Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-11-28
2003-04-29
Niland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S590000, C524S591000, C524S839000, C524S840000
Reexamination Certificate
active
06555614
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a resin for printing ink, and more particularly, to a method for preparing a water-based urethane resin composition suited for use as a binder in gravure printing ink.
2. Description of Related Art
The demand for a binder and printing ink comprising the binder, which are superior in productivity, has recently increased, not to mention consideration for environmental conservation on a global scale. For example, Japanese Unexamined Patent Application, First Publication Nos. 9-286945, 10-231342 and 10-279650 each discloses a method for preparing a water-based urethane resin composition which is dispersed or dissolved in water, comprising reacting a urethane prepolymer, which has an isocyanate group at a terminal end and has a carboxyl group in a molecular side chain, a chain extender, and a basic compound such as triethylamine or ammonia in a reaction solvent made of an organic solvent having high toxicity such as acetone, toluene or methyl ethyl ketone. However, in these methods, the use of organic solvents, which have high toxicity and are inflammable, such as acetone, toluene and methyl ethyl ketone requires a desolvation step, which takes a long time, and therefore, these methods are not satisfactory with respect to either productivity or consideration of environmental conservation.
BRIEF SUMMARY OF THE INVENTION
An object to be achieved by the present invention is to provide a water-based resin composition which has advantages in view of environmental conservation considerations and has good productivity and excellent physical properties such as water resistance, and is also suited for use as a binder for water-based printing inks.
As a result of diligent research, the present inventors have found that the object described above can be achieved by a method for preparing a water-based urethane resin composition by reacting a urethane prepolymer (A), which has an isocyanate group at a terminal end and has a carboxyl group in a molecular side chain, a chain extender (B) of the urethane prepolymer (A), and a basic compound (C) in a reaction solvent (D), which satisfies the following conditions (1) to (3):
(1) using, as the urethane prepolymer (A), which has an isocyanate group at a terminal end and has a carboxyl group in a molecular side chain, a urethane prepolymer (a) in which 70 molar % or more of terminal isocyanate groups are attached to carbon of secondary and/or tertiary aliphatic hydrocarbons, the urethane prepolymer being soluble in an alcohol solvent (d),
(2) using, as the chain extender (B) of the urethane prepolymer (A), a polyamine (b) having two or more amino groups containing active hydrogen, and
(3) using, as the reaction solvent (D), a water-based solvent containing the alcohol solvent (d).
According to the method which satisfies the conditions (1) to (3), since the reaction between the isocyanate group attached to carbon of secondary and/or tertiary aliphatic hydrocarbons of the urethane prepolymer (a) and the hydroxyl group of the alcohol solvent (d) proceeds slowly, synthesis of the urethane resin by means of the chain extension reaction between the urethane prepolymer (a) and the polyamine (b) as well as neutralization of the carboxyl group in the urethane prepolymer (a) or urethane resin by means of the basic compound (C) easily proceed and the resulting urethane resin can be easily dispersed or dissolved in a water-based medium comprising the alcohol solvent (d) and water (E), thereby making it possible to prepare a water-based urethane resin composition which is superior in physical properties such as water resistance and is suited for use as a binder for water-based printing ink.
Moreover, since this method does not require the use of organic solvents having high toxicity, such as acetone, toluene and methyl ethyl ketone, a desolvation step, which takes a long time, is not required. Therefore, the method has high productivity and is effective with regard to environmental conservation.
Thus, the present invention provides a method for preparing a water-based urethane resin composition by reacting a urethane prepolymer (A), which has an isocyanate group at a terminal end and has a carboxyl group in a molecular side chain, a chain extender (B) of the urethane prepolymer (A), and a basic compound (C) in a reaction solvent (D), which comprises:
(1) using, as the urethane prepolymer (A), which has an isocyanate group at a terminal end and has a carboxyl group in a molecular side chain, a urethane prepolymer (a) in which 70 molar % or more of terminal isocyanate groups are attached to carbon of secondary and/or tertiary aliphatic hydrocarbons, the urethane prepolymer being soluble in an alcohol solvent (d),
(2) using, as the chain extender (B) of the urethane prepolymer (A), a polyamine (b) having two or more amino groups containing active hydrogen, and
(3) using, as the reaction solvent (D), a water-based solvent containing the alcohol solvent (d).
The method for preparing a water-based urethane resin composition of the present invention is a method which has advantages in view of environmental conservation consideration because an alcohol solvent is used as an organic solvent, and is also superior in productivity because the method includes no desolvation step. Moreover, according to the method of the present invention, it is made possible to provide a water-based printing ink which is suited for use as water-based printing ink and is superior in balance between performances such as hot water resistance, water resistance and adhesion.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will now be described in detail.
In the present invention, the isocyanate group attached to carbon of the aliphatic hydrocarbon refers to an isocyanate group attached to carbon of a linear aliphatic hydrocarbon and an isocyanate group attached to carbon of a ring structure of a cyclic aliphatic hydrocarbon. For example, an isocyanate group attached directly to an isoprene group attached to a benzene ring, such as bis(1-isocyanate-1-methylethyl)benzene is also an isocyanate group attached to carbon of the aliphatic hydrocarbon. The isocyanate group attached to carbon of a primary, secondary or tertiary aliphatic hydrocarbon refers to an isocyanate group attached to primary, secondary or tertiary carbon of a linear aliphatic hydrocarbon and an isocyanate group attached to primary, secondary or tertiary carbon of a ring structure of a cyclic aliphatic hydrocarbon.
The urethane prepolymer (a) used in the present invention is not specifically limited as long as it is a linear urethane prepolymer which has an isocyanate group attached to carbon of the aliphatic hydrocarbon at a terminal end and has a carboxyl group in a molecular side chain, in which 70 molar % or more of isocyanate groups attached to carbon of the terminal aliphatic hydrocarbon are isocyanate groups attached to carbon of secondary and/or tertiary aliphatic hydrocarbons, the urethane prepolymer being soluble in an alcohol solvent (d) described hereinafter to form a solution. Among these, preferred is a linear urethane prepolymer in which 85 molar % or more of isocyanate groups attached to carbon of the terminal aliphatic hydrocarbon are isocyanate groups attached to carbon of secondary and/or tertiary aliphatic hydrocarbons, and more preferred is a linear urethane prepolymer (a′) in which all isocyanate groups attached to carbon of the terminal aliphatic hydrocarbon are isocyanate groups attached to carbon of secondary and/or tertiary aliphatic hydrocarbons.
In the urethane prepolymer, when the proportion of isocyanate groups attached to carbon of secondary and/or tertiary aliphatic hydrocarbons among isocyanate groups attached to carbon of the terminal aliphatic hydrocarbon is less than 70 molar %, the reaction between the hydroxyl group of the alcohol solvent (d) and the isocyanate group of the urethane prepolymer is liable to occur, thereby decreasing the molecular weight of the resulting urethane resin and deter
Motomura Masatoshi
Muramatsu Ichirou
Takanashi Hirotsugu
Armstrong Westerman & Hattori, LLP
Dainippon Ink and Chemicals Inc.
Niland Patrick D.
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