Preparation method of lead-based halloysite composite heat stabilizer

Abstract

The application relates to a preparation method of a lead-based load halloysite composite stabilizer, and belongs to the technical field of heat stabilizer preparation, which is characterized by comprising the following steps: S1, preparing a precursor; S2, synthesizing a lead-based load halloysite; S3, organically modifying the lead-based load halloysite; and S4, preparing a composite heat stabilizer; the prepared composite heat stabilizer has excellent heat stability, good dispersibility and compatibility with PVC resin, and is not prone to migration.

Description

Technical Field

[0001] This invention relates to the field of heat stabilizer preparation technology, and in particular to a method for preparing a lead-based supported halloysite composite heat stabilizer. Background Technology

[0002] Polyvinyl chloride (PVC) is the second largest general-purpose plastic in terms of production volume after polyethylene (PE). It possesses advantages such as high strength, corrosion resistance, flame retardancy, good insulation, and high transparency, and is widely used in industrial construction, agriculture, daily necessities, packaging, power, and public utilities. However, PVC products are prone to degradation during processing and molding. If this degradation is not controlled, the physical properties of the products will significantly decrease, even rendering them unusable. Heat stabilizers can effectively inhibit this degradation.

[0003] Lead salt stabilizers are the most commonly used heat stabilizers for PVC materials. They effectively improve the thermal stability of PVC materials, especially long-term thermal stability, and are inexpensive. They have long held over 70% of the PVC heat stabilizer market share. Commonly used lead salt stabilizers include tribasic lead sulfate and dibasic lead phosphite. However, lead salt stabilizers have poor dispersibility and poor compatibility with PVC resins. In the preparation of transparent products, they can severely affect the transparency of the material. In the application of flexible PVC products such as cable materials, the use of large amounts of plasticizers causes lead salt stabilizers to easily migrate to the surface of the product, thus harming the environment. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a lead-based supported halloysite composite heat stabilizer. The prepared composite heat stabilizer has good thermal stability and good dispersibility and compatibility with PVC resin, and is not easily migrated.

[0005] The above-mentioned technical objective of the invention is achieved through the following technical solution: a method for preparing a lead-based supported halloysite composite heat stabilizer, comprising the following steps:

[0006] Step S1: Prepare the precursor by adding halloysite and dilute hydrochloric acid solution to a reaction vessel, stirring thoroughly, and reacting for 1-3 hours. Then, precipitate the solid in the reaction vessel, wash and dry it to obtain the precursor. The mass ratio of halloysite to dilute hydrochloric acid solution is (5-30):1.

[0007] Step S2: Synthesize lead-based supported halloysite. Add the precursor to a hydrothermal synthesis reactor, then add lead nitrate solution to the reactor, wherein the mass fraction ratio of precursor to lead nitrate is 100:(1-10). Purge the hydrothermal synthesis reactor with inert gas to remove air, then gradually add sodium hydroxide solution dropwise to the reactor, wherein the mass fraction ratio of precursor to sodium hydroxide is 400:(1-10). React at 120-200℃ for 3-5 hours, then filter and separate the solid reactants in the solution, wash and dry to obtain lead-supported halloysite.

[0008] Step S3, organic modification of lead-supported halloysite: preheat lead-supported halloysite to 110℃-160℃, then add lead-supported halloysite, stearic acid, maleic acid ester and coupling agent to a high-speed mixer in sequence, disperse and stir evenly, and let stand to room temperature to obtain the modified lead-supported halloysite.

[0009] The mass fraction ratio of lead-loaded halloysite, stearic acid, maleic acid ester, and coupling agent is 10:(1-3):(1-3):(2-5);

[0010] Step S4: Prepare a composite heat stabilizer by compounding modified lead-supported halloysite, phosphite, epoxy compound, and polyol in a mass ratio of 10:(0.5-2):(0.5-1.5):(0.5-2) and mixing them evenly to obtain the lead-based supported halloysite composite heat stabilizer.

[0011] Preferably, in step S1, the halloysite selected has an outer diameter of 20-60 nm, an inner diameter of 5-20 nm, and a length of 300-3000 nm.

[0012] Preferably, the coupling agent is any one or more of silane coupling agents, titanate coupling agents, aluminate coupling agents, phosphate coupling agents, and borate coupling agents.

