Molecular migration-resistant heat transfer printing ink and preparation method, application method and performance evaluation method thereof

Abstract

The invention belongs to the technical field of ink synthesis, and relates to heat transfer printing ink, in particular to a preparation method, an application method and a performance evaluation method of molecular migration resistant heat transfer printing ink. The printing ink is prepared by taking polymethyl methacrylate (PMMA) resin, polystyrene (PS) resin and carbon black as main raw materials through a grinding process; the number-average molecular weight of the polymethyl methacrylate PMMA resin is 300,000-400,000, and the polymethyl methacrylate PMMA resin is obtained by carrying out free radical polymerization reaction on a methyl methacrylate MMA monomer serving as a main raw material under the action of an initiator. The ink has excellent molecular migration resistance, heat resistance and chemical stability, and can meet strict requirements of industries such as medicine and food on heat transfer printing ink. After being prepared into a heat transfer printing film, the ink is printed on a product package through heat transfer printing, is convenient and rapid, and is easy for industrial production. According to the performance evaluation method provided by the invention, the molecular migration resistance of the ink can be truly and effectively evaluated through a simulation test of an actual application scene.

Description

Technical Field

[0001] The invention belongs to the technical field of ink synthesis, relates to a thermal transfer ink, and in particular to a preparation method, an application method and a performance evaluation method of a molecular migration resistant thermal transfer ink. Background Art

[0002] Thermal transfer ink is a kind of ink that transfers graphic information to the surface of the substrate through the transfer film at high temperature. In the pharmaceutical, food and other industries, thermal transfer ink is widely used in the identification and decoration of products such as infusion soft bags and drug packaging.

[0003] For example, Chinese invention patent application CN117924995A provides a thermal transfer ink and its preparation method and the application of the ink in the field of printing. The patent application shows that thermal transfer technology has the characteristics of green environmental protection, simple operation, no need for plate making, one-time drawing of multi-color patterns, no need for color matching, bright colors of images and texts after transfer, rich layers and high precision, which greatly improves the added value and grade of products and is widely used in industrial products such as cosmetics, food packaging, glass bottles, stainless steel kettles, electrical appliances and toys. Therefore, the patent application adopts a thermal transfer ink comprising the following components by mass: 3 to 15 parts of polymer materials, 6 to 45 parts of pigments, 0.5 to 10 parts of additives, and 50 to 85 parts of solvents, wherein the polymer materials include chloroacetate resins, polymers and cellulose materials, and the chloroacetate resins are selected from at least one of ternary chloroacetate resins, ternary hydroxychloroacetate resins, and ternary carboxylchloroacetate resins; the cellulose materials are selected from at least one of ester cellulose and ether cellulose. The benzene-free and ketone-free ink in the application document can retain good fineness, viscosity, and low solvent residue, and does not contain harmful ketone and benzene solvents. It is more environmentally friendly and safe, and can make thermal transfer printed products completely free of unpleasant odors, meeting higher-level requirements.

[0004] However, in addition to the common environmental and safety issues mentioned above, traditional thermal transfer inks are prone to molecular migration during use, resulting in blurred graphic information and reduced color fastness, which will also seriously affect product quality and safety. In addition, the evaluation method for the molecular mobility in inks is also urgently needed to be developed. Summary of the invention

[0005] Based on this, the purpose of the present invention is to provide a molecular migration resistant thermal transfer ink, which has excellent molecular migration resistance and chemical stability and can meet the strict requirements of the pharmaceutical, food and other industries for thermal transfer inks.

[0006] The present invention also provides a preparation method, an application method and a performance evaluation method of the molecular migration resistant thermal transfer ink.

[0007] To achieve the above object, the present invention adopts the following technical solutions: The invention provides a molecular migration resistant thermal transfer ink, which is prepared by a grinding process with polymethyl methacrylate (PMMA) resin and polystyrene (PS) resin as main raw materials and carbon black added in proportion.

[0008] Furthermore, the number average molecular weight of the polymethyl methacrylate (PMMA) resin is 300,000-400,000, and the crystalline transition temperature is 90-100° C.; the number average molecular weight of the polystyrene (PS) resin is 800,000-1.2 million, and the crystalline transition temperature is 90-110° C.

