Calcium-zinc composite heat stabilizer and preparation method thereof

Abstract

This invention relates to the field of plastic additives technology, specifically disclosing a calcium-zinc composite heat stabilizer and its preparation method. The calcium-zinc composite heat stabilizer, by weight, comprises the following components: 8-10 parts of a main stabilizer, 0.8-2 parts of pentaerythritol bismaleate, and 0.8-2 parts of cerium p-methylbenzoate; the main stabilizer is a mixture of calcium stearate and zinc stearate; the pentaerythritol bismaleate is obtained by esterification of diethylene glycol ether maleate and pentaerythritol at a molar ratio of 1:2.4-2.6. The calcium-zinc composite heat stabilizer of this invention uses pentaerythritol bismaleate and cerium p-methylbenzoate as auxiliary components. The components exhibit good synergistic effects, effectively improving the stabilization time of the calcium-zinc heat stabilizer. Simultaneously, it is not easily migrated or precipitated during processing, exhibits good compatibility with PVC, and improves the stabilization effect on PVC.

Description

Technical Field

[0001] This invention relates to the field of plastic additives technology, and in particular to a calcium-zinc composite heat stabilizer and its preparation method. Background Technology

[0002] Polyvinyl chloride (PVC) is an amorphous, white powder. Due to its unique physical and chemical properties, mature synthesis process, and low production cost, it has become one of the world's five major general-purpose resins. The decomposition and plasticizing temperatures of pure PVC resin are both in the range of 160-220℃. When the temperature rises to 160℃, PVC decomposes to produce hydrogen chloride, which further accelerates the decomposition of PVC, leading to a continuous decline in the mechanical and physical properties of the finished product. Therefore, heat stabilizers must be added during the plasticizing and molding process of PVC to inhibit thermal degradation and improve its thermal stability.

[0003] Currently, commonly used heat stabilizers include lead salt heat stabilizers, calcium-zinc soap heat stabilizers, rare earth heat stabilizers, and organotin heat stabilizers, each with different stabilization mechanisms and properties. For example, lead salt heat stabilizers have good stability but are highly toxic, and their use is restricted in many plastic product fields; rare earth heat stabilizers have high production costs and complex manufacturing processes, which limits their large-scale application; organotin heat stabilizers are expensive, have a strong odor during processing, and are prone to pollution; calcium-zinc heat stabilizers are recognized as non-toxic and environmentally friendly, but their stabilization effect on PVC is poor, and PVC is easily degraded during processing, leading to substandard product performance. While compounding with components (mainly organic or inorganic small molecules) can extend the heat stabilization time of calcium-zinc stabilizers, these compounded components have poor compatibility with PVC, are prone to precipitation, and are difficult to process. Therefore, developing heat stabilizers with good heat stabilization effects and easy large-scale production remains a pressing technical problem for those skilled in the art. Summary of the Invention

[0004] Therefore, the present invention provides a calcium-zinc composite heat stabilizer with good long-lasting heat stabilization effect.

[0005] In a first aspect, the present invention provides a calcium-zinc composite heat stabilizer, comprising, by weight, the following components: 8-10 parts of a main stabilizer, 0.8-2 parts of pentaerythritol bismaleate, and 0.8-2 parts of cerium p-methylbenzoate; wherein the main stabilizer is a mixture of calcium stearate and zinc stearate; and wherein the pentaerythritol bismaleate is obtained by esterification of diethylene glycol ether maleate and pentaerythritol in a molar ratio of 1:2.4-2.6.

