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

Abstract

This invention proposes a low-cost intumescent flame retardant composition and a flame-retardant polyolefin resin composition, belonging to the field of flame retardants. The composition contains (A) piperazine pyrophosphate, (B) melamine pyrophosphate, and (C) calcium phosphate; the mass ratio of component (A) to the sum of component (B) and (C) [(A) component]:[(B) component + (C) component] is 70:30 to 30:70; the mass ratio of component (B) to component (C) [(B) component]:[(C) component] is 60:40 to 95:5. The composition also contains (D) a flame retardant synergist and (E) a coupling agent. This invention introduces inexpensive calcium phosphate into the combination of piperazine pyrophosphate and melamine pyrophosphate, which can significantly improve the flame retardant efficiency of the flame retardant composition; simultaneously, the mass proportion of piperazine pyrophosphate in the flame retardant composition can be lower than the proportion published in existing literature, thereby reducing the cost of the flame retardant composition.

Description

Technical Field

[0001] The invention relates to the field of flame retardants, in particular to a low-cost intumescent flame retardant composition and a flame-retardant polyolefin resin composition containing the flame retardant composition. Background Art

[0002] Polyolefin intumescent flame retardant is considered to be a green flame retardant with great development potential due to its advantages of halogen-free, high flame retardant efficiency, low smoke, low toxicity and no droplets during combustion. Intumescent flame retardant is usually composed of three components: acid source (dehydrating agent), carbon source (carbon-forming agent) and gas source (foaming agent). Its working principle is that when the material burns, the phosphorus-containing flame retardant burns at the same time to generate combustion products with dehydration effect, which are dehydrated into carbon in the system. At the same time, the gas source produces inert gas to become a foaming agent, forming a dense porous carbon layer on the surface of the material. The carbon layer has the function of heat insulation and oxygen isolation, which can not only prevent the further degradation of the inner layer polymer and the release of combustibles to the surface, but also prevent the transfer of heat source to the polymer and isolate the oxygen source, thereby effectively preventing the spread and propagation of flames and achieving the purpose of flame retardancy.

[0003] The intumescent flame retardant currently used is mainly made of ammonium polyphosphate as the acid source, melamine and a carbon-forming agent. This type of flame retardant has unsatisfactory effects, poor compatibility with the base material, great influence on the electrical properties, insulation properties, mechanical properties, etc. of the polymer, easy migration, poor hydrolysis stability and thermal stability. Piperazine pyrophosphate-based intumescent flame retardant is a new type of flame retardant composition. Compared with ammonium polyphosphate-based flame retardant compositions, it has better flame retardant effect, heat stability and water precipitation resistance, and can be widely used in materials such as polypropylene, polyethylene, acrylonitrile-butadiene-styrene, epoxy resin and polyurethane. Patent No. CN201880042218.X discloses a flame retardant composition, which is mainly composed of piperazine pyrophosphate salt, melamine pyrophosphate salt and silicone oil, wherein the mass fraction of piperazine pyrophosphate salt and melamine pyrophosphate salt ranges from 90:10 to 50:50, that is, the mass fraction of piperazine pyrophosphate salt cannot be less than 50 parts. "Du Yuying. Study on the flame retardant effect of piperazine pyrophosphate-based intumescent flame retardant on polyolefins. Qingdao University of Science and Technology. Dissertation, 2019." The flame retardant system described in the study is used for polyethylene and polypropylene. The optimal mass ratio of piperazine pyrophosphate salt to melamine pyrophosphate salt is 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 shows that even if piperazine pyrophosphate and melamine pyrophosphate work synergistically with ZnO, the mass ratio of piperazine pyrophosphate to melamine pyrophosphate salt still needs to be close to 2:1.

[0004] According to the known method, such as "Zhao Zhen et al. Synthesis and characterization of piperazine pyrophosphate. Chemical Technology. 2022, 30(5): 18-21" and "Zhang Lingling et al. Synthesis of polyphosphate melamine. Chemical Industry Journal. 2013, 27(11): 14-17", piperazine pyrophosphate salt is synthesized by neutralizing phosphoric acid and piperazine and then condensing and dehydrating. Similarly, melamine pyrophosphate salt is synthesized by neutralizing phosphoric acid and melamine and then dehydrating them. Since the price of piperazine, the main raw material for synthesizing both, is significantly higher than that of melamine, in the flame retardant composition used in practice, if the proportion of piperazine pyrophosphate salt is high, it means high application cost. For example, the mass fraction of piperazine pyrophosphate salt described in the previous patents and papers cannot be less than 50 parts. This indicates that the flame retardant formulation system currently disclosed has a high use cost due to the high mass fraction of piperazine pyrophosphate salt. Summary of 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 reduce the mass fraction of piperazine pyrophosphate salt in the system, thereby having a lower application cost.

