A thermoset plastic that can be continuously extrusion reprocessed, a method of preparation and a method of reprocessing the thermoset plastic

Abstract

The application discloses a kind of continuously extruded reworkable thermosetting plastics and preparation method thereof, preparation method includes that thermosetting plastics is soaked in water after taking out and obtains the continuously extruded reworkable thermosetting plastics;Wherein, the thermosetting plastics is with azelaic acid, 1,3-diamino-2-propanol as monomer, polymerization is formed under the action of inert gas and catalyst.The application is designed by polymer structure, significantly improves the melt flow rate of polymer after water absorption, and then the material can be directly processed by twin-screw extruder at relatively low temperature, so that it realizes continuous extrusion processing, solves the current reworkable thermosetting plastics limited to long time hot-pressing inefficient method of processing.The application also proposes a kind of rework method of thermosetting plastics used, and the performance of rework plastic is good.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thermosetting resin materials, and particularly relates to a thermosetting plastic capable of continuous extrusion and reprocessing, a preparation method and a reprocessing method of the thermosetting plastic. BACKGROUND

[0002] Thermosetting resin is a polymer material with a cross-linked chemical network, and usually has a highly cross-linked structure after curing reaction. Due to its excellent dimensional stability, good chemical resistance, excellent thermal and mechanical properties, they have aroused great interest and been widely used in the fields of coatings, adhesives, composites and electronic packaging. It can be said without exaggeration that the application range of thermosetting plastics is very wide and they are everywhere in daily life. However, the cross-linked chemical network exists, which leads to its non-recyclability, and almost all waste thermosetting plastics are regarded as waste. At present, the industrial way of recycling traditional thermosetting resin is low in efficiency and not environmentally friendly, such as landfill and combustion. Therefore, it is necessary to achieve a longer service life by allowing its reusability or recyclability (remolding, repairable, degradable, cleavable, etc.). By combining reprocessable cleavage bonds, the material is endowed with thermosetting and reprocessability, and thus the purpose of reusing thermosetting resin is achieved.

[0003] Although the development of reprocessable thermosetting resin can avoid resource waste and environmental pollution to a certain extent, its special chemical structure is destined to exist the present situation of reprocessing difficulty. The current reprocessable thermosetting plastic often accelerates the exchange of internal chemical bonds by long-time high-temperature hot pressing, and then makes it into a mold, which is a low-efficiency processing method and greatly limits the industrial application of reprocessable thermosetting resin.

[0004] Chinese patent application CN112920403A discloses a method for preparing a reprocessable thermosetting polyester amide, comprising the following steps: (1) heating and dissolving 30-200 parts by weight of liquid dicarboxylic acid and 15-95 parts by weight of a diamine compound containing β-hydroxyl to form a reaction solution; the liquid dicarboxylic acid includes azelaic acid, and the diamine compound containing β-hydroxyl is 1,3-diamino-2-propanol; (2) adding 0.05-0.5 parts by weight of catalyst and heating at 65-100°C for 1-6 h under a nitrogen atmosphere; (3) heating the reaction solution to 100-180°C for 3-18 h; (4) heating the reaction system of the reaction solution to 180-240°C for 0.5-4 h; (5) cooling the reaction system of the reaction solution to 100-180°C. The presence of amide bonds, ester bonds, and hydroxyl groups in polyesteramide gives it high heat resistance and allows for repeated processing. However, its melting properties are poor. When extruded using a twin-screw extruder, the extrusion temperature is high and the surface of the extruded material is not smooth, resulting in poor performance and the inability to be drawn into filaments. During reprocessing, prolonged high-temperature hot pressing is required to accelerate the exchange of internal chemical bonds, thereby enabling it to be molded. This results in low efficiency and limits its application. Summary of the Invention

[0005] The technical problem to be solved by this invention is how to address the current issue of poor extrusion performance of reprocessable thermosetting resins using twin-screw extruders, which results in low processing efficiency due to prolonged hot pressing.

[0006] The present invention solves the above-mentioned technical problems through the following technical means:

[0007] A method for preparing a thermosetting plastic that can be continuously extruded and reprocessed includes immersing the thermosetting plastic in water and then taking it out to obtain the thermosetting plastic that can be continuously extruded and reprocessed; wherein the thermosetting plastic is polymerized using azelaic acid and 1,3-diamino-2-propanol as monomers under the action of an inert gas and a catalyst.

[0008] Preferably, the soaking time in water is 1-10 hours.

