Flame retardant packaging material and preparation method thereof

Abstract

The invention discloses a flame-retardant packaging material and a preparation method thereof, and belongs to the technical field of polymer materials. The flame-retardant packaging material comprises the following raw materials by weight: 85-95 parts of polyethylene, 8-15 parts of auxiliary agents, 4-8 parts of talcum powder, 1-2 parts of coupling agents, 0.5-1 parts of antioxidants, 0.5-1 parts of ultraviolet absorbers, and 0.03-0.05 initiators. Under the action of initiators and coupling agents, a hybrid cross-linked network structure is formed between auxiliary agents, talcum powder and polyethylene, and auxiliary agents and talcum powder containing phosphorus, nitrogen elements and chitosan, long carbon chains can be highly dispersed and stably present in packaging materials, giving full play to their effects. Therefore, the packaging material of the present invention has excellent and stable flame retardancy and antibacterial properties, can absorb odor, and has strong toughness. In addition, the combined action of the remaining raw materials, the packaging material of the present invention also has excellent aging resistance and other properties.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a flame retardant packaging material and a preparation method thereof. Background Art

[0002] Plastic packaging materials are made of synthetic or natural polymer resins as the main materials. After adding various additives, they have ductility under certain temperature and pressure, and can fix their shape after cooling. Several commonly used plastic packaging materials include polyethylene, polypropylene, polystyrene, polyvinyl chloride and polyethylene terephthalate. Polyethylene (PE) has the advantages of good chemical stability, corrosion resistance, non-toxicity and low cost. However, the low polyethylene oxide index, high flammability, poor fire resistance and no antibacterial effect have greatly limited its application.

[0003] At present, most flame retardants are introduced into polyolefin matrix by melt blending to improve the flame retardancy and thermal stability of polyolefin materials. Flame retardant modification usually involves adding flame retardant additives to polyolefins, which are divided into halogen flame retardants and halogen-free flame retardants. Since halogen flame retardants are prone to cause secondary hazards, most flame retardants currently use halogen-free flame retardants. Halogen-free flame retardants are mainly divided into phosphorus-based flame retardants, nitrogen-based flame retardants, intumescent flame retardants, hydroxide flame retardants, etc. Inorganic flame retardants have poor flame retardancy and usually require a large amount of filling to achieve the required flame retardant effect. In addition, their dehydration temperature is low and they are not suitable for plastic products with high processing temperatures. Some common halogen-free flame retardants such as aluminum hypophosphite and melamine cyanurate (MCA) have good flame retardant effects and are simple to prepare, but as the material is used for a longer time, there will be a problem of slow precipitation, resulting in a decrease in flame retardant properties. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a flame retardant packaging material and a preparation method thereof.

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

[0006] A flame retardant packaging material comprises the following raw materials in parts by weight: 85-95 parts of polyethylene, 8-15 parts of auxiliary agents, 4-8 parts of talcum powder, 1-2 parts of coupling agents, 0.5-1 parts of antioxidants, 0.5-1 parts of ultraviolet absorbers, and 0.03-0.05 parts of initiators.

[0007] Furthermore, the auxiliary agent is prepared by the following steps:

[0008] S1. Add cyanuric chloride, N-methylallylamine and xylene to a dry three-necked flask under nitrogen protection, stir until completely dissolved, then slowly add 20wt% sodium bicarbonate solution, control the temperature at 0-5°C to react for 8h after the addition is complete, add deionized water after shaking and stand for stratification after completion of the reaction, separate the aqueous phase and measure the pH until the pH of the aqueous phase is neutral, then take the organic phase and dry it with anhydrous magnesium sulfate, filter it, and distill the filtrate under reduced pressure to obtain intermediate 1; the molar ratio of cyanuric chloride to N-methylallylamine is 1:2.05-2.1;

[0009] Under alkaline conditions, the two -Cl groups of cyanuric chloride and the -NH- of N-methylallylamine undergo nucleophilic substitution reaction. The reaction process is as follows:

[0010]

[0011] S2. Under nitrogen protection, add intermediate 1 and DMSO (dimethyl sulfoxide) into a dry three-necked flask, stir thoroughly until completely dissolved, then slowly add 1,3-propylene glycol, and then heat to 50° C. and stir to react for 3 hours. During the entire reaction, the pH value of the system is adjusted to 7 by 10wt% sodium carbonate solution. After the reaction is completed, cool to room temperature, first centrifuge and wash 3 times with deionized water, then centrifuge and wash 3 times with ethanol, and finally dry at 80° C. for 12 hours to obtain intermediate 2; the molar ratio of intermediate 1 to 1,3-propylene glycol is 1:1.05-1.1;

