Macromolecular antioxidant as well as preparation method and application thereof

Abstract

The invention discloses a macromolecular antioxidant as well as a preparation method and application thereof, the structural formula of the antioxidant is # imgabs0 #, and R is an antioxidant group; m, n and x are positive numbers; and the antioxidant group is one or more of # imgabs 1 #. The macromolecular antioxidant material is obtained through double decomposition copolymerization and hydrogenation of the olefin monomer containing antioxidant groups and the cyclooctene monomer which are simple and easy to obtain or can be simply prepared, the macromolecular antioxidant material has the performance similar to that of a commercial antioxidant, the molecular structure can be accurately controlled through the ROMP-based method, the molecular weight is high, and the molecular weight is high. After the antioxidant is added into a polyolefin product, the performance including the mechanical property of the polyolefin product is not obviously changed, the polyolefin product has good thermal oxidation stability, and the migration amount of the antioxidant is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer material synthesis, and specifically relates to a macromolecular antioxidant and its preparation method and application. Background Art

[0002] Polyethylene (PE) is the cheapest and most widely used polyolefin material in the world. However, due to its relatively low melting temperature and susceptibility to oxygen-induced oxidation reactions, resulting in a mixture of chain degradation and cross-linked structures, its application at high temperatures is limited. High-density polyethylene (HDPE) also undergoes oxidative degradation during synthesis, processing, storage, transportation, and use, especially during processing when the polymer is heated and affected by catalysts, and the degradation is more obvious. To reduce the oxidative degradation rate of the polymer, antioxidants are usually added during its synthesis or processing.

[0003] In the polyolefin process, it is common practice to add a small amount (<1 wt%) of antioxidant to the HDPE product immediately after polymerization. Commonly used antioxidants include two categories: phenols (such as thiophenols, triazine hindered phenols, isocyanurate hindered phenols, etc.) and amines (such as naphthylamine, diphenylamine, p-diphenylamine, quinoline derivatives, etc.). During application, it is difficult to maintain the state of a homogeneous mixture between the small-molecule polar antioxidant and the highly crystalline non-polar HDPE. This incompatibility also causes the antioxidant to continuously diffuse from the main body region to the surface region, and when it is exposed to solvents, heat, or a strong electric field, it accelerates the loss of the antioxidant, making it difficult for the antioxidant to maintain the lowest effective antioxidant concentration during application.

[0004] Macromolecular antioxidants have high molecular weight and antioxidant function, and have better thermal oxidation stability and compatibility compared with low-molecular-weight antioxidants, and also reduce the loss of antioxidants when exposed to harsh environments. Summary of the Invention

[0005] The technical problem to be solved by the present invention is how to obtain a macromolecular antioxidant for polyolefins that is resistant to migration and has performance equivalent to that of commercial antioxidants.

[0006] The present invention solves the above technical problem through the following technical means:

[0007] A macromolecular antioxidant (coM), whose structural formula is shown as follows:

[0008]

[0009] Wherein, R is an antioxidant group; m and n are the number of polyolefin segments, x is the degree of polymerization of the polymer,

[0010] m, n, and x are all positive numbers; the antioxidant group is one or more of them; wherein the wavy line in the antioxidant group represents the connection position of the group.

[0011] Preferably, the range of m:n is 1-10:100, and x = 10-500.

[0012] Preferably, the macromolecular antioxidant has one of the following structural formulas:

[0013]

[0014] Preferably, the number-average molecular weight of the macromolecular antioxidant is 10 kDa - 500 kDa.

[0015] The present invention also provides a preparation method of the macromolecular antioxidant, comprising the following steps: ring octene monomer (COE) and an olefin monomer containing an antioxidant group are subjected to a metathesis copolymerization reaction under the action of a metathesis catalyst to obtain a copolymer, and then a chemical hydrogenation reaction is carried out to obtain the macromolecular antioxidant;

[0016] Wherein, the olefin monomer containing an antioxidant group is one or more of the following structural formulas:

[0017]

[0018] Preferably, the metathesis catalyst is Grubbs second-generation catalyst (GⅡ).

[0019] Preferably, the molar ratio of the ring octene monomer to the olefin monomer containing an antioxidant group is 100:1-10.

[0020] Preferably, the molar amount of the metathesis catalyst used is 0.01-0.1% of the molar amount of the ring octene monomer used.

