Preparation method of hydrogen-containing MT methyl silicone resin with narrow molecular weight distribution

Abstract

The invention discloses a preparation method of hydrogen-containing MT methyl silicone resin with narrow molecular weight distribution, and mainly relates to the technical field of chemical engineering, and the preparation method comprises the following steps: mixing methyltrimethoxysilane with acetic acid, then adding a catalyst for reaction, then cooling, rectifying to remove byproducts, and sequentially reacting tetramethyldisiloxane, acetic acid and acetic anhydride to obtain the hydrogen-containing MT methyl silicone resin. Removing by-products through vacuum rectification, adding methylbenzene as a solvent for extraction, adding deionized water, stirring and washing for multiple times, and finally distilling for a period of time under vacuum to obtain hydrogen-containing MT methyl silicone resin; the hydrogen-containing MT methyl silicone resin with narrow molecular weight distribution can be prepared, and the yield of the hydrogen-containing MT methyl silicone resin is improved.

Description

Technical Field

[0001] The invention mainly relates to the technical field of chemical industry, and in particular to a method for preparing a hydrogen-containing MT methyl silicone resin with a narrow molecular weight distribution. Background Art

[0002] Hydrogenated MT methyl silicone resin is composed of monofunctional M units (H(CH3)2SiO1 / 2) and trifunctional T units (CH3SiO3 / 2). Its hydrogenated active end groups (Si-H bonds) impart excellent crosslinking capabilities and are widely used in LED encapsulants, addition-type silicone rubber, and semiconductor packaging materials.

[0003] Traditional processes face problems such as wide molecular weight distribution, difficult by-product separation, and high gelation rate, resulting in poor optical uniformity of products and insufficient curing stability.

[0004] Chinese invention patent publication number CN102875810B discloses a phenyl-containing MT-type resin and its preparation method. The molecular weight is controlled by adjusting the acid concentration, but toluene / xylene solvents are required. The desolvation step easily leads to small molecule residues, affecting the purity of the resin. Although its polydispersity coefficient (PDI) can be controlled within 1.5-2.0, the refractive index fluctuates greatly (1.483-1.563), and it is easy to become turbid during compounding.

[0005] Another Chinese invention patent, CN103242531A, discloses a method for preparing phenyl hydrogenated MT silicone resins. The method uses co-hydrolysis of hydrogenated chlorosilanes and non-hydrogenated chlorosilanes. This method requires the use of a strong acid (e.g., hydrochloric acid), which produces hydrogen halides that corrode the equipment. Subsequent multi-step water washing and neutralization are required, resulting in high wastewater treatment costs and a yield of only 70–80%.

[0006] In addition, for example, the Chinese invention patents CN111057241AMT hydrogenated methylphenyl silicone resin and its preparation method, and CN108003346A preparation method of silicone compatibilizer material, which are also disclosed, each have defects. The disclosed content of CN111057241AMT hydrogenated methylphenyl silicone resin and its preparation method shows that phenyltrimethoxysilane is used as the raw material, and cationic resin is required for staged catalysis. The reaction temperature needs to be precisely controlled (30-80°C), otherwise local cross-linking will be excessive and gelation will be triggered, and the by-product methanol is difficult to remove.

[0007] The preparation method of CN108003346A organosilicon compatibilizer material utilizes distillation technology. This existing distillation technology requires high temperature (>100°C) to remove low-boiling substances, resulting in Si-H bond breakage and resin degradation, with a loss rate of up to 15%.

[0008] Therefore, the development of a preparation method for a narrow molecular weight distribution hydrogenated MT methyl silicone resin with mild reaction conditions, controllable process, and no need for high-temperature purification is of great significance for breaking through the bottleneck of high-end silicone materials and promoting industrial upgrading. Summary of the Invention

[0009] (1) Technical issues to be resolved In view of the above problems, the present invention needs to provide a method for preparing hydrogenated MT methyl silicone resin with narrow molecular weight distribution, so as to solve the problems of wide molecular weight distribution, easy gelation and low yield in traditional hydrolysis polycondensation.

