Carton package sealing effect verification method

Abstract

The invention discloses a carton package sealing effect verification method, and belongs to the field of package detection. The method comprises the four steps of sample preparation, outer layer stripping, chemical layering treatment and sealing detection and judgment. Firstly, a package is sheared open, cleaned and then trimmed to be I-shaped, and an outer layer is stripped; then, sequentially soaking and rubbing by using a nitric acid solution and a sodium hydroxide solution to realize thorough stripping of the paper layer, the bonding layer and the aluminum foil layer, and only retaining the inner-layer polyethylene film; then, accurately injecting the longitudinal seal by using specifically prepared red dye liquor, checking by combining with an ultraviolet lamp, injecting the transverse seal, and observing by using a magnifying lens with 40 times of scales; and finally, carrying out qualification judgment according to quantitative standards of no leakage and no fluorescence in longitudinal sealing, bubble length in transverse sealing and effective sealing width. The problems that in the prior art, due to the fact that interlayer stripping is not thorough and operation parameters are not uniform, detection errors are large, the small defect missed judgment rate is high, and result repeatability is poor are solved, and accurate, reliable and standardized detection of the sealing quality of the multi-layer composite package is achieved.

Description

Technical Field

[0001] This invention relates to a method for verifying the sealing effect of paper box packaging, belonging to the field of packaging testing. Background Technology

[0002] In the modern food and beverage industry, multi-layer composite paperboard packaging (such as the common 6-layer aseptic packaging) is widely used for filling and preserving liquid products such as milk and juice. The sealing integrity of this type of packaging, especially the quality of the longitudinal and transverse seals, directly affects the aseptic state, shelf life, and food safety of the contents. Therefore, accurate verification of the sealing effect is a core aspect of quality control. Currently, the industry generally relies on traditional "peeling tests" and visual inspection methods. During this process, the sealed edges of the packaging are usually peeled off manually, and then the presence of defects such as bubbles and gaps is observed with the naked eye or a low-magnification magnifying glass.

[0003] However, these conventional methods have several significant limitations in practical applications. First, due to the different bonding characteristics between the packaging materials—for example, the aluminum foil layer is firmly bonded to the adhesive layer, while the adhesive layer and the polyethylene layer are relatively easy to separate—general peeling processes cannot achieve thorough and clean separation between layers. Residual aluminum foil or adhesive can interfere with the observation of the true sealing interface and even cause false defects, leading to large errors in the test results. Second, the entire testing process lacks unified operating standards. For example, the concentration, injection speed, and dosage of the red dye solution largely depend on personnel experience, and the observation of the horizontal seal is mostly limited to the naked eye or a 10x magnifying glass, resulting in poor repeatability of test results from different personnel and different batches, with a deviation rate exceeding 25%. More importantly, limited by the observation precision, existing methods are severely inadequate in identifying microbubbles (0.5-2 mm), hidden micro-cracks (0.05 mm level), and microleakage, with a false negative rate of over 30%. These undetected defects constitute potential quality risks to the product during storage and transportation. Furthermore, the determination of whether something is qualified or not often relies on subjective experience and lacks a unified standard based on objective measurement data (such as bubble size and effective sealing width), which further increases the uncertainty of the results.

[0004] Therefore, there is an urgent need to propose a method for verifying the sealing effect of cardboard packaging in order to solve the above-mentioned technical problems. Summary of the Invention

[0005] This invention achieves thorough and clean separation of multi-layered packaging structures through stepwise acid-base treatment and standardized reagent preparation, eliminating interference from interlayer material residues in the detection process. Simultaneously, by precisely controlling the injection parameters of the red dye solution and combining ultraviolet light and high-magnification observation, an objective and quantitative judgment standard is established, thereby improving the accuracy of identifying sealing defects and resolving the problem of inconsistent test results caused by differences in operator experience. A brief overview of this invention is provided below to offer a basic understanding of certain aspects of the invention. It should be understood that this overview is not an exhaustive summary of the invention. It is not intended to identify key or essential parts of the invention, nor is it intended to limit the scope of the invention.

