JP2006022132A - Aqueous polyurethane emulsion, method for producing the same and aqueous printing ink by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous polyurethane emulsion, capable of obtaining a coated film excellent in re-dissolving property, close adhesion, etc., especially suitable for an aqueous printing ink, and without using any organic solvent or a powerful agitator in its production. <P>SOLUTION: This aqueous polyurethane emulsion is obtained by emulsifying in water a polyurethane resin obtained by reacting (A) an organic polyisocyanate containing (A1) an allophanate-modified polyisocyanate obtained from (A1-1) an alkoxypoly(oxyalkylene) glycol containing ≥50 mol % oxyethylene group in its recurring units and (A1-2) hexamethylene diisocyanate and substantially not containing isocyanurate group, with (B) an active hydrogen-containing compound. Also, (B) the active hydrogen-containing compound preferably contains (B1) a high molecular polyol having at least ≥500 number-average molecular weight and (B2) a low molecular polyamine having <500 number-average molecular weight and/or water. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a water-based polyurethane emulsion suitable for aqueous printing inks, a water-based printing ink using the same, and a method for producing the same.

  Aqueous polyurethane emulsions are excellent in adhesion to substrates, abrasion resistance, impact resistance, solvent resistance, etc., so paper, plastics, films, metals, paints, inks, adhesives, and various coating agents It has been widely used in textile products and various methods for producing the same have been studied. For example, acetone, methyl ethyl ketone (hereinafter abbreviated as MEK), N-methylpyrrolidone (hereinafter abbreviated as NMP), an aromatic organic solvent, etc. are used alone or mixed in a mixed solvent and then dispersed in water. In addition, aqueous polyurethane resins such as emulsions, colloidal dispersions, and aqueous solutions have been developed through a solvent removal process.

  Allophanate-modified polyisocyanates generally have low viscosity compared to other urethane-modified polyisocyanates and isocyanurate-modified polyisocyanates, and various side chain groups are introduced into the isocyanate skeleton depending on the choice of the modifier. be able to. For example, if a polyoxyethylene group is introduced, a hydrophilic polyisocyanate can be obtained. If a hydrocarbon group having a large number of carbon atoms is introduced, a poor solvent-soluble polyisocyanate can be obtained.

  Patent Document 1 discloses an aqueous polyurethane emulsion in which an allophanate-modified polyisocyanate having a polyoxyethylene group introduced into a side chain is used as an isocyanate component of a polyurethane resin.

JP-A-1-104612

  However, in Patent Document 1, two raw materials of allophanate-modified polyisocyanate have different reactivities such as 2,4-tolylene diisocyanate (hereinafter abbreviated as 2,4-TDI), isophorone diisocyanate (IPDI), and the like. An organic diisocyanate having an isocyanate group (asymmetric diisocyanate) is used. Since general asymmetric organic diisocyanates usually have a ring structure (a kind of ladder structure), the flexibility of the molecular skeleton is low and the viscosity tends to be high. For this reason, the allophanate-modified polyisocyanate disclosed in Patent Document 1 uses NMP during its production. NMP has an effect as a film-forming aid during film formation, and has advantages such as lowering the viscosity during emulsion production, but also causes coloration and precipitation over time, and contains it. Depending on the amount, the emulsion may have a flash point. N-methylpyrrolidone is difficult to remove because it is mixed with water at an arbitrary ratio and has a boiling point higher than that of water.

  Patent Document 2 proposes a method that does not use an organic solvent when producing an aqueous polyurethane resin dispersion.

JP-A-10-265539

  However, in the production method of Patent Document 2, since the viscosity of the isocyanate group-terminated prepolymer is very high, water dispersion does not proceed unless a homomixer, homogenizer, or microfluidizer having a strong shearing force is used. In many cases, it is necessary to modify the manufacturing equipment.

  The aqueous polyurethane emulsion of the present invention uses an alkoxypoly (oxyalkylene) glycol that contains substantially no isocyanurate group and contains 50 mol% or more of oxyethylene groups in the repeating unit as the isocyanate component of the polyurethane resin. Since the allophanate modified product of hexamethylene diisocyanate (hereinafter abbreviated as HDI) is used, the polyurethane resin intermediate can be produced without using an organic solvent during the production (especially the production of an isocyanate group-terminated prepolymer). Low viscosity. Of course, the resulting emulsion also contains no organic solvent. In addition, the coating film obtained from the aqueous polyurethane emulsion is excellent in redissolvability, adhesion, and the like, and when used in aqueous printing ink, the plate clogging property is further improved.

