Low-cost intumescent flame retardant composition and flame-retardant polyolefin resin composition

Abstract

To provide a low-cost expansion type flame retardant composition and a flame-retardant polyolefin resin composition.SOLUTION: A low-cost expansion type flame retardant composition comprises (A) piperazine pyrophosphate, (B) melamine pyrophosphate, and (C) calcium phosphate, wherein a mass ratio of component (A) to a sum of component (B) and component (C) [(A) component]:[(B) component+(C) component] is 70:30 to 30:70, and a mass ratio of component (B) to component (C) [(B) component]:[(C) component] is 60:40 to 95:5. The composition further comprises (D) a flame retardant synergist and (E) a coupling agent. The present invention can improve flame retardant efficiency of the flame retardant composition by introducing inexpensive calcium phosphate into a combination of piperazine pyrophosphate and melamine pyrophosphate, and can reduce the cost of the flame retardant composition by lowering the mass ratio of the piperazine pyrophosphate in the flame retardant composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to the field of flame retardants, and more particularly to a low-cost intumescent flame retardant composition and a flame-retardant polyolefin resin composition containing the flame retardant composition. [Background technology]

[0002] Polyolefin intumescent flame retardants are considered a promising green flame retardant due to their halogen-free nature, high flame retardancy, low smoke, low toxicity, and no molten droplets. Intumescent flame retardants generally consist of three components: an acid source (dehydrating agent), a carbon source (carbonizing agent), and a gas source (blowing agent). Their mechanism of action is that when a material burns, the phosphorus-containing flame retardant simultaneously burns to produce dehydrating combustion products, which dehydrate to carbon in the system. At the same time, the gas source generates inert gases and becomes a blowing agent, forming a dense, porous carbon layer on the surface of the material. This carbon layer provides thermal insulation and oxygen barrier properties, preventing further decomposition of the inner polymer and the release of combustible materials to the surface. It also blocks the transfer of heat to the polymer and blocks the oxygen source, effectively preventing the spread and propagation of flames, thereby achieving the flame retardant objective.

[0003] Currently used intumescent flame retardants are mainly obtained by blending ammonium polyphosphate as an acid source with melamine and a carbonizing agent. This type of flame retardant has problems such as poor effectiveness, poor compatibility with the substrate, significant impact on the electrical, insulating, and mechanical properties of the polymer, ease of migration, and poor hydrolytic and thermal stability. Piperazine pyrophosphate-based intumescent flame retardants are a new type of flame retardant composition. Compared with ammonium polyphosphate-based flame retardant compositions, they have better flame retardancy, heat resistance, and water precipitation resistance, and can be widely applied to materials such as polypropylene, polyethylene, acrylonitrile-butadiene-styrene, epoxy resin, and polyurethane. Patent No. CN201880042218.X discloses a flame retardant composition primarily composed of a combination of piperazine pyrophosphate, melamine pyrophosphate, and silicone oil, where the ratio of piperazine pyrophosphate to melamine pyrophosphate by weight ranges from 90:10 to 50:50, meaning the ratio of piperazine pyrophosphate must not be less than 50 parts by weight. The flame retardant system described in "Du Yuying. Study on the Flame Retardant Effect of Piperazine Pyrophosphate-Based Intumescent Flame Retardants on Polyolefins. Qingdao University of Science and Technology. Thesis, 2019," when used with polyethylene and polypropylene, has a comparatively good ratio of piperazine pyrophosphate to melamine pyrophosphate by weight of 2.5:1. "Chen Cheng et al. Synergistic flame retardancy of ZnO with piperazine pyrophosphate / melamine polyphosphate in PP. Polymer Testing, 2023, 117:107878" also showed that even when piperazine pyrophosphate and melamine pyrophosphate cooperate with ZnO, the mass ratio of piperazine pyrophosphate to melamine pyrophosphate still needs to be close to 2:1.

