Calcium silicate hydrate with flaky embedded spherical crystals and preparation method of calcium silicate hydrate

Abstract

The invention provides hydrated calcium silicate of flaky embedded spherical crystals and a preparation method of the hydrated calcium silicate, and belongs to the technical field of calcium silicate preparation. The preparation method comprises the steps that calcium oxide, silicon dioxide and water are mixed and subjected to a pre-reaction, mixed slurry is obtained, the molar ratio of the silicon dioxide to the calcium oxide is 0.8-1.2, and the solid-to-liquid ratio is 1: 10-1: 15; putting the mixed slurry into a still kettle, carrying out steam-curing reaction at 130-200 DEG C for 10-20 hours, introducing a steam pipeline into the still kettle, cooling a product to room temperature after the reaction is finished, adding water, and stirring and dispersing; and after solid-liquid separation, sequentially drying and grinding the obtained solid to obtain the hydrated calcium silicate, wherein the hydrated calcium silicate is a spherical crystal formed by mutually embedding sheets. Calcium oxide, silicon dioxide and water are used as raw materials, the hydrated calcium silicate crystal which is good in dispersity, uniform in morphology and size, high in crystallinity and high in purity is prepared on the basis of steam curing reaction, and the morphology of the hydrated calcium silicate crystal is of a spherical structure formed by embedding cloud-shaped sheets.

Description

Technical Field

[0001] The invention belongs to the technical field of calcium silicate hydrate preparation, and particularly relates to calcium silicate hydrate formed by embedding flakes into spherical crystals and a preparation method thereof. Background Art

[0002] Calcium silicate hydrate (CSH for short) is the main product of the reaction between Portland cement and water. Its chemical formula is usually expressed as Ca5Si6O 16 (OH)·4H2O; mainly composed of SiO2-CaO-H2O, but the actual composition of hydrated calcium silicate is quite complex. Due to the poor crystallinity of CSH, the structure of CSH is relatively complex, and its composition, morphology, structure and performance vary depending on the raw materials, temperature, synthesis method, etc. Hydrated calcium silicate is not only widely used in the field of building materials, but also expanded to the fields of environmental protection and medical treatment.

[0003] At present, hydrated calcium silicate is mainly synthesized by dynamic hydrothermal method, which is as follows: calcium raw materials and silicon raw materials are mixed in a certain water-solid ratio, stirred in a hydrothermal reactor, reacted at high temperature, separated solid and liquid, dehydrated, dried, and ground to obtain hydrated calcium silicate. The dynamic hydrothermal method has low production capacity, long time consumption, high energy consumption, and high requirements for equipment; in addition, it consumes a lot of water and requires a lot of waste liquid to be treated later.

[0004] Research has found that the calcium silicate produced by the dynamic hydrothermal method is mainly composed of amorphous hydrated calcium silicate (CSH) and crystalline hydrated dicalcium silicate (C2SH), and its morphology is flocculent particles with defects such as poor crystallinity, low purity, and uneven size. Summary of the invention

[0005] In view of this, the present invention aims to provide a hydrated calcium silicate with a flake-like interlocking structure and a preparation method thereof, aiming to solve at least one technical problem in the background technology.

[0006] The present invention is achieved in that:

[0007] The first aspect of the present invention provides a method for preparing hydrated calcium silicate that is formed by flakes interlocking into spherical crystals. The raw materials for the preparation include silicon dioxide, calcium oxide and water; in terms of molar ratio, silicon dioxide: calcium oxide = 0.8-1.2:1;

[0008] The preparation method comprises the following steps:

[0009] Mixing calcium oxide, silicon dioxide and water in a preset ratio for pre-reaction to obtain a mixed slurry, wherein the solid-liquid ratio is 1:10 to 1:15;

[0010] The mixed slurry is placed in an autoclave for curing reaction at a temperature of 130°C to 200°C for 10 hours to 20 hours; during the curing reaction, a steam pipeline is introduced into the autoclave to allow the steam to directly heat and stir the mixed slurry;

[0011] After the reaction is completed, the product is cooled to room temperature, and water is added and stirred to disperse;

[0012] After solid-liquid separation, the obtained solid is dried and ground in sequence to obtain hydrated calcium silicate. The morphology of the hydrated calcium silicate is a spherical structure composed of flakes embedded in each other.

