JPS6123650A - Chipping-resistant coating - Google Patents

Abstract

PURPOSE:The titled coating which has good reactivity, excellent compatibility and storage stability and gives a coating film having excellent toughness, hardness, and strength, which comprises an intercoating containing a specified resin component, a curing agent, and pigments. CONSTITUTION:90-70pts.wt. of one or more straight-chain polyester resins (A) which have a molecular weight of 5,000-25,000 and contain isophthalic or terephthalic acid as the acid component; 10-30pts.wt. curing agent (B) comprising a melamine resin (e.g. a benzoguanamine resin) or a highly reactive polyisocyanate; pigments in an amount of 0.4-1pt.wt. per 1pt.wt. (A+B); and if necessary, a thinner (D) which has high polarity and contains slowly evaporating cyclohexanone are mixed to give the titled coating. This coating is applied in one coat in one step to give an intercoat layer comprising a cured coating film having excellent appearance and tensile properties such as Young's modulus of 1.5X10<10>dyn/ cm<2> or higher, tensile strength of 250kg/cm<2> or higher, and an elongation of 20% or greater.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) This invention relates to a chipping-resistant paint, particularly to a chipping-resistant paint for the outer panel of an automobile body.

(Conventional technology) While the vehicle is running, pebbles, gravel, ice blocks, etc. collide with the exterior panels of the vehicle body, destroying or abrading the paint film, and rusting from the exposed iron base deteriorates the appearance and strength of the vehicle body. However, it has become a problem that the functionality is significantly reduced, and this coating film destruction phenomenon is called chipping.

More specifically, hard chipping is when the underfloor or side sills are affected by heavy weight and a large impact, while soft chipping is when the relatively lightweight and small impact is applied to the upper part of the vehicle body, such as the tip of the hood. Therefore, to prevent hard chipping, a coating film of about 200 to 2,000 μm called Stone Guard Coat or Hard Chip Coat has been applied to prevent hard chipping.
To prevent soft chipping, a coating film called a chipping primer with a thickness of around 2σμm was provided between the electrodeposition coating film and the intermediate coating to protect the car body from rust caused by chipping.

(Problems to be Solved by the Invention) However, in such conventional chipping-resistant coating systems, the chipping-resistant effect is mainly due to the film thickness effect due to additional coating of stone guard coat or chipping brusher. However, extremely thick coating deteriorates the finished appearance and cannot be applied to areas where appearance is important, such as the upper part of the car body. There is also a risk of dripping on vertical surfaces. Therefore, there is a demand for paints with a thin film and excellent chipping resistance for areas subject to so-called soft chipping. Therefore, conventional chipping primers are made by dispersing pigments including flat pigments such as talc in ordinary paint resins such as alkyd and melamine resins. This was to prevent the wound from reaching the source by spreading it in the same direction. However, this type of failure prevention is due to sacrificial cohesive failure of the chipping brimer whose cohesive force in the thickness direction is weakened by the addition of pigments, so there is a problem that the scratch area increases.

There was also the problem that chipping and large exposed scratches on the brimer, which had a different color from the top coat, significantly impaired the aesthetic appearance.

Conventional intermediate coats or chipping primers include those shown in Table 1, and the physical properties of each cured film are also shown in the same table.

When the above intermediate coating paint was designed with emphasis on hardness and strength, its elongation (toughness) was inferior, and when it was designed with emphasis on toughness, its hardness and strength were inferior.

The inventor investigated the influence of these conventional coating film physical properties on chipping resistance and found that none of the physical properties had sufficient chipping resistance. That is, if the toughness is insufficient, the coating film cannot follow the deformation caused by the collision of the chip material and undergoes brittle fracture. Furthermore, if the hard viscosity is insufficient, the movement of the chip material cannot be stopped within a predetermined film thickness, leading to scratches on the iron base.

