JP2851526B2 - Aqueous resin dispersion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous resin dispersion for coating for baking for metals, and more particularly to a coating for can coating, and a primer coating for precoated steel sheets.
The present invention relates to an aqueous resin dispersion capable of forming an excellent coating film as an undercoat paint for automobiles and the like.

[0002]

2. Description of the Related Art Conventionally, an epoxy resin or a modified resin thereof having excellent toughness, flexibility, adhesion, chemical resistance and the like has been used as a paint for the inner surface of a metal can for food and drink and a primer for a precoated steel sheet. Solvent-type paints and vinyl chloride-based paints as main components have been used in many cases. However, in recent years, from the viewpoints of environmental pollution, working environment, resource saving or energy saving, it has been desired to switch from a solvent-based coating to a metal-based coating for metal cans. For this reason, various techniques for making epoxy resins aqueous have been developed.

For example, JP-A-53-1228 discloses a vinyl monomer containing a carboxyl group-containing vinyl monomer such as methacrylic acid by using a free radical generator such as benzoyl peroxide as an epoxy resin. An aqueous coating resin composition is disclosed in which a monomer mixture is copolymerized, and the obtained grafted epoxy resin composition is dispersed in an aqueous medium containing a base.

Japanese Patent Application Laid-Open No. Sho 53-1285 discloses that
An epoxy resin from which free epoxy groups have been removed with a terminator such as phenol or carboxylic acid is reacted with an addition polymerizable monomer in the presence of a free radical generator, and the resulting grafted epoxy resin composition is obtained. An aqueous coating resin composition dispersed in an aqueous medium containing a base is disclosed.

Further, Japanese Patent Application Laid-Open No. 57-112016 discloses a vinyl resin containing a vinyl monomer having a carboxyl group such as methacrylic acid by using a free radical generator such as benzoyl peroxide as a phenoxy resin. There is disclosed an aqueous coating resin composition in which a monomer mixture is copolymerized and the obtained grafted phenoxy resin composition is dispersed in an aqueous medium containing a base.

JP-A-55-75460 and JP-A-56-109243 disclose a carboxyl group-excess partial reaction in which an acrylic resin is reacted with a relatively high-molecular-weight aromatic epoxy resin. An aqueous coating resin composition is disclosed in which the product is dispersed in an aqueous medium in the presence of ammonia or an amine.

Further, JP-A-55-3481 and JP-A-55-3482 disclose a self-emulsifying property obtained by reacting a carboxyl group-containing polymer with an epoxy resin in the presence of an amine. An aqueous coating resin composition comprising an epoxy ester copolymer mixture is disclosed.

On the other hand, JP-A-57-105418 and JP-A-58-198513 disclose that a (meth) acrylic acid is partially reacted with an aromatic epoxy resin, and an epoxy group is contained in one molecule obtained. An aqueous resin composition is disclosed in which a monomer mixture containing (meth) acrylic acid is copolymerized with a low molecular compound having a (meth) acryloyl group and a low molecular compound having a (meth) acryloyl group, and the resulting mixture is neutralized with a basic compound.

[0009]

However, the above-mentioned conventional resin compositions for water-based coatings have a particularly large difference between the solvent-based epoxy-based paint and the PVC-based sol-based paint, especially the coating film and the metal to be coated. The adhesion to the material, especially aluminum, is significantly poor, and the workability is reduced when trying to improve the adhesion, and the adhesion and retort whitening resistance are reduced when trying to improve the workability. It is difficult to obtain a well-balanced retort whitening resistance, so that there is a problem that the use is limited.

In particular, when the inside of a can for food and drink is painted, for example, an aluminum plate which has been painted in advance is generally used for the easy open end of the can, for example, but a conventional aqueous resin coating composition is used. In this case, the adhesion was insufficient and the phenomenon of film residue of the coating film was likely to occur when the lid was opened.

When a punched can or drawn can is processed from a pre-painted plate material, the adhesion between the coating film and the metal material is poor, and a conventional aqueous coating resin composition is used for these purposes. It was impossible to do.

