Method for producing gypsum composition, gypsum composition, mineral raw material for gypsum composition, and method for producing hardened body

Abstract

The purpose of the present invention is to address, by a simple and easy means, the technical problem regarding the high viscosity of a slurry generated by adding, to water, a gypsum composition containing a mineral, calcined gypsum, and a polycarboxylate-based water-reducing agent. The purpose is achieved by performing, in the gypsum composition containing a mineral, calcined gypsum, and a polycarboxylate-based water-reducing agent, a pre-treatment of pre-providing to the mineral a liquid polyamide polyamine and / or alkylene oxide adduct of the polyamide polyamine such that the proportion of same with respect to the calcined gypsum falls within the range of 0.1-10 wt% in terms of solid content.

Description

[Technical Field]

[0001] The present invention relates to a gypsum composition that is prepared by adding water and mixing a mineral, calcined gypsum, and a polycarboxylate-based water-reducing agent to form a calcined gypsum slurry, which is then used to form a hardened body. The calcined gypsum slurry has a low viscosity and exhibits good fluidity (moldability). The present invention relates to a useful technology that enables the formation of hardened bodies of gypsum-based building materials and the like with improved functionality, such as fire resistance, strength, and sound insulation, using the slurry. [Background technology]

[0002] In recent years, due to societal demands for reducing the volume of industrial waste, the proportion of recycled gypsum in the materials used to form gypsum-based building materials, including gypsum boards, has been increasing. As the proportion of recycled gypsum in the materials used to form gypsum-based building materials increases, the amount of water mixed in to impart fluidity to the calcined gypsum slurry used in the formation of the building materials increases. This increases the amount of water mixed, which in turn increases the drying energy required. To address the problem of increased water mixed, it has been proposed to reduce the amount of water mixed in by adding a chemical with a water-reducing effect (called a water-reducing agent) to the gypsum composition that constitutes the calcined gypsum slurry. For example, Patent Document 1 proposes a dicarboxylic acid-based gypsum water-reducing agent for use in dental gypsum slurries. Furthermore, Patent Document 2, a prior art document, describes the recent trend toward switching to polycarboxylic acid-based water-reducing agents, which do not generate formaldehyde, in gypsum-water slurries used in gypsum boards.

[0003] Meanwhile, in order to improve the fire resistance of the formed gypsum-based building material, it has been proposed to add a mineral (colemanite) to a gypsum composition constituting a calcined gypsum slurry (see Patent Document 3). Patent Document 4 discloses that by configuring a gypsum-based molded body to which colemanite has been added, it is possible to improve not only the fire resistance performance but also the neutron shielding performance. In this way, adding a mineral to a gypsum composition makes it possible to enhance the functionality of the formed gypsum-based building material. For this reason, it is desired to develop a gypsum composition that can realize the formation of building materials with desired improved functions by adding various minerals. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 230028 [Patent Document 2] Patent No. 6293584 [Patent Document 3] Special Publication No. 57-11864 [Patent Document 4] Patent No. 5596933 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the present inventors have found that when preparing a calcined gypsum slurry containing a mineral, using a water-reducing agent to reduce the amount of mixed water may result in failure to obtain desired water-reducing performance. Specifically, the present inventors have found that when water is added to a gypsum composition containing a mineral, calcined gypsum, and a polycarboxylate-based water-reducing agent to prepare a calcined gypsum slurry, the viscosity increases, making the calcined gypsum slurry poor in fluidity, which affects moldability, and therefore needs to be improved.

[0006] Therefore, an object of the present invention is to solve, by a simple means, the technical problem discovered by the inventors that the viscosity of the slurry increases when water is added to a gypsum composition containing a mineral, calcined gypsum, and a polycarboxylate-based water-reducing agent to form a calcined gypsum slurry. Generally, by adding a mineral to a calcined gypsum slurry for forming a hardened body of a gypsum-based building material or the like, the hardened body of the building material or the like formed using the slurry has improved functionality such as fire resistance, strength, and sound insulation. Therefore, if a gypsum composition that solves the above technical problem in a simple manner and can realize a mineral-containing calcined gypsum slurry with excellent low-viscosity fluidity (moldability) is provided, it would be extremely useful industrially. [Means for solving the problem]

[0007] The above object can be achieved by the following method for producing a gypsum composition of the present invention. [1] A method for producing a gypsum composition containing a mineral, calcined gypsum, and a polycarboxylate-based water-reducing agent, the method comprising a pretreatment step of the mineral, in which a liquid polyamide polyamine and / or an alkylene oxide adduct of a polyamide polyamine is applied to the mineral in advance in the pretreatment step so that the ratio of the liquid polyamide polyamine and / or the alkylene oxide adduct to the calcined gypsum is within a range of 0.1 to 10 wt% by mass, calculated as a solid content.

