CA1067642A

CA1067642A - Halogenated rubber-polyolefin compositions

Info

Publication number: CA1067642A
Application number: CA235,930A
Authority: CA
Inventors: John R. Dunn; Sheikh Mohammed; John Walker
Original assignee: Polysar Ltd
Current assignee: Polysar Ltd
Priority date: 1975-09-19
Filing date: 1975-09-19
Publication date: 1979-12-04
Also published as: SE446308B; GB1533181A; DE2641966A1; BR7606191A; FR2324679B1; JPS5238553A; BE846165A; IT1068744B; AU501173B2; NL7610185A; SE425169B; SE8003114L; DE2641966C2; FR2324679A1; SE7610037L; AU1770776A

Abstract

Abstract of the Disclosure Novel thermoplastic compositions are disclosed which comprise a mixture of a halogenated rubber and a poly-olefin, which may optionally be crosslinked, which are useful as substrates of painted decorative or trim items. The sub-strate does not have to be painted with a priwer before the application of the top coat paint.

Description

~06q642 HALOGENATED RUBBER - POLYOLEFIN COMPOSITIONS
-This application is directed to painted, novel compositions and methods of manufacture thereof which composi-tions are especially useful for decorative and/or trim purposes such as in the automotive industry.
A growing need is developing for compositions which can be used for decorative'or trim purposes for many consumer and mechanized goods. Such'compositions must be relatively low in cost, be readily formed and be'able to be colour matched. Certain special synthetic elastomeric polymers such as the polyurethanes are'being used in such applications.
More recently, certain thermoplastic compositions have been developed for these applications, the advantage of the thermo-plasticity being in the'ability to reprocess or recycle s'crap thereby further reducing costs.
For many of these'decorative or trim articles, colour matching is achieved by painting of the surface.
Painting of any surface'can be'expensive if it is necessary to go through many stages such'as and including preparation : .
' and cleaning of the surface'to ~e painted, applying one or -.. 7 ~ 20 more coats of primer to the'surface and applying one or more '~ top coats. Elimination of any one or more of these stages contributes to a reduction in the cost of the article.
; It has now been discovered that c~rtain thermo-, plastic compositions which comprise a halog~nated rubber mixed `;, with a polyolefin have highly desirable properties making them suitable for use in decorative or trim applications and ~, which have the further advantage of not requiring application , ~ of a primer before the top coat of paint is applied.
''~ It is an o~ject of t~is invention to provide novel ~ 30 thermoplastic compositions comprising a mixture of a : `:
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halogenated rubber and a polyolefin.
It is a furt~er o~j'ect of this invention to provide novel, painted thermoplastic compositions being a substrate comprising a mixture of a halogenated rubber and a polyolefin, said substrate being coated with paint.
It is a still further objective of this invention to provide novel, painted thermoplastic shaped articles being shaped substrates comprising a ha'logenated rubber and a poly-olefin, said substrates having a painted surface.
Halogenated rubbers are well known in the art.
Isoolefîn-multiolef;n polymers are'weIl known; a preferred isoolefin is isobutylene and a preferred multiolefin is isoprene, the preferred composition being known as butyl rubber. Halogenated derivatives of butyl rubber, in which the halogen is one'of bromîne'or chlorine, are commercially availabIe materials and are'known as bromobutyl and chloro-butyl respectively. Ethylene-propylene-diene monomer polymers "
in which the'diene monomer îs 5-ethylidene-2-norbornene may ' be halogenated to yield thé'corresponding bromo- or chloro-' 20 derivatives. ChIorosulphonated polyethylene is a weil known commercially availabIe'polymer. The'halogenated rubbers of this invention are'seIected from chIorobutyl, bromobutyl, brominated or chlorinated EPDM wherein the'diene monomer is ''''i ethylidene-norbornene'and from chlorosulphonated polyethylene.
