Layered composite metal hydroxide as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of polymer functional aids, and discloses a layered composite metal hydroxide and a preparation method and application thereof, the chemical expression of the layered composite metal hydroxide is M < 2 + > 1-xM < 3 + > x (OH) 2 (A < n->) x / n.mH < 2 > O (at) P, m < 2 + > is selected from any one or two of Mg < 2 + >, Zn < 2 + >, Ni < 2 + >, Ca < 2 + >, Fe < 2 + > and Cu < 2 + >; m < 3 + > is selected from any one or two of Al < 3 + >, Co < 3 + >, Ti < 3 + >, Fe < 3 + > and Cr < 3 + >; a < n-> is selected from the group consisting of beta-(3, 5-di-tert-butyl-4-hydroxyphenyl) propionate, 3, 5-di-tert-butyl-4-hydroxybenzoic acid or beta-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate; x ranges from 0.1 to 0.5; n is 1 or 2; m ranges from 0.4 to 1.5; p is selected from chitosan, chitin, polyglucosamine, polyallylamine or polyethylene polyamine; based on the total weight of the layered composite metal hydroxide, the content of P is 5-15 wt%. The layered composite metal hydroxide provided by the invention has excellent migration resistance when being used as a polymer antioxidant.

Description

Technical Field

[0001] This invention relates to the field of polymer functional additives technology, and more specifically, to a layered composite metal hydroxide, its preparation method, and its application. Background Technology

[0002] Polypropylene (PP) is one of the most widely used commercial thermoplastics, possessing excellent properties such as good transparency, corrosion resistance, and high insulation, making it widely used in various aspects of life. However, due to the presence of a large number of unstable α-H atoms in its structure, it undergoes auto-oxidative degradation reactions under the influence of external factors such as ultraviolet light, heat, and oxygen, directly leading to changes in the molecular weight of polymer products and a decline in mechanical properties. Given the widespread demand for polypropylene and its susceptibility to thermo-oxidative aging in the environment, the addition of antioxidants and other anti-aging additives is necessary to inhibit its degradation reaction and improve long-term stability, which has significant practical application value.

[0003] The fundamental principle for preventing thermo-oxidative degradation of polypropylene is to inhibit the formation of free radicals. This can be achieved using functional additives. Functional additives are typically small organic molecule compounds whose main function is to capture free radicals generated during thermo-oxidative degradation, thereby breaking the chain reaction. However, during use, due to their low relative molecular mass, these small molecule functional additives cannot be fixed within the polymer, causing them to easily migrate to the polymer surface. After migration, polypropylene products exhibit yellowing and brittleness, reduced resistance to thermo-oxidative aging, and a shorter service life. Furthermore, they can pollute the environment and harm human health. Therefore, to increase the migration resistance of functional additives, researchers have recently proposed immobilizing polymer functional additives onto inorganic particle carriers, thereby improving the service life of polypropylene.

[0004] Layered double hydroxides (LDHs) are two-dimensional materials with a layered composite metal hydroxide molecular structure. Their chemical composition can be represented as [M... 2+ 1-x M 3+ x [(OH)2](A n- ) x / n ·mH2O, A n-These are inorganic or organic anions with non-framework charge compensation. Based on the tunable nature of the host layer's chemical composition, guest species and quantity, intralayer elastic space, and host-guest interactions, small-molecule antioxidants are intercalated into the interlayer of LDHs to prepare intercalated antioxidant structures. Under the protection of host-guest interactions and lattice energy, the antioxidant's migration resistance is significantly enhanced. Intercalation assembly is universal and widely used in migration-resistant functional additives. However, in daily use, the antioxidants at the interlayer edges are always in close contact with solvents and air, inevitably leading to some antioxidants being extracted and exchanged out of the intercalated structure by solvents and CO2. Therefore, it is necessary to block the interlayer edges to prevent the antioxidants at the edges from migrating out of LDHs, further enhancing the migration resistance of the intercalated antioxidant structure.

