Octamethylsilsesquioxane and a method for producing the same

Abstract

The present invention relates to a method for preparing octamethyltetrasiloxane from CH3Si(OR)3, wherein R is selected from C 1‑6 alkyl, preferably methyl triethoxysilane as raw material (or called precursor), in a mixed solvent containing oxygen heterocyclic compound and water, with organic amine as catalyst. The method has a yield of >60%, product purity ≥99%, and the raw material is easy to obtain, simple operation, can avoid the generation of a large amount of waste solvent and waste water, friendly to the environment, suitable for large-scale industrialization.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis, and particularly relates to the synthesis of octamethylsilsesquioxane. Background Technology

[0002] Silsesquioxanes (POSS, polyhedral oligomeric silsesquioxanes, also known as cage-like polysilsesquioxanes) are organic-inorganic hybrid materials with a Si-O-Si core and an outer layer of organic groups. The inorganic core imparts excellent thermal stability to the hybrid material, while the organic groups can improve the compatibility between the inorganic core and the polymer and impart good mechanical properties through both physical interactions and chemical bonding. Octamethylsilsesquioxane is the smallest stable silsesquioxane, with the structural formula shown below. R stands for methyl, which, due to its simple structure, has long been used as a model material for studying silsesquioxane compounds. In addition, it is also used as an additive, added to other polymer materials by chemical bonding or material blending to improve the material's hardness, modulus, temperature resistance, and flame retardancy.

[0003] Patent applications CN113354817A, "A method for preparing double-cage POSS using a solvothermal method," and CN113234225A, "A simple and efficient method for preparing T8-POSS," disclose methods for preparing POSS. However, both patent applications use a solvothermal method, which requires a closed system, such as an autoclave, and the reaction temperature is generally above 100°C, placing high demands on the equipment. Furthermore, this method is only suitable for preparing octoploids with relatively large side groups, such as phenyl, as can be seen from the examples in the aforementioned patent applications (all octoploids of phenyl). If the above method is used to produce methyl-based silsesquioxanes, the high pressure and high temperature environment will generate polyploids such as decaploids or dodecloids, making it difficult to obtain high-purity octoploids.

[0004] The most common method for preparing octamethylsilsesquioxane is the sol-gel method (existing technology 3 mentioned below), which involves the hydrolysis and condensation of methyltrialkoxysilane under acidic or alkaline conditions to obtain octamethylsilsesquioxane. This preparation method has problems such as long reaction time (>24h), low yield (<30%), many side reactions, and low product purity.

[0005] Another method is to use cyclosiloxanes containing hydrogen or alkoxy groups as raw materials to prepare octamethylsilsesquioxanes through dehydrogenation condensation (previous technologies 1 and 2 mentioned below). Although this method can improve the yield and product purity, the starting materials are expensive, the product preparation cost is high, and the reaction process generates a large amount of hydrogen, which is extremely dangerous. The equipment requirements and process control are extremely strict, making it difficult to scale up production.

[0006] Existing technology 1: CN106279695B, using tetramethyltetrahydrocyclotetrasiloxane as raw material, firstly, in a buffer system, Pd / C is used to catalyze the generation of hydroxyl-containing methyl rings, and then, tris(pentafluorophenylboron) is used as a catalyst to dehydrogenate and condense the hydroxyl-containing methyl rings with tetramethyltetrahydrocyclotetrasiloxane to generate octamethylsilsesquioxane.

[0007] Prior art 2: Handke B, W, Mozgawa W, Kowalewska A. Journal of Molecular Structure, 2008, 887(1). Kowalewska A, Rózga-Wijas K, Handke Me-Polymers, 2013, 8(1). Using alkoxycyclosiloxane as a precursor and tetrabutylammonium fluoride as a catalyst, dehydrogenation condensation was performed to generate octamethylsilsesquioxane.

[0008] Existing technology 3: Luo, Q., Tang, D., Li, X., Wang, Q., Wang, Z., Zhen, Z., and Liu, X. "Preparation of Polysilsesquioxane (CH3SiO)" 1.5 )8 Crystals from Swollen PHEMA. The Chemical Society of Japan, 2006, 35(3). Using methanol as solvent and hydrochloric acid or ammonia as catalyst, methyltriethoxysilane is pre-coated in poly(hydroxyethyl methacrylate). Then, methanol is added as solvent and hydrochloric acid or ammonia as catalyst. Poly(hydroxyethyl methacrylate) swells in methanol and slowly releases methyltriethoxysilane. Under the action of hydrochloric acid or ammonia, octamethylsilsesquioxane is slowly generated. Technical advantages: The process is mild and controllable. Disadvantages: Poly(hydroxyethyl methacrylate) is difficult to remove, affecting the purity of the product.

