JPH0441572A - Aqueous intercoating material - Google Patents

Abstract

PURPOSE:To obtain an aqueous intercoating material which is free from the problems of skims or runs and can provide a smooth coating film and a vivid topcoat by employing, as main components, a specific polyester resin, a specific polyether polyol, an aqueous amino resin and an alkyl ether of benzoin. CONSTITUTION:A polyester resin with an acid value of 10-100 and an OH value of 200-300 (e.g. a urethane-modified polyester resin obtained by reacting ethylene glycol, trimethylolpropane and phthalic anhydride; reacting the formed resin with tolylene diisocyanate trimellitic anhydride; and neutralizing the resultant with dimethylethanolamine), a polyether polyol of formula I (R is a group represented by formula II to III; and (n) is 2-10), an aqueous amino resin (e.g. an imino group-containing melamine resin), and an alkyl ether of benzoin (e.g. benzoin ethyl ether) are employed as main components.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention has coating workability (scratching resistance, sagging resistance) equivalent to or superior to organic solvent-based intermediate coating paints, as well as smoothness and sharpness of top coating. This invention relates to a new water-based intermediate coating paint useful for finishing a coating film with excellent properties.

CH.

CH3n is an integer from 2 to 10. ] The polyether polyol shown by (D) Alkyl etherified benzoin and conventional techniques and their problems The intermediate coating is used in a coating system in which a primer coating, an intermediate coating and a top coating are applied sequentially,
This is important from the point of view of improving the smoothness, sharpness, and finished appearance of the coating film obtained with the coating system.

Conventionally, organic solvent-based intermediate paints have been the mainstream, but there is a strong demand for conversion to water-based paints from the viewpoints of disaster prevention safety, non-pollution, and resource conservation. .

Examples of water-based paints include thermosetting water-based paints containing polyhydric carboxylic acid resins, amino resins, and benzoin as main components (Japanese Patent Publication No. 2-390), polyhydric carboxylic acid resins, amino resins, and diphenyl polyether polyols. Thermosetting water-based high solid paint with main component (Special Publication No. 61-
No. 50106) and the like are known, but there are various problems when using these as intermediate coatings.

In other words, when the above water-based paint is used as an intermediate coating, the coating itself does not have sufficient smoothness or sharpness, and moreover, compared to conventional organic solvent-based intermediate coatings, it evaporates during the curing of the coating. Components (for example, water) tend to bump and cause so-called "flanks", and this phenomenon is observed even in film thicknesses of 30 to 40 μm, causing a deterioration in the finished appearance. In this case, in order to avoid paint film defects due to armpits, preheating is performed at a low temperature (approximately 60°C) to volatilize most of the water in the uncured paint film, and then the temperature is raised to heat cure.
The temperature of the uncured coating film rises before the moisture is sufficiently volatilized, and the viscosity of the coating film decreases, causing sag in the vertical portions. Also,
In order to prevent this sagging, adding rheology control agents, extender pigments, etc. to increase the structural viscosity will reduce the flowability of the applied coating liquid, and the smoothness of the intermediate coating film after heat curing will deteriorate. Become. Furthermore, when a fatty acid-modified polyester resin with a low glass transition temperature is used as a base resin to prevent wrinkles, it tends to sag, the hardness of the coating film decreases, and the sharpness of the topcoat after the topcoat is applied is insufficient.

Means for Solving the Problems As a result of intensive research in order to solve the problems of the above-mentioned prior art, the present inventor has developed a method that uses a specific polyester resin, an aqueous amino resin, a specific polyether polyol, and an alkyl etherified benzoin as main components. It was discovered that the objective could be achieved using water-based paint. That is, the paint is heated to a temperature (usually about 140 to 160°C) for hardening immediately after application without preheating for volatilization of water, and the cured film thickness is, for example, 60 μm or more. Moreover, by using it as an intermediate coating in the above-mentioned coating system, the smoothness of the coating film and the sharpness of the topcoat are good, and it has good chipping resistance, moisture resistance, and interlayer coating. We have discovered that it is possible to form a composite coating film with excellent adhesion.

The present invention has been completed based on these new findings.

That is, the present invention provides (A) an acid value of 10 to 100 and a hydroxyl value of 20 to 30;
0 polyester resin, (B) water-based amino resin, (C) - formula % formula %) [However, R is CH.

CH.

CH30 is an integer from 2 to 10. ] It concerns on the water-based intermediate coating material characterized by having as a main component the polyether polyol shown by these, and fD) alkyl etherified benzoin.

