CN116120777A - A kind of preparation method of modified silica sol for water-based ink - Google Patents

Abstract

The invention belongs to the technical field of water-based ink, and in particular relates to a preparation method of a modified silica sol used for water-based ink. The method of the present invention uses a phenylsilane compound with a large steric hindrance structure and strong hydrophobicity as a modifying agent, and polymerizes after heating and hydrolysis to obtain a uniform modified silica sol. The obtained modified silica sol has high compatibility with ink emulsion (styrene-acrylic emulsion or silicon-acrylic emulsion), high concentration of modified silica sol, high addition amount, good stability, quality meets requirements, and improves ink hydrophobicity; The modification steps are simple, the raw materials are easy to obtain and the cost is low.

Description

A kind of preparation method of modified silica sol for water-based ink

technical field

The invention belongs to the technical field of water-based ink, and in particular relates to a preparation method of a modified silica sol used for water-based ink.

Background technique

The addition of nanoscale inorganic fillers can improve the performance of waterborne coatings without affecting the flexibility properties of the polymers in the emulsion. Silica nanoparticles have received special attention due to their high surface area, low production cost, and easy surface functionalization. Hybrid silica materials combine the rigidity and high thermal stability of an inorganic component with the flexibility, ductility and processability of a polymer matrix. When used in polymer coating formulations, silica nanoparticles can also add new functionality to the film through surface modification, protecting the film from water, temperature, friction, radiation and corrosion, etc.

The synthetic strategy of hybrid latex usually encapsulates inorganic nano-silica particles into monomer droplets, followed by polymerization to generate stable composite latex particles containing polymer and inorganic components. However, the method of directly incorporating inorganic nano-silica particles into the latex polymer colloid can not destroy the stability of the latex polymer colloid, and can be modified and regulated on the surface of the inorganic nano-particles. The use of monodisperse silica in hybrid polymer coatings has not been fully explored and holds great promise. Shi et al prepared an epoxy coating containing monodisperse silica as a corrosion inhibitor 8-hydroxyquinoline reservoir. Liu et al. further demonstrated the preparation of mesoporous silica coatings on graphene oxide nanosheets and their incorporation into styrene-butadiene rubber composites to enhance their thermal conductivity. Ho s sain Ri azi et al. modified silicon nanoparticles with silane coupling agents containing unsaturated carbon double bonds to increase their hydrophobicity. However, in attempts to manufacture water-based hydrophobic coatings, although hydrophilic inorganic nanofillers can be dispersed in water, due to the poor interfacial compatibility between inorganic and organic components, the mechanical stability of the ink system is poor, phase separation and precipitation occur. . Therefore, it is necessary to develop inorganic silica sols with hydrophobically modified surfaces, which can be modified to control the amphiphilicity of the particle surface to increase the affinity of silica-polymers (by promoting van der Waals forces, hydrogen bonds or ionic interactions). , to maximize the interfacial stability between silica and polymer matrix to achieve good compatibility in inks and improve ink performance.

In the prior art, there have been reports on silane-modified colloidal silica particles that can be used in ink emulsions. For example, a method for preparing silane-modified colloidal silica particles that can be used in ink emulsions includes the following steps:

1. Ion exchange of soluble silicate to produce polysilicic acid, and increase the pH to allow growth of anionic colloidal silica particles to prepare colloidal silica sol;

2. Dilute the silane compound to form a pre-mixture of silane and water, with a weight ratio of 1.5:1 to silane;

3. Silane and colloidal silica particles are mixed in a silane weight ratio ranging from 0.5 to 0.8, and the amount of silane added to the colloidal silica particles can be 1 to ² silane molecules per nm of the surface area of the silica particles;

4. Silane can be slowly added to silica colloidal silica sol at a controlled rate by vigorous stirring at a temperature of 40 to 90°C;

5. Continue mixing for 1 to 10 minutes after cessation of silane addition.

However, there are following defects in the preparation method of modified silicon dioxide in the above-mentioned prior art:

1. The steric hindrance of the modified silane group used in the preparation is small, and the modified silica sol obtained after modification has poor hydrophobicity, poor compatibility with ink emulsion (styrene-acrylic emulsion or silicon-acrylic emulsion), and is easy to Agglomeration or precipitation occurs.

2. The hydrophobic group of the modified silane used in the preparation has low hydrophobicity, and the modified silica sol obtained by grafting has poor hydrophobicity, and has poor compatibility with ink emulsion (styrene-acrylic emulsion or silicon-acrylic emulsion). Agglomeration or precipitation occurs.

