Preparation process of anti-dripping flame-retardant polyamide composite material

Abstract

The invention discloses a preparation process of an anti-droplet flame-retardant polyamide composite material, belongs to the technical field of polyamide composite materials, and discloses a composite material preparation process for improving the droplet phenomenon of a polyamide 6-melamine cyanurate flame-retardant system by using an auxiliary flame retardant and a synergist. Specifically, polyamide 6, melamine cyanurate, an auxiliary flame retardant and a synergist which are prepared in advance are pretreated and then mixed by using a high-speed mixer, and extrusion processing is performed by using a twin-screw extruder; then, the materials are subjected to granulation treatment; therefore, the polyamide composite material with anti-dripping and flame-retardant properties is obtained. Due to the addition of the auxiliary flame retardant and the synergist, the phenomenon of melt dripping during combustion of a polyamide 6 composite system is effectively solved, so that the technical problem of how to improve melt dripping during combustion of an existing polyamide 6 composite material is solved.

Description

Technical Field

[0001] The invention relates to the technical field of polyamide composite materials, in particular to a process for producing a droplet-resistant flame-retardant polyamide composite material. Background Art

[0002] Flame retardant polyamide 6 is a material with flame retardant properties and is an important modified variety of PA-6 engineering plastics. It is mainly used in high-tech industries such as electronics and electrical, and can be used to manufacture internal plug-ins, connectors, circuit boards, switches, panels, sockets, etc. At the same time, it is also widely used in the fields of automobiles and aviation. In recent years, with the rapid development of the electronics, electrical, communications and home appliance industries, especially the rapid promotion of the automotive electronics industry, the demand for flame retardant polyamide 6 will increase.

[0003] Flame-retardant polyamide 6 composite materials are generally divided into two categories: halogen-containing and halogen-free. In recent years, as people pay more attention to fire safety and environmental protection, the application of halogen-containing flame-retardant polyamide 6 composite materials has been greatly restricted. Halogen-free flame-retardant polyamide 6 composite materials, based on their low smoke and non-toxic characteristics, meet the requirements of green environmental protection, and are gradually replacing halogen-containing flame-retardant PA-6 composite materials. They are widely used in industrial production, and the demand is rising. Halogen-free flame retardants commonly used in flame-retardant PA-6 materials include phosphorus-based flame retardants, chlorine-based flame retardants, metal hydroxides, etc.

[0004] Based on this, Chinese patent CN111349334B discloses a high-performance MCA flame-retardant nylon material and its preparation method. The flame-retardant nylon material is composed of the following components: PA6 resin, MCA flame retardant, chopped glass fiber, antioxidant and lubricant. In the technical solution disclosed in the patent, the flame-retardant nylon material obtained by a special extrusion process has a bimodal distribution of the retained length of the chopped glass fiber, so that the flame-retardant nylon material has excellent glow-wire properties; at the same time, it also has excellent mechanical properties and heat resistance, and can be used in low-voltage electrical appliances, electronic appliances, connectors and other fields.

[0005] However, the high-performance MCA flame-retardant nylon material disclosed above still has the technical problem of easy generation of molten dripping. Specifically, the ammonia flame retardant melamine cyanurate, namely MCA, is an efficient halogen-free additive flame retardant for polyamide 6 materials. The chemical properties of MCA and polyamide 6 are very similar, and the flame retardant requirements can be met with a small amount of addition. However, the addition of MCA easily reduces the viscosity of the polyamide composite material, and further, it is easy to cause the polyamide 6 composite material to produce molten dripping when burning. Molten dripping may cause secondary injuries, such as burns and disasters, such as molten dripping causing electrical short circuits or igniting other items; thus, the further promotion and application of MCA flame-retardant nylon composites in the fields of electronics, new energy vehicles, etc. is limited. In order to make the MCA flame-retardant polyamide 6 composite material suitable for actual production applications, the problem of molten dripping generated when the polyamide 6 / MCA composite material is burned must be solved. Summary of the invention

[0006] Based on this, it is necessary to provide a process for producing anti-melt drop flame-retardant polyamide composite materials in order to improve the technical problem of how to improve the easy generation of melt dripping when the polyamide 6 / MCA composite materials are burned.

