Sample preparation method and thickness test method for coating on packaging paper surface

Abstract

The present invention relates to the field of testing technology, and discloses a method for preparing a sample of a coating on the surface of packaging paper and a method for testing its thickness. The method for preparing a sample of a coating on the surface of packaging paper comprises: applying curing glue to the side of a rough coating sample cut from the packaging paper that is adhered with paper scraps, the curing glue is used to penetrate the paper scraps, and after hardening, the paper scraps are solidified in the glue layer to obtain a first intermediate sample; the first intermediate sample is embedded in a transparent resin to obtain a second intermediate sample; the second intermediate sample is polished toward the edge of the rough coating sample to grind off the edge of the coating. The method for testing the thickness of the coating on the surface of packaging paper comprises: obtaining a coating sample by adopting the above-mentioned sample preparation method; and testing the thickness of the coating in the coating sample. The solution provided in the present application grinds off the edge of the coating with inaccurate thickness, and after polishing, each layer of the coating in the sample is clearly distributed and has accurate thickness. Testing each film layer of the coating in the sample can obtain more accurate test results.

Description

Technical Field

[0001] The invention relates to the field of testing technology, in particular to a sample preparation method and a thickness testing method for a coating layer on a packaging paper surface. Background Art

[0002] Cardboard is the main raw material for the production of corrugated boxes, cartons and other products. Its performance directly or indirectly affects the intrinsic quality and performance of the product. For packaging products such as corrugated boxes and cartons, it is necessary to have wear resistance, waterproof and moisture resistance. Therefore, the packaging paper needs to be processed after printing during the manufacturing process. Post-printing processing includes glazing coating. The surface of the cardboard is coated with glazing to enhance the water resistance, sunlight resistance, abrasion resistance and pollution resistance of the printed product. Glazing coating includes oily glazing oil used for glazing by printing press, water-based and oily glazing oil used for glazing by glazing machine, solvent-based glazing coating, UV glazing coating, etc.

[0003] Common thick film testing methods: metallographic thickness measurement, X-ray fluorescence thickness measurement (XRF), SEM thickness measurement, XPS depth profiling, step thickness measurement, etc.

[0004] The X-ray spectroscopy method for measuring the thickness of the coating is based on the interaction of an intense and narrow beam of polychromatic X-rays with the substrate and the coating. This interaction produces secondary radiation of discrete wavelengths and energies, which have the characteristics of the elements that constitute the coating and the substrate. The scanning electron microscope (SEM) method for testing thickness has a wide test range and is suitable for testing metal or non-metallic film layers with a thickness of 0.01μm to 1mm. This method is suitable for testing film layers with nanometer thickness. The XPS device can test the elemental composition of the sample surface (the information depth of each test is about 5nm), and can directly sputter the sample surface in the sample chamber to remove the surface material of the specified thickness (nanometer level). The combination of these two functions can test the thickness of the nanometer-level film layer. Some of the above schemes require filters for testing, and the error in the test is relatively large. The thickness of the entire cross section cannot be seen, and it is difficult to simultaneously test the thickness of multiple film layers on the surface of multiple packaging papers. The packaging paper coating is usually a multi-layer structure. Therefore, conventional testing methods are difficult to obtain the accurate thickness of each film layer of the packaging paper coating.

[0005] In addition, no matter what thickness measurement method is used, a sample with accurate thickness is required to obtain accurate test results. The coating peeled off from the surface of the cardboard has paper scraps and the thickness of the peeled edge will have a certain deviation under the action of external force, so it cannot be directly used for thickness testing. Therefore, providing accurate and clear test samples is one of the solutions to solve inaccurate test results.

[0006] In view of this, the present invention is proposed. Summary of the invention

[0007] The purpose of the invention is to provide a method for preparing a sample of a coating on the surface of packaging paper and a method for testing its thickness.

[0008] The present invention is achieved in that:

[0009] In a first aspect, the present invention provides a method for preparing a sample of a surface coating of packaging paper, comprising:

[0010] Applying curing glue to the side of the rough coated sample separated from the packaging paper with paper scraps adhered thereto, wherein the curing glue is used to penetrate the paper scraps and, after hardening, solidify the paper scraps in the glue layer to obtain a first intermediate sample;

[0011] embedding the first intermediate sample in a transparent resin to obtain a second intermediate sample;

[0012] Grind the second intermediate sample towards the edge of the rough coating sample to grind off the edge where the coating thickness is inaccurate.

