JP2002020671A - Uv-curable marking ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solvent-free, UV-curable marking ink free from pollution problems in working environments and ignition problems, excellent adhesion to a substrate, capable of easy wiping-off the ink with a solvent after use. SOLUTION: This UV-curable marking ink comprises a UV-curable resin, a reactive solvent having a polymerizable double bond in the molecule and a colorant, and does not substantially contain any nonreactive solvent. The amount of eluted materials into methyl alcohol from the ink after UV curing according to the method disclosed in the specification is 10-20 mass%. This ink is excellent in quick curing properties and wiping-off properties with solvents.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultraviolet-curable marking ink, and more particularly to a flaw detecting portion detected by a non-destructive flaw detection method for a metal material such as a steel plate or a tube, or various synthetic resin products or rubber products. Mark to facilitate the detection in the downstream process, or in the case of producing multiple products on one production line, when classifying intermediate products and performing lot management, The present invention relates to a marking ink used for marking characters, figures, figures, and the like.

[0002]

2. Description of the Related Art Marking inks are liquid-based inks used to apply identification marks to surfaces of various metal products, synthetic resin products, rubber products (including intermediate products such as plates, pipes, and wires). The most widely used coloring material is a marking used for marking a flaw detection part found in a quality inspection such as a flaw detection test by a steel material manufacturer or for lot management.

As a marking ink used in such applications, a volatile solvent type ink has been widely used.
Recently, a shift to a solvent-free type has been studied from the viewpoint of work environment problems and the prevention of ignition, and hot melt type inks have been developed. However, the hot-melt type marking ink has a relatively narrow application temperature range, and it is difficult to obtain sufficient adhesion under low-temperature conditions.When it is exposed to high temperatures after marking, it softens and is transferred to sites other than the marking locations. And the use is considerably limited.
Moreover, it is generally difficult to remove a hot-melt ink having a high sticking force, and it is troublesome and troublesome to remove the mark at the time of product shipment after use as a mark.

[0004] An ultraviolet curable ink is also known as another non-solvent type marking ink. Since this ultraviolet curable ink is a non-solvent type ink, it does not have a problem of deterioration of working environment and no problem of ignition. It is recommended as a high-performance marking ink because it has excellent fixation strength indicated by the melt-type ink, particularly excellent under low-temperature conditions, and does not transfer ink even at high temperatures.

[0005]

The present applicant has long been studying such a solvent-free type ink for UV-curable marking, but the only difficulty found in the ink is that the ink after use has been used. It is difficult to wipe the mark. That is, this type of ink has a strong cross-linking structure after being cured by ultraviolet light, and thus exhibits an excellent fixing force. On the other hand, this feature causes a disadvantage that the work of removing the used mark becomes complicated. That is, the mark used as a landmark for lot management and product classification as an intermediate product must be removed at the time of shipment as a final product, but the mark is firmly fixed to the surface to be marked with a cross-linked structure. For,
It is difficult to wipe off with a solvent, and if it is forcibly peeled off with a spatula or the like, the marked product may be damaged.

The present invention has been made in view of such a problem, and has as its object to eliminate the advantages of the solventless marking ink, particularly, without causing the problem of working environment contamination and ignition, and preventing the ink from being ignited. It is an object of the present invention to provide a marking ink which can be easily wiped off from the surface to be marked with a solvent after use, while enjoying the feature of exhibiting an excellent fixing force to a mark material.

[0007]

Means for Solving the Problems The marking ink of the present invention which can solve the above problems includes an ultraviolet curable resin, a reactive solvent having a polymerization reactive double bond in a molecule, and a colorant. A UV curable marking ink substantially free of non-reactive solvents, having a gist in which the amount of elution to methyl alcohol determined by the following method after marking is 10 to 20% by mass. I have.

[Amount of Elution in Methyl Alcohol] A 0.05 g sample ink is applied on a glass plate so as to have a dry thickness of about 80 μm.
° C) and ultraviolet light (wavelength: 365 nm, output: 160 mV /
cm ² ) for 5 seconds, and then the mass (X ₀ ) of the glass plate having the cured ink film is measured. Next, the glass plate having the ink film was immersed in methyl alcohol at 25 ° C. for 6 hours, and then the methyl alcohol was wiped off and dried, and the mass (X ₁ ) was measured. ). Elution amount (% by mass) = [X ₁ / (X ₀ −X ₁ )] × 100

