A polyamide composition and its preparation method and application

Abstract

The present invention discloses a polyamide composition, a preparation method and application thereof. The polyamide composition comprises the following components in parts by mass: 30-65 parts of aliphatic polyamide, 10-20 parts of semi-aromatic polyamide, 10-30 parts of flat glass fiber, 0.1-0.5 parts of a stabilizer, and 1-2 parts of a metal salt modifier. The metal salt modifier comprises one or more of lithium chloride and calcium chloride. The weight of the metal salt modifier accounts for 1.1-2.5% of the polyamide composition. The polyamide composition has good flatness, high light transmittance and good mechanical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of engineering plastics, and in particular to a polyamide composition, a preparation method and an application thereof. Background Art

[0002] Polyamide, the world's first synthetic fiber, is a general term for thermoplastic resins containing repeating amide groups in their molecular backbone. Polyamides possess excellent mechanical and electrical insulation properties, high mechanical strength, and good toughness. They also possess excellent heat resistance, weather resistance, and abrasion resistance, making them widely used in automotive, electronics, and consumer electronics. In actual production, individual components must be assembled and connected to form a complete product. Common connection methods include bonding, mechanical fastening, and welding. Plastic laser welding utilizes lasers to heat the interface of plastic parts, melting and welding them together. This requires the upper material to be laser-transparent and the lower material to be laser-absorbent. Laser welding works by irradiating the upper material with laser light, causing the lower material to absorb the laser energy and melt along with the upper, light-transmitting material. Upon cooling and solidification, the materials form a single, integrated structure. Laser welding requires high laser transmittance and absorption properties of the upper and lower materials, as well as the smoothness of the weld surface. Traditional glass-fiber-reinforced polyamides exhibit significant warping and poor laser transmittance, making laser welding prone to weld failure. In order to meet the current application requirements of laser welding polyamide products, we need to develop polyamide materials with high flatness and high laser transmittance.

[0003] Prior art patent application No. 202211103789.4 discloses a glass fiber-reinforced composite made from carbon monoxide-ethylene-propylene copolymer and polyamide. The composite exhibits low water absorption and water vapor permeability, while also being laser-weldable. The laser transmittance of a 2mm plate at 980nm is 18-40. Patent application No. 202110632506.4 discloses a glass fiber-reinforced composite made from styrene-methyl methacrylate copolymer and polyamide, exhibiting low water absorption and high laser transmittance. The laser transmittance of a 2mm plate at 980nm is 20-33. Patent application No. 201510355624.X discloses a glass fiber-reinforced, laser-weldable polyamide material with a total light transmittance of 30-50% and a high-transmittance synergist, such as amorphous nylon or aromatic nylon.

[0004] However, none of the above-mentioned related technologies can solve the problem of laser welding failure caused by flatness problems of polyamide materials. Summary of the Invention

[0005] In view of this, the present application provides a polyamide composition and a preparation method and application thereof, which has good flatness, high light transmittance and small dimensional deformation.

[0006] In order to achieve the above technical objectives, this application adopts the following technical solutions:

[0007] In a first aspect, the present application provides a polyamide composition comprising the following components in parts by mass: 30-65 parts of aliphatic polyamide, 10-20 parts of semi-aromatic polyamide, 10-30 parts of flat glass fiber, 0.1-0.5 parts of a stabilizer, and 1-2 parts of a specific metal salt modifier; the metal salt modifier comprises one or more of lithium chloride and calcium chloride.

[0008] Preferably, the mass of the metal salt modifier accounts for 1.1-2.5% of the polyamide composition; more preferably, the mass of the metal salt modifier accounts for 1.8-2.0% of the polyamide composition.

[0009] In this embodiment, the sum of the mass of the aliphatic polyamide and the semi-aromatic polyamide accounts for more than 52% of the total mass of the polyamide composition. Preferably, the sum of the mass of the aliphatic polyamide and the semi-aromatic polyamide accounts for 55.3%-87% of the total mass of the polyamide composition.

[0010] Preferably, a polyamide composition comprises the following components in parts by mass: 50-60 parts of aliphatic polyamide, 10-15 parts of semi-aromatic polyamide, 25-30 parts of flat glass fiber, 0.2-0.4 parts of stabilizer, and 1.5-2 parts of metal salt modifier.

[0011] Preferably, the aliphatic polyamide includes one or more of PA66, PA610, PA612, PA1010, PA 1012, and PA1212, which are obtained by polycondensation of aliphatic dicarboxylic acid and aliphatic diamine as raw materials; or by ring-opening polymerization of lactam with 6-12 carbon atoms or self-condensation of α,ω-aminocarboxylic acid.

[0012] Preferably, the semi-aromatic polyamide includes one or more of PAMXD6, PA6I, PA10T, PA6T, PA4T, PA9T, and PA12T, which are obtained by polycondensation of an aliphatic diamine and a diacid containing a benzene ring; or by polycondensation of a diamine containing a benzene ring and an aliphatic diacid.

[0013] Preferably, the mass of the semi-aromatic polyamide accounts for 10-25% of the polyamide composition; more preferably, the mass of the semi-aromatic polyamide accounts for 18-20% of the polyamide composition.

