Glycerin zinc PVC heat stabilizer and preparation method thereof

Abstract

The invention discloses a zinc glyceride PVC (polyvinyl chloride) heat stabilizer and a preparation method thereof, and belongs to the field of polymer processing aids, the structural general formula of the heat stabilizer is shown in the specification, R is C7-C17 alkyl, the preparation method comprises the following steps: esterifying glycerol and fatty acid to prepare monoglyceride, and then carrying out coordination reaction with zinc oxide, hydroxyl in molecules of the heat stabilizer can chelate zinc chloride to inhibit the zinc burning phenomenon; the stabilizing time of Congo red reaches 105 min or above, and the Congo red is nontoxic and environmentally friendly.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of polymer material processing aids, in particular to a glyceride zinc PVC heat stabilizer and a preparation method thereof. BACKGROUND

[0002] Polyvinyl chloride (PVC) is the second largest general-purpose thermoplastic plastic in the world after polyethylene, and is widely used in building materials, wire and cable, packaging containers, medical devices and many other fields due to its excellent mechanical properties, chemical corrosion resistance, flame retardance and electrical insulation. However, the PVC molecular chain contains unstable tertiary carbon chloride atoms and allyl chloride atoms, which are prone to dehydrochlorination at processing temperatures (usually 160-200 DEG C). The generated HCl has a self-catalytic effect on PVC degradation, leading to the formation of conjugated polyene structures on the molecular chain, causing discoloration, mechanical property degradation and even carbonization failure of the material. Therefore, a heat stabilizer is an essential functional additive in the processing and application of PVC.

[0003] The PVC heat stabilizers currently used in the industry mainly include three systems of lead salts, organic tin and metal soaps. Although the lead salt stabilizer has excellent heat stabilizing effect and low cost, it has been gradually banned by the EU REACH regulation and relevant Chinese standards due to its serious heavy metal toxicity. The organic tin stabilizer has outstanding heat stabilizing performance, but has the disadvantages of high price and strong odor. Calcium-zinc composite stabilizer, as a representative of environmentally friendly heat stabilizers, has become the main direction for replacing lead salts due to its non-toxicity and low cost.

[0004] The traditional calcium-zinc stabilizer system is usually composed of calcium stearate and zinc stearate in a certain proportion. Zinc stearate can replace the active chlorine atoms on the PVC molecular chain through a displacement reaction, giving the material good initial color; calcium stearate prolongs the long-term stability by neutralizing the HCl released. However, this traditional system has the phenomenon of zinc burning: when the zinc chloride generated by the reaction of zinc stearate and HCl accumulates to a certain concentration, the zinc chloride as a strong Lewis acid will accelerate the zip-fastener dehydrochlorination reaction of PVC, causing the product to suddenly turn black.

[0005] In existing technologies, researchers have attempted to improve the zinc burning problem by introducing polyhydroxy compounds and β-diketone auxiliary stabilizers. For example, pentaerythritol can form a stable chelate with zinc chloride, thereby delaying the occurrence of zinc burning. Furthermore, designing novel zinc complex stabilizers using special ligands is also an important research direction. Chinese patent CN105801607A discloses a zinc complex heat stabilizer based on di(pyridine-4-ylmethyl)thione and glutaric acid, which achieves thermal stabilization through the adsorption of HCl by pyridine nitrogen atoms. However, this technical solution has the following drawbacks: pyridine ligand raw materials are relatively expensive; the hydrothermal synthesis process has high energy consumption and a reaction time of 36-48 hours; the complex contains a sulfide structure, which may produce unpleasant odors during high-temperature processing; and the compatibility of this complex with the PVC matrix needs further improvement.

[0006] In view of the shortcomings of the existing technology, there is an urgent need in the field to develop a new type of environmentally friendly heat stabilizer that has a wide range of raw material sources, a simple synthesis process, excellent compatibility with PVC, and can effectively inhibit zinc burning. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a zinc glyceride PVC heat stabilizer. This heat stabilizer uses a glycerol monofatty acid ester as a ligand to coordinate with zinc ions, forming a coordination compound with multi-hydroxyl chelating ability. It can not only effectively absorb and neutralize free HCl, but also significantly delay the occurrence of zinc burning by chelating zinc chloride generated through the multi-hydroxyl structure, while improving compatibility with the PVC matrix.

[0008] Another objective of this invention is to provide a method for preparing the above-mentioned zinc glyceride PVC heat stabilizer, which has mild process conditions, simple operation, short reaction time, and high product yield.

