JPS61255967A - Emulsion ink for porous printing - Google Patents

Abstract

PURPOSE:To obtain ink which does not cause any increase in print density when, initiating printing after standing in a rotary porous printing press, and causes neither whirling up of paper nor offsetting of ink, by incorporating a solvent having a specified b.p. in the oil phase of a W/O emulsion. CONSTITUTION:The titled ink is obtd. by incorporating at least 5wt% (based on the total quantity of the water phase of an emulsion) solvent having a b.p. of 180-270 deg.C in the oil phase of a W/O emulsion consisting of 10-50wt% oil phase and 90-50wt% water phase. The b.p. (180-270 deg.C) of the solvent is higher than that of water and lower than that of non-drying oil or nonvolatile mineral oil which is the main component of the oil phase. When a solvent having a b.p. of lower than 180 deg.C is used and a porous printing press is left to stand without conducting printing over a long period of time, ink is dried on a plate cylinder to cause clogging, while when the b.p. exceeds 270 deg.C, lower ing in viscosity after standing can not be prevented as in a conventional oil phase.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to emulsion ink for stencil printing, and more specifically, to increase printing density after standing, paper flying up,
The present invention relates to an emulsion ink for stencil printing which prevents ink set-off and is suitably used in rotary stencil printing machines, particularly single cylinder stencil printing machines.

(Prior Art) In recent years, rotary stencil printing machines have become increasingly automated using microcomputers, etc., making them easier to operate.As a result, there is a demand for being able to obtain high-quality printed matter immediately after printing begins. There is.

However, in conventional rotary stencil printing machines, unlike offset printing machines, the ink is kept dry so that it does not need to be cleaned every day. However, 1
When printing overnight or after being left for 2-3 days, the printing density is higher than normal printing density, and the printing paper sticks to the plate cylinder, causing paper to fly up or jamming, and the ink to set off more often. However, in order to obtain good quality printed materials, a considerable number of sheets (especially 1,000 sheets or more in the case of a single-cylinder stencil printer) must be printed.

Conventional emulsion ink for stencil printing uses high-boiling point solvents such as non-drying oils and non-volatile mineral oils (motor oil, liquid paraffin, spindle oil, machine oil, castor oil, etc.)
No. 65), when this emulsion ink is left in a stencil printing machine, only the water in the emulsion evaporates, which upsets the balance between water and oil and increases the proportion of oil. As a result, the proportion of water is relatively reduced, the viscosity of the emulsion ink is reduced, and the ink becomes soft.

As a result of this softening of the ink, when printing starts after being left unused, the ink flows out of the plate cylinder and a large amount of ink adheres to the paper, resulting in the print density being higher than the normal print density as described above. In addition, the printing paper sticks to the plate cylinder, causing paper to fly up or jam.Furthermore, the next paper overlaps with the ink transferred to the paper before it dries, causing ink to adhere to the back side of the paper and cause ink to dry. A phenomenon of increased set-off occurs.

(Problems to be Solved by the Invention) An object of the present invention is to eliminate the drawbacks of the prior art described above, and to avoid increasing the print density at the start of printing after being left unused in a rotary stencil printing machine, and to prevent paper flying up and ink. To provide an emulsion ink for stencil printing that does not cause set-off.

(Means for Solving the Problems) In order to achieve the above object, the present inventors have conducted various studies and found that the oil phase of water-in-oil emulsion ink has a boiling point of 18.
5% of the solvent at 0 to 270°C to the total amount of the aqueous phase of the emulsion.
By containing more than % by weight, as the water in the emulsion evaporates, the oil solvent also evaporates slightly, keeping the amount of change in the ratio of water to oil small, thereby preventing a decrease in the viscosity of the ink and preventing softening. The present invention was achieved by discovering that this can be done.

The present invention has an oil phase of about 10-50% by weight and an aqueous phase of about 90-50% by weight.
Consisting of a water-in-oil emulsion consisting of ffi amount%,
The emulsion ink for stencil printing is characterized in that the oil phase contains a solvent having a boiling point of 180 to 270° C. in an amount of 5% by weight or more based on the total amount of the aqueous phase.