[0014] Preferably, the stabilizer includes one or more of an antioxidant, a UV absorber, a hindered amine stabilizer, and a polyamide stabilizer. The antioxidant may be pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] or n-octadecylβ-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate. The UV absorber may be 2,2′-methylene-bis[4-tert-octyl-6-(2H-benzotriazolyl-2)]phenol or 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole. The hindered amine stabilizer may be 4,4'-bis(α.α-dimethylbenzyl)diphenylamine or N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-benzenediamide. The polyamide stabilizer may be tris[2,4-di-tert-butylphenyl]phosphite or bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite.

[0015] In a second aspect, the present application provides a method for preparing a polyamide composition, comprising the following steps: melt-blending an aliphatic polyamide, a semi-aromatic polyamide, a stabilizer, and a metal salt modifier according to the composition, adding flat glass fibers, and extruding and granulating to obtain the polyamide composition; wherein the screw barrel temperature is 220-280°C and the screw speed is 200-350 rpm. Preferably, the twin-screw extruder has a screw length-to-diameter ratio of 40:1, the screw barrel temperature is 270°C, and the screw speed is 200 rpm.

[0016] In a third aspect, the present application provides a polyamide composition for use in laser welding parts, such as automobile remote control keys, motor housings and other parts.

[0017] The beneficial effects of this application are as follows:

[0018] The present application adds semi-aromatic polyamide, flat glass fiber and metal salt modifier to aliphatic polyamide, wherein the semi-aromatic polyamide and metal salt modifier work together to reduce crystallinity, thereby reducing warping deformation; by blending aliphatic polyamide and semi-aromatic polyamide, the crystallinity of the composite material is reduced, thereby reducing warping deformation; the flat glass fiber used in the present application can reduce the shrinkage difference in the lateral and longitudinal directions of the material; the metal salt modifier used in the present application, through complexation and coordination, limits the crystallization of polyamide molecules, reduces crystallinity, greatly improves the infrared transmittance of the material, and reduces warping deformation; the polyamide composition obtained by formulating according to the components of the present application has high strength, good toughness, small dimensional deformation, high infrared transmittance, and more stable laser welding. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0020] The present application provides a polyamide composition, comprising the following components in parts by mass: 30-60 parts of aliphatic polyamide, 10-20 parts of semi-aromatic polyamide, 10-30 parts of glass fiber, 0.1-0.5 parts of stabilizer, and 1-2 parts of metal salt modifier, wherein the glass fiber is flat glass fiber.

[0021] The polyamide composition prepared according to the components of the present application has high strength, good toughness, small dimensional deformation, high infrared transmittance, and more stable laser welding.

[0022] The flat glass fiber is chopped glass, has a cross-sectional width of 10 to 40 μm, a cross-sectional thickness of 5 to 18 μm, and a length ratio of the major axis to the minor axis of the flat glass fiber of 2.2 to 4.8:1.

[0023] The metal salt modifier includes one or more of lithium chloride and calcium chloride.

[0024] Aliphatic polyamides are obtained by polycondensation reaction of aliphatic dicarboxylic acids and aliphatic diamines, including but not limited to one or more of PA66, PA610, PA612, PA1010, PA1012, and PA1212.

[0025] The aliphatic polyamide is obtained by ring-opening polymerization of lactam with 6 to 12 carbon atoms or self-condensation of α,ω-aminocarboxylic acid, including but not limited to one or more of PA6, PA7, PA11 and PA12.

[0026] Semi-aromatic polyamides are obtained by polycondensation of aliphatic diamines and diacids containing a benzene ring. The semi-aromatic polyamides herein include, but are not limited to, one or more of PAMXD6, PA6I, PA10T, PA6T, PA4T, PA9T, and PA12T.

[0027] Stabilizers include one or more of an antioxidant, a UV absorber, a hindered amine stabilizer, and a polyamide stabilizer. The antioxidant may be one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and n-octadecylβ-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate. The UV absorber may be one or more of 2,2'-methylene-bis[4-tert-octyl-6-(2H-benzotriazol-2-yl)]phenol and 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole. The hindered amine stabilizer may be one or more of 4,4'-bis(α,α-dimethylbenzyl)diphenylamine and N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-benzenediamide. Other types of polyamide stabilizers may be one or more of tris[2,4-di-tert-butylphenyl]phosphite and bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite.

[0028] The present application provides a method for preparing a polyamide composition, comprising the following steps: preparing the components, melt-blending aliphatic polyamide, semi-aromatic polyamide, stabilizer, and metal salt modifier, adding flat glass fiber, and extruding and granulating to obtain the polyamide composition.

[0029] Specifically, the preparation method of the polyamide composition includes the following steps: S1: weighing each component according to a ratio, and premixing each component except flat glass fibers to obtain a premix; S2: feeding the premix from step S1 into an extruder for melt blending, feeding the flat glass fibers via a side feed method, and extruding and granulating to obtain a polyamide composition; wherein the twin-screw extruder has a screw length-to-diameter ratio of 36:1 to 48:1, a barrel temperature of 220 to 280°C, and a screw speed of 200 to 350 rpm. Preferably, the twin-screw extruder has a screw length-to-diameter ratio of 40:1, a barrel temperature of 270°C, and a screw speed of 200 rpm.

