A high flame-retardant, low smoke density, and low heat release polyethylene material, its preparation and application.

Abstract

This invention relates to a polyethylene material with high flame retardancy, low smoke density, and low heat release, as well as its preparation and application. The material comprises the following raw material components in parts by weight: PE 50-90 parts; organophosphorus flame retardant 0.1-30 parts; organosilicon flame retardant 0.1-25 parts; ceramic charring agent 0.1-3 parts; ionic liquid flame retardant 0.1-10 parts; lubricant 0.1-5 parts; and antioxidant 0.1-5 parts. The PE material prepared by this invention can reliably pass tests such as UL94V-0 rating at a 0.8mm size, and also possesses excellent mechanical properties, solving problems such as low flame retardancy, significant mechanical impact, and high smoke / heat release in polyethylene parts.

Description

Technical Field

[0001] This invention belongs to the field of flame retardant materials technology, and relates to a polyethylene material with high flame retardancy, low smoke density, and low heat release, as well as its preparation and application. Background Technology

[0002] Polyethylene (PE) is a thermoplastic polymer material produced by the polymerization of ethylene. PE materials with different degrees of polymerization and molecular chain structures have different properties. Based on molecular weight differences, PE materials can also be divided into high-density polyethylene (HDPE), ultra-high-density polyethylene (UHMWPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE), among others. Due to its long-chain chemical structure, PE has excellent aging resistance and acid and alkali resistance. Its long-chain structure also gives it excellent flexibility and processing window, making it widely used in industries such as chemical engineering, optical fiber cables, packaging pipes, and construction. However, precisely because of PE's long, straight carbon chain structure, it is difficult for it to form charcoal when ignited, and it produces significant molten droplets, posing a serious fire risk. Furthermore, the absence of side chains in the PE material structure means that its main chain bond energy is higher than that of the side chain bond energy, making it difficult for traditional flame retardants to extract carbon elements from the PE molecule's main chain to form an expanded carbon layer.

[0003] Traditional halogenated flame retardants are being phased out due to regulatory restrictions and the risk of carcinogens, while halogen-free flame retardants are becoming a research trend due to their safety and high efficiency. Hydroxides, as commonly used inorganic flame retardants, require an addition of over 50% to achieve a V-0 rating in PE materials; such a high addition significantly degrades the material's mechanical properties. High-polymerization-degree ammonium polyphosphate, with its excellent thermal decomposition temperature and phosphorus content, forms a highly efficient intumescent flame retardant when combined with char-forming agents, and is widely used in polyolefin materials. However, when this system is applied to PE materials, it still severely impacts the mechanical properties of PE itself. Furthermore, during processing, the significant polarity difference between ammonium polyphosphate and PE can easily lead to precipitation and white spots.

[0004] Therefore, current flame-retardant modifications of PE materials are increasingly focused on high efficiency, low toxicity, and low smoke. Chinese patent CN202210414492.3 provides a halogen-free, environmentally friendly flame-retardant polyethylene material and its preparation method. This invention first prepares a novel NPB halogen-free, environmentally friendly flame retardant, and then uses this flame retardant to modify polyethylene through blending. The NPB flame retardant is prepared by first reacting phenylboronic acid and triethanolamine to prepare compound A, then reacting compound A with methanol, ammonia, and phosphorus trichloride to prepare compound B, and finally isomerizing compound B to obtain compound C. This flame retardant not only does not contain halogens and has good environmental performance, but it also comprehensively leverages the advantages of N-series, P-series, and B-series flame retardants, achieving a good flame-retardant effect on polyethylene. However, it does not address issues such as smoke release from PE materials. Furthermore, with the increasing demands for flame-retardant performance of PE materials, this patent also fails to address the issue of high flame retardancy at thinner component thicknesses.

[0005] PE is used in thin-walled or even film products. Traditional char-forming flame retardant systems are difficult to achieve high flame retardancy ratings. Furthermore, as the comprehensive performance requirements of cables and electronic devices become increasingly stringent, the requirements for materials such as smoke density and heat release are also becoming more and more stringent.

