JPH01170622A - Coating of frp molded article - Google Patents

Abstract

PURPOSE:To obtain at low cost a coated FRP molded article of good appearance, free from coating film defects such as pinholes over the whole surface thereof, using, as the primer coating, a two-pack urethane resin coating spiked with a tin compound at specified temperatures when the original article is to be coated. CONSTITUTION:A primer coating prepared by formulating (A) an acrylpolyol (pref. with a number-average molecular weight of 10,000 to 80,000, hydroxyl value of 20 to 120 and acid value of <=50), (B) a polyisocyanate compound (e.g., haxamethylane diisocyanate) and (C) a tin compound (e.g., dibutyltin laurate) in such amounts that the molar ratio: NCO in the component A to OH in the component B=0.8-1.0 and 0.001-0.5 pts.wt. based on 100 pts.wt. of the components A and B, of the component C is applied on a FRP molded article at coating liquid temperature of <60 deg.C (pref. 20 to 40 deg.C) followed by main coating.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for painting FRP molded products.

(Prior Art) Since FRP molded products have many pinholes on the material surface, various methods have been used to prevent coating defects caused by pinholes when painting them.

For example, Japanese Patent Publication No. 58-50254 describes a method for preventing paint film defects by applying a urethane resin paint as a primer paint and then applying an amino alkyd resin paint on top of it in a wet-on-wet state. ing.

In addition, as another method, as a primer paint,
There is a method of applying urethane-based paint and baking it at a low temperature (80"C). There is also a method of preventing paint defects due to pinholes by using urethane-based or epoxy-based putty. Furthermore, a method of obtaining a sealing effect by increasing the amount of pigment blended in the paint is also being considered.

(Problem to be solved by the invention) However, in the case of a product having an adhesive surface, there are more pinholes on the surface near the adhesive surface than on other parts, and the pinhole diameter are of various sizes. Therefore, as in the air spoiler described in Utility Model Application No. 61-124481, the adhesive part becomes the design surface.
When painting RP molded products, many defects in the paint film due to pinholes occur near the bonded parts, resulting in more serious appearance defects than when painting ordinary FRP molded products. In particular, in recent years, FRP molded parts are expected to have the same initial quality and durability as the general parts of the car body.
It is highly desirable to prevent these coating film defects.

In order to prevent paint film defects when painting FRP molded products with such adhesive surfaces, the above-mentioned Japanese Patent Publication No. 58-
The method of No. 50254 is insufficient. Further, in a method in which a urethane paint is applied as a primer paint and baked at a low temperature, the number of pinholes generated is slightly reduced due to the lower baking temperature, but this is not sufficient. In addition, methods using urethane-based, epoxy-based putty, etc.
In particular, when used in combination with the method of Japanese Patent Publication No. 58-50254, a high effect can be obtained, but a large number of man-hours are required for salting the putty, which increases the number of man-hours and reduces work efficiency. In addition, this method cannot fill relatively small pinholes with a diameter of 50 μm or less, so
There is also the problem that a sufficient sealing effect cannot be obtained.

Furthermore, the method of obtaining a sealing effect by increasing the amount of pigment blended in the paint significantly deteriorates the appearance after topcoating, and the sealing effect is not sufficient. Therefore, an object of the present invention is to provide a method for coating an FRP molded product that can sufficiently prevent paint film defects due to pinholes even on the surface near the adhesive surface and does not require an increase in the number of man-hours. .

(Means for Solving the Problems) In order to achieve the above object, the coating method for FRP molded products of the present invention is based on a primer coating consisting of an acrylic polyol and a polyisocyanate compound, and a tin compound added thereto. It is characterized in that the liquid urethane resin paint is applied at a liquid temperature of less than 60°C.

As the acrylic polyol, for example, a copolymer containing a methacrylic acid ester and a hydroxyl group-containing polymerizable monomer can be used. The copolymer preferably has a number average molecular weight of about 10,000 to 80,000, a hydroxyl value of 20 to 120, and an acid value of 50 or less.

