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

Abstract

The application provides a preparation and application of NBR / PVC rubber-plastic alloy modified material suitable for flared special-shaped pipes, and the alloy modified material is prepared from the following raw materials in mass fractions: 50-100 parts of nitrile rubber, 10-50 parts of polyvinyl chloride, 60-80 parts of fast extrusion furnace 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, 0.5-3 parts of surface modifier, 0.2-1.2 parts of vulcanizing agent and 2-5 parts of vulcanization accelerator. The prepared NBR / PVC rubber-plastic alloy modified material has better oil resistance, ozone resistance and aging resistance, the rubber pipe product prepared from the material has better adaptability and anti-pulling-off property for joints, can better adapt to more complex installation space and reduce stress concentration, and prolongs the service life.

Description

Technical Field

[0001] This invention belongs to the field of polymer rubber material synthesis technology, specifically to the preparation and application of NBR / PVC rubber-plastic alloy modified material suitable for flared and shaped pipes. Background Technology

[0002] Nitrile butadiene rubber (NBR) possesses excellent oil resistance, making it widely used in oil-resistant products. However, harsh working conditions and increasingly stringent standards have gradually exposed NBR's shortcomings in ozone resistance and heat aging resistance. Therefore, NBR / PVC modified materials have been introduced, which combine the excellent oil resistance of NBR with the shortcomings of poor ozone resistance and heat aging resistance, while significantly reducing formulation costs.

[0003] However, because PVC molecular chains have high crystallinity and their structure differs greatly from that of NBR molecular chains, the interaction between molecular chains is enhanced, which restricts the movement of molecular chains and reduces the overall elasticity and tear resistance of the material. Consequently, when NBR / PVC is used in flared and shaped pipes, vertical cracks are prone to occur at the ends and bends, which severely limits the application of NBR / PVC.

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

[0005] The first NBR / PVC rubber-plastic alloy modified material of this invention is suitable for flared shaped pipes. This material effectively improves the problems of poor elasticity and tear resistance caused by the inherent structure of NBR / PVC materials. It further solves the technical difficulty of easy cracking at the ends and bends when NBR / PVC is used as a base material in flared shaped hose products. Therefore, this material has superior oil resistance, ozone resistance, and aging resistance.

[0006] The second objective of this invention is to provide a method for preparing NBR / PVC rubber-plastic alloy modified material suitable for flared and shaped pipes, which is simpler and less expensive.

[0007] The third objective of this invention is to provide an application of NBR / PVC rubber-plastic alloy modified material for flared shaped pipes in oil-resistant rubber.

[0008] To achieve the above-mentioned objectives of this invention, the following technical solution is adopted:

[0009] This invention provides an NBR / PVC rubber-plastic alloy modified material suitable for flared and shaped pipes, which is mainly made from the following raw materials by weight: 50-100 parts of nitrile rubber, 10-50 parts of polyvinyl chloride, 60-80 parts of fast-pressed carbon black, 25-40 parts of plasticizer, 1-3 parts of organic activator, 5-10 parts of inorganic activator, 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.

[0010] Preferably, as a further specific embodiment, the composition includes 55-75 parts of nitrile rubber, 30-45 parts of polyvinyl chloride, 60-70 parts of fast-pressing carbon black, 28-35 parts of plasticizer, 1.2-2 parts of organic activator, 5-8 parts of inorganic activator, 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.

[0011] Preferably, as a further specific embodiment, the mixture comprises 60 parts of nitrile rubber, 40 parts of polyvinyl chloride, 60 parts of fast-pressing carbon black, 30 parts of plasticizer, 1.5 parts of organic activator, 5 parts of inorganic activator, 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.

[0012] In this invention, citrate ester plasticizers are intentionally introduced, which can better penetrate the rubber molecular chains and reduce the intermolecular forces. At the same time, silane compounds are introduced to modify its own structure, changing its crystallinity and making its dispersion with nitrile rubber more uniform. This also makes the NBR / PVC blend more compatible with other fillers, effectively improving the problems of poor elasticity and poor tear resistance of NBR / PVC materials caused by their own structure.

