CN1298745C - Method for preparing hollow microspheres self film-formed in latex of low soap system - Google Patents

Abstract

The invention discloses a method for preparing hollow microspheres in a low-soap system in which an emulsion can self-form a film, and belongs to the emulsion paint technology. The method process includes: first preparing polyacrylate seed emulsion and carboxyl-containing polyacrylate core latex particles in a low-soap system, and then using styrene/acrylonitrile and other monomers to polymerize on the core latex particles to obtain a coating The styrene-acrylic polymer latex particles with the middle layer are coated with acrylate and styrene copolymers with good film-forming properties on the outermost layer, and finally treated with alkali to obtain good monodispersity in particle size, regular hollow structure, and Styrene-acrylic polymer microspheres with a certain strength and emulsion self-forming film. The advantage of the present invention is that the process of nucleation and growth of latex particles is effectively controlled by using the low-soap emulsion polymerization technology combined with the starvation feeding method, so as to obtain a hollow styrene-acrylic polymer with certain strength and self-film-forming emulsion. object microspheres. The particle size of the hollow styrene-acrylic polymer microsphere can reach more than 1000nm.

Description

Preparation method of hollow microspheres capable of self-forming film in emulsion in low-soap system

Technical field

The invention relates to a method for preparing hollow microspheres in a low-soap system in which an emulsion can self-form a film, and belongs to the emulsion coating technology.

Background technique

People such as Charles J.McDonalds (Hollow latex particles: synthesis and applications) adopt alkali osmotic swelling method to make submicron hollow latex particles, and this method prepares porous latex particles and has following defects: (a) emulsifier consumption is relatively large, Not only uneconomical but also the post-treatment of emulsifier is more difficult; (b) each step is a one-time feeding, and the prepared latex particles have a smaller particle size and uneven distribution; (c) the latex particles have a simple structure and a narrower range of applications. Therefore, we propose a method for preparing hollow styrene-acrylic polymer microspheres with good monodispersity, large particle size, certain strength and self-film-forming emulsion by using low-soap technology.

Contents of Invention

The object of the present invention is to provide a method for preparing hollow microspheres in which the emulsion can form a film in a low-soap system. The hollow latex particles obtained by the method have obvious hollow shape, good particle size monodispersity, and high interlayer strength. The outer layer is easy to form a film. It can be widely used in various fields such as coatings, papermaking, and cosmetics.

The present invention is realized through the following technical scheme, that is, a method for preparing monodisperse large-diameter hollow styrene-acrylic polymer microspheres in a low-soap system. Its characteristics include the following processes:

(1) solid content mass ratio is the preparation of 1.0～10% seed emulsion: will account for the emulsifier sodium dodecylbenzene sulfonate of 0.2～1% of monomer gross mass and join in the reactor together with deionized water, in Heat up to 60-80°C under stirring, then add one or two kinds of acrylate monomers and methacrylic acid or acrylic acid in a mass ratio of (95-100):(5-10) to obtain a monomer mixture, Continue to stir for 0-0.5h, then add a solution made up of 5-10% initiator ammonium persulfate accounting for the total mass of the monomer, keep it warm at 60-80°C for 1-4h, and make the solid content mass ratio 1.0-10% seed emulsion.

(2) The preparation of the carboxylated core emulsion with a solid content mass ratio of 7.0 to 15%: add deionized water to the seed emulsion prepared in step (1) at 60 to 80°C for dilution, heat while stirring, and then add dropwise One or two kinds of acrylate monomers and methacrylic acid or acrylic acid and divinylbenzene or ethylene glycol dimethacrylate according to (50-100): (5-50): (2-5) mass ratio The mixed solution is added dropwise with an aqueous solution prepared by emulsifier sodium dodecylbenzenesulfonate of 0.2-1% of the total mass of monomers in this step and initiator ammonium persulfate of 0.3-3%. The dropping time is 2-10 hours, and after the dropping of all the raw materials is completed, the reaction is kept for 2-4 hours to prepare a carboxyl-bearing nuclear emulsion with a solid content mass ratio of 7.0-15%.

