A method and device for removing pearl pigments using laser

Abstract

The present invention discloses a method and a device for removing pearl pigments by laser. The pearl grains are soaked in a pearl brightening liquid for 20 to 30 hours. After soaking, the pearl grains and cooling water are put into a diversion trough for instant laser irradiation for decolorization. The laser light source is a He-Cd laser with a wavelength of 3500 to 6500 angstroms, a power of 1 to 30 W, and a pulse of 1 to 6 ps. The pearl grains after laser irradiation are boiled to achieve a complete decolorization effect. By using the device of the present invention, after the laser passes through a diffraction grating, several diffraction strip-shaped light spots spanning across the diversion trough can be formed in the diversion trough to ensure that each passing pearl grain can obtain uniform instant irradiation. The unabsorbed laser can be reflected by the reflecting film of the device of the present invention onto the pearl grains, enabling the pearl grains to uniformly receive instant laser irradiation.

Description

Technical Field

[0001] The invention belongs to the field of pearl processing, and relates to a pearl decolorization technology and a device thereof, and specifically to a method and a device thereof for decolorizing pearl pigments by using laser. Background Art

[0002] Not all pearls produced by pearl oysters are crystal clear and dazzling. Most of them need to be free of impurities and colors to meet the requirements of jewelry pearls. Most pearls have more or less colors, especially freshwater pearls, which are colorful. Most people like white and translucent pearls. Therefore, pearl processing removes the color and impurities of pearls as much as possible. The impurities contained in pearls are easy to remove, but the process of removing the pigment color of pearls is more complicated.

[0003] The removal process of the existing technology is basically: ammonia solution and methanol solution are repeatedly treated alternately, also called brightening, to remove lipid substances and water-soluble substances between the pearl layers and increase the permeability of water and solvents between the pearl layers; after brightening, the pearls are boiled for a long time to destroy the pearl pigments and destroy them into unstable light-colored or colorless substances; then bleaching, using hydrogen peroxide to oxidize the damaged pearl pigments so that they cannot be restored to colored substances, and at the same time oxidize the remaining organic impurities. If some pigments in the boiling stage, such as orange-red pigments, are relatively stable and decompose slowly and cannot be removed completely, or purple dark pearls cannot be completely decomposed within a certain period of time due to the high pigment concentration, then the pigments cannot be bleached and oxidized during bleaching. If the pearls are boiled long enough, the pigment may be removed completely. However, the long boiling time will seriously affect the pearl luster and dissolve the pearl protein, causing damage to the nacre structure. Long-term oxidation with high-concentration hydrogen peroxide may also remove the pearl pigment completely, but it will oxidize and destroy the protein between the nacre layers, causing the nacre to fall off easily and seriously damaging the quality of the pearls.

[0004] Pearl pigments are mainly porphyrins, with a melting point of over 300°C, and some are insoluble in water. If the pearls are heated directly to 300°C, the organic components in the pearls will carbonize and turn black, and the pearl structure will be damaged. Therefore, pearl grain processing and bleaching are difficult and time-consuming. Conventional processing methods cannot completely remove high-concentration pigments, resulting in large pigment residues, which affects the value of the product. Summary of the invention

[0005] The object of the present invention is to provide a method for removing pearl pigments by using laser. Since pearl pigments have photosensitivity, within a certain wavelength range, they are more likely to absorb light than nacre. Utilizing this characteristic of pearl pigments, high-energy laser is used for instantaneous irradiation. The pearl pigments absorb the laser, and the temperature instantaneously rises above the melting point of the pigment crystals and melts, dissolves in the solution in the pearl layer, and is emulsified by the emulsifier in the solution, achieving the decolorization effect. While the non-pigment part of the pearl absorbs less laser and the temperature rises slowly, and it will not damage the nacre when irradiated within a limited time.

[0006] In order to achieve the above object, the technical solution of the present invention is: to provide a method for removing pearl pigments by using laser, comprising the following steps:

[0007] Step S1: Immerse the pearl grains in the pearl brightening liquid for 20 - 30h, take them out and set aside;

[0008] Step S2: Put the pearl grains after immersion in Step S1 and the cooling water into the feeding hopper together;

[0009] Step S3: The discharge port of the feeding hopper is connected to a diversion trough with a certain inclination angle; a laser light source is arranged in the vertical direction of the diversion trough, and the laser light source irradiates into the inside of the diversion trough through a diffraction grating, forming multiple strip-shaped light spots across the diversion trough; each time a pearl grain passes through 1 light spot, it will be instantaneously irradiated by the laser; the reflecting film arranged on the device can reflect the light spots, and the unabsorbed laser is repeatedly projected into the inside of the diversion trough to form more strip-shaped light spots, so as to make full use of the light source.

