JPS5891709A - (meth)acrylic acid/itaconic acid copolymer, manufacture and scale preventive - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to novel copolymers of itaconic acid and acrylic or methacrylic acid, processes for their preparation and their use as scale inhibitors.

Aqueous systems containing dissolved inorganic salts are commonly subjected to operations such as heating, cooling and evaporative distillation, including heat transfer. This salt often becomes insoluble during this operation and deposits as scale on the heat transfer surfaces, resulting in reduced heat transfer and accidental equipment failure. In general, inorganic scale salts (4) include alkaline earth or other metal cations such as calcium, magnenium, iron and lead, and bicarbonates, carbonates, hydroxides, sulfates and phosphates. Derived from anions. Many factors influence scale formation, including, for example, the nature of the 7'Hz dissolved salts in the water and the operating temperature.

Many additives have been proposed as inhibitors of inorganic scale adhesion. Particularly important is 1 part F + bar mm:ty (part per m1lli
on)'! It is an additive known as a critical scale control agent, which exhibits scale control at extremely low additive concentrations below that level. Included in this critical scale control agent are homopolymers of acrylic and methacrylic acid and copolymers with such as maleic anhydride and fumaric acid. Although these additives have been proven to be effective at critical concentrations, their manufacture generally uses non-aqueous solvent systems that are expensive and pose problems of solvent contamination of the polymer product. . Therefore, also
Aqueous Solution (5) There is a need for an effective critical scale control agent that can be produced as easily and inexpensively as during yarn handling.

(Metho)acrylic acid/itaconic acid copolymers have been prepared in aqueous systems in the past, but the use of such copolymers as scale inhibitors has not been published. Thus, the (meth)acrylic acid/itaconic acid copolymer of U.S. Pat. No. 8,808,067 is used as a detergent builder, whereas that of U.S. Pat. No. 8,866,509 is intended as a sizing agent. , and U.S. Patent No. 8,5
The copolymer of No. 07,647 is used in lithographic printing processes. Published British application GB2054548A shows the use of (meth)acrylic acid/itaconic acid copolymers in the removal of boiler scale. ,J.
Org, Chgms241.599 (1959) and Nagai et al., Polymer Chemistry, -! 7.748
(1960) describes a method for producing (meth)acrylic acid/itaconic acid polymers, but does not describe the uses of the resulting copolymers (6). All of these published processes involve conventional copolymerization using an aqueous medium and standard initiator systems that yield relatively high molecular weight copolymers.

Therefore, it is particularly effective as a limit scale inhibitor.
It is a primary object of the present invention to provide a new process for the preparation of substantially homogeneous, controlled low molecular weight (meth+-)acrylic acid/itaconic acid copolymers.

Here, a virtually homogeneous low molecular weight coelectrolyte of acrylic or methacrylic acid, or mixtures thereof, with itaconic acid is prepared by separately and controllably combining (meth)acrylic acid monomers and a polymerization initiator. , was found to be easily produced by adding itaconic acid monomer to an aqueous solution.

Accordingly, the present invention provides substantially homogeneous, number average molecular weight about 5
00 to 7,000 (meth)acrylic acid/itaconic acid copolymers, the process involves a method for producing a (meth)acrylic acid/itaconic acid copolymer of about 95 to 10 molar percentages of itaconic acid monomer (about 5 to 7). 90 mole percent acrylic or methacrylic acid monomer and about 5 to 2 mol percent, based on the total amount of the two monomers.
contacting in an aqueous medium at a temperature of about 80 to 120° C. for about 2 to 8 hours in the presence of 0 mole percent initiator, wherein at least half of the initiator is Separately and essentially continuously during the above period, itaconic monomers are added to the solution in the medium.

In a preferred embodiment of this process, about 95 to 60 mole percent itaconic acid monomer is copolymerized with about 5 to 40 mole percent methacrylic acid monomer, and the initiator is a redox system.

In a preferred method, the itaconic acid monomer and about 2 to 25 percent of the initiator are first dissolved in an aqueous medium, and the remaining initiator is introduced during the polymerization and the resulting copolymer is The solution is held at polymerization pressure for about IO to 120 minutes after this addition.

