JP3333873B2 - Aqueous screen printing ink and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous screen printing ink capable of performing screen printing on a paper surface, and a method for producing the same.

[0002]

2. Description of the Related Art At present, an oil-based ink containing a large amount of an organic solvent is mainly used for screen printing on a paper surface. This is because the use of aqueous ink when printing on paper causes problems such as curling of the paper surface and wrinkling of the paper.

[0003] The oil-based ink contains a large amount of volatile organic solvent, so that it not only pollutes the air and may harm the health of workers, but also reduces the concentration and viscosity of the ink because the organic solvent evaporates rapidly. The problem is that it has to be constantly adjusted. In addition, the ink on the stencil that does not come into contact with the squeegee or ink return surface is dried and the film is formed. Therefore, after operating for 1 to 2 hours, the machine is stopped, the ink on the stencil is removed, and the stencil is cleaned with an organic solvent. There is a need to. Failure to do so will cause clogging of the stencil and eventually destroy the stencil. In addition, at the end of the work, the ink on the stencil must be promptly removed and wiped off with an organic solvent, so that the worker is constantly in an atmosphere of an evaporating organic solvent, which impairs health. . Note that writing characters on ink-based screen-printed paper with ink or the like with a brush or the like also has a drawback such that a repelling phenomenon occurs and characters cannot be written.

[0004]

As described above, the conventional solvent-based screen printing method using an oil-based ink pollutes the air, erodes the human body of the worker, and is extremely inefficient. The poor workability of solvent-based inks
At present, the price range is greatly affected, and screen printing paper is expensive. Screen printing on paper using water-based ink instead of using such oil-based ink is conceivable. However, there are many problems that must be overcome when water-based screen printing is performed on paper. That is, the ink is not formed on the screen stencil, the clogging of the screen stencil is not caused, the wrinkles are not generated on the printing paper, the printing paper is not curled, and the obtained screen printing film is tough and has elasticity and weather resistance. This is an issue that must be excellent.

Further, the screen printing ink repeatedly shears due to the pressure of the squeegee, and the ink return moves. Therefore, an aqueous ink having good mechanical stability that can withstand the shear of the squeegee and the ink return is required. The ink on the screen plate is extruded from a hole by a squeegee and pressed against paper, and then subjected to a drying process to be completed as characters and patterns. Screen printing of plastics, metals, cloths, and the like is performed with water-based ink, but there is no practical example of screen printing on porous paper with water-based ink except water-based UV ink.

[0006] The aqueous UV ink cures the ink with strong ultraviolet light. Therefore, aqueous UV
When screen printing is performed on paper using ink, a major problem arises in that when the paper is irradiated with ultraviolet rays to cure the ink, the irradiated paper is discolored. Further, there is also a problem that the current technology cannot apply twice to a printing surface which has been printed and cured with UV ink. Furthermore, UV irradiation devices for UV inks are too expensive, uncommon and not practical.

[0007] The reason why curling or wrinkling occurs on a printing paper when screen printing is performed with an aqueous ink is simple. Except for specially processed paper, as-made paper is hydrophilic and very compatible with water. Paper is formed by arranging pulp fibers evenly and by the power of a glue. However, when moisture is given, the glue constituting the paper is violated and the arrangement of the pulp fibers is disrupted. These are the causes of curls and wrinkles. To eliminate these causes, it is necessary to start drying quickly after printing without allowing moisture to permeate the printing paper.

The present invention has been completed as a result of conducting various studies to solve the above-mentioned problems in the use of aqueous inks. The present invention provides an aqueous screen printing ink for paper and a method for producing the same which could not be used conventionally. The present invention solves various problems in the natural environment, work environment, workability, price range, and the like, which have occurred in the conventional solvent-type printing.

[0009]

In order to solve the above-mentioned problems, the present invention has the following configuration. That is, the screen printing ink according to the present invention has a saponification degree of 9
8.0-99.0moie% polyvinyl alcohol
Is dissolved in an aqueous solution having a concentration of 24-26% by weight.
Len glycol, useful microorganisms, waterproofing agent, defoamer, d
Characterized by containing appropriate amounts of marjon and pigment
And

The molecular weight of the above polyethylene glycol is
It is preferably 4000 or more. In addition, Emarjo
The resin concentration is 30% or more and the viscosity is 500 cps or less.
Lower high-concentration, low-viscosity type with minimum film formation temperature (MFT) of 25
It is preferable to use an emulsion at about 50 ° C.

