Method for evaluating quality stability of ink for cigarette paper

Abstract

The invention belongs to the field of tobacco products, and relates to a method for evaluating the quality stability of ink for cigarette paper, which comprises the following steps: respectively mixing reference ink and ink to be detected with first and second organic solvents, separating out first and second liquids with the maximum layer thickness, concentrating or drying, and dissolving to obtain a first concentrated solution / solution and a second concentrated solution / solution; performing infrared spectrum detection on the first concentrated solution / solution, and performing matching degree calculation on all waveforms of a spectrogram; comparing the spectrogram with a standard spectrogram to determine main resin types; detecting the second concentrated solution / solution by gel permeation chromatography, calculating the number-average molecular weight of main resin by an external standard method according to a chromatogram, and then calculating the deviation ratio of the number-average molecular weight of the main resin of the to-be-detected ink and the reference ink; and calculating the comprehensive score according to the formula that the comprehensive score = w1 * all waveform matching degrees of the infrared spectrogram + w2 * (1-main resin number-average molecular weight deviation ratio). The method provided by the invention can rapidly and accurately evaluate the quality stability of the printing ink for the cigarette paper.

Description

Technical Field

[0001] This invention belongs to the field of tobacco products, and specifically relates to a method for evaluating the quality stability of inks used in cigarette paper. Background Technology

[0002] As consumers increasingly demand higher aesthetics, texture, and quality from cigarette products, and with growing environmental awareness, manufacturers have placed higher requirements on the printing of cigarette paper in recent years. In response, ink manufacturers are constantly adjusting ink formulations to improve ink quality. Furthermore, the global economic climate has led to tight supply and fluctuating prices in the chemical raw material market. Against this backdrop, ink manufacturers also need to update their formulations and find alternative materials to alleviate cost pressures from the raw material market. All these factors affect the stability of ink quality, and consequently, the quality stability of printed cigarette paper. Therefore, it is necessary to establish methods for evaluating the stability of ink quality to ensure the quality stability of printed cigarette paper.

[0003] Traditional methods for evaluating the stability of ink quality mainly involve testing indicators such as ink adhesion, ink coating abrasion resistance, and gloss of printed materials on cigarette paper. However, these testing procedures are lengthy and involve many steps, making it impossible to complete the tests quickly. Moreover, the lengthy procedures and numerous steps increase the likelihood of human error, which may affect the accuracy of the tests.

[0004] There is an urgent need for a rapid and accurate method to evaluate the quality stability of inks used in cigarette paper. Summary of the Invention

[0005] The purpose of this invention is to provide a method for evaluating the quality stability of inks used in cigarette paper, which can quickly and accurately evaluate the quality stability of inks.

[0006] To achieve the above objectives, the present invention provides a method for evaluating the quality stability of inks used in cigarette paper, comprising:

[0007] The reference ink and the ink to be tested are mixed with the first organic solvent, and the solid and liquid are separated. The first liquid with the largest layer thickness is separated from the resulting liquid phase.

[0008] The first liquid is concentrated to obtain a first concentrated solution; or the first liquid is dried and then dissolved in the first organic solvent to obtain a first solution.

[0009] Infrared spectroscopy is used to detect the first concentrated liquid or the first solution prepared from the reference ink and the ink to be tested, respectively, to obtain the infrared spectra of the reference ink and the ink to be tested. The infrared spectra of the ink to be tested and the infrared spectra of the reference ink are then used to calculate the matching degree of all waveforms.

[0010] The infrared spectrum of the reference ink is compared with a standard spectral library to determine the main resin types;

[0011] The reference ink and the ink to be tested are respectively mixed with a second organic solvent, and solid-liquid separation is performed to separate the second liquid with the largest layer thickness from the resulting liquid phase.

[0012] The second liquid is concentrated to obtain a second concentrate; or the second liquid is dried and then dissolved in the second organic solvent to obtain a second solution.

[0013] Gel permeation chromatography was used to detect the second concentrated solution or the second solution prepared from the reference ink and the test ink, respectively, and chromatograms were obtained.

[0014] Based on the chromatogram and the identified main resin types, the number-average molecular weights of the main resins in the reference ink and the test ink were calculated using external standard analysis. Then, the deviation rate of the number-average molecular weights of the main resins between the test ink and the reference ink was calculated.

