Printing ink composition

Abstract

To provide a printing ink composition and a method for producing the same, the composition containing a post-industrial recycled wax without impairing abrasion resistance, blocking resistance, and the like shown by a printing ink composition formulated with virgin wax.SOLUTION: A printing ink composition containing a post-industrial recycled wax, wherein the content of the post-industrial recycled wax is 0.1-5 wt%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a printing ink composition, and more particularly to a printing ink composition containing post-industrial recycled wax. [Background technology]

[0002] Waxes are incorporated into printing ink compositions to improve the abrasion resistance of the printed film, reduce tackiness, prevent blocking, and impart water resistance and water repellency. Here, wax is a general term for organic compounds primarily composed of aliphatic components that are solid at room temperature but melt when heated to form a low-viscosity fluid. Traditionally, printing inks for lithographic and offset printing, for example, have used large amounts of petroleum-derived synthetic waxes such as paraffin wax, microcrystalline wax, polyethylene wax, polypropylene wax, fatty acid amides, and polytetrafluoroethylene. When wax is used in printing inks, the wax particles present on the surface of the printed film improve abrasion resistance. This is thought to occur because the wax protruding from the ink surface is crushed by external physical pressure, spreading thinly over the ink film on paper or various film substrates, protecting the ink surface.

[0003] Meanwhile, with the need to achieve carbon neutrality and strengthen responses to the problems of marine plastic waste and climate change, promoting plastic recycling is becoming increasingly important. Recycled materials are generally classified into post-consumer recycled materials (hereinafter sometimes abbreviated as PCR) and post-industrial recycled materials (hereinafter sometimes abbreviated as PIR). PCR refers to materials collected or recycled after a product has been used and discarded by consumers, while PIR refers to materials collected or recycled from waste generated during the manufacturing process before the product reaches the consumer. Compared to PCR materials, PIR materials have less variation in quality due to degradation and other factors, making them more likely to produce stable products when used as recycled raw materials.

[0004] A method for producing wax from waste plastics (hereinafter sometimes abbreviated as waste plastics) (Patent Document 1) and a method for utilizing the wax (Patent Document 2) have been proposed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5964825 [Patent Document 2] Patent No. 6880051 Summary of the Invention [Problem to be solved by the invention]

[0006] The recycled wax proposed in Patent Documents 1 and 2 is made from recycled plastics, which is PCR material, and therefore suffers from poorer hue and impurity contamination compared to virgin wax, limiting its usage and applications. In particular, when used as a printing ink composition, the deterioration in hue is significant, making it difficult to achieve the target quality.

[0007] Therefore, an object of the present invention is to provide a printing ink composition using recycled wax produced from waste plastics, which has the same quality as that obtained when conventional virgin wax is used. [Means for solving the problem]

[0008] As a result of extensive research into solving the above-mentioned problems, the present inventors have discovered that by incorporating PIR wax, which is obtained by thermally decomposing waste PIR plastics, particularly discarded polyethylene resins, into a printing ink composition, it is possible to obtain a printing ink composition that has abrasion resistance, blocking resistance, etc. that are comparable to those of a printing ink composition that incorporates virgin wax, and have thereby completed the present invention.

[0009] That is, the embodiments of the present invention are [1] to [4] shown below. [1] A printing ink composition containing post-industrial recycled wax, wherein the content of the post-industrial recycled wax is 0.1 to 5% by weight. [2] The printing ink composition according to [1], wherein the post-industrial recycled wax satisfies the following (i) to (iii): (i) The number average molecular weight measured by gel permeation chromatography (GPC) is 500 or more and 8,000 or less. (ii) The ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) (molecular weight distribution: Mw / Mn) measured by GPC is 1.0 or more and less than 4.0. (iii) The melting point measured by differential scanning calorimetry (DSC) is 90°C or higher and 125°C or lower. [3] The printing ink composition according to [1], wherein the post-industrial recycled wax is a polyethylene wax. [4] The printing ink composition according to any one of [1] to [3], which is used in offset printing, flexographic printing, gravure printing, or screen printing. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a printing ink composition using PIR wax as a raw material, which further enables a reduction in waste plastics, and is therefore of extremely high industrial value. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below.