Further, as a three-piece can using a tin-free steel material, an adhesive can having a seam of a can body stuck with a polyamide-based adhesive is often used, but a conventional resin composition for aqueous coating is a base can. There was no sufficient adhesion to the material and the polyamide adhesive.

An object of the present invention is to have the same degree of adhesion to a metal material as a solvent-based paint or a PVC-based paint containing an epoxy resin or its modified resin as a main component, workability and preservation of contents resistant. It is an object of the present invention to provide a novel aqueous resin dispersion which is excellent in resilience, is resistant to retort whitening, and is not deteriorated by heat and pressure sterilization.

[0014]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to overcome the above-mentioned problems, and as a result, a pre-bonded phenoxy resin and a phenol resin were converted to a monomer containing acrylic acid. The present inventors have found that the object is achieved by graft modification with the mixture, and made the present invention. In the present invention, an unsaturated aliphatic carboxylic acid monomer and an unsaturated monomer copolymerizable with the unsaturated aliphatic carboxylic acid monomer are added to a pre-bonded product (C-1) of the phenoxy resin (A) and the phenolic resin (B). An aqueous resin dispersion obtained by polymerizing a monomer mixture and dispersing a composite resin composition containing the obtained carboxylic acid-modified graft polymer (C-2) in an aqueous medium in the presence of ammonia or an amine.

The phenoxy resin (A) used in the present invention comprises:
It is produced from bisphenol A or the like and epichlorohydrin.Specifically, bisphenol A or the like and epichlorohydrin are condensed to a high molecular weight in the presence of an alkali catalyst, or bisphenol A or the like and epichlorohydrin as an alkali catalyst. It is produced by condensing with a low molecular weight epoxy resin in the presence and subjecting this low molecular weight epoxy resin to a bisphenol A or the like polyaddition reaction,
A thermoplastic phenoxy resin having a number average molecular weight of 10,000 or more is used. If the molecular weight is less than 10,000, processability is poor. Commercially available products include Phenothote YP-50 manufactured by Toto Kasei Co., Ltd., and phenoxy resin PKHH manufactured by Union Carbide Corporation of the United States.

The phenoxy resin (A) accounts for 50 to 90% by weight of the total weight of the composite resin composition. If it is less than 50% by weight, adhesion and processability are poor, and if it exceeds 90% by weight, it is difficult to disperse in water.

On the other hand, the phenolic resin (B) is produced by subjecting a phenol and an aldehyde, particularly formaldehyde, to addition condensation in the presence of a catalyst by a commonly used well-known method. The hydroxyl group may be modified with a low molecular weight alcohol. As the catalyst, ammonia, ethylamine, butylamine, organic amines such as diethanolamine, sodium hydroxide, magnesium hydroxide, calcium hydroxide, basic catalysts of alkali hydroxides such as barium hydroxide, or hydrochloric acid, phosphoric acid, sulfuric acid, An acidic catalyst such as acetic acid is used. As phenols, phenol; o,
m or p-cresol, p-tert-butylphenol, m or p-ethylphenol, 2,3-, 2,
Alkyl phenols such as 5- or 3,5-xylenol; resorcin; m-methoxyphenol; bisphenol (B) and the like are used.

The phenolic resin (B) includes an allylic etherified phenolic resin obtained by reacting a phenolic resin with an allyl halide in a solution having a high alkali concentration and allylicifying a phenolic hydroxyl group. Further, after allyl etherification, the alcoholic hydroxyl group may be modified with a low molecular weight alcohol. These phenolic resins (B) can be used as a mixture of two or more.

The phenolic resin (B) preferably has a number average molecular weight of 200 to 300,000. If it is less than 200, not only the adhesion is inferior, but also the flavor preservability is inferior,
Unsuitable for use in can coatings, 300,000
If it exceeds, workability is inferior.

