Optical coating processing method of TPU injection molding part ejection sheet

Abstract

The invention relates to the technical field of optical coating, and particularly discloses an optical coating processing method of a TPU injection molding part ejection sheet. The method comprises the following steps: S1, pretreatment: putting a TPU injection molding part ejection sheet into ultrasonic cleaning equipment for deoiling, degreasing and cleaning; after drying, spraying organic silicon modified resin on the TPU injection molding part ejection sheet, and after curing, forming an additional layer on the surface of the TPU injection molding part ejection sheet; and S2, optical coating is conducted, specifically, the pretreated TPU injection molding part ejection piece is placed in vacuum coating equipment to be vacuumized, ion beam assisted magnetron sputtering or electron beam evaporation deposition is utilized, and coating is conducted on the surface of the TPU injection molding part ejection piece through a coating material. According to the invention, through deoiling and degreasing and additional connecting layer spraying in the pretreatment method, the organic silicon modified resin of the connecting layer can form chemical bonding with the TPU material, meanwhile, a good adhesion basis is provided for the coating layer, the coating adhesion reaches the 0-level standard, and the problem of coating falling is effectively avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of optical coating, and in particular discloses a method for processing optical coating of a TPU injection molded part. Background Art

[0002] TPU injection molded parts are widely used in various industries, such as footwear, fashion accessories, and electronic product casings, due to their excellent flexibility, wear resistance, and mechanical strength. As market demand continues to change, consumers' requirements for product appearance are increasing, and products with unique optical effects are becoming increasingly popular.

[0003] Traditional surface treatment methods for TPU injection molded parts, such as painting and electroplating, have numerous drawbacks. The painting process is prone to problems such as sagging and uneven particle size, and the color effect is relatively monotonous, making it difficult to achieve complex, dazzling colors. While the electroplating process can provide a metallic texture, it poses environmental pollution, high costs, and insufficient adhesion to the TPU material, making the coating prone to detachment during subsequent use. Furthermore, traditional processes for surface treatment of TPU injection molded parts have significant shortcomings in increasing product added value and meeting high-end market demands. Therefore, developing a new optical coating processing method is of great significance for improving the appearance quality and market competitiveness of TPU injection molded parts. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for optical coating processing of TPU injection molded parts.

[0005] The present invention discloses an optical coating processing method for a TPU injection molded part, which adopts the following technical solution:

[0006] A method for processing an optical coating of a TPU injection molded part, comprising the following steps:

[0007] S1. Pretreatment: Degreasing and deoiling the TPU injection molded part in an ultrasonic cleaning device; spraying the TPU injection molded part with a silicone modified resin after drying, and forming a bonding layer on the surface of the TPU injection molded part after curing;

[0008] S2. Optical coating: Place the pre-treated TPU injection molded piece in a vacuum coating device and evacuate the vacuum. Then use ion beam assisted magnetron sputtering or electron beam evaporation to deposit the coating material on the surface of the TPU injection molded piece.

[0009] Preferably, the organosilicon-modified resin is POSS-modified organosilicon resin, polyester-modified organosilicon resin or epoxy-modified organosilicon resin.

[0010] Preferably, in the spraying of the silicone-modified resin in the S1 pre-treatment, the spray gun pressure is controlled at 0.3-0.4 MPa, the spraying distance is maintained at 15-20 cm, and the thickness is controlled at 5-8 μm. After spraying is completed, the injection molded part is placed in an oven at 80-90° C. for curing for 20-30 minutes.

[0011] Preferably, in the S1 pretreatment, a degreasing agent is added, and ultrasonic cleaning is performed at a temperature of 40 to 50° C. for 15 to 20 minutes; after cleaning, the surface is repeatedly rinsed with deionized water to remove the residual degreasing agent, and then dried in an oven at 60 to 70° C. for 1 to 2 hours.

[0012] Preferably, the S1 pre-treatment further includes sandblasting: after sandblasting the surface of the TPU injection molded part's ejection sheet, the surface is placed in an ultrasonic cleaning device for degreasing and deoiling.