  An object of the present invention is to provide a water-based polyurethane emulsion particularly suitable for water-based printing inks, which can provide a film excellent in re-solubility and adhesion.

  That is, this invention is shown by the following (1)-(4).

(1) Allophanate substantially free of isocyanurate groups obtained from alkoxypoly (oxyalkylene) glycol (A1-1) and HDI (A1-2) containing 50 mol% or more of oxyethylene groups in the repeating unit An aqueous polyurethane emulsion in which a polyurethane resin obtained by reacting an organic polyisocyanate (A) containing a modified polyisocyanate (A1) and an active hydrogen group-containing compound (B) is emulsified in water.

(2) The active hydrogen group-containing compound (B) contains at least a polymer polyol (B1) having a number average molecular weight of 500 or more, a low molecular polyamine having a number average molecular weight of less than 500, and / or water (B2). The aqueous polyurethane emulsion of (1) above.

(3) A reaction between a low molecular polyamine having a number average molecular weight of less than 500 and / or an active hydrogen group-containing compound (B) other than water (B2) and the organic polyisocyanate (A) in the substantial absence of an organic solvent. And the resulting isocyanate group-terminated prepolymer is emulsified in water and subjected to a chain extension reaction with a low molecular weight polyamine and / or water (B2). .

(4) A water-based printing ink using the water-based polyurethane emulsion of (1) or (2).

  The organic polyisocyanate (A) used in the present invention contains an allophanate-modified polyisocyanate (A1) that does not substantially contain an isocyanurate group. When the isocyanurate group is substantially contained, the viscosity of the organic polyisocyanate (A) is increased. For this reason, it is necessary to reduce the viscosity by diluting the organic solvent during the production of the aqueous polyurethane emulsion.

  The allophanate-modified polyisocyanate (A1) is obtained from alkoxy poly (oxyalkylene) glycol (A1-1) and HDI (A1-2) containing 50 mol% or more of oxyethylene groups in the repeating unit. Here, when the oxyethylene group in the repeating unit of (A1) is less than 50 mol%, the water dispersibility of the resulting polyurethane resin becomes insufficient. In addition, organic diisocyanates other than HDI, such as TDI and IPDI, have a ring structure (a kind of ladder structure), so that the molecular skeleton has low flexibility and tends to have high viscosity. For this reason, when manufacturing such an allophanate modified polyisocyanate, since an organic solvent is required, it is not preferable in the present invention.

  The isocyanate content of the allophanate-modified polyisocyanate (A1) is preferably 3 to 15% by mass, particularly preferably 5 to 13% by mass. The viscosity at 25 ° C. is preferably 2,000 mPa · s or less, particularly preferably 100 to 800 mPa · s. If the isocyanate content is too low or the viscosity is too high, the viscosity of the intermediate reactant during the reaction becomes high, and a large load is applied to the production apparatus. When the isocyanate content is too high or the viscosity is too low, the allophanate modification degree of (A1) is often insufficient, and the dispersibility of the resulting polyurethane resin tends to be insufficient.

  The production method of this allophanate-modified polyisocyanate (A1) is as follows. An excess amount of HDI (alkoxy poly (oxyalkylene) glycol / HDI = 1/5 to 1/20 (molar ratio) is preferred) is added to the alkoxy poly (oxyalkylene) glycol, and a urethanization reaction is performed. Next, an allophanatization catalyst such as a metal salt of a carboxylic acid is charged and an allophanatization reaction is performed. A reaction terminator such as phosphoric acid is charged to stop the allophanatization reaction, and unreacted HDI is removed by thin film distillation or the like to obtain the desired allophanate-modified polyisocyanate.

  Preferred allophanatization catalysts are zirconium carboxylate, zirconyl carboxylate, and tin (divalent) carboxylate. Other allophanatization catalysts have a high degree of side reaction such as isocyanurate reaction and a low content of the desired allophanate-modified polyisocyanate. The polyisocyanate obtained by such a method has a large average number of functional groups, and gelation tends to occur during the production of a polyurethane resin. Specific examples of the allophanatization catalyst include Nikka Octix Zircon (manufactured by Nippon Chemical Industry Co., Ltd.).

  When an allophanate-modified polyisocyanate is produced using an organic diisocyanate widely distributed in the market other than HDI and using the above-mentioned zirconium catalyst, the allophanate-forming reaction is insufficient, and the desired allophanate-modified polyisocyanate is It is difficult to obtain.

