A melt-flow-stable PBT flame-retardant reinforced material and its preparation method

Abstract

This invention relates to a melt-flow-stable PBT flame-retardant reinforced material and its preparation method, comprising PBT resin, stabilizer, flame retardant, flame retardant synergist, glass fiber, toughening agent, antioxidant, lubricant, and nucleating agent. Due to its melt flow stability, this invention enables stable continuous production of structural and functional components through molding processes such as injection molding, extrusion, and compression molding. It can be widely used in fields such as cooling fans, motor housings, relays, and plugs and sockets in the electronics and electrical industries.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of engineering plastics, and particularly relates to a PBT flame-retardant reinforced material with stable melt flow and a preparation method thereof. BACKGROUND

[0002] Polybutylene terephthalate (PBT) engineering plastics have been widely used in modified plastics as electronic and electrical functional parts, spinning products as fibers, and extrusion products as packaging films and optical fiber sheaths due to excellent electrical properties, heat resistance, weather resistance, chemical resistance, high gloss, low water absorption, and easy processability. PBT fibers have excellent resilience, alkali resistance, easy dyeability, and good hand feeling, and are widely used as textile fabrics, special medical products such as medical bandages, and adhesive tape base cloth. As monofilament, PBT fibers are often made into wigs and brush filaments such as cosmetic pens, oil painting pens, oil brushes, and toothbrush bristles. In addition to PBT as a modified plastic, which is a composite material, the other polyester fibers as fabrics and the extruded films and sheaths are generally PBT pure resin products. A large amount of waste is generated in the production process or after the use of these fibers and extruded products. With the increasing market demand for polyester, the amount of waste polyester materials also increases year by year. In order to protect the environment, promote green economic sustainable development, and save energy and reduce carbon emissions, more and more businesses and researchers pay attention to recycling and reusing waste polyester. SUMMARY

[0003] The technical problem to be solved by the present application is to provide a PBT flame-retardant reinforced material with stable melt flow and a preparation method thereof. The material has stable melt flow, and can be widely used in the fields of heat dissipation fans, motor housings, relays, and plug sockets in the electronic and electrical industries by using molding processes such as injection molding, extrusion, and mold pressing to realize stable and continuous production and obtain structural and functional components.

[0004] The present application provides a PBT flame-retardant reinforced material with stable melt flow, which comprises the following components in parts by weight:

[0005]

[0006]

[0007] The stabilizer is an epoxy resin with an epoxy equivalent of 2500-3000 g / eq and / or an ethylene-acrylate-glycidyl methacrylate terpolymer with a GMA content of 5-8%.

[0008] The epoxy equivalent and GMA content were determined by titration. Approximately 1g of nucleating agent was weighed and dissolved in 100ml of toluene. The solution was heated to dissolve and cooled to below 60℃. The solution was then accurately transferred to 20ml of 0.05mol / L KOH methanol solution, heated under reflux for 1 hour, cooled to room temperature, and titrated to the endpoint with 0.05mol / L HCl-isopropanol standard solution using 1% phenolphthalein ethanol solution as an indicator. The epoxy equivalent or GMA content was then calculated according to the formula.

[0009] The PBT resin is virgin PBT resin and / or recycled PBT resin.

[0010] The melt flow rate of the recycled PBT resin at 235°C and 1.2 kg was 20–50 g / 10 min, and the melt flow rate fluctuation of the recycled PBT resin was 50–150%. The melt flow rate was measured according to ISO 1133-2011 standard. The melt flow rate fluctuation was defined as the rate of change between two consecutive cuts of the same cut order, i.e., melt flow rate fluctuation = (m... i(1) -m k(2) ) / m i(1) ×100%, m i(1) Let m be the weight of any cut within the first 5 cuts. k(2) For the second 5 cuts with m i(1) The cutting weight is the same for the same cutting sequence. Because virgin PBT has relatively stable viscosity, its melt flow rate fluctuation is also relatively stable. However, recycled PBT resin, due to its different thermal history, has significantly different molecular weights and distributions, resulting in large viscosity fluctuations and consequently, large variations in its melt flow rate fluctuation. Extensive research in this application has found that when the melt flow rate of recycled PBT resin at 235℃ and 1.2kg is 20–50 g / 10 min, and the melt flow rate fluctuation is 50–150%, the melt flow stability is better, leading to better stability in the produced structural and functional components.

