CN102030873A - Method for preparing nano silicon/polyacrylate composite emulsion - Google Patents

Abstract

The invention discloses a preparation method of nano silicon dioxide/polyacrylate composite emulsion. Add hydrochloric acid solution and emulsifier to deionized water, mix with ethyl orthosilicate, silane coupling agent and acrylate monomer, and pre-emulsify to obtain a modified nano-silica pre-emulsion; then raise the temperature and add the initiator , using the combination of in-situ emulsion polymerization and seed emulsion polymerization to prepare nano-silica/polyacrylate composite emulsion. This method is simple in process, avoids the problem of "secondary agglomeration" that occurs in the process of emulsion polymerization of traditional nano-silica, and effectively ensures the smooth progress of the polymerization reaction. The prepared nano-silica/polyacrylate composite emulsion has Good stability, excellent heat resistance of the coating film.

Description

A kind of preparation method of nano silicon dioxide/polyacrylate composite emulsion

technical field

The invention relates to a polyacrylate composite emulsion, in particular to a preparation method of a nano silicon dioxide/polyacrylate composite emulsion.

technical background

Organic/inorganic nanocomposite emulsions emerged in the late 1980s. It not only combines the excellent film-forming properties, transparency, flexibility, and ease of processing of polymer materials, but also the good wear resistance, high hardness, and Scratch resistance, UV resistance, etc., but also has the characteristics of non-toxic environmental protection, mild reaction conditions, etc., and has become a hot spot in current research.

Polyacrylate emulsion has excellent gloss retention, color retention, and weather resistance. It is a matrix resin widely used in coatings, adhesives, and fabric finishing agents. However, it has low hardness, poor abrasion resistance, and solvent resistance. Insufficient performance and other shortcomings limit its further application. Due to its wide range of sources, low price, and the excellent reinforcing effect of nanoparticles, nano-silica has been compounded with polyacrylate emulsions to improve the performance of the emulsion.

At present, with the development of emulsion polymerization technology, the preparation method of nano-silica/polyacrylate composite emulsion has developed from the traditional physical blending method to the direction of in-situ emulsion polymerization. For example, Chinese invention patent CN 1908022A (application number: 200610037040.9) discloses the preparation of nano silicon dioxide in ethanol using tetraethyl orthosilicate, and uses silane coupling agent to its surface modification, and then the prepared surface modified Silica was redispersed into acrylate monomer for in-situ emulsion polymerization to obtain nano-silica modified acrylate emulsion. Zhu et al. dispersed fumed silica in toluene, modified its surface with a silane coupling agent, redispersed the obtained modified silica into water, and added acrylate monomers for in-situ emulsion polymerization to obtain excellent properties. Nano silica/polyacrylate composite emulsion (Zhu A., Cai A., Yu Z., et al.Film characterization of poly(styrene-butylacrylate-acrylate)-silica nanocomposite[J].Journal of Colliod and Interface Science, 2008, 322(1): 51-58). The in-situ emulsion polymerization method can disperse the surface-modified nano-silica in the polymer more uniformly, and improve its physical and mechanical properties to a certain extent. However, the process of preparing nano-silica/polyacrylate composite emulsion by this method is relatively complicated, and the modified nano-silica is prone to secondary agglomeration during the preparation and dispersion process, thus affecting the reaction stability of emulsion polymerization.

Contents of the invention

The purpose of the present invention is to overcome the disadvantages of complex process and easy agglomeration of nano-silica in the preparation of nano-silica/polyacrylate composite emulsion by in-situ emulsion polymerization, and provide a method that avoids the problem of agglomeration of nano-silica. The polymerization process is stable, and the preparation method of the nano silicon dioxide/polyacrylate composite emulsion is simple in the preparation process.

In the present invention, in the pre-emulsion formed by the acrylate monomer and the emulsifier, tetraethyl orthosilicate and the silane coupling agent are hydrolyzed and condensed under the catalysis of hydrochloric acid to directly obtain a stable modified nano-silica pre-emulsion, and then The pre-emulsion was heated up and an initiator was added, and the nano-silica/polyacrylate composite emulsion was prepared by combining in-situ emulsion polymerization and seed emulsion polymerization.