[0008] Preferred embodiments of the method for producing the gypsum composition of the present invention are as follows. [2] The method for producing a gypsum composition according to the above [1], wherein in the pretreatment step, the liquid polyamide polyamine and / or alkylene oxide adduct of polyamide polyamine is sprayed onto the mineral, and then the mineral is dried.

[0009] As another embodiment, the present invention provides the following gypsum composition. [3] A gypsum composition for preparing a calcined gypsum slurry, comprising a mixture of a mineral with water, calcined gypsum, and a polycarboxylate-based water-reducing agent, wherein the mineral has been previously provided with a polyamide polyamine and / or an alkylene oxide adduct of a polyamide polyamine in an amount, calculated as a solid content, that is within a range of 0.1 to 10 wt% by mass relative to the calcined gypsum.

[0010] Preferred embodiments of the gypsum composition of the present invention are as follows. [4] The gypsum composition according to the above [3], wherein the mineral is at least one selected from the group consisting of bentonite, colemanite, diatomaceous shale, vermiculite, shirasu, and natural gypsum. [5] The gypsum composition according to the above [3] or [4], wherein the ratio of the mineral to the calcined gypsum is within the range of 0.01 to 60 wt% on a mass basis.

[0011] In another embodiment, the present invention provides a mineral raw material for a gypsum composition as described below. [6] A mineral raw material constituting a gypsum composition used in a calcined gypsum slurry containing a mineral, calcined gypsum, and a polycarboxylate-based water-reducing agent, which is obtained by adding and mixing with water, characterized in that the mineral raw material for a gypsum composition is provided with a polyamide polyamine and / or an alkylene oxide adduct of a polyamide polyamine in a ratio to the mineral in the range of 0.02 to 120 wt% by mass, calculated as a solid content.

[0012] As another embodiment, the present invention provides the following method for producing a building material. [7] A method for producing a hardened body, comprising using the gypsum composition according to any one of [3] to [5] above, mixing the gypsum composition with water to form a calcined gypsum slurry, and using the slurry to mold the hardened body.

[0013] A preferred embodiment of the method for producing the building material of the present invention is as follows. [8] The method for producing a hardened body according to the above [7], wherein the viscosity of the slurry (25°C) is 150 dPa s or less when the amount of water mixed is 15 to 60 wt% by mass based on the gypsum composition. [Effects of the Invention]

[0014] The present inventors have discovered a technical problem of high viscosity in calcined gypsum slurries produced by adding water to a gypsum composition containing a mineral, calcined gypsum, and a polycarboxylate-based water-reducing agent. The present invention solves this problem with an extremely simple approach: simply adding a polyamide polyamine and / or an alkylene oxide adduct of a polyamide polyamine (hereinafter also referred to as a polyamide polyamine) to the mineral used. According to the present invention, the above-described simple method makes it possible to provide a mineral-containing calcined gypsum slurry that has low viscosity and excellent fluidity (moldability). As a result, by adding a mineral to the calcined gypsum slurry, it becomes possible to easily and consistently provide gypsum hardened bodies, such as useful gypsum-based building materials, that have improved functionality, such as fire resistance, strength, and sound insulation. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention will be described in detail below with reference to preferred embodiments. The inventors have investigated calcined gypsum slurries containing colemanite, which has been proposed in the prior art cited above and is believed to be capable of further improving the fire resistance of building materials. Colemanite is a calcium borate compound containing five molecules of crystal water, a natural mineral containing boric acid, and has the chemical formula 2CaO 3B 2 O 3 5H 2 O. In recent years, the neutron shielding effect of colemanite has attracted attention.

[0016] In the course of the above-mentioned investigations, the inventors discovered that when water is added to a gypsum composition containing colemanite, calcined gypsum, and a polycarboxylate-based water-reducing agent to form a calcined gypsum slurry, the viscosity of the slurry increases to about 300 dPa·s, making it hard and resulting in poor moldability, which is a technical problem.In contrast, when water is added to a gypsum composition to form a calcined gypsum slurry and the slurry is used to form a gypsum hardened body, taking into consideration its moldability, handleability, and the like, it is desirable that the viscosity of the calcined gypsum slurry be 150 dPa·s or less, preferably about 20 to 100 dPa·s, and more preferably about 20 to 50 dPa·s.

