An alkyl side chain-containing polyamide-modified hydrotalcite intercalated polymer, and a preparation method and application thereof

Abstract

The application discloses an alkyl side chain-containing polyamide modified hydrotalcite intercalation polymer and a preparation method and application thereof, and belongs to the technical field of PVC heat stabilizers. The alkyl side chain-containing polyamide modified hydrotalcite intercalation polymer is obtained by modifying hydrotalcite by using an alkyl side chain-containing polyamide which is generated by polyacrylic acid and a primary amine through the action of a condensation agent, and has the advantages that, as an auxiliary heat stabilizer, the alkyl side chain-containing polyamide modified hydrotalcite intercalation polymer can improve the heat stability, mechanical properties and water resistance of PVC pipes.

Description

Technical Field

[0001] This application belongs to the field of PVC heat stabilizer technology, and in particular relates to a hydrotalcite intercalated polymer modified with alkyl side chain polyamide, its preparation method and application. Background Technology

[0002] Polyvinyl chloride (PVC) materials are thermosensitive due to their molecular structure. During processing, heat stabilizers are added to inhibit thermal degradation, thereby maintaining their physical properties and significantly improving processing heat resistance, colorfastness, and overall product quality. While traditional lead salt stabilizers possess excellent thermal stability, the environmental risks posed by their heavy metal toxicity have drawn global attention. Organotin stabilizers exhibit excellent thermal stability, light stability, and product transparency; however, their high cost limits their application primarily to high-end transparent PVC product manufacturing. Calcium-zinc stabilizers are recognized as non-toxic and environmentally friendly heat stabilizers, but they suffer from insufficient processing heat stabilization time and poor heat stabilization effect, failing to meet practical production needs. Such composite systems typically consist of two or more main stabilizers synergistically enhanced with auxiliary components (such as hydrotalcite), significantly improving thermal stability through intermolecular interactions.

[0003] Hydrotalcite, rich in hydroxyl groups, can effectively adsorb hydrogen chloride (HCl) produced by the thermal decomposition of PVC, thereby inhibiting the auto-accelerated degradation effect induced by hydrogen chloride. However, the hydroxyl groups enriched on its surface generate strong intermolecular attraction due to hydrogen bonding, which easily leads to particle agglomeration and uneven dispersion in the PVC matrix, especially during long-term heat processing, phase separation is likely to occur.

[0004] Existing technology discloses an environmentally friendly calcium-zinc composite heat stabilizer and its preparation method. This involves dissolving expanded vermiculite in nitric acid solution, sequentially adding zinc nitrate and lanthanum nitrate for ion exchange, then introducing an organic acid and adjusting the pH to an alkaline environment. Finally, organic acid-intercalated hydrotalcite is obtained with the assistance of sodium bicarbonate. Although this technology uses sodium organic acid salts for surface modification, the hydrophilic nature of the hydroxyl groups on the surface of the hydrotalcite layers remains fundamentally unchanged, resulting in a material that still exhibits significant polar characteristics. When combined with hydrophobic vinyl chloride, it easily forms water molecule diffusion channels in humid environments, leading to swelling stress concentration at the composite interface. This ultimately causes microcrack propagation and macroscopic cracking, severely limiting the material's water resistance. Furthermore, this patented process fails to effectively control the degree of interlayer delamination in the hydrotalcite; the layered stacking structure only partially dissociates, failing to fully expose the active hydroxyl sites at the layer edges and thus failing to maximize the auxiliary heat stabilizing effect.

[0005] Therefore, developing a hydrotalcite intercalated polymer modified with alkyl side chain polyamide as an auxiliary heat stabilizer to improve the thermal stability, mechanical properties and water resistance of PVC pipes is of great research significance and application value. Summary of the Invention

[0006] To address the technical problem that existing hydrotalcite-assisted stabilizers are insufficient to improve the thermal stability, mechanical properties, and water resistance of PVC pipes, the primary objective of this invention is to provide a hydrotalcite intercalated polymer modified with alkyl side-chain polyamide.

