Preparation method of reactive flame-retardant fiber reinforced nylon plate

Abstract

The invention discloses a preparation method of a reactive flame-retardant fiber reinforced nylon plate, and belongs to the field of functional modification of high polymer materials, and the preparation method comprises the following steps: reacting an active flame retardant with a caprolactam monomer and sodium hydroxide to obtain flame-retardant caprolactam sodium; adding the flame-retardant sodium caprolactam, a caprolactam monomer and isocyanate into a glue injection machine, heating, vacuumizing and dehydrating to obtain a mixture; and injecting the mixture into a mold through a glue injection machine, and carrying out polymerization reaction on the flame-retardant sodium caprolactam, caprolactam and isocyanate under the action of a temperature field, so as to prepare the reactive flame-retardant fiber reinforced nylon plate. The phenyl-containing phosphorus-based active flame retardant is directly polymerized onto a molecular chain of caprolactam in the polymerization stage of sodium caprolactam, the flame retardant is combined with nylon molecules through firm covalent bonds, the problem of precipitation of the flame retardant is fundamentally solved, and the phenyl group of the flame retardant can improve the thermal stability of nylon.

Description

Technical Field

[0001] The invention belongs to the field of functional modification of polymer materials, and in particular relates to a method for preparing a reactive flame-retardant fiber-reinforced nylon sheet. Background Art

[0002] Unmodified nylon has poor flame retardancy, and its vertical combustion can only reach UL94 V-2 level, and its oxygen index is about 24, and dripping occurs during the combustion process, which is a flammable material and is very easy to cause fire during use. Therefore, the flame retardant modification of nylon has become a topic of common concern and research in the current academic and industrial circles. At present, the conventional practice is to directly blend the flame retardant with the nylon resin, and then extrude and mold to prepare the flame-retardant nylon sheet. For example, the invention CN113861672B provides an anti-aging halogen-free flame-retardant nylon composite material and a preparation method thereof, wherein nylon resin, halogen-free flame retardant, antioxidant, colorant, etc. are blended, and then a melting operation is performed to obtain a molten mixture, and the molten mixture is dried to obtain an anti-aging halogen-free flame-retardant nylon composite material. Invention CN102675866A discloses a formula for enhanced flame-retardant nylon 6, including nylon 6, flame retardant, compatibilizer, toughening agent, plasticizer and filler. The flame retardant is tricresyl phosphate and zinc borate. This flame retardant method is also a blending process, not a reactive flame retardant process. Summary of the invention

[0003] The purpose of the present invention is to solve the problem that unmodified nylon has poor flame retardant properties and drips during combustion, which is very likely to cause fire during use, and to propose a method for preparing a reactive flame retardant fiber reinforced nylon sheet.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A processing method for preparing a reactive flame-retardant fiber-reinforced nylon sheet comprises the following steps:

[0006] (1) reacting an active flame retardant with caprolactam monomer and sodium hydroxide to obtain flame-retardant sodium caprolactam;

[0007] (2) adding flame retardant sodium caprolactam, caprolactam monomer and isocyanate into a glue injection machine, heating, vacuumizing and dehydrating to obtain a mixture;

[0008] (3) The mixture is injected into a mold for laying fibers through a glue injection machine. Under the action of the temperature field, the flame-retardant sodium caprolactam, caprolactam and isocyanate undergo polymerization reaction to prepare a reactive flame-retardant fiber-reinforced nylon sheet.

[0009] The method for preparing a reactive flame-retardant fiber-reinforced nylon sheet is characterized in that in step (1), the active flame retardant is a phenyl-containing phosphorus-based carboxylic acid flame retardant or a phenyl-containing phosphorus-based diamine flame retardant; the molar ratio of the active flame retardant, caprolactam monomer, and sodium hydroxide is 0.5-1.5:2:0.2.

