CN117623966A - Synthesis and application of a green source of recycled polyethylene terephthalate additives - Google Patents

Abstract

The invention discloses synthesis and application of a green-source recycled polyethylene terephthalate auxiliary agent, which can greatly improve the crystallization temperature and the intrinsic viscosity of the recycled polyethylene terephthalate through the actions of attached crystallization, chemical nucleation and the like. Most importantly, the raw material terephthalic acid for synthesizing the auxiliary agent can be obtained by depolymerizing the recycled polyethylene terephthalate, and the other raw material serine has a bio-based source, so that the green source attribute of the raw material is truly achieved, and the auxiliary agent has important significance for the development of the mechanical recycling industry of the polyethylene terephthalate under the background of carbon peak and carbon neutralization at present.

Description

Synthesis and development of a green source of recycled polyethylene terephthalate additives application

Technical field

The invention relates to the synthesis and application of a green source of recycled polyethylene terephthalate additives, and belongs to the technical field of polymer materials.

Background technique

Polyethylene terephthalate is an engineering plastic with excellent performance and is mainly used in food and beverage packaging. With the rapid development of industry, the demand for polyethylene terephthalate is also increasing. A large amount of polyethylene terephthalate accumulates in the natural environment and is difficult to be degraded by air or microorganisms. This It has caused serious harm to human production and life. Efficient polyethylene terephthalate recycling and reuse is therefore critical, helping to reduce waste generation, demand on finite resources and negative environmental impact.

Currently, the commonly used methods for recycling polyethylene terephthalate include chemical recycling and mechanical recycling. The chemical recycling method uses methods such as catalytic depolymerization to degrade polyethylene terephthalate into "green source" terephthalic acid and ethylene glycol. However, the method’s complex operation limits its ability to solve polyethylene terephthalate recycling problems. The mechanical recycling method is to crush and classify discarded polyethylene terephthalate products, and then obtain recycled polyethylene terephthalate particles through melt processing. However, moisture and ultraviolet rays in the early use of the product will cause the breakage of its molecular chain, and during the secondary processing after recycling, the breakage of the molecular chain may be more serious due to secondary heating, which directly leads to After recycling and processing, its intrinsic viscosity drops sharply and its crystallization properties continue to deteriorate, making it difficult to meet the requirements of high-performance products.

In the current "double carbon" context, not only the base polymer needs to be of "green" origin, but the design and synthesis of its additives also has such a trend. Therefore, how to use the raw materials obtained from chemical recycling of polyethylene terephthalate to design and develop an additive with green source and stable molecular structure to solve the possible problems of polyethylene terephthalate in mechanical recycling processing? The resulting problems such as a sharp decrease in intrinsic viscosity and continued deterioration of crystallization properties are of great significance to the development of the polyethylene terephthalate mechanical recycling industry.

Contents of the invention

In order to solve the problems existing in the existing technology, the present invention provides a synthesis and application of a green source of recycled polyethylene terephthalate additives, which has the ability to increase the crystallization temperature of recycled polyethylene terephthalate. The most important thing is that the raw material terephthalic acid can be obtained by depolymerizing recycled polyethylene terephthalate. Another raw material, serine, has a bio-based source. These two raw materials have green attributes and low prices. It is of great significance in the field of recycling polyethylene terephthalate modification.

The synthesis and application of a green-source recycled polyethylene terephthalate additive provided by the invention is characterized in that its molecular structure is as follows:

The synthesis and application of a green source of recycled polyethylene terephthalate additives, characterized in that the preparation method includes the following steps:

Dissolve 7.9 g terephthalic acid and 10 g serine in 200 mL N,N-dimethylformamide solution, add 0.2 g methylsulfonic acid, and stir for 8 h using an electric stirrer at 800 rpm at 120 °C. , after the reaction is completed, wash the obtained solid with 350 mL of N,N-dimethylformamide solution, and dry to constant weight at 80°C to obtain intermediate product A. Place 8.5 g of intermediate product A and 2 g of sodium hydroxide in 200 mL of deionized water, stir for 6 h using an electric stirrer at 800 rpm at 80°C, and wash the obtained solid with acetone and deionized water in sequence. Neutral, dry at 80°C to constant weight to obtain a green source of recycled polyethylene terephthalate additives.

In addition, the present invention also provides the synthesis and application of a green source of recycled polyethylene terephthalate additives.

