WO1999042286A1

WO1999042286A1 - A multi-layered structure

Info

Publication number: WO1999042286A1
Application number: PCT/GB1999/000428
Authority: WO
Inventors: James Graham Bonner
Original assignee: Bp Chemicals Limited
Priority date: 1998-02-18
Filing date: 1999-02-11
Publication date: 1999-08-26
Also published as: GB9803415D0

Abstract

A multi-layered structure comprising a first polyolefin layer and a second polyketone layer, the first and second layers being bonded together with an intermediate layer of an adhesive composition comprising a graft copolymer having a polyolefin backbone grafted with a polyamide. The polyolefin backbone of the polyamide graft copolymer may itself be a graft copolymer of a polyolefin and a polymerisable ethylenically unsaturated carboxylic acid or derivative thereof.

Description

A MULTI-LAYERED STRUCTURE

The present invention relates to adhesive compositions and multi-layered structures comprising the adhesive compositions, in particular, multi-layered structures comprising at least one layer of a polyketone composition.

For the purposes of this patent, polyketones are defined as linear polymers having an alternating structure of (a) units derived from carbon monoxide and (b) units derived from one or more olefinically unsaturated compounds. Although for the purposes of this patent polyketones correspond to this idealised structure, it is envisaged that materials corresponding to this structure in the main but containing small regimes (i.e. up to 10wt%) of the corresponding homopolymer or copolymer derived from the olefinically unsaturated compound, also fall within the definition.

Such polyketones have the formula:

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[(CR₂-CR₂)C]_m (I) where the R groups are independently hydrogen or hydrocarbyl groups, and m is a large integer; they are disclosed in several patents e.g. US 3694412. Processes for preparing the polyketones are disclosed in US 3694412 and also in EP 181014 and EP 121965.

Adhesive compositions, also known as tie-layers or melt adhesives, are employed to bind together layers of materials which otherwise do not stick together satisfactorily. Polyolefin-containing blends suitable for use as adhesive layers in multi-layered structures are known. For example, US Patent 2081723 discloses a modified polyolefin adhesive blend comprising (A) a graft copolymer of a polyethylene back-bone grafted with at least one polymerisable ethylenically unsaturated carboxylic acid or carboxylic acid anhydride and (B) a blending resin

1 mixture comprising a linear low density polyethylene and polypropylene. The patent states that the adhesive blends can be used to join polypropylene to a number of polar materials or to join two polar materials together.

US 4,822,688 relates to an adhesive composition consisting essentially of the reaction product of (a) a polypropylene compound consisting of polypropylene modified by grafting thereto an unsaturated monomer bearing an acid anhydride group, with (b) a compound R, bearing at least two amine groups which are reactive with the anhydride group and wherein the compound R includes, amongst others, alpha, omega-diamino polyamide oligomers. According to related patent US 4,735,992, the compound R has a molecular weight of less than 50,000.

Neither US 4,822,688 or US 4,735,992 teach that such adhesive compositions can be used to join a polyolefin to a polyketone.

WO 9509212 relates to a polyolefin-containing adhesive blend suitable for bonding polyolefins, in particular, polyethylene or polypropylene to polyketones which blend has good adhesion to polyolefins while maintaining good adhesion to the polyketone. The polyolefin-containing adhesive blend is said to comprise: (A) 1 to 30 parts by weight of a graft copolymer having a polyolefin backbone grafted with 0.001 to 30% by weight of at least one polymerisable ethylenically unsaturated carboxylic acid or derivative thereof, (B) 70 to 99 parts by weight of a polyolefin provided that at least 5 parts by weight of (B) is (C) a polyolefin having a density of less than 930kgm^"3 wherein the graft copolymer (A) has been reacted with a compound (D) which has at least two primary or secondary amino groups at least one of which is a primary amino group, the sum of (A), (B) and (C) being 100 parts by weight.

We have now discovered that other adhesive compositions can successfully bind polyolefins to polyketones.

Thus, the present invention provides a multi-layered structure which comprises a first layer and a second layer, the first layer comprising a polyolefin composition and the second layer comprising a polyketone composition, the first and second layers being bonded together with an intermediate layer of an adhesive composition comprising a graft copolymer having a polyolefin backbone grafted with a polyamide.

