Method and apparatus for reducing methanol content of cigarette banderols

Abstract

The present application relates to the technical field of cigarette paper, in particular to a method and device for reducing the methanol content of cigarette trademark paper. The method comprises the following steps: vacuum ultraviolet and short-wave ultraviolet are used to irradiate the cigarette trademark paper simultaneously, the irradiation distance between the light source of vacuum ultraviolet or / and short-wave ultraviolet and the cigarette trademark paper is 150-250 mm, the irradiation intensity is 250-300 mW / cm 2 , and the irradiation time is 3-10 s. The present application uses long-distance, short-time and high-intensity ultraviolet irradiation to control the intensity of ultraviolet thermal shock, which is sufficient to drive the methanol desorption inside the cigarette trademark paper, but insufficient to conduct heat to the paper fiber skeleton to cause its deformation; the use of vacuum ultraviolet and short-wave ultraviolet achieves the sudden drop of the methanol concentration on the paper surface, and forms the methanol concentration gradient to drive the diffusion of deep-layer methanol; finally, the purpose of reducing the methanol content on the surface and inside of the cigarette trademark paper without affecting the quality of the cigarette trademark paper is achieved.

Description

Technical Field

[0001] This invention relates to the field of cigarette paper technology, and in particular to a method and apparatus for reducing the methanol content of cigarette label paper. Background Technology

[0002] In the tobacco packaging industry, the control of volatile organic compound (VOC) residues has always been a core indicator of quality supervision. With the increasingly stringent industry standards such as YC / T 207-2014 for the determination of VOCs in cigarette packs and carton packaging paper, and the growing health awareness of consumers, reducing solvent residues in cigarette packaging materials has become a key technological challenge for major printing and packaging companies.

[0003] Among numerous controlled solvents, methanol stands out as one of the most challenging components to control due to its unique physicochemical properties and formation mechanism. Unlike ethanol, ethyl acetate, and other VOCs primarily derived from ink solvents, methanol exhibits an anomalous "rebound" phenomenon in cigarette label paper (commonly known as "cigarette labels"). That is, even after the printing and drying process, and despite initial testing being satisfactory, the methanol content often increases rather than decreases under high-temperature and high-humidity storage conditions. This phenomenon seriously troubles manufacturers because traditional physical heating drying methods not only fail to remove this potential methanol but may also accelerate the hydrolysis of its precursors due to thermal activation, leading to the risk of the finished product exceeding quality standards after delivery to the cigarette factory.

[0004] Currently, methanol residue on cigarette labels is reduced through natural evaporation or heated drying. Natural evaporation involves air-drying the printed label paper, allowing the methanol to evaporate on its own. Its disadvantages include being time-consuming, occupying significant storage space, and impacting production efficiency; furthermore, the released methanol poses environmental pollution and safety hazards; and at higher temperatures with poor ventilation, methanol levels can actually rise. Heated drying accelerates solvent evaporation by increasing temperature. While this method shortens evaporation time, excessively high temperatures can damage the paper's physical properties and printing quality. Furthermore, high-temperature drying is energy-intensive and costly, making it uneconomical.

[0005] Furthermore, some industries use ultraviolet (UV) photocatalytic oxidation to treat methanol. However, the targets are usually waste gas or wastewater containing methanol (TGDAEPI11-2022 Technical Specification for Industrial Organic Waste Gas Treatment by UV Photocatalytic Oxidation). In these waste gases or wastewaters, methanol is in a released, free state, making it effectively removed by UV light. However, in cigarette label paper, methanol remains adsorbed, encapsulated, or even hydrogen-bonded within the complex paper fibers (a porous medium). Conventional UV technology, with short-term irradiation, only affects the surface of cigarette label paper, failing to address methanol residue deep within the fibers; while long-term irradiation can damage the physical properties and printing quality of the cigarette label paper (e.g., paper deformation, ink color changes). Summary of the Invention

[0006] The present invention aims to solve the above-mentioned problems by providing a method and apparatus that can reduce the methanol content on the surface and inside of cigarette label paper without affecting the quality of the cigarette label paper.

[0007] The technical solution to the problem solved by this invention is:

[0008] First, a method for reducing the methanol content of cigarette label paper is provided, comprising the following steps: simultaneously irradiating the cigarette label paper with vacuum ultraviolet light and short-wave ultraviolet light, wherein the irradiation distance between the vacuum ultraviolet light source and / or short-wave ultraviolet light source and the cigarette label paper is 150–250 mm, and the irradiation intensity is 250–300 mW / cm². 2 The irradiation time is 3 to 10 seconds.

