Preparation method of low-viscosity hydroxyl-terminated phenyl silicone oil

Abstract

The invention belongs to the technical field of organic silicon, and relates to a preparation method of low-viscosity hydroxyl-terminated phenyl silicone oil, which comprises the following steps: (S1) adding diphenyl silanediol, organic anhydride and an acid catalyst into an aprotic polar organic solvent for acylation reaction to obtain an acylated product; (S2) dropwise adding the acylation product into an alkaline aqueous solution in a stirring state until the system is neutral, then carrying out hydrolytic polycondensation, and separating out an upper oil phase after the reaction is ended, so as to obtain a phenyl-containing prepolymer; and (S3) mixing the phenyl-containing prepolymer, cyclosiloxane and an alkali metal catalyst, carrying out a ring-opening copolymerization reaction in an inert atmosphere, and purifying after the reaction is finished to obtain the low-viscosity hydroxyl-terminated phenyl silicone oil. The prepared hydroxyl-terminated phenyl silicone oil is low in viscosity, the viscosity is 200-1000 mPa.s at the temperature of 25 DEG C, the phenyl content is adjustable, no methoxy group exists, meanwhile, the preparation cost is low, and the preparation process is environmentally friendly.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic silicon, and in particular relates to a method for preparing low-viscosity hydroxyl-terminated phenyl silicone oil. Background Art

[0002] Introducing phenyl groups into the polymethylsiloxane chain can significantly improve its temperature resistance and compatibility with organic resins, broadening its application in the preparation of various products using it as a raw material, such as the preparation of radiation-resistant room temperature vulcanized silicone rubber and high temperature vulcanized silicone rubber. The preparation of polysiloxanes containing phenyl groups on the chain terminated with different active groups, such as vinyl or epoxy groups, can be obtained by "chain extension" using low-viscosity hydroxyl-terminated phenyl silicone oil as a raw material. Low-viscosity hydroxyl-terminated phenyl silicone oil has a high hydroxyl content and strong reactivity with resins. Therefore, low-viscosity hydroxyl-terminated phenyl silicone oil has a high market value, and its preparation method has become one of the technologies that the silicone industry is competing to develop. However, the following problems still exist in the preparation of low-viscosity hydroxy-terminated phenyl silicone oil in the existing technology: 1) The degree of polymerization of the prepared low-viscosity hydroxy-terminated phenyl silicone oil is still relatively high and difficult to control, that is, the viscosity needs to be further reduced; 2) The phenyl content in the product prepared from the low-viscosity hydroxy-terminated phenyl silicone oil is difficult to control; 3) The methoxy content in the low-viscosity hydroxy-terminated phenyl silicone oil product is relatively high, which affects the subsequent application of the product; 4) The prepared low-viscosity hydroxy-terminated phenyl silicone oil product contains a ring mixture, which is difficult to remove from the system; 5) The cost of the phenyl ring raw materials is high, the preparation process is complicated, and environmentally unfriendly reagents will be used.

[0003] Luo Mengxian et al. (Organic Silicone Materials, 2008, 22(6):335-338) used methylphenylcyclosiloxane as a raw material and reacted it with low-molar-mass hydroxy silicone oil in the presence of an alkaline catalyst to prepare hydroxyl-terminated polymethylphenylsiloxane through a balanced copolymerization reaction. However, the process used phenyl rings, which are relatively expensive, as a raw material, and the resulting hydroxyl-terminated polymethylphenylsiloxane product was not easily controlled within a low viscosity range.

[0004] CN103524740B discloses a method for preparing a methylphenylhydroxy silicone oil with a low tetracyclic ring content. The method uses 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane as a raw material, reacts with water as a capping agent in the presence of a basic catalyst in an organic solvent, and produces the methylphenylhydroxy silicone oil with a low tetracyclic ring content. The product has a low tetracyclic ring content, but the process uses phenyl rings, which are relatively expensive, as raw materials.