[0011] In the method of manufacturing a screen printing ink according to the present invention, an aqueous solution of polyvinyl alcohol
While stirring, add an appropriate amount of defoamer and useful microorganisms,
Separately dissolved polyethylene glycol solution and water resistant
Of adding and mixing the appropriate amount of the agent to obtain an ink base
And add the emulsion to the ink base
Viscosity adjustment process to adjust the viscosity, and ink base after the viscosity adjustment
And adding and mixing an aqueous paste pigment
It is characterized by obtaining a desired aqueous screen printing ink .

[0012] The saponification degree of polyvinyl alcohol used in this manufacturing method, degree of concentrated polyvinyl alcohol solution, the preferred range of molecular weight, such as polyethylene glycol to be added is as described above.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to specific examples. The aqueous screen printing ink contains an aqueous solution of polyvinyl alcohol (PVA) as an essential component. PVA has long been used for adhesives and the like, but there is no example used as a main component in printing ink. As the PVA used in the present invention, it is most preferable to use completely saponified PVA having a degree of saponification of 98.0 to 99.0 moie%. PVA was found to be an optimal resin as a raw material for aqueous inks in terms of the properties of a dried film of an aqueous solution, workability, safety, environmental friendliness, and price. Also,
The higher the concentration of the PVA aqueous solution and the lower the standing temperature, the higher the viscosity and gelation. The concentration of the PVA resin in the aqueous solution in the ink of the present invention is from 20 to 20 to form a film excellent in pigment conjugation power, toughness of a dry film, weather resistance and the like.
It is preferably 30% (% by weight, hereinafter the same).
More preferably, it is set to ~ 26%.

The viscosity of the PVA aqueous solution at room temperature is preferably 1500 to 2000 cps. P
This range is selected as the viscosity of the VA aqueous solution because it is the upper limit viscosity as an ink used in a high-speed screen printing machine that is completely automated from printing to drying. In addition, the PVA aqueous solution has an extremely low initial adhesive force in a viscosity range of about 1500 to 2000 cps as compared with other polymers and emulsions, and therefore has the advantage of not curling or wrinkling the printing paper.
For this reason, the ink pressed on the screen-printed paper has a weak penetrating power into the paper, and does not sufficiently adapt to the paper. However, after printing, the printed matter is melted in a drying oven and adheres strongly to the paper, so that poor initial adhesive strength is advantageous in preventing wrinkles and curls from occurring.

The viscosity of the PVA aqueous solution changes remarkably depending on the liquid temperature. Although it differs depending on the type and grade of PVA, the viscosity becomes 400 cps at a liquid temperature of 90 ° C. and 10,000 cps at a normal temperature of 25 ° C. based on a resin concentration of 25% by weight. For screen printing inks, the liquid temperature of the ink must be maintained at a normal temperature of 25 ° C. from the viewpoint of the properties, safety and accuracy of the screen stencil, and a method of reducing the viscosity by increasing the liquid temperature is adopted. Can not. On the other hand, in order to obtain an aqueous PVA solution, P.
VA is charged and heated. 60 after the liquid temperature reaches about 95 ° C
It is completely dissolved in the quantile, and the viscosity at that time is about 400 cps at 25% concentration as described above. However, the viscosity at an ambient temperature of 25 ° C. becomes 10,000 cps, and the gelation occurs when the standing temperature is low. An aqueous solution alone does not provide a viscosity suitable for screen printing.

Further, since the PVA aqueous solution has a bubble property, the stirring must be gentle, and the stirring machine must be rotated at a rotation speed within a range that does not involve air. It is also necessary to add an antifoaming agent. As an antifoaming agent, a silicon-based antifoaming agent is not suitable because it causes repelling or printing spots on a printing surface, and other antifoaming agents, for example, SN Deformer 483 (trade name) manufactured by Sannobuco Co., Ltd. are used. Is effective.

