Normal saline-resistant non-curled printing ink for breathable film and preparation method of normal saline-resistant non-curled printing ink

Abstract

The invention discloses normal saline-resistant non-curled printing ink for a breathable film and a preparation method of the normal saline-resistant non-curled printing ink, the printing ink comprises a binder, an auxiliary agent, a pigment and a solvent, and the binder is a combination of polyether polyurethane and nitrocotton liquid; the invention relates to a nitrocotton coating which comprises the following components in percentage by mass: 9.0-9.6% of polyether polyurethane, 18-19% of nitrocotton liquid with solid content of 35% in 1 / 16 seconds, 0.7-0.8% of wax powder, 0.5-0.6% of nano silicon dioxide and the balance of auxiliaries and solvents. After the ink is fully printed on the LDPE breathable film with the gram weight of 15 gsm and the thickness of 18 microns, the breathable film is not rolled and folded, and the edge warping height is smaller than or equal to 0.5 mm. The printing ink has the advantages of being good in normal saline resistance, free of edge curling, resistant to high temperature and heat sealing, free of peculiar smell, stable and qualified in friction coefficient, resistant to heat adhesion / aging and free of discoloration, after the printing ink forms a film, the printing ink has the similar soft characteristic with a breathable film, and the body feeling comfort of the breathable film making contact with the skin of the human body can still be kept after printing; the environment-friendly property is good, and the production efficiency of the breathable film product can be remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of inks, and particularly to an ink for a breathable film that is resistant to physiological saline and does not curl, and a preparation method thereof. Background Art

[0002] Sanitary napkins, diapers, etc. are commonly used nursing products for women and infants. The main structure consists of a high-molecular water-absorbing material wrapped by a breathable film and cotton. The breathable film is generally made by co-blown film of LDPE, HDPE, and LLDPE in different ratios according to different requirements. In order to identify the brand and for aesthetics, manufacturers will print words or patterns on the breathable film using ink. In the use of breathable film printing ink, problems such as ink resistance to physiological saline, adhesion, and odor will be involved. There will also be problems such as non-curling, high-temperature heat-sealing resistance, and no color change at high temperature and high humidity in the manufacturing process.

[0003] Nowadays, most of the high-temperature surface printing inks on the market, in order to improve the high-temperature heat-sealing resistance, add about 35% of nitrocellulose solution to improve the heat resistance, which makes the printed products of the breathable film hard and curl. On the automatic packaging line, due to the two sides tilting up, the automatic heat-sealing process cannot be adopted.

[0004] Some ink manufacturers, in order to solve the curling problem, add refined dammar or aldehyde-ketone resin to reduce the hardness and enhance the softness and adhesion of the ink. However, the release of aldehyde-ketone and refined dammar in ester solvents is not thorough enough, resulting in an odor in the printed products.

[0005] Some manufacturers also use rosin for improvement. However, only when the rosin accounts for more than 20% can there be a slight non-curling effect, but it will lead to a decline in the high-temperature heat-sealing performance, which does not meet the high-temperature heat-sealing requirements of the breathable film (coating film). Moreover, rosin and substances such as ethyl acetate are restricted in the products of some companies, such as the list of restricted substances in the products of Kimberly-Clark in the health care field (referred to as KC requirements).

[0006] There are also manufacturers who use the scheme of alcohol-soluble polyurethane combined with ternary vinyl chloride-vinyl acetate resin and add wax powder and silica powder to solve the adhesion of alcohol-soluble polyurethane on the PE film. Although the anti-adhesion problem is solved, the friction coefficient of the wax powder and silica powder is too low, resulting in slipping out of the production line on the high-speed automatic packaging machine and unable to produce normally. There are also some manufacturers who use the scheme of acrylic emulsion combined with polyurethane emulsion. Although this scheme has a low odor, it is not resistant to high-temperature heat-sealing at 180 degrees Celsius, and it curls after complete drying, and cannot adapt to the high-speed automatic heat-sealing process, seriously affecting production efficiency.

[0007] CN115537064A uses polyether-type polyurethane, polyurethane acrylate copolymer, and polyamide resin as binders, which can be resistant to physiological saline, but does not mention heat-sealing resistance and non-curling.

[0008] CN109796805A uses polyurethane resin liquid and nitrocellulose resin liquid as binders. Utilizing the characteristics of aliphatic epoxy-modified polyester-type polyurethane having good adhesion fastness and shrinkage rate on shrinkable PE film, as well as the strong rigidity and excellent solvent release property of nitrocellulose resin, it completely solves the problems of poor fastness of inks in the same application system on PE shrinkable film, ink dropping during film shrinkage, and ink color change. However, due to the relatively high hardness of polyester-type polyurethane, it will cause the breathable film to become severely hardened and curled, and it cannot be adapted to the printing of breathable films.