[0012] The printing ink composition according to one embodiment of the present invention contains 0.1 to 5% by weight of PIR wax.

[0013] The PIR wax preferably has a number average molecular weight (Mn) measured by gel permeation chromatography (GPC) of 500 to 8,000, more preferably 500 to 3,000. When the number average molecular weight (Mn) is 500 or more, the viscosity of the printing ink composition does not decrease, resulting in excellent blocking resistance and abrasion resistance. On the other hand, when the number average molecular weight (Mn) is 8,000 or less, the viscosity of the printing ink composition does not increase, resulting in good printability.

[0014] The PIR wax preferably has a ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) (molecular weight distribution: Mw / Mn) measured by GPC of 1.0 or more and less than 4.0, more preferably 1.0 or more and less than 3.3. When the molecular weight distribution is less than 4.0, the printing ink composition has good blocking resistance.

[0015] Furthermore, the melting point of the PIR wax is preferably from 90° C. to 125° C., more preferably from 100° C. to 115° C. When the melting point is 90° C. or higher, the printing ink composition has good blocking resistance and abrasion resistance, and when the melting point is 125° C. or lower, the viscosity and particle size of the printing ink composition do not increase, and the printing suitability is good.

[0016] Next, a method for producing the PIR wax will be described.

[0017] PIR wax is produced by feeding waste PIR plastic into an extruder and pyrolyzing it within the extruder.

[0018] The waste plastic for PIR materials is preferably polyethylene resin, and examples of such waste plastics include high-density polyethylene, low-density polyethylene, linear low-density polyethylene, and ultra-high molecular weight polyethylene. A mixture of these waste plastics is also acceptable. Furthermore, the form of the plastic is not limited to pellets or powder, but may also include molded products such as films, sheets, bottles, fibers, pipes, and injection-molded products, as well as their crushed parts. Examples of such waste plastics include used products, non-standard products, and discarded products. Of these, waste polyethylene generated during the extrusion lamination molding process is the most preferred. When the waste plastic is a resin composition, it may be in a state where the components are melted and mixed together, or in a state where the components are physically mixed in the form of solids such as pellets or scraps.

[0019] PIR waste plastics can be used as they are, with antioxidants added during manufacturing or when they are molded into products such as film.Furthermore, antioxidants can be added to prevent oxidative degradation during the thermal decomposition reaction, and the thermal decomposition reaction can also be carried out.

[0020] The extruder is not particularly limited, and examples thereof include single-screw extruders, co-rotating twin-screw extruders, counter-rotating twin-screw extruders, multi-screw extruders such as four-screw or eight-screw extruders with three or more screws arranged in parallel in the cylinder of the extruder, and tandem extruders, such as those in which two or more extruders are connected in series, those in which the outlet of one extruder is connected to the inlet of the other extruder to form an L-shape, and those in which the outlet of one extruder is connected to the side of the other extruder to form a T-shape. Furthermore, each extruder constituting the tandem extruder may be a single-screw extruder or a multi-screw extruder with two to eight screws, and two or more of these extruders can be combined to form a tandem extruder. Among these extruders, co-rotating twin-screw extruders, four- to eight-screw multi-screw extruders, and tandem extruders are preferred because they produce PIR waxes of particularly stable quality and have excellent stability in torque and output during extrusion. It is preferable to install a side feeder in these extruders for feeding the modifier.

[0021] The extruder is preferably equipped with a vacuum vent port to efficiently discharge pyrolyzed low-molecular-weight gas components outside the extruder. Furthermore, the ratio (L / D) of screw length (L) to screw diameter (D) is preferably 30 or more, particularly 40 or more, because this allows for efficient pyrolysis of waste plastics and results in PIR wax of stable quality.

