Preparation method and application of modified silicone resin micropowder

Abstract

A method for preparing modified silicone resin micropowder comprises the following steps: S1: preparing a modified liquid: adding acid to an ethanol aqueous solution to adjust the pH value, then adding a silane crosslinking agent or a coupling agent, stirring and hydrolyzing to obtain a modified liquid. S2: preparing a reaction stock solution: diluting a methyl silicate solution with water and stirring evenly; adding acid to adjust the pH value to 7-10. S3: surface modification of silicone resin micropowder: taking an appropriate amount of modified liquid and adding it to a silicone resin micropowder reaction system, stirring the reaction; adding acid again to adjust the pH value of the reactant to 6-7; filtering, washing with water, and drying to obtain ultrafine silicone resin micropowder. The present invention uses a methyl silicate aqueous solution as a reaction precursor, and reacts the hydrolyzed solution of a silane crosslinking agent or a coupling agent with the silanol groups on the surface of silicone resin particles to prepare modified silicone resin micropowders with different surface characteristics, which can effectively improve the lipophilicity of the silicone resin micropowder, make the silicone resin micropowder have better compatibility with plastics and resins, and improve its dispersion effect in organic substrates.

Description

Technical Field

[0001] The invention relates to the technical field of surface modification of silicone resin micropowder, in particular to a preparation method of modified silicone resin micropowder and application of the modified silicone resin micropowder in LED lamp housings and coatings. Technical Background

[0002] Silicone resin powder is mainly used in LED lamp housings and as a coating additive. As an LED lamp housing, silicone resin powder can make light scattering uniformly and achieve a uniform light effect. As a coating additive, silicone resin powder can improve the feel and increase the wear resistance of the coating. The preparation of silicone resin powder usually uses alkoxysilane as a precursor, such as methyltrimethoxysilane, phenyltrimethoxysilane, vinyltrimethoxysilane or propyltrimethoxysilane, etc., which are hydrolyzed under acidic or alkaline conditions to generate alkyl silicate RSi(OH)3 (R is methyl, phenyl, vinyl and propyl, etc.), and the pH value of the reaction system is adjusted to condense RSi(OH)3 to generate ultrafine silicone resin particles, and the particle size is usually between hundreds of nanometers and several microns. A large amount of by-product methanol will be generated in the above production process. Taking methyltrimethoxysilane as an example, the reaction equation is as follows:

[0003] CH3Si(OCH3)3+3H2O=CH3Si(OH)3+3CH3OH

[0004] CH3Si(OH)3=CH3SiO 1.5 ++1.5H2O

[0005] Methyl silicate may also be used as a precursor instead of alkoxysilane, and the reaction system may be controlled under weak alkaline conditions to condense and generate ultrafine silicone resin particles.

[0006]

[0007]

[0008] The core of the above preparation method is the condensation of silanol groups to form highly cross-linked silicone resin particles. A large number of silanol groups remain on the surface of the particle product, which affects the performance of the silicone resin powder. On the one hand, silanol groups easily form hydrogen bonds with water molecules, affecting the moisture content of the product; on the other hand, a large number of silanol groups on the surface of silicone resin powder are not conducive to its dispersibility in plastics (such as PC, PS, PP, etc.), resins (such as epoxy resins, acrylic resins, alkyd resins, etc.) and organic solvents. The dispersion state of the powder particles in the substrate will significantly affect the performance of the product.

[0009] In order to improve the compatibility of silicone resin powder with organic matter, silane coupling agent can be used to modify its surface. The principle of modification is to introduce organic group R2 on the surface of silicone resin powder by the reaction of silanol -SiOH on the surface of silicone resin powder with alkoxy group OR1 in silane coupling agent R2Si(OR1)3. The reaction equation is as follows:

[0010]

[0011] The usual process is to add silane coupling agent to the reaction system after the silicone resin powder is generated to perform surface modification. However, the reaction rate of silanol and alkoxy is very slow. The above process requires a large amount of silane coupling agent to be added, and the reaction conversion rate is low. As a result, a large part of the silane coupling agent is not used and is discharged with the wastewater, and the modification effect of the silicone resin powder is not good. Summary of the invention

[0012] The present invention aims to provide an efficient method for surface modification of silicone resin particles. This method can significantly increase the reaction rate of silane coupling agent with silanol groups on the surface of silicone resin micropowder, increase the utilization rate of silane coupling agent, and greatly improve the surface modification effect of silicone resin micropowder. This is conducive to improving the dispersibility of the product in organic matter; at the same time, it improves the compatibility and reactivity of silicone resin particles with organic resins.

