A composite heat stabilizer for PVC and its preparation method

Abstract

The present invention provides a composite heat stabilizer for PVC and a preparation method thereof. The composite heat stabilizer for PVC comprises the following raw materials in parts by weight: 30 - 50 parts of zinc stearate; 40 - 60 parts of calcium stearate; 1 - 5 parts of a ketone compound; and the ketone compound has a structure shown in formula (Ⅰ). The composite heat stabilizer for PVC of the present invention has good heat stabilization effect and good long-term heat stability, and can effectively inhibit problems such as "zinc burning".

Description

Technical Field

[0001] The present invention relates to the field of polyvinyl chloride processing, and particularly to a composite heat stabilizer for PVC and a preparation method thereof. Background Art

[0002] Polyvinyl chloride (PVC) is the second largest general-purpose resin after polyethylene. Due to its advantages such as low price and excellent performance, it is widely used in fields such as films and pipes. However, when the PVC molecular chain is above 110 °C, HCl will be released, and the released HCl will accelerate the thermal degradation of PVC, resulting in a darker color and poorer mechanical properties of PVC products. Therefore, a heat stabilizer needs to be added during the processing of PVC products to prevent thermal degradation.

[0003] Currently, metal soap heat stabilizers, especially calcium-zinc heat stabilizers, have become the mainstream products in PVC heat stabilizers due to their advantages such as non-toxicity, environmental protection, and moderate price. However, zinc salts have a strong ability to inhibit the discoloration of PVC, so the initial color of the product is good. But later, because the generated ZnCl2 has a strong catalytic effect on HCl removal, its long-term heat resistance is poor, and it is prone to severe discoloration and zinc burning phenomenon in the later stage, making the PVC product have black spots or turn completely black. Therefore, the long-term thermal stability is poor. Summary of the Invention

[0004] The purpose of the present invention is to provide a composite heat stabilizer for PVC to solve the problem of poor long-term thermal stability of the existing composite heat stabilizer for PVC.

[0005] To solve the above technical problems, the technical solution of the present invention is as follows:

[0006] A composite heat stabilizer for PVC, comprising the following raw materials in parts by weight:

[0007] 30 - 50 parts of zinc stearate; 40 - 60 parts of calcium stearate; 1 - 5 parts of a ketone compound;

[0008] Among them, the ketone compound has a structure shown in formula (Ⅰ):

[0009]

[0010]

[0011] The CAS number of the ketone compound is 105685 - 96 - 9.

[0012] Preferably, the composite heat stabilizer for PVC further comprises an auxiliary metal salt; the dosage of the auxiliary metal salt is 10 - 15 parts.

[0013] Preferably, the auxiliary metal salt is obtained by reacting an organic acid having the structure shown in formula (Ⅱ) with sodium hydroxide, and then reacting with calcium chloride and zinc chloride;

[0014]

[0015] The CAS number of the organic acid is 128043-82-3.

[0016] The present invention also provides a preparation method of the composite heat stabilizer for PVC, comprising the following steps: uniformly mixing zinc stearate, calcium stearate and a ketone compound to obtain the product.

[0017] Preferably, the preparation method of the composite heat stabilizer for PVC further comprises the step of adding an auxiliary metal salt thereto, and the auxiliary metal salt is obtained by the following method:

[0018] (1) Take a sodium hydroxide solution, add an organic acid having the structure shown in formula (Ⅱ) thereto, and stir and react at 25-45 °C for 1-3 h to obtain a solution containing sodium organic acid;

[0019]

[0020] (2) Add calcium chloride and zinc chloride to the solution containing sodium organic acid obtained in step (1), and react at 25-45 °C for 2-5 h to obtain the auxiliary metal salt.

[0021] Preferably, in step (1), the concentration of the sodium hydroxide solution is 8-10 mol / L.

[0022] Preferably, in step (1), the volume ratio of the organic acid to the sodium hydroxide solution is 1:(10-20).

[0023] Preferably, the weight ratio of the organic acid, the calcium chloride and the zinc chloride is 1:(1-3):(0.5-1.0).

[0024] Preferably, in step (2), it specifically comprises the following steps: first add zinc chloride to the solution containing sodium organic acid obtained in step (1), and stir and react for 1-2 h; then adjust the pH value of the reaction solution to 7-8, add calcium chloride thereto, and stir and react for 1-2 h.

[0025] Preferably, in step (2), it further comprises the steps of filtering, washing and drying the obtained auxiliary metal salt.

