Rubber composition for stator gasket and motor assembly

Abstract

This application provides a rubber composition for stator lining and a motor assembly, relating to the field of rubber material technology. The rubber composition for stator lining, by weight, comprises: 100 parts of nitrile rubber, 10-14 parts of plasticizer, 60-70 parts of reinforcing component, 1-5 parts of silane coupling agent, and 10-15 parts of vulcanizing component; wherein, based on the weight of the nitrile rubber, the acrylonitrile content in the nitrile rubber is 30%-40%. The technical solution of this application can effectively solve the problems of insufficient adhesion strength and poor interfacial bonding stability between the stator lining layer and the metal housing in the prior art, which leads to cracking and delamination of the stator during use.

Description

Technical Field

[0001] This invention relates to the field of rubber materials technology, and more specifically, to a rubber composition for stator lining and a motor assembly. Background Technology

[0002] Currently, screw drills are widely used as power tools for downhole drilling in complex conditions such as vertical, directional, and horizontal wells. Their core power component is the motor assembly, which consists of a metal housing and a rubber stator liner. In existing technologies, the stator liner typically uses elastomeric materials such as nitrile rubber, bonded to the inner wall of the metal housing through a molding and vulcanization process to achieve torque transmission and wear resistance.

[0003] However, because rubber stator liners are organic polymer materials with strong chemical inertness and lack active groups that can form stable chemical bonds with the metal surface, the adhesion strength between the rubber stator liner and the metal interface decreases significantly, and the interfacial bonding stability is reduced. This ultimately leads to cracking, peeling, and even large-area detachment of the stator liner, especially in the area near the drill bit tip, severely shortening the service life of the screw drill bit. Furthermore, the low molecular weight plasticizers used in traditional formulations tend to precipitate to the bonding interface during service, weakening the stability of the adhesive layer and further reducing the adhesion durability between the rubber stator liner and the metal interface. Summary of the Invention

[0004] The main objective of this invention is to provide a rubber composition for stator lining and a motor assembly, in order to solve the problems of insufficient bonding strength and poor interfacial bonding stability between the stator lining layer and the metal housing in the prior art, which leads to cracking and glue peeling of the stator of the motor assembly during use.

[0005] To achieve the above objectives, according to one aspect of the present invention, a rubber composition for stator lining is provided, comprising, by weight parts: 100 parts of nitrile rubber, 10-14 parts of plasticizer, 60-70 parts of reinforcing component, 1-5 parts of silane coupling agent, and 10-15 parts of vulcanizing component; wherein, by weight of nitrile rubber, the acrylonitrile mass fraction in nitrile rubber is 30%-40%.

[0006] Furthermore, the plasticizer includes at least one of liquid nitrile rubber, liquid polysulfide rubber, and liquid fluororubber, and the relative number-average molecular weight of the plasticizer is 4500~6000.

[0007] Furthermore, the silane coupling agent includes at least one of γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and 3-isocyanate-propyltriethoxysilane.

[0008] Furthermore, the rubber composition for stator lining comprises 1 to 2 parts by weight of silane coupling agent.

[0009] Furthermore, the reinforcing components include carbon black N550, carbon black N774, and silica; based on the mass of the reinforcing components, the mass fraction of carbon black N550 is 35%~45%, the mass fraction of carbon black N774 is 45%~60%, and the mass fraction of silica is 5%~10%.

[0010] Furthermore, the sulfurizing components include sulfur, N-oxodiethylene-2-benzothiazole sulfenamide, and dimorpholine disulfide; based on the mass of the sulfurizing components, the mass fraction of sulfur is 30%~35%, the mass fraction of N-oxodiethylene-2-benzothiazole sulfenamide is 30%~35%, and the mass fraction of dimorpholine disulfide is 30%~40%.

[0011] Furthermore, by weight, the rubber composition for stator lining also includes: 7-10 parts of activating component and 5-15 parts of protective component.

[0012] Furthermore, the protective components include antioxidant 4020 and antioxidant RD; based on the mass of the protective components, the mass fraction of antioxidant 4020 is 45%~55%, and the mass fraction of antioxidant RD is 45%~55%.

[0013] Furthermore, the activating components include zinc oxide, stearic acid, and zinc methacrylate; based on the mass of the activating components, the mass fraction of zinc oxide is 55%~65%, the mass fraction of stearic acid is 5%~20%, and the mass fraction of zinc methacrylate is 25%~40%.

[0014] According to a second aspect of the present invention, a motor assembly is provided, the motor assembly including a rotor and a stator, wherein the stator includes a stator housing and a stator rubber liner disposed on the inner wall of the stator housing, the stator rubber liner comprising a rubber composition for stator lining of any of the above-mentioned embodiments.

[0015] By applying the technical solution of this invention, and by controlling the mass fractions of nitrile rubber, plasticizer, reinforcing component, silane coupling agent, and vulcanizing component, and further controlling the range of acrylonitrile content in nitrile rubber, the stator lining rubber composition, under the synergistic effect of each component, when applied as a stator lining layer to a motor assembly, not only helps to improve the bonding strength and coverage rate between the stator lining layer and the metal housing, but also improves the interfacial bonding stability, reduces the risk of lining layer cracking and delamination during the use of the motor assembly stator, thereby extending the service life of the screw drill bit. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the motor assembly prepared in Example 1 of this application;

[0017] Explanation of reference numerals in the attached figures:

[0018] 1-Stator housing; 2-Stator rubber lining layer; 3-Rotor; 4-Adhesive layer. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0020] As described in the background section of this invention, existing technologies suffer from insufficient bonding strength and poor interfacial stability between the stator rubber lining layer and the metal housing of motor assemblies, leading to cracking and rubber detachment of the stator during use. To address these issues, in a typical embodiment of this invention, a rubber composition for stator lining is provided. This composition, by weight, comprises: 100 parts of nitrile rubber, 10-14 parts of plasticizer, 60-70 parts of reinforcing component, 1-5 parts of silane coupling agent, and 10-15 parts of vulcanizing component; wherein, based on the mass of the nitrile rubber, the acrylonitrile content in the nitrile rubber is 30%-40%.

