Preparation method and use method of 3D printed crystal violet lactone temperature monitoring label

Abstract

The invention discloses a preparation method and a use method of a 3D printed crystal violet lactone temperature monitoring label, and belongs to the technical field of material synthesis and indication products. The invention provides a preparation method of a 3D printed crystal violet lactone temperature monitoring label, and monitoring of different temperature thresholds is realized by utilizing a specific temperature phase change principle of an acid solvent and a crystal violet lactone acid color development principle; the label for temperature monitoring is designed in combination with the 3D printing technology, the temperature monitoring label provided by the invention is simple in preparation process flow and controllable in preparation cost, customized production can be realized according to actual monitoring requirements, and multi-scene temperature monitoring demands are met. The temperature monitoring label can provide real-time visual signal response for the temperature change of the transportation and storage environment through the color change of the inner circle.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method and use method of a 3D printed crystal violet lactone temperature monitoring label, belonging to the technical field of material synthesis and indication products. BACKGROUND

[0002] Temperature monitoring is a core and key link to ensure food safety and quality, and its core essence lies in accurately controlling and tracing the temperature of the whole chain of food storage, transportation and sales. Most fresh foods, dairy products, vegetables and other categories are extremely sensitive to temperature fluctuations. Even if they deviate from the appropriate preservation temperature range for a short period of time, they are prone to cause problems such as the rapid growth of microorganisms, the oxidation and loss of nutrients, and the rapid deterioration of inherent flavors, which not only greatly reduces the food value and commodity attributes, but also may induce food safety risks, posing a potential threat to consumer health.

[0003] Traditional temperature monitoring methods rely on electronic sensors, temperature recorders and other equipment, which can record temperature data continuously, but have the outstanding defects of high hardware cost, cumbersome installation and operation, inability to intuitively feedback whether the temperature is out of range, difficulty in achieving independent monitoring and tracing of individual foods, and poor adaptability in bulk food, short-distance distribution, small-batch circulation and other scenarios, which cannot meet the actual application needs of the food industry for temperature monitoring "low cost, visualization, wide coverage, traceability".

[0004] Crystal violet lactone, as a classic leuco dye, its core color change characteristic is closely related to the molecular structure transformation induced by acidic environment. Broadly Lewis acid (proton of weak acid or metal cation) abstracts electron from crystal violet lactone, inducing its lactone ring-opening to expand its conjugated system and develop color. The literature "Irreversible temperature indicator based cellulose membranes conjugated with leuco-dye pigment" discloses the preparation of a thermochromic bilayer film using cellulose acetate, crystal violet lactone and salicylic acid, which has irreversible color change, but this scheme can only be used for fixed temperature points (15 ℃ or 35 ℃), cannot realize multi-threshold, series temperature monitoring by simple method, cannot realize subzero temperature monitoring, and is difficult to meet the whole chain temperature monitoring needs from cold storage to ultra-low temperature freezing. In addition, this structure has obvious shortcomings in practical application. The acid agent needs to diffuse through the upper film to contact and trigger the color developing layer, which has low efficiency and is greatly affected by the tightness of the film-to-film fit, resulting in delayed color response, uneven color change and weak color intensity.

[0005] With the continuous innovation of intelligent manufacturing technology, 3D printing technology has gained widespread application and rapid development in the field of functional device fabrication due to its significant advantages such as flexible customization, high molding accuracy, low material cost, and simple production process. However, there are currently few applications of 3D printing technology in temperature detection labels.

[0006] Therefore, developing a 3D-printed crystal violet lactone temperature monitoring tag that can adjust the temperature detection range according to actual application scenarios has extremely high practical and economic value. Summary of the Invention

[0007] To address the aforementioned issues, this invention proposes a method for fabricating a 3D-printed crystal violet lactone temperature monitoring tag. Utilizing the phase change of an acidic solvent at a specific temperature and the acidic color development principle of crystal violet lactone, a specific temperature threshold can be monitored. Combined with 3D printing technology, a tag for temperature monitoring is designed. The temperature monitoring tag provided by this invention features a simple fabrication process, controllable manufacturing costs, and can be customized to meet specific monitoring needs, adapting to various temperature monitoring scenarios. The temperature monitoring tag of this invention provides a real-time visual signal response to changes in the temperature of the transportation and storage environment through changes in the color of its inner circle.

