WO1991013119A1

WO1991013119A1 - Impact modified thermoplastic polyester

Info

Publication number: WO1991013119A1
Application number: PCT/GB1991/000271
Authority: WO
Inventors: Jacques Paul Eugene Joseph Horrion; Vincent Bernard Benoît Ghislain GALLEZ; Silvestro Cartasegna
Original assignee: Exxon Chemical Limited; Exxon Chemical Patents Inc.
Priority date: 1990-02-21
Filing date: 1991-02-21
Publication date: 1991-09-05

Abstract

A polyester blend including an impact modifier comprising: (A) an elastomeric component; and (B) a component being one or more of ethylene/epoxy copolymers and ethylene/epoxy polymers containing units derived from other monomers, said elastomeric component (A) being cross-linked to said component (B) or being a partially crystalline polymer blend containing at least one semi-crystalline component and at least one low crystalline to amorphous component, both components of said partially crystalline polymer blend being ethylene based elastomeric polymers of monomers selected from ethylene and alpha-olefin, diolefin and vinyl polar monomers copolymerisable therewith. Such a blend has improved impact strength and ductility.

Description

IMPACT MODIFIED THERMOPLASTIC POLYESTER

The present invention relates to a blend of a thermoplastic polyester and an agent which improves the impact properties, in particular the low temperature impact properties, of the polyester, a process for producing the blend and a process for improving the impact properties of a polyester.

So-called "engineering resins,", such as thermoplastic polyesters, polycarbonates and polyamides, are strong and may be moulded to produce shaped articles. However, they suffer from the disadvantage of poor impact properties, especially at low temperature. Indeed, polycarbonates are particularly susceptible to surface problems when moulded, and tend to suffer from surface delamination effects immediately after injection moulding. Notches and cracks in the article are places of weakness and it only requires a relatively small impact to break the material at this point. The moulding of such resins e.g. by extrusion or injection, results in imperfections at the corners and surfaces of the moulded articles. There is therefore interest in providing an improved resin which is not so susceptible to impacts, especially at low temperature.

Elastomers such as ethylene/alpha olefin copolymer rubbers and their terpolymer counterparts which contain a small proportion, say 1-10 weight percent of polyenes such as dienes, exemplified by ethylene propylene rubber (EPR) and ethylene propylene diene terpolymer (EPDM) , provide good impact properties and may therefore be dispersed within an engineering resin to toughen it, provided that good compatibility is achieved between the elastomer and the resin matrix, i.e. there is good adhesion between rne matrix phase and the dispersed elastomer.

Unmodified ethylene/alpha olefin copolymer and terpolymer rubbers such as EPR or EPDM are substantially non-polar, whereas engineering resins tend to have a high polarity. Consequently, adhesion between unmodified elastomer and engineering resins is poor. The inclusion of a functional group such as maleic anhydride (MANH) in the elastomer, commonly as a graft of the anhydride onto EPR or EPDM, is a well known way to toughen polya ide/elastomer blends. Graft copoiymers between the maleic anhydride and the polyamide are formed during blending. Good adhesion is achieved via the maleic anhydride between the polyamide and the elastomer. However, the reactivity of maleic anhydride towards other engineering resins is not sufficient to form compatibiUsing graft copoiymers at the interface between the resin and the MANH-containing elastomer. The adhesion between the elastomer and the engineering resins is therefore too low to achieve a significant improvement in the impact properties of the resin.

Thermoplastic polyesters (such as polyethylenetere- phthalate (PET) and polybutyleneterephthalate (PBT) and polycarbonates) do not have a particularly high reactivity with MANH. They are more reactive to epoxy groups but it has not proved possible to form a suitable terpolymer of an epoxy-containing monomer with ethylene and propylene monomers. Moreover, only very limited success has been achieved when attempting to graft epoxy-containing monomers onto pre-formed EPR or EPDM. Difficulties are encountered with this approach because the epoxy-containing monomer tends to homopolymerise. Grafting efficiency is therefore poor, and furthermore the homopoly er of the epoxy-containing monomer is difficult to eliminate from the product. Radical copolymerisation of epoxy-containing monomers is feasible with ethylene and vinyl ester monomers. However, the copoiymers and terpolymers obtained are generally of low molecular weight. Even if such copoiymers and terpolymers adhere well to polyesters, their structural parameters do not make them effective impact behaviour improvers especially at low temperature.

EP-A-89042 discloses a thermoplastic polycarbonate based blend which includes rubber modified copolymer and an epoxy-group containing olefin copolymer or terpolymer for improving impact behaviour at room temperature. The rubber modified copolymer has to comprise a graft copolymer of a rubber and a copolymer of at least two components, which are typically aromatic vinyl compounds such as styrene and vinyl cyanides or esters. The only specific materials described and tested comprise rubber modified styrene-acryeonitrile. There is no specific disclosure of non-aromatic copoiymers. Furthermore, no guidance is given on how to obtain improved low temperature impact strength.

