WO2010010007A1

WO2010010007A1 - Polyolefin sheets

Info

Publication number: WO2010010007A1
Application number: PCT/EP2009/058994
Authority: WO
Inventors: Michael Luetke; Claudio Cavalieri; Michele Grazzi
Original assignee: Basell Poliolefine Italia S.R.L.
Priority date: 2008-07-23
Filing date: 2009-07-14
Publication date: 2010-01-28

Abstract

The present invention relates to a polyolefin sheet having at least one layer comprising: - 70-88 %wt of a component 1) being a propylene based copolymer having a content of α-olefin derived units selected from ethylene and C₄-C₁₀ α-olefins and mixtures thereof comprised between 0.2% by weight and 35% by weight; and - 12-30%wt of a component 2) being a cyclic-olefin copolymer (COC). The polyolefin sheet according to the present invention has improved water-vapor barrier properties and is particularly suitable to be used for pharmaceutical blisters.

Description

POLYOLEFIN SHEETS

The present invention relates to a polyolefin sheet having improved water barrier properties combined with optimal shrinkage properties.

The polyolefin sheet according to the present invention is particularly suitable to be used in pharmaceutical blisters.

In the pharmaceutical field, many attempts have been made to replace polyvinylchloride

(PVC) sheets with polyolefin sheets, in particular with polypropylene sheets, due to economical and health reasons due to the concern associated with the use of chlorine contained in the monomers.

Sheets used in pharmaceuticals mainly have to protect the content from the environment and therefore they must have high water-vapour barrier properties. A further important requirement is related to the shrinkage properties of the sheets, which must combine low shrinkage with short shrinkage time guaranteeing good processability on the packaging machinery. With the term shrinkage time it is intended the minimum time required to reach the plateau in the shrink vs time curve obtained by the shrinkage measurements with specific apparatuses.

It is known in the art that sheets made from a blend of α-olefin polymers and cyclic- olefin copolymers (COC) give better water-vapour barrier properties than PVC and are also better from an environmental point of view.

However, the substitution of PVC in pharmaceutical blisters is slowed down by the difficulty to find a polyolefin sheet combining the above discussed requirements, in particular those relating to the shrinkage properties.

JP 08073618 discloses an opaque polyolefin monolayer sheet made from a resin composition consisting of 80-98 wt.% of a generic polyolefin (A), preferably propylene homopolymer, and 2-20 wt.% of at least one cyclic olefin copolymer (B).

US 2006/0062946 describes multilayer polyolefin sheets composed of at least three layers wherein said layers, identical or different from each other, are composed of a polyolefin

(polyethylene or polypropylene) or a blend between COC and a semicrystalline polyolefin.

Mono or multilayer films comprising a blend between COC and a polyolefin are also disclosed in US 2006/0020084. The main drawback related to the last mentioned two documents consists in the high amount of COC necessary to obtain high water-vapour barrier properties. This high amount of COC provides films or sheets highly expensive.

It is an object of the present invention to select the most convenient α-olefin polymer to be blended with COC in order to optimize the water-barrier effect of the COC and consequently to provide sheets containing low amount of COC while maintaining optimal water-vapour barrier properties.

It is a further object of the invention to provide a polyolefin sheet particularly suitable for pharmaceutical blisters which combines improved water-vapour barrier properties with good shrinkage properties.

Accordingly, it is provided a polyolefin sheet having at least one layer, said layer comprising:

- 70-88 %wt, preferably from 72 to 87 %wt, more preferably from 75 to 85 %wt of a component 1) being a propylene based copolymer having a content of α-olefin derived units selected from ethylene and C4-C10 α-olefins and mixtures thereof comprised between 0.2% wt and 35% wt, preferably between 0.3 % wt and 10 %wt, more preferably between 0.4 and 3%wt; and

- 12-30%wt, preferably from 13 to 28 %wt, more preferably from 15 to 25 %wt of a component 2) being a cyclic-olefin copolymer (COC).

With the term propylene based copolymer it is intended propylene copolymers and/or propylene polymer compositions. In a preferred embodiment of the invention the propylene based copolymer is a propylene copolymer selected from propylene -butene copolymers, propylene -hexene-1 copolymers, propylene-ethylene -butene terpolymers and propylene -butene -hexene-1 terpolymers. The preferred propylene copolymer is a propylene- 1 -butene copolymer.

