Environment-friendly rubber sealing element modified material and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, and discloses an environment-friendly rubber sealing element modified material and a preparation method thereof.The modified material is prepared from biodegradable polyester resin, acid-rich rubber pre-dispersed masterbatch, a metal ion cross-linking agent, an antioxidant and a lubricant; wherein the acid-rich rubber pre-dispersed masterbatch is a physical mixture of a functionalized rubber matrix and solid organic acid. The preparation method comprises the following steps: carrying out reactive blending by using a twin-screw extruder, releasing organic acid by using rubber master batch to initiate an interfacial acidolysis reaction, reducing the viscosity of a system so as to promote micronized dispersion of a rubber phase, and then adding a metal ion crosslinking agent through side feeding to initiate a coordination reaction so as to construct an ionic crosslinking network. The problems that a biodegradable material is poor in rebound resilience and rubber is difficult to disperse are solved, and the obtained material has a low compression permanent deformation rate, can be recycled for multiple times based on thermal reversibility of ionic bonds, and is suitable for manufacturing environment-friendly sealing parts.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer materials, in particular to an environment-friendly rubber sealing component modified material and a preparation method thereof. BACKGROUND

[0002] With the increasingly stringent environmental regulations, developing biodegradable elastomer materials to replace traditional non-degradable vulcanized rubber has become a development trend in the sealing component industry. Although biodegradable polyester resins such as polybutylene adipate terephthalate (PBAT) have good biodegradability, they mainly exhibit the characteristics of thermoplastic plastics at room temperature, and have poor resilience and high compression set, which cannot directly meet the long-term use requirements of sealing components for dimensional stability and resilience.

[0003] In order to improve the resilience of biodegradable polyester, the existing technology usually adopts a dynamic vulcanization process to introduce and disperse a rubber phase in a polyester matrix. However, this modification method has obvious limitations in practical application. Since the thermal stability of biodegradable polyester is relatively poor and the melt viscosity is low, while the Mooney viscosity of the rubber matrix is usually high, there is a viscosity mismatch between the two when they are melt blended, which makes it difficult to achieve micron-level refinement of the dispersed phase and weakens the interfacial bonding force, thereby affecting the final mechanical properties of the material. At the same time, traditional dynamic vulcanization systems mostly use peroxides or sulfur as crosslinking agents, which can easily produce irritating volatile substances during the reaction process, resulting in odor residue problems in the material, which is difficult to meet the index requirements of low volatile organic compounds (VOC) for environmentally friendly sealing components.

[0004] In addition, the covalent bond crosslinking network formed by the traditional vulcanization system belongs to irreversible chemical crosslinking structure, so that the modified material cannot be recycled through melt processing once it is formed, which limits the application value of the material in the field of circular economy. Therefore, how to solve the dispersion problem of high-viscosity rubber in low-viscosity polyester matrix while ensuring biodegradability and recyclability, and build a reversible crosslinking network with excellent resilience, is a problem to be solved in current technology. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides an environment-friendly rubber sealing component modified material and a preparation method thereof, which solves the problems of poor resilience, high compression set of existing biodegradable polyester elastomer materials, and uneven dispersion due to viscosity mismatch between rubber and polyester matrix, which makes it difficult to balance excellent mechanical properties and recyclability.

[0006] To achieve the above purpose, the present application provides the following technical solutions:

[0007] In a first aspect, the present application provides an environmentally friendly rubber seal modification material, which is made of raw materials containing the following weight parts:

[0008] biodegradable polyester resin 98.0-102.0 parts;

[0009] acid-rich rubber pre-dispersed masterbatch 20.0-50.0 parts;

[0010] metal ion crosslinking agent 1.0-6.0 parts;

[0011] antioxidant 0.1-2.0 parts;

[0012] lubricant 0.1-2.0 parts;

[0013] wherein the acid-rich rubber pre-dispersed masterbatch is a physical mixture of a functionalized rubber matrix and a solid organic acid.

[0014] By adopting the above technical solution, the present application utilizes the acid-catalyzed interfacial reaction and the coordination of metal ions to construct a thermoreversible ionic crosslinking network inside the material. The specific mechanism is as follows:

[0015] dispersion control of acid source: the solid organic acid is dispersed in the rubber matrix through a premixing process. This physical mixing state avoids direct contact between the organic acid and the polyester resin at the initial stage of mixing, thereby preventing uncontrollable bulk degradation of the polyester matrix.

[0016] interfacial reaction and phase state optimization:

[0017] During processing, the released organic acid catalyzes the chemical reaction between polyester and rubber at the interface, generating a graft copolymer; at the same time, acidolysis reduces the melt viscosity of the polyester matrix, which is beneficial to the formation of fine and uniform dispersed phase of high-viscosity rubber phase under shear action.

[0018] formation of ionic network:

[0019] The metal ion crosslinking agent neutralizes the acidic components in the system, terminating the degradation process of the molecular chain; at the same time, the metal ions form metal carboxylate ion clusters with the carboxyl groups on the polyester and rubber molecular chains. The ion clusters act as physical crosslinking points, limiting the slip of the molecular chain and reducing the compression permanent set of the material.

[0020] thermoreversibility:

[0021] Based on the physical properties of ion dissociation at high temperature and association at low temperature, the material has the elastic rebound performance of elastomers at room temperature and the rheological performance of thermoplastic plastics at high temperature, thereby realizing the recycling and reprocessing of the material.

[0022] Preferably, the biodegradable polyester resin is selected from one or a combination of polybutylene adipate, polybutylene terephthalate and polybutylene succinate;

[0023] The metal ion crosslinking agent is selected from one or a combination of active zinc oxide and anhydrous zinc acetate;

[0024] The solid organic acid is selected from one or a combination of anhydrous citric acid and DL-malic acid.

[0025] By adopting the technical scheme, the reactivity of each component is matched, which is conducive to forming ion crosslinking points with uniform distribution.

[0026] Preferably, in the acid-rich rubber pre-dispersion masterbatch:

[0027] The weight ratio of the functionalized rubber matrix and the solid organic acid is 100.0:1.5-6.0;

[0028] The functionalized rubber matrix is selected from one of epoxidized natural rubber and carboxylated nitrile rubber; and the solid organic acid is dispersed in the form of microparticles inside the functionalized rubber matrix.

[0029] By adopting the technical scheme, the ratio of acid to rubber and the dispersion form are limited, so that the release rate of acid can be controlled, and the performance degradation caused by excessive local acid concentration can be avoided.

[0030] Preferably, the melting point of the solid organic acid ranges from 130.0-160.0℃;

[0031] The Mooney viscosity ML(1+4)100℃ of the functionalized rubber matrix ranges from 40.0-60.0.

[0032] By adopting the technical scheme, the melting point of the solid organic acid is adapted to the processing temperature range, so that the reaction occurs in the interfacial diffusion zone.

[0033] The viscosity range ensures the dispersion ability of the rubber matrix in the shear field.

[0034] By adopting the technical scheme, the material exhibits excellent dimensional stability and aging resistance, and retains the mechanical strength after multiple thermal processes.

[0035] In a second aspect, the present application provides a preparation method of an environmentally friendly rubber sealing material modification material, which adopts a double-screw extruder for reactive blending, and the steps include:

[0036] S1, masterbatch preparation step: plasticize the functionalized rubber matrix, and mix the solid organic acid at a temperature lower than the melting point of the solid organic acid to obtain an acid-rich rubber pre-dispersion masterbatch;

[0037] S2, a melting acidolysis step: the biodegradable polyester resin, the acid-rich rubber pre-dispersed masterbatch, the antioxidant, and the lubricant are mixed uniformly and fed into the main feeding port of the twin-screw extruder; the mixture is heated and melted in the conveying melting zone and the interface diffusion and acidolysis reaction zone, and interface acidolysis reaction occurs to form an acidolysis modified melt;

[0038] S3, an ion crosslinking step: the metal ion crosslinking agent is fed into the acidolysis modified melt through the side feeding port located after the interface diffusion and acidolysis reaction zone, and coordination reaction occurs in the ion crosslinking and reconstruction zone to form an ion crosslinked melt;

[0039] S4, an extrusion molding step: the ion crosslinked melt is extruded through the die head, cooled, and pelletized to obtain an environmentally friendly rubber sealing component modified material.