[0021] Preferably, the temperature of the metathesis copolymerization reaction is 20-40 °C, and the time is 4-12 h; the temperature of the chemical hydrogenation reaction is 140 °C, and the time is 12-24 h.

[0022] Preferably, p-toluenesulfonyl hydrazide and tri-n-propylamine are used as raw materials for the chemical hydrogenation reaction, and the mass ratio of the copolymer to p-toluenesulfonyl hydrazide and tri-n-propylamine is 1:3:3.

[0023] Preferably, the preparation method of the macromolecular antioxidant comprises the following steps: Under a nitrogen atmosphere, dissolve the cyclooctene monomer and the olefin monomer containing an antioxidant group in dichloromethane, then dissolve the metathesis catalyst in dichloromethane and add it to the above reaction for reaction. After the reaction is completed, concentrate the solvent, add methanol to precipitate the copolymer, filter, wash, and dry. Add the dried copolymer to a reaction device, add p-toluenesulfonyl hydrazide, tri-n-propylamine, and xylene solvent, reflux at 140 °C, react for a period of time under a nitrogen atmosphere, add methanol to precipitate the polymer, filter, and dry to obtain the target product of the macromolecular antioxidant.

[0024] Preferably, the olefin monomer M1 containing an antioxidant group is obtained by the esterification reaction of the following 5-norbornene-2-methanol and 2,5,7,8-tetramethyl-6-hydroxy chroman-2-carboxylic acid (abbreviated as P-1); the olefin monomer M2 containing an antioxidant group is obtained by the esterification reaction of the following 5-norbornene-2-methanol and 3,5-di-tert-butyl-4-hydroxybenzoic acid (abbreviated as P-2); the olefin monomer M3 containing an antioxidant group is obtained by the esterification reaction of the following 5-norbornene-2-methanol and 3,5-di-tert-butyl-4-hydroxy phenylpropionic acid (abbreviated as P-3);

[0025]

[0026] Preferably, the preparation method of the olefin monomer M1 containing an antioxidant group comprises the following steps: Under a nitrogen atmosphere, dissolve 5-norbornene-2-methanol, 2,5,7,8-tetramethyl-6-hydroxy chroman-2-carboxylic acid, and 4-dimethylaminopyridine (DMAP) together in a tetrahydrofuran solvent, then add a tetrahydrofuran solution of 1,3-dicyclohexylcarbodiimide (DCC) and react at room temperature, filter, wash, concentrate, and obtain the target monomer product M1 through column purification.

[0027] Preferably, the preparation method of the olefin monomer M2 containing an antioxidant group comprises the following steps: Under a nitrogen atmosphere, dissolve 5-norbornene-2-methanol, 3,5-di-tert-butyl-4-hydroxybenzoic acid, and 4-dimethylaminopyridine (DMAP) together in a tetrahydrofuran solvent, then add a tetrahydrofuran solution of 1,3-dicyclohexylcarbodiimide (DCC) and react at room temperature, filter, wash, concentrate, and obtain the target monomer product M2 through column purification;

[0028] Preferably, the preparation method of the olefin monomer M3 containing an antioxidant group comprises the following steps: 5-norbornene-2-methanol, 3,5-di-tert-butyl-4-hydroxycinnamic acid, and 4-dimethylaminopyridine (DMAP) are dissolved together in a tetrahydrofuran solvent under a nitrogen atmosphere, and then a tetrahydrofuran solution of 1,3-dicyclohexylcarbodiimide (DCC) is added, and the reaction is carried out at room temperature, followed by filtration, washing, concentration, and column purification to obtain the target monomer product M3.

[0029] Preferably, the molar ratio of 5-norbornene-2-methanol to P-1 is preferably 1:1 - 1.2, and the reaction time is 12 - 24 h.

[0030] Preferably, the molar ratio of 5-norbornene-2-methanol to P-2 is preferably 1:1 - 1.2, and the reaction time is 12 - 24 h.

[0031] Preferably, the molar ratio of 5-norbornene-2-methanol to P-3 is preferably 1:1 - 1.2, and the reaction time is 12 - 24 h.

[0032] The present invention also provides an application of the macromolecular antioxidant described above in polyolefins.

[0033] Preferably, the mass ratio of the macromolecular antioxidant to the polyolefin is 0.58:9.42.

[0034] Preferably, the polyolefin is polyethylene or polypropylene.

[0035] Preferably, the polyethylene is high-density polyethylene.

