Halogen-free flame-retardant 5VA grade polypropylene composite material, preparation method and application thereof

Abstract

The application discloses a kind of halogen-free flame-retardant 5VA grade polypropylene composite material and its preparation method and application, it is related to modified plastics processing technical field.The application provides a kind of halogen-free flame-retardant 5VA grade polypropylene composite material, including the following weight parts of component: polypropylene resin 50-60 parts, flame retardant 25-35 parts, flame-retardant synergist 5-15 parts, antioxidant 0.1-0.5 parts, lubricant 0.1-0.5 parts;Wherein, the flame retardant is N-P system intumescent flame retardant, the flame-retardant synergist is the mixture of ethylene-cycloolefin copolymer and low-density polyethylene, and wherein, the weight ratio of ethylene-cycloolefin copolymer and low-density polyethylene is greater than or equal to 1.The application is successful by the flame retardant and the flame-retardant synergist system of specific component and weight part selection, replaces PTFE with environmental risk, realizes good halogen-free flame-retardant, and good anti-dripping effect is realized, simultaneously, solve the burning-through problem caused by multiple flame application in the process of 5VA grade polypropylene composite material square board test.

Description

Technical Field

[0001] This invention relates to the field of modified plastics processing technology, and in particular to a halogen-free flame-retardant 5VA grade polypropylene composite material, its preparation method, and its application. Background Technology

[0002] In 2023, the European Chemicals Agency (ECHA) published a draft regulation on restrictions for perfluorinated and polyfluoroalkyl substances (PFAS). The proposed restriction defines PFAS as any fluorinated chemical substance (with a few exceptions) containing at least one perfluorinated methyl (CF3-) or methylene (-CF2-) carbon atom (without any H / Cl / Br / I). The main reason for the restriction is the high persistence of PFAS in the environment; without regulation, they would have negative impacts on human health and the environment. In the field of flame-retardant modified plastics, polytetrafluoroethylene (PTFE) is a commonly used modifier, used as an anti-dripping agent, especially for high flame-retardant polypropylene materials (5VA grade), where it is an indispensable component. Due to the complex composition and numerous types of perfluorinated compounds, PTFE inevitably contains small amounts of PFAS-restricted substances during the synthesis process.

[0003] Polypropylene (PP) materials, due to their low oxygen index, exhibit higher flammability compared to other engineering plastics, making flame-retardant modification more challenging, especially for 5VA-level halogen-free flame-retardant systems with a thickness of less than 2.0 mm. 5VA combustion tests require simultaneous testing of both test strips and square plates. During the combustion test, square plates of the PP flame-retardant system exhibit significant "shrinkage," leading to burn-through and failure to pass the test. Current solutions include adding glass fiber, mineral fillers, heat insulation agents, and anti-dripping agents. However, adding fillers significantly reduces the material's physical properties. While anti-dripping agents can mitigate this issue to some extent, they do not completely solve the problem and introduce PFAS-restricted substances.

[0004] Therefore, it is of great significance to develop a halogen-free flame-retardant 5VA grade flame-retardant polypropylene material. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to overcome the shortcomings of the prior art and provide a halogen-free flame-retardant 5VA grade flame-retardant polypropylene material, its preparation method and application.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a halogen-free flame-retardant 5VA grade polypropylene composite material, comprising the following components in parts by weight: 50-60 parts of polypropylene resin, 25-35 parts of flame retardant, 5-15 parts of flame retardant synergist, 0.1-0.5 parts of antioxidant, and 0.1-0.5 parts of lubricant; wherein the flame retardant is an NP-based intumescent flame retardant, and the flame retardant synergist is a mixture of ethylene-cycloolefin copolymer and low-density polyethylene, wherein the weight ratio of ethylene-cycloolefin copolymer to low-density polyethylene is ≥1.

