Aqueous dispersion of polyamide resin, printing ink, and method for producing aqueous dispersion of polyamide resin

Abstract

The present invention provides an aqueous polyamide resin dispersion that does not require the removal of organic solvents and exhibits excellent storage stability, adhesion to PET and OPP substrates, ejection stability when used as an inkjet ink, and abrasion resistance of printed materials. [Solution] A polyamide resin aqueous dispersion containing a polyamide resin (A) and a surfactant (B), wherein the total amine value of the polyamide resin (A) is less than the acid value of the polyamide resin (A), the total amine value of the polyamide resin (A) is 0.5 to 10 mg KOH / g, the surfactant (B) contains a polyoxyalkylene alkyl ether, and the content of the surfactant (B) is 9 to 35% by weight based on the total weight of (A) and (B).

Description

Technical Field

[0001] The present invention relates to an aqueous dispersion of a polyamide resin, a printing ink, and a method for producing an aqueous dispersion of a polyamide resin.

Background Art

[0002] A polyamide resin having an amide bond is a resin obtained by a dehydration condensation reaction using a polycarboxylic acid component and a polyamine component, and is used in a wide range of fields such as food packaging applications and industrial applications. However, since the polyamide resin is solid, it does not become a suitable liquid for use without heating, and there are limitations in the VOC problem (regulation of volatile chemical substances) and solvent solubility in toluene and the like, and the type of solvent is also limited. For these reasons, it is difficult to apply a thin film to paper and various plastic films, and it is not generally used for these applications at present. On the other hand, if the polyamide resin can be dispersed in water, it is considered that the above problems can be solved. However, since the polyamide resin has a strong polar amide bond in the molecule, the particles of the polyamide resin exhibit polyvalent electrolyte behavior in water, and an interaction that causes aggregation acts, making it difficult to form a stable dispersion. Even with a water dispersion technique such as a general phase inversion emulsification method, a low-viscosity aqueous dispersion can be obtained during heating, but it becomes unstable with high viscosity or solidification when cooled, so it is insufficient for practical use. Therefore, studies have been conducted to stably disperse the polyamide resin by using an acidic compound or the like (Patent Documents 1 and 2). However, the aqueous polyamide resin dispersions obtained in Patent Documents 1 and 2 require organic solvents such as tetrahydrofuran and isopropyl alcohol in the water dispersion step during production. Not only the generation of VOCs but also a large amount of heat is required for distilling off the organic solvent after water dispersion, which is also a problem. In addition, the adhesion and storage stability of the obtained resin aqueous dispersion to polyethylene terephthalate (PET) and polypropylene (OPP) substrates are also insufficient for practical use in printing inks and the like.

Prior Art Documents

Patent Documents

[0003] [Patent Document 1] Japanese Patent Publication No. 2012-31261 [Patent Document 2] Japanese Patent Publication No. 2001-270987 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The present invention has been made in view of the above-mentioned problems, and aims to provide an aqueous polyamide resin dispersion that does not require the removal of organic solvents and has excellent storage stability, adhesion to PET and OPP substrates, ejection stability when used as an inkjet ink, and abrasion resistance of printed materials. [Means for solving the problem]

[0005] The present inventors have diligently studied to achieve the above objective and have arrived at the present invention. That is, the present invention is a polyamide resin aqueous dispersion containing a polyamide resin (A) and a surfactant (B), wherein the total amine value of the polyamide resin (A) is less than the acid value of the polyamide resin (A), the total amine value of the polyamide resin (A) is 0.5 to 10 mg KOH / g, the surfactant (B) contains a polyoxyalkylene alkyl ether, and the content of the surfactant (B) is 9 to 35% by weight based on the total weight of (A) and (B); the aqueous component of the polyamide resin A printing ink containing a dispersion; a method for producing an aqueous dispersion of polyamide resin, comprising the step of dispersing a polyamide resin (A) in water in the presence of a surfactant (B), wherein the total amine value of the polyamide resin (A) is less than the acid value of the polyamide resin (A), the total amine value of the polyamide resin (A) is 0.5 to 10 mg KOH / g, the surfactant (B) contains a polyoxyalkylene alkyl ether, and the content of the surfactant (B) is 9 to 35% by weight based on the total weight of (A) and (B). [Effects of the Invention]

[0006] The aqueous dispersion of polyamide resin of the present invention does not require the removal of organic solvents and exhibits excellent storage stability, adhesion to PET and OPP substrates, and ejection stability and abrasion resistance of printed materials when used as an inkjet ink. [Modes for carrying out the invention]

[0007] The aqueous dispersion of polyamide resin in the present invention contains a polyamide resin (A) and a surfactant (B).

[0008] Polyamide resin (A) can be obtained by mixing a polycarboxylic acid component and a polyamine component and carrying out a polycondensation reaction.

