TWI668238B - Method of fabricating cross-linked polymer microparticles using low quantity of surfactant - Google Patents

Abstract

The present invention provides a method of producing a plurality of crosslinked polymeric microparticles using a low amount of a surfactant. According to the method of the present invention, crosslinked polymeric microparticles are produced by a seed swelling polymerization process. In the seed swelling polymerization process, the amount of surfactant used in accordance with the method of the present invention is greater than or equal to 0.5 critical cell concentration (CMC) and less than 1 CMC.

Description

Method for producing a plurality of crosslinked polymer microparticles using a low amount of surfactant

The present invention relates to a method for producing crosslinked polymeric microparticles having a uniform particle size superior to room temperature in a high temperature environment, and in particular, the present invention relates to the use of a low amount of surfactant to produce a crosslinked type. The method of polymer microparticles.

A cross-linking type polymer fine particle having a high degree of crosslinking and excellent heat resistance and solvent resistance, and can be applied to a modifier of a lubricating property of a resin film starting from various electrical and electronic materials such as various spacers and conductive fine particles. , in the fields of chromatography carriers, biomedical devices, and the like. In general, these crosslinked polymer fine particles can be produced by a suspension polymerization method, an emulsion polymerization method, a seed swelling polymerization method, a dispersion polymerization method, or the like.

The crosslinked polymer microparticles are electrolessly plated with a conductive metal layer, and then mixed and kneaded with a binder resin or a viscous adhesive, and are widely used, for example, anisotropic conductive paste, anisotropic conductive ink, and various directions. An anisotropic conductive material such as an anisotropic conductive adhesive, an anisotropic conductive film, or an anisotropic conductive sheet.

The electronic components used for anisotropic conductive materials tend to be in a high temperature environment higher than room temperature as the number of use/operation hours increases, and the durability of electronic components decreases.

The above crosslinked polymer microparticles generally have a uniform particle size Features with appropriate mechanical properties (particle compression deformation recovery rate). However, in recent years, with the rapid advancement or development of electronic devices, the industry has demanded that the crosslinked polymer microparticles used as conductive particles have good mechanical properties to enhance the durability of electronic devices.

Regarding the prior art of the crosslinked polymer microparticles, the Republic of China Patent No. I418568 mentions that the Cv% (coefficient of variation of the particle size distribution) of the crosslinked polymer microparticles is preferably 10% or less, and more preferably 5% or less, and more preferably 3% or less. When the Cv% value is too large, when the conductive particles are used for the connection between the electrodes, the interval between the electrodes is likely to be uneven.

The Republic of China Patent Publication No. 200948881 mentions the improvement of the mechanical properties (particle compression recovery rate) of the crosslinked polymer microparticles, and helps to connect the resistance value when the electroconductive particles electrically connect the electrodes of the substrate. Lowering, connection reliability can be improved. The compression recovery rate of the embodiment of the Republic of China Patent Publication No. 200948881 does not exceed 50%.

Prior art conductive particles are used in electronic devices. It is often found that as the operating hours of electronic devices increase, the ambient temperature increases. In this case, the mechanical properties of crosslinked polymer microparticles decrease with temperature. The risk is that the durability of the electronic device is reduced.

In recent years, along with the improvement of the durability of electronic equipment in a high temperature environment, crosslinked polymer microparticles having good mechanical properties in a high temperature environment are being actively studied.

With regard to the manufacture of highly crosslinked monodisperse micronized particles, the use of high added surfactants is unavoidable. The use of a surfactant can increase the stability of the swelling monomer in the dispersion medium during the production of the crosslinked polymer microparticles. Japanese Patent Publication No. 3130437 states that when the amount of the surfactant added is more than 6 times the critical micelle concentration (CMC) or less than 1 time CMC, the particle size distribution results are not satisfactory. Japanese Patent Publication No. 3130437 discloses that the amount of surfactant added is too small. Many large particle sizes are formed, and if the amount of the surfactant added is too large, too many small particle diameters are generated. It can be seen that to produce uniform particle size crosslinked particles, it is quite important to control the amount of surfactant added. However, the addition of high-dose surfactants is not completely harmless. In addition to increasing production and purification costs, additional additives have an impact on product properties, mechanical properties, and subsequent processing.

