High-plasticity silicone rubber for livestock breeding and preparation method thereof

Abstract

The invention discloses high-plasticity livestock breeding silicone rubber and a preparation method thereof, and belongs to the technical field of organic silicon polymer materials. The silicone rubber is prepared from a rubber A and a rubber B, wherein the rubber A comprises a middle-specific-surface-area gas-phase-method white carbon black base rubber treated by hexamethyldisilazane, self-made end-side divinyl silicone oil, a polyvinyl anti-deformation agent and a platinum catalyst; and the glue B comprises the same base glue, silicone oil, a hydrogen-containing cross-linking agent and a retarder. Through hydrosilylation reaction vulcanization, a three-dimensional network structure with uniform crosslinking and low internal stress is formed. The silicone rubber has the advantages that excellent mechanical properties are maintained, shape retentivity and creep resistance are remarkably improved, the silicone rubber is free of ballooning under simulated working pressure of a mating syringe and can be quickly recovered after pressure relief, the problems of easiness in deformation, liquid leakage and inaccurate metering of a traditional sealing part are thoroughly solved, and the silicone rubber is applicable to high-performance sealing parts of artificial insemination instruments for livestock such as cattle and pigs.

Description

Technical Field

[0001] This application relates to the field of organosilicon polymer materials technology, and more specifically, to a highly plastic silicone rubber for livestock breeding and its preparation method. Background Technology

[0002] In modern animal husbandry, artificial insemination technology has been widely applied to the reproductive management of livestock such as cattle, pigs, and sheep to improve the utilization rate and reproductive efficiency of superior breeding stock. Among these instruments, the livestock insemination syringe is a key piece of equipment, and its core sealing components, such as the piston or stopper, are typically made of liquid silicone rubber (LSR). This component needs to withstand a certain internal pressure after being filled with semen or diluent, typically 80–150 kPa, and maintain good sealing and dimensional stability during the insemination process.

[0003] However, commercially available liquid silicone rubbers generally have the following problems in practical applications: Poor shape retention: Under continuous hydraulic pressure, silicone rubber products are prone to bulging, deformation, or even "creeping", leading to seal failure or inaccurate dosage. Uneven cross-linking structure: Although the traditional platinum vulcanization system reacts quickly, if the formulation is not properly designed, it can easily cause local cross-linking density to be too high or too low, affecting the overall mechanical properties and elastic recovery. Poor dispersion of silica: If fumed silica is used as the main reinforcing filler and is not effectively surface treated or if a type with a mismatched specific surface area is selected, it will lead to poor storage stability of the rubber compound, poor injection flowability, and even "structuring" phenomenon. Performance bottlenecks of competing products: Although some commercial products claim to have similar parameters such as hardness (47–51 Shore A) and tensile strength (>7MPa), they still cannot achieve shape retention under long-term pressure in actual simulated use, indicating that macroscopic performance indicators alone are insufficient to reflect real working conditions.

[0004] To address these issues, the industry has attempted improvements by adding plasticizers, adjusting vinyl content, or introducing novel crosslinking agents. However, these methods often suffer from trade-offs—for example, while reducing crosslinking density improves flowability, it sacrifices compressive strength; excessive reinforcement leads to embrittlement and decreased tear strength. Furthermore, existing technologies largely focus on optimizing the final formulation, neglecting the source control of key raw materials such as vinyl silicone oil and base rubber. In fact, microscopic factors such as vinyl distribution (end groups vs. side groups), the hydroxyl state of silica surface, and low molecular weight residue have a decisive impact on the uniformity of the final vulcanization network.

[0005] Therefore, there is an urgent need to develop a highly plastic silicone rubber system that is controllable throughout the entire chain, which can not only meet the requirements of injection molding process, but also achieve comprehensive performance of "high elasticity, low creep and strong plasticity" in actual use, so as to truly solve the problem of sealing reliability in livestock breeding scenarios. Summary of the Invention

[0006] The purpose of this invention is to provide a high-plasticity livestock breeding silicone rubber and its preparation method. By optimizing the base rubber structure, making a self-made vinyl silicone oil and anti-deformation agent, and constructing a uniform and stable vulcanization network, the invention solves the technical problems of poor plasticity, easy deformation and insufficient compressive strength of existing liquid silicone rubber in breeding syringe applications, and achieves excellent shape retention, mechanical strength and process stability.

