CA2050526A1

CA2050526A1 - High impact thermoplastic molding compositions

Info

Publication number: CA2050526A1
Application number: CA 2050526
Authority: CA
Inventors: Doris Zeltner; Friedrich Seitz; Klaus Muehlbach; Heike Feldmann
Original assignee: Individual
Current assignee: BASF SE
Priority date: 1990-09-14
Filing date: 1991-09-03
Publication date: 1992-03-15
Also published as: EP0475157A2; JPH04258664A; EP0475157A3; DE4029190A1

Abstract

O.Z. 0050/41887 Abstract of the Disclosure: The molding composition comprises, based on the sum total of A, B, C and D, A: not less than 5 % by weight of a polyphenylene ether A
B: not less than 5 % by weight of an impact modified polystyrene B
C: 1 - 20 % by weight of a block copolymer C of styrene and a conjugated diene D: 1 - 20 % by weight of a copolymer D obtained by grafting styrene onto an EPDM rubber.

Description

t'~ t~ 3 1, _i f~
O.Z. 0050/41887 Hiqh impact thermoplastic moldinq compositions The present inver.tion relates to thermoplastic molding compositions comprising polyphenylene ethers, impact modified polystyrene and a block copolymer of styrene and a diene. Such molding compositions are des-cribed for example in the following references (1) to (7):
~1) DE 20 00 118 (2) DE 22 55 930 (3) DE 27 50 514 (4) J5 9140-257 (5) EP 52 854 (6) EP 83 049 (7) DE 25 06 094.
Polymer mixtures which contain polyphenylene ethers and block rubbers of aromatic vinyl compounds and dienes are disclosed for example in (1) and (2). The disadvantage of the molding compositions is a lack of thermal stability. Moreover, ready-produced articles which contain higher proportions of hydrogenated block rubber show signs of delamination; that is, long flow paths give rise to inhomogeneous layer structures.
Reference (3) describes an impact resistant thermoplastic composition which in addition to a poly-phenylene ether and high impact polystyrene contains amixture of an olefinic resin (e.g. EP) and a linear or radial block copolymer of an aromatic vinyl compound and a diene. However, the molding compositions have the disadvantage that the multiaxial toughness is insufficient.
Reference (4) describes an impact resistant polyphenylene ether resin composition which in addition to a polyphenylene ether and high impact polystyrene contains a two-block copolymer of an aromatic monovinyl compound and an olefinic block and also a styrene-grafted ethylene-propylene ~opolymer. Again these molding - 2 - O.Z. 0050/41887 compositions have the disadvantage of delam.ination in processing.
References (5), (6~ ancl (7) describe mixtures of polyphenylene ethers and high impact polystyrene which contain a styrene-grafted EPDM rubber as essential component. Once again, if the proportion of EPDM rubber is high, the ready-produced article is found to be prone to delamination. Also, the multiaxial toughness is inadequate.
It has now been found that molding compositions which are based on blends of polyphenylene ethers (PPEs~
and high impact polystyrene (~IPSJ and additionally contain a block copolymer of styrene and a diene and also a styrene-modified ethylene-~-olefin polyene terpolymer have excellent properties. Of note is the high impact strength and the multiaxial toughness at low tempera-tures~ as well as the excellent weather resistance and thermooxidation resistance coupled with good heat resis-tance and good flowability. The molding compositions can be processed into test specimens which are free of delamination.
Accordingly, the present invention provides a molding composition comprising - based on the sum total of A, B, C and D -A: not less than 5, preferably 20-80, % by weight of a polyphenylene ether A
B: not less than 5, preferably 20-80, % by weight of an impact modified polystyrene B
