Preparation method and application of bio-based zinc adenine salt environment-friendly PVC heat stabilizer

Abstract

The invention discloses a preparation method and application of a bio-based zinc adenine salt environment-friendly PVC heat stabilizer, and belongs to the field of fine chemical synthesis and plastic additive application. The nitrogen-containing organic metal heat stabilizer adenine zinc complex is prepared by taking adenine and zinc acetate as main raw materials through a one-step method. The method is simple and environment-friendly in preparation process, easily available in raw materials and suitable for industrial production. The prepared heat stabilizer zinc adenine is used as a heat stabilizer, can effectively absorb hydrogen chloride generated by PVC thermal decomposition, and can replace allyl chlorine atoms, so that the heat stability of a PVC product is improved, PVC has more excellent heat stability, and the heat stabilizer is expected to replace a traditional commercially available heat stabilizer.

Description

Technical Field

[0001] The present invention relates to a preparation method and application of a bio-based zinc adenine salt environmental protection PVC heat stabilizer, belonging to the fields of fine chemical synthesis and plastic additive application. Background Art

[0002] Polyvinyl chloride (PVC) is the third most produced general-purpose plastic after polyethylene and polypropylene. Due to its low price, chemical resistance, biocompatibility, good mechanical properties and other advantages, it is widely used in various fields such as chemical processes, construction, packaging materials, and electronic components. However, due to its structural defects, it is prone to thermal decomposition to release HCl and form a conjugated olefin structure, resulting in a significant decline in its performance and unacceptable discoloration. Therefore, heat stabilizers are one of the indispensable additives in the processing of PVC products. Common PVC heat stabilizers include lead salts, organotin compounds, organoantimony compounds, calcium zinc compounds, rare earth compounds, etc. Lead salt heat stabilizers are toxic and have been strictly restricted by the European Union; organotin heat stabilizers are usually used in rigid high-transparency products, but they are expensive and have a small usage amount; organoantimony heat stabilizers have poor transparency and are extremely prone to precipitation, so they are also used less. Currently, PVC heat stabilizers are mainly developing towards non-toxic, efficient, and environmentally friendly directions. Among them, environmentally friendly calcium zinc heat stabilizers are widely used due to their low cost, and organonitrogen-containing heat stabilizers have developed rapidly in recent years. Because of the characteristics of nitrogen atoms, they have good coordination ability and the ability to combine with HCl. Therefore, combining the characteristics of nitrogen-containing heat stabilizers with calcium zinc heat stabilizers, the obtained nitrogen-containing organometallic heat stabilizers have good research significance and development potential. For example, zinc semicarbazide pyrimidine maleamate reported in the prior art (Design of Nitrogen-containing Organic Thermal Stabilizer with Resistance to “Zinc Burning” and Its Application [J]. Vinyl and Additive Technology. 2023, 29(1): 66-75.), zinc uracil salt PVC heat stabilizer disclosed in China and patent literature (CN103183644A), etc. However, although these nitrogen-containing calcium zinc heat stabilizers have a certain effect on improving thermal stability, they still do not have long-term thermal stability and good initial whiteness retention. As the main heat stabilizer, they still need to be further improved. Summary of the Invention

[0003] [Technical Problem]

[0004] The present invention aims to provide a preparation method and application of a bio-based adenine zinc salt environmentally friendly PVC heat stabilizer, and develop a heat stabilizer with excellent performance, environmental protection and non-toxic characteristics, and its process is simple and suitable for industrial production.

[0005] For the bio-based adenine zinc salt environmentally friendly PVC heat stabilizer of the present invention, the adenine molecular structure includes an amino group and a purine ring, which can undergo a coordination reaction with some metal ions to prepare an adenine zinc salt heat stabilizer; moreover, the structure contains abundant nitrogen atoms, and since the nitrogen atoms have lone pair electrons, they can absorb hydrogen chloride or replace unstable allyl chloride, and complex with Lewis acid ZnCl2, thereby inhibiting the catalytic effect of ZnCl2 on the thermal degradation of PVC, while delaying the generation of a large number of conjugated double bonds, improving the thermal stability and initial whiteness of PVC, and finally enabling PVC to have long-term thermal stability and good initial whiteness retention effect. Therefore, the adenine zinc prepared from adenine and zinc acetate can be used as a main heat stabilizer, and its heat stability performance can be improved in multiple heat stabilization mechanisms.

