A halogen-free flame-retardant polyolefin composition, its preparation method and application

Abstract

This invention discloses a halogen-free flame-retardant polyolefin composition, its preparation method, and its application. The halogen-free flame-retardant polyolefin composition comprises the following components in parts by weight: 4-25 parts of silicone rubber-grafted polyolefin; 15-36 parts of polyolefin elastomer; and 55-65 parts of stearic acid-modified magnesium hydroxide; wherein the polyolefin in the silicone rubber-grafted polyolefin and the polyolefin elastomer have the same most abundant polyolefin species. By using silicone rubber-grafted polyolefin and polyolefin elastomer as base materials, adjusting the most abundant polyolefin species in the silicone rubber-grafted polyolefin and polyolefin elastomer to be the same, and combining stearic acid-modified magnesium hydroxide, the halogen-free flame-retardant polyolefin composition of this invention can effectively improve the flexural resistance of the composition, while also possessing good flame-retardant and mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of halogen-free flame retardant technology, specifically relating to a halogen-free flame retardant polyolefin composition, its preparation method, and its application. Background Technology

[0002] PVC materials are widely used in power cord materials due to their low cost and excellent flame retardant, bending, and flexural properties. However, they contain halogen components, which do not meet current international environmental requirements for halogen-free materials. Halogen-free flame-retardant polyolefins have become a research hotspot.

[0003] Commonly used halogen-free flame retardants are metal hydroxides, which have the advantages of low cost, low smoke, and environmental friendliness. However, their flame retardant efficiency is relatively low, and a large amount of flame retardant needs to be added to meet higher flame retardant ratings, which reduces the material's bending resistance. Therefore, there is a need in this field for a halogen-free flame-retardant polyolefin material that also has good bending resistance. Summary of the Invention

[0004] The purpose of this invention is to overcome the limitations of existing halogen-free flame-retardant polyolefin compositions in achieving both good flame retardant effect and flexural resistance, and to provide a halogen-free flame-retardant polyolefin composition.

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

[0006] Another object of the present invention is to provide the application of the halogen-free flame retardant composition.

[0007] To achieve the above objectives, the present invention employs the following technical solution:

[0008] A halogen-free flame-retardant polyolefin composition comprising the following components in parts by weight:

[0009] 4-25 parts of silicone rubber grafted polyolefin;

[0010] 15-36 parts of polyolefin elastomer;

[0011] Stearic acid-modified magnesium hydroxide, 55-65 parts;

[0012] The silicone rubber grafted polyolefin and the polyolefin elastomer contain the same type of polyolefin with the highest content.

[0013] In this invention, by selecting silicone rubber grafted polyolefin and polyolefin elastomer as matrix resins, adding stearic acid-modified magnesium hydroxide, and adjusting the highest content of polyolefin in silicone rubber grafted polyolefin and polyolefin elastomer to be the same, the resulting halogen-free flame-retardant polyolefin composition has good flame-retardant properties, while also having good bending resistance and mechanical properties.

[0014] Specifically, stearic acid-modified magnesium hydroxide can improve the oleophilicity of magnesium hydroxide and enhance its compatibility with the matrix resin. Grafting silicone rubber onto polyolefin can effectively improve compatibility. On the one hand, silicone rubber can act as a lubricant; on the other hand, it has good toughness and can improve bending resistance. In synergy with stearic acid-modified magnesium hydroxide and matrix resin, it can improve extrusion performance, bending resistance, and mechanical properties.

[0015] Specifically, the silicone rubber grafted polyolefin is a process in which silicone rubber is used as a side chain and grafted onto the polyolefin molecular chain.

[0016] Specifically, the polyolefin in the silicone rubber grafted polyolefin described in this invention is the same type of polyolefin as the polyolefin elastomer with the highest content.

[0017] When the silicone rubber grafted polyolefin is polyethylene grafted silicone rubber, the polyolefin elastomer is a vinyl elastomer; when the silicone rubber grafted polyolefin is polypropylene grafted silicone rubber, the polyolefin elastomer is a propylene-based elastomer.

[0018] The vinyl elastomer contains more than 70 wt% ethylene. Specifically, the vinyl elastomer includes ethylene-octene copolymers and / or ethylene-butene copolymers.

[0019] Specifically, the propylene-based elastomer contains more than 70 wt% propylene, preferably a propylene-ethylene copolymer.

