Method for producing silicon dioxide and toothpaste

Abstract

The present application relates to a method for preparing silica, and belongs to the technical field of silica. The present application provides a specific method for preparing silica, which controls the temperature, process pH and stirring speed in the step of preparing silica solution in the middle, so as to affect the stability of the silica solution gel system. The silica solution prepared in the middle has low viscosity, and the finally prepared silica has high dispersibility. Since the silica solution prepared in the middle has low viscosity and does not adhere to the reaction tank, it is easy to discharge. The silica prepared by the above method is used to make toothpaste. Since the silica has large BET specific surface area, low oil absorption value and low viscosity, it has high dispersibility. The prepared toothpaste body is not easy to caking, and is easy to rinse. In addition, the prepared toothpaste body shows high stability in the toothpaste viscosity stability tracking test, and is suitable for long-term storage.

Description

Technical Field

[0001] This invention belongs to the field of silicon dioxide technology, specifically, it relates to a method for preparing silicon dioxide and toothpaste. Background Technology

[0002] The main ingredient in regular toothpaste is an abrasive, which accounts for approximately 20% to 50% of the toothpaste's weight. The viscosity of the abrasive significantly affects the toothpaste's viscosity and dispersibility. Silica, due to its stable physical and chemical properties, resistance to acids and alkalis, high temperatures, and lack of environmental pollution, possesses excellent cleaning performance and abrasiveness. Furthermore, it exhibits good compatibility with toothpaste ingredients and high compatibility with fluoride, making it a suitable abrasive for toothpaste. Patent document CN114538452A discloses a method for preparing silica wet gel with a narrow particle size distribution. This method uses a gelation process, but the silica has excessively high viscosity (greater than 3000 cp), resulting in poor dispersion of the toothpaste. On one hand, it easily clumps under the high-frequency vibration of an electric toothbrush, making it difficult to achieve thorough and uniform cleaning. On the other hand, its viscous texture makes it difficult to penetrate between teeth and rinse off, requiring multiple rinses, which in turn washes away beneficial oral components from the toothpaste. In addition, during the preparation of silica solution in the traditional gelation process, the silica produced adheres to the reaction vessel in a gel state, making it difficult to discharge and causing difficulties in subsequent pressure filtration and washing processes. Summary of the Invention

[0003] The first objective of this invention is to provide a method for preparing silica, which produces silica with low viscosity and high dispersibility.

[0004] The second objective of this invention is to provide a toothpaste that uses the aforementioned silica as an abrasive. The silica exhibits high dispersibility when applied to toothpaste, resulting in a toothpaste with low viscosity that is not too thick and does not easily clump.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A method for preparing silicon dioxide includes the following steps:

[0007] Sodium silicate solution and sulfuric acid solution are provided;

[0008] Preparation of silica solution: Take 45-60 wt% water of the total system after addition, heat to 40-60°C, and add sulfuric acid solution dropwise while stirring until the pH is 0.5-3.0. The stirring speed during the dropwise addition is 350-500 rpm. Then, add sodium silicate solution and sulfuric acid solution dropwise simultaneously for 1-1.5 h until the sodium silicate solution accounts for 30-45 wt% of the total system after addition and the sulfuric acid solution accounts for 8-15 wt%. The dropwise addition rate is stable, the pH in the reaction vessel is 0.5-3.0, and the temperature is 40-60°C. Then, age and stir for 30-60 min at a stirring speed of 350-500 rpm. After aging and stirring, adjust the final pH to 2-5 with the sodium silicate solution to obtain silica solution.

[0009] Preparation of solid silica: The silica solution is washed with water pressure to obtain a filter cake, which is then dried, crushed, and sieved to obtain silica.

[0010] As a preferred embodiment of the present invention, the concentration of the sodium silicate solution is 0.50 to 1.50 mol / L.

[0011] As a preferred embodiment of the present invention, the sodium silicate solution is prepared by the following operation: adding solid water glass to a reactor, then adding hot water and steam to liquefy the solid water glass to obtain a concentrated sodium silicate solution, and diluting the concentrated sodium silicate solution with water to obtain a sodium silicate solution.

[0012] In a preferred embodiment of the present invention, the concentration of the sulfuric acid solution is 2.00 to 8.00 mol / L.

[0013] As a preferred embodiment of the present invention, the salt content of the filter cake obtained by pressure filtration and washing is controlled to be ≤5wt% in the preparation of silica solid.

[0014] In a preferred embodiment of the present invention, the content of volatiles in the silica after drying the filter cake is controlled to be 20-25% at 105°C.