[0013] In an optional embodiment, the curing glue includes at least one of 502 glue, CC-33A adhesive and 401 glue.

[0014] In an optional embodiment, the transparent resin includes at least one of epoxy resin, crystal glue resin and AB glue resin.

[0015] In an optional embodiment, before applying the curing glue to the side of the rough coating sample with paper scraps adhered thereto, the method further comprises:

[0016] The sample cut from the packaging paper is soaked in water. After the paper layer softens, the paper layer is peeled off, and then the moisture of the remaining sample is removed to obtain a rough coating sample.

[0017] In an optional embodiment, the method of removing moisture is drying, air-drying or hot air drying.

[0018] In an optional embodiment, before soaking the wrapping paper sample cut from the wrapping paper in water, the method further comprises:

[0019] Cut a wrapping paper sample of the target size from the wrapping paper.

[0020] In an optional embodiment, the first intermediate sample is embedded in the transparent resin by placing the first intermediate sample in liquid transparent resin and obtaining the second intermediate sample after the transparent resin is solidified.

[0021] In an optional embodiment, the grinding method is: first use coarse sandpaper for rough grinding, and then change to nano-grade sandpaper for fine grinding when it is about to be ground close to the rough sample of the coating.

[0022] In a second aspect, the present invention provides a method for testing the thickness of a coating on a surface of packaging paper, comprising obtaining a coating sample by adopting a sample preparation method as described in any one of the aforementioned embodiments; and testing the thickness of the coating in the coating sample.

[0023] In an optional embodiment, the thickness of the coating in the test coating sample is:

[0024] The coating samples were sliced ​​and the thickness of the coating was tested using a metallographic microscope.

[0025] The present invention has the following beneficial effects:

[0026] The sample preparation method provided in the present application uses a curing glue to penetrate and cure the paper scraps adhered to the coating, and then embeds the sample in a transparent resin, grinds the edge of the coating, and grinds off the edge with inaccurate thickness. After polishing, the distribution of each layer of the coating in the sample is clear and the thickness is accurate. Testing each film layer of the coating in the sample can obtain more accurate test results.

[0027] The testing method provided in the present application includes the sample preparation method provided in the present application, and therefore, the testing method can obtain the accurate thickness of the coating layer of the tested packaging paper and each film layer in the coating layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 This is a structural diagram of the packaging paper coating provided in the embodiments of the present application;

[0030] Figure 2 is the front view of the second intermediate sample;

[0031] Figure 3 is a top view of the second intermediate sample;

[0032] Figure 4 This is a photo of the sample slice under a metallographic microscope.

[0033] Icon: 10-plating layer; 11-inner film; 12-light-shielding layer; 13-laser substrate; 14-laser embossing layer; 15-laser aluminum plating layer; 16-printing coating; 17-ink layer; 20-transparent resin. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0035] The following is a detailed description of the packaging paper surface coating sample preparation method and thickness testing method provided in this application.

[0036] The present invention provides a method for preparing a sample of a surface coating of packaging paper, comprising:

[0037] Applying curing glue to the side of the rough coated sample cut from the packaging paper with paper scraps, the curing glue is used to penetrate the paper scraps and solidify the paper scraps in the glue layer after hardening to obtain a first intermediate sample;

[0038] embedding the first intermediate sample in a transparent resin to obtain a second intermediate sample;

[0039] Grind the second intermediate sample towards the edge of the rough coating to grind off the edge of the coating.

[0040] If a sample of the target size is cut from the wrapping paper using scissors, the edge of the coating is squeezed during the cutting process, and the thickness at the squeezed part is bound to be smaller than the normal thickness. If the sample of the target size is directly torn off from the wrapping paper, the obtained sample may also cause the thickness of the sample edge to change due to the tearing force during the tearing process. Therefore, no matter which sampling method is used, the coating thickness at the edge of the sample may change. The sample preparation method provided by the present application uses a curing glue to infiltrate and solidify the paper scraps adhered to the coating, and then embeds the sample in a transparent resin, grinds the edge of the coating, and grinds off the edge with inaccurate thickness. After grinding, the distribution of each layer of the coating in the sample is clear and the thickness is accurate. Testing each film layer of the coating in the sample can obtain more accurate test results.

