Low density foamed glass and method of manufacture

Abstract

The application discloses low-density foam glass and a preparation method thereof, and belongs to the technical field of inorganic thermal insulation materials, and has the technical scheme as follows: a preparation method of low-density foam glass, which comprises the following steps: S1, grinding and pulverizing mineral wool waste; S2, mixing the mineral wool waste with a foaming agent, a foam stabilizer and a dissolving aid, and then wet grinding to obtain a mixture; and S3, drying the mixture, grinding and sieving, tabletting and sintering to obtain the low-density foam glass. The mineral wool waste is used in a high-value way for the second time, the production raw material cost of the foam glass is reduced, and the problems of foaming bulging, layering and uneven large pores are solved through adjustment of the process.

Description

Technical Field

[0001] This invention relates to the field of inorganic thermal insulation materials technology, and in particular to a low-density foam glass and its preparation method. Background Technology

[0002] Foamed glass, an inorganic thermal insulation material with numerous closed micropores, has been widely used in building insulation, pipeline insulation, and industrial insulation due to its advantages such as low thermal conductivity, non-combustibility, corrosion resistance, low water absorption, and dimensional stability. With the increasing demands for insulation and heat resistance across industries, the market demand for foamed glass continues to grow, driving research and development in related technologies to further improve its performance and reduce production costs to meet broader engineering needs. It plays a significant role in ensuring building energy efficiency, improving the stability of industrial production processes, and reducing energy consumption.

[0003] Traditionally, foam glass production primarily uses waste flat glass and bottle glass as the sole base material. The manufacturing process typically involves collecting, screening, and cleaning these glass raw materials to remove impurities and dirt. They are then processed into suitable particle sizes through crushing and grinding, mixed with additives such as foaming agents and foam stabilizers, and subjected to a series of processes including high-temperature firing to produce foam glass products. Meanwhile, the mineral wool production industry generates a large amount of waste annually, which is commonly disposed of through incineration or landfill.

[0004] However, existing foam glass production methods have significant drawbacks. Using waste flat glass and bottle glass as the sole matrix raw material results in a limited source of raw materials, making it difficult to meet ever-increasing production demands and leading to relatively high raw material costs. Furthermore, the disposal of mineral wool waste not only results in a significant waste of fiber resources but also generates dust, exhaust gases, and other pollutants through incineration or landfill, causing serious environmental pollution. Currently, there is a lack of effective high-value recycling pathways. Summary of the Invention

[0005] To address the problems in the prior art, this invention provides a low-density foamed glass and its preparation method, enabling the secondary high-value utilization of mineral wool waste, reducing the raw material cost of foamed glass production, and solving the problems of foaming bulging, delamination, and large and uneven pores through process adjustments.

[0006] The present invention provides a low-density foamed glass and its preparation method, which adopts the following technical solution: A method for preparing low-density foam glass includes the following steps: S1. Crush and grind the mineral wool waste into fine powder; S2. After mixing mineral wool waste with foaming agent, foam stabilizer and co-solvent, wet milling is performed to obtain a mixture. S3. After drying the mixture, grind, sieve, press, and sinter to obtain low-density foam glass.

[0007] Preferably, the average particle size of the mineral wool waste after crushing and grinding in step S1 is 300-350 mesh.

[0008] Preferably, by weight percentage, the mineral wool waste accounts for 87-95%, the foam stabilizer accounts for 2-4%, the foaming agent accounts for 1-3%, and the co-solvent accounts for 1-9%.

[0009] Preferably, the foaming agent is calcium carbonate; And / or the foam stabilizer is sodium phosphate; And / or the co-solvent is one of boric acid and borax.

[0010] Preferably, in step S3, the intermediate mixture between the 40-mesh sieve and the 200-mesh sieve after grinding and sieving is pressed into tablets.

[0011] Preferably, the sintering includes a preheating stage, a rapid heating stage, a foaming and heat preservation stage, and a cooling stage.

[0012] Preferably, the preheating stage temperature is 0-200℃ and the preheating time is 30min; the rapid heating stage is 200-880℃ and the heating time is 30min; the foaming and heat preservation stage is 880℃ and the heat preservation time is 30min; and the cooling stage is 880-500℃.

