High-strength gypsum plasterboard incorporating milled waste mineral wool for improved flexural strength

Abstract

The present invention relates to a high-strength gypsum plasterboard incorporating milled waste mineral wool. The plasterboard comprises milled waste mineral wool in a range of 0.1% to 10% by weight relative to stucco, with fibre lengths ranging from 0.1 to 2000 μm. The milled waste mineral wool enhances the flexural strength and core hardness of the plasterboard. The effective utilization of milled waste mineral wool contributes to sustainability by repurposing industrial by-products and enhancing the performance characteristics of gypsum plasterboards in construction applications.

Description

[0001] HIGH-STRENGTH GYPSUM PIASTERBOARD INCORPORATING MILLED WASTE MINERAL WOOL FOR IMPROVED FLEXURAL STRENGTH

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to building materials, specifically high-strength gypsum plasterboards enhanced with milled waste mineral wool and a method thereof. The invention focuses on improving the mechanical properties of plasterboards, including flexural strength and core hardness, through the incorporation of sustainable additives.

[0004] BACKGROUND TO THE INVENTION

[0005] In the realm of building materials, gypsum plasterboards are widely used for interior wall and ceiling applications due to their ease of installation, fire resistance, and acoustic properties. These boards typically consist of a gypsum core encased in paper liners, providing a versatile surface for finishing treatments such as paint or wallpaper.

[0006] The gypsum is derived from natural sources. It is finely ground to desired particles size for further processing. These particles undergo calcination, transforming calcium sulphate dihydrate (CaSO4 2H2O) into calcium sulphate hemihydrate (CaSO4 0.5H2O), also known as stucco. The calcination process is optimized to maximize the formation of stucco, a key ingredient in plasterboard production.

[0007] In plasterboard manufacturing process, stucco is mixed with water to achieve the desired consistency, incorporating additives such as retarders to delay setting, accelerators to hasten it, starch for enhanced bonding, water reducing agents for consistency, and foaming agents to reduce board weight. This slurry is poured on paper or glass mat liner, covered by a second liner, extruded to the desired dimensions, and undergoes a setting process where the stucco reverts to gypsum upon water absorption and recrystallisation. After reaching the desired setting ratio, the boards are cut to size and dried to less than 0.4% moisture content. Boards are subjected to rigorous quality testing including flexural strength measurements.

[0008] However, while gypsum plasterboards offer several advantages, there is a continuous drive within the construction industry to enhance their properties, particularly in terms of strength and durability. Flexural strength, which measures a material's ability to withstand bending without breaking, is crucial for ensuring the longevity and structural integrity of plasterboards under various loads and environmental conditions. Core hardness, on the other hand, determines the board's resistance to impacts and indentation, contributing to its overall robustness.

[0009] Mineral wool elements, such as glass or stone wool, are commonly utilized in various applications like acoustical panels, ceiling tiles, and thermal insulation. However, the production of mineral wool, whether in the form of glass or stone wool, results in significant waste. This waste is also generated during the manufacturing process of mineral wool elements and includes rejected pieces or sections removed during shaping. Additionally, waste is produced during the installation phase of mineral wool systems, comprising trimmed sections or leftover elements post-installation. Finally, waste may accumulate after the end-of-life demounting of mineral wool systems. Historically, recycling waste in the form of mineral wool elements generated during manufacturing, installation, or end-of-life demounting has presented significant challenges in terms of efficiency.

[0010] Furthermore, waste generated during manufacturing, installation, or after end-of-life disposal has traditionally been difficult to recycle efficiently.

[0011] US11787741B2 discloses a method for producing acoustical panel elements using waste mineral wool such as stone wool and glass wool in combination with a geopolymer. However, this document does not discuss the possibility of utilizing waste mineral wool in plasterboards.

[0012] EP4201913A1 discloses a cementitious product incorporating stone wool objects. The document mentions improving fire resistance properties by incorporating unmodified waste stone wool objects (as generated by the stone wool production process).

[0013] Despite existing methods for incorporating waste mineral wool into construction materials like geopolymer-based acoustical panels or cementitious products, the integration of milled waste mineral wool into high-strength plasterboard to maintain weight and enhance environmental friendliness remains unexplored.

[0014] The current challenge lies in developing a gypsum board with increased strength through the inclusion of milled waste mineral wool, without compromising the board's overall weight or cost-effectiveness, while maintaining environmental sustainability. OBJECTS OF THE INVENTION

[0015] Therefore, it is primary object of the present invention to integrate mineral wool, a fibrous waste material, into the plasterboard manufacturing process to enhance mechanical properties without adversely affecting the production process parameters.