[0010] As a further description of the above technical solution:

[0011] The method for preparing a processing method for reactive flame-retardant fiber-reinforced nylon sheet is characterized in that, in the flame-retardant sodium caprolactam polymerization stage, a unique step-by-step heating and constant negative pressure polymerization process is adopted, specifically: first, caprolactam monomer is added, the reactor heating temperature is 100°C, and vacuum is drawn after the caprolactam monomer is melted, the vacuum degree is -0.98MPa, and the vacuum drawing time is 30-45min; then, nitrogen is filled, active flame retardant and sodium hydroxide are added, and vacuum drawing is continued, the vacuum degree is -0.98MPa, and at the same time, the temperature in the reactor is stepped up to 110°C, 120°C, and 130°C respectively, and each temperature node is stayed for 10-20min, and vacuum drawing is stopped after the active flame retardant reacts fully with the caprolactam monomer and sodium hydroxide; finally, nitrogen is filled, the material is discharged, and the vacuum sealing is packaged for standby use.

[0012] As a further description of the above technical solution:

[0013] The method for preparing a reactive flame-retardant fiber-reinforced nylon sheet is characterized in that the molar ratio of caprolactam monomer, flame-retardant sodium caprolactam and isocyanate is 100:2:1.0-1.5.

[0014] As a further description of the above technical solution:

[0015] The method for preparing a reactive flame-retardant fiber-reinforced nylon sheet is characterized in that, in step (2), the heating temperature of the glue injection machine is 105-110° C., the heating time is 60-90 min, and the vacuum degree is -0.98 MPa.

[0016] As a further description of the above technical solution:

[0017] The method for preparing a reactive flame-retardant fiber-reinforced nylon sheet is characterized in that, in step (3), the injection pressure of the glue injection machine is 0.5-1MPa, and the injection pipelines are heated and insulated, and the heating temperature is 100-110°C.

[0018] As a further description of the above technical solution:

[0019] The method for preparing a reactive flame-retardant fiber reinforced nylon sheet is characterized in that, in step (3), the mold size is 200×200 mm, the thickness is 10 mm, the mold heating temperature is 150-180° C., the reaction time is 15-20 min, and after the reaction is completed, it is cooled to room temperature and demolded to obtain the reactive flame-retardant fiber reinforced nylon sheet.

[0020] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0021] In the present invention, a phenyl-containing phosphorus-based active flame retardant or a phenyl-containing phosphorus-based diamine flame retardant is directly polymerized onto the molecular chain of caprolactam during the polymerization stage of sodium caprolactam, and the flame retardant is combined with nylon molecules through a strong covalent bond, thereby fundamentally solving the problem of flame retardant precipitation. The phenyl group of the flame retardant itself can improve the thermal stability of nylon, and the flame retardant group is bonded to the nylon polymer material through a chemical reaction to achieve long-term flame retardancy. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The microstructure of the reactive flame-retardant fiber-reinforced nylon sheet prepared in Example 1 of the present invention;

[0023] Figure 2 The present invention is a schematic diagram of the preparation process of the reactive flame-retardant fiber reinforced nylon sheet. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] See also Figure 1-Figure 2 , the present invention provides a technical solution:

[0026] Example 1

[0027] A processing method for preparing a reactive flame-retardant fiber-reinforced nylon sheet comprises the following steps:

[0028] (1) reacting an active flame retardant with caprolactam monomer and sodium hydroxide to obtain flame-retardant sodium caprolactam;

[0029] (2) adding flame retardant sodium caprolactam, caprolactam monomer and isocyanate into a glue injection machine, heating, vacuumizing and dehydrating to obtain a mixture;

[0030] (3) The mixture is injected into a mold for laying fibers through a glue injection machine. Under the action of the temperature field, the flame-retardant sodium caprolactam, caprolactam and isocyanate undergo polymerization reaction to prepare a reactive flame-retardant fiber-reinforced nylon sheet.

