Amino-modified polysiloxane gum and method for producing the same

Abstract

The application discloses an amino-modified polysiloxane gum and a preparation method thereof, and belongs to the technical field of silicone materials. The amino-modified polysiloxane gum is prepared by anionic ring-opening equilibrium polymerization of a trimethylsiloxy-terminated side-chain amino silicone oil and a cyclic siloxane monomer. The preparation method comprises two steps: firstly, a hydrolysis reaction is carried out by mixing a first cyclic siloxane monomer, an amino silane coupling agent, an end-capping agent and water, and a trimethylsiloxy-terminated side-chain amino silicone oil is obtained through first anionic ring-opening equilibrium polymerization and post-treatment; and secondly, the side-chain amino silicone oil is mixed with a second cyclic siloxane monomer, and a target amino-modified polysiloxane gum is obtained through second anionic ring-opening equilibrium polymerization and post-treatment. The amino component is introduced in stages, and the polysiloxane main chain is further polymerized, so that the amino-modified polysiloxane gum with a relatively high viscosity-average molecular weight and different amine values can be obtained.

Description

Technical Field

[0001] This invention relates to the field of organosilicon materials technology, and in particular to an amino-modified polysiloxane raw rubber and its preparation method. Background Technology

[0002] Amino-modified polysiloxanes combine the flexibility, weather resistance, and low surface energy of organosilicon backbones with the reactivity and interfacial affinity of amino groups, making them suitable for applications in textile finishing, organosilicon elastomers, polymer interface modification, coatings, and related auxiliaries. When amino-modified polysiloxanes are used as raw rubber, their molecular weight, amine value, and end-group structure affect subsequent processing performance and final material properties. Therefore, the introduction of amino segments, the formation of end-group structures, and the growth of the polysiloxane backbone must be carefully considered during preparation.

[0003] Existing amino-modified polysiloxanes are typically prepared through alkaline-catalyzed equilibrium polymerization involving cyclic siloxanes, aminosilane coupling agents, and end-capping agents. In this process, the alkoxy groups in the aminosilane coupling agent can undergo hydrolysis and condensation, and may participate in the end-capping process. This causes the introduction of amino segments, the formation of end groups, and the growth of the polysiloxane backbone to occur simultaneously, with all three influencing each other. When a higher molecular weight amino-modified polysiloxane raw rubber is desired, the control of the polymerization process becomes correspondingly more difficult.

[0004] Patent CN115449079A discloses a method for preparing amino silicone oil. This method uses a mixture of dimethylsiloxanes as starting material, adds a catalyst, water, and a silane coupling agent, and obtains amino silicone oil through a heated reaction, vacuum descaling, and subsequent heated reactions, all under nitrogen protection. This method mainly focuses on the process design for preparing amino silicone oil and controlling the viscosity and amine value of the resulting product. Its preparation targets and reaction control methods differ from those for preparing high molecular weight amino-modified polysiloxane raw rubber, and it does not address the staged adjustment of the relationship between the introduction of amino chain segments, the formation of end-group structures, and the growth of the polysiloxane backbone.

[0005] Patent CN104530434A discloses an organosilicon polymer and its synthesis method. This technology involves the synthesis of organosilicon polymers, and the reaction process includes the reaction between an organosilicon component containing epoxy groups and an amino component. Patent CN112646189A discloses a method for synthesizing amino-modified organosilicon polymers. This method first removes low-boiling substances from terminal hydroxyl oligosiloxanes under vacuum, and then performs a condensation reaction between the treated terminal hydroxyl oligosiloxanes and aminosilane monomers to obtain amino-modified organosilicon polymers. Although the above technologies all involve the preparation of amino-containing organosilicon polymers, their amino introduction methods and polymerization reaction pathways differ from the process of preparing amino-modified polysiloxane raw rubber by anionic ring-opening equilibrium polymerization of cyclic siloxanes. They do not address the coordinated control between amino chain segment introduction, end group structure formation, and the continuous growth of the polysiloxane backbone.