[0009] Cigarette label paper is typically coated paper or white cardboard, with a thickness of approximately 0.2–0.4 mm, making it difficult for ultraviolet light to penetrate. Therefore, this invention primarily utilizes the ultraviolet thermal effect and the methanol concentration gradient diffusion caused by photolysis to achieve the technical effect of reducing deep methanol in cigarette label paper. This invention employs high-intensity irradiation over medium to long distances for extremely short periods, which instantly heats the surface of the label paper. This causes a dramatic increase in the kinetic energy of adsorbed methanol molecules on the label paper surface, overcoming the hydrogen bond binding of cellulose and resulting in significant desorption. Simultaneously, above the label paper, vacuum ultraviolet (VUV, 185 nm) generates ozone, and short-wave ultraviolet (UVC, 254 nm) photolyzes the ozone into highly reactive free radicals. These free radicals react rapidly with the gaseous methanol that has desorbed and migrated to the surface. This process reduces the methanol content and passivates the methanol-generating precursor groups exposed on the surface (lignin degradation groups in paper fibers are potential sources of methanol), blocking the surface hydrolysis pathway. Furthermore, it causes the surface methanol concentration to drop sharply to near zero, creating a decreasing methanol concentration gradient from the inside out of the cigarette label paper. This drives the deeper methanol to diffuse outwards for ultraviolet treatment. In addition, because of the extremely short duration of high-intensity irradiation, the paper fibers have a relatively large heat capacity and a short heat residence time, meaning the paper fibers do not reach the thermal degradation and / or yellowing temperature. Therefore, curling and yellowing do not occur, ensuring the quality of the cigarette label paper.

[0010] The combined use of vacuum ultraviolet (UV) and short-wave UV is fundamental to achieving a rapid decrease in methanol concentration on the paper surface, thereby forming a concentration gradient diffusion. Although vacuum UV can also generate active free radicals, this invention uses a medium-to-long distance, meaning the active free radicals generated by vacuum UV are deactivated before reaching the paper surface. Ozone reaching the paper surface has a relatively slow methanol treatment rate, which cannot meet the extremely short treatment window of this invention, making it difficult to establish a concentration gradient. However, short-wave UV can convert ozone reaching the paper surface into active free radicals, thereby efficiently treating the methanol on the paper surface and establishing a concentration gradient.

[0011] Irradiation distance of 150–250 mm, 250–300 mW / cm 2 The irradiation intensity and irradiation time of 3–10 s are used to control the thermal shock generated by ultraviolet light. The intensity is just sufficient to drive the internal methanol desorption, but not enough to conduct heat to the paper fiber skeleton, causing it to deform. For example, the irradiation distance can be 150 mm, 160 mm, 170 mm, 180 mm, 190 mm, 200 mm, 210 mm, 220 mm, 230 mm, 240 mm, or 250 mm, preferably 200 nm. The irradiation intensity can be 250 mW / cm². 2 255 mW / cm 2 260 mW / cm 2 265 mW / cm2 270 mW / cm 2 275 mW / cm 2 280 mW / cm 2 285 mW / cm 2 290 mW / cm 2 295 mW / cm 2 300 mW / cm 2 The preferred value is 280 mW / cm 2 The irradiation time can be 3 s, 4 s, 5 s, 6 s, 7 s, 8 s, 9 s, or 10 s, with 5 s being the preferred value.

[0012] In some embodiments, as a preferred embodiment of the present invention, the irradiance of vacuum ultraviolet light reaching the surface of the cigarette label paper accounts for 8% to 15% of the total ultraviolet irradiance. For example, it can be 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%. Vacuum ultraviolet light is the main energy source for achieving instantaneous thermal shock. If its proportion is too low, it can easily lead to the disappearance of the driving force for thermal desorption of deep methanol; however, if its proportion is too high, it will lead to a sharp increase in the heat load on the paper surface, while reducing the proportion of short-wave ultraviolet light, decreasing the conversion efficiency of ozone to free radicals, and making it difficult to maintain the surface concentration gradient.

[0013] In this invention, vacuum ultraviolet and short-wave ultraviolet can be emitted by the same lamp or by different lamps; to maintain irradiation uniformity, the former is preferred, so that the non-uniformity of ultraviolet irradiance within the dealcoholization site range of the cigarette label paper is less than 5%.

