Moisture-curable resin sheet, vehicle component, vehicle, and method for manufacturing vehicle and vehicle component

Abstract

A moisture-curable resin sheet includes a transfer layer and a resin layer containing a (meth)acrylic resin (A) having an isocyanate group.

Description

Moisture-curing resin sheet, vehicle part, vehicle, and method for manufacturing vehicle and vehicle part

[0001] The present invention relates to a moisture-curing resin sheet, a vehicle part, a vehicle, and a method for manufacturing a vehicle and a vehicle part.

[0002] Conventionally, various products such as furniture, steel plates, and vehicle bodies have been painted to impart functions such as design, durability, weather resistance, and scratch resistance. Painting is generally performed by spraying with air or electrostatic force. Spray painting has the following drawbacks: loss during painting, CO2 emissions from factories, etc. ２ In view of the need for large-scale capital investment, replacement with decorative technology using resin films has been considered recently.

[0003] Decoration technology is a technique that achieves high functionality and design by adhering a resin film (decorative film) printed with letters or pictures using white, black, or color ink to an adherend to decorate it. For example, a thermosetting resin sheet containing a thermosetting resin and a curing agent is known to be used as the decorative film. The thermosetting resin sheet is attached to the adherend and then heated to harden it, allowing it to cover the adherend with high adhesive strength.

[0004] However, since thermosetting resin sheets require heating after lamination, they may not be applicable to some types of adherends. Therefore, the use of moisture-curing resin sheets as decorative films has been considered. Generally, moisture-curing urethane resins are widely used as moisture-curing resins, as disclosed in, for example, Patent Document 1. It is also known that an acrylic skeleton is introduced into a urethane prepolymer used in a moisture-curing urethane resin, as disclosed in, for example, Patent Document 2.

[0005] Patent No. 7363124 Patent No. 6584382

[0006] Incidentally, decorative resin sheets (resin layers) are sometimes laminated on a transfer layer to facilitate bonding to the adherend. In this case, if the transfer layer of the resin sheet bonded to the adherend is peeled off before curing and the resin is cured in an exposed state, foreign matter may adhere to the resin sheet or the resin may be damaged. Furthermore, peeling off the transfer layer in an uncured state can cause a stick-slip phenomenon, resulting in streaks or the resin may adhere to the transfer layer, causing the surface to become rough. Therefore, to maintain a smooth surface of the resin layer, it is desirable to cure the resin layer with the transfer layer still attached.

[0007] However, according to the inventors' investigations, when a urethane resin, which is a common moisture-curing resin, is used in a decorative resin sheet and the resin is cured with the transfer layer attached, gases such as carbon dioxide generated during curing do not escape, and air bubbles remain in the coating film after curing, causing surface roughness. Also, the resin composition disclosed in Patent Document 2 is a coating-type hot-melt resin composition, and it is difficult to apply it to a decorative resin sheet.

[0008] Therefore, an object of the present invention is to provide a moisture-curable resin sheet that can form a coating with a good surface condition by suppressing the generation of bubbles during curing.

[0009] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by incorporating a (meth)acrylic resin having an isocyanate group into a moisture-curing resin sheet having a transfer layer and a moisture-curing resin layer, and have thus completed the present invention. Specifically, the present invention provides the following [1] to

[12] . [1] A moisture-curing resin sheet comprising a transfer layer and a resin layer containing a (meth)acrylic resin (A) having an isocyanate group. [2] The moisture-curing resin sheet according to [1] above, wherein the (meth)acrylic resin (A) has a weight-average molecular weight of 10,000 or more and 500,000 or less. [3] The moisture-curing resin sheet according to [1] or [2] above, further comprising a compound (B) having two or more isocyanate groups other than the (meth)acrylic resin (A). [4] The moisture-curing resin sheet according to [3] above, wherein the compound (B) has a molecular weight of 1,000 or less. [5] The moisture-curing resin sheet according to any one of [1] to [4] above, wherein the content of the (meth)acrylic resin (A) in the resin layer is 30% by mass or more. [6] The moisture-curing resin sheet according to any one of [1] to [5] above, wherein the (meth)acrylic resin (A) has an isocyanate group in a side chain. [7] The moisture-curing resin sheet according to any one of [1] to [6] above, wherein the isocyanate group content in the (meth)acrylic resin (A) is 0.5% by mass or more and 15% by mass or less. [8] The moisture-curing resin sheet according to any one of [1] to [7] above, wherein the resin layer contains a pigment. [9] A vehicle component having a coating formed using the moisture-curing resin sheet according to any one of [1] to [8] above.

[10] A vehicle having a coating formed using the moisture-curing resin sheet according to any one of [1] to [8] above.

[11] A method for manufacturing a vehicle, comprising a step of coating using the moisture-curing resin sheet according to any one of [1] to [8] above.

[12] A method for manufacturing a vehicle part, comprising a step of painting using the moisture-curing resin sheet according to any one of [1] to [8] above.

[0010] According to the present invention, it is possible to provide a moisture-curable resin sheet that forms a coating with a good surface condition by suppressing the generation of bubbles during curing.

[0011] 1 is a schematic cross-sectional view showing an embodiment of a moisture-curable resin sheet, and FIG. 2 is a schematic cross-sectional view showing an embodiment of a moisture-curable resin sheet.

[0012] <Moisture-curing resin sheet> Hereinafter, the moisture-curing resin sheet of the present invention will be described with reference to an embodiment. As shown in Figures 1 and 2, the moisture-curing resin sheet 10 includes a resin layer 11 and a transfer layer 12, with the transfer layer 12 laminated on one side of the resin layer 11. As shown in Figure 1, the moisture-curing resin sheet 10 may be composed of the resin layer 11 and the transfer layer 12, or as shown in Figure 2, it may further include a release layer 13, which is preferably laminated on the surface of the resin layer 11 opposite to the surface on which the transfer layer 12 is provided. Hereinafter, each component of the moisture-curing resin sheet will be described in detail.

