TITLE OF THE INVENTION

Polyolefin composition having high melt strength

FIELD OF INVENTION

The invention relates to a filled polyolefin composition comprising at least one fibrous submicron structured polymeric material, an inorganic filler and a mixture of polyolefin resins. The invention also relates to a method for preparing the composition and to the articles arid products prepared thereof.

BACKGROUND

Polyolefin compositions are widely used for the manufacture of various articles and products. Polyolefin, especially polypropylene, exhibit good resistance to deformation at elevated temperatures and has high tensile strength, surface hardness, and good toughness at ambient temperatures. Sheets and films of polypropylene are conveniently prepared by extrusion. Polypropylene resin sheets and films are, however, not commonly used in industrial processes such as thermoforming, melt spinning, blow molding and foaming due to the requirement, in such processes, of superior elasticity of the sheets in order to resist sagging. Due to their sharp melting point, polyolefins such as polypropylene pass through the viscoelastic plateau very rapidly on heating, resulting in poor melt strength and sag. The occurrence of sagging in industrial processes such as thermoforming may lead to irregularity in articles or even result in tearing of the polymer sheet used for the process.

WO200012572 discloses a long-chain branched polypropylene with high melt strength and good processability formed by contacting propylene monomers in a reactor with an inert hydrocarbon solvent and one or more single site catalysts capable of producing stereospecific propylene at

40-120° C. However, the improvement in melt strength by the use of such high-melt-strength

polypropylene in this disclosure is very limited. JP5175761 discloses a polypropylene sheet laminated onto a sagging-free sheet of a resin different from polypropylene. H ( owever, lamination means for sag reduction tend to be rather cumbersome and cost intensive and may also result voids in the formed products. US6770697 discloses a high melt strength polyolefϊn- nanoclay composite for thermoforming application. There is scope for further improvement in melt strength and sag resistance of polyolefin compositions.

DETAILED DESCRIPTION

Accordingly, the invention provides a filled polyolefin composition comprising at least one fibrous submicron structured polymeric material, inorganic filler(s) and. a mixture of polyolefin resins.

In one embodiment the invention provides a filled polyolefin composition comprising at least one fibrous submicron structured polymeric material, an inorganic filler and a mixture of polyolefin resins,, the mixture comprising a first polyolefin resin having a melt flow index in the range of 0.1 to 1.4 g/10 minutes and a second polyolefin resin having a melt flow index in the range of 1.5 to 15 g/10 minutes.

In another embodiment the invention provides a filled polyolefin composition comprising at least one fibrous submicron structured polymeric material, an impact modifier, an inorganic filler and a mixture of polyolefin resins, the mixture comprising a first polyolefin resin having a melt flow index in the range of 0.1 to 1.4 g/10 minutes and a second polyolefin resin having a melt flow index in the range of 1.5 to 15 g/10 minutes.

In one embodiment the invention provides a filled polyolefin composition comprising at least one fibrous submicron structured polymeric material, optionally an impact modifier, an inorganic filler and a mixture of polyolefin resins,, the mixture comprising a first polyolefin

resin having a melt flow index in the range of 0.1 to 1.4 g/10 minutes and a second polyolefin resin having a melt flow index in the range of 1.5 to 15 g/10 minutes.

In another embodiment the invention provides a filled polyolefin composition comprising at least one fibrous submicron structured polymeric material, optionally an impact modifier, an inorganic filler and a mixture of polyolefin resins,, the mixture comprising a first polyolefin resin having a melt flow index in the range of 0.1 to 1.4 g/10 minutes and a second polyolefin resin having a melt flow index in the range of 1.5 to 15 g/10 minutes wherein the mixture is present in an amount ranging from 53 to 95.99% by weight of the composition, the fibrous submicron structured polymeric material is present in an amount ranging from 0.01 to 2% by weight of the composition, the impact modifier is present in an amount ranging from 3 to 25% by weight of the composition and the inorganic filler is present in an amount ranging from 1 to 20% by weight of the composition.