[0006] Therefore, how to coordinate the relationship between the introduction of amino repeating units, the formation of end groups and the growth of the polysiloxane backbone, and obtain amino-modified polysiloxane raw rubber with high molecular weight while introducing amino repeating units, has become an urgent problem to be solved. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the technical problem this invention aims to solve is to provide an amino-modified polysiloxane raw rubber and its preparation method, thereby obtaining a high molecular weight amino-modified polysiloxane raw rubber while introducing amino linkages. To solve the above-mentioned technical problem, this invention provides the following technical solution: A first aspect of the present invention relates to a method for preparing amino-modified polysiloxane raw rubber, comprising the following steps: S1. The first cyclic siloxane monomer, aminosilane coupling agent, end-capping agent and water are mixed and subjected to hydrolysis reaction; after removing the low molecular weight by-products generated by the hydrolysis reaction, the first anionic ring-opening equilibrium polymerization is carried out under the action of the first alkaline catalyst; the first alkaline catalyst is deactivated and the low molecular weight by-products are removed under vacuum to obtain trimethylsiloxy-terminated side-chain aminosilicone oil. S2. Under anhydrous conditions, the trimethylsiloxy-terminated side-chain amino silicone oil is mixed with a second cyclic siloxane monomer, and a second anionic ring-opening equilibrium polymerization is carried out under the action of a second alkaline catalyst; the second alkaline catalyst is deactivated and low-molecular-weight byproducts are removed under vacuum to obtain amino-modified polysiloxane raw rubber.

[0008] Further, in step S1, based on a total mass of 100 parts by weight of the first cyclic siloxane monomer and the aminosilane coupling agent, the amount of the aminosilane coupling agent added is 20 to 56 parts by weight, the amount of the end-capping agent added is 7.5 to 11.5 parts by weight, and the amount of water added is 4 to 11 parts by weight.

[0009] Further, in step S1, the hydrolysis reaction temperature is 60–80°C, and the reaction time is 1–3 hours; after the hydrolysis reaction is completed, water, alcohols, and other low-molecular-weight byproducts are removed at 100–120°C under inert gas purging conditions for 1–3 hours; then the reaction system is cooled to below 50°C, the first alkaline catalyst is added, and the first anionic ring-opening equilibrium polymerization is carried out under an inert atmosphere for 3–5 hours; after the first alkaline catalyst is deactivated, low-molecular-weight byproducts are removed under vacuum at 180–190°C and a vacuum gauge pressure of -0.100 to -0.098 MPa for 1–2 hours.

[0010] Furthermore, the first cyclic siloxane monomer is octamethylcyclotetrasiloxane; The aminosilane coupling agent is selected from one of 3-aminopropylmethyldiethoxysilane and 3-aminopropylmethyldimethoxysilane; The end-capping agent is trimethylsiloxy-terminated dimethyl silicone oil, and the average degree of polymerization of the trimethylsiloxy-terminated dimethyl silicone oil is 30-50. The first alkaline catalyst is selected from one of tetramethylammonium hydroxide, tetramethylammonium siloxane, potassium hydroxide, and potassium siloxane.

[0011] Furthermore, based on a total mass of 100 parts by weight of the first cyclic siloxane monomer and the aminosilane coupling agent, the amount of the first alkaline catalyst added is 0.25 parts by weight. When the first alkaline catalyst is tetramethylammonium hydroxide or tetramethylammonium siloxane, the temperature of the first anionic ring-opening equilibrium polymerization is 100-120°C, and after the polymerization reaction is completed, it is treated at 140-160°C for 1-2 hours. When the first alkaline catalyst is potassium hydroxide or potassium siloxaneol, the temperature of the first anionic ring-opening equilibrium polymerization is 130-140°C. After the polymerization reaction is completed, a neutralizing agent is added for neutralization treatment for 2 hours. The neutralizing agent is selected from one or more of acetic acid, phosphoric acid and organic phosphate esters.

[0012] Further, in step S2, based on a total mass of 100 parts by weight of the second cyclic siloxane monomer and the trimethylsiloxy-terminated side-chain amino silicone oil, the amount of the trimethylsiloxy-terminated side-chain amino silicone oil added is 1.0 to 4.0 parts by weight, and the amount of the second alkaline catalyst added is 0.25 to 0.4 parts by weight.

[0013] Furthermore, the second cyclic siloxane monomer is octamethylcyclotetrasiloxane; The second alkaline catalyst is selected from one of tetramethylammonium hydroxide, tetramethylammonium siloxane, potassium hydroxide, and potassium siloxane.

[0014] Further, in step S2, the second anionic ring-opening equilibrium polymerization time is 5-7 hours; after the polymerization reaction is completed, the second alkaline catalyst is deactivated by heating or adding a neutralizing agent, and low molecular weight byproducts are removed under vacuum at 180-190°C and a vacuum gauge pressure of -0.100 to -0.098 MPa for 2-5 hours; after the low molecular weight byproducts are removed under vacuum, the product is cooled to below 40°C and pressure filtered.

