JPH10314794A - Scale inhibitor - Google Patents

Abstract

(57) [Problem] To provide a scale inhibitor effective for preventing adhesion of various scales generated in a boiler, a cooling water system or the like. A copolymer having 5 to 30 mol% of 2,3-dihydroxypropyl allyl ether units, 10 to 35 mol% of a monomer unit having a sulfonic acid group and 60 to 85 mol% of an acrylic acid unit or a methacrylic acid unit, or a copolymer thereof. A scale inhibitor comprising a salt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a scale inhibitor. More particularly, the present invention relates to scale inhibitors such as boilers, cooling water systems and the like.

[0002]

2. Description of the Related Art Scale disturbances occur on heat transfer surfaces and pipes in contact with water, such as cooling water systems and boiler water systems. Particularly, in the open circulation type cooling water system, from the standpoint of resource saving and energy saving, when performing high concentration operation by reducing the discharge (blowing) of cooling water to the outside of the system, dissolved salts are concentrated and heat transfer is performed. The surface becomes susceptible to corrosion and becomes a sparingly soluble salt and scales. The resulting scale can cause serious difficulties in the operation of boilers and heat exchangers, such as reduced thermal efficiency and blocked pipes. As the scale species to be generated,
Calcium carbonate, calcium sulfate, calcium sulfite,
Calcium phosphate, calcium silicate, magnesium silicate, magnesium hydroxide, zinc phosphate, zinc hydroxide,
And basic zinc carbonate. For calcium-based and magnesium-based scales, a polymer having a carboxyl group obtained by polymerizing maleic acid, acrylic acid, itaconic acid, etc. is effective as a scale inhibitor, and a monomer having a carboxyl group, vinyl sulfonic acid, allyl A copolymer in which monomers having a sulfonic acid group such as sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, and 2-hydroxy-3-allyloxy-1-propanesulfonic acid are combined according to the target water quality, as a scale inhibitor Commonly used. For silica-based scales, acrylamide-based, quaternary ammonium salt-based, scale-inhibiting agents using polyethylene glycol, and the like have been proposed, and polymers are used depending on the scale type. The water used in the cooling water system is usually industrial water, tap water, or the like, and therefore various ionic species are present in the water. Therefore, especially in the case of performing a high concentration operation, a scale inhibitor which can effectively cope with all scale species is required, but such a scale inhibitor has not yet been developed. In particular, at present, there is no polymer effective for preventing the adhesion of silica-based scale. In Japanese Patent Publication No. 5-57040, a scale inhibitor containing an acrylamide polymer and an acrylic acid polymer is proposed as a scale inhibitor having an excellent effect of preventing silica scale. However, although this scale inhibitor has a scale preventing effect when the silica concentration in water is low, the effect is insufficient when the silica concentration is high.

[0003]

SUMMARY OF THE INVENTION The present invention relates to a boiler,
The object of the present invention is to provide a scale inhibitor effective for preventing adhesion of various scales generated in a cooling water system or the like.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that 2,3-dihydroxypropylallyl ether unit, a monomer unit having a sulfonic acid group and acrylic acid or A copolymer having methacrylic acid units at a specific ratio or a salt thereof has been found to have an excellent scale-inhibiting effect,
Based on this finding, the present invention has been completed. That is, the present invention relates to a copolymer having 5 to 30 mol% of 2,3-dihydroxypropyl allyl ether units, 10 to 35 mol% of a monomer unit having a sulfonic acid group, and 60 to 85 mol% of an acrylic acid unit or a methacrylic acid unit. Or a scale inhibitor characterized by containing a salt thereof.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The scale inhibitor of the present invention comprises 2,2
3-dihydroxypropyl allyl ether unit 5 to 30
Mol%, 10 to 35 monomer units having a sulfonic acid group
Mol% and acrylic acid or methacrylic acid units 60 to 85
It contains a copolymer having a mole% or a salt thereof. Two,
The 3-dihydroxypropyl allyl ether unit is a monomer unit represented by the formula [1].

Embedded image In order to introduce 2,3-dihydroxypropyl allyl ether unit into the copolymer, for example, 2,3-dihydroxypropyl allyl ether represented by the formula [2] can be copolymerized, or the formula [3] After copolymerizing the allyl glycidyl ether represented by the formula, the oxirane ring in the copolymer can react with water to open the ring.

Embedded image

In order to introduce a monomer unit having a sulfonic acid group into the copolymer, a monomer having a sulfonic acid, for example, vinyl sulfonic acid, styrene sulfonic acid, allyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid , 2-hydroxy-3-allyloxy-1-propanesulfonic acid, isobrenesulfonic acid, and other monomers or their salts can be copolymerized. There is no particular limitation on the method of introducing acrylic acid units or methacrylic acid units into the copolymer, for example, acrylic acid or methacrylic acid or a salt thereof can be copolymerized, or acrylic acid ester, methacrylic acid ester, After copolymerizing acrylic acid or a methacrylic acid derivative such as acrylamide or methacrylamide, the copolymer can be hydrolyzed into acrylic acid units or methacrylic acid units.