US-A-4172859 discloses a multi-phase thermoplastic composition comprising polyester, polycarbonate and a random copolymer, which has improved impact strength at room temperature. The random copolymer may include many possible repeating units, including ethylene and epoxy units but is a single component and there is no separate polyolefin rubber component. Furthermore, the problem of low temperature impact resistance is not addressed. The same is true of EP-A-300051 which relates to a blend of a thermoplastic polycarbonate with an epoxy-modified olefin copolymer. EP-A-180648 describes a thermoplastic composition which includes a polyester and a polycarbonate together with (1) unmodified, apparently amorphous alpha-olefin copolymer and (2) an ethylene/glycidyl methacrylate copolymer or an ethylene/glycidyl methacrylate/vinyl acetate terpolymer. This is said to achieve improved impact strength at room temperature.

EP-A-72455 discloses a thermoplastic polyester- based blend which includes an unmodified, apparently amorphous ethylene/alpha-olefin rubber component and an ethylene/glycidyl ester copolymer or an ethylene/glycidyl ester/vinyl acetate terpolymer. Such a blend is said to have improved low temperature impact strength. Similarly, J89-26380 discloses a polyester- based thermoplastic composition which includes (l) an unmodified ethylene/alpha-olefin/nonconjuga ed diene terpolymer and (2) an alpha-olefin/glycidyl ester copolymer having improved low temperature .impact strength.

However, whilst there have been attempts in the prior art to improve the impact behaviour of polyester blends, there remains a need for polyester and/or polycarbonate blends having improved ductility or reduced brittleness combined with improved impact strength especially at low temperature.

It has now been found by the present inventors that a surprising improvement in ductility or a reduction in brittleness and improved impact strength, particularly at low temperature, may be imparted to polyester and/or polycarbonate blends by incorporating in the blend an impact modifier comprising an elastomeric/rubber component and an epoxy component, in which the elastomeric/rubber component is able to achieve bonding and/or a stronger interaction with the epoxy component.

Thus, according to a first aspect of the present invention there is provided a polyester blend comprising an impact modifier which comprises: (A) an elastomeric component; and

(B) a component being one or more of ethylene/epoxy copoiymers and ethylene/epoxy polymers containing units derived from other monomers said elastomeric component (A) being cross-linked to said component (B) or being a partially crystalline polymer blend containing at least one semi-crystalline component and at least one low crystalline to amorphous component, both components of said partially crystalline polymer blend being ethylene based elastomeric polymers of monomers selected from ethylene and alpha-olefin, diolefin and vinyl polar monomers copolymerisable therewith.

According to a further aspect of the invention there is provided a polyester blend including an impact modifier which comprises:

(A) an elastomeric component which is one or more of (Al) functionalised ethylene/alpha olefin copolymer functionalised ethylene/alpha olefin/diene terpolymer and ethylene based polymers copolymerised with ethylenically unsaturated carboxyl, anhydride, ester or alcohol monomers; (A2) partially crystalline polymer blend containing at least one semi-crystalline component and at least one low crystalline to amorphous component, both components of said partially crystalline polymer blend being ethylene based elastomeric polymers of monomers selected from ethylene and alpha-olefin, diolefin and vinyl polar monomers copolymerisable therewith; and

(A3) ethylene/alpha olefin copoiymers and ethylene/ alpha olefin/diene terpolymers together with a cross-linking agent; and

(B) a component being one or more of ethylene/epoxy copoiymers and ethylene/epoxy polymers containing units derived from other monomers. Component (A) achieves a stronger bonding/interaction with component (B) , and this leads to increased impact resistance and ductility (reduced brittleness) , particularly at low temperature, of the blend.

By "functionalised" it is meant that the chemical reactivity of component (A)' with the epoxy groups of component (B) has been increased. This may be achieved by incorporating in component (A) functional groups which are reactiv- to epoxy groups. By "partially crystalline polymer blends" is meant blends of two or more ethylene-containing elastomers wherein at least one of such elastomers is sufficiently crystalline to interact with component (B) and at least one of which is sufficiently low in crystallinity to provide the impact improvement. The low crystalline component should preferably have a crystallinity less than about 55 wt %.

Suitable as the partially crystalline polymer are any homo-, co-, terpoly ers based on ethylene and having an E-modulus less than 150 kPA (kilo-Pascals) . Included are ethylene with ^"alpha-olefins; dj.olefins; vinyl esters, acids/anhydrides, amides, etc. The amorphous, low crystallinity polymers are suitably the EP/EPDM type, optionally with other alpha-olefins such as 1- butene and 1-hexane.

