FR2483429A1 - NEW PROPYLENE POLYMER - Google Patents

Abstract

THE INVENTION RELATES TO POLYMER CHEMISTRY. IT CONCERNS A NEW POLYMER OF PROPYLENE HAVING A MELTED FLOW RANGE OF ABOUT 0.2 TO APPROXIMATELY 30G10MINUTES, AN ISOTACTICITY INDEX NOT LESS THAN ABOUT 92, A DIMERE-QUARTER CONTENT NOT EXCEEDING 4GKG OF POLYMER, A CRYSTALLINE MELTING POINT OF AT LEAST ABOUT 165C, AN MPMN RATIO OF AT LEAST 7 AND TOTAL TI, MG, CL AND ASH CONTENTS NOT RESPECTIVELY EXCEEDING APPROXIMATELY 3PPM, ABOUT 40PPM, ABOUT 100PPM AND ABOUT 400PPM. THE PROLYPROPYLENE OF THE INVENTION IS IN PARTICULAR WITH EXCELLENT PROCESSING ABILITY WHEN IT IS EXTRUDED OR MOLDED BY INJECTION.

Description

The classical catalyst system used in the past for the

  propylene polymerization contained a

  component consisting of an unmodified titanium halide or

  modified by an electron donor, activated by a

  catalyst of the type of an organic aluminum compound. Representative examples of conventional propylene polymerization catalyst systems include catalysts

  with titanium trichloride and aluminum trichloride

  crystallites, of general formula n.TiCl3.AlCl3, activated with.

  diethylaluminum chloride or triethylaluminum. The co-crystallization product of titanium trichloride and aluminum trichloride may have been subjected to a modifying treatment with a suitable electron donor compound in order to increase its activity or stereospecificity. Such compounds include phosphorus compounds, inorganic and organic acid esters, ethers and many other compounds. Novel catalysts which are much more active than the conventional catalysts mentioned above in the polymerization of Olefins have recently been proposed. In short, these catalysts are formed of a titanium halide,

  which constitutes the catalytic component fixed on a

  magnesium halide, and an aluminum alkyl compound which may be present as a complex with an electron donor compound. These catalyst components have been described in the patent literature (see, for example, U.S. Patent Nos. 3,830,787,

  Nos. 3,953,414, 4,051,313, 4,115,319 and 4,149,990).

  The advantages of the polymerization of propylene in the presence of the above-described magnesium halide catalyst are the improved yields (polymer / titanium, weight / weight) and stereospecificity (= isotacticity index or percentage of insolubles). in heptane), while the mechanical properties are

essentially unchanged.

  The object of the present invention is to find a novel propylene polymer which has improved processability when extruded or injection-molded compared to conventional propylene polymers. Another object of the present invention is to find a novel polypropylene which can be processed at lower extrusion or molding temperatures and / or lower extrusion or molding pressures than

  conventional polypropylenic resins having the same

in the molten state.

  Other features and benefits of the

  present invention will emerge from the detailed description

who will follow.

  The present invention provides a novel propylene polymer having a melt flow range of about 0.2 to about 30 g / 10 minutes, an isotactic index of not less than about 92%, a dimer content of trimer not exceeding about 4 g / kg of polymer, having a crystalline melting point of at least about 1651C, a ratio of weight average to number average molecular weight of at least about 7 , a Ti content not exceeding about 3 parts per million, a Mg content not exceeding about 40 parts per million, a Cl content not exceeding about 100 parts per million and a total mineral salt content not exceeding not exceeding

400 parts per million.

  The components of the catalyst used in the process for producing the propylene polymer of the invention may consist of any of the recent high activity magnesium halide supported catalyst components, and components of organometallic cocatalyst derivatives. of aluminum described, for example, in U.S. Patent Nos. 3,830,787, 3,953,414, 4,051,313, 4,115,319 and 4,149,990.

supra. -

  Normally, such a catalyst composition is a two-component composition, the components of which are separately introduced into the polymerization reactor. The component (a) of such a composition is advantageously chosen from trialkylaluminums containing 1 to 8 carbon atoms in the alkyl group, such as

  triethylaluminium, trimethylaluminum, tri-n-butyl-

  aluminum, triisobutylaluminum, triisohexylaluminum, tri-noctylaluminum and triisooctylaluminum. The trialkylaluminium is very advantageously complexed with an electron donor before introduction into the polymerization reactor. The best results are obtained when carboxylic acid esters or diamines, in particular esters of aromatic acids, are used.

as electron donors.

