MXPA96003216A - Dual donor catalyst system for olefi polymerization - Google Patents

Abstract

The present invention provides a catalyst system that exhibits unexpected control of desired properties in polyolefin products. The catalyst system includes a catalyst supported on titanium in combination with a mixture of tetraethoxysilane (TEOS) and dicyclopentyldimethoxysilane (DCPMS). This catalyst system has been found to be effective for preparing polypropylene and polypropylene copolymers having relatively high melt flow rates and relatively large molecular weight distribution.

Description

DUAL DONOR CATALYST SYSTEM FOR THE POLYMERIZATION OF OLEFINS BACKGROUND Field of the Invention The present invention relates to catalyst components for polymerization of olefins, which can produce polyolefins, and in particular polypropylene having a high crystallinity and relatively high melt flow rates (MFR), and consequently processing properties. adequate. Description of the Prior Art Propylene homopolymers and copolymers generally have certain properties that are unsatisfactory for specific applications. Therefore, it is necessary to modify certain characteristics during the manufacture of polypropylene to make the polymer more useful for certain final results. For example, if the stiffness of the propylene polymer or copolymer is improved, it is possible to reduce the thickness of the resulting molded product formed therefrom. There are numerous processes and catalyst systems for polymerization and copolymerization in the prior art from which it is possible to design a processing catalyst system to obtain a specific set of properties of a resulting polymer or copolymer. For example, in certain applications, a product with a higher melt flow rate is desirable. Such a product has a lower melt viscosity than a product with a lower melt flow rate. Many manufacturing processes of polymers or copolymers that operate with high shear rates, such as injection molding, oriented film and heat-bonded fibers, would benefit from a lower viscosity product by improving yield rates and reducing energy costs. Generally, the olefin polymers obtained using an active catalyst component of the magnesium supported type (MgCl 2) have a limited range of melt flow rate and limited mechanical properties. However, as indicated, for certain applications, polypropylene polymers that flow easily during melting have improved processing characteristics. The discovery of more suitable co-catalysts or electron donors to accompany the magnesium-supported catalyst components has been of great benefit to improve the efficiency of the catalyst systems and the quality control of the polymeric product. In such catalyst systems, the co-catalyst activates the catalyst and provides initiation of a polymer chain. The co-catalyst that has historically worked well with magnesium supported catalysts is that of organoaluminum compounds, more typically triethylaluminum ("TEAL") or other trialkyl compounds. Examples of other useful organoaluminum compounds include aluminum alkyl dihalide. , trialcoxialuminium, dialkyl aluminum halide and triisobutyl aluminum. An electron donor compound is used in the polymerization reactor to control the stereoregularity and shape of the polymer. Although a wide range of compounds are generally known as electron donors, a particular catalyst can have a specific compound or group of compounds with which it is especially compatible. The discovery of an appropriate type of electron donor can lead to a significant improvement in the properties of the polymer product, such as the distribution of molecular weights and the melt flow. It would be highly advantageous to discover a specific group of electron donors for magnesium supported catalysts that would provide beneficial results. The present invention is directed to the use of a mixture of silane electron donors. In EP 385765A (published September 5, 1990), a catalyst system composed of a titanium catalyst component supported on magnesium in combination with two silane electron donors is disclosed., a specific embodiment of a donor mixture of which is directed to dicyclopentyl dimethoxysilane ("DCPMS") and propyltriethoxysilane ("PTES"). In U.S. Patent No. 5,100,981, a catalyst system composed of a titanium supported catalyst in magnesium and a mixture of two electron donors, cyclohexylmethyl dimethoxysilane ("CMMS") and phenyltriethoxy silane ("THER") is disclosed. . EPO 601 496 A1 discloses a process for preparing an olefin polymer by polymerizing an olefin in the presence of a catalyst including A) a solid titanium catalyst containing magnesium, titanium, halogen and an electron donor, B) a compound of organo-aluminum, and C) an electron donor represented by a silicon compound [R ^ Si (OR2) 2] and a second olefin polymer using (A), (B) and D) an electron donor of a silicon compound [R ^ Si- (OR2) 4-n]. This document suggests that C) and D) are temporarily exchanged in other reaction schemes. C) may include dicyclopentyl dimethoxysilane (DCPMS), but neither C) nor D) describe triethoxysilane (TEOS). It has now surprisingly been found that the use of two different organo-silicon compounds as electron donors, in combination with a magnesium supported catalyst, is capable of generating highly isotactic polypropylene polymers having a moderately