A halogen-free flame-retardant outer mold material for a salt spray test data cable plug and its preparation method

Abstract

This invention discloses a halogen-free flame-retardant outer mold material for a data cable plug designed for salt spray testing, and its preparation method. The outer mold material comprises polypropylene resin, a toughening agent, an organosilicon-coated aluminum hypophosphite flame retardant, melamine cyanurate, a flame retardant synergist, a compatibilizer, an anti-aging agent, and a lubricant. This invention solves the problem of corrosion and blackening of the iron shell during salt spray testing of data cable plugs caused by the high water solubility and acidity of aluminum hypophosphite through organosilicon coating of the flame retardant. Simultaneously, the organosilicon-coated aluminum hypophosphite provides excellent scratch and abrasion resistance to the flame-retardant outer mold material.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, and more specifically, to a halogen-free flame-retardant outer mold material for a salt spray test data cable plug and its preparation method. Background Technology

[0002] Consumer electronics USB cables typically consist of a cable and USB Type A and USB Type C plugs. The plug body includes a nickel-plated iron shell and a flame-retardant outer mold material. As fast charging in consumer electronics becomes increasingly popular, USB cable materials require the cable sheath and outer mold material to have good flame-retardant properties. Since the phosphorus-nitrogen halogen-free system of aluminum hypophosphite combined with melamine cyanurate has very good flame-retardant properties for the outer mold material, most outer mold materials on the market currently use this phosphorus-nitrogen halogen-free flame-retardant system.

[0003] Because aluminum hypophosphite has a certain degree of water solubility and is also highly acidic, the outer mold material prepared using this halogen-free flame retardant system is significantly acidic. During the plug salt spray test, a 5% sodium chloride solution was sprayed onto the plug at 35°C for 48 hours. Due to the acidity of the aluminum hypophosphite flame retardant itself and the hypophosphite produced by the trace hydrolysis of aluminum hypophosphite, the plating of the nickel-plated iron shell was corroded and damaged, partially exposing the inner layer of the carbon steel shell. Once the protective nickel layer was damaged, the carbon steel inside underwent galvanic corrosion in the salt spray. The carbon in the carbon steel acted as the cathode, and oxygen and water underwent a reduction reaction in the cathode. The tinplate acted as the anode, undergoing an oxidation reaction. The combined reaction formed dark-colored ferric hydroxide, ferric chloride, and other colored substances, resulting in obvious discoloration of the plug.

[0004] If other phosphorus-containing flame retardants are directly chosen for the modification of the outer mold material, such as piperazine pyrophosphate, melamine polyphosphate, and ammonium polyphosphate systems, these three types of flame retardants are all acidic. Not only will they fail to solve the salt spray problem, but they will also fail the double 85 high temperature and high humidity (85℃, 85% relative humidity) precipitation test of the outer mold material. If diethylphosphonate aluminum flame retardant is chosen, its initial decomposition temperature (around 400℃) is too high and does not match the initial decomposition temperature of the polypropylene substrate (around 290℃). Therefore, it is difficult to pass the 6mm V0 test during flame retardant combustion. Furthermore, diethylphosphonate aluminum is also weakly acidic, and while its hydrolysis resistance is significantly improved, it still cannot stably pass the salt spray test. Therefore, the salt spray test is a crucial indicator limiting the performance of halogen-free flame-retardant outer mold materials. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned defects in the prior art and provide a halogen-free flame-retardant outer mold material for salt spray test data cable plugs and its preparation method.

[0006] To achieve the above objectives, a first aspect of the present invention provides a method for preparing a halogen-free flame-retardant outer mold material for a salt spray test data cable plug, comprising the following steps:

[0007] 40-60 parts of polypropylene resin, 2-8 parts of toughening agent, 8-12 parts of silicone-coated aluminum hypophosphite flame retardant, 22-28 parts of melamine cyanurate, 0.1-0.5 parts of flame retardant synergist, 1-3 parts of compatibilizer, 0.5-1 part of anti-aging agent, and 0.5-2 parts of lubricant are mixed evenly in a high-speed mixer and then extruded and granulated in a twin-screw extruder at 190-200℃ to obtain halogen-free flame-retardant outer mold material for salt spray resistant data cable plugs.

[0008] The preparation method of the organosilicon-coated aluminum hypophosphite flame retardant includes the following steps:

[0009] Add 0.005~0.01 parts of catalyst to 1~2 parts of vinyl-terminated silicone oil, and stir at 250~350 rpm for 5~10 minutes at 20~30℃ to mix them evenly, and then seal and store the catalyst mixture.

