Process for the preparation of medium and low viscosity vinyl silicone oils

Abstract

The present application relates to a kind of preparation methods of medium-low viscosity vinyl silicone oil, comprising linear body siloxane raw material is carried out dehydration treatment, then linear body siloxane raw material is reacted with end-capping agent and catalyst under nitrogen atmosphere, and the medium-low viscosity vinyl silicone oil of the present application is obtained.The method of the present application is simple, cost-effective, and the reaction temperature is mild, the volatile fraction of the obtained product is low, the product yield is high, and it is very suitable for a variety of downstream applications.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of silicone oil. More particularly, the present application relates to a method for preparing a medium / low viscosity vinyl silicone oil. BACKGROUND

[0002] Medium / low viscosity vinyl silicone oil refers to a compound containing vinyl groups (CH2=CH-) on the end groups and / or side chain groups of linear polydimethylsiloxane, with a viscosity range of typically 1-10000 mm 2 / s. The preparation of low viscosity vinyl silicone oil is generally more difficult. Vinyl silicone oil can be used as a key raw material for the preparation of various downstream products such as silicone rubber, silicone emulsion and silicone release products, etc. For example, silicone rubber can be vulcanized by reacting vinyl silicone oil with a compound containing SiH bonds to establish a crosslinked network. In addition, medium / low viscosity vinyl silicone oil can also be used as a capping agent for the production of high viscosity vinyl silicone oil, vinyl gum, etc.

[0003] In the prior art, the main methods for preparing medium / low viscosity vinyl silicone oil directly from siloxane intermediate raw materials (siloxane ring body or linear body) are as follows:

[0004] A common process includes using a siloxane ring body as a raw material, first polymerizing the siloxane ring body into a long-chain linear polymer, and then polycondensing it into a target product with a specific molecular weight through an equilibrium reaction. For example, a mixed ring body raw material containing octamethylcyclotetrasiloxane and a capping agent are heated to a polymerization temperature (typical value > 100°C), and in the presence of a catalyst, undergo a polymerization process of chain growth-chain transfer-chain termination, and are kept at the reaction temperature for a period of time to polycondense to the desired viscosity, then a terminating agent is added to terminate the reaction, and then low volatile substances (such as small molecule low boiling substances) are removed by elevated temperature and reduced pressure distillation, thereby obtaining the target product. Various Brønsted acids / bases, Lewis acids / bases can be used as catalysts for the polymerization process.

[0005] However, due to the low molecular weight of medium / low viscosity vinyl silicone oil, a long time is required for the entire polymerization reaction process. In addition, due to the equilibrium reaction, about 10-15% of siloxane ring body is produced, which requires a long time for distillation to remove low volatile substances including siloxane ring body. However, since the medium / low viscosity vinyl silicone oil as a product also has a low boiling point, they are likely to be taken away at the same time as the low volatile substances are removed, thereby reducing the yield and production efficiency. In addition, the medium / low viscosity vinyl silicone oil product still contains a large amount of siloxane ring body, which reduces the purity of the product and is not conducive to downstream applications. In the case of catalyst deactivation and / or neutralization, the product obtained by the above process may also contain part of the residual catalyst, which significantly affects the activity of the product and the stability of subsequent production or terminal application.

[0006] Another common process includes using siloxane linear body as raw material, and obtaining target product through condensation polymerization-rearrangement equilibrium reaction. This process needs to first perform condensation reaction step, and then perform secondary rearrangement equilibrium reaction after the product of condensation process meets the requirement of hydroxyl content. Therefore, this process is a typical two-step process including condensation-rearrangement, and the process condition requirement is high, and the space-time efficiency is limited. At the same time, a large amount of catalyst remains in the system and cannot be removed, which affects the stability of the product.

[0007] CN114058016A discloses a method and device for continuously producing high-viscosity dimethyl silicone oil, which uses dimethylcyclosiloxane mixture (DMC) as siloxane raw material, hexamethyldisiloxane as end-capping agent, and tetramethylammonium hydroxide as catalyst, and realizes continuous production of the product through polymerization kettle-balance kettle-subsection low volatile removal device connected in sequence, and is particularly suitable for producing high-viscosity dimethyl silicone oil.