[0040] By adopting the above technical scheme, the preparation method realizes step-by-step reaction process through control of the feeding position and temperature zone:

[0041] In the masterbatch preparation stage, the rubber matrix is used to physically coat the solid organic acid, and the acid source is isolated;

[0042] In the melting acidolysis stage, the material is heated and melted, the organic acid diffuses to the interface catalytic reaction, the melt viscosity is reduced, and the dispersion and refinement of the rubber phase are promoted;

[0043] In the ion crosslinking stage, the metal ion is introduced through the side feeding, the metal ion rapidly reacts with the carboxyl group to form an ionic bond, and the melt viscosity rapidly rises, thereby fixing the microstructure and constructing a three-dimensional network.

[0044] Preferably, in the S1 step:

[0045] The mixing and mixing temperature control range of the plasticated rubber matrix is 40.0-60.0°C;

[0046] The discharge temperature control range of the acid-rich rubber pre-dispersed masterbatch is 70.0-90.0°C;

[0047] The mixing time control range after mixing the solid organic acid is 1.0-3.0 minutes.

[0048] By adopting the above technical scheme, the low-temperature mixing condition ensures that the solid organic acid does not melt or chemically react during the dispersion process.

[0049] Preferably, the temperature range of the conveying melting zone of the twin-screw extruder is set to 130.0-145.0°C;

[0050] The temperature range of the interface diffusion and acidolysis reaction zone of the twin-screw extruder is set to 145.0-160.0°C;

[0051] The temperature range of the ion crosslinking and reconfiguration zone of the double screw extruder is set to 170.0-190.0 DEG C.

[0052] By adopting the technical scheme, the setting of each temperature zone corresponds to the energy conditions required by acid diffusion, interface reaction and ion coordination, and continuous reaction control is realized.

[0053] Preferably, in the S3 step:

[0054] The side feeding port is arranged at a position with a length-diameter ratio L / D of 26.0-30.0 of the double screw extruder;

[0055] Before entering the side feeding port, the melt flow rate MFI of the acidolysis modified melt after melt acidolysis evolves in a range of 18.0-35.0 g / 10min;

[0056] After the metal ion crosslinking agent is added, the melt flow rate MFI of the ion crosslinked melt after ion crosslinking evolves in a range of 1.0-3.0 g / 10min.

[0057] By adopting the technical scheme, the evolution data of the melt flow rate verify that the molecular structure undergoes a process of degradation and dispersion first and then crosslinking and reconfiguration, and the performance of the final material meets the design requirements.

[0058] Preferably, the screw rotation speed of the double screw extruder is set in a range of 200.0-350.0 r / min, and the total length-diameter ratio L / D of the double screw extruder ranges from 40.0 to 48.0.

[0059] By adopting the technical scheme, it is ensured that the material has sufficient residence time and shearing effect in the extruder, so that the reaction is fully carried out.

[0060] The application provides an environmentally friendly rubber sealing material and a preparation method thereof.

[0061] 1、The application improves the resilience of the material by constructing an ion coordination crosslinking network between the biodegradable polyester resin and the functionalized rubber matrix. The metal ion crosslinking agent reacts with the carboxyl and functional groups on the molecular chain to form metal carboxylate ion clusters. These ion clusters act as physical crosslinking points to limit the sliding of the polymer molecular chain at room temperature, so that the modified material has a low compression permanent set, solving the problem that conventional biodegradable materials are difficult to apply in the sealing field due to insufficient resilience.

[0062] 2, The application solves the contradiction between the difficulty of dispersing high-viscosity rubber in a polyester matrix and the excessive degradation caused by acid by using acid-rich rubber pre-dispersed masterbatch combined with a step-by-step reaction extrusion process. Solid organic acid is pre-dispersed in the rubber to achieve physical isolation and controlled release. In the early stage of processing, the acid catalyzes the interfacial reaction and moderately reduces the viscosity of the matrix, promoting the fine dispersion of the rubber phase. In the later stage of processing, the metal ions neutralize the acidic components and reconfigure the viscosity, ensuring the uniformity of the material's microstructure and the stability of the structure.

[0063] 3, The modified material prepared by the application has high elasticity of vulcanized rubber and processability of thermoplastic plastic based on the thermal reversible mechanism of ionic bonds, realizing efficient recycling and utilization of the material. Ionic bonds dissociate under high-temperature shear, giving the material good flow processing performance; after cooling and setting, they re-associate to restore the mechanical strength of the material. Experiments show that the tensile strength retention rate of the material remains at a high level after multiple recycling and reprocessing, meeting the requirements of environmental protection and resource recycling. DETAILED DESCRIPTION

[0064] The technical solutions in the embodiments of the application will be described below in conjunction with the preparation examples, embodiments and comparative examples of the application. Obviously, the described embodiments are only a part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the application.

[0065] In order to fully support the generalization of component types and ratio ranges (such as the change of the ratio of acid to rubber), and verify the universality of the process for different rubber matrices and acid types, the following provides three preparation examples of intermediates (acid-rich rubber masterbatch) with different parameters and components.

[0066] Preparation Example 1-3:

[0067] Preparation Example 1: This preparation example provides a high-acid-content epoxidized natural rubber pre-dispersed masterbatch, which includes 100 parts of epoxidized natural rubber (ENR-50) and 5 parts of anhydrous citric acid by weight. The preparation method includes the following steps:

[0068] Set the temperature of the internal mixer to 50℃ and the speed to 40r / min;

[0069] Put 100 parts of epoxidized natural rubber (ENR-50) into the internal mixer and plasticize for 2 minutes;

[0070] Add 5 parts of dried anhydrous citric acid powder in three times, mix for 1.5 minutes after each addition, control the temperature of the rubber to be no more than 80℃, and use shear force to physically disperse the anhydrous citric acid in the form of solid particles in the rubber matrix;

[0071] The rubber is discharged and sheeted out by an open mill, and granulated to obtain the high-acid-content epoxidized natural rubber pre-dispersion masterbatch, which is sealed and packaged for use.

[0072] Preparation Example 2: The present preparation example provides a low-acid-content epoxidized natural rubber pre-dispersion masterbatch, which includes, by weight parts, 100 parts of epoxidized natural rubber (ENR-50) and 2 parts of anhydrous citric acid. The preparation method includes the following steps:

[0073] The temperature of the internal mixer is set to 50°C, and the rotating speed is set to 40 r / min;

[0074] 100 parts of epoxidized natural rubber (ENR-50) are put into the internal mixer for plasticizing for 2 minutes;

[0075] 2 parts of dried anhydrous citric acid powder are added, and the mixing is continued for 4 minutes, during which the temperature of the rubber compound is controlled to be no more than 80°C;

[0076] The rubber is discharged and sheeted out by an open mill, and granulated to obtain the low-acid-content epoxidized natural rubber pre-dispersion masterbatch, which is sealed and packaged for use.

