Gypsum slurry composition and moisture resistant gypsum composite material thereof

Abstract

This application provides a gypsum composition slurry comprising: 52-60% plaster; 40-45% water; 0-1% starch; 0.03-0.5% additives selected from cement, sodium carboxymethyl cellulose, guar gum, or combinations thereof; and 0.18-1.2% moisture-proofing agent. The gypsum slurry, when cast into a gypsum composite material, exhibits moisture-proof properties. Furthermore, this application also provides a method for preparing a moisture-proof gypsum composite material (specifically, gypsum board).

Description

Technical Field

[0001] This disclosure generally relates to a gypsum slurry composition, and more particularly to such compositions that can be set to form gypsum composite materials. More specifically, this disclosure provides gypsum slurry compositions having specific additives or modifiers, and combinations thereof. Gypsum articles or composite materials formed by casting from such gypsum slurries exhibit enhanced moisture-barrier properties. Background Technology

[0002] Gypsum is a common mineral composed of calcium sulfate dihydrate. It is widely mined and used as a fertilizer, and specifically as a major component in various forms of gypsum products, blackboard / road chalk, and drywall. Dense, fine-grained white or slightly tinted varieties of gypsum are used for sculpting. Gypsum is used in a variety of gypsum products for a variety of reasons, most commonly as a building material, such as wall panels and fiberboard sheets. These are easy to process into continuous walls of desired shapes and sizes. They are durable, easy to install and repair, and have beneficial insulating, fire-resistant, and acoustic properties. Decorative finishes such as wallpaper or paint can be easily applied to its surface, allowing for a wide variety of decorative options.

[0003] More specifically, a wide variety of molded gypsum products are known, such as gypsum boards, slatted boards, decorative panels, sound insulation boards, and gypsum blocks, which possess various properties depending on the nature of the gypsum. Typically, such products or composite materials are produced by preparing a slurry composition containing plaster, dispersants, additives, binders, and water, pouring it into a mold, and subsequently drying it to allow it to set and harden. For this production process, the gypsum slurry composition needs to have sufficient fluidity, and most importantly, it must exhibit excellent strength and a variety of other properties after hardening.

[0004] When discussing the excellent strength and performance of this composite material, lightweight, high strength, fire resistance, sound insulation, high ductility, water resistance, and moisture resistance are some of the widely studied properties. Specifically, in the modern construction field, gypsum is a primary material used in the construction industry. It is well known that hardened gypsum board, with its excellent strength and various performance characteristics, can be used for wall, ceiling, and partition systems in residential, public, and commercial buildings. To control the performance of gypsum composite materials, additives or modifiers are added to the gypsum plaster composition, which further solidifies to form the gypsum composite material.

[0005] Various methods have been proposed in the prior art to improve the strength of gypsum board products or modify their properties to achieve better performance characteristics. Some methods involve adding one or more additives to the gypsum slurry to affect the properties of the resulting dried board products. For example, foaming agents, inorganic compounds, and other additives may be included to adjust density, strength, and other properties. However, some proposed additives or modifiers may affect the viscosity, tackiness, or other properties of the slurry. For example, excessively high slurry viscosity leads to increased mixing time, increased energy requirements, and consequently increased costs. Worse still, if the viscosity increase becomes too large, it can result in incompletely mixed slurry or poorly formed boards. Incompletely mixed slurry has an uneven setting profile and therefore severely affects the forming of gypsum boards during manufacturing.

[0006] Furthermore, adding additives to gypsum slurries to enhance performance properties can lead to compatibility issues with other slurry components. Some additives, for example, have surface-active or surfactant functions. These additives may disrupt or interfere with the stability of the slurry foaming additives. Some additives also have the potential for inadequate dispersion in the slurry. For example, for viscous liquids or gel additives, high viscosity and limited residence time in the slurry mixer can lead to the risk of inadequate mixing.

[0007] Specifically, gypsum composite materials (such as moisture-resistant gypsum board) are used in numerous industrial, commercial, and residential buildings in areas with high humidity or dampness, such as bathrooms, kitchens, laundry rooms, equipment rooms, or basement areas. Moisture-resistant gypsum board is commonly used in environments where ceramic tiles are laid on top of gypsum board.

[0008] A comprehensive review of the prior art has shown that there are generally two main categories of additives that can be added to or mixed with gypsum plaster slurry compositions to make the boards water-resistant (or moisture-proof, waterproof, or hydrophobic, depending on the terminology used by the inventors in various patent applications). These attempts have included incorporating waterproofing materials such as metallic soaps, bitumen, waxes, resins, etc., into the gypsum plaster (i.e., calcium sulfate hemihydrate) slurry during the manufacturing process.

