Green calcium silicate hydrate board and method thereof

Abstract

A composition and a manufacturing method of a calcium silicate hydrate board, comprising the steps of preparing a slurry of a mixture of a silica-based material, a lime material, spherical xonotlite particles, synthetic wollastonite, and reinforcing fibers with the remaining water; forming the slurry into a board by a sheet forming method; steam-curing the board; and drying the board.

Description

Technical Field

[0001] Technical Field The present invention relates to a calcium silicate hydrate composition for boards for architectural use, fire protection and heat insulation, a method for manufacturing the calcium silicate hydrate material, and the use of a calcium silicate hydrate board containing synthetic wollastonite.

Background Art

[0002] Background of the Invention The calcium silicate hydrate board, commonly known as the calcium silicate board, disclosed by GB2,085,044, contains a calcium silicate binder, spherical zonnolite particles, natural acicular wollastonite and reinforcing fibers, and has very good mechanical properties and durability during its service life, while maintaining good thermal stability at high temperatures (for example, at 1000 °C).

[0003] The above board has conventionally been manufactured by mixing a calcareous raw material and a siliceous raw material, pre-prepared spherical zonnolite particles, natural acicular or needle-like wollastonite, reinforcing fibers and the balance of water to form a slurry. Molding is carried out by a conventional process, such as a filter press process.

[0004] Regarding filter press molding, it usually includes a perforated molding surface into which the slurry is poured. A perforated mechanical piston compresses and dehydrates the slurry to the point where it stands on its own, in addition to the shape of the mold. The filter press molding method is carried out in the absence of any heating and under sufficient pressure to drain water from the slurry in the filter press and form solid articles such as pipe coatings and flat boards. The filter press molding method is described in US4,477,397.

[0005] The shaped body is further cured under hydrothermal conditions by reacting a silica-based material and a lime material and, optionally, reacting these materials with the surface of the spherical particles of xonotlite. Thereby, a matrix containing tobermorite and / or xonotlite as a binder is produced. The steam curing step is carried out in an autoclave under a steam pressure of 6 to 18 kg / cm 2 for a sufficient time until the silica-based material and the lime material are converted to tobermorite and / or xonotlite.

[0006] After hydrothermal curing, the calcium silicate hydrate board is removed from the autoclave and dried if necessary. The drying temperature must be below the decomposition point of the organic fibers in order to obtain the required properties.

[0007] Once dried, the final board may be cut and sanded to form the required dimensions. This produces some manufacturing waste, namely, cutting waste and sanding dust. Some of them can be recycled directly in the manufacturing process. However, the amount is limited in order to maintain the product specifications of the material performance.

[0008] Natural acicular or needle-like wollastonite, such as Nyad-G sold by Imerys, is an important raw material. It certainly helps to improve strength, maintain high-temperature stability, prevent cracking, and improve machinability.

[0009] However, due to the pandemic crisis, the supply of natural acicular wollastonite has become a problem, exploration has been interrupted, and shipping costs have skyrocketed due to lockdowns. Without this needle-like wollastonite, the production of these products would have to be reduced or stopped.

Summary of the Invention

Problems to be Solved by the Invention

[0010] Summary of the Invention Therefore, the object of the present invention is to explore alternatives to natural acicular wollastonite and ensure production.

[0011] Another object is to recover wollastonite, a strategic raw material for calcium silicate compositions, from calcium silicate hydrate waste, preferably the company's own calcium silicate waste.

[0012] Another object is to reuse all manufacturing waste of calcium silicate hydrate, abolish landfilling, improve the industrial applicability of the technology, and assist in the circular economy.

Means for Solving the Problems

[0013] The present invention is defined in the appended independent claims. Preferred embodiments are defined in the dependent claims. Specifically, the present invention relates to i. A calcareous material and a siliceous material having a CaO / SiO2 molar ratio of 0.6 to 1.2, ii. Spherical xonotlite particles obtained by hydrothermal synthesis, iii. Wollastonite, iv. Reinforcing fibers such as cellulose fibers and / or organic fibers and / or inorganic fibers, v. The balance of water A composition for producing a calcium silicate hydrate board, comprising The above wollastonite is synthesized and is produced by calcining calcium silicate hydrate waste, and relates to the composition.