[0006] Currently, few patents can simultaneously solve the following problems in the application of PE materials:

[0007] 1) Due to the long carbon chain structure of PE material, it is difficult to form char in time, making it difficult to achieve a high flame retardant rating at a thickness as low as 0.8mm;

[0008] 2) Smoke and heat hazards are the primary hazards of fire. Significantly reducing the low smoke and heat release during the combustion of PE materials is particularly important for the main application areas of PE materials.

[0009] 3) Maintain the high mechanical properties of PE materials while ensuring flame retardancy, low smoke, and low heat hazard. Summary of the Invention

[0010] The purpose of this invention is to provide a polyethylene material with high flame retardancy, low smoke density, and low heat release, as well as its preparation and application, to solve at least one of the problems existing in PE parts, such as low flame retardancy rating, large mechanical impact, and high flame retardancy due to smoke / heat release.

[0011] The objective of this invention can be achieved through the following technical solutions:

[0012] One of the technical solutions of the present invention provides a polyethylene material with high flame retardancy, low smoke density, and low heat release, comprising the following raw material components in parts by weight:

[0013]

[0014] Furthermore, the component proportions of this polyethylene material are as follows:

[0015]

[0016] Furthermore, the organophosphorus flame retardant is preferably present in 5-25 parts by weight, more preferably in 10-25 parts by weight.

[0017] More specifically, the preferred amount of silicone flame retardant is 4-15 parts, more preferably 10-15 parts.

[0018] Furthermore, the PE is one of high-density polyethylene, low-density polyethylene, and linear low-density polyethylene.

[0019] Furthermore, the organophosphorus flame retardant is an organophosphorus flame retardant with a phosphorus content >12%, a melting point >200℃, and a decomposition temperature >200℃.

[0020] Furthermore, the organophosphorus flame retardant is a flame retardant containing a cyclic structure, and its chemical structure is as follows:

[0021]

[0022] Wherein, X1 and X2 are independently selected from alkyl, triazine, phenyl, naphthyl, and anthracene, respectively. More specifically, X1 and X2 are phenyl.

[0023] Furthermore, the organosilicon flame retardant is a cage-like polysilsesquioxane with the structural formula (R1SiO2). 3 / 2 ) n Wherein, R1 is methyl, vinyl, amino, or phenyl, and the Si content is >10%, and n is a positive integer. Preferably, R1 is vinyl.

[0024] Furthermore, the ceramic charring agent is selected from one or a mixture of several of hollow glass microspheres, zinc borate, boron nitride, and aluminum hydroxide. It exhibits melting properties at high temperatures and, during combustion, can form a cross-linked ceramic structure with SiO2 formed by the organosilicon flame retardant, thereby inhibiting material combustion.

[0025] Furthermore, the ionic liquid flame retardant is one or a mixture of several ionic liquids containing borate, sulfonate, or phosphate structures. Preferably, the ionic liquid flame retardant is an ionic liquid with a phosphate anionic structure and a thermal decomposition temperature >200°C. This ionic liquid structure has a relatively reasonable P / N ratio, thus it can exert a flame-retardant effect simultaneously in the condensed phase and the gas phase during combustion. Furthermore, the high-valence P element it contains has a superior char-promoting effect.

[0026] More preferably, the structure of the ionic liquid is as follows:

[0027]

[0028] Furthermore, the lubricant is one or more of the following: natural paraffin wax, liquid paraffin wax, microcrystalline wax, polyethylene wax, butyl stearate, oleamide, ethylene bis-stearamide, and silicone powder.

[0029] Furthermore, the antioxidant is one or more of the following: 2,6-di-tert-butyl-p-cresol, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)trimethylbenzene, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), and 4,4'-di-tert-octyldiphenylamine.

[0030] The second technical solution of the present invention provides a method for preparing a polyethylene material with high flame retardancy, low smoke density, and low heat release, comprising the following steps:

[0031] Weigh each component according to the weight proportions and mix them evenly to obtain the base material-additive composition;

[0032] The additive-base composition is added to a twin-screw extruder, mixed and extruded to obtain the target product.

[0033] Furthermore, the raw material components are mixed in a triaxial multi-functional mixer with different rotation speeds for the three shafts, while the inner and outer shafts rotate in the same direction. Specifically, the A shaft rotates at 20-40 rpm, the B shaft at 10-20 rpm, and the C shaft at 10-20 rpm.