[0013] Preferably, as a further specific embodiment, the plasticizer is a citrate ester plasticizer;

[0014] Preferably, the citrate plasticizer is any one or more of triethyl acetylglucosyl citrate, tributyl acetylglucosyl citrate, triethyl citrate, or tributyl citrate;

[0015] Preferably, the citrate plasticizer is either triethyl acetylglucosyl citrate or tributyl citrate;

[0016] Preferably, the citrate plasticizer is triethyl acetylcitrate.

[0017] Preferably, as a further specific embodiment, the surface modifier is a silane compound modifier;

[0018] Preferably, the silane compound modifier is one or more of γ-mercaptopropyltrimethoxysilane, bis-(γ-trimethoxysilylpropyl)disulfide, or γ-mercaptopropylmethyldimethoxysilane;

[0019] Preferably, the silane compound modifier is either γ-mercaptopropyltrimethoxysilane or bis-(γ-trimethoxysilylpropyl)disulfide;

[0020] Preferably, the silane compound modifier is γ-mercaptopropyltrimethoxysilane.

[0021] Preferably, as a further specific embodiment, the acrylonitrile content in the nitrile rubber is 41%-45%;

[0022] 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;

[0023] Preferably, the degree of polymerization of polyvinyl chloride is 1100 DP and the number average molecular weight is 70000 g / mol.

[0024] Preferably, as a further specific embodiment, the antioxidant is at least four of the following: N,N-di-n-butyldithiocarbamate, 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;

[0025] Preferably, the antioxidant is a mixture of four substances: N,N-di-n-butyldithiocarbamate, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, N-cyclohexyl-N'-phenyl-p-phenylenediamine, and microcrystalline wax.

[0026] Preferably, the antioxidant is a mixture of N,N-di-n-butyldithiocarbamate, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, N-cyclohexyl-N'-phenyl-p-phenylenediamine, and microcrystalline wax in a mass ratio of 0.5:1:1:1;

[0027] In this invention, the selection of anti-aging agents achieves the "principle of four-fold synergistic protection," that is, through the linkage of physical shielding, chemical passivation, free radical capture, and peroxide decomposition, the problem of aging failure of flared and special-shaped tubes under complex working conditions is effectively solved; at the same time, the dosage of each substance is limited, which can not only effectively improve the anti-aging performance and extend the life of metal joints, but also avoid environmental pollution.

[0028] Preferably, the organic activator is stearic acid;

[0029] Preferably, the inorganic activator is either zinc oxide or magnesium oxide;

[0030] Preferably, the inorganic activator is zinc oxide.

[0031] Preferably, the vulcanizing agent is one of insoluble sulfur or 2,4-di-tert-butyl peroxide;

[0032] Preferably, the vulcanizing agent is insoluble sulfur.

[0033] Preferably, the inorganic filler is a silicon carbide material;

[0034] Preferably, the carbon silicon material is any one of silicon dioxide, clay, talc, or carbon black-silica hybrid material;

[0035] Preferably, the silicon carbide material is silicon dioxide.

[0036] Preferably, as a further specific embodiment, the vulcanization accelerator is at least two of 2,2'-dithiodibenzothiazole, N-cyclohexyl-2-benzothiazole sulfenamide, 4,4'-dithiodimorpholine, tetramethylthiuram disulfide, zinc dimethyldithiocarbamate, and copper dimethylaminodithiocarbamate.

[0037] Preferably, the vulcanization accelerator is a mixture of 2,2'-dithiodibenzothiazole, N-cyclohexyl-2-benzothiazole sulfenamide, and tetramethylthiuram disulfide;

[0038] Preferably, the vulcanization accelerator is a mixture of 2,2'-dithiodibenzothiazole, N-cyclohexyl-2-benzothiazole sulfenamide and tetramethylthiuram disulfide in a mass ratio of 1.5:1:0.3.

[0039] Under this ratio, it can solve the problem of vertical cracks caused by stress concentration in the flared or bent parts, suppress cracks, and increase the flared ratio; at the same time, it can balance the vulcanization rate, avoid premature vulcanization leading to material scorching, or insufficient performance due to under-vulcanization, and effectively reduce the crack rate of flared special-shaped tubes.

[0040] This invention also provides a method for preparing the above-mentioned NBR / PVC rubber-plastic alloy modified material suitable for flared shaped pipes, comprising the following steps:

[0041] S1. At 80°C, the surface modifier is slowly added to the polyvinyl chloride until it is completely absorbed, thus obtaining polyvinyl chloride that has undergone swelling treatment.

