Flexible flame-retardant polypropylene cable material and preparation method thereof
By grafting the reaction product of DOPO and fumarate onto polypropylene, the problem of uneven dispersion of DOPO in the polypropylene matrix is solved, achieving stable dispersion of the flame retardant and maintaining the flexibility of the material, making it suitable for soft cable materials.
Patent Information
- Application Number
- CN202511246133.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-02
- Publication Date
- 2025-11-14
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
In the prior art, DOPO is not evenly dispersed in the polypropylene matrix, which leads to reduced flame retardant efficiency, decreased material flexibility and impact performance, and easy migration under long-term use or high temperature, posing environmental and health hazards.
By reacting DOPO with fumarate to generate a flame-retardant intermediate containing phosphono- and diester groups, and then grafting it onto the side chains of polypropylene to form a covalent graft structure, compatibility and dispersibility are improved, migration is avoided, and flexible side chains are introduced to retain the flexibility of the material.
It achieves uniform dispersion of flame retardants in polypropylene, with stable flame retardant properties, excellent material flexibility and impact resistance, and is suitable for soft cable materials, reducing formulation complexity and cost.
Smart Images
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Abstract
Description
Technical Field
[0001] This invention relates to the field of polymer materials technology, and in particular to a flexible and flame-retardant polypropylene cable material and its preparation method. Background Technology
[0002] Polypropylene (PP) is widely used in cable sheathing and other fields due to its low density, good chemical resistance, excellent processing performance, and low price. However, PP is a flammable polyolefin material with a limiting oxygen index (LOI) of only about 18%, making it prone to rapid combustion and dripping under the influence of an ignition source, which limits its application in situations requiring high flame retardancy. To improve flame retardancy, phosphine-based flame retardants are often added industrially. Among them, 9,10-dihydro-9-oxo-10-phosphine-phenanthrene (DOPO) has attracted much attention due to its high flame retardant efficiency, good thermal stability, and low smoke toxicity.
[0003] In existing technologies, DOPO is mostly added directly to the PP matrix through physical mixing. This method is simple, but because DOPO molecules contain highly polar phosphino groups (P=O) and rigid aromatic ring structures, while PP molecular chains are nonpolar hydrocarbon chains, the significant polarity difference between the two leads to poor interfacial compatibility and easy phase separation, resulting in uneven dispersion of the flame retardant in the matrix. This dispersion defect not only reduces flame retardant efficiency but also creates stress concentration points within the material, significantly reducing the flexibility and impact resistance of PP. Furthermore, free-state DOPO easily migrates to the material surface during long-term use or under high-temperature environments, causing flame retardant performance degradation, surface whitening, and potential environmental and health safety hazards.
[0004] To improve compatibility, some solutions introduce polar compatibilizers (such as maleic anhydride-grafted polypropylene, PP-g-MAH) into the formulation to improve the dispersion and binding of DOPO. However, these methods incur additional costs, and the introduction of compatibilizers can alter the rheological properties of the system, and in some cases, reduce the material's flexibility, which is detrimental to the application requirements of flexible cable materials.
[0005] On the other hand, existing chemical grafting modifications also have shortcomings. Although grafting flame-retardant monomers onto the PP backbone via free radicals can improve compatibility and durability, traditional flame-retardant monomers are mostly rigid structures, which can significantly increase the rigidity of polymer chain segments, leading to a decrease in material flexibility and making them unsuitable for cable sheaths that require high flexibility.
[0006] Therefore, there is an urgent need for a technical solution that can stably maintain the dispersion of flame retardants and prevent migration in PP systems, while also preserving the original flexibility and processability of the material. Summary of the Invention
[0007] Objective of the Invention: This invention provides a flexible flame-retardant polypropylene cable material and its preparation method. The method involves reacting 9,10-dihydro-9-oxo-10-phosphine-phenanthrene (DOPO) with fumarate to generate a phosphine-based flame-retardant intermediate containing phosphoxy groups and diester groups. Subsequently, a free radical initiator is used to graft the flame-retardant intermediate onto the side chains of polypropylene, resulting in a suitable highly flexible, flame-retardant polypropylene cable material that improves upon the characteristics of DOPO as a flame retardant, such as poor dispersion and high rigidity.
[0008] The technical solution of the present invention:
[0009] In a first aspect, the present invention provides a flexible flame-retardant polypropylene cable material, wherein, by weight parts, the raw materials of the flexible flame-retardant polypropylene cable material comprise:
[0010] 50-70 parts of modified polypropylene;
[0011] Antioxidant 0.5-1.0 parts;
[0012] 0.5-1.0 parts of ultraviolet absorber;
[0013] 2-5 parts pigment.
