A modified polypropylene recycled material and preparation method thereof

Abstract

The invention discloses a modified polypropylene recycled material and a preparation method thereof, and belongs to the technical field of polypropylene materials. The invention comprises the following raw materials by weight: 70-90 parts of polypropylene recycled material, 20-30 parts of high-density polyethylene, 10-20 parts of modified glass fiber, 5-15 parts of auxiliary agent, 0.1-0.3 parts of initiator, and 3-5 parts of lubricant. The prepared modified recycled material can greatly enhance the mechanical strength of the material by adding chopped glass fiber and high-density polyethylene; by modifying the chopped glass fiber, the strength of the material is greatly improved; the prepared auxiliary agent molecule contains a variety of functional groups, which can play a synergistic role, significantly enhance the antibacterial and antioxidant properties of the recycled material, and the performance is stable and not easy to fall off. Therefore, the modified recycled material prepared by the present invention has stable and efficient antibacterial and antioxidant properties, and excellent mechanical properties, and has important application value in the technical field of polypropylene materials.

Description

Technical Field

[0001] The invention belongs to the technical field of polypropylene materials, and in particular relates to a modified polypropylene recycled material and a preparation method thereof. Background Art

[0002] Polypropylene is a thermoplastic with light specific gravity, high surface hardness, high elasticity, good heat resistance, chemical stability and insulation. It is widely used in automotive parts, household appliances and other fields. In 2019, China's apparent consumption of polypropylene reached 27.1663 million tons, which is the second largest type of plastic after polyethylene (PE). However, with the development of industry, the amount of polypropylene waste has increased year by year. These waste polypropylenes are called white pollution like plastic bags and films that are difficult to degrade naturally, and have become an increasingly serious social and environmental problem. Recycling can not only alleviate the environmental pollution caused by plastics to a certain extent, but also save oil resources. Many companies have begun to recycle polypropylene.

[0003] After multiple processing and use, the recycled polypropylene material is aged by ultraviolet radiation and oxidized by the natural environment, causing the molecular weight of the material to decrease. Its performance has been significantly attenuated, the mechanical properties have dropped significantly, the material has become brittle, and the melt index has increased, which seriously affects the subsequent reuse of the material. Therefore, in order to better utilize the recycled material, it is generally modified to improve the strength and aging resistance of polypropylene. In addition, since polypropylene materials are often used as packaging materials, they are in frequent contact with food and the human body, and polypropylene materials have poor antibacterial properties. Various bacteria are easy to grow on their surface, which will not only cause great damage to the material itself, but also endanger human health. Therefore, it is urgent to invent a polypropylene recycled material that can solve the above problems to meet the higher demands in the field of polypropylene material technology. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a modified polypropylene recycled material and a preparation method thereof.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing modified polypropylene recycled material comprises the following steps:

[0007] The polypropylene recycled material and high-density polyethylene are mixed, dried in an oven for 24 hours, and then mixed with modified glass fiber, additives, initiators and lubricants, added to a twin-screw extruder, melt blended, extruded, and granulated to obtain modified polypropylene recycled material.

[0008] Furthermore, the raw materials are calculated in parts by weight as follows: 70-90 parts of polypropylene recycled material, 20-30 parts of high-density polyethylene, 10-20 parts of modified glass fiber, 5-15 parts of additives, 0.1-0.3 parts of initiator, and 3-5 parts of lubricant.

[0009] Furthermore, the initiator is one of benzoyl peroxide and lauroyl peroxide.

[0010] Furthermore, the lubricant is one of paraffin and stearamide fatty acid.

[0011] Adding high-density polyethylene has good compatibility with polypropylene recycled materials, makes them easy to process, and can also enhance the mechanical strength of the recycled materials.

[0012] Furthermore, the modified glass fiber is prepared by the following steps:

[0013] The chopped glass fibers were soaked in acetone for 24 h, washed with distilled water, dried, placed in an ethanol aqueous solution, and γ-aminopropyltriethoxysilane (silane coupling agent KH-550) was added. The temperature was controlled at 80 °C, stirred for 6 h, and the pH value was adjusted to 5 with glacial acetic acid. The modified glass fibers were vacuum dried for 2 h to obtain modified glass fibers.