[0013] Preferably, in step S3, the mass fraction ratio of lead-loaded halloysite, stearic acid, maleate, and titanate coupling agent is 10:1.5:1.5:3.

[0014] Preferably, the epoxy compound is any one or more of epoxidized soybean oil, epoxidized flaxseed oil, epoxidized butyl stearate, and epoxidized octyl stearate.

[0015] Preferably, the polyol is any one or more of pentaerythritol, dipentaerythritol, polyvinyl alcohol, tetramethylolcyclohexanol, dimethylolpropane, carbitol, sorbitol, mannitol, xylitol, and maltitol.

[0016] Preferably, in step S4, the mass fraction ratio of modified lead-supported halloysite, phosphite, epoxide, and polyol is 10:1:1:5.

[0017] In summary, the present invention has at least one of the following beneficial technical effects:

[0018] 1. This invention involves acid etching of natural halloysite nanotubes to partially remove the alumina layer on the inner surface of the nanotubes, significantly increasing the internal cavity space and active sites of the halloysite nanotubes and enhancing their adsorption and loading capacity for lead metal ions. Simultaneously, hydrothermal treatment is used to load soluble lead ions into the halloysite precursor tubes under alkaline conditions, allowing soluble free lead to be deposited and anchored on the inner surface of the halloysite nanotubes, preventing the harmful effects of lead-based free migration. Furthermore, the nanoscale size structure of the selected halloysite nanotube matrix allows the loaded lead-based elements to achieve nanoscale dispersion, greatly improving the stabilizer efficacy of lead-based materials.

[0019] 2. This invention utilizes the abundant hydroxyl groups on the outer surface of halloysite nanotubes to perform a grafting and crosslinking reaction with PVC resin under the action of coupling agents, thereby improving the dispersibility and compatibility of lead-based loaded halloysite in PVC resin and inhibiting its migration to the surface of PVC resin.

[0020] 3. This invention utilizes the synergistic effect principle of composite stabilizers to combine auxiliary heat stabilizers such as phosphites with modified lead-supported halloysite, thereby further improving its dynamic and static thermal stability and processing usability during PVC processing. Detailed Implementation

[0021] To more clearly illustrate the present invention, the following detailed description is provided in conjunction with embodiments. Those skilled in the art should understand that the following description is an analytical explanation of the invention and not a limitation thereof; therefore, it should not be construed as limiting the scope of protection of the present invention.

[0022] Example

[0023] Example 1

[0024] A method for preparing a lead-based supported halloysite composite heat stabilizer includes the following steps:

[0025] Step S1: Prepare the precursor by adding halloysite and dilute hydrochloric acid solution to a reaction vessel, stirring thoroughly, and reacting for 1 hour. The solid in the reaction vessel is then precipitated, washed, and dried to obtain the precursor. The mass ratio of halloysite to dilute hydrochloric acid solution is 30:1.

[0026] Step S2: Synthesize lead-based supported halloysite. Add the precursor to a hydrothermal synthesis reactor, then add lead nitrate solution to the reactor, wherein the mass ratio of precursor to lead nitrate is 100:10. Purge the hydrothermal synthesis reactor with nitrogen to purge the air, then gradually add sodium hydroxide solution to the reactor, wherein the mass ratio of precursor to sodium hydroxide is 400:1. React at 120°C for 3 hours, then filter and separate the solid reactants in the solution, wash and dry to obtain lead-supported halloysite.

[0027] Step S3, organic modification of lead-supported halloysite: preheat lead-supported halloysite to 110°C, then add lead-supported halloysite, stearic acid, maleic acid ester and silane coupling agent to a high-speed mixer in sequence, disperse and stir evenly, and let stand to room temperature to obtain the modified lead-supported halloysite.

[0028] The mass fraction ratio of lead-supported halloysite, stearic acid, maleic acid ester, and silane coupling agent is 10:1:1:2.

[0029] Step S4: Prepare the composite heat stabilizer by compounding modified lead-supported halloysite, phosphite, epoxidized soybean oil, and pentaerythritol in a mass ratio of 10:0.5:0.5:0.5 and mixing them evenly to obtain the lead-based supported halloysite composite heat stabilizer.