[0004] According to known methods, such as those described in "Zhao Zhen et al., Synthesis and Characterization of Piperazine Pyrophosphate, Chemical Engineering Technology, 2022, 30(5):18-21" and "Zhang Lingling et al., Synthesis of Melamine Polyphosphate, Chemical Engineering Times, 2013, 27(11):14-17," piperazine pyrophosphate is synthesized by first neutralizing phosphoric acid and piperazine, followed by condensation and dehydration. Similarly, melamine pyrophosphate is synthesized by first neutralizing phosphoric acid and melamine, followed by dehydration. Because piperazine, the main raw material used to synthesize both, is significantly more expensive than melamine, a high proportion of piperazine pyrophosphate in a flame retardant composition for practical use means higher application costs. For example, the parts by mass of piperazine pyrophosphate described in the aforementioned patents and papers should not be less than 50 parts. This suggests that the parts by weight of piperazine pyrophosphate salt are relatively high in the currently disclosed flame retardant formulations, resulting in relatively high costs of use. Summary of the Invention [Problem to be solved by the invention]

[0005] Based on the above technical problems, the present invention proposes a low-cost intumescent flame retardant composition which can provide good flame retardancy, and can reduce the mass part of piperazine pyrophosphate salt in the system, and has lower application cost. [Means for solving the problem]

[0006] The technical solutions adopted in the present invention are as follows:

[0007] A low-cost intumescent flame retardant composition, the composition comprising: (A) piperazine pyrophosphate; (B) melamine pyrophosphate; and (C) calcium phosphate; The mass ratio of the component (A) to the sum of the components (B) and (C) [component (A)]:[component (B) + component (C)] is 70:30 to 30:70.

[0008] In the above flame retardant composition, the mass ratio of the component (A) to the sum of the components (B) and (C) [component (A)]:[component (B) + component (C)] is more preferably 65:70 to 30:70, and more preferably 50:70 to 40:70.

[0009] In the flame retardant composition, the mass ratio of the component (B) to the component (C) [component (B)]:[component (C)] is 60:40 to 95:5, more preferably 36:19 to 35:5, and more preferably 30:10 to 40:10.

[0010] The flame retardant composition further contains (D) a flame retardant synergist and (E) a coupling agent, The composition contains 0.01 to 20 parts by mass of the component (D) and 0.001 to 0.5 parts by mass of the component (E) relative to a total of 100 parts by mass of the components (A), (B), and (C).

[0011] More preferably, the composition contains 5 to 15 parts by mass of the component (D) and 0.2 to 0.3 parts by mass of the component (E) per 100 parts by mass of the total of the components (A), (B), and (C).

[0012] In the flame retardant composition, component (D) is one or a combination of two or more of titanium oxide, aluminum oxide, magnesium oxide, zinc oxide, talc, zeolite, montmorillonite, antimony trioxide, zinc borate, hydrotalcite, nano-montmorillonite, aluminum hydroxide, and magnesium hydroxide.

[0013] In the flame retardant composition, the component (E) is one or a combination of a titanate ester, a methylsilicone oil, and a methylhydrogensilicone oil.

[0014] In the above flame retardant composition, component (C) may be added in a designed ratio when component (B) is synthesized, or may be added when components (A) and (B) are mixed and pulverized.

[0015] After clarifying the components and the amounts used, the flame retardant composition can be produced by a conventional method.

[0016] The present invention further provides a flame-retardant polyolefin resin composition, which employs the above-described low-cost intumescent flame retardant composition and contains 10 to 60 parts by mass of the flame retardant composition per 100 parts by mass of the flame-retardant polyolefin resin composition.

[0017] Preferably, the flame-retardant polyolefin resin composition contains 15 to 45 parts by mass of the flame retardant composition.

[0018] Furthermore, the flame-retardant polyolefin resin composition may further contain additives such as an antioxidant, a lubricant, and a neutralizer. [Effects of the Invention]

[0019] The beneficial technical effects of the present invention are as follows:

[0020] (1) The present invention can clearly improve the flame retardant efficiency of a flame retardant composition by introducing inexpensive calcium phosphate into a combination of piperazine pyrophosphate and melamine pyrophosphate, and can also reduce the cost of the flame retardant composition by lowering the mass ratio of piperazine pyrophosphate in the flame retardant composition compared to the ratio disclosed in the prior art publications.