[0009] The present invention also provides a method for preparing a molecular migration resistant thermal transfer ink, comprising the following steps: S1, pre-treating polymethyl methacrylate (PMMA) resin and polystyrene (PS) resin by recrystallization and purification; S2, mixing the polymethyl methacrylate (PMMA) resin and the polystyrene (PS) resin purified in S1 in proportion, and dissolving the mixture in a solvent at 60-70° C. to form a mixed resin solution; S3, adding carbon black into the mixed resin solution in S2 in proportion to form a mixture; S4, grinding the mixture in S3, and obtaining the molecular migration resistant thermal transfer ink after being tested and found to be qualified.

[0010] Furthermore, the purification pretreatment process described in S1 includes: dissolving the polymethyl methacrylate PMMA resin and polystyrene PS resin in a solvent respectively, maintaining the dissolution at 65-75°C for ≥2 hours, then cooling to below 15°C to allow it to recrystallize, and completing the purification after filtering, washing and drying.

[0011] Furthermore, the mass ratio of the polymethyl methacrylate (PMMA) resin to the polystyrene (PS) resin in S2 is 2-3:1; the mass concentration of the mixed resin solution is 10%-12%; and the mass ratio of the carbon black to the mixed resin solution in the mixture in S3 is 1:8-10.

[0012] Furthermore, the molecular migration resistant thermal transfer ink described in S4 has a viscosity of 11.5-14.5s, and an ink particle diameter of 0.5-1.0 μm.

[0013] Furthermore, the polymethyl methacrylate (PMMA) resin in S1 comprises the following preparation steps: S11, gradually adding methyl methacrylate MMA monomer into a reaction container containing a diluent according to a proportion, and then adding an initiator and a chain transfer agent in sequence, setting the dropping speed of the initiator, and controlling the dropping time within 45-60 minutes, setting the dropping speed of the chain transfer agent, and controlling the dropping time within 1-2 hours; heating to 70-80° C., stirring at a constant temperature to fully dissolve and polymerize; S12, after reacting for 24-30 hours, adding a terminator to stop the polymerization reaction; and obtaining the polymethyl methacrylate (PMMA) resin after cooling, precipitation, filtering, washing and drying.

[0014] Furthermore, the added amounts of the diluent, initiator and chain transfer agent in S11 are 15%-20%, 0.8%-1% and 0.9-1.5% of the total molar mass of each monomer, respectively; the remainder of the total molar mass of each monomer is methyl methacrylate MMA monomer; the remainder of the total molar mass of each monomer is methyl methacrylate MMA monomer; the terminator includes isobutyl alcohol, and the chain transfer agent includes tert-dodecyl mercaptan.

[0015] The present invention further provides an application method of the molecular migration resistant thermal transfer ink, wherein the molecular migration resistant thermal transfer ink is made into a thermal transfer film and then printed on the surface of a substrate by thermal transfer; the substrate includes pharmaceutical or food packaging products, and the pharmaceutical packaging products are preferably infusion bags made of 48μmPP material.

[0016] Finally, the present invention provides a method for evaluating the molecular migration resistance performance of the molecular migration resistant thermal transfer ink. The substrate printed with the molecular migration resistant thermal transfer ink is filled with pure water, sealed, and placed at 121±5°C. The substrate is heated for 5±0.5 hours and taken out. The pure water in the substrate is analyzed for impurity components using a gas chromatograph.

[0017] The beneficial effects of the present invention are: 1. The molecular migration resistant thermal transfer ink provided by the present invention has excellent molecular migration resistance, heat resistance and chemical stability, and can meet the strict requirements of the pharmaceutical, food and other industries for thermal transfer inks.

[0018] 2. The molecular migration resistant thermal transfer ink provided by the present invention uses a macromolecular polymethyl methacrylate PMMA resin with a number average molecular weight of 300,000-400,000 as the core raw material, and the raw material is synthesized by free radical polymerization. During the preparation process, the polymerization temperature and the amount of initiator are strictly controlled to slow down the polymerization rate; the strategy of gradually adding each monomer is adopted to control the growth of the polymerization rate and molecular weight; a small amount of chain transfer agent can be added to regulate the molecular weight to obtain a raw material with a suitable molecular weight.

[0019] 3. The molecular migration resistant thermal transfer ink provided by the present invention utilizes the synergistic plasticizing effect of macromolecular polymethyl methacrylate PMMA resin and macromolecular polystyrene PS resin to achieve clear images and texts after printing and significantly improve the color fastness of the ink.