[0007] Another object of the present invention is to provide an auxiliary stabilizer comprising the above-described alkyl-side-chain polyamide-modified hydrotalcite intercalated polymer.

[0008] Another object of the present invention is to provide a stabilizer composition comprising the above-described alkyl-side-chain polyamide-modified hydrotalcite intercalated polymer.

[0009] Another object of the present invention is to provide the use of the above-mentioned auxiliary stabilizers in the preparation of PVC pipes.

[0010] Another object of the present invention is to provide a PVC composition comprising the above-described alkyl-side-chain polyamide-modified hydrotalcite intercalated polymer.

[0011] Another object of the present invention is to provide PVC pipes comprising the above-mentioned alkyl-side-chain polyamide-modified hydrotalcite intercalated polymer.

[0012] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: This invention protects a hydrotalcite intercalating polymer modified with alkyl side chain polyamide, which is prepared by the following method; S1. Polyacrylic acid, primary amine and condensing agent are dissolved in N-methylpyrrolidone and reacted to obtain polyamide containing alkyl side chains; S2. The solution obtained by adding S1 to the hydrotalcite dispersion reacts to obtain the hydrotalcite intercalated polymer; The primary amine is (CH3). x -NH2, where x is an integer from 6 to 12; The degree of polymerization of the polyacrylic acid is 100~200; In the hydrotalcite dispersion, the mass ratio of hydrotalcite to alkyl-side-chain polyamide is 3~9:1.

[0013] By employing an amphiphilic polyacrylic acid (PAA) modifier, its free carboxyl groups (-COOH) are anchored to the positively charged surface of the hydrotalcite via electrostatic adsorption, and interact with interlayer CO3. 2-Ion exchange is conducted to strengthen interfacial bonding. Simultaneously, the steric hindrance effect of long-chain alkyl groups is utilized to expand the interlayer spacing of the hydrotalcite, creating channels for polymer chain intercalation. Furthermore, the micro-jets generated by ultrasonic cavitation overcome interlayer forces, driving the polymer chains to diffuse directionally into the interlayer domains to form stable chemical bonds. In addition, the hydrophobic association of alkyl chains reduces the surface energy of the hydrotalcite, inhibits nanoparticle aggregation, and constructs a hydrophobic-oleophilic interface in the PVC matrix, promoting uniform dispersion and forming a three-dimensional physical cross-linked network. This solves the compatibility problem between inorganic fillers and organic matrices, thus preventing the formation of water molecule diffusion channels in humid environments and avoiding cracking, thereby improving the water resistance of the material.

[0014] Regarding the principle of enhanced thermal stability, the hydroxyl groups (-OH) in the hydrotalcite layers and the interlayer CO3... 2- Through chemical adsorption and ion exchange (CO3) 2- + 2Cl - → CO2↑ + 2Cl⁻) This synergistically captures HCl / Cl produced during degradation. - The hydrotalcite inhibits autocatalytic reactions, while the expanded interlayer spacing forms a nano-confined space, blocking free radical diffusion paths and delaying PVC chain breakage. Regarding the mechanical property enhancement mechanism, the two-dimensional nanosheet structure of hydrotalcite enhances PVC rigidity through stress transfer, while the flexible interface layer of the intercalated polymer induces crazing shear bands, dissipating impact energy and achieving toughening. Furthermore, the interlayer organic segments form topological entanglements with the PVC molecular chains, strengthening interfacial stress transfer and inhibiting phase separation.

[0015] Preferably, x in the primary amine is 8 to 12.

[0016] Preferably, the primary amine is one or more of n-butylamine, dodecyl primary amine, or n-octylamine.

[0017] Preferably, the condensing agent is N,N'-dicyclohexylcarboimide (DCC).

[0018] Preferably, the reaction conditions in step S2 are 25~60℃ for 12~72 hours.

[0019] Preferably, the mass ratio of the hydrotalcite to the alkyl-side-chain polyamide is 1:1.5~9.

[0020] Preferably, 20-30% of the acrylic groups in the alkyl-side-chain polyamide-modified hydrotalcite intercalated polymer are replaced with amide alkyl groups.

