JP7649027B2 - Composition for forming surface layer, surface layer formed from said composition, and surface material for writing on oil-based ink - Google Patents

Description

The present invention relates to a composition for forming a surface layer, etc. More specifically, the present invention relates to a composition for forming a surface layer, etc., which can obtain a surface layer that can be written on with oil-based ink, and that can erase the handwriting with a plastic eraser, and further that can be erased with a plastic eraser and cloth.

Various proposals have been made so far regarding inks that can erase handwriting written on paper. The aim of these is to allow the ink to be written repeatedly on the same piece of paper. However, these technologies are only intended to be used for writing on "paper". There is also technology that makes it possible to erase handwriting written with ink such as a magic marker using a commercially available eraser, but this technology mainly relies on the composition of the ink ingredients.

On the other hand, there are surface processing technologies that pursue both writing and erasing functions. For example, the surface of the adhesive tape disclosed in the following Patent Document 1 is a release agent layer that contains an organic resin with a specific glass transition point, such as polyurethane resin, and an addition-reactive silicone. These two components form a seaweed structure, which allows the writing (printing) properties of oil-based marker to be exhibited.

In addition, the following Patent Document 2 discloses a technology related to a water-based matte paint. The water-based matte paint contains a polyurethane resin, a compound having a polymerizable unsaturated group, a granular filler, and colloidal silica. The surface formed by the water-based matte paint has a stain-resistant effect, as it is possible to erase the handwriting of an oil-based marker with a cloth.

Japanese Patent Application Publication No. 11-228924 JP 2018-178066 A

In the above Patent Document 1, the use of a surface coating containing a polyurethane resin makes it possible to write with oil-based marker, but no evaluation of the erasability of the handwriting of the oil-based marker is disclosed, and the aim is not to achieve both the ease of writing with oil-based marker and the erasability of the handwriting. Furthermore, the above Patent Document 2 is a technology that focuses on "resistance to contamination," and in order to verify the effect of resistance to contamination, it is merely verified whether or not the handwriting of oil-based marker can be erased with "cloth." It is not a technology that aims to obtain a surface layer that can be repeatedly written on with oil-based ink by erasing the handwriting with a plastic eraser or cloth.

The main objective of the present invention is to provide a surface layer forming composition etc. that allows repeated writing with oil-based ink on a surface layer where no oil-based ink marks remain, by making it possible to easily erase written oil-based ink marks with a commercially available plastic eraser, or even by rubbing with a plastic eraser and a cloth.

That is, the present invention is a surface layer forming composition that forms a surface layer that can be written on with oil-based ink and can erase written marks with a plastic eraser, or even when rubbed with a plastic eraser and cloth. More specifically, a surface layer forming composition that contains at least a polyol and an aliphatic or aromatic polyisocyanate and can form a polyurethane resin surface layer is proposed. An example of a suitable composition for the surface layer forming composition according to the present invention is a surface layer forming composition in which the polyol is an alkyd polyol (also called alkyd polyol) and the polyisocyanate is pentamethylene diisocyanate, hexamethylene diisocyanate, xylene diisocyanate, or isophorone diisocyanate. Among them, when the polyisocyanate is pentamethylene diisocyanate, the equivalent ratio of isocyanate group/hydroxyl group of the surface layer forming composition is preferably 0.5 or more and 2.5 or less. In addition, when the polyisocyanate is hexamethylene diisocyanate, the equivalent ratio of isocyanate group/hydroxyl group of the surface layer forming composition is preferably 0.5 or more and 4.0 or less. In addition, when the polyisocyanate is xylylene diisocyanate, the equivalent ratio of isocyanate group/hydroxyl group of the surface layer forming composition is preferably 0.5 or more and 3.0 or less. In addition, when the polyisocyanate is isophorone diisocyanate, the equivalent ratio of isocyanate group/hydroxyl group of the surface layer forming composition is preferably 0.4 or more and 2.2 or less. Furthermore, from the viewpoint of realizing erasability with both plastic eraser and cloth, a composition in which the equivalent ratio of isocyanate group/hydroxyl group is 1.2 or more and 2.0 or less and further contains polyolefin wax is particularly suitable.
In addition, one example of a suitable composition of the surface layer forming composition according to the present invention is a composition in which the polyol is a fluorine polyol, the polyisocyanate is pentamethylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate or isophorone diisocyanate, and further contains a silicon modified acrylic polymer having a hydroxyl group. In particular, in this composition, it is preferable that the equivalent ratio of isocyanate group/hydroxyl group is 0.65 or more and 2.0 or less. And, it is preferable that the equivalent ratio of the silicon modified acrylic polymer having a hydroxyl group to be added is 0.1 or more and 1.2 or less with respect to 100 parts by mass of the fluorine polyol.
The present invention further provides a surface layer formed from the above-mentioned composition for forming a surface layer, and a surface material for writing on oil-based ink, which comprises at least the surface layer.

The surface layer forming composition according to the present invention makes it possible to provide a new surface layer on which writing can be done with oil-based ink and the handwriting can be easily erased with a plastic eraser or with a plastic eraser and cloth, and a surface material for writing on oil-based ink that includes such a surface layer.

FIG. 2 is a diagram for explaining the basic layer structure of a panel having a surface layer according to the present invention.

The present invention first provides a composition for forming a surface layer. More specifically, the present invention provides a composition for forming a surface layer that can be written on with oil-based ink and that can easily erase the handwriting with a plastic eraser, or even when rubbed with a plastic eraser and a cloth.

The type of "oil-based ink" mentioned above is not narrowly limited, and can be any oil-based ink commonly used in oil-based markers and oil-based ballpoint pens. The "oil-based marker" that is the subject of the present invention is not narrowly limited, but can be, for example, a marking pen in which an absorbent containing oil-based ink is placed in a cylindrical container and a fiber or plastic pen tip is attached to the absorbent.

