Preparation and application of NBR / PVC rubber and plastic alloy modified material suitable for flaring special pipe

Abstract

The invention provides preparation and application of an NBR / PVC rubber and plastic alloy modified material suitable for a flaring special-shaped pipe. The alloy modified material is mainly prepared from the following raw materials: 50-100 parts of nitrile rubber, 10-50 parts of polyvinyl chloride, 60-80 parts of fast extruding furnace carbon black, 25-40 parts of a plasticizer, 1-3 parts of an organic active agent, 5-10 parts of an inorganic active agent, 5-10 parts of an anti-aging agent, 10-30 parts of an inorganic filler, 0.5-3 parts of a surface modifier, 0.2-1.2 parts of a vulcanizing agent and 2-5 parts of a vulcanization accelerator. The prepared NBR / PVC rubber and plastic alloy modified material has better oil resistance, ozone resistance and aging resistance, rubber pipe products made of the material have better adaptation universality and pull-out resistance to joints, meanwhile, the rubber pipe products can better adapt to more complex installation spaces, stress concentration is reduced, and the service life is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer rubber material synthesis, in particular to the preparation and application of an NBR / PVC rubber-plastic alloy modified material suitable for flared special-shaped pipes. Background Art

[0002] Nitrile butadiene rubber (NBR) has excellent oil resistance and is therefore widely used in oil-resistant products. However, harsh operating conditions and increasingly stringent standards have gradually exposed NBR's shortcomings in terms of ozone resistance and heat aging resistance. This led to the introduction of NBR / PVC modified materials, which combine NBR's excellent oil resistance with its poor ozone and heat aging resistance, while significantly reducing formulation costs.

[0003] However, because the PVC molecular chain has high crystallinity and has a large structural difference from the NBR molecular chain, the interaction between the molecular chains is enhanced, which restricts the movement of the molecular chains and reduces the overall elasticity and tear resistance of the material. As a result, when NBR / PVC is used in flared special-shaped pipes, vertical cracks are easily generated at the ports and bends, which seriously limits the application of NBR / PVC.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The present invention discloses a first modified NBR / PVC rubber-plastic alloy material suitable for flared special-shaped hoses. This material effectively improves the poor elasticity and tear resistance inherent in NBR / PVC materials due to their inherent structure. It further addresses the technical dilemma of cracking at the ends and bends of flared special-shaped hoses using NBR / PVC as a base material. This material thus exhibits superior oil resistance, ozone resistance, and aging resistance.

[0006] The second purpose of the present invention is to provide a method for preparing an NBR / PVC rubber-plastic alloy modified material suitable for flared special-shaped pipes, which is simpler and has a lower cost.

[0007] The third object of the present invention is to provide an application of an NBR / PVC rubber-plastic alloy modified material for a flared special-shaped tube in oil-resistant rubber.

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted: The invention provides an NBR / PVC rubber-plastic alloy modified material suitable for flared special-shaped pipes. The modified material is mainly prepared from the following raw materials, calculated by weight: 50-100 parts of nitrile rubber, 10-50 parts of polyvinyl chloride, 60-80 parts of quick-pressed carbon black, 25-40 parts of plasticizer, 1-3 parts of organic active agent, 5-10 parts of inorganic active agent, 5-10 parts of antioxidant, 10-30 parts of inorganic filler, 1-3 parts of surface modifier, 0.2-1.2 parts of vulcanizing agent and 2-5 parts of vulcanization accelerator.

[0009] Preferably, as a further specific embodiment, 55-75 parts of nitrile rubber, 30-45 parts of polyvinyl chloride, 60-70 parts of quick-pressed carbon black, 28-35 parts of plasticizer, 1.2-2 parts of organic active agent, 5-8 parts of inorganic active agent, 6-8 parts of antioxidant, 15-25 parts of inorganic filler, 1.5-2.5 parts of surface modifier, 0.5-1 part of vulcanizing agent and 2.5-4 parts of vulcanization accelerator.

[0010] Preferably, as a further specific embodiment, 60 parts of nitrile rubber, 40 parts of polyvinyl chloride, 60 parts of quick-pressed carbon black, 30 parts of plasticizer, 1.5 parts of organic active agent, 5 parts of inorganic active agent, 7 parts of antioxidant, 20 parts of inorganic filler, 2 parts of surface modifier, 0.8 parts of vulcanizing agent and 2.8 parts of vulcanization accelerator.

[0011] In the present invention, a citrate plasticizer is deliberately introduced, which can better penetrate the rubber molecular chain and reduce the interaction force between the molecular chains. At the same time, a silane compound is introduced to modify its own structure, changing its own crystallinity while making it more evenly dispersed with the nitrile rubber and making the NBR / PVC blend more compatible with other fillers, effectively improving the poor elasticity and poor tear resistance of the NBR / PVC material caused by its own structure.