C: 1 - 20, preferably 3-15, % by weight of a block copolymer C of styrene and a conjugatPd diene D: 1 - 20, preferably 3-15, % by weight of a copolymer D obtained by grafting styrene onto an EPDM rubberO
There now follow specific remarks concerning the constituents of the molding composition of the present invention~
Component A:
The likely polyphenylene etherq A are known per - 3 - O.Z. 0050/41887 se and are preferably prepared by oxidative coupling of phenols which are disubstituted ~n the o-position.
Examples of s~lbstituent:s are halogen atoms such as chlorine or bromine and alkyl groups of from 1 to 4 carbon atoms which preferably have no ~-disposed tertiary hydrogen atom, e.gO methyl, ethyl, propyl and butyl. The alkyl groups may in turn ~e substituted by halogen such as chlorine or bromine or by hydroxyl.
Further examples of possible substituents are alkoYy, preferably of up to 4 carbon atoms, and phenyl which may be suhstituted by halogen and/or alkyl. It is also possible to use copolymers of various phenols, such as copolymers of 2,6-~imethylphenol and 2,3,6-trimethyl-phenol. It is of course also possible to use mixture of various polyphenylene ethers.
Preference is given to those polyphenylene ethers which are compatible with, i.e. wholly or substantially soluble in, aromatic vinyl polymers (cf. A. Noshay r ~lock Copolymers, pages 8 to 10, Academic Press~ 1977, and 20 O. Olabisil Polymer-Polymer Miscibility, 1979, pages 117-189).
Examples of polyphenylene ethers are poly(2,6-dilauryl-1,4-phenylene ether), poly(2,6-diphenyl-1,4-phenylene ether), poly(2,6-dimethoxy-1,4-phenylene ether), poly(2,6-diethoxy-1,4~phenylene ether), poly(2-methoxy-6-ethoxy-1,4-phenylene ether), poly(2-ethyl-6-stearyloxy-1,4-phenylene ether), poly(2,6-dichloro-1,4-phenylene ether), poly(2-methyl-6-phenylene-1,4-phenylene ether~, poly(2,6-dibenzyl-1,4-phenylene ether), poly~2-ethoxy-1/4-phenylene ether), poly(2-chloro-1,4-phenylene ether), poly~2,5-dibromu-1,4-phenylene ether).
Preference is given to using polyphenylene ethers where the substituents are alkyl groups of from 1 to 4 carbon atoms, such as - 4 - O.Z. 0050/41887 poly(2,6-dimethyl-1,4-phenylene ether), poly(2,6-diethyl-1,4-phenylene ether), poly(2-methyl-6-ethyl-1,4-phenylene ether), poly(2-methyl-5-propyl-1,4-phenylene ether), poly(2,6-dipropyl-1,4-phenylene ether) and poly(2-ethyl-6-propyl-1,4-phenylene ether)~
It is also possible ~o use graft copolymers of polyphenylene ethers and aromatic vinyl polymers such as styrene, ~-methylstyrene, vinyltoluene and chlorostyrene.
Suitable polyphenylene ethers generally have an intrinsic vlscosity ~5p/C of 0.2-0~7 dl/g, measured in chloroform at 25Co This corresponds approximately to the molecular ~eight range 10,000-60,000.
The molding compositions of the pre~ent invention are preferably based on poly~2,6-dimethyl-1,4-phenylene ether).
Component B.
Component B in the molding material according to the invention is impact resistant polystyrene resin, which, for the purposes of the present invention, is two-phase impact resistant polystyrene built up from a hard matrix and a soft phase. This polystyrene is generally known.
The hard matrix of component B comprises a styrene polymer and makes up :Erom 60 to 95 % by ~eight, preferably 80 to 95 % by weight, based on component A. A
suitable monomer for the hard matrix is, in particular, styrene or p-methylstyrene or mixtures of substituted styrenes, but the exclusive use of styrene is preferredf and the hard matrix thus preferably consists of poly-styrene.
The hard matrix is produced in a conventional manner during the preparation of component B by polymerizing, thermally or by means of free radicals, a soft phase, ieO a rubber, together with the styrene monomer later making up the hard matrix, to form graft copolymers of the rubber ~soft phase) and ungrafted ?

