Wire drawing process in plastic

Abstract

The invention relates to a wire drawing process in plastic. The wire drawing process comprises the following steps: carrying out electroplating UV (Ultraviolet) protection finish paint treatment on a plastic workpiece; and a flying wing wheel wire drawing wheel (scouring pad wire drawing wheel) is used for conducting wire drawing treatment on the UV protection finish paint of the plastic workpiece. According to the invention, electroplating UV is adopted to protect drawing on finish paint, so that the defect of poor appearance of an injection molded part caused by drawing on a mold is overcome, the cost of the mold and the difficulty of an injection molding process are reduced, the combination range and the processing adjustment space of subsequent procedures (CNC / polishing / electroplating and the like) of the injection molded part are improved, and the defects of the injection molded part are thoroughly overcome; meanwhile, wiredrawing on the electroplating UV protection finishing paint can avoid the problem that the effect of being covered by the paint is weakened, and the visual effect of wiredrawing can be better highlighted.

Description

Technical Field

[0001] The invention relates to the technical field of plastic surface processing, in particular to a wire drawing process in plastic. Background Art

[0002] Portable terminals, such as mobile phones and tablet computers, often use plastic materials as their shells. In order to improve the quality of the product, various decorative effects are usually made on the surface of the shell. For example, brushed texture is a common decorative effect. Currently, brushed texture is achieved by directly using mold processing on the plastic substrate.

[0003] However, drawing wire directly on the mold leads to poor appearance defects of the injection molded parts. Summary of the invention

[0004] Based on this, it is necessary to provide a wire drawing process in plastics.

[0005] To achieve the above object, the present invention provides a technical solution:

[0006] A wire drawing process in plastics, comprising the following steps:

[0007] Electroplating and spraying UV protective topcoat on plastic workpieces;

[0008] A wire drawing process is performed on the UV protective topcoat of the plastic workpiece using a scouring brush wire wheel.

[0009] Furthermore, during the wire drawing process, the rotation speed of the scouring wire drawing wheel is 30 to 60 revolutions per minute;

[0010] The running speed of the scouring brush wire wheel is 900MM / min;

[0011] The pressure of the scouring brush wire wheel is 40N;

[0012] The CT of the scouring pad is 2 to 3 min / pcs.

[0013] Further, the raw materials of the scouring brush wire wheel include fibers and sand;

[0014] The fibers include at least one of polyester fibers and nylon fibers;

[0015] The sand includes at least one of aluminum oxide and silicon carbide.

[0016] Furthermore, the thickness of the UV protective topcoat is 0.03 mm to 0.035 mm.

[0017] Furthermore, the hardness of the UV protective topcoat is pencil hardness F grade.

[0018] Furthermore, the viscosity of the UV protective topcoat is 8.4-8.6 Pa / s.

[0019] Furthermore, the electroplating and UV protective topcoat spraying treatment of the plastic workpiece includes:

[0020] The plastic workpiece is sequentially subjected to CNC processing, polishing of knife marks, spraying of the first treatment agent, spraying of the first UV primer, polishing of orange peel and oil accumulation, spraying of the second treatment agent, spraying of the second UV primer, electroplating of a silver metal layer, spraying of a mid-coat color paint, and spraying of a UV protective topcoat;

[0021] The processed plastic workpiece is subjected to wire drawing.

[0022] Furthermore, the first treatment agent includes a thermosetting coating and a UV curing coating.

[0023] Further, the second treating agent comprises a mixture of resin, solvent and auxiliary agent;

[0024] Wherein, the resin comprises at least one of acrylic resin and modified resin;

[0025] The solvent includes a diluent;

[0026] The auxiliary agents include leveling agents and dispersants.

[0027] Furthermore, the plastic workpiece is formed by injection molding.

