JPH09249839A - Photogravure ink composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a printing ink composition, enabling the improvement of printing or coating suitability without losing storage stability and capable of giving a homogeneous printing surface or coating surface free from unevenness in density. SOLUTION: This photogravure ink composition is composed of a binder resin, a solvent and a fluidity adjusting agent. As the fluidity adjusting agent, a nitrocellulose having a number average molecular weight of 1.5×10<5> to 3.0×10<5> or a weight average molecular weight of 3.5×10<5> to 6.0×10<5> and a nitrogen content of 11.5-12.2wt.% is used in the range of 0.1-25wt.% based on the total resin components in the ink composition.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a gravure ink composition used for cellophane for packaging foods, pharmaceuticals, clothing and the like, paper, plastic films, metal foils and the like.

[0002]

2. Description of the Related Art A solvent type gravure ink basically comprises a binder resin and a solvent, and various additives such as a colorant, a dispersant and a wax are used as necessary. The ink is obtained by dispersing and kneading a resin varnish dissolved in a solvent, a colorant and various additives with a ball mill or a sand mill. For the gravure ink, the viscosity and fluidity at the time of printing or coating are important characteristics for obtaining a uniform and precise coated surface, so that adjustment of the viscosity and fluidity of the ink is important. Generally, the fluidity of the gravure ink should be Newton's flow, and the Zahn cup No. 3
It is desirable that the viscosity of the product (manufactured by Separation Co., Ltd .: hole diameter 3 mm) is about 12 to 18 seconds.

As an additive for increasing the viscosity of gravure ink, finely divided silica (Japanese Patent Laid-Open No. 3-1
No. 40378), ethyl cellulose (JP-A 3-1
No. 92170), but there are many problems such as impairing dispersion of the pigment and poor yielding value of the ink due to poor compatibility with other resins. On the other hand, conventionally, nitrocellulose has been disclosed in JP-A-52-28524 and JP-B-60-40.
As disclosed in Japanese Patent Publication No. 993, etc., it is widely used as a main binder for gravure printing ink because of its excellent drying property, heat resistance and pigment dispersibility. However, nitrocellulose used as the main binder of gravure ink has a weight average molecular weight of 1.8 × 10 ^{3 to} 4.0 ×.
High molecular weight nitrocellulose having a relatively low molecular weight of 10 ³ and exceeding the above range has not been used because it significantly increases the viscosity of the ink when used as the main binder.

[0004]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a printing ink composition which improves printing or coating suitability without impairing storage stability and provides a uniform printing surface or coating surface without uneven density. To do.

[0005]

That is, the present invention comprises a binder resin, a solvent and a fluidity adjusting agent, and the fluidity adjusting agent has a number average molecular weight of 1.5 × 10 ^{5 to} 3.
0 × 10 ⁵ or weight average molecular weight 3.5 × 10 ⁵
Nitrocellulose having a concentration of 6.0 × 10 ⁵ and a nitrogen content of 11.5 to 12.2% by weight is used in an amount of 0.1 to 25% by weight based on the total resin content of the ink composition. A gravure ink composition is provided.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The gravure ink composition of the present invention contains a binder resin, a solvent and a fluidity adjusting agent, and if necessary, various additives such as colorants such as pigments and dyes, dispersants and waxes. including. Components other than the fluidity modifier in the ink are preferably compatible with nitrocellulose used as the fluidity modifier.

The number average molecular weight used as a fluidity regulator is 1.5 × 10 ^{5 to} 3.0 × 10 ^5, or the weight average molecular weight is 3.5 × 10 ^{5 to} 6.0 × 10 ⁵ or more and the nitrogen content is 1 or more.
1.5 to 12.2% by weight of nitrocellulose (hereinafter referred to as high molecular weight nitrocellulose) adjusts the viscosity and fluidity of the gravure ink within a suitable range. When the number average molecular weight and the weight average molecular weight of nitrocellulose are out of the above range, the viscosity of the obtained gravure ink,
The fluidity cannot be adjusted to a suitable range. Also,
When the nitrogen content of nitrocellulose is lower than 11.5% by weight, the solubility in the solvent used for the ink is poor, and
If it is more than wt%, it cannot be used because it increases the risk of spontaneous combustion.

