DE3027236A1 - TERPOLYMERS MADE FROM 2-ACRYLAMIDO-2-METHYL-PROPANSULFONIC ACID, ACRYLAMIDE AND ACRYLIC ACID IN THE FORM OF THEIR SALUE, ESPECIALLY ALKALI AND AMMONIUM SALTS, METHOD FOR THE PRODUCTION OF THESE TERPOLYMERS IN THE METHOD OF DISPRODUCTIONS - Google Patents

Description

Kl / hg June 17, 1980

Chemical factory Stockhausen & Cie., 4150 Krefeld, Bäkerpfad 25

Terpolymers of 2-acrylamido-2-methyl-propanesulfonic acid, Acrylamide and acrylic acid in the form of their salts, especially alkali and ammonium salts, processes for the production these terpolymers and methods for preventing incrustations in aqueous systems under Use of these terpolymers

The use of water-bearing systems in technical operations raises in the presence of salts that a number of problems tend to result in the formation of poorly soluble precipitates.

Deposits and deposits lead to a reduction the performance and service life of the

»F.

gen so that from economic! Establish on a regular basis Cleaning with acid must be carried out at intervals. The way deposits form is different.

On the one hand, it can be an accumulation of oxidation products act, caused by metal corrosion, on the other hand to poorly soluble alkaline earth compounds. The latter arise mainly from the hydrogen carbonates dissolved in the water used for use by increasing the temperature or increasing the concentration by evaporation of the water. It is about also in the majority of cases the removal of calcium / magnesium carbonates, sulfates and silicates. This scale formation is known as "scale formation".

There has been no lack of attempts in the past to remove the harmful deposits through the use of To prevent complexing agents and / or sequestering agents. It didn't matter if this got through the solubility of the salts was improved or the crystal growth was influenced. Consequently the following names can be found for the substances proposed as additives: scale inhibitor, Anti-scaling agents, anti-precipitation agents, anti-nucleating agents, Dispersants etc.

Those compounds which are already in sub-stoichiometric amounts in the water have proven to be of particular advantage added, prevented the formation of harmful deposits.

Alkali polyphosphates in particular showed these properties such as sodium tripolyphosphate and sodium hexametaphosphate, which, however, are hydrolytic in aqueous solution Processes can be largely dismantled in a short time

which and have therefore been replaced by products on an organic basis. The following should be mentioned here: Polyaminoalkylene phosphonates (DE-OS 25 39 687), alkali salts of low molecular weight polyacrylic acid (US-PS 3514 376, US-PS 4008 164), hydrolyzed polyacrylamide (U.S. Patent 343,730, U.S. Patent 400T 161, U.S. Patent 4,085,045) hydrolyzed Polyacrylonitrile (US Pat. No. 3,492,240) and low molecular weight copolymers of acrylic acid and / or methacrylic acid and / or acrylamide with water-soluble esters of unsaturated acids (DOS 2 461 164), such as acrylic acid glycol esters.

The molecular weights of the polymer products were between. see 500 and 100,000, preferably between 1000 and 12,000.

Acrylamide / acrylic acid copolymers with an unsymmetrical molecular weight distribution have also been used as scale inhibitors taken (U.S. Patent 4,072,607 and DOS 2,802,709).

With the use of the named polymer products as scale inhibitors in aqueous liquids remained however, the problem of iron corrosion is not taken into account. But this wins especially with high-quality machines such as turbines, steam generators, pumps and condensers are of equal importance.

It has now been found that low molecular weight copolymers of 2-acrylamido-2-methyl-propanesulfonic acid, Acrylamide and acrylic acid in the form of their alkali and ammonium salts both prevent scale formation as well as reducing iron corrosion.

The invention therefore relates to terpolymers

A) 2-acrylamido-2-methyl-propanesulfonic acid

B) acrylamide and

C) acrylic acid

in the form of their alkali and ammonium salts or salt mixtures of alkali and ammonium salts, which are obtained by copolymerization of the monomers in aqueous solution in the presence of radical formers under normal pressure and transfer are available in the corresponding salts. The addition of alkali can reduce the pH during polymerization can be chosen at will.

The terpolymers according to the invention have a 2-acrylamido-2-methyl-propanesulfonic acid content of 0.5 to 50%, preferably 1 to 10%, an acrylamide content of 5 to 40%, preferably 10 to 20%, and a remainder based on 100% acrylic acid content, the data being based on weight.

The molecular weights of the terpolymers according to the invention are between 500 and 20,000, preferably between 1,000 and 10,000. The molecular weight distribution can be symmetrical as well as asymmetrical with several maxima.

The average molecular weight was determined from that in the capillary viscometer measured intrinsic viscosity in 10% NaCl solution. Provided that the Contributions of the sulfonate-containing groups in the polymer chain to the inherent viscosity make the same contributions as the carboxyl groups, the following relationship was used:

= 0.025 * M ⁰ ' ⁷

(Korotkina et al .: Zh. Prikl. Khim. 38, 2533 (1965)).