[0013] Preferably, the parameters of the sandblasting treatment are: sandblasting particle size of 80-120 mesh, sandblasting pressure of 0.3-0.5 MPa, sandblasting distance of 10-15 cm, sandblasting angle of 80-90°, and sandblasting time of 30-60 s.

[0014] Preferably, the coating material includes metal oxide and fluoride.

[0015] Preferably, the coating material includes a base material and at least two stacking materials; in the S2 optical coating, a layer of base material with a thickness of 10nm to 15nm is first sputtered / deposited as the base material, and then multiple layers of stacking materials are alternately sputtered / deposited, and the thickness of each layer is controlled to be 5nm to 10nm.

[0016] Preferably, the base material includes titanium dioxide (TiO), tantalum pentoxide (TaO), or zirconium oxide (ZrO); and the laminated material includes silicon dioxide (SiO), magnesium fluoride (MgF), or calcium fluoride (CaF). Through the precise coating of multiple layers of metal oxides and fluorides and the principle of light interference, a dazzling and diverse effect unmatched by traditional painting and electroplating is achieved, meeting the personalized appearance needs of different consumers and significantly enhancing the product's visual appeal and market competitiveness.

[0017] Preferably, the base material is surface-modified using a silane coupling agent before coating, using a mixture of 95% ethanol and 5% water as a solvent, adjusting the silane coupling agent to a concentration of 2%, and immersing the base material in the silane coupling agent solution for 1 to 2 minutes, followed by rinsing with ethanol twice, drying, and then drying in an oven at 110°C for 5 to 10 minutes.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects:

[0019] The present invention effectively removes surface impurities and strengthens the bonding between the TPU and the coating through pretreatment steps such as degreasing and deoiling and spraying the bonding layer. The silicone-modified resin in the bonding layer chemically bonds with the TPU material and provides a good adhesion foundation for the coating. Testing has shown that the coating adhesion meets the Class 0 standard, effectively preventing the problem of coating shedding. DETAILED DESCRIPTION

[0020] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with specific embodiments.

[0021] Example 1

[0022] A method for processing an optical coating of a TPU injection molded part, comprising the following steps:

[0023] S1. Pretreatment: Place the TPU injection molded piece into an ultrasonic cleaning device, add an environmentally friendly degreasing agent, and ultrasonically clean it at 45°C for 18 minutes; rinse with deionized water after cleaning, and dry it in a 65°C oven for 1.5 hours; after cooling, use a spray gun to spray POSS modified silicone resin at a pressure of 0.35MPa and a distance of 18cm, then cure it in an 85°C oven for 25 minutes and let it stand for 24 hours. After curing, a bonding layer is formed on the TPU injection molded piece.

[0024] S2. Optical coating: Place the processed injection molded parts into the vacuum coating equipment and evacuate until the pressure is less than 5×10 - 4 Pa; ion beam assisted magnetron sputtering was used to sputter a layer of titanium dioxide with a thickness of 12nm as the bottom layer at a sputtering power of 150W, and then silicon dioxide and magnesium fluoride were sputtered alternately at a power of 100W, with each layer being 8nm thick, and a total of 5 layers were sputtered.

[0025] Example 2

[0026] A method for processing an optical coating of a TPU injection molded part, comprising the following steps:

[0027] S1. Pretreatment: The surface of the TPU injection molded part is sandblasted with a sandblasting particle size of 100 mesh, a sandblasting pressure of 0.3 MPa, a sandblasting distance of 15 cm, a sandblasting angle of 80-90°, and a sandblasting time of 60 s; the TPU injection molded part after sandblasting is placed in an ultrasonic cleaning device, an environmentally friendly degreasing agent is added, and ultrasonic cleaning is performed at 45°C for 18 min; after cleaning, it is rinsed with deionized water and dried in a 65°C oven for 1.5 h; after cooling, a POSS modified silicone resin is sprayed with a spray gun at a pressure of 0.35 MPa and a distance of 18 cm, and then cured in an 85°C oven for 25 min and allowed to stand for 24 h. After curing, a bonding layer is formed on the TPU injection molded part.

