High-compatibility mixed plastic composition and preparation method thereof

Abstract

The invention discloses a high-compatibility mixed plastic composition and a preparation method thereof, and belongs to the technical field of general-purpose plastics. The composition comprises the following components in parts by weight: 100 parts of mixed plastic, 0.2-1 part of a free radical initiator and 0.5-5 parts of a bismaleimide cross-linking agent containing dynamic disulfide bonds. The bismaleimide cross-linking agent with the dynamic disulfide bonds is prepared by taking 4, 4 '-dithio diphenylamine and maleic anhydride as raw materials, and the synthesis conditions are simple and mild. The cross-linking agent can be subjected to a cross-linking reaction with a C-H bond of common plastic in melt blending under the action of a free radical initiator to form a dynamic covalent cross-linked network taking a disulfide bond as a cross-linking point. Based on a co-crosslinking reaction and the reconstruction capability of a dynamic disulfide bond crosslinking network, the compatibility of the mixed plastic is remarkably improved, so that the physical and mechanical properties and high-temperature stability of the mixed plastic are improved. Meanwhile, the material has good thermoplastic processing performance, and upgrading and recycling of mixed plastic are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of general plastics, in particular to a high compatibility mixed plastic composition and a preparation method thereof. BACKGROUND

[0002] With the large use of plastic products, the number of waste plastics is increasing. The global plastic pollution control is facing severe challenges, especially the recycling of mixed plastics, which has complex composition and obvious performance decline after simple mechanical recycling due to the large difference in polarity of different plastics, and limited application value. Chemical recycling has problems such as high energy consumption, complex process, poor selectivity, etc.

[0003] Design and synthesis of block copolymers as compatibilizers for mixed plastics can improve the mechanical properties of mixed plastics after mechanical recycling, thereby improving their application value and realizing upgrade recycling [J. Am. Chem. Soc. 2024, 146, 19449-19459]. However, the synthesis of this type of compatibilizer is complex, and it generally only has good compatibilization effect on the two plastics corresponding to the block copolymer. By designing a synergistic crosslinking agent containing dynamic covalent bonds, the compatibility between mixed plastics can be improved through co-crosslinking reaction, and the compatibility between mixed plastics can be further promoted through network reconstruction, while maintaining the repeated processing performance of mixed plastics. It is a very promising method to realize the compatibilization of mixed plastics and the mechanical recycling of waste mixed plastics [Nature, 2023, 616, 731-739; Adv. Mater. 2024, 36, 2406203]. However, existing synergistic crosslinking agents containing dynamic covalent bonds are mostly based on supramolecular compounds, which are complex to synthesize and high in cost.

[0004] At present, there is still a lack of a simple synergistic crosslinking agent containing dynamic covalent bonds, and a corresponding high compatibility mixed plastic composition and a preparation method thereof. SUMMARY

[0005] In order to solve the problems of the prior art, the present application provides a high compatibility mixed plastic composition and a preparation method thereof. The preparation method provided by the present application is simple and can be applied to industrial production.

[0006] The present application provides the following technical solutions:

[0007] A high compatibility mixed plastic composition, comprising the following components in parts by weight:

[0008] 100 parts of mixed plastics,

[0009] 0.2-1 parts of a free radical initiator,

[0010] 0.5-5 parts of a bismaleimide crosslinking agent containing dynamic disulfide bonds.

[0011] The structure of the bismaleimide crosslinking agent containing dynamic disulfide bond is as follows:

[0012]

[0013] Further, the mixed plastics are two or more polymers of polyethylene, ethylene copolymer, polypropylene, polystyrene, polyvinyl chloride, polyethylene terephthalate, polylactic acid, or are two or more different grades of the same polymer.

[0014] Further, the mixed plastics further comprise an additive, which is one or a combination of two or more of an antioxidant, a filler, a processing aid, an antistatic agent, and a pigment.