broad molecular weight distribution, as well as relatively high melt flow rates. Summary of the Invention It has been found that a catalyst system based on ^ *? N solid catalyst component supported on magnesium, an organoaluminum catalyst component, and a mixture of two different electron donors, one of which dominates functionally to the other, it is capable of achieving highly crystalline polyolefins having the characteristics of a moderately broad molecular weight distribution and relatively high melt flow rates. In a preferred embodiment, it has been found that two electron donor compounds of organosilicon compound, dicyclopentydimethoxy silane ("DCPMS") and tetraethoxysilane ("TEOS"), provide an optimal mixture of electron donors in the catalytic system of the present invention. It has been discovered that DCPMS acts as the dominant donor in combination with the weaker donor, TEOS. It was found that a mixture of the two donors in a catalyst system generates isotactic polypropylene having product characteristics similar to the polypropylene product generated by a supported catalyst system employing 100% DCPMS such as high crystallinity and low melt flow rate. This discovery allows the use of the weaker donor to make polyolefin polymers in a first stage reaction with the polymeric characteristics of the TEOS donor, i.e., high melt flow rate, and polymerizing the resulting polyolefin in a second stage reaction with a mixture of the weak donor ("TEOS") and the stronger donor ("DCPMS") to achieve a high polyolefin polymer of high viscosity having beneficial characteristics of relatively high melt flow rate (MFR) and distribution of Molecular weights (MWD) moderately broad, these polymeric characteristics being independently obtainable in another way by the use of each silane electron donor alone. In summary, the use of the present dual donor system allows the production of a polyolefin final product with relatively high MFR, a moderately broad MWD, similar to those of the polymers generated by DCPMS. The surprising and unexpected result in the use of the dual donor system of the present invention lies in the dominant characteristics of the DCPMS. Ordinarily, it would have been expected that the use of DCPMS in combination with TEOS would result in physical characteristics in the final polymer attributable to the proportional amount of each electron donor used. However, the discovery that the use of these two donors in a catalyst system generates polyolefins with properties attributable to the dominant electron donor, DCPMS, has resulted in the development of a two-stage polymerization process in which It makes a polyolefin product of high MFR in the first stage, by using the TEOS donor, while the reaction of the second stage, using a TEOS / DCPMS mixture, allows the production of a highly crystalline polyolefin having the characteristics of moderately broad molecular weight distribution techniques < - '* "Relatively high MFR In sum, the use of TEOS as an electron donor in a first-stage olefin polymerization reaction, followed by the introduction of the electron donor DCPMS in a second-stage reaction, has resulted in the production of polyolefin crystalline products having the characteristics of moderately broad MWD of the polymer and relatively high MFR The present invention provides a catalyst system for the polymerization of olefins, comprising: (A) a magnesium supported solid catalyst component of magnesium; (B) an organoaluminum co-catalyst; and (C) a dual donor catalyst system comprising (1) a first electron donor compound, and (2) a second dominant electron donor compound, wherein the MFR (a) of a polyolefin obtained by polymerizing an alpha-olefin in presence of the dominant electron donor (2) and the MFR (b) of polyolefin polymerized under the same polymerization conditions, but using a mixed donor system of 50 mol% (1) and 50 mol% (2), satisfies the relationship LOG [MFR (a)] / [MFR (b)] is less than or equal to 1.2. The present invention is further directed to a process for making a homopolymer or copolymer, or a physical reactor mixture of homopolymer and copolymer (impact copolymer), of an alpha-olefin having a flow rate of, .. "-fused relatively high, high crystallinity and moderately broad molecular weight distribution, comprising polymerizing an alpha-olefin in a multi-step reaction in the presence of (1) a high activity magnesium supported titanium catalyst system, (2) a organoaluminum catalyst, and (3) a mixture of electron donors of two different compounds in at least two steps, comprising: (A) in the first step, polymerizing the alpha-olefin in the presence of a first electron donor ( i) to produce "one polyolefin, and (B) in another step, further polymerize the polyolefin polymer of step one in the presence of a mixture of electron donor donors (i) and a dominant electron donor (ii) to achieve a final polyolefin. Brief Description of the Drawings Figure 1 is a graph showing the relationship between MFR and hydrogen uptake. Figure 2 is a graph illustrating the relationship between MFR of the polyolefins herein in relation to varying amounts of the dual electron donor of the present invention. Figure 3 is a graph illustrating the melt heat ratio of the polyolefin prepared using varying amounts of the dual electron donor of the present invention.

