Flame-retardant regenerated plastic and preparation method therefor

Abstract

The present invention relates to the technical field of regenerated plastics, and in particular relates to a flame-retardant regenerated plastic and a preparation method therefor. The regenerated plastic comprises the following specific components: 90-100 parts of regenerated high-density polyethylene, 5-10 parts of high-density polyethylene, 1-2 parts of calcium stearate, 1-2 parts of carbon black, 8-12 parts of maleic-anhydride-grafted polyethylene, 2-3 parts of an antioxidant, and 6-8 parts of a polyurethane elastomer. The regenerated high-density polyethylene is used as a main material, the high-density polyethylene is added thereto, the maleic-anhydride-grafted polyethylene is used as a compatibilizer, and then polyhydroxy polybutadiene, epoxidized hydroxyl-terminated polybutadiene and polypropylene oxide glycol are compounded and react with diphenylmethane diisocyanate to generate a polyurethane elastomer, thereby toughening the regenerated polyethylene; moreover, a flame-retardant effect is achieved by means of the synergy of phosphorus and nitrogen; therefore, a regenerated polyethylene plastic with high tensile strength and good flame-retardant performance is prepared. The regenerated plastic can be widely used in a plurality of fields, and has a relatively high level of practicability.

Description

Flame retardant recycled plastic and preparation method thereof Technical Field

[0001] The present invention relates to the technical field of recycled plastics, in particular to a flame-retardant recycled plastic and a preparation method thereof. Background Art

[0002] Recycled plastic is the reuse of plastic. After a mechanical blade crushing operation, the plastic is reused. Polyethylene is one of the most widely used plastic categories and accounts for a relatively large proportion of waste plastics. How to recycle polyethylene in waste plastics is a research and development project that existing companies pay more attention to.

[0003] In addition, flame retardancy is a common modification method during plastic processing and is also one of the properties that is more valued when plastics are used. Therefore, in order to solve the recycling of recycled plastics and improve the flame retardancy of the prepared products, this application discloses a flame retardant recycled plastic and a preparation method thereof to solve this technical problem.

[0004] Summary of the Invention

[0005] The object of the present invention is to provide a flame retardant recycled plastic and a preparation method thereof, so as to solve the problems raised in the above background technology.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A method for preparing flame-retardant recycled plastic, the preparation method specifically comprising:

[0008] Step (1): mixing dimethyl methylphosphonate and trihydroxyethyl isocyanurate, stirring evenly, adding tetrabutyl titanate, heating to 140-150° C., keeping the temperature for reaction for 2-3 hours, continuing to heat to 190-200° C., reacting for 3-4 hours, washing with anhydrous ethanol after the reaction, and vacuum drying to obtain a flame retardant crosslinking agent;

[0009] Step (2): polyhydroxy polybutadiene, epoxidized hydroxyl-terminated polybutadiene, polyoxypropylene glycol and tetrahydrofuran are mixed, diphenylmethane diisocyanate and dibutyltin dilaurate are added under nitrogen environment, stirred at 70-80° C. for 1-1.5 hours, then a chain extender is added, and the reaction is continued for 1-2 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and then the mixture is poured into a mold and vacuum cured at 45-50° C. to obtain a polyurethane elastomer;

[0010] The chain extender is a compound of 1,4-butanediol and a flame retardant crosslinking agent, and the mass ratio of the 1,4-butanediol to the flame retardant crosslinking agent is 1:3;

[0011] Step (3): taking recycled high-density polyethylene, high-density polyethylene, calcium stearate, carbon black, maleic anhydride grafted polyethylene and antioxidant, mixing them, adding polyurethane elastomer, stirring evenly, and melt-extruding to obtain flame-retardant recycled plastic.

[0012] In the embodiment of the present application, in step (3), the amount of each component used is: in parts by mass, 90-100 parts of recycled high-density polyethylene, 5-10 parts of high-density polyethylene, 1-2 parts of calcium stearate, 1-2 parts of carbon black, 8-12 parts of maleic anhydride grafted polyethylene, 2-3 parts of antioxidant, and 6-8 parts of polyurethane elastomer.

[0013] In the embodiment of the present application, in step (2), the amount of each component used is: in parts by mass, 10 to 12 parts of polyhydroxy polybutadiene, 15 to 20 parts of epoxidized terminal hydroxy polybutadiene, 30 to 40 parts of polyoxypropylene glycol, 40 to 45 parts of diphenylmethane diisocyanate, 1 to 3 parts of dibutyltin dilaurate, and 3 to 8 parts of chain extender.

