The solid portion was collected by filtration and washed twice with a mixture of toluene

(239 ml) and titanium tetrachloride (26.5 ml). A brown-yellow solid precipitate was obtained.

The solid was then treated three times with a mixture of toluene (239 ml) and titanium tetrachloride (26.5 ml) at 110 °C for 30 minutes each. The solid was washed with hexane (4 x 10.5 ml).

Component (A) contained 1.91% titanium by weight, 18.86% magnesium by weight, 12.58% dibutyl phthalate by weight.

2. Preliminary Polymerization (Prepolymerization)

A 50-ml, jacketed, cone-bottom-shaped, glass vessel was used for the prepolymerization step. The reactor was first purged with nitrogen. Heptane (29 ml), triethyl aluminum (0.66 g,

6 mmol), and cyclohexylmethyldimethoxysilane (0.113 g, 0.6 mmol) were charged into the reactor. Component (A) (1.5 g) was then added. Nitrogen was pumped out and replaced with propylene at 80 torr. Prepolymerization was carried out at ambient temperature (ca. 25 °C) for 0.5 hr to reach a PP/catalyst level of 2-3. The dissolved propylene was pumped out and replaced with nitrogen. Aliquots (2 ml) from the prepolymerized slurry was syringed into small vials, diluted 10 times with heptane, and used for subsequent polymerization experiments.

3. Main Polymerization The standard 3 liter reactor was employed. Heptane (1200 ml), triethyl aluminum (0.095 g, 0.83 mmol), silane donor (0.017 g of a 60/40 molar mixture of CHMDMS and DCPDMS) at an Al:Si:Ti molar ratio of 200:20:1 were first charged into the reactor. The prepolymerized catalyst mixture (2.2 ml slurry, 11 mg catalyst) was charged at 55 °C against gaseous propylene into the polymerization reactor. The reactor was then closed, hydrogen

(400 ml) was added, and temperature and pressure set to final values of 70 °C and 1 Mpa within about 5 minutes. Polymerization was conducted for 2 hours. The following results were obtained:

Catalyst Activity 27.4 kg-PP/g-cat Isotactic Index 98.2

MFI 3.6

MWD 7.8

The data from Example 1 is also in Run No. 87 of Table 1.

Example 2 1. Preparation of solid catalyst component (A):

Anhydrous magnesium chloride (13 g, 0.14 mol), toluene (225 ml), epoxychloropropane (24 g, 0.26 mol) and tri-butyl phosphate (21 g, 0.078 mol) were introduced into a reactor which had thoroughly been purged with highly purified nitrogen. The temperature was raised to 50 °C with stirring, and the mixture was then maintained at this temperature for 2 hours, while the solids dissolved completely. Phthalic anhydride (3.2 g, 0.021 mol) was added to the solution, and then the solution was maintained for 2 hours at 50 °C. The solution was cooled to -28 °C. Titanium tetrachloride (151 ml, 1.37 mol) was added drop-wise over the course of 1 hour. The solution was heated to 80 °C over the course of 2 hours, while a solid product precipitated. Dibutyl phthalate (2.5 ml, 0.009 mol) was added and the mixture was maintained at a temperature of 80 °C for 1 hour. The solid portion was collected by filtration and washed twice with toluene (239 ml) and titanium tetrachloride (26.5 ml). A brown-yellow solid precipitate was obtained. The solid was then treated three times with a mixture of toluene (239 ml) and titanium tetrachloride (26.5 ml) at 110 °C for 30 minutes each. The solid was washed with hexane (4 x 10.5 ml).