[0021] (2) The flame retardant efficiency of the flame retardant composition of the present invention can be further improved by combining it with other flame retardant synergists. By modifying the coupling agent, the compatibility of the flame retardant composition with the polymeric material can be increased, thereby further reducing the amount of the flame retardant composition used and achieving the purpose of reducing application costs. DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention relates to a low-cost intumescent flame retardant composition and a flame-retardant resin composition, for example, a flame-retardant polyolefin resin composition. Hereinafter, the present invention will be described based on preferred embodiments thereof.

[0023] 1. Flame retardant composition The flame retardant composition of the present invention comprises (A) piperazine pyrophosphate, (B) melamine pyrophosphate, (C) calcium phosphate, (D) a flame retardant synergist, and (E) a coupling agent.

[0024] Here, the piperazine pyrophosphate of component (A) may be synthesized by first neutralizing phosphoric acid with piperazine to produce piperazine phosphate, and then dehydrating the resulting mixture at high temperature. The molar ratio of phosphoric acid to piperazine when synthesizing the piperazine phosphate is preferably 1:1.5 to 1:2.5.

[0025] The melamine pyrophosphate of component (B) may be produced by first neutralizing phosphoric acid and melamine to produce a melamine phosphate, and then dehydrating the resulting product at high temperature. The molar ratio of phosphoric acid to melamine when synthesizing the melamine phosphate is preferably 1:5 to 1:2.5.

[0026] The calcium phosphate of component (C) is commercially available calcium phosphate with a content of more than 99.0%, and may be added according to the design ratio when synthesizing component (B), or may be added when the component (A) and component (B) compositions are mixed and ground.

[0027] After extensive research, the present inventors have found that the introduction of inexpensive calcium phosphate into the combination of piperazine pyrophosphate and melamine pyrophosphate significantly improves the flame retardant efficiency of the composition. In particular, the present invention allows the mass parts of piperazine pyrophosphate in the flame retardant composition to be reduced while still ensuring the flame retardant effect, i.e., the mass parts of piperazine pyrophosphate in the composition can be less than 50 parts, thereby reducing the cost of using the flame retardant.

[0028] The flame retardant efficiency of the flame retardant composition of the present invention can be further improved by combining it with other synergists, and by modifying the coupling agent to increase the compatibility between the flame retardant composition and the polymer material, the amount used can be further reduced, thereby achieving the purpose of reducing application costs.

[0029] The flame retardant synergist of component (D) in the flame retardant composition is one or a combination of two or more of titanium oxide, aluminum oxide, magnesium oxide, zinc oxide, talc, zeolite, montmorillonite, antimony trioxide, zinc borate, hydrotalcite, nano-montmorillonite, aluminum hydroxide, and magnesium hydroxide, and is preferably zinc oxide and zinc borate.

[0030] The component (E) in the flame retardant composition is one or a combination of a titanate ester, a methyl silicone oil, and a methyl hydrogen silicone oil, and is preferably a methyl hydrogen silicone oil.

[0031] In the flame retardant composition of the present invention, from the viewpoints of flame retardancy and reduced application costs, the mass ratio of the component (A) to the sum of the components (B) and (C), i.e., [component (A)]:[component (B) + component (C)], is 70:30 to 30:70, preferably 65:70 to 30:70, and more preferably 50:70 to 40:70.

[0032] In the above flame retardant composition, from the viewpoints of flame retardancy, reduction in application costs, etc., the mass ratio of component (B) to component (C) [component (B)]:[component (C)] is 60:40 to 95:5, preferably 36:19 to 35:5, and more preferably 30:10 to 40:10.

[0033] The particle size of the solid content of the flame retardant composition is controlled to 0.1 μm≦D90≦80 μm, and preferably 1 μm≦D90≦50 μm.