The polyesters suitable for use herein may be any of the linear or branched saturated polyesters known to those skilled in this art. Generally, the polyesters will comprise linear saturated polyesters derived from C^C._g alkylene glycols such as ethylene glycol, propylene glycol, 1,4-butanediol, etc., including cycloaliphatic glycols, such as 1,4- cyclohexanedimethanol, and mixtures of any of these glycols with one or more aromatic dicarboxylic acids. Preferably, the polyesters will comprise polyf^-C₈ alkylene terephthalates) prepared by known techniques, such as the transesterification of esters of terephthalic acid alone or mixtures of esters of terephthalic acid and isophthalic acid, with the glycol or mixture of glycols and subsequent polymerization, by heating the glycols with the free acids or which halide derivatives thereof, and similar processes. These methods are described in U.S. Patents No. 2,465,319 and No. 3,047,539 incorporated herein by reference, and elsewhere. In addition, blends of one or more of these polyesters or copolyesters may be employed. A suitable poly(1,4-butylene terephthalate) resin is commercially available from General Electric Company under the trade designation VALOX 315; and poly(ethylene terephthalate) resins are also extremely well known and are abundantly available commerially.

Thermoplastic polyesters which are preferred in the blend of the present invention include PET (polyethylene terephthalate) , PBT (polybutylene terephthalate) and polycyclohexane terephthalate and thermoplastic polycarbonates.

Thermoplastic polycarbonates which may be used in the blend of the present invention include those possessing recurring structural units of the formula:

where A is a divalent aromatic radical. Polycarbonates which are widely used in engineering plastics applications have the typical general formula:

where R¹ and R² are, independently, hydrogen, alkyl or phenyl; X¹ and X² are independently hydrogen, halogen (e.g. chlorine or bromine), alkyl, alkenyl or alkaryl (optionally substituted) ; p and r represent the total number of substituents (other than hydrogen) on the rings and are, independently, integers from 0 to 4; and n represents the total number of monomer units in the polymer and typically is an integer of at least 30. The alkyl and alkenyl groups preferably have from 1 to 10, more frequently 1 to 6, carbon atoms inclusive. Aryl is preferably phenyl.

Polycarbonate homopolymers and copoiymers commonly used in engineering plastics applications and which may be used in the present invention typically have a molecular weight (number average) of from 8000 to 200000 or even higher, but preferably from 10000.to 80000, and an intrinsic viscosity of from about 0.3 to 1.0 decilitres per gram as measured in methylene chloride at 25^βC.

The polycarbonate resins are, for example, prepared from dihydric phenols, including 2,2-bis(4- hydroxypheny1) propane (bisphenol A), bis-(4- hydroxypheny1)methane, 2,2-bis(4-hydroxy-3- methylpheny1)propane, 4,4'-bis(4-hydroxypheny1)heptane, 2,2-(3,5,3• ,5'-tetrachloro-4,4'-dihydroxypropane, 2,2- (3,5,3' ,5*-tetrabromo-4-dihydroxydiphenyl)propane, and 3,3'-dichloro-4,4'-dihydroxy-diphenyl)methane. Still other dihydric phenols which are also suitable for producing polycarbonates are disclosed in US-A- 2,999,835, 3,028,365, 3,334,154 and 4,131,575. The aromatic polycarbonates can be prepared using known processes, such as, for example, by reacting a dihydric phenol with a carbonate precursor, e.g. phosgene, in accordance with the techniques set forth in the above cited patents and in US-A-4,018,750 and 4,123,436, or by transesterification processes such as those disclosed in US-A-3,153,008.

Also intended to be included within the term polyester as used herein are aromatic polyestercarbonates derived from a mixture of a dihydric phenol, a dicarboxylic acid or acid chloride and phosgene, for example, as disclosed in US-A-3,169,131 as well as branched polycarbonates such-as disclosed in US- A-4,001,184. The term polycarbonate as used herein is also intended to include blends of two or more aromatic polycarbonates, including any of those which have been described. There may also be utilized a blend comprising one or more of the above polyesters.

The epoxy-containing polymer (B) may be one or more of ethylene/epoxy copoiymers and ethylene/epoxy polymers containing units derived from other monomers. Thus, for example, (B) may be a copolymer of ethylene and an epoxy monomer or a terpolymer of ethylene/epoxy monomer with ethylenically unsaturated polar monomers such as vinyl esters, vinyl alcohols and acrylamides. The ethylene content for such terpolymers should preferably exceed 35 wt % to allow for ethylene segment interaction with elastomeric co-components.

