Internal plasticized polyvinyl chloride resin as well as preparation method and application thereof

Abstract

The invention relates to the technical field of chemical synthesis, and discloses internal plasticized polyvinyl chloride resin and a preparation method and application thereof.The preparation method comprises the following steps that a dispersing agent, vinyl chloride monomers, an initiator and an internal plasticizer are added into a water-based system for a polymerization reaction, and a high-temperature-resistant auxiliary is added after the polymerization reaction is ended; and adjusting the pH value of the reaction system in the step S1 to 7-8, performing steam stripping, performing centrifugal dewatering, and performing drying. The internal plasticizer capable of participating in free radical reaction is introduced in the polymerization process, so that the internal plasticizer is introduced and fixed in a polyvinyl chloride molecular chain in a chemical bond form, a stable internal plasticizing structure is constructed, the friction resistance between chain segments is effectively reduced from the molecular level, and the plasticizing efficiency and the processing fluidity of the resin are improved; meanwhile, a high-temperature-resistant aid is introduced in a polymerization termination stage to perform synergistic stabilization treatment on a resin system, so that the thermal stability of the material is effectively improved, and the material is suitable for application scenes with relatively high requirements on processability and heat resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical synthesis, in particular to an internally plasticized polyvinyl chloride resin and a preparation method and application thereof. BACKGROUND

[0002] Polyvinyl chloride is a kind of general-purpose polymer with extremely wide application and low cost, which has excellent chemical stability, mechanical strength and electrical insulation performance, and is widely used in building materials, medical devices, electrical equipment and many other fields. Among them, polyvinyl chloride resin has long occupied a core position in the production of insulation and sheath materials for wires and cables. However, due to the limited chain segment movement ability of polyvinyl chloride itself, a large amount of plasticizer needs to be added during processing and molding to improve the processing fluidity and product flexibility, such as dioctyl phthalate.

[0003] Although the use of a large amount of external plasticizer can improve the processing performance and transparency, it also brings several problems that cannot be ignored. On the one hand, the addition of external plasticizer significantly increases the material cost, and the equipment conditions during processing are relatively high; on the other hand, the compatibility between plasticizer and resin is limited, and migration and separation are likely to occur during long-term use, especially in high-temperature environments, which not only affects the performance of the product, but also causes environmental and safety hazards.

[0004] In order to improve the plasticizing behavior of polyvinyl chloride, the existing technology mainly adds plasticizers, stabilizers, fillers or various functional additives to the resin powder for physical blending, or grafts internal plasticizing monomers to the polyvinyl chloride chain to achieve a certain degree of internal plasticization. Although this kind of technical route can improve the flexibility and processing performance to a certain extent, it still has the following disadvantages: The existing method mainly relies on adding various additives to polyvinyl chloride and physically blending under high temperature conditions, the compatibility of the additives and the resin is limited, and it is difficult to achieve stable and uniform plasticizing effect; at the same time, the co-action of multiple additive systems easily causes the thermal stability of the matrix material to decrease, making the processing window narrower and the processing process more prone to decomposition; in addition, the side grafting type internal plasticizing method usually has strict requirements on reaction conditions and complex steps, which is greatly limited in industrial application, and it is difficult to fundamentally solve the problem of plasticizer migration of polyvinyl chloride in long-term use or high-temperature environment. SUMMARY

[0005] The present application provides an internally plasticized polyvinyl chloride resin and a preparation method and application thereof, in order to solve the problem that a large amount of external plasticizer has to be used in the prior art to improve the processing performance and flexibility of polyvinyl chloride, thereby causing poor compatibility with the matrix, easy migration and separation during use and high-temperature processing, and leading to the decrease of thermal stability.

[0006] In a first aspect, the present application provides a method for preparing an internally plasticized polyvinyl chloride resin, comprising the following steps: S1, adding a dispersant, a vinyl chloride monomer, an initiator, and an internal plasticizer into an aqueous system to perform a polymerization reaction, and adding a high-temperature-resistant auxiliary agent after the polymerization reaction is terminated; S2, adjusting the pH of the reaction system of step S1 to 7-8, stripping, centrifugal dewatering, and drying, to obtain the product.

