JP2002348295A - Method for recycling carbosilane with aromatic group - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for recycling a carbosilane with an aromatic group. SOLUTION: This recycling method of the carbosilane with the aromatic group includes a process for decomposing the carbosilane into the aromatic fragment and the silicon fragment adding an electrophile to the carbosilane with the aromatic group and a process for separating and recovering the produced aromatic fragment and/or silicon fragment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for recycling carbosilane having an aromatic group. More specifically, the present invention relates to a method for chemically decomposing carbosilane having an aromatic group and recycling the generated aromatic and silicon fragments.

[0002]

2. Description of the Related Art In recent years, attention has been focused on plastic recycling from the viewpoint of resource saving and environmental problems. Most of the recycling methods are thermal recycling (heat source) and material recycling (material source), and recycling in the true sense (chemical recycling: returning to raw materials)
It is far from the current situation. The reason is that most of the plastics currently used are manufactured without any consideration of recycling. On the other hand, most biodegradable polymers, which have recently attracted attention in academic societies and the industrial world, are chemically recycled because the concept of recycling is recycling to the natural world or recycling as fertilizer (composting). It is far from recycling.

[0003] Therefore, the present inventors have paid attention to organosilicon compounds. Silicon is an element that is present after oxygen in the earth's crust, and is easily used as a constituent element of a substance. Silicon is a highly safe element that has been closely adhered to industry and daily life as a constituent element of glass, cement, silica and silicone for a long time. As a characteristic of silicon, the Si—C bond of the organosilicon compound has a relatively large binding energy, but the cleavage may be easy depending on the reaction conditions. For example, Tamao-Fleming
Oxidation reaction (Kohei Tamao, Journal of the Society of Organic Synthesis, 46 , 861 (198
8)) or electrophilic substitution reaction with trifluoromethanesulfonic acid (W. Uhling, Chem. Ber., 129, 733 (199)
6)) is used. If these Si—C bond breaking reactions are applied to the decomposition reaction of an organosilicon compound (especially polycarbosilane), it is possible to decompose the organosilicon compound (especially polymer) into a raw material (monomer) in a simple reaction field. The present invention has been reached.

[0004]

As described above, it is an object of the present invention to provide a method for recycling aromatic fragments and silicon fragments from an organosilicon compound, specifically, a carbosilane having an aromatic group. is there.

[0005]

SUMMARY OF THE INVENTION The present invention comprises a step of adding an electrophile to a carbosilane having an aromatic group to decompose the carbosilane into an aromatic fragment and a silicon fragment; A method for recycling carbosilane having an aromatic group, comprising a step of separating and recovering fragments.

In a preferred embodiment of the present invention, an electrophile is added to carbosilane having an aromatic group to decompose the carbosilane into an aromatic fragment and a silicon fragment, and then a nucleophile is added to the reaction solution. This is a carbosilane recycling method for organizing the ends of silicon fragments and separating and recovering organosilanes as silicon fragments.

In another preferred embodiment of the present invention, an electrophile is added to a carbosilane having an aromatic group to decompose the carbosilane into an aromatic fragment and a silicon fragment, and then water is added to hydrolyze the silicon fragment. This is a carbosilane recycling method that decomposes and converts into silicone, and separates and recovers silicone as silicon fragments.

In another preferred embodiment of the present invention, an electrophile is added to a carbosilane having an aromatic group to decompose the carbosilane into an aromatic fragment and a silicon fragment, and then a nucleophile is added to the reaction solution. This is a method for carbosilane recycling in which the ends of silicon fragments are made organic to separate and recover organosilane as silicon fragments.

In another preferred embodiment of the present invention, an electrophile is added to a carbosilane having an aromatic group to decompose the carbosilane into an aromatic fragment and a silicon fragment, and then at least one of them is separated by distillation. This is a method for recycling the carbosilane to be recovered.

Another preferred embodiment of the present invention is a method for recycling carbosilane in which the electrophile used for decomposing the carbosilane having an aromatic group is a super strong acid.

Further, as a preferred embodiment of the present invention, after a carbosilane having an aromatic group is reacted with a super-strong acid, the resulting silicon fragment is reacted with an alcohol to convert the silicon fragment into an alkoxysilane, This is a method for recycling carbosilane to be regenerated.

In another preferred embodiment of the present invention, after carbosilane having an aromatic group is decomposed using an electrophile, an organic lithium compound is used as a nucleophile, and the terminal of the silicon fragment is organically recovered. This is a method for recycling carbosilane.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The carbosilane used in the present invention is a carbosilane having an aromatic group and is a polycarbosilane which is a low molecular weight compound or a polymer thereof. Among them, the recycling method of the present invention is particularly useful in the case of polycarbosilane, which is likely to be consumed in large quantities as an industrial material or a living material.

