JPH0782378A - Siloxane copolymer and method for synthesizing the same - Google Patents

Abstract

PURPOSE:To obtain a high-purity siloxane copolymer having a high mol.wt. and a low degree of dispersion and usable as an optical waveguide material by heating a specific siloxane prepolymer in a high-boiling solvent under reflux, removing the solvent from the resulting soln., and heating the resulting siloxane copolymer. CONSTITUTION:A siloxane prepolymer having a wt.-average mol.wt. of 20,000 or lower and contg. repeating structural units of formulas I and II [wherein R1 and R2 are each a group of formula III (wherein Y is H, heavy hydrogen, or halogen; and n>=5)] is refluxed in a high-boiling solvent for a specified time while removing water generated to give a siloxane copolymer soln., which is heated to remove the solvent and then heated at 200-300 deg.C for a specified time, thus giving the objective siloxane copolymer contg. repeating structural units of formulas I and II.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a siloxane copolymer and a method for synthesizing the same, and more particularly to a siloxane copolymer having a high purity, a high molecular weight and a low dispersity which can be used as a polymer optical waveguide material and a method for synthesizing the same.

[0002]

2. Description of the Related Art Polysiloxane, which is a type of silicon-based polymer, is a polymer having a repeating structural unit of Si--O bond and is generally excellent in film formability and heat resistance. Therefore, application to a protective film for electronic devices has been studied. In addition, recently, it has been studied to produce a polymer optical waveguide by utilizing its excellent light transmission property (Japanese Patent Laid-Open No. Hei 4 (1999) -54242).
-157402). Optical circuit parts such as optical multiplexers / demultiplexers made of polymer can be economically manufactured compared to those made of glass, which enables economicization of optical communication systems, especially subscriber communication systems. Is expected to do. As a siloxane-based polymer applicable to a polymer optical waveguide, a siloxane copolymer having a chemical structural unit represented by the following general formulas (I) and (II) as a repeating unit has been proposed.

[0003]

[Chemical 3]

(However, R ₁ and R ₂ are each C _n
Y _{2n + 1} (Y represents hydrogen, deuterium or a halogen atom, n is a positive integer of 5 or more), a halogenated alkyl group or a phenyl group represented by C ₆ Y _5. , A deuterium-substituted phenyl group or a halogenated phenyl group. The polymer optical waveguide generally has a cross-sectional structure shown in FIG. 2, and has a structure in which a core portion 3 is provided on a lower clad 2 provided on a substrate 1 and an upper clad 4 is provided on the core portion. is there. Here, since the refractive index of the core portion is larger than that of the cladding layer, light can be confined in the core portion and function as an optical waveguide.

A siloxane copolymer that can be used as an optical waveguide must satisfy the following conditions.

High molecular weight: A higher molecular weight is required for good film formation. GPC that standard polystyrene equivalent weight average molecular weight measured by (gel permeation chromatography) (hereinafter abbreviated as M _W) at least about 100,000 is needed inventors revealed. That is, when the molecular weight was less than 100,000, minute cracks were formed in the coating of the core layer and the light transmittance was deteriorated. Further, when the upper clad layer is provided on the core layer, there is a problem that a part of the interface is fused (intermixing), and the light transmittance is also deteriorated. Specifically, the molecular weight is 99,000 and the dispersity is 4.5.
In the case where the core layer was made of the polymer (1), the transmission loss was 1 dB / cm even in the former case.

Narrow molecular weight distribution: It is necessary that the molecular weight distribution is as narrow as possible in order to prevent obscuring of the interface between the clad / core portion due to overcoating. The present inventors have found that a dispersion degree of 5 or less, which is a degree of molecular weight distribution represented by a ratio Mw / Mn of Mw and Mn (Mn; standard polystyrene addition number average molecular weight) measured by GPC, is required. Revealed. That is, when the dispersity is less than 50,000, the above intermixing is likely to occur and the transmission loss is deteriorated. For example, the transmission loss of a waveguide having a core layer of a copolymer having a molecular weight of 100,000 and a dispersity of 5.1 was 1 dB / cm even in the best case.

High purity: Need to be free of organic, inorganic, and other impurities that can interfere with light transmission.

Low gel content: The microgel contained in the polymer is also a factor that impairs light transmission. To remove such microgels, the siloxane polymer solution needs to be filtered off with a filter of 1 μm or less before use. If many microgels are formed in the synthesized polymer, a great deal of labor is required for the filtering operation. Therefore, it is required that the gel content in the polymer after synthesis is extremely small.

