WO2004113438A1

WO2004113438A1 - Process for making visbroken olefins polymers

Info

Publication number: WO2004113438A1
Application number: PCT/IB2004/002061
Authority: WO
Inventors: Vu A. Dang; Cheng Q. Song; Ming Wu
Original assignee: Basell Poliolefine Italia S.R.L.
Priority date: 2003-06-20
Filing date: 2004-06-17
Publication date: 2004-12-29

Abstract

A process for making visbroken olefin polymers with low level of byproducts by using a reactive, peroxide-containing olefin polymer material comprising: a) preparing an olefin polymer mixture comprising: I. about 0.5 to about 90.0% by weight of a reactive, peroxide-containing olefin polymer material (A); and II. about 10.0 to about 99.5% by weight of an olefin polymer material (B); b) extruding or compounding in molten state the olefin polymer mixture, thereby producing a melt mixture; and optionally c) pelletizing the melt mixture.

Description

PROCESS FOR MAKING VISBROKEN OLEFINS POLYMERS

The present invention relates to a process for making visbroken olefin polymer compositions with improved rheological properties and reduced molecular weights in a post polymerization treatment. More particularly, the process includes visbreaking of polyolefins in the presence of reactive, peroxide-containing olefin polymer materials.

Polyolefins are well known commercial polymers, used for a variety of products such as packaging films and extruded and molded shapes. They are produced by polymerization of olefin monomers over transition metal coordination catalysts, specifically titanium halide containing catalysts or single site catalysts. Most commonly used polyolefins include polypropylene, polyethylene and polybutene. The olefin polymer usually has certain limitations in its use for applications that require improved flow performance and fabricating performance. It is known by those familiar with the manufacture of polyolefm polymers that production of high melt flow polymers in the reactor may be difficult due to chain transfer reaction limitations, and the products thereof may suffer embrittlement.

Visbreaking in extrusion equipment provides an alternative route to high melt flow without these adverse effects. For example, U.S. Pat. No. 4,493,923 discloses a polymer composition that has such improved flow performance as obtained through visbreaking by using organic peroxides. A process for modifying polyolefins is disclosed in U.S. Pat. No. 5,405,917, in which an organic peroxide was mixed with the polymer and then the mixture was fed through an extruder. It is well known that organic peroxides are unstable chemicals which are difficult for transportation, storage or application, hi addition, all the organic peroxides will release toxic by-products upon degradation in a chemical reaction. The most common degradation by-product is t-butyl alcohol. These toxic by-products exclude the use of the final polymer products in many applications, such as, toys, food packaging, medical device, etc.

The irradiation of olefin polymers has been described in a number of patents. For example, U.S. Patent Numbers 5,820,981 and 5,804,304 disclose a polymer that is subjected to electron beam irradiation in the substantial absence of oxygen, followed by a multistage treatment in the presence of a controlled amount of oxygen. Although the flow characteristics of the irradiated polymer will change after the irradiation treatment, these processes require the use of an electron beam generator and sophisticated processing equipment, which limit its use to only large scale applications. Therefore, there is a need to visbreak olefin polymers to modify their flow characteristics without using an irradiating source directly or without using an organic peroxide in order to obtain a final product with suitable flow characteristics without toxic by-products.

Accordingly, it is an object of this invention to eliminate the above mentioned difficulties in handling of organic peroxides and to avoid the toxic by-products resulted from their use.

It is another object of this invention to modify flow characteristics of olefin polymers using a batch or a continuous process without the need of direct irradiation.

It is still another object of this invention to provide a process to make an ionomer composition with improved flow characteristics.

In accordance with the present invention, a visbreaking process for making modified polyolefins by using a reactive, peroxide-containing olefin polymer material, is disclosed.

In one embodiment, the present invention relates to a process for making visbroken olefin polymers comprising: a) preparing an olefin polymer mixture comprising:

I. about 0.5 to about 90.0% by weight of a reactive, peroxide-containing olefin polymer material (A); and π. about 10.0 to about 99.5% by weight of an olefin polymer material (B) selected from a propylene polymer material and a butene-1 polymer material; wherein the sum of components I + II is equal to 100 wt%; b) extruding or compounding in molten state the olefin polymer mixture, thereby producing a melt mixture; and optionally c) pelletizing the melt mixture after it is cooled.

In another embodiment, the present invention relates to a process for making visbroken olefin polymers containing ionomer functionality comprising: (a) preparing an olefin polymer mixture comprising:

I. about 2.0 to about 90.0% by weight of a reactive, peroxide-containing olefin polymer material (A); LI. up to about 98.0%) by weight of an olefin polymer material (B) selected from a propylene polymer material and a butene-1 polymer material; and m. about 0.1 to about 10%> by weight of a base compound selected from metal oxides, hydroxides, and salts; wherein the sum of components I + II + III is equal to 100 wt%>;

(b) extruding or compounding in molten state the olefin polymer mixture, thereby producing a melt mixture; and optionally

(c) pelletizing the melt mixture after it is cooled.

Olefin polymer suitable as a starting material for preparing reactive, peroxide- containing olefin polymer materials is a propylene polymer material, an ethylene polymer material, a butene-1 polymer material, or mixtures thereof. The starting material used in the present invention can be selected from:

(a) a crystalline homopolymer of propylene having an isotactic index greater than about 80%, preferably about 90% to about 99.5%;

(b) a crystalline, random copolymer of propylene with an olefin selected from ethylene and C₄-C₁₀ α-olefins wherein the polymerized olefin content is about 1-10% by weight, preferably about 1% to about 4%, when ethylene is used, and about 1% to about 20% by weight, preferably about 1% to about 16%, when the C₄-C₁₀ α-olefin is used, the copolymer having an isotactic index greater than about 60%, preferably at least about 70%;

(c) a crystalline, random terpolymer of propylene and two olefins selected from ethylene and C₄-C₈ α-olefins wherein the polymerized olefin content is about 1% to about 5% by weight, preferably about 1% to about 4%, when ethylene is used, and about 1% to about 20% by weight, preferably about 1% to about 16%, when the C₄-C₁₀ α-olefins are used, the terpolymer having an isotactic index greater than about 85%>; and

(d) an olefin polymer composition comprising:

