An organic polysiloxane composition having good shape retention and a method for producing the same

Abstract

The present application aims to provide an organic polysiloxane composition with good shape retention and a preparation method thereof, which is suitable for small hole sealing, waterproof sealing and bonding of precision electronic components. The organic polysiloxane composition with good shape retention of the present application comprises at least the following components (A)-(E): (A) a mono-end or double-end alkyl-terminated polydimethylsiloxane with a viscosity of 50-20000 mPa.s, in particular an alkyl-terminated polydimethylsiloxane prepared by hydrogen-containing alkylsilane addition reaction after adsorption treatment with basic activated carbon; (B) a thickening and tackifying agent; (C) a water absorbing agent; (D) a crosslinking agent; (E) a catalyst; the present application uses ① hydrogen-containing alkylsilane after adsorption treatment with basic activated carbon as a terminating agent, and then terminates with mono-end or double-end vinyl polydimethylsiloxane to prepare alkyl-terminated polydimethylsiloxane; ② the coupling agent is pre-opened, and the surface of the filler is treated at high temperature, so that the thickening and tackifying agent obtained can effectively improve the intermolecular force between the organic polysiloxane composition molecules and the filler, so that it is more compact, can maintain high-level intermolecular force after dispensing and spraying, and does not spread, flow and overflow, achieving the effect of precise process control.

Description

Technical Field

[0001] This invention relates to an organopolysiloxane composition with good shape retention and its preparation method, belonging to the fields of RTV-cured silicone, adhesive sealing, and sealing solutions for electronic components. Background Technology

[0002] High-end electronic RTV encapsulation silicone generally uses alkoxy-terminated polydimethylsiloxane technology, as described in patent 201910067882.6. This technology uses single- and double-terminated alkoxy-terminated polydimethylsiloxanes to replace 107 adhesive as the base polymer, eliminating viscosity peaks during processing and making it easy to process. Simultaneously, it exhibits excellent storage stability; after 7 days of accelerated aging at 70°C, the surface drying time does not double, meeting the ever-growing demands for automation and productivity in the electronics manufacturing and assembly industry.

[0003] With the diversification and increasing precision of electronic component design, more and more subtle requirements are being placed on assembly processes. The industry often adjusts the amount of thixotropic agents (such as fumed silica) to achieve different viscosities and thixotropic properties, thereby meeting the assembly process requirements for dispensing, spraying, and flow properties. However, this method of process adjustment struggles to achieve a balance when low-viscosity spraying requirements coexist with non-spreading and shape-maintaining requirements, such as waterproof sealing bonding of small through-holes with a certain depth.

[0004] This invention uses hydrogen-containing alkoxysilanes treated with alkaline activated carbon as end-capping agents to obtain alkoxy-terminated polydimethylsiloxanes as the main resin. By pre-opening the coupling agent and treating the filler surface at high temperature, the resulting thickener can effectively improve the intermolecular forces between the organic polysiloxane composition molecules and the filler, making them more compact. After dispensing and spraying, it is not affected by the high-speed shearing during dispensing and spraying, maintaining a high level of intermolecular forces without spreading, flowing, or overflowing, thus achieving precise process control. Summary of the Invention

[0005] The purpose of this invention is to provide an organopolysiloxane composition with good shape retention and its preparation method, suitable for sealing and waterproofing small through-holes in precision electronic components. This invention uses a hydrogen-containing alkoxysilane treated with alkaline activated carbon as a capping agent to obtain alkoxy-terminated polydimethylsiloxane as the main resin; the coupling agent undergoes pre-ring-opening treatment, and the filler surface is treated at high temperature; the resulting organopolysiloxane composition exhibits stronger intermolecular forces between molecules and fillers. After dispensing and spraying, it remains unaffected by the high-speed shearing during dispensing and spraying, maintaining a high level of intermolecular forces without spreading, flowing, or overflowing. This achieves both low-viscosity spraying requirements and shape retention without spreading, thus achieving precise process control.

