JP7219098B2 - Method for producing isocyanate group-containing alkoxysilane - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an isocyanate group-containing alkoxysilane.

Conventionally, as a method for producing an isocyanate group-containing alkoxysilane, a method for obtaining an isocyanatoorganosilane by thermally decomposing a carbamate organosilane produced by reacting an aminoorganosilane and a dialkyl carbonate is known (for example, See Patent Document 1 below.).

In this method, a carbamate organosilane is pyrolyzed in a thin film evaporator to obtain a reaction product containing isocyanatoorganosilane, and then the isocyanatoorganosilane is purified by distilling the obtained reaction product. ing.

Japanese Patent Application Publication No. 2018-501206

In the method for producing an isocyanate group-containing alkoxysilane as described in Patent Document 1, it is required to efficiently obtain a high-purity isocyanate group-containing alkoxysilane.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for producing an isocyanate group-containing alkoxysilane capable of efficiently obtaining a highly pure isocyanate group-containing alkoxysilane.

The present invention [1] comprises a reaction step of reacting an amino group-containing alkoxysilane with a dialkyl carbonate to obtain a carbamate, thermally decomposing the carbamate to obtain an isocyanate group-containing alkoxysilane, and a pyrolysis/distillation step of purifying the contained alkoxysilane by distillation, wherein the pyrolysis/distillation step heats a mixture of the carbamate and the alcohol by-produced in the reaction step to obtain the alcohol. A first fraction, a second fraction containing the isocyanate group-containing alkoxysilane, and a third fraction containing a cyclic by-product represented by the following chemical formula are obtained. into the mixture.

Chemical formula:

(In the formula, R ₁ and R ₃ represent an alkyl group, and R ₂ represents an alkylene group.)
According to this method, in the thermal decomposition/distillation step, a mixture of carbamate and alcohol is heated and distilled to thermally decompose the carbamate and refine the resulting isocyanate group-containing alkoxysilane.

Thereby, the alcohol-containing first fraction and the cyclic by-product-containing third fraction can be separated from the isocyanate group-containing alkoxysilane-containing second fraction.

Therefore, a highly pure isocyanate group-containing alkoxysilane can be obtained by a simple process of heating and distilling a mixture of carbamate and alcohol.

Also, a third fraction containing cyclic by-products is mixed with the mixture obtained in the reaction step to react the alcohol in the mixture with the cyclic by-products to convert the cyclic by-products back to carbamate. be able to.

Thereby, the isocyanate group-containing alkoxysilane can be further produced from the carbamate returned from the cyclic by-product.

Therefore, while increasing the purity of the isocyanate group-containing alkoxysilane, the cyclic by-product can be reused to increase the yield of the isocyanate group-containing alkoxysilane.

In summary, a highly pure isocyanate group-containing alkoxysilane can be efficiently obtained from the viewpoint of both production process and yield.

In the present invention [2], the second fraction contains 99.0% by mass or more of the isocyanate group-containing alkoxysilane, and the third fraction contains 0.1% by mass of the cyclic by-product. A method for producing the isocyanate group-containing alkoxysilane of [1] above is included.

In the present invention [3], the third fraction comprises an initial fraction distilled before the second fraction and a rear fraction distilled after the second fraction. The method for producing the isocyanate group-containing alkoxysilane of the above [1] or [2] is included.

In the present invention [4], the thermal decomposition/distillation step is performed using a batch-type distiller, and the third fraction obtained in the thermal decomposition/distillation step this time is used in the next and subsequent The method for producing the isocyanate group-containing alkoxysilane according to any one of the above [1] to [3], which is mixed with the mixture subjected to the thermal decomposition/distillation step.

The method for producing an isocyanate group-containing alkoxysilane of the present invention can efficiently obtain a high-purity isocyanate group-containing alkoxysilane.

FIG. 1 is a flow chart showing one embodiment of the method for producing an isocyanate group-containing alkoxysilane of the present invention. FIG. 2 is a schematic configuration diagram of a batch-type distiller. FIG. 3 is a flow chart of the pyrolysis/distillation process shown in FIG. FIG. 4 is a schematic configuration diagram of a continuous distiller.

1. Method for Producing Isocyanate Group-Containing Alkoxysilane As shown in FIG. 1, the method for producing an isocyanate group-containing alkoxysilane of the present invention comprises a reaction step (S1), a thermal decomposition/distillation step (S2), and a mixing step (S4). including.

(1) Reaction Step In the reaction step (S1), an amino group-containing alkoxysilane and a dialkyl carbonate are reacted to obtain a carbamate.