[0006] Calcium stearate is a long-lasting heat stabilizer that reacts with HCl released during PVC degradation and binds to unstable chlorine molecules on the PVC molecular chain, thus improving PVC stability. Zinc stearate is a short-lasting heat stabilizer that effectively improves the initial colorability of PVC products; however, the zinc chloride generated later has a strong catalytic effect on deHCl removal, causing rapid aging and discoloration of the products, known as "zinc burning." This invention synthesizes pentaerythritol bismaleate from diethylene glycol ether maleate and pentaerythritol. It possesses multiple functional structures, including ester groups, ether bonds, carbon-carbon double bonds, and multiple hydroxyl groups, improving its compatibility with PVC, making it more difficult for alcohols to precipitate from PVC, and enhancing the PVC sample's resistance to discoloration. Pentaerythritol bismaleate exhibits a synergistic effect with metal soaps, forming complexes with zinc fatty acids and metal chlorides. This inhibits the catalytic effect of zinc chloride on the removal of hydrogen chloride, preventing the autocatalytic degradation of PVC and significantly delaying or even eliminating the "zinc burn" phenomenon of rapid thermal aging and blackening of PVC caused by zinc chloride. This extends the initial whiteness and improves long-term thermal stability. Simultaneously, the carbon-carbon double bond structure in maleic anhydride can undergo an addition reaction with the conjugated double bonds present in PVC to form a saturated polymer chain, thereby preventing the growth of conjugated polyene chains. Furthermore, the polyhydroxy structure of pentaerythritol can synergistically absorb and neutralize HCl released during PVC degradation with calcium stearate, further enhancing the long-term thermal stability of PVC.

[0007] This invention also includes cerium p-toluenebenzoate, which can complex with pentaerythritol, linking the broken chains of PVC and inhibiting PVC degradation. Simultaneously, cerium p-toluenebenzoate reacts with HCl produced from PVC degradation before zinc stearate, and absorbs free HCl with calcium stearate, delaying the autocatalytic effect of PVC and reducing "zinc burning," thereby improving the thermal stability of PVC. Furthermore, the use of low molecular weight benzoic acid in cerium p-toluenebenzoate increases its compatibility with PVC.

[0008] Optionally, the acid value of the pentaerythritol bismaleate is ≤0.5 mg KOH / g.

[0009] Optionally, the preparation method of the pentaerythritol bismaleate includes the following steps:

[0010] S1. After heating maleic anhydride to 100-120℃, diethylene glycol is added dropwise, and the reaction is stirred continuously for 2.5-4.5h to obtain the diethylene glycol ether maleate ester;

[0011] S2. The diethylene glycol ether maleate is heated to 150-170°C, pentaerythritol and catalyst are added, and the reaction is stirred continuously for 1-2 hours. After the reaction is completed, the product is distilled under reduced pressure to obtain the pentaerythritol bismaleic acid ester.

[0012] Optionally, the mass ratio of maleic anhydride to diethylene glycol is 1.8-2.2:1.

[0013] Optionally, the catalyst is selected from p-toluenesulfonic acid, thionyl chloride, or acetyl chloride.

[0014] Optionally, the method for preparing cerium p-toluenebenzoate includes the following steps:

[0015] Cerium carbonate and p-toluic acid were dissolved in anhydrous ethanol to prepare cerium carbonate ethanol solution and p-toluic acid ethanol solution, respectively. Then, the cerium carbonate ethanol solution was slowly added to the p-toluic acid ethanol solution, and the mixture was stirred at 60℃-80℃ for 30-60 min. After the reaction was completed, the pH of the mixed solution was adjusted to 6-7, and then the mixture was allowed to stand, filtered, washed, and dried in sequence to obtain the p-toluic acid cerium.

[0016] Optionally, the molar ratio of cerium carbonate to p-methylbenzoic acid is 1:3-3.2.

[0017] Optionally, the mass ratio of calcium stearate to zinc stearate is 1:1-2.

[0018] Secondly, the present invention also provides a method for preparing the above-mentioned calcium-zinc composite heat stabilizer, comprising the following steps:

[0019] The main stabilizer, pentaerythritol bismaleate, and cerium p-methylbenzoate are mixed evenly to obtain the calcium-zinc composite heat stabilizer.

[0020] Thirdly, the present invention also provides the application of the above-mentioned calcium-zinc composite heat stabilizer in the preparation of PVC products.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] Therefore, the components of the composite stabilizer have a good synergistic effect, which improves the thermal stability of the PVC sample.

