Continuous ring-opening polymerization method based on mixture of ring body and linear body and application of continuous ring-opening polymerization method

Abstract

The invention discloses a continuous ring-opening polymerization method based on a mixture of a ring body and a linear body and application, and the continuous ring-opening polymerization method comprises the following steps: S1, dissolving the mixture of the ring body and the linear body in a solvent, and heating to 90-110 DEG C to form a homogeneous solution; s2, adding an organic base catalyst and a single-terminated molecular weight regulator into the homogeneous solution, uniformly stirring, and reacting under a negative pressure condition for 2-5 hours to obtain polysiloxane; wherein the organic base catalyst is supported phosphazene base; the use amount of the organic base catalyst is 0.0014-0.025% of the total mass of the mixture of the linear body and the ring body, and the use amount of the single-terminated molecular weight regulator is 0.2-5% of the total mass of the mixture of the linear body and the ring body. According to the method, ring body ring opening and linear body polycondensation are synchronously catalyzed through the supported phosphazene base, energy consumption, raw material cost and waste discharge are remarkably reduced while efficient preparation of high-molecular-weight polysiloxane (ring body residues are smaller than or equal to 0.01%) is achieved, and the obtained product is controllable in molecular weight, excellent in performance and suitable for the application field of silicone rubber and the like.

Description

Technical Field

[0001] The present invention belongs to the field of synthesis of silicone materials, and particularly relates to a continuous ring-opening polymerization method and application based on a mixture of cyclic and linear bodies. Background Art

[0002] Due to their excellent heat resistance, insulation, and chemical stability, silicone compounds have been widely used in many industrial fields. Especially in industries such as electronics and electrical engineering, automotive manufacturing, and construction, the demand for silicone materials is increasing day by day. Dimethylchlorosilane is one of the important raw materials for silicone materials, and its hydrolysis products are usually a mixture of cyclic bodies (such as D4, D5, etc.) and linear bodies. However, cyclic bodies can pose potential hazards to the environment and human health. Therefore, effective treatment methods are needed to reduce their adverse effects.

[0003] Currently, the industrial method mainly uses high-temperature heating (180 - 240 °C) combined with negative pressure conditions to separate cyclic and linear bodies. In this process, the cyclic bodies are vaporized and then condensed and recovered, while the linear bodies remain in the liquid phase. This method can achieve a certain degree of separation, but it also has significant defects: First, high-temperature operation leads to high energy consumption and increased production costs; second, high precision in temperature control is required, and fluctuations are likely to affect the separation efficiency and product purity; in addition, the separated cyclic bodies need to undergo complex ring-opening reactions before they can be used, and the whole process is time-consuming and inefficient.

[0004] Therefore, there is an urgent need for a continuous ring-opening polymerization method and application based on a mixture of cyclic and linear bodies to solve the deficiencies of the existing technology. Summary of the Invention

[0005] In view of the above problems, the purpose of the present invention is to provide a continuous ring-opening polymerization method and application based on a mixture of cyclic and linear bodies. This method simultaneously catalyzes the ring-opening of cyclic bodies and the polycondensation of linear bodies by a supported phosphazene base, achieving the efficient preparation of high-molecular-weight polysiloxane (cyclic body residue ≤ 0.01%), while eliminating the traditional separation and neutralization steps, significantly reducing energy consumption, raw material costs, and waste emissions. The obtained product has a controllable molecular weight and excellent performance, and is suitable for application fields such as silicone rubber.

[0006] To achieve the above purpose, the first aspect of the present invention provides a continuous ring-opening polymerization method based on a mixture of cyclic and linear bodies, and the steps include: S1. Dissolve the mixture of cyclic and linear bodies in a solvent and heat it to 90 - 110 °C to form a homogeneous solution; S2. Add an organic base catalyst and a mono-capped molecular weight regulator to the homogeneous solution and stir evenly. Then, react for 2 - 5 h under negative pressure. After the reaction, remove the solvent to obtain the polysiloxane. The organic base catalyst is a supported phosphazene base, and the dosage of the organic base catalyst is 0.0014 - 0.025% of the total mass of the linear body and cyclic body mixture. The dosage of the mono-capped molecular weight regulator is 0.2 - 5% of the total mass of the linear body and cyclic body mixture.

