JPH107975A - Water-dispersed coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-dispersed coating compsn. which can form a coating film excellent in the prevention of whitening in hot water immersion or during drying and excellent in adhesive properties, durability, and storage stability. SOLUTION: This compsn. contains dispersed particles of a copolymer with particle sizes of 50-100nm, the copolymer having an average mol.wt. of 200.000-400,000, and is produced by subjecting 0.05-5wt.% (based on the resultant copolymer) emulsifier and a monomer mixture comprising 70-99.9wt.% ethylenically unsatd. monomer, 0.1-20wt.% ethylenically unsatd. monomer having an imidazoline group, and 0-10wt.% monomer copolymerizable with the foregoing monomers to emulsion copolymn. in a water-base medium in the presence of a free-radical polymn. initiator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to adhesiveness, durability,
Form a coating film with excellent heat-resistant water whitening property and storage stability,
The present invention relates to a water-dispersible coating composition useful for use in paints, adhesives, and paper processing agents, particularly for paints.

[0002]

2. Description of the Related Art Conventionally, an aqueous emulsion containing a polymer as a dispersoid has conventionally been used as a dispersant such as an anionic, nonionic, cationic or amphoteric surfactant, or polyvinyl alcohol, cellulose ether, polyvinyl pyrrolidone. It was manufactured by an emulsion polymerization method using a protective colloid such as

[0003] However, coating films obtained by forming these conventional aqueous emulsions have been problematic in their low water resistance and low hot water resistance.

On the other hand, although the coating film obtained by forming a film in a solution system using an organic solvent has good water resistance, the organic solvent has an adverse effect on the environment and living organisms (human body) and a risk of fire. Conversion to an aqueous emulsion has been promoted for reasons such as properties.

However, as described above, it is known that a coating film obtained by forming an aqueous emulsion is inferior in water resistance, particularly hot water resistance, as compared with that of a solution system, and this is improved. As a method, various methods such as a soap-free emulsion polymerization method using no dispersant, an emulsion polymerization method using a reactive emulsifier, and a method of copolymerizing a resin with an organopolysiloxane have been studied.

[0006] "Water resistance" is evaluated under relatively slow conditions such as immersion in warm water of 60 ° C or less for one hour, and whitening of the film under more severe conditions (85 ° C or more). In the research using organic polymers, there was a limit in the improvement of water resistance. Therefore, improvement of water whitening resistance and hot water whitening resistance was evaluated by using an inorganic polymer such as water glass and colloidal silica together with an organic polymer. A great deal of research has also been done.

Actually, a coating film obtained from a blend of colloidal silica and an organic polymer emulsion, or a coating film obtained from a coating mainly composed of an emulsion using colloidal silica at the time of polymerization has a high hardness, In addition, the hot water whitening property is good, but the mutual binding action between the inorganic polymer and the emulsion is weak, and as a result, a problem remains in the long-term durability of the coating film. Therefore, in order to strengthen the bond between the inorganic polymer and the organic polymer emulsion, a method of adding alkoxysilanes to a blend of these polymers and a method of using a polymerizable monomer having an alkoxysilane group have been proposed. ing. However, the water-dispersible coating composition obtained by these methods has poor stability in itself, and therefore has not yet been able to obtain satisfactory properties such as being unable to withstand long-term storage and storage. .

[0008] Further, the thermal resistance whitening property further includes thermal conditions in addition to the evaluation conditions of the "water resistance", so that the Tg value of the resin (glass transition point of the polymer) is also one of the influencing factors.
That is, if the Tg value is low, the whitening phenomenon occurs when immersed in water, and since the resin is soft, the absorbed water evaporates and the whitening phenomenon disappears when dried. On the other hand, when the Tg value is high, the whitening phenomenon is suppressed to some extent when immersed in water, and the whitening phenomenon is hard to disappear because the resin is hard after drying.

