Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/18—Manufacture of films or sheets
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
  • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
  • C08J2323/10—Homopolymers or copolymers of propene
  • C08J2323/14—Copolymers of propene
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S428/00—Stock material or miscellaneous articles
  • Y10S428/91—Product with molecular orientation
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31855—Of addition polymer from unsaturated monomers
  • Y10T428/31909—Next to second addition polymer from unsaturated monomers
  • Y10T428/31913—Monoolefin polymer
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31855—Of addition polymer from unsaturated monomers
  • Y10T428/31938—Polymer of monoethylenically unsaturated hydrocarbon

Definitions

• the present invention relates to improved bioriented polypropylene films (BOPP) based on a particular kind of propylene polymer or polymer composition.
• BOPP bioriented polypropylene films
• the films of the invention provide a better balance of elevated temperature draw characteristics and physical properties.
• the oriented films of the invention exhibit improved properties such as stiffness and oxygen barrier.
• the present invention provides bioriented polypropylene films (BOPP) wherein at least one layer comprises a propylene polymer containing at least 0.8% by weight of ethylene and optionally one or more - o -olefins, or a propylene polymer composition containing at least 0.8% by weight of one or more comonomers selected from ethylene and
• BOPP bioriented polypropylene films
• At least one layer is substantially made of the said propylene polymer or propylene polymer composition.
• the said propylene polymer is a random copolymer (I) containing such an amount of comonomer(s) as to have a melting temperature (measured by DSC, i.e. Differential Scanning Calorimetry) of 155 °C or higher.
• a melting temperature measured by DSC, i.e. Differential Scanning Calorimetry
• ethylene i.e. Differential Scanning Calorimetry
• C -C 1 o ⁇ -olefins are present, they are generally within 1 and 4 wt% by weight with respect to the weight of the polymer.
• a propylene polymer composition (II) comprising a first propylene (co)polymer (where the copolymer is a random copolymer) with an ethylene content between 0 and 1.5% by weight, and a second propylene random copolymer with an ethylene content between 0.8 and 5% by weight, the weight ratio of the second copolymer to the first (co)polymer being in the range from about 20:80 to about 80:20, preferably from 30:70 to 70:30, and the difference in the ethylene content between the two being preferably from 1 to 4 percentage units with respect to the weight of the (co)polymer concerned; or another propylene polymer composition (II) comprising a first propylene (co)polymer (where the copolymer is a random copolymer) with a comonomer content between 0 and 2% by weight, and a second propylene random copolymer with a comonomer content between 1.5 and 12% by weight,
• the present invention also relates to the said propylene polymer compositions.
• the Melt Flow Rate (MFR according to ISO 1133, 230 °C, 2.16 Kg load) of the said propylene polymer or polymer composition goes from 1 to 10 g/10 min., more preferably from 1 to 4 g/10 min..
• compositions to be used for the films the present invention are:
• the MFR values of the first propylene (co) polymer in composition (II) and of the second propylene random copolymer in composition (II) can be similar or substantially different. In a particular embodiment of the present invention the MFR value of the first propylene
• (co) polymer is lower than that of the second propylene random copolymer and the difference in the MFR values being preferably greater than 5 g/lOmin...
• Examples of said C 4 -C 1 o ⁇ -olefins are 1-butene, 1-pentene, 1-hexene, 4-methyl-l-pentene and 1-octene. Particularly preferred is 1-butene.
• compositions of the present invention can be prepared by polymerization in one or more polymerization steps. Such polymerization is carried out in the presence of stereospecific
• An essential component of said catalysts is a solid catalyst component comprising a titanium compound having at least one titanium-halogen bond, and an electron-donor compound, both supported on a magnesium halide in- active form.
• Another essential component co-catalyst is an organoaluminum compound, such as an aluminum alkyl compound.
• An external donor is optionally added.
• the catalysts generally used in the process of the invention are capable of producing polypropylene with an Isotacticity Index greater than 90%, preferably greater than 95%.
• Catalysts having the above mentioned characteristics are well known in the patent literature; particularly advantageous are the catalysts described in US patent 4,399,054 and European patent 45977. Other examples can be found in US patent 4,472,524.
• the solid catalyst components used in said catalysts comprise, as electron-donors (internal donors), compounds selected from the group consisting of ethers, ketones, lactones, compounds containing N, P and/or S atoms, and esters of mono- and dicarboxylic acids.