Component (B) contained 2.20% titanium by weight, 18.92% magnesium by weight, 9.28% dibutyl phthalate by weight. 2. Preliminary Polymerization (Prepolymerization)

A 50-ml, jacketed, cone-bottom-shaped, glass vessel was used for the prepolymerization step. The reactor was first purged with nitrogen. Heptane (29 ml), triethyl aluminum (0.66 g, 6 mmol), and cyclohexylmethyldimethoxysilane (0.113 g, 0.6 mmol) were charged into the reactor. Component (A) (1.5 g) was added. Nitrogen was pumped out and replaced with propylene at 80 torr. Prepolymerization was carried out at ambient temperature (ca. 25 °C) for

0.5 hr to reach a PP/catalyst level of 2-3. The dissolved propylene was pumped out and replaced with nitrogen. Aliquots (2 ml) from the prepolymerized slurry was syringed into small vials, diluted 10 times with heptane, and used for subsequent polymerization experiments. 3. Main Polymerization The standard 3 liter reactor was employed. Heptane (1200 ml), triethyl aluminum

(0.095 g, 0.83 mmol), silane donor (0.017 g of a 60/40 molar mixture of CHMDMS and DCPDMS) at an Al:Si:Ti molar ratio of 200:20:1 were first charged into the reactor. The prepolymerized catalyst mix (2.2 ml slurry, 11 mg catalyst) was charged at 55 °C against gaseous propylene into the polymerization reactor. The reactor was then closed, hydrogen (400 ml) was added, and temperature and pressure set to final values of 70 °C and 1 Mpa within about 5 minutes. Polymerization was conducted for 2 hours. The following results were obtained: Catalyst Activity 28.1 kg-PP/g-cat

Isotactic Index 98.0

MFI 4.1

MWD 7.5

The data from Example 1 is also in Run No. 93 of Table 1. Example 3

1. Preparation of a solid catalyst component (A):

Anhydrous magnesium chloride (13.2 g, 0.14 mol), toluene (225 ml), epoxychloropropane (24.3 g, 0.26 mol) and tributyl phosphate (21.2 g, 0.078 mol) were introduced into a reactor which had thoroughly been purged with highly purified nitrogen. The temperature was raised to 50 °C with stirring, and the mixture was then maintained at this temperature for 2 hours, while the solids dissolved completely. Phthalic anhydride (3.2 g, 0.21 mol) was added to the solution, and then the solution was maintained for 2 additional hours at 50 °C. The solution was cooled to -28 °C. Titanium tetrachloride (151 ml, 1.37 mol) was added drop-wise over the course of 1 hour. The solution was heated to 80 °C over the course of 2 hours, while a solid product precipitated. Dibutyl phthalate (5 ml, 0.018 mol) was added and the mixture was maintained at the temperature of 80 °C for 1 hour.

The solid portion was collected by filtration and washed twice with a mixture of toluene (239 ml) and titanium tetrachloride (26.5 ml). A brown-yellow solid precipitate was obtained. The solid was then treated three times with a mixture of toluene (239 ml) and titanium tetrachloride (26.5 ml) at 110 °C for 30 minutes. The solid was washed with hexane (4 x 10.5 ml). Component (A) contained 1.91% titanium by weight, 18.86% magnesium by weight,

12.58%o dibutyl phthalate by weight.

2. Preliminary Polymerization (Prepolymerization)

A 50-ml, jacketed, cone-bottom-shaped, glass vessel was used for the prepolymerization step. The reactor was first purged with nitrogen. Heptane (29 ml), triethyl aluminum (0.66 g, 6 mmol), and cyclohexylmethyldimethoxysilane (0.113 g, 0.6 mmol) were charged into the reactor. Component (A) (1.5 g) was added. Nitrogen was pumped out and replaced with propylene at 80 torr. Prepolymerization was carried out at ambient temperature (ca. 25 °C) for 0.5 hr to reach a PP/catalyst level of 2-3. The dissolved propylene was pumped out and replaced with nitrogen. Aliquots (2 ml) from the prepolymerized slurry was syringed into small vials, diluted 10 times with heptane, and used for subsequent polymerization experiments.

3. Main Polymerization

The standard 3 liter reactor was employed. Heptane (1200 ml), triethyl aluminum (0.095 g, 0.83 mmol), silane donor (0.002 g of a 60/40 molar mixture of CHMDMS and DCPDMS) at an Al:Si:Ti molar ratio of 200:2.5:1 were first charged into the reactor. The prepolymerized catalyst mix (2.2 ml slurry, 11 mg catalyst) was charged at 55 °C against a gaseous propylene into the polymerization reactor. The reactor was then closed, hydrogen (400 ml) was added, and temperature and pressure set to final values of 70 °C and 1 Mpa within about 5 minutes. Polymerization was conducted for 2 hours. The following results were obtained:

Catalyst activity 27.0 kg-PP/g-cat

Isotactic Index 95.1 MFI 6.9

MWD 9.9

The data from Example 1 is also in Run No. 90 of Table 1.