[0021] The present invention also protects an auxiliary stabilizer comprising the above-mentioned hydrotalcite intercalated polymer modified with alkyl side chain polyamide.

[0022] The present invention also protects a stabilizer composition comprising the following components in parts by weight: 2-6 parts of a primary stabilizer and 0.3-2.1 parts of an auxiliary stabilizer; wherein the primary stabilizer is a calcium-zinc stabilizer.

[0023] The application of the aforementioned auxiliary stabilizers in the preparation of PVC pipes is also within the scope of protection of this invention.

[0024] The present invention also protects a PVC composition comprising the following components in parts by weight: 80-100 parts of PVC resin, 2.5-8.5 parts of the above-mentioned stabilizer composition, 20-80 parts of filler, 0.5-2 parts of stearic acid, 0.5-2 parts of paraffin wax, and 4-10 parts of ACR toughening agent.

[0025] Preferably, the filler is one or more of zeolite, talc, zinc carbonate, or calcium carbonate.

[0026] More preferably, the filler is calcium carbonate.

[0027] The present invention also protects a PVC pipe made from the above-described PVC composition.

[0028] Compared with the prior art, the present invention has the following beneficial effects: This invention protects a hydrotalcite intercalated polymer modified with alkyl side-chain polyamide. The hydrotalcite is modified by generating alkyl side-chain polyamide from polyacrylic acid and primary amine through the action of a condensing agent. As an auxiliary heat stabilizer, it can improve the thermal stability, mechanical properties and water resistance of PVC pipes. Detailed Implementation

[0029] The present invention is further illustrated below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions in the art or as recommended by the manufacturer; the raw materials and reagents used, unless otherwise specified, are all commercially available from the conventional market. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention are within the scope of protection claimed by the present invention.

[0030] The reagents used in the various embodiments and comparative examples of this invention are described below: Hydrotalcite: Magnesium aluminum hydrotalcite: Mg6Al2(OH) 16 CO3·4H2O.

[0031] Test metrics: (1) Thermal stability time (min): According to GB / T 2917.1-2002 "Determination of hydrogen chloride and any other acidic products released at high temperature from blends and products mainly composed of vinyl chloride homopolymers and copolymers"; (2) Mass of precipitate (mg): The PVC pipe material was extruded using an extruder. After running the machine continuously for 4 hours, the precipitate at the shaping sleeve was observed and the mass of the precipitate was weighed. (3) Tensile yield stress (MPa): Tested in accordance with GB / T 8804.2-2003 "Determination of tensile properties of thermoplastic pipes - Part 2: Rigid polyvinyl chloride (PVC-U), chlorinated polyvinyl chloride (PVC-C) and high-impact polyvinyl chloride (PVC-HI) pipes"; (4) Tensile yield stress (after the pipe is submerged in water for 90 days) (MPa); (5) Strength retention rate: Strength retention rate = 100% × (tensile yield stress after the pipe is submerged in water for 90 days) / tensile yield stress.

[0032] Example 1 Preparation method of hydrotalcite intercalated polymer modified with alkyl side chain polyamide: 1.50 g of polyacrylic acid (0.694 mol) was dissolved in 1.5 L of N-methylpyrrolidone and heated to 60 °C until completely dissolved. 35.87 g of n-octylamine (0.278 mol) and 58.19 g of N,N'-dicyclohexylcarboimide (0.282 mol) were dissolved separately in 750 mL of N-methylpyrrolidone and then added to the polyacrylic acid solution. The temperature was maintained at 60 °C and stirred for 24 hours. After the reaction was complete, the mixture was cooled to room temperature, and the insoluble substances were filtered off, leaving the filtrate. The filtrate was neutralized with sodium hydroxide, and the precipitate was washed with hot (60 °C) N-methylpyrrolidone and methanol. The product was then redissolved in water and precipitated in methanol. Finally, the product was further purified by dialysis, and 28% of the acrylic acid groups were replaced with amide alkyl groups.