[0013] The present invention is achieved in that:

[0014] A method for preparing modified silicone resin powder comprises the following steps:

[0015] S1 configuration modification liquid

[0016] S1-1 Mix ethanol and water and stir evenly, wherein the mass ratio of ethanol to water is 0.25-4:1;

[0017] S1-2 Add acid to the ethanol solution to adjust the pH value to 2-5;

[0018] S1-3 adding a silane coupling agent to the acidic ethanol solution, wherein the mass fraction of the silane coupling agent in the mixed solution is 5-20%; stirring and heating, controlling the temperature to 20-50° C., and stirring at a constant temperature for 30-60 minutes to obtain a modified solution;

[0019] S2 Preparation of reaction stock solution

[0020] S2-1 dilute the methyl silicate solution with water to a mass fraction of 2%-20% and stir evenly;

[0021] S2-2 controls the temperature to 20°C-70°C, adds acid to adjust the pH value to 7-10, and stirs at a constant temperature for 1-4 hours to obtain a reaction stock solution;

[0022] Surface modification of S3 silicone resin powder

[0023] S3-1 Add alkali solution dropwise to the reaction stock solution and stir evenly;

[0024] S3-2 Add the modifying liquid to the reaction stock solution, the mass ratio of the modifying liquid to the reaction stock solution is 1:10-150; stir at a constant temperature for 1 hour;

[0025] S3-3 Add acid to the mixed solution and adjust the pH to 6-7;

[0026] S3-4 is filtered, washed with water, and dried to obtain a white powder, which is the target product, modified silicone resin micropowder.

[0027] Preferably, the methyl silicate described in step S2-1 is sodium methyl silicate CH3Si(OH)2ONa, or potassium methyl silicate CH3Si(OH)2OK.

[0028] Preferably, the general formula of the silane coupling agent described in step S1-3 is R2Si(OR1)3, wherein R1 is selected from methyl or ethyl, and R2 is selected from C8-C16 long-chain alkyl, or γ-aminopropyl, or γ-glycidyloxypropyl, or γ-methacryloxypropyl.

[0029] The modified silicone resin powder prepared by the above preparation method is used to manufacture LED lamp housing.

[0030] The modified silicone resin powder prepared by the above preparation method is used to manufacture coatings.

[0031] The micropowder obtained by the method for preparing modified silicone resin micropowder is used for manufacturing LED lamp housing.

[0032] The micropowder obtained by the method for preparing modified silicone resin micropowder is used for manufacturing coatings. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 and Figure 2 It is the particle size distribution diagram during the experiment of the present invention.

[0034] Beneficial Effects

[0035] The present invention uses methyl silicate as a precursor, controls the reaction system under weak alkaline conditions, and forms highly cross-linked silicone resin particles through silanol condensation. A large amount of silanol remains on the surface of the particle product, which affects the performance of the silicone resin micropowder. On the one hand, silanol easily forms hydrogen bonds with water molecules, affecting the water content of the product; on the other hand, a large amount of silanol exists on the surface of the silicone resin micropowder, which is not conducive to its dispersibility in plastics (such as PC, PS, PP, etc.), resins (such as epoxy resins, acrylic resins, alkyd resins, etc.) and organic solvents. The dispersion state of the powder particles in the substrate will significantly affect the performance of the product. The method of the present invention can be used to prepare modified silicone resin micropowder with excellent performance, which is beneficial to improve the dispersibility of the product in organic matter; different functional groups can also be introduced on the surface of silicone resin particles to improve the compatibility and reactivity of silicone resin particles with organic resins. The preparation method of the present invention has a simple process, a high utilization rate of silane coupling agent, a fast reaction speed, and a good surface modification effect of the silicone resin micropowder product. The obtained modified silicone resin powder can be used to manufacture LED lamp housing to achieve a uniform light effect; adding it to paint can improve the scratch and wear resistance of the paint surface and enhance the matte effect of the paint surface. Example

[0036] Embodiment 1:

[0037] 1.1 Preparation of modified liquid

[0038] Add 27g water and 27g ethanol to a 100mL flask, add 0.02g 0.1mol / L hydrochloric acid, stir evenly, and measure the pH value to be 3.7. Then add 6g glycidyloxypropyltrimethoxysilane, heat to 35°C, and stir for 30 minutes.

[0039] 1.2 Preparation of silicone resin powder

[0040] In a 1L flask, add 60g of 35% sodium methyl silicate aqueous solution, then add 540g of pure water, stir, heat to 50°C, add 9.3g of 1mol / L hydrochloric acid solution, measure the reaction system pH = 9.1, and stir at a constant temperature of 50°C for 150 minutes.

