Organopolysiloxane composition with good shape retention performance and preparation method therefor

Abstract

The present invention aims to provide an organopolysiloxane composition with good shape retention performance and a preparation method therefor. The organopolysiloxane composition is suitable for sealing and waterproof sealing bonding of small through-holes in precise electronic components and parts. The organopolysiloxane composition with good shape retention performance in the present invention at least comprises components (A)-(E) below: (A) a single-end or double-end alkoxy-terminated polydimethylsiloxane with a viscosity of 50-20,000 mPa.s, especially an alkoxy-terminated polydimethylsiloxane prepared by means of an addition reaction of a hydrogen-containing alkoxysilane that has been subjected to an adsorption treatment with alkaline activated carbon; (B) a thickening and tackifying agent; (C) a water absorbent; (D) a cross-linking agent; and (E) a catalyst. In the present invention, (1) a hydrogen-containing alkoxysilane that has been subjected to an adsorption treatment with alkaline activated carbon is used as an end-capping reagent, and the end-capping reagent and a single-end or double-end vinyl polydimethylsiloxane are then subjected to end capping, so as to prepare an alkoxy-terminated polydimethylsiloxane; and (2) a coupling agent is subjected to a pre-ring-opening treatment, the surface of a filler is treated at a high temperature at the same time, and therefore a thickening and tackifying agent obtained therefrom can effectively improve the intermolecular force between molecules of the organopolysiloxane composition and the filler, thereby making same closer together. Therefore, after adhesive dispensing and spraying, the organopolysiloxane composition is not affected by high-speed shearing action during the processes of adhesive dispensing and spraying, and a high level of intermolecular force can be maintained without the phenomena of spreading, flowing and overflowing, thereby achieving the effect of precise process control.

Description

An organopolysiloxane composition with good shape retention and preparation method thereof Technical Field

[0001] The invention relates to an organopolysiloxane composition with good shape retention and a preparation method thereof, belonging to the field of RTV curing silicone, adhesive sealing, and electronic component sealing solutions. Background Art

[0002] High-end electronic RTV encapsulation silicones typically utilize alkoxy-terminated polydimethylsiloxane technology. As described in Patent 201910067882.6, single- and dual-end alkoxy-terminated polydimethylsiloxanes replace 107 adhesive as the base polymer. This eliminates viscosity peaks during processing, making it easy to process. Furthermore, it exhibits excellent storage stability, with the tack-free time remaining unchanged after seven days of accelerated aging at 70°C. This meets the growing demand for automation and productivity in the electronics manufacturing and assembly industry.

[0003] The increasing diversification and sophistication of electronic component design has led to increasingly subtle demands on assembly processes. The industry often adjusts the dosage of thixotropic agents (such as fumed silica) to achieve varying viscosities and thixotropy to meet assembly process requirements for dispensing, spraying, and flow properties. However, this process adjustment approach struggles to achieve a balance when low-viscosity spraying requirements coexist with the need for non-spreading and shape retention, such as in the waterproof sealing of small through-holes of a certain depth.

[0004] The present invention uses hydrogen-containing alkoxysilane treated by alkaline activated carbon adsorption as a capping agent to prepare alkoxy-terminated polydimethylsiloxane as the main resin; by pre-ring-opening the coupling agent and treating the filler surface at high temperature, the thickening and tackifying agent obtained can effectively improve the intermolecular force between the organic polysiloxane composition molecules and the filler, making them closer. After dispensing and spraying, the intermolecular force can be maintained at a high level without being affected by the high-speed shearing effect during the dispensing and spraying process, and the phenomenon of spreading, flowing and overflowing can be avoided, thereby achieving the effect of precise process control.

[0005] Summary of the Invention

[0006] The purpose of the present invention is to provide an organopolysiloxane composition with good shape retention and a preparation method thereof, which is suitable for the waterproof sealing and bonding of small through-holes of precision electronic components. The present invention uses hydrogen-containing alkoxysilane treated with alkaline activated carbon adsorption as a capping agent to obtain alkoxy-terminated polydimethylsiloxane as the main resin; the coupling agent is pre-ring-opened and the filler surface is treated at high temperature; the intermolecular force between the molecules of the organopolysiloxane composition obtained in this way and the filler is more compact, and after the dispensing and spraying, it can be unaffected by the high-speed shearing effect during the dispensing and spraying process, and maintain a high level of intermolecular force without spreading, flowing or overflowing, thereby meeting the requirements of low-viscosity spraying and the requirements of non-spreading and shape retention, thereby achieving the effect of precise process control.