In another embodiment the invention provides a filled polyolefin composition comprising at least one fibrous submicron structured polymeric material, optionally an impact modifier, an inorganic filler and a mixture of polyolefin resins,, the mixture comprising a first polyolefin resin having a melt flow index in the range of 0.1 to 1.4 g/10 minutes and a second polyolefin resin having a melt flow index in the range of 1.5 to 15 g/10 minutes wherein the mixture is present in an amount ranging from 64 to 91.9% by weight of the composition, the fibrous submicron structured polymeric material is present in an amount ranging from 0.1 to 1% by weight of the composition, the impact modifier is present in an amount ranging from 5 to 20% by weight of the composition and the inorganic filler is present in an amount ranging from 3 to 15% by weight of the composition.

In another embodiment the invention provides a filled polyolefin composition comprising at least one fibrous submicron structured polymeric material, optionally an impact modifier, an inorganic filler and a mixture of polyolefin resins,, the mixture comprising a first polyolefin resin having a melt flow index in the range of 0.1 to 1.4 g/10 minutes and a second polyolefin resin having a melt flow index in the range of 1.5 to 15 g/10 minutes wherein the first polyolefin resin has a melt flow index in the range of 0.3 to 1 g/10 minutes and the second polyolefin resin has a melt flow index in the range of 1.5 to 3.5 g/10 minutes.

In another embodiment the invention provides a filled polyolefin composition comprising at least one fibrous submicron structured polymeric material, optionally an impact modifier, an inorganic filler and a mixture of polyolefin resins,, the mixture comprising a first polyolefin resin having a melt flow index in the range of 0.1 to 1.4 g/10 minutes and a second polyolefin resin having a melt flow index in the range of 1.5 to 15 g/10 minutes wherein the fibrous submicron structured polymeric material is selected from the group consisting of an ultra high molecular polyethylene, a cellullosic material and a fluoropolymer.

In another embodiment the invention provides a filled polyolefin composition comprising at least one fibrous submicron structured polymeric material, optionally an impact modifier, an inorganic filler and a mixture of polyolefin resins,, the mixture comprising a first polyolefin resin having a melt flow index in the range of 0.1 to 1.4 g/10 minutes and a second polyolefin resin having a melt flow index in the range of 1.5 to 15 g/10 minutes wherein impact modifier is an elastomer.

In another embodiment the invention provides a filled polyolefin composition comprising at least one fibrous submicron structured polymeric material, optionally an impact modifier, an inorganic filler and a mixture of polyolefin resins,, the mixture comprising a first polyolefin

resin having a melt flow index in the range of 0.1 tol.4 g/10 minutes and a second polyolefin resin having a melt flow index in the range of 1.5 to 15 g/10 minutes wherein the inorganic filler is selected from the group consisting of inorganic oxides, inorganic carbonates, silicate materials and clays.

In another embodiment the invention provides a filled polyolefin composition comprising at least one fibrous submicron structured polymeric material, optionally an impact modifier, an inorganic filler and a mixture of polyolefin resins,, the mixture comprising a first polyolefin resin having a melt flow index in the range of 0.1 tol.4 g/10 minutes and a second polyolefin resin having a melt flow index in the range of 1.5 to 15 g/10 minutes wherein the inorganic filler is clay or mica

In another embodiment the invention provides a filled polyolefin composition comprising at least one fibrous submicron structured polymeric material, optionally an impact modifier, an inorganic filler and a mixture of polyolefin resins, the mixture comprising a first polyolefin resin having a melt flow index in the range of 0.1 tol .4 g/10 minutes and a second polyolefin resin having a melt flow index in the range of 1.5 to 15 g/10 minutes wherein the polyolefin is polypropylene, polyethylene or a propylene-ethylene copolymer.

