WO2021210467A1 - Photocurable resin composition, coating material for vehicle, and coated article - Google Patents

Abstract

Provided is a photocurable resin composition which has an excellent filling effect, and with which the unevenness of the surface of an object to be coated can be concealed. The photocurable resin composition is characterized by comprising: a photocurable component (A) which is a polyfunctional acrylate having four or more (meth)acrylate groups; a hydroxyl group-containing acrylic resin (B-1) having a weight average molecular weight in the range of 3,000-8,000; a hydroxyl group-containing acrylic resin (B-2) having a weight average molecular weight in the range of 10,000-30,000; a particle component (C); and a polyisocyanate (D), wherein the mixing ratio of the polyisocyanate (D) is 10-100 mass% with respect to 100 mass% of the total amount of the photocurable component (A), the acrylic resin (B-1), the acrylic resin (B-2), and the particle component (C).

Description

Photocurable resin compositions, vehicle paints, and painted articles

The present invention relates to photocurable resin compositions, vehicle paints, and painted articles.

When painting a material with uneven surface, the convex part should be thickened to hide it, or it should be polished with sandpaper to make it smooth before painting, and the concave part should be pinned with a putty or the like. Measures such as filling holes and painting putty to smooth the surface have been taken. However, such pretreatment not only reduces productivity, but also has problems such as an increase in volatile organic compounds (hereinafter referred to as VOC) due to an increase in the amount of paint used. Also, if the cause of the recess is a pinhole generated by the air contained in the material, it is difficult to completely fill all the pinholes with putty before painting, and air remains in the pinholes. There was a case. If painting and baking are performed with air remaining in the pinhole, the liquid paint after painting will be sucked into the pinhole, or the air inside the pinhole will expand during baking and the paint film will be damaged. There was a problem that defects would occur.

Fiber reinforced plastic material (hereinafter referred to as FRP material) is lightweight while having excellent properties such as strength, rigidity, and dimensional stability compared to iron and aluminum. In automobile vehicle parts, widespread use is being studied as a material that contributes to improved fuel efficiency by reducing weight. However, it has been applied only to some vehicle members such as automobile lamp reflectors and spoilers. The FRP material is a material that is prone to unevenness because it is molded by kneading a plurality of materials. The unevenness referred to here is a segregated unevenness formed by the fibers appearing on the surface of the material due to insufficient mixing of the fibers, a convex due to the popping out of a single fiber, and a pin that is concave due to the appearance of air bubbles mixed when mixing the fibers on the surface. There are halls and so on. In addition, it is difficult to detect completely contained bubbles in the initial stage, and it is difficult to predict the place of occurrence and take proactive measures because the material and the coating film are destroyed during baking. As described above, the FRP material is a material in which coating defects are likely to occur, so that the productivity is poor, and the FRP material has been applied only to some parts such as those for luxury cars and competitions. Therefore, in order to increase the number of members using FRP material having excellent characteristics, it has been required to develop a putty paint having an excellent sealing effect and excellent suppression of coating defects.

Patent Document 1 contains (a) a mixed polyol of an acrylic polyol having a hydroxyl value of 15 to 25 and an acrylic polyol having a hydroxyl value of 35 to 45, and (b) a mixture of xylylene diisocyanate-based polyisocyanates having different isocyanate group contents. A coating method is disclosed in which a two-component urethane coating material is brought into contact with an atmosphere containing a tertiary amine vapor and cured.
However, such a coating method is inconvenient in terms of safety, environmental load, and cost, such as large-scale equipment for contacting with dangerous tertiary amine vapor and wastewater treatment, in addition to the conventional baking process. there were.

Patent Document 2 describes a photocurable component (A) containing a urethane (meth) acrylate having 6 or more (meth) acryloyl groups, a hydroxyl group-containing acrylic resin (B) having a hydroxyl value of 10 to 200 mgKOH / g, and a polyisocyanate (C). ) Is disclosed. However, this photocurable resin composition has not been studied as a putty for suppressing coating defects. Further, the hydroxyl group-containing acrylic resin (B) was not finely limited.

Japanese Unexamined Patent Publication No. 2-71876 Patent No. 6582927

In view of the above, the present invention relates to a photocurable resin composition having an excellent sealing effect. Further, when the above-mentioned photocurable resin composition is used as a putty, it is possible to suppress coating defects of topcoat coating materials such as colored coating materials and clear coating materials and improve the coating appearance. Further, since it has excellent adhesion to the topcoat paint, it is possible to obtain a multi-layer coating film having excellent strength and durability.

The present invention is a photocurable component (A), which is a polyfunctional acrylate having 4 or more (meth) acrylate groups.
A hydroxyl group-containing acrylic resin (B-1) having a weight average molecular weight in the range of 3000 to 8000,
It contains a hydroxyl group-containing acrylic resin (B-2), a particle component (C), and a polyisocyanate (D) having a weight average molecular weight in the range of 10,000 to 30,000.
The compounding ratio of the polyisocyanate (D) is 10 to 100% by mass with respect to 100% by mass of the total amount of the photocurable component (A), the acrylic resin (B-1), the acrylic resin (B-2) and the particle component (C). The present invention relates to a photocurable resin composition characterized by being%.