[0015] The comprehensive score of the ink to be tested is calculated according to the following formula; if the comprehensive score is > 0.95, the quality stability of the ink to be tested is "excellent"; if 0.85 < comprehensive score ≤ 0.95, the quality stability of the ink to be tested is "qualified"; if the comprehensive score ≤ 0.85, the quality stability of the ink to be tested is "unqualified".

[0016] Overall score = w1 × matching degree of all waveforms in the infrared spectrum + w2 × (1 - deviation rate of the number average molecular weight of the main resin)

[0017] Where w1+w2=1, w1 is 0.5-0.8, for example 0.5, 0.6, 0.7, 0.8.

[0018] Unconstrained by theoretical limitations, the resin system of cigarette paper ink includes a main resin and other functional reinforcing resins. The first and second organic solvents of this invention have different solubilities for different types of resins, causing the dissolved liquid phase system to separate into layers. The thickest layer is the liquid from which the main resin in the ink has dissolved. In any embodiment, the reference ink and the ink to be tested are inks with the same formulation but different production batches.

[0019] In any implementation, the reference ink can be any batch of ink from different batches, or it can be the batch of ink with the best quality from different batches.

[0020] In any implementation, the matching degree of all waveforms in the infrared spectrum of the ink to be tested and the infrared spectrum of the reference ink is calculated by the software built into the infrared spectrometer.

[0021] In any embodiment, the deviation rate of the number-average molecular weight of the main resins in the test ink and the reference ink is the absolute value of the difference between the ratio of the number-average molecular weight of the main resins in the test ink and the reference ink and 1.

[0022] In any embodiment, the first organic solvent includes one or more of n-propyl ester, methanol, and ethyl acetate.

[0023] In any embodiment, the ratio of the reference ink or the ink to be tested to the first organic solvent is 1:50 g / ml to 1:20 g / ml, for example, 1:50 g / ml, 1:45 g / ml, 1:40 g / ml, 1:35 g / ml, 1:30 g / ml, 1:25 g / ml, or 1:20 g / ml.

[0024] The first organic solvent used in this application has different solubilities and layers for different types of resins in the ink. It has high solubility for the main resin, and by separating the main resin solution layer for detection, the interference of other resins on the detection is reduced. At the same time, the sample prepared by the first organic solvent is suitable for infrared spectroscopy detection.

[0025] The ratio of the reference ink or the ink to be tested to the first organic solvent can ensure that the main resin of the ink is fully and uniformly dispersed in the solvent. At the same time, an appropriate ratio can shorten the time consumed in sample pretreatment and achieve rapid detection.

[0026] In any embodiment, the second organic solvent includes one or more of tetrahydrofuran, dichloromethane, and N-methylpyrrolidone.

[0027] In any embodiment, the ratio of the reference ink or the ink to be tested to the second organic solvent is 1:50 g / ml to 1:20 g / ml, for example, 1:50 g / ml, 1:45 g / ml, 1:40 g / ml, 1:35 g / ml, 1:30 g / ml, 1:25 g / ml, or 1:20 g / ml.

[0028] The second organic solvent used in this application exhibits varying solubility and stratification for different types of resins in the ink, while possessing high solubility for the main resin. By separating the main resin solution layer for detection, interference from other resins is reduced. Furthermore, samples prepared with the second organic solvent are suitable for gel permeation chromatography (GPC). The inventors discovered through experiments that ethyl acetate has poor compatibility with the chromatographic column packing material in GPC, easily causing interference. Methanol has slightly lower solubility for the main resins in the ink than tetrahydrofuran. Other solvents that can achieve dissolution and stratification of different types of resins in the ink may undergo side reactions with the GPC column packing material, shortening the column life. The accuracy and reproducibility of detection using the aforementioned second organic solvent are both high.

[0029] The ratio of the reference ink or the ink to be tested to the second organic solvent can ensure that the main resin of the ink is fully and uniformly dispersed in the solvent. At the same time, an appropriate ratio can shorten the time consumed in sample pretreatment and achieve rapid detection.

[0030] In any embodiment, the solid-liquid separation is performed by centrifugation.

