JPH09176453A - Thermosetting resin composition and method for forming coating film therefrom - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thermosetting resin composition based on a polymer containing a half-ester of an acid anhydride and improved in water resistance and weather resistance. SOLUTION: This resin composition comprises an acid-anhydride-group-free copolymer (I) obtained by forming a copolymer of an acid-anhydride-group- containing radical polymerizable monomer with other copolymerizable monomers and half-esterifying the acid anhydride groups of the copolymer, a copolymer (II) obtained by copolymerizing a monomer composition containing 30-79wt.% epoxy-containing radical-polymerizable monomer, 10-50wt.% hydroxyl-containing radical-polymerizable monomer and the balance of other radical-polymerizable monomers (the percentages are based on monomer (II) and having an epoxy equivalent of 100-800, a hydroxy equivalent of 200-1,200 and a molecular weight of 1,000-8,000 and a quat. ammonium salt (III) as a curing catalyst.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosetting resin composition used for top coatings for automobiles, coatings for coil coatings, home electric appliances, plastics, electric materials and the like. In particular, it relates to a high solid content thermosetting resin composition which is non-toxic and has a long pot life, and a coating film forming method using the same.

[0002]

2. Description of the Related Art A combination of a hydroxyl group-containing polymer and a melamine resin curing agent is generally used as a top coating for automobiles. A coating film obtained from a coating material using the melamine resin curing agent generally has poor acid resistance, and a coating film defect may occur due to acid rain, which has become a big problem in recent years. This poor acid resistance is considered to be caused by the triazine nucleus in the melamine resin, and this drawback is accompanied as long as the melamine resin is used.

A curing system using a polyisocyanate compound has been proposed as a coating material which does not use a melamine resin, but has a problem of toxicity derived from isocyanate.

In order to remedy the above-mentioned drawbacks, the present inventors have already proposed a thermosetting composition containing a polymer containing a half ester of an acid anhydride group, a hydroxyl compound and an epoxy compound (JP-A-2- 45577). This composition eliminates the above-mentioned drawbacks and has excellent coating film performance, but further improvement in water resistance and weather resistance is desired.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to further improve the water resistance and weather resistance of the thermosetting composition already proposed by the present inventors.

[0006]

In order to achieve the above object, excellent effects can be obtained by using a half-esterified copolymer and a compound containing both an epoxy group and a hydroxyl group in the molecule. The present invention has been completed and the present invention has been completed.

That is, according to the present invention, (I) a radical-polymerizable monomer having an acid anhydride group and another copolymerizable monomer are formed in a copolymer, and then the acid anhydride group in the copolymer is half-converted. Copolymer having no acid anhydride group, obtained by esterification, (II) (i) 30 to 70% by weight of radical polymerizable monomer having epoxy group, (ii) radical polymerizable having hydroxyl group Epoxy equivalent obtained by copolymerizing a monomer composition containing 10 to 50% by weight of the monomer, and (iii) the balance of the other radically polymerizable monomer (however,% is based on the total amount of the monomer of the component (II)). Provided is a thermosetting resin composition containing 100 to 800, a copolymer having a hydroxy equivalent of 200 to 1200 and a molecular weight of 1,000 to 8,000, and (III) a quaternary ammonium salt as a curing catalyst.

The present invention also provides a method of forming a coating film on a substrate, which comprises applying a base coat, then applying a clear paint on the base coat by wet on wet, and then forming a coating film on the substrate to be cured. After forming a copolymer of a radically polymerizable monomer having an anhydride group and another copolymerizable monomer, an acid anhydride obtained by half-esterifying the acid anhydride group in the copolymer, an acid anhydride A copolymer having no physical group, (II) (i) 30 to 70% by weight of a radical polymerizable monomer having an epoxy group, (ii) 10 to 50% by weight of a radical polymerizable monomer having a hydroxyl group, and (iii) Epoxy equivalent of 100 to 800 and hydroxy equivalent of 20 obtained by copolymerizing a monomer composition containing the remaining amount of other radically polymerizable monomer (however,% is based on the total amount of monomer of component (II)). To 1,200, a molecular weight of 1,000 to 8,000, and (III) a coating film is formed on a substrate containing a thermosetting resin composition containing a quaternary ammonium salt as a curing catalyst. Provide a way.

Radical-polymerizable monomers containing an acid anhydride group for forming the copolymer (I) include itaconic anhydride, maleic anhydride, citraconic anhydride and the like.