The acrylic resin (B-1) preferably has a hydroxyl value in the range of 120 to 200 mgKOH / g.
The acrylic resin (B-2) preferably has a hydroxyl value in the range of 5 to 70 mgKOH / g.

Furthermore, the present invention relates to a vehicle coating material comprising the above-mentioned photocurable resin composition.
The present invention also relates to a coated article having a cured coating film obtained by combining the above-mentioned photocurable resin composition with UV curing and thermosetting.

Since the photocurable resin composition of the present invention has an excellent sealing effect, it is possible to hide the unevenness on the surface of the object to be coated. Further, it is possible to obtain the effect of suppressing subsequent coating defects.

It is a figure which shows concretely the reading method at the time of reading Tg from a chart in the method of measuring Tg in this invention.

The present invention comprises a photocurable component (A) which is a polyfunctional acrylate having 4 or more (meth) acrylate groups, a hydroxyl group-containing acrylic resin (B-1) having a weight average molecular weight in the range of 3000 to 8000. A photocurable resin composition containing a hydroxyl group-containing acrylic resin (B-2), a particle component (C), and a polyisocyanate (D) having a weight average molecular weight in the range of 10,000 to 30,000.

It is particularly preferable that the photocurable resin composition of the present invention is used by directly coating it on a resin base material having many surface irregularities such as FRP. It may be used on a polished substrate.

Since the photocurable resin composition contains a high molecular weight hydroxyl group-containing acrylic resin (B-2) and a particle component (C), the fluidity of the liquid paint is controlled after painting, and the base material is used. It is possible to reduce the occurrence of concave defects generated by flowing into the segregated concaves and pinholes above. Further, the high molecular weight hydroxyl group-containing acrylic resin (B-2) is designed to have a low hydroxyl value to reduce the influence of shrinkage due to thermal curing with the polyisocyanate (D), thereby improving dimensional stability. It is also possible to improve the adhesion with the base material and the topcoat paint.

Further, since the photocurable resin composition contains a photocurable component (A) and a hydroxyl group-containing acrylic resin (B-1) having a low molecular weight, a coating film having a higher surface crosslink density than UV curing can be obtained. Since it can be formed and heat-cured to form a coating film with a high crosslink density inside the coating film, the air inside the pinholes expands in the process after applying the topcoat paint, causing damage to the coating film. Painting defects can be reduced.
Further, since the photocurable resin composition contains the photocurable component (A) and the hydroxyl group-containing acrylic resin (B-1) having a low molecular weight, the coating film thickness can be increased by concealing the convex portions. Even if it becomes thick and UV light does not reach the inside sufficiently, the cross-linking density of the surface due to UV curing and the cross-linking density of the inside due to thermosetting are maintained, so that air expands from the inside with various film thicknesses. This makes it possible to reduce coating defects such as damage to the coating film. Such a curing method that combines UV curing and thermosetting is effective not only for FRP substrates but also for members such as three-dimensional shaped objects that cannot be coated with a uniform coating film on the entire surface.

The photocurable resin composition of the present invention contains a high molecular weight hydroxyl group-containing acrylic resin (B-2) and a particle component (C), so that the viscosity immediately after painting is controlled and the smoothness is not sucked into the recess. High coating film can be obtained. In addition, a coating film having good adhesion to the base material and the top coat can be obtained by a thermal reaction with the polyisocyanate (D). Further, by the photoreaction of the photocurable component (A) and the thermosetting of the low molecular weight hydroxyl group-containing acrylic resin (B-1) and the polyisocyanate (D), a coating film having a high crosslink density can be obtained even at various film thicknesses. Therefore, the convex portion can be concealed, the expansion of the air remaining in the uneven portion can be suppressed, and the smooth state of the comprehensive coating film coated with the topcoat paint can be maintained. Therefore, the photocurable resin composition of the present invention is suitably used for an object to be coated having irregularities, and particularly has excellent performance as a putty.
Hereinafter, the present invention will be described in detail.

Photo-curing component (A)
The photocurable resin composition of the present invention contains a polyfunctional acrylate having 4 or more (meth) acrylate groups as the photocurable component (A).
The polyfunctional (meth) acrylate having 4 or more (meth) acrylate groups described above has good polymerization activity when irradiated with active energy rays. When the photocurable resin composition contains a polyfunctional (meth) acrylate having 4 or more (meth) acrylate groups, there is an advantage that a coating film having a high crosslink density can be obtained on the surface. ..

The polyfunctional (meth) acrylate can be prepared by dealcoholizing the polyhydric alcohol and the (meth) acrylate. Specific examples of the polyfunctional (meth) acrylate include 4 such as pentaerythritol tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, tripentaerythritol tetra (meth) acrylate, and trimethylolpropane tetra (meth) acrylate. Functional (meth) acrylate;
Five-functional (meth) acrylates such as dipentaerythritol penta (meth) acrylate and tripentaerythritol penta (meth) acrylate;
Hexa-functional (meth) acrylates such as dipentaerythritol hexa (meth) acrylate and tripentaerythritol hexa (meth) acrylate;
7-functional or higher (meth) acrylates such as tripentaerythritol hepta (meth) acrylate and tripentaerythritol octa (meth) acrylate;
And so on.