[0030] Example 2

[0031] The only difference between Example 2 and Example 1 is that, in step S3, the mass fraction ratio of lead-loaded halloysite, stearic acid, maleic acid ester, and silane coupling agent is 10:1.5:1.5:3.

[0032] Example 3

[0033] The only difference between Example 3 and Example 1 is that, in step S3, the mass fraction ratio of lead-loaded halloysite, stearic acid, maleic acid ester, and silane coupling agent is 10:3:3:5.

[0034] Example 4

[0035] The only difference between Example 4 and Example 1 is that in step S4, modified lead-supported halloysite, phosphite, epoxidized soybean oil, and pentaerythritol are compounded in a mass ratio of 10:1:1:1.5.

[0036] Example 5

[0037] The only difference between Example 5 and Example 1 is that in step S4, modified lead-supported halloysite, phosphite, epoxidized soybean oil, and pentaerythritol are compounded in a mass ratio of 10:2:1.5:2.

[0038] Example 6

[0039] A method for preparing a lead-based supported halloysite composite heat stabilizer includes the following steps:

[0040] Step S1: Prepare the precursor by adding halloysite and dilute hydrochloric acid solution to a reaction vessel, stirring thoroughly, and reacting for 2 hours. The solid in the reaction vessel is then precipitated, washed, and dried to obtain the precursor. The mass ratio of halloysite to dilute hydrochloric acid solution is 30:1.

[0041] Step S2: Synthesize lead-based supported halloysite. Add the precursor to a hydrothermal synthesis reactor, then add lead nitrate solution to the reactor, wherein the mass ratio of precursor to lead nitrate is 100:10. Purge the hydrothermal synthesis reactor with nitrogen to purge air, then gradually add sodium hydroxide solution dropwise to the reactor, wherein the mass ratio of precursor to sodium hydroxide is 400:1. React at 120°C for 4 hours, then filter and separate the solid reactants in the solution, wash and dry to obtain lead-supported halloysite.

[0042] Step S3, organic modification of lead-supported halloysite: preheat lead-supported halloysite to 110°C, then add lead-supported halloysite, stearic acid, maleic acid ester and silane coupling agent to a high-speed mixer in sequence, disperse and stir evenly, and let stand to room temperature to obtain the modified lead-supported halloysite.

[0043] The mass fraction ratio of lead-supported halloysite, stearic acid, maleic acid ester, and silane coupling agent is 10:1:1:2.

[0044] Step S4: Prepare the composite heat stabilizer by compounding modified lead-supported halloysite, phosphite, epoxidized soybean oil, and pentaerythritol in a mass ratio of 10:0.5:0.5:0.5 and mixing them evenly to obtain the lead-based supported halloysite composite heat stabilizer.

[0045] Example 7

[0046] A method for preparing a lead-based supported halloysite composite heat stabilizer includes the following steps:

[0047] Step S1: Prepare the precursor by adding halloysite and dilute hydrochloric acid solution to a reaction vessel, stirring thoroughly, and reacting for 3 hours. The solid in the reaction vessel is then precipitated, washed, and dried to obtain the precursor. The mass ratio of halloysite to dilute hydrochloric acid solution is 5:1.

[0048] Step S2: Synthesize lead-based supported halloysite. Add the precursor to a hydrothermal synthesis reactor, then add lead nitrate solution to the reactor, wherein the mass ratio of precursor to lead nitrate is 100:10. Purge the hydrothermal synthesis reactor with nitrogen to purge the air, then gradually add sodium hydroxide solution dropwise to the reactor, wherein the mass ratio of precursor to sodium hydroxide is 400:10. React at 120°C for 5 hours, then filter and separate the solid reactants in the solution, wash and dry to obtain lead-supported halloysite.

[0049] Step S3, organic modification of lead-supported halloysite: preheat lead-supported halloysite to 110°C, then add lead-supported halloysite, stearic acid, maleic acid ester and silane coupling agent to a high-speed mixer in sequence, disperse and stir evenly, and let stand to room temperature to obtain the modified lead-supported halloysite.

[0050] The mass fraction ratio of lead-supported halloysite, stearic acid, maleic acid ester, and silane coupling agent is 10:1:1:2.

