A composite heat stabilizer and a preparation method thereof

Abstract

This invention relates to the field of heat stabilizers, and provides a composite heat stabilizer and its preparation method. By weight, the composite heat stabilizer comprises the following raw materials: 5-15 parts of a composite rare earth stabilizer, 2-8 parts of an organozinc metal compound, 2-8 parts of a polyol, 0.5-3 parts of modified hydrotalcite, 1-5 parts of filler, and 0.5-2 parts of lubricant. The composite heat stabilizer provided by this invention is environmentally friendly, has strong thermal stability, and provides both initial and long-term stability, thus possessing good commercial application value.

Description

Technical Field

[0001] This invention relates to the field of heat stabilizers, and in particular to a composite heat stabilizer and its preparation method. Background Technology

[0002] Polyvinyl chloride (PVC) is an inexpensive and high-performance plastic, one of the three major general-purpose plastics, and has a wide range of applications. However, during the production and use of PVC, a dehydrochlorination reaction occurs, which can easily lead to PVC degradation. Heat stabilizers are important additives that can prevent or reduce cross-linking or degradation of PVC resin due to heat during processing, and extend the service life of PVC products.

[0003] With increasing environmental awareness, lead salts and heavy metal soaps, which are low-cost but highly toxic and polluting, have gradually lost their market advantage. Therefore, developing non-toxic, environmentally friendly, and efficient heat stabilizers has become an urgent need for the sustainable development of the plastics industry. Rare earth heat stabilizers, made primarily from rare earth elements, are additives. Due to their high atomic numbers and complex electronic structures, rare earth elements can absorb and convert energy through various mechanisms such as absorption, scattering, and emission, effectively improving the heat resistance and stability of materials. Furthermore, rare earth heat stabilizers are non-toxic and environmentally friendly, possessing enormous development potential.

[0004] Despite the excellent characteristics mentioned above, the biggest problem with a single rare earth heat stabilizer is its poor thermal stability and low resistance to discoloration in the initial stage of action. Therefore, it needs to be used in combination with polyols and other heat stabilizers such as zinc-based heat stabilizers to form a composite heat stabilizer. However, zinc-based heat stabilizers are still prone to "zinc burning", which may lead to a decrease in the thermal stability of the composite heat stabilizer.

[0005] Patent CN 107163443B discloses an acetylacetone-based rare earth composite heat stabilizer and its PVC material. The raw materials of the composite heat stabilizer include rare earth acetylacetone, organozinc metal compounds, auxiliary heat stabilizers, lubricants and fillers, which can effectively improve the initial coloring and long-term thermal stability of PVC. However, although the auxiliary heat stabilizer in this application is hydrotalcite, which can effectively solve the problem of "zinc burning" of zinc-based heat stabilizers, it does not solve the problem of poor dispersibility of hydrotalcite, which may lead to a decrease in the thermal stability of the composite heat stabilizer.

[0006] Therefore, there is an urgent need in the market for a composite heat stabilizer that is environmentally friendly, has strong thermal stability, and provides both initial and long-term stability. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention uses a composite rare earth stabilizer as the main component of the heat stabilizer, and combines it with organic zinc metal compounds, polyols and modified hydrotalcite to synthesize a composite heat stabilizer, which has the characteristics of being environmentally friendly, having strong thermal stability and having both initial and long-term stabilizing effects.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] The present invention provides a composite heat stabilizer, which, by weight, comprises the following raw materials: 5-15 parts of composite rare earth stabilizer, 2-8 parts of organozinc metal compound, 2-8 parts of polyol, 0.5-3 parts of modified hydrotalcite, 1-5 parts of filler, and 0.5-2 parts of lubricant.

[0010] The organozinc metal compound is zinc stearate or zinc acetylsalicylate; the filler is at least one of calcium carbonate, silicon dioxide, and titanium dioxide; and the lubricant is epoxidized soybean oil or polyethylene wax.

[0011] In some embodiments of the present invention, the preparation method of the composite rare earth stabilizer includes the following steps:

[0012] (1) Add cerium nitrate and lanthanum nitrate to deionized water, stir, and obtain solution 1 for later use. Add 4-propylpiperidine-4-carboxylic acid to deionized water, heat to 60-70℃, stir, add solution 1, stir, add ammonia to adjust pH=6-7, stir, boil and evaporate until solid appears, dry, wash, dry, and obtain rare earth stabilizer 1 for later use.

