Elastomer functionalized by grafted carboxyl or ester groups and

Details Elastomer functionalized by grafted carboxyl or ester groups and Elastomer functionalized by grafted carboxyl or ester groups and

1997-08-22

1998-09-08

Szekely, Peter A.

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

Synthetic resins

Processes of preparing a desired or intentional composition...

525289, 525290, 525291, C08L 9500, C08F27300

Patent

active

058046194

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1) Field of the Invention
The invention relates to an elastomer functionalized by carboxyl or ester groups which are carried by grafted sequences of controlled length. It also relates to the application of this functionalized elastomer to the production of functionalized elastomer/bitumen compositions which can be used as coatings and in particular as road surfacings, as bituminous mixes or alternatively as watertight facings.
2) Background Art
Functionalized elastomer/bitumen compositions are known which are composed of a mixture of one or a number of bitumens, of a functionalized elastomer carrying carboxylic acid or derived functional groups, for example carboxylic acid esters or anhydrides, and optionally of a salifying agent capable of reacting with the functional groups of the functionalized elastomer and thus of resulting in the formation of bridgings between the macromolecular chains of the functionalized elastomer (U.S. Pat. Nos. 5,189,083, 5,214,082, 5,278,207 and EP-A-0,548,412).
The functionalized elastomer can be composed of a block copolymer of styrene and of a conjugated diene, such as butadiene or isoprene, which additionally contains at least one block deriving from an acrylic monomer capable of providing carboxylic acid functional groups by hydrolysis (U.S. Pat. Nos. 5,189,083, 5,214,082 and 5,278,207), or alternatively it can be composed of a block copolymer of styrene and of a conjugated diene, such as butadiene or isoprene, carrying grafted chains containing carboxylic acid or carboxylic anhydride functional groups (U.S. Pat. No. 5,278,207 and EP-A-0,548,412).
The salifying agent can be chosen from amines, quaternary ammonium salts, metal oxides and hydroxides, alkali metal or alkaline-earth metal carbonates, metal carboxylates, alcohols, aminoalcohols and epoxides (EP-A-0,548,412). In particular, the salifying agent can be taken from polyfunctional amines having at least two amino functional groups (U.S. Pat. No. 5,278,207).
The elastomers functionalized by carboxylic acid or derived groups used to produce the functionalized elastomer/bitumen compositions of the abovementioned citations only possess to a limited extent carboxyl or derived functional groups attached along the macromolecular chains of the elastomer and capable of inducing crosslinkings or bridgings of the said chains with one another and/or with the bitumen, directly or after addition of the salifying agent. For this reason, the physicomechanical characteristics of the functionalized elastomer/bitumen compositions obtained, in particular plasticity range (difference between the ring-and-ball softening temperature and the Fraass brittleness point) and mechanical characteristics at low temperatures of use, are not entirely satisfactory.


SUMMARY OF THE INVENTION

According to the invention, an elastomer functionalized by grafted carboxyl or ester functional groups is provided, which elastomer exhibits a polydispersity index very similar to that of the corresponding non-functionalized elastomer and an improved distribution of the functional groups along the macromolecular chains of the elastomer, which makes it possible, during the use of such a functionalized elastomer in the preparation of functionalized elastomer/bitumen compositions, to obtain functionalized elastomer/bitumen compositions which exhibit an expanded plasticity range as well as improved tensile mechanical characteristics.
The functionalized elastomer according to the invention is of the type containing a substrate elastomer, having a weight-average molecular weight (Mw).sub.0 of between 10,000 and 600,000 daltons and a polydispersity index PI.sub.0 of less than 5, onto which are grafted, in an amount representing 0.1 to 10% by weight of the substrate, sequences carrying carboxyl or ester functional groups and it is characterized in that its weight-average molecular weight Mw is such that the ratio ##EQU2## is less than 20% and preferably less than 12% and in that the sequences grafted onto the substrate correspond to the form

REFERENCES:
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