JP3470347B2 - Aqueous resin composition for coating with good storage stability - Google Patents

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention has excellent storage stability when used as a coating for substrates such as plastic film, metal, paper, glass, that is, as a printing ink, paint, sealant, adhesive, surface treatment agent and the like. The present invention relates to an aqueous resin composition for coating.

[0002]

2. Description of the Related Art Conventionally, as an aqueous resin composition having a curability, a water-soluble resin obtained by neutralizing a resin having a carboxyl group, for example, an acrylic resin, a polyester resin, an alkyd resin with an organic amine or ammonia. A composition comprising a polymerizable resin and a compound having at least two or more aziridinyl groups in the molecule is known (Japanese Patent Laid-Open No. S60-18753).
48-94734 and JP-A-54-159447). In such a composition, the organic amine or ammonia forms a salt with the resin to make the resin water-soluble, and at the same time, acts as a block agent to enhance stability, but dissociation of the salt is inevitable, and therefore the reaction does not occur. A highly reactive carboxyl group exists and causes a reaction with aziridine. In other words, the organic amine and ammonia only play a life-prolonging effect of preventing a significant increase in viscosity of the coating composition in the reaction with aziridine, and these increase in viscosity over time and thus the coating suitability,
It causes problems in printability. Further, since the coating liquid having an increased viscosity cannot be reused, there is a cost problem.

On the other hand, the present inventors have found that an aprotic polar solvent has a reaction accelerating effect in the curability of an acrylic resin and an aziridine compound.
Japanese Patent Publication No. 3276 discloses an aqueous resin composition having excellent storage stability. However, this composition has a problem that the aprotic polar solvent causes a decrease in the drying property and odor of the coating liquid. Also, a composition of an aziridine compound and an aqueous resin dispersion having a carboxyl group is disclosed in JP-A-57-44692.
It is disclosed in the publication. In this composition, since the aqueous resin dispersion uses an ordinary surfactant, the coating suitability and printability are insufficient, and the stability of the aqueous resin dispersion is poor, and it is difficult to react with aziridine. There was a problem in storage stability due to aggregation and thickening of the aqueous resin dispersion.

[0004]

DISCLOSURE OF THE INVENTION As a result of investigations by the present inventors, in order to enhance the storage stability after compounding an aziridine compound, the carboxyl group-containing resin of the coating composition is neutralized with an organic amine or ammonia. While the water-soluble resin is not sufficient, the carboxyl group-containing resin emulsion obtained by emulsion polymerization of ethylenically unsaturated monomer in the presence of a specific water-soluble resin is stored after blending the aziridine compound. The inventors have found that they have excellent performances in stability, coatability, and coating properties after drying, and have completed the present invention.

[0005]

That is, the present invention provides an acid value
Water-soluble resin obtained by neutralizing 70 to 350 resins with ammonia or organic amines. Carboxyl group-containing obtained by emulsion polymerization of 20 to 1000 parts by weight of ethylenically unsaturated monomer in the presence of 100 parts by weight. Provided is a coating aqueous resin composition comprising a resin emulsion (A) and a compound (B) having two or more aziridinyl groups. In the present invention, a water-soluble resin obtained by neutralizing a resin having a specific acid value with ammonia or an organic amine is used as a protective colloid,
Moreover, the amount of the ethylenically unsaturated monomer at the emulsion polymerization with respect to the protective colloid is important.

Resins having an acid value of 70 to 350 include styrenes such as styrene and methylstyrene, methyl (meth) acrylate,
Ethyl (meth) acrylate Butyl (meth) acrylate,
Propyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, stearyl (meth) acrylate, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, propoxyethyl (meth) acrylate,
Methoxyethoxyethyl (meth) acrylate, (meth)
Aliphatic 1 to 18 carbon atoms such as ethoxyethoxyethyl acrylate and butoxyethoxyethyl (meth) acrylate
1 of monohydric alcohol, ester of (meth) acrylic acid with ethylene glycol monoalkyl ether having 3 to 30 carbon atoms or diethylene glycol monoalkyl ether having 3 to 30 carbon atoms, vinyl acetate, maleic acid ester, acrylonitrile, etc. It is obtained by polymerizing two or more species.

The composition of the monomers is such that the acid value of the resin obtained is 70
It is appropriately selected to be in the range of to 350. If the acid value is less than 70, the resin obtained by the neutralization procedure described below has poor water solubility and is not suitable as a protective colloid. Also,
When the acid value exceeds 350, the water-soluble resin obtained by neutralizing the resin has good performance as a protective colloid, but the resin emulsion obtained by emulsion polymerization of ethylenically unsaturated monomers in the presence of , When the aziridine compound was added, the viscosity increased greatly and the storage stability was poor. In addition, the water resistance of the coating material is poor, which is not preferable. The molecular weight of the water-soluble resin is preferably 3000 to 60,000.