[0023] The calcium-zinc composite heat stabilizer of the present invention uses pentaerythritol bismaleate and cerium p-methylbenzoate as auxiliary components. The components have a good synergistic effect, which effectively improves the stabilization time of the calcium-zinc heat stabilizer. At the same time, it is not easy to migrate and precipitate during processing, has good compatibility with PVC, and improves the stabilization effect on PVC. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of this invention.

[0025] To better illustrate the present invention, further examples are provided below.

[0026] Example 1

[0027] This embodiment provides a calcium-zinc composite heat stabilizer, comprising the following components by weight: 9 parts of main stabilizer (calcium stearate and zinc stearate in a mass ratio of 1:1.5), 1.5 parts of pentaerythritol bismaleate, and 1.5 parts of cerium p-methylbenzoate. The preparation method is as follows:

[0028] (1) Cerium carbonate and p-toluic acid were dissolved in anhydrous ethanol to prepare cerium carbonate ethanol solution and p-toluic acid ethanol solution, respectively. The molar ratio of cerium carbonate to p-toluic acid was 1:3.1. Then, the cerium carbonate ethanol solution was slowly added to the p-toluic acid ethanol solution and stirred at 70°C for 45 min. After the reaction was completed, a 2 mol / L sodium hydroxide ethanol solution was added to adjust the pH of the mixed solution to 6.5. The mixture was then stirred at a constant temperature for 1 h, allowed to stand for 12 h, filtered, washed successively with anhydrous ethanol, water, and anhydrous ethanol, and dried at 70°C to obtain cerium p-toluic acid.

[0029] (2) After heating maleic anhydride to 110°C, diethylene glycol was slowly added dropwise at a mass ratio of 2:1. The mixture was stirred continuously for 3.5 h to obtain diethylene glycol ether maleate. The diethylene glycol ether maleate was then heated to 160°C, and pentaerythritol and p-toluenesulfonic acid were added at a molar ratio of 1:2.5:0.2. The mixture was stirred continuously for 1.5 h. The acid value (≤0.5 mg KOH / g) was measured to calculate the esterification rate and determine the reaction endpoint. After the reaction was complete, excess water and reactants were removed by vacuum distillation to obtain pentaerythritol bismaleate.

[0030] (3) Mix the main stabilizer, pentaerythritol bismaleic acid and cerium p-methylbenzoate evenly to obtain a calcium-zinc composite heat stabilizer.

[0031] Example 2

[0032] This embodiment provides a calcium-zinc composite heat stabilizer, comprising the following components by weight: 8 parts of main stabilizer (calcium stearate and zinc stearate in a mass ratio of 1:1), 0.8 parts of pentaerythritol bismaleate, and 0.8 parts of cerium p-methylbenzoate. The preparation method is as follows:

[0033] (1) Cerium carbonate and p-toluic acid were dissolved in anhydrous ethanol to prepare cerium carbonate ethanol solution and p-toluic acid ethanol solution, respectively. The molar ratio of cerium carbonate to p-toluic acid was 1:3. Then, the cerium carbonate ethanol solution was slowly added to the p-toluic acid ethanol solution and stirred at 60℃ for 30 min. After the reaction was completed, a 2 mol / L sodium hydroxide ethanol solution was added to adjust the pH of the mixed solution to 6. The mixture was then stirred at a constant temperature for 1 h, allowed to stand for 12 h, filtered, and washed successively with anhydrous ethanol, water, and anhydrous ethanol. The mixture was then dried at 70℃ to obtain cerium p-toluic acid.

[0034] (2) After heating maleic anhydride to 100°C, diethylene glycol was slowly added dropwise at a mass ratio of 1.8:1. The mixture was stirred continuously for 2.5 h to obtain diethylene glycol ether maleate. The diethylene glycol ether maleate was then heated to 150°C, and pentaerythritol and p-toluenesulfonic acid were added at a molar ratio of 1:2.4:0.2. The mixture was stirred continuously for 1 h, and the acid value (≤0.5 mg KOH / g) was measured to calculate the esterification rate and determine the reaction endpoint. After the reaction was complete, excess water and reactants were removed by vacuum distillation to obtain pentaerythritol bismaleate.