[0031] In any embodiment, the centrifugal rotation speed is independently 3000-12000 rpm, for example 4000 rpm, 5000 rpm, 6000 rpm, 7000 rpm, 8000 rpm, 9000 rpm, 10000 rpm, 11000 rpm, and the centrifugal separation time is independently 15-40 minutes, for example 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes.

[0032] Centrifugation can separate the mixed system into a bottom precipitate and an upper multi-layer liquid phase. The multi-layer liquid phase is caused by the different solubilities of organic solvents for different types of resins. The thickest layer can be regarded as the solution layer of the main resin.

[0033] In any embodiment, the first liquid and / or the second liquid are filtered through a filter membrane before concentration or drying.

[0034] In any embodiment, the pore size of the filter membrane is independently greater than 0.1 μm and less than or equal to 0.4 μm, for example 0.15 μm, 0.2 μm, 0.22 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm.

[0035] Sequential membrane filtration helps remove interference from insoluble impurities, improving detection accuracy. Specifically, a membrane pore size greater than 0.1 μm ensures that the main resin in the ink is not trapped, allowing it to fully dissolve in the solvent. Centrifugation at speeds not exceeding 12,000 rpm and for durations not exceeding 40 minutes minimizes the risk of excessive resin degradation or side reactions due to over-centrifugation, thus further improving detection accuracy.

[0036] In any embodiment, the concentration of the first concentrate or the first solution is 0.5-1.0 g / ml, for example 0.5 g / ml, 0.8 g / ml, or 1.0 g / ml.

[0037] Therefore, when performing infrared spectroscopy, sample concentration within the above range can reduce the intensity of solvent characteristic absorption peaks, thereby reducing interference with the detection.

[0038] In any embodiment, the concentration of the second concentrate or the second solution is 0.0015-1.0 g / ml, for example 0.0015 g / ml, 0.002 g / ml, 0.005 g / ml, 0.01 g / ml, 0.02 g / ml, 0.04 g / ml, 0.5 g / ml, 0.8 g / ml, or 1.0 g / ml.

[0039] In any implementation, the operating conditions for the infrared spectrum include one or more of the following:

[0040] The infrared spectrum is a Fourier transform infrared spectrum;

[0041] The infrared spectrum was obtained by using a KBr crystal to hold the sample.

[0042] The infrared spectrum is tested at a temperature of 20℃-25℃ (e.g., 21℃-25℃) and a relative humidity of 45%-55% (e.g., 50%).

[0043] The infrared spectrum scanning range is 4000-400cm. -1 ;

[0044] The infrared spectrum is scanned 30-40 times, for example 32 times;

[0045] The resolution of the infrared spectrum is 2-6 cm. -1 For example, 4 cm -1 ;

[0046] The gain of the infrared light source is 1.0;

[0047] The acceptable maximum energy of the infrared spectrum is 6-7.

[0048] In any embodiment, the operating conditions for gel permeation chromatography include one or more of the following:

[0049] The chromatographic column was an Agilent PLgel MIXED.

[0050] The injection volume is 15-25 μL, for example, 20 μL;

[0051] The mobile phase is tetrahydrofuran;

[0052] The flow rate of the mobile phase is 0.5-1.5 mL / min, for example, 1.0 mL / min;

[0053] The column temperature of the chromatographic column is 35℃-45℃, for example, 40℃;

[0054] The detector is a differential refractive index detector.

[0055] In any embodiment, the step of calculating the number-average molecular weight of the major resins in the reference ink and the ink to be tested by external standard analysis includes:

[0056] Dissolve the main resin standards of different molecular weights in the second organic solvent to obtain a series of standard solutions;

[0057] A series of standard solutions were detected by gel permeation chromatography to obtain a series of chromatograms. Based on the series of chromatograms, the retention times of the main resins with different molecular weights were determined, and a standard curve of retention time versus molecular weight was established.

[0058] By substituting the retention times from the chromatograms of the reference ink and the test ink into the standard curve, the molecular weights M of the main resins in the reference ink and the test ink were obtained. i ;

[0059] The detection intensity H corresponding to each retention time in the chromatograms of the reference ink and the test ink. i Divide by the corresponding molecular weight M respectively i The molecular weights M were obtained. i The corresponding number of molecules N i ;

[0060] The number-average molecular weight M of the main resins in the reference ink and the test ink is calculated using the following formula. n ;

[0061]

[0063] Alternatively, the operating conditions for gel permeation chromatography are as described above.