[0034] Furthermore, the operating vacuum pressure of the twin-screw extruder is 20-30 kPa, the main engine speed is 200-300 rpm, the feeding frequency is 20-30 Hz, and the temperatures of the melting section, conveying section, mixing section, homogenizing section, and metering section are 180-200℃, 180-200℃, 180-200℃, 180-200℃, and 180-200℃, respectively.

[0035] Furthermore, the twin-screw extruder is a type 20 co-rotating twin-screw extruder, and its screw structure is as follows: the melting section uses a small-lead conveying screw, the conveying section uses a large-lead conveying screw, the mixing section uses a superposition of 30°, 60°, and 30° shearing screws, the homogenization section uses a superposition of 30° shearing screws and large-lead conveying screws, and the metering section uses a superposition of large-lead conveying screws and reverse screws to establish pressure and increase distribution capacity.

[0036] Furthermore, the polyethylene granules obtained by the twin-screw extruder are dried at 80°C for 4 hours before being placed in an injection molding machine for further processing.

[0037] The third technical solution of the present invention provides an application of a high flame retardant, low smoke density, and low heat release polyethylene material in the preparation of high-voltage cables, optical cables, low smoke halogen-free cables and other PE products.

[0038] Compared with the prior art, the present invention has the following advantages:

[0039] 1) The high flame retardancy, low smoke density, and low heat release polyethylene material of the present invention addresses the defect that PE material is difficult to char in time under thin dimensions. It adopts a composite of organophosphorus and organosilicon flame retardants. The phosphoric acid structure produced when organophosphorus decomposes can promote the char formation of PE and organosilicon, forming a P-Si shell structure, thus overcoming the problems of dripping and charring under thin dimensions.

[0040] 2) Introducing a ceramicized charring agent forms a stable and robust ceramicized structure during combustion, further increasing the charring effect of the PE material and suppressing the release of internal heat and flue gas, achieving a low-smoke and low-heat release effect.

[0041] 3) An ionic liquid containing phosphoric acid structure was introduced. On the one hand, it has a catalytic effect on reactions such as Friedel-crafts alkylation, which can improve the char content and reduce the generation of flue gas. On the other hand, the ionic liquid can be adsorbed on the interior and surface of the lamellae ceramic charring agent through electrostatic interaction, which increases the dispersibility of the ceramic charring agent, improves the flame retardant efficiency, and reduces the impact on mechanical properties. Detailed Implementation

[0042] The present invention will now be described in detail with reference to specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0043] The components used in the following embodiments are as follows:

[0044] Commercially available low-density polyethylene (component A): grade 2102TN00, purchased from Qilu Petrochemical;

[0045] Organophosphorus flame retardant (component B): brand name FCX-210, purchased from Teijin Corporation, Japan;

[0046] Polysilsesquioxane (component C): Spherical silicone resin micro powder of grade HY-7000, purchased from Hangzhou Yuheng Technology Co., Ltd.

[0047] Ceramic carbonization agent (component D): Boron nitride, grade NS-BN, purchased from Suzhou Napu Materials Technology Co., Ltd.

[0048] Ionic liquid flame retardant (component E): 1-Butyl-3-methylimidazolium dibutyl phosphate salt, purchased from Shanghai Chengjie Chemical Co., Ltd.;

[0049] Lubricant (component F): Silicone powder (Hangzhou Kaijie Plastics Technology Co., Ltd.);

[0050] Antioxidant (component G): Grade AT-10 (Albemarle Chemicals Ltd.);

[0051] 1-Butyl-3-methylimidazolium p-toluenesulfonate (component H): purchased from Shanghai Chengjie Chemical Co., Ltd.

[0052] The testing methods and standards for PE materials are as follows:

[0053] According to UL94, the following fire resistance categories are obtained:

[0054] HB: The lowest flame retardant rating in the UL94 standard. Requirements include a burning rate of less than 40 mm / min for samples 3 to 13 mm thick; a burning rate of less than 70 mm / min for samples less than 3 mm thick; or extinguishing before reaching the 100 mm mark.

[0055] V-2: After two 10-second burning tests on the sample, the flame extinguishes within 30 seconds. It can ignite cotton wool up to 30cm below.

