New graft modification method for high-acid-value oxidized polyethylene wax

Abstract

Disclosed in the present invention is a new graft modification method for a high-acid-value oxidized polyethylene wax. The method comprises: subjecting a polyethylene wax to an oxidation reaction to produce polar functional groups such as hydroxyl groups and carboxyl groups; then subjecting the groups, such as the hydroxyl groups and the carboxyl groups, to an esterification reaction with acid anhydrides or amino acids to further increase polar functional groups; and then performing precipitation and separation to obtain a graft-modified high-acid-value oxidized polyethylene wax. The oxidized polyethylene wax prepared by the present invention exhibits a pure-white microbead-like appearance and morphology, and has the characteristics of a high acid value, a low viscosity, a high whiteness index, good lubricating and dispersing properties, etc., wherein the whiteness index exceeds 85, and the acid value reaches 35-60 mg KOH / g. Furthermore, the process is simple, and the prepared oxidized polyethylene wax contains sufficient polar functional groups, such as carboxyl groups, and has a high and controllable acid value.

Description

Novel high-acid-value oxidized polyethylene wax graft modification method TECHNICAL FIELD

[0001] The present application relates to the technical field of oxidized polyethylene wax preparation, in particular to a novel high-acid-value oxidized polyethylene wax graft modification method. BACKGROUND

[0002] Polyethylene wax, also known as low relative molecular mass polyethylene, is divided into polymerization type polyethylene wax and cracking type polyethylene wax according to different manufacturing methods. The former is a by-product during ethylene polymerization, and the latter is obtained by heating and cracking polyethylene resin. As a kind of low molecular weight polyethylene, they all have high softening point, low melt viscosity, no odor, no toxicity, good chemical stability, excellent blending property and dielectric property, etc. The polyethylene wax without modification is actually a mixture of low molecular weight polyethylene with different molecular weight distribution and physical properties, which is only used as a general dispersant and additive and cannot meet special purposes, with lower value.

[0003] Oxidized polyethylene wax is a product obtained by oxidizing polyethylene wax. With the rapid development of color masterbatch, plastic, paint, ink and other industries, the demand for high-performance additives is increasing. Oxidized polyethylene wax has been widely concerned due to its unique performance. Traditional polyethylene wax has limitations in some applications, such as compatibility, dispersibility and wettability. Through oxidation treatment, oxygen-containing functional groups such as carboxyl and hydroxyl can be introduced into the molecular chain of polyethylene wax, thereby improving its performance. Oxidized polyethylene wax has the following advantages: ① good compatibility, which can be compatible with various polymers and resins, improving the comprehensive performance of materials; ② excellent dispersibility, which helps the uniform dispersion of pigments, fillers and other materials in the matrix; ③ good lubricity, which reduces the friction coefficient and improves the processing performance; ④ enhanced surface activity, which improves the surface performance of materials, such as improving the adhesion and gloss of coating.

[0004] With the continuous progress of technology, the production process of oxidized polyethylene wax is constantly improving and perfecting to meet the higher requirements of different industries on its performance. At present, the commonly used oxidation methods include air oxidation method and peroxide oxidation method, etc., and different methods have their own characteristics and application range.

[0005] The academic and industrial circles have been actively developing the modification of polyethylene wax, the main purpose of which is to introduce polar groups such as hydroxyl and carboxyl into the non-polar polyethylene wax to improve its solubility and emulsifying properties. Chemical oxidation and maleic anhydride grafting are two commonly used methods. Chemical oxidation introduces hydroxyl, carboxyl and other polar functional groups through oxidation to enhance its hydrophilicity and emulsifying properties. Maleic anhydride grafting is a free radical polymerization that grafts maleic anhydride and other polar groups onto the carbon chain of polyethylene wax. However, both methods have obvious shortcomings, such as the gas-solid two-phase reaction involved in the gas oxidation of the oxidation method, poor mass transfer, uneven oxidation, and low oxidation efficiency. The grafting rate of maleic anhydride grafting from polyethylene wax is slow, and is accompanied by side reactions such as chain scission and crosslinking, resulting in low grafting rate.