[0017] The present inventors are not sure why the viscosity increases when water is added to a gypsum composition containing colemanite, calcined gypsum, and a polycarboxylate-based water-reducing agent to form a calcined gypsum slurry, as described above, but speculate as follows. As described in the above-cited patent documents, polycarboxylate-based water-reducing agents are used in gypsum compositions. The present inventors, on the other hand, believe that the reason for the increase in the viscosity of the slurry is that when a mineral such as colemanite is present in the gypsum composition and water is added and mixed to prepare a calcined gypsum slurry, the polycarboxylate-based water-reducing agent is adsorbed to the mineral before the gypsum, resulting in the generation of boric acid esters and the like, which increases the viscosity of the slurry.

[0018] Based on the above reasoning, the present inventors have intensively studied a method for preventing a polycarboxylate-based water-reducing agent present in a gypsum composition from adsorbing onto the mineral constituting the gypsum composition before the gypsum, in order to solve the technical problem of high viscosity of the calcined gypsum slurry made from the gypsum composition having the above-mentioned configuration, and have arrived at the present invention. Specifically, the present inventors have found that by configuring the mineral used to obtain a calcined gypsum slurry containing a mixture of mineral, calcined gypsum, and a polycarboxylate-based water-reducing agent with water, in advance, a specific amount of polyamide polyamine or the like is added to the mineral, thereby realizing a low viscosity without causing the problem of high viscosity of the calcined gypsum slurry.

[0019] More specifically, the inventors have found that the excellent effects of the present invention can be achieved by configuring the mineral used to obtain a calcined gypsum slurry containing a mineral, calcined gypsum, and a polycarboxylate-based water-reducing agent to have a polyamide polyamine or the like added to it in an amount, calculated as a solid content, relative to the calcined gypsum, within a range of 0.1 to 10 wt%. Furthermore, in order to stably obtain a low-viscosity calcined gypsum slurry, it has been found that it is preferable that the mineral used as a raw material has a polyamide polyamine or the like added to it in advance in an amount, calculated as a solid content, relative to the mineral, within a range of about 0.02 to 120 wt% by mass.

[0020] [Gypsum composition] First, each raw material constituting the gypsum composition of the present invention will be described. <Minerals> The minerals constituting the present invention are not particularly limited. For the purpose of enhancing the desired functionality of a building material formed using a calcined gypsum slurry containing a mineral or imparting a new desired functionality, any of the minerals listed below may be appropriately selected and used. In the present invention, for example, minerals having a volume average particle size (MV) of about 10 μm to 3 mm, more preferably about 20 μm to 1 mm, may be used, and minerals whose particle size has been adjusted by pulverization or the like may also be used. Furthermore, the amount of mineral used will vary depending on the type of mineral and the purpose for which the mineral is used, but according to the inventors' investigations, it is preferable to use each mineral in an amount within the range shown below.

[0021] Examples of minerals constituting the present invention include bentonite, colemanite, diatomaceous shale, vermiculite, shirasu, and natural gypsum. They can be appropriately selected from the above-listed minerals depending on the application and desired function. Although colemanite has been described as a representative example of a mineral in the present specification, the "mineral" constituting the present invention is not limited to colemanite, and can be appropriately selected from minerals having a variety of properties as described below depending on the purpose. Furthermore, by using these minerals with a unique structure in which polyamide polyamines or the like have been added in advance, the useful effects of the present invention can be obtained regardless of the mineral used.