In another embodiment the invention provides a method for preparing a filled polyolefin composition, the method comprising blending a composition comprising a mixture of polyolefin resins, at least one fibrous submicron structured polymeric material, an impact modifier and an inorganic filler in a twin-screw extruder at a temperature in the range of 150°C to 250°C at a specific energy in the range of 0.1 to 2.5 kilo watt hr/kg.

In another embodiment the invention provides a method for manufacturing articles, the method comprising thermoforming the filled polyolefin composition

In another embodiment the invention provides a method for manufacturing articles, the method comprising melting by heating the filled polyolefin composition, extruding the molten composition into a hollow tube and inflating the extruded melt to the desired shape.

In a further embodiment the invention provides shaped articles prepared from the filled polyolefin compositions

The filled polyolefin compositions of the invention comprise a mixture of polyolefin resins having different flow characteristics. In particular, mixture of polyolefin comprise one polyolefin having a low melt flow index (MFI) and another polyolefin resin having relatively high melt flow index. The low MFI polyolefin used in the invention is preferably one selected from the group consisting of polypropylene having MFI in the range of 0.1 to 1.4 g/10min, polyethylene having MFI in the range of 0.1 to 1.4 g/10min and ethylene-propylene copolymer having MFI in the range of 0.1 to 1.4 g/10min. The high MFI polyolefin is preferably one selected from the group consisting of polypropylene having MFI in the range of 1.5 to 15 g/10min, polyethylene having MFI in the range of 1.5 to 15 g/10min and ethylene- propylene copolymer having MFI in the range of 1.5 to 15 g/10min. The polyolefin resins used include thermoplastic and/or crosslinkable polyolefins as well as random, block or graft copolymers of ethylene and propylene. Polyolefin used to prepare the compositions of the invention can be made using olefin polymerization reaction carried out in the gas phase, slurry phase and solution phase The catalysts used for the polymerization reaction include, but are not limited to, coordination anionic catalysts, cationic catalysts, free radical catalysts, Ziegler-Natta catalysts as well as metallocenes reacted with an alkyl or alcoxy metal compound, or with an ionic

compound. The catalysts can also be in the form of catalyst precursor compositions that are partially or completely activated and those catalysts modified by pre-polymerization or any similar technique for the catalyst conditioning. A definition of Ziegler-Natta catalysts may be found in the chapter "Definitions, stereochemistry, experimental methods and commercial polymers", from the book by John Boor, Jr., "Ziegler-Natta Catalysts and Polymerizations", p. 32-35, Academic Press. Polyolefin can be a homopolymer or copolymer of monomers not limited to ethylene, propylene, alpha-olefms such as 1-butene, 1-pentene, 1-hexene, 4-methyl-l- pentene, 1-octene, 1-decene, other linear, branched or cyclic olefins having of from 4 to 12 carbon atoms.

In addition to the mixture of polyolefin resins the filled polyolefin composition of the invention comprise inorganic fillers, impact modifiers and at least one fibrous submicron structured polymeric material. The fillers used in the invention include fillers and solid compounding ingredients or agents commonly used in polymeric compounds. Typical fillers include all kinds of clays, layered silicate materials, carbon black, wood flour either with or without oil, various forms of silica including common sand, glass, metals, metal oxides such as aluminum oxide and titanium oxide, aluminum trihydrate and titanium dioxide magnesium oxide, calcium carbonate, barium carbonate, magnesium carbonate, barium sulfate, antimony trioxide, calcium silicate, diatomaceous earth, fuller earth, kieselguhr, mica, talc, slate flour, volcanic ash, cotton flock, asbestos, kaolin, sulfates of barium, calcium sulfate, titanium, organically modified clays, zeolites, vanadium oxide, wollastonite, titanium boride, zinc borate, tungsten carbide, ferrites, molybdium disulfide, asbestos, cristobalite, silica and layered silicate materials including Vermiculite, bentonite, montmorillonite, Na-montmorillonite, Ca-montmorillonite, kaolinite, mica, hectorite, fluorohectorite, saponite, beidelite, nontronite, stevensite, hallosite, volkonskoite, suconite, magadite and kenyalite in the modified or unmodified form. Modifiers are usually organic substances having atleast one functional group selected from primary

