AU2002100211A4

AU2002100211A4 - Compositions

Info

Publication number: AU2002100211A4
Application number: AU2002100211A
Authority: AU
Inventors: Ian Jacobs
Original assignee: MARTIN SUCHTA
Current assignee: Suchta Martin
Priority date: 2002-03-19
Filing date: 2002-03-19
Publication date: 2002-04-18
Anticipated expiration: 2010-03-19

Description

PCT/AU98/00255 (hereafter referred to as the"255 patenf) and which is incorporated herein by reference, describes a process and materials for the injection moulding of supple low thickness (<0.99mm) receptacles suitable for the packaging of food, industrial chemical, cosmetic and other fluid products and which provide a number of advantages hitherto unattainable by existing manufacturing methods due to technical constraints. The '255 patent describes a wide variety of polymer types and blends that may be used to manufacture the receptacles described therein, and a method for selecting suitable blends. AU200020674, AU 200072146 and Australian Innovation Patent No. 20001100093, all of which are incorporated by reference, also address the subject matter of the'255 patent, and suggest various improvements for receptacle design and polymer types and blends suitable for the manufacture of the receptacles cited therein.

The present invention relates to improved blends of two-or-more ethylene-based polymers and/or copolymers and, optionally, one or more higher (C 3 -C20) a-olefin polymers and copolymers which are suitable for the production of the subject matter of the'255 patent. The two-or-more ethylene-based polymer blend components consist of an at-least-one ethylenebased polymer (at-least-one polymer) and one or more ethylene-based compatible polymers (compatible polymers).

The at-least-one ethylene-based polymer is a polyethylene or ethylene/a-olefi copolymer or ethylene copolymer copolymerised with copolymers containing functional groups such as acetate, acrylate, methacrylate etc. Preferably the at-least-one ethylene-based polymer is a polyethylene or ethylene/ C 3

-C

20 a-olefin copolymer. More preferably the at-least-one polymer has an MFI (measured as 12) >10, preferably >20 more preferably >30 and most preferably >50. Even more preferably the at-least-one polymer has an MFI >10, preferably more preferably >30 and most preferably >50, and a density <0.913g/cm3, more preferably a density <0.90g/cm3 and most preferably a density <0.89g/cm3. Most preferably the at-least-one polymer has an MFI >10, preferably >20, more preferably >30 and most preferably >50, a density <0.913g/cm3, more preferably a density <0.90g/cm3 and most preferably a density <0.89g/cm3 and is made using a metallocene or similar catalyst capable of producing polymers characterised by super-random distribution of the copolymers between and within the molecular chains of the at-least-one polymer.

The one or more ethylene-based compatible polymer is either a polyethylene or ethylene/ C 3

C

20 a-olefin copolymer or ethylene/a-olefin copolymer copolymerised with copolymers containing functional groups such as acetate, acrylate, methacrylate etc., more preferably a polyethylene or ethylene/ C 3

-C

20 a-olefin copolymer having an MFI (measured as 12) preferably >20, more preferably >30 and most preferably >50. More preferably the one or more ethylene-based compatible polymer is either a polyethylene or ethylene/ C 3

-C

20 a-olefin copolymer having an MFI >10, preferably >20, more preferably >30 and most preferably and a density greater than the density of the at-least-one polymer with which it is blended.

Even more preferably the one or more ethylene-based compatible polymer is either a polyethylene or ethylene/ C 3

-C

20 a-olefin copolymer having an MFI >10, preferably more preferably >30 and most preferably >50, a density greater than the density of the atleast-one polymer with which it is blended and is made using a metallocene (or similar) catalyst and/or a Z-N (or similar) catalyst and/or a high-pressure reactor process. Yet even more preferably the one or more ethylene-based compatible polymer is either a polyethylene or ethylene/ C 3

-C

20 a-olefin copolymer having an MFI >10, preferably >20, more preferably and most preferably >50, a density greater than the density of the at-least-one polymer with which it is blended, made using a Z-N (or similar) catalyst and/or a high-pressure reactor process and is characterised by having a branched structure non-linear) and melting points, crystallinities and MFIs greater than those of the at-least-one polymer in the blend.