[0010] Step S4: Control the flow rate of the cooling water and the sliding amount of the pearl grains, and the pearl grains and the cooling water roll into the diversion trough at a certain flow rate and roll from top to bottom along the inner bottom plate of the diversion trough to the outlet; the wavelength of the laser light source is a He - Cd laser of 3500 - 6500 Å, the power is 1 - 30W, and the pulse width is 1 - 6ps;

[0011] Step S5: Put the pearl grains after laser irradiation into clean water, immerse them, continuously heat and keep them at a constant temperature of 90 °C for 24h for decolorization.

[0012] Preferably, in Step S1, the pearl brightening liquid is prepared from water, sodium dodecyl sulfate, glycerol, and sodium tripolyphosphate.

[0013] Preferably, based on 100 parts by weight of water, the pearl brightening liquid contains 0.01 - 10 parts by weight of sodium dodecyl sulfate, 0.1 - 1 part by weight of glycerol, and 0.1 - 0.5 part by weight of sodium tripolyphosphate.

[0014] Preferably, the inclination angle of the diversion trough is 40 - 50 degrees, and the length is 50 - 80 cm, so as to ensure that the pearl grains pass through the diversion trough at a certain speed.

[0015] Preferably, in step S4, the cooling water flow rate is controlled to be 0.02 L / s.

[0016] Preferably, in step S4, the falling amount of pearl grains is controlled to be 0.2 L / s.

[0017] Another object of the present invention is to provide a device for removing pearl pigments by laser ablation, comprising a feed hopper, a diversion trough connected to the bottom of the feed hopper, a rhombic cylinder cover arranged in the vertical direction of the diversion trough, and a laser light source arranged above the rhombic cylinder cover; the diversion trough has an inclination angle of 40-50 degrees; the rhombic cylinder cover covers the entire diversion trough, the bottom of the rhombic cylinder cover is communicated with the diversion trough, and a diffraction grating is arranged between the rhombic cylinder cover and the laser light source.

[0018] Preferably, a cooling water inlet pipe is arranged above the feed hopper, and a water pipe switch is arranged on the cooling water inlet pipe. When the pearl grains are instantaneously melted at high temperature by laser to decolorize the pearl pigments, the cooling water can cool the pearl grains.

[0019] Preferably, a reflective film is arranged on the inner bottom plate of the diversion trough and the inner wall of the rhombic cylinder cover. The reflective film can ensure that in addition to directly irradiating the pearl surface, the laser strip-shaped light spot will be reflected multiple times by the reflective film and then irradiate the pearl surface again, so as to make full use of the light source, improve the irradiation effect, and reduce the leakage of the light source.

[0020] Preferably, a bearing is arranged at the upper end of the bottom of the diversion trough, and an adjusting screw is arranged at the lower end of the bottom. The height of the bottom of the diversion trough can be adjusted by rotating the screw, thereby adjusting the inclination angle of the diversion trough and controlling the falling speed of the pearl grains.

[0021] Preferably, while the pearl pigments are melted by laser irradiation, the pigments are emulsified by a solution containing a surfactant in the pearl layer to prevent the pigments from recrystallizing.

[0022] The working principle of the present invention:

[0023] Pearl pigments are mainly biological porphyrin pigments, which mainly exist as crystalline solids in pearls. They have a melting point as high as 300 - 400 °C. Some are insoluble in water and dissolve slowly in organic solvents. They have high stability. Usually, boiling water heating does not exceed 100 °C, and it is very difficult to melt them. Bleaching methods such as boiling in water and oxidation with hydrogen peroxide cannot completely remove them, or the removal is slow. Some pigments are tightly wrapped by the pearl layer, and it is difficult for solvents to reach them. However, pearl pigments are sensitive to high-energy light of a certain wavelength, easily absorb high-energy light, generate heat and can produce linear oxygen, resulting in their own disintegration. When a high-energy laser irradiates a pearl grain instantaneously, the pearl pigment quickly absorbs the laser energy, the temperature rises above the pigment melting point and melts, and is emulsified by the surfactant in the surface-active agent solution infiltrating into the pearl layer, thus dissolving in water and is also easily soluble in organic solvents. Even when the temperature drops, it will not recrystallize. The pigment fully mixed with solvents such as water is easily destroyed when boiling the pearls and is also easily diffused in water and carried away from the pearls.