Good refractive index controllability: The refractive index of a siloxane polymer changes depending on the number of phenyl groups contained in the polymer, and the higher the phenyl group content, the higher the refractive index. Therefore, for example, in the general formulas (I) and (II), when R ₁ = R ₂ = C ₆ H ₅ (phenyl group), the more the component of the general formula (I) in the copolymer, the higher the refractive index. To do. Here, in order to control the refractive index, it is desirable that the charging ratio of the raw materials and the copolymer composition ratio in the polymer always have a constant relationship.

Conventionally, as for a method for synthesizing a polysiloxane which is not a copolymer (referred to as polysiloxane), for example, a known document; J. F. Brown et al., Journal
Of American Chemical Society, Vol. 6, 6
Pages 194-6195 (1960) or Japanese Patent Publication No. 4
No. 0-15989. That is,
It is a starting material phenyltrichlorosilane (C ₆ H ₅ SiC
It is said that a polymer having a high molecular weight can be obtained by heating a hydrolyzate obtained by hydrolyzing l ₃ ) together with potassium hydroxide (KOH) as a catalyst in a high boiling point solvent for a long time. However, when a siloxane copolymer is synthesized using this method, Mw is at most 3
There was a problem that only about 50,000 polymers could be obtained. Further, when a high melting point solvent such as biphenyl which is solid at room temperature is used, there is a problem that the solvent component remains in the polymer even after the post-treatment after the reaction. Further, there is a problem that the refractive index of the obtained polymer does not have a good correlation with the charging ratio of the raw materials. The problem of the correlation between the refractive index and the charging ratio seems to be due to elimination of some of the substituents in the polymer.

[0012]

An object of the present invention is to provide a siloxane copolymer which can be used as a polymer optical waveguide material and has a high molecular weight, a low dispersion degree, a high purity and a good refractive index controllability, and a method for synthesizing the same. Is to provide.

[0013]

The present invention has been made in view of the above-mentioned drawbacks of the prior art. The first invention is the following general formulas (I) and (II).

[0014]

[Chemical 4]

(However, R ₁ and R ₂ are each C _n
Y _{2n + 1} (Y represents hydrogen, deuterium or a halogen atom, n is a positive integer of 5 or more), a halogenated alkyl group or a phenyl group represented by C ₆ Y _5. , A deuterium-substituted phenyl group or a halogenated phenyl group. In the siloxane copolymer having a chemical structural unit represented by the formula (1) as a repeating unit, the weight average molecular weight is 100,000 or more and the ratio of the weight average molecular weight to the number average molecular weight is 5 or less.

The second invention is the following general formulas (I) and (II).

[0017]

[Chemical 5]

(However, R ₁ and R ₂ are each C _n
Y _{2n + 1} (Y represents hydrogen, deuterium or a halogen atom, n is a positive integer of 5 or more), a halogenated alkyl group or a phenyl group represented by C ₆ Y _5. , A deuterium-substituted phenyl group or a halogenated phenyl group. In a siloxane copolymer having a chemical structural unit represented by the formula (1) as a repeating unit, a weight average molecular weight of at least (A) containing the chemical structural unit represented by the general formulas (I) and (II) as a repeating unit. 10,000 or less of a siloxane copolymer prepolymer is refluxed for a certain period of time in a high-boiling-point solvent while removing generated water, and (B) the siloxane copolymer solution obtained in the first step. The second step of removing the high-boiling solvent by heating (C), and (C) the siloxane copolymer obtained in the second step, from 200 ° C to 300 ° C.
And a third step of heating for a certain period of time in an atmosphere of a constant temperature in the above range.

In a third aspect of the invention, in the second step,
50 ml (milliliter) removal rate of high boiling point solvent
/ Hour or less.

In a fourth aspect of the invention, in the third step,
The temperature accuracy of the temperature atmosphere is ± 1 ° C. or less.

[0021]

Here, the siloxane copolymer prepolymer as the synthetic raw material is, for example, RSiCl ₄ (mono-substituted silicon trichloride) and R ₂ SiCl ₂ (di-substituted silicon dichloride) or RSi ( OR ') ₃ (mono-substituted silicon trialkoxide) and R ₂ Si (OR') ₂
(Di-substituted silicon dialkoxide) is mixed at an arbitrary ratio, this is hydrolyzed, and then a polymer having a low molecular weight is prepared by the following method.

(A) The hydrolyzate is refluxed with toluene or xylene as a solvent for about 24 hours while removing generated water, reprecipitated with a solvent such as methanol, filtered, and dried.

(B) The hydrolyzate is catalyzed by KOH or the like using toluene, xylene or the like as a solvent for 24 to 48 hours,
The mixture is refluxed while removing generated water, reprecipitated with a solvent such as methanol, filtered, and dried.