[0014] In the embodiment of the present application, in step (1), the molar ratio of dimethyl methylphosphonate to trishydroxyethyl isocyanurate is 1:(1-1.1); the amount of tetrabutyl titanate used is 0.5wt%-0.6wt% of the total amount of dimethyl methylphosphonate and trishydroxyethyl isocyanurate.

[0015] In the embodiment of the present application, the preparation steps of the polyhydroxy polybutadiene are as follows: take terminal hydroxy polybutadiene, vacuum dehydrate at 115-120°C, cool to 40-45°C, add isopentenol, dibenzoyl peroxide and petroleum ether, stir evenly, heat to reaction reflux under nitrogen environment, and continue the reaction for 3-4 hours to obtain polyhydroxy polybutadiene.

[0016] In the embodiment of the present application, the mass ratio of the terminal hydroxyl polybutadiene and isopentenol is 100:(1-2); the amount of the dibenzoyl peroxide is 0.05wt%-0.06wt% of the terminal hydroxyl polybutadiene; the mass ratio of the terminal hydroxyl polybutadiene and petroleum ether is 1:1.

[0017] In the present embodiment, the preparation steps of epoxidized hydroxy-terminated polybutadiene are as follows: hydroxy-terminated polybutadiene, glacial acetic acid, toluene, and a sulfonic acid catalyst are mixed uniformly, heated to 50-55° C., hydrogen peroxide is added, and the reaction is continued for 6-7 hours. After the reaction is completed, the reaction is allowed to stand and separate into layers, the organic layer is washed until neutral, and rotary evaporated for 2-3 hours to obtain the epoxidized hydroxy-terminated polybutadiene. The hydrogen peroxide is a 30% by mass aqueous solution of hydrogen peroxide.

[0018] In the embodiment of the present application, the mass ratio of the hydrogen peroxide, glacial acetic acid, and hydroxyl-terminated polybutadiene is (2-2.1): (0.9-1): 1, and the amount of toluene used is 140 wt% to 150 wt% of the hydroxyl-terminated polybutadiene.

[0019] In the embodiment of the present application, the sulfonic acid catalyst is 732 type cation exchange resin, and the amount of the sulfonic acid catalyst used is 15wt% to 20wt% of the hydroxyl-terminated polybutadiene.

[0020] In the embodiments of the present application, the recycled plastic is prepared according to any one of the above methods for preparing a flame-retardant recycled plastic.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The invention discloses a flame-retardant recycled plastic and a preparation method thereof. The recycled plastic comprises 90-100 parts of recycled high-density polyethylene, 5-10 parts of high-density polyethylene, 1-2 parts of calcium stearate, 1-2 parts of carbon black, 8-12 parts of maleic anhydride grafted polyethylene, 2-3 parts of an antioxidant, and 6-8 parts of a polyurethane elastomer. The recycled high-density polyethylene is used as a main material, high-density polyethylene is added, maleic anhydride grafted polyethylene is used as a compatibilizer, and the polyurethane elastomer is used as a toughening agent. A flame-retardant component is introduced into the polyurethane elastomer to prepare a recycled polyethylene plastic with high tensile strength and excellent flame-retardant performance. The recycled plastic can be widely used in multiple fields, and its excellent mechanical properties make it highly practical.

[0023] In the scheme, this application first uses terminal hydroxyl polybutadiene and isopentenol as raw materials, and grafts isopentenol onto the terminal hydroxyl polybutadiene chain segment under the action of dibenzoyl peroxide, thereby realizing polyhydroxyl polybutadiene containing multiple hydroxyl groups, and utilizing polyhydroxyl polybutadiene to provide hydroxyl groups for the polyurethane elastomer, thereby improving the crosslinking density of the polyurethane elastomer; at the same time, the scheme also utilizes terminal hydroxyl polybutadiene, glacial acetic acid, toluene and sulfonic acid catalyst to prepare epoxidized terminal hydroxyl polybutadiene, and defines "the mass ratio of hydrogen peroxide, glacial acetic acid and terminal hydroxyl polybutadiene as (2-2.1): (0.9-1): 1"; the introduction of epoxidized terminal hydroxyl polybutadiene can improve the thermal stability of the polyurethane elastomer and improve its heat aging resistance. The scheme compounded polyhydroxyl polybutadiene, epoxidized terminal hydroxyl polybutadiene and polyoxypropylene glycol, and reacted them with diphenylmethane diisocyanate to form a polyurethane elastomer to achieve excellent toughening of recycled polyethylene.