[0077] Preparation Example 3: The present preparation example provides a carboxylated nitrile rubber pre-dispersion masterbatch, which includes, by weight parts, 100 parts of carboxylated nitrile rubber (XNBR) and 4 parts of DL-malic acid. The preparation method includes the following steps:

[0078] The temperature of the internal mixer is set to 55°C, and the rotating speed is set to 45 r / min;

[0079] 100 parts of carboxylated nitrile rubber (XNBR) are put into the internal mixer for plasticizing for 2.5 minutes;

[0080] 4 parts of DL-malic acid powder are added, and the mixing is continued for 5 minutes, during which the temperature of the rubber compound is controlled to be no more than 90°C, so as to ensure that the DL-malic acid does not melt or chemically react;

[0081] The rubber is discharged and sheeted out by an open mill, and granulated to obtain the carboxylated nitrile rubber pre-dispersion masterbatch, which is sealed and packaged for use.

[0082] Example 1-5:

[0083] Example 1: The present example provides an environmentally friendly rubber sealing material and a preparation method thereof, which includes the following steps:

[0084] The following raw materials are weighed by weight parts: 100 parts of polybutylene adipate terephthalate (PBAT), 31.5 parts of high-acid-content epoxidized natural rubber pre-dispersed masterbatch prepared in Preparation Example 1 (equivalent to 30 parts of ENR-50 and 1.5 parts of anhydrous citric acid), 3.0 parts of active zinc oxide, 0.5 parts of antioxidant 1010, and 0.5 parts of ethylene bis-stearamide (EBS);

[0085] The PBAT, the high-acid-content epoxidized natural rubber pre-dispersed masterbatch, the antioxidant 1010, and the EBS are uniformly mixed and fed into the main feeding port of the co-rotating twin-screw extruder with a length-diameter ratio of 44:1;

[0086] The active zinc oxide is added through the side feeding metering scale from the side feeding port at the middle section of the twin-screw extruder;

[0087] The temperature parameters of each zone of the twin-screw extruder are set as follows: the temperature of the conveying melting zone (Zone 1-2) is 135-140°C; the temperature of the interface diffusion and acidolysis reaction zone (Zone 3-5, located between the main feeding port and the side feeding port) is 150-155°C, to initiate the acidolysis and ester exchange reaction at the interface; the temperature of the ion crosslinking and reconstruction zone (Zone 6-8, located after the side feeding port) is 175-180°C, to promote the metal ion coordination reaction; and the temperature of the die head is 170°C;

[0088] The screw rotation speed is set to 250 r / min, and the material is extruded, water-cooled, air-dried, cut into particles, and dried at 80°C for 4 hours to obtain the rubber sealing component modification material.

[0089] Example 2 provides an environmentally friendly rubber sealing component modification material and a preparation method thereof, including the following steps:

[0090] The following raw materials are weighed by weight parts: 100 parts of polybutylene adipate terephthalate (PBAT), 25.5 parts of low-acid-content epoxidized natural rubber pre-dispersed masterbatch prepared in Preparation Example 2 (equivalent to 25 parts of ENR-50 and 0.5 parts of anhydrous citric acid), 1.5 parts of active zinc oxide, 0.5 parts of antioxidant 1010, and 0.5 parts of antioxidant 168;

[0091] The PBAT, the low-acid-content epoxidized natural rubber pre-dispersed masterbatch, the antioxidant 1010, and the antioxidant 168 are uniformly mixed and fed into the main feeding port of the co-rotating twin-screw extruder;

[0092] The active zinc oxide is added through the side feeding metering scale from the side feeding port at the middle section of the twin-screw extruder;

[0093] Set the temperature parameters of each zone of the twin-screw extruder: the temperature of the conveying melting zone is 130-140℃; the temperature of the interfacial diffusion and acidolysis reaction zone is 145-150℃; the temperature of the ion crosslinking and reconstruction zone is 170-175℃; the temperature of the head is 165℃;

[0094] Set the screw rotation speed to 200r / min, and the material is extruded, water-cooled, air-dried, granulated, and dried at 80℃ for 4 hours to obtain the modified material of the rubber sealing element.

[0095] Example 3: The present embodiment provides an environmentally friendly modified material of a rubber sealing element and a preparation method thereof, comprising the following steps:

[0096] The following raw materials are weighed by weight parts: 100 parts of polybutylene adipate terephthalate (PBAT), 42.0 parts of high-acid-content epoxidized natural rubber pre-dispersed masterbatch prepared in Preparation Example 1 (equivalent to 40 parts of ENR-50 and 2.0 parts of anhydrous citric acid), 5.0 parts of active zinc oxide, 0.5 parts of antioxidant 1010, and 0.5 parts of EBS;

[0097] The PBAT, high-acid-content epoxidized natural rubber pre-dispersed masterbatch, antioxidant 1010, and EBS are uniformly mixed and fed into the main feeding port of the co-rotating twin-screw extruder;

[0098] The active zinc oxide is added through the side feeding metering scale from the side feeding port of the rear section of the twin-screw extruder;

[0099] The temperature parameters of each zone of the twin-screw extruder are set: the temperature of the conveying melting zone is 140-145℃; the temperature of the interfacial diffusion and acidolysis reaction zone is 155-160℃; the temperature of the ion crosslinking and reconstruction zone is 185-190℃; the temperature of the head is 175℃;

[0100] Set the screw rotation speed to 350r / min, and the material is extruded, water-cooled, air-dried, granulated, and dried at 80℃ for 4 hours to obtain the modified material of the rubber sealing element.

[0101] Example 4: The present embodiment provides an environmentally friendly modified material of a rubber sealing element and a preparation method thereof, comprising the following steps:

[0102] The following raw materials are weighed by weight parts: 100 parts of polybutylene adipate terephthalate (PBAT), 42.0 parts of high-acid-content epoxidized natural rubber pre-dispersed masterbatch prepared in Preparation Example 1 (equivalent to 40 parts of ENR-50 and 2.0 parts of anhydrous citric acid), 5.0 parts of active zinc oxide, 0.5 parts of antioxidant 1010, and 0.5 parts of EBS;

[0103] The PBAT, high-acid-content epoxidized natural rubber pre-dispersed masterbatch, antioxidant 1010, and EBS are uniformly mixed and fed into the main feeding port of the co-rotating twin-screw extruder;

[0104] The anhydrous zinc acetate is added from the side feeding port of the rear section of the twin-screw extruder through a side feeding metering scale;

[0105] The temperature parameters of each zone of the twin-screw extruder are set as follows: the temperature of the conveying melting zone is 130-135°C; the temperature of the interfacial diffusion and acidolysis reaction zone is 140-145°C (matching the melting point of DL-malic acid); the temperature of the ion crosslinking and reconstitution zone is 170-175°C; and the temperature of the head is 160°C.

[0106] The screw rotation speed is set to 280 r / min, and the material is extruded, water-cooled, air-dried, cut into particles, and dried at 80°C for 4 hours to obtain the rubber sealing component modification material.

[0107] Example 5: This example provides an environmentally friendly rubber sealing component modification material and a preparation method thereof. Except for changing the process parameters, the remaining raw material components are completely the same as those in Example 1. The specific process steps are as follows:

[0108] The temperature parameters of each zone of the twin-screw extruder are set as follows: the temperature of the conveying melting zone is 140°C; the temperature of the interfacial diffusion and acidolysis reaction zone is increased to 160°C to speed up the interfacial diffusion rate; the temperature of the ion crosslinking and reconstitution zone is 180°C; and the temperature of the head is 175°C. The screw rotation speed is set to 300 r / min to provide a higher shear rate. The other operations are the same as those in Example 1.

[0109] Comparative Examples 1-5:

[0110] Comparative Example 1: Compared with Example 1, the difference lies in that no anhydrous citric acid (component C) is added. The specific operation is as follows: the high-acid-content epoxidized natural rubber pre-dispersed masterbatch in Preparation Example 1 is replaced with an equal amount of pure epoxidized natural rubber (ENR-50), and the remaining raw material types, amounts, and process steps are the same as those in Example 1.