(i) about 10%) to about 60% by weight, preferably about 15% to about 55%, of a crystalline propylene homopolymer having an isotactic index at least about 80%, preferably about 90 to about 99.5%o, or a crystalline copolymer of monomers selected from (a) propylene and ethylene, (b) propylene, ethylene and a C₄-C₈ α-olefin, and (c) propylene and a C₄- C₈ α-olefin, the copolymer having a polymerized propylene content of more than about 85% by weight, preferably about 90% to about 99%, and an isotactic index greater than about 60%>; (ii) about 3% to about 25% by weight, preferably about 5% to about 20%, of a copolymer of ethylene and propylene or a C₄-C₈ α-olefin that is insoluble in xylene at ambient temperature; and (iii) about 10% to about 80% by weight, preferably about 15% to about 65%, of an elastomeric copolymer of monomers selected from (a) ethylene and propylene, (b) ethylene, propylene, and a C₄-C₈ α-olefin, and (c) ethylene and a C₄-C₈ α-olefin, the copolymer optionally containing about 0.5% to about 10%> by weight of a polymerized diene and containing less than about 70%> by weight, preferably about 10% to about 60%), most preferably about 12%) to about 55%>, of polymerized ethylene, and being soluble in xylene at ambient temperature and having an intrinsic viscosity of about 1.5 to about 4.0 dl/g; wherein the total of (ii) and (iii), based on the total olefin polymer composition is about 50%) to about 90%> by weight, and the weight ratio of (ii)/(iii) is less than about 0.4, preferably 0.1 to 0.3, and the composition is prepared by polymerization in at least two stages;

(e) homopolymers of ethylene;

(f) random copolymers of ethylene and an α-olefin selected from C₃-C₁₀ α-olefins having a polymerized α-olefin content of about 1 to about 20% by weight, preferably about 1% to about 16%;

(g) random terpolymers of ethylene and two C₃-C₁₀ α-olefins having a polymerized α-olefin content of about 1%> to about 20%> by weight, preferably about 1% to about 16%>;

(h) homopolymers of butene- 1 ;

(i) copolymers or terpolymers of butene-1 with ethylene, propylene or C₅-C₁₀ alpha-olefin, the comonomer content ranging from about 1 mole % to about 15 mole %>; and (j) mixtures thereof.

Olefin polymers suitable as the olefin polymer material (B) is a propylene polymer material, a butene-1 polymer material, or mixtures thereof. The propylene polymer material used in the present invention can be selected from:

(a) a crystalline homopolymer of propylene having an isotactic index greater than about 80%), preferably about 90 to about 99.5;

(b) a crystalline, random copolymer of propylene with an olefin selected from ethylene and C₄-Cιo α-olefins wherein the polymerized olefin content is about 1-10%) by weight, preferably about 1% to about 4%>, when ethylene is used, and about 1%> to about 20%> by weight, preferably about 1% to about 16%>, when the C₄-C₁₀ α-olefin is used, the copolymer having an isotactic index greater than about 60%, preferably at least about 70%;

(c) a crystalline, random terpolymer of propylene and two olefins selected from ethylene and C₄-C₈ α-olefins wherein the polymerized olefin content is about 1%) to about 5%> by weight, preferably about 1% to about 4%, when ethylene is used, and about 1%> to about 20%> by weight, preferably about 1% to about 16%, when the C₄-C₁₀ α-olefins are used, the terpolymer having an isotactic index greater than about 85%>;

(d) an olefin polymer composition comprising:

(i) about 10%) to about 60%> by weight, preferably about 15%> to about 55%), of a crystalline propylene homopolymer having an isotactic index at least about 80%, preferably about 90%> to about 99.5%>, or a crystalline copolymer of monomers selected from (a) propylene and ethylene, (b) propylene, ethylene and a C₄-C₈ α-olefin, and (c) propylene and a C₄-C₈ α-olefin, the copolymer having a propylene content of more than about 85%> by weight, preferably about 90% to about 99%), and an isotactic index greater than about 60%;

(ii) about 3% to about 25% by weight, preferably about 5%> to about 20%), of a copolymer of ethylene and propylene or a C₄-C₈ α-olefin that is insoluble in xylene at ambient temperature; and

(iii) about 10%> to about 80% by weight, preferably about 15%> to about 65%), of an elastomeric copolymer of monomers selected from (a) ethylene and propylene, (b) ethylene, propylene, and a C₄-C₈ α-olefin, and (c) ethylene and a C₄-C₈ α-olefin, the copolymer containing less than about 70%) by weight, preferably about 10%> to about 60%>, most preferably about 12%> to about 55%, of polymerized ethylene and being soluble in xylene at ambient temperature and having an intrinsic viscosity of about 1.5 to about 4.0 dl/g; wherein the total of (ii) and (iii), based on the total olefin polymer composition is about 50%) to about 90%, and the weight ratio of (ii)/(iϋ) is less than about 0.4, preferably about 0.1 to about 0.3, wherein the composition is prepared by polymerization in at least two stages; and (e) mixtures thereof. The butene-1 polymer material used in the present invention can be selected from:

(a) homopolymers of butene- 1 ;

(b) copolymers or terpolymers of butene-1 with ethylene, propylene or C₅-Cιo alpha-olefin, the comonomer content ranging from about 1 mole % to about 15 mole %; and

(c) mixtures thereof.

The useful polybutene- 1 homo or copolymers can be isotactic or syndiotactic and have a melt flow rate (MFR) from about 0.1 to 150 dg/min, preferably from about 0.3 to 100, and most preferably from about 0.5 to 75.

These butene-1 polymer materials, their methods of preparation and their properties are known in the art. Suitable polybutene- 1 polymers can be obtained, for example, by using Ziegler-Natta catalysts with butene-1, as described in WO 99/45043, or by metallocene polymerization of butene-1 as described in WO 02/102811, the disclosures of which are incorporated herein by reference.

Preferably, the butene-1 polymer materials contain up to about 15 mole %> of copolymerized ethylene or propylene. More preferably, the butene-1 polymer material is a homopolymer having a crystallinity of at least about 30% by weight measured with wide- angle X-ray diffraction after 7 days, more preferably about 45%> to about 70%, most preferably about 55%> to about 60%o.

The olefin polymer material (B) and the starting material for the reactive, peroxide- containing olefin polymer material can be the same or different from each other.