[0013] (2) Add cerium nitrate and lanthanum nitrate to anhydrous ethanol, stir, and obtain solution 2 for later use. Add 7-ketooctanoic acid to anhydrous ethanol, heat to 70-80℃, stir, add solution 2, stir, add anhydrous ethanol solution of sodium hydroxide, stir, cool to room temperature, rotary evaporate, wash, dry, and obtain rare earth stabilizer 2 for later use.

[0014] (3) Mix the rare earth stabilizer 1 from step (1) and the rare earth stabilizer 2 from step (2), stir, and ball mill to obtain the composite rare earth stabilizer.

[0015] In some embodiments of the present invention, in step (1), the molar ratio of cerium nitrate, lanthanum nitrate and 4-propylpiperidine-4-carboxylic acid is 1:(2.5-3.5):(2.5-3.5).

[0016] Preferably, in step (1), the molar ratio of cerium nitrate, lanthanum nitrate and 4-propylpiperidine-4-carboxylic acid is 1:3:3.

[0017] In some embodiments of the present invention, in step (2), the molar ratio of cerium nitrate, lanthanum nitrate and 7-ketooctanoic acid is 1:(2.5-3.5):(4.5-5.5).

[0018] Preferably, in step (2), the molar ratio of cerium nitrate, lanthanum nitrate and 7-ketooctanoic acid is 1:3:5.

[0019] In some embodiments of the present invention, in step (3), the mass ratio of rare earth stabilizer 1 to rare earth stabilizer 2 is 1:(1-2).

[0020] Preferably, in step (3), the mass ratio of rare earth stabilizer 1 to rare earth stabilizer 2 is 1:1.5.

[0021] Rare earth stabilizers are stabilizers synthesized mainly from carboxylate or fatty acid salts containing rare earth elements. They are not only safe and environmentally friendly, but also have excellent thermal stability, light stability, transparency and coloring power. However, rare earth stabilizers generally have problems such as poor early thermal stability and poor coloring inhibition.

[0022] The applicant selected cerium nitrate, lanthanum nitrate, and 4-propylpiperidine-4-carboxylic acid as raw materials, and cerium nitrate, lanthanum nitrate, and 7-ketooctanoic acid as raw materials to prepare rare earth stabilizer 1 and rare earth stabilizer 2, respectively. Rare earth stabilizer 1 and rare earth stabilizer 2 were then mixed by ball milling to obtain a composite rare earth stabilizer. On the one hand, rare earth lanthanum has a strong ability to absorb HCl gas, which can significantly improve thermal stability, but it is expensive. The applicant uses a specific ratio of cerium nitrate and lanthanum nitrate as a composite rare earth salt, which can ensure good thermal stability while also having a good cost-performance ratio. On the other hand, the applicant... The prepared rare earth stabilizer 1 has a piperidine structure, and the prepared rare earth stabilizer 2 has a ketone group and a long-chain alkyl structure, which gives the composite rare earth stabilizer good thermal stability and good early thermal stability. This may be due to the effect of the ketone group structure. In addition, the ball milling method used in the preparation of the composite rare earth stabilizer may have generated certain hydrogen bonding between the piperidine group in rare earth stabilizer 1 and the ketone group in rare earth stabilizer 2, which enhances the stability of the composite rare earth stabilizer and further strengthens its thermal stability.

[0023] In some embodiments of the present invention, the polyol is any one of pentaerythritol, 1,4-butanediol, and glycerol.

[0024] In some embodiments of the present invention, the method for preparing the modified hydrotalcite includes the following steps:

[0025] 1) Add fluorinated graphene to an aqueous ethylene glycol solution and sonicate to obtain solution 1 for later use. Add Zn(NO3)2·6H2O and Al(NO3)3·9H2O to deionized water and stir to obtain solution 2 for later use.

[0026] 2) Mix liquid 1 and liquid 2 from step 1), add sodium hydroxide aqueous solution to adjust pH to 6.5-7.5, reflux under an inert atmosphere, let stand, centrifuge, wash, freeze dry, and obtain the product for later use;

[0027] 3) Add the product from step 2) to deionized water, stir, add sodium stearate, heat to 75-85℃, stir for 3.5-4.5h, filter, wash, and dry to obtain modified hydrotalcite.

