WO2010104628A1

WO2010104628A1 - Polyolefin masterbatches and films

Info

Publication number: WO2010104628A1
Application number: PCT/US2010/022984
Authority: WO
Inventors: Stijn Van Lierde; Jurgen Schroeyers
Original assignee: Exxonmobil Chemical Patents Inc.
Priority date: 2009-03-12
Filing date: 2010-02-03
Publication date: 2010-09-16

Abstract

Polyolefin compositions can be improved by blending an additive composition into the polyolefin composition. The additive composition comprises a hydrocarbon resin, the resin having a molecular weight lower than that of the polyolefin in which it is blended. The additive composition further comprises a high performance nucleating agent for increasing the crystallization temperature of modified polyolefin composition in comparison to a modified polyolefin composition in which the nucleating agent is absent.

Description

POLYOLEFIN MASTERBATCHES AND FILMS

FIELD OF THE INVENTION

[0001] The present invention relates to a polyolefin masterbatch or film comprising an additive or modifier composition.

BACKGROUND OF THE INVENTION

[0002] Polyolefin based materials, particularly polyethylene and polypropylene, are useful for making a wide variety of products including films due to their combination of stiffness, barrier properties, temperature properties, optical properties and low cost. The products may also be in the form of a masterbatch or concentrate which is subsequently molten, extended with additional components, and formed into desired end-products.

[0003] Modifiers or additives may be added using masterbatches. Terpenes and hydrocarbon resins may be added to improve their properties. Hydrocarbon resins are widely used in oriented polypropylene (OPP) films to improve their barrier properties, degree of crystallinity, and the glass transition temperature. Relatively high levels of hydrocarbon resin are required to cause substantial improvements in barrier properties of the polypropylene film, typically in the range of 5% to 25% by weight. However, adding resin at these levels typically cause the non-oriented films to be brittle. In OPP film, the orientation imparted on the polymer can offset the negative effect of the resin on ductility, so that films with good mechanical properties can be produced despite a high loading of hydrocarbon resin required to impart improvements in barrier properties.

[0004] Ethylene polymers differ from polypropylene polymers with respect to their crystallinity level, glass transition temperature, and amorphous character. The effects of hydrocarbon resins in polyethylene films cannot therefore be predicted based on an analogy with oriented polypropylene films. Additionally, because most polyethylene films possess a relatively low degree of molecular orientation as compared to OPP films, when hydrocarbon resins are incorporated at an effective level, the mechanical properties of the material are often compromised. [0005] EP 0 288 227 discloses a process for the production of oriented films based on polyolefins comprising blending a polyolefin with a rosin or hydrocarbon resin to form a blend under high shear conditions containing from 10 to 90 wt% of the resin or rosin and subsequently blending the concentrate with a polyolefin and extruding the resulting blend to form a film. [0006] The presence of the resin or rosin in the blend affects the mechanical properties of the films. In addition, sealability, shrink, coefficient of friction (measured in accordance with ASTM D 1894) and the optical properties of films produced from this blend are also compromised. [0007] US 2008/0171834 discloses a composition comprising a blend of a polypropylene and a nucleating agent comprising a carboxylic acid salt compound.

[0008] In the production of the above described polyolefm based materials, the crystallization speed of the polyolefm blends limits production of products on high throughput machinery such as films lines and extruders. Also in the production of masterbatches in pellet form, the crystallization speed causes agglomeration of the pellets. This is particularly a problem in polyethylene materials and polyethylene based masterbatches. [0009] The present invention aims to obviate or mitigate the above described problems and/or to provide improvements generally. SUMMARY [0010] There is provided a masterbatch comprising at least 10 to 97 weight % of a polyolefm and 90 to 3 weight % of said additive composition, said additive composition comprising (i) a hydrocarbon resin, the resin having a number average molecular weight lower than that of the polyolefm and (ii) a nucleating agent for increasing the crystallization temperature of the polyolefm in comparison to a blend of said polyolefm and said modifier in which said nucleating agent is absent. The increased crystallization temperature decreases the crystallization time, which in turn allows manufacturing speeds to be increased. [0011] In another embodiment of the invention, there is provided a film comprising at least one layer comprising 70 to 97 weight % of a polyolefm and 30 to 3 weight % of an additive composition, said additive composition comprising a hydrocarbon resin, the resin having a number average molecular weight lower than that of the polyolefm, wherein the composition further comprises a nucleating agent for increasing the crystallization temperature of the layer in comparison to a layer comprising a blend of said polyolefm and said additive in which the nucleating agent is absent. Preferably, the polyolefm comprises a polypropylene polyolefm. The additive composition may further comprise a further polyolefm which is compatible with the polyolefm in the film or masterbatch. The term compatible in this context means that the further polyolefm can be blended with the polyolefm in the film or masterbatch such that the blend has macroscopically uniform physical properties throughout its entire whole volume. Preferably, the further polyolefin corresponds to or is the same as the polyolefin in the film or masterbatch.

[0012] In yet another embodiment of the invention there is provided the use of an additive composition in a film to increase the crystallization temperature of the film in comparison to a film in which the additive is absent, the film comprising at least one layer comprising 70 to 97 weight % of a polyolefin and 30 to 3 weight % of said additive, said additive composition comprising a resin and a nucleating agent, the resin having a number average molecular weight lower than that of the polyolefin. In this way, the peak crystallization temperature may be increased by from at least I⁰C to 2O⁰C, preferably from at least 5⁰C to 1O⁰C. [0013] In a further embodiment of the invention, there is provided a modifier or additive composition for use in a masterbatch, the masterbatch comprising a blend of at least 70 to 97 weight % of a polyethylene and 30 to 3 weight % of said additive composition, said additive composition comprising a hydrocarbon resin, the resin having a number average molecular weight lower than that of the polyethylene, wherein the composition further comprises a nucleating agent for increasing the crystallization temperature of the blend in comparison to said blend in the absence of said nucleating agent. DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] In polyolefin based compositions, limitations in crystallization speed hinder the production of intermediate products and end-products. For example, if crystallization is too slow, agglomeration of pellets can occur.

