Halogen-free flame-retardant high-load polypropylene master batch

Abstract

The invention discloses a halogen-free flame-retardant high-load polypropylene master batch which comprises the following raw materials: polypropylene, a compatilizer, a flame retardant, an interface modifier and a lubricant, the flame retardant accounts for 43% or more of the total mass of the master batch, and the flame retardant is a first coupling agent modified phosphorus-nitrogen flame retardant; the interface modifier is prepared by reacting long-chain-segment amino-terminated polydimethylsiloxane and a short-chain-segment second coupling agent with 1, 4-butanediol diglycidyl ether; the first coupling agent and / or the second coupling agent are / is one or a combination of a secondary amino coupling agent and a primary amino coupling agent. A phosphorus-nitrogen flame retardant is modified by a first coupling agent, and is combined with an interface modifier prepared by reacting amino-terminated polydimethylsiloxane and a second coupling agent with 1, 4-butanediol diglycidyl ether, so that the dispersity of the flame retardant is optimized, and the content of a halogen-free flame retardant in the polypropylene master batch is increased on the premise of ensuring the mechanical property; the flame-retardant effect is improved.

Description

Technical Field

[0001] This invention relates to the field of flame retardant masterbatch technology, specifically to a halogen-free flame retardant high-load polypropylene masterbatch. Background Technology

[0002] Polypropylene, one of the five major general-purpose plastics, is widely used in electronic and electrical housings, automotive interior parts, and other fields. However, its limiting oxygen index is only 17% to 18%, posing a serious fire hazard. Traditional brominated flame retardants are limited by environmental issues, while inorganic flame retardants need to be added at more than 50% to achieve a V-0 rating, which seriously damages the mechanical properties of the material.

[0003] In the existing technology, although phosphorus and nitrogen flame retardants have environmental advantages, their high polarity characteristics and the non-polar molecular chains of polypropylene have serious interfacial incompatibility problems, which makes the flame retardants easy to agglomerate in the substrate, forming stress concentration points. When the addition amount exceeds 30%, "powdering" is likely to occur, resulting in a decrease in melt strength and blooming on the surface of the product.

[0004] Therefore, it is necessary to solve the problems of interfacial compatibility and processing rheology caused by high flame retardant filling in polypropylene masterbatch. Summary of the Invention

[0005] One of the objectives of this invention is to overcome the deficiencies in the prior art and provide a halogen-free flame-retardant high-load polypropylene masterbatch. This masterbatch is modified by a first coupling agent using a phosphorus-nitrogen flame retardant, combined with an interface modifier prepared by reacting an amino-terminated polydimethylsiloxane and a second coupling agent with 1,4-butanediol diglycidyl ether. This optimizes the dispersibility of the flame retardant and, while ensuring mechanical properties, increases the content of the halogen-free flame retardant in the polypropylene masterbatch, thereby improving the flame-retardant effect.

[0006] To achieve the above-mentioned process effects, the technical solution of the present invention is as follows: a halogen-free flame-retardant high-load polypropylene masterbatch, the raw materials of which include polypropylene, compatibilizer, flame retardant, interface modifier and lubricant, wherein the flame retardant accounts for more than 43% of the total mass of the masterbatch, and the flame retardant is a first coupling agent modified phosphorus-nitrogen flame retardant. The interface modifier is prepared by reacting a long-chain segment terminal amino polydimethylsiloxane and a short-chain segment second coupling agent with 1,4-butanediol diglycidyl ether. The first coupling agent and / or the second coupling agent is one or a combination of secondary amino coupling agents and primary amino coupling agents.

[0007] A preferred technical solution is as follows: The raw materials of the polypropylene masterbatch, by mass fraction, include 21.6%~43.3% polypropylene, 3.8%~11.2% compatibilizer, 43%~67.3% flame retardant, 2.3%~9.0% interface modifier, and 0.7%~3.5% lubricant. Further, the raw materials of the polypropylene masterbatch include 24%~40% polypropylene, 5%~10% compatibilizer, 50%~65% flame retardant, 3%~8% interface modifier, and 1%~3% lubricant. Even further, the flame retardant percentage of the total masterbatch mass can be selected as 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 67.3%, or any two ratios as a range of maximum and minimum values.