[0008] CN114349966A discloses a method for preparing high-purity methyl silicone oil by cracking raw material, which uses recovered DMC after cracking and purification as siloxane raw material, hexamethyldisiloxane as end-capping agent, and self-made solid catalyst, and obtains high-purity methyl silicone oil through polymerization-balance process.

[0009] CN114213660A discloses a preparation method of organic silicone oil and a related catalyst, which uses tetraethylammonium hydroxide or tetrapropylammonium hydroxide as catalyst active ingredient. The product obtained after heating decomposition of the catalyst active ingredient has little odor and little irritation, and avoids the odor problem caused by the commonly used catalyst tetramethylammonium hydroxide.

[0010] CN111690138B discloses a production method of low-viscosity hydroxyvinyl silicone oil, which uses methyl and vinyl siloxane ring body as siloxane raw material, and acetic anhydride and acid as catalyst, and can prepare vinyl hydroxy silicone oil with high hydroxyl content and high vinyl content.

[0011] The above several patents represent the conventional polymerization method of silicone oil, that is, using siloxane ring body as siloxane raw material, and producing target product through three steps of ring-opening polymerization-balance-low volatile removal under the presence of catalyst at a specific temperature, but this kind of method has the disadvantages of high siloxane ring content in the product and low reaction yield.

[0012] Moreover, the ring-opening polymerization process using siloxane ring body as raw material is completely different from the condensation polymerization process of the present application using linear body as raw material. In the ring-opening polymerization process, there is no condensation step, so it is not necessary to promote the reaction equilibrium to the right side by dehydration, but in the condensation polymerization process of the present application, a large amount of water is produced due to the condensation step, so dehydration is needed to promote the reaction equilibrium to the right side.

[0013] In addition, although CN114058016A dehydrates by passing nitrogen before the ring-opening polymerization reaction, it is completely different from the dehydration by passing nitrogen during the polycondensation reaction of the linear polymer in the present application. The CN patent uses a siloxane ring body as a reaction raw material to carry out ring-opening polymerization, and dehydrates by passing nitrogen before the reaction to prevent a very small amount of moisture in the raw material from participating in the reaction as an end-capping agent, affecting the viscosity and hydroxyl value of the product. That is, the dehydration before the reaction in the CN patent is to purify the reactants by removing impurities from the raw materials. In the present application, the linear polymer is used as a reaction raw material to carry out polycondensation, and a large amount of water generated during the reaction exists in the polymer. If it is not dehydrated in time, it is difficult to ensure that the reaction equilibrium continues to proceed to the right.

[0014] In addition, although CN114213660A passes nitrogen during the polymerization process, it is completely different from the dehydration by passing nitrogen during the polycondensation process of the present application. The CN patent is still a ring-opening polymerization route using a siloxane ring body as a raw material, and nitrogen is passed during the polymerization process to remove carbon dioxide, otherwise the accumulated carbon dioxide may react with the catalyst used to form a non-decomposable salt, resulting in a decrease in product transparency. In addition, passing nitrogen at the later stage of the reaction can remove the malodorous catalyst decomposition products.

[0015] US5420221 discloses a method for preparing a low viscosity organopolysiloxane by condensation and disproportionation of organopolysiloxane raw materials with different molecular weights. First, the raw material hydroxyl-terminated organosiloxane is subjected to a condensation reaction in the presence of a catalyst until the Si-OH content is reduced to below 1000 ppm, and then the condensed siloxane mixture is subjected to a disproportionation reaction in the presence of an end-capping agent and a disproportionation catalyst. Although the above patent uses a siloxane linear body as a siloxane raw material, the reaction goes through two steps of condensation-disproportionation, and after the Si-OH content is reduced to a certain extent in the condensation step, the end-capping agent and catalyst are added for disproportionation reaction, which is not a one-step polycondensation-rearrangement as in the present application. In addition, the condensation reaction in the above patent uses the traditional vacuum water removal method, and the volatile content of the obtained product is relatively high (>3%).