[0015] To prevent agglomeration, the masterbatches are extruded in strands in cooling water and kept in contact with cooling water for a significant time until crystallization, before they can be cut into pellets. The period of time required for cooling until the crystallization temperature is reached, limits extruder output and hampers the production of masterbatches on a large, commercially attractive scale.

[0016] Masterbatches are generally defined as blends in which additives are dispersed in a carrier material such as a polyolefin and a hydrocarbon resin. In certain embodiments, the masterbatch may be used directly to make a film without diluting with another material. In other embodiments, the masterbatch may be used to make a film by diluting the masterbatch with additional polyolefin.

[0017] In the production of end-products in the form of polyolefin films, sealability, crystallization time, shrink, slip and the optical properties of the film all limit processing speeds. Also, in the production of polyolefin products, the crystallization time and the requirement for films having good optical properties constrain the production speeds. [0018] It would be desirable to improve the properties of polyolefin compositions to arrive at intermediate product and end-products which have improved properties, in particular properties which affect processing speeds.

[0019] Polyolefin compositions can be improved by blending an additive composition into the polyolefin composition. The additive composition comprises a hydrocarbon resin, the resin having a number average molecular weight lower than that of the polyolefin in which it is blended. The additive composition further comprises a nucleating agent for increasing the crystallization temperature of the modified polyolefin composition in comparison to a modified polyolefin composition in which the nucleating agent is absent. [0020] The presence of the nucleating agent in the additive composition increases the crystallization temperature; therefore a smaller quantity of resin is necessary to achieve the desired increased crystallization temperature in comparison to a film layer comprising the polyolefin and the additive in which the nucleating agent is absent. This has the advantage that any compromising effects of the hydrocarbon resin on the mechanical properties of the film are reduced. The presence of the additive composition thus results in a film having an increased crystallization temperature and improved mechanical properties which can be achieved without or with limited mechanical orientation of the film. [0021] The presence of the nucleating agent in the additive in comparison to additive compositions in which no nucleator is present, may result in an increase of the crystallization temperature of the polyolefin by up to 50%, particularly from 10% to 50%, more particularly from 10% to 40%, and even more particularly from 15% to 35%. The crystallization temperature or peak crystallization is the temperature at which the majority of the polymer is crystallized. This temperature is readily recognized as a peak in a differential scanning calorimetry (DSC) plot. Generally, the crystallization temperature is measured in accordance with ASTM D3418.

[0022] Particularly in films and masterbatches comprising polypropylene and polyethylene based polyolefms, the slow crystallization speed reduces the speed at which the product can be extruded as considerable cooling is required to prevent agglomeration of the product. The additive composition is preferably for use in a film but may also be used in a polyolefin masterbatch. [0023] In a preferred embodiment the nucleating agent is present in the film at a concentration ranging from 10 to 3000 ppm, preferably from 100 to 2500 ppm, more preferably from 100 to 2000 ppm, even more preferably from 200 to 1400 ppm. The nucleating agent may also be present at a concentration from 400 to 1000 ppm, particularly from 500 to 800 ppm and most particularly at concentration from 500 to 700 ppm. Generally, the nucleating agent is present in higher concentrations in masterbatches of typically from 50 to 9,000 ppm or from 500 to 5,000 ppm or from 1,000 to 3,000 or from 1,500 to 2,800, or even more and even more typically from 2,000 to 2,500. [0024] In another embodiment of the invention, the crystallization temperature is increased by from at least I⁰C to 2O⁰C, preferably from at least 5⁰C to 1O⁰C, more preferably from at least 6⁰C to 9⁰C. The nucleating agent may induce a peak crystallization temperature of at least 125⁰C for the polyolefm in the film layer.

[0025] The resin may have a softening point of from 80 to 180 ⁰C as measured according to ASTM E28. Preferably, the resin comprises a softening point from 110 to 150 ⁰C, more preferably a softening point from 115 to 150 ⁰C.

[0026] In another embodiment, the additive composition comprises a further polyolefm which is compatible with the polyolefm in the film or masterbatch. Preferably, the further polyolefm is the same as the polyolefm in the film or masterbatch. The additive composition may comprise a polymer of a mono-alpha olefin containing 2 to 4 carbon atoms per molecule. [0027] Preferably, the additive composition is used in a film comprising at least one layer, the layer comprising 70 to 90 weight % polyolefm and 10 to 30 weight % additive composition. All other aspects of the additive composition as described herein also apply to this preferred embodiment. In a separate preferred embodiment, the polyolefm may comprise an isotactic polypropylene having a density of from 0.86 to 0.98 g/cm³ measured at 23 ⁰C according to ASTM D 1505 and a melt flow rate from 1 to 15 g/10 min as determined according to ASTM D1238 at 23O⁰C and 2.16 kg.

[0028] The polyolefm may also comprise polyethylene polymer having a density range from 0.75 to 0.98 g/cm³ measured at 23°C and a melt index as determined according to ASTM D1238 at 190⁰C and 2.16kg of 0.01 to 3000. Hydrocarbon Resin

[0029] Hydrocarbon resins ("HCRs") can serve to enhance or modify the flexural modulus, improve processability, or improve the barrier properties of the film. The hydrocarbon resin is preferably a low number average molecular weight hydrocarbon. Optionally, the resin can be hydrogenated. The resin can have a number average molecular weight less than 5000, preferably less than 2000, most preferably in the range of from 500 to 1000. The resin can be natural or synthetic and can have a softening point in the range of from 60 to 18O⁰C. [0030] Hydrocarbon resins are generally derived from petroleum streams, and may be hydrogenated or non-hydrogenated resins. Useful hydrocarbon resins include, but are not limited to, aliphatic hydrocarbon resins, aromatic modified aliphatic hydrocarbon resins, aliphatic/aromatic resins, polycyclic resins, hydrogenated polycyclic resins, hydrogenated polycyclic aromatic resins, hydrogenated aromatic resins in which a substantial portion of the benzene rings are converted to cyclohexane rings, gum rosins, gum rosin esters, wood rosins, wood rosin esters, tall oil rosins, tall oil rosin esters, polyterpenes, aromatic modified polyterpenes, terpene phenolics, and combinations thereof.