Figure 4 is a graph illustrating the balance of crystallinity versus melt flow rate of the polymers of the invention using a two-step, mixed donor process. Detailed Description of the Invention The present invention is directed to the combination of a mixture of two electron donors ("dual donor") with a particular type of catalyst component for use in the polymerization of polyolefins. This combination of dual donor and catalyst component comprises a catalyst system that results in better control of the crystallinity and the melt flow rate than that provided by either of the electron donor compounds of the dual donor system. Moreover, the present catalyst system maintains a high catalyst efficiency relative to other suitable catalyst systems and, additionally, the catalyst system of the present invention retains most of its high activity over time. These and other beneficial advantages will be more apparent from the following detailed description of the invention and the accompanying examples. Electron donors are typically used in two ways in the formation of a Ziegler-Natta catalyst and a catalyst system. First, an internal electron donor can be used in the catalyst formation reaction when the transition metal halide is reacted with the metal hydride or metal alkyl. Examples of internal electron donors include: amines, amides, ethers, esters, aromatic esters, ketones, nitriles, phosphines, stibines, arsines, phosphoramides, thioethers, thioesters, aldehydes, alcoholates and salts of organic acids. The second use for an electron donor in a catalyst system is as an external electron donor and stereo-regulator in the polymerization reaction. The same compound can be used in both cases, although they are typically different. An external, common electron donor is an organosilicon compound, for example tetraethoxysilane, a dual donor of those used in the present invention. A description of the two types of electron donors is provided is U.S. Patent No. 4,535,068, the disclosure of which is incorporated herein by reference. By referring particularly to the present invention to external electron donors, the term "electron donor", as used herein, refers to the external donor. The external electron donor acts as a stereo-regulator to control the amount of atactic form of the polymer produced. It can also increase the production of isotactic polymers. In these functions, the MWD, the high crystallinity, and the MFR of the polymer produced will be affected by the particular donor used. Organic silicon compounds for use as electron donors are known in the art. Examples of electron donors which are organic silicon compounds are described in U.S. Patent Nos. 4,218,339; 4,395,360; 4,328,122; Y 4,473,660. As mentioned, a particular catalyst can produce better results when coupled with a particular group of electron donors. Examples of this conjunction of catalyst and electron donors are described in U.S. Patent Nos. 4,562,173 and 4,547,552. The effectiveness of the electron donor depends to a large extent on its compatibility with the catalyst with which it is used. Apparently, there is some electrical and / or steric compatibility between certain donors and particular catalysts that yield better results than with the same catalyst and less compatible donors. This compatibility is not fully understood, nor is it predictable, as there are no external suggestions that an electron donor would work better than another with a particular catalyst, and as demonstrated by the present invention, it can be discovered that A certain combination of electron donors is more compatible with a particular type of catalyst than would otherwise be predictable. It has been discovered herein that a particular combination of electron donors significantly improves the catalytic properties of a specific type of catalyst. The catalyst involved in the present invention is a Ziegler-Natta type titanium catalyst for the polymerization of olefins. The catalyst system of the present invention comprises a solid catalyst component in combination with a dual donor., and comprises: (A) a titanium catalyst component, highly active, supported on magnesium, consisting essentially of magnesium, titanium, halogen and an internal electron donor, (B) an organoaluminum compound, and (C) a dual donor, where one electron-donor compound dominates the other. Processes for polymerizing or copolymerizing olefins in the presence of these Ziegler-Natta type catalysts are described in Japanese patent publications, open to the public Nos. 83006/1983, 138705/1983, 138706/1983, 138707/1983, 138708/1983, 138709/1983, 138710/1983 and 138715/1983. Typical solid titanium supported catalyst systems and their preparations are outlined in U.S. Patent Nos. 4,990,479 and 5,159,021, the disclosures of which are incorporated herein by reference. Briefly, the catalyst component (A) can be obtained by (i) suspending dialkoxy magnesium in an aromatic hydrocarbon which is