[0024] The method and device for removing pearl pigments by laser according to the present invention have the following beneficial effects:

[0025] 1. The present invention is different from technologies such as laser freckle removal. Laser freckle removal is a technology that uses laser of a certain wavelength to be easily absorbed by skin biological pigments, heats the pigment cells to destroy them, and normal cells are not affected. The purpose is not to melt the pigment. Even if the pigment melts, it will recrystallize when the temperature drops. It is also different from a laser cleaning machine. The laser cleaning machine uses laser of a certain intensity to burn contaminants such as dust to achieve a cleaning effect. The present invention uses laser of a certain intensity and wavelength to irradiate the surface of the pearl. The laser penetrates through the pearl layer. Pearl pigments are high-melting-point photosensitive biological pigments, which easily absorb light of a certain wavelength (mainly blue light and wavelengths below it), generate heat and release active oxygen, which can cause the pigment crystals to melt by themselves or the pigment molecules to be destroyed; the melted pigment is immediately emulsified by the surfactant infiltrating into the pearl layer and dissolves in water, and will not recrystallize, and is easily carried out of the pearl or destroyed by boiling in water. By using a blue light wavelength and a pulse width range of 1 - 6 ps, the nacre absorbs much less laser energy than the pearl pigment. While instantaneously melting the pearl pigment, the temperature of the nacre does not increase significantly, avoiding damage to the nacre.

[0026] 2. By using the technology of the present invention, while dissolving pearl pigments, it can also destroy pearl pigments, achieving a certain degree of bleaching effect. If the present invention is combined with conventional bleaching methods, it is also easy to bleach dark pearls, shorten the pearl bleaching time, and improve the commercial value of pearls.

[0027] 3. By using the device of the present invention, after the laser passes through the diffraction grating, several diffraction strip-shaped light spots spanning the flow guide groove can be formed in the flow guide groove to ensure that each passing pearl grain can obtain uniform instantaneous irradiation; the unabsorbed laser can be reflected by the reflective film of the device of the present invention onto the pearl grain, enabling the pearl grain to uniformly receive instantaneous laser irradiation.

[0028] 4. In the unified pearls, about 20 - 30% of the freshwater pearl grains cannot be bleached by conventional bleaching methods due to their too dark color, and have to be sold as natural color pearls, while the natural color pearls are not the preferred pearl color of customers. The present invention can completely decolorize this part of the natural color pearls to become qualified commercial pearls. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic structural diagram of the device for removing pearl pigments by laser according to the present invention;

[0030] In the figure: 1. Water pipe switch; 2. Cooling water inlet pipe; 3. Feeding funnel; 4. Discharge port; 5. Feeding hopper switch; 6. Bearing; 7. Flow guide groove; 8. Adjusting screw; 9. Pearl recovery port; 10. Reflective film; 11. Schematic light beam; 12. Prismatic cylinder cover; 13. Diffraction grating; 14. Laser light source. DETAILED DESCRIPTION OF THE INVENTION

[0031] The features and advantages of the present invention can be further understood through the following detailed description in conjunction with the drawings. The provided embodiments are only illustrative of the present invention and do not limit the remaining content disclosed by the present invention in any way. The experimental methods in the following embodiments are all conventional methods unless otherwise specified. The materials, reagents, etc. used in the following embodiments can all be obtained from commercial channels unless otherwise specified.

[0032] As Figure 1 shown, the device for removing pearl pigments by laser according to the present invention includes a feeding funnel 3, a flow guide groove 7 connected to the bottom of the feeding funnel 3, a prismatic cylinder cover 12 arranged in the vertical direction of the flow guide groove 7, and a laser light source 14 arranged above the prismatic cylinder cover 12.