  The alkoxypoly (oxyalkylene) glycol (A1-1) used for the allophanate-modified polyisocyanate (A1) is generally a compound having one hydroxyl group having 1 to 10 carbon atoms and 50 mol of ethylene oxide. % Or more of alkylene oxide is contained by ring-opening addition. Here, as initiators, saturated aliphatic alcohol compounds such as methanol, ethanol, propanol (including various isomers), butanol (including various isomers), pentanol (including various isomers), allyl alcohol, and the like An unsaturated aliphatic alcohol compound, a phenol compound such as phenol, an araliphatic alcohol such as benzyl alcohol, and the like. In the present invention, an aliphatic alcohol having 5 or less carbon atoms is preferable, and a saturated aliphatic alcohol having 2 or less carbon atoms is particularly preferable in order to enhance the effect of imparting hydrophilicity. Further, the ethylene oxide content of the alkylene oxide is more preferably 70 mol% or more in consideration of the water dispersibility of the obtained polyurethane resin.

  The number average molecular weight of the alkoxy poly (oxyalkylene) glycol (A1-1) is preferably 200 to 2,000, particularly preferably 300 to 1,000. When the number average molecular weight of the alkoxy poly (oxyalkylene) glycol (A1-1) is too low, the effect of imparting hydrophilicity in the allophanate-modified polyisocyanate (A1) is small, and the water dispersibility of the polyurethane resin using this is insufficient. It is. If the number average molecular weight is too large, the viscosity of the resulting allophanate-modified polyisocyanate (A1) is increased or solidified due to crystallization of the polyoxyethylene chain, and an aqueous polyurethane emulsion can be used without using a solvent. It will be difficult to manufacture.

  In the present invention, an organic polyisocyanate other than the allophanate-modified polyisocyanate (A1) can be used together. For example, 2,4-TDI, 2,6-toluene diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane Aromatic diisocyanates such as diisocyanate, 4,4′-diphenylmethane diisocyanate, diphenyldimethylmethane diisocyanate, dibenzyl diisocyanate, naphthylene diisocyanate, phenylene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, tetramethylene diisocyanate, HDI, lysine diisocyanate, 2-methylpentane-1,5-diisocyanate, 3-methylpentane-1,5-diisocyanate, Aliphatic diisocyanates such as 2,4,4-trimethylhexahylene-1,6-diisocyanate, 2,4,4-trimethylhexahylene-1,6-diisocyanate, IPDI, cyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, hydrogen There are alicyclic diisocyanates such as added diphenylmethane diisocyanate and hydrogenated trimethylxylylene diisocyanate. These organic diisocyanates can be used alone or in a mixture. Furthermore, modified products such as these adduct-modified products, carbodiimide-modified products, allophanate-modified products (excluding those mentioned above), burette-modified products, uretdione-modified products, uretoimine-modified products, and isocyanurate-modified products can also be used. In this case, it is preferable that the allophanate-modified polyisocyanate (A1) is 25% by mass or more based on the entire organic polyisocyanate (A). When there are too many organic polyisocyanates other than (A1), since the intermolecular force of the polyurethane resin obtained becomes too large, it becomes easy to aggregate.

  The active hydrogen group-containing compound used in the present invention preferably contains at least a polymer polyol (B1) having a number average molecular weight of 500 or more, a low molecular polyamine having a number average molecular weight of less than 500, and / or water (B2). This is to obtain a resin by the prepolymer method described later. In the prepolymer method, a urethane group imparting adhesiveness and adhesion and a urea group effective in heat resistance and strength development are balanced with polyurethane. This is because it can be introduced into the resin skeleton and the viscosity during the reaction can be lowered.

  The number average molecular weight of the polymer polyol (B1) is 500 or more, preferably 1,000 to 5,000. Moreover, 2-4 are preferable and, as for the average functional group number of this (A) polyol, 2-3 are still more preferable. When the number average molecular weight of the polymer polyol is less than the lower limit, the coating film tends to break. On the other hand, when the upper limit is exceeded, it is difficult to form a film having sufficient physical properties. The number average molecular weight of the polymer polyol is calculated from the average number of functional groups and the terminal group weight determined by the terminal group determination method.

  Specific examples of the polymer polyol (B1) include polyester polyols, polyamide ester polyols, polyether polyols, polyether ester polyols, polycarbonate polyols, polyolefin polyols, and animal and plant polyols.

