JP2007084751A - Reactive hot-melt coating composition and coated woody base material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reactive hot-melt coating composition capable of obtaining a coated woody base material with cracking resistance and hardness compatible with each other, to provide such a coated woody base material using the composition, and to provide a method for producing the woody base material. <P>SOLUTION: The reactive hot-melt coating composition comprises an epoxy acrylate oligomer component having a bisphenol A skeleton and a molecular weight of 300-2,500 and 1-10 mass%, based on the oligomer component, of a photoradical polymerization initiator but substantially contains no reactive diluent. This coating composition is solid or in the form of a solid solution at 20-50°C. The coated woody base material is such that the surface of a woody base material bears a cured layer of the above reactive hot-melt coating composition. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a reactive hot-melt coating composition and a method for producing a coated wooden substrate obtained by coating the coating composition on a plywood or a solid wooden product.

  Conventionally, the surface of base materials such as paper, plastic, glass, metal, wood, and ceramic has been coated to protect the surface by adding various functions and design features such as high hardness and stain resistance. Yes. In recent years, the demand for active energy ray-curable coatings has been expanding in response to environmental problems. Under such circumstances, in the field of building materials, there is a demand for painted building materials for various uses such as ceiling materials, wall materials, floor materials, etc., having a cured coating film of an active energy ray curable coating material, particularly an ultraviolet curable coating material. In recent years, hot carpets and floor heating facilities have been developed, and flooring materials such as flooring are exposed to a wide range of temperature differences.

  When a plywood or a solid woody substrate is exposed to a severe temperature difference, expansion and contraction occur, so that the coating film cannot withstand it and may crack. In some cases, the wooden substrate itself may crack.

  As a method for preventing this, firstly, it has been proposed to prevent expansion and contraction of the plywood base material itself by incorporating a reinforcing paper or HDF layer directly under the surface veneer, but it is expensive (for example, Patent Documents 1 and 2).

  On the other hand, attempts have been made to improve the anti-cracking performance by applying a thick UV curable paint, but it is difficult to achieve the hardness required for general flooring. It was difficult to paint with a “feel”.

  Secondly, the coating film is made by containing a flexible resin component in the ultraviolet curable paint so as to prevent the expansion or contraction of the wooden base material from the paint surface or to have flexibility sufficient to withstand the expansion and contraction. However, at the present stage, it is extremely difficult to completely prevent the expansion and contraction of wood with only an ultraviolet curable paint (see, for example, Patent Document 3). In order to make the paint containing the oligomer component an appropriate coating viscosity when applied with the current equipment, it is necessary to dilute with a low-molecular active energy ray polymerizable diluent monomer, organic solvent, etc. When diluted with a diluted monomer, the physical properties of the coating film do not show sufficient strength, and dilution with a solvent cannot be substantially employed from the viewpoint of sick house syndrome.

  Currently, in order to provide crack resistance and increase hardness, the wood substrate is reinforced, and a highly flexible coating is applied as thinly as possible. This is the current situation. However, thick coating of a high-hardness coating film is not only costly, but also has a plastic-like surface property and tends to impair the bark feel that consumers demand.

  In the building material coating industry, there was not much idea of applying high-temperature paint to wood that is vulnerable to temperature changes, and in current line painting, basically all heating, oil-based, water-based, and drying are all In general, coating at 50 ° C. or lower is generally performed because a method of obtaining a heat source from steam derived from a boiler has been adopted. Therefore, the adoption of the hot melt method requires capital investment such as a heater, and furthermore, it is difficult to produce a highly viscous paint.

Japanese Patent Laid-Open No. 11-2222995 Japanese Patent Laid-Open No. 2000-240265 JP 2000-007753 A

  SUMMARY OF THE INVENTION An object of the present invention is to solve such problems of the prior art, and a reactive hot melt coating composition for obtaining a coated wood base material having both crack resistance performance and hardness, and the coating composition Another object of the present invention is to provide a method for producing a painted wooden substrate, particularly a wooden flooring.