As the polyisocyanate compound, one containing two or more isocyanate groups in one molecule can be used. Examples of these include hexamethylene diisocyanate,
Xylylene diisocyanate, hydrogenated xylylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, meta-xylylene diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), isophorone diisocyanate, reaction products of these diisocyanates with water or polyhydric alcohols , polymers of these diisocyanates, and mixtures of the above compounds.

The ratio of acrylic polyol to polyisocyanate compound is 0.4 to 1 based on NGOloH (molar ratio).
．． 2, particularly preferably in the range of 0.8 to 1.0.

The tin compound is added as a curing accelerator, and for example, the following can be used. Dibutyltin laurate, dibutyltin acetate, tetrabutyltin, tributyltin chloride,
Dibutyltin dichloride, butyltin trichloride, tin chloride, tributyltin-○-fert, tributyltin cyanate, tin octylate, tin oleate, tin tartrate, dibenzyltin di(2-ethylhexoate), dibutyltin dilaurate, dibutyltin diisooctyl maleate, dibutyltin sulfide, dibutyltin dibutoxide, dibutyltin bis(0-phenylferrate), dibutyltin bis(acetylacetonate),
Di(2-ethylhexyl)tin oxide, also the following -
The organotin compound represented by the formula: (wherein R represents the same or different alkyl group, and X represents the same or different halogen atom, hydroxyl group, alkoxy group or acyloxy group) also has an isocyanate group and water or a hydroxyl group. Since it has a catalytic effect on the reaction, it can be preferably used in the present invention.

゛ Specific examples of such organic tin compounds include, for example, tetra-n-butyl-1,3-diacetyloxydistanoxane, tetra-n-propyl-1,3-diacetyloxydistanoxane, and tetra-n-propyl-1,3-diacetyloxydistanoxane. 1-chloro-3-hydroxydistanoxane, tetra-n-butyl-1-chloro-3-hydroxydistanoxane, tetramethyl-1,3-diacetyloxydistanoxane,
Tetramethyl-1-chloro-3-acetyloxydistanoxane, Tetra-n-butyl-1,3-diformyloxydistanoxane, Tetra-n-butyl-1,3-diacryloxydistanoxane, Tetra -n-butyl-
1,3-dioleyloxydistanoxane, tetra-n
-Butyl-1,3-distearyloxydistanoxane, tetra-n-butyl-1゜3-diphenylacetyloxydistanoxane, tetra-n-butyl-1,3-diisocyanodistanoxane, tetra- n-butyl-1-
Acetyloxy-3-hydroxydistanoxane, tetra-n-propyl-1-acetyloxy-3-hydroxydistanoxane, tetramethyl-1-acetyloxy-3-hydroxydistanoxane, tetra-n-butyl-1 , 3-dichlorodistanoxane, tetramethyl-1
, 3-dichlorodistanoxane, tetramethyl-1゜3
-dichlorodistanoxane, tetra-n-butyl-1,
3-dipropoxydistanoxane, tetra-n-propyl-1,3-dipropoxydistanoxane, tetra-n
-butyl-1-propoxy-3-acetyloxydistanoxane, tetra-n-propyl-1-hydroxyl 3
-Nitoxydistanoxane, 1,1-diptyl-3,3
-dipropyl-1-hydroxy-3-acetyloxydistanoxane, 1,3-dipropyl-1,3-dibutyl-1-chloro-3-hydroxydistanoxane, and the like.

The amount of the curing accelerator added is preferably 0.001 to 0.5 parts by weight per 100 parts by weight of the acrylic polyol and the polyisocyanate compound.

Furthermore, conductive powder such as conductive carbon or graphite can be suitably blended into the primer paint used in the present invention, if necessary.

In the present invention, the primer coating preferably has a dry film thickness of 10 to 40 μm, particularly preferably 15 to 3 μm.
less than 60°C, preferably 20 to 40°C so that the temperature is 0 μm
It is applied at a liquid temperature of
Let stand for ~10 minutes.

