Abrasion-resistant rubber hydraulic hose with gradient variation and method for manufacturing the same

Abstract

The application discloses a wear-resistant rubber hydraulic hose with gradient change and a preparation method thereof. The preparation method comprises the following steps: (1) respectively feeding and blending inner rubber and outer rubber, and the two rubbers are both blended with NBR / PVC alloy rubber and chlorosulfonated polyethylene rubber as a blended matrix; (2) adopting a concentric double-layer co-extrusion ring-shaped die head, the mixed inner rubber and the mixed outer rubber are respectively conveyed to independent ring-shaped flow channels in the die head, and are co-extruded to form a double-layer tubular blank; (3) the co-extruded double-layer tubular blank is placed in a clean constant-temperature and constant-humidity environment for storage, and the rubber molecules, additives and fillers of the two layers of rubber are driven by concentration difference to form a continuous component transition zone; and (4) the double-layer tubular blank after storage is placed in a high-pressure steam vulcanization tank, and a vulcanization process of sectional control of temperature and pressure according to time sequence is adopted to complete curing, so that the two layers of rubber are synchronously crosslinked, and a continuous interpenetrating crosslinked network is formed at the interface.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a wear-resistant rubber hydraulic hose with gradient changes and its preparation method. Background Technology

[0002] Rubber hydraulic hoses are widely used in the hydraulic systems of construction machinery, where operating conditions are generally harsh. To mitigate wear on rubber hydraulic hoses, early solutions typically employed external protective structures: one involved wrapping the hose with asbestos cloth for insulation to delay rubber aging, followed by a braided stainless steel wire layer; the other involved installing a heat-shrinkable, wear-resistant polyester fiber braided sheath over the hose. Because the second solution requires customizing the sheath's length and outer diameter based on the hose assembly's length and outer diameter, and the heat-shrinkable polyester fiber braided sheath requires subsequent high-temperature thermoforming, production costs are higher. Therefore, more manufacturers opted for the first solution. However, the first solution not only has a complex process and significantly increases hose weight, but also noticeably reduces the hose's overall flexibility, negatively impacting the operational flexibility of construction machinery.

[0003] To simplify the process and reduce costs, existing technologies have developed high-abrasion-resistant rubber material compositions. Through formulation optimization, these compositions directly enhance the abrasion resistance of the outer rubber layer, allowing for the direct braiding of stainless steel wire layers onto the surface of the rubber hydraulic hose without the need for an additional protective layer, and using a silica-based adhesive system for interlayer fixation. This rubber hydraulic hose typically uses NBR / PVC alloy rubber and chlorosulfonated polyethylene rubber as the base material, employing a blend of silica and carbon black treated with a silane coupling agent as a reinforcing system. This effectively reduces the wear of the outer rubber layer and significantly extends the hose's service life. However, in practical applications, such high wear-resistant formulations have encountered the problem of insufficient adhesion between the rubber hydraulic hose and the stainless steel wire layer: the bonding between the rubber hydraulic hose and the stainless steel wire layer usually adopts the resorcinol-formaldehyde-fumed silica (RFS) bonding system. The high content of polar fillers such as fumed silica in the formulation has a strong adsorption effect, which will consume a large amount of the effective components in the bonding system, resulting in insufficient concentration of adhesive additives reaching the steel wire interface; at the same time, the high filler content will increase the melt viscosity of the rubber compound, making it difficult for the rubber compound to fully wet the surface of the stainless steel wire layer, and failing to form a complete chemical bond layer and mechanical interlocking structure, ultimately resulting in low bonding strength between the outer rubber layer and the steel wire braided layer.

[0004] Under long-term operating conditions of repeated bending and high-pressure impact in construction machinery, if the surface layer of the rubber hydraulic hose delaminates from the stainless steel wire layer, the hose will be easily scratched by the steel wire, accelerating the decline of pressure resistance and seriously affecting the safety and service life. Currently, conventional improvement methods mostly involve directly increasing the amount of adhesive additives, but due to the limitations of filler adsorption effects, the improvement in adhesive strength is limited, and it further increases production costs. Some solutions improve adhesion by adding an independent intermediate adhesive layer, but interfacial delamination easily occurs between independent adhesive layers, and the process complexity increases significantly, failing to simultaneously meet the requirements of high wear resistance and high adhesive reliability. Summary of the Invention

[0005] The purpose of this invention is to disclose a wear-resistant rubber hydraulic hose with gradient changes and its preparation method, so as to solve one or more technical problems existing in the existing methods and provide at least one beneficial option or create conditions.

