阅读说明：本技术 烷氧基封端聚二甲基硅氧烷及其制备方法 (Alkoxy-terminated polydimethylsiloxane and preparation method thereof ) 是由 何运伟 平翔林 于 2021-11-17 设计创作，主要内容包括：本发明涉及有机硅材料技术领域,具体而言,涉及烷氧基封端聚二甲基硅氧烷及其制备方法。烷氧基封端聚二甲基硅氧烷的制备方法包括：将羟基硅油、含有烷氧基的封端剂和固体碱催化剂混合进行反应,其中,所述固体碱催化剂主要通过碱金属的硝酸盐负载于载体上制备得到。本发明实施例提供的烷氧基封端聚二甲基硅氧烷的制备方法采用特定的固体碱催化剂进行反应,不仅能够在温和的反应条件下实现良好的烷氧基封端效果,同时,其催化活性高,能够进一步促进反应进行。(The invention relates to the technical field of organic silicon materials, in particular to alkoxy-terminated polydimethylsiloxane and a preparation method thereof. The preparation method of the alkoxy-terminated polydimethylsiloxane comprises the following steps: hydroxyl silicone oil, an end capping agent containing alkoxy and a solid base catalyst are mixed for reaction, wherein the solid base catalyst is mainly prepared by loading nitrate of alkali metal on a carrier. The preparation method of the alkoxy-terminated polydimethylsiloxane provided by the embodiment of the invention adopts the specific solid base catalyst for reaction, so that a good alkoxy-terminated effect can be realized under mild reaction conditions, and meanwhile, the preparation method is high in catalytic activity and can further promote the reaction.)

1. A method for preparing alkoxy-terminated polydimethylsiloxane, which is characterized by comprising the following steps: hydroxyl silicone oil, an end capping agent containing alkoxy and a solid base catalyst are mixed for reaction, wherein the solid base catalyst is mainly prepared by loading nitrate of alkali metal on a carrier.

2. The method of claim 1, comprising: and after the hydroxyl silicone oil, the end-capping reagent and the solid base catalyst are mixed and reacted, filtering a reaction system, recovering the solid base catalyst and removing low-boiling-point substances to form an alkoxy end-capped polydimethylsiloxane intermediate product.

3. The method of claim 2, wherein the amount of the solid base catalyst is 0.1 to 1.0% by weight of the total weight of all reaction raw materials for forming the intermediate product of the alkoxy-terminated polydimethylsiloxane;

preferably, the temperature of the reaction is 60-90 ℃;

preferably, the conditions for removing low boilers comprise: the temperature is 130 ℃ and 140 ℃, the vacuum degree is-0.09 to-0.1 MPa, and the time is 1.5 to 3 hours.

4. The method of preparing an alkoxy-terminated polydimethylsiloxane according to claim 2, wherein the hydroxy silicone oil has a structural formula shown below:

wherein m is₁＝8-18。

5. The method of preparing an alkoxy-terminated polydimethylsiloxane according to claim 2, wherein the capping agent comprises a polyalkoxysilane;

preferably, the end-capping agent comprises any one of tetramethoxysilane, methyltrimethoxysilane and methyltriethoxysilane;

preferably, the molar ratio of the hydroxyl silicone oil to the end-capping agent is 1: 5-10.

6. The method of claim 2, further comprising: carrying out chain extension reaction on the alkoxy-terminated polydimethylsiloxane intermediate product, dimethyl cyclosiloxane and the solid base catalyst;

preferably, the preparation method further comprises: and carrying out chain extension reaction on the alkoxy-terminated polydimethylsiloxane intermediate product, the dimethyl cyclosiloxane and the solid base catalyst obtained by filtering and recycling in the process of forming the alkoxy-terminated polydimethylsiloxane intermediate product, and then filtering and removing low-boiling-point substances.

7. The method for preparing alkoxy-terminated polydimethylsiloxane according to claim 6, wherein the solid base catalyst is used in an amount of 0.3 to 1.0% of the total weight of all reaction raw materials for chain extension reaction;

preferably, the temperature of the chain extension reaction is 100-120 ℃;

preferably, the conditions for removing low boiling point materials include: the temperature is 140 ℃ and 160 ℃, the vacuum degree is-0.09 to-0.1 MPa, and the time is 1.5 to 3 hours.

8. The method of claim 6, wherein the dimethylcyclosiloxane comprises at least one of octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, or dodecamethylcyclohexasiloxane;

preferably, the dimethyl cyclosiloxane is octamethylcyclotetrasiloxane, and the molar ratio of the alkoxy-terminated polydimethylsiloxane intermediate to the octamethylcyclotetrasiloxane is 1: 25-70.

