Preparation method and application of nucleating agent for recycling PET

Abstract

The present invention discloses a preparation method and application of a nucleating agent for recycled PET, relating to the technical field of recycled PET modification. The nucleating agent for recycled PET is synthesized through a chemical reaction using p-aminobenzoic acid, terephthaloyl chloride, and sodium hydroxide as raw materials. This solves the problems of low crystallization temperature and poor rigidity of recycled PET, thereby promoting the industrial development of recycled PET reuse.

Description

Technical Field

[0001] The invention relates to a preparation method and application of a nucleating agent for recycling PET, belonging to the technical field of polymer materials. Background Art

[0002] Polyethylene terephthalate (PET) is an excellent engineering plastic widely used in food and beverage packaging. However, the accumulation of large amounts of PET, which is extremely difficult to degrade by air or microorganisms, in the natural environment poses a serious threat to human production and life. Therefore, how to effectively utilize PET and reduce or even eliminate its harmful effects is a pressing issue in the PET recycling industry.

[0003] Currently, the primary method for utilizing recycled PET both domestically and internationally is mechanical recycling, a method that is simple and low-cost. However, because the recycled PET molecular chains contain ester bonds, trace amounts of water can cause these chains to break at high temperatures during the secondary processing of mechanical recycling. This lowers the crystallization temperature and reduces its rigidity, making it difficult to meet the requirements of high-performance products. Therefore, modification is required during the secondary processing to increase the crystallization temperature and obtain recycled PET materials with higher rigidity.

[0004] Chinese invention patent publication number CN 114292285A describes a novel additive for improving the mechanical properties of recycled PET by synthesizing dibenzylidene sorbitol and montan wax acid. This method fully considers the compatibility of the additives and even the influence of the crystal structure on the toughness of recycled PET. However, sorbitol nucleating agents cannot maximize their ability to control the spatial arrangement of the main chain plane of recycled PET molecules, and there is currently no clear data on their effectiveness in improving the rigidity of recycled PET. Summary of the Invention

[0005] The present invention provides a preparation method and application of a nucleating agent for recycled PET. The nucleating agent has a stable molecular structure and can provide heterogeneous nucleation sites for recycled PET. Its microstructure provides an epitaxial crystallization surface for the recycled PET, thereby controlling the spatial arrangement of the recycled PET molecular main chain planes, significantly improving the crystallization temperature and flexural strength of the recycled PET, and effectively resolving the problems existing in the prior art.

[0006] The present invention provides a nucleating agent for recycling PET, characterized in that its characteristic structure is as follows:

[0007]

[0008] A nucleating agent for recycling PET, characterized in that the preparation method comprises the following steps:

[0009] 13.71 g of p-aminobenzoic acid was dissolved in 200 mL of acetone and stirred at 800 rpm at 25°C for 30 minutes. 7.58 mL of terephthaloyl chloride was then added, and the mixture was stirred at 800 rpm at 25°C for 12 hours. After the reaction, the resulting solid was washed with 500 mL of acetone and 1000 mL of distilled water, respectively. 200 mL of acetone and 3.2 g of sodium hydroxide were then added, and the mixture was stirred at 800 rpm at 25°C for 8 hours. The resulting solid was washed with distilled water until neutral and dried at 80°C to constant weight to obtain the nucleating agent for recycled PET.

[0010] The various reaction conditions and parameters in the preparation method of the nucleating agent for recycling PET described in the present invention are all optimal conditions verified by experiments.

[0011] The present invention also provides an application of a nucleating agent for recycling PET, characterized in that the usage amount of the nucleating agent is 0.1%-1% of the mass of the recycled PET.

[0012] Preferably, the amount of the nucleating agent used is 0.5%.

[0013] The amount of the nucleating agent synthesized in the present invention must be appropriate. Too little addition will not achieve the desired effect, while too much addition will cause the nucleating agent to agglomerate, affecting its effect. The above addition amount is the optimal condition verified by experiments.

[0014] Compared with the prior art, the present invention has the following technical effects.