[0031] The active flame retardant is a phosphorus-based carboxylic acid flame retardant containing phenyl, and the molar ratio of the active flame retardant, caprolactam monomer, and sodium hydroxide is 0.5.0:2:0.2. In the polymerization stage of the flame retardant sodium caprolactam auxiliary agent, a unique step-by-step temperature increase and constant negative pressure polymerization process is adopted, specifically: first add the caprolactam monomer, the reactor heating temperature is 100°C, and vacuum is drawn after the lactam monomer is melted, the vacuum degree is -0.98MPa, and the vacuum time is 30-45min; then fill with nitrogen, add the active flame retardant and sodium hydroxide, continue to vacuum, the vacuum degree is -0.98MPa, and at the same time, the temperature in the reactor is stepped up to 110°C, 120°C, and 130°C respectively, and each temperature node stays for 10min. After the active flame retardant reacts fully with the caprolactam monomer and sodium hydroxide, stop vacuuming; finally, fill with nitrogen, discharge, and vacuum seal and package for standby use.

[0032] The molar ratio of caprolactam monomer, flame retardant sodium caprolactam and isocyanate is 100:2:1.0, the heating temperature of the glue injection machine is 105℃, the heating time is 60min, and the vacuum degree is -0.98MPa. The injection pressure of the glue injection machine is 0.5MPa, and the injection pipeline must be heated and kept warm at 100℃. The mold heating temperature is 150℃, the reaction time is 15min, and after the reaction is completed, it is cooled to room temperature and demolded to obtain a reactive flame retardant fiber reinforced nylon sheet. After testing, the limiting oxygen index of the reactive flame retardant fiber reinforced nylon sheet is 28.2, and the combustion grade sample has reached V0 level.

[0033] Example 2

[0034] The active flame retardant is a phosphorus-based diamine flame retardant containing phenyl, and the molar ratio of the active flame retardant, caprolactam monomer, and sodium hydroxide is 1.0:2:0.2. In the polymerization stage of the flame retardant sodium caprolactam auxiliary agent, a unique step-by-step temperature increase and constant negative pressure polymerization process is adopted, specifically: first add the caprolactam monomer, the reactor heating temperature is 105°C, and after the lactam monomer is melted, vacuum is drawn, the vacuum degree is -0.98MPa, and the vacuum time is 40min; then fill with nitrogen, add the active flame retardant and sodium hydroxide, continue to vacuum, the vacuum degree is -0.98MPa, and at the same time, the temperature in the reactor is raised to 110°C, 120°C, and 130°C respectively by step-by-step temperature increase, and each temperature node stays for 15min.

[0035] The molar ratio of caprolactam monomer, flame retardant sodium caprolactam and isocyanate is 100:2:1.2, the heating temperature of the glue injection machine is 105℃, the heating time is 60min, and the vacuum degree is -0.98MPa. The injection pressure of the glue injection machine is 0.75MPa, and the injection pipeline must be heated and insulated. The heating temperature is 100℃, the mold heating temperature is 170℃, and the reaction time is 18min. After the reaction is completed, it is cooled to room temperature and demolded to obtain a reactive flame retardant fiber reinforced nylon sheet. After testing, the limiting oxygen index of the reactive flame retardant fiber reinforced nylon sheet is 29.5, and the combustion grade sample has reached V0 level.

[0036] Example 3

[0037] The active flame retardant is a phosphorus-based diamine flame retardant containing phenyl, and the molar ratio of the active flame retardant, caprolactam monomer, and sodium hydroxide is 1.5:2:0.2. In the polymerization stage of the flame retardant sodium caprolactam auxiliary agent, a unique step-by-step temperature increase and constant negative pressure polymerization process is adopted, specifically: first add the caprolactam monomer, the reactor heating temperature is 105°C, and after the lactam monomer is melted, vacuum is drawn, the vacuum degree is -0.98MPa, and the vacuum time is 45min; then fill with nitrogen, add the active flame retardant and sodium hydroxide, continue to vacuum, the vacuum degree is -0.98MPa, and at the same time, the temperature in the reactor is raised to 110°C, 120°C, and 130°C respectively by step-by-step temperature increase, and each temperature node stays for 20min.