[0006] [Technical Solution]

[0007] The present invention provides a bio-based adenine zinc salt environmentally friendly PVC heat stabilizer with the structure shown in Formula I:

[0008]

[0009] The present invention also provides the application of the adenine zinc salt with the structure shown in Formula I in the preparation of an environmentally friendly PVC heat stabilizer.

[0010] The present invention also provides the application of the above bio-based adenine zinc salt environmentally friendly PVC heat stabilizer in the preparation of flexible PVC materials.

[0011] In one embodiment of the present invention, during the application process, the above bio-based adenine zinc salt environmentally friendly PVC heat stabilizer is used as the main heat stabilizer.

[0012] The present invention also provides a PVC formulation, which, by weight, comprises the following components: 50 - 60 parts of PVC powder, 50 - 60 parts of PVC paste, and 3 - 3.5 parts of the above bio-based adenine zinc salt environmentally friendly PVC heat stabilizer.

[0013] In one embodiment of the present invention, the formulation further comprises zinc stearate and / or calcium stearate.

[0014] In one embodiment of the present invention, the formulation further comprises 30 - 50 parts of other additives.

[0015] In one embodiment of the present invention, the other additives include one or more of diisooctyl phthalate, dioctyl terephthalate, pentaerythritol, and liquid paraffin.

[0016] The present invention also provides a preparation method of a bio-based zinc adenine salt environmentally friendly PVC heat stabilizer with the structure shown in Formula I. This method uses adenine, zinc acetate, and potassium hydroxide (KOH) as raw materials, and obtains the adenine zinc environmentally friendly PVC heat stabilizer through a one-step metathesis reaction.

[0017] In one embodiment of the present invention, the synthetic route of the bio-based zinc adenine salt environmentally friendly PVC heat stabilizer is as follows:

[0018]

[0019] In one embodiment of the present invention, the preparation method includes the following steps: The specific steps are as follows:

[0020] Mix adenine, KOH with a solvent to obtain a mixed solution, and then slowly drip the zinc acetate solution into the mixed solution, and heat and react for a period of time; after the reaction is completed, filter by suction, collect the precipitate, wash, and dry.

[0021] In one embodiment of the present invention, the solvent is any one or several of water, ethanol, and methanol.

[0022] In one embodiment of the present invention, the solvent is a mixed solution of methanol and water, and the volume ratio of methanol to water is 1-2:1.

[0023] In one embodiment of the present invention, in the metathesis reaction, the molar ratio of adenine to zinc acetate is 1.5-2:1.

[0024] In one embodiment of the present invention, the molar ratio of adenine to KOH is 0.8-1.5:1.

[0025] In one embodiment of the present invention, the dosage of the solvent is 15-20 mL / mmol adenine.

[0026] In one embodiment of the present invention, the concentration of the zinc acetate solution is 25-45 g / L.

[0027] In one embodiment of the present invention, the temperature of the metathesis reaction is 90-120 °C, and the reaction time is 1-3 h.

[0028] In one embodiment of the present invention, during the suction filtration process, the pressure of the suction pump is 0.08-0.1 MPa.

[0029] In one embodiment of the present invention, the collected precipitate is washed with a solvent, and the solvent is any one or several of water, ethanol, and methanol.

[0030] In one embodiment of the present invention, drying is carried out in an oven at a temperature of 60-80°C for 6-8 hours.

[0031] Both the raw materials and products of the present invention are widely sourced, non-toxic and environmentally friendly. There is no need to use toxic solvents during the reaction process, which is environmentally friendly. The reaction process flow is simple and suitable for industrial development.