[0022] Bentonite is a general term for clays primarily composed of montmorillonite. It has high viscosity and adhesiveness, and is widely used as a functional material such as a moisturizer or thickener. It is also widely used in the field of building materials, which is the subject of the present invention. The amount of bentonite used (blended) is preferably, for example, an amount equivalent to a mass ratio of 0.01 to 30 wt% relative to the calcined gypsum when used in a calcined gypsum slurry. Colemanite is a natural mineral containing boron and is used as a weed control agent and a secondary steel material. In recent years, for example, mixing boron into concrete walls to shield against highly penetrating neutron radiation has been proposed, and the use of colemanite is being investigated. The amount of colemanite used is preferably, for example, an amount equivalent to a mass ratio of 0.1 to 60 wt% relative to the calcined gypsum when used in a calcined gypsum slurry. Diatomaceous shale is a porous natural mineral composed of fossilized diatom shells. Due to its unique properties, it is widely used in humidity-regulating building materials, health building materials, and everyday items. The amount of diatomaceous shale used is preferably such that, when made into a calcined gypsum slurry, the mass ratio of the calcined gypsum to the gypsum is, for example, 0.1 to 50 wt%. Vermiculite is a porous and very light mineral with water retention and breathability, and is used as a soil conditioner and an aggregate for fire-resistant building materials. The amount of vermiculite used is preferably such that, when made into a calcined gypsum slurry, the mass ratio of the calcined gypsum to the gypsum is, for example, 0.01 to 30 wt%. Shirasu is a fine-grained pumice or volcanic ash distributed as a thick layer throughout southern Kyushu. Due to its unique properties, it is used as a concrete aggregate and health building material. The amount of shirasu used is preferably an amount such that, when a calcined gypsum slurry is prepared, the mass ratio to the calcined gypsum is, for example, 0.1 to 50 wt%. Natural gypsum is a naturally occurring raw material of gypsum dihydrate, and can be used as a mineral constituting the present invention. Natural gypsum is used as a bulking agent as is, but in many cases it is heated to form hemihydrate gypsum (calcined gypsum) and used as a material for building materials and gypsum molds. When gypsum dihydrate is used as a bulking agent as is, it can be applied to the mineral constituting the present invention, and not only natural gypsum but also by-product gypsum and recycled gypsum can be applied.In this case, the amount of gypsum dihydrate used is preferably an amount such that, when a calcined gypsum slurry is prepared, the mass ratio to the calcined gypsum is, for example, about 0.1 to 50 wt%. As will be described later, gypsum dihydrate can also be used as a hardening accelerator added as needed to the gypsum composition of the present invention. When used as a hardening accelerator, it can also be applied to the minerals constituting the present invention, and in this case, not only natural gypsum but also by-product gypsum and recycled gypsum can be used as the gypsum dihydrate. In this case, the amount used is about 0.1 to 5 wt% by mass to the calcined gypsum, which is a smaller amount than when used as a bulking agent.

[0023] <Polyamide polyamine, alkylene oxide adduct of polyamide polyamine> The technical feature of the present invention is that a mineral that has been pretreated with a specific compound is used as a mineral constituting a gypsum composition used in preparing a calcined gypsum slurry containing a mineral, calcined gypsum, and a polycarboxylate-based water-reducing agent, which is a mixture with water. Specifically, the present invention is characterized in that a liquid polyamide polyamine or the like is added to the above-mentioned mineral constituting the present invention in advance so that the ratio of the calcined gypsum to the mineral in terms of solid content is within a range of 0.1 to 10 wt% by mass.

[0024] The "polyamide polyamine or alkylene oxide adduct of polyamide polyamine" used in the pretreatment of the mineral constituting the present invention is used as a forming component when obtaining a gypsum dispersant (water-reducing agent), as described in, for example, Japanese Patent No. 4844878 and Japanese Patent No. 6095644. For example, Japanese Patent No. 6095644 describes a gypsum dispersant (water-reducing agent) that contains a polyamide polyamine and / or its alkylene oxide adduct having a weight-average molecular weight of 500 to 4800, obtained by reacting (A) a polycarboxylic acid polymer with (B) a polyalkylene polyamine and a dibasic acid as essential components, and in which the mass ratio of component (A) to component (B) is (A):(B) = 1:1 to 30:1. The publication also describes an effect that by using the component (A) and the component (B) in combination, even when raw gypsum of different qualities is used, sufficient fluidity can be stably imparted to the gypsum slurry regardless of the type of raw gypsum.

[0025] As mentioned above, the present inventors discovered a technical problem: when water is added to a gypsum composition containing a mineral, calcined gypsum, and a polycarboxylate-based water-reducing agent to prepare a calcined gypsum slurry, the viscosity of the slurry increases to about 300 dPa·s and the slurry becomes hard. To address this problem, the present inventors, referring to the prior art described above, attempted to premix a polyamide polyamine with the calcined gypsum constituting the gypsum composition and use the carboxylate-based water-reducing agent and the polyamide polyamine in combination. However, the calcined gypsum slurry containing the mineral prepared in this manner ended up having a high viscosity, and it was not possible to obtain a low-viscosity calcined gypsum slurry that can stably impart sufficient fluidity, as is the objective of the present invention.

[0026] In response to the above, the present inventors have further investigated how to make a calcined gypsum slurry containing a mineral low in viscosity and stably imparted with sufficient fluidity by a simple means.As a result, as described above, the inventors have found that it is possible to obtain a low-viscosity calcined gypsum slurry that is stably imparted with sufficient fluidity by a very simple means of using a mineral that has been pretreated in advance to have a specific range of amount of polyamide polyamine or the like attached (imparted) thereto as a material for the calcined gypsum slurry.

[0027] Although details will be described later, the treatment of the mineral that characterizes the present invention is carried out by previously adding (adhering) a liquid polyamide polyamine or the like to the mineral so that the ratio to the calcined gypsum, calculated as solid content, is within the range of 0.1 to 10 wt% by mass. More preferably, the polyamide polyamine or the like is added (adhered) to the mineral so that the ratio to the calcined gypsum, calculated as solid content, is within the range of 0.2 to 5 wt% by mass, or even within the range of 0.5 to 1 wt% by mass.