[0026] The above solution of the present invention has at least the following beneficial effects:

[0027] (1) The composite heat stabilizer for PVC of the present invention comprises the following raw materials in parts by weight: 30 - 50 parts of zinc stearate; 40 - 60 parts of calcium stearate; 1 - 5 parts of a ketone compound; the ketone compound has a structure shown in formula (Ⅰ). The composite heat stabilizer for PVC has good heat stabilization effect and good long-term heat stability, and can effectively solve problems such as "zinc burning".

[0028] Among them, the zinc element of the zinc stearate has electronegativity and relatively strong electron-withdrawing ability, and can form a coordination bond with the unstable chloride ions in the PVC molecular chain, thereby preventing PVC from releasing HCl. And the calcium element in the calcium stearate has relatively small electronegativity and weak electron-withdrawing ability, but can form a synergistic effect with the zinc stearate to extend the long-term heat stability of the composite heat stabilizer for PVC. And for the ketone compound, on the one hand, the imidazole group and carbon-alkoxy group it has can undergo nucleophilic substitution reactions with the unstable chlorine atoms on the PVC main chain to displace the unstable chlorine atoms. And the nitrogen atom on the imidazole group has relatively strong proton-binding ability under acidic conditions, can neutralize the HCl released by the PVC molecular chain, and inhibit its catalytic effect on the thermal degradation of PVC. On the other hand, the long-chain structure it has has good compatibility with the PVC main chain, and is not easy to form two phases after being mixed with the PVC resin in the molten state, so that the PVC product has relatively high transparency and also helps to exert the heat stability performance.

[0029] (2) For the composite heat stabilizer for PVC of the present invention, the auxiliary metal salt is obtained by reacting an organic acid having a structure shown in formula (Ⅱ) with sodium hydroxide, and then reacting with calcium chloride and zinc chloride. The auxiliary metal salt has a similar structure to the ketone compound, and the two have good compatibility. More importantly, the auxiliary metal salt can undergo a displacement reaction with the HCl released from the PVC molecular chain, and has a cyclic tri-ketone structure. The conjugated system formed by it can capture free radicals in the degradation process through electron delocalization, interrupt the free radical chain reaction, and effectively complex the zinc ions in the ZnCl2 generated by the displacement reaction, reduce the catalytic activity of the zinc ions, inhibit the "zinc burning" phenomenon, and improve the long-term heat stability of the heat stabilizer. Detailed implementation manners

[0030] In each embodiment of the present invention, those not specified in specific conditions are carried out according to conventional conditions or conditions recommended by the manufacturer. For the reagents or instruments not specified in the manufacturer, they are all conventional products that can be obtained through commercial purchase. Raw materials from different manufacturers and models do not affect the implementation of the technical solution of the present invention and the realization of the technical effects.

[0031] In the following embodiments, the ketone compound has a structure shown in formula (Ⅰ):

[0032]

[0033] The organic acid has a structure as shown in formula (II):

[0034]

[0035] Example 1

[0036] The composite heat stabilizer for PVC in this example comprises raw materials in the following parts by weight:

[0037] 30 parts of zinc stearate; 50 parts of calcium stearate; 1 part of a ketone compound; 12 parts of an auxiliary metal salt;

[0038] Among them, the auxiliary metal salt is obtained by reacting an organic acid having a structure as shown in formula (II) with sodium hydroxide, and then reacting with calcium chloride and zinc chloride.

[0039] The preparation method of the composite heat stabilizer for PVC described in this example comprises the following steps: Mix zinc stearate, calcium stearate, the ketone compound, and the auxiliary metal salt evenly to obtain it.

[0040] Among them, the auxiliary metal salt is obtained by the following method:

[0041] (1) Take a sodium hydroxide solution, add an organic acid having a structure as shown in formula (II) thereto, and stir and react at 25 °C for 3 h to obtain a solution containing sodium organic acid;

[0042] Among them, the concentration of the sodium hydroxide solution is 10 mol / L; the volume ratio of the organic acid to the sodium hydroxide solution is 1:20.

[0043] (2) First, add zinc chloride to the solution containing sodium organic acid obtained in step (1), stir and react for 1 h; then adjust the pH value of the reaction solution to 7.5, add calcium chloride thereto, stir and react for 2 h, filter, wash, and dry the obtained auxiliary metal salt to obtain it.

[0044] Among them, the weight ratio of the organic acid, the calcium chloride, and the zinc chloride is 1:2:0.5.