Example 4 1. Preparation of a solid catalyst component (A):

Anhydrous magnesium chloride (13.2 g, 0.14 mol), toluene (225 ml), epoxychloropropane (24.3 g, 0.26 mol) and tributyl phosphate (21.2 g, 0.078 mol) were introduced into a reactor which had thoroughly been purged with highly purified nitrogen. The temperature was raised to 50 °C with stirring, and the mixture was then maintained at this temperature for 2 hours, while the solids dissolved completely. Phthalic anhydride (3.2 g, 0.021 mol) was added to the solution, and then the solution was maintained for 2 additional hours at 50 °C. The solution was then cooled to -28 °C. Titanium tetrachloride (151 ml, 1.37 mol) was added drop-wise over the course of 1 hour. The solution was heated to 80 °C over the course of 2 hours, while a solid product precipitated. Dibutyl phthalate (2.5 ml, 0.009 mol) was added and the mixture was maintained at the temperature of 80 °C for 1 hour.

The solid portion was collected by filtration and washed twice with a mixture of toluene (239 ml) and titanium tetrachloride (26.5 ml). A brown-yellow solid precipitate was obtained. The solid was then treated thee times with a mixture of toluene (239 ml) and titanium tetrachloride (26.5 ml) at 110 °C for 30 minutes each. The solid was washed with hexane (4 x 10.5 ml).

Component (B) contained 2.20% titanium by weight, 18.92%) magnesium by weight and 9.28% dibutyl phthalate by weight. 2. Preliminary Polymerization (Prepolymerization)

0.5 hr to reach a PP/catalyst level of 2-3. The dissolved propylene was pumped out and replaced with nitrogen. Aliquots (2 ml) from prepolymerized slurry was syringed into small vials, diluted 10 times with heptane, and used for subsequent polymerization experiments. 3. Main Polymerization The standard 3 liter reactor was employed, heptane (1200 ml), triethyl aluminum (0.095 g,

0.83 mmol), silane donor (0.002 g of a 60/40 molar mixture of CHMDMS and DCPDMS) at an Al:Si:Ti molar ratio of 200:2.5:1 were first charged into the reactor. The prepolymerized catalyst mix (2.2 ml slurry, 11 mg catalyst) was charged at 55 °C against gaseous propylene into the polymerization reactor. The reactor was then closed, hydrogen (400 ml) was added, and temperature and pressure set to final values of 70 °C and 1 Mpa within about 5 minutes.

Polymerization was conducted for 2 hours. The following results were obtained: Catalyst activity 29.2 kg PP/g-cat

Comparison Example 5

1. Preparation of a solid catalyst component (A):

Anhydrous magnesium chloride (13.2 g, 0.14 mol), toluene (225 ml), epoxychloropropane (24.3 g, 0.26 mol) and tributyl phosphate (21.2 g, 0.078 mol) were introduced into a reactor which had thoroughly been purged with highly purified nitrogen. The temperature was raised to 50 °C with stirring, and the mixture was then maintained at this temperature for 2 hours, while the solids dissolved completely. Phthalic anhydride (3.2 g, 0.021 mol) was added to the solution, and then the solution was maintained for 2 additional hours at 50 °C. The solution was then cooled to -28 °C. Titanium tetrachloride (151 ml, 1.37 mol) was added drop-wise over the course of 1 hour. The solution was heated to 80 °C over the course of 2 hours, while a solid product precipitated. Dibutyl phthalate (5 ml, 0.018 mol) was added and the mixture was maintained at 80 °C for 1 hour. The solid portion was collected by filtration and washed twice with a mixture of toluene (239 ml) and titanium tetrachloride (26.5 ml). A brown-yellow solid precipitate was obtained. The solid was then treated three times with a mixture of toluene (239 ml) and titanium tetrachloride (26.5 ml) at 110 °C for 30 minutes each. The solid was washed with hexane (4 x 10.5 ml).