[0005] Currently, no methods for interlayer blocking of LDHs have been reported, but blocking structures are commonly found in drug-release materials. For example, the literature R. Meng, Z. Wu, QTXie, JSCheng, B. Zhang, Preparation and characterization of zein / carboxymethyl dextrin nanoparticles to encapsulate curcumin: Physicochemical stability, antioxidant activity and controlled release properties, Food Chem. 340(2021)127893 uses zein and carboxymethyl dextrin to achieve encapsulation of curcumin through electrostatic interactions, hydrogen bonds, and hydrophobic interactions. However, the preparation of such blocking materials is relatively cumbersome and difficult to use for blocking interlayer guests in LDHs. Therefore, it is necessary to develop and study methods suitable for interlayer blocking of LDHs. Summary of the Invention

[0006] The purpose of this invention is to provide a layered composite metal hydroxide, its preparation method, and its application. When used as a polymer antioxidant, the layered composite metal hydroxide of this invention exhibits excellent migration resistance.

[0007] To achieve the above objectives, a first aspect of the present invention provides a layered composite metal hydroxide, the chemical formula of which is M. 2+ 1-x M 3+ x (OH)2(A n- ) x / n ·mH2O@P;

[0008] Among them, M 2+ Selected from Mg 2+Zn 2+ Ni 2+ Ca 2+ Fe 2+ and Cu 2+ Any one or two of them, preferably Mg 2+ and / or Zn 2+ M 3+ Selected from Al 3+ Co 3+ Ti 3+ Fe 3+ and Cr 3+ Any one or two of them, preferably Al 3+ ;

[0009] A n- It is selected from β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 3,5-di-tert-butyl-4-hydroxybenzoate or β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate, preferably β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate;

[0010] x is 0.1 to 0.5, preferably 0.16 to 0.35; n is 1 or 2; m is 0.4 to 1.5;

[0011] P is selected from chitosan, chitin, polyglucosamine, polyallylamine or polyethylene polyamine, preferably chitosan; the content of P is 5 to 15 wt% based on the total weight of the layered composite metal hydroxide.

[0012] A second aspect of the present invention provides a method for preparing a layered composite metal hydroxide, the method comprising:

[0013] (1) In the presence of a solvent, a divalent metal salt, a trivalent metal salt, a precipitant and a guest anionic compound are reacted to obtain a reaction solution;

[0014] (2) In the presence of a protective gas, the reaction liquid and the blocking agent solution are brought into contact and reacted to obtain the layered composite metal hydroxide.

[0015] A third aspect of the present invention provides a layered composite metal hydroxide prepared by the above-described preparation method.

[0016] A fourth aspect of the present invention provides the application of the above-described layered composite metal hydroxide as a polymer antioxidant, wherein the polymer is preferably polypropylene.

[0017] The technical solution of the present invention has the following beneficial effects:

[0018] (1) When the layered composite metal hydroxide of the present invention is used as a polymer antioxidant, it has excellent migration resistance.

[0019] (2) The preparation method of the present invention is simple to operate, easy to scale up production, and has industrial application value.

[0020] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0021] Exemplary embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

[0022] Figure 1 The XRD patterns of layered composite metal hydroxides according to Examples 1-5 of the present invention are shown. Detailed Implementation

[0023] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0024] A first aspect of the present invention provides a layered composite metal hydroxide, the chemical formula of which is M. 2+ 1-x M 3+ x (OH)2(A n- ) x / n ·mH2O@P;

[0025] Among them, M 2+ Selected from Mg 2+ Zn 2+ Ni 2+ Ca 2+ Fe 2+ and Cu 2+ Any one or two of them, preferably Mg 2+ and / or Zn 2+ M 3+ Selected from Al 3+ Co 3+ Ti 3+ Fe 3+ and Cr 3+ Any one or two of them, preferably Al 3+ ;

[0026] A n- It is selected from β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 3,5-di-tert-butyl-4-hydroxybenzoate or β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate, preferably β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate;

[0027] x is 0.1 to 0.5, preferably 0.16 to 0.35; n is 1 or 2; m is 0.4 to 1.5;

[0028] P is selected from chitosan, chitin, polyglucosamine, polyallylamine or polyethylene polyamine, preferably chitosan; the content of P is 5 to 15 wt% based on the total weight of the layered composite metal hydroxide.