[0014] In embodiments emitted by the same lamp, the irradiation distances of vacuum ultraviolet (UV) and short-wave UV relative to the cigarette label paper are the same. However, the attenuation of 185 nm light in air is much greater than that of 254 nm, which leads to a decrease in the actual irradiance ratio of vacuum UV reaching the paper surface. Therefore, it is necessary to adjust the material of the UV lamp, selecting a synthetic fused silica tube and adjusting the hydroxyl ratio to increase the initial proportion of vacuum UV, so that at a distance of 150–250 mm, the irradiance falls within the aforementioned range after air attenuation.

[0015] As a preferred embodiment of the present invention, the vacuum ultraviolet and short-wave ultraviolet are generated by the same synthetic fused silica low-pressure mercury lamp tube, wherein the hydroxyl content of the quartz tube material of the lamp tube is less than 1 ppm; in the initial spectrum of the lamp tube at the emission window, the irradiance at wavelength 185 nm accounts for 25% to 35% of the total irradiance at wavelengths 185 nm and 254 nm, for example, it can be 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, or 35%.

[0016] In some embodiments, as a preferred embodiment of the present invention, the initial moisture content of the cigarette label paper before exposure to ultraviolet light is 4% to 8%, for example, it can be 4%, 5%, 6%, 7%, or 8%. The moisture content determines the swelling state of the paper fibers and the density of the hydrogen bond network. An appropriate moisture content range can ensure that the pores of the paper fibers are in an open state, reduce the diffusion resistance of methanol molecules, and at the same time utilize the moderate thermal buffering effect of moisture to avoid overheating damage to the paper surface during ultraviolet irradiation.

[0017] Preferably, the moisture content of the cigarette label paper after ultraviolet irradiation is 4% to 8%, for example, it can be 4%, 5%, 6%, 7%, or 8%. Controlling the moisture content after ultraviolet irradiation to ensure paper quality is crucial.

[0018] To control the moisture content after ultraviolet irradiation from becoming too low, in some embodiments, as a preferred embodiment of the present invention, the cigarette label paper is subjected to ventilation during the simultaneous irradiation with vacuum ultraviolet and short-wave ultraviolet light. Preferably, the surface temperature of the cigarette label paper does not exceed 40°C.

[0019] On the one hand, by cooling the paper through ventilation and combining it with appropriate irradiation distance, intensity, and time, the surface temperature of the cigarette label paper is comprehensively controlled to not exceed 40°C. This ensures that methanol desorption and diffusion are promoted while preventing heat accumulation, excessive moisture loss from the cigarette label paper, and heat-induced damage to the paper. On the other hand, by creating a slight negative pressure through ventilation and / or breaking the stagnant air layer on the paper surface to reduce mass transfer resistance, the methanol diffusion process can be accelerated. At the same time, the photolysis products of methanol can be removed, preventing them from accumulating on the paper surface, absorbing ultraviolet light, or / and competing with active species, thus reducing treatment efficiency.

[0020] Preferably, the direction of the exhaust airflow is parallel to the thickness direction of the cigarette label paper, and the airflow direction is the same as the methanol diffusion direction, thereby improving the diffusion efficiency.

[0021] Preferably, under ventilated conditions, the static pressure difference between the upper and lower surfaces of the cigarette label paper is 50–200 Pa, for example, it can be 50 Pa, 75 Pa, 100 Pa, 125 Pa, 150 Pa, 175 Pa, or 200 Pa. This avoids removing the ozone before it reaches the paper surface to take effect, and also prevents the paper surface from cooling excessively.

[0022] In some embodiments, as a preferred embodiment of the present invention, during the simultaneous irradiation with vacuum ultraviolet and short-wave ultraviolet light, the cigarette label paper is subjected to a supplementary gas treatment. The relative humidity of the supplementary gas source is 20%–40%, and the supplementary gas flow rate is 0.15–0.3 L / min. For example, the relative humidity can be 20%, 25%, 30%, 35%, or 40%; the flow rate can be 0.15 L / min, 0.2 L / min, 0.25 L / min, or 0.3 L / min. The use of gas containing a small amount of water vapor increases the yield of active hydroxyl radicals and improves the removal efficiency of methanol; the low flow rate avoids affecting ventilation and disturbing the photochemical reaction zone.