The polyolefin used as the backbone of the graft copolymer can be a homopolymer of an olefin e.g. ethylene or propylene, in particular high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE) or very low density polyethylene (NLDPE), preferably LLDPE, or a copolymer of an olefin e.g. propylene with ethylene, butene or other unsaturated aliphatic hydrocarbons or a terpolymer of an olefin e.g. ethylene with propylene and a diene. Such homopolymers, copolymers and teφolymers are known and any such polymer can be used. Blends of two or more polyolefins can be used. It is preferred that the polyolefin backbone of the graft copolymer is an ethylene-propylene rubber or an ethylene/propylene/diene polymer (EPDM), most preferably EPDM. EPDM is an amorphous elastomeric polyolefin having a random distribution of units derived from ethylene, propylene and one or more dienes (e.g. butadiene, ethylidene norbornene) along the polymer backbone.

The polyolefin used as the backbone of the graft copolymer may itself be a graft copolymer in which case the polyolefin is a graft copolymer having a polyolefin backbone grafted with at least one polymerisable ethylenically unsaturated carboxylic acid or derivative thereof.

Polymerisable ethylenically unsaturated carboxylic acids and derivatives thereof include, for example, acrylic acid, methacrylic acid, maleic acid, itaconic acid, citraconic acid, mesaconic acid, maleic anhydride, 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-octahydronaphthalene-2,3 dicarboxylic acid anhydride, 2-oxa-l,3-diketospiro (4.4) non-7-ene, bicyclo (2.2.1) hept-5-ene-2,3 -dicarboxylic acid anhydride, maleopimaric acid, tetrahydrophthalic anhydride, x-methyl-bicyclo (2.2.1) hept-5-ene -2,3-dicarboxylic acid anhydride, x-methyl-norborn-5-ene-2, dicarboxylic acid anhydride, norborn-5-ene-2,3-dicarboxylic acid anhydride. Preferably, maleic anhydride is used. When maleic anhydride is used as the polymerisable ethylenically unsaturated carboxylic acid anhydride, the amount which is graft copolymerised with a polyolefin backbone is typically from 0.001 to 30%, preferably from 0.1 to 10% more preferably from 0.15 to 5 % by weight of the grafted copolymer. Methods for preparing graft copolymers are well known and any suitable method can be used to prepare the graft copolymer having a polyolefin backbone grafted with a polymerisable ethylenically unsaturated carboxylic acid or derivative thereof. One such suitable method comprises blending together the polyolefin and the polymerisable ethylenically unsaturated carboxylic acid or derivative thereof in the presence of a free radical initiator, such as an organic peroxide or hydroperoxide, at a temperature which is above the melting point of the polyolefin polymer and which provides a suitable half-life of the free radical initiator. Suitable free radical initiators are well known. This grafting process can be carried out using known mixing equipment such as, for example, a Brabender mixer, a Banbury mixer or a roll mill. Preferably, the grafting process is carried out in a closed vessel. A convenient method of preparing the graft copolymer is therefore to extrude the polyolefin polymer which forms the polymer backbone, the polymerisable ethylenically unsaturated carboxylic acid or derivative thereof and an organic peroxide or hydroperoxide through a single or multiple screw extruder. Alternatively, the polyolefin polymer may be dissolved or suspended in a solvent and the resulting solution or suspension is mixed with the polymerisable ethylenically unsaturated carboxylic acid or derivative thereof and the free radical initiator.

By "polyamide" is meant a condensation product which contains recurring amide groups as integral parts of a polymeric chain. These polyamides are well known in the art and are often referred to as Nylons.