Component (A) contained 1.91% titanium by weight, 18.86% magnesium by weight, 12.58%) dibutyl phthalate by weight.

2. Preliminary Polymerization (Prepolymerization) A 50-ml, jacketed, cone-bottom-shaped, glass vessel was used for the prepolymerization step. The reactor was first purged with nitrogen. Heptane (29 ml), triethyl aluminum (0.66 g, 6 mmol), and cyclohexylmethyldimethoxysilane (0.113 g, 0.6 mmol) were charged into the

U reactor. Component (A) (1.5 g) was added. Nitrogen was pumped out and replaced with propylene at 80 torr. Prepolymerization was carried out at ambient temperatures (ca. 25 °C) for 0.5 hr to reach a PP/catalyst level of 2-3. The dissolved propylene was pumped out and replaced with nitrogen. Aliquots (2 ml) from the prepolymerized slurry was syringed into small vials. diluted 10 times with heptane, and used for subsequent polymerization experiments.

3. Main Polymerization

The standard 3 liter reactor was employed. Heptane (1200 ml), triethyl aluminum (0.095 g, 0.83 mmol), silane donor, cyclohexylmethyldimethoxysilane (0.016 g, 0.083 mmol), at molar ratio of 200:20:1 were first charged into the reactor. The prepolymerized catalyst mix (2.2 ml slurry, 11 mg catalyst) was charged at 55 °C against a gaseous propylene into the polymerization reactor. The reactor was then closed, hydrogen (400 ml) was added, and temperature and pressure set to final values of 70 °C and 1 Mpa within about 5 minutes. Polymerization was conducted for 2 hours. The following results were obtained: Catalyst activity 21.2 kg-PP/g-cat Isotactic Index 98.9

MFI 3.6

MWD 6.9.

The data from Example 1 is also Run No. 39 of Table 1.

Table 1. Effect of External Modifiers on Catalyst Performance.

[Conditions: amount of catalyst = 10.4-13.8 mg; TEAl:D:Ti prepolymerized at 10:1 :1 (mol); main polymerization at 1.0 MPa and 70 °C for 2 hours.]

Table 2. Characteristics of Polymers Prepared Using Various External Modifiers (Polymerization Conditions as in Table 1.)

Table 3. Effect of external modifiers (donors) on performance of catalysts with reduced I.I.

Conditions: amount of catalyst = 10.1-13.8 mg; TEAl:D:Ti prepolymerized at 10: 1 :1 (mol); main polymerization at 1.0 MPa and 70 °C for 2 hours.

Table 2. Heptane Extractables and DSC Standard Data of Polymers Prepared Using

Various External Modifiers and Catalyst with Reduced II

(Polymerization Conditions as in Table 1.)

Table: Effect of Various External Modifiers (donors) on Performance of Several Catalysts and Properties of the Relevant Polymers Prepared.

PART A

PARTB

As taught by the present invention and disclosed by the data in the above tables, the present invention gives a polymer with a broad molecular weight distribution. The molecular weight distribution (MWD) of a polymer affects many of its physical properties. For example, the propylene polymer that is used for making BOPP film requires a polymer that has a relatively broad MWD. The broad MWD is important in giving the polymer sufficient strength so that it will not tear easily when stretched. This is important in the application of the polymer as well as in processing of the polymer. The higher strength, i.e. broad MWD allows the processing equipment (i.e., the equipment that stretches the polymer to make the film) to run faster without film breakage.

Traditionally, polypropylene produced using older first or second generation TiCl₃ catalysts gives polymer with MWD (as measured by MJM_n using GPC) in the range of 8 to 10, which has been found to be suitable for making BOPP films.

Polypropylene produced using more recent third or forth generation high activity catalyst typically give polymer with MWD of 4 to 5. Experience has found that this type of polymer is not suitable for making BOPP films. The catalyst system of the present invention forms polymers with the MWD in the range of 8-10, suitable for making BOPP films and has a high activity.

