A non-halogen flame-retardant polyamide composition and a method for preparing the same

Abstract

The present application relates to a kind of anti-extraction halogen-free flame-retardant polyamide composition and its preparation method.It includes the following components by weight fraction: polyamide resin 30-95 parts;Reinforcing material 0-50 parts;Halogen-free flame retardant 5-30 parts;Dicalcium silicate 1-5 parts;Tricalcium silicate 0.2-1 part;Other auxiliary agent 0.5-5 parts.The present application uses the principle of hydration hardening, dicalcium silicate and tricalcium silicate generate calcium hydroxide and calcium silicate gel when encountering water, with the viscoelasticity of colloid, along the water molecule capillary distribution and occupy the extraction channel, further, at the interface of channel and air, react with carbon dioxide to generate calcium carbonate, harden, block capillary channel, block extraction.1500h still not extract under high temperature and high humidity (85℃, 85% RH), without affecting other properties, and raw material is easy to get, simple processing.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of polyamide, and particularly relates to a halogen-free flame-retardant polyamide composition resistant to precipitation and a preparation method thereof. BACKGROUND

[0002] Polyamide is the most widely used resin among general-purpose engineering plastics in terms of production, variety and application. Halogen-free flame-retardant polyamide has been widely used in the fields of electronics, electrical appliances, household appliances, automobiles and rail transit due to its excellent flame-retardant performance and electrical performance. Compared with halogen-containing flame-retardant polyamide, halogen-free flame-retardant polyamide is more environmentally friendly due to its low smoke and low toxicity. With the promulgation of laws and regulations at home and abroad for limiting the use of halogen, halogen-free flame-retardant polyamide will become the development trend in the future.

[0003] Currently, the main halogen-free flame retardants such as melamine cyanurate (MCA), melamine polyphosphate (MPP) and aluminum diethyl phosphinate (ADP) have poor compatibility with polyamide. Under high temperature and high humidity conditions or long-term storage, the flame retardant will precipitate on the surface of the product, thereby affecting the appearance and even causing safety hazards such as corrosion, short circuit and electrical breakdown. In view of the problem that the halogen-free flame retardant in the halogen-free flame-retardant polyamide is prone to precipitation under high temperature and high humidity environment, the common improvement methods in the industry are as follows:

[0004] (1) Adding anti-precipitation agent: Patent CN114292517A discloses a flame-retardant polyamide composite, which reduces the amount of melamine polyphosphate by adding polyvinylpyrrolidone as an anti-precipitation agent, thereby reducing the amount of precipitation. Patent CN113549321A discloses a black phosphorus flame-retardant polyamide composite capable of high-definition laser marking and resistant to precipitation under humid heat, which improves the water resistance and anti-precipitation performance under high temperature and high humidity environment by adding zinc stannate, hydroxyapatite and copper salt hydrolysis-resistant agent as anti-precipitation agents.

[0005] (2) Modification of flame retardant for anti-precipitation: Patent CN114231025A discloses a high-heat-resistant and anti-precipitation environmentally friendly flame-retardant polyamide composition, which modifies melamine polyphosphate by replacing part of melamine with aniline. The modified melamine polyphosphate has relatively fewer hydrophilic groups, which can prevent the migration and precipitation of the flame retardant. Patent CN116285328A discloses a high-strength and low-precipitation halogen-free flame-retardant polyamide composition, which modifies the flame-retardant synergist zinc aluminum tripolyphosphate by using a silane coupling agent to improve the compatibility with the resin. The use of ethylene maleic anhydride copolymer connects the zinc aluminum tripolyphosphate and the resin interface through a chemical bond, thereby increasing the dispersibility of the flame-retardant synergist and reducing the risk of precipitation.

[0006] (3) Resin body is modified to resist precipitation: Patent CN109679338A discloses a low-precipitation halogen-free flame-retardant polyamide alloy material, which uses two different solubility parameters of polyamide, so that the flame retardant cannot directly precipitate across the two phases, and the precipitation path is prolonged. Patent CN112795183A discloses a high-strength, low-shrinkage, low-precipitation environmentally friendly flame-retardant polyamide composition, which has 0.2-1% phosphorus element in the polyamide molecular chain by in-situ polymerization, and also adds liquid crystal flame retardant to block the migration of the flame retardant and reduce the precipitation under high temperature and high humidity conditions.

[0007] In summary, the existing technology for improving the precipitation of halogen-free flame retardants in polyamide is still limited. For example, the heat resistance of the anti-precipitation agent itself is not enough, which affects other properties, and the modification of the resin body to resist precipitation often involves multi-step synthesis and pretreatment, which is difficult to control in the process, and the market materials are not popular. SUMMARY

[0008] The purpose of the present application is to provide an anti-precipitation halogen-free flame-retardant polyamide composition that can significantly reduce the precipitation of flame retardants under high temperature and high humidity conditions, has a long effect time, does not affect other properties, and the raw materials are easy to obtain and the processing is simple. To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0009] An anti-precipitation halogen-free flame-retardant polyamide composition, characterized in that it comprises the following components by weight:

[0010] 30-95 parts of polyamide resin;

[0011] 0-50 parts of reinforcing material;

[0012] 5-30 parts of halogen-free flame retardant;

[0013] 1-5 parts of di-calcium silicate;

[0014] 0.2-1 parts of tri-calcium silicate;

[0015] 0.3-3 parts of coupling agent;

[0016] 0.5-5 parts of other additives.