[0111] Comparative Example 2: Compared with Example 1, the difference lies in the change in the addition method of the raw materials, which adopts a one-pot direct mixing process. The specific operation is as follows: instead of preparing a rubber pre-dispersed masterbatch, 100 parts of PBAT, 30 parts of pure ENR-50, 1.5 parts of powdered anhydrous citric acid, 3.0 parts of active zinc oxide, and other additives are all uniformly mixed, and then directly added from the main feeding port of the twin-screw extruder at one time. The remaining process parameters are the same as those in Example 1.

[0112] Comparative Example 3: Compared with Example 1, the difference lies in that no active zinc oxide (component D) is added. The specific operation is as follows: no active zinc oxide is added from the side feeding port of the twin-screw extruder, and the remaining raw material types, amounts, and process steps are the same as those in Example 1.

[0113] Comparative Example 4: Compared with Example 1, the difference is that the addition position of active zinc oxide (component D) is changed. Specifically, 3.0 parts of active zinc oxide is mixed with PBAT, rubber masterbatch and other raw materials, and then added from the main feeding port, without side feeding operation. The rest is the same as Example 1.

[0114] Comparative Example 5: Compared with Example 1, the difference is that the traditional peroxide dynamic vulcanization system is used instead of the acid / ionic system of the application. Specifically, no anhydrous citric acid and active zinc oxide is added, but the masterbatch of Preparation Example 1 is replaced with an equal amount of pure ENR-50, and 0.5 parts of dicumyl peroxide (DCP) is added at the side feeding port to initiate dynamic vulcanization. The rest is the same as Example 1.

[0115] Test Examples 1-6:

[0116] Test Example 1:

[0117] Melt flow rate (MFI) evolution test:

[0118] 1. Experimental description:

[0119] This test aims to monitor the change of rheological behavior of modified materials at different stages of the process, in order to verify the reaction mechanism of interfacial acidolysis viscosity reduction and ionic reconstruction viscosity increase.

[0120] Sampling point setting: In order to accurately capture the reaction progress, three sampling monitoring points are set:

[0121] Stage A (initial state): Pure PBAT matrix resin and corresponding formula mixture raw materials without processing.

[0122] Stage B (process state): Open the exhaust hole at the L / D=26 of the twin-screw extruder (i.e. after passing through the interfacial reaction zone but before reaching the side feeding port) to take samples quickly, and immediately put the melt sample into liquid nitrogen for quenching to freeze its chemical state. After crushing, dry for standby.

[0123] Stage C (final state): The final product granules after extrusion through the die and granulation.

[0124] Test method: Refer to GB / T 3682.1-2018 "Determination of the Melt Mass-Flow Rate and Melt Volume-Flow Rate of Thermoplastics - Part 1: Standard Method", test with melt flow rate instrument.

[0125] Test conditions: Temperature 190℃, load 2.16kg.

[0126] Preheating time: 240 seconds.

[0127] Cutting interval: 10 seconds.

[0128] Data record: Each sample was tested 5 times, and the average value was taken after removing the extreme value. The unit of the result was g / 10 min.

[0129] 2. Experimental data:

[0130] Table 1 Melt flow rate data of each example and comparative example at different processing stages

[0131] Sample No. Phase A: Initial raw material (g / 10 min) Phase B: Mid-extrusion sample (g / 10 min) Phase C: Final finished pellet (g / 10 min) Pure PBAT matrix 4.23 4.31 4.35 Example 1 4.23 26.85 1.74 Example 2 4.23 18.92 2.15 Example 3 4.23 31.04 1.12 Comparative Example 1 (no acid) 4.23 4.58 4.62 Comparative Example 2 (one-pot method) 4.23 72.19 15.63 Comparative Example 3 (no ZnO) 4.23 25.47 28.91 Comparative Example 4 (ZnO pre- addition) 4.23 5.82 4.95

[0132] (Note: The data of stage A uniformly uses the PBAT matrix value as the reference; the data difference of stages B and C reflects the chemical structure evolution in the processing process.)

[0133] Result analysis and conclusion:

[0134] Based on the test data in Table 1 and the technical principle of the application, the following conclusions are drawn:

[0135] The occurrence and control of acidolysis reaction The MFI value of Example 1 at stage B increased sharply from the initial 4.23 g / 10 min to 26.85 g / 10 min. The increase in MFI value corresponds to the decrease in melt viscosity, indicating that in the front section of the twin-screw extruder, the organic acid dispersed in the rubber is successfully released and diffuses to the interface, catalyzing the ester bond cleavage of polyester molecules, resulting in a decrease in molecular weight. This controlled low viscosity state is conducive to the fine dispersion and infiltration of the dispersed phase (rubber) in the matrix.

[0136] Ion reconfiguration and network formation The MFI value of Example 1 at stage C fell to 1.74 g / 10 min, which is lower than the initial raw material. This change confirms that after the addition of active zinc oxide by side feeding, the system undergoes rapid chemical reaction. The metal ions neutralize the carboxyl groups in the system, terminate the chain scission process, and reconnect the broken molecular chains through coordination, forming an ion crosslinked network of polyester, metal, and rubber. This network restricts the movement of molecular chains, which macroscopically manifests as a significant increase in melt viscosity.

[0137] Comparison of the effectiveness of the process path:

[0138] Comparison with Comparative Example 1 (without acid): The MFI of Comparative Example 1 changes little throughout the process, indicating that no chemical reaction occurs, only physical blending, and lacking interface modification.

[0139] Comparison with Comparative Example 2 (one-pot method): The MFI of Comparative Example 2 in Stage B is as high as 72.19 g / 10 min, indicating that if the pre-dispersion masterbatch process is not used, the free acid will contact the polyester matrix to cause severe bulk degradation. Although the subsequent addition of zinc oxide makes its final state MFI fall to 15.63 g / 10 min, its value is still much higher than the raw material, indicating that the matrix has suffered irreversible damage and cannot rebuild an effective skeleton structure.

[0140] Comparison with Comparative Example 4 (ZnO pre-positioning): The Stage B MFI of Comparative Example 4 is only 5.82 g / 10 min, indicating that the zinc oxide added too early neutralizes the organic acid, inhibiting the acidolysis viscosity reduction process, resulting in the failure to utilize the low viscosity advantage for phase dispersion.

[0141] In summary, the MFI evolution data strongly supports the technical route of the present application of first controlled acidolysis and then ion reconstruction, confirming that the process can realize the dynamic regulation of molecular chain structure.

[0142] Test Example 2:

[0143] Gel content (Gel Content) and swelling test:

[0144] 1. Experimental explanation:

[0145] This test determines the content and swelling behavior of the insoluble fraction in the modified material by solvent extraction method, to qualitatively and semi-quantitatively characterize the formation degree and structure type of the crosslinked network inside the material.

[0146] Experimental solvent: chloroform (CHCl3). This solvent is a good solvent for PBAT matrix resin and uncrosslinked elastomers, and is used to distinguish between physically dissolved parts and crosslinked parts that form network structures.

[0147] Experimental steps:

[0148] Sample preparation: Freeze and crush the test material in a liquid nitrogen environment, pass through an 80-mesh standard sieve, and place the obtained powder in a 60°C vacuum drying oven for 24 hours to constant weight.

[0149] Weighing and coating: Accurately weigh about 1.0 g of dry sample powder (record the mass as ) and place it in a 300-mesh stainless steel mesh bag of known mass (the mass of the mesh bag is recorded as ) and tightly seal.

[0150] Soxhlet extraction: Place the coated sample mesh bag in a Soxhlet extractor, add 150 mL of chloroform to the round-bottom flask. Heat to make the solvent boil and reflux, and set the extraction time to 24 hours to ensure that the free polyester and rubber molecules not involved in network construction are fully dissolved.

[0151] Swelling weight: After extraction, the bag was taken out, the surface adhering solvent was quickly absorbed with filter paper, and then immediately placed in a sealed weighing bottle for weighing (the total mass was recorded as ) for calculating the swelling degree.