[0028] The fluorinated graphene has a fluorine content of 40-60%.

[0029] In some embodiments of the present invention, in step 1), the mass ratio of Zn(NO3)2·6H2O, Al(NO3)3·9H2O and fluorinated graphene is 1:(1-1.2):(0.04-0.06).

[0030] Preferably, in step 1), the mass ratio of Zn(NO3)2·6H2O, Al(NO3)3·9H2O and fluorinated graphene is 1:1.1:0.05.

[0031] In some embodiments of the present invention, in step 3), the mass ratio of the product to sodium stearate is 1:(4.5-5.5).

[0032] Preferably, in step 3), the mass ratio of the product to sodium stearate is 1:5.

[0033] Hydrotalcite has good heat resistance and can effectively solve the "zinc burning problem" of zinc-based heat stabilizers, and is widely used in heat stabilizers. However, the surface of hydrotalcite has active hydroxyl functional groups, which easily cause hydrogen bonds to form between its particles, resulting in agglomeration. This leads to poor surface structure stability and poor dispersibility. Moreover, most heat stabilizers are added to PVC matrix, and the hydrophilicity of hydrotalcite makes it less compatible with hydrophobic PVC, resulting in poor dispersibility of the heat stabilizer in PVC and a decrease in its heat stabilizing effect.

[0034] The applicant synthesized fluorinated graphene-modified zinc-aluminum hydrotalcite (product) using Zn(NO3)2·6H2O and Al(NO3)3·9H2O as raw materials and fluorinated graphene with a fluorine content of 40-60% as a modifying material. On the one hand, the applicant controlled the ratio of zinc to aluminum to achieve good dispersibility and stability of the zinc-aluminum hydrotalcite. On the other hand, fluorinated graphene introduces fluorine atoms into graphene, which not only possesses the high strength and high temperature resistance of graphene but also improves the hydrophobicity of hydrotalcite. This allows the hydrotalcite in the heat stabilizer to be better compatible with the PVC matrix, thereby improving the dispersibility of the hydrotalcite. Furthermore, the applicant used sodium stearate to modify the surface of the product, improving the dispersibility and thermal stability of the hydrotalcite, thereby enhancing the thermal stability of the composite heat stabilizer.

[0035] In another aspect, the present invention provides a method for preparing the composite heat stabilizer described in the above technical solution, comprising the following steps:

[0036] The composite rare earth stabilizer, organozinc metal compound, polyol, modified hydrotalcite, filler and lubricant are mixed and stirred at 1300-1700 r / min for 30-50 min to obtain the composite heat stabilizer.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) This invention uses a composite rare earth stabilizer as the main component of the heat stabilizer, and combines it with organic zinc metal compounds, polyols and modified hydrotalcite to synthesize a composite heat stabilizer. Through the synergistic effect between the components, the composite heat stabilizer has the characteristics of being environmentally friendly, having strong thermal stability and having both initial and long-term stability effects.

[0039] (2) In this invention, rare earth stabilizer 1 and rare earth stabilizer 2 were prepared by using cerium nitrate, lanthanum nitrate and 4-propylpiperidine-4-carboxylic acid as raw materials and cerium nitrate, lanthanum nitrate and 7-ketooctanoic acid as raw materials, respectively. Rare earth stabilizer 1 and rare earth stabilizer 2 were mixed by ball milling to obtain a composite rare earth stabilizer, which improved the early heat stability of the rare earth stabilizer and further improved the thermal stability of the composite rare earth stabilizer.

[0040] (3) This invention uses Zn(NO3)2·6H2O and Al(NO3)3·9H2O as raw materials and fluorinated graphene with a fluorine content of 40-60% as a modifying raw material to synthesize fluorinated graphene-modified zinc aluminum hydrotalcite, and further introduces sodium stearate to synthesize modified hydrotalcite, so that the modified hydrotalcite has good dispersibility and thermal stability.