9. The method for producing an alkoxy-terminated polydimethylsiloxane according to any one of claims 1 to 8, wherein the solid base catalyst is produced by: mixing a solution containing alkali metal nitrate with a carrier, and then carrying out ultrasonic treatment, drying and roasting;

preferably, the solid base catalyst is prepared according to the following method: mixing the solution containing the alkali metal nitrate with a carrier, performing ultrasonic treatment under the condition of 25-40kHz, stirring for 8-10h at 70-90 ℃, then drying for 10-12h at 110 ℃, and then roasting for 2-4h in a muffle furnace at 400-600 ℃;

preferably, the amount of the alkali metal nitrate supported per gram of the carrier is 0.2 to 3 mmol;

preferably, the alkali metal nitrate salt comprises potassium nitrate or sodium nitrate;

preferably, the support comprises any one of alumina, silica and diatomaceous earth.

10. An alkoxy-terminated polydimethylsiloxane produced by the method for producing an alkoxy-terminated polydimethylsiloxane according to any one of claims 1 to 9, wherein the alkoxy-terminated polydimethylsiloxane has a structural formula shown below:

wherein R is₁Is alkyl or alkoxy, R₂Is alkoxy, m₂＝50-400；

Preferably, R₁Is methyl or methoxy, R₂Is methoxy or ethoxy.

Technical Field

The invention relates to the technical field of organic silicon materials, in particular to alkoxy-terminated polydimethylsiloxane and a preparation method thereof.

Background

The dealcoholized silicone rubber has the advantages of good bonding performance and high curing speed, and has wide application prospect in the industries of energy, electronics, electrics, environment-friendly home decoration and the like. In the process of preparing dealcoholized silicone rubber, the hydroxyl-terminated polydimethylsiloxane can react rapidly after contacting with a catalyst, and the viscosity of the system rises rapidly, so that silicone rubber with excellent performance cannot be obtained.

Therefore, the alkoxy is adopted to replace the hydroxyl for end capping, so that the reaction activity of the hydroxyl end-capped polydimethylsiloxane can be reduced, the adverse effect of quick rise of viscosity on reaction mass transfer and heat transfer is effectively improved, and the smooth production of the dealcoholized silicone rubber is realized.

In the prior art, hydroxyl-terminated polydimethylsiloxane and alkoxy silane are generally subjected to condensation reaction to prepare alkoxy-terminated polydimethylsiloxane, and common catalysts mainly comprise sodium fatty alkoxide, potassium silanol, alkali metal hydroxide, diethylamine, methylethylamine and organic tin compound, but the catalysts have some defects. For example, patent CN106674524A discloses the use of alkali metal hydroxide to catalyze the condensation reaction of hydroxyl-terminated polysiloxane and silsesquioxane with alkoxy groups to obtain alkoxy-terminated polydimethylsiloxane. The alkali metal hydroxide catalyst is highly corrosive and requires neutralization after the reaction is completed, which increases the production cost.

The invention patent CN108219143B discloses a method for producing alkoxy-terminated polydimethylsiloxane by reacting hydroxyl-terminated polydimethylsiloxane with alkoxysilane, wherein the catalyst is one of dimethylamine, diethylamine, dipropylamine, methylethylamine and pyrrolidine, dimethylamine is a gas with strong irritation to eyes and respiratory tracts, and diethylamine is a combustible liquid which is volatile and has strong ammonia odor, and the use of organic amine catalyst is limited by the factors.

The organotin compounds have high toxicity and are not favorable for production operation and environmental protection, and the application of the catalyst is also restricted.

In view of this, the invention is particularly proposed.

Disclosure of Invention

The invention aims to provide alkoxy-terminated polydimethylsiloxane and a preparation method thereof. The preparation method of the alkoxy-terminated polydimethylsiloxane provided by the embodiment of the invention adopts the specific solid base catalyst for reaction, so that a good alkoxy-terminated effect can be realized under mild reaction conditions, and meanwhile, the preparation method is high in catalytic activity and can further promote the reaction.

The invention is realized by the following steps:

in a first aspect, the present invention provides a method for preparing an alkoxy-terminated polydimethylsiloxane, comprising: hydroxyl silicone oil, an end capping agent containing alkoxy and a solid base catalyst are mixed for reaction, wherein the solid base catalyst is mainly prepared by loading nitrate of alkali metal on a carrier.

It should be noted that in the embodiments of the present invention, a titanate test method is used to determine whether there is a "viscosity peak" phenomenon, and determine the end-capping effect. Measuring the hydroxyl content in the polymer before and after the reaction by adopting a volumetric method, and calculating according to the following formula: the end capping ratio (1-hydroxyl group content after reaction/hydroxyl group content before reaction) × 100%.

In an alternative embodiment, the method comprises the following steps: and after the hydroxyl silicone oil, the end-capping reagent and the solid base catalyst are mixed and reacted, filtering a reaction system to recover the solid base catalyst and remove low-boiling-point substances to form an alkoxy end-capped polydimethylsiloxane intermediate product.

