A nucleating agent having good compatibility with recycled polyethylene terephthalate

Abstract

The application designs and synthesizes a nucleating agent with good compatibility with recycled polyethylene terephthalate. The nucleating agent can effectively solve the technical problems of slow crystallization rate and poor heat resistance of recycled polyethylene terephthalate. The nucleating agent is simple to synthesize, has good effect, can effectively improve the crystallization temperature, crystallization rate and heat distortion temperature of recycled polyethylene terephthalate, and further promotes the wide application of recycled polyethylene terephthalate.

Description

TECHNICAL FIELD

[0001] The present application relates to a nucleating agent with good compatibility with recycled polyethylene terephthalate, belonging to the technical field of high polymer materials. BACKGROUND

[0002] Polyethylene terephthalate is a widely used thermoplastic plastic, which has relatively ideal toughness, electrical insulation, little temperature influence, and advantages such as transparency, non-toxicity, heat resistance, etc., and is mainly used in food, beverage packaging and other aspects. Polyethylene terephthalate plastic has very high recycling value. However, during the recycling process of polyethylene terephthalate, the molecular chain will be broken, resulting in a substantial decrease in heat resistance and crystallization rate. Most of the current nucleating agents have poor interfacial compatibility with recycled polyethylene terephthalate, which limits their effect.

[0003] The Chinese invention patent with publication number CN114276465A synthesizes an additive for improving the heat resistance of polyethylene terephthalate by using melamine, activated cellulose powder, phenyl phosphonic acid and p-toluenesulfonic acid. This method considers the heat resistance of the additive and its influence on the notched impact strength of polyethylene terephthalate, but the small molecular weight of the additive still has the disadvantage of poor compatibility with recycled polyethylene terephthalate. The Chinese invention patent with publication number CN114292285A is prepared by catalyzing dibenzyl sorbitol and long-chain carbon wax acid. Although the compatibility of the additive is considered, the effect of improving the heat resistance and crystallization rate of recycled polyethylene terephthalate is not explicitly shown.

[0004] Therefore, it is urgent to develop a nucleating agent with good interfacial compatibility with recycled polyethylene terephthalate, promote its uniform dispersion in the recycled polyethylene terephthalate matrix, and maximize the advantages of the nucleating agent to obtain recycled polyethylene terephthalate with excellent performance and contribute to the recycled plastic industry in China. SUMMARY

[0005] To solve the problems existing in the prior art, the present application provides a preparation method and application of a nucleating agent with good compatibility with recycled polyethylene terephthalate, to improve the crystallization rate and heat resistance of recycled polyethylene terephthalate, and to promote its recycling.

[0006] The present application provides a nucleating agent with good compatibility with recycled polyethylene terephthalate, characterized in that the molecular structure is as shown in the following formula:

[0007]

[0008] A nucleating agent with good compatibility with recycled polyethylene terephthalate, characterized by a preparation method comprising the following steps:

[0009] Step one, 5.9 g of trimesic acid and 10 g of threonine are dissolved in 200 mL of N,N-dimethylformamide solution, stirred at 1200 rpm using an electric stirrer at 120 DEG C for 3 h, after the reaction is completed, dried at 80 DEG C to constant weight to obtain intermediate product A. 4 g of intermediate product A and 10 g of montanic acid are dissolved in 200 mL of N,N-dimethylformamide solution, 0.2 g of zirconium sulfate tetrahydrate is added, stirred at 1200 rpm using an electric stirrer at 120 DEG C for 8 h, after the reaction is completed, the obtained solid is washed to neutral using 400 mL of N,N-dimethylformamide solution, dried at 80 DEG C to constant weight to obtain intermediate product B;

[0010] Step two, 14.45 g of intermediate product B and 1 g of sodium hydroxide are dissolved in 200 mL of deionized water, stirred at 1200 rpm using an electric stirrer at 80 DEG C for 6 h, after the reaction is completed, the obtained solid is washed to neutral in the order of 50 DEG C ethanol, 25 DEG C deionized water, dried at 80 DEG C to constant weight, to obtain a nucleating agent with good compatibility with recycled polyethylene terephthalate.

[0011] The application is verified, the optimal amount of montanic acid in step one is 10 g, too much or too little will hinder the improvement of its compatibility.

[0012] The application is verified, the optimal stirring time in step one is 8 h, too long or too short will hinder the improvement of its compatibility.