[0010] (2) Technical solution In view of the above technical problems, the present invention provides a method for preparing a hydrogen-containing MT methyl silicone resin with a narrow molecular weight distribution, comprising methyltrimethoxysilane as a raw material, and comprising the following steps: S1, methyltrimethoxysilane and acetic acid were mixed, trifluoromethanesulfonic acid was added as a catalyst, and the temperature was raised, followed by reflux reaction; S2, then cooling, and performing vacuum distillation for a period of time to continuously remove by-products methyl acetate and methanol; S3, after adding tetramethyldisiloxane, heating, and sequentially adding acetic acid and acetic anhydride at corresponding intervals to react; S4, distilling under reduced pressure under vacuum for a certain period of time to initially remove the by-product methyl acetate; S5, adding toluene as a solvent to extract the target product in the system, then adding deionized water and stirring and washing it several times to wash away water-soluble impurities; then decolorizing and filtering; S6. Maintain vacuum distillation at a certain temperature for a period of time to remove the solvent and low molecular weight, and finally cool to obtain the target product, hydrogenated MT methyl silicone resin.

[0011] Furthermore, in S1, the molar ratio of methyltrimethoxysilane to acetic acid is 1:0.75-1.2; The required amount of trifluoromethanesulfonic acid is 1000-2000ppm based on the total mass of methyltrimethoxysilane and acetic acid; The temperature range of the heating is 55-80°C, and the reflux reaction time is 2-3h.

[0012] Furthermore, in S2, the temperature range of cooling is 10-20°C, and vacuum distillation is performed for a period of time under vacuum, the vacuum degree is 101.265-101.295 kPa, and the distillation period is 4-5 hours.

[0013] Furthermore, in S3, the molar ratio of the added tetramethyldisiloxane to the methyltrimethoxysilane in S1 is 0.36-0.9:1; The temperature range for warming is 40-60°C; Acetic acid is first added dropwise within a specified time to react, and after the reaction is completed, acetic anhydride is added dropwise within a specific time to react again.

[0014] The molar ratio of acetic acid to methyltrimethoxysilane in S1 is 0.6~1.5:1; The molar ratio of acetic anhydride to methyltrimethoxysilane in S1 is 0.3~0.75:1; If the specified time is within 1-2 hours, the reaction time is 1 hour; if the specific time is within 1-2 hours, the re-reaction time is 1 hour.

[0015] Furthermore, at S4, the vacuum degree is 95-100 kPa, and lasts for a certain time of 0.5-1 h.

[0016] Furthermore, the mixture is washed with water 4-8 times in S5.

[0017] Furthermore, at S6, the temperature is 90-130°C, the vacuum degree is 100-101.325 kPa, and the distillation time is specifically 1-3 hours.

[0018] The present invention has the following advantages over the prior art: 1. The results obtained by implementing the method steps of the present invention have a molecular weight distribution of PDI <1.5 (narrow distribution). In the prior art, PDI >2.0. Even though the prior art can achieve PDI <1.5, the yield is low. The present invention has a higher yield of >92%. The method of the present invention uses an integrated process of chain extension by acyl oxidation and low-temperature vacuum distillation. The integrated distillation can reduce losses. Compared with the prior art with a yield of <85% and large losses in multiple purification steps, the yield of the hydrogenated MT methyl silicone resin is greatly improved. 2. In terms of gel control, the present invention does not exhibit gelation, and by-products can be removed in real time during production, which overcomes the drawbacks of the prior art of excessive by-products, difficulty in removal, and gel formation (gel rate >10%). The present invention can represent a major breakthrough in the production of high-end organosilicon materials, and the produced hydrogenated MT methyl silicone resin can have superior performance, including better heat resistance and chemical resistance. DETAILED DESCRIPTION

[0019] The present invention will be further described below with reference to specific embodiments. The present invention is explained through the exemplary embodiments and descriptions of the present invention, but is not intended to limit the present invention.