The resin having an acid value of 70 to 350 can be produced by a well-known polymerization method such as bulk polymerization, solution polymerization, emulsion polymerization and suspension polymerization. For example, in the case of solution polymerization method,
It can be easily produced by polymerizing a predetermined amount of the constituent monomers in the presence of an appropriate organic solvent. As the polymerization initiator, a catalyst such as benzoyl peroxide or azobisisobutyronitrile can be used. If necessary, mercaptans and the like can be added to the reaction system, and the degree of polymerization can be adjusted accordingly.

The resin having an acid value of 70 to 350 obtained as described above is added with ammonia or an organic amine such as triethylamine, trimethylamine, dimethylaminoethanol, monoethanolamine or the like into the reaction system after completion of the polymerization reaction. A desired water-soluble resin can be obtained by neutralizing. The addition amount of ammonia or the like is preferably in the range in which the neutralization ratio of the carboxyl groups in the resin is about 70 to 120%. If the neutralization rate is too low, the ability of the resulting water-soluble resin as a protective colloid is reduced, which is not preferable.

The carboxyl group-containing resin emulsion (A) is used in the presence of 100 parts by weight of the water-soluble resin obtained as described above, 20 to 1000 parts by weight of ethylenically unsaturated monomer, preferably 50 to 600 parts by weight. Is obtained by emulsion polymerization. The ethylenically unsaturated monomer is selected in consideration of hardness, heat resistance, adhesiveness, film-forming property and the like of the resulting coating aqueous composition. Specific examples thereof include a (meth) acrylic acid ester having 1 to 22 carbon atoms of an alkyl group, a hydroxyl group,
Examples thereof include amino group-containing (meth) acrylic acid ester, (meth) acrylic acid amide, (meth) acrylonitrile, styrene, (meth) acrylic acid, and maleated monoester. The above monomers may be used alone or in combination of two or more.

It is important to use a specific amount of the ethylenically unsaturated monomer with respect to the water-soluble resin. If it is used in an amount less than 20 parts by weight, the content of the water-soluble resin component will be large, and the viscosity increase when the aziridine compound is added will be large, resulting in poor storage stability. On the other hand, 1000
When it is used in an amount exceeding the parts by weight, the obtained resin emulsion causes aggregation and thickening, resulting in poor storage stability. In addition, thixotropy becomes large, and the smoothness of the coating is poor. As the initiator for emulsion-polymerizing the ethylenically unsaturated monomer, specifically, ammonium persulfate is used. Examples thereof include persulfate catalysts such as potassium persulfate and redox catalysts obtained by combining these with acidic sulfites. Further, a molecular weight modifier or a surfactant may be added to the emulsion polymerization reaction system of the present invention, if necessary.

The compound (B) having two or more aziridinyl groups is a compound having two or more groups represented by the following general formula.

[Chemical 1] [In the formula, R and R'represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and at least one of R and R'is preferably a hydrogen atom. ]

As the compound (B), trimethylolpropane tris (2-aziridinylpropionate) [hereinafter, abbreviated as TPA]. ], 4,4'-Bis (ethyleneiminocarbonylamino) diphenylmethane, 2,4-diethylurea toluidine, (L) -aziridinylpropionic acid-2,2-
Examples thereof include dihydroxymethylbutanol-triester, 1,6-hexamethylenediethyleneurea, 1,3,5-triethylureabenzene and the like. Among them, TPA is preferable because it has both storage stability and curability.

The compound (B) having two or more aziridinyl groups is a carboxyl group-containing resin emulsion (A).
It is usually used in an amount of 0.1 to 50 parts by weight, preferably 3 to 30 parts by weight, per 100 parts by weight of the solid content. If it is less than 0.1 part by weight, the crosslink density of the resulting coating aqueous resin composition tends to be low, and the solvent resistance and water resistance of the coating after drying tend to be slightly inferior, and if it exceeds 50 parts by weight, the coating aqueous resin obtained The storage stability of the composition tends to be slightly lower.