[0013] Preferably, the cooling rate during the cooling stage is 15-20°C / min.

[0014] The present invention further provides a low-density foam glass, obtained by the preparation method described above, wherein the density of the low-density foam glass is ≤0.7 g / cm³. 3 Porosity > 70%.

[0015] In summary, this invention uses mineral wool waste to produce foam glass, which not only reduces the production cost of foam glass, but also solves the problems of easy bulging, delamination, large pores, and high density of mineral wool waste foam through the coordinated treatment between processes and the segmented gradient sintering process. The foam glass prepared by the method of this invention has fine and uniform pores, no through defects, excellent foaming performance, and the whole process is stable and controllable, making it easy to industrialize. Detailed Implementation

[0016] The present invention will be further described in detail below with reference to embodiments. All details not specifically stated herein are based on conventional conditions or conditions recommended by the manufacturer. All reagents and instruments, unless otherwise stated below, are commercially available conventional reagent products.

[0017] To address the problem that the treatment of mineral wool waste in existing technologies not only leads to resource waste but also causes environmental pollution, this invention provides a method for preparing low-density foam glass, comprising the following steps: S1, crushing and grinding the mineral wool waste; S2, mixing the mineral wool waste with a foaming agent, a foam stabilizer, and a co-solvent, and then wet-milling to obtain a mixture; S3, drying the mixture, then grinding, sieving, pressing, and sintering to obtain low-density foam glass.

[0018] In a preferred embodiment, the average particle size of the mineral wool waste after pulverization and grinding in step S1 is 300-350 mesh. Pulverizing the mineral wool waste into fine powder with a particle size in the range of 300-350 mesh facilitates sufficient contact and uniform mixing between the mineral wool waste and the foaming agent, foam stabilizer, and co-solvent, which is fundamental to obtaining foamed glass with a uniform structure. Furthermore, the fine raw material particles help form a more uniform glass phase during sintering, promoting uniform nucleation and growth of bubbles.

[0019] In a preferred embodiment, by weight percentage, the mineral wool waste accounts for 87-95%, the foam stabilizer accounts for 2-4%, the foaming agent accounts for 1-3%, and the co-solvent accounts for 1-9%.

[0020] As an example, the proportion of mineral wool waste can be 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%; the proportion of foam stabilizer can be 2%, 3%, 4%; the proportion of foaming agent can be 1%, 2%, 3%; and the proportion of co-solvent can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%.

[0021] When mineral wool waste is in the range of 87-95%, the utilization rate of solid waste can be maximized and the production cost reduced. Foam stabilizers can prevent bubbles from merging or breaking at high temperatures. At this ratio, the pore size and distribution can be effectively controlled to form uniform closed-cell bubbles. Foaming agents are the key to forming porous structures. At this addition amount, they can provide an appropriate amount of gas, achieving low density while avoiding pore wall rupture or excessively large pore size due to excessive gas. Co-solvents have the effect of lowering the softening point and viscosity of the glass phase, forming a sufficient liquid phase at lower temperatures, which is conducive to the uniform distribution of bubbles and the densification of the product.

[0022] In a preferred embodiment, the foaming agent is calcium carbonate, the foam stabilizer is sodium phosphate, and the co-solvent is one of boric acid and borax.

[0023] In a preferred embodiment, in step S3, the intermediate mixture between the grinding and sieving processes using a 40-mesh sieve and a 200-mesh sieve is pressed into tablets.

[0024] When 40-mesh and 200-mesh sieve particles are used for tableting, the small powder particles fill the gaps formed by the accumulation of coarse particles. This gradation can significantly improve the bulk density of the green body. Moreover, the coarse particles, as a skeleton, can prevent excessive shrinkage from causing cracking and optimize the pore structure of the final product. In addition, the addition of coarse particles can improve fluidity and make the tableting more uniform.

[0025] In a preferred embodiment, sintering includes a preheating stage, a rapid heating stage, a foaming and heat preservation stage, and a cooling stage.

[0026] In a preferred embodiment, the preheating stage temperature is 0-200℃ and the preheating time is 30min; the rapid heating stage is 200-880℃ and the heating time is 30min; the foaming and heat preservation stage is 880℃ and the heat preservation time is 30min; and the cooling stage is 880-500℃.