Specifically, in the reaction step (S1), the amino group-containing alkoxysilane and the dialkyl carbonate are heated while being mixed in the presence of a catalyst. Then, as shown in the following chemical reaction formula (1), the amino group-containing alkoxysilane and the dialkyl carbonate react to produce carbamate and alcohol as a by-product. That is, a mixture of carbamate and alcohol is obtained by the reaction step (S1).

Chemical reaction formula (1):

(In the formula, R ₁ and R ₃ represent an alkyl group, and R ₂ represents an alkylene group.)
R ₁ in Chemical Reaction Formula (1) is, for example, an alkyl group having 1 to 4 carbon atoms such as methyl group and ethyl group.

R ₂ in Chemical Reaction Formula (1) is, for example, an alkylene group having 1 to 4 carbon atoms such as ethylene group and propylene group.

R ₃ in Chemical Reaction Formula (1) is, for example, an alkyl group having 1 to 4 carbon atoms such as methyl group and ethyl group. R ₃ is preferably the same alkyl group as R ₁ .

As shown in chemical reaction formula (1), the amino group-containing alkoxysilane is an alkoxysilane having at least one amino group (NH ₂ ). Examples of amino group-containing alkoxysilanes include amino group-containing trialkoxysilanes such as 3-aminopropyltrimethoxysilane and 3-aminopropyltriethoxysilane.

Dialkyl carbonates include, for example, dimethyl carbonate and diethyl carbonate. When the amino group-containing alkoxysilane is 3-aminopropyltrimethoxysilane, preferably dimethyl carbonate is selected as dialkyl carbonate. When the amino group-containing alkoxysilane is 3-aminopropyltriethoxysilane, preferably diethyl carbonate is selected as dialkyl carbonate.

Examples of catalysts include alkali metal alkoxides such as sodium methoxide and sodium ethoxide. Sodium methoxide is preferably selected as catalyst when the amino group-containing alkoxysilane is 3-aminopropyltrimethoxysilane and the dialkyl carbonate is dimethyl carbonate. When the amino group-containing alkoxysilane is 3-aminopropyltriethoxysilane and the dialkyl carbonate is diethyl carbonate, preferably sodium ethoxide is selected as catalyst. In addition, the catalyst may be prepared as an alcohol solution.

The resulting carbamate is methyl N-[3-(trimethoxysilyl)propyl]carbamate when the amino group-containing alkoxysilane is 3-aminopropyltrimethoxysilane and the dialkyl carbonate is dimethyl carbonate. Further, when the amino group-containing alkoxysilane is 3-aminopropyltriethoxysilane and the dialkyl carbonate is diethyl carbonate, it is ethyl N-[3-(triethoxysilyl)propyl]carbamate.

The heating temperature in the reaction step (S1) is, for example, 70°C or higher and 90°C or lower. The heating time in the reaction step (S1) is, for example, 5 hours or more and 10 hours or less.

The mixture obtained in the reaction step (S1) contains, for example, 5% by mass or more, preferably 10% by mass or more, and, for example, 15% by mass or less of alcohol.

(2) Thermal decomposition/distillation step Next, in the thermal decomposition/distillation step (S2), the carbamate is thermally decomposed to obtain an isocyanate group-containing alkoxysilane, and the obtained isocyanate group-containing alkoxysilane is purified by distillation.

Specifically, the thermal decomposition/distillation step (S2) is performed using a batch-type distiller 1, as shown in FIG. A batch-type distiller 1 includes a vessel 2 , a distillation column 3 and a condenser 4 . The container 2 is charged with the mixture obtained in the reaction step (S1). Container 2 has a thermometer for measuring the temperature of the contents. Container 2 may have a stirring device for stirring the contents. A distillation column 3 is connected with the vessel 2 . The distillation column 3 extends vertically. A condenser 4 is connected to the distillation column 3 . A tank is connected to the condenser 4 . In this embodiment, the first tank 5 and the second tank 6 are connected to the condenser 4 . A second fraction, which will be described later, is stored in the first tank 5 . The second tank 6 stores a third fraction, which will be described later.

In the pyrolysis/distillation step (S2), the mixture is heated in the vessel 2 in the presence of a catalyst. At this time, the container 2 may be heated while stirring the mixture.