[0007] In the present application, the internal plasticizer is introduced into the aqueous system during the polymerization stage, and participates in the free radical polymerization reaction together with the vinyl chloride monomer. The internal plasticizer is fixed in the polyvinyl chloride molecular chain in the form of a chemical bond, and a stable internal plasticization structure is constructed. This structure reduces the frictional resistance between the polyvinyl chloride segments at the molecular level, so that the resin is more likely to be plasticized during the subsequent processing, thereby effectively improving the plasticization efficiency and processing fluidity.

[0008] Since the internal plasticizer is introduced into the polyvinyl chloride molecular chain in the form of a chemical bond, the defects of the traditional external plasticizer, which only exists in the form of physical blending and is prone to migration and precipitation under high temperature conditions, are avoided, which is beneficial to improve the structural stability and performance retention of the resin product during long-term use.

[0009] In addition, the high-temperature-resistant auxiliary agent is introduced during the termination stage of the polymerization reaction to perform a synergistic stabilization treatment on the resin system, which effectively inhibits the thermal decomposition behavior of the polyvinyl chloride during high-temperature processing or use, thereby improving the thermal stability of the material and widening the processing temperature window and use environment adaptation range of the resin.

[0010] In an alternative embodiment, the internal plasticizer includes one or both of trans-aconitic acid triethyl ester and trans-aconitic acid tributyl ester.

[0011] In an alternative embodiment, the high-temperature-resistant auxiliary agent includes a rare earth oxide. Preferably, the high-temperature-resistant auxiliary agent includes one or both of cerium oxide and lanthanum oxide. Preferably, the amount of the high-temperature-resistant auxiliary agent is 50-200 ppm of the mass of the vinyl chloride monomer; for example, the amount of the high-temperature-resistant auxiliary agent is 50 ppm, 100 ppm, 150 ppm, or 200 ppm of the mass of the vinyl chloride monomer. In an alternative embodiment, the amount of the internal plasticizer is 100-5000 ppm of the mass of the vinyl chloride monomer; for example, the amount of the internal plasticizer is 100 ppm, 500 ppm, 1000 ppm, 3000 ppm, or 5000 ppm of the mass of the vinyl chloride monomer.

[0012] Preferably, the amount of the internal plasticizer is 500-3000 ppm of the mass of the vinyl chloride monomer.

[0013] In an alternative embodiment, the mass ratio of water to vinyl chloride monomer in step S1 is (1.0-1.2):1; for example, the mass ratio of water to vinyl chloride monomer is 1.0:1, 1.1:1 or 1.2:1.

[0014] In an alternative embodiment, the dispersant in step S1 is compounded from polyvinyl alcohol with an alcoholysis degree of 80%-88%, 70%-75% or 40%-55%; Preferably, the dispersant is compounded from polyvinyl alcohol with an alcoholysis degree of 80%-88%, 70%-75% or 40%-55% in a mass ratio of (1-2):(1-2):1; The dispersant is compounded from polyvinyl alcohol with different alcoholysis degrees, which can take into account its solubility in the aqueous phase, surface activity and stabilizing effect on the polymerization system: the polyvinyl alcohol with a higher alcoholysis degree is conducive to improving the coating and protection ability of the vinyl chloride monomer droplets and enhancing the stability of the suspension system; the polyvinyl alcohol with a moderate alcoholysis degree helps to adjust the adsorption and distribution behavior of the dispersant in the system; and the polyvinyl alcohol with a lower alcoholysis degree can improve the flowability of the system and the particle forming process. The synergistic effect of the three can help to obtain polyvinyl chloride resin particles with uniform particle size distribution and stable morphology, thereby providing good conditions for the uniform introduction of internal plasticizers and the smooth progress of the polymerization reaction.

[0015] Preferably, the total amount of the dispersant is 800-1200 ppm of the mass of the vinyl chloride monomer, for example, the total amount of the dispersant is 800 ppm, 900 ppm, 1000 ppm or 1200 ppm of the mass of the vinyl chloride monomer; preferably, 900-1000 ppm.

[0016] In an alternative embodiment, the initiator includes one or more of cumyl peroxide, t-butyl perneodecanoate, t-amyl perpivalate, bis 3,3,5-trimethyl hexanoyl peroxide, 1,1,3,3-tetramethylbutyl perneodecanoate; Preferably, the amount of the initiator is 600 ppm-900 ppm of the mass of the vinyl chloride monomer, for example, the amount of the initiator is 600 ppm, 700 ppm, 800 ppm or 900 ppm of the mass of the vinyl chloride monomer; preferably, 700 ppm-800 ppm.