[0051] Step S4: Prepare the composite heat stabilizer by compounding modified lead-supported halloysite, phosphite, epoxidized soybean oil, and pentaerythritol in a mass ratio of 10:0.5:0.5:0.5 and mixing them evenly to obtain the lead-based supported halloysite composite heat stabilizer.

[0052] Example 8

[0053] A method for preparing a lead-based supported halloysite composite heat stabilizer includes the following steps:

[0054] Step S1: Prepare the precursor by adding halloysite and dilute hydrochloric acid solution to a reaction vessel, stirring thoroughly, and reacting for 1 hour. The solid in the reaction vessel is then precipitated, washed, and dried to obtain the precursor. The mass ratio of halloysite to dilute hydrochloric acid solution is 30:1.

[0055] Step S2: Synthesize lead-based supported halloysite. Add the precursor to a hydrothermal synthesis reactor, then add lead nitrate solution to the reactor, wherein the mass ratio of precursor to lead nitrate is 100:10. Purge the hydrothermal synthesis reactor with nitrogen to purge the air, then gradually add sodium hydroxide solution dropwise to the reactor, wherein the mass ratio of precursor to sodium hydroxide is 400:1. React at 160°C for 3 hours, then filter and separate the solid reactants in the solution, wash and dry to obtain lead-supported halloysite.

[0056] Step S3, organic modification of lead-supported halloysite: preheat lead-supported halloysite to 140°C, then add lead-supported halloysite, stearic acid, maleic acid ester and silane coupling agent to a high-speed mixer in sequence, disperse and stir evenly, and let stand to room temperature to obtain the modified lead-supported halloysite.

[0057] The mass fraction ratio of lead-supported halloysite, stearic acid, maleic acid ester, and silane coupling agent is 10:1:1:2.

[0058] Step S4: Prepare the composite heat stabilizer by compounding modified lead-supported halloysite, phosphite, epoxidized soybean oil, and pentaerythritol in a mass ratio of 10:0.5:0.5:0.5 and mixing them evenly to obtain the lead-based supported halloysite composite heat stabilizer.

[0059] Example 9

[0060] A method for preparing a lead-based supported halloysite composite heat stabilizer includes the following steps:

[0061] Step S1: Prepare the precursor by adding halloysite and dilute hydrochloric acid solution to a reaction vessel, stirring thoroughly, and reacting for 1 hour. The solid in the reaction vessel is then precipitated, washed, and dried to obtain the precursor. The mass ratio of halloysite to dilute hydrochloric acid solution is 30:1.

[0062] Step S2: Synthesize lead-based supported halloysite. Add the precursor to a hydrothermal synthesis reactor, then add lead nitrate solution to the reactor, wherein the mass ratio of precursor to lead nitrate is 100:10. Purge the hydrothermal synthesis reactor with nitrogen to purge the air, then gradually add sodium hydroxide solution dropwise to the reactor, wherein the mass ratio of precursor to sodium hydroxide is 400:1. React at 200°C for 3 hours, then filter and separate the solid reactants in the solution, wash and dry to obtain lead-supported halloysite.

[0063] Step S3, organic modification of lead-supported halloysite: preheat lead-supported halloysite to 160°C, then add lead-supported halloysite, stearic acid, maleic acid ester and silane coupling agent to a high-speed mixer in sequence, disperse and stir evenly, and let stand to room temperature to obtain the modified lead-supported halloysite.

[0064] The mass fraction ratio of lead-supported halloysite, stearic acid, maleic acid ester, and silane coupling agent is 10:1:1:2.

[0065] Step S4: Prepare the composite heat stabilizer by compounding modified lead-supported halloysite, phosphite, epoxidized soybean oil, and pentaerythritol in a mass ratio of 10:0.5:0.5:0.5 and mixing them evenly to obtain the lead-based supported halloysite composite heat stabilizer.

[0066] Example 10

[0067] A method for preparing a lead-based supported halloysite composite heat stabilizer includes the following steps:

[0068] Step S1: Prepare the precursor by adding halloysite and dilute hydrochloric acid solution to a reaction vessel, stirring thoroughly, and reacting for 1 hour. The solid in the reaction vessel is then precipitated, washed, and dried to obtain the precursor. The mass ratio of halloysite to dilute hydrochloric acid solution is 15:1.