In the scale inhibitor of the present invention, two adjacent hydroxyl groups of the 2,3-dihydroxypropyl allyl ether unit in the copolymer form a hydrogen bond with the hydroxyl group of silica, and the sulfonic acid group has a scale dispersing effect. It is considered that the carboxyl group of the acrylic acid unit or the methacrylic acid unit adsorbs cations such as calcium ions and magnesium ions, and these effects act synergistically to exhibit an excellent scale prevention effect. The proportion of monomer units in the copolymer used in the scale inhibitor of the present invention is such that 5 to 30 mol% of 2,3-dihydroxypropyl allyl ether units and 10 to 35 mol% of monomer units having a sulfonic acid group. , Acrylic acid or methacrylic acid units are 60 to 85 mol%. When the ratio of each monomer unit is out of the above range and becomes small, it becomes difficult for each monomer unit to fulfill a role to be fulfilled, so that a sufficient scale prevention effect may not be obtained. In addition, when the ratio of each monomer unit is increased beyond the above range, the ratio of other monomer units is inevitably reduced, and it becomes difficult to fulfill the role that the monomer unit should play. The effect may not be sufficiently obtained.

In the copolymer used for the scale inhibitor of the present invention, a monomer unit other than a 2,3-dihydroxypropyl allyl ether unit, a monomer unit having a sulfonic acid group, an acrylic acid unit or a methacrylic acid unit may be introduced, if necessary. can do. Monomers that can be copolymerized to obtain such copolymers include, for example, acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, N-methylacrylamide, N, N-dimethylacrylamide, methyl acrylate, methyl methacrylate, ethyl Acrylate, ethyl methacrylate, styrene, nonionic monomers such as allyl alcohol, crotonic acid, maleic acid, fumaric acid, anionic monomers such as itaconic acid and alkali metal salts thereof, allylamine, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, Quaternary ammonium salts or tertiary salts such as diethylaminoethyl acrylate and diethylaminoethyl methacrylate, diallyldimethylammonium chloride And the like. The copolymerization method for obtaining the copolymer used in the present invention is not particularly limited. For example, a water-soluble polymerization initiator such as an azo type or a peroxide type is used, the monomer concentration is 5 to 50% by weight, and the polymerization temperature is 50. At 100 ° C. to 100 ° C., ordinary aqueous radical polymerization can be performed. In addition to the aqueous solution radical polymerization, solution polymerization in an organic solvent, emulsion polymerization, suspension polymerization, and bulk polymerization can also be performed. If necessary, an alcohol such as methanol or propanol can be added as a chain transfer agent for controlling the molecular weight.

The copolymer used in the scale inhibitor of the present invention preferably has a molecular weight of 2,000 or more.
When the molecular weight is 2,000 or more, a good scale preventing effect can be exhibited. The molecular weight of the copolymer is
It can be measured by gel permeation chromatography. The scale inhibitor of the present invention can be added to an applied aqueous system as an aqueous solution adjusted to an arbitrary concentration. Usually, it is preferable to add the copolymer so that the concentration of the copolymer in water to be applied is 1 to 100 mg / liter. The scale inhibitor of the present invention can be used in combination with another scale inhibitor as needed. As the scale inhibitor to be used in combination, for example, polyacrylic acid, polymaleic acid, acrylic acid and 2-acrylamide-2-
Copolymers with methylpropanesulfonic acid, N, N, N ',
A reaction product of N'-tetramethylethylenediamine with epichlorohydrin and a reaction product of N, N, N ', N'-tetramethylethylenediamine with dichloroethyl ether can be exemplified. The scale inhibitor of the present invention can be added to the same solution as an anticorrosive such as an organic phosphonate, a bactericide such as hydrazine, if necessary, or separately, It can also be injected.

The water quality conditions and the operating conditions of the boiler and heat exchanger when the scale inhibitor of the present invention is applied are not particularly limited, and the present invention is applied to the ordinary operating conditions and water quality of boilers and heat exchangers. Can be. Scale inhibitor of the present invention, calcium carbonate, calcium sulfate, calcium phosphate, zinc phosphate, zinc hydroxide, magnesium silicate, silica, etc., boiler, formed in a cooling water system,
The scale attached to the heat transfer surface and the pipe wall surface can be effectively prevented. Although the detailed mechanism of action of the scale inhibitor of the present invention for suppressing the adhesion of scale is unknown,
Adsorption by hydrogen bonding between two adjacent hydroxyl groups of 3-dihydroxypropyl allyl ether unit and hydroxyl group of silica, adsorption of carboxyl group of acrylic acid unit or methacrylic acid unit to cations such as calcium ion and magnesium ion, and It is considered that the combination of the dispersing effect of the scale by the sulfonic acid group of the monomer unit having the sulfonic acid group effectively prevents the adhesion to the wall surface of the scale.