[0022] The conditions for pyrolysis of waste plastics after feeding them into the extruder should be adjusted appropriately depending on the molecular weight of the desired pyrolysis wax, but since pyrolysis can be carried out in a short time and the odor of the resulting pyrolysis wax can be easily suppressed, the cylinder temperature in the pyrolysis zone can be in the range of 330 to 480°C, more preferably 350 to 460°C, and particularly preferably 380 to 450°C. The residence time in the pyrolysis zone can be in the range of 0.5 to 30 minutes, more preferably 1 to 20 minutes, and particularly preferably 1.5 to 15 minutes.

[0023] In addition, since this reduces the odor of the resulting PIR wax and makes it easier to control the molecular weight and degree of modification, it is preferable to replace the atmosphere inside the extruder with an inert gas such as hydrogen, helium, argon, nitrogen, or carbon dioxide during pyrolysis, and nitrogen gas is particularly preferable.The wax extruded from the extruder can be made into pellets by methods such as hot cutting, mist cutting, or underwater cutting, or by cooling on a steel belt and then cutting.

[0024] PIR waxes can be used in any form, including pellets, powder, flakes, granules, grains, and pastes.

[0025] Next, a method for producing the printing ink composition will be described.

[0026] The amount of PIR wax added is 0.1 to 5 wt %, preferably 0.5 to 3 wt %, based on the total amount of the printing ink composition. An amount less than 0.1 wt % cannot ensure sufficient abrasion resistance, while an amount exceeding 5 wt % raises the risk of excess wax accumulating on rollers and other surfaces. The PIR waxes can be used singly or in combination. When the PIR wax content is within the above range, the coating material tends to have an excellent balance between abrasion resistance and blocking resistance. The PIR wax can be added at any step in the conventional printing ink manufacturing process. That is, the pigment and PIR wax may be dispersed and kneaded together in a varnish to form an ink, or the PIR wax may be mixed with the varnish that has been subjected to the dispersion and kneading steps to form an ink.

[0027] Examples of printing ink compositions include inks containing 5-30% by weight of pigment, 20-50% by weight of binder resin, 1-40% by weight of vegetable oil, 1-45% by weight of solvent, and 0.1-5% by weight of PIR wax as an anti-friction agent. These inks are primarily used as printing ink compositions for offset printing, flexographic printing, gravure printing, screen printing, etc., but are not limited to these.

[0028] Examples of pigments include general inorganic and organic pigments, such as yellow lead, zinc yellow, iron blue, barium sulfate, cadmium red, titanium oxide, zinc white, red iron oxide, alumina white, calcium carbonate, ultramarine, carbon black, graphite, and aluminum powder. Examples of organic pigments include azo pigments such as soluble azo pigments C (β-naphthol), 2B, and 6B (β-oxynaphthoic) pigments; insoluble azo pigments such as β-naphthol, β-oxynaphthoic acid anilide, monoazo yellow, disazo yellow, and pyrazolone; condensed azo pigments such as acetoacetate arylide; phthalocyanine pigments such as copper phthalocyanine (α-blue, β-blue, ε-blue), copper phthalocyanine halides (chlorine, bromine, etc.), metal-free phthalocyanine pigments; and polycyclic pigments such as perylene, perinone, quinacridone, thioindigo, dioxazine, isoindolinone, and quinophthalone pigments. The amount of pigment added is preferably 5 to 30% by weight of the total weight of the printing ink composition.

[0029] The binder resin refers to rosin-modified phenolic resin, rosin-modified maleic acid resin, alkyd resin, polyester resin, petroleum resin, etc., which can be used alone or in combination of two or more. Furthermore, the binder resin preferably has a clouding temperature of 40 to 140°C when diluted 10% with AF Solvent 6 manufactured by Nippon Oil Corporation. (The clouding temperature was measured using a Chemotic manufactured by Novocontrol.) A temperature of 40°C or higher provides sufficient gel elasticity when made into a varnish, while a temperature of 140°C or lower provides good affinity with the solvent.

