Method for producing thermally expandable microspheres containing hydrophilic organically modified colloidal silica

Abstract

The present application provides a method for producing thermally expandable microspheres containing hydrophilic organically modified colloidal silica. In the production method, a mixture of hydrophilic organically modified colloidal silica, a monomer material capable of forming a thermoplastic polymer shell by polymerization, and at least one foaming agent is mixed to form an emulsion, and the emulsion is polymerized to form thermally expandable microspheres. In the present application, the colloidal silica surface-modified with a hydrophilic organic group has excellent salt resistance stability and can be stabilized even in salt water, which is advantageous for the production of thermally expandable microspheres. The produced microspheres have a narrow particle size distribution, can be easily dispersed in water and organic systems, and have good wettability. The present invention also relates to thermally expandable microspheres and their use.

Description

Technical Field

[0001] This application belongs to the field of manufacturing microspheres, and specifically relates to a method for manufacturing thermally expandable microspheres containing hydrophilic organically modified colloidal silica.

Background Art

[0002] Thermally expandable microspheres are core-shell type polymer microspheres with a thermoplastic polymer as the shell and one or more foaming agents as the core. Under heating conditions, the foaming agent inside the microspheres vaporizes to generate pressure, and at the same time, the polymer shell reaches the glass transition temperature and softens. Due to the action of the internal pressure, the microspheres expand to obtain expanded microspheres. Here, the particle size of the thermally expandable microspheres is usually 1 to 20 μm, and the particle size of the expanded microspheres reaches 20 to 100 μm. Accordingly, the volume increases by several to several tens of times.

[0003] Currently, common thermally expandable microspheres mainly include expandable microspheres of dry powder / wet material and expanded microspheres of dry powder / wet material. Expandable microspheres and expanded microspheres have a wide range of applications. They are mainly used to provide cells for reducing the density of materials to the materials, and can also be used in heat insulation materials, sound insulation materials, etc. For example, as a lightweight filler, it can be used in the manufacture of materials such as paper, cork, paint, and shoe soles.

[0004] Suspension polymerization is a common method for manufacturing thermally expandable microspheres. For this purpose, it is necessary that an oil phase mainly composed of a monomer, a foaming agent, an initiator, and a crosslinking agent can form a stable emulsion with an aqueous phase by the action of a dispersant or an emulsifier. In the subsequent heating process of the emulsion, the polymerization of the monomer is initiated by the initiator in the oil droplets. Since the foaming agent is a poor solvent for the polymer, the formed polymer gradually precipitates and continuously moves to the interface between water and oil to form a polymer shell. On the other hand, the foaming agent is encapsulated by the polymer shell, and finally thermally expandable microspheres are formed.

[0005] The most important thing in this process is the stabilization of the oil-phase droplets. Only in this way can the polymerization of the monomer occur inside the oil droplets and a shell be further formed. If the emulsion is not stable, aggregation of the droplets occurs, and finally the particle size distribution of the microspheres becomes wide. More importantly, it leads to the generation of polymer capsules that cannot encapsulate the foaming agent, which is disadvantageous to the stability and yield of the product.

[0006] Existing patents disclose that the main stabilizers that can be used in this process are magnesium hydroxide and silica. The main principle of using silica as a stabilizer is based on the Pickering emulsion stabilization mechanism. Patent TW203072B mentions that the polymerization of acrylonitrile is not suitable in an alkaline environment, and the silica-based system has good stability and can be used even under acidic conditions, so it is more suitable for the synthesis of expandable microspheres.

[0007] Silica as a stabilizer of the emulsion often requires the addition of some co-stabilizers to play the role of stabilizing the emulsion. For example, Patent US3615972 describes the use of a combination of silica and a co-stabilizer. The co-stabilizer may be metal ions such as chromium ions and iron ions, or a flocculant, and may also contain a reducing agent. The interaction between silica, metal ions, and the flocculant is utilized to prevent the coalescence of the droplets and stabilize the emulsion.

[0008] EP2327475A2, US2005 / 0079351A1, WO2004 / 07260, and US3615972 disclose methods of manufacturing expandable microspheres by using silica together with one or more of co-stabilizers such as potassium dichromate, polyvinylpyrrolidone, and polyvinylamine.

[0009] The use of co-stabilizers can cause many problems. For example, since metal ions are harmful or toxic, specialized operations and disposal are required when using them. Also, since metal ions remain in the product, specialized handling and operations are required for the product, and furthermore, it may affect specific uses of the product, such as uses that may come into contact with food or beverages. After the product (expandable microspheres, expanded microspheres) dries, these metal ions may be present on the surface of the microsphere powder, and since these dry powders are likely to form dust, they may pose a threat to the health of workers and users. When using a flocculant, other problems such as a decrease in the storage stability of the product due to the hydrolysis of the flocculant occur, so a special selection and design of the flocculant are required, which is a complex process.

[0010] CN109414672A discloses a method of using hydrophobic organically modified colloidal silica for the manufacture of expandable microspheres. This method solves the use of co-stabilizers and flocculants and avoids the above problems.