[0036] The advantages of the present invention are as follows:

[0037] The present invention obtains a macromolecular antioxidant through metathesis copolymerization and hydrogenation of a simple and easily preparable olefin monomer containing an antioxidant group and a cyclooctene monomer. This macromolecular antioxidant not only has properties similar to those of commercial antioxidants, but also this ROMP-based method can precisely control the molecular structure, enabling it to have a relatively high molecular weight, and at the same time ensuring a high antioxidant capacity in polyolefins. After being added to polyolefin products, its properties include no obvious change in mechanics, and it has good thermal oxidation stability, and the migration amount of the antioxidant is reduced. Description of the Drawings

[0038] Figure 1 1H NMR spectrum of the M1 monomer prepared in Example 1 of the present invention;

[0039] Figure 2 13C NMR spectrum of the M1 monomer prepared in Example 1 of the present invention;

[0040] Figure 3Mass spectrometry diagram of M1 monomer prepared in Example 1 of the present invention;

[0041] Figure 4 1H NMR spectrum diagram of M2 monomer prepared in Example 1 of the present invention;

[0042] Figure 5 13C NMR spectrum diagram of M2 monomer prepared in Example 1 of the present invention;

[0043] Figure 6 Mass spectrometry diagram of M2 monomer prepared in Example 1 of the present invention;

[0044] Figure 7 1H NMR spectrum diagram of M3 monomer prepared in Example 1 of the present invention;

[0045] Figure 8 13C NMR spectrum diagram of M3 monomer prepared in Example 1 of the present invention;

[0046] Figure 9 Mass spectrometry diagram of M3 monomer prepared in Example 1 of the present invention;

[0047] Figure 10 GPC spectrum diagram of macromolecular antioxidant coM-1 prepared in Example 2 of the present invention;

[0048] Figure 11 1H NMR spectrum diagram of macromolecular antioxidant coM-1 prepared in Example 2 of the present invention;

[0049] Figure 12 1H NMR spectrum diagram of macromolecular antioxidant coM-2 prepared in Example 2 of the present invention;

[0050] Figure 13 1H NMR spectrum diagram of macromolecular antioxidant coM-3 prepared in Example 2 of the present invention;

[0051] Figure 14 Infrared spectrum diagram of the material prepared in Example 3 of the present invention;

[0052] Figure 15 Dynamic mechanical analysis diagram of the materials prepared in Example 3 and Example 4 of the present invention;

[0053] Figure 16 Thermodynamic analysis diagram of the materials prepared in Example 3 and Example 4 of the present invention;

[0054] Figure 17 DSC analysis diagram of the materials prepared in Example 3, Example 4 and Example 5 of the present invention. Detailed implementation manners

[0055] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0056] The test materials, reagents, etc. used in the following embodiments can be obtained from commercial channels without special instructions.

[0057] For those not specifying specific techniques or conditions in the embodiments, they can all be carried out according to the techniques or conditions described in the literature in the field or according to the product specifications.

[0058] Example 1

[0059] Preparation of olefin monomers M1, M2 and M3 containing antioxidant groups

[0060]

[0061] The preparation method of M1 includes the following steps:

[0062] Under a nitrogen atmosphere, 5-norbornene-2-methanol (50.0 mmol), 2,5,7,8-tetramethyl-6-hydroxy chroman-2-carboxylic acid (55.0 mmol), and 4-dimethylaminopyridine (10 mmol) were dissolved in 250 mL of tetrahydrofuran solvent, and then a 50 mL tetrahydrofuran solution of 1,3-dicyclohexylcarbodiimide (55.0 mmol) was added. The reaction was carried out at room temperature for 12 h. After the reaction was completed, the filtrate was obtained by filtration, washed with an aqueous NaCl solution, dried over anhydrous Na2SO4, and concentrated. The target product M1 was obtained by column purification with a yield of 63%; among them, the 1H NMR 1 H NMR (CDCl3), 13C NMR 13 C NMR (CDCl3) and mass spectrum are shown in Figure 1 , Figure 2 and Figure 3 respectively.

