High-transparency, thin-wall, flame-retardant, high-glow-wire polypropylene material, preparation and application thereof

Abstract

This invention relates to a high-transparency, thin-walled, flame-retardant, high-glow-wire polypropylene material, its preparation, and its application. The material comprises the following raw material components in parts by weight: PP 50-90 parts; polyphosphate 0.1-30 parts; metal phosphate 0.1-25 parts; NOR-type flame retardant 0.1-3 parts; melamine cyanurate 0.1-10 parts; polysilsesquioxane 0.1-3 parts; lubricant 0.1-5 parts; and antioxidant 0.1-5 parts. Compared with existing technologies, this invention can solve the problems of low flame retardancy, low transparency, and low glow-wire performance in thin-walled polypropylene parts.

Description

Technical Field

[0001] This invention belongs to the field of flame retardant materials technology, and relates to a high-transparency, thin-walled flame retardant, high-glow-wire polypropylene material and its preparation and application. Background Technology

[0002] Many plastics are flammable due to their chemical composition. To meet the demands of plastic processing and, to a certain extent, stringent flame retardancy requirements imposed by legislators, plastics typically require the addition of flame retardants. Many different flame retardants and flame retardant synergists are known for this purpose and are commercially available. Non-halogenated flame retardant systems have been preferred for some time due to their more favorable side effects in terms of smoke density and composition in fire conditions, as well as from an ecological perspective.

[0003] Polypropylene materials are widely used in various fields, but their long carbon chain structure makes them highly flammable and difficult to extinguish. With the continuous advancement of flame retardant technology, intumescent flame retardants in polypropylene materials rapidly form char, locking in internal heat and continuously transferring gas, thereby extinguishing ignited materials. For example, when ammonium polyphosphate and triazine charring agents are used together at a 25% addition level, polypropylene materials can reliably pass the UL94 V-0 (1.6mm) rating. However, the flame-retardant mechanism of this type of flame retardant relies on the rapid formation of an intumescent carbon layer. For thinner products, such as those in electronic products with a thickness of 0.4-0.6 mm or even less, the following challenges arise: First, intumescent flame-retardant polypropylene materials struggle to quickly form a sufficient amount of high-strength carbon layer, making it difficult to suppress combustion. Second, the supporting strength of thin-walled components decreases with thickness, making it difficult to provide sufficient support to prevent dripping during combustion. Furthermore, the heat and combustible material transfer paths are shorter. Therefore, flame retardancy of thin-walled PP materials has always been a challenge for the industry.

[0004] Currently, most drip-type flame retardants achieve their flame-retardant purpose by rapidly dripping, carrying the heat and flame generated during combustion. For example, tannin-based flame retardants, when used in combination with hypophosphite flame retardants, can achieve rapid dripping in polypropylene materials, enabling the material to reach a V-2 flammability rating. However, increasing the amount of this type of flame retardant does not achieve a higher flame-retardant rating, and excessive addition will deteriorate the physical properties of the material.

[0005] For thin-walled or even thin-film products, traditional char-forming flame retardant systems are difficult to achieve high flame retardancy ratings. Furthermore, thin-film products generally require high transparency and localized heat resistance, as well as requirements regarding glow wire temperature.

[0006] For example, Chinese patent CN 115322491 A discloses a polypropylene composition with low gloss, low stress whitening and low density. It can achieve a flame retardant effect of V-2 through a small amount of melamine cyanurate / inorganic hypophosphite / methyl methacrylate flame retardant synergistic system, but the effect is not mentioned at thinner thicknesses.

[0007] Meanwhile, there has been considerable research on the flame retardancy of thin-walled polycarbonate, mainly involving the combination of sulfonates and silicone-based flame retardants, which can achieve high flame retardancy ratings for thin-walled PCs. However, there are few patents published for the flame retardancy of thin-walled polypropylene materials.