(Means for Solving the Problems) This invention was made by focusing on the above-mentioned problems.
By imparting strength and toughness, it prevents scratches caused by chipping from reaching the iron base and minimizes the scratch area. In this way, the physical properties required for the paint of the present invention are contradictory properties such as high hardness, high strength, and high elongation, so the resin base material has a molecular weight of 5,000 to 25, which is higher than that in conventional paints. ,000 polyester resin uses isophthalic acid or terephthalic acid as the acid component, so it is necessary to use a linear polyester resin alone or in a blend, and a pigment such as titanium oxide is dispersed in this resin and a curing agent is used. It consists of the following. The reason why the molecular weight of the polyester used is 5,000 or more is to satisfy the required physical properties.
The reason why the molecular weight is set to 000 or less is that if the molecular weight is larger than this, a stringing phenomenon will occur during spray coating.

Conventionally, this type of polyester resin has been made into a paint for pre-coating and galvanized iron, but its high molecular weight makes it difficult to spray and causes stringiness.Z Because it has a high molecular weight, it has a high viscosity and when diluted. It has a low solids content, has few 11,0H groups (only at the ends), has poor reactivity, and requires high-temperature baking, so it has never been used as an automobile paint. Baking is performed at 140°C for 80 minutes, while methylated melamine is often used as a hardening agent, and baking is performed at a high temperature of 180 to 280°C for 1 to 10 minutes.

In contrast, in the present invention, a melamine resin, preferably a benzoguanamine resin, or a highly reactive polyvalent incyanate is used as the curing agent.

Further, as mentioned above, the polyester resin used in this invention is structurally linear and has few crosslinking points, so that when baking and curing the paint, the polyester resin can be heated to 80°C at 140°C.
In this case, molecular slippage and changes in arrangement are likely to occur, and after deformation of a few percent, stretching begins without breaking, showing toughness, and the stretched part is further strengthened and become more difficult to destroy.

Furthermore, in the paint G of this invention, stringiness can be eliminated by adding cyclohexanone, which is slow to fly, to the thinner through polar holes, and by making the thinner difficult to fly, the dilution viscosity before spraying can be set to be high. However, it is possible to prevent stringiness during spraying and flow properties after application.

According to the paint of the present invention, an intermediate coating layer with a good finished appearance can be formed in one stage and one layer, whereas conventional intermediate coating processes were applied in two stages.

The resulting coating film is stretchable, exhibiting high hardness and high strength at the initial stage of deformation, then yields, and stretching begins, maintaining strength while increasing elongation rate, and exhibiting good coating film properties. Young's modulus for physical properties, that is, tensile properties: 1.5 x 1.0
10aVn/cm2 or more, tensile strength (yield stress) 25
(L kg/cm2 or more, elongation rate of 20% or more + 71 physical properties.

In the paint of this invention, if a melamine resin, particularly a benzoguanamine resin, is used as a curing agent, a paint with good reactivity, excellent compatibility, and excellent storage stability can be obtained.

Specifically, in order to have the above-mentioned physical properties, the polyester resin is, for example, Vylon 20 (1,
■: Byron 800, ■; Byron GK +
130, ■・Pai・N560 is commercially available.
1. Four types of resins, Nippon Shokubai Chemical Co., Ltd.
From ■: Alloplatz 0B56, ■: Alloplatz 0B
Two types of resins are commercially available under the trade name 59 from Mitsui Toatsu Chemical Co., Ltd.: Almatex P-695, ■;
Two types of resins are commercially available under the trade name Almatex P647BC, from Hitachi Chemical Co., Ltd. ■: Sbel 1
Two types of resins commercially available under the trade names 820 and @+Nispel 188-60 are preferably used. As a curing agent, for example, a butylated melamine type product is commercially available from Hitachi Chemical Co., Ltd. under the trade name Furan 21A1 Melan 22, and Dainippon Ink Industries Co., Ltd. under the trade name Super Beckamin L-117. Preferred examples of methylated melamine include those commercially available under the trade name Nikaratsuku MS-11 from Sanso Chemical Co., Ltd. and Sumimaru M4 from Sumimaru Kagaku Co., Ltd.
Preferred are those commercially available under the trade name 0-8, and examples of butylated benzoguanamines include Melan x81 from Hitachi Chemical Co., Ltd. and Corban 91 from Mitsui Toatsu Chemical Co., Ltd.
Preferred are those commercially available under the trade names ``-55'' and methylated benzoguanamines such as NIKARATSUK BL-60 and NIKARATSUK BX from Sanso Chemical Co., Ltd.
The one commercially available under the trade name -55H is preferred;
Among the incyanate-based resins, those commercially available from Nippon Polyurethane Co., Ltd. under the trade name "Koshine" HL are preferred.