[0027] In a preferred embodiment, the cooling rate during the cooling stage is 15-20°C / min.

[0028] During the preheating stage, slow heating removes free water and some bound water from the raw materials, preventing rapid steam escape during rapid heating that could cause cracking of the billet. During the rapid heating stage, when the temperature reaches the foaming temperature, the foaming agent concentrates and rapidly produces constant gas at its decomposition temperature. This helps bubbles to nucleate and be locked in large numbers when the melt viscosity is suitable, rather than slowly dissipating. During the foaming and heat preservation stage, the billet is fully softened and the foaming agent is completely decomposed, giving the bubbles ample time to grow and distribute evenly. Rapid cooling after foaming quickly freezes and fixes the bubble structure formed at high temperature, resulting in a closed-cell structure with uniform pore size. Conversely, slow cooling can cause bubbles to merge, grow, or collapse.

[0029] The present invention will be further described below with reference to embodiments, comparative examples and experimental data. Example 1

[0030] A method for preparing low-density foam glass includes the following steps: S1. Mineral wool waste is crushed and ground to obtain mineral wool waste with an average particle size of 300 mesh; S2. The mineral wool waste obtained in S1 is mixed with calcium carbonate, sodium phosphate, and borax, and then ball-milled for 10 hours to obtain a mixture, wherein the proportion of mineral wool waste is 95 wt%, sodium phosphate is 3 wt%, calcium carbonate is 1 wt%, and borax is 1 wt%. S3. After drying the mixture for 4 hours, further grind and sieve the intermediate mixture between a 40-mesh sieve and a 200-mesh sieve for pressing and sintering to obtain low-density foam glass. The sintering process is as follows: first, raise the temperature from 0℃ to 200℃ for 30 minutes, then raise the temperature from 200℃ to 880℃ for 30 minutes, hold at 880℃ for 30 minutes for foaming treatment, and then cool from 880℃ to 500℃ at a rate of 15℃ / min. Example 2

[0031] A method for preparing low-density foam glass includes the following steps: S1. Mineral wool waste is crushed and ground to obtain mineral wool waste with an average particle size of 300 mesh; S2. The mineral wool waste obtained in S1 is mixed with calcium carbonate, sodium phosphate, and boric acid, and then ball-milled for 10 hours to obtain a mixture, wherein the proportion of mineral wool waste is 92 wt%, sodium phosphate is 3 wt%, calcium carbonate is 1 wt%, and borax is 4 wt%. S3. After drying the mixture for 4 hours, further grind and sieve the intermediate mixture between a 40-mesh sieve and a 200-mesh sieve for pressing and sintering to obtain low-density foam glass. The sintering process is as follows: first, raise the temperature from 0℃ to 200℃ for 30 minutes, then raise the temperature from 200℃ to 880℃ for 30 minutes, hold at 880℃ for 30 minutes for foaming treatment, and then cool from 880℃ to 500℃ at a rate of 15℃ / min. Example 3

[0032] A method for preparing low-density foam glass includes the following steps: S1. Mineral wool waste is crushed and ground to obtain mineral wool waste with an average particle size of 300-350 mesh. S2. The mineral wool waste obtained in S1 is mixed with calcium carbonate, sodium phosphate, and borax, and then ball-milled for 10 hours to obtain a mixture, wherein the proportion of mineral wool waste is 91 wt%, sodium phosphate is 3 wt%, calcium carbonate is 1 wt%, and borax is 5 wt%. S3. After drying the mixture for 4 hours, further grind and sieve the intermediate mixture between a 40-mesh sieve and a 200-mesh sieve for pressing and sintering to obtain low-density foam glass. The sintering process is as follows: first, raise the temperature from 0℃ to 200℃ for 30 minutes, then raise the temperature from 200℃ to 880℃ for 30 minutes, hold at 880℃ for 30 minutes for foaming treatment, and then cool from 880℃ to 500℃ at a rate of 15℃ / min. Example 4