[0021] The stator lining rubber composition provided by this invention can serve as a base material for forming the stator lining layer of a motor assembly. The stator lining layer formed by this composition can inherit the comprehensive properties brought about by each component and its content. Specifically, the stator lining rubber composition of this invention is mainly composed of nitrile rubber, wherein the acrylonitrile content is 30%~40%, and plasticizers, reinforcing components, silane coupling agents, and vulcanizing components are synergistically introduced. Among them, the silane coupling agent enhances the interfacial bonding between the reinforcing component and the nitrile rubber matrix by chemically bonding with the cyano groups in the nitrile rubber, which helps to improve the adhesive strength and interfacial stability. Combining the excellent polarity matching of the high acrylonitrile content with the synergistic effect of the reinforcing components, when the stator lining rubber composition is used to form the stator lining layer of a motor assembly, it helps to improve the adhesive strength, interfacial bonding stability, lining layer strength, and anti-cracking and anti-delamination properties.

[0022] Nitrile butadiene rubber (NBR), as the main component of the rubber composition for stator lining, primarily serves to form the continuous phase of the stator lining layer, thereby providing the layer with basic elasticity, resistance to media, and structural support. Simultaneously, the NBR molecular chain contains polar cyano groups, which enhance the polar interaction between the rubber composition and the metal shell surface, thus improving the adhesion of the rubber composition to the metal shell. Based on this, the present invention controls the amount of NBR to 100 parts, thus making it a basic skeletal phase that provides stable performance support for the stator lining rubber composition.

[0023] This invention, by controlling the acrylonitrile mass fraction in nitrile rubber to 30%~40%, facilitates the combination of good polarity and suitable processing properties in nitrile rubber. On the one hand, it enhances the interfacial interaction between the rubber composition and the metal shell; on the other hand, it helps reduce insufficient interfacial interaction due to excessively low acrylonitrile content, or the adverse effects of excessively high acrylonitrile content on the rubber's flexibility and processability. Therefore, the synergistic control of nitrile rubber and its acrylonitrile content range contributes to the excellent adhesion and service stability of the stator lining rubber composition when used as the stator lining layer.

[0024] Plasticizers in stator lining rubber compositions primarily improve the processing performance, component compatibility, and flexibility of the rubber composition, making it easier to achieve uniform dispersion and stable bonding of the components during mixing, molding, and subsequent formation of the stator lining layer. Simultaneously, the addition of plasticizers also improves the flexibility of the stator lining layer, preventing excessive local deformation or stress concentration under stress, thus helping to maintain the bonding stability between the stator lining layer and the metal shell. Based on this, the present invention controls the amount of plasticizer to 10-14 parts, ensuring that while improving processing performance and interfacial compatibility, it reduces the risk of insufficient plasticizer dosage leading to ineffective regulation, or excessive plasticizer dosage resulting in an overly soft rubber composition, decreased interfacial strength, or even increased risk of precipitation and migration. This helps to balance and improve the processing performance, interfacial bonding performance, and service stability of the stator lining layer.

[0025] In stator lining rubber compositions, reinforcing components are primarily used to enhance the bulk strength, durability, and load-bearing capacity of the rubber composition. Since the stator of the motor assembly needs to withstand complex stresses during use, insufficient bulk strength of the rubber can lead to delamination and peeling even with good interfacial adhesion, due to instability, localized damage, or stress concentration in the stator lining layer. Therefore, by introducing reinforcing components, the stator lining rubber composition can improve interfacial adhesion while also enhancing the structural support capacity under complex downhole conditions. Based on this, the present invention controls the amount of reinforcing component to 60-70 parts, so that while enhancing the bulk strength and stability of the rubber, it mitigates the problems of insufficient mechanical support of the stator lining layer due to insufficient reinforcement, or the impact on flexibility, processability, and interfacial compatibility due to excessive reinforcement, thereby balancing the adhesive strength, toughness, and interfacial stability of the stator lining layer.

[0026] Silane coupling agents primarily function as interface modifiers and interfacial bridges in rubber compositions used for stator linings. Specifically, the organic functional groups in the silane coupling agent molecule chemically bond with the polar cyano groups of the nitrile rubber molecular chain, while the siloxane groups form stable siloxane bonds with the hydroxyl groups on the metal shell surface. This creates a strong and tough chemical bridging structure at the interface between the nitrile rubber and the metal shell, improving interfacial adhesion, reducing interfacial delamination, and ultimately increasing the bond strength between the stator lining layer and the metal shell. Therefore, this invention controls the amount of silane coupling agent to 1-5 parts to maximize its interfacial strengthening effect.

[0027] In stator lining rubber compositions, the vulcanizing component primarily serves to induce a vulcanization reaction, thereby forming a stator lining layer with certain strength, elasticity, and stability. The vulcanizing component not only facilitates the vulcanization reaction of the rubber composition, forming a stable three-dimensional cross-linked network structure, thus giving the stator lining layer better mechanical properties and deformation resistance, but also improves the bonding stability between the stator lining layer and the metal shell. Based on this, the present invention controls the amount of the vulcanizing component to 10-15 parts to ensure that the rubber composition can form a suitable cross-linked network, while reducing the risk of insufficient structural strength and stability due to insufficient vulcanizing component, or excessive vulcanizing component leading to an overly hard and brittle rubber system. This achieves a balance between improving the adhesive strength, toughness, and interfacial durability of the stator lining layer.