[0008] Currently, no relevant technologies have been found that can simultaneously solve the following problems of polypropylene materials used in the field of electronic materials:

[0009] 1) Due to the low support force of polypropylene during combustion, it is difficult for thin-walled polypropylene (0.4-0.6mm) parts to achieve a high flame retardant rating, requiring them to pass the VTM-0 rating;

[0010] 2) Transparency issues in thin-walled (0.4-0.6mm) parts;

[0011] 3) When used in the electronics field, it may cause local overheating and combustion due to problems such as short circuits. Summary of the Invention

[0012] The purpose of this invention is to provide a high-transparency, thin-walled flame-retardant, high-glow-wire polypropylene material, its preparation and application, to solve at least one of the problems existing in thin-walled polypropylene parts, such as low flame retardancy rating, low transparency, and low glow-wire performance.

[0013] The objective of this invention can be achieved through the following technical solutions:

[0014] One of the technical solutions of the present invention provides a high-transparency, thin-walled flame-retardant, high-glow-wire polypropylene material, comprising the following raw material components in parts by weight:

[0015]

[0016] Furthermore, the component proportions of this polypropylene material are as follows:

[0017]

[0018]

[0019] More specifically, the metal phosphate is preferably in the form of 5-15 parts by weight, more preferably 5-10 parts by weight.

[0020] More specifically, the amount of polyphosphate added is preferably 4-15 parts, more preferably 4-10 parts.

[0021] Furthermore, the PP is a homopolymer or copolymer polypropylene with a melt index >3 g / 10 min. Preferably, the polypropylene is a homopolymer or copolymer polypropylene with a melt index >10 g / 10 min.

[0022] Furthermore, the polyphosphate ester is a solid polyphosphate ester with a degree of polymerization >10, a thermal decomposition temperature >250℃, and a phosphorus content >8%. Even further, the polyphosphate ester is a polyphosphate ester containing phenolic hydroxyl groups with a molecular weight >1000 and a thermal decomposition temperature >300℃.

[0023] Furthermore, the metal phosphate is selected from one or more of aluminum hypophosphite, calcium hypophosphite, cerium hypophosphite, aluminum phosphite, calcium phosphite, cerium phosphite, diethyl aluminum hypophosphite, diethyl zinc hypophosphite, dimethyl aluminum hypophosphite, dimethyl zinc hypophosphite, diphenyl zinc hypophosphite, diphenyl aluminum hypophosphite, methylethyl zinc hypophosphite, or methylethyl aluminum hypophosphite. Preferably, the metal phosphate is one or more of diethyl aluminum hypophosphite, diethyl zinc hypophosphite, or dimethyl aluminum hypophosphite.

[0024] Furthermore, the NOR-type flame retardant is an N-alkoxy flame retardant with the following chemical structure:

[0025] Wherein, R is a melamine derivative.

[0026] Furthermore, in the NOR-type flame retardant, R is a melamine derivative structure with a nitrogen content > 20%.

[0027] More preferably, the chemical structural formula of R is:

[0028]

[0029] Furthermore, the melamine cyanurate is a melamine cyanurate with a decomposition temperature >300℃, a particle size <20μm, and an N content >40%.

[0030] Furthermore, the polysilsesquioxane is a cage-like polysilsesquioxane with the structural formula (R1SiO2). 3 / 2 ) n Wherein, R1 is methyl, vinyl, amino, or phenyl. Preferably, R1 is methyl.

[0031] Further, the lubricant is one or a mixture of natural paraffin wax, liquid paraffin wax, microcrystalline wax, polyethylene wax, butyl stearate, oleamide, ethylene bis-stearamide, and silicone powder. Preferably, the lubricant is one or a mixture of natural paraffin wax, liquid paraffin wax, microcrystalline wax, polyethylene wax, butyl stearate, oleamide, ethylene bis-stearamide, and silicone powder. More preferably, the lubricant is one or a mixture of ethylene bis-stearamide and silicone powder.

[0032] Further, the antioxidant is one or more 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. Preferably, the antioxidant is any one or more of 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), and 2,2'-methylenebis(4-methyl-6-tert-butylphenol).