4. The modified silane has self-condensation phenomenon during the modification process, and does not polymerize with the silicon hydroxyl group (Si-OH) on the surface of the silica to form a Si-O-Si bond, which makes the prepared modified silane not stable enough and prone to aggregation .

Contents of the invention

In order to solve the above-mentioned problems in the prior art, the present invention provides a preparation method of modified silica sol for water-based ink. In the present invention, a silane compound having a large steric hindrance structure and strong hydrophobicity is used as a modifying agent, and is polymerized after heating and hydrolyzing to obtain a uniform modified silica sol. The obtained modified silica sol has high compatibility with ink emulsion (styrene-acrylic emulsion or silicon-acrylic emulsion).

To achieve the above object, the present invention adopts the following technical solutions:

A preparation method for a modified silica sol of water-based ink, specifically comprising the following steps:

(1) Add silica sol in the reactor, then add modifier under stirring condition;

(2) Put the reactor in step (1) into a homogeneous reactor, and react under certain conditions to obtain a uniform solution, which is the modified silica sol.

Preferably, the modifying agent in step (1) is a phenylsilane compound with a large steric hindrance structure and strong hydrophobicity.

Preferably, the modifying agent is diphenyldiethoxysilane or trimethoxy(4-methoxyphenyl)silane.

Preferably, the modifying agent also includes: diphenyldiethoxysilane, trimethoxy [3-(anilino) propyl] silane, trimethoxy (4-methoxyphenyl) silane, (para Methylphenyl)trimethoxysilane, tert-butyldiphenylmethoxysilane, dimethoxydi-p-tolylsilane, triethoxy(1-phenylvinyl)silane, phenyltrimethoxy Silane, methylphenyldimethoxysilane, dimethylphenylmethoxysilane, etc.

Preferably, the silica sol in step (1) is neutral (pH 6.5-7.5) or alkaline silica sol (pH 8.5-10.5), and the silica particle size is 8-50 nm.

Preferably, when the modifying agent is diphenyldiethoxysilane, the silica sol is 40% silica sol, and the grafting density is 0.2-0.25 molecules/nm ² . The reaction conditions described in step (2) are: rotating reaction at 80° C. for 2 h, and then rotating reaction at 100° C. for 5 h to obtain a white homogeneous solution.

Preferably, when the modifying agent is trimethoxy(4-methoxyphenyl)silane, the silica sol is 30% silica sol, and the grafting density is 1.28 molecules/nm ² . The reaction conditions described in the step (2) are: rotate the reaction at 40° C. for 2 hours to obtain a homogeneous solution.

Beneficial effect

The invention discloses a method for preparing a modified silica sol for water-based inks. Compared with the prior art, the invention has the following beneficial effects:

1. Diphenyldiethoxysilane has large steric hindrance and strong hydrophobicity, and the obtained modified silica sol has a slightly higher viscosity, which can be compared with higher viscosity ink emulsion (styrene-acrylic emulsion or silicon-acrylic emulsion). Good compatibility; the grafted group of triphenylethoxysilane has a large steric hindrance, and the obtained modified silica sol has a slightly higher viscosity, which can be mixed with ink emulsions with higher viscosity (styrene-acrylic emulsion or silicon-acrylic emulsion) ) have better compatibility.

2. The phenyl group on the surface of the modified silica sol particle modified by diphenyldiethoxysilane has the same structure as the phenyl group in the ink emulsion (styrene-acrylic emulsion or silicon-acrylic emulsion). According to the principle of similar miscibility, The modified silica sol has better compatibility; the modified silica sol particle surface obtained by trimethoxyl (4-methoxyphenyl) silane modification contains oxygen (O) and ink emulsion (styrene-acrylic emulsion or silicon The hydroxyl groups in the acrylic emulsion) and a large number of hydroxyl groups in the silica sol can form hydrogen bonds, so that the modified silica sol has better compatibility in the ink emulsion.

3. Modified silica sol has high concentration, high addition amount, good stability, and the quality meets the requirements.

4. The modification step is simple and the raw material cost is low.

Description of drawings

Figure 1: Photo of film-forming sample of ink emulsion without adding silica sol;

Figure 2: Photo of ink emulsion film-forming sample with modified silica sol added at 26%;

Figure 3: Photo of film-forming sample of ink emulsion with modified silica sol added at 30%.