[0012] Preferably, as a further specific embodiment, the plasticizer is a citrate plasticizer; Preferably, the citrate plasticizer is any one or more of acetyl triethyl citrate, acetyl tributyl citrate, triethyl citrate or tributyl citrate; Preferably, the citrate plasticizer is any one of acetyl triethyl citrate or tributyl citrate; Preferably, the citrate plasticizer is acetyl triethyl citrate.

[0013] Preferably, as a further specific embodiment, the surface modifier is a silane compound modifier; Preferably, the silane compound modifier is one or more of γ-mercaptopropyltrimethoxysilane, bis-(γ-trimethoxysilylpropyl) disulfide or γ-mercaptopropylmethyldimethoxysilane; Preferably, the silane compound modifier is any one of γ-mercaptopropyltrimethoxysilane and bis-(γ-trimethoxysilylpropyl) disulfide; Preferably, the silane compound modifier is γ-mercaptopropyltrimethoxysilane.

[0014] Preferably, as a further specific embodiment, the acrylonitrile content in the nitrile rubber is 41%-45%; Preferably, the degree of polymerization of polyvinyl chloride is 1000-1300 DP and the number average molecular weight is 62000 g / mol-80000 g / mol; Preferably, the degree of polymerization of the polyvinyl chloride is 1100 DP and the number average molecular weight is 70,000 g / mol.

[0015] Preferably, as a further specific embodiment, the antioxidant is at least four of N,N-di-n-butyldithiocarbamate nickel, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, N-cyclohexyl-N'-phenyl-p-phenylenediamine, microcrystalline wax, 2,3-benzofuran, 2-mercaptobenzimidazole, and N-phenyl-1-naphthylamine; Preferably, the antioxidant is a mixture of nickel N,N-di-n-butyldithiocarbamate, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, N-cyclohexyl-N'-phenyl-p-phenylenediamine, and microcrystalline wax; Preferably, the antioxidant is nickel N,N-di-n-butyldithiocarbamate, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, N-cyclohexyl-N'-phenyl-p-phenylenediamine, and microcrystalline wax mixed in a mass ratio of 0.5:1:1:1; The selection of antioxidant types in the present invention realizes the "quadruple synergistic protection principle", that is, through the linkage of physical shielding + chemical passivation + free radical capture + peroxide decomposition, the problem of aging and failure of expanded special-shaped pipes under complex working conditions is effectively solved; at the same time, the amount of each substance is limited, which can not only effectively improve the anti-aging performance, but also extend the life of the metal joint and avoid environmental pollution.

[0016] Preferably, the organic activator is stearic acid; Preferably, the inorganic activator is any one of zinc oxide or magnesium oxide; Preferably, the inorganic activator is zinc oxide.

[0017] Preferably, the vulcanizing agent is one of insoluble sulfur or 2,4-di-tert-butylcumene peroxide; Preferably, the vulcanizing agent is insoluble sulfur.

[0018] Preferably, the inorganic filler is a carbon silicon material; Preferably, the carbon silicon material is any one of silicon dioxide, clay, talc or carbon black-white carbon black hybrid material; Preferably, the carbon silicon material is silicon dioxide.

[0019] Preferably, as a further specific embodiment, the vulcanization accelerator is at least two of 2,2'-dibenzothiazole disulfide, N-cyclohexyl-2-benzothiazole sulfenamide, 4,4'-dimorpholine disulfide, tetramethylthiuram disulfide, zinc dimethyldithiocarbamate, and copper dimethylaminodithiocarbamate; Preferably, the vulcanization accelerator is a mixture of 2,2'-dibenzothiazole disulfide, N-cyclohexyl-2-benzothiazole sulfenamide and tetramethylthiuram disulfide; Preferably, the vulcanization accelerator is a mixture of 2,2'-dibenzothiazole disulfide, N-cyclohexyl-2-benzothiazole sulfenamide and tetramethylthiuram disulfide in a mass ratio of 1.5:1:0.3.

[0020] Under this ratio, the vertical cracks caused by stress concentration in the flared or bent parts can be solved, the cracks can be suppressed, and the flaring ratio can be increased; at the same time, the vulcanization speed can be balanced to avoid premature vulcanization leading to material burning, or insufficient performance due to lack of vulcanization, which can effectively reduce the crack rate of the flared special-shaped tube.

