Bi-component addition type liquid silicone rubber composition as well as preparation method and application thereof

Abstract

The invention discloses a bi-component addition type liquid silicone rubber composition and a preparation method and application thereof. The composition comprises a component A and a component B. The component A comprises vinyl-terminated polysiloxane, a fumed silica treating agent, fumed silica, water, MQ resin, a platinum catalyst and optional alkenyl silane. The component B comprises vinyl-terminated polysiloxane, a fumed silica treating agent, fumed silica, water, MQ resin, hydrogen-containing silicone oil, an inhibitor and optional alkenyl silane. According to the invention, vinyl-terminated polysiloxane is used as main vinyl silicone oil, fumed silica is used as a reinforcing filler, hydrogen-containing silicone oil is used as a cross-linking agent, alkenyl silane is used as a functional auxiliary agent to reduce the hardness and improve the tear strength, and under a platinum catalyst, the tensile strength is improved; the preparation method is used for preparing the double-component addition type liquid silicone rubber with low viscosity, low hardness, strong tear resistance and excellent flexibility, is suitable for lipstick silicone rubber molds, and meets the requirements of small-batch customized production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer materials, in particular to a strong-tear, low-viscosity and low-hardness two-component addition type liquid silicone rubber composition and a preparation method thereof. The silicone rubber is particularly suitable for a lipstick silicone mold, has high tear strength, low viscosity, low hardness and excellent flexibility, and can meet the needs of small-batch customized production of lipsticks. BACKGROUND

[0002] During the production of lipsticks, small-batch production and customization are often required, especially for personalized needs or niche markets. Silicone molds can be flexibly adapted to non-standardized production. As the preferred material for lipstick silicone molds, two-component addition type silicone can meet the needs of rapid, low-cost and rapid switching during the research and development and sample making stages of lipsticks.

[0003] However, existing silicone molds often have high hardness, low tear strength and insufficient flexibility, which can cause the mold to be easily damaged, have a small number of mold turnover times and have a short service life. For example, traditional silicone rubber often has insufficient tear strength when the hardness is low, and silicone rubber with high tear strength usually has high hardness, which is difficult to meet the requirements of softness and durability of lipstick molds.

[0004] In the prior art, although the performance can be improved by adding fillers or adjusting crosslinking agents, other performances are often sacrificed. For example, increasing the content of fumed white carbon black can increase the tear strength, but can cause the hardness to rise and the processability to deteriorate, the viscosity to be too high and the flowability to be too poor; using a multifunctional crosslinking agent can reduce the hardness, but can reduce the tear strength.

[0005] Therefore, it is of great significance to develop a silicone mold with high tensile and tear resistance, a large number of mold turnover times, good softness and no easy deformation, which can be repeatedly used. SUMMARY

[0006] In order to solve the problem that the existing silicone rubber cannot simultaneously have low hardness and high tear strength, resulting in the problems of easy damage, a small number of mold turnover times and a short service life of the silicone mold, the present application provides a strong-tear, low-viscosity and low-hardness two-component addition type liquid silicone rubber composition and a preparation method and application thereof, which has high tear strength, low viscosity, low hardness and excellent flexibility, is particularly suitable for a lipstick silicone mold and can meet the needs of small-batch customized production of lipsticks.

[0007] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions: The present application provides a two-component addition type liquid silicone rubber composition, which is composed of alkenyl silane, end-vinyl polysiloxane, fumed silica treatment agent, fumed white carbon black, reinforcing resin, hydrogen-containing silicone oil, platinum catalyst, inhibitor and water; The structure of the alkenyl silane is as follows: The methoxy group or the ethoxy group R1, R2, R3 are the same or different, representing a hydrogen atom, an alkyl group, an aralkyl group, an aryl group or a heterocyclic group.

[0008] Specifically, the vinyl mass percentage of the terminal vinyl polysiloxane is 0.1-1.0%, and the viscosity at 25°C is 1000-10000 mPa.

[0009] Specifically, the hydrogen-containing silicone oil is one or more of a side hydrogen-containing silicone oil, a terminal hydrogen-containing silicone oil, and a terminal-side hydrogen-containing silicone oil, and the hydrogen mass percentage is 0.05-1%.

[0010] Further preferably, the hydrogen-containing silicone oil is a side hydrogen-containing silicone oil and a terminal hydrogen-containing silicone oil in a ratio of (10-15):1.

[0011] Specifically, the reinforcing resin is an MQ resin.

[0012] Further preferably, the MQ resin is a vinyl MQ silicone resin, and the vinyl content is 1-4%.