[0006] Patent CN202410415239.9 proposes to use a mixed foaming agent technology to prepare foamed polyethylene wax, then absorb the initiator by immersing it in an initiator solution, and then perform an oxidation reaction in an autoclave to obtain a new type of oxidized polyethylene wax. This technology has advantages over solid-phase oxidation in terms of controlling the pore density and pore size of the polymer, but it still uses high-temperature and high-pressure reactions, and the operation process is relatively complex, with an acid value of no more than 30 mgKOH / g. Patent CN202311039555.2 proposes a method for preparing high-density oxidized polyethylene wax in a solid phase, which places the selected resin particles in an oven for oxidation in a solid phase, resulting in an oxidized polyethylene wax with an acid value of 10-50 mgKOH / g. However, this method has high requirements for the raw material, which needs to be sieved through a vibrating screen to obtain resin particles with an average particle size of 60-100 mesh, and the whiteness value is unknown. Patent CN202110095685.2 discloses a method for preparing high-density oxidized polyethylene wax, which first performs thermal cracking, then uses a high-pressure plunger pump to spray the high-density polyethylene wax into a powder, and then performs oxidation in air to prepare oxidized polyethylene wax. However, the thermal cracking step at a high temperature of 500°C is likely to cause carbonization of the polyethylene, and the prepared oxidized polyethylene wax has an acid value of less than 30 mgKOH / g. Patents CN201910790539.4 and CN201911269909.6 propose polyethylene wax modification methods similar to other reported modification methods, which use polyethylene wax as the raw material and perform free radical reaction with maleic anhydride under the action of an initiator to graft maleic anhydride onto the carbon chain of polyethylene wax. This invention utilizes the polar functional groups such as hydroxyl and carboxyl on the carbon chain of oxidized polyethylene wax to further perform efficient esterification with acid anhydride and amino acid, which can easily graft the structure of acid anhydride and amino acid onto the carbon chain of polyethylene wax to achieve high acid value and grafting rate. This process has not been reported. Therefore, improving the modification method of polyethylene wax, increasing the polar group, and increasing the acid value have great value in broadening the application of oxidized polyethylene wax.

[0007] SUMMARY

[0008] The present application aims to provide a novel high-acid-value oxidized polyethylene wax graft modification method to solve the problems of low acid value and complex preparation method of the prepared oxidized polyethylene wax.

[0009] To achieve the above-mentioned purpose, the present application provides a novel high-acid-value oxidized polyethylene wax graft modification method in the first aspect, comprising the following steps:

[0010] S1: Oxidation reaction: polyethylene wax is dissolved in a solvent at 90-150℃ for 2-4 hours, then an oxidizing agent is added for oxidation reaction for 4-12 hours, and then deionized water is added for washing;

[0011] S2: Esterification reaction: the oxidized polyethylene wax solution obtained in step S1 is heated to 100-140℃ for dissolution and stirring, then an activating agent is added, and then an acid anhydride or amino acid is slowly added dropwise for esterification reaction for 2-8 hours, and then the temperature is reduced to room temperature, and the solvent is recovered by reduced pressure distillation;

[0012] S3: Precipitation: the polyethylene wax obtained in step S2 is added to a solvent, and stirred at 90-120℃ for 1-3 hours, then the temperature is reduced to 40-60℃, and then a precipitant is slowly added to crystallize the polyethylene wax to obtain high-acid-value oxidized polyethylene wax.

[0013] Preferably, the solvent in step S1 is one or more of petroleum ether, n-hexane, cyclohexane, n-heptane, carbon tetrachloride, toluene, xylene, tetrahydrofuran, and dioxane.

[0014] Preferably, the mass / volume ratio of polyethylene wax and solvent in step S1 is 0.1-1g / mL.

[0015] Preferably, the oxidizing agent in step S1 is one or more of air, oxygen, hydrogen peroxide, sodium hypochlorite, and nitric acid.

[0016] Preferably, the gaseous oxidizing agent gas flow is 25-100mL / min, and the mass ratio of liquid and solid oxidizing agent to polyethylene wax is (0.05-0.2):1.

[0017] Preferably, the temperature of the oxidation reaction in step S1 is 90-150℃.

[0018] In the oxidation reaction process of the present application, hydroxyl groups, carboxyl groups and other polar groups can be generated in the carbon chain of the polyethylene wax, thereby forming oxidized polyethylene wax to a certain extent.

[0019] Preferably, the activator in step S2 is one or more of sulfuric acid, acetic acid, triethylamine, sodium bicarbonate, dicyclohexyl carbodiimide (DCC), diisopropyl carbodiimide (DIC), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDCI).

[0020] Preferably, the anhydride-based reactant in step S2 is one or more of maleic anhydride, acetic anhydride, propionic anhydride, succinic anhydride, Boc anhydride, ethyl propionic anhydride; and the amino acid-based reactant is one or more of glycine, alanine, leucine, aspartic acid, glutamic acid, lysine.

[0021] Preferably, the mass ratio of the anhydride-based reactant to the polyethylene wax in step S2 is (0.01-0.1):1.

[0022] Preferably, the mass ratio of the amino acid-based reactant to the polyethylene wax in step S2 is (0.01-0.1):1.