[0016] It is another object of the present invention to provide a high strength plaster board by incorporating milled waste mineral wool.

[0017] Yet another object of the present invention is to provide a high strength plaster board through the inclusion of milled waste mineral wool, without compromising the board's overall weight or cost-effectiveness, while maintaining environmental sustainability.

[0018] SUMMARY OF THE INVENTION

[0019] According to a first aspect of the invention, there is provided a high-strength gypsum plasterboard that incorporates milled waste mineral wool as a key additive. The plasterboard composition comprises milled waste mineral wool in a range of 0.1% to 10% by weight relative to gypsum stucco. The milled waste mineral wool used in this invention has fibre lengths ranging from 0.1 to 2000 pm, optimizing its reinforcement properties within the plasterboard matrix.

[0020] The said plasterboard demonstrates enhanced flexural strength compared to traditional boards due to the inclusion of milled waste mineral wool. This improvement is observed both in the machine direction (MD) and cross direction (CD). Additionally, the core hardness of the plasterboard is also increased, providing better resistance to impacts and loads.

[0021] Another aspect of the invention provides a method for manufacturing this high-strength plasterboard. Said method involves incorporating milled waste mineral wool into a gypsum slurry, carefully adjusting slurry parameters for consistency, and drying the boards to achieve the desired mechanical properties.

[0022] More specifically, the present invention provides a versatile solution for enhancing the structural integrity and durability of gypsum plasterboards through the sustainable use of milled waste mineral wool, benefiting various construction applications where robustness and performance are paramount.

[0023] BRIEF DESCRIPTION OF THE FIGURES

[0024] The above, as well as additional objects, features and advantages of the present invention, will be better understood through the following illustrative and non-limiting detailed description of preferred embodiments of the present invention, with reference to the appended drawings, where the same reference numerals will be used for similar elements, wherein:

[0025] FIG. 1 illustrates a particle size distribution of milled waste stone wool and milled waste glass wool materials.

[0026] FIG. 2A illustrates a SEM analysis of milled waste stone wool, showing fibre diameters.

[0027] FIG. 2B illustrates a SEM analysis of milled waste stone wool, showing fibre length.

[0028] FIG. 3 illustrates a SEM analysis of milled waste glass wool in fibre form.

[0029] FIG. 4 illustrates a SEM analysis of a second sample of milled waste stone wool in fibre form.

[0030] DETAILED DESCRIPTION

[0031] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and fully convey the scope of the invention to the skilled person.

[0032] The present invention provides a high-strength gypsum plasterboard containing at least one type of milled waste mineral wool, wherein the plasterboard exhibits improved flexural strength compared to boards without milled waste mineral wool.

[0033] The term "Milled waste" indicates that the mineral wool being used is derived from recycled or waste sources, which have been processed (milled) to create a usable form. This approach supports sustainability by reusing materials that might otherwise be discarded as waste. The milled waste mineral wool can be incorporated into gypsum plasterboard to enhance its properties, such as improving flexural strength.

[0034] Flexural strength refers to the ability of a material to resist deformation under bending. In the context of plasterboard (also known as dry wall or gypsum board), flexural strength specifically refers to its resistance to bending or breaking when subjected to a load applied perpendicular to its surface. The flexural strength of plasterboard has been tested according to standards IS2095 and EN520.

[0035] When gypsum plasterboard is installed as a wall or ceiling panel, it may experience various forces such as wind pressure, impacts, or loads from hanging objects. Flexural strength is crucial because it determines how much load or stress the plasterboard can withstand before it bends excessively or cracks.

[0036] Higher flexural strength means the plasterboard can bear greater loads without deforming or breaking. This property is essential for ensuring the durability and structural integrity of walls and ceilings in buildings. Plasterboards with improved flexural strength are less likely to sag, crack, or fail under typical structural loads encountered during their use.

[0037] The high-strength gypsum plasterboard of the present disclosure comprising gypsum stucco and milled waste mineral wool in amounts ranging from about 0.1% to about 10% by weight relative to the stucco.

[0038] In an embodiment of the present disclosure, the milled waste mineral wool used in this composition has fibre lengths ranging from 0.1 to 2000 pm. This specific inclusion enhances the plasterboard's flexural strength, making it more resilient to bending forces.