Further, other copolymerizable monomers include styrene, α-methylstyrene and acrylic acid esters.
(For example, methyl acrylate, ethyl acrylate, propyl acrylate, acrylate-n, i, and t-butyl,
2-ethylhexyl acrylate, lauryl acrylate, etc.), methacrylic acid esters (eg, methyl methacrylate, ethyl methacrylate, propyl methacrylate, methacrylic acid-n, i, and t-butyl, 2-methacrylic acid)
Ethylhexyl, lauryl methacrylate, etc.), acrylamide, methacrylamide, etc.

In the composition of the reaction product in the copolymerization reaction, the radical-polymerizable monomer containing the acid anhydride group is preferably 10 to 40% by weight, more preferably 15 to 30% by weight, based on all the monomers.

The copolymerization is carried out by a known method, for example, solution polymerization such as radical polymerization. The number average molecular weight of the copolymer is 500 to 40,000, particularly 1,000 to 20,000.
0 is preferred. If it is more than 40,000, the viscosity of the copolymer becomes high, and it is difficult to obtain a high solid content thermosetting composition. If it is less than 500, the curability is insufficient.
The molecular weight is determined by the GPC method. The acid anhydride group has at least two, preferably 2 to 15 in one molecule. If it is less than 2, the curability is insufficient.

Half-esterification is carried out after polymerization. The half-esterifying agent used for the half-esterification is a low molecular weight alcohol, specifically, methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, t-butanol,
Methyl cellosolve, ethyl cellosolve, dimethylaminoethanol, diethylaminoethanol, acetol,
Examples include allyl alcohol and propargyl alcohol.
Particularly preferred compounds are acetol, allyl alcohol, propargyl alcohol, and methanol.

The half-esterification reaction is carried out according to a conventional method at a temperature of room temperature to 120 ° C. in the presence of a catalyst. Examples of the catalyst include tertiary amines (such as triethylamine and tributylamine) and quaternary ammonium salts (such as benzyltrimethylammonium chloride, benzyltrimethylammonium bromide, benzyltributylammonium chloride and benzyltributylammonium bromide). To be

Copolymer blended in the resin composition of the present invention
(II) has 2 to 10 epoxy groups, preferably 3 to 8 epoxy groups, and 2 to 12 hydroxyl groups, preferably 4 to 8 epoxy groups in the molecule.
I have 10. The epoxy equivalent is 100 to 800, preferably 200 to 600, and the hydroxy equivalent is 200 to
It is 1,200, preferably 400 to 1,000. If the epoxy equivalent is smaller than the above lower limit, the curability is insufficient,
On the other hand, if it exceeds the upper limit, it becomes too hard and the weather resistance deteriorates, which is not preferable. Further, if the hydroxy equivalent is less than 200, the water resistance of the cured coating film is not sufficient, and conversely, if it exceeds 1,200, a high solid content is unlikely to occur, which is not preferable.

The copolymer (II) comprises (i) 30 to 70% by weight of a radical polymerizable monomer having an epoxy group, (ii) 10 to 50% by weight of a radical polymerizable monomer having a hydroxyl group, and (iii) another radical. Epoxy equivalent 100-800 obtained by copolymerizing a monomer composition containing the remaining amount of the polymerizable monomer (however, based on the total amount of the monomer), hydroxy equivalent 200-1200, molecular weight 500-40,00.
It has 0.

Examples of the monomer (i) include (meth)
Examples thereof include glycidyl acrylate and 3,4-epoxycyclohexanyl methyl methacrylate.

Examples of the above-mentioned monomer (ii) include (meth)
2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate, Praxel FM-1 (manufactured by Daicel) and the like can be mentioned.

Examples of the other monomer (iii) include those exemplified as the "other copolymerizable monomer" in the copolymer (I).

The copolymer (II) comprises the monomers (i) to
(iii) and radical polymerization initiator (this may be one commonly used in radical polymerization, and examples thereof include t-butylperoxy 2 ethylhexanoate and dimethyl 2,2′-azobisisobutyrate). It is obtained by radical polymerization of a monomer composition containing In the composition of the monomer composition, the amounts of the monomers (i) to (iii) are 30 to 70% by weight, 10 to 50% by weight, and the remaining amount based on the total amount of all the monomers.
Further, the radical polymerization initiator is used in an amount of 3 to 15 with respect to all monomers.
wt% is preferred. A chain transfer agent or the like may be added to the monomer composition as other additives.

The copolymerization reaction for forming the copolymer (II) may be carried out by an ordinary radical polymerization method at a polymerization temperature of 100 to 140.
The polymerization can be performed at a temperature of 3 ° C. for 3 to 8 hours.