A preferred composition of the marking ink according to the present invention is an ultraviolet curable resin: 10 to 50% by mass, a reactive solvent having a polymerization reactive double bond in a molecule:
40 to 80% by mass, and particularly preferred as the ultraviolet curable resin is epoxy acrylate,
It is a resin containing at least one monomer component selected from the group consisting of polyester acrylate, urethane acrylate, and polyether acrylate. As the reactive solvent, at least one selected from a monofunctional acrylic monomer and a monofunctional vinyl monomer is preferably used. In order to shorten the marking time by accelerating the curing by UV irradiation,
It is desirable to add an appropriate amount of a polymerization initiator and / or a photosensitizer. As the colorant, an inorganic pigment or dye such as titanium white can be arbitrarily selected and used.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The ultraviolet-curable marking ink of the present invention comprises, as essential components, an ultraviolet-curable resin, a reactive solvent having a polymerization-reactive double bond in a molecule, and a pigment, as described above. , UV-curable resin: 10% by mass or more, 50% by mass, more preferably 20% by mass or more,
40% by mass or less, a reactive solvent having a polymerizable double bond in the molecule: 40% by mass or more and 80% by mass or less, more preferably 50% by mass or more and 70% by mass or less, and a pigment: 1% by mass or more. UV curing containing 20% by mass or less, more preferably 5% by mass or more and 15% by mass or less, preferably further containing a small amount of a polymerization initiator and / or a photosensitizer, and substantially containing no non-reactive solvent. This is a marking ink, and a polymerization reactive solvent is used as a solvent, and a suitable viscosity can be ensured by the reactive solvent, so that excellent marking workability can be obtained. In addition, since the reactive solvent is polymerized and solidified by irradiation with ultraviolet rays, the solvent is not volatilized and emitted out of the system, and problems of pollution of the working environment and ignition can be avoided. Further, the marking ink of the present invention has an ultraviolet curable resin as a main curing component, and is cross-linked by ultraviolet irradiation and firmly adheres to the surface of the mark target material. The cured product is obtained by the above method. Elution amount to methyl alcohol is 10% by mass or more, 2
It is 0% by mass or less, and after use, can be easily wiped and removed by using a ketone-based solvent such as acetone.

Hereinafter, the functions, types, and preferable contents of the constituent components of the marking ink of the present invention will be described in detail.

[Ultraviolet curable resin] This resin is a general term for resins having a functional group in a molecule which undergoes a polymerization reaction when excited by ultraviolet rays. Preferred examples thereof include epoxy (meth) acrylate and polyester (meth). ) Acrylate, urethane (meth) acrylate, polyether (meth) acrylate, polybutadiene (meth) acrylate, polystyryl (meth) acrylate, polycarbonate diacrylate, tripropylene glycol di (meth) acrylate, hexanediol di (meth) acrylate, triacrylate Methylol propane tri (meth) acrylate, pentaerythritol tri (meth)
An oligomer or a low molecular weight polymer containing a polyfunctional (meth) acrylate such as acrylate as at least one kind of monomer component is exemplified. Of these, particularly preferred are oligomers and low molecular weight polymers containing at least one of epoxy acrylate, polyester acrylate, urethane acrylate and polyether acrylate as a monomer component. These can be used alone or in combination of two or more as needed.

These UV-curable resins give the ink according to the present invention an appropriate viscosity so as to enhance the workability of marking and to promote the curing by UV rays in a short time.
It is desirable to use those having an average molecular weight of 200 or more and 10,000 or less, more preferably 300 or more and 3,000 or less.

The UV-curable resin preferably used in the present invention is, for example, "Aronix" (trade name, manufactured by Toagosei Co., Ltd.), "Unidick" (trade name, manufactured by Dainippon Ink), "Hitaroid" (trade name, manufactured by Hitachi Chemical Co., Ltd.) "Viscort" manufactured by Osaka Organic Co., Ltd. "XP Series" manufactured by Nippon Gosei Co., Ltd.
And so on.

The preferred amount of the UV-curable resin in the ink is 10% by mass or more and 50% by mass or less. If the amount is less than 10% by mass, the curing speed by the irradiation of ultraviolet rays becomes slow, and fast curing (quick drying) occurs. However, if the amount is more than 50% by mass, the viscosity of the ink becomes too high, and the marking workability is deteriorated or the storage stability is deteriorated. Can also get worse. The lower limit of the compounding amount is more preferably 20% by mass, more preferably 25% by mass, and the more preferable upper limit is 40% by mass, more preferably considering storage stability, marking workability, adhesion, curing speed, and the like. 35% by mass.

