A low-smoke halogen-free polyolefin composition and its preparation method and application

Abstract

The present invention discloses a low-smoke, halogen-free polyolefin composition, its preparation method, and application. The composition comprises the following components, calculated by weight: 30-60 parts of polyolefin resin; 3-10 parts of a compatibilizer; 45-65 parts of a halogen-free flame retardant; 15-25 parts of low-melting-point glass powder; and 3-8 parts of zirconium phosphate. The low-melting-point glass powder has a melting point of 400-675°C, and the mass ratio of the low-melting-point glass powder to zirconium phosphate does not exceed 6.5:1. By selecting a polyolefin resin as the base resin and adding an appropriate amount of zirconium phosphate and glass powder with a specific melting point, the composition can achieve both low smoke density and excellent mechanical properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of cable materials, and in particular relates to a low-smoke halogen-free polyolefin composition, a preparation method thereof, and an application thereof. Background Art

[0002] Due to rapid economic development, national policies are placing increasing emphasis on fire safety. Power cables used in buildings and rail transit must possess high charring properties to ensure that the char layer maintains a certain degree of integrity after the outer sheath of the cable burns in the event of a fire. Cables contain a large amount of non-flame-retardant insulation. In a fire, if the flames reach the internal structure, a large amount of non-flame-retardant insulation will ignite, dramatically increasing the release of combustion heat and volatile flammable substances, leading to a wider ignition rate. The outer char layer of the cable must not break or crack, preventing flames from reaching the inner cable layer and protecting the integrity of the cable's internal structure. This ensures that the inner insulation and core layer of the cable are not significantly damaged, ensuring that normal power and signal transmission can be maintained even in the event of a fire. Current sheath materials are mostly heavily filled with magnesium hydroxide or aluminum hydroxide. While magnesium-aluminum systems offer excellent flame retardancy, their charring strength is limited. During bundled combustion tests, the char layer can crack and drip, posing a risk of burning the internal structure, and exhibits poor smoke suppression.

[0003] Statistics show that 80% of fire deaths are caused by asphyxiation from smoke and toxic gases. Furthermore, smoke significantly reduces visibility, delaying firefighting and rescue efforts. While adding conventional smoke suppressants directly to hydroxide-flame-retardant polyolefin systems can improve smoke suppression, it can also degrade the material's mechanical properties. Therefore, the present invention provides a low-smoke, halogen-free polyolefin composition with superior smoke suppression and mechanical properties. Summary of the Invention

[0004] The object of the present invention is to overcome the deficiencies or defects in the above-mentioned prior art and to provide a low-smoke halogen-free polyolefin composition.

[0005] Another object of the present invention is to provide a method for preparing the low-smoke halogen-free polyolefin composition.

[0006] Another object of the present invention is to provide an application of the low-smoke halogen-free polyolefin composition.

[0007] To achieve the above objectives, the present invention adopts the following technical solutions:

[0008] A low-smoke halogen-free polyolefin composition, comprising the following components calculated in parts by weight:

[0009]

[0010]

[0011] The low-melting-point glass powder has an initial melting temperature of 400-675° C., and the mass ratio of the low-melting-point glass powder to zirconium phosphate is no more than 6.5:1.

[0012] In the present invention, by selecting polyolefin resin as the matrix resin and adding an appropriate amount of zirconium phosphate and low-melting glass powder with an initial melting temperature of 400-675°C, the polyolefin composition can have lower smoke density and better mechanical properties.

[0013] Specifically, the zirconium phosphate has a large specific surface area and abundant acidic sites, and has both catalytic and adsorption effects, which can reduce the generation of smoke and dust; at the same time, it can adsorb already generated small solid particles and small molecular suspended matter to further improve the smoke suppression performance; however, if the amount of zirconium phosphate added is too high, it will lead to poor dispersion in the system, resulting in a decrease in smoke suppression performance and mechanical properties; combined with low-melting-point glass powder with an initial melting temperature of 400-675°C, it makes it difficult to form small solid particles, thereby reducing smoke density.

[0014] It should be noted that, in the low-smoke halogen-free polyolefin composition of the present invention, the content of the polyolefin resin is preferably not less than 20 wt %.

[0015] It should be noted that the mass ratio of the low-melting-point glass powder and zirconium phosphate in the present invention does not exceed 6.5:1. For example, but not limited to, not more than 6.2:1, 6:1, 5.8:1, 5.5:1, 5.2:1, 4.8:1, 4.5:1, 4:1, 3.8:1, 3.5:1, 3.2:1, 3:1, 2.8:1, 2.5:1, 2.2:1 or 2:1 can all achieve the present invention.

[0016] Furthermore, the mass ratio of the low-melting-point glass powder to zirconium phosphate is 2:1 to 4:1.