[0010] Add 5-10 parts of vinyl-terminated silicone oil and 0.1-0.5 parts of hydrogen-containing silicone oil with silanol side chains to 450-600 parts of ethyl acetate solution. Stir at 250-350 rpm for 1-3 minutes at 20-30°C. Then add 100-200 parts of aluminum hypophosphite flame retardant and stir at 250-350 rpm for 5-10 minutes to form a uniformly dispersed powder mixture. Next, add the prepared catalyst mixture and continue mixing at 20-30°C for 10-15 minutes. Then filter and wash the powder mixture. Heat the obtained flame retardant solid at 100-120°C for 20-30 minutes and finally pulverize to obtain organosilicon-coated aluminum hypophosphite flame retardant.

[0011] Preferably, the catalyst is an organosilicon coordination of platinum, having a structure of platinum(O)-1,3-diethylene-1,1,3,3-tetramethyldisiloxane (CAS No. 68478-92-2) and bis(1,3-divinyl-1,1,3,3-tetramethyldisiloxane)platinum (CAS No. 81032-58-8) or a mixture of both.

[0012] Preferably, the vinyl-terminated silicone oil has a viscosity of 1000~5000 cP / 20~30℃ and a vinyl content of 0.06~0.11 mmol / g; the hydrogen-containing silicone oil with hydroxyl groups in the side chain has a viscosity of 50~500 cP / 20~30℃ and a hydroxyl group content of 1~6 mmol / g.

[0013] By uniformly dispersing terminal vinyl silicone oil and side-chain silane-containing hydrogen silicone oil in an ethyl acetate solution, the surface of aluminum hypophosphite flame retardant particles can effectively adsorb terminal vinyl silicone oil and side-chain silane-containing hydrogen silicone oil. Under the catalytic action of the organosilicon coordination of platinum metal, the terminal vinyl silicone oil and side-chain silane-containing hydrogen silicone oil are cured on the surface of aluminum hypophosphite particles into a thin-layer vulcanized silicone rubber.

[0014] The reaction mechanism is shown in the figure below:

[0015]

[0016] Preferably, the particle size range of the aluminum hypophosphite flame retardant is 20~40µm.

[0017] Due to its large specific surface area, aluminum hypophosphite adsorbs most of the terminal vinyl silicone oil and the hydrogen-containing silicone oil with silanol side chains. The unadsorbed terminal vinyl silicone oil and the hydrogen-containing silicone oil with silanol side chains are separated by vacuum filtration. By selecting the optimal aluminum hypophosphite particle size, filter paper or filter cloth with a pore size of 15~20µm is selected for vacuum filtration to separate the surface-modified aluminum hypophosphite flame retardant.

[0018] Preferably, the polypropylene resin is composed of homopolymer polypropylene and random copolymer polypropylene, wherein the melt index of the homopolymer polypropylene is 30~50g / 10min (230℃, 2.16kg), the melt index of the random copolymer polypropylene is 10~30g / 10min (230℃, 2.16kg), and the mass ratio of homopolymer polypropylene to random copolymer polypropylene is 3:1~1:1.

[0019] Data cables in consumer electronics devices must undergo a 136°C high-temperature cracking test, requiring the plug's outer mold material to remain crack-free. Furthermore, since the outer mold material is injection molded onto a nickel-plated iron shell, polypropylene exhibits a significant shrinkage tendency after injection molding. This necessitates the outer mold material to withstand certain stresses, requiring it to possess good toughness. Homopolymer polypropylene has high heat resistance, while random copolymer polypropylene has high impact strength. Using both in combination balances the material's heat resistance and toughness.

[0020] Preferably, the toughening agent is a propylene-based elastomer, wherein, by mass percentage, the propylene unit accounts for 85% to 95% and the ethylene unit accounts for 5% to 15%.

[0021] Propylene-based elastomers and polypropylene substrates have excellent compatibility, and can further improve the toughness of the outer mold material.

[0022] Preferably, the compatibilizer is polypropylene grafted with maleic anhydride, the grafting rate of maleic anhydride is 0.6~1.2%, and the melt index is 10~20g / 10min (190℃, 0.325kg).

[0023] Polypropylene grafted with maleic anhydride can effectively improve the compatibility between powder flame retardants and polypropylene resin, and enhance the material's impact strength and scratch resistance.

[0024] Preferably, the flame retardant synergist is polycarboxylate.

