JPS6295356A - Composition for acrylic urethane coating material - Google Patents

Abstract

PURPOSE:The titled two-pack type composition, obtained by incorporating a specific acrylic polyol with an aliphatic polyisocyanate, having a long pot life in mixing, useful for low-temperature baking and drying with improved gloss and weather resistance and suitable for household appliances, etc. CONSTITUTION:A composition obtained by incorporating (A) an acrylic polyol, having secondary hydroxyl groups in the side chain and 18-80 hydroxyl number thereof and prepared by mixing 10-40wt% styrene in the monomer composition and polymerizing the monomer composition, e.g. copolymer of hydroxypropyl methacrylate with styrene, with an organic solvent, e.g. ketonic solvent, and catalyst, e.g. tertiary amine, etc., to give a main agent and mixing (A) the resultant main agent with (B) an aliphatic polyisocyanate, e.g. hexamethylene diisocyanate, as a curing agent to give 0.7-1.5 equivalent ratio of isocyanate groups to hydroxyl groups.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an acrylic urethane coating composition that forms a coating film through a crosslinking reaction between the hydroxyl groups of the acrylic polyol in the base agent and the isocyanate groups in the curing agent. More specifically, the present invention relates to an acrylic urethane coating composition that has a long pot life when the main agent and curing agent are heated, is useful for drying when baked at a low temperature of 120°C or less, and has excellent gloss and weather resistance.

The acrylic urethane coating composition of the present invention can be used in various fields such as plastics, vehicle repair, and home appliances.

[Prior art] Two-component acrylic urethane resin paints have urethane bonds in the resulting coating film, and the coating film has excellent physical properties such as hardness, flexibility, abrasion resistance, and chemical resistance. It is used in various fields. However, after mixing the two liquids, the base agent and the curing agent, when left at air temperature, they gradually react, and the viscosity gradually increases, eventually making it impossible to coat. The time from the time of mixing until it becomes unpaintable is generally the pot life (
(hereinafter referred to as "pot life"), and a product with a long pot life is desired from the viewpoint of reducing the troublesome preparation and loss of paint. However, there is a negative correlation between the pot life and the reaction rate of the coating film, and as the pot life becomes longer, the reaction rate decreases and curing takes longer and higher temperatures are required. If you try to do this, there is a problem that the pot life will be shortened. Various methods have been proposed to solve these problems.

For example, as seen in JP-A-59-226062, isocyanate groups are blocked with a blocking agent such as oxime, lactam, phenol, or tertiary alcohol,
There is a method of unblocking the polyol by heating and causing the water of the polyol to react with the isocyanate group. With this method, since the blocking agent hardly dissociates with regular crystals, the bottle life is almost negligible and the blocking agent is almost negligible.
It is possible. This is a particularly preferred method because it rapidly reacts and cures by heating.

In addition, a method using a ketone solvent such as methyl ethyl phenylene or cyclohexanone as a solvent is also commonly used. In this method, the phenylene group associates with the hydroxyl group and the isocyanate group to mask each reactive group. In a solution state, the pot life is long.Then, when the ketone solvent evaporates after painting, the mask is released and the curing reaction progresses, so this is a preferable method.Furthermore, the monomer composition of the acrylic polyol is adjusted. However, there are also methods to lower the reactivity by lowering the hydroxyl value or raising the glass transition point.

[Problems to be Solved by the Invention] The above-mentioned conventional method does have a long pot life (although the method using a blocking agent generally requires a high temperature of 120'C or higher to dissociate the blocking agent). , 120
It is not practical if the reaction is carried out at a low temperature below ℃. Furthermore, even if a blocking agent that dissociates at low temperatures is used, there is a problem that the pot life will not be extended. In the method using a ketone-based solvent, there is a problem that the ketone-based solvent has a strong odor and strong dissolving power, so that it corrodes the painting hose or the object to be coated. Furthermore, the method of extending the pot life by adjusting the acrylic polyol itself has the disadvantage that the physical properties of the half-coated film deteriorate.