[0011] The flame retardant is at least one of brominated epoxy resin, brominated polystyrene, brominated polycarbonate, and aluminum diethylphosphinate; the flame retardant synergist is at least one of antimony trioxide, melamine polyphosphate, and melamine cyanurate.

[0012] The toughening agent is at least one of ethylene-methyl acrylate (EMA) and ethylene-butyl acrylate (EBA).

[0013] The glass fiber is alkali-free glass fiber with a diameter of 10-13 μm.

[0014] The antioxidant is at least one of hindered phenol antioxidant and phosphite antioxidant.

[0015] The lubricant is at least one of fatty acid ester and polyolefin wax lubricant. Preferably, the fatty acid ester includes at least one of pentaerythritol tetra stearate, pentaerythritol tri stearate and dipentaerythritol stearate. The polyolefin wax lubricant is at least one of oxidized polyethylene wax and polyethylene wax.

[0016] The nucleating agent is superfine talc powder. The particle size D50 of the superfine talc powder is 0.5-0.7 μm.

[0017] The melt flow rate fluctuation of the PBT flame-retardant reinforced material is 1-5%.

[0018] Preferably, the addition amount of the stabilizer is 3-6 parts. The addition amount of the glass fiber is 20-35 parts. The addition amount of the toughening agent is 2-5 parts. The addition amount of the antioxidant is 0.1-0.5 parts. The addition amount of the nucleating agent is 0.5-1.5 parts.

[0019] The application further provides a preparation method of the melt flow stable PBT flame-retardant reinforced material.

[0020] The virgin PBT resin or the recycled PBT resin after pre-drying is mixed with other components except the glass fiber in a high-speed stirring mixer according to the proportion or is separately fed into a premixer through a metering feeder to obtain a premix. The premix is fed into a double screw extruder, the glass fiber is added according to the proportion in the double screw extruder, and then melt plasticization, kneading, mixing, extrusion through a die head, drawing, cooling, granulation and drying are performed to obtain the melt flow stable PBT flame-retardant reinforced material.

[0021] The mixing temperature of the double screw extruder is 220-250 ℃, and the screw rotation speed is 300-500 rpm.

[0022] The application further provides an application of the melt flow stable PBT flame-retardant reinforced material in electronic and electrical devices, such as heat dissipation fans, motor housings, relays and plug sockets and other structural and functional components with high stability requirements.

[0023] The source process of the recycled PBT raw material, such as spinning, extrusion blown film, recycling and regranulation, is through the double action of high temperature and shearing, or through multiple cycle processing, resulting in a significant reduction in viscosity, so the melt flowability of the recycled PBT is very unstable. If the melt flow of the recycled PBT material is directly used for flame-retardant glass fiber reinforced modified material, the flow performance of the final modified material will also fluctuate greatly. When the modified material is injection molded or extruded, due to the instability of the flowability, it is difficult to continuously and stably produce.

