A laser foaming LDS-PBT composition and its preparation and application

Abstract

The present invention belongs to the field of composite materials, and discloses a laser-foaming LDS-PBT composition, its preparation and application. The laser-foaming LDS-PBT composition comprises the following components in weight percentages (wt%): 69% - 89.9% of PBT resin; 2% - 10% of laser foaming agent; 4% - 10% of LDS additive; 4% - 10% of toughening agent; 0.1% - 1% of antioxidant. The present invention utilizes the nitrogen gas generated by the high-temperature decomposition reaction of the laser foaming agent during the laser engraving process for foaming, increasing the surface roughness and surface area of the plastic part after laser engraving, so that more LDS metal oxide nuclei are exposed on the surface layer after laser engraving, and the plating effect and the adhesion of the coating are significantly improved compared with the sample without adding the laser foaming agent. At the same time, when ensuring that the adhesion of the metal coating and the coating thickness meet the mass production requirements, the dosage of the LDS additive can be reduced, reducing the cost of the composition.

Description

Technical Field

[0001] The present invention belongs to the field of composite materials, and particularly relates to a laser foaming LDS-PBT composition, its preparation and application. Background Art

[0002] The laser direct structuring process (LDS) was developed by the German company LPKF. It is a 3D production technology integrating professional laser processing, injection molding, and electroplating processes. Its principle is to endow ordinary plastic components / circuit boards with functions such as electrical interconnection, support for components, support and protection of plastic shells, as well as functions such as shielding and antennas generated by the combination of mechanical entities and conductive patterns. The LDS technology surpasses the physical and economic limits of traditional antenna manufacturing technologies (such as soft metals or stamped metals). The entire production process, from mold making to laser structuring and plastic spraying, is fast and easy to design. The main advantages of this technology include: more flexible design changes and the ability to create antenna structures on three-dimensional surfaces. These functions allow customers to achieve a higher level of product integration, reduce component parts, and lower costs.

[0003] The process flow of laser direct structuring usually includes three main steps: injection molding, laser engraving, and chemical plating. Laser engraving, also known as laser activation, refers to the process of using a laser to ablate the plastic layer on the surface of a plastic part, exposing the LDS additive (usually a metal compound) on the surface. Laser engraving can precisely engrave the target circuit pattern on the surface of a 3D plastic part. Chemical plating is the process of restoring metals (such as copper, nickel, gold, etc.) on the surface after laser engraving. The surface roughness after laser engraving affects the adhesion between the metal layer deposited on the surface of the plastic part and the plastic part after chemical plating. As the designs of terminals such as smart phones and smart watches become more precise, there are more 3D hole positions and 3D narrow corner structural designs in LDS components, and the control of laser focusing and laser incident angle becomes more difficult during mass production. When the laser focusing of the 3D hole position is slightly misaligned or the laser incident angle is slightly large, the depth of surface ablation at this position will become shallower, and the products after chemical plating are likely to fail after reliability tests such as high-temperature water boiling. Chinese Patent Publication No. CN109486165A discloses an LDS polyphenylene ether / polystyrene composition adding hollow glass microspheres and metal oxides coated with hollow glass microspheres. By introducing hollow glass microspheres, the proportion of LDS additives is reduced, the metal adhesion can be improved, and the addition proportion of LDS additives can be reduced. However, adding hollow glass beads will cause a serious decrease in the tensile strength, notch impact strength, and compressive strength of the material. Summary of the Invention

[0004] To solve the problem of the decreased adhesion in the 3D structure laser engraving and plating process, the primary object of the present invention is to provide a laser foaming LDS-PBT composition. The present invention adds a laser foaming agent to the composition. Under normal circumstances, the laser foaming agent can be evenly dispersed in the plastic as a filler, and the material remains dense without a hollow structure, and the tensile strength and notch impact strength do not decrease significantly. When laser engraving is performed on the surface, the foaming agent dispersed on the surface foams at high temperature to form micropores, which increases the surface roughness and surface area, and thus improves the adhesion of the plated metal after plating.

[0005] Another object of the present invention is to provide a preparation method for the above-mentioned laser foaming LDS-PBT composition.

[0006] Another object of the present invention is to provide the application of the above-mentioned laser foaming LDS-PBT composition in LDS antennas of 3C products such as smart watches and smart phones.