In view of the above-mentioned circumstances, the present invention has been made to solve these problems by providing a coating composition which has excellent anti-whitening properties when immersed in hot water or dried and has excellent adhesion, durability and storage stability. It is intended to provide a water-dispersible coating composition that forms a film.

[0010]

Means for Solving the Problems The present inventor has made various efforts without impairing the advantages and features of conventional aqueous emulsions.
As a result of intensive studies on a method for improving the hot water whitening resistance, in addition to excellent whitening prevention properties against hot water, adhesion,
The inventors have found a water-dispersible coating composition that forms a coating film having characteristics such as durability and storage stability, and have completed the present invention.

The gist of the present invention is to obtain 0.05 to 5% by weight of an emulsifier based on the resin by emulsion copolymerization with a monomer mixture in an aqueous medium in the presence of a radical polymerization initiator. Water-dispersible coating composition, wherein said monomer mixture comprises: (a) 70-99.9% by weight of an ethylenically unsaturated monomer; (b) 0.1-20% by weight of an ethylenically unsaturated monomer having imidazoline groups; And the monomers
(c) copolymerizable with (a) and (b), comprising from 0 to 10% by weight of a hydrophilic ethylenically unsaturated monomer, and wherein the water-dispersible coating composition has an average molecular weight of from 200,000 to 400,000, and particles A water-dispersible coating composition comprising dispersion particles having a diameter of 50 to 100 nm.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The water-dispersible coating composition of the present invention uses a dispersion of a polymer-based dispersoid in a dispersion medium containing water as a main component.

The average particle size of the dispersoid is in the range of 50 to 100 nm. This means that, when trying to obtain particles with a particle size of 50 nm or less, they tend to have low solids due to viscosity and other factors, making them impractical as a paint base, and when the particle size is larger than 100 nm. , Due to a decrease in hot water whitening property. The molecular weight of the water-dispersible coating composition having an average molecular weight of 200,000 to 400,000
When the molecular weight is not more than 00,000, reduction in hot water whitening property and weather resistance are recognized, and when the molecular weight is 400,000 or more, adhesion and freeze-thaw adhesion are determined in consideration of reduction.

The emulsion polymerization method is not particularly limited. For example, (a) an ethylenically unsaturated monomer and (b) an imidazoline group capable of undergoing radical polymerization in the presence of water, an emulsifier, and an initiator. A monomer dropping method of dropping a mixture of ethylenically unsaturated monomers having: a mixture of (a) an ethylenically unsaturated monomer and (b) an ethylenically unsaturated monomer having an imidazoline group, which is radically polymerizable, is mixed with water and an emulsifier. A pre-emulsion method in which emulsification is carried out in the presence and polymerization is carried out while dropping the water; or water, an emulsifier, an initiator, (a) an ethylenically unsaturated monomer and (b)
A one-bath polymerization method in which radical polymerization is performed in the presence of a mixture of all ethylenically unsaturated monomers having an imidazoline group can be used in the present invention. In the monomer dropping method and the pre-emulsion method, 1 to 50% by weight, preferably 3 to 30% by weight of the total dropping amount can be added in advance at the start of polymerization. From the viewpoint of safety, the monomer dropping method and the pre-emulsion method are preferable, and the pre-emulsion method is particularly preferable.

The above-mentioned (a) ethylenically unsaturated monomers applicable to the present invention include, for example, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, cyclohexyl acrylate,
2-ethylhexyl acrylate, lauryl acrylate, stearyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, methacrylic acid C1-C24 alkyl or cycloalkyl esters of (meth) acrylic acid such as stearyl; C2-C8 hydroxyalkyl esters of (meth) acrylic acid such as hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate; Aromatic unsaturated monomers such as styrene, vinyltoluene, α-methylstyrene, N-vinylpyrrolidone and vinylpyridine; (Meth) acrylates containing epoxy groups such as acrylate and glycidyl methacrylate; 1-methyl 2-pyrrolidone acrylate, 1-ethyl 2-pyrrolidone acrylate, 1-methyl 2-pyrrolidone methacrylate, 1-ethyl methacrylate 2 -(Meta) such as pyrrolidone
C1-C24 alkyl esters containing a pyrrole ring of acrylic acid; 1-methyl 2-oxazolidone acrylate, 1-ethyl 2-oxazolidone acrylate, 1-methyl methacrylate
Oxazole ring-containing C1 to C24 alkyl esters of (meth) acrylic acid such as 2-oxazolidone and 1-ethyl 2-oxazolidone methacrylate; or a combination of one or more of the aforementioned compounds.