[0009] Preferably, the mass ratio of azelaic acid to 1,3-diamino-2-propanol is 100:34-48.

[0010] Preferably, the mass ratio of azelaic acid to 1,3-diamino-2-propanol is 100:34-40.

[0011] Preferably, the inert gas is nitrogen; the catalyst is sodium hypophosphite; and the mass of the catalyst is 0.05-1% of the mass of azelaic acid.

[0012] Preferably, the preparation method of the thermosetting plastic comprises the following steps: mixing azelaic acid, 1,3-diamino-2-propanol and a catalyst, heating to 120-140 DEG C under inert gas protection for 1-6 hours, then heating to 150-170 DEG C for 1-5 hours, heating to 180-200 DEG C for 0.5-4 hours, heating to 220-240 DEG C until the polymer appears climbing effect, and cooling to 100-180 DEG C to obtain the thermosetting plastic.

[0013] Preferably, the preparation method of the thermosetting plastic comprises the following steps: mixing azelaic acid, 1,3-diamino-2-propanol and a catalyst, heating to 130 DEG C under inert gas protection for 2 hours, then heating to 160 DEG C for 2 hours, heating to 180 DEG C for 2 hours, heating to 220 DEG C until the polymer appears climbing effect, and cooling to 140 DEG C to obtain the thermosetting plastic.

[0014] The application further provides a thermosetting plastic which can be continuously extruded and reprocessed, and is prepared by the preparation method of the thermosetting plastic which can be continuously extruded and reprocessed.

[0015] The application further provides a reprocessing method of the thermosetting plastic used in the preparation method, which comprises the following steps: soaking the thermosetting plastic in water, crushing and then extruding through a double-screw extruder.

[0016] Preferably, the soaking time in water is 1-10 hours.

[0017] Preferably, the temperature of the double-screw extrusion is 80-140 DEG C.

[0018] Beneficial effect: 80 DEG C can destroy hydrogen bonds and improve flowability, and the temperature should not be too high, otherwise the water will evaporate rapidly.

[0019] Preferably, the temperature of the double-screw extrusion is 120 DEG C.

[0020] The application further provides a thermosetting plastic used in the preparation method of the thermosetting plastic which can be continuously extruded and reprocessed.

[0021] The application has the following advantages:

[0022] (1) The application improves the melt flow rate of the polymer after water absorption through polymer structure design, and then the material can be directly processed by double-screw extrusion at a relatively low temperature, so that the continuous extrusion processing is realized, and the low-efficiency processing method of the current reprocessable thermosetting plastic which is limited to long-time hot pressing is solved.

[0023] (2) The performance adjustment of the material can be realized by adjusting the material ratio and humidity, and the use of plasticizers is avoided.

[0024] (3) For specific thermosetting plastics, the reprocessing method of the present application has low extrusion temperature and good extrusion quality, which is beneficial to commercial application. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The infrared spectrum of the product synthesized in Example 1 and Examples 5-7 of the present application;

[0026] Figure 2 The glass transition temperature change graph of the product synthesized in Example 1 and Examples 5-7 of the present application;

[0027] Figure 3 The stress-strain curve of the product of Example 1 and Example 7 of the present application;

[0028] Figure 4 The modulus change graph of the product synthesized in Example 1 and Examples 5-7 of the present application;

[0029] Figure 5 The stress-strain curve of the product of Example 1 of the present application under different humidity;

[0030] Figure 6 The stress-strain curve of the product of Example 1 of the present application repeated for 5 times;

[0031] Figure 7 The test of the product of Example 1 of the present application on the melt flow rate instrument;

[0032] Figure 8 The melt flow rate of the product of Examples 1-4 of the present application at different temperatures;

[0033] Figure 9 The process graph of the extrusion processing of Example 4 of the present application;

[0034] Figure 10 The sample morphology of the product of Example 1 of the present application extrusion processed at 220 degrees Celsius. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0036] The test materials and reagents used in the following examples, etc. can be obtained from commercial channels if not otherwise specified.

[0037] Unless otherwise indicated, technical and scientific terms used in the examples have the same meaning as those which are described in the literature of the art and products described herein.

[0038] Example 1

[0039] A method for preparing a thermoset plastic, comprising the steps of: taking azelaic acid 100 g, 1,3-diamino-2-propanol 34.2 g, sodium hypophosphite 670 mg into a 500 ml three-necked round-bottom flask, under the environment of flowing high-purity nitrogen and mechanical stirring, first heating to 130°C for 2 hours, then heating to 160°C for 2 hours, heating to 180°C for 2 hours, heating to 220°C until the polymer appears climbing effect, cooling to 140°C, and taking out to obtain the product of Example 1.