[0008] The first objective of this invention is to provide a method for using a 3D-printed crystal violet lactone temperature monitoring label, which monitors the runaway status of product storage temperature by measuring the proportion of discolored area in the inner circle of the 3D-printed crystal violet lactone temperature monitoring label. If the discoloration area of ​​the inner circle is less than 15%, it indicates that the product storage temperature is not out of control and the product storage is stable. If the discoloration area of ​​the inner circle is 15% to 20%, it indicates that the product storage temperature fluctuates, and it is necessary to confirm whether the product quality has deteriorated. If the discoloration area of ​​the inner circle is greater than 20%, it indicates that the product storage temperature is out of control and the product quality has deteriorated irreversibly. The preparation method of the 3D printed crystal violet lactone temperature monitoring tag includes the following steps: (1) Cellulose acetate is dissolved in acetone and heated and stirred to obtain a cellulose acetate-acetone solution; after cooling the cellulose acetate-acetone solution, crystal violet lactone is added, and after stirring, glycerol is added and stirred to obtain a mixed solution; the mixed solution is poured into the inner circular area of ​​the label mold to form a film; (2) The acidic solution was frozen and sealed in the outer ring area of ​​the label mold to obtain a 3D printed crystal violet lactone temperature monitoring label; The label mold is an integrated mold prepared by a 3D printing technology, and the structure comprises an inner circle area, a slope and an outer ring area, and the inner circle area and the outer ring area are connected through the slope; the radius of the inner circle area is 6-8 mm, the ring width of the outer ring area is 5-7 mm, the slope ratio of the connecting part is 1:0.8-1.2, and the slope angle is 40°-50°. The acidic solution is an acidic binary mixed solvent composed of methyl methacrylic acid, tetradecane and n-octanoic acid adjusted by dilute hydrochloric acid, or an acidic ethylene glycol aqueous solution adjusted by dilute hydrochloric acid; The monitoring product storage temperature is-68℃-15℃.

[0009] In an embodiment, the inner circle color change area ratio in the 3D printed crystal violet lactone temperature monitoring label is used to monitor the out-of-control situation of the environmental temperature; Slight coloration (area <15%): indicating that the temperature fluctuation is slight and short, and the product under this storage condition belongs to the acceptable range; Partial coloration (area 15%-20%): indicating that the temperature has been out of control for a certain period of time, and the product under this storage condition has reached the critical window of quality safety, which needs to be paid attention to; Significant coloration / complete coloration (area >20%): indicating that it is in a clear high temperature exposure risk, and the product under this storage condition has experienced serious or long-term temperature out-of-control, and the quality has been irreversibly deteriorated, which is not recommended to continue to use; The preparation method of the 3D printed crystal violet lactone temperature monitoring label comprises the following steps: (1) Dissolve cellulose acetate in acetone, heat and stir to dissolve to obtain a cellulose acetate-acetone solution; after the cellulose acetate-acetone solution is cooled, crystal violet lactone is added, stirred and then glycerol is added, and the mixed solution is poured into the inner circle area of the label mold to form a film; (2) Freeze and package the acidic solution in the outer ring area of the label mold to obtain a 3D printed crystal violet lactone temperature monitoring label; The label mold is an integrated mold prepared by a 3D printing technology, and the structure comprises an inner circle area and an outer ring area, wherein the radius of the inner circle area is 6-8 mm, the ring width of the outer ring area is 5-7 mm, and the slope ratio of the connecting part is 1:0.5-1.8, and the slope angle is 30°-60°.

[0010] In an embodiment, the slope angle is 40°-50°, and the slope ratio is 1:0.8-1.2.

[0011] In an embodiment, when the slope angle is 30°, the slope ratio is 1:0.58; when the slope angle is 45°, the slope ratio is 1:1; and when the slope angle is 60°, the slope ratio is 1:1.73.

[0012] In an embodiment, the range of temperature monitoring is changed by changing the acidic solution; the acidic solution comprises methacrylic acid, an acidic binary mixed solvent consisting of tetradecane and n-octanoic acid adjusted by dilute hydrochloric acid, an acidic ethylene glycol aqueous solution adjusted by dilute hydrochloric acid; When the 3D-printed crystal violet lactone temperature monitoring label is used to monitor 15℃, the acidic solution is methacrylic acid; When the 3D-printed crystal violet lactone temperature monitoring label is used to monitor 4℃, the acidic solution is a binary mixed solvent consisting of tetradecane and n-octanoic acid adjusted by dilute hydrochloric acid; When the 3D-printed crystal violet lactone temperature monitoring label is used to monitor -68 ℃ below zero, the acidic solution is an ethylene glycol aqueous solution adjusted by dilute hydrochloric acid.

[0013] In an embodiment, the volume fraction of tetradecane in the binary mixed solvent is 48% to 52%; The volume fraction of ethylene glycol in the ethylene glycol aqueous solution adjusted by dilute hydrochloric acid is 0 to 100%.

[0014] In an embodiment, the amount of cellulose acetate, acetone, crystal violet lactone and glycerol in step (1) is 1 to 3 g: 20 to 50 mL: 0.25 to 1 g: 500 to 1000 mL.

