GB2282142A

GB2282142A - Polymer composition

Info

Publication number: GB2282142A
Application number: GB9419038A
Authority: GB
Inventors: James Graham Bonner; Colin James Humphris
Original assignee: BP Chemicals Ltd
Current assignee: BP Chemicals Ltd
Priority date: 1993-09-28
Filing date: 1994-09-21
Publication date: 1995-03-29
Also published as: GB9319972D0; GB9419038D0

Abstract

A polymer blend composition comprises a polyketone and a copolymer of acrylonitrile and methyl acrylate where the copolymer contains at least 65mol% monomer units derived from acrylonitrile.

Description

POLYMER COMPOSITION The present invention relates to a polymer blend composition comprising a polyketone and a copolymer of acrylonitrile and methyl acrylate, in particular where the copolymer is Barex.

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.

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. 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 10 wt%) of the corresponding homopolymer or copolymer derived from the olefinically unsaturated compound, also fall within the definition.

The polyketones prepared by these processes whilst being thermoplastics, suffer from the disadvantage that they have relatively high melting points which are close to the temperatures at which they undergo chemical degradation. This causes a problem since the materials are thus difficult to process using conventional melt technology.

In order to overcome this problem a number of potential approaches have been explored. EP 213671 teaches that polyketones comprised of carbon monoxide, ethylene and alpha olefin (e.g.

propylene) units have lower melting points than corresponding copolymers comprised only of carbon monoxide and ethylene units.

Whilst this approach goes some way to alleviating the problem, there is still a need to improve further the melt processing stability of polyketones by decreasing the glass transition temperature if they are to be processed on a commercial scale. Since polyketones are crystalline in nature, a further approach to lower melting points, other than incorporation of a third monomer (alpha olefin) as above, is to blend the polyketone with an amorphous polymer. However, in this case it is important that the two polymers are compatible and therefore do not phase separate which would result in poor physical properties when thermoformed.

It has now been found that the melt processability of polyketones can be improved by blending the polyketones with a copolymer of acrylonitrile and methylacrylate to give a compatible blend.

Thus according to the present invention there is provided a polymer blend composition comprising a polyketone and a copolymer of acrylonitrile and methyl acrylate wherein the copolymer contains at least 65 molU monomer units derived from acrylonitrile.

The present invention solves the problem of improving the melt processability of polyketones by blending with a copolymer of acrylonitrile and methyl acrylate.

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 C12 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 C6 normal 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.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.

As regards the copolymer of acrylonitrile and methyl acrylate it will contain at least 65mol% preferably 70mod%, more preferably 75mop monomer units derived from acrylonitrile based upon the total number of monomer units derived from acrylonitrile and methyl acrylate. The copolymer will typically be rubber toughened; this is achieved by growing the copolymer on an elastomer latex which itself is a copolymer of acrylonitrile and butadiene. The rubber will in these cases be incorporated into the acrylonitrile/methyl acrylate (AN/MA) copolymer and will comprise up to 20% by weight of the total weight of the (AN/MA) copolymer plus the rubber. These AN/MA copolymers and rubber-toughened AN/MA copolymers are sold commercially under the trade name of Barex.

The polymer blend composition of the present invention can be prepared using conventional techniques and equipment for batch or continuous blending.

The ratio of polyketone to copolymer of acrylonitrile and methyl acrylate is suitably in the range 1:10 to 10:1 preferably 1:3 to 3:1 more preferably 1:1.5 to 1.5:1 for example 1:1. However, where the thermoformability of polyketone is to be improved, then it is preferred to use 1-20% by weight of AN/MA copolymer preferably 515% e.g. 10%. On the other hand, if the softening point of the AN/MA copolymer is to be increased, then 1-20% preferably 5-15% e.g. 10% by weight of the polyketone based upon the polymer blend composition will typically be used. Other polymers may be blended with the blend composition of the present invention; the nature and amount of such a polymer will depend upon what modifications of the polymer properties are required.Furthermore the blends of the present invention may contain conventional polymer additives such as antioxidants, stabilisers, and mould release agents.

The invention is illustrated by the following example: Example 1 A 50/50 wt/wt blend of an ethylene/propylene/CO polyketone (EPCO)and Barex 210E was prepared using a co-rotating twin-screw extruder with a barrel set temperature of 2002C, a screw speed of 100 rpm and an output of -lOkg/h. The blend properties are directly compared with the polymer components as set out in Table 1 The EPCO was prepared by standard techniques and comprised 4mol% of propylene. The Barex 210E is available commercially from BP Chemicals Ltd.

Property EPCO Barex 210E EPCO/Barex 210E (50/50 w/w) Melting point ("C) 216 - non detectable by DSC Glass transition 11 92 6,88.

temp.( C) Vicat Softening Point 209 79 92 (2C) Melt viscosity (Pa.s) 6.818 x 103 4.071 x 103 4.176 x 104 (2402C, Is-l) Stability Ranking 3 2 1 (1 to 3, 1 being most stable) Tensile strength (mPa) 52.8 41.1 30.1

Claims

Claims: 1. A polymer blend composition comprising a polyketone and a copolymer of acrylonitrile and methyl acrylate where the copolymer contains at least 65mol% monomer units derived from acrylonitrile.