IE54381B1 - Polycarbonate-based thermoplastic polymer blends - Google Patents

Abstract

Thermoplastic polymer blends are prepared by mixing together an aromatic polycarbonate, one or more polyterephthalates derived from the condensation of terephthalic acid with a glycol of formula HO-(CH2)n-OH where n is from 2 to 10, and an olefin elastomer. The materials thus obtained have a high impact strength even at low temperature, a good solvent resistance, and a better processability than polycarbonate.

Description

Polycarbonate ts a resin known to possess exceptional nechanlcal characteristics, particularly 1n tarns of Inpact strength, but It has certain defects which prevent Its use In nany large-consunptlon applications, the main defects being a substantial brlttHng beyond a certain critical thickness, a very low resistance to nany organic solvents, and a poor Inpact strength at low tenperature.

These defects have greatly United the use of polycarbonate in one field, nanely the autonobile field, which requires naterlals of outstanding nechanlcal properties and of excellent resistance to those agents (petrol, lubricants, detergents, etc.) which habitually or accidentally cone into contact with the polycarbonate during Its operational life.

The prior art describes exanples of blends prepared by nixing a polycarbonate with a polyester (AU-55998, US-4188314, US-349485), or by nixing together a polycarbonate, a polyolefin and a third conponent-such as an acrylic polymer (US-4245058), a hydrogenated block copolymer (US-4122131), or an epoxidisable polydiene (GB-1149695). The prior art also describes a thermoplastic polymer blend (68-1007724) comprising at least 50% by weight of polycarbonate and not more than 50% of an olefin polymer which can be partially substituted by a polyester resin, such that the weight ratio of the olefin polymer to the polyester 1s always greater than unity. However, because of the substantial plasticising effect which polyolefins have : on polycarbonate, this gksnd has a rather low load distortion tenperature, this being -25438 a Uniting characteristic for many application, Including the automobile field.

According to the present Invention, there 1s provided a thermoplastic polymer blend comprising: (a) a polycarbonate of bisphenol A*, (b) one or more polyalkyleneterephthalates In which the number of carbon atoms of the alkylene radical 1s from 2 to 10; (c) an Impact energy absorption modifier selected from : (I) a copolymer of ethylene and propylene and a diene monomer; (II) a mixture of polyethylene and/or polypropylene with Impact energy absorption modifier (0 (III) a mixture of polyethylene and/or polypropylene with a polyethylenevlnylacetate copolymer; (IV) a mixture of polyethylene and/or polypropylene with Impact energy absorption modifier.

(I) and with a polyethylenevlnylacetate copolymer ; wherein components (b) and (c) are present In a quantity of from 5 to 50% by weight and such that the weight ratio of component (c) to component (b) 1s equal to or less than 1.

The polymer blends of the Invention have Improved thermal properties. Although they have an Impact strength which 1s very close to that of polycarbonate, compared with the latter they have an excellent solvent resistance, a low sensitivity with respect to thickness, and an Improved Impact strength at low temperature, and are easier to mould. -35438 1 The polymer blends and the products obtained from the· demonstrate physical, chemical and electrical characteristics which overall are better than those of polycarbonate when used either as such er in mixtures as described In the aforesaid patents.

The polyalkyleneterephthalates may be prepared by condensing terephthalic acid with a glycol such as one of general formula H0-(CH2)n - OH wherein n 1s from 2 to 10.

The polycarbonate used Is preferably one having an Intrinsic viscosity in methylene chloride at 20°C of from 0.46 to 1.2 dl/g.

Although not essential, best results are obtained by carrying out one or more premixing operations on the components, then reducing the resulting blend to granules, and then moulding the blend. The apparatus used for mixing 1s of no special Importance.

Thus single screw extruders, double screw extruders, Banbury mixers and all machinery normally used in Industrial practice are suitable for this purpose.

The thermoplastic polymer blend of the present invention can be 1n various forms such as In the form of powder, granules, spheres, discolds or other forms, prepared for example either by extrusion or by Injection.