[0011] However, when using hydrophobic organically modified colloidal silica, another problem arises. For example, hydrophobic organically modified colloidal silica is extremely unstable under high-concentration brine conditions and is not suitable for use in high-concentration brines. In the production of swellable microspheres, in order to suppress the dissolution of highly water-soluble monomers in water, a high-concentration sodium chloride solution is usually required to reduce the solubility of the monomers in water. For example, acrylonitrile monomer, which is a monomer raw material commonly used in the production of swellable microspheres, has a high solubility in water. If the solubility in water is not suppressed, polymerization is very likely to become uncontrollable or polymerization may fail.

[0012] Since hydrophobic organically modified colloidal silica has hydrophobic groups grafted thereon, in order to form a stable sol in water, it is necessary to obtain stability depending on a certain charge, and its main form is the electric double layer. Therefore, hydrophobic modified colloidal silica is extremely likely to cause the destruction of the electric double layer in a salt-containing system, and salting out and aggregation are likely to occur. Therefore, it is not suitable for use in a salt-containing system.

[0013] On the other hand, silica as an emulsion stabilizer adheres to the surface of the microspheres after polymerization to form a silica layer. When using hydrophobic organically modified colloidal silica as an emulsion stabilizer, the adhesion to the surface of the microspheres affects the wettability of the microspheres and the dispersibility in water, and affects the use in specific fields such as aqueous systems such as aqueous paints. This is because it is difficult to disperse in water.

[0014] In addition, since there are hydrophobic groups on the surface of hydrophobic organically modified silica, it is disadvantageous for stability in an aqueous solution. Generally, silica is often used for the stabilization of emulsions in the form of a colloidal aqueous solution of silica. However, the presence of hydrophobic groups is disadvantageous for the storage stability of colloidal silica. Therefore, colloidal silica needs to be used as soon as possible after production. Summary of the Invention Problems to be Solved by the Invention

[0015] The following is an overview of the subject matter described in detail in this specification. This overview is not intended to limit the scope of the claims.

[0016] An object of the present application is to provide a method for producing thermally expandable microspheres. The microspheres contain hydrophilic organic-modified colloidal silica, and the colloidal silica modified with a hydrophilic organic group is used as an emulsion stabilizer in the production process of the expandable microspheres, reducing the complexity in the use of colloidal silica, avoiding the use of metal ions and flocculants, reducing the generation of non-microsphere polymer scraps, obtaining an expandable microsphere product with good morphology and good dispersion in water and organic solvents.

Means for Solving the Problems

[0017] In order to achieve the object of the above application, the present application adopts the following technical solutions.

[0018] A method for producing thermally expandable microspheres, comprising mixing hydrophilic organic-modified colloidal silica with a mixture of a monomer material capable of forming a thermoplastic polymer shell by polymerization and at least one blowing agent to form an emulsion, and polymerizing the emulsion to form thermally expandable microspheres.

[0019] The reason why the hydrophilic modified colloidal silica of the present application has excellent technical effects is that the introduction of hydrophobic groups into hydrophobic organic modified colloidal silica weakens the interaction between silica and water, and the stability of colloidal silica greatly depends on the electrical double layer of particles. As a result, hydrophobic modified colloidal silica cannot be used under salt-containing conditions. The introduction of hydrophilic groups into hydrophilic organic modified colloidal silica enhances the interaction between silica particles and water, and also plays a role in blocking the space between particles. The stability of colloidal silica comes to depend on the combined action of the electrical double layer and hydrophilic organic groups. Therefore, hydrophilic organic modified colloidal silica has better stability and salt tolerance. Also, due to the improvement of lipophilicity by the introduction of organic groups, when used as an emulsifying stabilizer similar to hydrophobic organic modified colloidal silica, the use of co-stabilizers, aggregating agents, etc. can be avoided. The "colloidal silica" mentioned in the present application refers to a nanosilica colloidal solution produced by methods such as the water glass method, single silicon method, ion exchange method, etc. This silica colloid has a particle size at the nanometer level and can stably exist in an aqueous solution without rapidly aggregating.

[0020] In the present application, the hydrophilic organic modified colloidal silica is obtained by the reaction of a hydrophilic group-containing compound with the silanol groups on the surface of colloidal silica. Preferably, it is obtained by the reaction of a compound containing one or more of a hydroxy group, a carboxyl group, and a siloxanyl group with the silanol groups on the surface of colloidal silica. More preferably, it is obtained by the reaction of one or more of ethylene glycol, oxalic acid, tetraethylene glycol, short-chain polyethylene oxide, polypropylene oxide, and organosilane containing active hydrogen with the silanol groups on the surface of colloidal silica. Preferably, the organosilane containing active hydrogen has an A-B-C structure, where A is -SiR1(OR2)(OR3) or -Si(OR1)(OR2)(OR3), where R 1、 R 2、R3 is a hydrocarbyl group of C1 - C4, B is a hydrocarbylene group of C1 - C10, which may or may not contain one or more oxygen atoms on the main chain of the hydrocarbylene group, C is one or more of a glycosyl group, a monoglyceryl group, a diglyceryl group, a polyglyceryl group, a xylitol group, an ethylene glycol group, a polyethylene glycol group, an amino group, a ureido group. Preferably, the active hydrogen - containing organosilane is one or more of 3 - aminopropyltrimethoxysilane, 3 - ureidopropyltriethoxysilane, 3 - aminopropyldimethoxymethylsilane, γ - glycidyloxypropyltrimethoxysilane, 3 - glycidyloxypropyltriethoxysilane. In one embodiment, the active hydrogen groups such as the monoglyceryl group, diglyceryl group, polyglyceryl group, etc. may be those generated by hydrolyzing a precursor containing an epoxy group, for example, as follows.