[0013] [Resin Layer] The resin layer of the present invention contains a (meth)acrylic resin (A) having an isocyanate group. By containing the (meth)acrylic resin (A) having an isocyanate group, the resin layer suppresses the generation of bubbles during curing, even when the transfer layer is cured in a laminated state, thereby preventing surface roughening during curing and forming a cured layer with a good surface condition. Although the mechanism behind this is unclear, it is presumed that the (meth)acrylic resin (A) having an isocyanate group suppresses gas generation even when moisture curing progresses, or generates gas in a manner that prevents the formation of bubbles, thereby preventing surface roughening during curing. It is presumed that the generation of gas during curing is suppressed due to the polarity of the ester group of the (meth)acrylic resin, which has the ability to adsorb water and carbon dioxide to a certain extent and gradually releases the gas after adsorption, thereby suppressing the generation of gas during curing.

[0014] ((Meth)acrylic resin (A)) The (meth)acrylic resin (A) is a moisture-curable resin having moisture-curing properties due to the presence of an isocyanate group. The (meth)acrylic resin (A) preferably has an isocyanate group in its side chain. The (meth)acrylic resin (A) may also have two or more isocyanate groups in one molecule. The (meth)acrylic resin (A) is not particularly limited as long as it has an isocyanate group, but it is preferable to use a (meth)acrylate having an isocyanate group as a raw material. Therefore, the (meth)acrylic resin (A) is preferably a polymer containing a structural unit derived from a (meth)acrylate having an isocyanate group. The (meth)acrylic resin (A) has a structural unit derived from a (meth)acrylate having an isocyanate group, so that the isocyanate group is positioned close to the main chain, resulting in a relatively regular molecular arrangement after curing and good curability. Therefore, it is easy to improve the hardness of the resin layer after curing while improving the surface condition.

[0015] In the (meth)acrylate having an isocyanate group used as a raw material, the (meth)acrylate-derived portion of the compound preferably constitutes the main chain of the polymer, and the isocyanate group is preferably located in a side chain of the polymer. A single molecule of the (meth)acrylic resin (A) preferably contains a plurality of isocyanate groups in the side chain. The (meth)acrylic resin (A) may have an isocyanate group at its terminal, but may not have an isocyanate group at its terminal. In this specification, the term "(meth)acrylate" is used to mean either one or both of acrylate and methacrylate, and the same applies to other similar terms.

[0016] The (meth)acrylic resin (A) is a polymer obtained by polymerizing a monomer (a) containing a (meth)acrylate, and may have a structural unit derived from the (meth)acrylate in the main chain. However, it is preferably a polymer obtained by polymerizing a monomer (a) containing a (meth)acrylate having an isocyanate group, and more preferably a polymer obtained by polymerizing a monomer (a) containing a (meth)acrylate having an isocyanate group and an alkyl (meth)acrylate. The use of an alkyl (meth)acrylate can impart adhesiveness to the resin layer before curing. Furthermore, the monomer (a) may further contain a monomer (other monomer) other than the (meth)acrylate and alkyl (meth)acrylate having an isocyanate group.

[0017] Examples of (meth)acrylates having an isocyanate group include isocyanatoalkyl (meth)acrylates such as 2-isocyanatoethyl (meth)acrylate, 4-isocyanatobutyl (meth)acrylate, and 6-isocyanatohexyl (meth)acrylate, as well as 2-(2-isocyanatoethoxy)ethyl (meth)acrylate and 1,1-bis(acryloyloxymethyl)ethyl isocyanate. Of these, isocyanatoalkyl (meth)acrylates are preferred. The number of carbon atoms in the alkyl group in the isocyanatoalkyl (meth)acrylate is not particularly limited, but is, for example, about 1 to 10, and preferably 2 to 4.

[0018] Examples of the alkyl (meth)acrylate include alkyl (meth)acrylates having an alkyl group with about 1 to 18 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, myristyl (meth)acrylate, isomyristyl (meth)acrylate, and stearyl (meth)acrylate. From the viewpoint of imparting adhesive strength before curing to the resin layer, the alkyl(meth)acrylate is preferably an alkyl(meth)acrylate in which the alkyl group has 1 to 12 carbon atoms. Furthermore, from the viewpoint of improving adhesive strength before curing, the alkyl(meth)acrylate more preferably contains an alkyl(meth)acrylate in which the alkyl group has 3 to 10 carbon atoms.

[0019] Furthermore, examples of other monomers other than (meth)acrylates and alkyl (meth)acrylates having an isocyanate group include alicyclic (meth)acrylates such as cyclohexyl (meth)acrylate and isobornyl (meth)acrylate; (meth)acrylates having an aromatic ring such as benzyl (meth)acrylate and phenoxydiethylene glycol (meth)acrylate; styrene-based monomers such as styrene, α-methylstyrene, α-ethylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-ethoxystyrene, p-chlorostyrene, m-chlorostyrene and o-chlorostyrene; and vinyl monomers having a vinyl ester group such as vinyl acetate and vinyl propionate.

[0020] The amount of (meth)acrylate having an isocyanate group used in the monomer (a) constituting the (meth)acrylic resin (A) is preferably 2 mol% or more and 40 mol% or less, more preferably 5 mol% or more and 30 mol% or less, and even more preferably 8 mol% or more and 25 mol% or less. By setting the amount of (meth)acrylate having an isocyanate group used within the above range, it is easy to suppress the generation of bubbles during curing, even when the transfer layer is cured in a state where it is laminated on the resin layer. In addition, it is easy to achieve a good balance between the adhesive strength before curing, the adhesive strength after curing, and the hardness after curing.

[0021] The amount of alkyl (meth)acrylate used in the monomer (a) is preferably 50 mol% or more and 98 mol% or less, more preferably 65 mol% or more and 95 mol% or less, and even more preferably 70 mol% or more and 92 mol% or less. By setting the amount of alkyl (meth)acrylate used to be equal to or greater than the lower limit, flexibility is increased and adhesive strength before curing is easily improved. By setting it to be equal to or less than the upper limit, it is easy to contain a certain amount or more of isocyanate groups, and adhesive strength and hardness after curing are easily improved.