[0015] In an embodiment, the heating and stirring in step (1) is 65 to 75℃, 400 to 800 rpm stirring for 10 to 30 min.

[0016] In an embodiment, the amount of mixed solution pouring in step (1) is 0.5 to 2 mL.

[0017] In an embodiment, the amount of acidic solution packaged in step (2) is 0.5 to 1.5 mL.

[0018] The second object of the present application is to provide a preparation method of a 3D-printed crystal violet lactone temperature monitoring label, comprising the steps of: (1) Cellulose acetate is dissolved in acetone, heated and stirred to dissolve to obtain a cellulose acetate-acetone solution; after the cellulose acetate-acetone solution is cooled, crystal violet lactone is added, stirred, then glycerol is added, and stirred to obtain a mixed solution; the mixed solution is poured into the inner circular area of the label mold to form a film; (2) The acidic solution is frozen and packaged in the outer annular area of the label mold to obtain a 3D-printed crystal violet lactone temperature monitoring label; The label mold is an integrated mold prepared by 3D printing technology, and the structure comprises an inner circle area, a slope and an outer ring area, and the inner circle area and the outer ring area are connected through the slope; the radius of the inner circle area is 6-8 mm, the ring width of the outer ring area is 5-7 mm, the slope ratio of the connecting part is 1:0.5-1.8, and the slope angle is 30°-60°. The acidic solution is methacrylic acid, an acidic binary mixed solvent composed of tetradecane and n-octanoic acid adjusted by dilute hydrochloric acid, or an acidic ethylene glycol aqueous solution adjusted by dilute hydrochloric acid.

[0019] In an embodiment, when the slope angle is 30°, the slope ratio is 1:0.58; when the slope angle is 45°, the slope ratio is 1:1; and when the slope angle is 60°, the slope ratio is 1:1.73.

[0020] In an embodiment, the range of temperature monitoring is changed by changing the acidic solution; the acidic solution comprises methacrylic acid, an acidic binary mixed solvent composed of tetradecane and n-octanoic acid adjusted by dilute hydrochloric acid, and an acidic ethylene glycol aqueous solution adjusted by dilute hydrochloric acid. When the 3D-printed crystal violet lactone temperature monitoring label is used to monitor 15℃, the acidic solution is methacrylic acid. When the 3D-printed crystal violet lactone temperature monitoring label is used to monitor 4℃, the acidic solution is a binary mixed solvent composed of tetradecane and n-octanoic acid adjusted by dilute hydrochloric acid. When the 3D-printed crystal violet lactone temperature monitoring label is used to monitor -68℃ below zero, the acidic solution is an ethylene glycol aqueous solution adjusted by dilute hydrochloric acid.

[0021] In an embodiment, the volume fraction of tetradecane in the binary mixed solvent is 48%-52%. The volume fraction of ethylene glycol in the ethylene glycol aqueous solution adjusted by dilute hydrochloric acid is 0-100%.

[0022] In an embodiment, the amount of cellulose acetate, acetone, crystal violet lactone and glycerol in step (1) is 1-3 g: 20-50 mL: 0.25-1 g: 500-1000 mL.

[0023] In an embodiment, the heating and stirring in step (1) is 65-75℃, 400-800 rpm stirring for 10-30 min.

[0024] In an embodiment, the amount of mixed solution pouring in step (1) is 0.5-2 mL.

[0025] In an embodiment, the amount of acidic solution packaged in step (2) is 0.5-1.5 mL.

[0026] A third object of the present application is to provide the 3D printed crystal violet lactone temperature monitoring label prepared by the above method.

[0027] A fourth object of the present application is to provide the application of the above 3D printed crystal violet lactone temperature monitoring label in temperature monitoring of food, drug or biological product transportation and storage.

[0028] Advantages of the present application (1) The present application combines the specific temperature phase change characteristics of the acid solvent and the acid-induced coloration principle of crystal violet lactone, realizes the monitoring of different temperature thresholds, and provides intuitive and clear visual temperature warning signals.

[0029] (2) The color change of the inner circle of the label in the present application is an irreversible process, which can effectively prevent the temperature monitoring data tampering behavior that may occur during food storage and transportation, and provide a more reliable basis for temperature monitoring.

[0030] (3) The present application relies on 3D printing technology to integrally prepare the label mold, the process flow is simple, the cost is controllable, and the shape, size and structure of the label can be flexibly adjusted according to actual monitoring needs, supporting customized production of multiple scenes and multiple temperature thresholds.

