Process for the preparation of bitumen-polymer compositions cont

Details Process for the preparation of bitumen-polymer compositions cont Process for the preparation of bitumen-polymer compositions cont

1996-07-09

2000-01-04

Henderson, Christopher

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Processes of preparing a desired or intentional composition...

524 69, C08L 9500

Patent

active

060110945

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1) Field of the Invention
The invention relates to a process for the preparation of bitumen/polymer compositions with improved mechanical properties. It further relates to the application of the compositions obtained to the production of pavements, and in particular of road surfacings, of bituminous mixes or else of watertight facings, and it also relates to a mother solution of polymers which can be employed for obtaining the said compositions.
2) Background Art
It is known to employ bituminous compositions as various surface coatings and especially as road surfacings, on condition that these compositions have a certain number of essential mechanical properties.
These mechanical properties are in practice assessed by determining, using standardized tests, a series of mechanical characteristics, the most widely employed of which are the following: ring-and-ball test defined by NF Standard T 66 008, according to IP Standard 80/53, Standard T 66 004, 46 002, and comprising the quantities:
An indication of the temperature susceptibility of the bituminous compositions can also be obtained from a correlation between the p en etrability (abbreviated to pen) and the softening point (abbreviated to RBT) of the said compositions, known by the name of Pfeiffer's number (abbreviated to PN).
This number is calculated using the relation:
The temperature susceptibility of the bituminous composition is proportionally lower the greater the value of Pfeiffer's number or, what amounts to the same thing, the lower the value of the quantity A. In the case of conventional bitumens, Pfeiffer's number assumes values which lie in the neighborhood of zero.
In general, conventional bitumens do not simultaneously exhibit the combination of the required properties and it has been known for a long time that the addition of various polymers to these conventional bitumens allows the mechanical properties of the latter to be favourably modified and bitumen-polymer compositions to be formed which have mechanical properties that are improved in relation to those of bitumens alone.
The polymers liable to be added to the bitumens are in most cases elastomers such as polyisoprene, butyl rubber, polybutene, polyisobutene, ethylene/vinyl acetate copolymers, polymethacrylate, polychloroprene, ethylene/propylene/diene (EPDM) torpolymer, polynorbornene or else random or block copolymers of styrene and of a conjugated diene.
Among the polymers which are added to bitumens, random or block copolymers of styrene and of a conjugated diene, and especially of styrene and butadiene or of styrene and isoprene, are particularly effective because they dissolve very easily in bitumens and endow them with excellent mechanical and dynamic properties and especially with very good viscoelasticity properties.
It is further known that the stability of the bitumen-polymer compositions can be improved by chemical coupling of the polymer to the bitumen, this improvement in addition making it possible to widen the field of use of the bitumen-polymer compositions.
Bitumen-polymer compositions in the case of which a random or block copolymer of styrene and of a conjugated diene, such as butadiene or isoprene, is coupled to the bitumen can be prepared by making use of the processes described in references FR-A-2376188, FR-A-2429241, FR-A-2528439 and EP-A-0360656. In these processes the said copolymer and a source of sulphur are incorporated into the bitumen, the operation being carried out between 130.degree. C. and 230.degree. C. and with stirring, and the mixture thus formed is then kept stirred and at a temperature between 130.degree. C. and 230.degree. C. for at least fifteen minutes. The source of sulphur consists of chemically unbonded sulphur (FR-A-2376188 and FR-A-2429241), of a polysulphide (FR-A-2528439) or of a sulphur-donor vulcanization accelerator employed by itself or in combination with chemically unbonded sulphur and/or a polysulphide or a vulcanization accelerator which is not a sulphur-donor (EP-A-0360656) and the incorporat

REFERENCES:
patent: 4567222 (1986-01-01), Hagenbach
patent: 5266615 (1993-11-01), Omeis
patent: 5331028 (1994-07-01), Goodrich

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