liquid at normal temperatures, (ii) contacting the dialkoxy magnesium with a titanium halide and, in addition, (iii) putting contacting the resulting composition a second time with the titanium halide, and contacting the dialkoxy magnesium with a diester of an aromatic dicarboxylic acid at some point during the treatment with the titanium halide in (ii). The component (B) of the present catalyst system is an organoaluminum co-catalyst. The organoaluminum compound must be free of halogen. Suitable halogen-free organoaluminum compounds (component (B)) are, in particular, branched, unsubstituted alkyl aluminum compounds of the formula A1R3, where R denotes an alkyl radical having from 1 to 10 carbon atoms, such as for example trimethylaluminum, triethylaluminum, triisobutylaluminum, and tridyisobutylaluminum. Additional suitable compounds are readily available and have been widely disclosed in the prior art, including U.S. Patent No. 4,990,477, incorporated herein by reference. The above-described catalyst component supported on magnesium (A) exhibits an efficiency comparable to that of previously known catalyst systems, when the component (A) is combined with an appropriate silane electron donor, such as TEOS or DCPMS, but that control it is significantly improved when the catalyst is combined with a combination of both of these electron donors when used in the multi-step process of the present invention. This improved control of MFR / isotacticity results in improved control of the properties of the polymeric product. In a preferred embodiment of the present invention, the external electron donors chosen are the silane compounds dicyclopentyldimethoxysilane and tetraethoxysilane. It has been found that when these silanes are used in combination as a dual donor in a magnesium supported catalyst system, DCPMS acts as a dominant donor by generating polyolefins having crystallinity (melting heat) and MFR properties similar to those resulting from the use of DCPMS alone. This discovery allows a two-stage olefin polymerization process in which the weaker donor, TEOS, is used in the first stage to make polyolefins with the superior MFR characteristics of TEOS and employing in a second stage polymerization with a mixture of TEOS and DCPMS to produce a final polyolefin with a relatively high MFR, high crystallinity and moderately broad MWD. Although one might ordinarily expect a combination of polymeric characteristics from the use of a catalyst system employing two different stereo-regulatory electron donors, the unexpected result here is that there is a dominant donor effect and that the effects of the two donors are not averaged. As a result, smaller amounts of DCPMS in combination with TEOS can be used to generate polyolefin polymers having the high crystallinity and low MFR associated with the use of DCPMS. Operational quantities of the DCPMS silane electron donor of the preferred dual donor mixture are about 10-99 mol% DCPMS, TEOS being present in amounts of about 90-1 mole%. A preferred "DCPMS to TEOS approach is about 30-70% DCPMS and 70-30% TEOS." More preferred relationships of DCPMS to TEOS, in the dual donor catalyst system of the present invention are 45- 55 mole% DCPMS at 55-45 mole% TEOS Examples of olefins that can be used in the polymerization process of the present invention are alpha-olefins having 20 carbon atoms such as ethylene, propylene, 1-butene , 4-methyl-l-pentene, 1-octene, 1-hexene, 3-methyl-1-pentene, 3-methyl-1-butene, 1-decene, 1-tetradecene, and 1-elcosine. preferred embodiment of the invention, there is provided a multi-step process for the preparation of a polyolefin, in which the alpha-olefin is polymerized in two stages in the presence of (1) a catalyst system supported on magnesium, and (2) a electron donor mixture of the two silane compounds, TEOS and DCPMS, comprising the steps of: (A) polymerizing in a first step u α-olefin in the presence of a TEOS silane electron donor, to produce a polyolefin having an MFR of between 10 and 1,200; (B) In another step, further polymerize the polyolefin of step (A) in the presence of a mixture of TEOS / DCPMS, thereby producing a polyolefin polymer having an MFR of between 1 and 120, and a MWD of less than 6. The complete set of data for Figures 1, 2 and 3 is tabulated is Tables I, II and III . The response curves "FR-H2 when using TEOS or DCPMS, respectively, are shown in Figure 1. The very high MFRs typical of the TEOS donor are shown, and the low MFRs typical of the DCPMS donor. to build this figure is tabulated in Tables I and II The dramatic DCPMS domain is shown in Figures 2 and 3, showing the behavior of MFR and (H) as a function of the polymerized DCPMS / TEOS molar ratio in each reactor Figure 2 shows that MFR is virtually unchanged from 100% DCPMS to 10% DCPMS Figure 3 shows a similar behavior with the crystallinity, measured by the DSC heat of fusion, again, the crystallinity is virtually unchanged from 100 to 10% DCPMS.