The present invention has been made in view of the above problems, and provides an acrylic urethane coating composition that has a long pot life, can be cured at a low temperature of 100°C or less, has high gloss, and has good l1ii41 properties. The purpose is to provide

[Means for Solving the Problems] The acrylic urethane coating composition of the present invention includes a main component containing an acrylic polyol as a main component and a curing agent containing a polyisocyanate as a main component, which are mixed at the time of use. In the liquid-type acrylic urethane coating composition, the polyisocyanate is an aliphatic polyisocyanate, and the acrylic polyol has at least a secondary hydroxyl group in its side chain, and the acrylic polyol has at least a secondary hydroxyl group in its side chain. Hydroxyl value according to 2j is 18~
80, synthesized by containing 10 to 40% by weight of styrene monomer in the monomer composition, and the isocyanate group of the polyisocyanate at the time of mixing and the ?
The equivalent ratio of the hydroxyl group of the kryl polyol to 0.7 to 1.5
It is characterized by the following.

The acrylic urethane coating composition of the present invention is composed of a main agent containing an acrylic polyol as a main component and a curing agent containing a polyisocyanate as a main component.

The main ingredients include various organic solvents such as aromatic hydrocarbon solvents, aliphatic hydrocarbon solvents, ester solvents, and ketone solvents, metal salts, catalysts such as tertiary amines, various organic and non-classified pigments, Various commonly used paint formulations such as dyes and various additives can be selected and blended depending on the purpose.

One feature of the present invention lies in the composition of the acrylic polyol in the base ingredient.

Acrylic polyols are generally produced in solution I by radical polymerization.
? It is a copolymer synthesized by , and is synthesized by selecting various types of monomers and blending machines in consideration of the desired 4&I properties. The present invention has a major feature in this monomer composition.

The acrylic polyol used in the acrylic urethane coating composition of the present invention has at least 1 liter of secondary water in its side chain.
! group, and water W u I [ due to its secondary hydroxyl group
i is 18-80. This second class water 1ylLt i
Human xypropyl methacrylate (IP~1△)
, acrylic alcohol hydroxypropyl (HPΔ), etc.

The hydroxyl group of conventional acrylic polyols was generally introduced by methacryl PIi 2-hydroxyethyl (2-HEMΔ) 7-mer and was a primary hydroxyl V. The primary hydroxyl group is highly reactive and causes a short pot life.

The present inventors introduced a secondary hydroxyl group into the side chain of an acrylic polyol, and carefully adjusted its 6i, the composition of other monomers, and the weighing and blending of the polyisocyanate. The present invention was completed by discovering a composition with excellent properties, gloss, and weather resistance.

The secondary hydroxyl group is water I! 1
It is introduced into the acrylic polyol so that the base value is 18 to 80, preferably 39 to 5.

This is 111 for HP M△ monomer! i, the HP MA monomer accounts for about 5 to 20 (preferably 10 to 15) weight percent of the total blended monomers. When the hydroxyl value is lower than 18, the crosslinking density of the coating film becomes lower (q), resulting in a decrease in the physical properties of the coating film, and when it becomes higher than 80, the hardness of the coating film increases, but the adhesion to the coated object decreases. Also, the pot life will be shorter.

The acrylic polyol used in the acrylic urethane coating composition of the present invention contains a styrene component in the resin skeleton. This styrene component makes polyisocyanate 1-
High gloss can be imparted to the coating film reacted with.

The styrene component is introduced by blending 10 to 40 feet of 1% styrene monomer into the monomer composition during acrylic polyol synthesis and copolymerizing it with other U-summers. If the styrene monomer content is less than 5% by weight, the gloss will be poor, and if it is more than 40% by weight, the weather resistance will be poor.

In addition, since styrene has a benzene ring in its composition,
It is a well-known fact that coating films containing styrene components have poor weather resistance. However, it is difficult to obtain high gloss unless a styrene component is introduced. In the composition of the present invention, by setting the styrene component within the above range, it is possible to
3 and weather resistance is approximately V″4 plus.

As for the functional groups other than the secondary hydroxyl groups in the acrylic polyol, divine functional groups such as carboxyl groups, primary hydroxyl groups, and epoxy groups that act as internal catalysts can be introduced in the same way as in the past. For J3 first class water Ml, water 71 J? It is necessary to introduce it so that the value is lower than 13. V] If you go from 13 to 13, your life will become shorter. Note that this amount is about 3% by weight or less in the total blended monomer in terms of 2-HIE MΔ monomer.

In addition, the glass transition temperature (T
The temperature is preferably 0°C to 60″C.