The silane composition described in the present invention is a convenient starting point in obtaining a broader MWD. While a 60:40 molar ratio of CHMDMS and DCPDMS is preferred, the present invention also works if the silane mixture is changed from the present 60:40 molar ratio. The workable range is actually determined by the type of polymer desired. The important part of this mixture is not in the molar or weight composition of the mixture, but in the choice of components in the mixture. The preferred silanes are chosen based on their hydrogen sensitivity. If the hydrogen sensitivity of the two silanes is similar, the polymer formed does not have a broadened MWD.

The primary objective of the present invention is to broaden the MWD by using different external electron donors (donors). The variables studied were the type of donor, materials including: cyclohexylmethyldimethoxysilane (CHMDMS), dicyclopentyldimethoxysilane (DCPDMS), diisobutyldimethoxysilane (DIBDMS), isobutylisopropylmethylmethoxysilane

(IBIPDMS), tetramethylpiperidine (TMP), and CRM-1 (CHMDMS & DCPDMS). The level of donor, i.e. ratio of donor to catalyst, level studied included donoπTi ratios of 20, 10, 5 and 2.5.

Two other characteristics of the polymer prepared were considered as typical and important from the application point of view: (i) flexural modulus (reflecting the polymer stiffness) which should be as high as possible for most applications; and (ii) molecular weight distribution which should be wide enough to cope with the BOPP film applications.

Characteristic (i) is obtainable using external modifiers exhibiting a high stereospecifying potential, such as DCPDMS. Characteristic (ii) poses problems when prior catalysts are employed and considerable effort has been exerted worldwide to meet demands of both converters and end users. The simplest way to widen the MWD seems to be a tailor-made formulation of external modifier(s) and one of the most important aspects of the present invention is an achievement of this result.

All the data used for the following discussion is summarized in the above Tables. It also includes the main conditions of the polymer preparation and assessment of the as-polymerized product (RDS, II, MFI and BD) reported earlier. For runs 3-65 DSC, GPC and flexural modulus data were acquired and reported. For Runs 67-97, DSC data were also included with the remaining data.

It follows from all preceding data that the catalyst system of the present invention increases stereospecificity upon increasing the D/Ti ratio for all efficient external modifiers. The stereospecificity can be expressed — under certain simplifications — in terms of the crystallinity of polymer prepared. The crystallinity is most easily obtainable via DSC measurement and the long-term experience shows that the enthalpy of crystallization (-ΔHJ is the best correlatable parameter of the DSC data. It will be shown below that the last statement is applicable to most of the data obtained within a study. There is a general tendency of increasing the polymer crystallinity (in terms of -ΔHJ upon increasing the D/Ti ratio. As shown earlier, the catalyst itself plays also an important role. The decreasing order of "inherent" stereospecificity of the particular lots are as follows: 9314 > 156 > 241 > 242 > 158. This order is valid for CMDMS and DCPDMS.

As for other data related to the catalyst system stereospecificity (II and RDS), it follows expected patterns: as shown in the tables, isotacticity indices virtually increase and RDSs decrease upon increasing the Si:Ti ratio.

DCPDMS and CRM-1 provide higher activity in the catalyst system than CMDMS. In general terms, the activity is less dependent on the Si:Ti ratio (see the table). The flexural modulus is primarily controlled by the polymer crystallinity (expressed in terms of -ΔH_) as shown in the above tables.

The polymer MWD is of high importance, particularly for BOPP applications. The problem recognized worldwide is that there is no simple tool to measure the MWD with a sufficient accuracy. If GPC data are used for this purpose, it is advisable to obtain the whole set of data within a short period of time to avoid unacceptable shift and scatter of the data. This principle was applied as much as feasible in this study.

Several attempts were made to pick up a suitable variable for correlations with MWD. Eventually, the polymer crystallinity (expressed in term of -ΔH.) was found to be an acceptable correlatable parameter. Its advantage is seen also in the fact that the BOPP applications usually require a suppressed crystallinity. Hence, a tuned combination of a lower crystallinity and a widened MWD meet the demands of both BOPP converters and end users. The M_w/M₁₁ is not strikingly dependent on -ΔH_C for most of the catalyst systems except when CMDMS is employed as a modifier. A similar conclusion can be made for DCPDMS, but due to much narrower -ΔH_C range, it is difficult to prove its universal validity. It should be remarked that it is not easy to enlarge the -ΔH_C range with DCPDMS due to a very high stereospecifying potential of this particular silane. Again, a too narrow -ΔH_C range does not enable a clear conclusion on the correlation. It seems to be, however, that the MWD width is larger for CRM-1 as compared to

π the other two modifiers. In other words, CRM-1 would be the best performer as the MWD widener.