ammonium to quaternary ammonium, phosphonium, maleate, succinate, acrylate, benzylic hydrogen, oxazoline, and dimethyldistearylammonium groups. Aluminosilicates like calcium aluminum magnesium silicate hydroxide, pyrophyllite, magnesium aluminum silicate, lithium aluminium silicates and zirconium silicates as well as silica which includes precipitated or hydrated, fumed or pyrogenic, vitreous, fused or colloidal and hydroxides of aluminium or ammonium or magnesium, zirconia, nanoscale titania and their suitable combinations are also used as fillers. Inorganic oxide or mixtures of two or more inorganic oxides are also used as fillers to prepare the composition of the invention. Such fillers include oxides of the metals in periods 2, 3, 4, 5 and 6 of Groups Ib, lib, Ha, IHb, IVa, IVb (except carbon), Va, Via, Villa and VIII of the Periodic Table.

The fillers used in the composition of the invention could also be fibrous fillers which include fibers like glass fibers, basalt fibers, aramid fibers, carbon fibers, carbon nanofibers, melamine fibers, polyamide fibers, metal fibers. Fillers like carbon nanotubes, carbon buckyballs, potassium titanate whiskers, aluminum borate whiskers can also be used. Preferred fillers are those selected from the group consisting of calcium carbonate, talc, glass fibers, carbon fibers, mica, organically modified clay, kaolin, wollastonite, calcium sulfate, barium sulfate, titanium, silica, carbon black and their suitable combinations. When a layered silicate material is used as filler in the composition, it is optionally pre-blended with functionalized polyolefin. The functionalized polyolefin is at least one compound selected from the group consisting of ethylene-ethylene anhydride-acrylic acid copolymer, ethylene-ethyl acrylate copolymer,ethylene-alkyl acrylate-acrylic acid copolymer, maleic anhydride modified (graft) polyethylenes, ethylene-alkyl (meth) acrylate-(meth)acrylic acid copolymer, ethylene-butyl acrylate copolymer, ethylene-vinyl acetate copolymer, maleic anhydride modified (graft) ethylene-vinyl acetate copolymer and maleic anhydride modified polypropylenes.

Any elastomer or rubbery material in any form can be used as impact modifier for preparing the compositions of the invention. The impact modifier is typically a copolymer or terpolymer, consisting of monomers selected from ethylene, C _3-20 α-olefins and unsaturated comonomers like C _4-2 o dienes, vinyl aromatic compounds, (meth)acrylic compounds and (meth)acrylate compounds. The copolymer or terpolymer is a random, block or graft copolymer. The impact modifier is optionally a blend of (homo/co)polyolefins and rubber, in varied relative amounts of each component. Preferably, impact modifiers based on Ethylene-α-olefin copolymers are used.

The fibrous sub micron structured material used in the composition of the invention is selected from UHMWPE (Ultra High Molecular Weight Polyethylene), cellulosic material or fluoropolymers. Suitable fluoropolymers include homopolymers and copolymers comprising structural units derived from one or more fluorinated alpha-olefin monomers, that is, an alpha- olefin monomer that includes at least one fluorine atom in place of a hydrogen atom. The fluoropolymer can contain structural units derived from two or more fluorinated alpha-olefin, for example tetrafluoroethylene, hexafluoroethylene, and the like. The fluoropolymer can also contain structural units derived from one or more fluorinated alpha-olefin monomers and one or more non-fluorinated monoethylenically unsaturated monomers that are copolymerizable with the fluorinated monomers, for example alpha-monoethylenically unsaturated copolymerizable monomers such as ethylene, propylene, butene, acrylate monomers (e.g., methyl methacrylate and butyl acrylate), vinyl ethers, (e. g., cyclohexyl vinyl ether, ethyl vinyl ether, n-butyl vinyl ether, vinyl esters) and the like. Specific examples of fluoropolymers include polytetrafluoroethylene, polyhexafluoropropylene, polyvinylidene fluoride, polychlorotrifluoroethylene, ethylene tetrafluoroethylene, fluorinated ethylene-propylene, polyvinyl fluoride, and ethylene chlorotrifluoroethylene. Combinations of the foregoing fluoropolymers may also be used.

