JP4087401B2 - Polyurethane water dispersion for heat-resistant heat-sensitive sheet binder, production method thereof, composition and heat-sensitive sheet using the water dispersion - Google Patents

Description

  The present invention relates to a polyurethane water dispersion for a heat-resistant heat-sensitive sheet binder, a method for producing the same, a composition using the water dispersion, and a heat-sensitive sheet. More specifically, an undercoat layer is not required, and heat resistance and adhesion. The present invention relates to a polyurethane water dispersion for heat-resistant and heat-sensitive sheet binders that is excellent in printing properties and has good printing characteristics, a method for producing the same, a composition using the water dispersion, and a heat-sensitive sheet.

  2. Description of the Related Art Conventionally, a recording medium for an image printer used for X-ray photography or the like has been formed by forming a heat-sensitive layer that develops color on heat on a plastic base sheet. In this heat-sensitive layer, a binder in which a color former is dispersed is used, and a polyurethane water dispersion is known as a resin used in the binder (Patent Document 1).

  However, since a conventional polyurethane water dispersion has low adhesion even when directly applied to a plastic base sheet, it is necessary to previously apply an undercoat layer to the base sheet. A polyurethane water dispersion for sheet binders that can exhibit sufficient adhesion without using this undercoat layer is desired.

In addition, the urethane polymer contained in the conventional polyurethane water dispersion for sheet binder has an anionic hydrophilic group for imparting dispersibility, and this hydrophilic group is neutralized at the prepolymer stage. Is normal. For example, a metal hydroxide such as caustic soda can be considered as an alkali that can be used for neutralization. However, when a metal hydroxide is used, the contact portion of a thermal head or the like that heats the film and develops color tends to corrode. There is. In addition, when amines such as triethylamine are used, the color former is adversely affected and printing characteristics are impaired. Therefore, it is conceivable to use ammonia for neutralization. However, when ammonia is used as a neutralizing agent, the following problems occur. That is, the heat-sensitive layer of the recording medium of the image printer is also required to have heat resistance, and in order to improve the heat resistance, it is necessary to increase the molecular weight of the prepolymer. The prepolymer cannot be increased in molecular weight by reacting with the terminal isocyanate group, and emulsification or dispersion tends to be difficult. As a result, there is a problem in that the heat resistance of the heat sensitive layer is lowered, and the sticking resistance, head durability and the like are lowered. Further, a method using a polymer terminal as a hydroxyl group and ammonia as a neutralizing agent is conceivable, but even in this case, it is difficult to increase the molecular weight due to a synthesis problem.
JP 2005-68228 A

  The present invention has been made to solve such problems of the prior art, and the object of the present invention is to exhibit sufficient adhesion even when an undercoat layer is not used, and to be heat resistant. An object is to provide a polyurethane water dispersion for heat-resistant and heat-sensitive sheet binders that is excellent and has good printing characteristics, a method for producing the same, a composition using the water dispersion, and a heat-sensitive sheet.

  The polyurethane water dispersion for a heat-resistant heat-sensitive sheet binder of the present invention has (A) a polyol, at least one hydrophilic group other than a hydroxyl group, and at least one active hydrogen-containing group. (H) a hydrophilic group-containing active hydrogen compound And (B) a part or all of the molecular terminal isocyanate groups of the intermediate prepolymer constituted by (B) an organic polyisocyanate and (D) an alkoxysilane derivative having at least one active hydrogen-containing group. (E) The urethane prepolymer obtained by making it contain, (F) hydrophilic group containing water-based polyurethane resin emulsified or disperse | distributed to water, It is characterized by the above-mentioned.

  Moreover, the manufacturing method of the polyurethane water dispersion for heat-resistant heat-sensitive sheet binders of the present invention comprises (A) a polyol, (B) an organic polyisocyanate, at least one hydrophilic group other than a hydroxyl group, and at least an active hydrogen-containing group. (C) an intermediate prepolymer is obtained from (H) a hydrophilic group-containing active hydrogen compound having one kind, and at least one activity of a part or all of the molecular terminal isocyanate groups of the (C) intermediate prepolymer (E) Urethane prepolymer is obtained by reacting with (D) alkoxysilane derivative having hydrogen-containing groups, and (F) hydrophilic group-containing aqueous polyurethane resin is produced by emulsifying or dispersing the (E) urethane prepolymer in water. It is characterized by making it.

  Furthermore, the heat-resistant heat-sensitive sheet binder composition of the present invention comprises a polyurethane water dispersion for the heat-resistant heat-sensitive sheet binder and an anionic hydrophilic group contained in the (F) hydrophilic group-containing aqueous polyurethane resin of the dispersion. It contains 0 to 2 equivalents of a carbodiimide crosslinking agent or an oxazoline crosslinking agent.

  The heat-sensitive sheet of the present invention is characterized in that a coating liquid containing the heat-resistant heat-sensitive sheet binder composition is applied.

  The polyurethane water dispersion for heat-resistant and heat-sensitive sheet binder of the present invention exhibits high adhesion to a plastic base sheet, and has a high molecular weight by introducing a networked siloxane bond with an alkoxysilane derivative. Therefore, the heat sensitive sheet produced using this exhibits sufficiently high heat resistance.