[0024] In view of the instability of the recycled PBT source and the different melt flow rates, the low melt flow rate recycled PBT source process is simple, such as through one or two processing processes, while the high melt flow rate recycled PBT may have undergone multiple processing processes. The present application uses a compound containing an epoxy group capable of reacting with the terminal carboxyl group of recycled PBT or an ethylene-acrylic acid-glycidyl methacrylate terpolymer as a melt flow stabilizer, and at the same time, a certain amount of lubricant is compounded, so that the melt flowability of the final recycled flame-retardant reinforced modified polyester composite is relatively stable (even if the melt flow rate of the recycled PBT resin fluctuates by 50-100%, after using the scheme of the present application, the melt flow rate fluctuation range of the PBT flame-retardant reinforced material is controlled within 1-5%), the melt flow test value is not much different (the difference between the second and first melt flow, the difference fluctuation range is between-0.4-1.4), and the weight change of each cut sample is also relatively small. Compared with the cases of not using a stabilizer or not using enough stabilizer, and not using a lubricant or not using enough or too much lubricant, the melt flowability of the recycled flame-retardant reinforced modified polyester composite obtained by two tests fluctuates greatly (the difference between the second and first melt flow, the difference fluctuation range is between-3.6-15.6), and the weight change of each cut sample is also obvious. If the amount of stabilizer is too high, the melt flowability will decrease significantly and show a gradual decreasing trend, which may be due to the crosslinking reaction caused by the high content of epoxy. The lubricant plays a role in dispersing the stabilizer and the flame retardant in the base resin. If the lubricant is not used or the amount is not enough, the stabilizer and the flame retardant will be dispersed unevenly, resulting in large melt flowability fluctuation and unstable flame retardancy. If the amount of lubricant is too high, the melt strength of the recycled flame-retardant reinforced modified polyester composite will decrease, which will also produce flow instability and affect the flame retardant effect, and dripping will occur during combustion.

[0025] Advantages

[0026] The application has the stability of melt flow, and can be widely applied to the fields of heat dissipation fans, motor housings, relays and plugs and sockets in the electronic and electrical industries by realizing stable continuous production of structural and functional components through molding processes such as injection molding, extrusion and molding. DETAILED DESCRIPTION

[0027] The application will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the application and not used to limit the scope of the application. Furthermore, it should be understood that those skilled in the art can make various modifications or changes to the application after reading the content of the application, and these equivalent forms also fall within the scope of the appended claims.

[0028] The reagents, methods and equipment used in the application are conventional reagents, methods and equipment in the technical field unless otherwise specified.

[0029] The recycled PBT resin is obtained by collecting various types of waste PBT resin materials, classifying them according to their types, colors and uses, compressing and packaging the waste PBT resin materials, and then transporting them to a waste treatment plant.

[0030] In order to obtain a recyclable recycled PBT resin, various types of waste PBT resin materials are collected, classified according to their types, colors and uses, compressed and packaged, and then transported to a waste treatment plant. In the present application, the waste PBT resin materials are offcuts, rejects and scrap produced during the production of PBT filaments, PBT bristles and PBT films. After being identified, sorted, classified and picked out by experienced workers, the pure PBT bristles, filaments and film sheets are fed into a single-screw extruder, melted and extruded into granules, but the present application is not limited thereto.

[0031] The processing method of the recycled PBT resin includes, for example, physically and mechanically crushing a portion of the waste PBT resin material to reduce the time and energy required for melting and recycling the material, then melting the crushed recycled material to make it in a molten state, filtering the recycled material in a molten state with a screen to remove solid impurities from the recycled material, and finally extruding and granulating the filtered recycled material to form the recycled PBT resin with a certain melt flow rate and melt flow rate fluctuation rate. The present application is not limited thereto.

[0032] The raw materials used in the following examples and comparative examples are as follows:

[0033] PBT resin:

[0034] Recycled PBT resin A1 : Melt flow rate 20 g / 10 min @ 235 °C, 1.2 kg, Melt flow rate fluctuation 90 %;

[0035] Recycled PBT resin A2: Melt flow rate 37 g / 10 min @ 235 °C, 1.2 kg, Melt flow rate fluctuation 110 %;

[0036] Recycled PBT resin A3: Melt flow rate 50 g / 10 min @ 235 °C, 1.2 kg, Melt flow rate fluctuation 120 %;

[0037] Common virgin PBT resin A4: PBT GX121, Yizheng Chemical Fibre, Melt flow rate 8 g / 10 min @ 235 °C, 1.2 kg, Melt flow rate fluctuation 1-4 %;

[0038] Stabilizer:

[0039] B1 : Epoxy resin YD-019, epoxy equivalent weight 2800 g / eq, Guoduo Chemical;