• Particularly suitable electron-donor compounds are 1,3-diethers of formula:
• R 1 and R ⁇ are the same or different and are Cj-C 18 alkyl, C 3 -C 18 cycloalkyl or C 7 - C 18 aryl radicals;
• R m and R are the same or different and are - alkyl radicals; or are the 1,3-diethers in which the carbon atom in position 2 belongs to a cyclic or polycyclic structure made up of 5, 6, or 7 carbon atoms, or of 5-n or 6-n' carbon atoms, and respectively n nitrogen atoms and n' heteroatoms selected from the group consisting of N, O, S and Si, where n is 1 or 2 and n' is 1, 2, or 3, said structure containing two or three unsaturations (cyclopolyenic structure), and optionally being condensed with other cyclic structures, or substituted with one or more substituents selected from the group consisting of linear or branched alkyl radicals; cycloalkyl, aryl, aralkyl, alkaryl radicals and
• dieters are 2-methyl-2-isopropyl-l,3-dimethoxypropane.
• Other suitable electron-donor compounds are phthalic acid esters, such as diisobutyl, dioctyl, diphenyl and benzylbutyl phthalate.
• a MgCl 2 . nROH adduct (in particular in the form of spheroidal particles) wherein n is generally from 1 to 3 and ROH is etha ⁇ ol, butanol or isobutanol, is reacted with an excess of TiCl containing the electron-donor compound.
• the reaction temperature is generally from 80 to 120 °C.
• the solid is then isolated and reacted once more with TiCl 4 , in the presence or absence of the electron-donor compound, after which it is separated and washed with aliquots of a hydrocarbon until all chlorine ions have disappeared.
• the titanium compound, expressed as Ti is generally present in an amount from 0.5 to 10% by weight.
• the quantity of electron-donor compound which remains fixed on the solid catalyst component generally is 5 to 20% by moles with respect to the magnesium dihalide.
• the titanium compounds which can be used for the preparation of the ..solid catalyst component are the halides and the halogen alcoholates of titanium. Titanium tetrachloride is the preferred compound.
• the active form of magnesium halide in the solid catalyst component can be recognized by the fact that in the X-ray spectrum of the catalyst component the maximum intensity reflection appearing in the spectrum of the nonactivated magnesium halide (having a surface area smaller than 3 m 2 /g) is no longer present, but in its place there is a halo with the maximum intensity shifted with respect to the position of the maximum intensity reflection of the nonactivated magnesium dihalide, or- by the fact that the maximum intensity reflection shows a width at half-peak at least 30% greater than the one of the maximum , intensity reflection which appears in the spectrum of the nonactivated magnesium halide.
• the most active forms are those where the above mentioned halo appears in the X-ray spectrum of the solid catalyst component.
• magnesium chloride is preferred.
• the X-ray spectrum of the solid catalyst component shows a halo instead of the reflection which in the spectrum of the nonactivated chloride appears at 2.56 A.
• the Al-alkyl compounds used as co-catalysts comprise the Al-trialkyls, such as Al-triethyl,
• the Al-alkyl compound is generally used in such a quantity that the Al/Ti ratio be from 1 to
• the electron-donor compounds that can be used as external donors include aromatic acid esters such as alkyl benzoates, and in particular silicon compounds containing at least one
• Si-OR bond where R is a hydrocarbon radical.
• silicon compounds are (tert-butyl) 2 Si (OCH 3 ) 2 , (cyclohexyl) (methyl) Si
• the random copolymers are preferably prepared by using catalysts containing a phthalate a inside donor and (cyclopentyl) Si (OCH 3 ) 2 as outside donor, or the said 1,3- diethers as inside donors.
• the polymerization process can be carried out in one or more steps.
• composition (II) it can be carried out in at least two sequential steps, wherein the first propylene (co)polymer and the second propylene random copolymer are prepared in separate subsequent steps, operating in each step, except the first step, in the presence of the polymer formed and the catalyst used in the preceding step.
• the composition (II) contains additional (co)polymers, it becomes necessary to add further polymerization steps to produce them.
• the said polymerization steps can be carried out in separate reactors, or in one or more reactors where gradients of monomer concentrations and polymerization conditions are generated.
• the catalyst is generally added only in the first step, however its activity is such that it is still active for all the subsequent step(s).
• the regulation of the molecular weight is carried out by using known regulators, hydrogen in particular.
• the whole polymerization process which can be continuous or batch, is carried out following known techniques and operating in liquid phase, in the presence or not of inert diluent, or in gas phase, or by mixed liquid-gas techniques.
• Reaction time, pressure and temperature relative to the two steps are not critical, however it is best if the temperature is from 20 to 100 °C.
• the pressure can be atmospheric or higher.