[0042] S2. Plasticize the polyvinyl chloride that has undergone swelling treatment, and add nitrile rubber while the polyvinyl chloride is softening to obtain a premixed rubber.

[0043] S3. Plasticize the premixed rubber to obtain plasticized rubber;

[0044] S4. The plasticized rubber is mixed in two stages to obtain a compounded rubber material;

[0045] S5. The compounded rubber is vulcanized and shaped to obtain the final product.

[0046] In S1, the methoxy group (-OCH3) in the silane compound undergoes a hydrolysis reaction to generate silanol (SI-OH). The silanols then undergo a self-condensation reaction to form an SI-O-SI network structure, which further enhances the interfacial bonding between the two phases and improves the stability of the material.

[0047] The thiol group (-SH) in the silane compound in S2 undergoes a nucleophilic substitution reaction with the chlorine atom (Cl) in polyvinyl chloride (PVC) to generate the PVC grafted silanol intermediate (PVC-S-(CH2)3-SI(OH)3).

[0048] The thiol group (-SH) in the silane compound in S3 undergoes an addition reaction with the carbon-carbon double bond (C=C) in nitrile rubber (NBR) to generate the NBR grafted silanol intermediate (NBR-S-(CH2)3-SI(OH)3).

[0049] The self-condensation reaction of nitrile rubber (NBR) and polyvinyl chloride (PVC) grafted silanol intermediate generated by the silane compound bridging in S4 indirectly and better combines nitrile rubber (NBR) and polyvinyl chloride (PVC), thereby significantly improving their compatibility and interfacial bonding.

[0050] Preferably, as a further specific implementation, step S4 specifically includes:

[0051] The first stage of compounding involves mixing the plasticized rubber for 15-45 seconds, then adding organic activator, inorganic activator, fast-extrusion carbon black, plasticizer, antioxidant, and inorganic filler, and mixing at 90℃-100℃ for 5-7 minutes. When the mixing temperature reaches 140℃-150℃, the rubber is discharged, thinly passed through, sheeted, and left to stand for 8-10 hours to obtain the first stage of compounded rubber.

[0052] The first section of compound is mixed for 15-45 seconds, then vulcanizing agent and vulcanization accelerator are added and mixed for 3-4 minutes. When the mixing temperature reaches 115℃-125℃, the compound is discharged, sheeted, and left to stand for 24-28 hours to obtain the final product.

[0053] Preferably, the specific steps of S5 are as follows:

[0054] The obtained compounded rubber is extruded at a die head temperature of 70℃, a screw temperature of 60℃, a plasticizing section temperature of 60℃, and a feed port temperature of 50℃ to obtain a single-layer tube preform; straight tube mandrels, flared (16mm x 24mm) straight tube mandrels, (90°-120°) shaped tube mandrels, and (90°-120°) shaped (16mm x 24mm, flaring ratio of 10%-50%) flared mandrels are respectively fitted and vulcanized at a temperature of 170℃ and a pressure of 0.5MPa for 25 minutes to obtain the corresponding NBR / PVC rubber tubes;

[0055] Preferably, the flaring ratio can be 10%, 20%, 30%, or 50%;

[0056] Preferably, the flaring ratio is 50%;

[0057] Preferably, the irregular angle is 90° or 120°;

[0058] Preferably, the irregular angle is 90°.

[0059] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0060] (1) In view of the large difference in molecular structure between nitrile rubber and polyvinyl chloride, which leads to the enhanced interaction between PVC molecular chains and NBR molecular chains, the molecular chain movement is hindered and the overall elasticity of the material decreases, citrate ester plasticizers are specially introduced, which can better penetrate the rubber molecular chains and reduce the interaction force between molecular chains.

[0061] (2) In view of the problem that the high crystallinity of PVC material itself leads to the overall reduction of the elasticity of composite materials, silane compounds are introduced to modify its own structure, change its own crystallinity, make its dispersion with nitrile rubber more uniform, and make the NBR / PVC blend have better compatibility with other fillers, effectively improving the problem of poor elasticity and poor tear resistance of NBR / PVC material due to its own structure.