Copolymer (II) obtained as described above
Is an epoxy equivalent of 100 to 800, preferably 200 to 6
00, hydroxy equivalent 200 to 1200, preferably 400 to 1000, and molecular weight 500 to 40,000,
It preferably has 1,000 to 20,000.

The resin composition of the present invention usually contains a curing catalyst (I
II) is included. The curing catalyst may be one normally used in the esterification reaction (reaction of acid / epoxy), but it is specifically a quaternary ammonium salt. More specifically, in addition to the quaternary ammonium salt exemplified in the above copolymer (I),
Examples thereof include benzyltriethylammonium chloride or bromide, tetrabutylammonium chloride or bromide.

In addition, a melamine-formaldehyde resin may be added to the resin composition of the present invention in order to increase the crosslink density and improve the water resistance. In addition, orthoesters (eg, ethyl orthoformate or methyl, ethyl orthoacetate or methyl, etc.) may be added as a means for extending the pot life. In addition, in order to improve the weather resistance of the coating film, TINUVIN-900 (manufactured by Ciba Geigy), Sanol L
S-292 (manufactured by Sankyo Co., Ltd.) or the like may be added. Further, a microgel or a surface conditioner may be added as a rheology control agent. Further, alcohol-based solvents (eg, methanol, ethanol, propanol, butanol, etc.), hydrocarbons, esters, etc. may be used as diluents for adjusting the viscosity.

Since the resin used in the present invention has an acid group as a functional group, it can be neutralized with an amine to form an aqueous resin composition using water as a medium.

In the composition of the resin composition of the present invention, the total number of epoxy groups of the copolymer (II) / the total number of half-esterified acid anhydride groups of the copolymer (I) = 0.5 to 1. 5, particularly preferably 0.6 to 1.2, and the copolymer (II)
Total number of hydroxyl groups / total number of half-esterified acid anhydride groups of copolymer (I) = 0.1 to 1.5, particularly 0.3 to 1.2
It is preferred that Specifically, the blending amount of the copolymer (II) that gives such a ratio is, for example, 100% of the copolymer (I).
50 to 250 parts by weight, and particularly 80 to 150 parts by weight, are preferred with respect to parts by weight. When the amount of the copolymer (II) used is less than 50 parts by weight, sufficient curing cannot be performed and the water resistance and weather resistance of the cured coating film are deteriorated, which is not preferable. On the other hand, if it exceeds 250 parts by weight, unreacted carboxyl groups remain and the chemical resistance decreases, which is not preferable. The compounding amount of the curing catalyst is preferably 0.01 to 1.0 wt% with respect to the resin solid content. Also, melamine
Addition amount of formaldehyde resin is 2 to resin solid content
30% by weight, especially 5 to 15% by weight is preferred. Furthermore, the diluent is preferably up to 60% by weight, particularly preferably 20 to 55% by weight, based on the total weight of the resin composition containing the diluent.

The thermosetting resin composition of the present invention may be formulated as a clear coating composition, or they may be blended with a pigment to give an enamel coating. As a secondary effect, the modified polymer of the acid anhydride group has excellent pigment dispersibility by being amphoterized by having an acid and an amine in the molecule when modified with dimethylaminoethanol, for example. . The pigment may be of any conventional type, for example, iron oxide, lead oxide, strontium chromate, carbon black, coal dust, titanium dioxide, talc, barium sulfate, cadmium yellow, cadmium red, chrome yellow and It may be a metallic pigment, such as aluminum flakes. Further, it may be an organic pigment, and examples thereof include phthalocyanine blue and Shinkashia red. And pearl mica can also be used.

The pigment content in paints is usually expressed as the weight ratio of pigment to non-volatile content of the coating composition. In the practice of this invention, the pigment to coating composition has a nonvolatile weight ratio of 2:
It may be as high as 1, often in the range of 0.05 to 1: 1.

The method for preparing the thermosetting resin composition of the present invention is not particularly limited, and the above-mentioned compounding agents (I) to (III), the above-mentioned additives as required, and a pigment in the case of an enamel paint are used. It may be carried out by kneading with a kneader or roll.

The coating composition of the present invention may be applied by spray coating, brush coating, dip coating, roll coating, flow coating or the like. The coating method when the resin composition of the present invention is used as a clear coating may be a usual method,
After the base coat is applied on a suitable substrate, the base coat may be applied so-called wet-on-wet.
The base coat paint may be either water-based or oil-based, but if a water-based paint is used, the base coat should be pre-coated at 60 to 100 ° C. before applying the clear paint in order to obtain a good-finished coating film. It is preferable to heat for 10 minutes.