In particular, among the above ten types of polyester resins, for example, ■, ■, [phase] may be used alone, or ■ and ■ may be used alone such as "/@ -'/6 to 8//2, ■ and ■ ζ = ' / 8 ~ 1 - 1 ■ and ■ ■ 4 = 44 ~ -1
■ and ■ and ■')7. - You may use by blending in a ratio of 4/6 to 6/4.

Moreover, it is preferable that the mixing ratio of the polyester resin and the curing agent is polyester/curing agent -907 to 7-o.

Further, the pigment is preferably added in a weight ratio of 0.4 to 1 per 1 of the total amount of the polyester resin and curing agent.

Incidentally, among the above-mentioned curing agents, those having good compatibility with the polyester resin are selected and used as the curing agent.

(Example) Example Intermediate paints were prepared using the blending ratios A to F shown in Table 2.

At this time, the dispersion was carried out by adding pigment in an amount of 4 to 5 times the solid content of the polyester resin, and shaking the mixture in a paint shaker for 4 hours. Table 2 also shows the physical properties of the coating film. Further, Table 3 Nα1 to Nα6 shows the performance of the overall coated plates coated with the paints shown in Table 2 A to F according to the following test method.

The chipping resistance test method is 751111 x 150 x 0.8
After performing alkaline degreasing and chemical conversion treatment on our cold rolled steel sheet, 20 pm of electrodeposition paint (Baku-Top ■50, manufactured by Nippon Paint) was applied and baked at 175°C for 80 minutes. Next, 40μ of the paint shown in Table 2 A-F was spray applied as an intermediate coat, and baked at 140℃ for 30 minutes to give a total film thickness of 100μ.
It was set as m. In the chipping test, the test piece prepared by the above method was kept at 20°C, and 10 square regular octahedral artificial diamonds were heated at 90 kl/hr.

A total of 50 shots were made, 15 points, 15 points, and 20 points, respectively, at speeds of 180 km/hr and 170"l/hr,
I counted the number of scratches that reached the substrate. The number of repetitions was 6 and the average was taken and rounded to the nearest whole number.

In the cut area test, 250 pieces of No. 6 crushed stone were shot with a gravel meter at an air pressure of 4''/cm2, and the appearance was visually evaluated.

Topcoat gloss was evaluated by measuring with a gloss needle.

In the paint film physical property test, the paint was applied on tin foil, baked under specified conditions, and then peeled off using the mercury amalgam method.
The sample was cut out to a size of m. The conditions are sample length 4C.
Comparative Example An intermediate coating material was prepared in the same manner as in the example using the compounding ratio of G-H shown in Table 2, with a tensile rate of 5 fl/m, a tensile rate of 5 fl/, and a temperature of 20°C. The physical properties of the coating film are also listed in Table 2, and the paints shown in G-H in Table 2 and the paints (pitting primer ~) shown in Table 1 were tested according to the same test methods as in the examples.
The performance of the overall coated board using as an intermediate coating is shown in Table 3 [7-]2.

