JPS6038482A - Ink for ink jet recording - Google Patents

Abstract

PURPOSE:To provide the titled ink having clear color tone with excellent fastness to light and excellent viscosity stability etc., by using, as a base, colored water-base polymer obtd. by dyeing a water-soluble polymer contg. sulfo groups with a basic dye. CONSTITUTION:A water-soluble polymer having a sulfo group content of at least 2X10<-5>g equivalent/g of polymer is prepd. either by preparing a polymer and then introducing the sulfo groups into the polymer, or by (co)polymerizing a radical-polymerizable vinyl monomer contg. a sulfo group, such as vinylsulfonic acid or methacryl sulfonic acid. The water-soluble polymer is then dyed with a basic dye such as C.I. Basic Red 38. The resulting colored water-base polymer is used as a base, and additives such as a wetting agent, a mildew proofing agent, etc. are added thereto to obtain the desired ink for ink jet recording.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inkjet recording ink. More specifically, the present invention relates to an inkjet recording ink whose base material is a water-based colored polymer obtained by dyeing a water-washable polymer in which a specific hydrophilic group is introduced with a basic dye.

The ink used for inkjet recording is required to meet various basic conditions, although these conditions vary depending on the recording method.

First, in order to be compatible with the method of generating ink droplets and the method of controlling the flying direction of ink droplets, it is necessary that the viscosity, surface tension, specific conductivity, etc. of the ink be within appropriate ranges.

For example, it is preferable that the flying speed of the ink is high in order to improve the printing quality, but for this reason, the ink viscosity is preferably low, and is generally required to be 10 cpθ or less. In addition, the higher the surface tension, the better the response to one driving frequency for the generation of flying ink droplets, but on the other hand, if the surface tension is too high, the ink tends to get wet and have poor fixation on paper, and the surface Tension is generally 40-65 dyneAm
It can be said that it is desirable to be within the range of .

Furthermore, the specific conductivity is desirably 1 mv%m (25°C) or more, and is adjusted with triethanolamine, cationic surfactant, etc.

Conventionally, many proposals have been made as inkjet recording inks. For example, a water-soluble dye is bath-dissolved in water,
Although there are inks to which wetting agents, preservatives, etc. are added, in reality, no ink for inkjet recording has been obtained that satisfies all of the above conditions.

As a result of research into inkjet recording inks that satisfy the various requirements that such inkjet recording inks should have, the present inventors dyed a water-soluble polymer in which a specific hydrophilic group was introduced with a basic dye. The present invention was completed based on the discovery that a water-based colored polymer exhibits excellent performance as a base material for inkjet recording inks.

That is, the present invention provides an inkjet recording ink based on a water-based colored polymer obtained by dyeing with a basic dye a water-bathable polymer containing at least 2 x 10-5 grams of sulfonic acid groups per gram of polymer. It provides:

The polymer containing a sulfonic acid group used in the present invention may be produced by introducing a sulfonic acid group into a previously produced polymer, or by polymerizing a radically polymerizable vinyl monomer containing a sulfonic acid group. Alternatively, there is a method of copolymerizing a radically polymerizable vinyl monomer containing a sulfonic acid group with another radically polymerizable vinyl monomer.

As a method for later introducing a sulfonic acid group into a pre-produced polymer, a sulfonic acid group of a polymer by a conventionally known sulfonation reaction can be adopted. For example, there is a method of sulfonating polystyrene or styrene-maleic anhydride fj, i copolymer with sulfuric acid, sulfuric anhydride, etc. in a suitable organic bath agent.

Furthermore, as a method of polymerizing a radically polymerizable vinyl monomer containing a sulfonic acid group, or copolymerizing a radically polymerizable vinyl monomer containing a sulfonic acid group with another radically polymerizable vinyl monomer,
For example, 1
The polymerization may be carried out at a polymerization temperature of 0°C to 90°C. Examples of the radically polymerizable vinyl monomer containing a sulfonic acid group include vinyl sulfone, methallyl sulfone, allyl sulfone, styrene sulfonic acid,
Examples include vinylbenzyl sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, and their lithium salts, sodium salts, potassium salts, and ammonium salts.

Furthermore, other vinyl monomers copolymerizable with such radically polymerizable hydrophilic vinyl monomers include 2
-Hydroxyethyl acrylate.

Hydrophilic vinyl monomers such as 2-hydroxyethyl methacrylate, acrylamide, methacrylamide, methylol acrylamide, methylol methacrylamide, methyl acrylate, ether acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n -butyl methacrylate, 2-ethylhexyl methacrylate +) v
) r Vinyl acetate, vinyl propionate, vinyl chloride.

Examples include hydrophobic monomers such as vinylidene chloride and styrene.

These seven polymers are polymerized in a hot medium (e.g., water) using an ordinary radical polymerization initiator at a polymerization temperature of usually 10°C to 90°C. Ammonium persulfate, potassium persulfate, t-
Examples include butyl hydroperoxide and cumene hydroperoxide. Of course, redox polymerization initiators that are used in combination with conventionally known polymerization initiators and reducing agents such as sodium bisulfite, autophilic sodium thiosulfate, and ferrous Wl sulfate can also be used.