[0006] To achieve the above objectives, the present invention provides the following technical solution: The first aspect of this invention is to provide a method for preparing a wear-resistant rubber hydraulic hose with gradient changes. The preparation method includes the following steps: (1) feeding and mixing inner and outer rubber compounds separately, both of which use NBR / PVC alloy rubber and chlorosulfonated polyethylene rubber as the blend matrix, both adopt a vulcanization system with the same mechanism composed of sulfur and accelerator, and both are obtained by a two-stage mixing process in an internal mixer; (2) using a concentric double-layer co-extrusion annular die head, the mixed inner and outer rubber compounds are respectively transported to independent annular channels in the die head, the molten rubber compounds converge at the die head outlet, and are extruded together to form a double-layer tubular shape. (3) The co-extruded double-layer tubular preform is placed in a clean, constant temperature and humidity environment. The rubber molecules, additives and fillers of the two layers of rubber spontaneously diffuse across the interface in the radial direction under the drive of the concentration difference, forming a continuous component transition zone; (4) The placed double-layer tubular preform is placed in a high-pressure steam vulcanizing tank and cured by a vulcanization process that controls the temperature and pressure in segments according to the time sequence, so that the two layers of rubber complete the cross-linking reaction simultaneously and form a continuous interpenetrating cross-linking network at the interface, resulting in a wear-resistant rubber hydraulic hose with gradient changes. The preparation method provides a thermodynamic compatibility basis for interlayer molecular interpenetration through the design of homologous matrix and vulcanization system with the same mechanism; room temperature pre-diffusion enables the components to spontaneously form a continuous transition, eliminating clear geometric interfaces; segmented vulcanization achieves a balance between molecular diffusion and cross-linking reaction, and finally forms a continuous interpenetrating cross-linking network without clear layering. The resulting wear-resistant rubber hydraulic hose exhibits a continuous gradient distribution of filler concentration decreasing and adhesive activity increasing radially from the inside to the outside along the hose wall. This design not only provides excellent wear resistance but also allows for compatibility with the RFS adhesive system, achieving good adhesion with the stainless steel wire layer. In a further embodiment of the first aspect of the present invention, the inner rubber compound, by weight, comprises the following components: 60-65 parts NBR / PVC alloy rubber, 35-40 parts chlorosulfonated polyethylene rubber, 3-5 parts zinc oxide, 0.5-2 parts stearic acid, 6-8 parts tert-butylphenol resin, 0.2-1 parts antioxidant NBC, 1-2 parts antioxidant 4010NA, 0.3-0.4 parts cobalt borylate, 2 parts protective wax, 3-4 parts silane coupling agent Si-69, 55-60 parts silica, 35-40 parts carbon black N220, 6-8 parts magnesium oxide, 35-38 parts dioctyl terephthalate, 4-8 parts adhesive RC, 0.3-0.5 parts anti-scorching agent CTP, 1.8-2.5 parts sulfur, and accelerator DCBS. 1~1.5 parts; the outer rubber compound, by weight, contains the following components: 70~75 parts NBR / PVC alloy rubber, 25~30 parts chlorosulfonated polyethylene rubber, 3~5 parts zinc oxide, 0.5~2 parts stearic acid, 3~4 parts tert-butylphenol resin, 0.2~1 parts antioxidant NBC, 1~2 parts antioxidant 4010NA, 0.6~0.8 parts cobalt borate, 1~2 parts silane coupling agent Si-69, 30~35 parts silica, 20~25 parts carbon black N220, 4~5 parts magnesium oxide, 42~45 parts dioctyl terephthalate, 4~8 parts adhesive RC, 0.3~0.5 parts anti-scorching agent CTP, 1.8~2.5 parts sulfur, 0.8~1 parts accelerator DCBS, and 0.2~0.3 parts accelerator CZ. The inner rubber compound uses a high proportion of reinforcing fillers and chlorosulfonated polyethylene rubber to ensure the mechanical strength, wear resistance, and media resistance of the tube. The outer rubber compound reduces the filler content and increases the amount of adhesive additives and plasticizers to improve the surface wettability and adhesive reactivity of the rubber compound, making it suitable for subsequent surface bonding processes. The two formulations have the same matrix and consistent vulcanization system, ensuring interlayer thermodynamic compatibility and molecular diffusion capability, providing a component basis for continuous gradients and interpenetrating networks. The protective wax is only applied to the inner rubber compound to prevent it from precipitating to the surface and affecting the bonding effect of the outer compound.