  Moreover, in the structure which introduce | transduced what neutralized part or all of the anionic hydrophilic group with ammonia as a hydrophilic group, in addition to said heat resistance, the heat sensitive sheet excellent in printing characteristics, such as contrast, is obtained.

  In the present invention, as (A) polyol, (A1) polyester polyol alone, (A2) polycarbonate polyol alone, or (A1) both polyester polyol and (A2) polycarbonate polyol may be used. it can.

  As the (A1) polyester polyol that can be used in the present invention, known ones can be used. For example, polyethylene adipate diol, polybutylene adipate diol, polyhexamethylene adipate diol, polyneopentyl adipate diol, polyethylene- Butylene adipate diol, polyneopentyl-hexamethylene adipate diol, poly 3-methylpentane adipate diol, polyethylene terephthalate diol, polybutylene terephthalate diol, polyhexamethylene terephthalate diol, polyneopentyl terephthalate diol, polyethylene-butylene terephthalate diol, polyneo Pentyl-hexamethylene terephthalate diol, poly-3-methylpentane terephthalate Diol, polyethylene isophthalate diol, polybutylene isophthalate diol, polyhexamethylene isophthalate diol, polyneopentyl isophthalate diol, polyethylene butylene isophthalate diol, polyneopentyl-hexamethylene isophthalate diol, poly 3-methylpentaneiso A phthalate diol etc. can be illustrated.

  Among these polyester polyols, those in which the glycol component constituting the polyester polyol is an aliphatic branched glycol are preferable from the viewpoint of improving adhesion. As such aliphatic branched glycols, 1,2-propylene glycol, 1-methyl-1,3-butylene glycol, 2-methyl-1,3-butylene glycol, neopentyl glycol, 1-methyl-1,4-pentylene Lenglycol, 2-methyl-1,4-pentylene glycol, 1,2-dimethyl-neopentyl glycol, 2,3-dimethyl-neopentyl glycol, 1-methyl-1,5-pentylene glycol, 2-methyl- 1,5-pentylene glycol, 3-methyl-1,5-pentylene glycol, 1,2-dimethylbutylene glycol, 1,3-dimethylbutylene glycol, 2,3-dimethylbutylene glycol, 1,4-dimethylbutylene A glycol etc. can be illustrated. These aliphatic branched glycols are used alone or in combination of two or more kinds or aromatic glycols.

  Of the above polyester polyols, the dicarboxylic acid component constituting the polyester polyol is preferably an aromatic dicarboxylic acid from the viewpoint of improving adhesion. As such aromatic dicarboxylic acids, phthalic acid, isophthalic acid, terephthalic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, biphenyldicarboxylic acid, tetrahydrophthalic acid Etc. can be illustrated. These aromatic dicarboxylic acids are used alone or in combination of two or more or aliphatic dicarboxylic acids. These (A1) polyester polyols can be used in combination of two or more.

  In the present invention, known polycarbonate polyols (A2) that can be used in the present invention can be used. For example, various diols can be used as the monomer for producing the polycarbonate polyol, but ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 1 , 5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 1,8-nonanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedi Examples thereof include methanol and bisphenol-A. These may be used alone or in combination of two or more. Among these polycarbonate polyols, those in which the glycol component constituting the polycarbonate polyol is an aliphatic branched glycol are preferable from the viewpoint of reducing the viscosity of the polycarbonate polyol and improving the adhesion. As such aliphatic branched glycols, 1,2-propylene glycol, 1-methyl-1,3-butylene glycol, 2-methyl-1,3-butylene glycol, neopentyl glycol, 1-methyl-1,4-pentylene Lenglycol, 2-methyl-1,4-pentylene glycol, 1,2-dimethyl-neopentyl glycol, 2,3-dimethyl-neopentyl glycol, 1-methyl-1,5-pentylene glycol, 2-methyl -1,5-pentylene glycol, 3-methyl-1,5-pentylene glycol, 1,2-dimethylbutylene glycol, 1,3-dimethylbutylene glycol, 2,3-dimethylbutylene glycol, 1,4-dimethyl Examples include butylene glycol. These aliphatic branched glycols are used alone or in combination of two or more kinds or aromatic glycols. These (A2) polycarbonate polyols can be used in combination of two or more.

  In the present invention, as (A) polyol, in addition to (A1) polyester polyol and (A2) polycarbonate polyol, one such as polyether polyol, polyolefin polyol, polysiloxane polyol, polyamide polyol, polycaprolactone polyol, etc. Those having the above hydroxyl groups can be used in combination.

  Examples of (B) organic polyisocyanate that can be used in the present invention include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymeric MDI, hexamethylene diisocyanate (HMDI), xylylene diisocyanate (XDI), and tetramethyl. Examples thereof include organic polyisocyanate compounds such as xylylene diisocyanate (TMXDI), isophorone diisocyanate (IPDI), and hydrogenated MDI (H12MDI). These (B) organic polyisocyanates can be used in combination of two or more.

  The (H) hydrophilic group-containing active hydrogen compound in the present invention has at least one hydrophilic group other than a hydroxyl group and at least one active hydrogen-containing group having reactivity with an isocyanate group. As a hydrophilic group other than a hydroxyl group, an anionic hydrophilic group such as a carboxyl group and a sulfonic acid group, a neutralized part or all of these anionic hydrophilic groups, a polyoxyethylene group having a molecular weight of 500 to 2000, and the like It can be illustrated. Among these hydrophilic groups, an ammonium salt obtained by neutralizing part or all of a carboxyl group and a sulfonic acid group with ammonia, and a mixture thereof are preferable from the viewpoint of printing characteristics. Examples of the active hydrogen-containing group include a hydroxyl group and an amino group.

