Flexographic ink based on alcohol, high retort packing film using flexographic printing based flexographic ink and method of manufacturing the same

Abstract

An alcohol-based flexographic ink, a high-retort packaging material using flexographic printing based thereon, and a method for manufacturing the same are disclosed. The epoxy polyol contained in the urethane resin used in the flexographic ink comprises a bisphenol A type epoxy of the following chemical formula and acetic acid. Here, the bisphenol A type epoxy is an epoxy having one non-self-polymerized repeating unit and no hydroxyl groups within the molecule. [ Chemical Formula ]

Description

Technology Field

[0001] The present invention relates to an alcohol-based flexo ink, a high-retort packaging material using flexo printing based on the flexo ink, and a method for manufacturing the same. Background Technology

[0002] Currently, gravure ink is generally used to manufacture packaging materials, but recently, attempts have been made to manufacture packaging materials through flexographic printing, yet there is no technology to manufacture high-retort packaging materials.

[0003] Since gravure printing uses solvents such as MEK, EA, and toluene, the resin dissolves well, but when alcohol-based, the solubility is low and the resin does not dissolve well. Therefore, for flexographic printing, it is necessary to develop flexographic inks containing resins that dissolve in alcohol. In particular, there is a need to develop flexographic inks capable of manufacturing high-retort packaging materials. Prior art literature

[0004] (Patent Document 0001) KR 10-2012-0043931 A The problem to be solved

[0005] The present invention provides an alcohol-based flexo ink, a high-retort packaging material using flexo printing based on the flexo ink, and a method for manufacturing the same. means of solving the problem

[0006] To achieve the above-mentioned purpose, the epoxy polyol contained in the urethane resin according to one embodiment of the present invention comprises a bisphenol A type epoxy of the following chemical formula; and acetic acid. Here, the bisphenol A type epoxy is an epoxy having one self-nonpolymerized repeating unit and no hydroxyl groups within the molecule.

[0007] [ Chemical Formula ]

[0008]

[0009] A urethane resin used in a flexo ink according to one embodiment of the present invention comprises a general polyol; an epoxy polyol having hydroxyl groups; and an isocyanate. Herein, the general polyol is propylene glycol (PEG), diethylene glycol (DEG), polypropylene oxide glycol, propylene diol (NPD), or polyester polyol.

[0010] A urethane resin used in a flexo ink according to another embodiment of the present invention comprises a plurality of polyols; and an isocyanate. Herein, at least one of the polyols has a benzene ring structure and a hydroxyl group capable of reacting with the isocyanate.

[0011] The urethane resin used in the flexo ink according to another embodiment of the present invention comprises a polyol. Here, the polyol has a benzene ring structure so that the product manufactured by printing with the flexo ink has good characteristics as a result of retort evaluation at 120°C to 135°C, and the polyol having the benzene ring structure has a content of more than 0% by weight and less than or equal to 5% by weight based on 100% by weight of the urethane resin.

[0012] A flexo ink used for flexo printing according to one embodiment of the present invention comprises a pigment; an alcohol; and a urethane resin. Herein, the urethane resin comprises a plurality of polyols; and an isocyanate, wherein at least one of the polyols has a benzene ring structure and a hydroxyl group capable of reacting with the isocyanate, and the urethane resin is soluble in the alcohol.

[0013] High-retort packaging manufactured using flexographic printing according to one embodiment of the present invention uses a urethane resin for the flexographic ink for the flexographic printing. The urethane resin comprises a general polyol; an epoxy polyol having hydroxyl groups; and an isocyanate, wherein the general polyol is propylene glycol (PEG), diethylene glycol (DEG), polypropylene oxide glycol, propylene diol (NPD), or polyester polyol. Effects of the invention

[0014] The flexo ink used for flexo printing according to the present invention can be formed from a urethane resin having an epoxy polyol. Consequently, since the urethane resin is well soluble in alcohol, an alcohol-based flexo ink can be smoothly manufactured.

[0015] In addition, since the epoxy polyol has a benzene ring structure, the heat resistance of the urethane resin can be excellent, and high-temperature retort sterilization can be achieved. Therefore, high-retort packaging materials can be manufactured using the flexo ink. Brief explanation of the drawing

[0016] Figure 1 is a drawing illustrating gravure printing. Figure 2 is a drawing illustrating flexographic printing. Specific details for implementing the invention

[0017] As used in this specification, singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "composed" or "comprising" should not be interpreted as necessarily including all of the various components or steps described in the specification, and should be interpreted as meaning that some of the components or steps may be excluded, or that additional components or steps may be included. Furthermore, terms such as "...part," "module," etc., as used in the specification refer to a unit that processes at least one function or operation, which may be implemented in hardware or software, or a combination of hardware and software.