Most preferably the one or more ethylene-based compatible polymer consists of at least two polyethylene and/or ethylene/ C 3 -C20 a-olefin copolymers having MFIs >10, preferably more preferably >30 and most preferably >50, densities greater than the density of the atleast-one polymer with which it is blended, are made using a Z-N (or similar) catalyst and/or a high-pressure reactor process and are characterised by having melting points, crystallinities and MFIs greater than that of the at-least-one polymer in the blend.

It has been demonstrated (as for example by Zhou et al, Polymer, Vol 24, p. 2520 (1993) and which is incorporated by reference), that large strain properties of polymer blends, such as toughness, tear, impact and fracture resistance, can be improved by the presence of 'tie moleculeg'in the blend, and that as a generalisation, the greater the proportion of tie molecules in the blend, the greater the improvement in large strain properties. High molecular weight molecules with the highest comonomer content (that is, the highest degree of short chain branching and hence lower density and crystallinity) are responsible for the formation of most of the tie molecules upon crystallization. Thus attempts to maximize properties such as toughness, modulus, impact strength and fracture resistance without sacrificing processability has resulted in the preparation and use of blend compositions made out of two or more polymer components of differing molecular structures. Fracture resistance is defined as the resistance of a polymer and mouldings made therefrom to withstand the deleterious effects of aggressive agents such as the various surfactants, such agents being commonly used to determine fracture resistance. A test for determining the fracture resistance of polymers for use in the manufacture of receptacles as described in the'255 patent is detailed in the'255 patent.

Blends consisting of a relatively high molecular weight relatively low MFI) copolymer in combination with a relatively low molecular weight relatively high MFI) homopolymer or copolymer with higher crystallinity than the high molecular weight polymer have been found to possess good processability and excellent low temperature mechanical properties, and provided they pass the fracture resistance test described in the'255 patent, are particularly suited for the manufacture of receptacles described in the'255 patent. This is particularly the case for blends with an MFI (12) greater than 10, more preferably >20 and most preferably and most preferably >50. While not wishing to be bound by any theory, it is believed that the low MFI copolymers, preferably polyolefin a-olefin copolymers, more preferably polyethylene or polypropylene a-olefin copolymers, even more preferably polyethylene aolefin copolymers and most preferably polyethylene a-olefin copolymers characterised by super-random distribution of the comonomers within and amongst the polymer chains, produce a high number of'tie' molecules within the blend, resulting in improved ESCR and other physical and chemical properties.

The high MFI component(s) of such blends are preferably homo or a-olefin copolymers with a lower copolymer content than the low MFI component(s), and are preferably polyolefin homopolymers or a-olefin copolymers, more preferably polyethylene or polypropylene homopolymers or a-olefin copolymers and most preferably polyethylene a-olefin copolymers not characterised by super-random distribution of comonomers within the polymer chains (eg.

Z-N catalysed polymers and high pressure reactor polymers). When the high MFI component(s) are polyethylenes, they may be ultra-low, low, medium and/or high density polyethylene homo or copolymers.

It is believed that the high MFI component(s) provide the blend with improved processing characteristics relative to the low MFI component, and in addition improve the cycle time of the moulding process by accelerating the crystallisation of the low MFI blend component by acting as nucleating agents, thereby enabling the moulding to be removed from the mould sooner than would otherwise be the case. Also, because the high MFI component(s) preferably has a higher crystallinity than the low MFI component, they usually make removal of the moulding from the tool easier than would otherwise be the case if the low MFI component(s) alone comprised the blend. An additional advantage of the high MFI component(s) is that it raises the MFI of the blend, thereby enabling lower injection pressure than would otherwise be necessary to fill the mould and minimising the chances of core flexing and other problems associated with high injection pressures associated with low MFI blends, and which may be a particular problem with regard to the process of injection moulding receptacles of the type described in the'255 patent.

Some of the advantages of the use of two or more compatible polymers with different melting points for the production of receptacles described in the'255 patent are described in United States Patent 5,082,902, which is incorporated by reference. The 5,082,902 patent teaches that a single component of a blend, preferably a polyolefin component, more preferably a polyethylene component and even more preferably a medium or high density (>0.935 g/cm 3 polyethylene component, may advantageously be substituted with a blend of 2 or more of the same polymer type to achieve a density similar to that of the single substituted component.