Preferably, the olefin polymer material (B) and the starting material for making the reactive, peroxide-containing olefin polymer material is a propylene polymer material, more preferably a propylene homopolymer having an isotactic index greater than about 80%o. In the visbroken olefin polymer composition, the reactive, peroxide-containing olefin polymer material can be present in an amount from about 0.5 to about 90%) by weight, preferably about 1 to about 30%>, more preferably about 2 to about 20%>. The balance of the composition up to 100%> by weight is the olefin polymer material.

Typically, the reactive, peroxide-containing olefin materials are prepared by exposing the starting material to high-energy ionizing radiation under a blanket of inert gas, preferably nitrogen. The ionizing radiation should have sufficient energy to penetrate the mass of polymer material being irradiated to the extent desired. The ionizing radiation can be of any kind, but preferably includes electrons and gamma rays. More preferred are electrons beamed from an electron generator having an accelerating potential of 500-4,000 kilovolts. Satisfactory results are obtained at a dose of ionizing radiation of about 0.1 to about 15 megarads ("Mrad"), preferably about 0.5 to about 9.0 Mrad.

The term "rad" is usually defined as that quantity of ionizing radiation that results in the absorption of 100 ergs of energy per gram of irradiated material regardless of the source of the radiation using the process described in U.S. Pat. No. 5,047,446. Energy absorption from ionizing radiation is measured by the well-known convention dosimeter, a measuring device in which a strip of polymer film containing a radiation-sensitive dye is the energy absorption sensing means. Therefore, as used in this specification, the term "rad" means that quantity of ionizing radiation resulting in the absorption of the equivalent of 100 ergs of energy per gram of the polymer film of a dosimeter placed at the surface of the olefin material being irradiated, whether in the form of a bed or layer of particles, or a film, or a sheet.

The irradiated olefin polymer material is then oxidized in a series of steps. According to a preferred preparation method, the first treatment step consists of heating the irradiated polymer in the presence of a first controlled amount of active oxygen greater than 0.004%o by volume but less than 15%> by volume, preferably less than 8% by volume, more preferably less than 5%> by volume, and most preferably from 1.3%o to 3.0%o by volume, to a first temperature of at least 25°C but below the softening point of the polymer, preferably about 25°C to 140°C, more preferably about 40°C to 100°C, and most preferably about 50°C to 90°C. Heating to the desired temperature is accomplished as quickly as possible, preferably in less than 10 minutes. The polymer is then held at the selected temperature, typically for about 5 to 90 minutes, to increase the extent of reaction of the oxygen with the free radicals in the polymer. The holding time, which can be determined by one skilled in the art, depends upon the properties of the starting material, the active oxygen concentration used, the irradiation dose, and the temperature. The maximum time is determined by the physical constraints of the fluid bed used to treat the polymer.

In the second treatment step, the irradiated polymer is heated in the presence of a second controlled amount of oxygen greater than 0.004% by volume but less than 15% by volume, preferably less than 8%> by volume, more preferably less than 5%> by volume, and most preferably from 1.3% to 3.0%> by volume to a second temperature of at least 25°C but below the softening point of the polymer. Preferably, the second temperature is from 80°C to less than the softening point of the polymer, and greater than the temperature of the first treatment step. The polymer is then held at the selected temperature and oxygen concentration conditions for about 10 to 300 minutes, preferably 20 to 180 minutes, most preferably about 30 to 60 minutes, to increase the rate of chain scission and to minimize the recombination of chain fragments so as to form long chain branches, i.e., to minimize the formation of long chain branches. The holding time is determined by the same factors discussed in relation to the first treatment step.

In the optional third step, the oxidized olefin polymer material is heated under a blanket of inert gas, preferably nitrogen, to a third temperature of at least 80°C but below the softening point of the polymer, and held at that temperature for about 10 to about 120 minutes, preferably about 60 minutes. A more stable product is produced if this step is carried out. It is preferred to use this step if the reactive, peroxide-containing olefin polymer material is going to be stored rather than used immediately, or if the radiation dose that is used is on the high end of the range described above. The polymer is then cooled to a fourth temperature of about below 50°C under a blanket of inert gas, preferably nitrogen, before being discharged from the bed. In this manner, stable intermediates are formed that can be stored at room temperature for long periods of time without further degradation.

As used in this specification, the expression "room temperature" or "ambient" temperature means approximately 25°C. The expression "active oxygen" means oxygen in a form that will react with the irradiated olefin polymer material. It includes molecular oxygen, which is the form of oxygen normally found in air. The active oxygen content requirement of this invention can be achieved by replacing part or all of the air in the environment by an inert gas such as, for example, nitrogen. The preferred method of making the reactive, peroxide-containing olefin polymer material is to carry out the treatment by passing the irradiated polymer through a fluid bed assembly operating at a first temperature in the presence of a first controlled amount oxygen, passing the polymer through a second fluid bed assembly operating at a second temperature in the presence of a second controlled amount of oxygen, and then maintaining the polymer at a third temperature under a blanket of nitrogen, in a third fluid bed assembly. In commercial operation, a continuous process using separate fluid beds for the first two steps, and a purged, mixed bed for the third step is preferred. However, the process can also be carried out in a batch mode in one fluid bed, using a fluidizing gas stream heated to the desired temperature for each treatment step. Unlike some techniques, such as melt extrusion methods, the fluidized bed method does not require the conversion of the irradiated polymer into the molten state and subsequent re-solidification and comminution into the desired fonn. The fluidizing medium can be, for example, nitrogen or any other gas that is inert with respect to the free radicals present, e.g., argon, krypton, and helium.

The concentration of peroxide groups formed on the reactive, peroxide-containing polymer can be controlled easily by varying the radiation dose during the preparation of the reactive, peroxide-containing olefin polymer and the amount of oxygen to which such polymer is exposed after irradiation. The oxygen level in the fluid bed gas stream is controlled by the addition of dried, filtered air at the inlet to the fluid bed. Air must be constantly added to compensate for the oxygen consumed by the formation of peroxides in the polymer. The typical peroxide concentration of the reactive, peroxide-containing olefin polymers is ranging from about 10 to about 100 milli-equivalent of peroxide in one kilogram of the reactive, peroxide-containing olefin polymer (meq/kg).