[0020] 4. The preparation method of the molecular migration resistant thermal transfer ink provided by the present invention creatively adopts the process of recrystallization and purification of macromolecular polymethyl methacrylate PMMA resin and polystyrene PS resin for the first time, completely removing low molecular weight impurities and preventing low molecular weight migration. At the same time, the raw materials are easy to select and obtain, and the specific raw material ratio and grinding preparation process are controlled, which is easy to industrialize and mass produce.

[0021] 5. After the molecular migration resistant thermal transfer ink provided by the present invention is made into a thermal transfer film, it can be printed on the packaging of pharmaceutical or food products by thermal transfer, which is convenient and fast, easy to automate production, and saves labor costs.

[0022] 6. The molecular migration resistance performance evaluation method of the molecular migration resistant thermal transfer ink provided by the present invention can reasonably and effectively evaluate the molecular migration resistance performance of the ink in the actual application scenario of the product by simulating the high-temperature steam sterilization process of at least 5±0.5 hours at 121±5°C used in the use of pharmaceutical or food products. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Attached Figure 1 This is an example of complete and clear printing after printing with the ink provided by the present invention.

[0025] Attached Figure 2 This is an example of an example in which the printing is incomplete and blurred after ink printing in the comparative example. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. The embodiments mentioned are all implemented on the premise of the technical solutions of the present invention, and detailed implementation processes are given, but it should be stated that the protection scope of the present invention is not limited to the following embodiments.

[0027] In the following examples, the raw materials used are all common commercial products that can be directly purchased in the art or can be prepared by conventional methods in the art.

[0028] Embodiment 1: A method for preparing a molecular migration resistant thermal transfer ink comprises the following steps: 1. Preparation of polymethyl methacrylate (PMMA) resin: (1) Raw material preparation: Methyl methacrylate (MMA) is used as the monomer. Azobisisobutyronitrile (AIBN) is used as the initiator. Tert-dodecyl mercaptan is used as the chain transfer agent. Toluene is used as the diluent to adjust the viscosity of the reaction system. A temperature control device is selected to maintain a polymerization temperature of 70-80°C.

[0029] (2) Polymerization reaction and molecular weight control: Add the MMA monomer required for the reaction to a reactor containing 15% of the total mass of diluent at an addition rate of 5% per minute. Then add 0.8% of the initiator, set the dripping speed, and control the dripping time to 50 minutes. Then add 0.9% of the chain transfer agent, set the dripping speed, and control the dripping time to 1 hour. Raise the temperature to 70°C. Keep stirring at a constant temperature to allow each monomer to fully dissolve and polymerize.

[0030] (3) Reaction termination: After 25 hours of reaction, the terminator isobutyl alcohol was added to stop the polymerization reaction.

[0031] (4) Post-treatment: After the reaction is completed, the polymer is cooled and precipitated and filtered to remove unreacted monomers and low molecular weight impurities. The PMMA resin is further washed with ethanol to completely remove residual monomers and small molecular impurities. Finally, it is dried to obtain a pure PMMA resin product.

[0032] (5) Determination of molecular weight and molecular weight distribution: The molecular weight and molecular weight distribution of the prepared polymethyl methacrylate (PMMA) resin were determined by gel permeation chromatography (GPC) to ensure that the product meets the requirements. The molecular weight test results are shown in Table 1.

[0033] 2. Preparation of molecular migration resistant thermal transfer ink (1) Purify the prepared polymethyl methacrylate (PMMA) resin and polystyrene (PS) resin by recrystallization. Select butanone to dissolve the two resins respectively, keep them dissolved at 65°C for 2 hours to obtain a saturated solution, then cool to below 15°C to recrystallize them, and further purify them by filtering and washing with ethanol. Among them, the polystyrene (PS) resin with a number average molecular weight of 900,000 is used.

[0034] (2) Dissolve the dried and purified resin in butanone at a predetermined mass ratio of 2:1 at 60-70°C to prepare a 10% solution.

[0035] (3) Carbon black was added to the prepared butanone solution at a mass ratio of 10:1, and the solution was ground 12 times using a rod-cut sand mill at a flow rate of 5 kg / min. The ink viscosity was tested using a 4-cup tester, and the ink particle size was tested using a laser particle size analyzer. The test results are detailed in Table 1.