Preferably, as an improvement, the reaction temperature in the first step of the synthesis of a green source of recycled polyethylene terephthalate auxiliary is 120°C, the reaction time is 8 h, and the reaction time in the second step is The reaction temperature was 80°C and the reaction time was 6 h.

The reaction temperature and time of the present invention are determined based on the boiling point and reactivity of the solvent, and the above reaction conditions are the optimal conditions verified through experiments.

Preferably, in the step, the product is washed in the order of washing with acetone and deionized water, and the solid obtained is dried at 80°C to a constant weight.

The present invention has been verified that sequential washing with acetone and deionized water can fully remove unreacted impurities. In addition, the drying effect of the product cannot be guaranteed if the drying temperature is too high or too low. The above impurity removal and drying conditions are verified by experiments. better conditions.

In addition, various reaction conditions and parameters in the synthesis and application of a green-source recycled polyethylene terephthalate additive described in the present invention are optimal conditions verified by experiments.

Preferably, the usage amount of the recycled polyethylene terephthalate additive from green sources is 0.3% of the recycled polyethylene terephthalate.

The green source recycled polyethylene terephthalate additive synthesized by the present invention must be added in an appropriate amount in order to better exert its beneficial effects. The above-mentioned added amount is the optimal condition verified by experiments.

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

1. The carboxylic acid sodium salt segment on the molecular chain of this additive reacts chemically with the ester group at the end of the recycled polyethylene terephthalate molecular chain during the processing process, playing a chemical nucleation role. At the same time, the microscopic morphology of this additive can induce the epitaxial crystallization of recycled polyethylene terephthalate, causing its crystallization free energy to decrease sharply during the crystallization process. Therefore, this additive simultaneously acts on the crystallization process of recycled polyethylene terephthalate from both nucleation and crystal growth aspects, thereby greatly increasing its crystallization temperature.

2. The chemical reaction between the carboxylic acid sodium salt segment on the molecular chain of the additive and the terminal ester group of the recycled polyethylene terephthalate molecular chain can simultaneously promote the partial cross-linking of the recycled polyethylene terephthalate. This effect can greatly increase its intrinsic viscosity, thus avoiding the breakage of its molecular chain during secondary processing and the negative impact of the decrease in intrinsic viscosity on the recycling of polyethylene terephthalate.

3. The raw materials of this additive are combined through chemical bonds during the synthesis process, and the chemical structure is stable. The molecular segments of each component will not be separated during the melting process of recycled polyethylene terephthalate, resulting in the effect of weaken or disappear.

Specific implementation methods

In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clear, the present invention will be further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention and do not serve to illustrate the present invention. to limit the present invention. Unless otherwise specified, the raw materials, reagents and equipment used in the present invention are commercially available in this technical field.

Example 1

Dissolve 7.9 g terephthalic acid (CAS: 100-21-0) and 10 g serine (CAS: 302-84-1) in 200 mL N,N-dimethylformamide solution, and add 0.2 g methyl sulfonate Acid (CAS: 75-75-2), stir at 120°C using an electric stirrer at 800 rpm for 8 h. After the reaction is completed, use 350 mL of N,N-dimethylformamide solution to wash the solid obtained , dried at 80°C to constant weight to obtain intermediate product A. Place 8.5 g of intermediate product A and 2 g of sodium hydroxide (CAS: 1310-73-2) in 200 mL of deionized water, stir with an electric stirrer at 800 rpm for 6 h at 80°C, and add acetone, Wash the solid obtained with deionized water to neutrality, and dry it to a constant weight at 80°C to obtain a green-source recycled polyethylene terephthalate additive.

After mixing the auxiliary and recycled polyethylene terephthalate (recycled beverage bottle material) in a high-speed mixer at a mass ratio of 0.3:100 (mixing speed 3000 rpm, mixing time 5 min), in a conventional After extrusion and granulation in a twin-screw extruder, the test sample is obtained by injection molding on an injection molding machine. The intrinsic viscosity is calculated according to the following formula. The specific data are shown in Table 1.

(In the formula, α=0.77, K=2.75×10 ^-4 )

The crystallization temperature was measured according to the method described in the GB/T 19466.3-2004 standard. The specific data are shown in Table 1.