The pre-combination (C-1) of the phenoxy resin (A) and the phenolic resin (B) is obtained by combining the phenoxy resin (A) and the phenolic resin (B) in the presence or absence of an organic solvent. It is obtained by reacting at 50 ° C. to 150 ° C. for 10 minutes to 10 hours. The degree of bonding varies depending on the amount of the phenolic resin (B), the baking temperature after coating the base material, and the like, but the larger the degree of bonding, the better, and it is preferable that the phenolic resin (B) be reacted by 1% or more. The degree of binding by the reaction can be measured by GPC (gel permeation chromatography).

In producing the pre-combined product (C-1) of the phenoxy resin (A) and the phenolic resin (B), triethylamine, triethanolamine, dimethylethanolamine and the like are used in order to accelerate the addition reaction. A promoting catalyst such as a tertiary amine may be used.

The weight of the phenolic resin (B) is desirably 0.5 to 60% by weight, preferably 1 to 30% by weight, based on the weight of the phenoxy resin (A).
When the weight of the phenolic resin (B) is less than 0.5% by weight, adhesion and retort whitening resistance are poor, and when it is more than 60% by weight, processability is poor.

Next, in the present invention, the pre-combined product (C-C) of the phenoxy resin (A) and the phenolic resin (B)
1) contains a carboxylic acid-modified graft polymer (C-2) by graft-polymerizing a monomer mixture comprising an unsaturated aliphatic carboxylic acid monomer and an unsaturated monomer copolymerizable therewith. A composite resin composition is manufactured.

The unsaturated aliphatic carboxylic acid monomer contained in the monomer mixture is preferably a monobasic unsaturated carboxylic acid monomer such as acrylic acid and methacrylic acid.

The unsaturated monomers copolymerizable with the unsaturated aliphatic carboxylic acid monomer include methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, and (meth) acrylic acid. N-butyl acid, (meth)
Isobutyl acrylate, hexyl (meth) acrylate,
(Meth) acrylates such as 2-ethylhexyl (meth) acrylate and nonyl (meth) acrylate; styrenes such as styrene, vinyltoluene, 2-methylstyrene, t-butylstyrene, chlorostyrene and α-methylstyrene Glycidyl (meth) acrylate,
Glycidyl crotonate, glycidyl allyl ether,
Examples thereof include (meth) acrylamide, N-methylol (meth) acrylamide, (meth) acrylonitrile, vinylidene chloride, 2-hydroxyethyl (meth) acrylate, and hydroxypropyl (meth) acrylate. These polymerizable unsaturated monomers can be used as one kind or as a mixture of two or more kinds. In particular, a mixed monomer of styrene-based monomers and (meth) acrylates or (meth)
Acrylic esters are preferred.

Carboxylic acid-modified graft polymer (C-2)
Is prepared by adding the monomer mixture to the pre-bonded product (C-1) and a conventional radical polymerization initiator such as benzoyl peroxide in an amount of 0.1% or more based on the weight of the monomer mixture, preferably The reaction is carried out at a temperature of 80 ° C. to 150 ° C. in the presence of 0.5% or more, more preferably 3% or more.

The amount of the unsaturated aliphatic carboxylic acid monomer contained in the monomer mixture depends on the acid value of the composite resin composition.
It is desirable that the amount be 200. If it is less than 30, it is difficult to disperse in water, and if it is more than 200, not only corrosion resistance and workability are poor, but also high viscosity and workability are poor.

The composite resin composition referred to in the present invention includes a carboxylic acid-modified graft polymer (C-2) as a main component, a copolymer derived from a monomer mixture, and a pre-bonded product (C-1).
And the like.

In the present invention, the aqueous resin dispersion is prepared by
So that the pH of the final aqueous resin dispersion is 4 to 11,
The composite resin composition may be dispersed in an aqueous medium to which ammonia or an amine has been added. Examples of the amine include alkylamines such as trimethylamine, triethylamine and tributylamine; alcohol amines such as 2-dimethylaminoethanol, diethanolamine, triethanolamine and aminomethylpropanol; and morpholine. Further, polyamines such as ethylenediamine and diethylenetriamine can also be used.