[0006] The technical solution of this invention:

[0007] A method for verifying the sealing effect of cardboard box packaging includes the following steps:

[0008] S1. Preparation of I-shaped sample: Take the cardboard box to be tested, cut the package along the direction parallel to its longitudinal seal, clean out all the contents inside, retain the complete structure of the horizontal and longitudinal seal areas, and trim the package into an I-shape.

[0009] S2. Outer layer peeling: Manually peel off and remove the printed layer and polyethylene protective layer on the outer surface of the I-shaped sample;

[0010] S3. Chemical layering treatment:

[0011] S31. Acidic immersion peeling: Immerse the sample treated by S2 completely in a 30% nitric acid solution for 30 to 40 minutes at room temperature; after removal, gently rub it under running water until the paper layer and the first adhesive layer bonded to it are completely removed, exposing the aluminum foil layer in the middle of the I-shaped sample.

[0012] S32. Alkaline immersion peeling: Immerse the I-shaped sample treated in S31 completely in a sodium hydroxide solution with a concentration of 2.0% to 2.5% and soak at about 35°C for 10 to 15 minutes; then peel off the aluminum foil layer to obtain the sample piece with only the innermost food contact polyethylene film remaining; rinse the sample piece with clean water and air dry.

[0013] S4. Inspection and judgment of the sealing joint:

[0014] S41. Longitudinal seal test: Use a syringe to draw red dye solution and insert it into the polyethylene film at a 45-degree angle about 1 mm from the edge of the longitudinal seal line. Inject 0.5 ml of red dye solution at a rate of 0.5 ml / s. First, observe with the naked eye and wait for 1 minute before irradiating with a 365 nm wavelength ultraviolet lamp for inspection.

[0015] S42. Horizontal seal test: Using the same syringe, slowly inject 0.5 ml of red dye into the horizontal seal interlayer; then, use a 40x magnifying glass with a scale to observe and measure the maximum length of the air bubble at the horizontal seal.

[0016] S43. Acceptance Criteria: If no red dye seepage or fluorescence is observed at the longitudinal seal under the naked eye or ultraviolet light, and the maximum length of the air bubble at the transverse seal is less than 2.0 mm, the packaging is deemed to be sealed effectively; otherwise, it is deemed unacceptable.

[0017] Preferably, in step S1, the horizontal sealing area is trimmed into a straight edge with a width of 1.0 to 1.5 cm.

[0018] Preferably, the red dye solution used in steps S41 and S42 is prepared by dissolving 1.5 grams of erythrosine dye in 1 liter of isopropanol.

[0019] Preferably, in step S32, if there is still residual adhesive on the polyethylene film that the food comes into contact with after peeling off the aluminum foil layer, it is gently brushed off with a soft brush.

[0020] Preferably, in step S42, the width of the bubble-free continuous area at the horizontal seal is measured using the 40x magnifying glass, and the width is not less than 1.0 mm.

[0021] Preferably, the nitric acid solution and sodium hydroxide solution used in the method are stored separately in containers made of polytetrafluoroethylene.

[0022] Preferably, the method further includes a waste liquid treatment step, in which the used acidic waste liquid and alkaline waste liquid are neutralized to pH 6-8 respectively before being treated uniformly.

[0023] Preferably, the cardboard packaging is a 6-layer composite packaging material for liquid food, consisting of, from the outside to the inside: a polyethylene layer, a printed paper layer, a first adhesive layer, an aluminum foil layer, a second adhesive layer, and a food contact polyethylene layer.

[0024] The present invention has the following beneficial effects:

[0025] 1. This invention achieves thorough and clean separation of a specific 6-layer composite packaging structure through a targeted acid-base step-by-step treatment process, completely eliminating observational interference and misjudgments caused by interlayer material residues, and fully exposing the true state of the sealing interface. Simultaneously, by combining standardized red dye solution, precisely controlled injection parameters, and synergistic observation with ultraviolet light and a 40x magnifying glass, it can identify various sealing defects, including micro-cracks at the 0.05mm level and micro-bubbles at 0.5-2mm, resulting in an extremely low false negative rate and ensuring absolute accuracy of the test results.

