A laser-weldable, flame-retardant, yellowing-resistant nylon material and a method for making the same

Abstract

The application discloses a kind of laser-weldable flame-retardant nylon materials and preparation method thereof, comprising the following weight parts of raw materials: nylon resin 15.5~69.96%;Glass fiber 10~40%;Light-transmitting component 5~15%;Flame retardant 15~25%;Nucleating agent 0.01~1%;Anti-yellowing auxiliary agent 0.01~1%;Antioxidant 0.01~1%;Light stabilizer 0.01~1%;Lubricant 0~0.5%;Anti-yellowing auxiliary agent is the complex of strontium stannate and manganese hypophosphite, sodium pyrophosphate dihydrogen di-sodium one of them.The beneficial effects of the application are: the application uses complex anti-yellowing auxiliary agent, uses the synergistic effect of strontium stannate and manganese hypophosphite or sodium pyrophosphate dihydrogen di-sodium one of them, improves the yellowing of nylon material, and by optimizing light-transmitting component and additives, selecting high-transmittance flame retardant system, increasing the light transmittance, can meet the requirements of laser welding on materials, break through the bottleneck of existing flame-retardant nylon as laser welding light-transmitting component and easy yellowing in high-temperature environment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer modified materials, and particularly relates to a preparation method of a yellowing-resistant laser-weldable flame-retardant nylon material. BACKGROUND

[0002] Nylon material is a general term for a class of synthetic polymers composed of polyamides, and is the most widely used in the five engineering plastics, involving automobiles, household appliances, transportation and other fields, and in many cases it can even replace metal parts. However, nylon material is a flammable material, and commonly used nylon materials such as PA6 and PA66 have a fireproof rating of V-2 or HB under the UL94 flammability standard, which belongs to flammable materials. The current widely used method for flame-retardant modification of nylon is to melt blend and extrude different types of flame retardants and nylon masterbatch, which is simple in process, high in efficiency and meets the needs of industrial production.

[0003] With the increasingly mature application of nylon materials, higher requirements are placed on the assembly method of nylon parts. Compared with traditional glue bonding, vibration welding, hot plate welding and ultrasonic welding, plastic laser welding technology has good application prospects due to its short forming cycle, good welding quality, cleanliness and no vibration, and avoidance of internal stress, and is one of the key technologies to achieve automobile lightweight. The principle of laser welding is that the light-transmitting layer and the light-absorbing layer are arranged in overlap, the laser beam is absorbed and melted by the light-absorbing layer after passing through the light-transmitting layer, and a firm weld is formed after cooling under a certain pressure. Therefore, the optical characteristics of the material are very important, especially the high transparency of the light-transmitting layer in the laser wavelength range. In recent years, with the rise of new energy electric cars, the battery system, circuit module and other peripheral parts require high welding difficulty, high flame retardancy and stability in high temperature harsh environment, which puts forward urgent needs for laser-weldable flame-retardant nylon. However, for glass fiber reinforced flame-retardant nylon material, due to the high filling of glass fiber and flame retardant, the laser transmittance of the light-transmitting layer is difficult to meet the requirements of laser welding. Therefore, the development of laser-weldable flame-retardant nylon material is extremely important.

[0004] The molecular chain segment structure determines the performance, and the strong polar amide group and regular structure of nylon determine its good mechanical properties and excellent properties such as wear resistance and fatigue resistance; however, nylon material is prone to complex chemical reactions under light and thermal oxidation conditions, leading to aging degradation and yellowing of appearance. For color parts with strict color requirements, the color is prone to change. At present, the most commonly used solution is to add hindered phenol, phosphite, phosphite salt antioxidant, which is used singly or in combination, and has been proved by practical application to inhibit or slow down the yellowing of nylon. It can meet the use requirements of dark color parts and most light color parts, but better yellowing resistance is required for yellowing-sensitive colors, and the current commonly used antioxidants, stabilizers and their combinations cannot meet the requirements and have a high risk. SUMMARY

[0005] The application provides a laser-weldable flame-retardant nylon material with yellowing resistance and a preparation method thereof, and mainly solves the technical problem of how to effectively improve the anti-oxidation and yellowing resistance of nylon materials and apply the nylon materials in the field of laser-weldable flame-retardant nylon materials, thereby filling the technical gap.

[0006] To achieve the technical purposes, the application adopts the technical scheme of:

[0007] The application provides a laser-weldable flame-retardant nylon material with yellowing resistance and a preparation method thereof, and mainly solves the technical problem of how to effectively improve the anti-oxidation and yellowing resistance of nylon materials and apply the nylon materials in the field of laser-weldable flame-retardant nylon materials, thereby filling the technical gap.

[0008]

[0009] The yellowing resistance auxiliary agent is composed of strontium stannate and one of manganese hypophosphite and disodium pyrophosphate; the manganese hypophosphite is treated by removing combined water, and the disodium pyrophosphate is kept dry and constant weight.

[0010] The weight ratio of the strontium stannate and one of the manganese hypophosphite and the disodium pyrophosphate is 1: (0.1-10).