[0028] The amount of polyamide polyamine or the like to be applied to the mineral is preferably in the range of 0.02 to 120 wt % by mass, and more preferably 0.2 to 20 wt %, in terms of solid content, relative to the mineral.

[0029] <Polycarboxylate-based water-reducing agent> Next, the polycarboxylate-based water-reducing agent constituting the present invention will be described. A water-reducing agent is a substance that, when water is added to a gypsum composition containing a mineral and calcined gypsum to form a calcined gypsum slurry, facilitates mixing of the gypsum composition with water, thereby reducing the amount of water used during mixing and improving the strength of the formed body after hardening. Adding a water-reducing agent reduces the viscosity of the slurry without increasing the amount of mixed water, improving fluidity and enhancing mixability and workability. Furthermore, suppressing an increase in the amount of mixed water means that the drying energy can be reduced, which is highly desirable from the perspective of industrial applicability.

[0030] Known water-reducing agents include those with surfactant effects, such as lignin sulfonates, oxycarboxylates, naphthalene sulfonates, melamine sulfonates, polystyrene sulfonates, and polycarboxylates. The present invention aims to solve the technical problems associated with the use of polycarboxylate-based water-reducing agents, and therefore requires the use of a polycarboxylate-based water-reducing agent. By appropriately selecting usage conditions such as pH, polycarboxylate-based water-reducing agents can exhibit excellent water-reducing performance for gypsum slurries. Furthermore, polycarboxylate-based water-reducing agents are solid under standard conditions, which also makes them effective in the present invention. When obtaining a gypsum composition containing a polycarboxylate-based water-reducing agent, it is preferable to use a powdered polycarboxylate-based water-reducing agent, as this reduces the number of steps required.

[0031] Examples of polycarboxylate-based water reducers include the following, and any of the following can be used in the present invention. Specifically, water-soluble salts of copolymers of chain olefins having 5 or 6 carbon atoms and ethylenically unsaturated dicarboxylic anhydrides, copolymers of polyethylene glycol monoallyl ether and unsaturated dicarboxylic acids, copolymers of polyalkylene glycol mono(meth)acrylates and (meth)acrylic acid, copolymers of (meth)acrylic acid amides having sulfonic groups at their terminals, acrylic esters, and (meth)acrylic acid, copolymers of monomers having sulfonic groups such as vinyl sulfonates, aryl sulfonates, and methacrylic sulfonates with (meth)acrylic acid and other monomers, copolymers of monomers having aromatic rings substituted with sulfonic groups and maleic acid, and quaternary copolymers of monomers having sulfonic groups at their terminals with polyalkylene glycol mono(meth)acrylates, polyalkylene glycol mono(meth)acrylate ethers, and (meth)acrylic acid can be used.

[0032] The amount (blending amount) of the water reducing agent used is preferably, for example, in the range of about 0.01 to 10 parts by mass per 100 parts by mass of calcined gypsum. Furthermore, the water reducing agent is more preferably used in the range of about 0.3 to 3.0 parts by mass per 100 parts by mass of calcined gypsum. If the amount of water reducing agent used is too small, the viscosity will be high and the desired fluidity will not be obtained. If the amount used is too large, the desired viscosity and fluidity will be obtained, but the amount will plateau at a certain level, which is undesirable from an economical standpoint.

[0033] <Cast plaster> The calcined gypsum constituting the gypsum composition of the present invention is called gypsum hemihydrate, and there are α-type hemihydrate and β-type hemihydrate depending on the calcination method. α-type hemihydrate is produced by a wet method and is obtained by calcining gypsum dihydrate in water (including in steam). β-type hemihydrate is produced by a dry method and is obtained by calcining gypsum dihydrate in the atmosphere. Either α-type hemihydrate or β-type hemihydrate can be used as the calcined gypsum constituting the present invention, and they may be mixed appropriately. α-type hemihydrate has the advantage that less water is required for hardening than β-type hemihydrate, and it has higher strength when hardened.

[0034] <Other additives> The gypsum composition of the present invention may contain, as needed, other conventional additives such as setting time adjusters, pH adjusters, and antifoaming agents in addition to the above-mentioned components. For example, as the setting retarder, citrates such as sodium citrate, succinates, acetates, malates, borates such as borax, sucrose, hexametaphosphates, ethylenediaminetetraacetate, diethylenetriaminepentaacetic acid, starch, and protein hydrolysates can be used. As the antifoamer, for example, commonly used agents such as polyethers, silicones, alcohols, mineral oils, vegetable oils, and nonionic surfactants can be used as appropriate.

