JP2005272775A - Process for production of aqueous one pack urethane resin adhesive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process for stable production of an aqueous one pack urethane resin adhesive with excellent resistances such as to heat and water without forming two pack type adhesive by combination with a crosslinking agent. <P>SOLUTION: This aqueous one pack urethane resin adhesive is characterized in the process for production by dissolving a polyurethane resin having a carboxyl group (A) in a solvent, neutralizing with a basic compound (B), adding and mixing 0.3-10 pts.mass of a crosslinking agent (C) to 100 pts.mass of the polyurethane resin (A), wherein the mixing of water in performed just after the neutralization or is done for a while thereafter, to make water dispersed condition. Water is further added while mixing at a room temperature to 100°C to make dispersed state of the polyurethane resin (A) in water. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing an aqueous one-component urethane resin adhesive. More specifically, the present invention relates to various films having improved heat resistance and water resistance by cross-linking the inside of an aqueous dispersion of urethane resin. The present invention relates to a method for producing an aqueous one-component urethane resin adhesive useful for an adhesive for food packaging, an industrial adhesive for bonding a film and paper, a metal plate, or the like.

  In recent years, due to problems such as pollution and the environment, interest in water-based adhesives has been increasing in place of conventional solvent-based adhesives. As a result, research on water-based adhesives, especially urethane resin water-based adhesives, has been conducted a lot. There is a tendency. The urethane resin used as a raw material for urethane resin water-based adhesives can be produced by an emulsion method using an emulsifier, a self-emulsification method in which a hydrophilic group is introduced into the urethane resin, or a solvent such as acetone in the emulsion method or self-emulsification method. In general, an acetone method using a prepolymer and a prepolymer mixing method for forcibly emulsifying a urethane resin are performed.

  However, for example, when polymerizing in a solvent in the above-mentioned acetone method, only a linear polymer can be obtained. Therefore, when used as an adhesive, the adhesive performance is not sufficient. It was necessary to crosslink with an isocyanate adduct or the like. In the prepolymer mixing method, the prepolymer can be branched and forcibly emulsified to internally crosslink, but side reactions with water occur, and there is a problem in reproducibility. It was difficult to achieve both heat resistance. As described above, the urethane resin water-based adhesive is rarely used in one liquid urethane resin, and is used in a two-pack type in combination with a crosslinking agent such as an epoxy resin or an aqueous polyisocyanate adduct.

On the other hand, an attempt to increase heat resistance and water resistance by adding an epoxy resin to a self-emulsifying type urethane resin emulsion having no internal crosslinking and crosslinking it is described in JP-A-63-15816. However, there are problems in that there are few parts that act on internal cross-linking, inter-particle cross-linking and the like occur, a gel is easily formed in the emulsion, and a product with stable physical properties cannot be obtained.
JP-A 63-15816

  An object of the present invention is to provide a method for stably producing an aqueous one-component urethane resin adhesive excellent in heat resistance, water resistance and the like without using a two-component type combined with a crosslinking agent.

  As a result of various studies to solve the above problems, the present inventors have dissolved the carboxyl group-containing polyurethane resin (A) in a solvent, neutralized with a basic compound (B), and added water to cause phase inversion. In the step of emulsifying, immediately before adding water or when water is dispersed in the polyurethane resin (A) solution by adding water, the crosslinking agent (C) is added, and emulsion particles are added. It has been found that the object of the present invention can be achieved by carrying out crosslinking inside, and the present invention has been achieved.

  When a linear polyurethane resin alone is used as an adhesive for soft packaging materials, it is necessary to lower the glass transition temperature (Tg) of the polyurethane resin and increase the adhesive strength with adhesive strength in order to improve the adhesive strength. . However, a resin having low Tg and adhesive strength is softened when heat is applied, and the adhesive strength is significantly reduced. When filling soft packaging materials with food, etc., it is usually sealed with heat sealing, but since heat is applied at this time, the resin of the adhesive softens and the adhesive strength decreases significantly, and the bottom of the packaging material is broken during filling Cause. On the other hand, when a resin having a high Tg is used, the adhesive strength is reduced, and the adhesive force of the packaging material to the base material is significantly reduced. For this reason, the adhesive for soft packaging materials is made into a two-pack type by combining a linear polyurethane resin and a cross-linking agent to satisfy both adhesive force and heat resistance. However, in the case of a two-pack type adhesive, it is necessary to mix two liquids before use, and there is a disadvantage that the pot life and the like are short and the remaining meat cannot be used. In addition, the water-dispersed polyurethane resin can achieve both adhesive force and heat resistance even if it is a one-component type by making the dispersed particles internally cross-linked. However, the balance between the two easily collapses depending on the degree of internal crosslinking. That is, it is necessary to accurately control the degree of internal crosslinking. The present invention was completed based on such knowledge.