[0009] Therefore, there is an urgent need to develop an ink for breathable film that is resistant to physiological saline and does not curl, which has the advantages of good resistance to physiological saline, non-curling, low friction coefficient, high-temperature heat sealability, and no peculiar smell, and also has good environmental protection performance, meeting the requirements of GB38507-2020 "Limit of Volatile Organic Compounds (VOCs) Content in Inks" and KC requirements. Summary of the Invention

[0010] Aiming at the above existing problems, the purpose of the present invention is to provide an ink for breathable film that is resistant to physiological saline and does not curl, and its preparation method, which has the advantages of good resistance to physiological saline, non-curling, high-temperature heat sealability, and no peculiar smell, and also has good environmental protection performance, meeting the requirements of GB 38507-2020 "Limit of Volatile Organic Compounds (VOCs) Content in Inks" and KC requirements.

[0011] To solve the above problems, the technical solutions adopted by the present invention are as follows:

[0012] An ink for breathable film that is resistant to physiological saline and does not curl, characterized in that it includes a binder, additives, pigments, and solvents, and the binder is a combination of polyether-type polyurethane and nitrocellulose solution;

[0013] By mass percentage, polyether-type polyurethane is 9.0 - 9.6%, nitrocellulose solution with a solid content of 35% in 1 / 16 second is 18 - 19%, wax powder is 0.7 - 0.8%, and nano-silica is 0.5 - 0.6%, and the balance is additives and solvents.

[0014] Preferably, after full-page printing on an LDPE breathable film with a grammage of 15 gsm and a thickness of 18 μm, the breathable film has no curling and the warping height ≤ 0.5 mm.

[0015] Preferably, the wax powder is PE wax powder with a melting point ≥ 120°C.

[0016] Preferably, the dispersant is an active polymer dispersant.

[0017] Preferably, the solvent is a composition of isopropyl alcohol and n-propyl ester.

[0018] Preferably, by mass percentage, n-propyl ester accounts for 85-88% of the solvent, and the balance is isopropanol.

[0019] Preferably, the nano-silica is hydrophobic fumed nano-silica.

[0020] Preferably, the auxiliary agent includes an antifoaming agent and a dispersant.

[0021] Preferably, it does not contain rosin and ethyl acetate.

[0022] The preparation method of the ink of the present invention includes the following steps:

[0023] S1. High-speed disperse nitrocellulose solution, dispersant, n-propyl ester, nano-silica, wax powder and pigment for 30-60 minutes, and then grind to fineness to obtain a color paste;

[0024] S2. Emulsify polyether-type polyurethane with a solvent to obtain a polyether-type polyurethane resin solution with a solid content of 30% and a viscosity (mPa·s / 25°C)

[0025] of 700-1200.

[0026] S3. Disperse isopropanol, antifoaming agent, the color paste obtained in S1 and the polyether-type polyurethane resin solution obtained in S2 evenly to obtain the ink of the present invention.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1. The present invention uses polyether-type polyurethane resin and nitrocellulose solution in combination as the binder of the ink. The polyether-type polyurethane resin has good elasticity and adhesion, and has good resilience under external force or stretching, ensuring that when the ink is printed on the breathable film, it is not easily damaged by external force; combined with the harder nitrocellulose solution, the nitrocellulose solution combines rigidity and flexibility, so that after the ink is completely dried, the breathable film has a good non-curling effect.

[0029] 2. By strictly controlling the polyether-type polyurethane resin, nitrocellulose resin solution and the ratio of each component, the present invention can achieve a non-curling effect with a curling height of the breathable film ≤ 0.5 mm, which can be applied to the heat-sealing process of the automatic packaging line, significantly improving production efficiency. Compared with the flexographic printing polyurethane ink with the same performance indicators, it has obvious heat-sealing advantages.

[0030] 3. The formula of the present invention does not contain ethyl acetate and rosin, which can meet the KC requirements, and there are no adhesion-enhancing resins, accelerators, and high-boiling solvents commonly used in traditional high-temperature surface printing inks in the components, realizing the characteristic of no residual odor after baking in an oven at 50°C for 30 minutes.

