CA1204535A - Partially quaternary modified acrylamide polymers contained in the form of water-in-oil emulsions - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
An improved process for preparing stable partially quaternized amino methylated acrylamide polymers which are in the form of water-in-oil emulsions, which emulsions are thermally stable and readily invert in alkaline waters which comprises the steps of: preparing a formaldehyde adduct of a secondary amine containing 2 - 8 carbon atoms as a 0.1 to 55% by weight aqueous solution;
adding the formaldehyde adduct in an amount sufficient only to aminomethylate between 5 - 80% of the acrylamide groups therein to a water-in-oil emulsion of a finely divided acrylamide polymer reacting the acrylamide polymer with the formaldehyde adduct; reacting said partially amino methylated acrylamide poly-mer contained in the water-in-oil emulsion with more than 6% by weight based on the water in the emulsion of sodium bisulfite to provide a stabilized water-in-oil emulsion; and finally reacting the water-in-oil emulsion of a finely divided stabilized amino methylated acrylamide polymer with a quaternizing agent containing 1 - 7 carbon atoms. These modified polymers exhibit higher thermal stability and better solution characteristics after long term storage than the known acrylamide polymers.

Description

~Z~4535 It is known that water-in-oil emulsions of polyacrylamide can be reacted with formaldehyde and secondary ami.nes to produce amino methylated acrylamides. These cationically modified water-in-oil emulsions of polyacryl-amide may be further reacted with a quaternizing agent to convert the tertiary amine groups to quaternary ammonium salt groups. This technology is disclosed in United States 4,010,131. This patent shows that either a portion, or all, of the amido groups contained in the polyacrylamide may be converted to the quaternary ammonium salt groups.
It has been found that when less than all of the amido groups are converted to quaternary ammonium salt groups, the resultant water-in-oil emul-sions containing the cationically modified polyacrylamide tend to be sensitive to elevated temperatures and also, under conditions of long term storage, no longer are capable of being readily dissolved in water using the solubilization techniques taught in Anderson/Frisque United States Re. 28,474 and United States Re. 28,576.
It has been found that these problems are aggravated in the case of water-in-oil emulsions of acrylamide polymers, which polymers have molecular weights greater than 5,000,000.
If it were possible to prepare the above described partially quaternized acrylamide polymers which are in the form of water-in-oil emulsions which would be thermally stable and would readily invert, an advance in the art would be made.
This invention seeks to overcome these problems by providing an improved process or preparing stable partially quaternized amino~methylated acrylamide polymers which are in the form of water-in-oil emulsions, which emulsions are thermally stable and readily invert in alkaline waters which compries the steps of:

en ~)4~i35 A. preparing a formaldehyde adduct of a secondary amine con-taining 2 - 8 carbon atoms by mixing together an aqueous formaldehyde solutioQ
and a secondary amine containing 2 - 8 carbon atoms in a mole ratio of from