[0019] In gravure printing, as shown in FIG. 1, the gravure ink in the cylinder is printed directly onto the substrate (film), whereas in flexographic printing, as shown in FIG. 2, the ink in the cylinder moves through Janilox to a plate (a resin plate capable of creating an image) and is then printed onto the substrate (film) from the plate. At this time, gravure printing is an intaglio printing method, whereas flexographic printing is a relief printing method.

[0020] Unlike gravure printing, flexographic printing dilutes the ink, but the dilution ratio is not fixed; instead, it is diluted according to viscosity, which has the advantage of having low product variation. Previously, gravure printing was mainly used to satisfy the physical properties of packaging materials, but gravure ink used toluene, a VOC-regulated substance, as an organic solvent, which had harmful effects on the human body. Accordingly, the present invention proposes a flexographic printing ink that satisfies the physical properties of packaging materials without using VOC-regulated substances.

[0021] In particular, the present invention proposes a flexographic ink suitable for alcohol-based flexographic printing, a high-retort packaging material using flexographic printing, and a method for manufacturing the same. The resins of conventionally used gravure inks (e.g., chlorine resins) do not dissolve well in alcohol, and as a result, it is not possible to manufacture alcohol-based flexographic inks using the resins used in gravure inks.

[0022] In order to manufacture an alcohol-based flexo ink, it is necessary to use a resin that dissolves in alcohol. Accordingly, the present invention proposes a flexo ink using resins that dissolve in alcohol, in particular a newly developed resin.

[0023] According to one embodiment, the urethane resin used in the flexo ink may have a benzene ring structure and hydroxyl groups. As a result, the urethane resin dissolves in alcohol and possesses heat resistance and moisture resistance, thereby enabling the production of an alcohol-based flexo ink that satisfies the physical properties of a product manufactured by flexo printing, such as packaging material. Accordingly, the present invention can manufacture a high-retort packaging material.

[0025] Hereinafter, various embodiments of the present invention will be described in detail with reference to the attached drawings.

[0026] The flexo ink of the present invention is an alcohol-based flexo ink capable of withstanding a high temperature and high humidity sterilization process, and may contain a resin having a benzerin structure with excellent heat resistance. Therefore, a hydrotort packaging material can be manufactured using the flexo ink.

[0027] In addition, the above flexo ink can have excellent printability because it uses a resin that dissolves well in alcohol, that is, an alcohol-friendly resin.

[0028] According to one embodiment, the flexo ink may contain a pigment, a newly developed urethane resin for dispersion or adhesion of the pigment, ethyl alcohol, an antifoaming agent, and an antistatic agent. The pigment, the antifoaming agent, and the antistatic agent may be materials that were previously used, and thus, various materials may be used without being limited to specific materials.

[0029] The above urethane resin is a newly developed resin that is compatible with alcohol, and therefore, I will explain the flexo ink mainly using the above urethane resin below.

[0031] Below, we will examine the composition and manufacturing process of the urethane resin of the present invention.

[0032] Example 1

[0033] According to one embodiment, the urethane resin of the present embodiment can be manufactured using a general polyol, an epoxy polyol, and an isocyanate.

[0034] For example, propylene glycol (PEG) of Formula 1 below may be used as the general polyol, methylene diphenyl diisocyanate (MDI) of Formula 2 below may be used as the isocyanate, and dimethylol propanoic acid (DMPA) of Formula 3 below may be used as the polyol having an acid. In addition, the epoxy polyol may be prepared by synthesizing it separately.

[0035] Of course, the above general polyols are not limited to those that are alcohol-friendly, and for example, diethylene glycol (DEG), polypropylene oxide glycol, propylene diol (NPD), or polyester polyol may be used.

[0036] In addition, TDI (toluene diisocyanate) or HDI (hexamethylene diisocyanate) may be used as the isocyanate, and DMBA (dimethylol butanoic acid) may be used as the polyol having acid.

[0037]

[0038]

[0039]

[0040] The above epoxy polyol has hydroxyl groups to enable bonding with the above isocyanate, and in particular, may have a benzene ring structure to improve heat resistance.

