JPH07113102B2 - Resin composition for water-based paint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a pigment dispersibility which is a characteristic of a polyester resin,
The present invention relates to an aqueous coating composition that provides an excellent coating film having flexibility, weather resistance, stain resistance, and chemical resistance, which are characteristics of acrylic resins.

(Prior Art) A resin mixture in which a curing agent is combined with a polyester resin or an acrylic resin as a base resin and dissolved or dispersed in water can reduce the volatilization of an organic solvent at the time of forming a coating film, so that resource saving and low pollution ( It becomes a paint for air pollution, etc., and is widely used as a water-based thermosetting paint for home appliances, pre-coated metal, automobiles, cans, etc.

When the water-based paint is based on a polyester resin, it has good dispersibility for the pigment used for coloring and gives a smooth and glossy coating film. It is used for cans that require processing, as intermediate coatings for automobiles that require resistance to flying stones, and as top coats for home appliances that require a beautiful color tone and suitability for various pigments.

On the other hand, when an acrylic resin is used as a base, a coating film having excellent characteristics of hardness, weather resistance, stain resistance, and chemical resistance can be obtained. Therefore, for home electric appliances, cans, etc. that require these characteristics. Is used for.

(Problems to be Solved by the Invention) Of course, polyester or acrylic thermosetting paints which are used by making use of their respective characteristics in these various uses are required to have their respective characteristics. However, the polyester resin and the acrylic resin have poor compatibility, and when they are simply blended and used, phase separation occurs, and a uniform resin solution cannot be obtained, so that they cannot be put to practical use as paints.

The present invention is a novel resin in which a polyester resin and an acrylic resin are hybridized in order to take advantage of the excellent features of each of the coatings using a polyester resin and an acrylic resin as a base resin, which are used as an aqueous thermosetting coating. It is an object of the present invention to provide a resin composition for an aqueous paint using the above.

(Means for Solving the Problems) The inventors of the present invention have diligently studied a hybrid resin composition of both systems that makes use of the excellent characteristics of both polyester and acrylic coatings, and as a result, have found that they are essentially hydrophobic polyesters. A hydrophilic resin containing an acid component is reacted with each other to give a stable resin composition when dissolved or dispersed in water, which gives an aqueous paint that has the excellent features of both systems. The present invention has been achieved by finding out that it is possible.

That is, the present invention comprises 5 to 95 parts by weight of a polyester resin having a hydroxyl value of 5 to 200 KOHmg / g and 95 to 5 parts by weight of an acrylic resin having a hydroxyl value of 5 to 200 KOHmg / g and an acid value of 10 to 300 KOHmg / g. A resin composition for water-based coatings, which comprises a resin composition (A) which has been reacted with each other, neutralized with a base, and dissolved or dispersed in water, and an amino resin.

The polyester resin used in the present invention must have a hydroxyl value of 5 to 200 KOHmg / g, and a hydroxyl value of 20 to 150 KOHmg.
It is preferably / g. If the hydroxyl value is less than 5 KOHmg / g, the reaction with the acrylic resin does not proceed sufficiently and the compatibility is poor, resulting in phase separation. On the other hand, when the hydroxyl value exceeds 200 KOHmg / g, the reaction with the acrylic resin proceeds rapidly, gelation is likely to occur, reaction control is difficult, and gelation occurs partially and a uniform solution cannot be obtained. The hydroxyl groups other than those involved in the reaction with the acrylic resin act as a cross-linking reaction group with the curing agent.

Such polyester resin, for example, terephthalic acid, isophthalic acid, phthalic anhydride, naphthalenedicarboxylic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, 1,10 decanedicarboxylic acid, cyclohexanedicarboxylic acid, trimellitic acid as a carboxylic acid component. Acids, polyvalent carboxylic acids such as maleic acid and fumaric acid and lower alcohol esters thereof, hydroxycarboxylic acids such as paraoxybenzoic acid and monovalent carboxylic acids such as benzoic acid can be used.

Further, as the alcohol component, for example, ethylene glycol, diethylene glycol, 1,3-propanediol,
1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol, 3-methyl-pentanediol, 2,2'-
Diethyl-1,3-propanediol, 2-ethyl 1,3-hexanediol, neopentyl glycol, trimethylolethane, trimethylolpropane, glycerin, pentaerythritol, ethylene oxide adduct of bisphenol A, propylene oxide addition of bisphenol A Compounds, hydrogenated bisphenol A ethylene oxide adducts, hydrogenated bisphenol A propylene oxide adducts, and the like.