The "oil-based ink" of the oil-based marker described above is not limited narrowly, but is an ink having a composition that includes at least an organic solvent, a resin, and a dye. A more detailed representative composition example of an oil-based ink for oil-based markers is an oil-based ink composed of a solvent containing a total of 65 to 91 mass% of propylene glycol monomethyl ether, ethyl alcohol, isopropyl alcohol, benzyl alcohol, methyl ethyl ketone, etc., 1 to 10 mass% of resin, and 1 to 20 mass% of dye.

The "oil-based ballpoint pen" that can be used in the present invention is not narrowly limited, but can be, for example, a pen that supplies ink from the refill by a rotatable ball attached to the tip of a long, thin cylindrical refill containing oil-based ink.

The oil-based ink for the oil-based ballpoint pen is not particularly limited, but may have a general composition that includes at least an organic solvent, a resin, and a dye. A more specific example of an ink for an oil-based ballpoint pen is an oil-based ink composed of a solvent containing 40 to 65% by mass of phenyl cellosolve and benzyl alcohol in total, 15 to 25% by mass of resin, and 20 to 30% by mass of dye.

The "plastic (synthetic resin) eraser" (hereinafter "eraser") that can be used in this invention is a commercially available synthetic resin eraser (so-called rubber eraser) that is generally used mainly to erase drawings made with a pencil or mechanical pencil. One example is a plastic eraser whose main component is polyvinyl chloride.

The "fabric" applicable to the present invention is a commonly used fibrous fabric. For example, it may be 100% cotton fiber, 100% polyester fiber, or a blend of cotton and polyester. It may also be tissue paper, which is a commonly used fiber in daily life, but is not necessarily limited to this.

The surface layer forming composition according to the present invention is used to form the surface layer of various surface materials that require writing with oil-based ink. The surface materials are not limited to flat shapes, but can also be used on the surfaces of articles of various shapes, and can be widely used not only for stationery but also for wall materials for structures, cards, furniture such as desks, cases for home appliances, etc.

The method for forming the surface layer on the substrate is not particularly limited, but for example, the composition for forming the surface layer can be directly applied to the substrate or sprayed. Alternatively, a sheet can be prepared in advance from the composition for forming the surface layer, and the sheet can be attached to the substrate with an adhesive or the like.

The composition for forming the surface layer contains (A) a polyol and (B) an aliphatic or aromatic polyisocyanate, and forms (C) a composition capable of forming a polyurethane structure.

(A) Regarding polyols.
Polyol is a general term for a compound having two or more hydroxyl groups in a molecule, and can be selected from various known polyols. A suitable polyol that can be used in the present invention is, for example, an alkyd polyol. The surface layer formed of a composition having a polyurethane structure formed by an alkyd polyol and a polyisocyanate has a property that the solvent or dye of an oil-based ink is difficult to penetrate appropriately, so that the oil-based ink can be easily fixed to the surface without being repelled when written, and the oil-based ink can be easily erased.

Examples of polyol components that can be used in the present invention include alkyd polyols, among which polyester polyols derived from vegetable oils (e.g., castor oil, coconut oil fatty acids) are preferred. Examples include alkyd polyols obtained by condensation polymerization of castor oil and polybasic acids and polyhydric alcohols. Here, the polybasic acids may include, for example, adipic acid, phthalic acid, sebacic acid, etc. In addition, other suitable polyol components that can be used in the present invention include fluorine polyols.

Furthermore, an example of a polyol component that can be used in the present invention is a fluorine polyol. The fluorine polyol contains one or more fluorines in the molecule, and the resin formed from this fluorine polyol has some parts that are partially covered with fluorine. This allows the resin to exhibit properties such as chemical resistance, weather resistance, and heat resistance that are unique to fluorine-containing compounds, and also provides the same effect on oil-based inks as when an alkyd polyol is used. One example of a fluorine polyol that can be used in the present invention is one that contains a copolymer of tetrafluoroethylene and a vinyl monomer.

(B) Regarding polyisocyanates.
Polyisocyanate is a general term for compounds having two or more isocyanate groups in the molecule, and in the present invention, it is possible to suitably select from various known aliphatic or aromatic polyisocyanates. Suitable polyisocyanates that can be used in the present invention include, for example, aliphatic polyisocyanates such as pentamethylene diisocyanate and hexamethylene diisocyanate. Examples of aromatic polyisocyanates include xylene diisocyanate. Examples of alicyclic isocyanates include isophorone diisocyanate.

(C) Regarding polyurethane structure.
The surface layer forming composition according to the present invention is configured to form a polyurethane structure by a reaction between an isocyanate group and a hydroxyl group. The surface layer having this polyurethane structure may be either light-transmitting or light-opaque.

Regarding the equivalent ratio of isocyanate groups to hydroxyl groups.
The equivalent ratio of isocyanate group/hydroxyl group is a physical property value that determines the affinity (particularly lipophilicity) of the surface layer formed from the polyurethane resin and the permeability of oil-based ink. In the present invention, depending on the composition of the composition components, for example, in a composition in which the polyol is an alkyd polyol and the polyisocyanate is pentamethylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate or isophorone diisocyanate, the suitable equivalent ratio range differs depending on the type of the isocyanate. For example, when the polyisocyanate is pentamethylene diisocyanate, the equivalent ratio of isocyanate group/hydroxyl group of the surface layer forming composition is preferably 0.5 or more and 2.5 or less. Also, when the polyisocyanate is hexamethylene diisocyanate, the equivalent ratio of isocyanate group/hydroxyl group of the surface layer forming composition is preferably 0.5 or more and 4.0 or less. In addition, when the polyisocyanate is xylylene diisocyanate, the equivalent ratio of isocyanate group/hydroxyl group in the surface layer forming composition is preferably 0.5 to 3.0.In addition, when the polyisocyanate is isophorone diisocyanate, the equivalent ratio of isocyanate group/hydroxyl group in the surface layer forming composition is preferably 0.4 to 2.2.
Furthermore, for example, in a composition in which the polyol is a fluorine polyol and the polyisocyanate is pentamethylene diisocyanate, hexamethylene diisocyanate, xylene diisocyanate or isophorone diisocyanate, the equivalent ratio is preferably in the range of 0.65 or more and 2.0 or less.