[0013] In addition, the reaction conditions and parameters in the preparation method of the nucleating agent with good compatibility with recycled polyethylene terephthalate are the optimal conditions verified by experiments.

[0014] The application also provides a nucleating agent with good compatibility with recycled polyethylene terephthalate, characterized in that the use amount of the nucleating agent with good compatibility with recycled polyethylene terephthalate is 0.1%-1% of the recycled polyethylene terephthalate.

[0015] Preferably, the use amount of the nucleating agent with good compatibility with recycled polyethylene terephthalate is 0.5% of the recycled polyethylene terephthalate.

[0016] The adding amount of the nucleating agent synthesized by the present application and having good compatibility with the recycled polyethylene terephthalate must be appropriate, so as to better play its role effect. The adding amount is the relatively optimal condition verified by experiments.

[0017] Compared with the prior art, the present application has the following technical effects.

[0018] 1. The sodium carboxylate on the molecular chain of the nucleating agent and the recycled polyethylene terephthalate will chemically react to form ion clusters at high-temperature processing. The ion clusters will become the nucleating agent to play a nucleating role in the melt, accelerating the crystallization rate. On the other hand, the local crystallization acceleration promotes the crystallization of the whole system, greatly improving the crystallization temperature and crystallization rate of the recycled polyethylene terephthalate. At the same time, the accelerated local crystallization rate will also promote the crystallization of the recycled polyethylene terephthalate system. The two effects work together to greatly improve the crystallization rate of the recycled polyethylene terephthalate.

[0019] 2. The sodium carboxylate chemically reacts with the ester bond on the end group of the recycled polyethylene terephthalate to generate sodium ion clusters, inducing the chemical nucleation of the recycled polyethylene terephthalate, leading to local crosslinking of the recycled polyethylene terephthalate, thereby improving the heat distortion temperature of the recycled polyethylene terephthalate. In addition, there are three sodium ion sites on the molecular chain of the nucleating agent, so the effect of improving the heat distortion temperature of the recycled polyethylene terephthalate is more obvious.

[0020] 3. The addition of the long carbon chain reduces the polarity of the whole molecular structure, improves the interfacial compatibility of the recycled polyethylene terephthalate and the nucleating agent, and promotes the nucleating agent to be more uniformly distributed in the recycled polyethylene terephthalate. In addition, the long carbon chain can also play a lubricating role, reducing the friction between molecules, making the crystal arrange more regularly, and providing a basis for further improving the crystallization temperature and crystallization rate of the recycled polyethylene terephthalate.

[0021] 4. The humic acid, trimesic acid, sodium hydroxide, and threonine are combined to form a new chemical structure through chemical reaction, and the chemical structure is stable. The components are not easy to decompose during the melt processing of the recycled polyethylene terephthalate, and can ensure the stable performance. Specific implementation method

[0022] In order to make the technical problems, technical solutions and beneficial effects of the present application clearer and more apparent, the following embodiments are used to further illustrate the present application. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application. Unless otherwise specified, the raw materials, reagents and equipment used in the present application are commercially available in the technical field.

[0023] Example 1

[0024] 5.9 g of trimesic acid (CAS: 554-95-0) and 10 g of threonine (CAS: 72-19-5) were dissolved in 200 mL of N,N-dimethylformamide solution, stirred at 120 °C for 3 h using an electric stirrer at a speed of 1200 rpm, and after the reaction was completed, dried at 80 °C to a constant weight to obtain intermediate product A. 4 g of intermediate product A and 10 g of montanic acid (CAS: 506-48-9) were dissolved in 200 mL of N,N-dimethylformamide solution, 0.2 g of zirconium sulfate tetrahydrate (CAS: 7446-31-3) was added, stirred at 120 °C for 8 h using an electric stirrer at a speed of 1200 rpm, and after the reaction was completed, the obtained solid was washed to neutral with 400 mL of N,N-dimethylformamide solution, and dried at 80 °C to a constant weight to obtain intermediate product B;

[0025] 14.45 g of intermediate product B and 1 g of sodium hydroxide (CAS: 1310-73-2) were dissolved in 200 mL of deionized water, stirred at 80 °C for 6 h using an electric stirrer at a speed of 1200 rpm, and after the reaction was completed, the obtained solid was sequentially washed to neutral with 50 °C ethanol and 25 °C deionized water, and dried at 80 °C to a constant weight to obtain a nucleating agent having good compatibility with recycled polyethylene terephthalate.