Examples of the catalyst include tetravalent dibutyltin (IV) dilaurate, dioctyltin (IV) dilaurate, dibutyltin (IV) bis(acetylacetonate), dibutyltin (IV) diacetonate, dibutyltin (IV) dioctoate, and the like. Organotin compounds, e.g. divalent organotin compounds such as tin(II) diacetate, tin(II) dilaurate, organic tin compounds such as titanates, titanium(IV) isopropoxide, titanium(IV) acetylacetate Titanium compounds, e.g. organic zirconium compounds such as zirconium (IV) acetylacetonate, e.g. iron (III) acetylacetonate, organic iron compounds such as iron (II) acetylacetonate, e.g. cobalt (III) acetylacetonate organocobalt compounds such as, for example, organomanganese compounds such as manganese acetylacetonate; organozinc compounds; organometallic compounds such as, for example, organobismuth compounds. Preferably, the catalyst includes a tetravalent organotin compound.

Further, in the pyrolysis/distillation step (S2), if necessary, the mixture can be mixed with a solvent.

The solvent is not particularly limited as long as it can dissolve at least carbamate and does not denature by heating or react with carbamate and isocyanate group-containing alkoxysilane generated in the pyrolysis/distillation step (S2). Preferably, the solvent has a higher boiling point than the alkoxysilane containing carbamate and isocyanate groups.

Solvents are, for example, aromatic hydrocarbons. Commercially available aromatic hydrocarbon solvents include, for example, barrel process oil B-01 (boiling point: 176° C.), barrel process oil B-03 (boiling point: 280° C.), and barrel process oil B-04AB. (boiling point: 294°C), barrel process oil B-05 (boiling point: 302°C), barrel process oil B-27 (boiling point: 380°C), barrel process oil B-28AN (boiling point: 430°C), barrel process oil B -30 (boiling point: 380 ° C.) barrel process oil B series (manufactured by Matsumura Oil Co., Ltd.), for example, barrel therm 200 (boiling point: 382 ° C.), barrel therm 300 (boiling point: 344 ° C.), barrel therm 400 (boiling point: 390°C), Barreltherm 1H (boiling point: 215°C), Barreltherm 2H (boiling point: 294°C), Barreltherm 350 (boiling point: 302°C), Barreltherm 470 (boiling point: 310°C), Barreltherm PA (boiling point: 176°C), Barreltherm 330 (boiling point: 257°C), and Barreltherm 430 (boiling point: 291°C) (manufactured by Matsumura Oil Co., Ltd.), for example, NeoSK-OIL1400 (boiling point: 391°C), NeoSK-OIL1300 (boiling point: 291°C), NeoSK-OIL330 (boiling point: 331°C), NeoSK-OIL170 (boiling point: 176°C), NeoSK-OIL240 (boiling point: 244°C) (manufactured by Soken Technics Co., Ltd.), for example, KSK series (manufactured by Soken Technics Co., Ltd.) such as KSK-OIL260 (boiling point: 266° C.) and KSK-OIL280 (boiling point: 303° C.).

The thermal decomposition/distillation step (S2) may be performed subsequent to the reaction step (S1). In this case, the reaction step (S1) described above may be performed in the vessel 2 intended for use in the pyrolysis/distillation step (S2). Moreover, the thermal decomposition/distillation step (S2) may be performed independently of the reaction step (S1). In this case, the mixture may be transferred from the container 2 used in the reaction step (S1) to another container for temporary storage, and then subjected to the thermal decomposition/distillation step (S2).

Specifically, in the thermal decomposition/distillation step (S2), first, the mixture is heated at a first temperature while reducing the pressure in the system.

The atmospheric pressure in the system is, for example, 50 kPa or less, preferably 15 kPa or less, and for example, 1 kPa or more, preferably 5 kPa or more.

The first temperature is a temperature that can evaporate alcohol and unreacted dialkyl carbonate from the mixture. The first temperature varies depending on the atmospheric pressure in the system, but is, for example, 80° C. or higher, preferably 150° C. or higher, for example, 210° C. or lower, preferably 200° C. or lower.

By heating the mixture at the first temperature, a first fraction is distilled off from the mixture as shown in FIG. 3 (S11). The first fraction contains alcohol and unreacted dialkyl carbonate, and does not contain isocyanate group-containing alkoxysilane and cyclic by-products described later.

Next, in the thermal decomposition/distillation step (S2), the pressure in the system is continuously reduced, and the mixture from which the first fraction has been distilled off is heated at a second temperature higher than the first temperature. .

The second temperature is a temperature at which the carbamate in the mixture can be thermally decomposed and a temperature at which the isocyanate group-containing alkoxysilane obtained by thermally decomposing the carbamate can be vaporized. The second temperature varies depending on the atmospheric pressure in the system, but is, for example, 170° C. or higher, preferably 220° C. or higher, and for example, 260° C. or lower, preferably 250° C. or lower.

