JPH0667516B2 - Scale inhibitor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel scale inhibitor, and more specifically, it relates to a polymer sulfonic acid-based agent used in boilers, condensers, heat exchangers, gas scrubbers, etc. It relates to scale inhibitors.

(Prior art) Generally, in a water system such as a boiler, a condenser, a heat exchanger, a gas scrubber, etc., corrosion or scale is generated on the metal pipe surface, the wall surface of the water passage, the heat transfer surface of the boiler, etc., leading to a decrease in efficiency. Not only this, but it can also lead to pipe blockage accidents, so that great care is taken to prevent corrosion and scale formation.

In order to prevent such an obstacle, an additive called a scale inhibitor is usually added to such an aqueous system to recirculate the water. Conventionally, as the scale inhibitor, a polymerized phosphate or a carboxylic acid polymer compound salt having a relatively low molecular weight (for example, polyacrylate, polymaleate, etc.) is used. However, although the polymerized phosphate is effective, it has a non-permanent scale-inhibiting power, and its amount must be limited due to the problem of eutrophication. On the other hand, carboxylate-based polymer compound salts (Japanese Patent Publication No. 53-20475).
No. 54-29998, etc.) has the same efficacy as polymerized phosphate when used in a cooling water system, etc.,
When the metal ion concentration becomes high, there is a drawback that it forms an insoluble salt and does not act effectively. For example, when the concentration of calcium ions, which is a hardness component of water, increases, it enters a turbid region (turbidity region), and water is opaque due to the formation of an insoluble salt. In extreme cases, precipitation may occur. Water systems such as boilers, condensers, heat exchangers, and gas scrubbers often contain a large amount of metal ions, and improvement in performance in this respect has been strongly desired.

(Problems to be Solved by the Invention) In such a situation, the present inventors have conducted a search for a scale inhibitor that does not contain phosphorus, and does not form an insoluble salt with a metal ion and is difficult to enter into a territory region.
The inventors have found that a salt of a polymer compound having a specific structure containing a sulfonic acid group which is a strong acid in the molecule is useful, and completed the present invention.

(Means for Solving Problems) Thus, according to the present invention, a water-soluble salt of a dicarboxylic acid-based polymer sulfonic acid containing a sulfonic acid group bonded through an acid imide bond in the molecule is contained as an active ingredient. An anti-scale agent is provided.

The dicarboxylic acid type polymer sulfonic acid used in the present invention has a sulfonic acid group bonded through an acid imide bond in the molecule. Such polymeric sulfonic acids are usually
Having a molecular weight of 500 to 50,000, preferably 1,000 to 10,000,
And a polymer or copolymer synthesized by appropriately combining three kinds of monomer units of (A), (B) and (C) as defined below, that is, 2 to 100 mol% of (A) sulfonic acid type monomer, Preferably 5 to 100 mol%, (B) unsaturated carboxylic acid monomer 0 to 98 mol%, preferably 0
˜95 mol% and (C) another vinyl monomer, 0 to 90 mol%, preferably 0 to 60 mol%.

Here, the (A) sulfonic acid type monomer means an imide of an α, β-unsaturated dicarboxylic acid having a sulfonic acid group bonded via an acid imide bond, and a sulfonic acid group means
In addition to a narrowly defined sulfonic acid group represented by SO ₃ H, a sulfonic acid ester residue represented by —OSO ₃ H is also included.

Specific examples of such α, β-unsaturated dicarboxylic acid imides include α, β-unsaturated dicarboxylic acids such as maleic acid, citraconic acid, and itaconic acid, and aminomethanesulfonic acid, aminoethanesulfonic acid, amino- 2-
Methyl propane sulfonic acid, aminobutane sulfonic acid,
Aniline monosulfonic acid, aniline disulfonic acid, aminotoluenesulfonic acid, naphthylaminomonosulfonic acid, naphthylamine disulfonic acid, naphthylamine trisulfonic acid, amide sulfuric acid, monoaminoethyl sulfate, monoaminopropyl sulfate, monoaminobutyl sulfate, monoamino sulfate Examples thereof include imides with a primary amino group-containing sulfonic acid containing 1 to 3 sulfonic acid groups such as hexyl and monoaminooctyl sulfate, and among them, aliphatic or aromatic primary having 1 to 10 carbon atoms. The imide with an amino group-containing sulfonic acid is preferred.

Incidentally, the monomer unit (A) is represented by the general formula [I] by taking maleic acid imide as an example.

(In the formula, A represents a divalent to tetravalent organic residue, a and b both represent 0 or 1, c represents an integer of 1 to 3, and when b = 1, c = 1.) ) The unsaturated carboxylic acid-based monomer refers to an unsaturated monomer having a carboxyl group or an acid anhydride group,
Specific examples thereof include acrylic acid, methacrylic acid,
Α, β-unsaturated dicarboxylic acids such as crotonic acid,
Α, β such as maleic acid, fumaric acid, itaconic acid
-Α, β-unsaturated dicarboxylic acid anhydrides such as unsaturated dicarboxylic acid, maleic anhydride, itaconic acid anhydride, citraconic acid anhydride, etc. are exemplified, and among them, α, β-unsaturated dicarboxylic acid anhydrides are preferred. To be done.