[0024] The present invention uses 1,4-butanediol and a flame retardant crosslinking agent as a chain extender when preparing a polyurethane elastomer. The flame retardant crosslinking agent is prepared by reacting dimethyl methylphosphonate and trihydroxyethyl isocyanurate in a molar ratio of 1: (1 to 1.1). The flame retardant effect is achieved through the synergy of phosphorus and nitrogen, and the flame retardancy is correlated with the polyurethane elastomer. No other flame retardants need to be added when preparing polyethylene. While improving the flame retardant performance of the product, the process is greatly simplified and the cost is reduced.

[0025] The invention discloses a flame-retardant recycled plastic and a preparation method thereof. The scheme prepares a recycled polyethylene plastic with high mechanical properties and excellent flame retardant properties. After heat aging, the plastic can still maintain relatively excellent mechanical properties and has high practicality. DETAILED DESCRIPTION

[0026] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0027] It should be noted that all raw materials involved in this invention are purchased from sources without any particular restrictions. Examples include: hydroxy-terminated polybutadiene: number average molecular weight 1500 g / mol, hydroxyl number 1.5 mmol / g, provided by Luoyang Liming Chemical Research Institute; sulfonic acid catalyst: 732 type strong acid cation exchange resin, provided by Shanghai Chemical Reagent Company of China National Pharmaceutical Group; polyoxypropylene glycol (N210): Mn = 1000, provided by Yantai Wanhua Polyurethane Co., Ltd.; recycled high-density polyethylene (HDPE) obtained from recycled plastic bottle caps and milk bottle caps, cut, cleaned, and dried, with a melt index (MFI, 190°C / 5 kg) of 5.8 g / 10 min, provided by Xiongxian Tianhai Plastic Products Factory; HDPE 2200J, provided by China National Petroleum Corporation; maleic anhydride-grafted polyethylene: MV206, MAH grafting rate 1%, provided by Shanghai Rizhisheng New Technology Development Co., Ltd.; hydrogen peroxide: aqueous hydrogen peroxide solution, 30% by mass; antioxidant: antioxidant 1010.

[0028] Example 1: A method for preparing flame-retardant recycled plastic, the preparation method is specifically as follows:

[0029] Step (1): The flame retardant crosslinking agent is prepared by mixing 0.2 mol of dimethyl methylphosphonate and 0.2 mol of tris(hydroxyethyl)isocyanurate, stirring evenly, adding tetrabutyl titanate, heating to 140°C, keeping the temperature for reaction for 3 hours, then heating to 190°C, reacting for 3 hours, washing with anhydrous ethanol after the reaction, and vacuum drying to obtain the flame retardant crosslinking agent. The amount of tetrabutyl titanate used is 0.5 wt% of the total amount of dimethyl methylphosphonate and tris(hydroxyethyl)isocyanurate.

[0030] Step (2): polyhydroxy polybutadiene, epoxidized hydroxyl-terminated polybutadiene, polyoxypropylene glycol and tetrahydrofuran are mixed, diphenylmethane diisocyanate and dibutyltin dilaurate are added under nitrogen environment, stirred at 70°C for 1.5 hours, and then a chain extender is added, and the reaction is continued for 1 hour. After the reaction is completed, the solvent is removed by rotary evaporation, and then poured into a mold, and vacuum cured at 50°C to obtain a polyurethane elastomer.

[0031] The amounts of the components used are as follows, by mass: 12 parts polyhydroxy polybutadiene, 20 parts epoxidized hydroxyl-terminated polybutadiene, 40 parts polyoxypropylene glycol, 45 parts diphenylmethane diisocyanate, 2 parts dibutyltin dilaurate, and 8 parts chain extender. The chain extender is a mixture of 1,4-butanediol and a flame retardant crosslinker, with the mass ratio of 1,4-butanediol to the flame retardant crosslinker being 1:3.

[0032] The preparation steps of the polyhydroxy polybutadiene are as follows: taking 100 g of hydroxy-terminated polybutadiene, vacuum dehydrating at 120° C., cooling to 40° C., adding 2 g of isopentenol, 0.05 g of dibenzoyl peroxide and 100 g of petroleum ether, stirring evenly, heating to reaction reflux under a nitrogen environment, and continuing the reaction for 4 hours to obtain polyhydroxy polybutadiene.

[0033] The preparation steps of epoxidized hydroxyl-terminated polybutadiene are as follows: take 30g of hydroxyl-terminated polybutadiene, 28.5g of glacial acetic acid, 45g of toluene and 4.5g of sulfonic acid catalyst, stir evenly, heat to 50°C, add 60g of hydrogen peroxide, continue the reaction for 7h, let it stand after the reaction is completed, wash the organic layer until it is neutral, and rotary evaporate for 2h to obtain epoxidized hydroxyl-terminated polybutadiene.