[0069] Step S2: Synthesize lead-based supported halloysite. Add the precursor to a hydrothermal synthesis reactor, then add lead nitrate solution to the reactor, wherein the mass fraction ratio of precursor to lead nitrate is 100:10. Purge the hydrothermal synthesis reactor with nitrogen to purge the air, then gradually add sodium hydroxide solution to the reactor, wherein the mass fraction ratio of precursor to sodium hydroxide is 400:5. React at 120°C for 3 hours, then filter and separate the solid reactants in the solution, wash and dry to obtain lead-supported halloysite.

[0070] Step S3, organic modification of lead-supported halloysite: preheat lead-supported halloysite to 110°C, then add lead-supported halloysite, stearic acid, maleic acid ester and silane coupling agent to a high-speed mixer in sequence, disperse and stir evenly, and let stand to room temperature to obtain the modified lead-supported halloysite.

[0071] The mass fraction ratio of lead-supported halloysite, stearic acid, maleic acid ester, and silane coupling agent is 10:1:1:2.

[0072] Step S4: Prepare the composite heat stabilizer by compounding modified lead-supported halloysite, phosphite, epoxidized soybean oil, and pentaerythritol in a mass ratio of 10:0.5:0.5:0.5 and mixing them evenly to obtain the lead-based supported halloysite composite heat stabilizer.

[0073] Example 11

[0074] A method for preparing a lead-based supported halloysite composite heat stabilizer includes the following steps:

[0075] Step S1: Prepare the precursor by adding halloysite and dilute hydrochloric acid solution to a reaction vessel, stirring thoroughly, and reacting for 1 hour. The solid in the reaction vessel is then precipitated, washed, and dried to obtain the precursor. The mass ratio of halloysite to dilute hydrochloric acid solution is 5:1.

[0076] Step S2: Synthesize lead-based supported halloysite. Add the precursor to a hydrothermal synthesis reactor, then add lead nitrate solution to the reactor, wherein the mass ratio of precursor to lead nitrate is 100:10. Purge the hydrothermal synthesis reactor with nitrogen to purge air, then gradually add sodium hydroxide solution to the reactor, wherein the mass ratio of precursor to sodium hydroxide is 400:10. React at 120°C for 3 hours, then filter and separate the solid reactants in the solution, wash and dry to obtain lead-supported halloysite.

[0077] Step S3, organic modification of lead-supported halloysite: preheat lead-supported halloysite to 110°C, then add lead-supported halloysite, stearic acid, maleic acid ester and silane coupling agent to a high-speed mixer in sequence, disperse and stir evenly, and let stand to room temperature to obtain the modified lead-supported halloysite.

[0078] The mass fraction ratio of lead-supported halloysite, stearic acid, maleic acid ester, and silane coupling agent is 10:1:1:2.

[0079] Step S4: Prepare the composite heat stabilizer by compounding modified lead-supported halloysite, phosphite, epoxidized soybean oil, and pentaerythritol in a mass ratio of 10:0.5:0.5:0.5 and mixing them evenly to obtain the lead-based supported halloysite composite heat stabilizer.

[0080] Example 12

[0081] A method for preparing a lead-based supported halloysite composite heat stabilizer includes the following steps:

[0082] Step S1: Prepare the precursor by adding halloysite and dilute hydrochloric acid solution to a reaction vessel, stirring thoroughly, and reacting for 1 hour. The solid in the reaction vessel is then precipitated, washed, and dried to obtain the precursor. The mass ratio of halloysite to dilute hydrochloric acid solution is 30:1.

[0083] Step S2: Synthesize lead-based supported halloysite. Add the precursor to a hydrothermal synthesis reactor, then add lead nitrate solution to the reactor, wherein the mass ratio of precursor to lead nitrate is 100:1. Purge the hydrothermal synthesis reactor with nitrogen to purge air, then gradually add sodium hydroxide solution dropwise to the reactor, wherein the mass ratio of precursor to sodium hydroxide is 400:1. React at 120°C for 3 hours, then filter and separate the solid reactants in the solution, wash and dry to obtain lead-supported halloysite.

[0084] Step S3, organic modification of lead-supported halloysite: preheat lead-supported halloysite to 110°C, then add lead-supported halloysite, stearic acid, maleic acid ester and silane coupling agent to a high-speed mixer in sequence, disperse and stir evenly, and let stand to room temperature to obtain the modified lead-supported halloysite.