The term "carbosilane having an aromatic group" as used herein means a compound having a bond in which at least one aromatic group is directly bonded to a silicon element, and a plurality of such bonds may be present. The number of aromatic groups may be one or more. When there are a plurality of bonds between an aromatic group and a silicon element, these bonds may be on the same aromatic group or on different aromatic groups. These aromatic groups may be substituted with an alkyl group such as a methyl group and an ethyl group, but are not limited by the type of the substituent.

Specific examples of these compounds include low-molecular weight compounds such as trimethylsilylbenzene, trimethylsilylnaphthalene, 4-trimethylsilylbiphenyl, 1,6-bis (trimethylsilyl) naphthalene,
4'-bis (trimethylsilyl) biphenyl, 1,2-
Examples of bis (dimethylnaphthyl) disilane, 1,2-bis (dimethylbiphenyl) disilane, and polycarbosilane include poly [1,4- (tetramethyldisilanilene)
Phenylene], poly [1,4- (tetramethyldisilanylene) -2,5-dimethylphenylene], poly [4,4 ′
-(Tetramethyldisilanilene) biphenylylene] and the like, but are not limited thereto. Polycarbosilane is a compound having a silicon atom bonded to an aromatic group in the main chain. By breaking this bond, the polymer can be recycled as a low molecular weight compound.

Since the mechanism of the Si—C bond breaking reaction performed in the present invention is an electrophilic substitution reaction on an aromatic ring, for example, nitration with a mixed acid (nitric acid and sulfuric acid), sulfonation with sulfuric acid, iron catalyst Halogenation with chlorine, bromine, etc. in the presence of, alkylation by Friedel-Crafts reaction using alkyl chloride in the presence of Lewis acid catalyst, or acylation by Friedel-Crafts reaction using acyl chloride in the presence of Lewis acid catalyst Reactions such as conversion can be used.

In the present invention, most electrophiles can be used for the decomposition reaction. For example, acids such as sulfuric acid and nitric acid, ClSO ₃ H, H ₂ SO ₄ —SO ₃ , FSO ₃ H, FS
O ₃ H-SO ₃ , FSO ₃ H-SbF ₅ , HF-SbF ₅ ,
CF ₃ SO ₃ H or the like of a superacid, boron trifluoride, aluminum trichloride, Lewis acids iron chloride, nitronium ion (NO ^+), halogen ions (X ^+), acylium ions (RCO ^+), Hydroxonium ion (H ₃ O ⁺ )
And so on. Preferred among these are super strong acids,
Particularly preferred is CF ₃ SO ₃ H.

A monovalent aromatic group is represented by Ar (I), a divalent aromatic group is represented by Ar (II), and CF ₃ S is used as an electrophile.
When O ₃ H (expressed as TfOH) is used, the decomposition reaction in the present invention is performed according to the following reaction formula.

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Thus, the low molecular weight carbosilane is decomposed into silicon fragments and aromatic fragments,
Polycarbosilane is decomposed and reduced in molecular weight, and decomposed into two types of compounds, a silicon fragment and an aromatic fragment.

The silicon fragment generated by the decomposition reaction of carbosilane can be converted into a stable compound by using a nucleophile if necessary and recycled.

For example, silicon fragments produced by the above reaction can be converted into a stable compound by the following reaction and recycled.

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The nucleophile to be reacted with the silicon fragment is not particularly limited, but may be an organic Grignard reagent, a metal alkoxide, an alcohol, a mercaptan, an amine, an organic metal or water, and specifically, methylmagnesium bromide, phenyl Magnesium iodide, ethyl alcohol, ethyl mercaptan, trimethylamine or dimethylphenylsilyllithium,
An organic lithium compound such as diethylphenylsilyllithium, triphenylsilyllithium or phenyllithium or water can be exemplified. Of these, organic lithium compounds such as dimethylphenylsilyllithium and phenyllithium, alcohols and water are preferred.

When an alcohol (ethyl alcohol) is reacted with a silicon fragment, the reaction proceeds according to the following reaction formula, and super strong acid (TfOH) is regenerated. Ar-SiMe ₃ + TfOH → TfO-SiMe ₃ + ArH TfO-SiMe ₃ + EtOH → EtO-SiMe ₃ + TfOH

Since the super-strong acid thus regenerated is used again for the decomposition reaction of carbosilane, the decomposition reaction can be advanced by adding a small amount (catalytic amount) of the super-strong acid. As the alcohol, lower aliphatic alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, and butyl alcohol are preferable. When ditriflate is hydrolyzed by adding water, the silicon fragments are recycled as silicone.