In an alternative embodiment, the solid base catalyst is used in an amount of 0.1 to 1.0% by weight of the total weight of all reaction raw materials forming the alkoxy-terminated polydimethylsiloxane intermediate;

preferably, the temperature of the reaction is 60-90 ℃;

preferably, the conditions for removing low boilers comprise: the temperature is 130 ℃ and 140 ℃, the vacuum degree is-0.09 to-0.1 MPa, and the time is 1.5 to 3 hours.

In an alternative embodiment, the hydroxy silicone oil has the following structural formula:wherein m is₁＝8-18。

In alternative embodiments, the capping agent comprises a polyalkoxysilane;

preferably, the end-capping agent comprises any one of tetramethoxysilane, methyltrimethoxysilane and methyltriethoxysilane;

preferably, the molar ratio of the hydroxyl silicone oil to the end-capping agent is 1: 5-10.

In an alternative embodiment, the method of making further comprises: carrying out chain extension reaction on the alkoxy-terminated polydimethylsiloxane intermediate product, dimethyl cyclosiloxane and the solid base catalyst;

preferably, the preparation method further comprises: and carrying out chain extension reaction on the alkoxy-terminated polydimethylsiloxane intermediate product, the dimethyl cyclosiloxane and the solid base catalyst obtained by filtering and recycling in the process of forming the alkoxy-terminated polydimethylsiloxane intermediate product, and then filtering and removing low-boiling-point substances.

In an optional embodiment, when the chain extension reaction is performed, the amount of the solid base catalyst is 0.3 to 1.0 percent of the total weight of all reaction raw materials for performing the chain extension reaction;

preferably, the temperature of the chain extension reaction is 100-120 ℃;

preferably, the conditions for removing low boiling point materials include: the temperature is 140 ℃ and 160 ℃, the vacuum degree is-0.09 to-0.1 MPa, and the time is 1.5 to 3 hours.

In alternative embodiments, the dimethylcyclosiloxane comprises at least one of octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, or dodecamethylcyclohexasiloxane;

preferably, the dimethyl cyclosiloxane is octamethylcyclotetrasiloxane, and the molar ratio of the alkoxy-terminated polydimethylsiloxane intermediate to the octamethylcyclotetrasiloxane is 1: 25-70.

In an alternative embodiment, the solid base catalyst is prepared as follows: mixing a solution containing alkali metal nitrate with a carrier, and then carrying out ultrasonic treatment, drying and roasting;

preferably, the solid base catalyst is prepared according to the following method: mixing the solution containing the alkali metal nitrate with a carrier, performing ultrasonic treatment under the condition of 25-40kHz, stirring for 8-10h at 70-90 ℃, then drying for 10-12h at 110 ℃, and then roasting for 2-4h in a muffle furnace at 400-600 ℃;

preferably, the amount of the alkali metal nitrate supported per gram of the carrier is 0.2 to 3 mmol;

preferably, the alkali metal nitrate salt comprises potassium nitrate or sodium nitrate;

preferably, the support comprises any one of alumina, silica and diatomaceous earth.

In a second aspect, the present invention provides an alkoxy-terminated polydimethylsiloxane prepared by the method of preparing an alkoxy-terminated polydimethylsiloxane according to any one of the preceding embodimentsThe alkoxy-terminated polydimethylsiloxane is prepared by the method, and the structural formula of the alkoxy-terminated polydimethylsiloxane is shown as follows:wherein R is₁Is alkyl or alkoxy, R₂Is alkoxy, m₂＝50-400；

Preferably, R₁Is methyl or methoxy, R₂Is methoxy or ethoxy.

The invention has the following beneficial effects: according to the embodiment of the invention, a specific solid base catalyst is adopted for reaction, so that a good alkoxy end capping effect can be realized under mild reaction conditions, the catalytic activity is high, the reaction can be further promoted, the solid base catalyst is easy to separate from a reaction system, neutralization treatment is not needed, and the process operation is simple and convenient.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The embodiment of the invention provides a preparation method of alkoxy-terminated polydimethylsiloxane, which comprises the following steps:

s1, preparing a solid base catalyst;

mixing a solution containing alkali metal nitrate with a carrier, and then carrying out ultrasonic treatment, drying and roasting; specifically, mixing a solution containing alkali metal nitrate with a carrier, performing ultrasonic treatment under the condition of 25-40kHz, stirring for 8-10h at 70-90 ℃, then drying for 10-12h at 110 ℃, and then roasting for 2-4h in a muffle furnace at 400-600 ℃; wherein the amount of the alkali metal nitrate supported per gram of the carrier is 0.2-3 mmol; the alkali metal nitrate comprises potassium nitrate or sodium nitrate; the carrier includes any one of alumina, silica and diatomaceous earth. The adoption of the process and the conditions can be favorable for ensuring the performance of the prepared solid base catalyst and further is favorable for forming the alkoxy-terminated polydimethylsiloxane.

