JPH0570729A - Emulsion ink for porous printing - Google Patents

Abstract

PURPOSE:To provide the title ink which is free from increase density of in the printing, rise of a paper container, clogging, and set off of the ink by compounding a salt of a pyrrolidonecarboxylic acid deriv. into a water phase or by compounding an oil having a surface tension of a specified value into an oil phase. CONSTITUTION:The title ink is prepd. by thermally dissolving an evaporation preventive (e. g. a rosin-modified glycerin ester) in a motor oil at about 120 deg.C, cooling the resulting soln. to 30 deg.C, adding a colorant (e.g. carbon black) and an emulsifier (e.g. sorbitan monooleate) to the soln., dispersing the colorant on a three-roll mill, etc., adding to the soln. an aq. soln. contg. 1-70wt.% salt of a pyrrolidonecarboxylic acid deriv. (e. g. sodium DL-2-pyrrolidone-5- carboxylate) to give an emulsion, and passing the emulsion through a three-roll mill, etc., or by mixing an oil having a surface tension of 25dyn/cm or lower (e. g. a silicone oil) in an amt. accounting for at least 20wt.% of the whole oil component, the colorant, the motor oil, and the emulsifier, adding water, the evaporation preventive, etc., to the mixture, and emulsifying it by stirring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an emulsion ink for stencil printing, and more specifically, for heat-sensitive stencil printing having a proper viscosity and capable of obtaining a large number of high-quality printed matter without causing ink set-off. Regarding emulsion ink.

[0002]

2. Description of the Related Art The stencil printing method uses a stencil printing base paper as is well known, and ink is moved from one side of the base paper to the other side through a perforation portion formed by plate-making the base paper. Printing is performed on the surface of a printing target such as paper.

The perforated portion of this stencil printing base paper is, for example,
If it is a typewriter base paper, it is formed by a method of applying an impact force, and if it is a wax base paper, it is formed by a method of applying a frictional force with a writing brush or a method of utilizing electric energy such as discharge breakdown. The perforated portion formed by such a perforation method has a relatively small opening area. Therefore, in order to achieve the required movement of the ink through the perforated portion, it is relatively soft and has fluidity as a copy ink. It is necessary to use abundant ink or pressurize during printing to transfer the ink. However, using fluid ink,
When the ink is used for printing after being strongly pressed, it often causes inconvenient situations such as set-off of ink and roll-up of printing paper, as will be mentioned later.

By the way, in recent years, stencil printing base paper, in which plate making (perforation) is carried out using flash exposure or thermal energy of a thermal head or the like, has become popular. Since the stencil printing base paper suitable for plate making in such a heat-sensitive system is different from the stencil printing base paper of the type that is plate-made by the impact force, frictional force or electric energy, the hole diameter of the perforated plate is large. , When a conventional soft copying ink is used, more ink than necessary passes through the perforated portion, so-called "protrusion" or "bleeding" occurs, and a clear printed image cannot be obtained. There is a drawback. Such a phenomenon becomes more remarkable when the transfer ink during printing is strongly pressed. Recently, the copying machine has been moved from the two-cylinder type to the single-cylinder type in order to make the mechanism simple and compact. Due to the mechanism of the two-body type copying machine, more ink than necessary is not supplied to the surface of the base paper, so there is no problem even if soft ink is used, but in the case of the single-body type copying machine, Has a problem that when a soft ink is used, the ink leaks to the rear end portion of the master and stains the press roller or the printed matter. In addition to these, the ink (emulsion ink for stencil printing) that has been conventionally used has a non-drying oil to prevent it from drying on the plate cylinder during standing to prevent clogging of the perforated part of the printing plate. High boiling point solvents such as non-volatile minerals are used. However, if this emulsion ink is left in the stencil printing machine, only the water in the emulsion evaporates, the balance between water and oil is lost, and the proportion of oil increases. As a result, the proportion of water decreases relatively,
The viscosity of the emulsion ink decreases and the ink softens.