The epoxy monomer may be, for example, a glycidyl ether or ester, an alicyclic epoxide or an epoxy compound of the general formula:

in which R₁, R₂, R₃ and R₄ may independently be hydrogen, a saturated organic radical e.g. alkyl or an unsaturated organic radical e.g. alkenyl, with the proviso that at least one of R._|- ₄ must be unsaturated. A simple example of such an epoxy compound is:

0 /\ CH₂ =CH-R-HC-CH₂

where R is an organic radical, for example alkylene. Preferably the epoxy-containing monomer is glycidyl acrylate or glycidyl methacrylate. A preferred epoxy- containing polymer is a copolymer of ethylene and glycidyl methacrylate (GMA) , containing from 7 to 17, preferably from 10 to 14, weight percent of GMA. The epoxy-containing copolymer may be a terpolymer containing a vinyl polar monomer, for example an ester of acrylic or methacrylic acid, such as methyl, ethyl, propyl or butyl acrylate or methacrylate. The vinyl ester may for example be incorporated in the copolymer in an amount up to 25 percent by weight depending on the nature of (A) . The epoxy-containing copolymer may be a terpolymer containing acrylamides, e.g. methacrylamide.

In general, components where no vinyl ester monomers are present are preferred since their glass transition temperatures are lower and their interaction with the polyolefin core is better giving increased impact strength. In any case, the ethylene content should be sufficient to provide for interaction with the elastomer. A content of for example greater than 35 wt % is preferred.

The basic components (A) which may be used in the present invention cover a broad range.

The basic components (Al) of blends according to the invention are ethylene/alpha olefin copolymer rubbers, optionally including polyene units as in corresponding terpolymer rubbers which include an additional polyene monomer such as non-conjugated diene.

The alpha-olefins suitable for use may be branched or straight chained, cyclic, and aromatic substituted or unsubstituted, and are preferably ^-C^ alpha-olefins. Mixed olefins can be used (e.g., mixed butenes) .

The alpha-olefin copolymer rubbers, when substituted, should not be aromatic substituted on the 2-carbon position (e.g. moieties such as CH₂ =CH-phenyl should not be employed) , since such an aromatic group interferes with the subsequent desired polymerization. Illustrative of such substituted alpha-olefins are compounds of the formula H₂ C=CH-C_nH_2n-X wherein n is an integer from 1 to 20 carbon atoms (preferably to 10 carbon atoms), and X comprises aryl, alkaryl or cycloalkyl. Exemplary of such X substituents are aryl of 6 to 10 carbon atoms (e.g. phenyl, naphthyl and the like) , cycloalkyl of 3 to 12 carbon atoms (e.g. cyclopropyl, cyclobutyl, cyclohexyl, cyclooctyl, cyclodecyl, cyclododecyl and the like), alkaryl of 7 to 15 carbon atoms (e.g. tolyl, xylyl, ethylphenyl, diethylphenyl, ethylnapthyl and the like). Also useful are alpha-olefins substituted by one or more such X substituents wherein the substituents(s) are attached to a non-terminal carbon atom, with the proviso that the carbon atom so substituted is not in the 1- or 2-carbon position in the olefin, in addition to alkyl-substituted bicyclic and bridged alpha-olefins of which C₁-C₉ alkyl substituted norbornenes are preferred (e.g. 5-methyl-2- norbornene, 5-ethyl-2-norbornene, 5-(2'-ethylhexyl)-2- norbornene and the like) .

Illustrative non-limiting examples of preferred alpha-olefins are propylene, 1-butene, 1-pentene, 1- hexene, 1-octene and 1-dodecene. The ethylene is generally contained in component (Al) in an amount of from 40 to 90 wt%, more preferably from 45 to 85 wt%.

The polymer may optionally contain a third type of polymer chain monomer which is an easily polymerizable polyene such as a non-conjugated diene. Non-conjugated dienes suitable for the purposes of the present invention can be straight chain, hydrocarbon di-olefins or cycloalkenyl-substituted alkenes, having from 6 to 15 carbon atoms, for example:

I. straight chain acyclic dienes, such as 1,4- hexadiene and 1,6-octadiene; II. branched chain acyclic dienes, such as 5- methyl-l,4-hexadiene 3,7-dimethyl-l,6-octadiene, 3,7- dimethyl-l,7-octadiene and the mixed isomers of dihydro- myricene and dihydro-ocinene;

III. single ring alicyclic dienes, such as 1,3- cyclopentadiene, 1,4-cyclohexadiene, 1,5-cyclo-octadiene and 1,5-cyclododecadiene;

IV. multi-ring alicyclic fused and bridged ring dienes, such as tetrahydroindene, methyl- tetrahydroindene, dicyclopentadiene, bicyclo-(2.2.1)- hepta-2,5-diene, alkenyl, alkylidene, cycloalkenyl and cycloalkylidene norbornenes, such as 5-methylene-2- norbornene (MNB) , 5-propenyl-2-norbornene, 5- isopropylidene-2-norbornene, 5-(4-cyclopentenyl)-2- norbornene, 5-cyclohexylidene-2-norbornene and 5-vinyl- 2-norbornene;

V. cycloalkenyl-substituted alkenes, such as allyl cyclohexene, vinyl cyclooctene, allyl cyclodecene and vinyl cyclododecene.

