Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-03-03
2004-02-03
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S277000, C524S310000, C524S313000, C524S763000, C524S812000
Reexamination Certificate
active
06686417
ABSTRACT:
The present invention relates to a method for making polyacrylamide and in particular by the inverse emulsion polymerisation method using a particular combination of surfactants and to the use of such polymers in waste water treatment, as a flocculant or a dehydrating agent, in paper manufacturing as a paper chemical or sizing agent, or in oil recovery and textile printing as thickeners.
Major industrial uses of polyacrylamide (PAM) include uses in aqueous systems and for such use it is desirable for the PAM to be available as an aqueous solution. Unfortunately, except at extreme dilution, aqueous solutions of PAM usually have very high viscosity. The handling of systems with such high viscosities is difficult on a large scale and so the industrial manufacture of PAM is usually carried out is an indirect manner.
Typically, PAM is made by so-called inverse emulsion polymerisation. In this, acrylamide monomer, together with any co-monomer(s), and a polymerisation initiator, usually a free radical initiator, are dissolved in water, this solution is emulsified in an oil and the polymerisation initiated, typically by raising the temperature. The water-in-oil emulsion is typically stabilised by a surfactant system. At the end of polymerisation the system is a dispersion of water droplets, containing dissolved PAM, in the oil phase. Although the viscosity of the aqueous PAM solution is high, the effective viscosity of the emulsion is determined primarily by that of the oil and this is chosen to be suitably low. To introduce the PAM effectively into the aqueous systems in which it is to be used, the emulsion has to be broken. Typically, the system is designed so that it undergoes inversion on simple dilution into water. This general type of synthetic method is usually referred to as inverse polyacrylamide emulsion polymerisation, commonly abbreviated to “inverse PAM polymerisation”.
The requirements for the surfactant system used in inverse PAM polymerisation are thus somewhat unusual because it must provide adequate emulsion stability before, during and after (for storage) the polymerisation reaction, but must permit ready breaking of the emulsion during inversion on dilution into water, to facilitate rapid release of the polyacrylamide polymer into the water phase in which it will act.
Conventionally, the oil used in the emulsion polymerisation process has been mineral oil and the limited biodegradability of mineral oils in the end uses has led to moves towards the use of biologically sourced oils, particularly vegetable oils in the end use products. Unfortunately, carrying out the emulsion polymerisation using a continuous phase of vegetable oil has not to date proved successful, although it has been possible, at extra cost, to replace the mineral oil with vegetable oil after emulsion polymerisation for example by distilling off the mineral oil and replacing it with vegetable oil.
The present invention is directed to a way of making water-in-oil emulsion polymerised PAM which enables ester based oils, particularly ester oils derived from vegetable sources, to be used as or included as major components of the oil (continuous) phase of the emulsion. The invention is particularly desirably applied where the ester oil, especially one derived from a vegetable source, is the major and desirably substantially the only oil used in the emulsion polymerisation To do this successfully we use a combination of three surfactant t materials, a polymeric surfactant, a low HLB emulsifier and a long chain fatty acid or ester as an oil phase structurant. Within specific ranges of proportions, we have found that such as combination can enable successful polymerisation without excessive loss of polymer through coagulation and give emulsion products having satisfactory inversion properties on dilution into water. The method enables the manufacture of anionic cationic and non-ionic inverse PAM emulsion polymers.
Accordingly the invention provides a method of making polyacrylamide by inverse emulsion polymerisation which comprises dispersing an aqueous solution of polymerisable monomers including acrylamide in an oil phase including at least one ester based oil, particularly one or more vegetable oils, the system also including a surfactant composition which includes:
a polymeric carboxylic surfactant;
b a low HLB emulsifier; and
c an oil phase structurant,
and polymerising the polymerisable monomers to form a colloidal suspension of particles, of a solution or dispersion of the resulting polyacrylamide polymer in water, in the oil.
The invention includes a surfactant combination including: a) a polymeric surfactant; b) a low HLB emulsifier; and c) an oil phase structurant, and the use of the surfactant combination in inverse emulsion polymerisation of polyacrylamides.
The invention further includes a method of water treatment that comprises diluting an inverse polyacrylamide emulsion, made by the method or made using a surfactant combination of the invention, into the water to be treated such that the emulsion is inverted releasing the polyacrylamide into the water and emulsifying the ester based oil phase in the dilution water. The term inverse polyacrylamide emulsion refers to a solution of a polyacrylamide polymer or copolymer in an aqueous solvent, usually water, as the disperse phase of a water-in-oil emulsion. In the inverse polyacrylamide emulsion made by the present invention the oil phase is an ester based oil, particularly a vegetable oil.
The polymeric carboxylic surfactant is an oil soluble, and usually water insoluble, surfactant which includes a polymeric hydrophobe group, containing at least 30 carbon atoms, linked to a carboxyl function itself further linked to a hydrophile group. Examples of suitable polymeric hydrophobe groups include polymeric hydrocarbyl groups and polyester groups.
When the hydrophobe is a hydrocarbyl polymeric group it typically, contains at least 30, and usually at least 50, carbon atoms and may contain up to 1000, more usually up to 500 carbon atoms. The hydrocarbyl polymeric group is typically based on an olefin polymer. Particularly suitable monomers are butylenic monomers especially iso-butylene. The hydrocarbyl group may be linked directly to the carboxyl group or indirectly through a linking group. An especially convenient way of linking the hydrocarbyl to the carboxyl group is to link the hydrocarbyl group to a succinic acid group. The succinic acid group provides two carboxyl functions and there are two other carbon atoms to which the hydrocarbyl group can be linked. Such compounds can be made by a condensation reaction between the corresponding hydrocarbyl olefin and maleic anhydride to give a hydrocarbyl substituted succinic anhydride that can be further reacted to make the surfactant In such compounds, at least one of the carboxyl groups of the succinic acid group is linked to a hydrophile group. The other one may be a free carboxyl group or linked directly or indirectly to a further hydrophile group.
When the hydrophobe is a polyester group, it will typically be a polyester derived from a hydroxy fatty acid, particularly a hydroxy C
12
to C
20
fatty acid such as hydroxy-stearic acid (usually 12-hydroxystearic acid). The polyester group will typically on average contain from about 50 to about 200 carbon atoms, more usually about 100 to 150, and especially about 115 to 135, carbon atoms. Because commercially available hydroxystearic acid typically contains about 15% stearic acid, polymerisation to form the polyester typically results in a polyester product containing on average no more than about 7 hydroxystearate residues.
The hydrophile group can be a short chain hydrophile group in particular one derived from an alcohol or polyol, an amine or polyamine, a compound containing both amine and hydroxyl groups, optionally including other groups such as carboxyl groups, or functional derivatives of such amino-, or hydroxyl, or carboxyl groups.
Alternatively, the hydrophile group can be a polymeric hydrophile group e.g. a polyalkylene glycol group, particu
Cornet Phillip
Reekmans Steven Irene Jozef
Egwim Kelechi C.
Imperial Chemical Industries PLC
Pillsbury & Winthrop LLP
Wu David W.
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