[0007] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention uses the mixture of cyclic body and linear body after hydrolysis of dimethylchlorosilane as the raw material. Through the supported phosphazene base, the ring-opening of the cyclic body and the condensation polymerization of the linear body are carried out simultaneously, which enables the raw material to be converted into high-molecular-weight polysiloxane. This process not only improves the utilization rate of the raw material but also significantly reduces the residual amount of the cyclic body (residual amount ≤ 0.01%), thereby reducing the low-boiling removal energy consumption and improving the environmental protection and safety of the product. At the same time, the added molecular weight regulator ensures the controllability of the molecular weight of the polymer, making the finally obtained polysiloxane have good comprehensive properties and be suitable for applications in fields such as silicone rubber.

[0008] 2. The present invention uses the mixture of cyclic body and linear body after hydrolysis of dimethylchlorosilane as the raw material and directly catalyzes the ring-opening to prepare polysiloxane, eliminating the high-energy-consuming separation step and significantly reducing the raw material cost.

[0009] 3. The present invention uses a supported phosphazene base to achieve the dynamic release - absorption of the catalyst, avoiding the neutralization and filtration steps of the traditional KOH method and the temperature-raising step for breaking the medium of tetramethylammonium hydroxide. The catalyst can be reused, further reducing the production cost and the emission of waste.

[0010] Furthermore, the mass ratio of the cyclic body in the mixture of the cyclic body and the linear body of the present invention is 5 - 95%. For example, the mass ratio of the cyclic body in the mixture of the cyclic body and the linear body can be, but is not limited to, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%.

[0011] Further, the solvent in step S1 of the present invention is n-octane, which has good solubility and can effectively dissolve cyclic siloxanes (such as D4, D5, etc.) and linear siloxanes (such as α,ω-dihydroxypolydimethylsiloxane). At the same time, its boiling point is 125.6 - 126.0 °C, which is suitable for the reaction temperature range of 90 - 110 °C and is convenient for subsequent removal by vacuum distillation. Of course, the type of solvent is not limited to n-octane only, and other organic solvents that can dissolve the mixture of cyclic siloxanes and linear siloxanes can also be used in the present invention. For example: alkanes: such as n-hexane, n-heptane, cyclohexane, etc.; aromatic hydrocarbons: such as toluene, xylene, ethylbenzene, etc.; ethers: such as tetrahydrofuran (THF), etc. The selection of these solvents needs to comprehensively consider solubility, boiling point, reaction stability and subsequent easy removability.

[0012] Further, the heating temperature in step S1 of the present invention can specifically be, but is not limited to, 90 °C, 95 °C, 98 °C, 102 °C, 107 °C, 110 °C.

[0013] Further, the cyclic siloxanes of the present invention mainly consist of octamethylcyclotetrasiloxane (D4), and its content is not less than 50% of the total mass of the cyclic siloxanes; the remaining components are selected from at least one of hexamethylcyclotrisiloxane (D3), decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6), tetradecamethylcycloheptasiloxane (D7), hexadecamethylcyclooctasiloxane (D8), octadecamethylcyclononasiloxane (D9), and eicosamethylcyclodecasiloxane (D10).

[0014] Further, the viscosity of the linear siloxane of the present invention is 65 - 150 cs. For example, the viscosity of the linear siloxane can be, but is not limited to, 65 cs, 75 cs, 95 cs, 105 cs, 125 cs, 135 cs, 145 cs, 150 cs.

[0015] Further, the preparation of the supported phosphazene base of the present invention includes: loading the phosphazene base on a porous adsorbent and coating it with a coating agent. The organic base catalyst is formed by loading the phosphazene base on a porous adsorbent and then coating it with a coating agent to form stable supported phosphazene base particles. During the reaction process of step S2, the high temperature of 90 - 110 °C improves the solubility of the phosphazene base in the reaction system, resulting in a certain degree of desorption. Therefore, the adsorbed base and the desorbed base simultaneously catalyze the reaction, improving the catalytic efficiency and reducing the occurrence of side reactions, so that the final polysiloxane product does not contain cyclic siloxanes or the content of cyclic siloxanes is extremely low (≤0.01%). After the reaction is completed and the temperature decreases, due to the polar adsorption effect, the supported phosphazene base particles can adsorb the free phosphazene base again, and the catalyst can be reused. Therefore, by using the supported phosphazene base, the simultaneous ring-opening polymerization of cyclic siloxanes and polycondensation of linear siloxanes can be effectively promoted, which is beneficial to maintaining the stability of ring-opening and polymerization of the overall system.

