JPH03153782A - Water-base acrylic resin composition - Google Patents

Abstract

PURPOSE:To prepare the title resin compsn. which adheres well to an inorg. plate and forms a coating film excellent in the gloss and resistance to weathering and staining by incorporating, as the main component, a copolymer comprising an unsatd. carboxylic acid and a (meth)acrylic ester and having a specified acid value and wt.-average mol.wt. into the compsn. CONSTITUTION:The title resin compsn. contains, as the main component, a copolymer comprising an unsatd. carboxylic acid [e.g. (meth)acrylic acid, maleic acid, or fumaric acid] and a (meth)acrylic ester [e.g methyl (meth)acrylate and having an acid value of 25-65 and wt.-average mol.wt. of 3000-100000. The compsn. adheres well to, e.g. a metallic plate, forms a coating film excellent in the gloss and resistance to weathering and staining, and is superior in the safety, odor, and penetration into a substrate material with a high moisture content to a solvent-base resin compsn.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to various surface treatment agents for inorganic boards, water-based exterior paints and clear coat agents that require water resistance, surface treatment agents for paper, etc. The present invention relates to (meth)acrylic acid ester aqueous solution resins used in

[Conventional technology and issues]

Conventionally, various aqueous resins have been developed in order to solve various problems such as odor and work environment pollution caused by organic solvents such as paints. Among them, water-soluble acrylic resins are widely used because they have good gloss and excellent light resistance and chemical resistance.

However, the aqueous acrylic ester resins that have been commonly used have an acid value of 150 to 500, and have the disadvantage that the film of the cured product dissolves or swells with water. Therefore, these are unsuitable for applications such as primer coatings for inorganic boards and exterior paints for cold regions, which require extremely severe water resistance and repeated hot water resistance in practical use.

As a result of extensive research, the present inventors have overcome the drawbacks of the conventional aqueous resins and have developed an acrylic aqueous resin composition whose film has extremely excellent water resistance.

[Means to solve the problem]

That is, the present invention mainly consists of a copolymer of unsaturated carboxylic acid and (meth)acrylic acid, which has an acid value of 25 to 65 and a weight average molecular weight of 3,000 to 100,000.
The present invention aims to solve the above problems by providing an aqueous acrylic resin composition.

More specifically, in the present invention, the acid value is reduced to a level that allows it to be made into an aqueous solution, and the weight average molecular weight is reduced from 3,000 to
The present invention aims to provide an aqueous acrylic resin with good water resistance by controlling the amount within the range of o and ooo, preferably using a dropwise polymerization method, and selecting a suitable hydrophilic organic solvent.

The aqueous acrylic resin of the present invention is prepared by co-producing an unsaturated carboxylic acid and a (meth)acrylic ester together under appropriate conditions to obtain a predetermined acid value, preferably in the presence of a hydrophilic organic solvent. It is produced by polymerizing, neutralizing if necessary, and diluting with water. Here, the acid value is measured as the amount of carboxyl groups contained in the copolymer.

The acrylic water-based resin of the present invention is characterized by excellent water resistance by controlling the acid value of the resin contained therein to 25 to 65 and adjusting the weight average molecular weight to 3,000 to 100,000. This is to obtain a coating resin.

At this time, in order to obtain an aqueous solution or a homogeneous and stable aqueous liquid, it is necessary to adjust the molecular weight to suit the intended use and to select a hydrophilic solvent. Moreover, this product exhibits excellent film-forming properties regardless of the glass transition point of the resin composition.

When the aqueous resin composition of the present invention is used, for example, as a sealer for inorganic boards, by diluting it with a large amount of water, the resin becomes a micro micelle state and is stably dispersed, resulting in an aqueous dispersion with good permeability. It becomes resin. This resin also has better permeability into the inorganic board at a microscopic scale than emulsion sealers, and also has a reinforcing effect. It also has superior safety, odor, and permeability to substrates with high moisture content than solvent types.

The aqueous resin composition of the present invention has good adhesion to metal plates and the like, and can be fully used as a top coat material with high gloss and excellent weather resistance and stain resistance.

Furthermore, it has good miscibility with pigments such as carbon black and titanium white, and can be made into a paint to create a high-gloss coating material.

If the acid value is less than 25, the resin will not become water-soluble even when neutralized and will turn into a gel.If the acid value is more than 65, the resin will dissolve and swell in water, making it extremely water resistant. It becomes a bad aqueous resin. Furthermore, similarly with respect to the molecular weight, if it is too or ooo or more, it has a very high viscosity and cannot be water-solubilized, and if it is less than 3,000, a resin with good water resistance cannot be obtained even if the acid value is decreased.

Examples of unsaturated carboxylic acids used in the present invention include acrylic acid, methacrylic acid, maleic acid, itaconic acid, and fumaric acid.

As the (meth)acrylic acid ester monomer, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, methyl methacrylate, butyl methacrylate, etc. are used.

As the radical polymerization initiator for polymerizing these monomers, commonly used oil-soluble catalysts are suitable, and in particular, azobisisobutyronitrile, benzoyl peroxide, etc. are used.