  When the hydrophilic group other than the hydroxyl group is one obtained by neutralizing a part or all of the anionic hydrophilic group, the acid value of the (E) urethane prepolymer before neutralizing the anionic hydrophilic group is solid. It is preferably 5 to 50 mg KOH / g per minute. When the acid value is less than 5 mgKOH / g, the adhesion to the base sheet tends to be lowered. When the acid value is more than 50 mgKOH / g, the hydrophilicity is increased, and the water resistance of the resulting film tends to be lowered. .

  The alkoxysilane derivative (D) that can be used in the present invention has at least one active hydrogen-containing group, and a conventionally known alkoxysilane derivative can be used, and 3-aminopropyltrimethoxy Silane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, N-2 (aminoethyl) 3-aminopropylmethyldimethoxysilane, N-2 (aminoethyl) 3 -Aminopropyltrimethoxysilane, N-2 (aminoethyl) 3-aminopropyltriethoxysilane, etc. can be illustrated. Among these, (E) From the viewpoint of the stability of the alkoxysilane group of the urethane prepolymer, compounds having an ethoxysilane structure such as 3-aminopropyltriethoxysilane and 3-aminopropylmethyldiethoxysilane are preferred. Further, 3-aminopropyltriethoxysilane is particularly preferable from the viewpoints of water resistance, solvent resistance, and heat resistance. These (D) alkoxysilane derivatives can be used in combination of two or more.

  The active hydrogen-containing group of the (D) alkoxysilane derivative in the present invention is formed by the reaction of the above (A) polyol, (H) a hydrophilic group-containing active hydrogen compound, and (B) an organic polyisocyanate. It reacts with some or all of the molecular terminal isocyanate groups of the body prepolymer. The (D) alkoxysilane derivative functions to polymerize the (C) intermediate prepolymer upon emulsification or dispersion in water. As described above, (H) a carboxyl group or sulfonic acid group exists in the intermediate prepolymer as a hydrophilic group other than the hydroxyl group of the hydrophilic group-containing active hydrogen compound, and this carboxyl group or sulfonic acid group is neutralized with ammonia. Also in this case, the alkoxyl group of the (D) alkoxysilane derivative does not react with ammonia unlike the isocyanate group, and therefore is not affected by this. Therefore, in the present invention, despite the neutralization of the carboxyl group or sulfonic acid group with ammonia, (D) the high molecular weight of the intermediate prepolymer is achieved by (D) the alkoxysilane derivative. It is possible.

  In the present invention, a chain extender may be added during the preparation of (C) the intermediate prepolymer. Examples of the chain extender include 1,4-butanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, ethylene glycol, neopentyl glycol, diethylene glycol, cyclohexanedimethanol, trimethylolpropane, glycerin and the like. Glycol or triol can be exemplified.

  In the present invention, in the preparation of (C) the intermediate prepolymer, a monoalcohol can be appropriately used as long as the heat resistance is not impaired. Examples of such a monoalcohol include polyoxyethylene monoalkyl ether having a molecular weight of 500 to 2000.

  The polyurethane water dispersion for heat-resistant heat-sensitive sheet binder of the present invention can be produced by the following method.

  First, (A) polyol and (B) organic polyisocyanate are reacted. Next, (C) an intermediate prepolymer is obtained by reacting (H) a hydrophilic group-containing active hydrogen compound having at least one hydrophilic group other than a hydroxyl group and at least one active hydrogen-containing group. The (H) hydrophilic group-containing active hydrogen compound may be added simultaneously with the reaction of the (A) polyol and (B) the organic polyisocyanate.

  Next, (C) a part or all of the molecular terminal isocyanate group of the intermediate prepolymer is reacted with (D) an alkoxysilane derivative having at least one active hydrogen-containing group to obtain (E) a urethane prepolymer. .

  Here, when the hydrophilic group other than the hydroxyl group of the (H) hydrophilic group-containing active hydrogen compound is an anionic hydrophilic group, (E) a part or all of the anionic hydrophilic group contained in the urethane prepolymer Neutralized ones are preferable, and neutralization with ammonia is more preferable from the viewpoint of improving printing characteristics.

  The (A) intermediate prepolymer constituted by the components (A1), (A2), (H) and (B) has an average number of functional groups of active isocyanate groups per molecule of 1 to 4 Preferably there is. If the average number of functional groups is less than 1, the resulting film has low heat resistance, and if the average number of functional groups is greater than 4, the viscosity of the (C) intermediate prepolymer increases, making synthesis difficult. It is not preferable.

  It is preferable that the melting temperature of the film formed using the polyurethane water dispersion for heat-resistant and heat-sensitive sheet binder of the present invention is 120 ° C. or more and up to a temperature just before carbonization occurs.

  In the present invention, the (E) urethane prepolymer is emulsified or dispersed in water to obtain (F) a hydrophilic group-containing aqueous polyurethane resin. (E) When the urethane prepolymer is emulsified or dispersed in water, a surfactant may be blended as necessary in order to improve emulsifiability or dispersibility. The compounding quantity of surfactant is 0 to 20 weight% with respect to (E) urethane prepolymer.