[0031] In one or more embodiments, the hydrocarbon resin contains one or more petroleum resins, terpene resins, styrene resins, and/or cyclopentadiene resins. In one or more embodiments, the hydrocarbon resin can be selected from the group consisting of aliphatic hydrocarbon resins, hydrogenated aliphatic hydrocarbon resins, aliphatic/aromatic hydrocarbon resins, hydrogenated aliphatic aromatic hydrocarbon resins, cycloaliphatic hydrocarbon resins, hydrogenated cycloaliphatic resins, cycloaliphatic/aromatic hydrocarbon resins, hydrogenated cycloaliphatic/aromatic hydrocarbon resins, hydrogenated aromatic hydrocarbon resins, polyterpene resins, terpene-phenol resins, rosins and rosin esters, hydrogenated rosins and rosin esters, and combinations thereof. Preferred aliphatic olefins are C₄ to C20, preferably C₄ to C₇, even more preferably C5 to C₆, linear, branched, or alicyclic olefins or non-conjugated diolefins. Preferred aromatic olefins include one or more of styrene, indene, derivatives of styrene and derivatives of indene. Particularly preferred aromatic olefins include styrene, alpha-methylstyrene, beta-methylstyrene, indene and methylindenes, and vinyl toluenes. In preferred embodiments, the HCR comprises monomers derived from piperylene, isoprene, amylene, cyclics, styrene, indene, or combinations thereof. [0032] Piperylenes are generally a distillate cut or synthetic mixture of C5 diolefins, which include, but are not limited to, cis-l,3-pentadiene, trans-l,3-pentadiene, and mixed 1,3- pentadiene. In general, piperylenes do not include branched C5 diolefins such as isoprene.

[0033] Cyclics are generally a distillate cut or synthetic mixture of C₅ and C₆ cyclic olefins, diolefins, and dimers therefrom. Cyclics include, but are not limited to, cyclopentene, cyclopentadiene ("CPD"), dicyclopentadiene ("DCPD"), cyclohexene, 1,3-cyclohexadiene, and 1,4-cyclohexadiene. The term dicyclopentadiene is defined to include both the endo and exo forms of DCPD. A preferred cyclic is cyclopentadiene. The cyclic may be substituted; preferred substituted cyclics include CPDs and DCPDs substituted with a Cl to C40 linear, branched, or cyclic alkyl group, preferably one or more methyl groups. Methylcyclopentadiene is a preferred substituted cyclopentadiene.

[0034] The hydrocarbon resin may include one or more styrenic components, such as styrene, derivatives of styrene, and substituted styrenes. In general, styrenic components do not include fused-rings, such as indene. The hydrocarbon resin may include one or more indenic components, such as indene and derivatives of indene. In some embodiments, the styrenic component may have a lowering effect on the HCR' s softening point. Other aromatics (especially indenics) may tend to increase the HCR' s softening point. In other embodiments, the hydrocarbon resin may include CPD and DCPD which have a broadening effect on number average molecular weight distribution and tend to increase the HCR' s softening point. [0035] The hydrocarbon resin may be produced by methods generally known in the art for the production of hydrocarbon resins. See for example, the Kirk-Orthmer Encyclopedia of Chemical Technology, 4^th Ed., Vol. 13, pp. 717-744. For example, in some embodiments, the hydrocarbon resin is produced by thermal polymerization, while in other embodiments the hydrocarbon resin may be produced by catalytic polymerization. The polymerization and stripping conditions may be adjusted according to the nature of the feed to obtain the desired resin.

[0036] In one embodiment, the hydrocarbon resin may be prepared by thermal polymerization. For example, the resin may be thermally polymerized prepared from a feed containing cyclopentadiene in a benzene or toluene solvent for 2.0 to 4.0 hours at 22O⁰C to 28O⁰C and about 14 bars pressure, with conditions being adjusted to control the number average molecular weight and softening point of the resin. The feed may further contain alkyl cyclopentadienes, dimers and codimers of cyclopentadiene and methylcyclopentadiene, and other acyclic dienes such as 1,3-piperylene and isoprene. Other copolymerizable unsaturated monomers such as vinyl aromatics including styrene, α-methylstyrene, indene, and vinyl toluene may also be present.