[0029] A second aspect of the present invention provides a method for preparing a layered composite metal hydroxide, the method comprising:

[0030] (1) In the presence of a solvent, a divalent metal salt, a trivalent metal salt, a precipitant and a guest anionic compound are reacted to obtain a reaction solution;

[0031] (2) In the presence of a protective gas, the reaction liquid and the blocking agent solution are brought into contact and reacted to obtain the layered composite metal hydroxide.

[0032] In this invention, the reaction solution obtained in step (1) is a nucleation slurry.

[0033] In this invention, contact can be made using conventional contact methods in the art, such as drop-feed contact.

[0034] In this invention, preferably, the protective gas is an inert gas, and more preferably at least one of nitrogen, argon and helium.

[0035] In order to address the problem of easy extraction or exchange of guest antioxidants at the interlayer edges in existing intercalated antioxidant structures, this invention provides a layered composite metal hydroxide and its preparation method. In the layered composite metal hydroxide of this invention, the guest antioxidant ions are not only protected by host-guest interactions and lattice energy, but also trapped by the external cage of the layers, significantly suppressing their migration behavior. Therefore, when used as a polymeric antioxidant, the layered composite metal hydroxide of this invention exhibits excellent migration resistance.

[0036] In this invention, a preferred embodiment is as follows: (1) a divalent metal salt and a trivalent metal salt are dissolved in a first solvent to obtain a mixed solution of metal salts; a precipitant, a guest anionic compound and a first solvent are mixed evenly to obtain a mixed solution of precipitant and guest anionic compound; wherein, the first solvent is preferably water;

[0037] Preparation of the blocking agent solution: The blocking agent is ground, and a second solvent is added during the grinding process for preliminary dissolution. Grinding continues to obtain a blocking agent mother liquor. Then, the blocking agent mother liquor is diluted with water to obtain a blocking agent solution. The second solvent is an aqueous acetic acid solution.

[0038] (2) The metal salt mixed solution and the mixed solution of the precipitant and the guest anionic compound are mixed in a colloid mill for 3-8 min to obtain a nucleating slurry; then the nucleating slurry is dispersed in an ultrasonic bath for 15-25 min.

[0039] (3) In the presence of a protective gas, the nucleating slurry obtained by ultrasonic dispersion in step (3) is added to the blocking agent solution under stirring, and then an aging reaction is carried out to obtain the layered composite metal hydroxide. The preferred temperature for the aging reaction is 40-180℃.

[0040] Another preferred embodiment is as follows: (1) a divalent metal salt and a trivalent metal salt are dissolved in a first solvent to obtain a mixed solution of metal salts; a precipitant, a guest anionic compound and a first solvent are mixed evenly to obtain a mixed solution of precipitant and guest anionic compound; wherein, the first solvent is preferably water;

[0041] Preparation of the blocking agent solution: The blocking agent is ground, and a second solvent is added during the grinding process for preliminary dissolution. Grinding continues to obtain a blocking agent mother liquor. Then, the blocking agent mother liquor is diluted with water to obtain a blocking agent solution. The second solvent is an aqueous acetic acid solution.

[0042] (2) The mixed solution of the metal salt and the mixed solution of the precipitant and the guest anionic compound are stirred at 400-600 rpm for 0.5-1.5 h to obtain a nucleating slurry; then the nucleating slurry is dispersed in ultrasound for 15-25 min;

[0043] (3) In the presence of a protective gas, the nucleating slurry obtained by ultrasonic dispersion in step (3) is added to the blocking agent solution under stirring, and then an aging reaction is carried out to obtain the layered composite metal hydroxide. The preferred temperature for the aging reaction is 40-180℃.

[0044] This invention utilizes the long-chain polyamino structure of a blocking agent. By combining amino groups with the hydroxyl groups of the top and bottom metal layers of the intercalated antioxidant, a cage-like structure is formed within the intercalated antioxidant, locking in the interlayer antioxidant guests and preventing their migration to the outside. This invention is the first to propose a cage structure for improving the migration resistance of intercalated antioxidants, breaking through the traditional structural pattern of open interlayer intercalated antioxidants, achieving structural innovation, and significantly improving the migration resistance of interlayer antioxidant guests.

[0045] The preparation method of the present invention has advantages such as simplicity, low energy consumption, small scale-up effect, and ease of large-scale production.

