FI61498C - CRYSTAL POLYMER AV PROPEN - Google Patents

Description

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Italy-Italy (IT) 267UU A / 75 (71) Montedison SpA, 31, Foro Buonaparte, Milan, Italy-Italy (lT) (72) Luciano Luciani, Ferrara, Pier Camillo Barbe, Ferrara, Italy-Italy (lT) ( 7U) Oy Kolster Ab (5U) Crystalline polymer of propylene - Crystal polymer of propylene

The invention relates to a crystalline propylene polymer having a melt index of 0.5 to 30 g / 10 min, an isotactic index of 90 to 96, a flexural stiffness of 13,000 to 18,000 kg / cm 2 (determined according to ASTM D 747-40) and containing up to 2 % by weight of oils extractable with acetone at 25 ° C.

The polymer of the invention is characterized in that the polymer is a crude polymerization product which has not undergone treatments to extract the atactic polymer fraction and is prepared by polymerizing propylene in the presence of hydrogen as a molecular weight regulator and in the presence of a catalyst prepared by l-aluminum , which is an alkyl ester of an aromatic carboxylic acid, reacts with a solid catalyst component prepared by reacting MgCl 2 with TiCl 3 in the presence of a Lewis base, wherein the Lewis base is an alkyl ester of the aromatic carboxylic acid, with an ester / Ti molar 3 and the solid catalyst component has a Ti content of 1 to 7% by weight.

2 61498

Most industrial processes hitherto used for the preparation of crystalline polymers and copolymers of propylene with good mechanical properties are characterized by the polymerization of propylene or mixtures thereof with ethylene in the liquid phase in the presence of stereospecific Ziegler-Natta catalysts containing essential catalyst of organometallic compounds, and that when the polymer leaves the polymerization zone, it is treated to remove catalyst residues and the atactic polymer fractions are extracted as completely as possible.

These treatments try to obtain a polymer with the highest possible isotacticity index. The isotacticity index means the percentage by weight of polypropylene that is insoluble in boiling n-heptane. This is because the higher the isotacticity index, the more typical the mechanical properties of polypropylene, such as flexural stiffness, are - with the same melt index. The purpose of these treatments is to minimize atactic polymer fractions, and in particular low molecular weight fractions (oils) soluble in acetone at room temperature, which adversely and very significantly affect the mechanical properties of the polymers.

Thus, the Ziegler-Natta catalysts heretofore used in the stereospecific polymerization of propylene cannot guarantee in advance that crystalline polymers or copolymers of propylene with good mechanical properties will be obtained without treating the polymers to extract active polymer fractions. In particular, it is impossible to prepare polypropylene with good mechanical properties using methods in which all or most of the polymerization solvent or liquid propylene used as the reaction medium is removed, e.g., by expansion distillation or steam stripping, which involves a solvent or monomer phase change and therefore remove or only partially remove the amorphous polymer fractions formed during the polymerization.

Polymerization catalysts for propylene, which are highly active, have good stereospecificity under the conditions of use and are prepared from organometallic compounds of Al and solid catalyst components containing compounds consisting of Ti, Mg and Lewis base, have recently been described. (GB Patent Publication No. 3,61498, 1,387,890).

Since the yield of polymer per gram of titanium used is good, the catalysts could make it possible to avoid purification of the polymers from the catalyst waste, thus simplifying the polypropylene production processes.

The isotactic index of the polymers prepared with the above catalysts under the manufacturing and operating conditions described in GB Patent 1,387,890 reaches values of 92-93 at most.

The melt index of the polymers in the above process is very low (less than 0.3 g / 10 min.) Because the polymerization is carried out without hydrogen.

It has been found that when hydrogen is used in polymerization processes using the above catalysts to control the molecular weight of the polymers, the isotacticity index decreases significantly.

The higher the achievable polymer melt index, the more significant the decrease in index. For example, the index decreases from 92-93 (polymer melt index less than 0.3 g / 10 min.) To 85-86 with a melt index of 8-10 g / 10 min.

Because propylene is significantly wasted in the form of atactic polymers of little or no practical interest when using hydrogen to control molecular weight, it is practically impossible to use these catalysts.