  The heat-resistant heat-sensitive sheet binder composition of the present invention is 0 to the anionic hydrophilic group contained in the polyurethane water dispersion for the heat-resistant heat-sensitive sheet binder and the (F) hydrophilic group-containing aqueous polyurethane resin of the dispersion. -2 equivalent carbodiimide type crosslinking agent or oxazoline type crosslinking agent is mix | blended. As the carbodiimide-based crosslinking agent and the oxazoline-based crosslinking agent, any compound having a carbodiimide skeleton and an oxazoline skeleton can be used.

  The polyurethane water dispersion for heat-resistant heat-sensitive sheet binder of the present invention and the composition using this water dispersion use an undercoat layer on a base sheet such as polyethylene terephthalate, polypropylene, nylon, polyolefin (polyethylene, etc.). And can be applied directly. Adhesion can be further improved by using a sheet that has been subjected to a surface treatment such as a corona discharge treatment.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to a following example. In the present specification, “%” and “part” represent “% by weight” and “part by weight”, respectively, unless otherwise specified.

((A1) Polyester polyol)
As the polyester polyol (A1) in the following Examples and Comparative Examples, polyester polyols composed of the following aliphatic branched glycols and aromatic dicarboxylic acids were used. A mixture of terephthalic acid, isophthalic acid and adipic acid (terephthalic acid / isophthalic acid / adipic acid = 2/3/1 (equivalent ratio)) as an acid component, and a mixture of ethylene glycol and neopentyl glycol (ethylene glycol / It is a polyester polyol having a number average molecular weight of about 2000 synthesized from neopentyl glycol = 1/2 (equivalent ratio).

Example 1
(A1) Polyester polyol 72.6 parts by weight, polyethylene glycol (Mw600, trade name PEG600S, Daiichi Kogyo Seiyaku Co., Ltd.) 5 parts by weight, 2,2'-diphenylmethane diisocyanate 19.2 parts by weight, methyl ethyl ketone 40 parts by weight A portion was placed in a reaction vessel, and the reaction was conducted while maintaining the temperature at 70 to 75 ° C. to obtain a compound having an NCO content of 2.7% (per solid content). To the obtained compound, 3.2 parts by weight of dimethylolpropionic acid (DMPA) and 40 parts by weight of methyl ethyl ketone were added and the reaction was carried out while maintaining the temperature at 70 to 75 ° C., and the NCO content was 0.5% (per solid content). An intermediate prepolymer was obtained (average number of functional groups of 2 active isocyanate groups per molecule of intermediate prepolymer). 3-aminopropyltriethoxysilane (trade name KBE-903, Shin-Etsu Silicone Co., Ltd.) is added to the obtained intermediate prepolymer in an equivalent amount with respect to the terminal isocyanate group, and the reaction is carried out at 30 to 35 ° C. After confirming disappearance of the reaction, the reaction was terminated (acid value 13 mgKOH / g). Next, a urethane prepolymer was obtained by adding an aqueous ammonia (10% aqueous solution) in an equivalent amount to the carboxyl group and neutralizing. The obtained urethane prepolymer was diluted with 300 parts by weight of water, and methyl ethyl ketone was recovered to obtain a polyurethane water dispersion for a heat-resistant and heat-sensitive sheet binder having a nonvolatile content of 25%.

(Example 2)
(A1) Polyester polyol 36.3 parts by weight, polycarbonate polyol (Mw2000, trade name PCDL T6002, Asahi Kasei Chemicals) 36.3 parts by weight, polyethylene glycol (Mw600, trade name PEG600S, Daiichi Kogyo Seiyaku Co., Ltd.) )) 5 parts by weight, 19.2 parts by weight of 2,2′-diphenylmethane diisocyanate and 40 parts by weight of methyl ethyl ketone were placed in a reaction vessel, and the reaction was carried out while maintaining the temperature at 70 to 75 ° C., so that the NCO content was 2.7% (solid (Per minute) was obtained. Intermediate obtained by adding 3.2 parts by weight of dimethylolpropionic acid and 40 parts by weight of methyl ethyl ketone to the obtained compound and carrying out the reaction while maintaining at 70 to 75 ° C., and having an NCO content of 0.5% (per solid content) A body prepolymer was obtained (average number of functional groups of active isocyanate groups per molecule of intermediate prepolymer 2). 3-aminopropyltriethoxysilane (trade name KBE-903, Shin-Etsu Silicone Co., Ltd.) is added to the obtained intermediate prepolymer in an equivalent amount with respect to the terminal isocyanate group, and the reaction is carried out at 30 to 35 ° C. After confirming disappearance of the reaction, the reaction was terminated (acid value 13 mgKOH / g). Next, a urethane prepolymer was obtained by adding an aqueous ammonia (10% aqueous solution) in an equivalent amount to the carboxyl group and neutralizing. The obtained urethane prepolymer was diluted with 300 parts by weight of water, and methyl ethyl ketone was recovered to obtain a polyurethane water dispersion for a heat-resistant and heat-sensitive sheet binder having a nonvolatile content of 25%.

