Length-adjustable large-size SBR rubber mold pressing foaming material and preparation method thereof

Abstract

The invention discloses a length-adjustable large-size SBR rubber mould pressing foaming material which comprises the following raw materials in parts by weight: synthetic rubber C, vulcanizing agent insoluble sulfur medicine rubber, an accelerant DM, an accelerant M, a foaming agent AC6000, urea grease, argil, light calcium carbonate, talcum powder and mixed oil Y. The synthetic rubber C contains silicon-aluminum micro powder; the preparation method comprises the following steps: preparing mixed oil Y, preparing natural rubber premixed rubber A, preparing black smoke rubber masterbatch B, preparing synthetic rubber C, preparing rubber compound D and the like. The large-size foam material with the length of 11-12 m and the width of 1.5-1.6 m is successfully prepared through the three-step process of'primary low-temperature width fixing, secondary high-temperature extension and room-temperature shrinkage shaping 'in combination with precise regulation and control of the silicon-aluminum micro powder on a foam structure, the length can be flexibly adjusted according to actual requirements, and the large-size foam material is suitable for large-size foam materials with the length of 11-12 m and the width of 1.5-1.6 m. The problems of high splicing loss and poor adaptability of products with conventional sizes are solved, and the technical blank of large-size adjustable SBR foaming materials is filled.

Description

Technical Field

[0001] This invention relates to the field of polymer material preparation technology, specifically to a length-adjustable large-size SBR rubber molding foam material and its preparation method. Background Technology

[0002] Styrene-butadiene rubber (SBR) foam materials are widely used in building insulation, outdoor equipment, and industrial protection due to their advantages such as low density, excellent resilience, and controllable cost. With the expansion of high-end applications such as large-scale stadium insulation, military tents, and giant equipment protection, the demand for large-size foam materials exceeding 11 meters in length and 1.5 meters in width is becoming increasingly urgent. Standard-sized products (1300mm × 3300mm × 50mm) require glue for splicing, resulting in high wastage (typically ≥15%), uneven physical properties, and short service life.

[0003] In existing technologies, the preparation of large-size SBR foam materials faces three major technical bottlenecks: First, uneven heat conduction leads to inconsistent cell sizes, with density differences between inner and outer layers exceeding 30%; second, bubbles are prone to fusion and rupture during foaming, making it difficult to increase the foaming ratio and resulting in poor cell structure stability; third, mechanical properties degrade significantly after size expansion, with tensile strength typically decreasing by ≥25%, while dimensional stability is insufficient and thermal shrinkage is high. Although some studies have shown that silica-alumina micropowder can be used as a foaming nucleating agent to improve the performance of conventional-size SBR foam materials, its suitable dosage, particle size parameters, and mechanism of action in large-size materials are still unclear, and there is a lack of industrial production schemes that match actual test data.

[0004] Silicon-aluminum micropowder, a high-value-added byproduct of the lithium smelting industry, is mainly composed of SiO2 (69.15%) and Al2O3 (27.51%), and features small particle size, large specific surface area, and excellent thermal stability. Its high specific surface area provides numerous nucleation sites, while the rigidity of SiO2 and Al2O3 reinforces the matrix. Furthermore, its good thermal stability makes it suitable for high-temperature foaming processes. This invention, through systematic research on the mechanism of action of silicon-aluminum micropowder in large-size SBR foaming, optimizes the formulation and process parameters, solves the technical challenges of large-size foaming materials, and achieves stable preparation of large-size products with adjustable length. Summary of the Invention

[0005] This application provides a length-adjustable large-size SBR rubber molding foam material and its preparation method, focusing particularly on the core role of aluminosilicate micropowder in regulating the cell structure of large-size SBR foam materials, improving mechanical properties and dimensional stability, as well as a precise control scheme in industrial production.

[0006] A length-adjustable large-size SBR rubber molding foam material, wherein the compound D comprises the following raw materials in parts by weight: Synthetic Rubber C 100 parts Insoluble sulfur adhesive vulcanizing agent: 1.2-2.0 parts Accelerator DM 0.4-0.7 parts Accelerator M 0.3-0.5 parts 1-2 parts of foaming agent AC6000 1-2 parts of urea ester 50-80 parts clay 20-40 parts of light calcium carbonate 5-15 parts talcum powder Blended oil Y 15-30 parts The synthetic adhesive C contains 20-30 parts of silicon-aluminum micro powder, which meets the following requirements: SiO2 mass fraction 69.15%±1%, Al2O3 mass fraction 27.51%±1%, particle size 3-5μm (D50=4μm), specific surface area 30-35m² / g, thermal weight loss ≤3.8% at 800℃, and moisture content ≤0.05%. The foaming agent AC4000 has a decomposition temperature of 160-165℃, gas generation ≥210mL / g, and decomposition residue content ≤0.5%.

[0007] Further, the synthetic adhesive C comprises: 100 parts of emulsion styrene-butadiene rubber Natural rubber premix A 15-25 parts Black smoke glue masterbatch B 55-80 parts Dispersant DA 1-1.5 parts Food-grade antioxidant BHT 2-3 parts 3-6 parts of PEG4000 polyethylene glycol 15-18 parts zinc oxide 20-30 parts of silica-alumina micro powder 2-3 servings of Vaseline The weight ratio of the silica-alumina micro powder to the dispersant DA is 13-30:1 to ensure that the silica-alumina micro powder is uniformly dispersed in the rubber matrix (agglomerate particle size ≤20μm).

[0008] Further, the natural rubber premix A comprises: 100 parts of natural rubber (Mounney viscosity ML1+4 100℃=60) EVA (VA content 25%, melt flow rate 2.5 g / 10 min) 10-20 parts Stearic acid (CH-220, purity ≥98%) 2.5-3.5 parts Zinc stearate (zinc content ≥10.5%) 0.5-1 part.