[0046] According to the present invention, preferably, the divalent metal ion provided by the divalent metal salt is Mg. 2+ Zn2+ Ni 2+ Ca 2+ Fe 2+ and Cu 2+ Any one or two of them, preferably Mg 2+ and / or Zn 2+ ;

[0047] The trivalent metal salt provides Al ions. 3+ Co 3+ Ti 3+ Fe 3+ and Cr 3+ Any one or two of them, preferably Al 3+ ;

[0048] Both the divalent and trivalent metal salts are inorganic metal salts.

[0049] According to the present invention, preferably, the precipitant is at least one selected from NaOH, KOH, ammonia, hexamethylenetetramine, and urea.

[0050] In this invention, NaOH is NaOH powder and KOH is KOH powder.

[0051] According to the present invention, preferably, the guest anionic compound is a hindered phenolic compound, preferably at least one of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, sodium β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid, sodium β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate, 3,5-di-tert-butyl-4-hydroxybenzoic acid, and sodium 3,5-di-tert-butyl-4-hydroxybenzoate; more preferably, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid.

[0052] According to the present invention, preferably, the blocking agent is a polyamino polymer, preferably chitosan, chitin, polyglucosamine, polyallylamine or polyethylene polyamine, and more preferably chitosan.

[0053] According to the present invention, preferably, the molar ratio of divalent metal ions to trivalent metal ions is (2-4):1;

[0054] The ratio of the sum of the molar contents of the divalent and trivalent metal salts to the molar contents of the precipitant is 1:(1.5-3);

[0055] The molar ratio of the guest anionic compound to the trivalent metal ion is 1:(0.5-10);

[0056] The mass ratio of the blocking agent to the sum of the contents of the divalent and trivalent metal salts is 1:(3-50).

[0057] According to the present invention, preferably, in step (1), the solvent is water; and the reaction time is 5-80 min.

[0058] In step (2), the reaction time is 0.5-12 h, and the reaction temperature is 25-180 °C, preferably 40-180 °C;

[0059] The blocking agent solution is an aqueous solution of the blocking agent in acetic acid.

[0060] A third aspect of the present invention provides a layered composite metal hydroxide prepared by the above-described preparation method.

[0061] A fourth aspect of the present invention provides the application of the above-described layered composite metal hydroxide as a polymer antioxidant, wherein the polymer is preferably polypropylene.

[0062] The present invention is further illustrated by the following examples:

[0063] In the following embodiments and comparative examples:

[0064] All NaOH used was NaOH powder;

[0065] The chitosan used is ACROS chitosan with a molecular weight of 100,000-300,000;

[0066] The chitin used was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0067] Example 1

[0068] Step 1: Dissolve 4 mmol Mg(NO3)2 and 2 mmol Al(NO3)3 in 200 mL of deionized water and dissolve for 10 min with the aid of ultrasound to prepare mixed solution A; dissolve 12 mmol NaOH and 4 mmol β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid (DBHP) in 200 mL of deionized water to prepare mixed solution B.

[0069] Step 2: Take 0.1g of chitosan (CS) and grind it thoroughly in a mortar. During the grinding process, add 2mL of 2wt% acetic acid aqueous solution to initially dissolve the chitosan. Continue grinding for 5min to obtain chitosan mother liquor. Dilute the chitosan mother liquor with water to 500mL and denote it as solution C.

[0070] Step 3: Add solution A and solution B to a colloid mill and mix for 5 minutes to obtain a nucleating slurry. Disperse the nucleating slurry in an ultrasonic bath for 20 minutes.

[0071] Step 4: Under a nitrogen atmosphere, the well-dispersed nucleating slurry was added dropwise to solution C under stirring at a rate of 50 mL / min at 80 °C. After the addition was complete, the reaction was continued at 80 °C for 4 h. The resulting product was washed three times each with deionized water and ethanol. The wet filter cake was dried in a vacuum oven at 60 °C for 8 h to obtain a layered composite metal hydroxide. The chemical formula is Mg 0.67 Al 0.33 (OH)2(D - ) 0.33 • 0.88H2O@CS, based on the total weight of the layered composite metal hydroxide, the CS content is 11.6wt%; wherein, D - It represents β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0072] Example 2

[0073] Step 1: Dissolve 4 mmol Mg(NO3)2 and 2 mmol Al(NO3)3 in 200 mL of deionized water and dissolve for 10 min with the aid of ultrasound to prepare mixed solution A; dissolve 12 mmol NaOH and 4 mmol β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid in 200 mL of deionized water to prepare mixed solution B.