2:1 to 1:2 so as to produce a 0.1 to 55% by weight aqueous solution of the formaldehyde adduct of the secondary amine;
B. adding the formaldehyde adduct of Step A in an amount sufficient only to aminomethylate between 5 - 80% of the acrylamide groups to a water-in-oil emulsion of a finely divided acrylamide polymer which contains:
a. 10 - 50% polymer by weight;
b. 30 - 95% of an aqueous phase comprising the polymer and water;
c. 5 - 70% by weight of a hydrophobic liquid;
d. 0.1 - 21.0% by weight of a water-in-oil emulsifying agent having a low HLB; the acrylamide polymer being further characterized as having particle size of from 2 millimicrons to 5 microns within the emulsion, and having a molecular weight between 5 million and 10 million;
C. reacting the acrylamide polymer with the formaldehyde adduct at a temperature between 30F - 200F with mixing, thereby providing a parti-ally amino-methylated acrylamide polymer;
D. reacting the partially amino-methylated acrylamide polymer contained in the water-in-oil emulsion with more than 6% by weight based on the water in the emulsion of sodium bisulfite to provide a stabilized water-in-oil emulsion;
E. reacting the water-in-oil emulsion of a finely divided - stabilized amino methylaLed acrylamide polymer of Step D with an alkylating agent containing 1 - 7 carbon atoms in a mole ratio oE alkylating agent to tertiary amine groups on the cationically modified acrylamide polymer of from 2:1 to 1:0.1, at temperatures of Erom 20 - 100 C, and for a -time suEficient to ,, ! ,~3, quaternize the cationically modified acrylamide polymer to produce a water-in-oil emulsion of a finely divided partially quaternized modified acrylamide polymer.
As previously mentioned, the preparation of cationic acrylamide polymers which are in the form of water-in-oil ernulsions of finely divided acryl-amide polymers is disclosed in United States ~,010,131. Portions (modified) of the specification of this patent dealing with this technique are set forth below:
"In general, the polymer emulsions are stable yet at the same time contain relatively large amounts of polymer. The polymers dispersed in the emulsion are quite stable when the particle size of the polymer is within the range of 2 millimicrons up to about 5 microns. The preferred particle size is within the range of 5 millimicrons and 3 microns.
The stable water-in-oil emulsion comprises:
1. An aqueous phase;
2. A hydrophobic liquid; and

3. A water-in-oil emulsifying agent.
The polymer-containing emulsion of this invention is comprised of an aqueous phase ranging between 30 and 95% by weight of the emulsion. The aqueous phase is defined as the sum of the polymer or copolymer and the water present in the composition. The preferred range is between 70 and 90% by weight of the emulsion. The most preferred range is between 70 and 80% by weight of the emulsion.
The present invention has a polymer concentration between 10 and 50%
by weight of the emulsion. A preferred range is between 25 and ~0% by weight of the emulsion. The most preferred range is between 25 and 35% by weight of the emulsion.

~Z04~i35 The polymers most commonly used in application of the invention are acrylamide polymers which include polyacrylamide and its water-soluble copoly-meric derivatives such as, for instance, acrylic acid, methacrylic acid, itaconic acid, acrylonitrile, and styrene. The copolymers contain from about 15 to 85% by weight ox acrylamide. The molecular weights of such polymers and copolymers exceed 500,000.
A polymer also useful in the practice of this invention is hydro-lyzed polyacrylamide which has from 1 to 50% by the original carboxamide groups hydrolyzed to carboxyl groups. The molecular weights of the hydrolyzed poly-acrylamides range from 500,000 to 1 million or more.
The molecular weight of the polymers described above may vary over a wide range, e.g., 10,000 to 25 million. I'he preferred polymer has a molecular weight in excess of l million.
The organic or oil phase of the emulsion is comprised of an inert hydrophobic liquid. The hydrophobic liquid comprises between 5 and 70% by weight of the emulsion. The preferred range is between 5 and 30% byweight of the emulsion. The most preferred range is between 20 and 30% by weight of the emulsion.
The oils used in preparing these emulsions may be selected from a large group of organic liquids which include liquid hydrocarbons and substituted liquid hydrocarbons. A preferred group of organic liquids are hydrocarbon compounds, which contaln from 4 to 8 carbon atoms. Thus, such organic hydro-carbon liquids as benzene, xylene, toluene, mineral oils, kerosenes9 naphtha, and in certain instances, petroleums may be used. A particularly useful oil from the standpoint of its physical and chemical properties is the ranchch~in isoparaffinic solvent sold by Humble Oil and Refinery Company under the trade-mark Isopar M. Typical specifications of this nàrrow-cut isoparaffinic solvent : L2~53S

are set forth below in Table I.