[0009] Furthermore, the black smoke adhesive masterbatch B comprises: Natural rubber premix A 100 parts Solution-polymerized styrene-butadiene rubber 1205 (27% bound benzene content) 20-30 parts Carbon black N330 (oil absorption 110mL / 100g, DBP oil absorption value 105-115mL / 100g) 10-15 parts Mixed oil Y 15-20 parts.

[0010] Furthermore, the mixed oil Y is composed of 150 paraffin oil (viscosity 25 mm² / s, 40℃; flash point ≥ 220℃) and 4006# naphthenic oil (viscosity 45 mm² / s, 40℃; flash point ≥ 210℃) in a ratio of 1:10.

[0011] Furthermore, the finished product dimensions meet the following requirements: length 11000-12000mm, width 1500-1600mm, thickness 65-68mm, dimensional accuracy ±0.8%-±1.2%; mechanical properties meet the following requirements: tensile strength (skin) 4.5-6.5kg / cm², tensile strength (intermediate) 3.5-5.5kg / cm², elongation at break (skin) 150%-220%, elongation at break (intermediate) 130%-220%, tear strength (skin) 1.8-3.2kg / cm, tear strength (intermediate) 1.3-2.2kg / cm, density (skin) 0.16-0.22g / cm³, density (intermediate) 0.13-0.17g / cm³; heat shrinkage rate (70℃ / 24h) ≤2.5% in the X direction, ≤3.5% in the Y direction; compression set (50% compression at room temperature for 22h) ≤35%.

[0012] A method for preparing a large-size SBR rubber molding foam material with adjustable length includes the following steps: (1) Preparation of mixed oil Y First, preheat the oil drums containing 150 paraffin oil and 4006# naphthenic oil respectively. Then, put the 150 paraffin oil and 4006# naphthenic oil into the electrically heated temperature-controlled oil drums and preheat them to 50℃±2℃. Pump them into a 1m³ double-layer mixing tank (the outer layer is wrapped with electric heating wire and the inner layer is heated by hollow spiral blades) at a ratio of 1:10 using a self-priming centrifugal oil pump. Stir at a speed of 30r / min for 60min, and maintain the temperature inside the tank at 48-52℃ during the process to obtain mixed oil Y, which is then sealed for later use. (2) Preparation of natural rubber premix A Natural rubber, EVA, stearic acid, and zinc stearate were sequentially fed into an ML-110 internal mixer. The temperature was set to 100-105℃ and the pressure to 7.5 kg / cm². The mixer was pressed down four times (the first press was for 150 seconds, and the second to fourth presses were for 120 seconds each, with a 15-second interval). After 500-600 seconds of refining, the mixture was discharged. The discharged colloid was then fed into an X(S)K-160 type two-roll mill. The gap between the rollers was adjusted to 2 mm, and the mixture was refining for 500 seconds. During this time, cooling water (20℃) was continuously circulated through the inner wall of the rollers. The temperature of the colloid was controlled to be ≤90℃. The mixture was then allowed to stand at room temperature (23℃±2℃) for 24 hours to obtain premixed rubber A. (3) Preparation of black smoke glue masterbatch B Stearic acid and carbon black N330 were added to an internal mixer, and the temperature was set to 110-115℃ and the pressure to 7.5 kg / cm². The mixture was then mixed for 300 seconds until the carbon black was completely dispersed. Mixed oil Y was added and the mixture was mixed for another 200 seconds. Premixed rubber A and solution-polymerized styrene-butadiene rubber 1205 were then added. The temperature was raised to 120-125℃ and the mixture was mixed for 400 seconds. During this period, the Mooney viscosity (ML1+4 at 100℃) of the colloid was monitored and controlled at 80-90. The mixture was then passed through a two-roll mill (5 mm gap between rollers) twice and allowed to stand at room temperature for 24 hours to obtain masterbatch B. (4) Preparation of synthetic rubber C Stearic acid, dispersant DA, antioxidant BHT, PEG4000, zinc stearate, calcium stearate, zinc oxide, silica-alumina micro powder, and petrolatum were sequentially added to a mixer. The temperature was set to 105-110℃ and the pressure to 7.5 kg / cm². The mixer was then mixed for 300 seconds until the powder was fully incorporated. Emulsion styrene-butadiene rubber 1502, premixed rubber A, and masterbatch B were added. The temperature was raised to 115-120℃ and the mixer was mixed for 500 seconds. During this period, the temperature of the colloid was monitored every 100 seconds to ensure that it did not exceed 125℃. The colloid was then turned over in a two-roll mill (8 mm gap between rollers) for 500 seconds. After passing through a thin mill 6 times, the colloid was sheeted (8 mm thick) and allowed to stand at room temperature for 24 hours to obtain synthetic rubber C. (5) Preparation of compound rubber D Add the vulcanizing agent (insoluble sulfur adhesive), accelerator (DM), clay, light calcium carbonate, and talc to a mixing tank. Add mixed oil (Y) and stir at 25 rpm for 30 minutes, during which time disperse the mixture for 10 minutes using a high-speed disperser (1500 rpm) to ensure that the powder agglomerates are ≤50μm. Add the mixture to an internal mixer, add synthetic rubber (C), and set the temperature to 110-115℃ and the pressure to 7.5 kg / cm², and mix for 400 seconds. Add accelerator (M), foaming agent (AC4000), and urea ester, cool to 100-105℃, and mix for 200 seconds, controlling the discharge temperature at 105-110℃. Pass the mixture through a 10mm thin mill 6 times, divide it into 8 equal portions (each portion weighing ±0.5 kg), and let it stand at room temperature for 12 hours to obtain compound rubber (D). (6) Extrusion Mixed rubber D was blended in 8-hand units (each hand was divided into 8 parts for cross-mixing), fed into an open mill (roller gap 5mm), set at 72℃±5℃, and refluxed for 500 seconds, during which cooling water (water temperature 18℃) was continuously circulated; then extruded through a 250mm diameter, 1:12 length-to-diameter hot-feed single-screw extruder, with the barrel temperature set to 65℃ in zone 1, 70℃ in zone 2, 75℃ in zone 3, and 75℃ at the die head, at a speed of 1-2 meters per minute, automatically cut into sheets (thickness 26mm±0.5mm), and allowed to cool to room temperature (≤30℃) to obtain rubber preform E; (7) First in-mold closed-cell foaming The preform E is precisely weighed using an electro-hydraulic lifting electronic scale (single mold weight error ≤1%) and evenly laid in a dedicated 1150mm×5500mm×26mm molding foam mold, ensuring no wrinkles or overlaps (edge ​​blank ≤5mm). After the mold is closed, it is heated by circulating heat transfer oil at a set temperature of 130℃±3℃, maintaining an oil pressure of 10-15MPa, and molding at constant temperature and pressure for 45-50 minutes. During this period, the temperature of each area of ​​the mold cavity is monitored in real time by 6 temperature sensors built into the mold (temperature difference ≤2℃). The pressure is quickly released to normal pressure (pressure release time ≤2 seconds), the mold is opened, and the intermediate body (dimensions 1300mm×8500mm×45mm±2mm) is removed. The edges are trimmed to remove burrs (trimming width ≤10mm). (8) Second in-mold closed-cell foaming Lay the intermediate material flat on a 1600mm×10500-12000mm×65mm adjustable mold frame (adjust the mold frame extension section according to the target length), with the length direction of the intermediate material aligned with the length direction of the mold, and fix the edges with high-temperature resistant silicone strips; after the mold frame is closed, set the temperature to 162℃±5℃, maintain the oil pressure at 3.0-5MPa, and keep it at constant temperature and pressure for 45-55 minutes, during which the pressure fluctuation in the mold cavity should be controlled to ≤0.2MPa; slowly depressurize to 0.5-1MPa (ensuring that the edge of the foam does not overflow the mold frame), keep it at this temperature for 5-6 minutes, and then open the mold layer by layer (the opening speed of each layer should be ≤5mm / s), remove the preliminary foam (size 1600-1620mm×11800-12100mm×75mm), and allow it to cool naturally for 30 minutes (cooling ambient temperature 25℃±3℃). (9) Shaping: The preliminary foam is placed in a constant temperature and humidity shaping room (temperature 23℃±2℃, humidity 50%±5%) and cooled naturally for 72 hours. During this period, the dimensions are measured every 24 hours until the change in dimensions between two consecutive measurements is ≤0.3%, and the finished product is obtained. The foam is naturally cooled at room temperature. After the product has cooled and shrunk sufficiently, the resulting foam is 1510-1520mm (width) * 11100-1100mm (length) * 65-68mm (thickness) and then stored or processed into shape.

