CA1102479A

CA1102479A - Thermoplastic rubber compositions

Info

Publication number: CA1102479A
Application number: CA286,929A
Authority: CA
Inventors: Jochen Schnetger; Manfred Beck; Gunter Marwede; Gottfried Pampus
Original assignee: Bayer AG
Current assignee: Bayer AG
Priority date: 1976-09-18
Filing date: 1977-09-16
Publication date: 1981-06-02
Also published as: GB1582279A; DE2642053A1; ES462385A1; IT1090212B; FR2371479A1; PL200899A1; DD134237A5; DE2642053C2; SU645591A3; SE424331B; JPS5337754A; SE7710349L; PL104936B1; BE858783A; NL7710208A; FR2371479B1; BR7706195A

Abstract

THERMOPLASTIC RUBBER COMPOSITIONS

Abstract of the Disclosure Mixtures of isotactic polypropylene and sequential EPDM representing thermoplastic rubber compositions.

Description

This invention relat;es to -thermoplastic rubber compositions consisting of mixtures oE an isotactic polypropylene and an ethylene-propylene terpolymer ~EP~M), so-called saquenti~l copolymersbeing usecl as the EPDM-terpolymers~
German ~ffenlegungsschriften No. 2,202,706 and No. 2~202,738 have previously described mix-tures of isotactic polypropylene and ethylene-propylene or ethylene-prvpylene-diene rubbars which are either par-tial.ly cross-linked by the addition of vulcanising agent~ a-~ter m~ing or are produced with EPM or EPDM which has already been par-tially crosslinkedO
Un-fortunately, such mixtures do not satisfy all practical requiremen-ts because, in particular, their ~5 tensile streng-th values, their elongation at break values, ~hei.r tear propagation resistance values and also their hardness values, as measured at l00C are still in need of improvement ~
Mixtures of polyethylene with EPDM polymers with a crystallinlty of from 10% to 20~ are known from US Patent No. 3,919,358. Although these products show high ultimate tensile strengths9 their -thermal stability is inadequate on account of the low melting temperature o~ the polye-thylene.
Accordingly~ there is a need ~or pro~ucts which combine a high tensile strangth, elongation at break and flexib~ ty Le A l7 503 at low temperatures with a high thermal stability.
It has now been found tha-t mixt~res of isotactic polypropylene with sequential EPDM sa-tisfy these re~uirements both in regard to -thermal stabili-ty and also in regard to -the desired mechanical properties.
The mixtures according to German O~eenlegungsschri~t No. 2,202,706 and German 0-~:Eenlegungsschri~t No. 2,202,738 contain ethylene-propylene-diene rubbers which represent an amorphous, arbitrarily oriented elastomerlc polymer.
In con-trast to the statistical and, hence, amorphous polymers, the sequential polymers to be used in the mixtures in accordance with the present invention are charac-terised by very high crude strengths. Thus, -the crude strengths o~
standard commercial-grade statistical ethylene-propylene terpolymers are normally in the range ~rom 0.5 MPa to 2.0 MPa, whereas the values ~or sequen-tial polymers are in the range ~rom 8.0 to 20 MPa. The partial crystallinity o-~ -the sequential polymers accounts -~or their high strength (G. Schreier and G. Pei-tscher, Z. Anal. Chemie 258 (1972) 199).
In contrast to statistical ethylene-propylene-diene polymers which are substantially amorphous, crystallinity was de-tected both by X-ray spec~oscopy and also by Raman spectroscopy.
The ~egree o-~ crys-tallinity correlates both with -the e-thylene content and also with the crude streng-th. These sequential ~5 polymers are commercially available, ~or example, under the name BUNA AP ~47~ EPDM).
Accordingly, the present invention provides mix-tures L~ A 17 503 - 2 k-of uncrosslinked ethylene-propylene-unconjugated diene ter~sequential polymers with isotactic polypropylene.
The polypropylene used is in the isotactic form with a high degree of crystallinity~ polypropylene with a density of from 0.90 to 0.92 is particularly preferred.
Suitable ethylene-propylene-diene sequential terpolymers are polymers which consist of sequences of ethylene, propylene and a tercomponent, tlle tercomponent generally being an unconjugated diene for example l,~-hexadiene, dicyclopentadiene, alkylidene norbornene, such as methylene norbornene or ethylldene norbornene, or cyclooctadiene. In most cases, it is preferred to use dicyclopentadiene or ethylidene norbornene. The sequential terpolymers which may be used in accordance with the invention m the mixtures with the polyolefin resins have an ethylene content of from 63 to 90 parts by weight, preferably from 70 to 80 parts by weight, a propylene content of from 5 to 35 parts by weight, preferably from 15 to 25 parts by weight, and a tercomponent con~ent of from 1 to 15 parts by weight, pre~erably from 5 to 10 parts by weight. They are further characterised by a crude strength of > 3 MPa, preferably > 8 MPa.
The products may be produced in various ways. To this end, the components are mixed in granulate or powder form and then delivered to a mixing unit. In another method, the polypropylcne is initially introduced into a mixing unit. After melting, the rubber is then added. The reverse ~3~

