CA1269474A - Process for the preparation of inverse microlatexes, and inverse microlatexes thus obtained - Google Patents

Abstract

The invention relates to a process for the preparation of an inverse microlatex of a water-soluble vinyl monomer homopolymer, chosen from acrylamide, metacrylamide and N-vinylpyrrolidone, characterized in that it comprises: a step (a) in which a reverse microemulsion (of the water-in-oil type) is prepared by mixing: an aqueous solution containing the water-soluble vinyl monomer to be polymerized and at least one alkali metal salt of saturated aliphatic monocarboxylic acid, chosen from acetic and propionic acids and butyric in a weight ratio of said alkali metal salt to said vinyl monomer from 0.1 / 1 to 0.3 / 1; an oily phase comprising at least one hydrocarbon liquid; and a nonionic surfactant or a mixture of nonionic surfactants, having an HLB of 8 to 11, in a proportion sufficient to obtain a reverse microemulsion; and a step (b) in which the reverse microemulsion obtained in step (a) is subjected to thermal polymerization conditions using a compound generating free radicals or photochemical under ultraviolet irradiation. The invention also relates to the microlatex thus obtained which can be used in particular to improve the production of hydrocarbons (in techniques of enhanced recovery or of prevention of water inflows in production wells).

Description

9 ~ 74 The invention relates to a process for preparing microlatex reverse by polymerization in a reverse microemulsion of a mono-water-soluble vinyl mother and the inverse microlatex obtained by this process.
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It is known to prepare reverse latex polymers water-soluble by polymerization in a reverse emulsion resulting from the mixture of an aqueous phase containing the monomer (s) water-soluble to (co-) polymerize, an organic phase and one or more surfactants.
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In such formulations, the surfactant is most often chosen from non-ionic surfactants with low HLB (Lipophilic Hydrophilic Balance) allowing obtaining a water-in-oil emulsion. Most often it is a monooleate or sorbitan monostearate. Furthermore, it has also been shown that some higher HLB surfactants (~ 7) are also likely to lead to water-in-oil emulsions.

The major drawback of reverse latexes is their lack of stability, which is expressed over time by a strong decantation.

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On the other hand, has also been described before-laughing the preparation of reverse microlatex using anionic or cationic surfactants (request for FR-A-2524895).
Now, the Applicant has found a method of preparation of reverse microlatex using nonionic surfactants which allows, relative to the prior art, to increase the polymer content water soluble in reverse microlatex.
More particularly, the invention relates to a process for preparing a reverse microlatex of a water-soluble vinyl monomer homopolymer, characterized in that it includes:
- a step (a) in which a microemulsion is prepared reverse (of the water-in-oil type) by mixing:
- an aqueous solution containing the vinyl monomer water-soluble to polymerize and at least one salt of alkali metal aliphatic monocarboxylic acid saturated, in a weight ratio of said metal salt alkaline to said vinyl monomer from 0.1 / 1 to 0.3 / 1;
- an oily phase comprising at least one liquid paraffinic or isoparaffinic hydrocarbon;
- and a nonionic surfactant or a mixture of nonionic surfactants, having an HLB of 8 to 11, in a sufficient proportion to obtain a reverse microemulsion;
- and a step (b) in which the microemulsion is subjected inverse obtained in step (a) at polymeric conditions thermal sation using a compound that generates free radicals or photochemical under irradiation ultraviolet.
In reverse microemulsion formulations leading to the microlatexes of the invention, the monomer viny-water-soluble lique consists of acrylamide, methacryl-~ s, ~