[0041] (4) The composite heat stabilizer prepared by the present invention is environmentally friendly, has strong thermal stability and has both initial and long-term stability effects. It can be widely used in the field of PVC heat stabilizers and has good commercial application value. Detailed Implementation

[0042] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0043] In the following examples and comparative examples, except for the composite rare earth stabilizer and modified hydrotalcite, all other compound monomers and related reagents used were commercially available. Among them, the fluorinated graphene had a fluorine content of 50% and was purchased from Beijing Beike New Material Technology Co., Ltd.; the polyethylene wax was purchased from Shanghai Dingfen Chemical Technology Co., Ltd.; and the PVC was purchased from Dongguan Jingke Polymer Co., Ltd.

[0044] Preparation Example 1

[0045] The synthesis method of composite rare earth stabilizer A includes the following steps:

[0046] (1) Add 0.01 mol cerium nitrate and 0.03 mol lanthanum nitrate to 100 ml deionized water and stir for 30 min to obtain solution 1 for later use. Add 0.03 mol 4-propylpiperidine-4-carboxylic acid to 50 ml deionized water, heat to 65 °C, stir for 30 min, add solution 1, stir for 30 min, add 30 wt% ammonia water to adjust pH to 6.5, stir for 1 h, boil and evaporate until solid appears, dry at 60 °C for 12 h, wash 3 times with deionized water, dry at 60 °C for 12 h to obtain rare earth stabilizer 1 for later use.

[0047] (2) Add 0.01 mol cerium nitrate and 0.03 mol lanthanum nitrate to 100 ml anhydrous ethanol and stir for 30 min to obtain solution 2 for later use. Add 0.05 mol 7-ketooctanoic acid to 80 ml anhydrous ethanol, heat to 75 °C, stir for 1 h, add solution 2, stir for 30 min, add 75 ml anhydrous ethanol solution of 8 g / L sodium hydroxide, stir for 1 h, cool to room temperature, rotary evaporate, wash 3 times with deionized water, and dry at 60 °C for 12 h to obtain rare earth stabilizer 2 for later use.

[0048] (3) Mix 4g of rare earth stabilizer 1 from step (1) and 6g of rare earth stabilizer 2 from step (2), stir for 5 minutes, and ball mill for 30 minutes to obtain composite rare earth stabilizer A.

[0049] Preparation Example 2

[0050] Composite rare earth stabilizer B is implemented in the same way as composite rare earth stabilizer A, except that the number of moles of 4-propylpiperidine-4-carboxylic acid in step (1) is replaced with 0.02 mol.

[0051] Preparation Example 3

[0052] The specific implementation method of composite rare earth stabilizer C is the same as that of composite rare earth stabilizer A, except that the number of moles of 7-ketooctanoic acid in step (2) is replaced with 0.04 mol.

[0053] Preparation Example 4

[0054] The specific implementation method of composite rare earth stabilizer D is the same as that of composite rare earth stabilizer A, except that the mass of rare earth stabilizer 2 in step (3) is 3.5g.

[0055] Preparation Example 5

[0056] The specific implementation method of composite rare earth stabilizer E is the same as that of composite rare earth stabilizer A, except that the mass of rare earth stabilizer 2 in step (3) is 8.5g.

[0057] Preparation Example 6

[0058] The synthesis method of modified hydrotalcite A includes the following steps:

[0059] 1) Add 0.5g of fluorinated graphene to 100ml of 50wt% ethylene glycol aqueous solution and sonicate for 1h to obtain solution 1 for later use. Add 10g of Zn(NO3)2·6H2O and 11g of Al(NO3)3·9H2O to 100ml of deionized water and stir for 1h to obtain solution 2 for later use.

[0060] 2) Mix liquid 1 and liquid 2 from step 1), add 30wt% sodium hydroxide aqueous solution to adjust pH=7, reflux reaction for 12h under nitrogen atmosphere, let stand for 12h, centrifuge, wash 3 times with deionized water, freeze dry at -40℃ for 12h to obtain product for later use.

[0061] 3) Add 10g of the product from step 2) to 100ml of deionized water, stir for 1h, add 50g of sodium stearate, heat to 80℃, stir for 4h, filter, wash 3 times with deionized water, and dry at 60℃ for 12h to obtain modified hydrotalcite A.