[0034] Step (3): taking recycled high-density polyethylene, high-density polyethylene, calcium stearate, carbon black, maleic anhydride grafted polyethylene and antioxidant, mixing them, adding polyurethane elastomer, stirring evenly, and melt-extruding to obtain flame-retardant recycled plastic.

[0035] The amount of each component is: by mass, 95 parts of recycled high-density polyethylene, 10 parts of high-density polyethylene, 2 parts of calcium stearate, 2 parts of carbon black, 10 parts of maleic anhydride grafted polyethylene, 3 parts of antioxidant, and 7 parts of polyurethane elastomer.

[0036] Example 2: A method for preparing flame-retardant recycled plastic, the preparation method is specifically as follows:

[0037] Step (1): The flame retardant crosslinking agent is prepared by mixing 0.2 mol of dimethyl methylphosphonate and 0.2 mol of tris(hydroxyethyl)isocyanurate, stirring evenly, adding tetrabutyl titanate, heating to 145°C, keeping the temperature for reaction for 2.5 hours, then heating to 190°C, reacting for 3.5 hours, washing with anhydrous ethanol after the reaction, and vacuum drying to obtain the flame retardant crosslinking agent. The amount of tetrabutyl titanate used is 0.5 wt% of the total amount of dimethyl methylphosphonate and tris(hydroxyethyl)isocyanurate.

[0038] Step (2): polyhydroxy polybutadiene, epoxidized hydroxyl-terminated polybutadiene, polyoxypropylene glycol and tetrahydrofuran are mixed, diphenylmethane diisocyanate and dibutyltin dilaurate are added under nitrogen environment, stirred at 75°C for 1.5 hours, and then a chain extender is added, and the reaction is continued for 1.5 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and then poured into a mold, and vacuum cured at 50°C to obtain a polyurethane elastomer.

[0039] The amounts of the components used are as follows, by mass: 12 parts polyhydroxy polybutadiene, 20 parts epoxidized hydroxyl-terminated polybutadiene, 40 parts polyoxypropylene glycol, 45 parts diphenylmethane diisocyanate, 2 parts dibutyltin dilaurate, and 8 parts chain extender. The chain extender is a mixture of 1,4-butanediol and a flame retardant crosslinker, with the mass ratio of 1,4-butanediol to the flame retardant crosslinker being 1:3.

[0040] The preparation steps of the polyhydroxy polybutadiene are as follows: taking 100 g of hydroxy-terminated polybutadiene, vacuum dehydrating at 120° C., cooling to 45° C., adding 2 g of isopentenol, 0.05 g of dibenzoyl peroxide and 100 g of petroleum ether, stirring evenly, heating to reaction reflux under a nitrogen environment, and continuing the reaction for 3.5 hours to obtain polyhydroxy polybutadiene.

[0041] The preparation steps of epoxidized hydroxyl-terminated polybutadiene are as follows: 30g of hydroxyl-terminated polybutadiene, 28.5g of glacial acetic acid, 45g of toluene and 4.5g of sulfonic acid catalyst are taken, stirred evenly, heated to 55°C, 60g of hydrogen peroxide is added, and the reaction is continued for 6.5h. After the reaction is completed, the stratification is allowed to stand, the organic layer is washed to neutrality, and rotary evaporated for 2h to obtain epoxidized hydroxyl-terminated polybutadiene.

[0042] Step (3): taking recycled high-density polyethylene, high-density polyethylene, calcium stearate, carbon black, maleic anhydride grafted polyethylene and antioxidant, mixing them, adding polyurethane elastomer, stirring evenly, and melt-extruding to obtain flame-retardant recycled plastic.

[0043] The amount of each component is: by mass, 95 parts of recycled high-density polyethylene, 10 parts of high-density polyethylene, 2 parts of calcium stearate, 2 parts of carbon black, 10 parts of maleic anhydride grafted polyethylene, 3 parts of antioxidant, and 7.5 parts of polyurethane elastomer.

[0044] Example 3: A method for preparing flame-retardant recycled plastic, the preparation method is specifically as follows:

[0045] Step (1): The flame retardant crosslinking agent is prepared by mixing 0.2 mol of dimethyl methylphosphonate and 0.2 mol of tris(hydroxyethyl)isocyanurate, stirring evenly, adding tetrabutyl titanate, heating to 150°C, keeping the temperature for reaction for 2 hours, then heating to 190°C, reacting for 4 hours, washing with anhydrous ethanol after the reaction, and vacuum drying to obtain the flame retardant crosslinking agent. The amount of tetrabutyl titanate used is 0.5 wt% of the total amount of dimethyl methylphosphonate and tris(hydroxyethyl)isocyanurate.