[0014] Furthermore, the ratio of the chopped glass fiber, acetone, ethanol aqueous solution, and γ-aminopropyltriethoxysilane is 1 g:100 mL:100 mL:5.5 g.

[0015] Furthermore, the chopped glass fiber monofilaments have an average diameter of 5-10 μm and a length of 3-6 mm.

[0016] Chopped glass fibers have good reinforcing and filling effects. Treating the chopped glass fibers with silane coupling agents can change the interfacial effect of the chopped glass fibers, improve their hydrophobicity, and thereby enhance their compatibility with the polypropylene matrix, improve the bonding between the glass fibers and the surface of the polypropylene matrix, reduce the voids in the recycled material, and greatly improve the strength of the material.

[0017] Furthermore, the auxiliary agent is prepared by the following steps:

[0018] S1. Mix 3,5-di-tert-butyl-4-hydroxybenzaldehyde, piperidine (condensation agent) and toluene in a three-necked flask equipped with a stirring device, heat to 55°C, stir until the solid is completely dissolved, add diethylenetriamine, keep warm for 5 hours, and after the reaction is completed, cool naturally, filter, remove the solvent by vacuum distillation, wash with deionized water, and vacuum dry to obtain intermediate 1; the ratio of 3,5-di-tert-butyl-4-hydroxybenzaldehyde, piperidine, toluene and diethylenetriamine is 47.4g:15mL:100mL:11.4g;

[0019] Under the action of the condensation agent, the amino group on diethylenetriamine condenses with the aldehyde group on 3,5-di-tert-butyl-4-hydroxybenzaldehyde to form an imine group (C=N Schiff base structure), and by controlling the molar ratio of the two to be close to 1:2 and a slight excess of 3,5-di-tert-butyl-4-hydroxybenzaldehyde, two amino groups on diethylenetriamine participate in the reaction to obtain intermediate 1; the specific reaction process is as follows:

[0020] ;

[0021] S2. Place a three-necked round-bottom flask equipped with a thermometer stirrer and a reflux condenser in a water bath, mix and stir 4-bromo-1-butene and acetonitrile, and add 5-chloro-2-methylisothiazoline-3-one while stirring. After stirring evenly, control the reaction temperature to 85°C, condense and reflux to react for 7 hours. After the reaction is completed, remove the solvent acetonitrile by vacuum distillation under reduced pressure, wash and purify with acetone, and vacuum dry at 60°C for 8 hours to obtain intermediate 2; the ratio of 4-bromo-1-butene, acetonitrile and 5-chloro-2-methylisothiazoline-3-one is 13.4g:100mL:14.7g;

[0022] 4-Bromo-1-butene and 5-chloro-2-methylisothiazoline-3-one undergo quaternization reaction to obtain intermediate 2; the specific reaction is shown below:

[0023] ;

[0024] S3. At room temperature, in a three-necked flask equipped with a stirring device, mix intermediate 1, intermediate 2, toluene and triethylamine evenly under nitrogen protection, gradually heat to 75°C, keep warm for 6 hours, filter, distill under reduced pressure, and purify by column chromatography (the eluent is a mixed solvent of benzene / ethyl acetate, the volume ratio of the two is 3:2), remove the eluent by rotary evaporation, and vacuum dry to obtain an auxiliary agent; the ratio of intermediate 1, intermediate 2, toluene and triethylamine is 53.5g:20.4g:150mL:15mL;

[0025] Triethylamine is used as an acid-binding agent to remove the hydrogen chloride generated by the reaction, and intermediate 1 undergoes a nucleophilic substitution reaction with intermediate 2 to obtain an auxiliary agent. The specific reaction process is as follows:

[0026] ;