[0028] S2. Optical coating: Place the processed injection molded parts into the vacuum coating equipment and evacuate until the pressure is less than 5×10 - 4 Pa; ion beam assisted magnetron sputtering was used to sputter a layer of titanium dioxide with a thickness of 12nm as the bottom layer at a sputtering power of 150W, and then silicon dioxide and magnesium fluoride were sputtered alternately at a power of 100W, with each layer being 8nm thick, and a total of 5 layers were sputtered.

[0029] Example 3

[0030] A method for processing an optical coating of a TPU injection molded part, comprising the following steps:

[0031] S1. Pretreatment: Place the TPU injection molded piece into an ultrasonic cleaning device, add an environmentally friendly degreasing agent, and ultrasonically clean it at 45°C for 18 minutes; rinse with deionized water after cleaning, and dry it in a 65°C oven for 1.5 hours; after cooling, use a spray gun to spray POSS modified silicone resin at a pressure of 0.35MPa and a distance of 18cm, then cure it in an 85°C oven for 25 minutes and let it stand for 24 hours. After curing, a bonding layer is formed on the TPU injection molded piece.

[0032] S2. Optical coating: Place the processed injection molded parts into the vacuum coating equipment and evacuate until the pressure is less than 5×10 - 4 Pa; Using ion beam-assisted magnetron sputtering, a layer of titanium dioxide with a thickness of 12nm was sputtered as a base layer at a sputtering power of 150W. Then, silicon dioxide and magnesium fluoride were sputtered alternately at a power of 100W, with each layer being 8nm thick, for a total of 5 layers. Among them, the titanium dioxide was surface modified using a silane coupling agent before coating. A mixture of 95% ethanol and 5% water was used as the solvent, and the silane coupling agent was adjusted to a concentration of 2%. The titanium dioxide was immersed in the silane coupling agent solution for 1 minute, then rinsed twice with ethanol, dried, and dried in a 110°C oven for 10 minutes.

[0033] Example 4

[0034] A method for processing an optical coating of a TPU injection molded part, comprising the following steps:

[0035] S1. Pretreatment: The surface of the TPU injection molded part is sandblasted with a sandblasting particle size of 100 mesh, a sandblasting pressure of 0.3 MPa, a sandblasting distance of 15 cm, a sandblasting angle of 80-90°, and a sandblasting time of 60 s; the TPU injection molded part after sandblasting is placed in an ultrasonic cleaning device, an environmentally friendly degreasing agent is added, and ultrasonic cleaning is performed at 45°C for 18 min; after cleaning, it is rinsed with deionized water and dried in a 65°C oven for 1.5 h; after cooling, a POSS modified silicone resin is sprayed with a spray gun at a pressure of 0.35 MPa and a distance of 18 cm, and then cured in an 85°C oven for 25 min and allowed to stand for 24 h. After curing, a bonding layer is formed on the TPU injection molded part.

[0036] S2. Optical coating: Place the processed injection molded parts into the vacuum coating equipment and evacuate until the pressure is less than 5×10 - 4 Pa; Using ion beam-assisted magnetron sputtering, a layer of titanium dioxide with a thickness of 12nm was sputtered as a base layer at a sputtering power of 150W. Then, silicon dioxide and magnesium fluoride were sputtered alternately at a power of 100W, with each layer being 8nm thick, for a total of 5 layers. Among them, the titanium dioxide was surface modified using a silane coupling agent before coating. A mixture of 95% ethanol and 5% water was used as the solvent, and the silane coupling agent was adjusted to a concentration of 2%. The titanium dioxide was immersed in the silane coupling agent solution for 1 minute, then rinsed twice with ethanol, dried, and dried in a 110°C oven for 10 minutes.