In addition, it should be noted that in the case of polymerization in liquid propylene, due to the high percentage of atactic polymer to be removed, extraction methods different from those based on liquid propylene should be used, with only 2-3% extractable atactic polymers. For example, it would be necessary to perform washes with solvents such as butane to obtain polymers with a sufficiently high isotacticity index.

However, instead of simplifying, washing with butane complicates a possible process for the preparation of polypropylene in a liquid monomer using the catalysts described above.

If polymers prepared in the presence of an inert hydrocarbon solvent and the above catalysts undergo conventional extraction treatment in industrial processes for the production of polypropylene, it is possible to obtain polymers with a sufficiently high isotacticity index (above 96-97). excessive propylene losses in the form of amorphous polymers would make such a process uninteresting.

It has now surprisingly been found that even in the case of the polymerization of propylene in the presence of hydrogen and the catalysts of the present invention, it is not necessary to remove the crude polymeric atactic polymer fraction to obtain a polymer with comparable physico-mechanical properties and in some cases better than melt index - those polymers prepared with conventional TiCl 4 -based highly stereospecific catalysts with a much higher isotacticity index and from which the atactic fractions have been removed.

According to a preferred embodiment of the invention, propylene or mixtures thereof and ethylene and / or alpha-olefins are polymerized either in the presence or absence of an inert hydrocarbon diluent with catalysts which can give polymers with an isotacticity index between 92 and 96.

A particularly interesting feature of the polymers and copolymers of the invention is their low amount of oil extractable with acetone at room temperature. The low oil content makes it possible to considerably simplify the polypropylene production processes currently used.

Upon completion of the polymerization, the polymer product can be separated from the liquid phase by mechanical means, such as filtration instead of evaporation of the liquid phase.

Another interesting feature of the polymers and copolymers of this invention is their fine microcrystalline structure in which at least 70% of the spherolites have a size of less than 80 yu. This structure relates to a 3 mm thick plate pressed at 200 ° C and 200 atm for 5 minutes and cooled to room temperature in 20 minutes.

Such a structure is believed to be due to the catalyst residue remaining in the polymer acting as a nucleating agent. From this point of view, polymers and copolymers whose ash contains Mg and halogens in amounts corresponding to Mg halide contents of up to 150 ppm are of particular interest.

However, it is also possible to prepare polymers and copolymers by polymerizing propylene in the gas phase. In this case, 5,61498 catalysts and / or operating conditions are selected which are suitable for obtaining polymers having an isotacticity index of about 94-96.

The polymerization in both the liquid and gas phases can be carried out over a wide temperature range, generally in the range from 0 to 100 ° C and in particular in the range from 40 to 90 ° C.

The polymerization is carried out at or above normal pressure.

Propylene can be polymerized either as such or in a mixture with ethylene and / or alpha-olefins such as butene-1, 4-methylpentene-1, etc. Propylene can be polymerized in the first step, while ethylene-propylene blends are polymerized in the next step. The first step is performed under conditions to obtain a polymer having an isotacticity index between 90 and 95. In this case, polymers with improved embrittlement properties at low temperatures are obtained. The amount of polymerized ethylene incorporated by these methods does not exceed 30-36% by weight, while the copolymer content formed in the second step varies between 5-40% based on the total polymer preparation. The ethylene content of the copolymer varies between 70 and 90% by weight.

As mentioned above, the catalysts used in the preparation of the polymers and copolymers of this invention are prepared by reacting an aluminum trialkyl compound partially complexed with a Lewis base, an alkyl ester of an aromatic carboxylic acid, with a solid catalyst component prepared by reacting M in the presence of a base, wherein the Lewis base is an alkyl ester of an aromatic carboxylic acid, with an ester / Ti molar ratio of 0.5 to 3 and a Ti content of 1 to 7% by weight of the solid catalyst component.

Examples of such Lewis bases are, for example, alkyl esters of benzoic, p-ethoxybenzoic and p-toluic acids.

The molar ratio of Lewis base to aluminum trialkyl compound is less than 1 and preferably ranges from 0.2 to 0.4.