[0007] In a further embodiment of the first aspect of the present invention, the weight ratio of NBR to PVC in the NBR / PVC alloy rubber is 65~75:25~35; the chlorine content of the chlorosulfonated polyethylene rubber is 32.5~37.5%. This ratio of NBR / PVC alloy rubber exhibits excellent oil resistance, abrasion resistance, and processing fluidity, and exhibits optimal compatibility with chlorosulfonated polyethylene rubber. A specific chlorine content in the chlorosulfonated polyethylene rubber achieves an optimal balance between abrasion and weather resistance and processing viscosity, ensuring co-extrusion molding stability and the weather and abrasion resistance of the final product.

[0008] In a further embodiment of the first aspect of the present invention, the two-stage mixing process in step (1) includes a first stage of internal mixing to prepare masterbatch and a second stage of internal mixing to prepare final compound; the preparation process of the masterbatch includes: putting NBR / PVC alloy rubber and chlorosulfonated polyethylene rubber into an internal mixer and plasticizing for 2 minutes under a top pressure of 0.3~0.6 MPa; sequentially adding zinc oxide, stearic acid, antioxidant NBC, antioxidant 4010NA, tert-butylphenolic resin, and cobalt borate, and simultaneously adding protective wax to the inner side of the rubber compound, and maintaining pressure for 2 minutes; adding a premixed mixture of silica and silane coupling agent Si-69, and maintaining pressure for 2 minutes; finally adding carbon black N220, dioctyl terephthalate, and magnesium oxide, maintaining pressure for 2~3 minutes, and controlling the discharge temperature at 140~145℃. The final compound is prepared by: re-feeding the masterbatch into an internal mixer and pressurizing and plasticizing for 1 minute until the rubber temperature reaches 80~90℃; adding adhesive RC, anti-scorching agent CTP, sulfur, and accelerator DCBS, and simultaneously adding accelerator CZ to the outer rubber compound, pressurizing and holding for 30 seconds, and controlling the discharge temperature at 95~105℃; after discharge, it is thinly extruded through an internal mixer and cooled and left to stand for at least 4 hours. The first stage of high-temperature internal mixing can fully disperse the fillers, activators (zinc oxide, stearic acid), plasticizers (dioctyl terephthalate), and other components in the rubber matrix, maximizing the reinforcing and activating effects; the second stage of low-temperature short-time mixing is added to the vulcanization system and adhesive, which can effectively avoid early scorching of the rubber compound, ensure the processing safety of subsequent extrusion and standing processes, and at the same time ensure the uniform dispersion of vulcanization aids, so that the vulcanization characteristics of the two layers of rubber compound are stable and consistent, providing a uniform material basis for synchronous cross-linking and interpenetration.

[0009] In a further embodiment of the first aspect of the present invention, the temperature of the concentric double-layer co-extrusion annular extruder in step (2) is set in stages: 60~70 ℃ for the feeding section, 75~85 ℃ for the plasticizing section, and 85~95 ℃ for the die head section. This staged temperature setting allows the rubber compound to gradually plasticize and melt, avoiding premature scorching caused by excessively high temperatures in the feeding section. Simultaneously, it ensures that the rubber compound in the die head section has stable melt viscosity and fluidity, enabling the two layers of rubber compound to achieve a tight, gapless melt bond at the die head outlet, thus improving the surface smoothness and dimensional uniformity of the tube blank.

[0010] In a further embodiment of the first aspect of the present invention, the temperature is controlled to ensure that the difference in melt viscosity between the extruded inner and outer rubber compounds does not exceed 15%. A melt viscosity difference of less than 15% can effectively avoid defects such as interface shift, interlayer flow disorder, and uncontrolled wall thickness ratio during co-extrusion, ensuring uniform and stable gradient layer thickness, uniform interface diffusion, and ultimately forming a continuous and consistent interpenetrating transition zone, thereby improving the stability of product performance between batches.