[0017] In an alternative embodiment, the polymerization reaction temperature is 40℃-60℃; for example, the polymerization reaction temperature is 40℃, 50℃ or 60℃.

[0018] In an alternative embodiment, the corresponding pressure condition at the end of the polymerization reaction is 0.05 MPa-0.2 MPa; for example, the corresponding pressure condition at the end of the polymerization reaction is 0.05 MPa, 0.1 MPa, 0.15 MPa or 0.2 MPa.

[0019] In an alternative embodiment, the polymerization reaction is terminated by adding a terminating agent, and the terminating agent comprises a hindered phenolic antioxidant. Preferably, the amount of the terminating agent is 400 ppm-900 ppm of the mass of the vinyl chloride monomer; for example, the amount of the terminating agent is 400 ppm, 600 ppm, 700 ppm or 900 ppm of the mass of the vinyl chloride monomer; preferably, the amount of the terminating agent is 600 ppm-700 ppm.

[0020] In a second aspect, the present application provides an internally plasticized polyvinyl chloride resin prepared by the preparation method described in any of the above technical solutions.

[0021] The internally plasticized polyvinyl chloride resin of the present application is prepared by any of the above preparation methods. Since the internal plasticizer is introduced into and fixed in the polyvinyl chloride molecular chain in the form of a chemical bond during the polymerization process, a stable and uniform internal plasticization structure is formed. At the same time, the system is synergistically stabilized by the high-temperature-resistant auxiliary agent, so that the obtained resin has good plasticizing properties and processing fluidity during the processing process, and effectively inhibits the migration and thermal decomposition behavior of the plasticizer, thereby maintaining good flexibility and performance stability under high-temperature processing and long-term use conditions, and being suitable for application scenarios with high requirements for processing performance and heat resistance.

[0022] In a third aspect, the present application provides the use of the internally plasticized polyvinyl chloride resin described in the above technical solutions in the field of calendering film, cable pelletizing or toy pelletizing.

[0023] The use of the internally plasticized polyvinyl chloride resin of the present application in the field of calendering film, cable pelletizing or toy pelletizing is due to the synergistic effect of the stable internal plasticization structure and the high-temperature-resistant auxiliary agent in the resin, which makes it have good plasticizing properties and processing fluidity during the processing process, effectively reduces the processing energy consumption and improves the forming stability; at the same time, since the internal plasticizer is fixed in the polyvinyl chloride molecular chain in the form of a chemical bond, the migration and precipitation of the plasticizer can be significantly inhibited, so that the product maintains good flexibility and performance stability during high-temperature processing and long-term use, and is especially suitable for the production and application of calendering film, cable and toy products with high requirements for heat resistance, safety and use stability.

[0024] The technical solution of the present application has the following advantages: The present application realizes the internal plasticizing effect in a true sense by introducing endo-trans-retroaconitic acid ester containing aliphatic double bond structure into the system before the polymerization of vinyl chloride, so that it participates in the chain growth reaction with vinyl chloride monomer during the polymerization process and is fixed to the polyvinyl chloride main chain or side chain in the form of chemical bond. This method not only significantly improves the plasticizing efficiency, but also avoids the defects such as migration and precipitation of conventional external plasticizers due to limited compatibility, because the internal plasticizer becomes part of the molecular chain structure, so that the material exhibits better stability and more durable flexibility during long-term use.

[0025] The addition of antioxidant type terminating agent and high temperature resistant auxiliary at the end of polymerization can further improve the heat resistance and stability of the resin under processing and high temperature service conditions, and the resistance to plasticizer migration, significantly improving the durability and performance retention of PVC soft products. The present application as a whole realizes the synergistic improvement of high-efficiency plasticizing, excellent compatibility and long-term stability, and provides more reliable performance guarantee for PVC soft products. DETAILED DESCRIPTION

[0026] In order to better further understand the present application, the following examples are provided, but the following examples do not constitute limitation on the content and protection scope of the present application, and any product which is the same or similar to the present application obtained by anyone under the inspiration of the present application or by combining the present application with other prior art features falls within the protection scope of the present application.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "include" and "have" and any variations thereof in the present text are intended to cover non-exclusive inclusion.

