JPH0733493B2 - Resin composition for under floor coatings for vehicles - Google Patents

Description

TECHNICAL FIELD The present invention relates to a resin composition for a vehicle floor undercoat, and more specifically, to stone chipping resistance of a vehicle floor underside including a wheel house portion and the like. The present invention relates to an excellent resin composition for a vehicle floor undercoat.

[Conventional technology and its problems]

The underfloor paint on the vehicle is applied for the purpose of preventing rust on the periphery of the underfloor of the vehicle. Conventionally, asphalt-based, SBR-based, vinyl chloride sol, etc. have been coated, but in recent years vinyl chloride sol has been mainly used. However, the vinyl chloride sol requires a film thickness of 500 μm or more to satisfy the stone chipping resistance, which causes an increase in vehicle weight and also has a drawback that the stone chipping resistance after immersion in water is extremely reduced. is doing. In order to improve these drawbacks, a resin composition for a vehicle floor undercoating, which has a thin coating film thickness and is excellent in stone chipping resistance, has been desired.

An object of the present invention is to eliminate the above-mentioned drawbacks, that is, to provide a resin composition for a vehicle floor lining coating which has a thin coating film thickness and is excellent in stone chipping resistance.

[Means for solving problems]

That is, the present invention comprises the following components (A) and (B), wherein the equivalent ratio of the effective isocyanate group of (B) to the hydroxyl group of (A) is 0.5 to 2.0. A resin composition for underfloor paint.

Component (A): A polyol resin having an average of 0.5 to 4 urethane bonds in the molecule and a hydroxyl value of 30 to 300 mg-KOH / g.

Component (B): Blocked isocyanate resin having a content of effective isocyanate groups of 1 to 15% by weight.

The polyol resin (A), which is the first essential component of the composition of the present invention, has an average of 0.5 to 4 urethane bonds in the molecule and a hydroxyl value in the range of 30 to 300 mg-KOH / g. The polyol resin described in 1. It is a polyol obtained by reacting, for example, polyester polyol, polyether polyol, acrylic polyol, epoxy polyol, alkyd resin, fats and oils with a polyvalent isocyanate so as to have 0.5 to 4 urethane bonds in the molecule on average. It is a resin. Of these, the most preferred is a polyvalent isocyanate modified resin of polyester polyol.

This is because the properties required for the composition of the present invention include stone chipping resistance, stone chipping resistance after immersion in water, cold bending resistance, adhesion, impact resistance and the like. Epoxy polyols tend to have poor cold bending resistance due to their properties, and acrylic polyols and polyether polyols tend to have poor stone chipping resistance. In addition, alkyd resins and fats and oils tend to have slightly poor stone chipping resistance after immersion in water.

The above-mentioned polyester polyol is 150 to 250 ° C. in an equivalent excess ratio of hydroxyl groups to carboxyl groups.
A resin obtained by heat-condensing a polyhydric carboxylic acid and a polyhydric alcohol under the temperature condition of.

The polycarboxylic acid is a compound having at least two carboxyl groups in the molecule, such as aromatic polycarboxylic acid, saturated or unsaturated aliphatic polycarboxylic acid and alicyclic polycarboxylic acid. Yes, either can be used. As the aromatic polycarboxylic acid, for example, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid can be used. Examples of the saturated or unsaturated aliphatic polycarboxylic acid include succinic acid, azelaic acid, adipic acid,
There are pimelic acid, sebacic acid, maleic acid and fumaric acid. As the saturated or unsaturated alicyclic polycarboxylic acid,
For example, hexahydrophthalic acid, methylhexahydrophthalic anhydride, tetrahydrophthalic anhydride, and methyltetrahydrophthalic anhydride can be preferably used. Further, an oxycarboxylic acid having one or more carboxyl groups in one molecule and at least one hydroxyl group in the same molecule can also be used as the polycarboxylic acid. Examples of the oxycarboxylic acid include hydroxylbenzoic acid, hydroxystearic acid and tartaric acid.

The polyhydric alcohols are compounds having at least two hydroxyl groups in one molecule, for example, ethylene glycol, propylene glycol, butanediol, neopentyl glycol, trimethylpentanediol, diethylene glycol, dipropylene glycol, hydrogenated. Examples thereof include bisphenol A, glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol.

The polyester polyol and polyisocyanate,
The polyol resin (A) can be obtained by reacting at a temperature of room temperature to 100 ° C. at a ratio of excess hydroxyl groups and having 0.5 to 4 urethane bonds in the molecule.

