Modified hydrotalcite intercalation polymer containing alkyl side chain polyamide as well as preparation method and application of modified hydrotalcite intercalation polymer

Abstract

The invention discloses a modified hydrotalcite intercalation polymer containing alkyl side chain polyamide as well as a preparation method and application of the modified hydrotalcite intercalation polymer, and belongs to the technical field of PVC (polyvinyl chloride) heat stabilizers. The alkyl-containing side chain polyamide modified hydrotalcite intercalation polymer is obtained by generating alkyl-containing side chain polyamide through polyacrylic acid and primary amine under the action of a condensing agent and modifying hydrotalcite, and as an auxiliary heat stabilizer, the alkyl-containing side chain polyamide modified hydrotalcite intercalation polymer can improve the heat stability, the mechanical property and the water resistance of a PVC pipe.

Description

Technical Field

[0001] The present application belongs to the technical field of PVC heat stabilizers, and in particular relates to a hydrotalcite intercalation polymer modified with polyamide containing alkyl side chains, and a preparation method and application thereof. Background Art

[0002] Due to the heat-sensitive nature of its molecular structure, polyvinyl chloride (PVC) requires the addition of heat stabilizers during processing to inhibit thermal degradation, thereby maintaining its physical properties and significantly improving processing heat resistance, discoloration resistance, and overall product quality. While traditional lead salt stabilizers offer excellent thermal stability, the environmental risks posed by their heavy metal toxicity have drawn global attention. Organotin stabilizers excel in thermal stability, light stability, and product transparency, but due to their high cost, they are primarily used in the production of high-end transparent PVC products. Calcium-zinc stabilizers are recognized as non-toxic and environmentally friendly heat stabilizers, but they suffer from shortcomings such as insufficient processing thermal stabilization time and poor thermal stabilization effects, making them unsuitable for actual production needs. Such composite systems typically consist of two or more primary stabilizers synergistically enhanced with auxiliary components (such as hydrotalcite), significantly enhancing thermal stability through intermolecular interactions.

[0003] Hydrotalcite, rich in hydroxyl groups, effectively adsorbs hydrogen chloride (HCl) produced by the thermal decomposition of PVC, thereby inhibiting its self-accelerating degradation. However, the hydroxyl groups enriched on its surface generate strong intermolecular attraction through hydrogen bonding, which can easily lead to particle agglomeration and uneven dispersion within the PVC matrix, especially during prolonged thermal processing, which can cause phase separation.

[0004] The prior art discloses an environmentally friendly calcium-zinc composite thermal stabilizer and its preparation method, which is prepared by dissolving expanded vermiculite in a 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, and finally obtaining an organic acid intercalated hydrotalcite with the assistance of sodium bicarbonate. Although this technology uses organic acid sodium salt for surface modification, the hydrophilic nature of the hydroxyl groups on the surface of the hydrotalcite layer has not been fundamentally changed, and the modified material still exhibits obvious polar characteristics. When compounded with a hydrophobic polyvinyl chloride matrix, water molecule diffusion channels are easily formed in a humid environment, resulting in swelling stress concentration at the interface of the composite material, ultimately causing microcrack expansion and macrocracking, which seriously restricts the water resistance of the material. In addition, the patented process fails to effectively control the degree of interlayer delamination of the hydrotalcite, and the layered stacking structure only partially dissociates, failing to fully expose the active hydroxyl sites at the edge of the layer, and failing to maximize the auxiliary thermal stabilization effect.

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

[0006] In order to solve the technical problem in the prior art that hydrotalcite auxiliary stabilizers are difficult to improve the thermal stability, mechanical properties and water resistance of PVC pipes, the primary purpose of the present invention is to provide a hydrotalcite intercalation polymer modified with polyamide containing alkyl side chains.

[0007] Another object of the present invention is to provide an auxiliary stabilizer comprising the above-mentioned hydrotalcite intercalation polymer modified with polyamide containing alkyl side chains.

