JPH0625327B2 - Yellow-free variable-speed dry urethane resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a novel and useful yellow-free variable-speed dry type urethane coating resin composition, more specifically, for automobile coating (repair), building, A resin composition that can be used in the coating field for various materials to be coated such as building materials, electrical products or bridges, and that has a particularly excellent weather resistance and is a combination of a specific polyisocyanate and a specific acrylic polyol. Regarding things.

[Conventional technology]

Conventionally, a two-component non-yellowing urethane coating consisting of polyisocyanate which is a curing agent and acrylic polyol which is a main component is an extremely useful industrial material because it gives a coating film excellent in weather resistance, durability, mechanical properties and chemical resistance. Known to be.

However, conventional non-yellowing urethane paint takes a long time to dry (cure) when it is applied at room temperature, and dust adheres to it during that time to significantly reduce the finished appearance, resulting in a remarkable commercial value. It had a serious drawback in practical use such as damage.

That is, as the non-yellowing curing agent, usually, a polyol such as trimethylolpropane and an adduct type polyisocyanate which is an adduct of hexamethylene diisocyanate, or a biuret type polyisocyanate obtained from water and hexamethylene diisocyanate is used. However, these curing agents require a long drying time when used in combination with an acrylic polyol for non-yellowing urethane coatings.

As a method for improving such drawbacks, a method of using a curing agent having a high softening point derived from isophorone diisocyanate is partially adopted, but this type of curing agent has extremely low reactivity and also has a softening point. It is well known that cross-linking and hardening of the coating film is difficult to proceed due to the high value, and therefore the coating film performance is remarkably deteriorated.

Although attempts have been made to add a curing-accelerating catalyst to the above-mentioned slow-drying curing agent, such a method is a process that significantly reduces the pot life of the coating, and therefore it is unavoidable that it seriously hinders the coating work. I don't get it.

On the other hand, the softening point of the acrylic polyol used as the main ingredient is extremely increased by using a large amount of hard monomers such as styrene and methyl methacrylate, and in addition, a method of improving apparent dryness is also partially tried. However, such a method hinders the cross-linking and curing of the coating film, impairs the solvent resistance of the coating film, and significantly reduces the mechanical properties.

Furthermore, recently, a polyisocyanate having an isocyanurate ring has been developed as a non-yellowing curing agent, and although the drying property is improved as compared with the above-mentioned curing agents, the compatibility with acrylic polyol is remarkably high. It is inferior and therefore not practical.

[Problems to be solved by the invention]

As described above, the conventional technology of non-yellowing urethane paint is practically
It had serious drawbacks.

After all, as long as the conventional technique is followed, the reality is that no urethane coating that does not turn yellow, is quick-drying, and has good coating workability cannot be found.

Therefore, the problem to be solved by the present invention is to solve the above-mentioned technical present situation and solve the technical problem in a short time.

[Means for solving problems]

As described above, the inventors of the present invention have conducted extensive studies to overcome the drawbacks of the conventional non-yellowing urethane coating that it takes a long time to dry and the various problems associated with the coating work. It came to completion.

That is, the present invention has, as an essential component, a diisocyanate compound selected from the group consisting of alkylene, cycloalkylene- and aralkylene diisocyanate and a molecular weight having at least 3 hydrocarbon substituents in one molecule.
A polyisocyanate having an isocyanurate ring obtained by reacting 100 to 1,000 diol in the presence of an isocyanurate-forming catalyst, and a number average molecular weight of 2,000 to 30,000
And a yellow-free variable-speed dry urethane coating composition comprising an acrylic polyol having a hydroxyl value of 20 to 200, and the coating resin composition is capable of satisfactorily solving the conventional problems. You can

Here, first, as typical examples of the alkylene diisocyanate which is a constituent element of the present invention, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,2,4- or 2,4,4-trimethyl hexaisocyanate is used. Examples thereof include methylene diisocyanate, 2,6-diisocyanate methylcaproate (lysine diisocyanate), and mixtures thereof. Typical examples of cycloalkylene diisocyanates include 1,3-
Or 1,4-diisocyanate cyclohexane,
1,3- or 1,4-bis (isocyanatomethyl) -cyclohexane, dicyclohexylmethane-4,
4'-diisocyanate, isopropylidene-pis (4
-Cyclohexyl isocyanate), 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate), or a mixture thereof. Typical examples of the aralkylene diisocyanate include xylylene diisocyanate and
Tetramethylxylylene diisocyanate or 4,
4'-bis (isocyanatomethyl) -diphenylmethane or a mixture thereof may be used.