The polyvalent isocyanate is, for example, tolylene diisocyanate, metaphenylene diisocyanate, naphthylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, dicyclohexyl propane diisocyanate, aromatic such as trimethylpentane diisocyanate, fat Group or alicyclic polyvalent isocyanate; an adduct of these polyvalent isocyanate and polyhydric alcohol (adduct obtained by reacting polyvalent isocyanate in excess equivalent amount to polyvalent alcohol).

Examples of the polyhydric alcohol include resins such as polyester polyol, polyether polyol, acrylic polyol, and epoxy resin; ethylene glycol,
Diols such as propylene glycol and butanediol: trimethylolpropane, trimethylolethane,
Triols such as glycerin; quadrols such as pentaerythritol.

Here, if the average number of urethane bonds in the molecule of the polyol resin (A) is less than 0.5, the effect of improving the stone chipping resistance cannot be obtained. Also, the hydroxyl number is 30
If it is lower than mg-KOH / g, the number of hydroxyl groups that react with the effective isocyanate groups is small and the crosslinking density is insufficient, resulting in poor stone chipping resistance, stone chipping resistance after immersion in water, and poor adhesion. Hydroxyl number is 300 mg-K
When it is higher than OH / g, the effect coating film is inferior in impact resistance and cold bending workability, and cannot be used as a resin composition for a vehicle floor undercoat.

The blocked isocyanate resin (B), which is the second essential component of the composition of the present invention, is synthesized by reacting the above-mentioned polyisocyanate with a compound having active hydrogen to eliminate the active isocyanate group at room temperature. I mean something.

As the compound having active hydrogen, for example, methanol,
Aliphatic alcohols such as ethanol; cyclic alcohols such as phenol, benzyl alcohol, and cyclohexanol: oximes such as methylethylketoxime and methylisobutylketoxime; lactams such as ε-caprolactam and β-propiolactam; diethyl malonate, Examples thereof include active methylenes such as ethyl acetoacetate and butyl acetoacetate. It is preferable that these compounds having active hydrogen are reacted with the above-mentioned polyisocyanate at an equivalent ratio of 1.0 to 1.1 in an excess state of active hydrogen.

The effective isocyanate group content (% by weight) of the blocked isocyanate resin (B) as used in the present invention means the aromatic group,
Aliphatic or alicyclic polyvalent isocyanate or a polymer of these polyvalent isocyanate or the content weight of the isocyanate group of the adduct of these polyvalent isocyanate and polyhydric alcohol, with the total weight of the adduct of the isocyanate polymer It is the percentage of the value obtained by dividing the weight of the active hydrogen-containing compound reacted with these by the added weight.

In the present invention, the content of the above-mentioned effective isocyanate group is 1
It is not less than 15% by weight and more preferably not more than 3% by weight.
It is not less than 12% by weight and not more than 10% by weight. When the content of the effective isocyanate group is less than 1% by weight, the cross-linking is insufficient and the stone chipping resistance and the like are poor, so that the resin composition cannot be used as a resin composition for a vehicle floor lining paint. On the other hand, when the content is higher than 15% by weight, the effect coating film becomes hard and the impact resistance and the bending workability at low temperature are poor, so that it cannot be used as a resin composition for a vehicle floor lining paint.

In the present invention, the compounding ratio of the effective isocyanate group of the component (B) to the hydroxyl group of the component (A) is 0.5 to 2.0 in terms of an equivalent ratio, preferably 0.7 to 1.4. When this equivalent ratio is less than 0.5, the resulting coating film is insufficiently cured and crosslinked, and the stone chipping resistance and the stone chipping resistance after immersion in water are reduced. Also, this is 2.
When it is more than 0, the obtained cured coating film tends to be hard and the bending workability at low temperature is poor.