[0026] The nucleating agent and recycled polyethylene terephthalate (beverage bottle recyclate) were mixed in a high-speed mixer at a mass ratio of 0.5:100 (mixing speed 3000 rpm, mixing time 5 min), extruded and pelletized in a conventional twin-screw extruder, and then injection molded on an injection molding machine to obtain test samples. The heat distortion temperature was determined according to the method described in GB / T 1634.2-2004 standard.

[0027] The half-crystallization time (t 1 / 2 ) was determined according to the following method: 6 mg of the above sample was placed in an aluminum crucible and placed in a differential scanning calorimeter (DSC). The half-crystallization time (t 1 / 2 ) of the obtained mixture was tested by DSC, and the specific process was as follows: heated to 280 °C at a rate of 10 °C / min, then cooled to 230 °C at a rate of 40 °C / min and isothermal for 40 min, and finally cooled to 40 °C at a rate of 10 °C / min. The relative crystallinity X(t) was calculated according to the isothermal curve from the following formula, and t 1 / 2 was obtained according to X(t)=0.5. The specific data are shown in Table 1.

[0028]

[0029] The sample 6 mg was taken in an aluminum crucible, and the crystallization temperature (T cp ) of the sample was determined according to the method described in GB / T 19466.3-2004, and the specific data are shown in Table 1.

[0030] Example 2

[0031] This example is basically the same as Example 1, and a nucleating agent having good compatibility with recycled polyethylene terephthalate in this example is used to prepare a blended sample with recycled polyethylene terephthalate (beverage bottle recycled material) according to the method of Example 1, and the mass ratio of the nucleating agent synthesized in this example to recycled polyethylene terephthalate is 1:100, and the test data are shown in Table 1.

[0032] Example 3

[0033] This example is basically the same as Example 1, and a nucleating agent having good compatibility with recycled polyethylene terephthalate in this example is used to prepare a blended sample with recycled polyethylene terephthalate (beverage bottle recycled material) according to the method of Example 1, and the mass ratio of the nucleating agent synthesized in this example to recycled polyethylene terephthalate is 0.1:100, and the test data are shown in Table 1.

[0034] Comparative Example 1

[0035] Pure recycled polyethylene terephthalate (beverage bottle recycled material) was extruded and granulated in a conventional twin-screw extruder, and then injection molded into a test sample on an injection molding machine. The semi-crystallization time (t 1 / 2 ) of the sample was calculated according to the above method, the crystallization temperature (T cp ) of the sample was determined according to the method described in GB / T 19466.3-2004, and the heat distortion temperature (HDT) of the sample was determined according to the method described in GB / T 1634.2-2004, and the specific data are shown in Table 1.

[0036] Comparative Example 2

[0037] The raw materials of trimesic acid and recycled polyethylene terephthalate (beverage bottle recycled material) were mixed in a high-speed mixer at a mass ratio of 0.5:100 (mixing speed 3000 rpm, mixing time 5 min), and then extruded and granulated in a conventional twin-screw extruder, and then injection molded into a test sample on an injection molding machine. The semi-crystallization time (t 1 / 2 ) of the sample was calculated according to the above method, the crystallization temperature (T cp ) of the sample was determined according to the method described in GB / T 19466.3-2004, and the heat distortion temperature (HDT) of the sample was determined according to the method described in GB / T 1634.2-2004, and the specific data are shown in Table 1.

[0038] Comparative Example 3

[0039] The raw material threonine and recycled polyethylene terephthalate (beverage bottle recyclate) were mixed in a mass ratio of 0.5:100 in a high-speed mixer (mixing speed 3000 rpm, mixing time 5 min), then extruded, granulated in a conventional twin-screw extruder, and then injection molded on an injection molding machine to obtain test samples. The semi-crystallization time (t 1 / 2 ) of the samples was calculated according to the above method, the crystallization temperature (T cp ) was determined according to the method described in the standard GB / T 19466.3-2004, and the heat distortion temperature (HDT) was determined according to the method described in the standard GB / T 1634.2-2004. The specific data are shown in Table 1.

[0040] Comparative Example 4

[0041] The raw material lignoceric acid and recycled polyethylene terephthalate (beverage bottle recyclate) were mixed in a mass ratio of 0.5:100 in a high-speed mixer (mixing speed 3000 rpm, mixing time 5 min), then extruded, granulated in a conventional twin-screw extruder, and then injection molded on an injection molding machine to obtain test samples. The semi-crystallization time (t 1 / 2 ) of the samples was calculated according to the above method, the crystallization temperature (T cp ) was determined according to the method described in the standard GB / T 19466.3-2004, and the heat distortion temperature (HDT) was determined according to the method described in the standard GB / T 1634.2-2004. The specific data are shown in Table 1.