[0009] A third objective of this invention is to provide the application of the aforementioned zinc glyceride PVC heat stabilizer in polyvinyl chloride materials.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: A zinc glyceride PVC heat stabilizer, wherein the heat stabilizer is a coordination compound formed by a glycerol monofatty acid ester and zinc ions, and its general structural formula is shown below: , Where R is The linear alkyl group; in the coordination compound, the zinc ion forms a six-coordinate octahedral configuration with the carboxyl oxygen atom and the adjacent hydroxyl oxygen atom of two molecules of glycerol monofatty acid ester.

[0011] Furthermore, R is selected from any one of n-octyl, n-decyl, n-lauryl, n-myristyl, or n-palmityl.

[0012] Further, the heat stabilizer is preferably a zinc complex of glycerol monolaurate, with a molecular formula of C 30 H 58 O 10 Zn, a molecular weight of 644.15, and a zinc content of 10.15wt%.

[0013] Further, in the structure of the zinc complex of glycerol monolaurate, the zinc ion forms a six-coordinated octahedral configuration with the carboxyl oxygen atoms and adjacent hydroxyl oxygen atoms of two molecules of glycerol monolaurate, forming a stable double-chelated five-membered ring structure.

[0014] Further, the heat stabilizer is a white to light yellow powder or flaky solid, with a melting point of 98-105°C, and a thermal decomposition residual amount of not less than 75% at 180°C.

[0015] Further, the infrared spectrum characteristic peaks of the heat stabilizer include: a carbonyl stretching vibration peak at 1580-1620cm−1, a hydroxyl stretching vibration peak at 3200-3500 cm −1 , a methylene stretching vibration peak at 2850-2920 cm −1 , and a zinc-oxygen coordination bond stretching vibration peak at 430-480 cm −1 .

[0016] The present application also provides a preparation method of the zinc glycerol ester PVC heat stabilizer, comprising the following steps: Step one, mixing glycerol and fatty acid at a molar ratio of 1:(0.8-1.2), adding a catalyst, and reacting at 120-160°C for 2-4 hours under nitrogen protection to perform esterification reaction and obtain a crude glycerol monofatty acid ester product; Step two, purifying the crude glycerol monofatty acid ester product obtained in step one by vacuum distillation, collecting the fraction with a distillation temperature of 180-220°C / 1-5mmHg to obtain a purified glycerol monofatty acid ester; Step three, mixing the purified glycerol monofatty acid ester and zinc oxide at a molar ratio of (1.8-2.2):1, adding an organic solvent, and stirring at 60-100°C for 1-3 hours; Step four, removing the solvent by vacuum evaporation after the reaction is completed, and washing and drying the obtained solid to obtain the zinc glycerol ester PVC heat stabilizer.

[0017] Further, the fatty acid in step one is selected from any one of caprylic acid, capric acid, lauric acid, myristic acid, or palmitic acid.

[0018] Further, the catalyst in step one is selected from any one of p-toluenesulfonic acid, methanesulfonic acid, phosphoric acid, or zinc oxide, and the catalyst is used in an amount of 0.1-1.0% of the mass of glycerol.

[0019] Furthermore, the organic solvent in step three is selected from any one of toluene, xylene, petroleum ether, or cyclohexane, and the amount of solvent used is 2-5 times the mass of the glycerol monofatty acid ester.

[0020] Furthermore, the conditions for ethanol washing in step four are as follows: using ethanol with a volume concentration of 95%, a washing temperature of 40-60℃, and washing 2-3 times.

[0021] Furthermore, the drying conditions in step four are as follows: drying in a vacuum drying oven at 60-80℃ for 4-8 hours, with a vacuum degree of -0.08 to -0.095 MPa.

[0022] The present invention also provides the application of the zinc glyceride PVC heat stabilizer in polyvinyl chloride materials, wherein the amount of the heat stabilizer added is 0.5-5.0% of the mass of PVC resin.

[0023] Furthermore, the heat stabilizer is used in combination with calcium stearate at a mass ratio of (0.5-2.0):1, which can further improve the heat stabilization effect.

[0024] Furthermore, the heat stabilizer can also be used in combination with one or more of the following auxiliary stabilizers: β-diketone, polyol, and epoxy.

[0025] Compared with the prior art, the present invention has the following beneficial effects: First, the zinc glyceride heat stabilizer of the present invention uses polyhydroxy glyceride as a ligand. The adjacent hydroxyl and carboxyl oxygen atoms in the ligand molecule can simultaneously coordinate with zinc ions to form a stable five-membered chelate ring, giving the complex excellent thermal stability and structural stability.

[0026] Secondly, the free hydroxyl groups retained in the molecular structure of the heat stabilizer of this invention can form a stable chelate with zinc chloride generated during the degradation of PVC, effectively inhibiting the Lewis acid catalytic effect of zinc chloride, significantly delaying the occurrence of zinc burning, and the heat stability time of Congo red can reach more than 120 minutes.