[0037] In another embodiment, the hydrocarbon resin may be catalytically polymerized. A preferred method for production of the resins is combining the feed stream in a polymerization reactor with a Friedel-Crafts or Lewis Acid catalyst at a temperature between 0 ⁰C and 200 ⁰C, preferably between 20 ⁰C and 80 ⁰C. Friedel-Crafts polymerization is generally accomplished by use of known catalysts in a polymerization solvent, and removal of solvent and catalyst by washing and distillation. The polymerization process may be in a batchwise or continuous mode, continuous polymerization may be in a single stage or in multiple stages. The Friedel-Crafts catalysts to be used are generally Lewis Acids such as boron trifluoride (BF3), complexes of boron trifluoride, aluminum trichloride (A1C13), or alkyl-aluminum halides, particularly chloride. The amount of Lewis Acid to be used in the catalyst is in the range of from 0.3 to 3.0 wt%, based upon the weight of the feed blend, preferably 0.5 to 1.0 wt%. The aluminum trichloride catalyst is preferably used as a powder. [0038] In a preferred embodiment the resins may be hydrogenated. Any known process for catalytically hydrogenating hydrocarbon resins may be used to hydrogenate the resin. The hydrogenation of hydrocarbon resins may be carried out via molten or solution based processes by either a batchwise or, more commonly, a continuous process. Catalysts employed for the hydrogenation of hydrocarbon resins are typically supported monometallic and bimetallic catalyst systems. The catalysts which may be used may include Group VIII metals such as nickel, palladium, ruthenium, rhodium, cobalt, and platinum, Group VI metals such as tungsten, chromium, and molybdenum, Group VII metals such as rhenium, manganese, and copper, other catalysts may be based on group 9, 10, or 11 elements. These metals may be used singularly or in combination of two or more metals, in the metallic form or in an activated form and may be used directly or carried on a solid support such as alumina or silica-alumina. The support material is typically comprised of such porous inorganic refractory oxides such as silica, magnesia, silica-magnesia, zirconia, silica-zirconia, titanic silica-titania, alumina, silica-alumina, alumino-silicate, etc. Preferably, the supports are essentially free of crystalline molecular sieve materials. Mixtures of the foregoing oxides are also contemplated, especially when prepared as homogeneously as possible. Preferred supports include alumina, silica, carbon, MgO, TiO2, ZrO2, FeO3, or mixtures thereof. [0039] In one embodiment, the hydrocarbon resin has a ring and ball softening point of 10 ⁰C to 140 ⁰C, preferably 80 ⁰C to 120 ⁰C. In another embodiment, the hydrocarbon resin has a weight average molecular weight (Mw) of 4000 or less, preferably between 500 and 4000, preferably from 500 to 2500. In another embodiment, the hydrocarbon resin has a Mw/Mn of 3 or less, preferably between 1 and 2.4, or more preferably between 1 and 2. [0040] In another embodiment, the HCR can include 50-90 wt% piperylene, 0-5 wt% isoprene, 10-30 wt% amylene, 0-5 wt% cyclics, 0-10 wt% styrenic components, and 0-10 wt% indenic components. The resin may have a melt viscosity at 160 ⁰C of from 375 cPs to 515 cPs, a Mn of 700-900 g/mole, a Mw of 1400-1800 g/mole, a Mz of 3000-5000 g/mole, and a Tg of 45^oC to 50°C.

[0041] In a further embodiment, the hydrocarbon resin can include 60-90 wt% piperylene, 0-5 wt% isoprene, 0-10 wt% amylene, 5-15 wt% cyclics, 5-20 wt% styrenic components, and 0-5 wt% indenic components. The hydrocarbon resin may have a melt viscosity at 16O⁰C of from 375 cPs to 615 cPs, a Mn of 520-650 g/mole, a Mw of 1725-1890 g/mole, a Mz of 6000- 8200 g/mole, and a Tg of 48⁰C to 53⁰C. [0042] In yet another embodiment, the hydrocarbon resin can include dicyclopentadiene and methyl substituted dicyclopentadiene. The hydrocarbon resin can have a softening point of from about 115 to 130 ⁰C, a Tg of about 70 ⁰C, a Mn of about 410 g/mole, a Mw of about 630 g/mole, and a Mz of about 1020 g/mole.

[0043] Hydrocarbon resins that are suitable for use as described herein include Oppera™ PRlOO, 102, 103, 104, 113, 130 (commercially available from ExxonMobil Chemical Company of Baytown, TX); ARKON™ M90, MlOO, Ml 15 andM135 and SUPER ESTER™ rosin esters (commercially available from Arakawa Chemical Company of Japan); SYL V ARES™ phenol modified styrene, methyl styrene resins, styrenated terpene resins, ZONATAC™ terpene-aromatic resins, and terpene phenolic resins (commercially available from Arizona Chemical Company of Jacksonville, FL); SYLVATAC™ and SYLVALITE™ rosin esters (commercially available from Arizona Chemical Company of Jacksonville, FL); NORSOLENE™ aliphatic aromatic resins (commercially available from Cray Valley of France); DERTOPHENE™ terpene phenolic resins (commercially available from DRT Chemical Company of Landes, France); EASTOTAC™ resins, PICCOTAC™ C₅/C₉ resins, REGALITE™ and REGALREZ™ aromatic and REGALITE™ cycloaliphatic/aromatic resins (commercially available from Eastman Chemical Company of Kingsport, TN); WINGTACK™ ET and EXTRA™ (commercially available from Sartomer of Exton, PA); FORAL™, PENTAL YN™, and PERMAL YN™ rosins and rosin esters (commercially available from Hercules, now Eastman Chemical Company of Kingsport, TN); QUINTONE™ acid modified Cs resins, C5/C9 resins, and acid modified C5/C9 resins (commercially available from Nippon Zeon of Japan); and LX™ mixed aromatic/cycloaliphatic resins (commercially available from Neville Chemical Company of Pittsburgh, PA); CLEARON™ hydrogenated terpene aromatic resins (commercially available from Yasuhara of Japan); and PICCOL YTE™ (commercially available from Loos & Dilworth, Inc. of Bristol, PA). Other suitable hydrocarbon resins can be found in U.S. Patent 5,667,902, incorporated herein by reference. The preceding examples are illustrative only and by no means limiting.

[0044] Preferred hydrocarbon resins for use in the films described include saturated alicyclic resins. Such resins, if used, can have a softening point in the range of from 85 to 14O⁰C, or preferably in the range of 100 to 14O⁰C, as measured by the ring and ball technique. Examples of suitable, commercially available saturated alicyclic resins are ARKON-P^® (commercially available from Arakawa Forest Chemical Industries, Ltd., of Japan). Polvolefm [0045] The polyolefins which are described herein may comprise a polyolefm having at least two carbon atoms (C2 or higher). The polyolefm may be produced by polymerization of an olefin monomer.

