Rubber composite auxiliary agent with long-acting low-flooding performance and high mechanical performance as well as preparation method and application of rubber composite auxiliary agent

Abstract

The invention discloses a rubber composite additive with long-acting low-color-flooding performance and high mechanical performance as well as a preparation method and application of the rubber composite additive. The rubber composite additive comprises the following components: 60-90% of a high-molecular-weight long-chain aliphatic active agent; and 10% to 40% of a low molecular weight nonionic surfactant. The technical defects that an existing protection system is generally short in protection time efficiency, and the excellent mechanical property of a rubber matrix is difficult to consider are overcome. By constructing a space-time synergistic dispersing system and an in-situ mechanical compensation mechanism of the large and small molecular weight surfactants, the appearance and the mechanical property of the rubber product are synchronously improved. Through organic compounding of a large-molecular-weight active agent composite system and a small-molecular-weight active agent composite system, time-space dynamic synergistic dispersion of a long migration period of color-developing small molecules on the surface of rubber is realized from rapid blocking and stacking of small molecules at an initial stage to slow overflow relay of long-term macromolecules, and a product is endowed with relatively good long-acting low-color-flooding performance.

Description

Technical Field

[0001] This invention relates to the field of rubber additives, specifically to a rubber composite additive that combines long-lasting low bleed properties with high mechanical properties, its preparation method, and its application. Background Technology

[0002] Rubber, as a widely used elastomer material, typically requires the formulation of various functional additives (such as reinforcing systems like carbon black and silica, softening systems like aromatic oils and naphthenic oils, and protective systems like antioxidants) during industrial processing to meet stringent mechanical and anti-aging requirements. However, during the storage and service of rubber after vulcanization, driven by both internal concentration gradients and molecular thermal motion, small-molecule additives within the rubber compound are easily released from the matrix and slowly migrate to the surface of the finished product.

[0003] When a large number of free small molecules containing chromophores or auxochromic groups (such as conjugated systems in incompletely cracked polycyclic aromatic hydrocarbons, amines or phenolic antioxidants containing heteroatoms, etc.) migrate and precipitate onto the surface of a product, they are prone to aggregation and the formation of a microscopic continuous thin film layer. This surface-enriched liquid film induces a thin film interference effect in macroscopic optics, resulting in a "iridescent" appearance defect on the surface of rubber products, resembling a bluish or reddish iridescent film. Such appearance defects not only significantly reduce the appearance quality and added value of high-value-added rubber products (such as high-grade tire treads, high-grade daily-use seals, baby stroller tires, and decorative parts), but also pose potential bioirritants and health hazards to humans or the environment upon partial exposure to the polycyclic aromatic hydrocarbons. Furthermore, iridescent color development is often accompanied by blooming, which also affects the appearance. To address these surface defects and safety issues, existing technologies in this field mainly focus on constructing a microscopic passive constraint mechanism within the rubber matrix or achieving source-level slow release of components. Specifically, existing approximate technical solutions can be summarized into the following technical paths: 1. Physical Adsorption and Microencapsulation Sustained-Release Technology: This type of solution mainly achieves sustained release by extending the diffusion path of small molecules. For example, inert fillers with high specific surface area or mesoporous carbon from waste tires can be introduced into the rubber matrix for physical adsorption; or porous composite microcapsules can be constructed using nanocellulose, silica-alginate, etc., to encapsulate easily precipitated small molecules such as antioxidants, thereby reducing the local accumulation concentration of color-producing molecules on the surface of the product. (The above solutions are selected from application (patent) numbers: CN202310867542.8, CN202111258522.8 and CN202110125235.3) 2. Porous Synergistic Salting-Out Physical Immobilization Technology: This type of solution utilizes porous materials combined with ionic effects for microscopic confinement. For example, the well-developed porous structure of silica microspheres is used for physical adsorption, combined with the salting-out effect of sodium chloride to enhance the hydrophobic interactions within the polymer cross-linking network, thereby confining free chromogenic small molecules within the rubber matrix. (The above solution is selected from application (patent) number: CN202510444634.4) 3. Interlayer intercalation and chemical coordination complexation techniques: This type of approach introduces surface-modified sodium-based montmorillonite, specific silane coupling agent compositions, and active metal ions (such as Cu) into the system. 2+ (etc.) This method utilizes the physical confinement effect of montmorillonite's two-dimensional sheets, the π-π stacking effect of the hydrophobic ends of the coupling agent, and the coordination complexation between metal cations and chromophores or auxochromic groups (such as those containing O or N heteroatoms) to achieve chemical fixation of chromophore molecules. (The above scheme is selected from application (patent) number: CN202511566946.9) 4. Environmentally friendly component substitution and masking technology: This type of solution focuses on reducing the introduction of substances prone to color bleeding from the source of the formulation. For example, using bio-based plasticizers that do not contain polycyclic aromatic hydrocarbons to replace traditional processing oils, and supplementing with titanium dioxide for optical masking and adding polyether substances for surface condition adjustment. (The above solution is selected from application (patent) number: CN202410153516.3) The aforementioned existing approximate solutions, whether through physical pore barrier, chemical coordination fixation, or microcapsule sustained release, all slow down the migration rate of chromogenic small molecules to the rubber surface to a certain extent, or reduce their local enrichment concentration on the surface of the product, thereby effectively mitigating the initial coloration phenomenon of the product and providing technical reference for the treatment of rubber appearance defects in this field.