[0030] The binder resin can be prepared by adding vegetable oils and / or solvents and a gelling agent such as an aluminum chelate compound, dissolving the mixture at 190° C. or higher to form a varnish. The amount of binder resin added is preferably 20 to 50% by weight of the total amount of the printing ink composition.

[0031] Vegetable oils are vegetable oils and compounds derived from vegetable oils, and examples thereof include fatty acid monoesters obtained by esterifying triglycerides of glycerin and fatty acids, in which at least one fatty acid has at least one carbon-carbon unsaturated bond, with saturated or unsaturated alcohols, and fatty acid monoesters and ethers obtained by directly esterifying fatty acids of vegetable oils with monoalcohols.

[0032] Representative vegetable oils include hemp seed oil, linseed oil, perilla oil, oiticica oil, olive oil, cacao oil, kapok oil, tomato oil, mustard oil, apricot kernel oil, tung oil, kukui oil, walnut oil, poppy seed oil, sesame oil, safflower oil, radish seed oil, soybean oil, tung oil, camellia oil, corn oil, rapeseed oil, niger oil, rice bran oil, palm oil, castor oil, sunflower oil, grape seed oil, almond oil, pine seed oil, cottonseed oil, coconut oil, peanut oil, and dehydrated castor oil.

[0033] The fatty acid monoesters are those obtained by transesterification of the above-mentioned vegetable oils with monoalcohols or by direct esterification of fatty acids of vegetable oils with monoalcohols. Representative monoalcohols include saturated alcohols such as methanol, ethanol, n- or iso-propanol, n, sec- or tet-butanol, heptynol, 2-ethylhexanol, hexanol, octanol, decanol, and dodecanol, and unsaturated aliphatic alcohols such as oleyl alcohol, dodecenol, fisseteryl alcohol, sommaryl alcohol, gadoleyl alcohol, 11-icosenol, 11-docosenol, and 15-tetracosenol.

[0034] Representative examples of the ethers include di-n-octyl ether, dinonyl ether, diheptyl ether, dihexyl ether, didecyl ether, nonylhexyl ether, nonylheptyl ether, and nonyloctyl ether.

[0035] The solvent is a crude oil-derived solvent (petroleum-based solvent) with an aromatic hydrocarbon content of 1% by weight or less. The appropriate petroleum-based solvent is one with an aniline point between 70 and 110°C and a boiling point of 230°C or higher. An aniline point of 70°C or higher provides sufficient resin dissolving ability, preventing the ink viscosity from becoming too low and providing sufficient scumming resistance. An aniline point of 110°C or lower provides excellent resin solubility, resulting in excellent ink flowability and resulting in prints with good gloss and ink acceptance. A boiling point of 230°C or higher prevents excessive release of ink solvents on the printing press, reducing ink flowability and preventing ink buildup on rollers, plates, and blankets.

[0036] Any known kneading means may be used in the production of printing inks, but preferred examples include a twin-screw extruder, a single-screw extruder, a kneader, and a Banbury mixer. The printing ink composition may also contain various secondary materials, such as dispersants, emulsifiers, surfactants, stabilizers, wetting agents, thickeners, foaming agents, antifoaming agents, coagulants, gelling agents, antisettling agents, charge control agents, antistatic agents, antioxidants, softeners, plasticizers, fillers, colorants, fragrances, anti-tack agents, and release agents, to the extent that their performance is not impaired. [Example]

[0037] EXAMPLES The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these.