[0006] The technical solution adopted by the present invention is:

[0007] A low-cost intumescent flame retardant composition, the composition comprising (A) piperazine pyrophosphate salt, (B) melamine pyrophosphate salt and (C) calcium phosphate;

[0008] The mass ratio of the sum of the component (A) to the component (B) to the component (C) [component (A)]:[component (B)+component (C)] is 70:30 to 30:70.

[0009] In the flame retardant composition, the mass ratio of the sum of component (A), component (B) and component (C) [component (A)]:[component (B)+component (C)] is preferably 65:70 to 30:70, and more preferably 50:70 to 40:70.

[0010] 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. The mass ratio of the component (B) to the component (C) [component (B)]: [component (C)] is more preferably 36:19 to 35:5, and even more preferably 30:10 to 40:10.

[0011] The flame retardant composition further comprises (D) a flame retardant synergist and (E) a coupling agent;

[0012] The component (D) is contained in an amount of 0.01 to 20 parts by mass, and the component (E) is contained in an amount of 0.001 to 0.5 parts by mass, based on 100 parts by mass of the total of the components (A), (B), and (C).

[0013] More preferably, the component (D) is contained in an amount of 5 to 15 parts by mass and the component (E) is contained in an amount of 0.2 to 0.3 parts by mass based on 100 parts by mass of the total of the components (A), (B) and (C).

[0014] In the flame retardant composition, component (D) is a combination of one 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.

[0015] In the flame retardant composition, the component (E) is a combination of one or more of titanate, methyl silicone oil and methyl hydrogen silicone oil.

[0016] In the flame retardant composition, the component (C) may be added in a designed ratio when the component (B) is synthesized, or may be added when the components (A) and (B) are mixed and pulverized.

[0017] The flame retardant composition can be prepared in a conventional manner on the basis of clarifying each component and its amount.

[0018] The present invention also provides a flame retardant polyolefin resin composition, which uses the low-cost intumescent flame retardant composition as described above; and contains 10 to 60 parts by mass of the flame retardant composition relative to 100 parts by mass of the flame retardant polyolefin resin composition.

[0019] More preferably, the flame retardant composition is contained in an amount of 15 to 45 parts by mass in the flame retardant polyolefin resin composition.

[0020] Furthermore, antioxidants, lubricants and neutralizers are added to the flame retardant polyolefin resin composition.

[0021] The beneficial technical effects of the present invention are:

[0022] (1) The present invention introduces cheap calcium phosphate into the combination of piperazine pyrophosphate salt and melamine pyrophosphate salt, which can significantly improve the flame retardant efficiency of the flame retardant composition; at the same time, the mass ratio of piperazine pyrophosphate salt in the flame retardant composition can be lower than the ratio published in the existing public literature, thereby reducing the cost of the flame retardant composition.

[0023] (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, and the compatibility of the flame retardant composition with polymer materials can be increased by modification with coupling agents, thereby further reducing the usage amount and achieving the purpose of reducing application costs. DETAILED DESCRIPTION

[0024] The present invention relates to a low-cost intumescent flame retardant composition and a flame-retardant resin composition, such as a flame-retardant polyolefin resin composition. Hereinafter, the present invention will be described based on its preferred embodiments.

[0025] 1. Flame retardant composition

[0026] The flame retardant composition of the present invention consists of (A) piperazine pyrophosphate salt, (B) melamine pyrophosphate salt, (C) calcium phosphate, (D) flame retardant synergist and (E) coupling agent.

[0027] The (A) component piperazine pyrophosphate can be synthesized by first neutralizing phosphoric acid and piperazine to generate piperazine phosphate, followed by high temperature dehydration. The molar ratio of phosphoric acid to piperazine in synthesizing piperazine phosphate is preferably 1:1.5 to 1:2.5.

[0028] The component (B) pyrophosphate melamine salt can be prepared by first neutralizing phosphoric acid with melamine to form phosphate melamine salt, followed by high temperature dehydration. The molar ratio of phosphoric acid to melamine in synthesizing phosphate melamine salt is preferably 1:5 to 1:2.5.

[0029] The calcium phosphate component (C) is a commercially available calcium phosphate having a content of more than 99.0%. It can be added in a designed proportion during the synthesis of the component (B), or can be added during the mixing and pulverization of the component (A) and the component (B).