[0004] Existing mechanisms for suppressing the migration of color-developing small molecules based on internal passive constraints have significant capacity limitations. During long-term storage, once the filler and complexation sites reach adsorption saturation limits, a large number of uncaptured inferior molecules will still migrate to the surface and accumulate, leading to color development or blooming. On the other hand, from the conventional theoretical perspective of polymer surface modification, attempting to achieve macroscopic dynamic dispersion of the surface by simply introducing traditional low-molecular-weight surfactants (such as Span-type additives) will inevitably lead to a contradiction between appearance improvement and mechanical degradation. Although low-molecular-weight substances can rapidly migrate to the surface and break the stacking of color-developing molecules, the rapid release of these small molecules within the matrix will trigger a significant overplasticization effect and leave microstructural defects along the escape path. This physical evolution weakens the integrity of the polymer's three-dimensional cross-linked network, resulting in a decrease in the tensile strength of the vulcanizate, accompanied by a significant increase in Akron abrasion value and a deterioration in compression set, making it difficult to meet the long-term wear-resistant service requirements of rubber products under harsh working conditions. To address the technical challenge of simultaneously achieving dynamic surface protection and maintaining matrix mechanical integrity, this invention proposes a compound surfactant system based on a combination of large and small molecular weights. Summary of the Invention

[0005] The purpose of this invention is to provide a rubber composite additive that combines long-lasting low bleed properties with high mechanical properties, as well as its preparation method and application, in order to solve the technical defects of existing protective systems, such as short protective time and difficulty in taking into account the excellent mechanical properties of the rubber matrix.

[0006] This invention proposes to directly add a compounded low-coloring surfactant composition during the mixing process, aiming to actively intervene in and regulate the surface migration and aggregation behavior of small molecules such as colorants during the storage and service of rubber compounds. The selected rubber matrix materials include various primary raw rubbers, including natural rubber, butadiene rubber, styrene-butadiene rubber, and ethylene propylene diene monomer (EPDM) rubber. Given the extremely complex microstructure of the color-emitting small molecules migrating to the surface, which typically contain incompletely cleaved aromatic conjugated double bond systems and carry polar auxochrome groups, traditional internal micro-adsorption is easily saturated. Therefore, this invention departs from the traditional research and development approach that relies on internal blocking. Addressing the common physical characteristic that various complex color-emitting small molecules easily form ordered stacks on the surface and interfere with film formation, a surfactant system composed of large and small molecules is employed to achieve dynamic surface dispersal and in-situ mechanical compensation.

[0007] Furthermore, this invention achieves simultaneous improvement in the appearance and mechanical properties of rubber products by constructing a spatiotemporal synergistic dispersion system of surfactants of varying molecular weights and an in-situ mechanical compensation mechanism.

[0008] First, a surface dynamic relay dispersal mechanism is established. This invention adds an appropriate amount of small-molecule surfactants. These substances possess extremely high molecular thermal mobility in the early stages after rubber molding, enabling them to rapidly migrate to the rubber surface and reduce surface tension, effectively blocking the orderly stacking of molecules such as polycyclic aromatic hydrocarbons. To address the problem of insufficient long-term protection caused by the rapid consumption of small molecules, this system introduces high-molecular-weight surfactants with compliant backbones and polar structures as the main long-term protective component. Due to their significant steric hindrance, these high-molecular-weight surfactants diffuse slowly and persistently within the rubber matrix, enabling them to effectively suppress discoloration under long-term storage conditions.