The emulsion ink for stencil printing of the present invention has an oil phase of about 10
It consists of a water-in-oil emulsion comprising ~50% by weight of an aqueous phase and about 90-50% by weight of an aqueous phase.

The oil phase is composed of oil components, emulsifiers, colorants, resins, etc., and the aqueous phase is composed of water, water-soluble resins, electrolytes, fungicides, water evaporation inhibitors, antioxidants, etc.

As each of these components, known components that do not inhibit emulsion formation are used. Among these components, the components other than water, oil and emulsifier are optional components and can be added as appropriate.

Further, the emulsion ink for stencil printing of the present invention is as follows.

The oil phase contains a solvent having a boiling point of 180 to 270°C in an amount of 5% by weight or more, preferably 10% by weight or more, based on the total amount of the aqueous phase.

The boiling point of this solvent is 180 to 270°C, which is higher than the boiling point of water and lower than the boiling point of the non-drying oil and non-volatile mineral oil that form the main component of the oil phase (so-called medium boiling point solvent). If the boiling point of the solvent is less than 180° C., if the stencil printing machine is left unused for a long period of time without printing, the ink will dry on the plate cylinder and cause clogging. Moreover, if the boiling point exceeds 270°C, the components will not be different from those of conventional oil phases, and it will not be possible to prevent the viscosity from decreasing after standing.

The medium boiling point solvents mentioned above have a boiling point of 180 to 270.
Any petroleum solvent, such as ink solvent 24, can be used as long as it can melt the resin added to the ink at ℃.
01 point 242-260°C, produced by Mitsubishi Oil Co., Ltd.), 8-stone Isosol 400 (boiling point 206-257°C, manufactured by Nippon Oil)
Co., Ltd.), Shell Disbasol (boiling point 205-252℃)
, manufactured by Shell Chemical Co., Ltd.), Nisseki No. 4 solvent (boiling point 2
38 to 267°C, manufactured by Nippon Oil Co., Ltd.).

In the present invention, in addition to the solvents with a boiling point of 180 to 270°C, the solvents that form the oil phase include olive oil, castor oil, salad oil, sardine oil, whale oil, machine oil, spindle oil, etc. that are generally used in oil-based stencil inks. Non-drying oils and non-volatile mineral oils are used.

A resin is added to the emulsion ink of the present invention for the purpose of improving the storage stability of the ink, improving the adhesion of the ink to paper, the properties, and the quality of printed matter. Examples of these resins include phenol resins, maleic acid resins, petroleum resins, alkyto resins, and rubber derivative resins. Examples of water-soluble resins include carboxymethyl cellulose, methyl cellulose, and gum arabic. These resins also have the effect of preventing water evaporation.

In addition, as the emulsifier used to constitute the water-in-oil emulsion, nonionic surfactants are preferably used, and sorbitan higher fatty acid esters (for example, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan tristearate, sorbitan monooleate, sorbitan trioleate, sorbitan sesquioleate, etc.), fatty acid monoglycerides, such as oleic acid monoglyceride, oleic acid diglyceride, and ethylene oxide adducts of higher alcohols, alkylphenols, fatty acids, etc. Combining two or more of these low HLB and high HLB, H
A highly stable emulsion can be obtained by adjusting the LB.

As the evaporation inhibitor, polyhydric alcohols such as ethylene glycol, propylene glycol, sorbitol, and glycerin, polyethylene glycol, and the like are used. Further, as the coloring agent, known ones such as furnace carbon black, lamp blank, brilliant fast scarlet, etc. can be used. As the electrolyte, for example, sodium sulfate, sodium hydrogen phosphate, sodium borate, etc. are used. As the fungicide, for example, phenols, methyl p-oxybenzoate, ethyl p-oxybenzoate, sorbic acid, dehydroacetic acid, salicylic acid, etc. are used. As the antioxidant for resins, for example, dibutylhydroxytoluene, propyl gallate, butylhydroxyanisole, etc. are used.