[0152] Dry constant weight: The bag was placed in an 80°C vacuum oven for 24 hours to completely remove the solvent, and then taken out and placed in a desiccator to cool and weigh (the total mass was recorded as ).

[0153] Calculation formula:

[0154] ;

[0155] ;

[0156] 2. Experimental data:

[0157] Table 2 Gel content and swelling index test data of each example and comparative example

[0158] Sample No. Theoretical rubber mass fraction (%) Measured gel content (%) Swelling index Pure PBAT matrix 0 0.2 — Example 1 23.1 36.8 8.4 Example 2 16.6 29.3 7.9 Example 3 28.6 45.2 8.1 Comparative Example 1 (no acid) 23.1 5.6 15.2 Comparative Example 2 (one-pot method) 23.1 8.4 18.7 Comparative Example 3 (no ZnO) 23.1 4.1 — Comparative Example 4 (TPV / DCP) 23.1 58.9 4.2

[0159] (Note: The theoretical mass fraction of rubber refers to the mass percentage of the elastomer component in the total material in the formula; the swelling index reflects the compactness of the crosslinked network, and the lower the value represents the higher the crosslinking point density. In the table, - indicates that the swelling index cannot be accurately determined due to the low gel content.)

[0160] Result analysis and conclusion:

[0161] Based on the test data in Table 2 and combined with the theory of polymer physical network, the microstructure characteristics of each component are analyzed as follows:

[0162] The construction of the ionic coordination network confirms that the measured gel content of Example 1 is 36.8%, which is higher than the theoretical mass fraction of the rubber component in the formula (23.1%). This difference indicates that the insoluble substance not only contains rubber itself, but also contains a large number of PBAT molecular chains fixed by chemical bonding. The carboxylate zinc salt ionic clusters (Ionic Clusters) generated by active zinc oxide at the interface act as effective physical crosslinking points, anchoring the acid-modified rubber phase and the polyester matrix, forming an interpenetrating network structure, thereby retaining a high proportion of the skeleton component under continuous extraction in a good solvent.

[0163] The difference in the structure type of the comparative example 1 and the comparative example 4 (peroxide dynamic vulcanization system) is differentiated. The data shows that there is an essential difference between the network properties of the two. The comparative example 4 has a higher gel content (58.9%) and a lower swelling index (4.2), which is consistent with the characteristics of a dense and rigid network composed of carbon-carbon covalent bonds. In contrast, the swelling index of example 1 is higher (8.4), indicating that its network structure based on ion-dipole interaction is relatively loose, and there is a larger free volume between the segments. This structural feature gives the material excellent flexibility and resilience in the macroscopic, while avoiding the loss of processing flow caused by full covalent crosslinking.

[0164] The necessity of interface reaction is determined by the gel content of the comparative example 1 (without acid) and the comparative example 3 (without ZnO), which is as low as 5.6% and 4.1% respectively, close to the background value of pure PBAT matrix. This confirms that in the absence of acid-induced degradation or metal ion locking, the rubber phase and the PBAT matrix only maintain a simple physical mixing state, and no effective interface chemical reaction occurs. Under the action of the solvent, the dispersed phase rubber is easily separated from the matrix and dissolved, indicating that simple physical blending cannot build a stable phase interface.

[0165] The influence of process sequence on network formation is that the gel content of the comparative example 2 (one-pot method) is only 8.4%, which is much lower than that of example 1. This result is due to the loss of control of the reaction space-time distribution: the undispersed acid preferentially attacks the PBAT matrix to cause random chain scission, and fails to concentrate on the rubber matrix interface. Due to the lack of concentrated reaction at the interface and in-situ network formation, most of the low molecular weight PBAT and rubber after degradation cannot form a continuous skeleton, and are finally washed out by solvent extraction.

[0166] In summary, the gel content and swelling test confirm that the material prepared by the present application forms a special interface network structure with ionic bonds as the core inside the material. This structure is the physical basis for achieving the balance of high toughness, high resilience and reworkability of the material.

[0167] Test example 3:

[0168] Mechanical properties:

[0169] 1. Experimental explanation:

[0170] This test is based on the national standard to characterize the tensile properties and tear properties of the standard samples prepared by each group of modified materials, in order to evaluate the mechanical behavior and failure mode of the material under static load.

[0171] Sample preparation: After granulation, each group of materials is dried at 80°C for 4 hours, and an injection molding machine is used to injection molding at a temperature of 170-180°C.

[0172] Tensile specimen: 1A dumbbell-shaped specimen according to GB / T 1040.2-2006.

[0173] Tear specimen: right-angle specimen without cut according to GB / T 529-2008. All specimens were conditioned at 23±2℃, 50±5% relative humidity for 24 hours before testing.

[0174] Test procedure:

[0175] Tensile property test: using universal material testing machine, gauge length set as 50mm, tensile speed set as 500mm / min (simulating the working condition of elastomer). Record the maximum load and gauge length at break, calculate tensile strength and elongation at break.

[0176] Right-angle tear strength test: using universal material testing machine, tensile speed set as 500mm / min, record the maximum force value at tear failure, calculate tear strength.

[0177] Hardness test: using Shore A hardness tester, stack the specimen to 6mm thickness, read the instantaneous reading and 15 seconds delayed reading, take the average value.

[0178] Each group of data was tested with 5 parallel specimens, invalid data with break position outside the gauge length was removed, and the arithmetic mean value was taken.

[0179] 2. Experimental data:

[0180] Table 3 Mechanical property test data of each example and comparative example

[0181] Sample No. Tensile strength (MPa) Elongation at break (%) Angle tear strength (kN / m) Shore hardness (Shore A) Pure PBAT matrix 21.3 580 112.5 92(≈35D) Example 1 18.4 723 84.6 85 Example 2 19.8 615 91.2 88 Example 3 15.2 814 73.5 81 Example 4 17.9 695 82.1 86 Example 5 18.6 742 85.3 84 Comparative Example 1 (no acid) 9.2 145 34.8 83 Comparative Example 2 (one-pot method) 5.8 112 21.4 78 Comparative Example 3 (no ZnO) 7.6 285 29.6 75 Comparative Example 4 (TPV / DCP) 19.1 685 88.4 86

[0182] Result analysis and conclusion:

[0183] According to the data analysis in Table 3, the introduction method and reaction process of each component had a decisive influence on the final mechanical properties:

[0184] The decisive role of interface bonding on strength. Comparative Example 1 (18.4 MPa) and Comparative Example 2 (9.2 MPa) have basically the same formulation components, only lacking the acid-induced interfacial reaction. The tensile strength of Comparative Example 2 decreases by more than 50%, and the elongation at break is only 145%. This shows that without chemical compatibilization, there is phase separation between the polar PBAT matrix and the non-polar natural rubber, stress concentration occurs at the interface, and cracks are quickly initiated and propagated, showing typical brittle fracture characteristics. Example 1 maintains a high tensile strength, confirming that the acidolysis reaction successfully introduces chemical bonding at the interface, enabling effective stress transfer between the two phases.

[0185] The collapse of mechanical properties in Comparative Example 2 (one-pot method) results in a tensile strength of only 5.8 MPa, which has lost its value for use. The data show that direct exposure of organic acid to the polyester matrix initiates indiscriminate degradation of the PBAT molecular chain, resulting in a molecular weight of the matrix material itself that is too low to bear the load. In contrast, Example 1, through the rubber masterbatch pre-dispersion process, limits the acid mainly to the inside of the dispersed phase and the interface, achieving interfacial modification while maximizing the preservation of the skeletal integrity of the continuous phase matrix.