[0074] Step 2: Take 0.1g of chitin (CT) and grind it thoroughly in a mortar. During the grinding process, add 2mL of 2wt% acetic acid aqueous solution to initially dissolve the chitin. Continue grinding for 5min to obtain chitosan mother liquor. Dilute the chitosan mother liquor with water to 500mL and denote it as solution C.

[0075] Step 3: Add solution A and solution B to a colloid mill and mix for 5 minutes to obtain a nucleating slurry. Disperse the nucleating slurry in an ultrasonic bath for 20 minutes.

[0076] Step 4: Under a nitrogen atmosphere, the well-dispersed nucleating slurry was added dropwise to solution C under stirring at a rate of 50 mL / min at 80 °C. After the addition was complete, the reaction was continued at 80 °C for 4 h. The resulting product was washed three times each with deionized water and ethanol. The wet filter cake was dried in a vacuum oven at 60 °C for 8 h to obtain a layered composite metal hydroxide. The chemical formula is Mg 0.67 Al 0.33 (OH)2(D - ) 0.33 • 0.92H2O@CT, based on the total weight of the layered composite metal hydroxide, the CT content is 12.4 wt%; wherein, D - It represents β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0077] Example 3

[0078] Step 1: Dissolve 4 mmol Zn(NO3)2 and 2 mmol Al(NO3)3 in 200 mL of deionized water and dissolve under sonication for 20 min to prepare mixed solution A; dissolve 12 mmol NaOH and 3 mmol β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid in 200 mL of deionized water to prepare mixed solution B.

[0079] Step 2: Take 0.1g of chitosan (CS) and grind it thoroughly in a mortar. During the grinding process, add 2mL of 2wt% acetic acid aqueous solution to initially dissolve the chitosan. Continue grinding for 5min to obtain chitosan mother liquor. Dilute the chitosan mother liquor with water to 500mL and denote it as solution C.

[0080] Step 3: Add solution A and solution B to the flask and stir thoroughly at 500 rpm for 1 hour to obtain nucleation slurry. Disperse the nucleation slurry in ultrasound for 20 minutes.

[0081] Step 4: Under a nitrogen atmosphere, the well-dispersed nucleating slurry was added dropwise to solution C under stirring at a rate of 50 mL / min at 80 °C. After the addition was complete, the reaction was continued at 80 °C for 4 h. The resulting product was washed three times each with deionized water and ethanol. The wet filter cake was dried in a vacuum oven at 60 °C for 8 h to obtain a layered composite metal hydroxide with the chemical formula Zn. 0.66 Al 0.34 (OH)2(D - ) 0.34 • 0.78H2O@CS, based on the total weight of the layered composite metal hydroxide, the CS content is 11.5wt%; wherein, D - It represents β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0082] Example 4

[0083] Step 1: Dissolve 8 mmol Mg(NO3)2 and 2 mmol Al(NO3)3 in 200 mL of deionized water and dissolve for 10 min with the aid of ultrasound to prepare mixed solution A; dissolve 20 mmol NaOH and 2 mmol β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid in 200 mL of deionized water to prepare mixed solution B.

[0084] Step 2: Take 0.1g of chitosan (CS) and grind it thoroughly in a mortar. During the grinding process, add 2mL of 2wt% acetic acid aqueous solution to initially dissolve the chitosan. Continue grinding for 5min to obtain chitosan mother liquor. Dilute the chitosan mother liquor with water to 500mL and denote it as solution C.

[0085] Step 3: Add solution A and solution B to a colloid mill and mix for 5 minutes to obtain a nucleating slurry. Disperse the nucleating slurry in an ultrasonic bath for 20 minutes.