[0021] The present invention also provides a method for preparing the above-mentioned NBR / PVC rubber-plastic alloy modified material suitable for flared special-shaped pipes, comprising the following steps: S1. At 80° C., slowly adding a surface modifier to polyvinyl chloride until it is completely absorbed to obtain swollen polyvinyl chloride; S2, plasticizing the polyvinyl chloride that has been subjected to swelling treatment, adding nitrile rubber to blend when the polyvinyl chloride is softened, and obtaining a premixed rubber; S3, plasticizing the premixed rubber to obtain plasticized rubber; S4, dividing the plasticized rubber into two stages for mixing to obtain a mixed rubber material; S5, vulcanizing and shaping the mixed rubber material to obtain.

[0022] The methoxy group (-OCH3) in the silane compound in S1 undergoes a hydrolysis reaction to generate silanol (SI-OH), and the silanols undergo a self-condensation reaction to form a SI-0-SI network structure, further enhancing the interfacial bonding force between the two phases and improving the stability of the material.

[0023] The mercapto group (-SH) in the silane compound in S2 undergoes a nucleophilic substitution reaction with the chlorine atom (Cl) in polyvinyl chloride (PVC) to form a PVC grafted silanol intermediate (PVC-S-(CH2)3-SI(OH)3).

[0024] The mercapto group (-SH) in the silane compound in S3 reacts with the carbon-carbon double bond (C=C) in nitrile rubber (NBR) to form an NBR grafted silanol intermediate (NBR-S-(CH2)3-SI(OH)3).

[0025] The self-condensation reaction of the nitrile rubber (NBR) and the polyvinyl chloride (PVC) grafted silanol intermediate generated by the bridging action of the silane compound in S4 indirectly better combines the nitrile rubber (NBR) and the polyvinyl chloride (PVC), thereby significantly improving the compatibility and interfacial bonding strength between the two.

[0026] Preferably, as a further specific implementation, the step S4 is specifically as follows: In the first stage of mixing, the plasticized rubber is internally kneaded for 15-45 seconds, and then an organic activator, an inorganic activator, carbon black, a plasticizer, an antioxidant and an inorganic filler are added and mixed at 90-100°C for 5-7 minutes. When the mixing temperature reaches 140-150°C, the rubber is discharged, thinned, unrolled and left to stand for 8-10 hours to obtain the first stage of the mixed rubber; The first-stage mixed rubber is kneaded for 15-45 seconds, and the vulcanizing agent and the vulcanization accelerator are added and kneaded for 3-4 minutes. When the mixing temperature reaches between 115°C and 125°C, the rubber is discharged and thinned, and the sheet is removed and placed for 24-28 hours to obtain the product.

[0027] Preferably, the specific steps of S5 are: The obtained mixed rubber material was extruded at a die head temperature of 70°C, a screw temperature of 60°C, a plasticizing section temperature of 60°C, and a feed port temperature of 50°C to obtain a single-layer tube blank; a straight tube core rod, an expanded (16 expanded 24) straight tube core rod, a (90°-120°) special-shaped tube core rod, and a (90°-120°) special-shaped (16 expanded 24, the expansion ratio is 10%-50%) expanded core rod were respectively put on, and vulcanized at a temperature of 170°C and a pressure of 0.5MPa for 25 minutes to obtain the corresponding NBR / PVC rubber tube; Preferably, the flaring ratio may be 10%, 20%, 30% or 50%; Preferably, the flaring ratio is 50%; Preferably, the profile angle is 90° or 120°; Preferably, the profile angle is 90°.