[0186] The contribution of ionic crosslinking to toughness. The elongation at break of Example 1 (723%) is higher than that of pure PBAT (580%), showing elastomeric characteristics. This toughening effect comes from two aspects:

[0187] First, the uniform dispersion of the rubber phase initiates the craze shear band toughening mechanism;

[0188] Second, the ionic cluster network constructed by active zinc oxide acts as a reversible physical crosslinking point. During the stretching process, the ionic bond dissociates to dissipate energy, and after unloading, it gives the molecular chain the ability to recover. Comparative Example 3 (without ZnO) contains rubber, but lacks the locking of ionic crosslinking points, resulting in low strength and poor recovery after deformation.

[0189] Comparison with traditional technology. The comprehensive mechanical indicators of Example 1 (strength 18.4 MPa, elongation 723%) and Comparative Example 4 (strength 19.1 MPa, elongation 685%) using peroxide dynamic vulcanization are mutually advantageous, at the same performance level. This shows that the acidolysis and ionic reconstruction technology route proposed in this invention can completely replace the traditional peroxide vulcanization technology route to prepare elastomeric materials that meet the requirements of engineering applications, while avoiding the odor problem caused by the residue of vulcanizing agents.

[0190] In summary, the mechanical property test results verify that by precisely controlling the acidolysis position and ionic reconstruction timing, the invention successfully solves the common strength and toughness inversion problem in biodegradable plastic toughening modification.

[0191] Test Example 4:

[0192] Sealing performance test (compression set):

[0193] 1. Experimental description:

[0194] Compression set is a key indicator to measure the resilience of elastomer materials to maintain the ability to rebound under long-term compression load when used as a seal. The lower the value, the stronger the material's resistance to permanent deformation, and the higher the sealing reliability.

[0195] Test standard: Refer to GB / T 7759.1-2015 "Determination of Compression Set of Vulcanized or Thermoplastic Rubber Part 1: At Room Temperature and High Temperature Conditions", using B-type compression samples.

[0196] Sample preparation: Each group of granules is injection molded into a cylindrical sample with a diameter of 13.0±0.5mm and a thickness of 6.3±0.3mm. After injection molding, it needs to be adjusted for 24 hours in the standard laboratory environment (23℃) to eliminate internal stress.

[0197] Test steps:

[0198] Initial thickness measurement: Measure the center thickness of the sample using a thickness gauge with an accuracy of 0.01mm, denoted as .

[0199] Load compression: Place the sample between two parallel steel plates and control the compression amount by a restrictor. The compression rate is set to 25%, i.e. the height of the compressed sample is 75% of the initial height.

[0200] Environmental treatment: Place the clamp assembly under the following two experimental conditions for aging:

[0201] Condition A (high temperature working condition): 70±1℃ constant temperature oven for 22 hours.

[0202] Condition B (normal temperature working condition): 23±2℃ environment for 72 hours.

[0203] Recovery and measurement: After reaching the specified time, remove the clamp from the oven and immediately loosen the bolts to release the compression. Place the sample on a wooden board and allow it to recover freely in the standard laboratory environment for 30 minutes.

[0204] Final thickness measurement: Measure the center thickness of the sample again, denoted as .

[0205] Calculation formula:

[0206] ;

[0207] Where: is the initial thickness; is the thickness after recovery; To limit the height of the restrictor (i.e. the thickness in the compressed state).

[0208] 2. Experimental data:

[0209] Table 4 Compression set test data of each example and comparative example

[0210] Sample No. Rubber phase type / crosslinking method Condition A: 70 °C x 22 h (%) Condition B: 23 °C x 72 h (%) Pure PBAT matrix — 88.4 62.1 Example 1 ENR / ionic coordination 28.5 16.3 Example 2 ENR (low gel) / ionic coordination 34.2 21.7 Example 3 ENR (high gel) / ionic coordination 24.9 14.1 Example 4 XNBR / ionic coordination 27.6 15.8 Example 5 ENR / ionic coordination (strong shear) 26.8 15.4 Comparative Example 1 (no acid) ENR / physical blending 76.5 54.2 Comparative Example 2 (one-pot method) ENR / matrix degradation 82.1 68.9 Comparative Example 3 (no ZnO) ENR / no crosslinking 69.3 48.5 Comparative Example 4 (TPV) ENR / peroxide vulcanization 26.1 13.9

[0211] Result analysis and conclusion:

[0212] Through the analysis of the compression set data, the control mechanism of the micro network structure of the material on the macro sealing performance is revealed:

[0213] The compression set of Example 1 of the ion cluster network at 70°C is 28.5%, and at room temperature it is 16.3%. This value is much lower than that of pure PBAT matrix (88.4%), and is close to that of Comparative Example 4 using chemical covalent crosslinking (TPV data is 26.1%). This confirms that the metal carboxylate ion clusters reconstructed by acid dissociation in the present application form a high density of physical crosslinking points in the polymer matrix. The electrostatic force generated by these ion aggregates can effectively limit the slip of molecular chains at room temperature and moderate high temperature. When the external force is removed, the elastic potential energy stored in the ion bond network promotes the molecular chains to return to the initial conformation, thereby endowing the thermoplastic material with the rebound performance similar to that of vulcanized rubber.

[0214] The compression set of Comparative Example 1 (no acid) and Comparative Example 3 (no ZnO) is extremely high, reaching 76.5% and 69.3% respectively. In the absence of acid-induced grafting or the absence of metal ion coordination, only weak van der Waals forces exist between the rubber phase and the PBAT matrix. Under the action of continuous compression stress, the dispersed phase rubber undergoes irreversible plastic flow and phase rearrangement, resulting in stress relaxation, and the material loses the rebound ability and cannot meet the sealing requirements.

[0215] The data of Comparative Example 2 (one-pot method) is the worst, and its compression set is even close to that of pure PBAT. This is because the direct addition of organic acid causes the PBAT matrix to be severely degraded, and the molecular weight decreases sharply, destroying the skeleton support function of the continuous phase. At this time, even if there is local crosslinking in the system, the broken matrix cannot transmit stress or maintain the macroscopic shape, resulting in the collapse of the material under compression.

[0216] The temperature sensitivity and thermoplasticity characteristics of Example 1 and Comparative Example 4 are compared with the data of Example 1. The deformation rate of Example 1 at 70°C is slightly higher than that of Comparative Example 4 (about 2.4% difference), while the difference at room temperature is very small. This slight difference is determined by the thermal reversibility of ionic bonds. Although the binding energy of ionic bonds is high, it will exhibit certain ion hopping behavior at high temperatures, resulting in a small amount of creep. However, the data of Example still fully meets the use standard of conventional rubber seals (usually requires <35%). This thermal reversibility is the physical basis for the material to have melt reprocessing (thermoplasticity), while the full covalent crosslinking structure of Comparative Example 4 does not have this property.

[0217] In summary, the sealing performance test shows that the modified material prepared by the present application successfully constructs a stable elastic recovery network, which has both the elasticity of traditional vulcanized rubber and the processability of thermoplastic plastic under the premise of ensuring the sealing function.

[0218] Test Example 5:

[0219] Processing fluidity and recycling performance:

[0220] 1. Experimental explanation:

[0221] This test includes spiral flow length test and multiple thermal processing cycle test, which aims to quantitatively evaluate the melt processing forming ability and performance retention rate of the material during recycling, to verify the thermoplastic nature of the material and the thermal reversibility mechanism of the ionic crosslinking network.

[0222] A. Spiral flow test (Spiral Flow Test) This test is used to characterize the filling flow ability of the material under a certain injection pressure and temperature, which directly reflects the width of the processing window of the material.

[0223] Equipment: injection molding machine equipped with Archimedes spiral mold (flow channel cross section is semicircular, radius 3mm).

[0224] Steps:

[0225] Set the barrel temperature to 170°C (uniform temperature), and the mold temperature to 40°C.