[0015] Furthermore, when the second alkaline catalyst is tetramethylammonium hydroxide or tetramethylammonium siloxane, the temperature of the second anionic ring-opening equilibrium polymerization is 100-120°C, and after the polymerization reaction is completed, it is treated at 140-160°C for 1-2 hours. When the second alkaline catalyst is potassium hydroxide or potassium siloxane ol, the temperature of the second anionic ring-opening equilibrium polymerization is 130-140°C. After the polymerization reaction is completed, a neutralizing agent is added for neutralization treatment for 2-3 hours. The neutralizing agent is selected from one or more of acetic acid, phosphoric acid and organic phosphate esters.

[0016] A second aspect of the present invention relates to an amino-modified polysiloxane raw rubber, which is prepared by any of the above-described methods for preparing amino-modified polysiloxane raw rubber. The amino-modified polysiloxane raw rubber has a viscosity-average molecular weight of 320,000 to 490,000 and an amine value of 1.06 to 3.58 mg KOH / g.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) In this invention, trimethylsiloxy-terminated side-chain amino silicone oil is first prepared by hydrolysis, first anionic ring-opening equilibrium polymerization, catalyst deactivation, and vacuum desaturation. Then, the side-chain amino silicone oil is subjected to second anionic ring-opening equilibrium polymerization with a second cyclic siloxane monomer. This allows the introduction of amino segments and the further growth of the polysiloxane backbone to proceed in stages, avoiding the direct addition of free amino silane coupling agents in the second stage. Compared with a single-feed process, the two-stage process is beneficial for obtaining amino-modified polysiloxane raw rubber with a higher viscosity-average molecular weight.

[0018] (2) The present invention can adjust the viscosity-average molecular weight and amine value of the obtained amino-modified polysiloxane raw rubber by adjusting the composition of the side-chain amino silicone oil and its addition amount in the second anionic ring-opening equilibrium polymerization, thereby improving the degree of freedom in controlling molecular weight and amino content, so as to meet the requirements of different application scenarios for molecular weight and amino content. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the process flow for preparing an amino-modified polysiloxane raw rubber according to the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be described more clearly and completely below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0021] This invention provides a method for preparing amino-modified polysiloxane raw rubber, comprising the following steps: S1. The first cyclic siloxane monomer, aminosilane coupling agent, end-capping agent and water are mixed and subjected to hydrolysis reaction; after removing the low molecular weight by-products generated by the hydrolysis reaction, the first anionic ring-opening equilibrium polymerization is carried out under the action of the first alkaline catalyst; the first alkaline catalyst is deactivated and the low molecular weight by-products are removed under vacuum to obtain trimethylsiloxy-terminated side-chain aminosilicone oil. S2. Under anhydrous conditions, the trimethylsiloxy-terminated side-chain amino silicone oil is mixed with a second cyclic siloxane monomer, and a second anionic ring-opening equilibrium polymerization is carried out under the action of a second alkaline catalyst; the second alkaline catalyst is deactivated and low-molecular-weight byproducts are removed under vacuum to obtain amino-modified polysiloxane raw rubber.

[0022] Specifically, the "anhydrous conditions" referred to in this invention mean that all raw materials are dried before use, with a water content of less than 30 ppm, and the reaction is carried out under the protection of a dry inert gas.

[0023] In one possible implementation, in step S1, based on a total mass of 100 parts by weight of the first cyclic siloxane monomer and the aminosilane coupling agent, the amount of the aminosilane coupling agent added is 20 to 56 parts by weight, the amount of the end-capping agent added is 7.5 to 11.5 parts by weight, and the amount of water added is 4 to 11 parts by weight.

[0024] In one possible implementation, in step S1, the hydrolysis reaction is carried out at a temperature of 60–80°C for 1–3 hours. After the hydrolysis reaction is completed, water, alcohols, and other low-molecular-weight byproducts are removed at 100–120°C under inert gas purging conditions for 1–3 hours. Subsequently, the reaction system is cooled to below 50°C, the first alkaline catalyst is added, and the first anionic ring-opening equilibrium polymerization is carried out under an inert atmosphere for 3–5 hours. After the first alkaline catalyst is deactivated, low-molecular-weight byproducts are removed under vacuum at 180–190°C and a vacuum gauge pressure of -0.100 to -0.098 MPa for 1–2 hours.

