JPS6295359A - Composition for acrylic urethane coating material - Google Patents

Abstract

PURPOSE:The titled two-pack type composition, obtained by using a main agent prepared by mixing a specific acrylic polyol having secondary hydroxyl groups in the side chain with a monofunctional isocyanate, having a long pot life, cruable at low temperatures and capable of giving coating films having good physical properties. CONSTITUTION:A composition, obtained by initially mixing (A) an acrylic polyol, having secondary hydroxyl groups in the side chain and 18-80 hydroxyl number thereof as a main component with (B) a monofunctional isocyanate, preferably phenyl isocyanate, in an amount equivalent to the moisture contained in the main agent to prepare the main agent and combining the resultant main agent with a curing agent consisting essentially of a polyisocyanate, e.g. tolylene diisocyanate, and applicable by incorporating both agents in use. The secondary hydroxyl groups of the component (A) are preferably introduced by using a monomer, e.g. hydroxypropyl (meth)acrylate, etc.

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 mixing a base agent and a curing agent, and is useful for drying when baked at a low temperature of 120° C. or less.

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, there is a problem in that after mixing the two liquids, the base agent and the curing agent, they gradually react even at room temperature, 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 in which the hydroxyl groups and isocyanate groups of the polyol are reacted by unblocking them by heating. In this method, the blocking agent hardly dissociates at room temperature, so the pot life becomes negligibly long, and liquefaction 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 ketone or cyclohexanone as the solvent is also commonly used.

In this method, the carbon group associates with the hydroxyl group and the isocyanate group to mask the respective reactive groups, and in the solution state, the carbon 1-life becomes extremely good. This is a preferred method because when the ketone solvent evaporates after painting, the mask is released and the curing reaction proceeds. Furthermore, there is a method of lowering the reactivity by adjusting the monomer composition of the acrylic polyol to reduce the amount of water (1) or to raise the glass transition point.

[Problems to be Solved by the Invention] In the conventional method described above, the pot life is certainly longer, but in the method using a blocking agent, a high temperature of 120°C or higher is generally required to dissociate the blocking agent.
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 solvent, there is a problem that the ketone solvent has a strong odor and a strong dissolving power, so that it corrodes the painting board 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.

Furthermore, the acrylic polyol, organic solvent, pigment, etc. in the main ingredient generally contain a small amount of water.

Additionally, moisture in the air may be mixed in during stirring during paint manufacturing, and this moisture reacts with the isocyanate groups in the curing agent to form urea bonds, shortening pot life and reducing crosslink density. This caused a decline in the physical properties of the coating film.

In addition, an acrylic urethane coating film, especially when baked at a low temperature, appears to be hardened, but unreacted areas remain for a while immediately after baking. As a result, thermal softening may occur. In order to solve these problems, conventional methods have been used that use catalysts such as tertiary amines and gold FA salts. For example, in a metal salt, the isocyanate group coordinates to the metal and promotes the reaction.

However, there was a problem in that the metal salts were hydrolyzed by the above-mentioned moisture, making it impossible to effectively utilize the metal salts.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an aqueous urethane paint composition that has a long pot life and can be cured at a low temperature of 120°C or less.

[Means for Solving the Problems] The acrylic urethane coating composition of the present invention is prepared by mixing a main agent mainly composed of an acrylic polyol and a curing agent mainly composed of polyisocyanate. use 2
In the Fi-type acrylic urethane coating composition, the acrylic polyol has at least a secondary hydroxyl group in its side chain, the hydroxyl value of the secondary hydroxyl group is 18 to 80, and at least It is characterized by containing an equivalent amount of monofunctional isocyanate to the water contained in the base ingredient.

The acrylic urethane coating composition of the present invention is composed of a main component 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 inorganic pigments, and dyes. Alternatively, various commonly used paint formulations such as 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 polyol is generally a copolymer synthesized by solution polymerization using radical polymerization.
It is synthesized by selecting various types of monomers and various combinations m. The present invention has one feature in this monomer composition.

The acrylic polyol used in the acrylic urethane coating composition of the present invention has at least a secondary hydroxyl group in its side chain, and the hydroxyl value of the secondary hydroxyl group is 18 to 8.
It is 0. This secondary hydroxyl group is introduced by a hexamer such as hydroxypropyl methacrylate (HPMA) or hydroxypropyl acrylate (+-IPA).