[0011] In a further embodiment of the first aspect of the present invention, the concentric double-layer co-extrusion annular die head is equipped with a vacuum sizing sleeve. The traction speed and screw speed are linked to control the wall thickness. In the double-layer tubular preform, the inner rubber material accounts for 65-75% of the total wall thickness, and the outer rubber material accounts for 25-35%. Vacuum sizing can precisely control the inner diameter and roundness of the preform, ensuring the accuracy of the hose diameter. As the main body for wear resistance and mechanical load bearing, the larger proportion of the inner rubber material can ensure the overall wear resistance and pressure bearing performance of the tube. The outer rubber material mainly provides adhesive activity, optimizing the surface bonding ability without sacrificing the overall wear resistance, while controlling the total wall thickness to meet the general specifications of hydraulic hoses.

[0012] In a further embodiment of the first aspect of the present invention, the placement environment in step (3) is a temperature of 23±2 ℃ and a relative humidity of 50±10%; the double-layer tubular preform is left to stand for 2 to 6 hours. Under the temperature and humidity conditions of this placement environment, the rubber molecules have suitable kinematic activity. Combined with the corresponding standing time, the molecules, additives, and fillers of the two rubber compounds can fully diffuse across the interface to form a continuous component transition zone of suitable thickness, eliminating a clear geometric interface; at the same time, it can release the extrusion internal stress, avoid the occurrence of interface stress concentration during the subsequent vulcanization process, and lay the physical basis for the formation of cross-linked interpenetrating networks.

[0013] In a further embodiment of the first aspect of the present invention, the vulcanization process of controlling temperature and pressure in a time sequence as described in step (4) is specifically divided into three stages: (A) uniformly heating to 120 ℃ within 30 minutes, with the pressure inside the tank stabilizing at 0.2~0.3 MPa; (B) continuing to heat to 150 ℃, with the pressure inside the tank stabilizing at 0.42 MPa, and maintaining constant temperature and pressure for 90 minutes; (C) stopping the introduction of steam, slowly depressurizing and gradually introducing cooling water, and opening the tank to discharge the material after the temperature inside the tank drops below 80 ℃. Stage (A) is the pre-diffusion stage of heating, which further thickens the component transition zone at a low crosslinking rate to avoid premature crosslinking and locking of molecular chains due to rapid heating, thus ensuring the interpenetration depth. Stage (B) is the constant temperature crosslinking stage, in which the two rubber compounds simultaneously reach the positive vulcanization state, and the intertwined molecular chains at the interface participate in the crosslinking reaction, solidifying the physical diffusion structure into a continuous chemical interpenetrating network. The slow cooling process in stage (C) can avoid residual internal stress caused by a sudden drop in temperature and pressure, prevent damage to the interpenetrating interface, and ensure structural integrity and bonding strength.

[0014] A second aspect of the present invention is to provide a wear-resistant rubber hydraulic hose with a gradient change, prepared by the preparation method described in the first aspect of the present invention. Detailed Implementation

[0015] The main raw materials used in the following examples and comparative examples are all commercially available products commonly used in the rubber industry, with the following specific specifications: NBR / PVC alloy rubber M58: NBR to PVC weight ratio is 70:30; Chlorosulfonated polyethylene rubber 3305: chlorine content 32.5%~37.5%, Mooney viscosity ML(1+4) 100 ℃ is 55±5; Precipitated silica and carbon black N220: conventional reinforcing fillers used in the rubber industry; silane coupling agent Si-69, cobalt borylate, adhesive RC, antioxidant NBC, antioxidant 4010NA, protective wax LSB20, scorch inhibitor CTP, accelerator DCBS, accelerator CZ, dioctyl terephthalate, tert-butylphenol resin, zinc oxide, stearic acid, magnesium oxide, and sulfur are all general industrial-grade products used in rubber processing.