TABLE I

Specification Properties Minimum Maximum Test Method _ _ Gravity APl at 60/60F 48.0 51.0 ASTM D 287 Color, Saybolt 30 --- ASTM D 156 Aniline point, F 185 --- ASTM D 611 Sulfur, ppm --- 10 ASTM D 1266 (Nephelometric mod.) Dry point --- 495 Flash point, F
~Pensky-~artens closed cup) 160 --- ASTM D 93 Any conventional water-in-oil emulsifying agent can be used such as sorbitan monostearate,sorbitan monooleate, and the so-called low HLB materials which are all documented in the literature and are summarized in the Atlas HLB
Surfactant Selector. Although the mentioned emulsifiers are used in producing good water-in-oil emulsions, other surfactants may be used as long as they are capable of producing these emulsions. The water-in-oil emulsifying agent is usually present in amounts ranging between 0.1 and 21.0% by weight of the emul-sion. The preferred range is between l.0 and 15.0% by weight of the emulsion.
The most preferred range is between 1.2 and 10% by weight of the emulsion.
In the choice of a suitable emulsifier, it is important to take into account variations in monomer solubility, salt content, and the reactivity ofmonomer groups. Also, variations may occur which dictate what emulsifiers should be tried on a case-by-case method.
The polymers contemplated for use in this invention may be synthe-sized in emulsion form as described in Vanderhoff et Al United States Pat. No.

_ 5 ~4~35 3,284,393. The polymerization technique set forth in Vanderhoff is generally followed in preparing polymeric latexes used in this invention.
Also contemplated in the practice of this invention is the preparation of suitable water-in-oil emulsions of water-soluble polymers by the methods des-cribed in Anderson et al, United States Patent Nos. 3,624,019 and 3J734J873.1' The Formaldehyde Adduct This adduct can be conveniently prepared by mixing together an aqueous formaldehyde solution with a secondary amine. This reaction may take place at ambient temperature or may be perormed at elevated temperatures. However, the reaction proceeds at a rapid rate at ambient temperature. The preferred secondary amine is dimethylamine. The ratio of formaldehyde to dimethylamine may vary over a wide range, the preferred mole ratio is within the range of 2:1 to 1:2. Typically, it is advisable to have a molar excess of the amine present when making the adduct so as to inhibit crosslinking in later steps.
The adduct should be made in as high a concentration as possible, so as to avoid dilution of the end product during subsequent steps. Typically, the adducts are from 0.1 to 55% by weight in solution. When using a solution of 38% formaldehyde in water and a 60% aqueous soluticn of dimethylamine in a one to one mole ratio, a 48.7% solution by weight is obtained, of the N,N-dimethyl-aminomethanol adduct. I
While the preferred secondary amine is dimethylamine, other secondary amines, preferably those containing 3 - 8 carbon atoms and which include methy-lethylamine, morpholine, diethylamine, piperidine, diisopropylamine and dibut-ylamine can be used. The amines used can be aliphatic or cyclic, straight chained or branched.

, ;~ ' '' ' ' . ' ~Z~4535 The Water-ln-Oil Emulsion of a Finely Divided Quaternary ModiEied Acrylamide Polymer As with the acrylamide polymer in aqueous solution above, the formal-dehyde adduct once prepared is added to the water-in-oil emulsion of a finely divided acrylamide polymer. Typically, the aqueous formaldehyde adduct is added slowly with agitation to the water-in-oil emulsion. The mole ratio of the formaldehyde adduct to the polymer contained in the emulsion may vary from 0.1:1 to 10.01:1 and preferably between 0.3:1 to 3.0:1. The most preferred ratio of the formaldehyde adduct to the polymer containing emulsion is 1:2 to 2:1 based on amide functionality.
The reaction may be performed at ambient temperatures. However, the reaction may be heated to increase the reaction rate. The reaction is exothermic and is completed at ambient temperatures within approximately 60 minutes. If it is desired to increase the rate, temperatures as high as 200 P
may be used.
Due to the volume of water present in the formaldehyde adduct solution, it is often advisable to add an amount of hydrophobic liquid, such as Isopar M, along with additional water-in-oil surfactants to keep the water-in-oil emulsion stable and fluid. The optimum amount of additional hydrophobic liquid to be added must be determined based on the water-in-oil emulsion con-taining the acrylamide polymer on an individual basis; however, it is often 25 to 75% by weight of the aqueous formaldehyde solution to be added. The addi-tional water-in-oil emsulifier is added for stability purposes and also is determined on the basis of the acrylamide polymer emulsion being used, as well as the pH of operation and salt concentration. The additional emulsifier, how-ever, is usually added in a 1 to 25% level on the amount of additional hydro-phobic liquid added.