[0022] In order to increase flexibility and improve adhesive strength before curing, it is particularly preferable that the alkyl (meth)acrylate in the monomer (a) contains an alkyl acrylate having 3 to 10 carbon atoms in the alkyl group. The amount of the alkyl acrylate having 3 to 10 carbon atoms in the alkyl group in the monomer (a) used is preferably 30 mol% or more and 98 mol% or less, more preferably 35 mol% or more and 95 mol% or less, and even more preferably 40 mol% or more and 90 mol% or less.

[0023] The weight average molecular weight of the (meth)acrylic resin (A) is preferably 10,000 or more and 500,000 or less. By setting the weight average molecular weight of the (meth)acrylic resin (A) within the above range, it becomes easier to achieve a good balance of the coatability, curability, adhesion, extensibility, etc. of the resin layer. The weight average molecular weight of the (meth)acrylic resin (A) is more preferably 20,000 or more and 300,000 or less, and even more preferably 40,000 or more and 100,000 or less. In this specification, the weight average molecular weight is measured by gel permeation chromatography (GPC) and is calculated as a value converted into standard polystyrene.

[0024] The isocyanate group content in the (meth)acrylic resin (A) is preferably 0.5% by mass or more and 15% by mass or less, more preferably 1% by mass or more and 10% by mass or less, and even more preferably 2% by mass or more and 8% by mass or less. When it is 0.5% by mass or more, crosslinking is at a certain level, resulting in appropriate hardness and preventing deterioration of solvent resistance, etc. Furthermore, when it is 15% by mass or less, it does not become too hard and is less likely to crack, and deterioration of storage stability can also be prevented. The isocyanate group content referred to here is the proportion of the mass of NCO molecules (molecular weight 42) to the total mass of the (meth)acrylic resin (A), and can be determined, for example, by potentiometric titration in accordance with JIS K 1603-1. That is, the sample and di-n-butylamine are mixed and reacted, and the NCO amount can be determined by potentiometric titration of the remaining di-n-butylamine with a hydrochloric acid standard solution.

[0025] The content of the (meth)acrylic resin (A) in the resin layer may be, for example, 20% by mass or more, preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more. By making the content of the (meth)acrylic resin (A) a certain amount or more, it is possible to improve the surface condition of the resin layer while increasing the adhesive strength before curing, the hardness of the resin layer after curing, and the adhesion to the adherend. The content of the (meth)acrylic resin (A) in the resin layer may be 100% by mass or less, but from the viewpoint of containing a certain amount or more of other components such as compound (B), it is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 75% by mass or less.

[0026] (Compound (B)) The moisture-curable resin sheet preferably further contains a compound (B) (polyisocyanate compound) having an isocyanate group. By containing the compound (B), the moisture-curable resin sheet can increase the hardness of the resin layer after curing, and therefore the mechanical strength and scratch resistance of the resin layer after curing can be improved. The compound (B) preferably has two or more isocyanate groups. In addition, the compound (B) is preferably a compound other than the above-mentioned (meth)acrylic resin (A) and does not contain a polyacrylic skeleton.

[0027] Examples of the compound (B) include polyisocyanates such as aliphatic diisocyanate compounds such as hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate, lysine diisocyanate, norbornane diisocyanate, isophorone diisocyanate (IPDI), xylylene diisocyanate, hydrogenated xylylene diisocyanate (H6XDI), hydrogenated diphenylmethane diisocyanate, cyclohexane diisocyanate, bis(isocyanatomethyl)cyclohexane, and dicyclohexylmethane diisocyanate; and aromatic diisocyanate compounds such as 4,4-diphenylmethane diisocyanate, tolylene diisocyanate, and naphthalene-1,5-diisocyanate.

[0028] The compound (B) may be a modified product obtained by polymerizing the above-mentioned polyisocyanate, such as polymeric MDI, or may be a polyol-modified product (adduct) of a polyisocyanate such as a trimethylolpropane adduct of a polyisocyanate, a biuret of a polyisocyanate, an allophanate of a polyisocyanate, an isocyanurate of a polyisocyanate, or a condensate thereof, etc. Specific preferred examples include HDI adduct, HDI biuret, HDI allophanate, HDI isocyanurate, H6XDI isocyanurate, IPDI isocyanurate, IPDI adduct, etc. As the compound (B), it is preferable to select one that is flexible and has high adhesive strength in an uncured state, and from such a viewpoint, an aliphatic polyisocyanate or a modified product thereof is preferable, and among them, an adduct, a biuret, an allophanate, or an isocyanurate of an aliphatic polyisocyanate is more preferable, and an adduct, a biuret, an allophanate, or an isocyanurate of HDI or IPDI is even more preferable. The compound (B) may be used alone or in combination of two or more.

[0029] The molecular weight of compound (B) is not particularly limited, but is preferably 1000 or less. By reducing the molecular weight of compound (B), the adhesive strength of the resin layer before curing and the adhesion to the adherend after curing can be increased. The molecular weight of compound (B) is preferably 800 or less, more preferably 700 or less. The molecular weight of compound (B) is not particularly limited, but may be, for example, 160 or more, preferably 200 or more, more preferably 300 or more, and even more preferably 400 or more. The molecular weight of compound (B) is calculated from the structural formula. When two or more types of compound (B) are used in combination, the molecular weight refers to the weight average molecular weight.

[0030] When compound (B) is used, the content of compound (B) in the resin layer is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 20 parts by mass or more, when the total of the (meth)acrylic resin (A) and compound (B) is 100 parts by mass. By making the content of compound (B) a certain amount or more, it is easy to increase the hardness of the resin layer after curing. Furthermore, the content of compound (B) may be, for example, 80 parts by mass or less, but is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 40 parts by mass or less. By making the content of compound (B) a certain value or less, it is easy to improve the surface condition of the resin layer while improving the adhesive strength of the resin layer before curing and the adhesiveness after curing.