[0031] (4) The present application is suitable for temperature monitoring during food transportation and storage, and can be applied to food packaging to reflect real-time environmental temperature changes, play a warning role for food quality, and ensure product quality and safety. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is a schematic diagram of the half-section size of the mold, the structure of the 3D printed temperature monitoring label mold and the actual photo.

[0033] Figure 2 It is a color change image of crystal violet lactone film before and after being affected by acid reagent.

[0034] Figure 3 It is a scanning electron microscope image of the color change image of crystal violet lactone film before and after being affected by acid reagent.

[0035] Figure 4 It is an infrared image of the color change image of crystal violet lactone film before and after being affected by acid reagent.

[0036] Figure 5 It is a DSC curve of the 15℃ temperature monitoring label outer ring acid solvent methyl methacrylate.

[0037] Figure 6 It is a schematic diagram of the temperature monitoring label construction and an actual photo of the 15℃ temperature monitoring label placed at 4℃.

[0038] Figure 7Color change of 15℃ temperature monitoring label in temperature runaway process.

[0039] Figure 8 Images of 15℃ temperature monitoring label at different temperature points.

[0040] Figure 9 Temperature runaway monitoring results of 15℃ temperature monitoring label.

[0041] Figure 10 DSC curve of outer ring acidic solution of 4℃ temperature monitoring label.

[0042] Figure 11 Freezing point curve and phase diagram of outer ring acidic ethanol solution of 0~-68℃ temperature monitoring label. DETAILED DESCRIPTION

[0043] The preferred embodiments of the present application are described below, and it should be understood that the embodiments are for better explaining the present application and are not used to limit the present application.

[0044] The specific slope surface designed at the connection between the inner circle and the outer ring of the integrated mold in the present application creates an active and directional fluid channel. When the temperature reaches the threshold value, the slope surface can effectively guide the acid liquid to flow quickly and centrally to the inner circle color developing film after the outer ring acid agent melts, ensuring sufficient, uniform and reproducible contact between the acid agent and the color developing component, and further improving the color developing effect.

[0045] Compared with traditional molding, coating and other processes, the 3D printing technology can accurately control the shape structure, thickness size and internal functional layer distribution of the temperature monitoring label according to the needs of the actual application scene, realize uniform dispersion and accurate arrangement of functional materials, and does not need to prepare complex molds, effectively shortening the product research and development and large-scale production cycle. At the same time, its flexible forming capacity can adapt to the morphological characteristics and use requirements of different food packaging, successfully solving the technical pain points of single shape of traditional temperature label, low adhesion to packaging and limited adaptation scene. What is particularly important is that combined with the flexible replaceable acidic solution system, the 3D printing technology provides an innovative and efficient implementation way for conveniently preparing a series of monitoring labels covering different temperature thresholds.

[0046] The combination of the crystal violet color change principle and the precise design of 3D printed labels for preparing temperature monitoring labels can ensure quick and stable color development of the label when the critical temperature is reached, and the color developing trace is permanently retained, thereby providing intuitive and accurate judgment basis for whether the temperature in the whole chain transportation of food exceeds the standard.

[0047] Raw materials used in the examples: Cellulose acetate and crystal violet lactone were purchased from Aladdin Reagent Network.

[0048] Test method: Test of color change Add methacrylic acid to the crystal violet lactone film to create an acidic environment, and take pictures of the color development of the crystal violet lactone film under acidic conditions.

[0049] Place the temperature monitoring label in the environmental temperature chamber respectively, and record the label change image at different temperature points.

[0050] Use the prepared temperature monitoring label to monitor the temperature in the environmental temperature chamber, and record the label change image.

[0051] Test of DSC curve: Test the DSC of the outer ring acid reagent methacrylic acid, the test conditions are as follows: the temperature range is 0 ℃ to 30 ℃, the test amount is 10 mg, the heating rate and the cooling rate are both 10 ℃ / min, and the thermodynamic phase change characteristics of the prepared material are explored.

[0052] Test of scanning electron microscope: Use scanning electron microscope to take pictures of the planar and cross-sectional morphology changes of the crystal violet lactone film before and after color change.

[0053] Test of infrared: Use infrared to characterize respectively and explore the functional group changes of the crystal violet lactone film before and after color change.