[0016] Further, the supported phosphazene base of the present invention comprises, by mass parts, 20-30 parts of a porous adsorbent, 1-8 parts of a coating agent, and 40-55 parts of a phosphazene base. It can be seen therefrom that the highest concentration of the phosphazene base is 55 / (55 + 20 + 1)×100% = 72.4%; the lowest concentration is 40 / (40 + 8 + 30)×100% = 51.3%, that is, a mass concentration range of the phosphazene base of 51.3-72.4% can ensure that the phosphazene base exhibits excellent catalytic activity.

[0017] Further, the mass parts of the porous adsorbent of the present invention can be, but are not limited to, 20 parts, 22 parts, 25 parts, 28 parts, 30 parts. Specifically, the porous adsorbent of the present invention is selected from at least one of hollow silica, expanded graphite, and diatomaceous earth. Hollow silica, expanded graphite, and diatomaceous earth all have porous structures and are easy to adsorb the diluted phosphazene base. Preferably, the porous adsorbent is a mixture composed of hollow silica, expanded graphite, and diatomaceous earth; more specifically, the mass ratio of hollow silica, expanded graphite, and diatomaceous earth is 1:0.3:0.1.

[0018] Further, the mass parts of the coating agent of the present invention can be, but are not limited to, 1 part, 2 parts, 5 parts, 6 parts, 8 parts. Specifically, the coating agent is prepared by uniformly mixing polyethylene glycol, poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer, and liquid carboxyl-terminated polycaprolactone. More specifically, the mass ratio of polyethylene glycol, poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer, and liquid carboxyl-terminated polycaprolactone is 1:0-1:0.5-1.5; for example, the mass ratio of the three can be, but is not limited to, 1:0.5:1, 1:0.7:1.2, 1:0.8:1.5; this coating agent has better adhesiveness and is easy to form a coating film on the surface of the porous adsorbent adsorbed with the phosphazene base, which enables the organic base catalyst to release the phosphazene base when heated and keeps it in stable continuous polymerization in the overall system, so that the content of cyclic oligomers (D4-D10) in the final polysiloxane product is less than 0.01%.

[0019] Further, the mass fraction of the phosphazene base of the present invention can be, but is not limited to, 40 parts, 42 parts, 44 parts, 47 parts, 49 parts, 52 parts, 55 parts. Specifically, the phosphazene base is selected from at least one of phosphazene ligand P4-tert-butyl (P4-T-BU), cyclotriphosphazene base (CTPB), 2,4,6-tris[tris(dimethylamino)phosphoranylideneamino]-1,3,5-triazine (C3N3-Me-P3), and 2,4,6-tris[tris(1-pyrrolidinyl)phosphoranylideneamino]-1,3,5-triazine (C3N3-Py-P3). It should be particularly noted that the scope of phosphazene base substances involved in the present invention is not limited to these several, but also includes other unlisted derivatives or similar structures. More specifically, P4-T-BU (cas:111324-04-0), CTPB, C3N3-Me-P 3、 The structural formula of C3N3-Py-P3 is shown as follows:

[0020] Further, the negative pressure in step S2 of the present invention is 70-75 mmHg. Specifically, maintaining negative pressure can remove the water generated during the reaction.

[0021] Further, the preparation of the organic base catalyst of the present invention includes: (1) Divide the diluent into a first diluent and a second diluent, and dilute the coating agent diluent in the first diluent to obtain diluent A; and dilute the phosphazene base in the second diluent to obtain diluent B; (2) Mix diluent B with the porous adsorbent evenly to obtain adsorbent C; (3) Mix diluent A with adsorbent C evenly and then heat under reflux, and then successively perform reduced pressure distillation, drying, and pulverization treatments to obtain the organic base catalyst.

[0022] The organic base catalyst (supported phosphazene base) of the present invention can maintain stability for a long time in cyclic systems with different concentrations, thereby realizing the continuous and controllable release of the phosphazene base, ensuring the stability of the ring-opening polymerization process, making the residual amount of cyclic bodies in the final product ≤0.01%, and the obtained silicone rubber having excellent physical properties. Specifically, by dissolving the coating agent in the first diluent to form diluent A and dissolving the phosphazene base in the second diluent to obtain diluent B, the uniform dispersion of the coating agent and the phosphazene base can be ensured, enabling the adsorbent to effectively load the phosphazene base, and then forming a stable coating film structure through the coating agent to realize the slow-release effect of the catalyst. This not only avoids the residual of unopened cyclic bodies in the product, but also promotes the further reaction of cyclic bodies with linear bodies to generate low-molecular-weight polysiloxanes, thereby significantly improving the comprehensive performance of the material.