[0009] Other relevant literature concerning the preparation method of octamethylsilsesquioxane includes:

[0010] Rebrov EA,Tebeneva NA,Muzafarov AM,Ovchinnikov YE,Struchkov YT,Strelkova T V.ChemInform,1995,26(50);

[0011] Martynova TN, Korchkov V P. Journal of Organometallic Chemistry, 1983, 248(3): 241-249;

[0012] Iwamura T, Adachi K, Chujo Y. The Chemical Society of Japan, 2010, 39(4);

[0013] Scott DJAm.Chem.Soc.,1946,68;

[0014] Barry AJ, Daudt WH, Domicone JJ, Gilkey J W. Journal of the American Chemical Society, 1955, 77(16): 4248-4252.

[0015] These technologies primarily obtain octamethylsilsesquioxane by cleaving polymers of silsesquioxanes, while also generating multiple structural compounds. They are only suitable for laboratory research and not for large-scale production. Summary of the Invention

[0016] This invention provides a method for preparing octamethylsilsesquioxane, using CH3Si(OR)3, wherein R is selected from C. 1-6 Alkyl groups, as raw materials (or precursors), are used to prepare the product in a mixed solvent containing oxygen-containing heterocyclic compounds and water, with an organic amine as a catalyst.

[0017] Preferably, R is C 1-3 Alkyl group. In one embodiment of the invention, R is ethyl, i.e., methyltriethoxysilane is used as a precursor.

[0018] The molar ratio of water to precursor is 2-40:1, preferably 4-20:1, such as 4.5:1, 5:1, 5.5:1, 6:1, 7:1, 8:1, 8.5:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 16.5:1, 17:1, 17.5:1, 18:1, 18.5:1, 19:1, 19.5:1, etc. The water is preferably distilled water, deionized water, or tap water.

[0019] The molar ratio of the oxygen-containing heterocyclic compound to the precursor is 2-40:1, preferably 7-16:1, such as 7.5:1, 8:1, 8.5:1, 9:1, 10:1, 10.5:1, 11:1, 11.5:1, 12:1, 12.5:1, 13:1, 13.5:1, 14:1, 14.5:1, 15:1, 15.5:1, etc.

[0020] The oxygen-containing heterocyclic compound is a heterocyclic compound with three or more ring atoms containing one or more oxygen ring atoms. It can be a saturated or unsaturated ring structure, a monocyclic, bicyclic, or polycyclic structure, and a bridged or spirocyclic structure. Preferably, the oxygen-containing heterocyclic compound is selected from: tetrahydrofuran, tetrahydropyran, 3,4-dihydro-2H-pyran; propylene oxide, butane oxide, 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, 2,5-dimethyl-1,4-diane, 4,4-dimethyl-1,3-diane, paraformaldehyde, or one, two, or a mixture of crown ether compounds.

[0021] The amount of organic amine catalyst used is 0.05-3% of the amount of precursor, preferably 0.1%-1%, for example 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, etc., calculated as a percentage by mass.

[0022] The organic amine catalyst is selected from triethylamine, trimethylamine, diethylamine, dimethylamine, tetramethylethylenediamine, tetramethylpropylenediamine, triethanolamine, triethylenediamine, etc. Organic amine catalysts can promote intramolecular condensation, which is beneficial to the formation of octamethylsilsesquioxane.

[0023] The preparation method is preferably carried out under normal pressure.

[0024] The reaction temperature of the preparation method is 27-55℃, preferably 29-40℃, such as 30℃, 31℃, 32℃, 33℃, 34℃, 35℃, 36℃, 37℃, 38℃, 39℃, etc.

[0025] In one embodiment of the invention, the reaction is carried out under stirring at a speed of 10-2000 rpm, preferably 40-200 rpm, such as 45 rpm, 49 rpm, 50 rpm, 51 rpm, 55 rpm, 60 rpm, 65 rpm, 70 rpm, 75 rpm, 80 rpm, 85 rpm, 90 rpm, 95 rpm, 100 rpm, 110 rpm, 120 rpm, 130 rpm, 140 rpm, 150 rpm, 160 rpm, 170 rpm, 180 rpm, 190 rpm, etc.

[0026] In one embodiment of the present invention, the reaction time is 4-24 hours, preferably 8-20 hours.

[0027] The product obtained by the method has a purity of ≥99%.