[0034] 2. Flame-retardant polyolefin resin composition The flame-retardant polyolefin resin composition contains 10 to 60 parts by mass of the above flame retardant composition, preferably 15 to 45 parts by mass of the above flame retardant composition, per 100 parts by mass of the resin.

[0035] In the flame-retardant polyolefin resin composition, the polyolefin resin used may be one or a combination of a plurality of polyethylene-based resins such as polyethylene, low-density polyethylene, linear low-density polyethylene, and high-density polyethylene; polypropylene-based resins such as polypropylene, homopolypropylene, random copolymer polypropylene, block copolymer polypropylene, impact copolymer polypropylene, high-impact copolymer polypropylene, isotactic polypropylene, syndiotactic polypropylene, semi-isotactic polypropylene, and stereoblock polypropylene; α-olefin polymers such as polybutene, cyclic olefin polymers, poly-3-methyl-1-butene, poly-3-methyl-1-pentene, and poly-4-methyl-1-pentene; styrene-based monomer (styrene, vinyltoluene, etc.) homopolymers or copolymers; copolymers of styrene-based monomers and vinyl-based monomers; styrene-based graft copolymers; and styrene-based block copolymers.

[0036] In the above-mentioned flame-retardant polyolefin resin composition, common plastic additives such as antioxidants, plasticizers, lubricants, UV absorbers, fillers, nucleating agents, etc. may be added at the same time according to the actual requirements of processing and use, provided that the flame retardant does not have any antagonistic effect with the plastic additives.

[0037] The flame-retardant polyolefin resin composition may be mixed and processed by known plastic mixing and processing methods. The mixing may be performed by mixing with a mixer, agitator, etc., melt-kneading with an internal mixer, extruder, etc., or by mixing with a solvent and solution casting, and the processing may be performed by extrusion molding, injection molding, calendar molding, blow molding, compression molding, laminate molding, etc.

[0038] The present invention will be further described below in conjunction with specific examples.

[0039] Preparation of flame retardant compositions of Examples 1-16.

[0040] Basic raw materials: piperazine pyrophosphate is a commercial product with basic indicators: initial decomposition temperature greater than 280°C, volatile content ≦0.5%, particle size 1μm≦D90≦50μm, whiteness (YI) ≦8; melamine pyrophosphate is a commercial product with initial decomposition temperature greater than 280°C, volatile content ≦0.5%, particle size 1μm≦D90≦50μm, whiteness (YI) ≦6; calcium phosphate is a commercial product with a main content ≧99.5% and particle size 1μm≦D90≦50μm; flame retardant synergist is a commercial product with a main content ≧99.5% and particle size 1μm≦D90≦50μm; coupling agent is purchased from a commercial source with a purity of ≧99.0%.

[0041] According to the blending ratios shown in Table 1 below, (A) piperazine pyrophosphate, (B) melamine pyrophosphate, (C) calcium phosphate, (D) a flame retardant synergist, and (E) a coupling agent were mixed in a high-speed mixer for 15 minutes to obtain flame retardant compositions of Examples 1 to 16, which were designated as flame retardant compositions No. 1 to No. 16, respectively.

[0042] [Table 1]

[0043] Production of flame-retardant polyolefin resin compositions of Examples 17 to 32.

[0044] Base raw materials: The polyolefins selected for compounding were commercialized homopolymer polypropylene (PP-h) [MFR=8 dg / min], commercialized copolymer polypropylene (PP-b) [MFR=8 dg / min], and commercialized low-density polyethylene (LDPE) [MFR=8 dg / min], respectively. The mass parts of the polyolefin were 100 parts. Calcium stearate was selected as the neutralizing agent, and the amount used was 0.1 parts. Antioxidant 1010 and Antioxidant 168 were selected as the main antioxidant and auxiliary antioxidant, respectively, and the amounts used were both 0.05 parts. Glycerin monostearate was selected as the lubricant, and the amount used was 0.4 parts. The flame retardants were selected from the flame retardant compositions in Examples 1 to 16, and the amounts used were as shown in Table 3.