The blend can contain various additives such as stabilisers, dyes, flame retarders, lubricants, and.fillers, (e.g. glass fibre, carbon fibre, asbestos fibre and glass woo)).

The Invention will now be Illustrated by the following Example, wherein blends 1, 10, 19 and 28 are not within the scope of the invention and are for purposes of comparison only. -454381 EXAMPLE Various polymer blends, whose compositions were given In the following Tables 1 to 6, were prepared. The component granules of each blend were dried and mixed, and extruded 1n a single screw extruder at a temperature of 270°c· The P°1ler blend obtained 1n this manner was then granulated and Injection-moulded at a temperature of from 260 to 28O°C depending upon the composition, and the mould temperature being 60°c· The following tests were carried out on the products obtained. (a) Izod notched bar Impact test (ASTM D 256-61) (b) Vicat softening point at S kg (ASTM D 1525-72); (c) Modulus of elasticity In bending (ASTM D 790-70) ; (d) Stress cracking test, I.e. at tests wherein tension Is applied 1n accordance with ASTM 0 638 to samples which had been previously subjected to 0.7Ϊ tensile deformation and Immersed for 2 hours 1n a 1:1 (voluaetrlc) mixture of toluene and Isooctane to which 15% of methyl alcohol had been added, the percentage retention of the ultimate tensile stress of the non-1mmer$ed sample then being measured.

The results obtained, and the results obtained for polycarbonate treated In the same way, are given 1n the following Tables 1 to 6. -554381 ο ΙΛ Si 4 3 81 g in g f—» in ι rx ι g CM O g Ot § CM g g X S438i Ο LA LA LA CM CM σ* is.

LO CM o o r* CM LA CM o LA LA LA LO t*» tn «r CM tn CM o © LO CM © CM o o rs to S rs rs CO tn LU (Δ < © LO LA tn LA g tn 1“ CM © g t co © CM LA Is IO © Ol o © CM o CM CO is LA rs.

LA o 13 81 co © m © CM Ο O © © © co in o Ss Q- Q. in m η *n in cm co w m co trt V ε © £ in © UJ X o ο ο CD in o CM © CM O o co o © CM CM O © CO o CM Ρ ci** 5 8 P cn <8 e •j UJ © in (/) a (Λ UJ _l w tn z UJ os z uj o h- M £ 2 8. £ 8 4 3 Β 1 CM m O •f· +> •f· ΙΛ a g m in cm cm ο Ο mt Ο CM in in in CM CM CM in in CM CM in in in CM CM CM m «— <*> r* r- in <Λ s δ CM o o in σι o o <*» o CM s CM O CM o o io o CM o o «r o CM in V) £ l·m ui en o & a UJ hz Σ2 pS Z ·“· UI I- z 2 X 43 31 ABREVIATIONS PC Polycarbonate PET polyetbyleneterephthalate EPR ethylene-propylene rubber EPDM ethylene-propylene-d1ene monomer terpolyaer PBT polybutyleneterephthalate PP polypropylene PE polyethylene EVA ethylene-vinylacetate copolymer

Claims (2)

1. A thermoplastic polymer blend comprising (a) a polycarbonate of bisphenol A; (b) one or more polyalkyleneterephthalates In which the number of carbon atoms of the alkylene radical Is from 2 to 10; (c) an Impact energy absorption modifier selected from: (I) a copolymer of ethylene and propylene and/or a terpolymer of ethylene, propylene and a diene monomer. (II) a mixture of polyethylene and/or polypropylene with Impact energy absorption modifier (1) (III) a mixture of polyethylene and/or polypropylene with a polyethylenevlnylacetate copolymer; (IV) a mixture of polyethylene and/or polypropylene with Impact energy absorption modifier (1) and with a polyethylenevlnylacetate copolymer; wherein components (b) and (c) are present 1n a quantity of from 5 to 50X by weight and such that the weight ratio of component (c) to component (b) 1s equal to or less than 1.

2. Each of polymer blends 2 to 9, 11 to 18, 20 to 27 and 29 to 58 as given In the foregoing Example.