[0017] It should be noted that the low-melting point glass powder in the present invention is 15 to 25 parts, for example but not limited to 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts or 25 parts, etc. can all achieve the present invention.

[0018] It should be noted that the zirconium phosphate in the present invention is 3 to 8 parts, for example but not limited to 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts or 8 parts, etc. can all achieve the present invention.

[0019] The initial melting temperature of the low-melting-point glass powder in the present invention is 400-675°C, for example, but not limited to 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C, 630°C, 640°C, 650°C or 675°C, etc., can all achieve the present invention.

[0020] Furthermore, the low-melting-point glass powder has an initial melting temperature of 450-650°C.

[0021] Furthermore, the low-melting-point glass powder has an initial melting temperature of 500-620°C.

[0022] Specifically, the onset temperature of the low-melting-point glass powder is tested by a muffle furnace.

[0023] Specifically, the average particle size of the low-melting-point glass powder is ≤20μm, for example but not limited to ≤19μm, 18μm, 17μm, 16μm, 15μm, 14μm, 13μm, 12μm, 11μm, 10μm, 9μm, 8μm, 7μm, 6μm, 5μm, 4μm, 3μm, 2μm or 1μm, etc.

[0024] It should be noted that the polyolefin resin described in this invention can be selected from commonly used polyolefin resins based on existing techniques. For example, but not limited to, the polyolefin resin may include 10-20 parts ethylene-vinyl acetate copolymer, 15-30 parts metallocene linear low-density polyethylene, and 5-15 parts POE. These amounts are particularly suitable for cable sheathing materials.

[0025] Furthermore, the average particle size of the zirconium phosphate is ≤20 μm, for example but not limited to ≤19 μm, 18 μm, 17 μm, 16 μm, 15 μm, 14 μm, 13 μm, 12 μm, 11 μm, 10 μm, 9 μm, 8 μm, 7 μm, 6 μm, 5 μm, 4 μm, 3 μm, 2 μm or 1 μm, etc.

[0026] Specifically, the average particle size of the zirconium phosphate is 1 to 15 μm.

[0027] Specifically, the average particle sizes of the low-melting-point glass powder and zirconium phosphate are obtained by testing with a laser particle size analyzer.

[0028] Furthermore, the halogen-free flame retardant is a hydroxide flame retardant.

[0029] Furthermore, the hydroxide flame retardant is magnesium hydroxide and / or aluminum hydroxide.

[0030] Furthermore, the compatibilizer is a maleic anhydride grafted product.

[0031] Furthermore, the maleic anhydride grafted product is PE grafted maleic anhydride and / or POE grafted maleic anhydride.

[0032] Specifically, the maleic anhydride grafting rate of the compatibilizer is 0.5-2%.

[0033] Specifically, the test method for the maleic anhydride grafting rate is infrared spectroscopy.

[0034] Furthermore, the low-smoke halogen-free polyolefin composition further comprises 0.1 to 5 parts of an auxiliary agent.

[0035] Specifically, the auxiliary agent includes, for example but not limited to, one or more of an antioxidant, a metal deactivator, a lubricant, a weathering agent or a toner.

[0036] In the present invention, commonly used antioxidants may be selected, such as, but not limited to, one or more of hindered phenol antioxidants, phosphite antioxidants, or thioester antioxidants.

[0037] Specifically, the hindered phenol antioxidant is one or more of N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxyphenylpropionamide) (Irganox 1098), pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (Irganox 1010), 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (Irganox 259), β-(4-hydroxy-3,5-di-tert-butylphenyl)propionic acid n-octadecyl (Irganox 1076) or 3,9-bis{2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)acrylate]-1,1-dimethyl}-2,4,8,10-tetraoxaspirocycloundecane (ADK AO-80).

[0038] The phosphite antioxidant is one or more of tris(2,4-di-tert-butylphenyl)phosphite (Irganox 168), bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol phosphite (PEP-36) or 627A.

[0039] The thioester antioxidant is one or more of distearyl thiodipropionate, dilauryl thiodipropionate or pentaerythritol dodecylthiopropionate.

[0040] In the present invention, commonly used metal deactivators may be selected, such as but not limited to hydrazide metal deactivators and / or oxime metal deactivators.

[0041] Specifically, the hydrazide metal deactivator is N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine (MD-1024) and / or 2,2-oxalamido-bis[ethyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)]propionate.

[0042] Specifically, the oxime metal deactivator is dimethyl ketoxime and / or acetone carboxymethyl oxime.

[0043] The present invention can select commonly used lubricants, such as but not limited to one or more of vinyl bisstearamide, polysiloxane, calcium stearate, magnesium stearate, zinc stearate, silicone, PE wax, or PP wax.