Summarization of the results obtained in several preceding-studies and addition of new data obtained under strictly comparable conditions allow the following conclusions: (i) Activity of the catalyst system can be controlled within a certain range by a) the type of catalyst b) the type of silane (DCPDMS and CRM-1 being more efficient than CMDMS); and c) the hydrogen level (controlling the polymer MFI).

Stereospecificity of the catalyst systems can be controlled within a wide range by : a) the type of catalyst b) the type of silane c) the Si/Ti ratio (or silane concentration), the last variable being the most efficient one.

(iii) The polymer crystallinity (expressed in terms of -ΔH_C obtained via DSC measurement) seems to reflect most universally the catalyst system stereospecificity. (iv) The polymer flexural modulus is controlled within a wide range by the polymer crystallinity; however, the application of CRM-1 seems to be favorable in obtaining higher flexural moduli at the same crystallinity in comparison to CMDMS and DCPDMS. (v) The width of MWD (obtained via GPC measurement), is an important factor in BOPP applications, is apparently larger for CRM-1 as compared to CMDMS and DCPDMS. (vi) The catalyst exhibiting the highest "inherent" stereospecificity renders the polymer the narrowest MWD as compared to catalysts with reduced "inherent" stereospecificities.

These and other embodiments of the present invention have been described above in the Detailed Description. The invention, however, is only limited to the appended claims.

Claims

WHAT IS CLAIMED is:

1. A catalyst for the polymerization of olefins comprising:

(A) a solid catalyst component comprising a magnesium dihalide, a titanium halide and an electron donor; (B) an organic aluminum compound, having a general formula AlR^X_j ,,, wherein R is hydrogen, or a hydrocarbon group having 1-20 carbon atoms, preferably an alkyl, aralkyl, or aromatic group; X is halogen, preferably chlorine or bromine, and n is an integer of from 1 to 3; and (C) a first organic silane compound, characterized in that, when said first silane is used for polymerization in the absence of any other silanes, the slope of the line fitted to a plot of the amount of hydrogen used in the polymerization (X-axis) v. resultant polymer melt flow rate (Y-axis) is between 2.5 and 5.0, preferably 3.25 to 3.75; and a second organic silane compound, characterized in that, when said second silane is used for polymerization in the absence of any other silanes, the slope of the line fitted to a plot of the amount of hydrogen used in the polymerization (X-axis) v. resultant polymer melt flow rate (Y-axis) is between 0 and 1.5, preferably 0.5 and 1.0.

2. A catalyst according to claim 1 wherein said magnesium dihalide is magnesium chloride, said titanium halide is titanium tetrachloride and said electron donor is a phthalate diester.

3. A catalyst according to claim 2 wherein said solid catalyst component (A) additionally comprises either or both of the following: (i) an organic epoxy compound, and (ii) an organic phosphorus compound.

4. A catalyst according to claim 3 wherein said organic epoxy compound is selected from the group consisting of oxides of aliphatic olefins and diolefins, oxides of halogenated aliphatic olefins and diolefins, and glycidyl ethers all having 2 to 8 carbon atoms selected from the group consisting of ethylene oxide, propylene oxide, butylene oxide, butadiene oxide, butadiene dioxide, epoxy chloropropane, methyl glycidyl ether, and diglycidyl ether. 5. A catalyst according to claim 3 wherein said organic phosphorus compound is selected from the group consisting of trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, tributyl phosphite, and triphenyl phosphite.

6. A catalyst for the polymerization of olefins comprising:

(A) a solid catalyst component comprising a magnesium dihalide, a titanium halide and an electron donor;

(B) an organic aluminum compound, having a general formula AlR_X_3.n, wherein R is hydrogen, or a hydrocarbon group having 1-20 carbon atoms, preferably an alkyl, aralkyl or aromatic group; X is halogen, preferably chlorine or bromine, and n is an integer of from 1 to 3; and (C) a mixture of cyclohexylmethyldimethoxysilane and dicyclopentyldimethoxysilane.