[0027] The prepared auxiliary agent molecules contain isothiazolinone, quaternary ammonium salt, Schiff base, hindered phenol and carbon-carbon double bond structure. Among them, isothiazolinone has excellent properties such as strong antibacterial ability, environmental safety and broad antibacterial spectrum. It forms a disulfide bond with the sulfhydryl group on cysteine ​​in the pathogen protein through the bond active site on the heterocyclic ring, thereby inactivating the protein to achieve the purpose of sterilization and give the polypropylene matrix certain antibacterial properties; the introduction of quaternary ammonium salt ions will produce strong electrostatic interaction between the positively charged and negatively charged bacteria, and will have a strong adsorption effect on the bacteria. In addition, C=N Schiff The basic structure can interact with bacterial proteins and enzymes to hinder the synthesis of bacterial nucleotides and amino acids, and can work synergistically with isothiazolinone and quaternary ammonium salt ions to greatly enhance the antibacterial properties of the matrix. In addition, the introduction of two hindered phenol groups can not only greatly enhance the antioxidant properties of the matrix, but also act as an antioxidant in the production process, avoiding the addition of additional antioxidants and affecting the homogeneity of the recycled material. Finally, one end of the additive contains a carbon-carbon double bond, which can produce a cross-linking effect with the matrix, improve the interaction with the matrix, enhance the additive's resistance to migration and exudation, and improve the additive's stability.

[0028] Beneficial effects of the present invention:

[0029] 1. The modified recycled material prepared by the present invention can greatly enhance the mechanical strength of the material by adding chopped glass fibers and high-density polyethylene;

[0030] 2. By modifying the chopped glass fibers, the compatibility with the polypropylene matrix is ​​enhanced, the agglomeration phenomenon is reduced, and the strength of the material is greatly improved;

[0031] 3. The prepared additive molecules contain a variety of functional groups, which can play a synergistic role, significantly enhancing the antibacterial and antioxidant properties of the recycled materials, and the performance is stable and not easy to fall off.

[0032] Therefore, the modified recycled material prepared by the present invention has stable and efficient antibacterial and antioxidant properties, as well as excellent mechanical properties, and has important application value in the field of polypropylene material technology. DETAILED DESCRIPTION

[0033] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] Example 1

[0035] Preparation aids:

[0036] S1. In a three-necked flask equipped with a stirring device, 47.4 g of 3,5-di-tert-butyl-4-hydroxybenzaldehyde, 15 mL of piperidine and 100 mL of toluene were mixed, the temperature was raised to 55° C., and the mixture was stirred until the solid was completely dissolved. 11.4 g of diethylenetriamine was added, and the mixture was kept warm for 5 h. After the reaction was completed, the mixture was naturally cooled, filtered, and the solvent was removed by distillation under reduced pressure. The mixture was washed with deionized water and dried under vacuum to obtain intermediate 1.

[0037] S2. Place a three-necked round-bottom flask equipped with a thermometer stirrer and a reflux condenser in a water bath, mix and stir 13.4 g of 4-bromo-1-butene and 100 mL of acetonitrile, and add 14.7 g of 5-chloro-2-methylisothiazoline-3-one while stirring. After stirring evenly, control the reaction temperature to 85° C., condense and reflux to react for 7 hours. After the reaction is completed, remove the solvent acetonitrile by distillation under reduced pressure, wash and purify with acetone, and vacuum dry at 60° C. for 8 hours to obtain intermediate 2;

[0038] S3. At room temperature, in a three-necked flask equipped with a stirring device, 53.5 g of intermediate 1, 20.4 g of intermediate 2, 150 mL of toluene and 15 mL of triethylamine were mixed evenly under nitrogen protection. The temperature was gradually raised to 75°C and the reaction was kept warm for 6 hours. After the reaction was completed, the product was filtered and distilled under reduced pressure. The product was purified by column chromatography (the eluent was a mixed solvent of benzene / ethyl acetate in a volume ratio of 3:2). The eluent was removed by rotary evaporation and dried in vacuo to obtain an auxiliary agent.

[0039] Example 2

[0040] Preparation aids:

[0041] S1. In a three-necked flask equipped with a stirring device, 94.8 g of 3,5-di-tert-butyl-4-hydroxybenzaldehyde, 30 mL of piperidine and 200 mL of toluene were mixed, the temperature was raised to 55° C., and the mixture was stirred until the solid was completely dissolved. 22.8 g of diethylenetriamine was added, and the mixture was kept warm for 5 h. After the reaction was completed, the mixture was naturally cooled, filtered, and the solvent was removed by distillation under reduced pressure. The mixture was washed with deionized water and dried under vacuum to obtain intermediate 1.