[0025] In one possible implementation, the first cyclic siloxane monomer is octamethylcyclotetrasiloxane; The aminosilane coupling agent is selected from one of 3-aminopropylmethyldiethoxysilane and 3-aminopropylmethyldimethoxysilane; The capping agent is trimethylsiloxy-terminated dimethyl silicone oil, and the average degree of polymerization of the trimethylsiloxy-terminated dimethyl silicone oil is 30-50; in specific implementation, trimethylsiloxy-terminated dimethyl silicone oil with an average degree of polymerization of 40 is preferably used.

[0026] The first alkaline catalyst is selected from one of tetramethylammonium hydroxide, tetramethylammonium siloxane, potassium hydroxide, and potassium siloxane.

[0027] In one possible implementation, the amount of the first alkaline catalyst added is 0.25 parts by weight, based on a total mass of 100 parts by weight of the first cyclic siloxane monomer and the aminosilane coupling agent. When the first alkaline catalyst is tetramethylammonium hydroxide or tetramethylammonium siloxane, the temperature of the first anionic ring-opening equilibrium polymerization is 100-120°C, and after the polymerization reaction is completed, it is treated at 140-160°C for 1-2 hours. When the first alkaline catalyst is potassium hydroxide or potassium siloxaneol, the temperature of the first anionic ring-opening equilibrium polymerization is 130-140°C. After the polymerization reaction is completed, a neutralizing agent is added for neutralization treatment for 2 hours. The neutralizing agent is selected from one or more of acetic acid, phosphoric acid and organic phosphate esters.

[0028] In one possible implementation, in step S2, based on a total mass of 100 parts by weight of the second cyclic siloxane monomer and the trimethylsiloxy-terminated side-chain amino silicone oil, the amount of the trimethylsiloxy-terminated side-chain amino silicone oil added is 1.0 to 4.0 parts by weight, and the amount of the second alkaline catalyst added is 0.25 to 0.4 parts by weight.

[0029] In one possible implementation, the second cyclic siloxane monomer is octamethylcyclotetrasiloxane; The second alkaline catalyst is selected from one of tetramethylammonium hydroxide, tetramethylammonium siloxane, potassium hydroxide, and potassium siloxane.

[0030] In one possible implementation, in step S2, the second anionic ring-opening equilibrium polymerization time is 5 to 7 hours; after the polymerization reaction is completed, the second alkaline catalyst is deactivated by heating or adding a neutralizing agent, and low molecular weight byproducts are removed under vacuum at 180 to 190°C and a vacuum gauge pressure of -0.100 to -0.098 MPa for 2 to 5 hours; after the low molecular weight byproducts are removed under vacuum, the product is cooled to below 40°C and pressure filtered.

[0031] In one possible implementation, when the second alkaline catalyst is tetramethylammonium hydroxide or tetramethylammonium siloxane, the temperature of the second anionic ring-opening equilibrium polymerization is 100-120°C, and after the polymerization reaction is completed, it is treated at 140-160°C for 1-2 hours. When the second alkaline catalyst is potassium hydroxide or potassium siloxane ol, the temperature of the second anionic ring-opening equilibrium polymerization is 130-140°C. After the polymerization reaction is completed, a neutralizing agent is added for neutralization treatment for 2-3 hours. The neutralizing agent is selected from one or more of acetic acid, phosphoric acid and organic phosphate esters.

[0032] This invention provides an amino-modified polysiloxane raw rubber, which is prepared by any of the above-mentioned methods for preparing amino-modified polysiloxane raw rubber; The amino-modified polysiloxane raw rubber has a viscosity-average molecular weight of 320,000 to 490,000 and an amine value of 1.06 to 3.58 mg KOH / g.

[0033] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0034] Example 1: Please refer to Figure 1 This embodiment provides a method for preparing amino-modified polysiloxane raw rubber.

[0035] Step S1: Based on a total mass of 100 parts by weight of octamethylcyclotetrasiloxane and 3-aminopropylmethyldiethoxysilane, 28 parts by weight of 3-aminopropylmethyldiethoxysilane, 11 parts by weight of trimethylsiloxy-terminated dimethyl silicone oil with an average degree of polymerization of 40, and 6 parts by weight of water, the above raw materials are mixed and hydrolyzed at 60°C for 1 hour. Nitrogen gas is then introduced, and the temperature is raised to 110°C to remove water and low-molecular-weight substances such as ethanol, and maintained for 1 hour until no significant low-molecular-weight substances are distilled off.