[0016] It can be seen that the existing conventional method for preparing medium and low viscosity vinyl silicone oil is not satisfactory. There is still a need for an improved method which not only has the advantages of mild reaction temperature, catalyst not easy to deactivate, low volatile content of product, high yield, but also simple process steps and cost-effective. SUMMARY

[0017] Therefore, the present application aims to provide a method for preparing a medium or low viscosity vinyl silicone oil, which can complete the polycondensation and rearrangement of siloxane in one step, has simple process steps, is cost-effective, has mild reaction conditions, high yield, low content of siloxane ring body, low volatile content, and high product purity. The obtained product can be directly used as a capping agent for preparing high viscosity silicone oil and raw rubber, and can also be used in various downstream terminal applications.

[0018] Specifically, the present application provides a method for preparing a medium or low viscosity vinyl silicone oil, comprising:

[0019] (1) dehydrating linear body siloxane raw materials,

[0020] (2) reacting the linear body siloxane raw materials with a capping agent and a catalyst under a nitrogen atmosphere for 0.5-10 h, and then adding a terminating agent to terminate the reaction for 0.5-2 h to obtain a medium or low viscosity vinyl silicone oil.

[0021] The viscosity of the medium or low viscosity vinyl silicone oil ranges from 1-10000 mm 2 / s, for example, 10-5000 mm 2 / s, 10-3000 mm 2 / s, 10-1000 mm 2 / s, 5-500 mm 2 / s, 2-200 mm 2 / s, 1-100 mm 2 / s, or 1-50 mm 2 / s. Preferably, the viscosity of the medium or low viscosity vinyl silicone oil ranges from 1-1000 mm 2 / s, more preferably 1-100 mm 2 / s, and most preferably 1-50 mm 2 / s.

[0022] Preferably, the linear body siloxane raw materials are hydroxyl-terminated linear polydimethylsiloxane with a viscosity of 20-500 mm 2 / s.

[0023] Preferably, the catalyst is an acidic catalyst, such as phosphazene chloride, a carboxylic acid such as trichloroacetic acid, or a sulfonic acid such as triflic acid.

[0024] Preferably, the terminating agent is a basic substance, such as triethylamine, tripropylamine, diisopropylamine, hexamethyldisilazane, butyllithium, or a combination thereof.

[0025] Preferably, in step (2), no vacuum is used during the polycondensation reaction of the linear body siloxane raw materials with the capping agent and the catalyst, and during the termination reaction after adding the terminating agent.

[0026] Preferably, the linear siloxane raw material is subjected to polycondensation reaction with the end-capping agent and the catalyst under stirring with continuous nitrogen flow, and / or the termination reaction is carried out after adding the termination agent with continuous nitrogen flow. In this case, the nitrogen flow during the polycondensation reaction and / or the termination reaction is 0.1-6.0 nL / min / L of the reaction vessel, preferably 0.2-4.0 nL / min / L of the reaction vessel, and more preferably 0.6-1.5 nL / min / L of the reaction vessel. In this case, "nL" represents nanoliter.

[0027] Preferably, after the termination reaction by adding the termination agent, the low volatile fraction is removed, and then the medium-low viscosity vinyl silicone oil is obtained.

[0028] Preferably, in step (2), the temperature for the reaction of the linear siloxane raw material with the end-capping agent and the catalyst and the temperature for the termination reaction by adding the termination agent are 65-100°C, preferably 70-95°C, and more preferably 70-90°C.

[0029] Preferably, the polycondensation reaction time of the linear siloxane raw material with the end-capping agent and the catalyst is 1-8 h, more preferably 1-4 h, and most preferably 2 h.

[0030] Preferably, the time for the termination reaction by adding the termination agent is 0.5-2 h, more preferably 0.5-1 h, and most preferably 1 h.

[0031] Preferably, the low volatile fraction content of the obtained medium-low viscosity vinyl silicone oil is 0.1-3%, preferably 0.1-2%, and more preferably 0.3-0.5%.

[0032] Preferably, the yield of the obtained medium-low viscosity vinyl silicone oil is >60%, preferably >85%, and more preferably >91%.