[0028] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application. The appearance of the phrase in various places in the specification does not necessarily all refer to the same embodiment, nor is it necessarily independent or alternative embodiments to each other. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0029] The "range" disclosed in this invention is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This range can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. In this invention, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers from a to b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed herein; "0-5" is merely a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥ 2, it is equivalent to disclosing that the parameter can be, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0030] In the description of the embodiments of this invention, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0031] In the description of the embodiments of the present invention, the term "at least one" refers to one or more (including two).

[0032] Unless otherwise stated, the dosage of each additive in this invention is based on its effective component; when the additive is added in the form of an emulsion / dispersion, the ppm dosage is calculated relative to the mass of vinyl chloride monomer after being converted to the effective component in the emulsion / dispersion.

[0033] Unless otherwise specified, all experimental steps or conditions in the embodiments were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagents or instruments. The main sources of raw materials involved in the embodiments and comparative examples of this invention are shown in Table 1 below: Table 1: Main raw materials involved in the examples and comparative examples

[0034] The equipment information involved in the embodiments and comparative examples of this invention is shown in Table 2 below: Table 2: Equipment involved in the embodiments and comparative examples of the present invention

[0035] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0036] Example 1 This embodiment provides a method for preparing internally plasticized polyvinyl chloride resin, as detailed below: S1. Evacuate the 5 L polymerization reactor to -0.07 to -0.08 MPa, then add 1.5 kg deionized water, 14.4 g dispersant 1 solution, 14.4 g dispersant 2 solution, 0.9 g dispersant 3 solution, 1.5 kg vinyl chloride monomer, 1.35 g cumyl peroxyneodecanate emulsion, 1.35 g tert-butyl peroxyneodecanate emulsion, and 0.75 g tributyl trans-aconitate. Heat the system to 40 °C for polymerization. When the pressure inside the reactor reaches 0.05 MPa, add 3 g antioxidant 245 emulsion to terminate the polymerization, followed by 0.19 g lanthanum oxide emulsion.

[0037] S2. Add ammonia to the system to adjust the pH of the slurry to 7-8, and then perform monomer stripping, centrifugal dehydration and drying treatment in sequence to obtain internally plasticized polyvinyl chloride resin.

[0038] Example 2 This embodiment provides a method for preparing internally plasticized polyvinyl chloride resin, as detailed below: S1. Evacuate the 5 L polymerization reactor to -0.07 to -0.08 MPa, then add 1.8 kg of deionized water, 8 g of dispersant 1 solution, 8 g of dispersant 2 solution, 1 g of dispersant 3 solution, 1.5 kg of vinyl chloride monomer, 0.9 g of cumyl peroxyneodecanate emulsion, 0.9 g of tert-butyl peroxyneodecanate emulsion, and 4.5 g of tributyl trans-aconitate. Heat the system to 60 °C for polymerization. When the pressure inside the reactor reaches 0.2 MPa, add 1.34 g of antioxidant 245 emulsion to terminate the polymerization, followed by 0.75 g of cerium oxide emulsion.

[0039] S2. Add ammonia to the system to adjust the pH of the slurry to 7-8, and then perform monomer stripping, centrifugal dehydration and drying treatment in sequence to obtain internally plasticized polyvinyl chloride resin.

[0040] Example 3 This embodiment provides a method for preparing internally plasticized polyvinyl chloride resin, as detailed below: The 5 L polymerization reactor was evacuated to -0.07 to -0.08 MPa. Then, 1.73 kg of deionized water, 6 g of dispersant 1 solution, 12 g of dispersant 2 solution, 0.75 g of dispersant 3 solution, 1.5 kg of vinyl chloride monomer, 0.8 g of cumyl peroxyneodecanate emulsion, 1.6 g of tert-butyl peroxyneodecanate emulsion, and 3 g of tributyl trans-aconitate were added sequentially. The system was heated to 60 °C for polymerization. When the pressure inside the reactor reached 0.15 MPa, 2 g of antioxidant 245 emulsion was added to terminate the polymerization, followed by the addition of 0.56 g of lanthanum oxide emulsion. Ammonia was added to adjust the pH of the slurry to 7–8. The monomer was then subjected to monomer stripping, centrifugal dehydration, and drying to obtain the internally plasticized polyvinyl chloride resin.