After that, in a wet-on-wet state, apply an intermediate coating for car body exterior panels, such as alkyd-melamine resin paint, for 15 to 30 minutes.
Coated with a film thickness of 40 μm and heated at 130 to 150°C for 15 to 10 minutes.
It is preferable to bake for 30 minutes.

Moreover, this intermediate coating may be omitted.

After that, perform the main dipping, and then apply a top coat (polyester resin/melamine resin paint or two-component acrylic/urethane paint) to the specified film thickness, that is, 35 mm in the case of solid.
μm or more, 2 coats, 1 bake metallic base (2CI
In the case of B), the thickness is 15 to 20 μm.In the case of clear coat painting, the thickness is 30 μm or more, and the thickness is 130 to 15 μm.
15-30 minutes at 0℃ or 20 minutes at 70-90℃
Bake for ~40 minutes to complete the painting. Depending on your wishes,
Putty repair may be performed before honzuke.

In addition, if the ij thermal property of the FRP molded product is 140℃ or less, apply the above primer, apply a urethane-based top coat in a wet-on-wet state using the same method as above, and then heat the product to 140℃ or less. , especially at 70 to 100°C for 20 to 40 minutes.

The FRP molded product coated by the method of the present invention is made of plastic reinforced with a reinforcing material such as glass fiber,
Examples of the plastic include unsaturated polyester resin, epoxy resin, phenol resin, silicone, and melamine resin.

For the coating, a coating method such as spray coating, brush coating, etc., which is commonly used for coating FRP molded products, can be used.

(Function) In the method of painting FRP molded products of the present invention, since a two-component urethane resin paint containing a tin compound as a curing accelerator is used as a primer, pinholes may be formed near the adhesive surface and on other parts of the surface. This prevents paint film defects caused by

(Examples) Examples 1 to 6: Primer compositions containing an acrylic polyol resin, a pigment, a polyisocyanate compound, and a tin compound in the amounts (parts by weight) shown in Table 1 below (Examples 1 to 6) was manufactured.

Table 1 also shows processing conditions for primer coating and other processing steps, types of paint, test results, etc.

In the table, acrylic polyol resin 1) is styrene/methyl methacrylate/hydroxypropyl methacrylate/hydroxyethyl acrylate/acrylic acid (15
159/15/10/1 (weight ratio)), has a hydroxyl value of 80, and has a weight average molecular weight of 30,000.

Pigment blending amount 2> is shown as the weight content (%) of each pigment in the cured coating film. The polyisocyanate compound A'' is a reaction product of hexamethylene diisocyanate and water, and the polyisocyanate compound B0 is a reaction product of xylylene diisocyanate and trimethylolpropane.The tin compound 5> is diptyltin laurate. was used.NC010H'' indicates the ratio of isocyanate groups in the polyisocyanate compound per 1 mole of hydroxyl groups in the polyol resin. Coating viscosity 1 is upper toluene/ethyl acetate/Tsurpetz (40/30/30 (
Adjust with a mixture thinner consisting of (weight ratio)). Furthermore, TA in the topcoat column indicates a polyester resin/melamine resin coating, and TB indicates a two-component acrylic/urethane coating.

The above primer composition is prepared by uniformly mixing and dispersing an acrylic polyol resin and a pigment as a base component, then mixing a polyisocyanate compound as a curing agent with this base component, and further adding a tin compound as a curing accelerator. , by adding a solvent to adjust the coating viscosity. The solid content of the composition is 40 to 5.
It was 0% by weight.

By putting 500 cc of each of these primer compositions into a glass bottle until about 7 minutes, storing them tightly, and measuring the time until the viscosity rose to 20 seconds/20'C in a Ford cup #4, The performance (pot life) of the primer composition itself was investigated. The results are shown in Table 1.