In addition to the polyol resin (A) and the blocked isocyanate resin (B), the resin composition for a vehicle floor undercoating of the present invention contains, as a dissociation catalyst for the blocked isocyanate resin (B), tertiary amines, tin compounds and the like. The metal catalyst can be used in combination, and the blocked isocyanate resin (B) and the amino resin can be used in combination. Furthermore, for example, inorganic pigments such as titanium oxide, carbon black, red iron oxide, and oxide yellow; organic pigments such as phthalocyanine blue and phthalocyanine green; fillers such as clay, calcium carbonate, mica, hiruce, clay, perlite, and silica stone; As the leveling improver, cissing inhibitor, pigment dispersant, additive such as anti-sagging agent, and diluting solvent, for example, an organic solvent such as an aromatic solvent, an aliphatic solvent, a ketone, an ester, or an alcohol is used. , A disperser or the like, and a known disperser such as a ball mill, a sand grinder or a roll mill. Further, in the present invention, in addition to the above-mentioned respective components, a fibrin derivative, a petroleum resin, an epoxy resin, a melamine resin, a urea resin, a phenol, in a range that does not impair the effects of the present invention as a resin composition for vehicle floor undercoating. Resin, synthetic rubber, synthetic resin such as rosin, and natural resin can also be added.

The resin composition for vehicle floor undercoating comprising the above components has extremely good storage stability, and the coating film formed by applying it to the vehicle has stone chipping resistance and stone resistance after immersion in water. Excellent chipping, adhesion, impact resistance, cold bending resistance, corrosion resistance, etc.

INDUSTRIAL APPLICABILITY The resin composition for a vehicle floor undercoating of the present invention is most suitable for being applied to a vehicle to protect the vehicle from being damaged by gravel or rock salt. Examples of the application site include a floor back surface, a wheel house portion such as a wheel house inner surface, a rocker panel portion, a sill outer portion, front and rear apron portions, and the like, and lower portions around the vehicle.

The coating method is 100 to 2 for the viscosity of the resin composition for under floor coating of vehicles.
Generally, a paint adjusted to about 0000 cps is applied by airless spray coating or hot airless spray coating, but it is applied by brushing, roller coating, spatula coating, etc. without repairing or masking complex areas. Also available for methods.

These vehicle floor undercoat resin compositions, when applied to a vehicle, the undercoat electrodeposition coating on the coating film after electrodeposition curing,
It may be applied in any step such as on the cured coating film of the intermediate coating composition or on the cured coating film of the top coating composition. It is usually used on the underside of automobile floors and is therefore commonly applied on electrodeposition coatings. The protective film formed by application is about
It can be baked and cured at a temperature of 100 to 170 ° C for 10 to 40 minutes. In the present invention, the coating film thickness is 50 μm or more, 500 μm
It is less than m. When the coating film thickness is less than 50 μm, the stone chipping resistance and the stone chipping resistance after immersion in water are insufficient and the resin composition cannot be used as a vehicle floor undercoating composition. Further, when the coating film thickness is 500 μm or more, the possibility of weight reduction of the vehicle, which is one of the objects of the present invention, disappears, and thick coating of expensive urethane coating causes a problem in terms of cost. Hard to do.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. In the following, "part" and "%" are based on weight.

The average number of urethane bonds in the polyol resin is a value calculated from the number of functional groups in the polyester polyol, the number of molecules present in the resin, and the molar ratio of the polyester polyol to the polyisocyanate.

Example 1 Four-necked flask (with stirrer, thermometer and gas introduction tube)
In addition, 190 parts of phthalic anhydride, 384 parts of adipic acid, 60 parts of trimethylolpropane, 445 parts of neopentyl glycol, and 0.5 parts of dibutyltin oxide are charged, and dehydration reaction is performed at 180 to 240 ° C while passing nitrogen gas, and the acid value is 1.5. mg-KOH
The reaction was terminated when the amount reached / g. This reaction solution was diluted with 125 parts of xylol and 125 parts of cellosolve acetate,
A polyester polyol (C-1) having a hydroxyl value in terms of solid content of 80 mg-KOH / g was obtained. To 1000 parts of this polyester polyol (C-1), 50 parts of tolylene diisocyanate (containing 80% of 2,4-position) (hereinafter abbreviated as TDI) was gradually added, and reacted at 80 ° C. for 4 hours. Thus, a polyol resin (A-1) having a hydroxyl value in terms of solid content of 35 mg-KOH / g was obtained. This polyol resin (A-
1) has on average two urethane bonds in the molecule.