[0032] [Beneficial effects]

[0033] The present invention uses adenine and zinc acetate as the main raw materials, and through a one-step metathesis reaction, the nitrogen atoms on the purine ring are coordinated with metal ions. The zinc adeninate prepared by this method is a white powder with good compatibility with PVC. Compared with zinc stearate and calcium stearate applied in PVC, it endows PVC with better thermal stability. The environmentally friendly thermal stabilizer of natural bio-based zinc salt prepared in the present invention is expected to replace the traditional zinc stearate thermal stabilizer. Description of the drawings

[0034] Figure 1 It is the infrared spectrum diagram of adenine and zinc adeninate in Example 1.

[0035] Figure 2 It is the conductivity test diagram of the blank sample (without adding thermal stabilizer) and PVC samples respectively added with zinc stearate, calcium stearate and zinc adeninate.

[0036] Figure 3 It is the thermogravimetric test diagram of the blank sample (without adding thermal stabilizer) and PVC samples respectively added with zinc stearate, calcium stearate and zinc adeninate.

[0037] Figure 4 It is the hot oven aging test diagram of the blank sample (without adding thermal stabilizer) and PVC samples respectively added with zinc stearate, calcium stearate and zinc adeninate. Detailed implementation manners

[0038] Preparation of zinc adeninate thermal stabilizer in Example 1

[0039] Adenine, KOH and deionized water are added into a flask, where the molar ratio of KOH to adenine is 1:1, and 15 mL of deionized water is added per millimole of adenine. The mixture is continuously refluxed and stirred at 110°C until the solution becomes clear and transparent. Then, an aqueous zinc acetate solution with a mass concentration of 45 g / L is added, and the molar ratio of adenine to zinc acetate is 2:1. The reaction is carried out at 110°C for 2 hours; after the reaction is completed, filtration is carried out, and then the precipitate is washed with water and dried in an 80°C oven for 8 hours to obtain the final product, zinc adeninate thermal stabilizer.

[0040] Preparation of zinc adeninate thermal stabilizer in Example 2

[0041] Add adenine, KOH, and anhydrous methanol into a flask. The molar ratio of KOH to adenine is 1.2:1, and 20 mL of anhydrous methanol is added per millimole of adenine. Continuously reflux and stir at 100 °C until the solution becomes clear and transparent. Then add a zinc acetate methanol solution with a mass concentration of 25 g / L. The molar ratio of adenine to zinc acetate is 1.5:1, and react at 100 °C for 2.5 h. After the reaction, perform suction filtration, wash the precipitate with methanol, and then place it in an oven at 60 °C to dry for 10 h to obtain the final product, zinc adenine heat stabilizer.

[0042] Preparation of Zinc Adenine Heat Stabilizer in Example 3

[0043] Add adenine, KOH, and a mixed solution of methanol and water (volume ratio of methanol to water is 1:1) into a flask. The molar ratio of KOH to adenine is 1.5:1, and 15 mL of this anhydrous methanol and water mixed solution is added per millimole of adenine. Continuously reflux and stir at 120 °C until the solution becomes clear and transparent. Then add an aqueous zinc acetate solution with a mass concentration of 45 g / L. The molar ratio of adenine to zinc acetate is 1.5:1, and react at 120 °C for 1.5 h. After the reaction, perform suction filtration, wash the precipitate with water, and then place it in an oven at 70 °C to dry for 9 h to obtain the final product, zinc adenine heat stabilizer.

[0044] Preparation of Zinc Adenine Heat Stabilizer in Example 4

[0045] Add adenine, KOH, and a mixed solution of methanol and water (volume ratio of methanol to water is 2:1) into a flask. The molar ratio of KOH to adenine is 0.8:1, and 20 mL of this anhydrous methanol and water mixed solution is added per millimole of adenine. Continuously reflux and stir at 90 °C until the solution becomes clear and transparent. Then add a zinc acetate methanol solution with a mass concentration of 25 g / L. The molar ratio of adenine to zinc acetate is 1.7:1, and react at 90 °C for 3 h. After the reaction, perform suction filtration, wash the precipitate with methanol, and then place it in an oven at 80 °C to dry for 8 h to obtain the final product, zinc adenine heat stabilizer.