[0005] Zhang Liping et al. (Organic Silicone Materials, 2014, 2 8(3):145-148) used methylphenyldimethoxysilane as raw material and prepared terminal hydroxyl polymethylphenylsiloxane oligomers by hydrolysis and polycondensation under acidic catalysis. Although the viscosity was low, the methoxy content in the product was high.

[0006] CN103087320B discloses a method for preparing hydroxyl-terminated polymethylphenyl silicone oil. The method involves hydrolyzing and co-condensing methylphenyldichlorosilane (or diphenyldichlorosilane) and dimethyldichlorosilane to produce a phenyl-linked silane hydrolyzate. This product is then acylated with acetic anhydride in the presence of an acidic catalyst and then hydrolyzed to produce hydroxyl-terminated polymethylphenyl silicone oil. The resulting hydroxyl-terminated polymethylphenyl silicone oil still has a high viscosity, a high methoxy content, and difficulty controlling the phenyl content.

[0007] CN104292464B discloses a method for preparing phenylhydroxy silicone oil. The method first involves reacting diphenylsilanediol and octamethylcyclotetrasiloxane in toluene / isopropanol under alkaline catalyst conditions to obtain a semi-finished product, which is then end-capped with a short-chain silanol silicone oil. Finally, an organosilicon phosphate is added to neutralize the catalyst, the solvent is distilled off, and low molecules are removed to obtain phenylhydroxy silicone oil. This method is carried out under alkaline system catalysis, and the viscosity of the phenylhydroxy silicone oil obtained is relatively high. In addition, diphenylsilanediol and octamethylcyclotetrasiloxane are added simultaneously, i.e., a "one-pot" reaction. Due to the large steric hindrance of diphenylsilanediol, it is difficult to evenly condense into the molecular chain. In addition, the method uses a large amount of toluene, a toxic solvent, and has many process steps. Summary of the Invention

[0008] In view of the problems existing in the above-mentioned prior art, it is necessary to develop a method for preparing low-viscosity hydroxyl-terminated phenyl silicone oil, in which the phenyl content in the obtained hydroxyl-terminated phenyl silicone oil product is adjustable, the methoxy content is low, the preparation cost is low, and the preparation process is environmentally friendly.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] A method for preparing a low-viscosity hydroxyl-terminated phenyl silicone oil comprises the following steps:

[0011] (S1) adding diphenylsilanediol, an organic acid anhydride, and an acidic catalyst into an aprotic polar organic solvent to carry out an acylation reaction to obtain an acylated product;

[0012] (S2) adding the acylated product dropwise to an alkaline aqueous solution under stirring until the system becomes neutral, and then hydrolyzing and polycondensing the product. After the reaction is complete, the upper oil phase is separated to obtain a phenyl-containing prepolymer;

[0013] (S3) mixing a phenyl-containing prepolymer, a cyclosiloxane, and an alkali metal catalyst, and performing a ring-opening copolymerization reaction under an inert atmosphere. After the reaction is completed, the low-viscosity hydroxyl-terminated phenyl silicone oil is obtained through purification.

[0014] Taking acetic anhydride as the organic acid anhydride, strong acidic ion exchange resin as the acidic catalyst, and octamethylcyclotetrasiloxane (D4) as the cyclosiloxane as an example, the reaction equation is as follows:

[0015]