[0025] Polymers contain unstable C-C bonds in their molecular structure, which are easily broken when heated to generate free radicals. These free radicals can effectively capture highly reactive free radicals (such as OH· and H·) generated during polymer combustion, interrupting the chain reaction of combustion and thus slowing down the spread of flames.

[0026] Preferably, the lubricant is a dispersion of high molecular weight siloxane in polypropylene; more preferably, it can be an ultra-high molecular weight silicone masterbatch.

[0027] Preferably, the anti-aging agent is one or a combination of antioxidant 1024 (CAS No. 32687-78-8), light stabilizer 622 (CAS No. 70198-29-7), and ultraviolet absorber UV234 (CAS No. 70321-86-7).

[0028] The data cable plug has copper wire bonding points inside the outer mold. Antioxidant 1024 has a dual structure of hindered phenol and hydrazide, which can provide good antioxidant performance. At the same time, the hydrazide structure can complex copper ions and has a good anti-copper effect. The combination of light stabilizer 622 and ultraviolet absorber UV234 can improve the yellowing resistance of the outer mold material during long-term use.

[0029] A second aspect of the present invention provides a halogen-free flame-retardant outer mold material for a salt spray test data cable plug, comprising the following raw materials by weight:

[0030] The ingredients are: 40-60 parts polypropylene resin, 2-8 parts toughening agent, 8-12 parts organosilicon-coated aluminum hypophosphite flame retardant, 22-28 parts melamine cyanurate, 0.1-0.5 parts flame retardant synergist, 1-3 parts compatibilizer, 0.5-1 part anti-aging agent, and 0.5-2 parts lubricant.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] (1) In this invention, a layer of hydrophobic, self-lubricating and high-toughness organosilicon is sulfided on the surface of aluminum hypophosphite in ethyl acetate solution to form a dense core-shell structure of aluminum hypophosphite-organosilicon sulfidation, which improves the hydrophobicity of the flame retardant. By utilizing its self-lubricating properties and high toughness, the problem of coating layer cracking of conventional aluminum hypophosphite coating materials under the shear force of twin-screw processing is solved.

[0033] (2) This invention uses homopolymer polypropylene, random copolymer polypropylene and propylene-based elastomer as base materials to prepare data cable plug outer mold material. It makes balanced use of the heat resistance of homopolymer polypropylene and the toughness of random copolymer polypropylene, and further uses propylene-based elastomer to improve the toughness of the system. The prepared halogen-free flame-retardant outer mold material for data cable plug has high resistance to stress cracking and high temperature cracking.

[0034] (3) The present invention utilizes poly-linked flame retardant synergist, which can significantly reduce the amount of coated aluminum hypophosphite, thereby reducing costs and improving the pass rate of plug salt spray test.

[0035] (4) The present invention utilizes the prepared organosilicon-coated aluminum hypophosphite flame retardant to solve the problem that the halogen-free flame retardant outer mold material prepared by aluminum hypophosphite has high water solubility and high acidity, and the iron shell of the prepared material corrodes and turns black during the salt spray test of the data cable plug. At the same time, the organosilicon-coated aluminum hypophosphite provides excellent scratch resistance and wear resistance for the flame retardant outer mold material. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] The preparation methods of the organosilicon-coated aluminum hypophosphite flame retardants in the examples and comparative examples include the following steps:

[0038] Add 0.008 parts of catalyst to 1.8 parts of vinyl-terminated silicone oil, and stir at 300 rpm for 6 minutes at 25°C to mix them evenly, and then seal and store the catalyst mixture.

[0039] Eight parts of vinyl-terminated silicone oil and 0.4 parts of hydrogen-containing silicone oil with silanol side chains were added to 500 parts of ethyl acetate solution. The mixture was stirred at 300 rpm for 2 minutes at 25°C. Then, 120 parts of aluminum hypophosphite flame retardant with a particle size range of 20-40 µm were added and stirred at 300 rpm for 8 minutes to form a uniformly dispersed powder mixture. Next, the prepared catalyst mixture was added and the mixture was continuously mixed at 25°C for 12 minutes. The powder mixture was filtered through filter paper with a pore size of 15-20 µm and washed twice with ethyl acetate. The obtained flame retardant solid was heated at 100°C for 25 minutes and finally pulverized to obtain organosilicon-coated aluminum hypophosphite flame retardant.

