JP3829837B2

JP3829837B2 - Wood surface treatment

Info

Publication number: JP3829837B2
Application number: JP2003341106A
Authority: JP
Inventors: 敏鈴木; 渡辺　　孝; 修史森上; 久芳大隅
Original assignee: Yamaha Corp
Current assignee: Yamaha Corp
Priority date: 2003-01-28
Filing date: 2003-09-30
Publication date: 2006-10-04
Anticipated expiration: 2023-09-30
Also published as: JP2004249712A

Description

本発明は、木材の表面処理法に関する。 The present invention relates to a method for surface treatment of wood.

木材の表面を保護し、木材本来の自然な色調を維持するために、木材表面に透明塗料等の塗装を施すことが行われている。
しかし、この透明塗料もまた、時間がたつにつれて徐々に変色が進み、木材出荷時の塗色を維持することができないという問題がある。
この変色対策として、黄変がフェノール系抗酸化剤がキノンに変化することに起因するとの観点からフォスファイト系抗酸化剤を含有する塗料組成物の提案がある（例えば、特許文献１参照。）。また、塗料中に含まれる微量の金属イオンと紫外線吸収剤、フェノール系抗酸化剤との作用により黄変が生じるとの観点から金属不活性化剤を含有する塗料組成物の提案もある（例えば、特許文献２参照。）。更に、抗菌剤としてピリチオン塩を含む塗料は、自然光の成分である紫外線でピリチオン塩が分解して変色するとの観点から亜鉛化合物を含有する塗料の提案（例えば、特許文献３参照。）もある。また、３ウエット塗装システムで、水性ベース塗料、水性中塗り塗料として、揮発性の塩基性物質を含まない顔料分散剤を用いた顔料ペーストを配合したものを用いる提案もある（例えば、特許文献４参照。）。
特開平７−１１８５６８号公報特開平１０−２８９２４号公報特表２００１−５１３１２３号公報特開２００２−１２６６２７号公報 In order to protect the surface of the wood and maintain the original natural color tone of the wood, the wood surface is coated with a transparent paint or the like.
However, this transparent paint also has a problem that discoloration gradually progresses over time, and the paint color at the time of shipment of wood cannot be maintained.
As a measure against this discoloration, there is a proposal of a coating composition containing a phosphite antioxidant from the viewpoint that yellowing is caused by the change of the phenolic antioxidant to quinone (see, for example, Patent Document 1). . There is also a proposal of a coating composition containing a metal deactivator from the viewpoint that yellowing occurs due to the action of a trace amount of metal ions contained in the coating, an ultraviolet absorber, and a phenolic antioxidant (for example, , See Patent Document 2). Furthermore, a paint containing a pyrithione salt as an antibacterial agent has been proposed as a paint containing a zinc compound from the viewpoint that the pyrithione salt is decomposed and discolored by ultraviolet rays which are components of natural light (see, for example, Patent Document 3). There is also a proposal to use a three-wet coating system in which a pigment paste using a pigment dispersant that does not contain a volatile basic substance is blended as an aqueous base coating or an aqueous intermediate coating (for example, Patent Document 4). reference.).
JP-A-7-118568 Japanese Patent Laid-Open No. 10-28924 JP-T-2001-513123 JP 2002-126627 A

これらは、特定の要因による黄変を防止しようとするものであるが、塗料の変色は種々様々な要因によって生じる。特許文献１〜４に記載の提案では、それぞれ、特定の要因による変色を防止できたとしても、その他の要因による変色は防止できず、充分に変色を防止するのは困難である。
従って、出荷後は上記特定の要因以外の因子による変色が進むため、最終的な変色後の色を想定した出荷時の塗色管理が難しいという問題がある。 These are intended to prevent yellowing due to specific factors, but the discoloration of the paint is caused by various factors. In the proposals described in Patent Documents 1 to 4, even if the discoloration due to specific factors can be prevented, discoloration due to other factors cannot be prevented, and it is difficult to sufficiently prevent discoloration.
Therefore, since the color change due to factors other than the specific factors proceeds after shipment, there is a problem that it is difficult to manage the paint color at the time of shipment assuming the final color after the change.