In order to solve these drawbacks, (1) the evaporation of water is suppressed by adding a polyhydric alcohol such as ethylene glycol, propylene glycol, sorbitol or glycerin, or polyethylene glycol as an evaporation inhibitor in the aqueous phase. And (2) a method of thickening the copying ink using organic bentonite (Japanese Patent Publication No. 54-23601). However, according to the method (1), the effect of suppressing the evaporation of water is not always sufficient. On the other hand, in the method of (2) above, # 30
Although effective for mimetic ink containing highly viscous oil such as motor oil and # 40 motor oil,
A copying ink containing a low-viscosity oil has a drawback that its thickening effect is not sufficient. Further, the copying ink containing a high-viscosity oil has a slow penetration rate into a printing paper, which causes a problem that "set-off" occurs during printing. Further, when a pigment-based thickening agent is used, there is a problem in that the perforated portion of the stencil printing plate is clogged and the density decreases as the number of printed sheets increases. Furthermore,
It has also been proposed to use an oil with a low boiling point to speed up drying after transfer in order to improve the set-off of the ink. This causes problems such as slow start-up of printing and clogging of perforated portions of the printing plate.

[0006]

DISCLOSURE OF THE INVENTION An object of the present invention is to prevent the ink from "bleeding out" or "bleeding" by making the ink flowing out from the perforations formed in the stencil printing base paper have an appropriate hardness. It is intended to provide a W / O type stencil printing emulsion ink which does not occur, and gives a clear printed image without causing paper rising (rolling up) and ink "set-off". Another object of the present invention is to provide an emulsion ink for heat-sensitive stencil printing which is suitable for use not only in a two-cylinder type stencil printer but also in a single-cylinder type stencil printer.

[0007]

The first object of the present invention is to provide an emulsion ink for stencil printing in which at least a colorant, an emulsifier and an aqueous phase are dispersed in an oil phase, wherein salts of a pyrrolidonecarboxylic acid derivative are contained in the aqueous phase. It is characterized by containing. The second aspect of the present invention is to provide an emulsion ink for stencil printing in which at least a colorant, an emulsifier and an aqueous phase are dispersed in an oil phase, and 20% by weight or more of the oil content used in the oil phase has a surface tension of 25 dyn / cm or less. It is characterized by having been made.

The inventors of the present invention have studied and studied from various angles in order to achieve the above object, and as a result, the initial viscosity of the ink is maintained for a long period of time according to the first and second means, Therefore, it was confirmed that a good image can be obtained. The present invention is made by this.

The present invention will be described in more detail below. According to the first emulsion ink for stencil printing of the present invention,
Since the aqueous phase contains salts of a pyrrolidonecarboxylic acid derivative having a very high hygroscopicity, evaporation of water in the ink is suppressed even when the ink is left standing, so that a balance between the aqueous phase and the oil phase is obtained. Does not collapse, maintains the initial viscosity for a long time,
Softening can be prevented.

Specific examples of the pyrrolidonecarboxylic acid derivative include 2-pyrrolidone-5-carboxylic acid, 3-pyrrolidone-5-carboxylic acid and 2-pyrrolidone-4-carboxylic acid. Further, specific examples of salts are, for example, lithium salt, sodium salt, potassium salt, ammonium salt or quaternary salt of organic amine, and as organic amine, for example, mono-, di-, tri-alkylamine, ethanolamine, Propanolamine and the like.

The first emulsion ink for stencil printing of the present invention is a W / O type emulsion comprising about 10 to 50% by weight of an oil phase and about 90 to 50% by weight of an aqueous phase. The pyrrolidonecarboxylic acid derivative is added to the aqueous phase. 1 to 70% by weight, preferably 5 to 50% by weight, based on the total amount of the aqueous phase. If it is less than 1% by weight, the effect of suppressing the evaporation of water is weak, and if it is more than 70% by weight, moisture absorption becomes large in a high humidity environment.