[0007] This invention successfully replaces environmentally risky PTFE with a flame retardant and flame retardant synergist system selected by specific components and weight parts, achieving excellent halogen-free flame retardancy and good anti-dripping effect. Simultaneously, it solves the burn-through problem caused by repeated flame application during the testing of 5VA grade polypropylene composite square plates. The flame retardant selected in this invention is an NP-based intumescent flame retardant. The NP system belongs to the intumescent flame retardant mechanism. Combined with the specific components and weight parts of the flame retardant synergist system, on the one hand, it can promote the formation of the char layer, increase the density of the char layer, and the rapidly formed char layer can also effectively improve the system's strength and flame retardant efficiency, solving the burn-through problem caused by repeated flame application during the testing of 5VA grade polypropylene composite square plates. On the other hand, it can reduce the shrinkage of the square plate during combustion, reduce the orientation and stress during the square plate molding process, fundamentally solving the burn-through problem caused by repeated flame application in the testing of halogen-free flame-retardant 5VA grade polypropylene composite square plates.

[0008] In actual experiments, the inventors discovered that the weight ratio of ethylene-cycloolefin copolymer and low-density polyethylene in the flame retardant synergist affects the combustion performance of halogen-free flame retardant 5VA grade polypropylene composite material. When the weight ratio of ethylene-cycloolefin copolymer and low-density polyethylene in the flame retardant synergist is <1, the formation of the char layer is affected, and dripping and burn-through problems occur during the combustion process.

[0009] Preferably, the ethylene-cyclic olefin copolymer includes at least one of ethylene-norbornene copolymer and ethylene-tetracyclododecene copolymer.

[0010] Preferably, the weight percentage of the PP resin in the halogen-free flame-retardant 5VA grade polypropylene composite material is not less than 45%.

[0011] Optionally, the PP resin is in the range of 50 parts, 51 parts, 53 parts, 55 parts, 58 parts, and 60 parts by weight, or any two of these values; the flame retardant is in the range of 25 parts, 28 parts, 30 parts, 32 parts, and 35 parts by weight, or any two of these values; the flame retardant synergist is in the range of 5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 8.5 parts, 9 parts, 9.5 parts, 10 parts, 12 parts, and 15 parts by weight, or any two of these values; the antioxidant is in the range of 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, and 0.5 parts by weight, or any two of these values; and the lubricant is in the range of 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, and 0.5 parts by weight, or any two of these values.

[0012] Preferably, the ethylene-cycloolefin copolymer has a melt index of 10-30 g / 10 min at 260°C and 2.16 kg according to ISO 1133-2011, and the low-density polyethylene has a melt index of 0.2-5 g / 10 min at 190°C and 2.16 kg according to ISO 1133-2011.

[0013] Optionally, the ethylene-cycloolefin copolymer has a melt index of 10 g / 10 min, 12 g / 10 min, 15 g / 10 min, 20 g / 10 min, 22 g / 10 min, 23 g / 10 min, 25 g / 10 min, 28 g / 10 min, or 30 g / 10 min, according to ISO 1133-2011 at 260 °C and 2.16 kg, or any two of these ranges. Optionally, the low-density polyethylene, according to ISO 1133-2011 at 190°C and 2.16 kg, has a melt index of one or any two of the following: 0.2 g / 10 min, 0.5 g / 10 min, 1 g / 10 min, 2 g / 10 min, 2.5 g / 10 min, 3 g / 10 min, 3.5 g / 10 min, 4 g / 10 min, 4.5 g / 10 min, 4.8 g / 10 min, and 5 g / 10 min.

[0014] Preferably, the weight ratio of the ethylene-cycloolefin copolymer to low-density polyethylene is (5-7):(3-5). More preferably, the weight ratio of the ethylene-cycloolefin copolymer to low-density polyethylene is (5-6):5.

[0015] In actual experiments, the inventors discovered that the weight ratio of ethylene-cycloolefin copolymer and low-density polyethylene in the flame retardant synergist further affects the combustion performance of halogen-free flame retardant 5VA grade polypropylene composite material. When the weight ratio of ethylene-cycloolefin copolymer and low-density polyethylene is (5-6):5, it is more conducive to the formation of char layer, and the prepared polypropylene composite material has better flame retardant effect.

[0016] Preferably, the polypropylene resin is at least one of homopolymer polypropylene, block copolymer polypropylene, and random copolymer polypropylene, and the polypropylene has a melt index of 0.5-30 g / 10 min at 230°C and 2.16 kg according to ISO 1133-2011.

