JPH0627279B2 - Intermediate coating composition for automobiles - Google Patents

Description

TECHNICAL FIELD The present invention relates to an intermediate coating composition for automobiles having improved chipping resistance.

[Conventional technology]

In the field of automobile industry, it is strongly desired to prevent the durability of the coating, especially the deterioration of the corrosion resistance of the coating due to the peeling of the coating due to impact and the progress of corrosion of the substrate. Especially in cold regions such as Europe and America, gravel and the like mixed with a large amount of rock salt is often laid in order to prevent freezing of the motorway in winter. On the outer surface of an automobile running on this kind of road, the rock salt particles and pebbles bounced up by the wheels collide with the surface of the coating film, and the impact causes the coating film to locally peel off from the base material.
Causes so-called chipping. Due to this phenomenon, the metal surface is exposed at the impacted part, and rusting occurs quickly and corrosion progresses.

In order to prevent chipping and the progress of corrosion caused by this, various studies have been made on chemical conversion treatment, electrodeposition primer, intermediate coating, and top coating. In particular, with respect to the intermediate coating composition, many studies have been conducted in order to reduce the impact force and prevent the coating film from peeling off from the metal surface, which causes rusting. For example, Japanese Examined Patent Publication (Kokoku) No. 52-43657 discloses an intermediate coating composition for automobiles containing sericite in an amount of 10 to 75% by weight based on the total solid content in the coating.

Further, in JP-A-55-56165, an intermediate coating composition for automobiles containing, as essential components, 20 to 50 parts by weight of talc powder and 10 to 50 parts by weight of rust preventive pigment in an acidic resin having an acid value of 10 to 50. The thing is disclosed.

[Problems to be solved by the invention]

However, in such a conventional intermediate coating composition for automobiles, when a large amount of a pigment having a flat shape such as sericite or talc powder is contained and the impact force acts on the automobile coating film, an intermediate coating film is obtained. A relatively small impact force, which usually does not damage the coating, because the layer cohesively fails, thereby cushioning the impact force and preventing the entire coating from peeling from the metal surface. Even if the action of the intermediate coating film occurs, cohesive failure of the intermediate coating film occurs, and since the destruction area is large, rusting can be prevented when chipping occurs, but on the contrary, the aesthetic appearance of the vehicle is significantly impaired. There was a point.

[Means for solving problems]

The present invention has been made by paying attention to such conventional problems, and is a polycondensate obtained by transesterification of bis (hydroxyethyl) terephthalate and a chain diol as an organic binder component of an intermediate coating for automobiles. By using a polyester resin composed of a dehydration condensation product of a chain polyester diol and a polyvalent carboxylic acid, it is an object to solve the above problems.

The intermediate coating composition for an automobile of the present invention comprises 95 to 50 parts by weight of bis (hydroxyethyl) terephthalate and 3 to 3 carbon atoms.
10 to 80 parts by weight of a linear polyester diol having a molecular weight of 500 to 2000 and 90 to 20 parts by weight of another component containing a polyvalent carboxylic acid, which is a polycondensation product of a transesterification reaction of 5 to 50 parts by weight of a chain diol of 10 Number average molecular weight
An intermediate coating composition for an automobile comprising 2000 to 10000, 90 to 60 parts by weight of a polyester resin having an average of 2.1 to 2.8 hydroxyl groups in one molecule, and 10 to 40 parts by weight of a resin having a reactive group capable of reacting with hydroxyl groups. Is.

The polyester resin which is the first component of the coating material of the present invention is
It is the main component (main component) of the binder component, and contains polyester diol, which is a polycondensate obtained by transesterification of bis (hydroxyethyl) terephthalate, and chain diol having 3 to 10 carbon atoms, and polyvalent carboxylic acid. It is a dehydration condensate with the above component.

Bis (hydroxyethyl) terephthalate is obtained by reacting two carboxyl groups of terephthalic acid with ethylene glycol one by one, and a commercially available product can be used as it is.

As the chain diol having 3 to 10 carbon atoms, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexane are used. There are diol, 2-ethyl-1,3-hexanediol, 1,10-decanediol, diethylene glycol, triethylene glycol, dipropylene glycol, 2,2'-thiodiethanol, etc., and one or more of these may be used. Can be used.