Without bound by theory, the reactive, peroxide-containing olefin polymer material of the invention contains peroxide linkages that degrade during compounding to form various oxygen-containing polar functional groups, e.g., carboxylic acids, ketones and esters. In addition, the number average and weight average molecular weight of the reactive, peroxide- containing olefin polymer is usually much lower than that of the corresponding olefin polymer used to prepare the same, due to the chain scission reactions during irradiation and oxidation.

Suitable equipment for conducting visbreaking process is well known in the art and includes but not limited to single screw extruder, twin screw extruder, Ferrell Continuous Mixer (FCM), B anbury mixer, a kneading machine, and an autoclave, etc. Alternatively, the visbroken olefin polymers can be further melt processed with a base compound to form visbroken olefin polymers containing ionomer functionality. The process comprises: a) mixing about 90 to 99.9 wt% of a visbroken melt mixture or a pelletized mixture with about 0.1 to about 10 wt%» of a base compound of a metal oxide, a hydroxide or a salt, thereby producing a base mixture; b) extruding or compounding in molten state the base mixture, thereby producing a melt base mixture; and optionally c) pelletizing the melt base mixture after it is cooled;

Typically, according to the second embodiment of the present invention, visbroken olefin polymers containing ionomer functionality were prepared in the presence of a suitable base compound in the extrusion or compounding process. The base compound is defined as a substance that accepts a proton (Lowry-Bronsted definition) or as a substance that can furnish an electron pair to form a covalent bond (Lewis definition).

Suitable base compounds of metal oxides, hydroxides or salts include sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium carbonate monohydrate, sodium dihydrogenphosphate, sodium dihydrogenpyrophosphate, sodium hydrogenphosphate, sodium hydrogenphosphate heptahydrate, sodium pyrophosphate, sodium pyrophosphate decahydrate, sodium triphosphate, potassium hydroxide, potassium carbonate, potassium bicarbonate, potassium carbonate sesquihydrate, potassium hydrogenphosphate, potassium hydrogenphosphate trihydrate, potassium pyrophosphate, lithium hydroxide, lithium carbonate, lithium bicarbonate, lithium hydroxide monohydrate, lithium phosphate, zinc oxide, aluminum hydroxide, etc. hi a process to prepare the visbroken olefin polymer composition containing ionomer functionality, the reactive, peroxide-containing olefin polymer material can be present in an amount from about 2.0 to about 80.0 %> by weight, preferably about 4.0 to about 30%>, more preferably about 5.0 to about 20%>, and the base compound can be present in an amount of about 0.1 to about 10%_> by weight, preferably from about 0.2 to about 5%>, more preferably about 0.5 to about 1.5%. The balance of the composition up to 100% is the olefin polymer material. The polymer composition of the present invention may also contain conventional additives, for instance, anti-acid stabilizers, such as, calcium stearate, hydrotalcite, zinc stearate, calcium oxide, and sodium stearate.

In preparation of the polymer mixture of the present invention, the olefin polymer material, the reactive, peroxide-containing olefin polymer material, and the base when making visbroken olefin polymers containing ionomer functionality, can be combined at ambient temperature in conventional operations well known in the art; including but not limited to, drum tumbling, manual mixing, or with low or high speed mixers.

The resulting mixture is then extruded or compounded in the molten state to conduct the visbreaking reaction in any conventional manner well known in the art in batch or continuous mode; for example, by using a Banbury mixer, a kneading machine, a single screw extruder, a twin screw extruder or an autoclave equipped with adequate agitation. The melt mixture can then be optionally pelletized according to conventional methods well know in the art.

Unless otherwise specified, the properties of the olefin polymer materials, compositions and other characteristics that are set forth in the following examples have been determined according to the test methods reported below: Melt Flow Rate ("MFR"): ASTM D1238, units of dg/min; 230° C; 2.16 kg;

Polymer material with a MFR below 100, using full die; Polymer material with a MFR equal or above 100, using Vz die; unless otherwise specified. Isotactic Index ("LI."): Defined as the percent of olefin polymer insoluble in xylene.

The weight percent of olefin polymer soluble in xylene at room temperature is determined by dissolving 2.5 g of polymer in 250 ml of xylene at room temperature in a vessel equipped with a stirrer, and heating at 135°C with agitation for 20 minutes. The solution is cooled to 25 °C while continuing the agitation, and then left to stand without agitation for 30 minutes so that the solids can settle. The solids are filtered with filter paper, the remaining solution is evaporated by treating it with a nitrogen stream, and the solid residue is vacuum dried at 80°C until a constant weight is reached. These values correspond substantially to the isotactic index determined by extracting with boiling n-heptane, which by definition constitutes the isotactic index of polypropylene.

Peroxide Concentration: Quantitative Organic Analysis via Functional Groups, by S. Siggia et al., 4th Ed., NY, Wiley 1979, pp. 334-42.

Molecular Weight: The samples are prepared at a concentration of 70 mg/50 ml of stabilized 1, 2, 4 trichlorobenzene (250μg/ml BHT). The samples are then heated to 170 degC for 2.5 hours to solubilize. The samples are then run on a Waters GPCV2000 at 145 degC at a flow rate of 1.0 ml/min. using the same stabilized solvent. Three Polymer Lab columns were used in series (Plgel, 20 μm mixed ALS, 300 X 7.5 mm). Gas Chromatograph determination of reaction byproduct: ^■ Weigh accurately 7-8 g polymer sample into a 50 ml serum vial.