By heating the mixture at the second temperature, the carbamate is thermally decomposed to produce an isocyanate group-containing alkoxysilane as shown in chemical reaction formula (2) below.

Chemical reaction formula (2):

(In the formula, R ₁ and R ₃ represent an alkyl group, and R ₂ represents an alkylene group.)
In chemical reaction formula (2), R ₁ is the same as R ₁ in chemical reaction formula (1), R ₂ is the same as R ₂ in chemical reaction formula (1), and R ₃ is the chemical reaction Same as R3 in formula ( ₁ ).

The resulting isocyanate group-containing alkoxysilane is 3-isocyanatomethyltrimethoxysilane when the amino group-containing alkoxysilane is 3-aminopropyltrimethoxysilane and the dialkyl carbonate is dimethyl carbonate. The isocyanate group-containing alkoxysilane produced is 3-isocyanatoethyltriethoxysilane when the amino group-containing alkoxysilane is 3-aminopropyltriethoxysilane and the dialkyl carbonate is diethyl carbonate.

Moreover, by heating the mixture at the second temperature, a cyclic by-product is produced as shown in the following chemical reaction formula (3).

Chemical reaction formula (3):

(In the formula, R ₁ and R ₃ represent an alkyl group, and R ₂ represents an alkylene group.)
In chemical reaction formula (3), R ₁ is the same as R ₁ in chemical reaction formula (1), R ₂ is the same as R ₂ in chemical reaction formula (1), and R ₃ is the chemical reaction Same as R3 in formula ( ₁ ).

Also, by heating the mixture at the second temperature, alcohol is produced as a by-product as shown in the above chemical reaction formula (2) and the above chemical reaction formula (3).

Then, in the thermal decomposition/distillation step (S2), by heating the mixture at a second temperature, the second fraction (S13) containing the isocyanate group-containing alkoxysilane and the second fraction A first fraction (S12) that distills to the bottom and a rear fraction (S14) that distills after the second fraction are obtained. The first and last fractions are the third fraction. That is, in the pyrolysis/distillation step (S2), the mixture is heated to obtain a first fraction, a second fraction, and a third fraction.

The second fraction contains 99.0% by mass or more of the isocyanate group-containing alkoxysilane. The second fraction is stored in the first tank 5 (see Figure 2).

The second fraction may contain sulfonamides such as p-toluenesulfonamide and o-toluenesulfonamide. By blending the sulfonamide in the second fraction, the storage stability of the isocyanate group-containing alkoxysilane can be improved, particularly when the isocyanate group-containing alkoxysilane is 3-isocyanatomethyltrimethoxysilane. .

The blending ratio of the sulfonamide in the second fraction is, for example, 200 ppm or more, preferably 500 ppm or more, and for example, 1000 ppm or less.

The third fraction (initial fraction and secondary fraction) contains 0.1 mass % or more of cyclic by-products.

In addition, the initial fraction contains, for example, 95% by mass or more and less than 99% by mass of the isocyanate group-containing alkoxysilane. The rear fraction contains, for example, 90% by mass or more and less than 99% by mass of the isocyanate group-containing alkoxysilane.

The third fraction (initial fraction and subsequent fraction) may further contain light-boiling fractions such as alcohol by-produced in the thermal decomposition/distillation step (S2) and unreacted carbamate. . The initial fraction contains, for example, 0.1% by mass or more and 3.0% by mass or less of a low-boiling fraction and, for example, 0.1% by mass or more and 3.0% by mass or less of unreacted carbamate. .

A third fraction is stored in a second tank 6 (see FIG. 2).

(3) Mixing step Next, as shown in FIG. 1, the third fraction obtained in this thermal decomposition/distillation step (S2) and stored in the second tank 6 is mixed in the mixing step (S4) , is mixed with the mixture to be subjected to the subsequent thermal decomposition/distillation step (S2).

Specifically, when there is the third fraction recovered this time, in the subsequent thermal decomposition/distillation step (S2), it is determined whether the third fraction is to be mixed with the mixture (S3), and the third fraction is (S3: YES), the third fraction is mixed with the mixture (S4).

In addition, the criteria for judging whether or not to mix the third fraction with the mixture can be appropriately set. For example, the total amount of the third fraction collected this time may be mixed with the next mixture. Further, when the amount of the third fraction that has been accumulated before this time reaches a predetermined amount or more, a certain amount of the accumulated third fraction may be mixed with the next mixture.