[0064] The denominator of the above formula is the number of molecules N corresponding to each molecular weight. iThe sum, with each molecule being the molecular weight M. i With the corresponding number of molecules N i The sum of the products.

[0065] In any embodiment, the first liquid with the largest layer thickness in the resulting liquid phase is the uppermost liquid.

[0066] In any embodiment, the second liquid with the largest layer thickness in the resulting liquid phase is the uppermost liquid.

[0067] In any embodiment, during the step of preparing the first liquid, the mixing temperature is 20°C-30°C, for example, 25°C.

[0068] In any embodiment, the concentration temperature of the first liquid is 25°C-60°C, for example 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, or 60°C.

[0069] In any embodiment, the drying temperature of the first liquid is 25°C-60°C, for example 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, or 60°C.

[0070] In any embodiment, during the step of preparing the second liquid, the mixing temperature is 20°C-30°C, for example, 25°C.

[0071] In any embodiment, the concentration temperature of the second liquid is 25°C-60°C, for example 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, or 60°C.

[0072] In any embodiment, the drying temperature of the second liquid is 25°C-60°C, for example 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, or 60°C.

[0073] In any embodiment, the cigarette paper is cigarette packaging paper.

[0074] In any embodiment, the cigarette packaging paper includes one or more of the following: cigarette label paper, cigarette tipping paper, cigarette inner lining paper, and cigarette frame paper.

[0075] The present invention achieves at least one of the following technical effects:

[0076] 1. The method of the present invention can quickly and accurately evaluate the quality stability of inks used in cigarette paper.

[0077] 2. The method of the present invention can comprehensively, effectively and accurately reflect the stability of product quality and performance of ink in cigarette paper, which is conducive to the control of production quality stability. Attached Figure Description

[0078] Figure 1 This is the infrared spectrum of the reference ink in Embodiment 2 of the present invention.

[0079] Figure 2 This is a distribution diagram of the matching degree of all waveforms of the infrared spectra of different batches of ink and the reference ink in Example 2 of the present invention.

[0080] Figure 3 This is a gel permeation chromatogram of the reference ink in Example 2 of the present invention.

[0081] Figure 4 This is a distribution diagram of the number-average molecular weight ratio of the main resins in different batches of ink and the reference ink in Example 2 of the present invention. Detailed Implementation

[0082] Example 1: Evaluation Method for Ink Quality Stability

[0083] (1) Determination of infrared spectral matching degree of ink:

[0084] At 25°C, add 1.0g of ink to a 50ml centrifuge tube, then add 50ml of n-propyl ester solvent to dissolve it. Place the centrifuge tube in a high-speed centrifuge and centrifuge at 4000rpm for 20min. In the centrifuge tube, the bottom is a precipitate, and the upper part is a multi-layered liquid (dissolving different types of resins respectively). Obtain the thickest uppermost layer of liquid (dissolving the main type of resin). Place the uppermost layer of liquid in a petri dish and filter it multiple times using a 0.22μm polytetrafluoroethylene (PTFE) filter until clear. Place the filtrate in a petri dish. Dry the petri dish in a 50°C oven.

[0085] Clean KBr wafers were wiped with anhydrous ethanol, dried under a sodium lamp, and cooled before being placed in a Fourier transform infrared spectrometer for background acquisition. Then, 0.5g of the dried sample was placed in an agate mortar, 1ml of n-propyl ester solvent was added, and the mixture was ground to form a paste. The paste was then evenly spread onto the KBr wafers using a spatula, dried under a sodium lamp, and cooled before being detected in the Fourier transform infrared spectrometer. The operating conditions for the Fourier transform infrared spectrometer were: temperature 23±2℃; relative humidity 50±5%; scanning range 4000-400 cm⁻¹. -1 The number of scans was 32; the resolution was 4 cm. -1 Optical setup: Infrared light source; Gain 1.0; Acceptable maximum energy range 6-7.

[0086] The infrared spectrum was compared with the spectrum in the standard spectrum library to identify the main resin types in the ink.