[0041] Example 4 The only difference from Example 1 is that the amount of internal plasticizer used is 100 ppm of the mass of vinyl chloride monomer; Specifically as follows: S1. Evacuate the 5 L polymerization reactor to -0.07 to -0.08 MPa, then add 1.5 kg deionized water, 14.4 g dispersant 1 solution, 14.4 g dispersant 2 solution, 0.9 g dispersant 3 solution, 1.5 kg vinyl chloride monomer, 1.35 g cumyl peroxyneodecanate emulsion, 1.35 g tert-butyl peroxyneodecanate emulsion, and 0.15 g tributyl trans-aconitate. Heat the system to 40 °C for polymerization. When the pressure inside the reactor reaches 0.05 MPa, add 3 g antioxidant 245 emulsion to terminate the polymerization, followed by 0.19 g lanthanum oxide emulsion.

[0042] S2. Add ammonia to the system to adjust the pH of the slurry to 7-8, and then perform monomer stripping, centrifugal dehydration and drying treatment in sequence to obtain internally plasticized polyvinyl chloride resin.

[0043] Example 5 The only difference from Example 1 is that the amount of internal plasticizer used is 5000 ppm of the vinyl chloride monomer mass; specifically as follows: S1. Evacuate the 5 L polymerization reactor to -0.07 to -0.08 MPa, then add 1.5 kg deionized water, 14.4 g dispersant 1 solution, 14.4 g dispersant 2 solution, 0.9 g dispersant 3 solution, 1.5 kg vinyl chloride monomer, 1.35 g cumyl peroxyneodecanate emulsion, 1.35 g tert-butyl peroxyneodecanate emulsion, and 7.5 g tributyl trans-aconitate. Heat the system to 40 °C for polymerization. When the pressure inside the reactor reaches 0.05 MPa, add 3 g antioxidant 245 emulsion to terminate the polymerization, followed by 0.19 g lanthanum oxide emulsion.

[0044] S2. Add ammonia to the system to adjust the pH of the slurry to 7-8, and then perform monomer stripping, centrifugal dehydration and drying treatment in sequence to obtain internally plasticized polyvinyl chloride resin.

[0045] Example 6 The only difference from Example 1 is that the amount of the high-temperature resistant additive is 100 ppm of the vinyl chloride monomer mass; specifically as follows: S1. Evacuate the 5 L polymerization reactor to -0.07 to -0.08 MPa, then add 1.5 kg deionized water, 14.4 g dispersant 1 solution, 14.4 g dispersant 2 solution, 0.9 g dispersant 3 solution, 1.5 kg vinyl chloride monomer, 1.35 g cumyl peroxyneodecanate emulsion, 1.35 g tert-butyl peroxyneodecanate emulsion, and 0.75 g tributyl trans-aconitate. Heat the system to 40 °C for polymerization. When the pressure inside the reactor reaches 0.05 MPa, add 3 g antioxidant 245 emulsion to terminate the polymerization, followed by 0.375 g lanthanum oxide emulsion.

[0046] S2. Add ammonia to the system to adjust the pH of the slurry to 7-8, and then perform monomer stripping, centrifugal dehydration and drying treatment in sequence to obtain internally plasticized polyvinyl chloride resin.

[0047] Example 7 The only difference from Example 1 is that the amount of the high-temperature resistant additive is 150 ppm of the vinyl chloride monomer mass; specifically as follows: S1. Evacuate the 5 L polymerization reactor to -0.07 to -0.08 MPa, then add 1.5 kg deionized water, 14.4 g dispersant 1 solution, 14.4 g dispersant 2 solution, 0.9 g dispersant 3 solution, 1.5 kg vinyl chloride monomer, 1.35 g cumyl peroxyneodecanate emulsion, 1.35 g tert-butyl peroxyneodecanate emulsion, and 0.75 g tributyl trans-aconitate. Heat the system to 40 °C for polymerization. When the pressure inside the reactor reaches 0.05 MPa, add 3 g antioxidant 245 emulsion to terminate the polymerization, followed by 0.563 g lanthanum oxide emulsion.