[0026] 2. This invention overcomes the drawbacks of traditional methods that rely on personal experience. When different testing personnel follow this method, the deviation rate of the results can be reduced from more than 25% to an extremely low level, and the repeatability of the experiment is improved by more than 90%, providing stable, reliable, and comparable quality data support for the production process;

[0027] 3. This invention does not rely on complex and expensive large-scale equipment. It mainly utilizes conventional chemical reagents and portable testing tools, making it particularly suitable for rapid and efficient online or offline quality sampling inspections at food production sites. It can be directly applied to various packaging forms such as pillow-shaped and brick-shaped packaging. By identifying and rejecting substandard sealed products in advance and tracing verification, it can effectively reduce market complaints and quality risks, and improve the product qualification rate. At the same time, accurate test results help to accurately determine the sealing performance of packaging equipment, providing a clear basis for preventive maintenance and debugging of equipment, thereby improving the overall line operating efficiency. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the 6-layer aseptic paper box packaging described in the specific implementation method;

[0029] Figure 2 This is a schematic diagram illustrating the horizontal sealing effect observed with a 10x magnifying glass as described in the specific implementation method;

[0030] Figure 3 This is a schematic diagram of the horizontal sealing effect observed with a 40x magnifying glass with a scale, as described in the specific implementation method;

[0031] Figure 4 This is a schematic diagram illustrating the qualified effect of the horizontal seal magnified 40 times according to the specific implementation method.

[0032] In the diagram: 1-Polyethylene layer, 2-Paper and printing layer, 3-First adhesive layer, 4-Aluminum foil layer, 5-Second adhesive layer, 6-Food contact polyethylene layer. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below with reference to specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0034] Example 1: Combination Figures 1-4This embodiment describes a method for verifying the sealing effect of cardboard box packaging. The method comprises four main steps: preparation of an I-shaped sample, outer layer peeling, chemical delamination treatment, and detection and judgment of the sealing area. Through specific chemical reagents and precise operating parameters, it achieves the clean separation of multi-layer packaging structures and accurate identification of sealing defects. Specifically, it includes the following steps:

[0035] S1. Preparation and Pretreatment of I-shaped Samples

[0036] Take the cardboard box to be tested and use a cleaning tool to cut it open parallel to its longitudinal seal. Empty all contents (such as liquid food) to ensure the inside is empty. During this process, take special care to maintain the integrity of the transverse and longitudinal seal areas. Then, trim the empty packaging into an easy-to-handle I-shaped structure. Specifically, trim the transverse seal area to a straight edge with a width between 1.0 and 1.5 cm, ensuring the edges are free of folds and tears to obtain a standardized testing area.

[0037] S2. Outer layer peeling

[0038] For the I-shaped sample, the printed layer and the polyethylene layer serving as a protective layer on its outer surface are peeled off manually. The next structural layer exposed in this step is usually a paper layer.

[0039] S3. Chemical Stratification

[0040] This step aims to thoroughly and cleanly separate the intermediate barrier layer from the inner layer, which is crucial for eliminating detection interference.

[0041] S31. Acid Immersion Peeling: Immerse the S2-treated sample completely in a 30% (w / w, concentration error ≤ ±0.5%) nitric acid solution. This solution is stored separately in a corrosion-resistant sealed tank made of polytetrafluoroethylene (PTFE). Immerse for 30 to 40 minutes at room temperature (typically 20-25°C). After immersion, the operator must wear nitrile acid and alkali resistant gloves (recommended thickness ≥ 0.1 mm), remove the sample, and gently rub it under running process water (with force limited to avoid damaging the aluminum foil layer) until the paper layer and the first adhesive layer firmly bonded to it are completely removed, thus clearly exposing the intact aluminum foil layer in the middle.

[0042] S32. Alkaline Immersion and Peeling: Immerse the sample treated and rinsed in S31 completely in a sodium hydroxide solution with a concentration of 2.0% to 2.5% (w / w, concentration error ≤ ±0.1%). This solution can be stored in a polyethylene container. Immerse for 10 to 15 minutes at approximately 35°C (±2°C). Subsequently, peel off the aluminum foil layer. At this point, only the innermost food contact polyethylene film should remain on the sample. If there is any residue on the film due to incomplete dissolution of the second adhesive layer, gently brush it off with a soft brush dipped in clean water, avoiding damage to the film. Finally, rinse the sample thoroughly three times with running process water (each rinse lasting at least 30 seconds) until the rinse water is neutral (pH 6-8) as tested with precision pH test paper. Dry the surface moisture with a clean airflow (such as a hairdryer on a cool setting) for later use.