[0040] Example 2

[0041] A method for preparing a thermoset plastic that can be continuously extruded and reprocessed, comprising the steps of: soaking the product of Example 1 in water for 1 hour, then taking it out, and using filter paper to absorb the surface free water to obtain the sample, which is the thermoset plastic that can be continuously extruded and reprocessed.

[0042] Example 3

[0043] A method for preparing a thermoset plastic that can be continuously extruded and reprocessed, comprising the steps of: soaking the product of Example 1 in water for 4 hours, then taking it out, and using filter paper to absorb the surface free water to obtain the sample, which is the thermoset plastic that can be continuously extruded and reprocessed.

[0044] Example 4

[0045] A method for preparing a thermoset plastic that can be continuously extruded and reprocessed, comprising the steps of: soaking the product of Example 1 in water for 10 hours, then taking it out, and using filter paper to absorb the surface free water to obtain the sample, which is the thermoset plastic that can be continuously extruded and reprocessed.

[0046] Example 5

[0047] A method for preparing a thermoset plastic, comprising the steps of: taking azelaic acid 100 g, 1,3-diamino-2-propanol 47.88 g, sodium hypophosphite 670 mg into a 500 ml three-necked round-bottom flask, under the environment of flowing high-purity nitrogen and mechanical stirring, first heating to 130°C for 2 hours, then heating to 160°C for 2 hours, heating to 180°C for 2 hours, heating to 220°C until the polymer appears climbing effect, cooling to 140°C, and taking out to obtain the thermoset plastic.

[0048] Example 6

[0049] A method for preparing a thermosetting plastic, comprising the following steps: taking azelaic acid 100 g, 1,3-diamino-2-propanol 43.53 g, sodium hypophosphite 670 mg into a 500 ml three-necked round-bottom flask, under the environment of flowing high-purity nitrogen and mechanical stirring, first heating to 130 DEG C for 2 hours, then heating to 160 DEG C for 2 hours, heating to 180 DEG C for 2 hours, heating to 220 DEG C until the polymer appears climbing effect, cooling to 140 DEG C, and taking out to obtain the thermosetting plastic.

[0050] Example 7

[0051] A method for preparing a thermosetting plastic, comprising the following steps: taking azelaic acid 100 g, 1,3-diamino-2-propanol 39.90 g, sodium hypophosphite 670 mg into a 500 ml three-necked round-bottom flask, under the environment of flowing high-purity nitrogen and mechanical stirring, first heating to 130 DEG C for 2 hours, then heating to 160 DEG C for 2 hours, heating to 180 DEG C for 2 hours, heating to 220 DEG C until the polymer appears climbing effect, cooling to 140 DEG C, and taking out to obtain the thermosetting plastic.

[0052] Example 8

[0053] A method for preparing a thermosetting plastic, comprising the following steps: taking azelaic acid 100 g, 1,3-diamino-2-propanol 34.2 g, sodium hypophosphite 670 mg into a 500 ml three-necked round-bottom flask, under the environment of flowing high-purity nitrogen and mechanical stirring, first heating to 120 DEG C for 6 hours, then heating to 150 DEG C for 5 hours, heating to 200 DEG C for 0.5 hours, heating to 230 DEG C until the polymer appears climbing effect, cooling to 100 DEG C, and taking out to obtain the product of Example 8.

[0054] Example 9

[0055] A method for preparing a thermosetting plastic, comprising the following steps: taking azelaic acid 100 g, 1,3-diamino-2-propanol 34.2 g, sodium hypophosphite 670 mg into a 500 ml three-necked round-bottom flask, under the environment of flowing high-purity nitrogen and mechanical stirring, first heating to 140 DEG C for 1 hour, then heating to 170 DEG C for 1 hour, heating to 180 DEG C for 4 hours, heating to 240 DEG C until the polymer appears climbing effect, cooling to 180 DEG C, and taking out to obtain the product of Example 9.

[0056] Example 10

[0057] After the products of Examples 5-9 are respectively soaked in water for 10 hours, the samples obtained by absorbing the surface free water with filter paper are the thermosetting plastics which can be continuously extruded and reprocessed.