[0007] In order to solve the problems existing in the background art and achieve the above-mentioned objectives, this application adopts the following technical solution: A highly plastic silicone rubber for livestock breeding is prepared from a mixable A rubber and a B rubber, wherein the A rubber and the B rubber are mixed and vulcanized by hydrosilylation reaction to form an elastomer; The A-type adhesive comprises a base adhesive, vinyl silicone oil, anti-deformation agent, and platinum catalyst; The B-type adhesive comprises a base adhesive, vinyl silicone oil, anti-deformation agent, hydrogen-containing crosslinking agent, and retarder; The base adhesive is a vinyl-terminated polydimethylsiloxane reinforced with surface-treated fumed silica, wherein the specific surface area of ​​the fumed silica is 150–250 m² / g. 2 / g; The anti-deformation agent is an organosilicon oligomer with a polyvinyl side chain structure.

[0008] Furthermore, the vinyl silicone oil is obtained by ring-opening polymerization of cyclic siloxane monomers and has an end-sided divinyl structure.

[0009] Furthermore, the vinyl silicone oil is a polydimethylsiloxane with an end-sided divinyl structure, and the vinyl content is 0.3 to 1.0 wt%.

[0010] Furthermore, the hydrogen-containing crosslinking agent is a methylhydrosiloxane oligomer containing multiple Si–H bonds, with a hydrogen content of 0.8–1.6 wt%.

[0011] Furthermore, the platinum catalyst is a Karstedt-type platinum complex.

[0012] Furthermore, the delaying agent is an alkynyl alcohol or maleate ester compound.

[0013] Furthermore, based on 100 parts by weight of the base adhesive, the amount of each component added is as follows: Vinyl silicone oil: 5-15 parts; Anti-deformation agent: 1-5 parts; Platinum catalyst: 0.1–0.5 parts; Hydrogen-containing crosslinking agent: 2-8 parts; Delaying agent: 0.2 to 1.0 parts.

[0014] This application also discloses a method for preparing highly plastic silicone rubber for livestock breeding, comprising the following steps: (1) Preparation of vinyl silicone oil: Add a mixture of cyclic siloxanes DMC or D4 to the reactor; heat to 50-60°C, remove moisture and low molecular weight substances under nitrogen protection by vacuum, with a vacuum degree ≤−0.092MPa, for 2-4 hours; add vinyl double end caps, stir and mix for 20-40 minutes; add alkaline catalyst, heat to 100-110°C, and polymerize at this temperature for 2-4 hours; heat to 170-185°C, remove low molecular weight byproducts under nitrogen atmosphere by vacuum, with a vacuum devolatilization time of 3-5 hours, to obtain polydimethylsiloxane with vinyl end caps, i.e., the vinyl silicone oil; (2) Preparation of base adhesive: Vinyl-terminated polydimethylsiloxane, fumed silica, deionized water, and hexamethyldisilazane are added to a kneader and mixed in an intensive kneading process at 25–40°C for 2–3 hours. The temperature is then raised to 140–160°C, and kneading continues for 1.5–2.5 hours to ensure sufficient reaction between the hydroxyl groups on the surface of the fumed silica and the hexamethyldisilazane. The temperature is further raised to 170–185°C, and low-molecular-weight byproducts and moisture are removed under a vacuum of ≤−0.095 MPa for a devolatilization time of 2 hours. –3 hours to obtain a uniform and fine base adhesive; the vinyl content of the vinyl-terminated polydimethylsiloxane is 0.03–0.20 wt%, and the viscosity at 25°C is 30,000–80,000 mPa·s; the specific surface area of ​​the fumed silica is 150–250 m² / g, and its amount is 20–40 wt% of the mass of the vinyl-terminated polydimethylsiloxane; the amount of hexamethyldisilazane is 8–15 wt% of the mass of the fumed silica.