[0035] (3) Mix the main stabilizer, pentaerythritol bismaleic acid and cerium p-methylbenzoate evenly to obtain a calcium-zinc composite heat stabilizer.

[0036] Example 3

[0037] This embodiment provides a calcium-zinc composite heat stabilizer, comprising the following components by weight: 10 parts of a main stabilizer (calcium stearate and zinc stearate in a mass ratio of 1:2), 2 parts of pentaerythritol bismaleate, and 2 parts of cerium p-methylbenzoate. The preparation method is as follows:

[0038] (1) Cerium carbonate and p-toluic acid were dissolved in anhydrous ethanol to prepare cerium carbonate ethanol solution and p-toluic acid ethanol solution, respectively. The molar ratio of cerium carbonate to p-toluic acid was 1:3.2. Then, the cerium carbonate ethanol solution was slowly added to the p-toluic acid ethanol solution and stirred at 80°C for 60 min. After the reaction was completed, a 2 mol / L sodium hydroxide ethanol solution was added to adjust the pH of the mixed solution to 7. The mixture was then stirred at a constant temperature for 1 h, allowed to stand for 12 h, filtered, washed successively with anhydrous ethanol, water, and anhydrous ethanol, and dried at 70°C to obtain cerium p-toluic acid.

[0039] (2) After heating maleic anhydride to 120°C, diethylene glycol was slowly added dropwise at a mass ratio of 2.2:1. The mixture was stirred continuously for 4.5 h to obtain diethylene glycol ether maleate. The diethylene glycol ether maleate was then heated to 170°C, and pentaerythritol and p-toluenesulfonic acid were added at a molar ratio of 1:2.6:0.2. The mixture was stirred continuously for 2 h, and the acid value (≤0.5 mg KOH / g) was measured to calculate the esterification rate and determine the reaction endpoint. After the reaction was complete, excess water and reactants were removed by vacuum distillation to obtain pentaerythritol bismaleate.

[0040] (3) Mix the main stabilizer, pentaerythritol bismaleic acid and cerium p-methylbenzoate evenly to obtain a calcium-zinc composite heat stabilizer.

[0041] Comparative Example 1

[0042] This comparative example provides a calcium-zinc composite heat stabilizer, the preparation process of which is exactly the same as that of Example 1, except that pentaerythritol bismaleate is replaced with an equal amount of pentaerythritol.

[0043] Comparative Example 2

[0044] This comparative example provides a calcium-zinc composite heat stabilizer, the preparation process of which is exactly the same as that of Example 1, except that pentaerythritol bismaleate is obtained by esterification reaction of diethylene glycol ether maleate and pentaerythritol in a molar ratio of 1:2.

[0045] Comparative Example 3

[0046] This comparative example provides a calcium-zinc composite heat stabilizer, the preparation process of which is exactly the same as that of Example 1, except that cerium p-toluene is replaced with an equal amount of β-diketone.

[0047] Performance testing

[0048] The calcium-zinc heat stabilizer prepared in the above examples and comparative examples was used to prepare PVC products as follows: Raw materials: 100 parts PVC, 8 parts calcium-zinc composite heat stabilizer, 5 parts calcium carbonate, 1 part liquid paraffin, and 8 parts dioctyl phthalate; The raw materials were mixed evenly with a high-speed mixer and then plasticized into sheets by a two-roll mill. The temperature of the two-roll mill was 168°C, the roll gap was 0.3 mm, the roll speed was 40 r / min, the rolling time was 4 min, and the amount passing through the rolls was 65 g; After the initial plasticization into sheets, the plasticized PVC sample sheets were folded twice and passed through the rolls 8 times. After the rolling time was reached, the sheets were placed under a flat vulcanizing agent for pressing treatment. The temperature of the flat vulcanizing agent was 170°C, the pressure was 1T, and the pressing time was 3 min.