Accordingly, it is an object of the present invention to provide a method for producing crosslinked polymeric microparticles using a low amount of surfactant. The crosslinked polymeric microparticles produced by the method of the present invention are provided with a uniform particle size having temperature-regulating mechanical properties. Further, the conductive particles formed by the electroless plating of the metal layer produced by the crosslinked polymer microparticles produced by the method of the present invention should be applied to the anisotropic conductive material to electrically connect the connecting member. Improves the reliability and durability of electrical conduction in high temperature environments.

According to the method of the present invention, a plurality of polymethyl methacrylate (PMMA) primary microparticles are synthesized by subjecting a methyl methacrylate monomer to a non-emulsion emulsion polymerization process. Next, according to the method of the present invention, a plurality of PMMA primary microparticles are subjected to a first seed swelling polymerization process under the action of a first polymerization initiator and a molecular weight modifier and a first surfactant to synthesize a plurality of uncrosslinked PMMA seed particles. Finally, according to the method of the present invention, a plurality of uncrosslinked PMMA seed particles are further reacted with a crosslinking agent and a second surfactant to perform a second seed swelling polymerization process under the action of a second polymerization initiator. A plurality of crosslinked polymer microparticles are synthesized. The second surfactant is used in an amount of greater than or equal to 0.5 times CMC and less than 1 time CMC.

The crosslinked polymeric microparticles produced by the method of the present invention have a compression set recovery ratio of greater than 80% at 180 °C.

The cross-linking type polymer fine particles produced by the method of the present invention have a particle size variation coefficient Cv% of less than 10%. Manufactured according to the method of the present invention The crosslinked type polymer microparticles have an average particle diameter of from 1 micrometer to 10 micrometers.

In one embodiment, the first surfactant and the second surfactant may be sodium lauryl sulfate, sodium dodecylbenzene sulfonate, and lauryl polyoxyethylene, respectively. Sodium lauryl polyoxyethylene ether sulfate, sodium dioctyl sulfosuccinate, lauryl trimethyl ammonium chloride, polyoxyethylene alkyl ether Alkyl ethers), polyoxyethylene fatty acid esters, mixtures of the above surfactants, or other commercial surfactants.

The advantages and spirit of the present invention will be further understood from the following detailed description of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail. However, the invention is not limited to the following preferred embodiments.

According to the method of the present invention, the uniform particle size crosslinked particles are produced by dispersing the oil phase monomer/crosslinking agent in water via the seed particles under an aqueous medium, and emulsification of the oil phase monomer/crosslinking agent by an emulsification homogenizer An oil in water (O/W) type microemulsion is formed. Under appropriate conditions, the microemulsion is mixed with the seed particles, and the seed particles absorb the emulsified monomer and the crosslinking agent. After the seed particles are swollen and grown, the polymerization is further carried out to form a uniformly crosslinked microparticle having a uniform particle size. The method for producing a plurality of crosslinked polymer microparticles according to the present invention comprises a seed particle synthesis process and a crosslinked particle synthesis process. The synthesis method and steps of the seed particle synthesis process and the crosslinked particle synthesis process are detailed below.

Seed particle synthesis process

Step 1: According to the method of the present invention, a methyl methacrylate (MMA) monomer is first subjected to a soap free emulsion polymerization (SFS) process to synthesize a plurality of polymethyl methacrylate (poly ( Methyl methacrylate, PMMA) Initial microparticles.

In one example, methyl methacrylate (MMA) is used in accordance with the process of the invention to remove the inhibitor using Al ₂ O ₃ . According to the method of the present invention, 90 g of the reaction monomer, 540 g of deionized water and 1.8 g of a molecular weight regulator: 1-octanethiol were placed in a 1 L reaction flask. After degassing under nitrogen for 30 minutes according to the method of the present invention, the reactor was heated to 70 ° C and stirred (stirring speed of 200 rpm). The reaction monomer is subjected to polymerization under a heating flow back device. According to the method of the present invention, when the temperature of the reaction liquid reaches the reaction temperature, the initiator solution: potassium peroxydisulfate (KPS) / deionized water = 0.47 g / 18 g is added, and the particle size is about 0.4 after 12 hours of reaction. The solution has a molecular weight of about 16,600 PMMA particles.