[0009] The polycarboxylic acid components in this invention include dicarboxylic acids (a1) and polycarboxylic acids with a valentity of 3 or higher (a2). These may be used individually or in combination of two or more. The carbon number of the carboxylic acid components shown below includes the carbon number contained in the carboxyl group. Examples of dicarboxylic acids (a1) include aromatic dicarboxylic acids with 8 to 36 carbon atoms (phthalic acid, isophthalic acid, and naphthalenedicarboxylic acid, etc.), aliphatic dicarboxylic acids with 2 to 50 carbon atoms (oxalic acid, malonic acid, succinic acid, adipic acid, azelaic acid (nonannic acid, reparginic acid), sebacic acid, dodecanediic acid, butyloctanedioic acid, eicosanedioic acid, eicosadienediic acid, isoeicosanedioic acid, docosanedioic acid, isodocosanedioic acid, isodocosadienediic acid, etc.), alicyclic dicarboxylic acids with 6 to 44 carbon atoms [dimeric acid (dimerized linoleic acid), etc.], alkenedicarboxylic acids with 4 to 36 carbon atoms (alkenyl succinic acid such as dodecenyl succinic acid, maleic acid, fumaric acid, citraconic acid, and mesaconic acid, etc.), and ester-forming derivatives thereof. Here, ester-forming derivatives refer to carboxylic acid anhydrides, alkyl (methyl, ethyl, butyl, stearyl, etc., having 1 to 24 carbon atoms, preferably having 1 to 4 carbon atoms) esters, and partially alkyl esters.

[0010] Examples of polycarboxylic acids with a valency of 3 or higher (a2) include aromatic polycarboxylic acids with 9 to 20 carbon atoms (such as trimellitic acid and pyromellitic acid), aliphatic (including alicyclic) tricarboxylic acids with 6 to 66 carbon atoms (such as trimer acid, hexanetricarboxylic acid and decanetricarboxylic acid), and ester-forming derivatives thereof.

[0011] Of these polycarboxylic acid components, aliphatic dicarboxylic acids having 2 to 50 carbon atoms, alicyclic dicarboxylic acids having 6 to 44 carbon atoms, and aliphatic (including alicyclic) tricarboxylic acids having 6 to 66 carbon atoms are preferred from the viewpoint of adhesion to OPP substrates, boil / retort resistance, and inkjet suitability. More preferably, aliphatic dicarboxylic acids having 2 to 50 carbon atoms and alicyclic dicarboxylic acids having 6 to 44 carbon atoms are preferred, and even more preferably, alicyclic dicarboxylic acids having 36 to 44 carbon atoms are preferred. From the viewpoint of abrasion resistance, the dicarboxylic acid in the carboxylic acid component (a) of resin (P) is more preferably 60 to 100 mol%.

[0012] Furthermore, monocarboxylic acid components may be included as necessary as carboxylic acid components to obtain polyamide resin (A). Examples of monocarboxylic acids include aromatic monocarboxylic acids with 7 to 37 carbon atoms (benzoic acid, toluic acid, 4-ethylbenzoic acid, 4-propylbenzoic acid, etc.) and aliphatic (including alicyclic) monocarboxylic acids with 2 to 50 carbon atoms (acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, and behenic acid, etc.).

[0013] Examples of polyamine components include diamines and polyamines with a valent or higher nucleotide Examples of diamines include aromatic diamines with 6 to 36 carbon atoms (toluenediamine, piperazine, etc.), aliphatic diamines with 2 to 50 carbon atoms (ethylenediamine, propylenediamine, hexamethylenediamine, etc.), and alicyclic diamines with 6 to 44 carbon atoms (isophoronediamine, dimeramine, etc.). Examples of polyamines with a valency of 3 or higher include polyalkylene polyamines with 2 to 10 carbon atoms (such as diethylenetriamine, triethylenetetramine, and tetraethylenepentamine), and aliphatic (including alicyclic) triamines with 6 to 64 carbon atoms (trimeric triamines). Of these amine components, diamines are preferred from the viewpoint of adhesion to the OPP substrate and abrasion resistance, with aliphatic diamines having 2 to 50 carbon atoms and alicyclic diamines having 6 to 44 carbon atoms being more preferred. From the viewpoint of adhesion, the amount of diamine in the polyamine component of resin (A) is preferably 80 to 100 mol%.

[0014] In the present invention, the amide group content of the polyamide resin (A) is preferably 2.0 to 4.0 mol / kg, more preferably 2.5 to 3.6 mol / kg, and even more preferably 3.0 to 3.6 mol / kg, from the viewpoint of blocking resistance and adhesion.

[0015] The acid value of the polyamide resin (A) is preferably 5 to 30 mg KOH / g, more preferably 5 to 20 mg KOH / g, and even more preferably 10 to 20 mg KOH / g, from the viewpoint of particle size, ejection stability as an inkjet ink, and storage stability. The acid value can be measured using the method specified in JIS K0070.

[0016] The total amine value of the polyamide resin (A) is 0.5 to 10 mg KOH / g, preferably 0.5 to 5 mg KOH / g, and more preferably 0.5 to 3 mg KOH / g. If the total amine value of the polyamide resin (A) is less than 0.5 mg KOH / g, the adhesion to the PET film decreases, and if it exceeds 10 mg KOH / g, the storage stability of the aqueous dispersion deteriorates.

[0017] The total amine value of the polyamide resin (A) is smaller than the acid value of the polyamide resin (A). The difference obtained by subtracting the total amine value of the polyamide resin (A) from the acid value of the polyamide resin (A) is preferably 1 to 20 mgKOH / g, more preferably 3 to 19 mgKOH / g, and particularly preferably 5 to 19 mgKOH / g from the viewpoints of particle size and storage stability. When the total amine value of the polyamide resin (A) is the same as or greater than the acid value of the polyamide resin (A), there is a problem that the storage stability of the aqueous dispersion deteriorates.