[0033] The second technical solution of the present invention provides a method for preparing a high-transparency, thin-walled flame-retardant, high-glow-wire polypropylene material, comprising the following steps:

[0034] Weigh each raw material component according to the weight proportions and mix them evenly to obtain the base material-additive composition;

[0035] The additive-base composition is added to a twin-screw extruder, mixed and extruded to obtain the target product.

[0036] Furthermore, the raw material components are mixed in a triaxial multi-functional mixer with different rotation speeds for each shaft, while maintaining the same rotation direction for both the inner and outer shafts. Specifically, the A-shaft rotates at 20-40 rpm, the B-shaft at 10-20 rpm, and the C-shaft at 10-20 rpm. Preferably, the mixing process is performed intermittently in three stages, with each mixing session lasting no more than 3 minutes, to prevent the polyphosphate flame retardant from melting due to high-speed shear heating.

[0037] 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 200-220℃, 200-220℃, 200-220℃, 200-220℃, and 200-220℃, respectively.

[0038] 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.

[0039] Furthermore, the polypropylene 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.

[0040] The third technical solution of the present invention provides an application of a high-transparency, thin-walled, flame-retardant, high-glow-wire polypropylene material in the preparation of thin-walled polypropylene parts. More specifically, the thickness of the thin-walled polypropylene part is 0.4–0.6 mm.

[0041] Compared with the prior art, the present invention has the following advantages:

[0042] 1) The present invention provides a high transparency, thin-walled flame retardant, and high glow wire polypropylene material, which utilizes the special free radical capture and quenching effect in the structure of NOR-type flame retardant to achieve gas-phase flame retardancy during combustion, thereby overcoming the defect of traditional intumescent flame retardants that are difficult to char in thin-walled parts in a timely manner.

[0043] 2) By introducing hypophosphite and melamine cyanurate, the flame retardant rating of the material can be further improved by utilizing the free radical chain scission effect of the P element in the hypophosphite structure and the gas phase dilution effect of melamine cyanurate, thus achieving timely quenching.

[0044] 3) Due to its special molecular structure, polyphosphate is difficult to crystallize and therefore exhibits transparency when melted. Furthermore, its end group structure is phenolic hydroxyl, which has high-temperature reactivity. Therefore, when introduced into the system, not only can transparent parts be prepared, but the P element in the polycarbonate structure can also further suppress free radicals. Under the action of multiple gas phase effects, the flame retardant rating is effectively improved.

[0045] 4) Utilizing the ceramicization effect of polysilsesquioxane, a ceramicized heat-resistant structure is formed in a timely manner when the material is heated, creating a barrier effect and thus effectively improving the glow wire performance of the material. Detailed Implementation

[0046] 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.

[0047] The components used in the following embodiments are as follows:

[0048] Commercially available polypropylene (component A): grade BX3920, purchased from SK Group, South Korea;

[0049] Polyphosphate (component B): Grade OL1001, purchased from FRX Polymers;

[0050] Diethylaluminum hypophosphite (component C): grade OP1230, purchased from Clariant Chemicals Ltd.;

[0051] NOR type flame retardant (component D): grade NOR116, purchased from BASF Chemical Company;

[0052] Melamine cyanurate (component E): brand name MCA, purchased from Sichuan Fine Chemical Research Institute;

[0053] Polysilsesquioxane (component F): Grade HY-7000, purchased from Hangzhou Yuheng Technology Co., Ltd.;

[0054] Lubricant (component G): Silicone powder (Hangzhou Kaijie Plastics Technology Co., Ltd.);

[0055] Antioxidant (component H): Grade AT-10 (Albemarle Chemicals Ltd.).

[0056] The testing methods and standards for PP materials are as follows:

[0057] According to UL94, the following fire resistance categories are obtained:

[0058] Prepare a thin-walled part with a length of 200±5mm, a width of 50±1mm, and a thickness of 0.5mm±0.01mm, and roll it along the longitudinal axis into a cylinder with a diameter of 13mm.