[0036] The system was cooled to 50°C, and 0.25 parts by weight of potassium siloxaneol were added. The first anionic ring-opening equilibrium polymerization was carried out at 140°C for 4 hours under a nitrogen atmosphere. After polymerization, an organophosphate neutralizing agent was added and neutralized for 2 hours. Subsequently, vacuum desaturation was performed at 180°C and a vacuum gauge pressure of -0.098 MPa for 2 hours. The mixture was cooled and filtered to obtain trimethylsiloxy-terminated side-chain amino silicone oil.

[0037] Step S2: Based on a total mass of 100 parts by weight of octamethylcyclotetrasiloxane and the above-mentioned side-chain amino silicone oil, the side-chain amino silicone oil comprises 2.5 parts by weight, and the potassium siloxane alkoxide comprises 0.25 parts by weight. Under conditions of drying and nitrogen protection, a second anionic ring-opening equilibrium polymerization was carried out at 140°C for 6 hours. After polymerization, an organophosphate neutralizing agent was added and neutralized for 2 hours; subsequently, vacuum depressurization was performed at 180°C and a vacuum gauge pressure of -0.098 MPa for 3 hours. The mixture was then cooled to below 40°C and filtered to obtain amino-modified polysiloxane raw rubber.

[0038] Example 2: The raw material ratio, hydrolysis, and conditions for removing water and low-molecular-weight alcohols in step S1 are the same as in Example 1. The system was cooled to 50°C, and 0.25 parts by weight of tetramethylammonium siloxane alcohol was added. The first anionic ring-opening equilibrium polymerization was carried out at 110°C for 4 hours under a nitrogen atmosphere. After the polymerization was completed, the temperature was raised to 150°C and held for 1 hour to thermally deactivate the catalyst. Subsequently, the catalyst was vacuum deactivated at 180°C and a vacuum gauge pressure of -0.098 MPa for 2 hours to obtain side-chain amino silicone oil.

[0039] In step S2, based on a total mass of 100 parts by weight of octamethylcyclotetrasiloxane and the aforementioned side-chain amino silicone oil, the side-chain amino silicone oil comprises 2.5 parts by weight, and the siloxane alcohol tetramethylammonium comprises 0.25 parts by weight. Under conditions of drying and nitrogen protection, the raw materials undergo a second anionic ring-opening equilibrium polymerization at 110°C for 6 hours. After polymerization, the temperature is raised to 150°C and maintained for 1 hour to thermally deactivate the catalyst. Subsequently, the catalyst is vacuum depressurized at 180°C and a vacuum gauge pressure of -0.098 MPa for 3 hours, cooled, and filtered to obtain amino-modified polysiloxane raw rubber.

[0040] Example 3: Step S1 uses the same raw material ratio and reaction conditions as in Example 2 to prepare side-chain amino silicone oil. In step S2, based on a total mass of 100 parts by weight of octamethylcyclotetrasiloxane and the side-chain amino silicone oil, the side-chain amino silicone oil is 2.5 parts by weight, and potassium siloxane alkoxide is 0.25 parts by weight. Under the conditions of drying the raw materials and nitrogen protection, the second anionic ring-opening equilibrium polymerization is carried out at 140°C for 6 hours, neutralized with organophosphate ester for 2 hours, and then vacuum depressurized at 180°C and a vacuum gauge pressure of -0.098 MPa for 3 hours to obtain amino-modified polysiloxane raw rubber.

[0041] Example 4: Step S1 uses the same raw material ratio and reaction conditions as in Example 1 to prepare side-chain amino silicone oil. In step S2, based on a total mass of 100 parts by weight of octamethylcyclotetrasiloxane and the side-chain amino silicone oil, the side-chain amino silicone oil is 2.5 parts by weight and the siloxane alcohol tetramethylammonium is 0.25 parts by weight. Under the conditions of drying the raw materials and nitrogen protection, a second anionic ring-opening equilibrium polymerization is carried out at 110°C for 6 hours. After the polymerization is completed, it is treated at 150°C for 1 hour, and then vacuum depressurized at 180°C and a vacuum gauge pressure of -0.098 MPa for 3 hours to obtain amino-modified polysiloxane raw rubber.

[0042] Example 5: It is basically the same as Example 3, except that the amount of side-chain amino silicone oil added in step S2 is 1.0 parts by weight.