The hydroxyl groups of conventional acrylic polyols were generally introduced by 2-hydroxyethyl methacrylate (2-1-IEMA) monomer and were primary hydroxyl groups. The first class water II has high reactivity and causes a short pot life.

The present inventors have introduced a secondary hydroxyl group into the side chain of an acrylic polyol, and as a result of intensive research into the composition of other monomers, the type of polyisocyanate, the type of catalyst, etc., they have found that a product with a long pot life and hardening can be obtained. The present invention was completed by discovering a composition with excellent properties.

The secondary hydroxyl group is water W M due to the secondary hydroxyl group.
It is introduced into the acrylic polyol so that i& is 18 to 80, preferably 39 to 5.

In terms of HP MA monomer, this corresponds to about 5 to 20 (preferably 10 to 15) weight percent of HP MA monomer in all blended monomers. When the water M base value is lower than 18, the crosslinking density of the coating film made by 1q is lowered, resulting in a decrease in the physical properties of the coating film, and when it is 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.

Secondary water M in acrylic polyol! ! ! Other functional groups are carboxyl groups and primary hydroxyl groups that act as internal catalysts! Various functional groups such as epoxy groups and epoxy groups can be introduced in the same manner as in the past. As for the primary hydroxyl group, it is necessary to introduce it so that the hydroxyl value is lower than about 13. If it is higher than about 13, the pot life may be shortened or it may react with the monofunctional isocyanate described below, resulting in a decrease in physical properties. Note that this amount is about 3 times % or less in terms of 2-HEMA monomer based on the total blended monomers.

In addition, by adjusting the blending amounts of hard monomers such as methyl methacrylate (MMΔ) and soft monomers such as lobate acrylate, the glass transition temperature (TO) can be adjusted to 20°C to 6°C.
It is also preferable to set the temperature to 0°C.

As a result, an acrylic polyol having excellent reactivity with polyisocyanate and physical properties of a cured film can be obtained.

As in the past, the degree of polymerization of the acrylic polyol can be selected depending on the purpose. Generally, those having a weight average molecular weight 1 in the range of 15,000 to 40,000 are used.

As the polyisocyanate used in the curing agent, various polyisocyanates such as tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), hexamethylene diisocyanate (HMD f ), and isophorone diisocyanate (IPDI) can be used as in the past. According to the research conducted by the present inventors, it has become clear that the most desirable combination of the above-mentioned acrylic polyol is an aliphatic isocyanate such as HMD t. This is because it cures at low temperatures, has a good balance between pot life and curability, and has excellent weather resistance.

In addition, in the curing agent, various compounds such as various organic solvents, additives, etc. can be blended in accordance with the purpose, as in the case of the main ingredient. However, those having hydroxyl groups that react with isocyanates, such as alcohols, should of course be avoided.

The blending ratio of acrylic polyol and polyisocyanate can be variously selected depending on the purpose, but generally the equivalence ratio (index) of isocyanate group (NC○) to hydroxyl 1 (01-1) is 1. ○It is desirable to be nearby.

Another feature of the present invention is that a monofunctional isocyanate is blended into the main ingredient.

Monofunctional isocyanates have high reactivity with water and low reactivity with the hydroxyl groups of polyols. In particular, it hardly reacts with secondary hydroxyl groups. The present invention utilizes this property of monofunctional isocyanate and attempts to remove water in the main material of an acrylic urethane by blending monofunctional isocyanate-1 into the main material.

The monofunctional isocyanate is blended in an amount equivalent to at least the amount of water in the base ingredient. If the amount is less than this, water remains and reacts with the isocyanate in the curing agent during mixing, which is not preferable. In addition, in order to deal with moisture contamination during paint production, it is also preferable to increase the amount of the paint when the humidity is high. However, if the amount is too large, the paint or coating may become cloudy or the physical properties may deteriorate, so it is preferable to decide by trial or error depending on the composition of the base agent. Usually, a few percent or less is sufficient. If the acrylic polyol contains primary hydroxyl groups, the monofunctional isocyanate will react with the primary hydroxyl groups, so this should be taken into account when blending. In this case, the monofunctional isocyanate becomes a side chain of the acrylic polyol, and although there is little risk of clouding, care must be taken as it may lead to a decrease in physical properties. Therefore, it is desirable that all hydroxyl groups in the acrylic polyol be secondary.