The polyamide may be a homopolymer of an aminomonocarboxylic acid, typically having up to 16 carbon atoms inclusive, for example, Nylon 12 or Nylon 6. Alternatively, the polyamide may be a copolymer of a primary diamine and a dicarboxylic acid and/or a derivative thereof (for example, a dicarboxylic acid chloride). The primary diamine is preferably a terminal primary diamine having up to 16 carbon atoms inclusive and at least two carbon atoms between the primary amino groups which are located on terminal carbon atoms of the diamine structure. The diamines suitably contain aromatic moieties linking the amino groups as illustrated by phenylenediamine, 4,4'-diaminobiphenyl and di(4-aminophenyl)ether, or the linking group is cycloaliphatic as in the case of di(4- aminocyclohexyl)methane or 1,4-diaminocyclooctane. The preferred diamines, however, are acyclic terminal primary diamines of the formula

H₂N(CH₂)_nNH₂ wherein n is an integer from 2 to 16 inclusive. Such polymethylenediamines include trimethylenediamine, tetramethylenediamine, hexamethylenediamine, decamethylenediamine, dodecamethylenediamine and hexadecamethylenediamine.

The dicarboxylic acid suitably has up to 16 carbon atoms inclusive as illustrated by aromatic dicarboxylic acids such as isophthalic acid, terephthalic acid and 2,6-naphthalenedicarboxylic acid. The preferred dicarboxylic acids, however, are aliphatic dicarboxylic acids, particularly those of the formula

HO₂C(CH₂)_mCO₂H wherein m is an integer from 0 to 14 inclusive. Illustrative of such dicarboxylic acids are oxalic acid, pimelic acid, sebacic acid, suberic acid, azelaic acid, undecanedioic acid, and adipic acid.

The molecular weight of the polyamide is preferably at least 5000, more preferably at least 25000, most preferably at least 50000.

The polyolefin backbone may be grafted with a mixture of two or more polyamides. The amount of polyamide which is graft copolymerised with the polyolefin backbone may typically be from 5 to 95%, preferably from 10 to 90%, more preferably from 25 to 80% by weight of the polyamide graft copolymer.

The adhesive composition may comprise a mixture of two or more of the graft copolymers having a polyolefin backbone grafted with a polyamide. The polyolefin polymer used as the backbone of the graft copolymer may be graft copolymerised with a mixture of a polyamide and at least one polymerisable ethylenically unsaturated carboxylic acid or derivative thereof. Alternatively, the polyolefin may be graft copolymerised with at least one polymerisable ethylenically unsaturated carboxylic acid or derivative thereof prior to being graft copolymerised with a polyamide.

Optionally, a polyolefin is added to the adhesive composition to modify the rheological, viscoelastic or adhesive properties of the composition ("modifying polyolefin"). Any suitable polyolefin can be used e.g. polyethylene, polypropylene, copolymers of ethylene or copolymers of propylene with one or more comonomers e.g. butene. Suitably, the polyolefin may be a very low density polyethylene (VLDPE), linear low density polyethylene (LLDPE) or an ethylene propylene rubber. A mixture of two or more modifying polyolefins can be added to the adhesive composition, preferably two polyolefins e.g. a polypropylene and a NLDPE. Where a modifying polyolefin is added to the adhesive composition, the modifying polyolefin is present in amounts of from 5 to 95% by weight, preferably 5 to 25% by weight based on the total weight of polymers of the adhesive composition.

The adhesive composition may optionally comprise a polyketone. Where a polyketone is present in the adhesive composition it is preferred that the polyketone is present in the adhesive composition in amounts in the range 10 to 50% by weight, more preferably 20 to 40% by weight based on the total weight of the polymers of the adhesive composition.

The graft copolymer, the optional modifying polyolefin and the optional polyketone can be blended using known techniques and equipment for batch or continuous blending.

The adhesive composition may also contain conventional additives such as, for example, antioxidants, stabilisers, processing aids, fillers and mould release agents. Methods for using adhesive compositions to bond polyolefins to polar substrates are known and include lamination, coextrusion, extrusion lamination and coextrusion coating. In particular, the present invention relates to multi-layered structures when prepared by co-extrusion e.g. multi-layered film, multi-layered sheet, multi-layered receptacles (such as bottles, bowls, cups and trays), multi- layered pipe and multi-layered tubing produced by co-extrusion.