[0015] As a preferred embodiment of the present invention, the particle size of the silica particles obtained by crushing and sieving the filter cake in the preparation of silica solid is controlled to be 14-19 μm, and the material passing through a 325 mesh sieve is ≥98%.

[0016] A toothpaste that uses the aforementioned silica as an abrasive.

[0017] In a preferred embodiment of the present invention, the amount of silica added to the toothpaste is 1-30%.

[0018] The beneficial effects of this invention are:

[0019] 1. This invention provides a specific method for preparing silica. This method controls the temperature, process pH, and stirring speed during the intermediate silica solution preparation step to influence the stability of the silica solution gel system. The silica solution obtained during this intermediate step has low viscosity, and the final obtained silica solid has an oil absorption value of less than 100g / 100g and a BET specific surface area as high as 500-800m². 2 / g, with a viscosity as low as 20-100cp, resulting in high dispersibility; due to the low viscosity of the silica solution obtained in the middle, it will not adhere to the inside of the reaction vessel, thus making it easy to discharge.

[0020] 2. Toothpaste can be made using silica prepared by the above method. Silica has a large BET specific surface area, low oil absorption value, and low viscosity, so it exhibits high dispersibility. The resulting toothpaste is not prone to clumping and is easy to rinse. In addition, the toothpaste exhibits high stability in toothpaste viscosity stability tracking tests and is suitable for long-term storage. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to specific embodiments.

[0022] Example 1

[0023] Silicon dioxide is prepared by performing the following operations:

[0024] Preparation of sodium silicate solution: Add solid water glass to a liquefaction tank, add hot water and steam to the liquefaction tank, and liquefy the solid water glass under high temperature and high pressure to obtain a concentrated sodium silicate solution; take the concentrated sodium silicate solution and dilute it with water to prepare 5L of sodium silicate solution with a concentration range of 0.60mol / L for later use.

[0025] Preparation of sulfuric acid solution: Take 3 kg of the purchased concentrated sulfuric acid and dilute it with water to 2.00 mol / L for later use.

[0026] Preparation of silica solution: 3 kg of water (45 wt% of the total system after addition) was added to a reaction vessel, and the temperature was raised to 40°C. While stirring, the sulfuric acid solution was added dropwise until the pH was 0.5–3.0. During the addition, the stirring speed was 350 rpm. Then, the prepared sodium silicate solution and sulfuric acid solution were added dropwise simultaneously for 1 hour, keeping the addition rate stable, until the sodium silicate solution accounted for 45 wt% of the total system after addition and the sulfuric acid solution accounted for 10 wt%. The pH in the reaction vessel was controlled at 0.5–3.0 and the temperature at 40°C. After the addition of sodium silicate solution and sulfuric acid solution was completed, the mixture was aged and stirred at 350 rpm for 30 minutes. Then, the final pH was adjusted to 2–5 with 0.60 mol / L sodium silicate solution to obtain the silica solution.

[0027] Preparation of solid silica: The silica solution is filtered and washed with water to obtain a filter cake, reducing the product salt content to ≤5wt%. The filter cake is then dried, and the volatile content of silica at 105℃ is controlled to be 20-25%. The dried filter cake is crushed and sieved to obtain silica particles, with a particle size of 14-19μm and ≥98% passing through a 325-mesh sieve.

[0028] Example 2

[0029] Silicon dioxide is prepared by performing the following operations:

[0030] Preparation of sodium silicate solution: Add solid water glass to a liquefaction tank, add hot water and steam to the liquefaction tank, and liquefy the solid water glass under high temperature and high pressure to obtain a concentrated sodium silicate solution; take the concentrated sodium silicate solution and dilute it with water to prepare 5L of sodium silicate solution with a concentration range of 1.20mol / L for later use.

[0031] Preparation of sulfuric acid solution: Take 3 kg of the purchased concentrated sulfuric acid and dilute it with water to 5.00 mol / L for later use.

[0032] Preparation of silica solution: 3 kg of water (60 wt% of the total system after addition) was added to a reaction vessel, and the temperature was raised to 50°C. While stirring, the sulfuric acid solution was added dropwise until the pH was 0.5–3.0. During the addition, the stirring speed was 420 rpm. Then, the prepared sodium silicate solution and sulfuric acid solution were added dropwise simultaneously for 1.2 h, keeping the addition rate stable, until the sodium silicate solution accounted for 30 wt% of the total system after addition and the sulfuric acid solution accounted for 8 wt%. The pH in the reaction vessel was controlled at 0.5–3.0 and the temperature at 50°C. After the addition of sodium silicate solution and sulfuric acid solution was completed, the mixture was aged and stirred at 420 rpm for 45 min. Then, the final pH was adjusted to 2–5 with 1.20 mol / L sodium silicate solution to obtain the silica solution.