[0062] Preparation Example 7

[0063] Modified hydrotalcite B is implemented in the same way as modified hydrotalcite A, except that the mass of Al(NO3)3·9H2O in step 1) is replaced with 9g.

[0064] Preparation Example 8

[0065] Modified hydrotalcite C is implemented in the same way as modified hydrotalcite A, except that the mass of fluorinated graphene in step 1) is replaced with 0.2g.

[0066] Preparation Example 9

[0067] Modified hydrotalcite D is implemented in the same way as modified hydrotalcite A, except that the mass of sodium stearate in step 3) is replaced with 43g.

[0068] Example 1

[0069] A composite heat stabilizer, by weight, comprises the following raw materials: 10 parts of composite rare earth stabilizer A, 5 parts of zinc stearate, 5 parts of pentaerythritol, 2 parts of modified hydrotalcite A, 3 parts of filler, and 1 part of epoxidized soybean oil.

[0070] The filler is a mixture of calcium carbonate, silicon dioxide and titanium dioxide in a mass ratio of 2:1:1.

[0071] The preparation method of the composite heat stabilizer in this embodiment includes the following steps:

[0072] The composite heat stabilizer is obtained by mixing composite rare earth stabilizer A, zinc stearate, pentaerythritol, modified hydrotalcite A, filler and epoxidized soybean oil and stirring at 1500 r / min for 40 min.

[0073] Example 2

[0074] A composite heat stabilizer, by weight, comprises the following raw materials: 10 parts of composite rare earth stabilizer A, 2 parts of zinc acetylsalicylate, 2 parts of glycerol, 0.5 parts of modified hydrotalcite A, 1 part of filler, and 0.5 parts of polyethylene wax.

[0075] The packing material is the same as in Example 1.

[0076] The preparation method of the composite heat stabilizer in this embodiment includes the following steps:

[0077] The composite heat stabilizer is obtained by mixing composite rare earth stabilizer A, zinc acetylsalicylate, glycerol, modified hydrotalcite A, calcium carbonate and polyethylene wax, and stirring at 1300 r / min for 50 min.

[0078] Example 3

[0079] A composite heat stabilizer, by weight, comprises the following raw materials: 10 parts of composite rare earth stabilizer A, 8 parts of zinc stearate, 8 parts of 1,4-butanediol, 3 parts of modified hydrotalcite A, 5 parts of filler, and 2 parts of epoxidized soybean oil.

[0080] The packing material is the same as in Example 1.

[0081] The preparation method of the composite heat stabilizer in this embodiment includes the following steps:

[0082] The composite rare earth stabilizer A, zinc stearate, 1,4-butanediol, modified hydrotalcite A, filler and epoxidized soybean oil are mixed and stirred at 1700 r / min for 30 min to obtain the composite heat stabilizer.

[0083] Example 4

[0084] A composite heat stabilizer, by weight, comprises the following raw materials: 5 parts of composite rare earth stabilizer A, 3 parts of zinc stearate, 3 parts of pentaerythritol, 2 parts of modified hydrotalcite A, 2 parts of filler, and 0.6 parts of epoxidized soybean oil.

[0085] The filler is a mixture of calcium carbonate and silicon dioxide in a mass ratio of 1:1.

[0086] The preparation method of the composite heat stabilizer in this embodiment is the same as in Example 1.

[0087] Example 5

[0088] A composite heat stabilizer, by weight, comprises the following raw materials: 15 parts of composite rare earth stabilizer A, 7 parts of zinc stearate, 7 parts of pentaerythritol, 2 parts of modified hydrotalcite A, 4 parts of titanium dioxide, and 1.5 parts of polyethylene wax.

[0089] The preparation method of the composite heat stabilizer in this embodiment is the same as in Example 1.

[0090] Example 6

[0091] This embodiment provides a composite heat stabilizer and its preparation method. The specific implementation method is the same as that in Embodiment 1, except that composite rare earth stabilizer B replaces composite rare earth stabilizer A in an equal amount.

[0092] Example 7

[0093] This embodiment provides a composite heat stabilizer and its preparation method. The specific implementation method is the same as that in Embodiment 1, except that composite rare earth stabilizer C replaces composite rare earth stabilizer A in an equal amount.