[0031] (Moisture-Cure Accelerator Catalyst) The resin layer may contain a moisture-cure catalyst that accelerates the moisture-cure reaction. The use of a moisture-cure catalyst improves the moisture-cure properties of the resin layer, making it easier to increase the hardness of the resin layer and its adhesive strength after curing. Furthermore, even when the ambient temperature is low, such as in winter, the resin layer can be properly cured by leaving it in the air. Specific examples of moisture-cure accelerator catalysts include amine-based compounds and metal-based catalysts. Examples of amine-based compounds include compounds having a morpholine skeleton, such as di(methylmorpholino)diethyl ether, 4-morpholinopropylmorpholine, and 2,2'-dimorpholinodiethyl ether; dimethylamino-containing amine compounds having two dimethylamino groups, such as bis(2-dimethylaminoethyl)ether and 1,2-bis(dimethylamino)ethane; triethylamine; 1,4-diazabicyclo[2.2.2]octane; and 2,6,7-trimethyl-1,4-diazabicyclo[2.2.2]octane. Examples of the metal catalyst include tin compounds such as di-n-butyltin dilaurate, di-n-butyltin diacetate, and tin octoate, zinc compounds such as zinc octoate and zinc naphthenate, and other metal compounds such as zirconium tetraacetylacetonate, copper naphthenate, and cobalt naphthenate. The content of the moisture-cure-accelerating catalyst in the resin layer is preferably from 0.001 to 5 parts by mass, more preferably from 0.01 to 3.5 parts by mass, and even more preferably from 0.02 to 2 parts by mass, relative to 100 parts by mass of the total amount of the (meth)acrylic resin (A) and the compound (B).

[0032] (Surface Conditioner) The resin layer may contain a surface conditioner. The surface conditioner adjusts the surface tension and improves wettability. Examples of surface conditioners include silicone-acrylic copolymer-based, silicone-based, polyacrylate-based, and fluorine-based. By incorporating a surface conditioner into the resin layer, the wettability of the resin layer can be improved, thereby improving the peel strength to the adherend. Furthermore, the smoothness and slipperiness of the surface can be adjusted, thereby improving scratch resistance. The content of the surface conditioner in the resin layer is preferably 0.01 to 3 parts by mass, more preferably 0.05 to 2 parts by mass, and even more preferably 0.1 to 1 part by mass, relative to 100 parts by mass of the total amount of the (meth)acrylic resin (A) and the compound (B).

[0033] (Colorant) The resin layer may be used, for example, to protect or beautify the adherend. Therefore, the resin layer may contain a colorant to form a colored layer. The colorant may be a pigment, dye, or lustrous material. Among these, pigments are preferred. Examples of pigments used as colorants include metal oxide pigments such as titanium oxide and iron oxide, inorganic pigments such as carbon black, clay, kaolin, barium sulfate, barium carbonate, calcium carbonate, talc, silica, and alumina white, and organic pigments such as azo pigments, quinacridone pigments, diketopyrrolopyrrole pigments, perylene pigments, perinone pigments, benzimidazolone pigments, vat pigments, isoindoline pigments, isoindolinone pigments, metal chelate azo pigments, phthalocyanine pigments, indanthrone pigments, dioxane pigments, and indigo pigments, but are not limited thereto. Known dyes can be used, including azo dyes, anthraquinone dyes, indigoid dyes, and stilbene dyes. The lustrous material is a compound that can impart lustrous properties to the resin layer and can impart a glossy appearance when observed from multiple directions. Examples of lustrous materials include, but are not limited to, compounds in which a titanium oxide layer is provided on the surface of natural mica, synthetic mica, alumina flakes, glass flakes, etc. The content of the colorant in the resin layer is not particularly limited, but is preferably about 0.05% by mass to 15% by mass, preferably 0.1% by mass to 12% by mass, and more preferably 0.3% by mass to 8% by mass.

[0034] The resin layer may also be a clear layer that does not substantially contain a colorant. The clear layer is a transparent layer and only needs to have a transparency that allows the color of the colored layer to be visible from the outside through the clear layer, and for example, the transmittance of light with a wavelength of 450 nm should be 80% or more. The clear layer is preferably a resin layer that does not contain a colorant, but may contain a small amount of colorant as long as it does not impair its function. The content of the colorant in the clear layer is not particularly limited, but is, for example, 0 to 2% by mass, preferably 0 to 0.5% by mass, and more preferably 0 to 0.1% by mass.

[0035] The resin layer may also be used to provide a function other than the protection or beautification of the adherend, for example, as a heat-shielding coating. In this case, it is preferable that the coating formed by the resin layer functions as a heat-shielding coating, and in this case, the resin layer may contain a heat-shielding agent to form a heat-shielding layer. Furthermore, by providing the resin layer with surface irregularities, it is possible to impart surface properties such as matte or embossed finishes. In addition, functions such as rust prevention, mildew prevention, heat insulation, and antistatic properties can be achieved by incorporating components appropriate for the purpose (e.g., rust inhibitors, mildew inhibitors, antistatic agents, etc.) into the resin layer.

[0036] The resin layer may contain components other than those described above, for example, additives other than those described above. Examples of additives include plasticizers, inorganic fillers other than colorants and heat-shielding agents, dispersants, antioxidants, antioxidants, and ultraviolet absorbers. Furthermore, the resin layer may contain resin components other than the components (A) and (B) described above, as long as the effects of the present invention are not impaired.

[0037] The resin layer may be composed of a single layer or may have a multi-layer structure of two or more layers, but a single-layer structure is preferred. A single-layer structure makes it easier to manufacture the resin layer. Furthermore, a multi-layer structure allows various functions to be imparted to the coating formed from the resin layer. When the resin layer has a multi-layer structure, it is sufficient that the entire resin layer contains the above-described components in the above-described amounts, but it is preferred that each layer be a resin layer as described above. In the case of a multi-layer structure, the formulation of each layer may be the same as or different from each other, but is usually different from each other.

