JPH0832818B2 - Thermosetting resin composition - Google Patents

Description

The present invention relates to a thermosetting resin composition using a novel benzylpyridinium sulfonate that thermally cleaves to release a sulfonic acid as a thermal latent curing catalyst. Such a composition is useful as a vehicle for paints, adhesives, printing inks and the like. In a one-pack paint that uses an aromatic sulfonic acid, which is a proton donor, as a curing catalyst, the amine salt of sulfonic acid is blocked with a volatile amine in order to prevent an early curing reaction such as gelation of the paint during storage. Has been used. However, in such a sulfonic acid amine salt, there exists an equilibrium such as RSO ₃ ⁻・ H ⁺ N (R) ₃ > RSO ₃ ⁻ + H ⁺ N (R) ₃ > RSO ₃ ⁻ + H ⁺ + N (R) _3. Therefore, the amount of amine must be reduced in order to exert the effect of sulfonic acid at a relatively low temperature. Therefore, the amount of unblocked sulfonic acid increases, and the storage stability of the system decreases. When the amount of amine is increased to increase the storage stability, the amount of sulfonic acid that has become an amine salt also increases. Therefore, heating to a high temperature is necessary to exert the effect of sulfonic acid. As described above, in the system using the amine salt of sulfonic acid that has been conventionally used, it is difficult to achieve both control of the curing temperature and storage stability.

For example, a thermosetting resin composition composed of an acrylic resin, a polyester resin, an epoxy resin having a hydroxyl group and a melamine resin is widely used in the coating field.
These melamine resin-curing resin compositions contain a proton donor such as paratoluenesulfonic acid as a catalyst for the curing reaction. However, in a system containing a free acid, the resin tends to gel, and it is generally difficult to achieve both low-temperature curability and storage stability of the composition. Therefore, it has been proposed to use a compound obtained by blocking sulfonic acid with an amine as a catalyst, but its curability and storage stability have not always been satisfactory.

Therefore, the present invention is a thermosetting resin using a compound, which is stable up to the critical temperature near the curing temperature, but thermally cleaves when the critical temperature is reached and releases sulfonic acid to exert its catalytic effect. It is an object to provide a composition.

SUMMARY OF THE INVENTION The present invention provides a thermal latent curing catalyst of the formula The novel benzylpyridinium sulfonate of is used.

Wherein R ₁ , R ₂ , R ₃ and R ₆ are hydrogen, halogen, alkyl, alkoxy, nitro, amino, alkylamino, cyano, alkoxycarbonyl or carbamoyl, R ₄ and R ₅ are hydrogen, alkyl or halogen. And R ₇ is hydrogen or alkyl.

In terms of utilization, the present invention comprises: (a) a film-forming resin containing at least two hydroxyl groups per molecule; and (b) a solid content weight ratio of 50 to the hydroxyl group-containing resin.
A melamine resin in an amount of / 50 to 95/5, and (c) 0.01 to 10% by weight of the total amount of the hydroxyl group-containing resin and the melamine resin of the benzylpyridinium sulfonate in a solid content weight ratio. A thermosetting resin composition is provided.

The benzylpyridinium sulfonate compound is stable until it reaches a critical temperature and therefore does not exert the catalytic effect of sulfonic acid. However, when the temperature reaches the critical temperature, the bond between the benzyl group and the nitrogen atom is broken to generate a benzyl cation, which reacts with the OH group or water in the system to donate a proton, so that the sulfonic acid is supplied for the first time. It Therefore, the system containing the above-mentioned benzylpyridinium sulfonate compound as a catalyst does not cause a substantial curing reaction below the cleavage temperature of the compound, but the curing reaction proceeds only after heating above the cleavage temperature. Has stability.

Detailed Discussion I. Synthetic Formula of Benzylpyridinium Sulfonate The quaternary ammonium salt of The pyridine of the formula It can be produced by quaternizing with a benzyl halide of the formula (where X is halogen) and reacting the resulting halide anion of the pyridinium halide with the corresponding alkali metal salt of benzenesulfonic acid.

In the formula, R ₁ , R ₂ , R ₃ and R ₆ are hydrogen, halogen, alkyl,
It is selected from alkoxy, nitro, amino, alkylamino, cyano, alkoxycarbonyl or carbamoyl. R ₄ and R ₅ are selected from hydrogen, alkyl or halogen. R ₇ is hydrogen or alkyl having up to 20 carbons.