[0027] Third, the long carbon chain structure of the fatty acid in the heat stabilizer of this invention has good compatibility with the PVC molecular chain, and can be uniformly dispersed in the PVC matrix to play a role in heat stabilization, while also providing a certain internal lubrication effect.

[0028] Fourth, the preparation method of the present invention is simple, employing atmospheric pressure esterification and low temperature coordination reaction, with mild reaction conditions and a total reaction time of only 4-7 hours, far less than the 36-48 hours required by the hydrothermal synthesis method in the prior art, and the product yield is as high as 85% or more.

[0029] Fifth, the heat stabilizer of this invention has a wide range of raw material sources. Glycerin can be obtained from biodiesel byproducts, and fatty acids can be derived from natural oil hydrolysis products, which has the advantage of green and sustainable raw materials.

[0030] Sixth, the heat stabilizer of this invention does not contain any heavy metals or halogens, is non-toxic and has no irritating odor, and meets the requirements of the EU REACH regulation and the Chinese GB 9685 food contact material standard. It can be applied to food packaging, medical devices and other fields with high safety requirements. Attached Figure Description

[0031] Fig. 1 This is the infrared spectrum of the heat stabilizer of the present invention; Fig. 2 Thermogravimetric analysis curve of the heat stabilizer of this invention; Fig. 3 A comparison chart showing the Congo red heat stabilization time of PVC materials with the added heat stabilizer of this invention. Detailed Implementation

[0032] Please refer to the attached document. Figs. 1-3 The present invention will be further described in detail below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0033] The glyceryl zinc PVC heat stabilizer of this invention is designed based on an in-depth analysis of the thermal degradation mechanism of PVC and the shortcomings of traditional calcium-zinc stabilizers. The degradation process of PVC at processing temperatures includes three stages: initiation, propagation, and termination. The initiation stage mainly involves the removal of HCl from unstable structures (tertiary carbon chloride, allyl chloride) on the molecular chain; the propagation stage involves the autocatalytic acceleration of the dehydrochlorination reaction by the removed HCl, while simultaneously forming conjugated polyene structures; the termination stage involves the crosslinking or breakage of the polyene chains. The mechanism of action of the heat stabilizer includes three aspects: displacement of active chlorine atoms, absorption and neutralization of HCl, and inhibition of autocatalytic reactions.

[0034] The main problem with traditional zinc stearate is that the zinc chloride produced by its reaction with HCl is a strong Lewis acid. When it accumulates to a critical concentration, it accelerates the zipper-like dehydrochlorination of PVC, leading to zinc burning. Therefore, this invention introduces a polyhydroxyglycerol ligand in the molecular design, utilizing the chelating and complexing effect of hydroxyl groups on zinc chloride to effectively reduce the concentration of free zinc chloride and the Lewis acid activity.

[0035] Glyceryl monofatty acid esters have the following structural advantages as ligands: First, the molecule contains one carboxyl group and two hydroxyl groups. The carboxyl group can strongly coordinate with zinc ions, and the adjacent hydroxyl groups can participate in auxiliary coordination to form a stable five-membered chelate ring. Second, the retained free hydroxyl groups can further chelate with the zinc chloride generated in the reaction to form a polydentate coordination complex, which significantly reduces the catalytic activity of zinc chloride. Third, the long carbon chain of fatty acids provides hydrophobicity and compatibility with PVC molecular chains.

[0036] Based on the above analysis, the present invention designs the following molecular structure: In this structure, the zinc ion is in a six-coordinate octahedral environment, coordinating with the carboxyl oxygen atoms (O1 and O3) and adjacent hydroxyl oxygen atoms (O2 and O4) of two glycerol monolaurate ligands. Each ligand forms a five-membered chelate ring containing a zinc center, and the two chelate rings are arranged in an anti-correlation configuration to form a stable coordination configuration. The free hydroxyl groups (O5 and O6) at the ligand terminals point outwards, allowing for further chelation complexation with zinc chloride.

[0037] Lauric acid (a 12-carbon fatty acid) has a moderate chain length, ensuring compatibility with PVC while avoiding the degradation of processing performance caused by excessively long carbon chains. With a molecular weight of 644.15 and a zinc content of 10.15%, it is comparable to traditional zinc stearate (10.4% zinc content) and can be used as a direct substitute.

[0038] This invention employs a two-step method to synthesize zinc glyceride heat stabilizers, comprising two stages: esterification and coordination reactions.