[0062] (3) It further solves the technical dilemma that cracks easily occur at the ends and bends when NBR / PVC is used as the base material in flared and irregularly shaped rubber hose products. As a result, the material has better oil resistance, ozone resistance, aging resistance and price advantage. Rubber hose products made with this material have better compatibility and versatility of joints and better pull-out resistance. At the same time, it can better adapt to more complex installation spaces and reduce stress concentration, thus extending service life. Attached Figure Description

[0063] Figure 1 : This is a schematic diagram of the structure of the modified material of the present invention, where a is a silane compound, b is nitrile rubber (NBR), c is polyvinyl chloride (PVC), and d is silanol;

[0064] Figure 2: This is a flow chart of the polyvinyl chloride (PVC) bentonite pretreatment process;

[0065] Figure 3 : This is a flow chart of the premixed adhesive preparation process;

[0066] Figure 4 : This is a flow chart of the two-stage mixing preparation process;

[0067] Figure 5 The following are four types of finished pipe structures and shapes: (a) NBR / PVC straight pipe; (b) NBR / PVC flared pipe with a flare ratio of 20%; (c) NBR / PVC shaped pipe with a bend angle of 120°; (d) NBR / PVC shaped pipe with a bend angle of 90°; (e) NBR / PVC shaped flared pipe with a bend angle of 120° and a flare ratio of 50%; and (f) NBR / PVC flared shaped pipe with a bend angle of 90° and a flare ratio of 50%.

[0068] Figure 6 The reactions occurring in the five reaction steps of this invention are as follows: Reaction 1 is the hydrolysis of silane compound to generate silanol in step one; Reaction 2 is the self-condensation reaction of silanol in step two; Reaction 3 is the addition reaction of silane compound with NBR in step three to generate NBR-grafted silanol intermediate; Reaction 4 is the substitution reaction of silane compound with PVC in step four to generate PVC-grafted silanol intermediate; Reaction 5 is the combination of NBR and PVC-grafted silicone intermediate through silanol self-condensation reaction in step five. Detailed Implementation

[0069] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0070] Example 1

[0071] Weigh out the following substances separately: 70g of nitrile rubber, 30g of polyvinyl chloride, 70g of fast-pressed carbon black, 25g of tributyl acetylacetic acid, 1g of stearic acid, 6g of zinc oxide, 5g of antioxidant (including 0.8g of 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 silica, 1g of γ-mercaptopropyltrimethoxysilane, 0.4g of insoluble sulfur, and 2g of vulcanization accelerator (including 1g of 2,2'-dithiodibenzothiazole, 0.7g of N-cyclohexyl-2-benzothiazole sulfenamide, and 0.3g of tetramethylthiuram disulfide).

[0072] Among them, the acrylonitrile rubber is selected with an acrylonitrile content of 43%, the degree of polymerization of polyvinyl chloride is 1200DP, and the number average molecular weight is 70000g / mol.

[0073] Prepare the compounded rubber material and its finished pipe according to the following steps:

[0074] Step 1 (PVC Swelling Pretreatment): Place polyvinyl chloride (PVC) between the two rolls of an open mill, reduce the roll gap to 2 mm, and set the rotation speed to 70 r / min. When the roll temperature reaches 80℃, slowly add γ-mercaptopropyltrimethoxysilane to the PVC until it is completely absorbed (the PVC will appear continuously transparent). The reaction process is as follows: Figure 6 As shown in reaction 1.

[0075] Step 2 (Premixed Rubber Preparation): Pre-swelled PVC is placed between the two rolls of an open mill for plasticizing (roll gap reduced to 2mm). When the temperature reaches the PVC softening temperature, the roll gap is increased to 5mm while nitrile rubber is added for blending. This process lasts 12 minutes. Then, a thin pass (roll gap reduced to 2mm) is performed three times to ensure uniform mixing. Finally, the mixture is sheeted (roll gap increased to 8mm). The open mill speed is consistently set to 60 r / min. The reaction process is as follows: Figure 6 As shown in reaction 2.

[0076] Step 3 (Masturing): Take the premixed rubber and masticate it on a two-roll mill. Adjust the roll gap to 2mm and the roll temperature to 50℃. Continue forming triangular lumps for 10-12 minutes to obtain the masticated rubber. The reaction process is as follows: Figure 6 As shown in reaction 3.