[0046] Step (2): polyhydroxy polybutadiene, epoxidized hydroxyl-terminated polybutadiene, polyoxypropylene glycol and tetrahydrofuran are mixed, diphenylmethane diisocyanate and dibutyltin dilaurate are added under nitrogen environment, stirred at 80°C for 1 hour, and then a chain extender is added, and the reaction is continued for 2 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and then poured into a mold, and vacuum cured at 50°C to obtain a polyurethane elastomer.

[0047] The amounts of the components used are as follows, by mass: 12 parts polyhydroxy polybutadiene, 20 parts epoxidized hydroxyl-terminated polybutadiene, 40 parts polyoxypropylene glycol, 45 parts diphenylmethane diisocyanate, 2 parts dibutyltin dilaurate, and 8 parts chain extender. The chain extender is a mixture of 1,4-butanediol and a flame retardant crosslinker, with the mass ratio of 1,4-butanediol to the flame retardant crosslinker being 1:3.

[0048] The preparation steps of the polyhydroxy polybutadiene are as follows: taking 100g of hydroxy-terminated polybutadiene, vacuum dehydrating at 120°C, cooling to 45°C, adding 2g of isopentenol, 0.05g of dibenzoyl peroxide and 100g of petroleum ether, stirring evenly, heating to reaction reflux under a nitrogen environment, and continuing the reaction for 4h to obtain polyhydroxy polybutadiene.

[0049] The preparation steps of epoxidized hydroxyl-terminated polybutadiene are as follows: 30g of hydroxyl-terminated polybutadiene, 28.5g of glacial acetic acid, 45g of toluene and 4.5g of sulfonic acid catalyst are taken, stirred evenly, heated to 55°C, 60g of hydrogen peroxide is added, and the reaction is continued for 6h. After the reaction is completed, the mixture is allowed to stand and separate, the organic layer is washed until neutral, and rotary evaporated for 2h to obtain epoxidized hydroxyl-terminated polybutadiene.

[0050] Step (3): taking recycled high-density polyethylene, high-density polyethylene, calcium stearate, carbon black, maleic anhydride grafted polyethylene and antioxidant, mixing them, adding polyurethane elastomer, stirring evenly, and melt-extruding to obtain flame-retardant recycled plastic.

[0051] The amount of each component is: by mass, 95 parts of recycled high-density polyethylene, 10 parts of high-density polyethylene, 2 parts of calcium stearate, 2 parts of carbon black, 10 parts of maleic anhydride grafted polyethylene, 3 parts of antioxidant, and 8 parts of polyurethane elastomer.

[0052] Comparative Example 1: A method for preparing flame-retardant recycled plastic, the preparation method being specifically as follows:

[0053] Step (1): The flame retardant crosslinking agent is prepared by mixing 0.2 mol of dimethyl methylphosphonate and 0.2 mol of tris(hydroxyethyl)isocyanurate, stirring evenly, adding tetrabutyl titanate, heating to 150°C, keeping the temperature for reaction for 2 hours, then heating to 190°C, reacting for 4 hours, washing with anhydrous ethanol after the reaction, and vacuum drying to obtain the flame retardant crosslinking agent. The amount of tetrabutyl titanate used is 0.5 wt% of the total amount of dimethyl methylphosphonate and tris(hydroxyethyl)isocyanurate.

[0054] Step (2): polyhydroxy polybutadiene, terminal hydroxy polybutadiene, polyoxypropylene glycol and tetrahydrofuran are mixed, diphenylmethane diisocyanate and dibutyltin dilaurate are added under nitrogen environment, stirred at 80°C for 1 hour, and then a chain extender is added, and the reaction is continued for 2 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and then poured into a mold, and vacuum cured at 50°C to obtain a polyurethane elastomer.

[0055] The amounts of the components used are as follows, by mass: 12 parts polyhydroxy polybutadiene, 20 parts hydroxyl-terminated polybutadiene, 40 parts polyoxypropylene glycol, 45 parts diphenylmethane diisocyanate, 2 parts dibutyltin dilaurate, and 8 parts chain extender. The chain extender is a mixture of 1,4-butanediol and a flame retardant crosslinker, with the mass ratio of 1,4-butanediol to the flame retardant crosslinker being 1:3.