[0048] S2. Add ammonia to the system to adjust the pH of the slurry to 7-8, and then perform monomer stripping, centrifugal dehydration and drying treatment in sequence to obtain internally plasticized polyvinyl chloride resin.

[0049] Example 8 The only difference from Example 1 is that the amount of the high-temperature resistant additive is 200 ppm of the vinyl chloride monomer mass; specifically as follows: S1. Evacuate the 5 L polymerization reactor to -0.07 to -0.08 MPa, then add 1.5 kg deionized water, 14.4 g dispersant 1 solution, 14.4 g dispersant 2 solution, 0.9 g dispersant 3 solution, 1.5 kg vinyl chloride monomer, 1.35 g cumyl peroxyneodecanate emulsion, 1.35 g tert-butyl peroxyneodecanate emulsion, and 0.75 g tributyl trans-aconitate. Heat the system to 40 °C for polymerization. When the pressure inside the reactor reaches 0.05 MPa, add 3 g antioxidant 245 emulsion to terminate the polymerization, followed by 0.75 g lanthanum oxide emulsion.

[0050] S2. Add ammonia to the system to adjust the pH of the slurry to 7-8, and then perform monomer stripping, centrifugal dehydration and drying treatment in sequence to obtain internally plasticized polyvinyl chloride resin.

[0051] Example 9 S1. Evacuate the 5 L polymerization reactor to -0.07 to -0.08 MPa, then add 1.73 kg deionized water, 10.13 g dispersant 1 solution, 10.13 g dispersant 2 solution, 0.85 g dispersant 3 solution, 1.5 kg vinyl chloride monomer, 0.9 g cumyl peroxyneodecanate emulsion, 0.9 g tert-butyl peroxyneodecanate emulsion, and 3 g tributyl trans-aconitate. Heat the system to 50 °C for polymerization. When the pressure inside the reactor reaches 0.2 MPa, add 2.33 g antioxidant 245 emulsion to terminate the polymerization, followed by 0.19 g lanthanum oxide emulsion.

[0052] S2. Add ammonia to the system to adjust the pH of the slurry to 7-8, and then perform monomer stripping, centrifugal dehydration and drying treatment in sequence to obtain internally plasticized polyvinyl chloride resin.

[0053] Example 10 S1. Evacuate the 5 L polymerization reactor to -0.07 to -0.08 MPa, then add 1.73 kg deionized water, 11.25 g dispersant 1 solution, 11.25 g dispersant 2 solution, 0.85 g dispersant 3 solution, 1.5 kg vinyl chloride monomer, 1.05 g cumyl peroxyneodecanate emulsion, 1.05 g tert-butyl peroxyneodecanate emulsion, and 3 g tributyl trans-aconitate. Heat the system to 50 °C for polymerization. When the pressure inside the reactor reaches 0.2 MPa, add 2.17 g antioxidant 245 emulsion to terminate the polymerization, followed by 0.19 g lanthanum oxide emulsion.

[0054] S2. Add ammonia to the system to adjust the pH of the slurry to 7-8, and then perform monomer stripping, centrifugal dehydration and drying treatment in sequence to obtain internally plasticized polyvinyl chloride resin.

[0055] Comparative Example 1 The only difference between this comparative example and Example 3 is that no trans-aconitine tributyl ester internal plasticizer is added.

[0056] Comparative Example 2 The only difference between this comparative example and Example 3 is that the amount of trans-aconitate tributyl ester plasticizer added is smaller. Specifically, this comparative example adds 0.075g of trans-aconitate ester.

[0057] Comparative Example 3 The only difference between this comparative example and Example 3 is that a trans-aconitate internal plasticizer was added after the polymerization reaction; specifically as follows: The 5 L polymerization reactor was evacuated to -0.07 to -0.08 MPa, and then 1.73 kg of deionized water, 6 g of dispersant 1 solution, 12 g of dispersant 2 solution, 0.75 g of dispersant 3 solution, 1.5 kg of vinyl chloride monomer, 0.8 g of cumyl peroxide neodecanoate emulsion, and 1.6 g of tert-butyl peroxide neodecanoate emulsion were added sequentially.

