JPH08301643A - Gypsum-modifying agent, water-resistant gypsum composition and their production - Google Patents

Abstract

PURPOSE: To obtain a gypsum-modifying agent capable of improving the water resistance, mechanical properties and application workability of gypsum by dissolving the copolymer of a vinylic compound with an unsaturated dicarboxylic acid in water in the presence of a water-soluble alkaline compound. CONSTITUTION: A vinylic compound is copolymerized with an unsaturated dicarboxylic acid (anhydride) in a molar ratio of 2:1 to 4:1 to obtain the copolymer having an acid value of 200-400. The copolymer in an amount of 5-100g/l is dissolved in water in the presence of one or more kinds of water-soluble alkaline compounds selected from sodium hydroxide, potassium hydroxide, ammonia, ammonium hydroxide and alkanol amines to obtain a gypsum- modifying agent. The gypsum-modifying agent is added to gypsum dihydrate in an amount of 0.3-3wt.% based on the copolymer to obtain a water-resistant gypsum composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gypsum modifier for improving water resistance and mechanical properties of gypsum and workability during construction. The gypsum obtained by the present invention is applied to products using gypsum such as gypsum board and gypsum plaster.

[0002]

2. Description of the Related Art Conventionally, gypsum has been widely used as a gypsum board or gypsum plaster in buildings and the like because it is inexpensive and has excellent fireproofing and soundproofing properties. However, in spite of these characteristics, the use is limited because of poor water resistance.

Various proposals have been made to make up for the drawbacks of such plaster. For example, one using paraffin and oxidized paraffin as a water repellent (Japanese Patent Publication No. 55-5).
0906), using wax and carboxyl group-containing wax (JP-A-55-37423), adding a protective colloid aqueous solution prepared by using monomethyl ester of styrene-maleic acid copolymer to low molecular weight polyolefin and paraffin. To be used as (Japanese Patent Publication Sho 58-5
8304 and JP-A-55-94983), those in which an aqueous protective colloid solution prepared by using an α-olefin-maleic anhydride copolymer is added to low molecular weight polyolefin and paraffin (JP-A-60-22091).
0), a mixture of a wax, a petroleum resin, an ethylene-vinyl acetate copolymer, and a vinyl compound-maleic anhydride derivative for use (JP-A-4-304268).

However, in these methods, when the gypsum product was immersed in water for a long time, sufficient water resistance could not be obtained, and the stability of the obtained emulsion was also problematic. In addition, a styrene-maleic anhydride copolymer was used for emulsion-stabilizing wax and paraffin.
The ratio of styrene-maleic anhydride copolymer in the modifier of gypsum is low, and it is necessary to force emulsify for a long time at high pressure using a high shearing force strong stirrer, piston type high pressure emulsifier, colloid mill, etc. The emulsification was extremely difficult.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned drawbacks of conventional gypsum modifiers, and provides a gypsum composition which is easy to work during construction and has excellent water resistance and mechanical properties. The purpose is to

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventors have combined a specific copolymer of a vinyl compound and an unsaturated dicarboxylic acid or an anhydride thereof with a specific water-soluble alkaline compound to improve gypsum. It has been found that, by using it as a substance, surprisingly, gypsum excellent in water resistance and mechanical properties can be obtained without using other modifiers such as wax, and the present invention has been completed.

[0007]

That is, the present invention is a copolymer of a vinyl compound and an unsaturated dicarboxylic acid or an anhydride thereof and has an acid value of 2
The present invention relates to a gypsum modifier obtained by dissolving 100 to 400 in water in the presence of a water-soluble alkaline compound, a water-resistant gypsum composition obtained by using the same, and a method for producing the same.

The vinyl compound which is one component of the copolymer used in the present invention is ethylene, propylene, butene,
C2-C8 α-olefins such as isobutylene, isoamylene, and n-hexene, preferably C4-6 α
-Olefin, or styrene monomers such as styrene, α-methylstyrene, vinyltoluene, t-butylstyrene, chlorostyrene and derivatives thereof. Further, the unsaturated dicarboxylic acid or its anhydride is maleic acid, maleic anhydride, fumaric acid or the like. These monomers are polymerized under normal radical polymerization conditions.