[0033] Preparation of solid silica: The silica solution is filtered and washed with water to obtain a filter cake, reducing the product salt content to ≤5wt%. The filter cake is then dried, and the volatile content of silica at 105℃ is controlled to be 20-25%. The dried filter cake is crushed and sieved to obtain silica particles, with a particle size of 14-19μm and ≥98% passing through a 325-mesh sieve.

[0034] Example 3

[0035] Silicon dioxide is prepared by performing the following operations:

[0036] Preparation of sodium silicate solution: Add solid water glass to a liquefaction tank, add hot water and steam to the liquefaction tank, and liquefy the solid water glass under high temperature and high pressure to obtain a concentrated sodium silicate solution; take the concentrated sodium silicate solution and dilute it with water to prepare 5L of sodium silicate solution with a concentration range of 1.40mol / L for later use.

[0037] Preparation of sulfuric acid solution: Take 3 kg of the purchased concentrated sulfuric acid and dilute it with water to 8.00 mol / L for later use.

[0038] Preparation of silica solution: 3 kg of water (45 wt% of the total system after addition) was added to a reaction vessel, and the temperature was raised to 60°C. While stirring, the sulfuric acid solution was added dropwise until the pH was 0.5–3.0. During the dropwise addition, the stirring speed was 500 rpm. Then, the prepared sodium silicate solution and sulfuric acid solution were added dropwise simultaneously for 1.5 h, keeping the dropwise addition rate stable, until the sodium silicate solution accounted for 40 wt% of the total system after addition and the sulfuric acid solution accounted for 15 wt%. The pH in the reaction vessel was controlled at 0.5–3.0 and the temperature at 60°C. After the addition of sodium silicate solution and sulfuric acid solution was completed, the mixture was aged and stirred at 500 rpm for 60 min. The final pH was adjusted to 2–5 with 2.50 mol / L sodium silicate solution to obtain the silica solution.

[0039] Preparation of solid silica: The silica solution is filtered and washed with water to obtain a filter cake, reducing the product salt content to ≤5wt%. The filter cake is then dried, and the volatile content of silica at 105℃ is controlled to be 20-25%. The dried filter cake is crushed and sieved to obtain silica particles, with a particle size of 14-19μm and ≥98% passing through a 325-mesh sieve.

[0040] Comparative Example 1

[0041] Compared with Example 1, the only difference was that in the preparation of the silica solution, 3 kg of water, which accounted for 65 wt% of the total system after addition, was added to the reaction vessel; all other aspects were the same as in Example 1.

[0042] Comparative Example 2

[0043] Compared with Example 1, the only difference was that the particle size D50 of the prepared silica solid was controlled to be 20-25 μm, while the rest were the same as in Example 1.

[0044] Comparative Example 3

[0045] Compared with Example 1, the only difference was that the particle size D50 of the prepared silica solid was controlled to be 8-12 μm, while the rest were the same as in Example 1.

[0046] Comparative Example 4

[0047] Compared with Example 1, only the content of volatiles in the prepared silica solid after drying at 105°C was controlled to be 25-40%, and all other aspects were the same as in Example 1.

[0048] Comparative Example 5

[0049] Compared with Example 1, only the content of volatiles in the prepared silica solid after drying at 105°C was controlled to be 10-15%, and all other aspects were the same as in Example 1.

[0050] The silica prepared in Examples 1-3 and Comparative Examples 1-5 was tested as follows:

[0051] Experiment 1 tested the properties of the silica powders prepared in Examples 1-3 and Comparative Examples 1-5:

[0052] (a) Method for measuring the viscosity of silica:

[0053] 40g of the silica prepared in Examples 1-3 and Comparative Examples 1-5 were weighed into 300mL plastic cups, 200g of distilled water was added, and the mixture was stirred evenly with a glass rod and then stirred with a stirrer for 10 minutes at a speed of 25Hz. After stirring, the viscosity was measured using a DV-II+pro viscometer, and the results are shown in Table 1.

[0054] (II) Method for measuring the oil absorption value of silica:

[0055] Weigh 1.00g of the silica prepared in Examples 1-3 and Comparative Examples 1-5 respectively and place it on a glass plate. Add linseed oil dropwise from a microburette and stir continuously with a tongue depressor until the sample gradually thickens and becomes sticky. Finally, the sample is completely thickened and forms a clump, leaving no thickened material or silica powder on the plate.

[0056] The formula for calculating oil absorption value is as follows, and the results are shown in Table 1:

[0057]

[0058] In the formula:

[0059] X – Oil absorption value (g / 100g);

[0060] m1—sample amount (g);

[0061] m2 — Mass of flaxseed oil consumed (g).