The polyfunctional (meth) acrylate used in the present invention is not particularly limited in molecular weight, but is preferably having a molecular weight of 3000 or less. That is, it is preferable that the compound does not correspond to a polymer but has a relatively low molecular weight. Such a molecular weight is a value calculated from the chemical structural formula of the polyfunctional (meth) acrylate.
One of these polyfunctional (meth) acrylates may be used alone, or two or more thereof may be mixed and used.
Moreover, the photocurable resin composition of the present invention may be a combination of other photocurable compounds.

The blending ratio of the photocurable component (A) contained in the photocurable resin composition is the photocurable component (A), the hydroxyl group-containing acrylic resin (B-1), the hydroxyl group-containing acrylic resin (B-2) and the particles. It is preferably 6% by mass or more and 54% by mass or less, and more preferably 20% by mass or more and 40% by mass or less, based on 100% by mass of the total amount of the component (C).
When the blending ratio of the photocurable component (A) is 6% by mass or more, the crosslink density on the surface of the obtained coating film can be improved. Further, when it is 54% by mass or less, there is an advantage that the adhesion between the base material and the topcoat paint can be kept good by reducing excessive curing shrinkage.

Hydroxy group-containing acrylic resin (B-1)
The hydroxyl group-containing acrylic resin (B-1) is a low molecular weight hydroxyl group-containing acrylic resin having a weight average molecular weight in the range of 3000 to 8000.
In the present invention, it is an important requirement to use a low molecular weight hydroxyl group-containing acrylic resin (B-1) and a high molecular weight hydroxyl group-containing acrylic resin (B-2) described later in combination.
That is, by using these two types of hydroxyl group-containing acrylic resins in combination, it is possible to impart a good sealing effect and sufficient coating film strength as a putty coating film.

When the weight average molecular weight is in the range of 3000 to 8000, the hydroxyl group-containing acrylic resin (B-1) is crosslinked and a cured coating film having a high crosslink density is formed when the coating is applied on the coating and the heat is cured. can do. The weight average molecular weight is preferably 4000 or more, and more preferably 6000 or more.

The weight average molecular weight in the present specification is a value measured by gel permeation chromatography using HLC-8200 manufactured by Tosoh Corporation. The measurement conditions are as follows.
Column TSgel Super Multipore HZ-M 3 development solvent Tetrahydrofuran Column inlet oven 40 ° C.
Flow rate 0.35 ml
Detector RI
Standard polystyrene PS oligomer kit manufactured by Tosoh Corporation

In the present invention, the "acrylic resin" refers to a polymer obtained by polymerizing a monomer composition containing at least one monomer of acrylic acid and its ester, methacrylic acid and its ester.

A suitable monomer composition capable of forming the hydroxyl group-containing acrylic resin (B-1) according to the present invention and satisfying the above conditions includes, for example, a hydroxyl group such as 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate. Acrylic acid hydroxy ester; contains at least one of a hydroxyl group-containing methacrylic acid hydroxy ester such as 2-hydroxyethyl methacrylate, 4-hydroxybutyl methacrylate; and, if necessary, acrylic acid; Acrylic acid esters such as methyl acrylate, butyl acrylate, isobutyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, isobolonyl acrylate; methacrylic acid; methyl methacrylate, butyl methacrylate, methacrylic acid. Composition containing at least one of methacrylic acid esters such as isobutyl, t-butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, isobolonyl methacrylate; ethylenically unsaturated monomers having an aromatic ring such as styrene; Things can be mentioned. The composition of the monomer composition may be appropriately adjusted according to various physical properties required for the hydroxyl group-containing acrylic resin (B-1).

The monomer composition can be polymerized using a solvent such as butyl acetate. Further, the polymerization conditions such as the type of the solvent, the concentration of the monomer composition at the time of polymerization, the type and amount of the polymerization initiator, the polymerization temperature, the polymerization time, etc., have various physical properties required for the hydroxyl group-containing acrylic resin (B-1). It can be adjusted as appropriate. Therefore, the method for producing the hydroxyl group-containing acrylic resin (B-1) is not particularly limited, and a commercially available hydroxyl group-containing acrylic resin (B-1) may be used.

The hydroxyl group-containing acrylic resin (B-1) preferably has a hydroxyl value (OHV) in the range of 120 to 200 mgKOH / g. By setting the hydroxyl value within such a range, it is preferable in that a good crosslink density can be imparted to the coating film. The lower limit of the hydroxyl value is more preferably 150 mgKOH / g. The upper limit of the hydroxyl value is more preferably 170 mgKOH / g.
The hydroxyl value can be determined by the neutralization titration method using the potassium hydroxide aqueous solution described in JIS K 0070.