The water-based intermediate paint of the present invention (hereinafter sometimes abbreviated as "the present paint") is characterized by the combination of the above-mentioned (A) and (B) components with both the (C) and (D) components. be. That is, if a paint film lacking any of these components is immediately heated and cured without preheating for water volatilization, for example, in a system consisting of components (A), (B), and (C), Wrinkling is likely to occur during heat curing, and systems consisting of components (A), (B) and (D) are likely to cause wrinkling, and also have insufficient smoothness and sharpness.

On the other hand, (A), (B) (C) and (D
) The present paint containing all of the components eliminates all such defects and forms a coating film having the above-mentioned technical effects.

Components (A) to (D) constituting the main components of this paint will be specifically explained.

(A) Component: acid value is 10 to 100 and hydroxyl value is 20
~300 polyester resin.

The polyester resin includes ethylene glycol,
Polyhydric alcohols such as diethylene glycol, propylene glycol, butanediol, bentanediol, 2゜2-dimethylpropanediol, glycerin, trimethylolpropane, pentaerythritol, and m alcohols or 1 glycidyl in the molecule used in combination as necessary monoepoxy compounds having groups (for example, [
Cardura EJ (trade name, manufactured by Shell Chemical Co., Ltd.)) is used as an alcohol component, including phthalic anhydride, isophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, maleic anhydride, succinic anhydride, adipic acid, cepatic anhydride, and trihydrophthalic anhydride. The above alcohol component and the above acid component are condensed using polybasic acids such as mellitic acid and pyromellitic anhydride, and monobasic acids such as benzoic acid and t-butylbenzoic acid used in combination as necessary. oil-free polyester resin, or in addition to the alcohol component and the acid component, castor oil, dehydrated castor oil, tung oil, safflower oil, soybean oil, linseed oil, tall oil, coconut oil, etc., and fatty acids thereof. Examples include oil-modified polyester resins obtained by adding one oil component or a mixture of two or more oil components to the acid component and alcohol component and reacting the three components. Moreover, polyester resin grafted with acrylic resin or vinyl resin can also be used as component (A).

Further, it is preferable to use a urethane-modified polyester resin as the component (A) because it has excellent storage stability, scuffing resistance, sharpness, and chipping resistance.

The resin is obtained by reacting a polyester resin (preferably oil-free) obtained by reacting the alcohol component and acid component exemplified above with a polyisocyanate compound (preferably diisocyanate) in an excess of hydroxyl groups. Examples of the polyisocyanate compound include aromatic polyisocyanate compounds such as tolylene diisocyanate and 4,4'-diphenylmethane diisocyanate, araliphatic polyisocyanate compounds such as xylylene diisocyanate, meta- or para-tetramethylxylylene diisocyanate, and hexamethylene. Diisocyanate, isophorone diisocyanate, biuret and isocyanurate products thereof, aliphatic polyisonanates and alicyclic polyisocyanates such as trimethylhexamethylene diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated 4,4'-diphenylmethane diisocyanate, etc. can be mentioned. Among these, tolylene diisocyanate, xylylene diisocyanate and isophorone diisocyanate are preferred in order to improve the storage stability of the paint. The amount of the polyisocyanate compound used is preferably 1 to 40% by weight, particularly 4 to 30% by weight based on the polyester resin.

Component (A) has an acid value of 10 to 100, preferably 15 to 50, and a hydroxyl value of 20 to 300, preferably 50.
~230. If the acid value is less than 10, the water compatibility will be insufficient, if the hydroxyl value is less than 20, the curing of the coating will be insufficient, and if the acid value is more than 100 and 300, the water resistance of the coating will be poor. Both of these are unfavorable because they reduce chemical resistance.

Furthermore, regarding component (A), the weight average molecular weight is 1000-
20000. In particular, 3000 to 15000 is suitable.

A basic substance is added to these component (A) to neutralize 50% or more of the carboxyl groups to make it aqueous.

Examples of the basic substances used here include ammonia, methylamine, ethylamine, dimethylamine, diethylamine, trimethylamine, triethylamine,
Examples include dimethylethanolamine, jetanolamine, and triethanolamine, among which jetanolamine, dimethylethanolamine, triethanolamine, and the like are preferred.

Component (B): an aqueous amino resin.

This is a crosslinking agent for component (A), such as
Examples include tri-, tetra-, venter-, hexa-methylolmelamine and methyl etherified products thereof, urea-formaldehyde condensates, urea-melamine cocondensates, and the like.