[0033] The method of the present application has many excellent technical effects, including:

[0034] 1) The process is greatly simplified. On the one hand, the conventional ring-opening polymerization process using siloxane ring as raw material needs ring-opening polymerization-telomerization steps, and there is a large amount of ring volatile fraction in the product after reaction equilibrium, and the conversion rate and yield are low, while the present application uses linear siloxane as raw material to realize polycondensation rearrangement by one-step method, which is simple in steps and greatly reduces the cost. On the other hand, the conventional condensation polymerization process using linear siloxane as raw material needs two steps of polycondensation-rearrangement, and the catalyst is added during the polycondensation step and the rearrangement step, respectively, while the one-step method of the present application adds the raw material, the end-capping agent and the catalyst to the reaction system at the beginning of the reaction, and does not need to add the catalyst after polycondensation, which simplifies the process flow.

[0035] 2) The cost is significantly reduced, and the economy is improved. In the present application, the linear silicone is used as the raw material for condensation polymerization, and the continuous nitrogen is used for dehydration instead of the traditional vacuum dehydration during the termination reaction after the addition of the termination agent. In this way, the low volatile medium and low viscosity vinyl silicone oil with low volatile content can be obtained at a higher yield and at a significantly reduced cost. In the traditional vacuum dehydration method, the low molecular weight capping agent is also taken away by the vacuum, resulting in more than 80% loss of the capping agent. In contrast, the nitrogen dehydration method of the present application does not cause a large loss of the capping agent, significantly saves the raw material cost, improves the utilization rate of the raw material, and has significantly improved economy. In addition, the nitrogen dehydration method of the present application does not require the very high sealing requirement of the equipment as in the traditional vacuum dehydration method.

[0036] 3) The reaction efficiency is high, and the reaction conditions are mild. The present application does not require the vacuum conditions in the conventional condensation polymerization method, nor does it require the high polymerization temperature of more than 100°C required in the conventional ring-opening polymerization. Only continuous nitrogen is required.

[0037] 4) The product has low volatile content and low siloxane ring content, and the product yield is high. The low volatile content of the product before the low volatile content is removed is less than 5%, and the low volatile content of the product after the low volatile content is removed is less than 3%, which is much lower than the low volatile content of 10-20% on the market.

[0038] Compared with the traditional ring-opening polymerization method using siloxane ring as raw material, the method of the present application uses completely different raw materials, i.e. linear siloxane. Therefore, the process steps of the present application are significantly different from the conventional ring-opening polymerization method, and the siloxane ring content of the product is significantly reduced.

[0039] In addition, compared with the conventional condensation polymerization method using linear siloxane as raw material, the present application has significantly improved process steps, thereby simplifying the process, reducing energy consumption, and significantly reducing the siloxane ring content of the product. The present application uses nitrogen bubbling to promote the reaction, which significantly avoids the loss of the capping agent, reduces the cost, and improves the economy. Moreover, the mild reaction temperature makes the catalyst less likely to be deactivated, thereby avoiding the use of high vacuum for rapid water removal. Further, due to the less likely deactivation of the catalyst, the process steps can be shortened, and all raw materials can be added in one step to obtain the target product, instead of the commonly used two-step process route. The present application also has another benefit. Because the reaction temperature is more moderate, the activity of the raw material to produce ring siloxane with low volatile content is also low, and therefore the total volatile content of the product is lower. DETAILED DESCRIPTION

[0040] The technical solutions of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only examples of the technical solutions of the present application, rather than all of the technical solutions. And any modification and improvement made by those skilled in the art on the basis of the exemplary embodiments of the present application also falls within the scope of the present application.

[0041] Example 1

[0042] Put 260 g of linear body α, ω-dihydroxypolydimethylsiloxane (chemical formula HO- [SiMe2-O-] n H, wherein n is 1-500, the viscosity range is 10-300 mPa-s) into a 500 mL three-necked flask, and heat to 90°C under stirring, and dehydrate under vacuum for 1 h; remove the vacuum, and add 40 g of divinyltetramethyldisiloxane and 0.1 g of phosphazene chloride catalyst in toluene solution while bubbling nitrogen, and monitor the reaction progress by sampling. After 2 h, add 50 μL of hexamethyldisilazane, and terminate the reaction by stirring for 1 h while bubbling nitrogen. Then heat to 150°C, and remove low volatile components under reduced pressure at 10 kPa for 1 h, and discharge and package below 60°C. The nitrogen flow rate during the polycondensation reaction and the termination reaction is 1.0 nL / min / L reaction vessel, and 280 g of product is obtained, with a product viscosity of 27 mm 2 / s, a yield of 93.26%, a low volatile component content of 2.79%, and a vinyl content of 2.68%.