In a particularly preferred embodiment of this method, about 5 to 40 mole percent methacrylic acid monomer comprises about (8) 1 fr to 2 mole percent sodium persulfate and about 6 to 12 mole percent sodium bisulfite. separately at normal pressure and reflux temperature for about 8 to 5 hours,
an aqueous solution of about 95 to 60 mole percent itaconic acid monomer and about 0.02 to 0.04 mole percent ferric acid;
Hold at temperature for 5 to 75 minutes.

The present invention also provides essentially about 5 to 90 molar percentages of acrylic or methacrylic acid units and about 95 fr.
consisting of 10 mole percent itaconic acid units and having a number average molecular weight of about 500 to 7,000;
Substantially homogeneous copolymers are also necessarily involved. The copolymer preferably has about 5 to 40 mole percent methacrylic acid units and about 95 to 60 mole percent itaconic acid units; may be in the form of its alkali metal, ammonium, or amine salts. and is usually present as an aqueous solution containing about 1 to 60 weight percent of the copolymer.

(9) The present invention further provides an IE for preventing scale formation in water containing scale-forming impurities, such as seawater for seawater desalination.
The method also entails applying an effective amount of the copolymer, preferably at a temperature of about 0.5 to 10
ppm, by mixing with this water. The method may also preferably include adding something like sulfuric acid to the seawater in an amount to neutralize about 55 to 85 percent of the bicarbonate alkalinity of the seawater.

As described herein, the novel polymerization process of the present invention provides for the first time virtually homogeneous, controlled low molecular weight copolymers from the copolymerization of primary acrylic or methacrylic acid with itaconic acid. Moreover, these new copolymers exhibit improved scale repellent activity over prior art (meth)acrylic acid/itaconic acid copolymers, thereby reducing the use of seawater in the fR production of potable water. This means that they can be used more effectively during evaporation.

A homogeneous copolymer is technically defined as a composition with a narrow molecular weight distribution. This distribution is easily determined by analytical techniques such as high pressure liquid chromatography (HPLC) and is a homogeneous copolymer. Polymers are monobaric in nature. Heterogeneous copolymers, on the other hand, have very different reactivities between the two monomers, especially as in the case of (meth)acrylic acid and itaconic acid. It characteristically has a bipartite distribution.

The molecular weight distribution of the substantially homogeneous copolymers of the present invention, as determined by HPLC, is defined by the weight average molecular weight (MWw
) to the number average molecular weight (A#N) is less than 8 and is virtually monoclaved.

In this process, about 95 to 10 mole percent of itaconic acid is added in an aqueous medium, in the presence of a defined amount of polymerization initiator, and at a defined temperature and polymerization time.
Copolymerized with 0 mole percent of either acrylic or methacrylic acid, the acrylic or methacrylic acid monomer and initiator are added separately and simultaneously to the itaconic acid monomer. Acrylic acid and methacrylic acid copolymerize with itaconic acid in virtually the same way and are therefore interchanged or mixed in this step to form a copolymer of a given (meth)acrylic acid/itaconic acid molar ratio. It is possible to provide a product with virtually the same molecular weight and scale inhibitor properties as compared to

Since the process is carried out in an aqueous medium, considerable savings are realized in terms of solvent and processing costs, there is no problem of contamination of the product with solvents, and the product from the final reaction solution is The safety of isolation is removed. The amount of water present during the polymerization is critical only to the extent that the reaction mixture remains in solution during the polymerization and is sufficiently concentrated to titrate the time and temperature process parameters. in this way,
Polymerizations are usually carried out at monomer concentrations slightly below the water solubility of both itaconic acid and the resulting copolymer, typically in the range of 0.75 to 100 grams per gram of total 9N monomer. There will be. Although the polymerization is preferably carried out in water alone, the presence of small amounts of water-soluble solvents is possible if desired.

Any water-soluble free radical initiator can be used as the polymerization initiator in this step. A suitable initiator (l)
Persulfates such as sodium and potassium persulfates are included as well as redox systems. Redox systems such as ferrous sulfate/sodium persulfate/sthorium bioxide are preferred. The polymerization initiator should be present in an amount of about 5 to 20 mole percent, based on the total amount of monomer. All or at least half of the initiator is added separately from the (meth)acrylic acid monomer virtually continuously throughout the polymerization period. Preferably, about 2 to 25 percent of the initiator is dissolved in the aqueous medium with itaconic acid, after which the remaining initiator is introduced as an aqueous solution over the course of the polymerization. The concentration of initiator in the aqueous additive solution is usually about 5 to 25 weight percent.