[0017] Optionally, the polypropylene has a melt index of 0.5 g / 10 min, 1 g / 10 min, 2 g / 10 min, 2.5 g / 10 min, 3 g / 10 min, 3.5 g / 10 min, 4 g / 10 min, 4.5 g / 10 min, 4.8 g / 10 min, 5 g / 10 min, 7 g / 10 min, 9 g / 10 min, 10 g / 10 min, 12 g / 10 min, 15 g / 10 min, 20 g / 10 min, 22 g / 10 min, 23 g / 10 min, 25 g / 10 min, 28 g / 10 min, or 30 g / 10 min, according to ISO 1133-2011 at 230 °C and 2.16 kg, or any two of these ranges.

[0018] Preferably, the NP-based intumescent flame retardant is at least one of piperazine pyrophosphate, ammonium polyphosphate, and triazine charring agents; and / or, the antioxidant is at least one of hindered phenolic antioxidants and phosphite antioxidants; and / or, the lubricant is at least one of stearates, stearates, and ethylene bis-stearamides.

[0019] Optionally, the NP-based intumescent flame retardant includes piperazine pyrophosphate, ammonium polyphosphate, tris(phosphenanthrene-(hydroxymethyl)phenoxy)1,3,5-triazine, poly(4,6-dichloro-N-butyl-1,3,5-triazine-2-amino-ethylenediamine), 2,4-diamino-6-hydroxyethylamino-1,3,5-triazine, etc.

[0020] Optionally, the antioxidants include antioxidant 168 (tris[2,4-di-tert-butylphenyl]phosphite), antioxidant 1010 (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]), etc.

[0021] Optionally, the lubricant includes pentaerythritol stearate, zinc stearate, calcium stearate, etc.

[0022] Furthermore, the present invention provides a method for preparing the halogen-free flame-retardant 5VA grade polypropylene composite material, comprising the following steps: mixing the components evenly, performing melt extrusion and granulation to obtain the halogen-free flame-retardant 5VA grade polypropylene composite material.

[0023] Preferably, the temperature of the melt extrusion is 180-200℃ and the screw speed is 300-450 rpm.

[0024] Furthermore, this invention provides the application of the aforementioned halogen-free flame-retardant 5VA grade polypropylene composite material in the manufacture of household appliances and electronic appliances. Specifically, this invention provides the application of the aforementioned halogen-free flame-retardant 5VA grade polypropylene composite material in the manufacture of electrical control boxes, motor housings, and air conditioner handles.

[0025] Compared to existing technologies, the beneficial effects of this invention are as follows: This invention successfully replaces PTFE, which carries environmental risks, with a flame retardant and flame retardant synergist system selected by specific components and weight parts. This achieves excellent halogen-free flame retardancy and good anti-dripping effect, while simultaneously solving the burn-through problem caused by repeated flame application during the testing of 5VA grade polypropylene composite square plates. The flame retardant selected in this invention is an NP-based intumescent flame retardant. The NP system belongs to the intumescent flame retardant mechanism. Combined with the specific components and weight parts of the flame retardant synergist system, on the one hand, it can promote the formation of the char layer, increase the density of the char layer, and the rapidly formed char layer can also effectively improve the system's strength and flame retardant efficiency, solving the burn-through problem caused by repeated flame application during the testing of 5VA grade polypropylene composite square plates; on the other hand, it can reduce the shrinkage of the square plate during combustion, reduce the orientation and stress during the square plate molding process, fundamentally solving the burn-through problem caused by repeated flame application during the testing of halogen-free flame-retardant 5VA grade polypropylene composite square plates. Detailed Implementation

[0026] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments. The purpose is to provide a detailed understanding of the invention, not to limit it. All other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. Unless otherwise specified, the experimental reagents and instruments designed in the embodiments and comparative examples of this invention are commonly used reagents and instruments, all of which are commercially available. Unless otherwise specified, the experimental methods used in the embodiments and comparative examples are conventional methods; and unless otherwise specified, the raw materials used in parallel experiments are from the same batch.

[0027] The raw materials used in the embodiments and comparative examples are described below, but are not limited to these materials:

[0028] PP-1: HP500N, homopolymer polypropylene, melt index 12g / 10min (230℃, 2.16kg), CNOOC Shell Company;

[0029] PP-2: K8003, block copolymer polypropylene, melt index 3.0 g / 10 min (230℃, 2.16 kg), Yangzi Petrochemical Company;

[0030] PP-3: PPH-Y26, homopolymer polypropylene, melt index 25g / 10min (230℃, 2.16kg), Zhenhai Refining & Chemical Co., Ltd.