[0009] For example, one type is wax-based additives, which typically include waxes emulsified with other reagents, such as those described in U.S. Patent No. 6,585,820 B2, which discloses a waterproof plaster formulation comprising an emulsion containing multiple waxes, at least one saponified wax, complexed starch, polymeric alkylphenols, and a co-surfactant, or an emulsion comprising a single wax, a dual-surfactant system, complexed starch, and polymeric alkylphenols. U.S. Patent No. 6,010,596 teaches the use of paraffin wax and montmorillonite wax; U.S. Patent No. 5,437,722 teaches the use of paraffin-asphalt, etc. Waxes are typically petroleum-based waxes, such as paraffin wax, microcrystalline wax, montmorillonite wax, or wax-asphalt, wax-asphalt coke mixtures. Waxes are suspensions and typically require equipment to stabilize them. Furthermore, waxes are expensive and require high dosages.

[0010] Another very general category can be called other reagents, ranging from sulfur, calcium stearate, polyurethane, silanes, siloxanes, and high molecular weight organosilicon, alkyl silicates, or polyethylene compounds, which can be added to or coated onto plaster preparations. For example, U.S. Patent No. 6,323,268 discloses compositions that impart hydrophobicity to surfaces by combining (i) water; (ii) a methylhydrosiloxane polymer or copolymer; (iii) an alkoxysilane; (iv) an organosilicon resin; (v) a volatile methylsiloxane; (vi) an amino-functionalized polydimethylsiloxane cationic oil-in-water emulsion; and (vii) a surfactant. While these compositions can impart a variety of hydrophobic properties to surfaces, they are not suitable for applications involving high-temperature processing equipment. This is because compositions containing volatile silicon components tend to cause silica scaling in high-temperature processing equipment.

[0011] U.S. Patent Application Publication No. 2016 / 0258157 and U.S. Patent No. 7,892,472 similarly disclose gypsum panels with improved water resistance. In this case, polymerizable siloxanes are added to the slurry used to prepare the gypsum products. The siloxanes are added in emulsion form. A catalyst, such as magnesium oxide (MgO), is also added to accelerate the polymerization of the siloxanes. However, the polymerization of the siloxanes may be incomplete, resulting in the need for additional drying time to allow for more complete polymerization. EP1112986 A1 teaches that when polymerizable siloxanes are added to gypsum slurry and Portland cement is used as a catalyst, water resistance is significantly increased. The amount of siloxane emulsion added to the slurry is at least about 0.1% by weight of the total solids in the slurry. Preferably, about 1% to about 2% by weight of siloxane and 0.3-2% by weight of Portland cement are used to achieve a high level of water resistance.

[0012] Silicone oil is commonly used to provide moisture-proof properties to gypsum composites. However, the inventors have recognized that the amount of silicone oil used often exceeds what is required per unit mass to compensate for the characteristic of oil migration to the surface of the gypsum composite during the setting and drying of the gypsum core material, resulting in relatively low water resistance or moisture resistance in the center of the gypsum core material. Furthermore, the use of silicone oil in gypsum composites is also expensive.

[0013] Therefore, it can be noted from the prior art that polymethylhydrosiloxanes are widely used to achieve moisture resistance in gypsum boards. Among the various additives used in boards, siloxanes are the largest cost contributor. Siloxanes, with their low surface energy, tend to migrate to the interface between the slurry and the lining when mixed with water. Therefore, it is always desirable to ensure good dispersion of siloxanes in the gypsum slurry and to initiate their polymerization reaction as quickly as possible. This reduces the amount of siloxane used, which further helps to reduce their cost contribution, making them significantly more economical. Therefore, it is desirable in the art to discover modifiers / additives for gypsum slurry compositions that can further solidify into gypsum products with improved performance properties, specifically aimed at achieving improved moisture resistance at a reasonable cost and allowing the additive to be better distributed throughout the gypsum composite. In this invention, the co-emulsification of silicone oil with cement, guar gum, and other additives has a synergistic effect and provides improved moisture resistance for a given silicone oil concentration in the gypsum board.

[0014] Purpose of the invention The main objective of this invention is to provide a slurry composition that can be cast into a gypsum composite material.

[0015] In particular, another object of the present invention is to provide a gypsum slurry composition that, when cast to form a gypsum composite material, can exhibit enhanced moisture-barrier properties.

[0016] Another object of the present invention is to provide a gypsum slurry composition comprising emulsified silicone and a modifier, said modifier enhancing the distribution of silicone oil and thus reducing the amount of silicone oil used.

[0017] Furthermore, another object of the present invention is to provide a method for preparing a gypsum composite material, wherein the gypsum composite material has moisture resistance.