[0009] Secondly, an in-situ mechanical compensation mechanism for mechanical properties is introduced. Using conventional low-molecular-weight surfactants alone leaves microscopic defects along their escape pathways, leading to a significant decline in mechanical properties, especially tensile and abrasion resistance. The high-molecular-weight surfactant used in this invention possesses highly compliant aliphatic long chains and a certain number of polar groups, enabling it to deeply wedge into and physically entangle within the macromolecular three-dimensional cross-linked network of the rubber matrix. This strong anchoring effect of the long chains effectively inhibits the initiation and propagation of microcracks, counteracting the excessive plasticizing effect caused by the escape of small molecules, thereby endowing the composite material with excellent fracture toughness and wear resistance. The process of the surfactant driving away color-emitting molecules is described in [the following section is incomplete and requires further context]. Figure 1 .

[0010] The specific technical solution adopted in this invention is as follows: A rubber composite additive that combines long-lasting, low-bleeding properties with high mechanical properties. The main components of this composite surfactant are a high molecular weight long-chain aliphatic surfactant and a low molecular weight nonionic surfactant. In the composite surfactant masterbatch, the high molecular weight long-chain aliphatic surfactant accounts for 60% to 90% by mass, and the low molecular weight nonionic surfactant accounts for 10% to 40% by mass (the sum of the two mass percentages is 100%).

[0011] A further preferred embodiment is a rubber composite additive that combines long-lasting low bleed properties with high mechanical properties, comprising the following components by weight percentage: High molecular weight long-chain aliphatic surfactants: 70% to 85%; 15% to 30% low molecular weight nonionic surfactants.

[0012] The high molecular weight long-chain aliphatic surfactant is one or more combinations of poly(1,4-butanediol adipate) (PBA), poly(1,4-butanediol succinate) (PBS), and polycaprolactone (PCL). The number average molecular weight of this type of surfactant is limited to between 1000 and 5000 (preferably between 1000 and 3000), most preferably 2000, and all are produced by Shanghai Maclean Biochemical Technology Co., Ltd., with a purity greater than or equal to 98%.

[0013] The low molecular weight nonionic surfactant is one or a combination of two of sorbitan stearate or sorbitan monooleate, such as Span 60. The number average molecular weight of this type of high molecular weight surfactant is limited to 200-1000, and the molecular weight is less than 1000. It is produced by Shanghai Maclean Biochemical Technology Co., Ltd., with a purity of greater than or equal to 98%.

[0014] A method for preparing a rubber composite additive that combines long-lasting low bleed properties with high mechanical properties includes the following steps: High molecular weight long-chain aliphatic surfactants and low molecular weight nonionic surfactants are added to a mechanically stirred reactor with a temperature control system. The temperature is raised to 60-90 degrees Celsius. After the esters are completely melted, the mechanical stirrer is turned on to mix and stir thoroughly under high shear. The mixture is then removed, cooled to room temperature and allowed to solidify. Subsequently, it is pulverized and sieved to obtain composite surfactant masterbatch, which is a rubber composite additive that combines long-lasting low color fading performance with mechanical properties.

[0015] The application of the rubber composite additive possessing both long-lasting low bleed properties and high mechanical properties in the preparation of rubber with both properties. Specifically, the application includes: Raw rubber is added and plasticized until it completely covers the front roller. After being cut several times, it is discharged for later use. The temperature of the Hacker internal mixer is set to 75-85 degrees Celsius. The plasticized rubber is added to the mixer, followed by zinc oxide, stearic acid, carbon black, antioxidant, and aromatic oil in sequence. After mixing evenly, rubber compound additives with both long-lasting low color fading and mechanical properties are added. After further mixing, the rubber is discharged and finally vulcanized to obtain rubber with both long-lasting low color fading and mechanical properties.

[0016] The raw rubber is natural rubber or artificial rubber; the artificial rubber is butadiene rubber, styrene-butadiene rubber or ethylene propylene diene monomer (EPDM) rubber.

