JPH07228651A - Production of polyurethane emulsion - Google Patents

Abstract

PURPOSE:To obtain the subject emulsion, excellent in film-forming properties and thermal yellowing, water and solvent resistances and balance between hardness and elasticity and useful for coatings, adhesives, etc., by mixing a specific urethane prepolymer with a polyisocyanate compound and then reacting the resultant mixture with a hydrazine derivative. CONSTITUTION:This method for producing an emulsion is to mix (A) 100 pts.wt. urethane prepolymer, containing a diisocyanate compound such as 2,4-tolylene diisocyanate and polyols having 400-8000 molecular weight such as a polycarbonate polyol, derived from a compound having active hydrogen such as alpha,alpha'- dimethylolpropionic acid and having NCO groups with (B) 0.5-500 pts.wt. polyisocyanate compound such as 1,8-diisocyanato-4-isocyanatomethyloctane and then reacting the resultant mixture with (C) a hydrazine derivative such as oxalic acid hydrazide or trimellitic acid trihydrazide in the presence of water.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a polyurethane emulsion. Furthermore, the present invention relates to a method for producing a polyurethane emulsion excellent in heat yellowing resistance, solvent resistance and the like, and the obtained polyurethane emulsion is
It is useful as a coating agent or adhesive for a base material such as metal, plastic, paper, wood, cement, leather, and a fiber treatment agent.

[0002]

2. Description of the Related Art Polyurethane emulsions are excellent in film-forming properties and give coating films having abrasion resistance, adhesiveness, rubber elasticity, etc., and are therefore widely used in paints, adhesives, fiber treatment agents, coating agents, etc. It is used. However, in addition to not showing sufficient physical properties in terms of heat yellowing, solvent resistance, etc. required in the fields of paints, fiber treatment agents, etc., further improvement is desired in terms of balance of hardness and elasticity. .

To address these problems, a polyurethane emulsion having improved heat-resistant yellowing property, for example, by using carbodihydrazide as a chain extender, is disclosed in JP-A-5-8615.
No. 9 publication. However, although a film using the polyurethane emulsion obtained by this method can improve heat-resistant yellowing, it does not have sufficient water resistance, solvent resistance, balance between hardness and elasticity, and the like.

[0004]

SUMMARY OF THE INVENTION The present invention provides a method for producing a polyurethane emulsion capable of obtaining a film having improved heat yellowing resistance, water resistance, solvent resistance, and improved balance between hardness and elasticity.

[0005]

The present invention comprises a diisocyanate compound (a) and at least a number average molecular weight of 400-8.
Polyisocyanate compound (c) in 100 parts by weight of urethane prepolymer having NCO groups derived from compound (b) having active hydrogen containing 000 polyols.
A method for producing a polyurethane emulsion, which comprises mixing 0.5 to 500 parts by weight and then reacting with a hydrazine derivative in the presence of water.

The present invention will be described in detail below. In the present invention, examples of the diisocyanate compound (a) used for synthesizing the urethane prepolymer having an NCO group include 4,4′-methylenebiscyclohexyl diisocyanate (hydrogenated MDI), isophorone diisocyanate (IPDI), dimethylcyclohexane. Alicyclic diisocyanates such as diisocyanate (hydrogenated XDI), aliphatic diisocyanates such as hexamethylene diisocyanate (HDI), and further 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate and mixtures thereof (TDI), diphenylmethane -4,4'-diisocyanate (MDI), naphthalene-1,5-diisocyanate (NDI), 3,3-dimethyl-4,4-biphenylene diisocyanate (TODI), crude TD
I, polymethylene polyphenyl diisocyanate, aromatic diisocyanate such as crude MDI, xylylene diisocyanate (XDI), aromatic alicyclic diisocyanate such as phenylene diisocyanate, and the like, and combinations thereof.

Among these diisocyanate compounds,
Aliphatic and / or alicyclic diisocyanate compounds are preferred in terms of heat yellowing. In the present invention,
As the compound (b) having active hydrogen containing at least a number average molecular weight of 400 to 8000 polyols used for synthesizing a urethane prepolymer having an NCO group,
In addition to the number average molecular weight of 400 to 8000 polyols, polyhydric alcohols and / or polyvalent amines having a molecular weight of 400 or less, and nonionic and / or ionic hydrophilic groups (or can be subsequently converted into hydrophilic groups) A compound having an active hydrogen compound having a group) as an optional component is selected.