[0013] Specifically, the fumed silica treatment agent is one or more of dimethyldiethoxysilane, dimethyldimethoxysilane, dimethylcyclosiloxane, hexamethyldisilazane, and trimethylethoxysilane.

[0014] The fumed white carbon black is treated with the fumed silica treatment agent to be hydrophobic, and the specific surface area is 100-400 m 2 / g.

[0015] The platinum-gold catalyst is a tetramethyldivinylsiloxane complex of chloroplatinic acid, and the mass content of platinum is 1000-3000 ppm.

[0016] The inhibitor is a vinyl cyclohexanol or an ethynyl cyclohexanol.

[0017] The core of the present application is to balance the two performance indicators of "low hardness" and "high tear strength" which are usually contradictory through the synergistic effect of the components.

[0018] The following is a detailed analysis of the components: 1. Vinyl-terminated polysiloxane as the base polymer, forms the main skeleton of silicone rubber, is the basis of forming elastomers. The terminal vinyl group (-CH=CH2) is the main active group of addition type vulcanization reaction, and the Si-H bond of hydrogen-containing silicone oil reacts with the platinum catalyst to form a three-dimensional network structure. The length of the vinyl-terminated polysiloxane molecular chain (expressed as viscosity) and the vinyl content directly affect the hardness, strength and flexibility of the final product. The higher the molecular weight (the greater the viscosity), the lower the crosslinking network density, the softer the rubber, and the appropriate vinyl site ensures that the crosslinking reaction proceeds fully.

[0019] 2. Hydrogen-containing silicone oil as a crosslinking agent, crosslinks with vinyl-terminated polysiloxane to form a three-dimensional network structure, allowing liquid silicone to be cured into an elastomer.

[0020] The type (end hydrogen-containing, side hydrogen-containing) and hydrogen content of the hydrogen-containing silicone oil are the key to regulating the performance of the final product: Side hydrogen-containing silicone oil as the main crosslinking agent provides a large number of crosslinking points, forming a dense network and giving the rubber high mechanical strength.

[0021] End hydrogen-containing silicone oil can be used as a chain extender, which reacts with end vinyl silicone oil to preferentially extend the molecular chain rather than form dense crosslinking points, thereby reducing crosslinking density, increasing flexibility and elongation at break.

[0022] A large number of experimental demonstrations show that the hydrogen-containing silicone oil is preferably a side hydrogen-containing silicone oil and an end hydrogen-containing silicone oil in a ratio of (10-15):1.

[0023] 3. Alkenyl silane (such as vinyl trimethoxysilane or vinyl triethoxysilane) as a core functional additive is the core of achieving a balance of "high tear strength and low hardness". Its molecule contains one vinyl group and three hydrolyzable alkoxy groups (methoxy / ethoxy), the vinyl group participates in the main reaction and can act as a "end-capping agent" or "chain extender", affecting the length of the molecular chain and the network structure, which helps to reduce the crosslinking density and thus the hardness. After the reaction, the remaining three methoxy / ethoxy groups in the molecule hydrolyze in the presence of trace amounts of water in the air to form silicon hydroxyl groups. These silicon hydroxyl groups can condense with each other or form hydrogen bonds or chemical bonds with the hydroxyl groups on the surface of fillers such as white carbon black and MQ resin. This "secondary crosslinking" or "physical crosslinking point" significantly enhances the force between the molecular chains. When the material is subjected to a tearing stress, these additional forces can effectively disperse and absorb energy, preventing the rapid expansion of cracks, thereby significantly increasing the tear strength.

[0024] However, because the alkoxy groups in the alkenyl silane can weakly interact with the catalyst or inhibitor, slightly delaying the curing. Therefore, in the invention, the amount of platinum catalyst can be increased to compensate and optimize, which reflects the synergistic design between components.

[0025] 4. The fumed white carbon black and fumed silica treating agent as reinforcing filler, greatly improve the mechanical strength of silicone rubber, especially tensile strength and tear strength. Fumed white carbon black has a large specific surface area (100-400 m2 / g), the surface is rich in silanol groups, which can produce strong physical and chemical interaction (such as hydrogen bond) with polysiloxane molecular chain, effectively transfer stress, prevent microcrack propagation, thus play a reinforcing role. The role of fumed silica treating agent (such as hexamethyldisilazane) is to hydrophobize the white carbon black, because the untreated white carbon black surface silanol group will adsorb water, and poison the platinum gold catalyst, at the same time, it will thicken the system, and the flowability becomes poor. The treating agent converts the hydrophilic silanol group on the surface of fumed white carbon black into hydrophobic siloxane structure through chemical reaction, solves the above problems, and improves the compatibility of the filler and silicone oil matrix.