[0038] The physical properties in the production examples were determined by the following measurement methods. (1) GPC measurement Apparatus: HLC (registered trademark)-8321GPC / HT (detector: RI method) (manufactured by Tosoh Corporation) Columns: One column of (i) and three columns of (ii) below are used in series. (i) TSKgel® guardColumuH(HR)(30)HT (7.5mm I.D.) x 7.5cm) (Tosoh Corporation) x 1 (ii) TSKgel® GMH(HR)-H(20)HT (7.5mm I.D.) x 30cm) (Tosoh Corporation) x 3 Eluent: 1,2,4-trichlorobenzene (containing 0.05 wt% BHT) (Purchased from Fujifilm Wako Pure Chemical Industries, Ltd.) Flow rate: 1.0mL / min Injection volume: 0.3mL Column temperature: 140℃ System temperature: 40°C Sample concentration: 1 mg / mL Calibration curve: quintic approximation curve using standard polystyrene manufactured by Tosoh Corporation. However, the molecular weight was converted to PE equivalent molecular weight using the Q factor. (2) Melting point measurement Measurements were taken in accordance with JIS K7122 (2012).

[0039] The melting point of PIR wax was measured by differential scanning calorimetry (DSC) using a DSC7000X (Hitachi High-Tech Science). Approximately 10 mg of sample was sealed in an aluminum pan and heated from -20°C to 200°C at a rate of 10°C / min. The endothermic peak of the resulting curve was determined as the melting point. Prior to this temperature measurement, the sample was first heated to approximately 200°C, held there for 5 minutes, and then cooled to -20°C at a rate of 20°C / min to standardize the thermal history of the sample.

[0040] [Manufacturing Example 1] The extruder used was a co-rotating intermeshing twin-screw extruder with a screw diameter of 11 mm and a screw length L to screw diameter D ratio (L / D) of 40. Used PIR polyethylene (number average molecular weight 15,000) generated during resin switching in extrusion lamination molding of low-density polyethylene (Petrothene® 205, manufactured by Tosoh Corporation) was used as waste plastic. The waste plastic was crushed to an average particle size of 10 mm or less in a crusher, reduced in volume, and fed into the main feeder of the extruder at a feed rate of 200 g / hr along with a constant flow of nitrogen gas. The extruder was then melt-kneaded under conditions where the cylinder temperature in the thermal decomposition zone was 450 °C and the cooling zone was heated to 200 °C, allowing for thermal decomposition. The melt-kneaded mixture was then extruded onto a steel plate placed under a nitrogen atmosphere, cooled, and crushed to obtain powdered PIR wax. The resulting PIR wax (A-1) was subjected to GPC measurement, and the results showed that the number average molecular weight (Mn) was 2,900, the molecular weight distribution (Mw / Mn) was 3.5, and the melting point (Tm) was 110.5°C.

[0041] [Manufacturing Example 2] PIR wax was obtained in the same manner as in Example 1, except that polyethylene (number average molecular weight 13,000) from used PIR material, which was a laminate film remnant of low-density polyethylene (Petrothene (registered trademark) 203 manufactured by Tosoh Corporation), was used as the waste plastic. The analysis results of the obtained PIR wax (A-2) are shown in Table 1.

[0042] [Examples 1 to 3] A four-neck flask equipped with a stirrer, a reflux condenser with a water separator, and a thermometer was charged with 23 parts of a rosin-modified phenolic resin (Halifenol 1248 manufactured by Harima Chemicals Co., Ltd.), 20 parts of a petroleum resin (Petcol (registered trademark) 130 manufactured by Tosoh Corporation), 12 parts of soybean oil, 44 parts of a petroleum-based solvent (AF Solvent 7 manufactured by Eneos Corporation), and 1 part of a gelling agent (ALCH manufactured by Kawaken Fine Chemicals Co., Ltd.), and the mixture was heated and stirred at 190°C for 1 hour to obtain a varnish for offset printing ink.

[0043] To 70 parts of the varnish for offset printing ink, 17 parts of a red pigment (Lionol Red 6B manufactured by Toyo Ink Mfg. Co., Ltd.) and 13 parts of a petroleum-based solvent (AF Solvent 7 manufactured by Eneos Corporation) were added, and an offset printing ink composition was obtained using a three-roll mill according to the usual method.

[0044] The PIR wax (A-1) was added to the offset printing ink composition in the blending ratio shown in Table 2 and mixed, thereby obtaining the offset printing ink compositions of Examples 1 to 3.