[0014] The modified polypropylene is obtained by polymerizing flame retardant monomers with butyl acrylate and isooctyl acrylate; the flame retardant monomer is the reaction product of 9,10-dihydro-9-oxo-10-phospho-phenanthrene (DOPO) and fumarate.
[0015] In some embodiments, the fumarate ester contains double bonds and nitrogen. The nitrogen source releases non-flammable gases upon thermal decomposition and assists in the formation of a porous insulating layer. This, combined with the strong flame-retardant properties of DOPO phosphorus, enhances flame retardancy while maintaining overall flexibility, without compromising insulation performance.
[0016] In some embodiments, the method for preparing the modified polypropylene includes the following steps:
[0017] Step 1: Fumaric acid and 3-chloro-1-propanol are subjected to a monoesterification reaction to obtain fumaric acid monoester;
[0018] Step 2: Esterify fumarate monoester with N-hydroxypiperidine to obtain 3-chloropropyl O-(N-hydroxypiperidine)fumarate diester;
[0019] Step 3: Under anhydrous conditions, 3-chloropropyl O-(N-hydroxypiperidine) fumarate diester and dehydrated 1,8-diazabicyclo[5.4.0]undecane (DBU) were mixed and stirred, and the mixture was heated to obtain the dehalogenated product;
[0020] Step 4: Mix the dehalogenated product with DOPO, catalyst, and solvent, heat and stir; after the reaction is complete, post-treatment is performed to obtain the flame-retardant monomer;
[0021] Step 5: Mix the flame-retardant monomer with the soft monomer, solvent and initiator, heat and stir to react, and after the reaction is completed, post-process to obtain modified polypropylene.
[0022] In some embodiments, step 1, the monoesterification reaction, includes: adding fumaric acid and solvent to a flask, stirring and placing it in an ice bath; dissolving 3-chloro-1-propanol in a small amount of solvent and adding it to the fumaric acid solution; adding 4-dimethylaminopyridine, slowly adding N,N'-diisopropylcarbodiimide, stirring, then raising the temperature to room temperature and stirring the reaction, and after the reaction is completed, post-treatment to obtain fumaric acid monoester.
[0023] In some embodiments, step 2, the esterification reaction, includes: dissolving fumarate monoester in a solvent and cooling it to 0°C; adding N-hydroxypiperidine and reacting at low temperature; and then post-processing to obtain fumarate diester.
[0024] In some embodiments, the molar ratio of the dehalogenated product to DOPO in step 4 is 1.1-1.2:1; the reaction temperature is 70-110℃; and the reaction time is 2-6h.
[0025] In some embodiments, in step 5, the soft monomer is selected from one or more combinations of butyl acrylate, ethyl acrylate, isooctyl acrylate, butyl methacrylate, and isooctyl methacrylate.
[0026] In some embodiments, the soft monomers in step 5 are preferably butyl acrylate and isooctyl acrylate; further, the molar ratio of the dehalogenated product to butyl acrylate and isooctyl acrylate is 2-5:10-15:5-8.
[0027] In some embodiments, the reaction temperature in step 5 is 65-75°C and the reaction time is 6-8 hours.
[0028] By introducing flexible side chains through an addition reaction between DOPO and N-containing fumarate, and then covalently grafting them onto the PP side chains, the flame retardant molecules and the matrix are integrated, significantly improving compatibility and dispersibility, preventing migration, and retaining the material's softness. This method is particularly suitable for the preparation of soft flame-retardant cable materials. The N-containing fumarate and DOPO achieve a strong flame-retardant synergy, which can enhance flame retardancy while maintaining overall flexibility.
[0029] In a second aspect, the present invention provides a method for preparing the soft flame-retardant polypropylene cable material, specifically comprising: feeding each raw material into a mixer and mixing them evenly; feeding the evenly mixed material into a twin-screw extruder, extruding and pelletizing it, and drying it to obtain the polypropylene cable material.
[0030] Beneficial effects:
[0031] 1. Flame retardant molecules form an integrated structure with polypropylene through covalent grafting, which significantly improves the compatibility between polar phosphine-based flame retardants and non-polar polypropylene, avoiding the problems of flame retardant agglomeration and uneven dispersion in physical mixing.
[0032] 2. The grafted flame retardant is fixed on the polypropylene chain segment and will not migrate or precipitate under long-term use or high temperature conditions. The flame retardant performance is long-lasting and stable. The P and N elements achieve strong flame retardant synergy, which can improve flame retardancy while maintaining overall flexibility.