[0043] S4. Inspection and Judgment of Sealing Joints

[0044] S41. Longitudinal Seal Test: A 1 mL precision syringe is used to draw a specially prepared red staining solution. The red staining solution is prepared by dissolving 1.5 g (±0.1 g) of analytical grade erythrosine (purity ≥99%) in 1 L of analytical grade isopropanol, stirring magnetically (approximately 300 r / min) for 30 minutes, sealing and protecting from light, and allowing it to stand for 12 hours. The solution is then filtered through qualitative filter paper and stored in a brown reagent bottle at 4 °C for 30 days. At approximately 1 mm from the edge of the longitudinal seal line, insert the needle into the food-contact polyethylene film at a 45-degree angle, maintaining a constant injection speed of 0.5 ml / s, and inject 0.5 ml (±0.1 mL) of red dye solution. Perform two-step observation: First, visually inspect the seal for any red dye seepage under natural light; after standing for 1 minute, in a dark room, irradiate the entire longitudinal seal area with a 10W ultraviolet lamp with a main wavelength of 365 nm to check for any specific fluorescence caused by the dye seeping into the micro-cracks. This method can identify latent defects of approximately 0.05 mm.

[0045] S42. Horizontal Seal Inspection: Using the same syringe, slowly and parallelly inject 0.5 mL (±0.1 mL) of red dye into the horizontally sealed interlayer, ensuring the dye fully wets the entire sealing interface. After standing for 1 minute, observe using a 40x graduated magnifying glass with a minimum graduation of 0.1 mm. Clearly identify any air bubbles trapped within the sealing interface, and accurately measure and record the length of the largest bubble (in any direction). Simultaneously, measure and record the width of the continuous area between bubbles or between a bubble and the sealing edge, where there is a complete seal without any bubbles or defects; this is the effective seal width. S43. Acceptance Criteria: The following quantitative standards will be used for judgment:

[0046] Longitudinal sealing: Visual inspection revealed no red dye seepage, and no fluorescence was observed under 365nm ultraviolet light.

[0047] Horizontal seal: Observe under a 40x magnifying glass with graduations, such as Figure 3 As shown, the maximum length of all air bubbles must be less than 2.0 mm, and the effective sealing width at any position must be no less than 1.0 mm. Only samples that simultaneously meet all the above criteria for longitudinal and transverse sealing can be ultimately judged as having "qualified sealing effect". If either the longitudinal or transverse sealing condition is not met, it is judged as "unqualified".

[0048] Throughout the verification process of this embodiment, especially during acid and alkali immersion and stripping operations, operators must wear nitrile acid and alkali resistant gloves, chemical splash resistant goggles, and anti-corrosion aprons at all times. When preparing and handling the red dye solution, it is recommended to wear disposable PE gloves to avoid direct skin contact with erythrosine.

[0049] Nitric acid and sodium hydroxide solutions must be stored separately in clearly labeled, corrosion-resistant containers, away from sources of ignition, food ingredients, and power sources. Isopropanol in red dye is flammable and should be stored in a fume hood, ensuring the ambient concentration is below the lower explosive limit (<2%). If optical instruments such as 40x magnifying glasses become contaminated with reagents, they should be immediately wiped clean with dedicated lens paper.

[0050] Waste liquids generated during testing in this implementation method must be treated separately. Acidic waste liquids (nitric acid solution) should be neutralized by slowly adding solid sodium hydroxide or concentrated alkali solution; alkaline waste liquids (sodium hydroxide solution) should be neutralized by slowly adding dilute nitric acid solution. The pH value must be adjusted to the range of 6-8 and confirmed by testing before being poured into a dedicated chemical waste liquid recycling tank and handed over to a qualified unit for unified treatment. Direct discharge into the sewer system is strictly prohibited.

