CN102504258A - Method for preparing high-temperature resisting organic adhesive by utilizing liquid silicon carbide precursor - Google Patents

Abstract

A method for preparing a high-temperature-resistant organic adhesive from a liquid silicon carbide precursor. It is based on liquid silicon carbide precursor (liquid polysilane, polymethylsilane, liquid polycarbosilane), vinyl-containing low-molecular siloxane as the starting material, toluene or tetrahydrofuran as the solvent, and chloroplatinic acid as the catalyst. After mixing in a certain proportion, heat up to 20-300°C, keep warm for a certain period of time, cool down to a certain temperature, distill under reduced pressure, and cool to room temperature to obtain polycarbosiloxane, a high-temperature resistant organic adhesive. The raw material of the present invention is simple and easy to obtain, the source is reliable, and the reaction process is simple; the obtained product has excellent high temperature resistance, because it contains a large amount of active Si-H, Si-OH, Si-Si, CH= _CH2 groups, and is easy to trade Combined curing, with low surface energy, easy to spread and wet on the surface of ceramics, metals and other objects, and has good bonding performance. It has broad application prospects in bonding SiC ceramic materials, oxide ceramics, carbon materials, and titanium alloy materials.

Description

A method for preparing high temperature resistant organic adhesive from liquid silicon carbide precursor

technical field

The invention relates to a method for preparing polycarbosiloxane, a high-temperature-resistant organic adhesive, from a liquid silicon carbide precursor.

Background technique

At present, the main high-temperature-resistant organic adhesives used include epoxy resins, phenolic resins, polyimides, silicone resins, polybenzimidazoles, and polyphenylquinoxalines. The main chain of epoxy resin and phenolic resin is C-C structure, the bond energy is low, and it is easy to oxidize. The service temperature under air atmosphere generally does not exceed 500 °C; High (260-320°C); polybenzimidazole and polyphenylquinoxaline have high cost of raw materials, complex synthesis process, harsh use conditions (high curing temperature, high pressure, long time), and cannot enter the production field. Silicone resin has the characteristics of both inorganic and organic materials. It maintains its physical and chemical properties in a wide temperature range (-60-1200 ° C), has good fatigue properties, and has excellent thermal stability under high temperature conditions. , is a main direction for the development of high temperature resistant adhesives (500-1200°C) (US1994/5290897; Polymer, 2010, (51): 3867-3878; Carbon, 2008, (46): 1957-1965; Materials Science and Engineering A , 2011, (528):2952-2959). However, the inherent low bonding strength and high curing temperature of silicone resin limit its application range. In addition, in a high-temperature oxidizing atmosphere, silicone resin is also prone to degradation reactions, which will cause changes in the molecular structure of polysiloxane and reduce its use temperature.

In view of the shortcomings of silicone resins, the present invention starts from the liquid silicon carbide precursor, utilizes the excellent high temperature resistance and oxidation resistance of the Si-C bond in the silicon carbide precursor, and combines the high bond energy and the high bond energy of the Si-O-Si bond Good flexibility, combining the characteristics of the two, synthesize a polycarbosiloxane with good adhesive performance, excellent temperature resistance, and can be used in air atmosphere.

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Contents of the invention

The purpose of the present invention is to overcome the disadvantages of the prior art and provide a method for preparing polycarbosiloxane, a high-temperature-resistant organic adhesive, from a liquid silicon carbide precursor.

The object of the present invention is achieved through the following technical solutions: with liquid silicon carbide precursor (liquid polysilane, polymethylsilane, liquid polycarbosilane), vinyl-containing low-molecular siloxane as starting raw materials, toluene or Tetrahydrofuran is used as a solvent, and chloroplatinic acid is used as a catalyst. After mixing according to a certain ratio, the temperature is raised to 20-300° C., kept for a certain period of time, cooled to a certain temperature, then distilled under reduced pressure, and cooled to room temperature to obtain the final product.