  As a result of diligent study, the present inventors have applied the UV-curing paint in a hot melt system so that it can be applied with the proper viscosity even if the addition of diluted monomer is reduced, and the direct application utilizing the performance of the oligomer itself. Thus, the present inventors have found that a coating film having a degree of flexibility that does not break and a hardness required for a flooring material can be realized with a low coating amount.

  The present invention first comprises an epoxy acrylate oligomer component having a bisphenol A skeleton and a molecular weight of 300 to 2500, and 1 to 10% by mass of a photoradical polymerization initiator based on the oligomer component, and a reactive diluent. There is provided a reactive hot melt coating composition characterized by being a solid or a solid solution at 20 to 50 ° C.

  Secondly, the present invention provides a reactive hot melt coating composition as described above on a plywood or solid wood substrate having a substrate temperature of 0 to 100 ° C., and a viscosity of 100 to 100,000 mPa · s at a coating temperature of 50 to 150 ° C. It is characterized by having a cured layer of a reactive hot melt coating composition on the surface of a wooden base material, which is manufactured in a manufacturing process including a step of applying under the condition of s and a step of irradiating ultraviolet rays after application. Provide a painted wooden substrate.

  Thirdly, the present invention provides the above-mentioned reactive hot melt coating composition on a plywood or a solid wood substrate having a substrate temperature of 0 to 100 ° C., a coating temperature of 50 to 150 ° C., and a coating viscosity of 100 to 100 ° C. There is provided a method for producing a coated woody substrate characterized by having a step of applying under conditions of 100,000 mPa · s and a step of irradiating ultraviolet rays after application.

  According to the present invention, there is provided a reactive hot melt coating composition for obtaining a coated wooden substrate having a bark feel that has both crack resistance performance and hardness, a coated wooden substrate using the coating composition, and a method for producing the same. Can be provided.

  The present invention relates to a reactive hot-melt coating composition, a coated wooden substrate obtained by coating the coating composition on a plywood or a solid wooden product, and a method for producing the same.

  By adopting the hot melt method, coating at an appropriate coating temperature is possible, and a smooth coating surface can be obtained without disappearance of fluidity at the moment when the coating is transferred. In particular, the use of the ultraviolet curable hot-melt coating composition of the present invention allows the polymerization to be carried out after ultraviolet irradiation, so that the temperature during coating is lower than that of conventional non-reactive hot-melt coatings. , Low-viscosity coating becomes possible. In addition, the use of a solvent is unnecessary during the cleaning operation, and the safety in terms of painting workability such as gas generation and burns during painting can be improved. Furthermore, when used as an undercoat or intermediate coat, since it has UV-curable crosslinking points, a composite coating excellent in adhesion to the UV-curable coating on the top coat can be obtained.

  Hereinafter, the composition of the present invention will be described in detail with respect to a coating composition having an oligomer component and a radical photopolymerization initiator, a coating method, and ultraviolet irradiation conditions.

  The oligomer component used in the reactive hot melt coating composition of the present invention is an epoxy acrylate oligomer component having a bisphenol A skeleton and a molecular weight of 300 to 2500, possessing at least one acryloyl group in the same molecule, It can be polymerized.

  The epoxy acrylate is a photocurable resin composition obtained by reacting bisphenol A or a modified product of bisphenol A and an epoxy resin obtained by converting polyvalent vinyl ethers to glycidyl ether with an ethylenically unsaturated monobasic acid. It is a thing.

  In general, the reactive hot melt coating composition can use any conventionally known active energy ray-polymerizable monomer in the non-volatile content. However, the reactive hot melt coating composition of the present invention uses active energy ray polymerization. It is characterized by not containing substantially any functional monomer.

  The acrylate oligomer may be used alone, or two or more of different structures such as urethane acrylate oligomer and polyether acrylate oligomer may be used in combination.

  Moreover, in order to obtain an appropriate melting temperature, crack resistance, and hardness at the time of coating, the average molecular weight of the oligomer component is about 300 to 2,500, and preferably about 400 to 900.