[0017] The mass ratio of the raw rubber to the rubber compound additive that has both long-lasting low blemish properties and mechanical properties is 100:1.9~4.

[0018] Compared with the prior art, the present invention has the following two outstanding technical advantages: First, this invention breaks through the capacity saturation bottleneck commonly faced by traditional microscopic adsorption and complexation technologies. By pioneering a composite system of large and small molecular weight surfactants, it achieves spatiotemporal dynamic synergistic dispersion of small molecules that contribute to color on the rubber surface throughout their entire life cycle, from the initial rapid blocking and stacking of small molecules to the long-term slow overflow relay of large molecules, thus endowing the product with better long-lasting low color cast performance.

[0019] Secondly, this invention utilizes the physical entanglement effect of the main chain of high molecular weight surfactants and the strong interfacial forces of polar ester groups to counteract and repair in situ the microstructural defects caused by the escape of small molecules. Compared with simply adding small molecule surfactants, this invention reduces the tensile strength and Akron wear of the sample to a certain extent, while maintaining or even improving tensile strength and resistance to deformation, thus meeting the high standards required for mechanical applications under harsh modern working conditions. Attached Figure Description

[0020] Figure 1 This is a diagram of the surface color-emitting molecules dispersed by the surfactant in this invention. Detailed Implementation

[0021] Example 1: Preferred proportions of the present invention Step 1: Preparation of the composite surfactant masterbatch. Weigh 8 parts of poly(1,4-butanediol adipate) (molecular weight: 2000) and 2 parts of Span 60 (molecular weight: 500), and add them to a mechanically stirred reactor equipped with a temperature control system. Heat to 75 degrees Celsius. After the esters are completely melted, turn on the mechanical stirrer and mix thoroughly at 800 rpm for 2 hours under high shear. Remove and cool to room temperature to solidify. Then, pulverize and pass through an 80-mesh sieve to obtain a composite surfactant masterbatch with synergistic effects of large and small molecules for later use. (In this premix, the polyester surfactant accounts for 80% by mass, and the small molecule surfactant accounts for 20% by mass).

[0022] Step 2: Matrix Plasticizing and Mixing Process. Adjust the front and rear roll temperatures of the two-roll mill to 65°C and 60°C respectively. Add 100 parts of natural rubber (Guangxi Wusen New Material Technology Co., Ltd., 3L) and plasticize until it completely covers the front roll. After several cuts, discharge the material for later use. Set the temperature of the Hacker internal mixer to 80°C, add the plasticized rubber, and then add 5 parts of zinc oxide, 1 part of stearic acid, 50 parts of N220 carbon black, and 1.5 parts of antioxidant 4010NA according to the predetermined formula. After mixing evenly, add 2 parts of the above-prepared composite activator masterbatch, continue mixing for 3 minutes, and then discharge the rubber.

[0023] Step 3: Crosslinking and vulcanization molding process. Place the above-mentioned rubber compound into a two-roll mill, add 2 parts sulfur and 1.2 parts accelerator CZ, and after complete mixing, adjust the roll gap to 2mm and extrude the product into sheets. After the rubber compound has rested for one day, vulcanize it for 12 minutes at 10 MPa pressure on a fully automatic flatbed tablet press at 150 degrees Celsius. After cooling, remove it and let it rest at room temperature for 15 days before performance testing.

[0024] Example 2: Changing the masterbatch ratio The preparation method provided in this embodiment is the same as that in Example 1, except that the content of high molecular weight long-chain aliphatic surfactant in the first step is 6 parts, the content of Span 60 is 4 parts, and the total amount of masterbatch added is still 2 parts.

[0025] Example 3: Increasing the total amount of masterbatch added The preparation method provided in this embodiment is the same as that in Embodiment 1, except that the amount of composite activator masterbatch added in the second step is increased to 4 parts, which is mainly for special rubber products with extremely high appearance requirements.

[0026] Comparative Example 1: Blank Control Group The preparation method provided in this comparative example is the same as that in Example 1, except that no composite activator masterbatch is added in the second mixing step.

[0027] Comparative Example 2: Control group of pure small molecule surfactants The preparation method provided in this comparative example is the same as that in Example 1, except that it does not go through the first step of masterbatch preparation, but directly adds 2 parts of pure Span 60 in the second step of mixing. This group only has surface dispersive effect and no in-situ mechanical compensation mechanism.