[0077] Step 4 (Preparation of Compound): Place the plasticized rubber prepared in Step 3 into a Banbury mixer and mix for 30 seconds (speed set to 25 r / min). Then, raise the top bolt and add stearic acid, zinc oxide, quick-pressing carbon black, tributyl acetylacetic acid, antioxidant, and silica (speed set to 35 r / min). When the mixing temperature reaches 95℃, raise the bolt for 5 seconds and then lower it. Control the mixing time to 5-7 minutes. When the mixing temperature reaches 140℃-150℃, discharge the rubber and pass it through a two-roll mill once (roll gap set to 2 mm). Sheet the rubber to a thickness of 8-10 mm. The first stage of compound rubber is obtained and left to stand for 8-10 hours. Then, a second stage of compound rubber is prepared. The first stage compound rubber is returned to the internal mixer and mixed for 30 seconds (speed set to 25 r / min). A vulcanization accelerator (including 2,2'-dithiodibenzothiazole, N-cyclohexyl-2-benzothiazole sulfenamide, and tetramethylthiuram disulfide) is added and mixed for 3-4 minutes. The temperature is controlled between 115-125℃ for discharge. The mixture is then passed through a two-roll mill once (roll gap set to 2 mm) and sheeted to a thickness of 8-10 mm to obtain the second stage compound rubber. This is left to stand for 24 hours for later use. The reaction process is as follows: Figure 6 As shown in reaction 4.

[0078] Step 5 (Production of Finished Product): The compounded rubber prepared in Step 4 is extruded at a die head temperature of 70℃, a screw temperature of 60℃, a plasticizing section temperature of 60℃, and a feed port temperature of 50℃ to obtain a single-layer tube preform. Straight tube mandrels, flared (16mm x 24mm) straight tube mandrels, (90°) shaped tube mandrels, and (90°) shaped (16mm x 24mm, flaring ratio 50%) flared mandrels are then respectively vulcanized at 170℃ and 0.5MPa for 25 minutes to obtain the corresponding NBR / PVC rubber tubes. The reaction process is as follows: Figure 6 The reaction is shown in Figure 5.

[0079] Example 2

[0080] The specific preparation method is consistent with that in Example 1. The following substances are weighed: 80g of nitrile rubber, 20g of polyvinyl chloride, 80g of fast-pressed carbon black, 40g of tributyl acetylacetic acid, 3g of stearic acid, 10g of zinc oxide, 9g of antioxidant (including 1.2g of N,N-di-n-butyldithiocarbamate, 2.6g of 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 2.6g of N-cyclohexyl-N'-phenyl-p-phenylenediamine, and 2.6g of microcrystalline wax), 30g of silica, 3g of γ-mercaptopropyltrimethoxysilane, 4g of insoluble sulfur, and 4g of vulcanization accelerator (including 2.2g of 2,2'-dithiodibenzothiazole, 1.4g of N-cyclohexyl-2-benzothiazole sulfenamide, and 0.4g of tetramethylthiuram disulfide). Among them, the acrylonitrile rubber is selected with an acrylonitrile content of 41%, the degree of polymerization of polyvinyl chloride is 1300DP, and the number average molecular weight is 71000g / mol.

[0081] Example 3

[0082] The specific preparation method is consistent with that in Example 1. The following substances are weighed: 60g of nitrile rubber, 40g of polyvinyl chloride, 60g of fast-pressed carbon black, 30g of tributyl acetylacetic acid, 1.5g of stearic acid, 5g of zinc oxide, 7g of antioxidant (including 1g of 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 silica, 2g of γ-mercaptopropyltrimethoxysilane, 0.8g of insoluble sulfur, and 2.8g of vulcanization accelerator (including 1.5g of 2,2'-dithiodibenzothiazole, 1g of N-cyclohexyl-2-benzothiazole sulfenamide, and 0.3g of tetramethylthiuram disulfide).

[0083] Among them, the acrylonitrile rubber is selected with an acrylonitrile content of 45%, the degree of polymerization of polyvinyl chloride is 1100DP, and the number average molecular weight is 70000g / mol.

[0084] Comparative Example 1

[0085] The difference from Example 1 is that NBR is used directly as the main material, without introducing PVC material. The selection of each substance is as follows: 100g of nitrile rubber, 60g of fast-pressing carbon black, 30g of tributyl acetylacetic acid, 1.5g of stearic acid, 5g of zinc oxide, 7g of antioxidant (including 1g of 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 silica, 0.8g of insoluble sulfur, and 2.8g of vulcanization accelerator (including 1.5g of 2,2'-dithiodibenzothiazole, 1g of N-cyclohexyl-2-benzothiazole sulfenamide, and 0.3g of tetramethylthiuram disulfide).

