Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
  • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
  • B32B27/306—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising vinyl acetate or vinyl alcohol (co)polymers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
  • B32B7/04—Interconnection of layers
  • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2250/00—Layers arrangement
  • B32B2250/24—All layers being polymeric
  • B32B2250/246—All polymers belonging to those covered by groups B32B27/32 and B32B27/30
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
  • B32B2307/546—Flexural strength; Flexion stiffness
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2323/00—Polyalkenes
  • B32B2323/04—Polyethylene
  • B32B2323/043—HDPE, i.e. high density polyethylene
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2323/00—Polyalkenes
  • B32B2323/04—Polyethylene
  • B32B2323/046—LDPE, i.e. low density polyethylene
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2323/00—Polyalkenes
  • B32B2323/10—Polypropylene
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2329/00—Polyvinylalcohols, polyvinylethers, polyvinylaldehydes, polyvinylketones or polyvinylketals
  • B32B2329/04—Polyvinylalcohol

Definitions

• This invention relates to a novel multi-layered composite comprising a plurality of polymer layers and having good flexibility and high fiex-crack resistance.
• Composites comprising several polymers are well known.
• tie layers having adhesive properties between the virgin polymers.
• Such tie layers may comprise grafting of maleic anhydride or acrylate ester polymers on to one surface of a polyolefin film and then applying thereon a further layer of a virgin polymer or a metallic layer in order to produce the desired composite.
• Such composites have found uses in various industries including the production of protective garments, canning of food products, the so called 'bag-in-box' containers and barrier films for oxygen, gasoline or other industries where toxic or hazardous emissions have to be contained.
• Such composites have also been used to produce a flexible vapour containment liner (hereafter "VCL”) for a fuel tank system in order to minimise the risk of accidental ignition and to control emissions from such tanks whether eg they be used in automotive vehicles, aircraft or in oil tankers.
• VCL flexible vapour containment liner
• Most of these prior art laminates have been made from a layer of a hydrolysate of an ethylene-vinyl acetate copolymer, ie ethylene-vinyl alcohol copolymer (hereafter “EVOH”), sandwiched between layers of a polyolefin which may be polyethylene or polypropylene, optionally using a tie layer in between the polyolefin and the EVOH layers to improve adhesion thereof.
• EVOH ethylene-vinyl alcohol copolymer
• the primary problem has been their relatively low flex-crack resistance which causes them to lose their performance integrity. This loss of performance is particularly undesirable if the composite is used for storing liquids, especially consumable
• the present invention is a multi-layer composite comprising at least one sequence of layers comprising a heterophasic polypropylene (co)polymer layer/tie-layer/EVOH/tie-layer/polyolefin layer characterised in that the heterophasic polypropylene (co)polymer layer comprises a homopolymer of propylene or a co-polymer of propylene with ethylene and/or an alpha-olefin.
• composite as used herein and throughout the specification is meant a product prepared either by lamination of several layers and/or by coextrusion of a number of components in order to give the desired product.
• various components are referred to herein as “layers” for convenience, whether or not they have been laminated.
• EVOH signifies an ethylene-vinyl alcohol copolymer which may be derived by the hydrolysis of an ethylene-vinyl acetate copolymer.
• the heterophasic polypropylene (co)poiymer layer is suitably that derived by the copolymerisation of propylene with ethylene and/or an alpha olefin which has 2-8 carbon atoms such as eg (iso)butene, and may optionally contain other monomers such as dienes, eg butadiene, 1 ,4-hexadiene, 1 ,5-hexadiene and a mixture of ethylidene norbornene and diene monomers.
• Such heterophasic polypropylenes are suitably produced by an extended Spheripol® process of Himont which is the so called "catalloy” process and involves the use of a multi-component catalyst system to produce engineering resins and elastomers.
• the polymers are believed to behave as a polyolefin 'alloy' and hence the process is known as the catalloy process.
• Such polymers are usually copolymers of propylene/ethylene/butene made by a two-stage polymerisation process as described in the following published references: EP-A-0472 946, EP-A-0 477 662, EP-A-0 483 675 AND EP-A-0489 284. The processes described in these documents are incorporated herein by reference.
• Films made from such (co)polymers have a thickness of about 10-80 ⁇ m and have a flexural modulus of less than 150, suitably in the range of 20-100.
• a specific example of such a copolymer is HIFAX® 7029XCP (ex Himont).