[0018] This disclosure is developed by summarizing the above objectives. Summary of the Invention

[0019] One aspect of this disclosure discloses a gypsum slurry composition. The gypsum slurry composition comprises: 52-60% plaster; 40-45% water; 0-1% starch; 0.03-0.5% modifier selected from cement, sodium carboxymethyl cellulose, guar gum, or combinations thereof; and 0.18-1.2% moisture-resistant agent. The gypsum slurry thus cast into a gypsum composite material exhibits moisture resistance.

[0020] One aspect of this disclosure discloses a gypsum slurry composition. The gypsum slurry composition comprises: 52-60% plaster; 40-45% water; 0-1% starch; 0.012-0.3% cement; and 0.18-1.2% emulsified silicone oil.

[0021] Another aspect of this disclosure discloses a gypsum slurry composition. The gypsum slurry composition comprises 52-60% plaster; 40-45% water; 0-1% starch; 0.1-0.5% guar gum; and 0.18-1.2% emulsified silicone oil.

[0022] Another aspect of this disclosure discloses a gypsum slurry composition. The gypsum slurry composition comprises: 52-60% plaster; 40-45% water; 0-1% starch; 0.01-0.05% sodium carboxymethyl cellulose; 0.05-0.5% guar gum; and 0.18-1.2% emulsified silicone oil.

[0023] Furthermore, another aspect of this disclosure discloses a method for preparing a moisture-proof gypsum composite material. The method includes the following steps: forming a gypsum slurry; forming a layer of the mixture on a first liner; disposing a second liner on the layer, opposite to the first liner, to form an assembly with the layer sandwiched between the liner; hydrating the slurry; and drying the assembly to form the gypsum composite material.

[0024] Other features and aspects of this disclosure will be apparent from the following description and accompanying drawings. Detailed Implementation

[0025] As used herein, in each implementation, it should be understood that the phrase “plaster slurry” refers to a mixture of stucco and water.

[0026] As used herein, in each embodiment it should be understood that the terms “moisture-proof” or “wet-resistant” or “waterproof” are used interchangeably and refer to properties that provide better or enhanced resistance to moisture or water than conventional drywall.

[0027] The terms "gypsum composite material" or "gypsum product" are used interchangeably and refer to the product formed by pouring gypsum slurry according to the present invention. Specifically, the gypsum composite material mentioned in the present invention is not limited to gypsum board.

[0028] The terms “additive” or “modifier” are used interchangeably and refer to additional components included in the base plaster composition.

[0029] This application provides a gypsum slurry composition. According to one aspect of this disclosure, the gypsum slurry composition comprises: 52-60% plaster; 40-42% water; 0.2-1% starch; 0.03-0.5% modifier selected from cement, sodium carboxymethyl cellulose, guar gum, or combinations thereof; and 0.18-12% moisture-proofing agent. Cement is a pH adjuster, and sodium carboxymethyl cellulose and guar gum are water-retaining agents. Advantageously, when this composition is cast into a gypsum composite material, the gypsum composite material exhibits enhanced moisture resistance. Furthermore, advantageously, this gypsum composite material also possesses excellent strength, achieves better core morphology by reducing foam breakage, and reduces the use of silicone oil.

[0030] The inventors unexpectedly discovered that a modifier comprising cement, sodium carboxymethyl cellulose, and guar gum can be used in combination or alone with a base plaster slurry composition and emulsified silicone oil, which can be further cast to obtain a gypsum composite material with improved moisture-proof properties. Further advantageously, the inventors also found that by adding the aforementioned modifier, the silicone oil tends to be more uniformly distributed and better dispersed in the cast gypsum composite material, thereby reducing the amount of silicone oil required.

[0031] The inventors further and unexpectedly discovered that small amounts of these additives can be added to the base plaster slurry composition. The inventors of this disclosure have effectively overcome the challenges described in the background art by introducing additives in amounts as low as 0.012-0.3%. The addition of the additives, or combinations thereof, not only ensures water resistance or moisture resistance but also surprisingly improves the efficiency of silicone oil use. Silicone oil is effectively used to impart moisture-resistant properties to the gypsum core material, thereby reducing the amount of silicone oil migrating to the gypsum-liner interface. Reduced silicone oil migration at the gypsum-liner interface results in reduced silica dust formation in the dryer.