The polyolefin composition of the first layer may comprise a polyolefin, blends of polyolefins or blends of a polyolefin and a polymer other than a polyolefin (for example, a blend of a polyolefin and a polyamide). Preferably, the polyolefin composition of the first layer comprises a major proportion of a polyolefin. The polyolefin composition of the first layer may comprise a recycled polyolefin or a mixture of recycled and virgin polyolefin. The polyolefin composition of the first layer may contain conventional fillers. Suitable polyolefins include a homopolymer of an olefin e.g. ethylene or propylene, in particular polypropylene, a high density polyethylene (HDPE), a low density polyethylene (LDPE), a linear low density polyethylene (LLDPE) or a very low density polyethylene (VLDPE), preferably polypropylene, HDPE or LLDPE. Alternatively, the polyolefin may be a copolymer of an olefin e.g. propylene with ethylene, butylene or other unsaturated aliphatic hydrocarbons or a teφolymer of an olefin e.g. ethylene with propylene and a diene. The polyketone composition of the second layer comprises a linear polymer having an alternating structure of (a) units derived from carbon monoxide and (b) units derived from one or more olefinically unsaturated compounds. Suitable olefinic units are those derived from C₂ to d₂ alpha-olefins or substituted derivatives thereof or styrene or alkyl substituted derivatives of styrene. It is preferred that such olefin or olefins are selected from C₂ to Ce normal alpha-olefins (i.e. straight chain alpha-olefins) and it is particularly preferred that the olefin units are either derived from ethylene or most preferred of all from a mixture of ethylene and one or more C₃ to C₆ normal alpha-olefin(s) especially propylene or butylene. In these most preferable materials it is further preferred that the molar ratio of ethylene units to C₃ to Cβ normal alpha-olefin units is greater than or equal to 1 most preferably between 2 and 30. The polyketone composition of the second layer may comprise blends of polyketones or blends of polyketones and a polymer other than a polyketone (for example, polystyrene, polyamides, HDPE, LLDPE, LDPE or polypropylene). The polyketones employed in the invention preferably have a number average molecular weight of from 20000 to 500,000, preferably from 30,000 to 300,000, more preferably from 40,000 to 200,000 as determined by gel permeation chromatography.

The melting point of the polyketones is preferably between 175 and 300°C, preferably from 180 to 260°C.

The multi-layered structures according to the present invention can include further layers in addition to the three layers hereinbefore defined. For example, a five-layered structure can comprise a first layer of a polyolefin composition, a second layer of an adhesive composition as defined above, a third layer of a polyketone composition, a fourth layer of an adhesive composition as defined above and a fifth layer of a polyolefin composition.

It has been found that the use of the adhesive compositions defined above to produce multi-layered film or sheet provides a satisfactory bond when the film or sheet is subsequently thermoformed, i.e. the film or sheet does not have a tendency to delaminate after thermoforming, into articles e.g. receptacles (such bottles, cups, bowls and trays), pipes and tubing. The present invention includes articles produced by thermoforming a multi-layered film or sheet as previously defined.

According to a further aspect of the present invention there is provided an adhesive composition comprising a graft copolymer having a polyolefin backbone grafted with a polyamide wherein the polyamide has a molecular weight of greater than 50,000.

According to yet a further aspect of the present invention there is provided an adhesive composition comprising a graft copolymer having a polyolefin backbone grafted with a polyamide with the proviso that the polyamide is not an alpha, omega-diamino polyamide oligomer.

The polyolefin backbone and the polyamide have the preferred features described above.

The invention is illustrated by the following example: Materials

Polyketone (PK): Ethylene/propylene/CO terpolymer, melting point 200°C, melt flow rate (MFR) 70 g/10 minutes (250°C, 5 kg load);

Polyamide grafted ethylene/propylene/diene copolymer (PA-g-EPDM): Royaltuf X603 supplied by Uniroyal. Determination of Melt Flow Rate

The melt flow rate (MFR) of the polyketone (PK) was measured using a Davenport Melt Index Tester. Tests were carried out at a temperature of 250°C and an applied load of 5 kg. The MFR was calculated from the mass of extrudate pushed through a die (2.095 mm diameter) over a 30 second period on application of the load 4 minutes after charging the polymer into the barrel of the instrument at a temperature of 250°C. Otherwise, standard MFR procedures were followed (e.g. ISO 1133). Example

A compression moulded sheet (150 μm) of PA-g-EPDM was produced using a 20 tonne Moore press under the following conditions: a l5 x l5 cm x l30 μm "picture frame" mould was preheated for 5 minutes at 200°C, pressed at 15 tonnes for 5 minutes and crash cooled to room temperature.