[0036] 3. Application of molecular migration resistant thermal transfer ink and evaluation of molecular migration performance (1) The thermal transfer ink is made into a thermal transfer film and then thermally printed on a 48-micron PP infusion bag using a thermal transfer machine.

[0037] (2) Fill the infusion bag with pure water and seal the bag; place the infusion bag at a high temperature of 121°C and continue heating for 5 hours.

[0038] (3) Take out the infusion bag and use a gas chromatograph (inlet temperature: 150°C, column temperature: 70°C, detector temperature: 250°C) to compare and analyze the impurity components of the water in the bag and measure the impurity content in the water. The test results are detailed in Table 1.

[0039] Embodiment 2: 1. Preparation of polymethyl methacrylate (PMMA) resin: (1) Raw material preparation: Methyl methacrylate (MMA) is used as the monomer. Azobisisobutyronitrile (AIBN) is used as the initiator. Tert-dodecyl mercaptan is used as the chain transfer agent. Toluene is used as the diluent to adjust the viscosity of the reaction system. A temperature control device is selected to maintain a polymerization temperature of 70-80°C.

[0040] (2) Polymerization reaction and molecular weight control: Add the MMA monomer required for the reaction to a reactor containing 20% ​​of the total mass of diluent at an addition rate of 5% per minute. Then add 0.9% initiator, set the dripping speed, and control the dripping time to 50 minutes. Then add 1.1% chain transfer agent, set the dripping speed, and control the dripping time to 1 hour and 20 minutes. Raise the temperature to between 70°C and 80°C. Keep stirring at a constant temperature to allow the monomer to fully dissolve and polymerize.

[0041] (3) Reaction termination: After 30 hours of reaction, the terminator isobutyl alcohol was added to stop the polymerization reaction.

[0042] (4) Post-treatment: After the reaction is completed, the polymer is cooled and precipitated and filtered to remove unreacted monomers and low number average molecular weight impurities. The PMMA resin is further washed with ethanol to completely remove residual monomers and small molecular weight impurities. Finally, it is dried to obtain a pure PMMA resin product.

[0043] (5) Determination of molecular weight and molecular weight distribution: The molecular weight and molecular weight distribution of the prepared polymethyl methacrylate (PMMA) resin were determined by gel permeation chromatography (GPC) to ensure that the product meets the requirements. The molecular weight test results are shown in Table 1.

[0044] 2. Preparation of molecular migration resistant thermal transfer ink (1) Purify the prepared polymethyl methacrylate (PMMA) resin and polystyrene (PS) resin by recrystallization. Select butanone to dissolve the two resins respectively, keep them dissolved at 75°C for 3 hours to obtain a saturated solution, then cool them to below 15°C to recrystallize them, and further purify them by filtering and washing with ethanol. Among them, the polystyrene (PS) resin with a number average molecular weight of 1 million is used.

[0045] (2) Dissolve the dried and purified resin in butanone at a predetermined mass ratio of 3:1 at 60-70°C to prepare a 12% solution.

[0046] (3) Carbon black was added to the prepared butanone solution at a mass ratio of 10:1, and the solution was ground 12 times using a rod-cut sand mill at a flow rate of 5 kg / min. The ink viscosity was tested using a 4-cup tester, and the ink particle size was tested using a laser particle size analyzer. The test results are detailed in Table 1.

[0047] 3. Application of molecular migration resistant thermal transfer ink and evaluation of molecular migration performance (1) The thermal transfer ink is made into a thermal transfer film and then thermally printed on a 48-micron PP infusion bag using a thermal transfer machine.

[0048] (2) Fill the infusion bag with pure water and seal the bag; place the infusion bag at a high temperature of 121°C and continue heating for 5 hours.

[0049] (3) Take out the infusion bag and use a gas chromatograph (inlet temperature: 150°C, column temperature: 70°C, detector temperature: 250°C) to compare and analyze the impurity components of the water in the bag and measure the impurity content in the water. The test results are detailed in Table 1.

[0050] Embodiment 3: 1. Preparation of polymethyl methacrylate (PMMA) resin: (1) Raw material preparation: Methyl methacrylate (MMA) is used as the monomer. Azobisisobutyronitrile (AIBN) is used as the initiator. Tert-dodecyl mercaptan is used as the chain transfer agent. Toluene is used as the diluent to adjust the viscosity of the reaction system. A temperature control device is selected to maintain a polymerization temperature of 70-80°C.

