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: 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.

Polyketones have use as thermoplastics for the production of eg containers or parts for the automotive industry. Such uses require the polymer to have suitable impact properties. Accordingly, it is known to incorporate into polyketones additives which improve the impact resistance properties of the polymer. EP-A-451918 discloses that improved impact resistance, as measured by the Gardner test, can be obtained by blending into the polyketone a minor amount of a high rubber graft copolymer, obtainable by graft-polymerising a rigid (when polymerised) vinyl nitrile monomer in the presence of a preformed rubbery

substrate selected from 1,3-diene polymers and rubbery copolymers thereof. An example is a rigid styrene/acrylonitrile graft copolymer on a 1,3 diene substrate.

EP 0457374 relates to a polymer blend composition comprising: (1) a linear alternating polymer of carbon monoxide and at least one ethylenically unsaturated compound; (2) a toughened polymer blend including: (A) a graft rubber composition comprising a substrate rubber having a glass transition temperature below 0°C and monomers comprising a vinyl aromatic monomer and one or more polar monomers selected from the group consisting of Cl to C4 alkyl acrylates, Cl to C4 alkyl methacrylates, methacrylonitrile and acrylonitrile, said monomers having been polymerised in the presence of and grafted on to the substrate rubber; (B) a polyamide; (C) a carboxylic acid containing ethylene/alkyl acrylate copolymer having a glass transition temperature below 20°C.

Surprisingly, we have now found that the impact strength of polyketone polymers can be improved by the incorporation of certain styrene/acrylonitrile graft copolymers in the absence of the above components (B) and (C).

Accordingly, the present invention provides a polymer composition which comprises essentially: (A) a major amount of a polyketone having a linear alternating structure of (a) units derived from carbon monoxide and (b) units derived from one or more olefinically unsaturated compounds; and (B) a minor amount of a graft copolymer having a polyolefinic elastomeric backbone having a glass transition temperature below 0°C grafted with a styrene/acrylonitrile (SAN) resin.

An advantage of the polymer composition of the present invention is that the impact strength of the polyketone polymer is improved to such an extent that samples of the composition do not break under standard impact test conditions (at a temperature of 23°C).

The polyolefinic elastomer used as the backbone of the graft copolymer (B) can be a copolymer of an olefin e. g. propylene with ethylene, butene or other unsaturated aliphatic hydrocarbons or ethylene with propylene and a diene.-Such copolymers are known and any such polymer can be used. It is preferred that the elastomer used as the 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. dicyclopentadiene or hexa-1,4-diene) along the polymer backbone.

The styrene/acrylonitrile (SAN) resin is a copolymer formed from a vinyl nitrile monomer such as acrylonitrile and a vinyl aromatic monomer such as styrene or substituted styrenes. Illustrative substituted styrenes include a-methyl styrene, a-ethylstyrene, p-methylstyrene, m-methylstyrene, p-ethylstyrene, m- isopropylstyrene, divinyl benzene, a, 4-dimethylstyrene, chlorostyrene and vinyl benzene chloride. The amount of units derived from the vinyl nitrile monomer which are present in the copolymer may typically be from 5 to 50 % by weight, preferably 15 to 30 % by weight of the resin. Such resins are widely known and commercially available.

The amount of styrene/acrylonitrile (SAN) resin which is graft copolymerised with the polyolefinic elastomeric backbone may typically be from 5 to 60%, more preferably from 10 to 30% by weight of the graft copolymer.

Component (B) of the polymer composition of the present invention may comprise a mixture of two or more graft copolymers.

Methods for preparing graft copolymers are well known and any suitable method can be used to prepare the graft copolymer of the polyolefinic elastomer and the styrene/acrylonitrile (SAN) resin. One such suitable method comprises blending together the polyolefinic elastomer and the styrene/acrylonitrile (SAN) resin 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 polyolefinic elastomer 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 polyolefinic elastomer which forms the backbone of the graft copolymer, the styrene/acrylonitrile (SAN) resin and an organic peroxide or hydroperoxide through a single or multiple screw extruder. Alternatively, the polyolefinic elastomer which forms the backbone of the graft copolymer may be dissolved or suspended in a solvent and the resulting solution or suspension is mixed with the styrene/acrylonitrile (SAN) resin and the free radical initiator.