As the aqueous medium, water alone or a mixture with a hydrophilic organic solvent in which at least 10% by weight or more of water is used. As the hydrophilic organic solvent, methyl alcohol, ethyl alcohol, n-propyl alcohol, Isopropyl alcohol, n-butyl alcohol,
sec-Alkanols such as butyl alcohol and isobutyl alcohol; methyl cellosolve, ethyl cellosolve,
Propyl cellosolve, butyl cellosolve, methyl carbitol, ethyl carbitol, propyl carbitol,
Ether alcohols such as butyl carbitol; and dioxane, dimethylformamide, diacetone alcohol, acetone and the like are used. These hydrophilic organic solvents can be removed from the final aqueous resin dispersion. Further, a hydrophobic organic solvent can be used in combination with the hydrophilic organic agent.

To the aqueous resin dispersion of the present invention, if necessary, known and commonly used additives such as a plasticizer, a film forming aid, a dispersant, a surface conditioner, a preservative, an antifoaming agent, an anticorrosive, and a filler. An agent can be appropriately selected and added to be used as a paint.

The aqueous resin dispersion of the present invention can be applied to a treated or untreated metal plate such as an aluminum plate, a tin plate, a tin-free steel plate, a steel plate, a galvanized steel plate. It is suitably used for coating a treated aluminum alloy plate.

As a method for coating the aqueous resin dispersion, various methods known in the art, for example, roll coater coating,
Spray painting, immersion painting, electrodeposition painting etc. can be applied,
Among them, roll coater coating and spray coating are preferred.

The coating film is dried by heating in a hot air oven, electromagnetic induction heating, heat ray irradiation, or the like. The drying and curing conditions are 15
The temperature is preferably from 0 to 300 ° C. for 20 seconds to 30 minutes.

[0035]

In the aqueous resin dispersion of the present invention, the phenoxy resin and the phenolic resin are pre-bonded in advance, so that the adhesiveness can be improved without lowering the processability as compared with the conventional aqueous coating resin composition. Although it shows an extremely excellent effect of being able to improve the retort whitening resistance, the distribution of cross-linking points at the time of baking is lower than that obtained by simply adding a phenolic resin later (see Comparative Example 1). It is presumed to be due to the fact that it becomes uniform, and that the compatibility between the phenoxy resin and the phenolic resin is improved.

In addition, since phenolic resins generally act as polymerization inhibitors, they are considered to inhibit the grafting reaction, and it has generally been thought that radical polymerizable monomers cannot be polymerized in the presence of phenolic resins. However,
In the present invention, it is considered that graft polymerization has become possible by pre-bonding the phenoxy resin and the phenolic resin.

[0037]

Next, the present invention will be described more specifically with reference to examples and comparative examples. In the following, all parts and percentages are by weight unless otherwise specified.

Example 1 A phenothoto YP-50 (manufactured by Toto Kasei Co., Ltd.,
(Phenoxy resin) 140 parts, 50 parts of butyl cellosolve and 50 parts of n-butyl alcohol were charged and dissolved by heating at 120 ° C., and then Shonor PCL-681 (manufactured by Showa Polymer Co., Ltd., straight phenol resol resin, solid content 60%) Add 14.1 parts and add 4 at 125-130 ° C.
Time kept. GPC measurement confirmed that the phenolic resin and the phenoxy resin were pre-bonded.

In a separate container, 12.8 parts of methacrylic acid, 8 parts of styrene, 8.8 parts of ethyl acrylate and 2.3 parts of benzoyl peroxide were uniformly mixed and dissolved.
This monomer mixed solution is gradually added at a constant rate over a period of 60 minutes to the reaction vessel containing the pre-bonded solution, stirred for 1 hour while maintaining the temperature at 117 to 119 ° C, and then cooled to 80 ° C. did. Next, 10 parts of 2-dimethylaminoethanol was added, and the mixture was maintained for 30 minutes. 297.5 parts of water was added, the mixture was stirred at 60 ° C. until uniform, cooled to room temperature, and an aqueous resin dispersion having a nonvolatile content of 30% was added. I got

Example 2 Instead of phenothoto YP-50, phenoxy PKHH was used.
An aqueous resin dispersion was obtained in the same manner as in Example 1 except that 140 parts (Phenoxy resin, manufactured by Union Carbide Corporation) were used.

