Polymer silver-plated microspheres and preparation method thereof

Abstract

The preparation method of the polymer silver-plated microspheres, provided by the invention, comprises the following steps: (1) preparation of seed microspheres: firstly, pouring a chain transfer agent n-octyl mercaptan and methyl methacrylate into a four-neck flask placed in an oil bath pan, then adding water, ethanol and sodium chloride into the four-neck flask, introducing nitrogen, heating, and carrying out a polymerization reaction to obtain the seed microspheres; (2) surface modification of the microspheres: adding the seed microspheres obtained in the step (1) into water, adjusting the pH value of the system to 4-5, and then adding KH590 into the system to enable the surfaces of the microspheres to have sulfydryl; and (3) silver plating treatment of the microspheres: taking the microspheres with sulfydryl groups on the surfaces obtained in the step (2), adding a silver-ammonia solution, then adding a glucose solution into the solution, enabling Ag < + > adsorbed on the surfaces of the microspheres to be subjected to reduction reaction, and coating the Ag < + > on the surfaces of the microspheres to obtain the PMMA silver-plated microspheres. According to the method for preparing the polymer silver-plated microspheres, the preparation process can be simplified, and the silver plating effect can be improved.

Description

Technical Field

[0001] The invention relates to the field of conductive fillers, and in particular to polymer silver-plated microspheres and a preparation method thereof. Background Art

[0002] In the field of microsphere preparation technology, especially in the preparation of conductive microspheres, the traditional method mainly uses metal microspheres as conductive fillers. These metals are usually metals with high conductivity or high magnetic permeability, such as copper powder, silver powder, etc. However, these metals have some problems, such as low conductivity and easy oxidation of copper powder, and high cost and high density of silver powder.

[0003] In the field of silver plating technology, the existing solution is usually to plate silver on copper. Although this method reduces costs, the problem of high density still exists. Another solution is to plate silver on the surface of polymer microspheres. This method can not only reduce costs, but also solve the problem of high density. There are two main methods for modifying the surface of polymer microspheres for silver plating. One is as described in patent CN102212801A, first sensitizing with SnCl2 and then adding PdCl2 for activation. The other is to obtain groups that can adsorb or reduce Ag+ on the microspheres by grafting modification. For example, the microspheres are first modified with KH570 hydroxyl and then modified with Kh590 thiol. And amino groups are grafted on microspheres containing cyano groups for adsorption of Ag+.

[0004] However, the currently known methods for activating and modifying the microspheres are relatively complicated, and often require two or more steps to allow the base microspheres to obtain a better ability to adsorb Ag+. These activation and modification steps not only reduce efficiency, but also increase costs. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a method for preparing polymer silver-plated microspheres.

[0006] In order to achieve the above purpose, this technical solution mainly adopts the following technical means:

[0007] 1. Prepare seed microspheres by soap-free emulsion polymerization: MMA, chain transfer n-octyl mercaptan, initiator potassium persulfate (KPS), water / ethanol are used as raw materials to carry out soap-free emulsion polymerization to obtain seed microspheres. By controlling the reaction time and temperature, such as setting the oil bath temperature to 88°C and the time to 2h, more oligomers are obtained on the surface of the microspheres.

[0008] 2. Surface modification of microspheres: In the presence of surface oligomers, the microspheres can be directly modified with silane coupling agent KH590 to obtain microspheres with thiol groups on the surface. Compared with the existing technology, this modification method is simpler and can be completed in one step.

[0009] 3. Silver plating of microspheres: The modified microspheres can be used as excellent carriers for loading silver in silver ammonia solution to obtain microspheres whose surfaces are tightly wrapped with silver. Compared with the existing technology, this method does not require the two steps of sensitization and activation, is simpler to operate, and is conducive to large-scale production.

[0010] 4. Regulating the particle size of microspheres: The water / ethanol ratio can be adjusted in the system to prepare microspheres of different particle sizes as seed microspheres to adapt to different application scenarios. This method can flexibly adjust the particle size of microspheres according to actual needs, thereby improving the applicability of the product.

[0011] A method for preparing polymer silver-plated microspheres comprises the following steps:

[0012] (1) Preparation of seed microspheres: First, 0.15-0.2 parts of chain transfer agent n-octyl mercaptan are added to 15-20 parts of methyl methacrylate (MMA), and the mixture is poured into a four-necked flask placed in an oil bath. Water, ethanol and sodium chloride are then added thereto. While the mixture is stirred, nitrogen is introduced and the temperature is raised to 90° C. The condenser switch is turned on. After the temperature reaches 90° C., 0.075-0.1 parts of potassium persulfate are added to the mixture as a polymerization initiator. A polymerization reaction is carried out in an oil bath at 90° C. for 2 hours to obtain seed microspheres.

[0013] (2) Surface modification of microspheres: 10 parts of the seed microspheres obtained in step (1) were added to 70-80 parts of water, and the pH value of the system was adjusted to 4-5 after sufficient stirring and mixing. Then, 0.5-0.8 parts of KH590 were added thereto, and the reaction was stirred at room temperature for 4 hours to allow the microspheres to have thiol groups on their surfaces. The microspheres were obtained by centrifugation or filtration.