[0032] In some embodiments of the present invention, the gypsum slurry composition comprises, by weight: 52-60% plaster; 40-45% water; 0-1% starch; 0.18-1.2% moisture-proofing agent; and 0.012-0.3% additives or modifiers. The moisture-proofing agent of the present invention is selected from the group consisting of emulsified or non-emulsified silicone oil, silanol, hydrolyzed silane, alkyl / vinylalkoxysilane, alkyl / vinylsiloxane, alkyl / vinylsilanol, alkyl silicate, or combinations thereof. In one specific embodiment, the moisture-proofing agent is preferably emulsified silicone oil, silanol, or hydrolyzed silane. In a most preferred embodiment, the moisture-proofing agent is emulsified silicone oil.

[0033] The modifier of this invention is selected from the group consisting of cement, sodium carboxymethyl cellulose, guar gum, or combinations thereof. In an alternative embodiment, the modifier may also be selected from the group consisting of dicalcium silicate, tricalcium silicate, hydraulic cement, hydraulic lime, inorganic weak alkali, or fly ash. In some embodiments of this invention, the gypsum slurry composition includes various combinations of the modifier and the moisture-proofing agent.

[0034] According to one embodiment of the present invention, the gypsum slurry composition comprises, by weight: 52-60% plaster; 40-45% water; 0-1% starch; 0.18-1.2% emulsified silicone oil; and 0.012-0.3% cement additives.

[0035] In each embodiment of the invention, plaster is present in the gypsum slurry composition at a weight range of 52-60% by weight. In a preferred embodiment, plaster is present at a weight range of 55-59%. In a most preferred embodiment, plaster is present in the gypsum slurry composition at a weight of 58% by weight. It is known in the art that plaster can have a variety of compositions, depending on the source and the current application. According to the invention, plaster is a material having at least 75% calcium sulfate hemihydrate. It is typically provided by calcining gypsum to convert gypsum dihydrate to hemihydrate. Realistic samples of plaster typically include hemihydrate (e.g., present as α-calcium sulfate hemihydrate and β-calcium sulfate hemihydrate or a combination thereof), and one or more of calcium sulfate dihydrate, anhydrous calcium sulfate, inert calcium sulfate, and other impurities, depending on the source of the gypsum. The combination of plaster and water is referred to herein as calcium sulfate slurry or gypsum slurry.

[0036] The gypsum slurry composition according to the invention contains water in an amount of 40-45%. In a preferred embodiment, the water is present in an amount of 41%. The water provides fluidity to the slurry for easy handling and provides the moisture required for the hydration of the hemihydrate into gypsum. In one embodiment, the weight ratio of plaster to water in the gypsum slurry does not exceed 0.8:1, for example, not exceeding 0.75:1 or not exceeding 0.7:1. In various embodiments of the invention, the weight ratio of plaster to water in the gypsum slurry is in the range of 0.8:1 to 0.7:1. In a preferred embodiment, the weight ratio of plaster to water in the gypsum slurry is 0.7:1.

[0037] In each embodiment of the invention, starch is present in the gypsum slurry composition at a weight range of 0-1% by weight. In a preferred embodiment, starch is present at a weight range of 0.2-0.5%. In a most preferred embodiment, starch is present in the gypsum slurry composition at a weight of 0.3%. In alternative embodiments, high-viscosity modified starch may also be used in the gypsum slurry composition. In some embodiments, the starch may also be pregelatinized starch or pre-gelatinized starch. In an alternative embodiment, the starch according to the invention is acid-modified, chemically modified, or a combination thereof; and has various crop sources, including corn, sorghum, wheat, cassava, rice, peas, potatoes, and barley.

[0038] In a preferred embodiment of the invention, a small amount of cementitious additive is added to the base plaster slurry composition to obtain a gypsum composite material with moisture-proof properties. Cement is generally one of the cheapest pH adjusters and does not corrode process equipment such as silos and feeding systems. However, the addition of cement causes water droplets to form beads, creating stains on the slabs, and causing moisture condensation and blistering during drying. The addition of cement to the plaster slurry is indeed known to create many process challenges that outweigh its benefits. Cement is used to obtain the alkaline pH value of the gypsum slurry. In the alkaline pH range of 7.5 to 14, silicone polymerization is accelerated. This, in turn, enhances the effectiveness of the silicone oil, thereby enabling the cast gypsum composite material to acquire moisture-proof properties.

[0039] The inventors of this disclosure have effectively overcome these challenges by introducing cement in amounts as low as 0.012-0.3%, preferably 0.012-0.055%. The addition of a small amount of cement not only ensures the pH required for silicone oil polymerization but also surprisingly enhances the effectiveness of the silicone oil. It is generally believed that the higher the cement content, the faster the silicone oil polymerizes. However, a high cement content in mortar can affect paper-plaster bonding and may lead to setting within the dryer. While cement helps improve the effectiveness of the silicone oil, as mentioned above, it creates process challenges that outweigh its benefits (e.g., paper-plaster bonding and setting in the dryer).