Of the non-conjugated dienes typically used, the preferred dienes are dicyclopentadiene, 1,4-hexadiene, 5-methylene-2-norbornene and 5-ethylidene-2-norbornene. Particularly preferred diolefins are 5-ethylidene-2- norbornene (ENB) and 1,4-hexadiene. The non-conjugated diene is preferably present in the polymer in an amount of from 0.5 to 15 wt% more preferably from 1 to 10 wt%, e.g. 5 wt%. The most preferred components (Al) in accordance with the invention are ethylene/propylene monomer copolymer rubber (EPM) and ethylene/propylene/diene terpolymer rubber (EPDM), which terms are used herein in accordance with their ASTM designations. As noted above, functionalisation of component (A) may be achieved by incorporating a functional group which is reactive to epoxy groups in component (A) .

The functional group may be copolymerised with the other monomeric components, or it may be grafted onto the pre-formed polymer. Preferably the functional group is grafted on the pre-formed polymer.

If a pre-formed polymer is used as a base for the graft, this polymer may be an ethylene/alpha olefin co- or ter-polymer rubber as described hereinbefore. Alternatively, the pre-formed base for the graft may be an ethylene/vinyl ester copolymer. The vinyl ester monomer may be an ester of acrylic or methacrylic acid as described above in relation to Component (B) .

The functional group reactive to epoxy is preferably an unsaturated mono- or di-carboxylic acid or its anhydride such as maleic acid/anhydride, itaconic acid/anhydride, acrylic acid or ethacrylic acid. When the basic polymer is (Al) , the dicarboxylic acid or anhydride functional groups are preferred; when it is (A2) , then the mono-carboxylic acid functional groups are preferred. Preferably the polymer is an EPR on which has been grafted MANH. Suitably the polymer (Al) or (A2) contains from 0.1 to 2 percent, preferably 0.2 to 1 percent, by weight of grafted groups such as MANH.

The degree of functionality depends on the concentration of epoxy groups in the polymer (B) , since there must be sufficient epoxy groups present after reaction with the functional groups of (Al) and/or (A2) to give the necessary interaction with the polyester phase.

Without being limited to any theoretical explanation, it is believed that the following mechanism(s) might apply:

The epoxy component (B) and the elastomeric component (A) may form a single phase or, more usually, will form a core-shell structure in which the component (B) forms a shell around a core of component (A) . When there is a core-shell structure, modifier dispersed in the polyester commonly forms particles, the majority (i.e. at least 50%, preferably at least 80%, more preferably at least 90%) of which comprise a core of component (A) and a shell of component (B) . In the blends of the invention the core-shell particles are preferably below 5 micrometres, more preferably less than 1 micrometre, in diameter for optimised impact property improvement. The bond between component (B) and elastomer (A) may be covalent (when elastomer (A) carries functional groups reactive with epoxy groups or when a mixture of components A and B are cross-linked e.g. using peroxide) or may be achieved by Van der Waals interaction between the polyolefinic backbone of the epoxy component (B) and the crystalline regions of the partially crystalline elastomer (A) . In all cases, the interaction of (A) with (B) will be significantly stronger than when component (A) is unfunctionalised and wholly amorphous.

The epoxy groups of component (B) react with terminal acid or ester groups of the polyester to provide covalent bonds therewith. Thus, component (B) provides a strong bond between the polyester and the elastomer (A) .

The functionality (type or concentration) of the copoiymers (Al) and (A2) should be such that the graft copolymer formed on reaction with component (B) will contain unreacted epoxy groups. The polyester then interacts with these unreacted epoxy groups to form a graft copolymer as described hereinbefore.

The good adhesion between component (A) and component (B) and between component (B) and the polyester ensures that the polyester benefits from the elastomeric properties of the modifier

As indicated above the object of the present invention is also achieved when component (A) is partially crystalline. Thus, component (A) may be semi- crystalline or a mixture of amorphous and semi- crystalline. It is particularly preferred that component (A) be composed of an amorphous and a semi- crystalline component. Such a partially crystalline component (A) appears to be co-crystallised with component (B) . The impact improvement is increased with decreasing crystallinity of the modifier component. Thus, the disadvantages of partially crystalline elastomer can be offset by addition of a low crystallinity/amorphous component. This gives a strong van der Waals interaction between components (A) and (B) , the interaction being stronger than that between a solely amorphous component (A) and component (B) , thus leading to improved impact strength and ductility.