  The polymer polyol (B1) preferred in the present invention is a polyester polyol when importance is attached to adhesion, and is a polyether polyol or a polycarbonate polyol when importance is attached to water resistance.

  Polyester polyols include known phthalic acid, isophthalic acid, terephthalic acid, naphthalene dicarboxylic acid, succinic acid, tartaric acid, oxalic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, kurtaconic acid, azelaic acid, sebacin Acid, succinic acid, adipic acid, sebacic acid, azelaic acid, 1,4-cyclohexyldicarboxylic acid, α-hydromuconic acid, β-hydromuconic acid, α-butyl-α-ethylglutaric acid, α, β-diethylsuccin At least one kind of dicarboxylic acid or anhydride such as acid, maleic acid, fumaric acid and the like, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butane Diol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanedio 1,8-octanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, 3,3-dimethylolheptane, diethylene glycol, dipropylene glycol, neopentyl glycol, diethylene glycol, dipropylene glycol , Cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol, dimer acid diol, ethylene oxide and propylene oxide adducts of bisphenol A, bis (β-hydroxyethyl) benzene, xylylene glycol, glycerin, trimethylol It can be obtained from a polycondensation reaction with one or more low molecular polyols such as propane and pentaerythritol. Furthermore, there are lactone-based polyester polyols obtained from ring-opening polymerization of cyclic ester (so-called lactone) monomers such as ε-caprolactone, alkyl-substituted ε-caprolactone, δ-valerolactone, and alkyl-substituted δ-valerolactone. Further, a part of the low molecular polyol may be replaced with a low molecular polyamine such as ethylenediamine, hexamethylenediamine, and isophoronediamine, or a low molecular amino alcohol such as monoethanolamine. In this case, a polyester-amide polyol is obtained.

  As the polyether polyol, active hydrogen groups such as low molecular polyols used in the above-mentioned polyester polyol, low molecular polyamines such as ethylenediamine, propylenediamine, toluenediamine, metaphenylenediamine, diphenylmethanediamine, xylylenediamine, etc. Starting from a compound having 2 or more, preferably 2 to 3, alkylene oxides such as ethylene oxide, propylene oxide and butylene oxide, alkyl glycidyl ethers such as methyl glycidyl ether, and aryl glycidyl such as phenyl glycidyl ether It can be obtained by addition polymerization by a known method from a single or mixture of cyclic ether monomers such as ethers and tetrahydrofuran.

  The polycarbonate polyol is obtained from a dealcoholization reaction or a dephenol reaction between one or more low molecular diols or low molecular triols from the above-mentioned polyester polyol source and ethylene carbonate, diethyl carbonate, or diphenyl carbonate. In addition, the transesterification product of the above-mentioned polycarbonate polyol and polyester polyol can also be used suitably.

  Examples of polyether ester polyols include copolyols obtained from the aforementioned polyether polyols and the aforementioned dicarboxylic acids. Further, there are those obtained by reacting the aforementioned polyester or polycarbonate with epoxide or cyclic ether.

  Examples of the polyolefin polyol include polybutadiene having two or more hydroxyl groups, hydrogenated polybutadiene, polyisoprene, and hydrogenated polyisoprene.

  Examples of animal and plant-based polyols include castor oil-based polyols and silk fibroin.

  In addition, as long as the number average molecular weight is 500 or more (preferably 1,000 to 5,000) and one molecule has an average of one or more active hydrogen groups, a dimer acid polyol, a hydrogenated dimer acid In addition to the system polyol, an active hydrogen group-containing resin such as an epoxy resin, polyamide resin, polyester resin, acrylic resin, rosin resin, urea resin, melamine resin, phenol resin, coumarone resin, and polyvinyl alcohol can also be used as the polymer polyol.

  Examples of the component (B2) include a low molecular polyamine having a number average molecular weight of less than 500 and water. Examples of the low molecular weight polyamine having a number average molecular weight of less than 500 include hydrazine, ethylenediamine, tetramethylenediamine, hexamethylenediamine, isophoronediamine, dicyclohexylmethanediamine, diphenylmethanediamine, and diethylenetriamine. In the present invention, water, hydrazine, ethylene diamine, hexethylene diamine, and isophorone diamine are preferable in consideration of physical properties and durability of the resulting polyurethane resin coating.

  In the present invention, a low molecular polyol having a number average molecular weight of less than 500 can be used in consideration of physical properties of the obtained polyurethane resin film. As this low molecular polyol, the low molecular polyol which comprises the above-mentioned polyester polyol is mentioned.