[0033] S2. Disperse 20 g of hydrotalcite in 1980 mL of deionized water, dissolve 50 g of polymer in 950 mL of water, slowly add the hydrotalcite dispersion to the aqueous solution of polymer 1, stir at 70 °C for 4 h, then sonicate for 1.5 h, centrifuge, wash, and dry to obtain auxiliary heat stabilizer 1.

[0034] PVC pipe: 100 parts PVC resin, 3 parts calcium-zinc stabilizer, 20 parts calcium carbonate, 1 part stearic acid, 1 part paraffin wax, 6 parts ACR toughening agent, 2 parts auxiliary heat stabilizer.

[0035] Example 2 In the experimental method, steps S2 and the preparation of PVC pipes are the same as in Example 1, except that in step S1: 50 g of polyacrylic acid (0.694 mol) is dissolved in 1.5 L of N-methylpyrrolidone and heated to 60 °C until completely dissolved. 128.63 g of dodecyl primary amine (0.694 mol) and 143.19 g of N,N'-dicyclohexylcarboimide (0.694 mol) are dissolved in 1 L of N-methylpyrrolidone respectively, and then added to the polyacrylic acid solution. The temperature is maintained at 60 °C and stirred for 72 hours. After the reaction is complete, the mixture is cooled to room temperature, and the insoluble substances are filtered off, leaving the filtrate. The filtrate is neutralized with sodium hydroxide, and the precipitate is washed with hot (60 °C) N-methylpyrrolidone and methanol. The product is then redissolved in water and precipitated in methanol. Finally, the product is further purified by dialysis, and 25% of the acrylic acid groups are replaced with amide alkyl groups. .

[0036] Example 3 The PVC pipe composition is the same as in Example 1, except for step S1: 50 g of polyacrylic acid (0.694 mol) is dissolved in 1.5 L of N-methylpyrrolidone and heated to 60 °C until completely dissolved. 64.87 g of dodecyl primary amine (0.350 mol) and 72.21 g of N,N'-dicyclohexylcarboimide (0.350 mol) are dissolved in 1 L of N-methylpyrrolidone respectively, and then added to the polyacrylic acid solution. The temperature is maintained at 60 °C and stirred for 48 hours. After the reaction is complete, the mixture is cooled to room temperature, and the insoluble substances are filtered off, leaving the filtrate. The filtrate is neutralized with sodium hydroxide, and the precipitate is washed with hot (60 °C) N-methylpyrrolidone and methanol. The product is then redissolved in water and precipitated in methanol. Finally, the product is further purified by dialysis, and 15% of the acrylic acid groups are replaced with amide alkyl groups. .

[0037] Example 4 The PVC pipe composition is the same as in Example 1, except for step S1: 50 g of polyacrylic acid (0.694 mol) is dissolved in 1.5 L of N-methylpyrrolidone and heated to 60 °C until completely dissolved. 154.35 g of dodecyl primary amine (0.832 mol) and 171.67 g of N,N'-dicyclohexylcarboimide (0.832 mol) are dissolved in 1.5 L of N-methylpyrrolidone respectively, and then added to the polyacrylic acid solution. The temperature is maintained at 60 °C and stirred for 72 hours. After the reaction is complete, the mixture is cooled to room temperature, and the insoluble substances are filtered off, leaving the filtrate. The filtrate is neutralized with sodium hydroxide, and the precipitate is washed with hot (60 °C) N-methylpyrrolidone and methanol. The product is then redissolved in water and precipitated in methanol. Finally, the product is further purified by dialysis, and 35% of the acrylic acid groups are replaced with amide alkyl groups. .

[0038] Comparative Example 1 PVC pipe: 100 parts PVC resin, 3.0 parts calcium-zinc stabilizer, 20 parts calcium carbonate, 1.0 part stearic acid, 1.0 part paraffin wax, 6.0 parts ACR toughening agent, no auxiliary heat stabilizer in the material system.

[0039] Comparative Example 2 PVC pipe: 100 parts PVC resin, 3.0 parts calcium-zinc stabilizer, 20 parts calcium carbonate, 1.0 part stearic acid, 1.0 part paraffin wax, 6.0 parts ACR toughening agent, and 2.0 parts soybean oil auxiliary heat stabilizer are added to the above system.