On the other hand, when attention is paid to improving the ink permeability to printing paper without changing the ink adhesion amount, the ink adhesion amount is h = √ (Pr ² · t / η) h: Ink adhesion amount P : Printing pressure r: Opening radius of base paper t: Pressing time η: Ink viscosity is defined, and the penetration of ink to printing paper in a static state is d = √ (2πr · γcos θ / η) d: Penetration rate r: Capillary diameter of printing paper γ cos θ: Contact wettability between printing paper and ink η: Ink viscosity

Here, it is the viscosity of the ink and the contact wettability between the printing paper and the ink that influence the ink permeability to the printing paper. Even if the viscosity of the ink is lowered, the penetrability is increased, but as is clear from the above equation, the amount of the ink adhered is increased and the prevention of set-off and curling is not improved. Therefore, by improving the contact wettability between the printing paper and the ink without changing the viscosity of the ink, the penetrability of the ink is improved and a clear image without offset can be obtained.

The surface tension of the lubricating oil used conventionally is 35 to 40 dyn / cm. If the surface tension is large, γ cos θ becomes small. Therefore, in the second emulsion ink for stencil printing of the present invention, two oils having a surface tension of 25 dyn / cm or less are used among the oils used in the oil phase.
By using 0% by weight or more, γ cos θ can be increased, appropriate penetrability can be obtained, and offset can be prevented. Furthermore, such inks also do not roll up. The "surface tension" referred to here is measured at 25 ° C.

As the oil component in the oil phase used in the present invention, conventionally known ones can be applied, for example, liquid paraffin, spindle oil, light oil, kerosene, machine oil, mineral oil of lubricating oil; olive oil, rapeseed oil. Vegetable oils such as castor oil and soybean oil are used. Also, synthetic oils can be used in the present invention. When using synthetic oils, various compounds are available. Representative synthetic vehicles are polyisobutylene, polyisobutenes, hydrogenated polydecenes, trimethylolpropane esters, neopentyl esters and pentaerythritol esters, di (2-ethylhexyl) sebacate, di (2-ethylhexyl) adipate, dibutyl phthalate. , Fluorocarbons, silicic acid esters, silanes, esters of phosphorus-containing acids, liquid urea, ferrocene derivatives, hydrogenated synthetic oils, chain polyphenyls, siloxanes and silicones (polysiloxanes), butyl substitution Examples thereof include alkyl-substituted diphenyl ethers represented by bis (p-phenoxyphenyl) ethers and phenoxyphenyl ethers. However, in the second emulsion ink of the present invention,
As described above, 20% by weight or more of the oil component used in the oil phase has a surface tension of 25 dyn / cm or less.

The emulsifier used in the present invention is preferably a nonionic surfactant such as sorbitan higher fatty acid ester, polyoxyethylene sorbitan higher fatty acid ester, fatty acid monoglyceride, fatty acid diglyceride and higher alcohol, alkylphenol, fatty acid and the like. Ethylene oxide adduct, etc., and one or a combination of two or more of these having different HLBs is used to prepare a highly stable emulsion.

Examples of the colorant used in the present invention include organic and / or inorganic pigments such as furnace carbon black, lamp black, cyanine blue, cyanine green, lake red, titanium oxide and calcium carbonate. ..

An appropriate amount of resin is added to the oil phase for the purpose of improving the stability of the emulsion ink over time and improving the binding property of the ink to paper. Examples of such a resin include alkyd resin, rosin-modified alkyd resin, polymer castor oil, rosin, polymerized rosin, hydrogenated rosin, rosin ester, hydrogenated rosin ester,
Terpene resin, petroleum resin, rosin-modified phenol resin,
Examples include maleic acid resins and rubber derivative resins.