Component (B) is hydrophilic to the extent that it dissolves in water or is stably dispersed in water without layer separation or sedimentation.

Among the above components, melamine is preferred as component (B). The relationship between the functional groups of the melamine and the performance of this paint is as follows.

(1) Using a completely etherified methylolated melamine increases armpit resistance, but the crosslinking reaction temperature is high;
If an acid catalyst is not used to cure the coating film at about 140 to 150°C, the crosslinking reaction tends to be insufficient.

(i) Melamine, which has a mixture of methylol groups (-CH20H) and alkyl ether groups (-CH20R), has a fast initial curing and does not require an acid catalyst, but water and solvent do not volatilize sufficiently from the applied coating film. Over time, the coating may begin to harden on the surface, causing wrinkles.

(i) Imino group (>NH) and alkyl ether group (-C
For melamine mixed with H20R), 1
It crosslinks well with component (A) at about 40 to 150°C.

In addition, this crosslinking reaction is relatively slow and self-curing is not as fast as the methylol group, so crosslinking and curing begins after the organic solvent and water have volatilized and the coating has melted and flowed, resulting in good smoothness and no wrinkles. Moreover, a coating film with good curability can be obtained.

In the present invention, as component (B), in this sense,
(i) Imino group-containing water-soluble amino resins are most suitable.

(C) Component knee formula %formula%) [However, R is CH3 CH3 CH3 n is an integer from 2 to 10. ] It is a polyether polyol shown by

Here, if n in the above formula is smaller than 2, water solubilization will be insufficient, and if n is larger than 10, the water resistance of the coating will deteriorate, which is not preferable. In particular, n in the formula is most preferably 2 to 5.

By blending this (C1 component), the non-volatile content during painting increases, atomization during spray painting becomes better, and in particular, the applied paint spreads easily, improving the critical underarm film thickness. Good results can be obtained.

Component (D): alkyl etherified benzoin.

This is an alkyl (preferably carbon number 1 to 4) etherified product of benzoin, and specifically, benzoin methyl ether, benzoin ethyl ether, benzoin n-propyl ether, benzoin 1so-propyl ether, benzoin n-butyl ether, benzoin 1so-
Examples include butyl ether.

These can be used alone or in combination of two or more.

(Methods for adding the DJ acid component include (1) Adding at the time of pigment dispersion, (2) Adding to the aqueous solution of component (A) at room temperature or under heating and stirring and mixing, and Adding at the time of synthesis of component (A). There are several methods of addition, such as adding, and there is no effect on the underarm improvement effect using either addition method, but it is generally determined by taking into account the pigment content in the paint and the melting point of the (D>component). , method (2) is preferred.

By blending component (D), it is effective to suppress the occurrence of wrinkles and increase the thickness of the film where wrinkles occur.

This paint is the above (^) (B) (C1 and (
Component D) is essential, and the composition ratio of these components can be selected arbitrarily depending on the purpose, but based on the total weight of components (A), (B), and (C), component (A) is 30 to 8
5% by weight, especially 50-80% by weight, component (B) 10-80% by weight
40% by weight, especially 15-30% by weight, and component (C) 5-30% by weight, especially 5-20% by weight, respectively. In addition, component (D) includes (A), (B) and (
It is preferably 0.1 to 10% by weight, particularly 1 to 5% by weight, based on the total amount of component C).

(B) (C) (D>Each component used in this paint has the effect of improving armpit resistance even when used alone, but the extent of this effect is only about 40 μm (dry film thickness) in the armpit limit film thickness, and recently Intermediate coating thick film orientation (e.g. 45μm or more)
In this case, it is insufficient. This is because even if you spray paint to a film thickness of approximately 45 μm, some sagging or sagging may occur and the film thickness in that area may become 60 μm or more, so even if it is 60 μm or more, no wrinkles will occur. This is strongly desired, and with this paint,
By blending all of the components (B), (C), and (D) with the component (A), the underarm film thickness can be reduced to 60 μm.
It is now possible to do more than that. Note that these film thicknesses are for a system that was not preheated but was heated immediately after coating for crosslinking and curing.

This paint contains the above (A), (B), (C), and (D) components as essential components, and further includes an anti-cissing agent,
Antifoaming agents, leveling agents, anti-sag agents and curing accelerators (
Various modifiers and auxiliaries such as acid catalysts can be added as necessary. In addition, organic solvents that are freely miscible with water, such as alcohols, ether alcohols, esters, and ketones, can also be blended, and the amount to be blended is as follows:
A range of 20% by weight or less based on the resin solid content (weight) is suitable.