If Tg is lower than 20"C, the pot life will be shortened and the hardness of the coating film will be inferior. If it is higher than 60"C, the reactivity will decrease and the physical properties of coating 11ψ will also decrease.If the lower Q is within this range, Reactivity with polyisocyanates and coating I after curing
Acrylic polyol with excellent physical properties is 1! ? It will be done.

It is desirable that the base agent has a predetermined acid value. This is because this acid value promotes the reaction between the hydroxyl group and the isocyanate group. In order to have this acid value, it is possible to mix an acid component into the base resin, but it is also possible to use acid monomers such as acrylic acid, methacrylic acid, and maleic acid in the monomer composition of the acrylic polyol, and to It is desirable to copolymerize with -. In this case, since it acts as an internal catalyst that is integrally bonded to the main chain, there is no adverse effect on weather resistance. In this case, the acid value of the acrylic polyol is preferably 9 or less, and preferably as high as possible.

When it is larger than 9, the pot life becomes short and water resistance becomes inferior.

As in the past, the degree of polymerization of the acrylic polyol can be selected depending on the purpose. Generally, a resin having a weight average molecular weight in the range of 15,000 to 40,000 is used.

It is desirable to include an antioxidant such as hindered amine in the main ingredient. This antioxidant can prevent deterioration of the styrene component and further improve weather resistance. J3, the blending rate of the antioxidant is 0.3 to 1.5 f per 100 parts by weight of the solid content of the acrylic polyol resin.
1.5 parts by weight, preferably 0.5 to 1.0 parts by weight, less than 0.3 parts by weight, the effect is small, and 1.5 parts by weight or less.
Even if a large amount is added to the weight part, the effect will hardly change.

It also causes an increase in cost.

Another feature of the present invention is that polyisocyanate-1-(Φ class J
> and between the formulations.

In the present invention, the power 4]-methylene diisocyanene~1~<
Aliphatic polyisocyanates such as linear aliphatic isocyanates such as HMD [) and cycloaliphatic isocyanates such as isophorone diisocyanate (IPDI) are used. According to the research of the present inventors,
For the aforementioned acrylic polyols, combinations with HMDI are most desirable. This is because this combination cures at a low temperature of 120° C. or less, provides a good balance between durability and hardenability, and has excellent weather resistance.

In addition, in the curing agent, various compounds such as various organic solvents and additives can be blended in accordance with the purpose, similarly to the main ingredient. However, those with water 11 that reacts with the isocyanate, such as alcohols, should of course be avoided.

Although various blending ratios of acrylic polyol and polyisocyanate can be selected depending on the purpose, in the present invention, the equivalent ratio (index) of isocyanate W (NGO> to 1 m (OH) of water) is in the range of 0.7 to 1.5. If the index is smaller than 0°7, the crosslinking density will be low and the physical properties of the coating will be poor.If the index is larger than 1 or 5, the pot life will be short and the It reacts with moisture in the air and forms urea bonds, resulting in poor weather resistance and water resistance.

If the index is within the above range, a coating film with good physical properties can be obtained without such problems.

The acrylic urethane coating composition of the present invention can be prepared by adding other ingredients to adjust the main agent and curing agent in the same way as before, and after the treatment, it can be prepared using conventional methods such as air spray, roll coater, flow coater, etc. IH can be applied using any existing painting method.

It can be cured at various temperatures ranging from room temperature drying to high temperature baking drying of 140° C. or higher. However, in order to take advantage of the features of the present invention, it is desirable to harden by baking and drying at a low temperature of about 70 to 100°C. This is because the curing speed is fast and energy is saved.

[Operations and Effects of the Invention] According to the present invention, due to steric hindrance of the secondary hydroxyl group, the reaction between the secondary hydroxyl group and the isocyanate group at room temperature is slowed down, and the pot life can be improved. In addition, heating of the painted pattern activates molecular movement, and the reactivity of secondary hydroxyl groups (approaching the reactivity of primary hydroxyl groups).
If you perform low-temperature baking drying at about 0℃ to 100℃, it will be 11% second class water! JJ reacts with isocyanate groups in almost the same manner as primary hydroxyl groups, and a coating film that can be used for practical purposes is obtained. It is also clear that the reaction progresses gradually even after baking, and as the reaction curve becomes gentler,
The internal stress of the resulting coating film is reduced, resulting in a coating film with good adhesion and weather resistance. In the composition of the present invention, an aliphatic isocyanate is used as the polyisocyanate, and the polyisocyanate is mixed so that the index thereof is 0.7 to 1.5. As a result, a coating film with a good balance between ball life and curability and better physical properties such as weather resistance can be obtained.