The effect of this substitution will often result in the reduction of the crystallization half-time and mold cycle time of polymer blends as well as improved fracture resistance.. While not wishing to be bound to any theory, we believe the higher density polyethylene nucleates the lower density polyethylene, thereby accelerating the rate of crystallization. Since the blend freezes faster and at a higher temperature than a similar density single polymer, the molded article can be removed or ejected from the mold sooner, resulting in a shorter overall molding cycle time. Also, the modified crystal morphology of the molded blend provides improved physical properties total impact energy, fracture resistance, etc.) compared to a molded similar density single polymer. Polymer blends made according to, or incorporating components made according to, the abovementioned patent are suitable for use in the present invention for the production of receptacles as described in the'255 patent.

Not all blends conforming to the broad claims of the invention as outlined above will be suitable for the production of receptacles described in the'255 patent. The suitability of a particular blend for the production of receptacles described in the'255 patent will depend on a number of factors, including the specific moulding conditions used in the production of the production of specific receptacles described in the'255 patent as well as the type of product which will be packed into the specific receptacles. In general, the suitability of a blend for the manufacture of receptacles: 1. Decreases with increasing percentages of compatible polymers relative to the at-leastone polymers 2. Decreases with increasing MFIs of the compatible and/or at-least-one polymers 3. Decreases with increasing crystallinity of the compatible and/or at-least-one polymers 4. Increases with increases in the number of carbon atoms in the copolymer(s) used in the polymerisation of the at-least-one polymer and/or compatible polymer, eg. octene

(C

8 copolymers tend to produce better results than butene (C 4 copolymers and Increases with increasing comonomer percentage in the at-least-one polymer.

The suitability of a particular blend for a particular application will also be influenced by the extent and location of stresses moulded into the receptacle during its manufacture; for example, a particular blend moulded under conditions that will introduce more stresses into the receptacle will have lower fracture resistance than the same blend moulded under conditions that introduce less stresses into the same receptacle. It is therefore important to establish the suitability of a particular blend for the application for which it is intended under the moulding conditions used for the manufacture of a particular receptacle. A method for doing so is detailed in the '255 patent. The suitability of particular blends for the application can therefore be established by experimentation.

Examples of PE blends Bearing in mind the abovementioned factors that will influence the suitability of a particular formulation of at-least-one polymer and one or more compatible polymers for the manufacture of the receptacles described in the'255 patent, formulations of invention can be described as blends of at-least-one polymer and one or more compatible polymers in which the at-least-one polymer constitutes between 10% and 90% of the total polymer content of the formulation, preferably between 20% and 80% of the total polymer content of the formulation, even more preferably between 30% and 70% of the total polymer content of the formulation and most preferably between 40% and 70% of the total polymer content of the formulation In each of the above limitations, the difference between the total polymer content of the formulation and the percentage made up by the at-least-one polymer consists of the one-or-more compatible polymers. For example, if the at-least-one polymer constitutes of the total polymer content of a particular formulation, the compatible polymers will comprise the balance of 45% of the total polymer content.

The following are non-limiting examples of polymers and blends of the present invention.

Examples of at-least-one polymers: 1) Engage 8407-a 30 MFI, 0.87 density ethylene/octene metallocene PE (mPE) (Dupont- Dow) 2) Engage 8401-a 30 MFI, 0.885 density ethylene/octene mPE (Dupont-Dow) 3) Engage 8402-a 30 MFI, 0.91302 density ethylene/octene mPE (Dupont-Dow) 4) Engage 8403-a 30 MFI, 0.91313 density ethylene/octene mPE (Dupont-Dow) Exact 4038-a 125 MFI 0.885 density ethylene/butene mPE (ExxonMobil) Examples of compatible polymers: 1) LDPE 9595-a 55 MFI, 0.923 density PE from Dow 2) HDPE 38152M-a 40 MFI, 0.952 density PE from Dow 3) Dowlex IP-60-a 60 MFI, 0.952 density LLDPE from Dow 4) Dowlex 2503-a 105 MFI, 0.930 density LLDPE from Dow WSM 168-a 60 MFI, 0.918 density LDPE from Qenos 6) WSG 189-a 100 MFI, 0.918 density LDPE from Qenos.