[0014] In a preferred embodiment, the synthetic wollastonite is obtained from the calcined waste of a calcium silicate hydrate board produced using a composition comprising components i to v of the board of the above composition. The above object is to surely increase the use of the waste of the calcium silicate hydrate board and reuse it in the company's own production.

[0015] The above synthetic wollastonite is obtained by calcining calcium silicate hydrate manufacturing waste at a temperature below 1000°C. The manufacturing waste contains spherical particles of xonotlite having an interior where the xonotlite crystals are loosely intertwined and somewhat uniformly distributed, and an outer layer where the crystals are more tightly intertwined than in the interior.

[0016] In a preferred embodiment, the composition further contains recycled calcium silicate hydrate waste. This recycled calcium silicate hydrate waste has not been calcined.

[0017] More specifically, the composition i. 20 to 50 parts by weight of a mixture of a calcareous material and a siliceous material having a CaO / SiO2 molar ratio of 0.6 to 1.2, ii. 10 to 40 parts by weight of spherical xonotlite particles obtained by hydrothermal synthesis, iii. 5 to 50 parts by weight of synthetic wollastonite obtained by calcining calcium silicate hydrate waste, iv. 2 to 10 parts by weight of reinforcing fibers such as cellulose fibers and / or organic fibers and / or inorganic fibers, v. The balance of the manufacturing waste of calcium silicate hydrate, vi. The balance of water is included.

[0018] In a preferred embodiment, the above synthetic wollastonite has a particle size of about 2 mm or less. The calcium silicate hydrate waste used to produce the above synthetic wollastonite may preferably contain less than 50% by weight, more preferably less than 20% by weight, and even more preferably less than 5% by weight of tobermorite, based on the total weight of the calcium silicate hydrate waste.

[0019] The present invention is a method for manufacturing a calcium silicate hydrate board, comprising: i. A step of preparing synthetic wollastonite obtained by calcining calcium silicate hydrate waste at a temperature below 1000°C, ii. Preparing a slurry comprising lime and siliceous material produced by stirring to have a CaO / SiO₂ molar ratio of 0.6 to 1.2, spherical xonotlite particles obtained by hydrothermal synthesis, synthetic wollastonite, reinforcing fibers, and water; iii. Shaping the slurry; iv. Curing the shaped body under hydrothermal conditions of 160 to 210 °C and a pressure of 6 to 18 bar to form tobermorite and / or xonotlite binder; v. Drying the cured body and then removing water also relates to a method comprising.

[0020] The drying step removes free water but does not remove water of crystallization. The calcium silicate hydrate waste contains less than 50% of spherical particles of xonotlite having an interior where the xonotlite crystals are loosely intertwined and somewhat uniformly distributed, and an outer layer where the crystals are more tightly intertwined than the interior.

[0021] The calcium silicate hydrate waste may contain tobermorite. The shaping step may be performed by a Hatcheck process, a Magnani process, and a filter press process.

[0022] The spherical xonotlite particles are produced by hydrothermal synthesis in a stirred medium using an aqueous suspension of lime and an aqueous suspension of silica as described in WO2020152335, and the lime suspension is obtained by hydration in the presence of 0.2 to 2% by weight of sulfate based on the weight of lime.

[0023] The synthetic wollastonite can be produced batchwise or by flash calcination without calcination or at less than 1000 °C, preferably approximately 850 °C.

[0024] The calcium silicate hydrate board can be further heat-treated at a high temperature of less than 1000 °C.

[0025] The present invention also relates to the use of calcium silicate hydrate boards obtained by the above method for construction purposes, fire protection and high-temperature heat insulation.