[0087] Using any batch of ink from the same manufacturer as a reference ink, the matching degree of all waveforms of the infrared spectra of different batches of ink and the reference ink was calculated by the software built into the Fourier transform infrared spectroscopy. The matching degree between 0.90 and 0.95 was considered to be qualified for the stability of the main resin composition, and the matching degree greater than 0.95 was considered to be excellent for the stability of the main resin composition.

[0088] (2) Determination of the number-average molecular weight deviation rate of the main resins in the ink:

[0089] At 25℃, add 1.0g of ink to a 50mL centrifuge tube, then add 50mL of tetrahydrofuran solvent to dissolve it. Place the centrifuge tube in a centrifuge and centrifuge at 4000rpm for 20min. In the centrifuge tube, the bottom is a precipitate, and the upper part is a multi-layered liquid (dissolving different types of resins respectively). Obtain the thickest uppermost liquid (dissolving the main type of resin) and place it in a petri dish. Filter it using a 0.22μm polytetrafluoroethylene (PTFE) filter. Place the filtrate in a petri dish and then dry it in a 50℃ oven. Place 15mg of the dried sample in a 20mL glass bottle, add 10mL of tetrahydrofuran solvent, and shake thoroughly to dissolve and obtain the test solution.

[0090] Gel permeation chromatography (GPC) was used to detect the test solution. GPC operating conditions were as follows: PLgel 5 µm MIXED-C column (300 × 7.5 mm, two columns in series); injection volume: 20 μL; mobile phase: tetrahydrofuran; flow rate: 1.0 mL / min; column temperature: 40℃; detector: differential refractive index detector.

[0091] The main resin in the ink is qualitatively identified based on the infrared spectrum in section (1), and then the number-average molecular weight of the main resin is tested according to the following method:

[0092] Seven main resin standards with different molecular weights in the range of 2710-298900 were selected, and 1 ml of tetrahydrofuran was added to each to prepare a series of standard solutions. The series of standard solutions were then analyzed by gel permeation chromatography using the method described above, and the retention times were recorded to establish a standard curve relating molecular weight to retention time.

[0093] The molecular weights (M) of the main resins in the test solution were calculated based on the retention times and standard curves in the chromatograms of the test solution. i The detection intensity value corresponding to each retention time in the spectrum of the test solution is divided by the corresponding molecular weight M of the main resin. i The number of molecules N corresponding to each molecular weight of the main resin was obtained. i Then, calculate the number-average molecular weight of the main resin in the test solution using the following formula. ;

[0094]

[0096] Using any batch of ink from the same manufacturer as a reference ink, calculate the ratio of the number-average molecular weight of the main resin in different batches of ink to that in the reference ink. Then calculate the absolute value of the difference between this ratio and 1 to obtain the number-average molecular weight deviation rate of the main resin in different batches of ink. A number-average molecular weight deviation rate between 0.10 and 0.15 is considered to indicate acceptable stability of the main resin's number-average molecular weight, while a deviation rate < 0.10 is considered to indicate excellent stability.

[0097] (3) Comprehensive evaluation of ink quality stability

[0098] To take all factors into consideration, the following comprehensive quality stability scoring formula is established to calculate the above three indicators in a unified manner:

[0099] Overall score = w1 × infrared spectral matching degree + w2 × (1 - number mean molecular weight deviation rate)

[0100] Where w1 and w2 are weighting coefficients and w1+w2=1; based on the importance of each index to the ink performance, w1=0.7 and w2=0.3;

[0101] Application method: First, according to the methods described in (1) and (2), calculate the infrared spectral matching degree and the number-average molecular weight deviation rate of the main resins for the batch of ink to be evaluated. Then, substitute these two values ​​into the above formula to calculate the comprehensive score of the batch of ink. Finally, make a final judgment on the quality stability of the ink based on the following thresholds:

[0102] If the overall score is greater than 0.95, the quality stability is "excellent";

[0103] If 0.85 < overall score ≤ 0.95, then the quality stability is "qualified".

[0104] If the overall score is ≤0.85, the quality stability is "unqualified".

[0105] This comprehensive scoring method can more fully and objectively reflect the batch-to-batch quality stability of ink products.

[0106] Example 2

[0107] Using ink from the same manufacturer with batch number W22111017 as a reference ink, inks from different batches from the same manufacturer were tested according to the method in Example 1.