[0054] Example 1 1. A 3D printed crystal violet lactone temperature monitoring label, the preparation method comprising the steps of: (1) Label mold design and printing: Use Blender software to design a circular label mold, which consists of an inner circle and an outer ring. The radius of the inner circle is 6 mm, the ring width of the outer ring is 5 mm, the slope ratio of the connecting part is 1:1, and the slope angle is 45° (see Figure 1 ) for specific dimensions); the mold is provided with a guide slope at the connecting part of the inner circle and the outer ring, which is used to guide the directional flow of the outer ring acid solution when it melts, so as to ensure sufficient contact with the temperature-sensitive film, thereby optimizing the reliability and consistency of the color development reaction. The designed mold is 3D printed with polylactic acid material; (2) Preparation of crystal violet lactone film: 2.5 g of cellulose acetate is slowly added to 40 mL of acetone, stirred at 70 ℃ and 600 rpm for 10 min, until the cellulose acetate is completely dissolved (forming a clear, slightly viscous solution), obtaining a cellulose acetate-acetone solution; Cellulose acetate-acetone solution was cooled, 0.25 g crystal violet lactone was added, stirred at 600 rpm for 30 min, 500 μL of glycerol was added dropwise, and stirred at 600 rpm for 24 h to obtain a mixed solution; 1 mL of the mixed solution was uniformly poured into the inner circular area of the label mold, gently shaken to flow flat, and a uniform thin layer was formed; the mold was placed in a fume hood at room temperature, and after the acetone was naturally volatilized for about 30 min, a crystal violet lactone film (white film) was formed; (3) Outer ring solvent loading According to the temperature threshold (15 ℃), methacrylic acid was selected as the outer ring acidic solvent, and was frozen at-20 ℃, and was packaged in the outer ring area of the label mold, with a packaging amount of 1 mL, to obtain a crystal violet lactone temperature monitoring label suitable for 3D printing at 15 ℃.

[0055] 2. Performance detection of 3D printed crystal violet lactone temperature monitoring label (1) Circular label mold The structure and actual photo of the circular label mold are shown in Figure 1 .

[0056] (2) Crystal violet lactone film Take the crystal violet lactone film prepared in 1, add methacrylic acid to construct an acidic environment, and take color developing photos, scanning electron microscope tests and infrared tests, respectively. The test results are as follows: The color change images of the crystal violet lactone film before and after being affected by the acidic reagent are shown in Figure 2 , and the results show that after adding methacrylic acid, the crystal violet lactone film changes from white to blue-violet; The scanning electron microscope images of the crystal violet lactone film before and after being affected by the acidic reagent are shown in Figure 3 , and the results show that the crystal violet lactone film is affected by the environmental pH, and the surface morphology changes obviously; The infrared images of the crystal violet lactone film before and after being affected by the acidic reagent are shown in Figure 4 , and the results show that the crystal violet lactone film is affected by the environmental pH, and the functional groups change obviously, and the lactone ring is converted to carboxyl.

[0057] (3) Methacrylic acid The DSC curve of methacrylic acid is shown in Figure 5 , and the results show that the melting process of the material is between 10 and 20 ℃, and the melting point is 15 ℃, which can meet the subsequent experimental requirements.

[0058] (4) Temperature monitoring label The prepared 3D-printed crystal violet lactone temperature monitoring label at 15℃ can cause the outer ring solvent to melt and diffuse to the inner circle during the temperature runaway process (long time temperature exceeding 15℃), so that the crystal violet lactone film is in an acidic environment, and irreversible color change from white to blue occurs. The construction schematic and actual photo of the temperature monitoring label are shown in Figure 6 .

[0059] The 3D-printed crystal violet lactone temperature monitoring label at 15℃ was placed at 4℃ and 25℃, respectively, and then cooled to 4℃ again. The change process is shown in Figure 7 . The results show that during the temperature rising process, the prepared temperature monitoring label changes from white to blue, and even after recooling, the prepared temperature monitoring label still remains blue, which can effectively prevent data tampering behavior during the temperature monitoring process.

[0060] The 3D-printed crystal violet lactone temperature monitoring label at 15℃ was placed in an environmental temperature test box with a temperature rising from 14℃ to 26℃ at a speed of 2℃ / min. The color change of the label during the temperature rising process was recorded, and the results are shown in Figure 8 . The results show that as the outer ring solvent melts, the inner circle of the label gradually changes from white to blue.

[0061] The 3D-printed crystal violet lactone temperature monitoring label at 15℃ was placed in a temperature runaway condition for detection, and the results are shown in Figure 9 . As the temperature runaway process prolongs, the outer layer solvent gradually melts, and the inner circle of the label gradually changes from white to blue.

[0062] Based on the quantitative relationship between the color change area and the cumulative degree of temperature exposure, the following visual warning classification for product quality and safety can be established: Slight coloration (area < 15%): indicating that the product has experienced slight and short temperature fluctuations, which is within the acceptable range; Partial coloration (area 15%~20%): indicating that the product has experienced a certain time of temperature runaway, reaching the critical window of quality and safety, which needs attention; Significant coloration / complete coloration (area > 20%): indicating that the product is in a clear high-temperature exposure risk and has experienced severe or long-term temperature runaway, and the quality may have undergone irreversible deterioration, which is not recommended for continued use; Figure 9 At 3 h, a large area of blue color appeared.