  In the present invention, when synthesizing a polyurethane resin, a reaction terminator can be used if necessary, such as adjustment of molecular weight. Examples of the reaction terminator include monoalcohols and monoamines. In some cases, aminoalcohols can also serve as the reaction terminator. Monoisocyanates such as phenyl isocyanate, butyl isocyanate, cyclohexyl isocyanate and the like can also be used as a reaction terminator.

  Specific monoalcohols used as the reaction terminator include methanol, ethanol, propanol, isopropanol, 2-ethylhexanol and the like. Monoamines include primary amines such as ethylamine, propylamine, and butylamine, and secondary amines such as diethylamine and dibutylamine. Examples of amino alcohols include monoethanolamine and diethanolamine.

As a manufacturing method of an aqueous polyurethane emulsion, the main methods include the following methods.
・ One-shot method in which an organic polyisocyanate (A) and an active hydrogen group-containing compound (B) are reacted in an atmosphere with an excess of active hydrogen groups to synthesize polyurethane resin and dispersed in water ・ Organic polyisocyanate (A), low molecular weight polyamine An active hydrogen group-containing compound (B) other than (B2) is reacted in an isocyanate group-excess atmosphere to synthesize an isocyanate group-terminated prepolymer, and the prepolymer is dispersed in water, and then low molecular weight polyamine and / or water ( Prepolymer method for chain extension reaction in B2)

  In the case of the one-shot method, the isocyanate group / active hydrogen group molar ratio is 0.5 to less than 1, preferably 0.8 to less than 1. When it is less than 0.5, the molecular weight of the polyurethane polymer is too small, so that the durability is insufficient. In the case of 1 or more, gelation tends to occur when a polymer is synthesized.

  After urethanization, water is charged and the resin is dispersed to obtain the desired aqueous polyurethane emulsion. The faster the stirring speed at this time, the better.

  In the case of the prepolymer method, the molar ratio of isocyanate group / active hydrogen group during synthesis of the prepolymer is 1.1 to 5.0, preferably 1.2 to 4.0. When it is less than 1.1, the molecular weight of the prepolymer becomes too large and it is difficult to proceed to the subsequent reaction step. If it exceeds 5.0, the adhesion is poor.

  After prepolymerization, water is added to disperse the prepolymer, and a low molecular weight polyamine and / or water (B2), and if necessary, a reaction terminator is added to carry out an amine extension reaction to obtain a desired aqueous polyurethane emulsion. can get. The reaction temperature of the amine extension reaction is preferably 30 to 50 ° C. After the prepolymer is dispersed, the faster the stirring speed, the better.

  The aqueous polyurethane emulsion of the present invention is characterized by using an allophanate-modified polyisocyanate (A1) that is effective in reducing the viscosity of the resin. However, in the one-shot method, even when using the allophanate-modified polyisocyanate (A1) effective for lowering the viscosity, the number average molecular weight of the polyurethane resin immediately before water dispersion is often 10,000 or more, It becomes a moderately high viscosity (for example, 100,000 mPa · s or more at 75 ° C.), and water dispersion tends to be difficult. For this reason, a prepolymer method in which water dispersion is performed at the stage of a prepolymer having a low number average molecular weight (low viscosity) is preferable because solvent-free production can be achieved.

  In the urethanization reaction or prepolymerization reaction, a known so-called urethanization catalyst can be used as a reaction catalyst. Specific examples include organic metal compounds such as dioctyltin dilaurate, organic amines such as triethylenediamine, and salts thereof. The reaction temperature during urethanization is 10 to 100 ° C, preferably 30 to 80 ° C.

  The number average molecular weight of the polyurethane resin in the aqueous polyurethane emulsion thus obtained is preferably 5,000 or more, particularly preferably 10,000 or more. When the number average molecular weight of the polyurethane resin is less than 5,000, durability is poor. In the present invention, the number average molecular weight is measured by a gel permeation chromatography (GPC) method using a polyethylene glycol calibration curve.

  In the aqueous polyurethane emulsion, the average particle size of the resin component is 100 nm or less, preferably 80 nm or less. If the average particle size exceeds the upper limit, precipitation may occur over time. The average particle diameter is a value obtained by analyzing a value measured by a dynamic light scattering method by a cumulant method.

  The viscosity of the aqueous polyurethane emulsion at 25 ° C. is 2,000 mPa · s or less, preferably 50 to 1,000 mPa · s, at a solid content of 30% by mass. If the viscosity exceeds the upper limit, subsequent ink formation tends to be difficult.