[0006] An organopolysiloxane composition with good shape retention according to the present invention comprises at least the following components (A)-(G): The synthesis method of component (A), a single- or double-alkoxy-terminated polydimethylsiloxane with a viscosity of 50-20000 mPa·s, involves an addition reaction of single- or double-vinyl polydimethylsiloxane with a hydrogen-containing alkoxysilane catalyzed by a platinum catalyst. For specific preparation methods, refer to patent 201910067882.6. It is important to note that the added hydrogen-containing alkoxysilane specifically requires adsorption and stirring with alkaline activated carbon for 1-4 hours followed by filtration before the dropwise addition reaction. The amount of alkaline activated carbon used is 1-10 wt% of the hydrogen-containing alkoxysilane. The viscosity of the single- or double-vinyl polydimethylsiloxane used is 50-20000 mPa·s.

[0007] The preparation method of the thickening and tackifying agent (component B) is as follows: a certain amount of hydroxyl silicone oil (50-20000 mPa·s) and a pre-ring-opening polyhydroxy coupling agent are added to a reaction vessel and stirred evenly. Then, hydrophobic fumed silica and other functional fillers are added and stirred evenly. The mixture is then heated to 70-120℃ and subjected to high-temperature vacuum treatment for 1-4 hours to obtain the thickening and tackifying agent. By pre-ring-opening the coupling agent and simultaneously treating the filler surface at high temperature, the thickening and tackifying agent obtained can effectively improve the intermolecular forces between the organic polysiloxane composition molecules and the fillers. At the same time, the pre-ring-opening polyhydroxy coupling agent can also enhance the adhesion to the bonding interface during the product curing process. If the mass of hydroxyl silicone oil with a strength of 50-20000 mPa·s is 100 parts, then the amount of pre-ring-opening polyhydroxy coupling agent added is 0.5-10 parts, the mass of hydrophobic fumed silica is 5-30 parts, and the mass of other functional fillers is 0-50 parts. The functional fillers can be one or more of the following: carbon black, silica powder, titanium dioxide, alumina, aluminum hydroxide, magnesium hydroxide, phosphorus flame retardants, etc. Considering the aperture of the spray and dispensing, the appropriate filler particle size needs to be selected according to the aperture of the equipment.

[0008] The preparation process of the pre-ring-opening polyhydroxy coupling agent is as follows: a certain amount of small molecules containing polyepoxy structures are added to a reaction flask, and mercapto and amino coupling agents are slowly added dropwise. After the addition is completed, the temperature is raised to 100-160℃, and the reaction is carried out with stirring for 2-6 hours to obtain the pre-ring-opening polyhydroxy coupling agent. In this pre-ring-opening polyhydroxy coupling agent, each molecule contains at least 2-4 -CH2-OH groups, which can be used as a filler treatment agent to enhance the interaction between the matrix and the filler. In addition, each molecule also contains at least 6 silaneoxy groups, which can be used as a high-efficiency coupling agent to improve the adhesion of the composition to the interface of the adhesive material.

[0009] Small molecules with polyepoxy structures can be one or more of 1-(ethylene oxide-2-yl)-N,N-bis(ethylene oxide-2-ylmethyl)methylamine, butadiene diepoxide, diglycidyl ether, and pentaerythritol glycidyl ether; the thiol and amino coupling agents can be 3-aminopropyltriethoxysilane, mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane, 3-ureidopropyltrimethoxysilane, N-(2-aminoethyl)-aminopropyltrimethoxysilane, acrylamidopropyltrimethoxysilane, tert-butylpropylaminotrimethoxysilane, (3-aminopropyl)trimethoxysilane, N-n-butylaminopropyltrimethoxysilane, and nitrogen-(acetylglycyl)-3- One or more of aminopropyltrimethoxysilane, acetaminopropyltrimethoxysilane, and N-ethyl-3-trimethoxysilane-2-methylpropylamine; the ratio of active hydrogen of thiol and amino groups to functional groups of epoxy structures in small molecules with polyepoxy structures in the thiol and amino coupling agent is 0.9~3.1:1.