[0023] Further, step (1) of the present invention includes dividing the diluent into equal amounts of the first diluent and the second diluent.

[0024] Further, the drying condition in step (3) of the present invention is: drying at 45-55°C for 1.5-2.5 h.

[0025] Further, the heating reflux time in step (3) of the present invention is 5-7 h.

[0026] Further, the mass fraction of the diluent in the present invention is 7-39 parts; for example, the mass fraction of the diluent can be, but is not limited to, 7 parts, 10 parts, 15 parts, 20 parts, 28 parts, 33 parts, 39 parts. Specifically, the diluent can be, but is not limited to, ethyl acetate.

[0027] Further, the single-end capped molecular weight regulator of the present invention is at least one of trimethylsiloxy-capped polydimethylsiloxane hydride, trimethylsiloxy-capped polydimethylsiloxane alkane, vinyldimethylsiloxy-capped polydimethylsiloxane hydride, and vinyldimethylsiloxy-capped polydimethylsiloxane alkane. The structural formula of trimethylsiloxy-capped polydimethylsiloxane hydride is (CH3)3SiO((CH3)2SiO) n H, where n is 0-20; the structural formula of trimethylsiloxy-capped polydimethylsiloxane alkane is (CH3)3SiO((CH3)2SiO) n (CH2) m CH3, where n is 0-20 and m is 0-3; the structural formula of vinyldimethylsiloxy-capped polydimethylsiloxane hydride is CH2=CH(CH3)2SiO((CH3)2SiO) n H, where n is 0-20; the structural formula of vinyldimethylsiloxy-capped polydimethylsiloxane alkane is CH2=CH(CH3)2SiO((CH3)2SiO) n (CH2) m CH3, where n is 0-20 and m is 0-3.

[0028] Correspondingly, the second aspect of the present invention also provides an application of the polysiloxane prepared by the continuous ring-opening polymerization method based on the mixture of cyclic and linear bodies mentioned above in silicone rubber materials. Specific Embodiments

[0029] To better illustrate the purpose, technical solution and beneficial effects of the present invention, the present invention will be further described below in conjunction with specific embodiments. It should be noted that the methods described in the following embodiments are further explanatory descriptions of the present invention and should not be regarded as limitations of the present invention.

[0030] The detailed information of the main raw materials used in the following examples and comparative examples is as follows: The cyclic body is a mixture of 60% D4, 35% D5, and 5% D6; The linear body is α,ω-dihydroxypolydimethylsiloxane with a viscosity of 100 cs; The hollow silica is the hollow mesoporous silica microsphere powder purchased from Beijing Zhongke Keyou Nanotechnology Co., Ltd., with a pore diameter of 3 nm and a particle size of 100 nm; The expanded graphite is 200 - 300 mesh and is purchased from Qingdao Mingrun Chenyue Graphite Co., Ltd.; The diatomite is 325 - 600 mesh and is purchased from Shijiazhuang Huabang Mineral Products Co., Ltd.; The average molecular weight of polyethylene glycol is 1000; The poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer has a CAS number of 9003 - 11 - 6, an average molecular weight of 4400, and a poly(ethylene oxide) content of 30%. It is purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; The liquid carboxyl-terminated polycaprolactone has an average molecular weight of 1000; The phosphazene base is P4-T-BU with a cas: 111324 - 04 - 0.

[0031] Example 1 - 1 This example provides an organic base catalyst, which is a supported phosphazene base, and its preparation includes: (1) Divide 24 parts by mass of the diluent into 12 parts by mass of the first diluent and 12 parts by mass of the second diluent, and dilute 1 part by mass of the coating agent diluent in the first diluent to obtain diluent A; and dilute 55 parts by mass of the phosphazene base in the second diluent to obtain diluent B; (2) Mix diluent B evenly with 20 parts by mass of the porous adsorbent to obtain adsorbent C; (3) Mix diluent A and adsorbent C evenly, then heat under reflux for 6 h, then remove the diluent by vacuum distillation in sequence, and then dry in an oven at 50 °C for 2 h, and pulverize to obtain the organic base catalyst; Wherein the diluent is ethyl acetate; the porous adsorbent is hollow silica; the coating agent is obtained by mixing polyethylene glycol, poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer, and liquid carboxyl-terminated polycaprolactone evenly in a weight ratio of 1:0.5:1.125.