  Some representative examples of these compounds are methyl and ethyl benzoate, methyl and ethyl p-methoxybenzoate, diethyl carbonate, ethyl acetate, dimethyl maleate, triethyl borate and the like. the

  o-ethyl chlorobenzoate, ethyl naphthenate, p-naphthenate

  methyl toluate, ethyl toluate, ethyl p-butoxybenzoate, ethyl cyclohexanoate, ethyl pivalate,

  N, N, N ', N'-tetramethylenediamine, 1,2,4-trimethyl-

  piperazine, 2,5-dimethylpiperazine, etc. The molar ratio of aluminumalkyl to electron donor can be between 1 and 100, preferably between 2 and 5. Solutions of the electron donor and the aluminum trialkyl compound, as such or in a hydrocarbon such as hexane or heptane are preferably subjected to a prior reaction for a period of time, generally less than one hour, prior to the introduction of the mixture into the mixture.

  polymerization reaction zone.

  The other component of the catalyst composition is either a titanium trihalide or tetrahalide attached to a magnesium dihalide support, or a complex of a trihalide or titanium tetrahalide with a donor compound. electrons, fixed on an aluminum dihalide. The halogenides of the respective halides may be chlorine, bromine or iodine, the preferred halogen being chlorine. The electron donor optionally used in the formation of a complex is advantageously chosen between esters of inorganic or oxygenated organic acids and polyamines. Examples of these compounds are esters of aromatic carboxylic acids such as benzoic acid, p-methoxybenzoic acid and p-toluic acid, and in particular the alkyl esters of said acids,

  alkylenediamines, for example N ', N ", N"', N "" - tetramethyl-

  ethylene diamine. The molar ratio of magnesium to electron donor is equal to or greater than 1, and preferably between 2 and 10. Generally, the titanium content expressed as titanium metal is from 0.1 to 20% by weight and preferably from 1 to 3% by weight in the catalyst component

fixed on a support.

  The preparation of these supported catalyst components has been described in the prior art and these

  components are commercially available.

  Components (a) and (b) of the catalyst are charged to the reaction zone in selected amounts so that the Al / Ti molar ratio is maintained in the wide range of about 1 to about 10,000, and preferably

from about 10 to 200.

  It is essential that the polymerization process used to produce the polymer of the invention be a process in which propylene behaves as the liquid diluent, as well as the filler to be reacted, except for small amounts of inert hydrocarbons such as hexane, mineral oil, petrolatum, etc., which can be used for the introduction of the catalyst components into the reaction zone. The reaction conditions

  used in the process of the invention generally include

  polymerization temperatures ranging from about 46 to about 79 ° C, and preferably in the range of about 52 to about 71 ° C. The pressure must be high enough to maintain at least a portion of the propylene in phase. liquid. Advantageously, manometric pressures equal to or greater than 1.4 MPa are used, for example manometric pressures up to about 3.5 MPa. The proportion of total solids in the reaction zone, according to this system, is usually in the range of 15 to 50%, although lower or higher proportions, for example up to 5% of polymeric materials. solid, can obviously be achieved. However, to effectively handle the slurry, it is preferable to maintain the polymerization at the percentage of solids indicated above. The reaction is continuous and the monomeric feedstock and catalyst components are continuously fed to the reactor, and a slurry of the polymeric product and liquid propylene is withdrawn, preferably by a periodic discharge valve which simulates a continuous operation. Where appropriate, any of the various known modifiers such as hydrogen may be added for the purpose for which they are intended. The discharged polymer suspension is expanded, for example, to a pressure of 0.35 MPa or less in a low pressure zone (ie a zone maintained at a pressure lower than that prevailing in the polymerization reaction). As a result of the pressure drop and volatilization of the polymerization ingredients, these volatiles evaporate from the solid polymer. This evaporation, which can be facilitated by heating, gives a polymer powder, which is substantially dry, that is to say that it is a polymer containing at most 5% volatile matter. The unreacted monomer stream is discharged at the top of this low pressure expansion zone and at least a portion of this

  current is compressed and condensed and returned to the reactor.

  The polymer is usually transferred to a final drying zone for removal of residual volatiles.

  As an alternative, the liquid polymer medium

  The reaction can be filtered or centrifuged under pressure and the liquid propylene can be returned (after a suitable purge) to the reactor, thereby saving energy in the form of recompression. This method has the advantage that certain solid impurities (aluminum alkyls and organic esters) are removed from the polymer. This results in obtaining a polymeric product whose content of residual impurities is lower. 6. Due to the generally high productivity of the supported catalyst, expressed in kilograms of polymer produced per kilogram of titanium metal, it is not necessary to remove catalyst residues from the polymer in a demineralization stage, such as in the case

a conventional catalyst.