  The nonionic hydrophilic group (polyoxyethylene group) content of the polyurethane resin in the present invention is preferably 10 to 50% by mass, particularly preferably 15 to 40% by mass. When there is too much nonionic hydrophilic group content, the water resistance of a film tends to fall. If the amount is too small, it becomes difficult to disperse the resin or prepolymer in water just before water dispersion during production of the aqueous polyurethane emulsion.

  The total of the urethane group concentration and the urea group concentration of the polyurethane polymer used in the present invention is 1.0 to 3.0 mmol / g, preferably 1.3 to 2.7 mmol / g. When urea groups are not present in the polymer, the urethane group concentration is 1.0 to 3.0 mmol / g, preferably 1.3 to 2.7 mmol / g. When the sum of the urethane group concentration and the urea group concentration is less than the lower limit, the coating strength tends to be insufficient. If the upper limit is exceeded, ink adhesion tends to be insufficient.

  In the aqueous polyurethane emulsion of the present invention, additives and auxiliaries commonly used in aqueous systems can be used as necessary. For example, curing agents, pigments, dyes, antiblocking agents, dispersion stabilizers, viscosity modifiers, leveling agents, antigelling agents, light stabilizers, antioxidants, ultraviolet absorbers, inorganic and organic fillers, plasticizers, A lubricant, an antistatic agent, a reinforcing material, a catalyst and the like can be added.

  The aqueous polyurethane emulsion of the present invention can be used by blending with other resin emulsions. For example, acrylic emulsion, polyester emulsion, polyolefin emulsion, latex and the like.

  Next, although the Example and comparative example of this invention are demonstrated in detail, this invention is not limited to these Examples. Unless otherwise specified, “%” in the examples means “% by mass”.

(Synthesis of allophanate-modified polyisocyanate)
Synthesis example 1
A volume of 1 L reactor equipped with a stirrer, thermometer, cooler and nitrogen gas inlet tube was charged with 863 g of HDI, 137 g of MPEG-1, and 0.2 g of zirconium 2-ethylhexanoate at 90 ° C. for 2 hours. Reaction was performed. Next, 0.1 g of phosphoric acid was added and a stop reaction was performed at 50 ° C. for 1 hour. The isocyanate content of the reaction product after the termination reaction was 40.2%. This reaction product was subjected to thin film distillation at 130 ° C. × 0.04 kPa to obtain allophanate-modified polyisocyanate isocyanate ALP-1. ALP-1 had an isocyanate content of 11.4%, a viscosity at 25 ° C. of 140 mPa · s, and a free diisocyanate content of 0.1%. Further, when ALP-1 was analyzed by FT-IR and ¹³ C-NMR, almost no urethane groups and isocyanurate groups were confirmed, and the presence of allophanate groups was confirmed.

Synthesis example 2
A volume of 1 L reactor equipped with a stirrer, thermometer, condenser and nitrogen gas inlet tube was charged with 782.6 g of HDI, 217.4 g of MPEG-2, and 0.2 g of zirconyl 2-ethylhexanoate, 90 The reaction was carried out at 2 ° C. for 2 hours. Next, 0.1 g of phosphoric acid was added and a stop reaction was performed at 50 ° C. for 1 hour. The isocyanate content of the reaction product after the termination reaction was 36.5%. This reaction product was subjected to thin film distillation at 130 ° C. × 0.04 kPa to obtain allophanate-modified polyisocyanate isocyanate ALP-2. ALP-2 had an isocyanate content of 7.2%, a viscosity at 25 ° C. of 100 mPa · s, and a free diisocyanate content of 0.1%. Further, when ALP-2 was analyzed by FT-IR and ¹³ C-NMR, almost no urethane groups and isocyanurate groups were confirmed, and the presence of allophanate groups was confirmed.

Synthesis example 3
Capacity with stirrer, thermometer, cooler and nitrogen gas inlet tube: A 1 L reactor was charged with 200 g of NMP, 265.6 g of 2,4-TDI, and 534.5 g of MPEG-2. The reaction was urethanated for a period of time. At this time, the isocyanate content was 9.6%. Next, 0.5 g of PTSM and 0.025 g of zinc acetylacetone were charged and reacted at 100 ° C. for 5 hours to obtain allophanate-modified polyisocyanate ALP-3. The solid content of ALP-3 was 80%, the isocyanate content was 6.4%, the viscosity at 25 ° C. was 50 mPa · s, and the free diisocyanate content was 0.1%. Moreover, when ALP-3 was analyzed by FT-IR and ¹³ C-NMR, no urethane group was confirmed, and the presence of allophanate groups and isocyanurate groups were confirmed.