[0028] Furthermore, the method specifically includes:

[0029] S1: The precursor CH3Si(OR)3, where R is selected from C 1-6 Alkyl (preferably C) 1-3 Alkyl groups (e.g., ethyl groups) are added to a mixed solvent containing water and oxygen-containing heterocyclic compounds and mixed thoroughly.

[0030] S2: Add an organic amine catalyst and control the reaction temperature to 27-55℃, preferably 29-40℃, such as 30℃, 31℃, 32℃, 33℃, 34℃, 35℃, 36℃, 37℃, 38℃, 39℃, etc.; stir the reaction for 4-24 hours until the reaction system becomes a suspension.

[0031] S3: The solid product obtained by separation is octamethylsilsesquioxane.

[0032] in,

[0033] In step S1, the molar ratio of the amount of the oxygen-containing heterocyclic compound to the amount of the precursor is 2-40:1, preferably 7-16:1; the molar ratio of the amount of water to the amount of the precursor is 2-40:1, preferably 4-20:1.

[0034] In step S2, the stirring speed is controlled at 10-2000 rpm, preferably 40-200 rpm, such as 45 rpm, 49 rpm, 50 rpm, 51 rpm, 55 rpm, 60 rpm, 65 rpm, 70 rpm, 75 rpm, 80 rpm, 85 rpm, 90 rpm, 95 rpm, 100 rpm, 110 rpm, 120 rpm, 130 rpm, 140 rpm, 150 rpm, 160 rpm, 170 rpm, 180 rpm, 190 rpm, etc.; the reaction time is 4-24 hours, preferably 8-20 hours. The amount of organic amine catalyst used is 0.05-3% of the precursor amount, preferably 0.1%-1%, calculated as a mass percentage.

[0035] In step S3, the separation can be carried out in a conventional manner, such as a conventional solid-liquid separation method. In one embodiment of the present invention, it is carried out by spray drying, and the solvent is recovered.

[0036] During the hydrolysis and condensation process, CH3Si(OR)3 produces not only eight-ploid compounds but also a variety of other products, including some oligomers (tetraploids, hexaploids, etc.), polymers (decploids, dodecploids, etc.), and semi-cage compounds, see structural formula 1.

[0037]

[0038] To improve the yield of octoploids, this invention uses a heterocyclic compound containing oxygen atoms as a solvent, taking advantage of its solvation effect and ability to form hydrogen bonds to efficiently induce the formation of the intermediate methyl hydroxy four-membered ring, thereby generating octoploids (reaction equation 1).

[0039]

[0040] Furthermore, temperature control is also a key factor in this invention. During the hydrolysis and condensation process of CH3Si(OR)3, if the temperature is too low, more oligomers are generated, mainly triploid intermediates, with the final product being predominantly hexaploid; if the temperature is too high, polyploid intermediates such as pentaploid and hexaploid are generated, and the final product is a decaploid, dodecaploid, and other structures with higher degrees of polymerization. The temperature control of this invention between 27-55℃ is conducive to the generation of tetraploid intermediates, thereby increasing the yield of octoploids.

[0041] Furthermore, the spray drying method of this invention separates the product and can recover the solvent. Compared with the traditional ethanol washing method, it reduces equipment investment, simplifies the post-processing process, and avoids the generation of a large amount of waste solvent and wastewater.

[0042] Beneficial effects:

[0043] 1. This invention provides a novel method for synthesizing octamethylsilsesquioxane.

[0044] 2. The raw materials for this process are readily available, the operation is simple, and it is suitable for large-scale industrialization. The yield is >60%, the purity is ≥99%, and the obtained products are suitable for radiation-sensitive materials for vacuum submicron lithography. They can also be used as starting products for the synthesis of high molecular weight poly(organosilsesquioxanes).

[0045] 3. This production process avoids generating large amounts of waste solvents and wastewater, making it environmentally friendly. Attached Figure Description

[0046] Figure 1 SEM photos of the product in Example 1;

[0047] Figure 2 XRD pattern of the product in Example 1;

[0048] Figure 3 Example 1 Product 29 Si NMR spectrum. Detailed Implementation

[0049] The following testing methods were used in the examples:

[0050] SEM testing: Hitach SU-70 field emission scanning electron microscope. A small amount of sample was coated onto conductive tape, and the sample surface was purged with low-pressure gas to make the sample coating on the tape thin and uniform. Gold sputtering was then performed, and the morphology was observed on the SEM. The working distance was 8-15 mm, and the accelerating voltage was 5 kV.