[0016] Example 1 This embodiment describes the preparation of a gradient abrasion-resistant rubber hydraulic hose. The formulations (by weight) of the inner and outer rubber compounds are as follows: Inner rubber compound: 62 parts NBR / PVC alloy rubber, 38 parts chlorosulfonated polyethylene rubber, 4 parts zinc oxide, 1 part stearic acid, 7 parts tert-butylphenol resin, 0.4 parts antioxidant NBC, 1.5 parts antioxidant 4010NA, 0.35 parts cobalt borate, 2 parts protective wax, 3.5 parts silane coupling agent Si-69, 58 parts silica, 38 parts carbon black N220, 7 parts magnesium oxide, 36 parts dioctyl terephthalate, 6 parts adhesive RC, 0.4 parts anti-scorching agent CTP, 2.2 parts sulfur, and 1.2 parts accelerator DCBS.

[0017] Outer rubber compound: 72 parts NBR / PVC alloy rubber, 28 parts chlorosulfonated polyethylene rubber, 4 parts zinc oxide, 1 part stearic acid, 3.5 parts tert-butylphenol resin, 0.4 parts antioxidant NBC, 1.5 parts antioxidant 4010NA, 0.7 parts cobalt borate, 1.5 parts silane coupling agent Si-69, 32 parts silica, 22 parts carbon black N220, 4.5 parts magnesium oxide, 43 parts dioctyl terephthalate, 6 parts adhesive RC, 0.4 parts anti-scorching agent CTP, 2.1 parts sulfur, 0.9 parts accelerator DCBS, and 0.25 parts accelerator CZ.

[0018] The preparation steps are as follows: (1) Preparation of final rubber by two-stage mixing The inner and outer rubber compounds were prepared separately, both using a two-stage intensive mixing process: The first stage of internal mixing is used to prepare the masterbatch: NBR / PVC alloy rubber and chlorosulfonated polyethylene rubber of the corresponding formulation are put into an internal mixer, the top pressure is 0.5 MPa, and the mixture is plasticized under pressure for 2 minutes; zinc oxide, stearic acid, antioxidant NBC, antioxidant 4010NA, tert-butylphenol resin, and cobalt borate are added in sequence, and protective wax is added to the inner rubber compound at the same time, and the pressure is maintained for 2 minutes; a premixed mixture of silica and silane coupling agent Si-69 is added, and the pressure is maintained for 2 minutes; finally, carbon black N220, magnesium oxide, and dioctyl terephthalate are added, and the pressure is maintained for 2.5 minutes, and the discharge temperature is controlled at 142 ℃; after discharge, the mixture is transferred to an open mill, and after three wraps and two rolls, the rubber sheet is produced with a thickness of 5.0~7.0 mm. After cooling and drying, the sheet is left to stand at room temperature for 9 hours to obtain the masterbatch of the corresponding rubber compound.

[0019] The second stage of internal mixing is used to prepare the final rubber compound: The masterbatch is put back into the internal mixer, the top pressure is 0.5 MPa, and the pressure is applied for 1 minute until the rubber temperature rises to 85 ℃; the binder RC, anti-scorching agent CTP, sulfur, and accelerator DCBS are added, and the accelerator CZ is added to the outer rubber compound at the same time. The pressure is maintained for 30 seconds, and the discharge temperature is controlled at 100 ℃; after discharge, it is transferred to the open mill, and after passing through the thin mill 3 times, the rubber strip is produced with a thickness of 4.0~6.0 mm and a width of 120~150 mm. After cooling and drying, it is left to stand at room temperature for 5 hours to obtain the final rubber compound of the inner rubber compound and the final rubber compound of the outer rubber compound.

[0020] (2) Double-layer co-extrusion molding: Two cold-feed rubber extruders are equipped with concentric double-layer co-extrusion annular die heads. The inner extruder feeds the inner final compound, and the outer extruder feeds the outer final compound. The extruder temperature is divided into sections: feeding section 65℃, plasticizing section 80℃, and die head section 90℃. The melt viscosity difference between the two layers of rubber is 12% through temperature fine-tuning. The die head is equipped with a vacuum sizing sleeve, and the traction speed and screw speed are linked to control the wall thickness. The total wall thickness of the double-layer tubular preform is 1.5 mm, of which the inner rubber accounts for 70% of the total wall thickness and the outer rubber accounts for 30% of the total wall thickness. The preform is initially shaped by water cooling and the surface is kept clean throughout the process.