Bis (hydroxyethyl) terephthalate and 3 to 3 carbon atoms
A linear polyester diol, which is a polycondensation product obtained by transesterification of a chain diol of 10 with bis (hydroxyethyl) terephthalate and a chain diol having 3 to 10 carbon atoms at 200 to 250 ° C. under stirring. It is produced by a method of heating ethylene to a temperature and separating the desorbed ethylene glycol out of the system. At this time, the ratio of bis (hydroxyethyl) terephthalate to the chain diol having 3 to 10 carbon atoms is (9
5: 5) to (50:50). When the proportion of the chain diol having 3 to 10 carbon atoms is less than 5, the melting temperature of the linear polyester diol obtained by the polycondensation by the transesterification reaction becomes too high, and the subsequent synthesis of the polyester resin becomes difficult. In addition, the obtained polyester resin becomes difficult to dissolve in a solvent. When the proportion of bis (hydroxyethyl) terephthalate is less than 50, the strength of the resulting polyester resin is low and the desired improvement in chipping resistance is not sufficient.

Bis (hydroxyethyl) terephthalate and 3 to 3 carbon atoms
The linear polyester diol produced by polycondensation of 10 chain diols by transesterification reaction needs to have a molecular weight of 500 to 2000. When the molecular weight of the linear polyester diol is less than 500, the strength of the polyester resin obtained using this is insufficient and the improvement in chipping resistance is insufficient, and when it exceeds 2000, the melting temperature and viscosity are It is high, which makes subsequent production of polyester resin difficult.

The polyester resin which is the first component in the present invention is
The linear polyester diol obtained above is mixed with other polyhydric alcohols and carboxylic acids, and the method conventionally used for producing polyester resins for paints, that is, heating at 160 ° to 250 ° C. The water produced by the reaction is separated from the system.

Other polyhydric alcohols that can be used here include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol. , 2,3-butanediol, 1,5
-Pentanediol, neopentyl glycol, 1,6-
Hexanediol, 2-methyl-2,4-pentanediol, 2-ethyl-1,3-hexanediol, 1,10-decanediol, cyclohexane-1,4-dimethylol, hydrogenated bisphenol A, glycerin, trimethylolethane , Trimethylolpropane, pentaerythritol,
Solbit and the like can be used, and one or more of these can be used in combination.

Next, as the polycarboxylic acid, succinic acid, adipic acid, 1,10-decanedicarboxylic acid, fumaric acid, isophthalic acid, terephthalic acid, maleic anhydride, phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, Hexahydrophthalic anhydride, etc., and methyl esters thereof, etc. can be used alone or in combination of two or more.

In the production of the above polyester resin, for the purpose of controlling the molecular weight and improving the solubility, an 11-valent alcohol, a monovalent carboxylic acid, a monoepoxy compound or the like may be used, but the amount thereof is within a range not impairing the purpose of the present invention. And should be about 10% by weight or less in the polyester resin. Examples of monohydric alcohols that can be used include normal octyl alcohol, 2-ethylhexyl alcohol, lauryl alcohol and stearyl alcohol. As the monovalent carboxylic acid, caproic acid, caprylic acid, pelargonic acid,
In addition to isononanoic acid, lauric acid, stearic acid, oleic acid, benzoic acid, tert-butylbenzoic acid, various animal and vegetable oil fatty acids, such as soybean oil fatty acid, linseed oil fatty acid, safflower oil fatty acid, rapeseed oil fatty acid, castor oil fatty acid, Examples include dehydrated castor oil fatty acid, tall oil fatty acid, and rice bran oil fatty acid. Examples of the monoepoxy compound include phenyl glycidyl ether, normal butyl glycidyl ether, and glycidyl ester of versatic acid marketed by Shell Chemical Company under the trade name of Cardura E.

The raw material ratio of the polyester resin used in the present invention is 10 to 80 parts by weight of the linear polyester diol,
The total amount of other components, that is, polyhydric alcohol, polyhydric carboxylic acid, monohydric alcohol, monohydric carboxylic acid, monoepoxy compound and the like is 90 to 20 parts by weight.

When the amount of the linear polyester diol is less than 10 parts by weight, the strength of the obtained polyester resin is insufficient and the desired improvement in chipping resistance is not sufficient. On the other hand, when the amount of the linear polyester diol exceeds 80 parts by weight, the solubility in a solvent is poor and the dispersibility of the pigment is poor, which is not practical.