[0011] The nylon resin is PA66, the relative viscosity is 2.37±0.03, and the water content is ≤0.2%.

[0012] The glass fiber refers to chopped strands, the chopped length is 3 mm, the fiber diameter is 10 um, the combustible content is 0.45±0.15%, the water content is ≤0.10%, and the surface is coated with a silane-based impregnant.

[0013] The light-transmitting component is one of PA6I, PA56 and copolymer nylon.

[0014] The flame retardant is a non-halogen flame retardant based on organic hypophosphite.

[0015] The nucleating agent is one of P22, NAV101 and CAV102.

[0016] The antioxidant is a phosphite antioxidant.

[0017] The light stabilizer is a hindered amine light stabilizer.

[0018] The lubricant is OP wax.

[0019] The application further discloses a preparation method of the laser-weldable flame-retardant nylon material with yellowing resistance.

[0020] Step one: according to the weight percentage requirements, the raw materials are weighed; all the raw materials except glass fiber, including: nylon resin, light-transmitting component, flame retardant, nucleating agent, yellowing-resistant auxiliary agent, antioxidant, light stabilizer, lubricant, are mixed at high speed for 5 min.

[0021] Step two: the mixed premix is added into a twin-screw extruder (the length-diameter ratio of the extruder is L / D=36, and the screw diameter is 35 mm), the glass fiber is added by side feeding process, and extrusion granulation is carried out, so as to obtain the glass fiber reinforced flame-retardant nylon material; the main screw temperature is set to 260-285 DEG C, the screw rotation speed is 350-500 rpm, the extruded strip is cooled by a water tank, dried by air blowing, and then cut into particles to obtain the sample.

[0022] Compared with the prior art, the application has the beneficial effects as follows:

[0023] (1) for the natural color nylon material which is prone to yellowing, the yellowing at high temperature is effectively reduced, and compared with the existing products, the visual observation and color difference delta E are significantly improved, including short-term high-temperature, long-term high-temperature heat aging storage and multiple processing extrusion, and the additive amount is small, the cost is low, and the mechanical properties and heat resistance are not adversely affected.

[0024] (2) the strontium titanate of the perovskite type with oxygen as the octahedral connection base is compounded with one of manganese hypophosphite and disodium pyrophosphate, so as to effectively improve the free radical capture efficiency and inhibit the oxidation process; the strontium titanate has high thermal stability, and the phosphorus elements with different reaction activities, including manganese hypophosphite (+1) and disodium pyrophosphate (+5); the manganese hypophosphite is treated by removing combined water, so as to avoid the promotion process of water in the thermal oxidation aging.

[0025] (3) by optimizing the light-transmitting component: one of PA6I, PA56 and copolymerized nylon, using the nucleating agent as the heterogeneous crystal nucleus of semi-crystalline plastic, reducing the micro size of the high molecular crystal, and selecting the organic hypophosphite non-halogen flame retardant with high light transmittance, the requirements of the laser welding on the light-transmitting layer material are met, the bottleneck of the existing flame-retardant nylon as the light-transmitting component of laser welding and easy yellowing in high-temperature environment is broken, and the flame-retardant nylon is helpful to the more extensive application in more fields. DETAILED DESCRIPTION

[0026] In order to make the technical problems, technical solutions and beneficial effects of the application more clear, the application will be further described in detail in combination with specific examples. It should be understood that the specific examples described herein are only used to explain the application, and are not used to limit the application.

[0027] The specific examples of the application select the following materials:

[0028] Nylon resin PA66, EPR24, Pingdingshan Shenma

[0029] Glass fiber, 568H, Giant Stone Group

[0030] PA6I, TM01, commercially available

[0031] PA56, E-2260, Mingyuan Plastic

[0032] Copolymer nylon 6 / 66, 5033B, commercially available

[0033] Halogen-free flame retardant, Exolit OP1400, Klϋn

[0034] Bromine-based flame retardant, brominated polystyrene, commercially available

[0035] Auxiliary, strontium stannate, commercially available

[0036] Auxiliary, disodium pyrophosphate, Jindia America

[0037] Auxiliary, manganese hypophosphite monohydrate, Baishun Biology

[0038] Nucleating agent, NAV101 / CAV102 / P22, commercially available

[0039] Antioxidant 168: phosphite antioxidant, commercially available

[0040] Light stabilizer 944: hindered amine light stabilizer, commercially available

[0041] Lubricant, OP wax, commercially available

[0042] According to the examples 1-4 and comparative examples 1-5 described in Table 1, the specific preparation method includes the following steps:

[0043] Step one: according to the weight percentage requirements, the raw materials are weighed; all raw materials except glass fiber, including: nylon resin, light transmission component, flame retardant, nucleating agent, yellowing-resistant auxiliary, antioxidant, light stabilizer, lubricant, are mixed at high speed for 5 min.

[0044] Step two: the uniformly mixed premix is added to a twin-screw extruder (the length-diameter ratio of the extruder is L / D = 36, and the screw diameter is 35 mm), and the glass fiber is added by side feeding process, and extrusion granulation is carried out, to obtain a glass fiber reinforced flame-retardant nylon material, the main screw temperature is set to 260-285℃, the screw rotation speed is 350-500 rpm, and after the extruded strip is cooled in a water tank and dried by air blowing, it is cut into particles to obtain the sample.

