Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1996-03-11
1997-04-08
Szekely, Peter A.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
524 59, 524 69, 524 70, 524 71, C08L 9500
Patent
active
056188625
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 a reinforced multigrade character. It also relates to the application of the compositions obtained to the production of bitumen/polymer binders for surfacings and especially for road surfacings or for leakproof facings.
2) Background Art
Bitumen/polymer compositions with a reinforced multigrade character are intended, according to the invention, to mean bitumen/polymer compositions which have a wide plasticity range. The said range is defined as the difference between the ring-and-ball softening temperature (abbreviated to RBT), which reveals the properties of the binder or bitumen/polymer composition when heated, and the Fraass brittle point, which reveals the properties of the bitumen/polymer composition when cold. The wider the plasticity range, the better will the bituminous binder consisting of, or based on, the bitumen/polymer composition resist stresses when heated and when cold.
The abovementioned values of the ring-and-ball softening temperature (RBT) and Fraass brittle point are determined by standardized procedures as shown below: 66 008 and expressed in .degree.C.; expressed in .degree.C.
Crosslinking, using sulphur, of elastomers bearing unsaturations, especially copolymers of styrene and of a conjugated diene such as butadiene or isoprene, within bitumens produces bitumen/polymer compositions which have an improved stability and excellent physicomechanical characteristics, and which can be employed for the production of various dressings, especially road surface dressings, bituminous mixes or else leakproof facings exhibiting improved characteristics when compared with the dressings obtained from bitumens alone.
The preparation of bitumen/polymer compositions of the abovementioned type, in which the sulphur-cross-linkable elastomer is a copolymer of styrene and of a conjugated diene, is described, in particular, in references FR-A-2376188, FR-A-2528439 and EP-A-0360656.
It is also known that the properties of bituminous compositions consisting of mixtures of bitumens and of block copolymers of styrene and of a conjugated diene, especially block copolymers of styrene and of butadiene, can be improved by incorporating into said compositions a small quantity of a nonoxidizing. inorganic acid such as phosphoric acid (DE-A-2255173). The results obtained can be improved if the acid is added to the bitumen before the block copolymer is incorporated into it (U.S Pat. No. 5070123).
SUMMARY OF THE INVENTION
It has now been found that it is possible to widen the plasticity range of sulphur-crosslinked bitumen/polymer compositions by incorporating into these compositions, after the sulphur crosslinking stage, an inorganic adjuvant of the acid or acid anhydride type.
This result is of an unexpected nature in the light of the observations, made by the Applicant Company, that sulphur crosslinking of mixtures of a bitumen and of a block copolymer of styrene and of a conjugated diene already containing the inorganic adjuvant of the acid or acid anhydride type, incorporated into the bitumen before the addition of the copolymer or else added to the mixture of the bitumen and of the copolymer, produces bitumen/polymer compositions which do not have the improved characteristics of the bitumen/polymer compositions obtained by the process forming the subject of the invention, that is to say consisting in incorporating the inorganic adjuvant into the bitumen/polymer composition which has just undergone the sulphur crosslinking.
The bitumen/polymer compositions obtained by the process according to the invention have a widened plasticity range, a higher breaking stress and an improved elastic modulus.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The process according to the invention for the preparation of bitumen/polymer compositions with a reinforced multigrade character, that is to say exhibiting, inter alia, a wider plasticity range, is of the type in which, while ope
REFERENCES:
patent: 4145322 (1979-03-01), Maldonado et al.
patent: 4554313 (1985-11-01), Hagenbach et al.
patent: 4567222 (1986-01-01), Hagenbach et al.
patent: 5070123 (1991-12-01), Moran
patent: 5095055 (1992-03-01), Moran
patent: 5508112 (1996-04-01), Planche et al.
Germanaud Laurent
Planche Jean Pascal
Turello Patrick
Elf Antar France
Szekely Peter A.
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