This monofunctional isocyanate includes phenyl isocyanate, metachlorophenylisocyanate, parachlorophenylisocyanate, orthochlorophenylisocyanate, 3,4-dichlorophenylisocyanate, 2
．． Aromatic monofunctional isocyanates such as 5-dichlorophenylisocyanate, aliphatic monofunctional isocyanates such as methyl isocyanate, ethyl isocyanate, n-butyl isocyanate, n-propylisocyanate, and octadecyl isocyanate can be used. In addition,
Aromatic monofunctional isocyanates with high reactivity are preferred.

It is also desirable to blend tin octylate into the above base ingredient.

This tin octylate exhibits its effects at an accelerated rate as its concentration increases. Therefore, when it is diluted to the coating viscosity and the temperature of tin octylate is low, it has almost no catalytic effect and has almost no effect on pot life. When the solvent evaporates after painting and the concentration of tin octylate increases, the catalytic effect is accelerated and curing progresses. This improves tack-free properties. Furthermore, tin octylate has a high temperature dependence, and
Low-temperature baking is a particularly useful catalyst for drying, as it is particularly effective at temperatures above ~70°C. Note that non-adhesiveness is a measure of the heat softening property of a paint film, and it applies a constant load to the paint film surface through gauze at a predetermined temperature, and holds it for a predetermined time. The heat softening property is measured by the test method of pushing the mark.

Tin octylate is acrylic polyol solid content 100ff
It is preferable to mix the chain component in such a manner that the amount of the chain component is 0.005 to 0.5 times relative to the lffi portion. If the blend 1y is less than 0.005 parts by weight, it will hardly exhibit its catalytic effect, and if it is more than 0.5 parts by weight, the pot life will be shortened. Note that metal salts are hydrolyzed by moisture, but since the composition of the present invention has an extremely low moisture content, such problems can be prevented.

The acrylic urethane paint composition of the present invention is prepared by adding other ingredients to adjust the base agent and curing agent in the same way as in the conventional method, and after mixing, the composition can be applied by conventional methods such as air spray, roll coater, flow coater, etc. It can be done in 18 ways.

It can be cured at birch 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 sufficiently fast and energy is saved.

[Operation of the Invention, Effect 1] According to the present invention, the steric hindrance of the secondary hydroxyl group slows down the reaction between the secondary hydroxyl group and the isocyanate group at room temperature, making it possible to lengthen the pot life. Furthermore, heating after coating activates molecular movement, and the reactivity of the secondary hydroxyl groups approaches that of the primary hydroxyl groups. This results in 70'
If low-temperature baking drying is carried out at about C to 100 DEG C., the secondary hydroxyl groups will react with the isocyanate groups to the same extent as the primary water MM, and a coating film that can be put to practical use will be 1q. 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 becomes smaller, resulting in improved adhesion, weather resistance, etc. A coating film is obtained.

Further, the composition of the present invention has a monofunctional isocyanate in the main ingredient. Therefore, water in the base resin is removed, and the hydroxyl groups in the base resin and the isocyanate groups in the curing agent can be reliably reacted. This prevents problems such as a shortened pot life, and the resulting coating film has a high crosslinking density and excellent coating properties such as non-tackiness. Furthermore, if tin octylate is blended into the main ingredient, the non-tackiness will be further improved due to the catalytic action of tin octylate. Since hydrolysis of tin octylate due to moisture can be prevented, tin octylate can be used efficiently.

[Example] This will be explained in more detail below using specific examples.