[0032] Example 1 - 2 This example provides an organic base catalyst, which is a supported phosphazene base, and its preparation includes: (1) Divide 21.7 parts by mass of the diluent into 10.85 parts by mass of the first diluent and 10.85 parts by mass of the second diluent, and dilute 5.3 parts by mass of the coating agent diluent in the first diluent to obtain diluent A; and dilute 43 parts by mass of the phosphazene base in the second diluent to obtain diluent B; (2) Mix diluent B evenly with 25 parts by mass of the porous adsorbent to obtain adsorbate C; (3) Mix diluent A evenly with adsorbate C, then heat under reflux for 6 h, then remove the diluent by vacuum distillation in sequence, then dry in an oven at 50 °C for 2 h, and pulverize to obtain the organic base catalyst; The diluent is ethyl acetate; the porous adsorbent is hollow silica; the coating agent is obtained by mixing polyethylene glycol, poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer, and liquid carboxyl-terminated polycaprolactone evenly in a weight ratio of 1:0.5:1.125.

[0033] Examples 1 - 3 This example provides an organic base catalyst, which is a supported phosphazene base, and its preparation includes: (1) Divide 22 parts by mass of the diluent into 11 parts by mass of the first diluent and 11 parts by mass of the second diluent, and dilute 8 parts by mass of the coating agent diluent in the first diluent to obtain diluent A; and dilute 40 parts by mass of the phosphazene base in the second diluent to obtain diluate B; (2) Mix diluate B evenly with 30 parts by mass of the porous adsorbent to obtain adsorbate C; (3) Mix diluent A evenly with adsorbate C, then heat under reflux for 6 h, then remove the diluent by vacuum distillation in sequence, then dry in an oven at 50 °C for 2 h, and pulverize to obtain the organic base catalyst; The diluent is ethyl acetate; the porous adsorbent is hollow silica; the coating agent is obtained by mixing polyethylene glycol, poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer, and liquid carboxyl-terminated polycaprolactone evenly in a weight ratio of 1:0.5:1.125.

[0034] Examples 1 - 4 Examples 1 - 4 and Examples 1 - 2 are basically the same, and the difference between the two is only that: the porous adsorbent in Examples 1 - 4 is expanded graphite.

[0035] Examples 1 - 5 Examples 1 - 5 and Examples 1 - 2 are basically the same, and the difference between the two is only that: the porous adsorbent in Examples 1 - 5 is diatomite.

[0036] Examples 1 - 6 Examples 1 - 6 and Examples 1 - 2 are basically the same, and the difference between the two is only that: the porous adsorbent in Examples 1 - 6 is composed of hollow silica, expanded graphite, and diatomite in a weight ratio of 1:0.3:0.1.

[0037] Comparative Example 1 - 1 Comparative Example 1 - 1 and Examples 1 - 2 are basically the same, and the difference between the two is only that: the coating agent in Examples 1 - 2 is replaced with the porous adsorbent in equal amount.

[0038] Comparative Example 1-2 Comparative Example 1-2 is basically the same as Example 1-2, and the only difference between the two is that the liquid carboxyl-terminated polycaprolactone in Example 1-2 is replaced with polyethylene glycol in equal amount.

[0039] Example 1 This example provides a continuous ring-opening polymerization method based on a mixture of cyclic and linear monomers. The steps include: S1. Dissolve the mixture of cyclic and linear monomers in a solvent and heat to 100 °C to form a homogeneous solution; S2. Add the organic base catalyst and the mono-capped molecular weight regulator prepared in Example 1-1 to the homogeneous solution and stir evenly. Then react under a negative pressure of 75 mmHg for 3.5 h. After the reaction is completed, remove the solvent to obtain a polysiloxane; Among them, the dosage of the organic base catalyst is 0.02% of the total mass of the linear and cyclic monomer mixture, and the dosage of the mono-capped molecular weight regulator is 1% of the total mass of the linear and cyclic monomer mixture; the mono-capped molecular weight regulator is CH2=CH(CH3)2SiO((CH3)2SiO) 10 H; the solvent is n-octane.

[0040] Example 2 Example 2 is basically the same as Example 1, and the only difference between the two is that the organic base catalyst in Example 2 is the organic base catalyst prepared in Example 1-2.