[0007] A process for producing a drip-resistant flame-retardant polyamide composite material, comprising the following steps: S1: preparing various materials according to a preset ratio, including: polyamide 6, melamine cyanurate, auxiliary flame retardant and synergist; S2: pre-treating each raw material to remove moisture from the raw material by drying; S3: Put all the raw materials into a high-speed mixer to mix the ingredients evenly; S4: adding the pre-treated and fully mixed raw materials into the hopper of the twin-screw extruder, and the twin-screw extruder melts the raw materials and forms a molten state by heating and stirring; S5: During the melt extrusion process, the temperature, speed and pressure of the extruder are controlled according to preset parameters to fully melt the input raw materials; S6: Extruding the molten mixture into a continuous strip through the screw and die of the extruder; S7: Rapidly cool and solidify the molten masterbatch to keep its shape and size stable; S8: The cooled masterbatch is cut and granulated to obtain a masterbatch length of the composite material that meets the requirements.

[0008] Specifically, in step S1, the preset ratio of each material is as follows, by weight: polyamide 6, 100 parts, melamine cyanurate, 15-30 parts, auxiliary flame retardant + synergist, 12-24 parts.

[0009] Specifically, the ratio of the auxiliary flame retardant to the synergist is 20 / 80, 35 / 65, 50 / 50 or 65 / 35.

[0010] Specifically, the auxiliary flame retardant is silicone resin; the synergist is an organic metal salt, such as at least one of magnesium stearate, a mixture of ammonium polyphosphate and pentaerythritol, or aluminum hydroxide.

[0011] Specifically, in step S1, the preset ratio of each material is, by weight: 100 parts of polyamide 6, 15 parts of melamine cyanurate, 7.8 parts of silicone resin and 4.2 parts of magnesium stearate.

[0012] Specifically, in step S1, the preset ratio of each material is, by weight: 100 parts of polyamide 6, 30 parts of melamine cyanurate, 15.6 parts of silicone resin and 8.4 parts of magnesium stearate.

[0013] Specifically, in step S1, the preset ratio of each material is: 100 parts of polyamide 6, 25 parts of melamine cyanurate, 13 parts of silicone resin and 7 parts of magnesium stearate, calculated by weight.

[0014] Specifically, in step S1, the preset ratio of each material is, by weight: 100 parts of polyamide 6, 25 parts of melamine cyanurate, 12 parts of organic silica gel and 12 parts of potassium carbonate.

[0015] Specifically, in step S1, the preset ratio of each material is, by weight: 100 parts of polyamide 6, 25 parts of melamine cyanurate, 15.6 parts of organic silica gel and 8.4 parts of potassium carbonate.

[0016] In summary, the present invention discloses a process for producing a polyamide composite material with anti-melting droplet flame retardant, which uses auxiliary flame retardants and synergists to improve the dripping phenomenon of a polyamide 6-melamine cyanurate flame retardant system; specifically, the process comprises pre-treating the prepared polyamide 6, melamine cyanurate, auxiliary flame retardant and synergist, mixing the materials with a high-speed mixer and extruding the materials with a twin-screw extruder; thereafter, granulating the materials, so as to obtain a polyamide composite material with anti-melting droplet flame retardant properties. The addition of auxiliary flame retardants and synergists effectively solves the phenomenon of melt dripping during combustion of the polyamide 6-melamine cyanurate composite system, improves the LOI value of the composite system, and improves its flame retardant performance; the aforementioned auxiliary flame retardant acts as an effective anti-melt dripping flame retardant synergist because the addition of materials such as silicone increases the viscosity of the composite system and produces an expanded carbon layer when the composite material burns, and the carbon layer plays a role in heat insulation and oxygen isolation; therefore, the present invention provides a process for producing an anti-melt dripping flame retardant polyamide composite material that solves the technical problem of how to improve the problem of easy generation of melt dripping when the polyamide 6-melamine cyanurate composite material is burned. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention is a schematic diagram of the process for producing a droplet-resistant flame-retardant polyamide composite material. DETAILED DESCRIPTION