[0043] Example 2

[0044] Put 256 g of the linear body of Example 1 into a 500 mL three-necked flask, and heat to 70°C under stirring, and dehydrate under vacuum for 1 h; remove the vacuum, and add 44 g of divinyltetramethyldisiloxane and 0.15 g of phosphazene chloride catalyst in toluene solution while bubbling nitrogen, and monitor the reaction progress by sampling. After 2 h, add 50 μL of tripropylamine, and terminate the reaction by stirring for 1 h while bubbling nitrogen. Then heat to 150°C, and remove low volatile components under reduced pressure at 10 kPa for 1 h, and discharge and package below 60°C. The nitrogen flow rate during the polycondensation reaction and the termination reaction is 1.2 nL / min / L reaction vessel. 285 g of product is obtained, with a product viscosity of 14 mm 2 / s, a yield of 95.15%, a low volatile component content of 1.31%, and a vinyl content of 3.90%.

[0045] Example 3

[0046] The reaction was carried out according to Example 1, except that the linear polymer was 293 g, the divinyltetramethyldisiloxane was 7 g, the catalyst was 0.15 g, the terminating agent was diisopropylamine 50 μL, and the nitrogen flow rate during the polycondensation and termination reactions was 2.4 nL / min / L of reaction vessel. The product was 266 g, the product viscosity was 8770 mm 2 / s, the product yield was 88.67%, the low volatile content was 0.10%, and the vinyl content was 0.17%.

[0047] Example 4

[0048] The reaction was carried out according to Example 1, except that the linear polymer was 250 g, the end-capping agent was 50 g of a vinyl-terminated silicone oil having a viscosity of 20 mm 2 / s, the catalyst was 0.15 g, the terminating agent was diisopropylamine 50 μL, and the nitrogen flow rate during the polycondensation and termination reactions was 1.8 nL / min / L of reaction vessel. The product was 268 g, the product viscosity was 2799 mm 2 / s, the product yield was 89.33%, the low volatile content was 0.10%, and the vinyl content was 0.22%.

[0049] Example 5

[0050] The reaction was carried out according to Example 1, except that the linear polymer was 200 g, the end-capping agent was 101 g of a vinyl-terminated silicone oil having a viscosity of 20 mm 2 / s, the catalyst was 0.15 g, the terminating agent was diisopropylamine 50 μL, and the nitrogen flow rate during the polycondensation and termination reactions was 0.8 nL / min / L of reaction vessel. The product was 299 g, the product viscosity was 125 mm 2 / s, the yield was 99.34%, the low volatile content was 0.43%, and the vinyl content was 0.79%.

[0051] Example 6

[0052] The reaction was carried out according to Example 1, except that the linear polymer was 245 g, the divinyltetramethyldisiloxane was 55 g, the reaction temperature was 80°C, the catalyst was 0.15 g, the terminating agent was trioctylamine 70 μL, and the nitrogen flow rate during the polycondensation and termination reactions was 1.4 nL / min / L of reaction vessel. The product was 291 g, the product viscosity was 530 mm 2 / s, the yield was 97.00%, the low volatile content was 0.51%, and the vinyl content was 0.34%.

[0053] Example 7

[0054] The reaction was carried out according to Example 6, except that the linear polymer was 266 g, the end-capping agent was 34 g of a vinyl-terminated silicone oil having a viscosity of 20 mm 2A reaction vessel was prepared with vinyl-terminated silicone oil at a reaction temperature of 85°C, using 0.20 g of catalyst and 65 μL of diisopropylamine as a terminator. Nitrogen gas flow rate was 1.4 nL / min / L during the polycondensation and termination reactions. The product yielded 295 g of product with a viscosity of 946 mmHg. 2 / s, yield 98.34%, low volatile matter content 0.43%, vinyl content 0.26%.