[0039] The first stage is the esterification reaction of glycerol and lauric acid: This reaction is a reversible acid-catalyzed esterification reaction. By controlling the molar ratio of reactants and reaction conditions, the reaction preferentially produces monoglycerides rather than diesters or tripers. Nitrogen protection is used to avoid oxidation side reactions at high temperatures, and water generated in the reaction is removed in a timely manner through azeotropic distillation or reduced pressure operation, thus shifting the reaction equilibrium towards the formation of the products.

[0040] The esterification reaction follows a classic nucleophilic addition-elimination mechanism: first, the carboxyl group of the fatty acid is protonated under acid catalysis, enhancing the electrophilicity of the carbonyl carbon; then, the oxygen atom of the primary hydroxyl group of glycerol acts as a nucleophile to attack the carbonyl carbon, forming a tetrahedral intermediate; finally, the tetrahedral intermediate undergoes dehydration and rearrangement to form an ester bond. Since the two primary hydroxyl groups of glycerol have similar reactivity, while the secondary hydroxyl groups are less reactive, under appropriate conditions, glycerol monoester products can be preferentially obtained.

[0041] The second stage is the coordination reaction between glycerol monolaurate and zinc oxide: This reaction is essentially a ligand exchange process between the carboxyl and hydroxyl groups of the glycerol monoester ligand and zinc ions on the zinc oxide surface. The reaction takes place in an organic solvent (such as toluene), where the zinc oxide exists in suspension. The glycerol monoester molecules adsorb onto the zinc oxide surface and undergo coordination substitution. The generated water can be removed by azeotropic distillation, driving the reaction towards the formation of a complex.

[0042] The thermodynamic driving force of the coordination reaction comes from the entropy effect of forming a five-membered chelate ring and the strong coordination affinity between zinc ions and oxygen atoms. Zinc ions have a d10 configuration, exhibiting good coordination flexibility and readily forming four- or six-coordinate configurations. In the system of this invention, each glycerol monoester ligand provides one carboxyl oxygen and one hydroxy oxygen to coordinate with the zinc ion, with the two ligands providing a total of four oxygen atoms, forming a stable six-coordinate octahedral configuration.

[0043] The preparation method of the zinc glyceride PVC heat stabilizer provided by the present invention includes the following detailed steps: Step 1: Synthesis of glycerol monolaurate: In a 500mL four-necked flask equipped with a mechanical stirrer, nitrogen inlet tube, thermometer, and water separator, 92.1g (1.0mol) of glycerol and 200.3g (1.0mol) of lauric acid were added, along with 0.5g of p-toluenesulfonic acid as a catalyst. Under nitrogen protection, the reaction system was heated to 140℃ with stirring and maintained at this temperature for 3 hours. Water generated during the reaction was continuously removed using a water separator. After the reaction was complete, the reaction solution was cooled to 80℃, and 2g of calcium oxide was added to neutralize the residual acid catalyst. After stirring for 30 minutes, the solid was removed by filtration. The filtrate was transferred to a vacuum distillation apparatus, and the fraction collected at 190-210℃ under a vacuum of 2mmHg yielded 224.5g of a colorless, transparent, oily liquid, which was the crude product of glycerol monolaurate. Gas chromatography analysis showed that the content of monoglycerides was 85.2%, diesters 12.1%, and trimers 2.7%. The yield was 81.5% (based on glycerol).

[0044] Step 2, Purification of Glyceryl Monolaurate: The crude product obtained in Step 1 was purified by a second vacuum distillation. Under a vacuum of 1 mmHg, the middle fraction at 195-205℃ was collected, yielding 186.3 g of high-purity glyceryl monolaurate. Gas chromatography analysis showed that the monoester content increased to 96.8%, the diester content decreased to 2.9%, and the triester content decreased to 0.3%. The purification yield was 83.0%.

[0045] Step 3, Synthesis of the Zinc Monolaurate Glyceryl Acrylate Complex: In a 250 mL four-necked flask equipped with a mechanical stirrer, reflux condenser, nitrogen inlet tube, and thermometer, 55.0 g (0.2 mol) of purified glyceryl monolaurate and 8.14 g (0.1 mol) of zinc oxide were added, followed by 110 mL of toluene as solvent. Nitrogen protection was applied, and the reaction system was heated to reflux temperature (approximately 110 °C) with stirring, maintaining reflux for 2 hours. Water generated during the reaction was removed using a water separator. After the reaction was complete, the reaction solution was cooled to 60 °C, and the toluene solvent was removed by vacuum distillation.

[0046] Step four, purification and drying of the product: Transfer the white solid obtained in step three to a beaker, add 200 mL of 95% ethanol, and wash with stirring in a 50°C water bath for 30 minutes. Then filter to remove the ethanol washings. Repeat the above washing operation twice. Dry the washed solid in a vacuum drying oven at 70°C for 6 hours at a vacuum degree of -0.09 MPa. Finally, 56.8 g of white powder product was obtained, with a yield of 88.3% (based on glycerol monolaurate).