[0086] Among them, the acrylonitrile rubber is selected with an acrylonitrile content of 45%, the degree of polymerization of polyvinyl chloride is 1100DP, and the number average molecular weight is 70000g / mol.

[0087] Step 1 (Preparation of Compound): Directly add NBR raw rubber to the internal mixer and mix for 30 seconds (speed set to 25 r / min). Then, lift the top plug and add stearic acid, zinc oxide, fast-pressing carbon black, tributyl acetylacetic acid, antioxidant, and silica (speed set to 35 r / min). When the mixing temperature reaches 95℃, lift the top plug for 5 seconds and then press down. Control the mixing time to 5-7 minutes. When the mixing temperature reaches 140℃-150℃, discharge the rubber and pass it through a two-roll mill once (roll gap). Set the thickness to 2mm), cut the rubber into sheets with a thickness of 8-10mm to obtain a first-stage compound, and let it stand for 8-10 hours; then carry out a second-stage compounding, take the obtained first-stage compound and put it back into the internal mixer, mix for 30 seconds (speed set to 25r / min), add vulcanization accelerator and mix for 3-4 minutes, control the temperature between 115-125℃ and discharge the rubber, pass it through the open mill once (roll gap set to 2mm), cut it into sheets with a thickness of 8-10mm to obtain a second-stage compound, let it stand for 24 hours, and use it for later use.

[0088] Step 2 (Production of finished product): The compounded rubber prepared in Step 1 is extruded at a die head temperature of 70℃, a screw temperature of 60℃, a plasticizing section temperature of 60℃, and a feed port temperature of 50℃ to obtain a single-layer tube preform; straight tube mandrels, flared (16-expanded 24) straight tube mandrels, (90°) shaped tube mandrels, and (90°) shaped (16-expanded 24) flared mandrels are respectively taken and vulcanized at a temperature of 170℃ and a pressure of 0.5MPa for 25 minutes to obtain the corresponding rubber tubes.

[0089] Comparative Example 2

[0090] Introducing PVC without prior swelling treatment, and using it directly, details are as follows:

[0091] The following components of the formula were weighed separately: 70g of nitrile rubber, 30g of polyvinyl chloride, 60g of fast-pressing carbon black, 30g of tributyl acetylacetic acid, 1.5g of stearic acid, 5g of zinc oxide, 7g of antioxidant (including 1g of 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 silica, 0.8g of insoluble sulfur, and 2.8g of vulcanization accelerator (including 1.5g of 2,2'-dithiodibenzothiazole, 1g of N-cyclohexyl-2-benzothiazole sulfenamide, and 0.3g of tetramethylthiuram disulfide). The nitrile rubber was selected with an acrylonitrile content of 45%, and the polyvinyl chloride had a degree of polymerization of 1100 DP and a number-average molecular weight of 70,000 g / mol.

[0092] Step 1 (Preparation of Compound): Add NBR and PVC to a Banbury mixer in their respective proportions and mix for 30 seconds (speed set to 25 r / min). Then, lift the top bolt and add stearic acid, zinc oxide, fast-pressing carbon black, plasticizer, antioxidant, and inorganic filler (speed set to 35 r / min). When the mixing temperature reaches 95℃, lift the top bolt for 5 seconds and then lower it. Control the mixing time to 5-7 minutes. When the mixing temperature reaches 140℃-150℃, discharge the compound and pass it through a two-roll mill once (roll gap setting). The first stage of compound rubber is prepared by cutting the rubber into sheets with a thickness of 8-10 mm (2 mm) and letting it stand for 8-10 hours. Then, the second stage of compound rubber is prepared by taking the first stage of compound rubber and putting it back into the internal mixer and mixing for 30 seconds (speed set to 25 r / min). The vulcanizing agent and vulcanization accelerator are added and mixed for 3-4 minutes. The temperature is controlled between 115-125℃ for discharge. The rubber is then passed through a two-roll mill once (roll gap set to 2 mm) and cut into sheets with a thickness of 8-10 mm to obtain the second stage of compound rubber. The rubber is then left to stand for 24 hours for later use.