[0015] Further, the free radical initiator is one or a combination of two or more of dicumyl peroxide, benzoyl peroxide, di-tert-butyl peroxide isopropyl benzene, dodecanoyl peroxide, di-tert-butyl peroxide, and 2,5-di-tert-butyl peroxide-2,5-dimethyl hexane.

[0016] Further, the preparation steps of the bismaleimide crosslinking agent containing dynamic disulfide bond are as follows:

[0017] Dithiodianiline and maleic anhydride are dissolved in acetone, and a yellowish suspension is obtained by reacting at room temperature under inert gas for 4-8 hours. Then, acetic anhydride and sodium acetate are added in sequence, and a red-brown transparent liquid is obtained by reacting at 60-80°C for 4-8 hours. The liquid is poured into an aqueous sodium bicarbonate solution to precipitate, and then filtered. The filtered product is washed with deionized water and ethanol to obtain a yellowish solid product.

[0018] Further, the mass ratio of dithiodianiline, maleic anhydride, acetic anhydride, and sodium acetate is 14-14.7:12-12.6:55-57.75:1-1.05.

[0019] Further, the gel content of the high-compatibility mixed plastic composition is not less than 30%.

[0020] Further, the high-compatibility mixed plastic composition can be reprocessed after being broken.

[0021] A preparation method of a high-compatibility mixed plastic composition, comprising the following steps:

[0022] (1) The mixed plastics are weighed according to the proportion and then melt-blended;

[0023] (2) The initiator and the bismaleimide crosslinking agent are added and then melt-blended.

[0024] (3) melt-blended sample is hot-pressed to obtain a high compatibility mixed plastic composition.

[0025] A preparation method of a high compatibility mixed plastic composition, wherein in steps (1) and (2), the melt-blending temperature is 150-250 DEG C, and the time is 3-10 min; in step (3), the hot-pressing temperature is 150-250 DEG C, and the time is 3-10 min.

[0026] The application has the following advantages: based on the excellent compatibility of mixed plastics and the dynamic disulfide crosslinking network, the mechanical properties of the mixed plastic composition prepared by the application are significantly improved, and the high-temperature creep resistance is improved; based on the exchange reaction of disulfide bonds, the good repeated processing performance of mixed plastics is maintained, recycling is supported, and the upgrading recycling of mixed plastics is realized, which overcomes the problems of obvious performance degradation and low recycling value of traditional mixed plastics.

[0027] Compared with the prior art, the application has the following advantages:

[0028] (1) The bismaleimide crosslinking agent containing dynamic disulfide bonds provided by the application has simple and mild synthesis conditions, can be crosslinked with common plastics through conventional free radical reaction, and has simple process and can adapt to industrial production.

[0029] (2) The disulfide bond exchange reaction provided by the application does not need to introduce additional catalysts, and reduces the interference of exogenous components on the performance of the material. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 NMR hydrogen spectrum structure characterization of the bismaleimide crosslinking agent containing dynamic disulfide bonds;

[0031] Figure 2 Sample obtained by hot pressing through a flat plate vulcanization instrument in Example 7;

[0032] Figure 3 Scanning electron microscope (SEM) images of Comparative Examples 1, 2, 6, and Examples 1, 7, 5;

[0033] Figure 4 Temperature scanning (DMA) images of Comparative Examples 1, 2, and Examples 1, 6, 7, 8. DETAILED DESCRIPTION

[0034] The application will be specifically described below in combination with specific test examples, and it is necessary to point out here that the following test examples are only used to further illustrate the application, and cannot be understood as limiting the protection scope of the application, and some non-essential improvements and adjustments of the application made by those skilled in the art according to the content of the application still belong to the protection scope of the application.

[0035] Preparation example of bismaleimide crosslinking agent containing dynamic disulfide bond

[0036] Dissolve 1.991 g of dithiodiphenylamine and 1.768 g of maleic anhydride in 30-40 ml of acetone, and react at room temperature for 6 h under a nitrogen atmosphere to obtain a light yellow suspension. Then, sequentially add 8 ml of acetic anhydride and 0.144 g of sodium acetate, and react at 60°C for 6 h to obtain a red-brown transparent liquid. Pour the liquid into an aqueous sodium bicarbonate solution to precipitate, and then filter. Wash the filtered product with deionized water and ethanol to obtain a light yellow solid product. Dry the product in a vacuum oven at 50°C for 12 h to obtain a bright yellow product.