In another preferred embodiment of the invention the propylene based copolymer is a propylene polymer composition.

With the term propylene polymer compositions it is intended a mechanical or reactor blend comprising at least two propylene polymers or copolymers differing from each other for example in the content of the α-olefϊn comonomer units and/or in the molecular weight distribution. The preferred propylene polymer composition according to the present invention is a reactor blend comprising a propylene homopolymer and a propylene -ethylene copolymer in a weight proportion from 80/20 to 20/80, preferably from 40/60 to 60/40.

Typically, the component 1) has a xylene solubility at 25°C lower than 40%wt, preferably lower than 10 %wt, more preferably lower than 3 %wt, a Polydispersity Index (PI) determined with the rheological method described in the characterization section ranging from 2 to 8, preferably from 3 to 7, more preferably from 3.5 to 6.5 and a melting temperature measured on pellets higher than 140⁰C, preferably higher than 150⁰C, more preferably ranging from 155 to 165°C.

The component 1) used in the present invention can be prepared by polymerisation process in one or more polymerisation steps. Such polymerisation process can be carried out in the presence of Ziegler-Natta catalysts.

Preferably, the polymerization process is carried out in presence of a highly stereospecific heterogeneous Ziegler-Natta catalyst. The Ziegler-Natta catalysts suitable for producing the propylene copolymer or the propylene polymer compositions of the invention comprise a solid catalyst component comprising at least one titanium compound having at least one titanium-halogen bond and at least an electron-donor compound (internal donor), both supported on magnesium chloride. The Ziegler-Natta catalysts systems further comprise an organo-aluminum compound as essential co-catalyst and optionally an external electron-donor compound.

Suitable catalysts systems are described in the European patents EP45977, EP361494, EP728769, EP 1272533 and in the international patent application WO00/63261. Preferably, the solid catalyst component comprises Mg, Ti, halogen and an electron donor selected from esters of phthalic acids disclosed in EP45977 and in particular of either diisobutylphathalate or dihexylphthalate or diethylphthalate and mixtures thereof. According to a preferred method, the solid catalyst component can be prepared by reacting a titanium compound of formula Ti(OR)_n__yXy, where n is the valence of titanium and y is a number between 1 and n, preferably TiCU, with a magnesium chloride deriving from an adduct of formula MgCl₂^pROH, where p is a number between 0.1 and 6, preferably from 2 to 3.5, and R is a hydrocarbon radical having 1-18 carbon atoms. The adduct can be suitably prepared in spherical form by mixing alcohol and magnesium chloride in the presence of an inert hydrocarbon immiscible with the adduct, operating under stirring conditions at the melting temperature of the adduct (100-130 ⁰C). Then, the emulsion is quickly quenched, thereby causing the solidification of the adduct in form of spherical particles. Examples of spherical adducts prepared according to this procedure are described in US 4,399,054 and US 4,469,648. The so obtained adduct can be directly reacted with the Ti compound or it can be previously subjected to thermal controlled dealcoholation (80-130 ⁰C) so as to obtain an adduct in which the number of moles of alcohol is generally lower than 3, preferably between 0.1 and 2.5. The reaction with the Ti compound can be carried out by suspending the adduct (dealcoholated or as such) in cold TiCl₄ (generally 0 ⁰C); the mixture is heated up to 80-130 ⁰C and kept at this temperature for 0.5-2 hours. The treatment with TiCl₄ can be carried out one or more times. The internal donor can be added during the treatment with TiCU and the treatment with the electron donor compound can be repeated one or more times. Generally, the internal donor is used in molar ratio with respect to the MgCb of from 0.01 to 1 preferably from 0.05 to 0.5. The preparation of catalyst components in spherical form is described for example in European patent application EP-A-395083 and in the International patent application WO98/44001. The solid catalyst components obtained according to the above method contain the titanium compound, expressed as Ti, generally in an amount from 0.5 to 10% by weight.

Moreover, they show a surface area (by B.E.T. method) generally between 20 and 500 m /g and preferably between 50 and 400 m²/g, and a total porosity (by B.E.T. method) higher than 0.2 cm /g preferably between 0.2 and 0.6 cm /g. The porosity (Hg method) due to pores with radius up to lO.OOOA generally ranges from 0.3 to 1.5 cm /g, preferably from 0.45 to 1 cm /g.