[0046] In a further embodiment, the number average molecular weight of the polyolefin may also be greater than 10000. This composition is particularly suitable as an additive in high density polyolefin films.

[0047] In a further embodiment, the density of the polyolefin may range between 0.86 g/cm and 0.96 g/cm , more preferably between 0.865 g/cm and 0.95 g/cm . [0048] In one embodiment of the invention, the polyolefin may comprise an ethylene- based polymer backbone. Ethylene polymers may be homopolymers or copolymers of ethylene and higher α-olefms having from 3 to about 40 carbon atoms or from 1 to about 10 carbon atoms, such as, for example, 1-butene, 1-hexene and 1-octene. Generally, the higher - α-olefin content will range from about 1 wt% to 50 wt% or from about 5 wt% to about 30 wt%. [0049] Suitable ethylene polymers for use in the modifier component have a density range of about 0.865 to 0.889 g/cm³ and a peak melting point range of about 49°C to about 85°C. Ethylene polymers are commercially available from ExxonMobil Chemical Company, under the trademark EXACT. Ethylene polymers are also commercially available from Dow Plastics, Dow U.S.A., Midland, Mich., under the trademark ENGAGE, e.g., ENGAGE EG8100 (an ethylene/ 1-octene copolymer), or AFFINITY. [0050] In another embodiment of the invention, the polyolefin may comprise a propylene - based polymer backbone. The propylene -based polymer backbone preferably comprises propylene, one or more C2 or C4-C20 α-olefms, and optionally a non-conjugated diene. Most preferably, the propylene-based polymer backbone comprises propylene, ethylene, and optionally 5-ethylidene-2-norbornene (ENB) or a linear α-omega diene. [0051] As used herein, "polypropylene" refers to a propylene homopolymer, or a copolymer of propylene, or some mixture of propylene homopolymers and copolymers. In certain embodiments the polypropylene may have a level of isotacticity ranging from 50% to 99%. In certain embodiments the polypropylene may have a level of isotacticity ranging from 50% to 99%. In certain embodiments, the polypropylene described herein is predominately crystalline, thus the polypropylene may have a melting point (T_m) greater than 110⁰C or 115°C or 130⁰C or 140⁰C, or 150⁰C, or 160⁰C. The term "crystalline," as used herein, characterizes those polymers which possess high degrees of inter-and intra-molecular order. In certain embodiments the polypropylene has a heat of fusion (Hf) greater than 60 J/g or 70 J/g or 80 J/g or 90 J/g or 95 J/g or 100 J/g, as determined by DSC analysis. In another embodiment, the polypropylene has a heat of fusion from about 80 J/g to about 120 J/g and from about 90 J/g to about 110 J/g. In another embodiment, the propylene-based thermoplastic polymers may be characterized by an Hf that is equal to or greater than 125 J/g, and in other embodiments greater than 140 J/g as measured by DSC. The heat of fusion is dependent on the composition of the polypropylene; the thermal energy for the highest order of polypropylene is estimated at 189 J/g that is, 100% crystallinity is equal to a heat of fusion of 189 J/g. A polypropylene homopolymer will have a higher heat of fusion than a copolymer or blend of homopolymer and copolymer.

[0052] In certain embodiments, the polypropylene has a heptane insoluble amount of greater than about 95%, greater than about 96%, greater than about 97%, greater than about 98%, and greater than about 99%. Heptane insolubles are measured as follows. About 1.3 grams of grounded polypropylene pellets are placed in a thimble and refluxed in heptane for 1.5 hours. The undissolved PP is dried in a vacuum oven at 100⁰C for 40 minutes and weighed. The heptane insoluble measurement is the weight percent of undissolved polypropylene based on the weight of the ground polypropylene pellets. [0053] In other embodiments, the propylene based polymer can also be a heterophasic polypropylene having an isotactic PP phase and a dispersed rubber phase. In these cases, the melting point of the polypropylene will be between 165°C and 120⁰C.

[0054] The first polypropylene preferably has a melt flow rate of less than about 20, more preferably less than about 15, more preferably less than about 10, more preferably less than about 9, more preferably less than about 8, more preferably less than about 7, more preferably less than about 6, and more preferably less than about 5.

[0055] In certain embodiments, the polypropylene(s) are isotactic. Isotacticity of the propylene sequences in the polypropylenes can be achieved by polymerization with the choice of a desirable catalyst composition. The isotacticity of the polypropylenes as measured by ¹³C NMR, and expressed as meso diad content is greater than 90% (meso diads [m] > 0.90) or 95% or 97% or 98% in certain embodiments, determined as in US 4,950,720 by ¹³C NMR. Expressed another way, the isotacticity of the polypropylenes as measured by ¹³C NMR, and expressed as pentad content, is greater than 93% or 95% or 97% in certain embodiments. [0056] The polypropylene can vary widely in composition. For example, substantially isotactic polypropylene homopolymer or propylene copolymer containing equal to or less than 10 wt% of other monomer, that is, at least 90 wt% by weight propylene can be used. Further, the polypropylene can be present in the form of a graft or block copolymer, in which the blocks of polypropylene have substantially the same stereoregularity as the propylene-α- olefin copolymer so long as the graft or block copolymer has a sharp melting point above 110⁰C or 115°C or 130⁰C, characteristic of the stereoregular propylene sequences. The polypropylene may be a combination of homopolypropylene, and/or random, and/or block copolymers as described herein. When the polypropylene is a random copolymer, the percentage of the α-olefϊn derived units in the copolymer is, in general, up to 5% by weight of the polypropylene, 0.5% to 5% by weight in another embodiment, and 1% to 4% by weight in yet another embodiment. The preferred comonomer derived from ethylene or α-olefms containing 4 to 12 carbon atoms. One, two or more comonomers can be copolymerized with propylene. Exemplary α-olefms may be selected from the group consisting of ethylene; 1- butene; 1 -pentene-2-methyl- 1 -pentene-3 -methyl- 1 -butene; 1 -hexene-3 -methyl- 1 -pentene-4- methyl-l-pentene-3,3-dimethyl-l-butene; 1-heptene; 1-hexene; 1 -methyl- 1-hexene; dimethyl- 1-pentene; trimethyl-1 -butene; ethyl- 1-pentene; 1-octene; methyl- 1-pentene; dimethyl- 1- hexene; trimethyl- 1-pentene; ethyl- 1-hexene; 1-methylethyl- 1-pentene; 1 -diethyl- 1 -butene; propyl- 1-pentene; 1-decene; methyl- 1-nonene; 1-nonene; dimethyl- 1-octene; trimethyl- 1- heptene; ethyl- 1-octene; methylethyl-1 -butene; diethyl- 1-hexene; 1-dodecene and 1- hexadodecene.