[0037] Example 1

[0038] Polypropylene (PP) resin 50 parts (Xiaoxing, Korea, F600 brand), linear low density polyethylene (LLDPE) resin 50 parts (Exxon Mobil, FL201XV brand), free radical initiator (di-tert-butyl peroxide isopropyl benzene, Sinopharm Group Co., Ltd.) 0.5 parts, bismaleimide crosslinking agent containing dynamic disulfide bond 1 part. Preparation method:

[0039] (1) Weigh the polypropylene and linear low density polyethylene according to the proportion, melt blend at 170°C for 3 min;

[0040] (2) Add the free radical initiator and the bismaleimide crosslinking agent containing dynamic disulfide bond, and continue to melt blend at 170°C for 7 min.

[0041] (3) The blended sample is hot-pressed into a high compatibility mixed plastic composition by a flat plate vulcanizer at 180°C for 4 min.

[0042] Example 2

[0043] Polypropylene (PP) resin 50 parts (Xiaoxing, Korea, F600 brand), polyethylene terephthalate (PET) resin 50 parts (Wanhua Chemical, PET WR-801), free radical initiator (dicumyl peroxide, Sinopharm Group Co., Ltd.) 0.5 parts, bismaleimide crosslinking agent containing dynamic disulfide bond 1 part. Preparation method:

[0044] (1) Weigh the polypropylene and polyethylene terephthalate according to the proportion, melt blend at 250°C for 3 min;

[0045] (2) Add the free radical initiator and the bismaleimide crosslinking agent containing dynamic disulfide bond, and continue to melt blend at 250°C for 3 min.

[0046] (3) The blended sample is hot-pressed into a high compatibility mixed plastic composition by a flat plate vulcanizer at 250°C for 3 min.

[0047] Example 3:

[0048] Polypropylene (PP) resin 50 parts (Xiaoxing, Korea, grade F600), polylactic acid (PLA) resin 50 parts (NatureWorks, USA, 4032D), free radical initiator (di-tert-butyl peroxide, Sinopharm Chemical) 0.5 parts, double-maleimide crosslinking agent containing dynamic disulfide bond 1 part. Preparation method:

[0049] (1) Polypropylene and polylactic acid were weighed according to the proportion and melt blended at 170°C for 3 min;

[0050] (2) Add free radical initiator and double-maleimide crosslinking agent containing dynamic disulfide bond, continue to melt blend at 170°C for 7 min.

[0051] (3) The blended sample was hot-pressed into a high compatibility mixed plastic composition by a flat plate vulcanizer at 180°C for 4 min.

[0052] Example 4:

[0053] Polypropylene (PP) resin 50 parts (Xiaoxing, Korea, grade F600), polyvinyl chloride (PVC) resin 50 parts (Shin-Etsu Chemical, TK-1000), free radical initiator (benzoyl peroxide, Sinopharm Chemical) 0.5 parts, double-maleimide crosslinking agent containing dynamic disulfide bond 1 part. Preparation method:

[0054] (1) Polypropylene and polyvinyl chloride were weighed according to the proportion and melt blended at 185°C for 3 min;

[0055] (2) Add free radical initiator and double-maleimide crosslinking agent, continue to melt blend at 185°C for 7 min.

[0056] (3) The blended sample was hot-pressed into a high compatibility mixed plastic composition by a flat plate vulcanizer at 185°C for 4 min.