[0035] [Method of manufacturing gypsum composition] The method for producing a gypsum composition of the present invention relates to a technology that can produce a gypsum composition that, when prepared as a mixture with water, contains a mineral, calcined gypsum, and a polycarboxylate-based water-reducing agent, can stably produce a low-viscosity calcined gypsum slurry without increasing the viscosity of the slurry. A key feature of the method for producing a gypsum composition of the present invention is that the mineral constituting the gypsum composition is pretreated by adding a liquid polyamide polyamine or the like to the mineral so that the ratio of the liquid polyamide polyamine to the calcined gypsum falls within a range of 0.1 to 10 wt% by mass, calculated as solids, and then the pretreated mineral is used. For example, by a simple method such as spraying, dripping, or pouring a liquid polyamide polyamine or the like onto the mineral in the pretreatment step, followed by drying the mineral, a mineral raw material having a specific amount of polyamide polyamine or the like attached thereto, which characterizes the present invention, can be easily obtained.

[0036] Since the technical features and effects of the present invention are as described above, the gypsum composition obtained by the method for producing a gypsum composition of the present invention may, of course, be provided as a mixture containing a mineral, calcined gypsum, and a polycarboxylate-based water-reducing agent. However, the present invention is not limited to this, and may be a product in the form of mixing these individual materials when used on-site. Specifically, for example, a product obtained by combining a mixture of the above-described pretreated mineral with a material other than the mineral may be mentioned. [Example]

[0037] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the examples and comparative examples, "%" is based on mass unless otherwise specified.

[0038] Gypsum compositions with different formulations as shown in Table 1 were prepared, and water was added to and mixed with each of the resulting gypsum compositions to obtain calcined gypsum slurries. The properties of each of the resulting calcined gypsum slurries were then investigated. First, the basic structure of the gypsum composition for obtaining the calcined gypsum slurry used in the investigation and the method for obtaining the calcined gypsum slurry are as follows:

[0039] <Conditions for each experiment> In preparation, the blending of the gypsum composition was designed so that the target specific gravity of the gypsum hardened body obtained by hardening the calcined gypsum slurry would be 1.9, and the calcined gypsum slurry was obtained as follows. First, the materials used in the examples and comparative examples and the basic blending will be described.

[0040] For the calcined gypsum, 500.0 g of α-type hemihydrate gypsum (abbreviated as "α-St") was used. 254.1 g of powdered colemanite was used as the mineral. The mineral content relative to α-St was 50.8% / α-St. For the colemanite, "Carboron 40M" (trade name, manufactured by Kyoritsu Material Co., Ltd.) was used. The colemanite (2CaO·3B2O3·5H2O) had a volume-average particle size (MV value) of 30 μm. The mineral used in the examples was pretreated to have polyamide polyamine attached. Specifically, liquid polyamide polyamine was sprayed onto the mineral, and then dried in a dryer at 40°C until it reached a constant weight. For the polyamide polyamine liquid, "PCA-0302" (trade name, manufactured by Toho Chemical Industry Co., Ltd., solids content 30%) was used. The polycarboxylate-based water-reducing agent used was powdered "Mighty 21PN" (product name, manufactured by Kao Corporation). Additionally, gypsum dihydrate was used as a hardening accelerator.

[0041] The calcined gypsum slurry was prepared by adding 154.0 g of water (an amount equivalent to 30.8% α-St) to 500.0 g of α-hemihydrate gypsum among the materials in an appropriate blend, and stirring for 5 minutes using a hand mixer (1100 rpm). After preparation, the viscosity of the resulting gypsum slurry was measured, and the measured values are shown in Table 1. As mentioned above, when using the calcined gypsum slurry to form a gypsum hardened body, taking into consideration its formability and handleability, the viscosity of the calcined gypsum slurry is desired to be 150 dPa·s or less, preferably approximately 20 to 100 dPa·s, and more preferably approximately 20 to 50 dPa·s, although this will depend on the application.

[0042] [Example 1] A polyamide polyamine liquid was mixed with colemanite (mineral) in advance, followed by drying to adhere the polyamide polyamine to the colemanite, thereby preparing the mineral used in this example. The amount of polyamide polyamine adhered to the mineral was designed to be the following amount relative to the calcined gypsum after drying. The pretreated colemanite was then blended with other powder samples to obtain the gypsum composition of this example. Furthermore, the resulting gypsum composition was used to prepare a calcined gypsum slurry as described above. In this gypsum composition, 11.8 g of a polycarboxylate-based water-reducing agent was used. This amount was 2.3% / α-St relative to the calcined gypsum. The amount of liquid polyamide polyamine adhered to the colemanite was 1.2% / α-St relative to the calcined gypsum, so that the amount adhered to the colemanite after drying was 0.4% / α-St in terms of solid content. The amount of liquid polyamide polyamine used was 2.3% (5.9 g) relative to the colemanite. As another additive, a hardening accelerator was added at 2.0% / α-St (10.0 g) relative to the calcined gypsum.