The number average molecular weight of the polyols is 400 to
It is 8,000, preferably 500 to 4000.
As the polyols, polycarbonate polyol,
Polyether polyols, polyester polyols, polybutadiene glycols, etc., which are used alone or
It can be used in combination of one or more kinds. Of these, polycarbonate polyols are preferable from the viewpoints of heat yellowing resistance, water resistance, solvent resistance, weather resistance and the like.

Polycarbonate polyols include products obtained by reacting dihydric alcohols with a carbonate agent selected from phosgene, dialkyl carbonates, diallyl carbonates and alkylene carbonates in the presence or absence of a catalyst. Can be mentioned. Examples of the dihydric alcohols include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,
4-butanediol, neopentyl glycol, 1,5
-Pentanediol, 1,3-pentanediol, 1,
6-hexanediol and the like, or a combination of two or more of these may be used. The obtained polycarbonate polyol can be used alone or in combination of two or more kinds. Among these polycarbonate polyols, JP-A-2-289616 and JP-A-4-25264 are preferred from the viewpoint of flexibility and the like.
Amorphous polycarbonate polyols listed in, for example, are preferable, and polytetramethylene carbonate diol produced in the presence of an acidic substance in view of solvent resistance, hardness, etc. (described in Japanese Patent Application No. 4-258748). Method)
Is preferred.

Specific examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyoxyethylene-oxypropylene (random and / or block) glycol, polyoxyethylene-oxytetramethylene (random and / or (Block) glycol, polyoxypropylene-oxytetramethylene (random and / or block) glycol, polyhexamethylene glycol, and the like, and a combination of two or more thereof.

Specific examples of the polyester polyol include polyethylene adipate, polybutylene adipate, polyethylene butylene adipate, polybutylene hexamethylene adipate, polydiethylene adipate,
Examples thereof include poly (polytetramethylene ether) adipate, polyethylene azelate, polyethylene sebacate, polybutylene azelate, polybutylene sebacate, and polycaprolactone diol, and combinations of two or more thereof.

The polybutadiene glycols include polybutadiene homopolymer type having hydroxyl groups at both ends, polybutadiene copolymer type (styrene butadiene copolymer, acrylonitrile butadiene copolymer, etc.), and hydrogenation of some or all of these unsaturated double bonds. And the like, and combinations of two or more of these.

Further, in order to further improve the properties such as heat softening temperature, flexibility and hardness of the obtained polyurethane, it is necessary for a part of the compound (b) having active hydrogen to have a low molecular weight of 400 or less. A molecular active hydrogen compound can be used in combination. Specific examples thereof include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,3-pentane. Diols, 1,6-hexanediol, hydrogenated bisphenol A, dihydric alcohols such as cyclohexanedimethanol, trihydric or higher alcohols such as glycerin, trimethylolpropane and pentaerythritol, amino alcohols such as monoethanolamine and diethanolamine. , Aliphatic amines such as ethylenediamine, hexamethylenediamine, diethylenetriamine, alicyclic amines such as isophoronediamine, 4,4-methylenebis (cyclohexylamine), and the like, and two or more of these. I like the combination of.

If necessary, an active hydrogen compound having a nonionic and / or ionic hydrophilic group (or a group which can be subsequently converted into a hydrophilic group) is used in combination with a part of the compound (b) having active hydrogen. By doing so, the obtained polyurethane can be made into a self-emulsifying type. The self-emulsifying type is preferable because it improves the dispersion stability of the polyurethane emulsion and the water resistance of the film obtained therefrom.

Examples of the ionic hydrophilic group include anionic groups such as tertiary amine salts of carboxylic acids and cationic groups such as quaternary ammonium salts. Examples of the active hydrogen compound having an anion group (or a group which can be converted into an anion group later) include, for example, α, α′-dimethylolpropionic acid,
α, α'-dimethylolacetic acid, α, α'-dimethylolbutyric acid, α, α'-dimethylolvaleric acid and other α, α'-dimethylolalkanoic acids, taurine and other aminosulfonic acids, and combinations thereof To be Of these, α, α'-dimethylolpropionic acid is preferred. The acid group of these active hydrogen compounds can be converted into an anionic group by neutralizing with a base during synthesis of the urethane prepolymer or during emulsification. Examples of the base used for neutralization include amine compounds such as triethylamine, ammonia, diethanolamine, dimethylaminoethanol, methyldiethanolamine and dibutylamine; KOH, Na
Examples thereof include hydroxides of alkali metals such as OH and LiOH, and combinations thereof.