In the present invention, the molecular weight of the polyester resin is a number average molecular weight in the range of 2000 to 10000,
It is necessary to have 2.1 to 2.8 hydroxyl groups. The number average molecular weight can be determined from the polystyrene reduced molecular weight using gel permeation chromatography. Again 1
The average number of hydroxyl groups per molecule is calculated by the following formula from the hydroxyl value and number average molecular weight measured by the method described in ASTM-D1957-86.

When the number average molecular weight of the polyester resin is less than 2000, the strength of the polyester resin is insufficient and the chipping resistance is not sufficiently improved. When the number average molecular weight is more than 10,000, the viscosity is too high at the concentration of non-volatile components of ordinary paints, and the coating is difficult and not practical. When the average amount of hydroxyl groups in one molecule is less than 2.1, it is not practical because the water resistance, chemical resistance and solvent resistance after curing are poor.
If the number exceeds 2.8, the flexibility and adhesion of the coating film deteriorate, and the chipping resistance decreases.

The polyester resin thus obtained is diluted with an organic solvent to an appropriate concentration, preferably 30 to 70% by weight before use. Examples of organic solvents used include aromatic organic solvents such as benzene, toluene, xylene, Solvesso 100 and Solvesso 150 (both are trade names) commercially available from Exxon Chemical Company; methyl alcohol, ethyl alcohol, isopropyl alcohol. , Normal butyl alcohol, isobutyl alcohol, sec-butyl alcohol, amyl alcohol, cyclohexyl alcohol and other alcohols; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, ethylene acetate Glycol-based solvents such as glycol monoethyl ether; acetone, methyl ethyl ketone, methyl isobutyl ketone, Ketone solvents such as chillamyl ketone and cyclohexanone; ester solvents such as ethyl acetate, butyl acetate, isobutyl acetate, amyl acetate, methyl propionate and ethyl propionate, as well as dioxane, isophorone, 2-nitropropane, N-methylpyrrolidone, etc. And these can be used alone or in combination of two or more.

The intermediate coating composition for automobiles of the present invention comprises the polyester resin obtained above and a resin having a reactive group capable of reacting with a hydroxyl group. The resin having a reactive group capable of reacting with the hydroxyl group, which is the second component, serves as a curing agent component for reacting with the polyester resin and curing, and is a reactive group capable of reacting with the hydroxyl group of the polyester resin. There is no limitation as long as it is a resin having

As the resin having a reactive group capable of reacting with a hydroxyl group, an amino resin, a phenol resin, a ketone resin, a xylene resin,
There are furfural resin, polyisocyanate resin, blocked polyisocyanate resin in a form in which all or part of isocyanate groups are blocked, epoxy resin, etc., but in the present invention, amino resin, polyisocyanate resin and blocked polyisocyanate resin It is preferable to use one or more selected from the following. Examples of the amino resin include urea resin, melamine resin, acetoguanamine resin, benzoguanamine resin, and phthaloguanamine resin. Examples of the polyisocyanate resin include Desmodur-L and Desmodur-N, which are commercially available from Bayer, Coronate-EH, which is commercially available from Nippon Polyurethane Industry Co., Ltd., and are commercially available from Huls.
There is IPDI-T-1890 (both are trade names). As the blocked polyisocyanate resin, all or part of the isocyanate groups of these polyisocyanate resins may be a monohydric alcohol such as 2-ethylhexyl alcohol,
Those blocked with an oxime such as phenol, ε-caprolactam, methyl ethyl ketone oxime, or a blocking agent such as diethyl malonate or methyl acetoacetate can be used.

In the present invention, the weight ratio of the polyester resin and the resin having a reactive group capable of reacting with the hydroxyl group is 90:
It is in the range of 10 to 60:40. When the ratio of the resin having a reactive group capable of reacting with a hydroxyl group is less than 10, the coating film is insufficiently crosslinked and the water resistance, chemical resistance and solvent resistance are poor.
If the ratio of the resin having a reactive group capable of reacting with a hydroxyl group exceeds 40, the flexibility and adhesion of the coating film will decrease,
The chipping resistance is reduced.

The intermediate coating composition for automobiles of the present invention, in addition to the above components, coloring pigments such as titanium oxide, zinc oxide, carbon black, precipitable barium sulfate, calcium carbonate, red iron oxide, mapico yellow, lead chromate, and base. Antirust pigments such as basic lead sulfate, calcium molybdate, zinc chromate and the like can be contained. The ratio of these pigments is not particularly limited, but is usually in the range of 0.2 to 1.4 by weight ratio with respect to the organic binder component. In the intermediate coating composition for an automobile of the present invention, other various additives conventionally used in the field of coating materials such as a surface tension adjusting agent, a leveling agent, an anti-sagging agent, an antifoaming agent and an anti-settling agent. Agent,
A pigment dispersant or the like can be used.