本発明者等は、このような状況に鑑み、むしろ短時間で積極的に塗料の変色・硬化を進め、出荷時の塗色を最終的な変色後の塗色に近づけることにより、出荷後の変色が少なく、出荷時の塗色管理が容易になることを見出し、本発明に至った。
即ち、本発明は、酸硬化型アミノアルキッド樹脂塗料、酸硬化型フェノール樹脂塗料、ポリウレタン樹脂塗料のうちのいずれかの塗料を木材表面に塗布した後、前記塗料の変色を促進するために紫外線を照射することを特徴とする木材の表面処理法に関する。 In view of such a situation, the inventors of the present invention actively proceeded with discoloration / curing of the paint in a short time, and brought the paint color at the time of shipment closer to the paint color after the final discoloration. The present inventors have found that there is little discoloration and that it is easy to manage paint colors at the time of shipment.
That is, the present invention is an acid-curable amino alkyd resin paint, acid-hardening type phenol resin paint, after any of the coating of the polyurethane resin coating was applied to the wood surface, the ultraviolet light to promote discoloration of the paint The present invention relates to a surface treatment method for wood characterized by irradiation.

本発明の表面処理法によれば、出荷時の塗色を最終的な変色後の塗色に近づけることにより、出荷後の変色が少なく、出荷時の塗色管理が容易となる。 According to the surface treatment method of the present invention, by bringing the coating color at the time of shipment close to the final color after the color change, there is little discoloration after the shipment and the coating color management at the time of shipment becomes easy.

本発明において用いる塗料は酸硬化型アミノアルキッド樹脂塗料、酸硬化型フェノール樹脂塗料、ポリウレタン樹脂塗料であり、これらの塗料は紫外線照射時に発生する熱により塗料が硬化すると共に、黄変や褐変など変色を起こす。
酸硬化型アミノアルキッド樹脂塗料、酸硬化型フェノール樹脂塗料としては、熱硬化型塗料に用いられる酸硬化型アミノアルキッド樹脂塗料、酸硬化型フェノール樹脂塗料であればいずれも用いることができる。 The paints used in the present invention are acid curable amino alkyd resin paints, acid curable phenol resin paints, polyurethane resin paints, and these paints are cured by heat generated during UV irradiation, and are also discolored such as yellowing and browning. Wake up.
As the acid curable amino alkyd resin paint and the acid curable phenol resin paint, any acid curable amino alkyd resin paint and acid curable phenol resin paint used for thermosetting paints can be used.

ポリウレタン樹脂塗料としては、油変性型ウレタン樹脂、二液型ウレタン樹脂、光変色するトリレンジイソシアネート（ＴＤＩ）、キシリレンジイソシアネート（ＸＤＩ）系のイソシアネート硬化剤を用いるポリウレタン樹脂を用いた塗料等を挙げることができる。 Examples of polyurethane resin paints include oil-modified urethane resins, two-component urethane resins, paints using polyurethane resins using photo-discolored tolylene diisocyanate (TDI), xylylene diisocyanate (XDI) -based isocyanate curing agents, and the like. be able to.

本発明で用いる塗料には、ブロッキング防止剤、光安定剤、ベンゾイン、帯電防止剤あるいは酸化防止剤などのような、公知慣用の種々の塗料用添加剤類あるいは染料等を、必要に応じて加えて使用することが出来る。また、必要に応じて、顔料等を加えることもできる。 Various known paint additives or dyes such as antiblocking agents, light stabilizers, benzoin, antistatic agents or antioxidants are added to the coating materials used in the present invention as necessary. Can be used. Moreover, a pigment etc. can also be added as needed.

本発明で用いる塗料は、通常、有機溶剤に溶解した溶剤型塗料が用いられる。
塗料がウレタン樹脂の場合は、溶剤としては、エチルアセテート、ブチルアセテート、メチルグリコールアセテート、エチルグリコールアセテート等のエステル類；メチルエチルケトン、メチルイソブチルケトン、シクロヘキサノン等のケトン類、トルエン、キシレン等の芳香族炭化水素を挙げることができる。
塗料がフェノール樹脂の場合は、溶剤としては、メタノール、エタノール等のアルコール類、エチルエーテル等のエーテル類、トルエン、水等を挙げることができる。
塗装方法としては、特に制限はなく、カレンダ塗装、カーテン塗装、ロール塗装、ナイフ塗装、スプレー塗装、刷毛塗り塗装法などで塗装できる。 As the paint used in the present invention, a solvent-type paint dissolved in an organic solvent is usually used.
When the paint is a urethane resin, the solvent includes esters such as ethyl acetate, butyl acetate, methyl glycol acetate, and ethyl glycol acetate; ketones such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; and aromatic carbonization such as toluene and xylene. Mention may be made of hydrogen.
When the paint is a phenol resin, examples of the solvent include alcohols such as methanol and ethanol, ethers such as ethyl ether, toluene, and water.
The coating method is not particularly limited, and can be applied by calendar coating, curtain coating, roll coating, knife coating, spray coating, brush coating method, or the like.