The compounding ratio of the hydroxyl group-containing acrylic resin (B-1) is a total amount of 100 mass of the photocurable component (A), the hydroxyl group-containing acrylic resin (B-1), the hydroxyl group-containing acrylic resin (B-2) and the particle component (C). It is preferably 4% by mass or more and 36% by mass or less, and more preferably 10% by mass or more and 30% by mass or less.

The glass transition temperature of the hydroxyl group-containing acrylic resin (B-1) is preferably −15 ° C. or higher and 45 ° C. or lower, and more preferably 0 ° C. or higher and 30 ° C. or lower. When the glass transition temperature is within such a range, the coating film can have high crosslink density and elasticity. For the glass transition temperature in the present specification, a value measured by the following steps with a differential scanning calorimeter (DSC) (thermal analyzer SSC5200 (manufactured by Seiko Electronics Co., Ltd.)) was used. Specifically, a step of raising the temperature from 20 ° C. to 150 ° C. at a heating rate of 10 ° C./min (step 1) and a step of lowering the temperature from 150 ° C. to −50 ° C. at a temperature lowering rate of 10 ° C./min (step 2). ), In the step (step 3) of raising the temperature from −50 ° C. to 150 ° C. at a heating rate of 10 ° C./min, the value obtained from the chart at the time of raising the temperature in step 3 was defined as the glass transition temperature. That is, the temperature indicated by the arrow in the chart shown in FIG. 1 was defined as Tg (glass transition temperature).

The solid acid value (AV) of the hydroxyl group-containing acrylic resin (B-1) is preferably 0.5 mgKOH / g or more and 15 mgKOH / g or less, and more preferably 2 mgKOH / g or more and 10 mgKOH / g or less. .. When the acid value of the hydroxyl group-containing acrylic resin (B-1) is within such a range, the adhesion to the base material and the topcoat paint can be improved.

Hydroxy group-containing acrylic resin (B-2)
The hydroxyl group-containing acrylic resin (B-2) is a high molecular weight hydroxyl group-containing acrylic resin having a weight average molecular weight in the range of 10,000 to 30,000.
When the weight average molecular weight is in the range of 10,000 to 30,000, the viscosity of the photocurable resin composition of the present invention can be controlled, so that a good sealing effect can be imparted.
The weight average molecular weight is preferably 13000 or more, and preferably 23000 or less.

The above-mentioned hydroxyl group-containing acrylic resin (B-2) can be formed, and the suitable monomer composition satisfying the above-mentioned conditions is not particularly limited, and the one described in the above-mentioned hydroxyl group-containing acrylic resin (B-1) can be used.

The hydroxyl group-containing acrylic resin (B-2) preferably has a hydroxyl value (OHV) in the range of 5 to 70 mgKOH / g. When the hydroxyl value is within such a range, curing shrinkage during thermosetting can be reduced, and a coating film having good dimensional stability and excellent adhesion can be obtained. The hydroxyl value is more preferably 20 to 55 mgKOH / g.

The glass transition temperature of the hydroxyl group-containing acrylic resin (B-2) is preferably 40 ° C. or higher and 100 ° C. or lower, and more preferably 50 ° C. or higher and 80 ° C. or lower. When the glass transition temperature is within such a range, the coating film can have excellent adhesion to the substrate in particular.

The solid acid value (AV) of the hydroxyl group-containing acrylic resin (B-2) is preferably 0.5 mgKOH / g or more and 30 mgKOH / g or less, and more preferably 2 mgKOH / g or more and 10 mgKOH / g or less. .. When the acid value of the hydroxyl group-containing acrylic resin (B-2) is within such a range, the coating film can obtain particularly excellent adhesion to the substrate.

The compounding ratio of the hydroxyl group-containing acrylic resin (B-2) is a total amount of 100 mass of the photocurable component (A), the hydroxyl group-containing acrylic resin (B-1), the hydroxyl group-containing acrylic resin (B-2) and the particle component (C). It is preferably 4% by mass or more and 36% by mass or less, and more preferably 10% by mass or more and 30% by mass or less.

The SP values of the hydroxyl group-containing acrylic resins (B-1) and (B-2) are not particularly limited, but the difference is preferably less than 1. When the difference in SP value is less than 1, the compatibility of the hydroxyl group-containing acrylic resins (B-1) and (B-2) is high, so that a highly uniform coating film can be formed, thereby providing excellent physical properties. It is preferable in that a coating film having a coating film can be formed. The difference between the SP values is more preferably less than 0.5.
In addition, in this specification, the SP value means the SP value by the turbidity method. The SP value is an abbreviation for solubility parameter and is a measure of solubility. The larger the SP value, the higher the polarity, and conversely, the smaller the value, the lower the polarity.

Particle component (C)
The photocurable resin composition of the present invention further contains a particle component (C). By containing the particle component (C), the viscosity of the coating material can be controlled, and a film can be formed with a sufficient thickness for concealing unevenness. In addition, it becomes difficult for the liquid coating composition to enter the recesses and pinholes on the surface of the object to be coated immediately after coating, and a good sealing effect can be obtained.