(Example 3)
(A1) Polyester polyol 77.1 parts by weight, polyethylene glycol (Mw600, trade name PEG600S, Daiichi Kogyo Seiyaku Co., Ltd.) 5.3 parts by weight, tolylene diisocyanate 14.2 parts by weight, methyl ethyl ketone 40 parts by weight The reaction was carried out in a reaction vessel while maintaining the temperature at 70 to 75 ° C. to obtain a compound having an NCO content of 2.8% (per solid content). Intermediate obtained by adding 3.4 parts by weight of dimethylolpropionic acid and 40 parts by weight of methyl ethyl ketone to the obtained compound and carrying out the reaction while maintaining at 70 to 75 ° C., and having an NCO content of 0.5% (per solid content) A body prepolymer was obtained (average number of functional groups of active isocyanate groups per molecule of intermediate prepolymer 2). 3-aminopropyltriethoxysilane (trade name KBE-903, Shin-Etsu Silicone Co., Ltd.) is added to the obtained intermediate prepolymer in an equivalent amount with respect to the terminal isocyanate group, and the reaction is carried out at 30 to 35 ° C. After confirming disappearance of the reaction, the reaction was terminated (acid value 13 mgKOH / g). Next, a urethane prepolymer was obtained by adding an aqueous ammonia (10% aqueous solution) in an equivalent amount to the carboxyl group and neutralizing. The obtained urethane prepolymer was diluted with 300 parts by weight of water, and methyl ethyl ketone was recovered to obtain a polyurethane water dispersion for a heat-resistant and heat-sensitive sheet binder having a nonvolatile content of 25%.

Example 4
(A1) Polyester polyol 65.9 parts by weight, polyethylene glycol (Mw600, trade name PEG600S, Daiichi Kogyo Seiyaku Co., Ltd.) 5 parts by weight, 2,2′-diphenylmethane diisocyanate 25.9 parts by weight, methyl ethyl ketone 40 parts by weight A portion was placed in a reaction vessel, and the reaction was carried out while maintaining the temperature at 70 to 75 ° C. to obtain a compound having an NCO content of 5.2% (per solid content). 7.3 parts by weight of dimethylolpropionic acid and 40 parts by weight of methyl ethyl ketone were added to the obtained compound and the reaction was carried out while maintaining the temperature at 70 to 75 ° C., and the NCO content was 0.5% (per solid content). A body prepolymer was obtained (average number of functional groups of active isocyanate groups per molecule of intermediate prepolymer 2). 3-aminopropyltriethoxysilane (trade name KBE-903, Shin-Etsu Silicone Co., Ltd.) is added to the obtained intermediate prepolymer in an equivalent amount with respect to the terminal isocyanate group, and the reaction is carried out at 30 to 35 ° C. After confirming disappearance of the reaction, the reaction was terminated (acid value 30 mgKOH / g). Next, a urethane prepolymer was obtained by adding an aqueous ammonia (10% aqueous solution) in an equivalent amount to the carboxyl group and neutralizing. The obtained urethane prepolymer was diluted with 400 parts by weight of water, and methyl ethyl ketone was recovered to obtain a polyurethane water dispersion for heat-resistant and heat-sensitive sheet binder having a nonvolatile content of 20%.

(Example 5)
(A1) Polyester polyol 72.6 parts by weight, polyethylene glycol (Mw600, trade name PEG600S, Daiichi Kogyo Seiyaku Co., Ltd.) 5 parts by weight, 2,2'-diphenylmethane diisocyanate 19.2 parts by weight, methyl ethyl ketone 40 parts by weight A portion was placed in a reaction vessel, and the reaction was conducted while maintaining the temperature at 70 to 75 ° C. to obtain a compound having an NCO content of 2.7% (per solid content). Intermediate obtained by adding 3.2 parts by weight of dimethylolpropionic acid and 40 parts by weight of methyl ethyl ketone to the obtained compound and carrying out the reaction while maintaining at 70 to 75 ° C., and having an NCO content of 0.5% (per solid content) A body prepolymer was obtained (average number of functional groups of active isocyanate groups per molecule of intermediate prepolymer 2). 3-aminopropyltriethoxysilane (trade name KBE-903, Shin-Etsu Silicone Co., Ltd.) is added to the obtained intermediate prepolymer in an equivalent amount with respect to the terminal isocyanate group, and the reaction is carried out at 30 to 35 ° C. After confirming disappearance of the reaction, the reaction was terminated (acid value 13 mgKOH / g). Next, a urethane prepolymer was obtained by adding an aqueous ammonia (10% aqueous solution) in an equivalent amount to the carboxyl group and neutralizing. By adding 5 parts by weight of Neugen EA-157 (Nonionic Surfactant, Daiichi Kogyo Seiyaku Co., Ltd.) to the obtained urethane prepolymer, diluting with 400 parts by weight of water and recovering methyl ethyl ketone, A polyurethane water dispersion for 20% heat-resistant heat-sensitive sheet binder was obtained.