[0051] (2) Polymerization reaction and molecular weight control: Add all the MMA monomers required for the reaction into a reactor containing 18% of the total mass of diluent at a rate of 5% per minute. Then add 0.8% of the initiator, set the dripping speed, and control the dripping time to 60 minutes. Then add 1.3% of the chain transfer agent, set the dripping speed, and control the dripping time to 1 hour and 40 minutes. Raise the temperature to between 70°C and 80°C. Keep stirring at a constant temperature to allow the monomer to fully dissolve and polymerize.

[0052] (3) Reaction termination: After 28 hours of reaction, the terminator isobutyl alcohol was added to stop the polymerization reaction.

[0053] (4) Post-treatment: After the reaction is completed, the polymer is cooled and precipitated and filtered to remove unreacted monomers and low number average molecular weight impurities. The PMMA resin is further washed with ethanol to completely remove residual monomers and small molecular weight impurities. Finally, it is dried to obtain a pure PMMA resin product.

[0054] (5) Determination of molecular weight and molecular weight distribution: The molecular weight and molecular weight distribution of the prepared polymethyl methacrylate (PMMA) resin were determined by gel permeation chromatography (GPC) to ensure that the product meets the requirements. The molecular weight test results are shown in Table 1.

[0055] 2. Preparation of molecular migration resistant thermal transfer ink (1) Purify the prepared polymethyl methacrylate (PMMA) resin and polystyrene (PS) resin by recrystallization. Select butanone to dissolve the two resins respectively, keep them dissolved at 70°C for 4 hours to obtain a saturated solution, then cool to below 15°C to recrystallize them, and further purify them by filtering and washing with ethanol. Among them, the polystyrene (PS) resin with a number average molecular weight of 1.2 million is used.

[0056] (2) Dissolve the dried and purified resin in butanone at a predetermined mass ratio of 2:1 at 60-70°C to prepare a 10% solution.

[0057] (3) Carbon black was added to the prepared butanone solution at a mass ratio of 9:1, and the solution was ground 12 times using a rod-cut sand mill at a flow rate of 5 kg / min. The ink viscosity was tested using a 4-cup tester, and the ink particle size was tested using a laser particle size analyzer. The test results are detailed in Table 1.

[0058] 3. Application of molecular migration resistant thermal transfer ink and evaluation of molecular migration performance (1) The thermal transfer ink is made into a thermal transfer film and then thermally printed on a 48-micron PP infusion bag using a thermal transfer machine.

[0059] (2) Fill the infusion bag with pure water and seal the bag; place the infusion bag at a high temperature of 121°C and continue heating for 5 hours.

[0060] (3) Take out the infusion bag and use a gas chromatograph (inlet temperature: 150°C, column temperature: 70°C, detector temperature: 250°C) to compare and analyze the impurity components of the water in the bag and measure the impurity content in the water. The test results are detailed in Table 1.

[0061] Embodiment 4: 1. Preparation of polymethyl methacrylate (PMMA) resin: (1) Raw material preparation: Methyl methacrylate (MMA) is used as the monomer. Azobisisobutyronitrile (AIBN) is used as the initiator. Tert-dodecyl mercaptan is used as the chain transfer agent. Toluene is used as the diluent to adjust the viscosity of the reaction system. A temperature control device is selected to maintain a polymerization temperature of 70-80°C.

[0062] (2) Polymerization reaction and molecular weight control: Add all the MMA monomers required for the reaction into a reactor containing 20% ​​of the total mass of diluent at a rate of 5% per minute. Then add 0.8% initiator, set the dripping speed, and control the dripping time to 60 minutes. Then add 1.5% chain transfer agent, set the dripping speed, and control the dripping time to 2 hours. Heat to 7.5°C. Keep constant temperature and stir to allow the monomer to fully dissolve and polymerize.

[0063] (3) Reaction termination: After 30 hours of reaction, the terminator isobutyl alcohol was added to stop the polymerization reaction.

[0064] (4) Post-treatment: After the reaction is completed, the polymer is cooled and precipitated and filtered to remove unreacted monomers and low molecular weight impurities. The PMMA resin is further washed with ethanol to completely remove residual monomers and small molecular impurities. Finally, it is dried to obtain a pure PMMA resin product.