[0086] Step 4: Under a nitrogen atmosphere, the well-dispersed nucleating slurry was added dropwise to solution C under stirring at a rate of 50 mL / min at 80 °C. After the addition was complete, the reaction was continued at 80 °C for 4 h. The resulting product was washed three times each with deionized water and ethanol. The wet filter cake was dried in a vacuum oven at 60 °C for 8 h to obtain a layered composite metal hydroxide with the chemical formula Mg. 0.70 Al 0.30 (OH)2(D - ) 0.30 • 0.74H2O@CS, based on the total weight of the layered composite metal hydroxide, the CS content is 11.8 wt%; wherein, D - It represents β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0087] Example 5

[0088] Step 1: Dissolve 4 mmol Mg(NO3)2 and 2 mmol Al(NO3)3 in 200 mL of deionized water and dissolve for 10 min with the aid of ultrasound to prepare mixed solution A; dissolve 12 mmol NaOH and 4 mmol β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid (DBHP) in 200 mL of deionized water to prepare mixed solution B.

[0089] Step 2: Take 0.2g of chitosan (CS) and grind it thoroughly in a mortar. During the grinding process, add 2mL of 2wt% acetic acid aqueous solution to initially dissolve the chitosan. Continue grinding for 5min to obtain chitosan mother liquor. Dilute the chitosan mother liquor with water to 500mL and denote it as solution C.

[0090] Step 3: Add solution A and solution B to a colloid mill and mix for 5 minutes to obtain a nucleating slurry. Disperse the nucleating slurry in an ultrasonic bath for 20 minutes.

[0091] Step 4: Under a nitrogen atmosphere, the well-dispersed nucleating slurry was added dropwise to solution C under stirring at a rate of 50 mL / min at 80 °C. After the addition was complete, the reaction was continued at 80 °C for 4 h. The resulting product was washed three times each with deionized water and ethanol. The wet filter cake was dried in a vacuum oven at 60 °C for 8 h to obtain a layered composite metal hydroxide with the chemical formula Mg. 0.68 Al 0.32 (OH)2(D - ) 0.32• 0.76H2O@CS, based on the total weight of the layered composite metal hydroxide, the CS content is 12.1 wt%; wherein, D - It represents β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0092] Comparative Example 1

[0093] Step 1: Dissolve 4 mmol Mg(NO3)2 and 2 mmol Al(NO3)3 in 200 mL of deionized water and dissolve for 10 min with the aid of ultrasound to prepare mixed solution A; dissolve 12 mmol NaOH and 4 mmol β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid in 200 mL of deionized water to prepare mixed solution B.

[0094] Step 2: Add solution A and solution B to a colloid mill and mix for 5 minutes to obtain a nucleating slurry. Disperse the nucleating slurry in an ultrasonic bath for 20 minutes.

[0095] Step 3: Under a nitrogen atmosphere, the well-dispersed nucleation slurry was reacted at 80°C for 4 hours. The resulting product was washed three times each with deionized water and ethanol. The wet filter cake was dried in a vacuum oven at 60°C for 8 hours to obtain a layered composite metal hydroxide. The chemical formula is Mg. 0.67 Al 0.33 (OH)2(D - ) 0.33 0.92H2O.

[0096] Test Example 1

[0097] The layered composite metal hydroxides prepared in Examples 1-5 were vacuum dried and then ground into powder for XRD characterization. The crystal structure of the samples was characterized using a Shimadzu XRD-6000 X-ray powder diffractometer. The results are shown below. Figure 1 .

[0098] Depend on Figure 1 It can be seen that the layered composite metal hydroxide prepared in the example has LDH characteristic crystal plane diffraction peaks such as (003), (006) and (009) which are shifted due to the successful intercalation of guest anions. The interplanar spacing corresponding to the (003) characteristic peak is 2.62 nm, indicating that a layered composite metal hydroxide with an interlayer spacing of 2.62 nm was successfully prepared.

[0099] Test Example 2

[0100] The layered composite metal hydroxides finally prepared in Examples 1-5 and the comparative example were blended and molded with polypropylene (PP) to obtain polypropylene sheets. The amount of layered composite metal hydroxide added was 0.4% of the weight of PP. The blending and molding temperatures were both 180℃. The PP was homopolymer polypropylene powder (melting point 165℃, melt flow rate 8.0g / 10min (230℃, 2.16kg)). Then, the prepared samples were subjected to migration resistance tests, and the test results are shown in the table below. The test method was as follows: 24g of polypropylene sheet sample was placed in anhydrous ethanol at 60℃ and heated for 200h. The DBHP content in the ethanol was measured using UV-vis. The migration amount of DBHP in the DBHP-LDH / PP sample was analyzed to explore the migration resistance of the layered composite metal hydroxide.