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amide, or N-vinylpyrrolidone; and the alkali metal salt saturated aliphatic monocarboxylic acid is a salt alkaline acetic, propionic or butyric acid. In in practice, preference will be given to sodium acetate.
Obtaining a microemulsion in ~ erse requires in general the implementation of specific conditions the main parameters of which are as follows:
surfactants, HLB of surfactant or mixture of surfactants used, temperature, nature of the phase organic (or oily) and composition of the aqueous phase.
The monomer content in the aqueous phase is general from 20 to 80% and most often from 30 to 70% by weight.
In some cases, the aqueous phase may also contain soda or potash. We thus obtain in judiciously regulating the quantity of this product, a poly-hydrolyzed acrylamide which is particularly advantageous in some applications, especially in those concerning the Assisted Recovery of Hydrocarbons. A
other technique is to carry out the hydrolysis after having e ~ fectué the polymerization.
The choice of the organic phase is important considerable on the minimum surfactant concentration necessary to obtain a reverse microemulsion. This organic (or oily) phase can consist of a hydrocarbon or a mixture of hydrocarbons. Among them-there, hydrocarbons or mixtures of hydrocarbons paraffinic and / or isoparaffinic are best suited to obtain economical formulations (more ~ low surfactant content) of reverse microemulsions.
The weight ratio of the quantities of aqueous phase and of hydrocarbon (or oily) phase is chosen the most high possible, so that after polymerization a microlatex with a high polymer content. In the practical, this ratio can range for example from 0.5 to 3/1.

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Furthermore, the choice of surfactant (s) is guided by obtaining an HLB ranging from 8 to 11. In fact, apart from this field, obtaining inverse microlatex either is impossible or requires considerable amounts of incompatible surfactants with an economical process. By the way, in the HLB area as well defined, the surfactant content must be sufficient to obtain a reverse microlatex. Too low surfactant concentrations lead to obtaining reverse latexes analogous to those described previously and not part of this invention.

In the HLB interval considered, the minimum concentration male in surfactants compared to all the constituents of the microemulsion varies depending on the value of the HLB ~ no limit about 9% lower by weight is more particularly suitable for the HLB range is from about 8.5 to 9.5. For the domains of HLB from 8 to 8.5 and from 9.5 to 11, the lower limit is generally higher. So for example, for an HLB value of around 10, the minimum surfactant content is about 20 ~ by weight.

Regarding the upper concentration limit in surfactant, for economic reasons, it is desirable to limit to a concer.tration of 25 ~ by weight compared to all constituents of the reverse microemulsion.

When preparing the reverse microemulsion, it is important that the temperature of the mixture is carefully controlled, due to the temperature sensitivity of reverse microemulsions in the presence of nonionic surfactants This influence of the temperature erection is all the more sensitive as the concentration of surfactant is closer to the minimum content required to obtain a micro-reverse emulsion.
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To reduce the necessary surfactant content and to to overcome as much as possible the influence of temperature on stability bility of reverse microemulsions, the latter will be , ._ 4 ~ L ~

as possible prepared at a temperature as close as possible to that which will have been chosen for the polymerization.

The water-soluble vinyl monomer present in the micro-reverse emulsion described above is photo-polymerized chemical or thermal: the method consists in initiating photochemical polymerization, for example by ultraviolet irradiation, or thermally using a free radical generator is hydrophobic as that, for example, azobisisobutyronitrile is hydrophilic such that, for example ~ potassium persulfate.

The polymerization takes place very quickly, for example, by a few minutes pho ~ ochemically, quantitatively, and leads to the formation of stable and transparent microlatex whose radius of particles is around 20 to 50 nanometers with a distribution narrow in size.

The size of the particles dispersed in the microlatex inverses of the invention can be determined using diffusion quasi-elastic of light. The light source on the device light scattering consists of a Spectra Physics * laser ion-argon operating at 488 nm. The time correlation function of the scattered intensity is obtained using a digital correlator at 72 channels. Intensity correlation data has been processed using the cumulants method, which provides the decay time mean sance ~ r- 1> of the correlation function and the variance V.
The latter is a measure of the magnitude of the distribution of decay time and is given by:
V = (<r ~ 2 - <~ 2 ~) / <r ~ 2 where ~ r2 ~ is the second moment of the distribution.