[0020] Example 1: A method for preparing a hydrogenated MT methyl silicone resin with a narrow molecular weight distribution, comprising methyltrimethoxysilane as a raw material, comprising the following steps: S1, methyltrimethoxysilane and acetic acid were mixed, trifluoromethanesulfonic acid was added as a catalyst, and the temperature was raised, followed by reflux reaction; S2, then cooling, and performing vacuum distillation for a period of time to continuously remove by-products methyl acetate and methanol; S3, after adding tetramethyldisiloxane, heating, and sequentially adding acetic acid and acetic anhydride at corresponding intervals to react; S4, distilling under reduced pressure under vacuum for a certain period of time to initially remove the by-product methyl acetate; S5, adding toluene as a solvent to extract the target product in the system, then adding deionized water and stirring and washing it several times to wash away water-soluble impurities; then decolorizing and filtering; S6. Maintain vacuum distillation at a certain temperature for a period of time to remove the solvent and low molecular weight, and finally cool to obtain the target product, hydrogenated MT methyl silicone resin.

[0021] In S1, preferably, the molar ratio of methyltrimethoxysilane to acetic acid is 1:0.75-1.2; Preferably, the required amount of trifluoromethanesulfonic acid is 1000-2000 ppm based on the total mass of methyltrimethoxysilane and acetic acid.

[0022] The temperature range for heating is 55-80°C, and the reflux reaction time is 2-3h; this temperature range and reaction time are suitable temperature ranges. The specific steps below involve specific temperatures, but are not limited to the specific temperatures and times given below; the material amounts given in the present invention can also be values ​​within the range, and in actual operation, there can be more data possibilities.

[0023] In S2, the temperature range of cooling is 10-20°C, and vacuum distillation is performed for a period of time under vacuum, the vacuum degree is 101.265-101.295 kPa, and the distillation period is 4-5 hours.

[0024] In S3, preferably, the molar ratio of the added tetramethyldisiloxane to the methyltrimethoxysilane in S1 is 0.36-0.9:1.

[0025] The temperature range for warming is 40-60°C; Acetic acid is first added dropwise within a specified time to react, and after the reaction is completed, acetic anhydride is added dropwise within a specific time to react again.

[0026] Preferably, the molar ratio of acetic acid to methyltrimethoxysilane in S1 is 0.6-1.5:1.

[0027] Preferably, the molar ratio of acetic anhydride to methyltrimethoxysilane in S1 is 0.3-0.75:1.

[0028] If the specified time is within 1-2 hours, the reaction time is 1 hour; if the specific time is within 1-2 hours, the re-reaction time is 1 hour.

[0029] At S4, the vacuum degree is 95-100 kPa, and the duration is 0.5-1 h.

[0030] Wash 4-8 times in S5.

[0031] At S6, the temperature is 90-130°C, the vacuum degree is 100-101.325 kPa, and the distillation time is specifically 1-3 hours.

[0032] In the specific operation of this embodiment, the amount of methyltrimethoxysilane used is 136.22 g, acetic acid is 66.66 g, trifluoromethanesulfonic acid is 0.30 g, and tetramethyldisiloxane is 62.86 g in S1, and acetic acid is 46.84 g and acetic anhydride is 39.81 g in S3.

[0033] Specific steps: (1) Weigh 136.22 g of methyltrimethoxysilane and 66.66 g of acetic acid, mix them and put them into a four-necked flask, then add 0.30 g of trifluoromethanesulfonic acid, heat to 55 ° C, and reflux for 2 h; (2) Cooling to 10°C, and performing vacuum distillation at a vacuum degree of 101.295 kPa for 4 h to continuously remove the by-products methyl acetate and methanol; (3) Add 62.86 g of tetramethyldisiloxane, raise the temperature to 40°C, then add 46.84 g of acetic acid dropwise within 1 hour and react for 1 hour; then add 39.81 g of acetic anhydride dropwise within 1 hour and react for another 1 hour; (4) Distill under reduced pressure at a vacuum of 95 kPa to initially remove the by-product methyl acetate for 0.5 h; (5) Add toluene as the solvent to extract the target product, then add deionized water and stir and wash 4 times to remove water-soluble impurities; then decolorize and filter; (6) Maintaining a vacuum of 101 kPa at 130°C for 1 h, the solvent and low molecular weight components were removed by distillation under reduced pressure. The mixture was then cooled to obtain 118.40 g of hydrogenated MT methyl silicone resin with a polydispersity index of 1.47 and a yield of 99.28%. No gelation occurred during the entire reaction.