[0026] 5. The vinyl MQ silicone resin as "rigid" reinforcing unit, complementary to the "particulate" reinforcement of fumed white carbon black.

[0027] Specifically, the silicone rubber composition comprises A glue and B glue; The A glue comprises the following raw materials in parts by weight: vinyl-terminated polysiloxane 50-90 parts, fumed silica treating agent 3-10 parts, water 1-5 parts, fumed white carbon black 10-40 parts, reinforcing resin 30-70 parts, platinum gold catalyst 0.05-0.2 parts; The B glue comprises the following raw materials in parts by weight: vinyl-terminated polysiloxane 50-90 parts, fumed silica treating agent 3-10 parts, water 1-5 parts, fumed white carbon black 10-40 parts, reinforcing resin 30-70 parts, hydrogen-containing silicone oil 7-30 parts, inhibitor 0.1-0.5 parts; It also comprises 1-5 parts of alkenyl silane, which can be added to A glue or B glue.

[0028] Further preferably, the alkenyl silane is added to B glue, and the amount of alkenyl silane is 2-4 parts.

[0029] The application also provides a preparation method of the above-mentioned two-component addition type liquid silicone rubber composition, comprising the following steps: S1, preparing base material: adding end-vinyl polysiloxane, fumed silica treating agent, fumed white carbon black and water into a kneader in batches, stirring at room temperature for 1-4h; increasing temperature to 120-180℃, stirring under vacuum for 1-4h, stopping vacuum, to obtain base material; S2, preparing A component: adding base material, reinforcing resin and the rest of end-vinyl polysiloxane dilution into a kneader, stirring under vacuum for 1-2h, then adding platinum gold catalyst, stirring uniformly to obtain A component; S3, preparing B component: adding base material, reinforcing resin, the rest of end-vinyl polysiloxane, hydrogen-containing silicone oil and alkenyl silane dilution into a kneader, stirring under vacuum for 1-2h, then adding inhibitor, stirring uniformly to obtain B component; S4, mixing A component and B component uniformly according to mass ratio 1:1, room temperature vulcanization in a mold, to obtain silicone rubber.

[0030] The application further provides application of the silicone rubber prepared by the preparation method, and the silicone rubber is used for processing lipstick silicone rubber mold.

[0031] Compared with the prior art, the application has the following beneficial effects: The application uses end-vinyl polysiloxane as main vinyl silicone oil, fumed white carbon black as reinforcing filler, hydrogen-containing silicone oil as crosslinking agent, and alkenyl silane as functional additive to reduce hardness and improve tear strength, and under the action of platinum gold catalyst, a two-component addition type liquid silicone rubber with low viscosity, low hardness and strong tear is prepared to meet the requirements of high tear, certain softness and flexibility of the lipstick silicone rubber mold in the production of lipstick. DETAILED DESCRIPTION

[0032] The technical solutions in the application will be described clearly and completely in combination with specific embodiments. Obviously, the described embodiments are only some of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0033] The specific raw materials and amounts of the two-component addition type liquid silicone rubber compositions in the embodiments and comparative examples are shown in Tables 1 and 2.

[0034] Table 1: Specific raw materials and amounts of the two-component addition type liquid silicone rubber compositions in the embodiments Table 2: Specific raw materials and amounts of the two-component addition type liquid silicone rubber compositions in the comparative examples The raw materials used in the embodiments and comparative examples are described as follows: End vinyl polysiloxane: vinyl mass percentage 0.1-1.0%. The viscosity of the end vinyl polysiloxane in Example 1 and Example 2 was 1000 mPa-s (25°C), the viscosity of the end vinyl polysiloxane in Example 3 was 4000 mPa-s (25°C), the viscosity of the end vinyl polysiloxane in Example 4 was 5000 mPa-s (25°C), and the viscosity of the end vinyl polysiloxane in Example 5 was 10000 mPa-s (25°C).

[0035] The viscosity of the end vinyl polysiloxane in Comparative Example 5 was 500 mPa-s (25°C), the viscosity of the end vinyl polysiloxane in Comparative Example 6 was 20000 mPa-s (25°C), and the viscosity of the end vinyl polysiloxane in the other Comparative Examples was 1000 mPa-s (25°C).

[0036] The fumed silica treatment agent was hexamethyldisilazane.

[0037] The fumed white carbon black had a specific surface area of 100-400 m2 / g and was hydrophobically treated with the fumed silica treatment agent.

[0038] The vinyl resin was a vinyl MQ silicone resin, and the vinyl content was 1-4%.