Table I Hydrogen Effect on MFR with TEOS as Donator Reactor Table II Effect of Hydrogen on MFR with DCPMS as Donator Reactor Table III Effect of Hydrogen on MFR with TEOS and DCPMS as Donors Reactors Table IV Two Stage Polymerization Using Dual Donor (A) First Stage - One Hour Polymerization Time (B) Second Stage - One Hour Polymerization Time Table V Polypropylene with High MFR from Using TEOS Only Comparative Example Table VI Tables IV and V demonstrate the results using the two-step polymerization process of the present invention. They demonstrate high crystallinity for the two-stage polymer product compared to the use of TEOS alone, both being equal in MFR. As further evidence of the DCPMS domain over TEOS, Table VI above shows the typical MWD obtained with polymerization using TEOS, DCPMS and a 50/50 physical mixture of TEOS / DCPMS, respectively. The MWD data of the mixed donor system are unexpected and atypical. Catalyst systems with two donors without a dominant donor, when mixed, must produce polymers with a larger MWD than any polymer produced with a single donor. However, as can be seen from Table VI, the MWD of the mixed donor is not wider, and is very close to that of DCPMS. Processes for the practice of the present invention of mixed donor are outlined in the following manner: A. Process for Polymerization of Homopolymer / Copolymer of Polypropylene * in Reactors by Loads Polymerization of propylene inside a reactor by autoclave loads using a mixed donor catalyst system shows the dominant nature of DCPMS over TEOS. In combination with a TiCl4 catalyst system supported on magnesium, the donors generally stereo-regulate the polymerization of propylene to make polymers of greater or lesser crystallinity and the division between the amount of isotactic, syndiotactic and atactic polymer produced by the contribution of each of the mixed donors. The DCPMS acts as a highly stereo-regulatory donor, while TEOS is a low-stereo-regulatory donor. However, at the same level of H2, DCPMS produces a polymer with much lower melt flow rate than that of TEOS. When combined, the properties of the polymer produced follow more closely those of DCPMS than the heavy averages of the properties of the two pure systems. Charge polymerization of propylene-based polymer using mixed donor technology is used in two ways: (1) in a pure charge mode, where the two donors are pre-mixed and reacted with magnesium supported TiCl 4 catalyst , to form a slurry and injected in an autoclave type reactor, or (2) in a semi-load mode consisting of two stages. In the first stage, a single donor, TEOS, is pre-mixed and reacted with the TiCl4 catalyst supported on magnesium, formed in a slurry and injected into a reactor 'autoclave. Polymerization with this one-donor catalyst system continues for some period of time, followed by the injection of the second donor, DCPMS, where the polymerization again continues for a second preset time period. In pure charge mode, the created polymer closely resembles that of the DCPMS alone; while in the semi-load mode, only the polymer produced in the second stage closely resembles that of the DCPMS. The polymer produced in semi-loads is therefore an intimate mixture of (A) molecules produced by TEOS of high melt flow rate, low crystallinity, and (B) molecules produced by TEOS / DCPMS, of high crystallinity, low rate of melt flow. The polymerization window of the overall melt flow rate of the process in semi-loads, however, is much larger than that of the pure load process. B. Continuous Process for Making Impact Copolymer The polymerization was carried out using a continuous multi-stage process, where the first two reactors are stirred tank reactors of bulk liquid propylene slurry, followed by an additional reactor type bed reactor fluidized gas phase. Polypropylene homopolymer is produced by a polymerization of propylene within the bulk propylene slurry reactors followed by a polymerization of 20-80% ethylene and 80-20% propylene copolymer within the gas phase reactor. This intimate mixture of homopolymer and ethylene / propylene copolymer is known