[0056] V-1: After two 10-second burning tests on the sample, the flame extinguishes within 30 seconds. It cannot ignite cotton wool 30cm below.

[0057] V-0: After two 10-second burning tests on the sample, the flame extinguishes within 10 seconds. No burning material should fall.

[0058] The smoke density of the sample was determined according to GB / T 8323.2-2008 Plastic Smoke Generation Part 2: Test Method for Determination of Smoke Density by Single Chamber Method. DSn means the smoke density value at the nth minute.

[0059] A micro calorimeter was used to test parameters such as the peak heat release and total heat release of the material.

[0060] The tensile strength and elongation at break of the product were tested in accordance with GB / T 1040.1-2018 "Determination of tensile properties of plastics".

[0061] The sample size was 120×6.5×3.2mm, and the test was conducted on an HC-2 oxygen index tester (Jiangning Analytical Instrument Factory) according to ASTM D 2863-70 standard.

[0062] In addition, the embodiments of the present invention provide a specific process for preparing flame-retardant plastic molding materials:

[0063] The base material and additive components were mixed evenly in the proportions given in Table 1 and fed into the feed port of a twin-screw extruder (type 20). The homogenized polymer was pulled out, cooled in a water bath, and then granulated. After thorough drying, the molding compound was processed into test samples at a material temperature of 200°C on an injection molding machine and tested.

[0064] In the embodiments of the present invention, the operating vacuum pressure of the twin-screw extruder is controlled at around 25 kPa. The temperatures of the melting section, conveying section, mixing section, homogenizing section, and metering section of the twin-screw extruder are approximately 180°C, 200°C, 200°C, 200°C, and 200°C, respectively. The twin-screw extruder is a type 20 co-rotating twin-screw extruder, with its vacuum port located between the mixing and homogenizing sections. The screw structure of the type 20 co-rotating twin-screw extruder is as follows: the melting section uses a small-lead conveying thread; the conveying section uses a large-lead conveying thread; the mixing section uses a combination of 30°, 60°, and 30° shear threads; the homogenizing section uses a combination of 30° shear threads and large-lead conveying threads; and the metering section uses a combination of large-lead conveying threads and reverse threads.

[0065] In addition, unless otherwise stated, all comparisons were conducted under the same conditions (temperature program, screw structure, injection parameters) for each series of tests.

[0066] Examples 1-8 and Comparative Examples 1-7:

[0067] Table 1 provides specific data for the examples and comparative examples. Examples 1 to 3 analyze the effects of using different amounts of organophosphorus flame retardants alone on the flame retardant properties, smoke density, heat release, and mechanical properties of PE materials. It is evident that the chemical structure of FCX-210, with its phosphorus content exceeding 15%, significantly improves the flame retardant properties of PE materials. However, due to the high bond energy of the PE main chain and the lack of side chain groups, it is difficult for the phosphoric acid structure released from FCX-210 to be extracted and promote the formation of a char layer. Therefore, although its flame retardant effect is improved, it does not pass the V-0 rating at 1.6 mm and 0.8 mm thicknesses.

[0068] Examples 4-5 analyzed the effects of different ratios of organophosphorus and organosilicon composites on the material properties. The results showed that the composite use of organophosphorus and organosilicon exhibited a significant synergistic effect, with the LOI increasing to 27.5%, and reliably passing the V-0 level at a size of 1.6 mm. However, it only achieved the V-2 level at a size of 0.8 mm.

[0069] Based on this, Examples 6-7 introduced sheet-like boron nitride, which further improved the fire safety of the material in the longitudinal direction. It can pass the V-1 level at 0.8mm. At the same time, the THR and DS4 of the material are further reduced, indicating that BN can improve the flame retardant performance of the material on the one hand, and inhibit chain reaction in the gas phase on the other hand, reducing smoke and heat release.

[0070] Example 8 introduced an ionic liquid, which further improved the flame retardant properties of the PE composite material, reliably achieving the V-0 rating with an ultra-high dimension of 0.8 mm. Furthermore, its heat release and smoke release were significantly reduced. Tensile strength and elongation at break were also significantly improved compared to Examples 6-7, indicating that the introduction of the ionic liquid can improve flame retardant properties while reducing its impact on mechanical properties.