Chemical formula

[0021] In this application, a modifier without silane is prepared in solution D, the pH of the raw material colloidal silica is adjusted to obtain an acidic colloidal silica solution E, solution D is added to solution E, after reaction, it is replaced with water to obtain hydrophilic organic - modified colloidal silica, which is the manufacturing method I of the hydrophilic organic - modified colloidal silica. Exemplarily, the process of the method may be as follows.

Chemical formula

[0022] In this application, a silane - containing modifier is prepared in solution F, solution F is added to the raw material colloidal silica, after reaction, hydrophilic organic - modified colloidal silica is obtained, which is the manufacturing method II of the hydrophilic organic - modified colloidal silica. Exemplarily, the process of the method may be as follows.

Chemical formula

[0023] In order to obtain hydrophilic organic surface-modified colloidal silica with stable properties and excellent applicability, since it is difficult to accurately measure the degree of modification, in this application, the degree of modification is evaluated by the mass ratio of the modifying group to silica. In this application, the mass ratio of the modifier to the raw material colloidal silica in the above manufacturing method is (0.001 - 0.05):1, and the particle size of the raw material colloidal silica is 2 - 120 nm. This particle size refers to the average diameter of the colloidal silica, and this diameter can be measured by DLS (laser particle size analyzer).

[0024] This application includes providing a mixture of one or more monomer materials suitable for forming a thermoplastic polymer shell by polymerization and at least one blowing agent. The above mixture can form a stable emulsion due to the stabilizing effect of colloidal silica surface-modified with hydrophilic organic groups. Next, expandable microspheres can be formed by polymerization. The obtained microspheres have a controllable particle size and a narrow particle size distribution.

[0025] This application includes modifying colloidal silica with one or more hydrophilic organic groups. Next, a mixture of the colloidal silica modified with the hydrophilic organic group, water, and salt is brought into contact with a mixture of a monomer and a blowing agent.

[0026] This application can produce an emulsion by adding a mixture of one or more monomer materials and at least one blowing agent to surface-modified colloidal silica, and can also produce an emulsion by adding surface-modified colloidal silica to a mixture composed of one or more monomer materials and at least one blowing agent.

[0027] In the present application, in the above method, a salt is added to suppress the dissolution of the monomer in water. Preferably, the salt is one or more of sodium chloride, potassium chloride, calcium chloride, sodium sulfate, and sodium nitrate. More preferably, the salt is one or more of sodium chloride, potassium chloride, and sodium nitrate. Preferably, the amount of the salt used is 5 to 25 wt% of the total mass of water, colloidal silica, and the salt.

[0028] In the present application, the monomer is an organic compound capable of free radical polymerization having a double bond, and includes at least one monomer compound having one double bond and at least one monomer compound having a plurality of double bonds. Preferably, it is one or more of acrylonitrile, methacrylonitrile, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, ethylstyrene, halostyrene, methyl acrylate, methyl methacrylate, methacrylic acid, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, isobornyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate, vinyl acetate, vinyl laurate, vinyl stearate, vinyl halide, vinylidene halide, dihalogenated vinyl, acrylamide, N-isopropylacrylamide, methylacrylamide, 2-hydroxyethyl methacrylate, diallyl phthalate, allyl methacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, ethylene glycol dimethacrylate, trimethylolpropane triethylene glycol triacrylate, 1,6-hexanediol diacrylate, 2,2-bis(allyloxymethyl)-1-butanol, pentaerythritol triallyl ether, and dipropylene phthalate. Here, by adding a monomer compound containing a plurality of double bonds, the mechanical properties of the polymer shell are improved, and the addition amount of the monomer containing a plurality of double bonds is 0.1 to 10 wt% of the total monomers.

[0029] In the above method, a polymerization catalyst for catalyzing the polymerization of monomers is also required. In this application, the polymerization catalyst is a free radical initiator, and the initiator is selected from azo compounds and peroxide compounds. For example, it is one or more of azobisisobutyronitrile, azodiisovaleronitrile, azodiisoheptanitrile, dilauroyl peroxide, dibenzoyl peroxide, tert-butyl peroxyisobutyrate, bis(4-tert-butylcyclohexyl) peroxydicarbonate, tert-butyl peroxypivalate, diisopropyl peroxydicarbonate, and di-tert-butyl peroxide. Preferably, it is one or more of azobisisobutyronitrile, dilauroyl peroxide, and dibenzoyl peroxide. The usage amount of the initiator is 0.1 to 5 wt% of the monomer material.