[0023] In the esterification reaction, part of the carboxyl and hydroxyl groups in the oxidized polyethylene wax can further undergo anhydride reaction with the anhydride-based substance, which can graft the anhydride-based substance into the carbon chain of the oxidized polyethylene wax to further enhance the polar groups. Part of the carboxyl and hydroxyl groups in the oxidized polyethylene wax can undergo esterification reaction with the amino acid-based substance to produce an amide structure, which can successfully graft the amino acid into the carbon chain of the polyethylene wax, and also can further enhance the polar groups.

[0024] Preferably, the solvent in step S3 is one or more of petroleum ether, n-hexane, cyclohexane, n-heptane, toluene, xylene, tetrahydrofuran, dioxane.

[0025] Preferably, the precipitant in step S3 is one or more of methanol, ethanol, isopropanol, n-butanol, N,N-dimethylformamide, dimethyl sulfoxide.

[0026] Preferably, the mass-to-volume ratio of the polyethylene wax to the precipitant in step S3 is 0.5-4 g / mL.

[0027] Preferably, the temperature for precipitating and crystallizing in step S3 is 40-60℃.

[0028] In the present application, the polyethylene wax is fully dissolved in the solvent, and then a suitable precipitant is used to slowly crystallize the polyethylene wax, which can make the polyethylene wax maintain a high crystallinity, and further obtain high-purity oxidized polyethylene wax with good whiteness and high acid value.

[0029] The polyethylene wax prepared by the method of the present application has a white micro-bead appearance, contains sufficient polar functional groups such as carboxyl groups, and has a high and controllable acid value.

[0030] The second aspect of the present application provides a high-acid-value oxidized polyethylene wax prepared by the method described above.

[0031] The third aspect of the present application provides an application of the high-acid-value oxidized polyethylene wax, which is applied in the fields of color masterbatch, paint, ink, plastic processing, adhesive, rubber, textile, and papermaking.

[0032] Therefore, the present application adopts a new high-acid-value oxidized polyethylene wax graft modification method with the above structure, which has the following beneficial effects:

[0033] (1) The process flow of the method of the present application is simple, and the white microbead-shaped appearance morphology oxidized polyethylene wax with high whiteness and controllable acid value can be prepared by using polyethylene wax as raw material through the steps of oxidation, esterification, and precipitation.

[0036] (2) The present application can introduce polar groups such as carboxyl and hydroxyl into the carbon chain of polyethylene wax through the oxidation and esterification process, and in particular, the esterification reaction can further graft the carboxyl and hydroxyl groups together with anhydride and amino acid to strengthen the polar groups in the carbon chain of polyethylene wax. The esterification process is different from the commonly used maleic anhydride grafting method, and does not require an initiator, and further reacts with the original carboxyl and hydroxyl groups, with a higher yield.

[0037] (3) The oxidized polyethylene wax prepared by the present application has a high and controllable acid value, which can significantly achieve the following advantages: ① improve compatibility, have good compatibility with various resins and polymers, and improve the comprehensive performance of the product; ② improve lubricity, improve flowability during processing, and make the product easier to form; ③ enhance surface activity, improve the dispersibility of pigments and fillers, and improve the color uniformity and surface quality of the product; ④ increase adhesion, for some applications that require good adhesion, the high-acid-value oxidized polyethylene wax can improve the adhesion between the coating and the substrate; ⑤ improve weather resistance, enhance the anti-aging performance of the product, and improve its service life in outdoor environments. (4) The oxidized polyethylene wax prepared by the present application has good compatibility, lubricity, adhesion, and excellent weather resistance, and can be applied in the fields of color masterbatch, paint, ink, plastic processing, adhesive, rubber, textile, and papermaking, with a wider range of applications.

[0038] The technical solutions of the present application are further described in detail below through the accompanying drawings and examples.

[0039] BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 is a process flow diagram of the high-acid-value oxidized polyethylene wax graft modification method in the present application.

[0039] Figure 2 is a picture of the appearance of the high-acid-value oxidized polyethylene wax prepared in Example 1;

[0040] Figure 3 is a picture of the scanning electron microscope of the high-acid-value oxidized polyethylene wax prepared in Example 1;

[0041] Figure 4 is a picture of the transmission electron microscope of the high-acid-value oxidized polyethylene wax prepared in Example 1;

[0042] Figure 5 is a picture of the infrared spectrum of the high-acid-value oxidized polyethylene wax prepared in Example 1. DETAILED DESCRIPTION

[0043] The present application will be further described below. It should be noted that the present embodiment is based on the technical solution of the present application, and gives a detailed implementation and specific operation process, but the present application is not limited to the present embodiment.