in the art as "impact copolymer (ICP)". The composition of the final product is an ICP having between 0.50% ethylene / propylene copolymer and 100-50% propylene homopolymer. The total percentage ethylene of these products varies from 0 to 25%, and the typical ICP melt flow rates vary from 0.1 to 200. To achieve products with high MFR and moderately broad MWD, the two silane donors, TEOS and DCPMS , they are added separately to the two bulk liquid reactors: TEOS is first injected into the first reactor, followed by injection of DCPMS into the second reactor. In the used configuration, a recirculation system is returned to the second reactor. (No additional donor is introduced during the ethylene / propylene polymerization step). This effectively creates a multi-stage process where the first reactor has exclusively the TEOS donor, while the second reactor has a combination of TEOS and DCPMS. As DCPMS is dominant over TEOS, the second mixed donor reactor behaves very closely with DCPMS itself. It achieves a polymer with high heat of fusion, high MFR. Alternatively, if an ICP of high crystallinity is desired, a recirculation stream is returned to the first reactor. In the present description, a multi-stage process is created with TEOS and DCPMS within both reactors. The following Examples and Comparative Examples illustrate the present invention and its various advantages in greater detail. The results are summarized in Tables I-IV. Catalyst The catalysts provided herein are magnesium supported catalysts sold commercially by Toho Titanium Corporation of Japan and identified as THC-C type catalysts and that sold by Mitsui Petrochemical Corporation of Japan described as TK-220. Example 1 (I) One Stage Polymerization In a two liter autoclave polymerization reactor, which has been cleaned, dried and purged well with nitrogen, the millimols of silane donor (0.1M solution in hexane) are syringed. , followed by the addition of 2 millimoles of TEAL (triethyl aluminum in hexane). After isolating the reactor, the required amount of hydrogen was introduced into the reactor, as measured by the pressure drop from a 300 cc container. The 1,000 ml of propylene are then added to the reactor. The introduction of the required amount of catalyst in slurry in mineral oil as 15 or 20% by weight solids was followed, which was pushed into the reactor with 250 g of propylene. The temperature of the room temperature reactor temperature was raised to 70 ° C, and the reaction was continued for one hour. After the polymerization period, the excess propylene was vented outside the reactor and the polymer collected and dried in a vacuum oven. The polymer was formed into beads with the addition of 500 ppm BHT, and samples were taken for insolubility measurements in heptane, MFR, MWD and DSC. Example 2 (II) Two Stage Polymerization The polymerization process was similar to that of Example 1, except that 0.2 millimoles of TEOS were initially introduced into the reactor and 750 ml of propylene were first added to the reactor. After one hour of polymerization, 0.2 millimol of DCPMS was pushed into the reactor with 250 ml of propylene, and the polymerization was continued for an additional hour. The results showed 44.7 ° / min MFR, 94.0 HI, activity of 12,600 g PP / g-cat-hr, and 4.72 MWD of the polymer. The analysis of the polymer showed the following composition: * Obtained from Example 1 ** Obtained from retro-calculation using log / log physical mixture of MFRs of first and second stage polymer amount and MFR *** Obtained by difference These results demonstrate that the retro-calculated MFR of the polymerization of second stage corresponds to the expected MFR of the polymerization of Example 1 using a physical 50/50 molar "" blend of DCPMS / TEOS The following example is of a two step continuous polymerization using the dual donor of the present invention to make ICP Example 3 Two-Stage Process The continuous process consists of two reactors of bulk liquid in series, followed by a single gas-phase reactor, usually polymerizes homopolypropylene inside the bulk liquid reactors, followed by a