(Example 6)
(A1) Polyester polyol 65.9 parts by weight, polyethylene glycol (Mw600, trade name PEG600S, Daiichi Kogyo Seiyaku Co., Ltd.) 5 parts, trimethylolpropane 5 parts by weight, 2,2′-diphenylmethane diisocyanate 34 parts by weight Parts and 40 parts by weight of methyl ethyl ketone were placed in a reaction vessel and reacted while maintaining at 70 to 75 ° C. to obtain a compound having an NCO content of 2.9% (per solid content). Intermediate obtained by adding 3.2 parts by weight of dimethylolpropionic acid and 40 parts by weight of methyl ethyl ketone to the obtained compound and carrying out the reaction while maintaining at 70 to 75 ° C., and having an NCO content of 0.9% (per solid content) Body prepolymer was obtained (average number of functional groups of active isocyanate groups per molecule of intermediate prepolymer was 2.4). 3-aminopropyltriethoxysilane (trade name KBE-903, Shin-Etsu Silicone Co., Ltd.) is added to the obtained intermediate prepolymer in an equivalent amount with respect to the terminal isocyanate group, and the reaction is carried out at 30 to 35 ° C. After confirming disappearance of the reaction, the reaction was terminated (acid value 13 mgKOH / g). Next, a urethane prepolymer was obtained by adding an aqueous ammonia (10% aqueous solution) in an equivalent amount to the carboxyl group and neutralizing. The obtained urethane prepolymer was diluted with 300 parts by weight of water, and methyl ethyl ketone was recovered to obtain a polyurethane water dispersion for a heat-resistant and heat-sensitive sheet binder having a nonvolatile content of 25%.

(Example 7) Neutralization with triethylamine 72.6 parts by weight of the above (A1) polyester polyol, 5 parts by weight of polyethylene glycol (Mw600, trade name PEG600S, Daiichi Kogyo Seiyaku Co., Ltd.), 2,2'-diphenylmethane diisocyanate 19.2 parts by weight and 40 parts by weight of methyl ethyl ketone were placed in a reaction vessel and reacted while being kept at 70 to 75 ° C. to obtain a compound having an NCO content of 2.7% (per solid content). Intermediate obtained by adding 3.2 parts by weight of dimethylolpropionic acid and 40 parts by weight of methyl ethyl ketone to the obtained compound and carrying out the reaction while maintaining at 70 to 75 ° C., and having an NCO content of 0.5% (per solid content) A body prepolymer was obtained (average number of functional groups of active isocyanate groups per molecule of intermediate prepolymer 2). 3-aminopropyltriethoxysilane (trade name KBE-903, Shin-Etsu Silicone Co., Ltd.) is added to the obtained intermediate prepolymer in an equivalent amount with respect to the terminal isocyanate group, and the reaction is carried out at 30 to 35 ° C. After confirming disappearance of the reaction, the reaction was terminated (acid value 13 mgKOH / g). Next, an urethane prepolymer was obtained by adding an equivalent amount of triethylamine to the carboxyl group and neutralizing. The obtained urethane prepolymer was diluted with 300 parts by weight of water, and methyl ethyl ketone was recovered to obtain a polyurethane water dispersion for a heat-resistant and heat-sensitive sheet binder having a nonvolatile content of 25%.

(Comparative example 1) OH terminal, alkoxysilane derivative not used 81.3 parts by weight of the above-mentioned (A1) polyester polyol, 15.5 parts by weight of 2,2′-diphenylmethane diisocyanate, and 40 parts by weight of methyl ethyl ketone are placed in a reaction vessel. The reaction was performed while maintaining the temperature at 75 ° C. to obtain a compound having an NCO content of 1.8% (per solid content). To the obtained compound, 3.3 parts by weight of dimethylolpropionic acid and 40 parts by weight of methyl ethyl ketone were added and the reaction was carried out while maintaining the temperature at 70 to 75 ° C. After confirming that the isocyanate group had disappeared, the reaction was terminated (one molecule The average number of functional groups per active isocyanate group is 2, and the acid value is 13 mgKOH / g). Next, a urethane prepolymer was obtained by adding an aqueous ammonia (10% aqueous solution) in an equivalent amount to the carboxyl group and neutralizing. The obtained urethane prepolymer was diluted with 150 parts by weight of water, and methyl ethyl ketone was recovered to obtain a polyurethane water dispersion for a heat-resistant heat-sensitive sheet binder having a nonvolatile content of 40%.

(Comparative Example 2) Neutralization with triethylamine, no alkoxysilane derivative used (A1) 72.6 parts by weight of the polyester polyol, 5 parts by weight of polyethylene glycol (Mw600, trade name PEG600S, Daiichi Kogyo Seiyaku Co., Ltd.), diphenylmethane 19.2 parts by weight of diisocyanate and 40 parts by weight of methyl ethyl ketone were placed in a reaction vessel and reacted while being kept at 70 to 75 ° C. to obtain a compound having an NCO content of 2.7% (per solid content). Intermediate obtained by adding 3.2 parts by weight of dimethylolpropionic acid and 40 parts by weight of methyl ethyl ketone to the obtained compound and carrying out the reaction while maintaining at 70 to 75 ° C., and having an NCO content of 0.5% (per solid content) A body prepolymer was obtained (average number of functional groups of active isocyanate groups per molecule of intermediate prepolymer, acid value 13 mgKOH / g). A urethane prepolymer was obtained by adding an equivalent amount of triethylamine to a carboxyl group and neutralizing the obtained intermediate prepolymer. The obtained urethane prepolymer was diluted with 300 parts by weight of water, and methyl ethyl ketone was recovered to obtain a polyurethane water dispersion for a heat-resistant and heat-sensitive sheet binder having a nonvolatile content of 25%.