[0044] Example 1

[0045] The present embodiment is a novel high-acid-value oxidized polyethylene wax graft modification method, and the reaction steps are as follows:

[0046] (1) Oxidation reaction

[0047] The polyethylene wax (500 g) was placed in petroleum ether (500 mL) and stirred at 90°C for 2 hours, then air was continuously introduced into the reaction liquid (25 mL / min), and then the reaction was stirred vigorously for 4 hours, and then washed with deionized water.

[0048] (2) Esterification reaction

[0049] The above polyethylene wax solution was heated to 100°C, then sulfuric acid (10 g) was added, then maleic anhydride (5 g) was slowly added in batches, and the reaction was stirred at 100°C for 2 hours, then cooled to room temperature and washed with deionized water, and the solvent was recovered by reduced pressure distillation.

[0050] (3) Precipitation

[0051] The above polyethylene wax was added to petroleum ether (2500 mL) and stirred at 90°C for 1 hour, then the temperature was cooled to 40°C, and then methanol (1000 mL) was used as a precipitant to slowly crystallize the oxidized polyethylene wax.

[0052] Example 2

[0053] The present embodiment is a novel high-acid-value oxidized polyethylene wax graft modification method, and the reaction steps are as follows:

[0054] (1) Oxidation reaction

[0055] Polyethylene wax (500 g) was placed in n-hexane (500 mL) and toluene (500 mL) and stirred at 100°C for 3 hours, then oxygen was continuously supplied to the reaction (50 mL / min), and the reaction was stirred vigorously for 6 hours, and then deionized water was added for washing.

[0056] (2) Esterification reaction

[0057] The polyethylene wax solution was heated to 100°C, then acetic acid (25 g) was added, and acetic anhydride (25 g) was slowly added dropwise, and the reaction was stirred at 100°C for 4 hours, then cooled to room temperature, washed with deionized water, and the solvent was recovered by distillation under reduced pressure.

[0058] (3) Precipitation

[0059] The polyethylene wax was added to n-hexane (950 mL) and toluene (50 mL), and stirred at 100°C for 2 hours, then the temperature was cooled to 50°C, and then the oxidized polyethylene wax was slowly crystallized out using ethanol (500 mL) as a precipitant.

[0060] Example 3

[0061] This example is a new type of high-acid-value oxidized polyethylene wax graft modification method, and the reaction steps are as follows:

[0062] (1) Oxidation reaction

[0063] Polyethylene wax (500 g) was placed in cyclohexane (400 mL) and xylene (100 mL) and stirred at 110°C for 4 hours, then hydrogen peroxide (25 g) was added to the reaction, and the reaction was stirred vigorously for 8 hours, and then deionized water was added for washing.

[0064] (2) Esterification reaction

[0065] The polyethylene wax solution was heated to 110°C, then acetic acid (25 g) was added, and propionic anhydride (25 g) was slowly added dropwise, and the reaction was stirred at 110°C for 6 hours, then cooled to room temperature, washed with deionized water, and the solvent was recovered by distillation under reduced pressure.

[0066] (3) Precipitation

[0067] The polyethylene wax was added to cyclohexane (450 mL) and xylene (50 mL), and stirred at 110°C for 3 hours, then the temperature was cooled to 60°C, and then the oxidized polyethylene wax was slowly crystallized out using isopropanol (250 mL) as a precipitant.

[0068] Example 4

[0069] This example is a new type of high-acid-value oxidized polyethylene wax graft modification method, and the reaction steps are as follows:

[0070] (1) Oxidation reaction

[0071] The polyethylene wax (500 g) was placed in n-heptane (1000 mL) and tetrahydrofuran (100 mL) and stirred at 110°C for 2 hours, then sodium hypochlorite (50 g) was added to the reaction solution, and then the reaction was stirred vigorously for 12 hours, and then washed with deionized water.

[0072] (2) Esterification reaction

[0073] The above polyethylene wax solution was heated to 110°C, then triethylamine (50 g) was added, and then succinic anhydride (50 g) was slowly added dropwise, and the reaction was stirred at 110°C for 8 hours, then cooled to room temperature, washed with deionized water, and the solvent was recovered by distillation under reduced pressure.

[0074] (3) Precipitation

[0075] The above polyethylene wax was added to n-heptane (950 mL) and tetrahydrofuran (50 mL) and stirred at 110°C for 2 hours, then the temperature was cooled to 50°C, and then n-butanol (500 mL) was used as a precipitant to slowly crystallize the oxidized polyethylene wax.