[0020] It should be noted that in the halogen-free flame-retardant polyolefin composition of the present invention, the total content of the silicone rubber grafted polyolefin and the polyolefin elastomer is not less than 17 wt%, preferably not less than 35 wt%.

[0021] In this invention, the percentage of stearic acid-modified magnesium hydroxide in the total mass of silicone rubber grafted polyolefin and polyolefin elastomer is preferably no more than 350%.

[0022] It should be noted that the silicone rubber grafted polyolefin described in this invention is 4 to 25 parts, for example, but not limited to 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, or 25 parts, etc., all of which can achieve this invention.

[0023] The polyolefin elastomer described in this invention is 15 to 36 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, 25 parts, 26 parts, 27 parts, 28 parts, 29 parts, 30 parts, 31 parts, 32 parts, 33 parts, 34 parts, 35 parts, or 36 parts, etc., all of which can achieve this invention.

[0024] The stearic acid-modified magnesium hydroxide described in this invention is 55 to 65 parts, for example, but not limited to 55 parts, 56 parts, 57 parts, 58 parts, 59 parts, 60 parts, 61 parts, 62 parts, 63 parts, 64 parts or 65 parts, etc., all of which can achieve this invention.

[0025] Furthermore, the mass ratio of the silicone rubber grafted polyolefin to the polyolefin elastomer is 1:3 to 1:1, for example, but not limited to 1:3, 1:2.5, 1:2, 1:1.8, 1:1.5, or 1:1, all of which can achieve the present invention. Excessive use of polyolefin elastomer will result in poor extrusion appearance of the composition.

[0026] The silicone rubber grafted polyolefin described in this invention can be purchased or prepared in-house.

[0027] There are no particular restrictions on the preparation method of silicone rubber grafted polyolefin in this invention, and commonly used methods can be used in this invention.

[0028] In some specific embodiments, free radical initiation is used, and the preparation method of the silicone rubber grafted polyolefin is as follows:

[0029] It is obtained by extrusion granulation of polyolefin, silicone rubber and initiator.

[0030] The silicone rubber is a vinyl-containing silicone rubber, specifically selected from methyl vinyl silicone rubber and / or methyl phenyl vinyl silicone rubber.

[0031] The initiator can be selected from hydrogen peroxide, benzoyl peroxide, dicumyl peroxide, or bis(benzoyl) peroxide, etc.

[0032] Specifically, the product is obtained by mixing polyolefin, silicone rubber, and an initiator, and then extruding and granulating the mixture in a twin-screw extruder at 150–180°C. The initiator causes the double bonds in the silicone rubber to open, forming free radicals, which then react with the polyolefin molecular chains to form grafted products.

[0033] Specifically, the test standard for the melt flow rate of the silicone rubber grafted polyolefin is ASTM D-1238-2010.

[0034] Specifically, the melt flow rate of the silicone rubber grafted polyolefin at 190°C and a load of 2.16 kg is 0.1–5 g / 10 min.

[0035] Furthermore, the silicone rubber includes methyl vinyl silicone rubber and / or methyl phenyl vinyl silicone rubber.

[0036] Furthermore, the grafting rate of the silicone rubber grafted polyolefin is 0.5% to 1.8%. Specifically, the present invention can be achieved with grafting rates of 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, or 1.8%.

[0037] Specifically, the grafting rate is determined by infrared spectroscopy.

[0038] The grafting rate is controlled by adjusting the amount of silicone rubber and initiator. Specifically, the mass ratio of silicone rubber to initiator is 2:(0.1 to 0.15).

[0039] The amount of silicone rubber used is 1 to 4 wt% of the amount of polyolefin used.

[0040] Furthermore, the stearic acid-modified magnesium hydroxide has a particle size D50 < 10 μm. For example, but not limited to, particle sizes of < 10 μm, 9.5 μm, 9 μm, 8.5 μm, 8 μm, 7.5 μm, 7 μm, 6.5 μm, 6 μm, 5.5 μm, 5 μm, 4.5 μm, 4 μm, 3.5 μm, 3 μm, 2.5 μm, 2 μm, 1.5 μm, 1 μm, 0.5 μm, 0.4 μm, 0.3 μm, 0.2 μm, 0.1 μm, etc., can all achieve the present invention.

[0041] Specifically, the particle size of the stearic acid-modified magnesium hydroxide is determined by using a laser particle size analyzer.