Example 3 Instead of Shonor PCL-681, Shonor ARL
An aqueous resin dispersion was obtained in the same manner as in Example 1, except that 3.3 parts of -080 (manufactured by Showa Polymer Co., allyl etherified phenol resin, solid content: 60%) was used.

Example 4 Acrylic acid as an unsaturated aliphatic carboxylic acid monomer
An aqueous resin dispersion was obtained in the same manner as in Example 1, except that 7 parts, 14.5 parts of methyl methacrylate and 4.4 parts of 2-ethylhexyl acrylate were used as copolymerizable unsaturated monomers. Was.

Comparative Example 1 A phenotote YP-50 (manufactured by Toto Kasei Co., Ltd.,
Phenoxy resin), 140 parts of butyl cellosolve and 50 parts of n-butyl alcohol.
Was heated and dissolved. 12.8 methacrylic acid in another container
Parts, styrene 8 parts, ethyl acrylate 8.8 parts and benzoyl peroxide 2.3 parts were uniformly mixed and dissolved. This monomer mixed solution is gradually added at a constant rate over a period of 60 minutes to the reaction vessel containing the phenoxy resin solution, and the mixture is stirred for 1 hour while maintaining the temperature at 117 to 119 ° C, and then cooled to 80 ° C. did. Next, 10 parts of 2-dimethylaminoethanol was added and maintained for 30 minutes.
7.5 parts were added and stirred at 60 ° C. until uniform. After cooling to room temperature, add Shonor PCL-681 in 1
After 4.1 parts, an aqueous resin dispersion having a nonvolatile content of 30% was obtained.

Comparative Example 2 Epikote 1010 was used in place of the phenothot YP-50.
(Shell Chemical Co., epoxy resin) An aqueous resin dispersion was obtained in the same manner as in Example 1, except that 140 parts were used.

Comparative Example 3 Preparation of Phenol Resin Solution 136 parts of p-tert-butylphenol was added to a reaction vessel.
162 parts of a 7% aqueous formaldehyde solution and 160 parts of a 25% aqueous sodium hydroxide solution were charged, reacted at 50 ° C. for 3 hours, neutralized with hydrochloric acid, and water was separated. After water separation, 250 parts of p-tert-butylphenol, 3.7 parts of 10% hydrochloric acid and 250 parts of water were added, and the mixture was stirred for about 30 minutes.
At the end of the heat generation, 160 parts of a 25% aqueous sodium hydroxide solution and 120 parts of a 37% aqueous formaldehyde solution were added, reacted at 50 ° C. for 3 hours, neutralized with hydrochloric acid, and the aqueous layer was separated. Was repeated three times. This was dissolved in a mixed solvent of n-butyl alcohol / xylene = 1/1 to obtain a phenol resin solution having a concentration of 60%.

Preparation of Acrylic Resin Solution 300 parts of styrene 210 parts of ethyl acrylate 90 parts of methacrylic acid 388 parts of butyl cellosolve 388 parts of benzoyl peroxide 12 parts
The mixture was heated to 90 ° C., and while maintaining the temperature, the remaining amount was gradually added dropwise over 2 hours, followed by stirring for 2 hours. After cooling to room temperature, an acrylic resin solution was obtained.

Preparation of Epoxy Resin A reaction vessel was charged with 500 parts of Epicoat 1009 (Epoxy resin, epoxy equivalent 2,500, manufactured by Shell Chemical Co., Ltd.) and 333.3 parts of butyl cellosolve.
The mixture was stirred and dissolved for 1 hour, and then cooled to obtain an epoxy resin solution.