The temperature and duration of polymerization influence the properties of the resulting copolymer. Therefore, polymerization is limited to a temperature of about 80 to 120° C. during a monomer addition period of about 2 to 8 hours. Polymerization at atmospheric reflux (13) temperature is preferred. Since the presence of a minimum amount of monomer in the final product is desired, the final polymerization solution is generally maintained for a period of time after the addition period of the (meth)acrylic acid monomer and initiator. The polymerization temperature is maintained at the polymerization temperature for a suitable period of time, preferably about 10 to 120 minutes.

By selecting the above-mentioned reaction parameters within the defined ranges, virtually homogeneous (
Meth)acrylic acid/itaconic acid copolymers are easily produced. Thus, lower molecular weights can be obtained by using higher amounts of initiator and shorter addition times, higher temperatures and more dilute solutions. Conversely, higher molecular weights are achieved in more concentrated solutions at lower temperatures using smaller amounts of initiator and longer addition periods.

Preferred embodiments of this process include copolymerizing about 5 to 40 mole percent methacrylic acid with about 60 mole percent itaconic acid. In a particularly preferred method, about 5 (14) to 40 mole percent methacrylic acid,
Sodium persulfate and 6 to 1 molar cents
2 mole percent sodium bisulfite is added to an aqueous solution of about 60 to 95 mole percent itaconic acid and 0.02 to 0.04 mole percent ferrous sulfate at normal reflux temperature over a period of about 3 to 5 hours. , separately, and the polymerization solution was added for an additional 45 minutes following this addition.
The mixture is kept at reflux temperature for 75 minutes.

consisting essentially of about 5 to 90 mole percent acrylic or methacrylic acid units and about 95 to 10 mole percent itaconic acid units, with a number average molecular weight of about 500.
An essentially homogeneous copolymer having a
By standard techniques such as evaporation followed by drying,
It can be isolated in solid form from the final polymerization solution. However, this copolymer is commonly added to aqueous systems with 7J
I], the final polymerization solution will generally be used as is, optionally diluted or concentrated, without isolation of the copolymer product.

This solution can also be neutralized to form an aqueous solution of the alkali metal, ammonium or amine salt of the copolymer. Suitable alkali metal bases for neutralization include sodium hydroxide, potassium hydroxide and lithium hydroxide, while suitable ammonium and amine bases include ammonia, ammonium hydroxide, 1 to 5 in each alkyl group. There are mono-, di- and trialkylamines having carbon atoms, pyridine, morpholine and lutidine.

The essentially homogeneous (meth)acrylic acid/itaconic acid copolymers of the present invention have typical marginal scale-inhibiting properties, but are highly resistant to alkaline calcium and Particularly useful in preventing the formation of magnesium scale. In such applications, the copolymer is added to the treated water in an amount effective to prevent scale formation, usually at a level of about 0.1 to 100 ppm and preferably about 0.5 to 1 Oppm. added. In such additions, an aqueous copolymer solution of about 1 to 60 weight percent of the copolymer or its equivalent salt can be metered directly into the stream being treated; However, it is preferably diluted with water to a concentration of about 0.1 to 1 weight percent before addition. Evaluation of these essentially homogeneous, controlled, low molecular weight copolymers shows that they are superior to those of the prior art (
It was shown to be superior to meth)acrylic acid/itaconic acid copolymers.

Other additives commonly used in combination with critical scale inhibitors are also effective with the novel inhibitors of this invention. Particularly useful are mineral acids, especially sulfuric acid, with which a portion of the bicarbonate alkalinity present in the seawater etc. to be desalted is neutralized; the degree of bicarbonate neutralization is usually about 80 to 85 percent, especially about 55 to 85 percent
It is a percentage. For example, foam control agents, corrosion inhibitors, and oxygen scavengers can also be utilized with these novel scale inhibitors.

The following examples are merely illustrative (17) and should not be construed as limiting the invention, the scope of which is defined by the appended claims. has been done.