[0018] The total amine value in the present invention can be measured by the following method. The solvents shown below are merely examples, and if it is difficult to dissolve the sample in the following solvents, the solvent may be appropriately changed to a solvent capable of dissolving the sample. <Measurement method of total amine value> Dissolve 1 g of the sample in 50 ml of dimethylformamide, titrate with a 0.01 N hydrochloric acid / methanol solution, and calculate the total amine value from the following formula. Total amine value = 0.561 × (drop volume [ml]) × (titer of 0.01 N hydrochloric acid / methanol solution) / (sample weight [g])

[0019] The melting point of the polyamide resin (A) in the present invention is preferably 80°C or higher from the viewpoints of abrasion resistance and blocking resistance, and preferably 150°C or lower from the viewpoint of storage stability. More preferably, it is 90 to 130°C, and particularly preferably 100 to 120°C. The melting point is measured using a differential scanning calorimeter (DSC). In the present invention, the melting point of the polyamide resin (A) means that, using a differential scanning calorimeter (DSC), the polyamide resin is first heated from 20°C to 200°C at a rate of 10°C / min (first heating process), then held at 200°C for 1 minute, cooled from 200°C to 0°C at a rate of 10°C / min, then held at 0°C for 1 minute, and then heated from 0°C to 200°C at a rate of 10°C / min for the second time (second heating process). Among the DSC curves obtained, it is the temperature at the peak of the melting (endothermic) peak obtained in the second heating process.

[0020] The weight average molecular weight of the polyamide resin (A) is preferably from 3,000 to 150,000, more preferably from 10,000 to 80,000, and still more preferably from 20,000 to 60,000, from the viewpoints of filtration throughput and abrasion resistance.

[0021] In the present invention, the weight average molecular weight can be measured under the following conditions using gel permeation chromatography (GPC). Apparatus (example): HLC-8120 manufactured by Tosoh Corporation Column (example): Two TSK GEL GMH6 [manufactured by Tosoh Corporation] Measurement temperature: 40°C Sample solution: 0.25 wt% THF solution Solution injection volume: 100 μL Detector: Refractive index detector Reference substance: 12 standards of standard polystyrene (TSKstandard POLYSTYRENE) manufactured by Tosoh Corporation (molecular weights 500, 1,050, 2,800, 5,970, 9,100, 18,100, 37,900, 96,400, 190,000, 355,000, 1,090,000, 2,890,000) The measurement of the molecular weight is carried out by dissolving the sample in tetrahydrofuran (THF) to a concentration of 0.25 wt%, and filtering the insoluble matter through a PTFE filter with an aperture of 220 nm to obtain a sample solution.

[0022] As a method for producing the polyamide resin (A), it can be produced by mixing a polycarboxylic acid component and a polyamine component and carrying out a polycondensation reaction. Specifically, for example, dimer acid and ethylenediamine are subjected to a polycondensation reaction in an atmosphere of an inert gas (such as nitrogen gas) at a reaction temperature preferably of 100 to 300°C. Also, the reaction time is preferably 30 minutes or more, more preferably 2 to 40 hours, from the viewpoint of ensuring the polycondensation reaction. It is also effective to reduce the pressure in order to improve the reaction rate at the end of the reaction.

[0023] Furthermore, stabilizers may be added to ensure stable polymerization of the polyamide resin (A). Examples of stabilizers include hydroquinone, methylhydroquinone, and hindered phenol compounds.

[0024] The surfactant (B) in the present invention contains a polyoxyalkylene alkyl ether.

[0025] In the present invention, a polyoxyalkylene alkyl ether is a compound in which a polyoxyalkylene chain and an alkyl group are linked by an ether bond. The polyoxyalkylene chain in the polyoxyalkylene alkyl ether may be, for example, a polyoxyethylene chain, a polyoxypropylene chain, or a polyoxyethylene-polyoxypropylene chain. The polyoxyethylene-polyoxypropylene chain may be formed by random addition of ethylene oxide and propylene oxide, or by block addition of these.

[0026] From the viewpoint of storage stability of the polyamide resin, polyoxyethylene chains and polyoxyethylene polyoxypropylene chains are preferred as polyoxyalkylene chains in polyoxyalkylene ethers, with polyoxyethylene polyoxypropylene chains being particularly preferred. The ratio of the number of moles of ethylene oxide to polypropylene oxide added is not particularly limited, but for example, the ratio of the number of moles of polypropylene oxide added to the number of moles of polyethylene oxide added is preferably 0-10:3-30, more preferably 0-5:5-20, and particularly preferably 1-3:10-17.

[0027] The alkyl group in the polyoxyalkylene alkyl ether may be linear or branched. Furthermore, from the viewpoint of the storage stability of the polyamide resin, the number of carbon atoms in the alkyl group is preferably 6 to 36, more preferably 8 to 18, and particularly preferably 10 to 16.

[0028] Examples of polyoxyalkylene alkyl ethers include alkylene oxide adducts of synthetic alcohols having 10 to 16 carbon atoms, alkylene oxide adducts of octyl alcohol, alkylene oxide adducts of tetradecyl alcohol, and alkylene oxide adducts of lauryl alcohol. From the viewpoint of storage stability of aqueous dispersions, alkylene oxide adducts of synthetic alcohols having 10 to 16 carbon atoms are preferred. Commercially available polyoxyalkylene alkyl ethers include the Naroacty series, Emarumin series [manufactured by Sanyo Chemical Industries, Ltd.], Emulgen series [manufactured by Kao Corporation], Neugen series [manufactured by Daiichi Kogyo Seiyaku Co., Ltd.], Leox series, Leokol series, Lionol series [manufactured by Lion Corporation], Nonion series, and Persoft series [manufactured by NOF Corporation].