[0059] VTM-2: After two 3-second burning tests on the sample, the flame extinguishes within 30 seconds. It can ignite cotton wool up to 30cm below.

[0060] VTM-1: After two 3-second burning tests on the sample, the flame extinguishes within 30 seconds. It cannot ignite cotton wool 30cm below.

[0061] VTM-0: After two 3-second burning tests on the sample, the flame must extinguish within 10 seconds. No burning material should fall.

[0062] The transparency and haze values ​​of the samples were determined in accordance with GB / T 2410-2008 "Test Method for Transmittance and Haze of Transparent Plastics".

[0063] According to the environmental testing standard GB / T 5169.13-2013 "Part 13: Glow wire / hot wire basic test methods for materials - Glow wire ignition temperature (GWIT) test", the glow wire ignition temperature of the material was tested.

[0064] The main test examines the limits of a product's ability to withstand harsh environments with high temperature and humidity. This is achieved by measuring the melt volume index (MVR) at 280℃ / 2.16kg to determine the flowability of the molding composition. A higher MVR value indicates better flowability in the injection molding process.

[0065] In addition, the embodiments of the present invention provide a specific process for preparing flame-retardant plastic molding materials:

[0066] 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 220°C on an injection molding machine and tested.

[0067] In this embodiment of the 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 200°C, 220°C, 220°C, 220°C, and 220°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.

[0068] In addition, unless otherwise stated, all comparisons were conducted under the same conditions (temperature program, screw structure, injection parameters) for each series of tests.

[0069] Examples 1-8 and Comparative Examples 1-4:

[0070] Table 1 provides specific data for the examples and comparative examples. Examples 1 to 3 analyze the effects of using different amounts of polyphosphate alone on the flame retardant properties, transparency, and glow wire properties of thin-walled PP materials. It is evident that polyphosphate, due to its high phosphorus content, exhibits significant flame retardant properties. Furthermore, its melting characteristics at high temperatures have a relatively small impact on transparency. However, since it does not have a significant charring effect, it does not significantly improve the glow wire properties.

[0071] Examples 4-5 analyzed the effects of different ratios of polyphosphate and hypophosphite on the material properties. The results showed that the combination of hypophosphite and polyphosphate could further improve the flame retardant properties of the material.

[0072] Example 6 introduces MCA to further enhance the flame retardant effect in the gas phase. By employing the gas phase dilution effect, the flame retardant effect of thin-walled PP material is increased. The results show that the introduction of MCA improves the LOI of the material and reduces the impact of the flame retardant on the transparency.

[0073] Example 7 introduces a NOR-type flame retardant, which forms a quenching effect in the gas phase. This, combined with the dilution effect of MCA and the free radical scavenging effect of polyphosphate and hypophosphite, achieves a VTM-0 rating for thin-walled PP materials.

[0074] Example 8 introduces polymethylsilsesquioxane, which increases the glow wire temperature of the material to 800°C.

[0075] Compared to Example 8, Comparative Example 2 used hypophosphite alone, and the flame retardant rating of Example 8 reached VTM-0; Comparative Example 3 used MCA alone and had no flame retardant rating, while the flame retardant rating of Example 8 was improved to VTM-0; Comparative Example 3 used NOR116 alone and had no flame retardant rating, while the flame retardant rating of Example 8 was improved to VTM-0, and the glow wire temperature reached 800°C.

[0076] Table 1

[0077]

[0078] Table 2

[0079]

[0080]

[0081] Note: No indicates no flame retardant rating.

[0082] As can be seen from the data analysis and comparison in Examples 1-8 and Comparative Examples 1-4, the high transparency, thin-walled flame retardant, and high glow wire polypropylene material of the present invention overcomes the difficulties of traditional char-forming flame retardants in achieving high flame retardancy in thin-walled materials and the defects that affect the transparency of the material. It adopts the synergistic effect of multiple effects such as free radical capture effect, quenching effect, and dilution effect to solve the problem of thin-walled flame retardancy; it adopts crystallization control to solve the problem of high transparency; and it adopts ceramicization technology to solve the defect of low glow wire. The flame retardant PP material prepared has no smoke generation during processing, can achieve VTM-0 (0.5mm) level, reaches GWIT800℃ test, and has a transparency of 40%. It can be used for thin-walled parts in the fields of electronics, energy storage devices, etc.