On the other hand, in another four-neck flask similar to the above, 1000 parts of polypropylene glycol (PPG-1000, diol having a number average molecular weight of 1000), 134 parts of trimethylolpropane, 87 parts of TDI.
0 parts, xylol 429 parts, and cellosolve acetate 429
A portion was charged, and the reaction was carried out at 60 to 80 ° C. while passing a nitrogen gas, and the reaction was stopped when the isocyanate group content in terms of solid content reached 10%. 1000 parts of the obtained resin was placed in another four-necked flask, 150 parts of methyl ethyl ketoxime was gradually added dropwise with a dropping funnel, and the reaction was carried out at 60 to 80 ° C. After the dropping was completed, the temperature was raised to 80 ° C. and the reaction was carried out for about 1 hour, and the solid isocyanate content was diluted with xylol to obtain a blocked isocyanate resin (B-1). The content of effective isocyanate groups in this resin (B-1) was 8.
It was 2%.

Next, the resin (A-1) and the resin (B-
Using 1), a resin composition was produced with the following formulation.

Polyol resin (A-1) 100 parts Blocked isocyanate resin (B-1) 43 parts Calcium carbonate 173 parts Carbon black 2 parts Using this resin composition, thinner (xylol / cyclohexanone weight ratio = 1/1) Type viscometer 4500cps / 2
Dilute to 0 ° C. In addition, the compounding amounts of the resin (A-1) and the resin (B-1) and the equivalent ratio of the effective isocyanate group of the resin (B-1) to the hydroxyl group of the resin (A-1) are summarized in Table 1. .

Furthermore, pre-coat with an epoxy-based cationic electrodeposition coating,
The composition diluted with thinner is applied on a steel plate for vehicles which has been baked and cured to form an undercoating film by an airless coating machine so that the dry coating film becomes 350 μm, and baked and cured for 30 minutes at 140 ° C in an atmosphere. Let The performance of this coating film was evaluated by the test method described below, and the results are shown in Table 2.

Examples 2 and 3 and Comparative Example 1 The procedure of Example 1 was repeated except that the amount of the blocked isocyanate resin (B-1) was changed as shown in Table 1 to apply the resin composition and the composition to the steel sheet. A film was obtained. The evaluation results of the performance of this coating film are shown in Table 2.

Example 4 Four-necked flask (with stirrer, thermometer and gas introduction tube)
Adipic acid 1460 parts, neopentyl glycol 1768
Part, trimethylolpropane 134 parts, and dibutyltin oxide 3 parts were charged, and while passing nitrogen gas, 180 to 240
The dehydration reaction was carried out at 0 ° C, and the reaction was terminated when the acid value reached 1.5 mg-KOH / g. This reaction liquid was diluted with 500 parts of xylol and 500 parts of cyclohexanone to obtain a polyester polyol (C-2) having a hydroxyl value of 320 mg-KOH / g in terms of solid content.

1 part of TDI to 1000 parts of this polyester polyol (C-2)
06 parts was gradually added and reacted at 80 ° C. for 4 hours to obtain a polyol resin (A-2) having a hydroxyl value of 200 mg-KOH / g in terms of solid content. The polyol resin (A-2) has an average of 0.8 urethane bonds in the molecule.

Next, the same procedure as in Example 1 was carried out except that the polyol resin (A-1) was changed to the polyol resin (A-2) and the amount of the blocked isocyanate resin (B-1) was changed to 237 parts. Further, a coating film was obtained on the steel sheet.
The evaluation results of the performance of this coating film are shown in Table 2.

Example 5 Polyester polyol (C-2) synthesized in Example 4
Gradually add 237 parts of TDI to 1000 parts and react at 80 ° C. for 4 hours to give a hydroxyl value in terms of solid content of 88 mg-KOH /
A polyol resin (A-3) of g was obtained. The polyol resin (A-3) has an average of 3.5 urethane bonds in the molecule.

Next, in Example 1, the same procedure was carried out except that the polyol resin (A-1) was changed to the polyol resin (A-3) and the amount of the blocked isocyanate resin (B-1) was changed to 108 parts to obtain a resin composition. And a coating film was obtained on the steel plate. The evaluation results of the performance of this coating film are shown in Table 2.

Comparative Example 2 Four-necked flask (with stirrer, thermometer and gas introduction tube)
Into, MDI-CR-200 (manufactured by Mitsui Toatsu Chemicals, Inc., the content of the isocyanate group is 31%) 1000 parts, and 556 parts of xylol are charged, 674 parts of methyl ethyl ketoxime is gradually added dropwise from the dropping funnel, 60 to 80 The reaction was carried out at ° C. After the dropping is completed,
The temperature was raised to 80 ° C. and the reaction was carried out for about 1 hour, and the solid isocyanate content was diluted with xylol to obtain a blocked isocyanate resin (B-2). The content of effective isocyanate groups in this resin (B-2) was 18.5%.