  The photo radical polymerization initiator used in the reactive hot melt coating composition of the present invention is a compound that generates radicals upon irradiation with ultraviolet light, and examples thereof include a hydrogen abstraction type polymerization initiator and a photocleavable type. Examples of the hydrogen abstraction type polymerization initiator include conventionally known benzophenone, acetophenone, diethoxyacetophenone, benzyl, benzoylbenzoic acid, Michler's ketone, 2-chlorothioxanthone, 2,4-diethylthioxanthone and the like.

  Examples of the photocleavable radical polymerization initiator include benzoin ethyl ether, benzyl dimethyl ketal, hydroxycyclohexyl phenyl ketone, and 2-hydroxy-2-methylphenyl ketone. Among these hydrogen abstraction type and photocleavage type polymerization initiators, one or a combination of two or more types can be used.

  The blending ratio of the polymerization initiator in the coating composition containing the ultraviolet curable polymerizable oligomer component and the photopolymerization initiator is 1 to 10 parts by mass with respect to 100 parts by mass of the oligomer component.

  In addition, these polymerization initiators can be used in combination with known and commonly used photosensitizers. When using together, it is preferable that it is 1-15 mass parts with respect to 100 mass parts of oligomer components.

  The reactive hot melt coating composition of the present invention is further provided with various functions within a range not departing from the object of the present invention, if necessary, in order to impart colorants, extenders, lubricants, plasticizers, antifoaming agents. Additives such as antioxidants, coupling agents, organic solvents and chelating agents can be added.

  The method for producing the reactive hot melt coating composition of the present invention is not particularly limited, and any method may be adopted as long as a predetermined amount of each component to be blended can be uniformly kneaded. It must be produced under moderate heating conditions that allow the components to melt. In addition, kneading of each component during production may be performed in the absence of a solvent, and for example, it may be performed in an inert solvent such as an aromatic hydrocarbon, an acetate ester, or a ketone, but is performed in an inert solvent. In some cases, after kneading, it is necessary to remove the inert solvent by reducing pressure and / or heating. Specifically, each component is kneaded using one or more of a double helical ribbon bath or gate bath, a butterfly mixer, a planetary mixer, a three roll, a kneader-louder kneader, an extruder kneader extruder, etc. However, the apparatus for kneading each component is not limited to these.

  Moreover, it is preferable that the viscosity in 50-150 degreeC of the reactive hot melt coating composition of this invention containing the said component is 100-100,000 mPa * s. More preferably, the viscosity at 80 ° C. is 500 to 5000 mPa · s.

  As the wood base material used for the painted wood base material of the present invention, a plywood base material such as a normal plywood just laminated with a southern sea material such as lauan, a reinforced plywood impregnated with phenol resin, etc., or a solid wood base material Is used. Not only hard materials such as lauan, but also relatively soft materials such as softwood plywood can be used for various flooring materials by having the cured coating layer of the reactive hot melt coating composition of the present invention. Sex spreads.

  The present invention relates to a painted wooden substrate having a cured coating layer of a reactive hot melt coating composition on a plywood or a solid wooden substrate. In the coated wood base material of the present invention, the cured coating layer of the reactive hot melt coating composition is an undercoat layer directly applied to the wood base material through an undercoat layer, a sealer layer, a colored layer, etc. Any layer such as an intermediate coating layer applied to the undercoat layer and an overcoat layer as the outermost layer may be used.

  In order to obtain crack resistance performance and hardness more effectively, the hot melt layer is preferably an undercoat layer. The undercoat layer is a coating layer for the purpose of mainly bringing the substrate and the coating film into close contact with each other, and is a layer applied directly to the substrate immediately after the coloring and drying steps. Immediately after the coloring and drying steps, the substrate temperature is improved by the drying step, which is particularly preferable as the step of applying the hot melt paint.

  Further, it is more preferable that an intermediate coating layer and an overcoating layer are present on the structure as the undercoating layer. By obtaining the intermediate coating layer and the top coating layer on the cured coating film obtained from the reactive hot melt coating composition, it becomes easy to obtain better surface properties and gloss as a wood product.