[0041] Example 3 Example 3 is basically the same as Example 1, and the only difference between the two is that the organic base catalyst in Example 3 is the organic base catalyst prepared in Example 1-3.

[0042] Example 4 Example 4 is basically the same as Example 1, and the only difference between the two is that the organic base catalyst in Example 4 is the organic base catalyst prepared in Example 1-4.

[0043] Example 5 Example 5 is basically the same as Example 1, and the only difference between the two is that the organic base catalyst in Example 5 is the organic base catalyst prepared in Example 1-5.

[0044] Example 6 Example 6 is basically the same as Example 1, and the only difference between the two is that the organic base catalyst in Example 6 is the organic base catalyst prepared in Example 1-6.

[0045] Comparative Example 1 Comparative Example 1 is basically the same as Example 1, and the only difference between the two is that: the organic base catalyst in Comparative Example 1 is the organic base catalyst prepared in Comparative Example 1-1.

[0046] Comparative Example 2 Comparative Example 2 is basically the same as Example 1, and the only difference between the two is that: the organic base catalyst in Comparative Example 2 is the organic base catalyst prepared in Comparative Example 1-2.

[0047] Comparative Example 3 This comparative example provides a continuous ring-opening polymerization method based on a mixture of cyclic and linear monomers, and the steps include: S1. Dissolve the mixture of cyclic and linear monomers in a solvent, and heat it to 100 °C to form a homogeneous solution; S2. Add a phosphazene base and a mono-capped molecular weight regulator to the homogeneous solution and stir evenly, and then react under a negative pressure of 75 mmHg for 2 h. After the reaction is completed, remove the solvent to obtain a polysiloxane; wherein the dosage of the phosphazene base is 0.014% of the total mass of the mixture of linear and cyclic monomers, and the dosage of the mono-capped molecular weight regulator is 5% of the total mass of the mixture of linear and cyclic monomers; the mono-capped molecular weight regulator is (CH3)3SiO((CH3)2SiO) 10 H; the solvent is n-octane.

[0048] Comparative Example 4 This comparative example provides a continuous ring-opening polymerization method based on a mixture of cyclic and linear monomers, and the steps include: S1. Dissolve the mixture of cyclic and linear monomers in a solvent, and heat it to 100 °C to form a homogeneous solution; S2. Add a phosphazene base and a mono-capped molecular weight regulator to the homogeneous solution and stir evenly, and then react under a negative pressure of 75 mmHg for 3.5 h. After the reaction is completed, remove the solvent to obtain a polysiloxane; wherein the dosage of the phosphazene base is 0.014% of the total mass of the mixture of linear and cyclic monomers, and the dosage of the mono-capped molecular weight regulator is 1% of the total mass of the mixture of linear and cyclic monomers; the mono-capped molecular weight regulator is (CH3)3SiO((CH3)2SiO) 10 H; the solvent is n-octane.

[0049] Comparative Example 5 This comparative example provides a continuous ring-opening polymerization method based on a mixture of cyclic and linear monomers, and the steps include: S1. Dissolve the mixture of cyclic and linear monomers in a solvent, and heat it to 110 °C to form a homogeneous solution; S2. Add a phosphazene base and a mono-capped molecular weight regulator to the homogeneous solution and stir evenly, and then react under a negative pressure of 75 mmHg for 3 h. After the reaction is completed, remove the solvent to obtain a polysiloxane; Among them, the dosage of phosphazene base is 0.00175% of the total mass of the mixture of linear body and cyclic body, and the dosage of the mono-capped molecular weight regulator is 0.2% of the total mass of the mixture of linear body and cyclic body; the mono-capped molecular weight regulator is (CH3)3SiO((CH3)2SiO) 10 H; the solvent is n-octane.

[0050] Comparative Example 6 Comparative Example 6 is basically the same as Comparative Example 4, and the only difference between the two is that: the mono-capped molecular weight regulator in Comparative Example 6 is (CH3)3SiO((CH3)2SiO) 10 (CH2)2CH3.

[0051] Comparative Example 7 Comparative Example 7 is basically the same as Comparative Example 4, and the only difference between the two is that: the mono-capped molecular weight regulator in Comparative Example 7 is CH2=CH(CH3)2SiO((CH3)2SiO) 10 H.