The preparation method of high temperature resistant polycarbosiloxane comprises the following steps:

(1) According to the mass ratio of raw materials: liquid silicon carbide precursor: vinyl-containing low-molecular siloxane ratio of 1:0.1-10, add raw materials, and then add 1-100ppm of chloroplatinic acid as a catalyst;

(2) Raise the temperature of the reaction system to 20-300°C at a heating rate of 0.1-30°C/min, stir mechanically, and keep warm for 1-20 hours under nitrogen protection.

(3) Lower the temperature of the reactor to room temperature to 250°C, distill under reduced pressure for 0.25 to 2 hours, and then lower the system to room temperature to obtain the target polymer product.

The liquid silicon carbide precursor is liquid polysilane or polymethylsilane or liquid polycarbosilane.

The liquid polysilane is a low-molecular-weight polysilane with a boiling point <200°C, and the polymethylsilane and liquid polycarbosilane are laboratory-made products with a weight-average molecular weight of 100 to 10,000; the vinyl-containing low-molecular Silicone is a silicone containing two or more vinyl groups.

The polycarbosiloxane prepared by the invention is composed of Si, C, O, H and other elements. According to needs, polymers with different degrees of polymerization such as liquid, viscous and solid can be obtained, and the polymers can be used in the preparation of high temperature resistant organic adhesives.

Compared with the existing method, the present invention has the following advantages: (1) The raw materials used are simple and easy to obtain, the source is reliable, and the reaction process is simple; (2) The obtained polymer has excellent high temperature resistance. By controlling the conditions, the obtained polymer The mass retention rates up to 1200°C under inert and air atmospheres are both greater than 80%. (3) The obtained polymer contains a large amount of active Si-H, Si-OH, Si-Si, CH=CH ₂ groups, easy to cross-link and solidify, has low surface energy, and is easy to spread on the surface of ceramics, metals and other objects , wetting, and has good adhesive properties. As a high temperature resistant adhesive, it has broad application prospects in bonding SiC ceramic materials, oxide ceramics, carbon materials and titanium alloy materials.

Description of drawings

Fig. 1 is the typical infrared spectrogram of embodiment 1 gained polycarbosiloxane;

Fig. 2 is the ¹ H-NMR spectrogram of polycarbosiloxane obtained in Example 1;

Figure 3 is the TG diagram (N ₂ ) of the polycarbosiloxane obtained in Example 1;

Figure 4 is the TG diagram (Air) of the polycarbosiloxane obtained in Example 1.

Detailed ways

The present invention will be further described below in conjunction with embodiment.

Example 1:

Add 20g of liquid polymethylsilane (self-made), 20ml of toluene, and 5g of tetramethyltetravinylcyclotetrasiloxane into a 250ml three-neck flask equipped with condensing reflux and mechanical stirring, heat to 180°C for 5 hours, and then cool down to 150°C, distilled under reduced pressure for 0.5h to remove the solvent and small molecules to obtain a light yellow viscous liquid, and the whole reaction process was under the protection of nitrogen.

See Figure 1 and Figure 2: According to IR and ¹ H-NMR analysis, the polymer contains Si-H, Si-OH, Si-CH ₃ , Si-O-Si, CH=CH ₂ and other chemical bonds. The polymer has excellent high temperature resistance, the weight loss is only 18.8% at 1200°C under N ₂ atmosphere, and only 8.6% at 1200°C under air atmosphere.

Example 2:

Add 20g of liquid polycarbosilane, 20ml of tetrahydrofuran, 20g of tetramethyltetraenylcyclotetrasiloxane into a 250ml three-neck flask equipped with condensing reflux and mechanical stirring, add 1.7ppm of platinum-containing catalyst, heat to 100°C and stir mechanically After 1.5h, the temperature was lowered to 80°C, and the solvent and small molecules were removed by distillation under reduced pressure for 0.25h to obtain a light yellow viscous liquid. The whole reaction process was under the protection of nitrogen. The weight loss of the obtained polymer at 1200°C under _N2 atmosphere was 20.4%, and the weight loss at 1200°C under air atmosphere was 14.5%.