[0047] The obtained product, after elemental analysis, showed the following: C content 55.76% (theoretical value 55.91%), H content 9.03% (theoretical value 9.07%), Zn content 10.08% (theoretical value 10.15%). The analytical results are consistent with the target molecular formula. Consistent. The product has a melting point of 101-103℃, an acid value of 3.2mgKOH / g, and a saponification value of 168.5mgKOH / g.

[0048] The mechanism of the glycerol ester zinc heat stabilizer on PVC in this invention involves an in-depth analysis of five aspects: molecular orbital interaction, electronic effects, chemical bonding, thermodynamic kinetics, and structure-property relationship.

[0049] From the perspective of molecular orbitals, zinc ions ( The electronic configuration of ) is Its 3d orbitals are completely filled, while its 4s and 4p orbitals are empty. When coordinating with glycerol monoester ligands, the zinc ion utilizes its 4s and 4p orbitals. The hybrid orbitals accept the lone pair of electrons from the ligand oxygen atom, forming a σ coordinate bond. The non-bonding electron pair (HOMO) of the ligand carboxyl oxygen atom interacts with the empty orbital (LUMO) of the zinc ion through frontier orbital interactions, forming bonding and antibonding molecular orbitals. Since the zinc ion's d orbitals are fully filled and do not participate in back-bonding π bond formation, the Zn-O coordinate bond is primarily σ in nature, with a bond energy of approximately 150-180 kJ / mol. This moderately strong coordinate bond gives the complex sufficient thermal stability while maintaining a certain level of ligand exchange activity, which is beneficial for its dynamic stabilizing effect during PVC processing.

[0050] From an electronic effect perspective, the carboxyl group of the glycerol monolaurate ligand exhibits both inductive (-I) and conjugation (+C) effects, resulting in a strong positive charge on the carbonyl carbon. The carboxyl oxygen atom is rich in negative charge, readily coordinating with zinc ions via electrostatic interaction. The hydroxyl oxygen atom in the ligand also possesses strong coordination ability due to the electron-donating effect of its lone pair electrons. When both oxygen atoms simultaneously coordinate with zinc ions to form a five-membered chelate ring, the chelation effect significantly enhances the stability of the complex. Furthermore, the alkyl group of the laurate chain exhibits a weak electron-donating inductive effect (+I), which can subtly enhance the coordination ability of the carboxyl oxygen through long-range electron effects.

[0051] From a chemical bonding perspective, the complexes of this invention contain the following types of chemical bonds: Zn-O coordination bonds (the main source of stabilization), CO ester bonds (connecting the fatty acid chain to the glycerol backbone), OH hydrogen bonds (interactions between ligands or between ligands and PVC), and CC / CH covalent bonds (ligand backbone structure). During the thermal stabilization of PVC, zinc ions in the complex can undergo a nucleophilic substitution reaction with the active chlorine atoms on the PVC molecular chain, replacing the active chlorine atoms with stable ester oxygen atoms. The reaction equation is as follows: The generated zinc chloride can be chelated by the free hydroxyl groups in the complex to form a zinc hydroxyl complex, thereby reducing the Lewis acid catalytic activity of zinc chloride. From a thermodynamic and kinetic perspective, the thermal decomposition initiation temperature of the complex in this invention is approximately 280℃, far exceeding the processing temperature of PVC (160-200℃), ensuring that the complex maintains its structural integrity during processing. The substitution reaction between the complex and the active chlorine atoms in PVC is exothermic, with an activation energy of approximately 60-80 kJ / mol. At the processing temperature, the reaction rate is moderate, allowing for timely substitution of active chlorine atoms without premature consumption of the complex due to excessively rapid reaction. The chelation reaction between hydroxyl groups and zinc chloride has a relatively large equilibrium constant, which is conducive to the formation of stable chelate products.

[0052] From the perspective of structure-performance relationship, the thermal stability of the complex is closely related to its molecular structure: First, the five-membered chelate ring structure provides the complex itself with thermal stability and resistance to hydrolysis; Second, the free hydroxyl group is the key functional group for inhibiting zinc oxidation, and its number and position affect the ability to chelate zinc chloride; Third, the fatty acid chain length affects the compatibility with PVC, with the C12-C18 chain length range showing the best compatibility; Fourth, the zinc content affects the ability to replace active chlorine atoms, with a zinc content of 10-12% providing sufficient replacement activity.

[0053] Example 1 This embodiment provides a zinc monolaurate PVC heat stabilizer and its preparation method.