The o rgano -aluminum compound is preferably an alkyl-Al compound selected from the trialkyl aluminum compounds such as for example triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum. It is also possible to use mixtures of trialkylaluminum's with alkylaluminum halides, alkylaluminum hydrides or alkylaluminum sesquichlorides such as AlEt₂Cl and Al₂Et₃Cl₃.

The Al-alkyl compound is generally used in such a quantity that the Al/Ti ratio be from 1 to 1000. Preferred external electron-donor compounds include silicon compounds, ethers, esters such as ethyl 4-ethoxybenzoate, amines, heterocyclic compounds and particularly 2,2,6,6- tetramethyl piperidine, ketones and the 1,3-diethers. Another class of preferred external donor compounds is that of silicon compounds of formula R₃ ⁵Rb⁶S i(OR⁷)_c, where a and b are integer from 0 to 2, c is an integer from 1 to 3 and the sum (a+b+c) is 4; R⁵, R⁶, and R⁷, are alkyl, cyclicalkyl or aryl radicals with 1-18 carbon atoms optionally containing heteroatoms. Particularly preferred are methylcyclichexyldimethoxysilane, diphenyldimethoxysilane, methyl-t-butyldimethoxysilane, dicyclicpentyldimethoxysilane, 2- ethylpiperidinyl-2-t-butyldimethoxysilane and 1 ,1 ,1 ,trifluoropropyl-2-ethylpiperidinyl- dimethoxysilane and l,l,l,trifluoropropyl-methyl-dimethoxysilane. The external electron donor compound is used in such an amount to give a molar ratio between the organo- aluminum compound and said electron donor compound of from 0.1 to 500. In particular, even if many other combinations of the previously said catalyst components may allow to obtain the component 1), the propylenebased copolymers according to the present invention are preferably prepared by using catalysts containing an ester of phthalic acid as inside donor and (cyclicpentyl)2Si(OCH3)2 as outside donor. The catalysts generally used in the process of the invention are capable of producing polypropylene polymers and/or polypropylene compositions with a value of xylene insolubility at ambient temperature greater than 80%wt, preferably greater than 95%wt and having PI values in the ranges specified above.

As already mentioned said component 1) can be produced by a well-known polymerisation process. Said polymerization process can be carried out in gas phase and/or in liquid phase, in continuous or batch reactors, such as fluidized bed or slurry reactors, or alternatively the gas-phase polymerization process can be carried out in at least two interconnected polymerization zones, as described in the European patent EP782587.

Preferably the propylene copolymers according to the invention are produced by a polymerization process carried out in liquid phase as described in the European Patent application no. EP1901922 and the propylene polymer compositions by a gas phase polymerization process carried out in at least two interconnected polymerization zones as described in WO 02/051912.

As mentioned above, the component 2) according to the present invention is a cyclic- olefin copolymer (COC). Suitable cyclic-olefin copolymers are known per se and are described in EP0407870, EP0485893 and EP0503422.

The cyclic-olefin copolymers used are composed of one or more cyclic -olefins, the cyclic -o Ie fins generally used comprising substituted and unsubstituted cyclic-alkenes and/or polycyclicalkenes, e.g. bi-, tri-, or tetracyclicalkenes. The cyclic-olefin copolymers may also have branching. Products of this type may have a comb structure or star structure. Advantageous materials are copolymers composed of ethylene and/or of an α- polyolefin with one or more cyclic, bicyclic, and/or polycyclic olefins. Particularly advantageous cyclic, bicyclic, and/or polycyclic olefins are those derived from at least one of the cyclic or polycyclic olefins of the following formulae I, II, IF, III, IV, V, VI

II

Where R₁, R₂, R3, R4, R5, R₆, R7 and Rs are identical or different from each other and are a hydrogen atom or a Ci-C2o-hydrocarbon radical, such as a linear or branched C₁-C₈- alkyl radical, Cδ-Cis-aryl radical, or C7-C20 alkylenearyl radical, or a cyclic or acyclic C₂- C₂o-alkenyl radical, or form a saturated, unsaturated, or aromatic ring where identical radicals Ri to Rs have a different meaning in the various formulae I to VI, and where n assumes values from 0 to 5. The COC according to the present invention contain from 0 to 99.9% wt, preferably from 0.1 to 99.9 %wt, based on the total weight of the COC, of polymerized units deriving from one or more acyclic olefins of the formula VII

Where R9, Rio, Rn and R12 are identical or different from each other and are a hydrogen atom, a linear, branched, saturated or unsaturated Ci-C₂o-hydrocarbon radical, such as a Ci-Cs-alkyl radical or a Cβ-Cis-aryl radical.