[0033] A method for preparing low-density foam glass includes the following steps: S1. Mineral wool waste is crushed and ground to obtain mineral wool waste with an average particle size of 300 mesh; S2. The mineral wool waste obtained in S1 is mixed with calcium carbonate, sodium phosphate, and borax, and then ball-milled for 10 hours to obtain a mixture, wherein the proportion of mineral wool waste is 89 wt%, sodium phosphate is 3 wt%, calcium carbonate is 1 wt%, and borax is 7 wt%. S3. After drying the mixture for 4 hours, further grind and sieve the intermediate mixture between a 40-mesh sieve and a 200-mesh sieve for pressing and sintering to obtain low-density foam glass. The sintering process is as follows: first, raise the temperature from 0℃ to 200℃ for 30 minutes, then raise the temperature from 200℃ to 880℃ for 30 minutes, hold at 880℃ for 30 minutes for foaming treatment, and then cool from 880℃ to 500℃ at a rate of 15℃ / min. Example 5

[0034] A method for preparing low-density foam glass includes the following steps: S1. Mineral wool waste is crushed and ground to obtain mineral wool waste with an average particle size of 300 mesh; S2. The mineral wool waste obtained in S1 is mixed with calcium carbonate, sodium phosphate, and borax, and then ball-milled for 10 hours to obtain a mixture, wherein the proportion of mineral wool waste is 87 wt%, sodium phosphate is 3 wt%, calcium carbonate is 1 wt%, and borax is 9 wt%. S3. After drying the mixture for 4 hours, further grind and sieve the intermediate mixture between a 40-mesh sieve and a 200-mesh sieve for pressing and sintering to obtain low-density foam glass. The sintering process is as follows: first, raise the temperature from 0℃ to 200℃ for 30 minutes, then raise the temperature from 200℃ to 880℃ for 30 minutes, hold at 880℃ for 30 minutes for foaming treatment, and then cool from 880℃ to 500℃ at a rate of 15℃ / min. Example 6

[0035] A method for preparing low-density foam glass includes the following steps: S1. Mineral wool waste is crushed and ground to obtain mineral wool waste with an average particle size of 300 mesh; S2. The mineral wool waste obtained in S1 is mixed with calcium carbonate, sodium phosphate, and borax, and then ball-milled for 10 hours to obtain a mixture, wherein the proportion of mineral wool waste is 90 wt%, sodium phosphate is 3 wt%, calcium carbonate is 2 wt%, and borax is 5 wt%. S3. After drying the mixture for 4 hours, further grind and sieve the intermediate mixture between a 40-mesh sieve and a 200-mesh sieve for pressing and sintering to obtain low-density foam glass. The sintering process is as follows: first, raise the temperature from 0℃ to 200℃ for 30 minutes, then raise the temperature from 200℃ to 880℃ for 30 minutes, hold at 880℃ for 30 minutes for foaming treatment, and then cool from 880℃ to 500℃ at a rate of 15℃ / min. Example 7

[0036] A method for preparing low-density foam glass includes the following steps: S1. Mineral wool waste is crushed and ground to obtain mineral wool waste with an average particle size of 300 mesh; S2. The mineral wool waste obtained in S1 is mixed with calcium carbonate, sodium phosphate, and borax, and then ball-milled for 10 hours to obtain a mixture, wherein the proportion of mineral wool waste is 89 wt%, sodium phosphate is 3 wt%, calcium carbonate is 3 wt%, and borax is 5 wt%. S3. After drying the mixture for 4 hours, further grind and sieve the intermediate mixture between a 40-mesh sieve and a 200-mesh sieve for pressing and sintering to obtain low-density foam glass. The sintering process is as follows: first, raise the temperature from 0℃ to 200℃ for 30 minutes, then raise the temperature from 200℃ to 880℃ for 30 minutes, hold at 880℃ for 30 minutes for foaming treatment, and then cool from 880℃ to 500℃ at a rate of 15℃ / min. Example 8