When the polyol is an alkyd polyol, if the equivalent ratio of isocyanate/hydroxyl group for each isocyanate is less than the lower limit, the hydroxyl group of the unreacted polyol is present in excess, and in some experimental examples, the coating film becomes sticky over time and the erasability with an eraser or cloth is reduced, which is not preferable. In addition, the equivalent ratio is low, so the strength of the polyurethane resin structure is reduced, and the wear resistance and scratch resistance against the friction of the eraser are reduced. On the other hand, if the equivalent ratio of isocyanate/hydroxyl group for each isocyanate exceeds the upper limit, the isocyanate is present in excess, so the lipophilicity of the coating film increases and the fixation of the oil-based ink is excessively improved, and in some experimental examples, erasing with an eraser or cloth is difficult. In other words, although the range varies depending on the type of isocyanate, from the viewpoint of the effect sought by the present invention, as long as the isocyanate group/hydroxyl group equivalent ratio is at least 0.5 and less than 2.2, the writability of oil-based ink and erasability with an eraser or cloth are compatible, regardless of the type of alkyd polyol or isocyanate. Note that when the polyol is a fluorine polyol and the isocyanate group/hydroxyl group equivalent ratio is less than 0.65, the addition of the hydroxyl group-containing silicon-modified acrylic polymer increases the number of unreacted hydroxyl groups, making the coating surface even more sticky and tending to worsen the writability of oil-based ink. On the other hand, there are experimental examples in which an isocyanate/hydroxyl group equivalent ratio exceeding 2.0 is unsuitable for the same reason as in the case of alkyd polyol.

About hydroxyl-containing silicone modified acrylic polymer.
When a "fluoropolyol" is used as the polyol, the polyisocyanate is preferably pentamethylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate or isophorone diisocyanate, and in this case, a composition further containing an appropriate amount of a silicon-modified acrylic polymer having a hydroxyl group is particularly desirable.

In addition, silicone-modified acrylic polymers that have hydroxyl groups (reactive) are stably fixed to the urethane resin structure by the bond between the reactive hydroxyl groups and isocyanate groups, so the silicone is not easily removed and the erasability of oil-based ink is maintained even over time. However, if non-reactive silicone (no hydroxyl groups, does not react with isocyanate) is used, the silicone will fall off over time, reducing the erasability of oil-based ink, making it unsuitable.

The amount of silicon-modified acrylic polymer with hydroxyl groups added should desirably be between 0.1 and 1.2 in terms of equivalent ratio. If the amount added is less than 0.1 equivalent, erasability with an eraser or cloth will not improve. On the other hand, if the amount added exceeds 1.2, as mentioned above, there will be an excess of hydroxyl groups on the coating surface, making the coating surface even more sticky and worsening the writing properties of oil-based ink.

About polyolefin wax.
When an alkyd polyol is used as the polyol, and pentamethylene diisocyanate, hexamethylene diisocyanate, xylene diisocyanate or isophorone diisocyanate is used as the polyisocyanate, and the equivalent ratio of isocyanate group/hydroxyl group is 1.2 or more and 2.0 or less, a composition further containing an appropriate amount of polyolefin wax is particularly desirable. The addition of polyolefin wax improves the slipperiness of the surface, and erasability is achieved not only with plastic erasers but also with cloth.

Here, the basic layer structure of the surface material having the surface layer according to the present invention will be described with reference to the attached drawings. Figure 1 is a cross-sectional view showing an example of the layer structure.

First, the surface material denoted by reference numeral 1 comprises at least a base layer 11 and a surface layer 12 laminated on the base layer 11. In a configuration in which the surface layer 12 is formed into a sheet and then laminated on the base layer 11, an adhesive layer (not shown) is interposed between the base layer 11 and the surface layer 12. The surface layer 12 may be formed directly on the base layer 11 by coating or spraying. The total number of layers in the layer structure is not particularly limited. In other words, a layer required according to the purpose may be interposed between the base layer 11 and the surface layer 12.

The present invention will be described below based on experimental examples, but the present invention is not limited to these experimental examples. Each of the experimental examples of the surface layer forming composition having the composition shown in Tables 1 to 5 below was prepared by the following method.

(Experimental Examples 1 to 3)
The polyol component, alkyd polyol (TOKYD-25C, manufactured by Toshin Yushi Co., Ltd., hydroxyl value 105 to 160) and ethyl acetate (solvent) were mixed and stirred for 3 minutes at 1000 rpm using a propeller mixer. Ethyl acetate was added in an amount that would result in a solid content of 35% by mass after the addition of the isocyanate. Then, 1,5-pentamethylene diisocyanate (STABIO D-370N, Mitsui Chemicals), an aliphatic isocyanate, was added in an amount that would result in an isocyanate group/hydroxyl group equivalent ratio (hereinafter, NCO/OH equivalent ratio) of 0.5 to 2.5 according to Table 1. These solvents were mixed and stirred for 3 minutes at 1000 rpm using a propeller mixer to obtain a surface layer forming composition. The alkyd polyol used in Experimental Examples 1 to 3 was a polyester polyol derived from castor oil.

(Experimental Examples 4 to 9)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 1 to 3, except that a trimer of hexamethylene diisocyanate (hereinafter, hexamethylene diisocyanate) (Coronate HXR, manufactured by Tosoh Corporation), which is an aliphatic isocyanate, was used as the isocyanate component, and the hexamethylene diisocyanate was added in an amount such that the NCO/OH equivalent ratio was 0.5 to 4.0 according to Table 1.

(Experimental Examples 10 to 15)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 1 to 3, except that a trimer of xylene diisocyanate (hereinafter, xylene diisocyanate) (isocyanurate of XDI, Takenate D-131N, manufactured by Mitsui Chemicals, Inc., 78% ethyl acetate solution) which is an aromatic isocyanate was used as the isocyanate component, and the xylene diisocyanate was added in an amount such that the NCO/OH equivalent ratio was 0.5 to 3.0 according to Table 1.