[0108] (1) Infrared spectral matching degree of ink: The infrared spectrum of the reference ink is as follows Figure 1 As shown. Figure 1By comparing the infrared spectra with the standard spectrum, the resin in the ink can be qualitatively identified as polyurethane. Table 1 shows the infrared spectral matching degree between different batches of ink and the reference ink, with batch W22111017 serving as the reference ink. A matching degree distribution chart of different batches of ink was generated based on the matching degree, as shown below. Figure 2 As shown, the infrared spectra of different batches of ink products conform to a normal distribution.

[0109] Table 1. Infrared spectral matching degree between different batches of ink and reference ink

[0110] The consistency of resin composition among the ink batches can be preliminarily assessed based on the infrared spectral matching data in Table 1. Batch W22120819 has a matching degree as high as 0.9924, indicating that its main resin composition is almost completely identical to the reference ink. Most batches (such as W22120108 and W22111403) have matching degrees concentrated between 0.93 and 0.95, indicating that the main resin structure is consistent with minor fluctuations. However, batches W23033004 and W23033005 have matching degrees significantly lower than 0.90, indicating that these batches may have significant deviations in the main resin types, proportions, or structures.

[0111] (2) Number-average molecular weight deviation rate of the main resins in the ink: Gel permeation chromatography of the reference ink as follows Figure 3 As shown in Table 2, the number-average molecular weight ratios of the main resins in different batches of ink compared to the reference ink were calculated according to the method in Example 1 (2), where batch W22111017 is the reference ink. The absolute values ​​of the differences between the number-average molecular weight ratios of the main resins in different batches of ink compared to the reference ink and 1 were calculated to obtain the deviation rate of the number-average molecular weight ratios of the main resins in different batches of ink compared to the reference ink. The results are summarized in Table 3 below.

[0112] A ratio distribution chart was generated based on the ratio of the number-average molecular weight of the main resins in different batches of ink to the reference ink, such as... Figure 4 As shown, the ratio of the number-average molecular weight of the main resins in different batches of ink to the reference ink conforms to a normal distribution.

[0113] Table 2. Test results of the ratio of the number average molecular weight of the main resins between different batches of ink and the reference ink.

[0114] (3) Comprehensive evaluation of ink quality stability

[0115] Based on the comprehensive quality stability scoring formula established in Example 1 (3), the data in Tables 1 and 2 are calculated. The weighting coefficients are w1=0.7 and w2=0.3. The comprehensive score and quality stability determination results are shown in Table 3 below.

[0116] Table 3 Comprehensive Evaluation of Ink Quality Stability in Different Batches

[0117] Example 3: Verification of the Quality Stability Evaluation Method

[0118] To verify the accuracy of the above-mentioned quality stability evaluation results, batches with comprehensive scores of "excellent", "qualified", and "unqualified" in Example 2 were randomly selected for printing adaptability testing. This test is directly related to the performance of the final product and is a traditional method for evaluating ink quality stability. The test method refers to industry standards and specifically includes:

[0119] 1. Adhesion test: Tested according to the ASTM D3359 cross-cut method, and the test results are graded from 5B - 0B, a total of 6 levels; 5B / 4B: The incision edge is completely smooth without any peeling, regarded as "excellent"; 3B / 2B: There is a small amount of peeling along the incision, and the peeling area accounts for less than 15% of the total area, regarded as "qualified"; 1B / 0B: The peeling area accounts for 15% or more of the total area, regarded as "unqualified".

[0120] 2. Abrasion resistance test: Tested using an abrasion resistance tester according to the GB / T 7707-2008 standard, and record the number of friction times required to wear through. Generally, greater than or equal to 200 times is regarded as qualified.

[0121] 3. Printing glossiness test: Measured using a 60° specular glossmeter according to the GB / T 9754-2007 standard, and determine the gloss percentage relative to the standard plate. A relative value ≥ 96% of the standard plate gloss is regarded as "excellent"; a relative value of 86% - 95% of the standard plate gloss is regarded as "qualified"; a relative value < 86% of the standard plate gloss is regarded as "unqualified".