[0042] Comparative Example 5

[0043] The raw material sodium hydroxide and recycled polyethylene terephthalate (beverage bottle recyclate) were mixed in a mass ratio of 0.5:100 in a high-speed mixer (mixing speed 3000 rpm, mixing time 5 min), then extruded, granulated in a conventional twin-screw extruder, and then injection molded on an injection molding machine to obtain test samples. The semi-crystallization time (t 1 / 2 ) of the samples was calculated according to the above method, the crystallization temperature (T cp ) was determined according to the method described in the standard GB / T 19466.3-2004, and the heat distortion temperature (HDT) was determined according to the method described in the standard GB / T 1634.2-2004. The specific data are shown in Table 1.

[0044] Comparative Example 6

[0045] The raw materials 1 g of sodium hydroxide, 5.9 g of trimesic acid, 10 g of threonine, and 10 g of montanic acid were simply mixed in a high-speed mixer (mixing speed 3000 rpm, mixing time 5 min), and then mixed with recycled polyethylene terephthalate (beverage bottle recycling material) in a mass ratio of 0.5:100 in a high-speed mixer (mixing speed 3000 rpm, mixing time 5 min). The mixture was then extruded and granulated in a conventional twin-screw extruder, and then injection molded on an injection molding machine to obtain a test sample. The semi-crystallization time (t 1 / 2 ) of the sample was calculated according to the above method, the crystallization temperature (T cp ) was measured according to the method described in GB / T 19466.3-2004 standard, and the heat distortion temperature (HDT) was measured according to the method described in GB / T 1634.2-2004 standard. The specific data are shown in Table 1.

[0046] Comparative Example 7

[0047] The intermediate product A and recycled polyethylene terephthalate (beverage bottle recycling material) were mixed in a high-speed mixer in a mass ratio of 0.5:100 (mixing speed 3000 rpm, mixing time 5 min), and then extruded and granulated in a conventional twin-screw extruder. The mixture was then injection molded on an injection molding machine to obtain a test sample. The semi-crystallization time (t 1 / 2 ) of the sample was calculated according to the above method, the crystallization temperature (T cp ) was measured according to the method described in GB / T 19466.3-2004 standard, and the heat distortion temperature (HDT) was measured according to the method described in GB / T 1634.2-2004 standard. The specific data are shown in Table 1.

[0048] Comparative Example 8

[0049] The intermediate product B and recycled polyethylene terephthalate (beverage bottle recycling material) were mixed in a high-speed mixer in a mass ratio of 0.5:100 (mixing speed 3000 rpm, mixing time 5 min), and then extruded and granulated in a conventional twin-screw extruder. The mixture was then injection molded on an injection molding machine to obtain a test sample. The semi-crystallization time (t 1 / 2 ) of the sample was calculated according to the above method, the crystallization temperature (T cp ) was measured according to the method described in GB / T 19466.3-2004 standard, and the heat distortion temperature (HDT) was measured according to the method described in GB / T 1634.2-2004 standard. The specific data are shown in Table 1.

[0050] Table 1 Test results of each example and comparative example

[0051] t 1 / 2 (min) HDT (°C) T cp (°C) Example 1 5.64 75.61 226.52 Example 2 7.07 71.23 219.63 Example 3 7.28 69.57 213.85 Comparative Example 1 20.34 60.34 189.40 Comparative Example 2 17.52 62.82 199.36 Comparative Example 3 16.58 61.59 197.51 Comparative Example 4 16.39 61.31 203.21 Comparative Example 5 19.76 61.21 195.53 Comparative Example 6 15.61 66.76 208.21 Comparative Example 7 13.80 64.58 204.96 Comparative Example 8 11.74 65.43 205.97

[0052] According to the experimental results of Table 1, the crystallization temperature and heat distortion temperature of the recycled polyethylene terephthalate added with the nucleating agent prepared in Examples 1-3 are higher than those of the comparative examples, and the half-crystallization time (t 1 / 2 ) is lower than that of the comparative examples, wherein the amount of the nucleating agent added in Example 1 is 0.5%. Compared with the pure recycled polyethylene terephthalate of Comparative Example 1, it is shown that the nucleating agent synthesized in the present application has a significant effect on improving the heat distortion temperature and crystallization rate of the recycled polyethylene terephthalate. In addition, too much or too little addition of the nucleating agent will adversely affect the crystallization temperature, heat distortion temperature and half-crystallization time (t 1 / 2 ) of the recycled polyethylene terephthalate.