In the case of an aqueous resin composition containing a water-soluble resin and an aziridine compound, since the resin is in a uniformly dissolved state, the reaction in the solution after addition of the aziridine compound occurs uniformly in the dissolution system, and the system is crosslinked by crosslinking. The formation of the entire mesh, which causes a remarkable increase in viscosity. On the other hand, in the case of the aqueous resin composition containing the specific resin emulsion of the present invention and the aziridine compound, the functional groups of the resin involved in the reaction are considered to be in a non-uniform state in the system, and the network formed after the addition of the aziridine compound is considered. It is considered that the formation of the non-uniformity also becomes non-uniform and the increase in viscosity is suppressed.

In addition to the above (A) and (B), the coating aqueous resin composition of the present invention may further contain phthalocyanine blue and phthalocyanine green. Organic or inorganic pigments such as titanium oxide and carbon black, dyes, extenders such as calcium carbonate, precipitated barium sulfate and clay, thixotropic agents such as fine powder silica, colloidal silica, sols such as alumina sol, polyvinylpyrrolidone, polyvinyl Alicol, shellac, water-soluble polyester resin,
Water-soluble or water-dispersible polyurethane resin or polyamide resin, water-soluble or water-dispersible resin, emulsifier, defoaming agent, leveling agent, tackifying resin, water-soluble or hydrophilic solvent such as ethanol or carbitol, antiseptic An agent, a fungicide, etc. are blended and dispersed, mixed or kneaded by a known disperser, mixer, kneader or the like.

The aqueous resin composition for coating of the present invention is a gravure printing machine, a flexographic printing machine, a roll coater, a spray coater, a spin coater, a brush, a roller coater, a roll coater, a reverse coater, a knife coater, depending on the purpose. By means such as plastic, paper, metal,
It is printed or applied as a printing ink, paint, sealant, adhesive, surface treatment agent, etc. on a substrate such as wood, glass, concrete, slate, non-woven fabric, leather, synthetic leather, etc., and is heated or dried at room temperature. To be done.

[0018]

EXAMPLES The present invention will now be described in more detail by way of examples. In the examples, "part" means "part by weight" and "%" means "% by weight". [Production Examples 1 to 4] Isopropyl alcohol 300 in a reaction vessel equipped with a stirrer, a thermometer, a dropping device and a reflux condenser.
Then, 200 parts of the monomer mixture having the composition shown in Table 1 and 6 parts of azobisisobutyronitrile were added dropwise over 2 hours, and the mixture was reacted at 83 ° C. for 4 hours. Next, all the isopropyl alcohol was distilled off under reduced pressure, 600 parts of ammonia water containing an equivalent amount of ammonia to the carboxyl group in the reaction product was added, and the carboxyl group-containing resin aqueous solution (solid content 25%) (a) ~ I got (d). The acid values shown in Table 1 are for each of the carboxyl group-containing resin aqueous solutions.

[0019]

[Table 1]

[Production Example 5] 400 parts of the resin aqueous solution (a) was charged in the same reactor as in Production Examples 1 to 4 and heated to 80 ° C., and 10 parts of methyl methacrylate and 10 parts of ethyl hexyl acrylate were added.
Solution and 0.84 part of ammonium persulfate in 0.76 part of purified water are added dropwise over 30 minutes, then 90 parts of
The mixture was reacted at ℃ for 1 hour, and purified water was added to adjust the solid content to 28%. A carboxyl group-containing resin emulsion (e) having a viscosity of 3000 cps. At 25 ° C was obtained.

[Production Example 6] 400 parts of the resin aqueous solution (c) and 80 parts of purified water were charged in the same reactor as in Production Examples 1 to 4, and
Heated to ℃, 100 parts of methyl methacrylate, methacrylic acid
0.5 part, butyl acrylate 99.5 parts, and ammonium persulfate 1.0 part were dissolved in 9.0 parts of purified water, 10 parts of an aqueous solution was added dropwise over 120 minutes, and then the mixture was reacted at 90 ° C for 1 hour. The minute was adjusted to 42%. Resin emulsion containing carboxyl groups with a viscosity of 1200 cps. At 25 ℃ (f)
Got

[Production Example 7] 400 parts of the resin aqueous solution (b) and 400 parts of purified water were charged in the same reactor as in Production Examples 1 to 4.
An aqueous solution obtained by heating to 80 ° C and dissolving 400 parts of n-butyl methacrylate, 200 parts of 2-ethylhexyl acrylate, 3 parts of 2-ethylhexyl thioglycolate as a molecular weight modifier and 1.0 part of ammonium persulfate in 9.0 parts of purified water. The mixture was added dropwise over 150 minutes and then reacted at 90 ° C for 1 hour, and purified water was added to adjust the solid content to 46%. Resin emulsion containing carboxyl group with viscosity of 230 cps. At 25 ℃ (g)
Got