[0122] If all three items meet the passing line and at least one item is "excellent", it can be regarded as overall excellent. The corresponding relationship between the test results and the comprehensive evaluation of quality stability is shown in Table 4 below.

[0123] Table 4 Comprehensive Evaluation of Quality Stability and Verification Results of Printing Performance

[0124] As shown in Table 4, batches with an overall score of "Excellent" (W22120819) exhibited excellent performance in all aspects of printability; batches with an overall score of "Pass" (W22120108, etc.) demonstrated good printability and met basic usage requirements; while batches with an overall score of "Fail" (W23033007, W23042608) showed significant declines in key performance indicators such as adhesion, abrasion resistance, and gloss, failing to meet usage requirements. This verification result demonstrates that the ink quality stability evaluation method established in Example 1 of this invention can effectively and accurately predict the consistency of product quality and performance in practical applications, providing a reliable basis for production quality control.

[0125] Comparative Example

[0126] Evaluation method: The infrared spectral matching degree between different batches of ink and the reference ink (W22111017) was determined using only the method described in Example 1 (1). The evaluation criteria were set as follows: a matching degree greater than 0.95 was considered "excellent", a matching degree between 0.90 and 0.95 was considered "qualified", and a matching degree less than 0.90 was considered "unqualified".

[0127] The same batch as in Example 2 was used for evaluation, and the results are shown in Table 5 below. For ease of comparison, the overall evaluation results of Example 2 are also listed.

[0128] Table 5 Comparison of Infrared Spectral Matching Degree Evaluation and Comprehensive Evaluation Results

[0129] As shown in Table 5, when using only infrared spectral matching for evaluation, the evaluation results of 10 out of 24 batches were inconsistent with those of the comprehensive evaluation method. Although the infrared spectral matching degree of these batches of inks did not reach the single-index pass line of 0.90, the deviations of the main resin molecular weight distribution from the reference ink were within acceptable ranges, resulting in their comprehensive score being qualified. The single-index evaluation method relies too heavily on the consistency of infrared spectra, which may misjudge inks that actually meet the performance requirements as "unqualified," leading to excessive rejection and waste in production.

[0130] The comprehensive evaluation method of Embodiment 1 of the present invention, through weighted scoring of infrared spectral matching degree and the number-average molecular weight deviation rate of major resins, can more comprehensively and objectively reflect the overall quality stability of ink, effectively reduce misjudgment, and make the evaluation results more scientific and reliable.

[0131] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for evaluating the quality stability of inks used in cigarette paper, comprising: The reference ink and the ink to be tested are mixed with the first organic solvent, and the solid and liquid are separated. The first liquid with the largest layer thickness is separated from the resulting liquid phase. The first liquid is concentrated to obtain a first concentrated solution; Alternatively, the first liquid can be dried and then dissolved in the first organic solvent to obtain a first solution; Infrared spectroscopy is used to detect the first concentrated liquid or the first solution prepared from the reference ink and the ink to be tested, respectively, to obtain the infrared spectra of the reference ink and the ink to be tested. The infrared spectra of the ink to be tested and the infrared spectra of the reference ink are then used to calculate the matching degree of all waveforms. The infrared spectrum of the reference ink is compared with a standard spectral library to determine the main resin types; The reference ink and the ink to be tested are respectively mixed with a second organic solvent, and solid-liquid separation is performed to separate the second liquid with the largest layer thickness from the resulting liquid phase. The second liquid is concentrated to obtain a second concentrate; or the second liquid is dried and then dissolved in the second organic solvent to obtain a second solution. Gel permeation chromatography was used to detect the second concentrated solution or the second solution prepared from the reference ink and the test ink, respectively, and chromatograms were obtained. Based on the chromatogram and the identified main resin types, the number-average molecular weights of the main resins in the reference ink and the test ink were calculated using external standard analysis. Then, the deviation rate of the number-average molecular weights of the main resins between the test ink and the reference ink was calculated. The comprehensive score of the ink to be tested is calculated according to the following formula; if the comprehensive score is > 0.95, the quality stability of the ink to be tested is "excellent"; if 0.85 < comprehensive score ≤ 0.95, the quality stability of the ink to be tested is "qualified"; if the comprehensive score ≤ 0.85, the quality stability of the ink to be tested is "unqualified". Overall score = w1 × matching degree of all waveforms in the infrared spectrum + w2 × (1 - deviation rate of the number average molecular weight of the main resin) Where w1+w2=1, w1 is 0.5-0.