Polyolefins are'well known compositions. Poly-~;~ -olefins which are solîd, high molecular weight thermoplastics ' in which the olefin is predominantly ethylene or propylene , are commercially availabIe. These'polymers constitute from . . .
100% of ethylene'or propylene'to about 95% of ethylene or 'i 30 propylene combined wi'th up to about 5% of a copolymerizable ., ~ .
:, ;.~' monomer. Such polymers and copolymers are available with a variety of characteristics including low, medium and high density and a wide range of flow characteristics. For this application, those polymers classîfied as having low and medium flow are preferred, while those polymers classified as being high flow may be used ~ut are not preferred. The flow characteristic of the polyolefin is selected based on the molding procedure'to be used for the thermoplastic composition ' - for example, if the thermoplastic composition is to be in- -'~ 10 jection molded a medium flow polyolefin'is preferred whereas if the thermoplastic composition is to ~e compression molded a '~
. low flow polyolefin is preferred. A preferred polyolefin 'j is polypropylene.' ` The thermoplastic compositions of this invention ., ~i comprise from about 70 to about 40 parts by weight of halo-;' genated ru~ber in admixture with from about 30 to about 60 ; parts by weight of polyolefin. Preferred thermoplastic '~ compositions comprise'from 60 to 50 parts by weight of halo-genated rubber mixed with'from 40 to 50 parts by weight of polyolefin. The thermoplastic compositions may also contain minor amounts, from a~out 0.1 to about 5 weight per cent each, ' of coloring agents, heat stabilizers and antioxidants. Such'~ heat stabilizers and antioxidants are those well known in the art and may include'a single compound or mixtures of com-. pounds. In general, antioxidants used with the halogenated '~ rubbers, such as bromo~utyl, and those'used with the poly-' olefins, such as polypropylene,' are'suitable for use with these compositions.
The thermoplastic compositions preferably are lightly crosslinked. Suita~le'crosslinking agents are the .,, : ' organic per-compounds including organic peroxides, organic hydroperoxides and organic peresters as sources of free radicals Amounts of such crosslinklng agents that may be mixed with the thermoplastic ccmpositions are from 0.05 to 1 weight per cent based on the thermoplastic composition and preferably are from 0.5 to 1.0 weight per cent. Examples of such crosslinking agent include dicumyl peroxide and tertiary butyl peroxide as examples of organic peroxidesJ tertiary butyl hydroperoxide as an exam-ple of organic hydroperoxîdes, and tertiary butyl perbenzoate as an example of organic peresters. Suitable crosslinking agents also include the maleimides, the bis-maleimides being preferred. Suitable maleimides include N-phenyl maleimide and especially NJN'-m-phenylene-bis-maleimide. Amounts of malei-mides that may be'used are'from 0.025 to about 0.075 weight per cent based on the thermoplastic compositionJ preferably from 0.035 to 0~.065 weight per cent. Further J a combination of an organic peroxide'or ~ydroperoxide with a maleimide, especiall N,N'-m-phenylene-bis-maleimideJ may-~è used as crosslinking agent. Preferably an organic peroxide'is used in combination .. ..
,~ 20 with ~,N'-m-phenylene-bis-maleimide.' The'amounts of the com-ponents when used in combination are'from 0.05 to 0.1 weight ; per cent of organic peroxide'and from 0.025 to about 0.075 weight per cent of bis-maleimide,' the amount of each component , being selected to yield a suitable level of crosslinks.
';, preferred organic peroxide is dicumyl peroxide which is com-,'; mercially available as a product containing about 40 per cent ~`'' of dicumyl peroxide combined with about 60 per cent of inert ; material. The quantities referred to above'are directed to quantities of the'pure materials. The'crosslinking agents are ~' 30 added to the halogenated rubber-polyolefin mixture during the :,' ... ... .