Example 2

This embodiment is basically the same as Example 1. A green source of recycled polyethylene terephthalate auxiliary in this embodiment is used to prepare and recover polyethylene terephthalate ( Beverage bottle recycled material) blended sample, and the mass ratio of the synthetic additives and recycled polyethylene terephthalate in this example is 1:100. The test data are shown in Table 1.

Example 3

This embodiment is basically the same as Example 1. A green source of recycled polyethylene terephthalate auxiliary in this embodiment is used to prepare and recover polyethylene terephthalate ( Beverage bottle recycled material) blended sample, and the mass ratio of the synthesized additives and recycled polyethylene terephthalate in this example is 0.1:100. The test data are shown in Table 1.

Comparative example 1

Pure recycled polyethylene terephthalate (beverage bottle recycled material) is extruded and granulated in a conventional twin-screw extruder, and then injection molded on an injection molding machine to obtain a test sample. The intrinsic viscosity was calculated according to the method of Example 1, and the crystallization temperature was measured according to the method described in the GB/T19466.3-2004 standard. The specific data are shown in Table 1.

Comparative example 2

Mix the raw material terephthalic acid and recycled polyethylene terephthalate (beverage bottle recycled material) in a high-speed mixer at a mass ratio of 0.3:100 (mixing speed 3000 rpm, mixing time 5 min) in a conventional double After extrusion and granulation in a screw extruder, the test sample is obtained by injection molding on an injection molding machine. Calculate the intrinsic viscosity according to the above method, and measure the crystallization temperature according to the method described in the GB/T 19466.3-2004 standard. The specific data are shown in Table 1.

Comparative example 3

The raw material serine and recycled polyethylene terephthalate (beverage bottle recycled material) are mixed in a high-speed mixer at a mass ratio of 0.3:100 (mixing speed 3000 rpm, mixing time 5 min) and then extruded through a conventional twin-screw extruder. After extrusion and granulation in the machine, the test sample is obtained by injection molding on the injection molding machine. Calculate the intrinsic viscosity according to the above method, and measure the crystallization temperature according to the method described in the GB/T19466.3-2004 standard. The specific data are shown in Table 1.

Comparative example 4

Mix the raw material sodium hydroxide and recycled polyethylene terephthalate (beverage bottle recycled material) in a high-speed mixer at a mass ratio of 0.3:100 (mixing speed 3000 rpm, mixing time 5 min) in a conventional twin-screw After extrusion and granulation in the extruder, the test sample is obtained by injection molding on the injection molding machine. Calculate the intrinsic viscosity according to the above method, and measure the crystallization temperature according to the method described in the GB/T19466.3-2004 standard. The specific data are shown in Table 1.

Comparative example 5

Simply mix the raw materials 10 g serine, 7.9 g terephthalic acid, and 2 g sodium hydroxide in a high-speed mixer (mixing speed 3000 rpm, mixing time 5 min), and mix them with recycled polyethylene terephthalate ( Beverage bottle recycled material) is mixed in a high-speed mixer at a mass ratio of 0.3:100 (mixing speed 3000 rpm, mixing time 5 min), extruded and granulated in a conventional twin-screw extruder, and then injection molded on an injection molding machine. Get test samples. Calculate the intrinsic viscosity according to the above method, and measure the crystallization temperature according to the method described in the GB/T 19466.3-2004 standard. The specific data are shown in Table 1.

Comparative example 6

After mixing the intermediate product A and recycled polyethylene terephthalate (beverage bottle recycled material) in a high-speed mixer at a mass ratio of 0.3:100 (mixing speed 3000 rpm, mixing time 5 min), the mixture was extruded in a conventional twin-screw extruder. After extrusion and granulation in the machine, the test sample is obtained by injection molding on the injection molding machine. Calculate the intrinsic viscosity according to the above method, and measure the crystallization temperature according to the method described in the GB/T19466.3-2004 standard. The specific data are shown in Table 1.

Table 1 Test results of each embodiment and comparative example

Intrinsic viscosity (dL/g) Crystallization temperature (℃) Example 1 0.925 224.53 Example 2 0.821 217.26 Example 3 0.782 211.74 Comparative example 1 0.526 189.40 Comparative example 2 0.563 205.83 Comparative example 3 0.568 207.31 Comparative example 4 0.534 190.07 Comparative example 5 0.577 207.43 Comparative example 6 0.609 209.59

According to the experimental results in Table 1, it can be seen that the crystallization temperature of the recovered polyethylene terephthalate added with the additive prepared by the present invention in Examples 1-3 is higher than that of the comparative example. Among them, Example 1 with an addition amount of 0.3% is the best. Compared with the pure recycled polyethylene terephthalate in Comparative Example 1, it shows that the additive synthesized in the present invention has the effect of significantly increasing the crystallization temperature of the recycled polyethylene terephthalate. In addition, adding too much or too little additives will adversely affect the intrinsic viscosity and crystallization temperature of recycled polyethylene terephthalate.