[0041] According to one embodiment, the epoxy polyol can be produced by synthesizing a bisphenol A type epoxy of the following chemical formula 4 and acetic acid of the following chemical formula 5.

[0042]

[0043]

[0044] Looking at the reaction mechanism, when acetic acid and bisphenol A type epoxy are reacted in a 2:1 ratio under a catalyst, the epoxy functional group reacts with the acid, causing the epoxy ring to open and produce an epoxy polyol with a hydroxyl group (-OH) attached.

[0045] Meanwhile, there may be epoxy with a molecular weight increased as shown in Chemical Formula 6 below, which is self-polymerized from the above bisphenol A type epoxy. However, the bisphenol A type epoxy used in the present invention is a pure epoxy that has not self-polymerized, has one repeating unit, and has no hydroxyl groups within the molecule. Self-polymerized epoxy contains one or more hydroxyl groups in its molecular structure, but since this part is unnecessary, self-polymerized epoxy is not used in the present invention. This is because if self-polymerized epoxy is used, three or more hydroxyl groups are present, making it difficult to bond with a difunctional isocyanate.

[0046] The epoxy polyol of the present invention has a structure containing only two hydroxyl groups, and as a result, only a linear reaction may occur in subsequent reactions with a difunctional isocyanate.

[0047] When the above acetic acid is synthesized with a non-self-polymerized bisphenol A type epoxy, an epoxy polyol as shown in Chemical Formula 7 below can be produced. Specifically, the epoxy polyol has a benzene ring structure in the center that has heat / moisture resistance, two hydroxyl groups that can react with isocyanate, and a structure advantageous for adhesion and heat / moisture resistance may be located at the ends.

[0048] [ Reaction Mechanism ]

[0049]

[0050]

[0051]

[0053] Below, we will examine the process of synthesizing urethane resin using a general polyol (propylene glycol), an epoxy polyol of chemical formula 7, and an isocyanate (MDI).

[0054] First, when a general polyol, an epoxy polyol, and an isocyanate are mixed in the first step of the reaction, an intermediate polyol containing an epoxy structure can be produced, and the molecular weight of the produced polyol increases as it undergoes a specific reaction, and finally, a polymeric urethane resin containing an epoxy structure can be manufactured by undergoing a termination reaction to remove NCO.

[0055] [ Intermediate Polyol Formation ]

[0056]

[0057] [ Molecular Weight Increase Reaction ]

[0058]

[0059] [ Termination reaction (Terminal NCO removal) ]

[0060]

[0062] Example 2

[0063] The urethane resin of the present embodiment can be prepared by synthesizing a general polyol, an epoxy polyol, an isocyanate, and a polyol having an acid, and dissolving them in a solvent. That is, the urethane resin may additionally contain a polyol having an acid, and the polyol having an acid may be used to ensure the urethane resin has stability in alcohol. Stability can be improved because the acid structure dissolves by undergoing a neutralization reaction with the hydroxyl group of the alcohol. DMPA (dimethylol propanoic acid) or DMBA (dimethylol butanoic acid) may be used as such a polyol having an acid, but is not limited thereto.

[0064]

[0065] Looking at Table 1 above, the urethane resin can be produced by using propylene glycol as a general polyol, the epoxy polyol produced above, MDI as an isocyanate, DMPA as an acidic polyol, and acetone and ethanol as solvents. In this case, among the solvents, acetone may be added first and ethanol may be added later.

[0066] Alcohol compatibility refers to the determination of stability in a dissolved state in alcohol. The prepared urethane resin was placed in a refrigerator at -5°C and left for 24 hours, after which the state of the solution was determined. At this time, the alcohol compatibility is judged to be good if transparency is maintained and fluidity is good.

[0067] Looking at Table 1 above, it can be confirmed that urethane resins No. 3 through 5 have good alcohol compatibility. In other words, if the amount of acid is too low, defects occur, and it can be confirmed that a certain amount of acid is required. Of course, if there is no acid, alcohol compatibility may decrease significantly.

[0068] According to one embodiment, at least 2 weight% (weight ratio) of an acidic polyol may be required based on 100 weight% (weight ratio) of the urethane resin.

[0069] In addition, as shown in figures 4 to 6, it can be confirmed that alcohol compatibility is reduced if the epoxy polyol is too high. According to one embodiment, the epoxy polyol may be greater than 0 weight% and less than 8.33 weight% based on 100 weight% of the urethane resin, and preferably 3.3 weight% to 5 weight%.