[0013] Furthermore, the steaming reaction temperature is 130° C. to 180° C., and the time is 10 h to 15 h.

[0014] Furthermore, the pre-reaction time is 30 min to 60 min.

[0015] Furthermore, the time for adding water, stirring and dispersing is 0.5h to 2h.

[0016] Furthermore, the drying temperature is 150° C. to 250° C., and the drying time is 7 h to 10 h.

[0017] Furthermore, the particle size of the ground product is 100 mesh.

[0018] The second aspect of the present invention provides a hydrated calcium silicate obtained by the above-mentioned preparation method, which is a flake-shaped calcium silicate embedded into spherical crystals.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention uses calcium oxide, silicon dioxide and water as raw materials, and obtains hydrated calcium silicate crystals with good dispersibility, uniform morphology and size, high crystallinity and high purity based on steaming reaction. The morphology is a spherical structure composed of cloud-shaped flakes embedded in each other.

[0021] 2. The present invention controls the proportion of each raw material and the temperature and time of each step to ensure the reaction between the raw materials, promote the growth and development of spherical crystals, adopts a steaming process to simulate a hydrothermal process, reduces process costs, and ensures the purity of the product hydrated calcium silicate crystals.

[0022] 3. The process of the present invention is simple, and the equipment used in the steam curing process is an autoclave, which is suitable for large-scale industrial production, has high production capacity and high production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The scanning electron microscope images of the hydrated calcium silicate prepared in Example 1 of the present invention at different magnification ratios are shown;

[0024] Figure 2This is the XRD diagram of the hydrated calcium silicate prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific implementation cases described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] A method for preparing hydrated calcium silicate in which flakes are embedded into spherical crystals, the method comprising the following steps:

[0027] S1, mixing calcium oxide, silicon dioxide and water for pre-reaction for 30 minutes to 60 minutes to obtain a mixed slurry; wherein the molar ratio of silicon dioxide to calcium oxide is 0.8:1 to 1.2:1, that is, Si / Ca=0.8 to 1.2;

[0028] S2, putting the mixed slurry into an autoclave for curing reaction at a temperature of 130°C to 200°C for 10h to 20h; preferably, the curing reaction temperature is 130°C to 180°C for 10h to 15h; the autoclave is provided with two steam pipes, one of which is used for heating outside the autoclave, and the other is connected to the inside of the autoclave, so that the steam is directed into the mixed slurry, and the slurry is stirred by the moving airflow; on the one hand, the steam directly heats the slurry, and on the other hand, the slurry is in a moving state during the reaction process;

[0029] S3, after the reaction is completed, the product is cooled to room temperature, and water is added and stirred to disperse for 0.5h to 2h; after the steaming reaction is completed, the product condenses to form a block solid state, rather than the original powder state. In this step, water is added and stirred to break up the block solid state to form a powder;

[0030] S4. After solid-liquid separation, the obtained solid is dried and ground in sequence to obtain hydrated calcium silicate, wherein the drying temperature is 150° C. to 250° C. and the time is 7 h to 10 h; after grinding, the solid is sieved through a 100-mesh sieve.

[0031] The morphology of the hydrated calcium silicate prepared by the method is a spherical structure composed of interlocking flakes, and the hydrated calcium silicate is spherical crystalline hydrated calcium silicate CSH.

[0032] Example 1

[0033] A method for preparing hydrated calcium silicate by embedding flakes into spherical crystals, the specific steps are as follows:

[0034] S1, take 4.8wt.% calcium oxide, 4.2wt.% silicon dioxide, and 91.0wt.% water and mix them in a mixer for 30 minutes;

[0035] S2: placing the mixed slurry obtained in S1 into an autoclave and performing steam curing reaction at 130° C. to 150° C. for 10 hours; during the steam curing reaction, a steam pipe is introduced into the autoclave to allow the steam to directly heat and stir the mixed slurry;

[0036] S3: After the reactants in step S2 are cooled after reaction, water is added and stirred for 1 hour;

[0037] S4: After centrifugation and filtration of the mixture obtained in step S3, the obtained solid 4 is dried in a dryer at 250° C. for 10 hours, ground and sieved through a 100-mesh sieve to obtain spherical hydrated calcium silicate.