[0057] The weight average molecular weight (Mw) of the polypropylene can be between 50,000 to 3,000,000 g/mol, from 90,000 to 500,000 g/mol in another embodiment or from 200,000 g/mol to 400,000 g/mol in another embodiment. The polypropylene can have a molecular weight distribution (MWD, Mw/Mn) within the range from 1.5 to 2.5 or 1.5 to 3.0 or 1.5 to 4.0 or 1.5 to 5.0 or 1.5 to 20.0 in certain embodiments. In one embodiment, the polypropylene has a MWD of greater than about 4.0. The polypropylene can have an MFR (2.16kg/ 23O⁰C) within the range from 10 to 15 or 10 to 18 or 10 to 30 or 10 to 35 or 10 to 40 or 10 to 50 dg/min in certain embodiments. In another embodiment, the MFR is from 1 to 10 dg/min or from 1 to 5 dg/min or from 2 to 4 dg/min.

[0058] There is no particular limitation on the method for preparing the polypropylenes described herein. However, for example, the polymer is a propylene homopolymer obtained by homopolymerization of propylene in a single stage or multiple stage reactor. Copolymers may be obtained by copolymerizing propylene and ethylene or an α-olefm having from 4 to 20 carbon atoms in a single stage or multiple stage reactor. Polymerization methods include, but are not limited to, high pressure, slurry, gas, bulk, or solution phase, or a combination thereof, using any suitable catalyst such as traditional Ziegler-Natta catalyst or a single-site, metallocene catalyst system, or combinations thereof including bimetallic (i.e, Ziegler-Natta and metallocene) supported catalyst systems.

[0059] Exemplary commercial polypropylenes include the family of Achieve™ polymers (ExxonMobil Chemical Company, Baytown, TX). The Achieve polymers are produced based on metallocene catalyst system. In certain embodiments, the metallocene catalyst system produces a narrow molecular weight distribution polymer. The MWD is typically in the range of 1.5 to 2.5. However, a broader MWD polymer may be produced in a process with multiple reactors. Different MW polymers can be produced in each reactor to broaden the MWD. Achieve polymer such as Achieve 3854, a homopolymer having an MFR of 24 dg/min can be used as a blend component described herein. Alternatively, an Achieve polymer such as Achieve 6936G1, a 1500 dg/min MFR homopolymer, can be used as a blend component described herein. Other polypropylene random copolymer and impact copolymer may also be used. The choice of polypropylene MFR can be used as means of adjusting the final MFR of the blend, especially the facing layer composition. Any of the polypropylenes described herein can be modified by controlled rheology to improve spinning performance as is known in the art. [0060] Although the "polypropylene" component of the fiber and fabric compositions is sometimes discussed as a single polymer, also contemplated by the term are blends of two or more different polypropylenes having the properties within the ranges described herein. In certain embodiments, the polypropylene may be present in the fabric layer (or fabric layer composition) within the range from 75 or 70 to 80 or 90 or 95 or 99 or 99.9 wt%, by weight of the fabric layer/composition.

[0061] In another embodiment, the propylene-based polymer backbone has a DSC melting point of about 120⁰C or less, preferably about 115°C or less, more preferably about 105⁰C or less, more preferably about 100⁰C or less, more preferably 90⁰C or less, more preferably about 85°C or less, and most preferably about 75°C or less, and a heat of fusion of about 75 J/g or less, preferably about 70 J/g or less, more preferably about 65 J/g or less, and most preferably about 60 J/g or less. The propylene-based polymer backbone is preferably a propylene-ethylene copolymer, preferably with a propylene content of at least about 75 wt% and ethylene content in the range of about 4 wt% to about 25 wt%, more preferably about 5 to about 24 wt%, more preferably about 7 to about 20 wt%, more preferably about 7 to about 16 wt%, and most preferably about 8 to about 15 wt%. In further embodiments, the propylene- based polymer backbone preferably comprises a suitable grade of VISTAMAXX™ elastomer (ExxonMobil Chemical Company, Baytown, TX, USA), a suitable grade of VERSIFY™ polymer (The Dow Chemical Company, Midland, Michigan, USA), a suitable grade of Tafmer™ XM or a suitable grade of Notio™ (The Mitsui Company of Japan), or a suitable grade of Softel™ (Basell Company of the Netherlands). Nucleating Agent [0062] In a further embodiment, the nucleating agent may be selected from the group comprising sodium benzoate, talc, glycerol alkoxide salts, cyclic carboxylic acid salts, bicyclic carboxylic acid salts, glycerolates, and hexahydrophtalic acid salts. Nucleating agents include Hyperform, such as HPN-68, HPN-68L, HPN-20, HPN-20E, Millad additives (e.g., Millad 3988) (Milliken Chemicals, Spartanburg, SC), and organophosphates like NA-I l and NA-21 (Amfine Chemicals, Allendale, NJ). In another embodiment, the nucleating agent is at least one bicyclic carboxylic acid salt. In another embodiment, the nucleating agent is bicycloheptane dicarboxylic acid, disodium salt such as bicycle [2.2.1] heptene dicarboxylate. In still another embodiment, the nucleating agent is a blend of components comprising bicyclo [2.2.1] heptane dicarboxylic acid, disodium salt, 13-docosenamide, and amorphous silicon dioxide. In still another embodiment, the nucleating agent is cyclohexanedicarboxylic acid, calcium salt or a blend of cyclohexanedicarboxylic acid, calcium salt and zinc stearate. [0063] Furthermore, bicyclic compounds, such as bicyclic dicarboxylic acid and salts, have been taught as polyolefm nucleating agents as well within Patent Cooperation Treaty Application WO 98/29494, 98/29494, and 98/29496, all assigned to Minnesota Mining and Manufacturing. The best working examples of this technology are embodied in disodium bicylo [2.2.1] heptene dicarboxylate and camphanic acid.