[0007] The organopolysiloxane composition of the present invention having good shape retention comprises at least the following components (A) to (G):

[0008] The synthesis method of component (A) with a single- or double-ended alkoxy-terminated polydimethylsiloxane having a viscosity of 50-20,000 mPa.s is prepared by the addition reaction of single- or double-ended vinyl polydimethylsiloxane with a hydrogen-containing alkoxysilane under a platinum catalyst. The specific preparation method is referenced in patent 201910067882.6. It should be noted that the added hydrogen-containing alkoxysilane specifically needs to be subjected to alkaline activated carbon adsorption and stirring treatment for 1-4 hours and filtration before the dropwise addition reaction can be carried out. The amount of alkaline activated carbon used is 1-10wt% of the hydrogen-containing alkoxysilane. The single- or double-ended vinyl polydimethylsiloxane used has a viscosity of 50-20,000 mPa.s.

[0009] The thickening and tackifying agent component (B) is prepared by adding a certain amount of 50-20,000 mPa.s hydroxy silicone oil and a pre-opened polyhydroxy coupling agent to a reactor, stirring evenly, then adding hydrophobic fumed silica and other functional fillers, stirring evenly, heating to 70-120°C, and performing a high-temperature vacuum treatment for 1-4 hours to obtain the thickening and tackifying agent. The coupling agent is pre-ring-opened, and the filler surface is treated at high temperature. The resulting thickening and tackifying agent can effectively increase the intermolecular forces between the organopolysiloxane composition molecules and the filler. At the same time, the pre-opened polyhydroxy coupling agent can also enhance the adhesion of the bonding interface during the product curing process. Taking the mass of 50-20000mPa.s hydroxy silicone oil as 100 parts, the addition amount of pre-opened ring polyhydroxy coupling agent is 0.5-10 parts, and the mass of hydrophobic fumed silica is 5-30 parts; the mass of other functional fillers is 0-50 parts, and the functional fillers can be one or more of carbon black, silica powder, titanium dioxide, alumina, aluminum hydroxide, aluminum hydroxide, magnesium hydroxide, phosphorus flame retardant, etc. Considering the aperture of spraying and dispensing, it is necessary to select the appropriate filler particle size according to the aperture of the equipment.

[0010] The preparation process of the pre-opened-ring polyhydroxy coupling agent is as follows: a certain amount of small molecules containing a polyepoxy structure is added to a reaction bottle, and a thiol and an amino coupling agent are slowly added dropwise thereto. After the addition is completed, the temperature is raised to 100-160°C, and the mixture is stirred and reacted for 2-6 hours to obtain a pre-opened-ring polyhydroxy coupling agent. In the pre-opened-ring 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 or more silane 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.

[0011] The small molecule of polyepoxy structure can be one or more of 1-(oxiran-2-yl)-N, N-bis(oxiran-2-ylmethyl)methylamine, diepoxy butadiene, diglycidyl ether, pentaerythritol glycidyl ether; the thiol and amino coupling agents can be 3-aminopropyl triethoxysilane, mercaptopropyl trimethoxysilane, mercaptopropyl triethoxysilane, 3-ureidopropyl trimethoxysilane, N-(2-aminoethyl)-aminopropyl trimethoxysilane, acrylamidopropyl trimethoxysilane, One or more of oxysilane, tert-butylpropylaminotrimethoxysilane, (3-aminopropyl)trimethoxysilane, N-n-butylaminopropyltrimethoxysilane, nitrogen-(acetylglycyl)-3-aminopropyltrimethoxysilane, acetylaminopropyltrimethoxysilane, and N-ethyl-3-trimethoxysilane-2-methylpropylamine; the ratio of the thiol and amino active hydrogen in the thiol and amino coupling agent to the functional group of the epoxy structure in the small molecule with polyepoxy structure is 0.9 to 3.1:1.

[0012] The water absorbent is a mixture of one or more silane coupling agents such as silazane and acetoxysilane, preferably silazane; the crosslinking agent is a mixture of one or more of methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, methyl orthosilicate, ethyl orthosilicate, phenyltrimethoxysilane, and phenylmethyldimethoxysilane; the catalyst is one or more of an organotin coupling agent, an organotitanium coupling agent, and an organozirconium coupling agent. From the perspective of environmental protection and reaction activity, an organotitanium coupling agent is preferred, including but not limited to one or more of n-butyl titanate, tetraisopropyl titanate, TYZOR 9000, TYZOR 722, TYZOR 726, KR-38S, KR-12, and KR-TTS from Kenrich.

[0013] The organopolysiloxane composition of the present invention having good shape retention can be prepared by conventional mixing under an inert atmosphere. Preferably, component (A) is first mixed evenly at room temperature with a single-end or double-end alkoxy-terminated polydimethylsiloxane having a viscosity of 50-20,000 mPa.s, particularly an alkoxy-terminated polydimethylsiloxane obtained by addition reaction of a hydrogen-containing alkoxysilane treated with alkaline activated carbon adsorption, and component (B) is mixed evenly with a thickening and tackifying agent, and then degassed. Components (C) a water absorbent, component (D) a crosslinking agent, and component (E) a catalyst are then added and stirred evenly.