[0040] Therefore, the inventors not only reduced the cement content to overcome process challenges, but also ensured that the cement content contributed to improving the effectiveness of the silicone oil.

[0041] In another embodiment of the invention, a small amount of guar gum additive is added to the base plaster slurry composition to obtain a gypsum composite material with moisture-proof properties. In a preferred embodiment, guar gum is present in the range of 0.1-0.5%. In another preferred embodiment, guar gum is present in an amount of 0.2%. It is presumed that guar gum provides viscosity to the gypsum slurry by altering the electrokinetic properties of the slurry, thereby reducing silicone oil migration. Guar gum is used to reduce silicone oil migration to the surface during the preparation of gypsum composites, particularly gypsum boards. Guar gum also acts as a thickener and helps retain siloxanes in the slurry. Guar gum undergoes hydration and produces a thickening effect when mixed with water. The hydration rate of guar gum and the achievement of the final viscosity are highest at neutral pH. The thickening effect of guar gum, in turn, helps retain silicone oil in the slurry during the production of moisture-proof gypsum boards. Therefore, the effectiveness of silicone oil is improved. It has been reported that the hydration rate of guar gum slows down and results in lower viscosity at pH values ​​of 9 and above. Therefore, maintaining a low cement content helps keep the pH value within the range of 7-9, allowing guar gum thickening and silicone oil polymerization to occur simultaneously. In fact, the pH range of gypsum slurry without pH adjusters is 6.5-7. At the pH of the gypsum slurry, time is needed to initiate the silicone oil polymerization reaction. During this period, the silicone oil migrates to the surface, which impairs the moisture-proof properties of the gypsum core material. To obtain a pH value greater than 7, cement is added, which accelerates polymerization, thereby achieving moisture-proof properties.

[0042] In each preferred embodiment of the invention, the emulsified silicone oil is present in the gypsum slurry composition at a weight range of 0.18-1.2% by weight. Preferably, the silicone oil is present in an amount of 0.2-1.2%. In a most preferred embodiment, the silicone oil is present in the gypsum slurry composition at a weight of 0.25% by weight. Those skilled in the art will understand that the silicone oil may comprise a variety of different polysiloxanes. These polysiloxanes may include hydrogen and other functional groups to modify the polysiloxane backbone. For example, polymethylhydrosiloxanes simultaneously comprise Si-H and Si-CH3 bonds. According to the invention, the silicone oil is preferably a polymethylhydrosiloxane.

[0043] In the most preferred embodiment of the invention, the silicone oil is provided in the form of an aqueous emulsion of silicone oil in the base slurry. In some embodiments, the aqueous emulsion of silicone oil can be provided by emulsifying organosilicon in water. In some alternative embodiments, silicone oil can be provided to the base slurry by mixing it into the base slurry, provided that conditions are sufficient to form an emulsion. In some alternative embodiments, silicone oil can be provided to the remaining process water by mixing it into the process water. The silicone oil according to the invention has a low hydrogen content.

[0044] In another embodiment, various organosilicones can be used in the gypsum slurry composition. In some embodiments of the invention, the silicone oil comprises alkyl-functionalized organosilicones. Alkyl-functionalized organosilicones are polysiloxanes with alkyl functionalization. For example, in some embodiments, the silicone oil comprises methyl-functionalized organosilicones, ethyl-functionalized organosilicones, propyl-functionalized organosilicones, or butyl-functionalized organosilicones. In some embodiments, the silicone oil is polydimethylsiloxane. However, in some embodiments, the silicone oil may be a copolymer of dimethylsiloxanes, such as with methylsiloxanes or phenylsiloxanes (in an amount that results in a low hydride content). In a most preferred embodiment, according to the invention, the molar content of dimethylsiloxane units in the silicone oil is at least 90%, or at least 95%, or at least 99%. Surprisingly, very small amounts of additives (used alone or in combination) in the gypsum slurry are sufficient to emulsify the polymethylhydrosiloxane in water and give the emulsion sufficient stability to polymerize and, as necessary, to uniformly distribute the emulsified silicone oil in the gypsum slurry.

[0045] The silicone oil according to the invention has an average droplet size in the range of 5-75 μm, preferably in the range of 12-25 μm. This can be the droplet size of the silicone oil emulsion added to the gypsum slurry composition and / or the droplet size of the silicone oil in the slurry itself. The aqueous emulsion according to the invention is formed by mixing water and silicone oil in a ratio ranging from 1:10 to 1:50. In one specific embodiment, the ratio of water to silicone oil is 1:25.

