A low dielectric constant laser-weldable polyamide composite material and its preparation method and application

Abstract

The present invention discloses a low dielectric constant laser-weldable polyamide composite material and its preparation method and application. The polyamide composite material, in parts by weight, includes the following components: 30-50 parts of polyamide resin, 10-20 parts of polypropylene resin, 2-5 parts of compatibilizer, 10-25 parts of hollow glass microspheres, 0.1-0.5 parts of stabilizer, and 1-2 parts of laser transmittance improver, wherein the particle size D50 of the hollow glass microspheres is 15-35 μm. The polyamide composite material of the present invention can maintain high rigidity while taking into account low dielectric constant and high laser transmittance.

Description

Technical Field

[0001] The present invention relates to the technical field of engineering plastics, and in particular to a low-dielectric-constant laser-weldable polyamide composite material, a preparation method thereof, and applications thereof. Background Art

[0002] With the promotion of 5G technology, the progress of the Internet of Everything is accelerating, and the requirements for signal transmission are becoming increasingly higher. In order for signal transmission equipment to protect signal transmission and data exchange as much as possible, the materials used in signal transmission equipment must have a low dielectric constant.

[0003] Polyamide, the world's first synthetic fiber, is a generic term for thermoplastic resins containing repeating amide groups in their molecular backbone. Polyamide exhibits excellent mechanical and electrical insulation properties, high mechanical strength, and good toughness. It also possesses excellent heat, weather, and abrasion resistance, making it widely used in automotive, electrical, and consumer electronics applications.

[0004] In actual production, common methods for assembling and connecting components to form a complete product 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. The laser welding process works by illuminating the lower material with laser light. The laser energy absorbs the laser energy and heats the lower material, melting it along with the upper, transparent material. Once the material cools and solidifies, it forms a single piece. Laser welding is a future trend in high-speed production.

[0005] The most common method for modifying polyamide is to use glass fiber fillers for reinforcement and modification, thereby achieving excellent properties of high rigidity and high modulus. However, the addition of glass fiber will increase the dielectric constant of the polyamide material, which will greatly affect signal transmission and data exchange when used in the communications field, greatly limiting the application of reinforced polyamide materials in the communications field. The laser welding process has high requirements for the laser transmittance of the upper material, the laser absorption of the lower material, and the flatness of the welding position. Traditional glass fiber modified polyamide has large warping deformation and poor laser transmittance due to the anisotropy of the glass fiber and the difference in shrinkage rate in different directions, which can easily lead to weld failure when using the laser welding process.

[0006] In order to meet the current application needs of laser-weldable polyamide products in the 5G field, it is urgent to develop a polyamide composite material with low dielectric constant and high laser transmittance. Summary of the Invention

[0007] In view of the defects in the prior art, the present invention proposes a low dielectric constant laser-weldable polyamide composite material and a preparation method and application thereof.

[0008] The present invention provides a low-dielectric-constant laser-weldable polyamide composite material, comprising the following components, measured in parts by weight: 30-50 parts of a polyamide resin, such as 30, 35, 40, 45, or 50 parts, preferably 40-50 parts; 10-20 parts of a polypropylene resin, such as 10, 12, 14, 16, 18, or 20 parts; 2-5 parts of a compatibilizer, such as 2, 3, 4, or 5 parts; 10-25 parts of hollow glass microspheres, such as 10, 12, 15, 18, 20, 22, or 25 parts; and 1-2 parts of a laser-transmittance improving agent, such as 1, 1.5, or 2 parts. The mass percentage of the polyamide resin in the composite is not less than 36%.

[0009] The particle size D50 of the hollow glass microspheres is 15-35 μm, such as 15, 18, 20, 22, 25, 28, 30, 32, and 35 μm. According to GB / T 19077-2016-Particle Size Distribution-Laser Diffraction Method, the smaller the particle size of the hollow glass microspheres, the smaller the refraction of light and the stronger the laser transmittance. However, the smaller the particle size, the larger the dielectric constant. The particle size D50 of the hollow glass microspheres in this range can take into account the balance between the dielectric constant and the laser transmittance, and maintain the flatness of the material parts.