[0038] In the case of a multilayer structure, the resin layer may include, for example, at least one of a colored layer containing a colorant and a clear layer substantially free of a colorant, but preferably includes both a colored layer and a clear layer. When a colored layer and a clear layer are included, the clear layer and the colored layer are preferably arranged in this order from the transfer layer side. With such a layer configuration, when the moisture-curing resin sheet is attached to an adherend, the colored layer and the clear layer are arranged in this order from the adherend side. As described above, by having a colored layer, the resin layer can color the adherend with the paint formed by the resin layer. Furthermore, by providing a clear layer in addition to the resin layer, the colored layer can be protected or glossed. Note that the colored layer in the multilayer structure only needs to have a colorant content within the above range, and the clear layer also only needs to have a colorant content within the above range.

[0039] Of course, when the resin layer has a multi-layer structure, it is not limited to a two-layer structure of a clear layer and a colored layer, and various laminate structures are possible, such as a three-layer or more structure with two or more colored layers and one or more clear layers, or a structure consisting of two colored layers without the clear layer. Also, two or more clear layers may be provided. Furthermore, a heat-shielding layer or the like may be provided between the clear layer and the colored layer, resulting in a three-layer or more structure.

[0040] The thickness of the resin layer is not particularly limited, but is, for example, about 5 μm to 1000 μm, preferably 15 μm to 500 μm, and more preferably 20 μm to 200 μm. The thickness of the resin layer refers to the total thickness of the resin layer when the resin layer has a multilayer structure. When a colored layer and a clear layer are provided on the resin layer, the thickness of the colored layer is not particularly limited, but is, for example, 5 μm to 500 μm, preferably 10 μm to 100 μm, and more preferably 15 μm to 50 μm. The thickness of the clear layer is not particularly limited, but is, for example, 5 μm to 500 μm, preferably 10 μm to 100 μm, and more preferably 15 μm to 50 μm.

[0041] (Transfer Layer) The transfer layer is a member that protects the resin layer from scratches and adhesion of foreign matter, and also serves as a support when attaching the resin layer to an adherend. The transfer layer is preferably formed from a resin film. The resin used in the resin film is preferably a thermoplastic resin, but may be a resin other than a thermoplastic resin. Specific examples of resins used in the resin film include polyolefin resins such as cyclic polyolefin resins, polyethylene resins, and polypropylene resins, ethylene vinyl acetate copolymer resins, polyester resins such as polybutylene terephthalate, polybutylene terephthalate, polyamide resins, acrylonitrile butadiene styrene resins, polycarbonate resins, acrylic resins, fluororesins, vinyl chloride resins, polymethylpentene resins, and tetrafluoroethylene resins.

[0042] The resin film constituting the transfer layer may be a single-layer film consisting of one single layer, or may be a multilayer film consisting of two or more layers. Furthermore, in the resin film constituting the transfer layer, the resin contained in the resin film may be used alone, or two or more types may be used in combination. When two or more types of resins are used in combination, a multilayer film may be formed by using different types of resins in each layer. Furthermore, a single-layer film may be formed by mixing two or more types of resins, or one or more layers in a multilayer film may be formed. Furthermore, the resin film used in the transfer layer may be a stretched resin film or a non-stretched resin film.

[0043] The transfer layer may have at least one surface that has been subjected to a release treatment with a release agent such as a silicone-based release agent or a fluorine-based release agent. When the transfer layer is release-treated, it is preferable that the release-treated surface constitutes the surface on the resin layer side. The release treatment of the transfer layer makes it easier to peel it from the resin layer. However, the transfer layer does not need to be release-treated as long as it can be peeled from the resin layer.

[0044] The thickness of the transfer layer is not particularly limited, but is, for example, from 10 μm to 1000 μm, preferably from 30 μm to 700 μm, and more preferably from 50 μm to 500 μm. When the thickness of the transfer layer is within the above range, the transfer layer can be imparted with a certain level of strength and flexibility.

[0045] (Release layer) The release layer is a member that protects the resin layer from scratches and foreign matter adhesion. The release layer is preferably formed from a resin film. The resin used in the resin film for the release layer is preferably a thermoplastic resin, but may be a resin other than a thermoplastic resin. Specific examples of the resin used in the resin film for the release layer are the same as those listed as the resin used in the transfer layer. The resin used in the release layer and the resin used in the transfer layer may be the same or different.

[0046] The resin film forming the release layer may be a single-layer film consisting of one single layer, or may be a multilayer film consisting of two or more layers. Furthermore, in the resin film constituting the release layer, the resin contained in the resin film may be used alone, or two or more types may be used in combination. When two or more types of resins are used in combination, different types of resins may be used in each layer to form a multilayer film. Furthermore, a single-layer film may be formed by mixing two or more types of resins, or one or more layers in a multilayer film may be formed. Furthermore, the resin film used in the release layer may be a stretched resin film, or may be a non-stretched resin film.

[0047] The release layer may have at least one surface that has been release-treated with a release agent such as a silicone-based release agent or a fluorine-based release agent. When the release layer is release-treated, it is preferable that the release-treated surface constitutes the surface on the resin layer side. The release layer is easily released from the resin layer by being release-treated. However, the release layer does not need to be release-treated as long as it can be released from the resin layer. The thickness of the release layer is not particularly limited, but is, for example, 10 μm or more and 1000 μm or less, preferably 30 μm or more and 700 μm or less, and more preferably 50 μm or more and 500 μm or less.

[0048] (Method for manufacturing moisture-curing resin sheet) The method for manufacturing the moisture-curing resin sheet is not particularly limited, but can be manufactured by a known method. For example, a moisture-curing resin composition is prepared, and the prepared moisture-curing resin composition is applied to a transfer layer and dried as necessary to form a resin layer. The moisture-curing resin composition may contain a (meth)acrylic resin (A), but may optionally contain a compound (B), a surface conditioner, a moisture-cure accelerating catalyst, a colorant, or other components. The details and contents of each component in the moisture-curing resin composition are as described above for the resin layer. However, if the content standard is a resin layer, the solid content excluding the volatile content of the moisture-curing resin composition instead of the resin layer may be used as the content standard.