Add 25 ml methylene chloride by pipette and cap the vial tightly with a teflon-lined septum seal (crimp the cap tightly to ensure seal is secure). Place the vial in a ultrasonic bath at room temperature. Remove a portion of the extract and analyze by Gas Chromotograph (Agilent 5890 or equivalent). In this specification, all parts, percentages and ratios are by weight unless otherwise specified. The reactive, peroxide-containing propylene polymers are prepared according to the following procedures. Preparation 1

A polypropylene homopolymer having a MFR of 0.7 dg/min and LI. of 95.6% commercially available from Basell USA h e. was irradiated at 0.5 Mrad under a blanket of nitrogen. The irradiated polymer was then treated with 2.5% by volume of oxygen at 55°C for 60 minutes and then with 2.5% by volume of oxygen at 140°C for an additional 60 minutes. The oxygen was then removed. The polymer was then heated at 140°C under a blanket of nitrogen for 90 minutes, cooled and collected. The MFR of the resultant polymer material was 1300 dg/min. The peroxide concentration was 28 meq/kg of polymer. Preparation 2

A reactive, peroxide-containing propylene polymer was prepared from a propylene homopolymer, commercially available from Basell USA Inc., having a MFR of 12.0 dg/min and LI. of 95.0%> according to the procedure of Preparation 1, except that the irradiated polymer was treated with 1.75% by volume of oxygen at 80°C for 60 minutes and then with 1.75%) by volume of oxygen at 140°C for another 60 minutes. The oxygen was then removed. The polymer was then heated at 140°C under a blanket of nitrogen for 60 minutes, cooled and collected. The MFR of the resultant polymer material was 852 dg/min. The peroxide concentration was 38.0 meq/kg of polymer. Preparation 3

A reactive, peroxide-containing propylene polymer was prepared from a propylene homopolymer, commercially available from Basell USA Inc., having a MFR of 1.5 dg/min and LI. of 96.0% according to the procedure of Preparation L. except that the irradiated polymer was treated with 2.0% by volume of oxygen at 80°C for 90 minutes and then with 2.0% by volume of oxygen at 140°C for 60 minutes. The oxygen was then removed. The polymer was then heated at 140°C under a blanket of nitrogen for 60 minutes, cooled and collected. The MFR of the resulting polymer material was 709 dg/min. The peroxide concentration was 43.4 meq/kg of polymer. Preparation 4

A reactive, peroxide-containing propylene polymer was prepared from a propylene homopolymer, commercially available from Basell USA Inc., having a MFR of 1.5 dg/min and LI. of 96.0% according to the procedure of Preparation 3, except that the irradiated polymer was treated with 2.2%> by volume of oxygen in both treatment steps. The MFR of the resulting material was 890 dg/min. The peroxide concentration was 43.4 meq/kg of polymer. Preparation 5

A reactive, peroxide-containing propylene polymer was prepared from a propylene homopolymer, commercially available from Basell USA Inc., having a MFR of 0.48 dg/min and LI. of 95.4%>, according to the procedure of Preparation 1, except that the irradiated polymer was first treated with 3.0%> by volume of oxygen at 80°C for 5 minutes, then with 3.0%) by volume of oxygen at 140°C for 60 min and finally with 5%_> by volume of oxygen at 130 °C for 3 hours. The MFR of the resulting polymer material was 17,000 dg/min. The peroxide concentration was 102 meq/kg of polymer. Example 1

This example shows the characteristics of a blend of a propylene homopolymer, and a reactive, peroxide-containing olefin polymer material. The comparative sample uses organic peroxide, Lupersol 101, commercially available from ELF Atochem in place of the reactive, peroxide-containing olefin polymer as a visbreaking agent.

The propylene homopolymer has a MFR of 4.0 and I.I. of 95.5%, commercially available from Basell USA Inc.

All materials were simultaneously dry-blended and bag mixed with Irganox B225 antioxidant and calcium stearate. Irganox B225 antioxidant is a 1:1 blend of Irganox 1010 antioxidant and Irgafos 168 tris(2,4-di-t-butylphenyl) phosphite anitoxidant and is commercially available from Ciba Specialty Chemicals Corporation. The composition of each sample is shown in Table 1. The amounts given for the stabilizers are in parts per hundred parts of the polymer composition.

Compounding was performed in a 1.5" Wayne single-screw extruder, commercially available from Wayne Machine & Die Company, with a barrel temperature of 232.2°C and a screw speed of 60 r.p.m.

The by-product of t-butanol in the polymer was measured using Gas Chromatograph determination as defined therein.

The comparative sample 2 shows a high level of t-butanol residue in the polymer after visbreaking reaction, whereas the samples containing a reactive, peroxide-containing olefin polymer have very low or are absent of t-butanol. The resulting polymer shows a low level of t-butanol, which provides a major advantage due to its purity.

The samples 1-3 show the melt flow increases with the increase of the reactive, peroxide-containing olefin polymer content. The visbreaking process effectively reduced molecular weight of the polymer and at the same time narrowed the molecular weight distribution. Table 1

Example 2

This example shows the characteristics of a blend of an olefin copolymer, and a reactive, peroxide-containing polypropylene.

The olefin copolymer was a copolymer of ethylene and propylene with ethylene content of 19.5%), having a MFR of 0.65 and LI. of 41.0%, commercially available from Basell USA Inc.

All materials were simultaneously dry-blended and bag mixed with Irganox B225 antioxidant and calcium stearate. The composition of each sample is shown in Table 2. The amounts given for the stabilizers are in parts per hundred parts of the polymer composition.

The samples 1-3 show the melt flow increases with the increase of the content of the reactive, peroxide-containing olefin polymer material. Table 2

Example 3

This example shows the characteristics of a blend of a propylene homopolymer, and an reactive, peroxide-containing olefin polymer.

The propylene homopolymer has a MFR of 3.5 and LI. of 95.0%, commercially available from Basell USA Inc.

All materials were¹ 'simultaneously dry-blended and bag mixed with Irganox B225 antioxidant and calcium stearate. The amounts given for the stabilizers are in parts per hundred parts of the polymer composition.

Compounding was performed in a 30 mm co-rotating intermeshing Leistritz LSM 34 GL twin-screw extruder commercially available from Leistritz AG, with a barrel temperature of 210°C and a screw speed of 200 r.p.m.

The composition of each sample containing a reactive, peroxide-containing olefin polymer is shown in Table 3. The samples 1-4 in Table 3 show the melt flow increases with the increase of the content of the reactive, peroxide-containing olefin polymer.

Table 3

In order to compare the dilution effect of the addition of a high melt flow polymer, five comparative samples containing a high MFR propylene homopolymer (A) with a MFR of 1100 and LI. of 97.0, commercially available from Basell USA Inc., were also prepared.

Table 4 shows the composition of the comparative samples containing a high MFR propylene homopolymer as controls. The comparative samples 2-6 in Table 4 show the melt flow increases with the increase of the high MFR propylene homopolymer (A) due to the dilution effect. The rate increase in MFR is much slower than that of polymer blends disclosed in Table 3. Therefore, the reactive, peroxide-containing olefin polymer provides additional visbreaking for the propylene homopolymer due to its peroxide functionality.