(Comparative example 3) NCO terminal, alkoxysilane derivative not used The above (A1) polyester polyol 72.6 parts by weight, polyethylene glycol (Mw600, trade name PEG600S, Daiichi Kogyo Seiyaku Co., Ltd.) 5 parts by weight, diphenylmethane diisocyanate 19 .2 parts by weight and 40 parts by weight of methyl ethyl ketone were placed in a reaction vessel and reacted while maintaining at 70 to 75 ° C. to obtain a compound having an NCO content of 2.7% (per solid content). Intermediate obtained by adding 3.2 parts by weight of dimethylolpropionic acid and 40 parts by weight of methyl ethyl ketone to the obtained compound and carrying out the reaction while maintaining at 70 to 75 ° C., and having an NCO content of 0.5% (per solid content) A body prepolymer was obtained (average number of functional groups of active isocyanate groups per molecule of intermediate prepolymer, acid value 13 mgKOH / g). A urethane prepolymer was obtained by adding an aqueous ammonia (10% aqueous solution) in an equivalent amount to the carboxyl group and neutralizing the obtained intermediate prepolymer. The obtained urethane prepolymer was diluted with 300 parts by weight of water, and methyl ethyl ketone was recovered to obtain a polyurethane water dispersion for a heat-resistant and heat-sensitive sheet binder having a nonvolatile content of 25%.

<Performance test of thermal sheet>
The following performance tests were conducted using the polyurethane water dispersions for heat-resistant and heat-sensitive sheet binders of each Example and each Comparative Example, and the results are shown in Table 1.

(Manufacture of thermal sheet)
1. (I) Preparation of Liquid (Coloring Agent Dispersion) 3-Dibutylamino-7- (o-chloroanilino) fluorane 25 parts 25% polyvinyl alcohol aqueous solution 20 parts Water 55 parts
(100 copies in total)
This mixture was dispersed using a horizontal bead mill.

2. (II) Preparation of liquid (developer dispersion) Bis (3-allyl-4-hydroxyphenyl) sulfone 25 parts 25% aqueous polyvinyl alcohol solution 20 parts Water 55 parts
(100 copies in total)
This mixture was dispersed using a horizontal bead mill.

3. Preparation of thermosensitive coloring layer (I) Liquid 25 parts (II) Liquid 50 parts Polyurethane aqueous dispersion (solid content 20% adjusted product) 25 parts
(100 copies in total)
This mixture was sufficiently stirred to obtain a thermal recording layer coating solution. The obtained coating solution was applied to the surface of a stretched polyethylene terephthalate film having a thickness of 100 μm so that the coating amount after drying was 5 g / m ² and dried with a dryer at 50 ° C. to obtain a heat-sensitive sheet.

(Evaluation of thermal sheet)
(1) Sticking resistance When printing was performed on the thermal sheet using an image printer UP-701 manufactured by Sony Corporation, the adhesion state of the sample to the thermal head was determined.

A: The heat-sensitive sheet ran without any adhesion. O: The heat-sensitive sheet ran with almost no adhesion. X: The heat-sensitive sheet did not run smoothly, resulting in poor printing.

(2) Head inertia When printing on a thermal sheet with the image printer, the state of wrinkle adhesion to the thermal head was visually determined.

A: There was no wrinkle adhesion after printing. B: There was almost no wrinkle adhesion.

(3) Color development characteristics When printing on a heat-sensitive sheet with the image printer, an unprinted portion of the image surface was visually confirmed.

A: The unprinted portion is transparent. O: The unprinted portion is almost transparent.

(4) Film adhesion test The polyurethane water dispersion for heat-resistant heat-sensitive sheet binders obtained in each Example and each Comparative Example was applied to a stretched polyethylene terephthalate film having a thickness of 100 μm so as to have a dry film thickness of 10 μm. Heat treatment was carried out at 5 ° C. for 5 minutes. The adhesion of the coating film was evaluated based on the cross-cut tape method of JIS K5400. That is, 100 mm squares of 2 mm squares were formed on the coated surface, cellophane adhesive tape was affixed, and adhesion was evaluated from the number of squares from which the film peeled off from the film when this was rapidly peeled off. The evaluation results were displayed as follows.

Evaluation criteria A: 100% of coating layer remains
○: More than 80% of the coating layer remains
X: The coating layer is less than 80%.

(5) Heat resistance test The water-based polyurethane resin film obtained in each Example and each Comparative Example was heat-treated at 80 ° C for 6 hours so as to have a dry film thickness of 100 µm, and then heat-treated at 120 ° C for 1 hour. A sample of was prepared. The produced film was cut into a square with a side of 2 mm to obtain a heat resistance measurement sample. The heat resistance was measured using a viewer-type micro melting point measuring apparatus MP-500V manufactured by Yanaco Instrument Development Laboratory, and the temperature at which the sample became completely liquid was defined as the melting temperature.

The heat-sensitive sheet using the polyurethane water dispersion of the present invention exhibits sufficient adhesion even when an undercoat layer is not used, has excellent heat resistance, and has good printing characteristics. Therefore, it is used for X-ray photography. It can be used in the field of photographic film.