8.

2. The method according to claim 1, wherein, The first organic solvent includes one or more of n-propyl ester, methanol, and ethyl acetate; and / or, The ratio of the reference ink or the ink to be tested to the first organic solvent is 1:50 g / ml to 1:20 g / ml.

3. The method according to claim 1 or 2, wherein, The second organic solvent includes one or more of tetrahydrofuran, dichloromethane, and N-methylpyrrolidone; and / or, The ratio of the reference ink or the ink to be tested to the second organic solvent is 1:50 g / ml to 1:20 g / ml.

4. The method according to any one of claims 1 to 3, wherein, The solid-liquid separation is performed by centrifugation. Optionally, the centrifugal speed is independently 3000-12000 rpm, and the centrifugal time is independently 15-40 minutes.

5. The method according to any one of claims 1 to 4, wherein, Before concentration or drying, the first liquid and / or the second liquid are filtered through a filter membrane. Optionally, the pore size of each filter membrane is independently greater than 0.1 μm and less than or equal to 0.4 μm.

6. The method according to any one of claims 1 to 5, wherein, The concentration of the first concentrate or the first solution is 0.5-1.0 g / ml; and / or, The concentration of the second concentrate or the second solution is 0.0015-1.0 g / ml.

7. The method according to any one of claims 1 to 6, wherein, The operating conditions for the infrared spectroscopy include one or more of the following: The infrared spectrum is a Fourier transform infrared spectrum; The infrared spectrum was obtained by using a KBr crystal to hold the sample. The infrared spectroscopy test temperature is 20℃-25℃, and the relative humidity is 45%-55%. The infrared spectrum scanning range is 4000-400cm. -1 ; The infrared spectrum is scanned 30-40 times, for example 32 times; The resolution of the infrared spectrum is 2-6 cm. -1 For example, 4 cm -1 ; The gain of the infrared light source is 1.0; The acceptable maximum energy of the infrared spectrum is 6-7.

8. The method according to any one of claims 1 to 7, wherein, The operating conditions for gel permeation chromatography include one or more of the following: The chromatographic column was an Agilent PLgel MIXED. The injection volume is 15-25 μL, for example, 20 μL; The mobile phase is tetrahydrofuran; The flow rate of the mobile phase is 0.5-1.5 mL / min, for example, 1.0 mL / min; The column temperature of the chromatographic column is 35℃-45℃, for example, 40℃; The detector is a differential refractive index detector.

9. The method according to any one of claims 1 to 8, wherein, The steps for calculating the number-average molecular weight of the main resins in the reference ink and the ink to be tested using external standard analysis include: Dissolve the main resin standards of different molecular weights in the second organic solvent to obtain a series of standard solutions; A series of standard solutions were detected by gel permeation chromatography to obtain a series of chromatograms. Based on the series of chromatograms, the retention times of the main resins with different molecular weights were determined, and a standard curve of retention time versus molecular weight was established. By substituting the retention times from the chromatograms of the reference ink and the test ink into the standard curve, the molecular weights M of the main resins in the reference ink and the test ink were obtained. i ; The detection intensity H corresponding to each retention time in the chromatograms of the reference ink and the test ink. i Divide by the corresponding molecular weight M respectively i The molecular weights M were obtained. i The corresponding number of molecules N i ; The number-average molecular weight M of the main resins in the reference ink and the test ink is calculated using the following formula. n ; 。 10. The method according to any one of claims 1 to 9, characterized in that... One or more of the following: The first liquid with the greatest thickness in the resulting liquid phase is the uppermost liquid layer. The second liquid with the largest layer thickness in the resulting liquid phase is the uppermost liquid layer. In the step of preparing the first liquid, the mixing temperature is 20℃-30℃; The concentration temperature of the first liquid is 25℃-60℃; The drying temperature of the first liquid is 25℃-60℃; In the step of preparing the second liquid, the mixing temperature is 20℃-30℃; The concentration temperature of the second liquid is 25℃-60℃; The drying temperature of the second liquid is 25℃-60℃; The cigarette paper mentioned is cigarette packaging paper.

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