塗料の塗布量は固形分で５〜１００ｇ／ｍ^２であることが好ましく、５〜３０ｇ／ｍ^２であることがより好ましい。塗布量を５ｇ／ｍ^２以上とすることで、紫外線照射により、塗料の変色量が良好となる。１００ｇ／ｍ^２を超えてもそれ以上の効果はなく、その後の研削に手間がかかるため、１００ｇ／ｍ^２以下、より好ましくは３０ｇ／ｍ^２以下であることが好ましい。 The coating amount of the coating is preferably from 5 to 100 g / ^{m 2} by solid content, and more preferably 5 to 30 g / ^{m 2.} By setting the coating amount to 5 g / m ² or more, the amount of discoloration of the paint is improved by ultraviolet irradiation. Even if it exceeds 100 g / m ² , there is no further effect, and the subsequent grinding takes time. Therefore, it is preferably 100 g / m ² or less, more preferably 30 g / m ² or less.

木材に塗料塗布後は、すぐに紫外線照射してもよいが、３０分〜２時間程度、室温に放置する、いわゆるセッティングを行うことが好ましい。このセッティングを行うと、硬化反応に関係ない溶剤が飛散し、硬化反応が速やかに進む。また、硬化塗膜中に残存する溶剤が少なくなるため、充分な塗膜物性が得られるようになる。 After applying the paint to the wood, it may be irradiated with ultraviolet rays immediately, but it is preferable to perform so-called setting in which it is left at room temperature for about 30 minutes to 2 hours. When this setting is performed, the solvent unrelated to the curing reaction is scattered and the curing reaction proceeds promptly. Further, since the solvent remaining in the cured coating film is reduced, sufficient coating film properties can be obtained.

紫外線照射に用いる紫外線発生源としては、水銀ランプ、高圧水銀ランプ、メタルハライドランプ、水銀キセノンランプ、ブラックライト等を挙げることができる。
塗料を塗布した木材への紫外線照射量は、５００〜３０００ｍＪ／ｃｍ^２であることが好ましい。３０００ｍＪ／ｃｍ^２を超える量照射してもそれ以上効果は上がらない。 Examples of ultraviolet ray generation sources used for ultraviolet irradiation include a mercury lamp, a high-pressure mercury lamp, a metal halide lamp, a mercury xenon lamp, and a black light.
It is preferable that the ultraviolet irradiation amount to the wood which applied the coating material is 500-3000 mJ / cm < ² >. Irradiation in an amount exceeding 3000 mJ / cm ² does not increase the effect any further.

本発明においては、木材に上述の塗料を塗布、紫外線照射により塗料を硬化・変色させた後、塗装面全体の表面塗料層を研削、同種の塗料塗布、紫外線照射による塗料層の硬化・変色の操作を１回以上行うことがより好ましい。
この研削にあたっては、表面に付着した埃等を除去し、塗膜表面が平滑になるように研削するものである。
研削は、例えば、研磨布やサンドペーパーを用いて行うことができる。研磨布やサンドペーパーの砥粒の粒度は、１〜３μｍであることが好ましい。
塗料塗布、紫外線照射を複数回行う場合は、上記の塗布量、紫外線照射量は１回あたりの塗布量、紫外線照射量である。
この塗料の塗布、紫外線照射による硬化・変色の操作は５回以上繰り返して行っても到達変色度はさほど変わらず、手間が煩雑になるだけであるので、４回以下であることが好ましく、３回以下であることがより好ましい。 In the present invention, the above-mentioned paint is applied to wood, the paint is cured and discolored by ultraviolet irradiation, the surface paint layer of the entire painted surface is ground, the same kind of paint is applied, and the paint layer is cured and discolored by ultraviolet irradiation. It is more preferable to perform the operation once or more.
In this grinding, dust or the like adhering to the surface is removed and grinding is performed so that the coating film surface becomes smooth.
The grinding can be performed using, for example, an abrasive cloth or sandpaper. The particle size of the abrasive grains of the polishing cloth or sandpaper is preferably 1 to 3 μm.
When the coating application and the ultraviolet irradiation are performed a plurality of times, the coating amount and the ultraviolet irradiation amount are the coating amount and the ultraviolet irradiation amount per one time.
Even if this coating application and curing / discoloration operation by ultraviolet irradiation are repeated 5 times or more, the reached discoloration degree does not change so much and only the labor is complicated. Therefore, it is preferably 4 times or less. More preferably, the number of times is less than the number of times.