[0043] Example 6: It is basically the same as Example 4, except that the amount of side-chain amino silicone oil added in step S2 is 4.0 parts by weight.

[0044] Example 7: The method is basically the same as in Example 1, except that in step S1, 20 parts by weight of 3-aminopropylmethyldiethoxysilane, 11.5 parts by weight of trimethylsiloxy-terminated dimethyl silicone oil with an average degree of polymerization of 40, and 4 parts by weight of water are used; and in step S2, 3.5 parts by weight of side-chain amino silicone oil are added.

[0045] Example 8: The method is basically the same as in Example 1, except that in step S1, 3-aminopropylmethyldiethoxysilane is 56 parts by weight, trimethylsiloxy-terminated dimethyl silicone oil with an average degree of polymerization of 40 is 7.5 parts by weight, and water is 11 parts by weight; in step S2, the amount of side-chain amino silicone oil added is 1.1 parts by weight.

[0046] Example 9: It is basically the same as Example 2, except that the amount of siloxane alcohol tetramethylammonium added in step S2 is 0.4 parts by weight.

[0047] Comparative Example 1: It is basically the same as Example 1, except that the amount of potassium siloxane ol added in step S2 is 0.1 parts by weight.

[0048] Comparative Example 2: It is basically the same as Example 1, except that the polymerization reaction in step S2 is not kept in an inert atmosphere throughout.

[0049] Comparative Example 3: Amino-modified polysiloxanes were prepared using a one-step feeding method. Based on a total mass of 100 parts by weight of octamethylcyclotetrasiloxane and 3-aminopropylmethyldiethoxysilane, 0.77 parts by weight of 3-aminopropylmethyldiethoxysilane, 0.8 parts by weight of trimethylsiloxy-terminated dimethyl silicone oil with an average degree of polymerization of 40, and 0.25 parts by weight of potassium siloxane alkoxide. The feeding weights of 3-aminopropylmethyldiethoxysilane and trimethylsiloxy-terminated dimethyl silicone oil with an average degree of polymerization of 40 were determined by converting the theoretical equivalent of the amino groups and the theoretical equivalent of the effective end-capping groups corresponding to the 2.5 parts by weight of side-chain amino silicone oil in step S2 of Example 1, ensuring that the amount of amino groups introduced and the amount of effective end-capping groups are essentially equivalent.

[0050] The raw materials were mixed and reacted at 140°C for 6 hours under a nitrogen atmosphere. The mixture was then neutralized with an organophosphate for 2 hours and vacuum de-lowered at 180°C and a vacuum gauge pressure of -0.098 MPa for 3 hours to obtain the comparative product.

[0051] Comparative Example 4: Amino-modified polysiloxanes were prepared using a one-step feeding method. Based on a total mass of 100 parts by weight of octamethylcyclotetrasiloxane and 3-aminopropylmethyldiethoxysilane, 0.77 parts by weight of 3-aminopropylmethyldiethoxysilane, 0.8 parts by weight of trimethylsiloxy-terminated dimethyl silicone oil with an average degree of polymerization of 40, and 0.25 parts by weight of tetramethylammonium siloxane alcohol. The feeding weights of 3-aminopropylmethyldiethoxysilane and trimethylsiloxy-terminated dimethyl silicone oil with an average degree of polymerization of 40 were determined by converting the theoretical equivalent of the amino groups and the theoretical equivalent of the effective end-capping groups corresponding to the 2.5 parts by weight of side-chain amino silicone oil in step S2 of Example 2, ensuring that the amount of amino groups introduced and the amount of effective end-capping groups are essentially equivalent.

[0052] The raw materials were mixed and reacted at 110°C for 6 hours under a nitrogen atmosphere. The temperature was then raised to 150°C for 1 hour to thermally deactivate the catalyst. Finally, the catalyst was deactivated under vacuum at 180°C and a vacuum gauge pressure of -0.098 MPa for 3 hours to obtain the comparative product.

[0053] Performance testing methods: (1) Viscosity-average molecular weight: The dilute solution capillary viscosity method was used, and the determination was carried out in accordance with GB / T 1632.1-2024. The test temperature was 25℃, and the solvent was carbon tetrachloride. Four to five groups of dilute solutions of different concentrations were prepared, and the outflow time of pure solvent and solutions of each concentration through the Ubbelohde capillary viscometer was measured. Each group was measured in parallel three times and the average value was taken. The relative viscosity and specific viscosity of each concentration of sample solution were calculated based on the outflow time. The intrinsic viscosity of the sample was obtained by linear extrapolation according to the Huggins relationship, and the viscosity-average molecular weight was calculated according to the Mark-Houwink relationship. The same test conditions and parameters were used for calculation in all examples and comparative examples.

