阅读说明：本技术 一种低导热低堆积密度白炭黑的制备方法及其应用 (Preparation method and application of low-heat-conductivity and low-bulk-density white carbon black ) 是由 胡明涛 任立荣 王文君 张和强 赵孝敏 于 2019-11-11 设计创作，主要内容包括：本发明属于白炭黑技术领域,公开了一种低导热低堆积密度白炭黑的制备方法及其应用。本发明所述制备方法包括：配制硅酸钠溶液和稀硫酸溶液；往反应釜中加入水和硅酸钠溶液,加热,在搅拌下加入稀硫酸溶液至pH为8.5～9,有凝胶生成；提升搅拌速率,升温,加入硅酸钠溶液和稀硫酸溶液,控制反应体系pH,并在特定时间点加入强电解质控制粒径,得白炭黑稀浆料,过滤洗涤,打浆得白炭黑浓浆；加入分散剂进行研磨后经醇洗恒沸蒸馏干燥后即得。该制备工艺通过在凝胶结构上继续反应,醇洗恒沸蒸馏干燥的手段提升产品孔容值,降低保温板的导热系数；通过强电解质与分散剂的加入、超细研磨减小产品粒径,缩窄粒径分布,降低产品堆积密度。(The invention belongs to the technical field of white carbon black, and discloses a preparation method and application of low-heat-conductivity and low-bulk-density white carbon black. The preparation method comprises the following steps: preparing a sodium silicate solution and a dilute sulfuric acid solution; adding water and a sodium silicate solution into a reaction kettle, heating, adding a dilute sulfuric acid solution under stirring until the pH value is 8.5-9, and generating gel; increasing the stirring speed, heating, adding a sodium silicate solution and a dilute sulfuric acid solution, controlling the pH of a reaction system, adding a strong electrolyte at a specific time point to control the particle size to obtain a white carbon black dilute slurry, filtering, washing and pulping to obtain a white carbon black concentrated slurry; adding a dispersing agent, grinding, washing with alcohol, constant boiling, distilling and drying to obtain the product. According to the preparation process, the pore volume value of a product is improved and the heat conductivity coefficient of the insulation board is reduced by means of continuous reaction on a gel structure and alcohol washing, constant boiling, distillation and drying; the particle size of the product is reduced, the particle size distribution is narrowed and the product bulk density is reduced by adding strong electrolyte and a dispersing agent and carrying out superfine grinding.)

1. The preparation method of the low-heat-conductivity and low-bulk density white carbon black is characterized by comprising the following steps of:

(1) preparing a sodium silicate solution and a dilute sulfuric acid solution;

(2) adding water and a sodium silicate solution into a reaction kettle, heating, adding a dilute sulfuric acid solution under stirring until the pH of the system is reduced to 8.5-9, and generating gel;

(3) increasing the stirring speed to break up the gel, heating to 80-90 ℃, adding a sodium silicate solution and a dilute sulfuric acid solution, controlling the pH of the reaction to be 10.5-11, adding a strong electrolyte after 30-40 min, and continuing the reaction for 15-25 min;

(4) stopping adding the sodium silicate solution, continuously adding dilute sulfuric acid until the pH value is reduced to 6.0-6.5 to obtain a white carbon black dilute slurry, filtering and washing the dilute slurry to obtain a filter cake, and pulping the filter cake to obtain a white carbon black concentrated slurry;

(5) adding a dispersing agent into the white carbon black thick slurry, and carrying out wet superfine grinding to obtain superfine white carbon black thick slurry;

(6) adding fatty alcohol into the superfine white carbon black thick slurry to form a fatty alcohol-water binary system, firstly heating to the constant boiling point of the binary system, removing water by constant boiling distillation, and then continuously heating to remove the fatty alcohol to obtain the final product.

2. The preparation method of the low-thermal-conductivity and low-bulk-density white carbon black according to claim 1, wherein the concentration of the sodium silicate solution in the step (1) is 1-1.3 mol/L, and the modulus is 3-3.5; the mass fraction of the dilute sulfuric acid solution is 10-15%.

3. The preparation method of the low-thermal-conductivity and low-bulk-density white carbon black according to claim 1, wherein the heating temperature in the step (2) is 50-60 ℃, and a dilute sulfuric acid solution is added at a stirring speed of 30-50 r/min.

4. The preparation method of the low-thermal-conductivity and low-bulk density white carbon black according to claim 1, wherein the stirring speed in the step (3) is increased to 70-90 r/min to break up the gel.

5. The method for preparing white carbon black with low thermal conductivity and low bulk density according to claim 1, wherein the strong electrolyte in the step (3) is one or more of sodium sulfate, sodium chloride or sodium phosphate; preferably, the addition amount of the strong electrolyte in the step (3) is 0.5-3% of the final yield of the white carbon black.

6. The method for preparing white carbon black with low thermal conductivity and low bulk density according to claim 1, wherein the dispersant in the step (5) is one or more of sodium hexametaphosphate, sodium dodecyl sulfate or sodium lignosulfonate.