本発明の表面処理法の対象となる木材は、その種類を問わず適用可能であり、木材の構成としても、合板、集成材、繊維板、積層板等のボード類のいずれも対象とすることができる。 The wood to be subjected to the surface treatment method of the present invention can be applied regardless of the type, and the structure of the wood should be any of boards such as plywood, laminated wood, fiberboard, and laminated board. Can do.

以下に、実施例を用いて、本発明をさらに詳しく説明する。
＜実施例１＞
メープル（Maple）素材及びバーチ（Birch）素材からなるドラム用胴に酸硬化タイプのフェノール系塗料を固形分で１０ｇ／ｍ^２となるようにワイピング塗布した。
塗布後、そのまま室温に６０分放置（セッティング）した後、約５分間紫外線を照射した。この時の紫外線光量は約２０００ｍＪ／ｃｍ^２であった。
紫外線照射後の胴の表面をＰ１０００サンドペーパーで研削して塗料層を研削した。
研削した胴に上記のフェノール系塗料の塗布・セッティング、紫外線照射を行い、さらに研削・塗料塗布・セッティング・紫外線照射を行った。
得られた胴表面の色を分光測色機（商品名：データカラーマイクロフラッシュ、データカラーインターナショナル社製）により測定した。これを２２℃、６０％ＲＨに調湿された室内に２８日間放置し、７日後、１４日後、２１日後、２８日後に上記と同様にして胴の色を測定し、塗布後の色との差（ΔＥ）を求めた。その結果を表１に示す。
なお、２８日放置後の胴を目視観察したところ、胴には、変形もひびも全く認められなかった。 Hereinafter, the present invention will be described in more detail with reference to examples.
<Example 1>
An acid-curing type phenolic paint was applied by wiping to a drum body made of Maple material and Birch material so as to have a solid content of 10 g / m ² .
After coating, the mixture was allowed to stand at room temperature for 60 minutes (setting), and then irradiated with ultraviolet rays for about 5 minutes. The amount of ultraviolet light at this time was about 2000 mJ / cm ² .
The surface of the cylinder after UV irradiation was ground with P1000 sandpaper to grind the paint layer.
The above-mentioned phenolic paint was applied to the ground cylinder, setting and UV irradiation were performed, and further, grinding, coating application, setting and UV irradiation were performed.
The color of the obtained cylinder surface was measured with a spectrocolorimeter (trade name: Data Color Micro Flash, manufactured by Data Color International). This was left in a room conditioned at 22 ° C. and 60% RH for 28 days, and after 7 days, 14 days, 21 days, and 28 days, the color of the cylinder was measured in the same manner as above, The difference (ΔE) was determined. The results are shown in Table 1.
In addition, when the cylinder after being left for 28 days was visually observed, neither deformation nor crack was observed in the cylinder.

＜実施例２＞
１回あたりの紫外線照射時間を約３．５分（紫外線光量：約１５００ｍＪ／ｃｍ^２）とした以外は実施例と同様にした。その結果を実施例１の結果と共に表１に示す。
なお、２８日放置後の胴を目視観察したところ、胴には、変形もひびも全く認められなかった。 <Example 2>
The same procedure as in the example was performed except that the time of ultraviolet irradiation per one time was about 3.5 minutes (ultraviolet light amount: about 1500 mJ / cm ² ). The results are shown in Table 1 together with the results of Example 1.
In addition, when the cylinder after being left for 28 days was visually observed, neither deformation nor crack was observed in the cylinder.

＜実施例３＞
１回あたりの紫外線照射時間を約１．５分（紫外線光量：約５００ｍＪ／ｃｍ^２）とした以外は実施例と同様にした。その結果を実施例１の結果と共に表１に示す。
なお、２８日放置後の胴を目視観察したところ、胴には、変形もひびも全く認められなかった。 <Example 3>
The same procedure as in the Example was performed except that the time of ultraviolet irradiation per one time was about 1.5 minutes (the amount of ultraviolet light: about 500 mJ / cm ² ). The results are shown in Table 1 together with the results of Example 1.
In addition, when the cylinder after being left for 28 days was visually observed, neither deformation nor crack was observed in the cylinder.