[0037] Comparative Example 1

[0038] A method for processing an optical coating of a TPU injection molded part, comprising the following steps:

[0039] S1. Pretreatment: Place the TPU injection molded piece into an ultrasonic cleaning device, add an environmentally friendly degreasing agent, and ultrasonically clean it at 45°C for 18 minutes; after cleaning, rinse with deionized water and dry in a 65°C oven for 1.5 hours.

[0040] S2. Optical coating: Place the processed injection molded parts into the vacuum coating equipment and evacuate until the pressure is less than 5×10 - 4 Pa; ion beam assisted magnetron sputtering was used to sputter a layer of titanium dioxide with a thickness of 12nm as the bottom layer at a sputtering power of 150W, and then silicon dioxide and magnesium fluoride were sputtered alternately at a power of 100W, with each layer being 8nm thick, and a total of 5 layers were sputtered.

[0041] Comparative Example 2

[0042] A method for processing an optical coating of a TPU injection molded part, comprising the following steps:

[0043] S1. Pretreatment: Place the TPU injection molded piece into an ultrasonic cleaning device, add an environmentally friendly degreasing agent, and ultrasonically clean it at 45°C for 18 minutes; rinse with deionized water after cleaning, and dry in a 65°C oven for 1.5 hours; prepare a mold that matches the TPU injection molded piece, apply UV glue inside the mold, place the TPU injection molded piece on the mold coated with UV glue, extrude the TPU injection molded piece and the UV glue through a transfer machine, then place it in a UV drying tunnel, cure it with an ultraviolet lamp, peel off the cured TPU injection molded piece from the transfer mold, and form a UV layer on the surface of the TPU injection molded piece.

[0044] S2. Optical coating: Place the processed injection molded parts into the vacuum coating equipment and evacuate until the pressure is less than 5×10 - 4 Pa; ion beam assisted magnetron sputtering was used to sputter a layer of titanium dioxide with a thickness of 12nm as the bottom layer at a sputtering power of 150W, and then silicon dioxide and magnesium fluoride were sputtered alternately at a power of 100W, with each layer being 8nm thick, and a total of 5 layers were sputtered.

[0045] Performance testing

[0046] The following performance tests were performed on the coated TPU injection molded pieces of Examples 1-4 and Comparative Examples 1-2:

[0047] 1. Adhesion test

[0048] The 100-grid method was used for testing. A cutter was used to draw a 10×10 grid on the coating surface with a grid spacing of 1mm. 3M tape was then applied to the grid to ensure full contact between the tape and the coating surface. The tape was then quickly removed to observe the coating shedding in the grid.

[0049] The criteria for judging coating adhesion are as follows:

[0050] Level 0: The coating in the grid is completely intact.

[0051] Level 1: The coating peeling area in the grid is less than 5%.

[0052] Level 2: The coating peeling area in the grid is between 5% and 15%.

[0053] Level 3: The coating peeling area in the grid is between 15% and 35%.

[0054] Level 4: The coating peeling area in the grid is between 35% and 65%.

[0055] Level 5: The coating peeling area in the grid is greater than 65%.

[0056] 2. Bending test

[0057] Fix the sample on the bending tester, make sure the long side of the sample is parallel to the bending axis, bend the sample at an angle of 180°, bend the sample 1-2 times per minute, perform 5 round trip bends, and observe the changes on the coating surface.

[0058] The criteria for judging the bending resistance of the coating are as follows:

[0059] Level 0: There is no crack or peeling on the coating surface after bending.

[0060] Level 1: There are slight cracks on the coating surface after bending, but no peeling.

[0061] Level 2: There are obvious cracks or slight peeling on the coating surface after bending.

[0062] Level 3: There are a lot of cracks or large areas of peeling on the coating surface after bending.

[0063] 3. Abrasion resistance test

[0064] Fix the sample on the platform of the friction tester, select a suitable friction head (such as CS-10 or H-18 friction head), set the friction number to 1000 times and the load to 500g, start the friction tester, and perform the friction test. After the test, observe the wear of the coating surface.

[0065] The criteria for judging the abrasion resistance of the coating are as follows:

[0066] Level 0: There is no obvious wear on the coating surface after friction.