[0010] The water-absorbing agent is one or more of silane coupling agents such as silazane and acetoxysilane, preferably silazane; the crosslinking agent is one or more of methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, methyl orthosilicate, ethyl orthosilicate, phenyltrimethoxysilane, and phenylmethyldimethoxysilane; the catalyst is one or more of organotin coupling agents, organotitanium coupling agents, and organozirconium coupling agents. Considering environmental protection and reactivity, organotitanium coupling agents are preferred, including but not limited to n-butyl titanate, tetraisopropyl titanate, TYZOR 9000, TYZOR 722, TYZOR 726, Kenrich KR-38S, KR-12, and KR-TTS.

[0011] The organopolysiloxane composition with good shape retention of the present invention can be prepared by mixing under a conventional inert atmosphere. Preferably, component (A) with a viscosity of 50-20000 mPa·s, a single- or double-ended alkoxy-terminated polydimethylsiloxane, particularly an alkoxy-terminated polydimethylsiloxane obtained by the addition reaction of hydrogen-containing alkoxysilane after adsorption treatment with alkaline activated carbon, and component (B) thickener and viscous agent are mixed evenly at room temperature and degassed. Then, component (C) water absorbent, component (D) crosslinking agent and component (E) catalyst are added and stirred evenly.

[0012] The beneficial effects of this invention are as follows: Alkaline activated carbon adsorption-treated hydrogen-containing alkoxysilanes are used as end-capping agents to obtain alkoxy-terminated polydimethylsiloxanes as the main resin; the coupling agent undergoes pre-ring-opening treatment, and the filler surface is treated at high temperature; the resulting organopolysiloxane composition exhibits stronger intermolecular forces between molecules and fillers. After dispensing and spraying, it remains unaffected by the high-speed shearing during dispensing and spraying, maintaining a high level of intermolecular forces without spreading, flowing, or overflowing. This achieves both low-viscosity spraying requirements and non-spreading shape retention, thus achieving precise process control. Detailed Implementation

[0013] The following specific embodiments describe the principles and features of the present invention. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0014] Example 1 Preparation of pre-ring-opening polyhydroxy coupling agent (G): A certain amount of small molecules containing polyepoxy structures are added to a reaction flask, and thiol and amino coupling agents are slowly added dropwise. After the addition is complete, the temperature is raised to 100-160℃, and the reaction is maintained at this temperature with stirring for 2-6 hours to obtain the pre-ring-opening polyhydroxy coupling agent. Specific examples are shown in the table below: G-1 1-(ethylene oxide-2-yl)-N,N-bis(ethylene oxide-2-ylmethyl)methylamine 3-Aminopropyltriethoxysilane 140 3 2:1 G-2 Biepoxide Butadiene mercaptopropyltrimethoxysilane 100 6 1:1 G-3 diglycidyl ether 3-Ureapropyltrimethoxysilane 120 2 3:1 G-4 Pentaerythritol glycidyl ether N-Ethyl-3-trimethoxysilane-2-methylpropylamine 160 4 1:1

[0015] Example 2 Preparation of thickener and tackifier (B): A certain amount of hydroxyl silicone oil (50-20000 mPa·s) and a pre-ring-opening polyhydroxy coupling agent are added to a reaction vessel and stirred evenly. Then, hydrophobic fumed silica and other functional fillers are added and stirred evenly. The mixture is then heated to 70-120℃ and subjected to high-temperature vacuum treatment for 1-4 hours to obtain the thickener and tackifier. Specific examples and comparative examples are shown in the table below: Example B-1 100 100 G-1 10 R106 30 none 0 70 4 Example B-2 1000 100 G-2 5 TS720 20 carbon black 5 90 3 Example B-3 5000 100 G-3 0.5 H2000 10 Silica powder 30 100 2 Example B-4 20000 100 G-4 3 DM-30 5 Aluminum hydroxide 50 120 1 Comparative Examples B1-5 20000 100 3-Aminopropyltriethoxysilane 3 DM-30 5 Aluminum hydroxide 50 120 1