[0008] A preferred technical solution is as follows: The reaction raw materials of the interface modifier, by weight, include 50-80 parts of amino-terminated polydimethylsiloxane, 4-16 parts of a second coupling agent, and 100 parts of 1,4-butanediol diglycidyl ether. Further, the reaction raw materials of the interface modifier include 55-75 parts of amino-terminated polydimethylsiloxane, 5-15 parts of a second coupling agent, and 100 parts of 1,4-butanediol diglycidyl ether. Even further, the reaction raw materials of the interface modifier include 60-70 parts of amino-terminated polydimethylsiloxane, 6-12 parts of a second coupling agent, and 100 parts of 1,4-butanediol diglycidyl ether.

[0009] A preferred technical solution is as follows: the phosphorus-nitrogen flame retardant is composed of ammonium polyphosphate and melamine cyanurate, wherein the mass ratio of ammonium polyphosphate to melamine cyanurate is (2~3):1, and the amount of the first coupling agent added in the flame retardant is 3%~5% of the phosphorus-nitrogen flame retardant. Further, the mass ratio of ammonium polyphosphate to melamine cyanurate can be selected as 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1, or any two ratios within a range of maximum and minimum values.

[0010] The preferred technical solution is that the compatibilizer comprises a combination of maleic anhydride-grafted polypropylene and maleic anhydride-grafted polyolefin elastomer.

[0011] A preferred technical solution is that the mass ratio of maleic anhydride-grafted polypropylene to maleic anhydride-grafted polyolefin elastomer is 1:(0.5~1.2). Further, the mass ratio of maleic anhydride-grafted polypropylene to maleic anhydride-grafted polyolefin elastomer can be selected as 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, or any two ratios within a range of maximum and minimum values.

[0012] A preferred technical solution is that the lubricant comprises a combination of vinyl bis-stearamide and oxidized polyethylene wax. Further, the mass ratio of vinyl bis-stearamide to oxidized polyethylene wax is 1:(0.8~1.5). Further, the mass ratio of vinyl bis-stearamide to oxidized polyethylene wax can be selected as 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, or any two ratios within a range of maximum and minimum values.

[0013] The preferred technical solution is that the polypropylene is a homopolymer polypropylene with a melt index of 15~30g / 10min, and the isotacticity of the homopolymer polypropylene is ≥96%.

[0014] The preferred technical solution is that both the first coupling agent and the second coupling agent are γ-aminopropyltriethoxysilane.

[0015] The preferred technical solution is as follows: the preparation method of the interface modifier is as follows: under the protection of nitrogen atmosphere, the terminal amino polydimethylsiloxane and the second coupling agent are mixed evenly, the temperature is raised to 60~70℃, and then 1,4-butanediol diglycidyl ether is added, and the reaction is kept at the temperature for 5~8h.

[0016] The advantages and beneficial effects of this invention are as follows: By modifying the first coupling agent with a phosphorus-nitrogen flame retardant and combining it with an interface modifier prepared by reacting terminal amino polydimethylsiloxane and a second coupling agent with 1,4-butanediol diglycidyl ether, the dispersibility of the flame retardant is optimized. Under the premise of ensuring mechanical properties, the content of halogen-free flame retardant in polypropylene masterbatch is increased, thereby improving the flame retardant effect. Detailed Implementation

[0017] The specific embodiments of the present invention will be further described below with reference to examples. These examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0018] Interface modifiers The raw materials for the interface modifier include 50-80 parts of amino-terminated polydimethylsiloxane, 4-16 parts of the second coupling agent, and 100 parts of 1,4-butanediol diglycidyl ether.

[0019] Among them, the molecular weight of amino-terminated polydimethylsiloxane is 1000~3000.

[0020] Long-chain terminal amino-terminated polydimethylsiloxane improves the interfacial compatibility between the interface modifier and the polypropylene resin substrate, while short-chain secondary coupling agent increases the interaction point between the interface modifier and the inorganic flame retardant. Therefore, excessive content of long-chain terminal amino-terminated polydimethylsiloxane improves the interfacial compatibility between the interface modifier and the polypropylene resin substrate, but weakens the compatibility between the interface modifier and the flame retardant. Furthermore, excessive long-chain content creates steric hindrance, reducing the interaction point with the flame retardant and leading to decreased compatibility of the flame retardant in the masterbatch. Conversely, insufficient content of long-chain terminal amino-terminated polydimethylsiloxane decreases the interfacial compatibility between the interface modifier and the polypropylene resin substrate, negatively impacting the compatibility of the flame retardant in the masterbatch. Insufficient content of 1,4-butanediol diglycidyl ether is detrimental to the formation of the interface modifier molecular chain, thus resulting in poor interface modification effect in the masterbatch.