The solid catalyst component is generally characterized by having at least one chlorine in its X-ray spectrum, the maximum intensity of which is included between the interplanar distances d = 2.43 A and d = 3.20 A when chlorine is present in the component at a Cl / Mg ratio of more than 1.

The catalyst component can be prepared by contacting the halogenated Ti compound and the Lewis base with Mg chloride in activated form having a surface area (or specific surface area) greater than 2,61498 β than 3 m / g, or by operating under conditions in which it is possible to prepare a product having an X-ray spectrum as defined above.

The catalytic component can be prepared, for example, by mixing a Ti compound, a Lewis base and a Mg compound, or by grinding a complex compound formed by Mg chloride and a Ti compound and a Lewis base. The Ti content of the catalyst compound generally ranges from 0.5 to 10% by weight; The Mg / Ti ratio is greater than 1 and especially between 2-10.

The Al / Ti ratio used in the preparation of the catalyst is greater than 1 and generally ranges from 5 to 10,000.

Catalysts that meet the above definition are described, for example, in GB Patent 1,387,889, 1,387,888, 1,538,472 and 1,513,480, BE Patent 785,333 and FR Patent 2,113,313. Other suitable catalysts are described in In DE-A-2 504 036.

In the preparation of these catalysts, it is possible to obtain the Lewis base, the ratio of base to organometallic compound of Al and the polymerization conditions (catalyst and monomer concentration »polymerization temperature and residence times) directly during polymerization and in very high yields more than 0.5) and an isotacticity index of 92-95, which makes it possible to eliminate or minimize polymer washing to remove atactic polymer fractions.

By using these catalysts under the conditions defined above, polypropylene production processes can be significantly simplified.

Some typical examples of catalysts which, in the polymerization of propylene in a liquid monomer, make it possible to obtain the above results are those obtained from Al-trialkyls (Al-triethyl, Al-triisobutyl, etc.) partially complexed with benzoic acid, p-toluic acid. or an alkyl ester of p-alkoxybenzoic acid (ethyl p-methoxybenzoate, methyl ester of p-toluic acid, etc.) and a catalyst component prepared by grinding anhydrous Mg chloride in the presence of TiCl 2 and an alkyl ester of benzoic acid or by co-grinding Mg chloride with TiCl -ate (ethyl benzoate, methyl benzoate, etc.) with a complex compound.

The Ti content of the catalyst component ranges from 1 to 7% by weight; the ester is used in such an amount that the ester / TiCl 4 molar ratio of 7,61498 is generally between 0.5 and 3.

The molar ratio between the ester and the Al-trialkyl is between 0.2 and 0.4 (increasing this ratio makes it possible to increase the isotacticity index; in this case, however, the polymer yield decreases).

The concentration of the solid catalyst component generally ranges from 0.02 to 0.08 g / kg of liquid propylene.

The polymerization temperature ranges from 50 to 85 ° C (the isotacticity index increases as the temperature increases in addition to the concentration of the solid catalyst component).

The catalysts may contain modifiers, inert solid diluents, agglomerating agents, etc. In particular, compounds of elements of Groups I, II, III and IV of the Periodic Table, other than Mg compounds, and compounds which do not react with Mg chloride are utilized.

The following examples are provided to illustrate the features of the invention.

The isotacticity index values shown in the description of the invention and reported in the examples refer to a powdered polymer that has not yet been granulated, i.e. the polymer is under the granulometric conditions under which it is obtained during polymerization.

It has been found that for the polymers and copolymers of the invention, the isotacticity index values determined from the obtained granular polymer powder are generally higher (1-2 units) than when using the polymer in the form of a powder obtained during polymerization. This is especially the case when the polymer is obtained in liquid propylene and the bulk density is relatively low (less than 0.4 g / cm 3).

The isotacticity index is determined on a Kumagawa extractor over 24 hours.

Flexural stiffness is determined according to ASTM D 747-40 (between 50 mm); according to ASTM D 1238-70; bulk density according to DIN 53194; Vicat temperature according to ASTM D 1525-70 (5 kg); and Rockwell hardness according to ASTM D 785-70 Method B, scale alpha.