(Experimental Examples 16 to 18)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 1 to 3, except that an alicyclic isocyanate, isophorone diisocyanate (Desmodur Z 4470 BA, manufactured by Sumika Covestro Urethane Co., Ltd.), was used as the isocyanate component, and the isophorone diisocyanate was added in an amount such that the NCO/OH equivalent ratio was 0.4 to 2.2 according to Table 1.

(Experimental Example 19)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 1 to 3, except that an alkyd polyol (NT-11NX, manufactured by Toshin Yushi Co., Ltd., hydroxyl value 70 to 80) was used as the polyol component, and the same 1,5-pentamethylene diisocyanate as in Experimental Examples 1 to 3 was used as the isocyanate component, and the 1,5-pentamethylene diisocyanate was added in an amount such that the NCO/OH equivalent ratio was 1.0. The alkyd polyol used in this Experimental Example 19 was a polyester polyol derived from coconut oil fatty acid.

(Experimental Example 20)
A surface layer-forming composition was obtained in the same manner as in Experimental Example 19, except that the same hexamethylene diisocyanate as in Experimental Examples 4 to 9 was used as the isocyanate component and that the hexamethylene diisocyanate was added in an amount such that the NCO/OH equivalent ratio was 1.0.

(Experimental Example 21)
A surface layer-forming composition was obtained in the same manner as in Experimental Example 19, except that the same xylylene diisocyanate as in Experimental Examples 10 to 15 was used as the isocyanate component and that the xylylene diisocyanate was added in an amount such that the NCO/OH equivalent ratio was 1.0.

(Experimental Example 22)
A surface layer-forming composition was obtained in the same manner as in Experimental Example 19, except that the same isophorone diisocyanate as in Experimental Examples 16 to 18 was used as the isocyanate component and that the isophorone diisocyanate was added in an amount such that the NCO/OH equivalent ratio was 1.0.

(Experimental Examples 23 to 25)
A fluoropolyol (Zeffle GK570, Daikin Industries, Ltd.) as a polyol component, ethyl acetate, and a hydroxyl-containing silicon-modified acrylic polymer (BYK-SILCLEAN3700, BYK-Chemie) as an additive were stirred and mixed with a propeller stirrer at 1000 rpm for 3 minutes. The ethyl acetate as a solvent was added in an amount that would result in a solid content of 35% by mass after the addition of the isocyanate. The hydroxyl-containing silicon-modified acrylic polymer as an additive (auxiliary agent) was added in an amount of 0.7 parts by mass per 100 parts by mass of the fluoropolyol. Then, 1,5-pentamethylene diisocyanate (STABIO D-370N, Mitsui Chemicals, Inc.) as an aliphatic isocyanate was added in an amount that would result in an NCO/OH equivalent ratio of 0.5 to 2.2 according to Table 2. These solvents were stirred and mixed with a propeller stirrer at 1000 rpm for 3 minutes to obtain a surface layer forming composition.

(Experimental Examples 26 to 30)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 23 to 25, except that a trimer of hexamethylene diisocyanate (hereinafter, hexamethylene diisocyanate) (Coronate HXR, manufactured by Tosoh Corporation), which is an aliphatic isocyanate, was used as the isocyanate component, and the hexamethylene diisocyanate was added in an amount such that the NCO/OH equivalent ratio was 0.5 to 2.0 according to Table 2.

(Experimental Examples 31 to 36)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 23 to 25, except that a trimer of xylene diisocyanate (hereinafter, xylene diisocyanate) (isocyanurate of XDI, Takenate D-131N, manufactured by Mitsui Chemicals, Inc., 78% ethyl acetate solution) which is an aromatic isocyanate was used as the isocyanate component, the xylene diisocyanate was added in an amount such that the NCO/OH equivalent ratio was 0.65 to 2.5 according to Table 2, and the hydroxyl group-containing silicon-modified acrylic polymer was not added only in Experimental Example 31.

(Experimental Examples 37 to 39)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 23 to 25, except that an alicyclic isocyanate, isophorone diisocyanate (Desmodur Z 4470 BA, manufactured by Sumika Covestro Urethane Co., Ltd.), was used as the isocyanate component, and the isophorone diisocyanate was added in an amount such that the NCO/OH equivalent ratio was 0.65 to 2.0 according to Table 2.

(Experimental Examples 40 and 41)
A fluoropolyol (Zeffle GK570, Daikin Industries, Ltd.) as a polyol component, ethyl acetate, and a hydroxyl-containing silicon-modified acrylic polymer (BYK-SILCLEAN3700, BYK-Chemie) as an additive were stirred and mixed with a propeller stirrer at 1000 rpm for 3 minutes. The ethyl acetate as a solvent was added in an amount that would result in a solid content of 35% by mass after the addition of the isocyanate. The hydroxyl-containing silicon-modified acrylic polymer as an additive (auxiliary agent) was added in an amount of 0.1 or 1.2 parts by mass per 100 parts by mass of the fluoropolyol according to Table 2, and 1,5-pentamethylene diisocyanate (Stabio D-370N, Mitsui Chemicals, Inc.) was added in an amount that would result in an NCO/OH equivalent ratio of 1.6. The solvent was then stirred and mixed with a propeller stirrer at 1000 rpm for 3 minutes to obtain a surface layer forming composition.

(Experimental Examples 42 and 43)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 40 and 41, except that the same hexamethylene diisocyanate as in Experimental Examples 26 to 30 was used as the isocyanate component.

(Experimental Examples 44 and 45)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 40 and 41, except that the same xylylene diisocyanate as in Experimental Examples 31 to 36 was used as the isocyanate component.

(Experimental Example 46)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 40 and 41, except that the same isophorone diisocyanate as in Experimental Examples 37 to 39 was used as the isocyanate component and that the hydroxyl group-containing silicon-modified acrylic polymer was not added.