[0010] Furthermore, the xylene soluble content of the polypropylene resin is ≤7%, preferably ≤4%, and the xylene soluble content is tested according to GB / T 24282-2009.

[0011] Furthermore, the polyamide composite material further comprises 0.1-0.5 parts of a stabilizer, such as 0.1, 0.2, 0.3, 0.4, or 0.5 parts.

[0012] Furthermore, the laser transmittance improver is one or more of lithium chloride, calcium chloride or PVP, preferably one or both of lithium chloride or calcium chloride. The amide group in the polyamide resin has a certain ability to complex with metal ions. The addition of metal ions can affect the hydrogen bond structure between nylon molecules and significantly reduce the crystallinity of nylon. Moreover, by optimizing the laser transmittance improver, the effect of the polypropylene resin on the reduction of laser transmittance can be balanced.

[0013] Furthermore, the polyamide resin is selected from polyamides obtained by polycondensation of at least one dicarboxylic acid and a diamine, such as any one or more of PA66, PA610, PA612, PA1010, PA1012, PA1212, PA MXD6, PA MXD10, and PA6T / 66. It can also be selected from polyamides obtained by polycondensation of at least one amino acid or lactam with itself, wherein the amino acid can be produced by hydrolysis and ring opening of the lactam ring, such as any one or more of PA6, PA7, PA11, and PA12.

[0014] Furthermore, the stabilizer is one or more of an antioxidant, an ultraviolet absorber, and a hindered amine stabilizer; wherein the antioxidant can be tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate]pentaerythritol, β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, tris[2,4-di-tert-butylphenyl] phosphite (Antioxidant 168), bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite (Antioxidant 626) The UV absorber may be one or more of 2,2′-methylene-bis[4-tert-octyl-6-(2H-benzotriazol-2)]phenol, 2-(2′-hydroxy-5′-tert-octylphenyl)benzotriazole, etc.; the hindered amine stabilizer may be one or more of 4,4′-bis(α,α-dimethylbenzyl)diphenylamine, N,N′-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-benzenediamide, etc.

[0015] Furthermore, the compatibilizer is any one of maleic anhydride grafted octene ethylene copolymer, maleic anhydride grafted EPDM rubber, maleic anhydride grafted polypropylene, maleic anhydride grafted polyethylene or SEBS, preferably maleic anhydride grafted polypropylene.

[0016] The present invention also provides a method for preparing the polyamide composite material, comprising the following steps:

[0017] S1: Weigh each component by weight, and put the remaining components except the hollow glass microspheres into a mixer and mix until uniform to obtain a premix;

[0018] S2: The obtained premix is put into a twin-screw extruder for melt mixing, hollow glass microspheres are fed into the extruder by side feeding, and the mixture is extruded and granulated to obtain the polyamide composite material.

[0019] Furthermore, in step S2, the screw length-diameter ratio of the twin-screw extruder is 36:1-48:1, the barrel temperature is 220-300° C., and the screw speed is 200-750 rpm.

[0020] The present invention also provides the use of the polyamide composite material in the preparation of 5G base station antenna housings, especially in the preparation of products such as robots and drone detection radars.

[0021] In summary, compared with the prior art, the present invention achieves the following technical effects:

[0022] (1) The polyamide composite material of the present invention has a low dielectric constant, especially a low dielectric constant at 2.5 GHz.

[0023] (2) The polyamide composite material of the present invention has high laser transmittance, is suitable for laser welding, and has high welding strength.

[0024] (3) The polyamide composite material of the present invention has high rigidity and a high flexural modulus (rigidity equilibrium modulus).

[0025] (4) The polyamide composite material of the present invention has small warping deformation and high material flatness. DETAILED DESCRIPTION

[0026] In order to help those skilled in the art better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the embodiments described 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 those skilled in the art without making any creative efforts should fall within the scope of protection of the present invention.