[0076] Example 5

[0077] A new method for grafting modification of high-acid-value oxidized polyethylene wax was provided in this example, and the reaction steps were as follows:

[0078] (1) Oxidation reaction

[0079] The polyethylene wax (500 g) was placed in petroleum ether (1000 mL) and dioxane (100 mL) and stirred at 120°C for 2 hours, then nitric acid (50 g) was added to the reaction solution, and then the reaction was stirred vigorously for 8 hours, and then washed with deionized water.

[0080] (2) Esterification reaction

[0081] The above polyethylene wax solution was heated to 120°C, then sodium bicarbonate (50 g) was added, and then Boc anhydride (50 g) was slowly added, and the reaction was stirred at 120°C for 8 hours, then cooled to room temperature, washed with deionized water, and the solvent was recovered by distillation under reduced pressure.

[0082] (3) Precipitation

[0083] The above polyethylene wax was added to petroleum ether (850 mL) and dioxane (50 mL) and stirred at 120°C for 2 hours, then the temperature was cooled to 40°C, and then a mixture of ethanol (350 mL) and N,N-dimethylformamide (50 mL) was used as a precipitant to slowly crystallize the oxidized polyethylene wax.

[0084] Example 6

[0085] This embodiment is a new method for graft modification of high acid value oxidized polyethylene wax, and the reaction steps are as follows:

[0086] (1) Oxidation reaction

[0087] Polyethylene wax (500 g) was placed in petroleum ether (800 mL) and carbon tetrachloride (100 mL) and stirred at 120°C for 2 hours, then oxygen was continuously introduced into the reaction solution (100 mL / min), and then the reaction was stirred for 8 hours, and then washed with deionized water.

[0088] (2) Esterification reaction

[0089] The above polyethylene wax solution was heated to 120°C, then sulfuric acid (25 g) was added, then ethyl propionic anhydride (25 g) was slowly added, and the reaction was stirred at 120°C for 8 hours, then cooled to room temperature, then washed with deionized water, and the solvent was recovered by vacuum distillation.

[0090] (3) Precipitation

[0091] The above polyethylene wax was added to petroleum ether (750 mL) and carbon tetrachloride (50 mL) and stirred at 120°C for 2 hours, then the temperature was cooled to 40°C, then a mixture of ethanol (250 mL) and dimethyl sulfoxide (50 mL) was used as a precipitant to slowly crystallize the oxidized polyethylene wax.

[0092] Example 7

[0093] This embodiment is a new method for graft modification of high acid value oxidized polyethylene wax, and the reaction steps are as follows:

[0094] (1) Oxidation reaction

[0095] Polyethylene wax (500 g) was placed in petroleum ether (800 mL) and carbon tetrachloride (100 mL) and stirred at 120°C for 2 hours, then air was continuously introduced into the reaction solution (100 mL / min), and then the reaction was stirred for 8 hours, and then washed with deionized water.

[0096] (2) Esterification reaction

[0097] The above polyethylene wax solution was heated to 120°C, then sulfuric acid (25 g) was added, then ethyl propionic anhydride (25 g) was slowly added, and the reaction was stirred at 120°C for 8 hours, then cooled to room temperature, then washed with deionized water, and the solvent was recovered by vacuum distillation.

[0098] (3) Precipitation

[0099] The above polyethylene wax is added to petroleum ether (750 mL) and carbon tetrachloride (50 mL), stirred at 120°C for 2 hours, then the temperature is cooled to 40°C, and then the oxidized polyethylene wax is crystallized out slowly using a mixture of ethanol (250 mL) and dimethyl sulfoxide (50 mL) as a precipitant.

[0100] Example 8

[0101] This embodiment is a new graft modification method of high-acid-value oxidized polyethylene wax, and the reaction steps are as follows:

[0102] (1) Oxidation reaction

[0103] The polyethylene wax (500 g) is placed in petroleum ether (1000 mL) and toluene (200 mL), stirred at 130°C for 2 hours, then oxygen is continuously introduced into the reaction solution (50 mL / min), and then the reaction is stirred for 12 hours with strong stirring, and then washed with deionized water.

[0104] (2) Esterification reaction

[0105] The above polyethylene wax solution is heated to 140°C, then DCC (50 g) is added, and then glycine (50 g) is slowly added, and then the reaction is stirred at 140°C for 6 hours, and then cooled to room temperature and washed with deionized water, and the solvent is recovered by reduced pressure distillation.

[0106] (3) Crystallization and precipitation

[0107] The above polyethylene wax is added to petroleum ether (650 mL) and toluene (50 mL), stirred at 110°C for 2 hours, then the temperature is cooled to 50°C, and then the oxidized polyethylene wax is crystallized out slowly using a mixture of ethanol (100 mL) and isopropanol (25 mL) as a precipitant.