[0034] Example 2: In this example, 136.22 g of methyltrimethoxysilane was used, 70.06 g of acetic acid, 0.21 g of trifluoromethanesulfonic acid, and 48.36 g of tetramethyldisiloxane were used in S1, and 36.03 g of acetic acid and 30.63 g of acetic anhydride were used in S3; Specific steps: (1) Weigh 136.22 g of methyltrimethoxysilane and 70.06 g of acetic acid, mix them and put them into a four-necked flask, then add 0.21 g of trifluoromethanesulfonic acid, heat to 70°C, and reflux for 2.5 h; (2) Cooling to 15°C, and performing vacuum distillation at a vacuum degree of 101.28 kPa for 4.5 h to continuously remove the by-products methyl acetate and methanol; (3) Add 48.36 g of tetramethyldisiloxane, raise the temperature to 40°C, then add 36.03 g of acetic acid dropwise within 1 hour and react for 1 hour; then add 30.63 g of acetic anhydride dropwise within 2 hours and react for another 1 hour; (4) Distill under reduced pressure at a vacuum of 98 kPa to initially remove the by-product methyl acetate for 1 h; (5) Add toluene as the solvent to extract the target product, then add deionized water and stir and wash 4 times to remove water-soluble impurities; then decolorize and filter; (6) Maintaining a vacuum of 101 kPa at 130°C for 1 h, the solvent and low molecular weight components were removed by distillation under reduced pressure. Finally, the mixture was cooled to obtain 105.38 g of hydrogenated MT methyl silicone resin with a polydispersity index of 1.36 and a yield of 98.30%. No gelation occurred during the entire reaction.

[0035] Example 3: In this example, 136.22 g of methyltrimethoxysilane, 45.04 g of acetic acid in S1, 0.36 g of trifluoromethanesulfonic acid, 120.89 g of tetramethyldisiloxane, 90.08 g of acetic acid in S3, and 76.57 g of acetic anhydride were used; Specific operation steps; (1) Weigh 136.22 g of methyltrimethoxysilane and 45.04 g of acetic acid, mix them and put them into a four-necked flask, then add 0.36 g of trifluoromethanesulfonic acid, heat to 80°C, and reflux for 3 h; (2) Cooling to 20°C, and performing vacuum distillation at a vacuum degree of 101.265 kPa for 5 h to continuously remove the by-products methyl acetate and methanol; (3) Add 120.89 g of tetramethyldisiloxane, raise the temperature to 60°C, then add 90.08 g of acetic acid dropwise within 2 hours and react for 1 hour; then add 76.57 g of acetic anhydride dropwise within 1 hour and react for another 1 hour; (4) Distill under reduced pressure at a vacuum of 100 kPa to initially remove the by-product methyl acetate for 1 h; (5) Add toluene as the solvent to extract the target product, then add deionized water and stir and wash 8 times to remove water-soluble impurities; then decolorize and filter; (6) Maintaining a vacuum of 101 kPa at 90°C for 3 h, the solvent and low molecular weight components were removed by distillation. Finally, the mixture was cooled to obtain 165.48 g of hydrogenated MT methyl silicone resin with a polydispersity index of 1.30 and a yield of 98.79%. No gelation occurred during the entire reaction.

[0036] In the three embodiments of the present invention, the results obtained are: a polydispersity coefficient of 1.47, a yield of 99.28% of hydrogenated MT methyl silicone resin, and no gelation during the entire reaction; The polydispersity coefficient is 1.36, the yield is 98.30% of hydrogenated MT methyl silicone resin, and there is no gelation during the reaction. The polydispersity coefficient is 1.30, the yield is 98.79% of hydrogenated MT methyl silicone resin, and there is no gelation during the entire reaction process; The polydispersity index of the present invention can be controlled to PDI <1.5, and specifically in application, a result parameter of less than 1.30 may be obtained, which can significantly narrow the molecular weight distribution. The yields in the three embodiments of the present invention are all >92%, which is significantly higher than the prior art and can maximize the yield.