Further, it is a matter of course that flaxseed oil, tung oil, safflower oil, dehydrated castor oil, cottonseed oil, coconut oil and fatty acids thereof can be used if necessary.

Such a polyester resin can be obtained by a general transesterification method or a direct esterification reaction of one or more kinds of the above-mentioned carboxylic acid component and one or more kinds of the above-mentioned alcohol component.

The number average molecular weight of the polyester resin measured by the GPC method is preferably 500 to 10,000. The acid value is preferably 20 KOHmg / g or less.

The acrylic resin used in the present invention has a hydroxyl value of 5 to 5.
It is necessary to be 200 KOHmg / g, preferably 20 to 150 KOHmg / g. If the hydroxyl value is less than 5 KOHmg / g, the reaction with the polyester resin does not proceed sufficiently and the compatibility is poor,
Phase separate. When the hydroxyl value exceeds 200 KOHmg / g,
The reaction with the polyester resin rapidly progresses, gelation easily occurs, and it is difficult to control the reaction. Further, gelation occurs partially and a uniform solution cannot be obtained.

The acrylic resin contains an acid component, and when the acid component is made into a hybrid resin, it is essential for neutralizing with a base and expressing the hydrophilicity of the resin with respect to water. Acid value is 10 ~
It is necessary to be 300 KOHmg / g, preferably 50 to 150 KOHmg / g. When the acid value is less than 10 KOHmg / g, the affinity for water is poor and it becomes difficult to dissolve or disperse in water. When the acid value exceeds 300 KOHmg / g, the coating film has poor water resistance and cannot be put to practical use.

For such an acrylic resin, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, 1,4-butanediol mono (meth) acrylate and the like can be used as the hydroxyl group-containing monomer.

As the acid group-containing monomer, (meth) acrylic acid, itaconic acid, maleic acid, fumaric acid and itaconic acid, maleic acid, a lower alcohol-modified monoalkyl ester of fumaric acid and the like can be used. Further, if necessary, methyl (meth) acrylate, ethyl (meth) as a copolymerization monomer
Acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, stearyl (meth)
Acrylate, tridecyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, phenyl (meth) acrylate, glycidyl (meth) acrylate, α-methylglycidyl (meth) acrylate, β-methylglycidyl (meth) acrylate, Esters of acrylic acid and methacrylic acid such as dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate can be used. Other copolymerizable monomers, styrene, α-methylstyrene, vinyltoluene, acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, acrylamide, methacrylamide, methylol acrylamide, methylol methacrylamide, vinyl chloride, propylene, Examples thereof include ethylene and C _{4 to} C ₂₀ α-olefins.

Such an acrylic resin can be produced by any known polymerization method such as a solution polymerization method, a suspension polymerization method, a bulk polymerization method and an emulsion polymerization method. At that time, as a polymerization initiator, azobisisobutyronitrile, 4,4′-azobis (4-cyanopentanoic acid), benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, cumene hydroperoxide, Potassium persulfate, hydrogen peroxide, 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) propioamide and the like can be used, and if necessary, dodecyl mercaptan as a chain transfer agent,
Mercaptoethanol or the like can be used.

The number average molecular weight of the acrylic resin measured by the GPC method is 500.
~ 20,000 is preferred.

In the resin composition (A) of the present invention, the polyester resin and the acrylic resin are reacted with each other, but the polyester resin is more than 95 parts by weight or the acrylic is less than 5 parts by weight in the composition. In this case, only the characteristics of the polyester resin are emphasized and the excellent coating film having the features of both resins, which is the object of the present invention, cannot be formed.
In addition, the acrylic resin portion containing the acid, which is the hydrophilic portion, is reduced, the affinity for water is insufficient, and it becomes difficult to dissolve or disperse it in water. On the contrary, when the acrylic resin is more than 95 parts by weight or the polyester resin is less than 5 parts by weight, only the characteristics of the acrylic resin are emphasized and the object of the present invention cannot be achieved.