[0108] Example 9

[0109] This embodiment is a new graft modification method of high-acid-value oxidized polyethylene wax, and the reaction steps are as follows:

[0110] (1) Oxidation reaction

[0111] The polyethylene wax (500 g) is placed in petroleum ether (1000 mL) and toluene (200 mL), stirred at 130°C for 2 hours, then oxygen is continuously introduced into the reaction solution (50 mL / min), and then the reaction is stirred for 12 hours with strong stirring, and then washed with deionized water.

[0112] (2) Esterification reaction

[0113] The polyethylene wax solution was heated to 140°C, then DIC (50 g) was added, followed by slow addition of alanine (50 g), and the reaction was stirred at 140°C for 4 hours, then cooled to room temperature and washed with deionized water, and the solvent was recovered by distillation under reduced pressure.

[0114] (3) Precipitation

[0115] The polyethylene wax was added to petroleum ether (550 mL) and xylene (50 mL), and the reaction was stirred at 120°C for 2 hours, then the temperature was cooled to 40°C, and the oxidized polyethylene wax was slowly crystallized out using ethanol (200 mL) as a precipitant.

[0116] Example 10

[0117] This example is a novel method for graft modification of high-acid-value oxidized polyethylene wax, and the reaction steps are as follows:

[0118] (1) Oxidation reaction

[0119] The polyethylene wax (500 g) was placed in petroleum ether (900 mL) and xylene (200 mL), and the reaction was stirred at 130°C for 2 hours, then nitric acid (50 g) was added to the reaction solution, and the reaction was stirred vigorously for 8 hours, then washed with deionized water.

[0120] (2) Esterification reaction

[0121] The polyethylene wax solution was heated to 120°C, then EDCI (25 g) was added, followed by slow addition of leucine (25 g), and the reaction was stirred at 120°C for 6 hours, then cooled to room temperature and washed with deionized water, and the solvent was recovered by distillation under reduced pressure.

[0122] (3) Precipitation

[0123] The polyethylene wax was added to petroleum ether (650 mL) and xylene (50 mL), and the reaction was stirred at 100°C for 2 hours, then the temperature was cooled to 50°C, and the oxidized polyethylene wax was slowly crystallized out using methanol (500 mL) as a precipitant.

[0124] Example 11

[0125] This example is a novel method for graft modification of high-acid-value oxidized polyethylene wax, and the reaction steps are as follows:

[0126] (1) Oxidation reaction

[0127] The polyethylene wax (500 g) was placed in n-hexane (800 mL) and xylene (100 mL), and the reaction was stirred at 120°C for 2 hours, then hydrogen peroxide (100 g) was added to the reaction solution, and the reaction was stirred vigorously for 12 hours, then washed with deionized water.

[0128] (2) Esterification reaction

[0129] The polyethylene wax solution was heated to 120°C, then EDCI (25 g) was added, followed by slow addition of aspartic acid (25 g). The reaction was stirred at 120°C for 8 hours, then cooled to room temperature and washed with deionized water. The solvent was recovered by distillation under reduced pressure.

[0130] (3) Precipitation

[0131] The polyethylene wax was added to n-hexane (650 mL) and xylene (50 mL), and the reaction was stirred at 110°C for 2 hours. The temperature was then cooled to 50°C, and the oxidized polyethylene wax was crystallized by slow precipitation using methanol (400 mL) as the precipitant.

[0132] Example 12

[0133] This example is a novel method for graft modification of high-acid-value oxidized polyethylene wax, and the reaction steps are as follows:

[0134] (1) Oxidation reaction

[0135] The polyethylene wax (500 g) was placed in cyclohexane (700 mL) and toluene (100 mL), and the reaction was stirred at 110°C for 2 hours. Hydrogen peroxide (50 g) was then added to the reaction solution, and the reaction was stirred vigorously for 12 hours. Deionized water was added for washing.

[0136] (2) Esterification reaction

[0137] The polyethylene wax solution was heated to 110°C, then DCC (25 g) was added, followed by slow addition of glutamic acid (25 g). The reaction was stirred at 110°C for 8 hours, then cooled to room temperature and washed with deionized water. The solvent was recovered by distillation under reduced pressure.

[0138] (3) Precipitation

[0139] The polyethylene wax was added to cyclohexane (750 mL) and xylene (50 mL), and the reaction was stirred at 100°C for 2 hours. The temperature was then cooled to 40°C, and the oxidized polyethylene wax was crystallized by slow precipitation using n-butanol (300 mL) as the precipitant.