[0016] The present invention first reacts diphenylsilanediol with an organic acid anhydride in a homogeneous system under an acidic catalyst to produce an oily acylated product. The oily acylated product is then hydrolyzed and polycondensed in a heterogeneous system to produce a phenyl-containing prepolymer with a low degree of polymerization. The phenyl-containing prepolymer with a low degree of polymerization is then ring-opening copolymerized with a cyclosiloxane to produce a low-viscosity hydroxyl-terminated silicone oil. Because the hydrolysis and polycondensation of the oily acylated product is carried out in a heterogeneous system, the reaction is relatively mild and easy to control. At the same time, the two phenyl groups attached to the silicon atom have a certain inhibitory effect on the polycondensation reaction, resulting in a low degree of polymerization of the phenyl-containing prepolymer. The hydroxyl-terminated silicone oil produced by the ring-opening copolymerization of the phenyl-containing prepolymer with a low degree of polymerization and the cyclosiloxane has a low viscosity. That is, the process of the present invention of first performing the acylation reaction and then performing the heterogeneous hydrolysis and condensation is very critical to ensure that a phenyl-containing prepolymer with a low degree of polymerization is first obtained, and then the phenyl-containing prepolymer with a low degree of polymerization is ring-opening copolymerized with a cyclosiloxane, rather than using a "one-pot method" to perform ring-opening copolymerization of a diphenylsilane diol monomer and a cyclosiloxane.

[0017] At the same time, in step (S3), the present invention can prepare hydroxyl-terminated phenyl silicone oils with different phenyl content by adjusting the ratio of the phenyl-containing prepolymer to the cyclosiloxane. In addition, the present invention uses diphenylsilanediol and organic acid anhydride as raw materials. On the one hand, the prepared product does not contain methoxy groups; on the other hand, compared with using phenyl ring bodies as raw materials, the raw material cost of the present invention is lower.

[0018] The low-viscosity hydroxyl-terminated phenyl silicone oil of the present invention has a viscosity of 200 to 1000 mPa·s at 25° C.

[0019] Furthermore, in step (S1), the molar ratio of diphenylsilanediol to organic acid anhydride is 1:(2.1-2.5), preferably 1:(2.2-2.5); the amount of the acidic catalyst is 1-5 wt% of the sum of the mass of diphenylsilanediol and acid anhydride.

[0020] Furthermore, in step (S1), the organic acid anhydride is selected from at least one of acetic anhydride, propionic anhydride, and butyric anhydride; the acidic catalyst is at least one of a strong acidic ion exchange resin, p-toluenesulfonic acid, camphorsulfonic acid, and trifluoromethanesulfonic acid, preferably a strong acidic ion exchange resin, which is removed by filtration after the reaction is completed; and the aprotic polar organic solvent is selected from at least one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), and dimethyl sulfoxide (DMSO).

[0021] Furthermore, in step (S1), the acylation reaction is carried out under the following conditions: stirring at 75-100° C. under normal pressure for 4-10 hours.

[0022] Furthermore, in step (S2), the alkaline aqueous solution is at least one of KOH aqueous solution, NaOH aqueous solution, Na2CO3 aqueous solution, NaHCO3 aqueous solution, K2CO3 aqueous solution, and KHCO3 aqueous solution, and its concentration is 2 to 20 wt%.

[0023] Furthermore, in step (S2), the conditions for the hydrolysis and polycondensation are: temperature 40-70°C, preferably 50-60°C, and time 2-10h, preferably 3-5h.

[0024] In step (S2), the viscosity of the phenyl-containing prepolymer at 25° C. is 50 to 100 mPa·s.

[0025] Furthermore, in step (S3), the cyclosiloxane is hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4), or decamethylcyclotetrasiloxane (D5), preferably octamethylcyclotetrasiloxane (D4). D3, D4, and D5 differ in ring tension, stability, and compatibility with phenyl-containing prepolymers, resulting in different levels of controllability and the production of cyclic oligomer byproducts during ring-opening copolymerization. D4 has moderate ring tension, strong controllability, and fewer byproducts, making it more suitable for industrial production.

[0026] In step (S3), the mass ratio of the phenyl-containing prepolymer to the cyclosiloxane is 1:(1-8), and the mass ratio of the two can be specifically adjusted according to the requirement of the phenyl content in the final product.

[0027] Furthermore, in step (S3), the amount of the alkali metal catalyst is 10 to 100 ppm based on the total mass of the phenyl-containing prepolymer and the cyclosiloxane; the alkali metal catalyst is one of an alkali metal hydroxide, an alkali metal alkoxide, an alkali metal silicon alkoxide, a quaternary ammonia base, and a quaternary phosphonium base.