Examples of the aqueous polymerization inhibitor include sodium nitrite, cuprous chloride, ferric chloride, and sulfur. These can be used alone or in combination of two or more types.

Step 2: According to the method of the present invention, a plurality of PMMA primary microparticles are subjected to a first seed swelling polymerization process under the action of a first polymerization initiator and a molecular weight modifier and a first surfactant to synthesize a plurality of uncrosslinked PMMA seed particles. The first polymerization initiator may be azobisisobutyronitrile (AIBN) or bnezoyl peroxide (BPO). The molecular weight regulator may be 1-octanethiol. The first surfactant may be sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium lauryl polyoxyethylene ether sulfate, sodium amber octyl sulfonate, cetyltrimethylammonium chloride, respectively. , polyoxyethylene alkyl ethers, polyoxyethylene fatty acid esters, mixtures of the above surfactants, or other commercial Surfactant.

In one example, according to the method of the present invention, the reaction oil phase is 110 g of the MMA monomer after removing the inhibitor, 2.2 g of the molecular weight regulator and 1.1 g of the first polymerization initiator, and the aqueous phase is 440 g of deionized water. An interfacial surfactant of 1.1 g was first mixed with an oil phase and an aqueous phase and dispersed at an emulsifier of 12000 rpm/10 minutes. Next, the method according to the invention was again shaken by an ultrasonic pulverizer for 5 minutes. A 1 L reaction flask was charged with 76.8 g of the above-mentioned 0.4 μm molecular weight 16,600 PMMA particles (13.3% of PMMA particle solution dispersion solid content), nitrogen gas was introduced thereto, and a heating reflux apparatus was installed, and the stirring blade rotation speed was 100 rpm. Next, the liquid in which the oil-water phase was uniformly mixed was injected into the 1 L reactor at a time according to the method of the present invention, and the PMMA particles were swollen for 24 hours. Next, according to the method of the present invention, 3.6 wt% of a stabilizer: 220 g of a polyvinyl alcohol (PVA) aqueous solution was added, and then the reactor was further heated to 55 ° C for 6 hours, and then further heated to 80 ° C for 1.5 hours. After the reaction, a seed particle having a particle diameter of about 0.6 μm and a molecular weight of about 16,500 PMMA was obtained.

For the molecular weight of PMMA particles, the present invention is calculated by the following steps. The molecular weight information of the seed polymer microparticles is obtained by gel permeation chromatography (GPC) measurement. The measurement procedure is as follows. First, a calibration curve is prepared by using a standard molecular weight polystyrene polymer, and then the seed polymer to be tested is used. The microparticles were taken in tens of milligrams in tetrahydrofuran, and injected into a gel permeation chromatograph using a micro syringe. The device software was used to compare the relative molecular weight of the sample.

Molecular weight information can be obtained by aligning the Agilent 1100 series equipment with the chromatography column Styragel ® HR 5 manufactured by Waters via the software HP GPC-Addon Rev A.01.03.

Crosslinked particle synthesis process

According to the method of the present invention, the plurality of uncrosslinked PMMA seed particles are further reacted with a crosslinking agent and a second surfactant to perform a second seed swelling polymerization process under the action of a second polymerization initiator. A plurality of crosslinked polymeric microparticles are synthesized, wherein the second surfactant is used in an amount greater than or equal to 0.5 times the critical microcell concentration (CMC) and less than 1 time CMC. The second polymerization initiator may be azobisisobutyronitrile (AIBN) or benzoic acid peroxide (BPO). The second surfactant may be sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium lauryl polyoxyethylene ether sulfate, sodium amber octyl sulfonate, cetyl trimethyl ammonium chloride, respectively. A polyoxyethylene alkyl ether, a polyoxyethylene fatty acid ester, a mixture of the above surfactants, or other commercial surfactant.