[0052] Comparative Example 8 Comparative Example 8 is basically the same as Comparative Example 4, and the only difference between the two is that: the mono-capped molecular weight regulator in Comparative Example 8 is CH2=CH(CH3)2SiO((CH3)2SiO) 10 (CH2)2CH3.

[0053] Comparative Example 9 Comparative Example 9 is basically the same as Comparative Example 4, and the only difference between the two is that: S1. Dissolve the mixture of cyclic body and linear body in a solvent and heat it to 80 °C to form a homogeneous solution.

[0054] Comparative Example 10 Comparative Example 10 is basically the same as Comparative Example 4, and the only difference between the two is that: the phosphazene base in Comparative Example 4 is replaced with a KOH catalyst in equal amount.

[0055] By adjusting the feeding ratio of the cyclic body and the linear body, three groups of mixtures of cyclic body and linear body with different ratios are prepared: Low cyclic body content group: 30 wt% cyclic body + 70 wt% linear body (Experiment 1) Medium cyclic body content group: 60 wt% cyclic body + 40 wt% linear body (Experiment 2) High cyclic body content group: 80 wt% cyclic body + 20 wt% linear body (Experiment 3) Then, using the above three groups of mixtures of cyclic body and linear body with different ratios as raw materials, polydimethylsiloxane is prepared respectively by the continuous ring-opening polymerization method based on the mixture of cyclic body and linear body in Examples 1-6 and Comparative Examples 1-10.

[0056] The residual amount of cyclic siloxanes in the prepared polysiloxane was measured by gas chromatography (GC); among them, Grade 1: the cyclic siloxane content is less than 0.01%, Grade 2: the cyclic siloxane content is 0.01 - 0.50%; Grade 3: the cyclic siloxane content is 0.51 - 1.00%, Grade 4 cyclic siloxane content is 1.10 - 5%, and Grade 5 cyclic siloxane content is greater than 5%.

[0057] Table 1 Residual amount of cyclic siloxanes in polysiloxane

[0058] As can be seen from Table 1, the cyclic siloxane content in Examples 1 - 6 is less than 0.01%, which indicates that whether the raw material has a high or low cyclic siloxane content, the continuous ring-opening polymerization method based on the mixture of cyclic siloxanes and linear siloxanes of the present invention can significantly reduce the residual cyclic siloxanes in polysiloxane (residual amount ≤ 0.01%). This is because the organic base catalyst (supported phosphazene base) of the present invention can remain stable for a long time in cyclic siloxane systems with different concentrations, thereby realizing the continuous and controllable release of phosphazene base, ensuring the stability of the ring-opening polymerization process, making the residual amount of cyclic siloxanes in the final product ≤ 0.01% and the obtained silicone rubber having excellent physical properties.

[0059] As can be seen from Table 1, when the cyclic siloxane content in the raw material is relatively high, the continuous ring-opening polymerization method of Comparative Example 1 cannot significantly reduce the residual cyclic siloxanes in polysiloxane, which indicates that removing the coating agent will affect the adsorption of phosphazene base on the surface of the porous adsorbent and thus affect the stability of the ring-opening polymerization process.

[0060] As can be seen from Table 1, when the cyclic siloxane content in the raw material is relatively high, the continuous ring-opening polymerization method of Comparative Example 2 also cannot significantly reduce the residual cyclic siloxanes in polysiloxane. This is because carboxyl-terminated polycaprolactone reacts with polyethylene glycol and poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer to form a polymer on the surface of the catalyst, playing a coating role; therefore, if polyethylene glycol is removed, chain extension does not occur, the polymer molecular weight is relatively small, and it is easy to dissolve into the system, resulting in an unsatisfactory coating effect.

[0061] As can be seen from Table 1, when the cyclic siloxane content in the raw material is relatively high or medium, the continuous ring-opening polymerization methods of Comparative Examples 3 - 8 also cannot significantly reduce the residual cyclic siloxanes in polysiloxane. This may be because compared with phosphazene base, the present invention uses a porous adsorbent to load phosphazene base and then coats it with a coating agent to form stable supported phosphazene base particles, and this supported phosphazene base has a better slow-release effect, thereby maintaining the stability of the entire ring-opening and polymerization processes and reducing the cyclic siloxane content in the final product.

[0062] As can be seen from Table 1, even when the cyclic content in the raw material is very low, the continuous ring-opening polymerization method of Comparative Example 9 cannot significantly reduce the cyclic residue in the polysiloxane at low temperature. This indicates that dissolving the mixture of cyclic and linear bodies in a solvent and forming a homogeneous solution at 90-110 °C is beneficial to maintaining the stability of ring-opening and polymerization of the overall system.