[0008] Another object of the present invention is to provide a stabilizer composition comprising the above-mentioned hydrotalcite intercalation polymer modified with polyamide containing alkyl side chains.

[0009] Another object of the present invention is to provide a use of the auxiliary stabilizer in the preparation of PVC pipes.

[0010] Another object of the present invention is to provide a PVC composition comprising the above-mentioned hydrotalcite intercalation polymer modified with polyamide containing alkyl side chains.

[0011] Another object of the present invention is to provide a PVC pipe comprising the above-mentioned hydrotalcite intercalation polymer modified with polyamide containing alkyl side chains.

[0012] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions: The present invention protects a hydrotalcite intercalation polymer modified with polyamide containing alkyl side chains, which is prepared by the following method; S1. dissolving polyacrylic acid, a primary amine and a condensing agent in N-methylpyrrolidone and reacting to obtain a polyamide containing an alkyl side chain; S2 was added to the hydrotalcite dispersion solution obtained in S1 to react to obtain a hydrotalcite intercalated polymer; The primary amine is (CH3) x -NH2, 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 polyamide containing alkyl side chains is 3-9:1.

[0013] By using amphiphilic polyacrylic acid (PAA) modifier, its free carboxyl group (-COOH) is anchored on the positively charged surface of hydrotalcite by electrostatic adsorption and interacts with the interlayer CO3 2-Ion exchange occurs to strengthen interfacial bonding, and the steric hindrance effect of long-chain alkyl groups is used to expand the interlayer spacing of hydrotalcite, creating channels for polymer chain intercalation. The microjets generated by the ultrasonic cavitation effect are then used to overcome the interlayer forces and drive the polymer chains to diffuse directionallly into the interlayer domain to form stable chemical bonds. In addition, the hydrophobic association of the alkyl chains reduces the surface energy of the hydrotalcite, inhibits the agglomeration of nanoparticles, and constructs a hydrophobic-lipophilic interface in the PVC matrix, promoting uniform dispersion to form a three-dimensional physical cross-linked network, solving the compatibility problem between inorganic fillers and organic matrices. As a result, it is not easy to form water molecule diffusion channels in a humid environment, and cracking and other phenomena will not occur, thereby improving the water resistance of the material.

[0014] In terms of the thermal stability enhancement mechanism, the hydroxyl groups (-OH) of the hydrotalcite layers and the interlayer CO3 2- By chemical adsorption and ion exchange (CO3 2- + 2Cl - → CO2↑+ 2Cl⁻)synergistically captures HCl / Cl produced by degradation - , inhibiting autocatalytic reactions. At the same time, the expanded interlayer spacing forms a nano-confined space, blocking the diffusion path of free radicals and delaying the breakage of PVC chains. In terms of the mechanical property strengthening mechanism, the two-dimensional nanosheet structure of hydrotalcite enhances the rigidity of PVC through stress transfer, while the flexible interface layer of the intercalated polymer induces silver shear bands, dissipating impact energy to achieve toughening. Furthermore, the interlayer organic chain 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 8-12.

[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'-dicyclohexylcarboximide DCC.

[0018] Preferably, the reaction conditions in step S2. are 25-60° C. and 12-72 hours.

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

[0020] Preferably, 20-30% of the acrylic acid groups in the hydrotalcite intercalation polymer modified with polyamide containing alkyl side chains are substituted with amide alkyl groups.

[0021] The present invention also protects an auxiliary stabilizer, which comprises the above-mentioned hydrotalcite intercalation polymer modified with polyamide containing alkyl side chains.

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

[0023] The use of the above auxiliary stabilizer in the preparation of PVC pipes is also within the scope of protection of the present 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 stabilizer composition, 20-80 parts of filler, 0.5-2 parts of stearic acid, 0.5-2 parts of paraffin, and 4-10 parts of ACR toughener.