[0007] The object of the present invention is achieved by the following solutions:

[0008] A laser foaming LDS-PBT composition, comprising the following components in weight percentage (wt%):

[0009] PBT resin 69% - 89.9%;

[0010] Laser foaming agent 2% - 10%;

[0011] LDS additive 4% - 10%;

[0012] Toughening agent 4% - 10%;

[0013] Antioxidant 0.1% - 1%.

[0014] Preferably, the above-mentioned laser foaming LDS-PBT composition comprises the following components in weight percentage (wt%):

[0015] PBT resin 74% - 89.9%;

[0016] Laser foaming agent 2% - 5%;

[0017] LDS additive 4% - 10%;

[0018] Toughening agent 4% - 10%;

[0019] Antioxidant 0.1% - 1%.

[0020] The laser foaming agent is at least one of MPP (melamine polyphosphate) and MCA (melamine cyanurate).

[0021] The LDS additive is copper chromite black with a particle size of 1 - 2 μm.

[0022] The antioxidant described above is at least one of phosphite antioxidants and hindered phenol antioxidants.

[0023] The toughening agent is at least one of EMA (ethylene-methyl acrylate copolymer), POE (polyolefin elastomer), EBA (ethylene-butyl acrylate copolymer) elastomers and grafted or copolymerized products of the above elastomers with GMA (glycidyl methacrylate), and the commercially available specifications are Arkema AX8900, Dow PTW, etc.

[0024] In addition to the above key components, the laser foaming LDS-PBT composition described in the present invention can also add auxiliaries such as mold release agents, lubricants, anti-UV agents, etc. to improve processing, aging resistance and other properties. Fillers such as glass fibers and carbon fibers can also be added to enhance the strength and modulus of the material.

[0025] The present invention adds a laser foaming agent to the composition. Under normal circumstances, the laser foaming agent can be uniformly dispersed in the plastic as a filler, and the material remains dense without a hollow structure, and the tensile strength and notch impact strength will not decrease significantly. When laser engraving is performed on the surface, the foaming agent dispersed on the surface foams at high temperature to form micropores, which increases the surface roughness and surface area, and then improves the adhesion of the plated metal after chemical plating.

[0026] A preparation method of the above laser foaming LDS-PBT composition, which includes the following steps: mixing PBT resin, laser foaming agent, LDS additive, toughening agent, and antioxidant according to the above weight percentages, and then extruding and pelletizing through a double-screw extruder. The pelletizing temperature is 225-260°C to obtain laser foaming LDS-PBT composition particles.

[0027] The application of the above laser foaming LDS-PBT composition in LDS antennas of 3C products such as smart watches and smart phones.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] The present invention uses the nitrogen gas generated by the high-temperature decomposition reaction of the laser foaming agent during the laser engraving process to foam, increasing the surface roughness and surface area of the plastic part after laser engraving, so that more LDS metal oxide nuclei are exposed on the surface layer after laser engraving. The plating effect and the adhesion of the coating are significantly improved compared with the samples without adding the laser foaming agent. At the same time, while ensuring that the adhesion and thickness of the metal coating meet the mass production requirements, the dosage of the LDS additive can be reduced, reducing the cost of the composition. Detailed implementation manners

[0030] The present invention will be further described in detail below in conjunction with embodiments, but the embodiments of the present invention are not limited thereto. For those not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0031] The PBT resin described in the embodiments includes PBT resins polymerized by direct esterification or transesterification methods. Specifically, commercially available grades include Changchun 1100-211D, Changchun 1100-211X, etc.; the LDS additive described in the embodiments is copper chromite black with a particle size of 1-2 μm; the antioxidant described in the embodiments is at least one of phosphite antioxidants and hindered phenol antioxidants. Specifically, commercially available specifications include Basf IRGANOX 168, Basf IRGANOX 1010, BASF Irganox® 1076, etc. The toughening agent is at least one of elastomers such as EMA (ethylene-methyl acrylate copolymer), POE (polyethylene oxide), TPEE (thermoplastic polyester elastomer), and grafted or copolymerized products of the above elastomers and GMA (glycidyl methacrylate). Specifically, commercially available specifications include Arkema AX8900, Dow PTW, etc.

[0032] In the following embodiments, the tensile strength, elongation at break, and notch impact strength are tested by the standard methods of ASTM D638 and ASTM D256;

[0033] To simulate the environmental conditions of the focus fluctuation of the hole positions of 3D structural parts and high incident angles, in the present invention, the laser incident angle during laser engraving of each group of samples is uniformly controlled at 75°, the laser power is 12 W, the linear velocity is 2 m / s, and the parameters such as the temperature and time of chemical plating are kept consistent.