[0049] In addition, when the moisture-curable resin sheet has a release layer, the moisture-curable resin composition may be applied to the release layer and dried as necessary to form a resin layer, and a transfer layer may be further laminated to the resin layer formed on the resulting release layer to obtain a moisture-curable resin sheet. When applying the curable resin composition to the transfer layer or release layer, the curable resin composition may be appropriately diluted with a solvent or the like. Examples of the solvent include ethyl acetate, butyl acetate, and toluene. The solvent may be, for example, the solvent used when producing the (meth)acrylic resin (A).

[0050] Furthermore, when the resin layer is multilayered, it may be formed by sequentially forming and laminating each layer. For example, when a clear layer and a colored layer are present, the clear layer and the colored layer may be laminated in this order on the transfer layer. Furthermore, when the moisture-curing resin sheet has a release layer, the moisture-curing resin sheet may be obtained by laminating one or more resin layers formed on the release layer with one or more resin layers formed on the transfer layer. In the case of a multilayered resin sheet, as described above, it is preferable that each layer is made of a moisture-curing resin composition containing the above-mentioned components in the above-mentioned amounts. The formulations of each layer may be the same or different, but are usually different from each other. It is preferable that the resin layer is formed in a low-humidity environment so as not to cause curing to proceed due to moisture absorption.

[0051] [Coating method] The moisture-curable resin sheet of the present invention may be used as a coating sheet by laminating it to an adherend and then curing the resin layer to form a coating made of a cured resin layer on the surface of the adherend.

[0052] Hereinafter, one embodiment of a coating method for forming a coating on an adherend using the moisture-curing resin sheet of the present invention will be described in detail. The coating method according to one embodiment of the present invention comprises the following first and second steps. First step: A step of attaching the moisture-curing resin sheet to the adherend. Second step: A step of curing the moisture-curing resin sheet.

[0053] (First step) The first step is a step of attaching a moisture-curing resin sheet to an adherend. Before being attached to an adherend, the moisture-curing resin sheet may have a release layer laminated on the surface of the resin layer opposite to the surface on which the transfer layer is provided. When a release layer is laminated, the moisture-curing resin sheet may be attached to an adherend by peeling the release layer from the resin layer to expose the resin layer before being attached to the adherend. The method for peeling the release layer is not particularly limited, and may be peeled off using a peeling device or by hand. Of course, the release layer may be omitted from the moisture-curing resin sheet.

[0054] In this step, the moisture-curable resin sheet with the exposed resin layer may be attached to the adherend so that the resin layer is in contact with the adherend. The method of attaching the moisture-curable resin sheet to the adherend is not particularly limited, and may be performed by hand or using a laminating device. The resin layer is made of a moisture-curable resin composition and is in a pre-cured state when attached, making it easier to ensure a certain degree of flexibility. Therefore, the resin layer can be properly adhered to the adherend and temporarily fixed to the adherend with appropriate adhesive strength.

[0055] The moisture-curing resin sheet may also be attached by so-called water lamination. Water lamination can be performed by first applying water to the adherend, laminating the moisture-curing resin sheet to the water-coated surface, and then using a squeegee or the like to push out the water between the moisture-curing resin sheet and the adherend. This pushes out any bubbles or air that may be present between the moisture-curing resin sheet and the adherend along with the water, allowing the moisture-curing resin sheet to be neatly attached to the adherend. The water applied to the adherend may be water alone, or additives such as surfactants or organic solvents may be added as appropriate.

[0056] The moisture-curing resin sheet may be preformed by vacuum forming, press forming, compressed air forming, or the like, and may be shaped to have a shape corresponding to the shape of the adherend, and the shaped moisture-curing resin sheet may be attached to the adherend. When the moisture-curing resin sheet has a release layer, preforming may be performed before the release layer is peeled off from the resin layer, or after the release layer is peeled off from the resin layer. By performing preforming, even if the adherend has a complex shape, the moisture-curing resin sheet can be easily attached by adhering it to the adherend. Among the above methods, preforming is preferably performed by vacuum forming. Preforming may be performed by pressing the coated sheet against a jig or mold by vacuum forming, and shaping it into a shape corresponding to the surface shape of the adherend while stretching the moisture-curing resin sheet using the jig or mold. Here, the vacuum forming is preferably TOM forming. TOM stands for "Three Dimension Overlay Method," and applying TOM molding makes it possible to form complex shapes.

[0057] (Second Step) The second step is a step performed after the first step, in which the resin layer of the moisture-curable resin sheet is cured. In this step, the resin layer is cured to an extent that it can be used as a coating. The curing of the resin layer is not particularly limited as long as it is cured by moisture, but it is usually done by leaving it at room temperature or a temperature thereabout (e.g., 0 to 45°C, preferably 5 to 30°C) in the atmosphere or in a humidified environment (e.g., an environment of 50% RH or higher). The time left in the atmosphere or in a humidified environment is not particularly limited, but is, for example, about 1 hour to 2 weeks, but preferably about 1 day to 1 week. The moisture-curable resin sheet of the present invention can be cured simply by leaving it in the atmosphere, so the resin layer can be cured industrially without the need for large-scale equipment. Furthermore, even when the adherend is large and difficult to heat, or when the adherend has low heat resistance, the resin layer can be properly cured.

[0058] The coating method of the present invention may further include a step of peeling the transfer layer from the resin layer. The transfer layer may be peeled off using a peeling device or manually. The transfer layer may be peeled off before, after, or during the second step described above, but is preferably peeled off after the resin layer has cured to a certain extent. Therefore, it is preferable to peel off the transfer layer after leaving it in the atmosphere for a certain period of time (e.g., one hour or more, preferably one day or more). Once the resin layer has cured to a certain extent, the uncured or undercured resin layer is prevented from being exposed to the outside, thereby preventing dust and scratches from being attached to the uncured resin layer. Furthermore, peeling the transfer layer off from a resin layer that has cured to a certain extent also prevents scratches on the resin layer during peeling.