[0042] S2. Place a three-necked round-bottom flask equipped with a thermometer stirrer and a reflux condenser in a water bath, mix and stir 26.8 g of 4-bromo-1-butene and 200 mL of acetonitrile, and add 29.4 g of 5-chloro-2-methylisothiazoline-3-one while stirring. After stirring evenly, control the reaction temperature to 85° C., condense and reflux to react for 7 hours. After the reaction is completed, remove the solvent acetonitrile by distillation under reduced pressure, wash and purify with acetone, and vacuum dry at 60° C. for 8 hours to obtain intermediate 2;

[0043] S3. At room temperature and under nitrogen protection, in a three-necked flask equipped with a stirring device, 107 g of intermediate 1, 40.8 g of intermediate 2, 300 mL of toluene and 30 mL of triethylamine were mixed evenly, and the temperature was gradually raised to 75°C. The reaction was kept warm for 6 hours. After the reaction was completed, it was filtered, evaporated under reduced pressure, and purified by column chromatography (the eluent was a mixed solvent of benzene / ethyl acetate in a volume ratio of 3:2). The eluent was removed by rotary evaporation and dried in vacuo to obtain an auxiliary agent.

[0044] Example 3

[0045] Preparation of modified glass fiber:

[0046] 1 g (single fiber diameter of 5 μm, length of 3 mm) of chopped glass fiber was soaked in 100 mL of acetone for 24 h, washed with distilled water, dried, placed in 100 mL of ethanol aqueous solution, and 5.5 g of γ-aminopropyltriethoxysilane was added. The temperature was controlled at 80 ° C. After stirring for 6 h, the pH value was adjusted to 5 with glacial acetic acid, and vacuum dried for 2 h to obtain modified glass fiber.

[0047] Example 4

[0048] Preparation of modified glass fiber:

[0049] 2 g (single fiber diameter of 10 μm, length of 6 mm) of chopped glass fiber was soaked in 200 mL of acetone for 24 h, washed with distilled water, dried, placed in 200 mL of ethanol aqueous solution, and 11 g of γ-aminopropyltriethoxysilane was added. The temperature was controlled at 80 ° C. After stirring for 6 h, the pH value was adjusted to 5 with glacial acetic acid, and vacuum dried for 2 h to obtain modified glass fiber.

[0050] Example 5

[0051] 70 g of polypropylene recycled material and 20 g of high-density polyethylene were mixed and dried in an oven for 24 h, then mixed with 10 g of the modified glass fiber prepared in Example 3, 5 g of the additive prepared in Example 1, 0.1 g of benzoyl peroxide and 3 g of paraffin, added to a twin-screw extruder, melt blended, extruded, and granulated to obtain modified polypropylene recycled material.

[0052] Example 6

[0053] 80 g of polypropylene recycled material and 25 g of high-density polyethylene were mixed and dried in an oven for 24 h, then mixed with 15 g of the modified glass fiber prepared in Example 4, 10 g of the additive prepared in Example 2, 0.2 g of lauroyl peroxide and 4 g of stearamide fatty acid, added to a twin-screw extruder, melt blended, extruded, and granulated to obtain modified polypropylene recycled material.

[0054] Example 7

[0055] 90 g of polypropylene recycled material and 30 g of high-density polyethylene were mixed and dried in an oven for 24 h, then mixed with 20 g of the modified glass fiber prepared in Example 4, 15 g of the additive prepared in Example 2, 0.3 g of lauroyl peroxide and 5 g of stearamide fatty acid, added to a twin-screw extruder, melt blended, extruded, and granulated to obtain modified polypropylene recycled material.

[0056] Comparative Example 1

[0057] The auxiliary agent in Example 7 was replaced by a commercially available antibacterial agent of equal quality, and the remaining steps were the same as those in Example 7 to obtain a recycled material.

[0058] Comparative Example 2

[0059] Use commercially available PP recycled materials.

[0060] Examples 5-7 and Comparative Examples 1-2 were made into corresponding shapes according to different test standards and subjected to the following performance tests:

[0061] According to the national standard GB / T 16422.2-1999 "Plastics Laboratory Light Source Exposure Test Method Part 2: Xenon Arc Lamp", the sample was placed in a xenon lamp aging test chamber for accelerated aging for 480 hours. The aging conditions were air atmosphere, xenon lamp wavelength 280-800nm, and irradiation intensity 550W / m 2 , test the tensile strength of the specimens before and after aging (GB / T 1040-2006);

[0062] The notched impact strength is measured using the national standard GB / T 1843-2008 "Determination of Izod Impact Strength of Plastics";

[0063] The oxidation induction time was determined using the national standard GB / T 19466.6-2009 "Plastic Differential Scanning Calorimetry";

[0064] QB / T 2591-2003A "Test Methods and Antibacterial Effects of Antibacterial Plastics" was used to determine the antibacterial rates of Staphylococcus aureus and Escherichia coli before and after the samples were placed at room temperature for 180 days.