Further, (C) the other vinyl monomer may be any radical polymerizable compound other than the above, and specific examples thereof include ethylene, propylene, butene, pentene, hexene, octene, decene, cyclopentene, cyclohexene, and styrene. , Vinyltoluene, α-methylstyrene, coumarone, indene, vinyl ether, ethyl acrylate, methyl methacrylate, acrylamide,
Mention may be made of polar or non-polar vinyl monomers such as acrylonitrile, vinyl acetate and the like.

The dicarboxylic acid type polymer sulfonic acid used in the present invention is not limited by the production method, and can be appropriately produced according to a conventional method. Also, if necessary, directly without passing through the dicarboxylic acid type polymer sulfonic acid,
It is also possible to produce a dicarboxylic acid-based polymer sulfonate. Specific examples of such a method include, for example, a method in which a sulfonic acid-based monomer is copolymerized with another monomer as necessary, and a carboxylic acid-based polymer having an acid anhydride group is reacted with an amino group-containing sulfonic acid in a non-aqueous system. Method (US Pat. No. 3,039,870), a carboxylic acid polymer having an acid anhydride group and a salt of an amino group-containing sulfonic acid are reacted at high temperature in the presence of water to directly synthesize a polymer sulfonate. A method (British Patent No. 1,246,953) and the like can be exemplified.

In the present invention, such a water-soluble salt of dicarboxylic acid type polymer sulfonic acid is used as an active ingredient of the scale inhibitor. The dicarboxylic acid-based polymer sulfonate is a sulfonic acid group present in the molecule and a carboxyl group optionally present, or at least a part of an acid anhydride group, preferably 50
Any salt may be used as long as it forms a salt in an amount of not less than mol%, and specific examples thereof include alkali metal salts such as sodium and potassium, and amine salts such as ammonia, triethylamine and triethanolamine. Among them, sodium salt is the most prized in terms of economy.

The method for producing these dicarboxylic acid-based polymer sulfonates is not particularly limited, and as described above, a method for directly synthesizing without passing through the dicarboxylic acid-based polymer sulfonic acid, a dicarboxylic acid-based polymer sulfonic acid was synthesized. After that, any method of neutralizing in the presence of a base according to a conventional method may be adopted.

The amount used in the system when used as a scale inhibitor can be appropriately selected, but is usually 0.1 to 1000 ppm, preferably 0.5 to 5
It is 0 ppm. Further, as long as the effects of the present invention are not substantially impaired, commonly used agents, for example, other scale inhibitors, alka agents, anticorrosive agents, bactericides and the like can be appropriately used in combination.

(Effect of the invention) Thus, according to the present invention, a scale inhibitor capable of preventing precipitation even in a system having a high metal ion concentration can be obtained. Therefore, scale deposition in the system to be reused is prevented and, of course, the system to be used does not adhere to the vessel wall.

(Example) Hereinafter, the present invention will be described more specifically with reference to Examples. The parts and% in the examples and reference examples are based on weight unless otherwise specified.

Reference Example 1 (Preparation Method of Sample) (1) Sample 1 154 parts of isobutylene-maleic anhydride copolymer having a molecular weight of 4,000 (molar ratio 1: 1, sample A), 50 parts with respect to the maleic anhydride part in the copolymer. Charge 148 parts of mol% sodium aminoethanesulfonate and 700 parts of water into an autoclave,
The sulfonation reaction was carried out by reacting at 180 ° C. for 5 hours while stirring. By this reaction, the maleic anhydride moiety was quantitatively reacted, and a sample containing a sulfonic acid group bonded through an acid imide bond in the polymer was obtained.

(2) Samples 2 to 4 Samples 2 to 4 were obtained in the same manner as in Sample 1 by changing the kind of the sulfonating agent to aminomethanesulfonic acid, anilinesulfonic acid or anilinedisulfonic acid.

(3) Samples 5 to 7 According to the same method as in Sample 1, the maleic anhydride polymer (molecular weight was used instead of the inbutylene-maleic anhydride copolymer) was used.
1500, sample B), acrylic acid-maleic anhydride copolymer (molecular weight 4000, molar ratio 7: 3, sample C) or isoamylene-maleic anhydride copolymer (molecular weight 6000, molar ratio 1:
1, Samples D) were used to obtain Samples 5-7.

Example 1 (Effect of preventing calcium carbonate scale) Aqueous calcium chloride solution (250 ppm, CaC adjusted to pH 8.5)
To an Erlenmeyer flask filled with 500 ml of O ₃ min), a predetermined amount of each scale inhibitor was added, and then immersed in a constant temperature water bath at 60 ° C., and allowed to stand for 20 hours. After that, this aqueous solution was subjected to a membrane filter to quantify the calcium concentration of the solution. The scale prevention effect is represented by the scale inhibition rate of the following equation.

The results are summarized in Table 1.

Example 2 (Observation of cloudy region) Aqueous calcium chloride solution (1000 ppm, Ca adjusted to pH 8.5)
CO ₃ minutes), 1ppm of scale inhibitor prepared in Reference Example 1
After the addition, the presence or absence of turbidity or a precipitate in the aqueous solution was visually observed. The results are summarized in Table 2.

From the above results, it is understood that the scale inhibitor of the present invention is superior to the conventional product in the effect of suppressing scale precipitation of calcium carbonate.

Claims (1)

[Claims] 1. A scale inhibitor comprising a water-soluble salt of a dicarboxylic acid type polymer sulfonic acid having a sulfonic acid group bonded through an acid imide bond in the molecule as an active ingredient.