[0033] A cooling water inlet pipe 2 is arranged above the feeding funnel 3, and a water pipe switch 1 is arranged on the cooling water inlet pipe 2; a discharge port 4 is arranged at the bottom of the feeding funnel 3, the discharge port 4 is connected to the flow guide groove 7, a feeding hopper switch 5 is arranged at the discharge port 4, the height of the discharge port 4 is greater than the diameter of a single pearl grain and less than the diameter of two pearl grains, ensuring that the pearl grains do not accumulate and roll into the flow guide groove 7, and at the same time, by adjusting the size of the discharge port 4, the flow rate of the material can be adjusted. The water from the cooling water inlet pipe 2 can flow along with the pearl grains in the flow guide groove 7.

[0034] The diversion chute 7 is inclined at an angle of 40 to 50 degrees. A pearl rolling inlet is provided above the diversion chute 7, and the pearl rolling inlet is connected to the discharge port of the feed hopper. A pearl recovery port 9 is provided below the diversion chute 7. The inner bottom of the diversion chute 7 is a flat slide plate. The upper part of the diversion chute 7 is open and communicates with the rhombic cylinder cover 12. A reflective film 10 is provided on the inner bottom plate of the diversion chute 7. A bearing 6 is provided at the upper end of the bottom of the diversion chute 7, and an adjusting screw 8 is provided at the lower end of the bottom. The inclination angle of the diversion chute 7 can be adjusted through the bearing 6 and the adjusting screw 8, so as to adjust the sliding speed of the pearls.

[0035] The rhombic cylinder cover 12 covers the entire diversion chute 7. The bottom of the rhombic cylinder cover 12 communicates with the diversion chute 7. A diffraction grating 13 is provided between the rhombic cylinder cover 12 and the laser light source 14; the diffraction grating 13 adopts a diffraction linear grating. The laser passes through the diffraction grating 13, and the distance between the grating and the light source is adjusted to form several laser diffraction light spots across the diversion chute 7 in the diversion chute 7. The width of the light spots is less than 1 mm, and the length can be obtained by adjusting the distance between the grating and the light source. The length of the light spots is consistent with the inner width of the diversion chute. In the case of a laser emission power of 5 to 30 w, the number of light spots can be set to 5 to 30, without affecting the effect. A reflective film is provided on the inner wall of the rhombic cylinder cover 12. The bottom of the rhombic cylinder cover 12 is a rectangle, the width of which is consistent with the outer width of the diversion chute 7, and the length is consistent with the length of the diversion chute 7, so as to cover the entire diversion chute 7 and reduce the leakage of the laser. There is an opening in the middle of the conical cylinder tip of the rhombic cylinder cover 12 facing the laser light source side, and the size of the opening is about 1.5 times the size of the laser light spot at this position. The laser passing through the diffraction grating 13 enters from the opening. In addition to irradiating the surface of the pearls, it will also be reflected by the reflective film multiple times and then irradiate the surface of the pearls, so as to make full use of the light source and improve the irradiation effect.

[0036] The laser light source 14 comes from the laser head of the laser. The laser spot of the laser is relatively small. After being diffracted by the grating into a strip-shaped light spot, it is ensured that each pearl passing through the light spot can be irradiated by the laser. A reflective film 10 is pasted on the inner bottom of the diversion chute 7 in the laser irradiation area, which can reflect the laser. The laser emitted by the laser has the best wavelength close to the absorption peak of the pearl pigment. The laser used irradiates with a certain power, and at the same time maintains a certain sliding speed of the pearl grains, which not only achieves the effect of melting the pigment, but also avoids the pearl absorbing too much light energy and damaging the pearl. Let the cooling water be mixed with the pearl grains, which can play a cooling role during laser irradiation and reduce the damage of the high-energy laser to the pearls. The pearl grains roll during the sliding process, which can make the laser irradiation uniform.