• the olefin copolymer layer may be a blend.
• 7029XCP (80% wt/wt) can be blended with Himont EP2S12B (20% wt/wt, ex Himont), a random copolymer of polypropylene and polyethylene.
• the thickness of this layer in the composite is suitably in the range from 10-80 ⁇ m, preferably from 20-40 ⁇ m, eg 30 ⁇ m.
• heteroophasic polypropylene (co)polymer as used herein and throughout the specification signifies that such a polymer may be a homopolymer or a copolymer of propylene.
• At least one end layer of the composite is of a heterophasic polypropylene (co)polymer.
• the olefin polymer layer at the other end (opposite to the heterophasic (co)polymer) of such a composite such olefin polymer may itself be a homo-polymer or co-polymer of ethylene, propylene or mixtures thereof with one another or with other comonomers such as vinyl acetate, acrylic acid, alkyl acrylates and alkyl methacrylates.
• such olefin polymers may be selected from one or more of a heterophasic polypropylene (co)polymer, a polypropylene homopolymer, a polypropylene copolymer, linear low density polyethylene (hereafter “LLDPE”), low density polyethylene (hereafter “LDPE”), high density polyethylene (hereafter “HDPE”), medium density polyethylene (hereafer “MDPE”), very low density polyethylene (hereafter “VLDPE”), ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ionomers such as eg SURLYN® and IOTEK®, ethylene-acrylic acid copolymer, ethylene- methacrylic acid copolymer, a polycarbonate, a polyamide and any blend thereof.
• LLDPE linear low density polyethylene
• LDPE low density polyethylene
• HDPE high density polyethylene
• MDPE medium density polyethylene
• VLDPE
• a blend of LLDPE containing some octene comonomer and VLDPE is preferred. Particularly preferred is a blend of STAMYLEX® 09016 (ex, DSM, 80% wt/wt) and a conventional LDPE grade LD150BW (ex Exxon, 20% wt/wt).
• the polyolefin layer suitably has the same thickness as that of the heterophasic polypropylene (co)polymer, ie a range of 10-80 ⁇ m, preferably 20-40 ⁇ m, eg 30 ⁇ m.
• the tie-layer in the composite is the adhesive layer which binds the polyolefin layer or the polyolefin copolymer layer with the layer of EVOH.
• the tie-layer may be formed by grafting at least one polymerizable ethylenically unsaturated monomer (hereafter "EUM") which is suitably an ethylenically unsaturated carboxylic acid, ester or anhydride on to a material which is the same as the adjacent polyolefinic end layer to form a graft-copolymer.
• EUM polymerizable ethylenically unsaturated monomer
• This enables the tie layer to key in and blend into the polyolefin or heterophasic polypropylene (co)polymer end layer as the case may be when preparing the composite.
• the tie-layer is a graft copolymer of polypropylene and a polymerizable ethylenically unsaturated monomer.
• polymerizable ethylenically unsatured monomers include maleic acid (hereafter “MA”), maleic anhydride (hereafter “MAH”), acrylic acid (hereafter “AA”), alkyl acrylate esters (hereafter “AAE”), methacrylic acid (hereafter “MAA”), alkyl methacrylate esters (hereafter “AME”), itaconic acid, citraconic acid, mesaconic acid, 4-methyl cyclohex-4-ene-1 ,2-dicarboxylic acid anhydride, bicyclo (2.2.2)oct-5-ene-2,3-dicarboxylic acid anhydride, 1 ,2,3, 4,5,8, 9, 10-octahydrona
• maleic anhydride tetrahydrophthalic anhydride and bicyclo(2.2.1 )hept-5-ene-2,3-dicarboxylic acid anhydride are preferred.
• a typical and preferred example of a tie-layer is the graft copolymer derived from a polyolefin and maleic anhydride and sold as ADMER® grades, especially ADMER® NF 530E and ADMER® AT 851. Conjugated unsaturated esters, in addition to the alkyl acrylates and alkyl methacrylates mentioned above, may also suitably be used for co- grafting.
• esters include, eg, dialkyl maleates, dialkyl fumarates, dialkyl itaconates, dialkyl mesaconates, dialkyl citraconates, alkyl crotonates, alkyl tiglates wherein the alkyl group aliphatic, cycloaliphatic, alicyclic or an arlkyl group and suitably has 1-12 carbon atoms.
• Dibutyl maleate, diethyl fumarate and dimethyl itaconate are particularly preferred.