Using the above primer composition, FRP was prepared as follows.
The molded product was painted. As FRP molded products, SMC (Sheet Molding) with adhesive structure is used.
A molded product (Con+pound) was used. First, secondary processing consisting of deburring, sanding, adhesion, scraping of adhesive, putty repair, and draining was performed (however, putty repair was performed only in Example 1) to produce a secondary processed product. After degreasing this, the primer composition produced above was heated to 2.
While adjusting the temperature between o''C and 4℃, the dry film thickness is 15~
3ot! It was spray-painted to a thickness of m, and then left at room temperature for 3 to 10 minutes. This was coated with an intermediate coating for car body exterior panels (alkyd-melamine resin paint) in a wet-on-wet state so that the dry film thickness was 15 to 40 μm, and then heated to 15 to 30 μm at 130 to 150"C. (Excluding Example 2).After that, Examples 1 to
3 was repaired with putty again. Thereafter, water was drained with sandpaper, and after drying, a top coat was applied to a thickness of 35 to 40 μm based on the cured film.

As the top coat, use polyester resin/melamine resin paint (TA) or two-component acrylic/urethane paint (TB). If TA is used, after painting,
The coating was completed by baking at 30"C to 150"C for 15 to 30 minutes. In addition, in the case of TB, after painting, 70 to 9
The coating was completed by baking at 0°C for 20 to 40 minutes. For each of the obtained painted products, the effectiveness in preventing paint film defects was evaluated by counting the number of pinholes on the surface near the adhesive surface and in other parts. The pinhole has a diameter of 200 to 600
Measurements were made for those with a diameter of 70 to 200 μm (large in the table), and those with a diameter of 10 to 70 μm (small in the table).

The appearance of the coating film and the adhesion of the coating film were also evaluated, and the results are shown in Table 1.

Regarding adhesion, we used a single-edged razor to make 100 base marks at two square intervals on the surface of the test plate, sufficiently crimped cellophane adhesive tape (JIS Z 1522) on top of the base marks, and then pulled them all at once in a 90° direction. Evaluation was made by peeling it off and examining the peeling condition on the surface. In addition, a method of repairing with putty both during secondary processing and after painting the intermediate coat (reduction rate 0%)
), the reduction rate of repairs was investigated and shown in Table 1.

Comparative Examples 1 to 3: For comparison, primer compositions (Comparative Examples 1 to 3) containing an acrylic polyol resin, a pigment, and a polyisocyanate compound in the amounts (parts by weight) shown in Table 1 were mixed with a tin compound. It was manufactured according to the method of Examples 1 to 7 except that . Performance of the obtained primer composition itself (
The pot life) was investigated. The results are shown in Table 1.

An SMC molded article similar to that in Example 1 was molded and painted in the same manner as in Example 1. However, the presence or absence of intermediate coating and the presence or absence of putty repair during secondary processing shall be as shown in Table 1.

First, secondary processing consisting of deburring, sanding, adhesion, scraping of adhesive, putty repair (excluding Comparative Example 3), and pickling was performed to produce a secondary processed product. The primer composition produced above was applied to this in the same manner as in Example 1, and then an intermediate coating for car body outer panels (alkyd-melamine resin paint) was applied in a wet-on-wet state (
Comparative Examples 1 and 2 only), then a top coat was applied, and baking was performed under the same conditions as Examples 1 to 6 to complete the coating. The pinhole prevention effect, coating appearance, and adhesion of the resulting coated product were measured in the same manner as in Example 1.

The results are shown in Table 1.

(Effects of the Invention) When a molded product with an adhesive structure is painted using the method for painting an FRP molded product of the present invention, there will be no defects due to pinholes even in the vicinity of the adhesive surface, and the appearance will be very good over the entire surface of the molded product. Excellent painted products can be obtained. Therefore, the number of man-hours previously spent on repairing defects such as pinholes can be significantly reduced.

Further, the labor, cost, etc. for painting can be significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the steps of an embodiment of a method for painting an FRP molded product. Patent applicant Toyota Motor Corporation Uchihama Kogyo Co., Ltd. Kansai Paint Co., Ltd. No.

Claims (1)

[Claims] As a primer paint for painting FRP molded products,
A two-component urethane resin paint consisting of an acrylic polyol and a polyisocyanate compound to which a tin compound has been added is
A method for coating FRP molded products, characterized by coating at a liquid temperature of less than 0°C.