In the present invention, 11 of the sulfonic acid groups contained in the water-bathable polymer has a sulfonic acid group of at least 2 x 105 gram equivalent/gram polymer, preferably I x 10-' in view of the sunlight fastness of the ink and the viscosity stability of the ink.
If the content is at least gram equivalent/gram polymer, it can exhibit satisfactory physical properties as a base material for the inkjet recording ink of the present invention.

When a water-soluble polymer having the requirements of the present invention is obtained by a polymerization method such that such an introduction rate is achieved, the molecular weight of the resulting water-soluble polymer is determined by the concentration of each monomer present in the polymer thread, the radical polymerization initiation It depends on the amount of agent used, the polymerization temperature, etc. The concentration of nanatsuma can be freely selected, but it is generally 5 to 50 wt.
, Ovrt%. Polymerization at high concentrations is not preferred because the viscosity of the polymerization system becomes high and it becomes difficult to remove the heat of polymerization.

Furthermore, polymerization at too low a concentration is not preferred for economic reasons. In addition, as the amount of radical polymerization initiator used increases, the molecular force of the water-soluble polymer tends to become smaller.
When the amount of radical polymerization initiator is small (the molecular weight of the water-soluble polymer tends to increase).

The molecular weight of the sulfonic acid group-containing paddy polymer thus obtained is an important factor since it affects the viscosity of the ink, but the average molecular weight may be 5x105 or less, preferably 2x10' or less.

In view of the purpose of the present invention, the present invention is not limited in any way by the method of obtaining such a water-soluble polymer.

Next, the resulting water-bathable polymer is dyed using the usual triphenylmethane, azo, and methine dyes.

Conventional basic dyes and cationic dyes known as oxazine-based or anth-2-quinone-based dyes classified according to the classification described in the Dye Handbook (published by Marukubi) may be used.

Industrially, the simplest method for dyeing is to adjust the pH of the water-based polymer to 2 to 7, preferably 5 to 5, with an organic acid such as formic acid, acetic acid, or butyric acid, or an inorganic acid such as hydrochloric acid, 8 sulfuric acid, and dye. It can be carried out by a staining method in which a solution is added.

Such a dyeing method is not limited in view of the spirit of the present invention.

When the thus obtained aqueous colored polymer of the present invention is used as a one-ink jet recording ink, conventionally known adjuvants such as glycerin, ethylene glycol, propylene glycol are added.

Diethylene glycol, polyethylene glycol.

Triethanolamine, N-methyl 2-pyrrolidone, 1
．． It may also be used with wetting agents such as 5-dimethylimidacillin, anti-gold agents such as sodium omazine, and dioxine.

The inkjet recording ink using the aqueous colored polymer of the present invention has features that have not been seen in the past.

First, the present invention makes it possible to print with bright color tones, using basic dyes and cationic dyes that are distinctive for their wide variety of colors and their brightness, and with the presence of a water-soluble polymer, the sunlight fastness is the same as above. Ta. Furthermore, the second effect is the viscosity stability of the ink. That is, by intervening a chemically stable polymer,
The present invention will be described in more detail with reference to Examples below, but the present invention is not limited to the Examples in any way.

Water-soluble polymer synthesis example-1 50 parts of water was charged into a polymerization flask purged with nitrogen, and the temperature was raised to 90°C. A monomer aqueous solution was prepared by dissolving 244 parts of spinomer Na5S (sodium p-styrene sulfonate, pure 11ti 82.0%, manufactured by Toyo Soda Kogyo) in 720 parts of water.

Eight polymerization initiator water bath solutions were prepared by dissolving 10 parts of ammonium persulfate in 30 parts of water.

A monomer aqueous solution and a polymerization initiator aqueous solution were each added to a polymerization flask over a period of 3 hours, and polymerization was carried out at 90°C.

Further, polymerization was continued at 90°C for 2 hours and cooled to 25°C, but the viscosity of the solution at 25°C was 9.5 cps.

When unreacted sodium p-styrene sulfonate was quantified by the bromine addition method, the polymerization rate of the monomer was 99. O
It was more than wt%.

The polymer was purified by dropping an aqueous polymer solution into absolute ethanol to obtain a water-bathable polymer powder. The average molecular weight was determined by gel vermi- cation chromatography (hereinafter referred to as "GPC method") and was found to be 12w1.1x.
It was 10'.

Water Bathable Polymer Synthesis Example-2 40 parts of water was charged into a polymerization flask purged with nitrogen, and the temperature was raised to 70°C. An aqueous monomer solution was prepared by dissolving 117 parts of Spinomer-IJass (p-styrene sulfone aqueous sodium, purity 132.0%, manufactured by Toyo Roda Kogyo) and 24 parts of acrylic powder in 400 parts of water.

An aqueous polymerization initiator solution was prepared by dissolving 6 parts of ammonium in 20 parts of water.

A monomer aqueous solution and a polymerization initiator aqueous solution were added over 6 hours and polymerized at 706C. It was further polymerized at 70°C for 2 hours and cooled to 25°C, but the viscosity of (89) at 25°C was
It was cps.