[0055] Example 8

[0056] The reaction was carried out according to Example 1, with the only differences being: 253 g of the linear polymer, 47 g of divinyltetramethyldisiloxane, 1.2 g of trichloroacetic acid catalyst, 1.2 mL of triethylamine terminator, and a reaction vessel with a nitrogen flow rate of 0.6 nL / min / L during the polycondensation and termination reactions. 191 g of product was obtained, with a viscosity of 130 mmHg. 2 / s, yield 63.59%, low volatile matter content 0.91%, vinyl content 0.73%.

[0057] Example 9

[0058] The reaction was carried out according to Example 1, with the only differences being: 256g of the linear polymer, 44g of divinyltetramethyldisiloxane, 0.3g of trifluoromethanesulfonic acid catalyst, 0.5g of sodium bicarbonate neutralizer, and a reaction vessel with a nitrogen flow rate of 0.8 nL / min / L during the polycondensation and termination reactions. 206g of product was obtained, with a viscosity of 130 mmHg. 2 / s, yield 68.54%, low volatile matter content 0.85%, vinyl content 0.73%.

[0059] Comparative Example 1

[0060] Using 260g of octamethylcyclotetrasiloxane (D4) as raw material, after vacuum dehydration at elevated temperature, 40g of divinyltetramethyldisiloxane was used as the end-capping agent, and 0.5g of potassium hydroxide silanolate was used as the catalyst. The mixture was added to a flask and polymerized at 130℃ for 4 hours. Then, 1.2g of phosphoric acid was added as a neutralizing agent, and stirring was continued for 2 hours. Finally, the volatile matter was reduced at 150℃ to obtain 248g of product with a viscosity of 20 mmHg. 2 / s, yield 82.67%, low volatile matter content 10.2%, vinyl content 2.83%.

[0061] Comparative Example 2

[0062] Using 260g of linear α,ω-dihydroxypolydimethylsiloxane as raw material, with 21g of 20mm viscosity... 2Vinyl terminated silicone oil with viscosity of 100 / s was heated to 140℃ under stirring, and dehydrated under vacuum for 1h. After removing the vacuum, 0.15g of catalyst solution of phosphonium chloride was added, and the vacuum was turned on again, and the system was maintained at <10kPa. The reaction progress was monitored by sampling. After 3h, the viscosity of the system remained unchanged, and the viscosity was 5312mm 2 / s. After removing the vacuum, 19g of divinyltetramethyldisiloxane and 0.20g of catalyst solution were added, and the rearrangement reaction was continued. The reaction progress was monitored by sampling. After 3h, 50μL of tripropylamine was added and stirred for 1h to terminate the reaction. Then the temperature was increased to 150℃, and the low volatile fraction was removed under reduced pressure at 10kPa for 1h. The product was discharged and packaged below 60℃. 271g of product was obtained, and the viscosity of the product was 43mm 2 / s, and the yield was 90.33%. The low volatile fraction content was 0.7%, and the vinyl content was 1.82%.

[0063] Comparative Example 3

[0064] The reaction was carried out according to Example 1, except that the linear polymer was 260g, divinyltetramethyldisiloxane was 40g, the catalyst was tetramethylammonium silanolate ammonium gel 0.40g, the reaction temperature was 110℃, and after the reaction was completed, the temperature was increased to 150℃, the medium was broken to deactivate the catalyst, and then the low volatile fraction was removed under vacuum. 167g of product was obtained, and the viscosity of the product was 220mm 2 / s, the yield was 55.67%, the low volatile fraction content was 6.52%, and the vinyl content was 0.61%.

[0065] Comparative Example 4

[0066] The reaction was carried out according to Example 1, except that nitrogen was not used to remove water during the condensation reaction with the end-capping agent and the catalyst, and during the termination reaction with the termination agent. As a result, the reaction could not proceed normally, because the water produced by condensation was not removed in time, and the presence of a large amount of water in the product after the reaction started caused the equilibrium to fail to proceed to the right. Although the water in the final product could be removed after the low volatile fraction was removed, the viscosity of the product (21300mm 2 / s) was much higher than the theoretical calculated value (about 20mm 2 / s).