[0057] Example 5:

[0058] Polypropylene (PP) resin 40 parts (Xiaoxing, Korea, grade F600), linear low density polyethylene (LLDPE) resin 30 parts (Exxon Mobil, grade FL201XV), polylactic acid (PLA) resin 30 parts (Nature Works, USA, 4032D), free radical initiator (di-tert-butyl peroxide, Sinopharm Chemical) 0.5 parts, double-maleimide crosslinking agent containing dynamic disulfide bond 1 part. Preparation method:

[0059] (1) Polypropylene, linear low density polyethylene and polylactic acid were weighed according to the proportion and melt blended at 180 °C for 3 min;

[0060] (2) Free radical initiator and bismaleimide crosslinking agent were added and melt blended at 180 °C for 7 min.

[0061] (3) The blended sample was hot pressed at 180 °C for 4 min by a flat plate vulcanizing instrument to obtain a high compatibility mixed plastic composition.

[0062] Example 6:

[0063] The specific process was the same as that in Example 1, and the amount of crosslinking agent (bismaleimide crosslinking agent containing dynamic disulfide bond) was changed to 0.5 parts.

[0064] Example 7:

[0065] The specific process was the same as that in Example 1, and the amount of crosslinking agent (bismaleimide crosslinking agent containing dynamic disulfide bond) was changed to 2 parts.

[0066] Example 8:

[0067] The specific process was the same as that in Example 1, and the amount of crosslinking agent (bismaleimide crosslinking agent containing dynamic disulfide bond) was changed to 5 parts.

[0068] The specific process was the same as that in Example 1, and the amount of free radical initiator was changed to 0.2 parts.

[0069] Example 10:

[0070] The specific process was the same as that in Example 1, and the amount of free radical initiator was changed to 1 part.

[0071] Example 11:

[0072] The specific process was the same as that in Example 1, and the melt blending temperature in step (1) of the preparation method was changed to 150 °C, and the blending time was 10 min; the melt blending temperature in step (2) was 150 °C, and the blending time was 10 min; the hot pressing temperature in step (3) was 150 °C, and the hot pressing time was 10 min.

[0073] Example 12:

[0074] The specific process was the same as that in Example 1, and the melt blending temperature in step (1) of the preparation method was changed to 160 °C, and the blending time was 10 min; the melt blending temperature in step (2) was 160 °C, and the blending time was 10 min; the hot pressing temperature in step (3) was 170 °C, and the hot pressing time was 10 min.

[0075] Example 13:

[0076] The specific procedure is the same as that in Example 1, except that the melt blending temperature in step (1) of the preparation method is changed to 180°C, and the blending time is 2 min; the melt blending temperature in step (2) is 180°C, and the blending time is 5 min; and the hot-pressing temperature in step (3) is 180°C, and the hot-pressing time is 5 min.

[0077] Comparative Example 1

[0078] The specific procedure is the same as that in Example 1, except that the free radical peroxide initiator and the bismaleimide crosslinking agent are not used in the components.

[0079] Comparative Example 2

[0080] The specific procedure is the same as that in Example 1, except that the bismaleimide crosslinking agent is not used in the components.

[0081] Comparative Example 3

[0082] The specific procedure is the same as that in Example 2, except that the free radical peroxide initiator and the bismaleimide crosslinking agent are not used in the components.

[0083] Comparative Example 4

[0084] The specific procedure is the same as that in Example 3, except that the free radical peroxide initiator and the bismaleimide crosslinking agent are not used in the components.

[0085] Comparative Example 5

[0086] The specific procedure is the same as that in Example 4, except that the free radical peroxide initiator and the bismaleimide crosslinking agent are not used in the components.

[0087] Comparative Example 6

[0088] The specific procedure is the same as that in Example 5, except that the free radical peroxide initiator and the bismaleimide crosslinking agent are not used in the components.