[0046] The inventors of this invention speculate that using emulsified silicone oil in combination with a single additive or a compound additive at the above-mentioned amounts helps to limit the migration of silicone oil in the gypsum core of gypsum composite materials (usually gypsum board), thereby making the silicone oil concentration more uniform throughout the thickness of the composite material.

[0047] The gypsum slurry composition of the present invention may further comprise one or more accelerators, retarders, fluidizing agents, dispersants, foaming agents, and / or glass fibers. In some embodiments, the aforementioned agents are present in an amount not exceeding 1% by weight of the gypsum slurry composition. In various embodiments, the aforementioned agents are present in an amount not exceeding 0.8% by weight or not exceeding 0.5% by weight of the gypsum slurry composition. Those skilled in the art will use suitable groups of the aforementioned agents for the desired gypsum slurry composition.

[0048] In one specific embodiment, the retarder is present in an amount ranging from 0.01% to 0.04%, and is selected from the group consisting of amino acids, citric acid, or tartaric acid. In a most preferred embodiment, the retarder is present in an amount of 0.01% and is an amino acid. The retarder according to the invention delays setting according to the production line speed.

[0049] In one specific embodiment, the heat-resistant accelerator is present in an amount ranging from 0.2% to 5%, and is selected from the group consisting of magnesium, calcium sulfate, milled gypsum, or potassium sulfate. In a most preferred embodiment, the heat-resistant accelerator is present in an amount of 0.2%, and is calcium sulfate. The accelerator according to the invention is added to accelerate the mortar setting time.

[0050] In one specific embodiment, the fluidizing agent is present in an amount ranging from 0.1% to 0.5%, and is selected from the group consisting of polynaphthalene sulfonate, lignin sulfonate, polycarboxylate, or combinations thereof. In a most preferred embodiment, the fluidizing agent is present in an amount of 0.1%, and is polynaphthalene sulfonate or lignin sulfonate. The fluidizing agent according to the invention is used as a water-reducing agent to obtain slurry fluidity.

[0051] In one specific embodiment, the foaming agent is selected from the group consisting of ethoxylated surfactants or lauryl surfactants. In a most preferred embodiment, the foaming agent is present in an amount of 0.1% and is an ethoxylated surfactant.

[0052] The gypsum slurry composition according to the invention is poured to form a gypsum composite material. The gypsum composite material can be, for example, a panel, board, wall, base, plate, column, sheet, casting, or shaft component. In some embodiments, the gypsum composite material is a panel, board, or sheet. In a preferred embodiment, the gypsum composite material is a gypsum board.

[0053] This application also discloses a method for preparing a moisture-proof gypsum composite material. The method includes the following steps: forming a gypsum slurry composition; forming a layer of the mixture on a first liner; and disposing a second liner on the layer, opposite to the first liner, to form an assembly with the layer sandwiched between the liner. Further, the slurry is hydrated, and the assembly is dried to form the gypsum composite material.

[0054] In one embodiment of the invention, gypsum slurry is formed by mixing the components of gypsum slurry. The formed mixture is applied as a first layer onto a first lining, and then a second layer is formed on the opposite side of the first lining to form an assembly having the first and second layers. The slurry is sandwiched between the first and second layers. The assembly is placed in an environment for curing and hardening to form a gypsum board. The lining may be a paper lining or a fiberglass felt lining.

[0055] The gypsum composite material of the present invention, particularly gypsum board, has a modulus of rupture in the range of 450-550 Newtons and a tested water absorption rate of less than 4.9%, for example less than 4.6% or less than 4%.

[0056] The gypsum composite material produced according to this disclosure has moisture-proof / water-resistant properties, improved silicone oil performance, and reduced tested water absorption rate. Preferably, this gypsum composite material can be applied to buildings, facades, panels, kitchen backsplashes, furniture (wardrobes, tabletops, worktops), cladding, elevator lobbies, etc.

[0057] Example

[0058] Table 1 shows the results of comparing the gypsum slurry compositions of Examples 1-3 of the present invention with comparative samples using non-emulsified silicone oil.

[0059] Plasterboard is prepared from the above slurry:

[0060] Prepare the slurry and pour it onto the paper backing. Prepare a 150×150 mm slurry on a laboratory scale. 2 The boards were prepared. Casting was performed on a vibrating table to facilitate uniform distribution of the slurry within the mold. After the slurry solidified, the boards were demolded and dried at 180°C for 90 minutes to remove excess moisture while simultaneously activating the starch to create a bond between the paper and the core. Two boards were prepared for each formulation. The dried boards were then transferred to a 40°C ventilated oven to remove the final moisture content over 24 hours.

[0061] After drying, the boards are placed in an environment of 23°C and 50% relative humidity for 48 hours for constant temperature and humidity curing. The cured boards are then immersed in water for 2 hours to quantify water absorption. The water absorption test procedure is performed according to EN520 standard, and the H1 category specifications are below 5 wt%.