The intermediate coating composition for automobiles of the present invention is produced by the apparatus and method conventionally used for producing intermediate coatings for automobiles. In this case, the polyester resin and the resin having a reactive group capable of reacting with a hydroxyl group may be mixed in advance in one liquid, or the two liquids may be separately mixed and mixed during coating. When a polyisocyanate resin is used as the resin having a reactive group capable of reacting with a hydroxyl group, a two-pack type is preferred.

[Action]

The intermediate coating composition for an automobile of the present invention is provided as it is or after being diluted with a thinner to an appropriate viscosity for coating. As a coating method, a method usually used for coating intermediate coatings in the automobile industry, for example, air spray coating, airless spray coating, air atomization electrostatic coating,
Any of bell rotary atomization type electrostatic coating and the like can be applied.

The intermediate coating composition for automobiles of the present invention is applied to an automobile body to which an undercoating paint such as an electrodeposition primer is previously applied so that the film thickness after curing is 10 to 70 μm, and then a polyisocyanate resin is blended. In the case of room temperature to 150 ° C for 10 minutes to 24 hours, when amino resin or blocked polyisocyanate resin is blended, it is cured by heating and drying at the temperature of 100 to 200 ° C for 5 minutes to 1 hour to prevent chipping. Very good and water resistant
A coating film with good chemical resistance and solvent resistance can be obtained. In this case, the hydroxyl group of the polyester resin reacts with the reactive group of the resin of the other component to cause cross-linking curing, and an excellent coating film is formed.

〔The invention's effect〕

As described above, according to the present invention, the constitution thereof is a linear polyester diol and a polyvalent carboxylic acid which are reaction products of bis (hydroxyethyl) terephthalate and a chain diol having 3 to 10 carbon atoms. Since the polyester resin obtained from the above and a resin having a reactive group capable of reacting with the polyester resin are used as components, a coating film with extremely tough and good adhesion is obtained, and chipping resistance is remarkably higher than that of conventional ones. improves.

〔Example〕

Hereinafter, the configuration, action, and effect of the present invention will be described in more detail with reference to Examples. Unless otherwise specified, the parts,%, and ratios in each example represent parts by weight,% by weight, and weight ratio, respectively.

The hydroxyl value was measured by the method described in ASTM-D1957-86 as follows, and based on this, the average number of hydroxyl groups per molecule was calculated.

Method for measuring hydroxyl value Accurately weigh about 3 g of polyester resin in a 250 ml Erlenmeyer flask. 5 ml of pyridine / acetic anhydride = 50
Add the / 50 solution with a pipette and dissolve by gently stirring. As a blank, take 5 ml of pyridine / acetic anhydride solution in another Erlenmeyer flask, and further add 10 ml of pyridine. Attach a reflux condenser to the Erlenmeyer flask, heat with a water bath and reflux for 1 hour. After refluxing for 1 hour,
From the top of the condenser, add 10 ml of pure water into the Erlenmeyer flask and continue refluxing for another 10 minutes. Remove the Erlenmeyer flask from the water bath and cool to room temperature with the condenser attached. After cooling to room temperature, 25 ml of neutral n-butyl alcohol are added. At this time, with the reflux condenser attached to one half, the inner wall of the condenser tube is washed off from the upper portion of the condenser tube, and the other half is added by washing the inner wall of the Erlenmeyer flask. Add phenolphthalein solution as an indicator and titrate with 0.5N alcoholic KOH solution.
The acid value of the polyester resin is measured separately, and the hydroxyl value is calculated by the following formula.

S = sample amount of polyester resin used for acetylation
(g) V = titration amount of KOH solution required for neutralization of acetylated sample (ml) C = sample amount of polyester resin used for acid value measurement
(g) A = Titration volume of KOH solution required for acid value measurement (ml) B = Titration volume of KOH solution required for blank neutralization (ml) N = Factor of KOH solution In the examples, polyester resin was used as solvent. Since the hydroxyl value was measured with a varnish diluted with, the hydroxyl value of the polyester resin itself was calculated by the following equation by dividing the hydroxyl value of the solution according to the above formula by the resin nonvolatile content (%).