[0026] The calcium silicate hydrate board has a dry density of approximately 250 to 1000 kg / m 3 , more preferably 400 to 900 kg / m 3 . The dry density is measured in accordance with standard EN12467.

Brief Description of the Drawings

[0027]

Figure 1

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Modes for Carrying Out the Invention

[0028] Detailed Description of the Invention The present invention relates to · A calcareous material and a siliceous material having a molar ratio of CaO / SiO2 of 0.6 to 1.2 · Spherical zonalite particles obtained by hydrothermal synthesis · Synthetic wollastonite produced by calcining calcium silicate hydrate waste, · Reinforcing fibers which are organic fibers such as cellulose and / or inorganic fibers, · The balance amount of water and relates to a composition for producing a calcium silicate hydrate material.

[0029] A method for converting tobermorite and zonnolite to wollastonite is known as described in US 3,967,974. However, the synthetic wollastonite of the present invention is different. The synthetic wollastonite is not composed of individual crystals. Rather, due to the form of the initial spherical zonnolite particles, it is acicular crystals aggregated in a spherical shape. It also includes a fractured fraction due to the sanding process. Surprisingly, it has been found that the synthetic wollastonite of the present invention can be used to replace the natural needle-like wollastonite in the above composition without any adverse effect on the mechanical strength and thermal stability of the final product at high temperatures. A good affinity between the spherical zonnolite and the synthetic wollastonite aggregates is considered to contribute to excellent performance.

[0030] According to the present invention, the synthetic wollastonite is produced by calcination at a temperature of less than 1000 °C, preferably approximately 850 °C, when tobermorite and zonnolite are converted to beta wollastonite, as confirmed by X-ray diffraction analysis. Temperatures above 1000 °C can also be used, but there is no advantage. Conventional calcination methods can be used, but flash calcination is preferred.

[0031] According to the present invention, the synthetic wollastonite is obtained by preferably calcining the waste of the company's calcium silicate hydrate product at a temperature of less than 1000 °C. The waste contains spherical zonnolite particles having an interior where the zonnolite crystals are loosely intertwined and somewhat uniformly distributed, and an outer layer where the crystals are more tightly intertwined than the interior.

[0032] The above composition may include a recycled calcium silicate hydrate material. The recycled calcium silicate hydrate material is not calcined. However, the amount of the recycled calcium silicate hydrate should not be higher than 30% by weight of the total dry weight of the above composition so as not to impair the thermal shrinkage of the board.

[0033] The preferred particle size of the synthetic wollastonite of the present invention is about 2 mm or less. A representative composition of the present invention is 20 to 50 parts by weight of a mixture of a calcareous material and a siliceous material having a CaO / SiO2 molar ratio of 0.6 to 1.2, 10 to 40 parts by weight of spherical xonotlite particles obtained by hydrothermal synthesis, 5 to 50 parts by weight of synthetic wollastonite obtained by calcining calcium silicate hydrate waste, 2 to 10 parts by weight of reinforcing organic fibers and / or inorganic fibers such as cellulose, the balance being calcium silicate hydrate production waste, and the balance being water including.

[0034] The percentage of synthetic wollastonite used in the present invention is between 5 and 50%, preferably between 10 and 35% by weight, based on the total dry weight of the above composition. In this amount, all calcium silicate hydrate production waste can be reused either as synthetic wollastonite or as recycled waste used directly in production. This reduces manufacturing costs, eliminates landfilling, and contributes to a circular economy.

[0035] The amount of the remaining water ranges from 5 to 25 times the total dry weight of the above composition. According to the present invention, next to synthetic wollastonite, the spherical xonotlite particles obtained by hydrothermal synthesis play an important role. These particles surrounded by a binder surely represent the main volume when the board is once made.

[0036] These aggregated spherical particles shown in FIG. 1 affect the form of the synthetic wollastonite aggregate after calcination.