The dry PVA film is flexible under high humidity but hard and brittle under low humidity. For this reason, it is unsuitable as a printing ink film as it is, but this problem has been solved as follows. That is, 5% of EM is slowly added to PVA with stirring at the same time as the dissolution of PVA is completed. EM stands for Effective Micr
o-organisms ("Useful Microorganisms"), which is a liquid form in which useful microorganisms such as photosynthetic bacteria, yeast, lactic acid bacteria, and Aspergillus are selected and coexisted from the natural world. Are gathering. E
M is a viscous liquid closest to water, and PH is about 3 strongly acidic. EM is said to have the ability to produce antioxidant proteins or low molecular weight antioxidants under certain circumstances,
An aqueous PVA solution or the like is considered to provide an environment suitable for this generation. By adding 5% of this EM to PVA, the PVA aqueous solution is kept at PH6 and is stable for a long time. The reason for keeping the aqueous PVA solution weakly acidic is that
A water-proofing agent described below is added to keep the dried film of the VA aqueous solution to a certain degree of water resistance. The effect of the water-proofing agent is that the PVA aqueous solution becomes more water-resistant on the acidic side.

The viscosity of the aqueous solution obtained by adding EM to the PVA aqueous solution is maintained at 4000 cps at an ambient temperature of 25 ° C. and does not increase in viscosity. In addition, EM has a large antioxidant effect,
It also has the effect of preventing rust and mold, and eliminates the need to add harmful preservatives and fungicides to the human body and the natural environment to the PVA aqueous solution. For this reason, it can be said that EM is almost indispensable for a practical aqueous screen printing ink for paper containing a PVA aqueous solution as a main component.

Furthermore, the hardness and brittleness of a dried film of a PVA aqueous solution under low humidity can be significantly improved by adding an appropriate amount of polyethylene glycol (PEG) to PVA. PEG has very good wettability and lubricity, and also has the effect of a slow drying agent that delays drying, so the ink slides well on the screen stencil and has a large effect of delaying drying on the screen stencil. . Further, it has the effect of preventing clogging of the ink in the holes of the screen stencil, and is an important factor of the aqueous screen printing ink composition for paper containing PVA as a main component. PEG has different hygroscopicity depending on the degree of polymerization, and the molecular weight of PEG in the present invention is 4
000 or more are preferred.

Further, addition of the emulsion viscosity of the paper water-screen printing inks, in order to adjust a prime preferable viscosity range. Water can be used to adjust viscosity, but emulsions are important for improving pigment binding, blocking resistance of printed surface, water resistance, gloss of printed surface, strength of printed surface, ink leveling, etc. Therefore, it is preferable to add this to adjust the viscosity. The emulsion is preferably a high-concentration low-viscosity emulsion having a resin concentration of 30% or more and a viscosity of 500 cps or less, and having a minimum film formation temperature (MFT) of about 25 to 50 ° C.

Further, when selecting an emulsion,
Emulsions having problems with light resistance and weather resistance, such as styrene, butadiene, NBR, SBR, vinyl chloride, vinyl acetate, and polyethylene, must be avoided. Further, the emulsion having a minimum film formation temperature (MFT) of 25 ° C. or more has an effect of delaying drying of the ink on the screen stencil. If an emulsion with a minimum film formation temperature is used, drying on the screen stencil will be accelerated, and trouble will occur on other equipment or other parts. Goes on,
It is not preferable because the holes may be clogged and the screen stencil may be damaged.

The main composition of the aqueous screen printing ink for paper containing PVA as a main component has been described above.
In order to improve the water resistance of a dry film having a composition containing a VA aqueous solution as a main component and EM, PEG, and an emulsion, it is preferable to add a water resistant agent. As the water-proofing agent, for example, a printability improving agent PA manufactured by Nippon PMC Co., Ltd.
620 (trade name) is very effective and has an effective printing aptitude in offset printing on screen printing paper, letterpress printing, printing by a word processor, and the like. Further, in order to complete the ink, 10-20% of an extender pigment and a coloring pigment according to the purpose of use are added. The extender and the color pigment are commercially available in the form of an aqueous paste, and may be added as needed.