[0062] (III) Method for measuring the BET specific surface area of ​​silica:

[0063] The BET specific surface area of ​​silica prepared in Examples 1-3 and Comparative Examples 1-5 was measured using a JW-BK112 static nitrogen adsorption instrument. The results are shown in Table 1.

[0064] (iv) Methods for measuring powder particle size distribution:

[0065] The particle size distribution was measured using a Baxter BT-9300H laser particle size analyzer, and the results are shown in Table 1.

[0066] (V) Method for measuring the volatiles of silicon dioxide at 105℃:

[0067] The measurements were performed according to the measurement method for "5.4 Volatile Matter" in QB / T 2346-2015, and the results are shown in Table 1.

[0068] (vi) Method for measuring the material passing through a 325-mesh sieve of silica:

[0069] The measurement was performed according to the method for "5.3 Undersize" in QB / T 2346-2015, and the results are shown in Table 1.

[0070] (vii) Method for measuring copper loss in silicon dioxide:

[0071] According to the paper "Study on Copper Consumption Value of Silica for Toothpaste": The copper sheet was washed with distilled water and dried, and its mass was marked and weighed. The copper sheet was fixed in the slot of the material pool, and the silica powder prepared in Examples 1-3 and Comparative Examples 1-5 was accurately dispersed in sorbitol. After stirring evenly, the mixture was poured into the material pool to immerse the copper sheet. After 10,000 cycles of back-and-forth rubbing, the copper sheet was cleaned and dried, and the difference in value before and after rubbing was measured to obtain the copper consumption value. The results are shown in Table 1.

[0072] Table 1

[0073]

[0074] As shown in Table 1, the silica prepared in the embodiments of the present invention has an oil absorption value of 40-60 g / 100 g, a viscosity of 23-85 cp, and a BET specific surface area of ​​622-761 m². 2The values ​​of silica ( / g) indicate that silica has a larger specific surface area, lower oil absorption value, and lower viscosity. Furthermore, the silica particle size D50 is 14–17 μm, the volatile matter at 105℃ is 20–24%, and the copper consumption is 0.5–0.8 mg, meeting the requirements for subsequent toothpaste preparation. In Comparative Example 1, the silica oil absorption value and viscosity are significantly improved. In Comparative Example 2, the silica particle size D50 is 24 μm, and in Comparative Example 3, the silica particle size D50 is 9 μm, neither of which meets the 14–19 μm requirement. Comparative Example 2 has a higher copper consumption value and a lower BET specific surface area, while Comparative Example 3 has a higher viscosity, making them unsuitable for toothpaste preparation. In Comparative Example 4, the silica volatile matter at 105℃ is 35%, and in Comparative Example 5, the silica volatile matter at 105℃ is 12%, neither of which meets the 20–25% requirement. Comparative Example 4 has a lower BET specific surface area, and Comparative Example 5 has a higher viscosity, making them unsuitable for toothpaste preparation.

[0075] The silica prepared in Examples 1-3 and Comparative Examples 1-5 were made into toothpaste according to the components in Table 2, as shown in Table 3.

[0076] Table 2

[0077] toothpaste ingredients mass percentage / % Sorbitol 50 Carboxymethyl cellulose 1.0 Sodium saccharin 0.2 Sodium dodecyl sulfate 2.0 spearmint oil 1.0 Sodium benzoate 0.2 water 20.4 Titanium dioxide 0.2 silicon dioxide 25.0 total 100

[0078] Table 3

[0079]

[0080] Toothpastes were prepared using Examples 1-3 and Comparative Examples 1-5, and the toothpaste groups are shown in Table 3. The toothpastes of Examples 4-6 and Comparative Examples 6-10 were tested as follows:

[0081] Experimental Example 2: Toothpaste Viscosity Test

[0082] Weigh 50g of toothpaste into 300ml plastic cups and let them stand at 25℃ until the toothpaste temperature reaches 25℃. Use a DV-II+pro viscometer to measure the viscosity. The viscosity here is the toothpaste viscosity tested on the day the toothpaste was made. The results are shown in Table 4.

[0083] Experimental Example 3: Method for Toothpaste Relaxation Time

[0084] Relaxation time is used to indicate the dispersibility of toothpaste; the shorter the relaxation time, the better the dispersibility of the toothpaste.

[0085] After the samples were kept at a constant temperature for 1 hour using a dry thermostat, the relaxation time of the toothpaste was tested using a LISICO LS-1 dispersion stability analyzer. The results are shown in Table 4.