(Example 1) (1) Synthesis of acrylic polyol As shown in Table 1, the acrylic monomers were 10 parts by weight of human xypropyl methacrylate, 30 fflffi parts of styrene,
Medyl methacrylate (MMA) 34.5 parts, n-butyl acrylate (BA) 25 parts by weight, acrylic acid (AA)
>0.5 parts by weight and 1.5 small parts of azobisisobutyronitrile were added as an initiator in a flask containing 40 parts by weight of toluene, 401 parts by weight of butyl acetate, and 20 parts by weight of xylene. While maintaining the temperature at 105°C in an NZ gas atmosphere, the remaining monomers were added dropwise over a period of 2 hours, followed by a reaction at 105°C for 6 hours to synthesize an acrylic polyol. The obtained acrylic polyol is
The hydroxyl value is 39, the acid value is 4.9, the Tg is 43°C, the average molecular weight is 25,000, and the non-volatile content is diluted to 50%.

(2')...Using the acrylic polyol equated according to the vA adjustment of the paint, titanium oxide powder was dispersed in a sand mill so that the amount was 50 fflfft parts per 50 parts by weight of the solid content of the acrylic polyol, and then Aromatic monofunctional isocyanate (Additive TI, manufactured by Sumitomo Bayer Urethane) at 1.51 parts per 100 Wffi parts of acrylic polyol solid content.
A white paint serving as a main ingredient was prepared by blending so as to contain 1 fi part. In addition, using the above acrylic polyol, aluminum paste (1109M1 manufactured by Toyo Aluminum Co., Ltd.) was added in an amount of 1 part by weight of aluminum powder per 90 parts by weight of the solid content of the acrylic polyol.
A metallic paint serving as a main ingredient was prepared by blending the same monofunctional isocyanate as above in the same amount as above.

For the above two types of paints, use HMDI (Coronate E H1 manufactured by Nippon Polyurethane Co., Ltd.) as a hardening agent (NGOlo).
-1-1,0 parts, 20 parts of toluene, 2C) If part of butyl acetate, 220 m1iit of xylene
1 part of 20ffi ethyl acetate, 10 parts by weight of Cellosolve Acedate, and 1 part of Tulpetz 100 for 15 seconds (no.
4 food cups, 20°C).

(3) Measurement of pot life The 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 point at which the surface smoothness deteriorated was measured and defined as the pot life. At the same time, an accelerated test was performed in which the paint, which had been 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 taken to determine the viscosity increase rate. did. The results are shown in Table 2.

(4) Painting Two types of paint with a viscosity of 15 seconds diluted with "UA adjustment of paint" are applied with an intermediate coat on the cationic electrodeposition film,
The ice age was 70111111X150mmXQ.

Each steel plate with a size of 8 mm was coated with air spray to a film thickness of 35 to 40μ, and heated at 80℃ for 30 minutes.
Separate baking drying was performed. Further, the test pieces were left at room temperature for 24 hours, and the following tests were conducted.

(5) Tests The following tests were conducted on the two types of coatings obtained above, the white coating film and the metallic coating film.

In the pencil hardness test, the hardness was measured by scratching the coating film at an angle of 45 degrees using a Mitsubishi UnitO brush. To check the adhesion, cut 100 1 mm square II holes into the coating film using a cutter knife.
Judgment was made based on the number of squares where the coating film remained when the cellophane tape was pressed and peeled off. Water-resistant adhesion was determined by immersing a test piece in warm water at 40°C for 10 days, and then conducting the above-mentioned adhesion test.

Gloss was measured by light (R meter) at 60 degrees gloss.

Weather resistance was determined by conducting a 1200 hour accelerated weather resistance test using a weather-o-meter, measuring the subsequent gloss, and calculating the gloss retention rate relative to the initial gloss. At the same time, Hunter's 1-ab ΔE was measured using a color difference meter (manufactured by Suga Test Instruments Co., Ltd.) with respect to that before the weather resistance test. To test for non-adhesiveness, gauze was placed on the surface of the coating, a 500 g weight having a circular bottom with a diameter of 3 cm was placed on top of the gauze, and the gauze was held at 70° C. for 2 hours. After taking it out, the traces of gauze on the surface of the coating film were visually judged. Note that ◎ means that there are almost no marks left, O means that slight marks remain in the form of dots, △ means that thin marks remain in the form of lines, but the gauze falls off the coating due to its own weight, and X means that The gauze adheres to the paint film and cannot be removed unless it is peeled off by hand. In addition, only the main ingredient was heated at 40°C.
The anti-tackiness test was also conducted on test pieces that were held for 0 days, then mixed with a curing agent in the same manner, painted, and dried in the same manner. The results are shown in Table 2.