[0033] 3. The introduced fumarate structure has flexible alkyl segments and diester groups, which can improve compatibility while reducing segment rigidity. This allows the material to maintain high flame retardancy while still possessing excellent flexibility and bending properties, making it very suitable for flexible cable materials.
[0034] 4. In the system of the present invention, the compatibility between the flame retardant and polypropylene is guaranteed by the structure itself, without the need to add additional compatibilizers such as maleic anhydride grafts, which reduces the complexity and cost of the formulation, while avoiding the adverse effects of compatibilizers on the rheological properties of the system.
[0035] 5. Grafted flame-retardant polypropylene can be directly used as a resin base material for processing. It has good melt flowability and is easy to mix with plasticizers, fillers, etc. It is suitable for conventional extrusion and injection molding processes and meets the needs of industrial production. Detailed Implementation
[0036] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.
[0037] Unless otherwise specified, all chemical reagents used in this invention are commercially available analytical grade reagents.
[0038] Preparation of modified polypropylene 1
[0039] Step 1: Add 50 mmol fumaric acid and 120 mL DCM to a flask, stir and cool to 0 °C; dissolve 55 mL 3-chloro-1-propanol in 50 mL DCM and add it to the fumaric acid solution; add 0.05 mmol 4-dimethylaminopyridine, slowly add 55 mmol N,N'-diisopropylcarbodiimide, stir for 30 min, then raise the temperature to room temperature and stir for 5 h. After the reaction is complete, filter, wash the organic phase, concentrate and rotary evaporate to obtain fumaric acid monoester.
[0040] Step 2: Under a nitrogen atmosphere, 50 mmol of fumarate monoester was dissolved in 120 mL of DCM and cooled to 0 °C. 55 mmol of N-hydroxypiperidine was added to 50 mL of DCM and dissolved. The solution was then added to the fumarate monoester solution. 55 mmol of N,N'-diisopropylcarbodiimide was slowly added dropwise. The mixture was stirred for 30 min and then cooled to room temperature and stirred for 4 h to carry out the esterification reaction. After filtration, washing, drying, concentration, and recrystallization, 3-chloropropyl O-(N-hydroxypiperidine)fumarate diester was obtained.
[0041] Step 3: Under anhydrous conditions, 50 mmol of 3-chloropropyl O-(N-hydroxypiperidine) fumarate diester was dissolved in 120 mL of LCM, and 0.15 mol of 1,8-diazabicyclo[5.4.0]undecane (DBU) was added. The mixture was heated to 40 °C and stirred for 3 h. After the reaction, the product was neutralized, separated, extracted, washed, dried and concentrated to obtain the dehalogenated product.
[0042] Step 4: Mix 50 mmol of the dehalogenated product with 52.5 mmol of DOPO, 0.05 mol of 4-dimethylaminopyridine, and 120 ml of dry toluene, heat at 80 °C and stir for 4 h; after the reaction is complete, cool, evaporate the solvent, and recrystallize to obtain the flame-retardant monomer;
[0043] Step 5: Mix 150 mmol of flame retardant monomer with 500 mmol of butyl acrylate, 250 mmol of isooctyl acrylate, 200 ml of toluene and 10 mmol of initiator AIBN, heat to 70 °C and stir for 6 h. After the reaction is completed, post-treatment is performed to obtain modified polypropylene masterbatch.
[0044] Preparation of modified polypropylene 2
[0045] The preparation steps are basically the same as in the preparation example of modified polypropylene 1, the only difference being that step 5 is modified as follows:
[0046] 150 mmol of flame retardant monomer was mixed with 500 mmol of butyl acrylate, 250 mmol of ethyl acrylate, 200 ml of toluene and 10 mmol of initiator AIBN, heated to 70 °C and stirred for 6 h. After the reaction was completed, the modified polypropylene masterbatch was obtained by post-treatment.
[0047] Preparation of modified polypropylene 3
[0048] The preparation steps are basically the same as in the preparation example of modified polypropylene 1, the only difference being that step 5 is modified as follows:
[0049] 150 mmol of flame retardant monomer was mixed with 500 mmol of butyl acrylate, 250 mmol of isooctyl methacrylate, 200 ml of toluene and 10 mmol of initiator AIBN, heated to 70 °C and stirred for 6 h. After the reaction was completed, the modified polypropylene masterbatch was obtained by post-treatment.
[0050] Preparation of modified polypropylene 4
[0051] The preparation steps are basically the same as in the preparation example of modified polypropylene 1, the only difference being that step 5 is modified as follows:
[0052] 300 mmol of flame retardant monomer was mixed with 400 mmol of butyl acrylate, 250 mmol of isooctyl methacrylate, 200 ml of toluene and 10 mmol of initiator AIBN, heated to 70 °C and stirred for 6 h. After the reaction was completed, the modified polypropylene masterbatch was obtained by post-treatment.