(Experimental Examples 47 and 48)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 40 and 41, except that the same isophorone diisocyanate as in Experimental Examples 37 to 39 was used as the isocyanate component.

(Experimental Examples 49 to 51)
The polyol component, alkyd polyol (TOKYD-25C, manufactured by Toshin Yushi Co., Ltd., hydroxyl value 105-160), ethyl acetate, and additive polyolefin wax (Disparlon PF-911, manufactured by Kusumoto Chemicals Co., Ltd.) were mixed and stirred for 3 minutes using a propeller mixer at 1000 rpm. Ethyl acetate was added in an amount that would result in a solid content of 35% by mass after the addition of isocyanate. The additive polyolefin wax was added in an amount of 5 parts by mass per 100 parts by mass of alkyd polyol. Then, the same 1,5-pentamethylene diisocyanate as in Experimental Examples 1 to 3 was added in an amount that would result in an isocyanate group/hydroxyl group equivalent ratio (hereinafter, NCO/OH equivalent ratio) of 1.2 to 2.0 according to Table 3. These solvents were mixed and stirred for 3 minutes using a propeller mixer at 1000 rpm to obtain a surface layer forming composition.

(Experimental Examples 52 to 54)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 49 to 51, except that the same hexamethylene diisocyanate as in Experimental Examples 4 to 9 was used as the isocyanate component.

(Experimental Examples 55 to 57)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 49 to 51, except that the same xylylene diisocyanate as in Experimental Examples 10 to 15 was used as the isocyanate component.

(Experimental Examples 58 to 60)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 49 to 51, except that the same isophorone diisocyanate as in Experimental Examples 16 to 18 was used as the isocyanate component.

(Experimental Examples 61 and 62)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 1 to 3, except that the 1,5-pentamethylene diisocyanate was added in an amount such that the NCO/OH equivalent ratio was 0.04 or 3.0 according to Table 4.

(Experimental Examples 63 and 64)
Compositions for forming a surface layer were obtained in the same manner as in Experimental Examples 4 to 9, except that the hexamethylene diisocyanate was added in an amount such that the NCO/OH equivalent ratio was 0.4 or 5.0 according to Table 4.

(Experimental Examples 65 and 66)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 10 to 15, except that the xylene diisocyanate was added in an amount such that the NCO/OH equivalent ratio was 0.4 or 3.5 according to Table 4.

(Experimental Examples 67 and 68)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 16 to 18, except that the isophorone diisocyanate was added in an amount such that the NCO/OH equivalent ratio was 0.3 or 2.5 according to Table 4.

(Experimental Examples 69 and 70)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 26 to 30, except that the hydroxyl group-containing silicon-modified acrylic polymer was not added and the hexamethylene diisocyanate was added in an amount such that the NCO/OH equivalent ratio was 1.1 and 0.65.

(Example 71)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 26 to 30, except that the hydroxyl group-containing silicon-modified acrylic polymer was not added, fluorine polyol 2 (Lumiflon LF200, manufactured by Asahi Glass Co., Ltd.) was used as the polyol component, and the hexamethylene diisocyanate was added in an amount such that the NCO/OH equivalent ratio was 1.1.

(Example 72)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 26 to 30, except that the hydroxyl group-containing silicon-modified acrylic polymer was not added, silicon-modified fluorine polyol 2 (ZX-022-H, manufactured by T&K TOKA Corporation) was used as the polyol component, and the hexamethylene diisocyanate was added in an amount such that the NCO/OH equivalent ratio was 1.0.

(Example 73)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 26 to 30, except that the hydroxyl group-containing silicon-modified acrylic polymer was not added, acrylic polyol 1 (XK-9012, manufactured by Toshin Yushi Co., Ltd.) was used as the polyol component, and the hexamethylene diisocyanate was added in an amount such that the NCO/OH equivalent ratio was 1.0.

(Example 74)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 31 to 36, except that the hydroxyl group-containing silicon-modified acrylic polymer was not added, acrylic polyol 2 (EXCELOL821, manufactured by Asia Kogyo Co., Ltd.) was used as the polyol component, and the isophorone diisocyanate was added in an amount such that the NCO/OH equivalent ratio was 1.0.

(Example 75)
The same acrylic polyol as in Experimental Example 74 and 50 parts by mass of ethyl acetate were mixed and stirred with a propeller stirrer at 1000 rpm for 3 minutes to obtain a composition for forming a surface layer. Experimental Example 75 is an experimental example in which no isocyanate component was blended.

(Experimental Examples 76 and 77)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 23 to 25, except that the 1,5-pentamethylene diisocyanate was added in an amount such that the NCO/OH equivalent ratio was 0.04 or 2.5 according to Table 5.

(Experimental Examples 78 and 79)
Compositions for forming a surface layer were obtained in the same manner as in Experimental Examples 26 to 30, except that the hexamethylene diisocyanate was added in an amount such that the NCO/OH equivalent ratio was 0.4 or 2.2 according to Table 5.

(Experimental Examples 80 and 81)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 31 to 36, except that the xylylene diisocyanate was added in an amount such that the NCO/OH equivalent ratio was 0.3 or 3.0 according to Table 5.

(Experimental Examples 82 and 83)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 37 to 39, except that the isophorone diisocyanate was added in an amount such that the NCO/OH equivalent ratio was 0.5 or 2.2 according to Table 5.

(Experimental Example 84)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 40 and 41, except that the hydroxyl group-containing silicon-modified acrylic polymer was not added.

(Example 85)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 40 and 41, except that the amount of the hydroxyl-containing silicon-modified acrylic polymer added was 1.5 parts by mass per 100 parts by mass of the fluorine polyol.

(Example 86)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 42 and 43, except that the hydroxyl group-containing silicon-modified acrylic polymer was not added.

(Example 87)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 42 and 43, except that the amount of the hydroxyl-containing silicon-modified acrylic polymer added was 1.5 parts by mass per 100 parts by mass of the fluorine polyol.

(Example 88)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 44 and 45, except that the hydroxyl group-containing silicon-modified acrylic polymer was not added.