[0012] Under heating conditions, the -Cl of intermediate 1 and the -OH of 1,3-propylene glycol undergo a substitution reaction, and the reaction process is as follows:

[0013]

[0014] S3, blow the three-necked flask with dry nitrogen for 30 minutes to drive away the air in the flask, then add DMSO, N, N-ditetradecanoylamine and pyridine into the dry three-necked flask, slowly add phosphorus oxychloride at 20°C with stirring, after the addition is complete, react at 20°C for 5 hours, after the reaction is completed, distill under reduced pressure to obtain intermediate 3; the amount ratio of phosphorus oxychloride, N, N-ditetradecanoylamine, pyridine and DMSO is 2.6mL:11.7g:3.4mL:120mL;

[0015] When pyridine is used as an acid binding agent, the molar ratio of phosphorus oxychloride and N,N-ditetradecylamine is controlled to be 1:1 and N,N-ditetradecylamine is slightly excessive, then phosphorus oxychloride and N,N-ditetradecylamine undergo a one-molecule substitution reaction, and the reaction process is as follows:

[0016]

[0017] S4, blowing a three-necked flask with dry nitrogen for 30 minutes to drive away the air in the flask, then adding DMF (N, N-dimethylformamide), intermediate 2 and triethylamine into the flask, stirring thoroughly until completely dissolved, slowly adding a mixed solution of intermediate 3 and DMF while stirring, after the addition is complete, react at room temperature for 8 hours, after the reaction is completed, distill under reduced pressure, purify by column chromatography (selecting a mixed solvent of chloroform and ether as the eluent, the volume ratio of chloroform and ether is 9:1), distill under reduced pressure to obtain intermediate 4; the amount ratio of intermediate 2, intermediate 3, triethylamine and DMF is 7.5g:13.2g:5.2mL:180mL;

[0018] When triethylamine is used as an acid binding agent, the molar ratio of intermediate 2 and intermediate 3 is controlled to be 1:1 and intermediate 2 is slightly excessive, then intermediate 2 and intermediate 3 undergo a one-molecule substitution reaction, and the reaction process is as follows:

[0019]

[0020] S5. Blow the three-necked flask with dry nitrogen for 30 minutes to drive away the air in the flask, then add DMF, chitosan and triethylamine into the dry three-necked flask, stir until completely dissolved, slowly add the mixed solution of intermediate 4 and DMF while stirring, react at 60°C for 7 hours after the addition, and distill under reduced pressure to obtain the auxiliary agent after the reaction is completed. The mass ratio of chitosan to intermediate 4 is 2:1.

[0021] Under triethylamine and heating conditions, intermediate 4 and chitosan undergo a substitution reaction. The reaction process is shown below

[0022]

[0023] The additives are rich in N and P elements. Phosphorus promotes the carbonization of the polymer matrix and forms a molten carbon layer on the surface of the polymer matrix. The non-combustible gases such as ammonia and nitrogen generated by the thermal decomposition of nitrogen not only dilute the concentration of oxygen and combustible gases in the flame zone, but also make the molten carbon layer formed on the surface of the polymer matrix expand and foam to form a porous foam structure. The expanded porous foam carbon layer will block the process of heat and oxygen exchange between the polymer matrix and the outside world, thereby preventing the polymer material from burning and achieving the ultimate flame retardant effect. Therefore, adding halogen-free additives to packaging materials can significantly improve the flame retardant effect of packaging materials, and the flame retardant effect is efficient and safe.

[0024] The additive contains chitosan, which is a deacetylated product of the natural polysaccharide chitin. It has rich amino groups on its surface and has broad-spectrum antibacterial properties. Chitosan mainly interacts with the cell wall of bacteria, causing the destruction of the cell membrane, thereby killing bacteria. Therefore, adding chitosan-containing additives to packaging materials can effectively inhibit the growth of bacteria, molds, etc. At the same time, chitosan has good adsorption capacity and is easy to absorb odors during storage; in addition, chitosan also has good moisture retention and preservation capabilities. The oil-soluble long carbon chains and heterocyclic rings in the additive increase the interfacial adhesion of chitosan in the polyethylene matrix and improve its compatibility, so that chitosan can fully exert its antibacterial, moisture-retaining, and odor-absorbing effects.