  That is, the present invention dissolves the carboxyl group-containing polyurethane resin (A) in a solvent, neutralizes with the basic compound (B), and immediately before adding water or by adding water, the polyurethane resin (A) When water is dispersed in the solution, 0.3 to 10 parts by mass of the crosslinking agent (C) per 100 parts by mass of the polyurethane resin (A) is added and mixed, and then water is further added to add water. The gist is a method for producing an aqueous one-component urethane resin adhesive, characterized in that mixing is continued at room temperature to 100 ° C. in a state where the polyurethane resin (A) is dispersed.

In the method for producing the aqueous one-component urethane resin adhesive of the present invention, the carboxyl group-containing polyurethane resin (A) is polyisocyanate compound (D), polyol (E) and chain extender (F) in the absence of a solvent. ) Under heating, preferably at 150 to 200 ° C.
The method for producing an aqueous one-component urethane resin adhesive of the present invention is characterized in that the crosslinking agent (C) is an aliphatic epoxy resin (G).
The method for producing an aqueous one-component urethane resin adhesive of the present invention is characterized in that the cross-linking agent (C) is a polyisocyanate adduct (H).
In the method for producing an aqueous one-component urethane resin adhesive of the present invention, the polyisocyanate compound (D) is tolylene diisocyanate or 4,4′-diphenylmethane diisocyanate, and the polyol (E) is a polyether polyol. The chain extender (F) is dimethylol butanoic acid.
The method for producing an aqueous one-component urethane resin adhesive of the present invention is characterized in that the aliphatic epoxy resin (G) has a solubility in water of 0% by mass or 70% by mass or less.
The method for producing an aqueous one-component urethane resin adhesive of the present invention is characterized in that the polyisocyanate adduct (H) is an adduct of tetramethylxylylene diisocyanate.

  The method of the present invention stably produces a one-component water-based urethane resin adhesive that does not require precise control of the degree of internal cross-linking and does not require mixing before use, which was essential in the two-component type. In addition, the adhesive obtained by the method is excellent in heat resistance, water resistance, etc., and is homogeneous and rich in storability.

  The carboxyl group-containing polyurethane resin (A), which is an essential component of the adhesive of the present invention, is produced by introducing a carboxyl group into a polyurethane resin obtained by reacting at least a polyisocyanate compound (D) and a polyol (E). However, those obtained by reacting the polyisocyanate compound (D), the polyol (E) and the carboxyl group-containing alcohol (F) with heating in the presence or absence of a solvent are preferred. Examples of the solvent used in this reaction include solvents having no active hydrogen, such as methyl ethyl ketone and ethyl acetate. However, when the reaction is carried out in the presence of a solvent, the solvent may remain in the final polyurethane resin, and if any solvent remains, the odor will remain in the laminate and reduce the flavor and the like. It is necessary to remove the solvent almost completely after making the water-soluble, which is not preferable as an adhesive production process. For these reasons, the reaction of the polyisocyanate compound (D), the polyol (E), and the carboxyl group-containing alcohol (F) is preferably carried out in the absence of a solvent at 150 to 200 ° C. to obtain a carboxyl group-containing polyurethane resin. It is particularly preferred to produce (A).

  Examples of the polyisocyanate compound (D) include tolylene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and 1,5-naphthalene diisocyanate. (NDI), xylylene diisocyanate (XDI) and the like can be mentioned, and TDI and MDI are particularly preferable. Examples of the polyol (E) include polyester polyols and polyether polyols, and polyether polyols are particularly preferable. Examples of the carboxyl group-containing alcohol (F) include dimethylolpropionic acid and dimethylolbutanoic acid, and dimethylolbutanoic acid is particularly preferable.

  When the polyisocyanate compound (D), polyol (E), and carboxyl group-containing alcohol (F) are reacted under heating, a chain extender such as a polyhydric alcohol or a polyamine may be used. As the polyhydric alcohol, trimethylolpropane and the like can be used in addition to glycols such as ethylene glycol, butylene glycol and neopentyl glycol. Examples of the polyvalent amine include ethylene diamine, hexamethylene diamine, and isophorone diamine.