[0062] According to the invention example and comparative example, the above method is used to cast gypsum slurry into gypsum board.

[0063] According to the present invention, the following tests were performed on the gypsum board compared with the comparative example to evaluate the performance of the claimed protection.

[0064] a) Test water absorption:

[0065] According to standard: EN520

[0066] The TWA was tested using the standardized procedures given in the standard, and the results of the inventive and comparative examples are listed in Table 2.

[0067] The typical water resistance (TWA) of gypsum board was measured using the requirement of TWA < 5% for H1 class boards in EN 520. As can be deduced from Table 2, the inventive examples exhibit better moisture resistance compared to the comparative examples.

[0068] As can be seen from Table 2 above, Invention Examples 1 [cement + guar gum + emulsified silicone oil + base plaster], 2 [guar gum + emulsified silicone oil + base plaster], and 3 [cement + emulsified silicone oil + base plaster] have demonstrated a required standard TWA of less than 5%.

[0069] However, in Comparative Examples 1 [base plaster without cement, guar gum and containing emulsified silicone oil], 2 [base plaster + cement + guar gum; containing non-emulsified silicone oil], 3 [base plaster + cement; containing non-emulsified silicone oil], and 4 [base plaster + guar gum; containing non-emulsified silicone oil], it has been shown that TWA is greater than 5% and 8%.

[0070] This clearly demonstrates that base plaster formulations containing individual or compound additives, combined with emulsified silicone oil, have achieved moisture-proof gypsum board, while base plaster formulations without emulsified silicone oil have not.

[0071] Note that not all of the described steps are necessary in the general description or embodiments above; some steps in a particular operation may be optional, and one or more additional steps may be performed in addition to the steps described.

[0072] The benefits, other advantages, and solutions to the problems have been described above with reference to specific embodiments. However, the benefits, advantages, and solutions to the problems described in this specification, as well as any features that bring about or further highlight the above benefits, advantages, and solutions, shall not be construed as key, essential, or core technical features of any or all of the claims.

[0073] The description and examples of embodiments described herein are intended to provide a general understanding of the structure of various embodiments. The description and examples are not intended as an exhaustive and comprehensive description of all elements and features of apparatuses and systems using the structures or methods described herein. For clarity, certain features are described in the context of independent embodiments, and these features may also be provided in combination in a single embodiment. Conversely, for brevity, various features described in the context of a single embodiment may also be provided independently or as sub-combinations. Furthermore, references to values ​​stated in the scope include every value within that scope. Many other embodiments will be apparent to those skilled in the art upon reading this specification. Other embodiments may be used and derived from this disclosure, such that structural substitutions, logical substitutions, or other changes can be made without departing from the scope of this disclosure. Therefore, this invention should be considered illustrative rather than restrictive.

[0074] The description provided in conjunction with the accompanying drawings is intended to aid in understanding and describing the teachings disclosed herein, and should not be construed as limiting the scope or applicability of the teachings. However, other teachings may be used in this application.

[0075] As used herein, the terms “comprises, comprising,” “includes, including,” “has, having,” or any other variations thereof are intended to cover non-exclusive inclusion.

[0076] Furthermore, the use of "a" or "an" is used to describe the elements and components described herein. This is merely for convenience and to give a general concept of the scope of the invention. Unless explicitly stated otherwise, it should be understood that this specification includes one or at least one, and the singular form also includes the plural form, and vice versa. For example, when a single item is described herein, more than one item may be used instead of a single item. Similarly, in the case where more than one item is described herein, a single item may replace the more than one item.

[0077] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Materials, methods, and examples are illustrative only and are not intended to be limiting. Where details of specific materials and processing operations are not described, such details may include conventional methods, which can be found in reference books and other sources in the field of manufacturing.

[0078] Although various aspects of this disclosure have been specifically shown and described with reference to the above embodiments, those skilled in the art will understand that various other embodiments can be conceived by modifying the disclosed machines, systems, and methods without departing from the spirit and scope of the disclosure. These embodiments should be understood to fall within the scope of this disclosure as defined by the claims and any equivalents.

Claims

1. A gypsum slurry composition comprising, by weight: 52-60% plaster; 40-45% water; 0-1% starch; 0.012-0.5% modifier; and 0.18-1.2% desiccant.

2. The gypsum slurry composition according to claim 1, wherein the modifier is selected from the group consisting of cement, sodium carboxymethyl cellulose, guar gum, or combinations thereof.