Based on the hydroxyl value thus obtained and the value of the number average molecular weight obtained from the polystyrene reduced molecular weight by gel permeation chromatography, the polyester resin 1
The average number of hydroxyl groups per molecule was calculated by the following formula.

Production Example A Production of Linear Polyester Diol A The following components were put in a reactor equipped with a heating device, a stirring device, a thermometer, a reflux cooling pipe equipped with an ethylene glycol separator, and a nitrogen gas introduction pipe.

Bis (hydroxyethyl) terephthalate 88.0 parts 1,5-pentanediol 12.0 parts The mixture was heated, and when the temperature reached 90 ° C., stirring was started, and a small amount of nitrogen gas was passed through the nitrogen gas introduction pipe. The temperature was further raised and the reaction was carried out at a temperature of 220 to 230 ° C. Since ethylene glycol was released, it was separated by an ethylene glycol separator. Four hours after the reaction was started, 3.0 parts of xylene was added to the reaction product, and the ethylene glycol separator was also filled with xylene, so that ethylene glycol and xylene were azeotropically distilled to promote desorption of ethylene glycol.

The reaction was terminated when 22.5 parts of ethylene glycol was released, cooled, and taken out. The product became a white solid on cooling, had a melting point of 130-140 ° C and a molecular weight of 671.

Examples 1 to 3 and Comparative Examples 1 to 2 (I) Production of Polyester Resin Using the linear polyester diol A produced in Production Example A, the number average molecular weight and the average in one molecule were obtained according to the formulation shown in Table 1. Polyester resins having different numbers of hydroxyl groups were produced as follows.

That is, a linear polyester diol A, neopentyl glycol, trimethylol propane, isophthalic acid, a reactor equipped with a heating device, a stirring device, a thermometer, a reflux cooling pipe with a water separator, and a nitrogen gas introduction pipe And adipic acid were added and heated. When the temperature reached 120 ° C., the nitrogen gas introduction tube was opened and nitrogen gas was passed through to start stirring. The mixture was gradually heated to 230 ° C over 3 hours, and the reaction was continued at 230 ° C for 1 hour. After 1 hour, 3 parts of xylene was added to the contents, and the water separator was also filled with xylene so that the reaction water was azeotropically distilled with xylene to promote desorption.

One hour after the addition of xylene, about 1 g of a sample was collected in an Erlenmeyer flask, dissolved from 10 ml of a neutral xylene / n-butyl alcohol solution, and titrated with a 0.1N alcoholic KOH solution using a phenolphthalein indicator. Then, the acid value was calculated by the following formula.

The reaction was continued while maintaining the temperature at a factor of N = KOH solution of 230 ° C, and the acid value was measured every hour. The reaction is terminated when the acid value becomes 7 or less,
Cooled. After cooling to 120 ° C., the varnish was diluted with a mixed solvent having the following composition so that the nonvolatile content was 60%.

Xylene 20.0% Solvesso No.150 30.0% (Exxon Chemical, trade name, high boiling aromatic solvent) Cyclohexanone 40.0% n-Butyl alcohol 10.0% Approximately 3 g of polyester resin varnish produced in this way
Was placed in a 250 ml Erlenmeyer flask, the hydroxyl value was measured by the above-mentioned hydroxyl value measuring method, and the average molecular weight was measured by gel permeation chromatography to obtain the results shown in Table 1.

(II) Preparation of paint The following ingredients were placed in a vessel of a ball mill disperser and dispersed using a ceramic ball for 48 hours.

Polyester resin varnish produced in (I) (nonvolatile content 60%) 25.4 parts Rutile type titanium oxide 27.6〃 Mapico yellow 1.0〃 carbon black 0.3〃 xylene 3.8〃 normal butyl alcohol 3.8〃 After dispersing, sieve ceramic balls and The ingredients were added and mixed with a dissolver to produce a paint.

Polyester resin varnish manufactured in (I) 16.9 parts Super Beckamine L-116-70 (Butylated melamine resin varnish manufactured by Dainippon Ink and Chemicals, Inc., non-volatile content 68%) 16.0 〃 xylene 5.2 〃 The resulting coating has a nonvolatile content of 65.2%, a polyester resin to melamine resin ratio of 70:30, and a pigment to organic binder component ratio of 0.8.

(III) Coating and coating performance test The intermediate coating prepared in (II) was used as Solvesso 150 (existing):
It was diluted with a thinner having a composition of 95: 5 normal butyl alcohol so that the viscosity was 25 seconds when measured at 20 ° C. using Ford cup No. 4.