[0063] Comparative Example 1 On the basis of Example 1, other 3D printing materials, acrylonitrile-butadiene-styrene and ethylene glycol modified polyethylene terephthalate, were used to replace polylactic acid, respectively, and the remaining steps were kept consistent to detect the coloration effect.

[0064] The results show that polylactic acid exhibits excellent interlayer bonding force and dimensional stability during printing, and the surface finish of the formed part is significantly better than that of other comparative materials. The low warping characteristics of the material effectively ensure the forming precision of large-size components, and almost no irritating odor is generated during printing, which reflects good environmental friendliness. In addition, polylactic acid also has certain acid resistance, which can meet the requirements of subsequent experiments on material corrosion resistance.

[0065] However, the labels printed with acrylonitrile-butadiene-styrene or ethylene glycol-modified polyethylene terephthalate as raw materials were corroded to varying degrees on the mold surface after adding the external acidic solvent, which prevented the experiment from continuing.

[0066] In contrast, polylactic acid (PLA) material was selected because of its good chemical resistance to the acidic solution, which ensures the structural integrity and dimensional stability of the mold throughout the experiment. As a commonly used 3D printing material, PLA has high printing precision, good mechanical properties of formed parts, small thermal deformation, low temperature resistance, and other advantages, making it particularly suitable for preparing functional molds with fine structure and dimensional stability requirements, and can also meet the demand for ultra-low temperature monitoring. PLA material itself provides a variety of color and transparency options (such as high transparency, white or other colors), which helps to further enhance the visual contrast and warning effect of the label.

[0067] Comparative Example 2 Based on Example 1, the stirring temperature in step (2) was changed to 50 ℃, 60 ℃ and 80 ℃, respectively, and the remaining steps were consistent with Example 1. The film effect was detected.

[0068] The results show that when the heating and stirring temperature is 70℃, the solubility of cellulose acetate is good, and the dispersion is relatively uniform, which can form a clear and slightly viscous solution. Under the conditions of 50℃ and 60℃, the cellulose acetate solution is not completely dissolved, and there is white flocculent precipitate. When the heating and stirring temperature is 80 ℃, the excess acetone volatilizes, which affects the actual ratio of cellulose acetate-acetone solution, and the film forming effect is not good, and the film surface is prone to cracks.

[0069] Comparative Example 3 Based on Example 1, other acids (acrylic acid) were used to replace methacrylic acid, and the remaining steps were consistent. The color development effect was detected.

[0070] The results show that acrylic acid cannot effectively trigger the expected temperature monitoring function. Due to the significant difference between the physical properties of acrylic acid and methacrylic acid, the melting point of acrylic acid (about 13°C) is close to but slightly lower than the target threshold of 15°C, and its volatility is stronger. In practical applications, acrylic acid has partially volatilized or undergone phase transition before reaching the precise monitoring threshold, making it impossible to accurately monitor the temperature threshold.

[0071] Comparative Example 4 The temperature label was prepared according to the method in the reference "Irreversible temperature indicator based cellulose membranes conjugated with leuco-dye pigment".

[0072] Comparing the temperature labels of Comparative Example 4 and Example 1, it is found that the method in the reference referred to by Comparative Example 4 produces a physically overlapped double-layer film structure, with the acid agent layer (containing solid acid and solvent) and the color developing layer (CVL film) only in surface contact. This structure has obvious shortcomings in practical applications: its color developing process relies on passive diffusion of the acid agent through the upper film, which is inefficient and significantly affected by the tightness of the film-to-film fit, directly leading to response delay, uneven color development, and even failure. At the same time, this mechanism is sluggish in temperature response, and after reaching the set temperature, a long diffusion process is required to trigger color change, affecting the sensitivity of temperature response. Due to the non-fixed diffusion path of the acid agent and environmental interference, this structure has low reliability in responding to a specific temperature threshold, making it difficult to achieve the precise, fast, and reproducible monitoring effect based on the integrated mold in Example 1.

[0073] The label of Example 1, however, has a specific slope surface designed at the connection between the inner circle and the outer ring of the integrated mold, creating an active and directional fluid channel. When the temperature reaches the threshold, the outer ring acid melts, and the slope surface can effectively guide the acid liquid to flow quickly and centrally to the inner circle color developing film, ensuring sufficient, uniform, and reproducible contact between the acid agent and the color developing components. This design physically overcomes the defect of relying on random diffusion in Comparative Example 4 and is a key structural innovation for achieving fast start, high sensitivity, and reliable color development.

[0074] Comparative Example 5 The reversible temperature-sensing material composed of crystal violet lactone and bisphenol A was prepared according to the patent (CN119060585B), and was printed into a temperature label with the help of a two-dimensional code ellipse.