On the other hand, as typical examples of diols having three or more hydrocarbon substituents in one molecule and having a molecular weight of 100 to 1,000, 1,
2,2-trimethyl-1,3-propanediol (2,2
2-dimethyl-1,3-butanediol), 2,2-dimethyl-3-isopropyl-1,3-propanediol (2,2,4-trimethyl-1,3-pentanediol), 2,2-dimethyl -3-Pendyl-1,3-propanediol (2,2-dimethyl-4-phenyl-1,
3-Putanediol), 2,2-dimethyl-3-isobutyl-1,3-propanediol (2,2,4-trimethyl-1,3-hexanediol), 2,2,3,3-
Tetramethyl-1,4-butanediol, 2,2,4-
Trimethyl-1,5-pentanediol, 2,2,4-
Trimethyl-1,6-hexanediol or 2,
4,4-trimethyl-1,6-hexanediol or a mixture thereof may be used.

Each of the above-mentioned diisocyanate compounds used in the present invention can be used alone or in combination of two or more as long as they are included in the range of each group, and a non-yellowing urethane having excellent drying property. It can be a polyisocyanate as a curing agent for paints.

However, in the case where the balance of physical properties such as mechanical properties and weather resistance is particularly taken into consideration while keeping the drying property of the curing agent optimum, 85-55 / 15-45 (weight ratio) of alkylene diisocyanate and cycloalkylene diisocyanate is used. It is extremely effective to use them together within the range.

Similarly, the combined use of alkylene diisocyanate and aralkylene diisocyanate in the range of 95 to 70/5 to 30 (weight ratio) is also effective in keeping the drying property or other performance of the curing agent optimum.

Further, cycloalkylene diisocyanate, especially isophorone diisocyanate, is particularly inferior in reactivity of the isocyanate group. Therefore, exceptionally, it is desirable to use the cycloalkylene diisocyanate not to be used alone but to be used in combination within the above range.

Molecular weight with 3 or more hydrocarbon substituents in one molecule 10
For example, Japanese Patent Application No. 59-3835 can be used for diols of 0 to 1,000.
As described in No. 6, the polyisocyanate having an isocyanurate ring does not impair the excellent drying property (curability) inherently possessed by the polyisocyanate, and the compatibility with the acrylic polyol, which is a drawback of the polyisocyanate, is remarkably high. It is extremely effective in improving. The amount of the diol used is suitably in the range of 0.3 to 30 mol% with respect to the total amount of the diisocyanate compound used,
It is more preferable to be in the range of 3 to 20 mol%, which is particularly desirable from the viewpoint of keeping the isocyanate content of the polyisocyanate high.

The use of ordinary diols such as propylene glycol and 1,3-butanediol is not preferable because it significantly impairs the drying property of polyisocyanate.

The same applies to monoalcohols and trifunctional or higher functional polyols, and the latter is not preferable because the latter causes the polyisocyanate to have too high a functionality and unnecessarily increases the viscosity of the polyisocyanate.

However, a small amount of monoalcohol, triol, or the like mixed or used in combination with the diol used in the present invention is acceptable as long as the characteristics of the polyisocyanate are not impaired.

The isocyanurate-forming catalyst that can be used in the present invention is preferably a compound containing an atom (group) having a low electron density and a strong cationic property, and examples thereof include N, N, N.
-Trimethyl, N-2-hydroxypropylammonium paratertiary-pentylpensoate [I], sodium ethylate, sodium propiate, etc. may be mentioned. Since the catalyst of (1) is easy to purify, it is suitable for the production of polyisocyanate.