Example 1

To a 135-liter autoclave equipped with a stirrer, 24 g of Al-triethyl (as a 12% by weight heptane solution), 37 kg of liquid propylene and 18.94 g of 61498 3-p-toluic acid methyl ester (dissolved in 120 cm of heptane) were further added in a propylene atmosphere. 3 kg propylene pressure.

The autoclave was heated to 60 ° C, after which 50 L of hydrogen (under normal conditions) and 2.486 g of a catalyst component prepared by grinding MgCl 2 with a complex of TiCl 4 and ethyl benzoate in a molar ratio of 1: 1 for 50 hours were added. The filling factor of the mill was 0.135 g / l. The ground product contained 4.85% by weight of Ti and 61.9% by weight of Cl. The autoclave temperature was then raised to 65 ° C and maintained at this value for 3 hours.

The residual propylene was then removed by expansion and the polymer was removed from the autoclave and dried in an oven at 70-80 ° C under a stream of nitrogen. The amount of polymer obtained, the properties of the polymer as powder and granulate are given in Table 1.

Example 2

The experiment of Example 1 was repeated, but using 85 L of hydrogen. At the end of the polymerization, the residual monomer was removed from the autoclave and replaced with 27 kg of fresh propylene. It was stirred for 1 hour at 30-35 ° C, after which the polymer was recovered and dried.

The results obtained are reported in Table 1.

table 1

Polymerization in liquid propylene

Example 1 Example 2

Obtained polymer kg 8,850 8.13

Properties of the powdered polymer:

Isotacticity index 94 95.5 at 23 ° C acetone soluble fraction% 0.9 0.4

Ti content ppm 9.5 6

Cl content ppm 165

Mg content ppm 33

Bulk density g / cm 0.39 0.42 dl / g 2.5 1.6

Properties of the granular polymer: 9 61 4 9 8

Melt index g / 10 '0.8 7.4 2

Bending stiffness kg / cm 13,800 18,000

Vicat softening point ° C 92 110 °

Rockwell hardness 65 86

Example 3 3 8.8 l of heptane, 630 cm of heptane containing 8 g of Al-triethyl and 4.68 g of ethyl p-methoxybenzoate, previously reacted with each other, were fed sequentially and under a propylene atmosphere into a 20 liter autoclave, which was equipped with a stirrer.

At the same time, 0.69 g of a catalyst component prepared by grinding anhydrous MgCl 2 in a vibratory mill with TiCl 4 and a 1: 1 molar complex of ethyl benzoate in a suspension containing 570 cm of heptane were fed to the autoclave. The ground product had a Ti content of 7.1% and a Cl content of 58.6%. 2.7 l of hydrogen and propylene were then added successively to a manometer pressure of 10 kg / cm. The temperature was then raised to 60 ° C and maintained at this value for 1.5 hours. The solvent was removed by evaporation. The amount of polymer obtained and its properties are given in Table 2.

Example 4

The experiment of Example 3 was repeated, but using 6.65 g of ethyl p-methoxybenzoate and 11.35 g of Al-triethyl. The pressure during the polymerization was 8 kg / cm. At the end of the experiment, the solvent was removed by evaporation.

The results obtained are reported in Table 2.

Example 5

The experiment of Example 3 was repeated, but using 0.65 g of a catalyst component prepared by grinding anhydrous MgCl 2 and an ethyl benzoate complex of TiCl 4 (molar ratio 1: 1).

The Ti content was 6.1% and the Cl content was 61.3%. An additional 5.72 g of ethyl p-methoxybenzoate was used. At the end of the polymerization, the solvent was removed from one part of the slurry by evaporation and the other part was separated by centrifugation at 50 ° C.

The results obtained are shown in Table 2: the properties of the polymer obtained by evaporation are in column A and the properties of the polymer obtained by centrifugation are in column B.

Example 6

The experiment of Example 3 was repeated except that the solid catalyst component contained 4.6% Ti and 61.7% Cl and was used in 0.68 g. In addition, 4.75 g of p-toluic acid methyl ester were used. The polymerization temperature was 75 ° C. The time required for polymerization was 3 hours. The solvent was separated by evaporation. The results obtained are reported in Table 2.