7 _ ~4535 After the formaldehyde adduct has been reacted with the water-in-oil emulsion of finely divided acrylamide polymer, the sodium bisulfite stabi-lizer is added and, then, an alkylating agent is added to the system. The mole ratio of alkylating agent to the tertiary amine functionality now present on the acrylamide polymer can vary from 2:1 to 0.01:2. The reaction proceeds at a rapid rate, and is usually complete within two hours at ambient temperature.
A preferred alkylating agent is methylchloride; however, other known quaterniz-ing agents such as methyl iodide, ethyl chloride and methyl iodide may be used.
The resulting product so obtained is a stable water-in-oil emulsion of a finely divided quaternary modified acrylamide polymer.
The stabilized water-in-oil emulsion of the quaternary modified acrylamide polymer must be heated or musk be stored at room temperature over a great length of time to enable the water-in-oil emulsion of a finely divided quaternary modified acrylamide polymer to fully invert when added to an aqueous solution and give high cationic charge values. The emulsion may be heated at temperatures of from 30 to 90C for a time sufficient to enable the quaternary modified acrylamide polymer to fully invert, giving high cationic charge value.
The length of time will vary according to the water-in-oil emulsifier used in making the original water-in-oil emulsion of the acrylamide polymer as well as the extent of the quaternization effected. It has been found that the polymer is usually activated after a period of 4 hours at 60C.
As previously indicated, the key for successful quaternization of the acrylamide polymers is the stabilization prior to quaternization of the amino-methylated acrylamide with sodium bisulfite. The amount used may vary between greater than 6% up to as much as about 15% by weight based on latex.
The degree of amino-methylization as indicated varies between 5% to as much as 80% by weight of the quaternary ammonium salt groups. Preferred ~2~4535 materials of the invention in their finished form have charge densities which vary between 20 - 65% by weight. Also, stable, partially quaternized polyp acrylamide backbones having intrinsic viscosities 10 - 18 and average molecular weights between approximately 5 million and 10 million, whichha~e excellent thermal stability and invertability have been prepared. One of the surprising factors of the invention is that sodium bisulfite appears to be unique in its ability to allow the products of the invention to be produced. As will be shown later, the other known stabilizing agents are ineffective as compared with sodium bisulfite.
A further aspect of the invention resides in the fact that it is possible to provide further stabilization by heating the finished quaternized polymer to between 30 - 90C. for a time ranging between about 1 - 8 hours.
This heating seems to destroy any excess bisulfite. Such heating should be conducted under an inert gas blanket using, for instance, nitrogen.
The finished water-in-oil emulsions containing the partially quater-nized acrylamide polymers are readily inverted into waters where they are to be used for such applications as coagulation and the like when the pH of the water is alkaline, e.g. about 8.~ or greater.

~2~4S35 Evaluation of_the Invention To evaluate the invention, the following is presented:
1. Mannich Amine Raw Materials Wt. in Grams Polyacrylamide Latex (27.3%) 650.18 LOPS (Low Odor Paraffin Solvent) 157.4 Tween 61* (Sorbitan monostearate R