(Example 89)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 44 and 45, except that the amount of the hydroxyl-containing silicon-modified acrylic polymer added was 2.5 parts by mass per 100 parts by mass of the fluorine polyol.

(Example 90)
A surface layer-forming composition was obtained in the same manner as in Experimental Examples 47 and 48, except that the amount of the hydroxyl-containing silicon-modified acrylic polymer added was 1.5 parts by mass per 100 parts by mass of the fluorine polyol.

Regarding evaluation.
In the surface layer forming composition produced by the above method, (1) NCO/OH equivalent ratio of each blended composition was calculated by the following method, and (2) PET (polyethylene terephthalate) adhesion, (3) oil-based marker writing property, (4) oil-based marker writing erasability, (5) oil-based marker writing cloth erasability, (6) oil-based ballpoint pen writing property, (7) oil-based ballpoint pen writing eraser erasability, and (8) oil-based ballpoint pen writing cloth erasability were evaluated by the following method. The results of each experiment example are shown in Tables 1 and 2 below together with the respective compositions.

(1) Method for Calculating Equivalent Ratio of Isocyanate Group/Hydroxyl Group The equivalent ratio of isocyanate group/hydroxyl group was calculated by calculating the molecular weight per one isocyanate group and the molecular weight per one hydroxyl group, and expressed as the ratio between them.
The isocyanate group equivalent, which indicates the molecular weight per one isocyanate group, was calculated according to the following formula 1.

In addition, since the hydroxyl value range of the polyols used in the present invention is known, the median value was used in the calculation as the hydroxyl value, and the hydroxyl equivalent, which indicates the molecular weight per hydroxyl group, was calculated using the following formula 2. The hydroxyl values of the polyols used in the calculation were 128 (TOKYD-25C) and 75 (NT-11NX), respectively.

The hydroxyl value of a polyol is the amount of potassium hydroxide (converted into mg) equivalent to the hydroxyl group contained in 1 g of polyol when the polyol is acetylated with acetic anhydride and the free acetic acid is quantified with potassium hydroxide. The molecular weight of KOH is 56.1.

(2) Adhesion to PET (Polyethylene Terephthalate) This evaluation item is for evaluating the adhesion of the surface layer to the substrate.
The composition of each experimental example was applied to a PET film (Toray Miller S10, 100 μm thick) using a No. 10 bar coder, and then heated in an oven at 150°C for 10 minutes. The resulting laminate was subjected to an adhesion test (cross-cut method; JIS K 5600-5-6:1999 General test methods for paints - Part 5: Mechanical properties of coatings - Section 6). More specifically, a grid pattern (6 cuts, grid width 1 mm, 100 squares) was applied to the surface layer using a cutter knife. Cellophane adhesive tape (width 25 mm) was completely pressed onto this grid pattern, and the end of the tape was grasped at an angle of 60° and instantly pulled away in 0.5 to 1.0 seconds so as to be sure to separate. The state of the grid pattern was then visually confirmed.

The adhesion to PET was evaluated according to three levels, as shown below.
◎ (Good): The edges of the cut are completely smooth and there is no peeling on any of the grid cells.
◯ (pass): There is minor peeling of the coating at the intersections of the cuts. The cross-cut area affected is not significantly greater than 5%.
× (fail): The coating has peeled off along the edges of the cuts and/or at the intersections. Clearly more than 5% of the cross-cut area is affected.

(3) Writability of oil-based marker The composition of each experimental example was applied to a PET film (Toray Mirror S10, thickness 100 μm) using a No. 10 barcoder, and then heated in an oven at 150° C. for 10 minutes. After 24 hours, writing was performed with an oil-based marker, and the handwriting was visually evaluated. The oil-based marker used in this experiment was Zebra's Mackie (registered trademark).

The writability was evaluated on a three-level scale according to the following criteria:
◎ (Good): I was able to write with oil-based ink without it repelling.
◯ (pass): Less than 5% of the oil-based ink was repelled.
× (fail): 5% or more of the oil-based ink was repelled, or writing was not possible.

(4) Erasability of oil-based marker writing The composition obtained in each experimental example was applied to a PET film (Toray mirror S10, thickness 100 μm) using a No. 10 bar coder, and then heated in an oven at 150° C. for 10 minutes. After 24 hours, writing was done with an oil-based marker, and after another 24 hours, the film was rubbed with a plastic eraser under specified conditions, and the handwriting was visually evaluated. The rub conditions were distance: 10 cm, speed: 10 round trips/6 seconds, and load: 800 g.

The erasability was evaluated on a three-level scale according to the following criteria:
◎ (Good): Erasing was possible with less pressure and fewer reciprocations than the test conditions.
◯ (Pass): Erased successfully.
× (failed): Erasing was not possible.

(5) Cloth erasability of oil-based marker marks The compositions obtained in each experimental example were applied to a PET film (Toray Mirror S10, thickness 100 μm) using a No. 10 bar coder, and then heated in an oven at 150° C. for 10 minutes. After 24 hours, the film was written on with an oil-based marker, and after another 24 hours, the film was rubbed with a cloth under specified conditions, and the handwriting was visually evaluated. The conditions were: distance: 10 cm, speed: 10 round trips/6 seconds, and load: 800 g.
The erasability was evaluated in the same manner as in the evaluation of erasability using the character eraser. The cloth used in this experiment was a 100% cotton cloth and tissue paper (Lorena, Nippon Paper Crecia Co., Ltd.).

The evaluation of (6) writability with oil-based ballpoint pen, (7) ability to erase marks left by oil-based ballpoint pen, and (8) ability to erase marks left by oil-based ballpoint pen on fabric was carried out in the same manner as the evaluation of oil-based marker pens.