Some non-limiting formulations typical of the present invention, and shown as percentages, are highlighted below. TABLE 1

FORMULATION

PRODUCT F1 F F3 F F F6 ngage 8407 35 ngage 8401 60 6 ngage 8402 3 ngage 8403 xact 4038 20 LDPE 9595 HDPE 38152 Dowlex IP-60 2 Dowlex 2503 50 20 WSM 168 40 WSG 189 20 1 TOTAL 100 10 10 10 10 100 Often it is desirable to improve the fracture resistance and other large strain properties of a particular blend ofpolyolefins as described above. For example, a particular blend of polyethylenes with otherwise good characteristics for the intended application may fail the fracture test. The fracture and other large strain property performance of blends of polyethylenes can frequently be significantly improved by adding an additional-compatiblepolymer (an'additional-compatible-polymef), said polymer not being a polyethylene-based polymer-i.e. it has less than 50% ethylene as a copolymer. The'additional-compatiblepolymef is preferably a C 3 -C20 a-olefin homo or copolymer, more preferably a C 3 or C 4 aolefin homo or copolymer and most preferably a C 3 a-olefin homo or copolymer with an MFI preferably >20, more preferably >30 and most preferably >50. Additional-compatiblepolymers with MFIs in excess of 100, such as Basell's SC973 polypropylene/ethylene copolymer, have been successfully used in the present invention. The additional-compatiblepolymer may form either the continuous or discontinuous phase of the blend, preferably the discontinuous phase, and may be added in sufficient quantity to increase the fracture resistance to the required level. In general, the greater the percentage of additionalcompatible polymer in a blend, the greater the fracture resistance. It is important to note that the suitability of a particular composition inclusive of the additional-compatible-polymer for a particular application will also be influenced by the extent and location of stresses moulded into the receptacle during its manufacture; for example, a particular blend moulded under conditions that will introduce more stresses into the receptacle will have lower fracture resistance than the same blend moulded under conditions that introduce less stresses into the same receptacle. It is therefore important to establish the suitability of a particular blend incorporating the additional-compatible-polymer for the application for which it is intended in conjunction with the moulding conditions used for the manufacture of a particular receptacle.

A method for doing so is detailed in the'255 patent. The suitability of particular blends for the application can therefore be established by experimentation.

The fracture resistance of a particular blend with different levels of'additional-compatiblepolymef and moulded under different conditions can be established by experimentation.

Because the additional-compatible-polymer may confer other desirable properties to the receptacle in addition to improving the fracture resistance of the receptacle, it may also be added in quantities in excess of those required simply to achieve the desired fracture resistance. Again, the level of'additional-compatible-polymer required to achieve a particular property(s) for the receptacle may be determined by experimentation.

The additional-compatible-polymer is advantageously a polypropylene homo and/or copolymer. Suitable polypropylene-based additional-compatible-polymers include isotactic, syndiotactic and atactic polypropylene of various MFIs, densities and crystallinities as would produce desired properties in products moulded by the process of the present invention.

Particularly when blended with at-least-one polymers containing low molecular weight plastomers and/or substantially linear polyethylenes as defined in the'255 patent, a wide variety of polypropylene polymers possessing a very wide range of MFIs densities and crystallinities will produce blends suitable for use in the process of the present invention.

The propylene-based polymers may be propylene homopolymers, block or random copolymers with various a-olefin copolymers, preferably copolymers ofpropylene with ethylene or butene in which the ethylene or butene component constitutes less than 35% of the polymer. It is further advantageous that the propylene-based polymer used as the additional-compatible-polymer has a crystallinity that is greater than the overall crystallinity of the at-least-one polymer/compatible polymer phase of the composition. The propylenebased polymer used as the additional-compatible-polymer may be manufactured using a variety of catalysts, including metallocene catalysts.

The formation of more refined structures of partially atactic and partially isotactic polypropylene which have elastomeric properties have been demonstrated. It is believed that in these components each molecule consists of portions which are isotactic, and therefore crystallisable, while the other portions of the same polypropylene molecule are atactic and therefore amorphous. Examples of these propylene homopolymers containing different levels of isotacticity in different portions of the molecule are described by R. Waymouth in U.S.