0.8 mm thick, 150 mm long, 70 mm wide automotive steel plate (JIS-G-3
141) treated with Bonderite No. 3004 (trade name of zinc phosphate coating manufactured by Nippon Parker Rising Co., Ltd.), and then Power Top U-100 (Nippon Paint Co., Ltd.)
15) made of cation type electrodeposition primer for automobile
Test plate coated to ~ 20μm thickness is air-sprayed so that the film thickness after baking diluted intermediate coating is 35-40μm, and set at room temperature for 10 minutes, then 30
It was baked and cured at a temperature of 140 ° C. for 1 minute. Then
Melami No.1500 red enamel (manufactured by NOF CORPORATION, automotive topcoat) as an overcoat was air-sprayed on the test plate so that the film thickness after baking was 35-40 μm, and then 10 minutes. After setting to room temperature, 140
It was baked for 30 minutes at a temperature of ° C to cure. With respect to the test plate prepared in this manner, while performing a coating film performance test based on JIS-D-0202 coating rules for automobile parts, a chipping resistance test of the following test method with a gravelometer,
The chipping resistance was evaluated.

Chipping resistance test method: ASTM-D-3170 “Standard Method of Test for Chip Resi
In accordance with "stance of Coatings", the chipping resistance test and evaluation are performed as follows.

(1) Testing equipment; QGR gravelometer (Q-Panel company product) (2) Chip material; Marble particles with a diameter of about 10 to 15 mm (3) Amount of chip material: Approx. 250 pieces (4) Spraying air pressure: Approx. 4.8Kg / cm ² (5) Test temperature; 20 ℃ (6) Evaluation method: Cover the periphery with gum tape leaving the center 40mm × 40mm of the test plate and attach it to the test plate holder.
The chip material is jetted at a pressure of 4.8 kg / cm ² , and the number of flaws caused by collision and the area of the flaw are measured, and the number of peeled pieces in an area of 40 mm × 40 mm and the average peeled area are recorded. Then JIS-Z-
Perform salt spray test with 2371 for 48 hours and record the number of rusts on the impacted part.

Production Examples B to F Production of Linear Polyester Diols B to F In the same manner as in the case of the linear polyester diol A of Production Example A, 5 kinds of linear polyester diols having different molecular weights were produced according to the formulation in Table 2. .

Examples 4 to 6 and Comparative Examples 3 to 4 (I) Production of Polyester Resin Varnish Linear polyester diol B produced in Production Examples BF
To F, polyester resins having different blending amounts of linear polyester diols were blended as shown in Table 3 in Example 1.
It was manufactured in the same manner as. Examples 4 to 6 and Comparative Example 3
The polyester resin of No. 60 has a nonvolatile content of 60 as in Example 1.
%, It became a transparent and viscous liquid, but the polyester resin of Comparative Example 4 did not proceed smoothly, and the non-volatile content was
It had an opaque appearance even at 60%.

(II) Preparation of coating material A coating material was produced in the same manner as in Example 1 except that the polyester resins of Examples 4 to 6 and Comparative Examples 3 to 4 were used.

(III) Coating and coating film performance test Using the five kinds of coating materials produced in (II), coating was performed in the same manner as in Example 1 to prepare a test plate, and a coating film performance test was conducted.

The above results are summarized in Table 4.

Production Examples G to L Production of Linear Polyester Diols G to L In the same manner as in the case of the linear polyester diol A of Production Example A, the proportion of the chain diol having 3 to 10 carbon atoms in the formulation of Table 5 was adjusted. Different linear polyesters G to K and linear polyester diol L containing no chain diol having 3 to 10 carbon atoms were produced.

Examples 7 to 10 and Comparative Examples 5 to 6 (I) Production of Polyester Resin Using the linear polyester diols G to L, 6 types of polyester resins having the composition shown in Table 6 were prepared in the same manner as in Example 1. Was manufactured. Regarding Examples 7 to 10 and Comparative Example 5, the varnish having a nonvolatile content of 60% was transparent as in Example 1, but the polyester resin of Comparative Example 6 using the linear polyester diol L was reacted. Did not proceed smoothly, the solubility of the obtained resin was poor, and it had an opaque appearance.

(II) Coating material Examples 7 to 10 and Comparative Example 5 as polyester resin
A coating material was produced in the same manner as in Example 1 except that the polyester resins of ~ 6 were used.