[0059] The moisture-curing resin sheet may be bonded to various adherends to form a coating. The adherend to which the moisture-curing resin sheet can be attached is not particularly limited, but includes vehicle interior materials such as automobile interior materials and interior materials for transportation equipment other than automobiles, automobile exterior materials, and vehicle exterior materials such as exterior materials for transportation equipment other than automobiles, typified by vehicle parts, exterior materials for heavy machinery, ships, aircraft, etc., exterior walls or roofing materials for houses and buildings, bridges, steel frames, plants, wind power generation blades, electrical appliances, miscellaneous goods, etc. Among these, it is preferable to use it for vehicles and vehicle parts, and in particular, it is preferable to use vehicle exterior materials such as exterior materials for transportation equipment other than automobiles as the adherend. The vehicle exterior material is preferably the exterior of the vehicle body, but may also be a hood, roof, door panel, bumper, fuel filler panel, trunk lid, rear gate, etc. When attached to a vehicle exterior material, the moisture-curing resin sheet may be attached to an exterior material attached to the vehicle body, or it may be attached to an exterior material before being attached to the vehicle body. The material of the adherend is not particularly limited, but may be any of a resin material, an inorganic material such as ceramic, and a metal material such as steel, among which metal materials such as steel are preferred. Furthermore, a base layer or the like may be appropriately formed on the surface of the adherend to which the moisture-curing resin sheet is attached.

[0060] The present invention also provides a method for manufacturing a vehicle or a vehicle part. The method for manufacturing a vehicle or a vehicle part of the present invention includes a step of painting using the moisture-curing resin sheet of the present invention. In the painting step, the vehicle or vehicle part may be painted by the method described in the painting method above.

[0061] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Measurement methods and evaluation methods in these examples are as follows.

[0062] (1) Evaluation of adhesive strength before curing A moisture-curing resin sheet was cut into a width of 1 inch (2.54 cm), and the PET film constituting the release layer was peeled off. The sheet was then attached to a coated plate (SPCC-SD urethane coated test piece, manufactured by Standard Test Piece Co., Ltd.) using a squeegee. The adhesive strength (N / inch) of the attached film was measured by a 180° peel test at 25°C and a pulling speed of 30 mm / sec.

[0063] (2) Air bubble generation After cutting the moisture-curing resin sheet film into 5 cm squares, the PET film constituting the release layer was peeled off, and the film was then attached to the same coated plate as in (1) by water lamination. The attached test piece was left in an environment of 25 ° C. and 70% RH for 5 days with the PET film constituting the transfer layer still attached, to moisture-cure the resin layer. After moisture curing, it was visually confirmed whether or not the PET film had lifted due to gas generation. A test piece in which bubbles or peeling occurred over the entire surface of the transfer layer due to gas generation was rated as "C", a test piece in which bubbles were partially generated was rated as "B", and a test piece in which there was no peeling or bubbles was rated as "A".

[0064] (3) Pencil Hardness In the same manner as in (2) above, the resin layer was adhered to a steel plate and moisture-cured, and then the PET film constituting the transfer layer was peeled off, and the pencil hardness of the exposed surface of the resin layer was measured in accordance with JIS K 5600-5-4.

[0065] (4) Cross-cut test evaluation: After bonding to a steel plate in the same manner as in (2) above and moisture-curing the resin layer, the PET film constituting the transfer layer was peeled off. A cross-cut test was carried out on the resin layer in accordance with JIS K 5600-5-6, and the evaluation was based on the following evaluation criteria. <Evaluation criteria> A: The test results were classified as 0 to 2. B: The test results were classified as 3 or higher.

[0066] (Production Example 1) A 1 L glass reaction vessel equipped with a stirrer, thermometer, and cooler was charged with 20 g of methyl methacrylate (hereinafter referred to as "MMA"), 77 g of butyl acrylate (hereinafter referred to as "BA"), 31 g of 2-isocyanatoethyl methacrylate (trade name "Karenz MOI" (manufactured by Resonac Corporation, hereinafter referred to as "MOI"), 2.0 g of 2,2'-azobis-2,4-dimethylvaleronitrile (manufactured by Wako Pure Chemical Industries, Ltd., trade name "V-65", hereinafter referred to as "V-65"), and 200 g of ethyl acetate (hereinafter referred to as "EA"), and the contents were uniformly dissolved at room temperature. While stirring the contents of the flask, the internal temperature was raised to 60°C under a nitrogen atmosphere, and solution polymerization was carried out over 6 hours to obtain a solution of acrylic resin (A-1) having an isocyanate group in the side chain (solid content 40% by mass). The weight-average molecular weight of the resulting acrylic resin (A-1) was 80,000. The monomers constituting the acrylic resin (A-1) were 20 mol% MMA, 60 mol% BA, and 20 mol% MOI. The isocyanate group content (NCO content) of the resulting acrylic resin (A-1) was 7.0 mass%.

[0067] (Production Example 2) 44 g of MMA, 56 g of BA, 18.5 g of MOI, 2.0 g of V-65, and 200 g of EA were charged into a 1 L glass reaction vessel equipped with a stirrer, thermometer, and condenser, and uniformly dissolved at room temperature. While stirring the contents of the flask, the internal temperature was raised to 60°C under a nitrogen atmosphere, and solution polymerization was carried out over 6 hours to obtain a solution of acrylic resin (A-2) having an isocyanate group in the side chain (solid content 38% by mass). The weight-average molecular weight of the obtained polymer was 70,000. The monomers constituting the acrylic resin (A-2) were 44 mol% MMA, 44 mol% BA, and 12 mol% MOI. The isocyanate group content of the obtained acrylic resin (A-2) was 4.6% by mass.

[0068] (Production Example 3) A solution of acrylic resin (A-3) (solid content 38% by mass) was obtained in the same manner as in Production Example 2, except that the amount of initiator V-65 in Production Example 2 was changed to 3.0 g. The weight-average molecular weight of the obtained polymer was 30,000. The monomers constituting the acrylic resin (A-3) were 44 mol % MMA, 44 mol % BA, and 12 mol % MOI, and the isocyanate group content of the acrylic resin (A-3) was 4.6 mol %.