[0037] A method for preparing low-density foam glass includes the following steps: S1. Mineral wool waste is crushed and ground to obtain mineral wool waste with an average particle size of 300 mesh; S2. The mineral wool waste obtained in S1 is mixed with calcium carbonate, sodium phosphate, and borax, and then ball-milled for 10 hours to obtain a mixture, wherein the proportion of mineral wool waste is 92 wt%, sodium phosphate is 2 wt%, calcium carbonate is 1 wt%, and borax is 5 wt%. S3. After drying the mixture for 4 hours, further grind and sieve the intermediate mixture between a 40-mesh sieve and a 200-mesh sieve for tableting. The sintering process is as follows: first, raise the temperature from 0℃ to 200℃ for 30 minutes, then raise the temperature from 200℃ to 880℃ for 30 minutes, hold at 880℃ for 30 minutes for foaming treatment, and then cool from 880℃ to 500℃ at a rate of 15℃ / min. Example 9

[0038] A method for preparing low-density foam glass includes the following steps: S1. Mineral wool waste is crushed and ground to obtain mineral wool waste with an average particle size of 300 mesh; S2. The mineral wool waste obtained in S1 is mixed with calcium carbonate, sodium phosphate, and borax, and then ball-milled for 10 hours to obtain a mixture, wherein the proportion of mineral wool waste is 90 wt%, sodium phosphate is 4 wt%, calcium carbonate is 1 wt%, and borax is 5 wt%. S3. After drying the mixture for 4 hours, further grind and sieve the intermediate mixture between a 40-mesh sieve and a 200-mesh sieve for pressing and sintering to obtain low-density foam glass. The sintering process is as follows: first, raise the temperature from 0℃ to 200℃ for 30 minutes, then raise the temperature from 200℃ to 880℃ for 30 minutes, hold at 880℃ for 30 minutes for foaming treatment, and then cool from 880℃ to 500℃ at a rate of 15℃ / min. Example 10

[0039] A method for preparing low-density foam glass includes the following steps: S1. Mineral wool waste is crushed and ground to obtain mineral wool waste with an average particle size of 300 mesh; S2. The mineral wool waste obtained in S1 is mixed with calcium carbonate, sodium phosphate, and borax, and then ball-milled for 10 hours to obtain a mixture, wherein the proportion of mineral wool waste is 89 wt%, sodium phosphate is 4 wt%, calcium carbonate is 2 wt%, and borax is 5 wt%. S3. After drying the mixture for 4 hours, further grind and sieve the intermediate mixture between a 40-mesh sieve and a 200-mesh sieve for pressing and sintering to obtain low-density foam glass. The sintering process is as follows: first, raise the temperature from 0℃ to 200℃ for 30 minutes, then raise the temperature from 200℃ to 880℃ for 30 minutes, hold at 880℃ for 30 minutes for foaming treatment, and then cool from 880℃ to 500℃ at a rate of 15℃ / min. Example 11

[0040] A method for preparing low-density foam glass differs from Example 1 in that the cooling rate in step S3 is 20°C / min, while all other steps are the same as in Example 1. Example 12

[0041] A method for preparing low-density foam glass differs from Example 1 in that, in step S1, mineral wool waste with an average particle size of 350 mesh is obtained after crushing and grinding. Comparative Example 1

[0042] A method for preparing foamed glass differs from Example 1 in that the proportion of mineral wool waste is 91 wt%, sodium phosphate is 3 wt%, calcium carbonate is 5 wt%, and borax is 1 wt%, while all other components are the same as in Example 1. Comparative Example 2

[0043] A method for preparing foamed glass differs from Example 1 in that the proportion of mineral wool waste is 92 wt%, sodium phosphate is 6 wt%, calcium carbonate is 1 wt%, and borax is 1 wt%, while all other components are the same as in Example 1. Comparative Example 3

[0044] A method for preparing foamed glass differs from Example 1 in that the proportion of mineral wool waste is 97 wt%, sodium phosphate is 1 wt%, calcium carbonate is 1 wt%, and borax is 1 wt%, while all other components are the same as in Example 1. Comparative Example 4

[0045] A method for preparing foam glass differs from Example 1 in that the temperature is directly raised from 0°C to 880°C during sintering, and the heating time is 1 hour. All other aspects are the same as in Example 1. Comparative Example 5

[0046] A method for preparing foam glass differs from Example 1 in that, during the cooling process after sintering in step S3, natural cooling is used; otherwise, the method is the same as in Example 1. Performance testing

[0047] The density, compressive strength, porosity, and average pore diameter of the foam glass obtained in the above embodiments and comparative examples were tested, and the test results are shown in the table below.