[0070] According to another embodiment, the alcohol compatibility of the urethane resin may be good only when the ratio of the general polyol to the epoxy polyol is 2:1 or higher. If the epoxy polyol is greater than the above ratio, storage stability may be reduced.

[0071] According to another embodiment, the total polyol content may be greater than 0 weight% (weight ratio) and less than or equal to 80 weight% (weight ratio) based on 100 weight% (weight ratio) of the urethane resin.

[0072] That is, since the flexo ink of the present invention uses alcohol, the urethane resin must have good alcohol compatibility, and for this purpose, an acidic polyol is required in an amount of 2% or more, and the epoxy polyol may be less than 8.33% or the ratio of general polyol to epoxy polyol may be 2:1 or more.

[0074] Below, we will examine the process of manufacturing flexo ink using alcohol and a newly developed urethane resin. However, the above flexo ink is a black ink and is one of the flexo inks that can be produced using alcohol and the above urethane resin. The above urethane resins were individually used as numbers 3 to 5 of Table 1.

[0075] division Content carbon pigment 12 PVB 4 Cellulose 1 Dispersant 1 ethyl alcohol 35 PMA (solvent) 10 Intermediate sum 63

[0076] A base can first be prepared using the formulation shown in Table 2 above. The physical properties of the prepared base were verified, and the results are shown in Table 3 below. Specifically, the materials in Table 2 were sequentially placed into a mixing container and dispersed for 1 hour using a bead mill with a bead size of 1.2 mm at a speed of 2,000 rpm. The process was carried out while scraping the walls of the mixing container to prevent particles from clumping, and after the dispersion was completed, the physical properties were verified based on bar coater #7.

[0077] division Result value Reference value Viscosity (Zahn Cup #4) 38sec 28 sec ~ 45 sec Concentration (concentration meter) 2.8 2.5 or higher Gloss (glossy system) 46° 30°

[0078] As shown in Table 3, it can be confirmed that the physical properties (viscosity, concentration, gloss) of the base are all good.

[0079] Flexo ink was manufactured using the base prepared in this way, and the mixing ratio is as shown in Table 4 below.

[0080] division Content base 63 ethyl alcohol 15 Urethane resins No. 3, 4, and 5 in Table 1 (for individual use) 21 Antifoamer 0.7 Antistatic agent 0.3 Total 100

[0081] The base prepared above was first diluted with ethyl alcohol and stirred at 1,500 rpm for 30 minutes. Then, urethane resin and additives (defoaming agent and antistatic agent) were added sequentially. Subsequently, stirring was carried out for 1 hour, followed by a filtration process, after which the physical properties were checked using the same bar coater #7. The results are shown in Table 5 below.

[0082] division Result value Reference value Viscosity (Zahn Cup #4) 25sec 22sec ~ 28sec Concentration (concentration meter) 2.61 2.5 or higher Gloss (glossy system) 51° 40° or more Particle size (Grindometer value) 3 4 or less PET material tape attachment Good Equivalent to the sample

[0083] As shown in Table 5 above, it can be confirmed that the physical properties (viscosity, concentration, gloss, particle size) of the urethane resins manufactured using urethane resins No. 3, 4, and 5 and alcohol are excellent, and that they adhere well to PET substrate tapes.

[0085] Below, we will examine the retort evaluation of a flexographically printed product using the flexographic ink manufactured in this way.

[0086] A printed product was produced by mixing and stirring ethanol at a weight ratio of 20 to 100 to the flexo ink prepared above, and then printing through a flexo printer (printing speed 180 m / min, based on PET substrate).

[0087] The above printed material was produced into a pouch through a lamination process. At this time, the lamination was carried out using a solvent dry method, and the lamination process was performed based on PET film + NYLON + aluminum film + CPR film, and the material was left in an aging room at 38°C to 45°C for 48 hours. Subsequently, the laminating printed material was cut and sealed to produce a pouch.

[0088] For the pouches produced above, tensile strength was measured after steam sterilization (125℃, 135℃ for 30 minutes), and for the evaluation of pouch contents rupture, water and cooking oil were placed in the pouch in a ratio of 40g + 40g, sealed, and it was confirmed whether rupture occurred during the steam sterilization test (125℃, 135℃ for 30 minutes). The retort evaluations at 120℃ to 135℃ are as shown in Table 6 below.