By mixing the third fraction with the mixture, the cyclic by-product in the third fraction reacts with the alcohol in the mixture to produce carbamate (reverse reaction of chemical reaction formula (3) above. ). The produced carbamate is subjected to the thermal decomposition/distillation step (S2).

3. Effect According to this method for producing an isocyanate group-containing alkoxysilane, as shown in FIGS. is thermally decomposed, and the obtained isocyanate group-containing alkoxysilane is purified.

As a result, from the second fraction (S13) containing the isocyanate group-containing alkoxysilane, the first fraction (S11) containing the alcohol, and the third fraction containing the cyclic by-product (S12, S14) can be separated.

Therefore, a highly pure isocyanate group-containing alkoxysilane can be obtained by a simple process of heating and distilling a mixture of carbamate and alcohol.

Further, as shown in FIG. 1, by mixing the third fraction containing the cyclic by-products with the mixture obtained in the reaction step (S3: YES, S4), the alcohol in the mixture is converted to the cyclic by-products. can be reacted with a compound to convert the cyclic by-product back to the carbamate (reverse reaction of equation (3) above).

Thereby, the isocyanate group-containing alkoxysilane can be further produced from the carbamate returned from the cyclic by-product (S2).

Therefore, while increasing the purity of the isocyanate group-containing alkoxysilane, the cyclic by-product can be reused to increase the yield of the isocyanate group-containing alkoxysilane.

In summary, a highly pure isocyanate group-containing alkoxysilane can be efficiently obtained from the viewpoint of both production process and yield.

4. Modification In the above-described embodiment, the thermal decomposition/distillation step (S2) is performed using a batch distiller, but as shown in FIG. can also

A continuous distiller 10 comprises a plurality of distillation columns 11 , 12 , 13 , 14 . Distillation column 11 distills off the alcohol from the mixed liquid. A distillation column 12 distills off unreacted dialkyl carbonate from the mixed liquid. The distillation column 13 heats the mixed liquid to thermally decompose the carbamate, and fractionally distills the obtained isocyanate group-containing alkoxysilane and the by-produced alcohol. Distillation column 14 distills the cyclic by-products and any remaining carbamate from the solvent. The cyclic by-products and carbamate distilled off by the distillation column 14 are mixed with the liquid mixture in the mixing step (S4, see FIG. 1) and supplied to the distiller 11 again.

Even in the modified example, the same effect as the above-described embodiment can be obtained.

Next, the present invention will be described based on examples and comparative examples, but the present invention is not limited by the following examples. "Parts" and "%" are based on mass unless otherwise specified. In addition, specific numerical values such as the mixing ratio (content ratio), physical property values, and parameters used in the following description are the corresponding mixing ratios ( Content ratio), physical properties, parameters, etc. be able to.

<Gas chromatography measurement conditions>
Gas chromatography in each example and comparative example was performed under the following measurement conditions.

Apparatus: Agilent 7890B GC system, manufactured by Agilent Technologies Column: VF-5ms (inner diameter: 0.25 mm, length: 30 m, film thickness: 0.25 μm) manufactured by Agilent Technologies Carrier gas: helium gas Carrier gas flow rate : 1.2 ml/min Detector: Flame ion detector (FID)
Injection temperature: 200°C
Column temperature: 100°C (1 minute) -10°C/min -280°C (6 minutes)
Detector temperature: 280°C
<Example 1>
3-isocyanatopropyltriethoxysilane was synthesized. A detailed description will be given below.

(1) First reaction step In a 1 L reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube and a cooling tube, 3-aminopropyltriethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) 584.0 was added under a nitrogen atmosphere. 0 parts by mass and 405.0 parts by mass of diethyl carbonate (manufactured by Mitsui Chemicals Fine Co., Ltd.) were mixed.

Next, 8.97 parts by mass of an ethanol solution of sodium ethoxide (concentration: 20% by mass, manufactured by Wako Pure Chemical Industries, Ltd.) was added as a catalyst to the mixed solution of 3-aminopropyltriethoxysilane and diethyl carbonate, A reaction was carried out at a reaction temperature of 80° C. for 6 hours to obtain a mixed solution containing ethyl N-[3-(triethoxysilyl)propyl]carbamate and ethanol. The conversion determined by titration with hydrochloric acid was 99.9 mol %. That is, almost the entire amount (99.9 mol %) of 3-aminopropyltriethoxysilane was converted to ethyl N-[3-(triethoxysilyl)propyl]carbamate.

