PROCESS FOR THE PREPARATION OF A COLORED POLYPROPYLENE

Abstract

A process for the preparation of a propylene polymer containing a coloring agent in an amount ranging from 0.2 to 30 ppm referred to the weight of propylene polymer, including the steps of: a) providing a solid ZN catalyst component made from or containing Mg, Ti, halogen and an internal electron donor compound, wherein the Ti being in an amount ranging from 0.1 to 10% of the total weight of solid catalyst component; b) providing a coloring agent made from or containing at least a pigment; c) mixing the ZN catalyst particles and the coloring agent in a liquid hydrocarbon medium, thereby obtaining a slurry and d) feeding the slurry to a polymerization reactor and subjecting the reactor to polymerization conditions, thereby yielding the propylene polymer.

Claims

1. A process for the preparation of a propylene polymer containing a coloring agent in an amount ranging from 0.2 to 30 ppm referred to the weight of propylene polymer, comprising the steps of: a) providing a solid ZN catalyst component comprising Mg, Ti, halogen and an internal electron donor compound, wherein the Ti being in an amount ranging from 0.1 to 10% of the total weight of solid catalyst component; b) providing a coloring agent comprising at least a pigment; c) mixing the ZN catalyst particles and the coloring agent in a liquid hydrocarbon medium, thereby obtaining a slurry; and d) feeding the slurry to a polymerization reactor and subjecting the reactor to polymerization conditions, thereby yielding the propylene polymer.

2. The process according to claim 1, wherein the ZN catalyst has a regular morphology and is obtained by reacting Ti-halides with precursors comprising adducts of formula MgCl.sub.2(R.sup.1OH).sub.n where R.sup.1 is a C.sub.1-C.sub.8 alkyl group, and n is from 2 to 6.

3. The process according to claim 1, wherein, in the ZN catalyst component the amount of Mg ranges from 8 to 30% and the amount of Ti ranges from 0.5 to 8% wt with respect to the total weight of solid catalyst component.

4. The process according to claim 3, wherein the electron donor compound is selected from esters, ethers, amines, silanes, carbamates and ketones or mixtures thereof.

5. The process according to claim 4, wherein the electron donor compound is selected from the group consisting of 1,3-diethers of formula (I) ##STR00003## where R.sup.I and R.sup.II are the same or different and are hydrogen or linear or branched C.sub.1-C.sub.18 hydrocarbon groups; R.sup.III groups, equal or different from each other, are hydrogen or C.sub.1-C.sub.18 hydrocarbon groups; R.sup.IV groups equal or different from each other, have the same meaning of R.sup.III except that R.sup.IV groups cannot be hydrogen.

6. The process according to claim 4, wherein the final amount of electron donor compound in the solid catalyst component ranges from 0.5 to 30% by weight.

7. The process according to claim 1, wherein the pigment is black or blue.

8. The process according to claim 7, wherein the pigment is Cu-Phthalocyanine.

9. The process according to claim 7, wherein the pigment is inorganic and selected from the group consisting of Ultramarine Blue and Carbon Black.

10. The process according to claim 1, wherein the coloring agent is used in an amount such that the weight ratio coloring agent of step b)/catalyst component of step a) ranges from 0.005 to 5.

11. The process according to claim 1, wherein the solid catalyst component of step a) and the coloring agent of step b) are separately contacted with a liquid inert hydrocarbon, at a temperature below about 60° C. before being introduced into the polymerization reactor.

12. The process according to claim 1, wherein, before being introduced into the reactor the solid catalyst component of step a), the coloring agent of step b), are contacted in a single step with an alkyl-Al compound, and optionally with an external donor, in the presence of a liquid inert hydrocarbon.

13. The process according to claim 12, wherein the alkyl-Al compound is the group consisting of trialkyl aluminum compounds.