[0051] The method described in this embodiment is particularly suitable for 6-layer aseptic cardboard packaging widely used in the dairy and beverage industries. Figure 1 As shown, its typical composite structure, from the outside to the inside, consists of: polyethylene layer 1 (outer protective layer), paper and printing layer 2 (carrying graphics), first adhesive layer 3, aluminum foil layer 4 (core barrier layer), second adhesive layer 5, and food contact polyethylene layer 6 (directly in contact with the contents). The design of this method fully considers the differences in bonding characteristics between the layers of this structure (such as the strong adhesion between the aluminum foil and the adhesive layer, and the easy peeling between the adhesive layer and the polyethylene), thereby achieving targeted and efficient separation.

[0052] Example 2: Combination Figures 1-4 This embodiment describes a method based on Specific Embodiment 1. This embodiment strictly follows the standard method described in Embodiment 1 and is specifically applied to a common 250mL pillow-shaped milk package on the market, demonstrating its complete practical process and verification results.

[0053] First, the preparations for implementing a method to verify the sealing effect of cardboard box packaging are as follows:

[0054] 1. Sample: Ten 250mL pillow-shaped packages (Tetra Pak®) were randomly selected from the filling section of a dairy production line as the experimental group.

[0055] 2. Reagent preparation:

[0056] Acidic immersion solution: For CIP (in-situ cleaning), the concentration of concentrated nitric acid should be greater than 30%, and it should be stored in a covered PTFE tank. If the concentration is too low, the immersion time should be extended appropriately.

[0057] Alkaline soaking solution: Take 500 mL of 2.0-2.5% (w / w) sodium hydroxide solution directly from the alkaline solution circulation pipeline of the CIP (in-situ cleaning) system of this production line and store it in a PE bottle.

[0058] Red staining solution: Accurately weigh 1.50g of analytical grade erythrosine, dissolve in 1.00L of analytical grade isopropanol, stir magnetically (300r / min) for 30 minutes, transfer to a brown bottle and let stand in a refrigerator at 4℃ for 12 hours, then filter with qualitative filter paper before use.

[0059] 3. Equipment and protection: PTFE tank, PE bottle, 1mL precision syringe (minimum graduation 0.01mL), 40x graduated magnifying glass (minimum graduation 0.1mm), 365nm UV lamp (10W), nitrile gloves (0.12mm), goggles, anti-corrosion apron, soft brush, hair dryer, stopwatch, precision pH test paper (range 5.5-9.0).

[0060] The procedure in Example 1 was followed for each of the 10 samples. The following details the procedure using sample number 1 as an example:

[0061] S1. Sample Preparation: Cut open the packaging parallel to the longitudinal seal and pour out the milk. Keep the horizontal seals intact at both ends and the longitudinal seal area undamaged. Using a ruler and compass, trim the horizontal seals at both ends to a straight edge with a width of (1.2±0.1) cm, forming a standard I-shape.

[0062] S2. Outer layer peeling: Manually peel off the outer colored printing film and polyethylene layer smoothly to expose the light brown paper layer.

[0063] S3. Chemical layering treatment:

[0064] S31: Immerse the sample in a 30% nitric acid solution (the liquid level should be about 1.5 cm above the sample) at room temperature (24°C) for 35 minutes. After removing the sample, gently rub it in running pure water (25°C, flow rate 2L / min) for about 2 minutes. The paper layer and the first adhesive layer will completely fall off and be washed away in a flocculent manner, revealing a silver, smooth aluminum foil layer.

[0065] S32: Transfer to a 2.0 - 2.5% sodium hydroxide solution, soak in a constant temperature water bath at 35°C for 12 minutes. After taking it out, the aluminum foil layer can be completely peeled off. The inner polyethylene film is transparent, and there are very few translucent colloidal particles remaining on the surface. Gently sweep and remove them with a soft brush dipped in water. Rinse the film three times with flowing pure water (each time for more than 10 seconds), and the pH of the last rinse water is 7.0 (tested with pH paper). Dry it with a hair dryer using cold air. The pH of the last rinse water and the raw water remains the same. According to experience, it is also possible not to use pH paper for testing.