[0053] The nucleating agent prepared in the present application is combined by chemical reaction, which can play a role in improving the crystallization rate, crystallization temperature and heat distortion temperature of the recycled polyethylene terephthalate. The above-mentioned effects cannot be fully played in Comparative Examples 2-5, which are only simple mixtures of single or multiple raw materials without chemical reaction. Among them, the trimesic acid added in Comparative Example 2, the threonine added in Comparative Example 3 and the humic acid added in Comparative Example 4 can all act as heterogeneous nucleating agents to improve the crystallization temperature and accelerate the crystallization rate of the recycled polyethylene terephthalate, but the effect is limited and has no contribution to the improvement of the heat distortion temperature. The sodium hydroxide added in Comparative Example 5 is a strong base, which only has a weak effect on improving the crystallization temperature and has no contribution to the improvement of the heat distortion temperature. At the same time, Comparative Example 6, which adds trimesic acid, threonine, humic acid and sodium hydroxide, only plays a role in heterogeneous nucleation and does not undergo chemical reaction to generate a structure that is beneficial to further improve the beneficial effect, so its improvement effect is only better than that of Comparative Examples 2-5 which add single components.

[0054] The intermediate product A (Comparative Example 7) obtained by adding trimesic acid and threonine for reaction and the intermediate product B (Comparative Example 8) obtained by adding the intermediate product A and humic acid for reaction, since part of the chemical reaction occurs, but not all the desired beneficial functional groups are formed, which makes the beneficial effect cannot be fully played, resulting in that the crystallization rate, half-crystallization time (t 1 / 2 ) and heat distortion temperature of Comparative Examples 7 and 8 are obviously better than those of Comparative Examples 2-6, but still have a large gap with Example 1.

[0055] Therefore, the chemical nucleating agent provided in the present application has good compatibility with the recycled polyethylene terephthalate and can play a beneficial effect, which further illustrates the importance of the synergistic effect of the nucleating agent synthesized in the present application, which has very important practical significance for broadening the practical application scenarios of the recycled polyethylene terephthalate.

[0056] The above merely provides the preferred embodiment of the present application, and not intended to limit the present application. Accordingly, any modification, equivalent replacement, and improvement made without departing from the spirit and principle of the present application shall fall in the scope of the present application.

Claims

1. Use of a nucleating agent having good compatibility with recycled polyethylene terephthalate in recycled polyethylene terephthalate, characterized in that, The preparation method of the nucleating agent comprises the following steps: Step one, 5.9 g of trimesic acid and 10 g of threonine are dissolved in 200 mL of N,N-dimethylformamide solution, stirred at 1200 rpm using an electric stirrer at 120 DEG C for 3 h, after the reaction, dried at 80 DEG C to constant weight to obtain intermediate product A; 4 g of intermediate product A and 10 g of humic acid are dissolved in 200 mL of N,N-dimethylformamide solution, 0.2 g of zirconium sulfate tetrahydrate is added, stirred at 1200 rpm using an electric stirrer at 120 DEG C for 8 h, after the reaction, the obtained solid is washed to neutral using 400 mL of N,N-dimethylformamide solution, dried at 80 DEG C to constant weight to obtain intermediate product B; Step two, 14.45 g of intermediate product B and 1 g of sodium hydroxide are dissolved in 200 mL of deionized water, stirred at 1200 rpm using an electric stirrer at 80 DEG C for 6 h, after the reaction, the obtained solid is washed to neutral in the order of 50 DEG C ethanol and 25 DEG C deionized water, dried at 80 DEG C to constant weight to obtain a nucleating agent having good compatibility with recycled polyethylene terephthalate.

2. The use of a nucleating agent having good compatibility with recycled polyethylene terephthalate according to claim 1 in recycled polyethylene terephthalate, characterized in that: The amount of the nucleating agent having good compatibility with recycled polyethylene terephthalate is 0.1%-1% of the mass of the recycled polyethylene terephthalate.

3. The use of a nucleating agent having good compatibility with recycled polyethylene terephthalate according to claim 1 in recycled polyethylene terephthalate, characterized in that: The amount of the nucleating agent having good compatibility with recycled polyethylene terephthalate is 0.5% of the mass of the recycled polyethylene terephthalate.

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