[0011]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. Table 1 shows the polymers used in Examples and Comparative Examples.

[0012]

[Table 1]

The scale deposition rate was determined by the following method. That is, in an open-circulation cooling water system with a heat transfer area of about 0.25 m ² and a retained water amount of 0.45 m ³ , water obtained by adding pure water and salts to Atsugi City water as circulation water and makeup water In addition, it was operated for 30 days while controlling the water quality to be constant. The material of the heat exchanger tube is SUS
At 304, an outer diameter of 19 mm was used. The circulating water inlet temperature is 45 ° C., the circulating water outlet temperature is 75 ° C., and the circulating water flow rate is 0.5 m / sec. A predetermined amount of scale inhibitor added to the water system, the scale deposited on the heat exchanger tubes were taken after 30 days, and weighed after drying at 105 ° C., the deposition rate of the scale (mg / cm ^2/30 days ) The unit was determined. Similarly collected, dried scales were weighed acid insolubles those ashed at 600 ° C. was determined deposition rate of silica scale (mg / cm ^2/30 days) units. Examples 1-4, Comparative Examples 1-4 pH 9.0, calcium hardness 100 mg / l, M alkalinity 150 mg / l, silica 160 mg / l, magnesium hardness 160 mg / l. A-4 and B-1 to B-4 were added in predetermined amounts to conduct a test. The results are shown in Table 2.

[0014]

[Table 2]

As can be seen in Table 2, it has 5 to 30 mol% of 2,3-dihydroxypropyl allyl ether units, 10 to 35 mol% of monomer units having sulfonic acid groups and 60 to 85 mol% of acrylic acid units. Polymer A-
In 1 to A-4 in Example 1-4 with the addition of not more than the scale deposition rate all 10mg / cm ^2/30 days,
An excellent scale prevention effect is exhibited. On the other hand, Comparative Example 1 in which polymaleic acid as a conventional scale inhibitor was added Comparative Example 2 in which polymer B-2 having no 2,3-dihydroxypropyl allyl ether unit was added, 2,3-dihydroxypropyl In Comparative Example 3 in which the polymer B-3 having a small number of allyl ether units was added and in Comparative Example 4 in which the polymer B-4 having a small number of acrylic acid units was added, the scale adhesion speed was high, and no good scale preventing effect was observed. Examples 5-8, Comparative Examples 5-8 Polymers A-1 to water having a pH of 9.0, calcium hardness of 500 mg / liter, M alkalinity of 500 mg / liter, silica of 200 mg / liter, and magnesium hardness of 200 mg / liter were used. A-4 and B-1 to B-4 were added in predetermined amounts to conduct a test. The results are shown in Table 3.

[0016]

[Table 3]

As can be seen in Table 3, 5 to 30 mol% of 2,3-dihydroxypropyl allyl ether units, 10 to 35 mol% of monomer units having sulfonic acid groups and 60 to 85 mol% of acrylic acid units Polymer A-
In Examples 5 to 8 to which 1 to A-4 were added, the scale adhesion speed was low, and an excellent scale prevention effect was exhibited. On the other hand, in Comparative Example 5, in which polymaleic acid as a conventional scale inhibitor was added, polymer B- having no 2,3-dihydroxypropyl allyl ether unit was used.
In Comparative Example 6 in which 2 was added, Comparative Example 7 in which polymer B-3 having a small amount of 2,3-dihydroxypropyl allyl ether units was added, and Comparative Example 8 in which polymer B-4 having a small amount of acrylic acid units was added, scale adhesion was observed. The speed is high and no good scale prevention effect is observed.

[0018]

The scale inhibitor of the present invention has an excellent effect of preventing scale adhesion in a boiler water system, a cooling water system or the like.

Continued on the front page (72) Inventor Rei Usui 3-4-7 Nishi-Shinjuku, Shinjuku-ku, Tokyo Inside Kurita Industry Co., Ltd.

Claims (1)

[Claims] 1. A copolymer comprising 5 to 30 mol% of 2,3-dihydroxypropyl allyl ether units, 10 to 35 mol% of sulfonic acid group-containing monomer units and 60 to 85 mol% of acrylic acid units or methacrylic acid units. A scale inhibitor comprising a salt thereof.