[0054] (2) Amine value: Accurately weigh a quantitative amount of amino gum sample, dissolve it in anhydrous ethanol-carbon tetrachloride mixed solvent, stir thoroughly until completely dissolved, use bromophenol blue as an indicator, and titrate with standard hydrochloric acid solution. Record the volume of acid consumed in the titration and the amine value of the sample. Calculate according to the following formula: ; In the formula, This is the amine value, expressed in mg KOH / g. The volume of hydrochloric acid standard solution consumed in the titration of the sample is expressed in mL. The volume of hydrochloric acid standard solution consumed in the blank test, in mL; This represents the concentration of the hydrochloric acid standard solution, in mol / L. The value represents the sample mass in grams; 56.11 is the molar mass conversion factor for potassium hydroxide. Each sample was measured in triplicate, and the average of the three measurements was taken.

[0055] (3) Small molecule cyclic residue test: The residual amounts of D4, D5 and D6 small molecule cyclic siloxanes in the samples were detected by gas chromatography. Acetone was used as the extraction solvent, and the content of small molecule cyclic residues in each sample was quantitatively analyzed.

[0056] The test results for each embodiment and comparative example are shown in Table 1.

[0057] Table 1 As shown in Table 1, the products obtained in Examples 1 to 9 were all clear and transparent amino-modified polysiloxane raw rubbers with a viscosity-average molecular weight of 321,443 to 488,455 and an amine value of 1.06 to 3.58 mg KOH / g. The individual residual amounts of D4, D5, and D6 in each example were all below 3000 mg / kg.

[0058] In Comparative Example 1, after reducing the second alkaline catalyst to 0.1 parts by weight, the viscosity-average molecular weight of the resulting product decreased to 269025, indicating that too low a catalyst dosage is not conducive to obtaining the target high molecular weight product.

[0059] Comparative Example 2 did not maintain an inert atmosphere throughout the second stage, resulting in a slightly whitish product, indicating that a dry, inert atmosphere is beneficial for improving the product's appearance stability. Comparative Examples 3 and 4 used a single-feed method, yielding products with viscosity-average molecular weights of 53870 and 51539, respectively, significantly lower than those obtained using the two-stage method. Under the raw material composition and reaction conditions used in this invention, the above results demonstrate that the process arrangement of first preparing side-chain amino silicone oil and then further participating in the second anionic ring-opening equilibrium polymerization is beneficial for obtaining amino-modified polysiloxane raw rubber with a higher viscosity-average molecular weight.

[0060] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A method for preparing amino-modified polysiloxane raw rubber, characterized in that, Includes the following steps: S1. The first cyclic siloxane monomer, aminosilane coupling agent, end-capping agent and water are mixed and subjected to hydrolysis reaction; after removing the low molecular weight byproducts generated by the hydrolysis reaction, the first anionic ring-opening equilibrium polymerization is carried out under the action of the first alkaline catalyst. The first alkaline catalyst was deactivated and low-molecular-weight byproducts were removed under vacuum to obtain trimethylsiloxy-terminated side-chain amino silicone oil. S2. Under anhydrous conditions, the trimethylsiloxy-terminated side-chain amino silicone oil is mixed with a second cyclic siloxane monomer, and a second anionic ring-opening equilibrium polymerization is carried out under the action of a second alkaline catalyst; the second alkaline catalyst is deactivated and low-molecular-weight byproducts are removed under vacuum to obtain amino-modified polysiloxane raw rubber.

2. The method for preparing amino-modified polysiloxane raw rubber according to claim 1, characterized in that, In step S1, based on a total mass of 100 parts by weight of the first cyclic siloxane monomer and the aminosilane coupling agent, the amount of the aminosilane coupling agent added is 20 to 56 parts by weight, the amount of the end-capping agent added is 7.5 to 11.5 parts by weight, and the amount of water added is 4 to 11 parts by weight.