[0028] Beneficial effects of the present invention:

[0029] The present invention adopts wire drawing on spraying UV protective topcoat, which solves the poor appearance defect of injection molded parts caused by wire drawing on the mold, reduces the cost of the mold and the difficulty of the injection molding process, increases the combination range and processing adjustment space of the post-process (CNC / grinding / electroplating, etc.) of the injection molded parts, and completely solves the defects of the injection molded parts;

[0030] At the same time, brushing on the electroplated UV protective topcoat can avoid the problem of weakening the effect due to paint coverage, and can better highlight the visual effect of brushing. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a drawing effect diagram in an embodiment;

[0032] Figure 2 This is a drawing effect diagram in an embodiment;

[0033] Figure 3 A diagram of a scouring brush wire wheel in one embodiment. DETAILED DESCRIPTION

[0034] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0035] In the examples, the test methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0036] A wire drawing process in plastics, comprising the following steps:

[0037] Electroplating and spraying UV protective topcoat on plastic workpieces;

[0038] Use a scouring brush wire wheel to perform wire drawing on the UV protective topcoat of the plastic workpiece.

[0039] In one embodiment, if Figure 1 , Figure 2 and Figure 3 As shown, the proportion of photoinitiator in the UV protective topcoat is reduced. The reduction of photoinitiator further reduces the curing density of the UV protective topcoat and the surface hardness of the UV protective topcoat (pencil hardness F grade). The rotating and swinging friction of the scouring brush wire wheel can easily form stable, uniform and delicate scratches on the surface of the UV protective topcoat, achieving a beautiful texture pattern.

[0040] In some embodiments, during the wire drawing process, the rotation speed of the scouring brush wire drawing wheel is 30 to 60 revolutions per minute;

[0041] The running speed of the scouring brush wire wheel is 900MM / min;

[0042] The pressure of the scouring brush wire wheel is 40N;

[0043] The CT of the scouring pad is 2 to 3 min / pcs.

[0044] In some embodiments, the raw materials of the scouring pad wire wheel include fibers and sand;

[0045] The fibers include at least one of polyester fibers and nylon fibers;

[0046] The sand includes at least one of aluminum oxide and silicon carbide.

[0047] Specifically, the wire drawing effect achieved by using other wire drawing wheels is not good, resulting in poor uniformity, consistency and stability of the depth, length and shape of the wire drawing texture.

[0048] The scouring brush wire drawing wheel of the present invention is a nylon sheet made of materials such as fiber and mineral sand glued together, adopts a three-dimensional structure, has large gaps and is elastic. When drawing wire on the surface of a plastic workpiece, it will not become fuzzy, discolored or leave residual substances due to overheating.

[0049] Furthermore, the nylon sheets are processed through cutting, stacking, extrusion, bonding and other processes to form a special insert wheel, and scouring pad wire wheels of different sizes and specifications can be produced according to different process requirements.

[0050] In some embodiments, the thickness of the UV protective topcoat is 0.03 mm to 0.035 mm.

[0051] In some embodiments, the UV protective topcoat has a hardness of F on the pencil hardness scale.

[0052] In some embodiments, the viscosity of the UV protective topcoat is 8.4-8.6 Pa / s.

[0053] In some embodiments, the plastic workpiece is formed by injection molding, and the electroplating and UV protective topcoat treatment of the plastic workpiece includes:

[0054] The plastic workpiece is processed by CNC in sequence, the knife marks are polished, the first treatment agent is sprayed, the first UV primer is sprayed, the orange peel and oil accumulation are polished, the second treatment agent is sprayed, the second UV primer is sprayed, the silver metal layer is electroplated, the middle paint is sprayed, and the UV protective topcoat is sprayed;

[0055] More specifically, the plastic workpiece formed by injection molding is processed by CNC (Computer Numerical Control) to perform straight edge processing on the appearance of the plastic workpiece.

[0056] Grinding the knife marks makes the surface of the injection molded workpiece smoother.