The purpose of the present invention is achieved through the following technical solutions:

A preparation method of nano silicon dioxide/polyacrylate composite emulsion, comprising the following steps:

(1) At room temperature, add 0.01-0.03 parts of hydrochloric acid solution and 0.6-3.15 parts of emulsifier into 10-50 parts of deionized water, and mix with 1.5-10 parts of ethyl orthosilicate, 0.1-1 parts of silane coupling agent Mix with 5-50 parts of acrylate monomer, pre-emulsify for 10-15 minutes, then stir and react for 8-24 hours to obtain a modified nano-silica pre-emulsion;

(2) At a temperature of 65-75°C, add the modified nano-silica pre-emulsion dropwise to 10-50 parts of deionized water, add 0.05-0.3 parts of the aqueous solution of the initiator, keep the reaction for 20-40 minutes, add 0.35-2.9 parts of emulsifier, 5-50 parts of acrylate monomer and 10-50 parts of deionized water, and pre-emulsify for 5-10 minutes to obtain acrylate pre-emulsion, which is composed of 0.05-0.3 parts of initiator and 5-10 parts of deionized water. The aqueous solution made of ionized water is added dropwise to the acrylate pre-emulsion, the temperature is continued to rise to 80-90°C, and the temperature is kept for 1.0-2.5h, and the temperature is lowered to room temperature to obtain a nano-silica/polyacrylate composite emulsion;

Described silane coupling agent is γ-methacryloxypropyltrimethoxysilane (KH-570), vinyltrimethoxysilane (A-171) or vinyltriethoxysilane (A- 151);

Described emulsifier is sodium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium allyloxy hydroxypropyl sulfonate, allyloxy nonylphenol ether, alkylphenol polyoxyethylene ether and One or two kinds of fatty alcohol polyoxyethylene ethers;

Described initiator is potassium persulfate or ammonium persulfate;

The acrylate monomer is methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate , one or more of methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate and acrylic acid.

To further realize the purpose of the present invention, the mass concentration of the hydrochloric acid solution is preferably 36-38%.

The modified nano-silica pre-emulsion is preferably added dropwise to 10-50 parts of deionized water at a rate of 0.4-0.6 g/min.

The aqueous solution composed of 0.05-0.3 parts of initiator and 5-10 parts of deionized water is preferably added dropwise to the acrylate pre-emulsion at a rate of 0.06-0.12 g/min.

The acrylate monomer is preferably methyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, hydroxypropyl methacrylate, methacrylic acid, butyl acrylate, hydroxypropyl acrylate esters and/or acrylics.

Compared with prior art, the present invention has following advantage:

(1) The modified nano-silica dispersion is prepared by the sol-gel method in the acrylate pre-emulsion, which has good dispersibility and can be directly applied to in-situ polymerization, which simplifies the process and avoids the modification of nano The problem of "secondary agglomeration" occurs during the preparation and application of silica.

(2) The combination of in-situ emulsion polymerization and seed emulsion polymerization ensures the smooth progress of the polymerization process. Polyacrylate can successfully coat nano-silica, and the prepared nano-silica/polyacrylate composite emulsion It has good stability, and its coating film has excellent heat resistance.

Description of drawings

Fig. 1 is the total reflection infrared spectrogram of the nano-silica/polyacrylate composite latex film.

Fig. 2 is the transmission electron micrograph of pure acrylic latex particle (a) and nano-silica/polyacrylate composite latex particle (b), wherein the content of nano-silica in the composite latex particle is 4%.

Fig. 3 is the thermogravimetric analysis figure of pure acrylic emulsion coating film (a) and nano silicon dioxide/polyacrylate composite emulsion coating film (b), wherein the content of nano silicon dioxide in the composite emulsion is 4%.

specific implementation plan

The present invention will be further described below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

Example 1

Add 2.0g allyloxy nonylphenol propanol polyoxyethylene ether ammonium sulfate (DNS-86) and 0.013g concentrated hydrochloric acid (mass concentration 36%) into 25g deionized water, and mix with 10g butyl acrylate, 10g formazan The mixed solution of methyl acrylate, 5.5g tetraethyl orthosilicate and 0.5g KH-570 was pre-emulsified for 10min, and stirred on a magnetic stirrer for 12h to prepare a modified nano-silica pre-emulsion.

At a temperature of 75° C., the modified nano-silica emulsion was added dropwise to 35 g of deionized water within 1.5 h, and 10 g of an aqueous solution of potassium persulfate with a weight concentration of 1.5% was added and kept for 30 min.

At the same time, pre-emulsify 0.4g DNS-86, 10g butyl acrylate, 10g methyl methacrylate, 1.6g acrylic acid and 20g deionized water for 5min to prepare acrylate pre-emulsion, and then add acrylate dropwise within 2h The pre-emulsion and 15 g of a 1% potassium persulfate aqueous solution. After dropping, the temperature was raised to 80°C, and the reaction was kept for 2 hours.

Finally, the temperature was lowered to room temperature to obtain a nano-silica/polyacrylate composite emulsion.