Next, in Example 1, 43 parts of the blocked isocyanate resin (B-1) was added to the blocked isocyanate resin (B-
2) Except for changing to 19 parts, operate in exactly the same manner,
Further, a coating film was obtained on the steel plate. The evaluation results of the performance of this coating film are shown in Table 2.

Comparative Example 3 Polyester polyol (C-1) synthesized in Example 1
Gradually add 10 parts of TDI to 1000 parts and react at 80 ° C for 4 hours to obtain a hydroxyl value of 70 mg-KOH /
A polyol resin (A-4) of g was obtained. This polyol resin (A-4) has an average number of less than 0.5 (about 0.2) in the molecule.
Individual) urethane bond.

Next, in Example 1, the same procedure was carried out except that the polyol resin (A-1) was changed to the polyol resin (A-4) and the amount of the blocked isocyanate resin (B-1) was changed to 87 parts to obtain a resin composition. And a coating film was obtained on the steel plate. The evaluation results of the performance of this coating film are shown in Table 2.

Comparative Example 4 Polyester polyol (C-1) constructed in Example 1
65 parts of TDI was gradually added to 1000 parts and reacted at 80 ° C. for 4 hours, and the hydroxyl value in terms of solid content was 22 mg-KOH /
A polyol resin (A-5) of g was obtained. This polyol resin (A-5) has an average of 0.5 or more (about 4
Individual) urethane bond.

Next, in Example 1, the same procedure was performed except that the polyol resin (A-1) was changed to the polyol resin (A-5) and the amount of the blocked isocyanate resin (B-1) was changed to 28 parts, and the resin composition was changed. And a coating film was obtained on the steel plate. The evaluation results of the performance of this coating film are shown in Table 2.

Coating film test method-Adhesion (cross-cut test): Electrodeposition coated steel plate (70 mm x 150 x
2mm vertically and horizontally on a sample with a specified film thickness of 0.8mm)
Cellophane tape is applied to each of the 10 cuts at intervals and then peeled off, and the presence or absence of peeling of the coating film is checked. Table 2 shows the number of adhesions after the peel test. In Table 2, normal temperature is in an atmosphere of 20 ° C, after deterioration in warm water is 10 days after immersion in 40 ° C hot water, and after deterioration is in a 70 ° C atmosphere for 10 days. It is a test condition that means returning to an atmosphere of 20 ° C. later.

-Cold resistance test: The same sample used for the adhesion test is kept at -30 ° C in a thermostat for 3 hours. Take it out,
Quickly bend the coated surface outward along a 25 mm diameter mandrel uniformly 180 °. The downward curved surface is peeled off with cellophane tape, and the coating film is examined for cracks, cracks, cracks and the like.

・ Impact resistance: The same sample as that used for the adhesion test,
Using an impact tester according to JIS-K-6830-26, apply an impact once from an angle of 90 °, and check for cracks and peeling of the coating film. In Table 2, normal temperature means an atmosphere of 20 ° C., and low temperature means an atmosphere of −30 ° C. after being held for 3 hours.

-Salt spray test: Using the same sample as that used for the adhesion test, a cut is made until the steel surface is reached at the center, and it is kept in the salt spray test tank for 10 days. Then, apply cellophane tape to the cut part and peel it off, and measure the maximum peeling width (mm) of the coating film.

・ Stone chipping resistance test: 3 types specified in JIS-B-1181-M on the same sample used for the adhesion test
-4 Drop a brass hexagon nut from a height of 3 m through a pipe diameter of 40 mm. At that time, the sample is inclined at an angle of 30 ° with respect to the falling direction of the hexagon nut. Weigh the hexagon nut (Kg) until the scratch on the coating reaches the steel surface. In Table 2, “after deterioration with hot water” is a test condition which means that the sample was immersed in warm water at 40 ° C. for 10 days.

Claims (1)

[Claims] 1. A method comprising the following components (A) and (B):
A resin composition for a vehicle floor undercoat, wherein the equivalent ratio of the effective isocyanate group of (B) to the hydroxyl group of (A) is 0.5 to 2.0. Component (A): A polyol resin having an average of 0.5 to 4 urethane bonds in the molecule and a hydroxyl value of 30 to 300 mg-KOH / g. Component (B): Blocked isocyanate resin having a content of effective isocyanate groups of 1 to 15% by weight.