＜実施例４＞
１回あたりの紫外線照射量を約３０００ｍＪ／ｃｍ^２とした以外は実施例１と同様にして塗装・セッティング・紫外線照射・研削を繰り返した塗装済み胴を得、これを２８日間放置して、塗装直後の色と２８日後の色の差を求めた。その結果を表１に示す。 <Example 4>
Except that the amount of UV irradiation per one time was about 3000 mJ / cm ² , a coated cylinder was obtained by repeating painting, setting, UV irradiation and grinding in the same manner as in Example 1, and this was left for 28 days to be painted. The difference between the color immediately after and the color after 28 days was determined. The results are shown in Table 1.

＜実施例５＞
実施例１で用いたと同様のメープル（Maple）素材及びバーチ（Birch）素材からなる胴に実施例１で用いたと同様の酸硬化タイプのフェノール系塗料を固形分で１０ｇ／ｍ^２となるようにワイピング塗布した。
塗布後、そのまま室温に６０分放置（セッティング）した後、約５分間紫外線を照射した。この時の紫外線光量は約２０００ｍＪ／ｃｍ^２であった。
この胴につき、実施例１と同様にして胴表面の色の測定、２８日間の放置、７日後、１４日後、２１日後、２８日後の胴の色の測定を行い、塗布後の色との差（ΔＥ）を求めた。その結果を表１に示す。 <Example 5>
The same acid-cured phenolic paint as used in Example 1 is applied to a cylinder made of the same Maple material and Birch material as used in Example 1 so that the solid content is 10 g / m ^2. Wiping was applied.
After coating, the mixture was allowed to stand at room temperature for 60 minutes (setting), and then irradiated with ultraviolet rays for about 5 minutes. The amount of ultraviolet light at this time was about 2000 mJ / cm ² .
With respect to this cylinder, the color of the cylinder surface was measured in the same manner as in Example 1 and left for 28 days. After 7 days, 14 days, 21 days, and 28 days, the cylinder color was measured, and the difference from the color after coating. (ΔE) was determined. The results are shown in Table 1.

＜実施例６＞
１回あたりの紫外線照射時間を約１．２分（紫外線光量：約４５０ｍＪ／ｃｍ^２）とし、塗料塗布、セッティング、紫外線照射、研削、塗料塗布、セッティング、紫外線照射の処理を行った以外は実施例と同様にした。その結果を実施例１の結果と共に表１に示す。
なお、２８日放置後の胴を目視観察したところ、胴には、変形もひびも全く認められなかった。 <Example 6>
The duration of each UV irradiation was about 1.2 minutes (UV light amount: about 450 mJ / cm ² ), except that coating, setting, UV irradiation, grinding, coating, setting, and UV irradiation were performed. Same as example. The results are shown in Table 1 together with the results of Example 1.
In addition, when the cylinder after being left for 28 days was visually observed, neither deformation nor crack was observed in the cylinder.

＜比較例１＞
実施例１で用いたと同様のメープル（Maple）素材及びバーチ（Birch）素材からなる胴に実施例１で用いたと同様の酸硬化タイプのフェノール系塗料を固形分で１０ｇ／ｍ^２となるようにワイピング塗布した。
次いで、塗料を塗布した胴を熱気乾燥室に入れ、４０℃で１６時間強制乾燥した。この乾燥済みの胴の表面を実施例１と同様にして、Ｐ１０００サンドペーパーで研削して塗料層を研削した。この胴につき、上記のフェノール系塗料の塗布・４０℃、１６時間の強制乾燥を行い、さらに研削・塗料塗布・強制乾燥を行った。
この胴につき、実施例１と同様にして胴表面の色の測定、２８日間の放置、７日後、１４日後、２１日後、２８日後の胴の色の測定を行い、塗布後の色との差（ΔＥ）を求めた。その結果を表１に示す。
なお、２８日放置後の胴を目視観察したところ、胴には、若干の変形が見られ、ひびが入ったものもあった。 <Comparative Example 1>
The acid-curing phenolic paint similar to that used in Example 1 is applied to a cylinder made of the same Maple material and Birch material as used in Example 1 so that the solid content is 10 g / m ^2. Wiping was applied.
Next, the cylinder to which the paint was applied was placed in a hot air drying chamber and forcedly dried at 40 ° C. for 16 hours. The surface of this dried cylinder was ground with P1000 sandpaper in the same manner as in Example 1 to grind the paint layer. This cylinder was coated with the above-described phenolic paint and forcedly dried at 40 ° C. for 16 hours, and further subjected to grinding, paint coating, and forced drying.
With respect to this cylinder, the color of the cylinder surface was measured in the same manner as in Example 1 and left for 28 days. After 7 days, 14 days, 21 days, and 28 days, the cylinder color was measured, and the difference from the color after coating. (ΔE) was determined. The results are shown in Table 1.
In addition, when the cylinder after being left for 28 days was visually observed, the cylinder was slightly deformed and some cracked.