[0065] (5) Determination of molecular weight and molecular weight distribution: The molecular weight and molecular weight distribution of the prepared polymethyl methacrylate (PMMA) resin were determined by gel permeation chromatography (GPC) to ensure that the product meets the requirements. The molecular weight test results are shown in Table 1.

[0066] 2. Preparation of molecular migration resistant thermal transfer ink (1) Purify the prepared polymethyl methacrylate (PMMA) resin and polystyrene (PS) resin by recrystallization. Select butanone to dissolve the two resins respectively, keep them dissolved at 70°C for 2 hours to obtain a saturated solution, then cool to below 15°C to recrystallize them, and further purify them by filtering and washing with ethanol. Among them, the polystyrene (PS) resin with a number average molecular weight of 800,000 is used.

[0067] (2) Dissolve the dried and purified resin in butanone at a predetermined mass ratio of 2:1 at 60-70°C to prepare a 10% solution.

[0068] (3) Carbon black was added to the prepared butanone solution at a mass ratio of 8:1, and the solution was ground 12 times using a rod-cut sand mill at a flow rate of 5 kg / min. The ink viscosity was tested using a 4-cup tester, and the ink particle size was tested using a laser particle size analyzer. The test results are detailed in Table 1.

[0069] 3. Application of molecular migration resistant thermal transfer ink and evaluation of molecular migration performance (1) The thermal transfer ink is made into a thermal transfer film and then thermally printed on a 48-micron PP infusion bag using a thermal transfer machine.

[0070] (2) Fill the infusion bag with pure water and seal the bag; place the infusion bag at a high temperature of 121°C and continue heating for 5 hours.

[0071] (3) Take out the infusion bag and use a gas chromatograph (inlet temperature: 150°C, column temperature: 70°C, detector temperature: 250°C) to compare and analyze the impurity components of the water in the bag and measure the impurity content in the water. The test results are detailed in Table 1.

[0072] Comparative Example 1 1. A method for preparing a thermal transfer ink, comprising the following steps: (1) Purification of polymethyl methacrylate (PMMA) resin BM-112 with a number average molecular weight of 320,000 and polystyrene (PS) resin with a number average molecular weight of 400,000 purchased from Shanghai Bolier Company: Recrystallization method was used. Butanone was selected to dissolve the two resins respectively, and the solution was kept at 65°C for 2 hours to obtain a saturated solution, which was then cooled to below 15°C to recrystallize, and further purified by filtering and washing with ethanol.

[0073] (2) Dissolve the dried resin in butanone at a predetermined ratio of 2:1 at 60-70°C to prepare a 10% solution; (3) Carbon black was added to the prepared butanone solution at a mass ratio of 8:1, and the solution was ground 12 times using a rod-cut sand mill at a flow rate of 5 kg / min. The ink viscosity was tested using a 4-cup tester, and the ink particle size was tested using a laser particle size analyzer. The test results are detailed in Table 1.

[0074] 2. Thermal transfer ink application and molecular migration performance evaluation (1) After the thermal transfer ink is made into a thermal transfer film, it is thermally printed on a 48-micron PP infusion bag using a thermal transfer machine, resulting in incomplete printing.

[0075] (2) Fill the infusion bag with pure water and seal the bag; place the infusion bag at a high temperature of 121°C and heat it for 5 hours; (3) Take out the infusion bag and use a gas chromatograph (inlet temperature: 150°C, column temperature: 70°C, detector temperature: 250°C) to compare and analyze the impurity components of the water in the bag and measure the impurity content in the water. The test results are detailed in Table 1.

[0076] Comparative Example 2 1. A method for preparing a thermal transfer ink, comprising the following steps: (1) The polymethyl methacrylate (PMMA) resin prepared by the method of Example 1 and the polystyrene (PS) resin used in Example 1 were dissolved in butanone at a predetermined ratio of 2:1, heated at 60-70° C. to prepare a 10% solution; (2) Carbon black was added to the prepared butanone solution at a mass ratio of 9:1, and the solution was ground 12 times using a rod-cut sand mill at a flow rate of 5 kg / min. The ink viscosity was tested using a 4-cup tester, and the ink particle size was tested using a laser particle size analyzer. The test results are detailed in Table 1.

[0077] 2. Thermal transfer ink application and molecular migration performance evaluation (1) After the thermal transfer ink is made into a thermal transfer film, it is thermally printed on a 48-micron PP infusion bag using a thermal transfer machine; incomplete printing occurs.