[0069] (Production Example 4) A solution of acrylic resin (A-4) (solid content 38% by mass) was obtained in the same manner as in Production Example 2, except that the amount of initiator V-65 in Production Example 2 was changed to 0.5 g. The weight-average molecular weight of the obtained polymer was 250,000. The monomers constituting the acrylic resin (A-4) were 44 mol % MMA, 44 mol % BA, and 12 mol % MOI, and the isocyanate group content of the acrylic resin (A-4) was 4.6 mol %.

[0070] (Production Example 5) A solution of acrylic resin (A-5) (solid content 38% by mass) was obtained in the same manner as in Production Example 2, except that the amounts of methyl methacrylate (hereinafter referred to as "MMA"), butyl acrylate (hereinafter referred to as "BA"), and 2-isocyanatoethyl methacrylate (trade name "Karenz MOI" (manufactured by Resonac Corporation; hereinafter referred to as "MOI") in Production Example 2 were changed to 10 g, 64 g, and 64 g, respectively. The weight-average molecular weight of the obtained polymer was 50,000. The monomers constituting the acrylic resin (A-5) were 10 mol % MMA, 50 mol % BA, and 40 mol % MOI, and the isocyanate group content of the acrylic resin (A-5) was 11.9 mol %.

[0071] (Production Example 6) A solution of acrylic resin (A-6) (solid content 38% by mass) was obtained in the same manner as in Production Example 2, except that the amounts of methyl methacrylate (hereinafter referred to as "MMA"), butyl acrylate (hereinafter referred to as "BA"), and 2-isocyanatoethyl methacrylate (trade name "Karenz MOI" (manufactured by Resonac Corporation; hereinafter referred to as "MOI") in Production Example 2 were changed to 37 g, 77 g, and 4.7 g, respectively. The weight-average molecular weight of the obtained polymer was 80,000. The monomers constituting the acrylic resin (A-6) were 37 mol % MMA, 60 mol % BA, and 3 mol % MOI, and the isocyanate group content of the acrylic resin (A-6) was 0.9 mol %.

[0072] In the resin layer, the components used other than the (meth)acrylic resin were as follows: Urethane prepolymer: trade name "Takenate M-605N", manufactured by Mitsui Chemicals, Inc. Polyisocyanate (1): trade name "Desmodur N3200A", manufactured by Covestro, HDI biuret, molecular weight 479 Polyisocyanate (2): trade name "Takenate D-140N", manufactured by Mitsui Chemicals, Inc., isophorone diisocyanate adduct, molecular weight 801 Surface conditioner: trade name "BYK-378", manufactured by BYK Catalyst: moisture curing accelerator catalyst, 2,2'-dimorpholinodiethyl ether (reagent manufactured by Tokyo Chemical Industry Co., Ltd.) Pigment: "NSP-UP 841B" manufactured by Nichiko Bix Co., Ltd., effective pigment concentration = 9 mass%, solid content concentration (NV) = 24 mass%

[0073] Example 1 To the solution of (meth)acrylic resin (A-1) obtained in Production Example 1 (100 parts by mass of (meth)acrylic resin (A-1) based on solids), 0.2 parts by mass of a surface conditioner was added to prepare a solution of a moisture-curable resin composition. The obtained solution of the moisture-curable resin composition was applied to a 50 μm-thick release-treated PET film (manufactured by Nakamoto Pax Co., Ltd., product name "NS-50B") as a release layer in a dry bench (dew point -50 ° C.) with a doctor knife so that the thickness of the coating film after drying would be 50 μm. Then, the solution was heated on a hot plate at 100 ° C. for 5 minutes to dry the solvent and form a resin layer. A release-treated PET film (manufactured by Nakamoto Pax Co., Ltd., product name "NS-50C") as a transfer layer was laminated on the obtained resin layer, and then stored in a moisture-proof bag.

[0074] Examples 2 to 9, Comparative Example 1 The same procedures as in Example 1 were carried out, except that the components were blended as shown in Table 1 to prepare moisture-curable resin compositions.

[0075] *The content of each component in Table 1 is based on the solid content. *The amount of active pigment component is the value in Table 1 multiplied by 9 / 24.

[0076] In Examples 1 to 9, by using a (meth)acrylic resin having an isocyanate group as the moisture-curing resin, it was possible to suppress the generation of bubbles and form a coating with a good surface condition even when moisture-curing was performed while the transfer layer was still laminated. In contrast, in Comparative Example 1, in which a urethane resin was used as the moisture-curing resin, it was not possible to suppress the generation of bubbles when moisture-curing was performed while the transfer layer was still laminated, and a coating with a good surface condition was not obtained.

Claims

1. A moisture-curable resin sheet comprising a transfer layer and a resin layer containing a (meth)acrylic resin (A) having an isocyanate group.

2. The moisture-curable resin sheet according to claim 1, wherein the weight average molecular weight of the (meth)acrylic resin (A) is 10,000 or more and 500,000 or less.

3. The moisture-curable resin sheet according to claim 1 or 2, further containing a compound (B) having two or more isocyanate groups other than the (meth)acrylic resin (A).

4. The moisture-curable resin sheet according to claim 3, wherein the compound (B) has a molecular weight of 1000 or less.

5. The moisture-curable resin sheet according to any one of claims 1 to 4, wherein the content of the (meth)acrylic resin (A) in the resin layer is 30% by mass or more.

6. The moisture-curable resin sheet according to any one of claims 1 to 5, wherein the (meth)acrylic resin (A) has an isocyanate group in the side chain.

7. The moisture-curable resin sheet according to any one of claims 1 to 6, wherein the isocyanate group content in the (meth)acrylic resin (A) is 0.5% by mass or more and 15% by mass or less.

8. The moisture-curable resin sheet according to any one of claims 1 to 7, wherein the resin layer contains a pigment.

9. A vehicle part having a coating formed by the moisture-curable resin sheet according to any one of claims 1 to 8.

10. A vehicle having a coating formed by the moisture-curable resin sheet according to any one of claims 1 to 8.

11. A method for manufacturing a vehicle, including a step of coating using the moisture-curable resin sheet according to any one of claims 1 to 8.

12. A method for manufacturing a vehicle part, including a step of coating using the moisture-curable resin sheet according to any one of claims 1 to 8.

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