Tables 1 to 5 show the composition ratios and evaluation results of the experimental examples of the present invention. Table 1 shows experimental examples of alkyd polyols and various isocyanates. Table 2 shows experimental examples of fluorine polyols and various isocyanates, and hydroxyl-containing silicon-modified acrylic polymers were added except for experimental example 31. Table 3 shows experimental examples in which polyolefin wax was added together with alkyd polyols and various isocyanates. The experimental examples shown in Tables 1 to 3 can be examples from the viewpoint of achieving both the writability of oil-based ink and the erasability with erasure or cloth. Table 4 shows experimental examples mainly of various polyols and various isocyanates. Only experimental example 75 has a composition that does not contain isocyanates. Table 5 shows experimental examples mainly of fluorine polyols and various isocyanates, and hydroxyl-containing silicon-modified acrylic polymers were added except for experimental examples 84, 86, and 88.

(Discussion of the Experimental Examples)
As shown in Tables 1 to 3 above, the compositions for forming a surface layer in Experimental Examples 1 to 60 passed the judgment results (◯ or ◎ symbol) for all evaluation items except for the evaluation item of the erasability of handwriting by oil-based marker and oil-based ballpoint pen on fabric. That is, all of the compositions for forming a surface layer in Experimental Examples 1 to 60 were excellent in both the writability with an oil-based ballpoint pen and oil-based marker and the erasability with an eraser, and further, were excellent in the adhesion of the surface layer to the substrate.

On the other hand, as shown in Tables 4 and 5 above, the compositions for forming the surface layer of Experimental Examples 61 to 90 failed (marked with an x) in at least one of the seven evaluation items (2) to (8). More specifically, Experimental Examples 61 to 75, 77, 79 to 81, 83, 84, 86, and 88 failed at least the evaluation of (4) erasability of handwritten marks by erasing with an oil-based marker. In addition, among the experimental examples listed in Tables 4 and 5 that failed the evaluation of (4), the erasability of the oil-based marker with a cloth was also failed, except for Experimental Example 66. On the other hand, Experimental Examples 76, 78, 82, 85, 87, 89, and 90 that at least passed the evaluation of (4) erasability of handwritten marks by erasing with an oil-based marker were all at least failed the evaluation of (3) writability of the oil-based marker. In other words, the surface layer-forming compositions of Experimental Examples 1 to 60 were all superior to Experimental Examples 61 to 90 in terms of the effect sought by the present invention, namely, the balance between the writability of oil-based ink and erasability with erasure or cloth.

Comparing Experimental Examples 1 to 22 (all of which used alkyd polyols) with Experimental Example 72 (which used a silicon-modified fluorine polyol), Experimental Example 73 (which used acrylic polyol 1), and Experimental Example 74 (which used acrylic polyol 2), it was shown that the type of polyol selected affects the effects of the writability and erasability of the present invention. According to these experimental examples, it was found that alkyd polyols are superior to silicon-modified fluorine polyols and acrylic polyols in terms of writability and erasability with an eraser, regardless of whether the isocyanate is pentamethylene diisocyanate, hexamethylene diisocyanate, xylene diisocyanate, or isophorone diisocyanate.

Furthermore, the results of Experimental Examples 1 to 18 (all of which used alkyd polyol 1) and Experimental Examples 19 to 22 (all of which used alkyd polyol 2) showed that the selected polyol was suitable for any alkyd polyol.

Regarding the effect of NCO/OH equivalent ratio.
As can be seen from the results of Experimental Examples 1 to 18 and Experimental Examples 61 to 68, when an alkyd polyol is used as the polyol, there is a suitable range for the NCO/OH equivalent ratio depending on the type of isocyanate selected.

The results of Experimental Examples 1 to 3 and Experimental Examples 61 and 62 show that when 1,5-pentamethylene diisocyanate is selected as the isocyanate, the NCO/OH equivalent ratio is preferably 0.5 or more and 2.5 or less.

Similarly, the results of Experimental Examples 4 to 9 and Experimental Examples 63 and 64 show that when hexamethylene diisocyanate is selected as the isocyanate, the NCO/OH equivalent ratio is preferably 0.5 or more and 4.0 or less.

Similarly, the results of Experimental Examples 10 to 15 and Experimental Examples 65 and 66 show that when xylylene diisocyanate is selected as the isocyanate, the NCO/OH equivalent ratio is preferably 0.5 or more and 3.0 or less.

Furthermore, the results of Experimental Examples 16 to 18 and Experimental Examples 67 and 68 show that when isophorone diisocyanate is selected as the isocyanate, the NCO/OH equivalent ratio is preferably 0.4 or more and 2.2 or less.

Next, in Experimental Examples 23 to 48, in which a fluorine polyol was used as the polyol, any of pentamethylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, or isophorone diisocyanate could be used as the isocyanate, and in any case of the isocyanate, in the composition in which a hydroxyl-containing silicon-modified acrylic polymer was added, both the writability of the oil-based ink and the erasability with an eraser were rated as pass or better. On the other hand, in Experimental Examples 69, 70, 71, 84, 86, and 88, in which a fluorine polyol was used but a hydroxyl-containing silicon-modified acrylic polymer was not added, it was not possible to achieve both the writability of the oil-based ink and the erasability with an eraser. In other words, when a fluorine polyol is used and the isocyanate is pentamethylene diisocyanate, hexamethylene diisocyanate, or xylene diisocyanate, it was found that the addition of a hydroxyl-containing silicon-modified acrylic polymer is essential to achieve both good writing properties and erasability with an eraser.

Regarding the effect of NCO/OH equivalent ratio.
Even when a fluorine polyol is used as the polyol, there is a suitable range for the NCO/OH equivalent ratio depending on the type of isocyanate selected, as can be seen from the results of Experimental Examples 23 to 39 and Experimental Examples 76 to 83. For example, the results of Experimental Examples 23 to 25 and Experimental Examples 76 and 77 show that when 1,5-pentamethylene diisocyanate is selected as the isocyanate, the NCO/OH equivalent ratio is preferably 0.5 or more and 2.2 or less.

Similarly, the results of Experimental Examples 26 to 30 and Experimental Examples 78 and 79 show that when hexamethylene diisocyanate is selected as the isocyanate, the NCO/OH equivalent ratio is preferably 0.5 or more and 2.0 or less.