[0014] The beneficial effects of the present invention are as follows: hydrogen-containing alkoxysilane treated by alkaline activated carbon adsorption is used as a capping agent to prepare alkoxy-terminated polydimethylsiloxane as a main resin; the coupling agent is pre-ring-opened, and the filler surface is treated at high temperature; the intermolecular force between the molecules of the organic polysiloxane composition obtained in this way and the filler is tighter, and after dispensing and spraying, the intermolecular force can be maintained at a high level without being affected by the high-speed shearing effect during the dispensing and spraying process, without spreading, flowing and overflowing, thereby meeting the requirements of low-viscosity spraying and the requirements of non-spreading and shape retention, thereby achieving the effect of precise process control. DETAILED DESCRIPTION

[0015] The following specific embodiments describe the principles and features of the present invention. The examples are only used to explain the present invention and are not used to limit the scope of the present invention.

[0016] Example 1

[0017] Preparation of pre-ring-opened polyhydroxy coupling agent (G): A certain amount of small molecules containing a polyepoxy structure is added to a reaction flask, and a thiol and amino coupling agent is slowly added dropwise thereto. After the addition is completed, the temperature is raised to 100-160°C, and the mixture is stirred and reacted for 2-6 hours to obtain a pre-ring-opened polyhydroxy coupling agent. Specific examples are shown in the table below:

[0018] Example 2

[0019] Preparation of thickening and tackifying agent (B): Add a certain amount of 50-20000 mPa.s hydroxy silicone oil and pre-opened polyhydroxy coupling agent to a reaction kettle and stir evenly. Then add hydrophobic fumed silica and other functional fillers and stir evenly. Heat to 70-120°C and perform high-temperature vacuum treatment for 1-4 hours to prepare the thickening and tackifying agent. Specific examples and comparative examples are shown in the table below:

[0020] Example 3

[0021] Preparation of single-end or double-end alkoxy-terminated polydimethylsiloxane (A): In an inert atmosphere, add single-end or double-end vinyl polydimethylsiloxane with a viscosity of 50-20,000 mPa.s and a platinum catalyst to a reactor, stir evenly, and react at 60°C for 1 hour. Then, add dropwise the hydrogen-containing alkoxysilane obtained by adsorption and stirring on alkaline activated carbon for 1-4 hours and filtering. After the addition is complete, react at 100°C for 5 hours to obtain the target single-end or double-end alkoxy-terminated polydimethylsiloxane. Specific examples and comparative examples are shown in the table below:

[0022] The specific formula compositions of Examples 4-7 and Comparative Examples 1-2 of the organopolysiloxane compositions with good shape retention, which are composed of the above examples, are as follows:

[0023] Note: Specific test items and test methods are as follows:

[0024] Testing method for pH value of activated carbon: Use pH meter Mettler FE28-standard, weigh 2.5 g of activated carbon, put it in a 100 ml conical flask, oscillate on an oscillator for 2h±5min, and perform pH test.

[0025] Viscosity and thixotropy test method: Brookfield DVIII viscometer, 25 ° C, rotation speed 5 rpm, viscosity value, thixotropy = 0.5 rpm viscosity value / 5 rpm viscosity value.

[0026] Surface drying time: For films >1mm thick, touch the film surface lightly with your finger and record the time until the glue surface becomes non-sticky.

[0027] Glue spreading rate: Take a drop of liquid sample and drop it on a horizontal glass plate. Record the initial diameter d0 within 5 seconds and let it spread due to gravity. When its area no longer changes (15 minutes), measure the spread droplet diameter d1. Glue spreading rate = d1 / d0-1.

[0028] Glue diffusion: The diameter of the mold hole is 1.7mm, the depth is 2.5-3mm, and there is a 0.5-1mm thick gap at the bottom of the hole. Spray glue into the mold hole and record the glue flow distance in the gap at the bottom of the hole after 15 minutes. This is the glue diffusion distance.

[0029] The results of Examples 4-6 show that the organopolysiloxane compositions obtained using the treatment method of the present invention can have a viscosity of approximately 20,000 mPa.s, or even as low as 5,000 mPa.s. Their thixotropy is not high, at approximately 2, but their adhesive spread is less than 10%, even less than 5%, and their spray spread is ≤0.5 mm, demonstrating excellent shape retention. Comparative Example 1, in which the hydrogenated alkoxysilane is treated with acidic activated carbon, exhibits essentially unchanged viscosity compared to Example 5, but exhibits a significant decrease in thixotropy, and both adhesive spread and spray spread are significantly increased. Comparative Example 2, in which conventional aminosilane is used as a coupling agent and filler treatment agent, exhibits significant changes in viscosity, thixotropy, adhesive spread, and spray spread compared to the pre-opened polyhydroxy coupling agent of the present invention. Furthermore, storage stability is significantly reduced (tack-free time after 30 days at room temperature). This is because the conventional amino coupling agent and the commonly used moisture catalyst react and consume each other during storage, thus affecting the product's storage stability. However, the pre-ring-opened polyhydroxy coupling agent of the present invention consumes the active hydrogen in advance, and thus has better storage stability.