[0101] Table 1

[0102]

[0103]

[0104] As shown in Table 1, compared with the layered composite metal hydroxide prepared in Comparative Example 1, the antioxidant migration rate of the PP material containing the layered composite metal hydroxide prepared in Examples 1-5 was reduced by 22.4% to 30.75%.

[0105] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A layered composite metal hydroxide, characterized in that, The chemical formula for this layered composite metal hydroxide is M. 2+ 1-x M 3+ x (OH)2(A n- ) x / n ·mH2O@P; Among them, M 2+ Selected from Mg 2+ Zn 2+ Ni 2+ Ca 2+ Fe 2+ and Cu 2+ Any one or two of them, preferably Mg 2+ and / or Zn 2 + M 3+ Selected from Al 3+ Co 3+ Ti 3+ Fe 3+ and Cr 3+ Any one or two of them, preferably Al 3+ ; A n- It is selected from β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 3,5-di-tert-butyl-4-hydroxybenzoate or β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate, preferably β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; x is 0.1 to 0.5, preferably 0.16 to 0.35; n is 1 or 2; m is 0.4 to 1.5; P is selected from chitosan, chitin, polyglucosamine, polyallylamine or polyethylene polyamine, preferably chitosan; the content of P is 5 to 15 wt% based on the total weight of the layered composite metal hydroxide.

2. A method for preparing a layered composite metal hydroxide, characterized in that, The preparation method includes: (1) In the presence of a solvent, a divalent metal salt, a trivalent metal salt, a precipitant and a guest anionic compound are reacted to obtain a reaction solution; (2) In the presence of a protective gas, the reaction liquid and the blocking agent solution are brought into contact and reacted to obtain the layered composite metal hydroxide.

3. The preparation method according to claim 2, wherein, The divalent metal ion provided by the divalent metal salt is Mg. 2+ Zn 2+ Ni 2+ Ca 2+ Fe 2+ and Cu 2+ Any one or two of them, preferably Mg 2+ and / or Zn 2+ ; The trivalent metal salt provides Al ions. 3+ Co 3+ Ti 3+ Fe 3+ and Cr 3+ Any one or two of them, preferably Al 3+ ; Both the divalent and trivalent metal salts are inorganic metal salts.

4. The preparation method according to claim 2, wherein, The precipitant is at least one of NaOH, KOH, ammonia, hexamethylenetetramine, and urea.

5. The preparation method according to claim 2, wherein, The guest anionic compound is a hindered phenolic compound, preferably at least one of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, sodium β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid, sodium β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate, 3,5-di-tert-butyl-4-hydroxybenzoic acid, and sodium 3,5-di-tert-butyl-4-hydroxybenzoate; more preferably β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid.

6. The preparation method according to claim 2, wherein, The blocking agent is a polyamine polymer, preferably chitosan, chitin, polyglucosamine, polyallylamine or polyethylene polyamine, and more preferably chitosan.

7. The preparation method according to claim 2, wherein, The molar ratio of divalent metal ions to trivalent metal ions is (2-4):1; The ratio of the sum of the molar contents of the divalent and trivalent metal salts to the molar contents of the precipitant is 1:(1.5-3); The molar ratio of the guest anionic compound to the trivalent metal ion is 1:(0.5-10); The mass ratio of the blocking agent to the sum of the contents of the divalent and trivalent metal salts is 1:(3-50).

8. The preparation method according to claim 2, wherein, In step (1), the solvent is water; the reaction time is 5-80 min; In step (2), the reaction time is 0.5-12 h, and the reaction temperature is 25-180 °C, preferably 40-180 °C; The blocking agent solution is an aqueous solution of the blocking agent in acetic acid.

9. A layered composite metal hydroxide prepared by the preparation method according to any one of claims 2-8.

10. The application of the layered composite metal hydroxide of claim 1 or 9 as a polymeric antioxidant, wherein the polymer is preferably polypropylene.

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