[0094] Example 8

[0095] This embodiment provides a composite heat stabilizer and its preparation method. The specific implementation method is the same as that in Embodiment 1, except that composite rare earth stabilizer D replaces composite rare earth stabilizer A in an equal amount.

[0096] Example 9

[0097] This embodiment provides a composite heat stabilizer and its preparation method. The specific implementation method is the same as that in Embodiment 1, except that composite rare earth stabilizer E replaces composite rare earth stabilizer A in an equal amount.

[0098] Example 10

[0099] This embodiment provides a composite heat stabilizer and its preparation method. The specific implementation method is the same as that in Embodiment 1, except that modified hydrotalcite A is replaced by modified hydrotalcite B in an equal amount.

[0100] Example 11

[0101] This embodiment provides a composite heat stabilizer and its preparation method. The specific implementation method is the same as that in Embodiment 1, except that modified hydrotalcite A is replaced by modified hydrotalcite C in an equal amount.

[0102] Example 12

[0103] This embodiment provides a composite heat stabilizer and its preparation method. The specific implementation method is the same as that in Embodiment 1, except that modified hydrotalcite A is replaced by modified hydrotalcite D in an equal amount.

[0104] Comparative Example 1

[0105] This comparative example provides a composite heat stabilizer and its preparation method. The specific implementation method is the same as that in Example 1, except that rare earth stabilizer 1 is used to replace composite rare earth stabilizer A in an equal amount.

[0106] The preparation method of rare earth stabilizer 1 is the same as that of preparation example 1.

[0107] Comparative Example 2

[0108] This comparative example provides a composite heat stabilizer and its preparation method. The specific implementation method is the same as that in Example 1, except that rare earth stabilizer 2 is used to replace composite rare earth stabilizer A in an equal amount.

[0109] The preparation method of rare earth stabilizer 2 is the same as that of preparation example 2.

[0110] Comparative Example 3

[0111] This comparative example provides a composite heat stabilizer and its preparation method. The specific implementation method is the same as in Example 1, except that commercially available conventional hydrotalcite is used to replace the modified hydrotalcite A in an equal amount.

[0112] Commercially available hydrotalcite was purchased from Jiangsu Jufeng Chemical Technology Co., Ltd.

[0113] Performance testing

[0114] The initial and long-term thermal stability properties of the composite heat stabilizers of Examples 1-12 and Comparative Examples 1-3 were tested, and the test results are shown in Table 1.

[0115] 100g of PVC and 1g of the composite heat stabilizer from Examples 1-12 and Comparative Examples 1-3 were mixed in a high-speed mixer for 30 minutes, and then placed on a two-roll mill and mixed at 200°C for 30 minutes to obtain PVC samples. The PVC samples were tested, with the samples without the composite heat stabilizer used as controls.

[0116] (1) Initial thermal stability

[0117] The initial thermal stability of the composite heat stabilizer is determined by testing the time of onset of color change of PVC samples using the Congo red method. The later the onset of color change, the better the initial thermal stability, according to standard GB / T 2917.1-2002.

[0118] (2) Long-term thermal stability

[0119] The PVC sample was cut into a 15mm×15mm square and subjected to an oven aging test at 180℃ using the oven method. After 120 minutes, the long-term thermal stability of the composite heat stabilizer was judged by observing the color change of the sample. The lighter the color, the better the long-term thermal stability, referring to the standard GB / T 9349-2002.

[0120] Table 1

[0121] Group Time to start color change (min) Color at 120 minutes Example 1 145 White Example 2 143 White Example 3 142 White Example 4 144 White Example 5 141 White Example 6 129 pale yellow Example 7 127 pale yellow Example 8 128 pale yellow Example 9 126 pale yellow Example 10 132 pale yellow Example 11 130 pale yellow Example 12 131 pale yellow Comparative Example 1 123 brown Comparative Example 2 121 brown Comparative Example 3 125 brown Comparison 110 Brownish black

[0122] As shown in Table 1, the composite heat stabilizers in Examples 1-5 of this invention exhibit a relatively late onset of color change and a lighter color at 120 minutes, indicating good initial and long-term thermal stability. Examples 6-9 altered the proportions of key components in the synthesis of the composite rare earth stabilizer, failing to significantly improve its initial thermal stability and also impacting its long-term thermal stability. Examples 10-12 changed the addition ratios of Al(NO3)3·9H2O, fluorinated graphene, and sodium stearate during the preparation of modified hydrotalcite, failing to improve the dispersibility of the modified hydrotalcite, thus leading to a decrease in both initial and long-term thermal stability. Comparative Examples 1-3 involved replacing composite rare earth stabilizer A with equal amounts of rare earth stabilizer 1 and rare earth stabilizer 2, and replacing modified hydrotalcite A with equal amounts of commercially available conventional hydrotalcite, respectively. Tests revealed poor initial and long-term thermal stability of the composite heat stabilizers.