[0028] Compared with the prior art, the present invention has the following beneficial effects: (1) In view of the large difference in molecular structure between nitrile rubber and polyvinyl chloride, which leads to enhanced interaction between PVC and NBR molecular chains, hindered molecular chain movement, and decreased overall elasticity of the material, citric acid ester plasticizers are specially introduced, which can better penetrate the rubber molecular chains and reduce the interaction between molecular chains; (2) In view of the problem that the PVC material itself has a high degree of crystallinity, which leads to a decrease in the overall elasticity of the composite material, silane compounds are introduced to modify its own structure, changing its own crystallinity while making it more evenly dispersed with nitrile rubber and making the NBR / PVC blend more compatible with other fillers, effectively improving the poor elasticity and tear resistance of the NBR / PVC material caused by its own structure; (3) The technical difficulty of cracking easily in ports and bends when using NBR / PVC as the base material for flared special-shaped hose products has been further resolved. This makes the material have better oil resistance, ozone resistance, aging resistance and price advantage. Hose products made with this material have better adaptability and resistance to pull-out of joints, and can better adapt to more complex installation spaces, reduce stress concentration, and extend service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 : is a schematic structural diagram of the modified material of the present invention, a is a silane compound, b is nitrile rubber NBR, c is polyvinyl chloride PVC, and d is silanol; Figure 2 :It is the process flow chart of polyvinyl chloride expansion pretreatment; Figure 3 :It is the process flow chart for preparing premixed rubber; Figure 4 :It is a two-stage mixing preparation process flow chart; Figure 5 : Four finished pipe structures and shapes; among them, (a) is NBR / PVC straight pipe; (b) is NBR / PVC expanded pipe with a flaring ratio of 20%; (c) is NBR / PVC shaped pipe with a bending angle of 120°; (d) is NBR / PVC shaped pipe with a bending angle of 90°; (e) is NBR / PVC shaped expanded pipe with a bending angle of 120° and an expansion ratio of 50%; (f) is NBR / PVC expanded pipe with a bending angle of 90° and an expansion ratio of 50%; Figure 6: The reactions occurring in the five reaction steps of the present invention; wherein, reaction 1 is the hydrolysis of the silane compound in step 1 to generate silanol; reaction 2 is the self-condensation reaction of silanol in step 2; reaction 3 is the addition reaction of the silane compound with NBR in step 3 to generate an NBR grafted silanol intermediate; reaction 4 is the substitution reaction of the silane compound with PVC in step 4 to generate a PVC grafted silanol intermediate; reaction 5 is the combination of the NBR and PVC grafted silicone intermediates in step 5 through the self-condensation reaction of silanol. DETAILED DESCRIPTION

[0030] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the scope of protection of the present invention. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified by the manufacturer are conventional products that can be purchased commercially.

[0031] Example 1 Weigh each substance separately: 70g of nitrile rubber, 30g of polyvinyl chloride, 70g of quick-pressed carbon black, 25g of acetyl tributyl citrate, 1g of stearic acid, 6g of zinc oxide, 5g of antioxidant (including 0.8g of nickel N,N-di-n-butyldithiocarbamate, 1.4g of 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 1.4g of N-cyclohexyl-N'-phenyl-p-phenylenediamine, and 1.4g of microcrystalline wax), 15g of silicon dioxide, 1g of γ-mercaptopropyltrimethoxysilane, 0.4g of insoluble sulfur, and 2g of vulcanization accelerator (including 1g of 2,2'-dibenzothiazole disulfide, 0.7g of N-cyclohexyl-2-benzothiazole sulfenamide, and 0.3g of tetramethylthiuram disulfide).

[0032] The nitrile rubber has an acrylonitrile content of 43%, a degree of polymerization of polyvinyl chloride of 1200DP, and a number average molecular weight of 70,000 g / mol.

[0033] Prepare the rubber compound and its finished pipe as follows: Step 1 (PVC swelling pretreatment): Place polyvinyl chloride (PVC) between the two rollers of the open mill, reduce the roller distance to 2mm, set the speed to 70r / min, and when the roller temperature reaches 80℃, slowly add γ-mercaptopropyltrimethoxysilane into the PVC until it is completely absorbed (PVC appears continuous and transparent). The reaction process is as follows Figure 6 As shown in reaction 1.

[0034] Step 2 (preparation of premixed rubber): Place the pre-treated PVC on the two rollers of the open mill for plasticizing (reduce the roller distance to 2mm). When the temperature reaches the softening temperature of PVC, increase the roller distance to 5mm and add nitrile rubber for blending. The process lasts for 12 minutes. Then, perform thin pass (reduce the roller distance to 2mm) three times to ensure uniform mixing. Finally, remove the sheet (increase the roller distance to 8mm). The speed of the open mill is always set at 60r / min. Figure 6 As shown in reaction 2.

[0035] Step 3 (plastication): Take the premixed rubber and plasticize it on an open mill. Adjust the roller distance to 2mm, set the roller temperature to 50℃, and continue to make triangle bags for 10-12 minutes to obtain plasticized rubber. The reaction process is as follows Figure 6 As shown in reaction 3.

[0036] Step 4 (preparation of rubber mix): take the plasticized rubber prepared in step 3 and put it into the internal mixer, mix for 30s (the speed is set to 25r / min), then lift the top bolt, add stearic acid, zinc oxide, fast-pressed carbon black, acetyl tributyl citrate, antioxidant, and silicon dioxide (the speed is set to 35r / min), when the mixing temperature reaches 95℃, lift the bolt for 5s and then press it down, and the mixing time is controlled at 5-7min. When the mixing temperature reaches 140℃-150℃, discharge the rubber, pass it through the open mill once (the roller distance is set to 2mm), and cut it into sheets with a thickness of 8-10mm to make Get a first-stage mixed rubber, stand for 8-10 hours; then carry out second-stage mixing, take the first-stage mixed rubber and put it back into the internal mixer, mix for 30 seconds (speed set to 25r / min), add vulcanization accelerator (including 2,2'-dibenzothiazole disulfide, N-cyclohexyl-2-benzothiazole sulfenamide, tetramethylthiuram disulfide) and mix for 3-4 minutes, control the temperature between 115-125℃ for rubber discharge, pass through the open mill once (roller distance set to 2mm), cut into sheets with a thickness of 8-10mm, and get the second-stage mixed rubber, stand for 24 hours, and use it. The reaction process is as follows Figure 6 As shown in reaction 4.