The polymer was purified by dropping an aqueous polymer solution into acetone to obtain a water-soluble polymer powder.

According to the analysis value of sulfur in the polymer, there is 5.8 sulfur in the polymer.
It contained 6 x 10-3 gram equivalents/gram polymer of sulfonic acid groups. Moreover, the average molecular weight by GPC method was Mw 5.4 x 10'.

Water Bathable Polymer Synthesis Example-6 50 parts of water was charged into a polymerization flask purged with nitrogen, and the temperature was raised to 90°C. An aqueous monomer solution was prepared by dissolving 20 parts of 2-hydroxyethyl methacrylate and 220 parts of Subinomer Na5s (p-styrene sulfone aqueous sodium, purity 82.0%, manufactured by Toyo Soda Kogyo) in 70-0 parts of water.

Next, 8 parts of ammonium persulfate was dissolved in 60 parts of water to prepare an aqueous solution of Togane initiator.

A seven-mer aqueous solution and a polymerization initiator aqueous solution were each added to a polymerization flask over a period of 6 hours, and polymerization was carried out at 90°C.

After further polymerization for 2 hours, the mixture was cooled to 25°C.

The core liquid viscosity at 25°C was 18 cps.

The average molecular weight of the polymer obtained as a precipitate by treating an aqueous polymer solution with a large amount of acetone was Mw7 by GPC method.
xiO! According to the sulfur analysis value, there is 4.3 in the polymer.
It contained 7x10-4 gram equivalents/gram polymer of sulfonic acid groups.

Examples 1 to 6 A basic dye (manufactured by Hodogaya Chemical Co., Ltd.) was added to the 20 wt% water bath solution 1002 of the water-soluble polymer obtained in Water-soluble Polymer Synthesis Example-1! LOy, water 100f, acetic acid 1.02 hot water 1
6. Gradually add the liquid and stir at 80℃ for 60 minutes.

After concentrating under reduced pressure using a rotary evaporator to about 1/2 volume, the concentrated solution was dropped into 21 ml of ethanol, and the colored polymer precipitate was dried under reduced pressure using a glass filter.

2.5 gr of these colored polymer powders, 101 g of tetraethylene glycol and 37.5 g of water. An ink was prepared by dissolving Km. The properties of the ink are as shown in Table 1, and the ink of the present invention can be filtered without clogging using Toyo P paper A1510 filter paper. Also, the ink temperature is 5°C225°C
After storage at 50°C for one month, there was no change in viscosity over time and no precipitates were observed.

Further, the ink of the present invention was applied to art paper using a 1 ml doctor blade, dried at room temperature, and then tested for sunlight fastness using a xenon arc fade meter, showing good sunlight fastness.

Table 1 The inks of Examples 1 to 5 were further filtered through a 0.45μ membrane filter, and the ink was jet-recorded on high-quality paper using a nozzle with an inner diameter of 50μ at a particle generation frequency of 100 kHz, resulting in clear prints. It was done.

Examples 4 to 6 Water-soluble polymer of 20 wt% water-soluble polymer obtained in Synthesis Example-2? Example 1 using f'f100rl
Colored polymer water bath liquid f obtained by performing the same operation as 5.
! : The colored polymer precipitated by dropping it into acetone (No. 21) was separated and dried under reduced pressure using a glass filter.

These colored polymer powders1. Of, 12 ml of diethylene glycol was dissolved in 67 g of water. Furthermore, the ink of the present invention was prepared by adjusting the pH to 6.5 using ethanolamine.

The properties of the ink are shown in Table 2, and the ink of the present invention can be filtered without clogging using Toyo P paper A1610E paper. Furthermore, when the ink was stored at 50° C. for one month, there was no change in viscosity over time and no precipitates were observed.

Further, the ink of the present invention was applied to art paper using a 1 ml doctor blade, dried at room temperature, and then tested for sunlight fastness using a xenon arc fade meter, showing good sunlight fastness.

Table 2 Examples 7 to 8 Colored polymer water bath liquids obtained by performing the same operations as Examples 1 to 3 using 20 wt water bath liquid 1002 of the water bathable polymer obtained in Synthesis Example 3. The precipitated colored polymer was separated by glass filter and dried under reduced pressure.

These colored polymer powders 402. The ink of the present invention was prepared by dissolving 10 parts of diethylene glycol moptyl ether in 56 parts of water.

The properties of the ink are as shown in Table 5, and the ink of the present invention was tested using Toyo Roshi Paper 1510ν paper to prevent clogging tr<
I was able to filter it. Furthermore, when the ink was stored at 50° C. for one month, there was no change in viscosity over time and no precipitates were observed.

Further, the ink of the present invention was coated on art paper with a doctor blade of 1 mi], dried at room temperature, and then tested for sunlight fastness using a xenon arc fade meter, and found to have good sunlight fastness.

Table-5

Claims (1)

[Claims] An inkjet recording ink based on an aqueous colored polymer obtained by dyeing a water-soluble polymer containing at least 2 x 101 gram equivalents/gram polymer of sulfonic acid groups with a basic dye.