(3) Preparation of polymer latex particles coated with an intermediate layer with a solid content mass ratio of 20 to 50%: at 60 to 80°C, add acrylates dropwise at a constant speed to the carboxyl core emulsion prepared in step (2) The mixture of monomer or styrene and divinylbenzene or ethylene glycol dimethacrylate in a mass ratio of (95-100): (0-5) is added dropwise at the same time, accounting for 0.2-5% of the total mass of monomers in this step. An aqueous solution of 1% sodium dodecylbenzenesulfonate and 0.3-3% ammonium persulfate. The dropping time is 2-10 hours. After the dropping of all the raw materials is completed, the reaction is kept for 2-4 hours to prepare the polymer latex particles coated with the middle layer with a solid content mass ratio of 20-50%.

(4) Preparation of a shell polymer with a solid content mass ratio of 20 to 50%: at 60 to 80°C, add acrylate monomers and styrene dropwise at a constant speed to the polymer emulsion prepared in step (3). According to (50～90):(10～50) mass ratio mixed solution, add dropwise the sodium dodecylbenzenesulfonate and 0.3～3% ammonium persulfate that account for the total monomer mass of this step 0.2～1% simultaneously into an aqueous solution. The dropping time is 2-10 hours, and after the dropping of all the raw materials is completed, the heat preservation reaction is carried out for 2-4 hours to prepare a core-shell emulsion with a solid content mass ratio of 20-50%.

(5) Alkali treatment: adjust the initial pH value of the core-shell emulsion obtained in step (4) to 7-13 with a sodium hydroxide solution with a concentration of 5-20%, and then neutralize and swell at a temperature of 90-120°C 1 to 5 hours to obtain hollow latex particles.

The advantages of the present invention are: using the low-soap emulsion polymerization technology, the seed polymerization is carried out in a micelle-free state, and through four polymerization stages, a starvation feeding method is adopted in the polymerization process to obtain large particle size and monodisperse particle size It is a hollow styrene-acrylic polymer emulsion with good resistance, regular hollow structure, certain strength and self-forming film. The synthesized hollow styrene-acrylic polymer microspheres can be widely used in high-performance coatings, papermaking, damping and sound-absorbing materials and other application fields.

Description of drawings

Figure 1 is an electron micrograph of the hollow microspheres prepared in Example 1. Figure 2 is an electron micrograph of the hollow microspheres prepared in Example 2. Figure 3 is an electron micrograph of the hollow microspheres prepared in Example 3. Figure 4 is an electron micrograph of the hollow microspheres prepared in Example 4.

Detailed ways

Example 1

(1) Preparation of seed emulsion 0.063g emulsifier sodium dodecylbenzene sulfonate and 485g deionized water are disposablely added in the reactor with thermometer, condenser, agitator and feeding device, until the temperature rises to Continue stirring for 0.5h after 80°C; then add 5.5g methyl methacrylate, 6.5g butyl acrylate, 0.56g methacrylic acid at one time, and stir for 0.5h; add 1.0g ammonium persulfate and 15g deionized water at one time to prepare The resulting aqueous solution was reacted for 2.0 hours to obtain the seed emulsion, which was lowered to room temperature and taken out for later use.

(2) Preparation of nuclear emulsion Add 25g of seed emulsion and 100g of deionized water to the same reactor as above, and heat up while stirring; simultaneously weigh 12g of methyl methacrylate, 5g of methacrylic acid, and 0.08g of divinylbenzene . To make monomer mixture, take 0.14g of ammonium persulfate, 0.024g of sodium dodecylbenzenesulfonate and 15g of deionized water to make an aqueous solution. After the temperature in the reactor rose to 80°C, the monomer mixture, initiator and emulsifier aqueous solution were added dropwise at the same time. The monomer mixture is added dropwise for 6 hours, and the aqueous solution of the initiator and emulsifier is added dropwise for 6.5 hours. After all the raw materials are fed, keep the temperature for 0.5 hours, then cool down and discharge.