[0045] Example 2

[0046] The composite heat stabilizer for PVC in this example comprises raw materials in the following parts by weight:

[0047] 50 parts of zinc stearate; 60 parts of calcium stearate; 3 parts of a ketone compound; 15 parts of an auxiliary metal salt;

[0048] Among them, the auxiliary metal salt is obtained by reacting an organic acid having a structure as shown in formula (II) with sodium hydroxide, and then reacting with calcium chloride and zinc chloride.

[0049] The preparation method of the composite heat stabilizer for PVC described in this embodiment includes the following steps: uniformly mix zinc stearate, calcium stearate, a ketone compound, and an auxiliary metal salt to obtain it.

[0050] Among them, the auxiliary metal salt is obtained through the following method:

[0051] (1) Take a sodium hydroxide solution, add an organic acid having the structure shown in formula (Ⅱ) thereto, and stir and react at 45 °C for 2 h to obtain a solution containing sodium organic acid;

[0052] Among them, the concentration of the sodium hydroxide solution is 8 mol / L; the volume ratio of the organic acid to the sodium hydroxide solution is 1:15.

[0053] (2) First, add zinc chloride to the solution containing sodium organic acid obtained in step (1), stir and react for 2 h; then adjust the pH value of the reaction solution to 8, add calcium chloride thereto, stir and react for 1 h, and filter, wash, and dry the obtained auxiliary metal salt to obtain it.

[0054] Among them, the weight ratio of the organic acid, the calcium chloride, and the zinc chloride is 1:3:1.0.

[0055] Example 3

[0056] The composite heat stabilizer for PVC in this embodiment includes the following raw materials in parts by weight:

[0057] 40 parts of zinc stearate; 40 parts of calcium stearate; 5 parts of a ketone compound; 10 parts of an auxiliary metal salt;

[0058] Among them, the auxiliary metal salt is obtained by reacting an organic acid having the structure shown in formula (Ⅱ) with sodium hydroxide, and then reacting with calcium chloride and zinc chloride.

[0059] The preparation method of the composite heat stabilizer for PVC described in this embodiment includes the following steps: uniformly mix zinc stearate, calcium stearate, a ketone compound, and an auxiliary metal salt to obtain it.

[0060] Among them, the auxiliary metal salt is obtained through the following method:

[0061] (1) Take a sodium hydroxide solution, add an organic acid having the structure shown in formula (Ⅱ) thereto, and stir and react at 35 °C for 1 h to obtain a solution containing sodium organic acid;

[0062] Among them, the concentration of the sodium hydroxide solution is 9 mol / L; the volume ratio of the organic acid to the sodium hydroxide solution is 1:10.

[0063] (2) First, add zinc chloride to the solution containing sodium organic acid obtained in step (1), and stir and react for 2 h; then adjust the pH value of the reaction solution to 7, add calcium chloride thereto, stir and react for 2 h, and filter, wash, and dry the obtained auxiliary metal salt to obtain the product.

[0064] Among them, the weight ratio of the organic acid, the calcium chloride, and the zinc chloride is 1:1:0.8.

[0065] Example 4

[0066] The composite heat stabilizer for PVC in this example comprises the following raw materials in parts by weight:

[0067] 35 parts of zinc stearate; 55 parts of calcium stearate; 5 parts of ketone compound; 15 parts of auxiliary metal salt;

[0068] Among them, the auxiliary metal salt is obtained by reacting an organic acid having the structure shown in formula (Ⅱ) with sodium hydroxide, and then reacting with calcium chloride and zinc chloride.

[0069] The preparation method of the composite heat stabilizer for PVC in this example comprises the following steps: uniformly mix zinc stearate, calcium stearate, ketone compound, and auxiliary metal salt to obtain the product.

[0070] Among them, the auxiliary metal salt is obtained by the following method:

[0071] (1) Take a sodium hydroxide solution, add an organic acid having the structure shown in formula (Ⅱ) thereto, and stir and react at 30 °C for 3 h to obtain a solution containing sodium organic acid;

[0072] Among them, the concentration of the sodium hydroxide solution is 10 mol / L; the volume ratio of the organic acid to the sodium hydroxide solution is 1:20.

[0073] (2) First, add zinc chloride to the solution containing sodium organic acid obtained in step (1), and stir and react for 2 h; then adjust the pH value of the reaction solution to 7, add calcium chloride thereto, stir and react for 2 h, and filter, wash, and dry the obtained auxiliary metal salt to obtain the product.