  The coloring of the substrate is not particularly limited and may be a conventionally known method. For example, it is applied by applying with a sponge reverse coater or wet coat method of natural coater. Moreover, a sealer (disposal coating) process or a base polishing process may be performed in advance before coloring. Further, it is particularly preferable that there is a drying step after the coloring so that the solvent and water used in the colorant can be sufficiently dried. In addition, as a paint used for coloring, any conventionally known oily or aqueous paint may be used, but an aqueous pigment dispersion is preferably used from the viewpoint of VOC.

  There may be another step between the hot-melt layer coating step and the topcoat layer coating step. For example, a sponge reverse coater or a natural coater may be used to paint the groove. Moreover, conventionally well-known thing can be used as a coating material used at these processes.

  The top coat may be applied by a conventionally known method, and a natural coater, a flow coater, a spray, or the like can be used. In order to perform painting that makes use of the wood texture, it is preferable to paint with a natural coater. Conventionally known paints can be used in these steps, but it is preferable to use an active energy ray-curable paint because of the VOC problem and the use of existing equipment.

  The coating thickness of the hot melt layer is preferably about 10 μm to 100 μm, and the top coat applied with a natural coater is preferably about 0.1 μm to 20 μm, but is not particularly limited in the present invention.

  Moreover, in the manufacturing method of the coated wooden base material of this invention, the base-material temperature at the time of coating is 0-100 degreeC. Below 0 ° C, it is difficult to obtain surface leveling after coating of the coated reactive hot-melt coating composition, and if the temperature exceeds 100 ° C, the wood substrate itself may be deteriorated, such as generation of burns. There is. From the leveling properties of the surface after coating and the stability of the wood substrate itself, the substrate temperature during coating is more preferably 40 to 90 ° C.

  In the method for producing a coated wood base material of the present invention, a conventionally known method can be applied as a coating method of the reactive hot melt coating composition, and among them, typical examples include roll coating and gravure coating. , Bar coat, flow coat and the like. Among these coating methods, when line coating is performed, coating by a natural roll coater or a natural reverse coater is preferable. Conventionally known rolls such as rubber rolls and metal rolls can be used for these coaters, but it is particularly preferable to use a metal roll equipped with warm water heating equipment in order to keep the coating temperature at a high temperature.

  As for the coating amount at the time of coating by the above-mentioned coating system, 10 micrometers-100 micrometers are preferable as a cured coating film, and 20 micrometers-60 micrometers are more preferable.

  In the method for producing a painted wooden base material of the present invention, the active energy rays used in the irradiation step are ionizing radiation, electromagnetic waves, etc., such as ultraviolet rays, electron beams, and γ rays. The line is preferably ultraviolet. When irradiating with ultraviolet rays, a known ultraviolet irradiating device including a high pressure mercury lamp, an excimer lamp, a metal halide lamp, or the like can be used.

  Hereinafter, the present invention will be described specifically by way of examples. The epoxy acrylate oligomer was prepared by a known and usual synthesis method. As the undercoat paint, each paint composition having the composition shown in Table 1 was prepared. Each coating composition was prepared by heating the oligomer component at 100 ° C., adding a monofunctional acrylate monomer and a photoradical polymerization initiator, stirring, and mixing. ACMO (manufactured by Kojin Co., Ltd.) was specified as the monofunctional acrylate monomer.

Each component in Table 1 is as follows.
Oligomer A: bisphenol A type epoxy acrylate, average molecular weight 430.
Oligomer B: Caprolactone-modified bisphenol A type epoxy acrylate, average molecular weight 900.
Oligomer C: bisphenol A dimer epoxy acrylate, average molecular weight 650.
Oligomer D: Aliphatic epoxy acrylate (Laromer LR8765, manufactured by BASF).
Radical polymerization initiator: Darocur 1173 (manufactured by Ciba Specialty Chemicals).

These coating compositions were applied to a plywood (Lawan plywood with oak veneer) that had been ground and sealed, so that the coating amount was 50 g / m ² at a material temperature of 60 ° C. and a coating temperature of 80 ° C. did. Each ultraviolet irradiation was cured at a room temperature of 25 ° C. with an ultraviolet irradiation amount of 100 mJ / cm ² . The obtained cured film was polished with a # 240 water-resistant abrasive paper, and each of the following top coats was applied.