[0057] At the same time, the first treatment agent and the first UV primer are sprayed to fill and polish the orange peel and oil accumulation, cover the shrinkage, depression, mold printing and other defects on the surface of the plastic workpiece, improve the density of the material, and reduce the orange peel effect of the plastic workpiece. Further, the first treatment agent includes thermosetting coating and UV curing coating. - There are two ways to cure the coating, heating and baking curing and ultraviolet curing. Thermosetting coating is mainly a coating with thermosetting resin as the main film-forming substance. When this coating is cured, the film-forming substance in the coating film reacts through cross-linking and other reactions to become a hard, insoluble and infusible body polymer network groove.

[0058] More specifically, the content of the thermosetting coating is 80 wt.%, the content of the UV curing coating is 20 wt.%, and the light energy of the UV curing coating is 200 mj / cm 2 ~300mj / cm 2 , thermosetting coatings can increase the sandability of the coating, and UV curing coatings can increase leveling;

[0059] The total coating film thickness of the first treatment agent and the first UV primer sprayed at the same time is 22um to 32um, and the thick coating process can cover the defects of the substrate.

[0060] When sanding orange peel and oil accumulation, use extra-hard sponge sand with a back velvet hardness of 1209, a fineness of 1200-1500 mesh, and a thickness of 5mm for roughing; use sponge sand with a back velvet hardness of 80, a fineness of 2000 mesh, and a thickness of 10mm for polishing. High-hardness, low-thickness rough sandpaper can ensure that sanding does not affect the refinement of the substrate structure, and low-hardness, high-thickness polishing sandpaper can ensure that the edges of the product structure are covered during sanding, reducing defects and improving the yield rate.

[0061] Spray the second treatment agent to increase the adhesion between the first treatment agent and the UV primer. The coating film thickness of the second treatment agent is 1um~3um, which cannot be too thick to avoid slight oil accumulation resulting in fat edges. The viscosity is 7.8 seconds, which cannot be too high to avoid too rough effect during spraying.

[0062] Spray the second UV primer to cover the sandpaper texture in the steps of polishing orange peel and oil accumulation, and at the same time increase the adhesion of the silver metal layer. The film thickness of the second UV primer sprayed is 15um~20um, the viscosity is 8s~8.2s, the diluent ratio is 30%, high leveling, low solid content, and slight fat edges can be seen in the spray wet film, but after baking, leveling, volatilization of diluent and UV curing, the fat edge effect is reduced.

[0063] The silver metal layer can be electroplated through the NCVM process (non conductive vacuum metallization). The silver metal can be 99.99% high-purity indium to increase the metal texture to achieve a mirror-like reflection effect.

[0064] The process of spraying mid-coat color paint can be NCVM process, and the mid-coat color paint is transparent resin and color paste of required color, and the color paste accounts for <10%.

[0065] The plastic workpiece is sprayed with UV protective topcoat. The viscosity of UV protective topcoat is 8.4s~8.6s, and the film thickness is 30um~35um. It meets the appearance without fat edges. High wear-resistant materials are used to avoid the thin coating that cannot meet the customer's stone vibration test. UV protective topcoat layer: protective layer, ensures wear resistance / hardness and other performance tests, improves the roughness of the color paint, and achieves a high leveling effect of the mirror surface.

[0066] Further, the second treating agent comprises a mixture of resin, solvent and auxiliary agent;

[0067] Wherein, the resin comprises at least one of acrylic resin and modified resin;

[0068] The solvent includes a diluent;

[0069] The auxiliary agents include leveling agents and dispersants.

[0070] Diluent is a liquid solvent with good miscibility with resin that is added to reduce the viscosity of the resin and improve its processing performance.

[0071] Leveling agent is a commonly used coating additive. It can help the coating form a flat, smooth and uniform coating film during the drying and film-forming process. It can effectively reduce the surface tension of the coating liquid and improve its leveling and uniformity.

[0072] Dispersant is a surfactant that has two opposite properties, lipophilicity and hydrophilicity, in its molecule. It can evenly disperse the solid and liquid particles of inorganic and organic pigments that are difficult to dissolve in liquids.

[0073] Modified resin refers to a mixture of normal metabolites or secretions of plant tissues and volatile oils and other components. It is a modified product with improved performance in all aspects after being processed and modified by filling, blending, reinforcement and other methods.