[0013] 1. Precise selection and dosage optimization of silicon-aluminum micropowder: Screen silicon-aluminum micropowder with a particle size of 3-5μm (D50=4μm) and a specific surface area of ​​30-35m² / g, and control the dosage at 20-30 parts by weight (optimal 25 parts by weight). This dosage range can provide sufficient nucleation sites through the high specific surface area, keeping the average cell diameter below 72μm, and can also offset the mechanical property degradation caused by size expansion through the rigid reinforcing effect of SiO2 and Al2O3, while avoiding the problem of decreased foaming ratio caused by excessive addition.

[0014] 2. The triple core mechanism of action of silicon-aluminum micropowder: (1) High efficiency nucleation effect: The polar groups on the surface of silicon-aluminum micro powder adsorb foaming gas and form uniform bubble nuclei, which reduces the coefficient of variation of bubble uniformity to below 0.16, solving the problem of bubble fusion and rupture in large-size foaming; (2) Rigid reinforcement effect: Rigid particles of SiO2 (Mohs hardness 7) and Al2O3 (Mohs hardness 9) are uniformly dispersed in the rubber matrix and cell walls, which improves the load-bearing capacity of the material and increases the tensile strength by more than 24% compared with the non-silicon aluminum micro powder system. (3) Thermal conduction optimization effect: The thermal conductivity of silicon-aluminum micro powder (0.8-1.0W / (m・K)) is significantly higher than that of rubber matrix (0.1-0.2W / (m・K)), which can reduce the temperature difference between the inner and outer layers of the mold cavity to ≤2℃, improve the uniformity of thermal conduction, and reduce the density difference between the inner and outer layers.

[0015] (4) Co-design of compound system and process: Natural rubber premix A (EVA content 15%) improves matrix toughness and increases elongation at break by ≥20%; black smoke rubber masterbatch B (carbon black N330 content 12 parts) further optimizes heat conduction efficiency; dispersant DA and silica-alumina micro powder are compounded in a specific ratio to solve the agglomeration problem (agglomerate particle size ≤20μm). Combined with the three-step process of "first low temperature width setting - second high temperature stretching - room temperature shrinkage setting", the length can be precisely adjusted to 11-12 meters with a dimensional accuracy of ±0.8%-±1.2%.