[0037] Step 5 (production of finished product): The mixed rubber compound prepared in step 4 is extruded at a die head temperature of 70°C, a screw temperature of 60°C, a plasticizing section temperature of 60°C, and a feed port temperature of 50°C to obtain a single-layer tube blank; a straight tube core rod, an expanded (16 to 24) straight tube core rod, a (90°) special-shaped tube core rod, and a (90°) special-shaped (16 to 24, expansion ratio of 50%) expanded core rod are respectively put on, and vulcanized at a temperature of 170°C and a pressure of 0.5MPa for 25 minutes to obtain the corresponding NBR / PVC rubber tube. The reaction process is as follows: Figure 6 As shown in reaction 5.

[0038] Example 2 The specific preparation method is consistent with that in Example 1, and the following substances are weighed respectively: 80 g of nitrile rubber, 20 g of polyvinyl chloride, 80 g of fast-pressed carbon black, 40 g of acetyl tributyl citrate, 3 g of stearic acid, 10 g of zinc oxide, 9 g of antioxidant (including 1.2 g of nickel N, N-di-n-butyldithiocarbamate, 2.6 g of 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 2.6 g of N-cyclohexyl-N'-phenyl-p-phenylenediamine, and 2.6 g of microcrystalline wax), 30 g of silicon dioxide, 3 g of γ-mercaptopropyltrimethoxysilane, 4 g of insoluble sulfur, and 4 g of vulcanization accelerator (including 2.2 g of 2,2'-dibenzothiazole disulfide, 1.4 g of N-cyclohexyl-2-benzothiazole sulfenamide, and 0.4 g of tetramethylthiuram disulfide). The acrylonitrile content of the nitrile rubber is 41%, the degree of polymerization of the polyvinyl chloride is 1300DP, and the number average molecular weight is 71000 g / mol.

[0039] Example 3 The specific preparation method is consistent with that in Example 1, and the following substances are weighed respectively: 60 g of nitrile rubber, 40 g of polyvinyl chloride, 60 g of fast-pressed carbon black, 30 g of acetyl tributyl citrate, 1.5 g of stearic acid, 5 g of zinc oxide, 7 g of antioxidant (including 1 g of nickel N, N-di-n-butyldithiocarbamate, 2 g of 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 2 g of N-cyclohexyl-N'-phenyl-p-phenylenediamine, and 2 g of microcrystalline wax), 20 g of silicon dioxide, 2 g of γ-mercaptopropyltrimethoxysilane, 0.8 g of insoluble sulfur, and 2.8 g of vulcanization accelerator (including 1.5 g of 2,2'-dibenzothiazole disulfide, 1 g of N-cyclohexyl-2-benzothiazole sulfenamide, and 0.3 g of tetramethylthiuram disulfide).

[0040] The acrylonitrile content of the nitrile rubber is 45%, the degree of polymerization of the polyvinyl chloride is 1100DP, and the number average molecular weight is 70000 g / mol.

[0041] Comparative Example 1 The difference from Example 1 is that NBR is directly used as the main material without introducing PVC material, and the selection of each substance is as follows: 100g of nitrile rubber, 60g of fast-pressed carbon black, 30g of acetyl tributyl citrate, 1.5g of stearic acid, 5g of zinc oxide, 7g of antioxidant (including 1g of nickel N,N-di-n-butyldithiocarbamate, 2g of 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 2g of N-cyclohexyl-N'-phenyl-p-phenylenediamine, and 2g of microcrystalline wax), 20g of silicon dioxide, 0.8g of insoluble sulfur, and 2.8g of vulcanization accelerator (including 1.5g of 2,2'-dibenzothiazole disulfide, 1g of N-cyclohexyl-2-benzothiazole sulfenamide, and 0.3g of tetramethylthiuram disulfide).

[0042] The acrylonitrile content of the nitrile rubber is 45%, the degree of polymerization of the polyvinyl chloride is 1100DP, and the number average molecular weight is 70000 g / mol.