[0031] Flame retardant-1: A mixture of ammonium polyphosphate and tris(phosphenanthrene-(hydroxymethyl)-phenoxy)-1,3,5-triazine (SR-207) in a weight ratio of 5:1, commercially available;

[0032] Flame retardant-2: piperazine pyrophosphate, commercially available;

[0033] Flame retardant-3: a mixture of octabromosyl ether and antimony trioxide in a weight ratio of 12:4, commercially available;

[0034] Ethylene-cycloolefin copolymer-1: Ethylene-tetracyclododecene copolymer, APL6013T, melt index 15g / 10min (260℃, 2.16kg), Mitsui Chemicals, Inc., Japan;

[0035] Ethylene-cycloolefin copolymer-2: Ethylene-tetracyclododecene copolymer, APL6011T, melt index 26g / 10min (260℃, 2.16kg), Mitsui Chemicals, Inc., Japan;

[0036] Ethylene-cycloolefin copolymer-3: Ethylene-tetracyclododecene copolymer, APL6015T, melt index 10g / 10min (260℃, 2.16kg), Mitsui Chemicals, Inc., Japan;

[0037] Ethylene-cycloolefin copolymer-4: Ethylene-norbornene copolymer, TOPAS 9506F-04, melt index 18g / 10min (260℃, 2.16kg);

[0038] Cycloolefin homopolymer-1: ZEONEX 350R, melt index 26 g / 10 min (260 °C, 2.16 kg), Zeon Corporation, Japan;

[0039] Low-density polyethylene-1: LDPE 2426H, melt index 2.0 g / 10 min (190℃, 2.16 kg), CNOOC Shell Company;

[0040] Low-density polyethylene-2: LDPE LD165, melt index 0.3g / 10min (190℃, 2.16kg), Yanshan Petrochemical Company;

[0041] Low-density polyethylene-3: LDPE 2426K, melt index 4.0 g / 10 min (190℃, 2.16 kg), Maoming Petrochemical Company;

[0042] Linear low-density polyethylene: LLDPE 7042, melt index 2.0 g / 10 min (190℃, 2.16 kg), Zhenhai Refining & Chemical Co., Ltd.

[0043] High-density polyethylene: HDPE 5000S, melt index 1.0g / 10min (190℃, 2.16kg), Dushanzi Petrochemical;

[0044] Anti-dripping agent: Polytetrafluoroethylene, commercially available;

[0045] Antioxidant: Antioxidant 1010 (tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl), commercially available);

[0046] Lubricant: Calcium stearate, commercially available;

[0047] Examples 1-14 and Comparative Examples 1-8

[0048] The composition of the halogen-free flame-retardant 5VA grade polypropylene composite material of the present invention is shown in Tables 1 and 2. The preparation method of the halogen-free flame-retardant 5VA grade polypropylene composite material includes the following steps: mixing the components uniformly, performing melt extrusion and granulation to obtain the halogen-free flame-retardant 5VA grade polypropylene composite material; wherein, the melt extrusion conditions are: screw speed 400 rpm; zone 1 temperature 180℃; zone 2 to 6 temperature 190℃; zone 7 to 10 temperature 200℃; and zone 11 temperature 190℃.

[0049] Table 1

[0050]

[0051]

[0052] Table 2

[0053]

[0054] Table 3

[0055]

[0056]

[0057] Performance testing

[0058] Testing process: The halogen-free flame-retardant 5VA grade polypropylene composite materials prepared in the above specific embodiments and comparative examples were tested for flame retardancy according to the UL-94-2006 standard. Test samples were prepared by injection molding, wherein the thickness of the burning sample strip was 1.5mm and the square plate size was 150mm×150mm×1.5mm.

[0059] Test performance parameters: The material can only reach the 5VA level when both the sample and the specimen meet the combustion test requirements.

[0060] (1) Vertical burning test, record the flame retardant rating according to the burning standard.

[0061] (2) 5VA sample test: Record whether the test is passed according to the combustion standard. If the test is passed, record the average value of the flame and flameless time (seconds) after the fifth ignition of the 3 samples. Also record whether the degreased cotton is ignited.