7. A catalyst according to claim 6, wherein solid component (A) is coprecipitated from a homogeneous solution comprising said magnesium dihalide and said titanium halide.

8. A catalyst according to claim 7 wherein said magnesium dihalide is magnesium chloride, said titanium halide is titanium tetrachloride, and said electron donor is a phthalate diester. 9. A catalyst according to claim 8, wherein said homogeneous solution additionally comprises either or both of the following: (i) an organic epoxy compound, and (ii) an organic phosphorus compound.

10. A catalyst according to claim 9 wherein said organic epoxy compound is selected from the group consisting of oxides of aliphatic olefins and diolefins, oxides of halogenated aliphatic olefins and diolefins, and glycidyl ethers all having 2 to 8 carbon atoms selected from the group consisting of ethylene oxide, propylene oxide, butylene oxide, butadiene oxide, butadiene dioxide, epoxy chloropropane, methyl glycidyl ether, and diglycidyl ether.

11. A catalyst according to claim 9 wherein said organic phosphorous compound is selected from the group consisting of trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, tributyl phosphite, and triphenyl phosphite.

12. A catalyst for the polymerization of olefins comprising: (A) a solid catalyst component comprising a magnesium dihalide, a titanium halide and an electron donor;

(B) an organic aluminum compound, having a general formula A1R-X₃._n, wherein R is hydrogen, or a hydrocarbon group having 1-20 carbon atoms, preferably an alkyl, aralkyl or aromatic group; X is halogen, preferably chlorine or bromine and n is an integer of from 1 to 3; and

(C) a mixture of two or more organic silane compounds, said mixture of two or more silanes used, by itself or in addition to other factors, to obtain a resultant polymer with a molecular weight distribution between 6 and 11, preferably between 7 and 10.

13. A catalyst according to claim 12 wherein said mixture of two or more organic silane compounds comprise cyclohexylmethyldimethoxysilane and dicyclopentyldimethoxysilane.

14. A catalyst according to claim 13 wherein said solid catalyst component (A) is coprecipitated from a homogeneous solution comprising said magnesium dihalide and said NOT FURNISHED UPON FILING

phosphorus compound to form a homogeneous solution, the organic epoxy compound being selected from the group consisting of oxides of aliphatic olefins and diolefins. oxides of halogenated aliphatic olefins and diolefins, and glycidyl ethers all having 2 to 8 carbon atoms selected from the group consisting of ethylene oxide, propylene oxide, butylene oxide, butadiene oxide, epoxy chloropropane, methyl glycidyl either and diglycidyl ether; and the organic phosphorus compound being selected from the group consisting of trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, tributyl phosphite, and triphenyl phosphite; (2) mixing the homogeneous solution with a liquid titanium tetrahalide having a formula TiX_n(OR²)₄__n wherein X is halogen, R² is an alkyl group being identical or different, and n is an integer from 0 to 4;

(3) adding at least one auxiliary precipitant selected from the group consisting of organic carboxylic acid anhydrides, organic carboxylic acids, ethers, and ketones to form a precipitate;

(4) adding at least one polycarboxylic acid ester when the precipitate appears;

(5) separating the precipitate from the mixture and treating the separated precipitate with titanium tetrahalide or a mixture of titanium tetrahalide in an inert diluent;

(6) prepolymerizing an olefin using a cocatalyst system comprising said precipitate and an organic aluminum compound having a general formula A1R_X₃.„, wherein R is hydrogen, or a hydrocarbon group having 1-20 carbon atoms, preferably an alkyl, aralkyl or aromatic group; X is halogen, preferably chlorine or bromine; and n is an integer of from 1 to 3;

(7) placing said precipitate, after prepolymerization, into a reaction vessel with an organic aluminum compound, having a general formula AlR_X_3.n, wherein R is hydrogen, or a hydrocarbon group having 1-20 carbon atoms, preferably an alkyl, aralkyl, or aromatic group; X is halogen, preferably chlorine or bromine; and n is an integer of from

1 to 3; and two or more organic silane compounds of the formula Si(R³)_ro(OR⁴)₄._m, wherein R³ and R⁴ are identical or different being selected from the group consisting of alkyl, aryl, and cycloalkyl;

(8) charging the reaction vessel with an olefin monomer; (9) closing the reactor and adding hydrogen gas.