The situation of (a) having functional groups in component (A) , (b) cross-linking a mixture of (A) and (B) with, e.g. peroxide, or (c) having a partially crystalline form of component (A) are not mutually exclusive. Combinations thereof may be used. In all cases there is a substantially increased bonding interaction between (A) and (B) which leads to the above-mentioned improved properties.

In the modifier the weight ratio of (A) to (B) is preferably from 1:1 to 20:1, more preferably 2:1 to 10:1, for example 3:1. The weight ratio of polyester to modifier in the blend of the invention is preferably from 99:1 to 60:40, more preferably from 90:10 to 70:30 and is typically about 80:20.

According to another aspect of the present invention, there is provided a process for preparing a polyester blend as hereinbefore defined, which process comprises blending a polyester with ah impact improving agent comprising a component (A) as defined above and a component (B) as defined above. However, the impact improving agent may be formed in the polyester in situ. Thus, according to another aspect of the present invention, there is provided a process for producing a thermoplastic polyester blend according to the invention, said process comprising mixing components (A) and (B) as defined above with a polyester.

Preferably the blend is formed in a two step process in which the modifier components are first blended together; the polyester is melted and the modifier is mixed into the melted polyester to form a homogeneous (ie. uniform) mixture.

According to a further aspect of the present invention there is provided an impact strength improving agent comprising

(A) an elastomeric component; and

(B) a component being one or more of ethylene/epoxy copoiymers and ethylene/epoxy polymers containing units derived from other monomers said elastomeric component (A) being cross-linked to said component (B) or being a partially crystalline polymer blend containing at least one semi-crystalline component and at least one low crystalline to amorphous component, both components of said partially crystalline polymer blend being ethylene based_, elastomeric polymers of monomers selected from ethylene and alpha-olefin, diolefin and vinyl polar monomers copolymerisable therewith.

There is also provided an impact strength improving agent comprising:

(A) an elastomeric component which is one or more of (Al) functionalised ethylene/alpha olefin copolymer, functionalised ethylene/alpha olefin/diene terpolymer and ethylene based polymers copolymerised with ethylenically unsaturated carboxyl, anhydride, ester or alcohol monomers; (A2) partially crystalline polymer blend containing at least one semi-crystalline component and at least one low crystalline to amorphous component, both components of said partially crystalline polymer blend being ethylene based elastomeric polymers of monomers selected from ethylene and alpha-olefin, diolefin and vinyl polar monomers copolymerisable therewith; and

(A3) ethylene/alpha olefin copoiymers and ethylene/ alpha olefin/diene terpolymers together with a cross-linking agent; and (B) a component being one or more of ethylene/epoxy copoiymers and ethylene/epoxy polymers containing units derived from other monomers. There is also provided the use of an impact strength improving agent as described above in improving the impact strength of a polyester.

In the modifier, when semi-crystalline component (A) is used, the weight ratio of semi-crystalline to amorphous component is preferably from 1:15 to 3:5, more preferably 1:10 to 1:3, especially 1:6.5.

The components (A) and (B) employed as impact improvers in the blends of the invention may be used in any combination of (Al) and/or (A2) with (Bl) and/or (B2) . However it is particularly preferred that the components are matched for optimum^ compatibility. Thus the components (A) with vinyl ester content are preferably matched with components (B) with vinyl ester content; and components (A) without vinyl ester content are preferably matched with components (B) without vinyl ester content. Particularly preferred combinations are (Al) and (Bl) or (A2) and (B2) .

The polyester blends may contain further additives such as dyes, pigments, fillers and reinforcing substances. Suitable dyes and pigments are well known in the art. Suitable fillers and reinforcing agents are e.g. glass fibres, talc, kaolin, clay and diatomaceous earth. The polyester blends may be moulded in the same way as polyester and/or polycarbonate may be moulded e.g. by melt extrusion or compression to form sheets or shaped articles. According to another aspect of the prevent invention there is provided a moulded article comprising a polyester blend as described above.

EXAMPLES Materials

Unless otherwise stated, the following abbreviations are used in the Examples: PBT 1: Polybutyleneterephthalate: POCAN 1505 (Bayer) , having melt flow rate (MFR) at 230^βC/10kg of 44 g/10 min.

PBT 2: VALOX 325 (General Electric) . PBT 3: VALOX 312 (General Electric) .

PBT 4: ORGATER (Atochem) .

EP1: ethylene/propylene rubber. 48 percent weight ethylene. Mooney Viscosity ML (1+8) at 127^*C = 63 (amorphous) VISTALON 606 (V 606) (Exxon Chemical) .