[0089] For the structural characterization of the bismaleimide crosslinking agent with dynamic disulfide bonds, the successful synthesis of the bismaleimide crosslinking agent is verified by 1H nuclear magnetic resonance spectroscopy (1H NMR). Figure 1 1H nuclear magnetic resonance spectroscopy (1H NMR) 1 The peak at 7.26 is the peak of deuterated chloroform (CDCl3). The peaks near 6.5-6.8 are the peaks of H on DTBMI. According to the number and integral area of the peaks, there are three different chemical environment H on DTBMI, among which the peak at 7.18 is a single peak, and the peak areas of the two groups of double peaks at 7.31, 7.33, 7.58, and 7.60 are approximately 1:1:1, and the number is equal, and the two groups of peaks are coupled and split according to the n+1 rule. The phenomenon of high inside and low outside in the two groups of peaks coupled with each other conforms to the centripetal rule, and therefore it is judged that DTBMI is successfully synthesized.

[0090] The gel fraction of Examples 1-13 and Comparative Examples 1-6 is shown in Table 1.

[0091] Gel fraction of Examples 1-13 and Comparative Examples 1-6

[0092] Gel fraction (%) a ]] Comparative Example 1 0 Comparative Example 2 0 Comparative Example 3 0 Comparative Example 4 0 Comparative Example 5 0 Comparative Example 6 0 Example 1 36 Example 2 35 Example 3 38 Example 4 38 Example 5 35 Example 6 30 Example 7 54 Example 8 75 Example 9 33 Example 10 43 Example 11 30 Example 12 37 Figure 1 35

[0093] Gel fraction was measured by Soxhlet extraction in xylene for 24h

[0094] From the data in Table 1, it can be seen that no gel was formed in the mixed plastics without the dynamic disulfide-containing bismaleimide crosslinking agent (Comparative Examples 1-6), and the gel content was formed in the mixed plastics with different contents of the crosslinking agent, which proved the formation of the crosslinking network. Meanwhile, when the content of the dynamic disulfide-containing bismaleimide crosslinking agent was increased from 0.5 phr to 5.0 phr (Example 1, Examples 6-8), the gel content of the blend was increased from 30% to 75%. In addition, as shown in the thermoplastic molding photo of Example 7, even if the gel fraction of the sample was 54%, the sample could still be thermoplastically molded under the conventional processing conditions. Figure 3

[0095] It was found by the tensile property test (Table 2) that the simple addition of the free radical initiator (such as Comparative Example 2 compared with Comparative Example 1) could only slightly improve the mechanical properties of the PP / PE mixed plastics, while the addition of the dynamic disulfide-containing bismaleimide crosslinking agent (such as Example 1 and Examples 6-8) could significantly improve the mechanical properties of the PP / PE mixed plastics. When the crosslinking agent was applied to other mixed plastic systems, it could also significantly improve the mechanical properties of the blended plastics (such as Comparative Examples 3-6 and Examples 2-5). This was mainly due to the fact that the dynamic disulfide-containing bismaleimide crosslinking agent could simultaneously covalently bond with different components in the mixed plastics through the free radical grafting reaction, enhance the compatibility in the mixed plastics, and form a network structure to further enhance the mechanical strength of the mixed plastics.

[0096] Table 2

[0097]

[0098]

[0099] The micro-morphological structures of Comparative Example 1, Comparative Example 2, Example 1, Example 7, Comparative Example 6 and Example 5 were analyzed by scanning electron microscopy, as shown in Figure 4 ​The comparative example 1 presents a typical "island-in-sea structure", the dispersed phase size is large, the interface is clear and sharp and there is local peeling, which is due to the insufficient compatibility of PP and PE caused by the difference in polarity, and physical mixing is difficult to achieve effective interface combination. In contrast, in the comparative example 2, after the introduction of 0.5 phr free radical initiator, the size of the dispersed phase is reduced, and the number of microspheres increases. This is because the free radical initiator decomposes to generate free radicals at high temperature, which can promote the crosslinking reaction between part of the PP and PE molecular chains, and enhance the interface combination and compatibility between the two phases. When further introducing the bismaleimide crosslinking agent containing dynamic disulfide bond (example 1 and example 7), it can be observed that the size of the dispersed phase is further significantly reduced, the interface is highly blurred, and the compatibility of the mixed plastics is significantly improved. At the same time, the same characteristics are observed in the ternary blending system. In the comparative example 6, the interface is clear and there is local separation, while in the example 5, after adding 1 phr bismaleimide crosslinking agent containing dynamic disulfide bond, the size of the dispersed phase is significantly reduced, the interface is blurred, indicating that the compatibility in the ternary blending system is also significantly improved, and indicating that such crosslinking agent is suitable for the ternary blending system.