The amount of the high molecular weight nitrocellulose used as the fluidity modifier is appropriately set within the range of 0.1 to 25% by weight based on the total resin content in the ink composition. When the amount of the high-molecular-weight nitrocellulose used is less than 0.1% by weight, the fluidity adjusting effect is not exhibited, and the viscosity of the obtained gravure ink composition stays at the same level as that of the solvent. Therefore, during printing or coating, Light and shade unevenness called streaks and swimming is likely to occur. Furthermore, even if the solid content concentration increases due to evaporation of the solvent during printing or coating, the viscosity of the gravure ink composition does not increase, making it difficult to control the amount of ink applied depending on the viscosity. In some cases, this may cause adverse effects such as different ink application amounts. On the other hand, if the amount of the high-molecular-weight nitrocellulose used exceeds 25% by weight, a phenomenon called whitening may occur when the ink is dried, the ink film is not glossy, and the adhesion to the printed material is poor, and the film This causes problems such as a marked decrease in strength.

The gravure ink composition of the present invention uses the high-molecular-weight nitrocellulose as a flow control agent to obtain a Zahn cup No. 3 (manufactured by Riaisha, hole diameter 3 mm)
It is preferable that the viscosity is adjusted to 12 to 24 seconds. Further, it is more preferable to adjust the viscosity to 12 to 18 seconds in order to improve the circulation of the ink by the pump provided in the printing machine or the coater and to improve the leveling of the ink during drying.

Examples of the binder resin include polyvinyl acetate, vinyl chloride / vinyl acetate copolymer, polyethylene, polypropylene, polyacetal, ethylene / vinyl acetate copolymer, ethylene / (meth) acrylic acid copolymer, α- Olefin / maleic anhydride copolymer, α
-Olefin / maleic anhydride copolymer esterification product, polystyrene, poly (meth) acrylic acid ester,
α-olefin / maleic anhydride / vinyl group-containing monomer copolymer, styrene / maleic anhydride copolymer, styrene / (meth) acrylic acid ester copolymer, polyamide, epoxy resin, xylene resin, ketone resin, petroleum resin , Rosin or its derivatives, coumarone indene resin, terpene resin, polyurethane resin, styrene / butadiene rubber, polyvinyl butyral, nitrile rubber, acrylic rubber, ethylene / propylene rubber, and other synthetic rubber,
Examples thereof include polyester resins, cellulose derivatives other than nitrocellulose, and sucrose esters, and one or more of these may be used.

Among them, polyester, acrylic resin,
Cellulose derivatives other than nitrocellulose, sucrose ester, and polyurethane have good compatibility with high-molecular-weight nitrocellulose and are therefore preferably used.

The solvent dissolves or stably disperses the binder resin and various additives such as a colorant, a dispersant and a wax, which are optionally used, and completely dissolves nitrocellulose added as a flow regulator. Must. Further, the solvent is preferably one that has excellent drying properties during gravure printing or coating. Examples of the solvent include hydrocarbon solvents such as toluene, xylene, n-hexane, n-heptane, cyclohexane and turpentine oil, methyl alcohol, ethyl alcohol,
Alcohol solvents such as isopropyl alcohol and butyl alcohol, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone,
Examples include methyl acetate, ethyl acetate, butyl acetate, ester solvents such as acetic acid / ethylene glycol monomethyl ether, acetic acid / ethylene glycol monoethyl ether, ether solvents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and tetrahydrofuran. , One or more of these are used. In the case of a mixed solvent composed of a plurality of solvents, it is sufficient that the mixed solvent has the above-mentioned characteristics.

The gravure ink composition of the present invention is used as a clear varnish for a top coat or the like when it does not contain a coloring agent. When it contains a colorant, it is used for printing as a general gravure ink. As the colorant, carbon black, azo lake type, insoluble azo type, condensed azo type, phthalocyanine type, quinacridone type, dioxazine type, isoindolinone type, benzimidazolone type, anthraquinone type, perylene type, perinone type, thioindigo type, Quinophthalone-based, aniline black-based, diketopyrrolopyrrole-based, nigrosine-based pigments and dyes are generally used.

Specific examples of the pigment include carbon black, fast yellow, cadmium yellow, yellow iron oxide, iron oxide black, chromophthal yellow, anthra pyridine yellow, isoindolinone yellow, nickel azo yellow, copper azomethine yellow,
Benzimidazolone yellow, quinophthalone yellow,
Nickel dioxin yellow, nickel dioxin yellow, flavans yellow, graphite, titanium yellow, disazo yellow, benzimidazolone orange, pyranthrone orange, perinone orange, para red, lake red, naphthol red, pyrazolone red, permanent red, madder lake, Thioindigo Bordeaux, Bengala, Lead Tan, Cadmium Red, Quinacridone Magenta, Perylene Vermilion, Perylene Red, Chromophthal Scarlet, Anthuanthrone Red, Gianthraquinolyl Red, Perylene Maroon, Benzimidazolone Carmine, Perylene Scarlet, Quinacridone Red, Pyran Sullon Red, Manganese Violet, Dioxazine Violet, Phthalocyanine Blue, Navy Blue, Cobalt Bu Over, ultramarine blue, indanthrone blue, phthalocyanine green, Pigment Green, chromium oxide, viridian, benzimidazolone Brown,
Examples thereof include bronze powder, white lead, zinc white, lithopone, titanium oxide, and pearl pigment, and one or more of these may be used. As the dye, one kind or two or more kinds of conventionally known dyes such as azo type, anthraquinone type and nigrosine type dyes are used alone or in combination with a pigment.