S2, forming an alkoxy-terminated polydimethylsiloxane intermediate;

hydroxyl silicone oil, an end-capping agent containing alkoxy and a solid base catalyst are mixed and reacted, specifically, after the hydroxyl silicone oil, the end-capping agent and the solid base catalyst are mixed and reacted, a reaction system is filtered to recover the solid base catalyst and remove low-boiling-point substances, and an alkoxy end-capped polydimethylsiloxane intermediate product is formed. Wherein, the solid base catalyst is mainly prepared by loading nitrate of alkali metal on a carrier.

The solid base catalyst prepared by loading the nitrate of the alkali metal on the carrier is adopted in the embodiment of the invention, so that alkoxy end capping can be well realized under mild reaction conditions, and then alkoxy end capping polydimethylsiloxane is prepared. The solid base catalyst has high catalytic activity, can further promote the reaction, is easy to separate from a reaction system, does not need neutralization treatment, and is simple and convenient in process operation.

Further, the structural formula of the hydroxyl silicone oil is shown as follows:

wherein m is₁8-18. The capping agent comprises a polyalkoxysilane; for example, the blocking agent includes any one of tetramethoxysilane, methyltrimethoxysilane, and methyltriethoxysilane, which are employed to facilitate alkoxy blocking.

Further, the dosage of the solid base catalyst is 0.1-1.0% of the total weight of all reaction raw materials for forming the alkoxy-terminated polydimethylsiloxane intermediate product; the reaction temperature is 60-90 ℃; the molar ratio of the hydroxyl silicone oil to the end-capping reagent is 1: 5-10; the conditions for removing low-boiling substances comprise: the temperature is 130-; the reaction is more favorably carried out by adopting the conditions.

S3, forming alkoxy-terminated polydimethylsiloxane;

carrying out chain extension reaction on the alkoxy-terminated polydimethylsiloxane intermediate product, dimethyl cyclosiloxane and the solid base catalyst; the solid base catalyst used in the chain extension reaction may be an additionally added solid base catalyst or a solid base catalyst recovered in S2.

Specifically, the alkoxy-terminated polydimethylsiloxane intermediate, the dimethyl cyclosiloxane and the solid base catalyst obtained by filtration and recovery in the process of forming the alkoxy-terminated polydimethylsiloxane intermediate are subjected to chain extension reaction, and then, low-boiling-point substances are filtered and removed.

Wherein the dimethylcyclosiloxane comprises at least one of octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane or dodecamethylcyclohexasiloxane; for example, the dimethylcyclosiloxane is octamethylcyclotetrasiloxane.

Further, during the chain extension reaction, the dosage of the solid base catalyst is 0.3-1.0% of the total weight of all reaction raw materials for the chain extension reaction; the temperature of the chain extension reaction is 100-120 ℃; the molar ratio of the alkoxy-terminated polydimethylsiloxane intermediate product to the octamethylcyclotetrasiloxane is 1: 25-70; the conditions for removing low boiling point materials include: the temperature is 140 ℃ and 160 ℃, the vacuum degree is-0.09 to-0.1 MPa, and the time is 1.5 to 3 hours.

In a second aspect, embodiments of the present invention provide an alkoxy-terminated polydimethylsiloxane prepared by the method of preparing an alkoxy-terminated polydimethylsiloxane according to any one of the preceding embodiments, and the alkoxy-terminated polydimethylsiloxane has a structural formula shown below:wherein R is₁Is alkyl or alkoxy, R₂Is alkoxy, m₂50-400; for example, R₁Is methyl or methoxy, R₂Is methoxy or ethoxy.

The features and properties of the present invention are described in further detail below with reference to examples.

Example 1

This example provides a method for preparing an alkoxy-terminated polydimethylsiloxane, comprising:

(1) preparation of solid base catalyst

2.0g of potassium nitrate was dissolved in 20.0g of distilled water, 10.0g of silica carrier was added, the mixture was placed in an ultrasonic oscillator of 40kHz, stirred at 80 ℃ for 10 hours, dried at 110 ℃ for 12 hours, and calcined at 500 ℃ in a muffle furnace for 3 hours to obtain a supported solid base catalyst.

(2) Preparation of alkoxy-terminated polydimethylsiloxane

The method comprises the following steps: adding hydroxyl silicone oil (m) according to the molar ratio of the hydroxyl silicone oil to the end-capping agent of 1:6₁(8) ═ 8) and methyltrimethoxysilane, stirring and heating to 80 ℃, adding the solid base catalyst which accounts for 0.7 percent of the total mass of the raw materials in the step, starting reaction under the protection of nitrogen, filtering and recovering the solid base catalyst after the reaction is finished, and removing low-boiling-point substances (2h) under the conditions that the temperature is 130 ℃ and the vacuum degree is-0.095 MPa to prepare an alkoxy end-capped polydimethylsiloxane intermediate product;

step two: adding octamethylcyclotetrasiloxane to the intermediate product of alkoxy-terminated polydimethylsiloxane prepared in the step I, wherein the molar ratio of the intermediate product of alkoxy-terminated polydimethylsiloxane to octamethylcyclotetrasiloxane is 1:25, adding solid base catalyst collected by filtering in the step I to a system, wherein the amount of the catalyst is 0.8% of the total mass of the reaction raw materials in the step, carrying out polymerization reaction at 110 ℃, filtering after the reaction is finished, removing low-boiling-point substances (2h) under the conditions that the temperature is 150 ℃ and the vacuum degree is-0.095 MPa, and obtaining the target product of alkoxy-terminated polydimethylsiloxane (m₂＝110)。