[0038] The molar ratio of caprolactam monomer, flame retardant sodium caprolactam and isocyanate is 100:2:1.5, the heating temperature of the glue injection machine is 110℃, the heating time is 90min, and the vacuum degree is -0.98MPa. The injection pressure of the glue injection machine is 1.0MPa, and the injection pipeline must be heated and kept warm. The heating temperature is 110℃, the mold heating temperature is 180℃, and the reaction time is 20min. After the reaction is completed, it is cooled to room temperature and demolded to obtain a reactive flame retardant fiber reinforced nylon sheet. After testing, the limiting oxygen index of the reactive flame retardant fiber reinforced nylon sheet is 30.1, and the combustion grade sample has reached V0 level.

[0039] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A processing method for preparing a reactive flame-retardant fiber-reinforced nylon sheet, characterized in that: The steps include: (1) reacting an active flame retardant with caprolactam monomer and sodium hydroxide to obtain flame-retardant sodium caprolactam; (2) adding flame retardant sodium caprolactam, caprolactam monomer and isocyanate into a glue injection machine, heating, vacuumizing and dehydrating to obtain a mixture; (3) The mixture is injected into a mold for laying fibers through a glue injection machine. Under the action of the temperature field, the flame-retardant sodium caprolactam, caprolactam and isocyanate undergo polymerization reaction to prepare a reactive flame-retardant fiber-reinforced nylon sheet.

2. The method for preparing a reactive flame-retardant fiber-reinforced nylon sheet according to claim 1, characterized in that: In step (1), the active flame retardant is a phenyl-containing phosphorus-based carboxylic acid flame retardant or a phenyl-containing phosphorus-based diamine flame retardant; the molar ratio of the active flame retardant, caprolactam monomer, and sodium hydroxide is 0.5-1.5:2:0.

2.

3. The method for preparing a reactive flame-retardant fiber-reinforced nylon sheet according to claim 2, characterized in that: In the flame-retardant sodium caprolactam polymerization stage, a unique step-by-step temperature increase and constant negative pressure polymerization process is adopted, specifically: first add caprolactam monomer, the reactor is heated to 100°C, and after the caprolactam monomer is safely melted, vacuum is drawn, the vacuum degree is -0.98MPa, and the vacuum time is 30-45min; then nitrogen is filled, active flame retardant and sodium hydroxide are added, and vacuum is continued, the vacuum degree is -0.98MPa, and at the same time, the temperature in the reactor is stepped up to 110°C, 120°C, and 130°C, respectively, and each temperature node is stayed for 10-20min. After the active flame retardant reacts fully with the caprolactam monomer and sodium hydroxide, the vacuum is stopped; finally, nitrogen is filled, the material is discharged, and the vacuum is sealed and packaged for standby use.

4. The method for preparing a reactive flame-retardant fiber-reinforced nylon sheet according to claim 3, characterized in that: The molar ratio of caprolactam monomer, flame retardant sodium caprolactam and isocyanate is 100:2:1.0-1.

5.

5. The method for preparing a reactive flame-retardant fiber-reinforced nylon sheet according to claim 4, characterized in that: In step (2), the heating temperature of the glue injection machine is 105-110° C., the heating time is 60-90 min, and the vacuum degree is -0.98 MPa.

6. The method for preparing a reactive flame-retardant fiber-reinforced nylon sheet according to claim 5, characterized in that: In step (3), the injection pressure of the glue injection machine is 0.5-1MPa, and the injection pipelines must be heated and kept warm at a heating temperature of 100-110°C.

7. The method for preparing a reactive flame-retardant fiber-reinforced nylon sheet according to claim 6, characterized in that: In step (3), the mold size is 200×200 mm, the thickness is 10 mm, the mold heating temperature is 150-180° C., the reaction time is 15-20 min, and after the reaction is completed, it is cooled to room temperature and demolded to obtain a reactive flame-retardant fiber reinforced nylon sheet.

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