• the catalysts can be pre-contacted with small amounts of olefins (prepolymerization).
• a process for the catalytic polymerization in the gas-phase carried out in at least two interconnected polymerization zones comprising feeding one or more monomers to said polymerization zones in the presence of catalyst under reaction conditions and collecting the polymer product from said polymerization zones, in which process the growing polymer particles flow upward through one of said polymerization zones (riser) under fast fluidisation conditions, leave said riser and .enter another polymerization zone (downcomer) through which they flow downward under the action of gravity, leave said downcomer and are reintroduced into the riser, thus establishing a circulation of polymer between the riser and the downcomer, the process being optionally characterised in that: means are provided which are capable of totally or partially preventing the gas mixture present in the riser from entering the downcomer, and a gas and/or liquid mixture having a composition different from the gas mixture present in the riser is introduced into the downcomer.
• Such polymerization process is illustrated in WO 00/02929.
• the introduction into the downcomer of the said gas and/or liquid mixture having a composition different from the gas mixture present in the riser is effective in preventing the latter mixture from entering the downcomer.
• composition (II) can also be obtained by preparing separately the said (co)polymers by operating with the same catalysts and substantially under the same polymerization conditions as previously explained (except that the said (co)polymers will be prepared in separate polymerization steps) and then mechanically blending said (co)polymers in the molten state.
• Conventional mixing apparatuses like screw extrudres, in particular twin screw extruders, can be used.
• the propylene polymers and propylene polymer compositions used for the films of the present invention can also contain additives commonly employed in the art, such as antioxidants, light stabilizers, heat stabilizers, nucleating agents, colorants and fillers.
• additives commonly employed in the art such as antioxidants, light stabilizers, heat stabilizers, nucleating agents, colorants and fillers.
• nucleating agents brings about a considerable improvement in important physical-mechanical properties, such as Flexural Modulus, Heat Distortion Temperature (HDT), tensile strength at yield and transparency.
• HDT Heat Distortion Temperature
• nucleating agents are the p-tert.-butyl benzoate and the 1,3- and 2,4- dibenzylidenesorbitols.
• the nucleating agents are preferably added in quantities ranging from 0.05 to 2% by weight, more preferably from 0.1 to 1% by weight with respect to the total weight.
• inorganic fillers such as talc, calcium carbonate and mineral fibers, also brings about an improvement to some mechanical properties, such as Flexural Modulus and
• the application sector of the present invention is that of biaxially stretched films, frequently called BOPP (biaxially oriented polypropylene) films.
• BOPP biaxially oriented polypropylene
• the films of the present invention can be prepared with the well known processes for the preparation of BOPPs, for example tentering or bubble blowing.
• the molten polymer materials are forced in continuous through a narrow slit.
• the extruded molten material is pulled away from the slit and cooled, then heated again and stretched both in the Machine Direction (MD), generally using hetaed rolls, and in the Transverse Direction (TD) with a tenter-frame.
• MD Machine Direction
• TD Transverse Direction
• the molten polymer materials are forced through a circular shaped slip to form a tube.
• the fim can be stretched contemporaneously in Machine and
• the film can be finally subjected to an annealing (heat set) treatment.
• the thickness of the films of the present invention is generally below 250 ⁇ m, preferably below 100 ⁇ m. They can be monolayer or multilayer films.
• At least the base layer (also called “support layer”) comprise the said propylene polymer or propylene polymer composition having the features
• the other layer may comprise other kinds of polymers.
• polymers a) isotactic or mainly isotactic propylene homopolymers, and homopolymers or copolymers of ethylene, like HDPE, LDPE, LLDPE; b) crystalline copolymers of propylene with ethylene and/or C -Cto ⁇ -olefins, such as for example 1-butene, 1-hexene, 4-methyl-l-pentene, 1-octene, wherein the total comonomer content ranges from 0.05% to 20% by weight with respect to the weight of the copolymer, or mixtures of said copolymers with isotactic or mainly isotactic propylene homopolymers; c) elastomeric copolymers of ethylene with propylene and/or a C 4 -C 1 o ⁇ -olefin, optionally containing minor quantities (in particular, from 1% to 10% by weight) of a diene, such as butad
• the films of the present invention can undergo a series of subsequent operations, such as: surface embossing, by heating the surface compressing it against the embossing roller; printing, after having made the surface ink sensitive through oxidating (for instance flame) ' or ionizing treatments (for instance corona discharge treatment); coupling with fabric or film, particularly polypropylene, by heating of the surfaces and compression; coextrusion with other polymeric or metallic materials (e.g. aluminum film); plating treatments (depositing a layer of aluminum through evaporation under vacuum, for example); application of an adhesive layer on one of the two faces of the film, thus producing an adhesive film.