[0085] The mass fraction ratio of lead-supported halloysite, stearic acid, maleic acid ester, and silane coupling agent is 10:1:1:2.

[0086] Step S4: Prepare the composite heat stabilizer by compounding modified lead-supported halloysite, phosphite, epoxidized soybean oil, and pentaerythritol in a mass ratio of 10:0.5:0.5:0.5 and mixing them evenly to obtain the lead-based supported halloysite composite heat stabilizer.

[0087] Example 13

[0088] A method for preparing a lead-based supported halloysite composite heat stabilizer includes the following steps:

[0089] Step S1: Prepare the precursor by adding halloysite and dilute hydrochloric acid solution to a reaction vessel, stirring thoroughly, and reacting for 1 hour. The solid in the reaction vessel is then precipitated, washed, and dried to obtain the precursor. The mass ratio of halloysite to dilute hydrochloric acid solution is 30:1.

[0090] Step S2: Synthesize lead-based supported halloysite. Add the precursor to a hydrothermal synthesis reactor, then add lead nitrate solution to the reactor, wherein the mass ratio of precursor to lead nitrate is 100:10. Purge the hydrothermal synthesis reactor with nitrogen to purge the air, then gradually add sodium hydroxide solution to the reactor, wherein the mass ratio of precursor to sodium hydroxide is 400:1. React at 120°C for 3 hours, then filter and separate the solid reactants in the solution, wash and dry to obtain lead-supported halloysite.

[0091] Step S3, organic modification of lead-supported halloysite: preheat lead-supported halloysite to 110°C, then add lead-supported halloysite, stearic acid, maleic acid ester and silane coupling agent to a high-speed mixer in sequence, disperse and stir evenly, and let stand to room temperature to obtain the modified lead-supported halloysite.

[0092] The mass fraction ratio of lead-supported halloysite, stearic acid, maleate ester, and titanate coupling agent is 10:1:1:2.

[0093] Step S4: Prepare the composite heat stabilizer by compounding modified lead-supported halloysite, phosphite, epoxidized linseed oil, and polyvinyl alcohol in a mass ratio of 10:0.5:0.5:0.5 and mixing them evenly to obtain the lead-based supported halloysite composite heat stabilizer.

[0094] Example 14

[0095] A method for preparing a lead-based supported halloysite composite heat stabilizer includes the following steps:

[0096] Step S1: Prepare the precursor by adding halloysite and dilute hydrochloric acid solution to a reaction vessel, stirring thoroughly, and reacting for 1 hour. The solid in the reaction vessel is then precipitated, washed, and dried to obtain the precursor. The mass ratio of halloysite to dilute hydrochloric acid solution is 30:1.

[0097] Step S2: Synthesize lead-based supported halloysite. Add the precursor to a hydrothermal synthesis reactor, then add lead nitrate solution to the reactor, wherein the mass ratio of precursor to lead nitrate is 100:10. Purge the hydrothermal synthesis reactor with nitrogen to purge the air, then gradually add sodium hydroxide solution to the reactor, wherein the mass ratio of precursor to sodium hydroxide is 400:1. React at 120°C for 3 hours, then filter and separate the solid reactants in the solution, wash and dry to obtain lead-supported halloysite.

[0098] Step S3, organic modification of lead-supported halloysite: preheat lead-supported halloysite to 110°C, then add lead-supported halloysite, stearic acid, maleic acid ester and silane coupling agent to a high-speed mixer in sequence, disperse and stir evenly, and let stand to room temperature to obtain the modified lead-supported halloysite.

[0099] The mass fraction ratio of lead-loaded halloysite, stearic acid, maleic acid ester, and phosphate coupling agent is 10:1:1:2.

[0100] Step S4: Prepare a composite heat stabilizer by compounding modified lead-supported halloysite, phosphite, epoxy stearate butyl ester, and sorbitol in a mass ratio of 10:0.5:0.5:0.5 and mixing them evenly to obtain the lead-based supported halloysite composite heat stabilizer.