[0040] The following details the specific grades of raw materials used in the examples and comparative examples: the vinyl-terminated silicone oil is Andisil® VS 2000 from Ambiar Specialty Silicones (Nantong) Co., Ltd.; the hydrogen-containing silicone oil with hydroxyl side chains is Andisil® XL 1340 from Ambiar Specialty Silicones (Nantong) Co., Ltd.; the homopolymer polypropylene is PP 1250 from Formosa Plastics Industrial (Ningbo) Co., Ltd.; the random copolymer polypropylene is PP 5090T from Formosa Plastics Industrial (Ningbo) Co., Ltd.; the propylene-based elastomer is ExxonMobil's Vistamaxx 3980FL; the compatibilizer is PC-1 from Foshan Nanhai Baichen Polymer New Materials Co., Ltd.; and the lubricant is Dow Corning MB 50-001.

[0041] Examples 1-5

[0042] The halogen-free flame-retardant outer mold material for a salt spray test data cable plug provided in Examples 1-5 is prepared by the following method:

[0043] (1) Add all raw materials into a high-speed mixer according to the mass fractions and mix at a mixing speed of 200 rpm / min for 4 min to obtain a mixture;

[0044] (2) The mixture is fed into a twin-screw extruder and extruded and granulated at 190~200℃ to obtain halogen-free flame-retardant outer mold material for salt spray resistant data cable plugs.

[0045] Comparative Examples 1-5

[0046] The preparation methods for Comparative Examples 1-5 are the same as those for the Examples. Specifically, Comparative Example 1 is based on Example 1, except that the self-made organosilicon-coated aluminum hypophosphite is replaced with commercially available aluminum hypophosphite; Comparative Example 2 is based on Example 2, except that the self-made organosilicon-coated aluminum hypophosphite is replaced with diethylphosphinate aluminum; Comparative Example 3 is based on Example 3, except that all random copolymer polypropylene is replaced with homopolymer polypropylene; Comparative Example 4 is based on Example 4, except that the polypropylene synergistic flame retardant is removed; and Comparative Example 5 is based on Example 5, except that all homopolymer polypropylene is replaced with random copolymer polypropylene.

[0047] Table 1: Raw material composition and parts for the examples and comparative examples

[0048]

[0049]

[0050] The halogen-free flame-retardant outer mold materials for data cable plugs obtained in Examples 1-5 and Comparative Examples 1-5 were subjected to physical property testing. At the same time, the obtained materials were subjected to data cable outer mold injection molding application tests. The injection molding process was 210-220℃ in the plasticizing section and 220-230℃ in the die head and eye mold. The results are shown in Table 2.

[0051] Table 2: Results of physical property testing, external mold injection molding testing, and finished plug testing for Examples 1-5 and Comparative Examples 1-5

[0052]

[0053]

[0054] Note: A total of 1000 samples were collected for the injection molding of the outer mold. After injection molding, the samples were placed at 20~30℃ for 24 hours, and the number of abnormal cracks was counted. The high-temperature cracking test conditions for the plugs were as follows: 10 plugs with normal appearance were placed in an oven at 136℃ for 168 hours. After the test, they were placed at 20~30℃ for 24 hours. If even one plug cracked, it was judged as NG. The salt spray test method was to use a 5% sodium chloride solution with the pH value controlled at 6.5~7.2 and the test temperature at 35℃±2℃. The plugs were sprayed continuously for 48 hours. If even one nickel-plated iron shell changed color, it was judged as NG.

[0055] Based on the test data, Examples 1-5 balanced the heat resistance of homopolymer polypropylene and the toughness of random copolymer polypropylene, and further improved the toughness of the system by using propylene-based elastomers. The halogen-free flame-retardant outer mold material prepared by using silicone-coated aluminum hypophosphite flame retardant, melamine cyanurate (MCA) and polymethyl methacrylate flame retardant synergist has good flame retardant properties, impact resistance and heat resistance. The outer mold injection molding process is stable and without abnormalities, and the finished plug has passed the salt spray test. Comparative Example 1, based on Example 1, replaced the silicone-coated aluminum hypophosphite with a commercially available aluminum hypophosphite flame retardant. The material properties and the external mold injection molding process were normal, but the plug failed the salt spray test. Comparative Example 2, based on Example 2, replaced the aluminum hypophosphite coating with diethylphosphite aluminum, which has lower water solubility. The prepared external mold material failed the 6mm V0 test, and the finished plug also failed the salt spray test. Comparative Example 3, based on Example 3, used only homopolymer polypropylene. Although the prepared external mold material had a high Vicat softening point, its impact strength was low, and the cracking defect rate during the external mold injection molding process reached 1.5%, which did not meet the requirements. Comparative Example 4, based on Example 4, removed the flame retardant synergist. The prepared external mold material failed the 6mm V0 test. Comparative Example 5, based on Example 5, used only random copolymer polypropylene. Although the prepared external mold material had good impact performance, its Vicat softening point was low, and it failed the high-temperature cracking test of the finished plug.