[0063] The preparation method of M2 includes the following steps:

[0064] Under a nitrogen atmosphere, 5-norbornene-2-methanol (50.0 mmol), 3,5-di-tert-butyl-4-hydroxybenzoic acid (55.0 mmol), and 4-dimethylaminopyridine (10 mmol) were dissolved in 250 mL of tetrahydrofuran solvent. Then, a 50 mL tetrahydrofuran solution of 1,3-dicyclohexylcarbodiimide (55.0 mmol) was added, and the reaction was carried out at room temperature for 12 h. After the reaction was completed, the filtrate was obtained by filtration, washed with an aqueous NaCl solution, dried over anhydrous Na2SO4, concentrated, and purified by column chromatography to obtain the target product M2 with a yield of 73%; among them, the 1H NMR 1 1H NMR (CDCl3), 13C NMR 13 13C NMR (CDCl3), and mass spectrum are shown in Figure 4 , Figure 5 and Figure 6 respectively.

[0065] The preparation method of M3 includes the following steps:

[0066] Under a nitrogen atmosphere, 5-norbornene-2-methanol (50.0 mmol), 3,5-di-tert-butyl-4-hydroxycinnamic acid (55.0 mmol), and 4-dimethylaminopyridine (10 mmol) were dissolved in 250 mL of tetrahydrofuran solvent. Then, a 50 mL tetrahydrofuran solution of 1,3-dicyclohexylcarbodiimide (55.0 mmol) was added, and the reaction was carried out at room temperature for 12 h. After the reaction was completed, the filtrate was obtained by filtration, washed with an aqueous NaCl solution, dried over anhydrous Na2SO4, concentrated, and purified by column chromatography to obtain the target product M3 with a yield of 85%; among them, the 1H NMR 1 1H NMR (CDCl3), 13C NMR 13 13C NMR (CDCl3), and mass spectrum are shown in Figure 7 , Figure 8 and Figure 9 respectively.

[0067] Example 2

[0068] Preparation of Macromolecular Antioxidants

[0069]

[0070] Among them, R is one of the following.

[0071] Under a nitrogen atmosphere, in a 200 mL Schlenk reaction flask, cyclooctene monomer (50 mmol, 5.5 g), olefin monomer M1 (5 mmol, 1.78 g) prepared in Example 1, and 100 mL of anhydrous dichloromethane were added. The reaction flask was placed in an oil bath at 40 °C. Then, Grubbs second-generation catalyst (17 μmol, 14 mg) was dissolved in 1 mL of dichloromethane and injected into the reaction flask. The reaction continued for 6 h. After the reaction was completed, the solvent was concentrated, 200 mL of methanol was added to precipitate the polymer, and after filtration, washing, and drying, the pre-hydrogenated polymer was obtained. Then, 5.0 g of the dried pre-hydrogenated polymer was added to a 500 mL reaction flask, 15.0 g of p-toluenesulfonyl hydrazide, 15.0 g of tri-n-propylamine, and 40 mL of xylene solvent were added. After refluxing at 140 °C for 12 h under a nitrogen atmosphere, 300 mL of methanol was added to the reaction flask to precipitate the polymer, and after filtration and drying, about 5.0 g of the macromolecular antioxidant (coM-1) was obtained. The number-average molecular weight was measured to be 124832, PDI = 2.01, and the GPC spectrum was as shown in Figure 10 shown. The 1H NMR spectrum 1 1H NMR (C2D2Cl4) was as shown in Figure 11 shown.

[0072] Using 5 mmol of olefin monomers M2 and M3 prepared in Example 1 to replace olefin monomer M1 respectively, macromolecular antioxidants coM-2 and coM-3 were prepared. The 1H NMR spectrum 1 1H NMR (C2D2Cl4) was as shown in Figure 12 , 13 shown.

[0073] Example 3

[0074] 0.58 g of the macromolecular antioxidant coM-1 obtained in Example 2 and 9.42 g of HDPE were mixed by a twin-screw extruder to obtain a blend HDPE / coM-1, and dumbbell-shaped specimens with a length of 5.0 cm, a width of 4.0 mm (narrowest part), and a thickness of 1.0 mm were prepared. The infrared spectrum of the blend HDPE / coM-1 was as shown in Figure 14 shown. According to the standard test method ASTM D638, the stress / strain experiment was carried out at a speed of 50 mm per minute at room temperature. At least three specimens were tested for each sample, as shown in Figure 15 shown.