When 2% of tetraisopropyl titanate is added into the target product, no viscosity peak phenomenon is observed, and the end capping effect is judged to be good. The end capping rate of the hydroxyl silicone oil was calculated to be 92.7% by measuring the hydroxyl content before and after the reaction. (the hydroxyl group content in the polymer before and after the reaction was measured by a volumetric method and calculated by the following formula: end capping ratio (1-hydroxyl group content before reaction/hydroxyl group content after reaction) × 100%, the same applies hereinafter).

Example 2

This example provides a method for preparing an alkoxy-terminated polydimethylsiloxane, comprising:

(1) preparation of solid base catalyst

1.5g of potassium nitrate was dissolved in 20.0g of distilled water, 10.0g of a diatomaceous earth carrier was added, the mixture was placed in an ultrasonic oscillator of 30kHz, stirred at 80 ℃ for 10 hours, dried at 110 ℃ for 12 hours, and calcined at 600 ℃ for 3 hours in a muffle furnace to obtain a supported solid base catalyst.

(2) Preparation of alkoxy-terminated polydimethylsiloxane

The method comprises the following steps: adding hydroxyl silicone oil (m) according to the molar ratio of the hydroxyl silicone oil to the end-capping agent of 1:8₁8) and methyltrimethoxysilane, stirring and heating to 70 ℃, adding the solid base catalyst accounting for 0.8 percent of the total mass of the raw materials in the step, starting reaction under the protection of nitrogen, filtering after the reaction is finished, and removing low-boiling-point substances (2h) under the conditions that the temperature is 130 ℃ and the vacuum degree is-0.09 MPa to prepare an alkoxy end-capped polydimethylsiloxane intermediate product;

step two: adding octamethylcyclotetrasiloxane to the intermediate product of alkoxy-terminated polydimethylsiloxane prepared in the step I, wherein the molar ratio of the intermediate product of alkoxy-terminated polydimethylsiloxane to octamethylcyclotetrasiloxane is 1:35, adding the catalyst collected by filtering in the step I to a system, wherein the dosage of the catalyst is 0.6% of the total mass of the reaction raw materials in the step, carrying out polymerization reaction at 120 ℃, filtering after the reaction is finished, removing low-boiling-point substances (3h) under the conditions that the temperature is 150 ℃ and the vacuum degree is-0.09 MPa, and preparing the target product, namely alkoxy-terminated polydimethylsiloxane (m₂＝150)。

When 2% of tetraisopropyl titanate is added into the target product, no viscosity peak phenomenon is observed, and the end capping effect is judged to be good. The end capping rate of the hydroxyl silicone oil was calculated to be 87.8% by measuring the hydroxyl group content before and after the reaction.

Example 3

This example provides a method for preparing an alkoxy-terminated polydimethylsiloxane, comprising:

(1) preparation of solid base catalyst

1.7g of sodium nitrate is dissolved in 20.0g of distilled water, 10.0g of alumina carrier is added, the mixture is placed in an ultrasonic oscillator with 40kHz, stirred for 8h at 90 ℃, dried for 10h at 110 ℃, and roasted for 4h in a muffle furnace with 500 ℃ to prepare the supported solid base catalyst.

(2) Preparation of alkoxy-terminated polydimethylsiloxane

The method comprises the following steps: adding hydroxyl silicone oil (m) according to the molar ratio of the hydroxyl silicone oil to the end-capping agent of 1:7₁13) and tetramethoxysilane are stirred and heated to 80 ℃, then the solid base catalyst accounting for 0.9 percent of the total mass of the raw materials in the step is added, the reaction is started under the protection of nitrogen, after the reaction is finished, filtration is carried out, and low-boiling-point substances are removed (for 2h) under the conditions that the temperature is 135 ℃ and the vacuum degree is-0.095 MPa, so as to prepare an alkoxy end-capped polydimethylsiloxane intermediate product;

step two: adding a mixture of octamethylcyclotetrasiloxane and decamethylcyclopentasiloxane into the intermediate product of the alkoxy-terminated polydimethylsiloxane prepared in the step I, wherein the molar ratio of the intermediate product of the alkoxy-terminated polydimethylsiloxane to the octamethylcyclotetrasiloxane to the decamethylcyclopentasiloxane is 1:25:4, adding the catalyst collected in the step I through filtration into a system, wherein the dosage of the catalyst is 0.8% of the total mass of the raw materials in the step, carrying out polymerization reaction at 100 ℃, filtering after the reaction is finished, removing low-boiling-point substances (3h) under the conditions that the temperature is 150 ℃ and the vacuum degree is-0.1 MPa, and obtaining the target product, namely alkoxy-terminated polydimethylsiloxane (m)₂＝135)。

2% tetraisopropyl titanate was added to the target product, and a slight "viscosity peak" phenomenon was observed, and it was judged that a small amount of unreacted silicon hydroxyl group remained in the product. The end capping rate of the hydroxyl silicone oil was calculated to be 83.3% by measuring the hydroxyl content before and after the reaction.