• surface embossing by heating the surface compressing it against the embossing roller
• printing after having made the surface ink sensitive through oxidating (for instance flame) ' or ionizing treatments (for instance corona discharge treatment)
• coupling with fabric or film, particularly polypropylene by heating of the surfaces and compression
• the films of the present invention can find many uses, the most important of which is goods and food packaging.
• FT Polydispersity Index
• modulus separation 54.6 x (modulus separation) " wherein the modulus separation (MS) is defined as:
• sample is dissolved in 200 mL of o-xylene, stabilized with 0.1 g/L of Irganox 1010 (pentaerytrityl tetrakis 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate).
• Irganox 1010 penentaerytrityl tetrakis 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate.
• the dissolution temperature is in the range of 125-135°C.
• the resulting solution is poured off into a column packed with glass beads and subsequently cooled down slowly in 16.5 h to 25°C.
• the first fraction is obtained at room temperature eluting with o-xylene.
• the second fraction is collected after having raised the column temperature up to 95 °C.
• the polymer component soluble between 25 and 95°C is collected as a single fraction.
• Example 1 The polymers of Examples 1 and 2 are prepared by polymerizing propylene and ethylene under continuous conditions in a plant comprising a gas phase polymerisation apparatus.
• the catalyst was sent to the gas phase polymerisation apparatus.
• the latter comprised two interconnected cylindrical reactors, riser 1 and downcomer 2.
• Fast fluidisation conditions were established in reactor 1 by recycling gas from the gas-solid separator.
• This stream was propylene fed in the larger upper part of the downcomer.
• the catalyst employed comprised a catalyst component prepared by analogy with Example 5 of EP A 728 769, but using microspheroidal MgCl 2 .1.7 C 2 H 5 OH instead of MgCl 2 .2.1
• Such catalyst component was used with dicyclopentyldimethoxysilane as external donor and with triethylaluminium (TEAL).
• TEAL triethylaluminium
• the weight ratio TEAL/catalyst component was 5; the weight ratio TEAL/external donor was 4.
• Other operative conditions and the characteristics of the produced polymers are indicated in Table 1.
• the polymers of the examples were biaxially stretched at different temperatures on a laboratory TM long stretcher.
• Figure 1 reports the biaxial stress at yield measured at the TM- long film stretcher as a function of the stretching temperature.
• the polymers of Ex. 1 and 2 showed substantially lower values of the biaxial stress at yield and a lower minimum stretching temperature.
• A-B-A structured BOPP film samples with a thickness of 20 ⁇ m were made, with the polymers of these examples.
• the skin layers consisted of the same resin as the core.
• the machine direction stretching ratio was 5 * 1.1 and the transverse direction stretch ratio was between 8.3 and 8.5.
• the min. PHT (pre heating temperature) in TD is a key parameter used to specify the processability.
• the minimum PHT is the lowest stretching temperature in the TD preheating zone which can be reached before breakage without having stretching bands.
• the thickness profile was checked by monitoring the thickness variation of the film (2 ⁇ ) in function of the time. The thickness variation was recorded for all the examples during a period of approximately 30 minutes. Looking at the data reported it is clear that all the polymers representing the invention had a more uniform thickness profile compared to that of the reference material (Comp. 2).
• the film characterisation includes the determination of the optical, mechanical and barrier properties.
• the mechanical properties of the film were measured in MD and TD.
• the work was done on an Instron according to ASTM 882.
• WNTR WNTR Rate
• the polymers of Ex. 3 and 5 had processing temperatures similar to those of Comp. 2, with better mechanical and barrier properties.
• the polymers of Ex. 2 to 4 showed in comparison with Comp. 2 a more uniform thickness profile.
• the polymer of Ex. 6 is prepared under the same conditions as in Ex. 1 and 2.
• the polymers used of the films of the invention compared to conventional polymers of substantially the same MFR, provide a substantially improved balance of elavated temperature drawing behaviour and mechanical properties of oriented film made therefrom.
• the results are reported in Table 6 wherein also the properties of a film obtained by processing, under the same conditions, the polymer of Comp. 1 are reported.

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• Medicinal Chemistry (AREA)
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• Chemical Kinetics & Catalysis (AREA)
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• Polymers & Plastics (AREA)
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• Manufacture Of Macromolecular Shaped Articles (AREA)
• Laminated Bodies (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
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• Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)

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