[0021] (3) Interface pre-diffusion: The co-extruded double-layer tubular preform is placed in a clean environment with a temperature of 23±2 ℃ and a relative humidity of 50±10% for 4 hours. The rubber molecules, additives and fillers of the two layers of rubber spontaneously diffuse across the interface in the radial direction under the drive of the concentration difference, forming a continuous component transition zone.

[0022] (4) Segmented vulcanization and curing: The tube blanks after being left to stand are evenly placed on the vulcanization rack and sent into the high-pressure steam vulcanization tank for curing using a three-stage vulcanization process: 1) The temperature is raised to 120 ℃ at a uniform rate within 30 minutes, and the pressure inside the tank is stabilized at 0.25 MPa; 2) Continue heating to 150 ℃, and stabilize the pressure inside the tank at 0.42 MPa. Maintain this constant temperature and pressure for 90 minutes. 3) Stop the steam supply, slowly depressurize and gradually introduce cooling water. After the temperature inside the tank drops to 75°C, open the tank and discharge the material. Allow it to cool naturally at room temperature for 24 hours to obtain the gradient wear-resistant rubber hydraulic hose of this embodiment.

[0023] Example 2 The difference between this embodiment and Embodiment 1 lies in the upper limit of the range of formula and process parameters, as detailed below: Inner rubber compound: 60 parts NBR / PVC alloy rubber, 40 parts chlorosulfonated polyethylene rubber, 5 parts zinc oxide, 2 parts stearic acid, 8 parts tert-butylphenol resin, 1 part antioxidant NBC, 2 parts antioxidant 4010NA, 0.4 parts cobalt borate, 2 parts protective wax, 4 parts silane coupling agent Si-69, 60 parts silica, 40 parts carbon black N220, 8 parts magnesium oxide, 38 parts dioctyl terephthalate, 8 parts adhesive RC, 0.5 parts anti-scorching agent CTP, 2.5 parts sulfur, 1.5 parts accelerator DCBS.

[0024] Outer rubber compound: 75 parts NBR / PVC alloy rubber, 25 parts chlorosulfonated polyethylene rubber, 5 parts zinc oxide, 2 parts stearic acid, 4 parts tert-butylphenol resin, 1 part antioxidant NBC, 2 parts antioxidant 4010NA, 0.8 parts cobalt borate, 2 parts silane coupling agent Si-69, 35 parts silica, 25 parts carbon black N220, 5 parts magnesium oxide, 45 parts dioctyl terephthalate, 8 parts adhesive RC, 0.5 parts anti-scorching agent CTP, 2.5 parts sulfur, 1 part accelerator DCBS, and 0.3 parts accelerator CZ.

[0025] The process parameters were adjusted as follows: total wall thickness of the tube blank was 2.0 mm, with the inner rubber compound accounting for 65% of the total wall thickness and the outer rubber compound accounting for 35%; the pre-diffusion resting time was 6 hours; and the pressure during the vulcanization heating stage was 0.3 MPa. The remaining preparation steps were the same as in Example 1.

[0026] Example 3 This embodiment corresponds to a small-diameter, thin-walled flexible tube scenario, and differs from Embodiment 1 in that: The total wall thickness of the tube blank is 1.0 mm, with the inner rubber compound accounting for 75% of the total wall thickness and the outer rubber compound accounting for 25%. The pre-diffusion resting time is 2 hours, and the vulcanization heating stage duration is adjusted to 20 minutes. The remaining formulation and preparation steps are the same as in Example 1.

[0027] Comparative Example 1 This comparative example is a conventional single-layer high abrasion-resistant rubber hydraulic hose. The formulation is completely consistent with the inner rubber compound of Example 1. It is formed by single-layer extrusion process with a total wall thickness of 1.5 mm. There is no pre-diffusion step. The vulcanization adopts the conventional process of directly heating to 150 ℃ and holding at a constant temperature for 90 minutes. The other mixing parameters are the same as those of Example 1.

[0028] Comparative Example 2 This comparative example is a regular double-layer co-extruded rubber hose. The inner and outer formulations are completely the same as those in Example 1, but there is no interface pre-diffusion and resting step. After extrusion, it is directly sent into the vulcanizing tank and a conventional vulcanization process of directly heating to 150 ℃ and holding at a constant temperature for 90 minutes is adopted. The other parameters are the same as those in Example 1.