[0023] Preferably, the gas source for replenishment is nitrogen or clean air.

[0024] Preferably, the direction of the supplementary airflow is parallel to the surface of the cigarette label paper.

[0025] In some implementations, ventilation and air replenishment are performed simultaneously.

[0026] Secondly, another object of the present invention is to provide an apparatus for carrying out the method of reducing the methanol content of cigarette label paper, comprising a conveyor belt for conveying cigarette label paper and having de-alcoholization sites, a light-shielding protective cover disposed at the de-alcoholization sites of the conveyor belt, and an ultraviolet light source disposed within the light-shielding protective cover by a bracket and suspended above the de-alcoholization sites of the conveyor belt.

[0027] The ultraviolet light source can be a single dual-peak ultraviolet light source, or it can be a vacuum ultraviolet light source and a short-wave ultraviolet light source arranged sequentially perpendicular to the conveyor belt's conveying direction.

[0028] As a preferred embodiment of the invention, it also includes an exhaust device, which includes an air inlet disposed inside the light-shielding protective cover and an air outlet disposed outside the light-shielding protective cover, the air outlet being connected to a negative pressure fan via an air duct.

[0029] As a preferred embodiment of the invention, it further includes an air replenishment device, which includes an air inlet disposed within the light-shielding protective cover and an air replenishment source connected to the air inlet via an air replenishment pipe and a flow valve.

[0030] As a preferred embodiment of the invention, a thermometer is also included for monitoring the temperature of the cigarette label paper surface at the dealcoholization point of the conveyor belt.

[0031] The beneficial effects of this invention are:

[0032] 1. This invention provides a method and apparatus for reducing the methanol content of cigarette label paper. It utilizes high-intensity ultraviolet (UV) irradiation of the cigarette label paper at medium to long distances and for extremely short durations. The intensity of the UV thermal shock is controlled to be just sufficient to drive the violent volatilization and escape of methanol inside the cigarette label paper, but insufficient to conduct heat to the paper fiber skeleton, causing deformation. By using vacuum UV and short-wave UV in combination, a sharp drop in methanol concentration desorbed to the paper surface is achieved, creating a methanol concentration gradient that decreases from the inside to the outside of the label paper. This drives the deep methanol to diffuse outwards, achieving UV treatment. Ultimately, this method achieves the goal of reducing the methanol content on the surface and inside of the cigarette label paper without affecting the quality of the cigarette label paper itself.

[0033] In some embodiments, the total methanol removal rate of cigarette label paper treated by the method of the present invention is increased to over 75%; and the methanol content of the treated cigarette labels does not increase significantly after being placed at 40 ℃ and 80% humidity for 15 days.

[0034] 2. The processing method of the present invention does not require the introduction of any chemical additives, nor does it change the original structural composition of the paper, and has the characteristics of simple process and strong applicability. Attached Figure Description

[0035] Figure 1 This is a plan view of a device for reducing the methanol content in cigarette label paper;

[0036] Figure 2 This is a three-dimensional diagram of a device for reducing the methanol content in cigarette label paper;

[0037] In the picture: 1. Cigarette label paper; 2. Ultraviolet light source; 3. Exhaust device; 4. Bracket; 5. Light-shielding protective cover. Detailed Implementation

[0038] The following are specific embodiments of the present invention, and the technical solution of the present invention will be further described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0039] Example 1

[0040] A device for reducing the methanol content of cigarette label paper, such as Figure 1 and Figure 2 As shown, the device includes a conveyor belt for conveying cigarette label paper 1. The conveyor belt is not limited and typically includes a mesh belt, an active roller and a passive roller for driving the mesh belt, and a motor for driving the active roller to rotate. The cigarette label paper 1 is laid flat on the mesh belt.

[0041] A light-shielding protective cover 5 is installed at a certain point on the conveyor belt; this point is designated as the de-alcoholization point of the conveyor belt. The light-shielding protective cover 5 faces downwards, covering the de-alcoholization point, and extends along both sides of the conveyor belt in the conveying direction (according to...). Figure 1The light shield 5 has openings on its left and right sides to allow the conveyor belt and the cigarette label paper 1 on it to enter and exit. Light-shielding curtains are installed at these openings to prevent ultraviolet light leakage without affecting entry and exit. Furthermore, its front and rear sides are closed, and an air inlet is provided on the top surface. The light-shielding protective cover 5 is preferably made of a metal material that does not transmit ultraviolet light, such as aluminum alloy, and its inner wall is coated with an ultraviolet-absorbing coating, such as iron oxide containing black pigment.