The siloxane copolymer prepolymer (Mw; 1000 to 20000) thus obtained was mixed with xylene (boiling point;
139 ° C), toluene (Mw; 110.8 ° C), anisole (Mw; 152 ° C), phenetole (Mw; 172).
C.), tetralin (Mw; 207.degree. C.) or the like in a high-boiling-point solvent, while heating to reflux for 10 to 48 hours while removing generated water (first step). When the reflux time is short, the molecular weight finally obtained tends to be small, which is not preferable. Here, it is desirable to use a solvent having substantially the same volume as the concentration of the prepolymer at the reflux, and the reaction is usually carried out in a container such as a glass flask. Then, the solvent is removed from the container at a rate of about 50 ml / hour (second step). The molecular weight increases to about 40,000 to 80,000 during this step, but if the removal rate is too fast, the uniformity of the reaction decreases, which is not preferable. As the heating source, a mantle heater or the like can be used as in the reflux operation. Then, the entire reaction vessel is placed in an electric constant temperature bath kept at a constant temperature in the range of 200 to 300 ° C. and heated for 10 to 72 hours (third step).
Here, it is desirable that the temperature accuracy of the heating temperature is as good as possible, and it is necessary to control the heating temperature within ± 1 ° C. As a heating method, for example, there is a method of heating the reaction container using a mantle heater, but in such a method, a part of the sample is heated to a high temperature and the temperature uniformity is insufficient.
For this reason, it is recognized that a part of the sample gels or, when it is significant, causes thermal decomposition. on the other hand,
Injecting argon or nitrogen gas into the reaction vessel
Effective for removing water and impurities. In addition, since the molecular weight increases with time, it is not preferable to heat for too long a time, because unnecessary gel components will be significantly generated. Therefore, it is preferable to appropriately sample a part of the reaction product, monitor the molecular weight thereof, and stop the heating when the target molecular weight is reached. GPC is the most accurate simple method for measuring the molecular weight, but more rapid evaluation methods include measuring the viscosity of a concentrated solution of the sample and measuring the dissolution rate of the sample in a solvent. , Etc. After completion of the reaction, tetrahydrofuran (TH
F) and the like are dissolved in a solvent such as methanol and reprecipitated in a poor solvent such as methanol, recovered, dried, and finally targeted to obtain a siloxane copolymer having a weight average molecular weight of 100,000 or more and Mw / Mn of 5 or less. A coalescence is obtained.

[0025]

EXAMPLES The present invention will be described in detail below with reference to examples, but it goes without saying that the present invention is not limited to these examples.

Example 1 Synthesis of Siloxane Copolymer Prepolymer: A siloxane copolymer prepolymer having a monophenylsiloxane unit: diphenylsiloxane unit = 95/5 was synthesized by the following procedure.

Dioxane 500 in a 1 liter reaction vessel
Add ml (milliliter) and add 60.9 ml of phenyltrichlorosilane and 4.2 ml of diphenyldichlorosilane.
Dissolve. With stirring, 200 ml of water is added dropwise over 3 hours to carry out the hydrolysis reaction. The reaction product is transferred to a separating funnel and mixed with 1 liter of toluene to dissolve the hydrolyzate in the toluene layer. 3 times the toluene layer with 800 ml of distilled water
Wash twice to remove residual hydrogen chloride. The toluene solution is concentrated to dryness with a rotary evaporator to obtain a hydrolyzate (60 g). To a reaction vessel (500 ml eggplant-shaped flask), 80 ml of toluene and 6 ml of 10% methanol solution of KOH are added, and reflux is started in a reactor equipped with a moisture meter (volume: 30 ml). With the progress of the polycondensation reaction, the removed water is removed in the meter. Reflux is continued for 40 hours in this state. After the reaction is completed, THF 80 ml
Was added to dissolve it, and the insoluble matter was filtered off.
Add 1 to neutralize KOH. It was reprecipitated in 2 liters of methanol, filtered, washed and dried to finally obtain 45 g of a siloxane copolymer prepolymer (Mw = 830).
0, Mw / Mn = 3.1; molecular weight was measured by GPC).

Synthesis of high molecular weight copolymer: 40 g of the siloxane copolymer prepolymer synthesized above was dissolved in 70 ml of xylene and a 10% KOH methanol solution of 0.6 m was prepared.
1 is added and the mixture is refluxed in a reaction vessel equipped with a water content meter. Thirty
The actual amount of solvent is 4 because ml moves to the moisture meter side.
It was 0 ml. Using the mantle heater as a heating source, 24
After continuing the reflux for a period of time, the cock of the moisture meter is released to start the removal of the solvent. After the lapse of 1 hour, the water content meter itself is removed to continue the removal of the solvent. After 3 hours, the solvent is almost removed from the reaction vessel and the solvent odor disappears. After that, the container itself is placed in an electric constant temperature bath kept at 250 ° C. (± 0.2 ° C.) to continue heating. At this time, argon gas was introduced into the reaction vessel at a flow rate of 50 ml / min. 24
After the lapse of time, heating was stopped, and after returning to room temperature, THF4
00 ml was added and dissolved. After removing the insoluble matter of the solution,
It was reprecipitated with 4 liters of methanol and dried at 80 ° C. for 10 hours to finally obtain a siloxane copolymer. The GPC curve of the copolymer thus obtained is shown in FIG. From this, the copolymer had Mw = 110,000 and Mw / Mn = 3.9, which were excellent properties in both molecular weight and molecular weight distribution. Copolymer 3
Spin coating from 100% monochlorobenzene solution (100
The film thickness of the thin film produced at 0 rpm) was 8 μm, and the refractive index of the thin film was 1.539 (measurement wavelength; 1.3 μm).