In Synthesis Examples 1 to 3, HDI: hexamethylene diisocyanate 2,4-TDI: 2,4-tolylene diisocyanate MPEG-1: methoxypolyethylene glycol
Number average molecular weight = 400
MPEG-2: Ethoxypolyethylene glycol
Number average molecular weight = 700
PTSM: methyl paratoluenesulfonate NMP: N-methylpyrrolidone

[Synthesis of aqueous polyurethane emulsion]
Example 1
A volume of 1 L reactor equipped with a stirrer, thermometer, nitrogen seal tube and cooler was charged with 128.6 g of polyol-1 and 8.0 g of NPG and uniformly mixed at 100 ° C. Thereafter, 165.6 g of ALP-1 and 0.05 g of DOTDL were charged and reacted at 80 ° C. for 3 hours to obtain an isocyanate group-terminated prepolymer. The isocyanate content of this prepolymer was 2.32%, and the viscosity at 75 ° C. was 1,150 mPa · s. Thereafter, 702 g of water was charged and emulsified, and then a chain extension reaction with water was performed at 40 ° C. The reaction was terminated when the presence of isocyanate groups was no longer confirmed by FT-IR, to obtain an aqueous polyurethane emulsion PU-1. The solid content of PU-1 was 30.1%, the viscosity at 25 ° C. was 40 mPa · s, the pH was 7, and the average particle size was 130 nm.

Examples 2 and 3
In Example 1, aqueous polyurethane emulsions PU-2 and 3 were obtained in the same procedure as in Example 1 except that polyol-1 was changed to polyols-2 and 3, respectively.

Example 4
A volume of 1 L reactor equipped with a stirrer, thermometer, nitrogen seal tube and cooler was charged with 118.2 g of polyol-1 and 9.2 g of NPG and uniformly mixed at 100 ° C. Thereafter, 171.5 g of ALP-2 and 0.05 g of DOTDL were charged and reacted at 80 ° C. for 3 hours to obtain an isocyanate group-terminated prepolymer. The isocyanate content of this prepolymer was 0.50%, and the viscosity at 75 ° C. was 3,750 mPa · s. Thereafter, 600 g of water was charged to emulsify the prepolymer. When emulsified, a chain extension reaction was carried out by adding amine water containing 100 g of water, 1.0 g of EDA and 0.1 g of MEA in advance. When the presence of isocyanate groups was no longer confirmed by FT-IR, the reaction was terminated to obtain an aqueous polyurethane emulsion PU-4. The solid content of PU-4 was 29.9%, the viscosity at 25 ° C. was 720 mPa · s, the pH was 10, and the average particle size was 91 nm.

Example 5
A volume of 1 L reactor equipped with a stirrer, a thermometer, a nitrogen seal tube and a condenser was charged with 124.9 g of polyol-1 and 9.7 g of NPG, and uniformly mixed at 100 ° C. Thereafter, 161.7 g of ALP-2, 5.2 g of HDI, and 0.05 g of DOTDL were charged and reacted at 80 ° C. for 3 hours to obtain an isocyanate group-terminated prepolymer. The isocyanate content of this prepolymer was 0.87%, and the viscosity at 75 ° C. was 4,250 mPa · s. Thereafter, 701 g of water was charged and emulsified, and then a chain extension reaction with water was performed at 40 ° C. When the presence of isocyanate groups was no longer confirmed by FT-IR, the reaction was terminated to obtain an aqueous polyurethane emulsion PU-5. The solid content of PU-5 was 30.0%, the viscosity at 25 ° C. was 850 mPa · s, the pH was 7, and the average particle size was 181 nm.

Comparative Example 1
Capacity with a stirrer, thermometer, nitrogen seal tube, and condenser: 1L reactor was charged with 64.2g of NMP, 126.0g of polyol-1 and 7.9g of NPG, and mixed uniformly at 100 ° C. did. Thereafter, 165.0 g of ALP-3 and 0.05 g of DOTDL were charged and reacted at 80 ° C. for 3 hours to obtain an isocyanate group-terminated prepolymer. The isocyanate content of this prepolymer was 0.53%, and the viscosity at 75 ° C. was 950 mPa · s. Thereafter, when 500 g of water was charged to emulsify the prepolymer, the whole was not uniformly dispersed.

