JPH11314953A - Dispersant for gypsum - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a dispersant for gypsum capable of imparting excellent flowability to an aq. slurry of gypsum even when a very small. amt. of the dispersant is added to the slurry. SOLUTION: A water-soluble salt (e.g. sodium salt) of a copolymer of an α,β-unsatd. carboxylic acid anhydride such as maleic anhydride and an alkenyl ether having 2-100 2-18C oxyalkylene groups such as a methoxypolyoxyethylene alkenyl ether is prepd. as an aq. soln. having 10-70 wt.% solid concn. to obtain the objective dispersant for gypsum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gypsum dispersant which imparts excellent fluidity to an aqueous slurry of gypsum.

[0002]

2. Description of the Related Art Gypsum produced by flue gas desulfurization (hereinafter collectively referred to as gypsum) is inexpensive, and is used as a raw material for construction materials such as gypsum board and gypsum plaster by utilizing its excellent fireproofing and soundproofing properties. I have. For example, a gypsum board or the like is obtained by calcining raw gypsum and then pulverizing it into fine particles, mixing this with water to prepare an aqueous slurry, and then sandwiching the aqueous slurry with two board base papers to a predetermined thickness. And then cured.

[0003] In the production of such a gypsum board, the water in the aqueous slurry is reduced, and the gypsum is evenly dispersed.
In addition, an appropriate dispersant is used to ensure fluidity. Conventionally, a naphthalenesulfonic acid formaldehyde condensate (hereinafter, referred to as NASF) -based dispersant has been used as a dispersant.

[0004]

However, according to our study, it has been found that the amount of addition must be increased to some extent in order to maintain the flowability of the aqueous slurry using a NASF-based dispersant. As a result, there is a problem that the cost is increased, and there is a demand for a dispersant capable of imparting excellent fluidity to the slurry with a small amount of addition.

An object of the present invention is to provide a gypsum dispersant capable of imparting excellent fluidity to an aqueous gypsum slurry with a very small amount of addition. As a result of various studies to achieve the above object, the present inventor has found that a water-soluble salt of a copolymer of maleic anhydride and methoxypolyoxyethylene monoalkenyl ether can be added to an aqueous slurry of gypsum with an extremely small amount of addition. The present invention has been found to impart the property, and based on this finding, the present invention has been completed.

[0006]

Thus, according to the present invention, there is provided a copolymer of an α, β-unsaturated carboxylic acid or an anhydride thereof and an alkenyl ether, and at least one water-soluble salt thereof. A gypsum dispersant is provided.

[0007]

Next, the present invention will be described in more detail with reference to preferred embodiments. The main component of the gypsum dispersant of the present invention is a copolymer of an α, β-unsaturated carboxylic acid or an anhydride thereof and an alkenyl ether (hereinafter sometimes simply referred to as a “copolymer”), or a water-soluble solution thereof. It is a salt. Examples of the water-soluble salt include a hydrolyzate of a copolymer, a metal of Group 1A of the periodic table, a metal salt with a metal of Group 2, an ammonium salt, an amine salt and an alkanolamine salt.

Examples of the α, β-unsaturated carboxylic acid and its anhydride include α, β-unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid; maleic acid, fumaric acid, itaconic acid, citraconic acid, and anhydride. Α, β-unsaturated dicarboxylic acids such as maleic acid, itaconic anhydride and citraconic anhydride and anhydrides thereof; Among them, α, β-unsaturated dicarboxylic acids having 4 to 10 carbon atoms and anhydrides thereof are preferable, and maleic anhydride is particularly preferable from the viewpoint of reactivity, quality, economy and the like. These α,
β-unsaturated carboxylic acids can be used alone or in combination of two or more.

The alkenyl ether has the following general formula (I)
It is represented by R ₁ O (AO) _n R ₂ (I) In the formula, AO is one or a mixture of two or more oxyalkylene groups having 2 to 18 carbon atoms. R ₁ is an alkenyl group having 2 to 5 carbon atoms, R ₂ is an alkyl group having 1 to 4 carbon atoms, and n is 2 to 100, preferably 5 to 50.

Specific examples of alkenyl ethers include, for example, methoxypolyoxyethylene monoallyl ether, ethoxypolyethylene monoallyl ether, butoxypolyethylene monoallyl ether, methoxypolyoxypropylene monoallyl ether, ethoxypolypropylene monoallyl ether, butoxypolypropylene monoallyl ether. Allyl ether and the like can be mentioned. Among these compounds, methoxypolyoxyethylene monoallyl ether is preferred. These alkenyl ethers can be used alone or in combination of two or more.