The particle component (C) is not particularly limited as long as it is usually blended in the resin composition, but the average particle size is preferably 20 μm or less. When the average particle size is 20 μm or less, a better sealing effect can be expected. The average particle size is more preferably 10 μm or less. The average particle size represents D50 measured using a laser diffraction type particle size distribution measuring device.

The particle component (C) may be an inorganic substance particle or an organic polymer particle. Examples of the inorganic substance particles include natural or synthetic mica, barium sulfate, aluminum powder, aluminum flakes, iron oxide, kaolin clay, talc, silica fine powder, titanium oxide and the like. Examples of the silica fine powder include wet silica, dry silica, colloidal silica and the like.

Examples of the organic polymer particles include fluororesins such as polytetrafluoroethylene, polyethylene, polypropylene, silicones, celluloses, urethanes, nylons, polyesters, phenol resins, acrylic resins, amino resins, polyamide resins and modified resins thereof. Can be mentioned.

The particle component (C) is preferably at least one selected from talc, silica, and kaolin clay. Moreover, you may use 2 or more types together.

The blending ratio of the particle component (C) is 100% by mass of the total amount of the photocurable component (A), the hydroxyl group-containing acrylic resin (B-1), the hydroxyl group-containing acrylic resin (B-2) and the particle component (C). , 6% by mass or more and 54% by mass or less, and more preferably 25% by mass or more and 45% by mass or less. If the blending ratio is less than 6% by mass, the fluidity of the coating liquid becomes high and may flow into the pinholes to impair the smoothness of the coating film surface. On the other hand, if an amount exceeding 54% by mass is blended, the fluidity is lowered, the smoothness of the coating film surface is impaired, and the hue and smoothness of the topcoat coating material may be lowered.

Polyisocyanate (D)
The photocurable resin composition of the present invention further contains polyisocyanate (D).
By blending the polyisocyanate (D), a crosslinked structure is formed with the hydroxyl group-containing acrylic resins (B-1) and (B-2) when the coating film formed above is thermoset, and the coating film is formed. The strength can be increased and coating defects can be suppressed.
In addition, the adhesion to the coating film layer formed on the top can be enhanced, and the strength as a multi-layer coating film can be enhanced.

The blending ratio of the polyisocyanate (D) is 100% by mass based on the total amount of the photocurable component (A), the hydroxyl group-containing acrylic resin (B-1), the hydroxyl group-containing acrylic resin (B-2) and the particle component (C). It is 10 to 100% by mass. If the blending ratio is less than 10% by mass, the crosslink density of the coating film becomes low, the coating film cannot follow the expansion of the air contained in the pinholes, and the appearance of the topcoat paint may be deteriorated. On the other hand, when an amount exceeding 100% by mass is blended, the total amount of the hydroxyl group-containing acrylic resin (B-2) and the particle component (C) becomes low, so that the fluidity of the coating film becomes high and flows into the pinhole. The smoothness of the coating film surface may be impaired.

The polyisocyanate (D) is not particularly limited as long as it is a compound having two or more isocyanate groups, and for example, aromatics such as tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, and metaxylylene diisocyanate. Group; Aliphatic such as hexamethylene diisocyanate; Alicyclic such as isophorone diisocyanate; Monomer thereof and multimers such as bullet type, nurate type, adduct type and the like.

Commercially available products of the polyisocyanate (D) include Duranate 24A-90PX (NCO: 23.6%, trade name, manufactured by Asahi Kasei Corporation), Sumijour N-3200-90M (trade name, manufactured by Sumitomo Bayer Urethane Co., Ltd.). Takenate D165N-90X (trade name, manufactured by Mitsui Chemicals, Inc.), Sumijour N-3300, Sumijour N-3500 (trade name, manufactured by Sumitomo Bayer Urethane), Duranate THA-100 (trade name, manufactured by Asahi Kasei). And so on. Further, if necessary, blocked isocyanates in which these are blocked can also be used.

The photocurable resin composition may further contain ordinary additives used in paints. Examples of the above-mentioned usual additives include coloring pigments, moisture-resistant pigments, other resins, dispersants, anti-settling agents, organic solvents, antifoaming agents, thickeners, rust inhibitors, ultraviolet absorbers, antioxidants, hindered amines, etc. Known additives such as surface conditioners can be mentioned.

The photocurable resin composition of the present invention is preferably adjusted in viscosity so as to exert a high sealing effect, and the tinx value of the paint to be coated is preferably 3 or more and 9 or less. If the tinx value of the paint is less than 3, the fluidity of the paint is high and it may flow into the pinholes to impair the smoothness of the paint film surface. If the chixo value of the paint exceeds 9, the fluidity of the paint is low and the surface of the paint after painting is not smoothed, so that the smoothness, hue and appearance of the topcoat paint are impaired. The chixo values in the present specification are values measured using a TVB-22L BL type viscometer manufactured by Toyo Seiki Co., Ltd.
The measuring method and the calculation method of the chixo value are as follows: the paint is adjusted to a liquid temperature of 20 ° C., a measuring rotor is attached to a BL type viscometer, and the rotor rotation speeds of 60 rotations / minute and 6 rotations / minute are measured. The method of calculating the chixo property is calculated by the following formula.