The polymerization is also preferably carried out in a hydrophilic organic solvent; examples of the hydrophilic organic solvent include; alcohols such as methanol, ethanol, isopropyl alcohol, and ethylene glycol; ethylene glycol monomethyl ether; diethylene glycol monomethyl ether; and diethylene glycol monoethyl. Ethers, glycol derivatives such as propylene glycol monomethyl ether, ethers such as dioxane, and ketones such as acetone are used.

In this case, prepolymerization facilitates the production of a high molecular weight polymer and is preferably used in the present invention.

The carboxylic acid neutralizer in the copolymer is optimally added in an equimolar amount to the amount of acid used. The basic neutralizing agents include: ammonia, primary amines, secondary amines, tertiary amines, and the like. Examples of these include monoethanolamine, jetanolamine, triethanolamine, N,N jetanolamine, aminomethylpropane, and the like.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

In a reaction vessel equipped with a thermometer, a stirrer, a reflux condenser, and an inert gas inlet, 300 parts by weight of ethanol, 33.6 parts of methyl methacrylate, 13 parts of 2-ethylhexyl acrylate, and 1 part of methacrylic acid were added. .3 parts and 1.9 parts of a polymerization initiator (azobisisobutyronitrile) were added, and the mixture was heated at reflux temperature for 2 hours.
The reaction was carried out for 0 minutes, and then methyl methacrylate 2
A solution prepared by dissolving 7 parts of a polymerization initiator in a mixture of 46 parts of 2-ethylhexyl acrylate, 95 parts of 2-ethylhexyl acrylate, and 15 parts of methacrylic acid was added dropwise over 3 hours to polymerize. After completion of the dropwise addition, it was aged for 3 hours, and after cooling, 17 parts of ethanolamine was added. The mixture was neutralized in 1 part and diluted with water to give a resin concentration of 40% to obtain an aqueous resin solution having an acid value of 26 and a weight average molecular weight of 20,000.

[Dog] L-2 The same method as in Example 1 was used, only the amount of methacrylic acid to be dropped was 20.7 parts, the acid value was 35, and the weight average molecular weight was 2.
0,000 aqueous resin was obtained.

Example 1 was carried out in the same manner as in Example 1, only the amount of methacrylic acid added was 98.7 parts, and an aqueous resin solution having an acid value of 133 and a weight average molecular weight of 20,000 was obtained.

It was carried out in the same manner as in Example 1, only the amount of methacrylic acid dropped was 6.7 parts, the acid value was 13, and the weight average molecular weight was 20.
,000 of the resin was obtained, but it could not be made into an aqueous solution and turned into a gel state.

The aqueous resin compositions obtained in Example 1.2 and Comparative Example 1 were tested for gloss and water resistance. The results are shown in Table 1.

Table 1 Gloss 2 Coating resin on metal plate, 24 hours at 20°C, R) 1
The gloss after drying was observed at 65%.

Water resistance: The state of the metal plate was observed after being immersed in water for 24 hours.

In Table 1 and the table below, ◎ is excellent. O゛ is good. Δ is slightly inferior, × is inferior, are shown respectively.

11'' Using the same apparatus as in Example 1, 80 parts of isopropyl alcohol, 1 part of β-mercaptopropionic acid, 18 parts of vinyl persate, 0.8 part of maleic anhydride,
0.7 parts of methacrylic acid, 13 parts of methyl methacrylate, 0.7 parts of polyethylene glycol diacrylate (4EGA).
02 parts, 2-ethylhexyl acrylate (2EHA)
Add 0.6 parts of azobisisobutyronitrile to 9 parts,
Closed polymerization was carried out at the boiling point for 20 minutes, followed by 80 parts of methyl methacrylate, 56 parts of 2EHA, 6 parts of methacrylic acid, and 4EG.
A mixture of 0.09 parts of A and 2.1 parts of azobisisobutyronitrile was added dropwise over 3 hours and 30 minutes to react, and the mixture was further aged for 3 hours and 30 minutes. After cooling the reaction mixture, the solution was diluted with 43 parts of dimethylethanolamine. A resin composition containing a copolymer with a solid content of 62% was obtained. The acid value of the solid content was 26.

Chestnut] L chestnuts - Yu According to the method of Example 3, the calculated glass transfer transfer was 3.
Polymerization was carried out by changing the amounts of methyl methacrylate and 2E)IA so that the temperature was 0°C, and a resin composition with a solid content of 62% was obtained.

The acid value was 26.

Next, the resin compositions obtained in Examples 3 and 4 were diluted with water to make a 20% aqueous solution, and a peel test and a water resistance test were conducted when used as a sealer for various inorganic boards. The results are shown in Table 2.

The peel test was based on JIS K-5400, and the water resistance test was also based on JTS K-5400.

Table 2 Good penetration into inorganic plates, water resistance, Stain resistance Forms an excellent coating film.

It is also cheaper than solvent type. All works, It also has excellent permeability to odor and high moisture content substrates.

Claims (1)

[Claims] Acid value is 25-65 and weight average molecular weight is 3,000-10
An aqueous acrylic resin composition containing as a main component a copolymer of an unsaturated carboxylic acid and (meth)acrylic acid having a molecular weight of 0,000.