Table 3: Bitter 1 Nippon Paint, O8-88 Kaoru 2 Kansai Paint, OH-5D ■3 Nihon Yushi, Epico 1500 Appearance of peeling Topcoat gloss ◎: No peeling ◎: 90 or more O: Barely peeled None O: 85~9°△: Slightly peeling △
: 8o~85×: Lots of peeling ×: 8o or less From Table 3, Young's modulus as intermediate coating is 1.5 X l □N
.

N using A-D in Table 2 having a dyn/cm2 or more, a tensile strength of 250 "9 layer cm" or more, and an elongation of 20% or more.
(Nil 1 to 4 have good chipping resistance and peeling appearance. However, Nil 1 to 8 are resins with high molecular weight (Vylon 200 and 800 have a molecular weight of around 20,000)
Because it uses a thinner with a low boiling point, diluting it with a low boiling point solvent may cause stringiness during spraying, so it is necessary to add a high boiling point component to the thinner. Nα4-6 are molecules) ↑Resin with low t (
5,000~s, ooo) was used to make the sprayability similar to that of the conventional product, but the physical properties deteriorated and the performance was slightly inferior to N11l~3, but it was better than the conventional product. Sample No. 104 lowered the pigment concentration to maintain toughness and obtained good physical properties, but the solid content was low and the film thickness was somewhat difficult to form.

No, 'I has a problem in that there are many even numbers.

No. 8 had physical properties that lacked toughness, caused brittle fracture, and was poor in both the evenness of the substrate and the appearance of peeling. Nα9 is strong
It has physical properties that lack 1 degree, and the even number of substrates is conventional product No.
It was considerably inferior to 10-12. Furthermore, since the hardness is insufficient, there is also the drawback that it is difficult to produce a glossy finish. Therefore, the desirable physical properties are Young's modulus of positive 1 to 6, 1°5× 1 o N.

dyn/cm2 or more, tensile strength of 250 kg//c, 2 or more, and elongation rate of 20% or more.

(Effects of the Invention) As explained above, the paint of the present invention uses one or more linear polyester resins with a molecular weight of 5,000 to 25,000 as a resin component, and uses a melamine resin, particularly a benzoguanamine resin, as a curing agent. By using a resin or polyvalent isocyanate and a pigment such as titanium oxide, it is possible to form an intermediate coating layer with a good finished appearance in one step and in one layer, and the cured coating film has tensile properties and is young. Ratio 1.5 x 1010 dyn/cm2 or more, tensile strength 250
Vcm2 or more and elongation rate of 20% or more, which have characteristics not found in conventional alkyd/melamine intermediate coating films.

Procedural amendment dated October 23, 1980 1. Indication of the case 1989 Patent Application No. 142162 2. Name of the invention Chipping-resistant paint 3. Person making the amendment Relationship to the case Patent applicant (899) Nissan Motor Co., Ltd. In the 5th column of paint name in Table 1 on page 4 of Company 1 Specification, "Brymer OH-5D, manufactured by Kansai Paint j" is corrected to "Flymer OH+4' io, manufactured by Kansai Paint."

2. On page 9, line IN 18, "kneepan" is corrected to "kneepan".

13 “Putter Top V50” on page 11, lines 12-18.
" has been corrected to "Power Top U50J.

4. On page 112, lines 17-18, "pitching primer" is corrected to "chipping primer."

5, Table 8 margin on page 14 [-X-2 Manufactured by Kansai Paint.

OH-5D J [■2 Kansai Paint +' OH-5
Correct to 0J.

Claims (1)

[Claims] 1. In a chipping-resistant paint used as an intermediate coating containing a resin component, a curing agent, and a pigment, the resin component is one or more linear polyester resins with a molecular weight of 500 to 25,000, and the curing agent is a melamine resin or polyester resin. isocyanate, and the cured coating film has tensile properties and Young's modulus of 1.5×10
^1^0dyn/cm^2 or more, tensile strength 250kg/c
A chipping-resistant paint characterized by having an elongation rate of m^2 or more and an elongation rate of 20% or more.