[0043] Step 1 (preparation of rubber mix): directly put NBR raw rubber into the internal mixer, mix for 30s (speed set to 25r / min), then lift the top bolt, add stearic acid, zinc oxide, quick-pressed carbon black, acetyl tributyl citrate, antioxidant, and silica (speed set to 35r / min), when the mixing temperature reaches 95℃, lift the bolt for 5s and then press it down, and control the mixing time to 5-7min. When the mixing temperature reaches 140℃-150℃, discharge the rubber and pass it through the open mill once (roller spacing Set to 2mm), cut into sheets with a thickness of 8-10mm to prepare a first-stage mixed rubber, and keep it for 8-10h; then carry out second-stage mixing, take the prepared first-stage mixed rubber and put it back into the internal mixer, mix it for 30s (the speed is set to 25r / min), add the vulcanization accelerator and mix it for 3-4min, control the temperature between 115-125℃ for rubber discharge, pass it through the open mixer thinly once (the roller distance is set to 2mm), cut into sheets with a thickness of 8-10mm to prepare a second-stage mixed rubber, keep it for 24h and use it.

[0044] Step 2 (production of finished products): The mixed rubber material prepared in step 1 is extruded at a die head temperature of 70°C, a screw temperature of 60°C, a plasticizing section temperature of 60°C, and a feed port temperature of 50°C to obtain a single-layer tube embryo; a straight tube core rod, an expanded (16 expanded 24) straight tube core rod, a (90°) special-shaped tube core rod, and a (90°) special-shaped (16 expanded 24) expanded core rod are respectively put on, and vulcanized at a temperature of 170°C and a pressure of 0.5MPa for 25 minutes to obtain the corresponding rubber tube.

[0045] Comparative Example 2 PVC is introduced but not pre-treated for swelling and is used directly. The specific contents are as follows: Weigh the following ingredients: 70g nitrile rubber, 30g polyvinyl chloride, 60g carbon black, 30g acetyl tributyl citrate, 1.5g stearic acid, 5g zinc oxide, 7g antioxidant (including 1g nickel N,N-di-n-butyldithiocarbamate, 2g 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 2g N-cyclohexyl-N'-phenyl-p-phenylenediamine, and 2g microcrystalline wax), 20g silicon dioxide, 0.8g insoluble sulfur, and 2.8g vulcanization accelerator (including 1.5g 2,2'-dibenzothiazole disulfide, 1g N-cyclohexyl-2-benzothiazole sulfenamide, and 0.3g tetramethylthiuram disulfide). The nitrile rubber should have an acrylonitrile content of 45%, and the polyvinyl chloride should have a degree of polymerization of 1100 DP and a number average molecular weight of 70,000 g / mol.

[0046] Step 1 (preparation of rubber mix): put NBR and PVC into the internal mixer according to their respective proportions, mix for 30 seconds (speed set to 25r / min), then lift the top bolt, add stearic acid, zinc oxide, carbon black, plasticizer, antioxidant, inorganic filler (speed set to 35r / min), when the mixing temperature reaches 95℃, lift the bolt for 5s and then press it down, the mixing time is controlled at 5-7min, when the mixing temperature reaches 140℃-150℃, discharge the rubber, and pass it through the open mill once (roller distance set to 2mm), cut into sheets with a thickness of 8-10mm to prepare a first-stage mixed rubber, and keep it for 8-10h; then carry out second-stage mixing, take the prepared first-stage mixed rubber and put it back into the internal mixer, mix it for 30s (the speed is set at 25r / min), add vulcanizing agent and vulcanization accelerator and mix for 3-4min, control the temperature between 115-125℃ for rubber discharge, pass it through the open mixer thinly once (the roller distance is set at 2mm), cut into sheets with a thickness of 8-10mm to prepare a second-stage mixed rubber, keep it for 24h and use it.

[0047] Step 2 (production of finished products): The mixed rubber material prepared in step 1 is extruded at a die temperature of 70°C, a screw temperature of 60°C, a plasticizing section temperature of 60°C, and a feed port temperature of 50°C to obtain a single-layer tube embryo; a straight tube core rod, an expanded (16 expanded 24) straight tube core rod, a (90°) special-shaped tube core rod, and a (90°) special-shaped (16 expanded 24) expanded core rod are respectively put on, and vulcanized at a temperature of 170°C and a pressure of 0.5 MPa for 25 minutes to obtain the corresponding NBR / PVC rubber tube.

[0048] Comparative Example 3 The specific preparation method is the same as that of Example 3, except that PVC is introduced and pre-treated with swelling, but the amount of surface modifier added is reduced. The specific contents are as follows: Only the amount of γ-mercaptopropyltrimethoxysilane used was changed to 0.5 g.