[0030] The researchers of the present invention have found through in-depth research that the introduction of cheap calcium phosphate into the combination of piperazine pyrophosphate salt and melamine pyrophosphate salt can significantly improve the flame retardant efficiency of the composition. In particular, the present invention can reduce the mass fraction of piperazine pyrophosphate salt in the flame retardant composition on the basis of ensuring the flame retardant effect, that is, the mass fraction of piperazine pyrophosphate salt in the composition can be less than 50 parts, thereby reducing the use cost of the flame retardant.

[0031] The flame retardant efficiency of the flame retardant composition of the present invention can be further improved by combining with other synergists, and the compatibility of the flame retardant composition with polymer materials can be increased by coupling agent modification, thereby further reducing the usage amount and achieving the purpose of reducing application costs.

[0032] The flame retardant synergist (D) in the flame retardant composition is a combination of one 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, preferably zinc oxide and zinc borate.

[0033] The component (E) in the flame retardant composition is a combination of one or more of titanate, methyl silicone oil and methyl hydrogen silicone oil, preferably methyl hydrogen silicone oil.

[0034] In the flame retardant composition of the present invention, from the aspects of flame retardancy and reduction of application cost, the mass ratio of the sum of component (A) and component (B) to component (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.

[0035] In view of flame retardancy and reduction of application cost, the mass ratio of component (B) to component (C) in the flame retardant composition is [component (B)]:[component (C)] of 60:40 to 95:5, preferably 36:19 to 35:5, and more preferably 30:10 to 40:10.

[0036] The particle size of the solid component of the flame retardant composition is controlled within the range of 0.1 μm ≤ D90 ≤ 80 μm, preferably 1 μm ≤ D90 ≤ 50 μm.

[0037] 2. Flame retardant polyolefin resin composition

[0038] A flame-retardant polyolefin resin composition comprising 10 to 60 parts by mass of the flame retardant composition, preferably 15 to 45 parts by mass of the flame retardant composition, based on 100 parts by mass of the resin.

[0039] In the above flame retardant polyolefin resin composition, the polyolefin resin used can be polyethylene, low-density polyethylene, linear low-density polyethylene and high-density polyethylene and other polyethylene resins; polypropylene, homopolypropylene, random copolymer polypropylene, block copolymer polypropylene, impact copolymer polypropylene, high impact copolymer polypropylene, isotactic polypropylene, syndiotactic polypropylene, semi-isotactic polypropylene, stereoblock polypropylene and other polypropylene resins; polybutene, cycloolefin polymer, poly-3-methyl-1-butene, poly-3-methyl-1-pentene, poly-4-methyl-1-pentene and other α-olefin polymers; styrene monomer (styrene, vinyl toluene, etc.) homopolymer or copolymer; copolymer of styrene monomer and vinyl monomer; styrene graft copolymer, styrene block copolymer and the like one or more combinations thereof.

[0040] The flame retardant polyolefin resin composition may be added with common plastic additives such as antioxidants, plasticizers, lubricants, ultraviolet absorbers, fillers, nucleating agents, etc. according to actual processing and use requirements. The flame retardant will not produce antagonistic effects with the plastic additives.

[0041] The above-mentioned flame retardant polyolefin resin composition can be mixed and processed by a known plastic mixing and processing method. The mixing can be carried out by a mixing method using a mixer, a stirrer, etc., a melt mixing method using an internal mixer, an extruder, etc., a method of mixing with a solvent for solution casting, etc.; the processing can be carried out by extrusion molding, injection molding, calendering molding, blow molding, compression molding, lamination molding, etc.

[0042] The present invention will be further described below in conjunction with specific embodiments.

[0043] Examples 1-16 Formulation of flame retardant compositions.

[0044] Basic raw materials: Piperazine pyrophosphate salt is a commercial product with basic indicators: initial decomposition temperature greater than 280°C, volatile matter ≤0.5%, particle size 1μm≤D90≤50μm, and whiteness (YI) ≤8; melamine pyrophosphate salt is a commercial product with initial decomposition temperature greater than 280°C, volatile matter ≤0.5%, particle size 1μm≤D90≤50μm, and whiteness (YI) ≤6; calcium phosphate is a commercial product with main content ≥99.5% and particle size 1μm≤D90≤50μm; flame retardant synergist is a commercial product with main content ≥99.5% and particle size 1μm≤D90≤50μm; coupling agent is purchased from commercial products with purity ≥99.0%.

[0045] According to the formula ratio shown in Table 1, (A) piperazine pyrophosphate salt, (B) melamine pyrophosphate salt, (C) calcium phosphate, (D) flame retardant synergist, and (E) coupling agent were mixed in a high-speed mixer for 15 minutes to obtain flame retardant compositions of Examples 1-16, which were marked as flame retardant compositions No. 1-No. 16, respectively.