[0086] Test Example 4: Toothpaste Performance Test

[0087] Forty volunteers were randomly divided into eight groups, and the appearance and brushing experience of the eight groups of toothpaste were tested. A scoring system was used for the brushing experience, rating the freshness of the taste and the quality of the dispersion: fresh taste was 3 points, fairly fresh taste was 2 points, and average taste was 1 point; good dispersion was 3 points, relatively good dispersion was 2 points, and average dispersion was 1 point. The average scores were calculated, and the results are shown in Table 4.

[0088] Table 4

[0089]

[0090]

[0091] As shown in Table 4, the toothpastes in Examples 4-6 of this invention have a viscosity of 15-23 cp and a relaxation time of 33-37 ms, exhibiting uniform consistency and uniform texture during brushing. In Comparative Example 6, the toothpaste viscosity is too high, resulting in a viscous paste; in Comparative Example 7, the toothpaste viscosity is too low, resulting in a thin paste; in Comparative Example 8, the toothpaste viscosity is too high, resulting in a viscous paste; in Comparative Example 9, the toothpaste viscosity is too low, resulting in a thin paste; and in Comparative Example 10, the toothpaste viscosity is too high, resulting in a thick paste. It is evident that the silica prepared in Examples 1-3 exhibits suitable viscosity and dispersibility in the toothpaste.

[0092] The toothpaste of Example 4 was tested as follows:

[0093] Experimental Example 5: Toothpaste Viscosity Stability Tracking Test

[0094] The toothpaste of Example 4 was tested for 90 days, and the specific viscosity data are shown in Table 5.

[0095] Table 5

[0096]

[0097]

[0098] As shown in Table 5, the viscosity of the toothpaste in Example 4 changed only from 23.0 wcp to 29.2 wcp at -10℃; from 23.2 wcp to 32.4 wcp at 25℃; and from 25.0 wcp to 39.8 wcp at 40℃. The toothpaste viscosity was stable and suitable for long-term storage.

[0099] The above description is merely an embodiment of the present invention and does not limit the scope of patent protection. Any non-substantial changes or substitutions made by those skilled in the art based on the present invention will still fall within the scope of patent protection.

Claims

1. A method for preparing silicon dioxide, characterized in that, Includes the following steps: Sodium silicate solution and sulfuric acid solution are provided; Preparation of silica solution: Take 45-60 wt% water of the total system after addition, heat to 40-60℃, and add the sulfuric acid solution dropwise while stirring until the pH is 0.5-3.

0. The stirring speed during the dropwise addition is 350-500 rpm. Then, add the sodium silicate solution and sulfuric acid solution dropwise simultaneously for 1-1.5 h until the sodium silicate solution accounts for 30-45 wt% of the total system after addition and the sulfuric acid solution accounts for 8-15 wt%. During the dropwise addition, the dropwise addition rate is stable, the pH in the reaction vessel is 0.5-3.0, and the temperature is 40-60℃. Then, the mixture is aged and stirred for 30-60 minutes at a stirring speed of 350-500 rpm. After aging and stirring, the final pH is adjusted to 2-5 with the sodium silicate solution to obtain a silica solution. Preparation of solid silica: The silica solution is washed with water pressure to obtain a filter cake, which is then dried, crushed, and sieved to obtain silica.

2. The preparation method according to claim 1, characterized in that, The concentration of the sodium silicate solution is 0.50-1.50 mol / L.

3. The preparation method according to claim 1, characterized in that, The sodium silicate solution is prepared by the following operation: adding solid water glass to a reactor, then adding hot water and steam to liquefy the solid water glass to obtain a concentrated sodium silicate solution, and then diluting the concentrated sodium silicate solution with water to obtain a sodium silicate solution.

4. The preparation method according to claim 1, characterized in that, The concentration of the sulfuric acid solution is 2.00~8.00 mol / L.

5. The preparation method according to claim 1, characterized in that, In the preparation of silica solid, the salt content of the filter cake obtained by pressure filtration and washing is controlled to be ≤5wt%.

6. The preparation method according to claim 1, characterized in that, In the preparation of solid silica, the content of volatiles in the silica after drying the filter cake is controlled to be 20-25% at 105°C.

7. The preparation method according to claim 1, characterized in that, In the preparation of solid silica, the particle size of silica particles obtained by controlling the crushing and sieving of the filter cake is 14~19μm, and the material passing through a 325-mesh sieve is ≥98%.

8. A toothpaste, characterized in that, The silica prepared by the preparation method according to any one of claims 1 to 7 is used as a friction agent.

9. The toothpaste according to claim 8, characterized in that, The amount of silica added to the toothpaste is 1~30wt%.

Images