[0016] Detailed design of material formulation 1. Detailed Explanation of Technical Parameters for Silicon-Aluminum Micropowder: (1) Chemical composition (mass fraction): SiO2 69.15%, Al2O3 27.51%, Li2O 0.90%, K2O 0.64%, CaO 0.56%, Na2O 0.50%, Fe2O3 0.40%, others 0.34%. The specific chemical composition ensures its compatibility with the rubber matrix and its reinforcing effect. (2) Physical properties: Particle size 3-5μm (tested by laser particle size analyzer, D10=3μm, D50=4μm, D90=5μm), specific surface area 32m² / g (BET method), thermal weight loss at 800℃ 3.8% (TGA test, air atmosphere, heating rate 10℃ / min), moisture content 0.03% (Karl Fischer method), ensuring no moisture absorption during storage and use and stable performance at high temperatures.

[0017] 2. Selection and compatibility of key adjuvants: (1) Foaming agent AC4000: decomposition temperature 160-165℃, precisely matched with secondary foaming temperature (162℃±5℃), gas generation 215mL / g, decomposition residue content 0.3%, avoiding residue from affecting cell structure; (2) Mixed oil Y: 150 paraffin oil and 4006# naphthenic oil are mixed at a ratio of 1:10 to balance processing fluidity and rubber flexibility. After the addition, the Mooney viscosity (ML1+4 100℃) of the rubber compound is controlled at 80-90, and there is no sticking to the mold during the extrusion process. (3) Dispersant DA: It forms hydrogen bonds with the polar groups of silicon-aluminum micro powder, significantly reducing the particle size of agglomerates from 80 μm to below 20 μm, ensuring uniform nucleation.

[0018] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages: 1. Size Breakthrough and Adjustability: Through a three-step process of "low-temperature width setting, high-temperature stretching, and room-temperature shrinkage setting," combined with precise control of the cell structure by silicon-aluminum micropowder, large-size foamed materials with a length of 11-12 meters and a width of 1.5-1.6 meters have been successfully prepared. The length can be flexibly adjusted according to actual needs, solving the pain points of high splicing loss and poor adaptability of conventional size products, and filling the technological gap in large-size adjustable SBR foamed materials.

[0019] 2. Synergistic Effect of Silicon-Aluminum Micropowder: Silicon-aluminum micropowder (SiO2 mass fraction 69.15%, Al2O3 mass fraction 27.51%) plays a triple role of "efficient nucleation + rigid reinforcement + thermal conduction optimization": as a nucleating agent, it reduces the average cell diameter to ≤72μm and the uniformity variation coefficient to below 0.16; as a reinforcing agent, it increases the surface tensile strength to 5.32kg / cm², which is more than 25% higher than the system without silicon-aluminum micropowder; as a thermal conduction optimizer, it reduces the mold cavity temperature difference to ≤2℃, significantly improves the thermal conduction uniformity of large-size foaming, and solves the technical bottlenecks of cell fusion and rupture and large density differences between inner and outer layers.

[0020] 3. Excellent consistency and stability of physical properties: Through the compounding system of natural rubber premix, black smoke glue masterbatch and synthetic rubber, combined with the synergistic dispersion design of silica-alumina micro powder and dispersant DA (aggregate particle size ≤20μm), the difference in tensile strength between the inner and outer layers of the finished product is ≤1.2kg / cm², the heat shrinkage rate (70℃ / 24h) is ≤1.8% in the X direction and ≤3.2% in the Y direction, and the compression set is ≤32.5%. While maintaining the physical property characteristics of the conventional 1300mm×3300mm×50mm size, high-performance and stable output under large size is achieved.

[0021] 4. High industrial feasibility: The amount of silicon-aluminum micro powder in the formula (20-30 parts by weight) is well compatible with existing processes. The mold design (1150mm×5500mm×26mm primary mold, 1600mm×10500mm×65mm adjustable secondary mold), temperature and pressure parameters (130℃±3℃ / 10-15MPa for primary foaming, 162℃±5℃ / 3.0-5MPa for secondary foaming) all meet the requirements for industrial production. The dimensional variation coefficient of three batches of scaled-up production is ≤0.2%, and the mechanical property variation coefficient is ≤0.7%, demonstrating stable mass production capability. The hydraulic press simultaneously realizes the multi-layer hot plate size and process working state, which is suitable for the adjustable and controllable length of foamed products from 7 to 11.5 meters, enabling stable batch production of foamed products.

[0022] 5. Significant environmental and application value: PAHs and halogens were not detected in the product, meeting the environmental protection requirements of high-end scenarios; it is suitable for large-scale building insulation, military protection, outdoor equipment manufacturing and other fields. It can be applied directly without splicing, greatly reducing processing losses (from the conventional ≥15% to ≤3%), extending service life, and has significant economic and social benefits. Detailed Implementation

[0023] To better understand the above technical solution, the following will provide a detailed explanation of the technical solution in conjunction with specific implementation methods.

[0024] 1. Experimental materials Emulsion styrene-butadiene rubber 1502: Qingdao Fukai Rubber & Plastics, with a benzene content of 23.5% and a Mooney viscosity of ML1+4 at 100℃ = 55; Silicon-aluminum micro powder: Tianqi Lithium Corporation, particle size 3-5μm, specific surface area 32m² / g (meets the technical parameters of claim 1); Natural rubber: Hainan Natural Rubber Industry Group, Mooney viscosity ML1+4 100℃=60; Carbon black N330: Xiamen Jiabos, oil absorption value 110mL / 100g, DBP oil absorption value 110mL / 100g; Mixed oil Y: 150 paraffin oil (Zibo Senjie Chemical) and 4006# naphthenic oil (Jinborun (Xiamen) Petrochemical) are mixed at a ratio of 1:10; Foaming agent AC4000: Tianyuan Aviation Materials Technology Co., Ltd., gas generation capacity 215mL / g; Other additives: Dispersant DA (Quanzhou Jingbo Trading), antioxidant BHT (food grade, Shanghai Yuanye Biotechnology), vulcanizing agent insoluble sulfur glue (Quanzhou Jingbo Trading), etc. are all industrial grade.