A preferred embodiment of the polymerization consists in part of the acrylic acid in the reaction vessel to be submitted and to be heated to the temperature necessary to carry out the polymerization. The other part of the acrylic acid is mixed with the comonomers in the dosing tank and by adding alkali neutralized or only partially neutralized.

At the end of the polymerization, a liquid product with still free acid groups is obtained, that with alkali and / or ammonia and / or amines can be adjusted to the desired pH.

Suitable amines are:

Ethylenediamine, mono-, di- and trialkylamines with linear and / or branched and / or cyclic alkyl radical of 1 to 6 carbon atoms such as methylamine, ethylamine, propylamine, Isopropylamine and cyclohexylamine, hydroxyalkylamines with up to 6 carbon atoms such as mono-, di- and triethanolamine, Isopropanolamine and dimethylisopropanolamine.

The terpolymers according to the invention are notable for their dispersibility while being given at the same time corrosion-reducing properties compared to iron and steel. Already 2 ppm are enough to cause the precipitation of calcium / magnesium carbonate from aqueous solutions. The longer one The loss of effectiveness that occurs over a period of time is irrelevant, as the precipitates that then arise are no longer in are able to form harmful deposits and can be easily removed using a filter.

It could also be observed that old deposits

from calcium-magnesium carbonate when exposed to the terpolymer were gradually redispersed again. The terpolymers according to the invention can be used in all Aqueous systems are used in which deposits, in particular from alkaline earth carbonates, sulfates and - silicates are to be prevented. As an example are mentioned:

Cooling and hot water circuits, cooking and evaporation stations, Heat exchangers, turbines and pumps.

Another possible use for-the anionic Terpolymer is geological in oil flooding Formations as anti-precipitation agents as well as in the production of drinking water in seawater desalination plants by evaporation or positive pressure osmosis.

The thermal stability of the polymers is given up to temperatures of about 300 ⁰ C. No decrease in the effect was found after such heat treatment.

example 1

In a reaction flask were 258 g of water, 3 g of acrylic acid and 12.0 g of hydrogen peroxide (35%) and heated to 90-2 ° C. A mixture of 354 g of acrylic acid and 22.5 g of 2-acrylamido-2-methylpropanesulfonic acid was placed in another vessel and 220 g of acrylamide (30% in water) with 270.2 g of sodium hydroxide solution (45%), partially neutralized and this solution then with stirring over a period of about 1 hour in the hydrogen registered peroxide-containing solution. 54 g of hydrogen peroxide were passed through a second inlet connection (35%) and 12g hydrooxylamine hydrochiride (dissolved in 40 g water) proportional to the partially neutralized micro

dosed. The temperature was constantly at 90 - held 2 ⁰ C.

After the addition was complete, the batch remained at this temperature for a further 4 hours. After the reaction mixture had cooled, it was adjusted to pH 8.5 with sodium hydroxide solution (45%). An approx. 40% strength solution of the sodium salt of a terpolymer of acrylamide / acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid _/ M = approx. 2900 (polymer 1) resulted.

10 Example 2

The polymerization of acrylamide, acrylic acid and 2-acrylamido-2-methyl-propanesulfonic acid happened in the same way as in Example 1, with the difference that the amount of 2-acrylamido-2-methyl-propanesulfonic acid increased to 45 g and accordingly the amount of acrylic acid was reduced by the same mole.

The reaction mixture was subsequently adjusted to pH 8.5 with potassium hydroxide solution (40%). It came into being an approx. 40% solution of the sodium / potassium salt of a terpolymer of acrylamide, acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid, M = approx. 3500 (polymer 2).

Example 3

Acrylamide, acrylic acid and 2-acrylamido-2-methyl-propanesulfonic acid were polymerized in the same manner as in Example 1, with the difference that the amount of 2-acrylamido-2-methyl-propanesulfonic acid increased to 90 g and accordingly the amount of acrylic acid is the same in moles was reduced. The reaction mixture was then neutralized with ethylenediamine (pH 8.5).

An approx. 42% solution was formed, consisting of the Sodium and ethylenediammonium salt of a terpolymer from acrylamide, acrylic acid and 2-acrylamido-2-methyl-propanesulfonic acid, S = approx. -3000 (polymer 3).

5 Example 4

Acrylamide, acrylic acid and 2-acrylamido-2-methyl-propanesulfonic acid were polymerized in the same manner as in Example 2. This was followed by neutralization with Diethanolamine. An approximately 47% solution of the sodium-diethanolammonium salt of a terpolymer was formed from acrylamide, acrylic acid and. 2-acrylamido-2-methylpropanesulfonic acid, M = approx. 4300 (polymer 4).