[0056] The preparation steps of the polyhydroxy polybutadiene are as follows: taking 100g of hydroxy-terminated polybutadiene, vacuum dehydrating at 120°C, cooling to 45°C, adding 2g of isopentenol, 0.05g of dibenzoyl peroxide and 100g of petroleum ether, stirring evenly, heating to reaction reflux under a nitrogen environment, and continuing the reaction for 4h to obtain polyhydroxy polybutadiene.

[0057] Step (3): taking recycled high-density polyethylene, high-density polyethylene, calcium stearate, carbon black, maleic anhydride grafted polyethylene and antioxidant, mixing them, adding polyurethane elastomer, stirring evenly, and melt-extruding to obtain flame-retardant recycled plastic.

[0058] The amount of each component is: by mass, 95 parts of recycled high-density polyethylene, 10 parts of high-density polyethylene, 2 parts of calcium stearate, 2 parts of carbon black, 10 parts of maleic anhydride grafted polyethylene, 3 parts of antioxidant, and 8 parts of polyurethane elastomer.

[0059] Taking Example 3 as a control, the epoxidized hydroxy-terminated polybutadiene was not introduced in Comparative Example 1 and was replaced with hydroxy-terminated polybutadiene, while the rest of the process remained unchanged.

[0060] Comparative Example 2: A method for preparing flame-retardant recycled plastic, the preparation method being as follows:

[0061] Step (1): The flame retardant crosslinking agent is prepared by mixing 0.2 mol of dimethyl methylphosphonate and 0.2 mol of tris(hydroxyethyl)isocyanurate, stirring evenly, adding tetrabutyl titanate, heating to 150°C, keeping the temperature for reaction for 2 hours, then heating to 190°C, reacting for 4 hours, washing with anhydrous ethanol after the reaction, and vacuum drying to obtain the flame retardant crosslinking agent. The amount of tetrabutyl titanate used is 0.5 wt% of the total amount of dimethyl methylphosphonate and tris(hydroxyethyl)isocyanurate.

[0062] Step (2): polyhydroxy polybutadiene, epoxidized hydroxyl-terminated polybutadiene, polyoxypropylene glycol and tetrahydrofuran are mixed, diphenylmethane diisocyanate and dibutyltin dilaurate are added under nitrogen environment, stirred at 80°C for 1 hour, and then a chain extender is added, and the reaction is continued for 2 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and then poured into a mold, and vacuum cured at 50°C to obtain a polyurethane elastomer.

[0063] The amounts of each component used are as follows, by mass: 12 parts polyhydroxy polybutadiene, 20 parts epoxidized hydroxyl-terminated polybutadiene, 40 parts polyoxypropylene glycol, 45 parts diphenylmethane diisocyanate, 2 parts dibutyltin dilaurate, and 8 parts chain extender. The chain extender is a mixture of 1,4-butanediol and a flame retardant crosslinker, with the mass ratio of 1,4-butanediol to flame retardant crosslinker being 3:1.

[0064] The preparation steps of the polyhydroxy polybutadiene are as follows: taking 100g of hydroxy-terminated polybutadiene, vacuum dehydrating at 120°C, cooling to 45°C, adding 2g of isopentenol, 0.05g of dibenzoyl peroxide and 100g of petroleum ether, stirring evenly, heating to reaction reflux under a nitrogen environment, and continuing the reaction for 4h to obtain polyhydroxy polybutadiene.

[0065] The preparation steps of epoxidized hydroxyl-terminated polybutadiene are as follows: 30g of hydroxyl-terminated polybutadiene, 28.5g of glacial acetic acid, 45g of toluene and 4.5g of sulfonic acid catalyst are taken, stirred evenly, heated to 55°C, 60g of hydrogen peroxide is added, and the reaction is continued for 6h. After the reaction is completed, the mixture is allowed to stand and separate, the organic layer is washed until neutral, and rotary evaporated for 2h to obtain epoxidized hydroxyl-terminated polybutadiene.

[0066] Step (3): taking recycled high-density polyethylene, high-density polyethylene, calcium stearate, carbon black, maleic anhydride grafted polyethylene and antioxidant, mixing them, adding polyurethane elastomer, stirring evenly, and melt-extruding to obtain flame-retardant recycled plastic.

[0067] The amount of each component is: by mass, 95 parts of recycled high-density polyethylene, 10 parts of high-density polyethylene, 2 parts of calcium stearate, 2 parts of carbon black, 10 parts of maleic anhydride grafted polyethylene, 3 parts of antioxidant, and 8 parts of polyurethane elastomer.

[0068] Taking Example 3 as a control, the amounts of the flame retardant cross-linking agent and 1,4-butanediol were adjusted in Comparative Example 2, while the other processes remained unchanged.