- 5 - O.Zq 0050/41887 styrene polymers, the hard matrix.
The soft phase is t:hus a graft copolymer comprising the monomer~s) of the resin matrix, ie. in particular styrene~ on a rubber or on a mixture of rubbers.
The hard matrix can have a viscosity number ySp/c in the range from 50 to 140, in paxticular in the range from 70 to 120. This corresponds to mean molecular weights (Mw) in the range from 100,000 to 350,000, in particular from 150,000 to 300,000.
In the end, the soft phase is finely dispersed in the hard matrix. The way in which a soft phase can be dispersed in a hard matrix is known. The soft phase is present in the hard m~trix in a proportion of from 3 to 40 % by weight, preferably from 5 to 20 % by weight, and has a mean particle size in the range from 0.01 to 10 ~m, preferably in the range from 0.3 to 8 ~m. The particle size range mentioned is the mean particle size determined by counting the nu~ber of particles shown in an electron photomicrograph, ie~ a number average. The weight average particle size of the soft component should be within the range from 0.2 to 6 ~m. This weight average particle size is to be understood as defined in DE-A-30 35 643. Of particular suitability are impact modified polymers where the weight average particle size is within the range from 0.5 to 4 ~m. The particles can he cellular or capsule particles. Such particles are described for example in A.
Echte, Styrolpolymere, Winnacker-Kuchler, Chemische Technologie, Volume 6l Organische Technologie II, Carl Hanaer Verlag, Munich-Vienna 1982, pp. 373-3~0.
The preferred soft phase is polybutadiene and the graft copolymer thereof with styrene. Polybutadi nes of the medium- or high-cis type having molecular weights in the range from 70,000 to 450,000 (weight average~ are particularly suitable. Medium-cis polybutadienes having molecular weights of from 300,000 to 400,000 are preferred~