7. The preparation method of the low-thermal-conductivity and low-bulk density white carbon black according to claim 1, wherein the addition amount of the dispersing agent in the step (5) is 1-3% of the mass of the white carbon black concentrated slurry.

8. The method for preparing white carbon black with low thermal conductivity and low bulk density according to claim 1, wherein the wet superfine grinding in the step (5) is performed by a pin-and-rod type sand mill.

9. The method for preparing white carbon black with low thermal conductivity and low bulk density according to claim 1, wherein the aliphatic alcohol in the step (6) is one or more of ethanol, isopropanol or n-butanol.

10. The application of the low-thermal-conductivity and low-bulk-density white carbon black prepared by the preparation method of any one of claims 1 to 9 is characterized in that the low-thermal-conductivity and low-bulk-density white carbon black is used as a core material main component to prepare the STP ultrathin vacuum insulation board.

Technical Field

The invention relates to the technical field of white carbon black, and particularly relates to a preparation method and application of low-heat-conductivity and low-bulk-density white carbon black.

Background

The white carbon black is a general term of white powdery X-ray amorphous silicic acid and silicate, comprises precipitated hydrated silica, fumed silica and silica aerogel, and related products are widely applied to the industries of tire rubber, silicon rubber, sole rubber, paint, animal feed, food additives and the like.

In recent years, white carbon black products are gradually applied and popularized in the industry of building external wall heat insulation materials. The STP ultrathin vacuum insulation board is an ultrathin insulation board prepared by compounding a core material prepared from superfine silicon dioxide, an additive and an auxiliary agent and a high-strength composite gas barrier film through a vacuumizing packaging technology, and has the remarkable advantages of high fire resistance grade (A grade) and low thermal conductivity (less than or equal to 0.01W/(m.K)). The realization of low thermal conductivity requires that the white carbon black as the core material has very low thermal conductivity; meanwhile, in order to reduce the filling quality of the white carbon black and reduce the production cost, the white carbon black is required to have lower bulk density. Most of current insulation board manufacturers fill white carbon black prepared by a gas phase method, the bulk density of products prepared by the gas phase method is about 50g/L, and the heat conductivity coefficient of the STP ultrathin vacuum insulation board prepared by taking the STP ultrathin vacuum insulation board as the main component of a core material is generally 0.007-0.008W/(m.K), so that the use requirement is met. However, the white carbon black prepared by the gas phase method is expensive, so that the price of the insulation board is increased, and the subsequent popularization of the product is influenced; the white carbon black product prepared by the common precipitation method generally has the problems of large heat conductivity coefficient (not less than 0.012W/(m.K)) and high bulk density (not less than 60g/L) of the insulation board.

Disclosure of Invention

The invention provides a preparation method of low-heat-conduction low-bulk density white carbon black, aiming at overcoming the defects that the white carbon black prepared by the existing gas phase method is high in price and the white carbon black prepared by the ordinary precipitation method is insufficient in performance. The method starts from the following three aspects, and solves the problems of high heat conductivity coefficient and large bulk density of the white carbon black by the common precipitation method:

(1) improving the pore volume of the white carbon black to reduce the thermal conductivity: the core material of the STP ultrathin vacuum insulation board is required to be vacuumized after being filled with the white carbon black, the larger the pore volume of the white carbon black is, the larger the occupied volume of the vacuumized gap part is, the higher the vacuum degree of the gap part is, the thermal conductivity is close to zero, and the lower the thermal conductivity of the insulation board prepared by the method is;

(2) narrowing the particle size distribution of the white carbon black to reduce the bulk density: as shown in the attached figure 1, if the white carbon black particles are regarded as solid spheres, when the white carbon black particles have only one diameter, namely in the extreme case shown in figure 1- (1), the bulk density is the minimum, when the white carbon black particles have multiple diameters, the more the particle size types are, namely the wider the particle size distribution is, the higher the bulk density is, which is the case shown in figures 1- (1) to 1- (3), in the preparation of the white carbon black powder, the particle size distribution can be narrowed through process control, so that the aim of reducing the bulk density is fulfilled;

(3) the white carbon black has the characteristics that the finer the powder is, the lower the bulk density is: the surface of the white carbon black powder has a large amount of silicon hydroxyl groups, the adsorption effect among the silicon hydroxyl groups is strong, large-volume loose aggregates are formed, and the more aggregates are, the lower the powder bulk density is; the finer the white carbon black powder, the more the silicon hydroxyl active sites exist on the surface of the particle per unit area, the stronger the adsorption effect is, the more and larger the formed aggregates are, and the naturally smaller the bulk density is, so that the proper reduction of the particle size of the white carbon black is beneficial to reducing the bulk density.