(3) Preparation of core-shell latex particles Weigh 80g of the above-mentioned core emulsion into the same reactor, add 25g of deionized water, heat up while stirring, and weigh 50g of styrene, 18g of acrylonitrile, 0.7g of divinyl Benzene is made into a monomer mixture, and 0.54 g of ammonium persulfate, 0.13 g of sodium dodecylbenzenesulfonate and 20 g of deionized water are taken to make an aqueous solution. When the temperature rises to 75°C, the monomer mixture, initiator and emulsifier aqueous solution are added dropwise. The feeding time of the monomer mixture is 3 hours, and the feeding time of the aqueous solution of the initiator and emulsifier is 3.5 hours. After all the raw materials are fed, the temperature is kept for 0.5 hours, and the temperature is discharged.

(4) Alkali treatment Weigh 100g of the prepared core-shell emulsion into a reactor with a stirring device and a reflux condenser, adjust the pH value of the emulsion to 9 with a pre-prepared 20% sodium hydroxide solution, and raise the temperature to 100 ℃, keep it warm for 2.5 hours under stirring, and cool down to obtain hollow latex particles containing water inside.

(5) Electron microscope test Dilute the above emulsion to a solid content of about 15%, then add 25 drops of the diluted polymer emulsion to 10ml of distilled water, and ultrasonically disperse for 10 minutes with a KQ-100DB numerically controlled ultrasonic disperser. Take the emulsion sample and drop it on a small copper grid dedicated to a transmission electron microscope with a supporting film, and then add 1 to 2 drops of ruthenium tetroxide aqueous solution with a mass percentage concentration of 2% on the small copper grid coated with the emulsion. Dry under light irradiation, and then use a Hitachi H-800 transmission electron microscope to take pictures of the samples under the condition of accelerating voltage 80kV. Electron micrographs are shown in Figure 1. It can be seen from the figure that the particle size of latex particles prepared by this method is about 1000nm, and the particle size has good monodispersity and the hollow structure is regular.

(6) Self-film-forming test Place a circular (d=8cm) glass mold on a horizontal plate, pour a certain amount of the above-mentioned latex with a thickness of about 1mm, and let it dry naturally at room temperature for 24 hours. Finally, a white powder is obtained, and a continuous smooth film cannot be formed

Example 2

(1) The preparation of seed emulsion is the same as the example 1 method.

(2) Preparation of nuclear emulsion Add 20g of seed emulsion and 80g of deionized water to the same reactor as above, and heat up while stirring; simultaneously weigh 10g of methyl methacrylate, 4g of methacrylic acid, and 0.064g of divinylbenzene . To make a monomer mixture, take 0.01g of ammonium persulfate, 0.018g of sodium dodecylbenzenesulfonate and 10g of deionized water to make an aqueous solution. After the temperature in the reactor rises to 80°C, the monomer mixed solution and the aqueous solution of initiator and emulsifier are added dropwise at the same time. The monomer mixture is added dropwise for 6 hours, and the aqueous solution of the initiator and emulsifier is added dropwise for 6.5 hours. After all the raw materials are fed, keep the temperature for 0.5 hours and then cool down and discharge.

(3) Preparation of the middle layer of latex particles Weigh 80g of the above nuclear emulsion into the same reactor, add 25g of deionized water, heat up while stirring, and weigh 50g of styrene, 18g of acrylonitrile, 0.7g of divinyl Benzene is made into a monomer mixture, and 0.54 g of ammonium persulfate, 0.13 g of sodium dodecylbenzenesulfonate and 20 g of deionized water are taken to make an aqueous solution. When the temperature rises to 75°C, the monomer mixture, initiator and emulsifier aqueous solution are added dropwise. The feeding time of the monomer mixture is 3 hours, and the feeding time of the aqueous solution of the initiator and emulsifier is 3.5 hours. After all the raw materials are fed, the temperature is kept for 0.5 hours, and the temperature is discharged.