[0029] The inclusion of polyoxyalkylene alkyl ether is preferable because it allows for the aqueous dispersion of polyamide resin without the use of organic solvents, thereby obtaining a stable dispersion. Polyoxyalkylene alkyl ethers may be used alone, in combination of two or more types, or in combination with surfactants other than polyoxyalkylene alkyl ethers.

[0030] Other surfactants (B) besides polyoxyalkylene alkyl ethers include anionic surfactants, nonionic surfactants other than polyoxyalkylene alkyl ethers, cationic surfactants, and amphoteric surfactants.

[0031] Examples of nonionic surfactants other than the polyoxyalkylene alkyl ethers mentioned above include alkylene oxide-added nonionic surfactants and polyhydric alcohol-type nonionic surfactants. Examples of alkylene oxide-added nonionic surfactants include polyoxyalkylene (2-4 carbon atoms, degree of polymerization 2-50) fatty acid (12-24 carbon atoms) esters, polyoxyalkylene (2-4 carbon atoms, degree of polymerization 2-50) polyhydric alcohol (2-6 valent, 2-12 carbon atoms) fatty acid (12-24 carbon atoms) esters, polyoxyalkylene (2-4 carbon atoms, degree of polymerization 2-50) alkyl (8-12 carbon atoms) phenyl ethers, polyoxyalkylene (2-4 carbon atoms, degree of polymerization 2-50) alkyl (8-24 carbon atoms) amino ethers, and polyoxyalkylene (2-4 carbon atoms, degree of polymerization 2-50) alkyl (12-24 carbon atoms) alkanol (2-12 carbon atoms) amides.

[0032] Examples of polyoxyalkylene fatty acid esters include ethylene oxide adducts of stearate and ethylene oxide adducts of laurate. Examples of polyoxyalkylene polyhydric alcohol fatty acid esters include polyethylene glycol laurate diester and polyethylene glycol oleate diester. Examples of polyoxyalkylene alkylphenyl ethers include nonylphenol ethylene oxide adducts and nonylphenol ethylene oxide propylene oxide block adducts. Examples of polyoxyalkylene alkylamino ethers include laurylamine ethylene oxide adducts and stearylamine ethylene oxide adducts. Examples of polyoxyalkylene alkyl alkanolamides include ethylene oxide adducts of hydroxyethyl lauric acid amide.

[0033] As the above-mentioned polyhydric alcohol-type nonionic surfactants, polyhydric (2-6 valent) alcohol (2-12 carbon atoms) fatty acid (8-24 carbon atoms) esters, polyhydric (2-6 valent) alcohol (2-12 carbon atoms) fatty acid (8-24 carbon atoms) ester alkylene oxide (2-4 carbon atoms) adducts (2-50 moles), polyhydric (2-6 valent) alcohol (2-12 carbon atoms) alkyl (1-24 carbon atoms) ethers, and polyhydric (2-6 valent) alcohol (2-12 carbon atoms) alkyl (1-24 carbon atoms) ether alkylene oxide (2-4 carbon atoms) adducts (2-50 moles) can be used. Examples of polyhydric alcohol fatty acid esters include pentaerythritol monolaurate and pentaerythritol monooleate. Examples of polyhydric alcohol fatty acid ester alkylene oxide adducts include ethylene glycol monooleate ethylene oxide adduct and ethylene glycol monostearate ethylene oxide adduct. Examples of polyhydric alcohol alkyl ethers include pentaerythritol monobutyl ether and pentaerythritol monolauryl ether. Examples of polyhydric alcohol alkyl ether alkylene oxide adducts include sorbitan monostearyl ether ethylene oxide adduct and methyl glycoside ethylene oxide propylene oxide random adduct.

[0034] The aforementioned amphoteric surfactants can be amino acid-type amphoteric surfactants or betaine-type amphoteric surfactants. Examples of amino acid-type amphoteric surfactants include sodium stearylaminopropionate, sodium laurylaminopropionate, and sodium laurylaminoacetate. Examples of betaine-type amphoteric surfactants include stearyldimethylaminoacetate betaine.

[0035] Examples of cationic surfactants include quaternary ammonium salt type cationic surfactants and amine salt type cationic surfactants. Examples of quaternary ammonium salt type cationic surfactants include lauryltrimethylammonium chloride and didecyldimethylammonium chloride. Examples of amine salt type cationic surfactants include inorganic or organic salts of laurylamine, inorganic or organic salts of ethylene oxide adducts of aliphatic amines, etc. Two or more of these may be used in combination. Of these surfactants, the anionic surfactant and the nonionic surfactant are preferred.

[0036] In an aqueous dispersion of polyamide resin, the volume-average particle diameter (Dv) of the polyamide resin (A) particles is preferably 30 to 400 nm, more preferably 30 to 250 nm, and particularly preferably 70 to 150 nm, from the viewpoint of storage stability and inkjet ejection stability.

[0037] The volume-average particle size (Dv) of the particles in (A) can be controlled by the amount of ionic groups, neutralizing agents, and surfactants in (A), as well as the type of disperser and dispersion conditions used in the dispersion process. The volume-average particle size (Dv) can be measured using a light scattering particle size distribution analyzer [Horiba Ltd. "LA950 V2"].

[0038] The viscosity of the aqueous dispersion of polyamide resin at 25°C, with a solid content concentration of 20% by weight, is preferably 2000 mPa·s or less, more preferably 500 mPa·s or less, and particularly preferably 100 mPa or less, from the viewpoint of handling. The viscosity can be measured using a BL-type viscometer.