  Various additives may optionally be incorporated in the polypropylene resin, for example

  fibers, fillers, antioxidants, deactivating agents,

  metal, heat and light stabilizers, dyes, pigments, lubricants, etc.

  The polymers can be used advantageously

  advantageously in the production of fibers, filaments and films by extrusion; rigid articles by injection molding; and

  bottles by blow molding techniques.

  The advantages of the polymers of the invention, compared with pellmers produced by conventional catalysts and having similar mechanical properties, include a wider range of processability, lower process energy requirements, improved processability, and improved processability. filling of narrow cavities and multi-cavity molds, better shrinkability, easier stretchability and higher processing speeds in the production of continuous filaments and

short fibers.

  For example, according to melt flow measurements (spiral), it has been found that polymers of the invention having melt flow (ASTM 1238) of about 2 to 12 g / m 2. 10 minutes could be processed at molding temperatures of 16.5-27.5 ° C lower, or at molding pressures of 1.05-2.45 MPa lower than conventional polymers of the same melt flow. (ASTM

1238).

  It is believed that the Mp / Mn molecular weight distribution is the parameter that best reflects the improvement in the rheological properties and processability of a polymer. Normally, polymerization in the presence of a conventional catalyst would give a polymeric product having an Mn-to-maximum ratio of 6.5 and generally less than 6, while the polymers of the invention have Mw / Mn ratios. at least 7, for example between about 7 and about 10. The following examples further illustrate the

  advantages offered by the present invention.

EXAMPLES 1 AND 2

  Homopolymerizations of propylene were conducted in large scale continuous operations in a pilot plant, in which monomer and catalyst components were continuously charged to a reactor equipped with a stirrer, the corresponding monomer introduction rate. at a residence time of 2 hours in the reactor. The organic aluminum compound of the catalyst composition consisted of a solution in

  hexane of triisobutylaluminum (TIBA) or triethyl

  aluminum (TEA) which had been treated prior to its introduction into the reactor with a hexane solution of methyl p-toluate (MPT), electron donor compound. The solid component of the catalyst, titanium halide supported on a support, was a commercial catalyst (FT-1) from Montedison, S.p.A., Milan, Italy. The supported catalyst component contained about 1.5% by weight of titanium, 20.3% by weight of magnesium, 60.0% by weight of chlorine and 9.6% by weight of volatile hydrocarbon substances. Ethyl benzoate was used in the

  preparation of the catalyst component fixed on the support.

  The two components of the catalyst were added at rates directly proportional to polypropylene production rates and in amounts sufficient to maintain a solid polymer concentration in the polymer.

  reactor suspension with a nominal value of about 40%.

  Catalyst productivity (kg of polymer / kg of titanium metal) was calculated in each case based on the rate of discharge of the polymer slurry, the solids content of the slurry and the rate of addition of the slurry. catalyst component containing titanium. The suitable operating conditions and results are reproduced in Table I which also indicates the normal properties as a (control) product of a demineralized polypropylene obtained with conventional catalyst components, i.e.

  co-crystallized 3TiC13.AlCl3, with diethyl chloride

aluminum as cocatalyst.

  As shown in the table, normal ASTM test methods were used to determine the

  most properties of the polymeric product.

  The Mp / Mn ratio was determined by chromatography

  in the liquid phase, the solvent being orthodichlorobenzene. The isotactic index was obtained by determining the percentage of insoluble in heptane after extraction of the boiling heptane polymer, and the dimer-trimer content was determined by the gas chromatographic analysis of the extract. in heptane

at room temperature.

  The melting point in the crystalline state has been

  determined by differential scanning calorimetry.

  The contents of -Ti, Mg and Al were determined by atomic absorption analysis of the polymer ash in solution in hydrochloric acid, and the chlorine content was determined by colorimetric analysis of the polymer sample. whose combustion was carried out in a bomb

Parr oxygen.