The acid value (mg potassium hydroxide required to neutralize 1 g of resin) of the copolymer of these vinyl compounds and unsaturated dicarboxylic acid or its anhydride is 200 to
It is preferably 400. The acid value of the copolymer can be adjusted by the monomer ratio, but it may be adjusted by partial esterification or partial amidation of the carboxylic acid or partial imidation after the copolymerization. When the acid value exceeds 400, the water resistance of the obtained gypsum becomes insufficient, and when the acid value is 200 or less, it becomes difficult to obtain a uniform aqueous solution.

As the monomer copolymerizable with the above monomers, vinyl cyanide compounds such as acrylonitrile and methacrylonitrile, acrylic acid esters such as methyl acrylic acid ester, ethyl acrylic acid ester and butyl acrylic acid ester, and methyl methacrylic acid. ester,
Examples thereof include methacrylic acid esters such as ethyl methacrylic acid ester and butyl methacrylic acid ester, vinyl carboxylic acids such as acrylic acid and methacrylic acid, acrylic acid amides, methacrylic acid amides, acenaphthylene, and N-vinylcarbazole.

In the present invention, a copolymer of styrene or its derivative and maleic anhydride is preferably used. In this case, the molar ratio of styrene or its derivative constituting the copolymer to maleic anhydride is 2:
It is preferably 1 to 4: 1.

The water-soluble alkaline compound used in the present invention includes alkali metal hydroxides such as lithium hydroxide, sodium hydroxide and potassium hydroxide, sodium carbonate,
Alkali metal carbonates such as potassium carbonate, ammonia, ammonium hydroxide, dimethylamine, trimethylamine, amines such as triethylamine, 2-aminoethanol, triethanolamine, diethanolamine,
It is selected from alkanolamines such as N, N-dimethylethanolamine, N-methyldiethanolamine and 2-amino-2-methyl-1-propanol. These may be used alone, or two or more kinds may be mixed and used. Particularly, in the present invention, alkanolamines are preferably used.

A copolymer of a vinyl compound and an unsaturated dicarboxylic acid anhydride is previously dissolved in water in the presence of a water-soluble alkaline compound and used as a gypsum modifier.
The concentration of the copolymer is usually 5 to 100 g / liter. Here, this aqueous solution can be prepared without stirring under high temperature and high pressure by using a strong stirrer with high shearing force. A water resistant gypsum composition (slurry) is obtained by mixing the obtained aqueous solution with calcined gypsum and kneading. After curing, if necessary, it is dried to obtain a final gypsum product having high water resistance. If water is added to the calcined gypsum first, the effect of the modifier cannot be obtained.

At this time, the amount of the copolymer used for the modification is preferably 0.3 to 3% by weight, more preferably 0.5 to 3% by weight based on the gypsum (dihydrate gypsum) finally obtained. Two
% By weight. When the amount of the copolymer is less than this, sufficient effect of modification cannot be obtained, and when the amount is large, the viscosity of the gypsum composition becomes high, workability may be deteriorated, fire resistance and economical efficiency may be lost. There is.

In the gypsum composition, if necessary, a water resistance improver such as wax, paraffins and low molecular weight hydrocarbon resin, an aggregate such as perlite and vermiculite, a coagulation rate adjusting agent, a reinforcing fiber, and a foaming agent. , And a modifier such as cement, slag, or fly ash can also be used in combination.

The present invention will be described below with reference to examples.
The present invention is not limited to the examples.

[0017]

[Examples] Table 1 shows the compositions of the gypsum compositions of Examples and Comparative Examples of the present invention, and Table 2 shows the properties of the gypsum compositions.
In the following examples and comparative examples, the obtained gypsum composition (slurry) was cast between gypsum board base papers to form gypsum boards and dried at 70 ° C. for about 2 hours. After this gypsum board was left at room temperature and a humidity of 50% for 24 hours, the water absorption and the flexural modulus were measured. Water absorption is 24 in water at 20 ° C
It was calculated from the weight increase after immersion in time. On the other hand, the curing time was determined as the time until the fluidity disappeared after the slurry was left at room temperature.