[0030] The blowing agent in this application may be a single compound or a combination of multiple compounds. This blowing agent should have a boiling point lower than the glass transition temperature of the thermoplastic polymer shell and should have a high saturated vapor pressure in the expansion temperature range in order to provide a driving force for expansion into microspheres. The blowing agent is mainly selected from hydrocarbon compounds that are liquid or liquid under high pressure, and this hydrocarbon compound may be a saturated or unsaturated hydrocarbon. The monomer material is mixed with at least one blowing agent to form an oil phase to achieve optimal expansion. In this application, the blowing agent is a low-boiling alkane blowing agent, preferably one or more of n-butane, isobutane, cyclohexane, isopentane, and methyl chloride. Preferably, the usage amount of the blowing agent is 5 to 50 wt% of the total mass of the monomer and the blowing agent.

[0031] In this application, the emulsion is polymerized under the conditions of stirring and heating to obtain thermally expandable microspheres.

[0032] In the present application, the thermally expandable microspheres are finally obtained in the form of a wet material or a dry powder. In the case of a dry powder, it is necessary to suction-filter an aqueous slurry of the microspheres to obtain a wet material filter cake, and the filter cake is dried in an oven or at room temperature to obtain an expandable microsphere powder.

[0033] Another object of the present application is to provide thermally expandable microspheres.

[0034] Thermally expandable microspheres, wherein the thermally expandable microspheres are produced by the above method, the thermally expandable microspheres contain hydrophilic organically modified colloidal silica, and preferably, the D50 of the thermally expandable microspheres is 2 to 20 μm and the particle size distribution is 1.01 to 1.2.

[0035] The obtained expandable microspheres can be expanded under heating conditions to obtain expanded microspheres. Depending on the monomers and blowing agents used, the expansion temperature of the expandable microspheres is 70 to 300 °C. Generally, those that expand below 100 °C are called low-temperature expandable microspheres, those that expand at 100 to 160 °C are called medium-temperature expandable microspheres, and those that expand at 160 to 300 °C are called high-temperature expandable microspheres.

[0036] A further object of the present application is to provide the use of thermally expandable microspheres.

[0037] The use of thermally expandable microspheres, wherein the thermally expandable microspheres are produced by the above method or are the above thermally expandable microspheres, and the thermally expandable microspheres are suitable for printing, paints, inks, polyurethane abrasives, shoe soles, and heat-insulating materials.

Advantages of the Invention

[0038] Compared with the prior art, the beneficial effects of the present application are as follows.

[0039] (1) The colloidal silica surface-modified with a hydrophilic organic group used in the present application can stably exist in concentrated brine without introducing a co-stabilizer, a flocculant, and / or metal ions. Therefore, an oil-phase material suitable for the production of expandable microspheres can form a stable emulsion in concentrated brine.

[0040] (2) In the existing methods for producing expandable microspheres, in order to suppress the dissolution of monomers in water, it is often necessary to use a high-concentration salt solution. By using concentrated brine, the occurrence of uncontrolled polymerization and nucleation in the aqueous phase can be avoided, which is more useful for the production of microspheres. On the other hand, the method according to the present application can be carried out in a high-concentration salt solution. In addition, this method is also suitable for systems without adding salts, has a wide application range, and has few process limitations.

[0041] (3) The method according to the present application can form a stable emulsion and avoid the occurrence of uncontrollable polymerization such as nucleation in the aqueous phase, reduce the generation of non-microsphere cas during the polymerization process, and obtain expandable microsphere powder with controllable particle size and narrow particle size distribution.

[0042] (4) The colloidal silica surface-modified with a hydrophilic organic group according to the present application can provide a certain degree of hydrophilicity on the surface of the microspheres adhering after the polymerization reaction, so that the dispersibility of the microspheres in water can be improved. Thereby, it has excellent dispersibility when applied to either an aqueous system or an oil-based system, and has a wider application range. Other aspects can be understood after reading and understanding the drawings and the detailed description.

Brief Description of the Drawings

[0043]

Figure 1

Figure 2

Mode for Carrying Out the Invention

[0044] Hereinafter, the present application will be further described with specific examples. However, the examples described in the present application are merely for explaining the present application and do not limit the scope of the present application.