In the copolymerization of an α, β-unsaturated carboxylic acid or its anhydride with an alkenyl ether, if necessary, an ethylenically unsaturated monomer can be further copolymerized. Examples of the ethylenically unsaturated monomer include ethylene, propylene, 1-butene, 2-butene,
Isobutylene, 1-pentene, 2-pentene (isoamylene), 2-methyl-1-butene, 2-methyl-2-butene, 4-methyl-1-pentene, 1-hexene, diisobutylene, 1-octene, 2, 2,4-trimethyl-
C2-C10 aliphatic chain monoolefins such as 1-pentene; C4-C10 aliphatic cyclic monoolefins such as cyclobutene, cyclopentene, cyclohexene, cyclooctene; styrene, α-methylstyrene, vinyltoluene, etc. Vinyl ethers such as methyl vinyl ether; (meth) acrylates such as ethyl acrylate and methyl methacrylate;
Vinyl esters such as vinyl acetate; and coumarone and indene. These ethylenically unsaturated monomers can be used alone or in combination of two or more. Among these ethylenically unsaturated monomers, aliphatic chain monoolefins having 4 to 10 carbon atoms, more preferably 4 to 6 carbon atoms, are preferred.

Although the method for producing the copolymer is not particularly limited, usually, a monomer mixture containing α, β-unsaturated carboxylic acid or its anhydride and alkenyl ether as essential components is mixed with a hydrocarbon solvent such as toluene. Among them, it can be easily produced by a method of copolymerizing the above monomer in the presence of a radical initiator such as an organic peroxide or an azo compound (see, for example, JP-A-1-297411). .

The copolymerization ratio of the α, β-unsaturated carboxylic acid or its anhydride to the alkenyl ether and the ethylenically unsaturated monomer is usually from 30 to 7 for the α, β-unsaturated carboxylic acid.
0 mol%, preferably 40 to 60 mol% and alkenyl ether 70 to 30 mol%, preferably 60 to 40 mol%, 0 to 65 mol%, preferably 0 to 50 mol% of the ethylenically unsaturated monomer. is there.

The weight average molecular weight of the above copolymer (in terms of standard polystyrene as measured by gel permeation chromatography (GPC)) is usually 50.
0 to 100,000, preferably 1,000 to 10,000
00. If the molecular weight is excessively large, the dispersibility decreases, and the viscosity and coagulation action are unfavorably increased. The copolymer can be used as it is or as a water-soluble salt.

When the copolymer used in the present invention is a copolymer of an anhydride of an α, β-unsaturated carboxylic acid and an alkenyl ether, it can be used as it is or as a water-soluble salt. Alternatively, the copolymer may be used in a form in which an acid anhydride group of the copolymer is hydrolyzed to be converted into a carboxyl group. Such a hydrolyzate can be easily obtained by dissolving the copolymer in water.

The water-soluble salt of the copolymer can be obtained by heating the copolymer with a basic compound or an aqueous solution or an aqueous dispersion thereof at a temperature of 100 ° C. by a conventional method to cause a salt-forming reaction. Can be. Examples of the basic compound include hydroxides or oxides of metals of Groups 1A, 2A, and 2B of the periodic table. Group 1A metals include lithium, sodium, potassium and the like. Examples of hydroxides or oxides of these metals include lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium oxide, sodium oxide and And potassium oxide. Of these, sodium hydroxide is preferred. The group 2A metal includes magnesium, calcium, barium and the like, and the group 2B metal includes zinc and the like. Examples of compounds of these metals include basic compounds such as magnesium hydroxide, calcium hydroxide, barium hydroxide, and zinc hydroxide.
Among these, magnesium hydroxide is preferred from the viewpoints of reactivity, quality, economy and the like.

Further, a copolymer of an α, β-unsaturated carboxylic acid or its anhydride and an alkenyl ether (α, β-
In the case of a copolymer of an anhydride of an unsaturated carboxylic acid and an alkenyl ether, the copolymer may be a product obtained by hydrolyzing the acid anhydride group) with ammonia to obtain monoethylamine, diethylamine, triethylamine. Or an alkanolamine compound such as monoethanolamine, diethanolamine, triethanolamine, etc., to obtain an ammonium salt, an amine salt, or an alkanolamine salt, respectively.

The amount of the basic compound used for the neutralization of the copolymer can be appropriately selected according to the amount of the copolymer and its carboxyl group. 30-100 mol% based on acid
(Degree of neutralization 30 to 100%), preferably 40 to 90 mol%.

The α, β- constituents of the gypsum dispersant of the present invention.
Copolymers of unsaturated carboxylic acids or their anhydrides and alkenyl ethers, or their ammonium salts, amine salts, alkanolamine salts, water-soluble salts such as metal salts,
It can be used in solid form or as an aqueous solution. From the viewpoint of handling, a form as an aqueous solution of 10 to 70% by weight is usually awarded.

The amount of the gypsum dispersant of the present invention is usually
0.01 parts by weight based on 100 parts by weight of gypsum powder
To 1.0 part by weight, preferably 0.05 to 0.5 part by weight. If the amount is too small, it is difficult to obtain the effect of reducing the fluidity of the aqueous gypsum slurry, and if it is too large, it is economically disadvantageous. By using the gypsum dispersant of the present invention, an aqueous slurry of gypsum excellent in fluidity can be produced with a small amount of use compared with the conventional NASF-based dispersant, using a small amount of water, and drying. It is possible to reduce time and energy required for evaporating water.

[0021]

EXAMPLES The present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to only these examples.