The additives prepared by the present invention are synthesized through chemical reactions, so that each chain segment can play a role at the same time, which can maximize the intrinsic viscosity and crystallization temperature of the recycled polyethylene terephthalate. Comparative Examples 2-5 are only a single raw material or a simple mixing of raw materials, and no chemical reaction is carried out, so the above effects cannot be fully exerted. Among them, the terephthalic acid added in Comparative Example 2 and the serine added in Comparative Example 3 can only serve as heterogeneous nucleating agents to increase the crystallization temperature of recycled polyethylene terephthalate, but their effects are limited. In addition, since the two raw materials have carboxyl functional groups, they can chemically react with the hydroxyl groups on their molecular chains during melt processing with recycled polyethylene terephthalate, thus slightly contributing to the increase in intrinsic viscosity. The sodium hydroxide added in Comparative Example 4 has no significant effect on the crystallization temperature and intrinsic viscosity of the system, so the improvement effect of Comparative Example 4 is only slightly better than that of Comparative Example 1. Comparative Example 5, in which the raw materials are simply mixed without chemical reaction, does not generate beneficial functional groups, so its improvement effect is only better than Comparative Examples 2-4 in which a single component is added. In contrast, the intermediate product added in Comparative Example 6 and the intermediate product in the simple mixture of sodium hydroxide can be used as a base for recycling polyethylene terephthalate epitaxial crystallization, thus increasing the crystallization temperature, but its There is a lack of chemical nucleation, so the crystallization temperature still has a certain gap compared with each embodiment. In addition, since the molecular chain of the intermediate product also contains carboxyl functional groups, it can chemically react with the hydroxyl groups on the molecular chain when it is melted with recycled polyethylene terephthalate, thus contributing to the improvement of its intrinsic viscosity.

Therefore, the green-source recycled polyethylene terephthalate auxiliary provided by the present invention can exert beneficial effects, thereby increasing its crystallization temperature and intrinsic viscosity, which is beneficial to the mechanical recycling of polyethylene terephthalate. The development of the industry has very important practical significance.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included in the scope of the present invention. .

Claims (5)

1. The synthesis and application of the recycled polyethylene terephthalate auxiliary agent from a green source are characterized in that the molecular structure is as follows:

2. the synthesis and application of a recycled polyethylene terephthalate auxiliary agent of green origin according to claim 1, characterized in that the preparation method comprises the following steps:

7.9 g terephthalic acid and 10 g serine are dissolved in 200 mL of N, N-dimethylformamide solution, 0.2 g methanesulfonic acid is added, the mixture is stirred at 120 ℃ by using an electric stirrer at 800 rpm for 8 h, after the reaction is finished, 350 mL of N, N-dimethylformamide solution is used for washing the obtained solid, and the obtained solid is dried at 80 ℃ until the weight is constant, thus obtaining an intermediate product A. Placing 8.5 g intermediate A and 2 g sodium hydroxide into 200 mL deionized water, stirring at 80 ℃ with an electric stirrer at 800 rpm for 6 h, washing the obtained solid with acetone and deionized water in sequence to be neutral, and drying at 80 ℃ to constant weight to obtain the recycled polyethylene terephthalate auxiliary agent with a green source.

3. Use of a recycled polyethylene terephthalate auxiliary of green origin according to claim 1 or 2 in the recycling of polyethylene terephthalate.

4. Use of a recycled polyethylene terephthalate auxiliary from green sources according to claim 3, characterized in that: the dosage of the recycled polyethylene terephthalate auxiliary agent from the green source is 0.1-1% of the mass of the recycled polyethylene terephthalate.

5. Use of a recycled polyethylene terephthalate auxiliary from green sources according to claim 3, characterized in that: the dosage of the recycled polyethylene terephthalate auxiliary agent with the green source is 0.3 percent of the mass of the recycled polyethylene terephthalate.