[0226] Set the injection pressure to 80 MPa, the holding pressure to 60 MPa, and the injection speed to 50 mm / s.

[0227] Perform injection molding and take out the sample after cooling, and measure the actual filling length of the spiral (cm). Each group of materials is tested for 10 molds, and the average value is taken.

[0228] B. Recycling cycle test (Recycling Cycle Test) This test simulates the recycling and reprocessing process of the material in industrial applications.

[0229] Steps:

[0230] Cycle 0: Test the tensile strength of the original granular injection sample.

[0231] Cycle 1: Crush the injection sample and runner material, add no new material, directly into the twin-screw extruder at 170℃, regranulation, injection molding again and test the tensile strength.

[0232] Cycle 3: Repeat the above crushing, granulation, injection molding steps until the third cycle, test the tensile strength.

[0233] Calculation: ;

[0234] 2. Experimental data:

[0235] Table 5 Processing flowability and recycling performance test data of each example and comparative example

[0236] Sample No. Helical flow length (cm) Initial tensile strength (MPa) Strength after 1 recycling (MPa) Strength after 3 recyclings (MPa) Retention after 3 recyclings (%) Pure PBAT matrix 48.5 21.3 20.9 19.8 93.0 Example 1 36.2 18.4 18.1 17.3 94.0 Example 2 39.4 19.8 19.4 18.6 93.9 Example 3 32.1 15.2 14.9 14.1 92.8 Example 5 35.8 18.6 18.3 17.5 94.1 Comparative Example 2 (one-pot method) 65.7 5.8 4.2 3.1 53.4 Comparative Example 4 (TPV) 18.3 19.1 15.6 12.4 64.9

[0237] (Note: The longer the helical line flow length, the better the flowability, but it also implies that the molecular weight is too low; Comparative Example 4 needs to increase the injection pressure to 110 MPa to fill the mold due to poor flowability, and the data in the table is the measured value under the standard pressure of 80 MPa.)

[0238] Result analysis and conclusion:

[0239] Based on the principles of rheology and network dynamics theory, the above processing and recycling data are analyzed as follows:

[0240] The thermal reversible dissociation mechanism of ionic bonds The helical line flow length of Example 1 is 36.2 cm, which is lower than that of pure PBAT matrix (48.5 cm), but much higher than that of Comparative Example 4 (18.3 cm). This indicates that the material of the present application exhibits good melt flowability under high temperature shear field. The physical mechanism is that the carboxylate ion clusters constructed by active zinc oxide are highly sensitive to temperature. Under the high temperature (170℃) and shear action of the injection molding machine, the ionic aggregates dissociate, the crosslinked network temporarily opens, and the molecular chains obtain the freedom of movement, showing the characteristics of thermoplastic melt; when the melt is filled and cooled, the ionic bonds reassociate and the crosslinked network is restored. This characteristic of dissociation at high temperature and association at low temperature solves the processing problem of traditional chemical crosslinked rubber that cannot be injection molded into precise thin-walled parts (such as the helical mold shown).

[0241] The processing limitation of chemical crosslinking Comparative Example 4 (TPV system) uses peroxide to initiate covalent bond crosslinking. Due to the extremely high bond energy of carbon-carbon covalent bond and irreversibility, the network cannot be disentangled at processing temperature, and the melt is actually a suspension system of crosslinked rubber microparticles dispersed in a small amount of thermoplastic matrix, with extremely high shear viscosity. The flow length of 18.3 cm in the data confirms that the processing window is narrow, it is difficult to form complex structures, and often requires higher energy consumption (higher pressure and temperature).

[0242] The essential difference in recycling ability is that the retention rate of tensile strength of Example 1 is as high as 94.0% after three thermal processing cycles, which is comparable to that of pure thermoplastic resin PBAT (93.0%), and even slightly better in numerical stability (benefiting from the repair effect of ions). This confirms that the reconstruction of the ionic crosslinking network is a completely reversible physical process, and multiple heating does not damage the crosslinking points themselves. On the contrary, the performance retention rate of Comparative Example 4 is only 64.9% after three recycling. This is because the covalently crosslinked rubber phase in TPV cannot re-form chemical bonds during crushing and re-extrusion, and can only exist as an inactive inert filler. As the number of recycling increases, the matrix resin degrades and cannot again wrap the rubber microparticles, resulting in failure of the phase interface and degradation of material performance.

[0243] Processing illusion caused by degradation Comparative Example 2 (one-pot method) has a flow length of up to 65.7 cm, but this is not a manifestation of excellent processing performance, but rather a result of severe degradation of the matrix, resulting in excessively low molecular weight and collapse of melt strength. Its recycling performance is extremely poor (retention rate of 53.4%), further confirming that the internal structure of the material has undergone irreversible chemical damage and does not have recycling value.

[0244] In summary, the processing and recycling performance tests conclusively prove that the material of the present application belongs to the category of thermoplastic elastomers, and successfully breaks through the technical barriers of traditional vulcanized rubber molding difficulty and difficulty in recycling by using the dynamic balance mechanism of ionic bonds, meeting the technical requirements of green circular economy.

[0245] Test Example 6:

[0246] Odor grade and volatile organic compound (VOC) release test:

[0247] 1. Experimental description:

[0248] This test aims to quantitatively evaluate the sensory odor characteristics and potential volatile organic compound release of the material, in order to verify the environmental safety of the material system in replacing traditional vulcanized rubber for use in automotive interiors, household appliance seals, and daily consumer goods.

[0249] A. Odor Test (Odor Test) was tested according to German Automobile Industry Association Standard VDA 270.

[0250] Sample treatment: The finished granules were injection molded into standard test pieces, and 50 ± 2 g samples were cut.

[0251] Test conditions: The samples were placed in 3 L odorless sealed glass jars and heated in an 80 ± 2 °C constant temperature oven for 2 hours (simulating high temperature sealing conditions), and after removal, cooled to 60 °C for evaluation.

[0252] Evaluation method: A team of 3 professionally trained odor evaluators smelled and scored immediately after opening the jar.

[0253] Scoring criteria (1-6 levels):

[0254] 1: No odor;

[0255] 2: Odor perceptible, but not disturbing;

[0256] 3: Distinct odor, but not disturbing;

[0257] 4: Disturbing odor;

[0258] 5: Strongly disturbing odor;

[0259] 6: Unbearable odor.

[0260] The final result is the arithmetic mean of the scores of the 3 evaluators, accurate to 0.5 levels.

[0261] B. Total volatile organic compounds (TVOC) and characteristic contaminant testing Referring to the VDA 278 standard, qualitative and quantitative analysis was performed using a thermal desorption gas chromatography / mass spectrometry (TD-GC / MS) instrument.

[0262] Procedure: 30 mg of sample was weighed into a thermal desorption tube and desorbed at 90 °C for 30 minutes. The volatile components were captured by a cold trap and then entered the GC-MS system for separation and detection.

[0263] Monitoring indicators:

[0264] TVOC value (µg / g): The sum of toluene equivalents corresponding to the peak areas of all compounds in the C6-C16 range was calculated.

[0265] Characteristic residues (µg / g): Acetophenone and 2-phenyl-2-propanol (decomposition products of traditional DCP vulcanizing agents) were detected.

[0266] 2. Experimental data:

[0267] Table 6 Odor level and VOC release test data of each example and comparative example

[0268] Sample No. VDA 270 odor grade (80 °C) Odor attribute description TVOC (µg / g) Acetophenone residue (µg / g) Pure PBAT matrix 1.5 Very faint waxy odor 12.4 Not detected Example 1 2.0 Faint acidic / fruit odor 38.6 Not detected Example 2 2.0 Faint acidic odor 32.1 Not detected Example 3 2.5 Slightly noticeable acidic odor 54.2 Not detected Example 4 2.0 Very faint caramel odor 41.5 Not detected Comparative Example 2 (one-pot method) 3.5 Piercingly acidic / degradation odor 185.3 Not detected Comparative Example 4 (TPV / DCP) 4.5 Irritating almond odor 462.8 85.4

[0269] (Note: Acetophenone is a typical by-product of decomposition of dicumyl peroxide DCP, with a strong irritating odor; not detected means content below the detection limit of the instrument 0.1 µg / g.)