[0025] The additive contains multiple long carbon chains (14 carbons), and the long methylene chains that can be freely extended and rotated increase the toughness of the polyethylene material. Under the action of the initiator, the multiple carbon-carbon double bonds in the additive have a chemical reaction with the unreacted carbon-carbon double bonds at the end of the polyethylene. Therefore, the additive can exist stably in the packaging material and is not easy to migrate or fall out, so that the packaging material has a long-lasting flame retardant effect, antibacterial effect and odor absorption effect.

[0026] Furthermore, the coupling agent is one or more of γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltri(β-methoxyethoxy)silane.

[0027] The silaneoxy end of the coupling agent can chemically bond with the hydroxyl group on the surface of talc, thereby reducing the surface energy of talc and improving its dispersibility. The organic end of the coupling agent contains a carbon-carbon double bond, which can react chemically with the carbon-carbon double bond in the auxiliary agent under the action of the initiator. This chemical reaction can not only further anchor the auxiliary agent and make it stably present in the packaging material, but also further promote the dispersion of talc and the auxiliary agent, thereby allowing the two to fully play their roles and increase the durability and quality of the packaging material.

[0028] Under the action of the coupling agent and the initiator, a hybrid cross-linked network structure is established between the additive, talcum powder and polyethylene. Therefore, the mechanical properties, flame retardant properties and antibacterial properties of the packaging material of the present invention are more excellent and stable and are not easily affected by the external environment.

[0029] Furthermore, the antioxidant is one or more of antioxidant 1010, antioxidant 168, antioxidant 1076, and antioxidant DLTP.

[0030] Furthermore, the ultraviolet absorber is one or more of ultraviolet absorber UV-531, ultraviolet absorber UVP-327, light stabilizer GW-540, and light stabilizer AM-101.

[0031] Furthermore, the initiator is one or more of dicumyl peroxide, dibenzoyl peroxide and azobisisobutyronitrile.

[0032] A method for preparing a flame retardant packaging material comprises the following steps:

[0033] The raw materials are weighed by weight and mixed evenly, then added to a mixer and stirred evenly, then added to an internal mixer for melt blending, finally injected into a twin-screw extruder for melting, extrusion and granulation, and the obtained granules are added to a film blowing machine for film blowing molding, heat sealing and fixing, and reel forming to obtain a flame-retardant packaging material.

[0034] The beneficial effects of the present invention are as follows: under the action of the initiator and the coupling agent, a hybrid cross-linked network structure is formed between the auxiliary agent, talc and polyethylene, and the auxiliary agents and talc containing phosphorus, nitrogen elements, chitosan, and long carbon chains can be highly dispersed and stably present in the packaging material and fully play their roles. Therefore, the packaging material of the present invention has excellent and stable flame retardancy and antibacterial properties, can absorb odors, and has strong toughness. In addition, due to the combined effect of other raw materials, the packaging material of the present invention also has excellent aging resistance and other properties. DETAILED DESCRIPTION

[0035] 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.

[0036] Example 1

[0037] Preparation of auxiliary agent, the specific steps are as follows:

[0038] S1. Under nitrogen protection, 4.6 g of cyanuric chloride, 5 mL of N-methylallylamine and 100 mL of xylene were added to a dry 250 mL three-necked flask, stirred until completely dissolved, and then 4 mL of 20 wt% sodium bicarbonate solution was slowly added. After the addition was completed, the temperature was controlled at 0-5 ° C to react for 8 hours. After the reaction was completed, deionized water was added and shaken, and then allowed to stand for stratification. The aqueous phase was separated and the pH was measured until the pH of the aqueous phase was neutral. The organic phase was then dried over anhydrous magnesium sulfate, filtered, and the filtrate was distilled under reduced pressure to obtain intermediate 1;

[0039] S2. Under nitrogen protection, 7.9 g of intermediate 1 and 120 mL of DMSO were added to a dry 250 mL three-necked flask, and the mixture was stirred until completely dissolved. Then, 2.4 mL of 1,3-propylene glycol was slowly added, and the mixture was heated to 50°C and stirred for reaction for 3 h. During the entire reaction, the pH value of the system was adjusted to 7 by using a 10 wt% sodium carbonate solution. After the reaction was completed, the mixture was cooled to room temperature, and the mixture was first centrifuged and washed 3 times with deionized water, and then centrifuged and washed 3 times with ethanol, and finally dried at 80°C for 12 h to obtain intermediate 2.