[Reactive solvent having a polymerization-reactive double bond in the molecule] This component has a polymerization-reactive double bond and acts as a solvent for the ultraviolet-curable resin. Styrene, methyl (meth) acrylate, phenoxyethyl (meth) acrylate, butyl (meth) acrylate, benzyl (meth) acrylate, allyl (meth) acrylate, butoxyethyl ( (Meth) acrylate, dicyclopentenyl (meth) acrylate, glycidyl (meth) acrylate, ethoxyethyl (meth) acrylate, hydroxyethyl (meth) acrylate,
Monofunctional acrylates and vinyl compounds such as vinyl acetate are exemplified. Of these, particularly preferred are methyl methacrylate, phenoxyethyl acrylate,
Glycidyl methacrylate, phenoxyethyl methacrylate, and styrene. These reactive solvents can be used alone or in combination of two or more as needed.

These reactive solvents have the function of imparting an appropriate viscosity to the ink according to the present invention to enhance the workability of marking, and also have the function of being excited by ultraviolet rays and polymerizing to shorten the curing time. In order to effectively exert such an effect, it is desirable to select the compounding amount from the range of 40% by mass or more and 80% by mass in the ink.

If the amount is less than 40% by mass, the absolute amount of the solvent tends to be insufficient, and the marking workability or storage stability tends to be deteriorated. In some cases, the absolute amount tends to be insufficient, and the curing speed is slow, and the quick-setting (quick-drying) tends to be insufficient. The lower limit of the compounding amount is more preferably 50% by mass, more preferably 55% by mass, and the upper limit is more preferably 70% by mass, and still more preferably 65% by mass, in consideration of the marking workability, storage stability, curing speed and the like. It is.

[Colorant] The colorant is a component to be added for the purpose of coloring the marking ink, and an inorganic or organic colorant is arbitrarily selected and used. Specifically, all pigments and dyes used for general inks and paints can be used, but the most common inks of the present invention for the purpose of marking are dispersion stability such as titanium white and zinc white. It is a fine-grained white inorganic pigment excellent in color, and it is recommended as a preferable white pigment for hiding the ground color of a metal or the like and making the mark as a mark clearer. Depending on the type (ground color) of the material to be marked, the effect of the mark may not be effectively exerted with a white pigment. In such a case, a colorant such as carbon black or an organic dye is used in combination. Any color may be used. The amount of these coloring agents varies depending on the type, and therefore cannot be determined uniformly. In short, the amount is not particularly limited as long as it can give the ink a color suitable for a mark, but the standard amount is shown. Then, the ratio in the ink is 5
It is not less than 15% by mass and not less than 15% by mass.

[Polymerization Initiator and / or Photosensitizer] These components are used for initiating polymerization or accelerating polymerization initiation upon irradiation of the ultraviolet curable resin and the reactive solvent with ultraviolet light. When a UV curable resin or a reactive solvent with high polymerization activity is used, it may not be blended. However, usually, the curing reaction proceeds rapidly to give quick curing (quick drying). Preferably 0.1 to the total of the resin and the reactive solvent.
It is desirable to use it in the range of not less than 5% by mass, more preferably not less than 0.5% by mass and not more than 1.5% by mass. If the amount is less than 0.1% by mass, the curing speed at the time of marking may be slow, resulting in insufficient short-curing. On the other hand, if the amount exceeds 5% by mass, the pot life as the ink may be shortened, and the marking workability may deteriorate. Or the cured product becomes excessively hard, and the solvent wiping property after use tends to deteriorate.

The type of the polymerization initiator is not particularly limited, and benzoin-based, acetophenone-based, benzophenone-based, and other compounds that generate radicals by ultraviolet light or heat can be used. Examples of the photosensitizer include aliphatic amines, aromatic amines, and thioxanthones.

The main components constituting the marking ink according to the present invention are as described above. In order to further enhance the adhesion of the marking film to the substrate, an appropriate amount of an adhesion improving component such as natural rosin or petroleum resin is used. A suitable amount of a plasticizer to contain hydrogenated petroleum resin, polyhydric alcohol, or to prevent cracking of the marking film, for example, dibutyl phthalate, dioctyl phthalate, epoxidized oil, tricresyl phosphate, rosin derivative, etc. It can also be contained.

The -marking ink of the present invention using the above-mentioned raw material components may be obtained by mixing and stirring the above-mentioned raw materials in an arbitrary order and uniformly dissolving or dispersing them.
This is a method in which the above-mentioned ultraviolet curable resin is dissolved in a reactive solvent, and a coloring agent is blended with the resin to uniformly mix and disperse it. When a dye or a plasticizer is compounded, it may be added at any time during the mixing and dispersion. When a polymerization initiator or a photosensitizer is blended, it is added at the end of ink preparation or blended immediately before use in order to extend the pot life as a marking ink and improve storage and marking workability. It is desirable.