[0101] Test methods

[0102] PVC material sample preparation

[0103] The heat stabilizer samples prepared in Examples 1-14 and the control heat stabilizer were used to prepare PVC samples according to the following method:

[0104] Weigh the following raw materials according to their mass fraction: 100 parts PVC resin granules, 3 parts heat stabilizer, 30 parts dioctyl phthalate, and 0.3 parts stearic acid.

[0105] After the raw materials are blended, they are added to a two-roll mill and mixed at 170-185℃ for 2-5 minutes. Then, a fully automatic hot press is used to press the PVC product at 170-185℃ and 100-110 bar for 1 minute. The sample is then cut into square sheets with a thickness of 2±0.02mm and a width of 10±0.1cm for later use.

[0106] The heat stabilizers selected for comparison were: control example 1 was tribasic lead sulfate; control example 2 was a composite stabilizer of tribasic lead sulfate and dibasic lead phosphite in a mass ratio of 2:1.

[0107] The PVC samples prepared from the heat stabilizer samples of Examples 1-14 were respectively labeled as test samples 1-14.

[0108] The PVC samples prepared from the heat stabilizer samples of Comparative Examples 1-2 were labeled as Comparative Examples 1-2.

[0109] PVC material sample performance testing

[0110] Test samples 1-14 and control samples 1-2 were tested for transparency, static thermal stability time of Congo red, and lead ion concentration, respectively.

[0111] The transparency performance test was conducted according to the method specified in the national standard GB / T2410-2008.

[0112] The static thermal stability time of Congo red was tested according to the method specified in GB 2917-1982.

[0113] The lead ion concentration test shall be conducted according to the following method:

[0114] Cut the sample into small granules with sides of approximately 2 mm. Pack the PVC granules into a glass test tube with a diameter of 17 mm and a length of 150 mm, ensuring the PVC material is approximately 2 cm high in the test tube. Pour distilled water into the test tube, ensuring the liquid level is approximately 10 cm high. Place the filled test tube in a 60°C water bath and heat for 12 hours. Filter the solution and determine the lead ion concentration according to the GB7470-1987 standard method. The test results are detailed in Table 1.

[0115]

[0116]

[0117] Table 1. Test data for test sample 1-14 and control sample 1-2

[0118] In the experimental operations of Examples 1-14, the controlled variables such as the amount and type of raw materials, temperature, and reaction time in the preparation process of lead-based supported halloysite composite heat stabilizers were changed. Specifically, Examples 1-3 changed the proportion of lead-supported halloysite, stearic acid, maleic acid ester, and silane coupling agent in step S3; Examples 1, 4, and 5 changed the proportion of modified lead-supported halloysite, phosphite, epoxidized soybean oil, and pentaerythritol in step S4; Examples 1, 6, and 7 changed the reaction time in the preparation of precursors and lead-based supported halloysite; Examples 1, 8, and 9 changed the reaction temperature in the preparation of lead-based supported halloysite and modified lead-based supported halloysite; Examples 1, 10, and 11 changed the amount of hydrochloric acid in the preparation of precursors and the amount of sodium hydroxide in the preparation of lead-based supported halloysite; Examples 1 and 12 changed the amount of lead nitrate in the preparation of lead-based supported halloysite; and Examples 1, 13, and 14 changed the types of coupling agent, epoxy compound, and polyol.

[0119] As shown in Table 1, the lead-based supported halloysite composite heat stabilizer synthesized in this invention significantly improves the thermal stability of PVC materials compared to traditional single lead salt stabilizers and composite lead salt stabilizers. In the static thermal stability time test of Congo red, the Congo red time of the example red reached a maximum of 51 min, while the Congo red time of the control example was a maximum of 39 min, representing an improvement of 30.8%.

[0120] In the application of transparent PVC materials, PVC samples using the composite heat stabilizer of this invention exhibit a significant improvement in light transmittance compared to PVC samples using traditional lead salt stabilizers. This is because halloysite is a well-crystallized natural nanotube structure with active hydroxyl groups on its surface and between layers. Using halloysite nanotubes as a lead-based loading matrix allows the functional groups for heat stability to reach the nanoscale size. Furthermore, through further organic modification, halloysite achieves better compatibility and dispersibility in PVC resin, thereby effectively reducing the impact of adding heat stabilizers on the light transmittance of the PVC material system. Consequently, PVC products using the heat stabilizer of this invention exhibit superior light transmittance compared to PVC products using conventional heat stabilizers.