As noted above 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. Suitable olefinic units are those derived from C2 to C20 alpha-olefins or substituted derivatives thereof or arylaliphatic olefinically unsaturated compounds such as styrene or alkyl substituted derivatives of styrene. It is preferred that such olefin or olefins are selected from C2 to C6 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 butene. In these most preferable materials it is further preferred that the molar ratio of ethylene units to C3 to C6 normal alpha-olefin units is greater than or equal to 1 most preferably between 2 and 30.

The polyketones employed in the invention preferably have a number average molecular weight of from 1000 to 500,000, preferably from 15,000 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 225°C.

The graft copolymer (B) is incorporated in the polyketone in an amount of between 0.5 and 50% by weight, preferably from 5 to 40% and more preferably from 10 to 30% by weight, based on the weight of the polyketone plus graft copolymer.

The composition of the present invention may also contain conventional additives such as antioxidants, stabilisers, processing aids, fillers etc.

It is envisaged that the composition of the present invention may optionally contain further toughening components other than components (B) and (C) of EP 0457374 as hereinbefore described.

The present invention provides a polyketone polymer composition having significant impact strength improvement compared with the unmodified polyketone polymer.

The scope of the present invention extends to moulded or extruded articles, including containers (for example, bottles, trays, cups), automotive parts, sheets and profile sections comprising the polymer compositions as defined hereinbefore.

A further aspect of the invention relates to the use of a graft copolymer (B) to increase the impact strength of a polyketone polymer.

The following Examples illustrate the invention.

Determination of Melt Flow Rate The Melt Flow Rate (MFR) of the polyketone was measured using a Davenport Melt Index Tester. Tests were carried out at a temperature of 240°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 240°C. Otherwise standard MFR procedures were followed (e. g.

ISO 1133).

EXAMPLE Polyketone/graft copolymer compositions were prepared using a PRISM TSE16 co-rotating twin screw extruder. The extruder was operated at a screw speed of 200rpm and with the following set of temperatures: zone 1 (feed) 195- 200°C; zone zone 3 (die) 215-230°C. The appropriate amount of graft copolymer was either preblended with the polyketone prior to being fed into the extruder or fed independently via an additional feeder. Appropriate levels of stabilisers and antioxidants were premixed with the polyketone. Extruder outputs were maintained at a level to give constant 60% torque on the screws.

The polyketone used was a terpolymer of ethylene, propylene and carbon monoxide, and had a melting point of 194°C and a melt flow rate (MFR) of 9g/lOminutes at 240°C and a 5kg load. The graft copolymer was an ethylene/propylene/non-conjugated diene (EPDM) grafted with styrene/acrylonitrile (SAN) resin. The SAN-g-EPDM used was Royaltuf 372 P20 or Royaltuf 372 PX (which differ in viscosity) supplied by Uniroyal Chemical.

After compounding, the polyketone/graft copolymer composition was compression moulded into plaques, 150 x 150 x 4mm, using the following conditions: Temp: 20°C above polyketone melting point Preheat time: 5 mins Pressing time: 5 mins under 15 tonnes Cooling: Crash cooled with water.

Samples for Izod impact testing were machined from the plaques and tested according to ASTM D256. Notched samples were tested, with a notch radius of

0.25mm. A pendulum weight and position was employed, such that it had a potential energy of 1545mJ.

Results of the impact testing are shown below: MATERIAL IZOD IMPACT (J/m) STRENGTH 23°C-40°C polyketone 122 18 polyketone + 20 wt% NB 38 SAN-g-EPDM (Royaltuf 372 P20) polyketone + 20 wt% NB 34 SAN-g-EPDM(Royaltuf 372 PX) NB = no break Surprisingly, the samples prepared from compositions according to the present invention had such improved impact strength compared with the unmodified polyketone that they did not break when the Izod impact test was carried out at a temperature of 23°C. When the Izod impact test was performed at a temperature of-40°C, a 2 fold increase in impact strength value was observed.