[0037] To produce spherical zonotlite particles, as described in WO2020152335 or WO99 / 46215, an aqueous suspension of lime and an aqueous suspension of silica react in a stirred medium under hydrothermal conditions, and the lime suspension is obtained by hydration in the presence of 0.2 to 2 wt% sulfate based on the weight of lime. The resulting spherical zonotlite particles have an interior where the crystals are loosely intertwined and somewhat uniformly distributed, and an outer layer where the crystals are more tightly intertwined than in the interior. The crystal aggregates have an average diameter between 20 and 150 microns, preferably between 40 and 80 microns, and the outer layer advantageously has a thickness between 4 and 10 microns, preferably between 4 and 6 microns.

[0038] The present invention relates to a method for manufacturing a calcium silicate hydrate board, comprising: - preparing synthetic wollastonite obtained by calcining calcium silicate hydrate waste at a temperature below 1000 °C; - preparing a slurry comprising lime and a silica material prepared by stirring to have a CaO / SiO2 molar ratio of 0.6 to 1.2, spherical zonotlite particles obtained by hydrothermal synthesis, synthetic wollastonite, reinforcing fibers, and water; - forming the slurry; - curing the formed body under hydrothermal conditions of 160 to 210 °C and a pressure of 6 to 18 bar to form tobermorite and / or zonotlite binder; - drying the cured body and then removing water. The present invention also relates to a method comprising the above steps.

[0039] The calcium silicate waste contains spherical zonotlite particles having an interior where the zonotlite crystals are loosely intertwined and somewhat uniformly distributed, and an outer layer where the crystals are more tightly intertwined than in the interior.

[0040] The calcium silicate hydrate waste may contain tobermorite. The above slurry is prepared from 20 to 50 parts by weight of a mixture of a calcareous material and a siliceous material having a CaO / SiO2 molar ratio of 0.6 to 1.2, 10 to 40 parts by weight of spherical xonotlite particles obtained by hydrothermal synthesis, 5 to 50 parts by weight of synthetic wollastonite obtained by calcining calcium silicate hydrate waste, and 2 to 10 parts by weight of reinforcing organic fibers and / or inorganic fibers such as cellulose.

[0041] Specifically, the above slurry may contain 5 to 35 parts by weight or 5 to 25 parts by weight or 5 to 15 parts by weight of synthetic wollastonite obtained by calcining calcium silicate hydrate waste.

[0042] The above slurry may further contain up to 30% by weight of the total dry weight of recycled waste, particularly calcium silicate hydrate waste.

[0043] The forming step may be carried out by a Hatcheck process, a Magnani process, or a filter press process.

[0044] The calcium silicate hydrate board according to the present invention can be further heat-treated at a high temperature, for example, below 1000 °C, if necessary.

[0045] The calcium silicate hydrate board according to the present invention has a dry density between approximately 250 and 1000 kg / m 3 and more preferably between 400 and 900 kg / m 3 .

Examples

[0046] Examples The calcium silicate hydrate board is manufactured according to the following procedure. All the dry components shown in Table 1 and the remaining amount of water are uniformly mixed. The formation is by a filter press. The formed body is autoclaved at 160 to 200 °C and 7 to 12 Bar for 10 hours and then oven-dried at 105 °C.

[0047] Figure 1 shows a scanning electron microscope (SEM) image of the spherical zonalite particles used in the examples. Figure 2 shows an SEM image of natural wollastonite. Figure 3 shows the synthetic wollastonite of the present invention.

[0048] Subsequently, the final product was tested according to the EN-standard. The flexural strength was measured according to EN12467:2012. The thermal shrinkage and loss on ignition (LOI%) were measured at 1000 °C according to EN1094-6:2000.

[0049] The results are shown in Table 2. They clearly demonstrate that the synthetic wollastonite of the present invention can replace natural acicular wollastonite without adversely affecting the mechanical strength and high-temperature stability.

[0050] [Table 1]

[0051] [Table 2]

[0052] Even if they had not been improved, in addition to maintaining the mechanical properties, the acoustic properties were also maintained.