In order to achieve the purpose of the invention, the preparation method of the low-heat-conduction low-bulk density white carbon black comprises the following steps:

(1) preparing a sodium silicate solution and a dilute sulfuric acid solution;

(2) adding water and a sodium silicate solution into a reaction kettle, heating, adding a dilute sulfuric acid solution under stirring until the pH of the system is reduced to 8.5-9, and generating gel;

(3) increasing the stirring speed to break up the gel, heating to 80-90 ℃, adding a sodium silicate solution and a dilute sulfuric acid solution, controlling the pH of the reaction to be 10.5-11, adding a strong electrolyte after 30-40 min, and continuing the reaction for 15-25 min;

(4) stopping adding the sodium silicate solution, continuously adding dilute sulfuric acid until the pH value is reduced to 6.0-6.5 to obtain a white carbon black dilute slurry, filtering and washing the dilute slurry to obtain a filter cake, and pulping the filter cake to obtain a white carbon black concentrated slurry;

(5) adding a dispersing agent into the white carbon black thick slurry, and carrying out wet superfine grinding to obtain superfine white carbon black thick slurry;

(6) adding fatty alcohol into the superfine white carbon black thick slurry to form a fatty alcohol-water binary system, firstly heating to the constant boiling point of the binary system, removing water by constant boiling distillation, and then continuously heating to remove the fatty alcohol to obtain the final product.

Further, the concentration of the sodium silicate solution in the step (1) is 1-1.3 mol/L, and the modulus is 3-3.5; the mass fraction of the dilute sulfuric acid solution is 10-15%.

Further, heating to 50-60 ℃ in the step (2), and adding a dilute sulfuric acid solution at a stirring speed of 30-50 r/min.

Further, in the step (3), the stirring speed is increased to 70-90 r/min to break up the gel.

Further, the strong electrolyte in the step (3) is one or more of sodium sulfate, sodium chloride or sodium phosphate; preferably, the addition amount of the strong electrolyte in the step (3) is 0.5-3% of the final yield of the white carbon black.

Further, the dispersing agent in the step (5) is one or more of sodium hexametaphosphate, sodium dodecyl sulfate or sodium lignosulfonate.

Preferably, the adding amount of the dispersing agent in the step (5) is 1-3% of the mass of the white carbon black concentrated slurry.

Further, the wet superfine grinding in the step (5) is performed by using a pin-and-rod type sand mill.

Preferably; the sand mill is a pin-type sand mill, 95 zirconia ceramic balls with the diameter of 0.6mm are used as grinding media, the rotating speed of a main shaft is 2100-2300 r/min, and the circulating grinding time is 12-18 min.

Further, in the step (6), the fatty alcohol is one or more of ethanol, isopropanol or n-butanol.

On the other hand, the invention also provides application of the white carbon black prepared by the method, namely the white carbon black is used as a core material main component to prepare the STP ultrathin vacuum insulation board.

The invention firstly prepares the silica gel with rich pore structure, and then the reaction is continued on the basis to prepare the multi-stage particles with larger pore volume. Wherein, the addition of the strong electrolyte can prevent the white carbon black particles from further agglomerating, thereby effectively reducing the particle size of the white carbon black particles; the particle size is further reduced by the grinding process and the addition of the dispersing agent, and agglomeration is avoided; when the aliphatic alcohol is added for azeotropic distillation drying, the lower surface tension of the aliphatic alcohol system can avoid the damage of a pore structure when the solvent is evaporated, and the higher pore volume is kept.

In addition, the method of the invention uses less strong electrolyte and dispersing agent, has low price, and the fatty alcohol is also treated by closed condensation and recovery, thus having great cost advantage compared with products prepared by a gas phase method. In addition, the white carbon black product prepared by the method is only used as a filling material when the insulation board is prepared, so that a small amount of electrolyte, a dispersing agent and the like remained in the product have no influence on the application of the product. The white carbon black prepared by the method has the pore volume of 2.2-2.6 ml/g and the bulk density of 50-60 g/L, and after the white carbon black is used as the main component of the core material to prepare the STP ultrathin vacuum insulation board, the heat conductivity coefficient is less than or equal to 0.01W/(m.K) through detection, so that the use requirement is basically met.

Drawings

FIG. 1 is a schematic diagram showing the influence of different particle size distributions on the bulk density of a powder;

FIG. 2 is a graph comparing the particle size distribution of the products of examples 1-2 of the present invention with that of comparative examples 1-2.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. It is to be understood that the following description is only illustrative of the present invention and is not to be construed as limiting the present invention.

The terms "comprises," "comprising," "includes," "including," "has," "having," "contains," "containing," or any other variation thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

When an amount, concentration, or other value or parameter is expressed as a range, preferred range, or as a range of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted to include the ranges "1 to 4", "1 to 3", "1 to 2 and 4 to 5", "1 to 3 and 5", and the like. When a range of values is described herein, unless otherwise stated, the range is intended to include the endpoints thereof and all integers and fractions within the range.

The indefinite articles "a" and "an" preceding an element or component of the invention are not intended to limit the number requirement (i.e., the number of occurrences) of the element or component. Thus, "a" or "an" should be read to include one or at least one, and the singular form of an element or component also includes the plural unless the number clearly indicates the singular. Further, the technical features of the embodiments of the present invention may be combined with each other as long as they do not conflict with each other.