[0121] Data from lead ion concentration tests show that the PVC material using the lead-based supported halloysite composite heat stabilizer of this invention exhibits a significantly lower lead ion concentration in the sample wetting solution compared to PVC materials using traditional lead salt stabilizers, making lead ion precipitation less likely. This is because the high specific surface area and high adsorption capacity of the active sites within the halloysite nanotubes, combined with the hydrothermal reaction, allow lead to be stably deposited within the halloysite nanotubes, making it difficult for free ions to escape. Furthermore, the lead-based supported halloysite is further modified through organic coating coupling, making it even more stable in the PVC resin matrix.

[0122] In summary, the composite heat stabilizer prepared by the method of the present invention has good thermal stability when used in PVC systems compared with existing lead salt heat stabilizers, and has good dispersibility and compatibility with PVC resin. The PVC products made from it have better light transmittance, and lead ions are not easily precipitated or migrated.

[0123] While specific embodiments of the invention have been described in detail by way of examples, those skilled in the art should understand that the examples are for illustrative purposes only and not intended to limit the scope of the invention. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of the invention. The scope of the invention is defined by the appended claims.

Claims

1. A method for preparing a lead-based supported halloysite composite heat stabilizer, characterized in that, The following steps are included: Step S1: Prepare the precursor by adding halloysite and dilute hydrochloric acid solution to a reaction vessel, stirring thoroughly, and reacting for 1-3 hours. Then, precipitate the solid in the reaction vessel, wash and dry it to obtain the precursor. The mass ratio of halloysite to dilute hydrochloric acid solution is (5-30):

1. Step S2: Synthesize lead-based supported halloysite. Add the precursor to a hydrothermal synthesis reactor, then add lead nitrate solution to the reactor, wherein the mass fraction ratio of precursor to lead nitrate is 100:(1-10). Purge the hydrothermal synthesis reactor with inert gas to remove air, then gradually add sodium hydroxide solution dropwise to the reactor, wherein the mass fraction ratio of precursor to sodium hydroxide is 400:(1-10). React at 120-200℃ for 3-5 hours, then filter and separate the solid reactants in the solution, wash and dry to obtain lead-based supported halloysite. Step S3, organic modification of lead-supported halloysite: preheat lead-supported halloysite to 110℃-160℃, then add lead-supported halloysite, stearic acid, maleic acid ester and coupling agent to a high-speed mixer in sequence, disperse and stir evenly, and let stand to room temperature to obtain the modified lead-supported halloysite. The mass fraction ratio of lead-loaded halloysite, stearic acid, maleic acid ester, and coupling agent is 10:(1-3):(1-3):(2-5). Step S4: Prepare a composite heat stabilizer by mixing modified lead-supported halloysite, phosphite, epoxy compound, and polyol in a mass ratio of 10:(0.5-2):(0.5-1.5):(0.5-2) and mixing them evenly to obtain the lead-based supported halloysite composite heat stabilizer.

2. The preparation method of a lead-based supported halloysite composite heat stabilizer according to claim 1, characterized in that: In step S1, the selected halloysite has an outer diameter of 20-60 nm, an inner diameter of 5-20 nm, and a length of 300-3000 nm.

3. The preparation method of a lead-based supported halloysite composite heat stabilizer according to claim 1, characterized in that: The coupling agent is any one or more of the following: silane coupling agent, titanate coupling agent, aluminate coupling agent, phosphate coupling agent, and borate coupling agent.

4. The preparation method of a lead-based supported halloysite composite heat stabilizer according to claim 1, characterized in that: In step S3, the mass fraction ratio of lead-loaded halloysite, stearic acid, maleic acid ester, and coupling agent is 10:1.5:1.5:

3.

5. The preparation method of a lead-based supported halloysite composite heat stabilizer according to claim 1, characterized in that: The epoxy compound is any one or more of epoxidized soybean oil, epoxidized flaxseed oil, epoxidized butyl stearate, and epoxidized octyl stearate.

6. The method for preparing a lead-based supported halloysite composite heat stabilizer according to claim 1, characterized in that: In step S4, the mass fraction ratio of modified lead-supported halloysite, phosphite, epoxy compound, and polyol is 10:1:1:1.5.

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