[0040] B2: Ethylene-acrylate-glycidyl methacrylate terpolymer AX8750, GMA content 5 %, Arkema;

[0041] B3: Ethylene-acrylate-glycidyl methacrylate terpolymer AX8900, GMA content 8 %, Arkema;

[0042] B4: Epoxy resin YD-020, epoxy equivalent weight 4000 g / eq, Guoduo Chemical;

[0043] B5: Ethylene-acrylate-glycidyl methacrylate terpolymer ELVALOY 4170, GMA content 10 %, Dow Chemical;

[0044] Flame retardant:

[0045] Halogen-containing flame retardant: C1 : Brominated epoxy F-2100, Dead Sea Bromine;

[0046] Halogen-free flame retardant: C2: Aluminum diethylphosphinate EXOLIT OP 1230, Clariant;

[0047] Flame retardant synergist:

[0048] Halogen-containing flame retardant synergist, D1 : Antimony trioxide, S-05N, Chenzhou Antimony Industry;

[0049] Halogen-free flame retardant synergist, D2: Melamine polyphosphate MPP, Shouguang Weidong Chemical;

[0050] Toughening agent:

[0051] E1: EMA ethylene-methyl acrylate binary copolymer ELVALOY AC 1125, DuPont;

[0052] E2: EBA ethylene-butyl acrylate binary copolymer ELVALOY AC 34035, DuPont;

[0053] Nucleating agent, F: inorganic nucleating agent ultrafine talcum powder HTP Ultra 5, Liaoning Aihai;

[0054] Glass fiber:

[0055] G1: ECS 13-4.5-534A (glass fiber diameter 13 μm, Jushi Group);

[0056] G2: HMG 436S-10-4.0 (glass fiber diameter 10 μm, Taishan Glass Fiber Co., Ltd.);

[0057] Lubricant:

[0058] H1: oxidized polyethylene wax, PED 521, Clariant;

[0059] H2: pentaerythritol tetrastearate, PETS, Fosun;

[0060] Antioxidant, 1010 and 168 compounded at a ratio of 1:1, Lianglong.

[0061] The composite materials of each example and comparative example were prepared by the following process:

[0062] (1) The recycled PBT resin particles were dried at 130°C for more than 3 hours, with the moisture controlled to less than 0.03%;

[0063] (2) The various raw materials were prepared according to the proportions;

[0064] (3) The virgin PBT resin or the recycled PBT particles after drying treatment were mixed with the flame retardant, flame retardant synergist, stabilizer, antioxidant, nucleating agent, and lubricant in a proportioning mixer at high speed to obtain a premix or were separately fed into a premixer through a metering feeder.

[0065] (4) The above mixture was fed into a twin-screw extruder, the feeding amount was adjusted to 450-800 kg / hour, the glass fiber was added in proportion in the side feeding of the twin-screw extruder, the temperature of each section of the screw of the twin-screw extruder was 220°C, 230°C, 230°C, 240°C, 250°C, 240°C, 240°C, 230°C, and 240°C from the feeding port to the head, and the screw speed was 400 rpm. Under the conveying and shearing action of the twin-screw extruder, the materials were sufficiently melted, plasticized, kneaded, mixed, extruded through the head, drawn, cooled, cut, dried, and finally packaged.

[0066] The examples and comparative examples were subjected to the following test methods or test standards:

[0067] The products obtained by extrusion and pelletization were dried at 120-130°C for 3-4 hours; test samples were prepared by injection molding according to the corresponding standards.

[0068] Tensile strength was tested according to the ISO 527-2012 standard, and flame retardant performance was tested according to the UL 94-2020 standard;

[0069] Melt flow stability: using a melt flow index testing instrument, 8-10 g of sample particles were taken, dried at 120°C for 4 hours, then added to the melt flow index instrument cylinder, preheated at the set temperature for 4 min, then loaded, and the interval time between extrusion and cutting was 5 s, and 5 times were continuously cut. The interval time between the first 5 times and the second 5 times was 10 s, the weight of the cut sample was recorded, the weight change was observed, and the melt flow rate fluctuation was recorded.