[0058] ByFigure 1 From the infrared spectrum, the product of the example appears the peak of amide bond and ester bond, and there is also hydroxyl group, which proves that both the double chemical network and the beta hydroxyl group exist in the reaction system, so the thermosetting resin example is successfully prepared.

[0059] By Figure 2 It can be seen that the glass transition temperature of the products of example 1 and examples 5-7 changes regularly, because the reaction method and reaction system of example 1 and examples 5-7 are the same, only the feeding ratio of the reaction raw materials azelaic acid and 1,3-diamino-2-propanol is changed to realize the adjustment of the thermal properties of the material. Figure 3 With Figure 2 The same regularity, only by changing the feeding, the tensile properties of the resin are adjusted, because examples 5 and 6 are too brittle, the stress-strain curve cannot be measured, but it can be seen that the tensile strength of the product of example 1 is worse than that of example 7, and the tensile strain is better than that of example 7. It can be found from the dynamic mechanical test that the initial modulus of the resin gradually decreases from example 5, example 6, example 7 to example 1, as shown in Figure 4 Therefore, the thermomechanical properties of the material can be adjusted by adjusting the feeding ratio.

[0060] The thermosetting resin in the application not only can realize the mechanical property regulation by the feeding ratio, but also can realize the performance regulation by adjusting the humidity. As shown in Figure 5 After the product of example 1 is placed in different humidity environments and balanced, the resin shows different mechanical properties, because the hydroxyl group and the amide bond in the polymer network form hydrogen bonds with the water molecules in the air, thereby affecting the tensile properties.

[0061] In order to prove that the product of example 1 has the reworkability, the example 1 resin is repeatedly pressed and broken, and in the stress-strain curve of Figure 6 It can be found that the strength of the product of example 1 does not decrease before and after the repetition, which shows that example 1 has good reworkability.

[0062] In order to verify the melt flow rate of the products of example 1 and examples 2-4, as shown in Figure 7 First, the product of example 1 is melt extruded from high temperature 200 degrees Celsius to 120 degrees Celsius, and when the temperature decreases to 120 degrees Celsius, the melt flow rate of the product of example 1 is 0 (as shown in Figure 8 ), which shows that the flowability of the product of example 1 at 120 degrees Celsius is 0. When testing the products of examples 2 to 4 at 120 degrees Celsius, it can be found that the melt index increases significantly from 0 to more than 80, and the flowability of the resin increases significantly, which shows that the crosslinking bond of the resin is recombined after water absorption, which can significantly increase the flowability of the resin.

[0063] On this basis, the product after soaking in Example 4 is broken and then reprocessed by twin-screw extrusion at 120 degrees Celsius (as shown in Figure 9 ), which can be smoothly extruded and drawn into a filament, and the filament can pull up a 240g weight in air and can be woven into a required shape and bear a 200g weight. The sample morphology of the product of Example 1 after extrusion processing at 220 degrees Celsius is shown in Figure 10 , from which it can be seen that the surface is not smooth and the product cannot be drawn into a filament; the product of Example 1 cannot continuously extrude a smooth product by twin-screw extrusion at a temperature lower than 220 degrees Celsius and draw it into a filament. Figure 10

[0064] The product of Example 10 is broken and then reprocessed by twin-screw extrusion at 120 degrees Celsius, which can also be smoothly extruded and drawn into a filament.

[0065] The above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.​

Claims

1. A method of reprocessing thermoset plastics, characterized by: The method comprises the following steps: soaking thermosetting plastic in water for 1-10 hours, crushing and extruding by a double screw extruder; the temperature of the double screw extrusion is 80-140 DEG C; the thermosetting plastic is polymerized by azelaic acid and 1, 3-diamino-2-propanol as monomers under the action of inert gas and catalyst; the mass ratio of azelaic acid and 1, 3-diamino-2-propanol is 100:34-48; the preparation method of the thermosetting plastic comprises the following steps: mixing azelaic acid, 1, 3-diamino-2-propanol and catalyst, heating to 120-140 DEG C under the protection of inert gas and reacting for 1-6 hours, then heating to 150-170 DEG C and reacting for 1-5 hours, then heating to 180-200 DEG C and reacting for 0.5-4 hours, heating to 220-240 DEG C until the polymer appears climbing rod effect, cooling to 100-180 DEG C to obtain the thermosetting plastic.

2. The method of reprocessing thermoset plastics according to claim 1, characterized in that: The inert gas is nitrogen; the catalyst is sodium hypophosphite; the mass of the catalyst is 0.05-1% of the mass of azelaic acid.

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