[0018]

Example 1 40 g of a styrene-maleic anhydride copolymer having a molar ratio of styrene and maleic anhydride of 3: 1, an acid value of 275, a melting point of 120 ° C. and a Tg of 125 ° C. was mixed with 900 ml of water. In addition, 17.8 g (1.02 times equivalent amount) of N, N-dimethylethanolamine (DMEA) was slowly added dropwise under stirring, and the stirring was continued until a uniform aqueous solution was maintained at 70 ° C, and after dissolution, the aqueous solution was added. Was cooled to room temperature and water was added to make the total volume 1000 ml (styrene-maleic anhydride copolymer concentration, 40 g / liter).

150 g of this aqueous solution and calcined gypsum (purity 97%
250 g of the above β hemihydrate gypsum) was mixed to obtain a gypsum composition (slurry). From Table 2, it can be seen that the obtained gypsum has a low water absorption rate, an improved flexural modulus, and a good fluidity of the slurry.

[0020]

Examples 2 to 4 The same styrene-maleic anhydride copolymer as in Example 1 and N, N-dimethylethanolamine (D
MEA) and the styrene-maleic anhydride copolymer concentration was 20 g / liter and 10 g in the same manner.
An aqueous solution of 60 g / liter was obtained. At this time, the amount of DMEA was 1.02 times the equivalent amount of the styrene-maleic anhydride copolymer. 150 g of these aqueous solutions and 250 g of calcined gypsum (β-hemihydrate gypsum with a purity of 97% or more) were mixed, and the concentration of the modifier with respect to gypsum dihydrate was 1.0% by weight,
A gypsum composition (slurry) of 5% by weight and 3.0% by weight was obtained. In all of these, the effect of improving the water absorption rate and the flexural modulus was recognized.

[0021]

Example 5 A styrene-maleic anhydride copolymer having a molar ratio of styrene to maleic anhydride of 2: 1 and having an acid value of 350, a melting point of 150 ° C. and a Tg of 124 ° C. was used. A gypsum composition having a modifier concentration of 1.0% by weight was obtained in the same manner as in Example 2. Also in this case, the effect of improving the water absorption and the flexural modulus was confirmed.

[0022]

Example 6 Same as Example 2 except that a styrene-maleic anhydride copolymer having a molar ratio of styrene to maleic anhydride of 4: 1 and having an acid value of 215 and a Tg of 125 ° C. was used. Then, a gypsum composition having a modifier concentration of 1.0% by weight was obtained. Also in this case, the effect of improving the water absorption and the flexural modulus was confirmed.

[0023]

Example 7 A gypsum composition having a modifier concentration of 1.0% by weight was obtained in the same manner as in Example 2 except that potassium hydroxide was used as the alkaline compound. Also in this case, the effect of improving the water absorption and the flexural modulus was confirmed.

[0024]

Example 8 The modifier concentration was 1.0 as in Example 2 except that sodium hydroxide was used as the alkaline compound.
A weight percent gypsum composition was obtained. Also in this case, the effect of improving the water absorption and the flexural modulus was confirmed.

[0025]

Example 9 As in Example 1, except that ammonium hydroxide was used as the alkaline compound, the modifier concentration was 2.
A gypsum composition of 0% by weight was obtained. Also in this case, the effect of improving the water absorption rate and the bending elastic modulus was recognized, but the water absorption rate was slightly larger than that in Example 1.

[0026]

Comparative Example 1 The characteristics of gypsum alone were measured without using an initiator.

[0027]

Comparative Example 2 A styrene-maleic anhydride copolymer having a molar ratio of styrene to maleic anhydride of 1: 1 and an acid value of 480, a melting point of 160 ° C. and a Tg of 154 ° C. was used. In the same manner as in Example 1, a gypsum composition having a modifier concentration of 2.0% by weight with respect to the finally obtained dihydrate gypsum composition was obtained. This gypsum composition did not harden even when left standing, and it was impossible to produce a gypsum board.

[0028]

Comparative Example 3 Same as Example 1 except that a styrene-maleic anhydride copolymer having a molar ratio of styrene to maleic anhydride of 5: 1, an acid value of 180 and a Tg of 125 ° C. was used. Then, a gypsum composition having a modifier concentration of 2.0% by weight was obtained. This gypsum composition did not show the effect of improving the water absorption rate.