Next, the obtained mixed solution was cooled to 40° C. and then neutralized by adding 2.65 parts by mass of 85% phosphoric acid (manufactured by Wako Pure Chemical Industries, Ltd.). The pH after neutralization was 7.5.

Analysis of the mixed liquid after neutralization by gas chromatography (area percentage method) revealed that the mixed liquid contained 13.4% by mass of ethanol, 8.0% by mass of diethyl carbonate, N-[3-(triethoxysilyl) It contained 77.8% by weight of ethyl propyl]carbamate.

(2) First Thermal Decomposition/Distillation Step A four-necked flask (500 ml) equipped with a thermometer, a rectifying column, a reflux head and a condenser was used as a reactor. Water at 20° C. was passed through the cooler.

In a flask, 250 parts by mass of the mixed solution obtained in the first reaction step, 62.5 parts by mass of NeoSK-OIL1400 (manufactured by Soken Technics Co., Ltd.), and dibutyltin dilaurate (manufactured by Tokyo Fine Chemicals Co., Ltd., L-101) 0 .5 parts by mass was charged, the flask was heated with a mantle heater while stirring, the temperature was raised to 200 ° C., and ethanol and a low-boiling fraction (first fraction) containing unreacted diethyl carbonate were distilled. let me Further, a cold trap cooled with cold methanol was connected to a vacuum pump to reduce the pressure in the system to 10.7 kPa, thereby distilling out light boiling fractions.

Next, hot water of 90 ° C. is flowed through the cooler, the temperature is raised to 245 ° C., the initial fraction (third fraction), the main fraction (second fraction), the rear fraction (third fraction) minutes) was distilled off.

126.3 parts by mass of the main fraction was obtained (yield 77.3% by mass). The main fraction was analyzed by gas chromatography (area percentage method) and found to contain 99.4% by mass of 3-isocyanatopropyltriethoxysilane.

An initial fraction of 9.7 parts by mass was obtained. The initial fraction was analyzed by gas chromatography (area percentage method) and found to contain 2.8% by mass of light boiling components, 95.7% by mass of 3-isocyanatopropyltriethoxysilane, N-[3-(triethoxysilyl ) propyl]ethyl carbamate 1.3% by weight, 0.2% by weight of cyclic by-products.

8.5 parts by mass of the rear fraction was obtained. The after-fraction was analyzed by gas chromatography (area percentage method) and found to contain 2.4% by mass of light boiling components, 92.5% by mass of 3-isocyanatopropyltriethoxysilane, N-[3-(triethoxysilyl ) propyl]ethyl carbamate 2.2% by weight, 0.4% by weight of cyclic by-products.

(3) Mixing step The initial fraction and the after-fraction obtained in the first thermal decomposition/distillation step were mixed with the liquid mixture obtained in the second reaction step. In addition, the reaction process of the 2nd time was performed similarly to the reaction process of the 1st time.

Analysis by gas chromatography showed that the peaks for 3-isocyanatopropyltriethoxysilane and cyclic by-products disappeared, and instead the peak for ethyl N-[3-(triethoxysilyl)propyl]carbamate increased. was

From this, 3-isocyanatopropyltriethoxysilane and the cyclic by-product reacted with ethanol in the mixture and changed to ethyl N-[3-(triethoxysilyl)propyl]carbamate. I understand.

(4) Second pyrolysis/distillation step The second pyrolysis/distillation step was performed in the same manner as the first pyrolysis/distillation step, except that the mixed liquid obtained in the mixing step was charged.

133.8 parts by mass of the main fraction was obtained (yield 81.8% by mass). The main fraction was analyzed by gas chromatography (area percentage method) and found to contain 99.3% by mass of 3-isocyanatopropyltriethoxysilane.

An initial fraction of 9.5 parts by mass was obtained. The initial fraction was analyzed by gas chromatography (area percentage method) and found to contain 2.3% by mass of light boiling components, 95.1% by mass of 3-isocyanatopropyltriethoxysilane, N-[3-(triethoxysilyl ) propyl]ethyl carbamate 1.6% by weight, 0.2% by weight of cyclic by-products.

8.1 parts by mass of the rear fraction was obtained. The after-fraction was analyzed by gas chromatography (area percentage method) and found to contain 2.1% by mass of light boiling components, 94.2% by mass of 3-isocyanatopropyltriethoxysilane, N-[3-(triethoxysilyl ) propyl]ethylcarbamate 2.5% by weight, 0.4% by weight cyclic by-products.