The recycling method of the present invention decomposes an aromatic carbosilane into an aromatic fragment and a silicon fragment using an electrophile as described above, and recycles each of them. A nucleophile is added to make it more stable and recycled. Such a nucleophilic reaction can be performed by adding a nucleophilic reagent to the reaction solution after the completion of the above-described electrophilic reaction, or can be performed after removing an aromatic fragment from the reaction solution.

A known method can be used for separating both fragments. That is, when the product is a liquid, distillation, extraction, and decantation (when both are insoluble liquids), and when the product contains a solid, filtration, decantation, recrystallization, extraction, and column separation , Centrifugation or the like, or a combination of a plurality of unit operations. Hereinafter, the present invention will be described specifically with reference to examples.

[0027]

Example 1 Decomposition reaction of 1,2-bis (dimethylnaphthyl) disilane Decomposition reaction of 1,2-bis (dimethylnaphthyl) disilane by trifluoromethanesulfonic acid in a toluene solvent by changing the mixing ratio of both And the reaction temperature was changed. According to gas chromatography analysis, 1,2-bis (dimethylnaphthyl) disilane was not detected in any of the reaction solutions at the end of the reaction. 4-5 ml of water was added to the reaction solution, and the organic layer was separated. Add chloroform to the aqueous layer.
５5 ml was added to separate the organic layer. This operation was performed twice, and the entire organic layer was subjected to silica gel (glass column φ10 mm
× 20 mm), and the solvent was removed under reduced pressure. The target aromatic fragment (naphthalene) was isolated under reduced pressure using a Kugelrohr distillation apparatus. The results are shown in Table 1. Distillation conditions: 32 to 54 ° C / 1.0 to 0.9 mmHg

[0028]

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[0029]

[Table 1]

According to Table 1, it is clear that naphthalene could be recovered in a high yield. This decomposition reaction is silicon-s
Using trifluoromethanesulfonic acid equivalent to the p2 carbon bond, it was found to proceed best at low temperature (5 ° C.). In No. 4, the yield is low because 0.5 equivalent of trifluoromethanesulfonic acid is used for the silicon-sp2 carbon bond. In addition, the compound of the one-side reaction was recovered.

Furthermore, dimethylphenylsilyllithium was added to a reaction solution obtained by decomposing 1,2-bis (dimethylnaphthyl) disilane with trifluoromethanesulfonic acid in order to simultaneously recycle aromatic fragments and silicon fragments. As a result, the former (naphthalene)
Was 62%, and the recovery of the latter (1,4-biphenyldecamethyltetrasilane) was 45%. The reaction formula is shown below.

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The reaction conditions are shown below. Decomposition reaction: 1,2-bis (dimethylnaphthyl) disilane 1.0 mm
ol trifluoromethanesulfonic acid 1.2 mmol toluene 5 ml reaction temperature 25 ° C, reaction time 1.0 hour Silicon fragment recovery reaction: dimethylphenylsilyllithium 2.2mmol reaction temperature 0 ° C, reaction time 1 hour

Example 2 Decomposition reaction of 1,2-bis (dimethylbiphenyl) disilane A decomposition reaction was carried out in the same manner as in Example 1 except that the silane compound was changed, and a 78% aromatic fragment (biphenyl) was obtained.
Was recovered. The reaction formula and reaction conditions are shown below.

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The reaction conditions are shown below. Decomposition reaction: 1,2-bis (dimethylbiphenyl) disilane 2.0 m
mol trifluoromethanesulfonic acid 2.3 mmol toluene 5 ml reaction temperature 25 ° C, reaction time 1.0 hour

Examples 3 to 5 Using silane compounds as 1-trimethylsilylnaphthalene (Example 3) and 4-trimethylsilylbiphenyl (Example 4)
The decomposition reaction was carried out in the same manner as described above, and the aromatic fragment was recovered. The results are shown in Table 2.

[0036]

[Table 2]

Example 6 First, the synthesis of poly [4,4 '-(tetramethyldisilanylene) biphenylylene] used for decomposition will be described. The synthesis is based on the Wurtz reaction (J. Oshita, T. Wata
nabe, D. Kanaya, H. Osaki, M. Ishikawa, Organometalli
cs, 13 , 5002 (1994)). The silylation reaction was carried out using the corresponding 4,4'-dibromobiphenyl, and a chlorine group was introduced on silicon. Then, by a Wurtz-type coupling reaction using metal sodium-anhydrous toluene,
The desired polymer was obtained. The molecular weight was calculated to be a number average molecular weight of 4,500 and a weight average molecular weight of 7,000 using GPC analysis in terms of standard polystyrene. The following decomposition reaction was performed using this polymer.