[0039] The milled waste mineral wool utilized in the plasterboard has not undergone any chemical or physical treatment prior to milling. This ensures that the properties of the mineral wool are preserved, contributing effectively to the performance of the plasterboard.

[0040] The presence of milled waste mineral wool significantly enhances the flexural strength of the plasterboard compared to boards without this additive. This improvement is critical for applications where the plasterboard is subjected to bending stresses, thereby increasing its durability and structural integrity. The milled waste mineral wool can be sourced from different materials such as stone wool and / or glass wool, further broadening the applicability and performance characteristics of the plasterboard based on specific project requirements.

[0041] In a preferred embodiment of the present disclosure, the milled waste mineral wool is milled waste stone wool.

[0042] In a preferred embodiment of the present disclosure, the milled waste mineral wool is milled waste glass wool.

[0043] In an embodiment of the present disclosure, the milled waste mineral wool is a mixture of milled waste stone wool and milled waste glass wool.

[0044] The flexural strength improvements are notable in both machine direction (MD) and cross direction (CD) of the plasterboard. In the MD, the flexural strength can increase by a range of 5 to 150 N, while in the CD, the increase ranges from 5 to 100 N. These enhancements ensure uniform strength properties across different orientations of the plasterboard.

[0045] In accordance with the present invention, the core hardness of the plasterboard is increased by a range of 1 to 15 N, which further contributes to its ability to withstand impact and loadbearing capabilities.

[0046] In an embodiment of the present disclosure, the flexural strength of the board is increased by up to 25 % in machine direction (MD).

[0047] In an embodiment of the present disclosure, the flexural strength of the board is increased by up to 20 % in machine direction (MD).

[0048] In an embodiment of the present disclosure, the core hardness in the board is increased by up to 15 %.

[0049] The milled waste mineral wool may optionally include binders, such as sugar-based or nonsugar binders, depending on specific manufacturing requirements or desired properties of the mineral wool. In a specific embodiment of the present disclosure, the high strength plaster board comprising at least 50% by number of the milled waste mineral wool fibres have lengths ranging from 10 to 100 pm, optimizing the reinforcement and mechanical properties of the plasterboard.

[0050] The invention further provides a method for manufacturing a high-strength gypsum plasterboard, involves several steps to incorporate milled waste mineral wool and optimize mechanical properties. Initially, milled waste mineral wool is introduced into a gypsum slurry, ensuring uniform distribution to enhance board strength. The slurry's consistency and setting parameters are meticulously maintained to achieve the desired mechanical properties, including flexural strength and core hardness. Subsequently, the boards are carefully dried and subjected to testing to confirm improvements in these mechanical characteristics.

[0051] In one embodiment of the present disclosure, the method involves milling the waste mineral wool to achieve the desired fibre length before incorporating it into the board.

[0052] The method includes adjusting the formulation of other additives such as retarders, accelerators, and water-reducing agents. These adjustments are crucial for optimizing the performance of the plasterboard while integrating milled waste mineral wool. The varying fibre sizes within the milled waste mineral wool further contribute to enhancing the overall strength of the boards.

[0053] Moreover, the method involves incorporating milled waste mineral wool into the plasterboard formulation. This substitution replaces a portion of conventional additives while ensuring that the behaviour of the gypsum slurry remains unaffected. This approach aims to enhance the sustainability of plasterboard manufacturing by utilizing waste materials.

[0054] EXAMPLES

[0055] Example 1

[0056] Milled waste mineral wool preparation

[0057] In the experiments discussed here, the stone wool used was derived from residual material resulting from the cutting of stone wool products. These products are typically made from fibres produced by rapidly spinning molten rock on centrifugal wheels. The residue from cutting, referred to here as waste, can originate during the manufacturing of products or during subsequent steps to shape and size them. Nevertheless, there are other potential sources of stone wool, particularly waste stone wool, that could also be considered.

[0058] The waste stone wool, which was sourced from India, was then processed through mechanical milling equipment such as shredder and rod mill. The purpose of milling was to reduce the size of the waste material into smaller particles or fibres. During the milling process, the waste stone wool underwent size reduction through a shredder and rod mill to achieve the desired particle size distribution. This step was crucial as it ensures uniformity in particle size. The physical properties of milled waste stone wool material (Inventive Example 1) are detailed in Table 1. SEM analysis of the sample (Inventive Example 1), as shown in Figs. 2A (fibre diameter) and 2B (fire length), indicates that the material retains its fibrous form even after milling.