[0069] Comparative Example 3: A method for preparing flame-retardant recycled plastic, the preparation method being as follows:

[0070] Step (1): The flame retardant crosslinking agent is prepared by mixing 0.2 mol of dimethyl methylphosphonate and 0.2 mol of tris(hydroxyethyl)isocyanurate, stirring evenly, adding tetrabutyl titanate, heating to 150°C, keeping the temperature for reaction for 2 hours, then heating to 190°C, reacting for 4 hours, washing with anhydrous ethanol after the reaction, and vacuum drying to obtain the flame retardant crosslinking agent. The amount of tetrabutyl titanate used is 0.5 wt% of the total amount of dimethyl methylphosphonate and tris(hydroxyethyl)isocyanurate.

[0071] Step (2): Mix terminal hydroxyl polybutadiene, polyoxypropylene glycol and tetrahydrofuran, add diphenylmethane diisocyanate and dibutyltin dilaurate under nitrogen environment, stir at 80°C for 1 hour, then add chain extender, continue to react for 2 hours, after the reaction is completed, remove the solvent by rotary evaporation, and then pour into a mold, and vacuum cure at 50°C to obtain a polyurethane elastomer.

[0072] The components used are as follows: 32 parts by mass of hydroxy-terminated polybutadiene, 40 parts of polyoxypropylene glycol, 45 parts of diphenylmethane diisocyanate, 2 parts of dibutyltin dilaurate, and 8 parts of a chain extender. The chain extender is a mixture of 1,4-butanediol and a flame-retardant crosslinker, with the mass ratio of 1,4-butanediol to the flame-retardant crosslinker being 1:3.

[0073] Step (3): taking recycled high-density polyethylene, high-density polyethylene, calcium stearate, carbon black, maleic anhydride grafted polyethylene and antioxidant, mixing them, adding polyurethane elastomer, stirring evenly, and melt-extruding to obtain flame-retardant recycled plastic.

[0074] The amount of each component is: by mass, 95 parts of recycled high-density polyethylene, 10 parts of high-density polyethylene, 2 parts of calcium stearate, 2 parts of carbon black, 10 parts of maleic anhydride grafted polyethylene, 3 parts of antioxidant, and 8 parts of polyurethane elastomer.

[0075] Taking Example 3 as a control, only hydroxy-terminated polybutadiene was used in Comparative Example 3, and the rest of the process remained unchanged.

[0076] Detection experiment:

[0077] 1. Take the recycled plastics prepared in Examples 1 to 3 and Comparative Examples 1 to 3, and injection mold them to obtain dumbbell-shaped samples at an injection molding temperature of 180°C; test the tensile strength according to the method disclosed in GB / T1040-2006 at a tensile rate of 50 mm / min and a gauge length of 25 mm.

[0078] 2. Take the recycled plastics prepared in Examples 1 to 3 and Comparative Examples 1 to 3, and injection mold them into sheets at an injection molding temperature of 180°C, a specimen thickness of 1 mm, and a specification of type 5. Heat age them at 120°C for 240 h, retest the tensile strength, and record the rate of change in tensile strength.

[0079] 3. Refer to the method disclosed in GB / T2406.2-2009 to test the limiting oxygen index of the sample. The sample size is 50mm×150mm×1mm.

[0080] Conclusion: Comparative Example 1 does not introduce epoxidized terminal hydroxyl polybutadiene on the basis of Example 3, but replaces it with terminal hydroxyl polybutadiene. Therefore, compared with Example 3, the tensile strength of the product decreases, and the rate of change of tensile strength after heat aging is greater, but its flame retardant performance does not basically decrease; Comparative Example 2 adjusts the amount of flame retardant cross-linking agent and 1,4-butanediol on the basis of Example 3, and its tensile strength decreases, but the decrease is significantly lower than that of Comparative Example 1; and the heat aging performance is also better than that of Comparative Example 1. At the same time, the flame retardant performance of the product of Comparative Example 2 decreases; In Comparative Example 3, only the terminal hydroxyl polybutadiene setting scheme is adopted on the basis of Example 3. The tensile strength of the product is the worst, and the rate of change of tensile strength after heat aging is the largest, but the flame retardant performance of the product is relatively excellent.

[0081] The invention discloses a flame-retardant recycled plastic and a preparation method thereof. The scheme prepares a recycled polyethylene plastic with high mechanical properties and excellent flame retardant properties. After heat aging, the plastic can still maintain relatively excellent mechanical properties and has high practicality.