[0067] Level 1: The coating surface is slightly worn after friction, but it does not affect the overall appearance and performance.

[0068] Level 2: The coating surface is obviously worn after friction, affecting the overall appearance and performance.

[0069] Level 3: The coating surface is severely worn after friction, resulting in the base material being exposed in some areas, seriously affecting the appearance and performance.

[0070] 4. Visual effects test

[0071] Visually inspect the color of the TPU injection molded parts under standard light (D65 light source). Check the color uniformity, brightness, and glossiness.

[0072] Criteria for judging the visual effect of coating:

[0073] Level 0: Colors are evenly distributed with no obvious color difference; colors are bright and visual effects are excellent; the surface is smooth with good reflection and no obvious defects.

[0074] Level 1: Slight color difference; average color vividness; average gloss; minor surface defects.

[0075] Level 2: There are many obvious color differences; the color is not bright; the gloss is low; there are many defects on the surface.

[0076] Level 3: There is serious color difference, affecting the overall visual effect; the color vividness is poor; the gloss is poor; there are serious defects on the surface.

[0077] The performance test results of Examples 1-4 and Comparative Examples 1-2 are shown in the following table:

[0078] Adhesion grade Bending resistance grade Abrasion resistance grade Visual Effects Level Example 1 Level 0 Level 1 Level 1 Level 0 Example 2 Level 0 Level 0 Level 0 Level 2 Example 3 Level 0 Level 0 Level 0 Level 1 Example 4 Level 0 Level 0 Level 0 Level 0 Comparative Example 1 Level 3 Level 1 Level 1 Level 0 Comparative Example 2 Level 1 Level 2 Level 1 Level 0

[0079] In Examples 1-4 of the optical coating processing method of the present invention, a bonding layer is formed by spraying a silicone-modified resin onto the TPU surface to chemically bond, thereby providing a good adhesion foundation for the coating layer without affecting the colorful effect of the optical coating. After being processed by this process, the TPU injection molded parts exhibit a brilliant rainbow effect, and the adhesion reaches level 0 in the 100-grid test. The coating layer performs well in the bending and friction tests, with ideal stability. Comparing Example 1 with Comparative Example 1, it can be seen that spraying the bonding layer significantly improves the performance of the optical coating. In addition, comparing Example 1 with Comparative Example 2, it can be seen that the conventional art uses general UV adhesive as a pretreatment for optical coating. The bonding between the UV adhesive and the TPU substrate is mainly through physical adsorption and mechanical intercalation. Although the UV adhesive can provide a certain degree of adhesion after curing, this adhesion is mainly dependent on the physical properties of the UV adhesive and the microstructure of the TPU surface. In complex use environments, such as frequent friction or bending, the UV adhesive may fall off or crack, resulting in less than ideal bending and friction resistance of the coating.

[0080] Except the pre-treatment that degreasing and deoiling and spraying adding junction layer are carried out to TPU surface, the present invention is also by carrying out sandblasting on TPU surface, the bonding force between TPU after surface sandblasting and POSS modified silicone resin is higher, this is because POSS modified silicone resin not only increases physical bite force by sandblasting, also further strengthens the adhesive force with TPU surface by its nanometer level three-dimensional structure and chemical bonding, thereby further improves the bending resistance and the wear-resisting property after TPU injection molding ejects sheet coating.Wherein, although sandblasting can significantly increase roughness and the specific surface area on TPU surface, thereby exposing more active sites is conducive to the bonding force adding junction layer, but owing to increasing the physical roughness on surface, coating glossiness is slightly affected, see the performance test result contrast of embodiment 1 and embodiment 2.