copolymerization. ethylene / propylene, the final product is called "Impact copolymer (ICP)". The two-stage, dual-donor process consists of feeding two different donors into the two bulk liquid reactors. In this example, TEOS is added in the first liquid reactor; and DCPMS is added in the second liquid reactor. In the initial reactor, the TEOS donor produces a resin with high MFR (20-1,000), while in the tail reactor, the donor mixture TEOS / DCPMS produces a resin with lower MFR (0.1-100). The resulting polymer is transferred to a gas phase reactor where an ethylene / propylene rubber is polymerized. The typical process conditions used are given as follows. The temperatures inside the bulk liquid reactors vary from 148 to 158 ° F. The concentrations of hydrogen and triethyl aluminum (TEAL) within the liquid reactors are? 10,000 and 60-78 ppm, respectively. The concentration of TEOS within the first stage was 16 ppm, while within the second stage, a mixture of TEOS (15 ppm) and DCPMS (22 ppm) was used. The typical production is divided between the first and second stage reactors in a ratio of 65:35. Within the gaseous phase reactor, the temperature was 158 ° F at a gauge pressure of 200 psi, with an ethylene to monomer ratio of 0.305. The total amount of ethylene / propylene copolymer produced within the gas phase reactor was 30% of the final ICP. Comparative Examples Two comparative examples of the dual donor system are given using a continuous single-step process. The first comparative example employs the use of a mixture of TEOS and DCPMS polymerized under conditions comparable to those shown in the two-step process. The second comparative example employs a single TEOS donor used under conditions similar to the two-stage process. Results Figure 4 shows that the polymer of the mixed donor, two-stage process has a higher balance of crystallinity versus melt flow rate. The two-stage process polymer has a high crystallinity (DSC crystallization temperature) and a high melt flow rate. This balance of crystallinity versus melt flow rate produced by the two-stage process is higher than the expected average properties of the two single-stage processes (TEOS and TEOS / DCPMS) These data show a polymer synergy when it is polymerized in a two-stage process.The preferred embodiments of the present invention, as described above, are not intended to limit the scope of the present invention, as demonstrated by the following claims, as a person skilled in the art , with minimal experimentation, can extend the scope of the embodiments.

Claims (16)

1. CLAIMS 1. A process for polymerizing olefins in at least two steps, comprising: a) polymerizing alpha-olefins in a first step in the presence of: (1) a magnesium supported solid titanium catalyst component, including a donor of internal electrons, preferably wherein said solid component, supported on magnesium is TiCl 4 supported on magnesium; (2) an organo-aluminum so-catalyst, preferably wherein said organoaluminum co-catalyst is selected from the group consisting of trimethyl aluminum, triethyl aluminum, triisobutyl aluminum and tri- diisobutyl aluminum, more preferably triethyl aluminum; and (3) a first external electron donor, TEOS; b) additionally polymerizing alpha-olefins in a second step using the catalyst system a) and both first and second external electron donors, where said first electron donor is TEOS and said second external electron donor is DCPMS, preferably where said DCPMS and TEOS are present in said second stage in the range of 10 to 99 mol% of DCPMS and 1 to 90 mol% of TEOS, with greater preference where said TEOS and said DCPMS are present in said second stage in the proportion of around 70 at 30% molar to around 30 to 70 molar%.
2. 2. The process of claim 1, wherein said alpha-olefin is selected from the group consisting of ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-octene, 1-hexene, 3-methyl-1-pentene , 3-methyl-1-butene, 1-decene, 1-tetra-decene, and 1-eicosine, preferably wherein said alpha-olefin is selected from the group consisting of propylene, ethylene and combinations thereof.