[0042] The de-alcoholization site is equipped with an ultraviolet light source 2 via a support 4. The ultraviolet light source 2 is located at the top inside the light-shielding protective cover 3, irradiating downwards. In this embodiment, the ultraviolet light source 2 is a dual-peak (185 nm and 254 nm) synthetic fused silica low-pressure mercury lamp. The support 4 includes pillars on both sides of the conveyor belt and extension arms on the pillars, which are used to fix the ultraviolet lamp. The extension arms and the ultraviolet lamp are detachably connected, and the detachable connection method is not limited. For example, a T-shaped insert is provided on the back of the ultraviolet lamp, and a narrow slot for inserting the insert is provided on the extension arm. The extension arm is detachably connected to the pillar to adjust the height of the extension arm. The detachable connection method is not limited. For example, the extension arm has a collar fitted onto the pillar, and the collar is connected to the pillar by a structure of several screws and nuts. In addition, the light-shielding protective cover 5 has an opening for the extension arm to pass through and a light-shielding curtain provided in the opening.

[0043] In some embodiments, an exhaust device 3 is also included. The exhaust device 3 includes an air inlet disposed on the top surface of the light-shielding protective cover 5. The air inlet is connected to the inner cavity of the light-shielding protective cover 5 and is in the shape of a narrow strip with a length equivalent to the length of the de-alcoholization site. It faces the paper surface and is used to draw gas from inside the cover. The exhaust device 3 also includes an air outlet disposed outside the light-shielding protective cover 5. The air outlet is connected to a negative pressure centrifugal fan through a duct. The fan is a variable frequency fan and the air volume can be adjusted.

[0044] In some embodiments, a gas replenishment device is also included, which includes a gas replenishment port disposed on the side of the light-shielding protective cover 5. The gas replenishment port is connected to a clean air source with a relative humidity of 30% through a gas replenishment pipeline. A mass flow controller is provided on the gas replenishment pipeline, and the gas replenishment direction is parallel to the surface of the cigarette label paper 1.

[0045] In some embodiments, a thermometer is also included. The thermometer is a non-contact infrared thermometer installed inside the light-shielding protective cover 5, with the probe aimed at the surface of the cigarette label paper 1 at the de-alcoholization site, for real-time monitoring of the paper surface temperature.

[0046] Example 2

[0047] A method for reducing the methanol content of cigarette label paper, using the apparatus of Example 1, includes the following steps:

[0048] A dual-peak (185 nm and 254 nm) high-ozone, low-hydroxyl synthetic fused silica low-pressure mercury lamp is installed on the extension arm. In the initial spectrum at the emission window, the irradiance at wavelength 185 nm accounts for approximately 30% of the total irradiance at wavelengths 185 nm and 254 nm. The installation height of the extension arm on the support is controlled to maintain a vertical distance of 200 mm between the lamp's emitting surface and the conveyor belt surface.

[0049] The cigarette label paper, with an initial moisture content of 6.5%, is conveyed into a light-shielding protective cover via a conveyor belt, reaching the area below the lamp tube. The lamp tube and exhaust system are then activated. The lamp tube emits both vacuum ultraviolet and short-wave ultraviolet light simultaneously. The distance between the ultraviolet light source and the cigarette label paper is 200 mm, and the irradiation intensity is 280 mW / cm². 2 The irradiation time was 5 seconds; of the ultraviolet irradiance reaching the surface of the cigarette label paper, the irradiance of vacuum ultraviolet light accounted for 11% of the total ultraviolet irradiance. At the same time, under ventilation, the static pressure difference between the upper and lower surfaces of the cigarette label paper was 100 Pa, and the temperature of the paper surface was monitored by a thermometer to be no more than 40 ℃.

[0050] After irradiation, the lamp is turned off, the exhaust device continues to run for 3 seconds and then shuts off, and the conveyor belt sends the cigarette label paper out of the light-shielding protective cover, completing the process.

[0051] Example 3

[0052] This embodiment is basically the same as Embodiment 2, except that the ultraviolet irradiation parameters are different: the distance between the ultraviolet light source and the cigarette label paper is 150 mm, and the irradiation intensity is 250 mW / cm². 2 The irradiation time is 10 seconds.