[0093] Step 2 (Production of finished product): The compounded rubber prepared in Step 1 is extruded at a die head temperature of 70℃, a screw temperature of 60℃, a plasticizing section temperature of 60℃, and a feed port temperature of 50℃ to obtain a single-layer tube preform; straight tube mandrels, flared (16-expanded 24) straight tube mandrels, (90°) shaped tube mandrels, and (90°) shaped (16-expanded 24) flared mandrels are respectively taken and vulcanized at a temperature of 170℃ and a pressure of 0.5MPa for 25 minutes to obtain the corresponding NBR / PVC rubber tubes.

[0094] Comparative Example 3

[0095] The specific preparation method is the same as in Example 3, except that PVC is introduced and a swelling pretreatment is performed, but the amount of surface modifier added is reduced. The details are as follows:

[0096] The amount of γ-mercaptopropyltrimethoxysilane was simply changed to 0.5g.

[0097] Among them, the acrylonitrile rubber is selected with an acrylonitrile content of 45%, the degree of polymerization of polyvinyl chloride is 1100DP, and the number average molecular weight is 70000g / mol.

[0098] Comparative Example 4

[0099] The specific preparation method is the same as in Example 1, except that the proportion of PVC introduced is increased, as detailed below:

[0100] 50g of nitrile rubber, 70g of polyvinyl chloride, 60g of fast-pressed carbon black, 30g of tributyl acetylacetic acid, 1.5g of stearic acid, 5g of zinc oxide, 7g of antioxidant (including 1g of 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 silica, 2g of γ-mercaptopropyltrimethoxysilane, 0.8g of insoluble sulfur, and 2.8g of vulcanization accelerator (including 1.5g of 2,2'-dithiodibenzothiazole, 1g of N-cyclohexyl-2-benzothiazole sulfenamide, and 0.3g of tetramethylthiuram disulfide).

[0101] Among them, the acrylonitrile rubber is selected with an acrylonitrile content of 45%, the degree of polymerization of polyvinyl chloride is 1100DP, and the number average molecular weight is 70000g / mol.

[0102] Comparative Example 5

[0103] The specific implementation method is the same as in Example 3, except that the mass of acetylsicitrin tributyl ester is changed to 60g.

[0104] Comparative Example 6

[0105] The specific implementation method is consistent with Example 3, except that the mass of acetylsicitrin tributyl ester is changed to 15g.

[0106] Comparative Example 7

[0107] The specific implementation method is consistent with Example 3, except that the amount of γ-mercaptopropyltrimethoxysilane is changed to 5g.

[0108] Comparative Example 8

[0109] The specific implementation method is consistent with Example 3, except that the ratio of each substance 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.

[0110] Comparative Example 9

[0111] The specific implementation method is consistent with Example 3, except that the ratio of each substance in the vulcanization accelerator is changed. Specifically, 2,2'-dithiodibenzothiazole, N-cyclohexyl-2-benzothiazole sulfenamide and tetramethylthiuram disulfide are mixed in a mass ratio of 2:1:1.

[0112] Experimental Example

[0113] The compound rubber materials finally obtained from the examples and comparative examples were subjected to performance tests.

[0114] Performance Test 1: The test included tensile strength, ozone resistance, oil resistance, aging resistance, and Mooney resistance. The test results are shown in Table 1.

[0115] Table 1: Tensile strength, ozone resistance, oil resistance, aging resistance, and Mooney test results for both examples and comparative examples.

[0116]

[0117] Performance Test 2: Performance tests were conducted on the finished tubes prepared in the examples and comparative examples. The tests included ozone resistance, burst pressure, and appearance. The test results are shown in Table 2.

[0118] Table 2: Ozone resistance, burst pressure, and appearance inspection results of the examples and comparative examples

[0119]

[0120]

[0121]

[0122]