(III) Coating and coating film performance test Using the coating material produced in (II), a test plate was prepared by coating in the same manner as in Example 1, and a coating film performance test was conducted to obtain the results shown in Table 7.

Examples 11 to 12 and Comparative Examples 7 to 8 (I) Production of Polyester Resin Using the linear polyester diol A produced in Production Example A and blending as shown in Table 8, polyester resins having different average number of hydroxyl groups in one molecule Was produced in the same manner as in Example 1.

(II) Coating material Examples 11 to 12 as a polyester resin and Comparative Example 7
A coating material was produced in the same manner as in Example 1 except that the polyester resins of ~ 8 were used.

(III) Coating and coating film performance test Using the coating material produced in (II), coating was performed in the same manner as in Example 1 to prepare a test plate, and a coating film performance test was conducted.

Examples 13 to 14 and Comparative Examples 9 to 10 (II) Preparation of Paint Using the polyester resin produced in (I) of Example 5,
Paints having different proportions of polyester resin and butylated melamine resin with the formulations shown in Table 9 were produced in the same manner as in Example 1.

(III) Coating and coating film performance test Using the coating material produced in (II), coating was performed in the same manner as in Example 1 to prepare a test plate, and a coating film performance test was conducted.

Example 15 (I) Production of polyester resin A polyester resin having the following composition was produced in the same manner as in Example 1.

Linear polyester diol A 30.0 parts Neopentyl glycol 23.6 〃 Trimethylol propane 4.1 〃 Isophthalic acid 30.0 〃 Adipic acid 12.3 〃 Dehydration amount 9.4 parts, the acid value is 4.5 and the hydroxyl value is 69.
9, number average molecular weight 2030, average number of hydroxyl groups in one molecule is 2.5
A polyester resin of 0 was obtained. This resin is xylene:
Cyclohexanone: Butyl isoacetate ratio of 50:40:10
It was diluted with the mixed solvent of to make the nonvolatile content 60%.

(II) Preparation of paint A paint using a polyisocyanate resin as a resin having a reactive group capable of reacting with a hydroxyl group was produced with the following formulation.

Polyester resin varnish manufactured in (I) (non-volatile content 75%) 50.5 parts Desmodur N (product name of polyisocyanate resin manufactured by Bayer, non-volatile content 60%) 9.5〃 rutile titanium oxide 27.9〃 mapicoello 1.0〃 carbon black 0.3 〃 xylene 5.8 〃 Butyl acetate 5.0 〃 The obtained paint has a ratio of polyester resin to polyisocyanate resin of 81:19, a ratio of hydroxyl groups to isocyanate groups of 1: 1 and a ratio of pigment to organic binder.
The content was 0.8 and the nonvolatile content was 66.6%.

(III) Coating and coating performance test The viscosity of the intermediate coating prepared in (II) was measured at 20 ° C with a thinner having a toluene: xylene ratio of 30:70 using a Ford cup No.4. Was diluted to 25 seconds.

The diluted intermediate coating composition was applied to a test plate coated with an electrodeposition primer in the same manner as in Example 1 to give a film thickness of 35 after baking.
After air-spray coating so as to have a thickness of ˜40 μm and setting at room temperature for 10 minutes, baking was performed at a temperature of 120 ° C. for 30 minutes to cure. Then, the top coating material was applied in the same manner as in Example 1. A coating film performance test was conducted on the test plate thus produced in the same manner as in Example 1.

Example 16 (II) Coating Using the polyester resin produced in Example 15 (I), a coating using a blocked polyisocyanate resin as a resin having a reactive group capable of reacting with a hydroxyl group was prepared by the following formulation. It was prepared in the same manner as in Example 1.

Polyester resin produced in Example 15 (I) 43.2 parts IPDI-B1370 (trade name of blocked polyisocyanate resin manufactured by Huls, non-volatile content 60%) 16.9 〃 dibutyltin dilaurylate (dissociation catalyst of blocking agent) 0.03 〃 Rutile-type titanium oxide 27.7〃 Mapico yellow 0.9〃 carbon black 0.3〃 xylene 6.67〃 butyl acetate 4.3〃 The resulting paint has a polyester resin / blocked polyisocyanate resin ratio of 72:28 and a hydroxyl group / isocyanate group ratio of 1 The ratio of the pigment to the organic binder was 0.8 and the nonvolatile content was 65%.