Preparation of aqueous resin dispersion Acrylic resin solution 50 parts Epoxy resin solution 100 parts Phenol resin solution 30 parts 2-Dimethylaminoethanol 4.8 parts Water 175.2 parts 100 ° C while
For 2 hours. GPC measurement before and after the reaction confirmed that a part of the phenol resin and the epoxy resin were bonded. The liquid temperature was lowered to 80 ° C., and the mixture was added, reacted for 30 minutes and cooled. GPC measurement before and after the reaction confirmed that the acrylic resin and the epoxy resin were bonded. With further stirring, was gradually added to obtain an aqueous resin dispersion having a nonvolatile content of 30%.

Test Example Each of the aqueous resin dispersions obtained in Examples 1 to 3 and Comparative Examples 1 to 3 was applied to an aluminum plate so as to have a thickness of 9 to 11 μm. A test plate was prepared by baking for seconds. The test results are shown in Table 1.

The test method is as follows. (1) Workability Using a Dupont-type impact tester, place a folded test plate at the bottom, and place a 1kg iron weight with a flat contact surface on the folded part when dropped from a height of 50cm. Was observed. A state without cracks was regarded as a pass. There are no cracks ◎,
Cracks are not visible to the naked eye, slight cracks are visible, and many cracks are X. (2) Can Lid Punching Property The # 301 can lid was punched with the coated surface of the test plate inside, and the presence or absence of peeling of the coating film was observed. A state without peeling was regarded as a pass. There is no peeling, and there is peeling. (3) Retort whitening resistance Place the test plate in a pressure cooker filled with water, cover and heat.
The plate was treated at 25 ° C. for 30 minutes, and the test plate was observed for whitening. Those that did not whiten were considered acceptable. Not whitened, whitened x. (4) Adhesiveness Two test plates with a width of 5 mm were aligned with the coated surfaces, a polyamide-based hot melt film was sandwiched between the test plates, and held at about 200 ° C. for 90 seconds in a hot press. 1
The peel strength (kg) was measured when the film was pulled at a speed of 200 mm / min in the direction of bending at 80 °. 2 kg or more was judged to be acceptable. 3 kg or more ◎, 2-3 kg ○, 1-2 kg △. (5) Corrosion resistance The test plate was immersed in a mixture of 3% salt and 3% citric acid, and
It was kept at 0 ° C. for 8 hours, and the corrosion state was observed. Those having no abnormality in the coating film were judged as acceptable. There is no abnormality in the coating film.

[0050]

[Table 1]

[0051]

Industrial Applicability The aqueous resin dispersion of the present invention has excellent adhesion and retort whitening resistance while exhibiting excellent processability, and is useful as a paint for baking metal plates.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tamio Iimure 1-1398-10-405, Mitsuhashi, Omiya City, Saitama (56) References JP-A-49-18988 (JP, A) JP-A-7-242792 (JP) , A) JP-B-45-12384 (JP, B1) JP-B-58-501036 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08L 51/08 C08F 283/00- 283/14 C09D 151/08

Claims (6)

(57) [Claims] 1. A pre-bonded product (C-1) of a phenoxy resin (A) and a phenolic resin (B) is prepared from an unsaturated aliphatic carboxylic acid monomer and an unsaturated monomer copolymerizable therewith. An aqueous resin dispersion obtained by polymerizing the resulting monomer mixture and dispersing the obtained composite resin composition containing the carboxylic acid-modified graft polymer (C-2) in an aqueous medium in the presence of ammonia or an amine. 2. The aqueous solution according to claim 1, wherein the phenoxy resin (A) is produced from bisphenol A and epichlorohydrin, and the phenolic resin (B) is produced from phenols and formaldehyde. Resin dispersion. 3. The aqueous resin dispersion according to claim 1, wherein the weight of the phenoxy resin (A) is 50 to 90% by weight based on the total weight of the composite resin composition. 4. The aqueous resin dispersion according to claim 1, wherein the unsaturated aliphatic carboxylic acid monomer is (meth) acrylic acid. 5. The aqueous resin dispersion according to claim 1, wherein the composite resin composition has an acid value of 30 to 200. 6. The copolymerizable unsaturated monomer is (meth)
2. A monomer mixture of an acrylate or a styrene monomer and a (meth) acrylate.
6. The aqueous resin dispersion according to any one of claims 1 to 5.