[0014] (3) Silver plating of microspheres: 0.5 parts of the microspheres with thiol groups on the surface obtained in step (2) are added to 50-80 parts of a silver ammonia solution (silver nitrate content is 15 g / L), stirred at room temperature for 1 hour, and then 20-32 parts of a reducing agent glucose solution (100 g / L) are added to the above solution to allow the Ag+ adsorbed on the surface of the microspheres to undergo a reduction reaction and be coated on the surface of the microspheres to obtain PMMA silver-plated microspheres.

[0015] Furthermore, in step (1), the particle size of the seed microspheres is 0.6-2 microns, which can be adjusted by adjusting the amount of water, ethanol and sodium chloride added.

[0016] In one embodiment, the amount of water added in step (1) is 85 parts, and the amount of ethanol and sodium chloride added is 0.

[0017] In one embodiment, in step (1), the amount of water added is 70 parts, the amount of ethanol added is 10 parts, and the amount of sodium chloride added is 0.

[0018] In one embodiment, in step (1), the amount of water added is 70 parts, the amount of ethanol added is 10 parts, and the amount of sodium chloride added is 2 parts.

[0019] Another aspect of the present invention provides a polymer silver-plated microsphere, which is prepared by the above method.

[0020] Compared with the existing technology, the beneficial effects of this technical solution are as follows:

[0021] 1. Simplified preparation process: The present invention prepares seed microspheres by soap-free emulsion polymerization. By adjusting the reaction time and temperature, more oligomers are present on the surface of the microspheres. Then, the microspheres are modified by silane coupling agent KH590 to obtain microspheres with thiol groups on the surface. This method can complete the modification in one step, greatly simplifying the preparation process and improving production efficiency.

[0022] 2. Improve the silver plating effect: Due to the presence of oligomers on the surface of the microspheres, the mercapto-containing silane coupling agent KH590 is more tightly combined with the microspheres, which is more conducive to the coating of Ag ions on the surface of the microspheres, thereby improving the silver plating effect.

[0023] 3. Improve the performance of microspheres: The present invention adopts PMMA microspheres to be silver-plated, which not only reduces the cost but also solves the problem of high density. At the same time, the microspheres prepared by soap-free emulsion polymerization have a narrow particle size distribution, and there are no impurities in the system, which will not have adverse effects on the use of silver-plated microspheres.

[0024] 4. Strong adaptability: The present invention can adjust the ratio of ethanol / water in the system to prepare microspheres of different particle sizes as seed microspheres to adapt to different application scenarios, and has strong adaptability. In general, compared with the prior art, the present invention not only simplifies the preparation process, improves the silver plating effect, but also improves the performance of the microspheres, has strong adaptability, and is a superior method for preparing PMMA silver-plated microspheres. DETAILED DESCRIPTION

[0025] The present invention is further described below by way of examples. In the examples listed, unless otherwise stated, all parts and percentages in the examples are parts and percentages by weight.

[0026] Embodiment 1:

[0027] Step (1): Preparation of seed microspheres: first, add 0.15 parts of chain transfer agent n-octyl mercaptan to 15 parts of methyl methacrylate (MMA), pour the mixture into a four-necked flask placed in an oil bath, add 85 parts of water, introduce nitrogen while stirring the mixture, raise the temperature to 90° C., turn on the condenser switch, and after the temperature reaches 90° C., add 0.075 parts of potassium persulfate as a polymerization initiator to the mixture, perform a polymerization reaction in an oil bath at 90° C. for 2 hours, and obtain seed microspheres with a particle size of 0.6 μm;

[0028] Step (2): Surface modification of microspheres: 10 parts of seed microspheres obtained in step 1 are added to 70 parts of water, and after sufficient stirring and mixing, the pH value of the system is adjusted to 4-5, and 0.5 parts of KH590 are added thereto. The reaction is stirred at room temperature for 4 hours to allow the surface of the microspheres to be provided with thiol groups, and the microspheres are obtained by centrifugation or filtration;

[0029] Step (3): Silver plating of microspheres: 0.5 parts of the microspheres with thiol groups on the surface obtained in step 2 are added to 50 parts of silver ammonia solution (silver nitrate content is 15 g / L), stirred at room temperature for 1 hour, and then 20 parts of reducing agent glucose solution (100 g / L) are added to the above solution to allow the Ag+ adsorbed on the surface of the microspheres to undergo a reduction reaction and be coated on the surface of the microspheres to obtain PMMA silver-plated microspheres.