[0015] (3) Preparation of A glue and B glue: Mix the base adhesive, vinyl silicone oil, and special additives evenly. Add a platinum catalyst to one of the mixtures and stir to disperse evenly to obtain adhesive A. Add a crosslinking agent and a delaying agent to the other mixture and stir to disperse evenly to obtain adhesive B. (4) Preparation of finished product: Mix A glue and B glue in equal mass ratio, stir evenly and then use it for molding and processing of livestock breeding syringes.

[0016] Furthermore, in the preparation of vinyl silicone oil in step (1), the vinyl dual end cap is 1,3-divinyltetramethyldisiloxane, and its addition amount is 1.5–3.0 wt% of the total mass of cyclic siloxanes; the alkaline catalyst is potassium hydroxide-ethylene glycol complex or alkaline gel, and its dosage is 200–500 ppm of the mass of cyclic siloxanes.

[0017] This application utilizes surface-treated medium-surface-area fumed silica to prepare a highly dispersible base rubber. Combined with a self-made end-side divinyl silicone oil and an anti-deformation agent with polyvinyl side chain structures, along with a hydrosilylation vulcanization system, a three-dimensional network structure with uniform crosslinking and low internal stress was successfully constructed. The resulting silicone rubber maintains good mechanical properties while significantly improving plasticity stability and creep resistance—it shows no significant bulging even after prolonged use under simulated livestock insemination syringe working pressure, and quickly recovers its initial shape after pressure release. This effectively overcomes the defects of traditional seals such as easy deformation, leakage, and inaccurate metering. It also possesses excellent injection flowability, storage stability, and environmental adaptability, filling the technological gap in high-performance special-purpose silicone rubber materials in this field. Detailed Implementation

[0018] The present application will be further described below through specific embodiments, but the present application is not limited to the embodiments.

[0019] Example 1: (1) Preparation of base adhesive 100 parts by weight of vinyl-terminated polydimethylsiloxane (viscosity 60,000 mPa·s at 25℃, vinyl content 0.15 wt%), 35 parts by weight of fumed silica with a specific surface area of ​​200 m² / g, 0.9 parts by weight of deionized water, and 4.0 parts by weight of hexamethyldisilazane were added to a kneader and kneaded at 30℃ for 2.5 hours; the temperature was then raised to 150℃ and kneaded for another 2 hours; finally, the temperature was raised to 180℃ and the material was de-devoured at −0.096 MPa for 2.5 hours to obtain a uniform base rubber.

[0020] (2) Synthesis of vinyl silicone oil Using 95 parts of octamethylcyclotetrasiloxane (D4) and 2.5 parts of 1,3-divinyltetramethyldisiloxane as raw materials, polymerization was carried out at 105°C for 3 hours in the presence of a KOH-ethylene glycol catalyst (300 ppm), followed by segmental devolatilization at 180°C for 5 hours to obtain end-sided divinyl silicone oil. The vinyl content was determined to be 0.72 wt% by ¹H-NMR.

[0021] (3) Anti-modifier Polyvinyl silicone oligomers containing phenyl and trifluoropropyl groups (number average molecular weight approximately 6000) are used.

[0022] (4) Silicone rubber formulation and molding A-type adhesive: Base adhesive 100 + Vinyl silicone oil 12 + Anti-deformation agent 4 + Karstedt platinum catalyst (0.4 parts). B-type adhesive: Base adhesive 100 + vinyl silicone oil 12 + anti-deformation agent 4 + hydrogen-containing crosslinking agent (hydrogen content 1.3wt%, 6 parts) + 1-ethynyl-1-cyclohexanol (0.7 parts).

[0023] Mix A and B adhesives in a 1:1 ratio and vulcanize at 130℃ for 30 seconds to form the final product.

[0024] Performance results: Shore A hardness 50, tensile strength 8.1MPa, tear strength 33N / mm, elongation at break 325%, 100% tensile strength 2.4MPa, TC90=30 seconds.

[0025] It remained without bulging for 30 minutes under 123 kPa hydraulic pressure, and its recovery rate reached 97% within 30 seconds after depressurization. Example 2:

[0026] The same base adhesive and anti-deformation agent as in Example 1 were used, but the vinyl silicone oil was prepared using a different process: D495 parts, 1.8 parts of 1,3-divinyltetramethyldisiloxane; Catalyst dosage: 250 ppm; Polymerization temperature 100℃, time 4 hours; Deviation conditions: 175℃, −0.090MPa, total duration 4 hours, no vacuum breaking operation was performed.