Example 4

This example provides a method for preparing an alkoxy-terminated polydimethylsiloxane, comprising:

(1) preparation of solid base catalyst

2.0g of sodium nitrate is dissolved in 20.0g of distilled water, 10.0g of alumina carrier is added, the mixture is placed in an ultrasonic oscillator with 40kHz, stirred for 8h at 90 ℃, dried for 10h at 110 ℃, and roasted for 4h in a muffle furnace with 500 ℃ to prepare the supported solid base catalyst.

(2) Preparation of alkoxy-terminated polydimethylsiloxane

The method comprises the following steps: adding hydroxyl silicone oil (m) according to the molar ratio of the hydroxyl silicone oil to the end-capping agent of 1:8₁13) and methyl triethoxysilane, stirring and heating to 90 ℃, adding the solid base catalyst accounting for 1.0 percent of the total mass of the raw materials in the step, starting reaction under the protection of nitrogen, filtering after the reaction is finished, and removing low-boiling-point substances (2h) under the conditions that the temperature is 135 ℃ and the vacuum degree is-0.095 MPa to prepare an alkoxy end-capped polydimethylsiloxane intermediate product;

step two: adding octamethylcyclotetrasiloxane to the intermediate product of alkoxy-terminated polydimethylsiloxane prepared in the step I, wherein the molar ratio of the intermediate product of alkoxy-terminated polydimethylsiloxane to octamethylcyclotetrasiloxane is 1:25, adding the catalyst collected by filtering in the step I to a system, wherein the amount of the catalyst is 0.6% of the total mass of the reaction raw materials in the step, carrying out polymerization reaction at 120 ℃, filtering after the reaction is finished, removing low-boiling-point substances (3h) under the conditions that the temperature is 150 ℃ and the vacuum degree is-0.1 MPa, and preparing the target product of alkoxy-terminated polydimethylsiloxane (m₂＝115)。

2% tetraisopropyl titanate was added to the target product, and a slight "viscosity peak" phenomenon was observed, and it was judged that a small amount of unreacted silicon hydroxyl group remained in the product. The end capping rate of the hydroxyl silicone oil is calculated to be 85.3 percent by measuring the hydroxyl content before and after the reaction.

Example 5

This example provides a method for preparing an alkoxy-terminated polydimethylsiloxane, comprising:

(1) preparation of solid base catalyst

2.0g of sodium nitrate is dissolved in 20.0g of distilled water, 10.0g of silicon dioxide carrier is added, the mixture is placed in an ultrasonic oscillator with 40kHz, stirred for 10h at 90 ℃, dried for 12h at 110 ℃, and roasted for 3h in a muffle furnace with 500 ℃ to prepare the supported solid base catalyst.

(2) Preparation of alkoxy-terminated polydimethylsiloxane

The method comprises the following steps: adding hydroxyl silicone oil (m) according to the molar ratio of the hydroxyl silicone oil to the end-capping agent of 1:6₁13) and methyltrimethoxysilane are stirred and heated to 90 ℃, then the solid base catalyst with the total mass of 1.0 percent of the total mass of the raw materials in the step is added, the reaction is started under the protection of nitrogen, after the reaction is finished, filtration is carried out, and low-boiling-point substances are removed (2h) under the conditions that the temperature is 140 ℃ and the vacuum degree is-0.09 MPa, thus obtaining an alkoxy end-capped polydimethylsiloxane intermediate product;

step two: adding octamethylcyclotetrasiloxane to the intermediate product of alkoxy-terminated polydimethylsiloxane prepared in the step I, wherein the molar ratio of the intermediate product of alkoxy-terminated polydimethylsiloxane to octamethylcyclotetrasiloxane is 1:50, adding the catalyst collected by filtering in the step I to a system, wherein the amount of the catalyst is 0.9% of the total mass of the reaction raw materials in the step, carrying out polymerization reaction at 100 ℃, filtering after the reaction is finished, removing low-boiling-point substances (2h) under the conditions of 160 ℃ and-0.1 MPa of vacuum degree, and preparing the target product of alkoxy-terminated polydimethylsiloxane (m)₂＝215)。

A weak "viscosity peak" was observed by adding 2% tetraisopropyl titanate to the target product, and it was judged that a small amount of unreacted silicon hydroxyl group remained in the product. The end capping rate of the hydroxyl silicone oil was calculated to be 75.9% by measuring the hydroxyl content before and after the reaction.