- 6 - O.Z. 0050/41887 - The impact-resistant styrene polymer is prepared in bulk, solution or suspension in a conventional manner (cf. Ullmanns Encyclopadie der Technischen Chemie, volume 19, pages 265-272, Verlag ('hemie, WeinheLm 1980).
Possible comonomers for preparing copolymers are for example (meth)a~rylic acid, (meth)acrylic esters having from 1 to 4 carbon atoms in the alkyl moiety, acrylonitrile and maleic anhydride and also maleimides.
The level of comonomer in the styrene polymer varies with the structure of the comonomer. The decisive determinant for the level of comonomer in the copolymer is the miscibility of the copolymer with the polyphenylene ether. Sl-ch miscibility limits are known and described for example in U5 ~atents 4,360,618 and 4,405,753 and in J.R. Fried, G.A. Hann, Polymer Eng. Sci., 22 (1982j, 705.
~he copolymers are prepared for example as described in Ullmanns Encyklopadie der techn. Chemie, volume 19, pages 27~ ff, Verlag Chemie, Weinheim (1980). The copolymers generally have weight average molecular weights (M~) of from 10,000 to 300,000, which can be determined in a conventional manner~
The most commonly employed methods for preparing impact modified styrene polymers are bulk or solution polymerization in the presence of a rubber, as described for example in US Patent 2,694,692, and bulk suspension polymerization as described for example in US Patent 2,862,906.
The rubbers used are the natural or synthetic rubbers which are customarily used for the impact modifi-cation of styrene polymers. Suitable rubbers for the purposes of the present invention, besides natural rubber, are for example polybutadiene, polyisoprene and copolymers of butadiene and/or isoprene with styrene and other comonomers which have a glass transition tempera~
ture, determined in accordance with R.H. Illers and H. Breuer, ~olloidzeitschrift 190 ~1963), 16-34 (1), of below -20C. However, it is also possible to use - 7 - O.Z. 0050/418~7 acrylate, ~PDM, polybutylene and polyoctenamer rubbers.
Component C
The block copolymers used according to the invention are elas-tomeric copolymers of the type AB, ABA' or (A/B)~-X, where A and A' are each a non-elastomeric polystyrene block and B is an elastomeric hydrogenated and/or non-hydrogenated block of a conjugated diene, n is an integer of at least 3, and X is the radical of a multifunctional coupling agent via which the branchings (A-B) of the block copolymer are chemically bonded together.
These compounds are known per se from EP-A-95 098.
Instead of styrene it is possible to use side chain alkylated styrene, such as ~-methylstyrene, and ring substituted styrene, such as vinyltoluene, ethyl-vinylbenzene and others. Preference is given to using styrene alone.
Conjugated dienes which are particularly suitable for forming the polymers of the present invention are for example 1,3-butadiene and isoprene. In the preparation of block copolymers these dienes are used either alone or mixed with one another.
Preference is given to a non-hydrogenated block copolymer, particularly to a non-hydrogenated ABA' three-block copolymer whose end blocks have a molecular weight within the range of about 2,000 - 100,000 while the central block has molecular weight within the range from about 25,000 to about 100,000, the molecular weight of the central block being greater than that of the combined end ~locks.
The block copolymers are prepared for example using an organometallic initiator based on sodium or lithium or an organic derivative thereof. The initiator may be monofunctional or difunctional.
The block copolymers are present in the molding compositicn of the present invention in a weight - 8 - O.Z. 0050/41887 proportion of from 1 to 20 %, preferably from 3 to 15 %.
Component D
This co~ponent is a styrene-grafted ethylene/~-olefin/polyene terpolymer. Preferred ~-olefin~ contain from 3 to 10 carbon atoms, for example propylene, l-butene, l-pentene, l-hexene and 1-heptene~ Propylene is preferredO The polyenes used are preferably cyclic or open-chain non-conjugated compounds. Examples are 1,4-hexadiene, 1,6-octadiene, 2-methyl-1,5-hexadiene, 6-methyl-1,5-heptadlene, 7-methyl-1,~-octadiene, 11-ethyl-1,11-tridecadiene,9-ethyl-1,9-undecadiene,iso-prene, 1,4-pentadiene, 1,3-pentadiene, 1,4,9-decatriene, 1-phenyl-1,3-butadiene, p-diallylbenzene, 4-vinyl-1-cyclohexene, 1,3,5-trivinylcyclohexane, trans-1/2-divinylcyclohexane, 1,5-cyclooctadiene, 1,3,5-cyclo-heptatriene, 1,5,9-cyclododecatriene, 1,4-cyclo-heptadiene, cyclopentadiene, 2,2'-dicyclopentenyl-1,~-bis(cyclopenten-2-yl)butane, 4,7,8,9-tetrahydroindene, bicyclo[3,3,03octadiene-2,6-dicyclopentadiene, 2-methyl-2,5-norbornadiene, 5-methylene-2-norbornene, 5-ethylidene-2-norbornen~, 5-isopropylidene-2~norbornene, 5-isopropenyl-2-norbornene, 5-(2'-methyl-1'-propenyl)-2-norbornene, 5-(1',2'-dimethyl-1'-propenyl)-2-norbornene, 5-(2'-butenylj-2-norbornene, 6-methyl-5-(2'-butenyl)-2-norbornene, 6-(3'-cyclohexenyl)-2-norbornene, tricyclo-pentadieneand6-chloromethyl-5-isopropenyl-2-norbornene.
The grafting base comprises at least 10 % by weight of ethylene, about 10 - 90 % by weight of ~-olefin and 0.1 - 30 % by weight of polyene. Preference is given to at least 40 % by weight of ethylene, 10 - 60 % by weight of ~-olefin and 0.3 - 10 % by weight of polyene.
Particular preference is given to 50 - 85 % by weight of ethylene, 15 - 50 % by weight of ~-olefin and 1 - 7 % by weight of polyene~
Possible grafting agents are all the above-mentioned styrenes. Styrene itself is preferred.