[0067] Comparative Example 5

[0068] The reaction was carried out according to Example 1, except that the nitrogen flow rate was 0.04nL / min / L reaction vessel (lower than the lower limit of the nitrogen flow rate required in this application). As a result, the viscosity of the product obtained after the reaction was much higher than that of Example 1, because the water produced during the condensation reaction could not be removed from the reaction system in time by sufficient nitrogen, which ultimately caused the reaction to fail to proceed normally.

[0069] Comparative Example 6

[0070] The reaction was carried out according to Example 1, except that the rate of nitrogen bubbling was 8.00 nL / min / L of reaction vessel (much higher than the upper limit of nitrogen flow rate required in this application). As a result, the viscosity of the product obtained after the reaction was also significantly higher than that of Example 1, because the end-capping agent was volatile, and the larger nitrogen flow rate carried a large amount of end-capping agent out of the reaction system, so that the effective end-capping agent involved in the reaction was less, and the product viscosity was larger.

[0071] Table 1

[0072]

[0073] From the above results, when using a siloxane ring as a raw material to prepare a medium or low viscosity silicone oil (such as Comparative Example 1, viscosity <100 mm 2 / s) by a traditional ring-opening polymerization method, the yield is low (<85%), and a large amount of low molecular weight linear and ring bodies entrained in the product cannot be removed by vacuum low volatile removal, resulting in high volatile content of the product, which is difficult to meet the application requirements. Moreover, the traditional two-step method needs to first ring-open the ring body raw material to obtain a silicone oil of a certain viscosity, and then additional end-capping agent is added for rearrangement, which is complicated, time-consuming, energy-consuming, and low in production efficiency. In comparison, the present application can obtain a medium or low viscosity vinyl silicone oil (viscosity range 1-10000 mm 2 / s) by a one-step method using a linear body as a raw material. The product yield is high, the volatile content is low, and the process is greatly simplified, and the cost is effective.

[0074] Compared with the traditional condensation-rearrangement two-step method for preparing a medium or low viscosity silicone oil using a linear body as a raw material (such as Comparative Example 2), the present application also uses a linear body as a raw material, but replaces the two-step method with a one-step method, and replaces vacuum water removal with continuous nitrogen flow, so that a medium or low viscosity vinyl silicone oil can be prepared at a lower temperature (<100°C), the operation is more simplified, and the cost is significantly reduced. Moreover, under a suitable catalyst (such as a phosphonium chloride catalyst), a low viscosity vinyl silicone oil (such as viscosity <1000 mm 2 / s) can be obtained at a higher yield (such as >91%) compared with the traditional condensation-rearrangement two-step method.

[0075] Compared with the use of an alkaline catalyst (such as Comparative Example 3), the acidic catalyst (such as phosphonium chloride) of the present application can obtain the target product at a significantly higher yield and much lower low volatile content. Without wishing to be bound by theory, it is believed that certain alkaline catalysts can initiate back-biting ring formation during the reaction, resulting in low yield and high low volatile content of the product.

[0076] When nitrogen is not used to remove water during the polycondensation reaction (for example, Comparative Example 4), the large amount of water formed during the reaction will hinder the reaction equilibrium from moving to the right, resulting in uncontrolled product viscosity, which is much higher than the theoretical calculated value. Further, when the nitrogen flow is not within the range defined in the present application (for example, Comparative Examples 5 and 6), it will also result in unqualified product viscosity, which deviates greatly from the theoretical calculated value.

Claims

1. A method for producing a medium or low viscosity vinyl silicone oil, comprising the steps of: (1) subjecting a linear silicone raw material to a dehydration treatment, (2) allowing the linear silicone raw material to react with a capping agent and a catalyst under a nitrogen atmosphere for 0.5 to 10 hours, and then adding a terminating agent to terminate the reaction for 0.5 to 2 hours, thereby obtaining a medium or low viscosity vinyl silicone oil, wherein in the step (2), neither the polycondensation reaction of the linear silicone raw material with the capping agent and the catalyst nor the termination reaction after the addition of the terminating agent is performed under vacuum, wherein in the step (2), the polycondensation reaction of the linear silicone raw material with the capping agent and the catalyst is performed under continuous nitrogen flow with stirring, and the termination reaction after the addition of the terminating agent is performed under continuous nitrogen flow, and wherein the nitrogen flow rate during the polycondensation reaction and the termination reaction in the step (2) is 0.1 to 6.0 nL / min / L of the reaction vessel.