[0040] Comparative Example 3 Referring to Example 1 of Chinese Patent CN119241911A - An Environmentally Friendly Calcium-Zinc Composite Heat Stabilizer and Its Preparation Method, organic acid intercalated hydrotalcite was prepared as an auxiliary stabilizer, and PVC pipes were prepared according to the following formula: 100 parts PVC resin, 3.0 parts calcium-zinc stabilizer, 20 parts calcium carbonate, 1.0 part stearic acid, 1.0 part paraffin wax, 6.0 parts ACR toughening agent, and 2.0 parts of the prepared organic acid intercalated hydrotalcite auxiliary stabilizer.

[0041] Comparative Example 4 In the experimental method, steps S2 and the preparation of PVC pipes are the same as in Example 1, except that in step S1: 50 g of polyacrylic acid (0.694 mol) is dissolved in 1.5 L of N-methylpyrrolidone and stirred at room temperature until completely dissolved. 8.22 g of propylamine (0.139 mol) and 29.09 g of N,N'-dicyclohexylcarboimide (0.141 mol) are dissolved in 300 mL of N-methylpyrrolidone, respectively, and then added to the polyacrylic acid solution. The temperature is maintained at 60°C and stirred for 12 hours. After the reaction is complete, the mixture is cooled to room temperature, and the insoluble substances are filtered off, leaving the filtrate. The filtrate is neutralized with sodium hydroxide, and the precipitate is washed with hot (60°C) N-methylpyrrolidone and methanol. The product is then redissolved in water and precipitated in methanol. Finally, the product is further purified by dialysis, and 30% of the acrylic acid groups are replaced with amide alkyl groups. .

[0042] Comparative Example 5 In the experimental method, steps S2 and the preparation of PVC pipes are the same as in Example 1, except for step S1: S1. 50 g of polyacrylic acid (0.694 mol) is dissolved in 1.5 L of N-methylpyrrolidone and heated to 60 °C until completely dissolved. 10.15 g of n-butylamine (0.139 mol) and 29.09 g of N,N'-dicyclohexylcarboimide (0.141 mol) are dissolved in 350 mL of N-methylpyrrolidone and then added to the polyacrylic acid solution. The temperature is maintained at 60 °C and stirred for 24 hours. After the reaction is complete, the mixture is cooled to room temperature, and the insoluble substances are filtered off, leaving the filtrate. The filtrate is neutralized with sodium hydroxide, and the precipitate is washed with hot (60 °C) N-methylpyrrolidone and methanol. The product is then redissolved in water and precipitated in methanol. Finally, the product is further purified by dialysis to obtain the following compound, in which 20% of the acrylic acid groups are replaced with amide alkyl groups: .

[0043] Comparative Example 6 In the experimental method, steps S2 and the preparation of PVC pipes are the same as in Example 1, except that in step S1: 50 g of polyacrylic acid (0.694 mol) is dissolved in 1.5 L of N-methylpyrrolidone and heated to 60°C until completely dissolved. 187.04 g of octadecylamine (0.694 mol) and 143.19 g of N,N'-dicyclohexylcarboimide (0.694 mol) are dissolved in 1.5 L of N-methylpyrrolidone respectively, and then added to the polyacrylic acid solution. The temperature is maintained at 60°C and stirred for 72 hours. After the reaction is complete, the mixture is cooled to room temperature, and the insoluble substances are filtered off, leaving the filtrate. The filtrate is neutralized with sodium hydroxide, and the precipitate is washed with hot (60°C) N-methylpyrrolidone and methanol. The product is then redissolved in water and precipitated in methanol. Finally, the product is further purified by dialysis, and 5% of the acrylic acid groups are replaced with amide alkyl groups. .

[0044] Comparative Example 7 The PVC pipe composition is the same as in Example 1, except that the mass ratio of the hydrotalcite to the polyamide containing dodecyl side chains is 2:1.

[0045] Comparative Example 8 The PVC pipe composition is the same as in Example 1, except that the mass ratio of the hydrotalcite to the polyamide containing dodecyl side chains is 10:1.