Next, the method for producing the aqueous ink of the present invention will be described in detail with reference to specific examples. First, a molecular weight of 40
Add 100 parts of boiling water to 100 parts of 00 or more PEG and stir. It dissolves completely in about 1-2 minutes.

In a separate container, water at room temperature is added, PVA is charged with slow stirring, and heating is started with stirring. When the solution temperature becomes 95 ° C., it becomes transparent and dissolves in about 60 minutes. When the dissolution is complete, the heating is stopped. While slowly stirring the completely dissolved PVA liquid, an appropriate amount of an antifoaming agent is added, and a predetermined amount of EM is further added. Further, the dissolved PEG solution is slowly added while stirring is continued, an appropriate amount of a water-proofing agent is added while stirring is continued, and the mixture is stirred for about 30 minutes and then aged for 12 hours. This gives a base for aqueous screen printing inks for paper.

The base of the water-based screen printing ink for paper obtained is transferred to another container of a heat retaining device which keeps the liquid temperature at 25 ° C., and the emulsion is added while stirring slowly until the viscosity becomes 1000 cps. Further, while stirring slowly, an appropriate amount of an antifoaming agent is added, and while still stirring slowly, a commercially available water-based paste pigment that matches the target color is added. After stirring for about 10 to 20 minutes, an aqueous screen printing ink for paper is completed.

[0026]

EXAMPLE Steam from a boiler was used as a heat source for heating. The container used had a double structure, and the outer part and the contents of the container were completely shut off and did not circulate with each other. In addition, the upper part of the container is open, so that water and other compounds can be easily charged, water is put in the outer part in advance, and it is connected to the pipe of the steam generating part, When the water temperature rises, the contents are heated. The stirrer was attached to stir the contents, and the rotation of the stirrer shaft was variable.
In addition, a thermometer is attached to the side of the tank where the workability is not hindered, so that the liquid temperature of the contents can be read quickly.

Into the contents of the container, 100 parts of normal-temperature water is charged, and while stirring slowly, granular fully saponified PVA 25 is added.
Add parts by weight slowly. After confirming that the particulate PVA is dispersed, the heating is started by opening the steam discharge valve in the external container containing water while stirring at such a speed that no bubbles are generated. When the temperature reached 95 ° C., the vapor discharge valve was squeezed to the minimum discharge amount, and the temperature was adjusted so that the liquid temperature did not fall below 95 ° C., and the liquid temperature did not exceed 100 ° C. After confirming that the granular PVA has dissolved after about 60 minutes,
The heating was completed by closing the steam discharge valve.

Next, 0.2% of an SN deformer 483K (trade name) manufactured by Sannobuco Co., Ltd. was added to 25 parts by weight of PVA, and M was manufactured by Sanko Sangyo Co., Ltd.
5% by weight of an EM solution of SK [environmental purification material] (trade name) was slowly added. As the EM, EM (trade name) manufactured by EM Laboratory, International Research and Development Center Division of Natural Agriculture, and EM (trade name) manufactured by Sunken Co., Ltd. could be used. In another container, PE manufactured by Daiichi Kogyo Seiyaku Co., Ltd.
1.5 kg flake PEG of G4000 (trade name)
Was added, and 1.5 kg of boiling water was slowly added with stirring. It dissolved completely after about 1-2 minutes. While stirring the PVA solution slowly so as not to generate bubbles,
The EG solution was added, and 0.6% of a printing adequacy improver PA620 (trade name) manufactured by Nippon PMC was added with further stirring. After stirring for an additional 30 minutes, the mixture was aged for 12 hours to complete the aqueous screen printing ink base for paper.

After the ripening was completed, the required amount of the aqueous base printing water-based screen printing ink was transferred to another container. The container is a circular container, an electric band heater is attached to the outer periphery of the container, and the liquid temperature of the ink is 25 ° C.
Is configured to keep. A stirrer whose rotation can be adjusted is also provided. While stirring the base of the aqueous screen printing ink for paper placed in this container,
Movinyl 9000 (trade name) manufactured by Hoechst Gosei Co., Ltd., acrylic copolymer resin emulsion (resin concentration 43
%, A viscosity of 300 cps, and a minimum film-forming temperature of 30 ° C.) were added in an amount of 20 parts to the base of the aqueous screen printing ink for paper. At that time, the viscosity was 1000 cps. While further stirring, 0.1% of an antifoaming agent was added.