The pyridinium sulfonate of the formula (I) is cleaved to generate a corresponding carbonium cation when the temperature rises, and the cation reacts with an OH group or water in the system to donate a proton to the sulfonate anion, thereby to generate an acid. The sulfonic acid, which functions as a catalyst, is supplied for the first time.

The cleavage temperature of the quaternary ammonium of the formula (I) can be controlled by selecting the α-position of the benzyl group and the kind and position of the substituents on the benzene ring and the pyridine ring.

II. Systems containing melamine resin Film-forming resins using melamine resin as a curing agent are widely used in the paint field.

Examples thereof are polyester resin, polylactone resin, epoxy resin, acrylic resin and the like. The polyester resin is obtained by a condensation reaction of a polyhydric carboxylic acid or its acid anhydride with a polyhydric alcohol, and a resin having a hydroxy group at the terminal and / or in the middle of the polyester chain can be used. Hydroxyl terminated polylactone resins may also be used.

Examples of the epoxy resin include resins having an epoxide group at the terminal and a hydroxy group in the middle of the molecular chain, such as bisphenol type epoxy resin and / or novolac type epoxy resin.

The acrylic resin having a hydroxyl group includes a hydroxy group-containing monomer such as 2-hydroxyethyl (meth) acrylate, methyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, and (meth) acrylic acid. Alkyl (meth) acrylate such as 2-ethylhexyl; obtainable by copolymerization with styrene and its derivatives, other monomers such as (meth) acrylonitrile and vinyl acetate by a conventional method.

Melamine resins are prepared by reacting a triazine compound such as melamine, benzoguanamine or acetoguanamine with formaldehyde and optionally partially or completely etherifying the methylol group of the condensation product with a lower alkanol such as methanol and butanol. can get.

Thermosetting resin compositions obtained by combining a film-forming resin having a hydroxyl group and a melamine resin are well known in the coating field, and the composition of the present invention uses the above-mentioned thermocleavable pyridinium sulfonate as a catalyst for a curing reaction. Except for this, it may be the same as the known melamine resin-curable thermosetting composition.

The ratio of the film-forming resin having a hydroxyl group to the melamine resin may be 50/50 to 95/5 by weight.

The pyridinium sulfonate is added in an amount of 0.01 to 10% by weight, preferably 0.05 to 5.0% by weight, based on the resin solid content. If this amount is too small, the curability will decrease,
If it is excessive, the cured product will be colored and the water resistance will be deteriorated, which will adversely affect the appearance and physical properties.

The composition may contain additives such as pigments and fillers depending on its use.

The composition of the present invention does not cure below the cleavage temperature of the pyridinium sulfonate and thus has good storage stability,
Hardens when heated above the cleavage temperature. Although the curing time depends on the temperature, it is generally within 1 hour.

The invention is illustrated by the following examples. "Part" in the examples
And "%" are by weight.

I. Production example Synthesis of polyester resin Production example 1 Hexahydrophthalic acid 36 was added to a reaction vessel equipped with a heating device, a stirrer, a reflux device, a water separator, a rectification column and a thermometer.
, 42 parts of trimethylolpropane, 50 parts of neopentyl glycol and 56 parts of 1,6-hexanediol are charged and heated. When the raw material melts and stirring becomes possible, start stirring and raise the temperature to 210 ° C. The temperature is raised from 210 ° C to 230 ° C over a period of 2 hours at a constant temperature, and the condensed water produced is distilled out of the system.

When the temperature reaches 230 ° C, keep the temperature constant and cool with a resin acid value of 1.0. After cooling, 153 parts of isophthalic acid is added, and the temperature is raised to 190 ° C again. The temperature is raised from 190 ° C to 210 ° C over a period of 3 hours at a constant rate, and the condensation water produced is distilled out of the system. When 210 ℃ is reached, add 3 parts of Xylei to the reaction tank,
Switch to condensation in the presence of solvent and cool to a resin acid value of 5.0.

After cooling, 190 parts of xylene was added to obtain a polyester resin solution [A].

Synthesis of acrylic resin Production example 2 90 parts of Solvesso 100 was charged into a reaction vessel equipped with a stirrer, thermometer, reflux condenser, N2 gas inlet pipe and dropping funnel, and the temperature was raised to 160 ° C while introducing N2 gas. After heating, a mixture of 23.2 parts of 2-hydroxyethyl methacrylate, 35.65 parts of n-butyl acrylate, 40.15 parts of methyl methacrylate, 1.0 part of methacrylic acid and 10 parts of tert-butyl peroxy-2-ethylhexanoate is added dropwise. It was dropped at a constant speed on a funnel.