Examples of the ethylenically unsaturated monomer (b) having an imidazoline group applicable to the present invention include 1-methyl 2-imidazolidone acrylate, 1-ethyl 2-imidazolidone acrylate, and methacrylic acid 1 Imidazole ring-containing C1-C24 alkyl esters of (meth) acrylic acid, such as -methyl 2-imidazolidone and 1-ethyl 2-imidazolidone methacrylate; or combinations of one or more of the aforementioned compounds.

Further, as the hydrophilic ethylenically unsaturated monomer (c) applicable to the present invention, for example, acrylic acid, methacrylic acid, maleic acid, crotonic acid, (meth) acrylate having a polyoxyethylene chain; Acrylamide, N-methylolacrylamide, N-butoxymethylacrylamide; or a combination of one or more of the foregoing compounds.

Next, the monomers (a), (b) and (c)
Is used in the following range with respect to the total amount of the resin. (A) ethylenically unsaturated monomer: 70 to 99.9% by weight, preferably 80 to 99% by weight; (b) imidazoline group-containing ethylenically unsaturated monomer: 0.1 to 20% by weight, preferably 0.5 to 5% by weight % And (c) hydrophilic ethylenically unsaturated monomer: 0-10% by weight,
Preferably, it is 0.5 to 5% by weight.

When the amount of the (a) ethylenically unsaturated monomer used is reduced, durability and adhesion are reduced. Therefore, the amount used is most preferably 90% by weight or more. In addition, when the amount of the ethylenically unsaturated monomer (b) having an imidazoline group is increased, the polymerization stability is reduced. Therefore, the amount is preferably 5% by weight or less. In addition, (c)
When the amount of the hydrophilic ethylenically unsaturated monomer used increases, the resulting emulsion becomes more hydrophilic, and the hot water resistance of the coating tends to decrease accordingly. Therefore, the amount used is preferably 10% by weight or less.

The emulsifier used in the present invention includes anionic surfactants, nonionic surfactants, amphoteric surfactants and the like. Specifically, as anionic surfactants, for example, fatty acid ester salts of higher alcohols, alkylbenzene sulfonates, aliphatic sulfonates and the like, and as nonionic surfactants, polyethylene glycol alkyl ester type, Alkyl ether type, alkyl phenyl ether type, etc., and further, as amphoteric surfactants, surfactants in which the anion portion is a carboxylate, sulfonate, sulfate ester salt, and the cation portion is an amine salt, quaternary ammonium salt Agents. Further, a reactive emulsifier in which a polymerizable functional group is introduced into the above-mentioned surfactant can be used. The proportion of these used is preferably 0.5 to 5% by weight, and more preferably 1 to 3% by weight, based on the resin in order to obtain good hot water resistance.