[0037] Example 1

[0038] A batch of dark purple pearl grains, 35.00 kg, with a particle size of 7 - 8 mm, being round or nearly round. Among them, 10 pearl grains are marked with numbers from 1 to 10. Next to the marks, the blue spectral value is measured using a color difference meter (with an 8 - mm aperture). Prepare a pearl brightening liquid: Add water to 100 weight parts, 0.3 weight parts of sodium dodecyl sulfate, 0.5 weight parts of glycerol, 0.3 weight parts of sodium tripolyphosphate. For 35 kg of pearl grains, add 50 L of the prepared pearl brightening liquid and soak for 24 h, then take out and set aside. The laser source is a He - Cd laser (blue light) with a wavelength of 4416 Å, a power of 10 W, and a pulse width of 6 ps. For the diffraction grating, by adjusting the distance between the grating focus and the light source, 10 diffraction light spots can be formed in the diversion trough. The width of the light spots is 1.2 mm, the length is 5 cm, and the distance between the light spots is 1 cm. The inner width of the diversion trough is 5 cm. Adjust the adjusting screw to control the inclination of the diversion trough at 45°; set the cooling water flow rate to 0.2 L / s; adjust the feed hopper switch to set the control of the pearl grain sliding rate at about 0.2 L / s.

[0039] Pour the soaked pearl grains into the feed hopper 3, turn on the water pipe switch 1, start the power supply, irradiate with laser, and at the same time turn on the feed switch 5. The pearl grains and cooling water fall along the bottom plate of the diversion trough 7 and are evenly irradiated by the laser. The material flows out from the bottom pearl recovery port 9, and one - time laser irradiation is completed.

[0040] After the 35 kg of pearl grains are laser - treated, effect detection is carried out.

[0041] Detect with a colorimeter. Taking the detection value of each label before treatment as the standard value A, after treatment, divide the detection value B by the standard value A, then subtract 1, and then convert it into a percentage sign %, which is the fading rate: Fading rate T=(1 - B / A)×100%. The detection results are as follows.

[0042] Table 1 Fading rate after He - Cd laser treatment (%)

[0043]

[0044] As shown in Table 1, the average fading rate is 98.2%. For the pearl grains not detected with a color difference meter, obvious fading can be seen with the naked eye, and almost no remaining color can be seen.

[0045] To further fade, assist with the water - boiling method for fading. Put the above - mentioned pearl grains into clean water, immerse them, continuously heat and keep at a constant temperature of 90 °C for 24 h. Continue to take the labeled pearl grains and detect them with a color difference meter. The standard value is still the value before treatment, and the calculation method is the same as above. The results are as follows:

[0046] Table 2 Fading rate after water - boiling (%)

[0047]

[0048] As shown in Table 2, the average fading rate is 100%. For the pearl grains not detected by the color difference meter, obvious fading can be seen with the naked eye, no residual color, good light transmittance and glossiness, and it is considered that they have completely faded, with great commercial value.

[0049] Control Group 1

[0050] For comparison, without using laser, the conventional light enhancement method is adopted. A batch of 35.00 kg of dark purple pearl grains, with a particle size of 7 - 8 mm, being round or nearly round. Among them, 10 grains are marked with numbers from 1 - 10. Next to the marks, the blue spectral value is measured with a color difference meter (aperture 8 mm). Soak them in an aqueous solution of 5% ammonia water and magnesium hydroxide, place them in an air-conditioned room at 20 °C for 48 h, then wash them, and then soak them in methanol at 40 °C for 48 h. Next, soak them in 0.1 dilute ammonia water at 40 °C for 48 h. Methanol and dilute ammonia water are used alternately, three times for methanol and two times for dilute ammonia water. After being treated by the above method, detect them with a color difference meter according to the method of Example 1, and the results are shown in Table 3. Then wash them clean, pour them into an electric heating cooking pot, add clear water to submerge them, and heat at 90 °C for 100 h. After the treatment is completed, detect them with a color difference meter according to the method of Example 1, and the results are shown in Table 4.

[0051] Table 3 Fading Rate after Conventional Treatment (%)

[0052]

[0053] As shown in Table 3, there is a slight sign of color deepening after conventional treatment.

[0054] Table 4 Fading Rate after Pearl Boiling Treatment (%)

[0055]

[0056] As shown in Table 4, obvious fading can be achieved after pearl boiling treatment, but there is still pigment residue visible to the naked eye. The average fading rate is 84.4%. Compared with the 100% fading rate of Example 1, there is still a deficiency. The fading rate is less than 99%, and there is still obvious color visible to the naked eye remaining, so the commercial value of Control Group 1 is not great.

[0057] Control Group 2

[0058] For comparison, other conditions are the same as those in Example 1, and the laser is changed to a Kr laser with a wavelength of 3480 Å, and other conditions are the same as those in Example 1.