[0043] [Example 2] As in Example 1, colemanite was pretreated in advance to allow polyamide polyamine to adhere to it, and this was used as the mineral for this example. Furthermore, the gypsum composition of this example was obtained in the same manner as in Example 1, except for the points listed below, and a calcined gypsum slurry was prepared using the obtained gypsum composition. In this example, 1.5 g of a polycarboxylate-based water-reducing agent was used. This amount was 0.3% / α-St relative to the calcined gypsum. The amount of liquid polyamide polyamine adhered to the colemanite was 2.3% / α-St relative to the calcined gypsum, and the amount adhered to the colemanite after drying was 0.7% / α-St in terms of solid content. The amount of liquid polyamide polyamine used was 4.6% (11.7 g) relative to the colemanite. As another additive, a hardening accelerator was blended at 1.0% / α-St (5.0 g) relative to the calcined gypsum.

[0044] [Example 3] In the same manner as in Example 1, colemanite was pretreated in advance to allow polyamide polyamine to adhere to it, and this was used as the mineral for this example. Furthermore, the gypsum composition of this example was obtained in the same manner as in Example 1, except for the points listed below, and a calcined gypsum slurry was prepared using the obtained gypsum composition. In this example, 12.5 g of a polycarboxylate-based water-reducing agent was used. This amount was 2.5% / α-St relative to the calcined gypsum. The amount of liquid polyamide polyamine used was 0.3% / α-St relative to the calcined gypsum, and the amount adhered to the colemanite after drying was 0.1% / α-St in terms of solid content. The amount of liquid polyamide polyamine used was 0.7% (1.7 g) relative to the colemanite. As another additive, a hardening accelerator was blended at 2.0% / α-St (10.0 g) relative to the calcined gypsum.

[0045] [Example 4] In the same manner as in Example 2, colemanite was pretreated in advance to allow polyamide polyamine to adhere to it, and this was used as the mineral for this example. Furthermore, the gypsum composition of this example was obtained in the same manner as in Example 2, except for the points listed below, and a calcined gypsum slurry was prepared using the obtained gypsum composition. The amount of liquid polyamide polyamine adhered to the colemanite was 3.3% / α-St relative to the calcined gypsum, and the amount adhered to the colemanite after drying was 1.0% / α-St in terms of solid content. The amount of liquid polyamide polyamine used was 6.6% (16.7 g) relative to the mineral.

[0046] [Example 5] In the same manner as in Example 2, colemanite was pretreated in advance to allow polyamide polyamine to adhere to it, and this was used as the mineral used in this example. Furthermore, the gypsum composition of this example was obtained in the same manner as in Example 2, except for the points listed below, and a calcined gypsum slurry was prepared using the obtained gypsum composition. The amount of liquid polyamide polyamine adhered to the colemanite was 33% / α-St relative to the calcined gypsum, and the amount adhered to the colemanite after drying was 10% / α-St in terms of solid content. The amount of liquid polyamide polyamine used was 66% (167 g) relative to the mineral.

[0047] Table 1 shows a summary of the blending of raw material components for the gypsum compositions of Examples 1 to 5. Also shown in Table 1 is a calcined gypsum slurry prepared by adding 30.8% / α-St of water relative to the calcined gypsum to the obtained gypsum composition, and the viscosity of the calcined gypsum slurry was measured. The viscosity was measured at room temperature (25°C) using a Rion Visco Tester VT-06 viscometer (trade name, manufactured by Rion Co., Ltd.). The viscosity measurement results are shown in Table 1.

[0048] TIFF0007722739000001.tif111170

[0049] [Comparative Example 1] In this comparative example, colemanite (mineral) was used without pretreatment with polyamide polyamine. Specifically, colemanite, calcined gypsum, a polycarboxylate-based water-reducing agent, and a hardening accelerator were mixed to prepare a comparative gypsum composition. In this comparative example, the polycarboxylate-based water-reducing agent was used at 2.7% / α-St (13.5 g) relative to the calcined gypsum, and the hardening accelerator was used at 0.2% / α-St (1.0 g) relative to the calcined gypsum. Similarly to the examples, water was added to the obtained comparative gypsum composition to prepare a calcined gypsum slurry, and its viscosity was measured and shown in Table 2.