Claims

1. i) CaO / SiO from 0.6 to 1.2 ２ a calcareous material and a siliceous material having a molar ratio of ii) spherical xonotlite particles obtained by hydrothermal synthesis; iii) wollastonite; iv) reinforcing fibers such as cellulose fibers and / or organic fibers and / or inorganic fibers; v) the balance water 1. A composition for producing a calcium silicate hydrate board, comprising:

1. A composition, characterized in that the wollastonite is synthetic and obtained by calcination of calcium silicate hydrate waste.

2. 2. The composition of claim 1, wherein the synthetic wollastonite is obtained by calcining waste calcium silicate hydrate boards made using a composition comprising components i to v of claim 1.

3. The synthetic wollastonite is obtained by calcining calcium silicate waste at a temperature below 1000°C; 3. The composition of claim 1 or 2, wherein the calcium silicate hydrate waste comprises spherical particles of xonotlite having an interior in which the xonotlite crystals are loosely entangled and somewhat uniformly distributed, and an outer layer in which the crystals are more tightly entangled than the interior.

4. 10. The composition of claim 1, further comprising recycled calcium silicate hydrate waste, wherein said recycled calcium silicate hydrate waste is uncalcined.

5. i. CaO / SiO from 0.6 to 1.2 ２ 20 to 50 parts by weight of a mixture of calcareous and siliceous materials having a molar ratio of ii. 10 to 40 parts by weight of spherical xonotlite particles obtained by hydrothermal synthesis; iii. 5 to 50 parts by weight of synthetic wollastonite obtained by calcination of calcium silicate hydrate waste; iv. 2 to 10 parts by weight of reinforcing fibers, such as cellulose fibers and / or organic fibers and / or inorganic fibers; v. remaining calcium silicate manufacturing waste; vi. Remaining water The composition of claim 1 comprising:

6. 6. The composition of claim 1, 2, or 5, wherein the synthetic wollastonite has a particle size of about 2 mm or less.

7. 2. The composition of claim 1, wherein the calcium silicate hydrate waste material used to make the synthetic wollastonite may contain tobermorite.

8. 1. A method for producing a calcium silicate hydrate board, comprising: vii. Preparing a synthetic wollastonite obtained by calcination of calcium silicate hydrate waste at a temperature below 1000°C; viii. CaO / SiO from 0.6 to 1.2 ２ preparing a slurry containing lime and a siliceous material, spherical xonotlite particles obtained by hydrothermal synthesis, synthetic wollastonite, reinforcing fibers, and water, the slurry being prepared by stirring the lime and siliceous material to have a molar ratio of: ix. forming the slurry; x. curing the compact under hydrothermal conditions at 160 to 210°C and a pressure of 6 to 18 bar to form a tobermorite and / or xonotlite binder; xi. drying the cured body to remove water therefrom; A method comprising:

9. 9. The method of claim 8, wherein the forming step can be done by the Hatcheck process, the Magnani process, and the filter press process.

10. 9. The method according to claim 8, wherein the spherical xonotlite particles are prepared by hydrothermal synthesis in a stirred medium using an aqueous suspension of lime and an aqueous suspension of silica, the lime suspension being obtained by hydration in the presence of 0.2 to 2% by weight of sulfate relative to the weight of lime.

11. 9. The method of claim 8, wherein the calcium silicate hydrate waste comprises spherical particles of xonotlite having an interior in which xonotlite crystals are loosely entangled and somewhat uniformly distributed, and an outer layer in which the crystals are more tightly entangled than the interior.

12. 11. The method of claim 8 or 10, wherein the synthetic wollastonite is prepared by calcination and / or flash calcination.

13. A calcium silicate hydrate board obtainable by the method of claim 10, which can be further heat treated at an elevated temperature below 1000°C.

14. Approximately 250 to 1000 kg / m ３ , preferably 400 to 900 kg / m ３ 14. The calcium silicate hydrate board of claim 13, having a dry density between

15. 11. Use of calcium silicate hydrate board obtained by the method according to claim 8 or 10 for construction applications, fire protection and high temperature insulation.

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