[0140] Example 13

[0141] This example is a novel method for graft modification of high-acid-value oxidized polyethylene wax, and the reaction steps are as follows:

[0142] (1) Oxidation reaction

[0143] The polyethylene wax (500 g) was placed in petroleum ether (800 mL) and toluene (100 mL) and stirred at 100°C for 2 hours, then oxygen was continuously bubbled into the reaction (50 mL / min) and the reaction was stirred vigorously for 8 hours, then deionized water was added for washing.

[0144] (2) Esterification reaction

[0145] The polyethylene wax solution was heated to 110°C, then DIC (25 g) was added, and then lysine (25 g) was slowly added, and the reaction was stirred at 100°C for 6 hours, then cooled to room temperature and washed with deionized water, and the solvent was recovered by distillation under reduced pressure.

[0146] (3) Precipitation

[0147] The polyethylene wax was added to petroleum ether (800 mL) and toluene (50 mL) and stirred at 100°C for 2 hours, then the temperature was cooled to 50°C, and then the oxidized polyethylene wax was crystallized by slowly adding ethanol (400 mL) as a precipitant.

[0148] Comparative Example 1

[0149] The difference between this comparative example and Example 1 is that maleic anhydride was not added in step (2).

[0150] Comparative Example 2

[0151] The difference between this comparative example and Example 1 is that the oxidized polyethylene wax after the oxidation reaction in step (1) was directly used as the product.

[0152] Example 14

[0153] The oxidized polyethylene wax prepared in Examples 1-13 and Comparative Examples 1-2 was used as a sample for whiteness value testing, and the whiteness was measured using a whiteness meter WSB-2 according to the plastic whiteness test method GB2913-82. The sample was evenly placed in the sample pool, a smooth glass plate was placed on the surface of the sample, the sample was pressed tightly, then the glass plate was carefully removed, the surface of the sample was kept smooth and free of scattered particles, the pressed sample was placed on the sample stage of the instrument, and the whiteness value was measured to 0.1%. The acid value of the oxidized polyethylene wax prepared in Examples 1-13 and Comparative Examples 1-2 was measured according to American Material Test Standard ASTM D-1386-78 and National Standard GB / 264-77. The test results are as follows:

[0154] From the above table, it can be seen that the oxidized polyethylene wax prepared in Examples 1-13 has a very ideal whiteness value, all of which exceed 80, indicating that the graft modification method of the oxidized polyethylene wax developed in the present application can improve the acid value of the polyethylene wax while maintaining the advantage of high brightness, and can well meet the market demand for high whiteness oxidized polyethylene wax. In addition, the acid value of the oxidized polyethylene wax prepared in Examples 1-13 is between 35-60, which indicates that the method can successfully produce carboxyl, hydroxyl and other groups on the carbon chain of the polyethylene wax, and the unique esterification process can further graft anhydride, amino acid and the like, and the ideal acid value can greatly broaden the application range of the polyethylene wax, improve its advantages in compatibility, lubricity, stability, adhesion, and improvement of weather resistance, etc.

[0155] Figure 2 is a picture of the appearance of the high-acid-value oxidized polyethylene wax prepared in Example 1, which can clearly see that it presents a high-brightness color, and the appearance is white microbead-shaped. This high-brightness appearance helps to improve the overall image of the product, and the white oxidized polyethylene wax is relatively stable in color during use, which helps to maintain the appearance consistency of the product, and also makes the product have good compatibility. In many applications, such as paints, inks, plastics and the like, the compatibility with other ingredients is good, and it will not have adverse effects on the color of the product, which is conducive to realizing accurate color matching.

[0156] Figure 3 is a scanning electron microscope picture of the high-acid-value oxidized polyethylene wax prepared in Example 1, which can be seen that the prepared oxidized polyethylene wax is composed of very small particles, and further Figure 4 is a transmission electron microscope, which can be seen that the oxidized polyethylene wax is these fine particles or flakes piled together, forming a significant wax-like structure. This structural feature shows that it will have good advantages in dispersibility, lubricity and the like, and can improve the compatibility and uniformity of the oxidized polyethylene wax with other materials.

[0157] Figure 5 is an infrared spectrum picture of the high-acid-value oxidized polyethylene wax prepared in Example 1, which can clearly see that there are very obvious absorption peaks at 2919 cm -1 and 2848 cm -1 , which are the stretching vibration peaks of saturated C-H bonds in the carbon chain of the polyethylene wax. 1464 cm -1 is the deformation vibration peak of C-H, and 720 cm -1 is the horizontal rocking vibration peak of -CH2. In addition, more significantly, there are significant absorption peaks at 1793 cm -1 and 1726 cm -1 , which are the stretching vibration peaks of C=O in the anhydride, and 1299 cm -1The absorption peak at 3543-3759 cm-1 is the stretching vibration peak of C-O-C in the anhydride, which indicates that the anhydride is grafted into the carbon chain of the oxidized polyethylene wax very successfully. -1 The absorption peak at 3543-3759 cm-1 is the stretching vibration peak of C-O-C in the anhydride, which indicates that the anhydride is grafted into the carbon chain of the oxidized polyethylene wax very successfully.