[0075] Example 4

[0076] Weigh 0.1 g of the small molecule commercial antioxidant 2,5,7,8-tetramethyl-6-hydroxy chroman-2-carboxylic acid (P-1) and 10.0 g of HDPE respectively, and mix the materials through a twin-screw extruder to obtain the blend HDPE / P-1, and prepare dumbbell-shaped splines with a length of 5.0 cm, a width of 4.0 mm (narrowest part), and a thickness of 1.0 mm. According to the standard test method ASTM D638, the stress / strain experiment was carried out at a speed of 50 mm per minute at room temperature. At least three specimens were tested for each sample, as Figure 15 shown.

[0077] Example 5

[0078] Dissolve the splines prepared in Example 3 and Example 4 in toluene solution at 110 °C, heat and stir for 12 h. After the reaction is completed, precipitate while it is hot in methanol solution, filter, and dry to obtain the washed mixture.

[0079] The infrared spectrum of the product of Example 3 is as Figure 14 shown, the dynamic mechanics of the materials of Example 3 and Example 4 are as Figure 15 shown, the thermodynamic properties of the materials of Example 3 and Example 4 are as Figure 16 shown, the oxidation induction time of the materials of Example 3, Example 4, and Example 5 was tested according to the standard test method ASTM D3895, and its DSC analysis chart is as Figure 17 shown.

[0080] It can be seen from Figure 14 that there are ester groups and phenolic hydroxyl groups in the blend, indicating that the macromolecular antioxidant has been successfully added to HDPE.

[0081] It can be seen from Figure 15 that the addition of the macromolecular antioxidant will not affect the mechanical properties of HDPE.

[0082] It can be seen from Figure 16 that for HDPE added with macromolecular antioxidant, small molecule antioxidant, the temperatures at which degradation is 5% are 382.4 °C, 375.3 °C respectively, and without antioxidant it is 364.8 °C, indicating that the macromolecular antioxidant has excellent antioxidant ability.

[0083] It can be seen from Figure 17 that the oxidation induction time of adding the macromolecular antioxidant is 38.6 min, which is better than that of the small molecule antioxidant and without antioxidant. And after washing with toluene and recrystallizing with methanol under extreme conditions, the oxidation induction time of adding the small molecule antioxidant changes from 8.5 min to 0 min, and the antioxidant ability has disappeared. While adding the macromolecular antioxidant still retains a relatively high oxidation induction time (30.3 min), with excellent antioxidant ability and migration resistance.

[0084] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A macromolecular antioxidant, characterized in that: Its structural formula is shown below: Wherein, R is an antioxidant group; m, n, and x are all positive numbers; the antioxidant group is One or more of .

2. The macromolecular antioxidant according to claim 1, characterized in that: Its number average molecular weight is 10kDa-500kDa.

3. A method for preparing a macromolecular antioxidant as claimed in claim 1 or 2, characterized in that: The method comprises the following steps: a cyclooctene monomer and an olefin monomer containing an antioxidant group are subjected to a metathesis copolymerization reaction under the action of a metathesis catalyst to obtain a copolymer, and then a chemical hydrogenation reaction is performed to obtain the macromolecular antioxidant; Wherein, the olefin monomer containing an antioxidant group is one or more of the following structural formulas:

4. The method for preparing the macromolecular antioxidant according to claim 3, characterized in that: The metathesis catalyst is a Grubbs second generation catalyst.

5. The method for preparing the macromolecular antioxidant according to claim 3, characterized in that: The molar ratio of the cyclooctene monomer to the olefin monomer containing an antioxidant group is 100:1-10.

6. The method for preparing the macromolecular antioxidant according to claim 3, characterized in that: The molar amount of the metathesis catalyst is 0.01-0.1% of the molar amount of the cyclooctene monomer.

7. The method for preparing the macromolecular antioxidant according to claim 3, characterized in that: The temperature of the metathesis copolymerization reaction is 20-40°C and the time is 4-12h; the temperature of the chemical hydrogenation reaction is 140°C and the time is 12-24h.

8. The method for preparing a macromolecular antioxidant according to any one of claims 3 to 7, characterized in that: The chemical hydrogenation reaction is carried out using p-toluenesulfonyl hydrazide and tri-n-propylamine as raw materials, and the mass ratio of the copolymer to p-toluenesulfonyl hydrazide and tri-n-propylamine is 1:3:

3.

9. Use of the macromolecular antioxidant as claimed in claim 1 or 2 in polyolefins.

10. The use of the macromolecular antioxidant in polyolefins according to claim 9, characterized in that: The mass ratio of the macromolecular antioxidant to the polyolefin is 0.58:9.42.

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