[0017] The polyamide resin is selected from at least one of PA6, PA56, PA66, and PA6 / 66.

[0018] The reinforcing material is selected from one or more of fibrous or flaky or powdery glass fibers, carbon fibers, basalt fibers, wollastonite fibers, potassium titanate whiskers, mica, and diatomite.

[0019] The halogen-free flame retardant is selected from melamine cyanurate (MCA), melamine polyphosphate (MPP), aluminum diethylphosphinate (ADP), polyaluminum phosphate, zinc stannate, zinc borate, etc.

[0020] The purity of the dicalcium silicate is ≥95%; the particle size is ≥1000 mesh, preferably 3000-50000 mesh.

[0021] The purity of the tricalcium silicate is ≥95%; the particle size is ≥1000 mesh, preferably 3000-50000 mesh.

[0022] The coupling agent is selected from silane coupling agent, titanate coupling agent, aluminate coupling agent, zirconate coupling agent, stannate coupling agent, etc.

[0023] The other auxiliary agents further include conventional processing agents, including one or a mixture of several of antioxidants, lubricants, nucleating agents, light stabilizers, toner.

[0024] The preparation method of the above-mentioned anti-precipitation halogen-free flame-retardant polyamide composition has the following steps:

[0025] (3) According to the material ratio in the table, the halogen-free flame retardant, dicalcium silicate, tricalcium silicate and coupling agent are first added to a high-speed mixer and uniformly mixed at high speed; then the polyamide and other auxiliary agents are put into the high-speed mixer and uniformly mixed to obtain a premix;

[0026] (4) The obtained premix is then put into a twin-screw extruder for melt mixing, the fiber-reinforced filler is fed by a side feeding process, and the composition is obtained by extrusion granulation; wherein the extrusion temperature is 230-280°C, and the screw rotation speed is set to 480-600 rpm.

[0027] The anti-precipitation mechanism of the present application is as follows: under long-term storage, the polar groups of polyamide easily absorb moisture in the air to form a water molecule capillary channel; under high temperature and humidity conditions, due to the strengthening effect of temperature and vapor pressure, the water absorption rate of polyamide increases and the water molecule capillary channel widens. The halogen-free flame retardant has poor compatibility with polyamide and is easy to migrate and precipitate to the surface of the polyamide composition. In the present application, the tricalcium silicate has a fast hydration reaction, and the initial setting to final setting time generally only needs 4-8h, which can timely hydrate with the water molecules entering the polyamide composition, block the precipitation channel and block the precipitation; the dicalcium silicate has a much slower hydration reaction, and only about 20% of the hydration is achieved at 28d age, and the setting and hardening is slow, which can continuously capture the entering water molecules and continuously play a hydration role, ensuring that the anti-precipitation effect time is long enough.

[0028] Compared with the prior art, the present application has the following beneficial effects:

[0029] 1) The invention adopts the principle of hydration hardening. When dicalcium silicate and tricalcium silicate meet water, calcium hydroxide and calcium silicate gel are generated, which has the viscoelasticity of colloid, is distributed along the water molecule capillary, and occupies the precipitation channel. Further, at the interface between the channel and air, calcium carbonate is generated by reacting with carbon dioxide, the capillary channel is hardened and blocked, and the precipitation is blocked.

[0030] 2) The proportioning of dicalcium silicate and tricalcium silicate is regulated, the timeliness and long-acting are considered, that is, the timely hydration hardening to block the precipitation channel to play the anti-precipitation role is ensured, and the anti-precipitation role time is long enough. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The photo of the "no precipitation" example of the invention;

[0032] Figure 2 The photo of the "slight precipitation" comparative example of the invention;

[0033] Figure 3 The photo of the "serious precipitation" comparative example of the invention; DETAILED DESCRIPTION

[0034] In order to make the technical scheme of the invention clearer and more explicit, the invention is further described below. Any scheme obtained by equivalent replacement and conventional reasoning of the technical features of the technical scheme of the invention falls within the protection scope of the invention.