[0027] Example

[0028] The present invention is further described below with reference to specific examples and comparative examples. The following specific examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the following examples, and are particularly not limited to the types of the various component raw materials used in the following specific examples.

[0029] 1. The sources of raw materials for the embodiments and comparative examples are as follows:

[0030] Polyamide resin #1: PA66 resin, PA66 U4800 NC01 SS, INVISTA, USA;

[0031] Polyamide resin #2: PA6 resin, HY-2500A, Haiyang Chemical Fiber;

[0032] Polyamide resin #3: PA6T / 66 resin, Advanced T2000, BASF;

[0033] Polypropylene resin #1: M1100, xylene soluble content 2%, PetroChina;

[0034] Polypropylene resin #2: N-Z30S, xylene solubles 7%, PetroChina;

[0035] Polypropylene resin #3: J501, xylene soluble content 4%, PetroChina;

[0036] Compatibilizer #1: Maleic anhydride grafted PP, CMG9801, Shanghai Jiayirong;

[0037] Compatibilizer #2: SEBS, 503T, Baling Petrochemical;

[0038] Laser transmittance improver #1: anhydrous lithium chloride, LiCl, Shanghai Zhongli Industrial Co., Ltd.;

[0039] Laser Transparency Improver #2: Polyvinylpyrrolidone, PVP-30, Gongbi Ke New Materials;

[0040] Hollow glass microspheres #1: S60HS, particle size D50 30 μm, 3M;

[0041] Hollow glass microspheres #2: IM30K, particle size D50 of 18 μm, 3M;

[0042] Hollow glass microspheres #3: HS46, particle size D50 20 μm, Saint-Wright;

[0043] Hollow glass microspheres #4: K46, particle size D50 40 μm, 3M;

[0044] Hollow glass microspheres #5: HM15, particle size D50 10 μm, Saint-Wright;

[0045] Stabilizer: antioxidant, IRGANOX 1098, BASF, Germany.

[0046] The preparation method of the polyamide composite material of the embodiment of the present invention and the comparative example comprises the following steps:

[0047] Except for the hollow glass microspheres, each component was weighed according to the formulation amount of the specific embodiment and comparative example described in Table 1 and then put into a mixer for mixing until uniform to obtain a premix; the obtained premix was then put into a twin-screw extruder for melt mixing, the hollow glass microspheres were fed by side feeding, and extrusion and granulation were performed to obtain a polyamide composite material with a low dielectric constant and high laser transmittance; wherein the screw aspect ratio of the twin-screw extruder was 40:1, the barrel temperature was 270-260-260-260-260-260-260-280°C, and the screw speed was 500 rpm.

[0048] 2. Various performance test methods

[0049] (1) Dielectric constant: The material was injection molded into a 2.0 mm thick square plate (100 mm * 100 mm). The dielectric constant was tested at 2.5 GHz using the resonance method according to EN 62562-2011.

[0050] (2) Flatness: A box with a length of about 200 mm, a width of about 100 mm, and a height of about 150 mm was injection molded. The bottom of the box was hollowed out. The flatness of the material was evaluated by comparing the maximum height of the warping of the four bottom feet of the box. The warping height was used to indicate the flatness.

[0051] (3) Laser transmittance: A 100*100*2mm sample was injection molded and its transmittance was tested using a laser transmittance tester. The test standard was GB / T 2410-2008, the equipment was Linshang Technology LS108H, and the laser wavelength was 940nm.

[0052] (4) Flexural modulus: Sample size and test standard refer to ISO 178-2019, load rate 2 mm / min, dry flexural modulus is the test result of standard injection molded specimens after conditioning at 23°C / 50% RH for 48 hours;

[0053] (5) Welding strength: Ordinary black nylon was used as the light-absorbing material. The light-transmitting layer material and the light-absorbing layer material were injection molded into 80*13*1mm strips. The head of the light-absorbing layer strip overlapped the tail of the light-transmitting layer material by 10mm. The overlapping portion was irradiated with laser light. The laser diameter was 2mm, the scanning distance was 10mm, and the pressing pressure was 0.5MPa to obtain a laser-welded body. A tensile test was performed, and the tensile strength obtained was used as the welding strength.