[0041] 1.3 Surface modification

[0042] Add 1g of 0.1mol / L sodium hydroxide solution to the reaction system described in 1.2. Take 5g of the modified solution described in 1.1 and add it to the reaction system, keep the constant temperature at 50℃, and stir for 1 hour. Then neutralize the reactants with 1mol / L hydrochloric acid solution, measure the pH of the reaction system to be 6.8, filter, wash with water, and dry to obtain a white powder product with an average particle size of 4.219 microns, a span of 1.303, and a particle size distribution as shown below: Figure 1 As shown:

[0043] Weigh two portions of 100g epoxy resin E44, add 5g of unmodified silicone resin powder (D50=4.5um, span 1.68) and 5g of the product of Example 1 respectively, disperse for 15 minutes with a high-speed disperser, take samples and scrape the fineness, the former fineness is 50um, the latter fineness is 30um. The silicone resin powder modified with glycidyloxypropyltrimethoxysilane has better dispersibility in epoxy resin.

[0044] Embodiment 2:

[0045] 2.1 Preparation of modified liquid

[0046] Add 12g water and 45g ethanol to a 100mL flask, add 0.04g 0.1mol / L hydrochloric acid, stir evenly, and measure the pH value to be 3.3. Then add 3g octyltriethoxysilane, heat to 40℃, and stir for 30min.

[0047] 2.2 Preparation of silicone resin powder

[0048] Add 90g of 35% sodium methyl silicate aqueous solution into a 1L flask, then add 510g of pure water, stir, heat to 70°C, add 9.3g of 1mol / L hydrochloric acid solution, measure the pH of the reaction system to be 9.3, and stir at a constant temperature of 70°C for 150 minutes.

[0049] 2.3 Surface modification

[0050] Add 1g of 0.1mol / L sodium hydroxide solution to the reaction system described in 2.2. Take 12g of the modified solution described in 2.1 and add it to the reaction system, keep the constant temperature at 70℃, and stir for 1 hour. Then neutralize the reactants with 1mol / L hydrochloric acid solution, measure the pH of the reaction system to be 6.9, filter, wash with water, and dry to obtain a white powder product with an average particle size of 5.746 microns, a span of 1.129, and a particle size distribution as shown in Figure 2 As shown:

[0051] The alkali solution in the surface modification step is selected from sodium hydroxide, potassium hydroxide or ammonia water.

[0052] Add 10% unmodified silicone resin powder to polypropylene PP plastic, use a single screw extruder for blending and granulation, and use a 2-layer 150-mesh filter screen for filtration. Usually, after 12-24 hours of production, powder particles will block the filter screen, and the head pressure will increase significantly, and the filter membrane needs to be replaced. Using octyl triethoxysilane modified silicone resin powder, under the same working conditions, it can run continuously for 48 hours, and the head pressure remains relatively stable. This shows that the silicone resin powder modified by octyl triethoxysilane has better compatibility with polypropylene.

[0053] The properties of surface-modified silicone resin micropowder are mainly reflected in improving the compatibility and dispersibility of powder and PP, and improving the production efficiency of powder and plastic mixing. Whether the powder is modified or not will have a certain impact on light diffusion. As a material for the outer shell of an LED lamp, the micropowder prepared by the present invention produces a significantly improved uniform light effect than the unmodified micropowder. As an additive for coatings, the micropowder prepared by the present invention significantly increases the scratch and wear resistance of the coating surface compared to the unmodified micropowder, and enhances the matte effect of the coating surface.

Claims

1. A method for preparing modified silicone resin powder, characterized in that: The following steps are involved: S1 configuration modification liquid S1-1 Mix ethanol and water and stir evenly, wherein the mass ratio of ethanol to water is 0.25-4:1; S1-2 Add acid to the ethanol solution to adjust the pH value to 2-5; S1-3 Add a silane coupling agent to the acidic ethanol solution. The general formula of the silane coupling agent is , wherein R1 is selected from methyl or ethyl, R2 is selected from C8-C16 long-chain alkyl, or γ-aminopropyl, or γ-glycidyloxypropyl, or γ-methacryloxypropyl; the mass fraction of the silane coupling agent in the mixed solution is 5-20%; stirring and heating, controlling the temperature to 20-50°C, stirring at a constant temperature for 30-60 minutes to obtain a modified solution; S2 Preparation of reaction stock solution S2-1 Dilute the sodium methyl silicate CH3Si(OH)2ONa or potassium methyl silicate CH3Si(OH)2OK solution with water to a mass fraction of 2%-20% and stir evenly; S2-2 control the temperature to 20 ℃ -70 ℃, add acid to adjust the pH to 7-10, stir at a constant temperature for 1-4 hours to obtain the reaction solution; Surface modification of S3 silicone resin powder S3-1 Add alkali solution dropwise to the reaction stock solution and stir evenly; S3-2 Add the modifying liquid to the reaction stock solution, the mass ratio of the modifying liquid to the reaction stock solution is 1:10-150; stir at a constant temperature for 1 hour; S3-3 Add acid to the mixed solution to adjust the pH to 6-7; S3-4 is filtered, washed with water, and dried to obtain a white powder, which is the target product, modified silicone resin micropowder.

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