[0049] The acrylonitrile content of the nitrile rubber is 45%, the degree of polymerization of the polyvinyl chloride is 1100DP, and the number average molecular weight is 70000 g / mol.

[0050] Comparative Example 4 The specific preparation method is the same as that in Example 1, except that the introduction ratio of PVC is increased. The specific contents are as follows: 50g of nitrile rubber, 70g of polyvinyl chloride, 60g of fast-pressed carbon black, 30g of acetyl tributyl citrate, 1.5g of stearic acid, 5g of zinc oxide, 7g of antioxidant (including 1g of nickel N,N-di-n-butyldithiocarbamate, 2g of 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 2g of N-cyclohexyl-N'-phenyl-p-phenylenediamine, and 2g of microcrystalline wax), 20g of silicon dioxide, 2g of γ-mercaptopropyltrimethoxysilane, 0.8g of insoluble sulfur, and 2.8g of vulcanization accelerator (including 1.5g of 2,2'-dibenzothiazole disulfide, 1g of N-cyclohexyl-2-benzothiazole sulfenamide, and 0.3g of tetramethylthiuram disulfide).

[0051] The acrylonitrile content of the nitrile rubber is 45%, the degree of polymerization of the polyvinyl chloride is 1100DP, and the number average molecular weight is 70000 g / mol.

[0052] Comparative Example 5 The specific implementation method is consistent with Example 3, except that the mass of acetyl tributyl citrate is changed to 60 g.

[0053] Comparative Example 6 The specific implementation method is consistent with Example 3, except that the mass of acetyl tributyl citrate is changed to 15 g.

[0054] Comparative Example 7 The specific implementation method is consistent with Example 3, except that the amount of γ-mercaptopropyltrimethoxysilane is changed to 5 g.

[0055] Comparative Example 8 The specific implementation method is consistent with Example 3, only the ratio of the substances in the antioxidant is changed, specifically: N,N-di-n-butyldithiocarbamate nickel, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, N-cyclohexyl-N'-phenyl-p-phenylenediamine, and microcrystalline wax are mixed in a mass ratio of 4:3:2:1.

[0056] Comparative Example 9 The specific implementation method is consistent with Example 3, except that only the ratio of the substances in the vulcanization accelerator is changed, specifically: 2,2'-dibenzothiazole disulfide, N-cyclohexyl-2-benzothiazole sulfenamide and tetramethylthiuram disulfide are mixed in a mass ratio of 2:1:1.

[0057] Experimental example The performance of the rubber compound materials finally prepared in the embodiment and the comparative example was tested. Performance test 1: The test content includes tensile strength, ozone resistance, oil resistance, aging resistance, and Mooney resistance. The test results are shown in Table 1.

[0058] Table 1: Tensile strength, ozone resistance, oil resistance, aging resistance, and Mooney test results of the examples and comparative examples

[0059] Performance Test 2: Performance tests were conducted on the finished pipes prepared in the examples and comparative examples. The test contents included ozone resistance, burst pressure, and appearance. The test results are shown in Table 2.

[0060] Table 2: Ozone resistance, burst pressure and appearance test results of Examples and Comparative Examples

[0061]

[0062]

[0063]

[0064] Results: From Comparative Example 1 and Example 1, it can be seen that compared with traditional NBR materials, the addition of PVC can significantly improve the aging resistance and ozone resistance of the composite rubber. This is due to the fact that the PVC structure itself can form a continuous phase in the composite system, which can effectively block the reaction between ozone and the double bonds in the NBR molecular chain and improve the overall stability of the material. From Comparative Example 2, it can be seen that although the addition of PVC improves the overall ozone resistance and aging resistance of the material to a certain extent, due to its own high crystallinity and the large difference in molecular chain structure with NBR, the elasticity and tear resistance of the overall material are reduced. The compatibility of PVC and NBR can be significantly improved by surface modifiers and specific process flow, which can improve the cracking of the bending section caused by the small bending angle of the hose to a certain extent. Comparative Example 4 shows that although the addition of excessive PVC can significantly improve the ozone resistance and aging properties of the material, the rigid structure of PVC itself increases the Mooney value of the composite material, seriously affecting the extrusion performance, thereby limiting its use. Finally, it can be seen from the data in Table 1 and Table 2 that the NBR / PVC modified composite material prepared according to the present invention has excellent oil resistance, aging resistance and ozone resistance in terms of material properties; in the extrusion process, it has excellent fluidity at high temperatures; in the finished product size, the flaring ratio of the hose product is increased from the original 20%~30% to 50%, and the bending angle is reduced from the original 100°~120° to 90°, which can meet more complex installation conditions; in terms of finished product function, it has better adaptability and anti-pullout properties, and reduces stress concentration in the product, extending the service life of the product, perfectly overcoming the shortcomings of flared special-shaped hose ports and bending sections that are prone to cracks, and improving product competitiveness.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A modified NBR / PVC rubber-plastic alloy material suitable for flared special-shaped pipes, characterized in that: The invention is prepared from the following raw materials, in parts by mass: 50-100 parts of nitrile rubber, 10-50 parts of polyvinyl chloride, 60-80 parts of quick-pressed carbon black, 25-40 parts of plasticizer, 1-3 parts of organic active agent, 5-10 parts of inorganic active agent, 5-10 parts of antioxidant, 10-30 parts of inorganic filler, 1-3 parts of surface modifier, 0.2-1.2 parts of vulcanizing agent and 2-5 parts of vulcanization accelerator.