Furthermore, the acrylic polyol contains a styrene component. This results in a coating film 17 with excellent gloss. In addition, adding an antioxidant prevents the deterioration of the styrene component and improves weather resistance.

[Example] A more detailed explanation will be given below using specific examples.

(Example 1) (1) Synthesis of acrylic polyol As shown in Table 1, acrylic monomers include 5 parts of hydroxypropyl methacrylate, 15 parts of styrene, and 54.5 parts of methyl methacrylate (MMA). Hanging part, n-butyl acrylate (BA) 25,000 hanging part, Acrylic M (>0.5i to A
1 hanging part, azobisisobutyronitrile 1.5f
fiffi part was added as an initiator, and the above compounded monomers were suspended in a flask containing 40 parts by weight of toluene, 40 parts by weight of butyl acetate, and 20 parts of J3 and xycin, while maintaining the temperature at 105°C in an N2 gas atmosphere. It took 2 hours to move south, and then reacted at 105°C for 6 hours to synthesize acrylic polyol. 1r? The obtained acrylic polyol had a water MWI+tb 19 , 5, 043° C., a syn average molecular weight of 25,000, and was diluted to a non-volatile content of 50%.

<2>...Adjustment of paint Using the acrylic polyol prepared above, disperse titanium oxide powder in a lean mill so that the amount becomes 50 parts by weight per 50 parts by weight of the solid content of the acrylic polyol. In addition, hindered amine (
A white paint was prepared by blending Tinuvin 144 (manufactured by Ciba Geigy) in an amount of 0.5 parts by weight per 100 parts of acrylic polyol solids. Using the above acrylic polyol, aluminum paste <1109M (manufactured by Toyo Aluminum Co., Ltd.) was mixed in such a manner that the aluminum powder was at most 10 parts per 90 parts by weight of the acrylic polyol, and the same amount of the antioxidant was mixed as above. Adjusted the metallic paint.

For the above two types of paints, HMDI (Coronate El-1, manufactured by Nippon Polyurethane Co., Ltd.) as a curing agent was added to NGOlo.
Blend so that l-1 = 1.0, 20 parts of toluene, 2 parts of butyl acetate, 2 parts of xylene
iffi part, ethyl acetate 20ii! With a thinner consisting of 1 part f, 10 parts Cellosolve Acetate, and 10 parts by weight of Tsurupez 100, the coating viscosity is 15
(No., 4 food cups, 20° C.).

(3) Measurement of pot life Two types of paints adjusted to a viscosity of 15 seconds as described above were kept in a sealed state at 40'C, taken out at regular intervals and painted with air spray. The pot life was determined by measuring the point at which the smoothness of the painted surface deteriorated. At the same time, an accelerated test was carried out in which the paint diluted to the viscosity of 15 seconds above was heated in a sealed state at 40°C for 8 hours, and the ratio of the viscosity after the accelerated test to the initial 15 seconds was calculated to determine the viscosity increase rate. And so.

The results are shown in Table 2.

(4) Painting Two types of paints with a viscosity of 15 seconds diluted in the "paint adjustment" were applied with an intermediate coat on the cationic electric coating film, and the size was 70 mm x 150 mm x □.

A steel plate with a size of 8 mm was coated with a film thickness of 35 to 40 μm using air spray, and then heated at 80°C for 30 min.
The following tests were conducted using test pieces 1 which were baked and dried for 2 minutes and left at room temperature for 24 hours.

(5)...Test The following tests failed for each of the two types of coatings, the white coating film and the metallic coating film, which were evaluated as 1q above.

! In the il brush hardness test, the hardness was measured by scratching the coating film at an angle of 7151 degrees using a Mitsubishi Koni pencil. Adhesion resistance was determined by the number of marks remaining on the coating film when the coating film was cut with a horn knife into 100 square holes of 1 mm square, and the cellophane tape was applied and peeled off. Water resistance adhesion is 40℃
The test pieces were immersed in warm water for 10 days, and then the adhesion test described above was conducted.