3. The gypsum slurry composition according to claim 1, wherein the moisture-proofing agent is selected from the group consisting of emulsified or non-emulsified silicone oil, silanol, hydrolyzed silane, alkyl / vinylalkoxysilane, alkyl / vinylsiloxane, alkyl / vinylsilanol, alkyl silicate, or combinations thereof.

4. The gypsum slurry composition according to claim 1, wherein the starch is acid-modified, chemically modified, pregelatinized, or a combination thereof; and has a variety of crop sources, including corn, sorghum, wheat, cassava, rice, peas, potatoes, and barley.

5. The gypsum slurry composition according to claim 1, comprising, by weight: 52-60% plaster; 40-42% water; 0-1% starch; 0.012-0.3% cement, 0.1-0.5% guar gum, and 0.18-1.2% emulsified silicone oil.

6. The gypsum slurry composition according to claim 1, comprising, by weight: 52-60% plaster; 40-42% water; 0-1% starch; 0.012-0.3% cement, and 0.18-1.2% emulsified silicone oil.

7. The gypsum slurry composition according to claim 1, comprising, by weight: 52-60% plaster; 40-42% water; 0-1% starch; 0.1-0.5% guar gum, and 0.18-1.2% emulsified silicone oil.

8. The gypsum slurry composition according to claim 1, comprising, by weight: 52-60% plaster; 40-42% water; 0-1% starch; 0.01-0.05% sodium carboxymethyl cellulose; 0.05-0.5% guar gum; as well as 0.18-1.2% emulsified silicone oil.

9. The gypsum slurry composition according to claim 1, wherein the moisture-proofing agent is an aqueous emulsion of silicone oil.

10. The gypsum slurry composition according to claim 1, further comprising a retarder, a heat-resistant accelerator (HRA), a fluidizing agent, and a foaming agent.

11. The gypsum slurry composition according to claim 1, wherein the retarder content is 0.01-0.04%, selected from the group consisting of amino acids, citric acid or tartaric acid.

12. The gypsum slurry composition according to claim 1, wherein the content of the heat-resistant accelerator is 0.2-5%, selected from the group consisting of: magnesium, calcium sulfate, ball milled gypsum or potassium sulfate.

13. The gypsum slurry composition according to claim 1, wherein the fluidizing agent content is 0.1-0.5%, selected from the group consisting of: polynaphthalene sulfonate, lignin sulfonate, polycarboxylate, or a combination thereof.

14. The gypsum slurry composition according to claim 1, wherein the foaming agent is selected from ethoxylated surfactants or lauryl surfactants.

15. The gypsum slurry composition according to claim 1, wherein the gypsum slurry is cast to form a gypsum composite material, such as a panel, board, wall, base, plate, column, sheet, casting, or well component.

16. The gypsum slurry composition according to claim 15, wherein the gypsum composite material exhibits moisture resistance.

17. The gypsum slurry composition according to claim 15, wherein the gypsum composite material has a modulus of rupture in the range of 450-550 Newtons.

18. The gypsum slurry composition according to claim 15, wherein the gypsum composite material has a total water absorption rate of about 4.1% when the cement content is 0.012-0.5% and the guar gum content is 0.1-0.5%.

19. The gypsum slurry composition according to claim 5, wherein the gypsum slurry is cast to form a gypsum composite material, such as a panel, board, wall, base, plate, column, sheet, casting, or well component, and wherein the gypsum composite material has a total water absorption rate of less than 4.9%.

20. The gypsum slurry composition according to claim 6, wherein the gypsum slurry is cast to form a gypsum composite material, such as a panel, board, wall, base, plate, column, sheet, casting, or well component, and wherein the gypsum composite material has a total water absorption rate of about 4.6%.

21. The gypsum slurry composition according to claim 15, wherein the gypsum composite material is preferably gypsum board.

22. The gypsum slurry composition of claim 21, wherein the gypsum board has a core material sandwiched between a pair of lining layers.

23. The gypsum slurry composition according to claim 21, wherein the lining is a paper lining or a glass fiber felt lining.

24. A method for preparing a moisture-proof gypsum composite material, the method comprising the following steps: a. Forming a slurry of the composition according to claim 1, b. Forming a layer of the mixture on the first liner; c. A second liner is disposed on the layer opposite to the first liner to form an assembly in which the layer is sandwiched between the liner; d. Hydrate the slurry; and e. Dry the components to form a gypsum composite material.

25. The method of claim 24, wherein the moisture-proofing agent is provided in the form of an aqueous emulsion, said aqueous emulsion being obtained by mixing water and silicone oil in a silicone / water ratio ranging from 1:10 to 1:

50.

26. The method of claim 24, wherein the aqueous emulsion of the silicone oil has a droplet size in the range of 12-25 μm.

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