[0030] In a third aspect, the present application provides a polyamide composition for use in laser welding components.

[0031] The present invention is further described below through specific examples.

[0032] The sources of the raw materials involved in this application are shown in Table 1.

[0033] Table 1 Sources of components

[0034]

[0035] Examples 1-5 and Comparative Examples 1-5

[0036] A polyamide composition comprises the following components in parts by weight: an aliphatic polyamide, a semi-aromatic polyamide, glass fiber, a stabilizer, and a metal salt modifier; the amounts of the components are shown in Table 2.

[0037] The preparation method of a polyamide composition comprises the following steps: weighing components according to a proportion, premixing the components except glass fiber to obtain a premix; feeding the premix into an extruder for melt blending, feeding the glass fiber into the extruder by side feeding, and extruding and granulating to obtain a polyamide composition; wherein the screw length-diameter ratio of the twin-screw extruder is 40:1, the screw barrel temperature is selected to be 270°C, and the screw speed is selected to be 200 rpm.

[0038] Table 2-1 Composition formulation of various embodiments

[0039]

[0040] Table 2-2 Composition formulation of each comparative ratio

[0041]

[0042] Evaluation Test

[0043] The polyamide compositions of Examples 1-8 and Comparative Examples 1-6 were tested, and the test results are shown in Table 3:

[0044] Tensile strength: Tensile strength is tested in accordance with the relevant standards of ISO 527-2-2012;

[0045] Izod notched impact strength: Izod notched impact strength: Izod notched impact strength is tested in accordance with the relevant standards of ISO 180-2019;

[0046] Flatness: Injection mold a box with a length of approximately 200 mm, a width of approximately 100 mm, and a height of approximately 150 mm. The bottom of the box is hollowed out. The flatness of the material is evaluated by comparing the maximum height of the warping of the four bottom feet of the box.

[0047] Infrared transmittance: A 100*100*2mm sample was injection molded and its transmittance was tested using a Linshang Technology LS108H laser transmittance tester with a laser wavelength of 940nm.

[0048] Table 3 Test results

[0049]

[0050] Compared with Comparative Example 1, Example 1 uses aliphatic polyamide alone, and the flatness and transmittance are greatly reduced; Comparative Example 2 increases the amount of semi-aromatic polyamide relative to Example 1, and the impact strength is greatly reduced; Comparative Example 3 changes the flat glass fiber to round glass fiber relative to Example 1, and the special-shaped structure reduces the difference in shrinkage of the material in the lateral and radial directions, and the effect of flatness and transmittance is greatly reduced; Comparative Example 4 does not use metal salt modifiers relative to Example 1, and the transmittance is greatly reduced and the flatness is also reduced; Comparative Example 5 uses too much metal salt modifier relative to Example 1, which limits the crystallization of the material, reduces the crystallinity, affects the rigidity of the material, and leads to a significant decrease in tensile strength, an increase in transmittance, but a decrease in flatness; Example 7 also has a low glass fiber content, which reduces the effect of glass fiber on transmittance. Although the lithium chloride content is low, the two have a combined effect, and the transmittance basically remains the same as the previous example; the above results show that the material obtained by this scheme has good rigidity, toughness, good flatness, and high laser transmittance. The above are only preferred specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A polyamide composition, characterized in that The invention comprises the following components in parts by mass: 30-65 parts of aliphatic polyamide, 10-20 parts of semi-aromatic polyamide, 10-30 parts of flat glass fiber, 0.1-0.5 parts of stabilizer, and 1-2 parts of metal salt modifier, wherein the metal salt modifier comprises one or more of lithium chloride and calcium chloride; The mass of the metal salt modifier accounts for 1.1-2.5% of the polyamide composition.

2. The polyamide composition according to claim 1, characterized in that The aliphatic polyamide includes one or more of PA66, PA610, PA612, PA1010, PA1012, and PA1212.

3. The polyamide composition according to claim 1, characterized in that The semi-aromatic polyamide includes one or more of PAMXD6, PA6I, PA10T, PA6T, PA4T, PA9T, and PA12T.

4. The polyamide composition according to claim 1, characterized in that The mass of the semi-aromatic polyamide accounts for 10-25% of the polyamide composition.

5. The polyamide composition according to claim 1, characterized in that The stabilizer includes one or more of an antioxidant, an ultraviolet absorber, a hindered amine stabilizer, and a polyamide stabilizer.

6. A method for preparing a polyamide composition according to any one of claims 1 to 5, characterized in that: The following steps are involved: The polyamide composition is prepared by melt-blending aliphatic polyamide, semi-aromatic polyamide, stabilizer and metal salt modifier, adding flat glass fiber and extruding and granulating.

7. Use of the polyamide composition according to any one of claims 1 to 5 as a laser welding component.

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