[0037] If the dispersion coefficient can be controlled at PDI < 1.5, it means that the hydrogenated MT methyl silicone resin produced will have more consistent performance, higher quality, wider application, and better application performance, such as better mechanical strength, better heat resistance and chemical resistance.

[0038] Any matters not described in the present invention are applicable to the prior art.

Claims

1. A method for preparing a hydrogenated MT methyl silicone resin with a narrow molecular weight distribution, comprising methyltrimethoxysilane as a raw material, characterized in that: The following steps are involved: S1, methyltrimethoxysilane and acetic acid were mixed, trifluoromethanesulfonic acid was added as a catalyst, and the temperature was raised, followed by reflux reaction; S2, then cooling, and performing vacuum distillation for a period of time to continuously remove by-products methyl acetate and methanol; S3, after adding tetramethyldisiloxane, heating, and sequentially adding acetic acid and acetic anhydride at corresponding intervals to react; S4, distilling under reduced pressure under vacuum for a certain period of time to initially remove the by-product methyl acetate; S5, adding toluene as a solvent to extract the target product in the system, then adding deionized water and stirring and washing it several times to wash away water-soluble impurities; then decolorizing and filtering; S6. Maintain vacuum distillation at a certain temperature for a period of time to remove the solvent and low molecular weight, and finally cool to obtain the target product, hydrogenated MT methyl silicone resin.

2. The method for preparing a hydrogenated MT methyl silicone resin with a narrow molecular weight distribution according to claim 1, characterized in that: In S1, the molar ratio of methyltrimethoxysilane to acetic acid is 1:0.75~1.2; The required amount of trifluoromethanesulfonic acid is 1000-2000ppm based on the total mass of methyltrimethoxysilane and acetic acid; The temperature range of the heating is 55-80°C, and the reflux reaction time is 2-3h.

3. The method for preparing a hydrogenated MT methyl silicone resin with a narrow molecular weight distribution according to claim 1, characterized in that: In S2, the temperature range of cooling is 10-20°C; and vacuum distillation is carried out for a period of time, the vacuum degree is 101.265-101.295 kPa, and the distillation period is 4-5 hours.

4. The method for preparing a hydrogenated MT methyl silicone resin with a narrow molecular weight distribution according to claim 1, characterized in that: In S3, the molar ratio of the added tetramethyldisiloxane to the methyltrimethoxysilane in S1 is 0.36~0.9:1; The temperature range for warming is 40-60°C; Acetic acid is first added dropwise within a specified time to react, and after the reaction is completed, acetic anhydride is added dropwise within a specific time to react again.

5. The method for preparing a hydrogenated MT methyl silicone resin with a narrow molecular weight distribution according to claim 4, characterized in that: The molar ratio of acetic acid to methyltrimethoxysilane in S1 is 0.6~1.5:1; The molar ratio of acetic anhydride to methyltrimethoxysilane in S1 is 0.3~0.75:1; If the specified time is within 1-2 hours, the reaction time is 1 hour; if the specific time is within 1-2 hours, the re-reaction time is 1 hour.

6. The method for preparing a hydrogenated MT methyl silicone resin with a narrow molecular weight distribution according to claim 1, characterized in that: At S4, the vacuum degree is 95-100 kPa, and lasts for a certain time of 0.5-1 h.

7. The method for preparing a hydrogenated MT methyl silicone resin with a narrow molecular weight distribution according to claim 1, characterized in that: Wash 4-8 times in S5.

8. The method for preparing a hydrogenated MT methyl silicone resin with a narrow molecular weight distribution according to claim 1, characterized in that: At S6, the temperature is 90-130°C, the vacuum degree is 100-101.325 kPa, and the distillation time is specifically 1-3 hours.