[0059] Table 5 Fading Rate after Kr Laser Treatment (%)

[0060]

[0061] As shown in Table 5, after the laser treatment of Control Group 2, the decolorization was obvious, and the average decolorization rate reached 80.9%. Compared with Example 1, there were obvious deficiencies. Overall observation showed that the surface of the pearls turned dark and charred, and 3.5% of the pearl grains were found to be cracked after statistics.

[0062] Table 6 Fading Rate after Boiling Pearl Treatment (%)

[0063]

[0064] As shown in Table 6, the average fading rate after boiling pearl treatment was 81.1%. Compared with Table 4, the decolorization was not obvious, and compared with Example 1, the decolorization rate was significantly lower. It indicates that irradiating pearl grains with a laser of a shorter wavelength results in a worse decolorization effect, and at the same time, the surface of the pearls is charred, forming a new color.

[0065] Control Group 3

[0066] For comparison, with other conditions the same as those in Example 1, the laser was changed to a carbon dioxide laser with a wavelength of 10600 Å, and other conditions were the same as those in Example 1.

[0067] Table 7 Fading Rate after Carbon Dioxide Laser Treatment (%)

[0068]

[0069] As shown in Table 7, after the carbon dioxide laser treatment, there was almost no decolorization, and the average decolorization rate reached 1.1%. Compared with Example 1, there were obvious deficiencies. Overall observation showed that there was no change on the surface of the pearls.

[0070] Table 8 Fading Rate after Boiling Pearl Treatment (%)

[0071]

[0072] As shown in Table 8, the average fading rate after boiling pearl treatment was 81.8%. Compared with Example 1, the decolorization rate was significantly lower. It indicates that irradiating pearl grains with an infrared wavelength laser has almost no decolorization effect.

[0073] Control Group 4

[0074] For comparison, instead of using the brightening liquid of the present invention, clean water was used as a substitute, and other conditions were the same as those in Example 1.

[0075] Table 9 Fading Rate after He-Cd Laser Treatment (%)

[0076]

[0077] As shown in Table 9, the average fading rate is 89.81%. For the pearl grains not detected by the color difference meter, obvious fading can be seen with the naked eye, and the fading rate is about 90%. Compared with Example 1, without using the brightening liquid of the present invention and with the same laser treatment, the fading rate is significantly lower.

[0078] To further fade, an auxiliary boiling method is used for fading. Put the above pearl grains into clean water, immerse them, continuously heat and keep them at a constant temperature of 90 °C for 24 h. Then continue to take the labeled pearl grains and detect them with a color difference meter. The standard value is still the value before treatment, and the calculation method is the same as above. The results are shown in Table 10.

[0079] Table 10 Fading rate after boiling (%)

[0080]

[0081] As shown in Table 10, the average fading rate is 93.3%. Compared with Example 1, there is still a certain gap. For the pearl grains not detected by the color difference meter, obvious fading can be seen with the naked eye, there is obvious remaining color, the light transmittance and glossiness are good, and it is considered that the fading is incomplete and it does not yet have commercial value.

[0082] Control group 5

[0083] For comparison, the brightening liquid of the present invention is changed to: sodium dodecyl sulfate is changed to polyethylene glycol (200), and the weight is 0.3, and other conditions are the same as in Example 1.

[0084] Table 11 Fading rate after He-Cd laser treatment (%)

[0085]

[0086] As shown in Table 11, the average fading rate is 92.4%. For the pearl grains not detected by the color difference meter, obvious fading can be seen with the naked eye, and the fading rate is about 90%. Compared with Example 1, when the key emulsifier sodium dodecyl sulfate is replaced with polyethylene glycol (200), a better fading effect can also be achieved, but there is still a certain gap, and the effect is not as good as that of Example 1.

[0087] To further fade, an auxiliary boiling method is used for fading. Put the above pearl grains into clean water, immerse them, continuously heat and keep them at a constant temperature of 90 °C for 24 h. Then continue to take the labeled pearl grains and detect them with a color difference meter. The standard value is still the value before treatment, and the calculation method is the same as above. The results are as follows:

[0088] Table 12 Fading rate after boiling (%)

[0089]

[0090] As shown in Table 12, the average fading rate is 97.1%, which shows significant progress compared to Control Group 4 without the brightening liquid of the present invention. However, there is still a certain gap compared to Example 1. For the pearl grains not detected by the color difference meter, obvious fading can be seen with the naked eye, with obvious remaining color, good light transmittance and glossiness. It is considered that the fading is incomplete and it does not yet have commercial value.