[0045] [Example 4] An offset printing ink composition was obtained in the same manner as in Example 1, except that the PIR wax (A-2) obtained in Production Example 2 was used instead of the PIR wax (A-1) used in Example 1.

[0046] [Comparative Example 1] An offset printing ink composition was obtained in the same manner as in Example 1, except that the PIR wax (A-1) used in Example 1 was replaced with Sanwax-131P (manufactured by Sanyo Chemical Industries, Ltd., physical properties of which are shown in Table 1).

[0047] Comparative Example 2 An offset printing ink composition was obtained in the same manner as in Example 1, except that the PIR wax (A-1) used in Example 1 was replaced with Hiwax 220P (manufactured by Mitsui Chemicals, Inc., physical properties of which are shown in Table 1).

[0048] [Table 1]

[0049] (3) Performance evaluation test of printing ink composition The performance evaluation results of the offset printing ink compositions of the above Examples and Comparative Examples are shown in Table 2. The test pieces for evaluation were prepared by applying the offset rotary inks obtained in Examples 1 to 4 and Comparative Examples 1 and 2 to a 0.3 cm diameter test piece using the front roll of an RI tester manufactured by Akebono Seisakusho. 3The ink was applied to Mitsubishi Paper Mills' Pearl Coat A in an amount of 100°C and dried in a hot air oven by blowing hot air over the paper surface until the temperature reached 100°C. [Evaluation method for abrasion resistance] The test piece was placed on a blank insert and rubbed 10 times with a load of 100 g in a Gakushin-type rub resistance tester manufactured by Toyo Seiki Co., Ltd., and the degree of rubbed test piece was compared. The degree of rubbed test piece was compared on a 5-point scale, with 1 being significant rubbed and 5 being good rubbed. [Blocking resistance evaluation method] After drying, two sheets of the ink-coated paper were stacked with the coated side facing inward, sandwiched between lath boards, and placed on a smooth table with a load of 10 g / cm. 2 After leaving it in a constant temperature and humidity environment (25°C, 50%) for 24 hours, the state of the two pieces of paper when pulled apart is evaluated on a 4-point scale. Printing condition (good) 4-3-2-1 (bad) 4: The printed surface is completely undamaged.

[0050] 3: Slight cohesive failure is observed in the ink on the peeled surface, and light force is required to peel it off.

[0051] 2: Clear cohesive failure is observed in the ink on the peeled surface, and a strong force is required to peel it off.

[0052] 1: Interfacial peeling between ink and paper is observed during peeling.

[0053] The printing ink compositions containing PIR wax (Examples 1 and 4) exhibited good abrasion properties and blocking resistance that were comparable to those of the printing ink compositions containing conventional wax (Comparative Examples 1 and 2).

[0054] [Table 2] [Industrial Applicability]

[0055] PIR wax, produced by simply and efficiently pyrolyzing waste plastic from PIR materials, helps reduce waste plastic and, when used as a printing ink raw material, provides a printing ink composition with excellent abrasion resistance and blocking resistance.

Claims

1. A printing ink composition containing post-industrial recycled wax, wherein the content of the post-industrial recycled wax is 0.1 to 5% by weight.

2. The printing ink composition according to claim 1, wherein the post-industrial recycled wax satisfies the following (i) to (iii): (i) The number average molecular weight measured by gel permeation chromatography (GPC) is 500 or more and 8,000 or less. (ii) The ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) (molecular weight distribution: Mw / Mn) measured by GPC is 1.0 or more and less than 4.

0. (iii) The melting point measured by differential scanning calorimetry (DSC) is 90°C or higher and 125°C or lower.

3. 2. The printing ink composition of claim 1, wherein the post-industrial recycled wax is a polyethylene wax.

4. 4. The printing ink composition according to claim 1, which is used in any one of offset printing, flexographic printing, gravure printing, and screen printing.

Images