[0021] The nitrogen atmosphere is used to prevent the second coupling agent from self-condensing or polymerizing with amino-terminated polydimethylsiloxane.

[0022] Reaction Principle: The long-chain segment terminal amino-terminated polydimethylsiloxane contains amino groups, and the short-chain segment second coupling agent also contains amino groups. Both react with the epoxy groups of 1,4-butanediol diglycidyl ether. By adjusting the ratio of the terminal amino-terminated polydimethylsiloxane and the second coupling agent to 1,4-butanediol diglycidyl ether, the molecular chain of the interface modifier retains epoxy groups after the reaction, further undergoing a cross-linking reaction with the surface-active amino groups of the phosphorus-nitrogen flame retardant treated with the first coupling agent. The long-chain segment exhibits good compatibility with the non-polar resin matrix polypropylene, further improving the compatibility and dispersibility of the flame retardant in the raw material system.

[0023] The long-chain segment terminal amino polydimethylsiloxane is a flexible segment with lubricating and toughening effects, and it is not easy to precipitate from the masterbatch after further forming a longer molecular chain.

[0024] Flame retardant The flame retardant is a phosphorus-nitrogen flame retardant modified with a first coupling agent. The phosphorus-nitrogen flame retardant is composed of ammonium polyphosphate and melamine cyanurate, with a mass ratio of (2~3):1. Modification by the first coupling agent, which is added at 3%~5% of the phosphorus-nitrogen flame retardant, not only improves the dispersibility of the flame retardant in the masterbatch raw material but also imparts amino groups to the masterbatch, enabling cross-linking with the interface modifier and compatibilizer.

[0025] compatibilizer The compatibilizer is a combination of maleic anhydride-grafted polypropylene and maleic anhydride-grafted polyolefin elastomer.

[0026] Furthermore, the mass ratio of maleic anhydride-grafted polypropylene to maleic anhydride-grafted polyolefin elastomer is 1:(0.5~1.2). Even further, the grafting rate of maleic anhydride-grafted polypropylene and / or maleic anhydride-grafted polyolefin elastomer is between 1% and 1.5%.

[0027] The compound of maleic anhydride-grafted polypropylene and maleic anhydride-grafted polyolefin elastomer serves as a compatibilizer. On the one hand, the non-polar polypropylene and polyolefin elastomer segments contained in the compatibilizer have similar polarity to the polypropylene substrate, resulting in good compatibility between maleic anhydride-grafted polypropylene and the polypropylene substrate. However, the polypropylene substrate itself is brittle and lacks toughness. Grafting maleic anhydride onto polyolefin elastomer improves the toughness of the substrate. On the other hand, the grafted maleic anhydride is a polar group, similar to the high polarity of phosphorus-nitrogen flame retardants, further improving the compatibility between the masterbatch raw materials.

[0028] The principle of intermolecular synergistic effect: During processing, the anhydride groups of maleic anhydride-grafted polypropylene and maleic anhydride-grafted polyolefin elastomers undergo esterification reactions with the hydroxyl groups on the surface of phosphorus-nitrogen flame retardant particles, as well as amino reactions after modification with the first coupling agent, resulting in chemical cross-linking at the interface. The polyolefin elastomer matrix in maleic anhydride-grafted polyolefin elastomers is mainly ethylene-octene copolymer, which exhibits better toughening effects compared to other types of base elastomers. The long octene chains of the maleic anhydride-grafted polyolefin elastomer become entangled with the polypropylene molecular chains through van der Waals forces, forming a rigid-flexible network structure, thereby improving the toughness of the polypropylene substrate.

[0029] Flame-retardant synergistic mechanism: Polyphosphoric acid, generated from the pyrolysis of ammonium polyphosphate (APP), is mixed with a polypropylene substrate and esterified with maleic anhydride-grafted polypropylene molecular chains to form a continuously expanding char layer. The olefin radicals generated from the thermal decomposition of maleic anhydride-grafted polyolefin elastomer undergo a quenching reaction with the nitrogen-containing radicals released by melamine cyanurate (MCA) upon heating, thereby reducing the flame propagation speed. First stage: APP decomposes to generate polyphosphoric acid, catalyzing the dehydration and pre-charring of PP; Second stage: MCA sublimates endothermically, lowering the system temperature and releasing inert gas to dilute oxygen; Third stage: Decomposition products (cyanuric acid) react with APP decomposition products (polyphosphoric acid) to generate a PNC cross-linked network, strengthening the char layer.