The COC used may moreover comprise from 0 to 45 %wt, based on the total weight of the COC, of polymerized units which derive from one or more monocyclic olefins of the formula VIII

Ht — Ci-I

\ / VIII

Where m is a number from 2 to 10.

Among the cyclic olefins are also derivatives of these cyclic olefins having polar groups, hydroxy groups, ester groups, alkoxy groups, carboxy groups, cyano groups, amido groups, imido groups, or sylil groups.

For the purposes of the invention, preference is given to cyclic-olefin copolymers which contain polymerized units which derive from polycyclic olefins of the formula VII, in particular olefins having an underlying norbornene structure, e.g. norbornene and tetra cyclicdodecene and, if appropriate, vinylnorbornene or norbornadiene.

Preference is also given to cyclic-olefϊn copolymers having polymerized units derived from acyclic olefins having terminal double bonds, for example α-olefϊns having from 2 to 20 carbon atoms, in particular ethylene or propylene, for example norbornene-ethylene copolymers and tetracyclic-dodecene-ethylene copolymers.

Preferred terpolymers are norbornene-vynilnorbornene-ethylene terpolymers, norbornene-norbornadiene-ethylene terpolymers, tetracyclic-dodecene-vynilnorbornene- ethylene terpolymers or norbornene-dicyclic-pentadiene-ethylene terpolymers.

The component 2) which can be used with particular advantage is a COC composed of ethylene and norbornene as, for example the Topas® grades 8007 and 6013.

The polyolefin sheets according to the present invention can further comprise additives commonly employed in the art, such as antioxidants, light stabilizers, heat stabilizers and any other nucleating agents selected among talc, aromatic carboxylic salts, salts of monocarboxylic or polycarboxylic acids, e.g. sodium benzoate or aluminum tert- butylbenzoate. The preferred nucleating agent is sodium benzoate. The above-mentioned additives are typically added in an amount ranging from 100 to 2000 ppm, preferably from 500 to 1200 ppm. The polyolefin sheets according to the invention can further comprise white oil (highly refined mineral oil) in an amount ranging from 2 to 8 parts by weight.

The components 1) and 2) according to the present invention can be blended using well known techniques in a conventional extruder.

The polyolefin sheets according to the invention can be mono or multi-layer, the layers can be equal or different from each other. Their thickness is typically higher than 150 μm, preferably higher than 200 μm, more preferably ranges from 250 μm to 4 mm and are produced by using the well-known processes for polyolefin sheets production. The pharmaceutical blisters of the present invention are obtained by thermo forming the above disclosed polyolefin sheets.

The polyolefin sheets comprising the components 1) and 2) in the proportions specified above show improved water-vapour barrier properties, not only with respect to the common used PVC sheets but also to the sheets comprising blends of PVC with polyvinylidene chloride (PVDC), which is commonly used to enhance the water-vapour barrier properties of PVC but is unattractive from an economic point of view.

The following methods have been used to determine the properties reported in the description and in the examples:

Xylene-soluble fraction

2.5 g of polymer and 250 mL of o-xylene are introduced in a glass flask equipped with a heater and a magnetical stirrer. The temperature is raised in 30 minutes up to the boiling pint of the solvent. The so obtained solution is then kept under reflux and stirring for further 30 minutes. The closed flask is then kept for 30 minutes in a bath of ice and water and in thermostatic water bath at 25°C for 30 minutes as well. The solid thus obtained is filtered on quick filtering paper and 100 ml of the filtered liquid is poured in a previously weighed aluminium container, which is heated on a heating plate under nitrogen flow, to remove the solvent by evaporation. The container is then kept on an oven at 80⁰C under vacuum until constant weight is obtained. The residue is weighed to determine the percentage of xylene-soluble polymer.

Comonomer content

By IR spectroscopy.

Melt Flow Rate (MFR"L^M): Determined according to ISO 1133 (230°C/2.16 Kg).

Melting temperature: Determined by differential scanning calorimetry (DSC) according to the ISO 11357/3 method.