Patent 5,594.080, in the article in the Journal American Chemical Society (1995), Vol. 117, page 11586, and in the article in the Journal American Chemical Society (1997), Vol. 119, page 3635, 3. Chien in the journal article in the Journal of 20 the American Chemical Society (1991), Vol. 113, pages 8569-8570; and S. Collins in the journal article in Macromolecules (1995) Vol. 28, pages 3771-3778. All the abovementioned articles and patents are incorporated by reference, and the polymers described therein may be suitable for use as additional-compatible-polymers in the present invention.

In general, it has been established that the higher the flexural modulus of the propylene-based additional-compatible-polymer in the compositions of the present invention, the higher the flexural modulus of the receptacle. Therefore if a softer'feef is required for a particular receptacle, it is advantageous to use a propylene-based polymer that has a lower flexural modulus. This in turn often translates into propylene/ethylene copolymers with higher percentages of ethylene copolymer, i.e. the higher the percentage of ethylene copolymer, the lower the flexural modulus of the composition. The flexural modulus of the additionalcompatible polymer component of a composition of the present invention may be reduced by the addition to it of a polypropylene-compatible low flexural modulus polymer. Examples of such a polymer are Baselrs Catalloy KS-084P and KS-357P these products are believed to be terpolymers of propylene, ethylene and butene. Other such copolymers and/or terpolymers may be used.

In general, the fracture resistance of a particular at-least-one polymer/compatible polymer/additional-compatible-polymer blend increases as the percentage of the ethylene content of the polypropylene-based additional compatible component of the composition increases. Thus for a given percentage of a composition, a propylene/ethylene copolymer will usually impart a higher fracture resistance to a particular at-least-one polymer/compatible polymer /additional-compatible-polymer composition than will the same percentage of propylene homopolymer with the same MFI.

In general, and provided that the propylene-based additional-compatible-polymer largely forms the disperse phase of a composition of the present invention, the MFI of the propylenebased additional-compatible-polymer doesfnt significantly affect the fracture resistance of the composition. Thus one can obtain the benefits of increasing the overall MFI of compositions of the present invention through the incorporation of very high MFI (+100) propylene-based additional-compatible-polymers into compositions of the present invention without causing significant degradation of the composition's fracture resistance. The use of very high MFI propylene-based compatible polymers relative to lower MFI propylene-based compatible polymers of the same type often has the additional effect of enabling the production of finer dispersions smaller particle size) of the propylene-based additional-compatible polymers within at-least-one polymer/compatible polymer blends. This in turn often results in improved large strain properties of the compositions.

The following are non-limiting examples of propylene-based additional-compatible polymers and blends of the present invention.

Examples of Propylene-based additional-compatible polymers: Some non-limiting formulations typical of the present invention, and shown as percentages, are highlighted below. 1. Adflex KS-084P-A 30 MFI low modulus thermoplastic olefin resin based on material produced from Basell's proprietary "Catalloy" process.

2. Adflex" Z104S A 25 MFI very high softness and low modulus thermoplastic olefin resin based on proprietary Basell technology 3. Pro-fax SR832M-A 35 MFI clarified, high melt flow polypropylene random copolymer resin from Basell 4. Pro-fax Ultra SC973-A 100 MFI impact polypropylene reactor copolymer resin from Basell Pro-fax PH920S-A 60 MFI polypropylene homopolymer resin from Basell 6. Metocene" X50081-A 60 MFI metallocene-catalysed polymer from Basell.

Some non-limiting formulations typical of the present invention incorporating a propylenebased additional-compatible polymer, and shown as percentages, are highlighted below. Note that'Fl','F2' etc. refer to the formulations in Table 1 above.