[0045] The origins of the main raw materials in the examples and comparative examples are as follows. Acrylonitrile: Shanghai Aladdin Biochemical Technology Co., Ltd., reagent grade 99%, Methyl methacrylate: Shanghai Aladdin Biochemical Technology Co., Ltd., reagent grade 99%, Methacrylic acid: Shanghai Aladdin Biochemical Technology Co., Ltd., reagent grade 99%, Vinylidene chloride: Shanghai Aladdin Biochemical Technology Co., Ltd., reagent grade 99%, Methyl acrylate: Wanhua Chemical Group Co., Ltd., industrial grade 99.5%, Acrylamide: Shanghai Aladdin Biochemical Technology Co., Ltd., reagent grade 99%, Methacrylonitrile: Huateng Pharmaceutical Co., Ltd., industrial grade 99.5%, Allyl methacrylate: Aite New Materials Co., Ltd., industrial grade 99%, Diallyl phthalate: Shandong Shangwei Chemical Import and Export Co., Ltd., industrial grade 99%, Pentaerythritol trimethacrylate: Guangdong Bluecolu New Materials Co., Ltd., industrial grade 99%, Ethylene glycol dimethacrylate: Shandong Chuangying Chemical Co., Ltd., industrial grade 99%, Dilauroyl peroxide: Nouryon Co., Ltd., industrial grade, active oxygen-containing peroxide 4.01%, Azobisisobutyronitrile: Shandong Kirin Chemical Co., Ltd., industrial grade 99%, Dibenzoyl peroxide: Noliang Co., Ltd., industrial grade 75%, Hydrochloric acid: Shanghai Aladdin Biochem Technology Co., Ltd., reagent grade 99%, Acetic acid: Shanghai Aladdin Biochem Technology Co., Ltd., Reagent grade 99%, Colloidal silica surface modified with hydrophobic organic groups Colloidal silica: Nolix Co., Ltd., CC401, industrial grade, solid content 37%, particle size 12nm, Sodium chloride: Shenghai Chemical Co., Ltd., industrial grade 99%, Potassium chloride: Liaoning Oriental Reagent Plant, industrial grade 98%, Sodium nitrate: Shanghai Yixin Chemical Co., Ltd., industrial grade 98%, Isopentane: Aladdin Group Co., Ltd., Industrial grade 99%, Isobutane: Liaoning Dat Gas Co., Ltd., industrial grade 99%, Cyclohexane: Jinan Guangyu Chemical Co., Ltd., industrial grade 99.9%, Polyethylene glycol-800: Tianjin Dai Asahi Chemical Trading Co., Ltd., industrial grade 99%, average molecular weight 500-700, 3-Aminopropyltrimethoxysilane: Maitu High-Tech Materials Group, industrial grade 98%, 3-Ureidopropyltriethoxysilane: Maitu High-Tech Materials Group, industrial grade 98%, 3-Aminopropyldimethoxymethylsilane: Maitu High-Tech Materials Group, industrial grade 98%, γ-Glycidyloxypropyltrimethoxysilane: Maitu High-Tech Materials Group, industrial grade 98%, 3-Glycidyloxypropyltriethoxysilane: Maitu High-Tech Materials Group, industrial grade 98%, Colloidal silica: Keran Silicon Products Co., Ltd., industrial grade, solid content ~30wt%, JN series colloidal silica.

[0046] The main test equipment and methods used in the examples and comparative examples are as follows: Laser particle size analyzer: The model is Bettersize2600, the test method is the wet method, the light shielding rate used for the test is 5% - 20%, and the test medium is water. TMA: The model is METTLER TMA / SDTA2 +, and the test method is 15°C / min. Manufacture of hydrophilic organic modified colloidal silica

[0047] Colloidal silica G: Weighed 0.1 g of polyethylene glycol - 800, dissolved it in 10 g of acetone, mixed uniformly, and prepared it into modifier solution D1. Weighed 100 g of colloidal silica (30%, 20 nm), adjusted its pH to 2 with hydrochloric acid to obtain colloidal silica solution E1. Slowly added D1 to E1, and reacted at 80°C and 300 rpm for 20 h. After the reaction, the solution was replaced with water to obtain hydrophilic modified colloidal silica G. Colloidal silica H: Weighed 0.5 g of 3 - glycidoxypropyltriethoxysilane, added it to 10 g of water, mixed uniformly to obtain solution F1. Added F1 to 100 g of colloidal silica (30%, 8 nm), and reacted at 30°C and 300 rpm for 20 h to obtain hydrophilic modified colloidal silica H. Colloidal silica I: Weighed 1 g of oxalic acid, dissolved it in 10 g of acetone, mixed uniformly, and prepared it into modifier solution D2. Weighed 100 g of colloidal silica (30%, 80 nm), adjusted its pH to 2 with hydrochloric acid to obtain colloidal silica solution E2. Slowly added D2 to E2, and reacted at 80°C and 300 rpm for 20 h. After the reaction, the solution was replaced with water to obtain hydrophilic modified colloidal silica I. Colloidal silica J: Weighed 4.7 g of γ - glycidoxypropyltrimethoxysilane, added it to 10 g of water, mixed uniformly to obtain solution F2. Added F2 to 100 g of colloidal silica (30%, 10 nm), and reacted at 30°C and 300 rpm for 20 h to obtain hydrophilic modified colloidal silica J. Colloidal silica K: 2 g of 3-aminopropyltrimethoxysilane was weighed and added to 10 g of water, and uniformly mixed to obtain solution F3. F3 was added to 100 g of colloidal silica (30%, 120 nm), and reacted at 30 °C and 300 rpm for 20 h to obtain hydrophilic modified colloidal silica K. Colloidal silica L: 3 g of 3-ureidopropyltriethoxysilane was weighed and added to 10 g of water, and uniformly mixed to obtain solution F4. F4 was added to 100 g of colloidal silica (30%, 2 nm), and reacted at 30 °C and 300 rpm for 20 h to obtain hydrophilic modified colloidal silica L. Colloidal silica M: 3 g of 3-aminopropyldimethoxymethylsilane was weighed and added to 10 g of water, and uniformly mixed to obtain solution F5. F5 was added to 100 g of colloidal silica (30%, 20 nm), and reacted at 30 °C and 300 rpm for 20 h to obtain hydrophilic modified colloidal silica M. (Example 1)