[0046] Table 1

[0047]

[0048] Example 17-32 Preparation of flame retardant polyolefin resin composition.

[0049] Basic raw materials: The polyolefins selected in the formula are commercial homopolypropylene (PP-h) [MFR = 8 dg / min], commercial copolymer polypropylene (PP-b) [MFR = 8 dg / min], and commercial low-density polyethylene (LDPE) [MFR = 8 dg / min], and the mass fraction of polyolefin is 100 parts; calcium stearate is selected as a neutralizer, and the amount is 0.1 parts; antioxidant 1010 and antioxidant 168 are selected as the main antioxidant and auxiliary antioxidant respectively, and the amount is 0.05 parts; glycerol monostearate is selected as a lubricant, and the amount is 0.4 parts; the flame retardants are selected from the flame retardant compositions in Examples 1-16, and the amounts are shown in Table 3.

[0050] The flame retardant composition, polyolefin, antioxidant, lubricant and acid neutralizer calcium stearate were mixed in a high-speed mixer for 30 minutes, added to a twin-screw extruder and extruded into granules at 190°C to 210°C, and then the particles were placed in a tablet press for compression molding. The molding pressure was 5 MPa and the molding temperature was 190°C to 220°C. After 20 minutes, the mold was taken out to cool, and the sample was cut into standard strips for vertical combustion performance testing.

[0051] The vertical combustion test was carried out in accordance with GB / T2408-2008. The size of the flame-retardant polypropylene composition sample was: 100mm×13mm×1.6mm, and the size of the flame-retardant polyethylene composition sample was: 100mm×13mm×0.8mm. The flame (blue flame height 20mm) was placed at the lower end of the vertically placed sample strip, ignited for 10s, the flame was removed, and the flame was extinguished. The sample was ignited again for 10s, and the time of flame combustion and flameless combustion of the sample strip after the flame was removed was recorded respectively. The flame combustion time of the first and second ignitions was recorded as t1 and t2 respectively. Table 2 is the judgment criteria for the vertical combustion test, requiring that the five samples in each group need to meet various indicators.

[0052] Table 2

[0053]

[0054] Table 3 shows the formulation composition and flame retardant performance test results of the flame retardant polyolefin resin composition of Examples 17-46.

[0055] Table 3

[0056]

[0057]

[0058] Table 3 only gives the dosage of polyolefin and flame retardant. It should be noted that other additives are added when preparing the flame-retardant polyolefin resin composition. Specifically, calcium stearate is selected as a neutralizer in an amount of 0.1 parts; antioxidant 1010 and antioxidant 168 are selected as the main antioxidant and auxiliary antioxidant, respectively, and the dosage is 0.05 parts; glycerol monostearate is selected as a lubricant in an amount of 0.4 parts.

[0059] It can be seen from Table 1 and Table 3 that the present invention introduces cheap calcium phosphate into the combination of piperazine pyrophosphate and melamine pyrophosphate, which can significantly improve the flame retardant efficiency of the flame retardant composition while reducing the amount of piperazine pyrophosphate in the flame retardant composition.

[0060] In order to further prove the effect of introducing calcium phosphate, the present invention also adds a group of comparative examples, that is, the dosage of each component is the same as that of Example 13, except that inorganic flame retardant silicon carbide is used to replace calcium phosphate. The flame retardant prepared is applied to copolymerized polypropylene (PP-b), and the dosage of each component is the same as that of Example 35. After experimental testing, the flame retardant grade of the flame retardant polyolefin composition finally obtained is V-2, and the flame retardant performance is significantly reduced.

Claims

1. A low-cost intumescent flame retardant composition, characterized in that: The composition contains (A) piperazine pyrophosphate salt, (B) melamine pyrophosphate salt and (C) calcium phosphate; The mass ratio of the sum of the component (A) and the component (B) and the component (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 contains (D) a flame retardant synergist and (E) a coupling agent; 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 100 parts by mass of the total of the components (A), (B) and (C); (D) component is a combination of one or more of zinc oxide, zinc borate and nano-montmorillonite; The component (E) is a combination of one or more of titanate, methyl silicone oil and methyl hydrogen silicone oil.

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

3. A flame retardant polyolefin resin composition, characterized in that: A low-cost intumescent flame retardant composition as claimed in any one of claims 1 or 2 is used; and the flame retardant composition is contained in an amount of 10 to 60 parts by mass relative to 100 parts by mass of the flame retardant polyolefin resin composition.

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