21. The process according to claim 20 wherein said two or more organic silane compounds comprise cyclohexylmethyldimethoxysilane and dicyclopentyldimethoxysilane.

22. The process according to claim 21 wherein said auxiliary precipitant is an organic carboxylic acid anhydride. 23. The process according to claim 21 wherein said auxiliary precipitant is phthalic anhydride.

24. The process according to claim 21 wherein said at least one polycarboxylic acid ester is a phthalic acid diester.

25. A catalyst for the polymerization of olefins comprising:

(A) a catalyst component consisting essentially of about 1.5-6.0% by weight of titanium, about 10-20%) by weight of magnesium, about 40-70% by weight of halide selected from the group consisting of chlorine, bromine, and iodine, about 5-25% by weight of polycarboxylic ester selected from the group consisting of the esters of aliphatic, aromatic, and alicyclic polycarboxylic acids; and about 0.1-2.5% by weight of an organic phosphorus compound selected from the group consisting of alkyl and aryl esters of phosphoric acid and phosphorous acid wherein each alkyl has 1 to 6 carbon atoms and each aryl has 5 to 10 carbon atoms, said catalyst component being prepared by a process having the following steps:

(1) dissolving in a solvent mixture a magnesium halide compound selected from the group consisting of magnesium halide, complexes of magnesium halide wherein the halide is replaced by any alkyl group or a haloalkyl group; the solvent mixture consisting of an organic epoxy compound, selected from the group consisting of oxides of aliphatic olefins and diolefins, oxides of halogenated aliphatic olefins and diolefins, glycidyl ethers all having 2 to 8 carbon atoms, and an organic phosphorus compound selected from the group consisting of alkyl phosphates, aryl phosphates, aralkyl phosphates, alkyl phosphites, aryl phosphites, aralkyl phosphites where alkyl has one to four carbon atoms and aryl has six to ten carbon atoms to form a homogeneous solution;

(2) mixing the homogeneous solution with a liquid titanium compound having the formula TiX_n(OR²)₄._n wherein X is halogen, R² is an alkyl group being identical or different, and n is an integer of 0 to 4;

(3) adding at least one auxiliary precipitant selected form the group consisting of carboxylic acid anhydrides, carboxylic acids, ethers, and ketones to form a precipitate;

(4) adding a polycarboxylic acid ester when a precipitate appears; (5) separating said precipitate and treating the separating precipitate with a titanium compound, TiX_n(OR²)₄._n, wherein X is halogen, R² is a hydrocarbon group and may be identical or different, and n is an integer of from 0 to 4, or a mixture thereof in an inert diluent; (B) an organic aluminum compound, having the general formula AIR^X^, wherein R is hydrogen, or a hydrocarbon group having 1-20 carbon atoms, preferably an alkyl, aralkyl or aromatic group; X is halogen, preferably chlorine or bromine and n is an integer of from 1 to 3; and

(C) a first organic silane compound, characterized in that, when said first silane is used for polymerization in the absence of any other silanes, the slope of the line fitted to a plot of the amount of hydrogen used in the polymerization (X-axis) v. resultant polymer melt flow rate (Y-axis) is between 2.5 and 5.0, preferably 3.25 to 3.75; and a second organic silane compound, characterized in that, when said second silane is used for polymerization in the absence of any other silanes, the slope of the line fitted to a plot of the amount of hydrogen used in the polymerization (X-axis) v. resultant polymer melt flow rate (Y-axis) is between 0 and 1.5, preferably 0.5 and 1.0.

26. A catalyst according to claim 25 wherein said first silane is cyclohexylmethyldimethoxy- silane and said second silane is dicyclopentyldimethoxysilane.

27. A catalyst according to claim 26 wherein said auxiliary precipitant is an anhydride of an organic carboxylic acid.