Decomposition reaction of poly [4,4 '-(tetramethyldisilanilene) biphenylylene] The reaction was carried out in the same manner as in Example 1 except that the silane compound was changed. The reaction was carried out at room temperature (25 ° C.). As a result, the reaction was completed in 15 minutes, and the aromatic fragment (biphenyl)
Was recovered 98%. The reaction formula is shown below.

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The reaction conditions are shown below. Decomposition reaction: Poly [4,4 '-(tetramethyldisilanilene) biphenylylene] 0.2 mmol / structural unit trifluoromethanesulfonic acid 0.4 mmol toluene 2 ml

Next, simultaneous recovery of an aromatic fragment and a silicon fragment was attempted under the same reaction conditions. That is, after decomposing the silane compound with trifluoromethanesulfonic acid,
Phenyl lithium was added. After that, add 4
The organic layer was separated by adding -5 ml. This operation was performed twice, and the entire organic layer was subjected to silica gel (glass column φ20 mm
× 40 mm), and the solvent was removed under reduced pressure. Distillation was performed under reduced pressure using a Kugelrohr distillation apparatus to obtain the desired biphenyl. Distillation conditions:
62-74 ° C / 0.4-0.75 mmHg

Further, 1,2-diphenyltetramethyldisilane was obtained from the distillation residue by distillation under reduced pressure using a Kugelrohr distillation apparatus. Distillation conditions: 70-
100 ° C./0.4-0.7 mmHg The yields were 100% and 72%, respectively.

The reaction formula is shown below.

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The reaction conditions are shown below. Decomposition reaction: poly [4,4 '-(tetramethyldisilanilene) biphenylylene] 2.0 mmol / structural unit trifluoromethanesulfonic acid 4.0 mmol toluene 20 ml Reaction temperature 25 ° C, reaction time 30 minutes Silicon fragment recovery reaction: phenyl Lithium 4.0mmol Reaction temperature 0 ° C, Reaction time 2 hours

Example 7 4-Trimethylsilylbiphenyl and poly [4,4'-
(Tetramethyldisilanilene) biphenylylene] in the presence of ethyl alcohol with trifluoromethanesulfonic acid. The results are shown in Table 3.

[0045]

[Table 3]

According to this, as described above, the silicon fragment produced by the decomposition reaction reacts with ethyl alcohol to regenerate trifluoromethanesulfonic acid, which is further involved in the decomposition reaction. It was found that the reaction proceeded easily by the addition of an amount of trifluoromethanesulfonic acid, and that an aromatic fragment was obtained in high yield.

Industrial Applicability The present invention has an industrial advantage in that carbosilane having an aromatic group is decomposed into an aromatic fragment and a silicon fragment, and each of them is recycled. The significance is great.

Claims (7)

[Claims] 1. A step of adding an electrophile to a carbosilane having an aromatic group to decompose the carbosilane into an aromatic fragment and a silicon fragment, and separating and recovering the generated aromatic fragment and / or silicon fragment. , A method of recycling carbosilane having an aromatic group. 2. An electrophilic reagent is added to a carbosilane having an aromatic group to decompose the carbosilane into an aromatic fragment and a silicon fragment, and then a nucleophile is added to the reaction solution to terminate the terminal of the silicon fragment. And
The method for recycling carbosilane according to claim 1, wherein the organosilane compound is separated and recovered as a silicon fragment. 3. An electrophilic reagent is added to the carbosilane having an aromatic group to decompose the carbosilane into an aromatic fragment and a silicon fragment, and then water is added to hydrolyze the silicon fragment to convert it into silicone.
The method for recycling carbosilane according to claim 1, wherein silicone is separated and recovered as silicon fragments. 4. The method according to claim 1, wherein an electrophile is added to the carbosilane having an aromatic group to decompose the carbosilane into an aromatic fragment and a silicon fragment, and then at least one of the carbosilane is separated and recovered by distillation. How to recycle carbosilane. 5. The method for recycling carbosilane according to claim 1, wherein the electrophile is a super strong acid. 6. A carbosilane having an aromatic group, which is added with a super-strong acid as an electrophile to decompose the carbosilane into an aromatic fragment and a silicon fragment, and then react the alcohol with the silicon fragment to convert the silicon fragment into an alkoxysilane. A method for recycling carbosilane having an aromatic group, which comprises converting and regenerating a super strong acid. 7. The method for recycling carbosilane according to claim 2, wherein the nucleophile is an organolithium compound or water.