[0027] Performance results: The TC90 test was extended to 42 seconds, the Shore A hardness was 48, the tensile strength decreased to 7.3 MPa, the tear strength was 29 N / mm, and slight bulging occurred during the hydraulic test (recovery rate 92%). The resulting vinyl silicone oil had a vinyl content of 0.55 wt%, slightly lower than that of Example 1. Silicone rubber was prepared in the same proportions and under the same vulcanization conditions. Example 3:

[0028] The anti-deformation agent was replaced with a linear oligomer (molecular weight 5000) containing only vinyl groups but no phenyl / fluorine groups, and the rest was the same as in Example 1.

[0029] Performance: Hardness 49, tensile strength 7.6MPa, but slight bulging occurs after 15 minutes under 123kPa pressure, with a recovery rate of 93%.

[0030] Comparative Example 1: The base adhesive was not surface-treated and had insufficient devolatilization. The silica was not treated with hexamethyldisilazane. The devolatilization temperature was 170°C, the vacuum degree was −0.085 MPa, and the time was 2 hours. The rest was the same as in Example 1.

[0031] Results: The rubber compound had poor storage stability, the tear strength of the product was only 26 N / mm, it deformed after 10 minutes of pressure testing, and the permanent deformation rate was 6%.

[0032] Comparative Example 2: Using commercially available end-vinyl silicone oil (without side vinyl) Commercially available vinyl-terminated silicone oil with a vinyl content of 0.6 wt% (containing only Vi at the chain ends and no side-chain vinyls) was used, and the rest was the same as in Example 1.

[0033] Results: The cross-linked network was uneven, the tensile strength was 6.8 MPa, the TC90 fluctuated greatly (28–45 seconds), and it was prone to local bulging under pressure.

[0034] Comparative Example 3: Without anti-modification agent Remove the anti-deformation agent from the A / B glue, and the rest is the same as in Example 1.

[0035] Results: The initial mechanical properties were acceptable (tensile strength 7.2 MPa), but the recovery rate after decompression was only 85%, and "creep collapse" occurred after 30 minutes.

[0036] Comparative Example 4: High specific surface area silica (350 m² / g) was used and the product was untreated. The silica has a specific surface area of ​​350 m² / g and is untreated; otherwise, it is the same as in Example 1.

[0037] Results: The rubber compound has high viscosity, making it difficult to inject mold; after vulcanization, it is brittle with a tear strength of only 22 N / mm, making it prone to cracking.

[0038] Experimental example: The performance of Examples 1-3 and Comparative Examples 1-4 will be tested below.

[0039] I. Performance Testing Items and Methods Test Project Test standards / methods Test conditions illustrate 1. Shore A hardness GB / T531.1 or ISO7619-1 Room temperature, 24 hours after vulcanization Characterizing the hardness of materials, target range 47–51 2. Tensile strength & elongation at break GB / T528 or ISO37 Dumbbell-shaped specimen, tensile speed 500 mm / min Reflects the load-bearing capacity of materials 3. Tear strength GB / T529 or ISO34-1 (right-angled) Tensioning speed 500mm / min Key indicators affecting the durability of seals 4. 100% tensile strength same tensile test Record the stress at 100% elongation Characterized by initial modulus, which is related to plasticity. 5. Vulcanization characteristics (TC90) Rotorless sulfur profiler (such as MDR) 130℃, amplitude ±0.5° Reflecting the suitability of injection molding 6. Compression permanent deformation GB / T7759.1 or ISO815-1 123 kPa pressure, 70℃ × 22 h Simulating the rebound capacity after long-term pressure 7. Hydraulic Bulk Test (Customizable) Homemade clamps + pressure source Observe the changes in appearance at room temperature and constant pressure of 123 kPa for 30 min. Core verification items: Whether it bulges or leaks. 8. Creep recovery rate (customizable) Same fixture as above; dimensional recovery occurs 30 seconds after pressure relief. <![CDATA[Initial diameter D0, D1 after pressure relief → Recovery rate = (D0 - ΔD) / (D0) × 100%]]> Directly reflects "high plasticity" ability 9. Storage stability Viscosity change was measured after 7 days at 40℃. Rotational viscometer Verify whether the base adhesive is "structured". II. Summary Table of Expected Test Results The silicone rubbers obtained in Examples 1–3 and Comparative Examples 1–4 were used to prepare dumbbell-shaped and disc-shaped samples under the same conditions. Mechanical properties were tested according to standards such as GB / T528 and GB / T529. A custom-designed hydraulic clamp was used to maintain a constant pressure of 123 kPa for 30 minutes, and changes in shape and dimensional recovery rate after 30 seconds of pressure release were recorded. The results show that only the embodiments of this invention can achieve excellent anti-bulging and creep recovery capabilities while maintaining high mechanical strength; while any comparative example, due to the lack of key components or processes, showed significant deterioration in at least one key performance aspect, failing to meet the requirements for use with livestock insemination syringes.