Similarly, the results of Experimental Examples 31 to 36 and Experimental Examples 80 and 81 show that when xylylene diisocyanate is selected as the isocyanate, the NCO/OH equivalent ratio is preferably 0.65 or more and 2.5 or less.

Furthermore, the results of Experimental Examples 37 to 39, 82, and 83 show that when isophorone diisocyanate is selected as the isocyanate, the NCO/OH equivalent ratio is preferably 0.65 or more and 2.0 or less.

Taking all these results together, it was shown that when a fluoropolyol is used as the polyol, the optimal range for the NCO/OH equivalent ratio is 0.65 or more and 2.0 or less.

Regarding the amount of hydroxyl-containing silicone modified acrylic polymer to be added.
In addition, this experimental example shows that there is a suitable range for the amount of the hydroxyl-containing silicon-modified acrylic polymer added. For example, the results of experimental examples 40 and 41 and experimental examples 84 and 85 show that when 1,5-pentamethylene diisocyanate is selected as the isocyanate, the amount of the hydroxyl-containing silicon-modified acrylic polymer added is preferably in the range of 0.1 parts by mass to 1.2 parts by mass per 100 parts by mass of the fluoropolyol.

Similarly, the results of Experimental Examples 42 and 43 and Experimental Examples 86 and 87 show that when hexamethylene diisocyanate is selected as the isocyanate, the amount of hydroxyl-containing silicon-modified acrylic polymer added is preferably in the range of 0.1 parts by mass to 1.2 parts by mass per 100 parts by mass of fluoropolyol.

Similarly, the results of Experimental Examples 44 and 45 and Experimental Examples 88 and 89 show that when xylylene diisocyanate is selected as the isocyanate, the amount of hydroxyl-containing silicon-modified acrylic polymer added is preferably in the range of 0.1 parts by mass to 1.2 parts by mass per 100 parts by mass of fluoropolyol.

Furthermore, the results of Experimental Examples 46 to 48 and Experimental Example 90 show that when isophorone diisocyanate is selected as the isocyanate, the amount of hydroxyl-containing silicon-modified acrylic polymer added is preferably in the range of 1.2 parts by mass or less per 100 parts by mass of fluorine polyol.

These results show that the optimal range for the amount of hydroxyl-containing silicon-modified acrylic polymer to be added is 0.1 to 1.2 per 100 equivalents of fluoropolyol.

Experimental example 75 is an experimental example of a composition that contains acrylic polyol but does not contain isocyanate, and such a composition does not form a polyurethane structure. In such an experimental example, the erasability of handwriting with oil-based marker or oil-based ballpoint pen using an eraser or cloth was unsatisfactory. According to this experimental example 75, it is considered that a polyurethane structure is essential for the composition according to the present invention. In the surface layer of experimental example 75, the surface layer itself is scraped off by an eraser or friction with a cloth, and the evaluation of PET adhesion is unsatisfactory, and as a result, the evaluation of erasability is also unsatisfactory. Therefore, it was concluded that a surface layer formed only with polyol is unsuitable as an example of a composition according to the present invention.

The above describes experimental examples that can achieve both the writability of oil-based markers and oil-based ballpoint pens and the erasability with an eraser, but even in these experimental examples, it is difficult to achieve erasability with cloth. For example, among the experimental examples in which alkyd polyol is used as the polyol, experimental examples 1, 3 to 5, 8 to 13, and 16 fail the ability to erase with cloth marks of oil-based markers or oil-based ballpoint pens. In contrast, by adding polyolefin wax as an additive, it becomes possible to achieve both the writability of oil-based markers and oil-based ballpoint pens and the erasability with an eraser and cloth.

The results of Experimental Examples 49 to 60 show that all evaluations are acceptable or better. In other words, when an alkyd polyol is used as the polyol and either pentamethylene diisocyanate, hexamethylene diisocyanate, xylene diisocyanate or isophorone diisocyanate is used as the isocyanate, by adding polyolefin wax, it is possible to achieve both the writability of oil-based markers and oil-based ballpoint pens and the ability to erase and be erased with a cloth, in a range where the NCO/OH ratio is 1.2 or more and 2.0 or more.

1 Face material 11 Base material layer 12 Surface layer

Claims (5)

A surface layer-forming composition that contains at least an alkyd polyol and pentamethylene diisocyanate and forms a polyurethane structure,
The equivalent ratio of isocyanate group/hydroxyl group is 0.5 or more and 2.5 or less,
The composition for forming a surface layer forms a surface layer on which writing can be performed with an oil-based ink and on which written marks can be erased when rubbed with a plastic eraser. A surface layer-forming composition that contains at least a polyol, an aliphatic or aromatic polyisocyanate, and a polyolefin wax and forms a polyurethane structure,
the polyol is an alkyd polyol,
The polyisocyanate is selected from pentamethylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, and isophorone diisocyanate;
an equivalent ratio of isocyanate group/hydroxyl group is 1.2 or more and 2.0 or less;
The composition for forming a surface layer forms a surface layer on which writing can be done with oil-based ink, the written handwriting can be erased when rubbed with a plastic eraser, and the written handwriting can be erased with a cloth. A surface layer-forming composition that contains at least a polyol, an aliphatic or aromatic polyisocyanate, and a silicon-modified acrylic polymer having a hydroxyl group, and that forms a polyurethane structure,
The polyol is a fluorine polyol,
The polyisocyanate is selected from pentamethylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, and isophorone diisocyanate;
an isocyanate group/hydroxyl group equivalent ratio of 0.65 or more and 2.0 or less;
the amount of the silicon-modified acrylic polymer having a hydroxyl group added is 0.1 or more and 1.2 or less relative to 100 parts by mass of the fluoropolyol;
The composition for forming a surface layer forms a surface layer on which writing can be performed with an oil-based ink and on which written marks can be erased when rubbed with a plastic eraser. A surface layer formed from the composition for forming a surface layer according to claim 1 . A surface material for writing on oil-based ink, comprising at least the surface layer according to claim 4 .