阅读说明：本技术 一种粒径可控的具有核壳结构的疏水白炭黑的制备方法 (Preparation method of hydrophobic white carbon black with controllable particle size and core-shell structure ) 是由 张和强 任立荣 胡明涛 王文君 赵孝敏 于 2019-10-23 设计创作，主要内容包括：本发明属于白炭黑领域,公开了一种粒径可控的具有核壳结构的疏水白炭黑的制备方法。本发明所述的制备方法包括：配制硅酸钠溶液,并在其中加入酸性催化剂,调节体系的PH值在10～10.5之间,反应20～35min,继续添加酸性催化剂,调节体系的PH值在3.5～4.6之间,反应40～60min后加入疏水改性剂,并加入共溶剂,然后在50～80℃反应1～12h,再通过压滤、洗涤、干燥得到核壳结构的疏水白炭黑。本发明通过白炭黑与疏水改性剂共缩合的方法降低了白炭黑表面的羟基数量,降低了干燥过程中白炭黑之间的聚集,从而实现了粒径可控、疏水性好、高比表、高吸油白炭黑的制备。(The invention belongs to the field of white carbon black, and discloses a preparation method of hydrophobic white carbon black with a core-shell structure and controllable particle size. The preparation method comprises the following steps: preparing a sodium silicate solution, adding an acid catalyst into the sodium silicate solution, adjusting the pH value of the system to be between 10 and 10.5, reacting for 20 to 35min, continuously adding the acid catalyst, adjusting the pH value of the system to be between 3.5 and 4.6, reacting for 40 to 60min, adding a hydrophobic modifier, adding a cosolvent, reacting for 1 to 12h at 50 to 80 ℃, and then performing filter pressing, washing and drying to obtain the hydrophobic white carbon black with the core-shell structure. According to the invention, the number of hydroxyl groups on the surface of the white carbon black is reduced by a method of co-condensing the white carbon black and the hydrophobic modifier, and aggregation of the white carbon black in a drying process is reduced, so that the preparation of the white carbon black with controllable particle size, good hydrophobicity, high specific surface area and high oil absorption is realized.)

1. The preparation method of the hydrophobic white carbon black with the controllable particle size and the core-shell structure is characterized by comprising the following steps:

(1) preparing a sodium silicate solution in a reaction kettle;

(2) adding an acid catalyst into a sodium silicate solution, adjusting the pH value of the system to be between 10 and 10.5, adjusting the reaction temperature to be between 50 and 90 ℃, stirring at the speed of 30 to 100rpm, reacting for 20 to 35 minutes, then continuously adding the acid catalyst, adjusting the pH value of the system to be between 3.5 and 4.6, and reacting for 40 to 60 minutes to obtain a white carbon black suspension;

(3) adding hydrophobic modifier RSi (OR) into the suspension₁)₃Adding a cosolvent, and reacting at 50-80 ℃ for 1-12h to obtain a suspension of the hydrophobic white carbon black;

(4) and carrying out filter pressing, washing and drying on the suspension of the hydrophobic white carbon black to obtain the hydrophobic white carbon black with the core-shell structure.

2. The preparation method of the hydrophobic white carbon black with the core-shell structure and the controllable particle size according to claim 1, wherein the concentration of the sodium silicate solution in the step (1) is 0.5-2.5 mol/L.

3. The preparation method of the hydrophobic white carbon black with the core-shell structure and the controllable particle size according to claim 2, wherein the modulus of the sodium silicate in the step (1) is 3-3.5.

4. The preparation method of the hydrophobic white carbon black with the core-shell structure and the controllable particle size according to claim 1, wherein the acidic catalyst in the step (2) is one or more of hydrochloric acid, nitric acid, phosphoric acid and p-toluenesulfonic acid.

5. The preparation method of the hydrophobic white carbon black with the core-shell structure and the controllable particle size according to claim 2, wherein the mass concentration of the acidic catalyst in the step (2) is 10-20%.