Examples of the active hydrogen compound having a cation group (or a group which can be converted into a cation group later) include N-alkyldialkanolamines such as N-methyldiethanolamine and N-butyldiethanolamine, triethanolamine and tripropanol. Trialkanolamines such as amines, N, N- such as N, N-dimethylethanolamine and N, N-diethylethanolamine
Examples thereof include dialkyl monoalkanolamines and the like, alkylene oxide (ethylene oxide, propylene oxide, etc.) adducts thereof having 2 to 4 carbon atoms, and a combination thereof. The tertiary amino group of these active hydrogen compounds can be converted into a cationic group by neutralizing with an acid or quaternizing with an alkylating agent during synthesis of a urethane prepolymer or during emulsification. Examples of the acid used for neutralization include acetic acid, lactic acid, hydrochloric acid, phosphoric acid, sulfuric acid and the like, and combinations thereof. Examples of the alkylating agent include dimethyl sulfate, diethyl sulfate, methyl chloride, methyl iodide, benzyl chloride and the like.

Examples of the nonionic hydrophilic group include a suspended polyoxyalkylene group, particularly a polyoxyethylene group. Examples of the active hydrogen compound having these groups include diols having a suspended polyoxyethylene chain as described in US Pat. No. 3,905,929. The urethane prepolymer of the present invention is obtained by subjecting (a) and (b) to a urethanization reaction at a temperature of about 30 ° C to about 130 ° C under substantially anhydrous conditions. The equivalent ratio of the NCO group of the diisocyanate compound (a) used in the production of the urethane prepolymer and the NCO group in the compound (b) having active hydrogen to the active hydrogen is 1.1 to 5.0: 1.0, Preferably 1.1-
It is 2.0: 1.0.

In producing the urethane prepolymer, a catalyst can be used if necessary. Specific examples of the catalyst include salts of metals such as dibutyltin dilaurate, stannous octoate, lead octylate, and organic and inorganic acids, and organic metal derivatives; organic tertiary amines such as triethylamine and triethylenediamine, diaza Examples thereof include bicycloundecene catalyst.

The urethane prepolymer can be produced without a solvent or in a solvent. As this solvent, one that is inactive to the NCO group or less active than the reaction components can be used. Specifically, acetone, methyl ethyl ketone, methyl isobutyl ketone cyclohexanone and other ketone solvents, dioxane, tetrahydrofuran, diethylene glycol dimethyl ether and other ether solvents, dimethylformamide, dimethylacetamide and other amide solvents, N-methyl-2-pyrrolidone, etc. Lactam solvent, sulfoxide solvent such as dimethyl sulfoxide; ester solvent such as ethyl acetate and cellosolve acetate; alcohols such as t-butanol and diacetone alcohol; aromatic hydrocarbon solvent such as toluene xylene; n-hexane And the like, and combinations thereof. Among these, acetone, methyl ethyl ketone, N-methyl-2, etc., from the viewpoint of emulsifying dispersibility in water and the like.
-Pyrrolidone is particularly preferred. The solvent may remain in the polyurethane emulsion, but it can also be distilled off by heating under normal pressure or reduced pressure after forming the emulsion.

In the present invention, N obtained by the above-mentioned method
After mixing the polyisocyanate compound with the urethane prepolymer having a CO group, it is important to use it for the next reaction. That is, this can increase the degree of internal cross-linking into the polyurethane emulsion, and thus can improve the solvent resistance of the formed film and the balance between hardness and elasticity. Further, it is not appropriate to mix the polyisocyanate compound during the synthesis of the urethane prepolymer. This is because when the effect of the polyisocyanate compound is to be fully exerted, the method of mixing during the urethane prepolymer synthesis causes a marked increase in the viscosity of the urethane prepolymer that is formed or gelation, so that the next reaction It is impossible to offer. (However, it is possible to synthesize a urethane prepolymer by using a small amount of a polyisocyanate compound that does not cause a remarkable increase in viscosity or gelation together with (a), and then mix a new polyisocyanate compound for use in the next reaction. As the polyisocyanate compound, 1,8-diisocyanato-4-isocyanatomethyloctane, and further, an NCO obtained by oligomerizing a diisocyanate compound by a buret bond, a urea bond, an isocyanurate bond, a urethane bond, an allophanate bond, a uretdione bond, or the like.
A group having 1 to 50% by weight, preferably 5 to 30% by weight is mentioned. Examples of the diisocyanate compound also include those exemplified as the raw material (a) of the urethane prepolymer.