Examples 1-5, Comparative Example 1, Table 1 Polyol-1: Polyester polyol obtained from 3-methyl-1,5-pentanediol and adipic acid
Number average molecular weight = 2,000
Polyol-2: polycarbonate polyol obtained from 1,6-hexanediol and diethyl carbonate
Number average molecular weight = 2,000
Polyol-3: poly (oxytetramethylene) diol
Number average molecular weight = 2,000
NPG: Neopentyl glycol DOTDL: Dioctyltin dilaurate EDA: Ethylenediamine MEA: Monoethanolamine

Average particle size measuring device:
Otsuka Electronics Co., Ltd. Electrophoretic light scattering system ELS-800

  In Examples 1 to 5, the target aqueous polyurethane emulsion was obtained, but in the comparative example, the prepolymer was not completely dispersed in the aqueous dispersion process of the prepolymer. This mixes NMP with water in any proportion. For this reason, it seems that the mixing speed of NMP with water became much faster than the hydration speed of the prepolymer, and the balance of dispersion became worse.

[Ink conversion test]
Application Examples 1-5
A white ink was prepared with the following composition. These inks were used for printing on various substrates, and the ink performance in the print samples was evaluated. The evaluation results are shown in Table 3.
(Ink formulation)
Ink formulation Prescription water-based polyurethane emulsion 26.7g
Titanium white 32.0g
17.3g of water
Isopropanol 4.0g
The mixture having the above composition was kneaded for 2 hours with a paint shaker using the same amount of glass beads as the dispersion medium. Next, the kneaded meat was filtered, and 8 g of an aqueous emulsion of Aquanate 200 (Aquanate (registered trademark) 200 / water = 100/100, mass ratio) was added thereto to prepare an aqueous printing ink evaluation sample. .
* Aquanate 200: Self-emulsifying polyisocyanate (manufactured by Nippon Polyurethane Industry)

Each test method in Table 2 is as follows.
(Evaluation item)
Pigment dispersion stability After leaving the ink blended for 48 hours, check for the presence of pigment precipitation, etc. Clogging of the plate After printing, on the gravure roll of a simple gravure printing machine, isopropanol / water = 1 / A mixed solvent of 1 (mass ratio) is poured and it is observed whether the ink can be washed off from the gravure roll.
Evaluation ○: Easily washed away ×: Adhesiveness that cannot be washed away simply by dropping the mixed solvent Immediately after printing and after standing overnight after printing, a cellophane tape is affixed to the printed surface, and this is rapidly applied I peeled it off.
Evaluation A: 90% to 100% of the printed film remained.
○: 70% to 80% of the printed film remained.
Δ: 50% to 70% of the printed film remained.
X: Only 50% or less of the printed film remained.
(Printing conditions)
Ink: White ink printer prepared above: Simple gravure printer equipped with gravure plate Printing speed: 20 m / min Ink thickness: Ink thickness 1 μ (dry)
Printing substrate: Corona-treated stretched polyester film (20 μm thick)
(Polyethylene terephthalate (PET) film)

The water-based printing ink of the present invention exhibited the performance that the plate clogging property was particularly good. This seems to be because the re-solubility of the used polyurethane resin is good.

Claims (4)

  Allophanate modification substantially free of isocyanurate groups obtained from alkoxypoly (oxyalkylene) glycol (A1-1) and hexamethylene diisocyanate (A1-2) containing 50 mol% or more of oxyethylene groups in the repeating unit An aqueous polyurethane emulsion in which a polyurethane resin obtained by reacting an organic polyisocyanate (A) containing a polyisocyanate (A1) and an active hydrogen group-containing compound (B) is emulsified in water.   The active hydrogen group-containing compound (B) contains at least a polymer polyol (B1) having a number average molecular weight of 500 or more, a low molecular polyamine having a number average molecular weight of less than 500, and / or water (B2). Item 4. The aqueous polyurethane emulsion according to Item 1.   A low molecular polyamine having a number average molecular weight of less than 500 and / or an active hydrogen group-containing compound (B) other than water (B2) and the organic polyisocyanate (A) are reacted in the substantial absence of an organic solvent. The method for producing an aqueous polyurethane emulsion according to claim 2, wherein the obtained isocyanate group-terminated prepolymer is emulsified in water and subjected to a chain extension reaction with a low molecular weight polyamine and / or water (B2). A water-based printing ink using the water-based polyurethane emulsion according to claim 1.