Example 7

To a 2.5-liter autoclave equipped with a stirrer were added 870 ml of hexane and 1.135 g of Al-triisobutyl, previously contacted with 0.3 g of p-toluic acid ethyl ester, under a propylene atmosphere. Then, 0.071 g of a suspension of hexane in anhydrous MgCl 2, TiCl 4 and ethyl benzoate was added as a suspension in hexane. The catalyst component had a Ti content of 1.9% by weight and a Cl content of 64.7% by weight. The total amount of hexane solution in the autoclave was 1 liter. 115 ml of 2 hydrogen and propylene were then added to a pressure of 5.4 kg / cm. The temperature was then raised to 60 ° C and held for 4 hours.

The solvent was removed by steam distillation. The amount of polymer obtained and its properties are shown in Table 2.

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Example 8

To a 135 liter autoclave equipped with a stirrer were added 40 kg of liquid propylene, 36 g of Al-triisobutyl and 12 g of p-toluic acid ethyl ester under a propylene atmosphere. The autoclave was heated to 60 ° C, after which 80 L of hydrogen and 1.26 g of a catalyst component prepared from anhydrous MgCl 2, TiCl 2 and ethyl benzoate were added. The catalyst component had a Ti content of 2.05% by weight, a Cl content of 64.75% by weight and a Mg content of 18.15% by weight. The temperature of the autoclave was then raised to 65 ° C and held for 3 hours.

The solvent was removed by expansion distillation and the polymer was removed from the autoclave and dried in an oven at 70 ° C under a stream of nitrogen for 3 hours. The amount of polymer obtained and its properties are shown in Table 3.

Table 3

Obtained polymer 8,660

Properties of the powdered polymer:

Isotacticity index 95.5

Ti content ppm 4

Cl content ppm 90

Mg content ppm 22

Bulk density g / cm 2 0.52

Properties of the granular polymer:

Melt index g / 10 min. 4.3 2

Bending stiffness kg / cm 15,840

Rockwell hardness 67

Example 9

The experiment of Example 7 was repeated with the difference that the polymerization pressure was 7 kg / cm. Upon completion of the polymerization, the solvent was separated by centrifugation and the polymer was washed with heptane and dried under a stream of nitrogen. The results are as follows:

Obtained polymer kg 0.269

Properties of the powdered polymer:

Isotacticity index 95.5

Ti content ppm 5

Cl content ppm - 3

Bulk density g / cm 0.46 CU 7 dl / g 2.5 13 61 498

Properties of the granular polymer:

Melt index g / 10 min. 1.5 2

Bending stiffness kg / cm 14,000

Example 10

To a 135-liter autoclave equipped with a stirrer was added 36 g of Al-triisobutyl (345 g / l in hexane), 36 kg of propylene, and 12.45 g of p-toluic acid methyl ester (227 g / l in hexane) and an additional 4 kg of propylene. by pressure.

The autoclave was heated to 62 ° C and 100 L of hydrogen and 1.05 g of the catalyst component dispersed in 200 mL of hexane were added. The catalyst component was prepared from MgCl 2, TiCl 4 and ethyl benzoate. It had a Ti content of 1.7, a Cl content of 63.4 g and a Mg content of 20.35% by weight.

The temperature of the autoclave was raised to 60 ° C and maintained for 3 hours. The polymerization mixture was then dispersed in water and evaporated under a stream of nitrogen at 70 ° C. 9 kg of polymer were obtained.

The properties of the polymer were as follows:

Properties of the powdered polymer: 3 Apparent density g / cm 0.57

Isotacticity index 96

Cnj dl / g 1.9

Fraction soluble in acetone at 20 ° C 1.9%

Fraction soluble in xylene at 20 ° C 2.2%

Properties of the granular polymer:

Melt index g / 10 min. 1.6

Bending stiffness kg / cm 15,650

Modulus of elasticity kg / cm 15,930

Rockwell hardness (alpha) 63 2

Izod impact toughness without notch kg.cm/cm 167 2

Tensile strength kg / cm 370

Elongation at break% 90