[0051] XRD testing: Shimadzu X-ray powder diffractometer, XRD-6000. Test conditions were: CuKα radiation tube voltage 40kV, tube current 40mA, scan step size 0.02°, and scan rate 6° / min.

[0052] 29 Si NMR: JEOL NMR-A400. Resonant frequency: 79.30MHz, pulse width: 5.00ms, relaxation time: 15s.

[0053] GC-MS: Agilent GC-MS 7000D. The powder sample was heated to 250°C in the headspace and held for 30 minutes before GC-MS testing.

[0054] Example 1

[0055] (1) Under nitrogen protection, add 100 kg of tetrahydrofuran (about 1386 mol) and 15 kg of deionized water (about 833 mol) to the reactor and stir until homogeneous;

[0056] (2) Add 30 kg of methyltriethoxysilane (about 168 mol) to the reactor, stir evenly, and control the temperature inside the reactor at 30°C;

[0057] (3) Control the stirring speed to 50 rpm, add 200 g of triethylamine (about 1.97 mol) into the reaction vessel at a uniform speed over about 30 min, and continue stirring for 10 h. The system is a milky white suspension.

[0058] (4) The above suspension was passed through a spray drying device with nitrogen protection and an organic solvent recovery system to obtain about 11 kg of white loose solid powder, with a yield of 67.4%.

[0059] (5) The obtained product was subjected to SEM, XRD, 29 Si NMR and GC-MS tests. Figure 1 SEM is used for preliminary morphological determination; octoploids are generally cubic blocks. Figure 2 The XRD pattern of the sample is the same as that of the standard octoploid. 29Si NMR characterization showed that the product only had a T structure (MeSiO). 1.5 The results of the three spectral analyses indicate that the product is a structurally regular octamethylsilsesquioxane with a purity of 99.5%.

[0060] Example 2

[0061] (1) Under nitrogen protection, 150 kg of dioxolane (about 2024 mol) and 22 kg of deionized water (about 1222 mol) were added to the reactor and stirred until homogeneous;

[0062] (2) Add 25 kg of methyltriethoxysilane (about 140 mol) to the reactor, stir evenly, and control the temperature inside the reactor at 30°C;

[0063] (3) Control the stirring speed to 50 rpm, add 100 g of triethanolamine (about 0.67 mol) into the reaction vessel at a uniform speed over about 30 min, and continue stirring for 16 h. The system is a milky white suspension.

[0064] (4) The above suspension was passed through a spray drying device with nitrogen protection and an organic solvent recovery system to obtain about 10 kg of white loose solid powder, with a yield of 73.5%.

[0065] (5) The obtained product was subjected to SEM, XRD, 29 Si NMR and GC-MS analysis confirmed that it is a structurally regular octamethylsilsesquioxane with a purity of 99.7%.

[0066] Example 3

[0067] (1) Under nitrogen protection, add 120 kg of paraformaldehyde (about 1332 mol) and 35 kg of deionized water (about 1944 mol) to the reactor and stir until homogeneous;

[0068] (2) Add 20 kg of methyltriethoxysilane (about 112 mol) to the reactor, stir evenly, and control the temperature inside the reactor at 30°C;

[0069] (3) Control the stirring speed to 50 rpm, add 50 g of triethylenediamine (about 0.48 mol) into the reaction vessel at a uniform speed over about 30 min, and continue stirring for 16 h. The system is a milky white suspension.

[0070] (4) The above suspension was passed through a spray drying device with nitrogen protection and an organic solvent recovery system to obtain about 7 kg of white loose solid powder, with a yield of 64.3%.

[0071] (5) The obtained product was subjected to SEM, XRD, 29Si NMR and GC-MS analysis confirmed that it is a structurally regular octamethylsilsesquioxane with a purity of 99.2%.

[0072] Comparative Example 1:

[0073] (1) Under nitrogen protection, add 80 kg of tetrahydrofuran and 20 kg of deionized water to the reactor and stir until homogeneous;

[0074] (2) Add 28 kg of methyltriethoxysilane to the reactor, stir until homogeneous, and control the temperature inside the reactor at 25°C;

[0075] (3) Control the stirring speed to 50 rpm, add 150 g of triethylamine to the reaction vessel at a uniform speed over about 30 min, and continue stirring for 20 h. The system is a milky yellow suspension.

[0076] (4) The above suspension was passed through a spray drying device with nitrogen protection and an organic solvent recovery system to obtain about 2 kg of yellow gel-like solid. Octamethylsilsesquioxane could not be obtained.