[0074] Among them, the weight ratio of the organic acid, the calcium chloride, and the zinc chloride is 1:2:0.6.

[0075] Comparative Example 1

[0076] This comparative example has the same raw materials and preparation method as the composite heat stabilizer for PVC in Example 4, and the only difference is that it does not include the auxiliary metal salt.

[0077] Comparative Example 2

[0078] This comparative example has the same raw materials and preparation method as the composite heat stabilizer for PVC in Example 4, with the only difference being that it does not include the ketone compound.

[0079] Comparative Example 3

[0080] This comparative example has the same raw materials as the composite heat stabilizer for PVC in Example 4, with the only difference being that the preparation method of the auxiliary metal salt is different. The auxiliary metal salt is obtained by reacting an organic acid having the structure shown in formula (Ⅱ) with sodium hydroxide and then reacting with calcium chloride.

[0081] Step (2) of this comparative example is specifically as follows: adjust the pH value of the solution containing sodium organic acid obtained in step (1) to 7, add calcium chloride thereto, stir and react for 2 h, and filter, wash, and dry the obtained auxiliary metal salt to obtain it.

[0082] Comparative Example 4

[0083] This comparative example has the same raw materials as the composite heat stabilizer for PVC in Example 4, with the only difference being that the preparation method of the auxiliary metal salt is different. The auxiliary metal salt is replaced with a product obtained by reacting stearic acid with sodium hydroxide and then reacting with zinc chloride and calcium chloride.

[0084] The auxiliary metal salt of this comparative example is obtained by the following method:

[0085] (1) Take a sodium hydroxide solution, add stearic acid thereto, and stir and react at 30 °C for 3 h to obtain a solution containing sodium organic acid;

[0086] Among them, the concentration of the sodium hydroxide solution is 10 mol / L; the volume ratio of the stearic acid to the sodium hydroxide solution is 1:20.

[0087] (2) First, add zinc chloride to the solution containing sodium organic acid obtained in step (1), stir and react for 2 h; then adjust the pH value of the reaction solution to 7, add calcium chloride thereto, stir and react for 2 h, and filter, wash, and dry the obtained auxiliary metal salt to obtain it.

[0088] Among them, the weight ratio of the stearic acid, the calcium chloride, and the zinc chloride is 1:2:0.6.

[0089] Comparative Example 5

[0090] This comparative example has the same raw materials and preparation method as the composite heat stabilizer for PVC in Example 4, with the only difference being that the ketone compound is replaced with 1-butylimidazolidine-2,4,5-trione.

[0091] The CAS number of 1-butylimidazolidine-2,4,5-trione is 40408-40-0 and it has the structure shown in formula (Ⅲ)

[0092]

[0093]

[0094] Comparative Example 6

[0095] This comparative example has the same raw materials and preparation method as the composite heat stabilizer for PVC in Example 4, and the only difference is that: the weight portion of the auxiliary metal salt is 20 parts.

[0096] Comparative Example 7

[0097] This comparative example has the same raw materials and preparation method as the composite heat stabilizer for PVC in Example 4, and the only difference is that: the weight portion of the ketone compound is 10 parts.

[0098] Comparative Example 8

[0099] This comparative example has the same raw materials and preparation method as the composite heat stabilizer for PVC in Example 4, and the only difference is that: it does not contain the ketone compound and the auxiliary metal salt.

[0100] Effect Experimental Example

[0101] To verify the technical effects of the preparation method of the composite heat stabilizer for PVC described in the present invention, the following tests were carried out:

[0102] The composite heat stabilizers for PVC were prepared by the methods in Examples 1 - 4 and Comparative Examples 1 - 8, and test specimens were prepared respectively according to the raw materials in the following weight portions:

[0103] 100 parts of PVC, 1.2 parts of the composite heat stabilizer for PVC, 1.0 part of ACR, 0.5 part of oxidized polyethylene wax.

[0104] The above raw materials were mixed evenly, placed on a two - roll plasticating mill with a roll temperature of 170 °C and a roll gap of 1 mm for plasticating for 5 min to obtain a sheet, which was cut into a size of 2 cm × 2 cm as a test specimen. According to the requirements of the GB / T7141 - 92 standard, the test specimen was placed in an aging oven for aging test at 190 ± 1 °C. The test specimen was taken out every 30 min, and the change of the yellowness value (Y) of the ASTM E313 standard was observed and recorded.