Polyketone (PK) and polyethylene (PE) sheets were made by a similar procedure to that given above. Multi-layered structures of PK/PA-g-EPDM/PE were prepared via the following procedure: three individual sheets (PK/PA-g-EPDM/PE) were placed within a l5 x l5 cm x 390 μm picture frame mould. This was preheated at 260°C for 30 seconds, pressed at 10 tonnes for 10 seconds and then crash cooled to room temperature. The resultant multi-layered structure was then cut into five 2.5 cm wide strips and the level of adhesion between each layer was assessed using a standard T-peel test (in accordance with BS 5350).

The PA-g-EPDM layer could not be peeled from either the polyketone (PK) or polyethylene (PE) sheets of the multi-layered structure.

Claims

Claims:

1. A multi-layered structure which comprises a first layer and a second layer, the first layer comprising a polyolefin composition and the second layer comprising a polyketone composition, the first and second layers being bonded together with an intermediate layer of an adhesive composition comprising a graft copolymer having a polyolefin backbone grafted with a polyamide.

2. A multi-layered structure as claimed in claim 1 wherein the polyolefin backbone of the graft copolymer of the adhesive composition is an ethylene- propylene rubber or an ethylene/propylene/diene polymer (EPDM).

3. A multi-layered structure as claimed in claims 1 or 2 wherein the polyolefin backbone of the graft copolymer of the adhesive composition is a graft copolymer having a polyolefin backbone grafted with at least one polymerisable ethylenically unsaturated carboxylic acid or derivative thereof.

4. A multi-layered structure as claimed in claim 3 wherein maleic anhydride is grafted with the polyolefin backbone in an amount of from 0.001 to 30% by weight of the grafted copolymer.

5. A multi-layered structure as claimed in any one of the preceding claims wherein the polyamide which is grafted with the polyolefin backbone is a homopolymer of an aminomonocarboxylic acid or a copolymer of a primary diamine and a dicarboxylic acid and/or a derivative thereof.

6. A multi-layered structure as claimed in any one of the preceding claims wherein the amount of polyamide which is graft copolymerised with the polyolefin backbone is from 5 to 95% by weight of the polyamide graft copolymer.

7. A multi-layered structure as claimed in any one of the preceding claims wherein a polyolefin is present in the adhesive composition in an amount of from 5 to 95% by weight based on the total weight of polymers in the adhesive

SUBSTTTuTE SHEET (RULE 26) composition.

8. A multi-layered structure as claimed in any one of the preceding claims wherein a polyketone is present in the adhesive composition in an amount of from 10 to 50% by weight based on the total weight of the polymers of adhesive composition.

9. A multi-layered structure as claimed in any one of the preceding claims wherein the polyketone composition of the second layer comprises a linear polymer having an alternating structure of (a) units derived from carbon monoxide and (b) units derived from one or more C₂ to C╬╣₂ alpha-olefins.

10. A multi-layered structure as claimed in claim 9 wherein the polyketone composition of the second layer comprises an ethylene/carbon monoxide copolymer, an ethylene/propylene/carbon monoxide terpolymer or an ethylene/butylene/carbon monoxide terpolymer.

11. An article comprising a multi-layered structure as claimed in any one of the preceding claims.

12. An article as claimed in claim 11 wherein the article is selected from the group consisting of receptacles, pipe and tubing.

13. An adhesive composition comprising a graft copolymer having a polyolefin backbone grafted with a polyamide wherein the polyamide has a molecular weight of greater than 50,000.

14. An adhesive composition comprising a graft copolymer having a polyolefin backbone grafted with a polyamide with the proviso that the polyamide is not an alpha, omega-diamino polyamide oligomer.

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