[0039] The pH of the aqueous dispersion of polyamide resin at 25°C is preferably 2 to 12, and more preferably 4 to 10, from the viewpoint of storage stability. The pH can be measured using a pH meter M-12 [manufactured by Horiba, Ltd.].

[0040] The solid content concentration (content of components other than volatile components) of the aqueous dispersion of polyamide resin is preferably 10 to 65% by weight, and more preferably 15 to 50% by weight, from the viewpoint of ease of handling. The solid content concentration can be obtained by spreading about 1 g of the aqueous dispersion thinly on a Petri dish, weighing it accurately, heating it in a circulating constant-temperature dryer at 130°C for 45 minutes, weighing the result, and calculating the ratio (percentage) of the remaining weight after heating to the weight before heating.

[0041] The content of the polyamide resin (A) is preferably 65 to 91% by weight, more preferably 77 to 91% by weight, and particularly preferably 81 to 90% by weight, based on the total weight of (A) and (B).

[0042] The content of surfactant (B) is 9 to 35% by weight, preferably 9 to 23% by weight, and more preferably 10 to 19% by weight, based on the total weight of (A) and (B). If the content of surfactant (B) is less than 9% by weight, the dispersion stability and filtration permeability of the aqueous dispersion will decrease, and if it exceeds 35% by weight, the adhesion and blocking resistance of the PET and OPP films will decrease.

[0043] The present invention relates to a method for producing an aqueous dispersion of polyamide resin, which includes the step of dispersing a polyamide resin (A) in water in the presence of a surfactant (B). The method is as follows:

[0044] A method for dispersing a polyamide resin (A) in water by stirring in the presence of a surfactant (B); the surfactant (B) may be dissolved in water beforehand, or it may be dissolved in water when dispersing the polyamide resin (A) by stirring, or it may be dispersed in water while contained in the polyamide resin. If necessary, the carboxyl groups of the polyamide resin may be converted into salts using a neutralizing agent such as potassium hydroxide.

[0045] The aqueous dispersion of polyamide resin is preferably heated and stirred at a temperature of 80 to 200°C, more preferably 100 to 150°C. When the temperature during heating and stirring is 80°C or higher, the dispersion of polyamide resin (A) tends to proceed more easily, while when it is 200°C or lower, the molecular weight of polyamide resin (A) is maintained, which is preferable. The stirring time can be appropriately selected depending on the equipment used, temperature, and resin composition, but is generally preferred to be between 1 minute and 100 hours, more preferably between 30 minutes and 8 hours, and particularly preferably between 1 hour and 4 hours.

[0046] The apparatus for dispersing the polyamide resin (A) in water in the present invention is not particularly limited, but it is preferable to use a rotary dispersion and mixing apparatus, an ultrasonic disperser, or a kneader, and among these, a rotary dispersion and mixing apparatus is even more preferable as it has particularly excellent dispersion capabilities.

[0047] Examples of rotary dispersion mixing devices include mixing devices with common agitators such as MaxBlend and helical blades, TK Homomixer [Primix Co., Ltd.], Creamix [M-Technique Co., Ltd.], Philmix [Primix Co., Ltd.], UltraTarlux [IKA Co., Ltd.], Ebara Milder [Ebara Corporation], Cavitron (Eurotech Co., Ltd.), and Biomixer [Nippon Seiki Co., Ltd.].

[0048] In the manufacturing method of the present invention, an organic solvent may be used from the viewpoint of promoting the dispersion of the polyamide resin in an aqueous medium. Preferred organic solvents are those with a boiling point of less than 100°C, such as acetone, methyl ethyl ketone, ethyl acetate, and tetrahydrofuran. Using an organic solvent with a boiling point of 100°C or higher is undesirable because it becomes difficult to completely remove only the organic solvent from the aqueous medium, and it remains in the aqueous dispersion, generating organic solvent during drying. Furthermore, it is undesirable because the organic solvent tends to remain in the film, causing the mechanical properties of the film to change over time.

[0049] The amount of organic solvent added is preferably 50% by weight or less of the total aqueous medium, and more preferably 30% by weight or less. It is particularly preferable not to use organic solvents from the viewpoint of VOCs and from the viewpoint of improving production efficiency by eliminating the need for solvent removal.

[0050] The printing ink of the present invention contains the aqueous polyamide resin dispersion (Q) of the present invention. By using (Q), a printing ink with excellent image adhesion and scratch resistance can be obtained. The content of polyamide resin (A) is preferably 0.1 to 50% by weight, and more preferably 1 to 30% by weight, based on the weight of the printing ink. The content of surfactant (B) is preferably 0.01 to 8% by weight, and more preferably 0.1 to 5% by weight, based on the weight of the printing ink.

[0051] Printing inks contain, in addition to an aqueous dispersion of polyamide resin, colorants as essential components, and optional components such as humectants, penetrants, water, and other additives.

[0052] Examples of colorants include dyes and pigments. While not particularly limited, depending on the media used, reactive dyes, vat dyes, naphthol dyes, sulfur dyes, direct dyes, acid dyes, metal complex dyes, disperse dyes, and cationic dyes can be selected.