[0078] (2) Fill the infusion bag with pure water and seal the bag; place the infusion bag at a high temperature of 121°C and heat it for 5 hours; (3) Take out the infusion bag and use a gas chromatograph (inlet temperature: 150°C, column temperature: 70°C, detector temperature: 250°C) to compare and analyze the impurity components of the water in the bag and measure the impurity content in the water. The test results are detailed in Table 1.

[0079] Comparative Example 3 1. A method for preparing a thermal transfer ink, comprising the following steps: (1) A polymethyl methacrylate (PMMA) resin BM-11 with a number average molecular weight of 60,000 and a polystyrene (PS) resin with a number average molecular weight of 200,000 produced by Shanghai Bolier Company were purified according to the method in Example 1, and dissolved in butanone at a predetermined ratio of 2:1 at 70°C to prepare a 10% solution; (2) Carbon black was added to the prepared butanone solution at a mass ratio of 9:1, and the solution was ground 12 times using a rod-cut sand mill at a flow rate of 5 kg / min. The ink viscosity was tested using a 4-cup tester, and the ink particle size was tested using a laser particle size analyzer. The test results are detailed in Table 1.

[0080] 2. Thermal transfer ink application and molecular migration performance evaluation (1) After the thermal transfer ink is made into a thermal transfer film, it is thermally printed on a 48-micron PP infusion bag using a thermal transfer machine; incomplete printing occurs.

[0081] (2) Fill the infusion bag with pure water and seal the bag; place the infusion bag at a high temperature of 121°C and heat it for 5 hours; (3) Take out the infusion bag and use a gas chromatograph (inlet temperature: 150°C, column temperature: 70°C, detector temperature: 250°C) to compare and analyze the impurity components of the water in the bag and measure the impurity content in the water. The test results are detailed in Table 1.

[0082] Comparative Example 4 1. A method for preparing a thermal transfer ink, comprising the following steps: (1) Polymethyl methacrylate (PMMA) resin BM-11 with a number average molecular weight of 60,000 and polystyrene (PS) with a number average molecular weight of 300,000 produced by Shanghai Bolier Company were purified according to the method in Example 1, and dissolved in butanone at a predetermined ratio of 2:1 at 70°C to prepare a 10% solution; (2) Carbon black was added to the prepared butanone solution at a mass ratio of 9:1, and the solution was ground 12 times using a rod-cut sand mill at a flow rate of 5 kg / min. The ink viscosity was tested using a 4-cup tester, and the ink particle size was tested using a laser particle size analyzer. The test results are detailed in Table 1.

[0083] 2. Thermal transfer ink application and molecular migration performance evaluation (1) After the thermal transfer ink is made into a thermal transfer film, it is thermally printed on a 48-micron PP infusion bag using a thermal transfer machine. Incomplete printing occurs.

[0084] (2) Fill the infusion bag with pure water and seal the bag; place the infusion bag at a high temperature of 121°C and heat it for 5 hours; (3) Take out the infusion bag and use a gas chromatograph (inlet temperature: 150°C, column temperature: 70°C, detector temperature: 250°C) to compare and analyze the impurity components of the water in the bag and measure the impurity content in the water. The test results are detailed in Table 1.

[0085] The material parameters and related performance evaluation results in Examples 1-4 and Comparative Examples 1-4 are shown in Table 1 below: Table 1 Material parameters and related performance evaluation The data in Table 1 show that the molecular migration resistant thermal transfer inks prepared by the preparation method provided by the present invention in Examples 1-4 are completely clear after printing on the substrate surface, and molecular migration does not occur. Comparative Example 1 directly uses the commercially available high molecular weight polymethyl methacrylate PMMA resin to prepare the thermal transfer ink, and the printing phenomenon is incomplete after printing; Comparative Example 2 uses the unpurified self-made high molecular weight polymethyl methacrylate PMMA resin and high molecular weight polystyrene PS resin to prepare the thermal transfer ink, and the printing phenomenon is incomplete after printing, and the presence of impurities is detected during the molecular migration performance evaluation. Comparative Examples 3 and 4 use the commercially available low molecular weight polymethyl methacrylate PMMA resin and polystyrene PS resin to prepare the thermal transfer ink, and the printing phenomenon is incomplete after printing, and the presence of impurities is detected during the molecular migration performance evaluation.