[0038] The hydrated calcium silicate prepared in the embodiment of the present invention was processed by scanning electron microscope at different magnification ratios (respectively 1000 times, 3000 times, 5000 times, and 10000 times), and the results are as follows Figure 1 As shown, it can be seen that the hydrated calcium silicate prepared by the present invention has good dispersibility and uniform morphology, and its morphology is a spherical structure composed of cloud-shaped flakes embedded in each other; in addition, it has high crystallinity and high purity, uniform size, and an average diameter of about 20 μm.

[0039] The XRD characteristics of the hydrated silicate prepared in the embodiment of the present invention are as follows: Figure 2 As shown, it can be seen that there are few impurity peaks in the figure, the diffraction peak intensity is high and the width is narrow, which further indicates that it has a high degree of crystallinity.

[0040] Example 2

[0041] A method for preparing hydrated calcium silicate by embedding flakes into spherical crystals, the specific steps are as follows:

[0042] S1. Take 4wt.% calcium oxide, 4wt.% silicon dioxide and 92.0wt.% water and mix them in a mixer for 50 minutes;

[0043] S2: placing the mixed slurry obtained in S1 into an autoclave and performing steam curing reaction at 150° C. to 160° C. for 15 hours; during the steam curing reaction, a steam pipe is introduced into the autoclave to allow the steam to directly heat and stir the mixed slurry;

[0044] S3: After the reactants in step S2 are cooled after reaction, water is added and stirred for 1 hour;

[0045] S4: After centrifugation and filtration of the mixture obtained in step S3, the obtained solid is dried in a dryer at 200° C. for 10 hours, ground and sieved through a 100-mesh sieve to obtain spherical hydrated calcium silicate.

[0046] Example 3

[0047] A method for preparing a spherical crystal by embedding flakes, the specific steps are as follows:

[0048] S1. Take 3wt.% calcium oxide, 3.5wt.% silicon dioxide and 93.5wt.% water and mix them in a mixer for 50 minutes;

[0049] S2: placing the mixed slurry obtained in S1 into an autoclave and performing steam curing reaction at 160° C. to 170° C. for 20 hours; during the steam curing reaction, a steam pipe is introduced into the autoclave to allow the steam to directly heat and stir the mixed slurry;

[0050] S3: After the reactants in step S2 are cooled after reaction, water is added and stirred for 1 hour;

[0051] S4: After centrifugation and filtration of the mixture obtained in step S3, the obtained solid is dried in a dryer at 250° C. for 10 hours, ground and sieved through a 100-mesh sieve to obtain spherical hydrated calcium silicate.

[0052] Example 4

[0053] A method for preparing hydrated calcium silicate by embedding flakes into spherical crystals, the specific steps are as follows:

[0054] S1, take 3.2wt.% calcium oxide, 4.1wt.% silicon dioxide, and 92.7wt.% water and mix them in a mixer for 50 minutes;

[0055] S2: putting the mixed slurry obtained in S1 into an autoclave and curing it at 180°C to 190°C for 15 hours;

[0056] S3: After the reactants in step S2 are cooled after reaction, water is added and stirred for 1 hour;

[0057] S4: After centrifugation and filtration of the mixture obtained in step S3, the obtained solid is dried in a dryer at 250° C. for 7 hours, ground and sieved through a 100-mesh sieve to obtain spherical hydrated calcium silicate.

[0058] Example 5

[0059] A method for preparing hydrated calcium silicate by embedding flakes into spherical crystals, the specific steps are as follows:

[0060] S1, take 3.6wt.% calcium oxide, 3.2wt.% silicon dioxide, and 96.8wt.% water in a mixer and mix them for 50 minutes;

[0061] S2: placing the mixed slurry obtained in S1 into an autoclave and performing steam curing reaction at 190° C. to 200° C. for 10 hours; during the steam curing reaction, a steam pipe is introduced into the autoclave to allow the steam to directly heat and stir the mixed slurry;

[0062] S3: After the reactants in step S2 are cooled after reaction, water is added and stirred for 1 hour;

[0063] S4: After centrifugation and filtration of the mixture obtained in step S3, the obtained solid is dried in a dryer at 250° C. for 10 hours, ground and sieved through a 100-mesh sieve to obtain spherical hydrated calcium silicate.