4 moles polyethylene oxide) x 10.09 Alkaterge T* (Low HLB substituted oxazoline) lO.09 Premix. Wt. in Grams Formaldehyde (37%) 50.66 Dimethylamine (60%) 46.87 Stabilizer:
Sodium bisulfite 99.20 _ _ . _ _ _ Average molecular weights between approximately 5 - 10 million.
Procedure:
Premix Make-u~:
1) Weigh formaldehyde into 500 ml flask.
2) Cool to 10 - 15C.
3) Begin dimethyl amine addition Add over a half-hour period. Maintain temperature 10 - 15C.
4) Allow solution to continue mixing for 15 minutes after dimethyl amine addition is complete.
Oil Phase Make-up:
1) Weigh LOPS, Tween 61~ and Alkaterge-T into 600 ml beaker.
2) Heat and stir until it i5 homogeneous.
*Trade Mark - 10 -~4535 Mannich Reaction 1) Weigh polyacrylamide backbone into a 2 liter resin flask and begin agitation.
2) Heat to 40C and add oil phase.
3) Begin Premix addition. Add over a 1/2 hour period.
4) Maintain temperature at 40 - 45 C for 3 hours.

5) Cool to room temperature.

6) Add the stabilizer.

7) Refrigerate.
2. Latex Mannich Quat Raw Materials Wt. in Grams .
Mannich Amine 800 Methyl Chloride (20% Excess) 32 Procedure:
1) Charge ~annich amine to 2 liter autoclave and button it up.
2) Raise the temperature to 100F.
3) Pump methyl chloride over 20 minute period.
4) Hold for 6 hours at 95 - 100F.
5) Discharge it.

Aging Studies:
The latex Mannich products were aged in ovens kept at 40C or 60C.
Periodically samples were withdrawn and colloid titrations were carried jut.
The above represents a typical preparation of the products of the invention. The stability of these products as well as their ability to invert as well as the demonstrations that other stabilizing agents don'k work is set forth in Table II.

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Claims (4)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An improved process for preparing stable partially quaternized amino methylated acrylamide polymers which are in the form of water-in-oil emulsions, which emulsions are thermally stable and readily invert in alkaline waters which comprises the steps of:
A. preparing a formaldehyde adduct of a secondary amine containing 2 - 8 carbon atoms by mixing together an aqueous formaldehyde solution and a secondary amine containing 2 - 8 carbon atoms in a mole ratio of from 2:1 to 1:2 so as to produce a 0.1 to 55% by weight aqueous solution of the formalde-hyde adduct of the secondary amine;
B. adding the formaldehyde adduct of Step A in an amount sufficient only to aminomethylate between 5 - 80% of the acrylamide groups to a water-in-oil emulsion of a finely divided acrylamide polymer which contains:
a. 10 - 50% polymer by weight;
b. 30 - 95 % of an aqueous phase comprising the polymer and water;
c. 5 - 70% by weight of a hydrophobic liquid;
d. 0.1 - 21.0% by weight of a water-in-oil emulsifying agent having a low HLB;
the acrylamide polymer being further characterized as having a particle size of from 2 millimicrons to 5 microns within the emulsion and having a molecular weight between 5 million and 10 million;
C. reacting the acrylamide polymer with the formaldehyde adduct at a temperature between 30°F - 200°F with mixing, thereby providing a partially amino methylated acrylamide polymer;
D. reacting the partially amino-methylated acrylamide polymer con-tained in the water-in-oil emulsion with more than 6% by weight based on the water in the emulsion of sodium bisulfite to provide a stabilized water-in-oil emulsion;
E. reacting the water-in-oil emulsion of a finely divided stabilized amino-methylated acrylamide polymer of Step D with an alkylating agent containing 1 - 7 carbon atoms in a mole ratio of alkylating agent to tertiary amine groups on the cationically modified acrylamide polymer of from 2:1 to 1:0.1 at temper-atures of from 20° - 100°C for a time sufficient to quaternize the cationically modified acrylamide polymer to produce a water-in-oil emulsion of a finely divided partially quaternized modified acrylamide polymer.

2. The method of claim 1 where the amine is dimethylamine.

3. The method of claim 1 including the additional step of heating the finely divided quaternary modified acrylamide polymers between 30°C and 90°C
for a period of from 1 hour to 8 hours.

4. The method of claim 1 wherein the alkylating agent is an alkyl halide chosen from methyl chloride, methyl iodide and ethyl chloride.