However, the isocyanurate-forming catalyst is not particularly limited to the compound represented by the above formula, and any catalyst can be used as long as it is effective for isocyanurate-forming.

Incidentally, the catalyst is usually a diluted solution with an organic solvent,
It is preferable to use an amount in the range of 10 to 1000 PPm, preferably 20 to 500 PPm, based on the diisocyanate compound.

The isocyanurate-forming reaction carried out when obtaining the polyisocyanate having an isocyanurate ring used in the present invention is usually carried out at a temperature range of 30 to 120 ° C., preferably 40 to 100 ° C. The conversion of 20 to 70 is based on the total charged amount of each diisocyanate compound and diol described above.
It is good to carry out in the range of 30% by weight, preferably 30 to 65% by weight. When the conversion rate is 70% or more, the molecular weight of the polyisocyanate produced becomes too high and the solubility is lowered, which is not preferable.

The reaction mixture after the reaction is terminated by deactivating the contained catalyst with a compound such as phosphoric acid, monochloroacetic acid, and dodecylpentenesulfonic acid, and then subjected to a method such as molecular distillation to remove the unreacted diisocyanate compound. , Polyisocyanate can be obtained.

The isocyanurate ring-containing polyisocyanate thus obtained usually has a number average molecular weight of 550 to 1,200,
Further, it is preferable that the isocyanate content in the solution diluted to 75% by weight with the organic solvent is in the range of 10 to 17%.

As the diluting solvent for the polyisocyanate, various organic solvents which are inert to isocyanate groups, such as ethyl acetate, butyl acetate, toluene, xylene, and cellosolve acetate, are used.

The above-mentioned acrylic polyol having a number average molecular weight of 2,000 to 30,000 and a hydroxyl value of 20 to 200, which is another constituent of the present invention, is an ethylene-based carbonization represented by the following general formulas [II] to [V]. It has a hydrogen derivative as a main component and is obtained by radical polymerization of these derivatives.

First, the general formula Examples of the compound represented by include styrene, α-methylstyrene, p-methylstyrene, p-methoxystyrene, paratertiarybutylstyrene, and the like.

Then the general formula As the compound represented by, methyl methacrylate,
Examples thereof include n-butyl methacrylate, iso-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate and 2-ethoxyethyl acrylate.

Also, the general formula [However, R ₃ in the formula is as described above. ] As a compound shown by these, beta-hydroxyethyl methacrylate, beta-hydroxypropyl methacrylate, beta-hydroxyethyl acrylate, etc. can be mentioned.

Furthermore, the general formula Examples of the compound represented by: diethyl fumarate, di-
Examples thereof include n-butyl fumarate, diisobutyl fumarate and di-2-ethylhexyl fumarate.

Furthermore, each of the above-mentioned general formulas [II] to [V]
Although not included in the above, examples of compounds that are the same type of ethylene hydrocarbon derivative and are used in obtaining the acrylic polyol include carboxy-containing ethylene hydrocarbons such as methacrylic acid, acrylic acid or itaconic acid. Or an oxirane ring-containing ethylene hydrocarbon derivative such as glycidyl methacrylate.

When preparing the acrylic polyol from the above various ethylene hydrocarbon derivatives, benzoyl peroxide, azobisisobutyronitrile, t-butyl peroctoate, di-t-butyl peroxide or t-butyl. A known radical polymerization initiator such as perbenzoate can be used to easily carry out the reaction according to a conventional radical polymerization reaction.

The radical polymerization reaction is usually carried out in an organic solvent such as toluene, xylene or butyl acetate at a temperature of 60 to 150 ° C.

As described above, it is preferable to use the acrylic polyol having a number average molecular weight of 2,000 to 30,000, and more preferably 3,000 to 20,000.

With respect to the polyol, if the molecular weight is too low, it becomes difficult to obtain a quick-drying paint, and conversely, if the molecular weight is too high, coating workability is impaired, which is not preferable.

On the other hand, the hydroxyl value of the polyol is preferably 20 to 200 in terms of resin solid content, and more preferably 3
Those of 0 to 120 are suitable.