The polyisocyanate compound is mixed in an amount of 0.5 to 500 parts by weight, preferably 5 to 100 parts by weight, based on 100 parts by weight of the urethane prepolymer. If the polyisocyanate compound is less than 0.5 parts by weight, the effect of the polyisocyanate compound will not be sufficiently exhibited, and if it is more than 500 parts by weight, the flexibility of the polyurethane will be impaired.

The polyurethane emulsion (A) in the present invention is obtained by reacting the mixture of the urethane prepolymer having an NCO group obtained by the above-mentioned method and the polyisocyanate compound with a hydrazine derivative in the presence of water. At this time, the equivalent ratio of the total NCO groups of the mixture of the urethane prepolymer and the polyisocyanate compound to the active hydrogen of the hydrazine derivative is usually 1.0: 0.1.
2.0, preferably 1.0: 0.5 to 1.5.

Examples of the hydrazine derivative include, in addition to hydrazine, water-soluble dihydrazines such as ethylene-1,2-dihydrazine, propylene-1,3-dihydrazine, butylene-1,4-dihydrazine, and hydrazide groups. Examples thereof include polyhydrazide compounds having at least two in one molecule. Among these, polyhydrazide compounds are preferable from the viewpoint of easy control of reactivity with NCO group and toxicity.

Examples of the polyhydrazide compound include oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, itaconic acid dihydrazide,
Dicarboxylic acid dihydrazides such as isophthalic acid dihydrazide and phthalic acid dihydrazide, tricarboxylic acid trihydrazides such as trimellitic acid trihydrazide, carbonic acid dihydrazides represented by the general formula (1), and bissemicarbazide represented by the general formula (2). And the like, and combinations thereof.

[0025]

[Chemical 1]

[0026]

[Chemical 2]

When the polyhydrazide compound is too hydrophobic, it does not disperse in water and it becomes difficult to react the mixture of the urethane prepolymer and the polyisocyanate compound in the presence of water. Preference is given to using the compounds having. Suitable representative examples include, for example, adipic acid dihydrazide, succinic acid dihydrazide, sebacic acid dihydrazide, carbodihydrazide and the like.

In the present invention, a method of reacting a mixture of a urethane prepolymer and a polyisocyanate compound with a hydrazine derivative in the presence of water is as follows:
A method of reacting by adding an aqueous solution of a hydrazine derivative to a mixture of a urethane prepolymer and a polyisocyanate compound. A method in which water is added to a mixture of a urethane prepolymer and a polyisocyanate compound with appropriate stirring to form a dispersion, and then an aqueous solution of a hydrazine derivative is added to react.
Examples include a method in which a mixture of a urethane prepolymer and a polyisocyanate compound is added to an aqueous solution of a hydrazine derivative under appropriate stirring and the mixture is reacted. In any of the above-mentioned methods, a surfactant may be added at any stage for the purpose of assisting or adding the dispersibility or dispersion stability of the mixture of the urethane prepolymer and the polyisocyanate compound, if necessary. When a cationic or anionic hydrophilic group is introduced into the urethane prepolymer, this surfactant may be the same ionic group or nonionic.

When the hydrazine derivative is reacted with the mixture of the urethane prepolymer and the polyisocyanate compound in the presence of water, a chain extender may be used together with the hydrazine derivative if necessary. As the chain extender, ethylenediamine, propylenediamine, hexamethylenediamine, tolylenediamine, xylylenediamine, diphenyldiamine, diaminodiphenylmethane, diaminocyclohexylmethane, piperazine, 2-methylpiperazine, isophoronediamine, and various other diamines, diethylenetriamine And the like, and combinations thereof.

The concentration of the resin component of the polyurethane emulsion according to the method of the present invention can be 0.1 to 95 wt%, but is preferably 10 to 50 wt% in terms of production. In addition, various additives may be contained, if necessary, for the purpose of improving weather resistance and the like in the production of the polyurethane emulsion. When an additive is used, it is usually added at the time of synthesizing the urethane prepolymer, but when the additive is water-soluble or reacts with a reaction component such as an isocyanate component, it is preferably added as a dispersion. As additives, hindered phenol-based, phosphite-based, thioether-based antioxidants, benzophenone-based, benzotriazole-based,
Examples thereof include a salicylate-based ultraviolet absorber, a hindered amine-based light stabilizer, an organic halogen-based flame retardant, an antistatic agent, a water repellent, and the like.