[0039] The hydrogen-containing silicone oil had a hydrogen mass percentage of 0.05-1%, and included a side hydrogen-containing silicone oil and an end hydrogen-containing silicone oil.

[0040] The platinum gold catalyst was a tetramethyldivinyl disiloxane complex of chloroplatinic acid, and the platinum content was 1000-3000 ppm.

[0041] The inhibitor was ethynylcyclohexanol.

[0042] The alkenyl silane was vinyltrimethoxysilane or vinyltriethoxysilane.

[0043] Unless otherwise specified, the silicone rubber prepared from the silicone rubber composition in each of the examples and comparative examples was prepared by the following method.

[0044] S1, preparing a base material: adding the end vinyl polysiloxane, the fumed silica treatment agent, the fumed white carbon black, and water into a kneader in batches, stirring at room temperature for 2 h; increasing the temperature to 180°C, stirring under vacuum for 2 h, stopping the vacuum, and obtaining a base material; S2, preparing component A: adding the base material, the reinforcing resin, and the remaining end vinyl polysiloxane dilution into a kneader, stirring under vacuum for 2 h, and then adding the platinum gold catalyst, and obtaining component A after uniform stirring; S3, Preparation of B component: add base material, reinforcing resin, residual end-vinyl polysiloxane, hydrogen-containing silicone oil and alkenyl silane diluent into a kneader, vacuum stirring for 2 h, then add inhibitor, and stirring uniformly to obtain B component; S4, uniformly mix A component and B component at a mass ratio of 1:1, and room temperature vulcanization in a mold to obtain a silicone rubber.

[0045] Performance test experiment: The tests of the two-component addition type liquid silicone rubber prepared in each example and comparative example are carried out according to the following standards and methods: (1) Tensile strength and elongation at break: uniformly mix A and B components of the obtained silicone rubber at room temperature, and room temperature vulcanization in a mold to obtain a rubber sheet with a thickness of 2 mm, then refer to ASTM D412-2006, the sample is dumbbell type, the test speed is 500 mm / min, and the test environment temperature is 23±2°C.

[0046] (2) Shore A hardness: refer to ASTM D2240-2010 for Shore hardness test, and the test environment temperature is 23±2°C.

[0047] (3) Tear strength: refer to ASTM D624-2007, use a right-angle sample, the test speed is 500 mm / min, and the test environment temperature is 23±2°C.

[0048] From the test results of the above examples and comparative examples, it can be seen that: The tensile strength, elongation at break, tear strength and hardness of the silicone rubber prepared in examples 1-6 are all in a moderate range, which ensures the requirements of softness and durability of the prepared lipstick mold.

[0049] The viscosity of the silicone rubber in examples 1-4 and example 6 is in a suitable range, which is convenient for subsequent processing and molding to form a lipstick mold. In example 5, the viscosity of the silicone rubber is high due to the use of end-vinyl polysiloxane with high viscosity, which leads to difficulty in subsequent processing and molding, and is not convenient for injection, but will not affect the performance of the molded lipstick mold.

[0050] Comparative example 1 does not add vinyl resin for reinforcement in the product system, which leads to a significant decrease in the tensile strength, tear strength and hardness of the silicone rubber. It is proved that the vinyl silicone resin is uniformly dispersed in the formula as a reinforcing resin, and plays a role in enhancing the strength with "ball rolling" effect.

[0051] The end hydrogen-containing silicone oil can increase the molecular chain length of the end vinyl polysiloxane, increase its elasticity and softness. Compared with Example 1, the product system of Comparative Example 2 does not add end hydrogen-containing silicone oil, resulting in a significant decrease in the elongation at break of the silicone rubber and no elasticity. However, in Comparative Example 3, the addition content of the end hydrogen-containing silicone oil is too high, which can cause the overall formula to be too soft, the elongation at break is very large, but the strength is low, and the overall silicone rubber is very soft.

[0052] In Comparative Example 7, the content of the side hydrogen-containing silicone oil added in the product system is too high, which causes the system to be excessively cross-linked, stress concentration, and a significant decrease in the tear strength, affecting the service life of the silicone mold.

[0053] Regarding the role of alkenyl silane, comparing Comparative Example 4 and Examples 1 and 2, the product system of Comparative Example 4 does not add alkenyl silane, resulting in a significant decrease in the tensile strength and tear strength. The addition of vinyl trimethoxysilane or vinyl triethoxysilane can significantly increase the tensile strength and tear strength, but can affect the room temperature curing time. In order to match the actual application time requirement, the content of platinum catalyst can be increased in specific applications. Vinyl trimethoxysilane and vinyl triethoxysilane mainly graft vinyl groups on the end vinyl polysiloxane, and their other groups (triethoxyl or trimethoxyl) can enhance the intermolecular force, moderately increase the chain rigidity, and increase the tear strength, but can decrease the overall curing speed, so the content of platinum catalyst needs to be increased or the inhibitor needs to be reduced to adjust the curing time.