EP2: ethylene/propylene ethylidene norbornene terpolymer. 70 percent weight of ethylene. Mooney Viscosity ML (H4) at 125°C = 60 (Crystalline) VISTALON 7000 (Exxon Chemical) . EP-Mal: ethylene/propylene rubber grafted with 0.3 percent by weight MANH. MFR (230°C/10 kg) = 5 g/10 min EXXELOR VA IX 1820 (Exxon Chemical) .

EP-Ma2: ethylene/propylene rubber grafted with 0.7 weight percent MANH. MFR (230*C/10 kg) = 8 g/10 min EXXELOR VA 1801 (Exxon Chemical) .

PE-GMA: copolymer of ethylene and 12 weight percent glycidyl methacrylate. Melt Index, MI (190'C/2.16kg) = 3.3 g/10 min IGETABOND E (Sumitomo) . In the following Tables, "C" signifies a comparative example, "B" signifies blends according to the invention, "NB" signifies "not broken", i.e. ductile, and "—" signifies not measured.

[The terms "POCAN", "VISTALON", "EXXELOR" and "IGETABOND" are registered trade marks] EXAMPLE 1 Procedure

Modifier blends were prepared by mixing the EP-Ma with PE-GMA at 200°C in a laboratory two roll mill operated at 18 RPM for 5 to 7 minutes.

Using the same mixer at 250^*C PBT was first melted then the desired amount of modifier was added. After melting, the mixing was continued for a further 3 to 4 minutes to ensure homogeneity, i.e. uniform dispersion.

10 The resulting blends were compression moulded at 250°C for 3 minutes under 50 bars pressure. Ten specimens were cut from the resulting sheets.

The samples were tested for their tensile strength at break (TSB) [ASTM D638], their E-modulus (E-MOD)

15 [ASTM D638] and their room temperature notched Izod impact strength (RTNIIS) [ISO R180] .

The composition of the blends and their properties when moulded are shown in Table 1 where "C" indicates a reference example.

20

TABLE 1

35 EXAMPLE 2: Procedure

Conditions for preparing blends and moulding were the same as in Example 1.

The samples were tested for the tangent flexural modulus (MPa) , their room temperature notched izod impact strength (RTNIIS) [ISO R180], and their notched izod impact strength at 0°C, -10*C and - 20"C respectively in the same manner as Example 1.

The composition of the blends and their properties when moulded are shown in Table 2 where "C" indicates a comparative example. In this table EP-Ma2 is ethylene/ propylene rubber grafted with 0.1 percent by weight MANH.

As is clear from Table 2, those compositions in which the rubber component is functionalised with, for example, maleic anhydride, show a very marked improvement in impact behaviour (Notched Izod Impact) over those in which the rubber is not functionalised, at low temperatures (0"c and below) .

Example 3: Peroxide Partial Cross-linking 1. Preparation of graft copoiymers of Components (A) and (B) in the presence of peroxide

Ethylene propylene rubber (EP, Vistalon V606 of Exxon) and polyethylene glycidyl methacrylate (PE GMA, "Igetabond E" of Sumitomo) were blended together in the mixing chamber of a Haake internal mixer at 160*C at a blade speed of 40 rpm. After stablization of the torque, an amount of peroxide (LUPERSOL 130) was added, and the mixing continued for another 15 minutes.

The following Table 3 gives the composition of four graft copoiymers according to the invention prepared in the above manner (B20 and B21) , together with a comparative composition excluding peroxide (C19):-

TABLE 3

2. Impact Improvement of Polybutylterephthalate (PBT)

Blends of compositions B20 and B21 and Cll with PBT were prepared in the same way as Example 1. The thus prepared blends were then subjected to testing to determine the tangent flexural modulus and the Notched Izod Impact value at both 25^βC and -20*C in the same way as Example 1. The results are given in the following Table 4.

TABLE 4

POLYMER C22 B23 B24

PBT (POCAN 1505) 80 80 80

C27 20 B20 20 B21 20

Tangent Flexural Modulus 1524 1569 1465 (MPa)

Notched Izod Impact (kJ/m²) 25"C NB NB NB -20"C 33.2 NB NB

EXAMPLE 4: Peroxide Partial Cross-Linking

Under similar conditions and testing regimes to Example 1, with substitution of the appropriate components the following results were obtained: Table 5

PBT: Pocan 1505 (BAYER) EP: Vistalon 606 (EXXON) PE-GMA: Igetabond E (SUMITOMO) C = Comparison

Table 5 clearly shows the low temperature Impact strength improvement that occurs on partially cross-linking the elastomeric and epoxy components.