Example 6

This example provides a method for preparing an alkoxy-terminated polydimethylsiloxane, comprising:

(1) preparation of solid base catalyst

3.0g of potassium nitrate was dissolved in 20.0g of distilled water, 10.0g of silica carrier was added, the mixture was placed in an ultrasonic oscillator of 40kHz, stirred at 90 ℃ for 10 hours, dried at 110 ℃ for 10 hours, and calcined at 600 ℃ for 3 hours in a muffle furnace to obtain a supported solid base catalyst.

(2) Preparation of alkoxy-terminated polydimethylsiloxane

The method comprises the following steps: adding hydroxyl silicone oil (m) according to the molar ratio of the hydroxyl silicone oil to the end-capping agent of 1:8₁(8) ═ 8) and methyltriethoxysilane, stirring and heating to 80 ℃, adding the solid base catalyst accounting for 1.0 percent of the total mass of the raw materials in the step, starting reaction under the protection of nitrogen, filtering after the reaction is finished, and removing low-boiling-point substances (2h) under the conditions that the temperature is 130 ℃ and the vacuum degree is-0.09 MPa to prepare an alkoxy end-capped polydimethylsiloxane intermediate product;

step two: adding a mixture of octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane and dodecamethylcyclohexasiloxane into the intermediate product of the alkoxy-terminated polydimethylsiloxane prepared in the step I, wherein the molar ratio of the intermediate product of the alkoxy-terminated polydimethylsiloxane to the octamethylcyclotetrasiloxane to the decamethylcyclopentasiloxane to the dodecamethylcyclohexasiloxane is 1:40:6:5, adding the catalyst collected in the step I into the system, wherein the dosage of the catalyst is 0.9% of the total mass of the reaction raw materials in the step, carrying out polymerization reaction at 100 ℃, filtering after the reaction is finished, removing low-boiling-point substances (3h) under the conditions that the temperature is 160 ℃ and the vacuum degree is-0.1 MPa, and preparing the target product of the alkoxy-terminated polydimethylsiloxane (m)₂＝230)。

2% tetraisopropyl titanate was added to the target product, and a weak "viscosity peak" phenomenon was observed, and it was judged that a small amount of unreacted silicon hydroxyl group remained in the product. The end capping rate of the hydroxyl silicone oil was calculated to be 79.6% by measuring the hydroxyl content before and after the reaction.

Example 7

This example provides a method for preparing an alkoxy-terminated polydimethylsiloxane, comprising:

(1) preparation of solid base catalyst: same as in example 1.

(2) Preparation of alkoxy-terminated polydimethylsiloxane

The method comprises the following steps: respectively adding hydroxyl into the mixture according to the molar ratio of the hydroxyl silicone oil to the end-capping reagent of 1:8Base silicone oil (m)₁16) and methyltrimethoxysilane, stirring and heating to 90 ℃, adding the solid base catalyst accounting for 0.5 percent of the total mass of the raw materials in the step, starting reaction under the protection of nitrogen, filtering after the reaction is finished, and removing low-boiling-point substances (2h) under the conditions that the temperature is 140 ℃ and the vacuum degree is-0.1 MPa to prepare an alkoxy end-capped polydimethylsiloxane intermediate product;

step two: adding octamethylcyclotetrasiloxane to the intermediate product of alkoxy-terminated polydimethylsiloxane prepared in the step I, wherein the molar ratio of the intermediate product of alkoxy-terminated polydimethylsiloxane to octamethylcyclotetrasiloxane is 1:70, adding the catalyst collected by filtering in the step I to a system, wherein the amount of the catalyst is 1.0% of the total mass of the reaction raw materials in the step, carrying out polymerization reaction at 100 ℃, filtering after the reaction is finished, removing low-boiling-point substances (3h) under the conditions of 160 ℃ and-0.1 MPa of vacuum degree, and preparing the target product of alkoxy-terminated polydimethylsiloxane (m)₂＝298)。

When 2% of tetraisopropyl titanate is added into the target product, no viscosity peak phenomenon is observed, and the end capping effect is judged to be good. The end capping rate of the hydroxyl silicone oil was calculated to be 89.1% by measuring the hydroxyl group content before and after the reaction.

Comparative example 1: catalyst supports outside the scope of the invention

(1) Preparation of solid base catalyst

2.0g of potassium nitrate was dissolved in 20.0g of distilled water, 10.0g of zirconium dioxide carrier was added, the mixture was placed in a 40kHz ultrasonic oscillator, stirred at 80 ℃ for 10 hours, dried at 110 ℃ for 12 hours, and calcined at 500 ℃ in a muffle furnace for 4 hours to obtain a supported solid base catalyst.

(2) Preparation of alkoxy-terminated polydimethylsiloxane: same as in example 1.

Adding 2% of tetraisopropyl titanate into the target product, observing an obvious viscosity peak phenomenon, and judging that the end capping effect is poor. The end capping rate of the hydroxyl silicone oil was calculated to be 59.9% by measuring the hydroxyl content before and after the reaction.