[0042] Furthermore, the stearic acid-modified magnesium hydroxide has a particle size D50 of 0.1–3.5 μm.

[0043] Furthermore, the halogen-free flame-retardant polyolefin composition also includes 0.5 to 1 part of processing aids.

[0044] Specifically, the processing aids include antioxidants and / or colorants.

[0045] In this invention, commonly used antioxidants can be selected, such as, but not limited to, one or more of hindered phenolic antioxidants, phosphite antioxidants, or thioester antioxidants.

[0046] Specifically, the hindered phenolic antioxidant is one or more of N,N'-hexamethylene bis(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), octadecyl β-(4-hydroxy-3,5-di-tert-butylphenyl)propionate (Irganox 1076), or 3,9-bis{2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)acrylic acid]-1,1-dimethyl}-2,4,8,10-tetraoxaspirocycloundecane (ADK AO-80).

[0047] The phosphite antioxidant is one or more of tris(2,4-di-tert-butylphenyl) phosphite (Irganox 168), bis(2,6-di-tert-butyl-4-tolyl) pentaerythritol phosphite (PEP-36), or 627A.

[0048] The thioester antioxidant is one or more of distearate thiodipropionate, dilaurate thiodipropionate, or pentaerythritol-based dodecathiopropyl ester.

[0049] This invention also protects a method for preparing the above-mentioned halogen-free flame-retardant polyolefin composition, comprising the following steps:

[0050] The components are mixed evenly and then extruded and granulated to obtain a halogen-free flame-retardant polyolefin composition.

[0051] Specifically, the extrusion granulation is performed using a twin-screw extruder.

[0052] Specifically, the extrusion temperature is 130–180°C.

[0053] This invention also protects the use of the above-mentioned halogen-free flame-retardant polyolefin composition in the preparation of cable sheath materials.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] This invention provides a halogen-free flame-retardant polyolefin composition, which uses silicone rubber grafted polyolefin as the base material, adds stearic acid modified magnesium hydroxide as the flame retardant, and adjusts the type of polyolefin with the highest content in the silicone rubber grafted polyolefin and the polyolefin elastomer to be the same, so that the obtained halogen-free flame-retardant polyolefin composition has good flame retardant properties, while also having good bending resistance and mechanical properties. Detailed Implementation

[0056] The present invention will be further described in detail below with reference to specific embodiments. These embodiments are only used to explain the present invention and are not intended to limit the scope of the present invention. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods; the materials and reagents used are commercially available unless otherwise specified.

[0057] Raw materials used in each embodiment and comparative example:

[0058] Polypropylene resin: C5608, purchased from Yanshan Petrochemical;

[0059] Polyethylene resin: LLDPE 3518CB, purchased from ExxonMobil;

[0060] Silicone rubber:

[0061] Silicone Rubber 1: Methyl vinyl silicone rubber, 110, purchased from Zhejiang Hesheng Silicon Industry;

[0062] Silicone Rubber 2: Methylphenyl vinyl silicone rubber, 100, purchased from Ningbo Daoruo Organosilicon Co., Ltd.

[0063] Silicone rubber grafted polyolefins were prepared according to the formulations in Table 1 using the following method:

[0064] Polyolefin, silicone rubber and dicumyl peroxide are mixed and fed into a twin-screw extruder for extrusion granulation at 165°C.

[0065] Table 1. Dosage (parts by weight) and grafting rate of each component in silicone rubber grafted polyolefin.

[0066] Silicone rubber grafted polyolefin 1 2 3 4 5 Polypropylene resin 100 - 100 200 70 Polyethylene resin - 100 - - - Silicone rubber 1 2 2 - 2 2 Silicone rubber 2 - - 2 - - dicumyl peroxide 0.13 0.13 0.13 0.1 0.15 Grafting rate (%) 1.3 1.3 1.2 0.8 1.5

[0067] Maleic anhydride-grafted PE: MC218, grafting rate 0.8%, purchased from Ningbo Nengzhiguang;

[0068] Polyolefin elastomers:

[0069] Polyolefin elastomer 1: Propylene-based elastomer, Vistamaxx 3020FL, purchased from ExxonMobil;

[0070] Polyolefin elastomer 2: Propylene-based elastomer, Vistamaxx 6202, purchased from ExxonMobil;

[0071] Polyolefin elastomer 3: Vinyl elastomer, ethylene-octene copolymer, POE 5371, purchased from ExxonMobil;

[0072] Polyolefin elastomer 4: Vinyl elastomer, ethylene-butene copolymer, POE 9061, purchased from ExxonMobil;

[0073] Stearic acid modified magnesium hydroxide:

[0074] Stearic acid modified magnesium hydroxide 1:LN-6, with a particle size D50 of 1.1μm, was purchased from Shinjima Chemical Industry Co., Ltd.