[0045] The above materials were dried at 100℃ for 4h, and then injection molded into different standard samples at a temperature of 265-285℃. After conditioning in a standard environment (23℃, 50% RH) for 24h, the relevant performance tests were carried out according to the following test methods, and the test results are shown in Table 1.

[0046] Product performance test method:

[0047] Tensile property: according to ISO 527 method, sample size: 170*10*4mm, speed: 50mm / min.

[0048] Notched impact strength: according to ISO 179-1 method, sample size: 80*10*4mm.

[0049] Total light transmittance: according to ISO 13468 method, sample size: 60*60*2mm, 980nm (LPKF TMG3).

[0050] Flame retardant property: according to UL94 method, sample size: 127*12.7*1.6mm.

[0051] Yellowing resistance: using a color difference meter, the color difference ΔE of the sample after different high temperature storage conditions compared with the initial sample, and the color difference ΔE of the particles after repeated extrusion of the screw compared with the initial sample.

[0052] Table 1: Formulation components and performance test results of examples 1-4 and comparative examples 1-5

[0053]

[0054]

[0055] As can be seen from the data in Table 1, the flame-retardant nylon material prepared by the present application has a significant yellowing resistance effect, and the color difference ΔE is small after high temperature baking and repeated processing, especially for storage at 180℃ / 24h, the color difference ΔE is ≤3, and there is almost no yellowing phenomenon visually; the material also has a high laser transmittance, and due to the presence of excess, it can meet the laser welding requirements of 2mm and thicker size parts. It breaks through the bottleneck of existing flame-retardant nylon as a laser welding light transmission component and easy yellowing in high temperature environment, and helps the flame-retardant nylon to be more widely used in more fields.

[0056] As can be seen from the examples and comparative examples 1-5, the yellowing resistance aid in the present application is compounded by strontium stannate and one of manganese hypophosphite and dihydrogen disodium pyrophosphate in a certain proportion, and the effect cannot be achieved without the components, alone use, and without compounding in the proportion of the present application.

[0057] As can be seen from the examples and comparative examples 1-5, the preferred light-transmitting component and nucleating agent of the present application have the best effect on the laser transmission when used in combination in the organic phosphorus flame-retardant system, and the gain effect is limited when the content used deviates from the range of the present application.

Claims

1. A flame retardant, laser weldable, yellowing resistant nylon material characterized by: The raw materials include the following by weight percentage: The anti-yellowing assistant is composed of strontium stannate and one of manganese hypophosphite and disodium pyrophosphate dihydrogen, with a weight ratio of 1:(0.1-10); the manganese hypophosphite is treated by removing bound water, and the disodium pyrophosphate dihydrogen is kept dry and constant weight.

2. A flame retardant, laser weldable, yellowing resistant nylon material according to claim 1, characterized in that: The nylon resin is PA66, with a relative viscosity of 2.37±0.03 and a water content of ≤0.2%.

3. The flame retardant, laser weldable, yellowing resistant nylon material of claim 1, wherein: The glass fiber refers to short-cut original filaments, with a short-cut length of 3mm, a fiber diameter of 10μm, a combustible content of 0.45±0.15%, a water content of ≤0.10%, and a surface coated with silane-based impregnant.

4. The flame retardant, laser weldable, yellowing resistant nylon material of claim 1, wherein: The light-transmitting component is one of PA6I, PA56, and copolymerized nylon.

5. The flame retardant, laser weldable, non-yellowing nylon material of claim 1, wherein: The flame retardant is a non-halogen flame retardant based on organic hypophosphite.

6. A flame retardant, laser weldable, nylon material that is resistant to yellowing according to claim 1, characterized in that: The nucleating agent is one of P22, NAV101, and CAV102.

7. The flame retardant, laser weldable, non-yellowing nylon material of claim 1, wherein: The antioxidant is a phosphite antioxidant.

8. The flame retardant, laser weldable, non-yellowing nylon material of claim 1, wherein: The light stabilizer is a hindered amine light stabilizer; and the lubricant is OP wax.

9. The method of making a laser weldable, flame retardant, yellowing resistant nylon material according to any one of claims 1-8, wherein, The method includes the following steps: Step one: weigh the raw materials according to the weight percentage; mix all the raw materials except the glass fiber, including nylon resin, light-transmitting component, flame retardant, nucleating agent, anti-yellowing assistant, antioxidant, light stabilizer, and lubricant, at high speed for 5min; Step two: add the mixed pre-mixture into a double-screw extruder, with a length-diameter ratio of L / D=36, a screw diameter of 35mm, and glass fiber added by side feeding process, to perform extrusion granulation, to obtain a glass fiber reinforced flame-retardant nylon material, with the main screw temperature set at 260-285℃, screw rotation speed at 350-500rpm, the extruded strip cooled by water tank and dried by air blowing, and then cut into granules to obtain the sample.

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