[0031] 4. The ink of the present invention has the advantages of good resistance to physiological saline, no curling, high-temperature heat-sealing resistance, no peculiar smell, low friction coefficient, and no color change during heat adhesion / aging. After the ink forms a film, it has similar compliance characteristics to the breathable film, and can still maintain the tactile comfort of the breathable film in contact with the human skin after printing; moreover, it has good environmental protection performance and meets the requirements of GB 38507-2020 "Limit of Volatile Organic Compounds (VOCs) Content in Inks" and KC. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a comparative test chart of Example 2 and the comparative example according to the first curling test method;

[0033] Figure 2 It is a test chart of Example 1 according to the second curling test method. DETAILED DESCRIPTION OF THE INVENTION

[0034] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant embodiments and drawings. The preferred embodiments of the present invention are given in the embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0036] The present invention will be further described below in specific embodiments:

[0037] It should be noted that the raw materials used in the technical solutions provided by the present invention are prepared by conventional means or purchased through commercial channels unless otherwise specified.

[0038] The components and mass percentages of an ink for a breathable film resistant to physiological saline and non-curling are shown in Table 1 below:

[0039]

[0040] Among the above components:

[0041] The polyether-type polyurethane is an alcohol-ester-soluble polyether-type polyurethane. When in use, the polyether-type polyurethane resin is emulsified with a solvent into a polyether-type polyurethane resin solution with a solid content of 30% and a viscosity (mPa·s / 25°C) of 700-1200.

[0042] Polyether-type polyurethane is formed by the reaction of polyether polyol (containing ester group -COO-) and isocyanate. It has a flexible molecular chain, good tear resistance, and better hydrolysis resistance than polyester-type polyurethane and polyamide with higher hardness. It is also resistant to weak acids and bases and microorganisms, and is more suitable for making envelopes for feminine and infant care products such as sanitary napkins and diapers.

[0043] The nitrocellulose solution is a 1 / 16-second nitrocellulose solution with a solid content of 35%. Nitrocellulose has the characteristic of high temperature resistance and can withstand a high temperature of 200 °C without decolorization. After being effectively combined with an alcohol-ester-soluble polyether-type polyurethane with a solid content of 30%, the printed matter of the ink can withstand a high temperature of ≥180 °C without decolorization.

[0044] The solvent is a composition of isopropyl alcohol and n-propyl ester. By mass ratio, n-propyl ester accounts for 85-88% of the solvent, and the balance is isopropyl alcohol.

[0045] n-Propyl ester is a true solvent for nitrocellulose and polyether-type polyurethane, which can completely dissolve nitrocellulose and polyether-type polyurethane, and can also be released completely after the mixed resin solution of nitrocellulose and polyether-type polyurethane dries into a film, making the printed matter odorless. Isopropyl alcohol has an antistatic effect, which can avoid defects such as mottling and ink whiskers in printing, and can improve the film-forming quality stability of the ink during high-speed printing.

[0046] The wax powder is PE wax powder with a melting point of 120-130 °C. In the above examples, Clariant 3620 was selected.

[0047] The nano-silica is hydrophobic fumed nano-silica. Nano-scale fumed silica particles can penetrate the ink layer of the printed matter and release the residual solvent, thereby reducing the odor of the printed matter. At the same time, it has an anti-thermal adhesion effect. It can also prevent the four-color overprint dots from spreading, with good overprint transfer effect and higher pattern reduction degree. Moreover, hydrophobic nano-silica can also improve the hydrophobicity of the film layer, keep the surface dry and have a stable low friction coefficient.

[0048] The dispersant is an active polymer dispersant, which can improve the dispersibility and grinding color development, and enhance the color strength of the ink. In the above examples, Solsperse 20000 dispersant was selected.

[0049] The defoamer selected is YS-A65 defoamer, which is easily soluble in isopropyl alcohol solvent and will not produce shrinkage holes.

[0050] In the above embodiments, the toner (red) is Red 146, the toner (yellow) is Yellow 83, the toner (blue) is phthalocyanine blue Blue 15:4, the toner (black) is Pigment Black 7 Cabot DL430, and the titanium dioxide is rutile Pigment White 6. The pigments used meet the KC requirements. The printed matter can be directly contacted with human skin, and all are lightfastness grade 7 or above, ensuring that the lightfastness and heat resistance of the formulated light special colors (such as sky blue, pink, etc.) do not change color.

[0051] In the formulation of the present invention, there is no ethyl acetate and rosin, which can meet the KC requirements. Moreover, there is no adhesion-enhancing resin, adhesion promoter, coupling agent, and high-boiling solvent commonly used in traditional high-temperature surface printing inks in the components, realizing the characteristic of no residual odor after baking in an oven at 50 °C for 30 minutes.