14. The process according to claim 12, wherein the external donor is present and selected from silicon compounds of formula R.sub.a.sup.5R.sub.b.sup.6Si(OR.sup.7).sub.c, where a and b are integer from 0 to 2, c is an integer from 1 to 3 and the sum (a+b+c) is 4; R.sup.5, R.sup.6, and R.sup.7, are alkyl, cycloalkyl or aryl radicals with 1-18 carbon atoms optionally containing heteroatoms.

15. The process according to claim 1, wherein the amount of coloring agent in the final propylene polymer ranges from 0.3 to 28 ppm.

Description

EXAMPLES

[0045] The data of the propylene polymer materials were obtained according to the following methods:

Xylene-Soluble Faction

[0046] 2.5 g of polymer and 250 mL of o-xylene were introduced into a glass flask equipped with a refrigerator and a magnetic stirrer. The temperature was raised in 30 minutes up to the boiling point of the solvent. The resulting solution was then kept under reflux and stirring for further 30 minutes. The closed flask was then kept for 30 minutes in a bath of ice and water and in thermostatic water bath at 25° C. for 30 minutes as well. The resulting solid was filtered on quick filtering paper, and the filtered liquid was divided into two 100 ml aliquots. One 100 ml aliquot of the filtered liquid was poured in a pre-weighed aluminum container, which was heated on a heating plate under nitrogen flow, to remove the solvent by evaporation. The container was then kept in an oven at 80° C. under vacuum until a constant weight was obtained. The residue was weighed to determine the percentage of xylene-soluble polymer.

Melt Flow Rate (MFR)

[0047] Determined according to ISO 1133 (230° C., 2.16 Kg)

Yellowness Index

[0048] The determination of the yellowness index (YI) was obtained by directly measuring the X, Y and Z tristimulus coordinates on pellets using a tristimulus colorimeter capable of assessing the deviation of an object color from a pre-set standard white towards yellow in a dominant wavelength range between 570 and 580 nm. The geometric characteristics of the apparatus allowed perpendicular viewing of the light reflected by two light rays that hit the specimen at 45°, at an angle of 90° to each other, coming from a “Source C” according to CIE standard. After calibration, the glass container was filled with the pellets to be tested and the X, Y, Z coordinates were obtained to calculate the yellowness index according to the following equation:

YI=100*(1.274976795*X−1.058398178*Z)/Y

EXAMPLES

General Procedure for the Polymerization of Propylene

[0049] A 4-liter steel autoclave equipped with a stirrer, pressure gauge, thermometer, catalyst feeding system, monomer feeding lines and thermostatic jacket, was purged with a nitrogen flow at 70° C. for one hour. A suspension containing 75 ml of anhydrous hexane, 0.6 g of triethyl aluminum (AlEt.sub.3, 5.3 mmol) and 0.006 to 0.010 g of solid catalyst component, pre-contacted for 5 minutes with 10 wt % of total AlEt.sub.3 and an amount of dicyclopentyldimethoxysilane, thereby providing a molar ratio between Al/dicyclopentyldimethoxysilane of 20 in a glass-pot, was charged. The autoclave was closed, and hydrogen was added (4500 cc). Then, under stirring, 1.2 kg of liquid propylene was fed. The temperature was raised to 70° C. in about 10 minutes and the polymerization was carried out at this temperature for 2 hours. At the end of the polymerization, the non-reacted propylene was removed; the polymer was recovered and dried at 70° C. under vacuum for 3 hours. The resulting polymer was weighed and characterized.

[0050] General Procedure for the Preparation of MgCl.sub.2.(EtOH)m Adducts.

[0051] An amount of microspheroidal MgCl.sub.2.2.8C.sub.2H.sub.5OH was prepared according to the method described in Example 2 of U.S. Pat. No. 4,399,054. The resulting adduct had an average particle size of 25 μm.