[0046] Perform infrared spectrum tests on the raw material adenine and the final product zinc adenine in Example 1. The test results are as Figure 1 shown. Figure 1 The infrared curves of zinc adenine and adenine are shown from top to bottom in -1 ., 3122.2 cm -1 . represent the stretching vibration peaks of the amino group (-NH2) in the adenine structure, and 1674.4 cm -1 . is its bending vibration peak. In the infrared spectrum of zinc adenine, compared with the adenine spectrum, at 3425.6 cm -1A broad peak representing the hydroxyl group (-OH) appears at [specific location], and originally, the peak of the amino group (-NH₂) of adenine at 1674.4 cm -1 shifts to a lower wavenumber, moving to 1629.2 cm -1 , which proves that the hydroxyl group and the amino group coordinate with zinc ions, indicating the successful preparation of the final product.

[0047] Application Example 1: Preparation of PVC film using zinc adenine heat stabilizer

[0048] Add 50 parts of PVC powder, 50 parts of PVC paste, 50 parts of dioctyl phthalate (DOP), and 3 parts of the zinc adenine heat stabilizer prepared in Example 1 into a beaker, stir with a glass rod until it becomes a viscous paste, then pour it onto a long glass plate and spread it into a film about 1 mm thick. Then place it in an oven at 120 °C and plasticize it for 30 - 50 minutes to obtain a PVC film containing the heat stabilizer.

[0049] Control sample: Using the same steps as above, prepare a blank sample without adding a heat stabilizer; referring to the above process, replace the zinc adenine heat stabilizer with an equal amount of zinc stearate and calcium stearate respectively to obtain the corresponding PVC control samples of zinc stearate and calcium stearate.

[0050] Conduct heat oven aging test, conductivity test, and thermogravimetric test on the PVC samples stabilized by the heat stabilizer of the present invention and the commercial heat stabilizers zinc stearate and calcium stearate. The specific properties are as Figure 2 、 3 shown in Figure 4.

[0051] Conduct conductivity test on the PVC samples prepared by the product of the present invention and the PVC control samples. The specific test results are as Figure 2 shown; the four curves are the conductivity curves of the PVC samples stabilized by zinc stearate, the blank sample, calcium stearate, and zinc adenine respectively. The conductivity curve reflects two time periods, namely the induction time T1 and the stabilization time T2. The induction time refers to the time when the conductivity starts to increase significantly, and the stabilization time is the time when the conductivity increases by 50 μS / cm. The curves of the PVC samples stabilized by zinc adenine have the longest two time periods and are significantly longer than the other three control samples, indicating that using zinc adenine as the main heat stabilizer can effectively delay the release of HCl, thereby inhibiting its autocatalytic effect on PVC.

[0052] Conduct thermogravimetric test on the PVC samples prepared by the product of the present invention and the PVC control samples. The specific thermogravimetric test results are as Figure 3As shown, the PVC stabilized by zinc adenine starts the first-stage weight loss at 220°C, with the weight loss rate in the first stage being 71.14%. It starts the second-stage weight loss at 380°C, where the weight loss rate in the second stage is 15.7%. The weight loss rates in both stages are the lowest compared to zinc stearate, calcium stearate, and the blank sample, and it has the highest carbon residue rate. Therefore, the zinc adenine heat stabilizer shows better thermal stability than other samples and can inhibit the thermal degradation of PVC.

[0053] According to the formula in Application Example 1, mix the PVC resin, DOP, and heat stabilizer (selecting the zinc adenine heat stabilizer, zinc stearate, or calcium stearate prepared in Example 1 respectively) and stir evenly, then spread them flat on a smooth glass plate; transfer them to an oven at 120°C for plasticization for 20 minutes, and after cooling, cut them into small square pieces of 1×1 cm. Place the PVC small square pieces in the aluminum foil inside an enamel tray, put them into an oven at 180°C, take samples every 10 minutes, and observe the color change of the PVC sample. The results of the heat oven aging test are as Figure 4 shown.

[0054] From Figure 4 it can be seen that the PVC sample stabilized by zinc adenine can maintain the thermal stability time up to 120 minutes, and it starts to turn red only at 50 minutes, with good initial whiteness. Compared with the zinc stearate heat stabilizer, the time is extended by 100 minutes, and the thermal stability time of the blank sample is significantly improved. It shows that the zinc adenine of the present invention is a long-term heat stabilizer, which can effectively extend the thermal stability time of PVC and has the potential to be compounded with other additives.