[0052] In the present invention, a polyether-type polyurethane resin is paired with a nitrocellulose solution as the binder of the ink. The polyether-type polyurethane resin has good elasticity and adhesiveness, and has good resilience under external force or stretching, ensuring that when the ink is printed on the breathable film, it is not easily damaged by external force; paired with a relatively hard nitrocellulose solution, the nitrocellulose solution combines hardness and softness, so that after the ink is completely dried, the breathable film has a good non-curling effect (after the ink forms a film, it has similar compliant characteristics to the breathable film, and can still maintain the tactile comfort of the contact between the breathable film and human skin after printing).

[0053] It should be particularly noted that the ratio of the polyether-type polyurethane resin and the nitrocellulose resin solution needs to be strictly controlled, and its ratio has an important impact on non-curling. The ink of the present invention can achieve a non-curling effect with a curling height of the breathable film ≤ 0.5 mm, and can be applied to the heat-sealing process of the automatic packaging line, significantly improving the production efficiency of nursing products using this breathable film. Compared with flexographic printing polyurethane inks with the same performance indicators, it has obvious heat-sealing advantages.

[0054] The ink of the present invention has excellent adhesion and light dot transfer rate on the breathable film. There is no need to add adhesion promoters, coupling agents, high-boiling solvents such as butyl ester and methyl ether and other additives, which can avoid the reactivity problems between the grinding resin and other resins in the formulation system, and can also avoid the slow volatilization of high-boiling solvents in rainy and low-temperature weather, thereby increasing the residual odor of the ink printed matter.

[0055] The nano-silica and PE wax powder in the formulation can improve the anti-blocking, stable low friction coefficient, wear resistance, scratch resistance and rubbing resistance of the ink at high temperature and high humidity.

[0056] The preparation method of the ink of the present invention includes the following steps:

[0057] S1. High-speed disperse nitrocellulose solution, dispersant, n-propyl ester, nano-silica, wax powder and pigment for 30 to 60 minutes, then transfer to grinding until the fineness ≤ 15um to obtain the color paste.

[0058] The color development effect of polyether-type polyurethane is not as good as that of nitrocellulose solution and it cannot be used as the grinding resin.

[0059] S2. Emulsify polyether-type polyurethane with a solvent to obtain a polyether-type polyurethane resin with a solid content of 30% and a viscosity (mPa·s / 25℃)

[0060] of 700 - 1200.

[0061] S3. Disperse isopropanol, defoamer, the color paste prepared in S1 and the polyether-type polyurethane resin solution prepared in S2 evenly to obtain the ink of the present invention.

[0062] Test the inks prepared in Examples 1 - 4 and the comparative example, and the test results of the main performance indicators are shown in Table 2 below:

[0063]

[0064] As can be seen from Table 2, the ink prepared by the present invention has the advantages of good resistance to physiological saline, no curling, high-temperature heat sealing, no peculiar smell, stable coefficient of friction, and no color change in anti-thermal adhesion / aging, and can adapt to high-speed intaglio printing and high-speed automatic heat sealing.

[0065] Test method:

[0066] 1. Test method for thermal adhesion / aging color change: After the printed matter is completely dry, take three single-sided printed breathable films. Stick two of them with the ink surfaces facing each other, and stick the ink surface of the remaining one to the non-ink surface of any one of them. Then clamp them in the middle of a glass plate, place them flat and apply a pressure of 5 kg, and place them in an oven at 70 degrees Celsius and 70% humidity for 24 hours. After taking out the printed matter and peeling it off, observe whether there is adhesion. Use an X-Rite exact color difference meter to test the color Lab value, record the total color difference △E number, △E ≤

[0067] 0.5, and when the human eye cannot distinguish the color difference, it means there is no color change.

[0068] 2. Test method for curling: It includes the test of the height of rolling and curling (curling and stacking into a cylindrical shape) and warping (edge warping). The breathable film sample is an LDPE breathable film with a gram weight of 15 gsm and a thickness of 18um; the printing method is full-color printing with an ink film thickness of 40um. Test using the following Methods 1 and 2, and it is required that there is no rolling and the warping height ≤ 0.5 mm.

[0069] When the height of rolling or warping is too large, it will affect the quality of automatic heat sealing due to the warping on both sides on the automatic packaging line.

[0070] a) Method 1: After the breathable film sample is printed, lay it flat on the table. After it is completely dry, visually inspect whether the edge of the breathable film is curled and measure the height of the curled edge.

[0071] As Figure 1 shown, on both sides of the breathable film sample, parallel proofing comparisons are carried out on the same proofing machine using Example 2 and the comparative example respectively. It can be seen that one side of the comparative example has been curled into a cylinder

[0072] shape, while the side of Example 2 is not curled and the height of the curled edge is less than 1.0 mm.