Example 1 (Comparative)

Preparation of a 9,9-bis(methoxymethyl)fluorene Containing Solid Catalyst Component

[0052] Into a 2.0 L round bottom glass reactor, equipped with mechanical stirrer, cooler and thermometer, 1.0 L of TiCl.sub.4 was introduced at room temperature under a nitrogen atmosphere. After cooling to −5° C., while stirring, 13.2 g of microspheroidal complex of MgCl.sub.2 and EtOH were introduced. The temperature was then raised from −5° C. to 40° C., and when this temperature was reached, an amount of 9,9-bis(methoxymethyl)fluorene, used as an internal electron donor, was introduced, thereby producing a Mg/9,9-bis(methoxymethyl)fluorene molar ratio of 6.

[0053] At the end of the addition, the temperature was increased to 100° C. and maintained at this value for 30 minutes. Thereafter, stirring was stopped, and the solid product settled. Then the supernatant liquid was siphoned off, leaving a fixed residual volume in the reactor of 300 cm.sup.3, while maintaining the temperature at 75° C. After the supernatant was removed, fresh TiCl.sub.4 and an additional amount of donor were added, thereby providing a Mg/9,9-bis(methoxymethyl)fluorene molar ratio of 20. The whole slurry mixture was then heated at 109° C. and kept at this temperature for 30 minutes. The stirring was interrupted; the solid product settled, and the supernatant liquid was siphoned off, while maintaining the temperature at 109° C. A third treatment in fresh TiCl.sub.4 (1 L of total volume) was repeated, keeping the mixture under agitation at 109° C. for 15 minutes, and then the supernatant liquid was siphoned off.

[0054] The solid was washed with anhydrous i-hexane five times (5×1.0 L) at 50° C. and one time (1.01) at room temperature.

[0055] The solid was finally dried under vacuum, weighed, and analyzed.

[0056] Catalyst composition: Mg=12.5 wt %; Ti=3.7 wt %; I.D.=20.7 wt %.

[0057] The catalyst was used in the polymerization of propylene. Results are shown in Table 1.

Example 2

Preparation of the Solid Catalyst Component/Coloring Agent Hydrocarbon Slurry

[0058] Into a 2-liter recipient, containing one liter of n-hexane, were introduced 40 grams of the catalyst component prepared as described in Example 1 and 17 grams of Cu-phthalocyanine. The slurry was stirred for at 350 rpm for 240 minutes and then stored at room temperature for 24 hours. After that time, the slurry was tested in the polymerization of propylene. Results are shown in Table 1.

Examples 3-4

[0059] A series of polymerization examples was carried out according to the polymerization procedure previously described, with the difference that the amount of Cu-Phthalocyanine reported in Table 1 was added to the pre-contacting glass-pot before being added to the polymerization reactor.

Examples 5-6

[0060] A series of polymerization examples was carried out as described in examples 3-4 with the difference that Ultramarine Blue was used instead of Cu-phthalocyanine.

Comparative Example 7

[0061] The catalyst was prepared, and polymerization carried out, in analogy with Example 2 with the difference that the catalyst component and the pigment were dry blended. Results are shown in Table 1.

Comparative Example 8-9

[0062] The same procedure described in Comparative Example 7 was followed with the difference that Ultramarine Blue, in the amount reported in Table 1, was used instead of Cu-Phthalocyanine.

TABLE-US-00001 TABLE 1 POLYMERIZATION PIGMENT/CAT Yellow Bulk Pigment EXAM- MIXTURE Activity XI Index Density in PP PLE Weight ratio Kg/gcat % wt — g/cm.sup.3 ppm C1 — 46 98.6 1.4 0.48 — 2 0.02:1  44 98.6 −0.9 0.51 0.4 3 0.3:1 50 98.4 −28 0.46 5 4 0.8:1 48 98.6 −85 0.47 22 5 0.4:1 55 98.8 −2.5 0.47 10 6 2.5:1 53 98.7 −7.8 0.45 26 C7 0.2:1 14 98.3 −27 0.390 10 C8 0.2:1 25 98.6 1.5 0.44 9 C9 0.5:1 27 97.8 −7.7 0.47 75