[0028] Furthermore, in step (S3), a co-catalyst is added. The co-catalyst is a supramolecular compound containing a macrocyclic cavity, selected from at least one of crown ethers, cryptands, β-cyclodextrin, and calixarene, preferably a crown ether and / or a cryptand. The amount of the co-catalyst is 1 to 10 ppm, preferably 5 to 10 ppm. The inventors have discovered that the combination of an alkali metal catalyst and a co-catalyst can provide a more stable and efficient catalytic effect. The possible reason is that when the co-catalyst is a crown ether or a cryptand, the crown ether or cryptand containing a large ring cavity coordinates with the alkali metal ion through the lone pair electrons of the oxygen atom to form an electrically neutral outer coordination complex. Due to the apparent charge dispersion and hydrophobic effect, the complex can be evenly dispersed in a non-polar solvent system, so that it can play a catalytic role more stably and efficiently; when the co-catalyst is β-cyclodextrin or calixarene, its hydrophobic cavity can encapsulate the hydrophobic part of the polymer chain (such as phenyl), reducing steric hindrance and facilitating copolymerization. At the same time, the inclusion effect forces the chain segment where the phenyl group is located to remain extended, reducing the intramolecular cyclization caused by chain folding, and making the product a highly linear polymer, which is beneficial to achieving low viscosity. Crown ethers are exemplified by 15-crown-5 or 18-crown-6, and cryptands are exemplified by cryptand [2.2.1] or cryptand [2.2.2]. The reason why crown ethers or cryptands are superior to β-cyclodextrin and calixarene may be that crown ethers or cryptands have unique metal ion coordination ability and hydrophobic effect, which can catalyze ring-opening copolymerization reactions more efficiently and stably, while the effects of β-cyclodextrin and calixarene are more limited to the regulation of steric hindrance, and their contribution to catalytic activity and inhibition of side reactions is limited.

[0029] Furthermore, in step (S3), the inert atmosphere is nitrogen and / or argon; and the conditions for the ring-opening copolymerization reaction are: stirring the reaction at 100-160° C. for 3-10 hours, preferably stirring the reaction at 120-150° C. for 5-8 hours.

[0030] Furthermore, in step (S3), the purification method is as follows: acid glue is added dropwise to the reaction system and stirred to react until the system is neutral, and then the reaction system is heated to 160-180°C and low-boiling substances are removed under vacuum for 1-2 hours with a vacuum degree of -0.1 MPa to -0.01 MPa. Acid glue and alkali glue are commonly used reagents in the field of organosilicon, wherein acid glue refers to a short-chain siloxane containing an acidic group, which is a protonic acid (H + donor), which is also a siloxane precursor and can participate in the end-capping of the siloxane chain while neutralizing the alkaline catalyst.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The low-viscosity hydroxyl-terminated phenyl silicone oil prepared by the present invention has a low viscosity, the viscosity at 25°C is in the range of 200 to 1000 mPa·s, and the phenyl content is adjustable.

[0033] 2. The low-viscosity hydroxyl-terminated phenyl silicone oil prepared by the present invention does not contain methoxy groups, which is convenient for subsequent applications.

[0034] 3. The raw material price of the present invention is relatively low, and the yield is high, thereby reducing the preparation cost; and the preparation process does not contain toxic reagents, and is suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is the infrared spectrum of the low-viscosity hydroxy-terminated phenyl silicone oil prepared in Example 1. DETAILED DESCRIPTION

[0036] To make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail below. The following examples are convenient for better understanding of the present invention, but are not intended to limit the present invention. The experimental methods in the following examples are all conventional methods unless otherwise specified.