[0041] Since the coating is thin and soft, it will curl up and be difficult to handle after being cut off from the packaging paper. Therefore, curing glue is applied to the side of the coating with paper scraps to solidify the paper scraps in the glue layer. On the one hand, the coating can be hardened and the coating will no longer curl when unfolded, making it easier to embed in the resin. On the other hand, the resin does not have good permeability. In the present application, curing glue is used to penetrate the paper scraps and then embed them in the resin. The cured layer formed by the penetration can have better connectivity with the resin, thus avoiding the problem of poor connectivity caused by direct fixation of the coating and the resin.

[0042] The specific sample preparation method is:

[0043] S1. Take samples from the packaging paper

[0044] Select the location to be tested and cut it with scissors to obtain a wrapping paper sample of the target size.

[0045] Soak the packaging paper sample in water, and after the paper layer scraps soften, separate the paper layer from the coating. Rub off the paper scraps adhering to the coating, and then blow dry the remaining sample to obtain a rough coating sample. There are still some difficult-to-remove paper scraps adhering to the surface of the rough coating sample.

[0046] S2. Coating and curing glue

[0047] A curing glue is applied to the side of the rough coating sample to which the paper scraps are adhered. The applied curing glue is used to penetrate the paper scraps, and after hardening, the paper scraps are solidified in the glue layer to obtain a first intermediate sample.

[0048] Preferably, the curing glue includes at least one of 502 glue, CC-33A adhesive and 401 glue.

[0049] Furthermore, in a preferred embodiment, the curing glue is 502 glue. 502 glue has good permeability and can be quickly cured after contact with air. 502 glue is widely used and easy to obtain.

[0050] S3, embedded in resin

[0051] Lay the first intermediate sample as flat as possible and immerse it in the liquid transparent resin, and wait until the transparent resin is completely solidified to obtain the second intermediate sample.

[0052] Preferably, the transparent resin includes at least one of epoxy resin, crystal glue resin and AB glue resin.

[0053] Furthermore, in a preferred embodiment, the transparent resin is epoxy resin.

[0054] S4. Polishing

[0055] The second intermediate sample is ground towards the edge of the rough sample of the coating to grind off the edge of the coating. For coatings with pigment layers, generally after grinding until the pigment layer is clearly visible, it can be basically determined that the position where the thickness of the coating edge is inaccurate has been ground off.

[0056] Preferably, the grinding method is: first use coarse sandpaper for rough grinding, and then change to nano-grade sandpaper for fine grinding when it is about to be ground close to the rough sample of the coating.

[0057] Using coarse sandpaper for rough grinding can make the grinding process more efficient. When grinding to a level close to the rough sample of the coating, switching to nano-scale fine sandpaper for grinding can avoid affecting the thickness of each film layer. Even if an error is caused, it is at the nanometer level, which has almost no effect on the test results.

[0058] The method for testing the thickness of the coating on the surface of packaging paper provided in the embodiment of the present application comprises obtaining a coating sample by adopting the sample preparation method provided in the embodiment of the present application; and testing the thickness of the coating in the coating sample.

[0059] The thickness testing method provided in the embodiment of the present application performs a thickness test on the coating sample provided in the embodiment of the present application, and therefore, the accurate thickness of each film layer of the coating of the tested packaging paper can be obtained.

[0060] The specific test method is:

[0061] The coating samples were sliced ​​and the thickness of the coating was tested using a metallographic microscope.

[0062] When the sample is sliced ​​and placed under a metallographic microscope, the structure of each layer can be clearly seen and the thickness of each layer can be accurately measured.

[0063] A specific embodiment is provided below to specifically illustrate the solution provided in this application.

[0064] Take a piece of W-shaped packaging cardboard, such as Figure 1 As shown, the coating 10 of the packaging paperboard includes: an inner film 11, a light shielding layer 12, a laser substrate 13, a laser embossing layer 14, a laser aluminum plating layer 15, a printing coating layer 16 and an ink layer 17 arranged in sequence.