[0123] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A composite heat stabilizer, characterized in that, The composite heat stabilizer comprises the following raw materials in parts by weight: 5-15 parts of composite rare earth stabilizer, 2-8 parts of organozinc metal compound, 2-8 parts of polyol, 0.5-3 parts of modified hydrotalcite, 1-5 parts of filler, and 0.5-2 parts of lubricant; The preparation method of the composite rare earth stabilizer includes the following steps: (1) Add cerium nitrate and lanthanum nitrate to deionized water, stir, and obtain solution 1 for later use. Add 4-propylpiperidine-4-carboxylic acid to deionized water, heat to 60-70℃, stir, add solution 1, stir, add ammonia water to adjust pH=6-7, stir, boil and evaporate until solid appears, dry, wash, dry, and obtain rare earth stabilizer 1 for later use. (2) Add cerium nitrate and lanthanum nitrate to anhydrous ethanol, stir, and obtain solution 2 for later use. Add 7-ketooctanoic acid to anhydrous ethanol, heat to 70-80℃, stir, add solution 2, stir, add anhydrous ethanol solution of sodium hydroxide, stir, cool to room temperature, rotary evaporate, wash, dry, and obtain rare earth stabilizer 2 for later use. (3) Mix the rare earth stabilizer 1 from step (1) and the rare earth stabilizer 2 from step (2), stir, and ball mill to obtain the composite rare earth stabilizer. The preparation method of the modified hydrotalcite includes the following steps: 1) Add fluorinated graphene to an aqueous ethylene glycol solution and sonicate to obtain solution 1 for later use. Add Zn(NO3)2·6H2O and Al(NO3)3·9H2O to deionized water and stir to obtain solution 2 for later use. 2) Mix liquid 1 and liquid 2 from step 1), add sodium hydroxide aqueous solution to adjust pH to 6.5-7.5, reflux under an inert atmosphere, let stand, centrifuge, wash, freeze dry, and obtain the product for later use; 3) Add the product from step 2) to deionized water, stir, add sodium stearate, heat to 75-85℃, stir for 3.5-4.5h, filter, wash, and dry to obtain modified hydrotalcite.

2. The composite heat stabilizer according to claim 1, characterized in that, In step (1), the molar ratio of cerium nitrate, lanthanum nitrate and 4-propylpiperidine-4-carboxylic acid is 1:(2.5-3.5):(2.5-3.5).

3. The composite heat stabilizer according to claim 1, characterized in that, In step (2), the molar ratio of cerium nitrate, lanthanum nitrate and 7-ketooctanoic acid is 1:(2.5-3.5):(4.5-5.5).

4. The composite heat stabilizer according to claim 1, characterized in that, In step (3), the mass ratio of rare earth stabilizer 1 to rare earth stabilizer 2 is 1:(1-2).

5. The composite heat stabilizer according to claim 1, characterized in that, The polyol is any one of pentaerythritol, 1,4-butanediol, and glycerol.

6. The composite heat stabilizer according to claim 1, characterized in that, In step 1), the mass ratio of Zn(NO3)2·6H2O, Al(NO3)3·9H2O and fluorinated graphene is 1:(1-1.2):(0.04-0.06).

7. The method for preparing the composite heat stabilizer according to claim 1, characterized in that, In step 3), the mass ratio of the product to sodium stearate is 1:(4.5-5.5).

8. A method for preparing a composite heat stabilizer according to any one of claims 1-7, characterized in that, Includes the following steps: The composite rare earth stabilizer, organozinc metal compound, polyol, modified hydrotalcite, filler and lubricant are mixed and stirred at 1300-1700 r / min for 30-50 min to obtain the composite heat stabilizer.