[0034] Plating performance test: The coating thickness of the sample is tested according to ASTM B568. To ensure the antenna performance, the coating thickness after chemical plating is required to be >10 μm to be qualified, and >13 μm is considered excellent in plating performance.

[0035] Boiling water cross-cut test: For the samples after chemical plating, the test is carried out according to the ASTM D3359 standard, specifically as follows: After treatment in boiling water at 80°C for 1 h, under the conditions of 23°C and a relative humidity of 50±5%, use a sharp blade (blade angle of 15°-30°) to draw 10x10 small grids of 1 mm x 1 mm on the surface of the test sample, and each scratch reaches the bottom layer of the coating; brush the test area clean with a brush; tape the tested small grids with 3M 600 tape, and use an eraser to wipe the tape forcefully to increase the contact area and force between the tape and the tested area; hold one end of the tape by hand and quickly tear off the transparent tape at a 60° angle in the vertical direction, and perform 2 identical tests at the same position. Result determination: The adhesion is required to be ≥4B to be qualified, and reaching 5B is excellent (the highest grade is 5B).

[0036] Example 1

[0037] This example aims to study the effects of adding different types of laser blowing agents on the plating performance, adhesion, and mechanical properties of the laser blowing LDS-PBT composition.

[0038] In this example, the laser blowing LDS-PBT compositions in Specimens 0 - Specimen 5 were all prepared by the following steps: Weigh the corresponding amounts of components according to the weight percentages of each component shown in Table 1, then mix the components and extrude and pelletize them with a twin-screw extruder to obtain the corresponding laser blowing LDS-PBT compositions. The pelletizing temperature is 225 - 260 °C. Then injection molding, laser engraving, and chemical plating were carried out, and the mechanical properties, metal coating thickness, and adhesion between the metal coating and the plastic PBT of the products after chemical plating were tested.

[0039] The weight percentages (wt%) of the raw materials of the corresponding laser blowing LDS-PBT compositions in Specimens 0 - 5 and the various properties of the obtained laser blowing LDS-PBT compositions are shown in Table 1.

[0040] Table 1 Effects of the type of laser blowing agent on the properties of the laser blowing LDS-PBT resin composition

[0041]

[0042] In Example 1, by comparing Specimen 0 and Samples 1 - 5, it can be seen that after adding 3 wt% of sodium carbonate and magnesium carbonate laser blowing agents, the boiling water cross-cut adhesion and coating thickness of the LDS-PBT composition have both increased to a certain extent, but the notch impact strength and elongation at break of the samples added with sodium carbonate and magnesium carbonate laser blowing agents will decrease significantly. After adding 3 wt% of MCA and MPP laser blowing agents, the boiling water cross-cut adhesion and coating thickness of the LDS-PBT composition have increased to a certain extent, and the mechanical properties have not decreased significantly. Adding 3 wt% of calcium carbonate laser blowing agent has no improvement in the boiling water cross-cut adhesion and coating thickness (presumably because the decomposition temperature of calcium carbonate is relatively high).

[0043] Example 2

[0044] This example aims to study the effects of the addition ratio of melamine-based laser blowing agents on the plating performance, adhesion, and mechanical properties of the laser blowing LDS-PBT composition.

[0045] In this embodiment, the laser-foaming LDS-PBT compositions in Specimens 5 to 11 are all prepared by the following steps: Weigh the corresponding amounts of components according to the weight percentages of the components shown in Table 2, then mix the components, and extrude and pelletize them with a twin-screw extruder to obtain the corresponding laser-foaming LDS-PBT compositions. The pelletizing temperature is 225-260°C. Then, injection molding, laser engraving, and chemical plating are carried out, and the mechanical properties, thickness of the metal coating, and adhesion between the metal coating and the plastic PBT of the products after chemical plating are tested.

[0046] The weight percentages (wt%) of the raw materials of the corresponding laser-foaming LDS-PBT compositions in Specimens 5 to 11 and the various properties of the obtained laser-foaming LDS-PBT compositions are shown in Table 2.