EXAMPLE 5: Semi-crystalline elastomeric/rubber component

An amorphous ethylene propylene rubber, a semi- crystalline EPR or EPDM and a EGMA were blended together in a mixing chamber of a HAAKE internal mixer at 160^βC at a blade speed of 40 rpm. After stabilization of the torque, the blend is used.

The following Table 6 gives the composition of six blends according to the invention. TABLE 6

10

Blends of compositions PI to P9 with PBT were prepared. The thus prepared blends were then subjected to testing to determine the tangent flexural modulus and the notched Izod Impact value at -20^*C in the same way

15 as Example 1. The results are given in the following Table 7:

TABLE

The morphology of the blends shows particles of size smaller than 2 microns.

EXAMPLE 6: Semi-crystalline elastomeric/rubber component

Similarly to Example 4 the following results were obtained: TABLE 8

Table 8 shows blends incorporating glass-fiber filler (GF 429 Y2 (O.C) ) .

Claims

Claims :

1. A polyester blend including an impact modifier which comprises: (A) an elastomeric component; and

2. A polyester blend including an impact modifier which comprises:

(A) an elastomeric component which is one or more of (Al) functionalised ethylene/alpha olefin copolymer, functionalised ethylene/alpha olefin/diene terpolymer and ethylene based polymers copolymerised with ethylenically unsaturated carboxyl, anhydride, ester or alcohol monomers; (A2) partially crystalline polymer blend containing at least one semi-crystalline component and at least one low crystalline to amorphous component, both components of said partially crystalline polymer blend being ethylene based elastomeric polymers of monomers selected from ethylene and alpha-olefin, diolefin and vinyl polar monomers copolymerisable therewith; and (A3) ethylene/alpha olefin copoiymers and ethylene/ alpha olefin/diene terpolymers together with a cross-linking agent; and (B) a component being one or more of ethylene/epoxy copoiymers and ethylene/epoxy polymers containing units derived from other monomers.

3. A blend as claimed in claim 1 or claim 2 wherein said component (A) is ethylene/propylene rubber or ethylene/propylene/diene terpolymer rubber comprising functional groups which are reactive to epoxy groups.

4. A blend as claimed in any one of claims 1 to 3 wherein said functional groups are derived from an unsaturated mono- or di-carboxylic acid or the anhydride thereof.

5. A blend as claimed in claim 4 wherein said functional groups are derived from maleic acid or its anhydride, itaconic acid or its anhydride, acrylic acid or methacrylic acid.

6. A blend as claimed in any one of claims 2-5 wherein the cross-linking agent specified in component (A) is a peroxide.

7. A blend as claimed in claim 1 wherein component (A) comprises a partially crystalline polymer blend in which the ratio of semi-crystalline: low- crystalline to amorphous component is 1:15 to 3:5.

8. A blend as claimed in claim 7, wherein the ratio of semi-crystalline: low-crystalline to amorphous component is 1:10 to 1:3.

9. A blend as claimed in any one of the preceding claims wherein the weight ratio of component (A) to component (B) is from 1:1 to 20:1.

10. A blend as claimed in claim 9 wherein the weight ratio of component (A) to component (B) is from 2:1 to 10:1.

11. A blend as claimed in any one of the preceding claims in which the polyester is a polycarbonate.

12. A blend as claimed in any one of the preceding claims wherein the weight ratio of polyester to the impact improving agent is from 99:1 to 60:40.

13. A blend as claimed in claim 14 wherein the weight ratio of polyester to the . impact improving agent is from 90:10 to 70:30.

14. A process for preparing a polyester blend as claimed in claim 1 which process comprises blending a polyester with an impact improving agent as defined in claim 1.

15. A process for preparing a polyester blend as claimed in claim 1 which process comprises mixing components (A) and (B) as defined in claim 1 with a polyester.

16. An impact modifier comprising

(A) an elastomeric component; and

17. An impact modifier comprising

(A) an elastomeric component which is one or more of

(Al) functionalised ethylene/alpha olefin copolymer functionalised ethylene/alpha olefin/diene terpolymer and ethylene based polymers copolymerised with ethylenically unsaturated carboxyl, anhydride, ester or alcohol monomers; (A2) partially crystalline polymer blend containing at least one semi-crystalline component and at least one low crystalline to amorphous component, both components of said partially crystalline polymer blend being ethylene based elastomeric polymers of monomers selected from ethylene and alpha-olefin, diolefin and vinyl polar monomers copolymerisable therewith; and (A3) ethylene/alpha olefin copoiymers and ethylene/ alpha olefin/diene terpolymers together with a cross-linking agent; and (B) a component being one or more of ethylene/epoxy copoiymers and ethylene/epoxy polymers containing units derived from other monomers.

18. A moulded article comprising a polyester blend as claimed in claim 1.

19. The use of an impact modifier as claimed in claim 16 or 17- in improving the impact strength of polyester.