If the hydroxyl value of the polyol is too low, it will be difficult to obtain a coating film with good performance. On the other hand, if it is too high, a large amount of expensive polyisocyanate will be used, resulting in disadvantages such as economical loss.

The glass transition point (Tg) of the acrylic polyol is not particularly limited even if it is desirable that it is not too low in order to obtain preferable drying property, but normally, this Tg is 25 ° C. or higher. Is preferred, 30 ° C
The above is more preferable. On the contrary, if the Tg of the polyol is too high, the flexibility of the coating film tends to be lost. Therefore, it is generally desirable to keep the temperature at 80 ° C or lower, and more preferably at 70 ° C or lower.

If desired, the polyol may be modified with a polyester containing an alkyd resin.

However, the amount of modification at that time is preferably 50% by weight or less, preferably 30% by weight or less, in order not to impair the excellent weather resistance of the acrylic polyol itself.

In order to use the resin composition of the present invention comprising the isocyanurate ring-containing polyisocyanate and acrylic polyol described above as essential components as a coating material, the isocyanate groups and hydroxyl groups of each of these components are equivalent, In other words, by blending so that NCO / OH = 1.0 (equivalent ratio), a quick-drying and good-performance paint can be obtained. However, if desired, this NCO / OH is 0.3 to 2.0, preferably 0.8.
You may use a polyisocyanate and a polyol in the compounding ratio which becomes-1.2.

The resin composition for urethane paints of the present invention can be used as a clear varnish as it is or as an enamel paint in a form containing various pigments or extender pigments such as titanium white, carbon black or cyanine blue.

The clear varnish or enamel as the composition of the present invention is a two-pack type coating composition composed of a curing agent composed of the isocyanurate ring-containing polyisocyanate, which is the essential component, and a base material composed of an acrylic polyol. The pigment in (2) is usually prepared by mixing and kneading with the main agent. As a diluting solvent necessary for forming such a paint, a usual thinner used for urethane paint can be used as it is.

When using the composition of the present invention as a paint,
Further, known additives such as cellulose acetate butyrate, nitrocellulose and other fibrin materials, solubilizers, leveling agents or surfactants may be used in combination, and a curing catalyst may be used in combination if desired. .

The two-pack type coating composition comprising the composition of the present invention is a conventional coating composition in which a curing agent and each coating material as a main component are blended when the composition is put into practical use, and air spray, airless spray, electrostatic coating or roll coater is used. According to the method, it is possible to obtain a coating film having good drying property and good coating performance.

Although the above description focuses on the room temperature curable paint, if desired, even if a method of forcibly drying at a temperature of 40 to 100 ° C. and obtaining a cured coating film in an extremely short time is adopted. A good coating film can be obtained.

Thus, the composition of the present invention is particularly useful as a suitable yellow-free variable-speed dry urethane coating for coating various base materials such as iron, various non-ferrous metals, inorganic materials or plastics materials. is there.

〔Example〕

Next, the present invention will be described with reference to examples, but the present invention is not limited thereto.

Hereinafter, "%" means "wt%" unless otherwise specified.

Example 1 A glass four-necked flask with a volume of 2 equipped with a stirrer, a nitrogen gas inlet tube, an air cooling tube and a thermometer was placed under a nitrogen gas atmosphere, and 1,400 g of hexamethylene diisocyanate (HMDI; molecular weight = 168.2) ( 8.32 mol) and 2,2,4-
50 g (0.34 mol) of trimethyl-1,3-bentanediol (TMPD; molecular weight = 146.2) was charged, the flask was equipped with an oil bath, the temperature was raised to 55 ° C. with stirring, and the temperature was maintained for about 1 hour. Then, as an isocyanurate-forming catalyst, N, N, N-trimethyl-N-is represented by the above structural formula [I].
20% of 2-hydroxypropyl ammonium para-tertiary butyl benzoate (CPB; molecular weight = 295.4)
When the butyl cellosolve solution was added in portions in a flask,
When 1.3 g (0.88 mmol) of the catalyst solution was added in total, the reaction started and exotherm was observed, and the temperature in the reaction vessel rose to 62 ° C. After the exotherm subsided, the reaction was continued for a total of 4.5 hours while maintaining the temperature inside the vessel at 60 ° C, and 1.3 g of a 6.8% xylene solution of monochloroacetic acid (molecular weight M = 94.5) was used as a catalyst deactivator. .
94 mmol) was added to the reactor to terminate the reaction.