[0053] Example 4

[0054] This embodiment is basically the same as Embodiment 2, except that the ultraviolet irradiation parameters are different: the distance between the ultraviolet light source and the cigarette label paper is 250 mm, and the irradiation intensity is 300 mW / cm². 2 The irradiation time is 3 seconds.

[0055] Example 5

[0056] This embodiment is basically the same as embodiment 2, except that: no ventilation process is performed.

[0057] The cigarette label paper is fed into a light-shielding protective cover via a conveyor belt, reaching the area below the lamp tube, which is then turned on. The lamp tube emits both vacuum ultraviolet and short-wave ultraviolet light simultaneously. The distance between the ultraviolet light source and the cigarette label paper is 200 mm, and the irradiation intensity is 280 mW / cm². 2The irradiation time is 5 seconds; the thermometer monitors the paper surface temperature to ensure it does not exceed 40°C. After irradiation, the lamp is turned off, and the conveyor belt sends the cigarette label paper out of the light-shielding protective cover, completing the process.

[0058] Example 6

[0059] This embodiment is basically the same as embodiment 2, except that the ultraviolet light source is different.

[0060] A standard synthetic fused silica low-pressure mercury lamp with dual main peaks (185 nm and 254 nm) is installed on the extension arm. In the initial spectrum at the emission window, the irradiance at wavelength 185 nm accounts for approximately 15% of the total irradiance at wavelengths 185 nm and 254 nm. The installation height of the extension arm on the support is controlled to maintain a vertical distance of 200 mm between the lamp's emitting surface and the conveyor belt surface.

[0061] The cigarette label paper is fed into a light-shielding protective cover via a conveyor belt, reaching the area below the lamp tube. The lamp tube and exhaust system are then activated. The lamp tube emits both vacuum ultraviolet and short-wave ultraviolet light simultaneously. The distance between the ultraviolet light source and the cigarette label paper is 200 mm, and the irradiation intensity is 280 mW / cm². 2 The irradiation time was 5 seconds; of the ultraviolet irradiance reaching the surface of the cigarette label paper, the irradiance of vacuum ultraviolet light accounted for 5% of the total ultraviolet irradiance. At the same time, under ventilation, the static pressure difference between the upper and lower surfaces of the cigarette label paper was 100 Pa, and the temperature of the paper surface was monitored by a thermometer to not exceed 40 ℃.

[0062] After irradiation, the lamp is turned off, the exhaust device continues to run for 3 seconds and then shuts off, and the conveyor belt sends the cigarette label paper out of the light-shielding protective cover, completing the process.

[0063] Example 7

[0064] This embodiment is basically the same as embodiment 2, except that it also includes gas replenishment treatment.

[0065] Air is replenished simultaneously with irradiation and ventilation. The replenishment air source is clean air with a relative humidity of 30% and a replenishment flow rate of 0.2 L / min.

[0066] Blank example

[0067] The same cigarette label paper as in the example, which has not been treated with ultraviolet light, was used as a blank example.

[0068] Comparative Example 1

[0069] This comparative example is basically the same as Example 2, except that it only undergoes vacuum ultraviolet irradiation.

[0070] A MgF2 filter is installed on a high-ozone, low-hydroxyl synthetic fused silica low-pressure mercury lamp tube, allowing only 185nm to pass through.

[0071] The cigarette label paper is fed into a light-shielding protective cover via a conveyor belt, reaching the area below the lamp tube. The lamp tube and exhaust system are then activated. The lamp tube emits vacuum ultraviolet light, with a distance of 200 mm between the ultraviolet light source and the cigarette label paper, and an irradiation intensity of 280 mW / cm². 2 The irradiation time was 5 seconds; at the same time, under ventilation, the static pressure difference between the upper and lower surfaces of the cigarette label paper was 100 Pa, and the temperature of the paper surface was monitored by a thermometer to be no more than 40 ℃.

[0072] After irradiation, the lamp is turned off, the exhaust device continues to run for 3 seconds and then shuts off, and the conveyor belt sends the cigarette label paper out of the light-shielding protective cover, completing the process.

[0073] Comparative Example 2

[0074] This comparative example is basically the same as Example 2, except that only short-wave ultraviolet irradiation is performed.

[0075] A single-peak (254 nm) ozone-free low-pressure mercury lamp is installed on the extension arm.