[0086] Therefore, the ink provided by the present invention has excellent molecular migration resistance, heat resistance and chemical stability, and can meet the strict requirements of the pharmaceutical, food and other industries for thermal transfer inks. After the ink is made into a thermal transfer film, it is printed on the product packaging by thermal transfer, which is convenient and easy to industrialize. The performance evaluation method provided by the present invention can truly and effectively evaluate the molecular migration resistance of the ink through simulation tests of actual application scenarios.

[0087] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A molecular migration resistant thermal transfer ink, characterized in that: The invention adopts polymethyl methacrylate (PMMA) resin and polystyrene (PS) resin as main raw materials, carbon black is added in proportion and the obtained product is prepared through a grinding process.

2. The molecular migration resistant thermal transfer ink according to claim 1, characterized in that: The number average molecular weight of the polymethyl methacrylate (PMMA) resin is 300,000-400,000, and the crystalline transition temperature is 90-100° C.; the number average molecular weight of the polystyrene (PS) resin is 800,000-1.2 million, and the crystalline transition temperature is 90-110° C.

3. A method for preparing the molecular migration resistant thermal transfer ink according to claim 1 or 2, characterized in that: The steps include: S1, pre-treating polymethyl methacrylate (PMMA) resin and polystyrene (PS) resin by recrystallization and purification; S2, mixing the polymethyl methacrylate (PMMA) resin and the polystyrene (PS) resin purified in S1 in proportion, and dissolving the mixture in a solvent at 60-70° C. to form a mixed resin solution; S3, adding carbon black into the mixed resin solution in S2 in proportion to form a mixture; S4, grinding the mixture in S3, and obtaining the molecular migration resistant thermal transfer ink after being tested and found to be qualified.

4. The preparation method according to claim 3, characterized in that: The purification pretreatment process in S1 includes: dissolving the polymethyl methacrylate PMMA resin and polystyrene PS resin in a solvent respectively, maintaining the dissolution at 65-75° C. for ≥2 hours to obtain a saturated solution, then cooling to below 15° C. to allow it to recrystallize, and completing the purification after filtering, washing, and drying.

5. The preparation method according to claim 3, characterized in that: The mass ratio of polymethyl methacrylate (PMMA) resin to polystyrene (PS) resin in S2 is 2-3:1; the mass concentration of the mixed resin solution is 10%-12%; the mass ratio of carbon black to the mixed resin solution in the mixture in S3 is 1:8-10.

6. The preparation method according to claim 3, characterized in that: The molecular migration resistant thermal transfer ink described in S4 has a viscosity of 11.5-14.5s, and an ink particle diameter of 0.5-1.0 μm.

7. The preparation method according to any one of claims 4 to 6, characterized in that: The preparation of the polymethyl methacrylate (PMMA) resin described in S1 comprises the following steps: S11, gradually adding methyl methacrylate (MMA) monomer into a reaction vessel containing a diluent according to a certain proportion, and then sequentially adding an initiator and a chain transfer agent, heating to 70-80° C. and stirring at a constant temperature to fully dissolve and polymerize; S12, after reacting for 24-30 hours, adding a terminator to stop the polymerization reaction; and obtaining the polymethyl methacrylate (PMMA) resin after cooling, precipitation, filtering, washing and drying.

8. The preparation method according to claim 7, characterized in that: The added amounts of the diluent, initiator and chain transfer agent in S11 are 15%-20%, 0.8%-1% and 0.9-1.5% of the total molar mass of each monomer, respectively, and the remainder of the total molar mass of each monomer is methyl methacrylate MMA monomer; the dripping time of the initiator is controlled at 45-60 minutes, and the dripping time of the chain transfer agent is controlled at 1-2 hours; the terminator includes isobutanol, and the chain transfer agent includes tert-dodecyl mercaptan.

9. A method for applying the molecular migration resistant thermal transfer ink according to claim 1 or 2, characterized in that: After the molecular migration resistant thermal transfer ink is made into a thermal transfer film, it is printed on the surface of a substrate through thermal transfer.

10. A method for evaluating the molecular migration resistance of the molecular migration resistance thermal transfer ink according to claim 1 or 2, characterized in that: The substrate printed with the molecular migration resistant thermal transfer ink is filled with pure water, sealed and placed at 121±5°C, heated for 5±0.5 hours, taken out, and the pure water in the substrate is analyzed for impurity components using a gas chromatograph.

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