[0015] The nucleating agent for recycled PET has a long strip-like microscopic morphology and can induce epitaxial crystallization of recycled PET. On the one hand, by controlling the spatial arrangement of the main chain plane of the recycled PET molecules, it promotes the transformation of the molecular structure from the cis amorphous state to the trans crystalline state. On the other hand, it significantly shortens the crystallization induction period and promotes the rearrangement of the molecular chains, thereby promoting the crystallization of recycled PET and increasing its crystallization temperature.

[0016] The nucleating agent for recycled PET has a special molecular structure. During the processing, it can act as a heterogeneous nucleating agent to refine the recycled PET spherulites, promote the orderly arrangement of the crystals, and increase the proportion of the rigid part. On the other hand, it can chemically react with the end of the recycled PET molecular chain, causing the partial molecular structure of the recycled PET to change, increasing the proportion of the rigid chain segment, and thereby improving its bending strength.

[0017] The nucleating agent for recycled PET has a stable chemical structure and can ensure the normal performance of its performance throughout the entire processing process. Specific implementation methods

[0018] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention is further described in detail below in conjunction with the examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. The raw materials, reagents and equipment used in the present invention are conventionally purchased in the art.

[0019] Example 1

[0020] 13.71 g of p-aminobenzoic acid (CAS: 150-13-0) was dissolved in 200 mL of acetone and stirred at 800 rpm at 25°C for 30 minutes. Subsequently, 7.58 mL of terephthaloyl chloride (CAS: 100-20-9) was added, and the mixture was stirred at 800 rpm at 25°C for 12 hours. After the reaction, the resulting solid was washed with 500 mL of acetone and 1000 mL of distilled water, respectively. Subsequently, 200 mL of acetone and 3.2 g of sodium hydroxide (CAS: 1310-73-2) were added, and the mixture was stirred at 800 rpm at 25°C for 8 hours. The resulting solid was washed with distilled water until neutral and dried at 80°C to constant weight to obtain the nucleating agent for recycled PET.

[0021] Recycled PET (beverage bottle regrind) and the nucleating agent were conventionally mixed in a high-speed mixer at a mass ratio of 100:0.5 (mixing speed 3000 rpm, mixing time 5 minutes). The mixture was extruded and pelletized in a conventional twin-screw extruder, and then injection molded on an injection molding machine to produce test samples. The flexural strength of the samples was measured according to the method specified in GB / T 22906.6-2008, and the crystallization temperature was measured according to the method specified in GB / T 19466.3-2004. The specific data are shown in Table 1.

[0022] Example 2

[0023] This embodiment is basically the same as Example 1, except that this embodiment uses the nucleating agent synthesized in Example 1 and recycled PET (beverage bottle recycled material) in a mass ratio of 100:0.1 to prepare samples. The test data are shown in Table 1.

[0024] Example 3

[0025] This embodiment is basically the same as Example 1, except that this embodiment uses the nucleating agent synthesized in Example 1 and recycled PET (beverage bottle recycled material) in a mass ratio of 100:1 to prepare samples. The test data are shown in Table 1.

[0026] Comparative Example 1

[0027] Pure recycled PET (recycled beverage bottle material) was extruded and pelletized in a conventional twin-screw extruder and then injection molded on an injection molding machine to produce test samples. Their flexural strength was measured according to the method specified in GB / T 22906.6-2008, and their crystallization temperature was measured according to the method specified in GB / T 19466.3-2004. Specific data are shown in Table 1.

[0028] Comparative Example 2

[0029] Recycled PET (beverage bottle regrind) and p-aminobenzoic acid were conventionally mixed in a high-speed mixer at a mass ratio of 100:0.5 (mixing speed 3000 rpm, mixing time 5 minutes). The mixture was extruded and pelletized in a conventional twin-screw extruder and then molded on an injection molding machine to produce test samples. The flexural strength of the samples was measured according to the method specified in GB / T 22906.6-2008, and the crystallization temperature was measured according to the method specified in GB / T 19466.3-2004. The specific data are shown in Table 1.