The articles made from the composition of the invention find applications in telecommunication and automotive industry as well as in the manufacture of home appliances and electrical components. The composition of the invention can be used for manufacturing various articles and products including aircrafts, automotives, trucks, military vehicles and of components such as panels, quarter panels, rocker panels, trim, fenders, doors, deck lids, trunk lids, hoods, bonnets, roofs, bumpers, fascia, grilles, mirror housings, pillar appliques, cladding, body side moldings, wheel covers, hubcaps, door handles, spoilers, window frames, headlamp bezels, headlamps, tail lamps, tail lamp housings, tail lamp bezels, license plate enclosures, roof racks, and running boards; enclosures, housings, panels, parts for outdoor vehicles and devices; enclosures for electrical and telecommunication devices; outdoor furniture and aircraft components. The composition is also suitable for the manufacture of boats and marine equipments, including trim, enclosures, and housings; outboard motor housings; depth finder housings, personal water-craft; jet-skis; pools; spas; hot-tubs; steps; step coverings and for building and construction applications such in glazing and in the manufacture of roofs, windows, floors, decorative window furnishings; treated glass covers for pictures, paintings, posters, display items; wall panels, and doors; counter tops; protected graphics; outdoor and indoor signs; enclosures, housings, panels, parts for automatic teller machines (ATM); computer and computer peripherals; FAX machine; copier; telephone; phone bezels; mobile phone; radio sender; radio receiver; enclosures, housings, panels, and parts for lawn and garden tractors, lawn mowers, and tools, including lawn and garden tools; window and door trim; sports equipment and toys; enclosures, housings, panels, and parts for snowmobiles; recreational vehicle panels and components; playground equipment; shoe laces; articles made from plastic-wood combinations; golf course markers; utility pit covers; light fixtures; lighting appliances; network interface device housings; transformer housings; air conditioner housings; cladding or seating for public transportation; cladding or seating for trains, subways, or buses; meter housings; antenna housings; cladding for satellite dishes; coated helmets and personal protective

equipment; coated synthetic or natural textiles; coated painted articles; coated dyed articles; coated fluorescent articles; coated foam articles; multilayered and bubble guard sheets, pipes; oriented polyolefin composite articles using films, tape, fiber, yarn or sheets; raffia bags or the like.

In the examples and results that follow, the melt flow index is determined by measuring the flow ability of the resin under a load of 2.1kg at 230°C in accordance with the ASTM D 1238 standard test method. The melt flow index expressed in terms of g/10 minutes.

Tensile strength and elongation at break was measured using a polyolefin specimen having a thickness of 2±0.5 mm. Measurement was carried out at a tensile speed of 50 mm/min. by a tensile tester in accordance with the ASTM D638 standard test method.

Flexural modulus of elasticity was determined by plotting a load curve while bending a bar at a speed of 5 mm/min., in accordance with the ASTM D790 standard test method. The flexural modulus of elasticity was obtained from the slope of initial linear section. Izod impact strength was measured by using a 3.2mm-thick injection-molded specimen in accordance with the ASTM D256 standard test method. Parison sag tests were carried out on a blow molding machine. The blow moulding machine is based on a standard extruder barrel and screw assembly to plasticise the polymer. The molten polymer is led through a right angle and through a die to emerge as a hollow (usually circular) pipe section called a parison. In parison sag test method, time is noted for the parison to reach a sufficient length (165cm). This parison is then allowed to fall under gravity. Melt strength will be determined by the time parison it takes to sag from 165 cm. If the melt strength is extremely superior, parison will not sag and freeze at the original distance. These tests were carried out at the extrusion temperature of 175°C at the start of the extruder and 210°C at the end of the extruder. The various polypropylene resins used to prepare

polypropylene compositions according to the procedure laid out in the ensuing examples are identified in table 1.