[0016] Example 3 Preparation of (A) of single- or double-alkoxy-terminated polydimethylsiloxane: In an inert atmosphere, single- or double-terminated vinyl polydimethylsiloxane with a viscosity of 50-20000 mPa·s and a platinum catalyst were added to a reaction vessel, stirred evenly, and reacted at 60°C for 1 h. Subsequently, hydrogen-containing alkoxysilanes obtained by adsorption and stirring with alkaline activated carbon for 1-4 h and then filtering were added dropwise. After the addition was complete, the reaction was maintained at 100°C for 5 h to obtain the target single- or double-alkoxy-terminated polydimethylsiloxane. Specific examples and comparative examples are shown in the table below:

[0017] The specific formulations of the organopolysiloxane compositions with good shape retention, as described in Examples 4-7 and Comparative Examples 1-2, are shown in the table below: Note: The specific test items and test methods are as follows: Method for testing the pH value of activated carbon: Using a Mettler FE28-standard pH meter, weigh 2.5 grams of activated carbon, place it in a 100 ml Erlenmeyer flask, and shake it on a shaker for 2 hours ± 5 minutes to test the pH value.

[0018] Viscosity and thixotropic testing methods: Brookfield DVIII viscometer, viscosity value at 25℃ and 5 rpm, thixotropic = viscosity value at 0.5 rpm / viscosity value at 5 rpm.

[0019] Surface drying time: For adhesive films thicker than 1mm, lightly touch the surface of the adhesive film with your finger and record the time it takes for the adhesive surface to become non-sticky.

[0020] Dispensing spread rate: Take 1 drop of liquid sample and drop it onto a horizontally placed glass plate. Record the initial diameter d0 within 5 seconds. Let it spread out under the action of gravity. When its area no longer changes (15 min), measure the diameter d1 of the spread droplet. Dispensing spread rate = d1 / d0 - 1.

[0021] Adhesive diffusion: The diameter of the adhesive spraying mold hole is 1.7mm, the hole depth is 2.5-3mm, and there is a 0.5-1mm thick gap at the bottom of the hole. The adhesive is sprayed into the mold hole, and after 15 minutes, the distance of the adhesive flowing through the gap at the bottom of the hole is the adhesive diffusion distance.

[0022] From the results of Examples 4-6, the organopolysiloxane compositions obtained using the treatment method of this invention have a viscosity of around 20,000 mPa·s, or even as low as 5,000 mPa·s, and a relatively low thixotropy of around 2. However, the dispensing spread rate is <10%, even lower than 5%, and the spray diffusion is ≤0.5 mm, exhibiting good shape retention. Comparative Example 1 used acidic activated carbon to treat the hydrogen-containing alkoxysilane. Compared with Example 5, the viscosity remained basically unchanged, but the thixotropy decreased significantly, and the dispensing spread rate and spray diffusion increased significantly. Comparative Example 2 used conventional aminosilane as a coupling agent and filler treatment agent. Compared with the pre-ring-opening polyhydroxy coupling agent of this invention, in addition to significant changes in viscosity, thixotropy, dispensing spread rate, and spray diffusion, the storage stability also decreased significantly (surface drying time after 30 days at room temperature). This is because conventional amino coupling agents and commonly used moisture catalysts react and consume each other during storage, thus affecting the storage stability of the product. However, the pre-ring-opening polyhydroxy coupling agent of the present invention pre-consumes the active hydrogen through reaction, thus exhibiting better storage stability.