[0077] Comparative Example 2:

[0078] (1) Under nitrogen protection, add 100 kg of tetrahydrofuran and 15 kg of deionized water to the reactor and stir until homogeneous;

[0079] (2) Add 30 kg of methyltriethoxysilane to the reactor, stir evenly, and control the temperature inside the reactor at 60°C;

[0080] (3) Control the stirring speed to 50 rpm, add 200 g of triethylamine into the reactor at a uniform speed over about 30 min, and continue stirring for 15 h. The system is a milky white suspension.

[0081] (4) The above suspension was passed through a spray drying device with nitrogen protection and an organic solvent recovery system to obtain about 14 kg of white loose solid powder. The sublimation test showed that about 3 kg of octamethylsilsesquioxane (yield 18.3%) was present, and the remainder was polymers with a degree of polymerization of 10 or above.

[0082] The above embodiments are a further detailed description of the technical solutions of the present invention. The mentioned embodiments are only a part of the present invention and not all of the present invention. They should not be construed as limiting the present invention or its application or use.

Claims

1. A method for preparing octamethylsilsesquioxane, characterized in that, The product was prepared using CH3Si(OR)3 as a precursor in a mixed solvent containing oxygen-containing heterocyclic compounds and water, with an organic amine as a catalyst. Where R is C 1-6 alkyl; The oxygen-containing heterocyclic compound is a heterocyclic compound with three or more ring atoms containing one or more oxygen ring atoms; The organic amine is selected from triethylamine, trimethylamine, diethylamine, dimethylamine, tetramethylethylenediamine, tetramethylpropylenediamine, triethanolamine, and triethylenediamine; The molar ratio of water to precursor is 2-40:1; the molar ratio of oxygen-containing heterocyclic compound to precursor is 2-40:1; the amount of organic amine is 0.05-3% of the amount of precursor, calculated as a mass percentage. The reaction temperature of the method is 27-55℃.

2. The method as described in claim 1, characterized in that, R is C 1-3 alkyl.

3. The method as described in claim 1, characterized in that, The molar ratio of water to precursor is 4-20:

1.

4. The method as described in claim 1, characterized in that, The molar ratio of the amount of oxygen-containing heterocyclic compound to the amount of precursor is 7-16:

1.

5. The method as described in claim 1, characterized in that, The amount of organic amine used is 0.1%-1% of the amount of precursor used, calculated as a percentage by mass.

6. The method according to any one of claims 1-5, characterized in that, The oxygen-containing heterocyclic compound is selected from: tetrahydrofuran, tetrahydropyran, 3,4-dihydro-2H-pyran; propylene oxide, butane oxide, 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, 2,5-dimethyl-1,4-dioxane, 4,4-dimethyl-1,3-dioxane, trioxymethylene, or one, two, or a mixture of crown ether compounds.

7. The method according to any one of claims 1-5, characterized in that, The reaction temperature of the method is 29-40℃.

8. The method according to any one of claims 1-5, characterized in that, The method is performed under normal pressure.

9. The method according to any one of claims 1-5, characterized in that, The reaction was carried out under stirring at a speed of 10-2000 rpm for 4-24 hours.

10. The method as described in claim 9, characterized in that, The stirring speed is 40-200 rpm.

11. The method as described in claim 9, characterized in that, The reaction time is 8-20 hours.

12. The method as described in claim 1, characterized in that, Includes the following steps: S1: Add the precursor CH3Si(OR)3 to a mixed solvent containing water and oxygen-containing heterocyclic compounds, and mix thoroughly. S2: Add organic amine, control the reaction temperature at 27-55℃, stir the reaction for 4-24 hours, and the reaction system becomes a suspension. S3: The solid product obtained by separation is octamethylsilsesquioxane.

13. The method as described in claim 12, characterized in that, The reaction temperature is 29-40℃.

14. The method as described in claim 12, characterized in that, In step S1, the molar ratio of the amount of the oxygen-containing heterocyclic compound to the amount of the precursor is 7-16:1; the molar ratio of the amount of water to the amount of the precursor is 4-20:1; and the amount of organic amine is 0.1%-1% of the amount of the precursor, calculated as a mass percentage.

15. The method as described in claim 12, characterized in that, In step S2, the stirring speed is controlled between 10-2000 rpm.

16. The method as described in claim 15, characterized in that, Control the stirring speed between 40-200 rpm.

17. The method as described in claim 12, characterized in that, In step S3, the separation is carried out by spray drying, and the solvent is recovered.

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