JPH0852496A - Scale preventing agent - Google Patents

Abstract

PURPOSE:To prevent the generation of a scale in a cooling water device for a cooling tower and seawater desalting device, etc., by constituting a scale preventing agent from a copolymer of alpha, beta-unsatd. carboxylic acid, a specified acrylate, and hydrophobic unsatd. monomer and further adding other copolymerizable monomer, at need. CONSTITUTION:This scale preventing agent is composed of the alpha, beta-unsatd. carboxylic acid (salt), (meth)acrylate of ethylene oxide adduct (additional mol. number of 15-50) to a 6-30C mono-ol, hydrophobic unsatd. monomer and further other copolymerizable monomer, at need. In a method to obtain a scale preventing effect, the scale preventing agent is injected continuously in a circulating water line with a constant rate pump, or injected intermittently, or injected only when concentrating ratio is increased. The scale preventing agent may be injected without diluting or may be injected after being diluted with water to an appropriate concn.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scale inhibitor composed of a specific copolymer. More specifically, the present invention relates to a scale inhibitor having an excellent scale inhibiting effect in a circulating water system having a high metal ion concentration.

[0002]

2. Description of the Related Art Conventionally, for cooling water such as a cooling tower,
Polycarboxylic acid polymers such as poly (meth) acrylic acid salts and polymaleic acid salts are used as scale inhibitors for desalination of seawater for securing industrial water and drinking water. However, these scale inhibitors are not sufficiently satisfactory for scale prevention in a circulating water system containing a large amount of inorganic ions such as calcium and magnesium. In order to improve the drawbacks of these polycarboxylic acid salt polymers, copolymers (salts) of (meth) acrylic acid and (meth) acrylic acid hydroxyethyl ester, copolymers of maleic acid and glycerin monoallyl ether are used. Polymers (salts), copolymers (salts) of (meth) acrylic acid and polyalkylene glycol monoallyl ether, etc. are known.

[0003]

However, even these improved scale inhibitors have a problem that the scale preventing effect in the circulating water system is still insufficient.

[0004]

The present inventors have arrived at the present invention as a result of extensive studies to obtain a scale inhibitor having a high scale preventing effect in a circulating water system. That is, the present invention includes (a) an α, β-unsaturated carboxylic acid (salt), and (b)
(Meth) acrylate of ethylene oxide adduct of monool having 6 to 30 carbon atoms (addition mole number of 15 to 50), (c) hydrophobic unsaturated monomer, and (d) if necessary.
It is a scale inhibitor comprising a copolymer (A) with another copolymerizable monomer.

In the present invention, the α, β-unsaturated carboxylic acid (salt) of (a) is, for example, (meth) acrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, itaconic anhydride, Α, β-unsaturated carboxylic acids or their anhydrides such as citraconic acid and citraconic anhydride;
And alkali metal (lithium, sodium, potassium, etc.) salts, alkaline earth metal (calcium, magnesium, etc.) salts, ammonium salts, organic amines (alkanolamines, lower alkylamines, etc.) salts of these α, β-unsaturated carboxylic acids , And combinations of two or more of these. Among these, preferred are (meth) acrylic acid, itaconic acid, maleic acid, fumaric acid, alkali metal salts or ammonium salts thereof, and combinations of two or more thereof.

In (b) the (meth) acrylate of 15 to 50 moles of monooleic ethylene oxide having 6 to 30 carbon atoms, the monool usually has 6 to 3 carbon atoms.
0, preferably 10 to 20, and the number of added moles of ethylene oxide is usually 15 to 50, preferably 20 to 4
0.

The mono-ol having 6 to 30 carbon atoms includes groups such as a linear or branched alkyl or alkenyl group, an aryl group, an aralkyl group, and an alkylaryl group having a linear or branched alkyl group. However, monools having 6 to 30 carbon atoms can be mentioned.

Specific examples of (b) include the following 1) to 5).
Compounds, but are not limited thereto. 1) (Meth) acrylate of nonylphenol ethylene oxide 20 mol adduct 2) (meth) acrylate of distyrenated phenol ethylene oxide 30 mol adduct 3) benzyl alcohol ethylene oxide 15 mol adduct (meth) acrylate 4) Lauryl alcohol ethylene (Meth) acrylate of 30 mol adduct of oxide 5) Stearyl alcohol (meth) acrylate of 40 mol adduct of ethylene oxide