[0029] Comparative Example 3 The difference between this comparative example and Example 1 is that two additional parts of protective wax were added to the outer adhesive material, while the rest of the formulation and preparation steps were completely consistent.

[0030] Performance Testing and Results Analysis The performance of the samples from each embodiment and comparative example was tested in accordance with the corresponding national standards. The test methods are as follows: Tensile strength and elongation at break: tested according to GB / T 528-2009; Abrasion resistance of outer coating: tested according to GB / T 12721-2007, under a load of 25 N and 2000 cycles; Interlayer peeling pattern: Peel off the inner and outer layers of the pipe wall, observe the damage pattern, and determine whether it is body tearing or interface separation; Oil volume change rate: tested according to GB / T 1690-2010, IRM903 standard oil, 100 ℃×72 hours; Steel wire pull-out force: After the outer surface of the sample is polished and activated, it is coated with RFS adhesive paste, and then braided with stainless steel wire. After secondary vulcanization and bonding at 120℃, the steel wire pull-out force is tested. Ozone resistance performance: Observe whether cracking occurs under the conditions of ozone concentration of 50 pphm and 40 ℃ for 72 hours according to Method 1 of GB / T 24134-2009.

[0031] The performance of each embodiment and comparative example was tested according to the corresponding national standards, and the test results are shown in Table 1: Table 1

[0032] The test results show that: 1. The wear loss of each embodiment remained below 0.02 g, which is close to the original single-layer high wear-resistant formula, proving that the gradient structure did not lose the core wear resistance performance of the outer adhesive; 2. The wire pull-out force of each embodiment is increased by more than 30% compared with Comparative Example 1, and the adhesion performance is significantly improved, effectively solving the problem of poor adhesion between the high wear-resistant outer adhesive and the stainless steel wire layer; In the embodiments, the outer adhesive layers all exhibit bulk tearing with no interface separation, proving that the gradient cross-linked interpenetrating structure forms a continuous overall network without any delamination risk; while in contrast, the ordinary double-layer co-extrusion comparative example 2 shows interface separation, and its overall structural integrity is far inferior to the solution of this invention.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a wear-resistant rubber hydraulic hose with gradient changes, characterized in that, Includes the following steps: (1) The inner rubber compound and the outer rubber compound are prepared separately. Both rubber compounds use NBR / PVC alloy rubber and chlorosulfonated polyethylene rubber as the blend matrix. They are both vulcanization systems with the same mechanism composed of sulfur and accelerator, and are both obtained by two-stage mixing process in a mixer. (2) A concentric double-layer co-extrusion annular die head is used to transport the inner rubber compound and the outer rubber compound that have been mixed to the independent annular flow channel in the die head. The molten rubber compound is merged at the die head outlet and extruded together to form a double-layer tubular preform. (3) The co-extruded double-layer tubular preform is placed in a clean, constant temperature and humidity environment. The rubber molecules, additives and fillers of the two layers of rubber spontaneously diffuse across the interface in the radial direction under the drive of the concentration difference, forming a continuous component transition zone. (4) The double-layer tubular blank after being placed in a high-pressure steam vulcanizing tank is cured by using a vulcanization process that controls the temperature and pressure in segments according to the time sequence, so that the two layers of rubber material can complete the cross-linking reaction simultaneously and form a continuous interpenetrating cross-linking network at the interface, thus obtaining a wear-resistant rubber hydraulic hose with gradient changes.

2. The preparation method according to claim 1, characterized in that, The inner rubber compound, by weight, comprises 60-65 parts NBR / PVC alloy rubber, 35-40 parts chlorosulfonated polyethylene rubber, 3-5 parts zinc oxide, 0.5-2 parts stearic acid, 6-8 parts tert-butylphenol resin, 0.2-1 parts antioxidant NBC, 1-2 parts antioxidant 4010NA, 0.3-0.4 parts cobalt borylate, 2 parts protective wax, 3-4 parts silane coupling agent Si-69, 55-60 parts silica, 35-40 parts carbon black N220, 6-8 parts magnesium oxide, 35-38 parts dioctyl terephthalate, 4-8 parts adhesive RC, 0.3-0.5 parts anti-scorching agent CTP, 1.8-2.5 parts sulfur, and 1-1.5 parts accelerator DCBS. The outer rubber compound, by weight, comprises 70-75 parts NBR / PVC alloy rubber, 25-30 parts chlorosulfonated polyethylene rubber, 3-5 parts zinc oxide, 0.5-2 parts stearic acid, 3-4 parts tert-butylphenol resin, 0.2-1 parts antioxidant NBC, 1-2 parts antioxidant 4010NA, 0.6-0.8 parts cobalt borate, 1-2 parts silane coupling agent Si-69, 30-35 parts silica, 20-25 parts carbon black N220, 4-5 parts magnesium oxide, 42-45 parts dioctyl terephthalate, 4-8 parts adhesive RC, 0.3-0.5 parts anti-scorching agent CTP, 1.8-2.5 parts sulfur, 0.8-1 parts accelerator DCBS, and 0.2-0.3 parts accelerator CZ.