6. The preparation method of the hydrophobic white carbon black with the core-shell structure and the controllable particle size according to claim 1, wherein the hydrophobic modifier in the step (3) has a structure of

Wherein R is-CH₂CH₂CH₂OOCCH₃C＝CH₂、-CH₂CH₂CH₂OCH₂CH(O)CH₂、-CH₃、-CH₂CH₃、-CH₂CH₂CH₃、-CH(CH₃)₂、-(CH₂)₁₁CH₃、-(CH₂)₁₅CH₃One of (1), R₁is-OCH₃、-OCH₂CH₃One or more of (a).

7. The preparation method of the hydrophobic white carbon black with the core-shell structure and the controllable particle size according to claim 2, wherein the mass ratio of the modifier to the white carbon black suspension in the step (3) is 1:20-1: 100.

8. The preparation method of the hydrophobic white carbon black with the core-shell structure and the controllable particle size according to claim 1, wherein the cosolvent in the step (3) is one or a mixture of ethanol, propanol, isopropanol, butanol, ethylene glycol, glycerol and ethyl acetate.

9. The preparation method of the hydrophobic white carbon black with the core-shell structure and the controllable particle size according to claim 2, wherein the mass ratio of the cosolvent added in the step (3) to the sodium silicate solution is 5:1-1: 5.

Technical Field

The invention relates to the field of white carbon black, in particular to a preparation method of hydrophobic white carbon black with a core-shell structure and controllable particle size.

Background

Silica is called white carbon, since it can act like carbon black reinforcement in rubber and its color is white. At present, the method for preparing the white carbon black mainly comprises two methods: the precipitation method and the gas phase method have the advantages that the gas phase method is complex in production process, high in cost and low in yield, so that all domestic methods for producing the white carbon black are mainly the precipitation method.

The white carbon black has stable chemical properties, is green and nontoxic, resists high temperature and has high specific surface area, so the white carbon black is widely applied to rubber industry, coatings, paints, defoaming agents and engineering plastics as a filler and a reinforcing agent. White carbon black is generally used as an additive in polymer materials, but the white carbon black has the following problems in use: (1) the compatibility of the white carbon black and the polymer material is poor, and the phase separation is easy to occur in the blending process; (2) the surface of the white carbon black contains a large amount of silicon hydroxyl, so that the white carbon black has high surface energy, and the white carbon black is easy to aggregate to form larger white carbon black particles, so that the white carbon black forms stress concentration in a polymer material, and the performance and the service life of the material are further reduced; (3) the particle size of the white carbon black prepared by the precipitation method is too large and generally reaches more than 10 mu m; (4) a large amount of hydroxyl on the surface of the white carbon black not only influences the compatibility of the white carbon black with rubber, but also increases the vulcanization time of the rubber and reduces the production efficiency. These problems limit the application field of white carbon black.

The currently common modification methods are mainly divided into two types: one is physical modification, namely a layer of organic matter is adsorbed on the surface of the white carbon black by utilizing the characteristics of porosity and high specific surface area of the surface of the white carbon black; the other is chemical modification, namely, silicon hydroxyl on the surface of the white carbon black reacts with a chemical surface modifier, and the number of the hydroxyl on the surface of the white carbon black is reduced, so that the white carbon black has hydrophobicity. The hydrophobic white carbon black prepared by physical modification has poor durability, and the prepared hydrophobic white carbon black has larger particle size, so the application prospect is poor.

At present, hydrophobic white carbon black is prepared by chemical modification mainly by taking a silane coupling agent, silicone oil containing functional end groups and the like as modifiers and adopting a physical grinding method or firstly dispersing the white carbon black in a proper solvent and then carrying out surface grafting modification. However, the two methods have the defects of complex preparation process, complex post-treatment and easy environmental pollution, and the particle size of the modified white carbon black is not obviously changed and still reaches dozens of microns to dozens of microns. At present, the preparation method of the white carbon black with small particle size is mainly prepared by a gas phase method, but the gas phase method has higher technical threshold, and the domestic market is basically monopolized by foreign enterprises. Most domestic enterprises prepare the small-particle-size white carbon black by a physical grinding method, the physical grinding method is generally divided into wet grinding and dry grinding, the dispersant is required to be added into the white carbon black in the wet grinding, the white carbon black still generates aggregation in the drying process, and impurities are introduced; the main disadvantages of dry grinding modification are that it is difficult to treat the surface of the white carbon black uniformly, a large amount of modifier is consumed, the used equipment is complex and expensive, and the production cost of enterprises is greatly increased.