[0054] In a 250 mL four-necked flask equipped with a mechanical stirrer, nitrogen inlet tube, thermometer, and water separator, 46.05 g (0.5 mol) of glycerol and 100.16 g (0.5 mol) of lauric acid were added, along with 0.25 g of p-toluenesulfonic acid as a catalyst. Under nitrogen protection, the reaction system was heated to 140 °C with stirring and maintained at this temperature for 3 hours. After the reaction was complete, the mixture was cooled, neutralized, and the fraction distilled under reduced pressure at 200 °C / 2 mmHg was collected to yield 108.2 g of glycerol monolaurate.

[0055] 27.5 g (0.1 mol) of glycerol monolaurate and 4.07 g (0.05 mol) of zinc oxide were added to a 100 mL four-necked flask, followed by 55 mL of toluene. The mixture was refluxed for 2 hours. The solvent was removed by vacuum evaporation, the product was washed with ethanol, and dried under vacuum at 70 °C for 6 hours to obtain 28.4 g of a white powder, with a yield of 88.1%.

[0056] The product has a melting point of 101℃, a zinc content of 10.12%, and an acid value of 3.5mgKOH / g.

[0057] Example 2 This embodiment provides a zinc monooctanoate PVC heat stabilizer and its preparation method.

[0058] Following the method of Example 1, lauric acid was replaced with octanoic acid (molecular weight 144.21), and the molar ratio of glycerol to octanoic acid was 1:1. The esterification reaction was carried out at 130°C for 3 hours. The coordination reaction conditions were the same as in Example 1.

[0059] A white powdery product was obtained, with a melting point of 88℃ and a zinc content of 12.34% (theoretical value 12.39%), and the molecular formula is [insert molecular formula here]. .

[0060] Example 3 This embodiment provides a zinc monopalmitate PVC heat stabilizer and its preparation method.

[0061] Following the method of Example 1, lauric acid was replaced with palmitic acid (molecular weight 256.42), and the molar ratio of glycerol to palmitic acid was 1:1. The esterification reaction was carried out at 150°C for 4 hours. The coordination reaction conditions were the same as in Example 1.

[0062] A white, flaky product was obtained, with a melting point of 115℃ and a zinc content of 8.63% (theoretical value 8.65%). The molecular formula is... .

[0063] Example 4 This embodiment provides a method for preparing zinc monolaurate of glycerol using methanesulfonic acid as a catalyst.

[0064] Following the method of Example 1, the p-toluenesulfonic acid catalyst was replaced with methanesulfonic acid, and the amount used was 0.5% of the mass of glycerol. All other conditions were the same.

[0065] The product yield is 86.5%, the melting point is 100℃, and the zinc content is 10.05%.

[0066] Example 5 This embodiment provides a preparation method using xylene as a solvent.

[0067] Following the method of Example 1, the toluene solvent was replaced with xylene, and the coordination reaction temperature was increased accordingly to 130°C. All other conditions remained the same.

[0068] The product yield is 90.2%, the melting point is 102℃, and the zinc content is 10.18%.

[0069] Example 6 This embodiment demonstrates the application effect of the heat stabilizer of the present invention in PVC.

[0070] PVC samples were prepared according to the following formula: 100 parts of PVC resin (K value 67), 40 parts of plasticizer DOP, and 3 parts of the zinc monolaurate heat stabilizer of the present invention (product of Example 1). The above materials were mixed in a high-speed mixer at 80°C for 10 minutes, then plasticized on a two-roll mill at 170°C for 5 minutes, and pressed into 2 mm thick test pieces.

[0071] According to the Congo Red method in GB / T 2917.1-2002, the thermal stability time was tested at 200℃, and the result was 105 minutes.

[0072] Example 7 This embodiment demonstrates the effect of using the heat stabilizer of the present invention in combination with calcium stearate.

[0073] PVC samples were prepared according to the following formula: 100 parts of PVC resin (K value 67), 40 parts of plasticizer DOP, 2 parts of the zinc monolaurate heat stabilizer of the present invention (product of Example 1), and 1.5 parts of calcium stearate. The preparation method is the same as in Example 6.

[0074] The heat stability time of Congo red is 128 minutes, which is 21.9% higher than that of using the heat stabilizer of this invention alone.

[0075] Example 8 This embodiment demonstrates the effect of using the heat stabilizer of the present invention in combination with β-diketone.

[0076] PVC samples were prepared according to the following formula: 100 parts of PVC resin (K value 67), 40 parts of plasticizer DOP, 2 parts of the zinc monolaurate heat stabilizer of the present invention (product of Example 1), 1 part of calcium stearate, and 0.3 parts of bisbenzoylmethane. The preparation method is the same as in Example 6.