As a method for evaluating the performance of the ultraviolet curable marking ink of the present invention thus obtained in advance, the following method is employed. That is, this ink cures in as short a time as possible assuming a marking operation in a continuous operation process, shows a softening temperature that does not transfer to other parts after curing, and uses a solvent such as acetone. It is necessary to be able to easily wipe off and remove them, and in the present invention, as a means for evaluating their performance, the elution amount to methyl alcohol after ultraviolet curing under the following conditions is evaluated.

That is, 0.05 g of the sample ink was coated on a glass plate so as to have a dry thickness of about 80 μm, and ultraviolet rays (wavelength: 365 ° C.) were applied from 3 cm above the coated surface at room temperature (25 ° C.).
nm, output: 160 mV / cm ² ) for 5 seconds, and then the mass (X ₀ ) of the glass plate having the cured ink film is measured. Next, the glass plate having the ink film was heated at 25 ° C.
After immersion in methyl alcohol for 6 hours, the methyl alcohol was wiped off and dried, and its mass (X ₁ ) was measured.
The elution amount (% by mass) with respect to methyl alcohol is determined by the following equation. Elution amount (% by mass) = [X ₁ / (X ₀ −X ₁ )] × 100

In the present invention, it is important that the amount of the ink cured product eluted with respect to methyl alcohol determined by the above method falls within the range of 10% by mass or more and 20% by mass or less. If it exceeds, the cured product (mark) as a mark is insufficiently cured, resulting in insufficient heat resistance. In particular, when applied to a high-temperature mark-receiving material, there is a fear that transfer to other parts may occur.
If the amount is less than 0% by mass, it is difficult to remove by wiping with acetone or the like. The particularly preferred elution amount is 11% by mass or more and 15% by mass or less for facilitating wiping with acetone or the like in a moderately cured state. Therefore, in preparing the ink of the present invention, the type and composition of the ultraviolet curable resin, the reactive solvent, the polymerization initiator and the photosensitizer, etc., so that the elution amount of the obtained ink is within the above range. It is necessary to adjust the amount and the like.

The marking method using the marking ink and the type of the marking device are not limited at all, and a known marking device such as a spray type, a roll coating type, and an ink jet type can be arbitrarily selected and used. Then, when ultraviolet light is irradiated from the outer surface side after marking, the ultraviolet polymerizable component in the ink component is polymerized together with the reactive solvent, and partially cures in a very short time of, for example, 1 to 7 seconds while being crosslinked. A mark that does not cause transfer to a mark can be obtained. At this time, for example, it is preferable to heat by sending warm air or the like, because the curing time can be further reduced.
However, if the temperature is too high, the three-dimensional crosslinking of the ink may proceed excessively and the solvent wiping property may be impaired. Therefore, it is desirable to suppress the heating temperature to about 50 ° C. or less.

At this time, the amount of the cured product eluted in methyl alcohol slightly changes depending on the intensity of the ultraviolet light to be irradiated, the irradiation time, the temperature at the time of the irradiation, and the like. It is the type and amount of the ultraviolet curable resin and the reactive solvent contained therein, and the type and amount of the polymerization initiator and the photosensitizer, and if these are properly adjusted at the ink preparation stage, the ultraviolet irradiation conditions Even if such changes slightly occur, the amount of the cured product eluted in methyl alcohol does not change significantly. However, if these conditions change excessively, even if the ink has the proper composition, the amount of elution to methyl alcohol may change considerably. It is good to adopt.

The present invention is constituted as described above. In particular, it is desirable to control the above-mentioned elution amount to methyl alcohol in a cured state of a marking ink essentially containing an ultraviolet curable resin and a reactive solvent within an appropriate range. Thereby, while preventing transfer of the cured product (mark) as a mark to other portions,
After use, it can be easily wiped off with acetone or the like, and it has become possible to provide a marking ink that satisfies the characteristics required as a temporary marker during continuous production of various products including intermediate products.

[0030]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples, and the present invention is not limited thereto. Modifications may be made and all of them are included in the technical scope of the present invention.