[0076] The cigarette label paper is fed into a light-shielding protective cover via a conveyor belt, reaching the area below the lamp tube. The lamp tube and exhaust system are then activated. The lamp tube emits short-wave ultraviolet light, with a distance of 200 mm between the ultraviolet light source and the cigarette label paper, and an irradiation intensity of 280 mW / cm². 2 The irradiation time was 5 seconds; at the same time, under ventilation, the static pressure difference between the upper and lower surfaces of the cigarette label paper was 100 Pa, and the temperature of the paper surface was monitored by a thermometer to be no more than 40 ℃.

[0077] After irradiation, the lamp is turned off, the exhaust device continues to run for 3 seconds and then shuts off, and the conveyor belt sends the cigarette label paper out of the light-shielding protective cover, completing the process.

[0078] Comparative Examples 3-8

[0079] Comparative Examples 3-8 are basically the same as Example 2, except that the ultraviolet irradiation parameters are different, as shown in Table 1 below.

[0080] Table 1.

[0081]

[0082] Methanol Residual Content Determination

[0083] The initial methanol residue in cigarette label paper in the examples, blank examples and comparative examples was determined according to the standard YC / T 207-2014 Determination of Solvent Residue in Cigarette Paper by Headspace-Gas Chromatography / Mass Spectrometry. The methanol residue after being placed at 40 ℃ and 80% humidity for 15 days was also determined. The results are shown in Table 2 below.

[0084] Quality testing of cigarette label paper

[0085] The whiteness of the cigarette label paper in the examples, blank examples and comparative examples was tested by a whiteness meter, and the results are shown in Table 2 below.

[0086] The moisture content of cigarette label paper in the examples, blank examples and comparative examples was tested according to GB / T 462-2008 Paper, Paperboard and Pulp Analysis Samples Determination of Moisture Content. The results are shown in Table 2 below.

[0087] The product's curl was measured using a ruler, and the results are shown in Table 2 below.

[0088] Table 2.

[0089]

[0090] As shown in Table 2, compared to the blank example, the methanol content of the cigarette label paper obtained by the method in Example 2 was reduced by more than 75%. Furthermore, after being placed at 40°C and 80% humidity for 15 days, the methanol content of the treated cigarette label paper did not increase significantly, indicating that it effectively removed methanol from the surface and interior of the cigarette label paper. Simultaneously, the whiteness of the treated cigarette label paper did not decrease significantly (i.e., the paper did not yellow), there was no physical curling deformation (curvature was 0), and the moisture content remained within the normal range of 6.3% (it did not lose water or become brittle due to excessive heating). This demonstrates that this treatment method effectively removes methanol while perfectly protecting the appearance and physical quality of the cigarette label paper.

[0091] In Comparative Example 1, only vacuum ultraviolet treatment was used, which generated a large amount of ozone. This ozone was insufficient to effectively treat the methanol desorbed onto the paper surface within 5 seconds, making it difficult to establish a concentration gradient. Furthermore, the strong oxidizing ozone accumulated on the paper surface severely impacted the quality of the cigarette label paper (whiteness dropped significantly to 84.5%, and noticeable yellowing occurred). In Comparative Example 2, only short-wave ultraviolet treatment was used. While this had a smaller impact on the quality of the cigarette label paper, it lacked sufficient thermal effect to promote the diffusion of deep methanol. This resulted in the release of deep methanol after a period of time, causing a rebound in methanol levels.

[0092] In Comparative Example 3, the irradiation distance was too close; in Comparative Example 6, the irradiation intensity was too high; and in Comparative Example 8, the irradiation time was too long. All of these factors caused thermal shock to penetrate the surface of the paper, resulting in a significant loss of moisture from the cigarette label paper (moisture content dropping below 3.0%). This led to irreversible adverse effects on the paper quality, manifested as severe yellowing (whiteness dropping below 82.5%) and severe curling exceeding 5mm. In Comparative Example 4, the irradiation distance was too far; in Comparative Example 5, the irradiation intensity was too low; and in Comparative Example 7, the irradiation time was too short. These factors failed to generate sufficient thermal shock energy to drive the desorption of methanol from the inside of the cigarette label paper, resulting in poor treatment of deep methanol and causing methanol rebound after a period of time.