[0073] b) Method 2: After the breathable film sample is printed, lay it flat on the table. After it is completely dry, use a blade to cut a 100-mm cross-shaped opening in the middle of the breathable film, and visually inspect whether the edges of the four corners of the cross-shaped cut are curled and measure the height of the curled edge.

[0074] As Figure 2 shown, when Example 1 is tested according to Method 2, the four corners of the cross-shaped cut are not curled and the height of the curled edge is less than 0.5 mm.

[0075] After testing by Method 1 and Method 2, the film layer after the ink is cured into a film does not curl with the breathable film, indicating that the ink film formed after the ink is cured has similar compliant characteristics to the breathable film, and can still maintain the tactile comfort of the breathable film in contact with the human skin after printing.

[0076] 3. Test method for the odor of printed products: According to GB / T35773-2017 "Evaluation of Odors of Packaging Materials and Products", disperse 40 printed breathable films of 100 mm * 100 mm into single sheets, and then put them into a glass bottle

[0077] for marking, and then cover the bottle cap. Then put the test sample glass bottle and the reference blank glass bottle into an oven at 50 °C for baking for 30 min, take them out and place them at room temperature for 20 min, and then conduct a blind nose test by 8 evaluators for comparison and evaluation. If the odor of the test sample glass bottle is the same as that of the reference blank glass bottle, it means there is no abnormal odor.

[0078] 4. Test method for resistance to physiological saline: After the printed product is completely dry, soak it in physiological saline for 36 hours,

[0079] the appearance of the saline does not change significantly; wipe the printed product after soaking for 36 hours with a tissue, and it does not decolorize.

[0080]

[0081] ​Those skilled in the art can make various other corresponding changes and deformations according to the technical solutions and concepts described above, and all such changes and deformations should fall within the protection scope of the claims of the present invention. Those skilled in the art can make various other corresponding changes and deformations according to the technical solutions and concepts described above, and all such changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. A saline-resistant, non-curling breathable film ink, characterized in that: It includes a connecting material, an auxiliary agent, a pigment and a solvent, wherein the connecting material is a combination of polyether polyurethane and nitrocellulose liquid; Calculated by mass percentage, 9.0-9.6% of polyether polyurethane, 18-19% of 1 / 16 second nitrocellulose liquid with a solid content of 35%, 0.7-0.8% of wax powder and 0.5-0.6% of nano silicon dioxide, and the balance is additives and solvents; The auxiliary agents include dispersants and defoamers.

2. The physiological saline-resistant, non-curling breathable film ink according to claim 1, characterized in that: After full printing on the LDPE breathable film with a gram weight of 15gsm and a thickness of 18um, the breathable film has no curling and the warping height is ≤0.5mm.

3. The physiological saline-resistant, non-curling breathable film ink according to claim 1, characterized in that: The wax powder is PE wax powder with a melting point of ≥120°C.

4. The physiological saline-resistant, non-curling breathable film ink according to claim 1, characterized in that: The dispersant is an active polymer dispersant.

5. The physiological saline-resistant, non-curling breathable film ink according to claim 1, characterized in that: The solvent is a combination of isopropyl alcohol and n-propyl acetate.

6. The physiological saline-resistant, non-curling breathable film ink according to claim 5, characterized in that: In terms of mass percentage, the n-propyl ester accounts for 85-88% of the solvent, and the remainder is isopropanol.

7. The physiological saline-resistant, non-curling breathable film ink according to claim 1, characterized in that: The nano silicon dioxide is hydrophobic gas-phase nano silicon dioxide.

8. The physiological saline-resistant, non-curling breathable film ink according to claim 1, characterized in that: The auxiliary agents include defoamers and dispersants.

9. The physiological saline-resistant, non-curling breathable film ink according to claim 1, characterized in that: Free of rosin and ethyl acetate.

10. A method for preparing ink, for preparing the physiological saline-resistant, non-curling breathable film ink as claimed in any one of claims 1 to 9, characterized in that: The following steps are involved: S1. Disperse nitrocellulose solution, dispersant, n-propyl ester, nano-silicon dioxide, wax powder and pigment at high speed for 30 to 60 minutes, grind to a fineness of ≤15um, and obtain color paste; S2. Emulsify the polyether polyurethane with solvent to a solid content of 30% and a viscosity (mPa·s / 25°C) 700-1200 polyether polyurethane resin liquid; S3, evenly dispersing isopropyl alcohol, defoaming agent, the color paste prepared in S1 and the polyether polyurethane resin liquid prepared in S2 to obtain a finished ink product.

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