Disclosure of Invention

The invention aims to overcome the defects of the background technology and provides a preparation method of hydrophobic white carbon black with a controllable particle size and a core-shell structure.

In order to achieve the purpose of the invention, the preparation method of the hydrophobic white carbon black with the controllable particle size and the core-shell structure comprises the following steps:

(1) preparing a sodium silicate solution in a reaction kettle;

(2) adding an acid catalyst into a sodium silicate solution, adjusting the pH value of the system to be between 10 and 10.5, adjusting the reaction temperature to be between 50 and 90 ℃, stirring at the speed of 30 to 100rpm, reacting for 20 to 35 minutes, then continuously adding the acid catalyst, adjusting the pH value of the system to be between 3.5 and 4.6, and reacting for 40 to 60 minutes to obtain a white carbon black suspension;

(3) adding hydrophobic modifier RSi (OR) into the suspension₁)₃Adding a cosolvent, and reacting at 50-80 ℃ for 1-12h to obtain a suspension of the hydrophobic white carbon black;

(4) and carrying out filter pressing, washing and drying on the suspension of the hydrophobic white carbon black to obtain the hydrophobic white carbon black with the core-shell structure.

Further, the concentration of the sodium silicate solution in the step (1) is 0.5-2.5 mol/L.

Further, the modulus of the sodium silicate in the step (1) is 3-3.5.

Further, the acidic catalyst in the step (2) is one or a mixture of hydrochloric acid, nitric acid, phosphoric acid and p-toluenesulfonic acid.

Further, the mass concentration of the acidic catalyst in the step (2) is 10-20%.

Further, the structure of the hydrophobic modifier in the step (3) is

Wherein R is-CH₂CH₂CH₂OOCCH₃C＝CH₂、-CH₂CH₂CH₂OCH₂CH(O)CH₂、-CH₃、-CH₂CH₃、-CH₂CH₂CH₃、-CH(CH₃)₂、-(CH₂)₁₁CH₃、-(CH₂)₁₅CH₃One of (1), R₁is-OCH₃、-OCH₂CH₃One or more of (a).

Further, the mass ratio of the modifier to the white carbon black suspension in the step (3) is 1:20-1: 100.

Further, the cosolvent in the step (3) is one or a mixture of ethanol, propanol, isopropanol, butanol, ethylene glycol, glycerol and ethyl acetate.

Further, the mass ratio of the cosolvent added in the step (3) to the sodium silicate solution is 5:1-1: 5.

The particle size of the hydrophobic white carbon black prepared by the invention is 1-5 mu m, and the hydrophobic white carbon black presents a core-shell structure, wherein the inside is solid silicon dioxide particles, and the outside is an organic layer with hydrophobicity.

At present, many methods have appeared in the research on hydrophobic silica, but the research on controlling the particle size of the silica through hydrophobic modification is very little. In the preparation process of the white carbon black, primary particles, secondary particles and tertiary particles are sequentially generated; the surface of the white carbon black contains a large amount of hydroxyl groups, the surface energy is high, and particles are mutually aggregated, so that the particle sizes of primary particles, secondary particles and tertiary particles of the white carbon black are sequentially increased.