For solutions of polymers of low polydispersity, the variance is related as a first approximation to the polydisper index-sity Mw / Mn (molecular weight by weight / molecular weight by number) by * (trade mark) 7 ~
- G -the relationship:

Mw / Mn = 1 + ~ V

The molecular weight of the polymers obtained depends of the activation mode chosen for the polymerization, a photochemical activation favoring the obtaining of masses very high molecular, as the temperature polymerization is kept below 20 C. This activation mode will be preferred in all cases where very high molecular weights are sought after, like in the case of inverted microlatex ~ s intended for ~
use in Assisted Hydrocarbon Recovery.
The method of the invention allows obtaining stable and transparent reverse microlatex containing a high content of water-soluble polymers, for example about 10 to 35% by weight, usually about 10 to 25%
in weight. Advantageously, the microlatex has a particle size between 20 and 50 nm, approx.
The inverse microlatex obtained according to the process of the invention can be used in many applications especially in the production techniques of petroleum: ~ Resisted Hydrocarbons recovery, soil consolidation, drilling mud production, prevention of water inflows during production start-up oil wells and as completion or fracturing.
Generally speaking, recovery methods assisted with aqueous polymer solutions ~ 30 consist in injecting these solutions into the deposit, by at minus an injection well, to circulate them through training and collecting the oil displaced by at least one production well.
The invention further relates to a method of ~ i9 ~ 7 '~
- 6a -preparation of a thickened aqueous solution, characterized in what we dilute in water a reverse microlatex such as previously defined so as to obtain a concentration in polymer from 50 to ~ 000 ppm by weight, as well as the thickened solution obtainedO
The invention further relates to a method for improve the production of hydrocarbons from a deposit, characterized in that one injects into an injection well or in a producing well a thickened aqueous solution such ~ ue previously defined.
The microlatex implementation methods invexses considered in the invention for recovery assisted do not differ significantly from those described previously for water-in-oil type emulsions.
The inverse microlatexes considered in the invention are self-reversing and is generally not necessary add an additional surfactant to favor; ser /

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inversion, as is the case in some of the methods already described. These microlatex are used, for example after dilution in water, at a content of 50 to 5000 ppm, preferably 100 to 2000 ppm, by weight, of copolymer relative to the aqueous phase 5 resulting. Laboratory tests have demonstrated the effectiveness of the reverse microlatex used.

The method for preventing water from entering wells production consists in injecting, from the production well, into the part of the deposit that we want to treat, an aqueous solution of 10 polymer, prepared in the invention by dissolving the microlatex reverse in water; the polymer is adsorbed in large quantities on the walls of the formation surrounding the well where it is injected. When this well is then put back into production, oil and / or gas selectively cross the treated area, while the passage of 15 the water is reduced.

In addition to these applications, the water-soluble polymers prepared in microemulsion can be used:

o coagulants to separate suspended solids in the liquids e flotation and drainage aids in the manufacture of papler dough; or, :
- flocculants in water treatment.
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The inverse microlatex obtained according to the process of the invention ; 9 ~

can also be used in the assembly of glass fibers, in the leather industry and in the field of paints.

The following examples illustrate the invention but should not in no way be considered limiting. Examples 1, ~, 10, 11, 15 and 16 given for comparison, are not part of the invention.

EXAMPLE 1. (comparative) 250 g of an aqueous solution containing 106 g of acrylamide 300 g of an isoparaffinic cut having an initial point of distillation of 207C and an end point of 25 ~ C and 157 g of a mixture nonionic surfactants made from sorbitan sesquioleate (22 g) and polyoxyethylene sorbitol hexaoleate (135 g). The mixture of surfactants has an HLB resulting from 9.3.
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: The monophasic mixture thus obtained is added with 0.32 g of azobisisobutyronitrile, degassed for 30 minutes and polymerized under UV irradiation at 19C for 15 minutes, which leads to obtaining a cloudy and unstable latex.
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~ ~ EXAMPLE 2.

:: If in example 1, all other things being equal, 15.9 g of sodium acetate are added to the aqueous phase, after which polymerization a stable and transparent reverse microlatex whose radius : particles, determined by quasi-elastic light scattering, is 37 nm, the variance being 3 ~.