Example 2 In Example 1, 59.0 ml of D-substituted phenyltrichlorosilane was used instead of phenyltrichlorosilane, and 8.6 ml of D-substituted diphenyldichlorosilane was used instead of diphenyldichlorosilane.
A D-substituted siloxane 90/10 copolymer was synthesized in the same manner except that it was used. Obtained polymer Mw = 120,000, M
It was w / Mn = 4.3. The refractive index of the thin film is 1.5
It was 43 (wavelength; 1.3 μm).

(Comparative Examples 1 to 3) A siloxane copolymer was synthesized in the same manner as in Example 1 except that each step was performed under the conditions shown in Table 1. The properties of the obtained copolymers are shown in the table, but all were inadequate.

[0031]

[Table 1]

(Application Example) Polymer optical waveguides having the copolymers obtained in Examples 1 and 2 as core materials were prepared. As the clad material, D-substituted phenylpolysiloxane (non-copolymer) having a molecular weight of 150,000 was used (refractive index was 1.533). Lower clad film thickness: 20 μm, core shape: 8 ×
8 μm ² , upper clad film thickness; 15 μm. When the light transmittance was evaluated, it was 0.5 dB / cm (1.3 μm) when the polymer of Example 1 was used, and 0.15 dB / cm when the polymer of Example 2 was used. It was possible to fabricate a polymer optical waveguide with a small value.

[0033]

As described above, according to the present invention, a high quality siloxane copolymer having the following characteristics, which can be used in a polymer optical waveguide, can be obtained.

The molecular weight is as large as 100,000 or more.

When the polydispersity is 5 or less, the molecular weight distribution is narrow.

There are few impurities and gel contents.

Strict control of the refractive index is possible.

[Brief description of drawings]

1 is a GP of the siloxane copolymer obtained in Example 1.
It is a diagram showing a C curve.

FIG. 2 is a cross-sectional view showing the structure of a polymer optical waveguide.

[Explanation of symbols]

 1 substrate 2 lower clad 3 core 4 upper clad

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Saburo Imamura 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (4)

[Claims] 1. The following general formulas (I) and (II): (However, R ₁ and R ₂ are each a C _n Y _{2n + 1} (Y represents hydrogen, deuterium or a halogen atom, and n is a positive integer of 5 or more) or a halogenated alkyl. Group or a phenyl group represented by C ₆ Y ₅ , a deuterium-substituted phenyl group or a halogenated phenyl group), the siloxane copolymer having a chemical structural unit represented by the repeating unit has a weight average molecular weight of 10 A siloxane copolymer having a weight average molecular weight and a number average molecular weight of not less than 5 and not more than 5. 2. The following general formulas (I) and (II): (However, R ₁ and R ₂ are each a C _n Y _{2n + 1} (Y represents hydrogen, deuterium or a halogen atom, and n is a positive integer of 5 or more) or a halogenated alkyl. Group or a phenyl group represented by C ₆ Y ₅ , a deuterium-substituted phenyl group or a halogenated phenyl group), the siloxane copolymer having a chemical structural unit represented by the following formula: at least (A) A siloxane copolymer prepolymer having a weight average molecular weight of 20,000 or less containing the chemical structural units represented by the general formulas (I) and (II) as a repeating unit in a high-boiling solvent,
A first step of refluxing for a certain period of time while removing generated water, and (B) a second step of removing the high boiling point solvent by heating the siloxane copolymer solution obtained in the first step And (C) a third step of heating the siloxane copolymer obtained in the second step in an atmosphere of a constant temperature in the range of 200 ° C. to 300 ° C. for a fixed time. Method for synthesizing siloxane copolymer. 3. The method for synthesizing a siloxane copolymer according to claim 2, wherein the removal rate of the high boiling point solvent in the second step is 50 ml / hour or less. 4. The temperature accuracy of the temperature atmosphere in the third step is ± 1 ° C. or less.
The method for synthesizing the siloxane copolymer according to 1.