[0071] Comparative Examples 2-7 are compared with Example 8 under the same flame retardant ratio. It can be seen that Example 8 has significantly improved flame retardant performance, mechanical properties and smoke and heat release performance compared with Comparative Examples 2-7.

[0072] Table 1

[0073]

[0074] Table 2

[0075]

[0076]

[0077] Note: No indicates no flame retardant rating, and THR stands for Total Heat Release.

[0078] The data analysis and comparison in Examples 1-8 and Comparative Examples 1-7 show that the high flame retardancy, low smoke density, and low heat release polyethylene material of the present invention introduces organophosphorus and organosilicon flame retardants to form a P-Si char layer structure, overcoming the traditional charring defect of PE materials. It also introduces a ceramicized charring agent, which forms a stable ceramicized structure during combustion, further increasing the charring effect of the PE material and suppressing the release of internal heat and smoke, achieving low smoke and low heat release. Furthermore, it introduces ionic liquid, which, while increasing flame retardancy, utilizes adsorption to increase the dispersion and flame retardant performance of the entire flame retardant system in the matrix, reducing the impact on mechanical properties and increasing flame retardant efficiency. The prepared flame-retardant PE material produces no smoke during processing, can achieve a V-0 (0.8mm) level, and has low smoke density and heat release, making it suitable for applications in high-voltage cables, optical cables, low-smoke halogen-free cables, and other PE products.

[0079] Example 9:

[0080] The majority of the components are the same as in Example 8, except that the low-density polyethylene is replaced with an equal mass of linear low-density polyethylene.

[0081] Example 10:

[0082] The majority of the components are the same as in Example 8, except that the proportions of each group are adjusted as follows:

[0083]

[0084] Example 11:

[0085] The majority of the components are the same as in Example 8, except that the proportions of each group are adjusted as follows:

[0086]

[0087] Example 12:

[0088] The majority of the components are the same as in Example 8, except that the proportions of each group are adjusted as follows:

[0089]

[0090]

[0091] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A polyethylene material with high flame retardancy, low smoke density, and low heat release, characterized in that, It is made from the following raw material components in parts by weight: PE 50~90 parts; 0.1 to 30 parts of organophosphorus flame retardant; 0.1 to 25 parts of organosilicon flame retardant; 0.1-3 parts of ceramicizing carbonizing agent; 0.1 to 10 parts of ionic liquid flame retardant; Lubricant 0.1~5 parts; Antioxidant 0.1-5 parts; The organophosphorus flame retardant has a phosphorus content >12%, a melting point >200℃, and a decomposition temperature >200℃. Its structure contains a cyclic structure, and its chemical structural formula is: ， Wherein, X1 and X2 are phenyl groups; The organosilicon flame retardant is a cage-like polysilsesquioxane with the structural formula (R1SiO2). 3 / 2 ) n Where R1 is methyl, vinyl, or phenyl, and the Si content is >10%, and n is a positive integer; The ceramic carbonizing agent is selected from one or a mixture of hollow glass microspheres, zinc borate, and boron nitride. The ionic liquid flame retardant is 1-butyl-3-methylimidazolium dibutyl phosphate salt.

2. The polyethylene material with high flame retardancy, low smoke density, and low heat release according to claim 1, characterized in that, The PE is one of high-density polyethylene, low-density polyethylene, and linear low-density polyethylene.

3. The polyethylene material with high flame retardancy, low smoke density, and low heat release according to claim 1, characterized in that, The lubricant is one or a mixture of natural paraffin, liquid paraffin, microcrystalline wax, polyethylene wax, butyl stearate, oleamide, ethylene bis-stearamide, and silicone powder. The antioxidant is one or a mixture of 2,6-di-tert-butyl-p-cresol, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)trimethylbenzene, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), and 4,4'-di-tert-octyldiphenylamine.

4. The method for preparing the high flame retardant, low smoke density, and low heat release polyethylene material as described in any one of claims 1-3, characterized in that, Includes the following steps: Weigh each component according to the weight proportions and mix them evenly to obtain the base material-additive composition; The additive-base composition is added to a twin-screw extruder, mixed and extruded to obtain the target product.

5. The application of the high flame retardant, low smoke density, and low heat release polyethylene material as described in any one of claims 1-3 in the preparation of optical cables or low smoke halogen-free cables.

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