The emulsion ink for stencil printing of the present invention can be prepared, for example, by heating and dissolving the oil component and resin, adding a colorant and an emulsifier to the mixture, mixing the mixture, and then gradually adding an aqueous electrolyte solution to emulsify the mixture. It can be manufactured by The mixing order of these components is not limited to the above and can be changed as appropriate.

(Effect of the invention) The emulsion ink for stencil printing of the present invention does not cause a decrease in ink viscosity even after being left for 2.3 days. Therefore, when rotary stencil printing is performed using the ink of the present invention, Even at the start of printing, it is possible to quickly shift to normal operation without causing an increase in printing density due to excessive ink outflow, paper flying up, clogging, ink set-off, etc.

Furthermore, although the emulsion ink of the present invention contains a solvent with a lower boiling point than conventional emulsion inks, it is a practical product that does not dry out in a stencil printing machine even if left for about 40 days. It has been found. Furthermore, when the emulsion ink for stencil printing of the present invention is used,
Set-off during normal printing is also reduced compared to when using conventional emulsion inks.

Therefore, the emulsion ink for stencil printing of the present invention,
When used in a rotary stencil printing machine, especially a single cylinder stencil printing machine, even when printing is started after being left unused, it is possible to return to a normal printing state in a short period of time with a significantly smaller number of test prints than in the past. Good printed matter can be obtained.

The present invention will now be explained in more detail with reference to Examples and Comparative Examples. Parts in the examples mean parts by weight.

(Example 1) Furnace carbon black (colorant) 3 parts Ink Solvent 240 (solvent) 14 parts Rosin-modified phenolic resin (resin) 9.8 parts Sorbitan sesquioleate (emulsifier) 5 parts dibutylhydroxytoluene (antioxidant) 0.1 part water
65 parts Sodium sulfate (electrolyte) 3 parts Methyl oxybenzoate (anti-mold agent) 0.1 part Ink Solvent 240 and rosin-modified phenol resin in the above ratio were melted by heating (170°C), dibutylhydroxytoluene was added, Carbon black and sorbitan sesquioleate are mixed into this liquid mixture, thoroughly kneaded with three rolls, and then an aqueous phase consisting of sulfuric acid and an aqueous sodium solution is gradually added thereto while stirring with a stirrer to emulsify the mixture. An inventive emulsion ink was obtained.

This emulsion ink was supplied to a single-cylinder rotary stencil printer RISOGRAPH AP7200 (manufactured by Riso Kagaku Kogyo Co., Ltd.), sufficient printing was carried out to spread the ink throughout the printing press, and printing was resumed after being left for 48 hours. At this time, the print density of the printed matter is measured using a reflective optical density needle (DM made by Dainippon Screen Co., Ltd.).
-400), and the results are shown in FIG. In FIG. 1, the horizontal axis shows the number of prints after being left and the vertical axis shows the optical density. Note that the printing density in the normal state is 0.7.

(Comparative Example 1) Furnace carbon black 3 parts Spindle oil (boiling point 270-378°C) 12 parts Rosin-modified phenolic resin 9.8 parts Sorbitan sesquioleate 5 parts Dibutylhydroxytoluene 0.1 part Water
67 parts Sodium sulfate 3 parts Methyl hydroxybenzoate 0.1 part Emulsification was carried out in the same manner as in Example 1 except that the above compound was used to obtain an emulsion ink of Comparative Example 1. This is risograph A
P7200, and after being left to stand, printing was performed in the same manner as in Example 1. The results are shown in Figure 1.

Example 2 Brilliant Fast Scarlet 3 parts Nisseki Isosol 400 14 parts Alkyd resin 9 parts Sorbitan monooleate 49 parts Butyl hydroxyanisole 0.1 part Water
60 parts ethylene glycol 5 parts sodium borate 1 part carboxymethyl cellulose 3 parts Emulsification was carried out in the same manner as in Example 1 except that the above compound was used to obtain an emulsion ink of the present invention. This is RISOGRAPH AP72
00, and after being left to stand, printing was performed in the same manner as in Example 1. As a result, a curve similar to that of Example 1 in FIG. 1 was obtained.