[0030] The preparation method of halogen-free flame-retardant high-load polypropylene masterbatch involves mixing the raw materials for halogen-free flame-retardant high-load polypropylene masterbatch as shown in Tables 1-2, and then extruding and granulating them using a twin-screw extruder. The twin-screw extruder has an L / D ratio of 45, a feed screw speed of 25 r / min, and a main screw speed of 200 r / min.

[0031] The examples and comparative examples include the following raw materials: The polypropylene used is homopolymer polypropylene with a melt index of 15~30 g / 10min, and the isotacticity of the homopolymer polypropylene is ≥96%. The grafting rate of maleic anhydride-grafted polypropylene is 1%~1.5%; The grafting rate of maleic anhydride-grafted polyolefin elastomers is 1%~1.5%; Vinyl bis-stearamide is industrial grade, 99%; Oxidized polyethylene wax is industrial grade, 99%; Ammonium polyphosphate is industrial grade, 99%; Melamine cyanurate is industrial grade, 99%; Both the first and second coupling agents are γ-aminopropyltriethoxysilane, industrial grade, 99%; The molecular weight of amino-terminated polydimethylsiloxane is 1000~3000; 1,4-Butanediol diglycidyl ether is industrial grade, 99%.

[0032] The raw materials for polypropylene masterbatch, by mass fraction, are shown in Table 1 below: Table 1

[0033] The raw materials for polypropylene masterbatch, by mass fraction, are shown in Table 2 below: Table 2

[0034] illustrate: APP stands for ammonium polyphosphate; MCA stands for melamine cyanurate.

[0035] Compatibilizer A1 represents maleic anhydride-grafted polypropylene; compatibilizer A2 represents maleic anhydride-grafted polyolefin elastomer.

[0036] Lubricant B1 represents vinyl bis-stearamide; lubricant B2 represents oxidized polyethylene wax.

[0037] The reaction raw materials for the interface modifier (sample 1) include 66 parts of amino-terminated polydimethylsiloxane, 10 parts of the second coupling agent, and 100 parts of 1,4-butanediol diglycidyl ether. The reaction raw materials for the interface modifier (sample 2) include 50 parts of amino-terminated polydimethylsiloxane, 16 parts of the second coupling agent, and 100 parts of 1,4-butanediol diglycidyl ether. The reaction raw materials for the interface modifier (sample 3) include 80 parts of amino-terminated polydimethylsiloxane, 4 parts of the second coupling agent, and 100 parts of 1,4-butanediol diglycidyl ether.

[0038] Among them, after mixing phosphorus-nitrogen flame retardants APP and MCA, a first coupling agent of 4% of the total mass of the two is added for further mixing to obtain flame retardant.

[0039] Preparation of interface modifier: Under nitrogen atmosphere protection, the terminal amino polydimethylsiloxane and the second coupling agent were mixed evenly, heated to 65℃, and then 1,4-butanediol diglycidyl ether was added and the reaction was maintained at the temperature for 6.5h.

[0040] Performance testing of protective film samples prepared in the examples and comparative examples: 1. Tensile strength and elongation at break: determined according to GB / T 1040.1-2018 standard.

[0041] 2. Melt Flow Rate (MFR): Measured according to GB / T 3682.1-2018 standard.

[0042] 3. Oxygen Index (LOI): Measured according to GB / T 2406.2-2009 standard.

[0043] The performance test results of the examples and comparative examples are shown in Table 3 below: Table 3

[0044] Compared to Example 1, Example 3 shows an increase in the amount of flame retardant added, but by increasing the amount of interface modifier, the mechanical properties of the masterbatch are optimized and do not decrease significantly.

[0045] Compared to Example 1, Example 7 shows an increase in the amount of terminal amino polydimethylsiloxane in the interface modifier, which increases steric hindrance during synthesis. At the same time, the amount of the second coupling agent is reduced, which is not conducive to the grafting of the second coupling agent. This has a negative impact on the compatibility of the interface modifier with the flame retardant and polypropylene substrate in the masterbatch raw material.

[0046] Compared to Example 1, the content of maleic anhydride-grafted polyolefin elastomer in the compatibilizer decreased in Examples 8 and 9, which had a negative impact on the toughness of the obtained masterbatch. Maleic anhydride-grafted polyolefin elastomer has a strong ability to act on flame retardants. The reduced amount added can easily lead to flame retardant agglomeration, affecting the dispersibility of the flame retardant, and thus the flame retardant performance tends to decline.