[0089] division Ratio of epoxy polyol to general polyol Retort evaluation results No. 3 Urethane Resin 40 : 10 Good No. 4 Urethane Resin 45 : 5 NG No. 5 Urethane Resin 35 : 15 Good

[0090] As shown in Table 6 above, it can be confirmed that epoxy polyol has a positive effect on the product's ability to withstand high temperature and high pressure retort processes, but it can be confirmed that a minimum amount of epoxy polyol is required, and if the amount of epoxy polyol is small, it does not have sufficient heat resistance. For example, to have sufficient heat resistance, the epoxy polyol may be 3.3% or more based on 100% by weight of urethane resin.

[0091] As can be seen in Table 6 above, when packaging materials are manufactured using the flexo ink of the present invention, it can be confirmed that the retort is good, that is, high-retort packaging materials can be manufactured.

[0092] The detailed retort results of the urethane resin manufactured using urethane resin No. 5 are as shown in Table 7 below.

[0093] No. 5 Urethane Resin Ink Reference value 125℃ Lamination Strength 427g / ㎠ 380g / ㎠ ~ 500g / ㎠ 135℃ Lamination Strength 438g / ㎠ 380g / ㎠ ~ 500g / ㎠ Whether rupture occurs at 125℃ retort Does not occur Does not occur Whether rupture occurs during retort at 135℃ Does not occur Does not occur

[0095] Meanwhile, the components of the aforementioned embodiments can be easily identified from a process perspective. That is, each component can be identified as a respective process. Industrial applicability

[0096] The embodiments of the present invention described above are disclosed for illustrative purposes only, and those skilled in the art with ordinary knowledge of the present invention may make various modifications, changes, and additions within the spirit and scope of the present invention, and such modifications, changes, and additions should be considered to fall within the scope of the following claims.

[0097] No content

Claims

Claim 1 delete Claim 2 delete Claim 3 delete Claim 4 A urethane resin used in flexo ink comprising a general polyol; an epoxy polyol having hydroxyl groups; and an isocyanate, wherein the general polyol is propylene glycol (PEG), diethylene glycol (DEG), polypropylene oxide glycol, or polyester polyol, and the bisphenol A type epoxy used in the epoxy polyol is an epoxy having one non-self-polymerized repeating unit and no hydroxyl groups within the molecule, and the epoxy polyol is characterized by having only two hydroxyl groups and not three or more hydroxyl groups so as to cause only a linear reaction when reacted with a difunctional isocyanate. Claim 5 A urethane resin according to claim 4, wherein the epoxy polyol is produced by synthesizing the bisphenol A type epoxy and acetic acid, and wherein the acetic acid and the bisphenol A type epoxy are polymerized in a weight ratio of 2:

1. Claim 6 A urethane resin according to claim 5, characterized in that the epoxy polyol has a content of 3.3% to 8.33% by weight based on 100% by weight of the urethane resin. Claim 7 A urethane resin according to claim 5, characterized in that the general polyol and the epoxy polyol have a weight ratio of 2:1 or more. Claim 8 delete Claim 9 A urethane resin according to claim 4, characterized in that the general polyol is propylene glycol and the isocyanate is MDI (methylene diphenyl diisocyanate). Claim 10 In claim 4, the urethane resin further comprises an acid-containing polyol, wherein the acid-containing polyol is 2 weight percent or more based on 100 weight percent of the urethane resin. Claim 11 A urethane resin characterized in that, in claim 10, the polyol having the acid is DMBA (dimethylol butanoic acid). Claim 12 A urethane resin according to claim 10, characterized in that the total polyol has a content of more than 0% by weight and less than or equal to 80% by weight based on 100% by weight of the urethane resin. Claim 13 In paragraph 4, the urethane resin further comprises acetone and ethanol as solvents, wherein the acetone is added before the ethanol. Claim 14 delete Claim 15 delete Claim 16 delete Claim 17 delete Claim 18 delete Claim 19 delete Claim 20 A high-retort packaging material manufactured using flexographic printing, wherein the flexographic ink for the flexographic printing uses a urethane resin, and the urethane resin comprises a general polyol; an epoxy polyol having hydroxyl groups; and an isocyanate, wherein the general polyol is propylene glycol (PEG), diethylene glycol (DEG), polypropylene oxide glycol, or polyester polyol, and the bisphenol A type epoxy used in the epoxy polyol is an epoxy having one non-self-polymerized repeating unit and no hydroxyl groups within the molecule, and the epoxy polyol has only two hydroxyl groups and does not have three or more hydroxyl groups so as to cause only a linear reaction when reacted with a difunctional isocyanate.

Images