Examples of the hydrophobic unsaturated monomer (c) include, but are not limited to, the following (c1) to (c4). (C1) Aromatic ethylenically unsaturated monomer: styrene, α
-Styrenes such as methylstyrene and vinyltoluene, halogen-substituted styrenes such as vinylnaphthalene and dichlorostyrene, etc. (c2) Aliphatic ethylenically unsaturated monomer: ethylene, propylene, butene, isobutylene, pentene, Heptene, diisobutylene, octene, dodecene, octadecene, butadiene, isoprene, etc. (c3) Alicyclic ethylenically unsaturated monomer: cyclopentadiene, pinene, limonene, indene, bicyclopentadiene, ethylidene norbornene, etc. (c4) Carbon number 1 An alkyl (meth) acrylate having an alkyl group of 50 to 50: methyl (meth) acrylate,
Ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, eicosyl (meth) acrylate ( Preferred among (c1) to (c4) are (c1),
Among (c2) and (C4), the alkyl group has 1 to 20 carbon atoms.

The other copolymerizable monomer (d) is another monomer copolymerizable with (a), (b) and (c), and is used if necessary. Examples of (d) include the following (d1) to (d3). (D1) Amide-containing ethylenically unsaturated monomer: (meth)
Acrylamide, N-methylol (meth) acrylamide, etc. (d2) Ethylenically unsaturated monomer having a hydroxyl group: hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, etc. Polyalkylene glycol other than (d3) and (b) Chain-containing ethylenically unsaturated monomer: polypropylene glycol (molecular weight 522) monoacrylate, methyl alcohol ethylene oxide 10 mol adduct (meth) acrylate, etc. Among (d1) to (d3), preferred ones are (d2) and It is (d3).

The proportion of monomers constituting the copolymer (A) is, on a weight basis, (a) usually 20 to 90%, preferably 30 to 60%; (b) usually 5 to 60%. , Preferably 10 to 40%; (c) is usually 5 to 50%, preferably 1
0-40%; (d) is usually 0-30%, preferably 0
20%.

The weight average molecular weight of the copolymer (A) is usually 1,000 to 500,000, preferably 3,000 to.
It is 100,000. More preferably from 7,000
It is 50,000. When the molecular weight is less than 1,000, a large amount of scale inhibitor is required and the scale inhibiting effect is insufficient, and the molecular weight is 500,0.
Even when it exceeds 00, the scale preventing effect is insufficient.

The method for producing the copolymer (A) is not particularly limited, and it can be produced, for example, by a solution polymerization method. Examples of the solution polymerization method include (a), (b), and (c)
And optionally (d) with a solvent [eg, water, isopropyl alcohol, toluene, ethylene dichloride,
Methyl ethyl ketone, a mixed solvent of two or more of these, etc.], and the polymerization is usually carried out at 50 to 150 ° C. under normal pressure or under pressure. For the polymerization, a radical polymerization initiator (persulfate, azobisisobutyronitrile, benzoyl peroxide, dicumyl peroxide, etc.) is usually added in an amount of 0.1 to 15 weights based on the total weight of (a) to (d). % Used. If necessary, a chain transfer agent (lauryl mercaptan, thioglycolic acid, mercaptoethanol, etc.) is used. When α, β-unsaturated carboxylic acid is used as (a), a neutralizing agent is optionally used after the polymerization to form a completely or partially neutralized salt of the copolymer. The organic solvent used in the reaction can be distilled off if necessary.

As a method for obtaining the scale prevention effect by using the scale inhibitor of the present invention, continuous injection with a metering pump into the circulating water system line or intermittent injection or a high concentration factor is possible. There is a method to inject only when it becomes. The scale inhibitor may be injected neat or diluted with water to a suitable concentration.

[0015]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto. In each example,
Parts and% are by weight unless otherwise specified.

Example 1 50 parts of water and 160 parts of isopropyl alcohol were placed in a reaction vessel.
Part, charged with nitrogen, heated to 80 ° C., stirred,
63.7 parts of methacrylic acid and polyoxyethylene (n = 2
0) 2-ethylhexyl ether methacrylate 1
A mixture of 0.0 parts and 10.0 parts of butyl methacrylate and 27 parts of 10% sodium persulfate aqueous solution were simultaneously added dropwise over 5 hours to react. After further aging at the same temperature for 1 hour, the mixture was neutralized with 98.8 parts of a 30% aqueous sodium hydroxide solution, and isopropyl alcohol was removed to give a solid content of 2
Water was added in an amount of 5% to obtain a copolymer salt having a weight average molecular weight of 6,500.

Example 2 Example 1 except that the monomer composition was changed as shown in Table 1.
A copolymer salt was obtained in the same manner as in.