The growth of the white carbon black particles is mainly realized by the condensation and mutual aggregation of hydroxyl groups on the surfaces of the white carbon black particles, so that the particle size and the particle size distribution of the white carbon black particles are controlled by eliminating the hydroxyl groups on the surfaces of the white carbon black particles, a hydrophobic modifier and a cosolvent are added at a proper time, then the reaction temperature is adjusted to hydrolyze the modifier, and the modifier is subjected to the co-condensation with the hydroxyl groups on the surfaces of the white carbon black particles, so that the purposes of eliminating the hydroxyl groups on the surfaces of the white carbon black particles and controlling the particle size of the white; and the hydrophobic modification of the white carbon black can be realized. The hydrophobic white carbon black prepared by the invention has the median diameter of 1-5 mu m, narrow particle size distribution (as shown in figure 3) and a core-shell structure; and the median diameter of the common white carbon black is more than 10 mu m.

In patent CN107662925A, white carbon black is prepared by a precipitation method, a binder is added after the reaction is finished, then an intermediate is obtained by filter pressing, washing and drying, the intermediate is added into a modifier solution to react for a period of time, and the hydrophobic adsorption white carbon black is obtained by filtering, washing and drying. In the production process of the white carbon black, the main energy consumption comes from the drying process, and the hydrophobic adsorption white carbon black prepared by the method needs two drying processes, so that the energy consumption is greatly increased, and the production cost is indirectly increased; the hydrophobic white carbon black prepared by the method only needs one-time drying process, and better meets the strategic requirements of national energy conservation and emission reduction. Patent CN110054914A discloses modifying with white carbon black powder, although the preparation process is simplified, the particle size of white carbon black cannot be controlled by this method. The particle size of the white carbon black is important for polymer matrixes such as silicone rubber or paint, the smaller the particle size is, the better the reinforcing effect on the polymer matrixes is, although the compatibility problem of the hydrophobic modified white carbon black can be solved to a certain extent, the white carbon black with large particle size can cause stress concentration in the polymer matrixes, so that the service life of the polymer materials is influenced.

In comparison, the method has the main characteristics of simple process and few auxiliary equipment, can directly modify the white carbon black finished product or semi-finished product by the precipitation method, is favorable for reducing the production cost of enterprises, and can also realize the control of the particle size and the particle size distribution of the white carbon black so as to realize the preparation of the narrow-distribution hydrophobic white carbon black.

Compared with the prior art, the invention has the advantages that:

1. the invention realizes the control of the particle size and the particle size distribution of the white carbon black through co-condensation, and the particle size of the prepared hydrophobic white carbon black is only 1-5 mu m and is far lower than the particle size (>10 mu m) of the common white carbon black; the smaller the particle size of the white carbon black, the narrower the particle size distribution, the larger the binding force between the white carbon black and rubber molecules, and the higher the reinforcing property of the white carbon black;

2. the hydrophobic white carbon black prepared by the method has high specific surface area and high oil absorption number (DBP); the specific surface area is as high as 231m²(iv)/g, oil absorption number 3.11; the larger the specific surface area is, the more active points on the surface of the white carbon black are, the higher the activity is; the higher the DBP value is, the more developed the spatial structure and pore structure of the white carbon black are; in the rubber mixing process, rubber molecular chains easily enter the pore structure of the white carbon black, so that the rheological property of the rubber and the dispersibility of the white carbon black in the rubber are improved, and the transparency of the rubber is further improved;

3. the hydrophobic white carbon black prepared by the invention has a core-shell structure, and the hydrophobic white carbon black is used for reinforcing a rubber material, so that the vulcanization efficiency can be improved, the vulcanization time can be shortened, the consumption of a vulcanizing agent can be reduced, and the purpose of reducing the cost can be further achieved.

Drawings

FIG. 1 is a schematic of a hydrophobic modification scheme;

FIG. 2 shows the dispersion of hydrophobic silica and silica in a water-toluene solvent mixture;

fig. 3 is a particle size distribution diagram of example 2 of the present invention and comparative example 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 singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. "optional" or "any" means that the subsequently described event or events may or may not occur, and that the description includes instances where the event occurs and instances where it does not.

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.

Furthermore, the description below of the terms "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily for the same embodiment or example. 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.