[0093] Furthermore, comparisons within the examples show that further control over the proportion of vacuum ultraviolet irradiance, ventilation, and gas replenishment during the processing can further optimize the treatment effect on cigarette label paper. In Example 5, the lack of ventilation and heat dissipation led to excessively high local temperatures and excessive moisture loss (moisture content dropped to 3.5%) in the cigarette label paper, adversely affecting its quality (significant yellowing and 5mm curling). In Example 6, the reduced proportion of vacuum ultraviolet irradiance affected the ozone content and free radical yield on the paper surface, thus impacting the methanol treatment efficiency and resulting in a less effective methanol removal than in Example 2. In Example 7, the introduction of gas replenishment with specific humidity increased the yield of hydroxyl free radicals, further improving the methanol photochemical degradation treatment effect (methanol residue reduced to an extremely low level of 2.5 mg / m³) while maintaining the paper moisture content (6.3%) and zero curling. 2 ).

[0094] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A method for reducing the methanol content of cigarette label paper, characterized in that: Includes the following steps: The cigarette label paper is irradiated simultaneously with vacuum ultraviolet and short-wave ultraviolet light. The irradiation distance between the vacuum ultraviolet and / or short-wave ultraviolet light source and the cigarette label paper is 150–250 mm, and the irradiation intensity is 250–300 mW / cm². 2 The irradiation time is 3 to 10 seconds.

2. The method for reducing the methanol content of cigarette label paper according to claim 1, characterized in that: The initial moisture content of the cigarette label paper before exposure to ultraviolet light is 4% to 8%, and the moisture content of the cigarette label paper after exposure to ultraviolet light is 4% to 8%.

3. A method for reducing the methanol content of cigarette label paper according to claim 1 or 2, characterized in that: During the simultaneous irradiation with vacuum ultraviolet and short-wave ultraviolet light, the cigarette label paper is subjected to ventilation treatment, and the surface temperature of the cigarette label paper does not exceed 40 ℃.

4. The method for reducing the methanol content of cigarette label paper according to claim 3, characterized in that: Under ventilation, the static pressure difference between the upper and lower surfaces of the cigarette label paper is 50-200 Pa, and the airflow direction generated by the ventilation process is parallel to the thickness direction of the cigarette label paper.

5. A method for reducing the methanol content of cigarette label paper according to claim 1 or 2, characterized in that: During the simultaneous irradiation of vacuum ultraviolet and short-wave ultraviolet, the cigarette label paper is subjected to gas replenishment treatment. The gas source is clean air or nitrogen, the relative humidity of the gas source is 20% to 40%, the gas flow rate is 0.15 to 0.3 L / min, and the direction of the gas flow is parallel to the surface of the cigarette label paper.

6. The method for reducing the methanol content of cigarette label paper according to claim 1, characterized in that: Of the ultraviolet irradiance reaching the surface of the cigarette label paper, vacuum ultraviolet irradiance accounts for 8% to 15% of the total ultraviolet irradiance; and within the dealcoholization site range of the cigarette label paper, the non-uniformity of ultraviolet irradiance is less than 5%.

7. The method for reducing the methanol content of cigarette label paper according to claim 6, characterized in that: The vacuum ultraviolet and short-wave ultraviolet are generated by the same synthetic fused silica low-pressure mercury lamp tube, and the hydroxyl content of the quartz tube of the lamp tube is less than 1 ppm; in the initial spectrum of the lamp tube at the emission window, the irradiance at wavelength 185 nm accounts for 25% to 35% of the total irradiance at wavelengths 185 nm and 254 nm.

8. An apparatus for reducing the methanol content of cigarette label paper as described in any one of claims 1 to 7, characterized in that: It includes a conveyor belt for conveying cigarette label paper (1) and having a de-alcoholization site, a light-shielding protective cover (5) set at the de-alcoholization site of the conveyor belt, and an ultraviolet light source (2) set inside the light-shielding protective cover (5) by a bracket (4) and suspended above the de-alcoholization site of the conveyor belt.

9. The apparatus for reducing the methanol content of cigarette label paper according to claim 8, characterized in that: It also includes an exhaust device (3), which includes an air inlet located inside the light-shielding protective cover (5) and an air outlet located outside the light-shielding protective cover (5). The air outlet is connected to a negative pressure fan via a duct.

10. The apparatus for reducing the methanol content of cigarette label paper according to claim 8, characterized in that: It also includes a thermometer for monitoring the surface temperature of the cigarette label paper (1) at the dealcoholization point of the conveyor belt.

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