[0059] Table 1 : Physical properties of milled stone wool waste

[0060] The parameters were assessed using established standard methods. To measure pH, a solution with a 10% concentration was prepared and tested. For determining moisture content, the wool was subjected to a drying process in an oven until all moisture was removed. The dried wool was then weighed to calculate the moisture content based on the weight difference. To evaluate density, the process involved measuring the weight of the fabric per unit area in kilograms per square meter (kg / m2) and then dividing this weight by the fabric's thickness in meters (m). This calculation provided the density of the fabric.

[0061] Sieve analysis tests for milled stone wool were done according to ASTM E-l 1 to understand the particle size distribution. The particle size distribution for the sample (Inventive Example 1) is given in table 2.

[0062] Table 2: particle size distribution of milled stone wool waste as per sieve analysis

[0063] From the sieve tests and SEM analysis, it is understood that the waste stone wool material remains in fibrous form even after milling, with fibre lengths ranging from less than 4 gm to 2000 gm.

[0064] The process of preparing milled waste stone wool involves converting discarded stone wool products into a valuable resource, thereby promoting sustainability by reducing waste and utilizing recycled materials in gypsum plaster boards.

[0065] Preparation of high strength plasterboard

[0066] In the industrial line production process, milled waste stone wool was incorporated into the plasterboard recipe, replacing a portion of the traditional additives, with no observed impact on slurry behaviour. The modified slurry, containing stone wool, was subsequently poured into paper liners, underwent setting, and then underwent cutting and drying processes.

[0067] Mechanics of boards

[0068] The mechanical properties of boards with and without milled waste stone wool materials were compared using test methods according to IS 2095 standards. Quality tests demonstrated improvements in the mechanical properties of boards with milled waste stone wool material (Table 3).

[0069] Table 3: Mechanical Properties of Boards without stone wool vs. with milled stone wool

[0070] Surprisingly, Table 3 clearly shows that the board with milled waste stone wool exhibited improved strength compared to the board without milled waste stone wool. Specifically, the flexural strength of the board containing milled waste stone wool increased by up to 49 N in the longitudinal or machine direction (MD). Similarly, the flexural strength increased by 34 N in the transverse or cross direction (CD). Additionally, the core hardness of the board in the inventive examples also increased by up to 8 N. Therefore, it is very clear from Table 3 that the strength increased by up to 9% in MD and up to 12% in CD, while core hardness of the board is increased by up to 8%.

[0071] Thus, the addition of milled stone wool waste enhances the mechanical properties of plasterboard without compromising other performance metrics such as bonding, slump, and water demand. The manufacturing process remains efficient and effective.

[0072] Example 2

[0073] Milled waste glass wool preparation

[0074] The waste glass wool, which was sourced from Brazil, was milled using Culatti Hammer mill to achieve the desired particle size. The sample was dispersed in water and ran through the Malvern Mastersizer 3000 laser granulometer to determine particle size distribution. Fig. 1 illustrates the particle size distribution of the milled waste glass wool material (Inventive Example 2) as determined by laser diffraction, with particle sizes ranging from 0.9 to 1000 pm. Fig. 3 depicts SEM analysis demonstrating that even after crushing, the material retains its fibrous form.

[0075] Preparation of high strength plasterboard

[0076] Samples were prepared following the British Gypsum method - "Producing Small Scale Lab Board Utilizing a Vertical Mould Method."

[0077] Method Overview: Dry ingredients were initially mixed with wet ingredients in a Kenwood dry blender on a low setting for 10 seconds, followed by an additional 20 seconds on setting. The resulting slurry was poured into a 300x300x12.5mm board mould. After 25 minutes, the board was carefully removed from the mould, dried with a towel to remove excess moisture, and any surplus paper was trimmed using a knife. The edges of the board were secured with masking tape and placed in a 180°C oven for 55 minutes. Subsequently, the board was transferred to a 40°C oven and left overnight, with a maximum duration of 2 days, before removal. Finally, samples measuring 300x50 mm were cut from the board using a circular saw.

[0078] Mechanics of boards

[0079] The mechanical properties of boards with and without milled waste glass wool materials were compared using test methods in accordance with EN 520 Standard Method- “Flexural Strength of Lab Scale Boards (50x300mm)”

[0080] Quality tests demonstrated improvements in the mechanical properties of boards with milled waste glass wool material (Table 4).