Claims

1. A type of organopolysiloxane composition with good shape retention, comprising at least the following components (A)-(E): (A) 60-80 parts of single- or double-alkoxy-terminated polydimethylsiloxane with a viscosity of 50-20000 mPa·s; (B) 20-50 parts of thickener and tackifier; (C) 0.5-3 parts of water absorbent; (D) 3-10 parts of crosslinking agent; (E) 0.1-3 parts of catalyst; wherein the single- or double-alkoxy-terminated polydimethylsiloxane with a viscosity of 50-20000 mPa·s in (A) is an alkoxy-terminated polydimethylsiloxane obtained by addition reaction of hydrogen-containing alkoxysilane after adsorption treatment with alkaline activated carbon; The preparation method of the thickening and tackifying agent of component (B) is as follows: 100 parts of hydroxyl silicone oil with a mass fraction of 50-20000 mPa·s and 0.5-10 parts of pre-ring-opening polyhydroxy coupling agent are added to a reaction vessel and stirred evenly. Then, 5-30 parts of hydrophobic fumed silica and 0-50 parts of other functional fillers are added and stirred evenly. The mixture is then heated to 70-120°C and subjected to high-temperature vacuum treatment for 1-4 hours to obtain the thickening and tackifying agent of component (B). The preparation process of the pre-ring-opening polyhydroxy coupling agent is as follows: a certain amount of small molecules with polyepoxy structures are added to a reaction flask, and a mercapto or amino coupling agent is slowly added dropwise. After the addition is complete, the temperature is raised to 100-160°C, and the reaction is carried out with stirring for 2-6 hours to obtain the pre-ring-opening polyhydroxy coupling agent. Each molecule of the pre-ring-opening polyhydroxy coupling agent contains at least 2 -CH2-OH groups and at least 6 silaneoxy groups. The small molecule with the polyepoxy structure is 1-(ethylene oxide-2-yl)-N,Nbis(ethylene oxide-2-ylmethyl) The thiol or amino coupling agent is one or more of the following: methylamine, butadiene diepoxide, diglycidyl ether, and pentaerythritol glycidyl ether; the thiol or amino coupling agent is one or more of the following: 3-aminopropyltriethoxysilane, mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane, 3-ureopropyltrimethoxysilane, N-(2-aminoethyl)-aminopropyltrimethoxysilane, acrylamide propyltrimethoxysilane, tert-butylpropylaminotrimethoxysilane, (3-aminopropyl)trimethoxysilane, N-n-butylaminopropyltrimethoxysilane, N-(acetylglycyl)-3-aminopropyltrimethoxysilane, acetylaminopropyltrimethoxysilane, and N-ethyl-3-trimethoxysilane-2-methylpropylamine; the ratio of the active hydrogen of the thiol or amino group to the functional group of the epoxy structure in the small molecule with the polyepoxy structure in the thiol or amino coupling agent is 0.9 to 3.1:

1.

2. The organopolysiloxane composition with good shape retention according to claim 1, characterized in that, The method for synthesizing the single- or double-alkoxy-terminated polydimethylsiloxane with a viscosity of 50-20000 mPa·s (A) is as follows: It is prepared by an addition reaction of single- or double-vinyl polydimethylsiloxane with a hydrogen-containing alkoxysilane under platinum catalyst catalysis. The single- or double-vinyl polydimethylsiloxane has a viscosity of 50-20000 mPa·s. The hydrogen-containing alkoxysilane is subjected to alkaline activated carbon adsorption and stirring treatment for 1-4 hours and then filtered before the reaction. The amount of alkaline activated carbon used is 1-10 wt% of the hydrogen-containing alkoxysilane.

3. The organopolysiloxane composition with good shape retention according to claim 1, characterized in that, The water-absorbing agent (component C) is one or more of silazane-based silane coupling agents and acetoxysilane-based silane coupling agents; the crosslinking agent (component D) is one or more of methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, methyl orthosilicate, ethyl orthosilicate, phenyltrimethoxysilane, and phenylmethyldimethoxysilane; the catalyst (component E) is one or more of organotin coupling agents, organotitanium coupling agents, and organozirconium coupling agents, specifically including one or more of tetrabutyl titanate, tetraisopropyl titanate, TYZOR9000, TYZOR 722, TYZOR726, Kenrich KR-38S, KR-12, and KR-TTS.

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