The gravure ink composition of the present invention is usually
It is produced by mixing and dispersing the raw materials using a kneading machine such as a ball mill, an attritor, a sand mill and a high speed agitator. When a pigment is contained as the colorant, after the pigment, the resin and the dispersant are mixed in advance, a high-concentration pigment dispersion in the form of paste or solid chips is produced by using a three-roll, two-roll or the like. It is manufactured by wet-dispersing with the above-mentioned kneading machine.
High molecular weight nitrocellulose is preferably dissolved in a solvent in advance and added to the gravure ink composition.

[0016]

The present invention will be described in more detail with reference to the following examples. “Parts” and “%” in each example represent “parts by weight” and “% by weight”, respectively. Table 1 shows the nitrogen content, number average molecular weight, and weight average molecular weight of the nitrocellulose used in the examples.

[0017]

[Table 1]

(Examples 1 to 8 and Comparative Examples 1 to 6) Table 2
The gravure ink composition having the composition shown in 1 was prepared by wet-dispersing the components excluding the nitrocellulose varnish in a sand mill for about 1 hour, and adding the nitrocellulose varnish after the dispersion. As nitrocellulose varnish, methyl ethyl ketone: toluene: isopropyl alcohol =
A solution prepared by dissolving nitrocellulose at a solid concentration of 5% in a mixed solvent of 45.35: 47.50: 2.15 was used.
The composition shown in Table 2 is the composition of the final ink.

[0019]

[Table 2]

With respect to the gravure ink compositions prepared in Examples and Comparative Examples, dispersion stability, viscosity and uniformity of coated surface were evaluated by the following methods. The results are shown in Table 3. (1) Dispersion stability The solid content concentration of the ink was diluted to 10% and left at room temperature, and the separation and sedimentation of the pigment was visually confirmed. ◯: Pigment does not sediment even after 1 week and is stably dispersed Δ: Pigment begins to sediment after 3 days ×: Pigment is precipitated in 1 day (2) Viscosity Zahn Cup No. The viscosity of the ink was measured with No. 3 (manufactured by Riaisha Co., Ltd., hole diameter 3 mm).

(3) Uniformity of coated surface A gravure ink composition prepared in Examples and Comparative Examples was applied to a substrate (a polyester film having a thickness of 6 μm) at a rate of 10 per minute.
Print at a speed of 0 m, dry thoroughly with hot air at 60 ° C,
The state of the coated surface was visually evaluated. Printing was performed by a direct gravure method using a solid plate of 250 lines of Heliocushograph (cell: Elongate 120 °). The WET coating amount of this plate was about 9 to 10 μm. ◯: Uniform application surface without unevenness of density such as swimming and streaks Δ: Application surface with slight unevenness of density such as swimming and streaks ×: Non-uniform application with unevenness of density such as swimming and streaks surface

[0022]

[Table 3]

As shown in Table 3, the gravure ink compositions prepared in the examples did not show remarkable thixotropy or the dispersion stability was impaired by the addition of nitrocellulose. The gravure ink compositions containing no fluidity modifier prepared in Comparative Examples 1 to 4 had considerably low viscosities, and were close to the viscosity of the solvent alone (about 11 seconds). There has occurred. Since the gravure ink composition prepared in Comparative Example 5 contained nitrocellulose having a relatively low molecular weight, the fluidity adjusting effect was small, and some swimming occurred on the coated surface. On the other hand, when the gravure ink compositions prepared in Examples 1 to 8 were used, a uniform coated surface could be obtained.

[0024]

Since the gravure ink composition of the present invention has good printing and coating suitability, it is possible to obtain a uniform coating surface without unevenness in density.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Motohiko Kashioka 2-3-13 Kyobashi, Chuo-ku, Tokyo Toyo Ink Manufacturing Co., Ltd.

Claims (1)

[Claims] 1. A binder resin, a solvent and a fluidity adjusting agent, wherein the fluidity adjusting agent has a number average molecular weight of 1.5.
× 10 ^{5 to} 3.0 × 10 ⁵ or a weight average molecular weight of 3.
5 × 10 ^{5 to} 6.0 × 10 ⁵ with a nitrogen content of 11.5 to 1
A gravure ink composition, wherein 2.2% by weight of nitrocellulose is used in the range of 0.1 to 25% by weight based on the total resin content in the ink composition.