[0048] S1: 100 g of water, 33 g of sodium chloride, and 2 g of colloidal silica G were weighed and mixed to prepare mixture A. S2: 10 g of methacrylonitrile, 5 g of acrylonitrile, 4 g of vinylidene chloride, 5 g of methyl methacrylate monomer, 0.048 g of allyl methacrylate, 20 g of isopentane as a foaming agent, and 0.05 g of azobisisobutyronitrile as a polymerization initiator were weighed and mixed to prepare mixture B. S3: Mixture A and mixture B were each placed in a sealed container and stirred at 1500 rpm for 25 min to form an emulsion. S4: The formed emulsion was polymerized at 60 °C and 300 rpm for 20 h. Dried at 60 °C in an oven to obtain expandable microspheres. The obtained microspheres had a D50 particle size of 5.4 μm and a particle size distribution width of 1.01. As a result of performing a TMA test on the obtained microspheres, the microspheres had a T start of 120 °C and a T max of 160 °C. (Example 2)

[0049] S1: Weighed 110 g of water, 6.5 g of potassium chloride, and 5 g of colloidal silica H, mixed them, and prepared mixture A. S2: Weighed 10 g of acrylonitrile, 2 g of methacrylonitrile, 8 g of methyl acrylate, 5 g of methyl methacrylate, 0.25 g of diallyl phthalate, 1.5 g of isobutane as a foaming agent, and 0.375 g of dilauroyl peroxide as a polymerization initiator, mixed them, and prepared mixture B. S3: Put mixture A and mixture B into sealed containers respectively, stirred them at 1200 rpm for 25 min to form an emulsion. S4: Polymerized the formed emulsion at 62 °C and 500 rpm for 20 h. Dried it at 60 °C in an oven to obtain expandable microspheres. The obtained microspheres have a D50 particle size of 10 μm and a particle size distribution width of 1.04. As a result of performing a TMA test on the obtained microspheres, the microspheres have a T start of 130 °C and a T max of 165 °C. (Example 3)

[0050] S1: Weighed 100 g of water, 25 g of sodium nitrate, and 8 g of colloidal silica I, mixed them, and prepared mixture A. S2: Weighed 10 g of methacrylonitrile monomer, 6 g of vinylidene chloride monomer, 5 g of methacrylic acid, 4 g of methyl methacrylate monomer, 0.15 g of ethylene glycol dimethacrylate as a crosslinking agent, 5 g of cyclohexane as a foaming agent, and 0.15 g of azobisisobutyronitrile as a polymerization initiator, mixed them, and prepared mixture B. S3: Put mixture A and mixture B into sealed containers respectively, stirred them at 1000 rpm for 25 min to form an emulsion. S4: Polymerized the formed emulsion at 65 °C and 400 rpm for 24 h. Dried it at 60 °C in an oven to obtain expandable microspheres. The obtained microspheres have a D50 particle size of 16 μm and a particle size distribution width of 1.15. As a result of performing a TMA test on the obtained microspheres, the microspheres have a T start of 110 °C and a T max of 145 °C. (Example 4)

[0051] S1: Weighed 110 g of water, 28 g of sodium chloride, and 6 g of colloidal silica J, mixed them, and prepared mixture A. S2: Weighed 5 g of acrylonitrile, 9 g of acrylamide, 7 g of vinylidene chloride, 4 g of methyl acrylate, 0.12 g of ethylene glycol dimethacrylate, 4 g of isobutane as a foaming agent, and 0.16 g of dibenzoyl peroxide as a polymerization initiator, mixed them, and prepared mixture B. S3: Put mixture A and mixture B into sealed containers respectively, stirred them at 1100 rpm for 25 min to form an emulsion. S4: Polymerized the formed emulsion at 80 °C and 300 rpm for 4 h. Dried it in an oven at 60 °C to obtain expandable microspheres. The obtained microspheres have a D50 particle size of 11 μm and a particle size distribution width of 1.14. The SEM photograph of the obtained microspheres is shown in Fig. 1, and the micrograph is shown in Fig. 2A. As a result of performing a TMA test on the obtained microspheres, the microspheres have a T start of 105 °C and a T max of 140 °C. (Example 5)

[0052] S1: Weighed 90 g of water, 10 g of sodium sulfate, and 4 g of colloidal silica K, mixed them, and prepared mixture A. S2: Weighed 10 g of methacrylonitrile, 10 g of methyl methacrylate, 5 g of methyl acrylate, 0.1 g of pentaerythritol trimethacrylate, 6 g of isopentane as a foaming agent, and 0.2 g of dibenzoyl peroxide as a polymerization initiator, mixed them, and prepared mixture B. S3: The mixture A and the mixture B were each placed in a sealed container and stirred at 1000 rpm for 25 min to form an emulsion. S4: The formed emulsion was polymerized at 70 °C and 600 rpm for 24 h. It was dried in an oven at 60 °C to obtain expandable microspheres. The obtained microspheres had a D50 particle size of 16 μm and a particle size distribution width of 1.17. As a result of performing a TMA test on the obtained microspheres, the microspheres had a T start of 135 °C and a T max of 165 °C. (Example 6)