1 hour after the dropping of the mixture was completed, 10 parts of xylene and
tert-butylperoxy-2-ethylhexanoate 1
Part of the mixture was added dropwise at a constant rate over 30 minutes. After completion of the dropping, the mixture was aged for 2 hours and then cooled to obtain an acrylic resin [A].

Example 1 Cymel 303 to 70 parts of Praxel 308 (trifunctional polycaprolactone polyol manufactured by Daicel, molecular weight 860)
(Mitsui Toatsu Co., Ltd. melamine resin) 30 parts and 4-methylbenzyl-4-cyanopyridinium-p-dodecylbenzenesulfonate 2 parts were added and mixed, and then applied to a tin plate.
Baking was performed at 0 ° C. to obtain a cured coating film. The curing reactivity and the storage stability test of the mixed solution were conducted under the conditions shown in Table 1, and Table 1
The results shown in are obtained.

Example 2 Cymel 303 to 70 parts of Praxel 308 (trifunctional polycaprolactone polyol manufactured by Daicel, molecular weight 860)
(Mitsui Toatsu Co., Ltd. melamine resin) 30 parts and 4-chlorobenzyl-2-methylpyridinium-p-dodecylbenzenesulfonate 5 parts were added and mixed, and applied to a tin plate. 14
Baking was performed at 0 ° C. to obtain a cured coating film. The following investigation was performed in the same manner as in Example 1.

Example 3 Cymel 303 to 50 parts of Praxel 308 (trifunctional polycaprolactone polyol manufactured by Daicel, molecular weight 860)
(Mitsui Toatsu Co., Ltd. melamine resin) 50 parts and 2,4-dichlorobenzyl-2-methylpyridinium-p-dodecylbenzenesulfonate 2 parts are added and mixed, and the mixture is applied to a tin plate and baked at 140 ° C. for curing coating. A film was obtained. The following investigation was performed in the same manner as in Example 1.

Example 4 Cymel 303 to 90 parts of polyester resin A solid content
(Mitsui Toatsu Co., Ltd. melamine resin) 10 parts and 2-methylbenzyl-2-methylpyridinium-p-dodecylbenzenesulfonate 2 parts were added and mixed, and then applied to a tin plate 14
Baking was performed at 0 ° C. to obtain a cured coating film. The following investigation was performed in the same manner as in Example 1.

Example 5 Polyester Resin A Uban 20 to 60 parts solid content
SE (melamine resin manufactured by Mitsui Toatsu Co., Ltd.) 40 as resin solids
Parts and 1,4-dimethylbenzyl-2-chloropyridinium-p-toluenesulphonate (1 part) were added and mixed, coated on a tin plate and baked at 140 ° C. to obtain a cured coating film. The following investigation was performed in the same manner as in Example 1.

Example 6 Polyester Resin A Uban 20 to 70 parts solid content
SE (melamine resin manufactured by Mitsui Toatsu) as resin solid content 30
Parts and 4-methoxybenzyl-3-chloropyridinium-p-toluenesulfonate 2 parts were added and mixed, coated on a tin plate and baked at 140 ° C. to obtain a cured coating film. The following investigation was performed in the same manner as in Example 1.

Example 7 Polyester Resin A Uban 20 to 60 parts solid content
SE (melamine resin manufactured by Mitsui Toatsu Co., Ltd.) 40 as resin solids
Parts and 2 parts of N- (α, α-dimethylbenzyl) -pyridinium-p-dodecylbenzene sulfonate were added and mixed, coated on a tin plate and baked at 140 ° C. to obtain a cured coating film. The following investigation was performed in the same manner as in Example 1.

Example 8 Polyester Resin A Uban 20 to 70 parts solid content
SE (melamine resin manufactured by Mitsui Toatsu) as resin solid content 30
Parts and N- (α-methylbenzyl) -pyridinium-p
-Add 2 parts of dodecylbenzene sulfonate and mix,
It was applied to a tin plate and baked at 140 ° C to obtain a cured coating film. The following investigation was performed in the same manner as in Example 1.