3. 3. A method for polymerizing or copolymerizing olefins, consisting essentially of: (A) forming a first catalyst component by: i) suspending dialkoxy magnesium in an aromatic hydrocarbon; ii) contacting the dialkoxy magnesium with a titanium halide; iii) contacting a product of i) and ii) with a titanium halide; iv) contacting the dialkoxy magnesium with a diester of an aromatic dicarboxylic acid during ii); (B) using a halogen-free organoaluminum compound with (A); (C) polymerizing an alpha-olefin, in the presence of (A), (B) and TEOS in a first reaction stage; (D) polymerizing an alpha-olefin in the presence of (A), (B) and a combination of DCPMS and TEOS in another reaction step. The method of claim 3, wherein said organoaluminum compound is triethyl aluminum, and wherein said "Combination of DCPMS and TEOS is present in the molar ratio of from about 30 to about 70% and from about 70 to about 30%, based on the relative presence of DCPMS and TEOS 5. A multi-step process for the preparation of a polyolefin, comprising: A) polymerizing alpha-olefins in a first step in the presence of: i) Solid TiCl4, supported on magnesium, ii) triethyl aluminum, and iii) tetraethoxysilane, producing a polyolefin having an MFR of between 10 and 1,200, B) further polymerizing the alpha-olefins of A) in another step with i) and ii) and a mixture of tetraethoxysilane and dicyclopentyldimethoxysilane, to produce a polyolefin having an MFR of between 1 and 120. 6. In a multi-step process for the preparation of a polyolefin, comprising: A) polymerizing alpha-olefins in a first step in pres of solid TiCl 4, supported on magnesium, triethyl aluminum, and a silicon compound; and B) further polymerizing the alpha-olefins of A) in another step, characterized in that the silicon compound in said first step is tetraethoxysilane and wherein a polyolefin produced by A) has an MFR of between 10 and 1,200; where in B) the additional polymerization includes a mixture of tetraethoxysilane and dicyclopentyldimethoxysilane, to produce in said B) a polyolefin having an MFR of between 1 and 120. 7. A catalyst system for the polymerization of olefin, comprising: A) TiCl 4 solid, supported on magnesium; B) triethyl aluminum; and C) a dual donor component that includes DCPMS and TEOS; wherein said DCPMS is present in said dual donor component in the range of about 45 to 55 mol% and said TEOS is present in said dual donor component in the range of about 55 to 45 mol%. 8. A process for making a homopolymer or copolymer of an alpha-olefin, which comprises polymerizing an alpha-olefin in a multi-step reaction in the presence of (1) a high activity magnesium supported titanium catalyst system (2). ) an organoaluminum co-catalyst, and (3) an electron donor mixture of two different compounds in at least two stages, comprising: (A) in the first step, polymerizing the alpha-olefin in the presence of a first electron donor (i) to produce a polyolefin, and (B) in another step, further polymerize the "'" polyolefin polymer of step one in the presence of a donor mixture of the electron donor (i) and an electron donor (ii) to achieve a final polyolefin having a relatively high melt flow rate, high crystallinity and a moderately broad molecular weight distribution. 9. A method for making a homopolymer or copolymer of an alpha-olefin having relatively high crystallinity, high melt flow rate and a moderately broad molecular weight distribution, comprising polymerizing an alpha-olefin in the presence of (1) a catalyst system of titanium, high activity, supported on magnesium, (2) an organoaluminum cocatalyst, and (3) an electron donor mixture composed of two different silane compounds in at least two stages, comprising: (A) in the first step, polymerizing an alpha-olefin in the presence of TEOS to produce a polyolefin having an MFR of at least 10; and (B) in another step, further polymerizing the polyolefin polymer of step one in the presence of the dominant DCPMS donor to achieve a polyolefin having an MFR of 0.1. The method of claim 9, wherein the homopolymer and copolymer products formed in step (A) comprise at least 15% by weight of the total amount of the final * polyolefin omopolymer produced. The method of claim 9, wherein the polymerization in each step is carried out continuously in series reactors. The method of claim 11, wherein the polymerization carried out in each step is carried out in the gas phase. The method of claim 9, wherein the polymerization is carried out in a single batch reactor. The method of claim 9, wherein the weight ratio of ethylene to propylene is present in the ratio of 20 to 80 mol%. The method of claim 9, wherein the molar percentage ratio of the dual donor of TEOS / DCPMS in steps (A) and (B) ranges from 10 to 90 to 95 to 5. 16. The method of claim 15, where the molar percentage of the dual donor is 50% molar of each donor.