  9. TABL Example number Catalyst 3TiCl Alkylaluminium Molar ratio trialkylalumium / MPT Al / Ti molar ratio Reactor temperature, C Manometric reactor pressure, MPa Residence time, h Productivity, kg / g Ti Additives: - BHT - ppm - "Irganox 1010", ppm - Calcium stearate, ppm Glycerol monostearate, ppm Hydrocalcite, ppm Properties: Dimer-trimer content, g / kg polymer - Isotactic index,% Melt flow, g / 10 minutes ( 1) - Specific gravity, g / cm3 (2) - Mn - Mp - Mp / Mn Tensile strength - at the limit - MPa (3) - at fracture - MPa (3) Elongation at break,% (3) ) Flexural modulus, kPa. 105 (4) Traction module, kPa.105 (3) Pressure heat distortion temperature of 0.46 MPa, C (5) Melting temperature in crystalline state, C Hardness (Rockwell) (6) WATER I Witness. 3.AlC: DEAC 1.8: 1 68.3 3.08 2.0 Nil 3.3

.9041

49 00 (

320 0ú

6.5 34.3 13.3 13.3 n 1

13 FT-1

TIBA 2.8 68.3 3.09 2.0 93.4 2.1

0 0.9029

0 39 300

D0 323 000

  8.2 33.25 21.14 13.09 11.97 FT-1 TEA 3.6 68.3 3.28 2.0, 6 4.1

.9029

36,000

297,000

8.3 36.75 21.98, 54 16.24

93 -

  10. Fragility at low temperature

 C 17) 22

  2.32 o Izod impact resistance, J / cm (8) Impurities in the polymer: Ash, ppm - Mg, ppm - Ti, ppm - Cl, ppm - Al, ppm

(1) ASTM D1238,

(2) ASTM D1505

(3) ASTM D638

(4) ASTM D790

(5) ASTM D648

(6) ASTM D785

(7) ASTM D746

(8) ASTM D256

condition L 4.25 3.86 on 11.

Claims (13)

  A propylene polymer, characterized in that it has a melt flow range of about 0.2 to 10 minutes, an isotactic index of not less than about 92%, an dimer-trimer content not exceeding about 4 g / kg, a crystalline melting point of at least about 165 C, a ratio of weight average to number average molecular weight (Mw / kg) Mn) of at least about 7, a titanium content not exceeding about 3 parts per million, a magnesium content not exceeding about 40 parts per million, a chlorine content not exceeding about 100 parts per million and a total ash content not exceeding about 400 parts per million. 2. - Polymer according to claim 1, characterized in that the ratio Mp / Mn is between: approximately 7 and about 10.   3. The polymer according to claim 1, obtained in a process consisting of: continuously loading monomeric propylene and catalyst components into. a polymerization reactor, to polymerize propylene at a temperature of between about 46 and about 79 ° C and at a pressure sufficiently high to maintain at least 1 part of the propylene in the liquid phase, to discharge the product in a substantially continuous manner under in the form of a suspension in liquid propylene, characterized in that the composition of the catalyst comprises the following components: (a) an aluminum trialkyl or an aluminum trialkyl at least partially complexed with an electron donor compound, and (b) ) a titanium tri-or tetrahalide attached to a magnesium dihalide support or a complex of a titanium tri- or tetrahalide with an electron donor compound attached to a magnesium dihalide.   4. - Polymer according to claim 3,   characterized in that the alkyl group of the aluminum   12. The trialkyl present as component (a) of the catalyst composition contains 1 to 8 carbon atoms, the component (a)   preferably being triisobutylaluminum.   5. - Polymer according to claim 3, characterized in that the electron donor component (a) of the catalyst composition is an ester of a carboxylic acid or a diamine, preferably an ester of an acid   aromatic, especially methyl p-toluate.   Polymer according to claim 3, characterized in that the molar ratio of trialkylaluminum to electron donor is in a range of about 1 to about 100, preferably in the range of about 2 to about 5. 7. - Polymer according to claim 3, characterized in that the component (a) --- is prepared by prior reaction of aluminum-trialkyl with the donor   of electrons for less than one hour before polymerization.   8. - Polymer according to claim 3, characterized in that the triou tetrahalide of titanium is   trichloride or titanium tetrachloride.   9. - Polymer according to claim 3, characterized in that the magnesium dihalide is magnesium dichloride.   10. Polymer according to claim 3, characterized in that the electron donor compound of component (b) is a polyamine or an ester of an inorganic or organic oxygen acid, preferably an ester of an acid.   aromatic carboxylic acid, especially ethyl benzoate.   11. Polymer according to claim 3, characterized in that the molar ratio of magnesium to the electron donor of component (b) is at least equal to 1, and   preferably between about 2 and about 10. -   12. The polymer according to claim 3, characterized in that the titanium content, expressed as titanium metal, ranges from about 0.1 to about 20% by weight, preferably from about 1 to about 3% by weight in the   component (b) of the catalyst fixed on a support.   13. - Polymer according to claim 3, 13. characterized in that the components (a) and (b) of the catalyst are introduced into the reaction zone in an Al / Ti molar ratio of about 1 to about 10,000, preference from about 10 to about 200.