The polyurethane emulsion obtained by the present invention contains, if necessary, a crosslinking agent, a pigment, a filler, a dispersant, a wetting agent, a thickener, a rheology control agent, an antifoaming agent, a plasticizer, a film-forming aid and an anticorrosive agent. Agents, etc. are selected and combined according to their respective purposes, and are used in various applications such as clear coat agents, top coat agents, paints, undercoat agents, cloth and paper impregnants, fiber treatment agents, and various adhesives. Can be used.

[0032]

EXAMPLES Parts in the examples mean parts by weight. The measuring method of each measured value used in the examples is as follows. Sample film used to measure physical properties (thickness is about 100μ
m, width 10 mm, length 60 mm), after forming a polyurethane emulsion on a glass plate at room temperature for 24 hours,
It was prepared by heat treatment at 120 ° C. for 30 minutes.

Tensile strength is measured by Tensilon tensile tester (Orientec RTA-100 Co., Ltd.), atmosphere 25
℃ × 65% RH, measuring length 30 mm, pulling speed 300 mm
It was measured in minutes. The water resistance was evaluated by the presence or absence of whitening in the film state after the sample film was immersed in ion-exchanged water at room temperature for 1 week. The solvent resistance was evaluated in the film state after the sample film was immersed in acetone at room temperature for 24 hours.
For the heat-resistant yellowing, the yellowing degree of the film was visually evaluated after the sample was heat-treated at 160 ° C. for 30 minutes.

[0034]

Example 1 1116 parts of polytetramethylene carbonate diol (C4PCDL) having a hydroxyl value of 54.6, 363 parts of isophorone diisocyanate (IPDI), 55 parts of triethylamine (TEA), 73 parts of dimethylolpropionic acid (DMPA), methylethylketone ( ME
K) 1607 parts, dibutyltin dilaurate (BTL)
0.04 parts was put into a reactor equipped with a reflux condenser, a thermometer and a stirrer, and a urethanization reaction was carried out at 80 ° C. for 6 hours to obtain an NCO-terminated prepolymer solution. “Duranate TPA” as a polyisocyanate compound was added to the prepolymer solution adjusted to 30 ° C. (Asahi Kasei Co., Ltd.).
Manufactured by Isocyanurate type oligomer of hexamethylene diisocyanate (NCO group content 23.1 wt%) 3
21 parts mixed, 6% adipic acid dihydrazide aqueous solution 45
13 parts, followed by 617 parts of ion-exchanged water, were added with stirring over about 30 minutes. Then, this was heated under reduced pressure to 80 ° C. over 3 hours and kept for 2 hours to remove MEK, and ion-exchanged water was added to adjust the concentration, and the solid content was 30% and the viscosity (B Type viscometer, No1,
60 rpm, 20 ° C.) 36 cps, particle size 1440, p
A polyurethane emulsion of H7.8 was obtained. The results of the physical property test of the film are shown in Table 1.

[0035]

Example 2, Comparative Examples 1-2 In the same manner as in Example 1,
Using the raw materials shown in Table 1, polyurethane emulsions having the properties shown in Table 1 were prepared. The results of the physical property test of the film are shown in Table 1.

[0036]

[Table 1]

[0037]

The polyurethane emulsion produced by the present invention not only excels in heat yellowing, but also
It is possible to obtain a film that exhibits sufficient physical properties in terms of water resistance, solvent resistance and the like, and that has a well-balanced hardness and elasticity. Therefore, according to the present invention, a clear coat agent, a top coat agent, a paint, an undercoat agent, an impregnating agent for cloth or paper,
It is possible to provide an excellent polyurethane emulsion that can be used for various purposes as a fiber treatment agent, various adhesives, and the like.

Claims (2)

[Claims] 1. An NCO derived from a diisocyanate compound (a) and a compound (b) having active hydrogen containing at least a polyol having a number average molecular weight of 400 to 8000.
A method for producing a polyurethane emulsion, which comprises mixing 0.5 to 500 parts by weight of a polyisocyanate compound (c) with 100 parts by weight of a urethane prepolymer having a group and then reacting the mixture with a hydrazine derivative in the presence of water. 2. The method for producing a polyurethane emulsion according to claim 1, wherein the hydrazine derivative is a hydrazide group-containing compound.