By precipitation in acetone and successive washes at acetone and methanol, we get with a total conversion a poly-acrylamide whose intrinsic viscosity determined at 25C in water containing 5.85 g / l NaCl was found equal to 920 cm3 / g.

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EXAMPLE 3.

If in example 2, all other things being equal, the aqueous phase contains 25.3 g of sodium acetate, a stable and transparent microlatex with very characteristic close to those mentioned in Example 2:

RH = 38 nm, variance = 3%

The intrinsic viscosity of polyacrylamide determined in the con-ditions indicated in Example 2, is equal to 847 cm3 / g.

EXAMPLE 4 (comparative) If in example 2, all other things being equal, the amount of sodium acetate is equal to 4.5 g, obtained after polymerization of an unstable latex.

EXAMPLE 5.

A 378 g of an aqueous solution containing 142 g of acrylamide and 34.5 g of sodium acetate, 470 g of the isoparaf cup are added finique of example 1 and 150 g of the mixture of surfactants of example 1. The single-phase mixture thus obtained is polymerized at 20 ° C.
UV irradiation for 15 minutes. The particle radius of the micro-reverse latex thus obtained is 42.3 nm with a variance of 5 ~. The :
intrinsic viscosity of the polymer obtained is equal to 772 cm3 / g at 25C.

EXAMPLE 6.
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550 g of an aqueous solution containing 218 g of acrylamide and 60.5 g of sodium acetate, 300 g of the isoparaf cup are added.
finique of example 1 and 150 g of the mixture of surfactants of example 1. The single-phase mixture thus obtained is polymerized at 20C under UV irradiation for lS minutes allowing obtaining a micro-stable and transparent latex. Polyacrylamide, isolated as described in , ~ i9 '~

Example 2 has an intrinsic viscosity of 878 cm3 / g at 25C.

EXAMPLE 7.

365 g of an aqueous solution containing 143 g of acrylamide and 21.4 g of sodium acetate, 419 g of dodecane and 216 g of mixture of surfactants from Example 1. The monophasic mixture thus obtained is heated to 45C for 3 hours allowing obtaining a stable and transparent reverse microlatex containing a polyacrylamide whose intrinsic viscosity at 250C is equal to 635 cm3 / g.

EXAMPLE 8.

If in example 7, all other things being equal, dodecane is replaced by decane, after polymerization is obtained a reverse microlatex containing a polyacrylamide whose viscosity ; intrinsic is equal to 533 cm3 / g.

EXF.MPLE 9.
-If in example 7, all other things being equal, dodecane is replaced by heptane, after polymerization is obtained a stable and transparent reverse microlatex containing a polyacrylamide whose intrinsic viscosity at 25 ~ C is equal to 453 cm3 / g EXAMPLE 10. (comparative) :
If in example 7, all other things being equal, we replace the dodecane with toluene, we obtain before polymerization an unstable emulsion.

EXAMPLE 11. (comparative) If in example 2, all other things being equal, the sodium acetate is replaced by the same weight of sodium chloride, ,, ~ i947 ~

after polymerization, a cloudy and unstable latex is obtained.

EXAMPLES 12 to 14.

Under the conditions of Example 5, the pro-portions of each of the surfactants and we determine for different HLB values the minimum surfactant content required for obtain a stable reverse microlatex e ~ transparent after polymerization.
The results obtained are collated in the following table:

_ Minimum content of surfactants for EX HLB obtain a stable and transparent microlatex 123 9'3 9 in ~ weight compared to all the starting constituents of the microemulsion.

EXAMPLE 15. (comparative) If under the conditions of Example 5, all things being also equal, the proportions of the two surfactants are modified way to have a HLB resulting from 7.5 it is not possible to obtain, under these conditions, reverse microemulsion, even in adding significant amounts of surfactants (greater than 45 in weight).

EXAMPLE 16. (comparative) If under the conditions of Example 5, all things being also equal, the proportions of two surfactants are modified In order to have a ~ ILB resulting from 11.5, it is not possible to obtain, under these conditions, reverse microemulsion, even in . ~ 2 ~ g47 ~

adding significant amounts of surfactants (greater than 25 in weight).