;hf-~ 2~

procedure may be adopted, depending upon the type of mixing unit used.
The mixing process may be carried out in conventional machines, including rollers, internal mi~ers or self-cleaning multiple-shaft screws. In cases where multiple-shaft screws axe used, -the process may be carried out continuously.
With modern screwsl it is possible~ depending on requirements, to var~ the ~ittings on the scre~ sha~t and hence to adapt the kneacling~ heating and hence the shearing oonditions to -the mi~ing ratio.
This is importan-t because the mechanical properties o~
the resulting products are dependent upon the -temperatures at which the mixtures are producea. It has been found that better mechanical propertie~ can be obtained at higher temperatures than at lowcr temperatures. The temperatures range ~rom 200 to 290C has proved to be ~avourable~
although it is pre~erred to work at temperatures in the range ~rom 230 to 280C.
In cases where screw machines are used? the product may be iurther processed in different ways. On the one hand, the strand leaving the scre~ may be ¢ooled in a water bath and subsequently granulated. On the o-ther hand, an u~der-water gr~nulation stage may be installed at the end o~ the screw, in which case a moi~t granulate i.8 obtained which may subse~uently be dried by conventional me-thods.
The mixtures according to the present 1nvention co~sist o~ ~rom 5 to 50 parts by weight of EPDM and oi ;0 to 95 parts Le A-17 503 - 4 -z~

by weight of polypropylene. ~hey represent thermoplastic ~1bber compositions which can he processed into shaped articles, ~or e~ample by moulding or extrusion. In cases where these mi~tures arè3se~ there is no need ~or a vulcanisation stage which is required a~ter the shaping or form-ing operation in the case o~ the u~ual rubber polymers. Examples o~ shaped articles pro~uced ~rom the mixtures o~ the present invention are -~ender coverings, seat shellsy visors, dashboards.
The invention is i:Llustrated by -the -~ollowing E~amples:
EXAMPLE I
A mi~ture o~ polypropylene and sequential EPDM in the ratio indicated was delivered in granulate ~rm to a self-cleaning two-sha-~t screw by way of a distributing bel-t weighing machine. The screw had a length of 120 om (without feed zone). Its volume was 0 4 1. ~he rotational speed ~as 300 rpm. The throughput was fi~ed at 17 kg/h~ The screw contained two kneading zones at intervals of ~0 cm and 90 cm from the beginning o~ the screw. ~he tempe~ature 10 cm behind the feed hopper was 174 C which rose to 268 C
in the vicinity o~ the kneading zones. At the output end of the screw, the temperature was 236C. The temperature o~ the external heating was 227C. Aiter leaving the screw, -the sband was cooled in a 4 metre long cooling tank and subsequently chopped to ~orm a granulate. The polypropylene used was hlghly isotactic. Its melt index (DIN 53 735, method C~ was 4.5~ its melting range 158 -to 164~C and its Le A 17 503 - 5 -