[0055] Aging test comparison of other nitrogen-containing organic zinc heat stabilizers in Comparative Example 1

[0056] Referring to the formula in Application Example 1, quantitatively replace the heat stabilizer with other nitrogen-containing organic zinc heat stabilizers shown in Table 1 to obtain PVC small square pieces of 1×1 cm. Place the PVC small square pieces in the aluminum foil inside an enamel tray, put them into an oven at 180°C, take samples every 10 minutes, and observe the color change of the PVC specimen.

[0057] The obtained results of the heat oven aging test are shown in Table 1.

[0058] Table 1

[0059] Heat stabilizer Heat oven aging test time (min) Adenine zinc (Example 1) 120 Uracil zinc salt <70 Semicarbazide uracil maleamic acid zinc 60 Tryptophan zinc 80 Bis(imidazole)-bis(ortho-hydroxybenzoic acid)-zinc <100

[0060] Note: The heat oven aging test time refers to the time corresponding to the PVC specimen turning "brown-black".

[0061] Zinc uracil salt was prepared referring to CN103183644A.

[0062] Semicarbazide pyrimidine maleamic acid zinc was prepared with reference to the existing literature "Design of Nitrogen-containing Organic Thermal Stabilizer with Resistance to “Zinc Burning” and Its Application [J]. Vinyl and Additive Technology. 2023, 29(1): 66-75."

[0063] Bis(imidazole)-bis(ortho-hydroxybenzoic acid)-zinc was prepared with reference to CN103183690A.

[0064] The embodiments provided above are not intended to limit the scope covered by the present invention, nor are the described steps intended to limit the order of their execution. Obvious improvements made by those skilled in the art in combination with the existing well-known general knowledge also fall within the protection scope defined by the claims of the present invention.

Claims

1. Bio-based zinc adenine salt environmental protection PVC heat stabilizer with the structure shown in Formula I:

2. The preparation method of the bio-based zinc adenine salt environmental protection PVC heat stabilizer according to claim 1, characterized in that, Using adenine, zinc acetate, and potassium hydroxide as raw materials, this bio-based zinc adenine environmental protection PVC heat stabilizer is obtained through a one-step metathesis reaction.

3. The preparation method according to claim 2, wherein The reaction route of the one-step metathesis reaction is as follows:

4. The preparation method according to claim 2 or 3, characterized in that, The preparation method includes the following steps: The specific steps are as follows: Mix adenine, potassium hydroxide with a solvent to obtain a mixed solution, and then slowly drop the zinc acetate solution into the mixed solution, and heat and react for a period of time; after the reaction, filter by suction, collect the precipitate, wash, and dry.

5. The preparation method according to claim 4, characterized in that, The solvent is any one or several of water, ethanol, and methanol; the molar ratio of adenine to zinc acetate is 1.5 - 2:1, the molar ratio of adenine to potassium hydroxide is 0.8 - 1.5:1, the dosage of the solvent is 15 - 20 mL / mmol adenine, the concentration of the zinc acetate solution is 25 - 45 g / L, the reaction temperature is 90 - 120 °C, and the reaction time is 1 - 3 h.

6. The application of an adenine zinc salt in the preparation of an environment-friendly PVC heat stabilizer, characterized in that, The structure of the adenine zinc salt is 7. Application of the bio-based zinc adenine salt environmental protection PVC heat stabilizer according to claim 1 in the preparation of flexible PVC materials.

8. A PVC formulation, characterized in that, By weight, the formulation contains the following components: 50 - 60 parts of PVC powder, 50 - 60 parts of PVC paste, and 3 - 3.5 parts of the bio-based zinc adenine salt environmental protection PVC heat stabilizer according to claim 1.

9. The PVC formulation according to claim 8, wherein, The formulation further contains zinc stearate and / or calcium stearate.

10. The PVC formulation according to claim 8, characterized in that, The formulation further contains 30 - 50 parts of other additives, and the other additives include one or more of diisooctyl phthalate, dioctyl terephthalate, pentaerythritol, and liquid paraffin.

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