[0028] Therefore, this invention controls the content of each component in the stator lining rubber composition, and further controls the acrylonitrile content in the nitrile rubber. The nitrile rubber provides basic performance support, the plasticizer improves the processability and compatibility of the stator lining rubber composition, the reinforcing component enhances the bulk strength and durability of the stator lining rubber composition, the silane coupling agent strengthens the interfacial bonding between the rubber composition and the metal housing, and the vulcanizing component promotes the formation of a stable three-dimensional cross-linked network structure in the rubber composition. The synergistic effect of these components helps to improve the adhesive strength of the stator lining layer. Thus, when the stator lining rubber composition of this invention is applied to the stator lining layer, it not only helps to improve the adhesive strength and coverage rate between the stator lining layer and the metal housing, but also improves the interfacial bonding stability, reducing the risk of cracking and delamination of the lining layer during the use of the motor assembly stator.

[0029] In some embodiments, the plasticizer includes at least one of liquid nitrile rubber, liquid polysulfide rubber, and liquid fluororubber, and the relative number-average molecular weight of the plasticizer is 4500-6000. By controlling the specific type of plasticizer, the above-mentioned plasticizer has high chemical similarity and excellent compatibility with the nitrile rubber matrix, which helps to effectively integrate the plasticizer into the nitrile rubber molecular network, reduce migration and precipitation, and thus help to further improve the long-term adhesion stability of the rubber composition to the metal shell interface. At the same time, by controlling the relative number-average molecular weight of the plasticizer, plasticizers in this relative number-average molecular weight range have both good flowability and plasticizing efficiency, which helps to further optimize the rubber processing performance, promote the formation of a dense, tough and firmly bonded composite structure in the rubber composition after vulcanization, thereby helping to alleviate the problem of rubber lining detachment caused by the precipitation of traditional plasticizers, and further improve the service reliability of the motor assembly stator under high torque and high wear conditions. Specifically, the relative number-average molecular weight of the plasticizer can be a range of 4500, 4800, 5000, 5300, 5600, 6000 or any combination thereof.

[0030] In some embodiments, the silane coupling agent includes at least one of γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and 3-isocyanopropyltriethoxysilane. By controlling the specific type of silane coupling agent, these silane coupling agents with specific structures all contain active amino functional groups, which help to form hydrogen bonds or covalent interactions with the nitrile groups on the nitrile rubber molecular chain during the vulcanization of the rubber composition. At the same time, through the condensation reaction between the siloxane groups and the hydroxyl groups on the surface of the metal shell, it helps to further promote the formation of a stable chemical bridging interface, which helps to improve the interfacial bonding strength and long-term durability between the rubber composition and the metal shell, thereby helping to reduce the problem of cracking and delamination of the stator lining under complex working conditions.

[0031] In some embodiments, the rubber composition for stator lining comprises 1 to 2 parts by weight of silane coupling agent. By further controlling the amount of silane coupling agent, it is helpful to reduce the problems caused by excessive use leading to silane self-hydrolysis and condensation or incompatibility imbalance with the rubber matrix, resulting in abnormal local crosslinking density, vulcanization network distortion, and stress concentration points. This helps to further improve interface durability, enhance the peel resistance and long-term service stability of the adhesive interface, and reduce production costs.

[0032] In some embodiments, the reinforcing components include carbon black N550, carbon black N774, and silica; by mass, carbon black N550 comprises 35%–45%, carbon black N774 comprises 45%–60%, and silica comprises 5%–10%. By controlling the specific composition of the reinforcing components, carbon black N550 helps provide high structural support and dynamic mechanical stability, carbon black N774 helps enhance the tear resistance and abrasion resistance of the nitrile rubber matrix, and silica, due to its abundant silanol groups on its surface, helps form strong chemical bonds with silane coupling agents, thereby helping to improve the polar adsorption and chemical anchoring effect at the interface between the nitrile rubber molecular chains and the metal shell. The synergistic effect of the three helps to disperse stress concentration problems and further suppresses the risk of local peeling and debonding between the stator liner and the metal shell under high torque and high vibration conditions, thereby further improving the long-term reliability and service life of the motor assembly stator in complex service environments.

[0033] In some embodiments, the vulcanizing components include sulfur, N-oxodiethylene-2-benzothiazole sulfenamide, and dimorpholine disulfide; based on the mass of the vulcanizing components, the mass fraction of sulfur is 30%~35%, the mass fraction of N-oxodiethylene-2-benzothiazole sulfenamide is 30%~35%, and the mass fraction of dimorpholine disulfide is 30%~40%. By controlling the specific composition of the vulcanizing components, it is helpful to further regulate the vulcanization reaction rate and crosslinking density, thereby helping to improve the uniformity and thermal stability of the rubber network structure. Under the synergistic effect of the three, it helps to reduce the risk of uneven vulcanization or over-vulcanization caused by the imbalance of component ratio in traditional vulcanization systems, and also helps to enhance the chemical bonding strength and durability between the nitrile rubber molecular chains and the metal shell, thereby helping to suppress the cracking and debonding of the stator liner of the motor assembly under high torque and high wear conditions, and further improving the reliability and service life of the screw drill.

[0034] In some embodiments, the stator lining rubber composition further includes, by weight, 7-10 parts of an activating component and 5-15 parts of a protective component. By further introducing the activating and protective components into the stator lining rubber composition, the crosslinking efficiency and long-term service stability of the rubber composition during vulcanization can be further improved. The activating component helps promote the uniform formation of the vulcanization network, thereby improving the initial adhesion strength between the rubber composition and the metal housing interface. The protective component helps suppress the attack of ozone, oxygen free radicals, and thermal aging on the nitrile rubber molecular chains, delaying the hardening and embrittlement of the rubber matrix. This helps to further improve the mechanical integrity of the bonding interface without destroying the chemical bonding bridge formed by the silane coupling agent, thereby further mitigating degumming and cracking problems caused by rubber aging, and ultimately extending the service life of the screw drill bit.