Production Example To an autoclave, 500 ml of toluene, 566 g of methoxypolyoxyethylene allyl ether (n = 25) and 49 g of maleic anhydride were added, and 10 g of benzoyl peroxide was further added. Polymerized. After completion of the polymerization reaction, the mixture was heated to 110 ° C. under a reduced pressure of about 10 mmHg, and the solvent was distilled off to obtain 610 g of a copolymer as a transparent viscous liquid. Add distilled water to this,
The mixture was stirred at 80 to 90 ° C. for 1 hour to obtain a 50% by weight aqueous solution of a copolymer hydrolyzate (Dispersant 1). The pH of this aqueous solution was 2.5. The aqueous solution of the above hydrolyzate
The pH was adjusted to 7.0 by adding 15 g of a 30% by weight aqueous solution of NaOH to one of them (dispersant 2).

Example 1 An aqueous solution of a dispersant was added to water, and a gypsum powder (Sakura-in baked gypsum B, manufactured by Yoshino Gypsum Co., Ltd.) was added to the mixture.
(Weight ratio) (Gypsum concentration 62.5% by weight) was added gradually with stirring to prepare a uniform aqueous gypsum slurry. Similarly, an aqueous slurry of gypsum using a conventional NASF-based dispersant was prepared. 3.5 minutes after the start of preparation of the aqueous slurry, each of the aqueous slurries was placed in a flow cone (upper diameter 75 mm, lower diameter 85 mm, height 40 mm).
mm), and the spread (mm) of the aqueous slurry after drawing out the flow cone was measured. Table 1 shows the measurement results of the amount of dispersant (solid) added (based on 100 parts by weight of gypsum) and the flow.

[0024]

[Table 1] (Note) (1) Mighty 150 manufactured by Kao Corporation

As apparent from Table 1, the hydrolyzate of the copolymer of methoxypolyoxyethylene allyl ether and maleic anhydride of the present invention (Example 2) and its Na salt (Example 1) were used as dispersants. When used, the conventional N
It can be seen that the flow rate of the aqueous slurry is equivalent to that of the ASF-based V dispersant (Comparative Example 1) at about 1/10 of the used amount. Therefore, by using the dispersant of the example, an aqueous slurry having a flow equivalent to that of a gypsum aqueous slurry not using a dispersant is produced with a smaller amount of water than when using a conventional dispersant. be able to.

[0026]

According to the present invention described above, there is provided a dispersant which is excellent in flowability and can obtain a gypsum aqueous slurry having a high gypsum concentration with a very small amount of use.

A preferred embodiment of the present invention is as follows. (1) In claim 1, the α, β-unsaturated carboxylic acid is at least one selected from acrylic acid, methacrylic acid, α, β-unsaturated dicarboxylic acid and anhydride thereof. (2) In (1), the α, β-unsaturated dicarboxylic acid and its anhydride are selected from the group consisting of maleic acid, fumaric acid, itaconic acid, citraconic acid, maleic anhydride, itaconic anhydride,
It is a compound having 4 to 10 carbon atoms such as citraconic anhydride. (3) In claim 1 or (2), the alkenyl ether is one or more of an oxyalkylene group having 2 to 18 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, and an alkyl having 1 to 4 carbon atoms. And a group having (4) In (3), the alkenyl ether is methoxypolyoxyethylene monoallyl ether. (5) In claim 1 or any one of (1) to (4), the weight average molecular weight of the copolymer is usually 500
~ 100,000, preferably 1,000 ~ 10,000
0.

(6) The copolymer according to claim 1 or any one of (1) to (5), wherein the copolymer is usually 30 to 70 mol%, preferably 40 to 60 mol% of an α, β-unsaturated carboxylic acid.
Mol% and alkenyl ether 70 to 30 mol%, preferably 60 to 40 mol%, and ethylenically unsaturated monomer 0 to 6
The copolymer is 5 mol%, preferably 0 to 50 mol%. (7) In claim 1 or any one of (1) to (6), the copolymer is a hydrolyzate or a water-soluble salt thereof. (8) In (7), the water-soluble salt of the copolymer is L
It is a metal salt with a compound of a Group 1A metal such as i, Na and K, a Group 2A metal such as Mg, Ca and Ba, and a Group 2B metal such as Zn. (9) In (8), the compound is sodium hydroxide or magnesium hydroxide. (10) In (7), the water-soluble salt of the copolymer is an ammonium salt, an amine salt, or an alkanolamine salt. (11) In (7) to (10), the degree of neutralization of the copolymer is usually 40 to 100%, preferably 50 to 9%.
0%. (12) In claim 1, the dispersant for gypsum is usually 10
It is in the form of a 70% aqueous solution. (13) In claim 1, the amount of the gypsum dispersant used is:
With respect to 100 parts by weight of gypsum, a solid content of 0.01 to
1.0 parts by weight, preferably 0.05 to 0.5 parts by weight.

Claims (1)

[Claims] 1. A gypsum dispersant comprising at least one selected from a copolymer of an α, β-unsaturated carboxylic acid or an anhydride thereof and an alkenyl ether, and a water-soluble salt thereof.