(4) Preparation of the shell layer emulsion Take 60g of the above-mentioned middle layer emulsion and put it into the reactor, add 20g of deionized water, heat up while stirring, simultaneously weigh 30g of butyl acrylate and 14g of styrene to form a monomer mixture, Weigh 0.64g of ammonium persulfate, 0.16g of sodium dodecylbenzenesulfonate and 20g of deionized water to prepare an aqueous solution. When the temperature rises to 75°C, add the monomer mixture, initiator and emulsifier solution dropwise. The feeding time of the monomer mixture is 3 hours, and the feeding time of the aqueous solution of the initiator and emulsifier is 3.5 hours. After all the raw materials are fed, keep the temperature for another 2 hours, and then cool down and discharge.

(5) Alkali treatment Weigh 100g of the prepared core-shell emulsion into a reactor with a stirring device and a reflux condenser, adjust the pH value of the emulsion to 9 with a pre-prepared 20% sodium hydroxide solution, and raise the temperature to 100 ℃, heat preservation under stirring for 4 hours, and then cool down to obtain hollow latex particles containing water inside.

(6) Electron microscope test Dilute the above-mentioned emulsion to a solid content of about 15%, then add 25 drops of the diluted polymer emulsion to 10ml of distilled water, and ultrasonically disperse for 10 minutes with a KQ-100DB numerically controlled ultrasonic disperser. Take the emulsion sample and drop it on a small copper grid dedicated to a transmission electron microscope with a supporting film, and then add 1 to 2 drops of ruthenium tetroxide aqueous solution with a mass percentage concentration of 2% on the small copper grid coated with the emulsion. Dry under light irradiation, and then use a Hitachi H-800 transmission electron microscope to take pictures of the samples under the condition of accelerating voltage 80kV. Electron micrographs are shown in Figure 1. It can be seen from the figure that the particle size of latex particles prepared by this method is about 1000nm, and the particle size has good monodispersity and the hollow structure is regular.

(7) Self-film-forming test The method is the same as that of Example 1. The end result is a thin white film that is smooth and crack-free.

Example 3

(1) Preparation of seeds Same as Example 1 method.

(2) Preparation of nuclear emulsion Add 25g of seed emulsion and 100g of deionized water to the same reactor as above, and heat up while stirring; simultaneously weigh 10g of methyl methacrylate, 6.5g of methacrylic acid, and 0.082g of divinyl Benzene. Make monomer mixed liquid, get 0.13g ammonium persulfate, 0.03g sodium dodecylbenzenesulfonate and make aqueous solution with 15g deionized water. After the temperature in the reactor rises to 80°C, the monomer mixed solution and the aqueous solution of initiator and emulsifier are added dropwise at the same time. The monomer mixture is added dropwise for 6.5 hours, and the aqueous solution of the initiator and emulsifier is added dropwise for 6 hours. After all the raw materials are fed, keep the temperature for 0.5 hours, then cool down and discharge.

(3) Preparation of the middle layer of latex particles Weigh 100g of the above-mentioned nuclear emulsion and put it into the same reactor, add 30g of deionized water, heat up while stirring, and weigh 60g of styrene, 21g of acrylonitrile, and 0.76g of divinyl Benzene is made into a monomer mixture, and 0.6g of ammonium persulfate, 0.2g of sodium dodecylbenzenesulfonate and 25g of water are taken to make an aqueous solution. When the temperature rises to 75°C, the monomer mixture, initiator and emulsifier aqueous solution are added dropwise. The feeding time of the monomer mixture is 3.5 hours, and the feeding time of the aqueous solution of the initiator and emulsifier is 4 hours. After all the raw materials are fed, the temperature is kept for 0.5 hours, and the temperature is discharged.

(4) Preparation of the shell layer emulsion Weigh 60g of the above-mentioned intermediate layer emulsion and put it into the reactor, add 20g of deionized water, heat up while stirring, and simultaneously weigh 24g of butyl acrylate and 22g of styrene to form a monomer mixture. Weigh 0.64g of ammonium persulfate, 0.16g of sodium dodecylbenzenesulfonate and 20g of water to form an aqueous solution, and when the temperature rises to 75°C, add the monomer mixture, initiator and emulsifier solution dropwise. The feeding time of the monomer mixture is 3 hours, and the feeding time of the aqueous solution of the initiator and emulsifier is 3.5 hours. After all the raw materials are fed, keep the temperature for another 2 hours, and then cool down and discharge.