Fig. 1 is the total reflection infrared spectrogram of the composite latex film of the present embodiment. In Fig. 1, 2958cm ^-1 is the stretching vibration absorption peak of CH bond, 1733cm ^-1 is the stretching vibration peak of carbonyl group, 1166cm ^-1 is the asymmetric stretching vibration absorption peak of COC, and 1070cm ^-1 and 809cm ^-1 It is the stretching vibration peak of the Si-O-Si bond, indicating that the acrylate monomer is grafted onto the nano-silicon dioxide by in-situ polymerization on the surface of the nano-silicon dioxide. The preparation of pure acrylic emulsion follows the formula and process of Example 1, the difference is that tetraethyl orthosilicate and KH-570 are not added in the formula.

Fig. 2 is the transmission electron microscope photo of this example and pure polyacrylate latex particles, comparing a and b in Fig. 2, it can be found that the composite latex particles prepared by the present invention are polyacrylate-coated nano-silica core-shell structures. The transmission electron micrographs of the polyacrylate latex particles in the following examples are similar to those shown in FIG. 2 . Fig. 3 is the thermogravimetric analysis curve of this example and pure polyacrylate latex film. It can be seen from Figure 3 that the maximum thermal weight loss rate temperature of the pure polyacrylate latex film is 407 ° C, while the maximum thermal weight loss rate temperature of the composite latex film is 417 ° C, an increase of 10 ° C. It can be seen that the coating film of the composite emulsion prepared by the present invention is improved in heat resistance. The thermogravimetric analysis curves of the following examples are basically similar to those of this example, and are not listed one by one.

Example 2

Add 1.3g DNS-86 and 0.01g concentrated hydrochloric acid (mass concentration 36%) into 25g deionized water, and mix with 2-ethylhexyl methacrylate, 5g methyl acrylate, 1.5g ethyl orthosilicate Pre-emulsify the mixed solution with 0.1g KH-570 for 10 minutes, and stir on a magnetic stirrer for 8 hours to prepare a modified nano-silica pre-emulsion. At 75° C., the modified nano-silica emulsion was added dropwise to 35 g of deionized water within 1 h, and 5 g of an aqueous solution of potassium persulfate with a weight concentration of 1% was added and kept for 20 min. At the same time, pre-emulsify 0.2g DNS-86, 10g butyl acrylate, 10g methyl methacrylate, 0.6g acrylic acid and 20g deionized water for 5min to prepare acrylate pre-emulsion, and then add acrylate dropwise within 2h Pre-emulsion and 5 g of 1% potassium persulfate aqueous solution. After the dropwise addition, the temperature was raised to 80° C., and the reaction was kept for 2 hours. Finally, the temperature was lowered to room temperature to obtain a nano-silica/polyacrylate composite emulsion.

Example 3

Add 1.5g DNS-86, 0.8g allyloxy nonylphenol propanol polyoxyethylene (ANPEO ₁₀ ) and 0.03g concentrated hydrochloric acid (mass concentration 36%) into 30g deionized water, and mix with 15g butyl acrylate, The mixed solution of 10g tetraethyl orthosilicate and 1gA-171 was pre-emulsified for 15min, and stirred on a magnetic stirrer for 24h to prepare a modified nano-silica pre-emulsion. At 70° C., the modified nano-silica emulsion was added dropwise to 35 g of deionized water within 1.5 h, and 10 g of an aqueous solution of potassium persulfate with a weight concentration of 1.5% was added and kept for 40 min. At the same time, 0.4g DNS-86, 0.2g ANPEO ₁₀ , 7.5g butyl acrylate, 7.5g methyl methacrylate, 0.5g methacrylic acid, 0.5g hydroxyethyl acrylate and 15g deionized water were pre-emulsified for 5min to prepare The acrylate pre-emulsion was obtained, and then the acrylate pre-emulsion and 15 g of an aqueous potassium persulfate solution with a mass concentration of 1% were added dropwise within 1.5 hours. After the dropwise addition, the temperature was raised to 85° C., and the reaction was kept for 2.5 hours. Finally, the temperature was lowered to room temperature to obtain a nano-silica/polyacrylate composite emulsion.

Example 4

Add 1.5g sodium lauryl sulfate, 0.8g nonylphenol polyoxyethylene ether and 0.01g concentrated hydrochloric acid (mass concentration 38%) into 25g deionized water, and mix with 20g butyl acrylate, 10g methyl acrylate, The mixed solution of 3g tetraethyl orthosilicate and 0.3g A-151 was pre-emulsified for 15 minutes, and stirred on a magnetic stirrer for 24 hours to prepare a modified nano-silica pre-emulsion. At 75° C., the modified nano-silica emulsion was added dropwise to 35 g of deionized water within 1.5 h, and 10 g of an aqueous solution of potassium persulfate with a weight concentration of 1.5% was added and kept for 30 min. At the same time, pre-emulsify 0.4g sodium lauryl sulfate, 0.2g nonylphenol polyoxyethylene ether, 20g butyl acrylate, 10g methyl methacrylate, 1.6g acrylic acid and 20g deionized water for 10min to prepare acrylic acid ester pre-emulsion, and then dropwise added the acrylate pre-emulsion and 15 g of 1% potassium persulfate aqueous solution within 2 hours. After the dropwise addition, the temperature was raised to 85° C., and the reaction was kept for 2.5 hours. Finally, the temperature was lowered to room temperature to obtain a nano-silica/polyacrylate composite emulsion.