[0053] Preparation of modified polypropylene 5
[0054] The preparation steps are basically the same as in the preparation example of modified polypropylene 1, the only difference being that step 5 is modified as follows:
[0055] 150 mmol of flame retardant monomer was mixed with 700 mmol of butyl acrylate, 200 ml of toluene and 10 mmol of initiator AIBN, heated to 70 °C and stirred for 6 h. After the reaction was completed, the modified polypropylene masterbatch was obtained by post-treatment.
[0056] Preparation of modified polypropylene 6
[0057] The preparation steps are basically the same as in the preparation example of modified polypropylene 1, the only difference being that step 5 is modified as follows:
[0058] 150 mmol of flame retardant monomer was mixed with 1000 mmol of butyl acrylate, 250 mmol of isooctyl methacrylate, 200 ml of toluene, and 10 mmol of initiator AIBN. The mixture was heated to 70 °C and stirred for 6 h. After the reaction was completed, the modified polypropylene masterbatch was obtained through post-treatment.
[0059] Preparation of modified polypropylene 7
[0060] The preparation steps are basically the same as in the preparation example of modified polypropylene 1, the only difference being that steps 1-4 are modified as follows:
[0061] Add 50 mmol DOPO to a two-necked round-bottom flask, then add 55 mmol anhydrous ethanol to the flask. Slowly add 60 mmol formaldehyde dropwise while stirring and heating to 85 °C. React for 8 hours to obtain the intermediate product.
[0062] Under nitrogen protection, 50 mmol of the intermediate was added to a two-necked round-bottom flask, followed by 500 mL of acetonitrile. The mixture was stirred in an ice-water bath for 6 h. Then, 100 mmol of triethylamine was added, and the mixture was stirred for another 1 h in the ice-water bath. Finally, 50 mmol of acryloyl chloride was added, and the reaction mixture was stirred for another 12 h at room temperature. After the reaction was complete, the reaction mixture was filtered, distilled under reduced pressure using a rotary evaporator, and then subjected to column chromatography to obtain the flame-retardant monomer.
[0063] Example
[0064] Weigh each raw material according to Table 1, add each raw material to a high-speed mixer, mix at 2000 rpm for 15 minutes to obtain a mixture; then send the mixture to a twin-screw extruder for melt extrusion to obtain polypropylene cable material.
[0065] Table 1 Formulation Table of Examples
[0066]
[0067]
[0068] Comparative Example
[0069] Weigh the raw materials according to Table 2, add the above components to a high-speed mixer, mix at 2000 rpm for 15 minutes to obtain a mixture; then send the mixture to a twin-screw extruder for melt extrusion to obtain a composite material.
[0070] Table 2 Comparative Formula Table
[0071]
[0072] Effect Example
[0073] The following tests verified the performance of the composite materials in the examples and comparative examples in the following aspects, and the test results are shown in Table 3.
[0074] 1. Shore hardness: Shore hardness test was performed in accordance with standard GB / T 531.1-2008.
[0075] 2. Flame retardant performance: Flame retardant performance was tested in accordance with standard GBT 2408-2008.
[0076] 3. Tensile modulus of elasticity: Bending strength was tested according to national standard GB / T 1040.2-2006;
[0077] 4. Notched impact strength: The notched impact strength is tested according to the national standard GB / T 1843-2008;
[0078] Table 3 Test Results
[0079]
[0080] As can be seen from Table 3, the flexible flame-retardant polypropylene cable materials prepared in Examples 1-3 of this application have good flexibility, flame retardancy, and impact strength. Furthermore, without the addition of additional flame retardants and compatibilizers, they still provide good mechanical properties and flame retardancy while maintaining flexibility.
[0081] Comparative Examples 4-6 varied the polypropylene monomer ratios. Table 3 shows that, compared to Example 1, all data in Examples 4-5 changed to varying degrees, indicating that the monomer ratio affects the final performance of the modified polypropylene. Since flame-retardant monomers, as "hard monomers," significantly influence the hardness and flexibility of the resin, selecting monomers with suitable ratios is more beneficial for improving material performance.