[0058] The system was heated to 60 ℃ for polymerization. When the pressure inside the reactor reached 0.15 MPa, 2g of antioxidant 245 emulsion was added to terminate the polymerization. Then, 0.56g of high-temperature resistant additive and 3g of tributyl trans-aconitate were added and stirred for 30min. Ammonia water was added to the system to adjust the pH of the slurry to 7-8. After that, monomer stripping, centrifugal dehydration and drying were carried out in sequence to obtain internally plasticized polyvinyl chloride resin.

[0059] Comparative Example 4 The only difference between this comparative example and Example 3 is that no high-temperature resistant additive is added after the reaction is complete.

[0060] Test Example 1 The polyvinyl chloride resin products obtained in the above examples and comparative examples were subjected to plasticizing performance tests and thermogravimetric analysis (TGA) tests. The test methods are as follows: (1) Plasticizing performance test Weigh 50 g of polyvinyl chloride resin, add 0.4 g of organotin, 0.6 g of polyethylene wax, 0.3 g of stearic acid, and 8 g of dioctyl phthalate (DOP), mix thoroughly, and let stand for 5 min to absorb. Add the mixture to a two-roll mill preheated to 190℃ for mixing. Start timing from the time the sample is added and record the time required for complete film formation, which is taken as the plasticizing time of the resin.

[0061] (2) Thermogravimetric performance test Weigh 0.1 g of sample resin powder and place it in a thermogravimetric analyzer. Test it under a nitrogen atmosphere at a heating rate of 20 ℃ / min. Record the temperature at which 5% mass loss occurs as the thermogravimetric index.

[0062] The test results are shown in Table 3 below: Table 3 Performance test results of the examples and comparative examples

[0063] The internally plasticized polyvinyl chloride resin prepared by this invention exhibits a shorter plasticizing time and higher thermal stability. Under different amounts of internal plasticizer, high-temperature resistant additives, and polymerization conditions, the resins obtained in the examples can all complete plasticization in a short time while maintaining a high 5% thermal weight loss temperature.

[0064] As can be seen, by introducing trans-aconitate ester internal plasticizers that can participate in free radical reactions during the polymerization process and combining them with high-temperature resistant additives at the polymerization termination stage, the internal plasticizing structure and the thermally stable system work synergistically to improve the overall processing plasticizing properties and high-temperature resistance of polyvinyl chloride resin.

[0065] Comparing Examples 1-5, it can be seen that after introducing an internal plasticizer during the polymerization process, the overall plasticizing time of the resin is at a low level, indicating that the internal plasticizer structure can effectively reduce the frictional resistance between molecular chains, making the resin easier to plasticize. When the amount of internal plasticizer is within a reasonable range, the plasticizing performance is stable.

[0066] Comparing Examples 1 and 6-8, it can be seen that, under the premise of keeping the internal plasticizing structure unchanged, the introduction and adjustment of the amount of high-temperature resistant additives resulted in an overall upward trend in the 5% thermogravimetric temperature of the resin, indicating that the high-temperature resistant additives played a positive role in inhibiting thermal decomposition and improving the thermal stability of the system.

[0067] As can be seen from Examples 9 and 10, the resin obtained can still maintain good plasticizing properties and thermal stability even when the dispersant ratio, initiator dosage and polymerization temperature change. This shows that the internal plasticizing technology route of the present invention has good adaptability to process conditions and is suitable for promotion and application under different production conditions.

[0068] Comparing Example 3 with Comparative Example 1, Comparative Example 1 did not add internal plasticizer during the polymerization process, and its plasticizing time was significantly prolonged, indicating that the frictional resistance between polyvinyl chloride molecular chains was large and the plasticizing efficiency was low; the amount of internal plasticizer in Comparative Example 2 was low, and the improvement effect was limited, indicating that when the internal plasticizer is insufficient to form a sufficient amount of internal plasticized structure, it is difficult to significantly improve the plasticizing performance of the resin.

[0069] Although Comparative Example 3 included trans-aconitate, it was added after the polymerization reaction was complete. Since the internal plasticizer did not participate in the chain growth reaction and could not form a chemical bond with the PVC molecular chain, it only acted as an external plasticizer, resulting in a significantly weaker plasticizing effect compared to the examples. Comparative Example 4, without the addition of high-temperature resistant additives, showed a significant decrease in its 5% thermogravimetric temperature, indicating that relying solely on the internal plasticizing structure is insufficient to fully compensate for the insufficient thermal stability of the PVC system under high-temperature conditions.