[0025] 2. Testing Standards Tensile strength and elongation at break: ASTM D412 (test speed 500 mm / min, test the skin and middle parts separately, 5 specimens per group, and take the average value). Tear strength: ASTM D624 (test speed 500 mm / min, test the skin and middle parts separately); Foaming ratio: GB / T 1033.3-2010 (densitometer method, calculating the density ratio of compound rubber to vulcanized rubber); Density: ASTM D1817 (electronic densitometer, accuracy 0.001 g / cm³, tested separately for the outer and middle parts). Heat shrinkage rate: ISO 188 (70℃ oven, 24h, tested in both X and Y directions); Compression set: ASTM D395 (tested after 22 hours of compression at 50% at room temperature, followed by 30 minutes of decompression and recovery). Dimensional accuracy: Laser rangefinder (accuracy ±0.1mm, test one point every 1 meter of the finished product length, and test one point every 0.5 meters of the width); Microstructure: JSM-6700F scanning electron microscope (SEM, liquid nitrogen cryogenic fracture, gold sputtering, accelerating voltage 10kV). Environmental performance: PAHs (AfPS GS 2014:01PAK, GC-MS), halogens (ion chromatography, detection limit 50 mg / kg).

[0026] 3. Examples 1-5 (Experiments on Gradient Dosage of Silicon-Aluminum Micropowder) Prepare materials according to the formulation in Table 1, following the preparation method described in claim 7, adjusting only the amount of silica-alumina micro powder in synthetic adhesive C while keeping other conditions constant: Example 3 (Optimal Solution - Detailed Operational Details) Formulation (parts by weight, based on 100kg batch of synthetic rubber C): Synthetic Rubber C: 100 parts latex styrene-butadiene rubber 1502, 20 parts natural rubber premix A, 65 parts black smoke rubber masterbatch B, 1.0 part dispersant DA, 2.5 parts food-grade antioxidant BHT, 4.5 parts PEG4000 polyethylene glycol, 16 parts zinc oxide, 25 parts silica-alumina micro powder, and 2.5 parts petrolatum; Compound D: 100 parts synthetic rubber C, 1.6 parts insoluble sulfur vulcanizing agent, 0.55 parts accelerator DM, 0.4 parts accelerator M, 1.5 parts foaming agent AC4000, 1.5 parts urea ester, 65 parts kaolin, 30 parts light calcium carbonate, 10 parts talc, and 22 parts mixed oil Y.

[0027] Preparation steps (industrial production scale, single batch yield 500kg): Preparation of mixed oil Y: 10 kg of 150 paraffin oil and 100 kg of 4006# naphthenic oil were placed in a 500L electrically heated temperature-controlled oil tank and preheated to 50℃. The mixture was then pumped into a 1m³ stirring tank and stirred at 30r / min for 60min while maintaining the temperature at 50℃. The mixture was then sealed and kept for later use. Preparation of premixed rubber A: 100kg of natural rubber, 15kg of EVA, 3kg of stearic acid, and 0.8kg of zinc stearate were put into an ML-110 internal mixer and kneaded at 102℃ and 7.5kg / cm² for 550 seconds, then kneaded on an open mill with a 2mm gap for 500 seconds. The cooling water temperature was 20℃, the colloid temperature was 85℃, and the mixture was allowed to stand for 24 hours. Preparation of Masterbatch B: 1.5 kg stearic acid and 12 kg carbon black N330 were mixed at 112°C for 300 seconds. 17 kg mixed oil Y was added and mixed for 200 seconds. 100 kg premixed rubber A and 25 kg solution-polymerized styrene-butadiene rubber 1205 were added and mixed at 123°C for 400 seconds. The Mooney viscosity was 85. The mixture was passed through a two-roll mill with a 5 mm gap twice and allowed to stand for 24 hours. Preparation of Synthetic Rubber C: 2.5 kg stearic acid, 1.0 kg dispersant DA, 2.5 kg antioxidant BHT, 4.5 kg PEG4000, 0.8 kg zinc stearate, 8 kg calcium stearate, 16 kg zinc oxide, 25 kg silica-alumina micro powder, 2.5 kg petrolatum; mix at 108℃ for 300 seconds; add 100 kg emulsion styrene-butadiene rubber 1502, 20 kg premixed rubber A, and 65 kg masterbatch B; mix at 118℃ for 500 seconds; colloid temperature 122℃; remix on an open mill with an 8 mm gap for 500 seconds; pass through a thin mill 6 times; let stand for 24 hours. Preparation of compound rubber D: 1.6 kg vulcanizing agent, 0.55 kg accelerator DM, 65 kg clay, 30 kg light calcium carbonate, 10 kg talc, 22 kg mixed oil Y, stir at 25 r / min for 30 min, disperse at 1500 r / min for 10 min, add 100 kg synthetic rubber C, mix at 112℃ for 400 seconds, add 0.4 kg accelerator M, 1.5 kg foaming agent, 1.5 kg urea ester, mix at 103℃ for 200 seconds, discharge temperature 108℃, pass through a 10 mm thin mill 6 times, divide into 8 portions (62.5 kg ± 0.5 kg each), and let stand for 12 h; Extrusion: After the compound rubber D is mixed, it is started at 72℃ for 500 seconds, cooled by 18℃ water, and extruded through a single screw extruder (zone 1 65℃, zone 2 70℃, zone 3 75℃, die head 75℃) at 1.5m / min, with a sheet thickness of 26mm, and cooled to 28℃. One-time foaming: The preform is weighed (single mold weight 120kg±1.2kg), laid in a 1150mm×5500mm×26mm mold, molded at 132℃ and 14MPa for 48 minutes, with 6 temperature sensors in the mold cavity monitoring a temperature difference of 1.5℃, pressure released for 10 seconds, and the intermediate body of 1300mm×8500mm×45mm is taken out and trimmed by 8mm. Secondary foaming: The intermediate body is laid flat on a 1600mm×10500mm×65mm mold frame (the extension section is adjusted to the target length of 11.8 meters), kept at 163℃ and 4.2MPa for 52 minutes, with pressure fluctuation of 0.1MPa, depressurized to 0.8MPa and kept at 0.8MPa for 5 minutes, the mold is opened layer by layer, and the initial foam body of 1610mm×11900mm×75mm is taken out and cooled at 25℃ for 30 minutes; Shaping: Place in a constant temperature and humidity chamber (23℃, 50% humidity) and cool for 72 hours. After 24 hours, the dimensions are 11750mm×1590mm×73mm, after 48 hours, the dimensions are 11720mm×1585mm×72.5mm, and after 72 hours, the dimensions are 11700mm×1580mm×72mm, with a dimensional change of 0.2%. Shaping is complete.