[0035] In some embodiments, the protective component includes antioxidant 4020 and antioxidant RD; the mass fraction of antioxidant 4020 is 45%~55% and the mass fraction of antioxidant RD is 45%~55% by weight of the protective component. By controlling the specific composition of the protective component, the two work synergistically to exert antioxidant and ozone protection effects, which helps to further inhibit the molecular chain oxidative breakage and interface aging of nitrile rubber under high temperature, high humidity and dynamic load conditions, and helps to slow down the deterioration of the bonding interface between the rubber composition and the metal shell caused by plasticizer migration and precipitation; wherein antioxidant 4020 mainly blocks free radical chain reaction, while antioxidant RD enhances the shielding effect against thermo-oxidative aging. By controlling the specific proportions of the two, it helps to improve the bonding stability and durability of the stator liner during long-term service, thereby reducing the debonding failure problem caused by the aging of the rubber composition for the stator liner.

[0036] In some embodiments, the activating components include zinc oxide, stearic acid, and zinc methacrylate; based on the mass of the activating components, the mass fraction of zinc oxide is 55%~65%, the mass fraction of stearic acid is 5%~20%, and the mass fraction of zinc methacrylate is 25%~40%. By controlling the specific composition of the activating components, it is helpful to improve the chemical activation efficiency of the interface between the rubber composition and the metal shell. In particular, the introduction of zinc oxide and stearic acid helps to further promote the uniformity of the vulcanization crosslinking reaction, while zinc methacrylate, as a metal chelating activator, can form a strong coordination effect with the polar nitrile groups in nitrile rubber and the metal surface. At the same time, it can also work together with silane coupling agents to form a stable interfacial chemical bonding network, thereby helping to enhance the thermal stability and anti-peeling ability of the stator lining layer under high temperature and high shear stress environment, reducing the problem of interfacial debonding failure caused by improper composition of traditional activation systems, and thus helping to further improve the long-term bonding reliability between the stator lining layer and the metal shell.

[0037] A second aspect of the present invention provides a motor assembly comprising a rotor and a stator, wherein the stator comprises a stator housing and a stator rubber liner disposed on the inner wall of the stator housing, the stator rubber liner comprising a rubber composition for stator lining as described above.

[0038] like Figure 1 As shown, the motor assembly includes a rotor 3 and a stator that cooperate with each other. The stator includes a stator housing 1 and a stator rubber lining layer 2 disposed on the inner wall of the stator housing. An adhesive layer 4 is also disposed between the stator housing 1 and the stator rubber lining layer 2. The rotor 3 is disposed in the inner cavity surrounded by the stator rubber lining layer 2. The outer wall shape of the rotor 3 is adapted to the inner wall shape surrounded by the stator rubber lining layer 2 so that the rotor 3 can cooperate with the stator to realize the operation of the motor assembly. The adhesive layer 4 is used to enhance the interfacial adhesion between the stator housing 1 and the stator rubber lining layer 2, thereby improving the bonding strength and bonding stability between the two, and helping to reduce the risk of interfacial peeling and delamination during use.

[0039] Because the high-performance rubber composition used for stator lining is adopted as the stator lining layer, the stator lining layer set on the inner wall of the stator housing not only has good strength, elasticity and service stability, but also has high bonding strength and good interfacial bonding stability with the metal housing. This helps to reduce the risk of cracking, interface peeling and adhesive loss of the stator of the motor assembly during use, and improves the service life and service reliability of the screw drill.

[0040] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0041] Example 1

[0042] I. Raw materials for rubber compositions used in stator lining

[0043] The raw materials of the rubber composition for stator lining, by weight, include: 100 parts of nitrile rubber, 12 parts of plasticizer, 70 parts of reinforcing component, 1.5 parts of silane coupling agent, 12 parts of vulcanizing component, 8 parts of protective component, and 9 parts of activating component.

[0044] The nitrile rubber includes 3430 parts and 3945 parts, and the mass fraction of acrylonitrile in the nitrile rubber is 36.5% based on the mass of the nitrile rubber.

[0045] The plasticizer is liquid nitrile rubber with a relative number average molecular weight of 5000; the silane coupling agent is γ-aminopropyltriethoxysilane.

[0046] The reinforcing components include: 30 parts of carbon black N550, 35 parts of carbon black N774, and 5 parts of silica; based on the mass of the reinforcing components, the mass fractions of carbon black N550, carbon black N774, and silica are 42.86%, 50%, and 7.14%, respectively.

[0047] The sulfurizing components include: 4 parts sulfur, 4 parts N-oxodiethylene-2-benzothiazole sulfenamide, and 4 parts dimorpholine disulfide; based on the mass of the sulfurizing components, the mass fractions of sulfur, N-oxodiethylene-2-benzothiazole sulfenamide, and dimorpholine disulfide are 33.33%, 33.33%, and 33.33%, respectively.

[0048] The protective components include: 4 parts of antioxidant 4020 and 4 parts of antioxidant RD; based on the mass of the protective components, the mass fractions of antioxidant 4020 and antioxidant RD are 50% and 50%, respectively.

[0049] The activating components include: 5 parts zinc oxide, 1 part stearic acid, and 3 parts zinc methacrylate; based on the mass of the activating components, the mass fractions of zinc oxide, stearic acid, and zinc methacrylate are 55.56%, 11.11%, and 33.33%, respectively.