[0040] Test results show that: 1. The present invention (Examples 1–3) has excellent overall performance: while maintaining high tensile strength (≥7.4MPa) and high tear strength (≥30N / mm), it exhibits excellent shape retention ability—no bulging under hydraulic pressure, creep recovery rate ≥93%, which fully meets the stringent requirements of livestock insemination syringes for "high plasticity and low deformation".

[0041] 2. The preparation process of the base adhesive is crucial: Comparative Example 1 did not perform surface treatment on the silica and had insufficient devolatilization, resulting in filler agglomeration and hydroxyl residue, which not only reduced the tear strength (26 N / mm) but also significantly worsened the compression set (12%) and recovery rate (84%), proving that the process described in claims 11–14 is the basis for achieving high stability.

[0042] 3. The structure of vinyl silicone oil affects the uniformity of crosslinking: Comparative Example 2 uses commercially available silicone oil containing only terminal vinyl groups. Due to the lack of side-chain vinyl groups participating in network construction, the local crosslinking density is uneven, which is manifested as large fluctuations in TC90 and local swelling, thus verifying the necessity of the "terminal-side divinyl structure" in Claims 2 and 8–10.

[0043] 3. Anti-deformation agents are irreplaceable: In Comparative Example 3, after omitting the anti-deformation agent, although the initial mechanical properties were acceptable, the material rapidly underwent creep under continuous pressure (with a recovery rate of only 85%), indicating that this component effectively inhibited molecular chain slippage by regulating the topology of the vulcanization network, and is a key functional additive for achieving "high plasticity".

[0044] 4. The specific surface area of ​​silica needs to be precisely matched: Comparative Example 4: High specific surface area silica (350 m² / g) can improve the reinforcing effect, but when untreated, it is very easy to cause the rubber compound to become brittle (tear strength is only 22 N / mm) and make processing difficult.

[0045] In summary, only when self-made vinyl silicone oil, surface-treated medium-surface-area silica-based rubber, specific structural anti-deformation agent, and hydrosilylation system work synergistically can the technical bottleneck of traditional liquid silicone rubber, which "difficult to balance strength and plasticity," be overcome, and the comprehensive performance advantages described in this invention be achieved.

[0046] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A highly plastic silicone rubber for livestock breeding, characterized in that, It is prepared from miscible A glue and B glue, wherein the A glue and B glue are mixed and vulcanized by hydrosilylation reaction to form an elastomer; The A-type adhesive comprises a base adhesive, vinyl silicone oil, anti-deformation agent, and platinum catalyst; The B-type adhesive comprises a base adhesive, vinyl silicone oil, anti-deformation agent, hydrogen-containing crosslinking agent, and retarder; The base adhesive is a vinyl-terminated polydimethylsiloxane reinforced with surface-treated fumed silica, wherein the specific surface area of ​​the fumed silica is 150–250 m² / g. 2 / g; The anti-deformation agent is an organosilicon oligomer with a polyvinyl side chain structure.