To graft the EPDM rubber it is possible to use - 9 O.Z. 0050/41887 any customary polymerization technique, such a~ suspen-sion polymerization, emulsion polymerization, solution polymerization or bulk polymerization. Preference is given to emulsion polymerization. The styrene content of the end product is for example 5 - 70 ~ by weight~
preferably 5 - 50 ~ by weight, particularly preferably 5 - 30 ~ by weight.
Examples of the preparation of Component D may be found for example in EP-A-83 049 and EP-A-52 854.
Component D is present in the molding composition of the present invention in an amount of from 1 to 20 %
by weight, preferably 3 - 15 % by weight.
Component E
Further additives for possible inclusion in the molding composition of the present invention are cus-tomary, in general mineral, reinforcing materials, such as glass ~alls, mineral fibers, whiskers, mica or in particular glass fibers in amounts of for example up to 30 % by weight, based on 100 % by weight of the sum total of the constituents of the molding composition.
Additionally~ yet further additives, such as flameproofing agents, heat and light stabilizers, lubri-cants, demolding agents and colorants such as dyes and pigments, may be present in customary amounts. The flameproofing agents used are preferably phosphorus-containing compounds, such as phosphine oxides or phosphates.
Preparation of molding compositions The thermoplastic molding compositions of the present invention are advantageously prepared by mixing the components at 200-350C, preferably 250-300C, in customary mixing apparatus, for example kneaders, Banbury mixers and single-screw extruders, preferably in a twin-screw extruder. To obtain a homogeneous molding com-position, intensive mixing is necessary. The residencetime is generally within the range from 0.5 to 30 min., preferably from 1 to 5 min. The order of mixing the - 10 ~ O.Z. 0050/41887 components may be varied: selected components may be premixed or else all the components may be mixed together.
The molding compositions of the present invention are highly suitable for producing moldings of any kind, for example by injection or extrusion molding. They can also be used for producing films and sheetware by thermo-forming or blow molding.
The molding compositions of the present invention are noteworthy in particular for very good toughness combined with high heat resistance and good flowability.
Of special significance is the good weathering and thermooxidation resistance and the excellent appearance of the articles molded therefrom, which show no sign of delamination.
To illustrate the advantages of the molding compositions, the following properties are determined:
the melt flow index (MFI3 at 250C and under 21.6 kg in accordance with German standard specification DIN 53735; the Vicat temperature VST/B in accordance with German standard specification DIN 53460; the notched impact strength a~ in accordance with German standard specification DIN 53453; and the penetration energy DSTA
in accordance with German standard specification DIN 53443 at 20C and -40C.
The thermooxidation resistance was tested in terms of a penetration test. To this end, the penetration energy was measured on specimens which had been stored at 110C for 7 and 14 days respectively. The specimens were stored ~or this purpose in a ~eraeus through-circulation cabinet model UT 6200.
The delamination tendency was determined by examining the appearance of the fracture site of Roundels using the penetration test and by examining moldings after cross-hatching.
The sp~cimens were injection molded at 2aooc.
The operati~e and comparative examples were ~ O.~. 0050/41887 conducted using the following components:
Component A:
A(1): poly(2,6-dimethyl-1,4-phenylene ether) having a limiting viscosity of 0.50 dl/g measured in chloroform Component B:
B(1): high impact polystyxene 586 from BASF AG
containing 10 % by weight of butadiene.
Component C:
C(l) SBS three-block rubber Cariflex TR 1101 from Shell AG.
Component D:
D(1): 40 g of an EPDM polymer (Vistalon 7000 from EXXON) were introduced into a 500 ccm glass autoclave together with 200 ccm of water. To this were added in succession with stirring a solution of 0.2 g of benzoyl peroxide in 40 g of styrene and a solution of 1.2 g of polyvinyl alcohol in 40 g of water. The mixture was first stirred for one hour then left to stand at 90C for 6 hours and finally at 115C for 2 hours. The product was isolated by filtration and dried under reduced pressure (for producing molding compositions of the present invention).
D(2): styrene-modified EPDM polymer as per Example 8 of EP 52 854 (for producing molding compositions of the present invention).
D(3): Vistalon 7000 from Exxon (for comparison).
The operative and comparative examples are listed in Table 1 and the properties of the corresponding molding compositions in Table 2.

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Claims

1. A molding composition comprising - based on the sum total of A, B, C and D -A: not less than 5 % by weight of a polyphenylene ether A
B: not less than 5 % by weight of an impact modified polystyrene B
C: 1 - 20 % by weight of a block copolymer C of styrene and a conjugated diene D: 1 - 20 % by weight of a copolymer D obtained by grafting styrene onto an EPDM rubber.

2. A molding composition as claimed in claim 1, wherein block copolymer C is a non-hydrogenated three-block copolymer.

3. A molding composition as claimed in claim 1, containing further additives and assistants E.

4. A method of using a molding composition as claimed in claim 1 for producing moldings.