[0075] Comparing the temperature label of Example 1 with that of Comparative Example 5, it is found that there is a fundamental difference between the two in the monitoring mechanism. The two-dimensional code label prepared in Comparative Example 5 relies on the reversible thermochromic properties of the crystal violet lactone-bisphenol A system; its irreversible mechanism is that the two-dimensional code pattern is blurred due to the heating, resulting in the inability to identify the result, which is an indirect and functional irreversible based on the determination of the readability of the pattern. This method is greatly affected by the observation angle, light, pattern printing quality and color contrast. The label of Example 1 is based on the irreversible ring-opening reaction of the lactone ring of crystal violet lactone under the action of acid, which produces a permanent change in the color of the material, which is intrinsic and objectively existing, and its interpretation is intuitive and reliable.

[0076] Comparative Example 6 On the basis of Example 1, the slope of the inclined surface at the connection between the inner circle and the outer ring in the 3D printing mold is changed to 30° and 60° The results show that when the slope of the inclined surface is 30°, the color development response is delayed due to the slow slope and insufficient driving force for liquid diffusion, and the response time is delayed by 10 minutes compared with the actual temperature change. When the slope of the inclined surface is 60°, the inclined surface is too steep, resulting in rapid acid accumulation, rapid color development initiation but uneven diffusion, and rapid initial growth of the color development area.

[0077] Example 2 On the basis of Example 1, a crystal violet lactone temperature monitoring label suitable for 3D printing at 4℃ is prepared, which is different in that the outer ring solvent is changed to an acidic binary mixed solvent composed of tetradecane and n-octanoic acid adjusted by dilute hydrochloric acid.

[0078] 1. Outer ring solvent loading According to the temperature threshold (4℃), tetradecane and n-octanoic acid are compounded into an outer ring solvent with different volume ratios, and the volume fraction of tetradecane is 48%, 50% and 52%. The pH of the mixed solution is adjusted to less than 5 using 0.01 mol / L dilute hydrochloric acid, which is confirmed by pH test paper. The prepared acidic solvent is frozen at-20℃, and is packaged in the outer ring area of the label mold with a packaging amount of 1 ml, to obtain a crystal violet lactone temperature monitoring label suitable for 3D printing at 4℃.

[0079] 2. Performance detection The DSC curves of the acidic binary mixed solvents composed of tetradecane and n-octanoic acid with different volume ratios are shown in Figure 10 The results show that the melting process of the material is between 0 and 10℃, and when the volume fraction of tetradecane is 50%, the melting point of the mixed solvent is closest to 4℃, and the temperature label prepared using this acidic solution can meet the subsequent experimental requirements.

[0080] Example 3 On the basis of embodiment 1, a crystal violet lactone temperature monitoring label suitable for 3D printing at each temperature point below zero (0~-68 ℃) is prepared, the difference lies in changing the outer ring solvent: glycol aqueous solution adjusted by dilute hydrochloric acid 1. Outer ring solvent load According to different temperature thresholds below zero, glycol aqueous solution is prepared, 0.01 mol / L dilute hydrochloric acid is used to adjust the pH of the mixed solution to less than 5, and pH test paper is used for confirmation. The prepared acidic solvent is frozen at-80 ℃, and is packaged in the outer ring area of the label mold, the packaging amount is 1 ml, and a crystal violet lactone temperature monitoring label suitable for 3D printing at each temperature point below zero (0~-68 ℃) is obtained.

[0081] 2. Performance test The freezing point of the glycol-water mixed solution with different volume fractions is determined by using a glycol freezing point instrument, and the results are shown in Figure 11 The experiment shows that the freezing point of the solution decreases regularly with the increase of the volume fraction of glycol, and the effective control range covers 0 ℃ to-68 ℃, and the corresponding solution ratio can be accurately selected according to the target temperature threshold.

[0082] For example, for a temperature threshold of-30 ℃, a glycol aqueous solution with a volume fraction of 47.8% can be selected for subsequent experiments. Figure 11 The phase diagram analysis result provides further theoretical basis for determining the corresponding relationship between the freezing point and the solution composition.

[0083] Although the present application has been disclosed as above with preferred embodiments, it is not intended to limit the present application, and anyone skilled in the art can make various modifications and modifications without departing from the spirit and scope of the present application, therefore the protection scope of the present application should be limited by the claims.

