Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-07-13
2003-05-06
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S071000, C525S089000, C525S280000, C525S299000, C525S312000
Reexamination Certificate
active
06559233
ABSTRACT:
A subject of the present invention is an aqueous composition comprising a block copolymer carrying at least two blocks of the same charge, combined with at least one ionic type carrying one or more charges opposite to those carried by the copolymer.
More particularly, the aqueous composition is found either in the form of a gel, or in the form of a viscous fluid.
In many fields, control of the rheology of formulas in variable conditions, pH and temperature for example is sought. To this end, there are various methods such as for example the structured phases of surfactants, and polymer dispersions.
The subject of the present invention more precisely relates to the field of compositions with a high viscosity and/or a high elasticity characteristic of gelatinous compositions, because of electrostatic interactions between the types present.
However, this type of composition remains very little developed, one of the main reasons being due to the fact that they exist only in very specific and relatively limited conditions. For example, and in the majority of cases, the said compositions are obtained only for precise combinations of compounds. In fact, the mixture of two different types of opposite charge often leads to a macroscopic separation of phases, resulting from the strong electrostatic combination of the types. Moreover, the conditions in which this type of drawback is not seen, and in which interesting and exploitable rheological properties are obtained, are also limited. In fact, such favourable conditions are found most of the time in a limited zone of the phase diagram and frequently not far from a biphasic region. Consequently, during the use of this type of system, the changing of certain parameters, caused for example by a dilution, can be such that the system tends towards an undesirable macroscopic separation of phases. A destabilization of the gel and the loss of the expected rheological properties are then often observed.
An aim of the present invention is therefore to propose compositions with a relatively high viscosity and/or gel properties, originating in the electrostatic interactions between the various elements constituting the said composition.
Moreover another aim of the invention is to propose compositions in which the above mentioned characteristics can be observed not only for a large range of compounds but also in a wide range of concentrations.
These aims and others are achieved by the present invention, a subject of which is thus an aqueous composition combining at least one block copolymer (A) comprising, in the pH conditions of the composition, at least two polyionic blocks of the same charge and at least one non-charged block, with at least one ionic or polyionic (B) type with a charge opposite to that of the said polyionic blocks, in the pH conditions of the composition; type (B) being chosen from ions carrying at least two charges, surfactants carrying at least one charge, oligomers and/or polymers carrying at least two charges and/or mineral particles carrying at least two charges: the block copolymer (A) content being such that the viscosity of the composition is at least greater than three times, preferably greater than or equal to ten times that of an aqueous solution of block copolymer (A) and to that of an aqueous solution of type (B), in the same conditions of temperature and concentration.
As already indicated above, the compositions according to the invention have the advantage, amongst others, of allowing access to electrostatic gels by using numerous compounds, in wide ranges of concentration.
Moreover, the compositions according to the invention are relatively insensitive to outside factors such as temperature.
Such a property makes the compositions according to the invention particularly suitable for applications in the field of exploration of oil or gas deposits, in particular as an additive in the composition of drilling fluids. In fact, the temperatures encountered most of the time in these applications are high and many additives used as thickening agents lose their capacity to thicken in such conditions, unlike the compositions according to the invention.
Moreover, the compositions according to the invention, in some cases, can also substantially preserve their high viscosity, as well as their gel characteristics where appropriate, even with the addition of hydrophobic compounds.
According to another characteristic of the compounds according to the invention, sensitivity to pH can be adapted as required, according to the nature of the charged units present on the corresponding blocks of the copolymer. In fact, if the units comprise a weak acid or a base, their charge varies according to the pH of the medium. This can represent a significant advantage where it is desired to develop the rheological characteristics of the composition in relation to this parameter (gel which can be stimulated by pH—pH responsive gels). For example in some applications it may be advantageous to have available agents acting almost instantaneously which make it possible to destructure a jellified composition or indeed on the contrary to jellify the composition.
Moreover, the present invention makes it possible to jellify and/or thicken compositions comprising cationic types, which is difficult for many standard thickeners. In fact the latter are in the majority of cases anionic compounds. When the latter are in contact with the said cationic types, a precipitation of the whole is generally observed.
But other advantages and characteristics of the present invention will appear more clearly from reading the description and examples which follow.
It is to be noted that the aqueous composition according to the invention may be presented in the form of a gel. By gel is more precisely meant compositions which have an elastic modulus (G′) greater than or equal to the loss modules (G″) over a frequency range between 1 and 10 Hz, with a geometry of cone plate type; the modules being measured in the linear visco-elastic system, at 25° C., with a Rheometrics or Carrimed rheometer.
In addition, in the following, the temperature and pH conditions of the composition relate to the composition as it was before its use, whether it comprises only the copolymer and the charged type, or whether it is combined with various other constituents necessary for obtaining complete formulations. These “conditions” can also relate to the composition during its use, more specifically during use of the complete formulation.
As has already been mentioned above, the first type of element constituting the composition according to the invention consists of one or more block copolymers (A) comprising, in the pH conditions of the composition, at least two polyionic blocks of the same charge and at least one non-charged block.
More particularly, the block copolymer (A) is chosen from among linear block copolymers, block copolymers with a comb structure, star structure or dendrimeric (hyperbranched) structure.
The linear block copolymers more particularly have a structure comprising at least three blocks. Preferably, the copolymers are copolymers comprising three blocks (triblocks).
The block copolymers with a comb structure preferably have a non-charged skeleton onto which charged segments are grafted. It is to be noted that other combinations are possible as soon as the copolymer has at least two charged blocks and at least one non-charged block.
As far as block copolymers with a star structure are concerned, several possibilities can be envisaged. According to a particular embodiment, if each arm of the star is considered, it can comprise either a block copolymer, preferably a diblock, of which one is charged and the other is not: or a homopolymer, charged or not. Whatever the variant adapted, the choice of blocks is such that the copolymer has at least two charged blocks and at least one non-charged block.
It is emphasized that the copolymer used in the present invention comprises a sum of blocks (fragments) containing at least five monomer repetition blocks. Moreover, th
Bavouzet Bruno
Destarac Mathias
Herve Pascal
Taton Daniel
Asinovsky Olga
Rhodia Chimie
Seidleck James J.
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