Claims

1. An organopolysiloxane composition with good conformal property, comprising at least the following components (A)-(E): (A) 60-80 parts of mono-terminal or di-terminal alkoxy-terminated polydimethylsiloxane with a viscosity of 50-20000 mPa·s; (B) 20-50 parts of thickening and viscosity-increasing agent; (C) 0.5-3 parts of water absorbent; (D) 3-10 parts of crosslinking agent; (E) 0.1-3 parts of catalyst; the (A) mono-terminal or di-terminal alkoxy-terminated polydimethylsiloxane with a viscosity of 50-20000 mPa·s is an alkoxy-terminated polydimethylsiloxane prepared by the addition reaction of hydrogen-containing alkoxysilane after being treated by adsorption with basic activated carbon.

2. An organopolysiloxane composition with good conformal properties according to claim 1, characterized in that, The synthesis method of the (A) mono-terminal or di-terminal alkoxy-terminated polydimethylsiloxane with a viscosity of 50-20000 mPa·s is: prepared by the addition reaction of mono-terminal or di-terminal vinyl polydimethylsiloxane and hydrogen-containing alkoxysilane under the catalysis of a platinum catalyst, the mono-terminal or di-terminal vinyl polydimethylsiloxane has a viscosity of 50-20000 mPa·s; the hydrogen-containing alkoxysilane is reacted after being stirred and treated by adsorption with basic activated carbon for 1-4 h and then filtered; the dosage of the basic activated carbon is 1-10 wt% of the hydrogen-containing alkoxysilane.

3. An organopolysiloxane composition with good conformal properties according to claim 1, characterized in that, The preparation method of the component (B) thickening and viscosity-increasing agent is: add 100 parts of hydroxy silicone oil with a viscosity of 50-20000 mPa·s and 0.5-10 parts of pre-ring-opening polyhydroxy coupling agent into a reaction kettle according to mass fraction, stir evenly, then add 5-30 parts of hydrophobic fumed silica and 0-50 parts of other functional fillers, stir evenly, and heat to 70-120 °C, and carry out high-temperature vacuum treatment for 1-4 h to obtain the component (B) thickening and viscosity-increasing agent.

4. An organopolysiloxane composition with good conformal property according to claim 3, characterized in that, The preparation process of the pre-ring-opening polyhydroxy coupling agent is as follows: Add a certain amount of small molecules with a poly-epoxy structure into a reaction flask, slowly dropwise add a mercapto and amino coupling agent thereto. After the dropping is completed, raise the temperature to 100 - 160 °C, and keep stirring and reacting for 2 - 6 h 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 silane oxygen groups; the small molecules with a poly-epoxy structure are one or more of 1-(oxiran-2-yl)-N,N-bis(oxiran-2-ylmethyl)methanamine, diepoxylated butadiene, diglycidyl ether, and pentaerythritol glycidyl ether; the mercapto and amino coupling agent is one or more of 3-aminopropyltriethoxysilane, mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane, 3-ureidopropyltrimethoxysilane, N-(2-aminoethyl)-aminopropyltrimethoxysilane, acrylamidopropyltrimethoxysilane, 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 mercapto and amino groups in the mercapto and amino coupling agent to the functional groups of the epoxy structure in the small molecules with a poly-epoxy structure is 0.9 - 3.1:

1.

5. An organopolysiloxane composition with good conformal property according to claim 1, characterized in that, The water absorbent of the component (C) is one or a mixture of silane coupling agents such as silazane and acetoxysilane; the crosslinking agent of the component (D) is one or a mixture of methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, methyl orthosilicate, ethyl orthosilicate, phenyltrimethoxysilane, and phenylmethyldimethoxysilane; the catalyst of the component (E) is one or several of organotin coupling agents, organotitanium coupling agents, and organozirconium coupling agents.

6. An organopolysiloxane composition with good conformal property according to claim 5, characterized in that, The water absorbent of the component (C) is.

7. An organopolysiloxane composition with good conformal properties according to claim 5, characterized in that, The catalyst of the component (E) is an organotin coupling agent.

8. An organopolysiloxane composition with good conformal properties according to claim 5, characterized in that, The specific organotitanium coupling agents include one or more of tetrabutyl titanate, tetraisopropyl titanate, TYZOR 9000, TYZOR 722, TYZOR 726, Kenrich KR-38S, KR-12, and KR-TTS.

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