[0044] In the present invention, commonly used weathering agents can be selected according to the prior art, such as but not limited to hindered amine light stabilizers and benzotriazole ultraviolet light absorbers.

[0045] Specifically, the hindered amine light stabilizer is 2,2,6,6-tetramethyl-4-piperidinyl stearate and / or bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate.

[0046] The present invention also provides a method for preparing the low-smoke halogen-free polyolefin composition, comprising the following steps:

[0047] The components are mixed uniformly, and the mixture is subjected to banburying and extrusion granulation to obtain a low-smoke flame-retardant polyolefin composition.

[0048] The present invention also protects the use of the low-smoke zero-halogen polyolefin composition in the preparation of low-smoke zero-halogen cable materials.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] The present invention provides a low-smoke halogen-free polyolefin composition. By adopting a polyolefin resin as a base resin and adding an appropriate amount of zirconium phosphate and a low-melting-point glass powder with a specific initial melting temperature, the smoke density of the polyolefin composition can be effectively reduced, and the mechanical properties of the composition can be improved. DETAILED DESCRIPTION

[0051] The present invention is further described in detail below with reference to specific examples. The examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods used in the following examples are conventional methods unless otherwise specified; the materials and reagents used are commercially available reagents and materials unless otherwise specified.

[0052] The raw materials used in each embodiment and comparative example are:

[0053] Polyolefin resin:

[0054] Linear low-density polyethylene (LLDPE): LLDPE ENGAGE 3518PA, produced by ExxonMobil;

[0055] Ethylene vinyl acetate copolymer (EVA): EVA 6020M, produced by Yangzi Petrochemical-BASF;

[0056] POE elastomer: POE 58750, produced by Dow Chemical;

[0057] Halogen-free flame retardant: magnesium hydroxide, H-5, Huber, USA;

[0058] Low melting point glass powder:

[0059] Low melting point glass powder 1: D250, melting point 500℃, Anmi Micron;

[0060] Low melting point glass powder 2: FD81A, melting point 650℃, Anmi Micron;

[0061] Low melting point glass powder 3: D245, melting point 450℃, Anmi Micron;

[0062] Low melting point glass powder 4: FD76B, melting point 620℃, Anmi Micron;

[0063] Low melting point glass powder 5: D235, melting point 350℃, Anmi Micron;

[0064] Low melting point glass powder 6: D270, melting point 700℃, Anmi Micron;

[0065] Zirconium phosphate:

[0066] Zirconium phosphate 1: RS-LSG-C, Ruisen New Materials Co., Ltd.;

[0067] Zirconium phosphate 2: Zirconium phosphate, Yaolong Chemical Co., Ltd.;

[0068] Zirconium silicate: Zirconium silicate, Shanghai Myril Biochemical Technology Co., Ltd.;

[0069] Compatibilizer: PE grafted maleic anhydride, MC-218, produced by Nengzhiguang;

[0070] Additives: a mixture of antioxidants PEP-36 and MD-1024 in a mass ratio of 2:1, both of which are commercially available; it should be noted that the same raw materials are used in the parallel experiments of the examples of the present invention and the comparative examples.

[0071] Examples 1 to 11 and Comparative Examples 1 to 7

[0072] According to the formula in Tables 1 and 2, a low-smoke halogen-free polyolefin composition was prepared according to the following preparation method:

[0073] The polyolefin resin, compatibilizer, halogen-free flame retardant, low-melting point glass powder, zirconium phosphate and additives are added to a high-speed mixer in proportion and mixed evenly at a speed of 1000-2000 rpm, and then put into an internal mixer. After internal mixing, the mixture is extruded and granulated through a two-stage single-screw extruder to obtain a low-smoke flame-retardant polyolefin composition. The temperature of the internal mixer is 120-140°C, and the extrusion temperature is 140-150°C.

[0074] Table 1 Amount of each component in the low smoke halogen-free polyolefin composition in Examples 1 to 11 (Unit: parts by weight)

[0075]

[0076]

[0077] Table 2 Amount of each component in the polyolefin composition of Comparative Examples 1 to 7 (Unit: parts by weight)

[0078]

[0079] Performance Testing

[0080] 1. Test Method

[0081] The low-smoke halogen-free polyolefin compositions prepared in the above examples and comparative examples were subjected to performance tests:

[0082] (1) Mechanical property test: The low-smoke halogen-free polyolefin compositions prepared in the above examples and comparative examples were pressed into sheets on a flat vulcanizer at 180°C for 10 min, with a pressure of 15 MPa and a thickness of 1 mm. After standing at room temperature for 16 h, the mechanical properties of the 1 mm thick sheets were measured in accordance with the standard GB / T 1040.2-2018.