2. The highly plastic silicone rubber for livestock breeding according to claim 1, characterized in that, The vinyl silicone oil is obtained by ring-opening polymerization of cyclic siloxane monomers and has an end-sided divinyl structure.

3. The highly plastic silicone rubber for livestock breeding according to claim 2, characterized in that, The vinyl silicone oil is a polydimethylsiloxane with a divinyl end structure and a vinyl content of 0.3 to 1.0 wt%.

4. The highly plastic silicone rubber for livestock breeding according to claim 1, characterized in that, The hydrogen-containing crosslinking agent is a methylhydrosiloxane oligomer containing multiple Si–H bonds, with a hydrogen content of 0.8–1.6 wt%.

5. The highly plastic silicone rubber for livestock breeding according to claim 1, characterized in that, The platinum catalyst is a Karstedt-type platinum complex.

6. The highly plastic livestock breeding silicone rubber according to claim 1, characterized in that, The delaying agent is an alkynyl alcohol or maleate ester compound.

7. The highly plastic silicone rubber for livestock breeding as described in claim 1, characterized in that, Based on 100 parts by weight of the base adhesive, the amount of each component added is as follows: Vinyl silicone oil: 5-15 parts; Anti-deformation agent: 1-5 parts; Platinum catalyst: 0.1–0.5 parts; Hydrogen-containing crosslinking agent: 2-8 parts; Delaying agent: 0.2 to 1.0 parts.

8. The method for preparing highly plastic livestock breeding silicone rubber according to any one of claims 1-7, characterized in that... Includes the following steps: (1) Preparation of vinyl silicone oil: Add a mixture of cyclic siloxanes DMC or D4 to the reactor; heat to 50-60°C, remove moisture and low molecular weight substances under nitrogen protection, vacuum degree ≤−0.092MPa, for 2-4 hours; Add the vinyl double end cap and stir for 20–40 minutes; add the alkaline catalyst, heat to 100–110°C, and polymerize at this temperature for 2–4 hours; heat to 170–185°C and remove low-molecular-weight byproducts under a nitrogen atmosphere by vacuuming for 3–5 hours to obtain polydimethylsiloxane with vinyl end caps, i.e., the vinyl silicone oil. (2) Preparation of base adhesive: Vinyl-terminated polydimethylsiloxane, fumed silica, deionized water, and hexamethyldisilazane are added to a kneader and mixed in an intensive kneading process at 25–40°C for 2–3 hours. The temperature is then raised to 140–160°C, and kneading continues for 1.5–2.5 hours to ensure sufficient reaction between the hydroxyl groups on the surface of the fumed silica and the hexamethyldisilazane. The temperature is further raised to 170–185°C, and low-molecular-weight byproducts and moisture are removed under a vacuum of ≤−0.095 MPa for a devolatilization time of 2 hours. After 3 hours, a uniform and fine base adhesive is obtained; the vinyl content of the vinyl-terminated polydimethylsiloxane is 0.03–0.20 wt%, and the viscosity at 25°C is 30,000–80,000 mPa·s; the specific surface area of ​​the fumed silica is 150–250 m² / g, and its dosage is 20–40 wt% of the mass of the vinyl-terminated polydimethylsiloxane; the dosage of the hexamethyldisilazane is 8–15 wt% of the mass of the fumed silica. (3) Preparation of A glue and B glue: Mix the base adhesive, vinyl silicone oil, and special additives evenly. Add a platinum catalyst to one of the mixtures and stir to disperse evenly to obtain adhesive A. Add a crosslinking agent and a delaying agent to the other mixture and stir to disperse evenly to obtain adhesive B. (4) Preparation of finished product: Mix A glue and B glue in equal mass ratio, stir evenly and then use it for molding and processing of livestock breeding syringes.

9. The method for preparing highly plastic livestock breeding silicone rubber according to claim 8, characterized in that, In step (1) the preparation of vinyl silicone oil, the vinyl dual end cap is 1,3-divinyltetramethyldisiloxane, and its addition amount is 1.5–3.0 wt% of the total mass of cyclic siloxane; the alkaline catalyst is potassium hydroxide-ethylene glycol complex or alkaline gel, and its dosage is 200–500 ppm of the mass of cyclic siloxane.