[0046] Table 1. Test results of the examples and comparative examples

[0047] Examples 1-4 provide a series of hydrotalcite intercalated polymers modified with alkyl side-chain polyamides, which achieve advantages in thermal stability time, low precipitate mass, tensile yield stress before and after immersion in water, and high strength retention.

[0048] Comparative Example 1, without the addition of an auxiliary stabilizer, exhibited the worst thermal stability and the most precipitates. Comparative Example 2 used soybean oil as an auxiliary stabilizer, but the traditional soybean oil auxiliary stabilizer had limited effectiveness, and its thermal stability and precipitates were inferior to those of the examples. Comparative Example 3 used organic acid-intercalated hydrotalcite as an auxiliary stabilizer. Although the existing technology has good initial thermal stability, it has poor water resistance, and its strength decreased from 46 to 37 MPa after immersion in water, exhibiting the defect of cracking due to water molecule diffusion. Comparative Example 4, using propylamine, showed decreased thermal stability, reduced strength retention, and decreased tensile yield stress both before and after immersion in water. Comparative Example 5, using n-butylamine, showed decreased thermal stability and increased precipitates. Comparative Example 6, using octadecylamine, had a low substitution ratio due to the large steric hindrance of the hydrophobic substituents, resulting in decreased mechanical properties after immersion in water. Comparative Example 7, with a low hydrotalcite content, showed a significant decrease in thermal stability, with both tensile yield stresses decreasing before and after immersion in water. Comparative Example 8, with a high hydrotalcite content, showed poor compatibility between the intercalated hydrotalcite composite and the PVC substrate material, leading to decreased thermal stability, increased precipitates, and unstable long-term performance.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A hydrotalcite intercalated polymer modified with alkyl side-chain polyamide, characterized in that, It is prepared by the following method: S1. Polyacrylic acid, primary amine and condensing agent are dissolved in N-methylpyrrolidone and reacted to obtain polyamide containing alkyl side chains; S2. The solution obtained by adding S1 to the hydrotalcite dispersion reacts to obtain the hydrotalcite intercalated polymer; The primary amine is CH3-(CH2). x-1 -NH2, where x is an integer from 6 to 12; The degree of polymerization of the polyacrylic acid is 100~200; In the hydrotalcite dispersion, the mass ratio of hydrotalcite to alkyl-side-chain polyamide is 3~9:1; In the alkyl-side-chain polyamide-modified hydrotalcite intercalated polymer, 20-30% of the acrylic groups are replaced with amide alkyl groups.

2. The hydrotalcite intercalated polymer modified with alkyl side chain polyamide according to claim 1, characterized in that, In the primary amine, x is 8~12.

3. The hydrotalcite intercalated polymer modified with alkyl side chain polyamide according to claim 1, characterized in that, The condensing agent is N,N'-dicyclohexylcarboimide (DCC).

4. The hydrotalcite intercalated polymer modified with alkyl side chain polyamide according to claim 1, characterized in that, The reaction conditions described in step S2 are 25~60℃ for 12~72 hours.

5. An auxiliary stabilizer, characterized in that, The auxiliary stabilizer includes the hydrotalcite intercalated polymer modified with alkyl side chain polyamide as described in any one of claims 1 to 4.

6. The use of the auxiliary stabilizer as described in claim 5 in the preparation of PVC pipes.

7. A stabilizer composition, characterized in that, It comprises the following components in parts by weight: 2-6 parts of primary stabilizer, 0.3-2.1 parts of auxiliary stabilizer as described in claim 5, wherein the primary stabilizer is a calcium-zinc stabilizer.

8. A PVC composition, characterized in that, The composition comprises the following components in parts by weight: 80-100 parts of PVC resin, 2.5-8.5 parts of the stabilizer composition according to claim 7, 20-80 parts of filler, 0.5-2 parts of stearic acid, 0.5-2 parts of paraffin wax, and 4-10 parts of ACR toughening agent.

9. A PVC pipe made from the PVC composition of claim 8.

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