Examples of the radical polymerization initiator used in the present invention include water-soluble or oil-soluble persulfates, peroxides, which can be radically decomposed by heat or a reducing substance to initiate addition polymerization to monomers. Azo compounds and the like can be used. For example, potassium persulfate, sodium persulfate,
Ammonium persulfate, hydrogen peroxide, t-butyl hydroperoxide, t-butyl peroxybenzoate,
There are 2,2-azobisisobutyronitrile, 2,2-azobis (2-diaminopropane) hydrochloride and the like, and water-soluble ones are particularly preferable from the viewpoint of easy handling. An amount of 2% by weight, preferably 0.1-0.5% by weight, is added. In addition, when accelerating the polymerization rate and performing the polymerization at a low temperature, sodium bisulfite, ferrous chloride,
A reducing agent such as ascorbate or Rongalit can be used in combination with the radical polymerization initiator.
It is also possible to add a chain transfer agent such as dodecyl mercaptan for controlling the molecular weight. The aqueous emulsion polymerized in the present invention exhibits stable dispersibility without neutralizing the carboxyl groups in the aqueous emulsion, but in order to maintain the dispersibility over a long period of time, for example, ammonia, sodium hydroxide, hydroxide The pH can be adjusted in the range of 6 to 10 using potassium and amines.

The aqueous emulsion of the present invention can also contain components usually added to water-based paints and the like, for example, thickeners, defoamers, pigments, dispersants, dyes, preservatives and the like.

[0023]

Next, the present invention will be described in detail with reference to examples and comparative examples. However, it should be understood that the present invention should not be construed as being limited by these disclosures. In the following Examples and Comparative Examples, all parts and percentages are by weight unless otherwise specified.

A. Sample Preparation Example 1 As a first step, 25 parts of methyl methacrylate and styrene were added to an aqueous solution containing 2% of a surfactant based on the total amount of monomers.
12 parts, butyl acrylate 7 parts, 1-ethyl methacrylate 2-
1 part of imidazoline and 0.6 part of acrylic acid were added using a stirrer while rotating at about 900 to 1500 rpm to obtain a uniform emulsion.

Next, as a second step, water, 0.4% of a surfactant with respect to the total amount of monomers, water in a 2 liter four-necked flask equipped with a stirrer, a reflux condenser, a dropping funnel and a thermometer were added. A part of the pre-emulsion obtained in the step was charged and heated to 75 ° C. under a nitrogen gas stream, a polymerization initiator was added thereto, and the remaining pre-emulsion / initiator aqueous solution was added dropwise over 4 hours. At this time, the polymerization temperature was maintained in the range of 80 to 85 ° C., and after maintaining for 1 hour in the same temperature range after the completion of the dropwise addition, the temperature was cooled to room temperature, and the pH was adjusted to 8 to 9 with a 25% aqueous ammonia solution. The mixture was filtered with a mesh filter cloth. The dry weight of the filtered agglomerates was very low, 0.002% of the total monomer. The nonvolatile content of the obtained aqueous emulsion is 45%, the average particle size is 91 nm, and the weight average molecular weight is 240,000.
Met. In addition, the non-volatile content is 100% of the aqueous emulsion.
Based on the weight of solids obtained after drying at 3 ° C. for 3 hours; and the average particle size was calculated using NICOM from Pacific Scientific.
By light scattering method using P Model 370; and the weight average molecular weight was determined by gel permeation chromatography (GPC) [mobile phase: TH
F (tetrahydrofuran), column: Ultra Styragel gel (manufactured by Waters) 10 ³ × 10 ⁴ × 10 ⁵ (polystyrene conversion)].

Example 2 The monomer added in the first step was methyl methacrylate 20
Parts, styrene 12 parts, ethyl acrylate 11 parts, acrylic acid
A sample was prepared in the same manner as in Example 1 except that the amount was 0.6 parts. The dry weight of the filtered agglomerate was very low, 0.003% of the total monomer. The obtained aqueous emulsion had a nonvolatile content of 45%, an average particle diameter of 90 nm, and a weight average molecular weight of 280,000.

Example 3 The amount of the surfactant used in the first step was based on the total amount of the monomers.
A sample was prepared in the same manner as in Example 1, except that 1.2% and the amount of the surfactant used in the second step was 1.2% based on all monomers. The dry weight of the filtered agglomerate was very low, 0.003% of the total monomer. The resulting aqueous emulsion has a nonvolatile content of 45% and an average particle size of 45%.
The weight average molecular weight was 60 nm, and the weight average molecular weight was 240,000.