Table 2

FORMULATION

PRODUCT F F F9 FI0 F11 F12 rofax SC973 25 25 dflex KS-084P dflex Z104S 2 ro-fax SR832M ro-fax PH920S etocene X50081 F1 F2 75 1 F3 4 6 otal 10 10 100 100 10 100 Recent developments in the production of highly-branched polyolefins with useful properties for the present invention have enabled the production of star, comb, nanogel and other similar polymers. US 6,355,757 and US 6,084,030, which are incorporated by reference, describe the production of such polymers. The rheological behaviour of these polymers with controlled branching shows surprising and useful features. These polymers frequently have a zero-shear viscosity that is larger than a linear polymer of the same molecular weight. They show a rapid drop in viscosity with shear rate (large degree of shear thinning); and a plateau modulus that is at least two times lower than that of prior art linear and branched polymers. This latter characteristic is especially surprising, since ethylene polymers of various types exhibit essentially the same plateau modulus. This was thought to be intrinsic to the monomer type and not dependent on polymer architecture. The lower plateau modulus means that the comb and similar polymers are much less entangled than the linears, thus giving them such low viscosity for their molecular weight. The utility of these properties of these polymers is that they have a very low viscosity for their molecular weights under melt processing conditions and so will process much more easily than the prior art polymers while exhibiting increased extensional viscosity indicative of increased melt strength.

The copolymers of the above and similar inventions have utility in blends suitable for the production of receptacles of the'255 patent, those blends comprising the branched copolymer of the inventions at from 0.1-99.9 wt. preferably from 0.3-50 wt. more preferably wt. and even more preferably 1.0-5 wt Depending on the properties of a specific highly-branched polymer of the above inventions and the desired properties of a particular formulation, said polymer may be used as a component of the at-least-one polymer or compatible polymer part of the composition of the present invention. Depending on their properties they may also be regarded as additives rather than components of the polymer portion of the present invention.

The blends in accordance with the invention may additionally comprise conventional additives or adjuvants in conventional amounts for conventional purposes. The blends according to the invention exhibit improved processing, largely due to the inclusion of the branched ethylene copolymer according to the invention, and can be more easily processed in conventional equipment. Depending on their nature and method of manufacture, these polymers may constitute part of either the at-least-one polymer or compatible polymer components of the formulations of the invention.

Polymer blends suitable for the present invention may also incorporate a variety of other additives. Examples of additional additives include further polymers, nucleating agents, pigments, dyes, fillers, antioxidants, plasticisers, oils, UV protection, viscosity modifying agents, additives capable of reacting with or absorbing deleterious chemicals such as oxygen and other mould release agents and melt strength modifiers amongst others. These additives may be added to one or more components of the polymer blend or the polymer blend as a whole prior to moulding in order to modify its properties to suit specific applications or to achieve specific effects in the end product. Some or all of the components of the the polymer blend may be prepared by mixing preferably intense mixing so as to produce a very fine dispersion of the individual components within the matrix followed by extrusion and chopping of the resultant polymer blend to be used in the injection moulding process of the present invention. Alternatively, the polymer blend may be provided in its component form and subjected to mixing before and during the melting of the polymer blend in the present process. It may also be prepared by a reactor process, in which the various components of the blends are polymerised sequentially or in parallel in reactor(s)-this process frequently resulting in very fine dispersions that are unable to be obtained by other means.

Because of the high injection pressures and speeds that are frequently required to produce receptacles of the'255 patent, it is advantageous-depending on the particular formulation-to add additives to the blend that improve the flow characteristics of the polymer blends under production conditions. Of particular value are additives that have the effect of reducing the resistance to flow of the polymers of the present invention when they are subjected to injection moulding conditions. There are a number of suitable additives that can be added to formulations to achieve this objective, some of which are detailed below. Because different polymer formulations will respond differently to different viscosity/processing modifiers, those skilled in the art will appreciate that the determination of the most suitable additives, their level of addition and means of incorporation is best carried out by appropriate experimentation.

WO9805711, which is incorporated by reference, highlights that various surfactants can significantly improve the processing characteristics of polymer compositions. Suitable surfactants can be chosen from a non-aromatic sulfonate or sulfate salt wherein a cation of the salt is selected from the group consisting of Na, K, Li, and other alkali cations and quaternary ammonium cations, said surfactant being essentially free of halogens. GB 1,104,662, which is incorporated by reference, suggests addition of alkali and alkaline earth metal salts of alkyl benzene sulfonic acids. GB 1,078,738, which is incorporated by reference, suggests that addition of an "external lubricant" to high molecular weight polyolefins can reduce occurrence of melt fracture. Suggested as external lubricants are salts of monovalent to tetra valent metals, and saturated or unsaturated carboxylic acids containing 10 to 50 carbon atoms.