[0028] Comparative Example 3: Control Group of Pure Macromolecular Surfactants The preparation method provided in this comparative example is the same as that in Example 1, except that it does not go through the first step of masterbatch preparation, but directly adds 2 parts of pure poly(1,4-butylene adipate) in the second step of mixing. This group has mechanical compensation effect but lacks an early rapid dispersion mechanism.

[0029] Performance testing methods and results Coloration test: After the molded vulcanized rubber sample was left at room temperature for 15 days, it was observed with the naked eye and under a microscope under the same lighting conditions and shooting angle.

[0030] Tensile properties test: Tested according to GB / T 528-2009 standard.

[0031] Wear performance test: Tested according to GB / T 25262-2010 standard.

[0032] Compression set test: The test was conducted in accordance with GB / T 7759.1-2015 standard.

[0033] Table 1. Mechanical properties of each example and comparative example

[0034] As can be seen from the data in the table above, the anti-coloring additive composition prepared by the present invention has both excellent anti-coloring performance and maintains the excellent mechanical properties of the material.

[0035] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A rubber composite additive that combines long-lasting low bleed properties with high mechanical properties, characterized in that, It consists of the following components, based on a 100% percentage of total mass: High molecular weight long-chain aliphatic surfactants, 60% to 90%; 10% to 40% low molecular weight nonionic surfactants.

2. The rubber composite additive with both long-lasting low bleed properties and high mechanical properties according to claim 1, characterized in that, The number average molecular weight of the high molecular weight long-chain aliphatic active agent is 1000 to 5000.

3. The rubber composite additive with both long-lasting low bleed properties and high mechanical properties according to claim 1, characterized in that, The high molecular weight long-chain aliphatic surfactant is one or more of poly(1,4-butanediol adipate), poly(1,4-butanediol succinate), and polycaprolactone.

4. The rubber composite additive with both long-lasting low bleed properties and high mechanical properties according to claim 1, characterized in that, The molecular weight of the low molecular weight nonionic surfactant is 200~1000.

5. The rubber composite additive with both long-lasting low bleed properties and high mechanical properties according to claim 1, characterized in that, The low molecular weight nonionic surfactant is one or a combination of two of sorbitan stearate and sorbitan monooleate.

6. The method for preparing the rubber composite additive with both long-lasting low bleed properties and high mechanical properties according to any one of claims 1 to 5, characterized in that, Includes the following steps: High molecular weight long-chain aliphatic surfactants and low molecular weight nonionic surfactants are added to a mechanically stirred reactor with a temperature control system. The temperature is raised to 60-90 degrees Celsius. After the esters are completely melted, the mechanical stirrer is turned on to mix and stir thoroughly under high shear. The mixture is then removed, cooled to room temperature and allowed to solidify. Subsequently, it is pulverized and sieved to obtain composite surfactant masterbatch, which is a rubber composite additive that combines long-lasting low color fading performance with mechanical properties.

7. The application of the rubber composite additive with both long-lasting low bleed properties and high mechanical properties as described in any one of claims 1 to 5 in the preparation of rubber with both long-lasting low bleed properties and high mechanical properties.

8. The application according to claim 7, characterized in that, Specifically, it includes: Raw rubber is added and plasticized until it completely covers the front roller. After being cut several times, it is discharged for later use. The temperature of the Hacker internal mixer is set to 75-85 degrees Celsius. The plasticized rubber is added to the mixer, followed by zinc oxide, stearic acid, carbon black, antioxidant, and aromatic oil in sequence. After mixing evenly, rubber compound additives with both long-lasting low color fading and mechanical properties are added. After further mixing, the rubber is discharged and finally vulcanized to obtain rubber with both long-lasting low color fading and mechanical properties.

9. The application according to claim 8, characterized in that, The raw rubber mentioned is natural rubber or synthetic rubber; The artificial rubber mentioned is butadiene rubber, styrene-butadiene rubber, or ethylene propylene diene monomer (EPDM) rubber.

10. The application according to claim 8, characterized in that, The mass ratio of the raw rubber to the rubber compound additive that has both long-lasting low blemish properties and mechanical properties is 100:1.9~4.

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