Further, in the crosslinked particle synthesis process, the crosslinker formulation employed in accordance with the method of the present invention comprises a hydrophobic monomer. The hydrophobic monomer has a solubility in water of less than 0.6 g/L. The proportion of hydrophobic monomer to one of the crosslinking agents is greater than or equal to 15% by weight. The hydrophobic monomer may be 1,6-hexanediol diacrylate, 1,6-Hexanediol dimethacrylate, dimethacrylate B. Ethyleneglycol dimethacrylate, divinylbenzene, Trimethylolpropane triacrylate, Trimethylol propane Trimethacrylate, pentaerythritol triacrylate (pentaerythritol) Tetraacrylate), diurethane dimethylacrylate, bisphenol A glycerolate diacrylate or a mixture of the above hydrophobic monomers.

Example 1

According to the method of the present invention, 48 g of the reaction monomer MMA after removing the inhibitor, 2.4 g of divinylbenzene (DVB) and 2.4 g of the second polymerization initiator (75 wt%) are added to the pre-configured 0.6 wt. 5% of the PVA aqueous solution was 550 ml, and the second surfactant was 0.125 wt% and the addition amount was 0.5 times CMC. According to the method of the present invention, dispersion was first carried out at an emulsifier of 12000 rpm/10 minutes, followed by oil/water dispersion by an ultrasonic pulverizer.

According to the method of the present invention, 6.54 g (solid content: 12.2%) of PMMA seed particles were first added to a 1 L reactor, nitrogen gas was introduced thereto, and a heating reflux apparatus was attached, and the particles were dispersed by stirring the blades (rotation speed: 100 rpm). The liquid in which the oil-water phase is uniformly mixed according to the method of the present invention is slowly injected into the 1 L reactor by an automatic injection machine for 3 hours, and then the PMMA seed particles are further swollen at 30 ° C for 3 hours, followed by the reactor. The temperature was raised to 80 ° C for 15 hours. The product after the reaction was separated by centrifugation, and washed three times with deionized water and methanol, and dried under vacuum to obtain spherical crosslinked polymer microparticles.

Example 2

In Example 2, the amount of monomer added in the reaction step was equivalent to that in Example 1. The difference is that the concentration and addition amount of the second surfactant in the aqueous phase solution is 0.17 wt% and 0.75 times CMC.

Example 3

In Example 2, the amount of monomer added in the reaction step was equivalent to that in Example 1. The difference is that the concentration and addition amount of the second surfactant in the aqueous phase solution is 0.23 wt% and 0.50 times CMC.

Comparative example 1

In Comparative Example 1, the amount of monomer added in the reaction step was equivalent to that in Example 1. The difference is that the concentration and the added amount of the second surfactant in the aqueous phase solution are 0.69 wt% and 3.0 times CMC.

Comparative example 2

In Comparative Example 2, the amount of monomer added in the reaction step was equivalent to that in Example 1. The difference is that the concentration and addition amount of the second surfactant in the aqueous phase solution is 1.16 wt%, 5.0 times CMC.

The spherical crosslinked polymer microparticles obtained by the reaction of each of the above examples and the comparative examples were evaluated by scanning electron microscopy (SEM) with Winroof particle size analysis software for the average particle diameter (Dn), average particle diameter and particle diameter. variation Coefficient (Cv%), and the thermal stability of the material was confirmed by a thermal analyzer (TGA).

The particle size variation coefficient Cv%=(ρ/Dn)×100, where ρ: the standard deviation of the diameter of the crosslinked polymer microparticles; Dn: the average particle diameter.

The spherical crosslinked polymer microparticles obtained by the reaction of each of the above examples and the comparative examples were measured by a Shimadzu MCT-511 microcompression machine to measure the mechanical properties such as the compression recovery ratio of the spherical polymer microparticles, and the mechanical compression conditions were as follows: 6mN. The above experimental conditions and results are summarized in Table 1.