On the other hand, in addition to water, conventionally known water-soluble resins, electrolytes, antifungal agents, antifreezing agents, antioxidants and the like can be used in combination with the aqueous phase.

In the emulsion ink of the present invention, the oil component in the oil phase is heated and dissolved and cooled (in the preparation of the first emulsion ink of the present invention, salts of pyrrolidonecarboxylic acid derivative are added together with the oil component. Heat to dissolve,
Allow to cool and heat melt together when adding resin. Further, in the preparation of the second emulsion ink of the present invention, 20% by weight or more of the oil component has a surface tension of 25 d.
yn / cm or less, and when a resin is added, it is heated and dissolved together with these oil components). It can be produced by adding a colorant and an emulsifier to this and mixing them, and then gradually adding the aqueous phase to emulsify. The order of mixing these components is not limited to the above, and can be changed as appropriate.

[0021]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples. Parts herein are by weight.

Example 1 Super oil (motor oil manufactured by Nippon Oil Co., Ltd.) 60 parts Rosin-modified glycerin ester 6.6 parts Carbon black 4 parts Sorbitan monooleate 4 parts Water 66 parts DL-2-pyrrolidone-5-carboxylic acid sodium salt 10 parts The rosin-modified glycerin ester was heated and dissolved in super oil at 120 ° C. in the above proportion and cooled to 30 ° C. Next, carbon black and sorbitan monooleate were added and dispersed with a three-roll mill. DL-2 in the dispersion
An aqueous solution in which sodium salt of pyrrolidone-5-carboxylic acid was dissolved was added and emulsified, and then the mixture was passed through a three-roll mill to obtain an emulsion ink for stencil printing. A commercially available heat-sensitive stencil printer (Ricoh Preport SS955) was used for this ink.
, The ink was sufficiently printed to spread the ink in the printing machine, and the printing was resumed after standing for 48 hours. The print density of the printed matter at this time was measured by a Macbeth densitometer RD-914. The print density in the normal state before standing was 1.05. The print density is 1.1 when restarted after being left for 48 hours.
It was 4. The set-off at that time was almost the same as in the normal state, and the paper did not rise or jam.

Example 2 An emulsion ink for stencil printing was obtained in the same manner as in Example 11 except that triethanolamine salt was used instead of the sodium salt of DL-2-pyrrolidone-5-carboxylic acid. This ink was tested in the same manner as in Example 1. The print density in the normal state before leaving is 1.12.
Met. The set-off at that time was almost the same as in the normal state, and there was no rise without paper or jamming.

Example 3 An emulsion ink for stencil printing was obtained in the same manner as in Example 1 except that the amount of DL-2-pyrrolidone-5-carboxylic acid sodium salt was increased to 20 parts. This ink was tested in the same manner as in Example 1. The print density in the normal state before standing was 1.04. The print density was 1.09 when the printing was resumed after being left for 48 hours. The set-off at that time was almost the same as in the normal state, and there was no rising or jam of the paper.

Comparative Example 1 An emulsion ink for stencil printing was obtained in the same manner as in Example 1 except that ethylene glycol was used in place of the sodium salt of DL-2-pyrrolidone-5-carboxylic acid. This ink was tested in the same manner as in Example 1. The print density in the normal state before standing was 1.05. When left for 48 hours and restarted, the print density is 1.2.
It was 8. The set-off at that time was more than twice as dirty as the normal state, and the paper was seen rising.