Examples and Comparative Examples UV curable resins, reactive solvents, pigments (titanium oxide), and curing catalysts were blended in the formulations shown in Tables 1 to 4 below to prepare UV curable marking inks. Was measured for the amount of methanol eluted by the method described above, and a sticking force measurement test and an acetone wiping test were performed by the following methods. The symbols of the ultraviolet curable resin and titanium oxide shown in each table are as follows. [Eluted amount in methyl alcohol]: Measured by the above method

[Measurement Method of Adhesion Force] 0.05 g of the sample ink was applied on a steel plate so that the dry thickness was about 80 μm, and ultraviolet rays (wavelength:
365 nm, output: 160 mV / cm ² ) for 5 seconds, then cut a 1 cm square into the center of each test piece to penetrate the coating film and reach the bare ground (100 divisions). The adhesion state of the coating film after sticking an adhesive tape on and peeling off is visually observed. Then, the adhesive strength is evaluated based on the number of portions where the coating film remains without being peeled during the 100 divisions.

[Acetone wiping test]
05 g was applied on a steel plate so as to have a dry thickness of about 80 μm, and 5 cm of ultraviolet light (wavelength: 365 nm, output: 160 mV / cm ² ) was applied from 3 cm above the coated surface at room temperature (25 ° C.).
After irradiation for 2 seconds, the surface of each test piece is wiped several times with a cloth impregnated with acetone, and the state of removal of the coating film after the wiping is visually evaluated according to the following criteria. ：: Easy wiping possible, △: Wiping takes time but possible wiping, ×: Wiping not possible.

[Product description] "Hitaloid @ 7851": UV curable resin "Aronix" M-9050 manufactured by Hitachi Chemical Co., Ltd .: UV curable resins "Unitic V-5510" and "Unitic V" manufactured by Toagosei Co., Ltd. -4421 ": UV curable resin manufactured by Dainippon Ink and" R-900 ": Titanium oxide manufactured by DuPont.

The results are as shown in Tables 1 to 4. Examples (Tables 1 and 2) satisfying the requirements of the present invention all have a methanol elution amount in an appropriate range, and have a fixing power and acetone. Good results were obtained in all of the wiping properties. On the other hand, in Comparative Examples (Tables 3 and 4) lacking the prescribed requirements of the present invention, the adhesion was poor or the acetone wiping property was poor, and thus the ink was not suitable as a marking ink.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

[Table 4]

[0040]

The present invention is constituted as described above, and the amount of eluted methyl alcohol in the cured state of the ultraviolet-curable marking ink essentially containing the ultraviolet-curable resin and the reactive solvent is adjusted to an appropriate range. By controlling, the original properties as an ultraviolet curable marking agent, that is, there is no solvent volatilization during use, there is no danger of atmosphere pollution and ignition, and it shows excellent adhesion to various mark materials. In addition to the features described above, the used ink can be easily wiped and removed with acetone or the like while preventing transfer after marking, and a marking ink that is extremely excellent in practical use can be provided.

Accordingly, this marking ink is used for various materials and shapes such as plates, rods, pipes and wires made of iron and steel, non-ferrous metals, glass, ceramics, various synthetic resins and rubber products. It can be used very effectively for marking.

Claims (5)

[Claims] An ultraviolet-curable marking ink comprising an ultraviolet-curable resin, a reactive solvent having a polymerization-reactive double bond in a molecule and a colorant, and substantially free of a non-reactive solvent, The amount of elution to methyl alcohol determined by the following method after ultraviolet curing is 10 to 20% by mass.
An ultraviolet-curable marking ink, characterized by being: [Amount dissolved in methyl alcohol] 0.05 g of sample ink
Is applied on a glass plate so as to have a dry thickness of about 80 μm, and 5 cm of ultraviolet light (wavelength: 365 nm, output: 160 mV / cm ² ) is applied from 3 cm above the coated surface at room temperature (25 ° C.).
After irradiation for 2 seconds, the mass (X ₀ ) of the glass plate having the cured ink film is measured. Then, after immersing the glass plate having the ink film in methyl alcohol at 25 ° C. for 6 hours,
The methyl alcohol is wiped off, dried, and its mass (X ₁ ) is measured. Elution amount (% by mass) = [X ₁ / (X ₀ −X ₁ )] × 100 2. UV-curable resin: 10 to 50% by mass,
Reactive solvent having a polymerization-reactive double bond in the molecule: 40
The ultraviolet-curable marking ink according to claim 1, wherein the ink contains about 80% by mass. 3. The resin according to claim 1, wherein the ultraviolet curable resin is a resin containing at least one monomer component selected from the group consisting of epoxy acrylate, polyester acrylate, urethane acrylate, and polyether acrylate. Marking ink. 4. The marking ink according to claim 1, wherein the reactive solvent is at least one selected from a monofunctional acrylic monomer and a monofunctional vinyl monomer. 5. The marking ink according to claim 1, further comprising a polymerization initiator and / or a photosensitizer.