[0062] (3) 5VA sample test: Record whether the sample is burned through according to the combustion standard.

[0063] Test results are shown in Table 4.

[0064] Table 4

[0065]

[0066]

[0067] As shown in the table above, the polypropylene composite materials prepared in the embodiments of the present invention can all pass the 5VA test, which fundamentally solves the problem of burn-through caused by multiple flame exposures in the test of halogen-free flame-retardant 5VA grade polypropylene composite square plates.

[0068] As can be seen from the comparison of Examples 1-10, when the flame retardant used in the polypropylene composite material is an NP-based intumescent flame retardant, and the flame retardant synergist is a mixture of ethylene-cycloolefin copolymer and low-density polyethylene, with a weight ratio of ethylene-cycloolefin copolymer to low-density polyethylene ≥1, and a melt index of 0.5-30 g / 10 min, polypropylene composite materials that pass the 5VA test can be obtained.

[0069] As can be seen from the comparison of Examples 1 and Examples 11-14, when the weight ratio of the ethylene-cycloolefin copolymer to low-density polyethylene is (5-7):(3-5), under the premise of 5VA test, the average flame and flameless time of the 1.5mm / 5VA-sample is ≤3.5 seconds, which is more conducive to the formation of char layer, and the flame retardant effect of the prepared polypropylene composite material is better.

[0070] As can be seen from the comparison of Example 1 and Comparative Examples 1-8, the present invention, through a flame retardant and flame retardant synergist system selected with specific components and weight parts, achieves excellent anti-dripping effect under the synergistic effect of ethylene-cycloolefin copolymer and low-density polyethylene, successfully replacing PTFE, which has environmental risks, and achieving fluorine-free flame retardancy. Furthermore, it can effectively reduce orientation and stress during the square plate molding process, fundamentally solving the burn-through problem caused by combustion shrinkage during the testing of 5VA square plates made of flame-retardant polyolefin material.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A halogen-free flame-retardant 5VA grade polypropylene composite material, characterized in that, The composition comprises the following components by weight: polypropylene resin 50-60 parts, flame retardant 25-35 parts, flame retardant synergist 5-15 parts, antioxidant 0.1-0.5 parts, lubricant 0.1-0.5 parts; wherein the flame retardant is N-P type intumescent flame retardant, the flame retardant synergist is a mixture of ethylene-cycloolefin copolymer and low density polyethylene, wherein the weight ratio of the ethylene-cycloolefin copolymer to the low density polyethylene is (5-7):(3-5).

2. The halogen-free flame-retardant 5VA polypropylene composite material according to claim 1, characterized in that, The ethylene-cycloolefin copolymer has a melt index of 10-30 g / 10 min under the condition of 260℃, 2.16 kg according to ISO1133-2011, and the low density polyethylene has a melt index of 0.2-5 g / 10 min under the condition of 190℃, 2.16 kg according to ISO1133-2011.

3. The halogen-free flame-retarded 5VA polypropylene composition of claim 1, wherein, The polypropylene resin is at least one of homopolymer polypropylene, block copolymer polypropylene, and random copolymer polypropylene, and the polypropylene has a melt index of 0.5-30 g / 10 min under the condition of 230℃, 2.16 kg according to ISO1133-2011.

4. The halogen-free flame-retarded 5VA polypropylene composition of claim 1, wherein the polypropylene is a heterophasic polypropylene. The N-P type intumescent flame retardant is at least one of piperazine pyrophosphate, ammonium polyphosphate, and triazine charring agent; And / or, the antioxidant is at least one of hindered phenol antioxidant and phosphite antioxidant; And / or, the lubricant is at least one of stearate, stearate ester, and ethylene bis-stearamide.

5. A process for the preparation of a halogen-free flame-retardant 5VA polypropylene composite material according to any one of claims 1 to 4, characterized in that, The method comprises the following steps: uniformly mixing the components, melt extruding and granulating to obtain the halogen-free flame-retardant 5VA grade polypropylene composite material.

6. Use of the halogen-free flame-retardant 5VA grade polypropylene composite material according to any one of claims 1-4 in the field of household appliances and electronic appliances.

7. Use of the halogen-free flame-retardant 5VA grade polypropylene composite material according to any one of claims 1-4 in the preparation of electric control boxes, motor housings, and air conditioner handles.

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