Example 5

Acrylamide, acrylic acid and 2-acrylamido-2-methyl-propane · Sulfonic acid were polymerized in the same way as in Example 2. The neutralization was with cyclohexylamine performed. A 47% solution of the sodium / cyclohexylammonium salt of a terpolymer was formed from acrylamide, acrylic acid and 2-acrylamido-2-methyl propanesulfonic acid, M = approx. 4200 (polymer 5).

Testing of the sequestering effect of the polymers

Polymers 1, 2, 3, 4 and 5 were tested as scale inhibitors according to the following procedure:

The polymer to be investigated was added in a concentration of 2 or 5 ppm to 2000 ml of tap water containing approx. 190 mg calcium oxide / l. The solution was within 60 minutes to 90-2 ⁰ C with a

Heating bath warmed up.

After the temperature of 90 ^° C. had been reached, 20 ml of freshly boiled tap water (without additives) were added. Then 50 ml samples were taken over 6 hours at 1 hour intervals and filtered through a Gooch crucible (type G 4). The calcium oxide content in the filtrate was determined complexometrically at pH 12 with murexide as an indicator. The amount of calcium oxide kept in solution was given as a percentage of the initial amount of calcium oxide in tap water (see table).

Polymer 1 was subjected to a heat treatment up to 300 ^{° C. to test the thermal stability.} The subsequent test of the dispersing effect showed no difference to the untreated sample.

Table 1

The calcium oxide kept in tap water at 90 ⁰ C in%,
based on the initial amount of calcium oxide depending on
currently

product no 0 Polymer 1 5 Polymer 2 5 Poly. 3 Poly. 4th 5 Poly . 5 Concentration ppm
(based on
Dry matter) 0 2 2 2 5 2 2 5 Time (hours) 93 100 100 100 1 - 75 100 98 100 99 99 1 00 99 99 99 100 2 76 62 97 96 95 99 98 99 97 99 97 99 3 66 53 95 96 96 99 96 99 95 98 94 97 4th 59 49 90 93 95 98 95 98 93 95 91 96 5 52 48 88 91 86 90 86 97 86 90 86 95 6th 48 194 82 187 . 77 189 78 90 75 188 76 90 mg CaO / 1 in
tap water 194 187 189
I. 190 1 90 188 191 191

t C * I · ·

OO O K) - <l K) Ca) CD

Examination of the corrosion protection effect of the

Polymers 1, 2, 3, 4 and 5 were subjected to the following corrosion protection test: 200 or 2000 mg of common salt were dissolved in 200 g of distilled water and these solutions were then dissolved mixed with 2 g of terpolymer (based on dry matter).

Iron sheets (steel 37) were then exposed to the aqueous media for 24 hours.

In the case of the samples without the addition of terpolymer, visible rust formation began after just 1 hour.

The rust formation was assessed on the following scale:

0 = no rust

1 = very slight rust formation

2 = slight rust formation

3 = medium rust formation

4 = moderate rust formation

5 = severe rust formation

6 = very severe rust formation

I - - - ..... ^ .., ■ 0.5% NaCl 1% NaCl Polymer 1 0 1 Polymer 2 0 1 Polymer 3 1 2 Polymer 4 0 0 Polymer 5 0 0 no addition 5 ι
6:

Claims (6)

Expectations Terpolymers of acrylamide with acrylic acid and another copolymerizable monomer, characterized in that that they are made by copolymerization of A) 2-acrylamido-2-methyl-propanesulfonic acid B) acrylamide and C) acrylic acid prepared in aqueous solution in the presence of radical formers under normal pressure and optionally by neutralization with alkalis, ammonia and / or amines into their alkali and / or ammonium salts have been convicted. 2) terpolymers according to claim 1, characterized by a content of A) 0.5-50, preferably 1-10% by weight, 2-acrylamido-2-methyl-propanesulfonic acid B) 5-40, preferably 10-20% by weight, acrylamide and C) 94.5-10% by weight acrylic acid. 3) Process for the preparation of the terpolymers according to Claims 1 to 2, characterized in that a Part of the acrylic acid in the polymerization vessel is heated to the polymerization temperature and the other Part after mixing with the other two comonomers before the polymerization of the total mixture is at least partially neutralized. 4) Method according to claim 3, characterized in that the mixture of acrylic acid and the two other comonomers with alkali, preferably sodium hydroxide solution, partially neutralized and after completion of the ORIGINAL INSPECTED Polymerization with either alkali, ammonia or an organic amine neutralized or weakly alkaline. 5) Procedure to prevent incrustations while protecting against corrosion in water-bearing Systems, characterized in that a terpolymer according to Claims 1 to 2 is added to the water as Adds alkali and / or ammonium salt. 6) Method according to claim 5, characterized in that the terpolymer in amounts of at least 2 ppm used.