(III) Coating and coating film performance test Using the intermediate coating composition obtained in (II), coating was performed in the same manner as in Example 1 to prepare a test plate, and a coating film performance test was conducted.

Reference Example A test plate coated with an electrodeposition primer in the same manner as in Example 1 was coated with a commercially available automotive intermediate coating paint Epico No. 1500 Chipping Sealer (trade name, manufactured by NOF CORPORATION) to give a film thickness after drying. Air spray paint to 35-40 μm,
It was cured by baking at 140 ° C for 30 minutes. Then Example 1
The topcoat paint was applied in the same manner as in. A coating film performance test was conducted on the test plate thus obtained in the same manner as in Example 1.

The above results are summarized in Table 10.

As is clear from the above examples, the intermediate coating composition for automobiles of the present invention has significantly better chipping resistance than the conventional intermediate coating composition for automobiles shown as a reference example, and also has other coating film performance. It is good. In contrast, in the case of Comparative Example 1 in which the number average molecular weight of the polyester resin is less than 2000, the effect of improving the chipping resistance is not sufficient, and in the case of Comparative Example 2 in which the number average molecular weight of the polyester resin exceeds 10,000, the coatability is Poorly, the appearance after top-coating is poor and it is unsuitable as an intermediate coating for automobiles. In Comparative Example 3, the linear polyester diol used as a component of the polyester resin has a molecular weight of less than 500, so that the chipping resistance is not sufficiently improved. In Comparative Example 4, the linear polyester diol has a molecular weight of 2000. Since the production of polyester resin did not proceed smoothly, the polyester resin was uneven,
The coating film performance is inferior.

In Comparative Example 5, the ratio of bis (hydroxyethyl) terephthalate in the composition of the linear polyester diol is less than 50, the chipping resistance is insufficient, and conversely, the chain diol having 3 to 10 carbon atoms is not contained. In Comparative Example 6 using the linear polyester diol, the production of the polyester resin did not proceed smoothly, the solubility in the solvent was poor, and the coating film performance was unsuitable as an intermediate coating composition for automobiles.

In Comparative Example 7, the number of hydroxyl groups in one molecule of the polyester resin is
When it is less than 2.1, the coating film performance is poor and the chipping resistance is not good. On the contrary, in Comparative Example 8, in one molecule of the polyester resin,
When it has 2.8 or more hydroxyl groups, the coating becomes too rigid and the chipping resistance is not sufficiently improved.

Comparative Example 9 is a case where the ratio of the resin having a reactive group capable of reacting with a hydroxyl group is less than 10, and the curing is insufficient, so that the resin does not have the performance as an intermediate coating composition for automobiles, and on the contrary, reacts with a hydroxyl group. In Comparative Example 10 in which the ratio of the resin having a reactive group that exceeds 40 is more than 40, the performance of the polyester resin is not sufficiently exhibited, the chipping resistance is not sufficiently improved, and the coating film performance is poor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroaki Harada 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (72) Inventor Hitoshi Kimura 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. ( 72) Inventor Kazuo Shimura, Nissan Motor Co., Ltd. 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa

Claims (3)

[Claims] 1. Bis (hydroxyethyl) terephthalate
95-50 parts by weight and chain diol having 3-10 carbon atoms 5-50
Polycondensate produced by transesterification of parts by weight, with a molecular weight of 50
A dehydration condensate of 10 to 80 parts by weight of a linear polyester diol of 0 to 2000 and 90 to 20 parts by weight of another component containing a polyvalent carboxylic acid, having a number average molecular weight of 2000 to 10000 in one molecule. Polyester resin with an average of 2.1 to 2.8 hydroxyl groups
An intermediate coating composition for an automobile, which comprises 90 to 60 parts by weight and 10 to 40 parts by weight of a resin having a reactive group capable of reacting with a hydroxyl group. 2. A chain diol having 3 to 10 carbon atoms is 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,3. 1 selected from 6-hexanediol, 2-ethyl-1,3-hexanediol, 1,10-decanediol, diethylene glycol, triethylene glycol, dipropylene glycol, and 2,2'-thiodiethanol
The intermediate coating composition for automobiles according to claim 1, which is one or more kinds. 3. A resin having a reactive group capable of reacting with a hydroxyl group is an amino resin, a phenol resin, a ketone resin, a xylene resin, a furfural resin, a polyisocyanate resin,
The intermediate coating composition for an automobile according to claim 1 or 2, which is one or more kinds selected from a blocked polyisocyanate resin and an epoxy resin.