Example 9 Acrylic resin A Cymel 303 to 90 parts of solid content
(Mitsui Toatsu's melamine resin) 10 parts and benzyl-2-
2 parts of methylpyridinium-p-dodecylbenzene sulphonate was added and mixed, coated on a tin plate and baked at 140 ° C. to obtain a cured coating film. The following investigation was performed in the same manner as in Example 1.

Example 10 Acrylic resin A Euban 20SE for 60 parts of solid content
(Mitsui Toatsu pressure melamine resin) as a resin solid content of 40 parts and 2-chlorobenzyl-2-cyanopyridinium-p
-Toluene sulphonate (0.1 part) was added and mixed, coated on a tin plate and baked at 140 ° C to obtain a cured coating film. The following investigation was performed in the same manner as in Example 1.

Example 11 Acrylic resin A Euban 20SE for 70 parts of solid content
(Mitsui Toatsu pressure melamine resin) as a resin solid content of 30 parts and 4-methoxybenzyl-4-chloropyridinium-
Two parts of p-toluene sulphonate were added and mixed, coated on a tin plate and baked at 140 ° C. to obtain a cured coating film. The following investigation was performed in the same manner as in Example 1.

Example 12 Acrylic resin A Cymel 303 to 90 parts of solid content
(Mitsui Toatsu Co., Ltd. melamine resin) 10 parts and N- (α-methylbenzyl) -4-cyanopyridinium-p-dodecylbenzene sulfonate 2 parts were added and mixed, coated on a tin plate and baked at 140 ° C. A cured coating film was obtained. Example 1 below
The same examination was carried out.

Example 13 Acrylic Resin A Uban 20SE for 70 parts solid content
(Mitsui Toatsu Co., Ltd. melamine resin) as a resin solid content of 30 parts and N- (α, α-dimethylbenzyl) -4-methylpyridinium-p-dodecylbenzene sulfonate 2 parts were added and mixed to obtain a tin plate. It was applied and baked at 140 ° C. to obtain a cured coating film. The following investigation was performed in the same manner as in Example 1.

Comparative Example 1 Cymel 303 to 70 parts of Praxel 308 (Daicel's trifunctional polycaprolactone polyol, molecular weight 860)
(Mitsui Toatsu Co., Ltd. melamine resin) 30 parts and p-toluenesulphonic acid triethylamine salt 2 parts were added and mixed, and the mixture was coated on a tin plate and baked at 140 ° C to obtain a cured coating film. The curing reactivity and the storage stability test of the mixed solution were conducted under the conditions shown in Table 1, and the results shown in Table 1 were obtained.

Comparative Example 2 Polyester Resin A Cymel 30 to 90 parts solid content
3 parts of melamine resin manufactured by Mitsui Toatsu Co., Ltd. and 2 parts of pyridine salt of p-dodecylbenzenesulphonic acid were added and mixed, coated on a tin plate and baked at 140 ° C. to obtain a cured coating film. The following investigation was performed in the same manner as in Example 1.

Comparative Example 3 Acrylic resin A Euban 20SE for 60 parts solid content
(Melamine resin manufactured by Mitsui Toatsu Co., Ltd.) as a resin solid content, 40 parts and 2 parts of p-toluenesulphonic acid pyridine salt were added and mixed, and the mixture was applied to a tin plate and baked at 140 ° C. to obtain a cured coating film. The following investigation was performed in the same manner as in Example 1.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshio Eguchi 19-17 Ikedanaka-cho, Neyagawa-shi, Osaka (56) Reference JP-A-2-178319 (JP, A)

Claims (2)

[Claims] 1. (a) a film-forming resin containing at least two hydroxyl groups per molecule; and (b) a solid content weight ratio of 50 to the hydroxyl group-containing resin.
Melamine resin in an amount of / 50 to 95/5, and (c) a formula of 0.01 to 10% by weight of the total amount of the hydroxyl group-containing resin and melamine resin in the solid content weight ratio. (Wherein R ₁ , R ₂ , R ₃ and R ₆ are hydrogen, halogen, alkyl, alkoxy, nitro, amino, alkylamino, cyano, alkoxycarbonyl or carbamoyl, and R ₄ and R ₅ are hydrogen, alkyl or halogen. And R ₇ is hydrogen or alkyl.) Benzylpyridinium sulfonate. 2. The thermosetting resin composition according to claim 1, wherein the hydroxyl group-containing resin is a hydroxyl group-containing polyester resin, a hydroxyl group-terminated polylactone resin, an epoxy resin, or a hydroxyl group-containing acrylic resin.