Chixo value = (Viscosity value of 60 rotations / minute) / (Viscosity value of 6 rotations / minute)

The photocurable resin composition of the present invention can be particularly suitably used as a putty made of a material having irregularities on its surface. The use as a putty will be described in detail below.
The material having irregularities on the surface is not particularly limited, and examples thereof include FRP materials in which fibers such as glass, carbon, Kevlar, high molecular weight polyethylene, boron, and zylon are composited. Further, even a resin having a high water absorption rate can prevent defects due to water evaporation during thermosetting, so that it can be applied to materials such as nylon, ABS, ASA, PET, PBT-PET, PMMA, and polycarbonate. can. These materials are widely used for automobile reflectors such as head lamps, tail lamps and side lamps, and vehicle members such as spoilers. Therefore, the photocurable resin composition of the present invention is suitable as a vehicle paint. Can be used. Such a vehicle paint is also one of the present inventions.

The method for coating the photocurable resin composition of the present invention is not particularly limited. For example, after cleaning the FRP molded product with an aqueous cleaning agent, the above photocurable resin composition is coated on the surface of the molded product, and then. A coating film can be formed by irradiating with ultraviolet rays. Further, after painting, in order to remove the solvent remaining in the paint, air drying may be performed before UV irradiation or a solvent removing step may be added to shorten the process.

The above coating is not particularly limited, and can be performed by a known method such as air spray coating, electrostatic coating, or immersion coating.
The coating is performed so that the dry film thickness is 10 to 70 μm, and air-dried or preheated at room temperature to 100 ° C. for 5 to 25 minutes, preferably 5 to 20 minutes before the irradiation with ultraviolet rays. It is preferable to evaporate the solvent. If the temperature of the preheat exceeds 100 ° C., the performance is not affected, but it is economically disadvantageous.
After the preheating, the ultraviolet irradiation is preferably performed under the condition of about ^{500 to 5000 mJ / cm 2.} The photocurable resin composition of the present invention can be cured by the above-mentioned ultraviolet irradiation. For the ultraviolet irradiation, active energy rays such as high-pressure mercury lamps, metal halide lamps, xenon lamps, UV-LED lamps, and electron beams, which are usually used in the art, can be used.
As described above, a coated article having a cured coating film obtained by curing the photocurable resin composition of the present invention is also one of the present inventions.

After the photocurable resin composition of the present invention is energy ray-cured, it is preferable to further coat a top coat such as a base paint and a clear paint. Further, a second primer coating may be applied, if necessary, before the coating of the top coating paint.
The second primer coating is not particularly limited, and for example, a known plastic primer may be applied.

In the photocurable resin composition of the present invention, it is preferable that after coating, UV irradiation is performed to cure the surface, and then base coating, clear coating and, if necessary, a second putty coating are performed. The heat curing may be performed for each coating of the second putty paint, the base paint, and the clear paint, or may be performed after the second putty paint, the base paint, and the clear paint are applied from the viewpoint of productivity. Further, in order to enhance the color development of the base paint, the putty paint may be heat-cured. By painting by such a method, a certain strength is given to the coating film of the photocurable resin composition, so that the appearance defect caused by the expansion of the gas remaining in the unevenness at the time of heating is caused. It can be significantly reduced.

The base coating and the clear coating are not particularly limited, and for example, the clear coating can be applied to a known solvent-based base coating or water-based base coating and heat-cured.

The method for applying the topcoat coating composition is not particularly limited, and for example, air spray coating, airless spray coating, bell coating, or the like can be adopted.

The baking temperature of the topcoat coating composition is preferably, for example, 70 to 130 ° C. in view of the balance between rapid curing and prevention of deformation of the FRP molded product. More preferably, it is 80 to 120 ° C. The baking time is usually 10 to 60 minutes, preferably 15 to 50 minutes, and more preferably 20 to 40 minutes. If the baking time is less than 10 minutes, the coating film is not sufficiently cured, and the performance such as water resistance and solvent resistance of the cured coating film is deteriorated. On the other hand, if the baking time exceeds 60 minutes, it is over-cured and the adhesion in recoating is lowered, the total time of the painting process is lengthened, and the energy cost is increased. In addition, this baking time means the time that the surface of the base material actually keeps the target baking temperature, and more specifically, the time until the target baking temperature is reached is not considered, and the target It means the time when the temperature is reached and the temperature is maintained.

Examples of the heating device used for simultaneously baking the uncured film of the paint include a drying furnace using a heating source such as hot air, electricity, gas, or infrared rays, and two or more of these heating sources are used in combination. It is preferable to use a drying oven because the drying time is shortened.

The photocurable resin composition of the present invention can be particularly preferably used as a paint for vehicles. Specific examples of the vehicle include automobile bodies made of FRP, various automobile parts such as spoilers, and the like.