  As the solvent for dissolving the carboxyl group-containing polyurethane resin (A), when the adhesive according to the present invention is used for food packaging materials, alcohol-based solvents such as ethanol, isopropanol, butanol, etc. are preferable, and when used other than food packaging materials Polyol ether solvents such as ethylene glycol dimethyl ether and diethylene glycol dimethyl ether are preferred.

  Examples of the basic compound (B) for neutralizing the carboxyl group-containing polyurethane resin (A) solution dissolved in the solvent include ammonia water, hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide, trimethylamine, triethylamine, and dimethyl. Examples include organic amine compounds such as aminoethanol.

  Examples of the crosslinking agent (C) include epoxy resins and polyisocyanate adducts. Examples of the epoxy resin include an aromatic oxy resin, an alicyclic oxy resin, and an aliphatic oxy resin. Examples of the polyisocyanate adduct include those obtained by reacting a polyisocyanate, preferably a diisocyanate and a trihydric or higher polyhydric alcohol or water. Examples of the trihydric or higher polyhydric alcohol include glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, 1,2,4-butanetriol, sorbitol, pentaerythritol and the like.

  Epoxy resins, polyisocyanate adducts, and the like are desirably those having low solubility in water, and those having solubility in water of 0% by mass or 70% by mass or less, particularly 30% by mass or less are desirable. When the solubility in water exceeds 70% by mass, the epoxy resin or polyisocyanate adduct does not stay in the urethane resin dispersion particles, but dissolves in water, causing cross-linking between particles, generating flaws, Stability may be impaired. For these reasons, an aliphatic epoxy resin is particularly preferable as the epoxy resin, and an adduct of tetramethylxylylene diisocyanate (TMXDI), particularly m-, which has low reactivity with water as the polyisocyanate adduct. A polyhydric alcohol adduct of TMXDI is preferred.

  Next, the present invention will be described more specifically with reference to examples and comparative examples. All percentages and parts in Examples and Comparative Examples are based on mass unless otherwise specified.

(Example 1)
In a 1 l four-necked flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet tube, and a dropping funnel, 77.8 parts of P-2000 (trade name, manufactured by Asahi Denka Kogyo Co., Ltd., polypropylene glycol) and dimethylolbutanoic acid 7 parts was added and heated to 120 ° C. with stirring to obtain a solution. Next, 25 parts of tolylene diisocyanate (TDI) was put into a dropping funnel, and 15 parts of the part was added dropwise at a time with stirring. Thereafter, the remaining TDI was dropped little by little while gradually raising the temperature. When the temperature reached 170 ° C., TDI was dropped little by little until a predetermined molecular weight was reached. Obtained. The number average molecular weight of the polyether urethane resin was 10,000, and the acid value was 53 mgKOH / g.
The polyether urethane resin was dissolved in 50 parts of isopropyl alcohol at 80 ° C., and 0.7 part of 5.6% ammonia water was gradually added dropwise with stirring to carry out a neutralization reaction. Next, 2 parts of Denacol EX-211 (trade name, manufactured by Nagase Kasei Co., Ltd., epoxy resin composed of neopentyl glycol diglycidyl ether, solubility in water 26%) is added, and after mixing well, water is gradually added dropwise. Then, an aqueous dispersion of the carboxyl group-containing polyurethane resin (A) was obtained. Further, the solvent isopropyl alcohol was removed while increasing the temperature until the solid content became 40%, and a carboxyl group-containing polyurethane resin (A) dispersion having an average particle size of 300 nm and a viscosity of 300 MPa · s was prepared.

(Example 2)
Example 1 except that Denacol EX-611 (trade name, manufactured by Nagase Chemicals, epoxy resin composed of neopentylglycol diglycidyl ether, solubility in water 50%) was used instead of Denacol EX-211 Thus, a carboxyl group-containing polyurethane resin (A) dispersion having an average particle size of 300 nm and a viscosity of 300 MPa · s was prepared.