[0082] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing flame-retardant recycled plastics, characterized in that: The preparation method is specifically as follows: Step (1): Mix dimethyl methylphosphonate and trihydroxyethyl isocyanurate, stir evenly, add tetrabutyl titanate, heat to 140-150° C., keep warm for 2-3 hours, continue to heat to 190-200° C., react for 3-4 hours, wash with anhydrous ethanol after the reaction is completed, and vacuum dry to obtain a flame retardant crosslinking agent; Step (2): Mix polyhydroxy polybutadiene, epoxidized terminal hydroxy polybutadiene, polyoxypropylene glycol and tetrahydrofuran, add diphenylmethane diisocyanate and dibutyltin dilaurate under nitrogen environment, stir at 70-80° C. for 1-1.5 hours, then add chain extender, continue to react for 1-2 hours, remove solvent by rotary evaporation after the reaction, pour into a mold, and vacuum cure at 45-50° C. to obtain a polyurethane elastomer; The chain extender is a compound of 1,4-butanediol and a flame retardant crosslinking agent, and the mass ratio of the 1,4-butanediol to the flame retardant crosslinking agent is 1:3; Step (3): taking recycled high-density polyethylene, high-density polyethylene, calcium stearate, carbon black, maleic anhydride grafted polyethylene and antioxidant, mixing, adding polyurethane elastomer, stirring evenly, and melt-extruding to obtain flame-retardant recycled plastic.

2. The method for preparing a flame retardant recycled plastic according to claim 1, characterized in that: In step (3), the amount of each component used is: by mass, 90-100 parts of recycled high-density polyethylene, 5-10 parts of high-density polyethylene, 1-2 parts of calcium stearate, 1-2 parts of carbon black, 8-12 parts of maleic anhydride grafted polyethylene, 2-3 parts of antioxidant, and 6-8 parts of polyurethane elastomer.

3. The method for preparing a flame retardant recycled plastic according to claim 1, characterized in that: In step (2), the amounts of the components are as follows: by mass: 10 to 12 parts of polyhydroxy polybutadiene, 15 to 20 parts of epoxidized terminal hydroxy polybutadiene, 30 to 40 parts of polyoxypropylene glycol, 40 to 45 parts of diphenylmethane diisocyanate, 1 to 3 parts of dibutyltin dilaurate, and 3 to 8 parts of a chain extender.

4. The method for preparing a flame retardant recycled plastic according to claim 1, characterized in that: In step (1), the molar ratio of dimethyl methylphosphonate to tris(hydroxyethyl)isocyanurate is 1:(1-1.1); and the amount of tetrabutyl titanate used is 0.5wt%-0.6wt% of the total amount of dimethyl methylphosphonate and tris(hydroxyethyl)isocyanurate.

5. The method for preparing a flame retardant recycled plastic according to claim 1, characterized in that: The preparation steps of the polyhydroxy polybutadiene are as follows: taking terminal hydroxy polybutadiene, vacuum dehydrating at 115-120° C., cooling to 40-45° C., adding isopentenol, dibenzoyl peroxide and petroleum ether, stirring evenly, heating to reaction reflux under nitrogen environment, and continuing the reaction for 3-4 hours to obtain polyhydroxy polybutadiene.

6. The method for preparing a flame retardant recycled plastic according to claim 5, characterized in that: The mass ratio of the terminal hydroxyl polybutadiene to isopentenol is 100:(1-2); the amount of the dibenzoyl peroxide is 0.05wt%-0.06wt% of the terminal hydroxyl polybutadiene.

7. The method for preparing a flame retardant recycled plastic according to claim 1, characterized in that: The preparation steps of epoxidized hydroxy-terminated polybutadiene are as follows: taking hydroxy-terminated polybutadiene, glacial acetic acid, toluene and sulfonic acid catalyst, stirring evenly, heating to 50-55° C., adding hydrogen peroxide, continuing the reaction for 6-7 hours, standing to separate layers after the reaction is completed, washing the organic layer to neutrality, and rotary evaporating to obtain epoxidized hydroxy-terminated polybutadiene.

8. The method for preparing a flame retardant recycled plastic according to claim 7, characterized in that: The mass ratio of hydrogen peroxide, glacial acetic acid and hydroxy-terminated polybutadiene is (2-2.1):(0.9-1):1, and the amount of toluene used is 140wt%-150wt% of the hydroxy-terminated polybutadiene.

9. The method for preparing a flame retardant recycled plastic according to claim 7, characterized in that: The sulfonic acid catalyst is 732 type cation exchange resin, and the amount of the sulfonic acid catalyst used is 15wt% to 20wt% of the terminal hydroxyl polybutadiene.

10. Recycled plastics prepared according to the method for preparing flame-retardant recycled plastics according to any one of claims 1 to 9.

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