[0040] S3, blow dry nitrogen gas into a 250 mL three-necked flask for 30 min to drive away the air in the flask, then add 120 mL DMSO, 11.7 g N, N-ditetradecylamine and 3.4 mL pyridine into the dry three-necked flask, slowly add 2.6 mL phosphorus oxychloride at 20° C. with stirring, react at 20° C. for 5 h, and after the reaction is completed, distill under reduced pressure to obtain intermediate 3;

[0041] S4, blowing a 500mL three-necked flask with dry nitrogen for 30min to drive away the air in the flask, then adding 140mL DMF, 7.5g intermediate 2 and 5.2mL triethylamine into the flask, stirring thoroughly until completely dissolved, slowly adding a mixed solution of 13.2g intermediate 3 and 40mL DMF while stirring, after the addition is complete, reacting at room temperature for 8h, after the reaction is completed, distilling under reduced pressure, purifying by column chromatography (selecting a mixed solvent of chloroform and ether as the eluent, the volume ratio of chloroform and ether is 9:1), distilling under reduced pressure to obtain intermediate 4;

[0042] S5. Blow dry nitrogen gas into a 250 mL three-necked flask for 30 min to drive away the air in the flask. Then add 120 mL of DMF, 10 g of chitosan and 1.3 mL of triethylamine into the dry three-necked flask and stir until completely dissolved. Slowly add a mixed solution of 5 g of intermediate 4 and 10 mL of DMF while stirring. After the addition is complete, react at 60°C for 7 h. After the reaction is completed, distill under reduced pressure to obtain an auxiliary agent.

[0043] Example 2

[0044] The specific steps for preparing flame retardant packaging materials are as follows:

[0045] Weigh each raw material by weight, and evenly mix 85 parts of polyethylene, 8 parts of the additive prepared in Example 1, 4 parts of talc, 1 part of γ-methacryloxypropyltrimethoxysilane, 0.25 parts of antioxidant 1010, 0.25 parts of antioxidant 168, 0.5 parts of ultraviolet absorber UV-531, and 0.03 parts of diisopropylbenzene peroxide, then add the mixture to a mixer and stir evenly, then add the mixture to an internal mixer for melt blending, and finally inject the mixture into a twin-screw extruder for melting, extrusion, and granulation. Add the obtained particles to a film blowing machine for film blowing molding, heat sealing fixation, and reel forming to obtain a flame-retardant packaging material.

[0046] Example 3

[0047] The specific steps for preparing flame retardant packaging materials are as follows:

[0048] Weigh each raw material by weight, and evenly mix 90 parts of polyethylene, 13 parts of the additive prepared in Example 1, 6 parts of talc, 1.5 parts of vinyl trimethoxy silane, 0.7 parts of antioxidant 1076, 0.4 parts of ultraviolet absorber UVP-327, 0.4 parts of light stabilizer GW-540, and 0.04 parts of dibenzoyl peroxide, then add them to a mixer and stir them evenly, then add them to an internal mixer for melt blending, and finally inject them into a twin-screw extruder for melting, extrusion, and granulation. The obtained particles are added to a film blowing machine for film blowing molding, heat sealing fixation, and reel molding to obtain a flame retardant packaging material.

[0049] Example 4

[0050] The specific steps for preparing flame retardant packaging materials are as follows:

[0051] Weigh each raw material by weight, and evenly mix 95 parts of polyethylene, 15 parts of the additive prepared in Example 1, 8 parts of talc, 2 parts of vinyl tri(β-methoxyethoxy) silane, 0.25 parts of antioxidant 168, 0.5 parts of antioxidant 1076, 0.25 parts of antioxidant DLTP, 0.5 parts of ultraviolet absorber UV-531, 0.25 parts of light stabilizer GW-540, 0.25 parts of light stabilizer AM-101, and 0.05 parts of diisopropylbenzene peroxide, then add the mixture to a mixer and stir evenly, then add the mixture to an internal mixer for melt blending, and finally inject the mixture into a twin-screw extruder for melting, extrusion, and granulation, and add the obtained particles to a film blowing machine for film blowing molding, heat sealing fixation, and reel forming to obtain a flame-retardant packaging material.

[0052] Comparative Example 1

[0053] Prepare packaging materials, the specific steps are as follows:

[0054] The remaining steps remained unchanged, except that the auxiliary agent in Example 4 was replaced by 10 parts of chitosan and 5 parts of flame retardant FRC-2 to prepare the packaging material.

[0055] Comparative Example 2

[0056] Prepare packaging materials, the specific steps are as follows:

[0057] The remaining steps remain unchanged, and the auxiliary agent in Example 4 is removed to prepare the packaging material.