[0123] Results: Comparative Example 1 and Example 1 show that, compared with traditional NBR materials, the addition of PVC significantly improves the aging resistance and ozone resistance of the composite compound. This is due to the fact that the structure of PVC 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, thereby improving the overall stability of the material. Comparative Example 2 shows that, although the addition of PVC improves the overall ozone resistance and aging resistance of the material to some extent, its high crystallinity and significant differences from the NBR molecular chain structure lead to a decrease in the overall elasticity and tear resistance of the material. The reduction in moisture content leads to noticeable cracks at the ends and bends of the flared, irregularly shaped rubber hoses after vulcanization, and they also exhibit some elongation after ozone resistance. Comparative Example 3 shows that surface modifiers and specific processes can significantly improve the compatibility of PVC and NBR, and to some extent, improve the cracking of the bends caused by the small bending angle of the hoses. Comparative Example 4 shows that although adding excessive PVC can significantly improve ozone resistance and aging resistance in terms of material properties, the rigid structure of PVC itself leads to an increase in Mooney density of the composite material, which seriously affects extrusion performance and thus limits its use. Finally, as shown in Tables 1 and 2, the NBR / PVC modified composite material prepared according to this invention exhibits excellent oil resistance, aging resistance, and ozone resistance in terms of material properties; excellent flowability at high temperatures in the extrusion process; increased flaring ratio of hose products from 20%~30% to 50% and reduced bending angle from 100°~120° to 90° in terms of finished product dimensions, meeting more complex installation conditions; and superior adaptability, versatility, and pull-out resistance in terms of finished product functionality, reducing stress concentration and extending product lifespan, perfectly overcoming the shortcomings of cracking at the ends and bends of flared and irregularly shaped hoses, thus improving product competitiveness.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions 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. An NBR / PVC rubber-plastic alloy modified material suitable for flared shaped pipes, characterized in that, It is made from the following raw materials in parts by weight: 50-100 parts of nitrile rubber, 10-50 parts of polyvinyl chloride, 60-80 parts of fast-extrusion carbon black, 25-40 parts of plasticizer, 1-3 parts of organic activator, 5-10 parts of inorganic activator, 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; The plasticizer is a citrate ester plasticizer; The surface modifier is a silane compound modifier; the silane compound modifier is one or more of γ-mercaptopropyltrimethoxysilane, bis-(γ-trimethoxysilylpropyl)disulfide or γ-mercaptopropylmethyldimethoxysilane; The antioxidant is a mixture of four substances: N,N-di-n-butyldithiocarbamate, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, N-cyclohexyl-N'-phenyl-p-phenylenediamine, and microcrystalline wax; the antioxidant is a mixture of N,N-di-n-butyldithiocarbamate, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, N-cyclohexyl-N'-phenyl-p-phenylenediamine, and microcrystalline wax in a mass ratio of 0.5:1:1:

1. The vulcanization accelerator is a mixture of 2,2'-dithiodibenzothiazole, N-cyclohexyl-2-benzothiazole sulfenamide, and tetramethylthiuram disulfide; the vulcanization accelerator is a mixture of 2,2'-dithiodibenzothiazole, N-cyclohexyl-2-benzothiazole sulfenamide, and tetramethylthiuram disulfide in a mass ratio of 1.5:1:0.

3.

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

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

4. A method for preparing an NBR / PVC rubber-plastic alloy modified material suitable for flared shaped pipes as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. At 80°C, the surface modifier is slowly added to the polyvinyl chloride until it is completely absorbed, thus obtaining polyvinyl chloride that has undergone swelling treatment. S2. Plasticize the polyvinyl chloride that has undergone swelling treatment, and add nitrile rubber while the polyvinyl chloride is softening to obtain a premixed rubber. S3. Plasticize the premixed rubber to obtain plasticized rubber; S4. The plasticized rubber is divided into two stages for mixing to obtain a compounded rubber material; S5. Vulcanize and shape the compounded rubber to obtain the final product; The S4 step is specifically as follows: The first stage of compounding involves mixing the plasticized rubber for 15-45 seconds, then adding organic activator, inorganic activator, fast-extrusion carbon black, plasticizer, antioxidant, and inorganic filler, and mixing at 90℃-100℃ for 5-7 minutes. When the mixing temperature reaches 140℃-150℃, the rubber is discharged, thinly passed through, sheeted, and left to stand for 8-10 hours to obtain the first stage of compounded rubber. The first section of compound is mixed for 15-45 seconds, then vulcanizing agent and vulcanization accelerator are added and mixed for 3-4 minutes. When the mixing temperature reaches 115℃-125℃, the compound is discharged, sheeted, and left to stand for 24-28 hours to obtain the final product.

5. The application of an NBR / PVC rubber-plastic alloy modified material for flared shaped pipes as described in any one of claims 1-3 in oil-resistant rubber.

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