[0081] To this end, a solution was obtained in an in-depth study of the sputtering test of the base material and the additional layer. By using a silane coupling agent to modify the surface of the base material before coating, although this operation affects the purity of the target material and reduces the transparency and reflectivity to a certain extent, see the comparison between Example 1 and Example 3, when sandblasting and base material surface modification are combined, see Example 4, since the silane coupling agent can chemically react with the hydroxyl groups on the surface of titanium dioxide to form a stable siloxane bond, this chemical bonding not only enhances the interaction between titanium dioxide and the organosilicon modified resin, but also improves the stability and dispersibility of titanium dioxide, thereby better filling the tiny pits formed on the surface of the additional layer covered after sandblasting. The uniform film layer can better reflect and refract light, thus solving the problem of visual effects caused by sandblasting and the reduction of target purity, while also better ensuring the material's bending and friction resistance.

[0082] The technical solution provided by the present invention is introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for optical coating of a TPU injection molded piece, characterized in that: The following steps are involved: S1. Pretreatment: Degreasing and deoiling the TPU injection molded part in an ultrasonic cleaning device; spraying the TPU injection molded part with a silicone modified resin after drying, and forming a bonding layer on the surface of the TPU injection molded part after curing; S2. Optical coating: Place the pre-treated TPU injection molded piece in a vacuum coating device and evacuate the vacuum. Then use ion beam assisted magnetron sputtering or electron beam evaporation to deposit the coating material on the surface of the TPU injection molded piece.

2. The optical coating processing method of the TPU injection molded part according to claim 1, characterized in that: The organosilicon-modified resin is POSS-modified organosilicon resin, polyester-modified organosilicon resin or epoxy-modified organosilicon resin.

3. The optical coating processing method for TPU injection molded parts according to claim 2, characterized in that: In the spraying of the silicone modified resin in the S1 pre-treatment, the spray gun pressure is controlled at 0.3-0.4 MPa, the spraying distance is maintained at 15-20 cm, and the thickness is controlled at 5-8 μm. After the spraying is completed, the injection molded part is placed in an oven at 80-90° C. for curing for 20-30 minutes.

4. The optical coating processing method for TPU injection molded parts according to claim 1, characterized in that: In the S1 pretreatment, a degreasing agent is added and ultrasonic cleaning is performed at a temperature of 40 to 50° C. for 15 to 20 minutes. After cleaning, the surface is repeatedly rinsed with deionized water to remove the residual degreasing agent, and then dried in an oven at 60 to 70° C. for 1 to 2 hours.

5. The optical coating processing method for TPU injection molded parts according to claim 1, characterized in that: The S1 pre-treatment also includes sandblasting: after sandblasting the surface of the TPU injection molded part, the surface is placed in an ultrasonic cleaning device for degreasing and deoiling.

6. The optical coating processing method for TPU injection molded parts according to claim 5, characterized in that: The parameters of the sandblasting treatment are as follows: sandblasting particle size of 80-120 mesh, sandblasting pressure of 0.3-0.5 MPa, sandblasting distance of 10-15 cm, sandblasting angle of 80-90°, and sandblasting time of 30-60 s.

7. The optical coating processing method for TPU injection molded parts according to claim 1, characterized in that: The coating material includes metal oxide and fluoride.

8. The optical coating processing method for TPU injection molded parts according to claim 7, characterized in that: The coating material includes a base material and at least two stacking materials; in the S2 optical coating, a layer of base material with a thickness of 10nm to 15nm is first sputtered / deposited as the base material, and then multiple layers of stacking materials are alternately sputtered / deposited, with the thickness of each layer controlled at 5nm to 10nm.

9. The optical coating processing method for TPU injection molded parts according to claim 8, characterized in that: The bottom layer material includes titanium dioxide (TiO), tantalum pentoxide (TaO) or zirconium oxide (ZrO); the stacked layer material includes silicon dioxide (SiO), magnesium fluoride (MgF) or calcium fluoride (CaF).

10. The optical coating processing method for TPU injection molded parts according to claim 9, characterized in that: The bottom material is surface-modified using a silane coupling agent before coating. A mixture of 95% ethanol and 5% water is used as a solvent, the silane coupling agent is adjusted to a concentration of 2%, and the bottom material is immersed in the silane coupling agent solution for 1 to 2 minutes, then rinsed twice with ethanol, dried, and then dried in a 110°C oven for 5 to 10 minutes.