2~7~9 density 0-906 ~ red = 3. This product is commercially B available for e~ample under the name Vestolen PP 4200.
The sequen-tial EPDM has an ethylene content o~ 67~o by weight and a propylene content o~ 27~ by weight. The number o~ double bonds per 1000 carbon atoms amounts to 12 The tercomponent was ethylidene norbornene. The Mooney viscosity was 85 and the crude strength amounted -to 12.0 MPa. A product such as this is com~ercially available, ~or example, under the name Buna AP 44?. Panels were moulded ~rom the granulate at a temperature o~ 190 C (10 minutes) These panel~ were tested in accordance with VIN 53 504 (tensile strength, elongation at break, modulus, standard ring I), DIN 53 505 (hardness), DIN 53 512 (shock elasticity) and DIN 53 453 (notched impact strength).
rubber Ratio ~ 80 60 40 20 0 polypropylene 20 ~ 80 100 Tensile strength MPa 6.5 8.9 16.6 23.6 33 Elongation at break ~ 620 425 255 85 3 Modulus 100% MPa 2.2 6.8 12.4 - -300~ MPa 4.3 8,4 - - -~ardness 23 Shore A A 71 93 92 93 9g ~' 100 ll A 11 55 88 91 97 23 " D 21 43 57 67 73 " 7o ~ D 0 12 33 44 57 Ela~ticity 23 ~0 64 42 40 41 46 " 70 % 46 46 4~ 47 ~2 Tear propagation resist~nce aceording 25to Pohle N 80 195 450 740 1045 E~modulus MPa 20 242 727 1210 1790 Notched impact 1) strength 23 + ~ ~ 13 3 Oo + + ~ 7 -10 ~ ~ 38 6 30 +

~, 1~ + = unbroken ~c~ ~'~ ~ ~

7'9 ~his Examples was c~rried out in order to demonstrate the superiority o~ polypropylene to polyeth~lene. Production was carried out as described in Example 1. The polyethylene used was characterised by the following data: melt inde~
(DIN 53 735) 8, density 0.923, and also by the me¢hanical value~
set out in the following Table. ~his product is commercially 1-9 , available under th~ name Baylon 19 N 430.

2a 2b 2c 2d 2e Ratio pO ~ 0 ~ Z~~~
~ .
Tensile strength 12,8 : 8.9 13.2 16.6 12~3 Elongation 600 ~25 720 255 95 Modulus 100~ 4.1 6.8 6.o 12.~ -" 300% ~.5 ~.4 6.3 - -15~ardness Shore A23 85 93 9 92 94 " " 70~ 59 71 7~ 94 87 " " 100 23 55 40 88 41 " " 120 ~ : ~3 0 :~76 0 " " ~ 150 0 ~ ~17. 0 32 0 Shock elasticity 2~ 46 42 37 40; 37 !1 70 47 : 46 40 48 33 20reslstance 125 lg5 210 450 280 It is clearthat, in the range~above 50~ of polyole~in, the products according to the invention (2d) are superior to the comparative mixtures containing polyethylene (Example 2c) both in their mechanical values (F,~M, E) and also in their thermal stability, which is illustrated by the Shore hardness:at elevated temperatures.

Le A 17 50~ _ 7 _ - 4 ~ k

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Mixtures of uncrosslinked ethylene-propylene-unconjugated diene-ter-sequential polymers with isotactic polypropylene.

2. Mixtures as claimed in claim 1, consisting of isotactic poly-propylene and ethylene-propylene-ter-sequential polymers in which dicyclo-pentadiene or ethylidene norbornene is used as ter-component.

3. Mixtures as claimed in claim 1 or 2, consisting of ethylene-propylene-ter-sequential polymers and isotactic polypropylene with a density of from 0.90 to 0.92.

4. Mixtures as claimed in claim 1 or 2, consisting of 5 to 50 parts by weight of ethylene-propylene-ter-sequential polymers and 50 to 95 parts by weight of isotactic polypropylene.

5. Mixtures as claimed in claim l or 2, consisting of isotactic poly-propylene and ethylene-propylene-ter-sequential polymers with the following composition:

63 to 90 parts by weight of ethylene, 5 to 90 parts by weight of propylene and 1 to 15 parts by weight of ter-component.

6. Mixtures as claimed in claim 1 or 2, containing an ethylene-propylene-ter-sequential polymer consisting of:
70 to 80 parts by weight of ethylene, 15 to 25 parts by weight of propylene, and 5 to 10 parts by weight of ter-component.

7. A process for producing the mixtures of claim 1, wherein the mixture components are mixed in suitable mixing machines at temperatures of from 200 to 290°C.

8. A process for producing the mixtures of claim 2, wherein the mixture components are mixed in suitable mixing machines at temperatures of from 200 to 290°C.