[0053] Examples of pigments include inorganic pigments (e.g., white pigments, black pigments, gray pigments, red pigments, brown pigments, yellow pigments, green pigments, blue pigments, purple pigments, and metallic pigments) and organic pigments (e.g., natural organic pigments, synthetic organic pigments, nitroso pigments, nitro pigments, pigment-type azo pigments, azo lakes made from water-soluble dyes, azo lakes made from poorly soluble dyes, lakes made from basic dyes, lakes made from acid dyes, xanthan lakes, anthraquinone lakes, pigments from vat dyes, and phthalocyanine pigments).

[0054] Of these colorants, pigments are preferred. Colorants may be used individually or in combination of two or more. The colorant content is preferably 50% by weight or less, and more preferably 30% by weight or less, based on the weight of the printing ink.

[0055] Examples of humectants, though not particularly limited, include ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, pentamethylene glycol, trimethylene glycol, 2-butene-1,4-diol, 2-ethyl-1,3-hexanediol, 2-methyl-2,4-pentanediol, tripropylene glycol, polyethylene glycol with Mn of 2000 or less, 1,3-propylene glycol, isopropylene glycol, isobutylene glycol, glycerin, mesoerythritol, pentaerythritol, 2-pyrrolidone, N-methyl-2-pyrrolidone, and N-ethyl-2-pyrrolidone. A single humectant may be used, or two or more may be used in combination.

[0056] Penetrating agents are not particularly limited, but include, for example, glycol ethers (ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol mono-t-butyl ether, triethylene glycol monobutyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether) Examples of organic solvents include ethers (such as propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, propylene glycol monobutyl ether, and dipropylene glycol monobutyl ether) and aliphatic diols having 4 to 8 carbon atoms (1,2-alkyl diols such as 1,2-pentanediol and 1,2-hexanediol, and linear alcohols such as 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, and 1,8-octanediol). Penetrating agents may be used individually or in combination of two or more.

[0057] Other additives include preservatives and pH adjusters. Examples of preservatives include sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, and 1,2-dibenzinthiazolin-3-one.

[0058] Examples of pH adjusting agents include potassium dihydrogen phosphate, disodium hydrogen phosphate, sodium hydroxide, lithium hydroxide, potassium hydroxide, ammonia, diethanolamine, triethanolamine, triisopropanolamine, potassium carbonate, sodium carbonate, and sodium bicarbonate.

[0059] Printing inks can be manufactured by known methods. For example, they can be manufactured by mixing a polyamide resin aqueous dispersion, a colorant, and optional components such as a humectant, penetrant, water, and other additives in a mixer or the like.

[0060] Printing methods using the printing ink of the present invention include conventional printing methods used for plastic printing, such as gravure printing, inkjet printing, offset printing, and thermal transfer printing. Among these, inkjet printing is particularly suitable as a printing method for the printing ink of the present invention.

[0061] The aqueous polyamide resin dispersion of the present invention can be used not only in printing inks, but also in pre-coating agents for printing, aqueous paints, aqueous adhesives, aqueous textile processing agents (binders for nonwoven fabrics, sizing agents for reinforcing fibers, binders for antibacterial agents, and raw materials for artificial and synthetic leather, etc.), aqueous coatings, and aqueous paper processing agents.

[0062] When used for these purposes, in addition to the pigments, humectants, penetrating agents, preservatives, and pH adjusters mentioned above, one or more other resins, crosslinking agents, viscosity modifiers, leveling agents, degradation inhibitors, stabilizers, and antifreeze agents may be added as needed.

[0063] (1) The present disclosure is an aqueous dispersion of a polyamide resin containing a polyamide resin (A) and a surfactant (B), wherein the total amine value of the polyamide resin (A) is less than the acid value of the polyamide resin (A), the total amine value of the polyamide resin (A) is 0.5 to 10 mg KOH / g, the surfactant (B) is a polyoxyalkylene alkyl ether, and the aqueous dispersion of the polyamide resin contains 9 to 35% by weight of the surfactant (B) based on the total weight of (A) and (B). Disclosure (2) is an aqueous dispersion of polyamide resin according to Disclosure (1), wherein the volume-average particle size of the polyamide resin (A) particles measured by light scattering is 30 to 400 nm. Disclosure (3) is a printing ink comprising an aqueous dispersion of polyamide resin as described in Disclosure (1) or (2). (4) The present disclosure is a method for producing an aqueous dispersion of a polyamide resin, comprising the step of dispersing a polyamide resin (A) in water in the presence of a surfactant (B), wherein the total amine value of the polyamide resin (A) is less than the acid value of the polyamide resin (A), the total amine value of the polyamide resin (A) is 0.5 to 10 mg KOH / g, the surfactant (B) is a polyoxyalkylene alkyl ether, and the surfactant (B) is contained in an amount of 9 to 35% by weight based on the total weight of (A) and (B). [Examples]

[0064] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0065] <Manufacturing Example 1> [Manufacturing of Polyamide Resin (A-1)] In a reaction vessel equipped with a condenser, thermometer, stirrer, and nitrogen inlet tube, 93.1 parts by weight of Haridimer 200 [C36 dimer acid, manufactured by Harima Chemicals Co., Ltd.], 3.0 parts by weight of oleic acid, and 9.5 parts by weight of ethylenediamine were added. The reaction was carried out at 200°C under a nitrogen stream for 6 hours while distilling off the water produced. The reaction was further carried out under reduced pressure of 0.5 to 2.5 kPa, and the reactants were removed from the reaction vessel to obtain polyamide resin (A-1). The physical properties of polyamide resin (A-1) are shown in Table 1.