[0030] Comparative Example 3

[0031] Recycled PET (beverage bottle regrind) and terephthaloyl chloride were mixed in a high-speed mixer at a mass ratio of 100:0.5 (3000 rpm, 5 min). The mixture was extruded and pelletized in a conventional twin-screw extruder and then injection molded on an injection molding machine to produce test samples. The flexural strength of the samples was measured according to the method specified in GB / T 22906.6-2008, and the crystallization temperature was measured according to the method specified in GB / T 19466.3-2004. The specific data are shown in Table 1.

[0032] Comparative Example 4

[0033] Recycled PET (beverage bottle regrind) and sodium hydroxide were mixed in a high-speed mixer at a mass ratio of 100:0.5 (3000 rpm, 5 min). The mixture was extruded and pelletized in a conventional twin-screw extruder and then injection molded on an injection molding machine to produce test samples. The flexural strength of the samples was measured according to the method specified in GB / T 22906.6-2008, and the crystallization temperature was measured according to the method specified in GB / T 19466.3-2004. The specific data are shown in Table 1.

[0034] Comparative Example 5

[0035] 13.71 g of p-aminobenzoic acid, 7.58 mL of terephthaloyl chloride, and 3.2 g of sodium hydroxide were briefly mixed in a high-speed mixer (mixing speed 3000 rpm, mixing time 5 minutes). The mixture was then conventionally mixed with recycled PET (beverage bottle recycled material) at a mass ratio of 0.5:100 in a high-speed mixer (mixing speed 3000 rpm, mixing time 5 minutes). The mixture was extruded and pelletized in a conventional twin-screw extruder and then injection molded on an injection molding machine to produce test samples. The flexural strength was measured according to the method specified in GB / T 22906.6-2008, and the crystallization temperature was measured according to the method specified in GB / T 19466.3-2004. The specific data are shown in Table 1.

[0036] Table 1 Test results of various embodiments and comparative examples

[0037] Flexural strength (MPa) Crystallization temperature (℃) Example 1 89.9 213.4 Example 2 85.6 208.9 Example 3 86.5 210.3 Comparative Example 1 60.8 186.1 Comparative Example 2 66.9 192.2 Comparative Example 3 61.2 186.9 Comparative Example 4 62.8 188.1 Comparative Example 5 68.7 195.8

[0038] The experimental results in Table 1 indicate that the addition of the nucleating agent prepared for recycled PET prepared in accordance with the present invention in Examples 1-3 resulted in relatively high flexural strength and crystallization temperature. Example 1, with a 0.5% addition, performed optimally. Compared to the pure recycled PET in Comparative Example 1, this demonstrates that the nucleating agent synthesized in accordance with the present invention significantly improves the flexural strength and crystallization temperature of recycled PET. Furthermore, either excessive or insufficient addition of nucleating agent can result in decreased flexural strength and crystallization temperature of the recycled PET.

[0039] The nucleating agent for recycled PET prepared by the present invention is synthesized through chemical reactions, so that each chain segment plays a role simultaneously. However, Comparative Examples 2-7 only use a single raw material or a simple mixture of raw materials, without a complete chemical reaction, and the above-mentioned effects cannot be fully exerted. Among them, the p-aminobenzoic acid added in Comparative Example 2 can play a certain heterogeneous nucleation role, improving the bending strength and crystallization temperature of the recycled PET, but the effect is limited. The terephthaloyl chloride added in Comparative Example 3 has almost no lifting effect. The sodium hydroxide added in Comparative Example 4 is strongly alkaline and only plays a weak heterogeneous nucleation role. Comparative Example 5, which adds p-aminobenzoic acid, terephthaloyl chloride and sodium hydroxide at the same time, has the best effect, but it does not undergo a chemical reaction and does not form a unique chemical structure, and can only play a certain heterogeneous nucleation role. Therefore, the lifting effect is significantly different from that of Example 1.

[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of the present invention.

Claims

1. An application of a nucleating agent for recycling PET in recycling PET, characterized in that: The molecular structure of the nucleating agent for recycling PET is as follows: 。 2. The use of a nucleating agent for recycling PET according to claim 1, wherein: The amount of the nucleating agent for recycled PET is 0.1%-1% of the mass of the recycled PET.

3. The use of a nucleating agent for recycling PET according to claim 1 in recycling PET, characterized in that: The amount of the nucleating agent for recycled PET is 0.5% of the mass of the recycled PET.

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