[0083] Example 9:

[0084] Most of the components are the same as in Example 8, except that the copolymer polypropylene is replaced with an equal mass of homopolymer polypropylene.

[0085] Examples 10-22:

[0086] Compared to Example 8, most of the contents are the same, except that the metal phosphates are replaced with equal masses of aluminum hypophosphite, calcium hypophosphite, cerium hypophosphite, aluminum phosphite, calcium phosphite, cerium phosphite, diethyl zinc hypophosphite, dimethyl aluminum hypophosphite, dimethyl zinc hypophosphite, diphenyl zinc hypophosphite, diphenyl aluminum hypophosphite, methyl ethyl zinc hypophosphite, or methyl ethyl aluminum hypophosphite.

[0087] Examples 23-25:

[0088] The majority of the contents are the same as in Example 8, except that polymethylsilsesquioxane is replaced with equal masses of polyvinylsilsesquioxane, polyaminosilsesquioxane, and polyphenylsilsesquioxane, respectively.

[0089] Examples 26-32:

[0090] Compared to Example 8, most of the contents are the same, except that the silicone powder is replaced with equal masses of natural paraffin, liquid paraffin, microcrystalline wax, polyethylene wax, butyl stearate, oleamide, and ethylene bis-stearamide.

[0091] Examples 33-40:

[0092] The majority of the contents are the same as in Example 8, except that antioxidant 1010 is replaced by equal masses 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.

[0093] Example 41:

[0094] Compared to Example 8, most of them are the same, except that the proportions of each raw material group are as follows:

[0095]

[0096] Example 42:

[0097] Compared to Example 8, most of them are the same, except that the proportions of each raw material group are as follows:

[0098]

[0099] Example 43:

[0100] Compared to Example 8, most of them are the same, except that the proportions of each raw material group are as follows:

[0101]

[0102] 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 high-transparency, thin-walled, flame-retardant, high-glow-wire polypropylene material, characterized in that, The raw material components include the following parts by weight: 50-90 PP; Polyphosphate ester 0.1~30 parts; Metal phosphates, 0.1-25 parts; 0.1 to 3 parts of NOR type flame retardant; 0.1 to 10 parts of melamine cyanurate; 0.1 to 3 parts of polysilsesquioxane; Lubricant 0.1~5 parts; Antioxidant 0.1-5 parts; The PP is a homopolymer or copolymer polypropylene with a melt index >3g / 10min; The polyphosphate ester, brand name OL1001, was purchased from FRX Polymers. The metal phosphate is selected from one or more of aluminum hypophosphite, calcium hypophosphite, cerium hypophosphite, aluminum phosphite, calcium phosphite, cerium phosphite, diethyl aluminum hypophosphite, diethyl zinc hypophosphite, dimethyl aluminum hypophosphite, dimethyl zinc hypophosphite, diphenyl zinc hypophosphite, diphenyl aluminum hypophosphite, methyl ethyl zinc hypophosphite, or methyl ethyl aluminum hypophosphite. The NOR-type flame retardant is an N-alkoxy flame retardant with the following chemical structure: The chemical structural formula of R is: ； The polysilsesquioxane is a cage-like polysilsesquioxane with the structural formula (R1SiO2). 3 / 2 ) n R1 is methyl, vinyl, amino, or phenyl.

2. The high-transparency, thin-walled flame-retardant, high-glow-wire polypropylene material according to claim 1, characterized in that, The lubricant is one or a mixture of 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.

3. The method for preparing a high-transparency, thin-walled flame-retardant, high-glow-wire polypropylene material as described in claim 1 or 2, 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.

4. The application of a high-transparency, thin-walled flame-retardant, high-glow-wire polypropylene material as described in claim 1 or 2 in the preparation of thin-walled polypropylene parts.

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