(Example 3) Furnace carbon black 3 parts Ink solvent 240 7 parts Spindle oil 7 parts Rosin-modified phenolic resin 9.8 parts Sorbitan sesquioleate 5 parts Dibutylhydroxytoluene 0.1 part Water
65 parts Sodium sulfate 3 parts Methyl dioxybenzoate 0.1 part The emulsion ink of the present invention was obtained by emulsifying the above compound in the same manner as in Example 1 except that the above compound was used. This is RISOGRAPH AP72
00, and after being left to stand, printing was performed in the same manner as in Example 1. The results are shown in Figure 1.

(Example 4) Furnace carbon black 3 parts Ink solvent 240 5.6 parts Spindle oil 8.4 parts Rosin modified phenolic resin 9.8 parts Sorbitan sesquioleate 5 parts Dibutyl hydroxytoluene 0.1 part Water
65 parts Sodium sulfate 3 parts Methyl dioxybenzoate 0.1 part The emulsion ink of the present invention was obtained by emulsifying the above compound in the same manner as in Example 1 except that the above compound was used. Apply this to Risograph AP
7200, and after being left to stand, printing was performed in the same manner as in Example 1. The results are shown in FIG.

(Example 5) Furnace carbon black 3 parts Ink Solvent 240 4.2 parts Spindle oil 9.8 parts Rosin modified phenolic resin 9.8 parts Sorbitan sesquioleate 5 parts Dibutylhydroxytoluene 0.1 part Water
65 parts Sodium sulfate 3 parts Methyl paraoxybenzoate 0.1 part Emulsification was carried out in the same manner as in Example 1 except that the above compound was used to obtain an emulsion ink of the present invention. Apply this to Ring Graph AP
? 200, and after being left to stand, printing was performed in the same manner as in Example 1. The results are shown in Figure 1.

(Comparative Example 2) Furnace carbon black 3 parts Ink Solvent 240 2.8 parts Spindle oil 11.2 parts Rosin modified phenolic resin 9.8 parts Sorbitan sesquioleate 5 parts Dibutylhydroxytoluene 0.1 part Water
65 parts Sodium sulfate 3 parts Methyl paraoxybenzoate 0.1 part Emulsification was carried out in the same manner as in Example 1 except that the above compound was used to obtain an emulsion ink. This was placed in a RISOGRAPH AP7200 and printed after being left in the same manner as in Example 1. The results are shown in Figure 1.

As is clear from the results in Figure 1, in the case of the emulsion ink using non-volatile mineral oil of Comparative Example 1, the initial printing density after standing was 0.35 higher than that of normal printed matter. 1600 to reach normal printing density
In contrast, in the case of the emulsion ink of the present invention, the density of the first printed matter is only 0.1 to 0.18 L higher than the normal state, and
After printing 00 sheets, the print density returns to almost the same level as the print density before being left unused.

Further, in the case of the present invention, neither paper flying up nor jamming occurred, and the degree of set-off was also the same as in normal printing.

Also, as is clear from the results in Figure 1, the boiling point is 180~2
In the case of Comparative Example 2, in which the solvent at 70° C. is contained in a droplet proportion of 5% by weight based on the total amount of the aqueous phase, the initial printing density after standing is lower than that in the case of using the emulsion ink of the present invention. The printing density is high, and the number of prints required to reach the normal print density is also quite large.

Note that the emulsion inks of Example 1 and Comparative Example 1,
The measured values of ink viscosity before and after standing were shown in Table 1. Ink viscosity is measured using a spread meter.
1 minute value (30°C) (diameter size after 1 minute has passed from the start of the test).

Table 1 From the results in Table 1, in the case of Example 1, the ink viscosity after standing was slightly softened compared to the ink viscosity before standing, but the viscosity decreased compared to Comparative Example 1. The difference is that there are very few.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the measurement results of printing density when printing was started after leaving the emulsion ink of the present invention for 48 hours.

Claims (1)

[Claims] (1) Consists of a water-in-oil emulsion consisting of about 10 to 50% by weight of an oil phase and about 90 to 50% by weight of an aqueous phase, and in the oil phase, 5% by weight or more based on the total amount of the aqueous phase has a boiling point of 180%.
An emulsion ink for stencil printing characterized by containing a solvent at ~270°C.