Production Example 8 A reactor similar to Production Examples 1 to 4 was charged with 400 parts of the resin aqueous solution (d) and 600 parts of purified water,
Heat to 80 ℃, 200 parts of ethyl methacrylate, acrylic acid
20 parts of an aqueous solution prepared by dissolving 400 parts of n-butyl, 200 parts of styrene, 5 parts of 2-ethylhexyl thioglycolate as a molecular weight modifier and 2.0 parts of ammonium persulfate in 18.0 parts of purified water was added dropwise over 150 minutes, and then 90 ° C. The mixture was allowed to react for 1 hour, and purified water was added to adjust the solid content to 47%. A carboxyl group-containing resin emulsion (h) having a viscosity of 860 cps. At 25 ° C was obtained.

[Production Example 9] 24 parts of a nonionic surfactant (“Emulgen 935” manufactured by Kao Atlas Co., Ltd.) was dissolved in 348 parts of purified water and heated to 70 ° C., 200 parts of styrene and 180 parts of ethyl acrylate were added. Part, 20 parts of methacrylic acid and 8 parts of ammonium persulfate dissolved in 40 parts of purified water, 48 parts of an aqueous solution was added dropwise over 3 hours, and then the mixture was reacted at 70 ° C until the solid content became 51%, and pH was adjusted to 7.8 with ammonia. Adjusted to. An acrylic resin emulsion (i) having a viscosity of 210 cps. At 25 ° C was obtained.

[Examples 1 to 4 and Comparative Examples 1 to 4] The compositions shown in Table 2 were mixed to prepare an aqueous resin composition for coating. The resulting coating aqueous resin composition was applied onto a corona discharge treated surface (wetting index 42 dyn / cm) of a corona discharge treated stretched polypropylene film having a thickness of 50 μm by a roll coater so that a dry coating film was 4 μm, and the temperature was 50 ° C. In a hot air oven for 5 minutes. Appearance state of the obtained dry coating film,
Table 2 shows the results of evaluation of solvent resistance, alkali resistance and water resistance. Table 2 shows the results of evaluating the viscosity stability of the coating aqueous resin composition when stored at 40 ° C for 7 days.
The evaluation method and the display of the results are as follows.

Appearance: Visual evaluation. ○: Good, ×;
Bad. Solvent resistance: Rubbing the surface of the coating film with absorbent cotton containing ethyl acetate, the number of reciprocations until the coating film peeled off was evaluated. ○: 100 times or more, △: 100 to 50, ×: 50 times or less. Alkali resistance: After immersing the sample in a 5% sodium hydroxide aqueous solution for 30 minutes, the sample was taken out, rubbed with absorbent cotton, and the surface condition of the coating film was visually evaluated. ◯: No change at all, Δ: There is a slight detachment of the coating film, ×: Slow detachment, XX: The coating film dissolves during immersion.

Water resistance: After immersing in hot water at 40 ° C for 10 hours, take it out and rub it with absorbent cotton in a wet state. Visual evaluation of the surface condition of the coating film. ◯: No change, Δ: Partially small coating film detachment, ×: Desorption is moderate. Storage viscosity stability: ○: viscosity increase of 10% or less, △: viscosity increase of 50% or less, ×: viscosity increase of 100% or less, XX: gelation.

[0028]

[Table 2] In the table, RIONOL BLUE FG-7330 is phthalocyanine blue manufactured by Toyo Ink Mfg. Co., Ltd., and Surfynol PC is an antifoaming agent manufactured by Air Products.

[0029]

EFFECTS OF THE INVENTION According to the present invention, it is possible to obtain an aqueous resin composition for coating which has excellent physical properties of a cured coating and good storage viscosity stability.

Claims (3)

(57) [Claims] 1. Emulsion polymerization of 20 to 1000 parts by weight of an ethylenically unsaturated monomer in the presence of 100 parts by weight of a water-soluble resin obtained by neutralizing a resin having an acid value of 70 to 350 with ammonia or an organic amine. Carboxyl group-containing resin emulsion (A) and compound (B) having two or more aziridinyl groups
An aqueous resin composition for coating containing: 2. An aziridinyl group is added to 100 parts by weight of the solid content of the carboxyl group-containing resin emulsion (A).
The aqueous composition for coating according to claim 1, wherein 0.1 to 50 parts by weight of the compound (B) having one or more compounds is blended. 3. The compound (B) having two or more aziridinyl groups is trimethylolpropane tris (2-aziridinyl propionate).
Alternatively, the coating aqueous composition according to the item 2.