The coating composition of the present invention may be used on essentially any substrate, such as wood, metal, glass, cloth, plastics, foams, or various primer surfaces. In particular, the coating is advantageous for plastic and metal surfaces such as steel and aluminum.

Generally, the film thickness will vary depending on the desired application. Often 0.5-3 mils are useful.

After coating the base material, the coating film is cured. Curing is performed at 100 to 180 ° C, preferably 120 ° C to 160 ° C to obtain a cured coating film having a high degree of crosslinking. The curing time varies depending on the curing temperature and the like, but curing at 120 ° C to 160 ° C for 10 to 30 minutes is suitable.

[0034]

When a polymer containing an acid anhydride group is simply used, the reaction with the active hydrogen compound proceeds even at around room temperature, so that it is not suitable to store it in the same system because it causes gelation. In the case of the present invention, since the acid anhydride group is modified (half-esterification), even if the active hydrogen compound is mixed, further reaction does not occur, and one-liquefaction (one-pack formation) is possible.

Further, in the curing reaction with the copolymer (II), the curing rate can be changed by variously changing the acid anhydride group-modifying agent, and a coating film having an excellent appearance can be obtained. Can be formed.

In the curing reaction of the resin composition of the present invention, first, the half-esterified and ring-opened acid anhydride-modified group in the copolymer (I) is closed again at the curing temperature to undergo acid anhydride. Return to the basics once. Then, the acid anhydride group and the copolymer (II)
The hydroxyl group therein reacts again to form a half ester, and the remaining carboxylate group reacts with the epoxide group in the copolymer (II) to form a diester to proceed with curing. That is, the curing reaction is carried out by bonding two groups, an epoxy group and a hydroxyl group, in the copolymer (II) to a carboxyl group and an ester group, which are acid anhydride-modifying groups in the copolymer (I), respectively. Therefore, the cured product has a solid structure and is excellent in weather resistance and chemical resistance.

Further, in the present invention, it is not necessary to use a basic resin such as a melamine resin, and therefore the cured film has excellent acid resistance.

Furthermore, the resin composition of the present invention can be water-solubilized and can be an effective coating composition in terms of pollution control.

[0039]

EXAMPLES The present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1 (Synthesis of Polymer Containing Epoxy Group and Hydroxyl Group) 500 parts by weight of butyl acetate were charged into a 2 liter reaction vessel equipped with a thermometer, a stirrer, a cooling tube, a nitrogen introducing tube, and a dropping funnel, and 125 ° C. The temperature was raised to.

The dropping funnel comprises 50 parts of styrene monomer, 400 parts of glycidyl methacrylate, 350 parts of 2-hydroxyethyl methacrylate, 200 parts of 2-ethylhexyl acrylate, and 70 parts of t-butylperoxy 2-ethylhexanoate. The monomer and initiator solutions were added dropwise over 3 hours. After the dropping was completed, the mixture was kept at 125 ° C. for 30 minutes and then t-butylperoxy 2-ethylhexanoate 1
A solution consisting of 0 part and 250 parts of xylene was added dropwise over 30 minutes. After the dropping was completed, the reaction was continued for another 2 hours at 125 ° C. to obtain an acrylic resin varnish having a nonvolatile content of 59% and a number average molecular weight of 4,000.

Examples 2 to 8 Each acrylic resin varnish was synthesized in the same manner as in Example 1 except that each compounding agent having the composition shown in Table 1 was used. The characteristic values of the obtained resin varnish are shown in Table-1.

[0043]

[Table 1]

Production Example 1 Synthesis of Polymer AI Containing Carboxylic Anhydride Group 80 parts by weight of xylene was charged into a 1 liter reaction vessel equipped with a thermometer, a stirrer, a cooling tube, a nitrogen introducing tube and a dropping funnel.
The temperature is raised to 15 ° C., and 25 parts by weight of styrene, 21 parts by weight of n-butyl acrylate, 95 parts by weight of n-butyl methacrylate, 34 parts by weight of 2-ethylhexyl methacrylate, 50 parts by weight of itaconic anhydride, 100 parts by weight of propylene glycol monomethyl ether acetate. Part, and a monomer consisting of 10 parts by weight of t-butylperoxy-2-ethylhexanoate and an initiator solution were added dropwise over 3 hours, and stirring was continued for 2 hours, and the nonvolatile content was 53% and the number average molecular weight was 5, 500 acrylic resin varnishes were obtained.