Then, while slowly stirring 100 parts by weight of the base of the ink containing an aged PVA aqueous solution as a main component, an aqueous white pigment (trade name: Sumika Color P)
MA) was added, and 0.3 part by weight of an aqueous pink pigment (trade name: Sumika Color PM-5BFP) was further added. After stirring for 15 minutes, the stirring was stopped. As a result, a light pink ink having a viscosity of 1020 cps was obtained.

As the screen printing paper, white Japanese paper of each leaf was used. The thickness of the Japanese paper is relatively thick with a basis weight of 120 g / m ² , and the dimensions of the Japanese paper are 800 mm in width and 560 in length.
mm. The design is a design in which cherry petals of about 3 mm are arranged on the entire surface, and the printing area occupying about the entire surface of the paper is about 80%. Because Japanese paper is porous and has a large water absorption, it is very easy to curl and it is necessary to start drying quickly after printing. The silk screen printing machine used was Sakurai Graphic Systems. The whole machine consists of a paper feed unit, a printing unit, a drying oven, and a paper discharging unit. The number of printing speeds can be adjusted in the range of 800 to 3500 sheets per hour. The internal temperature setting is a first drying oven, a second drying oven, a third drying oven, and a fourth drying oven, and the temperature setting in each oven is provided with a device that can be adjusted within a range of 0 to 100 ° C. . The mesh of the screen to be printed was 200 mesh. Printing speed is 2 per hour
Set the drying oven temperature to 500 sheets, the first drying oven to 41 ℃,
The second drying oven was set at 44 ° C, the third drying oven at 47 ° C, and the fourth drying oven at 50 ° C. Printing start speed is 25 per hour
00 sheets, about 3 seconds were required until the drying start time, about 15 minutes was required until the sheet was discharged from the drying oven, and the amount of used ink was 480 sheets with 1 kg of ink. The printed printing paper was firm, free of curls, and finished with a clear light-colored cherry blossom pattern. Furthermore, the dimensions of the printing paper were very stable and there was no error between the paper dimensions before and after printing.

[0032]

As is apparent from the above description, according to the present invention, aqueous screen printing for paper is far superior to conventional solvent-based inks in terms of natural environment, working environment, workability, price, etc. It has become possible to provide ink.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-9-245380 (JP, A) JP-A-9-143415 (JP, A) JP-A-63-183975 (JP, A) JP-A-63-183975 183974 (JP, A) JP-A-9-47746 (JP, A) JP-A-10-46146 (JP, A) JP-A-10-155476 (JP, A) Table 6-509599 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C09D 11/00-11/20

Claims (4)

(57) [Claims] 1. A saponification degree of 98.0 to 99.0 moie%.
Polyvinyl alcohol dissolved concentration of 24-26
% Aqueous solution, polyethylene glycol, useful microorganisms
Group, water-proofing agent, defoamer, emulsion and pigment in appropriate amounts
An aqueous screen printing ink characterized by being incorporated. 2. The polyethylene glycol having a molecular weight of 400
The aqueous screen printing ink according to claim 1, which is 0 or more . 3. The emulsion has a resin concentration of 30% or more and a viscosity of 30% or more.
High-concentration low-viscosity type with a temperature of 500 cps or less, minimum film forming temperature
The aqueous screen printing ink according to claim 1 or 2, wherein (MFT) is an emulsion at 25 to 50 ° C. 4. An aqueous solution of polyvinyl alcohol is stirred.
While adding an appropriate amount of defoamer and useful microorganisms,
Separately dissolved polyethylene glycol solution and waterproofing agent
Adding and mixing appropriate amounts to obtain an ink base;
Adjust viscosity by adding emulsion to the prepared ink base
Viscosity adjustment process, and water-based ink base after viscosity adjustment
Through the process of adding and mixing paste-like pigments
Water for obtaining an aqueous screen printing ink
For producing a screen printing ink.