Comparative Example 1 A sample was prepared in the same manner as in Example 1 except that the dripping time of the pre-emulsion initiator aqueous solution was changed to 2 hours.
The dry weight of the filtered agglomerate is 0.0
It was very slight at 03%. The obtained aqueous emulsion had a nonvolatile content of 45.0%, an average particle size of 120 nm and a weight average molecular weight of 220,000.

Comparative Example 2 A sample was prepared in the same manner as in Example 1 except that 0.1 part of t-dodecyl mercaptan was added to the monomer used in the second step. The dry weight of the filtered agglomerates was very low, 0.005% of the total monomer. The nonvolatile content of the obtained aqueous emulsion was 45.0%, the average particle diameter was 90 nm, and the weight average molecular weight was 150,000.

The details of the aqueous resin dispersions obtained in Example 1-3 and Comparative Example 1-2 are summarized in Table 1 below.

[0031]

[Table 1]

B. Test of Various Properties of Water-Dispersible Coating Composition Next, a water-dispersible solution prepared by further blending a film-forming aid and the like with the aqueous resin dispersion obtained in Example 1-3 and Comparative Example 1-2. With respect to the coating composition, heat resistance whitening property of the resin film, adhesion to a substrate, and durability test were performed.

[0033] 1. Preparation of composition sample A composition sample was prepared by blending using the formulation shown in Table 2 below.

[0034]

[Table 2]

[0035] 2. Preparation of Coating Preparation of Coating Sample for Hot Water Whitening Test The above composition sample was prepared using a bar coater No. 14 (RD Speci
alities, U.S.A.)
After drying for 3 minutes in a dryer at 05 ° C., it was subjected to a test.

Preparation of Coating Sample for Test of Adhesion and Durability The composition sample was spray-coated on a slate plate so as to have a coating amount of 150 g / m ² (wet), and dried at 105 ° C. for 3 minutes. After that, it was subjected to a test.

[0037] 3. Water whitening resistance test method 2. Was immersed in warm water at 40 ° C. for 24 hours. After taking out the acrylic plate from the warm water, it was quenched, the attached water was removed, and the degree of whitening was visually judged. Further, the film sample was dried at room temperature for 24 hours, and the degree of whitening of the film after drying was visually determined.

[0038] 4. Hot water whitening test method 2. Was immersed in hot water at 95 ° C. for 2 hours. After taking out from the warm water, it was quenched, the adhering water was removed, and the degree of whitening was visually judged. Further, the film sample was dried at room temperature for 24 hours, and the degree of whitening of the film after drying was visually determined.

[0039] 5. 2. Adhesion test method The slate plate obtained in the above was subjected to a cross-cut tape test specified in JIS K5400. That is,
Penetrate the coating on the slate plate, apply a cut to the bare ground in a grid pattern, paste an adhesive tape on the grid, and visually observe the adhesion state of the coated film after peeling. . The judgment at this time was evaluated based on a criterion of JIS K5400, based on a 10-point scale shown in Table 3 below.

[0040]

[Table 3]

6. Durability test method 6-1: Freeze-thaw adhesion test The freeze-thaw adhesion test specified in ASTM-C666A was performed on the slate obtained in the above. That is, the slate plate was placed on a support having a height of 3 mm placed at the bottom of the water tank so that the slate plate was completely surrounded by water (submerged). And a freezing step of reducing the temperature of the slate plate to 4.4 to -17.8 ° C;
The melting step of raising the temperature to -4.4 ° C was repeated for 40 cycles (the time required for one cycle was 4 hours, and 25% or more of the time was allocated for the melting step). Then, the state of the film on the slate plate after the completion of the predetermined 40 cycles was visually determined.

6-2: Accelerated Weathering Test About the slate plate obtained in
An acceleration test was performed for 400 hours using a tester (manufactured by Dainippon Plastics Co., Ltd.) to measure the gloss retention of the film.