3. The method for preparing amino-modified polysiloxane raw rubber according to claim 1, characterized in that, In step S1, the hydrolysis reaction is carried out at a temperature of 60–80°C for 1–3 hours. After the hydrolysis reaction is completed, water, alcohols, and other low-molecular-weight byproducts are removed at 100–120°C under inert gas purging conditions for 1–3 hours. Subsequently, the reaction system is cooled to below 50°C, the first alkaline catalyst is added, and the first anionic ring-opening equilibrium polymerization is carried out under an inert atmosphere for 3–5 hours. After the first alkaline catalyst is deactivated, low-molecular-weight byproducts are removed under vacuum at 180–190°C and a vacuum gauge pressure of -0.100 to -0.098 MPa for 1–2 hours.

4. The method for preparing amino-modified polysiloxane raw rubber according to claim 1, characterized in that: The first cyclic siloxane monomer is octamethylcyclotetrasiloxane; The aminosilane coupling agent is selected from one of 3-aminopropylmethyldiethoxysilane and 3-aminopropylmethyldimethoxysilane; The end-capping agent is trimethylsiloxy-terminated dimethyl silicone oil, and the average degree of polymerization of the trimethylsiloxy-terminated dimethyl silicone oil is 30-50. The first alkaline catalyst is selected from one of tetramethylammonium hydroxide, tetramethylammonium siloxane, potassium hydroxide, and potassium siloxane.

5. The method for preparing amino-modified polysiloxane raw rubber according to claim 4, characterized in that, Based on a total mass of 100 parts by weight of the first cyclic siloxane monomer and the aminosilane coupling agent, the amount of the first alkaline catalyst added is 0.25 parts by weight. When the first alkaline catalyst is tetramethylammonium hydroxide or tetramethylammonium siloxane, the temperature of the first anionic ring-opening equilibrium polymerization is 100-120°C, and after the polymerization reaction is completed, it is treated at 140-160°C for 1-2 hours. When the first alkaline catalyst is potassium hydroxide or potassium siloxane ol, the temperature of the first anionic ring-opening equilibrium polymerization is 130-140°C. After the polymerization reaction is completed, a neutralizing agent is added for neutralization treatment for 2 hours. The neutralizing agent is selected from one or more of acetic acid, phosphoric acid and organic phosphate esters.

6. The method for preparing amino-modified polysiloxane raw rubber according to claim 1, characterized in that: In step S2, based on a total mass of 100 parts by weight of the second cyclic siloxane monomer and the trimethylsiloxy-terminated side-chain amino silicone oil, the amount of the trimethylsiloxy-terminated side-chain amino silicone oil added is 1.0 to 4.0 parts by weight, and the amount of the second alkaline catalyst added is 0.25 to 0.4 parts by weight.

7. The method for preparing amino-modified polysiloxane raw rubber according to claim 6, characterized in that: The second cyclic siloxane monomer is octamethylcyclotetrasiloxane; The second alkaline catalyst is selected from one of tetramethylammonium hydroxide, tetramethylammonium siloxane, potassium hydroxide, and potassium siloxane.

8. The method for preparing amino-modified polysiloxane raw rubber according to claim 7, characterized in that: In step S2, the second anionic ring-opening equilibrium polymerization time is 5-7 hours. After the polymerization reaction is completed, the second alkaline catalyst is deactivated by heating or adding a neutralizing agent, and low molecular weight byproducts are removed under vacuum at 180-190°C and a vacuum gauge pressure of -0.100 to -0.098 MPa for 2-5 hours. After the low molecular weight byproducts are removed under vacuum, the product is cooled to below 40°C and pressure filtered.

9. The method for preparing amino-modified polysiloxane raw rubber according to claim 8, characterized in that: When the second alkaline catalyst is tetramethylammonium hydroxide or tetramethylammonium siloxane, the temperature of the second anionic ring-opening equilibrium polymerization is 100-120°C, and after the polymerization reaction is completed, it is treated at 140-160°C for 1-2 hours. When the second alkaline catalyst is potassium hydroxide or potassium siloxane ol, the temperature of the second anionic ring-opening equilibrium polymerization is 130-140°C. After the polymerization reaction is completed, a neutralizing agent is added for neutralization treatment for 2-3 hours. The neutralizing agent is selected from one or more of acetic acid, phosphoric acid and organic phosphate esters.

10. An amino-modified polysiloxane raw rubber, characterized in that, It is prepared by the method for preparing amino-modified polysiloxane raw rubber according to any one of claims 1 to 9; The amino-modified polysiloxane raw rubber has a viscosity-average molecular weight of 320,000 to 490,000 and an amine value of 1.06 to 3.58 mg KOH / g.

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