(Comparative Example 1)
In the same manner as in Example 1, a carboxyl group-containing polyether urethane resin was obtained. The polyether urethane resin was dissolved in 50 parts of isopropyl alcohol at 80 ° C., and 0.7 part of 5.6% ammonia water was gradually added dropwise with stirring to carry out a neutralization reaction. Subsequently, water was gradually added dropwise to obtain an aqueous dispersion of the polyether urethane resin. Further, after removing isopropyl alcohol as a solvent until the solid content becomes 40% while raising the temperature, Denacol EX-614B (trade name, manufactured by Nagase Kasei Co., Ltd., epoxy resin composed of neopentyl glycol diglycidyl ether, water 2 parts) was added and reacted at 80 ° C. for 3 hours to prepare a carboxyl group-containing polyurethane resin dispersion having an average particle size of 400 nm and a viscosity of 400 MPa · s.

(Comparative Example 2)
A carboxyl group-containing polyurethane resin dispersion having an average particle size of 390 nm and a viscosity of 400 MPa · s was prepared in the same manner as in Comparative Example 1 except that Denacol EX-211 was used instead of Denacol EX-614B.

(Comparative Example 3)
A carboxyl group-containing polyurethane resin dispersion having an average particle size of 330 nm and a viscosity of 500 MPa · s was prepared in the same manner as in Comparative Example 1 except that Denacol EX-614B was not added.

Using the carboxyl group-containing polyurethane resin dispersions obtained in the above Examples and Comparative Examples as an adhesive, a polyethylene terephthalate (PET) film (thickness 12 μm) and an aluminum-deposited CPP film (thickness 25 μm) are bonded together (adhesive) Application amount: 2 g / m ² ), hot tack property was tested. In addition, the occurrence state and stability over time of the above-mentioned carboxyl group-containing polyurethane resin dispersion were examined. The evaluation method is as follows. The results are shown in Table 1.

When a bonded product of a hot tack PET film and an aluminum vapor-deposited CPP film is heat-sealed at 140 ° C. and peeled off immediately after that, the CPP film is cohesive fractured, and the peeling on the adhesive surface is 10 % Is less than%, △ is also less than 10-50%, and x is more than 50%.
Generation status of lint 100 g of the above dispersion is filtered through a 225 mesh filter cloth, and the amount of clogging of the filter cloth is checked. A sample with a clogging amount of 0 is marked with ◎, a sample with less than 10 mg is marked with ◯, a sample with less than 10 to 100 mg is marked with Δ, and a sample with more than 100 mg is marked with ×.
Stability over time The dispersion is placed in a 225 ml mayonnaise bottle, and the appearance after 4 weeks at 40 ° C. is observed. ◎ indicates no precipitation, and Δ indicates that the precipitation is on the entire bottom of the mayonnaise bin.

  From Table 1, it can be seen that the aqueous one-component urethane resin adhesive obtained by the method of the present invention is excellent in hot tack property and stability over time, and the dispersion is free of solids and has a uniform shape. .

Claims (7)

  Water is dispersed in the polyurethane resin (A) solution by dissolving the carboxyl group-containing polyurethane resin (A) in a solvent, neutralizing with the basic compound (B), and immediately before adding water or by adding water. In such a state, 0.3 to 10 parts by mass of the crosslinking agent (C) per 100 parts by mass of the polyurethane resin (A) was added and mixed, and then water was added to the polyurethane resin (A). A process for producing an aqueous one-component urethane resin adhesive, characterized in that mixing is continued at room temperature to 100 ° C. in a state in which is dispersed.   The carboxyl group-containing polyurethane resin (A) is obtained by reacting a polyisocyanate compound (D), a polyol (E) and a carboxyl group-containing alcohol (F) with heating in the absence of a solvent. The method for producing an aqueous one-component urethane resin adhesive according to claim 1.   The method for producing an aqueous one-component urethane resin adhesive according to claim 1 or 2, wherein the crosslinking agent (C) is an aliphatic epoxy resin (G).   The method for producing an aqueous one-component urethane resin adhesive according to claim 1 or 2, wherein the cross-linking agent (C) is a polyisocyanate adduct (H).   The polyisocyanate compound (D) is tolylene diisocyanate or 4,4'-diphenylmethane diisocyanate, the polyol (E) is a polyether polyol, and the carboxyl group-containing alcohol (F) is dimethylolbutanoic acid. The method for producing an aqueous one-component urethane resin adhesive according to claim 2.   The method for producing an aqueous one-component urethane resin adhesive according to claim 3, wherein the aliphatic epoxy resin (G) has a solubility in water of 0% by mass or 70% by mass or less.   The method for producing an aqueous one-component urethane resin adhesive according to claim 4, wherein the polyisocyanate adduct (H) is an adduct of tetramethylxylylene diisocyanate.