  As the top coating, 50 parts of Unidic V-5508 (Dainippon Ink and Chemicals: Epoxy Acrylate) is used as the acrylate oligomer component, and trimethylolpropane diacrylate (Toagosei: Aronix M-220) is used as the bifunctional acrylate monomer. 20 parts as photopolymerization initiator, 5 parts Irgacure 184 (Ciba Specialty Chemicals), 1 part benzophenone, 15 parts Minex # 7 (Calcium Shiraishi) as a matting agent, Syloid E-50 (Grace Japan) 3 parts and 15 parts of MICRON WHITE 5000A (Hayashi Kasei) were mixed and stirred and mixed to obtain a paint.

The above-described top coating was applied so that the coating amount was 10 g / m ² at a material temperature of 40 ° C. and a coating temperature of 40 ° C. Each ultraviolet irradiation was cured at a room temperature of 25 ° C. with an ultraviolet irradiation amount of 160 mJ / cm ² . Both the JAS cold test and the JIS scratch hardness test (pencil method) were performed on the obtained cured film. The JAS cold test evaluated the superiority or inferiority of the performance by repeating a plurality of cycles for the same substrate.

(Crack resistance evaluation)
◎: No crack ○: Several cracks of 1cm or less △: 1-5 cracks of 1cm or more × Multiple cracks of 1cm or more

  The scratch hardness test was evaluated based on the upper limit of hardness at which plastic deformation (push) does not occur in the coating film when the cured coating film was scratched with a pencil. For example, in Example 1, it means that plastic deformation did not occur until hardness 2H, and plastic deformation occurred at hardness 3H. The evaluation results are shown in Table 2.

According to the present invention, there is provided a reactive hot melt coating composition for obtaining a coated wooden substrate having a bark feel that has both crack resistance performance and hardness, a coated wooden substrate using the coating composition, and a method for producing the same. Can be provided. As a result, the degree of freedom of use of the wooden base material is increased, and for example, it is suggested that wood that is relatively soft and unsuitable for a conventional floor board, such as domestic conifers, may be used for the floor board.

Claims (7)

An epoxy acrylate oligomer component having a bisphenol A skeleton having a molecular weight of 300 to 2500 and a radical photopolymerization initiator of 1 to 10% by mass with respect to the oligomer component, and substantially free of a reactive diluent; A reactive hot melt coating composition characterized by being a solid or a solid solution at 20 to 50 ° C. The reactive hot melt coating composition according to claim 1 is applied to a plywood or a solid wood substrate having a substrate temperature of 0 to 100 ° C at a coating temperature of 50 to 150 ° C, and the viscosity of the coating is 100 to 100, A coated woody material having at least one cured layer of a reactive hot-melt coating composition produced by a production process comprising a step of coating under the condition of 000 mPa · s and a step of irradiating ultraviolet rays after coating. Base material. The coated wooden substrate according to claim 2, wherein the cured layer of the reactive hot melt coating composition is an undercoat layer. The cured layer of the reactive hot melt coating composition described above is an undercoat layer, and the topcoat layer is one or more oligomer components selected from urethane acrylate oligomers, epoxy acrylate oligomers and polyether acrylate oligomers, and the oligomer components The coated wooden substrate according to claim 3, which is a cured layer of a coating composition containing 1 to 10% by mass of a radical photopolymerization initiator relative to. The coated woody base material according to any one of claims 2 to 4, wherein cracks do not occur in a cold and hot repeated B test defined in the Japanese Agricultural Standard (JAS) plywood standard. Coated wood according to any one of claims 2 to 5, wherein the hardness of the pencil that does not cause plastic deformation is F or higher in a scratch hardness test (pencil method) (K-5600, 5-4) according to Japanese Industrial Standards. Base material. The reactive hot melt coating composition according to claim 1 is applied to a plywood or a solid wood base material having a base material temperature of 0 to 100 ° C., and a paint viscosity of 100 to 100,000 mPa at the coating temperature of 50 to 150 ° C. -The manufacturing method of the coated wooden base material characterized by having the process of apply | coating on condition of s, and the process of irradiating an ultraviolet-ray after application | coating.