Example 5

Add 2.5g of 3-allyloxy-2-hydroxyl-1-propanesulfonate sodium and 0.01g of concentrated hydrochloric acid (mass concentration 36%) into 20g of deionized water, and mix with 15g of butyl methacrylate, 5.5g of n- The mixture of ethyl silicate and 0.5g KH-570 was pre-emulsified for 15 minutes, and stirred on a magnetic stirrer for 12 hours to prepare a modified nano-silica pre-emulsion. At 75° C., the modified nano-silica emulsion was added dropwise to 35 g of deionized water within 1 h, and 10 g of an aqueous potassium persulfate solution with a weight concentration of 1.5% was added, and then kept for 20 min. At the same time, 0.5g sodium 3-allyloxy-2-hydroxyl-1-propanesulfonate, 20g butyl acrylate, 20g 2-ethylhexyl acrylate, 8g methyl methacrylate, 1g acrylic acid, 1g methyl Hydroxypropyl acrylate and 30 g of deionized water were pre-emulsified for 10 min to prepare an acrylate pre-emulsion, and then the acrylate pre-emulsion and 15 g of a 1% potassium persulfate aqueous solution were added dropwise within 2.5 h. After the dropwise addition, the temperature was raised to 80° C., and the reaction was kept for 2.5 hours. Finally, the temperature was lowered to room temperature to obtain a nano-silica/polyacrylate composite emulsion.

Claims (5)

1. a preparation method of nano silicon dioxide/polyacrylate composite emulsion, is characterized in that comprising the following steps: (1) At room temperature, add 0.01-0.03 parts of hydrochloric acid solution and 0.6-3.15 parts of emulsifier into 10-50 parts of deionized water, and mix with 1.5-10 parts of ethyl orthosilicate, 0.1-1 parts of silane coupling agent Mix with 5-50 parts of acrylate monomer, pre-emulsify for 10-15 minutes, then stir and react for 8-24 hours to obtain a modified nano-silica pre-emulsion; (2) At a temperature of 65-75°C, add the modified nano-silica pre-emulsion dropwise to 10-50 parts of deionized water, add 0.05-0.3 parts of the aqueous solution of the initiator, keep the reaction for 20-40 minutes, add 0.35-2.9 parts of emulsifier, 5-50 parts of acrylate monomer and 10-50 parts of deionized water, and pre-emulsify for 5-10 minutes to obtain acrylate pre-emulsion, which is composed of 0.05-0.3 parts of initiator and 5-10 parts of deionized water. The aqueous solution made of ionized water is added dropwise to the acrylate pre-emulsion, the temperature is continued to rise to 80-90°C, and the temperature is kept for 1.0-2.5h, and the temperature is lowered to room temperature to obtain a nano-silica/polyacrylate composite emulsion; The silane coupling agent is γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane or vinyltriethoxysilane; Described emulsifier is sodium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium allyloxy hydroxypropyl sulfonate, allyloxy nonylphenol ether, alkylphenol polyoxyethylene ether and One or two kinds of fatty alcohol polyoxyethylene ethers; Described initiator is potassium persulfate or ammonium persulfate; The acrylate monomer is methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate , one or more of methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate and acrylic acid. 2. The preparation method of the nano-silica/polyacrylate composite emulsion according to claim 1, characterized in that: the mass concentration of the hydrochloric acid solution is 36-38%. 3. the preparation method of nano-silica/polyacrylate composite emulsion according to claim 1, is characterized in that: described modified nano-silica pre-emulsion is added drop-wise at the speed of 0.4-0.6g/min 10-50 parts deionized water. 4. the preparation method of nano-silica/polyacrylate composite emulsion according to claim 1 is characterized in that: the aqueous solution that described is made by 0.05-0.3 part initiator and 5-10 part deionized water is made from Add dropwise to the acrylate pre-emulsion at a speed of 0.06-0.12g/min. 5. the preparation method of nano silicon dioxide/polyacrylate composite emulsion according to claim 1 is characterized in that: described acrylate monomer is methyl methacrylate, butyl methacrylate, methacrylic acid - 2-Ethylhexyl, hydroxypropyl methacrylate, methacrylic acid, butyl acrylate, hydroxypropyl acrylate and/or acrylic acid.

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