[0083] (2) Smoke density test: The low-smoke halogen-free polyolefin compositions prepared in the above examples and comparative examples were prepared into samples of 100 mm×100 mm×1 mm, and the smoke density was measured according to the standard GB / T 8323.2-2008.

[0084] According to the GB / T32129-2015 standard, the tensile strength must be ≥10MPa, the elongation at break must be ≥160%, the flame smoke density must be ≤100, and the flameless smoke density must be ≤350.

[0085] (3) Flame Retardancy: The low-smoke halogen-free polyolefin compositions prepared in the above examples and comparative examples were prepared into 125 mm × 12.5 mm × 3 mm strips and tested for UL 94 vertical combustion, according to the method of ASTM 3801-2006. UL94 combustion grades are divided into four levels: V-0, V-1, V-2, and NR. The flame retardancy represented by the four grades V-0, V-1, V-2, and NR decreases in order, with V-0 being the best.

[0086] 2. Test results

[0087] The test results of the embodiments and comparative examples are shown in Table 3.

[0088] Table 3 Test results of various embodiments and comparative examples

[0089]

[0090]

[0091] As can be seen from Table 3, the low-smoke halogen-free polyolefin composition prepared by the present invention has low smoke density and good mechanical properties, tensile strength ≥12 MPa, elongation at break ≥200%, flame smoke density ≤100, and flameless smoke density ≤350, meeting the GB / T32129-2015 standard; further preferably, the flameless smoke density of the low-smoke halogen-free polyolefin composition prepared by the present invention is ≤330.

[0092] From the comparison between Comparative Examples 1 to 3 and Examples 1 to 5, it can be seen that without adding zirconium phosphate and glass powder, or adding only one of them, the smoke suppression performance is poor;

[0093] Comparative Examples 4 and 5 show that the smoke suppression performance of the polyolefin composition obtained by using glass frit with an incipient melting temperature that is too low or too high is poor. This may be because when the incipient melting temperature is too low, excessive flow occurs during combustion, resulting in almost no setting ability and low residual carbon content. When the incipient melting temperature is too high, the glass frit cannot be melted and dispersed in time, and the bonding and bridging effect cannot be fully achieved, resulting in a loose carbon layer, which leads to reduced smoke suppression performance.

[0094] It can be seen from Comparative Example 6 that when the ratio of low-melting-point glass powder to zirconium phosphate is too high, the smoke suppression performance of the obtained composition decreases;

[0095] It can be seen from Comparative Example 7 that when non-zirconium phosphate is compounded with glass powder, the smoke suppression performance cannot meet the requirements.

[0096] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A low-smoke halogen-free polyolefin composition, characterized in that: The composition comprises the following components calculated in parts by weight: 30-60 parts of polyolefin resin; 3-10 parts of compatibilizer; 45-65 parts of halogen-free flame retardant; 15-25 parts of low melting point glass powder; 3-8 parts of zirconium phosphate; The low-melting-point glass powder has an initial melting temperature of 400-675° C.; the mass ratio of the low-melting-point glass powder to zirconium phosphate is no more than 6.5:1; and the halogen-free flame retardant is a hydroxide flame retardant.

2. The low-smoke, halogen-free polyolefin composition according to claim 1, characterized in that: The mass ratio of the low-melting-point glass powder to zirconium phosphate is 2:1 to 4:

1.

3. The low-smoke halogen-free polyolefin composition according to claim 1, characterized in that: The low-melting-point glass powder has an initial melting temperature of 450-650°C.

4. The low-smoke, halogen-free polyolefin composition according to claim 1, characterized in that: The polyolefin resin comprises 10 to 20 parts of ethylene-vinyl acetate copolymer, 15 to 30 parts of metallocene linear low-density polyethylene, and 5 to 15 parts of POE.

5. The low-smoke halogen-free polyolefin composition according to claim 1, characterized in that: The compatibilizer is a maleic anhydride grafted compound.

6. The low-smoke, halogen-free polyolefin composition according to claim 1, characterized in that: The low-smoke halogen-free polyolefin composition further comprises 0.1 to 5 parts of an auxiliary agent.

7. The low-smoke, halogen-free polyolefin composition according to claim 6, characterized in that: The auxiliary agent includes one or more of an antioxidant, a metal deactivator, a lubricant, a weathering agent or a toner.

8. A method for preparing the low-smoke halogen-free polyolefin composition according to any one of claims 1 to 7, characterized in that: The steps include: The components are mixed uniformly, and the mixture is subjected to banburying and extrusion granulation to obtain a low-smoke flame-retardant polyolefin composition.

9. Use of the low-smoke zero-halogen polyolefin composition according to any one of claims 1 to 7 in the preparation of low-smoke zero-halogen cable materials.

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