[0066] S4. Detection and Judgment:

[0067] S41 Longitudinal Seal Detection: Draw red staining solution with a syringe. At a position 1 mm outside the longitudinal seal line, insert it at a 45° angle and inject 0.50 mL at a speed of 0.5 mL / s. Visual inspection: There is no red leakage around the injection point and along the longitudinal seal. Let it stand for 1 minute. Ultraviolet lamp (in a dark room) irradiation: There are no fluorescent bright spots in the entire longitudinal seal area.

[0068] S42 Transverse Seal Detection: Draw 0.50 mL of red staining solution with the same syringe, insert the needle parallel to the transverse seal edge into the interlayer, and slowly inject. After standing for 1 minute, place it under a 40 - fold magnifying glass. Observe several tiny bubbles, measure with the scale in the mirror, and the maximum length of the bubbles is 1.3 mm. At the same time, measure the narrowest intact sealed area between the bubbles, and the effective seal width is 1.5 mm.

[0069] S43 Qualification Judgment: For this sample, there is no leakage and no fluorescence in the longitudinal seal, the maximum length of the transverse seal bubbles (1.3 mm) < 2.0 mm, and the effective seal width (1.5 mm) ≥ 1.0 mm. It is judged as qualified. Usually, when the seal width ≥ 1.5 mm, larger sampling can be carried out for testing to determine the impact of equipment fluctuations on the product.

[0070] To quantify the effect of this embodiment, a comparative experiment is designed:

[0071] 1. Detection by the traditional method for the same sample group: Invite three operators (A, B, C) to judge the transverse seal of the above 10 polyethylene film samples processed according to this embodiment only by visual inspection and a 10 - fold magnifying glass (the longitudinal seal detection method is the same). As Figure 2 shown, the schematic diagram of the transverse seal effect observed with a 10 - fold magnifying glass Results: The differences in the recognition and size judgment of bubbles by the three people are significant, and the qualification judgment results for the 10 samples are not completely consistent. Through comprehensive calculation, the false negative rate for transverse seal defects (especially bubbles < 1 mm) reaches about 35%, and the mutual deviation rate of the judgment results of the three people is about 28%.

[0072] 2. Detection method in this embodiment: Another operator, Ding, strictly followed all the steps and parameters of Embodiment 1 of this invention (including measurement with a 40x magnifying glass) to test 10 samples in the same group. Results: Among the 10 samples, 2 samples were found to have air bubbles ≥2.0mm in the horizontal seal (2.1mm and 2.4mm respectively), and 1 sample showed punctate fluorescence under ultraviolet light in the vertical seal. Figure 4 The diagram shows the pass / fail effect of the horizontal seal magnified 40 times. These 3 samples were judged as unqualified, while the remaining 7 were qualified. All measurement data (bubble length, seal width) are objectively calibrated and recorded.

[0073] 3. Comparison of effects:

[0074] Accuracy: The method in this embodiment achieves objective and precise measurement of tiny bubbles (readable to 0.1 mm) using a 40x magnifying glass. Combined with the detection of hidden seams using ultraviolet light, the defect identification accuracy reaches 100% and the false negative rate is 0.

[0075] Repeatability and Consistency: Subsequently, after receiving standard training on the method of this invention, operators A, B, and C retested another batch of 10 samples. The three operators' final judgments were completely consistent, and also aligned with operator D's judgment. The deviation rate of the operational results decreased from approximately 28% to 0, and the repeatability of the experiment was fundamentally improved.

[0076] Practicality: All reagents and equipment in this embodiment are readily available and can be prepared in factory laboratories or quality control rooms. The complete testing time for a single sample is approximately one hour, which meets the frequency requirements of sampling inspections on the production line. Clear judgment criteria avoid human disputes.

[0077] Through specific practice and comparative data in Example 2, it is demonstrated that the paper box packaging sealing effect verification method provided by this invention systematically solves the technical problems of traditional methods, such as large interlayer interference, varying operation methods, high missed detection rate of minor defects, and poor result repeatability, by using standardized reagent configuration, targeted layering processing technology, precise defect detection methods, and objective quantitative judgment standards. This method significantly improves the accuracy, reliability, and consistency of detection, providing strong technical support for packaging sealing quality. It can be directly applied to production line quality control and has high practical value.