[0018] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0019] See also Figure 1 Specifically, the present invention provides a process for producing a droplet-resistant flame-retardant polyamide composite material, which comprises the following steps: S1: preparing various materials according to a preset ratio, including: polyamide 6, melamine cyanurate, auxiliary flame retardant and synergist; S2: Pre-treat each raw material to remove moisture from the raw material by drying. Since polyamide 6 raw materials are prone to moisture absorption during processing, moisture absorption will affect the performance of the material, so the raw material needs to be pre-treated. Pre-treatment usually uses a drying method to remove moisture from the raw material and improve the quality and processing performance of the material. Among them, commonly used drying methods include hot air drying and vacuum drying. S3: Put all the raw materials into a high-speed mixer to mix the ingredients evenly; S4: adding the pre-treated and fully mixed raw materials into the hopper of the twin-screw extruder, and the twin-screw extruder melts the raw materials and forms a molten state by heating and stirring; S5: During the melt extrusion process, the extruder parameters such as temperature, speed and pressure need to be strictly controlled; the setting of these parameters depends on the characteristics of the raw materials and the requirements of the product; the appropriate temperature can ensure that the raw materials are fully melted, while the appropriate speed and pressure help to form a uniform melt; S6: The molten mixture is extruded into continuous strips through the screw and die of the extruder. During the extrusion process, it is necessary to ensure that the shear mixing action of the screw is uniform to form a masterbatch with stable quality. S7: Rapidly cool and solidify the molten masterbatch to keep its shape and size stable; common cooling methods include water cooling and air cooling; the control of cooling speed has a great influence on the quality of the masterbatch. Too fast cooling may cause stress inside the masterbatch, while too slow cooling may affect production efficiency; S8: The cooled masterbatch needs to be cut to obtain the required masterbatch length; usually a cutting machine or cutter is used for cutting to ensure the uniformity and consistency of the masterbatch.

[0020] Specifically, in the aforementioned step S1, the preset ratio of each material is, by weight: 100 parts of polyamide 6, 15-30 parts of melamine cyanurate, and 12-24 parts of auxiliary flame retardant + synergist; wherein the ratio of auxiliary flame retardant to synergist is 20 / 80, 35 / 65, 50 / 50 or 65 / 35.

[0021] Furthermore, the auxiliary flame retardant may be silicone resin, for example, SFR-10; the synergist may be an organic metal salt, such as a mixture of magnesium stearate, ammonium polyphosphate and pentaerythritol, or a combination of one or more of aluminum hydroxide. Specifically, silicone resin is a transparent, viscous silicone polymer that can be partially cross-linked with a polymer through a structure similar to an interpenetrating network, which prevents it from migrating to the surface of the material and improves the smoothness of the polyolefin without changing other surface properties. Only a small amount is needed to meet general flame retardancy requirements and maintain the original performance of the substrate. Increasing the amount can obtain particularly excellent flame retardancy and smoke suppression.

[0022] Specifically, in the formula of the aforementioned materials, several specific embodiments are as follows: Embodiment 1

[0023] Polyamide 6, 100 parts, melamine cyanurate, 15 parts, auxiliary flame retardant, 7.8 parts and synergist, 4.2 parts. Embodiment 2

[0024] Polyamide 6, 100 parts, melamine cyanurate, 30 parts, auxiliary flame retardant, 15.6 parts and synergist, 8.4 parts. Embodiment 3

[0025] Polyamide 6, 100 parts, melamine cyanurate, 25 parts, auxiliary flame retardant, 13 parts and synergist, 7 parts. Embodiment 4

[0026] Polyamide 6, 100 parts, melamine cyanurate, 25 parts, auxiliary flame retardant, 10 parts and synergist, 10 parts. Embodiment 5

[0027] Polyamide 6, 100 parts, melamine cyanurate, 25 parts, auxiliary flame retardant 7 parts and synergist 13 parts. Embodiment 6

[0028] Polyamide 6, 100 parts, melamine cyanurate, 25 parts, auxiliary flame retardant 4 parts and synergist 16 parts.

[0029] Specifically, a vertical combustion test method can be used to verify the aforementioned embodiments. The vertical combustion test method can be specifically performed with reference to GB4609-7984 standard. The specific criteria for judgment are shown in Table 1 below.

[0030] Table 1: Vertical burning test standards

[0031] Furthermore, the present invention uses two comparative examples to compare the vertical combustion performance of different embodiments, wherein comparative example 1 is pure polyamide 6 material, and comparative example 2 is a combination of polyamide 6, 100 parts + melamine cyanurate, 25 parts, and each comparative example and embodiment is mixed, extruded and granulated according to the aforementioned composite material production process; and after injection molding the sample according to the preset size, the respective vertical combustion test results and combustion phenomena are shown in Table 2 below. Specifically, in this combustion test, the auxiliary flame retardant can be silicone resin, model SFR-10; the synergist is magnesium stearate.