[0047] Compared to Example 1, Example 10 shows that as the content of maleic anhydride-grafted polyolefin elastomer in the compatibilizer increases, it has a negative impact on the tensile strength of the obtained masterbatch; the increased entanglement with polypropylene molecular chains increases the melt viscosity, affecting the dispersibility of the flame retardant, and thus the flame retardant performance tends to decrease.

[0048] Compared to Example 1, Comparative Examples 1 and 2, with their combination of compatibilizer and interface modifier, work together to optimize the compatibility between the flame retardant and the polypropylene substrate, thus achieving optimal performance.

[0049] Compared to Example 1, Comparative Examples 3 and 4 show that the phosphorus-nitrogen flame retardants obtained by combining ammonium polyphosphate and melamine cyanurate work together on the polypropylene and polyolefin elastomer materials in the polypropylene masterbatch, resulting in better flame retardant effect of the polypropylene masterbatch.

[0050] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A halogen-free flame-retardant high-load polypropylene masterbatch, characterized in that, The raw materials include polypropylene, compatibilizer, flame retardant, interface modifier and lubricant, wherein the flame retardant accounts for more than 43% of the total mass of the masterbatch, and the flame retardant is a phosphorus-nitrogen flame retardant modified by the first coupling agent. The interface modifier is prepared by reacting a long-chain segment terminal amino polydimethylsiloxane and a short-chain segment second coupling agent with 1,4-butanediol diglycidyl ether. The first coupling agent and / or the second coupling agent is one or a combination of secondary amino coupling agents and primary amino coupling agents.

2. The halogen-free flame-retardant high-load polypropylene masterbatch according to claim 1, characterized in that, The raw materials of the polypropylene masterbatch, by mass fraction, include 21.6% to 43.3% polypropylene, 3.8% to 11.2% compatibilizer, 43% to 67.3% flame retardant, 2.3% to 9.0% interface modifier, and 0.7% to 3.5% lubricant.

3. The halogen-free flame-retardant high-load polypropylene masterbatch according to claim 1 or 2, characterized in that, The reaction raw materials of the interface modifier, by mass parts, include 50-80 parts of amino-terminated polydimethylsiloxane, 4-16 parts of the second coupling agent, and 100 parts of 1,4-butanediol diglycidyl ether.

4. The halogen-free flame-retardant high-load polypropylene masterbatch according to claim 1 or 2, characterized in that, The phosphorus-nitrogen flame retardant is composed of ammonium polyphosphate and melamine cyanurate, wherein the mass ratio of ammonium polyphosphate to melamine cyanurate is (2~3):1, and the amount of the first coupling agent added in the flame retardant is 3%~5% of the phosphorus-nitrogen flame retardant.

5. The halogen-free flame-retardant high-load polypropylene masterbatch according to claim 1 or 2, characterized in that, The compatibilizer comprises a combination of maleic anhydride-grafted polypropylene and maleic anhydride-grafted polyolefin elastomer.

6. The halogen-free flame-retardant high-load polypropylene masterbatch according to claim 5, characterized in that, The mass ratio of maleic anhydride-grafted polypropylene to maleic anhydride-grafted polyolefin elastomer is 1:(0.5~1.2).

7. The halogen-free flame-retardant high-load polypropylene masterbatch according to claim 1 or 2, characterized in that, The lubricant comprises a combination of vinyl bis-stearamide and oxidized polyethylene wax.

8. The halogen-free flame-retardant high-load polypropylene masterbatch according to claim 1 or 2, characterized in that, The polypropylene is a homopolymer polypropylene with a melt index of 15~30 g / 10 min, and the isotacticity of the homopolymer polypropylene is ≥96%.

9. The halogen-free flame-retardant high-load polypropylene masterbatch according to claim 3, characterized in that, Both the first coupling agent and the second coupling agent are γ-aminopropyltriethoxysilane.

10. The halogen-free flame-retardant high-load polypropylene masterbatch according to claim 9, characterized in that, The preparation method of the interface modifier is as follows: Under nitrogen atmosphere protection, the terminal amino polydimethylsiloxane and the second coupling agent are mixed evenly, heated to 60~70℃, and then 1,4-butanediol diglycidyl ether is added, and the reaction is kept at the temperature for 5~8h.

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