The reaction mixture was then cooled to room temperature, of which 1,000
331.3 g of the target polyisocyanate is subjected to molecular distillation.
g (conversion rate = 33.2%) and 668.7 g of distillate (recovery rate = 66.
8%).

The obtained polyisocyanate was a liquid substance which had fluidity at room temperature, and it was then diluted to 75% with ethyl acetate to obtain polyisocyanate. Hereinafter, this is referred to as sample number "P1".

The polyisocyanate P1 solution thus obtained had a nonvolatile content (NV) of 75.3% and a Gardner color number (hereinafter the same) of 1
Below, the Gardner viscosity at 25 ° C (same below) is A ₁
.About.A, and the isocyanate content was 15.0%. As a result of the analysis, it was confirmed that the compound contained an isocyanurate ring, and the measurement result of the molecular weight was 643.

On the other hand, when the distillate obtained by molecular distillation was analyzed, it was also confirmed that this was substantially pure HMDI.

About the above prototype polyisocyanate P1, this and "Acrydeik A-800" (acrylic polyol MW16,000, OHV50 manufactured by Dainippon Ink and Chemicals, Inc.)
A two-component urethane paint was prepared by using and, and the results of examination of coating film performance are shown in Table-2.
0 "[adduct-type non-yellowing polyisocyanate manufactured by Dainippon Ink and Chemicals, Inc.], which is superior in drying property to a coating composition comprising a commercial product A, a trial polyisocyanate, and T2, and has a good coating film. It turned out to have performance.

Examples 2 to 4 Polyisocyanates P2 to 4 having an isocyanurate ring were obtained by changing the raw material composition in the same manner as in Example 1. The raw material blends of P2 to P4, the properties and compositions of polyisocyanates are as shown in Table-1. It has excellent dryness as shown in (3).

As is clear from the results in Table 2, it is understood that the coatings obtained from P3 and P4 have excellent drying properties and well-balanced and good performance in terms of mechanical properties.

Comparative Examples 1 and 2 By the same method as in Example 1, polyisocyanates T1 and T2 having an isocyanurate ring were experimentally produced.

In addition, these polyisocyanates T1 and T2 were experimentally manufactured.

The raw material blends of these polyisocyanates T1 and T2 and the properties and compositions of the polyisocyanates are shown in Table 1.

Example 5 Number obtained by radical polymerization by a conventional method from an ethylene-based hydrocarbon derivative containing styrene and methyl methacrylate as a main hard monomer and soft monomer containing butyl acrylate, β-hydroxyethyl methacrylate and the like. An acrylic polyol with an average molecular weight of 18,000 and a hydroxyl value of 35 (nonvolatile content of 50.2
%, Viscosity X to Y, acid value 3.0, mixed diluent solvent consisting of toluene, xylene and butyl acetate) was used to test the dryness of polyisocyanates P1 to P4 with clear varnish. Atsuta

[Effects of the Invention] The composition of the present invention is not only excellent in weather resistance, but, in the conventional case, only good weather resistance but poor drying property was obtained. As such, the composition of the present invention is itself to be seen.

Moreover, the composition of the present invention has a characteristic effect that it does not turn yellow and has excellent compatibility.

Claims (1)

[Claims] 1. A diisocyanate compound selected from the group consisting of alkylene-, cycloalkylene- and aralkylene diisocyanate, and a diol having at least 3 hydrocarbon substituents in one molecule and having a molecular weight of 100 to 1,000. A polyisocyanate having an isocyanurate ring obtained by reacting in the presence of a nurate-forming catalyst and a number average molecular weight of 2,000 to 30,000, and a hydroxyl value of 20 to 200 comprising an acrylic polyol as an essential component, Yellow-free variable speed dry type urethane coating resin composition.