The data in Table 1 shows that during the process of raising the temperature from 25 ° C to 150 ° C, only the polymer microparticles of Example 1, Example 2, and Example 3 have a compression set recovery rate still higher than 80%, Comparative Example 1 The polymer microparticles of Comparative Example 2 were not. It was confirmed that the polymer fine particles of Example 1, Example 2, and Example 3 were excellent in mechanical properties in a high temperature environment.

The polymer microparticles (including the initial microparticles, the seed polymer microparticles, and the crosslinked polymer microparticles) produced by the method of the present invention have uniform particle diameters, and the average particle diameter is between 1 micrometer and 10 micrometers, and the particle diameter variation coefficient Preferably, Cv% is less than 10%, more preferably less than 8%, and even more preferably less than 5%.

From the above detailed description of the preferred embodiments of the present invention, it will be apparent that the method of the present invention uses a low amount of surfactant (usage amount < 1.0 times CMC) to produce crosslinked polymeric microparticles. The method of the invention also introduces flow field design and process control, especially a two-stage seed swelling polymerization process, and achieves the purpose of producing a crosslinked type polymer microparticle having a uniform cross-linking particle size by using a low surfactant active amount. The microparticle production process has the advantages of increasing product performance and reducing purification cost by reducing the amount of surfactant used in combination with reducing the surfactant residual ratio. Further, the crosslinked polymer fine particles produced by the method of the present invention have excellent mechanical properties, and in particular, the compression recovery ratio at a high temperature of 150 ° C is at least 80% or more.

The features and spirit of the present invention are intended to be more apparent from the detailed description of the preferred embodiments. On the contrary, the intention is to cover various modifications and equivalents that are within the scope of the invention as claimed. Therefore, the scope of the patent application of the present invention should be construed broadly in the light of the above description, so that it covers all possible changes and arrangements.

Claims (6)

A method for producing a plurality of crosslinked polymer microparticles, comprising the steps of: synthesizing a plurality of polymethyl methacrylate (PMMA) initial microparticles by subjecting a monomethyl methacrylate monomer to a non-emulsion emulsion polymerization process; The plurality of PMMA primary microparticles are subjected to a first seed swelling polymerization process under the action of a first polymerization initiator and a molecular weight modifier and a first surfactant to synthesize a plurality of uncrosslinked PMMA seed particles; And synthesizing the plurality of uncrosslinked PMMA seed particles with a second polymerization initiator under a second polymerization initiator and using a second surfactant to perform a second seed swelling polymerization process. The plurality of cross-linked polymer microparticles, wherein the second surfactant is used in an amount of 0.5 times or more of a critical microcell concentration (CMC) and less than 1 time CMC, and the cross-linked polymer at 150 ° C One of the microparticles has a compression deformation recovery ratio higher than 80%, and one of the plurality of crosslinked polymer microparticles has a particle size variation coefficient Cv% of less than or equal to 7.6%, and one of the plurality of crosslinked polymer microparticles has an average particle size. The diameter ranges from 1 micron to 10 microns. The method of claim 1, wherein the first surfactant and the second surfactant are selected from the group consisting of sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium lauryl polyoxyethylene ether sulfate, respectively. One of a group consisting of a mixture of salt, sodium amberoctyl sulfonate, cetyltrimethylammonium chloride, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, and the above surfactant. The method of claim 2, wherein the crosslinking agent formulation comprises a hydrophobic single The hydrophobic monomer has a solubility in water of less than 0.6 g/L, and the proportion of the hydrophobic monomer to the crosslinking agent is greater than or equal to 15% by weight. The method of claim 3, wherein the hydrophobic single system is selected from the group consisting of 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate (1) ,6-Hexanediol dimethacrylate), Ethyleneglycol dimethacrylate, divinylbenzene, Trimethylolpropane triacrylate, Trimethylolpropane trimethacrylate Trimethylol propane Trimethacrylate, pentaerythritol tetraacrylate, diurethane dimethylacrylate, bisphenol A glycerolate diacrylate, and a mixture of the above hydrophobic monomers One of the groups. The method of claim 4, wherein the first polymerization initiator and the second polymerization initiator are azobisisobutyronitrile or benzoyl peroxide, respectively. The method of claim 5, wherein the molecular weight regulator is n-octyl mercaptan.