Example 3

Add 20g of liquid polysilane and 10g of tetramethyltetravinylcyclotetrasiloxane to a 250ml three-necked flask equipped with condensing reflux and mechanical stirring, add 2.1ppm of chloroplatinic acid, heat to 150°C and mechanically stir for 1.5h, then Cool down to 80°C, and distill under reduced pressure for 0.25h to remove small molecules to obtain a white viscous liquid. The whole reaction process was under the protection of nitrogen. The obtained polymer lost 21.5% of its weight at 1200°C under N ₂ atmosphere, and 17.6% at 1200°C under air atmosphere.

Example 4

The product obtained in Example 1 was used to bond atmospheric pressure sintered silicon carbide ceramic blocks (20*10*5mm ³ ). Before bonding, the silicon carbide ceramic blocks were ultrasonically cleaned in ethanol for 30 minutes, and then dried in an oven at 80°C for 4 hours and taken out for use. Double-sided glue is used, and after being glued, it is clamped with a clamp and placed in an oven at 200 ° C for 2 hours to fully cure. The cured sample was placed in a muffle furnace at a rate of 20 °C/min to the set temperature for 2 hours, and then the shear strength was tested after cooling to room temperature. The shear strength of different temperature treatments is shown in Table 1.

Table 1

Processing temperature after curing 400°C 600°C 800℃ 1000℃ 1200℃ Shear strength/MPa 9.3 5.9 4.3 8.3 10.0 9.9

Example 5

Use the product obtained in Example 2 to bond alumina ceramic blocks (20*10*5mm ³ ). Before bonding, the alumina ceramic blocks were ultrasonically cleaned in ethanol for 30 minutes, and then dried in an oven at 80°C for 4 hours and taken out for use. Double-sided glue is used, and after being glued, it is clamped with a clamp and placed in an oven at 200 ° C for 2 hours to fully cure. The cured sample was placed in a muffle furnace at a rate of 20 °C/min to the set temperature for 2 hours, and then the shear strength was tested after cooling to room temperature. The shear strength of different temperature treatments is shown in Table 2.

Table 2

Processing temperature after curing 400°C 600°C 800℃ 1000℃ 1200℃ Shear strength/MPa 7.9 5.1 3.5 6.6 9.4 8.2

Claims (3)

1. one kind prepares the method for high temperature resistant organic adhesion agent by liquid silit precursor, it is characterized in that, may further comprise the steps:

(1) according to raw materials quality than liquid silit precursor: the low molecular weight polyorganosiloxane that contains vinyl is 1: 0.1～10 to add raw materials, and the Platinic chloride that adds 1～100ppm is again made catalyzer;

(2) temperature rise rate according to 0.1～30 ℃/min rises to 20～300 ℃ with temperature of reaction system, mechanical stirring, and insulation is 1～20 hour under nitrogen protection;

(3) temperature of reactor is reduced to room temperature～250 ℃, underpressure distillation 0.25～2 hour is reduced to room temperature with system again and is promptly obtained the subject polymer product.

2. according to claim 1ly prepare the method for high temperature resistant organic adhesion agent, it is characterized in that said liquid silit precursor is liquid polysilane or polymethyl silicane or liquid Polycarbosilane by liquid silit precursor.

3. the method for preparing high temperature resistant organic adhesion agent by liquid silit precursor according to claim 2; It is characterized in that; Said liquid polysilane is the low molecular weight polycaprolactone silane of boiling point＜200 ℃, and said polymethyl silicane and liquid Polycarbosilane are that the homemade weight-average molecular weight in laboratory is 100～10000 product; The said low molecular weight polyorganosiloxane that contains vinyl is the siloxanes that contains two or more vinyl.

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