[0070] Table 1 Comparison of components of examples and comparative examples

[0071]

[0072]

[0073]

[0074] Table 2 Test results of examples and comparative examples

[0075]

[0076]

[0077]

[0078]

[0079]

[0080]

[0081]

[0082]

[0083] From the test results of Examples 1-10, it can be seen that, after the scheme of the present application is adopted, the melt flow rate fluctuation range of the recycled PBT flame-retardant reinforced material can be controlled within 1-5%, which is similar to that of the common virgin PBT flame-retardant reinforced material of Example 11. From the comparison between Comparative Examples 1 and 4 and Example 1, it can be seen that, when no stabilizer or lubricant is added, the melt flow rate fluctuation range of the recycled PBT flame-retardant reinforced material is still large, and the flame-retardant performance is also poor. From Comparative Examples 2 and 3, it can be seen that, when the amount of the stabilizer is too large or too small, the technical effects as intended by the present application cannot be achieved. From Comparative Examples 5 and 6, it can be seen that, when the parameters for adding the stabilizer do not meet the above requirements, the technical effects as intended by the present application cannot be achieved either.

Claims

1. A melt flow stable PBT flame retardant reinforced material characterized in that: The raw materials include the following components by weight: PBT resin 30-50 parts; Stabilizer 2-8 parts; Flame retardant 8-15 parts; Flame retardant synergist 2.5-8 parts; Glass fiber 0-35 parts; Toughening agent 0-5 parts; Antioxidant 0-0.5 parts; Lubricant 0.5-1.5 parts; Nucleating agent 0-0.5 parts; The stabilizer is an epoxy resin with an epoxy equivalent weight of 2500-3000 g / eq and / or an ethylene-acrylate-glycidyl methacrylate terpolymer with a GMA content of 5-8%; the melt flow rate fluctuation of the PBT flame-retardant reinforced material is 1-5%; the PBT resin is a recycled PBT resin, the melt flow rate of the recycled PBT resin at 235℃ and 1.2 kg is 20-50 g / 10 min, and the melt flow rate fluctuation of the recycled PBT resin is 50-150%.

2. The melt flow stabilized PBT flame retardant reinforced material according to claim 1, characterized in that: The flame retardant is at least one of brominated epoxy resin, brominated polystyrene, brominated polycarbonate, and aluminum diethyl phosphinate; the flame retardant synergist is at least one of antimony trioxide, melamine polyphosphate, and melamine cyanurate; the toughening agent is at least one of ethylene-methyl acrylate copolymer EMA and ethylene-butyl acrylate copolymer EBA.

3. The melt flow stabilized PBT flame retardant reinforced material according to claim 1, characterized in that: The antioxidant is at least one of hindered phenolic antioxidant and phosphite antioxidant; the lubricant is at least one of aliphatic carboxylic acid ester and polyolefin wax lubricant; and the nucleating agent is ultra-fine talc powder with a particle size D50 of 0.5-0.7 μm.

4. The melt flow stabilized PBT flame retardant reinforced material according to claim 1, characterized in that: The addition amount of the stabilizer is 3-6 parts.

5. A preparation method of the melt flow stable PBT flame-retardant reinforced material according to claim 1, comprising the following steps: Mixing new PBT resin or pre-dried recycled PBT resin with other components except glass fiber in a high-speed stirring mixer according to the proportion to obtain a premix or feeding into a premixer through a metering feeder; feeding the premix into a twin-screw extruder, feeding glass fiber in the twin-screw extruder according to the proportion, melting, plasticizing, kneading, mixing, extruding through a die head, drawing, cooling, cutting, drying, and obtaining the melt flow stable PBT flame-retardant reinforced material.

6. The method of claim 5, wherein: The mixing temperature of the twin-screw extruder is 220-250℃, and the screw rotation speed is 300-500 rpm.

7. Application of the melt flow stable PBT flame-retardant reinforced material according to claim 1 in electronic and electrical devices.

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