[0082] In Comparative Example 7, DOPO flame-retardant monomers were prepared using a different method. Table 3 shows that, compared to the examples, the flame-retardant properties of the cable material obtained in Comparative Example 7 are slightly reduced. This is because the modified acrylic acid 7 lacks nitrogen atoms, making it unable to achieve strong flame-retardant synergy with the phosphorus elements in DOPO. Furthermore, the notched impact strength is reduced, indicating decreased flexibility. This is because fumarate was not used to connect DOPO and the main chain during the preparation of the modified acrylic acid 7; the increased rigidity of the branched chain segments leads to a decrease in the flexibility of the modified polypropylene main chain, which is unfavorable for use as a cable material.
[0083] As can be seen from Comparative Examples 5-6, the modified acrylic acid provided by this invention eliminates the need for a compatibilizer, further reducing costs. Furthermore, it maintains mechanical properties, flame retardancy, and flexibility, demonstrating technological advancement.
[0084] This invention can also be implemented in various other ways. Without departing from the spirit and essence of this invention, those skilled in the art can make various corresponding changes and modifications according to this invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.
Claims
1. A flexible, flame-retardant polypropylene cable material, characterized in that, The raw materials of the flexible flame-retardant polypropylene cable material, by weight parts, include: 50-70 parts of modified polypropylene; Antioxidant 0.5-1.0 parts; 0.5-1.0 parts of ultraviolet absorber; 2-5 parts pigment; The modified polypropylene is obtained by polymerizing flame retardant monomers with butyl acrylate and isooctyl acrylate; the flame retardant monomers are the reaction products of 9,10-dihydro-9-oxo-10-phosphine-phenanthrene and fumarate.
2. The flexible flame-retardant polypropylene cable material according to claim 1, characterized in that, The method for preparing the modified polypropylene includes the following steps: Step 1: Fumaric acid and 3-chloro-1-propanol are subjected to a monoesterification reaction to obtain fumaric acid monoester; Step 2: Esterify fumarate monoester with N-hydroxypiperidine to obtain 3-chloropropyl O-(N-hydroxypiperidine)fumarate diester; Step 3: Under anhydrous conditions, 3-chloropropyl O-(N-hydroxypiperidine)fumarate diester and dehydrated 1,8-diazabicyclo[5.4.0]undecane were mixed and stirred, and the mixture was heated to obtain the dehalogenated product; Step 4: Mix the dehalogenated product with DOPO, catalyst, and solvent, heat and stir; after the reaction is complete, post-treatment is performed to obtain the flame-retardant monomer; Step 5: Mix the flame-retardant monomer with the soft monomer, solvent and initiator, heat and stir to react, and after the reaction is completed, post-process to obtain modified polypropylene.
3. The flexible flame-retardant polypropylene cable material according to claim 2, characterized in that, Step 1, the monoesterification reaction, includes: adding fumaric acid and solvent to a flask, stirring and placing it in an ice bath; dissolving 3-chloro-1-propanol in a small amount of solvent and adding it to the fumaric acid solution; adding 4-dimethylaminopyridine, slowly adding N,N'-diisopropylcarbodiimide, stirring, then raising the temperature to room temperature and stirring the reaction, and after the reaction is completed, obtaining fumaric acid monoester through post-treatment.
4. The flexible flame-retardant polypropylene cable material according to claim 2, characterized in that, Step 2, the esterification reaction, includes: dissolving fumarate monoester in a solvent and cooling it to 0°C; adding N-hydroxypiperidine and reacting at low temperature; and then post-processing to obtain fumarate diester.
5. The flexible flame-retardant polypropylene cable material according to claim 2, characterized in that, The molar ratio of the dehalogenated product to DOPO in step 4 is 1.1-1.2:1; the reaction temperature is 70-110℃; and the reaction time is 2-6h.
6. The flexible flame-retardant polypropylene cable material according to claim 2, characterized in that, The soft monomer is selected from one or more combinations of butyl acrylate, ethyl acrylate, isooctyl acrylate, butyl methacrylate, and isooctyl methacrylate.
7. The flexible flame-retardant polypropylene cable material according to claim 2, characterized in that, In step 5, the soft monomers are butyl acrylate and isooctyl acrylate.
8. The flexible flame-retardant polypropylene cable material according to claim 7, characterized in that, The molar ratio of the dehalogenated product to butyl acrylate and isooctyl acrylate is 2-5:10-15:5-8.
9. The flexible flame-retardant polypropylene cable material according to claim 2, characterized in that, The reaction temperature in step 5 is 65-75℃, and the reaction time is 6-8h.
10. The method for preparing the flexible flame-retardant polypropylene cable material according to any one of claims 1-9, characterized in that, Includes the following steps: All raw materials are fed into a mixer and mixed evenly; the evenly mixed material is fed into a twin-screw extruder, extruded and pelletized, and then dried to obtain the polypropylene cable material.