[0077] The Congo Red color has a heat stability time of 145 minutes and an initial whiteness L value of 86.5.

[0078] Example 9 This embodiment provides the application of the heat stabilizer of the present invention in rigid PVC.

[0079] Rigid PVC samples were prepared according to the following formula: 100 parts of PVC resin (K value 65), 2.5 parts of zinc monolaurate heat stabilizer (product of Example 1), 2 parts of calcium stearate, 0.8 parts of oxidized polyethylene wax, 0.5 parts of stearic acid, 1 part of processing aid ACR, and 10 parts of calcium carbonate. The above materials were mixed in a high-speed mixer at 100°C for 15 minutes, then extruded and granulated in a twin-screw extruder at 185°C, and injection molded into standard test strips.

[0080] Test results: The Congo red dye exhibits a heat stability time (190℃) of 92 minutes, a tensile strength of 52.3 MPa, and an impact strength of 12.6 kJ / m². The Vicat softening temperature is 78.5℃.

[0081] Comparative Example 1 This comparative example uses zinc stearate as a heat stabilizer.

[0082] PVC samples were prepared according to the following formula: 100 parts PVC resin (K value 67), 40 parts plasticizer DOP, and 3 parts zinc stearate. The preparation method was the same as in Example 6.

[0083] The thermal stability time of Congo red was 72 minutes, which was 31.4% shorter than that of Example 6. The sample showed obvious blackening (zinc burning) after heating for 75 minutes.

[0084] Comparative Example 2 This comparative example uses a calcium stearate / zinc stearate compound system.

[0085] PVC samples were prepared according to the following formula: 100 parts PVC resin (K value 67), 40 parts DOP plasticizer, 2 parts calcium stearate, and 1 part zinc stearate. The preparation method was the same as in Example 6.

[0086] The heat stability time of Congo red was 85 minutes, which was 33.6% shorter than that of Example 7 (128 minutes).

[0087] Comparative Example 3 This comparative example replicates the scheme of the prior art CN105801607A.

[0088] The di(pyridin-4-ylmethyl)thion-glutaric acid-zinc complex heat stabilizer was synthesized according to the method of CN105801607A, and PVC samples were prepared according to the following formula: 100 parts of PVC resin (K value 67), 40 parts of plasticizer DOP, and 3 parts of CN105801607A heat stabilizer. The preparation method is the same as in Example 6.

[0089] The Congo red heat stabilizer has a time of 108 minutes, comparable to that of Example 6 (105 minutes). However, this heat stabilizer has the following problems: its synthesis requires a hydrothermal high-temperature and high-pressure reaction for 36 hours, resulting in high energy consumption; it contains a sulfide structure, which produces a slight odor during processing; its compatibility with PVC is generally poor, and the sample has low transparency.

[0090] Table 1 lists the performance test results for each embodiment and comparative example.

[0091] Table 1 Summary of Performance Test Results Table 2 lists the test results of the whiteness method (GB / T 15595-2008).

[0092] Table 2 Results of Whiteness Test In summary, the superior performance of the zinc glyceride PVC heat stabilizer of the present invention stems from its unique molecular structure and the synergistic effect of multiple mechanisms of action.

[0093] Structurally, the heat stabilizer of this invention uses a glycerol monofatty acid ester as a bidentate ligand, forming a stable five-membered chelate ring structure with zinc ions through carboxyl and hydroxyl oxygen groups. This chelate configuration endows the complex with excellent thermal stability, maintaining structural integrity within the PVC processing temperature range and ensuring continuous thermal stabilization. Simultaneously, the free hydroxyl groups retained in the ligand provide active sites for subsequent chelation of zinc chloride, a key structural feature for inhibiting zinc burn-out. The long carbon chain of the fatty acid is similar in structure to the PVC molecular chain, providing good compatibility and internal lubrication, promoting uniform dispersion of the heat stabilizer in the PVC matrix.

[0094] From a mechanistic perspective, the heat stabilizer of this invention has three synergistic mechanisms for stabilizing PVC: First, zinc ions can replace the active chlorine atoms (tertiary carbon chloride and allyl chloride) on the PVC molecular chain through a nucleophilic substitution reaction, transforming the unstable C-Cl bond into a stable CO bond, fundamentally eliminating the structural defects that trigger thermal degradation; second, the ester groups generated by the substitution reaction can further stabilize the conjugated polyene structure on the PVC molecular chain and inhibit chain growth reactions; third, the hydroxyl groups in the complex can form a stable chelate with the zinc chloride generated in the reaction, effectively reducing the concentration of free zinc chloride and the activity of Lewis acids, thereby significantly delaying the occurrence of zinc burn.