[0050] II. Preparation of Rubber Compositions for Stator Lining

[0051] Weigh each raw material according to the above proportions;

[0052] Add nitrile rubber to the open mill, adjust the open mill roll gap to 0.1 mm, and perform thin-pass plasticizing for 0.5 min to 1 min;

[0053] A single-stage mixing process is adopted. First, the activating component is added to the plasticized nitrile rubber and the mixture is milled for 1 min to 2 min. Then, the protective component is added and the mixture is milled for 0.5 min to 1 min. Next, the mill roll gap is adjusted to 1.0 mm, the reinforcing component and plasticizer are added and the mixture is milled for 2 min to 3 min. Finally, the silane coupling agent and vulcanizing component are added and the mixture is milled for 0.5 min to 1 min to ensure that the components are evenly dispersed.

[0054] After mixing, adjust the gap of the open mill rolls to 0, pass through the mill once, and make three triangular wraps to obtain the rubber composition for stator lining.

[0055] III. Preparation of Stator Liner

[0056] The inner wall of the stator housing is pre-treated to remove surface oil and impurities and increase the surface roughness of the housing to 7~9μm;

[0057] The inner surface of the stator shell is coated with a double-layer adhesive. The thickness of the primer is 20μm to 40μm, and the resting time is 12h to 72h. The total thickness of the topcoat is 60μm to 100μm, and the resting time is 12h to 168h. The adhesive is a mixture of polymers (such as halogenated polymers such as chlorinated rubber), organic compounds (such as polymaleamide, organocobalt salts, etc.) and other rubber additives dissolved or dispersed in an organic solvent system.

[0058] Place the coated stator shell in a drying oven for preheating at a temperature of 50℃~70℃ for 1h~8h.

[0059] After preheating, specific tooling and mold cores are inserted into the stator housing, ready for glue injection;

[0060] The above-mentioned stator lining rubber composition is injected into the inner wall of the stator housing after surface pretreatment;

[0061] The vulcanization process is carried out under heating and pressure conditions. The vulcanization process is a two-stage vulcanization, namely, the first stage vulcanization temperature is 120±10℃, the vulcanization pressure is ≥0.4MPa, and the vulcanization time is 20min~40min; the second stage vulcanization temperature is 150±10℃, the vulcanization pressure is ≥0.4MPa, and the vulcanization time is 2h~4h, so that the rubber composition for stator lining forms a stator lining layer.

[0062] After cooling with cooling water for 2 to 3 hours, the tooling is removed to obtain the stator of the motor assembly.

[0063] Example 2

[0064] The difference from Example 1 is that, by mass parts, the raw materials of the rubber composition for stator lining include: 100 parts of nitrile rubber, 10 parts of plasticizer, 60 parts of reinforcing component, 1 part of silane coupling agent, 10 parts of vulcanizing component, 5 parts of protective component, and 7 parts of activating component.

[0065] The nitrile rubber includes 3340 parts and 3556 parts, and the acrylonitrile content in the nitrile rubber is 34% by mass.

[0066] The plasticizer is liquid nitrile rubber with a relative number average molecular weight of 4500; the silane coupling agent is γ-aminopropyltriethoxysilane.

[0067] The reinforcing components include: 25 parts of carbon black N550, 31 parts of carbon black N774, and 4 parts of silica; based on the mass of the reinforcing components, the mass fractions of carbon black N550, carbon black N774, and silica are 41.67%, 51.67%, and 6.67%, respectively.

[0068] The sulfidation components include: 3 parts sulfur, 3 parts N-oxodiethylene-2-benzothiazole sulfenamide, and 4 parts dimorpholine disulfide; based on the mass of the sulfidation components, the mass fractions of sulfur, N-oxodiethylene-2-benzothiazole sulfenamide, and dimorpholine disulfide are 30%, 30%, and 40%, respectively.

[0069] The protective components include: 2.5 parts of antioxidant 4020 and 2.5 parts of antioxidant RD; based on the mass of the protective components, the mass fractions of antioxidant 4020 and antioxidant RD are 50% and 50%, respectively.

[0070] The activating components include: 4 parts zinc oxide, 0.5 parts stearic acid, and 2.5 parts zinc methacrylate; based on the mass of the activating components, the mass fractions of zinc oxide, stearic acid, and zinc methacrylate are 57.14%, 7.14%, and 35.71%, respectively.

[0071] Example 3

[0072] The difference from Example 1 is that, by mass parts, the raw materials of the rubber composition for stator lining include: 100 parts of nitrile rubber, 14 parts of plasticizer, 70 parts of reinforcing component, 5 parts of silane coupling agent, 15 parts of vulcanizing component, 15 parts of protective component, and 10 parts of activating component.

[0073] The nitrile rubber includes: 3430 50 parts of nitrile rubber and 4645 50 parts of nitrile rubber, and the acrylonitrile content in the nitrile rubber is 40% based on the mass of the nitrile rubber.

[0074] The plasticizer is liquid nitrile rubber with a relative number average molecular weight of 5600; the silane coupling agent is γ-aminopropyltriethoxysilane.

[0075] The reinforcing components include: 25 parts of carbon black N550, 39 parts of carbon black N774, and 6 parts of silica; based on the mass of the reinforcing components, the mass fractions of carbon black N550, carbon black N774, and silica are 35.71%, 55.71%, and 8.57%, respectively.

[0076] The sulfurizing components include: 5 parts sulfur, 5 parts N-oxodiethylene-2-benzothiazole sulfenamide, and 5 parts dimorpholine disulfide; based on the mass of the sulfurizing components, the mass fractions of sulfur, N-oxodiethylene-2-benzothiazole sulfenamide, and dimorpholine disulfide are 33.33%, 33.33%, and 33.33%, respectively.

[0077] The protective components include: 7 parts of antioxidant 4020 and 8 parts of antioxidant RD; based on the mass of the protective components, the mass fractions of antioxidant 4020 and antioxidant RD are 46.67% and 53.33%, respectively.