~6764Z

mixing stage, as hereinafter described.
For the overall best balance'of properties of the ther-moplastic composition ;t îs preferred that they be lightly cross ~- linked, as above. However, the degree of crosslinking of the ' compositions must be kept low in order that the composition may .
be processable such as to be abIe to form a continuous sheet on a mill or to be'abIe to flow sufficiently to be moldable in the desired end use shapes. The'extent of crosslinking is kept low by means of using the'low levels of curing agents defined above.
The presence of the low level of crosslinks in the thermoplastic ' composition improves, among other properties, the set charac-' teristics as compared to the'non-crosslinked compositions.
The thermoplastic compos;tions may also contain minor proportions of fillers such'as carbon black, clays, silicas, ' with carbon black being especially preferred. The levels of '~ such fillers are from 1 to about 20 weight per cent based on ' ' the final composition, with from 2 to 10 weight per cent ~s being preferred.
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'~ The'halogenated rub~'er, the'polyolefin and any fillers ' 20 or other additives except the antioxidant are added to a mix-'' ing'means at a slightly elevated temperature and mixed therein.
The antioxidant is added to thé mixture during the final stages '~' of the mixing. If the composition is to be crosslinked, the '~ ' crosslinking agent is added with the other components before mixing is started. The'mixing may be achieved on a two-roll ' ~ rubber mill or preferably in an internal mixer such as a Ban-bury or Farrell mixer. The mixing temperature must be high ~ enough to melt the polyolefin and therefore must be at least '~' about 250F(121C) at the inîtial stage'of the mixing and is al-' 30 lowed to increase'during the mixing up to a maximum of about 35 .

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to 360F (about 180C). Generally, the total mixing time will be about five to ten minutes, with the antioxidant being added during the last one to two mlnutes. On completion of the mixing, the composition may ~e sheeted out and cooled. It may then be granulated for ease of further handling, Forming of the composition into ;ts end-use shape may be'by any of the well known processes, including compression molding, injection ' molding and extrusion. Such'form;ng will normally be at ' temperatures of from about 170C to about 220C.
A further aspect-of this invention is directed to painted thermoplastic compositions, especially as shaped for decorative or trim applications. Such painted compositions are ' advantageous because the'thermoplastic composition of this "' invention does not need the application of a primer paint before the'application of the'top coat, although such a primer may be applied i'f desired. 'Once the'composition has been formed and shaped, the'surface or surfaces are painted in '' the normal manner by dipping, brushing or spraying, with spray application of the'paint being much preferred. The paint is of the type usually used in the industry for which the article ' is to be used - for example, for an a~ttomotive application, a urethane paint is usually used. The surface of the composi-`, tion to be painted is cleaned by any one'of the conventional procedures such as brushing or wiping, treatment with aqueous detergent solution, etc. to remove surface grease or contami-~` nat~on. No further treatment of the surface is necessary before the paint is applied which may be achieved without the ~'' use of the conventional primers. Excellent adhesion of the ' paint to the surface is achieved.
Preferably the paint is applied by spraying, a ,~ .