[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 PVC composition.

[0028] Compared with the prior art, the present invention has the following beneficial effects: The present invention protects a hydrotalcite intercalation polymer modified with polyamide containing alkyl side chains. The obtained polymer is obtained by modifying hydrotalcite with polyamide containing alkyl side chains generated by reacting polyacrylic acid and primary amine with a condensing agent. The polymer can be used as an auxiliary heat stabilizer to improve the thermal stability, mechanical properties and water resistance of PVC pipes. DETAILED DESCRIPTION

[0029] The present invention is further described below with reference to the examples. These examples are intended to illustrate the present invention only and are not intended to limit the scope of the present invention. Experimental methods in the following examples where specific conditions are not specified are generally performed in accordance with conventional conditions in the art or the conditions recommended by the manufacturer; the raw materials and reagents used, unless otherwise specified, are all commercially available from conventional markets. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention fall within the scope of protection claimed in the present invention.

[0030] Some of the reagents selected in the embodiments and comparative examples of the present invention are described as follows: Hydrotalcite: magnesium aluminum hydrotalcite: Mg6Al2(OH) 16 CO3·4H2O.

[0031] Test indicators: (1) Thermal stability time (min): in accordance with GB / T 2917.1-2002 “Determination of hydrogen chloride and any other acidic products released by blends and products based on vinyl chloride homopolymers and copolymers at high temperatures – Congo red method”; (2) Precipitate mass (mg): Use an extruder to perform a pipe extrusion experiment on PVC pipe material. After running the machine continuously for 4 hours, observe the precipitate at the calibrating sleeve and weigh the mass of the precipitate; (3) Tensile yield stress (MPa): Tested in accordance with GB / T 8804.2-2003 “Thermoplastic pipes - Determination of tensile properties - Part 2: Unplasticized 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 immersed in water for 90 days) (MPa); (5) Strength retention rate: Strength retention rate = 100% × (tensile yield stress of the pipe after 90 days of immersion in water) / tensile yield stress.

[0032] Example 1 Preparation method of hydrotalcite intercalation polymer modified with polyamide containing alkyl side chains: 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'-dicyclohexylcarbodiimide (0.282 mol) were separately dissolved in 750 mL of N-methylpyrrolidone and added to the polyacrylic acid solution. The temperature was maintained at 60°C and stirred for 24 hours. After the reaction, the mixture was cooled to room temperature, and the insoluble material was 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 redissolved in water and precipitated in methanol. Finally, the product was further purified by dialysis, revealing that 28% of the acrylic acid groups were replaced with amidoalkyl 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 dropwise to the aqueous solution of polymer 1, stir at 70°C for 4 h, and then ultrasonicate for 1.5 h. After ultrasonication, centrifuge, wash, and dry to obtain auxiliary thermal 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, 6 parts ACR toughening agent, 2 parts auxiliary heat stabilizer.

[0035] Example 2 Step S2 and the preparation of PVC tubing in the experimental method were the same as in Example 1, with the following differences: In step S1, 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. 128.63 g of dodecyl primary amine (0.694 mol) and 143.19 g of N,N'-dicyclohexylcarbodiimide (0.694 mol) were separately dissolved in 1 L of N-methylpyrrolidone and added to the polyacrylic acid solution. The temperature was maintained at 60°C and stirred for 72 hours. After the reaction, the mixture was cooled to room temperature, and the insoluble material was 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 redissolved in water and precipitated in methanol. Finally, the product was further purified by dialysis, resulting in 25% of the acrylic acid groups being replaced with amidoalkyl groups: .