[0065] Use scissors to cut a cardboard sample of a target size from the wrapping paper, then soak the cardboard sample in tap water, tear off the paper layer after it softens, rub off most of the paper scraps with hands, and then use a hair dryer to dry the remaining sample to obtain a rough coating sample.

[0066] 502 glue is applied on the side of the rough coated sample with paper scraps, and the first intermediate sample is obtained after the glue is cured.

[0067] The first intermediate sample is placed in liquid epoxy resin, so that the epoxy resin completely wraps the first intermediate sample, and after hardening, a second intermediate sample is obtained, such as Figure 2 and Figure 3 shown.

[0068] The second intermediate sample is polished toward the edge of the coating 10 until a clear pigment layer is just visible, and the polishing is stopped. The portion of the edge of the coating 10 with inaccurate thickness is polished off to obtain a sample of the coating 10.

[0069] The sample of the coating 10 is sliced, and the thickness of the coating 10 is tested using a metallographic microscope. Figure 4 As shown, Figure 4 This is a cross-section image of the coating 10 sample under a metallographic microscope, from which the coating 10 can be clearly seen.

[0070] In summary, the sample preparation method provided in the present application uses a curing glue to penetrate and cure the paper scraps adhered to the coating, and then embeds the sample in a transparent resin, grinds the edge of the coating, and grinds off the edge with inaccurate thickness. After polishing, the distribution of each layer of the coating in the sample is clear and the thickness is accurate. Testing each film layer of the coating in the sample can obtain more accurate test results.

[0071] The testing method provided in the present application is to perform thickness testing on the coating sample provided in the embodiment of the present application. Therefore, the testing method can obtain the accurate thickness of each film layer of the coating of the tested packaging paper.

[0072] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a sample of a surface coating of packaging paper, characterized in that: include: Applying curing glue to the side of the rough coated sample separated from the packaging paper with paper scraps adhered thereto, wherein the curing glue is used to penetrate the paper scraps and solidify the paper scraps in the glue layer after hardening to obtain a first intermediate sample; embedding the first intermediate sample in a transparent resin to obtain a second intermediate sample; The second intermediate sample is ground toward the edge of the coating rough sample to grind off the edge where the coating thickness is inaccurate.

2. The method for preparing a sample of a packaging paper surface coating according to claim 1, characterized in that: The curing glue includes at least one of 502 glue, CC-33A adhesive and 401 glue.

3. The method for preparing a sample of a packaging paper surface coating according to claim 1, characterized in that: The transparent resin includes at least one of epoxy resin, crystal glue resin and AB glue resin.

4. The method for preparing a sample of a packaging paper surface coating according to claim 1, characterized in that: Before applying curing glue to the side of the rough coating sample with paper scraps adhered thereto, the method further comprises: The sample cut from the packaging paper is soaked in water, and after the paper layer is softened, the paper layer is peeled off, and then the moisture of the remaining sample is removed to obtain the rough sample of the coating.

5. The method for preparing a sample of a packaging paper surface coating according to claim 4, characterized in that: Ways to remove moisture are by drying, hanging or blowing with hot air.

6. The method for preparing a sample of a packaging paper surface coating according to claim 4, characterized in that: The wrapping paper sample cut from the wrapping paper is immersed in water before: A wrapper sample of target size is cut from the wrapper.

7. The method for preparing a sample of a packaging paper surface coating according to claim 1, characterized in that: The method of embedding the first intermediate sample in the transparent resin is: placing the first intermediate sample in the liquid transparent resin, and obtaining the second intermediate sample after the transparent resin is solidified.

8. The method for preparing a sample of a packaging paper surface coating according to claim 1, characterized in that: The grinding method is: first use coarse sandpaper for rough grinding, and then change to nano-grade sandpaper for fine grinding when it is about to be ground close to the rough sample of the coating.

9. A method for testing the thickness of a coating on a packaging paper surface, characterized in that: The method comprises obtaining a coating sample by adopting the sample preparation method as described in any one of claims 1 to 8; and testing the thickness of the coating in the coating sample.

10. The thickness testing method according to claim 9, characterized in that: The thickness of the coating in the coating sample tested is: The coating sample is sliced, and the thickness of the coating is tested using a metallographic microscope.

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