Detailed ways

Hereinafter, the present invention will be described in detail. Before proceeding with the description, it should be understood that the terms used in this specification and appended claims should not be construed as limited to ordinary and dictionary meanings, but should be best interpreted while allowing the inventor to properly define the terms On the basis of the principles of the present invention, explanations are made based on meanings and concepts corresponding to the technical aspects of the present invention. Accordingly, the descriptions set forth herein are preferred examples for illustrative purposes only, and are not intended to limit the scope of the invention, so that it should be understood that other, etc. price or improvement.

The following examples are only listed as examples of embodiments of the present invention, and do not constitute any limitation to the present invention. Those skilled in the art can understand that modifications within the scope of not departing from the essence and design of the present invention all fall into the protection of the present invention. scope. Unless otherwise specified, the reagents and instruments used in the following examples are all commercially available products.

Example 1

A preparation method for a modified silica sol of water-based ink, specifically comprising the following steps:

1. Add 25.25g (168mmol) 40% silica sol to the reactor, then add 0.133g (0.489mmol) diphenyldiethoxysilane while stirring, the grafting density is ¹ molecule/4-5nm .

2. Put the reactor into a homogeneous reactor, rotate at 80°C for 2 hours, and then rotate at 100°C for 5 hours to obtain a white uniform solution, which is the modified silica sol.

Experimental example 1

In order to verify the compatibility of the modified silica sol gained in Example 1 with the water-based ink, the following experiments are now carried out:

Add 0.5 mL of the modified silica sol obtained in Example 1 to 0.5 mL of ink emulsion (styrene-acrylic emulsion) at one time, with a silicon dioxide content of about 20%, and sonicate for 10 minutes to obtain a uniform solution without precipitation.

Add 0.334 mL of the modified silica sol obtained in Example 1 to 0.5 mL ink emulsion (silicon acrylic emulsion) at one time, with a silicon dioxide content of about 16%, and sonicate for 10 minutes to obtain a uniform solution without precipitation.

Add 0.215 mL of the modified silica sol obtained in Example 1 to 0.5 mL ink emulsion (silicon acrylic emulsion) at one time, with a silicon dioxide content of about 16%, and sonicate for 10 minutes to obtain a uniform solution without precipitation.

Add 0.125 mL of the modified silica sol obtained in Example 1 to 0.5 mL of ink emulsion (silicon acrylic emulsion) at one time, with a silicon dioxide content of about 16%, and sonicate for 10 minutes to obtain a uniform solution without precipitation.

Above-mentioned experimental result shows, the steric hindrance of diphenyldiethoxysilane is big, and hydrophobicity is strong, and the viscosity of the modified silica sol that obtains is slightly higher, can be mixed with the higher ink emulsion (styrene-acrylic emulsion or silicon-acrylic emulsion) of viscosity. ) has better compatibility; the phenyl group on the surface of the modified silica sol particle obtained by diphenyldiethoxysilane modification is consistent with the phenyl group structure in the ink emulsion (styrene-acrylic emulsion or silicon-acrylic emulsion), According to the principle of similar miscibility, the modified silica sol has better compatibility.

Example 2

A preparation method for a modified silica sol of water-based ink, specifically comprising the following steps:

1. Add 5.05g (25.25mmol) 30% silica sol in the reactor, then add 0.1666g (0.706mmol) trimethoxyl (4-methoxyphenyl) silane in stirring, grafting density is 1.28 molecule/nm ² .

2. Put the reactor into a homogeneous reactor, rotate and react at 40° C. for 2 hours to obtain a uniform solution, which is the modified silica sol.

Experimental example 2

In order to verify the compatibility of the modified silica sol obtained in Example 2 with the water-based ink, the following experiments are now carried out:

Add 0.130mL of the modified silica sol obtained in Example 2 to 0.5mL ink emulsion (styrene-acrylic emulsion) at one time. The mass ratio of the modified silica sol is 22%, and the silica content is about 7.8%. Ultrasound for 10min, A homogeneous solution without precipitation was obtained.

Add 0.110mL of the modified silica sol obtained in Example 2 to 0.5mL ink emulsion (silicon acrylic emulsion) at one time, the mass ratio of the modified silica sol is 22%, the silica content is about 6.6%, and ultrasonic 10min, A homogeneous solution without precipitation was obtained.