(5) Alkali treatment Weigh 100g of the prepared core-shell emulsion into a reactor with a stirring device and a reflux condenser, adjust the pH value of the emulsion to 9 with a pre-prepared 20% sodium hydroxide solution, and raise the temperature to 100 ℃, keep it warm for 2.5 hours under stirring, and cool down to obtain hollow latex particles containing water inside.

(6) Electron microscope test method is the same as Example 1, and the electron microscope photo is as shown in Figure 2. It can be seen from the figure that the particle size distribution of latex particles is relatively uniform, about 800nm, but the hollow structure of some latex particles is not obvious and there are still a small number of latex particles with extremely small particle sizes. It shows that the alkali solution is not easy to penetrate into the carboxyl-containing core layer due to the short time and the thickness of the middle layer and the shell layer during the alkali treatment in the last step, resulting in incomplete alkali treatment. Moreover, the amount of emulsifier used in the preparation stage of the shell is too large, and new latex particles with very small particle sizes are generated.

(7) Self-film-forming test method is the same as Example 1. A thin white film with a few cracks was finally obtained.

Example 4

(1) Preparation of seeds Same as Example 1 method.

(2) Preparation of nuclear latex particles Add 20g of seed emulsion and 80g of deionized water to the same reactor as above, and heat up while stirring; simultaneously weigh 8g of methyl methacrylate, 6g of methacrylic acid, and 0.06g of divinyl Benzene. Make monomer mixed solution, get 0.1g ammonium persulfate, 0.04g sodium dodecylbenzenesulfonate and use 15g deionized water to make aqueous solution. After the temperature in the reactor rises to 80°C, the monomer mixed solution and the aqueous solution of initiator and emulsifier are added dropwise at the same time. The monomer mixture is added dropwise for 3.0 hours, and the aqueous solution of the initiator and emulsifier is added dropwise for 3.5 hours. After all the raw materials are fed, keep warm for 0.5 hours and then cool down and discharge.

(3) Preparation of latex particles in the middle layer Weigh 80g of the above nuclear emulsion into the same reactor, add 25g of deionized water, heat up while stirring, and weigh 45g of styrene, 17g of acrylonitrile, 0.6g of divinyl Benzene is made into a monomer mixture, and 0.46g of ammonium persulfate, 0.18g of sodium dodecylbenzenesulfonate and 20g of water are taken to make an aqueous solution. When the temperature rises to 75°C, the monomer mixture, initiator and emulsifier aqueous solution are added dropwise. The feeding time of the monomer mixture is 3 hours, and the feeding time of the aqueous solution of the initiator and emulsifier is 3.5 hours. After all the raw materials are fed, the temperature is kept for 0.5 hours, and the temperature is discharged.

(4) Alkali treatment Weigh 100g of the prepared middle layer emulsion and put it into a reactor with a stirring device and a reflux condenser, adjust the pH value of the emulsion to 9 with a pre-prepared 20% sodium hydroxide solution, and heat up to 100 ℃, heat preservation under stirring for 4 hours, and then cool down to obtain hollow latex particles containing water inside.

(5) Preparation of shell layer emulsion Weigh 60g of the above-mentioned alkali-treated intermediate layer emulsion into the reactor, add 20g of deionized water, heat up while stirring, and weigh 35g of butyl acrylate and 13g of styrene to form a single Mixture of monomers, weigh 0.64g of ammonium persulfate, 0.16g of sodium dodecylbenzenesulfonate and 20g of water to form an aqueous solution, wait until the temperature rises to 75°C, add the monomer mixture, initiator, and emulsifier aqueous solution dropwise at the same time . The feeding time of the monomer mixture is 3 hours, and the feeding time of the aqueous solution of the initiator and emulsifier is 3.5 hours. After all the raw materials are fed, keep the temperature for another 2 hours, and then cool down and discharge.