[0045] The flame retardant composition, polyolefin, antioxidant, lubricant, and acid neutralizer calcium stearate were mixed in a high-speed mixer for 30 minutes, then added to a twin-screw extruder and extruded at 190-210°C to form granules. The granules were then compressed into a tablet press at a compression pressure of 5 MPa and a compression temperature of 190-220°C. After 20 minutes, the mold was removed and allowed to cool. The samples were then cut into standard strips for vertical combustion performance testing.

[0046] Vertical burning experiments were conducted in accordance with GB / T 2408-2008. The flame-retardant polypropylene composition samples measured 100 mm x 13 mm x 1.6 mm, and the flame-retardant polyethylene composition samples measured 100 mm x 13 mm x 0.8 mm. A flame (20 mm high, blue flame) was placed at the bottom of the vertically positioned sample strip and ignited for 10 seconds. The flame was removed, and the sample was allowed to extinguish. The flame-ignition and flameless burning times of the sample strip after the flame was removed were recorded. The flaming times for the first and second ignitions were designated t1 and t2, respectively. Table 2 lists the criteria for the vertical burning experiments. Five samples from each group were required to achieve the respective indicators.

[0047] [Table 2]

[0048] Table 3 shows the blending compositions and flame retardant performance test results of the flame retardant polyolefin resin compositions of Examples 17 to 46.

[0049] [Table 3]

[0050] Table 3 shows only the amounts of polyolefin and flame retardant used. It should be noted that other additives were added when producing the flame-retardant polyolefin resin composition. Specifically, calcium stearate was selected as the neutralizing agent, with a usage amount of 0.1 part; antioxidant 1010 and antioxidant 168 were selected as the main antioxidant and auxiliary antioxidant, with a usage amount of 0.05 part each; and glycerin monostearate was selected as the lubricant, with a usage amount of 0.4 part.

[0051] As can be seen from Tables 1 and 3, the present invention can significantly improve the flame retardant efficiency of the flame retardant composition by introducing inexpensive calcium phosphate into the combination of piperazine pyrophosphate and melamine pyrophosphate, while reducing the amount of piperazine pyrophosphate used in the flame retardant composition.

[0052] To further demonstrate the effect of adding calcium phosphate, the present invention added a set of comparative examples, in which the amounts of each component were the same as in Example 13, except that calcium phosphate was replaced with inorganic flame retardant silicon carbide. The prepared flame retardant was then applied to copolymer polypropylene (PP-b), and the amounts of each component were the same as in Example 35. Experimental tests showed that the flame retardant level of the final flame-retardant polyolefin composition was V-2, which significantly reduced the flame retardant performance.

Claims

1. A low-cost intumescent flame retardant composition comprising: (A) piperazine pyrophosphate; (B) melamine pyrophosphate; and (C) calcium phosphate; the mass ratio of the component (A) to the sum of the components (B) and (C) [component (A)]:[component (B) + component (C)] is 65:70 to 30:70; the mass ratio of the component (B) to the component (C) [component (B)]:[component (C)] is 60:40 to 95:5; The composition further comprises (D) a flame retardant synergist and (E) a coupling agent; The composition contains 0.01 to 20 parts by mass of the (D) component and 0.001 to 0.5 parts by mass of the (E) component, relative to 100 parts by mass of the total of the (A), (B), and (C) components; Component (D) is one or a combination of zinc oxide, zinc borate, and nano-montmorillonite; A low-cost intumescent flame retardant composition, wherein component (E) is one or a combination of a titanate ester, a methyl silicone oil, and a methyl hydrogen silicone oil.

2. 2. The low-cost intumescent flame retardant composition according to claim 1, wherein the component (C) is added in a designed ratio when the component (B) is synthesized, or when the components (A) and (B) are mixed and crushed.

3. A flame-retardant polyolefin resin composition, characterized in that the low-cost intumescent flame retardant composition according to claim 1 or 2 is used, and the flame-retardant composition is contained in an amount of 10 to 60 parts by mass per 100 parts by mass of the flame-retardant polyolefin resin composition.