[0035] The examples and comparative examples of the invention use the following materials, but are not limited to the following materials:

[0036] PA6: M2400, Guangdong Xinhui Meida

[0037] PA66: EPR27, Shenma Group

[0038] Glass fiber: ECS301CL-4.5, Chongqing International Composite

[0039] Wollastonite: TH-108, Shanghai Tianhuan Mine Fiber Technology

[0040] Flame retardant 1: OP1230, main component ADP, no MPP, Clariant

[0041] Flame retardant 2: ADP30P, main component ADP, no MPP, Qingdao Oupuoli

[0042] Flame retardant 3: OP1314, main component ADP, contains MPP, Clariant

[0043] Flame retardant 4: MCA, Shouguang Weidong Chemical Industry

[0044] Dicalcium silicate: purity 99%, 3000 mesh, Macclin Biochemical Technology

[0045] Tricalcium silicate 1: purity 99%, 3000 mesh, Macklin Biochemical Technology

[0046] Tricalcium silicate 2: purity 99%, 400 mesh, Macklin Biochemical Technology

[0047] Coupling agent: KH550, Jinan Shanhai Chemical Industry

[0048] Lubricant: A-C540A, Honeywell

[0049] Antioxidant 1: Irganox 1098, BASF

[0050] Antioxidant 2: Irganox 168, BASF

[0051] Black masterbatch, N54 / 1044, GaoLai

[0052] According to the material ratio in the table, first add halogen-free flame retardant, dicalcium silicate, tricalcium silicate and coupling agent into the high-speed mixer, mix uniformly at high speed; then put polyamide and other additives into the high-speed mixer to mix uniformly, to obtain a premix; then put the obtained premix into a twin-screw extruder for melt mixing, the fiber reinforced filler is added by side feeding process, extrusion granulation is carried out, to obtain a composition; wherein the extrusion temperature is 230-280°C, and the screw rotation speed is set to 480-600 rpm.

[0053] Performance test method:

[0054] (1) Flame retardancy: 125*13*0.8mm is prepared by injection molding, and tested according to UL-94 standard.

[0055] (2) Mechanical properties: tensile strength: according to ISO 527 method, sample size 170*10*4mm, test speed 5mm / min; notched Charpy impact strength: according to ISO 179 / 1eA method, sample size 80*10*4mm.

[0056] (3) Anti-extrusion performance: place a 60*60*2mm sample plate in an environmental chamber, and set the environmental chamber to a temperature of 85°C and a humidity of 85%RH. At 168h and 1500h, respectively, visually evaluate the state of surface exudates.

[0057] Table 1: Component ratio (parts by weight) and performance test results of each example

[0058]

[0059]

[0060] Table 2: Component ratio (parts by weight) and performance test results of each example

[0061]

[0062] From the data shown in the table, the composition of the present application does not precipitate after 1500h of high temperature and humidity (85℃, 85%RH), and the technical effect is remarkable. Lack of or too low addition leads to insufficient anti-precipitation performance. Too low proportion of tricalcium silicate does not hydrate and harden in time to block the channel, and there will be precipitation in the early 168h (Comparative Example 6); too low proportion of dicalcium silicate will increase precipitation as time goes on (Comparative Example 8). Too high addition and unsuitable specifications will bring negative effects on the mechanics and flame retardant performance of the material (Comparative Examples 4, 5, 9). The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto.

Claims

1. A halogen-free flame-retardant polyamide composition with anti-emission properties, characterized in that, The components include the following parts by weight: 30-95 parts of polyamide resin; 0-50 parts of reinforcing material; 5-30 parts of halogen-free flame retardant; 1-5 parts of dicalcium silicate; Tricalcium silicate 0.2-1 part; Coupling agent KH550 0.3-3 parts; Other additives: 0.5-5 parts; The halogen-free flame retardant is selected from melamine cyanurate (MCA), melamine polyphosphate (MPP), and aluminum diethylphosphite (ADP); the dicalcium silicate has a purity ≥95% and a particle size ≥1000 mesh; the tricalcium silicate has a purity ≥95% and a particle size ≥1000 mesh.

2. The halogen-free flame-retardant polyamide composition for resisting exudation according to claim 1, characterized in that: The polyamide resin is selected from at least one of PA6, PA56, PA66, and PA6 / 66.

3. The halogen-free flame-retardant polyamide composition for resisting exudation according to claim 1, characterized in that: The reinforcing material is selected from one or more of the following: glass fiber, carbon fiber, basalt fiber, wollastonite fiber, potassium titanate whiskers, mica, diatomaceous earth in fibrous, sheet, or powder form.

4. The halogen-free flame-retardant polyamide composition for resisting exudation according to claim 1, characterized in that: The particle size of the dicalcium silicate is 3000-50000 mesh.

5. The halogen-free flame-retardant polyamide composition for resisting exudation according to claim 1, characterized in that: The tricalcium silicate has a particle size of 3000-50000 mesh.

6. The halogen-free flame-retardant polyamide composition for resisting exudation according to claim 1, characterized in that: The other additives include one or a mixture of antioxidants, lubricants, nucleating agents, light stabilizers, and colorants.

7. The method for preparing the anti-precipitation halogen-free flame-retardant polyamide composition according to any one of claims 1-6, characterized in that, The steps are as follows: (1) According to the material ratio in the table, first add the halogen-free flame retardant, dicalcium silicate, tricalcium silicate and coupling agent into the high-speed mixer and mix them evenly at high speed; then add them together with polyamide and other additives into the high-speed mixer and mix them evenly to obtain the premix. (2) The obtained premix is ​​then fed into a twin-screw extruder for melt mixing, and the fiber-reinforced filler is fed by a side-feeding process for extrusion granulation to obtain the composition; The extrusion temperature is 230-280℃, and the screw speed is set to 480-600rpm.

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