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iL067642 pressure operated spray gun being found to be most suitable.
Urethane-type paints - which are the'reaction products of polyols or polyesters with polyisocyanates - of the curing or enamel type and the non-curing or lacquer type may be used.
The paint is applied to the surface with a solvent removal , , ~ stage (or flashing) between applIcation of successive coats.
;~ Two or three'coats of paint are'generally sufficient. A
' longer flashing time may ~e'used after the application of the final coat. The painted surface'is then subjected to curing "'; 10 or baking at temperatures from about 180F C82C~ to about 260F (127C) for times- of from about 2 minutes to about 60 ` minutes. A preferred baking cycle'is 30 minutes at 250F
~' J (121~C). The'total thickness of the'paint may range from : . i ,; about 0.0005 to abbut 0.004 inches.
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~'~'' Evaluation of the'utility of the'compositions, both painted and unpainted, involves the determination of the ~' : .
' physical properties of the'composition and, for the painted ' .
'''' composition, determinatîon of the performance of the paint, '' ' including adhesion to the'surface.' The'physical properties, '''" 20 including the'stress s-train and flexural strength properties,. . ,~ .
''' were measured using standard ASTM procedures, the melt flow index being condition G of ASTM D-1238. Paint performance characteristics were determined using procedures accepted by the industry. Adhesion of the paint to the surface was ~
'' ` determined by the cross-hatch test in which a sharp knife was ~ used to form a series of connected X-cuts, each cut being ç about 1/4 inch long and the whble series being about 1.5 inches in total length. Adhesive'tape was then evenly and firmly ~ applied to the total cross-hatched area with a loose end of '~' 30 the tape'being left free' The'loose end was held and pulled -:
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1~67642 any removal of the paint showed poor paint adhesion.
Flat samples of the painted composition were immersed for l0 days in de-ionized water maintained at 90F - after immersion, the painted surface'was examined for blistering, dulling, yeIlowing or loss of paint adhesion by the cross-hatch test and any failure was noted.
Flexibility of the painted compositions was determined using strips of measured length of the painted thermoplastic composition which were'~ent around a 0.5 inch mandrel through 180 of the circumference.' After being heId at either 75F
~ (24C,~ or -20F (-29C) for 5 minutes, the samples were - removed and placed on a flat surface for 5 minutes at which time the length on the flat surface'occupied by the sample is measured and compared with the'length of the'original sample - there must be no more'than a 10% difference'in length to ,, pass this test. The'test at -20F ;s also known as the cold flexibility test.
' Samples of the'painted composition in the form of

2 in. x 5 in. x 118 in. strips were'held at one'end so that ,~ 20 4 in. of the sample ~ad no support. The strips were so held for 30 minutes at 250F and the'amount of sag of the'free end of the'sample was measured as- displacement from the horizontal.
The'following examples are'given to exemplify but not to limit the scope of the'invention. All parts are'parts by , weight unless otherwise specified.
Example' l ' ::
Thermoplastic compositions containing bromobutyl ' ~which had a Mooney ML 1 + 12 at 125C of 51 and contained ', 1.9 weight per cent bromlne~' and a medium flow polypropylene ' 30 avaîla~le as PROFAX 6524 CPROFAX is a Trademark~ were prepared 1 '.
: _ g _ -'' ', :~067642 by mixing for 8 minutes these materials plus a medium ther~al carbon black availa~le as THERMAX (THERMAX is a Trademark) in a Banbury mixer preheated to 25a~F (121C). The temperature in the Banbury mixer was permitted to increase during the mixing cycle to a maximum of 350F (162C) - when the tempera- ' ture reached this level, co'oling was applied to the mixer to maintain the temperature at a~out 360~F. At 7 minutes of the mixing cycle an antioxidant ~2,2'-methylene-bis(4-methyl-6 tertiary-butyl phenol~] was added. Thé compositions from the Banbury were'put on to a rubber mill at about 257F C125C~ and sheeted out, the sheets when cooled then being chopped into small pieces. The compositions used are shown in Table I. The chopped composition was then compression molded into specimens ' .
for determination of stress strain properties. The compression mould cavity was filled with'pieces of the'composition and, following a 2 minute preheat, molded for 5 minutes at a pressure of 30,000 psi. The temperature'of the mould was 347F (175C).
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' The'sheets so produced had the dimensions of 1 x 2.5 x 1/6 - inch. From these'samples dumbbells were cut out for the deter-i 20 mination of the tensile'strength,' eIongation, modulus and hardness. Bars were'separateIy compression moulded for deter-mination of the'flexural strength and modulus. Additional samples were'plied one'sheet above'the other for the compres-sion set determination. Further samples were aged for 70 hours at 212F (100C) and these properties were also measured. I
` Sheets of thickness 1/8 inch and of 6 x 6 inch dimension ¦were prepared from the'diced composition by the above compres-' sion moulding procedure. The sheets were wiped to remove any ~ surface d;rt, fingerprints, etc. and painted. The paint was ;~ 30 applied to these sheets wit~'an aIr spray gun operated at 50 ' ' .