[0037] Example 1

[0038] (S1) 21.6 g (0.1 mol) of diphenylsilanediol, 22.4 g (0.22 mol) of acetic anhydride, and 1.3 g of a strongly acidic ion exchange resin were added to 80 mL of N,N-dimethylformamide (DMF), stirred uniformly to form a mixed solution, and then stirred at 80° C. and 180 rpm for 6 h. After the reaction, the temperature was cooled to room temperature, and the strongly acidic ion exchange resin was removed by filtration to obtain an acylated product;

[0039] (S2) slowly adding the acylated product dropwise to a KOH aqueous solution (concentration 12 wt%) with stirring until the system becomes neutral, then heating to 50° C. for hydrolysis and polycondensation for 2 h. After the reaction is complete, the mixture is allowed to stand and the upper oil phase is separated to obtain a phenyl-containing prepolymer (viscosity at 25° C. measured by a capillary viscometer is 65 mPa·s);

[0040] (S3) 13 g of a phenyl-containing prepolymer, 87 g of octamethylcyclotetrasiloxane, 2.0 mg (i.e., 20 ppm) of KOH, and 0.5 mg (i.e., 5 ppm) of 18-crown ether-6 were mixed, and the mixture was stirred and reacted at 150 ° C. under a nitrogen atmosphere for 8 h; after the reaction, acid glue was added dropwise to the reaction system and stirred to react until the system became neutral, and then the system was heated to 170 ° C., low-boiling substances were removed at -0.08 MPa for 2 h, and then cooled to room temperature to obtain a low-viscosity hydroxy-terminated phenyl silicone oil.

[0041] The viscosity of the low-viscosity hydroxyl-terminated phenyl silicone oil obtained by rotational viscometer test is 205 mPa·s at 25°C.

[0042] The infrared spectrum of the prepared low viscosity hydroxyl-terminated phenyl silicone oil is as follows: Figure 1 shown.

[0043] Example 2

[0044] The rest is the same as Example 1, except that in step (S3), calix[8]arene of equal mass is used to replace 18-crown-6.

[0045] Example 3

[0046] The rest is the same as Example 1, except that: in step (S1), propionic anhydride is used in an equimolar amount to replace acetic anhydride, and the reaction conditions are adjusted accordingly; in step (S3), cryptand [2.2.2] is used to replace 18-crown-6; specifically:

[0047] (S1) 21.6 g (0.1 mol) of diphenylsilanediol, 28.6 g (0.22 mol) of propionic anhydride, and 1.5 g of a strongly acidic ion exchange resin were added to 80 mL of N,N-dimethylformamide (DMF), stirred uniformly to form a mixed solution, and then stirred at 90° C. and 180 rpm for 6 h. After the reaction, the temperature was cooled to room temperature, and the strongly acidic ion exchange resin was removed by filtration to obtain an acylated product;

[0048] (S2) slowly adding the acylated product dropwise to a KOH aqueous solution (concentration 12 wt%) with stirring until the system becomes neutral, then heating to 60° C. for hydrolysis and polycondensation for 2 h. After the reaction is complete, the mixture is allowed to stand and the upper oil phase is separated to obtain a phenyl-containing prepolymer (viscosity at 25° C. measured by a capillary viscometer is 52 mPa·s);

[0049] (S3) 13 g of a phenyl-containing prepolymer, 87 g of octamethylcyclotetrasiloxane, 2.0 mg (i.e., 20 ppm) of KOH, and 0.5 mg (i.e., 5 ppm) of cryptand [2.2.2] were mixed, and the mixture was stirred and reacted at 140° C. for 8 h under a nitrogen atmosphere; after the reaction, acid glue was added dropwise to the reaction system and stirred until the system became neutral, and the system was heated to 170° C., low-boiling substances were removed at -0.08 MPa for 2 h, and the mixture was cooled to room temperature to obtain a low-viscosity hydroxyl-terminated phenyl silicone oil.

[0050] The viscosity of the low-viscosity hydroxyl-terminated phenyl silicone oil obtained by rotational viscometer testing is 247 mPa·s at 25°C.