[0091] Control Group 6

[0092] For comparison, the device involved in the present invention was modified by removing the reflective film, and other conditions were the same as those in Example 1.

[0093] Table 13 Fading Rate after He-Cd Laser Treatment (%)

[0094]

[0095] As shown in Table 13, the average fading rate is 84.1%. For the pearl grains not detected by the color difference meter, obvious fading can be seen with the naked eye, and the fading rate is about 80%. Compared with Example 1, the decolorization rate is significantly reduced.

[0096] Control Group 7

[0097] For comparison, the laser pulse width was changed to 8 ps, and other conditions were the same as those in Example 1. The results are as follows: all the pearl grains were charred and damaged.

[0098] The above-disclosed are only the preferred embodiments of the present invention. Of course, the scope of the rights of the present invention cannot be limited thereby. Therefore, equivalent changes made according to the claims of the present invention still fall within the scope covered by the present invention.

Claims

1. A method for removing pearl pigments using laser, characterized in that it includes the following steps: Step S1: Immerse the pearl grains in the pearl brightening liquid for 20 - 30h, take them out and set aside; the pearl brightening liquid is prepared from water, sodium dodecyl sulfate, glycerol, and sodium tripolyphosphate; based on 100 parts by weight of water, the pearl brightening liquid contains 0.01 - 10 parts by weight of sodium dodecyl sulfate, 0.1 - 1 part by weight of glycerol, and 0.1 - 0.5 part by weight of sodium tripolyphosphate; Step S2: Put the pearl grains soaked in Step S1 and cooling water into the feeding hopper together; Step S3: The discharge port of the feeding hopper is connected to a diversion trough with a certain inclination angle; a laser light source is arranged in the vertical direction of the diversion trough, and the laser light source irradiates into the interior of the diversion trough through a diffraction grating, forming multiple strip-shaped light spots across the diversion trough; Step S4: Control the flow rate of the cooling water and the sliding amount of the pearl grains. The pearl grains and the cooling water roll into the diversion trough at a certain flow rate and roll from top to bottom along the inner bottom plate of the diversion trough to the outlet; the wavelength of the laser light source is He - Cd laser with 3500 - 6500 Å, the power is 1 - 30W, and the pulse width is 1 - 6ps; Step S5: Put the pearl grains irradiated by the laser into clean water, immerse them, continuously heat and keep them at a constant temperature of 90 °C for 24h for decolorization.

2. The method for removing pearl pigments using laser according to claim 1, characterized in that: the inclination angle of the diversion trough is 45 - 50 degrees.

3. The method for removing pearl pigments using laser according to claim 1, characterized in that: in Step S4, control the flow rate of the cooling water to be 0.02L / s.

4. The method for removing pearl pigments using laser according to claim 1, characterized in that: in Step S4, control the sliding amount of the pearl grains to be 0.2L / s.

5. A device for removing pearl pigments using laser, characterized in that: it includes a feeding hopper, a diversion trough connected to the bottom of the feeding hopper, a rhombic cylinder cover arranged in the vertical direction of the diversion trough, and a laser light source arranged above the rhombic cylinder cover; the diversion trough has an inclination angle of 40 - 50 degrees; the rhombic cylinder cover covers the entire diversion trough, the bottom of the rhombic cylinder cover is communicated with the diversion trough, and a diffraction grating is arranged between the rhombic cylinder cover and the laser light source.

6. The device for removing pearl pigments using laser according to claim 5, characterized in that: a cooling water inlet pipe is arranged above the feeding hopper, and a water pipe switch is arranged on the cooling water inlet pipe.

7. The device for removing pearl pigments using laser according to claim 5, characterized in that: reflective films are arranged on the inner bottom plate of the diversion trough and the inner wall of the rhombic cylinder cover.

8. The device for removing pearl pigments using laser according to claim 5, characterized in that: a bearing is arranged at the upper end of the bottom of the diversion trough, and an adjusting screw is arranged at the lower end of the bottom.

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