[0081] Table 4: Mechanical properties of boards without glass wool vs. with milled glass wool

[0082] It is evident from the above table 4 that the board with milled waste glass wool exhibited improved strength compared to the board without milled waste glass wool, regardless of whether sugar-based or non-sugar binders were used in glass wool manufacturing. Specifically, the flexural strength of the board containing milled waste stone wool increased by up to 89 N in the longitudinal or machine direction (MD). Similarly, the flexural strength increased by up to 47 N in the transverse or cross direction (CD). Therefore, table 4 clearly shows that the board's strength increased by up to 19% in MD, and up 13% in CD.

[0083] Example 3

[0084] Milled waste stone wool preparation

[0085] The waste stone wool, which was sourced from Spain, was milled using Culatti Hammer mill with a 200-micron sieve attachment to obtain the desired particle size. Fig. 1 illustrates the particle size distribution of the milled waste stone wool material (Inventive Example 3), with particle sizes ranging from 0.1 to more than 1000 pm. Fig. 4 depicts SEM analysis demonstrating that even after milling, the material retains its fibrous form.

[0086] Mechanics of boards

[0087] The mechanical properties of boards with and without milled waste stone wool materials were compared using test methods in accordance with EN 520 Standard Method - "Flexural Strength of Lab Scale Boards (50x300mm)"

[0088] Quality tests demonstrate improvements in the mechanical properties of boards with milled waste stone wool material (Table 5).

[0089] Table 5: Mechanical properties of boards without stone wool vs. with milled stone wool

[0090] From Table 5, it is clear that the board with milled waste stone wool exhibited improved strength compared to the board without it. Specifically, the flexural strength of the board containing milled waste stone wool increased by up to 31 N in the transverse or cross direction (CD). Therefore, table 5 clearly indicates that the board's strength increased by up to 9% in CD.

[0091] The incorporation of waste stone wool in plasterboard production addresses environmental concerns by reducing landfill waste. It simultaneously improves board strength and hardness, while seamlessly integrating into current manufacturing processes.

Claims

We Claim,1. A high-strength gypsum plasterboard comprising at least one milled waste mineral wool in an amount of from about 0.1% to about 10% by weight relative to stucco, characterized in that the milled waste mineral wool has fibre length ranging from 0.1 to 2000 pm, wherein said plasterboard exhibits improved flexural strength.

2. The high-strength gypsum plasterboard according to claim 1, wherein the milled waste mineral wool has not undergone any chemical or physical treatment prior to milling.

3. The high-strength gypsum plasterboard according to claim 1 , wherein said plasterboard comprising at least one milled waste mineral wool, has improved flexural strength compared to boards without milled waste mineral wool.

4. The high-strength gypsum plasterboard according to any one of the preceding claims, wherein the milled waste mineral wool is milled waste stone wool.

5. The high-strength gypsum plasterboard according to any one of the preceding claims, wherein the milled waste mineral wool is milled waste glass wool.

6. The high strength gypsum plasterboard according to any one of the preceding claims, wherein the flexural strength of the said plasterboard in the machine direction (IS MD) is increased by up to 25%.

7. The high strength gypsum plasterboard according to any one of the preceding claims, wherein the flexural strength of the said plasterboard in the cross direction (IS CD) is increased by up to 20%.

8. The high strength gypsum plasterboard according to claim 1, wherein the milled waste mineral wool optionally comprises sugar-based binder.

9. The high strength gypsum plasterboard according to claim 1, wherein the milled waste mineral wool optionally comprises non-sugar binder.

10. The high strength gypsum plasterboard according to any one of the preceding claims, wherein at least 50% by number of milled waste mineral wool has fibre length ranging from of 10 to 100 pm.

11. A method for manufacturing a high strength gypsum plasterboard according to claim 1, comprising: a. Incorporating milled waste mineral wool into a gypsum slurry; b. Maintaining slurry consistency and setting parameters to achieve desired mechanical properties; c. Drying the resulting boards; and d. Optionally testing the resulting boards for improved flexural strength and core hardness.

12. The method according to claim 11, wherein the method involves milling the waste mineral wool to achieve the desired fibre length before incorporating it into the board.

13. The method according to claim 12, wherein the milled waste mineral wool material comprises fibres of varying sizes, contributing to enhanced board strength.

14. The method according to claim 11, further comprising adjusting the formulation of other additives such as retarders, accelerators, and water reducing agents to optimize performance with waste mineral wool inclusion.

15. The method according to claim 11, wherein the milled waste mineral wool is incorporated into the plasterboard recipe, replacing a portion of the traditional additives without impacting slurry behaviour.

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