[0029]

Comparative Example 4 The same styrene-maleic anhydride copolymer as in Example 1 and N, N-dimethylethanolamine (DME
In the same manner as in (A), the modifier concentration is 4.0% by weight.
A gypsum composition of was obtained. This gypsum composition was so viscous that it was impossible to make a board.

[0030]

COMPARATIVE EXAMPLE 5 10 g of the same styrene-maleic anhydride copolymer as in Example 1 and 1.02 times as much ammonium hydroxide as maleic anhydride and water were mixed, and the total volume was 100.
The solution was stirred at 70 ° C. in ml to obtain a uniform aqueous solution. The same gypsum of 250 g as in Example 1 and 90 g of water were mixed, and 60 ml of the above emulsion was added to obtain a gypsum composition (slurry). In this case, the effect of improving the water absorption rate and the flexural modulus was not observed even though the modifier having the same concentration as that of the example was used.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

According to the present invention, compared with the case of using a conventional water repellent emulsion composition, it is possible to improve the water resistance and mechanical properties of gypsum by a simple operation without requiring a special emulsifying device. Became possible. The gypsum board obtained using the gypsum modifier of the present invention can be expected to be used in places where water is used, such as a bathroom, a washroom, and a kitchen.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshiyuki Miyagi, 1 Awata-cho, Nakado-ji, Shimogyo-ku, Kyoto, Kyoto Elf Atchem Japan Co., Ltd. Kyoto Technical Center

Claims (10)

[Claims] 1. A gypsum modifier obtained by dissolving a copolymer of a vinyl compound and an unsaturated dicarboxylic acid or an anhydride thereof having an acid value of 200 to 400 in water in the presence of a water-soluble alkaline compound. Agent. 2. The gypsum modified according to claim 1, wherein the copolymer is composed of styrene or its derivative and maleic anhydride, and the molar ratio of styrene or its derivative and maleic anhydride is 2: 1 to 4: 1. Pledget. 3. The water-soluble alkaline compound is selected from sodium hydroxide, potassium hydroxide, ammonia, ammonium hydroxide, and alkanolamines.
The gypsum modifier according to claim 1, which is a compound of at least one kind. 4. An alkanolamine is selected from 2-aminoethanol, triethanolamine, diethanolamine, N, N-dimethylethanolamine, N-methyldiethanolamine, 2-amino-2-methyl-1-propanol. The gypsum modifier according to claim 3, which is a compound of at least one kind. 5. A gypsum modifier obtained by dissolving a copolymer of a vinyl compound and an unsaturated dicarboxylic acid anhydride having an acid value of 200 to 400 in water in the presence of a water-soluble alkaline compound. A water resistant gypsum composition comprising gypsum and having a copolymer to dihydrate gypsum ratio of 0.3 to 3% by weight. 6. The water resistant gypsum according to claim 5, wherein the copolymer is styrene or its derivative and maleic anhydride, and the molar ratio of styrene or its derivative and maleic anhydride is 2: 1 to 4: 1. Composition. 7. The water-soluble alkaline compound is selected from sodium hydroxide, potassium hydroxide, ammonia, ammonium hydroxide, and alkanolamines.
The water-resistant gypsum composition according to claim 6, which is a compound of at least one kind. 8. The alkanolamines are selected from 2-aminoethanol, triethanolamine, diethanolamine, N, N-dimethylethanolamine, N-methyldiethanolamine, 2-amino-2-methyl-1-propanol. The water-resistant gypsum composition according to claim 7, which is one or more kinds of compounds. 9. A copolymer of a vinyl compound and an unsaturated dicarboxylic acid or an anhydride thereof, having an acid value of 200 to 400, is obtained by previously dissolving it in water in the presence of a water-soluble alkaline compound. A method for producing a water-resistant gypsum composition, which comprises mixing an aqueous solution with calcined gypsum. 10. The copolymer comprises styrene or its derivative and maleic anhydride, and the molar ratio of styrene or its derivative and maleic anhydride is 2: 1 to 4: 1.
The method for producing a water resistant gypsum composition according to claim 9.