The resin composition (A) of the present invention is a polyester resin 5 to 95.
180 parts by weight and acrylic resin 95-5 parts by weight are mixed.
10 minutes to 5 hours at a temperature of 80 ° C, preferably 30 minutes to 3 hours,
It can be produced by reacting the ester group and the hydroxyl group present in both resins with each other under the condition that the transesterification reaction can be carried out. The transesterification reaction does not necessarily have to proceed completely, and only a part thereof may have reacted. Then, butylated melamine, methylated melamine, butylated urea,
Amino resin such as methylated urea or hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, xylylene diisocyanate or water adducts thereof, trimethylolpropane adduct,
By reacting a polyvalent isocyanate compound such as an isocyanurate with 0.1 to 5% by weight of the resin solid content, the hydroxyl groups remaining in the acrylic resin and the polyester resin can be bonded to each other to promote the reaction.

The resin composition (A) of the present invention contains an acid group containing an aliphatic amine, an aromatic amine, an alkanolamine, ammonia,
It is neutralized with an organic or inorganic base such as KOH or NaOH. At that time, the equivalent ratio of acid and base is 0.5: 2 to 2: 0.5.
Is preferred.

In order to dissolve or disperse the resin composition (A) in water, after neutralization, water may be added with stirring, and any one of adding the resin composition (A) into water with stirring may be used. The method is also possible. The amount of water contained in the resin composition (A) is usually 40.
It is about 90%. In dissolving or dispersing in water, toluene, aromatic solvents such as xylene, ethyl acetate, ester solvents such as butyl acetate or cellosolve acetate, methyl ethyl ketone, methyl isobutyl ketone, ketone solvents such as cyclohexanone, n-butanol, iso An alcohol solvent such as butanol or butyl cellosolve, an ether solvent such as dioxane or tetrahydrofuran, or a chlorine solvent such as tetrachloroethane may be used alone or in combination.

Further, in the present invention, an amino resin is used as a curing agent. The amino resin is a resin synthesized from at least one of melamine, urea, benzoguanamine, glycoluril, etc. and formaldehyde, such as methanol,
An alkyl ether of a part or all of the methylol group is used with a lower alcohol such as ethanol, propanol, isopropanol, butanol or isobutanol.

Any of the amino resins used in the present invention is a curing agent component that cross-links with the hydroxyl groups in the resin composition (A) during baking of the paint to form a coating film.

In the present invention, the solid content weight ratio of the resin composition (A) and the amino resin in the coating composition is preferably 5 to 50 parts by weight with respect to 100 parts by weight of the former. This ratio is 5
If the amount is less than parts by weight, the cross-linking density of the cured coating film is not sufficient, and thus the physical properties of the coating film such as chemical resistance, solvent resistance and water resistance are not sufficient. On the other hand, if the amount exceeds 50 parts by weight, the cured coating film becomes extremely hard and is not practicable due to poor flexibility and bending property.

In addition, as various materials generally used for paints, coloring pigments such as titanium oxide, carbon black and red iron oxide, and extender pigments such as clay and calcium carbonate,
Barium sulfate, talc, alumina, silica, silica powder, etc. can be blended and used.

In addition, fibrin derivatives, petroleum resins, phenolic resins, ketone resins, synthetic rubbers, unsaturated polyester resins, natural resins such as rosin, synthetic resins, leveling agents, anti-sagging agents, defoaming agents, surfactants, and curing accelerators. Various auxiliaries such as agents can also be used.

The coating composition of the present invention can be prepared by a method known per se. For example, the above components are charged into a mixing / dispersing machine such as a steel mill, a pepper mill, an attritor, a sand mill, and a bladed high-speed agitator. It can be adjusted by uniformly mixing and dispersing.

The coating composition of the present invention can be coated on metals, plastics, wood products and the like by a conventional coating method such as spray coating, brush coating or roll coating. Examples of the method for curing the coating film include heating at 100 ° C. to 250 ° C. for 1 minute to 60 minutes.

(Examples) Next, the present invention will be specifically described with reference to Reference Examples, Examples and Comparative Examples. All parts and% are based on weight unless otherwise specified.

Reference Example 1 (Example of adjusting polyester resin) A raw material shown in Table 1 was charged into a four-necked flask equipped with a stirrer, a thermometer, a condenser with a stack din, and a nitrogen introducing tube, and the temperature was about 220 ° C in a nitrogen stream at about 220 ° C. Reaction is carried out while distilling off the reaction product for 10 hours, and polyester resin A-1 ~ A
Got -5.