[0078] The activating components include: 6 parts zinc oxide, 1.5 parts stearic acid, and 2.5 parts zinc methacrylate; based on the mass of the activating components, the mass fractions of zinc oxide, stearic acid, and zinc methacrylate are 60%, 15%, and 25%, respectively.

[0079] Example 4

[0080] The difference from Example 1 is that, by mass parts, the raw materials of the rubber composition for stator lining include: 100 parts of nitrile rubber, 12 parts of plasticizer, 70 parts of reinforcing component, 2 parts of silane coupling agent, 12 parts of vulcanizing component, 8 parts of protective component, and 9 parts of activating component; wherein the silane coupling agent is γ-aminopropyltriethoxysilane.

[0081] Example 5

[0082] The difference from Example 1 is that the plasticizer is liquid polysulfide rubber with a relative number average molecular weight of 5600; and the silane coupling agent is γ-methacryloyloxypropyltrimethoxysilane.

[0083] Example 6

[0084] The difference from Example 1 is that the plasticizer is liquid nitrile rubber with a relative molecular weight of 6000.

[0085] Example 7

[0086] The difference from Example 1 is that the plasticizer is di(2-ethylhexyl) phthalate.

[0087] Example 8

[0088] The difference from Example 1 is that, by mass parts, the raw materials of the rubber composition for stator lining include: 100 parts of nitrile rubber, 12 parts of plasticizer, 70 parts of reinforcing component, 1.5 parts of silane coupling agent, 12 parts of vulcanizing component, and 8 parts of protective component; that is, no activating component is added.

[0089] Example 9

[0090] The difference from Example 1 is that, by mass parts, the raw materials of the rubber composition for stator lining include: 100 parts of nitrile rubber, 12 parts of plasticizer, 70 parts of reinforcing component, 1.5 parts of silane coupling agent, 12 parts of vulcanizing component, and 9 parts of activating component; that is, no protective component is added.

[0091] Example 10

[0092] The difference from Example 1 is that the plasticizer is liquid nitrile rubber with a relative molecular weight of 10,000.

[0093] Example 11

[0094] The difference from Example 1 is that, by mass parts, the raw materials of the rubber composition for stator lining include: 100 parts of nitrile rubber, 12 parts of plasticizer, 70 parts of reinforcing component, 1.5 parts of silane coupling agent, 12 parts of vulcanizing component, 8 parts of protective component, and 9 parts of activating component.

[0095] The reinforcing components include: 35 parts of carbon black N550 and 35 parts of carbon black N774; based on the mass of the reinforcing components, the mass fractions of carbon black N550 and carbon black N774 are 50% and 50%, respectively.

[0096] The sulfurizing components include: 6 parts sulfur and 6 parts dimorpholine disulfide; based on the mass of the sulfurizing components, the mass fractions of sulfur and dimorpholine disulfide are 50% and 50%, respectively.

[0097] Example 12

[0098] The difference from Example 1 is that, by mass parts, the raw materials of the rubber composition for stator lining include: 100 parts of nitrile rubber, 12 parts of plasticizer, 70 parts of reinforcing component, 1.5 parts of silane coupling agent, 12 parts of vulcanizing component, 8 parts of protective component, and 9 parts of activating component.

[0099] The protective components include: 8 parts of antioxidant 4020;

[0100] The activating components include: 7 parts zinc oxide and 2 parts stearic acid; based on the mass of the activating components, the mass fractions of zinc oxide and stearic acid are 77.78% and 22.22%, respectively.

[0101] Comparative Example 1

[0102] The difference from Example 1 is that, by mass parts, the raw materials of the rubber composition for stator lining include: 100 parts of nitrile rubber, 12 parts of plasticizer, 70 parts of reinforcing component, 12 parts of vulcanizing component, 8 parts of protective component, and 9 parts of activating component; that is, no silane coupling agent is added.

[0103] Comparative Example 2

[0104] The difference from Example 1 is that the nitrile rubber includes: 50 parts of 4630 nitrile rubber and 5055 nitrile rubber, and the acrylonitrile content in the nitrile rubber is 48% based on the mass of the nitrile rubber.

[0105] Comparative Example 3

[0106] The difference from Example 1 is that, by mass parts, the raw materials of the rubber composition for stator lining include: 100 parts of nitrile rubber, 1 part of plasticizer, 70 parts of reinforcing component, 1.5 parts of silane coupling agent, 12 parts of vulcanizing component, 8 parts of protective component, and 9 parts of activating component.

[0107] Comparative Example 4

[0108] The difference from Example 1 is that, by mass parts, the raw materials of the rubber composition for stator lining include: 100 parts of nitrile rubber, 12 parts of plasticizer, 50 parts of reinforcing component, 1.5 parts of silane coupling agent, 30 parts of vulcanizing component, 8 parts of protective component, and 9 parts of activating component.

[0109] The reinforcing components include: 4 parts of carbon black N550, 5 parts of carbon black N774, and 1 part of silica; based on the mass of the reinforcing components, the mass fractions of carbon black N550, carbon black N774, and silica are 40%, 50%, and 10%, respectively.

[0110] The sulfurizing components include: 12 parts sulfur, 12 parts N-oxodiethylene-2-benzothiazole sulfenamide, and 16 parts dimorpholine disulfide; based on the mass of the sulfurizing components, the mass fractions of sulfur, N-oxodiethylene-2-benzothiazole sulfenamide, and dimorpholine disulfide are 30%, 30%, and 40%, respectively.

[0111] Comparative Example 5

[0112] The difference from Example 1 is that, by mass parts, the raw materials of the rubber composition for stator lining include: 100 parts of nitrile rubber, 12 parts of plasticizer, 70 parts of reinforcing component, 10 parts of silane coupling agent, 12 parts of vulcanizing component, 8 parts of protective component, and 9 parts of activating component.