The gloss was measured using a gloss meter at 60 degrees gloss.

For weather resistance, a 1200 hour accelerated weather resistance test was carried out using a weather-o-meter, the subsequent gloss was measured, and the gloss retention rate relative to the initial gloss was determined by cotton weight. At the same time, using a color difference meter (manufactured by Suga Test Instruments Co., Ltd.), the ΔE of the weather resistance test surface and Hunter's jab were measured. The results are shown in Table 2.

(Examples 2 to 3) 1-11) 10 and 20 fold flI) parts of M△, MM
The acrylic polyols were synthesized in exactly the same manner as in Example 1 except that A was 49.5 and 39.5 times thicker, the paint was prepared in the same way for each, and the coating and drying were carried out in the same manner. The pot life was measured and a similar test was conducted.

The results are shown in Table 2.

<Examples 4 to 6) 10 parts of HPMA, 8 parts of 30 parts of styrene, MMA
Example 1 An acrylic polyol was synthesized in exactly the same manner as in Example 1, except that the interlaminar part was 34.5, and the index was 0.7, 1, 0.1, and 5, respectively. The paints were prepared in the same manner as in 1, and the coating and drying were performed in the same manner, the pot life was measured in the same manner, and the same test was conducted. The results are not shown in Table 2.

(Comparative Examples 1 to 3) HPMA was not used, and 2-HEMA was used at 5.10.
20 heavy baths, MMA 54.5.49.5.3 respectively
Each acrylic polyol was synthesized in exactly the same manner as in Example 1 except that the amount was 9.5 parts by weight, the LjJi material was similarly adjusted for each, the coating and drying were carried out in the same manner, and the pot life was measured in the same manner. , conducted a similar test. The results are shown in Table 2.

(Comparative Examples 4 to 5) Using the acrylic polyols synthesized in Examples 4 to 5, each paint was prepared in the same manner as in Example 1, except that the index was set to 0.5 and 2.0, respectively. The pot life was measured in the same manner after painting and drying, and the same test was conducted. The results are shown in Table 2.

<Evaluation> It is clear from Table 2 that Examples 1 to 6 and Comparative Examples 4 to 5
Compared to Comparative Examples 1 to 3, the pot life is sufficiently long at 8 hours or more, and the thickening rate is also small. It is clear that this is due to the effect of the secondary hydroxyl group of HPMA. Moreover, Examples 4 to 6 and Comparative Examples 4 to 5 were better than Examples 1 to 6.
The gloss is better than that of No. 3 and Comparative Examples 1 to 3. This shows that the gloss improves as the amount of styrene increases. Furthermore, by comparing Examples 5 to 6 and Comparative Examples 4 to 5, it is clear that when the index is in the range of 0.7 to 1.5, the gloss retention rate and color difference are excellent, that is, the weather resistance is excellent. be.

Claims (5)

[Claims] (1) In a two-component acrylic urethane paint composition in which a base agent containing an acrylic polyol as a main component and a curing agent containing a polyisocyanate as a main component are mixed at the time of use, the polyisocyanate is an aliphatic polyester. isocyanate, and the acrylic polyol has at least a secondary hydroxyl group in a side chain, and the hydroxyl value of the secondary hydroxyl group is 18 to 1.
80, and 10% of styrene monomer in the monomer composition.
A composition for an acrylic urethane paint synthesized containing ~40% by weight, characterized in that the equivalent ratio of the isocyanate groups of the polyisocyanate and the hydroxyl groups of the acrylic polyol at the time of mixing is 0.7 to 1.5. thing. (2) The acrylic urethane coating composition according to claim 1, wherein the secondary hydroxyl group is a hydroxyl group of hydroxypropyl methacrylate in the acrylic polyol main chain. (3) The acrylic urethane paint composition according to claim 1, wherein the main ingredient contains 0.5 to 1.5 parts by weight of an antioxidant per 100 parts by weight of the solid content of the acrylic polyol resin. (4) The acrylic urethane coating composition according to claim 1, wherein the acrylic polyol has an acid value of 2 to 9. (5) The acrylic urethane coating composition according to claim 1, wherein the acrylic polyol has a glass transition temperature (Tg) of 20 to 60°C.