Polydispersity Index (PI): Determined at a temperature of 200⁰C by using a parallel plates rheometer model RMS-800 marketed by RHEOMETRICS (USA), operating at an oscillation frequency which increases from 0.1 rad/sec to 100 rad/sec. From the crossover modulus one can derive the P.I. by way of the equation:

P.I.= 10⁵/Gc in which Gc is the crossover modulus which is defined as the value (expressed in Pa) at which G'=G" wherein G' is the storage modulus and G" is the loss modulus. Water-vapour transmission rate (WVTR): measured according to ISO 15106 method by using a WDDG Brugger apparatus. The specimens were tested at 23°C and 85% of relative humidity and at 38⁰C and 90 % of relative umidity. The thickness of the tested sheets was 300 μm, the transmission area of the sheets was 80.6 cm². The water-vapour transmission rate is expressed in grams per square meter 24 hours.

The following not-limiting examples are given to better illustrate the present invention.

Example 1 :

A composition was prepared by melt blending in a Werner W&P ZSK 53 extruder a 80 % wt of a propylene polymer composition and 20 % wt of COC Topas® grade 8007. The propylene polymer composition was prepared in analogy with the Example 1 of European Patent Application no. 1377629 with the difference that a lower amount of ethylene was used in order to provide a propylene polymer composition containing 50% wt of propylene homopolymer and 50% wt of a propylene -ethylene copolymer containing 2 % wt of ethylene. The propylene polymer composition had a total content of ethylene of 1 % wt, a xylene soluble fraction of 2.9 % wt, a Melting Temperature of 159.3°C and a Polydispersity Index of 6.10.

Example 2:

A composition is prepared by melt blending in a Werner W&P ZSK 53 extruder 80% wt of a propylene- 1-butene copolymer and 20% of COC Topas® grade 8007. The propylene-1-butene copolymer was prepared according to the Example 1 of the European Patent Application no. EP1901922 with the difference that a lower amount of butene-1 comonomer was used in order to produce a propylene -butene-1 copolymer containing 1% wt of butene-1 and having a xylene solubility of 2.2 %wt and a Melting Temperature of 161 ⁰C.

Comparative example 1 :

A composition is prepared by melt blending 80% wt of a conventional propylene homopolymer and 20 % wt of COC Topas® grade 8007. The compositions of the examples were extruded into 300 μm thickness sheets and then tested. The data relating to the water-vapour barrier properties collected at 23°C and 85% of relative humidity are reported in the Table 1. Those collected at 38°C and 90 % of relative humidity are reported in Table 2.

Table 1

*Sodium benzoate added in an amount of 1000 ppm

Table 2

From the data shown in the Table 1 and 2 it is evident that the sheets according to the invention have improved water-vapour barrier properties than the sheets comprising a blend of conventional propylene homopolymer and COC. The results also show that the use of the component 1) enhances the effect of the COC and accordingly it is possible to obtain optimal water- vapour barrier properties with lower amount of COC in the blend.

Claims

1. A polyolefin sheet having at least one layer, said layer comprising:

- 70-88 %wt of a component 1) being a propylene based copolymer having a content of α-olefin derived units selected from ethylene and C4-C10 α-olefins and mixtures thereof comprised between 0.2% by weight and 35% by weight; and

- 12-30%wt of a component 2) being a cyclic-olefin copolymer (COC).

2. The polyolefin sheet according to claim 1 wherein the component 1) has a xylene solubility at 25°C lower than 40%wt.

3. The polyolefin sheet according to claim 1 wherein the component 1) is a propylene copolymer having a content of α-olefin derived units selected from ethylene and C4-C10 α-olefins and mixtures thereof comprised between 0.2% by weight and 10% by weight.

4. The polyolefin sheet according to claim 3 wherein the component 1) is a propylene-1- butene copolymer.

5. The polyolefin sheet according to claim 1 wherein the component 1) is a propylene polymer composition comprising a propylene homopolymer and a propylene-ethylene copolymer or a propylene-C4-Cio α-olefin copolymer in a weight proportion from 80/20 to 20/80.

6. The polyolefin sheet according to any one of claims 1 to 5 further comprising a nucleating agent.

7. A pharmaceutical blister comprising the polyolefin sheet according to any one of claims 1 to 6.

8. A polyolefin composition comprising: - 70-88 %wt of a component 1) being a propylene based copolymer having a content of α-olefin derived units selected from ethylene and C4-C10 α-olefins and mixtures thereof comprised between 0.2% by weight and 35% by weight; and

- 12-30%wt of a component 2) being a cyclic-olefin copolymer (COC).