[0051] Example 4

[0052] The rest is the same as Example 1, except that the hydrolysis and polycondensation conditions in step (S2) are different, specifically:

[0053] (S1) Same as Example 1;

[0054] (S2) slowly adding the acylated product dropwise to a KOH aqueous solution (concentration 12 wt%) with stirring until the system becomes neutral, then heating to 70°C for hydrolysis and polycondensation for 2 h. After the reaction is complete, the mixture is allowed to stand and the upper oil phase is separated to obtain a phenyl-containing prepolymer (viscosity at 25°C measured by a capillary viscometer is 72 mPa·s);

[0055] (S3) Same as Example 1.

[0056] The viscosity of the low-viscosity hydroxyl-terminated phenyl silicone oil obtained by rotational viscometer testing is 320 mPa·s at 25°C.

[0057] Example 5

[0058] The rest is the same as Example 1, except that: the raw material usage ratio in step (S3) is different, that is, the usage of the phenyl-containing prepolymer is increased, specifically:

[0059] (S1) Same as Example 1;

[0060] (S2) Same as Example 1;

[0061] (S3) 24 g of a phenyl-containing prepolymer, 80 g of octamethylcyclotetrasiloxane, 2.1 mg (i.e., 20 ppm) of KOH, and 0.52 mg (i.e., 5 ppm) of 18-crown ether-6 were mixed, and the mixture was stirred and reacted at 150 ° C. under a nitrogen atmosphere for 8 h; after the reaction, acid glue was added dropwise to the reaction system and stirred to react until the system became neutral, and then the system was heated to 170 ° C., low-boiling substances were removed at -0.08 MPa for 2 h, and then cooled to room temperature to obtain a low-viscosity hydroxyl-terminated phenyl silicone oil.

[0062] The viscosity of the low-viscosity hydroxyl-terminated phenyl silicone oil obtained by rotational viscometer testing is 676 mPa·s at 25°C.

[0063] Example 6

[0064] The rest is the same as Example 1, except that: the raw material usage ratio in step (S3) is different, that is, the usage of the phenyl-containing prepolymer is increased, specifically:

[0065] (S1) Same as Example 1;

[0066] (S2) Same as Example 1;

[0067] (S3) 40 g of a phenyl-containing prepolymer, 60 g of octamethylcyclotetrasiloxane, 2.0 mg (i.e., 20 ppm) of KOH, and 0.8 mg (i.e., 8 ppm) of 18-crown ether-6 were mixed, and the mixture was stirred and reacted at 150 ° C. under a nitrogen atmosphere for 8 h; after the reaction, acid glue was added dropwise to the reaction system and stirred to react until the system became neutral, and then the system was heated to 170 ° C., low-boiling substances were removed at -0.08 MPa for 2 h, and then cooled to room temperature to obtain a low-viscosity hydroxyl-terminated phenyl silicone oil.

[0068] The viscosity of the low-viscosity hydroxyl-terminated phenyl silicone oil obtained by rotational viscometer testing is 971 mPa·s at 25°C.

[0069] Example 7

[0070] The rest is the same as Example 1, except that the co-catalyst 18-crown ether-6 is not used in step (S3).

[0071] The viscosity of the low-viscosity hydroxyl-terminated phenyl silicone oil obtained by rotational viscometer test is 420 mPa·s at 25°C.

[0072] Comparative Example 1

[0073] The difference from Example 1 is that steps (S1) and (S2) are omitted, and in step (S3), diphenylsilanediol and cyclosiloxane are directly subjected to a ring-opening copolymerization reaction, that is, a "one-pot process" is adopted, specifically:

[0074] 15 g of diphenylsilanediol, 87 g of octamethylcyclotetrasiloxane, 0.1 g of concentrated sulfuric acid, and 1.22 mg (i.e., 12 ppm) of calix[8]arene were mixed and stirred at 150 ° C for 8 h under a nitrogen atmosphere. After the reaction, alkali glue was added dropwise to the reaction system and stirred until the system became neutral. The system was then heated to 170 ° C, low-boiling substances were removed at -0.08 MPa for 2 h, and the system was cooled to room temperature to obtain hydroxyl-terminated phenyl silicone oil.