[0053] S1: 100 g of water, 20 g of sodium chloride, and 8 g of colloidal silica L were weighed and mixed to prepare mixture A. S2: 15 g of methacrylonitrile, 10 g of methyl acrylate, 0.1 g of diallyl phthalate, 3 g of n-hexane as a foaming agent, and 0.2 g of azobisisobutyronitrile as a polymerization initiator were weighed and mixed to prepare mixture B. S3: The mixture A and the mixture B were each placed in a sealed container and stirred at 1150 rpm for 25 min to form an emulsion. S4: The formed emulsion was polymerized at 54 °C and 300 rpm for 24 h. It was dried in an oven at 60 °C to obtain expandable microspheres. The obtained microspheres had a D50 particle size of 10.5 μm and a particle size distribution width of 1.12. As a result of performing a TMA test on the obtained microspheres, the microspheres had a T start of 136 °C and a T max of 170 °C. (Example 7)

[0054] S1: 100 g of water, 20 g of sodium chloride, and 8 g of colloidal silica L were weighed and mixed to prepare mixture A. S2: Weighed 15 g of acrylonitrile, 5 g of acrylamide, 5 g of methyl acrylate, 0.2 g of ethylene glycol dimethacrylate, 8 g of isopentane as a foaming agent, and 0.35 g of dilauroyl peroxide as a polymerization initiator, and mixed them to prepare mixture B. S3: Put mixture A and mixture B into sealed containers respectively, stirred at 1150 rpm for 25 min to form an emulsion. S4: Polymerized the formed emulsion at 60 °C and 400 rpm for 8 h. Dried at 60 °C in an oven to obtain expandable microspheres. The obtained microspheres have a D50 particle size of 10.5 μm and a particle size distribution width of 1.15. As a result of performing a TMA test on the obtained microspheres, the microspheres have a T start of 155 °C and a T max of 180 °C. (Comparative Example 1)

[0055] Compared with Example 4, the difference is hydrophobic modified colloidal silica. S1: Weighed 110 g of water, 28 g of sodium chloride, and 6 g of colloidal silica CC401 surface-modified with a hydrophobic organic group, and mixed them to prepare mixture A. S2: Weighed 5 g of acrylonitrile, 9 g of acrylamide, 7 g of vinylidene chloride, 4 g of methyl acrylate, 0.12 g of ethylene glycol dimethacrylate, 4 g of isobutane as a foaming agent, and 0.16 g of dibenzoyl peroxide as a polymerization initiator, and mixed them to prepare mixture B. S3: Put mixture A and mixture B into sealed containers respectively, stirred at 1100 rpm for 25 min to form an emulsion. S4: Polymerized the formed emulsion at 75 °C and 300 rpm for 4 h. Dried at 60 °C in an oven to obtain expandable microspheres. After this reaction was completed, a lot of filtration residues were generated. The micrograph of the obtained microspheres is shown in Fig. 2B. As a result of microscopic observation, the sphericity was low and many nuclear structures were observed. The obtained microspheres have a D50 particle size of 13 μm and a particle size distribution width of 1.5. As a result of performing a TMA test on the obtained microspheres, the microspheres have a T start of 105 °C and a T max of 140 °C. (Comparative Example 2)

[0056] Compared with Example 4, the difference is the use of non-modified colloidal silica. S1: Weighed 110 g of water, 28 g of sodium chloride, and 6 g of non-modified colloidal silica JN-30, and mixed them to prepare a mixture A. S2: Weighed 5 g of acrylonitrile, 9 g of acrylamide, 7 g of vinylidene chloride, 4 g of methyl acrylate, 0.12 g of ethylene glycol dimethacrylate, 4 g of isobutane as a foaming agent, and 0.16 g of dibenzoyl peroxide as a polymerization initiator, and mixed them to prepare a mixture B. S3: Put mixture A and mixture B into sealed containers respectively, and stirred them at 1100 rpm for 25 min to form an emulsion. S4: Polymerized the formed emulsion at 75 °C and 300 rpm for 4 h. Dried it in an oven at 60 °C to obtain expandable microspheres. Similarly, after this reaction was completed, many filtration residues were generated, and as a result of microscopic observation, the sphericity was low. The obtained microspheres have a D50 particle size of 15 μm and a particle size distribution width of 2.1. As a result of performing a TMA test on the obtained microspheres, the microspheres have a T start of 105 °C and a T max of 140 °C.

[0057]

Table 1

[0058]

Table 2

[0059] Note: This percentage is calculated based on the input amount of Mixture B, that is, the ratio of the total mass of the obtained filtration residue and Mixture B.

[0060]

Table 3

[0061] As can be seen from the above test results, the colloidal silica surface-modified with the hydrophilic organic group used in the present application has good stability, salt tolerance, less filtration residue of the obtained microspheres, a narrow particle size distribution, and good hydrophilicity of the microspheres in the production of expandable microspheres.