psi air pressure. The palnt used was a polyester urethane enamel available as DURETHANE 100 (DURETHANE is a Trademark).
The paint was applied as three coats with a three minute flash after the application of the first and second coats and a 20 minute flash after the application of the third coat. Each coat was applied to a thickness of 0.0005 to 0.0006 inches.
The painted sheet was then baked at 250F (120C,) for 30 minutes. The painted sheets were'evaluated by the cross-hatch test, water immersion, flexibilîty and sag.
The results for all of these tests are shown in Table I.
For comparison purposes, sheets of bromobutyl and of ' polypropylene were'prepared and painted and the paint adhesion was evaluated. These'results are'shown in Table'I.
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~ - 12 -The compositions of the invention possess acceptable strength properties and excellent adhesion of the paint to the surface.
In comparison, the paint did not adhere to the polypropylene and, although it adhered to the ~romobutyl, the surface was unacceptable due to roughness.
Example 2 Compositions, test-samples and painted samples were prepared followîng the procedure of Example 1, using as : - .
the halogenated rubber component chlorobutyl, brominated EPDM
and chlorosulphonated polyethylene. The chIorobutyl was a commercially available materîal containing 1.O weight per cent - of chlorine and having a Mooney QML 1 + 3 at 260F) of 50.
The brominated EPDM was an EPDM containing 70 weight per cent ethylene, 2-3 weight per cent ethylidene norbornene and 3.6 i ; weight per cent bromine, and had a Mooney of 56. The chloro-~ sulphonated polyethylene was a commercially available polymer .
containing 1.0 weight per cent sulp~ur, 35 weight per cent chlorine and having a Mooney of 55.
The compositions all contained 60 parts of the halo-genated rubber and 40 parts of polypropylene, plus 5 parts of thermal black and 1 part of the antîoxidant.
The properties of these compositions were acceptable and thè paint adhesion characteristics of the painted samples ~` are shown in Table II.

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~067642 ' TABLE II
Composition # 1 2 3 - Polypropylene 40 40 40 ~ ' ChIorobutyl 60 - -Brominated EPDM - 60 Chlorosulphonated polyethylene - - - 60 Carbon Black 5 5 5 Antioxidant Paint Adhesion Pass Pass Pass ` (cross-hatch'test~
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E~xample 3 .; Blends of 60 parts of ~romobutyl and 40 parts of ~ polypropylene plus 5 parts of thermal black and 1 part of - antioxidant were'prepared following the procedure of Example :: 1, with the following exception. Dicumyl peroxide was added ', to each mixture at the'start of the mixing time. The amount . of dicumyl peroxide'which was added to each composition (the ''' amount shown being of DICUP-40C, which is a 40 per cent active commercial material [DICUP is a Trademark]) and the results ' obtained in the'evaluation are'given in Table III. In the .~' 20 paint evaluation, the'cold impact test was a procedure wherein ~` a disc sample'was clamped onto a base, cooled to -20C and a 2.5 pound weight was dropped from a height of 2 feet onto the ~', sample - this is ASTM D-3029-72 (Procedure B). Any shattering ' or cracking of the substrate or cracking of the pain~ is con-sidered failure to pass the test.
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From the melt flow characteristics it is clear that the control compositions # 5 and 6 were too highly crosslinked and difficulty was experienced in molding samples for the physical tests. The' compression set improves as the level of dicumyl peroxide is increased, especially at peroxide levels of from 0.5 to 1 part.
Examnle' 4 Three separate mixtures were prepared of bromobutyl and polypropylene at the 60/40 rat;o, 5 parts of the`rmal black and 1 part of antioxidant following the'procedure of Example 1.
Prior to the start of t~e'mixing, to one mixture was added 0.025 parts of N,N'-m-phenylene-bis-maleimide, to the second mixture was added 0.075 parts of N,N'-m-phenylene-bis-maleimide and to the'third mixture was added 0.1 parts of dicumyl peroxide and 0.025 parts of N,N'-m-phenylene-~is-maleimide.
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. Table IV.
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TABLE I~
Composition #
Dicumyl peroxide parts 0.1 - -N,N'-m-phenylene-bis-maleimide parts 0.0250.025 0.075 Physical Properties Tensile strength kg/cm2 82 72 120 Elongation % 2 205 200 250 100% Modulus kg/cm 73 69 95 :
Hardness Shore D 39 39 40 Compression set (22 ~ours at 25~C) % 71 72 58 ~ '~