[0064] The additive composition is prepared by dispersing the nucleating agent or nucleator in the hydrocarbon resin. In a preferred embodiment, the nucleating agent is dispersed in a blend of a polyolefϊn and the hydrocarbon resin. The nucleating agent may be dispersed under shear in a mixing vessel. The mixing vessel may be an extruder. Other suitable mixing apparatus known to the skilled person are also suitable for adding the nucleating agent under shear to the dispersion. EXAMPLES [0065] The invention will now be illustrated by way of example only with reference to the accompanying Examples.

[0066] The packaging industry is always keen to increase line speeds. With conventional resin modified biaxially oriented polypropylene packaging films, particularly in thinner films which are typically used to wrap packs (for example tobacco packs), line speeds are not limited by the capabilities of the machinery but they are limited by the desired end properties of the packaging film. With an increase in line speed, the combination of the sealability of the film, and the shrink, slip and optical properties of the film are all compromised. [0067] In most machine set-ups, the temperature during shrinking in combination with the heat energy which is introduced during the sealing, are adequate to shrink the film around the pack and to seal the edges. When the line speed of the machine is increased, the temperature of the sealing bars of the machine must also be increased. If the crystallization temperature of the film is too low and the crystallization speed of the film is too slow, this causes deformation of the seals due to friction between the packs and between the pack and the machine. [0068] The composition which is disclosed herein allows line speeds to be increased without compromising the properties of the film. This will be illustrated with reference to the below Examples.

[0069] In the following examples, all parts, proportions, and percentages are by weight unless otherwise indicated. Unless specified otherwise, ppm is based on weight relative to the total weight of the composition. All listed products are supplied by ExxonMobil Corporation. The following materials were used: Oppera™ PA 609 - Masterbatch. Blend of 50% polypropylene A (melt flow rate 2.9 @

230 ⁰C) and 50% dicyclopentadiene (DCPD) based hydrocarbon resin having a softening point of 140 ⁰C;

EMPA™85 IN - Masterbatch. Blend of 50% Polyethylene I and 50% DCPD-based hydrocarbon resin having a softening point of 125 ⁰C;

EMPA™901 - Masterbatch. Blend of 50% polyethylene II (melt index 0.15) and

50% DCPD-based hydrocarbon resin having a softening point of 140 0C; and

Polypropylene A - Polypropylene polymer, melt flow rate 2.9 as measured following ASTM D-1238 @ 230⁰C with 2.16kg weight;

Polyethylene I - Polyethylene polymer, melt index (MI) 3.0 (as measured following

ASTM D-1238); density 0.882 g/cm³;

DCPD-based resin - resin derived from dicyclopentadiene (DCPD); and

Polyethylene II - High density polyethylene (HPDE) with a melt index (MI) of 0.15 having a density of 0.952 g/cm³.

Example 1

[0070] The following compositions were prepared: PEl (comparative) - EMPA 85 IN [masterbatch] (without nucleating agent);

PE2 - EMPA 85 IN [masterbatch] nucleated with 600 ppm of a bicyclic carboxylic acid salt nucleator (Miliken HPN-68);

PE3 - EMPA 85 IN [masterbatch] nucleated with 2000 ppm of a bicyclic carboxylic acid salt nucleator (Miliken HPN-68); PE4 - EMPA 85 IN [masterbatch] nucleated with 600 ppm of a bicyclic carboxylic acid salt nucleator (Miliken HPN-20e); and

PE5 - EMPA 85 IN [masterbatch] nucleated with 2000 ppm of a bicyclic carboxylic acid salt nucleator (Miliken HPN -2Oe).

Differential scanning calorimetry (DSC) analysis in accordance with ASTM D3418 was conducted to measure the melting point T_m, crystallization temperature T_c and the relative rate of crystallization. The relative rate of crystallization is the ratio of the normalized heat flow for the (peak) crystallization temperature and the base line measurement of the normalized heat flow before crystallization of the Sample. The results are set out in the below Table 1.

Example 2 [0071] In this Example, the following compositions were prepared:

PE6 (comparative) - EMPA 901 [masterbatch] (without nucleating agent);

PE7 EMPA 901 [masterbatch] nucleated with 2000 ppm of a bicyclic carboxylic acid salt nucleator (Miliken HPN-68); and

PE8 EMPA 901 [masterbatch] nucleated with 2000 ppm of a bicyclic carboxylic acid salt nucleator (Miliken HPN -2Oe). Differential scanning calorimetry (DSC) analysis as set out in detail above was conducted to measure the melting point T_m, crystallization temperature T_c and the relative rate of crystallization. The results are set out in the below Table 2.