Above-mentioned experimental result shows, the grafting group steric hindrance of trimethoxy (4-methoxyphenyl) silane is big, the viscosity of the modified silica sol that obtains is slightly high, can be mixed with the higher ink emulsion (styrene-acrylic emulsion) of viscosity Or silicone acrylic emulsion) have better compatibility. The group on the surface of the modified silica sol particle obtained by trimethoxyl (4-methoxyphenyl) silane modification contains oxygen (O) and the hydroxyl group in the ink emulsion (styrene-acrylic emulsion or silicon-acrylic emulsion), and in the silica sol A large number of hydroxyl groups can form hydrogen bonds, making the modified silica sol have better compatibility in the ink emulsion.

Experimental example 3

(1) Compatibility test between diphenyldiethoxysilane modified silica sol and ink:

Add x uL diphenyldiethoxysilane modified silica sol to 0.5mL ink emulsion at one time, and ultrasonicate for 10min. The compatibility test data are shown in Table 1 below.

Table 1. Compatibility test data of diphenyldiethoxysilane modified silica sol and ink

(2) Trimethoxy (4-methoxyphenyl) silane modified silica sol and ink compatibility test:

Add x uL modified silica sol to 0.5mL ink emulsion at one time, ultrasonic for 10min, the compatibility test data are shown in Table 2 below.

Table 2. Trimethoxy (4-methoxyphenyl) silane modified sol and ink compatibility test data

(3) Ink film formation test:

Prepare a 10um ink film on a plastic substrate with a four-sided preparer, and heat at 90°C for 1-2min. Use a dyne pen to test on the surface of the film to obtain the dyne value.

The film-forming sample of the ink emulsion without adding silica sol is shown in Figure 1. The surface is smooth and transparent, with a small amount of particles precipitated, and the dyne value is 30.

The film-forming sample of the ink emulsion with an addition amount of 26% of trimethoxy (4-methoxyphenyl) silane-modified silica sol is shown in Figure 2, the surface is smooth and transparent, and the dyne value is 33.

The film-forming sample of ink emulsion with 30% addition of trimethoxy (4-methoxyphenyl) silane modified silica sol is shown in Figure 3, the surface is smooth and transparent, and the dyne value is 36.

After adding the modified silica sol, the dyne value of the ink is significantly increased, and the higher the value, the higher the surface energy of the film surface and the higher the hydrophobicity. The higher the addition amount, the higher the dyne value, indicating that the addition of hydrophobically modified silica to the ink improves the hydrophobicity of the ink film, and there is a linear relationship between the amount of modified silica sol and the hydrophobicity of the film surface within a certain range .

The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art can still understand the foregoing embodiments. Modifications are made to the technical solutions described, or equivalent replacements are made to some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions claimed in the present invention.

Claims (7)

1. The preparation method of the modified silica sol for the water-based ink is characterized by comprising the following steps of:

(1) Adding silica sol into a reactor, and adding a modifier under stirring;

(2) Placing the reactor in the step (1) into a homogeneous reactor, and reacting under certain conditions to obtain a uniform solution, namely the modified silica sol;

the modifier is a silane compound with a large steric hindrance structure and strong hydrophobicity.

2. The method for preparing a modified silica sol for aqueous ink according to claim 1, wherein the modifier is a phenylsilane compound.

3. The method for preparing a modified silica sol for aqueous ink according to claim 2, wherein the modifier phenylsilane compound comprises: one or more of diphenyldiethoxysilane, trimethoxy [3- (anilinopropyl) silane, trimethoxy (4-methoxyphenyl) silane, (p-methylphenyl) trimethoxysilane, t-butyldiphenylmethoxysilane, dimethoxydi-p-tolylsilane, triethoxy (1-phenylvinyl) silane, phenyltrimethoxysilane, methylphenyldimethoxysilane, dimethylphenylmethoxysilane.

4. The method for producing a modified silica sol for aqueous ink according to claim 1, wherein the silica sol in step (1) is neutral (pH value of 6.5 to 7.5) or alkaline silica sol (pH of 8.5 to 10.5), and the silica particle diameter is 8 to 50nm.

5. The method for preparing a modified silica sol for water-based ink according to claim 2, wherein the modifier is a phenylsilane compound, the silica sol is 30-40% silica sol, and the grafting density is 0.2-1.8 molecules/nm ² 。

6. The method for preparing modified silica sol for water-based ink according to claim 2, wherein the modifier is phenylsilane compound, the silica sol is 30-40% silica sol, and the addition amount of the modifier is 0.5% -5%.

7. The method for producing a modified silica sol for aqueous ink according to claim 5, wherein the reaction conditions in step (2) are: the reaction was carried out at 40-90℃for 2 hours and then at 5 hours to give a white homogeneous solution.

Images