[0064] Comparative Example 1

[0065] A method for preparing hydrated calcium silicate, the specific steps are as follows:

[0066] S1, take 4.8wt.% calcium oxide, 4.2wt.% silicon dioxide, and 91wt.% water and mix them in a mixer for 30 minutes;

[0067] S2: placing the mixed slurry obtained in S1 into a hydrothermal reactor and performing hydrothermal reaction at 130° C. to 150° C. for 10 hours;

[0068] S3: After the reactants in step S2 are cooled after reaction, water is added and stirred for 1 hour;

[0069] S4: After centrifugation and filtration of the mixture obtained in step S3, the obtained solid is dried in a dryer at 250° C. for 10 hours, ground and sieved through a 100-mesh sieve to obtain hydrated calcium silicate.

[0070] Comparative Example 2

[0071] A method for preparing hydrated calcium silicate, the specific steps are as follows:

[0072] S1, take 4.8wt.% calcium oxide, 4.2wt.% silicon dioxide, and 91wt.% water and mix them in a mixer for 30 minutes;

[0073] S2: placing the mixed slurry obtained in S1 into an autoclave and performing steam curing reaction at 115° C. to 125° C. for 10 hours; during the steam curing reaction, a steam pipe is introduced into the autoclave to allow the steam to directly heat and stir the mixed slurry;

[0074] S3: After the reactants in step S2 are cooled after reaction, water is added and stirred for 1 hour;

[0075] S4: After centrifugation and filtration of the mixture obtained in step S3, the obtained solid is dried in a dryer at 250° C. for 10 hours, ground and sieved through a 100-mesh sieve to obtain hydrated calcium silicate.

[0076] Comparative Example 3

[0077] A method for preparing hydrated calcium silicate, the specific steps are as follows:

[0078] S1, take 4.8wt.% calcium oxide, 4.2wt.% silicon dioxide, and 91wt.% water and mix them in a mixer for 30 minutes;

[0079] S2: placing the mixed slurry obtained in S1 into an autoclave and performing steam curing reaction at 210° C. to 220° C. for 10 hours; during the steam curing reaction, a steam pipe is introduced into the autoclave to allow the steam to directly heat and stir the mixed slurry;

[0080] S3: After the reactants in step S2 are cooled after reaction, water is added and stirred for 1 hour;

[0081] S4: After centrifugation and filtration of the mixture obtained in step S3, the obtained solid is dried in a dryer at 250° C. for 10 hours, ground and sieved through a 100-mesh sieve to obtain hydrated calcium silicate.

[0082] Comparative Example 4

[0083] A method for preparing hydrated calcium silicate by embedding flakes into spherical crystals, the specific steps are as follows:

[0084] S1. Take 2wt.% calcium oxide, 4.2wt.% silicon dioxide and 93.8wt.% water and mix them in a mixer for 30 minutes;

[0085] S2: placing the mixed slurry obtained in S1 into an autoclave and performing steam curing reaction at 130° C. to 150° C. for 10 hours; during the steam curing reaction, a steam pipe is introduced into the autoclave to allow the steam to directly heat and stir the mixed slurry;

[0086] S3: After the reactants in step S2 are cooled after reaction, water is added and stirred for 1 hour;

[0087] S4: After centrifugation and filtration of the mixture obtained in step S3, the obtained solid is dried in a dryer at 250° C. for 10 hours, ground and sieved through a 100-mesh sieve to obtain hydrated calcium silicate.

[0088] Comparative Example 5

[0089] A method for preparing hydrated calcium silicate by embedding flakes into spherical crystals, the specific steps are as follows:

[0090] S1, take 4.8wt.% calcium oxide, 2wt.% silicon dioxide, and 94wt.% water and mix them in a mixer for 30 minutes;

[0091] S2: placing the mixed slurry obtained in S1 into an autoclave and performing steam curing reaction at 130° C. to 150° C. for 10 hours; during the steam curing reaction, a steam pipe is introduced into the autoclave to allow the steam to directly heat and stir the mixed slurry;

[0092] S3: After the reactants in step S2 are cooled after reaction, water is added and stirred for 1 hour;

[0093] S4: After centrifugation and filtration of the mixture obtained in step S3, the obtained solid is dried in a dryer at 250° C. for 10 hours, ground and sieved through a 100-mesh sieve to obtain hydrated calcium silicate.