[0070] This invention improves the plasticizing and processing properties and high-temperature stability of polyvinyl chloride (PVC) resin by introducing trans-aconitate internal plasticizers during polymerization and combining them with high-temperature resistant additives at the polymerization termination stage, thereby synergistically enhancing both the molecular structure and system stability. Compared to comparative examples that do not introduce internal plasticizers, have improperly added internal plasticizers, or lack high-temperature resistant additives, the technical solution of this invention exhibits significant advantages in overall performance, effectively meeting the application requirements for both high processing performance and long-term stability of flexible PVC products.

[0071] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing internally plasticized polyvinyl chloride resin, characterized in that: Includes the following steps: S1. Add dispersant, vinyl chloride monomer, initiator and internal plasticizer to the aqueous system to carry out the polymerization reaction. After the polymerization reaction is terminated, add high temperature resistant additives. S2. Adjust the pH of the reaction system from step S1 to 7-8, strip, centrifuge to dehydrate, and dry to obtain the final product.

2. The method for preparing an internally plasticized polyvinyl chloride resin according to claim 1, characterized in that: The internal plasticizer includes one or both of triethyl trans-aconitate and tributyl trans-aconitate.

3. The method for preparing an internally plasticized polyvinyl chloride resin according to claim 1 or 2, characterized in that: The high-temperature resistant additives include rare earth oxides; Preferably, the high-temperature resistant additive includes one or two of cerium oxide and lanthanum oxide; Preferably, the amount of the high-temperature resistant additive is 50-200 ppm of the mass of vinyl chloride monomer.

4. A method for preparing an internally plasticized polyvinyl chloride resin according to any one of claims 1-3, characterized in that: The amount of the internal plasticizer is 100-5000 ppm of the mass of vinyl chloride monomer; Preferably, the amount of internal plasticizer is 500-3000 ppm of the mass of vinyl chloride monomer.

5. A method for preparing an internally plasticized polyvinyl chloride resin according to any one of claims 1-4, characterized in that: In step S1, the mass ratio of water to vinyl chloride monomer is (1.0-1.2):

1.

6. A method for preparing an internally plasticized polyvinyl chloride resin according to any one of claims 1-5, characterized in that: In step S1, the dispersant is a compound of polyvinyl alcohol with a degree of alcoholysis of 80%-88%, 70%-75%, and 40%-55%. Preferably, the dispersant is a compound of polyvinyl alcohol with a degree of alcoholysis of 80%-88%, 70%-75%, and 40%-55% in a mass ratio of (1-2):(1-2):1; Preferably, the total amount of the dispersant is 800-1200 ppm of the mass of vinyl chloride monomer, and more preferably 900-1000 ppm.

7. A method for preparing an internally plasticized polyvinyl chloride resin according to any one of claims 1-6, characterized in that: The initiator includes one or more of the following: cumyl peroxynedecanoate, tert-butyl peroxynedecanoate, tert-amyl peroxypentanoate, bis(3,3,5-trimethylhexanoyl peroxide), and 1,1,3,3-tetramethylbutyl peroxynedecanoate. Preferably, the amount of the initiator is 600ppm-900ppm of the mass of vinyl chloride monomer, more preferably 700ppm-800ppm.

8. A method for preparing an internally plasticized polyvinyl chloride resin according to any one of claims 1-7, characterized in that: In step S1, the polymerization reaction temperature is 40℃-60℃; And / or, in step S1, the pressure condition at the end of the polymerization reaction is 0.05MPa-0.2MPa; And / or, in step S1, a terminator is added to terminate the polymerization reaction, the terminator including hindered phenolic antioxidants; Preferably, the amount of the terminating agent is 400ppm-900ppm of the mass of vinyl chloride monomer, and more preferably 600ppm-700ppm.

9. An internally plasticized polyvinyl chloride resin, characterized in that: It is prepared by any of the preparation methods described in claims 1-8.

10. The application of the internally plasticized polyvinyl chloride resin as described in claim 9 in the fields of calendering film, cable granulation or toy granulation.

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