[0028] Comparative example (reference formulation, without silicon-aluminum micro powder) The formula and preparation method of "A large-size non-standard SBR rubber blend closed-cell secondary molding foam material and its preparation method" are adopted from patent ZL 201911413171.6, applied for on December 31, 2019. It does not contain silica-alumina micropowder. Specific parameters are as follows: Formula: 100 parts synthetic rubber, 1.5 parts insoluble sulfur-based vulcanizing agent, accelerator system (0.4 parts DM + 0.3 parts M + 0.25 parts DPG, etc.), foaming agent system (2.5 parts DPT + 9 parts AC6000 + 1.5 parts OBSH), 90 parts clay, 55 parts light calcium carbonate, 18 parts magnesium oxide powder, and 39 parts mixed oil T; Process: First foaming at 135℃ for 48 minutes, second foaming at 168℃ for 30 minutes, set and allowed to cool naturally at room temperature for 7 days; Finished product dimensions: 1720mm×7500mm×62mm (adjustable lengths of 11 meters or more are not possible).

[0029] Experimental Results and Analysis Performance comparison of Examples 1-5 with comparative examples Note: 1. Conversion between kg / cm² and MPa: 1 kg / cm² ≈ 0.098 MPa; 2. ND = Not detected (less than the method detection limit); 3. Conversion between g / cm³ and kg / m³: 0.1 g / cm³ = 100 kg / m³. Analysis of the mechanism of action of silicon-aluminum micro powder SEM microstructure characterization results showed that when the comparative example (a) (AlSi-0) 70μm silica-alumina powder and the corresponding compound D of Example 3 (b) (AlSi-10) 72μm silica-alumina powder were used in 10.17 parts (based on 100 parts of synthetic rubber C, the actual weight of silica-alumina powder in 120kg single mold preform was 5.25kg), the SBR foam exhibited a uniform closed-cell structure with an average cell diameter of 72μm and a coefficient of variation of only 0.16; while the comparative example cell diameter distribution was discrete (50-180μm), with a coefficient of variation as high as 0.35, and the uniformity was significantly worse than that of Example 3.

[0030] The silica-alumina micropowder possesses a high specific surface area of ​​32 m² / g, providing ample nucleation sites for the foaming process. This results in a 62% increase in the number of bubbles compared to the control group, effectively mitigating the bubble growth imbalance caused by uneven heat conduction in large-size foaming scenarios and ensuring the consistency of the bubble structure. Furthermore, granular silica-alumina micropowder was observed inside the bubbles in the SBR cross-section, suggesting weak interfacial bonding between it and the SBR matrix. These weak areas are likely to become preferred sites for bubble generation and expansion.

[0031] Based on comprehensive microstructure observation and performance data, it can be further inferred that: as a highly efficient nucleating agent in the SBR foaming process, the appropriate addition of silica-alumina micropowder (such as 10.17 parts in Example 3) can not only significantly promote cell formation, but also precisely control the cell size and distribution uniformity, thus playing a unique structural control function and providing key technical support for the preparation of high-performance SBR closed-cell foam.

[0032] Verification of the reinforcing effect: The tensile strength of Example 3 (5.32 kg / cm² for the skin and 4.12 kg / cm² for the middle) increased by 25.2% and 32.1% respectively compared with the comparative example (4.25 kg / cm² for the skin and 3.12 kg / cm² for the middle), while the compression set (32.5%) decreased by 32.3% compared with the comparative example (48.0%). This is due to the rigidity of SiO2 and Al2O3, which are uniformly dispersed in the cell walls, improving the load-bearing capacity of the cell structure and offsetting the mechanical property degradation caused by large-size expansion.

[0033] Thermal conduction optimization verification: In Example 3, the temperature difference between the inner and outer layers of the mold cavity was controlled at 1.5℃, while the temperature difference in the comparative example exceeded 5℃. The high thermal conductivity of the silicon-aluminum micropowder accelerated heat transfer, making the temperature of each area of ​​the compound uniform during foaming, thereby reducing the difference in cell size and the density deviation between the inner and outer layers, and ensuring the consistency of physical properties of large-size products.

[0034] Dosage suitability analysis: In mixed adhesive C, as the dosage of silica-alumina micro powder increased from 20 parts to 30 parts, the foaming ratio initially stabilized and then decreased slightly, while the mechanical properties gradually improved. When the dosage was 25 parts, the best balance between the foaming ratio (145%) and mechanical properties was achieved, while the dimensional accuracy was also optimal (±0.8%), making it the optimal dosage scheme.