Production Examples 2 to 5 Polymers A-II to AV containing carboxylic acid anhydride groups
To obtain a polymer containing carboxylic anhydride groups with the ingredients shown in Table 2 in the same manner as formed in Production Example 1.

[0046]

[Table 2]

Production of Half-Esterified Polymer Production Example 6 To 385 parts of Polymer A-I obtained in Production Example 1, 1.35 parts of triethylamine dissolved in 35 parts of butyl acetate and 18.2 parts of methanol were added at 40 ° C. The reaction was carried out for 12 hours to obtain polymer A-VI. Absorption of acid anhydride group by IR (17
It was confirmed that 85 cm ^-1 ) completely disappeared.

Production Examples 7 to 12 Half esterified polymers VII to XII were obtained in the same manner as in Production Example 6 with the formulations shown in Table 3. As a result of investigating the obtained varnish by IR, it was confirmed that the absorption of the acid anhydride group had disappeared.

[0049]

[Table 3]

Preparation of Clear Paint Example 9 A clear paint was prepared with the following composition, and the performance of the resulting coating film was evaluated. Varnish obtained in Example 1 100 parts Varnish obtained in Production Example 6 (Polymer A-VI) 133.0 parts Tetrabutylammonium bromide 0.3 part Tinuvin-900 1.2 parts Sanol LS-299 0.6 Part 235.1 part

The obtained clear paint was diluted to a paint viscosity with a thinner composed of butyl acetate / xylene = 1/1.
Processed by coating Nippon Paint Co., Ltd. Power Top U-30 and Olga P-2 on phosphoric acid-treated steel plate, Nippon Paint Co., Ltd. Superlac H-90 metallic base is applied, and then the above is cleared by wet on wet. Was applied and baked at 140 ° C. for 30 minutes. The coating film evaluation results are shown in Table-5.

Examples 10 to 16 In the same manner as in Example 9, clear paints were prepared with the formulations shown in Table 4 and the coating film performance was evaluated. The evaluation results are shown in Table-5.

[0053]

[Table 4]

[0054]

[Table 5]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C09D 163/00 PJK C09D 163/00 PJK (72) Inventor Seigo Miyazoe 19 Ikedanaka-cho, Neyagawa-shi, Osaka No. 17 Japan Paint Co., Ltd. (72) Inventor Koichi Hagiwara 19-17 Ikedanaka-cho, Neyagawa-shi, Osaka Japan Paint Co., Ltd. (72) Hiroshi Miwa 19-17 Ikedanaka-cho, Neyagawa-shi, Osaka Japan Inside Paint Co., Ltd.

Claims (2)

[Claims] 1. After forming a copolymer of (I) a radical-polymerizable monomer having an acid anhydride group and another copolymerizable monomer, the acid anhydride group in the copolymer is half-esterified. The resulting copolymer having no acid anhydride group, (II) (i) 30 to 70% by weight of the radical polymerizable monomer having an epoxy group, and (ii) the radical polymerizable monomer having a hydroxyl group 10 To 50% by weight, and (iii) an epoxy equivalent of 100 to 100 obtained by copolymerizing a monomer composition containing the balance of other radically polymerizable monomers (however,% is based on the total amount of monomers of component (II)). A thermosetting resin composition containing 800, a copolymer having a hydroxy equivalent of 200 to 1,200, a molecular weight of 1,000 to 8,000, and (III) a quaternary ammonium salt as a curing catalyst. 2. A method of forming a coating film on a substrate, which comprises applying a clear coat on the base coat by wet-on-wetting after applying a base coat and then forming a coating film on a substrate to be cured, wherein the clear paint comprises (I) an acid anhydride group. After forming a copolymer of a radically polymerizable monomer having and another copolymerizable monomer, an acid anhydride group obtained by half-esterifying the acid anhydride group in the copolymer, Copolymer not having (II) (i) 30 to 70% by weight of radically polymerizable monomer having an epoxy group, (ii) 10 to 50% by weight of radically polymerizable monomer having a hydroxyl group, and (iii) other radical Epoxy equivalent of 100 to 800 and hydroxy equivalent of 200 to 1200 obtained by copolymerizing a monomer composition containing the remaining amount of the polymerizable monomer (however,% is based on the total amount of the monomer of the component (II)). Copolymer having a molecular weight of 1,000 to 8,000, and (III) a method of forming a coating on a substrate containing a thermosetting resin composition containing a quaternary ammonium salt as a curing catalyst.