In addition, inorganic pigments such as titanium oxide, barium sulfate, calcium carbonate, and clay are used to improve the film thickness retention of the intermediate coating film, painting workability, and physical strength of the paint film, as well as inorganic pigments such as swelling pigments. The various pigments of (A) (B) (
It is preferable that 1 to 200 parts by weight be distributed based on 100 parts by weight of the total resin solid content of components C) and (D).

This paint is adjusted to the appropriate viscosity with water and applied by spray painting or electrostatic painting. The suitable thickness of the coating film is 30 to 50 μm in flat areas, based on the cured coating film. The coating film usually undergoes a crosslinking reaction by heating at 140° C. or higher to form a cured coating film. Further, the undercoat paint and topcoat paint such as electrodeposition paint (anionic type, cationic type) in the above-mentioned coating system using the present paint are not particularly limited and may be those already commonly used.

Effects of the Invention Even if the water-based intermediate coating of the present invention is immediately heated for the crosslinking and curing reaction without preheating, the underarm film thickness limit is 60 μm.
The coating has the above properties, exhibits high armpit resistance, and has a good coated surface smoothness.

The preheating required by conventional water-based intermediate coatings to prevent undercoating reduces sagging resistance, and the technology for imparting structural viscosity to the paint, which is necessary to counteract sagging, is a The vicious cycle of decreasing smoothness is wiped out by the paint of the present invention, and the occurrence of wrinkles and sagging is suppressed.
Moreover, it was well-balanced with excellent smoothness. Furthermore, in terms of topcoat sharpness, interlayer adhesion, chipping resistance, etc., it is completely comparable to general-purpose organic solvent-based intermediate coatings.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to production examples, working examples, and comparative examples. In each example, parts and percentages are generally based on weight.

I Example of producing component (A)■ 19.6 parts of ethylene glycol, 18.5 parts of trimethylolpropane and 46.7 parts of phthalic anhydride were mixed into 16 parts of
After reacting 15.7 parts of tolylene diisocyanate (tolylene diisocyanate) at 120°C to a polyester resin obtained by reacting at 0 to 230°C for 7 hours, 5.2 parts of trimellitic anhydride was further added and the mixture was heated to 180°C. The weight average molecular weight is 6 after reacting for a period of time.
000, a urethane modified polyester resin having an acid value of 40 and a hydroxyl value of 112 was obtained. This was neutralized in an equivalent amount with dimethylethanolamine to obtain a urethane-modified polyester resin (■). The amount of polyisocyanate used is 17% by weight based on the polyester resin.

■ 19.3 parts of ethylene glycol, 18.2 parts of trimethylolpropane and 46.2 parts of phthalic anhydride
After reacting 16.8 parts of xylylene diisocyanate at 120°C to a polyester resin obtained by reacting at 0 to 230°C for 7 hours, 5.1 parts of trimellitic anhydride was further added and reacted at 180°C for 1 hour. Weight average molecular weight is 6
200, an acid value of 40, and a hydroxyl value of 110, a urethane-modified polyester resin was obtained. This was neutralized in an equivalent amount with jetanolamine, and the urethane-modified polyester resin was
And so. The amount of polyisocyanate used is 18% by weight based on the polyester resin.

■ 27.7 parts of ethylene glycol, 10 parts of glycerin.
3 parts and 50.0 parts of phthalic anhydride at 160-230°C
After reacting 9.7 parts of tolylene diisocyanate at 120°C with the polyester resin obtained by reacting for 7 hours,
Further, 8.3 parts of phthalic anhydride was added and reacted at 160° C. for 3 hours to obtain a urethane-modified polyester resin having a weight average molecular weight of 4500, an acid value of 50, and a hydroxyl value of 220. This was neutralized with an equivalent amount of triethanolamine, and
It was made into urethane-modified polyester resin (■).

The amount of polyisocyanate used is 10% by weight based on the polyester resin.

■Examples 1 to 3 and Comparative Examples 1 to 3 Aqueous intermediate coatings were obtained according to the compositions shown in Table 1.

As pigments, 80 parts of titanium oxide white, 20 parts of barium sulfate, and 0.3 parts of carbon black were blended per 100 parts of the total solid content of components (A), (B), and (C).