[0035] Industrial production stability verification Example 3 was subjected to three batches of industrial-scale production (500 kg per batch), and the test results are as follows: Batch 1: Length 11700mm, width 1580mm, thickness 72mm, tensile strength 5.32kg / cm², foaming ratio 145%; Batch 2: Length 11680mm, Width 1578mm, Thickness 71.8mm, Tensile Strength 5.29kg / cm², Foaming Ratio 144%; Batch 3: Length 11720mm, Width 1582mm, Thickness 72.2mm, Tensile Strength 5.35kg / cm², Foaming Ratio 146%; Batch-to-batch coefficient of variation: size ≤ 0.2%, mechanical properties ≤ 0.7%, proving that the formulation and process of this invention have good industrial stability.

[0036] in conclusion This invention introduces silicon-aluminum micropowder with specific technical parameters as a core functional additive, clarifying its triple mechanism of "efficient nucleation + rigid reinforcement + optimized thermal conduction" in large-size SBR foam materials. By synergistically optimizing the compound system and step-by-step molding process, it successfully achieves the large-scale preparation of length-adjustable large-size SBR foam materials with dimensions of 11-12 meters and width of 1.5-1.6 meters. Excellent results are achieved with 20-30 parts by weight of silicon-aluminum micropowder, with 25 parts by weight being the optimal dosage. At this dosage, the finished product dimensions are 11700mm × 1580mm × 72mm, the foaming ratio is 145%, the tensile strength (skin) is 5.32 kg / cm², the elongation at break (skin) is 175%, the thermal shrinkage rate is ≤3.2%, and the compression set is 32.5%, demonstrating optimal overall performance. This invention solves the technical problems of uneven cell structure, decreased mechanical properties, and poor dimensional stability in large-size foamed materials in the prior art. The provided formula and process are precise and reproducible, laying the foundation for the industrial application of large-size SBR foamed materials and having broad market prospects.

[0037] The above description is merely an embodiment of the invention's technical content. Any modifications or variations made by those skilled in the art using this invention are within the scope of the invention's claims, and are not limited to those disclosed in the embodiments.

Claims

1. A large-size SBR rubber molding foam material with adjustable length, characterized in that, The ingredients include the following proportions by weight: Synthetic Rubber C 100 parts Insoluble sulfur adhesive vulcanizing agent: 1.2-2.0 parts Accelerator DM 0.4-0.7 parts Accelerator M 0.3-0.5 parts 1-2 parts of foaming agent AC6000 1-2 parts of urea ester 50-80 parts clay 20-40 parts of light calcium carbonate 5-15 parts talcum powder Blended oil Y 15-30 parts The synthetic adhesive C contains 20-30 parts of silicon-aluminum micro powder, which meets the following requirements: SiO2 mass fraction 69.15%±1%, Al2O3 mass fraction 27.51%±1%, particle size 3-5μm, specific surface area 30-35m² / g, thermal weight loss ≤3.8% at 800℃, and moisture content ≤0.05%. The foaming agent AC4000 has a decomposition temperature of 160-165℃, gas generation ≥210mL / g, and decomposition residue content ≤0.5%.

2. The adjustable-length large-size SBR rubber molding foam material according to claim 1, characterized in that, The synthetic adhesive C comprises: 100 parts of emulsion styrene-butadiene rubber Natural rubber premix A 15-25 parts Black smoke glue masterbatch B 55-80 parts Dispersant DA 1-1.5 parts Food-grade antioxidant BHT 2-3 parts 3-6 parts of PEG4000 polyethylene glycol 15-18 parts zinc oxide 20-30 parts of silica-alumina micro powder 2-3 servings of Vaseline The weight ratio of the silicon-aluminum micro powder to the dispersant DA is 13-30:1 to ensure that the silicon-aluminum micro powder is uniformly dispersed in the rubber matrix.

3. The adjustable-length large-size SBR rubber molding foam material according to claim 2, characterized in that, The natural rubber premix A includes: 100 parts natural rubber EVA 10-20 parts Stearic acid 2.5-3.5 parts 0.5-1 part zinc stearate.

4. The adjustable-length large-size SBR rubber molding foam material according to claim 3, characterized in that, The black smoke adhesive masterbatch B includes: Natural rubber premix A 100 parts Solution-polymerized styrene-butadiene rubber 1205 20-30 parts Carbon black N330 10-15 parts Mixed oil Y 15-20 parts.

5. The adjustable-length large-size SBR rubber molding foam material according to claim 4, characterized in that, The mixed oil Y is composed of 150 paraffin oil and 4006# naphthenic oil in a ratio of 1:

10.

6. A length-adjustable large-size SBR rubber molding foam material according to any one of claims 1-5, characterized in that, The finished product dimensions meet the following requirements: length 11000-12000mm, width 1500-1600mm, thickness 65-68mm, dimensional accuracy ±0.8%-±1.2%; mechanical properties meet the following requirements: tensile strength 4.5-6.5kg / cm², tensile strength 3.5-5.5kg / cm², elongation at break 150%-220%, elongation at break 130%-220%, tear strength 1.8-3.2kg / cm, tear strength 1.3-2.2kg / cm, density 0.16-0.22g / cm³, density 0.13-0.17g / cm³; heat shrinkage rate ≤2.5% in the X direction and ≤3.5% in the Y direction, compression set ≤35%.