Example 3 A reaction vessel was charged with 210 parts of ethylene dichloride and 47.9 parts of maleic anhydride, the atmosphere was replaced with nitrogen, the temperature was raised to 80 ° C., and polyoxyethylene (n = 35) lauryl ether was stirred. Acrylate 13.0 parts, styrene 3
A mixture of 9.1 parts and 9 parts of an azobisisobutyronitrile 10% ethylene dichloride solution were simultaneously added dropwise over 3 hours for reaction. After further aging for 1 hour at the same temperature, neutralized with 130.4 parts of a 30% aqueous sodium hydroxide solution, ethylenedichloride was removed, and the solid content was 30%.
Was added to obtain a copolymer salt having a weight average molecular weight of 12,000.

Example 4 Example 1 except that the monomer composition was changed as shown in Table 1.
A copolymer salt was obtained in the same manner as in.

Comparative Examples 1 to 3 Example 1 except that the monomer composition was changed as shown in Table 1.
A copolymer was obtained in the same manner as in.

[0021]

[Table 1]

A-1: sodium methacrylate a-2: sodium acrylate a-3: disodium maleate a-4: potassium itaconate b-1: poly (n = 20) oxyethylene 2-ethylhexyl ether methacrylate b-2: acrylate of poly (n = 20) oxyethylene nonylphenyl ether b-3: acrylate of poly (n = 35) oxyethylene lauryl ether c-1: styrene c-2: butyl methacrylate c-3: methyl acrylate d-1: hydroxyl ethyl methacrylate d-2: poly [oxyethylene (n = 5) / oxypropylene (n = 2)] monoallyl ether

Performance Evaluation Example The copolymers obtained in Examples 1, 2, 3 and 4 and the (co) polymers of 1, 2, and 3 as comparative examples were used to evaluate the scale inhibiting effect against calcium carbonate. Scale prevention evaluation method: Mix 250 ml of deionized water with 50 ml of 0.29% calcium chloride aqueous solution, 50 ml of 0.44% sodium hydrogen carbonate, and 50 ml of scale inhibitor aqueous solution containing 100 ppm of the above polymer (equivalent to addition of 10 ppm). After adjusting the pH to 8.5 with 0.1N sodium hydroxide, deionized water was added to 500 ml to prepare a 5 times supersaturated aqueous solution of calcium carbonate at 25 ° C. Further, a solution in which the scale inhibitor addition amount was changed to 5 ppm and 20 ppm was prepared by the same method. Place 300 ml of these solutions in a glass bottle, stopper tightly, and cool at 60 ° C for 24
The mixture was allowed to stand for a time and the amount of calcium carbonate deposited was observed. Table 2 shows the results. As shown in Table 2, the copolymer of the present invention has an excellent scale preventing effect.

[0024]

[Table 2] ⊚: No precipitate, ◯: Little precipitate, Δ: Many precipitates, ×: Very many precipitates.

[0025]

EFFECTS OF THE INVENTION By using the scale inhibitor of the present invention, it is possible to prevent the generation of scale in cooling water (circulating water) for cooling towers, seawater desalination equipment, etc., and to prevent the reduction of thermal efficiency due to scale adhesion.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Nao Yamauchi 1-11, Hitotsubashi-honcho, Higashiyama-ku, Kyoto Sanyo Kasei Kogyo Co., Ltd. (72) Inami Nami Ohsagaya 1-11, 11-Hashino-no-cho, Higashiyama-ku, Kyoto Sanyo Kasei Industry Co., Ltd.

Claims (5)

[Claims] 1. (a) α, β-unsaturated carboxylic acid (salt)
And (b) a (meth) acrylate of an ethylene oxide adduct of monool having 6 to 30 carbon atoms (addition mol number of 15 to 50), (c) a hydrophobic unsaturated monomer, and (d) if necessary. ) Copolymer (A) with other copolymerizable monomer
An anti-scaling agent comprising: 2. The compound (a) is at least one compound selected from the group consisting of (meth) acrylic acid, itaconic acid, maleic acid, fumaric acid, and alkali metal salts or ammonium salts thereof. Scale inhibitor. 3. (c) is an aromatic ethylenically unsaturated monomer, an aliphatic ethylenically unsaturated monomer and a carbon number 1 to 2
The scale inhibitor according to claim 1 or 2, which is at least one monomer selected from the group consisting of (meth) acrylates having 0 alkyl group. 4. The copolymer (A), on a weight basis,
4. A copolymer containing 20 to 90% of (a), 5 to 60% of (b), 5 to 50% of (c), and 0 to 30% of (d) as a constitutional unit. The scale inhibitor according to any one of 1. 5. The weight average molecular weight of the copolymer (A) is
The scale inhibitor according to any one of claims 1 to 4, which is 1,000 to 500,000.