[0054] Comparative Example 5 and Example 1, the viscosity of the end vinyl polysiloxane in the product system is lower (500 mPa.s), the viscosity is too low after mixing, and the performance of the silicone rubber is poor, resulting in a too soft lipstick mold.

[0055] Comparative Example 6 and Example 1, the viscosity of the end vinyl polysiloxane in the product system is higher (20000 mPa.s), the viscosity is too high after mixing, which has seriously affected the subsequent injection processing, resulting in very difficult mold processing and forming, and the silicone rubber is too hard, which is not suitable as a lipstick mold.

[0056] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and changes can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A two-component addition type liquid silicone rubber composition characterized in that, It is composed of alkenyl silane, vinyl-terminated polysiloxane, fumed silica treatment agent, fumed silica, reinforcing resin, hydrogen-containing silicone oil, platinum catalyst, inhibitor and water; The structural formula of alkenylsilane is as follows: R1, R2, and R3 may be the same or different, representing hydrogen atoms, alkyl groups, aralkyl groups, aryl groups, or heterocyclic groups.

2. The two-component addition type liquid silicone rubber composition according to claim 1, characterized by, The vinyl-terminated polysiloxane has a vinyl mass percentage of 0.1-1.0% and a viscosity of 1000-10000 mPa at 25°C.

3. The two-component addition type liquid silicone rubber composition according to claim 1, characterized by, The hydrogen-containing silicone oil is one or more of the following: side-containing hydrogen-containing silicone oil, end-containing hydrogen-containing silicone oil, and end-side-containing hydrogen-containing silicone oil, with a hydrogen mass percentage of 0.05-1%.

4. The two-component addition type liquid silicone rubber composition according to claim 3, characterized by, The hydrogen-containing silicone oil is a side-containing hydrogen-containing silicone oil and an end-containing hydrogen-containing silicone oil with a dosage ratio of (10-15):

1.

5. The two-component addition type liquid silicone rubber composition according to claim 1, characterized by, The reinforcing resin is MQ resin.

6. The two-component addition-curing liquid silicone rubber composition according to claim 5, characterized in that, The MQ resin is a vinyl MQ silicone resin with a vinyl content of 1-4%.

7. The two-component addition-curing liquid silicone rubber composition according to claim 1, characterized in that, The silicone rubber composition includes adhesive A and adhesive B; Among them, Glue A includes the following raw materials in parts by weight: 50-90 parts of vinyl-terminated polysiloxane 3-10 parts of fumed silica treatment agent 1-5 parts water 10-40 parts of fumed silica 30-70 parts of reinforcing resin Platinum catalyst 0.05-0.2 parts; Glue B comprises the following raw materials in parts by weight: 50-90 parts of vinyl-terminated polysiloxane 3-10 parts of fumed silica treatment agent 1-5 parts water 10-40 parts of fumed silica 30-70 parts of reinforcing resin 7-30 parts of hydrogen-containing silicone oil Inhibitor 0.1-0.5 parts; It also includes 1-5 parts of alkenylsilane, which can be added to glue A or glue B.

8. The two-component addition-curing liquid silicone rubber composition according to claim 7, characterized in that, Alkenyl silane is added to glue B, and the amount of alkenyl silane used is 2-4 parts.

9. A method for preparing a two-component addition-curing liquid silicone rubber composition according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Preparation of base material: Add vinyl-terminated polysiloxane, fumed silica treatment agent, fumed silica and water in batches to a kneader and stir at room temperature for 1-4 hours; raise the temperature to 120-180℃ and stir under vacuum for 1-4 hours, then stop the vacuum to obtain the base material. S2. Preparation of component A: Add base material, reinforcing resin and remaining terminal vinyl polysiloxane dilution to a kneader, stir under vacuum for 1-2 hours, then add platinum catalyst, stir evenly to obtain component A; S3. Preparation of component B: Add base material, reinforcing resin, remaining terminal vinyl polysiloxane, hydrogen-containing silicone oil and alkenyl silane dilution to a kneader, stir under vacuum for 1-2 hours, then add inhibitor, stir evenly to obtain component B. S4. Mix component A and component B at a mass ratio of 1:1 until homogeneous, and vulcanize at room temperature in a mold to obtain silicone rubber.

10. An application of silicone rubber prepared by the method of claim 9, characterized in that, The silicone rubber is used to process silicone molds for lipsticks.

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