Example 4 Carbon black (colorant) 4 parts Motor oil # 40 24 parts Silicone oil (surface tension 20 dyn / cm) 6 parts Span emulsifier (HLB 3.7) 2.5 parts Twin emulsifier (HLB10.0) 2 parts Methyl paraoxybenzoate (preservative) 0.1 part Ethylene glycol (antifreeze) 4 parts Water 57.4 parts At the above ratio, first add carbon black and silicone oil and motor oil # 40 to 2 parts, and add span. Half of each of the system softener and the twin softener was added and kneaded with three rolls to sufficiently disperse the carbon. Next, the remaining motor oil # 40 and the emulsifier are added to this and mixed to form an oil phase. A water phase obtained by mixing water, ethylene glycol and a preservative is dropped into the above oil phase and stirred and emulsified at high speed to obtain W / O.
A type emulsion ink was prepared. When this ink was evaluated by a commercially available heat-sensitive stencil printer (manufactured by Ricoh Co., Ltd., Preport SS955), set-off did not occur, and winding up was not observed even when printing was performed at a printing speed of 120 sheets / minute.

Example 5 Carbon black (colorant) 4 parts Motor oil # 30 15 parts Silicon oil (surface tension 25 dyn / cm) 15 parts Span emulsifier (HLB 3.7) 2.5 parts Twin emulsifier (HLB10.0) 2 parts Methyl paraoxybenzoate (preservative) 0.1 part Ethylene glycol (antifreeze) 4 parts Water 57.4 parts An emulsion ink was prepared in the same manner as in Example 4 at the above ratio. The same evaluation as in Example 4 was recognized for this ink.

Example 6 Carbon black (colorant) 7 parts Motor oil # 30 15 parts Silicone oil (surface tension 21 dyn / cm) 10 parts Span emulsifier (HLB 3.7) 3.1 parts Twin emulsifier (HLB10.0) 2.5 parts Methyl paraoxybenzoate (preservative) 0.1 part Ethylene glycol (antifreeze) 4 parts Water 58.3 parts An emulsion ink was prepared in the same manner as in Example 1 at the above ratio. The same evaluation as in Example 4 was recognized for this ink.

Comparative Example 2 Carbon black (colorant) 4 parts Motor oil # 40 30 parts Span emulsifier (HLB3.7) 2.5 parts Twin emulsifier (HLB10.0) 2 parts Methyl paraoxybenzoate (preservative) 0 1 part Ethylene glycol (antifreeze agent) 4 parts Water 57.4 parts An emulsion ink was prepared in the same manner as in Example 1 at the above ratio. When this ink was evaluated in the same manner as in Example 4, set-off occurred and, when printing was performed at a printing speed of 120 sheets / min, winding occurred frequently.

Comparative Example 3 Carbon black (coloring agent) 7 parts Motor oil # 40 25 parts Span emulsifier (HLB 3.7) 3.1 parts Twin emulsifier (HLB10.0) 2.5 parts Methyl paraoxybenzoate (preservative) ) 0.1 part Ethylene glycol (antifreezing agent) 4 parts Water 58.3 parts An emulsion ink was prepared in the same manner as in Example 1 at the above ratio. When this ink was evaluated in the same manner as in Example 4, set-off occurred and, when printing was performed at a printing speed of 120 sheets / min, winding up occurred frequently.

[0031]

As is clear from the description of the examples, the use of the W / O type emulsion ink for stencil printing of the present invention causes an appropriate amount of ink to flow out from the stencil printing base paper, thus increasing the printing density. In addition, high-quality printed matter can be obtained without raising the paper container, clogging, and ink set-off.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Tateishi 1-3-3 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (3)

[Claims] 1. An emulsion ink for stencil printing in which at least a colorant, an emulsifier and an aqueous phase are dispersed in an oil phase, wherein the aqueous phase contains salts of a pyrrolidonecarboxylic acid derivative. Emulsion ink for printing. 2. The emulsion ink for stencil printing according to claim 1, wherein the proportion of the salts of the pyrrolidonecarboxylic acid derivative in the entire aqueous phase is 1 to 70% by weight. 3. An emulsion ink for stencil printing in which at least a colorant, an emulsifier and an aqueous phase are separated in the oil phase, wherein 20% by weight or more of the oil content used in the oil phase has a surface tension of 25 dyn / cm or less. Emulsion ink for stencil printing, characterized in that