6. The method according to claim 1, wherein the catalyst is an acidic catalyst.

7. The method according to claim 1, wherein the catalyst is a chlorinated phosphazene, a carboxylic acid, or a sulfonic acid. wherein the linear polysiloxane starting material is a hydroxyl terminated linear polydimethylsiloxane having a viscosity of 20-500 mm 2 / s, 8. The method according to claim 1, wherein the terminating agent is a basic substance.

9. The method according to claim 1, wherein the terminating agent is triethylamine, tripropylamine, diisopropylamine, hexamethyldisilazane, butyllithium, or a combination thereof.

10. The method according to claim 1, wherein the nitrogen flow rate during the polycondensation reaction and the termination reaction in the step (2) is 0.2 to 4.0 nL / min / L of the reaction vessel.

2. The method of claim 1, wherein the medium to low viscosity vinyl silicone oil has a viscosity ranging from 1 to 10,000 mm2 / s. 2 / s.

3. The method of claim 2, wherein the medium to low viscosity vinyl silicone oil has a viscosity ranging from 1 to 1000 mm2 / s. 2 / s.

4. The method of claim 2, wherein the medium to low viscosity vinyl silicone oil has a viscosity ranging from 1 to 100 mm2 / s. 2 / s.

5. The method of claim 2, wherein the medium to low viscosity vinyl silicone oil has a viscosity ranging from 1 to 50 mm2 / s. 2 / s.

11. The method according to claim 1, wherein the nitrogen flow rate during the polycondensation reaction and the termination reaction in the step (2) is 0.6 to 1.5 nL / min / L of the reaction vessel.

12. The method according to claim 1, wherein after the termination reaction by the addition of the terminating agent, low volatile components are removed, and then the medium or low viscosity vinyl silicone oil is obtained.

13. The method according to claim 1, wherein the temperature at which the linear silicone raw material is reacted with the capping agent and the catalyst in the step (2) and the temperature at which the terminating agent is added to terminate the reaction are 65 to 100°C.

14. The method according to claim 13, wherein the temperature at which the linear silicone raw material is reacted with the capping agent and the catalyst in the step (2) and the temperature at which the terminating agent is added to terminate the reaction are 70 to 95°C.

15. The method according to claim 13, wherein the temperature at which the linear silicone raw material is reacted with the capping agent and the catalyst in the step (2) and the temperature at which the terminating agent is added to terminate the reaction are 70 to 90°C.

16. The method according to claim 1, wherein the polycondensation reaction time of the linear silicone raw material with the capping agent and the catalyst is 1 to 8 hours.

17. The method according to claim 16, wherein the polycondensation reaction time of the linear silicone raw material with the capping agent and the catalyst is 1 to 4 hours.

18. The method according to claim 16, wherein the polycondensation reaction time of the linear silicone raw material with the capping agent and the catalyst is 2 hours.

19. The method according to claim 1, wherein the time for which the terminating agent is added to terminate the reaction is 0.5 to 2 hours. ​ ​ ​ ​ ​ 20. The method of claim 19, wherein the time for adding the terminating agent to terminate the reaction is 0.5-1 h.

21. The method of claim 19, wherein the time for adding the terminating agent to terminate the reaction is 1 h.

22. The method of claim 1, wherein the low volatile content of the resulting medium or low viscosity vinyl silicone oil is 0.1-3%.

23. The method of claim 22, wherein the low volatile content of the resulting medium or low viscosity vinyl silicone oil is 0.1-2%.

24. The method of claim 22, wherein the low volatile content of the resulting medium or low viscosity vinyl silicone oil is 0.3-0.5%.

25. The method of claim 1, wherein the yield of the resulting medium or low viscosity vinyl silicone oil is >60%.

26. The method of claim 25, wherein the yield of the resulting medium or low viscosity vinyl silicone oil is >85%.

27. The method of claim 25, wherein the yield of the resulting medium or low viscosity vinyl silicone oil is >91%.

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