2. The NBR / PVC rubber-plastic alloy modified material suitable for flared special-shaped pipes according to claim 1, characterized in that: 55-75 parts of nitrile rubber, 30-45 parts of polyvinyl chloride, 60-70 parts of quick-pressed carbon black, 28-35 parts of plasticizer, 1.2-2 parts of organic active agent, 5-8 parts of inorganic active agent, 6-8 parts of antioxidant, 15-25 parts of inorganic filler, 1.5-2.5 parts of surface modifier, 0.5-1 part of vulcanizing agent and 2.5-4 parts of vulcanization accelerator.

3. The NBR / PVC rubber-plastic alloy modified material suitable for flared special-shaped pipes according to claim 1, characterized in that: The plasticizer is a citrate plasticizer.

4. The NBR / PVC rubber-plastic alloy modified material suitable for flared special-shaped pipes according to claim 1, characterized in that: The modifier is a silane compound modifier.

5. The NBR / PVC rubber-plastic alloy modified material suitable for flared special-shaped pipes according to claim 1, characterized in that: The acrylonitrile content in the nitrile rubber is 41%-45%.

6. The NBR / PVC rubber-plastic alloy modified material suitable for flared special-shaped pipes according to claim 1, characterized in that: The antioxidant is at least four of N,N-di-n-butyldithiocarbamate nickel, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, N-cyclohexyl-N'-phenyl-p-phenylenediamine, microcrystalline wax, 2,3-benzofuran, 2-mercaptobenzimidazole, and N-phenyl-1-naphthylamine.

7. The NBR / PVC rubber-plastic alloy modified material suitable for flared special-shaped pipes according to claim 1, characterized in that: The accelerator is at least two of 2,2'-dibenzothiazole disulfide, N-cyclohexyl-2-benzothiazole sulfenamide, 4,4'-dimorpholine disulfide, tetramethylthiuram disulfide, zinc dimethyldithiocarbamate, and copper dimethylaminodithiocarbamate.

8. A method for preparing a modified NBR / PVC rubber-plastic alloy material suitable for flared special-shaped pipes according to any one of claims 1 to 7, characterized in that: The steps include: S1. At 80° C., slowly adding a surface modifier to polyvinyl chloride until it is completely absorbed to obtain swollen polyvinyl chloride; S2, plasticizing the polyvinyl chloride that has been subjected to swelling treatment, adding nitrile rubber to blend when the polyvinyl chloride is softened, and obtaining a premixed rubber; S3, plasticizing the premixed rubber to obtain plasticized rubber; S4, dividing the plasticized rubber into two stages for mixing to obtain a mixed rubber material; S5, vulcanizing and shaping the mixed rubber material to obtain.

9. The method for preparing the NBR / PVC rubber-plastic alloy modified material suitable for flared special-shaped pipes according to claim 8, characterized in that: The S4 step is specifically as follows: In the first stage of mixing, the plasticized rubber is internally kneaded for 15-45 seconds, and then an organic activator, an inorganic activator, carbon black, a plasticizer, an antioxidant and an inorganic filler are added and mixed at 90-100°C for 5-7 minutes. When the mixing temperature reaches 140-150°C, the rubber is discharged, thinned, unrolled and left to stand for 8-10 hours to obtain the first stage of the mixed rubber; The first-stage mixed rubber is kneaded for 15-45 seconds, and the vulcanizing agent and the vulcanization accelerator are added and kneaded for 3-4 minutes. When the mixing temperature reaches between 115°C and 125°C, the rubber is discharged and thinned, and the sheet is removed and placed for 24-28 hours to obtain the product.

10. Use of the NBR / PVC rubber-plastic alloy modified material of the flared special-shaped tube according to any one of claims 1 to 7 in oil-resistant rubber.

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