[0050] Comparative Example 2 In this comparative example, a polyamide polyamine was mixed with calcined gypsum in advance and dried for pretreatment. The amount of polyamide polyamine attached to the calcined gypsum was the same as the amount attached to the colemanite in Example 2, so that the amount attached to the calcined gypsum after drying was 0.7% / α-St in terms of solid content. This pretreated calcined gypsum was then blended with another powder sample to prepare the gypsum composition of this comparative example. In this comparative example, as in Example 2, a polycarboxylate-based water-reducing agent was blended with the calcined gypsum at 0.3% / α-St (1.5 g) and a hardening accelerator was blended with the calcined gypsum at 1.0% / α-St (5.0 g). As in the examples, water was added to the obtained comparative gypsum composition to prepare a calcined gypsum slurry, and the viscosity was measured and shown in Table 2.

[0051] Comparative Example 3 A liquid polyamide polyamine was mixed with powders of calcined gypsum, colemanite (mineral), and a polycarboxylate-based water-reducing agent in advance, and then dried. A hardening accelerator was then added to prepare a gypsum composition for this comparative example. The materials used and their amounts were the same as those in Example 2. Water was then added to the obtained comparative gypsum composition, as in the example, to prepare a calcined gypsum slurry. The viscosity of the slurry was measured and shown in Table 2.

[0052] TIFF0007722739000002.tif91170

[0053] As described above, the viscosity of the calcined gypsum slurries obtained using the gypsum compositions of the Examples was lower than that of the calcined gypsum slurries obtained using the gypsum compositions of the Comparative Examples, and all were 100 dPa·s or less. Therefore, it was confirmed that the calcined gypsum slurries obtained in each Example had better fluidity than the Comparative Examples, were easier to mold, and that a good hardened body could be obtained using a calcined gypsum slurry with a moderate viscosity. It was also confirmed that the gypsum compositions of the Examples could reduce viscosity compared to the gypsum compositions of the Comparative Examples when the amount of water-reducing agent was the same, and were effective in terms of raw material costs.

Claims

1. A method for producing a gypsum composition containing a mineral, calcined gypsum, and a polycarboxylate-based water-reducing agent, The mineral is at least one selected from the group consisting of bentonite, colemanite, diatomaceous shale, vermiculite, shirasu, and natural gypsum, and the ratio of the mineral to the calcined gypsum is within the range of 0.01 to 60 wt% on a mass basis, The method for producing a gypsum composition includes a pretreatment step for the mineral, wherein in the pretreatment step, a liquid polyamide polyamine and / or an alkylene oxide adduct of a polyamide polyamine is applied to the mineral in advance so that the ratio of the polyamide polyamine and / or the alkylene oxide adduct to the calcined gypsum is within a range of 0.1 to 10 wt % on a mass basis, calculated as a solid content.

2. 2. The method for producing a gypsum composition according to claim 1, wherein in the pretreatment step, the liquid polyamide polyamine and / or the alkylene oxide adduct of polyamide polyamine is sprayed onto the mineral, and then the mineral is dried.

3. A gypsum composition for preparing a calcined gypsum slurry, comprising a mixture of a mineral, calcined gypsum, and a polycarboxylate-based water-reducing agent with water, The gypsum composition is characterized in that the mineral is at least one selected from the group consisting of bentonite, colemanite, diatomaceous shale, vermiculite, shirasu, and natural gypsum, the proportion of the mineral is adjusted so that the ratio to the calcined gypsum is within a range of 0.01 to 60 wt % on a mass basis, and further, a polyamide polyamine and / or an alkylene oxide adduct of a polyamide polyamine is added to the mineral in advance in an amount, calculated as a solid content, such that the ratio to the calcined gypsum is within a range of 0.1 to 10 wt % on a mass basis.

4. A mineral raw material for a gypsum composition used in a calcined gypsum slurry containing a mineral, calcined gypsum, and a polycarboxylate-based water-reducing agent, which is prepared by adding and mixing with water, wherein the raw material is provided with a polyamide polyamine and / or an alkylene oxide adduct of a polyamide polyamine in a ratio to the mineral, calculated as a solid content, within a range of 0.02 to 120 wt % by mass, and the mineral is at least one selected from the group consisting of bentonite, colemanite, diatomaceous shale, vermiculite, shirasu, and natural gypsum.

5. A method for producing a hardened body, comprising: using the gypsum composition according to claim 3; mixing the gypsum composition with water to form a calcined gypsum slurry; and molding the hardened body using the slurry.

6. 6. The method for producing a hardened body according to claim 5, wherein the viscosity (25 ° C.) of the slurry is 150 dPa s or less when the amount of water mixed is 15 to 60 wt % by mass with respect to the gypsum composition.

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