[0113] Comparative Example 6

[0114] The difference from Example 1 is that, by mass parts, the raw materials of the rubber composition for stator lining include: 100 parts of nitrile rubber, 50 parts of reinforcing component, 10 parts of silane coupling agent, 12 parts of vulcanizing component, 8 parts of protective component, and 9 parts of activating component.

[0115] Test methods

[0116] The adhesive strength of the stators of the motor assemblies prepared in Examples 1-12 and Comparative Examples 1-6 were tested according to GB / T 7760-2003, and the failure modes and adhesive coverage were recorded. The test results are shown in Table 1.

[0117] Table 1

[0118]

[0119] As shown in Table 1, compared to Comparative Examples 1-6, the stators of the motor assemblies prepared in Examples 1-12 exhibit higher adhesive strength and better coating properties between the stator lining layer and the metal housing due to the use of the stator lining rubber composition system specified in this application. Specifically, the adhesive strength of Examples 1-12 is ≥16.6 kN / m, the coating rate is ≥96%, and the failure modes are mainly HR or TR. However, due to the absence of a silane coupling agent, it is difficult to form a stable and effective interfacial bridge between the rubber composition and the metal housing, resulting in poor interfacial adhesion between the stator lining layer and the metal housing. The adhesive strength is reduced to 11.3 kN / m, the coating rate is reduced to 70%, and the failure mode is SR. This indicates that the addition of the silane coupling agent plays an important role in improving the interfacial adhesive strength and coating properties. This application demonstrates that by synergistically defining nitrile rubber, plasticizer, reinforcing components, silane coupling agents, vulcanizing components, activating components, and protective components, it can effectively improve the adhesion strength between the stator liner and the metal shell, improve the interfacial bonding state, reduce the risk of interfacial peeling and delamination, thereby improving the service reliability of the motor assembly stator. Comparative Example 2, due to the increased acrylonitrile content in the nitrile rubber to 48%, exceeding the limits of this application, resulted in a decrease in the flexibility and processing adaptability of the rubber material, which was detrimental to balancing interfacial effects and bulk properties. Its adhesion strength decreased to 15.8 kN / m, the rubber coverage rate decreased to 80%, and the failure mode was TR. Comparative Example 3, due to the plasticizer dosage being only 1 part, significantly lower than the limits of this application, resulted in insufficient improvement in the processing performance, component compatibility, and flexibility of the rubber composition. Its adhesion strength decreased to 15.2 kN / m, the rubber coverage rate decreased to 75%, and the failure mode was TR, indicating that insufficient plasticizer dosage is detrimental to forming a stable interfacial bonding state. Comparative Example 4, due to insufficient reinforcing component and excessive vulcanizing component, suffered from an imbalance in the rubber composition's bulk strength, toughness, and cross-linking state. Its bond strength decreased to 14.3 kN / m, and the coverage rate decreased to 72%, with a failure mode of TR (transverse adhesion). This indicates that an imbalance in the amounts of reinforcing and vulcanizing components negatively impacts the stable bonding between the stator liner and the metal shell. Comparative Example 5, with its silane coupling agent dosage increased to 10 parts, easily caused system compatibility imbalance or abnormal local cross-linking. Its bond strength decreased to 13.5 kN / m, and the coverage rate decreased to 75%, with a failure mode of TR. Comparative Example 6, due to the absence of plasticizer and insufficient reinforcing component, negatively affected the rubber composition's flexibility, bulk strength, and interfacial compatibility. Its bond strength decreased to 14.2 kN / m, and the coverage rate decreased to 81%, with a failure mode of TR. This demonstrates that both plasticizers and reinforcing components play important roles in improving the bonding performance between the stator liner and the metal shell.Therefore, it can be seen that by synergistically limiting the types and dosage ranges of each component, this application can significantly improve the bonding strength and coverage rate between the stator liner and the metal housing, and improve the failure mode, thereby improving the overall reliability of the motor assembly stator.

[0120] Furthermore, compared to Example 7, Examples 1-6, by further controlling the plasticizer to be liquid nitrile rubber and controlling the relative number-average molecular weight of the plasticizer to be 4500-6000, resulted in the stator bonding strength of the motor assemblies prepared in Examples 1-6 reaching 21.7kN / m-26.8kN / m, the glue coverage reaching 99%-100%, and the failure mode being HR. In contrast, Example 7, by replacing the plasticizer with di(2-ethylhexyl) phthalate, had lower compatibility with the nitrile rubber matrix and lower resistance to migration and exudation than liquid nitrile rubber, resulting in a decrease in bonding strength to 18.6kN / m and a decrease in glue coverage to 98%. Compared to Example 8, Examples 1-6, by further controlling the inclusion of 7-10 parts of activating components in the rubber composition for stator lining, and further controlling the activating components to include zinc oxide, stearic acid, and zinc methacrylate, resulted in further improvements in the adhesive strength and rubber coverage of the stator of the motor assemblies prepared in Examples 1-6, with all failure modes being HR. In contrast, Example 8, due to the absence of activating components, suffered from the uniformity of the vulcanization reaction and the initial bonding state of the interface, resulting in a decrease in adhesive strength to 17.5 kN / m and a decrease in rubber coverage to 98%. This indicates that the activating components help to further promote the uniform formation of the vulcanization network and improve the interfacial bonding strength between the stator lining layer and the metal shell.