[0075] Stearic acid modified magnesium hydroxide 2: Vertex 60HST, particle size D50 of 3.3μm, purchased from Qiu Bo, USA;

[0076] Stearic acid modified magnesium hydroxide 3: Vertex 100ST1, particle size D50 of 1.8μm, purchased from Qiu Bo, USA;

[0077] Silane-modified magnesium hydroxide: V-6, particle size D50 of 1.1 μm, purchased from Shinjima Chemical Industry Co., Ltd.

[0078] Processing aids:

[0079] Antioxidant: 1010, commercially available; the same raw materials were used in parallel experiments of the examples and comparative examples.

[0080] Examples 1-12 and Comparative Examples 1-7

[0081] According to the formulations in Tables 2-3, prepare halogen-free flame-retardant polyolefin compositions using the following preparation methods:

[0082] Silicone rubber grafted polyolefin, stearic acid modified magnesium hydroxide, polyolefin elastomer and processing aids were added to a twin-screw extruder in proportion and extruded and granulated at 165°C to obtain a halogen-free flame-retardant polyolefin composition.

[0083] Table 2. Amounts of each component in the halogen-free flame-retardant polyolefin compositions of Examples 1-12 (unit: parts by weight)

[0084]

[0085]

[0086] Table 3. Amounts of each component in the halogen-free flame-retardant polyolefin compositions of Comparative Examples 1–7 (unit: parts by weight)

[0087]

[0088]

[0089] Performance testing

[0090] 1. Testing Method

[0091] The halogen-free flame-retardant crosslinked polyolefin compositions prepared in the above examples and comparative examples were subjected to performance tests:

[0092] (1) Mechanical property test: The halogen-free flame-retardant polyolefin compositions prepared in the above examples and comparative examples were pressed into sheets at 180℃ for 10 min on a flat vulcanizing machine with a pressure of 15 MPa and a sheet thickness of 1 mm. After being placed at room temperature for 16 h, the mechanical properties of the 1 mm thick sheet were measured in accordance with standard GB / T 1040.2-2018. According to UL 2556-2021 standard, the elongation at break of the power cord is required to be >250%.

[0093] (2) Flame retardant performance test: 3 kg of the halogen-free flame retardant polyolefin composition prepared in the above examples and comparative examples was dried at 100°C for 2 hours, and then extruded into wire with a conductor of 1.5 mm. 2 The outer diameter of the wire is approximately 3.0mm or 4.5mm; the reference standard UL1581-2006 is used to test VW-1 flame retardancy; the smaller the outer diameter, the more difficult it is to pass the flame retardancy test.

[0094] (3) Cold bending performance test: The halogen-free flame retardant polyolefin compositions prepared in the above examples and comparative examples were tested according to the standard UL 2556-2021. The samples were placed at -20℃ for 4 hours and then wound and bent at -20℃. The requirement was that no cracking was required, which indicates that the composition has good bending resistance.

[0095] (4) Extrusion performance test: The halogen-free flame-retardant polyolefin compositions prepared in the above examples and comparative examples were extruded using an extruder. The extruded appearance was observed and divided into grades 1 to 3. Grade 1 is smooth surface without sanding or other phenomena; Grade 2 is relatively dull surface with slight unevenness; Grade 3 is melt fracture with severe sharkskin, and the surface has pits or particles.

[0096] 2. Test Results

[0097] Table 4 Performance test results for each embodiment and comparative example

[0098]

[0099]

[0100] As can be seen from Table 4, the halogen-free flame-retardant polyolefin composition prepared by the present invention has good mechanical properties and flame-retardant properties, as well as good bending resistance and extrusion performance. Specifically, the elongation at break is not less than 250%, which meets the UL 2556-2021 standard; it achieves 4.5mm VW-1 flame retardancy; and it can pass the cold bending test.