[0078] It should be noted that in the above embodiments, as long as the technical solutions are not contradictory, they can be permuted and combined. Those skilled in the art can exhaust all possibilities based on the mathematical knowledge of permutation and combination. Therefore, the present invention will not describe the technical solutions after permutation and combination one by one, but it should be understood that the technical solutions after permutation and combination have been disclosed by the present invention.

[0079] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for verifying the sealing effect of cardboard box packaging, characterized in that, Includes the following steps: S1. Preparation of I-shaped sample: Take the cardboard box to be tested, cut the package along the direction parallel to its longitudinal seal, clean out all the contents inside, retain the complete structure of the horizontal and longitudinal seal areas, and trim the package into an I-shape. S2. Outer layer peeling: Manually peel off and remove the printed layer and polyethylene protective layer on the outer surface of the I-shaped sample; S3. Chemical layering treatment: S31. Acidic immersion peeling: Immerse the sample treated by S2 completely in a 30% nitric acid solution for 30 to 40 minutes at room temperature; after removal, gently rub it under running water until the paper layer and the first adhesive layer bonded to it are completely removed, exposing the aluminum foil layer in the middle of the I-shaped sample. S32. Alkaline immersion peeling: Immerse the I-shaped sample treated in S31 completely in a sodium hydroxide solution with a concentration of 2.0% to 2.5% and soak at about 35°C for 10 to 15 minutes; then peel off the aluminum foil layer to obtain the sample piece with only the innermost food contact polyethylene film remaining; rinse the sample piece with clean water and air dry. S4. Inspection and judgment of the sealing joint: S41. Longitudinal seal test: Use a syringe to draw red dye solution and insert it into the polyethylene film at a 45-degree angle about 1 mm from the edge of the longitudinal seal line. Inject 0.5 ml of red dye solution at a rate of 0.5 ml / s. After waiting for 1 minute, observe first and then examine with a 365 nm wavelength ultraviolet lamp. S42. Horizontal seal test: Using the same syringe, slowly inject 0.5 ml of red dye into the horizontal seal interlayer; then, use a 40x magnifying glass with a scale to observe and measure the maximum length of the air bubble at the horizontal seal. S43. Acceptance Criteria: If no red dye seepage or fluorescence is observed at the longitudinal seal under the naked eye or ultraviolet light, and the maximum length of the air bubble at the transverse seal is less than 2.0 mm, the packaging is deemed to be sealed effectively; otherwise, it is deemed unacceptable.

2. The method for verifying the sealing effect of cardboard box packaging according to claim 1, characterized in that, In step S1, the horizontal sealing area is trimmed into a straight edge with a width of 1.0 to 1.5 cm.

3. The method for verifying the sealing effect of cardboard box packaging according to claim 1, characterized in that, The red dye solution used in steps S41 and S42 is prepared by dissolving 1.5 grams of erythrosine dye in 1 liter of isopropanol.

4. The method for verifying the sealing effect of cardboard box packaging according to claim 1, characterized in that, In step S32, after peeling off the aluminum foil layer, if there is still residual adhesive on the polyethylene film that the food comes into contact with, gently brush it off with a soft brush.

5. The method for verifying the sealing effect of cardboard box packaging according to claim 1, characterized in that, In step S42, the width of the bubble-free continuous area at the horizontal seal is measured using the 40x magnifying glass, and the width is not less than 1.0 mm.

6. The method for verifying the sealing effect of cardboard box packaging according to claim 1, characterized in that, The nitric acid solution and sodium hydroxide solution used in the method are stored separately in containers made of polytetrafluoroethylene.

7. The method for verifying the sealing effect of cardboard box packaging according to claim 1, characterized in that, The method also includes a waste liquid treatment step, in which the used acidic waste liquid and alkaline waste liquid are neutralized to pH 6-8 respectively before being treated uniformly.

8. The method for verifying the sealing effect of cardboard box packaging according to claim 1, characterized in that, The cardboard packaging is a 6-layer composite packaging material for liquid food, consisting of, from the outside to the inside: a polyethylene layer, a printed paper layer, a first adhesive layer, an aluminum foil layer, a second adhesive layer, and a food contact polyethylene layer.

Images