[0075] The viscosity of the hydroxyl-terminated phenyl silicone oil obtained by rotational viscometer test at 25°C is 4320 mPa·s.

[0076] Testing and Analysis

[0077] 1) Structural analysis

[0078] Figure 1 This is the infrared spectrum of the low-viscosity hydroxyl-terminated phenyl silicone oil prepared in Example 1. Figure 1 Medium 3076cm -1 and 3051cm -1 The CH stretching vibration peak on the benzene ring is 1593 cm -1 The peaks at 1100 to 1000 cm-1 are attributed to the benzene ring. The intensities of these three peaks indicate the presence of phenyl groups. -1The broad and strong absorption peak in the range of 950cm is attributed to the Si-O-Si asymmetric stretching vibration; -1 Up to 810cm -1 The broad absorption peaks at the sites are attributed to the Si-OH bonds; the above proves that the prepared product is hydroxyl-terminated phenyl silicone oil.

[0079] 2) Viscosity and phenyl content

[0080] Viscosity: The viscosity of the hydroxyl-terminated phenyl silicone oils prepared in the Examples and Comparative Examples was tested using a rotational viscometer at 25°C. The results are shown in Table 1.

[0081] Phenyl content: The phenyl content in the hydroxy-terminated phenyl silicone oils prepared in the examples and comparative examples was measured by nuclear magnetic resonance. That is, the phenyl content was calculated by the integrated area ratio of phenyl ring hydrogen (7.0-7.5 ppm) to silyl methyl hydrogen (0.1-0.5 ppm) in hydrogen nuclear magnetic resonance spectrum (1HNMR). The results are shown in Table 1.

[0082] Table 1 Viscosity and phenyl content test of hydroxyl-terminated phenyl silicone oil

[0083] Group Viscosity (mPa·s) Phenyl content (%) Example 1 205 10.02 Example 2 350 9.80 Example 3 247 9.91 Example 4 320 9.88 Example 5 676 19.98 Example 6 971 39.78 Example 7 420 9.71 Comparative Example 1 4320 7.32

[0084] As can be seen from Table 1, the viscosity of the hydroxyl-terminated phenyl silicone oil obtained in the embodiment of the present invention is relatively low, and the viscosity at a temperature of 25°C is in the range of 200 to 1000 mPa·s. The viscosity of the hydroxyl-terminated phenyl silicone oil obtained in Comparative Example 1 is much higher than that in the embodiment, and when the amount of raw materials is close to that in Example 1, its phenyl content is lower than that in Example 1. By comparing Example 1, Example 4, and Example 5, it can be seen that by adjusting the amount ratio of the phenyl-containing prepolymer to the cyclosiloxane, products with different phenyl contents can be obtained, that is, the phenyl content is easy to regulate. In addition, the present invention uses diphenylsilanediol and organic acid anhydride as raw materials, and the prepared product does not have a methoxy group, and the raw material cost is low and the preparation process is environmentally friendly.

[0085] From the comparison between Example 1 and Example 7, it can be seen that the viscosity of the hydroxyl-terminated phenyl silicone oil prepared without the use of a co-catalyst is higher and the phenyl content is slightly lower, so the use of a co-catalyst is preferred. At the same time, from the comparison between Example 1, Example 2 and Example 3, it can be seen that the co-catalysts 18-crown-6 and cryptand [2.2.2] are superior to calix[8]arene.