Example 1 1 B 0.1 y (0.70 mol) of itaconic acid and 5.95 F (0.025 mol) of sodium persulfate are mixed in a 300 ml solution equipped with a stirrer, reflux condenser and nitrogen inlet. 100 ml of distilled water in a round bottom flask
It was dissolved in The system was purged with nitrogen and the solution was heated to reflux under a nitrogen atmosphere. 25.8? (0
, 80 mol) of methacrylic acid and 60 ml of water.
A separate stream of an aqueous solution of 99 (0,075 mol) sodium persulfate was added continuously to this refluxing solution using a syringe pump over a period of 5 hours. Once the addition was complete, the solution was refluxed (108° C.) for an additional 60 minutes. The solution thus obtained was then distilled at atmospheric pressure to obtain 8Q
ml of water was removed to produce a concentrate of 239.7f, an orange solution containing 584 weight percent solids. This represents a product yield of 99.5 percent by weight, based on the combined weight of monomer and persulfate initiator r1B) charged.

The molecular weight distribution and chemical homogeneity of the polymer product are 1
25 in triplicate using an acetate-phosphate buffered eluent adjusted to pH 7.4 using N-sodium hydroxide solution.
High pressure liquid chromatography CHPL on cIn60A1L-poradil (u-Porα5il) gel permeation separation tube
C) is determined by this Polan /l/ (
The separator tube was calibrated with 1,2,8° 4-butanetetracarboxylic acid and Goodrite) K 782 and 752 polyacrylic acid esters of known molecular weight. With this analysis,
The product was shown to be a homogeneous copolymer with a number average molecular weight of 1600 and a weight average molecular weight of 2940.

Using sodium persulfate initiators at various acrylic acid/itaconic acid and methacrylic acid/itaconic acid monomer ratios and various mole percent relative to total monomers, as shown in Table 1. Then, repeat the manufacturing method of Example 1. As a result, for each MI'a example V, the indicated number and weight l
A virtually homogeneous co-weighted body with an average molecular weight of 5V was obtained.

68 ynl of water to the reactor of Example 1, stirred.

Ferrous sulfate 7-eternal 0.08 F (0.8 mmol)
39.09 (0.80 mol) of itaconic acid and itaconic acid were charged. The reactor was purged nine times and the resulting solution was heated to reflux (100° C.) while maintaining a positive nitrogen atmosphere. 3.69 F (15,0
mmol) of sodium persulfate, 9.9 mmol in 80 me of water
Separate streams of 2 f (95,0 mmol) of sodium bisulfite and 50,4 f (0,70 mol) of icy acrylic acid were refluxed continuously over a period of 3.5 h. added to the solution. Once the simultaneous additions were complete, the solution was kept at reflux temperature I for an additional 60 minutes. The resulting yellow solution had a solids content of 52.8 percent by weight.
The weight was 1i205.6f, representing a yield of 105.2 weight percent based on the reactants charged. II PLC analysis of the product solution indicates that the product is a substantially homogeneous (meth)acrylic acid/itaconic acid copolymer with a number average molecular weight of 12,210 and a weight average molecular weight of 4,460. showed that.

Itaconic acid/°acrylic acid molar ratio 70. /30 and
Repeating this process using 1.5 mole percent sodium persulfate, 9.5 mole percent sodium bisulfite, and 0.08 mole percent ferrous sulfate redox initiators resulted in a number average molecular weight 900 and a weight average molecular weight of 191O was obtained with a product yield of 68.2 weight percent.

Example 4 123.5 f (0.95 mol) of itaconic acid was added to 4
4.8 F (0.05 mol) at 80°C in the presence of 7.6 F (20 mol percent) sodium persulfate
The preparation method of Example 1 is repeated except that it is copolymerized with methacrylic acid. The icy methacrylic acid and sodium persulfate (as a 10% aqueous solution (21)) are all added continuously in separate streams over an 8 hour period. After completing the attachment, continue for another 10 minutes7
Continue the JIl fever. A substantially homogeneous low molecular weight (meth)acrylic acid/itaconic acid copolymer similar to the copolymer of Example 1 is obtained.

Comparative Example 1 - Nis Marvel (C, S, Mατvel) and T H N Ephard (T, H, 5heph
-erd) Journal Organic Chemistry
-C1 (meth)acrylic acid/itaconic acid copolymer (
65/35 acrylic acid/itaconic acid) was prepared in water. Number average molecular weight as determined by HPLC is 80
Copolymers greater than 00 were obtained in high yields.