• These monomers may be used either alone or in combination with the anhydrides listed above and are suitably applied to at least one side of the adjacent polyolefinic layer.
• Methods of grafting these monomers on to the polyolefin layer or polyolefin copolymer layer are well known in the art. For instance, methods of grafting MAH to the polyolefin layer are described eg in US-A-2973344 and US-A- 3290415.
• the grafting may be performed in a solvent by placing the monomer in a solvent followed by irradiation as described in US-A-3290415 with peroxides.
• the grafting may be carried out, eg in the case of polypropylene, by melt mixing with peroxides.
• the peroxides that may be used include, eg, t-butyl hydroperoxide, p-menthane hydroperoxide, pinane hydroperoxide and cumene hydroperoxide.
• Other grafting techniques include extrusion grafting and coating the polyolefin surface with a molten monomer followed by irradiation as described eg in US-A-3290415. These methods are incorporated herein by reference to these prior publications.
• the thickness of the tie layer is suitably in the range from 2-1 O ⁇ m, preferably from 3-6 ⁇ m, eg 5 ⁇ m.
• the EVOH used is suitably of a grade which contains from 25-50 mol% of ethylene, preferably from 29-44 mol% and even more preferably from 32- 38 mol %.
• EVOH grades that may be used include inter alia, the so-called EVAL® LCH 101 or EPJ 102B (both ex Kuraray Industries).
• the thickness of the EVOH layer is suitably in the range from 2-25 ⁇ m, preferably from 4-1 O ⁇ m, eg 6 ⁇ m.
• the thickness of each of the layers in the composite is suitably in the following range: Polypropylene copolymer : 10-80 ⁇ m, preferably 20-50 ⁇ m eg 30 ⁇ m
• Each tie layer 2-1 O ⁇ m, preferably 4-6 ⁇ m eg 5 ⁇ m
• EVOH layer 2-25 ⁇ m, preferably 4-1 O ⁇ m eg 6 ⁇ m
• Polyolefin blend 10-80 ⁇ m, preferably 20 ⁇ 40 ⁇ m eg 30 ⁇ m
• the total thickness of the composite is from 35-180 ⁇ m, preferably from 60-1 OO ⁇ m, typically 80 ⁇ m.
• the composite is produced by co-extrusion, this is suitably carried out within an overall average temperature in the range from 170-260° C.
• the polyolefin layers ie both the heterophasic polypropylene (co)polymer layer and the olefin blend layer at the opposite end are suitably maintained at 180-220°C, the EVOH layer at 180-220°C, and the tie layer at upto 250°C.
• the adhesive used to combine such sequences is suitably a polyurethane adhesive.
• additional examples of such adhesives that may be used include a polyester/polyurethane adhesive or a polyether/polyurethane adhesive.
• the composite preferably has at least two such sequences and the grades of any of the generic components in each sequence may be same or different.
• a feature of the composites of the present invention is that they have: a. low permeability to oxygen and other gases; b. good heat sealability for conversion of the composites into bags or other containers; c. a very high degree of flexibility thereby allowing collapse of the bag when the contents thereof are dispensed; and d. excellent flex-crack resistance which enable them to retain performance integrity.
• EXAMPLE Several types of laminates prepared by co-extrusion of various components (shown below) into a 5-layer tubular blown film using a BARMAG four-component five-layer extruder) were tested for their flex crack resistance and other physical properties.
• the materials used for preparing the various coextruded films are identified below in Table 1 : TABLE 1
• VLDPE Very low density polyethylene
• the films were also subjected to an oxygen transmission test (OTR) and the test was carried out using a Mocon Ox-Tran 100 Twin tester.
• OTR oxygen transmission test
• the composite films of the present invention when compared with conventional films, show a. a much better flex-crack resistance (as shown by the Gelbo test); b. a lower stiffness (as shown by the tensile properties and Secant Modulus); and c. a greater resistance to pinholing and therefore reduced OTR.

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• 1994
  • 1994-03-28 GB GB9406106A patent/GB9406106D0/en active Pending
• 1995
  • 1995-03-17 EP EP95911416A patent/EP0700338A1/de not_active Withdrawn
  • 1995-03-17 AU AU18992/95A patent/AU1899295A/en not_active Abandoned
  • 1995-03-17 WO PCT/GB1995/000584 patent/WO1995026268A1/en not_active Application Discontinuation

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