Hereinafter, the present invention will be described by way of examples. In the examples, "%" and "parts" in the blending ratio mean "mass%" and "parts by mass" unless otherwise specified. The present invention is not limited to the examples described below.

Production Example 1 Synthesis of hydroxyl group-containing acrylic resin 1- (1) 100 parts of butyl acetate in a four-necked flask equipped with a heating device, agitating device, thermometer, reflux condenser, nitrogen introduction tube, and dropping device. Was charged, and the temperature was raised to 120 ° C. while stirring and introducing nitrogen. Then, from the dropping device, 9.9 parts of styrene, 54.3 parts of 2-ethylhexyl methacrylate, 34.8 parts of 2-hydroxyethyl methacrylate, 1.0 part of methacrylic acid and 10 parts of kaya ester-O which is a polymerization initiator. The mixed solution of the above was added dropwise over 3 hours. Then, stirring was continued for 120 minutes to complete the reaction, and the desired hydroxyl group-containing acrylic resin 1- (1) was obtained (resin solid content 50%). Table 1 shows the blending amount and physical properties of the hydroxyl group-containing acrylic resin 1- (1).

Production Examples 2 to 10 Production of Acrylic Resins 1- (2) to 1- (10) Table 1 shows the same equipment as that used for the synthesis of the hydroxyl group-containing acrylic resin 1- (1). The synthesis procedure and operation similar to the operation of the hydroxyl group-containing acrylic resin 1- (1) except that the solvent, the monomer, the initiator, and the polymerization temperature were changed so as to obtain the listed compounding amount were carried out, and the hydroxyl group content shown in Table 1 was carried out. Acrylic resins 1- (2) to 1- (10) were obtained. The physical characteristics are also shown in Table 1.

(Hydroxy group value (OHV))
The hydroxyl value was determined by the neutralization titration method using an aqueous potassium hydroxide solution described in JIS K 0070.

(Weight average molecular weight)
The weight average molecular weight (Mw) is a value measured by GPC (gel permeation chromatography) and is a polystyrene-equivalent weight average molecular weight.

(Solubility parameter (SP value))
The solubility parameter (SP value) was actually measured by the method described herein.

(Glass transition temperature (Tg))
The glass transition temperature (Tg) was measured using a DSC (Differential Scanning Calorimetry) manufactured by Seiko Electronics Inc.

St: Styrene EHMA: 2-Ethylhexyl methacrylate HEMA: 2-Hydroxyethyl methacrylate MAA: Methacrylic acid polymerization initiator: Kayaester-O (hydrogen peroxide-based polymerization initiator manufactured by Kayaku Akzo Corporation)

Production Examples 11 to 19 Production of Acrylic Resins 2- (1) to 2- (9) Table 2 shows the same equipment as that used for the synthesis of the hydroxyl group-containing acrylic resin 1- (1). Table 2 shows the same synthesis procedure and operation as those for the synthesis of the hydroxyl group-containing acrylic resin 1- (1) except that the solvent, monomer, initiator, and polymerization temperature were changed so as to obtain the stated blending amount. A hydroxyl group-containing acrylic resin 2- (1) to 2- (9) was obtained. The physical characteristics are also shown in Table 2.

Photo-curing component (A)
The photocurable component (A) used is as follows.
Pentaerythritol tetraacrylate (manufactured by Sartmer: SR295)
Ditrimethylolpropane tetraacrylate (manufactured by Sartmer: SR355)
Dipentaerythritol pentaacrylate (manufactured by Sartmer: SR399)
Dipentaerythritol hexaacrylate (manufactured by Sartmer: DPHA)

Particle component (C)
The particle component (C) used is as follows.

Polyisocyanate (D)
The polyisocyanate (D) used is as follows.
TPA-100 (Isocyanurate type): Hexamethylene isocyanurate 24A-100 (Burette type) manufactured by Asahi Kasei Corporation: Hexamethylene diisocyanate P301-75E (Adduct type) manufactured by Asahi Kasei Corporation: Hexamethylene isocyanurate manufactured by Asahi Kasei Corporation

Example 1
Each component shown in Table 4 was placed in a container equipped with a stirrer, MEK in an amount such that the final coating material had NV = 30% was placed while stirring, and the mixture was stirred for 30 minutes to obtain a photopolymerizable resin composition. .. The obtained photopolymerizable resin composition was spray-coated so that the dry film thickness was 35 μm, and heated in a hot air drying oven at 80 ° C. for 5 minutes to remove the solvent. Next, using a high-pressure mercury lamp (ECS-4011GX manufactured by Eye Graphics Co., Ltd.) ^{, ultraviolet rays having an integrated light intensity of 2000 mJ / cm 2} were irradiated to obtain a cured coating film. Here, the amount of light in the ultraviolet irradiation was measured using an eye ultraviolet integrated illuminance meter UV METER UVPF-A1 (light receiving unit 365 nm) manufactured by Eye Graphics.