Comparative Example 2 A (meth)acrylic acid/itaconic acid composite (50150 acrylic acid/itaconic acid and methacrylic acid) was prepared according to the process described in Example 1 of U.S. Pat. No. 8,366,509. acid/itaconic acid) was produced. The metathallyl/ichconic acid conjugate formed a rubbery gel in water that prevented isolation and scale control testing. The acrylic acid/itaconic acid copolymer was obtained in virtually quantitative yield, i o, o o as determined by HPLC.
It had a number average molecular weight greater than o.

EXAMPLES & The methacrylic acid/itaconic acid and acrylic acid/itaconic acid copolymers of each of the previous examples were tested in a laboratory single-stage flattened evaporator using synthetic seawater to determine their scale control. determined the effect.

Methods for operating and testing laboratory evaporators are described in Desalination (1) esalination, 31.279 (
Auerbach and Carrushers (1979). Synthetic seawater sails with increased bicarbonate content to increase the likelihood of scale formation. /
kg7i-containing salt water office (the office)
of 5a-1ine Water) (23). The copolymer concentration in this test was 8 parts per million based on active solids.

The results of the test are summarized in Section ①. The percent adhesion scale is calculated from Eq. Copolymers that give a lower "% Adhesion Scale" at a given usage rate will give superior efficacy.

(2nd Table ■ IA/MAA, 90/10 2A 1
9.4IA/MAA, 50150 2E
18.5IA, /MAA, 10/90 2F
21. OIA/AA, TO/80 8
19.6IA, /AA, 85/65
Comparative example 1 24.3IA, /AA, 50
150 Comparative Example 2 88.2 Control (without additives)
48.5 special if' 7.111
ilT person Fufui Nozomi-I7koP↓-Chiad'(
26)

Claims (1)

Claims: 1) about 957 mole percent LIO itaconic acid monomer and about 5 to 90 mole percent acrylic or methacrylic acid monomer, based on the total amount of the two monomers. in the presence of about 5 to 20 mole percent polymerization initiator at a temperature of about 80 to 120°C.
during said period of time, said acrylic or methacrylic acid monomer and at least half of said initiator are separately and essentially continuously brought into contact with said itaconic acid monomer in solution in said medium. A method for producing a substantially homogeneous (meth)acrylic acid/itaconic acid copolymer having a number average molecular weight of about 500 to 7000, comprising: 2) about (1) 2 to 25 percent of said itaconic acid monomer and said initiator are dissolved in said medium and the remainder of said initiator is introduced over said period of time; Method. 3) A method according to claim 1 or 2, wherein the resulting copolymer solution is maintained at said temperature for about 10 to 120 minutes after said addition. 4) Claim 1 in which the initiator is an acid system.
A method according to paragraph 1131. 5) The method of claim 1, wherein about 95 to 60 mole percent itaconic acid monomer is copolymerized with about 5 to 40 mole percent methacrylic acid monomer. 6) Separately about 5 to 40 mole percent methacrylic acid monomer, about 1 to 2 mole percent sodium persulfate, and about 6 to 12 mole percent sodium bisulfite at ambient pressure and reflux temperature of about 3. Add 1 to an aqueous solution of about 95 to 60 mole percent itaconic acid monomer and about 0.02 to 04 mole percent ferrous sulfate over a period of from 1 to 5 hours, and after this addition, reduce the solution to about 8. A method according to claim 8, wherein the temperature is maintained for a period of from 45(2) to 75 minutes. 7) A substantially homogeneous copolymer consisting essentially of about 5 to 90 mole percent acrylic or methacrylic acid units and about 95 to 10 mole percent itaconic acid units and having a number average molecular weight of about 500 to 7000. . 8) The copolymer of claim 7 having about 5 to 40 mole percent methacrylic acid units and about 95 to 60 mole percent itaconic acid units. 9) % Alkali metal, ammonium or amine salt of the copolymer according to claim 7. 10) An aqueous solution containing about 1 to 60 weight percent of the copolymer according to claim 7 or 9. ■) mixing an effective amount of the copolymer according to claim 7 or 9 with water containing scale-forming impurities; Scale (3) How to prevent formation. 12. The method of claim 11, wherein said copolymer is mixed with said water at a concentration of about 0.5 to 1' Oppm. B) The method according to claim 11, wherein the water is seawater for seawater desalination. 14) The method of claim 13 further comprising adding sufficient sulfuric acid to the seawater to neutralize about 55 to 85 percent of its bicarbonate alkalinity.