Comparative example 2: the calcination temperature in the catalyst preparation process is out of the scope of the invention

(1) Preparation of solid base catalyst

2.0g of potassium nitrate was dissolved in 20.0g of distilled water, 10.0g of silica carrier was added, the mixture was placed in an ultrasonic oscillator of 40kHz, stirred at 80 ℃ for 10 hours, dried at 110 ℃ for 12 hours, and calcined at 300 ℃ for 4 hours in a muffle furnace to obtain a supported solid base catalyst.

(2) Preparation of alkoxy-terminated polydimethylsiloxane: same as in example 1.

Adding 2% of tetraisopropyl titanate into the target product, observing an obvious viscosity peak phenomenon, and judging that the end capping effect is poor. The end capping rate of the hydroxyl silicone oil was calculated to be 62.4% by measuring the hydroxyl content before and after the reaction.

Comparative example 3: the temperature at which the intermediate alkoxy-terminated polydimethylsiloxane is prepared is outside the scope of the invention

(1) Preparation of solid base catalyst: same as in example 1.

(2) Preparation of alkoxy-terminated polydimethylsiloxane

The method comprises the following steps: adding hydroxyl silicone oil (m) according to the molar ratio of the hydroxyl silicone oil to the end-capping agent of 1:6 respectively₁8) and methyltrimethoxysilane, stirring and heating to 40 ℃, adding the solid base catalyst accounting for 1.0 percent of the total mass of the raw materials, starting reaction under the protection of nitrogen, filtering after the reaction is finished, and removing low-boiling-point substances (2h) under the conditions that the temperature is 130 ℃ and the vacuum degree is-0.095 MPa to prepare an alkoxy end-capped polydimethylsiloxane intermediate product;

step two: same as in example 1.

Adding 2% of tetraisopropyl titanate into the target product, observing an obvious viscosity peak phenomenon, and judging that the end capping effect is poor. The end capping rate of the hydroxyl silicone oil was calculated to be 65.3% by measuring the hydroxyl content before and after the reaction.

Comparative example 4: the amount of catalyst used in the preparation of the alkoxy-terminated polydimethylsiloxane intermediate is outside the scope of the invention

(1) Preparation of solid base catalyst: same as in example 1.

(2) Preparation of alkoxy-terminated polydimethylsiloxane

The method comprises the following steps: adding hydroxyl silicone oil (m) according to the molar ratio of the hydroxyl silicone oil to the end-capping agent of 1:6₁8) and methyltrimethoxysilane, stirring and heating to 60 ℃, adding the solid base catalyst accounting for 2.0 percent of the total mass of the raw materials, starting reaction under the protection of nitrogen, filtering after the reaction is finished, and removing low-boiling-point substances (2h) under the conditions that the temperature is 135 ℃ and the vacuum degree is-0.095 MPa to prepare an alkoxy end-capped polydimethylsiloxane intermediate product;

step two: same as in example 1.

Adding 2% of tetraisopropyl titanate into the target product, observing an obvious viscosity peak phenomenon, and judging that the end capping effect is poor. The end capping rate of the hydroxyl silicone oil was calculated to be 69.9% by measuring the hydroxyl content before and after the reaction.

Comparative example 5: using unsupported potassium hydroxide as catalyst

The method comprises the following steps: adding hydroxyl silicone oil (m) according to the molar ratio of the hydroxyl silicone oil to the end-capping agent of 1:6₁= 8) and methyltrimethoxysilane, stirring and heating to 80 ℃, adding potassium hydroxide which accounts for 0.7% of the total mass of the raw materials as a catalyst, starting the reaction under the protection of nitrogen, adding 1.0% of phosphoric acid into the system after the reaction is finished for neutralization, filtering, and removing low-boiling-point substances (2h) under the conditions that the temperature is 135 ℃ and the vacuum degree is-0.095 MPa to obtain an alkoxy end-blocked polydimethylsiloxane intermediate product;

step two: adding octamethylcyclotetrasiloxane to the intermediate product of alkoxy-terminated polydimethylsiloxane prepared in the step I, wherein the molar ratio of the intermediate product of alkoxy-terminated polydimethylsiloxane to octamethylcyclotetrasiloxane is 1:25, adding a potassium hydroxide catalyst accounting for 0.7% of the total mass of the raw materials into the system, carrying out polymerization reaction at 110 ℃, adding 1.0% of phosphoric acid for neutralization after the reaction is finished, filtering, removing low-boiling-point substances (3h) under the conditions that the temperature is 150 ℃ and the vacuum degree is-0.09 MPa, and preparing the target product of alkoxy-terminated polydimethylsiloxane (m₂＝110)。

2% tetraisopropyl titanate was added to the target product, and a weak "viscosity peak" phenomenon was observed, and it was judged that a small amount of unreacted silicon hydroxyl group remained in the product. The end capping rate of the hydroxyl silicone oil was calculated to be 78.4% by measuring the hydroxyl content before and after the reaction.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.