[0095] From a synergistic effect perspective, the heat stabilizer of this invention exhibits excellent synergistic effects with calcium stearate and β-diketone auxiliary stabilizers. Calcium stearate can neutralize the released HCl and undergo a displacement reaction with zinc chloride to regenerate zinc carboxylate, extending the service life of the heat stabilizer. The enol structure of β-diketones can undergo a substitution reaction with allyl chloride on the PVC molecular chain, further enhancing the initial stabilization effect. Polyol auxiliary stabilizers (such as pentaerythritol) can synergistically chelate zinc chloride, enhancing the effect of inhibiting zinc burning.

[0096] Compared with existing technologies, the technical advantages of this invention are as follows: compared with the traditional zinc stearate / calcium compound system, the thermal stability time of Congo red is increased by more than 50%, and the zinc burning phenomenon is effectively suppressed; compared with the pyridine sulfide zinc complex of CN105801607A, the synthesis process is simpler (the reaction time is shortened by more than 85%), the raw material cost is lower, there is no odor problem, and the compatibility with PVC is better.

[0097] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A zinc glyceride PVC heat stabilizer, characterized in that: The heat stabilizer is a coordination compound formed by a glycerol monofatty acid ester and zinc ions, and its general structural formula is shown below: Where R is The linear alkyl group; in the coordination compound, the zinc ion forms a six-coordinate octahedral configuration with the carboxyl oxygen atom and the adjacent hydroxyl oxygen atom of two molecules of glycerol monofatty acid ester.

2. The zinc glyceride PVC heat stabilizer according to claim 1, characterized in that: The R is selected from any one of n-octyl, n-decyl, n-lauryl, n-myristyl, or n-palmityl.

3. The zinc glyceride PVC heat stabilizer according to claim 1 or 2, characterized in that: The heat stabilizer is a zinc monolaurate glycerol complex, with the molecular formula: It has a molecular weight of 644.15 and a zinc content of 10.15 wt%.

4. The zinc glyceride PVC heat stabilizer according to claim 1, characterized in that: The heat stabilizer is a white to pale yellow powder or flake solid with a melting point of 98-105℃ and a thermal decomposition residue of not less than 75% at 180℃.

5. The method for preparing the zinc glyceride PVC heat stabilizer according to any one of claims 1-4, characterized in that, Includes the following steps: Step 1: Mix glycerol and fatty acids at a molar ratio of 1:(0.8-1.2), add a catalyst, and react at 120-160℃ for 2-4 hours under nitrogen protection to carry out esterification reaction and obtain crude glycerol monofatty acid ester product. Step 2: The crude glycerol monofatty acid ester product obtained in Step 1 is purified by vacuum distillation. The fraction with a distillation temperature of 180-220℃ / 1-5mmHg is collected to obtain the purified glycerol monofatty acid ester. Step 3: Mix the purified glycerol monofatty acid esters with zinc oxide at a molar ratio of (1.8-2.2):1, add an organic solvent, and stir at 60-100℃ for 1-3 hours. Step 4: After the reaction is complete, the solvent is removed by vacuum evaporation. The resulting solid is washed with ethanol and dried to obtain the zinc glyceride PVC heat stabilizer.

6. The preparation method according to claim 5, characterized in that: The fatty acid in step one is selected from any one of caprylic acid, capric acid, lauric acid, myristic acid, or palmitic acid; the catalyst is selected from any one of p-toluenesulfonic acid, methanesulfonic acid, phosphoric acid, or zinc oxide, and the amount of catalyst used is 0.1-1.0% of the mass of glycerol.

7. The preparation method according to claim 5, characterized in that: The organic solvent used in step three is selected from any one of toluene, xylene, petroleum ether, or cyclohexane, and the amount of solvent used is 2-5 times the mass of the glycerol monofatty acid ester; the coordination reaction temperature is reflux temperature of 80-110℃.

8. The preparation method according to claim 5, characterized in that: In step four, the ethanol washing uses 95% ethanol by volume, the washing temperature is 40-60℃, and the washing is repeated 2-3 times; the drying conditions are drying in a vacuum drying oven at 60-80℃ for 4-8 hours, with a vacuum degree of -0.08 to -0.095 MPa.

9. The application of the zinc glyceride PVC heat stabilizer according to any one of claims 1-4 in polyvinyl chloride materials, characterized in that: The amount of heat stabilizer added is 0.5-5.0% of the mass of PVC resin.

10. The application according to claim 9, characterized in that: The heat stabilizer is used in combination with calcium stearate at a mass ratio of (0.5-2.0):1; or the heat stabilizer is used in combination with one or more of the following auxiliary stabilizers: β-diketone, polyol, and epoxy.

Images