[0030] Embodiment 2:

[0031] Step (1): Preparation of seed microspheres: First, add 0.2 parts of chain transfer agent n-octyl mercaptan to 20 parts of methyl methacrylate (MMA), pour into a four-necked flask placed in an oil bath, then add 70 parts of water and 10 parts of ethanol, and while stirring the mixture, introduce nitrogen and heat to 90°C, and turn on the condenser switch. After the temperature reaches 90°C, add 0.1 parts of potassium persulfate as a polymerization initiator to the mixture, and perform a polymerization reaction in a 90°C oil bath for 2 hours to obtain seed microspheres with a particle size of 1.2 microns;

[0032] Step (2): Surface modification of microspheres: 10 parts of seed microspheres obtained in step 1 are added to 70 parts of water, and after sufficient stirring and mixing, the pH value of the system is adjusted to 4-5, and 0.6 parts of KH590 are added thereto. The reaction is stirred at room temperature for 4 hours to allow the surface of the microspheres to be provided with thiol groups, and the microspheres are obtained by centrifugation or filtration;

[0033] Step (3): Silver plating of microspheres: 0.5 parts of the microspheres with thiol groups on the surface obtained in step 2 are added to 60 parts of silver ammonia solution (silver nitrate content is 15 g / L), stirred at room temperature for 1 hour, and then 20 parts of reducing agent glucose solution (100 g / L) are added to the above solution to allow the Ag+ adsorbed on the surface of the microspheres to undergo a reduction reaction and be coated on the surface of the microspheres to obtain PMMA silver-plated microspheres.

[0034] Embodiment 3:

[0035] Step (1): Preparation of seed microspheres: first, add 0.18 parts of chain transfer agent n-octyl mercaptan to 18 parts of methyl methacrylate (MMA), pour the mixture into a four-necked flask placed in an oil bath, then add 70 parts of water, 10 parts of ethanol and 2 parts of sodium chloride, introduce nitrogen while stirring the mixture, raise the temperature to 85° C., turn on the condenser switch, and after the temperature reaches 85° C., add 0.08 parts of potassium persulfate as a polymerization initiator to the mixture, perform a polymerization reaction in an 85° C. oil bath for 2 hours, and obtain seed microspheres with a particle size of 2 μm;

[0036] Step (2): Surface modification of microspheres: 15 parts of seed microspheres obtained in step 1 are added to 80 parts of water, and the pH value of the system is adjusted to 4-5 after sufficient stirring and mixing. 0.8 parts of KH590 are added thereto, and the reaction is stirred at room temperature for 4 hours to allow the surface of the microspheres to be provided with thiol groups, and the microspheres are obtained by centrifugation or filtration;

[0037] Step (3): Silver plating of microspheres. Take 1 part of the microspheres with thiol groups on the surface obtained in step 2 and add them to 80 parts of silver ammonia solution (silver nitrate content is 15 g / L). Stir at room temperature for 1 hour. Then, add 32 parts of reducing agent glucose solution (100 g / L) to the above solution to make the Ag+ adsorbed on the surface of the microspheres undergo reduction reaction and be coated on the surface of the microspheres to obtain PMMA silver-plated microspheres.

Claims

1. A method for preparing polymer silver-plated microspheres, comprising the following steps: (1) Preparation of seed microspheres: First, 0.15-0.2 parts of chain transfer agent n-octyl mercaptan are added to 15-20 parts of methyl methacrylate (MMA), and the mixture is poured into a four-necked flask placed in an oil bath. Water, ethanol and sodium chloride are then added thereto. While the mixture is stirred, nitrogen is introduced and the temperature is raised to 90° C. The condenser switch is turned on. After the temperature reaches 90° C., 0.075-0.1 parts of potassium persulfate are added to the mixture as a polymerization initiator. A polymerization reaction is carried out in an oil bath at 90° C. for 2 hours to obtain seed microspheres. (2) Surface modification of microspheres: 10 parts of the seed microspheres obtained in step (1) were added to 70-80 parts of water, and the pH value of the system was adjusted to 4-5 after sufficient stirring and mixing. Then, 0.5-0.8 parts of KH590 were added thereto, and the reaction was stirred at room temperature for 4 hours to allow the microspheres to have thiol groups on their surfaces. The microspheres were obtained by centrifugation or filtration. (3) Silver plating of microspheres: 0.5 parts of the microspheres with thiol groups on the surface obtained in step (2) are added to 50-80 parts of a silver ammonia solution (silver nitrate content is 15 g / L), stirred at room temperature for 1 hour, and then 20-32 parts of a reducing agent glucose solution (100 g / L) are added to the above solution to allow the Ag+ adsorbed on the surface of the microspheres to undergo a reduction reaction and be coated on the surface of the microspheres to obtain PMMA silver-plated microspheres.

2. The method for preparing polymer silver-plated microspheres according to claim 1, characterized in that: The particle size of the seed microspheres in step (1) is 0.6-2 microns, which can be adjusted by adjusting the amount of water, ethanol and sodium chloride added.

3. The method for preparing polymer silver-plated microspheres according to claim 1, characterized in that: In the step (1), the amount of water added is 85 parts, and the amount of ethanol and sodium chloride added is 0.

4. The method for preparing polymer silver-plated microspheres according to claim 1, characterized in that: In the step (1), the amount of water added is 70 parts, the amount of ethanol added is 10 parts, and the amount of sodium chloride added is 0.

5. The method for preparing polymer silver-plated microspheres according to claim 1, characterized in that: In the step (1), the amount of water added is 70 parts, the amount of ethanol added is 10 parts, and the amount of sodium chloride added is 2 parts.

6. A polymer silver-plated microsphere, characterized in that: The polymer silver-plated microspheres are prepared by any method described in claims 1-5.