Table 4

Example 4

This example shows the characteristics of a blend of a propylene copolymer, and a reactive, peroxide-containing olefin polymer.

The propylene copolymer has a MFR of 3.8, LI. of 88.6%, and ethylene content of 9.4%), commercially available from Basell USA Inc.

All materials were simultaneously dry-blended and bag mixed with Irganox B225 antioxidant and calcium stearate. The amounts given for the stabilizers are in parts per hundred parts of the polymer composition.

Compounding was performed in a 30 mm co-rotating intermeshing Leistritz LSM 34 GL twin-screw extruder commercially available from Leistritz AG, with a barrel temperature of 210°C and a screw speed of 200 r.p.m. The composition of each sample containing reactive, peroxide-containing olefin polymer is shown in Table 5. The samples 1-3 in Table 5 show the melt flow increases with the increase of the reactive, peroxide-containing olefin polymer content.

Table 5

In order to evaluate the dilution effect, a high MFR propylene homopolymer (A) with a MFR of 1100 and LI. of 91.0%, commercially available from Basell USA h e, was added in place of the reactive, peroxide-containing olefin polymer in comparative samples.

Table 6 shows the composition of comparative samples containing a high MFR propylene homopolymer as controls. The comparative samples 2-5 in Table 6 show the melt flow of the polymer blend containing propylene copolymer increases with the addition of the high MFR propylene homopolymer (A) due to the dilution effect. But the rate increase in MFR is much slower that of polymer blends disclosed in Table 5. Therefore, the reactive, peroxide-containing olefin polymer provides additional visbreaking for the propylene copolymer due to its peroxide functionality.

Table 6

Example 5

The propylene copolymer has a MFR of 3.8, I.I. of 88.6%, and ethylene content of 9.4%o, commercially available from Basell USA Inc.

Compounding was performed in a 30 mm co-rotating intermeshing Leistritz LSM 34 GL twin-screw extruder commercially available from Leistritz AG, with a barrel temperature of 193°C and a screw speed of 250 r.p.m.

The composition of each sample containing reactive, peroxide-containing olefin polymer is shown in Table 7. The samples 1-2 in Table 7 show the melt flow increases with the increase, of the reactive, peroxide-containing olefin polymer content.

Table 7

Example 6

The propylene copolymer has a MFR of 0.5, LI. of 37.5%>, and ethylene content of 21.7%, commercially available from Basell USA Lhc.

All materials were simultaneously dry-blended and bag mixed with Irganox B225 antioxidant and calcium stearate. The amounts given for the stabilizers are in parts per hundred parts of the polymer composition. Compounding was performed in a 30 mm co-rotating intermeshing Leistritz LSM 34 GL twin-screw extruder commercially available from Leistritz AG, with a barrel temperature of 193°C and a screw speed of 250 r.p.m.

The composition of each sample containing a reactive, peroxide-containing polymer is shown in Table 8. The samples 1-3 in Table 8 show the melt flow increases with the increase of the reactive, peroxide-containing olefin polymer content.

Table 8

Example 7

This example shows the characteristics of a blend of a propylene copolymer, and a reactive, peroxide-containing olefin polymer, containing ionomer functionality.

The propylene copolymer has a MFR of 2.0, LI. of 93.8%>, and ethylene content of 3.4%o, commercially available from Basell USA Inc.

Sodium carbonate, potassium carbonate and zinc oxide were obtained from Aldrich Chemical Company, Inc. without further purification. The amounts given for the base are in parts per hundred parts of the polymer composition.

The composition of each sample containing reactive, peroxide-containing olefin polymer is shown in Table 9. The samples 1-3 in Table 9 show the melt flow characteristics of the visbroken olefin polymers containing ionomer functionality made by using various base compounds. Table 9

Example 8

The propylene copolymer has a MFR of 2.0, LI. of 93.8%, and ethylene content of 3.4%o, commercially available from Basell USA Inc.

The composition of each sample containing a reactive, peroxide-containing olefin polymer is shown in Table 10. The samples 1-3 in Table 10 show the melt flow characteristics of the visbroken olefin polymers containing ionomer functionality made by using various bases. Table 10

Example 9

This example shows the characteristics of a blend of a propylene homopolymer, and a reactive, peroxide-containing olefin polymer, containing ionomer functionality.

The propylene homopolymer has a MFR of 0.7, and LI. of 95.6%, commercially available from Basell USA Inc.

The composition of each sample containing a reactive, peroxide-containing olefin polymer is shown in Table 11. The samples 1-3 in Table 11 show the melt flow characteristics of the visbroken olefin polymers containing ionomer functionality made by using various bases. Table 11

Example 10

This example shows the characteristics of a blend of a propylene homopolymer, and a reactive, peroxide-containing olefin polymer. In order to compare the dilution effect of the addition of high melt flow polymers, two high melt flow propylene homopolymers were used in the comparative samples.

The propylene homopolymer has a MFR of 5.4 and LI. of 95.0%>, commercially available from Basell USA Inc. Two high MFR propylene homopolymers were used to evaluate the dilution effect. The first high MFR homopolymer (A) has a MFR of 695 dg/ml and the second high MFR homopolymer (B) has a MFR of 1051 dg/ml.

All materials were simultaneously dry-blended and bag mixed with calcium stearate. The amounts given for the calcium stearate is in parts per hundred parts of the polymer composition.

The composition of each sample containing a reactive, peroxide-containing olefin polymer and comparative samples is shown in Table 12. The samples 1-2 in Table 12 show the melt flow increases with the increase of the reactive, peroxide-containing olefin polymer content. The visbreaking process effectively reduced molecular weight of the polymer and at the same time narrowed the molecular weight distribution as compared with the comparative samples 2 and 3, which showed only dilution effect. Table 12

Other features, advantages and embodiments of the invention disclosed herein will be readily apparent to those exercising ordinary skill after reading the foregoing disclosures. In this regard, while specific embodiments of the invention have been described in considerable detail, variations and modifications of these embodiments can be effected without departing from the spirit and scope of the invention as described and claimed.