Examples 2-35, Comparative Examples 1-10
The coating films of Examples 2 to 35 and Comparative Examples 1 to 10 were formed in the same manner as in Example 1 except that the formulations were changed to those shown in Tables 4 to 9, and final coated plates were obtained.

Formation of Laminated Film After the putty paints of the above Examples and Comparative Examples were applied and cured, a laminated film was formed by the following method.
After the putty paints of the above Examples and Comparative Examples were applied and cured, the solvent-based base paint composition (manufactured by Nippon Paint Automotive Coatings Co., Ltd .: R-160) was applied so that the film thickness of the dry coating film was 15 μm. After coating, a clear coating composition (manufactured by Nippon Paint Automotive Coatings Co., Ltd .: R-2830) was applied so that the film thickness of the dry coating film was 25 μm. After the coating was completed, the mixture was allowed to stand for 10 minutes and then heat-cured at 80 ° C. for 30 minutes to obtain a test piece having a multi-layer coating film.

[Effect of sealing function (evaluation of photocurable resin composition on cured film)]
・ Sealing effect that suppresses the inflow of paint into the dents and pinholes on the FRP material and hides it. ◎ when the dent or pinhole is concealed and there is no visual defect, ○ when a slight dent or pinhole is found, △ when either the dent or pinhole is not concealed, dent or pin The time when the hall was not hidden was marked as x.

⊚: When the concave or pinhole of the FRP material is concealed and there is no visual defect ○: When a slight concave or pinhole is found △: When either the concave or the pinhole is not concealed ×: Concave And pinholes are not hidden

[Effect of sealing function (evaluation with laminated film)]
・ Sealing effect that suppresses air expansion contained in the FRP material The FRP material coated with the photocurable resin composition is coated with a base paint and a clear paint, and air bubbles are formed on the coating film surface with a heat-cured evaluation plate. ◎ when there is no defect formed by rupture, ○ when there is slight swelling of the coating film but no defect due to rupture, △ when there are many swelling of the coating film but no defect due to rupture, When there were many swellings of the membrane and many defects due to rupture, it was marked as x.

⊚: When there is no defect formed by bursting bubbles on the coating film surface ○: When there is a slight swelling of the coating film but there is no defect due to rupture Δ: There are many swelling of the coating film but there is no defect due to rupture When ×: When there is swelling of the coating film and there are many defects due to rupture

[Adhesion of laminated film]
Base paint and clear paint are applied to the FRP material coated with the photocurable resin composition, and 100 base stitches are made on the surface of the test piece with a single-edged sword at 2 m intervals using a thermosetting evaluation plate. A cellophane adhesive tape (JIS Z 1522) was sufficiently pressure-bonded onto the tape and quickly peeled off in the 90 ° direction, and the peeled state of the coating film was evaluated by the number of substrates of the remaining coating film. When 100 pieces remained as they were, it was evaluated as ◯, when 60 to 99 pieces remained, it was evaluated as Δ, and when it was less than 60 pieces, it was evaluated as ×.
[Adhesion of coating film]
◯: When 100 pieces remain as they are Δ: When 60 to 99 pieces remain ×: When less than 60 pieces

[Hot water resistance test]
The test piece prepared in the same manner as the initial adhesion evaluation described above is immersed in warm water at 40 ° C. for 240 hours, pulled out of the water, dried at room temperature for 1 hour, and then adhered to the substrate in the same manner as the initial adhesion evaluation. I checked the sex.
[Adhesion after hot water resistance test]
◯: When 100 pieces remain as they are Δ: When 60 to 99 pieces remain ×: When less than 60 pieces

 

From the results of each of the above-mentioned examples, it is clear that the photocurable resin composition of the present invention can obtain coatability and good coating film physical properties.

The photocurable resin composition of the present invention can be suitably used as a resin composition to be directly coated on a resin member having irregularities on the surface.

Claims (5)

1. Photocurable component (A), which is a polyfunctional acrylate having 4 or more (meth) acrylate groups,
   A hydroxyl group-containing acrylic resin (B-1) having a weight average molecular weight in the range of 3000 to 8000,
   It contains a hydroxyl group-containing acrylic resin (B-2), a particle component (C), and a polyisocyanate (D) having a weight average molecular weight in the range of 10,000 to 30,000.
   The compounding ratio of the polyisocyanate (D) is 10 to 100% by mass with respect to 100% by mass of the total amount of the photocurable component (A), the acrylic resin (B-1), the acrylic resin (B-2) and the particle component (C). A photocurable resin composition characterized by being%.
2. The photocurable resin composition according to claim 1, wherein the acrylic resin (B-1) has a hydroxyl value in the range of 120 to 200 mgKOH / g.
3. The photocurable resin composition according to claim 1 or 2, wherein the acrylic resin (B-2) has a hydroxyl value in the range of 5 to 70 mgKOH / g.
4. A vehicle paint comprising the photocurable resin composition according to claim 1, 2 or 3.
5. A coated article having a cured coating film obtained by curing the photocurable resin composition according to claim 1, 2 or 3.
   

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