(Example 2) Using the same acrylic polyol and monofunctional isocyanate as in Example 1, a paint was prepared in the same manner as in Example 1, except that 3.01 parts of ffi were added to 100 parts of acrylic polyol solid content. Adjust and paint as well,
The pot life was measured in the same manner after drying, and the same test was conducted. The results are shown in Table 2.

(Examples 3 to 4) Using the same acrylic polyol and monofunctional isocyanate as in Example 1, tin octylate as a metal salt catalyst,
The paints were prepared in the same manner as in Example 1 and Example 2, except that 0.05 parts by weight of the original chain component was added to 100 parts by weight of the solid content of the acrylic polyol, 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.

(Comparative Example 1) A paint was prepared in the same manner as in Example 1, except that the same acrylic polyol as in Example 1 was used and the monofunctional isocyanate was not used, and the coating and drying were performed in the same manner. The life was measured and a similar test was conducted. The results are shown in Table 2.

(Comparative Example 2) The same acrylic polyol as in Example 1 was used, except that no monofunctional isocyanate was used, and 0.051 ffi part of a metal salt catalyst (tin octylate) was blended as a chain component.
In exactly the same manner as in Example 1, the paint was prepared, applied and dried in the same manner, the pot life was measured in the same manner, and the same test was conducted.

The results are shown in Table 2.

(Comparative Examples 3 to 5) 5.10.20 weights (6) of 1-IP MA, respectively
An acrylic polyol was synthesized in the same manner as in Example 1, except that styrene was 15 parts by weight, MMA was 54.5.49, 5.39.5 parts by weight, and acrylic acid was 0.5 parts by weight, respectively. However, each paint was prepared in the same manner as in Example 1, except that the monofunctional isocyanate and the metal salt catalyst were not used, and the coating and drying were performed in the same manner.
The pot life was measured in the same manner and the test was conducted in the same manner. The results are shown in Table 2.

(Conventional Examples 1 to 3) Acrylic polyols were synthesized in the same manner as Comparative Examples 3 to 5, except that 5.10.2 Olffi parts of 2-1-I EMA were used instead of I-1 P MA, The paints were prepared in the same manner as in Example 1, except that the monofunctional isocyanate and the metal salt catalyst were not used, and the coating and drying were performed in the same manner, the pot life was measured in the same manner, and the test was conducted in the same manner. The results are shown in Table 2.

(Evaluation) Examples 1 and 2 are superior in weather resistance and pot life compared to Comparative Examples 1 and 2. Also, the pot life is particularly good when using white paint. It is clear that this is due to the effect of the monofunctional isocyanate. It is also clear that by blending tin octylate, the pot life is hardly affected and the non-tackiness is improved, that is, the curability is improved.

Examples 3 and 4 have better weather resistance and pot life, and are also better than Comparative Example 2 in terms of non-tackiness after storing the main ingredient at 40°C for 30 days. This is because in Comparative Example 2, a portion of the metal salt catalyst was hydrolyzed due to the influence of water contained in the main ingredient, resulting in a decrease in effectiveness. That is, by using a monofunctional incyanate and a metal salt catalyst together,
Hydrolysis of metal salt catalysts can be prevented and good non-stick properties can be maintained.

Comparative Examples 3 to 5 have a pot life of 8, although the various physical properties of the coating film are almost the same as those of Conventional Examples 1 to 3.
It is sufficiently long, exceeding hours, and the viscosity increase rate is also small. This is clearly due to the secondary water M group to HPM.

Claims (4)

[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 acrylic polyol is added to the side chain. It has at least a secondary hydroxyl group, and the hydroxyl value of the secondary hydroxyl group is from 18 to
80, and the composition for an acrylic urethane coating is characterized in that at least an amount of monofunctional isocyanate equivalent to the amount of water contained in the base ingredient is blended in the base ingredient. (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) Acrylic polyol resin solid content in the base resin is 100
The chain component of tin octylate is 0.005 to 0 for the overlapping part.
．． 5 parts by weight of the acrylic urethane coating composition according to claim 1. (4) The acrylic urethane coating composition according to claim 1, wherein the polyisocyanate is an aliphatic polyisocyanate.