[0074] In one embodiment, a scouring brush is used to rotate the wire drawing wheel at a low speed and rub it up and down to scratch the UV protective topcoat protective layer to form irregular, non-obvious matte random lines, so as to achieve the metal wire drawing effect and texture. In order to avoid the problem of the wire drawing wheel sticking to the resin, water needs to be sprayed during the wire drawing process to reduce the heat generated by friction and remove some friction dust. Because the product shape trajectory is used for wire drawing, a uniform wire drawing effect can be achieved around the side of the wire drawing product.

[0075] After the wire drawing is completed, the product is removed, ultrasonic cleaning is performed to remove the dust on the product and it is baked and dried. The grease treatment agent is wiped off to increase the brightness of the wire drawing surface and solve the problem of wire drawing fog.

[0076] In the prior art, wire drawing is usually used on the mold slide. The intersection of the four slides is prone to produce clamping steps. Multi-point glue injection during injection molding will produce bonding lines and air marks defects. In the post-processing, normal spraying of electroplating paint (about 0.09mm thick) will cover the wire drawing effect, so a thin coating (about 0.05mm thick) process will be used. However, the thin coating process cannot cover the clamping lines, bonding lines, and air marks on the surface of the injection molding material, and may even magnify the defects.

[0077] The present invention eliminates the need for wire drawing on the mold slides and directly draws the wire in the plastic workpiece after injection molding, thereby avoiding the clamping problem of the four slides and injection molding defects such as shrinkage / air marks / joint lines on the product appearance.

[0078] It should be noted that the specific parameters or some reagents in the above embodiments are specific embodiments or preferred embodiments of the present invention, rather than limiting the present invention; those skilled in the art can make adaptive adjustments within the scope of the present invention.

Claims

1. A wire drawing process in plastics, characterized in that: The following steps are involved: Electroplating and spraying UV protective topcoat on plastic workpieces; A wire drawing process is performed on the UV protective topcoat of the plastic workpiece using a scouring brush wire wheel.

2. The wire drawing process according to claim 1, characterized in that: During the wire drawing process, the speed of the scouring brush wire drawing wheel is 30 to 60 revolutions per minute; The running speed of the scouring brush wire wheel is 900MM / min; The pressure of the scouring brush wire wheel is 40N; The CT of the scouring pad is 2 to 3 min / pcs.

3. The wire drawing process according to claim 1, characterized in that: The raw materials of the scouring pad wire wheel include fibers and sand particles; The fibers include at least one of polyester fibers and nylon fibers; The sand includes at least one of aluminum oxide and silicon carbide.

4. The wire drawing process according to claim 1, characterized in that: The thickness of the UV protective topcoat is 0.03mm to 0.035mm.

5. The wire drawing process according to claim 1, characterized in that: The hardness of the UV protective topcoat is pencil hardness F grade.

6. The wire drawing process according to claim 1, characterized in that: The viscosity of the UV protective topcoat is 8.4-8.6 Pa / s.

7. The wire drawing process according to claim 1, characterized in that: The electroplating and UV protective topcoat spraying treatment of the plastic workpiece includes: The plastic workpiece is subjected to CNC machining of the appearance, grinding of the knife marks, spraying of the first treatment agent, spraying of the first UV primer, grinding of orange peel and oil accumulation, spraying of the second treatment agent, spraying of the second UV primer, electroplating of a silver metal layer, spraying of a mid-coat color paint, and spraying of a UV protective topcoat in sequence; The processed plastic workpiece is subjected to wire drawing processing.

8. The wire drawing process according to claim 7, characterized in that: The first treating agent includes a thermosetting coating and a UV curing coating.

9. The wire drawing process according to claim 7, characterized in that: The second treating agent comprises a mixture of resin, solvent and auxiliary agent; Wherein, the resin comprises at least one of acrylic resin and modified resin; The solvent includes a diluent; The auxiliary agents include leveling agents and dispersants.

10. The wire drawing process according to claim 1, characterized in that: The plastic workpiece is formed by injection molding.

Images