[0121] Furthermore, compared to Example 9, Examples 1-6, by further controlling the inclusion of 5-15 parts of protective components in the rubber composition for stator lining, and further controlling the inclusion of antioxidant 4020 and antioxidant RD in the protective components, resulted in the stator adhesive strength of the motor assemblies prepared in Examples 1-6 reaching 21.7 kN / m-26.8 kN / m, the rubber coverage rate reaching 99%-100%, and the failure mode being HR. In contrast, Example 9, due to the absence of protective components, experienced a decrease in the anti-aging ability and interfacial stability of the stator lining layer, leading to a reduction in adhesive strength to 17.2 kN / m, a reduction in rubber coverage rate to 96%, and a failure mode changing to TR. This indicates that the protective components help to further maintain the interfacial bonding stability of the stator lining layer during long-term service. Compared to Example 10, Examples 1-6, by further controlling the relative number-average molecular weight of the plasticizer to 4500-6000, resulted in further improvements in the adhesive strength and rubber coverage of the stator of the motor assemblies prepared in Examples 1-6, with the failure mode being HR. However, in Example 10, the number-average molecular weight of the liquid nitrile rubber increased to 10000, exceeding the range defined in this application, leading to a decrease in its flowability and plasticizing efficiency, a reduction in adhesive strength to 16.9 kN / m, a reduction in rubber coverage to 98%, and a failure mode changing to TR.

[0122] Furthermore, compared to Example 11, Examples 1-6, by further controlling the reinforcing components to include carbon black N550, carbon black N774, and silica, and by further controlling the vulcanizing components to include sulfur, N-oxodiethylene-2-benzothiazole sulfenamide, and dimorpholine disulfide, resulted in the stators of the motor assemblies prepared in Examples 1-6 exhibiting better adhesive strength and a rubber coating rate of 99%-100%, with all failure modes being HR. In contrast, Example 11, lacking silica in the reinforcing components and N-oxodiethylene-2-benzothiazole sulfenamide in the vulcanizing components, affected the reinforcing effect of the rubber composition and the uniformity of the vulcanization system, leading to a decrease in adhesive strength to 17.3 kN / m, a decrease in rubber coating rate to 99%, and a failure mode of TR. This indicates that the specific composition of the reinforcing and vulcanizing components helps to further balance bulk strength, crosslinking uniformity, and interfacial bonding performance. Compared to Example 12, Examples 1-6, by further controlling the protective components to include antioxidant 4020 and antioxidant RD, and by further controlling the activating components to include zinc oxide, stearic acid, and zinc methacrylate, resulted in a further enhanced adhesive strength of the stator of the motor assemblies prepared in Examples 1-6, with a coating rate of 99%-100%, and all failure modes being HR. In contrast, Example 12, because the protective component only included antioxidant 4020 and the activating component lacked zinc methacrylate, weakened the synergistic effect of the protective and activating systems, leading to a decrease in adhesive strength to 16.6 kN / m, a decrease in coating rate to 97%, and a failure mode of TR. This indicates that the specific composition of the protective and activating components helps to further improve the long-term adhesive reliability between the stator liner and the metal shell. Therefore, this application, by further controlling the type and molecular weight of the plasticizer, the introduction and specific composition of the activating and protective components, as well as the specific composition of the reinforcing and vulcanizing components, can achieve higher bonding strength, higher coverage rate and better failure mode between the stator rubber lining and the metal housing, thereby further improving the service reliability and service life of the motor assembly stator.

[0123] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A rubber composition for stator lining, characterized in that, The stator lining rubber composition comprises, by weight parts: 100 parts of nitrile rubber, 10-14 parts of plasticizer, 60-70 parts of reinforcing component, 1-5 parts of silane coupling agent, and 10-15 parts of vulcanizing component; wherein, by weight of the nitrile rubber, the acrylonitrile mass fraction of the nitrile rubber is 30%-40%.

2. The rubber composition for stator lining according to claim 1, characterized in that, The plasticizer includes at least one of liquid nitrile rubber, liquid polysulfide rubber, and liquid fluororubber, and the relative number-average molecular weight of the plasticizer is 4500~6000.

3. The rubber composition for stator lining according to claim 1 or 2, characterized in that, The silane coupling agent includes at least one of γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and 3-isocyanate-propyltriethoxysilane.

4. The rubber composition for stator lining according to claim 3, characterized in that, The stator lining rubber composition comprises 1 to 2 parts of the silane coupling agent by weight.

5. The rubber composition for stator lining according to claim 4, characterized in that, The reinforcing components include carbon black N550, carbon black N774, and silica; based on the mass of the reinforcing components, the mass fraction of carbon black N550 is 35%~45%, the mass fraction of carbon black N774 is 45%~60%, and the mass fraction of silica is 5%~10%.

6. The rubber composition for stator lining according to claim 4, characterized in that, The sulfurizing components include sulfur, N-oxodiethylene-2-benzothiazole sulfenamide, and dimorpholine disulfide; based on the mass of the sulfurizing components, the mass fraction of sulfur is 30%~35%, the mass fraction of N-oxodiethylene-2-benzothiazole sulfenamide is 30%~35%, and the mass fraction of dimorpholine disulfide is 30%~40%.

7. The rubber composition for stator lining according to claim 4, characterized in that, The stator lining rubber composition further includes, by weight parts: 7-10 parts of activating component and 5-15 parts of protective component.

8. The rubber composition for stator lining according to claim 7, characterized in that, The protective component includes antioxidant 4020 and antioxidant RD; based on the mass of the protective component, the mass fraction of antioxidant 4020 is 45%~55%, and the mass fraction of antioxidant RD is 45%~55%.

9. The rubber composition for stator lining according to claim 7, characterized in that, The activating components include zinc oxide, stearic acid, and zinc methacrylate; based on the mass of the activating components, the mass fraction of zinc oxide is 55%~65%, the mass fraction of stearic acid is 5%~20%, and the mass fraction of zinc methacrylate is 25%~40%.

10. A motor assembly, characterized in that, The motor assembly includes a rotor and a stator, wherein the stator includes a stator housing and a stator rubber lining layer disposed on the inner wall of the stator housing, the stator rubber lining layer comprising the rubber composition for stator lining according to any one of claims 1 to 9.

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