[0049] According to GB / T2917.1-2002, the thermal stability time of Congo red was determined as follows: PVC product samples prepared in Examples 1-3 and Comparative Examples 1-3 were added to glass test tubes respectively. The mixture was sealed with a rubber stopper with a hollow glass tube, and Congo red test paper was fixed with the hollow glass tube. Each test tube containing the sample was placed in an oil bath, and the time for the Congo red test paper to change color was observed and recorded. The test results are shown in Table 1. The distance between the Congo red test paper and the mixture was 25 mm, and the oil bath temperature was 185℃.

[0050] The samples were placed in a heat aging test chamber at a temperature of (190±1)℃ for static heat aging experiments. One small sample was taken out every 20 minutes to observe the color change. The time it took for the sample to turn black was taken as the static heat aging time of the PVC. The results are shown in Table 1.

[0051] Table 1 Test Results

[0052] thermostable / s heat aging / s example 1 2843 365 example 2 2787 354 example 3 2776 351 comparative example 1 1556 158 comparative example 2 1732 171 comparative example 3 1849 180

[0053] As can be seen from Table 1, the thermal stability of PVC changes with the adjustment of the components and ratios in the heat stabilizer. Metal soap, pentaerythritol bismaleate and cerium p-methylbenzoate have a good synergistic effect, which can further improve the thermal stability of PVC.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A calcium-zinc composite heat stabilizer, characterized in that, By weight, it comprises the following components: 8-10 parts of main stabilizer, 0.8-2 parts of pentaerythritol bismaleate and 0.8-2 parts of cerium p-toluenebenzoate; The main stabilizer is a mixture of calcium stearate and zinc stearate; The pentaerythritol bismaleate is obtained by esterification of diethylene glycol ether maleate and pentaerythritol in a molar ratio of 1:2.4-2.

6. The preparation method of the pentaerythritol bismaleic acid ester includes the following steps: S1. After heating maleic anhydride to 100-120℃, diethylene glycol is added dropwise, and the reaction is stirred continuously for 2.5-4.5h to obtain the diethylene glycol ether maleate ester; S2. The diethylene glycol ether maleate is heated to 150-170°C, pentaerythritol and catalyst are added, and the reaction is stirred continuously for 1-2 hours. After the reaction is completed, the product is distilled under reduced pressure to obtain the pentaerythritol bismaleic acid ester.

2. The calcium-zinc composite heat stabilizer as described in claim 1, characterized in that, The acid value of the pentaerythritol bismaleate is ≤0.5 mg KOH / g.

3. The calcium-zinc composite heat stabilizer as described in claim 1, characterized in that, The mass ratio of maleic anhydride to diethylene glycol is 1.8-2.2:

1.

4. The calcium-zinc composite heat stabilizer as described in claim 1, characterized in that, The catalyst is selected from p-toluenesulfonic acid, thionyl chloride, or acetyl chloride.

5. The calcium-zinc composite heat stabilizer as described in claim 1, characterized in that, The method for preparing cerium p-methylbenzoate includes the following steps: Cerium carbonate and p-toluic acid were dissolved in anhydrous ethanol to prepare cerium carbonate ethanol solution and p-toluic acid ethanol solution, respectively. Then, the cerium carbonate ethanol solution was slowly added to the p-toluic acid ethanol solution, and the mixture was stirred at 60℃-80℃ for 30-60 min. After the reaction was completed, the pH of the mixed solution was adjusted to 6-7, and then the mixture was allowed to stand, filtered, washed, and dried in sequence to obtain the p-toluic acid cerium.

6. The calcium-zinc composite heat stabilizer as described in claim 5, characterized in that, The molar ratio of cerium carbonate to p-methylbenzoic acid is 1:3-3.

2.

7. The calcium-zinc composite heat stabilizer as described in claim 1, characterized in that, The mass ratio of calcium stearate to zinc stearate is 1:1-2.

8. A method for preparing the calcium-zinc composite heat stabilizer according to any one of claims 1-7, characterized in that, Includes the following steps: The main stabilizer, pentaerythritol bismaleate, and cerium p-methylbenzoate are mixed evenly to obtain the calcium-zinc composite heat stabilizer.

9. The use of the calcium-zinc composite heat stabilizer according to any one of claims 1-7 in the preparation of PVC products.