[0058] Performance Testing

[0059] The packaging materials prepared in Examples 2-4 and Comparative Examples 1-2 were made into standard samples, and the tensile strength and elongation at break were measured according to Part 3 of GB / T1040.3-2006 "Determination of tensile properties of plastics"; the limiting oxygen index was tested using the method specified in GB / T 2406.2-2009; and the vertical burning grade was tested using UL94. The test results are shown in Table 1 below:

[0060] Table 1

[0061]

[0062] It can be seen from the data in the above table that the packaging materials prepared in Examples 2-4 of the present invention have excellent mechanical properties and flame retardant effects.

[0063] The polymer food packaging bags prepared in Examples 2-4 and Comparative Examples 1-2 were made into standard samples, and the antibacterial properties were tested according to GB / T31402-2015. The test results are shown in Table 2 below:

[0064] Table 2

[0065]

[0066] It can be seen from the data in the above table that the packaging materials prepared in Examples 2-4 of the present invention have better antibacterial stability.

[0067] 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.

[0068] 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 flame retardant packaging material, characterized in that: The raw materials include the following parts by weight: 85-95 parts of polyethylene, 8-15 parts of auxiliary agents, 4-8 parts of talc, 1-2 parts of coupling agents, 0.5-1 parts of antioxidants, 0.5-1 parts of ultraviolet absorbers, and 0.03-0.05 parts of initiators; Wherein, the auxiliary agent is prepared by the following steps: S1. Add cyanuric chloride, N-methylallylamine and xylene into a flask under nitrogen protection, add 20 wt% sodium bicarbonate solution after stirring, react at 0-5°C for 8 hours, add deionized water, separate the layers, dry the organic phase, filter, and distill the filtrate under reduced pressure to obtain intermediate 1; S2. Add intermediate 1 and DMSO into a flask under nitrogen protection, add 1,3-propylene glycol after stirring, and react at 50° C. for 3 h. During the reaction, adjust the pH value of the system to 7, wash, and dry to obtain intermediate 2. S3, after nitrogen blowing into the flask, add DMSO, N,N-ditetradecylamine and pyridine, add phosphorus oxychloride at 20°C, react at 20°C for 5h, and distill under reduced pressure to obtain intermediate 3; S4, after nitrogen blowing into the flask, add DMF, intermediate 2 and triethylamine, stir, add intermediate 3 and DMF, react at room temperature for 8h, distill under reduced pressure, purify by column chromatography, and distill under reduced pressure to obtain intermediate 4; S5, after nitrogen blowing into the flask, add DMF, chitosan and triethylamine, stir, add intermediate 4 and DMF, react at 60°C for 7h, and distill under reduced pressure to obtain an auxiliary agent; The molar ratio of cyanuric chloride and N-methylallylamine in step S1 is 1:2.05-2.1; the molar ratio of intermediate 1 and 1,3-propylene glycol in step S2 is 1:1.05-1.1; the usage ratio of phosphorus oxychloride, N,N-ditetradecylamine, pyridine and DMSO in step S3 is 2.6mL:11.7g:3.4mL:120mL; the usage ratio of intermediate 2, intermediate 3, triethylamine and DMF in step S4 is 7.5g:13.2g:5.2mL:180mL; the mass ratio of chitosan and intermediate 4 in step S5 is 2:

1.

2. A flame retardant packaging material according to claim 1, characterized in that: The coupling agent is one or more of γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane and vinyltri(β-methoxyethoxy)silane.

3. The flame retardant packaging material according to claim 1, characterized in that: The antioxidant is one or more of antioxidant 1010, antioxidant 168, antioxidant 1076, and antioxidant DLTP.

4. The flame retardant packaging material according to claim 1, characterized in that: The ultraviolet absorber is one or more of the ultraviolet absorber UV-531, the ultraviolet absorber UVP-327, and the light stabilizer AM-101.

5. The flame retardant packaging material according to claim 1, characterized in that: The initiator is one or more of dicumyl peroxide, dibenzoyl peroxide and azobisisobutyronitrile.

6. The method for preparing a flame retardant packaging material according to claim 1, characterized in that: The following steps are involved: The raw materials are weighed by weight and mixed evenly, then added to a mixer and stirred evenly, then added to an internal mixer for melt blending, finally injected into a twin-screw extruder for melting, extrusion and granulation, and the obtained granules are added to a film blowing machine for film blowing molding, heat sealing and fixing, and reel forming to obtain a flame-retardant packaging material.

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