<Example 2>
As raw materials, 3-aminopropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) was used instead of 3-aminopropyltriethoxysilane, and dimethyl carbonate (manufactured by Mitsui Chemicals Fine Co., Ltd.) was used instead of diethyl carbonate. 3-Isocyanatopropyltrimethoxysilane was synthesized in the same manner as in Example 1, except that sodium methoxide was used as the catalyst in the process. A detailed description will be given below.

(1) First reaction step In a 1 L reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube and a cooling tube, 3-aminopropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) 600.N under a nitrogen atmosphere. 9 parts by mass and 392.6 parts by mass of dimethyl carbonate (manufactured by Mitsui Chemicals Fine Co., Ltd.) were mixed.

Next, 4.52 parts by mass of a methanol solution of sodium methoxide (concentration: 28% by weight, manufactured by Wako Pure Chemical Industries, Ltd.) was added as a catalyst to the mixed solution of 3-aminopropyltrimethoxysilane and dimethyl carbonate, A reaction was carried out at a reaction temperature of 60° C. for 6 hours to obtain a mixed liquid containing methyl N-[3-(trimethoxysilyl)propyl]carbamate and methanol. The conversion determined by titration with hydrochloric acid was 99.9 mol %. That is, almost the entire amount (99.9 mol %) of 3-aminopropyltrimethoxysilane was converted to methyl N-[3-(trimethoxysilyl)propyl]carbamate.

Next, the obtained mixed solution was cooled to 40° C. and then neutralized by adding 2.58 parts by mass of 85% phosphoric acid (manufactured by Wako Pure Chemical Industries, Ltd.). The pH after neutralization was 7.5.

Analysis of the neutralized mixture by gas chromatography (area percentage method) revealed that the mixture contained 11.7% by mass of methanol, 5.0% by mass of dimethyl carbonate, N-[3-(trimethoxysilyl)propyl ] contained 82.6% by mass of methyl carbamate.

(2) First Thermal Decomposition/Distillation Step A four-necked flask (500 ml) equipped with a thermometer, a rectifying column, a reflux head and a condenser was used as a reactor. Water at 20° C. was passed through the cooler.

A flask was charged with 360 parts by mass of the reaction mixture obtained in the first reaction step, 90 parts by mass of NeoSK-OIL1400 (manufactured by Soken Technics Co., Ltd.), and dibutyltin dilaurate (L-101, manufactured by Tokyo Fine Chemicals Co., Ltd.). 72 parts by mass of the flask was charged, and the flask was heated with a mantle heater while stirring to raise the temperature to 180° C., thereby distilling out the low-boiling components (methanol and dimethyl carbonate). Furthermore, a cold trap cooled with cold methanol was connected to a vacuum pump to reduce the pressure in the system to 8.7 kPa, thereby distilling out light boiling fractions.

Then, hot water of 80°C was flowed through the cooler, the temperature was raised to 240°C, and a first fraction, a main fraction, and a rear fraction were distilled.

201.4 parts by mass of the main fraction was obtained (yield 81.2% by mass). The main fraction was analyzed by gas chromatography (area percentage method) and found to contain 99.8% of 3-isocyanatopropyltrimethoxysilane. 0.10 parts by mass (500 ppm) of p-toluenesulfonamide was added to the main fraction as a stabilizer.

5.0 parts by mass of the initial fraction was obtained. The initial fraction was analyzed by gas chromatography (area percentage method) and found to contain 0.8% by mass of light boiling components, 95.7% by mass of 3-isocyanatopropyltrimethoxysilane, N-[3-(trimethoxysilyl ) propyl]methylcarbamate, 0.5% by weight, 0.2% by weight of cyclic by-products.

10.0 parts by mass of the rear fraction was obtained. The after-fraction was analyzed by gas chromatography (area percentage method) and found to contain 1.6% by mass of light boiling components, 93.4% by mass of 3-isocyanatopropyltrimethoxysilane, N-[3-(trimethoxysilyl ) propyl]methylcarbamate 1.9% by weight, 0.5% by weight cyclic by-products.

(3) Mixing step The initial fraction and the after-fraction obtained in the first thermal decomposition/distillation step were mixed with the liquid mixture obtained in the second reaction step. Analysis by gas chromatography showed that the peaks for 3-isocyanatopropyltrimethoxysilane and cyclic by-products disappeared, and instead the peak for methyl N-[3-(trimethoxysilyl)propyl]carbamate increased. was

From this, 3-isocyanatopropyltrimethoxysilane and the cyclic by-product reacted with methanol in the mixed liquid and changed to N-[3-(trimethoxysilyl)propyl]methyl carbamate. I understand.