EXAMPLE 17.

A 369 g of an aqueous solution containing 145 g of acrylamide and 18.6 g of sodium acetate, 530 g of the isoparaf cup are added finique of Example 1 and 101 g of a mixture of surfactants consisting 20.3 g of sorbitan sesquioleate and 80.7 g of sorbitan hexaoleate polyoxyethylenated bitol. The mixture of surfactants has a resulting HLB
8.9.

0.48 g of single-phase mixture thus obtained is added of azobisisobutyronitrile, degassed for 30 minutes and polymerized under UV irradiation at 19C for 30 minutes' which leads to obtaining of a reverse microlatex, transparent and of low viscosity.

A 404 g of an aqueous solution containing 168 g of acrylamide ; ~ and 20.2 g of sodium acetate, 497 g of the cup are added : ~ of isoparaffinic hydrocarbons used in Example 1 and 99 g of : ~ same mixture of surfactants as in Example 17 (HLB = 8.9).

The polymerization is carried out under the same conditions as in example 17. We obtain a transparent inverse microlatex containing about 16.8% by weight of high mass polymer : molecular.

Claims (12)

The embodiments of the invention about which a exclusive right of property or lien is claimed, are defined as follows: 1. Process for the preparation of a reverse microlatex of a water-soluble vinyl monomer homopolymer, chosen from acrylamide, methacrylamide and N-vinylpyrrolidone, characterized in that it includes:
- a step (a) in which a microemulsion is prepared reverse (of the water-in-oil type) by mixing:
- an aqueous solution containing the monomer water-soluble vinyl to be polymerized and at least one metal salt alkali of saturated aliphatic monocarboxylic acid, chosen from acetic, propionic and butyric acids in a weight ratio said alkali metal salt to said vinyl monomer from 0.1 / 1 to 0.3 / 1;
- an oily phase comprising at least one paraffinic or isoparaffinic hydrocarbon liquid;
- and a nonionic surfactant or a mixture of nonionic surfactants, having an HLB of 8 to 11, in one sufficient proportion to obtain a reverse microemulsion;
- and a step (b) in which the reverse microemulsion obtained in step (a) under conditions of thermal polymerization using a radical-generating compound free or photo-chemical under ultraviolet irradiation. 2- Method according to claim 1, characterized in that the alkali metal salt is sodium acetate. 3- A method according to claim 1, characterized in that that, in step (a), the weight ratio between the aqueous solution of the monomer and the oily phase is from 0.5 to 3/1. 4- Method according to claim 1, 2 or 3, characterized in that, in step (a), the proportion of surfactant or mixture of surfactants is greater than about 9% by weight per relative to all of the constituents of said reverse microemulsion. 5- Method according to claim 1, 2 or 3, characterized in that, in step (a), the proportion of surfactant or mixture of surfactants is at most 25% by weight relative to all the constituents of said reverse microemulsion. 6- A method according to claim 1, 2 or 3, characterized in that the nonionic surfactant is a mixture of sesquioleate sorbitan and polyoxyethylenated sorbitol hexaoleate. 7- Inverse microlatex, characterized in that it is obtained by a method as defined in claim 1, and in that it is stable, transparent and contains a high content of polymers water-soluble. 8- reverse microlatex according to claim 7, characterized in that its polymer content is approximately 10 to 35% by weight. 9- Inverse microlatex according to claim 7, characterized in that it has a particle size of about 20 at 50 nm. 10- Process for the preparation of a thickened aqueous solution, characterized in that a reverse microlatex such as as defined in claim 7, so as to obtain a polymer concentration from 50 to 5000 ppm by weight. 11- A thickened aqueous solution, characterized in that that it obtained by implementing the method of claim 10. 12- Process for improvement. hydrocarbon production a deposit, characterized in that one injects into a well injection or in a producing well a thickened aqueous solution as defined in claim 11.