[0100] The high temperature performance of the material was characterized by dynamic mechanical analysis (DMA) ​ The results show that the introduction of dynamic covalent crosslinking network significantly improves the high temperature stability of the material. The storage modulus test data shows that the modulus of all crosslinked samples in the range of 30-250℃ is basically higher than that of pure PP / PE system, which proves that the crosslinking network enhances the high temperature stability of the material, and the higher the crosslinking degree, the better the high temperature stability.

Claims

1. A highly compatible mixed plastic composition, characterized in that, It comprises the following components by weight parts: 100 parts of mixed plastics, 0.2-1 parts of free radical initiator, 0.5-5 parts of bismaleimide crosslinking agent containing dynamic disulfide bond; The structure of the bismaleimide crosslinking agent containing dynamic disulfide bond is:

2. A highly compatible mixed plastic composition as claimed in claim 1, wherein, The mixed plastics are two or more than two kinds of polymers in polyethylene, vinyl copolymer, polypropylene, polystyrene, polyvinyl chloride, polyethylene terephthalate, polylactic acid, or are two or more than two different grades of mixture of the same polymer.

3. A highly compatible mixed plastic composition as claimed in claim 1, wherein, The mixed plastics also include additives, which are one or a combination of two or more of antioxidants, fillers, processing aids, antistatic agents, pigments.

4. A highly compatible mixed plastic composition as claimed in claim 1, wherein, The free radical initiator is one or a combination of two or more of dicumyl peroxide, benzoyl peroxide, di-tert-butyl peroxide isopropyl benzene, dodecanoyl peroxide, di-tert-butyl peroxide, 2,5-di-tert-butyl peroxide-2,5-dimethyl hexane.

5. A highly compatible mixed plastic composition as claimed in claim 1, wherein, The preparation steps of the bismaleimide crosslinking agent containing dynamic disulfide bond are as follows: Dissolve dithiodiphenylamine and maleic anhydride in acetone, react at room temperature under inert gas conditions for 4-8h to obtain a light yellow suspension, then add acetic anhydride and sodium acetate in turn, react at 60-80℃ for 4-8h to obtain a red-brown transparent liquid, pour into sodium bicarbonate aqueous solution to precipitate, then filter, and wash the filtered product with deionized water and ethanol to obtain a light yellow solid product.

6. A highly compatible mixed plastic composition as claimed in claim 5, wherein, The mass ratio of dithiodiphenylamine, maleic anhydride, acetic anhydride, and sodium acetate is 14-14.7:12-12.6:55-57.75:1-1.

05.

7. The method for preparing a highly compatible mixed plastic composition as described in claim 1, characterized in that, The gel content of the high compatibility mixed plastic composition is not less than 30%.

8. The method for preparing a highly compatible mixed plastic composition as described in claim 1, characterized in that, The high compatibility mixed plastic composition can be reprocessed after crushing.

9. A process for the preparation of a highly compatible mixed plastic composition as claimed in any one of claims 1 to 8, characterized in that, Comprising the following steps: (1) melt blending after weighing the mixed plastics according to the proportion; (2) add the pre-mixed initiator and bismaleimide crosslinking agent, and continue melt blending; (3) hot pressing of the melt blended sample to obtain the high compatibility mixed plastic composition.

10. A process for the preparation of a highly compatible mixed plastic composition as claimed in claim 9, wherein, In steps (1) and (2), the melt blending temperature is 150-250℃, and the time is 3-10min; in step (3), the hot pressing temperature is 150-250℃, and the time is 3-10min.

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