[0101] As can be seen from Examples 1 to 3, the smaller the particle size of stearic acid-modified magnesium hydroxide, the higher the elongation at break of the halogen-free flame-retardant polyolefin composition and the better the flame-retardant performance.

[0102] As can be seen from Comparative Examples 1 and 2, if the polyolefin in the silicone rubber grafted polyolefin and the polyolefin elastomer with the highest content are different, the resulting halogen-free flame-retardant polyolefin composition has a rough extrusion appearance and a reduced elongation at break.

[0103] As can be seen from Comparative Example 3, if silicone rubber is added directly to polyolefin resin, phase separation is easily formed, which leads to a significant decrease in its bending resistance and extrusion performance, and the reduced elongation at break fails to meet the requirements.

[0104] As can be seen from Comparative Example 4, if other modified magnesium hydroxides are used instead of stearic acid-modified magnesium hydroxides, the oleophilicity of magnesium hydroxides cannot be improved well, resulting in poor compatibility between magnesium hydroxides and the matrix resin. This leads to a significant decrease in flexural strength and extrusion performance, and the reduced elongation at break fails to meet the requirements.

[0105] As can be seen from Comparative Example 5, if too much stearic acid-modified magnesium hydroxide is used, the overall performance of the halogen-free flame-retardant polyolefin composition decreases, as do its elongation at break and flexural strength.

[0106] As can be seen from Comparative Example 6, if other polyolefin grafts are used instead of silicone rubber grafted polyolefins, they cannot simultaneously act as lubricants and improve bending performance.

[0107] As can be seen from Comparative Example 7, if the amount of polyolefin elastomer added is too small, the elongation at break of the prepared halogen-free flame-retardant polyolefin composition decreases, and the bending resistance also decreases, failing to meet the requirements.

[0108] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A halogen-free flame-retardant polyolefin composition, characterized in that, Includes the following components, calculated in parts by weight: 4-25 parts of silicone rubber grafted polyolefin; 15-36 parts of polyolefin elastomer; Stearic acid-modified magnesium hydroxide, 55-65 parts; Wherein, the silicone rubber grafted polyolefin is polyethylene grafted silicone rubber, and the polyolefin elastomer is a vinyl elastomer; or the silicone rubber grafted polyolefin is polypropylene grafted silicone rubber, and the polyolefin elastomer is a propylene-based elastomer; the grafting rate of the silicone rubber grafted polyolefin is 0.5~1.8%.

2. The halogen-free flame-retardant polyolefin composition according to claim 1, characterized in that, The stearic acid-modified magnesium hydroxide has a particle size D50 < 10 μm.

3. The halogen-free flame-retardant polyolefin composition according to claim 1, characterized in that, The mass ratio of the silicone rubber grafted polyolefin to the polyolefin elastomer is 1:3 to 1:

1.

4. The halogen-free flame-retardant polyolefin composition according to claim 1, characterized in that, The vinyl elastomer contains more than 70 wt% ethylene and is at least one of ethylene-octene copolymer and ethylene-butene copolymer; the propylene-based elastomer contains more than 70 wt% propylene.

5. The halogen-free flame-retardant polyolefin composition according to claim 4, characterized in that, The propylene-based elastomer is a propylene-ethylene copolymer.

6. The halogen-free flame-retardant polyolefin composition according to claim 1, characterized in that, The preparation method of the silicone rubber grafted polyolefin is as follows: It is obtained by extrusion granulation of polyolefin, silicone rubber and initiator.

7. The halogen-free flame-retardant polyolefin composition according to claim 6, characterized in that, The silicone rubber is methyl vinyl silicone rubber and / or methyl phenyl vinyl silicone rubber; the initiator is one or more of hydrogen peroxide, benzoyl peroxide, dicumyl peroxide or bis(benzoyl) peroxide.

8. The halogen-free flame-retardant polyolefin composition according to claim 1, characterized in that, The halogen-free flame-retardant polyolefin composition further includes 0.5 to 1 part of processing aids, which include antioxidants and / or colorants.

9. A method for preparing the halogen-free flame-retardant polyolefin composition according to any one of claims 1 to 8, characterized in that, Includes the following steps: The components are mixed evenly and then extruded and granulated to obtain a halogen-free flame-retardant polyolefin composition.

10. The use of the halogen-free flame-retardant polyolefin composition according to any one of claims 1 to 8 in the preparation of cable sheath material.

Images