7 Storage stability test method Was left in a dryer at 60 ° C. for 10 days, and the viscosity and appearance of the obtained film were confirmed.

Test 3 ~ 7. Table 4 below summarizes the test results.

[0045]

[Table 4]

[0046]

As is apparent from the results of the various tests described above, according to the present invention, a coating excellent in anti-whitening properties when immersed in hot water or when dried, and excellent in adhesion, durability and storage stability. The formation of a film was realized, and a water-dispersible coating composition having the intended characteristics was obtained.

Further, the water-dispersible coating composition of the present invention can be easily and inexpensively manufactured on an industrial scale by the same manufacturing equipment and manufacturing conditions as in the case of the conventional water-dispersible coating composition. It is also possible to supply large quantities.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical indication location // C09D 139/04 PGL C09D 139/04 PGL

Claims (4)

[Claims] A water-dispersible coating composition obtained by emulsion-copolymerizing a monomer mixture in a water-based medium with 0.05 to 5% by weight of an emulsifier based on a resin in the presence of a radical polymerization initiator. Wherein said monomer mixture comprises: (a) 70-99.9% by weight of an ethylenically unsaturated monomer, (b) 0.1-20% by weight of an ethylenically unsaturated monomer having imidazoline groups, and said monomers (a) and (b) (C) comprising from 0 to 10% by weight of a hydrophilic ethylenically unsaturated monomer copolymerizable with water and the water-dispersible coating composition has an average molecular weight of 200,000 to 400,000 and a particle size of 50 to 100 nm. A water-dispersible coating composition comprising body particles. 2. The (a) ethylenically unsaturated monomer is methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, C1 of (meth) acrylic acid such as stearyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, stearyl methacrylate, etc. (Meth) acryls such as C24 alkyl or cycloalkyl esters, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate C2-C8 hydroxyalkyl esters of acids, styrene, vinyltoluene, α-methylstyrene, N-
Aromatic unsaturated monomers such as vinylpyrrolidone and vinylpyridine, epoxy group-containing (meth) acrylates such as glycidyl acrylate and glycidyl methacrylate, 1-methyl 2-pyrrolidone acrylate, 1-ethyl acrylate
C1-C24 alkyl esters containing a pyrrole ring of (meth) acrylic acid, such as 2-pyrrolidone, 1-methyl 2-pyrrolidone methacrylate, 1-ethyl 2-pyrrolidone methacrylate, 1-methyl 2-oxazolidone acrylate, acrylic Oxazole ring-containing C1-C of (meth) acrylic acid such as 1-ethyl 2-oxazolidone methacrylate, 1-methyl 2-oxazolidone methacrylate, 1-ethyl 2-oxazolidone methacrylate
The water-dispersible coating composition of claim 1, wherein the monomer is a monomer selected from the group consisting of 24 alkyl esters, and a combination of one or more of the foregoing compounds. 3. The (b) ethylenically unsaturated monomer having an imidazoline group is 1-methyl 2-imidazolidone acrylate, 1-ethyl 2-imidazolidone acrylate, 1-methyl 2-imidazolidone methacrylate, 1-methacrylic acid -C2-C containing imidazole ring of (meth) acrylic acid such as -ethyl 2-imidazolidone
The water-dispersible coating composition according to claim 1, wherein the water-dispersible coating composition is a monomer selected from the group consisting of 24 alkyl esters, and a combination of at least one of the compounds described above. 4. The (c) hydrophilic ethylenically unsaturated monomer comprises acrylic acid, methacrylic acid, maleic acid, crotonic acid,
(Meth) acrylate having a polyoxyethylene chain;
Acrylamide, N-methylolacrylamide, N-
The water-dispersible coating composition according to any one of claims 1 to 3, which is a monomer selected from the group consisting of butoxymethylacrylamide, and a combination of at least one of the compounds described above.