[0158] Therefore, the present application adopts a new type of high acid value oxidized polyethylene wax grafting modification method with the above structure. The preparation method first performs an oxidation reaction on the polyethylene wax to manufacture polar functional groups such as hydroxyl and carboxyl groups, and then performs an esterification reaction on the hydroxyl and carboxyl groups and a series of anhydrides to further increase the polar functional groups. Then, the high acid value oxidized polyethylene wax after grafting modification is obtained by precipitation. The prepared oxidized polyethylene wax presents a white micro-bead appearance, the whiteness value is more than 85, and the acid value is 35-60. The process of the present application is simple, the prepared oxidized polyethylene wax contains sufficient polar functional groups such as carboxyl groups, the acid value is high and controllable, and the compatibility, lubricity, surface activity, adhesion, weather resistance and other aspects can be significantly improved.

[0159] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application but not to limit it. Although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can still be modified or replaced by equivalents, and these modifications or replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A novel high acid value oxidized polyethylene wax graft modification process characterized by: The method comprises the following steps: S1: oxidation reaction: polyethylene wax is dissolved in a solvent at 90-150℃ for 2-4 hours, then an oxidant is added for oxidation reaction for 4-12 hours, and then deionized water is added for washing; S2: esterification reaction: the oxidized polyethylene wax solution obtained in step S1 is heated to 100-140℃ for dissolution and stirring, then an activating agent is added, and then an acid anhydride or amino acid is slowly added dropwise for esterification reaction for 2-8 hours, and then the temperature is reduced to room temperature, and the solvent is recovered by distillation under reduced pressure; S3: precipitation: the polyethylene wax obtained in step S2 is added to a solvent, and stirred at 90-120℃ for 1-3 hours, then the temperature is reduced to 40-60℃, and then a precipitant is slowly added to crystallize and precipitate the polyethylene wax to obtain high-acid-value oxidized polyethylene wax.

2. The method of graft modification of a novel high acid value oxidized polyethylene wax according to claim 1, characterized in that: The solvent in step S1 is one or more of petroleum ether, n-hexane, cyclohexane, n-heptane, carbon tetrachloride, toluene, xylene, tetrahydrofuran, and dioxane.

3. The method of graft modification of a novel high acid value oxidized polyethylene wax according to claim 1, characterized in that: The oxidant in step S1 is one or more of air, oxygen, hydrogen peroxide, sodium hypochlorite, and nitric acid.

4. The method of graft modification of a novel high acid value oxidized polyethylene wax according to claim 1, characterized in that: The activating agent in step S2 is one or more of sulfuric acid, acetic acid, triethylamine, sodium bicarbonate, dicyclohexyl carbodiimide, diisopropyl carbodiimide, and 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide.

5. The method of graft modification of a novel high acid value oxidized polyethylene wax according to claim 1, characterized in that: The acid anhydride in step S2 is one or more of maleic anhydride, acetic anhydride, propionic anhydride, succinic anhydride, Boc anhydride, and ethyl propionic anhydride; and the amino acid is one or more of glycine, alanine, leucine, aspartic acid, glutamic acid, and lysine.

6. The method of graft modification of a novel high acid value oxidized polyethylene wax according to claim 1, characterized in that: The solvent in step S3 is one or more of petroleum ether, n-hexane, cyclohexane, n-heptane, toluene, xylene, tetrahydrofuran, and dioxane.

7. The method of graft modification of a novel high acid value oxidized polyethylene wax according to claim 1, characterized in that: The precipitant in step S3 is one or more of methanol, ethanol, isopropanol, n-butanol, N,N-dimethylformamide, and dimethyl sulfoxide.

8. The method of grafting modification of a novel high acid value oxidized polyethylene wax according to claim 1, characterized in that: The temperature for precipitation and crystallization in step S3 is 40-60℃.

9. A high acid value oxidized polyethylene wax characterized by: The high-acid-value oxidized polyethylene wax is prepared by the method of any one of claims 1-8.

10. Use of a high acid value oxidized polyethylene wax according to claim 9, characterized in that: The high-acid-value oxidized polyethylene wax is applied in the fields of color master batch, paint, ink, plastic processing, adhesive, rubber, textile, and papermaking.

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