Example 3

[0072] In the following Example, the following film compositions were prepared;

PPl (comparative) - A blend of polypropylene A with 30% of Oppera TM PA609 [masterbatch] (without nucleating agent);

PP2 A blend of polypropylene A with 30% of Oppera PA 609 [masterbatch] nucleated with 600 ppm of sodium benzoate (NaBz) nucleator based on the masterbatch;

PP2 A blend of polypropylene A with 30% of Oppera PA609 [masterbatch] nucleated with 600 ppm of ADK Palmarole NA-21 (trademark) nucleator based on the masterbatch; and

PP4 A blend of polypropylene A with 30% of Oppera PA 609 [masterbatch] nucleated with 600 ppm of a bicyclic carboxylic acid salt nucleator based on the masterbatch (Miliken HPN-68).

Differential scanning calorimetry (DSC) analysis (equipment etc.) as set out in detail above was conducted to measure the melting point, crystallization temperature and the relative rate of crystallization. The results are set out in the below Table 3.

[0073] These Examples provide evidence that the crystallization temperatures and crystallization rates may be improved in polyolefin compositions by the presence of an additive composition comprising a nucleator in combination with a hydrocarbon resin.

[0074] There is thus provided an additive or modifier composition for use in a polyolefm based compositions, the additive composition comprising a resin, the resin having a molecular weight lower than that of the polyolefin, wherein the composition further comprises a nucleating agent for increasing the crystallization temperature of the polyolefin based composition in comparison to a polyolefin based composition comprising the modifier in the absence of the nucleating agent. In this way, the crystallization temperature and crystallization rate of the polyolefin based composition are increased.

Claims

1. A masterbatch composition for use in a film, the masterbatch comprising at least 10 to 97 weight % of a polyolefin and 90 to 3 weight % of an additive composition, said additive composition comprising:

(i) a hydrocarbon resin, the resin having a molecular weight lower than that of the polyolefin, and

(ii) a nucleating agent for increasing the crystallization temperature of the polyolefin in comparison to a blend of said polyolefin and said additive composition in which said nucleating agent is absent.

2. The masterbatch composition of claim 1 , wherein the crystallization temperature of the film is increased by from at least I⁰C to 4O⁰C, preferably from at least I⁰C to 20⁰C, and more preferably from 5⁰C to 1O⁰C.

3. The masterbatch composition of any of the previous claims, wherein the resin has a softening point of from 100 to 18O⁰C as measured according to ASTM E28.

4. The masterbatch composition of any one of claims 2 to 3, wherein the claim comprises 70 to 90 weight % polyolefin and 10 to 30 weight % resin.

5. The masterbatch composition of any of the preceding claims, wherein the additive composition comprises a further polyolefin, said further polyolefin being compatible with the polyolefin in the film or masterbatch.

6. The masterbatch composition of claim 5, wherein the further polyolefin corresponds to the polyolefin in the film or masterbatch.

7. The masterbatch composition of any of the preceding claims, wherein the polyolefin comprises a polymer of a mono-alpha olefin containing 2 to 8 carbon atoms per monomer, preferably 3 carbon atoms per monomer.

8. The masterbatch composition of any of the preceding claims, wherein the polyolefin comprises an isotactic polypropylene having a density of from 0.86 to 0.98 g/cm³ measured at 23 ⁰C according to ASTM D 1505 and a melt flow index of from 1 to 15 g/10 min as determined according to ASTM D1238 at 23O⁰C and 2.16 kg.

9. The masterbatch composition of any of the preceding claims, wherein the resin comprises a hydrogenated petroleum resin.

10. The masterbatch composition of any one of the preceding claims, wherein the nucleating agent is present in a concentration of from 2,000 to 2,500 ppm.

11. The masterbatch composition of any of the preceding claims, wherein the nucleating agent increases in the crystallization temperature by from 10 to 50%, more particularly from 15 to 35% in comparison to a blend of said polyolefm and said additive composition in which said nucleating agent is absent.

12. The masterbatch composition of any of the preceding claims, wherein the nucleating agent is selected from the group comprising bicyclic carboxylic acid salts, and hexahydrophtalic acid salts.

13. The masterbatch composition of any of the preceding claims, wherein the nucleating agent is bicycloheptane dicarboxylic acid, disodium salt.

14. A biaxially oriented film comprising at least one layer comprising 70 to 97 weight % of a polyolefm and 30 to 3 weight % of an additive composition, said additive composition comprising a hydrocarbon resin, the resin having a molecular weight lower than that of the polyolefm, wherein the additive composition further comprises a nucleating agent for increasing the crystallization temperature of the layer in comparison to a layer comprising said polyolefm and said modifier in the absence of said nucleating agent.

15. The film of claim 14 wherein said nucleating agent is present at a concentration of from 100 to 2500 ppm.

16. The film of claim 14 wherein said nucleating agent is present at a concentration of from 400 to 1000 ppm.

17. A method for increasing the crystallization temperature of an oriented polyolefm film comprising the step of mixing a blend comprising a polyolefin and an additive wherein the blend comprises 70 to 97 wt% of a polyolefin and 30 to 3 wt% of said additive composition, said additive composition comprising a hydrocarbon resin and a nucleating agent, the resin having a molecular weight lower than that of the polyolefin.

18. A process for the production of oriented polypropylene films comprising:

(i) blending a polypropylene and an additive composition to form a masterbatch containing from 10 to 97 wt % of the polypropylene wherein the polypropylene in the masterbatch has:

1. a melt flow rate of from 1 to 5 dg.min; 2. a melting point greater than 150⁰C;

3. a heat of fusion of greater than 90 Joules/gram; and

4. a polydispersity greater than about 4; and wherein the additive composition in the masterbatch comprises:

1. a hydrocarbon resin comprising a hydrogenated polycylic resin, and

2. a nucleating agent comprising a bicyclic carboxylic acid salt at a concentration of 50 to 9,000 ppm.

(ii) blending the masterbatch with additional polypropylene; and

(iii) extruding the resultant blend to form a film.