Claims

1. A process for making visbroken olefin polymers comprising: a) preparing an olefin polymer mixture comprising:

I. about 0.5 to about 90.0 wt% of a reactive, peroxide-containing olefin polymer material (A); and π. about 10.0 to about 99.5 wt% of an olefin polymer material (B) selected from a propylene polymer material and a butene-1 polymer material; wherein the sum of components I + II is equal to 100 wt%; b) extruding or compounding in molten state the olefin polymer mixture, thereby producing a melt mixture; and optionally c) pelletizing the melt mixture after it is cooled, thereby producing a pelletized mixture.

2. The process of claim 1 wherein the reactive, peroxide-containing olefin polymer material (A) is prepared from a polyolefin starting material selected from:

(a) a crystalline homopolymer of propylene having an isotactic index greater than about 80%;

(b) a crystalline, random copolymer of propylene with an olefin selected from ethylene and C₄-C₁₀ α-olefins wherein the polymerized olefin content is about 1-10% by weight when ethylene is used, and about l%o to about 20% by weight when the C₄-C₁₀ α-olefin is used, the copolymer having an isotactic index greater than about 60%>;

(c) a crystalline, random terpolymer of propylene and two olefins selected from ethylene and C₄-C₈ α-olefins wherein the polymerized olefin content is about 1%) to about 5%) by weight when ethylene is used, and about 1%> to about 20% by weight when the C₄-C₁₀ α-olefins are used, the terpolymer having an isotactic index greater than about 85%>;

(d) an olefin polymer composition comprising:

(i) about 10%) to about 60%> by weight of a crystalline propylene homopolymer having an isotactic index at least about 80%> or a crystalline copolymer of monomers selected from (a) propylene and ethylene, (b) propylene, ethylene and a C₄-C₈ α-olefin, and (c) propylene and a C₄-C₈ α-olefin, the copolymer having a polymerized propylene content of more than about 85%> by weight, and an isotactic index greater than about 60%>; (ii) about 3% to about 25%> by weight of a copolymer of ethylene and propylene or a C₄-C₈ α-olefin that is insoluble in xylene at ambient temperature; and (iii) about 10% to about 80%> by weight of an elastomeric copolymer of monomers selected from (a) ethylene and propylene, (b) ethylene, propylene, and a C₄-C₈ α-olefin, and (c) ethylene and a C₄-C₈ α-olefin, the copolymer optionally containing about 0.5% to about 10%o by weight of a polymerized diene and containing less than about 70%) by weight of polymerized ethylene, and being soluble in xylene at ambient temperature and having an intrinsic viscosity of about 1.5 to about 4.0 dl g; wherein the total of (ii) and (iii), based on the total olefin polymer composition is about 50%) to about 90%> by weight, and the weight ratio of (ii)/(iii) is less than about 0.4, and the composition is prepared by polymerization in at least two stages;

(e) homopolymers of ethylene;

(f) random copolymers of ethylene and an α-olefin selected from C₃-C₁₀ α-olefins having a polymerized α-olefin content of about 1 to about 20% by weight;

(g) random terpolymers of ethylene and C₃-C₁₀ α-olefins having a pplymerized α- olefin content of 1 to 20%> by weight;

(h) homopolymers of butene- 1 ;

(i) copolymers or terpolymers of butene-1 with ethylene, propylene or C₅-C₁₀ alpha-olefin, the comonomer content ranging from about 1 mole % to about 15 mole %; and (j) mixtures thereof.

3. The process of claim 2 wherein the starting material is a crystalline homopolymer of propylene having an isotactic index greater than 80%. process of claim 1 wherein the propylene polymer material in a) (II) is selected from:

(a) a crystalline homopolymer of propylene having an isotactic index greater than 80%;

(b) a crystalline random copolymer of propylene with an olefin selected from ethylene and C4-C10 α-olefins wherein the polymerized olefin content is about 1-10% by weight when ethylene is used and about 1% to about 20% by weight when the C₄-C₁₀ α-olefin is used;

(c) a crystalline random terpolymer of propylene and two olefins selected from ethylene and C₄-C₈ α-olefins wherein the polymerized olefin content is about 1% to about 5% by weight when ethylene is used, and about 1% to about 20% by weight when the C₄-C₁₀ α-olefins are used;

(d) an olefin polymer composition comprising:

(i) about 10%) to about 60% by weight of a crystalline propylene homopolymer having an isotactic index at least 80%o, or a crystalline copolymer of monomers selected from (a) propylene and ethylene, (b) propylene, ethylene and a C₄-C₈ α-olefin, and (c) propylene and a C₄- C₈ α-olefin, the copolymer having a propylene content of more than 85% by weight, and an isotactic index greater than 60%>; (ii) about 3% to about 25%> by weight of a copolymer of ethylene and propylene or a C₄-C₈ α-olefin that is insoluble in xylene at ambient temperature; and (iii) about 10%> to about 80% by weight of an elastomeric copolymer of monomers selected from (a) ethylene and propylene, (b) ethylene, propylene, and a C₄-C₈ α-olefinj and (c) ethylene and a C₄-C₈ α-olefin, the copolymer containing less than about 70% by weight of ethylene, and being soluble in xylene at ambient temperature and having an intrinsic viscosity of 1.5 to 4.0 dl/g; wherein the total of (ii) and (iii), based on the total olefin polymer composition being from about 50% to about 90%>, and the weight ratio of (ii)/(iii) being less than 0.

4, wherein the composition is prepared by polymerization in at least two stages; and

(e) mixtures thereof.

5. The process of claim 1 wherein the butene-1 polymer material in a) (II) is selected from:

(a) homopolymers of butene- 1 ;

(b) copolymers or terpolymers of butene-1 with ethylene, propylene or C₅- ₀ alpha-olefin, the comonomer content ranging from about 1 mole % to about 15 mole %>; and

(c) mixtures thereof.

6. The process of claim 1 wherein the propylene polymer material in a) (II) is a crystalline homopolymer of propylene having an isotactic index greater than 80%.