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed, are defined as follows:

1. A thermoplastic composition comprising from about 70 to about 40 parts by weight of a halogenated rubber admixed with from about 30 to about 60 parts by weight of a polyolefin, said halogenated rubber being selected from bromobutyl and brominated or chlorinated EPDM wherein the diene monomer is ethylidene norbornene, and said polyolefin being selected from a solid high molecular weight polyolefin in which the olefin is predominantly ethylene or propylene.

2. The composition of Claim 1 which also contains from 1 to 20 weight per cent of a filler.

3. The composition of Claim 1 or 2 which has been crosslinked by reaction with one of from 0.05 to 1 weight per cent based on the thermoplastic composition of an organic peroxide, organic hydroperoxide or organic perester, from 0.025 to about 0.075 weight per cent based on the thermoplastic composition of a maleimide, or a mixture of from 0.05 to 0.1 weight per cent based on the thermoplastic composition of an organic peroxide or hydroperoxide and from 0.025 to about 0.075 weight per cent based on the thermoplastic composition of a maleimide.

4. A painted thermoplastic composition being a substrate comprising from about 70 to about 40 parts by eight of a halogenated rubber admixed with about 30 to about 60 parts by weight of a polyolefin, said substrate having 2 layer of paint on a surface, the halogenated rubber of said substrate being selected from bromobutyl and brominated or chlorinated EPDM wherein the diene monomer is ethylidene norbornene and polyolefin of the substrate being selected from a solid high molecular weight polyolefin in which the olefin is predominantly ethylene or propylene.

5. The painted substrate of Claim 4 wherein the substrate has been crosslinked by reaction with one of from 0.05 to 1 weight per cent based on the substrate of an organic peroxide, organic hydroperoxide or organic perester, from 0.025 to about 0.075 weight per cent based on the substrate of a maleimide, or a mixture of from 0.05 to 0.1 weight per cent based on the substrate of an organic peroxide or hydroperoxide and from 0.025 to about 0.075 weight per cent based on the substrate of a maleimide.

6. A process of producing a thermoplastic composi-tion in which from about 70 to about 40 parts by weight of a halogenated rubber is mixed with from about 30 to about 60 parts by weight of a polyolefin, said mixing being on a two-roll rubber mill or in an internal mixer for a time of from about 5 to about 10 minutes at above a temperature of about 121°C, the mixing temperature being allowed to increase to a maximum of about 180°C, the halogenated rubber being selected from bromobutyl and brominated or chlorinated EPDM wherein the diene monomer is ethylidene norbornene, the polyolefin being selected from solid high molecular weight polyolefin in which the olefin is predominantly ethylene or propylene.

7. The process of Claim 6 in which an antioxidant is added during the final states of mixing.

8. The process of Claim 6 in which a crosslinking agent is also present at the start of the mixing, said cross-linking agent being selected from organic peroxides, organic hydroperoxides or organic peresters in an amount of from 0.05 to 1 weight per cent based on the thermoplastic composi-tion, or from a maleimide in an amount of from 0.025 to about 0.075 weight per cent based on the thermoplastic composition, or from a mixture of an organic peroxide or hydroperoxide in an amount of from 0.05 to 0.1 weight per cent based on the thermoplastic composition and a maleimide in an amount of from 0.025 to about 0.075 weight per cent based on the thermoplastic composition.

9. The process of Claim 8 with the additional steps of shaping by compression or injection molding the thermoplastic composition and of applying by spraying to a cleaned surface of the shaped composition a urethane paint and baking of the painted shape.