[0048] Table 1. Results of Performance Testing of Foam Glass

[0049] Based on the test data in Table 1: The density of the foam glass obtained in this application embodiment is ≤0.7g / cm³. 3 With a porosity of over 70% and a compressive strength of over 2MPa, not only is lightweight foam glass obtained, but it also has good compressive strength.

[0050] Compared with Example 1, when the proportion of calcium carbonate exceeds 3%, due to the excessive gas produced, the bubbles expand rapidly and merge with each other, forming excessively large pores or even open-cell structures, resulting in low density of foam glass. Since the open-cell structure is a stress concentration point, the compressive strength is also significantly reduced.

[0051] Compared with Example 1, when the amount of foam stabilizer in Comparative Examples 2-3 is higher or lower than the limit of this application, the porosity of the foam glass obtained in Comparative Examples 2-3 is reduced. The reason is that when the amount of foam stabilizer is too large, the melt viscosity is too high, which will excessively inhibit the decomposition of the foaming agent, making it difficult for the bubbles to grow. Therefore, the average diameter of the pores is reduced, and the high viscosity leads to the pore walls being too thin, resulting in reduced compressive strength. When the amount of foam stabilizer is too small, the melt viscosity is insufficient, and the bubbles are easy to merge and escape, resulting in low porosity.

[0052] Compared with Example 1, when step-wise heating is not used in Comparative Example 4, the heating rate is slow in the range of 200-880°C. Gas is prone to escape before the melt reaches the most viscous temperature, resulting in insufficient foaming power. The final product has high density and low porosity. Furthermore, the existing bubbles continue to grow and merge, resulting in larger pore sizes and extremely uneven distribution. Large pores and interconnected pores become stress concentration points, significantly reducing compressive strength.

[0053] Compared with Example 1, when rapid cooling was not used, bubbles in Comparative Example 5 merged, grew, and collapsed during the slow cooling process, resulting in a significant increase in the pore diameter of the foam glass and a decrease in compressive strength.

[0054] The embodiments described herein are merely illustrative of preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing low-density foam glass, characterized in that: Includes the following steps: S1. Crush and grind the mineral wool waste into fine powder; S2. After mixing mineral wool waste with foaming agent, foam stabilizer and co-solvent, wet milling is performed to obtain a mixture. S3. After drying the mixture, grind, sieve, press, and sinter to obtain low-density foam glass.

2. The method for preparing low-density foam glass according to claim 1, characterized in that: In step S1, the average particle size of the mineral wool waste after crushing and grinding is 300-350 mesh.

3. The method for preparing low-density foam glass according to claim 1, characterized in that: By weight percentage, the mineral wool waste accounts for 87-95%, the foam stabilizer accounts for 2-4%, the foaming agent accounts for 1-3%, and the co-solvent accounts for 1-9%.

4. The method for preparing low-density foam glass according to claim 1, characterized in that: The foaming agent is calcium carbonate; And / or the foam stabilizer is sodium phosphate; And / or the co-solvent is one of boric acid and borax.

5. The method for preparing low-density foam glass according to claim 1, characterized in that: In step S3, the intermediate mixture between the 40-mesh sieve and the 200-mesh sieve after grinding and sieving is pressed into tablets.

6. The method for preparing low-density foam glass according to claim 1, characterized in that: The sintering process includes a preheating stage, a rapid heating stage, a foaming and heat preservation stage, and a cooling stage.

7. The method for preparing low-density foam glass according to claim 6, characterized in that: The preheating stage has a temperature of 0-200℃ and a preheating time of 30 minutes; the rapid heating stage has a temperature of 200-880℃ and a heating time of 30 minutes; the foaming and heat preservation stage has a temperature of 880℃ and a heat preservation time of 30 minutes; and the cooling stage has a temperature of 880-500℃.

8. The method for preparing low-density foam glass according to claim 7, characterized in that: The cooling rate during the cooling stage is 15-20℃ / min.

9. A low-density foamed glass, obtained by the preparation method according to any one of claims 1-8, characterized in that: The density of the low-density foam glass is ≤0.7g / cm³. 3 Porosity > 70%.

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