These pigments were placed in a container together with part of the ingredients (A), deionized water, and an antifoaming agent, and the particles were measured using a whelk gauge using a glass piece as a dispersion medium for 1 hour.
The particles were dispersed so that the particles were 5 μm or less.

(Book 1) (A) Component name.

■, ■, and ■ are those obtained in the above production example.

($2) (B) Component name.

(B-1): r Cymelf 03J (Mitsui Suyanamide ■ product, imino group-containing melamine resin) (B-2
): r Cynor 3F 0J (Mitsui Suyanamide■
Product, partially etherified methylolmelamine resin, Imino Foundation First) (Book 3) (C) Component name In the polyether polyol shown by the general formula, (C-1
): n=3 (C-2): n=4 (-) (D) Component name (D-1): Benzoin ethyl ether, (*5) Organic solvent diethylene glycol monoethyl ether. The blending amount is per 100 parts by weight of the total solid content of component FA), component (B) and component (C).

■Performance test results It is shown in Table 2 below.

The test method is as follows.

(N7) On a steel plate with an underarm film thickness of approximately 10 cm x 45 cm, apply water-based intermediate coating paint to a thickness of approximately 30 μm in the thin film area and approximately 70 μm in the thick film area using spray painting. ℃
After holding the coated plate horizontally for 10 minutes at a temperature of 70 to 75% RH, the coated plate is baked and hardened in a dryer at 150°C. At this time, the maximum film thickness without coating defects on the armpit is defined as the limit film thickness for the armpit.

(N8) A steel plate of the same size as the sag limit film thickness (N7), with a diameter of 10a along the long side.
Use one with holes of m in diameter at intervals of 4c1T1.

Painting is done in the same way as (*7). After painting, hold the paint plate vertically (so that the holes are lined up horizontally) during setting and baking. The maximum film thickness without any sag defects around the hole at this time is defined as the sag limit film thickness.

(*9) American Chain &
TUKON m1cr made by CableCompaDy
Measured using ohardness jester. The larger the number, the harder it becomes.

(N10) Overbake Adhesive surface treatment: Apply electrodeposition to the steel plate, then apply an intermediate coat (film thickness 45 μm), bake harden at 150°C for 30 minutes, and then apply an intermediate coat at 160°C for 1 hour. Immediately after cooling, a top coat ("Amirac" black enamel manufactured by Kansai Paint ■) was applied thereto and baked and hardened at 140° C. for 30 minutes. The degree of peeling of the coating film was examined using a cross-cut adhesive cellophane tape test. O indicates no peeling, and Δ indicates slight peeling.

($11) Top coat system ($10) Use the same process to apply water-based intermediate coat paint at 40±5
On top of the intermediate coat (without polishing, etc.), which was baked and cured at 150°C for 30 minutes, a top coat (Amilac black enamel manufactured by Kansai Paint Co., Ltd.) was applied to a thickness of 30 to 40 μm, and then baked at 140°C. Tests were based on coatings that were bake cured for 30 minutes.

(02) IMAGE CLARITY METE
Measured using R. Suga Test Instruments. The numbers in the table are ICM values that range from 0 to 100%; the higher the number, the better the image clarity, and if the ICM value is 85 or higher, the image clarity is excellent. shows.

(N13) Chipping resistance A stepping stone testing machine (Suga Test Machine Co., Ltd., JA-400 type) was used.

The painted test plate was mounted vertically on the sample holder of the testing machine, and 50g of No. 7 crushed stone was measured using the pressure gauge of the testing machine at 4kg/
The crushed stone is injected at crE air pressure to collide with the test plate at right angles. The degree of peeling damage at that time was evaluated in 5 grades from good (0) to poor (x).

(s14) Adhesive goban (100 pieces of IX1 mm) cellophane adhesive tape test. ○ indicates no peeling.

(Umbrella 15) Humidity Resistance Temperature: 50° C. Relative Humidity: 98-100% RH After being left in a blister box for 5 days, it was taken out and checked for blisters. ○ indicates no blistering.

(that's all)

Claims (1)

[Claims] (1) (A) An acid value of 10 to 100 and a hydroxyl value of 20
~300 polyester resins, (B) water-based amino resins, (C) general formulas ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [However, R is ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ or ▲ mathematical formulas, chemical formulas, tables, etc. etc. ▼, where n is an integer from 2 to 10. ] A water-based intermediate coating material characterized by containing as main components a polyether polyol shown by the following and (D) an alkyl etherified benzoin.