[0065] The measured results are shown in the following table:

[0066] ;

[0067] As can be seen from the above table, the modified recycled material prepared in the embodiment of the present invention has better antibacterial and antioxidant properties than the comparative example, and the modified recycled material prepared in the embodiment has stable performance and excellent mechanical properties; moreover, it can be seen from the table that in Examples 5-7, as the content of the auxiliary agent and the modified glass fiber continues to increase, the antibacterial, antioxidant and mechanical properties of the recycled material are enhanced accordingly. Therefore, the modified recycled material prepared in the present invention has important application value in the field of polypropylene material technology.

[0068] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0069] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A modified polypropylene recycled material, characterized in that: The raw materials include the following parts by weight: 70-90 parts of polypropylene recycled material, 20-30 parts of high-density polyethylene, 10-20 parts of modified glass fiber, 5-15 parts of additives, 0.1-0.3 parts of initiator, and 3-5 parts of lubricant; Wherein, the auxiliary agent is prepared by the following steps: S1. Mix 3,5-di-tert-butyl-4-hydroxybenzaldehyde, piperidine and toluene, heat to 55°C, stir until the solid is completely dissolved, add diethylenetriamine, keep warm for 5 hours, and after the reaction is completed, cool naturally, filter, distill under reduced pressure, wash, and vacuum dry to obtain intermediate 1; the ratio of 3,5-di-tert-butyl-4-hydroxybenzaldehyde, piperidine, toluene, and diethylenetriamine is 47.4g:15mL:100mL:11.4g; S2, 4-bromo-1-butene and acetonitrile were mixed and stirred, and 5-chloro-2-methylisothiazoline-3-one was added while stirring, and the mixture was uniformly stirred, and then condensed and refluxed at 85° C. for 7 h. After the reaction was completed, the mixture was distilled under reduced pressure, washed, purified, and dried to obtain intermediate 2; the ratio of 4-bromo-1-butene, acetonitrile, and 5-chloro-2-methylisothiazoline-3-one was 13.4 g:100 mL:14.7 g; S3, at room temperature, under nitrogen protection, mix intermediate 1, intermediate 2, toluene and triethylamine uniformly, gradually heat to 75°C, keep warm for 6 hours, and after the reaction is completed, filter, distill under reduced pressure, purify by column chromatography, rotary evaporate, and dry to obtain an auxiliary agent; the ratio of intermediate 1, intermediate 2, toluene and triethylamine is 53.5g:20.4g:150mL:15mL; Wherein, the modified glass fiber is prepared by the following steps: The chopped glass fibers were soaked in acetone, washed, dried, placed in an ethanol aqueous solution, and γ-aminopropyltriethoxysilane was added. The mixture was stirred at 80° C. for 6 h, the pH value was adjusted to 5, and vacuum dried to obtain modified glass fibers.

2. The modified polypropylene recycled material according to claim 1, characterized in that: The ratio of the chopped glass fibers, acetone, ethanol aqueous solution, and γ-aminopropyltriethoxysilane is 1 g:100 mL:100 mL:5.5 g.

3. The modified polypropylene recycled material according to claim 1, characterized in that: The chopped glass fiber monofilaments have an average diameter of 5-10 μm and a length of 3-6 mm.

4. The modified polypropylene recycled material according to claim 1, characterized in that: The initiator is one of benzoyl peroxide and lauroyl peroxide; and the lubricant is paraffin.

5. The method for preparing a modified polypropylene recycled material according to claim 1, characterized in that: The following steps are involved: The polypropylene recycled material and high-density polyethylene are mixed, dried, mixed with modified glass fiber, additives, initiators and lubricants, added into a twin-screw extruder, melt blended, extruded and granulated to obtain modified polypropylene recycled material.