Reference Example 2 (preparation example of acrylic resin) 100 parts of xylol and 50 parts of butanol were charged into a four-necked flask equipped with a stirrer, a thermometer, and a condenser, and heated to 120 ° C. Here, the raw materials shown in Table 2 were added dropwise over 4 hours, and then held at the same temperature for 6 hours to obtain acrylic resins B-1 to B-7 having a solid content of 40%.

Reference Example 3 (Preparation Example of Resin Composition (A)) The polyester resin and acrylic resin shown in Table 3 were placed in a four-necked flask equipped with a stirrer, a thermometer, and a condenser with a stack din, and heated and heated. Xylol, butanol, the reaction product was heated to 220 ° C. while distilling off, the reaction was carried out at the same temperature for 1 hour, the bases and solvents shown in Table 3 were added after cooling, and water was added with stirring. Solid content 30
% Resin solutions C-1 to C-5 and C-9 to C-12 were obtained.

Furthermore, the reaction conditions are as follows:
Got Further, C-7 to C-8 were obtained in the same manner except that the reaction was conducted at 180 ° C. for 3 hours.

Example 1 C-1 of the resin composition (A) shown in Table 3 and the curing agent, leveling agent and curing catalyst shown in Table 4 were added under stirring to obtain a coating composition. This was applied to a zinc phosphate-treated steel plate with a bar coater and heated at 140 ° C for 20 minutes to obtain a test plate. The coating performance is shown in Table-4.

Examples 2 to 6 Comparative Examples 1 and 6 In the same manner as in Example 1, the paints were adjusted in the proportions shown in Table 4 and test plates were obtained by the same method. The coating performance is shown in Table-4.

Comparative Example 2 C-5 of the resin composition (A) shown in Table 3 produced aggregates when water was added during the production thereof. Subsequent tests were stopped.

Comparative Example 3 C-9 of the resin composition (A) shown in Table 3 was phase-separated, and when water was added during the production, aggregates were formed. Subsequent tests were stopped.

Comparative Example 4 C-10 of the resin composition (A) shown in Table 3 generated a gel. The appearance of the coating film was inferior and the subsequent tests were stopped.

Comparative Example 5 C-11 of the resin composition (A) shown in Table 3 produced aggregates when water was added during the production thereof. Subsequent tests were stopped.

1) Amino resin: methylated melamine Cymel 350 (manufactured by Mitsui Siamid) 100% solid content 2) Curing catalyst: aromatic sulfonic acid Catalyst 6000
(Mitsui Toatsu Chemical Co., Ltd.) 3) Leveling agent: Acrylic resin Resmix RL-4
(Mitsui Toatsu Chemical Co., Ltd.) 4) Appearance of coating film: The finish of the coating film was visually observed, and a smooth and uniform coating film was evaluated as ⊚, and a film with poor uniformity was evaluated as x.

5) DuPont impact: 500g, performed under the condition of 1/2 inchφ.

6) Water resistance: The coating film was immersed in warm water at 60 ° C. for 10 days, and abnormalities such as blisters were observed. No change was evaluated as ⊚, and abnormal one was evaluated as x.

7) Secondary physical properties: After the test plate was immersed in seawater for 2 hours, a DuPont impact test and an Erichsen test were performed.

8) Storage stability of paint: Put the paint in a container, seal it tightly, and
After storage at 1 ° C for 1 week, those without aggregates were evaluated as ⊚, and those with slight aggregation were evaluated as ∘.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-58-40367 (JP, A) JP-A-57-98574 (JP, A) JP-A-59-202269 (JP, A) JP-B-53- 4523 (JP, B2) Japanese Patent Publication Sho 54-37895 (JP, B2)

Claims (1)

[Claims] 1. A polyester resin having a hydroxyl value of 5 to 200 KOHmg / g and 5 to 95 parts by weight and an acrylic resin having a hydroxyl value of 5 to 200 KOHmg / g and an acid value of 10 to 300 KOHmg / g. A resin composition for water-based coatings, which comprises an amino resin and a resin composition (A) which has been reacted with each other, neutralized with a base, and dissolved or dispersed in water.