[0094] Comparative Example 6

[0095] This comparative example is a method for preparing hydrated calcium silicate that is formed by embedding flakes into spherical crystals. Compared with Example 1, the method of introducing a steam pipe into the autoclave during curing is omitted. The specific steps are as follows:

[0096] S1, take 4.8wt.% calcium oxide, 4.2wt.% silicon dioxide, and 91.0wt.% water and mix them in a mixer for 30 minutes;

[0097] S2: putting the mixed slurry obtained in S1 into an autoclave and curing it at 130°C to 150°C for 10 hours;

[0098] S3: After the reactants in step S2 are cooled after reaction, water is added and stirred for 1 hour;

[0099] S4: After centrifugation and filtration of the mixture obtained in step S3, the obtained solid 4 is dried in a dryer at 250° C. for 10 hours, ground and sieved through a 100-mesh sieve to obtain spherical hydrated calcium silicate.

[0100] The non-products obtained in each embodiment and comparative example were analyzed, and the results are shown in Table 1.

[0101] Table 1

[0102]

[0103] It can be seen from Table 1 that the products obtained in Examples 1 to 5 of the present invention are spherical hydrated calcium silicate crystals with high purity, high crystallinity and uniform morphology.

[0104] Comparative Example 1 adopts conventional dynamic hydrothermal method to prepare hydrated calcium silicate, which is mainly composed of amorphous hydrated calcium silicate, and its morphology is irregular particles agglomerated by flocculent particles, and no obvious crystal particles are observed.

[0105] Compared with Example 1, in Comparative Example 2, the steaming temperature is lowered, the size of the single crystal flakes is reduced, and the crystals are clustered into a closed sphere, and the specific surface area is reduced.

[0106] Compared with Example 1, Comparative Example 3 increases the steaming temperature. The hydrated calcium silicate prepared in this comparative example is mainly in a flake structure, and part of the spherical structure is destroyed, resulting in an uneven structure and a reduced purity of the generated hydrated calcium silicate. The reason is that the steaming reaction at a temperature exceeding 200° C. also generates other substances.

[0107] Compared with Example 1, the Si / Ca ratio of Comparative Examples 4 and 5 was changed and was not within the range of 0.8 to 1.2. The purity of the generated hydrated calcium silicate was reduced and the structure showed an irregular amorphous structure.

[0108] Compared with Example 1, Comparative Example 6 deleted the steam pipeline in the autoclave during steam curing, which resulted in incomplete reaction and uneven morphology of calcium silicate.

[0109] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing hydrated calcium silicate in which flakes are embedded into spherical crystals, characterized in that: The raw materials for preparing the hydrated calcium silicate include silicon dioxide, calcium oxide and water; in terms of molar ratio, silicon dioxide:calcium oxide=0.8-1.2:1; The preparation method comprises the following steps: Mixing calcium oxide, silicon dioxide and water in a preset ratio for pre-reaction to obtain a mixed slurry, wherein the solid-liquid ratio is 1:10 to 1:15; The mixed slurry is placed in an autoclave for curing reaction at a temperature of 130°C to 200°C for 10 hours to 20 hours; during the curing reaction, a steam pipeline is introduced into the autoclave to allow the steam to directly heat and stir the mixed slurry; After the reaction is completed, the product is cooled to room temperature, and water is added and stirred to disperse; After solid-liquid separation, the obtained solid is dried and ground in sequence to obtain hydrated calcium silicate. The morphology of the hydrated calcium silicate is a spherical structure composed of flakes embedded in each other.

2. The method for preparing a hydrated calcium silicate in which flakes are embedded into spherical crystals according to claim 1, characterized in that: The steaming reaction temperature is 130°C to 180°C, and the time is 10h to 15h.

3. The method for preparing a hydrated calcium silicate in which flakes are embedded into spherical crystals according to claim 1, characterized in that: The pre-reaction time is 30 min to 60 min.

4. The method for preparing a hydrated calcium silicate in which flakes are embedded into spherical crystals according to claim 1, characterized in that: The time for adding water, stirring and dispersing is 0.5h to 2h.

5. The method for preparing a hydrated calcium silicate in which flakes are embedded into spherical crystals according to claim 1, characterized in that: The drying temperature is 150° C. to 250° C., and the drying time is 7 h to 10 h.

6. The method for preparing a hydrated calcium silicate in which flakes are embedded into spherical crystals according to claim 1, characterized in that: The particle size of the ground product is 100 mesh.

7. A hydrated calcium silicate obtained by the preparation method according to any one of claims 1 to 6 in which flakes are embedded into spherical crystals.

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