[0036] Example 3 The PVC tubing composition was the same as in Example 1, except that in step S1, 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. 64.87 g of dodecyl primary amine (0.350 mol) and 72.21 g of N,N'-dicyclohexylcarbodiimide (0.350 mol) were separately dissolved in 1 L of N-methylpyrrolidone and added to the polyacrylic acid solution. The temperature was maintained at 60°C and stirred for 48 hours. After the reaction, the mixture was cooled to room temperature, and the insoluble material was 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 redissolved in water and precipitated in methanol. Finally, the product was further purified by dialysis, resulting in 15% of the acrylic acid groups being replaced with amidoalkyl groups: .

[0037] Example 4 The PVC tubing composition was the same as in Example 1, except that in step S1, 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. 154.35 g of dodecyl primary amine (0.832 mol) and 171.67 g of N,N'-dicyclohexylcarbodiimide (0.832 mol) were separately dissolved in 1.5 L of N-methylpyrrolidone and added to the polyacrylic acid solution. The temperature was maintained at 60°C and stirred for 72 hours. After the reaction, the mixture was cooled to room temperature, and the insoluble material was 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 redissolved in water and precipitated in methanol. Finally, the product was further purified by dialysis, resulting in 35% of the acrylic acid groups being replaced with amidoalkyl groups: .

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

[0039] Comparative Example 2 PVC pipe: 100 parts of PVC resin, 3.0 parts of calcium zinc stabilizer, 20 parts of calcium carbonate, 1.0 parts of stearic acid, 1.0 parts of paraffin wax, 6.0 parts of ACR toughening agent, and 2.0 parts of 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, an organic acid-intercalated hydrotalcite was prepared as an auxiliary stabilizer, and PVC pipe was prepared according to the following formula: 100 parts of PVC resin, 3.0 parts of calcium-zinc stabilizer, 20 parts of calcium carbonate, 1.0 part of stearic acid, 1.0 part of paraffin wax, 6.0 parts of ACR toughening agent, and 2.0 parts of the prepared organic acid-intercalated hydrotalcite auxiliary stabilizer were added.

[0041] Comparative Example 4 The experimental method for step S2 and the preparation of PVC tubing was the same as in Example 1, with the following differences: In step S1, 50 g of polyacrylic acid (0.694 mol) was 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'-dicyclohexylcarbodiimide (0.141 mol) were separately dissolved in 300 mL of N-methylpyrrolidone and added to the polyacrylic acid solution. The temperature was maintained at 60°C and stirred for 12 hours. After the reaction, the mixture was cooled to room temperature, and the insoluble material was 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 redissolved in water and precipitated in methanol. Finally, the product was further purified by dialysis, resulting in 30% of the acrylic acid groups being replaced with amidoalkyl groups: .

[0042] Comparative Example 5 The experimental method for step S2 and the preparation of PVC tubing was the same as in Example 1, with the following differences: Step S1: 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. 10.15 g of n-butylamine (0.139 mol) and 29.09 g of N,N'-dicyclohexylcarboximide (0.141 mol) were separately dissolved in 350 mL of N-methylpyrrolidone and added to the polyacrylic acid solution. The temperature was maintained at 60°C and stirred for 24 hours. After the reaction, the mixture was cooled to room temperature, and the insoluble material was 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 redissolved in water and precipitated in methanol. Finally, the product was further purified by dialysis to yield the following compound, in which 20% of the acrylic acid groups were substituted with amidoalkyl groups: .

[0043] Comparative Example 6 The experimental method for step S2 and the preparation of PVC tubing was the same as in Example 1, with the following differences: In step S1, 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. 187.04 g of octadecylamine (0.694 mol) and 143.19 g of N,N'-dicyclohexylcarbodiimide (0.694 mol) were separately dissolved in 1.5 L of N-methylpyrrolidone and added to the polyacrylic acid solution. The temperature was maintained at 60°C and stirred for 72 hours. After the reaction, the mixture was cooled to room temperature, and the insoluble material was 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 redissolved in water and precipitated in methanol. Finally, the product was further purified by dialysis, resulting in 5% of the acrylic acid groups being replaced with amidoalkyl groups: .