[0062] The above is only a preferred embodiment of the present application. It should be noted that those skilled in the art can also make some improvements and supplements without departing from the method of the present application, and these improvements and supplements are also intended to be included in the protection scope of the present application.

Claims

1. A method for producing thermally expandable microspheres, comprising: mixing hydrophilic organically modified colloidal silica with a mixture of a monomer material capable of forming a thermoplastic polymer shell by polymerization and at least one foaming agent to form an emulsion, and polymerizing the emulsion to form thermally expandable microspheres.

2. The hydrophilic organically modified colloidal silica is obtained by reacting a hydrophilic group-containing compound with a silanol group on the surface of colloidal silica, preferably by reacting a compound containing one or more of a hydroxy group, a carboxyl group, and a siloxanyl group with a silanol group on the surface of colloidal silica, more preferably by reacting one or more of ethylene glycol, oxalic acid, tetraethylene glycol, short-chain polyethylene oxide, polypropylene oxide, and organosilane containing active hydrogen with a silanol group on the surface of colloidal silica. The method according to claim 1.

3. The organosilane containing active hydrogen has an A-B-C structure, Here, A is -SiR １ (OR ２ ) (OR ３ ) or -Si(OR １ ) (OR ２ ) (OR ３ ), where R １ , R ２ , R ３ are C1-C4 hydrocarbyl groups, wherein B is a C1-C10 hydrocarbylene group, which may or may not contain one or more oxygen atoms on the main chain of the hydrocarbylene group, C is one or more of a glycosyl group, a monoglyceryl group, a diglyceryl group, a polyglyceryl group, a xylitol group, an ethylene glycol group, a polyethylene glycol group, an amino group, and a ureido group, Optionally, the organosilane containing active hydrogen is one or more selected from 3-aminopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-aminopropyldimethoxymethylsilane, γ-glycidoxypropyltrimethoxysilane, and 3-glycidoxypropyltriethoxysilane. The method according to claim 2.

4. A method for producing the hydrophilic organically modified colloidal silica, which is Method I: preparing a modifier free of silane in solution D, adjusting the pH of the raw colloidal silica to obtain an acidic colloidal silica solution E, adding solution D to solution E, reacting, and then substituting with water to obtain the hydrophilic organically modified colloidal silica. Alternatively, preparing a silane-containing modifier in solution F, adding solution F to raw material colloidal silica, and reacting them to obtain hydrophilic organic-modified colloidal silica is Method II for manufacturing the hydrophilic organic-modified colloidal silica, the method according to any one of claims 1 to 3.

5. In the manufacturing method, the mass ratio of the modifier to the raw material colloidal silica is (0.001 to 0.05):1, and / or the particle size of the raw material colloidal silica used is 2 to 120 nm, the method according to any one of claims 1 to 4.

6. In the method, a salt is added to suppress the dissolution of the monomer in water, Optionally, the salt is one or more of sodium chloride, potassium chloride, calcium chloride, sodium sulfate, and sodium nitrate, preferably one or more of sodium chloride, potassium chloride, and sodium nitrate, the method according to any one of claims 1 to 5.

7. The monomer is an organic compound capable of free radical polymerization having a double bond, and includes at least one monomer compound having one double bond and at least one monomer compound having a plurality of double bonds, Optionally, the monomer is one or more selected from acrylonitrile, methacrylonitrile, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, ethylstyrene, halostyrene, methyl acrylate, methyl methacrylate, methacrylic acid, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, isobornyl methacrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, vinyl acetate, vinyl laurate, vinyl stearate, vinyl halide, vinylidene halide, dihalogenated vinyl, acrylamide, N-isopropylacrylamide, methylacrylamide, hydroxyethyl methacrylate, diallyl phthalate, allyl methacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, ethylene glycol dimethacrylate, trimethylolpropane triethylene glycol triacrylate, 1,6-hexanediol diacrylate, 2,2-bis(allyloxymethyl)-1-butanol, pentaerythritol triallyl ether, dipropylene phthalate, and / or, the blowing agent is a low-boiling alkane blowing agent, Optionally, the blowing agent is one or more selected from n-butane, isobutane, cyclohexane, isopentane, and methyl chloride. The method according to any one of claims 1 to 6.

8. In the method, a polymerization catalyst is added, Optionally, the polymerization catalyst is an organic peroxide and / or an azo compound. The method according to any one of claims 1 to 7.

9. Thermally expandable microspheres, Manufactured by the method according to any one of claims 1 to 8, the thermally expandable microspheres contain hydrophilic organic-modified colloidal silica, Optionally, the thermally expandable microspheres have a D50 of 2 to 20 μm and a particle size distribution of 1.01 to 1.

2. Thermally expandable microspheres.

10. Use of the thermally expandable microspheres, wherein the thermally expandable microspheres are those produced by the method according to any one of claims 1 to 8 or are the thermally expandable microspheres according to claim 9, and the thermally expandable microspheres are suitable for use in printing, paints, inks, polyurethane abrasives, shoe soles, and heat insulating materials.

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