Table 1 : Different polypropylene resins used to prepare the polypropylene compositions displayed in table 2

The invention is further illustrated by way of the following non limiting examples EXAMPLES

Example-1: Preparation of polyolefϊn resin-clay composition comprising a single polyolefin resin.

Pre-mix containing 83 weight % of polypropylene, 6 weight % of clay, 5 weight % of ethylene- octene copolymer and 6 weight % of malic anhydride - grafted - polypropylene were prepared using an internal mixture at room temperature. This pre-mix was then blended using a twin- screw extruder, extruding the mixture, cutting and drying the extrudate. The temperature profile in extruder ranged between 160 ⁰ C at first barrel to 210 ⁰ C at the last barrel. The specific energy during blending ranged between 0.3 to 1.5 kilo watt hr/kg. The properties of the polypropylene resin compositions are displayed in table 2(against experimental Nos 1,2 and 4)

Example-2: Preparation of polyolefin resin-mica composition comprising a single polyolefin resin.

Pre-mix containing 95 weight % of polypropylene and 5 weight % of mica were prepared using an internal mixture at room temperature. This pre-mix was then blended using a twin-screw extruder, extruding the mixture, cutting and drying the extrudate. The temperature profile in extruder ranged between 160°C at first barrel to 210°C at the last barrel. The specific energy during blending ranged between 0.3 to 1.5 kilo watt hr/kg. The properties of the polypropylene resin compositions are displayed in table 2(against experimental No 3)

Example-3: Preparation of filled polyolefin resin composition comprising a mixture of polyolefin resins, impact modifier, inorganic filler and fibrous submicron structured polymeric material.

Pre-mix containing 7.5 weight % of PPi, 80 weight % of PP ₃ , 6 weight % of clay (or 5 weight % of mica) , 6 weight % of malic anhydride - grafted - polypropylene and 0.5 weight % of polytetraflouroethylene (PTFE) were prepared using an internal mixture at room temperature. This pre-mix was then blended using a twin-screw extruder, extruding the mixture, cutting and drying the extrudate. The temperature profile in extruder ranged between 160°C at first barrel to 210°C at the last barrel. The specific energy during blending ranged between 0.3 to 1.5 kilo watt hr/kg. The properties of the polypropylene resin compositions are displayed in table 2(against experimental Nos 5 to 7)

Table: 2 Comparative study of the properties of the filled polyolefin resin compositions prepared by using polyolefin resin(s) identified in Table 1 and by following the procedure as given in the examples

tDDTM=Dimethyl dihydrogenated taloammonium modified montmorillonite 1^ Micai refers to dry ground mica 1^ Mica ₂ refers to wet ground mica

From table 2 it is evident that the filled polyolefin resin compositions of the invention (displayed against experiments 5 to 7) develop no sag during parison sag test. In comparison the polyolefin resin compositions (displayed against experiments 1 to 4) without the fibrous

submicron structured polymeric material and having only a single polyolefin resin developed sag and possess a low sag time during parison sag test.

Due to the absence of sag formation during thermoforming, the compositions of the invention lead to articles that are more regular and uniform as compared to those prepared from the conventional polyolefin resin compositions. Further the compositions of the invention exhibit good mechanical strength as evidenced by the high values of impact strength, tensile strength as well as flexural modulus (as displayed in table 2). Therefore the filled polyolefin composition of the invention enables to prepare quality articles and products.