Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1997-08-20
1999-11-09
Marquis, Melvyn I.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525286, 525293, 525301, 525302, C08F 2502
Patent
active
059816651
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a polyolefine based thermoplastic elastomer which can be prepared without a separate vulcanisation stage and which has been achieved by the polymerisation of acrylate into the polyolefine matrix. Especially the invention concerns such thermoplastic elastomers in which polyacrylate has been functionalised.
Thermoplastic elastomers are polymers which have the good processing properties of thermoplastics but have the same physical properties as vulcanised rubbers. This combination of properties can be obtained so that the material has both soft and elastic segments, with low glass transition temperature t.sub.g, and a rigid eventually crystalline segment with a high glass transition temperature or a high melting point. The rigid and soft segments must be thermodynamically incompatible with each other, so that they form separate phases. Thermoplastic elastomers do not need any separate vulcanising stage, in the contrary to conventional rubber, and they can be processed to different articles with the processing methods normally used with thermoplastics, like extrusion, injection moulding and blow moulding. On the contrary to rubber, thermoplastic elastomers can also be reprocessed if necessary, for example when recycling material from the processing stage.
Thermoplastic elastomers can be divided into two main groups, block copolymers and thermoplastic/elastomer blends. A well=known example of block copolymers which are thermoplastic elastomers is the anionically polymerised block copolymer of styrene and butadiene (SBS) and the hydrogenised form of the same (SEBS). Drawbacks of these polymers are poor weather resistance, poor oil resistance and the high price.
An example of materials which belong to the other main group of thermoplastic elastomers, are blends of polypropylene and ethylene/propylene rubber or ethylene/propylene/diene rubber. They are usually made by blending the two main components and additives in an extruder. Because the continuous phase is polypropylene the material has good oil resistance properties.
Finnish patent application FI931863 describes a method to produce a thermoplastic elastomer having a polyolefine as a continuous phase and a polyacrylate as a dispersed phase. The acrylate is polymerised into the polyolefin. In the patent application FI946055 it has been noticed that even better properties can be achieved and tailored by using a blend of two or more polyolefins, from which one is polar.
It has now, surprisingly, been observed that by copolymerising to the acrylate phase suitable functional monomers and by adding to the polyolefine phase polyolefines grafted with functional groups, chemical bonds or strong secondary effects can be achieved between the phases. Then also the physical and thermal properties of the elastomers are remarkably improved.
In the functional polyolefines, the functional monomers can be unsaturated carboxylic acids, their anhydrides or other carboxylic acid derivatives, like carboxylic acid esters. Typical examples of such monomers are maleic acid anhydride, acrylic and methacrylic acid and glycidyl(meth)acrylate. The amount of the functional monomer is 0.1-10% by weight, preferably 0.5-2% by weight, based on the amount of polyolefine. The functional polyolefine can be added either to the polyolefine before the impregnation of acrylates or it can be blended with the elastomer after the polymerisation.
According to the invention, the polyacrylate phase can thus be functionalised by adding to the acrylate monomer one or more functional monomers. The functional monomers can be of the same type which are used in the grafting of polyolefine. Especially recommendable are .alpha.-unsaturated carboxylic acids, oxazolines and epoxy-, amino- and hydroxyfunctionalised (meth)acrylates, from which, as examples, can be mentioned glycidylmethacrylate, 2-tertbutylaminoethylmethacrylate, propyleneglycolmonomethacrylate and monomethacryoloxyethylphthalate. The amount of the functional monomer is 0.1-15% by weight, preferably 0.5-10% by weight, of the am
Hanhi Kalle
Jukarainen Harri
Lonnberg Viveca
Vainio Tommi
Vestberg Torvald
Aylward D.
Marquis Melvyn I.
Optatech Corporation
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