Sulfonates corresponding to the fatty acid salts are also said to be suitable. However, stearates, palmitates and oleates are exemplified. JP A 59-176339, which is incorporated by reference, suggests the addition of fluorinated compounds including potassium salts of fluoroalkylsulfonic acids for improved processing characteristics. These potassium salts are said to exhibit preferable temperature dependence when compared to other cations such as sodium, calcium, lithium and ammonium. DE 2823507, which is incorporated by reference, suggests improving polymer processing by incorporation of alkali or alkaline earth mono sulfonates from the group alkyl sulfonates, alkenyl sulfonates, alkylaryl sulfonates and succinic acid dialkyl ester sulfonates. Sodium or calcium mono sulfonates are preferred. JP 58-212429 (60-106846), which is incorporated by reference, suggests the addition of magnesium salt or calcium salt of alkylsulfonic acid or alkylbenzenesulfonic acid and at least one substance selected from the group which includes dibenzylidene sorbitol or its nuclear substituted derivative. US 4,829,116, which is incorporated by reference, suggests polyolefin molding compositions that include a fluorine-containing polymer together with a wax. The fluorine containing compounds are preferably copolymers of vinylidene fluoride and hexafluoropropylene or terpolymers of these monomers with tetra fluoroethylene. Among the suitable waxes enumerated are alkylsulfates; or alkyl sulfonates containing straight chain or branched C3 to C26 alkyl radicals and an alkalai metal ion, preferably a sodium ion. Also common amongst processing aids that may be suitable for improving the processing characteristics of polymer blends of the present invention are various flouroelastomers of the type exemplified by the Dupont range of Viton Freeflow processing aids.

Nishida, et al., in Japanese Patent Application Publication Kokai 62-64847, which is incorporated by reference, discloses improved processing of injection molding compositions of ethylene/alpha olefin copolymers having a melt flow rate (MFR) of 0.2-200 g/10 minutes and a density of 0.850-0.945 g/cm 3 which incorporate 0.001-1% by weight of a fluorinated hydrocarbon polymer having a fluorine to carbon ratio of at least 1:2. Chu, in U.S. Pat. No.

4,740,341 which is incorporated by reference, discloses the processing improvements resulting from the addition of small amounts of fluorocarbon polymers and polysiloxanes.

Improved fluoropolymer process aid compositions have been disclosed in for example, U.S.

Pat. Nos.5,464,904; 5,132,368; and 5,587,429, all of which are incorporated by reference.

All of the abovementioned processing aids of various types may be of utility in improving the moulding characteristics of blends of the present invention. The precise utility, most appropriate method of incorporation and level of addition of each processing aid in blends of the present invention may be determined by experimentation.

Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the invention includes all such variations and modifications that fall within its spirit and scope. The invention also includes all of the steps, features, compositions and compounds referred to or indicated in this specification, individually or collectively, and any and all combinations of any two or more of said steps or features.

Claims: 1) Blends for the production of supple low thickness (<0.99mm) receptacles consisting of two-or-more ethylene-based polymers and/or copolymers (the at-least-one polymers), made up of an-at-least-one polymer and a compatible polymer and, optionally, one or more higher (C 3 -C20) a-olefin polymers and copolymers (the additional-compatible polymers).

2) A blend according to claim 1 in which the at-least-one polymer has an MFI preferably >20, more preferably >30 and most preferably >50, a density <0.913g/cm3, more preferably <0.90g/cm3 and most preferably <0.89g/cm3 and is made using a metallocene or similar catalyst capable of producing polymers characterised by super- 11 random distribution of the copolymers between and within the molecular chains of the at-least-one polymer.

3) A blend according to claiml in which the compatible polymer is a polyethylene and/or ethylene/ C 3

-C

20 a-olefin copolymer having an MFI >10, preferably >20, more preferably >30 and most preferably >50, a density greater than the density of the atleast-one polymer with which it is blended, is made using a Z-N (or similar) catalyst and/or a high-pressure reactor process and is characterised by having a melting point, crystallinity and MFI greater than that of the at-least-one polymer in the blend.

4) A blend according to claim 1 in which the additional-compatible polymer is preferably a C 3 -C20 a-olefin homo or copolymer, more preferably a C 3 or C 4 a-olefin homo or copolymer and most preferably a C 3 a-olefin homo or copolymer with an MFI preferably >20, more preferably >30 and most preferably