[0044] Comparative Example 7 The composition of the PVC pipe is the same as that of 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 composition of the PVC pipe is the same as that of 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 examples and comparative examples

[0047] Examples 1 to 4 provide a series of hydrotalcite intercalation polymers modified with polyamide containing alkyl side chains, which achieve thermal stability time, small precipitate mass, advantageous tensile yield stress before and after immersion in water, and high strength retention.

[0048] Comparative Example 1 does not add an auxiliary stabilizer, and the thermal stability is the worst and the precipitate is the most. Comparative Example 2 uses soybean oil instead of the auxiliary stabilizer. The traditional soybean oil auxiliary agent has limited effect, and the thermal stability and precipitate are inferior to those of the embodiment. Comparative Example 3 uses organic acid intercalated hydrotalcite as the auxiliary stabilizer. Although the existing technology has good initial thermal stability, it has poor water resistance. After immersion in water, the strength decreases from 46 to 37 MPa, and there is a defect of cracking caused by the diffusion of water molecules. Comparative Example 4 uses propylamine, which reduces thermal stability, reduces strength retention, and reduces tensile yield stress before and after immersion in water; Comparative Example 5 uses n-butylamine, which reduces thermal stability and increases precipitates; Comparative Example 6 uses octadecylamine, and the hydrophobic substituent has a low substitution ratio due to large reaction steric hindrance, and the mechanical properties decrease after immersion in water; Comparative Example 7 has a low hydrotalcite ratio, and the thermal stability decreases significantly, and the tensile yield stress decreases before and after immersion in water; Comparative Example 8 has a high hydrotalcite ratio, and the intercalated hydrotalcite composite has poor compatibility with the PVC base material, resulting in a decrease in thermal stability time, an increase in 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 the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A hydrotalcite intercalation polymer modified with polyamide containing alkyl side chains, characterized in that: Prepared by the following method: S1. dissolving polyacrylic acid, a primary amine and a condensing agent in N-methylpyrrolidone and reacting to obtain a polyamide containing an alkyl side chain; S2 was added to the hydrotalcite dispersion solution obtained in S1 to react to obtain a hydrotalcite intercalated polymer; The primary amine is (CH3) x -NH2, 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 polyamide containing alkyl side chains is 3-9:

1.

2. The hydrotalcite intercalation polymer modified with polyamide containing alkyl side chains according to claim 1, characterized in that: In the primary amine, x is 8 to 12.

3. The hydrotalcite intercalation polymer modified with polyamide containing alkyl side chains according to claim 1, characterized in that: The condensing agent is N,N'-dicyclohexylcarboximide DCC.

4. The hydrotalcite intercalation polymer modified with polyamide containing alkyl side chains according to claim 1, characterized in that: The reaction conditions in step S2 are 25-60° C. and 12-72 hours.

5. The hydrotalcite intercalation polymer modified with polyamide containing alkyl side chains according to claim 1, characterized in that: In the hydrotalcite intercalation polymer modified with polyamide containing alkyl side chains, 20-30% of the acrylic acid groups are substituted with amide alkyl groups.

6. An auxiliary stabilizer, characterized in that The auxiliary stabilizer comprises the hydrotalcite intercalation polymer modified with polyamide containing alkyl side chains as claimed in any one of claims 1 to 5.

7. Use of the auxiliary stabilizer according to claim 6 in the preparation of PVC pipes.

8. A stabilizer composition, characterized in that The invention comprises the following components in parts by weight: 2-6 parts of a main stabilizer and 0.3-2.1 parts of the auxiliary stabilizer according to claim 6, wherein the main stabilizer is a calcium zinc stabilizer.

9. A PVC composition, characterized in that The invention comprises the following components in parts by weight: 80-100 parts of PVC resin, 2-6 parts of main stabilizer, 2.5-8.5 parts of the stabilizer composition according to claim 8, 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.

10. A PVC pipe made from the PVC composition according to claim 9.

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