[0063] As can be seen from Table 1, even when the cyclic content in the raw material is very low, the continuous ring-opening polymerization method of Comparative Example 10 cannot significantly reduce the cyclic residue in the polysiloxane. This indicates that compared with the traditional KOH method, the supported phosphazene base can achieve a better slow-release effect, thereby maintaining the stability of the entire ring-opening and polymerization process and reducing the cyclic content in the final product.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A continuous ring-opening polymerization method based on a mixture of a cyclic body and a linear body, characterized in that the steps Comprising: S1. Dissolve the mixture of the cyclic body and the linear body in a solvent, and heat it to 90 - 110 °C to form a homogeneous solution; S2. Add an organic base catalyst and a mono-capped molecular weight regulator to the homogeneous solution and stir evenly, then react under negative pressure conditions for 2 - 5 h. After the reaction is completed, remove the solvent to obtain a polysiloxane; Wherein the organic base catalyst is a supported phosphazene base; the dosage of the organic base catalyst is 0.0014 - 0.025% of the total mass of the linear body and the cyclic body mixture, and the dosage of the mono-capped molecular weight regulator is 0.2 - 5% of the total mass of the linear body and the cyclic body mixture.

2. The continuous ring-opening polymerization method based on a mixture of a cyclic body and a linear body according to claim 1, characterized in that, The mass ratio of the cyclic body in the mixture of the cyclic body and the linear body is 5 - 95%.

3. The continuous ring-opening polymerization method based on a mixture of a cyclic body and a linear body according to claim 1, characterized in that, The preparation of the supported phosphazene base includes: loading the phosphazene base on a porous adsorbent and coating it with a coating agent.

4. The continuous ring-opening polymerization method based on the mixture of a cyclic body and a linear body according to claim 3, characterized in that, The supported phosphazene base includes 20 - 30 parts by mass of the porous adsorbent, 1 - 8 parts by mass of the coating agent, and 40 - 55 parts by mass of the phosphazene base.

5. The continuous ring-opening polymerization method based on a mixture of a cyclic body and a linear body as claimed in claim 3, wherein The coating agent is prepared by uniformly mixing polyethylene glycol, polyethylene oxide - polypropylene oxide - polyethylene oxide triblock copolymer, and liquid carboxyl-terminated polycaprolactone.

6. The continuous ring-opening polymerization method based on a mixture of a cyclic body and a linear body according to claim 3, characterized in that, The phosphazene base is selected from at least one of phosphazene ligand P4-tert-butyl, cyclic phosphazene base, 2,4,6-tris[tris(dimethylamino)phosphoranylideneamino]-1,3,5-triazine, and 2,4,6-tris[tris(1-pyrrolidinyl)phosphoranylideneamino]-1,3,5-triazine.

7. The continuous ring-opening polymerization method based on the mixture of a cyclic body and a linear body according to claim 3, wherein The porous adsorbent is selected from at least one of hollow silica, expanded graphite, and diatomite.

8. The continuous ring-opening polymerization method based on a mixture of a cyclic body and a linear body according to claim 3, characterized in that, The preparation of the organic base catalyst includes: (1) Divide the diluent into a first diluent and a second diluent, and dilute the coating agent diluent in the first diluent to obtain a dilution A; and dilute the phosphazene base in the second diluent to obtain a dilution B; (2) Mix the dilution B with the porous adsorbent evenly to obtain an adsorbate C; (3) Mix the dilution A with the adsorbate C evenly, then heat under reflux, and then successively carry out reduced pressure distillation, drying, and pulverization treatments to obtain an organic base catalyst.

9. The continuous ring-opening polymerization method based on a mixture of a cyclic body and a linear body as claimed in claim 1, characterized in that, The mono-capped molecular weight regulator is at least one of trimethylsiloxy-terminated polydimethylsiloxane hydride, trimethylsiloxy-terminated polydimethylsiloxane alkane, vinyldimethylsiloxy-terminated polydimethylsiloxane hydride, and vinyldimethylsiloxy-terminated polydimethylsiloxane alkane.

10. Application of the polysiloxane prepared by the continuous ring-opening polymerization method based on the mixture of the cyclic body and the linear body according to any one of claims 1 - 9 in a silicone rubber material.

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