[0054] Table 1 Example technical solutions and effects (units are parts by weight)

[0055]

[0056]

[0057] Table 2 Comparative Examples Technical Scheme and Effects (Units are parts by weight)

[0058]

[0059]

[0060] From Examples 1-11, the formulas of different matrix resin combinations have a dielectric constant of 2.96 or below, a flexural modulus greater than 4800 MPa, a laser transmittance of 47% or above, a warpage height less than 0.7 mm, and a welding strength of 39 MPa or above at 2.5 GHz. These have obvious advantages over the comparative examples and can effectively meet the high standards of customers and the market.

[0061] Comparative Examples 1-5 are compared with Example 1. In Comparative Example 1, too much laser transmittance improver is added. The laser improver will hinder the interaction of nylon molecular chains and reduce the crystallinity of the material. If there is too much laser improver, the crystallinity will be greatly reduced, and the mechanical properties will be reduced. At the same time, the uneven dispersion of the laser improver and the formation of stress concentration will also lead to performance degradation; in Comparative Example 2, too much polypropylene resin is added, and crystallization leads to a decrease in transmittance and a decrease in welding strength; in Comparative Example 3, the content of hollow glass microspheres is too little, and there are few holes formed in the composite material, resulting in an increase in dielectric constant and a decrease in rigidity; in Comparative Example 4, the particle size of the hollow glass microspheres is too small, and there are few holes formed. Although the laser transmittance increases slightly, the dielectric constant also increases accordingly; in Comparative Example 5, the particle size of the hollow glass microspheres is too large, and the compressive strength is low, so it is easy to break. The composite material has few holes, the dielectric constant increases, and the rigidity decreases. However, due to its poor pressure resistance, it will break into smaller fragments during the production process, resulting in an insignificant decrease in laser transmittance.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A polyamide composite material, characterized in that: Calculated by weight, it includes the following components: Wherein, the particle size D50 of the hollow glass microspheres is 15-35 μm; The laser transmittance improving agent is one or more of lithium chloride, calcium chloride or PVP.

2. The polyamide composite material according to claim 1, characterized in that The xylene soluble content of the polypropylene resin is ≤7%.

3. The polyamide composite material according to claim 1, characterized in that The invention also includes 0.1-0.5 parts by weight of a stabilizer.

4. The polyamide composite material according to claim 1, characterized in that The polyamide resin is selected from one or more of PA66, PA610, PA612, PA1010, PA1012, PA1212, PA MXD6, PA MXD10, PA6, PA7, PA11, PA12, and PA6T / 66.

5. The polyamide composite material according to claim 3, characterized in that The stabilizer is one or more of an antioxidant, an ultraviolet absorber, and a hindered amine stabilizer.

6. The polyamide composite material according to claim 1, characterized in that The compatibilizer is any one of maleic anhydride grafted octene ethylene copolymer, maleic anhydride grafted EPDM rubber, maleic anhydride grafted polypropylene, maleic anhydride grafted polyethylene or SEBS.

7. The method for preparing the polyamide composite material according to any one of claims 1 to 6, characterized in that: The steps include: S1: Weigh each component by weight, and put the remaining components except the hollow glass microspheres into a mixer and mix until uniform to obtain a premix; S2: The obtained premix is put into a twin-screw extruder for melt mixing, hollow glass microspheres are fed into the extruder by side feeding, and the mixture is extruded and granulated to obtain the polyamide composite material.

8. The method for preparing a polyamide composite material according to claim 7, wherein: In step S2, the screw length-diameter ratio of the twin-screw extruder is 36:1-48:1, the barrel temperature is 220-300° C., and the screw speed is 200-750 rpm.

9. Use of the polyamide composite material according to any one of claims 1 to 6 in the preparation of a 5G base station antenna housing.

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