3. The preparation method according to claim 2, characterized in that, The weight ratio of NBR to PVC in the NBR / PVC alloy rubber is 65~75:25~35; the chlorine content of the chlorosulfonated polyethylene rubber is 32.5~37.5%.

4. The preparation method according to claim 2, characterized in that, The two-stage mixing process in step (1) includes a first stage of intensive mixing to prepare masterbatch and a second stage of intensive mixing to prepare final rubber. The preparation process of the masterbatch includes: feeding NBR / PVC alloy rubber and chlorosulfonated polyethylene rubber into an internal mixer and plasticizing for 2 minutes under a top pressure of 0.3~0.6 MPa; sequentially adding zinc oxide, stearic acid, antioxidant NBC, antioxidant 4010NA, tert-butylphenolic resin, and cobalt borate, while simultaneously adding protective wax to the inner rubber compound, and maintaining pressure for 2 minutes; adding a premixed mixture of silica and silane coupling agent Si-69, and maintaining pressure for 2 minutes; finally adding carbon black N220, dioctyl terephthalate, and magnesium oxide, and maintaining pressure for 2~3 minutes, with the discharge temperature controlled at 140~145 ℃; after discharge, extruding the rubber through an open mill and cooling and storing for no less than 8 hours; The preparation process of the final rubber compound includes: re-feeding the masterbatch into the internal mixer and pressurizing and plasticizing for 1 minute until the rubber temperature reaches 80~90℃; adding the binder RC, anti-scorching agent CTP, sulfur, and accelerator DCBS, and simultaneously adding the accelerator CZ to the outer rubber compound; maintaining pressure for 30 seconds; controlling the discharge temperature at 95~105℃; after discharge, passing the rubber through a two-roll mill to form thin strips, and cooling and letting it stand for no less than 4 hours.

5. The preparation method according to claim 4, characterized in that, In step (2), the temperature of the concentric double-layer co-extrusion annular extruder is divided into three sections: feeding section 60~70 ℃, plasticizing section 75~85 ℃, and die head section 85~95 ℃.

6. The preparation method according to claim 5, characterized in that, Temperature control ensures that the difference in melt viscosity between the extruded inner and outer rubber compounds does not exceed 15%.

7. The preparation method according to claim 5, characterized in that, The concentric double-layer co-extrusion annular die head is equipped with a vacuum sizing sleeve. The traction speed and screw speed are linked to control the wall thickness. In the double-layer tubular preform, the inner rubber material accounts for 65-75% of the total wall thickness, and the outer rubber material accounts for 25-35% of the total wall thickness.

8. The preparation method according to claim 1, characterized in that, Step (3) The placement environment is 23±2 ℃ and 50±10% relative humidity; the double-layer tubular billet is placed for 2~6 hours.

9. The preparation method according to claim 1, characterized in that, Step (4) describes a vulcanization process that controls temperature and pressure in segments according to a time sequence, specifically divided into three stages: (A) The temperature is raised to 120 °C at a uniform rate within 30 minutes, and the pressure inside the tank is stabilized at 0.2~0.3 MPa; (B) Continue heating to 150 °C, and the pressure inside the tank stabilizes at 0.42 MPa. Maintain constant temperature and pressure for 90 minutes. (C) Stop the steam supply, slowly depressurize and gradually introduce cooling water. Open the tank and discharge the material after the temperature inside the tank drops below 80 ℃.

10. A wear-resistant rubber hydraulic hose with a gradient change, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 9.

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