[0066] <Manufacturing Examples 2-7, Comparative Manufacturing Examples 1-2> The polycarbonate and polyamine components listed in Table 1 were charged into a reaction vessel equipped with a condenser, a stirrer, and nitrogen inlet tube. The reaction was carried out in the same manner as in Production Example 1, yielding polyamide resins (A-2) to (A-7) and (A'-1) to (A'-2). The physical properties of each polyamide resin are shown in Table 1.

[0067] The composition of each raw material in Table 1 is as follows: HariDimer 200: C36 dimer acid, manufactured by Harima Chemicals, Inc. Priamine 1071: C36 dimer amine, manufactured by Cargill Japan Ltd.

[0068] [Table 1]

[0069] <Example 1> [Production of aqueous polyamide resin dispersion (Q-1)] In a simple pressurized reactor equipped with a stirrer and a heating device, 100 parts by weight of polyamide resin (A-1), 9.9 parts by weight of emulsion NL-110 (polyoxyalkylene alkyl ether) as a surfactant, 381 parts by weight of ion-exchanged water, and 20 parts by weight of 5% potassium hydroxide aqueous solution as a neutralizing agent were added. The mixture was heated to 130°C while stirring at 200 rpm, and the stirring was continued for 2 hours to disperse the polyamide resin (A-1) in water. After that, the mixture was cooled to room temperature while stirring to obtain an aqueous dispersion of polyamide resin (Q-1).

[0070] <Examples 2-7, Comparative Examples 1-4> [Production of aqueous polyamide resin dispersions (Q-2)-(Q-7) and (Q'-1)-(Q'-4)] Polyamide resin aqueous dispersions (Q-2) to (Q-7) and (Q'-1) to (Q'-4) were obtained in the same manner as in Example 1, except that the amount of raw materials used was changed to those listed in Table 1.

[0071] <Comparative Example 5> [Production of Polyamide Resin Aqueous Dispersion (Q'-5)] In a simple pressurized reactor equipped with a stirrer and heating device, 100 parts by weight of polyamide resin (A-4), 10 parts by weight of Demol N (β-naphthalene sulfonic acid formalin condensate sodium salt) as a surfactant, 362 parts by weight of ion-exchanged water, and 40 parts by weight of 5% potassium hydroxide aqueous solution as a neutralizing agent were added. The mixture was heated to 130°C while stirring at 200 rpm, and stirring was continued for 2 hours to disperse the polyamide resin (A-4) in the water. After cooling to room temperature while stirring, the polyamide resin precipitated, and an aqueous dispersion could not be obtained. Therefore, it was not evaluated.

[0072] <Method for evaluating the storage stability of aqueous polyamide resin dispersion (Q)> A polyamide resin aqueous dispersion (Q) placed in a sealed container was left to stand for one week at 70°C in a circulating air dryer [SPH-201, ESPEC Corporation]. After removal, the volume-average particle size and viscosity were measured using the method described above. The rate of change was calculated from the particle size and viscosity measurements before and after the test using the following formula, and the storage stability was evaluated. A smaller absolute value of the rate of change indicates better storage stability. Volume-average particle diameter change rate (%) = ((Volume-average particle diameter after standing for 1 week) - (Volume-average particle diameter immediately after preparation)) ÷ (Volume-average particle diameter immediately after preparation) × 100 Viscosity change rate (%) = ((Viscosity after standing for 1 week) - (Viscosity immediately after preparation)) ÷ (Viscosity immediately after preparation) × 100

[0073] <Method for evaluating the adhesion of an aqueous dispersion of polyamide resin (Q)> Test specimens were prepared by coating surface-treated polypropylene film [Toyobo Co., Ltd.'s "Pyrene P-2161" (thickness 30 μm)] as an OPP substrate and surface-treated polyester film [Toyobo Co., Ltd.'s "Espet E-5102" (thickness 12 μm)] as a PET substrate with polyamide resin aqueous dispersions (Q-1) to (Q-7) and (Q'-1) to (Q'-5) using a bar coater so that the thickness after drying was 2 μm. The specimens were dried at 90°C for 10 minutes to prepare test pieces coated with polyamide resin on each plastic film. In accordance with JIS K5600-5-6, 1 mm wide cuts were made on the dried film surface of the polyamide resin aqueous dispersion of the prepared test specimens using a utility knife to create 100 squares (10 x 10). A peel test was performed using transparent pressure-sensitive adhesive tape, and the number of squares remaining on the substrate film was counted. A higher number of remaining squares indicates better adhesion.

[0074] Table 2 shows the physical properties and evaluation results of the aqueous polyamide resin dispersion (Q). The composition of each raw material in Table 2 is as follows: Emulmin NL-110: Polyoxyalkylene alkyl ether (ethylene oxide adduct of natural lauryl alcohol), manufactured by Sanyo Chemical Industries, Ltd. Naroacty CL-140: Polyoxyalkylene alkyl ether (alkylene oxide adduct of synthetic higher alcohol), manufactured by Sanyo Chemical Industries, Ltd. Emulgen LS-106: Polyoxyalkylene alkyl ether (polyoxyethylene polyoxypropylene alkyl ether), manufactured by Kao Corporation. Demol N: Sodium salt of β-naphthalene sulfonic acid formalin condensate, manufactured by Kao Corporation.