[0056] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention are permitted.

Claims

1. A method for preparing a halogen-free flame-retardant outer mold material for a salt spray test data cable plug, characterized in that, Includes the following steps: 40-60 parts of polypropylene resin, 2-8 parts of toughening agent, 8-12 parts of silicone-coated aluminum hypophosphite flame retardant, 22-28 parts of melamine cyanurate, 0.1-0.5 parts of flame retardant synergist, 1-3 parts of compatibilizer, 0.5-1 part of anti-aging agent, and 0.5-2 parts of lubricant are mixed evenly in a high-speed mixer and then extruded and granulated in a twin-screw extruder at 190-200℃ to obtain halogen-free flame-retardant outer mold material for salt spray resistant data cable plugs. The preparation method of the organosilicon-coated aluminum hypophosphite flame retardant includes the following steps: Add 0.005~0.01 parts of catalyst to 1~2 parts of vinyl-terminated silicone oil, and stir at 250~350 rpm for 5~10 minutes at 20~30℃ to mix them evenly, and then seal and store the catalyst mixture. Add 5-10 parts of vinyl-terminated silicone oil and 0.1-0.5 parts of hydrogen-containing silicone oil with silanol side chains to 450-600 parts of ethyl acetate solution. Stir at 250-350 rpm for 1-3 minutes at 20-30°C. Then add 100-200 parts of aluminum hypophosphite flame retardant and stir at 250-350 rpm for 5-10 minutes to form a uniformly dispersed powder mixture. Next, add the prepared catalyst mixture and continue mixing at 20-30°C for 10-15 minutes. Then filter and wash the powder mixture. Heat the obtained flame retardant solid at 100-120°C for 20-30 minutes and finally pulverize to obtain organosilicon-coated aluminum hypophosphite flame retardant.

2. The preparation method according to claim 1, characterized in that, The vinyl-terminated silicone oil has a viscosity of 1000~5000 cP / 20~30℃ and a vinyl content of 0.06~0.11 mmol / g; the hydrogen-containing silicone oil with silanol groups in the side chain has a viscosity of 50~500 cP / 20~30℃ and a silanol group content of 1~6 mmol / g.

3. The preparation method according to claim 1, characterized in that, The catalyst is configured as an organosilicon coordination of platinum, and its structure is one or a mixture of two of platinum(O)-1,3-diethylene-1,1,3,3-tetramethyldisiloxane and bis(1,3-divinyl-1,1,3,3-tetramethyldisiloxane)platinum.

4. The preparation method according to claim 1, characterized in that, The particle size range of the aluminum hypophosphite flame retardant is 20~40µm.

5. The preparation method according to claim 1, characterized in that, The polypropylene resin is composed of homopolymer polypropylene and random copolymer polypropylene. The melt index of the homopolymer polypropylene is 30~50g / 10min (230℃, 2.16kg), and the melt index of the random copolymer polypropylene is 10~30g / 10min (230℃, 2.16kg). The mass ratio of homopolymer polypropylene to random copolymer polypropylene is 3:1~1:

1.

6. The preparation method according to claim 1, characterized in that, The toughening agent is configured as a propylene-based elastomer, wherein, by mass percentage, the propylene unit accounts for 85% to 95% and the ethylene unit accounts for 5% to 15%.

7. The preparation method according to claim 1, characterized in that, The compatibilizer is polypropylene grafted with maleic anhydride, with a grafting rate of 0.6-1.2% and a melt index of 10-20 g / 10 min (190℃, 0.325 kg).

8. The preparation method according to claim 1, characterized in that, The flame retardant synergist is polymethyl methacrylate, and the lubricant is ultra-high molecular weight silicone masterbatch.

9. The preparation method according to claim 1, characterized in that, The anti-aging agent is configured as one or a combination of antioxidant 1024, light stabilizer 622 and ultraviolet absorber UV234.

10. A halogen-free flame-retardant outer mold material for a salt spray test data cable plug, characterized in that, By mass parts Including the following raw materials: The ingredients are: 40-60 parts polypropylene resin, 2-8 parts toughening agent, 8-12 parts organosilicon-coated aluminum hypophosphite flame retardant, 22-28 parts melamine cyanurate, 0.1-0.5 parts flame retardant synergist, 1-3 parts compatibilizer, 0.5-1 part anti-aging agent, and 0.5-2 parts lubricant.

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