[0032] Table 2: Vertical combustion test results and combustion phenomena of each sample

[0033] Specifically, in general, the combustion process of polyamide 6 can be described as follows: In the initial stage, polyamide 6 is heated by flames and softens and melts at 202°C. When the temperature is continued to reach a certain temperature, thermal oxygen decomposition occurs on the surface of the polyamide 6 material, and the weak bonds of the polyamide 6 molecular chain begin to break: free radicals preferentially attack the hydrogen atoms on the methylene groups at the nitrogen atom position, oxidize to form hydroperoxides, and eventually cause the main chain to break. In addition, free radicals can also randomly attack all the methylene groups on the chain, leading to decomposition. At the same time, thermal decomposition occurs below the surface. The decomposition products are caprolactam, benzene, acetonitrile, and hydrocarbons below C5. These organic low-molecular combustibles diffuse into the gas phase to provide fuel for combustion. The oxygen index of polyamide 6 is 23, and the ignition temperature is 240°C. The melting phenomenon is obvious during the combustion process, and a large number of flaming droplets are produced.

[0034] Furthermore, in the vertical combustion test, the addition of melamine cyanurate effectively improves the flame retardant properties of polyamide 6. This is because when the composite system burns, melamine cyanurate sublimates at 350°C, absorbs heat and decomposes into melamine and cyanuric acid. The triazine ring further decomposes a large amount of inert non-combustible gas during the combustion process. These inert gases will dilute the concentration of oxygen and produce an inert gas protective layer. The production of inert gas can delay the intensity of combustion and effectively extend the ignition time of the system. Cyanuric acid can catalyze the degradation of polyamide 6 into oligomers and quickly leave the combustion area in the form of molten droplets, thereby transferring a large amount of heat to the environment, gradually producing a self-extinguishing phenomenon. However, although the burning time of this flame retardant system after leaving the flame is less than 10s, the molten drippings produced by its combustion can still ignite the absorbent cotton, and the burning flame does not spread to the fixture. That is, the addition of melamine cyanurate reduces the burning time of the composite system, but does not solve the problem of molten dripping of polyamide 6 material igniting the absorbent cotton during combustion. Molten dripping can easily cause secondary fires and burns, so the composite system of polyamide 6 and melamine cyanurate must be modified to resist molten dripping.

[0035] Therefore, in the process for producing a molten droplet-resistant flame-retardant polyamide composite material of the present invention, the phenomenon of molten droplets is improved by adding auxiliary flame retardants and synergists. Specifically, it can be seen from the aforementioned vertical combustion test that the addition of auxiliary flame retardants and synergists makes the system free of molten droplets during the combustion process in the vertical combustion experiment; and, it can be seen from the test process that the system has more carbon deposits on the surface after combustion, and the carbon layer effectively prevents the spread of the flame, allowing the material to extinguish itself in a shorter time, achieving good flame retardant and molten droplet-resistant effects.

[0036] Furthermore, the auxiliary flame retardant mentioned above may also be organic silica gel, and the corresponding synergist is potassium carbonate; the specific embodiments are as follows: Embodiment 7

[0037] Polyamide 6, 100 parts, melamine cyanurate, 25 parts, organic silica gel, 12 parts and potassium carbonate, 12 parts. Embodiment 8

[0038] Polyamide 6, 100 parts, melamine cyanurate, 25 parts, organic silica gel, 15.6 parts and potassium carbonate, 8.4 parts.

[0039] Correspondingly, the vertical flame retardant properties of the two embodiments are shown in Table 3 below: Table 3: Vertical combustion test results and combustion phenomena of Examples 7 to 8

[0040] Organic silica gel is a halogen-free flame retardant and a char-forming smoke suppressant. While giving polyamide 6 excellent flame retardancy and smoke suppression, it can also improve the processing performance of polyamide 6 and increase the mechanical strength of the material, especially the low-temperature impact strength. At the same time, as a processing aid for the flame retardant system, it reduces the torque during extrusion processing. It can also be used as a good dispersant to improve the dispersibility of flame retardants in polymer materials and reduce the mechanical properties of the materials. In addition, organic silica gel is a synergist of melamine cyanurate flame retardancy and can increase the oxygen index of this flame retardant system. In this regard, in the vertical combustion test, the combination of organic silica gel and potassium carbonate can produce more carbon covering the surface of the material when the polyamide burns, preventing the material from further burning while also inhibiting the formation of molten droplets.