[0047] Table 2 Influence of the addition ratio of the laser foaming agent on the properties of the laser-foaming LDS-PBT resin composition

[0048]

[0049] From the comparison of Specimens 5 to 11 in Example 2, it can be seen that on the basis of an LDS addition amount of 8 wt%, adding 2 wt% to 4 wt% of MPP can make the boiling water cross-cut adhesion test reach 4B, and the notch impact performance of the composition remains good. Adding 5 wt% of MPP can make the boiling water cross-cut adhesion test reach 5B, the coating thickness further increases, and the notch impact performance of the composition remains good. Continuing to increase the content of MPP, the boiling water cross-cut adhesion test reaches 5B, the coating thickness does not increase significantly, and the notch impact strength will decrease slowly. Considering the comprehensive mechanical properties, boiling water cross-cut adhesion, and coating thickness, the preferred addition ratio of the laser foaming agent MPP is 5 wt%.

[0050] Example 3

[0051] This embodiment aims to study the changes in the mechanical properties, boiling water cross-cut adhesion, and coating thickness of the laser-foaming LDS-PBT composition after reducing the content of the LDS additive copper chromite black under the condition of adding 5 wt% MPP.

[0052] In this embodiment, the laser-foaming LDS-PBT compositions in Specimens 9, 12 to 14 are all prepared by the following steps: Weigh the corresponding amounts of components according to the weight percentages of the components shown in Table 3, then mix the components, and extrude and pelletize them with a twin-screw extruder to obtain the corresponding laser-foaming LDS-PBT compositions. The pelletizing temperature is 225-260°C. Then, injection molding, laser engraving, and chemical plating are carried out, and the mechanical properties, thickness of the metal coating, and adhesion between the metal coating and the plastic PBT of the products after chemical plating are tested.

[0053] The weight percentages (wt%) of the raw materials of the corresponding laser-foamed LDS-PBT compositions in Specimen 0, Specimen 9, and Specimens 12 - 14, as well as the properties of the obtained laser-foamed LDS-PBT compositions, are shown in Table 3.

[0054] Table 3 Influence of the dosage of LDS additive on the properties of laser-foamed LDS-PBT composition

[0055]

[0056] From Comparative Sample 0 and Samples 9 - 14 in Example 3, it can be seen that when 5 wt% MPP is added and the content of copper chromite black as the LDS additive is reduced to 6% - 4%, the plating thickness can reach the plating effect of Specimen 0 with 8 wt% LDS additive, and the cross-cut adhesion after boiling water is higher. When the content of copper chromite black as the LDS additive is reduced to 2%, the plating thickness is unqualified, but the cross-cut adhesion after boiling water can reach 5B.

[0057] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent substitution methods and are all included in the protection scope of the present invention.

Claims

1. A laser foamed LDS-PBT composition, characterized in that It is composed of the following components in percentage by weight: PBT resin 69%~89.9%; Laser foaming agent 2%~10%; LDS additive 4%; Toughening agent 4%~10%; Antioxidant 0.1%~1%; The laser foaming agent is melamine cyanurate.

2. The laser foamed LDS-PBT composition according to claim 1, characterized in that It is composed of the following components in percentage by weight: PBT resin 74%~89.9%; Laser foaming agent 2%~5%; LDS additive 4%; Toughening agent 4%~10%; Antioxidant 0.1%~1%.

3. The laser foamed LDS-PBT composition according to claim 1, characterized in that: The LDS additive is copper chrome black, and the particle size is 1 to 2 μm.

4. The laser foamed LDS-PBT composition according to claim 1, characterized in that: The antioxidant is at least one of a phosphite antioxidant and a hindered phenol antioxidant.

5. The laser foamed LDS-PBT composition according to claim 1, characterized in that: The toughening agent is selected from at least one of the following substances: (1) Ethylene-methyl acrylate copolymer (EMA); (2) Polyolefin elastomer POE; (3) Ethylene-butyl acrylate copolymer EBA; (4) a graft product of any one of the above (1) to (3) and glycidyl methacrylate (GMA); (5) A copolymerization product of any one of the above (1) to (3) and glycidyl methacrylate (GMA).

6. A method for preparing the laser foamed LDS-PBT composition according to any one of claims 1 to 5, characterized in that The following steps are involved: PBT resin, laser foaming agent, LDS additive, toughening agent and antioxidant are mixed according to weight percentage, and then extruded and granulated by a twin-screw extruder to obtain a laser foaming LDS-PBT composition.

7. The method for preparing the laser foamed LDS-PBT composition according to claim 6, characterized in that: Granulation temperature 225-260℃.

8. Use of the laser foamed LDS-PBT composition according to any one of claims 1 to 5 in smart watches and smart phones.

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