[0270] Results analysis and conclusions:

[0271] Based on the chemical reaction mechanism and the above detection data, the environmental protection and sensory characteristics of the material are analyzed as follows:

[0272] The cross-linking mechanism fundamentally eliminates the odor source. The odor level of Example 1 is 2.0 (odor can be perceived but not disturbing), and the TVOC is only 38.6 µg / g, and acetophenone is not detected. This is due to the zinc acid ion coordination cross-linking mechanism used in the present application. The reaction between citric acid and zinc oxide belongs to acid-base neutralization and coordination reaction, and the only by-product is water (which has been volatilized during processing), without generating any low molecular weight organic volatile matter. The raw materials used (citric acid, PBAT, epoxidized natural rubber) are all environmentally friendly materials, some of which are even food contact grade, which blocks the generation of odor substances from the source.

[0273] The inevitable defects of the traditional vulcanization system The odor level of Comparative Example 4 (TPV system) is as high as 4.5 (interfering odor), and the TVOC is as high as 462.8 µg / g, and a high concentration of acetophenone (85.4 µg / g) is detected. This is an inherent defect of the peroxide dynamic vulcanization process: when the cross-linking agent dicumyl peroxide (DCP) initiates the free radical reaction, it will inevitably undergo homolysis decomposition to generate acetophenone and 2-phenyl-2-propanol. These small molecule by-products have high boiling points and are extremely difficult to completely remove during processing, eventually remaining in the material matrix and slowly releasing, resulting in a finished product with a persistent and unpleasant irritating odor, limiting its application in enclosed spaces such as passenger car cabins.

[0274] The influence of process control on sensory experience Comparative Example 1 and Comparative Example 2 (one-pot method), although the raw materials are the same, the odor level of Comparative Example 2 reaches 3.5, and the TVOC increases to 185.3 µg / g. This is because the one-pot method causes uncontrollable acidolysis degradation of the PBAT matrix, generating a large amount of terminal aldehyde, terminal ketone and oligomer fragments. These thermal degradation products have volatility and pungent odor. On the contrary, the pre-dispersion masterbatch process of the present application limits the acid reaction to the interface, avoiding a large amount of decomposition of the matrix, thereby ensuring the low odor properties of the material.

[0275] Optimization of odor properties The odor description of Example 1 and Example 4 is mainly light sour or light caramel, which is due to the natural odor of residual trace amounts of citric acid or malic acid. Compared with the sulfur odor or solvent odor of traditional rubber, this odor is closer to the natural base odor of bio-based materials and is more easily accepted by end consumers.

[0276] In summary, the environmental protection and sensory tests confirm that the present application successfully solves the problems of VOC exceeding the standard and odor residue of elastomer materials by abandoning the traditional sulfur or peroxide crosslinking system and instead using ion coordination crosslinking technology without by-products, thereby meeting the stringent requirements for material safety and comfort in high-end application fields.

Claims

1. An environmentally friendly rubber seal modifier material, characterized by, By weight parts, made of the following raw materials: Biodegradable polyester resin 98.0-102.0 parts; Acid-rich rubber pre-dispersed masterbatch 20.0-50.0 parts; Metal ion crosslinking agent 1.0-6.0 parts; Antioxidant 0.1-2.0 parts; Lubricant 0.1-2.0 parts; The acid-rich rubber pre-dispersed masterbatch is a physical mixture of a functionalized rubber matrix and a solid organic acid.

2. The environmentally friendly rubber seal modifier material according to claim 1, characterized in that, The biodegradable polyester resin is selected from one or a combination of two of polybutylene adipate, polybutylene terephthalate and polybutylene succinate; The metal ion crosslinking agent is selected from one or a combination of two of active zinc oxide and anhydrous zinc acetate; The solid organic acid is selected from one or a combination of two of anhydrous citric acid and DL-malic acid.

3. The environmentally friendly rubber seal modifier material according to claim 1, characterized in that, In the acid-rich rubber pre-dispersed masterbatch: The weight ratio of the functionalized rubber matrix to the solid organic acid is 100.0:1.5-6.0; The functionalized rubber matrix is selected from one of epoxidized natural rubber and carboxylated nitrile rubber; The solid organic acid is dispersed in the form of microparticles inside the functionalized rubber matrix.

4. The environmentally friendly rubber seal modifier material according to claim 3, characterized in that, The melting point of the solid organic acid ranges from 130.0-160.0℃; The Mooney viscosity ML1+4 of the functionalized rubber matrix at 100℃ ranges from 40.0-60.

0.

5. A method for preparing an environmentally friendly rubber seal modifier material, characterized by, A method for preparing an environmentally friendly rubber seal modifier material according to any one of claims 1-4, the method using a twin-screw extruder for reactive blending, the steps comprising: S1, masterbatch preparation step: plasticize the functionalized rubber matrix, mix in the solid organic acid at a temperature lower than the melting point of the solid organic acid, and prepare an acid-rich rubber pre-dispersed masterbatch; S2, melt acidolysis step: mix the biodegradable polyester resin, the acid-rich rubber pre-dispersed masterbatch, the antioxidant and the lubricant uniformly, add them from the main feeding port of the twin-screw extruder, heat the mixture in the conveying melting zone and the interface diffusion and acidolysis reaction zone to melt and cause interface acidolysis reaction, and form an acidolysis modified melt; S3, ion crosslinking step: add the metal ion crosslinking agent to the acidolysis modified melt through the side feeding port located after the interface diffusion and acidolysis reaction zone, cause coordination reaction in the ion crosslinking and reconstitution zone, and form an ion crosslinked melt; S4, extrusion molding step: extrude, cool and pelletize the ion crosslinked melt through the die head to obtain the environmentally friendly rubber seal modifier material.

6. The method for preparing an environmentally friendly rubber seal modifier material according to claim 5, characterized in that, In the S1 step: The temperature control range of the plasticizing, mixing and mixing of the functionalized rubber matrix is 40.0-60.0℃; The temperature control range of the discharge temperature of the acid-rich rubber pre-dispersed masterbatch is 70.0-90.0℃; The mixing time control range after mixing in the solid organic acid is 1.0-3.0 minutes.

7. The method for preparing an environmentally friendly modified rubber sealing material according to claim 5, characterized in that, The temperature range of the conveying melting zone of the twin-screw extruder is set to 130.0-145.0℃; The temperature range of the interface diffusion and acidolysis reaction zone of the twin-screw extruder is set to 145.0-160.0℃; The temperature range of the ion crosslinking and reconstitution zone of the twin-screw extruder is set to 170.0-190.0℃.

8. The method for preparing an environmentally friendly modified rubber sealing material according to claim 5, characterized in that, In the S3 step: The side feeding port is arranged at a length-diameter ratio L / D of 26.0-30.0 of the twin-screw extruder; The melt flow rate MFI of the acidolysis modified melt evolves in the range of 18.0-35.0 g / 10 min before entering the side feeding port; The melt flow rate MFI of the ion crosslinking melt evolves in the range of 1.0-3.0 g / 10 min after adding the metal ion crosslinking agent.

9. The method for preparing an environmentally friendly modified rubber sealing material according to claim 5, characterized in that, The screw rotation speed of the twin-screw extruder is set in the range of 200.0-350.0 r / min; The total length-diameter ratio L / D of the twin-screw extruder ranges from 40.0 to 48.0.