7. The process of claim 1 further comprising: d) mixing about 90 to 99.9 wt% of the melt mixture or the pelletized mixture obtained in step b) or c) with about 0.1 to about 10 wt%> of a base compound of a metal oxide, a hydroxide or a salt, thereby producing a base mixture; e) extruding or compounding in molten state the base mixture, thereby producing a melt base mixture; and optionally f) pelletizing the melt base mixture after it is cooled;

8. A process for making visbroken olefin polymers containing ionomer functionality comprising: a) preparing an olefin polymer mixture comprising:

I. about 2.0 to about 90.0 wt% of a reactive, peroxide-containing olefin polymer material (A); π. up to about 98.0 wt%> of an olefin polymer material (B) selected from a propylene polymer material and a butene-1 polymer material; and EL about 0.1 to about 10 wt%> of a base compound of a metal oxide, a hydroxide or a salt; wherein the sum of components I + II + III is equal to 100 wt%>; b) extruding or compounding in molten state the olefin polymer mixture, thereby producing a melt mixture; and optionally c) pelletizing the melt mixture after it is cooled.

9. The process of claim 8 wherein the reactive, peroxide-containing olefin polymer material (A) is prepared from a polyolefin starting material selected from:

(a) a crystalline homopolymer of propylene having an isotactic index greater than about 80%; (b) a crystalline, random copolymer of propylene with an olefin selected from ethylene and C₄-C₁₀ α-olefins wherein the polymerized olefin content is about 1-10%) by weight when ethylene is used, and about 1% to about 20%) by weight when the C₄-C₁₀ α-olefin is used, the copolymer having an isotactic index greater than about 60%>;

(c) a crystalline, random terpolymer of propylene and two olefins selected from ethylene and C₄-C₈ α-olefins wherein the polymerized olefin content is about 1%) to about 5% by weight when ethylene is used, and about 1%> to about 20%> by weight when the C₄-C₁₀ α-olefins are used, the terpolymer having an isotactic index greater than about 85%o;

(d) an olefin polymer composition comprising:

(i) about 10%) to about 60% by weight of a crystalline propylene homopolymer having an isotactic index at least about 80% or a crystalline copolymer of monomers selected from (a) propylene and ethylene, (b) propylene, ethylene and a C₄-C₈ α-olefin, and (c) propylene and a C₄-C₈ α-olefin, the copolymer having a polymerized propylene content of more than about 85% by weight, and an isotactic index greater than about 60%>;

(ii) about 3%> to about 25%> by weight of a copolymer of ethylene and propylene or a C₄-C₈ α-olefin that is insoluble in xylene at ambient temperature; and

(iii) about 10% to about 80% by weight of an elastomeric copolymer of monomers selected from (a) ethylene and propylene, (b) ethylene, propylene, and a C₄-C₈ α-olefin, and (c) ethylene and a C₄-C₈ α-olefin, the copolymer optionally containing about 0.5%> to about

10%) by weight of a polymerized diene and containing less than about

70% by weight of polymerized ethylene, and being soluble in xylene at ambient temperature and having an intrinsic viscosity of about 1.5 to about 4.0 dl/g; wherein the total of (ii) and (iii), based on the total olefin polymer composition is about 50% to about 90% by weight, and the weight ratio of (ϋ)/(iϋ) is less than about

0.4, and the composition is prepared by polymerization in at least two stages; (e) homopolymers of ethylene;

(f) random copolymers of ethylene and an α-olefin selected from C₃-C₁₀ α-olefins having a polymerized α-olefin content of about 1%> to about 20% by weight;

(g) random terpolymers of ethylene and two C₃-C₁₀ α-olefms having a polymerized α-olefin content of about 1%> to about 20% by weight;

(h) homopolymers of butene- 1 ;

10. The process of claim 9 wherein the starting material is a crystalline homopolymer of propylene having an isotactic index greater than 80%.

11. The process of claim 8 wherein the propylene polymer material in a) (II) is selected from:

(b) a crystalline random copolymer of propylene with an olefin selected from ethylene and C₄-C₁₀ α-olefins wherein the polymerized olefin content is about 1-10%) by weight when ethylene is used and about 1% to about 20%) by weight when the C₄-C₁₀ α-olefin is used;

(c) a crystalline random terpolymer of propylene and two olefins selected from ethylene and C₄-C₈ α-olefins wherein the polymerized olefin content is about 1%) to about 5%> by weight when ethylene is used, and about 1% to about 20% by weight when the C₄-C₁₀ α-olefins are used;

(d) an olefin polymer composition comprising:

(i) about 10%) to about 60% by weight of a crystalline propylene homopolymer having an isotactic index at least 80%, or a crystalline copolymer of monomers selected from (a) propylene and ethylene, (b) propylene, ethylene and a C₄-C₈ α-olefin, and (c) propylene and a C₄- C₈ α-olefin, the copolymer having a propylene content of more than 85%o by weight, and an isotactic index greater than 60%; (ii) about 3% to about 25 % by weight of a copolymer of ethylene and propylene or a C₄-C₈ α-olefin that is insoluble in xylene at ambient temperature; and (iii) about 10% to about 80%> by weight of an elastomeric copolymer of monomers selected from (a) ethylene and propylene, (b) ethylene, propylene, and a C₄-C₈ α-olefin, and (c) ethylene and a C₄-C₈ α-olefin, the copolymer containing less than about 70% by weight of ethylene, and being soluble in xylene at ambient temperature and having an intrinsic viscosity of 1.5 to 4.0 dl/g; wherein the total of (ii) and (iii), based on the total olefin polymer composition being from about 50%> to about 90%>, and the weight ratio of (ii)/(iϋ) being less than 0.4, wherein the composition is prepared by polymerization in at least two stages; and (e) mixtures thereof.

12. The process of claim 8 wherein the butene-1 propylene polymer material in a) (II) is selected from:

(a) homopolymers of butene-1;

(b) copolymers or terpolymers of butene-1 with ethylene, propylene or C₅-C1₀ alpha-olefm, the comonomer content ranging from about 1 mole % to about 15 mole %; and

(c) mixtures thereof.

13. The process of claim 8 wherein the propylene polymer material in a) (II) is a crystalline homopolymer of propylene having an isotactic index greater than 80%_>.

14. The process of claim 7 or 8 wherein the base compound is selected from: sodium carbonate, sodium bicarbonate, sodium carbonate monohydrate, potassium carbonate, potassium bicarbonate, lithium carbonate, lithium bicarbonate, zinc oxide, and aluminum hydroxide.