[0105] The experimental results are as follows:

[0106]

[0107]

[0108] According to the results of Examples 1-4 and Comparative Examples 1-8, the composite heat stabilizer for PVC of the present invention has good heat stabilization effect and good long-term heat stability, and can significantly inhibit the "zinc burning" phenomenon.

[0109] According to the results of Example 4 and Comparative Examples 1, 3, and 4, the addition of the auxiliary metal salt can significantly improve the heat stabilization effect of the composite heat stabilizer for PVC and delay the occurrence time of the "zinc burning" phenomenon. The product obtained by reacting a specific organic acid with a cyclic structure with sodium hydroxide and then reacting with calcium chloride can improve the heat stabilization effect of the composite heat stabilizer for PVC to a certain extent. However, compared with the auxiliary metal salt of Example 4, the heat stabilization effect is poor. The product prepared by the same method using stearic acid with a long-chain structure has little effect on improving the heat stabilization effect of the composite heat stabilizer for PVC.

[0110] According to the results of Example 4 and Comparative Examples 2 and 5, the addition of the ketone compound can significantly improve the heat stabilization effect of the composite heat stabilizer for PVC. However, for the ketone compound with a specific cyclic structure combined with a short chain, due to poor compatibility with the PVC system, although it can improve the heat stability to a certain extent, the yellowness value at 0 min is high, the initial coloring property is poor, and the long-term heat stability is not ideal enough.

[0111] According to the results of Example 4 and Comparative Examples 6 and 7, excessive amounts of the auxiliary metal salt and the ketone compound will have an adverse effect on the heat stabilization effect. In particular, when the ketone compound is in excess, it has a greater impact on the long-term heat stability effect.

[0112] According to the results of Example 4 and Comparative Examples 1, 2, and 8, there is a synergistic effect between the auxiliary metal salt and the ketone compound in improving the long-term heat stability of PVC.

[0113] It is known by common technical knowledge that the present invention can be implemented by other embodiments that do not depart from its spiritual essence or essential features. Therefore, the above-disclosed embodiments are illustrative in all aspects and are not the only ones. All changes within the scope of the present invention or within the scope equivalent to the present invention are encompassed by the present invention.

Claims

1. A composite heat stabilizer for PVC, characterized in that: The invention comprises the following raw materials in parts by weight: 30-50 parts of zinc stearate; 40-60 parts of calcium stearate; 1-5 parts of ketone compound; 10-15 parts of auxiliary metal salt; Wherein, the ketone compound has a structure as shown in formula (I): The auxiliary metal salt is obtained by reacting an organic acid having a structure as shown in formula (II) with sodium hydroxide, and then reacting with calcium chloride and zinc chloride; 2. A method for preparing the composite heat stabilizer for PVC according to claim 1, characterized in that: The method comprises the following steps: uniformly mixing zinc stearate, calcium stearate, ketone compounds and auxiliary metal salt to obtain the product; The auxiliary metal salt is obtained by the following method: (1) taking a sodium hydroxide solution, adding an organic acid having a structure as shown in formula (II) thereto, stirring and reacting at 25-45° C. for 1-3 hours to obtain a solution containing sodium organic acid; (2) Add calcium chloride and zinc chloride to the solution containing sodium organic acid obtained in step (1), and react at 25-45° C. for 2-5 hours to obtain an auxiliary metal salt.

3. The method for preparing a composite heat stabilizer for PVC according to claim 2, characterized in that: In step (1), the concentration of the sodium hydroxide solution is 8-10 mol / L.

4. The method for preparing a composite heat stabilizer for PVC according to claim 2, characterized in that: In step (1), the volume ratio of the organic acid to the sodium hydroxide solution is 1:(10-20).

5. The method for preparing a composite heat stabilizer for PVC according to claim 2, characterized in that: The weight ratio of the organic acid, the calcium chloride and the zinc chloride is 1:(1-3):(0.5-1.0).

6. The method for preparing a composite heat stabilizer for PVC according to claim 2, characterized in that: Step (2) specifically comprises the following steps: firstly, zinc chloride is added to the solution containing sodium organic acid obtained in step (1), and the mixture is stirred for reaction for 1-2 hours; then, the pH value of the reaction solution is adjusted to 7-8, calcium chloride is added thereto, and the mixture is stirred for reaction for 1-2 hours.

7. The method for preparing a composite heat stabilizer for PVC according to claim 2, characterized in that: Step (2) also includes filtering, washing and drying the obtained auxiliary metal salt.

Images