(6) Electron microscope test method is the same as Example 1, and the electron microscope photo is as shown in Figure 3. It can be seen from the figure that most latex particles have a hollow structure, but the particle size distribution is uneven, and some latex particles have a solid structure. It shows that the amount of emulsifier used in the preparation of core latex particles is too large and the feeding rate is too fast in the preparation process of the middle layer latex particles, which leads to the generation of new latex particles. These new latex particles do not contain carboxyl groups, so they are also treated with alkali. A hollow structure cannot be formed.

(7) Self-film-forming test method is the same as Example 1. A thin white film with a few cracks was finally obtained.

Claims (1)

1. the preparation method of monodispersed large grain-size hollow styrene-acrylic polymer microballoon in the low soap system, its feature comprises following process:

(1) the solid content mass ratio is the preparation of 1.0～10% seed emulsion: the emulsifying agent Sodium dodecylbenzene sulfonate that will account for monomer total mass 0.2～1% joins in the reactor with deionized water, under agitation be warming up to 60～80 ℃, add one or both acrylic ester monomers and methacrylic acid or vinylformic acid again by (95～100): the mass ratio of (5～10) mixes the monomer mixed solution that obtains, adding accounts for the solution that monomer total mass 5～10% initiator ammonium persulfates are made into after continuing to stir 0～0.5h, at 60～80 ℃ of following insulation reaction 1～4h, make the solid content mass ratio and be 1.0～10% seed emulsion;

(2) the solid content mass ratio is the preparation of 7.0～15% carboxylated nuclear emulsions: add the deionized water dilution in the seed emulsion that makes toward step (1) in the time of 60～80 ℃, heating while stirring, drip one or both acrylic ester monomers and methacrylic acid or vinylformic acid and Vinylstyrene or methacrylate glycol ester again by (50～100): (5～50): the mixed solution of (2～5) mass ratio, drip the aqueous solution that the initiator ammonium persulfate of the emulsifying agent Sodium dodecylbenzene sulfonate account for this step monomer total mass 0.2～1% and 0.3～3% is mixed with simultaneously, the dropping time is 2～10h, all raw materials dropwise back insulation reaction 2～4h, make the solid content mass ratio and be the nuclear emulsion of 7.0～15% band carboxyl;

(3) the solid content mass ratio is the preparation of the polyalcohol emulsion particle in 20～50% coated middle layers: in the time of 60～80 ℃, at the uniform velocity dropwise addition of acrylic acid esters monomer or vinylbenzene are pressed (95～100) with Vinylstyrene or methacrylate glycol ester in the prepared carboxyl of step (2) the nuclear emulsion: the mixed solution of (0～5) mass ratio, drip simultaneously and account for the Sodium dodecylbenzene sulfonate of this step monomer total mass 0.2～1% and the aqueous solution of 0.3～3% ammonium persulphate, the dropping time is 2～10h, all raw materials dropwise back insulation reaction 2～4h, make the solid content mass ratio and be 20～50% the coated polyalcohol emulsion particle in middle layer;

(4) the solid content mass ratio is the preparation of 20～50% shell polymkeric substance: in the time of 60～80 ℃, in the prepared polymer emulsion of step (3) at the uniform velocity dropwise addition of acrylic acid esters monomer and vinylbenzene by (50～90): the mixed solution of (10～50) mass ratio, drip simultaneously and account for the Sodium dodecylbenzene sulfonate of this step monomer total mass 0.2～1% and the aqueous solution that 0.3～3% ammonium persulphate is made into, the dropping time is 2～10h, all raw materials dropwise back insulation reaction 2～4h, make the solid content mass ratio and be 20～50% core-shell emulsion;

(5) alkaline purification: be initial pH value to 7～13 of 5～20% the resulting core-shell emulsion of sodium hydroxide solution regulating step (4) with concentration, under 90～120 ℃ of temperature, carrying out then and swelling 1～5h, obtain the hollow emulsion particle.

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