Claims

1. A method for preparing a low-viscosity hydroxyl-terminated phenyl silicone oil, characterized in that: The following steps are involved: (S1) adding diphenylsilanediol, an organic acid anhydride, and an acidic catalyst into an aprotic polar organic solvent to carry out an acylation reaction to obtain an acylated product; (S2) adding the acylated product dropwise to an alkaline aqueous solution under stirring until the system becomes neutral, and then hydrolyzing and polycondensing the product. After the reaction is complete, the upper oil phase is separated to obtain a phenyl-containing prepolymer; (S3) mixing a phenyl-containing prepolymer, a cyclosiloxane, and an alkali metal catalyst, and performing a ring-opening copolymerization reaction under an inert atmosphere. After the reaction is completed, the low-viscosity hydroxyl-terminated phenyl silicone oil is obtained through purification.

2. The preparation method according to claim 1, characterized in that The viscosity of the low-viscosity hydroxyl-terminated phenyl silicone oil at 25° C. is 200 to 1000 mPa·s.

3. The preparation method according to claim 1, characterized in that In step (S1), the molar ratio of diphenylsilanediol to organic acid anhydride is 1:(2.1-2.5), preferably 1:(2.2-2.5); the amount of the acidic catalyst is 1-5 wt% of the sum of the mass of diphenylsilanediol and acid anhydride.

4. The preparation method according to claim 1, characterized in that In step (S1), the organic acid anhydride is selected from at least one of acetic anhydride, propionic anhydride, and butyric anhydride; the acidic catalyst is at least one of a strongly acidic ion exchange resin, p-toluenesulfonic acid, camphorsulfonic acid, and trifluoromethanesulfonic acid, preferably a strongly acidic ion exchange resin, which is removed by filtration after the reaction is completed; the aprotic polar organic solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide; and / or The conditions of the acylation reaction are: stirring and reacting at 75-100° C. under normal pressure for 4-10 hours.

5. The preparation method according to claim 1, characterized in that In step (S2), the alkaline aqueous solution is at least one of KOH aqueous solution, NaOH aqueous solution, Na2CO3 aqueous solution, NaHCO3 aqueous solution, K2CO3 aqueous solution, and KHCO3 aqueous solution, and its concentration is 2 to 20 wt%; the conditions for the hydrolysis and condensation are: temperature 40 to 70°C, preferably 50 to 60°C, and time 2 to 10 hours, preferably 3 to 5 hours.

6. The preparation method according to claim 1, characterized in that In step (S3), the cyclosiloxane is hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, or decamethylcyclotetrasiloxane, preferably octamethylcyclotetrasiloxane; and the mass ratio of the phenyl-containing prepolymer to the cyclosiloxane is 1:(1-8).

7. The preparation method according to claim 1, characterized in that In step (S3), the amount of the alkali metal catalyst is 10 to 100 ppm based on the total mass of the phenyl-containing prepolymer and the cyclosiloxane; the alkali metal catalyst is one of an alkali metal hydroxide, an alkali metal alkoxide, an alkali metal silicon alkoxide, a quaternary ammonia base, and a quaternary phosphonium base.

8. The preparation method according to claim 1, characterized in that In step (S3), a co-catalyst is also added, which is a supramolecular compound containing a macrocyclic cavity, selected from at least one of crown ethers, cryptands, β-cyclodextrins, and calixarene, preferably crown ethers and / or cryptands; the amount of the co-catalyst is 1 to 10 ppm, preferably 5 to 10 ppm.

9. The preparation method according to claim 1, characterized in that In step (S3), the inert atmosphere is nitrogen and / or argon; the conditions for the ring-opening copolymerization reaction are: stirring reaction at 100-160°C for 3-10 hours, preferably stirring reaction at 120-150°C for 5-8 hours.

10. The preparation method according to claim 1, characterized in that In step (S3), the purification method is: adding acid gum dropwise to the reaction system and stirring the reaction until the system is neutral, then heating the reaction system to 160-180°C, and removing low-boiling substances in vacuum for 1-2 hours, with a vacuum degree of -0.1 MPa to -0.01 MPa.

Images