＜比較例２＞
実施例１で用いたと同様のメープル（Maple）素材及びバーチ（Birch）素材からなる胴に実施例１で用いたと同様の酸硬化タイプのフェノール系塗料を固形分で１０ｇ／ｍ^２となるようにワイピング塗布した。
次いで、塗料を塗布した胴を室温（約２０℃）に一夜放置した後、胴の表面を実施例１と同様にして、Ｐ１０００サンドペーパーで研削して塗料層を研削した。この胴につき、上記のフェノール系塗料の塗布・一夜放置を行い、さらに研削・塗料塗布・一夜放置を行った。 <Comparative example 2>
The same acid-cured phenolic paint as used in Example 1 is applied to a cylinder made of the same Maple material and Birch material as used in Example 1 so that the solid content is 10 g / m ^2. Wiping was applied.
Next, after the cylinder to which the paint was applied was left overnight at room temperature (about 20 ° C.), the surface of the cylinder was ground with P1000 sandpaper in the same manner as in Example 1 to grind the paint layer. The above-mentioned phenolic paint was applied to the cylinder and allowed to stand overnight, and further subjected to grinding, paint application, and left overnight.

表１の判定欄の判定基準は以下の通りである。
ΔＥ
◎：４以下
○：４を超え、５以下
△：５を超え、６以下
×：６を超えた The judgment criteria in the judgment column of Table 1 are as follows.
ΔE
◎: 4 or less ○: More than 4 or less than 5 △: More than 5 or less than 6 ×: More than 6

比較例１から、強制乾燥したものは変形や割れが生じやすく、また、表１に見られるように、放置による変色が大きいことがわかる。また、比較例２から、実施例で使用したと同様の塗料を塗布しても、一夜放置だけで紫外線照射していないものでは、放置による変色が大きいことがわかる。
これに対して、塗料を塗布して、紫外線照射・研磨を行ったものはいずれも、２８日間放置しても、塗料塗布直後に比べての変色の度合いが小さいことが分かる。これは、塗料の変色が上記処理により最終段階の近くまで進んだため、その後の変色が少なくなっていることを意味する。
なお、紫外線照射量を適度の範囲にすると、その後の変色をより小さくすることができることがわかる。
また、トータルの紫外線照射量が１０００ｍＪ／ｃｍ^２以上であると、その後の変色をより小さくすることができることがわかる。
３０００ｍＪ／ｃｍ^２を超える量照射してもそれ以上効果は上がらないことがわかった。 It can be seen from Comparative Example 1 that forced drying is likely to be deformed and cracked, and as shown in Table 1, the discoloration by standing is large. Further, it can be seen from Comparative Example 2 that even when the same paint as used in the example is applied, discoloration due to leaving is large when the coating is left alone and not irradiated with ultraviolet rays.
On the other hand, it can be seen that the color change after application of the paint, ultraviolet irradiation / polishing, and the like, is less discolored than that immediately after the application of the paint, even if left for 28 days. This means that the discoloration of the paint has progressed to the vicinity of the final stage by the above processing, and thus the discoloration after that has decreased.
In addition, it turns out that a subsequent discoloration can be made smaller if an ultraviolet irradiation amount is made into an appropriate range.
Moreover, it turns out that discoloration after that can be made smaller as a total ultraviolet irradiation amount is 1000 mJ / cm < ² > or more.
It was found that the effect does not increase any more even when the amount of irradiation exceeds 3000 mJ / cm ² .

Claims

After the acid-curable amino alkyd resin paint, acid-hardening type phenol resin paint, any paint of the polyurethane resin coating was applied to the wood surface, and wherein applying ultraviolet light to promote discoloration of the paint To treat wood surface.

The coating amount of the paint is 5 to 30 g / m in solid content ^２2 The wood surface treatment method according to claim 1, wherein:

The method for surface treatment of wood according to claim 1 or 2, wherein the ultraviolet irradiation amount is 500 mJ / cm ² or more.

After the paint applied to the wood surface is cured and discolored by the heat generated during UV irradiation, the cured and discolored paint layer is ground, the same paint is applied to the ground surface, and the series of operations for UV irradiation is performed at least once. The wood surface treatment method according to any one of claims 1 to 3, wherein the method is performed.