Claims (20)

A polyurethane water dispersion for a heat-resistant heat-sensitive sheet binder containing a polyurethane resin for retaining the color former and the developer in the color-forming layer of the heat-sensitive sheet,
(A) It is composed of a polyol, (H) a hydrophilic group-containing active hydrogen compound having at least one hydrophilic group other than a hydroxyl group and at least one active hydrogen-containing group, and (B) an organic polyisocyanate (C (E) Urethane prepolymer obtained by reacting part or all of the molecular terminal isocyanate group of the intermediate prepolymer with (D) an alkoxysilane derivative having at least one active hydrogen-containing group in water Alternatively, a polyurethane water dispersion for a heat-resistant heat-sensitive sheet binder, which contains a dispersed (F) hydrophilic group-containing aqueous polyurethane resin.   The polyurethane water dispersion for a heat-resistant thermosensitive sheet binder according to claim 1, wherein the (A) polyol contains at least one of (A1) a polyester polyol and / or (A2) a polycarbonate polyol. body.   The polyurethane water dispersion for a heat-resistant heat-sensitive sheet binder according to claim 2, wherein the (A) polyol is the (A1) polyester polyol.   The polyurethane water dispersion for a heat-resistant heat-sensitive sheet binder according to claim 2, wherein the (A) polyol is the (A2) polycarbonate polyol.   The polyurethane water dispersion for a heat-resistant thermosensitive sheet binder according to claim 3, wherein the glycol component constituting the (A1) polyester polyol contains at least one aliphatic branched glycol.   The polyurethane water dispersion for a heat-resistant heat-sensitive sheet binder according to claim 3 or 5, wherein the dicarboxylic acid component constituting the (A1) polyester polyol contains at least one aromatic dicarboxylic acid.   5. The polyurethane water dispersion for a heat-resistant heat-sensitive sheet binder according to claim 4, wherein the glycol component constituting the (A2) polycarbonate polyol contains at least one aliphatic branched glycol.   The hydrophilic group other than the hydroxyl group in the (E) urethane prepolymer is obtained by neutralizing a part or all of the anionic hydrophilic group. Polyurethane water dispersion for heat-resistant heat-sensitive sheet binder.   The polyurethane water dispersion for a heat-resistant heat-sensitive sheet binder according to claim 8, wherein the neutralization of a part or all of the anionic hydrophilic group is performed using ammonia.   The heat-resistant heat-sensitive sheet according to any one of claims 1 to 9, wherein the average number of functional groups of active isocyanate groups per molecule of the (C) intermediate prepolymer is in the range of 1 to 4. Polyurethane aqueous dispersion for binder.   10. The heat-resistant thermosensitive according to claim 8, wherein the acid value of the urethane prepolymer (E) before neutralization of the anionic hydrophilic group is 5 to 50 mg KOH / g per solid content. Polyurethane aqueous dispersion for sheet binder.   The polyurethane water dispersion for heat-resistant heat-sensitive sheet binders according to any one of claims 1 to 11, comprising a surfactant in an amount of 0 to 20% by weight based on the urethane prepolymer (E).   The polyurethane water dispersion for a heat-resistant heat-sensitive sheet binder according to any one of claims 1 to 12, wherein a melting temperature of a film formed using the polyurethane water dispersion for the heat-resistant heat-sensitive sheet binder is 120 ° C or higher. A method for producing a polyurethane water dispersion for a heat-resistant heat-sensitive sheet binder according to any one of claims 1 to 13,
(C) Intermediate from (A) polyol, (B) organic polyisocyanate, (H) hydrophilic group-containing active hydrogen compound having at least one hydrophilic group other than hydroxyl group and at least one active hydrogen-containing group Get a prepolymer,
(E) Urethane prepolymer is obtained by reacting part or all of the molecular terminal isocyanate group of the (C) intermediate prepolymer with (D) an alkoxysilane derivative having at least one active hydrogen-containing group,
(E) The urethane prepolymer is emulsified or dispersed in water to produce (F) a hydrophilic group-containing aqueous polyurethane resin. A method for producing a polyurethane water dispersion for heat-resistant and heat-sensitive sheet binders.   The polyurethane water for heat-resistant heat-sensitive sheet binder according to claim 14, wherein the (A) polyol contains at least one of (A1) polyester polyol and / or (A2) a polycarbonate polyol. A method for producing a dispersion.   (H) the hydrophilic group other than the hydroxyl group of the hydrophilic group-containing active hydrogen compound is an anionic hydrophilic group, and (E) further neutralizing part or all of the anionic hydrophilic group contained in the urethane prepolymer The manufacturing method of the polyurethane water dispersion for heat-resistant heat-sensitive sheet binders of Claim 14 or 15 which is included.   The method for producing a polyurethane water dispersion for a heat-resistant heat-sensitive sheet binder according to claim 16, wherein the neutralization of a part or all of the anionic hydrophilic group is performed using ammonia.   The heat-resistant heat-sensitive sheet according to any one of claims 14 to 17, wherein 0 to 20% by weight of a surfactant is added to the urethane prepolymer (E) and then emulsified or dispersed in water. A method for producing a polyurethane water dispersion for a binder.   The polyurethane water dispersion for heat-resistant heat-sensitive sheet binders according to claim 8, 9 or 11, and 0 to 2 equivalents of anionic hydrophilic groups contained in the (F) hydrophilic group-containing aqueous polyurethane resin of the dispersion. A heat-resistant thermosensitive sheet binder composition comprising a carbodiimide-based crosslinking agent or an oxazoline-based crosslinking agent.   A heat-sensitive sheet, wherein a coating liquid containing the heat-resistant heat-sensitive sheet binder composition according to claim 19 is applied to a substrate sheet.