(4) Second pyrolysis/distillation step The second pyrolysis/distillation step was performed in the same manner as the first pyrolysis/distillation step, except that the mixed liquid obtained in the mixing step was charged.

207.4 parts by mass of the main fraction was obtained. The main fraction was analyzed by gas chromatography (area percentage method) and found to contain 99.3% by mass of 3-isocyanatopropyltrimethoxysilane (yield 83.7% by mass).

5.2 parts by mass of the initial fraction was obtained. The initial fraction was analyzed by gas chromatography (area percentage method) and found to contain 0.9% by mass of light boiling components, 96.7% by mass of 3-isocyanatopropyltrimethoxysilane, N-[3-(trimethoxysilyl ) propyl]methyl carbamate, 0.4% by weight, 0.2% by weight of cyclic by-products.

A rear fraction of 9.8 parts by mass was obtained. The after-fraction was analyzed by gas chromatography (area percentage method) and found to contain 1.7% by mass of low-boiling components, 93.2% by mass of 3-isocyanatopropyltrimethoxysilane, N-[3-(trimethoxysilyl ) propyl]methyl carbamate 1.8% by weight, 0.5% by weight cyclic by-products.

<Comparative example>
The reaction step and thermal decomposition were carried out in the same manner as in Example 1, except that the initial fraction and the subsequent fraction were not recovered and the initial fraction and the subsequent fraction were not mixed with the mixture obtained in the next reaction step. • A distillation step was performed. A detailed description will be given below.

(1) Reaction Step In the same manner as in the first reaction step of Example 1, a mixed solution containing methyl N-[3-(trimethoxysilyl)propyl]carbamate and methanol was obtained.

(2) Thermal decomposition/distillation process In the same manner as the first thermal decomposition/distillation process in Example 1, after distilling the low-boiling fraction, hot water of 90 ° C. is flowed through the cooler and the temperature is raised to 245 ° C. All distillates (first fraction, main fraction and tail fraction) were collected.

140.6 parts by mass of distillate was obtained. The distillate was analyzed by gas chromatography (area percentage method) and found to contain 98.8% by mass of 3-isocyanatopropyltrimethoxysilane (yield 86.1% by mass).

1 batch type distiller S1 reaction process S2 pyrolysis/distillation process

Claims (2)

a reaction step of obtaining a carbamate by reacting an amino group-containing alkoxysilane represented by the following chemical formula (2) with a dialkyl carbonate represented by the following chemical formula (3) ;
a pyrolysis/distillation step of thermally decomposing the carbamate to obtain an isocyanate group-containing alkoxysilane, and purifying the obtained isocyanate group-containing alkoxysilane by distillation;
In the pyrolysis/distillation step, a mixture of the carbamate and alcohol by-produced in the reaction step is heated at a first temperature to obtain a first fraction containing the alcohol, and then heating the mixture after the first fraction has been distilled off at a second temperature higher than the first temperature to heat the carbamate in the mixture after the first fraction has been distilled off; It decomposes to produce the isocyanate group-containing alkoxysilane, and by-produces a cyclic by-product represented by the following chemical formula (1) to form a second fraction and before the second fraction. obtaining an initial fraction to be distilled and a rear fraction to be distilled after the second fraction, and using the initial fraction and the rear fraction as a third fraction;
The second fraction contains 99.0% by mass or more of the isocyanate group-containing alkoxysilane,
The initial fraction contains 95.0% by mass or more and less than 99.0% by mass of the isocyanate group-containing alkoxysilane,
The rear fraction contains 90.0% by mass or more and less than 99.0% by mass of the isocyanate group-containing alkoxysilane,
The third fraction contains 0.1% by mass or more of the cyclic by-product,
A method for producing an isocyanate group-containing alkoxysilane, wherein the third fraction is mixed with a mixture of the carbamate to be subjected to the thermal decomposition/distillation step and the alcohol by-produced in the reaction step.
Chemical formula (1) :

Chemical formula (2):

Chemical formula (3):

(In the formula, R ₁ and R ₃ represent an alkyl group having 1 to 4 carbon atoms, and R ₂ represents an alkylene group having 1 to 4 carbon atoms.) The pyrolysis/distillation step is performed using a batch-type still,
The third fraction obtained in the current thermal decomposition/distillation step is mixed with the mixture of the carbamate to be subjected to the subsequent thermal decomposition/distillation step and the alcohol by-produced in the reaction step. The method for producing an isocyanate group-containing alkoxysilane according to claim 1, characterized in that:

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