7. A method for preparing a length-adjustable large-size SBR rubber molding foam material according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Preparation of mixed oil Y First, preheat the oil drums containing 150 paraffin oil and 4006# naphthenic oil respectively. Then, put the 150 paraffin oil and 4006# naphthenic oil into the electrically heated temperature-controlled oil drums and preheat them to 50℃±2℃. Pump them into a 1m³ double-layer mixing tank at a ratio of 1:10 using a self-priming centrifugal oil pump. Stir at a speed of 30r / min for 60min, maintaining the temperature inside the tank at 48-52℃ during the process. The resulting mixed oil Y is then sealed and stored for later use. (2) Preparation of natural rubber premix A Natural rubber, EVA, stearic acid, and zinc stearate were sequentially fed into an ML-110 internal mixer. The temperature was set to 100-105℃ and the pressure to 7.5 kg / cm². The mixture was pressed down four times with a heavy hammer and kneaded for 500-600 seconds before being discharged. The discharged colloid was then fed into an X (S)K-160 type two-roll mill. The gap between the rollers was adjusted to 2 mm, and the mixture was kneaded for 500 seconds. During this time, cooling water was continuously circulated through the inner wall of the rollers to control the temperature of the colloid to ≤90℃. The mixture was then allowed to stand at room temperature for 24 hours to obtain premixed rubber A. (3) Preparation of black smoke glue masterbatch B Stearic acid and carbon black N330 were added to an internal mixer, and the temperature was set to 110-115℃ and the pressure to 7.5 kg / cm². The mixture was then mixed for 300 seconds until the carbon black was completely dispersed. Mixed oil Y was added and the mixture was mixed for another 200 seconds. Premixed rubber A and solution-polymerized styrene-butadiene rubber 1205 were then added. The temperature was raised to 120-125℃ and the mixture was mixed for 400 seconds. During this period, the Mooney viscosity of the colloid was monitored and controlled at 80-90. The mixture was then passed through a two-roll mill twice and allowed to stand at room temperature for 24 hours to obtain masterbatch B. (4) Preparation of synthetic rubber C Stearic acid, dispersant DA, antioxidant BHT, PEG4000, zinc stearate, calcium stearate, zinc oxide, silica-alumina micro powder, and petrolatum were sequentially added to an internal mixer. The temperature was set to 105-110℃ and the pressure to 7.5 kg / cm². The mixer was then mixed for 300 seconds until the powder was fully incorporated. Emulsion styrene-butadiene rubber 1502, premixed rubber A, and masterbatch B were added. The temperature was raised to 115-120℃ and the mixer was mixed for 500 seconds. During this period, the temperature of the colloid was monitored every 100 seconds to ensure that it did not exceed 125℃. The mixture was then rolled on a two-roll mill for 500 seconds, passed through a thin mill 6 times, and then sheeted. The sheet was allowed to stand at room temperature for 24 hours to obtain synthetic rubber C. (5) Preparation of compound rubber D Add the vulcanizing agent (insoluble sulfur adhesive), accelerator (DM), clay, light calcium carbonate, and talc to a mixing tank. Add mixed oil (Y) and stir at 25 r / min for 30 min, during which time disperse the mixture for 10 min using a high-speed disperser to ensure that the powder agglomerates are ≤50μm. Add the mixture to an internal mixer, add synthetic rubber (C), set the temperature to 110-115℃ and the pressure to 7.5 kg / cm², and mix for 400 seconds. Add accelerator (M), foaming agent (AC4000), and urea ester, cool to 100-105℃, and mix for 200 seconds. Control the discharge temperature at 105-110℃. Pass the mixture through a 10mm thin mill 6 times, divide it into 8 equal parts, and let it stand at room temperature for 12 hours to obtain compound rubber (D). (6) Extrusion Mixed rubber D was blended in units of 8 lots and fed into an open mill. The temperature was set at 72℃±5℃ and the mixture was tumbled for 500 seconds, during which cooling water was continuously circulated. The mixture was then extruded through a 250mm diameter, 1:12 length-to-diameter hot-feed single-screw extruder. The barrel temperature was set to 65℃ in zone 1, 70℃ in zone 2, 75℃ in zone 3, and 75℃ in the die head. The extrusion was carried out at a speed of 1-2 meters per minute, and the mixture was automatically cut into sheets. The sheets were then allowed to cool to room temperature to obtain rubber preform E. (7) First in-mold closed-cell foaming The preform E is precisely weighed using an electro-hydraulic lifting electronic scale and evenly laid on a 1150mm×5500mm×26mm special molding foam mold to ensure no wrinkles or overlaps. After the mold is closed, it is heated by circulating heat transfer oil at a set temperature of 130℃±3℃ and an oil pressure of 10-15MPa. The mold is then pressed at constant temperature and pressure for 45-50 minutes. During this time, the temperature of each area of ​​the mold cavity is monitored in real time by 6 temperature sensors built into the mold. The intermediate body is then removed from the mold and the edges are trimmed to remove burrs. (8) Second in-mold closed-cell foaming Lay the intermediate material flat on an adjustable mold frame of 1600mm×10500-12000mm×65mm, with the length of the intermediate material aligned with the length of the mold. Secure the edges with high-temperature resistant silicone strips. After closing the mold frame, set the temperature to 162℃±5℃ and maintain the oil pressure at 3.0-5MPa. Maintain constant temperature and pressure for 45-55 minutes, during which time control the pressure fluctuation in the mold cavity to ≤0.2MPa. Slowly depressurize to 0.5-1MPa and maintain the temperature for 5-6 minutes. Then, open the mold layer by layer, remove the preliminary foamed material, and allow it to cool naturally for 30 minutes. (9) Shaping: Place the preliminary foam into a constant temperature and humidity shaping room and let it cool naturally for 72 hours. During this period, measure the size every 24 hours until the size change is ≤0.3% in two consecutive measurements to obtain the finished product; The foam is naturally cooled at room temperature. After the product has cooled and shrunk sufficiently, the resulting foam is 1510-1520mm (width) * 11100-1100mm (length) * 65-68mm (thickness) and then stored or processed into shape.

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