The present invention relates to oxidized bitumen compositions which are modified with polymers, which can be used in the manufacture of soundproofing materials. More particularly, the present invention relates to bituminous compositions showing improved properties such as low volatility and high flow strength at high temperature. The present invention also relates to soundproofing materials made of the bituminous composition of the invention. More particularly, the present invention relates to materials designed for the automotive industry in order to soundproof the cars.
Bituminous compositions are known to be used in the building field since good characteristics are obtained in waterproofness use. Waterproofness systems for gardens-terraces which can contain oxidized bitumen reinforced with glass net or polyester are described in journal "Cahiers Techniques du Batiment" (N .degree.90, p.113-118, 1987/"Building Technical Journal"). Elastomer bitumen compositions are also described, i.e. refining bitumen modified with either atactic polypropylene or styrene-butadiene-styrene (SBS). SBS elastomer bitumen used in waterproofness of roofs and structures are described in journal "Revue Generale Etancheite Isolation" (Vol.30,N .degree.113, P.13-17, 1978). It is specified therein that oxidized bitumen is not suitable for mixing with SBS because their asphaltene content is too high. WO93/07220 patent application discloses waterproofing laminates comprising a bituminous layer comprising 26 to 62 weight percent of oxidized bitumen, 21 to 65 weight percent process oil and 9 to 25 weight percent of a statistical styrene-butadiene copolymer.
In the automotive industry, it is known to use compositions comprising polyvinyl chloride (PVC), a terpolymer of the ethylene-propylene-diene monomer type (EPDM) and/or a copolymer of the ethylene-propylene type (EPM), oils and plasticizers for soundproofness. However some of these compositions are no more wanted because of their PVC content.