[0075] [Table 2]

[0076] <Examples 8-14 and Comparative Examples 6-9> [Printing inks (L-1)-(L-7) and comparative printing inks (L'-1)-(L'-4)] In each of the polyamide resin aqueous dispersions (Q-1) to (Q-7) or (Q'-1) to (Q'-4) obtained in Examples 1 to 7 or Comparative Examples 1 to 4, 2.7 parts by weight each were used, along with 2.5 parts by weight of pigment [carbon black aqueous dispersion {Aqua-Black 162 manufactured by Tokai Carbon Co., Ltd., solid content concentration 20% by weight}], 1.0 part by weight of glycerin as a humectant, 0.1 part by weight of triethylene glycol, 0.1 part by weight of 1,2-hexanediol as a penetrating agent, and 3.6 parts by weight of water. These were placed in a container and mixed for 10 minutes to prepare printing inks (L-1) to (L-7) and comparative printing inks (L'-1) to (L'-4).

[0077] <Filtration and permeability of printing inks> The amount of ink that passed through 100g of printing ink using a vacuum filtration method until the filter became clogged was measured. If the entire amount of ink passed through, the amount was defined as 100g. A larger amount of ink passed through indicates less nozzle clogging during printing and more stable inkjet nozzle ejection. Clogging is mainly caused by large particles or aggregates of pigment or resin particles due to insufficient storage stability. Filter: MF-Millipore SMWP04700 Filtration pressure: 50kPa

[0078] <Abrasion resistance of printing inks> Polyester film [Toyobo Co., Ltd.'s "Espet E-5102" (thickness 12 μm)] was coated with printing ink using a bar coater so that the thickness after drying was 1 μm, and then dried at 90°C for 10 minutes to prepare test specimens on which polyamide resin was coated onto each resin film. Abrasion resistance tests were conducted on the ink-coated surfaces of the fabricated test specimens using a Japan Society for the Promotion of Science (JSPS) friction fastness tester. A friction element fitted with a 60mm x 60mm cotton cloth (Kanakin No. 3) was rubbed back and forth 100 times with a load of 200g. The images after the test were analyzed using image processing software [product name "WinROOF", version 5.5, manufactured by Mitani Corporation] to determine the area of ​​the remaining image (SA) and the area rubbed by the JSPS friction fastness tester (SB). The image retention rate was calculated using the following formula, and the abrasion resistance of the printing ink was evaluated. A higher retention rate indicates better abrasion resistance. Survival rate (%)=100×SA / SB

[0079] <Method for evaluating the blocking resistance of printing ink (L)> After applying printing ink to the entire surface of a polyester film [Toyobo Co., Ltd.'s "Espet E-5102" (thickness 12 μm)], it was cut into a 4 cm x 8 cm piece. The printed side of this sample was placed next to the untreated side of an unprinted film of the same size, and a pressure of 7 kg / cm² was applied at 50°C for 24 hours. The degree of peeling and resistance of the printed surface when the film was peeled off was observed. 5 points: No ink peeling was observed at all from the printed material, and there was no resistance when peeling it off. 4 points: No ink peeling was observed from the printed material, but there was resistance when peeling it off. 3 points: Some ink peeling was observed on the printed material, but it covered less than 10% of the entire printed surface. 2. Ink peeling from the printed material covered more than 10% but less than 50% of the total printed area. 1. Ink peeling occurred on more than 50% of the printed area of ​​the material. A score of 3 or higher indicates a practical level of performance.

[0080] <Method for evaluating the adhesion of printing ink (L)> The adhesion of the printing ink (L) was evaluated using the same method as the method for evaluating the adhesion of the polyamide resin aqueous dispersion (Q), except that printing inks (L-1) to (L-7) and (L'-1) to (L'-4) were used instead of the polyamide resin aqueous dispersion (Q).

[0081] The evaluation results for printing ink (L) are shown in Table 3.

[0082] [Table 3] [Industrial applicability]

[0083] The aqueous polyamide resin dispersion of the present invention is useful as a raw material for printing inks using recording media such as resin media like polycarbonate, rigid PVC, flexible PVC, polystyrene, expanded polystyrene, polymethyl methacrylate, polypropylene, polyethylene, and polyethylene terephthalate, paper media like fine paper, art paper, coated paper, and cast coated paper, and metal media like glass and stainless steel. In particular, it is suitable for flexible packaging using polypropylene (OPP) or polyethylene terephthalate (PET) as recording media.

Claims

1. An aqueous dispersion of a polyamide resin containing a polyamide resin (A) and a surfactant (B), wherein the total amine value of the polyamide resin (A) is less than the acid value of the polyamide resin (A), the total amine value of the polyamide resin (A) is 0.5 to 10 mg KOH / g, the surfactant (B) contains a polyoxyalkylene alkyl ether, and the content of the surfactant (B) is 9 to 35% by weight based on the total weight of (A) and (B).

2. The aqueous dispersion of polyamide resin according to claim 1, wherein the volume-average particle diameter of the polyamide resin (A) particles, as measured by light scattering, is 30 to 400 nm.

3. A printing ink comprising the aqueous dispersion of polyamide resin described in claim 1 or 2.

4. A method for producing an aqueous dispersion of a polyamide resin, comprising the step of dispersing a polyamide resin (A) in water in the presence of a surfactant (B), wherein the total amine value of the polyamide resin (A) is less than the acid value of the polyamide resin (A), the total amine value of the polyamide resin (A) is 0.5 to 10 mg KOH / g, the surfactant (B) is a polyoxyalkylene alkyl ether, and the content of the surfactant (B) is 9 to 35% by weight based on the total weight of (A) and (B).

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