Claims

1. A method for using a 3D-printed crystal violet lactone temperature monitoring tag, characterized in that, By using the proportion of discolored area in the inner circle of a 3D-printed crystal violet lactone temperature monitoring label, the uncontrolled state of product storage temperature can be monitored. If the discoloration area of ​​the inner circle is less than 15%, it indicates that the product storage temperature is not out of control and the product storage is stable. If the discoloration area of ​​the inner circle is 15% to 20%, it indicates that the product storage temperature fluctuates, and it is necessary to confirm whether the product quality has deteriorated. If the discoloration area of ​​the inner circle is greater than 20%, it indicates that the product storage temperature is out of control and the product quality has deteriorated irreversibly. The preparation method of the 3D printed crystal violet lactone temperature monitoring tag includes the following steps: (1) Cellulose acetate is dissolved in acetone and heated and stirred to obtain a cellulose acetate-acetone solution; after cooling the cellulose acetate-acetone solution, crystal violet lactone is added, and after stirring, glycerol is added and stirred to obtain a mixed solution; the mixed solution is poured into the inner circular area of ​​the label mold to form a film; (2) The acidic solution was frozen and sealed in the outer ring area of ​​the label mold to obtain a 3D printed crystal violet lactone temperature monitoring label; The label mold is an integrated mold made by 3D printing technology. Its structure includes an inner circular area, an inclined surface and an outer ring area. The inner circular area and the outer ring area are connected by the inclined surface. The radius of the inner circular area is 6~8 mm, the ring width of the outer ring area is 5~7 mm, the slope ratio of the inclined surface at the connection is 1:0.8~1.2, and the slope angle is 40°~50°. The acidic solution is methacrylic acid, an acidic binary mixed solvent consisting of tetradecane and n-octanoic acid adjusted by dilute hydrochloric acid, or an acidic aqueous solution of ethylene glycol adjusted by dilute hydrochloric acid. The product storage temperature is monitored to be between -68℃ and 15℃.

2. The method of use according to claim 1, characterized in that, By changing the acidic solution, the monitoring range of product storage temperature can be altered; Among them, when the storage temperature of the product detected by the 3D printed crystal violet lactone temperature monitoring label is 15℃, the acidic solution is methacrylic acid; When the storage temperature of the product detected by the 3D printed crystal violet lactone temperature monitoring label is 4℃, the acidic solution is a binary mixed solvent composed of tetradecane and n-octanoic acid adjusted by dilute hydrochloric acid. When the 3D-printed crystal violet lactone temperature monitoring label detects the product storage temperature of 0~-68 ℃, the acidic solution is an ethylene glycol aqueous solution adjusted by dilute hydrochloric acid.

3. The method of use according to claim 2, characterized in that, The volume fraction of tetradecane in the binary mixed solvent is 48%~52%; The volume fraction of ethylene glycol in an aqueous solution is 0-100%.

4. The method of use according to claim 1, characterized in that, In step (1), the ratio of cellulose acetate, acetone, crystal violet lactone and glycerol is 1~3 g: 20~50 mL: 0.25~1 g: 500~1000 mL.

5. The method of use according to claim 1, characterized in that, In step (1), the heating and stirring are carried out at 65~75℃ and 400~800 rpm for 10~30 min.

6. The method of use according to claim 1, characterized in that, The amount of mixed solution used in step (1) is 0.5~2 mL.

7. The method of use according to claim 1, characterized in that, In step (2), the amount of acidic solution packaged is 0.5~1.5 mL.

8. A method for preparing a 3D-printed crystal violet lactone temperature monitoring tag, characterized in that, Including the following steps: (1) Cellulose acetate is dissolved in acetone and heated and stirred to obtain a cellulose acetate-acetone solution; after cooling the cellulose acetate-acetone solution, crystal violet lactone is added, and after stirring, glycerol is added and stirred to obtain a mixed solution; the mixed solution is poured into the inner circular area of ​​the label mold to form a film; (2) The acidic solution was frozen and sealed in the outer ring area of ​​the label mold to obtain a 3D printed crystal violet lactone temperature monitoring label; The label mold is an integrated mold made by 3D printing technology. Its structure includes an inner circular area, an inclined surface and an outer ring area. The inner circular area and the outer ring area are connected by the inclined surface. The radius of the inner circular area is 6~8 mm, the ring width of the outer ring area is 5~7 mm, the slope ratio of the inclined surface at the connection is 1:0.8~1.2, and the slope angle is 40°~50°. The acidic solution is a mixture of methacrylic acid, a binary acidic solvent consisting of tetradecane and octanoic acid adjusted with dilute hydrochloric acid, or an acidic aqueous solution of ethylene glycol adjusted with dilute hydrochloric acid.

9. The 3D-printed crystal violet lactone temperature monitoring tag prepared by the preparation method of claim 8.

10. The application of the 3D-printed crystal violet lactone temperature monitoring tag of claim 9 in monitoring the transport and storage temperature of food, pharmaceuticals or biological products.

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