[0041] In summary, the present invention discloses a process for producing a polyamide composite material with anti-melting droplet flame retardant, which uses auxiliary flame retardants and synergists to improve the dripping phenomenon of a polyamide 6-melamine cyanurate flame retardant system; specifically, the process comprises pre-treating the prepared polyamide 6, melamine cyanurate, auxiliary flame retardant and synergist, mixing the materials with a high-speed mixer and extruding the materials with a twin-screw extruder; thereafter, granulating the materials, so as to obtain a polyamide composite material with anti-melting droplet flame retardant properties. The addition of auxiliary flame retardants and synergists effectively solves the molten dripping phenomenon of the polyamide 6-melamine cyanurate composite system during combustion, improves the LOI value of the composite system, and improves its flame retardant performance; the aforementioned auxiliary flame retardant acts as an effective anti-melting dripping flame retardant synergist because the addition of materials such as silicone increases the viscosity of the composite system and produces an expanded carbon layer when the composite material burns, and the carbon layer plays a role in heat insulation and oxygen isolation; therefore, the present invention provides a process for producing an anti-melting dripping flame-retardant polyamide composite material that solves the technical problem of how to improve the polyamide-melamine cyanurate composite material that is prone to molten dripping when burned.

[0042] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0043] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A process for producing a droplet-resistant flame-retardant polyamide composite material, characterized in that: It includes the following steps: S1: preparing various materials according to a preset ratio, including: polyamide 6, melamine cyanurate, auxiliary flame retardant and synergist; S2: pre-treating each raw material to remove moisture from the raw material by drying; S3: Put all the raw materials into a high-speed mixer to mix the ingredients evenly; S4: adding the pre-treated and fully mixed raw materials into the hopper of the twin-screw extruder, and the twin-screw extruder melts the raw materials and forms a molten state by heating and stirring; S5: During the melt extrusion process, the temperature, speed and pressure of the extruder are controlled according to preset parameters to fully melt the input raw materials; S6: Extruding the molten mixture into a continuous strip through the screw and die of the extruder; S7: Rapidly cool and solidify the molten masterbatch to keep its shape and size stable; S8: The cooled masterbatch is cut and granulated to obtain a masterbatch length of the composite material that meets the requirements.

2. The process for producing a drip-resistant flame-retardant polyamide composite material according to claim 1, characterized in that: In step S1, the preset ratio of each material is as follows, by weight: polyamide 6, 100 parts, melamine cyanurate, 15-30 parts, auxiliary flame retardant + synergist, 12-24 parts.

3. The process for producing a drip-resistant flame-retardant polyamide composite material according to claim 2, characterized in that: The ratio of the auxiliary flame retardant to the synergist is 20 / 80, 35 / 65, 50 / 50 or 65 / 35.

4. The process for producing a drip-resistant flame-retardant polyamide composite material according to claim 2, characterized in that: The auxiliary flame retardant is silicone resin; the synergist is an organic metal salt, such as at least one of magnesium stearate, a mixture of ammonium polyphosphate and pentaerythritol, or aluminum hydroxide.

5. The process for producing a drip-resistant flame-retardant polyamide composite material according to claim 4, characterized in that: In step S1, the preset ratio of each material is: 100 parts of polyamide 6, 15 parts of melamine cyanurate, 7.8 parts of silicone resin and 4.2 parts of magnesium stearate, calculated by weight.

6. The process for producing a drip-resistant flame-retardant polyamide composite material according to claim 4, characterized in that: In step S1, the preset ratio of each material is: 100 parts of polyamide 6, 30 parts of melamine cyanurate, 15.6 parts of silicone resin and 8.4 parts of magnesium stearate, calculated by weight.

7. The process for producing a drip-resistant flame-retardant polyamide composite material according to claim 4, characterized in that: In step S1, the preset ratio of each material is: 100 parts of polyamide 6, 25 parts of melamine cyanurate, 13 parts of silicone resin and 7 parts of magnesium stearate, calculated by weight.

8. The process for producing a drip-resistant flame-retardant polyamide composite material according to claim 4, characterized in that: In step S1, the preset ratio of each material is: 100 parts of polyamide 6, 25 parts of melamine cyanurate, 12 parts of organic silica gel and 12 parts of potassium carbonate, calculated by weight.

9. The process for producing a drip-resistant flame-retardant polyamide composite material according to claim 4, characterized in that: In step S1, the preset ratio of each material is: 100 parts of polyamide 6, 25 parts of melamine cyanurate, 15.6 parts of organic silica gel and 8.4 parts of potassium carbonate, calculated by weight.

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